Author(s) ID,Title,Year,DOI,Link,Abstract
"7005955015;53878006900;7404732357;","The hydrological cycle response to cirrus cloud thinning",2015,"10.1002/2015GL066795","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955171377&doi=10.1002%2f2015GL066795&partnerID=40&md5=4a64086c8c7657864070ab70677eb988","Recent multimodel studies have shown that if one attempts to cancel increasing CO2 concentrations by reducing absorbed solar radiation, the hydrological cycle will weaken if global temperature is kept unchanged. Using a global climate model, we investigate the hydrological cycle response to ""cirrus cloud thinning (CCT),"" which is a proposed climate engineering technique that seeks to enhance outgoing longwave radiation. Investigations of the ""fast response"" in experiments with fixed sea surface temperatures reveal that CCT causes a significant enhancement of the latent heat flux and precipitation. This is due to enhanced radiative cooling of the troposphere, which is opposite to the effect of increased CO2 concentrations. By combining CCT with CO2 increase in multidecadal simulations with a slab ocean, we demonstrate a systematic enhancement of the hydrological cycle due to CCT. This leads to enhanced moisture availability in low-latitude land regions and a strengthening of the Indian monsoon. © 2015. American Geophysical Union. All Rights Reserved."
"7501627905;","Anthropogenic aerosols and the distribution of past large-scale precipitation change",2015,"10.1002/2015GL066416","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955195119&doi=10.1002%2f2015GL066416&partnerID=40&md5=bd6e581bb4c18134425d20787704555d","The climate response of precipitation to the effects of anthropogenic aerosols is a critical while not yet fully understood aspect in climate science. Results of selected models that participated the Coupled Model Intercomparison Project Phase 5 and the data from the Twentieth Century Reanalysis Project suggest that, throughout the tropics and also in the extratropical Northern Hemisphere, aerosols have largely dominated the distribution of precipitation changes in reference to the preindustrial era in the second half of the last century. Aerosol-induced cooling has offset some of the warming caused by the greenhouse gases from the tropics to the Arctic and thus formed the gradients of surface temperature anomaly that enable the revealed precipitation change patterns to occur. Improved representation of aerosol-cloud interaction has been demonstrated as the key factor for models to reproduce consistent distributions of past precipitation change with the reanalysis data. © 2015. American Geophysical Union. All Rights Reserved."
"6701735773;56695480300;6603875926;7004714030;7004452524;23981063100;","Air moisture control on ocean surface temperature, hidden key to the warm bias enigma",2015,"10.1002/2015GL066764","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955209643&doi=10.1002%2f2015GL066764&partnerID=40&md5=a961d178f1abbc82f13f8bb70d1843c3","The systematic overestimation by climate models of the surface temperature over the eastern tropical oceans is generally attributed to an insufficient oceanic cooling or to an underestimation of stratocumulus clouds. We show that surface evaporation contributes as much as clouds to the dispersion of the warm bias intensity in a multimodel simulations ensemble. The models with the largest warm biases are those with the highest surface heating by radiation and lowest evaporative cooling in atmospheric simulations with prescribed sea surface temperatures. Surface evaporation also controls the amplitude of the surface temperature response to this overestimated heating, when the atmosphere is coupled to an ocean. Evaporation increases with temperature both because of increasing saturation humidity and of an unexpected drying of the near-surface air. Both the origin of the bias and this temperature adjustment point to the key role of near-surface relative humidity and its control by the atmospheric model. © 2015. American Geophysical Union. All Rights Reserved."
"35332943100;7405881408;8574117100;7005792005;37023271100;16064734200;7402107243;6603058638;55546696300;56697999400;6602535404;6602588942;56511043300;7103321653;37080285500;6603209377;7003798485;7402093221;56799678800;7401569549;7005183971;6603136620;6701674643;55921875600;24289281200;7005436715;7203087540;7005339628;6505950097;6603637077;6701455795;7004146716;7202420300;6701696141;6701375674;7102791212;7004462881;57216907006;7006392633;57016736600;6604078329;8691365600;55897417200;55764986000;6602740627;36946336000;56698026600;6602819437;7004453851;6602883825;6603847332;23974882500;7102770247;7003775081;56817075300;57016027800;6506421160;16314242500;6603777172;7003460109;24462857800;16243014700;7201705406;36551761100;","Rapid and highly variable warming of lake surface waters around the globe",2015,"10.1002/2015GL066235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955176607&doi=10.1002%2f2015GL066235&partnerID=40&md5=3de5e7482ea7f0b85e67626560b3d37e","In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade-1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors - from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade-1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade-1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes. © 2015. American Geophysical Union. All Rights Reserved."
"23034148100;7102167757;7004060399;","Recent Hadley cell expansion: The role of internal atmospheric variability in reconciling modeled and observed trends",2015,"10.1002/2015GL066942","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955213418&doi=10.1002%2f2015GL066942&partnerID=40&md5=b1135861b443e675334e3c768f719a40","Several studies have reported that global climate models underestimate the observed trend in tropical expansion, with the implication that such models are missing key processes of the climate system. We show here that integrations of a chemistry-climate model forced with observed sea surface temperatures (SSTs), greenhouse gases, and ozone-depleting substances can produce 1980 to 2009 expansion trends comparable to those found in most reanalyses data products. Correct representation of the SSTs changes is important for the Northern Hemisphere, while correct representation of stratospheric ozone changes is important for the Southern Hemisphere. The ensemble mean trend (which captures only the forced response) is nearly always much weaker than trends in reanalyses. This suggests that a large fraction of the recently observed changes may, in fact, be a consequence of internal atmospheric variability and not a response of the climate system to anthropogenic forcings. © 2015. American Geophysical Union. All Rights Reserved."
"12769875100;56493740900;7403282069;26324818700;","Covariance between Arctic sea ice and clouds within atmospheric state regimes at the satellite footprint level",2015,"10.1002/2015JD023520","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957426055&doi=10.1002%2f2015JD023520&partnerID=40&md5=813ccd1c45392ba51cfb985520449a93","Understanding the cloud response to sea ice change is necessary for modeling Arctic climate. Previous work has primarily addressed this problem from the interannual variability perspective. This paper provides a refined perspective of sea ice-cloud relationship in the Arctic using a satellite footprint-level quantification of the covariance between sea ice and Arctic low cloud properties from NASA A-Train active remote sensing data. The covariances between Arctic low cloud properties and sea ice concentration are quantified by first partitioning each footprint into four atmospheric regimes defined using thresholds of lower tropospheric stability and midtropospheric vertical velocity. Significant regional variability in the cloud properties is found within the atmospheric regimes indicating that the regimes do not completely account for the influence of meteorology. Regional anomalies are used to account for the remaining meteorological influence on clouds. After accounting for meteorological regime and regional influences, a statistically significant but weak covariance between cloud properties and sea ice is found in each season for at least one atmospheric regime. Smaller average cloud fraction and liquid water are found within footprints with more sea ice. The largest-magnitude cloud-sea ice covariance occurs between 500 m and 1.2 km when the lower tropospheric stability is between 16 and 24 K. The covariance between low cloud properties and sea ice is found to be largest in fall and is accompanied by significant changes in boundary layer temperature structure where larger average near-surface static stability is found at larger sea ice concentrations. © 2015. The Authors."
"56149492300;56612517400;36538539800;","Multiyear applications of WRF/Chem over continental U.S.: Model evaluation, variation trend, and impacts of boundary conditions",2015,"10.1002/2015JD023819","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957438899&doi=10.1002%2f2015JD023819&partnerID=40&md5=37f299844cfa3c368fe3aad66dfcfee4","Multiyear applications of an online-coupled meteorology-chemistry model allow an assessment of the variation trends in simulated meteorology, air quality, and their interactions to changes in emissions and meteorology, as well as the impacts of initial and boundary conditions (ICONs/BCONs) on simulated aerosol-cloud-radiation interactions over a period of time. In this work, the Weather Research and Forecasting model with Chemistry version 3.4.1 (WRF/Chem v. 3.4.1) with the 2005 Carbon Bond mechanism coupled with the Volatility Basis Set module for secondary organic aerosol formation (WRF/Chem-CB05-VBS) is applied for multiple years (2001, 2006, and 2010) over continental U.S. This work also examines the changes in simulated air quality and meteorology due to changes in emissions and meteorology and the model’s capability in reproducing the observed variation trends in species concentrations from 2001 to 2010. In addition, the impacts of the chemical ICONs/BCONs on model predictions are analyzed. ICONs/BCONs are downscaled from two global models, the modified Community Earth System Model/Community Atmosphere model version 5.1 (CESM/CAM v5.1) and the Monitoring Atmospheric Composition and Climate model (MACC). The evaluation of WRF/Chem-CB05-VBS simulations with the CESM ICONs/BCONs for 2001, 2006, and 2010 shows that temperature at 2m (T2) is underpredicted for all three years likely due to inaccuracies in soil moisture and soil temperature, resulting in biases in surface relative humidity, wind speed, and precipitation. With the exception of cloud fraction, other aerosol-cloud variables including aerosol optical depth, cloud droplet number concentration, and cloud optical thickness are underpredicted for all three years, resulting in overpredictions of radiation variables. The model performs well for O3 and particulate matter with diameter less than or equal to 2.5 (PM2.5) for all three years comparable to other studies from literature. The model is able to reproduce observed annual average trends in O3 and PM2.5 concentrations from 2001 to 2006 and from 2006 to 2010 but is less skillful in simulating their observed seasonal trends. The 2006 and 2010 results using CESM and MACC ICONs/BCONs are compared to analyze the impact of ICONs/BCONs on model performance and their feedbacks to aerosol, clouds, and radiation. Comparing to the simulations with MACC ICONs/BCONs, the simulations with the CESM ICONs/BCONs improve the performance of O3 mixing ratios (e.g., the normalized mean bias for maximum 8h O3 is reduced from -17% to -1% in 2010), PM2.5 in 2010, and sulfate in 2006 (despite a slightly larger normalized mean bias for PM2.5 in 2006). The impacts of different ICONs/BCONs on simulated aerosol-cloud-radiation variables are not negligible, with larger impacts in 2006 compared to 2010. © 2015. American Geophysical Union. All Rights Reserved."
"7005755107;7003686951;7005216212;54390358500;7003401367;57189490508;6506725113;","Ocean colour products from geostationary platforms, opportunities with Meteosat Second and Third Generation",2015,"10.5194/osd-12-3143-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042574164&doi=10.5194%2fosd-12-3143-2015&partnerID=40&md5=476b142b091c59559672312d09e00473","Ocean colour applications from medium-resolution polar-orbiting satellite sensors have now matured and evolved into operational services. The examples include the Sentinel-3 OLCI missions of the European Earth Observation Copernicus programme and the VIIRS missions of the US Joint Polar Satellite System programme. Key drivers for Copernicus ocean colour services are the national obligations of the EU member states to report on the quality of marine, coastal and inland waters for the EU Water Framework Directive and Marine Strategy Framework Directive. Further applications include CO2 sequestration, carbon cycle and climate, fisheries and aquaculture management, near-real-time alerting to harmful algae blooms, environmental monitoring and forecasting, and assessment of sediment transport in coastal waters. Ocean colour data from polar-orbiting satellite platforms, however, suffer from fractional coverage, primarily due to clouds, and inadequate resolution of quickly varying processes. Ocean colour remote sensing from geostationary platforms can provide significant improvements in coverage and sampling frequency and support new applications and services. EUMETSAT's SEVIRI instrument on the geostationary Meteosat Second Generation platforms (MSG) is not designed to meet ocean colour mission requirements, however, it has been demonstrated to provide valuable contribution, particularly in combination with dedicated ocean colour polar observations. This paper describes the ongoing effort to develop operational ocean colour water turbidity and related products and user services from SEVIRI. A survey of user requirements and a study of technical capabilities and limitations of the SEVIRI instruments are the basis for this development and are described in this paper. The products will support monitoring of sediment transport, water clarity, and tidal dynamics. Further products and services are anticipated from EUMETSAT's FCI instruments on Meteosat Third Generation satellites (MTG), including potential chlorophyll a products. © Author(s) 2015."
"7202660824;7403288995;7402064802;36856321600;","The strength of the tropical inversion and its response to climate change in 18 CMIP5 models",2015,"10.1007/s00382-014-2441-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929703897&doi=10.1007%2fs00382-014-2441-9&partnerID=40&md5=170bc37005cc6490577ff0e9f6190a32","We examine the tropical inversion strength, measured by the estimated inversion strength (EIS), and its response to climate change in 18 models associated with phase 5 of the coupled model intercomparison project (CMIP5). While CMIP5 models generally capture the geographic distribution of observed EIS, they systematically underestimate it off the west coasts of continents, due to a warm bias in sea surface temperature. The negative EIS bias may contribute to the low bias in tropical low-cloud cover in the same models. Idealized perturbation experiments reveal that anthropogenic forcing leads directly to EIS increases, independent of “temperature-mediated” EIS increases associated with long-term oceanic warming. This fast EIS response to anthropogenic forcing is strongly impacted by nearly instantaneous continental warming. The temperature-mediated EIS change has contributions from both uniform and non-uniform oceanic warming. The substantial EIS increases in uniform oceanic warming simulations are due to warming with height exceeding the moist adiabatic lapse rate in tropical warm pools. EIS also increases in fully-coupled ocean–atmosphere simulations where $$\hbox {CO}_{2}$$CO2 concentration is instantaneously quadrupled, due to both fast and temperature-mediated changes. The temperature-mediated EIS change varies with tropical warming in a nonlinear fashion: The EIS change per degree tropical warming is much larger in the early stage of the simulations than in the late stage, due to delayed warming in the eastern parts of the subtropical oceans. Given the importance of EIS in regulating tropical low-cloud cover, this suggests that the tropical low-cloud feedback may also be nonlinear. © 2014, Springer-Verlag Berlin Heidelberg."
"56592876500;56593223000;35094424100;6603480361;57203049177;35570389600;56405624900;7006532784;","A large ozone-circulation feedback and its implications for global warming assessments",2015,"10.1038/nclimate2451","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921802406&doi=10.1038%2fnclimate2451&partnerID=40&md5=4a32143a36b9afca7413acfa0c905ec8","State-of-the-art climate models now include more climate processes simulated at higher spatial resolution than ever. Nevertheless, some processes, such as atmospheric chemical feedbacks, are still computationally expensive and are often ignored in climate simulations. Here we present evidence that the representation of stratospheric ozone in climate models can have a first-order impact on estimates of effective climate sensitivity. Using a comprehensive atmosphere-ocean chemistry-climate model, we find an increase in global mean surface warming of around 1 °C (∼ 20%) after 75 years when ozone is prescribed at pre-industrial levels compared with when it is allowed to evolve self-consistently in response to an abrupt 4×CO2 forcing. The difference is primarily attributed to changes in long-wave radiative feedbacks associated with circulation-driven decreases in tropical lower stratospheric ozone and related stratospheric water vapour and cirrus cloud changes. This has important implications for global model intercomparison studies in which participating models often use simplified treatments of atmospheric composition changes that are consistent with neither the specified greenhouse gas forcing scenario nor the associated atmospheric circulation feedbacks."
"55332348600;26645289600;7003266014;7402064802;","The relationship between interannual and long-term cloud feedbacks",2015,"10.1002/2015GL066698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953637951&doi=10.1002%2f2015GL066698&partnerID=40&md5=a68eead74737481fa445c86b1b35fbdb","Analyses of Coupled Model Intercomparison Project phase 5 simulations suggest that climate models with more positive cloud feedback in response to interannual climate fluctuations also have more positive cloud feedback in response to long-term global warming. Ensemble mean vertical profiles of cloud change in response to interannual and long-term surface warming are similar, and the ensemble mean cloud feedback is positive on both timescales. However, the average long-term cloud feedback is smaller than the interannual cloud feedback, likely due to differences in surface warming pattern on the two timescales. Low cloud cover (LCC) change in response to interannual and long-term global surface warming is found to be well correlated across models and explains over half of the covariance between interannual and long-term cloud feedback. The intermodel correlation of LCC across timescales likely results from model-specific sensitivities of LCC to sea surface warming. © 2015. American Geophysical Union. All Rights Reserved."
"24402359000;7003591311;6506152198;14035836100;","Stratocumulus to cumulus transition in the presence of elevated smoke layers",2015,"10.1002/2015GL066544","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953638216&doi=10.1002%2f2015GL066544&partnerID=40&md5=4c08cef4a08cb41916eee3747ab2be24","The transition from stratocumulus to cumulus clouds in the presence of elevated light-absorbing smoke layers is investigated with idealized large-eddy simulations. A smoke layer is placed 1 km above stratocumulus top and evolves with the cloud fields over the course of a 3 day simulation. The simulations presented vary the smoke-generated heating and the moisture content of the smoke layer. A control case without smoke is simulated for comparison. On day 2 of the transition, when still above cloud, smoke generates a more broken cloud field than the control case, depending weakly on the strength of the aerosol heating but strongly on the water vapor content in the smoke layer. Following nighttime recovery and contact with the stratocumulus, smoke hinders the transition by strengthening the inversion, limiting boundary layer deepening and reducing precipitation-related breakup. This modulation delays the transition, which may extend the stratocumulus deck westward, with concomitant implications for climate forcing. © 2015. American Geophysical Union. All Rights Reserved."
"56457851700;7202145115;","Observations of a substantial cloud-aerosol indirect effect during the 2014-2015 Bár arbunga-Vei IVötn fissure eruption in Iceland",2015,"10.1002/2015GL067070","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953635064&doi=10.1002%2f2015GL067070&partnerID=40&md5=11d11aa94f8ce074cb8627cd34776fcc","The Bárarbunga-Vei ivötn fissure eruption lasted from 31 August 2014 to 28 February 2015, during which its sulfur emissions dwarfed anthropogenic emissions from Europe. This natural experiment offers an excellent opportunity to investigate the aerosol indirect effect and the effect of effusive volcanic eruptions on climate. During the eruption cloud droplet effective radius (re) over the region surrounding Iceland was at the lowest value in the 14 year Moderate Imaging Spectroradiometer data record during September and October 2014. The change in reflected solar radiation due to increased cloud reflectivity during September and October is estimated to exceed 2 W m-2 over the region surrounding Iceland, with increases of 1 W m-2 extending as far south as the Açores. The strength of the aerosol indirect effect diagnosed here reaffirms the ability of volcanic aerosols to affect cloud properties and ultimately the planetary albedo. © 2015. American Geophysical Union. All Rights Reserved."
"56311982900;9249255400;6506534909;35318562800;9942999600;7005920767;","Long-term trend analysis and climatology of tropical cirrus clouds using 16 years of lidar data set over Southern India",2015,"10.5194/acp-15-13833-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84951776757&doi=10.5194%2facp-15-13833-2015&partnerID=40&md5=74211e441ba4c9ab5f6e25c2dbb23c62","Sixteen-year (1998-2013) climatology of cirrus clouds and their macrophysical (base height, top height and geometrical thickness) and optical properties (cloud optical thickness) observed using a ground-based lidar over Gadanki (13.5° N, 79.2° E), India, is presented. The climatology obtained from the ground-based lidar is compared with the climatology obtained from 7 and a half years (June 2006-December 2013) of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations. A very good agreement is found between the two climatologies in spite of their opposite viewing geometries and the differences in sampling frequencies. Nearly 50-55 % of cirrus clouds were found to possess geometrical thickness less than 2 km. Ground-based lidar is found to detect a higher number of sub-visible clouds than CALIOP which has implications for global warming studies as sub-visible cirrus clouds have significant positive radiative forcing. Cirrus clouds with mid-cloud temperatures between -50 to -70 °C have a mean geometrical thickness greater than 2 km in contrast to the earlier reported value of 1.7 km. Trend analyses reveal a statistically significant increase in the altitude of sub-visible cirrus clouds which is consistent with the recent climate model simulations. The mid-cloud altitude of sub-visible cirrus clouds is found to be increasing at the rate of 41 ± 21 m year-1. Statistically significant decrease in optical thickness of sub-visible and thick cirrus clouds is observed. Also, the fraction of sub-visible cirrus cloud is found to have increased by 9 % in the last 16 years (1998 to 2013). This increase is mainly compensated by a 7 % decrease in thin cirrus cloud fraction. This has implications for the temperature and water vapour budget in the tropical tropopause layer. © Author(s) 2015."
"7410070663;25941200000;7403931916;48661551300;","On the aerosol and cloud phase function expansion moments for radiative transfer simulations",2015,"10.1002/2015JD023632","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958768017&doi=10.1002%2f2015JD023632&partnerID=40&md5=e64a79b3bc64522ebd46763b3a4cdef1","The accuracy of the Henyey-Greenstein (HG) approximation in radiative transfer process is systematically investigated for aerosol and cloud particles. For small-size aerosols, the phase function moment by the HG approximation is close to that of the true phase function; therefore, the differences in four-stream radiative transfer calculations are very small whether using the HG approximation or the true phase function moments. However, for large-size aerosols, liquid cloud droplets and ice crystals, the HG approximation produces very different phase function moment result compared to the true phase function. In case of small optical depth, the single layer four-stream radiative transfer calculations show that the HG approximation can produce relative errors larger than 20% while the errors are generally less than 5% by using true phase function moments. By applying the four-stream radiative transfer scheme to a multilayer atmosphere with aerosol and cloud, the differences in flux error are generally less than 2 Wm−2 by using either the HG approximation or true phase function moments, but can be over 10 Wm−2 for ice cloud case. The aerosol/cloud instantaneous radiative forcing has been analyzed in climate simulation. Compared to the four-stream radiative transfer scheme, the two-stream radiative transfer scheme overestimates the aerosol radiative flux in low-latitude regions and underestimates the upward flux for the high-latitude regions. By using the HG approximation, the difference in aerosol radiative forcing between the four-stream and the two-stream radiative transfer schemes is enhanced; the enhancement can be up to 0.5 Wm−2. The parameterization schemes for aerosol and cloud optical properties must be extended to contain higher-order phase function moments, if higher-order stream radiative transfer algorithms are to be used. © 2015. American Geophysical Union. All rights reserved."
"9844993400;6507863211;23567914700;9841756200;7401837283;7004741583;22946301100;35424750900;9233141200;56122795500;6603023560;6602859414;13609746100;7003386805;56015123400;","Evaluating a new homogeneous total ozone climate data record from GOME/ERS-2, SCIAMACHY/envisat, and GOME-2/MetOp-a",2015,"10.1002/2015JD023699","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948822769&doi=10.1002%2f2015JD023699&partnerID=40&md5=5da6a2cb99ef7d0ce17f7f5902d598ac","The European Space Agency’s Ozone Climate Change Initiative (O3-CCI) project aims at producing and validating a number of high-quality ozone data products generated from different satellite sensors. For total ozone, the O3-CCI approach consists of minimizing sources of bias and systematic uncertainties by applying a common retrieval algorithmto all level 1 data sets, in order to enhance the consistency between the level 2 data sets from individual sensors. Here we present the evaluation of the total ozone products from the European sensors Global Ozone Monitoring Experiment (GOME)/ERS-2, SCIAMACHY/Envisat, and GOME-2/MetOp-A produced with the GOME-type Direct FITting (GODFIT) algorithm v3. Measurements from the three sensors span more than 16 years, from 1996 to 2012. In this work, we present the latest O3-CCI total ozone validation results using as reference ground-based measurements from Brewer and Dobson spectrophotometers archived at the World Ozone and UV Data Centre of the World Meteorological Organization as well as from UV-visible differential optical absorption spectroscopy (DOAS)/Système D’Analyse par Observations Zénithales (SAOZ) instruments from the Network for the Detection of Atmospheric Composition Change. In particular, we investigate possible dependencies in these newGODFIT v3 total ozone data sets with respect to latitude, season, solar zenith angle, and different cloud parameters, using the most adequate type of ground-based instrument. We show that these three O3-CCI total ozone data products behave very similarly and are less sensitive to instrumental degradation, mainly as a result of the new reflectance soft-calibration scheme. The mean bias to the ground-based observations is found to be within the 1 ± 1% level for all three sensors while the near-zero decadal stability of the total ozone columns (TOCs) provided by the three European instruments falls well within the 1-3% requirement of the European Space Agency’s Ozone Climate Change Initiative project. © 2015. American Geophysical Union. All rights reserved."
"56612517400;36538539800;55893823700;7004347243;7102976560;55462884000;35285676700;6507575165;","CESM/CAM5 improvement and application: Comparison and evaluation of updated CB05-GE and MOZART-4 gas-phase mechanisms and associated impacts on global air quality and climate",2015,"10.5194/gmd-8-3999-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977615957&doi=10.5194%2fgmd-8-3999-2015&partnerID=40&md5=05c56ba2aeea67eab7afe914a992025f","Atmospheric chemistry plays a key role in determining the amounts and distributions of oxidants and gaseous precursors that control the formation of secondary gaseous and aerosol pollutants; all of those species can interact with the climate system. To understand the impacts of different gas-phase mechanisms on global air quality and climate predictions, in this work, a comprehensive comparative evaluation is performed using the Community Atmosphere Model (CAM) Version 5 with comprehensive tropospheric and stratospheric chemistry (CAM5-chem) within the Community Earth System Model (CESM) with the two most commonly used gas-phase chemical mechanisms: the 2005 Carbon Bond mechanism with Global Extension (CB05-GE) and the Model of OZone and Related chemical Tracers version 4 (MOZART-4) mechanism with additional updates (MOZART-4x). MOZART-4x and CB05-GE use different approaches to represent volatile organic compounds (VOCs) and different surrogates for secondary organic aerosol (SOA) precursors. MOZART-4x includes a more detailed representation of isoprene chemistry compared to CB05-GE. CB05-GE includes additional oxidation of SO2 by O3 over the surface of dust particles, which is not included in MOZART-4x. The results show that the two CAM5-chem simulations with CB05-GE and MOZART-4x predict similar chemical profiles for major gases (e.g., O3, CO, and NOx ) compared to the aircraft measurements, with generally better agreement for NOy profiles by CB05-GE than MOZART-4x. The concentrations of SOA at four sites in the continental US (CONUS) and organic carbon (OC) over the IMPROVE sites are well predicted by MOZART-4x (with normalized mean biases (NMBs) of -1.9 and 2.1 %, respectively) but moderately underpredicted by CB05-GE (with NMBs of -23.1 and -20.7 %, respectively). This is mainly due to the higher biogenic emissions and OH levels simulated with MOZART-4x than with CB05-GE. The concentrations of OC over Europe are largely underpredicted by both MOZART-4x and CB05-GE, with NMBs of -73.0 and -75.1 %, respectively, indicating the uncertainties in the emissions of precursors and primary OC and relevant model treatments such as the oxidations of VOCs and SOA formation. Uncertainties in the emissions and convection scheme can contribute to the large bias in the model predictions (e.g., SO2, CO, black carbon, and aerosol optical depth). The two simulations also have similar cloud/radiative predictions, with a slightly better performance of domain average cloud condensation nuclei (CCN) at supersaturation of 0.5% by CB05-GE, but slightly better agreement with observed CCN (at supersaturation of 0.2 %) profile over Beijing by MOZART-4x. The two gas-phase mechanisms result in a global average difference of 0.5Wm-2 in simulated shortwave cloud radiative forcing, with significant differences (e.g., up to 13.6Wm-2) over subtropical regions. © Author(s) 2015."
"36623061000;6603135449;55683038000;8152536600;6602136905;35221661700;26643041500;35461255500;57200562779;15047358600;7006593624;7006182491;","Reevaluating the contribution of sulfuric acid and the origin of organic compounds in atmospheric nanoparticle growth",2015,"10.1002/2015GL066459","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953637487&doi=10.1002%2f2015GL066459&partnerID=40&md5=423a1cef407ff0e25e01e189dad62ad0","Aerosol particles formed in the atmosphere are important to the Earth's climate system due to their ability to affect cloud properties. At present, little is known about the atmospheric chemistry responsible for the growth of newly formed aerosol particles to climate-relevant sizes. Here combining detailed aerosol measurements with a theoretical framework we found that depending on the gaseous precursors and size of the newly formed particles, the growth was dominated by either sulfuric acid accompanied by ammonium or organic compounds originating in either biogenic emissions or savannah fires. The contribution of sulfuric acid was larger during the early phases of the growth, but in clean conditions organic compounds dominated the growth from 1.5 nm up to climatically relevant sizes. Furthermore, our analysis indicates that in polluted environments the contribution of sulfuric acid to the growth may have been underestimated by up to a factor of 10. © 2015. American Geophysical Union. All Rights Reserved."
"26423853600;36866503400;","On the enigmatic similarity in Greenland δ18O between the Oldest and Younger Dryas",2015,"10.1002/2015GL066042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953639253&doi=10.1002%2f2015GL066042&partnerID=40&md5=11cde9c06b8c0c80a776bb832270acee","The last deglaciation (20.0-10.0 kyr B.P.) was punctuated by two major cooling events affecting the Northern Hemisphere: the Oldest Dryas (OD; 18.0-14.7 kyr B.P.) and the Younger Dryas (YD; 12.8-11.5 kyr B.P.). Greenland ice core δ18O temperature reconstructions suggest that the YD was as cold as the OD, despite a 50 ppmv increase in atmospheric CO2, while modeling studies suggest that the YD was approximately 4-5°C warmer than the OD. This discrepancy has been surmised to result from changes in the origin of the water vapor delivered to Greenland; however, this hypothesis has not been hitherto tested. Here we use an atmospheric circulation model with an embedded moisture-tracing module to investigate atmospheric processes that may have been responsible for the similar δ18O values during the OD and YD. Our results show that the summer-to-winter precipitation ratio over central Greenland in the OD is twice as high as in the YD experiment, which shifts the δ18O signal toward warmer (summer) temperatures (enriched δ18O values and it accounts for ∼45% of the expected YD-OD δ18O difference). A change in the inversion (cloud) temperature relationship between the two climate states further contributes (∼20%) to altering the δ18O-temperature-relation model. Our experiments also show a 7% decrease of δ18O-depleted precipitation from distant regions (e.g., the Pacific Ocean) in the OD, hence further contributing (15-20%) in masking the actual temperature difference. All together, these changes provide a physical explanation for the ostensible similarity in the ice core δ18O temperature reconstructions in Greenland during OD and YD. © 2015. American Geophysical Union. All Rights Reserved."
"35206636900;55087038900;","CALIPSO-inferred aerosol direct radiative effects: Bias estimates using ground-based raman lidars",2015,"10.1002/2015JD024095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958755126&doi=10.1002%2f2015JD024095&partnerID=40&md5=720bae47e56b59623d019b1969699130","Observational constraints on the change in the radiative energy budget caused by the presence of aerosols, i.e., the aerosol direct radiative effect (DRE), have recently been made using observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO). CALIPSO observations have the potential to provide improved global estimates of aerosol DRE compared to passive sensor-derived estimates due to CALIPSO’s ability to perform vertically resolved aerosol retrievals over all surface types and over cloud. In this study, uncertainties in CALIPSO-inferred aerosol DRE are estimated using multiple years of observations from the Atmospheric Radiation Measurement (ARM) program’s Raman lidars at midlatitude and tropical sites. We find that CALIPSO is unable to detect all radiatively significant aerosol, resulting in an underestimate in the magnitude of the aerosol DRE by 30–50% at the two ARM sites. The undetected aerosol is likely the consequence of random noise in CALIPSO measurements and therefore will affect global observations as well. This suggests that the global aerosol DRE inferred from CALIPSO observations are likely too weak. Also examined is the impact of the ratio of extinction-to-backscatter (i.e., the lidar ratio) whose value CALIPSO retrievals must assume to obtain the aerosol extinction profile. It is shown that if CALIPSO can reproduce the climatological value of the lidar ratio at a given location, then the aerosol DRE there can be accurately calculated (within about 3%). © 2015. American Geophysical Union. All rights reserved."
"56372089100;9738329300;7102314226;","A global electric circuitmodel within a community climate model",2015,"10.1002/2015JD023562","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956669081&doi=10.1002%2f2015JD023562&partnerID=40&md5=ba741b1da1479040000f5831d2f67119","To determine the complex dependencies of currents and electric fields within the Global Electric Circuit (GEC) on the underlying physics of the atmosphere, a new modeling framework of the GEC has been developed for use within global circulation models. Specifically, the Community Earth System Modeling framework has been utilized. A formulation of atmospheric conductivity based on ion production and loss mechanisms (including galactic cosmic rays, radon, clouds, and aerosols), conduction current sources, and ionospheric potential changes due to the influence of external current systems are included. This paper presents a full description of the calculation of the electric fields and currents within the model, which now includes several advancements to GEC modeling as it incorporates many processes calculated individually in previous articles into a consistent modeling framework. This framework uniquely incorporates effects from the troposphere up to the ionosphere within a single GEC model. The incorporation of a magnetospheric potential, which is generated by a separate magnetospheric current system, acts to modulate or enhance the surface level electric fields at high-latitude locations. This produces a distinct phasing signature with the GEC potential that is shown to depend on the observation location around the globe. Lastly, the model output for Vostok and Concordia, two high-latitude locations, is shown to agree with the observational data obtained at these sites over the same time period. © 2015. American Geophysical Union. All rights reserved."
"7801340314;7201520140;8559604100;","Transition into a Hothouse World at the Permian-Triassic boundary-A model study",2015,"10.1016/j.palaeo.2015.09.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943327743&doi=10.1016%2fj.palaeo.2015.09.008&partnerID=40&md5=074224dcb642ac8e9ce9c9cc99796787","The Permian-Triassic boundary (PTB, ~252.3Ma) marks the largest mass extinction of the Phanerozoic, with a loss of more than 90% of marine organisms, and is characterized by lethally hot surface temperatures. The PTB global warming has been linked to greenhouse gas emissions from the Siberian Traps and associated coal-bed intrusions and likely led to severe environmental consequences, such as ocean acidification, a decline in the marine productivity, and extensive hypoxia. In order to understand these changes, feedbacks in the climate system have been explored with sensitivity climate simulations and compared to temperature proxies from the sedimentary record. The response of the PTB ocean circulation to an atmospheric perturbation of ~5000PgC, comparable to Earth's total fossil fuel inventory, leads to a global temperature increase by 3-4°C and an increase in ocean stratification. The pole-to-equator temperature gradient decreases by 2°C with an increase in CO2-radiative forcing, predominately due to snow albedo feedbacks over Gondwana. The greenhouse-induced warming would have led to a weakening of the Hadley cell and an associated decrease in the trade winds and equatorial primary productivity. These climatic changes might have been amplified by cloud-feedback processes. A reduced concentration of cloud condensation nuclei due to a biologic decline of dimethylsulfide caused by the temperature stress or changes in airborne mineral particles could have reduced the cloud albedo, particularly in high latitudes. Results from a climate simulation with reduced cloud albedo suggest a polar warming of up to 7°C and a reduction of the pole-to-equator temperature gradient by ~4°C in addition to the reduction caused by the increase in greenhouse-induced radiative forcing. The scenario with reduced cloud albedo further leads to an increase in ocean stratification and widespread low-oxygen concentrations in the Panthalassa during the Early Triassic. © 2015 Elsevier B.V."
"55486290300;55682953900;13403510100;9235235300;7102862273;","Size-resolved cloud condensation nuclei concentration measurements in the Arctic: Two case studies from the summer of 2008",2015,"10.5194/acp-15-13803-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84951855070&doi=10.5194%2facp-15-13803-2015&partnerID=40&md5=2148f6a7d3d5bdfb4bcc4297627debc3","The Arctic is one of the most vulnerable regions affected by climate change. Extensive measurement data are needed to understand the atmospheric processes governing this vulnerability. Among these, data describing cloud formation potential are of particular interest, since the indirect effect of aerosols on the climate system is still poorly understood. In this paper we present, for the first time, size-resolved cloud condensation nuclei (CCN) data obtained in the Arctic. The measurements were conducted during two periods in the summer of 2008: one in June and one in August, at the Zeppelin research station (78°54′ N, 11°53′ E) in Svalbard. Trajectory analysis indicates that during the measurement period in June 2008, air masses predominantly originated from the Arctic, whereas the measurements from August 2008 were influenced by mid-latitude air masses. CCN supersaturation (SS) spectra obtained on the 27 June, before size-resolved measurements were begun, and spectra from the 21 and 24 August, conducted before and after the measurement period, revealed similarities between the 2 months. From the ratio between CCN concentration and the total particle number concentration (CN) as a function of dry particle diameter (Dp) at a SS of 0.4 %, the activation diameter (D50), corresponding to CCN / CN Combining double low line 0.50, was estimated. D50 was found to be 60 and 67 nm for the examined periods in June and August 2008, respectively. Corresponding D50 hygroscopicity parameter (κ) values were estimated to be 0.4 and 0.3 for June and August 2008, respectively. These values can be compared to hygroscopicity values estimated from bulk chemical composition, where κ was calculated to be 0.5 for both June and August 2008. While the agreement between the 2 months is reasonable, the difference in κ between the different methods indicates a size dependence in the particle composition, which is likely explained by a higher fraction of inorganics in the bulk aerosol samples. © Author(s) 2015."
"57002436500;8318179400;7006338905;7003542135;9240820800;","Evaluation of VIIRS land surface temperature using crest-safe air, snow surface, and soil temperature data",2015,"10.3390/geosciences5040334","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949811141&doi=10.3390%2fgeosciences5040334&partnerID=40&md5=b4d2ca1fab3e552c3768a4c537953ab3","In this study, the Visible Infrared Imager Radiometer Suite (VIIRS) Land Surface Temperature (LST) Environmental Data Record (EDR) was evaluated against snow surface (T-skin) and near-surface air temperature (T-air) ground observations recorded at the Cooperative Remote Sensing Science and Technology Center—Snow Analysis and Field Experiment (CREST-SAFE), located in Caribou, ME, USA during the winters of 2013 and 2014. The satellite LST corroboration of snow-covered areas is imperative because high-latitude regions are often physically inaccessible and there is a need to complement the data from the existing meteorological station networks. T-skin is not a standard meteorological parameter commonly observed at synoptic stations. Common practice is to measure surface infrared emission from the land surface at research stations across the world that allow for estimating ground-observed LST. Accurate T-skin observations are critical for estimating latent and sensible heat fluxes over snow-covered areas because the incoming and outgoing radiation fluxes from the snow mass and T-air make the snow surface temperature different from the average snowpack temperature. Precise characterization of the LST using satellite observations is an important issue because several climate and hydrological models use T-skin as input. Results indicate that T-air correlates better than T-skin with VIIRS LST data and that the accuracy of nighttime LST retrievals is considerably better than that of daytime. Based on these results, empirical relationships to estimate T-air and T-skin for clear-sky conditions from remotely-sensed (RS) LST were derived. Additionally, an empirical formula to correct cloud-contaminated RS LST was developed. © 2015 by the authors; licensee MDPI, Basel, Switzerland."
"35231763100;27468024100;56986683500;","Development of a global ~90m water body map using multi-temporal Landsat images",2015,"10.1016/j.rse.2015.10.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948767939&doi=10.1016%2fj.rse.2015.10.014&partnerID=40&md5=8362ce6e9cb764570b42af131a7651ab","This paper describes the development of a Global 3arc-second Water Body Map (G3WBM), using an automated algorithm to process multi-temporal Landsat images from the Global Land Survey (GLS) database. We used 33,890 scenes from 4 GLS epochs in order to delineate a seamless water body map, without cloud and ice/snow gaps. Permanent water bodies were distinguished from temporal water-covered areas by calculating the frequency of water body existence from overlapping, multi-temporal, Landsat scenes. By analyzing the frequency of water body existence at 3arc-second resolution, the G3WBM separates river channels and floodplains more clearly than previous studies. This suggests that the use of multi-temporal images is as important as analysis at a higher resolution for global water body mapping. The global totals of delineated permanent water body area and temporal water-covered area are 3.25 and 0.49millionkm2 respectively, which highlights the importance of river-floodplain separation using multi-temporal images. The accuracy of the water body classification was validated in Hokkaido (Japan) and in the contiguous United States using an existing water body databases. There was almost no commission error, and about 70% of lakes >1km2 shows relative water area error <25%. Though smaller water bodies (<1km2) were underestimated mainly due to omission of shoreline pixels, the overall accuracy of the G3WBM should be adequate for larger scale research in hydrology, biogeochemistry, and climate systems and importantly includes a quantification of the temporal nature of global water bodies. © 2015 Elsevier Inc.."
"57008785800;9846154100;56370907100;54402121000;57206535282;8336962200;7004296083;54410864500;7006595513;35461255500;8871497700;55950593000;","Variability of air ion concentrations in urban Paris",2015,"10.5194/acp-15-13717-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941721559&doi=10.5194%2facp-15-13717-2015&partnerID=40&md5=1ba8a8203110d848c500e90d6d3882c2","Air ion concentrations influence new particle formation and consequently the global aerosol as potential cloud condensation nuclei. We aimed to evaluate air ion concentrations and characteristics of new particle formation events (NPF) in the megacity of Paris, France, within the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric Pollution and climate effects, and Integrated tools for assessment and mitigation) project. We measured air ion number size distributions (0.8-42 nm) with an air ion spectrometer and fine particle number concentrations (> 6 nm) with a twin differential mobility particle sizer in an urban site of Paris between 26 June 2009 and 4 October 2010. Air ions were size classified as small (0.8-2 nm), intermediate (2-7 nm), and large (7-20 nm). The median concentrations of small and large ions were 670 and 680 cm-3, respectively, (sum of positive and negative polarities), whereas the median concentration of intermediate ions was only 20 cm-3, as these ions were mostly present during new particle formation bursts, i.e. when gas-to-particle conversion produced fresh aerosol particles from gas phase precursors. During peaks in traffic-related particle number, the concentrations of small and intermediate ions decreased, whereas the concentrations of large ions increased. Seasonal variations affected the ion population differently, with respect to their size and polarity. NPF was observed in 13 % of the days, being most frequent in spring and late summer (April, May, July, and August). The results also suggest that NPF was favoured on the weekends in comparison to workdays, likely due to the lower levels of condensation sinks in the mornings of weekends (CS weekdays 09:00: 18 × 10-3 s-1; CS weekend 09:00: 8 × 10-3 s-1). The median growth rates (GR) of ions during the NPF events varied between 3 and 7 nm h-1, increasing with the ion size and being higher on workdays than on weekends for intermediate and large ions. The median GR of small ions on the other hand were rather similar on workdays and weekends. In general, NPF bursts changed the diurnal cycle of particle number as well as intermediate and large ions by causing an extra peak between 09:00 and 14:00. On average, during the NPF bursts the concentrations of intermediate ions were 8.5-10 times higher than on NPF non-event days, depending on the polarity, and the concentrations of large ions and particles were 1.5-1.8 and 1.2 times higher, respectively. Because the median concentrations of intermediate ions were considerably higher on NPF event days in comparison to NPF non-event days, the results indicate that intermediate ion concentrations could be used as an indication for NPF in Paris. The results suggest that NPF was a source of ions and aerosol particles in Paris and therefore contributed to both air quality degradation and climatic effects, especially in the spring and summer. © 2015 Author(s)."
"55574195332;24463419100;56652533400;8524470300;6701864422;","Warm summer nights and the growth decline of shore pine in Southeast Alaska",2015,"10.1088/1748-9326/10/12/124007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84952950557&doi=10.1088%2f1748-9326%2f10%2f12%2f124007&partnerID=40&md5=ca90f63b1c25a4b61c9540dda9ae458b","Shore pine, which is a subspecies of lodgepole pine, was a widespread and dominant tree species in Southeast Alaska during the early Holocene. At present, the distribution of shore pine in Alaska is restricted to coastal bogs and fens, likely by competition with Sitka spruce and Western hemlock. Monitoring of permanent plots as part of the United States Forest Service Forest Inventory and Analysis program identified a recent loss of shore pine biomass in Southeast Alaska. The apparent loss of shore pine is concerning, because its presence adds a vertical dimension to coastal wetlands, which are the richest plant communities of the coastal temperate rainforest in Alaska. In this study, we examined the shore pine tree-ring record from a newly established plot network throughout Southeast Alaska and explored climate-growth relationships. We found a steep decline in shore pine growth from the early 1960s to the present. Random Forest regression revealed a strong correlation between the decline in shore pine growth and the rise in growing season diurnal minimum air temperature. Warm summer nights, cool daytime temperatures and a reduced diurnal temperature range are associated with greater cloud cover in Southeast Alaska. This suite of conditions could lead to unfavorable tree carbon budgets (reduced daytime photosynthesis and greater nighttime respiration) and/or favor infection by foliar pathogens, such as Dothistroma needle blight, which has recently caused widespread tree mortality on lodgepole pine plantations in British Columbia. Further field study that includes experimental manipulation (e.g., fungicide application) will be necessary to identify the proximal cause(s) of the growth decline. In the meantime, we anticipate continuation of the shore pine growth decline in Southeast Alaska. © 2015 IOP Publishing Ltd."
"57205067933;56803964400;8722794800;","Evaluation of soil moisture downscaling using a simple thermal-based proxy-the REMEDHUS network (Spain) example",2015,"10.5194/hess-19-4765-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949257775&doi=10.5194%2fhess-19-4765-2015&partnerID=40&md5=2a10d1dc13c62d7a04534046db807b37","Soil moisture retrieved from satellite microwave remote sensing normally has spatial resolution on the order of tens of kilometers, which are too coarse for many regional hydrological applications such as agriculture monitoring and drought prediction. Therefore, various downscaling methods have been proposed to enhance the spatial resolution of satellite soil moisture products. The aim of this study is to investigate the validity and robustness of the simple vegetation temperature condition index (VTCI) downscaling scheme over a dense soil moisture observational network (REMEDHUS) in Spain. First, the optimized VTCI was determined through sensitivity analyses of VTCI to surface temperature, vegetation index, cloud, topography, and land cover heterogeneity, using data from Moderate Resolution Imaging Spectroradiometer∼(MODIS) and MSG SEVIRI (METEOSAT Second Generation-Spinning Enhanced Visible and Infrared Imager). Then the downscaling scheme was applied to improve the spatial resolution of the European Space Agency's Water Cycle Multi-mission Observation Strategy and Climate Change Initiative (ESA CCI) soil moisture, which is a merged product based on both active and passive microwave observations. The results from direct validation against soil moisture observations, spatial pattern comparison, as well as seasonal and land use analyses show that the downscaling method can significantly improve the spatial details of CCI soil moisture while maintaining the accuracy of CCI soil moisture. The accuracy level is comparable to other downscaling methods that were also validated against the REMEDHUS network. Furthermore, slightly better performance of MSG SEVIRI over MODIS was observed, which suggests the high potential of applying a geostationary satellite for downscaling soil moisture in the future. Overall, considering the simplicity, limited data requirements and comparable accuracy level to other complex methods, the VTCI downscaling method can facilitate relevant hydrological applications that require high spatial and temporal resolution soil moisture. © 2015 Author(s)."
"56974414100;7005262634;7402846040;","A refined mapping of Arctic lakes using Landsat imagery",2015,"10.1080/01431161.2015.1110263","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947998426&doi=10.1080%2f01431161.2015.1110263&partnerID=40&md5=4e8c6c6c825351ee447fefc52a869b40","Effective mapping of water bodies at regional scales is a challenge with respect to the description and monitoring of hydrological, climatic, and landscape processes. In a region as sensitive to climate change as the Arctic, inaccurate representation of lake cover has probably led to underestimation of the role of lakes as landscape constituents and thus of their contribution to biochemical cycles. To estimate lake cover reliably (and perhaps also its change through time), the scientific community necessitates techniques for mapping water bodies using satellite sensors that include rich historical data sets and have sufficiently fine spatial resolution. Here we applied a density-slicing detection technique to 617 cloud-free Landsat images for the summer months 2006–2011. We developed a comprehensive database of Arctic lakes with a detection accuracy of 80% and examined spatial patterns of lake distribution in relation to landscape properties. We mapped about 3,500,000 lakes; these cover nearly 6% of the Arctic land surface (about 400,000 km2) and are typically small (<0.1 km2). Lake density and lake fraction analyses show that lakes are most common in lowland permafrost areas with tundra vegetation. The method described here can also be used to map and monitor lake cover at regional to hemispheric scales and to monitor changes in lake cover over time. © 2015 Taylor & Francis."
"57203288317;7004479957;23991212200;","Mean-state acceleration of cloud-resolving models and large eddy simulations",2015,"10.1002/2015MS000488","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959508800&doi=10.1002%2f2015MS000488&partnerID=40&md5=6cbe3d78fa6a50482226a94878fa3ec0","Large eddy simulations and cloud-resolving models (CRMs) are routinely used to simulate boundary layer and deep convective cloud processes, aid in the development of moist physical parameterization for global models, study cloud-climate feedbacks and cloud-aerosol interaction, and as the heart of superparameterized climate models. These models are computationally demanding, placing practical constraints on their use in these applications, especially for long, climate-relevant simulations. In many situations, the horizontal-mean atmospheric structure evolves slowly compared to the turnover time of the most energetic turbulent eddies. We develop a simple scheme to reduce this time scale separation to accelerate the evolution of the mean state. Using this approach we are able to accelerate the model evolution by a factor of 2-16 or more in idealized stratocumulus, shallow and deep cumulus convection without substantial loss of accuracy in simulating mean cloud statistics and their sensitivity to climate change perturbations. As a culminating test, we apply this technique to accelerate the embedded CRMs in the Superparameterized Community Atmosphere Model by a factor of 2, thereby showing that the method is robust and stable to realistic perturbations across spatial and temporal scales typical in a GCM. © 2015. The Authors."
"57033686900;7202145115;","On the influence of poleward jet shift on shortwave cloud feedback in global climate models",2015,"10.1002/2015MS000520","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959563799&doi=10.1002%2f2015MS000520&partnerID=40&md5=e47fa124f7dcfb637edef3940788bacd","Experiments designed to separate the effect of atmospheric warming from the effect of shifts of the eddy-driven jet on shortwave (SW) cloud feedback are performed with three global climate models (GCMs). In each model a warming simulation produces a robust SW cloud feedback dipole, with a negative (positive) feedback in the high-latitudes (subtropics). The cloud brightening in high-latitudes that characterizes warming simulations is not produced by jet shifts alone in any of the models, but is highly sensitive to perturbations of freezing temperature seen by the cloud microphysics scheme, indicating that thermodynamic mechanisms involving the phase of cloud condensate dominate the SW feedback at high-latitudes. In one of the models a poleward jet shift causes significant cloud dimming throughout the midlatitudes, but in two models it does not. Differences in cloud response to jet shifts in two of the models are attributed to differences in the shallow convection parameterizations. © 2015. The Authors."
"35768521600;25031430500;7102239370;57002623400;6506848305;57200319057;7103158465;56479186900;56479176700;23392868000;56477918600;7005920812;6602878057;56162305900;55913183200;7003666669;","A unified parameterization of clouds and turbulence using CLUBB and subcolumns in the Community Atmosphere Model",2015,"10.5194/gmd-8-3801-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949794819&doi=10.5194%2fgmd-8-3801-2015&partnerID=40&md5=4c685697554b385f0c36729ec72be081","Most global climate models parameterize separate cloud types using separate parameterizations. This approach has several disadvantages, including obscure interactions between parameterizations and inaccurate triggering of cumulus parameterizations. <br><br> Alternatively, a unified cloud parameterization uses one equation set to represent all cloud types. Such cloud types include stratiform liquid and ice cloud, shallow convective cloud, and deep convective cloud. Vital to the success of a unified parameterization is a general interface between clouds and microphysics. One such interface involves drawing Monte Carlo samples of subgrid variability of temperature, water vapor, cloud liquid, and cloud ice, and feeding the sample points into a microphysics scheme. <br><br> This study evaluates a unified cloud parameterization and a Monte Carlo microphysics interface that has been implemented in the Community Atmosphere Model (CAM) version 5.3. Model computational expense is estimated, and sensitivity to the number of subcolumns is investigated. Results describing the mean climate and tropical variability from global simulations are presented. The new model shows a degradation in precipitation skill but improvements in shortwave cloud forcing, liquid water path, long-wave cloud forcing, precipitable water, and tropical wave simulation. © Author(s) 2015."
"6602364115;","Attributing the behavior of low-level clouds in large-scale models to subgrid-scale parameterizations",2015,"10.1002/2015MS000503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959545996&doi=10.1002%2f2015MS000503&partnerID=40&md5=ac18563cf88f13037d42aac264d6143f","This study explores ways of establishing the characteristic behavior of boundary layer schemes in representing subtropical marine low-level clouds in climate models. To this purpose, parameterization schemes are studied in both isolated and interactive mode with the larger-scale circulation. Results of the EUCLIPSE/GASS intercomparison study for Single-Column Models (SCM) on low-level cloud transitions are compared to General Circulation Model (GCM) results from the CFMIP-2 project at selected grid points in the subtropical eastern Pacific. Low cloud characteristics are plotted as a function of key state variables for which Large-Eddy Simulation results suggest a distinct and reasonably tight relation. These include the Cloud Top Entrainment Instability (CTEI) parameter and the total cloud cover. SCM and GCM results are thus compared and their resemblance is quantified using simple metrics. Good agreement is reported, to such a degree that SCM results are found to be uniquely representative of their GCM, and vice versa. This suggests that the system of parameterized fast boundary layer physics dominates the model state at any given time, even when interactive with the larger-scale flow. This behavior can loosely be interpreted as a unique ""fingerprint"" of a boundary layer scheme, recognizable in both SCM and GCM simulations. The result justifies and advocates the use of SCM simulation for improving weather and climate models, including the attribution of typical responses of low clouds to climate change in a GCM to specific parameterizations. © 2015. The Authors."
"55714647400;26632168400;57206503877;","Evaluation of high-level clouds in cloud resolving model simulations with ARM and KWAJEX observations",2015,"10.1002/2015MS000478","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959563110&doi=10.1002%2f2015MS000478&partnerID=40&md5=a4b089c3c4242db2a057cd4ae4280c02","In this study, we evaluate high-level clouds in a cloud resolving model during two convective cases, ARM9707 and KWAJEX. The simulated joint histograms of cloud occurrence and radar reflectivity compare well with cloud radar and satellite observations when using a two-moment microphysics scheme. However, simulations performed with a single moment microphysical scheme exhibit low biases of approximately 20 dB. During convective events, two-moment microphysical overestimate the amount of high-level cloud and one-moment microphysics precipitate too readily and underestimate the amount and height of high-level cloud. For ARM9707, persistent large positive biases in high-level cloud are found, which are not sensitive to changes in ice particle fall velocity and ice nuclei number concentration in the two-moment microphysics. These biases are caused by biases in large-scale forcing and maintained by the periodic lateral boundary conditions. The combined effects include significant biases in high-level cloud amount, radiation, and high sensitivity of cloud amount to nudging time scale in both convective cases. The high sensitivity of high-level cloud amount to the thermodynamic nudging time scale suggests that thermodynamic nudging can be a powerful ""tuning"" parameter for the simulated cloud and radiation but should be applied with caution. The role of the periodic lateral boundary conditions in reinforcing the biases in cloud and radiation suggests that reducing the uncertainty in the large-scale forcing in high levels is important for similar convective cases and has far reaching implications for simulating high-level clouds in super-parameterized global climate models such as the multiscale modeling framework. © 2015 The Authors."
"57015826100;23991212200;","The effect of large-scale model time step and multiscale coupling frequency on cloud climatology, vertical structure, and rainfall extremes in a superparameterized GCM",2015,"10.1002/2015MS000493","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959536194&doi=10.1002%2f2015MS000493&partnerID=40&md5=d315f1dcaa4ecf6aea4d3ab402f7eed7","The effect of global climate model (GCM) time step-which also controls how frequently global and embedded cloud resolving scales are coupled-is examined in the Superparameterized Community Atmosphere Model ver 3.0. Systematic bias reductions of time-mean shortwave cloud forcing (-10 W/m2) and longwave cloud forcing (-5 W/m2) occur as scale coupling frequency increases, but with systematically increasing rainfall variance and extremes throughout the tropics. An overarching change in the vertical structure of deep tropical convection, favoring more bottom-heavy deep convection as a global model time step is reduced may help orchestrate these responses. The weak temperature gradient approximation is more faithfully satisfied when a high scale coupling frequency (a short global model time step) is used. These findings are distinct from the global model time step sensitivities of conventionally parameterized GCMs and have implications for understanding emergent behaviors of multiscale deep convective organization in superparameterized GCMs. The results may also be useful for helping to tune them. © 2015. The Authors."
"26647492000;7801642934;","A spatiotemporal stochastic model for tropical precipitation and water vapor dynamics",2015,"10.1175/JAS-D-15-0119.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950277497&doi=10.1175%2fJAS-D-15-0119.1&partnerID=40&md5=0404af320dfb048fef90aa0e500cebd8","A linear stochastic model is presented for the dynamics of water vapor and tropical convection. Despite its linear formulation, the model reproduces a wide variety of observational statistics from disparate perspectives, including (i) a cloud cluster area distribution with an approximate power law; (ii) a power spectrum of spatiotemporal red noise, as in the ""background spectrum"" of tropical convection; and (iii) a suite of statistics that resemble the statistical physics concepts of critical phenomena and phase transitions. The physical processes of the model are precipitation, evaporation, and turbulent advection-diffusion of water vapor, and they are represented in idealized form as eddy diffusion, damping, and stochastic forcing. Consequently, the form of the model is a damped version of the two-dimensional stochastic heat equation. Exact analytical solutions are available for many statistics, and numerical realizations can be generated for minimal computational cost and for any desired time step. Given the simple form of the model, the results suggest that tropical convection may behave in a relatively simple, random way. Finally, relationships are also drawn with the Ising model, the Edwards-Wilkinson model, the Gaussian free field, and the Schramm-Loewner evolution and its possible connection with cloud cluster statistics. Potential applications of the model include several situations where realistic cloud fields must be generated for minimal cost, such as cloud parameterizations for climate models or radiative transfer models. © 2015 American Meteorological Society."
"57022402900;7402989545;55701363700;","Quantifying contributions of model processes to the surface temperature bias in FGOALS-g2",2015,"10.1002/2015MS000459","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959463858&doi=10.1002%2f2015MS000459&partnerID=40&md5=fe1a5ab1d4d2452010a73387979d2fa5","To quantify the annual mean surface temperature bias due to various processes in Flexible Global Ocean-Atmosphere-Land-System model, Grid point version 2 (FGOALS-g2), the climate feedback-response analysis method (CFRAM) is used to isolate contributions from both radiative and nonradiative processes in the model by comparing the model simulation with ERA-Interim reanalysis. The observed surface temperature bias is decomposed into seven partial temperature biases associated with surface albedo, water vapor, cloud, both surface sensible and latent heat fluxes, land/ocean heat transport processes, and atmospheric transport processes. The global mean cold bias (-1.39 K) is mostly attributed to surface albedo and land/ocean heat transport processes while surface latent heat fluxes tend to weaken this bias. Cloud-induced bias is dominated by shortwave cloud radiative effect (SWCRE) over low-latitudes and longwave cloud radiative effect (LWCRE) over high latitudes. The mixed layer depth (MLD) bias is consistent with the bias due to ocean heat transport over North Pacific, North Atlantic, and the Southern Ocean. On global scale, contributions of radiative processes and nonradiative processes to the total observed cold bias are comparable, but tend to compensate each other over most regions except for the northern high latitudes. We suggest that the improvements in tropical clouds in the model may significantly decrease the global temperature bias through the interaction between clouds and circulation. © 2015. The Authors. Journal of Advances in Modeling Earth Systems published by Wiley Periodicals, Inc."
"23492864500;8866821900;23768540500;13006055400;","Observed and modeled patterns of covariability between low-level cloudiness and the structure of the trade-wind layer",2015,"10.1002/2015MS000483","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959546807&doi=10.1002%2f2015MS000483&partnerID=40&md5=d9685e9d91ca5ace5783cfc9e940ff03","We present patterns of covariability between low-level cloudiness and the trade-wind boundary layer structure using long-term measurements at a site representative of dynamical regimes with moderate subsidence or weak ascent. We compare these with ECMWF's Integrated Forecast System and 10 CMIP5 models. By using single-time step output at a single location, we find that models can produce a fairly realistic trade-wind layer structure in long-term means, but with unrealistic variability at shorter-time scales. The unrealistic variability in modeled cloudiness near the lifting condensation level (LCL) is due to stronger than observed relationships with mixed-layer relative humidity (RH) and temperature stratification at the mixed-layer top. Those relationships are weak in observations, or even of opposite sign, which can be explained by a negative feedback of convection on cloudiness. Cloudiness near cumulus tops at the trade-wind inversion instead varies more pronouncedly in observations on monthly time scales, whereby larger cloudiness relates to larger surface winds and stronger trade-wind inversions. However, these parameters appear to be a prerequisite, rather than strong controlling factors on cloudiness, because they do not explain submonthly variations in cloudiness. Models underestimate the strength of these relationships and diverge in particular in their responses to large-scale vertical motion. No model stands out by reproducing the observed behavior in all respects. These findings suggest that climate models do not realistically represent the physical processes that underlie the coupling between trade-wind clouds and their environments in present-day climate, which is relevant for how we interpret modeled cloud feedbacks. © 2015. The Authors."
"22635190100;7201496259;7402064802;36899513900;56986721000;7401936984;36183647300;15755995900;52464731300;56985140700;","An improved hindcast approach for evaluation and diagnosis of physical processes in global climate models",2015,"10.1002/2015MS000490","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959496097&doi=10.1002%2f2015MS000490&partnerID=40&md5=3dfc863542c3fa57a5784011ac9a4894","We present an improved procedure of generating initial conditions (ICs) for climate model hindcast experiments with specified sea surface temperature and sea ice. The motivation is to minimize errors in the ICs and lead to a better evaluation of atmospheric parameterization's performance in the hindcast mode. We apply state variables (horizontal velocities, temperature, and specific humidity) from the operational analysis/reanalysis for the atmospheric initial states. Without a data assimilation system, we apply a two-step process to obtain other necessary variables to initialize both the atmospheric (e.g., aerosols and clouds) and land models (e.g., soil moisture). First, we nudge only the model horizontal velocities toward operational analysis/reanalysis values, given a 6 h relaxation time scale, to obtain all necessary variables. Compared to the original strategy in which horizontal velocities, temperature, and specific humidity are nudged, the revised approach produces a better representation of initial aerosols and cloud fields which are more consistent and closer to observations and model's preferred climatology. Second, we obtain land ICs from an off-line land model simulation forced with observed precipitation, winds, and surface fluxes. This approach produces more realistic soil moisture in the land ICs. With this refined procedure, the simulated precipitation, clouds, radiation, and surface air temperature over land are improved in the Day 2 mean hindcasts. Following this procedure, we propose a ""Core"" integration suite which provides an easily repeatable test allowing model developers to rapidly assess the impacts of various parameterization changes on the fidelity of modeled cloud-associated processes relative to observations. © 2015. The Authors."
"52463601100;57188751935;56253852700;","An RCM multi-physics ensemble over Europe: multi-variable evaluation to avoid error compensation",2015,"10.1007/s00382-015-2529-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947496221&doi=10.1007%2fs00382-015-2529-x&partnerID=40&md5=5b6bd7f81d1e883986b45bb59309d271","Regional Climate Models are widely used tools to add detail to the coarse resolution of global simulations. However, these are known to be affected by biases. Usually, published model evaluations use a reduced number of variables, frequently precipitation and temperature. Due to the complexity of the models, this may not be enough to assess their physical realism (e.g. to enable a fair comparison when weighting ensemble members). Furthermore, looking at only a few variables makes difficult to trace model errors. Thus, in many previous studies, these biases are described but their underlying causes and mechanisms are often left unknown. In this work the ability of a multi-physics ensemble in reproducing the observed climatologies of many variables over Europe is analysed. These are temperature, precipitation, cloud cover, radiative fluxes and total soil moisture content. It is found that, during winter, the model suffers a significant cold bias over snow covered regions. This is shown to be related with a poor representation of the snow-atmosphere interaction, and is amplified by an albedo feedback. It is shown how two members of the ensemble are able to alleviate this bias, but by generating a too large cloud cover. During summer, a large sensitivity to the cumulus parameterization is found, related to large differences in the cloud cover and short wave radiation flux. Results also show that small errors in one variable are sometimes a result of error compensation, so the high dimensionality of the model evaluation problem cannot be disregarded. © 2015, Springer-Verlag Berlin Heidelberg."
"35175994700;56599268600;6602675795;","Customized rating assessment of climate suitability (CRACS): climate satisfaction evaluation based on subjective perception",2015,"10.1007/s00484-015-0990-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948568068&doi=10.1007%2fs00484-015-0990-1&partnerID=40&md5=00fa06295a421f4487dc9cbd7cc14c7b","Climate not only influences the behavior of people in urban environments but also affects people’s schedules and travel plans. Therefore, providing people with appropriate long-term climate evaluation information is crucial. Therefore, we developed an innovative climate assessment system based on field investigations conducted in three cities located in Northern, Central, and Southern Taiwan. The field investigations included the questionnaire surveys and climate data collection. We first analyzed the relationship between the participants and climate parameters comprising physiologically equivalent temperature, air temperature, humidity, wind speed, solar radiation, cloud cover, and precipitation. Second, we established the neutral value, comfort range, and dissatisfied range of each parameter. Third, after verifying that the subjects’ perception toward the climate parameters vary based on individual preferences, we developed the customized rating assessment of climate suitability (CRACS) approach, which featured functions such as personalized and default climate suitability information to be used by users exhibiting varying demands. Finally, we performed calculations using the climate conditions of two cities during the past 10 years to demonstrate the performance of the CRACS approach. The results can be used as a reference when planning activities in the city or when organizing future travel plans. The flexibility of the assessment system enables it to be adjusted for varying regions and usage characteristics. © 2015, ISB."
"35917252100;","On the mass-flux representation of vertical transport in moist convection",2015,"10.1175/JAS-D-14-0332.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950263629&doi=10.1175%2fJAS-D-14-0332.1&partnerID=40&md5=e0971d16e69888e25b01c6ed14e23fe5","This study investigates to what extent the convective fluxes formulated within the mass-flux framework can represent the total vertical transport of heat and moisture in the cloud layer and whether the same approach can be extended to represent the vertical momentum transport using large-eddy simulations (LESs) of six well-documented cloud cases, including both deep and shallow convection. Two methods are used to decompose the LES-resolved vertical fluxes: decompositions based on the coherent convective features using the mass-flux top-hat profile and by two-dimensional fast Fourier transform (2D-FFT) in terms of wavenumbers. The analyses show that the convective fluxes computed using the mass-flux formula can account for most of the total fluxes of conservative thermodynamic variables in the cloud layer of both deep and shallow convection for an appropriately defined convective updraft fraction, a result consistent with the mass-flux dynamic view of moist convection and previous studies. However, the mass-flux approach fails to represent the vertical momentum transport in the cloud layer of both deep and shallow convection. The 2D-FFT and other analyses suggest that such a failure results from a number of reasons: 1) the complicated momentum distribution in the cloud layer cannot be well described by the simple top-hat profile; 2) shear-driven small-scale eddies are more efficient momentum carriers than coherent convective plumes; 3) the phase relationship between vertical velocity and horizontal momentum components is substantially different from that between vertical velocity and conservative thermodynamic variables; and 4) the structure of horizontal momentum can change substantially from case to case even in the same climate regime. © 2015 American Meteorological Society."
"15050523700;15047538100;7404178566;36006968000;10045312900;6602135370;36242447900;","Impact of revised cloud microphysical scheme in CFSv2 on the simulation of the Indian summer monsoon",2015,"10.1002/joc.4320","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959537266&doi=10.1002%2fjoc.4320&partnerID=40&md5=ba776a02f641b5dd8f170f230320fd0b","Role of the cloud parameterization scheme and critical relative humidity (RHcrit) for large-scale precipitation is examined for simulating Indian summer monsoon (ISM) by the National Centers for Environmental Prediction (NCEP) climate forecast system version 2 (CFSv2). The major biases of the model simulations namely dry bias over the major continents, cold tropospheric temperature (TT) bias and cold sea surface temperature (SST) bias are related to biases in distribution of clouds. This study evaluates the role of variable RHcrit to get better simulation of high level clouds and reduce TT bias and cloud microphysical parameterization to improve the meridional gradient of TT towards achieving better simulation of south Asian monsoon precipitation. Sensitivity experiments of CFSv2 with the modified RHcrit and cloud microphysical scheme compared to the control simulation show that while the RHcrit leads to some development of the cloud distribution and contributes to some progress of the dry bias over India, the cloud microphysics changes lead to a significant improvement of the cloud simulations. Particularly, revised cloud microphysics scheme coupled with modified RHcrit results in a much improved global distribution of cloud fraction with zonal mean cloud fraction being close to observation. This leads to significant improvement in the meridional gradient of TT leading to rainfall over south Asian monsoon region. The dry bias is not only reduced over the Indian subcontinent but also over other regions of global tropics such as the central Africa and the northern South America. The annual cycle of all India rainfall is in good agreement with observation not only in amount but also in the onset and withdrawal phases. Thus, modifications in the cloud microphysical parameterization scheme in CFSv2 have played a vital role in simulation of the ISM in particular. The sensitivity experiments demonstrate the betterment of the mean monsoon and may lead to help improve monsoon forecasts. © 2015 Royal Meteorological Society."
"7004479957;6701346974;","Convective self-aggregation feedbacks in near-global cloud-resolving simulations of an aquaplanet",2015,"10.1002/2015MS000499","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959472519&doi=10.1002%2f2015MS000499&partnerID=40&md5=6026d1d194d6c8d368fb919a915127a4","Positive feedbacks between precipitable water, reduced radiative cooling and enhanced surface fluxes promote convective self-aggregation in limited-area cloud-resolving model (CRM) simulations over uniform sea-surface temperature (SST). Near-global aquaplanet simulations with 4 km horizontal grid spacing and no cumulus or boundary layer parameterization are used to test the importance of these feedbacks to realistically organized tropical convection. A 20,480 × 10,240 km equatorially centered channel with latitudinally varying SST is used. Realistic midlatitude and tropical cloud structures develop. The natural zonal variability of humidity and convection are studied in a 30 day control simulation. The temporal growth of a small white-noise humidity perturbation and intrinsic predictability implications are explored. Atmospheric column budgets of moist-static energy (MSE) quantify its covariation with precipitation, surface heat flux, and radiative energy loss. Zonal Fourier analysis partitions these budgets by length scale. Radiative feedbacks on MSE natural variability and perturbation growth are found to be positive, broadly similar across scales, and comparable to limited-area CRMs, capable of e-folding a column MSE perturbation in 6-14 days. Surface fluxes are highest in synoptic-scale dry intrusions, inhibiting aggregation by damping tropical MSE perturbations. Sub-4-day MSE variations are due mainly to advection. Both tropics and midlatitudes have large-scale intrinsic predictability horizons of 15-30 days. An identical simulation but with 20 km grid spacing has more mesoscale variability and low cloud. © 2015. The Authors."
"6602364115;","Exploring bin-macrophysics models for moist convective transport and clouds",2015,"10.1002/2015MS000502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959461388&doi=10.1002%2f2015MS000502&partnerID=40&md5=edcf824617db35f407209aa4aa8b2cb6","This study explores a mass flux framework for moist convective transport and clouds that is formulated in terms of discretized size densities. The properties of each bin in these histograms are estimated individually, making use of a rising plume model. In this framework, the number density acts as a weight, appearing in the area fraction of the mass flux. Such ""bin-macrophysics"" models have the benefit that bulk closures become redundant, and that scale-awareness is introduced at the basis of the formulation. Large-eddy simulation results are used to verify the design of this framework and to constrain associated constants of proportionality. The behavior of the framework is explored by means of single-column model simulations of various idealized cases of shallow and deeper surface-driven convection. A smoothly developing solution for a deepening marine shallow cumulus case is obtained, reproducing key aspects of transport and clouds that define this regime. Further investigation of the size statistics of the framework reveals that indirect interactions between size-bins play a key role in the equilibration process. An ""acceleration-detrainment"" layer is identified above cloud base in which the flux uptake by the largest plumes is counteracted by the detrainment by decelerating smaller plumes. This suppresses CIN, and thus acts to preserve the cloud-subcloud coupling. The convective mass flux shows sensitivity to environmental humidity in the deeper convective cases, reproducing transitions from shallow-to-deep convection. Sensitivity tests are performed to assess the impact of various components of the framework. © 2015. The Authors."
"57212215393;7202208382;","Global-scale convective aggregation: Implications for the Madden-Julian Oscillation",2015,"10.1002/2015MS000498","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959507321&doi=10.1002%2f2015MS000498&partnerID=40&md5=7e568dbb87702269f13d0e6864171738","Previous work has shown that convection will self-organize in cloud-system-resolving model simulations of radiative-convective equilibrium, and it has been suggested that the convective envelope of the Madden-Julian oscillation (MJO) may be organized by similar processes on a much larger scale. Here we present support for that hypothesis based on simulations with SP-CAM with globally uniform SST. Without rotation, convection self-organizes into large (-4000 km) clusters surrounded by dry regions, while with Earth-like rotation the model produces a robust MJO. The nonrotating aggregation and MJO are found to have similar budgets of moist static energy, both being supported by diabatic feedbacks, particularly cloud-longwave interaction. Mechanism denial experiments show that longwave heating anomalies associated with high clouds are essential to the nonrotating aggregation, and amplify the MJO. Simulations using the conventional CAM show a weaker MJO and a much weaker tendency for nonrotating aggregation, and both MJO activity and aggregation intensity are found to increase with the entrainment rate in the deep convection parameterization. © 2015. The Authors."
"57203053066;8920681600;23469562700;36438644200;","Tightly linked zonal and meridional sea surface temperature gradients over the past five million years",2015,"10.1038/ngeo2577","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948439538&doi=10.1038%2fngeo2577&partnerID=40&md5=92c0704ee29b6e9cfada0f798296db99","The climate of the tropics and surrounding regions is defined by pronounced zonal (east-west) and meridional (equator to mid-latitudes) gradients in sea surface temperature. These gradients control zonal and meridional atmospheric circulations, and thus the Earth's climate. Global cooling over the past five million years, since the early Pliocene epoch, was accompanied by the gradual strengthening of these temperature gradients. Here we use records from the Atlantic and Pacific oceans, including a new alkenone palaeotemperature record from the South Pacific, to reconstruct changes in zonal and meridional sea surface temperature gradients since the Pliocene, and assess their connection using a comprehensive climate model. We find that the reconstructed zonal and meridional temperature gradients vary coherently over this time frame, showing a one-to-one relationship between their changes. In our model simulations, we systematically reduce the meridional sea surface temperature gradient by modifying the latitudinal distribution of cloud albedo or atmospheric CO2 concentration. The simulated zonal temperature gradient in the equatorial Pacific adjusts proportionally. These experiments and idealized modelling indicate that the meridional temperature gradient controls upper-ocean stratification in the tropics, which in turn controls the zonal gradient along the equator, as well as heat export from the tropical oceans. We conclude that this tight linkage between the two sea surface temperature gradients posits a fundamental constraint on both past and future climates. © 2015 Macmillan Publishers Limited."
"37012954700;57205299839;57170027000;55420886400;56990454900;","Physical statistical algorithm for precipitable water vapor inversion on land surface based on multi-source remotely sensed data",2015,"10.1007/s11430-015-5211-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949108670&doi=10.1007%2fs11430-015-5211-6&partnerID=40&md5=08c426c63d228246a5a8b50617ec1b33","Water vapor plays a crucial role in atmospheric processes that act over a wide range of temporal and spatial scales, from global climate to micrometeorology. The determination of water vapor distribution in the atmosphere and its changing pattern is very important. Although atmospheric scientists have developed a variety of means to measure precipitable water vapor (PWV) using remote sensing data that have been widely used, there are some limitations in using one kind satellite measurements for PWV retrieval over land. In this paper, a new algorithm is proposed for retrieving PWV over land by combining different kinds of remote sensing data and it would work well under the cloud weather conditions. The PWV retrieval algorithm based on near infrared data is more suitable to clear sky conditions with high precision. The 23.5 GHz microwave remote sensing data is sensitive to water vapor and powerful in cloud-covered areas because of its longer wavelengths that permit viewing into and through the atmosphere. Therefore, the PWV retrieval results from near infrared data and the indices combined by microwave bands remote sensing data which are sensitive to water vapor will be regressed to generate the equation for PWV retrieval under cloud covered areas. The algorithm developed in this paper has the potential to detect PWV under all weather conditions and makes an excellent complement to PWV retrieved by near infrared data. Different types of surface exert different depolarization effects on surface emissions, which would increase the complexity of the algorithm. In this paper, MODIS surface classification data was used to consider this influence. Compared with the GPS results, the root mean square error of our algorithm is 8 mm for cloud covered area. Regional consistency was found between the results from MODIS and our algorithm. Our algorithm can yield reasonable results on the surfaces covered by cloud where MODIS cannot be used to retrieve PWV. © 2015, Science China Press and Springer-Verlag Berlin Heidelberg."
"55665325500;7410061434;39362449000;36870043700;7101808591;7102799735;","Mass gains of the Antarctic ice sheet exceed losses",2015,"10.3189/2015JoG15J071","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953280472&doi=10.3189%2f2015JoG15J071&partnerID=40&md5=9948a8e318d4227e7b953061f84ce2c9","Mass changes of the Antarctic ice sheet impact sea-level rise as climate changes, but recent rates have been uncertain. Ice, Cloud and land Elevation Satellite (ICESat) data (2003-08) show mass gains from snow accumulation exceeded discharge losses by 82±25Gta-1, reducing global sea-level rise by 0.23 mm a-1. European Remote-sensing Satellite (ERS) data (1992-2001) give a similar gain of 112±61 Gt a-1. Gains of 136 Gt a-1 in East Antarctica (EA) and 72 Gt a-1 in four drainage systems (WA2) in West Antarctic (WA) exceed losses of 97Gta-1 from three coastal drainage systems (WA1) and 29Gta-1 from the Antarctic Peninsula (AP). EA dynamic thickening of 147 Gt a-1 is a continuing response to increased accumulation (&gt;50%) since the early Holocene. Recent accumulation loss of 11 Gta-1 in EA indicates thickening is not from contemporaneous snowfall increases. Similarly, the WA2 gain is mainly (60Gta-1) dynamic thickening. In WA1 and the AP, increased losses of 66±16Gta-1 from increased dynamic thinning from accelerating glaciers are 50% offset by greater WA snowfall. The decadal increase in dynamic thinning in WA1 and the AP is approximately one-third of the long-term dynamic thickening in EA and WA2, which should buffer additional dynamic thinning for decades."
"54958151600;55706213200;55715297700;","Characteristics of the Trends in the Global Tropopause Estimated from COSMIC Radio Occultation Data",2015,"10.1109/TGRS.2015.2449338","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028219410&doi=10.1109%2fTGRS.2015.2449338&partnerID=40&md5=b3a6f226d672b10d81e76c62679f352b","This paper discusses the variabilities and trends in the global tropopause based on the gridded monthly mean Global Positioning System radio occultation data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission during July 2006-February 2014. We find that the tropopause height can reflect El Ninõ-Southern Oscillation (ENSO) events. The correlation coefficient between global tropopause height anomalies and the Ninõ 3.4 sea surface temperature index is 0.53, with a maximum correlation coefficient of 0.8 at a lag of three months. We present first the detailed investigations about the spatial distribution of trends in tropopause parameters in each 10° × 5° longitude-latitude grid cell over the globe and find that the rates of change in the tropopause parameters during this time period are high in some particular regions such as the Southern Indian Ocean, Antarctica, Western Europe, North Pacific, and the east coast of North America. An analysis of global monthly means of the tropopause parameters indicates a global tropopause height increase of 0.03 & 2.36 m/year during 2006-2014, with a corresponding temperature increase of 0.020 0.008 °C/year, and a pressure increase of 0.11 0.059 hPa/year. The upward trend of tropopause height is significantly weaker than that in the past years, which might be attributed to the expected stratospheric ozone recovery associated with the Montreal Protocol, the global warming slowdown, and the abnormal global climate change in recent years. The trends of the tropopause parameters are the most significant over the Southern Indian Ocean and Antarctica during September/October/November, which could be due to the stratospheric ozone recovery. © 2015 IEEE."
"57218357425;36740690700;57206531303;7801344746;","Spatial analysis of sunshine duration in complex terrain by non-contemporaneous combination of station and satellite data",2015,"10.1002/joc.4322","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959454410&doi=10.1002%2fjoc.4322&partnerID=40&md5=8e8cead8123e0cb9afde96a52fc64e90","Climate monitoring and environmental modelling are in need of spatial datasets of sunshine duration or surface radiation. Their development is complicated by the coarse resolution of station measurements and the limited temporal extent and consistency of satellite retrievals. We present a method for spatial analysis that combines station and satellite data. Instead of merging contemporaneous measurements from both sources, our approach relies on statistical patterns distilled from satellite data over a limited time period. This permits application outside the satellite period and reduces inconsistencies across satellite generations. The non-contemporaneous merging builds on principal component analysis and kriging with external drift. Its strengths are in regions of complex orography. We develop the non-contemporaneous combination to derive km-scale analyses of relative sunshine duration (monthly and daily) for Switzerland (1971-2012). The monthly analysis has a mean absolute error of 3-5% (per cent relative sunshine duration), and it explains 60-80% of the spatial variance in individual months. Errors of the daily analysis are 7-10% with an explained spatial variance of about 60% but strongly varying from day to day. The integration of satellite data systematically improves the analysis compared to interpolation from station data alone. The improvement is largest in autumn and winter, particularly because of better representation of low-level stratus. The non-contemporaneous merging realizes more than half the accuracy gain from satellite data obtained with the more informative contemporaneous merging. Hence, our alternative involves only a moderate compromise for the return of making pre-satellite Campbell-Stokes measurements exploitable for long-term grid datasets. © 2015 Royal Meteorological Society."
"56919397800;56893785200;26531637100;57196898961;13612339700;16549600900;","Model simulations of fungal spore distribution over the Indian region",2015,"10.1016/j.atmosenv.2015.10.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945123306&doi=10.1016%2fj.atmosenv.2015.10.020&partnerID=40&md5=e823328b84a9db9b502b3551c6c4225c","Fungal spores play important role in the health of humans, animals, and plants by constituting a class of the primary biological aerosol particles (PBAPs). Additionally, these could mediate the hydrological cycle by acting as nuclei for ice and cloud formation (IN and CCN respectively). Various processes in the biosphere and the variations in the meteorological conditions control the releasing mechanism of spores through active wet and dry discharge. In the present paper, we simulate the concentration of fungal spores over the Indian region during three distinct meteorological seasons by combining a numerical model (WRF-Chem) with the fungal spore emissions based on land-use type. Maiden high-resolution regional simulations revealed large spatial gradient and strong seasonal dependence in the concentration of fungal spores over the Indian region. The fungal spore concentrations are found to be the highest during winter (0-70 μg m-3 in December), moderately higher during summer (0-35 μg m-3 in May) and lowest during the monsoon (0-25 μg m-3 in July). The elevated concentrations during winter are attributed to the shallower boundary layer trapping the emitted fungal spores in smaller volume. In contrast, the deeper boundary layer mixing in May and stronger monsoonal-convection in July distribute the fungal spores throughout the lower troposphere (~5 km). We suggest that the higher fungal spore concentrations during winter could have potential health impacts. While, stronger vertical mixing could enable fungal spores to influence the cloud formation during summer and monsoon. Our study provides the first information about the distribution and seasonal variation of fungal spores over the densely populated and observationally sparse Indian region. © 2015 Elsevier Ltd."
"54889736700;7007026915;","The impacts of long-lived jet contrail 'outbreaks' on surface station diurnal temperature range",2015,"10.1002/joc.4303","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959514283&doi=10.1002%2fjoc.4303&partnerID=40&md5=6a7648b3f1affd67b88afb36f9abea6d","Multiple persistent jet aviation contrails - contrail 'outbreaks' - occur frequently over certain portions of the Continental United States (CONUS). The artificial cloudiness generated by contrail outbreaks alters the atmospheric radiation budget, potentially impacting the surface air temperature, particularly the diurnal temperature range (DTR), or difference between daytime maximum and nighttime minimum temperatures. This study evaluates the hypothesis that contrail outbreaks reduce the DTR relative to clear-sky conditions. We utilize a database of longer-lived (>4 h duration) jet contrail outbreaks for the CONUS previously determined from interpretation of high-resolution satellite imagery, for the January and April months of 2008 and 2009. The outbreak impact on DTR was determined by comparing maximum and minimum temperatures at pairs of surface weather stations (one outbreak and one non-outbreak) across two regions of climatologically high outbreak frequency; the South in January, and Midwest in April. We ensured that each station pair selected had broadly similar land use-land cover, soil moisture, and synoptic air mass conditions. For outbreaks in the South (January), there was a statistically significant reduction of DTR at the outbreak versus non-outbreak stations. This result was similar to that obtained for a smaller subset of outbreaks for which lower-level clouds could be confirmed as being absent (from North American Regional Reanalysis (NARR) output). For the Midwest (April), the results are mixed; statistically different for satellite-retrieved outbreaks, but not significantly different for the NARR-validated dataset. These results suggest that persistent jet contrails should be considered in short-term weather forecasting, and for their potential influence on the climatology of more frequently impacted areas. © 2015 Royal Meteorological Society."
"56531995000;55953398100;11539776800;56452518900;57203492395;","Statistical comparison of InSAR tropospheric correction techniques",2015,"10.1016/j.rse.2015.08.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941286537&doi=10.1016%2fj.rse.2015.08.035&partnerID=40&md5=1ec1265f01e169e22baa56fe0568a1a1","Correcting for tropospheric delays is one of the largest challenges facing the interferometric synthetic aperture radar (InSAR) community. Spatial and temporal variations in temperature, pressure, and relative humidity create tropospheric signals in InSAR data, masking smaller surface displacements due to tectonic or volcanic deformation. Correction methods using weather model data, GNSS and/or spectrometer data have been applied in the past, but are often limited by the spatial and temporal resolution of the auxiliary data. Alternatively a correction can be estimated from the interferometric phase by assuming a linear or a power-law relationship between the phase and topography. Typically the challenge lies in separating deformation from tropospheric phase signals. In this study we performed a statistical comparison of the state-of-the-art tropospheric corrections estimated from the MERIS and MODIS spectrometers, a low and high spatial-resolution weather model (ERA-I and WRF), and both the conventional linear and new power-law empirical methods. Our test-regions include Southern Mexico, Italy, and El Hierro. We find spectrometers give the largest reduction in tropospheric signal, but are limited to cloud-free and daylight acquisitions. We find a ~. 10-20% RMSE increase with increasing cloud cover consistent across methods. None of the other tropospheric correction methods consistently reduced tropospheric signals over different regions and times. We have released a new software package called TRAIN (Toolbox for Reducing Atmospheric InSAR Noise), which includes all these state-of-the-art correction methods. We recommend future developments should aim towards combining the different correction methods in an optimal manner. © 2015 ."
"8454768000;","Bi-decadal solar influence on climate, mediated by near tropopause ozone",2015,"10.1016/j.jastp.2015.08.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948961639&doi=10.1016%2fj.jastp.2015.08.005&partnerID=40&md5=56a4b8f2b04182418a22bc56933d53b2","The Sun's contribution to climate variations was highly questioned recently. In this paper we show that bi-decadal variability of solar magnetic field, modulating the intensity of galactic cosmic ray (GCR) at the outer boundary of heliosphere, could be easily tracked down to the Earth's surface. The mediator of this influence is the lower stratospheric ozone, while the mechanism of signal translation consists of: (i) GCR impact on the lower stratospheric ozone balance; (ii) modulation of temperature and humidity near the tropopause by the ozone variations; (iii) increase or decrease of the greenhouse effect, depending on the sign of the humidity changes. The efficiency of such a mechanism depends critically on the level of maximum secondary ionisation created by GCR (i.e. the Pfotzer maximum) - determined in turn by heterogeneous Earth's magnetic field. Thus, the positioning of the Pfotzer max in the driest lowermost stratosphere favours autocatalytic ozone production in the extra-tropical Northern Hemisphere (NH), while in the SH- no suitable conditions for activation of this mechanism exist. Consequently, the geomagnetic modulation of precipitating energetic particles - heterogeneously distributed over the globe - is imprinted on the relation between ozone and humidity in the lower stratosphere (LS). The applied test for causality reveals that during the examined period 1957-2012 there are two main centres of action in the winter NH, with tight and almost stationary winter ozone control on the near tropopause humidity. Being indirectly influenced by the solar protons, the variability of the SH lower stratospheric ozone, however, is much weaker. As a consequence, the causality test detects that the ozone dominates in the interplay with ULTS humidity only in the summer extra-tropics. © 2015 Elsevier Ltd."
"7007114756;7003995144;13007466900;6602137606;7101899282;6603196991;7006146719;6603789748;","Exploiting existing ground-based remote sensing networks to improve high-resolution weather forecasts",2015,"10.1175/BAMS-D-13-00283.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955476717&doi=10.1175%2fBAMS-D-13-00283.1&partnerID=40&md5=0800d096b1e2d9a9689a91e66687ea27","A recent Cooperation in Science and Technology (COST) action financed by the European Union, European Ground-Based Observations of Essential Variables for Climate and Operational Meteorology (EG-CLIMET) is reported. The final report identified four ground-based profiling instruments that are currently underexploited and that have the potential to provide profiles of aerosol and cloud backscatter, winds, temperature, and humidity in real time. These include automatic lidars and ceilometers (ALCs), Doppler lidars, wind profilers, and microwave radiometers. Low-power and sensitive ALCs transmit a short pulse of laser radiation, with wavelengths ranging from 355 to 1064 nm, and receive a backscattered signal with a delay that provides range information. Doppler lidars have the ability to continuously monitor the wind vector throughout the boundary layer using the return from aerosol particles and that the instruments can operate unmanned with minimal maintenance. The precise estimation of Doppler frequencies is performed through heterodyning followed by spectral estimation methods and only requires sufficiently stable radio frequency (RF) oscillators."
"7007144477;56315787900;56581808100;55486220500;","Synergistic and singular effects of river discharge and lunar illumination on dam passage of upstream migrant yellow-phase American eels",2015,"10.1093/icesjms/fsv052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959921023&doi=10.1093%2ficesjms%2ffsv052&partnerID=40&md5=c8b81ab9360904d8290be9a396cf6238","Monitoring of dam passage can be useful for management and conservation assessments of American eel, particularly if passage counts can be examined over multiple years. During a 7-year study (2007-2013) of upstream migration of American eels within the lower Shenandoah River (Potomac River drainage), we counted and measured American eels at the Millville Dam eel pass, where annual study periods were determined by the timing of the eel pass installation during spring or summer and removal during fall. Daily American eel counts were analysed with negative binomial regression models, with and without a year (YR) effect, and with the following time-varying environmental covariates: river discharge of the Shenandoah River at Millville (RDM) and of the Potomac River at Point of Rocks, lunar illumination (LI), water temperature, and cloud cover. A total of 17 161 yellow-phase American eels used the pass during the seven annual periods, and length measurements were obtained from 9213 individuals (mean = 294 mm TL, s.e. = 0.49, range 183-594 mm). Data on passage counts of American eels supported an additive-effects model (YR + LI + RDM) where parameter estimates were positive for river discharge (β = 7.3, s.e. = 0.01) and negative for LI (β = -1.9, s.e. = 0.34). Interestingly, RDM and LI acted synergistically and singularly as correlates of upstream migration of American eels, but the highest daily counts and multiple-day passage events were associated with increased RDM. Annual installation of the eel pass during late spring or summer prevented an early spring assessment, a period with higher RDM relative to those values obtained during sampling periods. Because increases in river discharge are climatically controlled events, upstream migration events of American eels within the Potomac River drainage are likely linked to the influence of climate variability on flow regime. © 2015 Published by Oxford University Press on behalf of International Council for the Exploration of the Sea 2015."
"56780996700;55913339000;55723065600;56780721900;56158622800;","Source and transportation of summer dust over the Tibetan Plateau",2015,"10.1016/j.atmosenv.2015.10.038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946568449&doi=10.1016%2fj.atmosenv.2015.10.038&partnerID=40&md5=574477f7980c84fb7f74bd547ef1bbaf","Satellite observational evidences (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, CALIPSO) have presented that the Tibetan Plateau (TP) is subject to heavy loading of dust aerosols during summer. Combining back trajectory and weather system analyses, the source and transportation of summer Tibetan dust from 2007 to 2014 were investigated. The Tibetan dust is mainly from the Taklimakan Desert and partially from the Gurbantunggut Desert and Great Indian Thar Desert. Case study indicates that the meteorological conditions together with the topography benefit the dust emission adjacent to the TP and the transport toward the plateau. When a cold advection or front developed by strong cold advection passes, dust particles are emitted into the atmosphere from the Taklimakan and Gurbantunggut deserts and then transported to the northern slope of the TP with northeasterly wind induced by the Altai and Tian Shan mountains. For the period from 2007 to 2014, the correlation coefficient of the monthly frequencies of summer dust events over the TP and cold advection passing the Taklimakan and Gurbantunggut deserts were as high as 0.68 and 0.34, respectively. Differently, although the correlation is limited, much TP dust mobilized from the Great Indian Thar Desert is associated with the passing low-pressure system activity and generally polluted by anthropogenic aerosols. The polluted dust is further transported to the southern slope of the TP by the prevailing westerly wind. Investigations on the source and transportation of summer dust over the TP provide a solid foundation of data that can be used to reveal the role of TP dust in the radiation balance, hydrological cycle, and monsoon cycle in India and East Asia. © 2015 Elsevier Ltd."
"57033058300;55694604100;55128001000;56178438700;57189215494;57189217997;56145346300;57194398949;15840948500;","Estimating roof solar energy potential in the downtown area using a GPU-accelerated solar radiation model and airborne LiDAR data",2015,"10.3390/rs71215877","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019352095&doi=10.3390%2frs71215877&partnerID=40&md5=d1aa87d1b9bde143efa626c81eace4a4","Solar energy, as a clean and renewable resource is becoming increasingly important in the global context of climate change and energy crisis. Utilization of solar energy in urban areas is of great importance in urban energy planning, environmental conservation, and sustainable development. However, available spaces for solar panel installation in cities are quite limited except for building roofs. Furthermore, complex urban 3D morphology greatly affects sunlit patterns on building roofs, especially in downtown areas, which makes the determination of roof solar energy potential a challenging task. The object of this study is to estimate the solar radiation on building roofs in an urban area in Shanghai, China, and select suitable spaces for installing solar panels that can effectively utilize solar energy. A Graphic Processing Unit (GPU)-based solar radiation model named SHORTWAVE-C simulating direct and non-direct solar radiation intensity was developed by adding the capability of considering cloud influence into the previous SHORTWAVE model. Airborne Light Detection and Ranging (LiDAR) data was used as the input of the SHORTWAVE-C model and to investigate the morphological characteristics of the study area. The results show that the SHORTWAVE-C model can accurately estimate the solar radiation intensity in a complex urban environment under cloudy conditions, and the GPU acceleration method can reduce the computation time by up to 46%. Two sites with different building densities and rooftop structures were selected to illustrate the influence of urban morphology on the solar radiation and solar illumination duration. Based on the findings, an object-based method was implemented to identify suitable places for rooftop solar panel installation that can fully utilize the solar energy potential. Our study provides useful strategic guidelines for the selection and assessment of roof solar energy potential for urban energy planning. © 2015 by the authors."
"7004356192;14523069600;55420219900;6602159587;36559326000;55532700400;","Determination of instantaneous and daily net radiation from TM - Landsat 5 data in a subtropical watershed",2015,"10.1016/j.jastp.2015.09.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944688793&doi=10.1016%2fj.jastp.2015.09.020&partnerID=40&md5=c42a21e5632e7e9cf4abd837f2ad845f","Remote sensing makes it possible to identify the changes that occur on the surface of the Earth as a result of natural and/or man-made phenomena. Such changes impact on the net radiation at surface which in turn controls the Earth's climate. The present study aims to determine the impact of land use changes on net radiation at surface in a tropical watershed in Brazil, based on satellite images. The instantaneous net radiation (Rn,ins) (at the time of the satellite overpass) and the daily net radiation (Rn,24h) were both estimated by TM - Landsat 5 images and complementary weather data. The net radiation (Rn) estimated from remote sensing data was compared to the measurements taken from two micrometeorological towers located in the study area. Most Rn,ins values were found to be between 457.4Wm-2 and 760.0Wm-2 during the months with more intense solar radiation (February, March, and November), especially in the areas with more vegetation cover (sugarcane and eucalyptus plantations and areas with woody savanna vegetation, locally called Cerradão). The months with the highest thermal and radiative contrast (June and November) were selected to show the spatial distribution of the daily (Instantaneous) Rn, which ranged from 28.0 (420)Wm-2 to 98.0 (520)Wm-2 in June and from 83.0 (450)Wm-2 to 264.0 (800)Wm-2 in November 9. The model used to calculate Rn,24h provided values close to those taken at surface, even on days with higher cloud cover after the satellite overpass. The Mean Absolute Error (MAE), Mean Relative Error (MRE), and Root Mean Square Error (RMSE) associated with the Rn,24h computations in the sugar cane plantation were 8.3Wm-2, 8.4%, and 10.4Wm-2, respectively, confirming the applicability and accuracy of the results. The Rn patterns registered on the woody savanna throughout the year differ very much from those found in cropped areas, particularly in sugar cane plots. This may cause an impact on the watershed climate. © 2015 Elsevier Ltd."
"55936559400;9246517900;6701606453;7202962414;56038150300;","Intercomparison of snowfall estimates derived from the CloudSat Cloud Profiling Radar and the ground-based weather radar network over Sweden",2015,"10.5194/amt-8-5009-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948799253&doi=10.5194%2famt-8-5009-2015&partnerID=40&md5=4ade328c0f9fb9b71bc067c3798cee76","Accurate snowfall estimates are important for both weather and climate applications. Ground-based weather radars and space-based satellite sensors are often used as viable alternatives to rain gauges to estimate precipitation in this context. In particular, the Cloud Profiling Radar (CPR) on board CloudSat is proving to be a useful tool to map snowfall globally, in part due to its high sensitivity to light precipitation and its ability to provide near-global vertical structure. CloudSat snowfall estimates play a particularly important role in the high-latitude regions as other ground-based observations become sparse and passive satellite sensors suffer from inherent limitations. In this paper, snowfall estimates from two observing systems-Swerad, the Swedish national weather radar network, and CloudSat-are compared. Swerad offers a wellcalibrated data set of precipitation rates with high spatial and temporal resolution, at very high latitudes. The measurements are anchored to rain gauges and provide valuable insights into the usefulness of CloudSat CPR's snowfall estimates in the polar regions. In total, 7.2×105 matchups of CloudSat and Swerad observations from 2008 through 2010 were intercompared, covering all but the summer months (June to September). The intercomparison shows encouraging agreement between the two observing systems despite their different sensitivities and user applications. The best agreement is observed when CloudSat passes close to a Swerad station (46-82 km), where the observational conditions for both systems are comparable. Larger disagreements outside this range suggest that both platforms have difficulty with shallow snow but for different reasons. The correlation between Swerad and CloudSat degrades with increasing distance from the nearest Swerad station, as Swerad's sensitivity decreases as a function of distance. Swerad also tends to overshoot low-level precipitating systems further away from the station, leading to an underestimation of snowfall rate and occasionally to missing precipitation altogether. Several statistical metrics-including the probability of detection, false alarm rate, hit rate, and Pierce's skill score-are calculated. The sensitivity of these metrics to the snowfall rate, as well as to the distance from the nearest radar station, are summarised. This highlights the strengths and the limitations of both observing systems at the lower and upper ends of the snowfall distributions as well as the range of uncertainties that can be expected from these systems in high-latitude regions. © 2015 Author(s)."
"55668854900;56003800800;","Different responses of Sea Surface Temperature in the North Pacific to greenhouse gas and aerosol forcing",2015,"10.1007/s11802-015-2535-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946412084&doi=10.1007%2fs11802-015-2535-y&partnerID=40&md5=cd6135d0e4dabef71d5923645f358c86","The responses of Sea Surface Temperature (SST) to greenhouse gas (GHG) and anthropogenic aerosol in the North Pacific are compared based on the historical single and all-forcing simulations with Geophysical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3). During 1860–2005, the effect of GHG forcing on the North Pacific SST is opposite to that of the aerosol forcing. Specifically, the aerosol cooling effect exceeds the GHG warming effect in the Kuroshio Extension (KE) region during 1950–2004 in the CM3 single forcing. The mid-latitude response of ocean circulation to the GHG (aerosol) forcing is to enhance (weaken) the Subtropical Gyre. Then the SST warming (cooling) lies on the zonal band of 40°N because of the increased (reduced) KE warm advection effect in the GHG (aerosol) forcing simulations, and the cooling effect to SST will surpass the warming effect in the KE region in the historical all-forcing simulations. Besides, the positive feedback between cold SST and cloud can also strengthen the aerosol cooling effect in the KE region during boreal summer, when the mixed layer depth is shallow. In the GHG (aerosol) forcing simulations, corresponding to warming (cooling) SST in the KE region, the weakened (enhanced) Aleutian Low appears in the Northeast Pacific. Consequently, the SST responses to all-forcing in the historical simulations are similar to the responses to aerosol forcing in sign and spatial pattern, hence the aerosol effect is quite important to the SST cooling in the mid-latitude North Pacific during the past 55 years. © 2015, Science Press, Ocean University of China and Springer-Verlag Berlin Heidelberg."
"23982847500;36620570600;7006815674;56507246300;56527443200;","Linking the southern annular mode to the diurnal temperature range shifts over southern Africa",2015,"10.1002/joc.4281","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957974145&doi=10.1002%2fjoc.4281&partnerID=40&md5=ca19cb60138aa83f842580de6bd42df7","The link between the diurnal temperature range (DTR) and the southern annular mode (SAM) over southern Africa for the October to December period during 1960 to 2012 is established using observations. The DTR shifts are consistent with the change of moisture and temperature advection over the subregion which is related to the SAM-induced circulation alterations. As such, we consider these changing circulation patterns as playing the dominant role in different types of the DTR development. In fact, for the long-term influence of changes in the large-scale circulation over southern Africa, the SAM circulation may have substantially contributed to the long-term development of cloud cover/precipitation, which can be used as a proxy for the DTR variability in recent decades. Therefore, cloud cover and precipitation changes acted as a disguise rather than the actual cause for the variations in DTR. At the same time, while the mean temperature trends over southern Africa are similar to the global trends that indicate general warming, this increase is superimposed on the significant DTR decadal variability. Consequently, the DTR can be considered as a possible radiative forced index independent of internal climate variations, which is able to provide additional information for the detection and attribution of climate change over southern Africa. © 2015 Royal Meteorological Society."
"56515507800;57200241494;56526563400;","Impact of two different sized Stevenson screens on air temperature measurements",2015,"10.1002/joc.4287","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957962455&doi=10.1002%2fjoc.4287&partnerID=40&md5=b283294e0599fa083316afeb8a81821f","In this study we evaluated the impact of the size of two naturally ventilated wooden Stevenson screens on air temperature measurements in the first-order meteorological station of Calamocha (northeastern Iberian Peninsula, Spain). The 1-year field experiment consisted of comparing air temperatures measured at the two most commonly sized Stevenson screens used by the Spanish Meteorological State Agency (AEMET) since last century; the medium-sized Stevenson screen employed at the second-order weather stations, versus the large-sized Stevenson screen mainly used at the first-order meteorological stations. The main objective was to report the air temperature difference between these two differently sized Stevenson screens, and to study the impact on the observed differences of some weather elements (i.e. relative humidity, wind speed, total cloud cover, atmospheric pressure and global solar radiation). The results show that the medium-sized Stevenson screen tended to overheat daily maximum air temperatures (0.54°C on yearly average) and also air temperatures recorded at 1300UTC. The differences on daily minimum air temperatures were negligible (-0.11°C on yearly average). This overheating bias (not statistically significant) occurred under anticyclonic situations that lead to clear skies, high solar radiation, weak winds and low relative humidity. The bias appeared throughout the whole year but in particular during the warm season from May through October. Air temperature observations from the nearby station Daroca confirmed an overheating bias introduced by a change from a large-sized Stevenson screen to a medium-sized one in Calamocha. © 2015 Royal Meteorological Society."
"57212768309;35190112700;55878640000;","Recent changes in summer precipitation in Northeast China and the background circulation",2015,"10.1002/joc.4280","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957937487&doi=10.1002%2fjoc.4280&partnerID=40&md5=279423f4211f988783b0efeed4ffef4a","This study documents recent changes in the characteristics of summer (July-August-September) precipitation in Northeast China (NEC). A significant shift to less precipitation occurred in 1999-2012 as compared with that in 1984-1998. The reduced precipitation in the later period is closely associated with the large-scale anomalous high pressure over East Asia and anomalous descending motion over NEC. Furthermore, the significant reductions in the total cloud cover and moisture content also contribute to the reduced precipitation over NEC. To investigate the possible mechanism for the decadal shift of summer precipitation, a northeast Asian summer monsoon (NEASM) index is defined to describe the monsoon circulation over NEC. The results indicate that the NEASM has weakened since 1999 and is concurrent with the shift of the Pacific Decadal Oscillation (PDO) to the negative phase. Warming sea surface temperature (SST) in the North Pacific can zonally reduce the land-sea thermal contrast and lead to a weak NEASM. Further investigation indicates that the negative phase of the PDO has significant impacts on the atmospheric circulation associated with the NEASM. Additionally, changes in synchronous Arctic sea ice cover (SIC) also likely induce an anomalous sinking movement and weaken water vapour transport; thus, the summer precipitation over NEC decreases. © 2015 Royal Meteorological Society."
"23482544500;15044387400;10042947300;36852946400;6603401783;","Sensitivity of wheat yield to temperature changes with regional sunlight characteristics in eastern Hokkaido",2015,"10.1002/joc.4276","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957963319&doi=10.1002%2fjoc.4276&partnerID=40&md5=e51b635681334932b7dc0ad4d5f4a62d","Air temperature and sunshine duration for agricultural fields were extracted from 1-km-resolution weather data, and their relationship with winter wheat yield was compared for the adjacent Tokachi and Okhotsk regions of eastern Hokkaido, Japan. Major climatic drivers of winter wheat yield were air temperature during spring and grain-filling period in Tokachi, and sunshine duration during grain-filling period in Okhotsk. The regional difference in the sensitivity of yield to air temperature is attributed to variations in sunshine duration during grain-filling period. In Tokachi, a shorter grain-filling period limits the cumulative sunlight available to plants, because sunshine duration declines from late June to late July. In Okhotsk, yields of winter wheat were attributed to receiving adequate sunlight, although the growth period was curtailed by higher air temperature. We found that different climatic drivers affected winter wheat yield even in adjacent regions. The sensitivity of winter wheat yield to temperature can be determined by a threshold of 4.5h daily sunshine duration regardless of region. Short sunshine duration during the grain-filling period exacerbated the sensitivity of wheat yield to temperature. Early summer in Okhotsk is characterized by sunnier weather than in Tokachi due to foehn, with respect to the southerly winds. Then, southerly wind was associated with significantly longer sunshine duration in Okhotsk. Regional cloud development affects sunshine duration as the climatic driver of wheat yield. © 2015 Royal Meteorological Society."
"10143371500;7005255870;24385771900;23980137600;24322005900;55539188976;7202060229;55585247700;37115472400;57219113417;","LSA SAF Meteosat FRP products-Part 2: Evaluation and demonstration for use in the Copernicus Atmosphere Monitoring Service (CAMS)",2015,"10.5194/acp-15-13241-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948693808&doi=10.5194%2facp-15-13241-2015&partnerID=40&md5=e7c691bea6057ece898c439a516cd3e4","Characterising the dynamics of landscape-scale wildfires at very high temporal resolutions is best achieved using observations from Earth Observation (EO) sensors mounted onboard geostationary satellites. As a result, a number of operational active fire products have been developed from the data of such sensors. An example of which are the Fire Radiative Power (FRP) products, the FRP-PIXEL and FRP-GRID products, generated by the Land Surface Analysis Satellite Applications Facility (LSA SAF) from imagery collected by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) series of geostationary EO satellites. The processing chain developed to deliver these FRP products detects SEVIRI pixels containing actively burning fires and characterises their FRP output across four geographic regions covering Europe, part of South America and Northern and Southern Africa. The FRP-PIXEL product contains the highest spatial and temporal resolution FRP data set, whilst the FRP-GRID product contains a spatiooral summary that includes bias adjustments for cloud cover and the non-detection of low FRP fire pixels. Here we evaluate these two products against active fire data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) and compare the results to those for three alternative active fire products derived from SEVIRI imagery. The FRP-PIXEL product is shown to detect a substantially greater number of active fire pixels than do alternative SEVIRI-based products, and comparison to MODIS on a per-fire basis indicates a strong agreement and low bias in terms of FRP values. However, low FRP fire pixels remain undetected by SEVIRI, with errors of active fire pixel detection commission and omission compared to MODIS ranging between 9-13 % and 65-77 % respectively in Africa. Higher errors of omission result in greater underestimation of regional FRP totals relative to those derived from simultaneously collected MODIS data, ranging from 35 % over the Northern Africa region to 89 % over the European region. High errors of active fire omission and FRP underestimation are found over Europe and South America and result from SEVIRI's larger pixel area over these regions. An advantage of using FRP for characterising wildfire emissions is the ability to do so very frequently and in near-real time (NRT). To illustrate the potential of this approach, wildfire fuel consumption rates derived from the SEVIRI FRP-PIXEL product are used to characterise smoke emissions of the 2007 ""mega-fire"" event focused on Peloponnese (Greece) and used within the European Centre for Medium-Range Weather Forecasting (ECMWF) Integrated Forecasting System (IFS) as a demonstration of what can be achieved when using geostationary active fire data within the Copernicus Atmosphere Monitoring Service (CAMS). Qualitative comparison of the modelled smoke plumes with MODIS optical imagery illustrates that the model captures the temporal and spatial dynamics of the plume very well, and that high temporal resolution emissions estimates such as those available from a geostationary orbit are important for capturing the sub-daily variability in smoke plume parameters such as aerosol optical depth (AOD), which are increasingly less well resolved using daily or coarser temporal resolution emissions data sets. Quantitative comparison of modelled AOD with coincident MODIS and AERONET (Aerosol Robotic Network) AOD indicates that the former is overestimated by ∼ 20-30 %, but captures the observed AOD dynamics with a high degree of fidelity. The case study highlights the potential of using geostationary FRP data to drive fire emissions estimates for use within atmospheric transport models such as those implemented in the Monitoring Atmospheric Composition and Climate (MACC) series of projects for the CAMS. © 2015 Author(s)."
"7201784177;28367935500;55544443300;56109268200;","Response of the intertropical convergence zone to zonally asymmetric subtropical surface forcings",2015,"10.1002/2015GL066027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956938195&doi=10.1002%2f2015GL066027&partnerID=40&md5=7f129123d459f3d3a50422ad1d71d20b","The energetic framework predicts no shift of the zonal mean Intertropical Convergence Zone (ITCZ) in response to zonally asymmetric forcings (zonal warming and cooling regions with zero zonal mean) assuming radiative feedbacks are linear. Here we show the ITCZ shifts southward in response to a zonally asymmetric forcing in the Northern Hemisphere subtropics in a slab ocean aquaplanet model. The southward shift is consistent with decreased zonal mean energy input to the atmosphere due to cloud radiative effect changes in the cooling region. When cloud-radiative feedbacks are disabled the ITCZ shifts northward consistent with changes in the warming region where increased energy input via surface heat fluxes and stationary Rossby-wave transport dominate. Competition between cooling and warming regions leads to changes in gross moist stability. Our results show rectification of zonally asymmetric forcings play an important role in zonal mean ITCZ dynamics and highlight the importance of assessing the momentum budget when interpreting ITCZ shifts. Key Points Energetic framework predicts no shift of ITCZ to zonally asymmetric forcing Opposite ITCZ shifts for radiative feedbacks and surface heat fluxes Momentum budget can be used to infer robustness of energetic framework. © 2015. American Geophysical Union. All Rights Reserved."
"26434217100;54931083200;6701363731;18434033000;56557053600;57193953105;6602742025;","On the ability of RegCM4 regional climate model to simulate surface solar radiation patterns over Europe: An assessment using satellite-based observations",2015,"10.5194/acp-15-13195-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948800056&doi=10.5194%2facp-15-13195-2015&partnerID=40&md5=0e54e6b0e338359028aa1f450707da4b","In this work, we assess the ability of RegCM4 regional climate model to simulate surface solar radiation (SSR) patterns over Europe. A decadal RegCM4 run (2000-2009) was implemented and evaluated against satellite-based observations from the Satellite Application Facility on Climate Monitoring (CM SAF), showing that the model simulates adequately the SSR patterns over the region. The SSR bias between RegCM4 and CM SAF is +1.5 % for MFG (Meteosat First Generation) and +3.3 % for MSG (Meteosat Second Generation) observations. The relative contribution of parameters that determine the transmission of solar radiation within the atmosphere to the deviation appearing between RegCM4 and CM SAF SSR is also examined. Cloud macrophysical and microphysical properties such as cloud fractional cover (CFC), cloud optical thickness (COT) and cloud effective radius (Re) from RegCM4 are evaluated against data from CM SAF. Generally, RegCM4 underestimates CFC by 24.3 % and Re for liquid/ice clouds by 36.1 %/28.3 % and overestimates COT by 4.3 %. The same procedure is repeated for aerosol optical properties such as aerosol optical depth (AOD), asymmetry factor (ASY) and single-scattering albedo (SSA), as well as other parameters, including surface broadband albedo (ALB) and water vapor amount (WV), using data from MACv1 aerosol climatology, from CERES satellite sensors and from ERA-Interim reanalysis. It is shown here that the good agreement between RegCM4 and satellite-based SSR observations can be partially attributed to counteracting effects among the above mentioned parameters. The potential contribution of each parameter to the RegCM4-CM SAF SSR deviations is estimated with the combined use of the aforementioned data and a radiative transfer model (SBDART). CFC, COT and AOD are the major determinants of these deviations on a monthly basis; however, the other parameters also play an important role for specific regions and seasons. Overall, for the European domain, CFC, COT and AOD are the most important factors, since their underestimations and overestimations by RegCM4 cause an annual RegCM4-CM SAF SSR absolute deviation of 8.4, 3.8 and 4.5 %, respectively. © 2015 Author(s)."
"56963229300;7403364008;6603711967;","The sensitivity of global climate to the episodicity of fire aerosol emissions",2015,"10.1002/2015JD024068","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955192101&doi=10.1002%2f2015JD024068&partnerID=40&md5=8492ec40f33007ab1af553c88c000f9f","Here we explore the sensitivity of the global radiative forcing and climate response to the episodicity of fire emissions. We compare the standard approach used in present day and future climate modeling studies, in which emissions are not episodic but smoothly interpolated between monthly mean values and that contrast to the response when fires are represented using a range of approximations of episodicity. The range includes cases with episodicity levels matching observed fire day and fire event counts, as well as cases with extreme episodicity. We compare the different emissions schemes in a set of Community Atmosphere Model (CAM5) simulations forced with reanalysis meteorology and a set of simulations with online dynamics designed to calculate aerosol indirect effect radiative forcings. We find that using climatologically observed fire frequency improves model estimates of cloud properties over the standard scheme, particularly in boreal regions, when both are compared to a simulation with meteorologically synchronized emissions. Using these emissions schemes leads to a range in global indirect effect radiative forcing of fire aerosols between −1.1 and −1.3 W m−2. In cases with extreme episodicity, we see increased transport of aerosols vertically, leading to longer lifetimes and less negative indirect effect radiative forcings. In general, the range in climate impacts that results from the different realistic fire emissions schemes is smaller than the uncertainty in climate impacts due to other aspects of modeling fire emissions. © 2015. American Geophysical Union. All Rights Reserved."
"7003630909;7201624920;8977139600;57004921500;7007124673;","Climate-induced mortality of spruce stands in Belarus",2015,"10.1088/1748-9326/10/12/125006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953230055&doi=10.1088%2f1748-9326%2f10%2f12%2f125006&partnerID=40&md5=71b2d564c61cb1aedb74e364b9e387e1","The aim of this work is an analysis of the causes of spruce (Picea abies L.) decline and mortality in Belarus. The analysis was based on forest inventory and Landsat satellite (land cover classification, climate variables (air temperature, precipitation, evaporation, vapor pressure deficit, SPEI drought index)), and GRACE-derived soil moisture estimation (equivalent of water thickness anomalies, EWTA). We found a difference in spatial patterns between dead stands and all stands (i.e., before mortality). Dead stands were located preferentially on relief features with higher water stress risk (i.e., higher elevations, steeper slopes, south and southwestern exposure). Spruce mortality followed a series of repeated droughts between 1990 and 2010. Mortality was negatively correlated with air humidity (r = -0.52), and precipitation (r = -0.57), and positively correlated with the prior year vapor pressure deficit (r = 0.47), and drought increase (r = 0.57). Mortality increased with the increase in occurrence of spring frosts (r = 0.5), and decreased with an increase in winter cloud cover (r = -0.37). Spruce mortality was negatively correlated with snow water accumulation (r = -0.81) and previous year anomalies in water soil content (r = -0.8). Weakened by water stress, spruce stands were attacked by pests and phytopathogens. Overall, spruce mortality in Belarussian forests was caused by drought episodes and drought increase in synergy with pest and phytopathogen attacks. Vast Picea abies mortality in Belarus and adjacent areas of Russia and Eastern Europe is a result of low adaptation of that species to increased drought. This indicates the necessity of spruce replacement by drought-tolerant indigenous (e.g., Pinus sylvestris, Querqus robur) or introduced (e.g., Larix sp. or Pseudotsuga menzieslii) species to obtain sustainable forest growth management. © 2015 IOP Publishing Ltd."
"55372257600;7004364155;","On the relative stability of CERES reflected shortwave and MISR and MODIS visible radiance measurements during the terra satellite mission",2015,"10.1002/2015JD023484","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955198110&doi=10.1002%2f2015JD023484&partnerID=40&md5=5f262b48d43b63d97ee1b38713642db8","Fifteen years of visible, near-infrared, and broadband shortwave radiance measurements from Clouds and the Earth’s Radiant Energy System (CERES), Multiangle Imaging Spectroradiometer (MISR), and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on board NASA’s Terra satellite are analyzed in order to assess their long-term relative stability for climate purposes. A regression-based approach between CERES, MODIS, and MISR (An camera only) reflectances is used to calculate the bias between the different reflectances relative to a reference year. When compared to the CERES shortwave broadband reflectance, relative drift between the MISR narrowbands is within 1% decade−1. Compared to the CERES shortwave reflectance, the MODIS narrowband reflectances show a relative drift of less than −1.33% decade−1. When compared to MISR, the MODIS reflectances show a relative drift of between −0.36% decade−1 and −2.66% decade−1. We show that the CERES Terra SW measurements are stable over the time period relative to CERES Aqua. Using this as evidence that CERES Terra may be absolutely stable, we suggest that the CERES, MISR, and MODIS instruments meet the radiometric stability goals for climate applications set out in Ohring et al. (2005). © 2015. American Geophysical Union. All Rights Reserved."
"55710683600;7202372861;12040382200;36080026700;36703455200;57059563300;56023500400;","The observed impacts of South Asian summer monsoon on the local atmosphere and the near-surface turbulent heat exchange over the Southeast Tibet",2015,"10.1002/2014JD022928","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954412139&doi=10.1002%2f2014JD022928&partnerID=40&md5=3332e5fdfc37eaacb0c715101756d0aa","The Southeast Tibet is an important region of the Tibetan Plateau bearing the interaction between the Tibetan and the neighbor atmospheric systems. The South Asian summer monsoon (SASM) as a basic climate system in Asia could impact the local atmosphere and the near-surface heat exchange process in the Southeast Tibet. An observational campaign, Observation on the Surface-to-air Exchange Processes in Southeast Tibet (OSEP2013), was carried out in this region during SASM in 2013. The atmospheric parameters and turbulent heat fluxes were observed and averaged over three different land surfaces of the inhomogeneous landscape during the observation campaign. Results show clear SASM impacts on the local atmosphere and near-surface heat exchange in the Southeast Tibet. The South Asian summer monsoon was onset on 1 June 2013 and experienced a south phase and north phase during OSEP2013. The convection and humidity were increased in the Southeast Tibet by SASM, especially during the north phase. The observation domain received low radiation energy due to the convective clouds brought by SASM, and the soil and air temperatures were lowered as consequence. In addition, the air humidity was increased over this region by the wet air transportation of SASM circulation. The sensible and latent heat transfers were decreased by the low land-air temperature difference and high air humidity during SASM. The latent heat transfer dominated the total heat transfer in the Southeast Tibet due to the low sensible heat transfer in the SASM situation, and the domination was increased as the sensible heat transfer was further decreased during the SASM north phase. © 2015. American Geophysical Union. All Rights Reserved."
"56095856700;8437626600;7004479395;35098748100;35762728800;23494302300;35313639700;","Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument",2015,"10.5194/amt-8-4931-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948738946&doi=10.5194%2famt-8-4931-2015&partnerID=40&md5=959b264e30cc1919a5995f8ec9e7256c","The principles of cloud droplet size retrieval via Polarization and Directionality of the Earth's Reflectance (POLDER) requires that clouds be horizontally homogeneous. The retrieval is performed by combining all measurements from an area of 150 km × 150 km to compensate for POLDER's insufficient directional sampling. Using POLDER-like data simulated with the RT3 model, we investigate the impact of cloud horizontal inhomogeneity and directional sampling on the retrieval and analyze which spatial resolution is potentially accessible from the measurements. Case studies show that the sub-grid-scale variability in droplet effective radius (CDR) can significantly reduce valid retrievals and introduce small biases to the CDR (∼ 1.5 μm) and effective variance (EV) estimates. Nevertheless, the sub-grid-scale variations in EV and cloud optical thickness (COT) only influence the EV retrievals and not the CDR estimate. In the directional sampling cases studied, the retrieval using limited observations is accurate and is largely free of random noise. Several improvements have been made to the original POLDER droplet size retrieval. For example, measurements in the primary rainbow region (137-145°) are used to ensure retrievals of large droplet (> 15 μm) and to reduce the uncertainties caused by cloud heterogeneity. We apply the improved method using the POLDER global L1B data from June 2008, and the new CDR results are compared with the operational CDRs. The comparison shows that the operational CDRs tend to be underestimated for large droplets because the cloudbow oscillations in the scattering angle region of 145-165° are weak for cloud fields with CDR > 15 μm. Finally, a sub-grid-scale retrieval case demonstrates that a higher resolution, e.g., 42 km × 42 km, can be used when inverting cloud droplet size distribution parameters from POLDER measurements. © 2015 Author(s)."
"55683727600;8942525300;13405658600;9235235300;55683891800;12753162000;7004469744;35547807400;7004864963;35461255500;7102830450;7005287667;35810775100;8942524900;","Impact of gas-to-particle partitioning approaches on the simulated radiative effects of biogenic secondary organic aerosol",2015,"10.5194/acp-15-12989-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948187324&doi=10.5194%2facp-15-12989-2015&partnerID=40&md5=8162df7eeba2f6ad1ac4607cd3b7caaa","The oxidation of biogenic volatile organic compounds (BVOCs) gives a range of products, from semi-volatile to extremely low-volatility compounds. To treat the interaction of these secondary organic vapours with the particle phase, global aerosol microphysics models generally use either a thermodynamic partitioning approach (assuming instant equilibrium between semi-volatile oxidation products and the particle phase) or a kinetic approach (accounting for the size dependence of condensation). We show that model treatment of the partitioning of biogenic organic vapours into the particle phase, and consequent distribution of material across the size distribution, controls the magnitude of the first aerosol indirect effect (AIE) due to biogenic secondary organic aerosol (SOA). With a kinetic partitioning approach, SOA is distributed according to the existing condensation sink, enhancing the growth of the smallest particles, i.e. those in the nucleation mode. This process tends to increase cloud droplet number concentrations in the presence of biogenic SOA. By contrast, an approach that distributes SOA according to pre-existing organic mass restricts the growth of the smallest particles, limiting the number that are able to form cloud droplets. With an organically mediated new particle formation mechanism, applying a mass-based rather than a kinetic approach to partitioning reduces our calculated global mean AIE due to biogenic SOA by 24 %. Our results suggest that the mechanisms driving organic partitioning need to be fully understood in order to accurately describe the climatic effects of SOA. © 2015 Author(s)."
"55914206700;8879755400;6602265575;7003422540;7006904374;","Cool city mornings by urban heat",2015,"10.1088/1748-9326/10/11/114022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949202697&doi=10.1088%2f1748-9326%2f10%2f11%2f114022&partnerID=40&md5=1d897675c794442d97a5dacc4adb7094","The urban heat island effect is a phenomenon observed worldwide, i.e. evening and nocturnal temperatures in cities are usually several degrees higher than in the surrounding countryside. In contrast, cities are sometimes found to be cooler than their rural surroundings in the morning and early afternoon. Here, a general physical explanation for this so-called daytime urban cool island (UCI) effect is presented and validated for the cloud-free days in the BUBBLE campaign in Basel, Switzerland. Simulations with a widely evaluated conceptual atmospheric boundary-layer model coupled to a land-surface model, reveal that the UCI can form due to differences between the early morning mixed-layer depth over the city (deeper) and over the countryside (shallower). The magnitude of the UCI is estimated for various types of urban morphology, categorized by their respective local climate zones. © 2015 IOP Publishing Ltd."
"56448430100;7202060229;24329221600;56000366900;55539188981;56986172300;8869265800;6603928297;6507813087;6701603958;","Feedbacks of dust and boundary layer meteorology during a dust storm in the eastern Mediterranean",2015,"10.5194/acp-15-12909-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948444030&doi=10.5194%2facp-15-12909-2015&partnerID=40&md5=2d5b2e210899c55752053ea8a611f985","Aerosols affect the atmosphere through direct interaction with short-wave and long-wave radiation and the microphysical properties of clouds. In this paper we report in detail on several mechanisms by which the short-term impact of dust on surface radiative fluxes can affect the dust loading of the atmosphere via modification of boundary-layer meteorology. This in turn affects the aerosol radiative forcing itself. Examples of these feedbacks between dust and boundary layer meteorology were observed during a series of dust storms in the Sahara and the eastern Mediterranean in April 2012. These case studies have been analysed using the Monitoring Atmospheric Composition and Climate-Interim Implementation (MACC-II) system. <br><br> The radiative fluxes in the short-wave and long-wave spectra were both significantly affected by the prognostic aerosol-radiation interaction, which in turn impacted the meteorological simulation. Reduced incoming solar radiation below the aerosol layers led to a decrease in maximum surface temperatures and to a more stable thermal stratification of the lower atmosphere. This in turn forced weaker surface wind speeds and eventually smaller dust emissions. Moreover, we also observed a secondary impact of the aerosol radiative forcing, whereby horizontal gradients of surface temperature were increased at the edge of the dust plume, which led to local increases of surface wind speeds due to the thermal wind effect. The differentiated impact of the aerosol layer on surface pressure also contributed to the increase in surface wind speed and dust production in the same area. Enhanced long-wave radiative fluxes by the dust mass were associated with opposite processes. Less stable thermal stratification at night, brought mainly by higher minimum temperatures at the surface, caused stronger surface winds. At the edge of the dust storm, weaker horizontal temperature and pressure gradients forced lower winds and reduced dust production. Regarding dust emissions, short-wave radiative forcing had a larger impact than long-wave radiative forcing, corroborating several previous studies. For surface temperature, short-wave and long-wave contribution were close in intensity. These feedbacks were amplified when using data assimilation to build the aerosol analysis of the MACC-II global system. This led to an improvement in the short-term forecasts of thermal radiative fluxes and surface temperatures. © 2015 Author(s)."
"37027011900;6603925960;7102410621;57207507108;30667558200;35203328900;6507495053;8669401600;","An EarthCARE/ATLID simulator to evaluate cloud description in climate models",2015,"10.1002/2015JD023919","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956775517&doi=10.1002%2f2015JD023919&partnerID=40&md5=d3b11c64643a9d276ee42fe3b14c8b71","Clouds still remain the largest source of uncertainty in model-based predictions of future climate; thus, the description of the clouds in climate models needs to be evaluated. In particular, the cloud detailed vertical distribution that impacts directly the cloud radiative effect needs to be evaluated. Active satellite sensors directly measure the cloud vertical distribution with high accuracy; their observations should be used for model evaluation together with a satellite simulator in order to allow fair comparison between models and observations. The next cloud lidar in space, EarthCARE/ATmospheric LIDar (ATLID), is planned for launch in 2018, while the current spaceborne cloud lidar CALIPSO/CALIOP is expected to stop collecting data within the next coming years. Here we describe the characteristics of the ATLID on board the EarthCARE satellite (spatial resolution, signal-to-noise ratio, wavelength, field of view, pulse repetition frequency, orbit, and high-spectral resolution lidar) that need to be taken into account to build a Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP)/ATLID simulator. We then present the COSP/ATLID simulator, and the low-, middle-, high-level cloud covers it produces, as well as the zonal mean cloud fraction profiles and the height-intensity histograms that are simulated by COSP/ATLID when overflying an atmosphere predicted by LMDZ5 global circulation model. Finally, we compare the clouds simulated by COSP/ATLID with those simulated by COSP/CALIPSO when overflying the same atmosphere. As the main differences between ATLID and CALIOP are taken into account in the simulators, the differences between COSP/ATLID and COSP/CALIPSO cloud covers are less than 1% in nighttime conditions Key Point EarthCARE simulator to evaluate cloud in climate models. © 2015. American Geophysical Union. All Rights Reserved."
"57198208348;12801992200;7006307463;24722339600;","The nonlinear relationship between albedo and cloud fraction on near-global, monthly mean scale in observations and in the CMIP5 model ensemble",2015,"10.1002/2015GL066275","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955180873&doi=10.1002%2f2015GL066275&partnerID=40&md5=5453078db7911dca21c97215e8150c6a","We study the relation between monthly mean albedo and cloud fraction over ocean, 60°S-60°N. Satellite observations indicate that these clouds all fall on the same near-exponential curve, with a monotonic distribution over the ranges of cloud fractions and albedo. Using these observational data as a reference, we examine the degree to which 26 climate models capture this feature of the near-global marine cloud population. Models show a general increase in albedo with increasing cloud fraction, but none of them display a relation that is as well defined as that characterizing the observations. Models typically display larger albedo variability at a given cloud fraction, larger sensitivity in albedo to changes in cloud fraction, and lower cloud fractions. Several models also show branched distributions, contrasting with the smooth observational relation. In the models the present-day cloud scenes are more reflective than the preindustrial, demonstrating the simulated impact of anthropogenic aerosols on planetary albedo. © 2015. American Geophysical Union. All Rights Reserved."
"37027011900;6603925960;7102410621;57207507108;30667558200;35203328900;6507495053;8669401600;","An EarthCARE/ATLID simulator to evaluate cloud description in climate models",2015,"10.1002/2015JD023919.","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029233955&doi=10.1002%2f2015JD023919.&partnerID=40&md5=a841e2f926210712fe99bf7f708280df","Clouds still remain the largest source of uncertainty in model-based predictions of future climate; thus, the description of the clouds in climate models needs to be evaluated. In particular, the cloud detailed vertical distribution that impacts directly the cloud radiative effect needs to be evaluated. Active satellite sensors directly measure the cloud vertical distribution with high accuracy; their observations should be used for model evaluation together with a satellite simulator in order to allow fair comparison between models and observations. The next cloud lidar in space, EarthCARE/ATmospheric LIDar (ATLID), is planned for launch in 2018, while the current spaceborne cloud lidar CALIPSO/CALIOP is expected to stop collecting data within the next coming years. Here we describe the characteristics of the ATLID on board the EarthCARE satellite (spatial resolution, signal-to-noise ratio, wavelength, field of view, pulse repetition frequency, orbit, and high-spectral resolution lidar) that need to be taken into account to build a Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP)/ATLID simulator. We then present the COSP/ATLID simulator, and the low-, middle-, high-level cloud covers it produces, as well as the zonal mean cloud fraction profiles and the height-intensity histograms that are simulated by COSP/ATLID when overflying an atmosphere predicted by LMDZ5 global circulation model. Finally, we compare the clouds simulated by COSP/ATLID with those simulated by COSP/CALIPSO when overflying the same atmosphere. As the main differences between ATLID and CALIOP are taken into account in the simulators, the differences between COSP/ATLID and COSP/CALIPSO cloud covers are less than 1% in nighttime conditions. © 2015. American Geophysical Union."
"7103016965;7005729142;","Importance of snow to global precipitation",2015,"10.1002/2015GL065497","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955194321&doi=10.1002%2f2015GL065497&partnerID=40&md5=5e4aa145d799c209654ae48df7eea60a","Precipitation controls the availability of drinking water and viability of the land to support agriculture. Failure to accurately predict the location, magnitude, and frequency of precipitation impacts not only numerical weather forecasting but also climate modeling. It has been proposed that most rainfall events originate from ice that has melted to form rain. Here we use remote sensing from spaceborne cloud radar to quantify that idea. A new metric is constructed to quantify the fraction of rain events at the surface that are linked to snow melting at a higher altitude. CloudSat is used to show the global variation of the importance of snow in the precipitation process. In the tropics, subtropics, midlatitude and polar regions 0.3, 0.4, 0.8, and >0.9, respectively, of all precipitation events (>1 mm/d) are linked to the production of snow in clouds. © 2015. American Geophysical Union. All Rights Reserved."
"55802031900;15726427000;6603126554;","Cloud regime evolution in the Indian monsoon intraseasonal oscillation: Connection to large-scale dynamical conditions and the atmospheric water budget",2015,"10.1002/2015GL066353","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955209801&doi=10.1002%2f2015GL066353&partnerID=40&md5=d4db20b1ddd5391cf31ad8b309ca030f","We examine the intraseasonal oscillation (ISO) of the Indian summer monsoon to establish the connections of cloud regimes to large-scale dynamical states defined by dynamical convergence and moisture advection. Over the Indian subcontinent, the developing phase toward ISO peaks (rainfall maximum) is associated with positive anomalies of moisture advection leading in 4-6 days to positive anomalies of dynamical convergence, triggering abrupt transitions from shallow cumulus to deep convections in 1-2 days. The decaying phase toward ISO troughs (rainfall minima) is associated with negative anomalies of moisture advection and decreasing dynamical convergence, accompanying opposite transitions in cloud regimes. Due to northward propagation of anomalies, processes over the Indian Ocean are similar but lead those over the subcontinent by ~10 days. During the transitions cirrus clouds always accompany but lag deep convective clouds by ~10 days. Over the equatorial Indian Ocean cirrus clouds are modulated by equatorial waves. © 2015. American Geophysical Union. All Rights Reserved."
"36969949500;7103206141;56244473600;6701752471;7005034250;","Radiative forcing and climate response to projected 21st century aerosol decreases",2015,"10.5194/acp-15-12681-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947207833&doi=10.5194%2facp-15-12681-2015&partnerID=40&md5=58c967db3e253609f0bf872f6273cc5c","It is widely expected that global emissions of atmospheric aerosols and their precursors will decrease strongly throughout the remainder of the 21st century, due to emission reduction policies enacted to protect human health. For instance, global emissions of aerosols and their precursors are projected to decrease by as much as 80 % by the year 2100, according to the four Representative Concentration Pathway (RCP) scenarios. The removal of aerosols will cause unintended climate consequences, including an unmasking of global warming from long-lived greenhouse gases. We use the Geophysical Fluid Dynamics Laboratory Coupled Climate Model version 3 (GFDL CM3) to simulate future climate over the 21st century with and without the aerosol emission changes projected by each of the RCPs in order to isolate the radiative forcing and climate response resulting from the aerosol reductions. We find that the projected global radiative forcing and climate response due to aerosol decreases do not vary significantly across the four RCPs by 2100, although there is some mid-century variation, especially in cloud droplet effective radius, that closely follows the RCP emissions and energy consumption projections. Up to 1 W m-2 of radiative forcing may be unmasked globally from 2005 to 2100 due to reductions in aerosol and precursor emissions, leading to average global temperature increases up to 1 K and global precipitation rate increases up to 0.09 mm day-1. However, when using a version of CM3 with reduced present-day aerosol radiative forcing (-1.0 W m-2), the global temperature increase for RCP8.5 is about 0.5 K, with similar magnitude decreases in other climate response parameters as well. Regionally and locally, climate impacts can be much larger than the global mean, with a 2.1 K warming projected over China, Japan, and Korea due to the reduced aerosol emissions in RCP8.5, as well as nearly a 0.2 mm day-1 precipitation increase, a 7 g m-2 LWP decrease, and a 2 μm increase in cloud droplet effective radius. Future aerosol decreases could be responsible for 30-40 % of total climate warming (or 10-20 % with weaker aerosol forcing) by 2100 in East Asia, even under the high greenhouse gas emissions scenario (RCP8.5). The expected unmasking of global warming caused by aerosol reductions will require more aggressive greenhouse gas mitigation policies than anticipated in order to meet desired climate targets. © Author(s) 2015."
"55619458300;7006033615;6701744876;","Weekly cycles of global fires - Associations with religion, wealth and culture, and insights into anthropogenic influences on global climate",2015,"10.1002/2015GL066383","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955205079&doi=10.1002%2f2015GL066383&partnerID=40&md5=759838366c7515a074562061e3b2e055","One approach to quantifying anthropogenic influences on the environment and the consequences of those is to examine weekly cycles (WCs). No long-term natural process occurs on a WC so any such signal can be considered anthropogenic. There is much ongoing scientific debate as to whether regional-scale WCs exist above the statistical noise level, with most significant studies claiming that anthropogenic aerosols and their interaction with solar radiation and clouds (direct/indirect effect) is the controlling factor. A major source of anthropogenic aerosol, underrepresented in the literature, is active fire (AF) from anthropogenic burning for land clearance/management. WCs in AF have not been analyzed heretofore, and these can provide a mechanism for observed regional-scale WCs in several meteorological variables. We show that WCs in AFs are highly pronounced for many parts of the world, strongly influenced by the working week and particularly the day(s) of rest, associated with religious practices. © 2015. American Geophysical Union. All Rights Reserved."
"24385808600;55809372400;","Direct aerosol effects during periods of solar dimming and brightening hidden in the regression residuals: Evidence from Potsdam measurements",2015,"10.1002/2015JD023669","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956759806&doi=10.1002%2f2015JD023669&partnerID=40&md5=94ef2b6ce588367a1ea9bbc10159bdd0","A recent empirical study of Stanhill et al. (2014), which was based on the Angstrom-Prescott relationship between global radiation and sunshine duration, was evaluated. The parameters of this relationship seemed to be rather stable across the dimming and brightening periods. Thus, the authors concluded that the variation in global radiation is more influenced by changes in cloud cover and sunshine duration than by the direct aerosol effects. In our study, done for the Potsdam station (one of six globally distributed stations, the source of one of the longest observational records and closely located to former hot spots of aerosol emission), we tested and rejected the hypothesis that the dimming of global radiation directly caused by aerosols is negligible. The residuals of the Angstrom-Prescott regression reveal a statistically significant positive temporal trend and a temporal level segmentation. The latter was consistent with the temporal emission patterns around Potsdam. The trend in the residuals only disappeared when the model intercept varied according to the temporal level segmentation. The magnitude of the direct aerosol effect on the level changes in global radiation derived from the modified Angstrom-Prescott relationship was in the range indicated in previous studies. Thus, from here, a specific request cannot be made for a revision of current climate models state-of-the-art representation of both the cooling effect directly caused by aerosols and the temperature sensitivity to the increase of greenhouse gases. © 2015. American Geophysical Union."
"55907872400;57203378050;7404548584;55476786400;6603652793;7005420497;","An improved method for retrieving nighttime aerosol optical thickness from the VIIRS Day/Night Band",2015,"10.5194/amt-8-4773-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947269613&doi=10.5194%2famt-8-4773-2015&partnerID=40&md5=130e21823d182b682808fda64c301768","Using Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) data, a method, dubbed the ""variance method"", is developed for retrieving nighttime aerosol optical thickness (τ) values through the examination of the dispersion of radiance values above an artificial light source. Based on the improvement of a previous algorithm, this updated method derives a semi-quantitative indicator of nighttime τ using artificial light sources. Nighttime τ retrievals from the newly developed method are inter-compared with an interpolated value from late afternoon and early morning ground observations from four AErosol RObotic NETwork (AERONET) sites as well as column-integrated τ from one High Spectral Resolution Lidar (HSRL) site at Huntsville, AL, during the NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign, providing full diel coverage. Sensitivity studies are performed to examine the effects of lunar illumination on VIIRS τ retrievals made via the variance method, revealing that lunar contamination may have a smaller impact than previously thought; however, the small sample size of this study limits the conclusiveness thus far. VIIRS τ retrievals yield a coefficient of determination (r2) of 0.60 and a root-mean-squared error (RMSE) of 0.18 when compared against straddling daytime-averaged AERONET τ values. Preliminary results suggest that artificial light sources can be used for estimating regional and global nighttime aerosol distributions in the future. © Author(s) 2015."
"8541838700;55661627100;27171116700;7404279220;9232335400;55823785600;","Characteristics of climate change in southwest China karst region and their potential environmental impacts",2015,"10.1007/s12665-014-3847-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932198066&doi=10.1007%2fs12665-014-3847-8&partnerID=40&md5=d46a6c833462e2d21b6e1d2dba89c1cb","Global warming, due to the enhanced greenhouse effect, is likely to have significant effect on the hydrological cycle, which would result in more evaporation, more precipitation, and uneven distribution of precipitation around the globe. Some parts of the world may see significant reduction in precipitation, or major alterations in the timing of wet and dry seasons, and increases in both floods and droughts. In China, a warming trend has been observed across the mainland region during the past 50 years, with an increasing temperature of about 0.2–0.3 °C/10 year in northern and less than 0.1 °C/10 year in southern China. To understand the characteristics of climate change, this study has conducted statistical analysis on climate parameters from 12 representative meteorological stations in southwest China karst region. The non-parametric Mann–Kendall rank statistic method and the Pettitt–Mann–Whitney change point statistics were used, respectively, for the change trend and change point analyses of daily temperature and precipitation at each station. The 5-year moving averages of 11 climate parameters showed a clear increase in the maximum and minimum annual average temperature in southwest China, however, no consistent increase for precipitation. In addition to temperature and precipitation, changes in the atmospheric pressure, wind speed, and cloud cover were also observed from this study. Changes in climate characteristics will or have altered the hydrologic cycle in the region, which would induce more frequent drought and flood, redistribution of water resources, rocky desertification, and carbon balance, and will ultimately have great impacts on the social, economic, and environmental life in the region. © 2014, Springer-Verlag Berlin Heidelberg."
"6603269313;57201311401;57201324809;57201312479;7404591111;","New patterns of establishment and growth of Picea, Abies and Betula tree species in subalpine forest gaps of Jiuzhaigou National Nature Reserve, Sichuan, southwestern China in a changing environment",2015,"10.1016/j.foreco.2015.07.032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006253613&doi=10.1016%2fj.foreco.2015.07.032&partnerID=40&md5=fcc5235737c885ff4ab73950cdf1b9eb","Temperature increase in the southeastern Tibetan Plateau in the past thirty years is high but its effects on tree dynamics of subalpine coniferous forests are not well understood. This study focuses on tree establishment and growth in 26 subalpine forest gaps between 2900 m and 3200 m in Jiuzhaigou National Nature Reserve, Sichuan, China. Normally Abies faxoniana and Picea purpurea dominate the canopy of subalpine forests in the reserve. Our study examined tree species establishment and growth, environmental conditions in these gaps, and the potential future changes in forest composition in the reserve. Seedlings, saplings and mature trees were counted, measured and cored to assess species’ numbers, age, and growth parameters. Root structure was also studied. Gap environmental conditions were recorded and climate changes examined. For a wide range of differently aged gaps, numerous seedlings, saplings and even mature canopy trees of Betula albo-sinensis, a deciduous broadleaf tree, were observed. B. albo-sinensis was most abundant in gaps with the following characteristics: (1) steep slopes (&gt;30°), (2) areas with thin soil (&lt;5 cm depth) or (3) large areas (&gt;600 m2) with deep soil (&gt;15 cm depth). In contrast, the site characteristics required for successful establishment of the two evergreen conifers A. faxoniana and P. purpurea are soil &gt;9 cm deep and slopes &lt;30°. B. albo-sinensis has shallower roots with smaller root:shoot ratio than the conifer species. Increasing temperature, declining cloud cover and increasing high rainfall incidences are increasing habitats that favor establishment and growth of B. albo-sinensis and inhibit the establishment and growth of A. faxoniana and P. purpurea in subalpine areas of Jiuzhaigou, southwestern China. © 2015 Elsevier B.V."
"6504637069;12647011300;56435308400;56436108200;56436745100;","δ18O characteristics of meteoric precipitation and its water vapor sources in the Guilin area of China",2015,"10.1007/s12665-014-3827-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932195714&doi=10.1007%2fs12665-014-3827-z&partnerID=40&md5=005d41f48ae20ed171f2a92ae65c2dde","The stable isotopic composition of meteoric precipitation is an important component of global and regional water cycle research. Stable isotope data can help reconstruct paleoclimate related to ice cores, lake sediments, and stalagmites. We investigated the daily variation in isotopic composition of meteoric precipitation from 2008 to 2012 in the Guilin region of China. δ18O of meteoric precipitation ranged from −14.21 to +2.38 ‰, with an average value of −5.78 ‰ (Vienna Standard Mean Ocean Water; VSMOW). Meteoric precipitation in the summer half-year (May through October) increased, with a relatively low δ18O value of −8.04 ‰ (VSMOW; average of 261 groups) and −56.03 ‰ (VSMOW) of average δD, accounting for 67.6 % of the total annual meteoric precipitation. Meteoric precipitation in the winter half-year (November through April) decreased, with a relatively high δ18O value of −2.89 ‰ (average of 210 groups) and −9.23 ‰ of average δD, accounting for 32.4 % of total meteoric precipitation. The local meteoric water line (LMWL) equation in Guilin area has local climate characteristics. By combining environmental isotope data of precipitation using a backwards trajectory, water vapor sources of the meteoric precipitation in Guilin area are inferred and traced. Our results show that the isotopic composition of meteoric water vapor sources in Guilin area are related to monsoon type, source of precipitation cloud masses, and precipitation properties. The isotopic composition of meteoric precipitation in the summer half-year (May through October) was mainly affected by the summer monsoon or summer typhoons, namely controlled by water vapor source from the Bay of Bengal and the South China sea, and the second the West Pacific, and the δ18O value of meteoric precipitation was strongly negative. There was a significant negative correlation between the δ18O values of meteoric precipitation and the amount of precipitation and temperature in the summer half-year. The amount effect of the meteoric precipitation often concealed the temperature effect. The isotopic composition of meteoric precipitation in the winter season or winter half-year was affected by the water vapor source of the warm moist air masses from the West Pacific and continental cold air masses from the Siberia–Mongolia/winter monsoon or local evaporation vapor circulation, and the δ18O value of meteoric precipitation was relatively positive, and indicated that the water vapor of meteoric precipitation along the water vapor trajectory was affected by the evaporation as well as the local water vapor evaporation. The research results have showed that different sources of water vapor has a significant influence on the δ18O variation of meteoric precipitation, therefore, analysis of δ18O in the meteoric precipitation, especially its seasonal variation characteristics of analysis, can conversely reveal the water vapor sources of local meteoric precipitation. © 2014, Springer-Verlag Berlin Heidelberg."
"55913339000;30767858100;56780996700;55913917200;56158622800;56959736200;","Modeling study on the transport of summer dust and anthropogenic aerosols over the Tibetan Plateau",2015,"10.5194/acp-15-12581-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947061481&doi=10.5194%2facp-15-12581-2015&partnerID=40&md5=85a96db676bfdeba24b87dd4865deb3b","The Tibetan Plateau (TP) is located at the juncture of several important natural and anthropogenic aerosol sources. Satellites have observed substantial dust and anthropogenic aerosols in the atmosphere during summer over the TP. These aerosols have distinct effects on the earth's energy balance, microphysical cloud properties, and precipitation rates. To investigate the transport of summer dust and anthropogenic aerosols over the TP, we combined the Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS) with a non-hydrostatic regional model (NHM). The model simulation shows heavily loaded dust aerosols over the northern slope and anthropogenic aerosols over the southern slope and the east of the TP. The dust aerosols are primarily mobilized around the Taklimakan Desert, where a portion of the aerosols are transported eastward due to the northwesterly current; simultaneously, a portion of the particles are transported southward when a second northwesterly current becomes northeasterly because of the topographic blocking of the northern slope of the TP. Because of the strong upward current, dust plumes can extend upward to approximately 7-8 km a.s.l. over the northern slope of the TP. When a dust event occurs, anthropogenic aerosols that entrained into the southwesterly current via the Indian summer monsoon are transported from India to the southern slope of the TP. Simultaneously, a large amount of anthropogenic aerosol is also transported from eastern China to the east of the TP by easterly winds. An investigation on the transport of dust and anthropogenic aerosols over the plateau may provide the basis for determining aerosol impacts on summer monsoons and climate systems. © Author(s) 2015."
"25031430500;","Putting the clouds back in aerosol-cloud interactions",2015,"10.5194/acp-15-12397-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942682922&doi=10.5194%2facp-15-12397-2015&partnerID=40&md5=0f9c67cb086c1d89de8d0d3784a6de87","Aerosol-cloud interactions (ACI) are the consequence of perturbed aerosols affecting cloud drop and crystal number, with corresponding microphysical and radiative effects. ACI are sensitive to both cloud microphysical processes (the ""C"" in ACI) and aerosol emissions and processes (the ""A"" in ACI). This work highlights the importance of cloud microphysical processes, using idealized and global tests of a cloud microphysics scheme used for global climate prediction. Uncertainties in key cloud microphysical processes examined with sensitivity tests cause uncertainties of nearly g'30 to +60 % in ACI, similar to or stronger than uncertainties identified due to natural aerosol emissions (-30 to +30 %). The different dimensions and sensitivities of ACI to microphysical processes identified in previous work are analyzed in detail, showing that precipitation processes are critical for understanding ACI and that uncertain cloud lifetime effects are nearly one-third of simulated ACI. Buffering of different processes is important, as is the mixed phase and coupling of the microphysics to the condensation and turbulence schemes in the model. © Author(s) 2015."
"57213229795;57218273453;25823927100;7103165085;56963294600;56601875800;8905764300;","An automatic and effective parameter optimization method for model tuning",2015,"10.5194/gmd-8-3579-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947261648&doi=10.5194%2fgmd-8-3579-2015&partnerID=40&md5=9c3da796b2ec703baca58cb5dd360386","Physical parameterizations in general circulation models (GCMs), having various uncertain parameters, greatly impact model performance and model climate sensitivity. Traditional manual and empirical tuning of these parameters is time-consuming and ineffective. In this study, a ""three-step"" methodology is proposed to automatically and effectively obtain the optimum combination of some key parameters in cloud and convective parameterizations according to a comprehensive objective evaluation metrics. Different from the traditional optimization methods, two extra steps, one determining the model's sensitivity to the parameters and the other choosing the optimum initial value for those sensitive parameters, are introduced before the downhill simplex method. This new method reduces the number of parameters to be tuned and accelerates the convergence of the downhill simplex method. Atmospheric GCM simulation results show that the optimum combination of these parameters determined using this method is able to improve the model's overall performance by 9 %. The proposed methodology and software framework can be easily applied to other GCMs to speed up the model development process, especially regarding unavoidable comprehensive parameter tuning during the model development stage. © Author(s) 2015."
"7003416980;6504570615;7006427809;","Long-term herbarium data reveal the decline of a temperate-water algae at its southern range",2015,"10.1016/j.ecss.2015.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948082591&doi=10.1016%2fj.ecss.2015.05.008&partnerID=40&md5=1ec85c59b0d31b4ae42ba7e715aad498","Distributional shifts of marine species have recently received attention as a result of increasing man-induced pressures on coastal ecosystems and global climate change (i.e. ocean warming). The southernmost geographical limit of the fucoid Fucus guiryi is the Canarian archipelago (Northeastern Atlantic Ocean) where this species is currently forming scarce and low-dense populations. Studies on long-term herbarium data revealed the decrease in size of morphological features (length and width of thallus and receptacles), and recent surveys confirmed the sharp decline, or even extinction, of F. guiryi from most sites previously documented. The increase of mean seawater surface temperature consistently matches the regression of populations of F. guiryi. Other environmental variables, such as wave exposure, cloud cover and chlorophyll-a concentration, contributed to explain local-scale spatial variability detected in Canarian populations. © 2015 Elsevier Ltd."
"55067058700;35302719200;36154810000;55782878600;6507506955;7006027075;56164814800;6506424404;7006643234;25629654200;9846347800;7004346367;7004462227;6603268269;6701845055;","Morphology of diesel soot residuals from supercooled water droplets and ice crystals: Implications for optical properties",2015,"10.1088/1748-9326/10/11/114010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949267036&doi=10.1088%2f1748-9326%2f10%2f11%2f114010&partnerID=40&md5=093c61080de380502b0f68d9502f8ac8","Freshly emitted soot particles are fractal-like aggregates, but atmospheric processes often transform their morphology. Morphology of soot particles plays an important role in determining their optical properties, life cycle and hence their effect on Earth's radiative balance. However, little is known about the morphology of soot particles that participated in cold cloud processes. Here we report results from laboratory experiments that simulate cold cloud processing of diesel soot particles by allowing them to form supercooled droplets and ice crystals at -20 and -40 °C, respectively. Electron microscopy revealed that soot residuals from ice crystals were more compact (roundness ∼0.55) than those from supercooled droplets (roundness ∼0.45), while nascent soot particles were the least compact (roundness ∼0.41). Optical simulations using the discrete dipole approximation showed that the more compact structure enhances soot single scattering albedo by a factor up to 1.4, thereby reducing the top-of-the-atmosphere direct radiative forcing by ∼63%. These results underscore that climate models should consider the morphological evolution of soot particles due to cold cloud processing to improve the estimate of direct radiative forcing of soot. © 2015 IOP Publishing Ltd."
"46461636700;26643041500;14034301300;7004296083;35461763400;24480463300;7005069415;16479877100;8568391400;56251307100;56333104300;16549600900;8720897100;35224765000;35085069400;35195849700;24558717100;34868441100;6603256829;23995325300;35461255500;57203053317;57189372185;6603172418;7006058570;6701378450;7006708207;8657171200;8871497700;55942083800;7403401100;13407563600;57214957433;7005287667;7006434689;8576496400;7006595513;55789354000;6602085876;","A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network",2015,"10.5194/acp-15-12211-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946238238&doi=10.5194%2facp-15-12211-2015&partnerID=40&md5=edb3c88efc04694d43a08a186f482f16","Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (NCCN) to the total number concentration of particles (NCN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations - exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A50 and A100, respectively) renders a much more stable dependence of A on S; A50 and A100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of NCCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of NCCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol-cloud interactions in various environments. © Author(s) 2015."
"54400559100;6603400519;6602506180;7006743561;7003627515;","A Retrospective, Iterative, Geometry-Based (RIGB) tilt correction method for radiation observed by Automatic Weather Stations on snow-covered surfaces: Application to Greenland",2015,"10.5194/tcd-9-6025-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961843401&doi=10.5194%2ftcd-9-6025-2015&partnerID=40&md5=2481e82bbb2fb1351e89698e3bc1c5b3","Surface melt and mass loss of the Greenland Ice Sheet may play crucial roles in global climate change due to their positive feedbacks and large fresh water storage. With few other regular meteorological observations available in this extreme environment, measurements from Automatic Weather Stations (AWS) are the primary data source for studying surface energy budgets, and for validating satellite observations and model simulations. Station tilt, due to irregular surface melt and/or compaction, causes considerable biases in the AWS shortwave radiation measurements. In this study, we identify tilt-induced biases in the climatology of surface shortwave radiative flux and albedo, and retrospectively correct these by iterative application of solar geometric principles. We found, over all the AWS from the Greenland Climate Network (GC-Net), the Kangerlussuaq transect (K-transect) and the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) networks, insolation on fewer than 40 % of clear days peaks within ±0.5 h of solar noon time, with the largest shift exceeding 3 h due to tilt. Hourly absolute biases in the magnitude of surface insolation can reach up to 200 W m-2. We estimate the tilt angles and their directions based on the solar geometric relationship between the simulated insolation at a horizontal surface and the observed insolation by these tilted AWS under clear-sky conditions. Our adjustment reduces the Root Mean Square Error (RMSE) against references from both satellite observation and reanalysis by ∼ 20W W m-2, and raises the correlation coefficients with them to above 0.95. Averaged over the whole Greenland Ice Sheet in the melt season, the adjustment in insolation to compensate station tilt is 18 ± 13 W m-2, enough to melt 0.40 ± 0.29 m of snow water equivalent. The adjusted diurnal cycles of albedo are smoother, with consistent semi-smiling patterns. The seasonal cycles and inter-annual variabilities of albedo agree better with previous studies. This tilt-corrected shortwave radiation dataset derived using the Retrospective, Iterative, Geometry-Based (RIGB) method provide more accurate observations and validations for surface energy budgets studies on the Greenland Ice Sheet, including albedo variations, surface melt simulations and cloud radiative forcing estimates. © Author(s) 2015."
"6603729297;29167612800;35459245100;6701620591;16063149700;9043533500;55986697600;15519671300;8720897100;7004935190;6602484195;25642590700;7006712143;57155049100;","Biotic stress accelerates formation of climate-relevant aerosols in boreal forests",2015,"10.5194/acp-15-12139-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946607261&doi=10.5194%2facp-15-12139-2015&partnerID=40&md5=26c86b513da6dd408ec13591393232c9","Boreal forests are a major source of climate-relevant biogenic secondary organic aerosols (SOAs) and will be greatly influenced by increasing temperature. Global warming is predicted to not only increase emissions of reactive biogenic volatile organic compounds (BVOCs) from vegetation directly but also induce large-scale insect outbreaks, which significantly increase emissions of reactive BVOCs. Thus, climate change factors could substantially accelerate the formation of biogenic SOAs in the troposphere. In this study, we have combined results from field and laboratory experiments, satellite observations and global-scale modelling in order to evaluate the effects of insect herbivory and large-scale outbreaks on SOA formation and the Earth's climate. Field measurements demonstrated 11-fold and 20-fold increases in monoterpene and sesquiterpene emissions respectively from damaged trees during a pine sawfly (Neodiprion sertifer) outbreak in eastern Finland. Laboratory chamber experiments showed that feeding by pine weevils (Hylobius abietis) increased VOC emissions from Scots pine and Norway spruce seedlings by 10-50 fold, resulting in 200-1000-fold increases in SOA masses formed via ozonolysis. The influence of insect damage on aerosol concentrations in boreal forests was studied with a global chemical transport model GLOMAP and MODIS satellite observations. Global-scale modelling was performed using a 10-fold increase in monoterpene emission rates and assuming 10 % of the boreal forest area was experiencing outbreak. Results showed a clear increase in total particulate mass (local max. 480 %) and cloud condensation nuclei concentrations (45 %). Satellite observations indicated a 2-fold increase in aerosol optical depth over western Canada's pine forests in August during a bark beetle outbreak. These results suggest that more frequent insect outbreaks in a warming climate could result in substantial increase in biogenic SOA formation in the boreal zone and, thus, affect both aerosol direct and indirect forcing of climate at regional scales. The effect of insect outbreaks on VOC emissions and SOA formation should be considered in future climate predictions. © Author(s) 2015."
"7005659847;35487016600;35568326100;55951906300;7004607037;7003469326;24366038500;7006005916;24069901800;54388456400;37099534700;25924917300;6507421167;6506897651;25923454000;55192470800;57148462400;6602838400;25626178000;37067325200;6603202832;35107283500;54411000800;16642991200;6701490421;6603379376;16444950900;56424987200;7102790108;23995341000;8302476700;36651412700;56151520300;10143908900;56052105000;54279446400;6701843178;6701338417;6602109913;8084443000;7005349573;6506901500;20735555400;7102113229;","EARLINET: Potential operationality of a research network",2015,"10.5194/amt-8-4587-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941013050&doi=10.5194%2famt-8-4587-2015&partnerID=40&md5=1b6d31e6ad2481d4bf059c0808fc9a39","In the framework of ACTRIS (Aerosols, Clouds, and Trace Gases Research Infrastructure Network) summer 2012 measurement campaign (8 June-17 July 2012), EARLINET organized and performed a controlled exercise of feasibility to demonstrate its potential to perform operational, coordinated measurements and deliver products in near-real time. Eleven lidar stations participated in the exercise which started on 9 July 2012 at 06:00 UT and ended 72 h later on 12 July at 06:00 UT. For the first time, the single calculus chain (SCC) - the common calculus chain developed within EARLINET for the automatic evaluation of lidar data from raw signals up to the final products - was used. All stations sent in real-time measurements of a 1 h duration to the SCC server in a predefined netcdf file format. The pre-processing of the data was performed in real time by the SCC, while the optical processing was performed in near-real time after the exercise ended. 98 and 79 % of the files sent to SCC were successfully pre-processed and processed, respectively. Those percentages are quite large taking into account that no cloud screening was performed on the lidar data. The paper draws present and future SCC users' attention to the most critical parameters of the SCC product configuration and their possible optimal value but also to the limitations inherent to the raw data. The continuous use of SCC direct and derived products in heterogeneous conditions is used to demonstrate two potential applications of EARLINET infrastructure: the monitoring of a Saharan dust intrusion event and the evaluation of two dust transport models. The efforts made to define the measurements protocol and to configure properly the SCC pave the way for applying this protocol for specific applications such as the monitoring of special events, atmospheric modeling, climate research and calibration/validation activities of spaceborne observations. © Author(s) 2015."
"6506504754;9638325500;36770436600;7005955015;53878006900;6506373162;7404732357;","An economic evaluation of solar radiation management",2015,"10.1016/j.scitotenv.2015.05.106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930630935&doi=10.1016%2fj.scitotenv.2015.05.106&partnerID=40&md5=f01a2f6a8d44228c0cfb2d5d624803b9","Economic evaluations of solar radiation management (SRM) usually assume that the temperature will be stabilized, with no economic impacts of climate change, but with possible side-effects. We know from experiments with climate models, however, that unlike emission control the spatial and temporal distributions of temperature, precipitation and wind conditions will change. Hence, SRM may have economic consequences under a stabilization of global mean temperature even if side-effects other than those related to the climatic responses are disregarded. This paper addresses the economic impacts of implementing two SRM technologies; stratospheric sulfur injection and marine cloud brightening. By the use of a computable general equilibrium model, we estimate the economic impacts of climatic responses based on the results from two earth system models, MPI-ESM and NorESM. We find that under a moderately increasing greenhouse-gas concentration path, RCP4.5, the economic benefits of implementing climate engineering are small, and may become negative. Global GDP increases in three of the four experiments and all experiments include regions where the benefits from climate engineering are negative. © 2015 Elsevier B.V."
"57008570500;7004114883;6505932008;54983414800;","Observed and modeled warm rainfall occurrence and its relationships with cloud macrophysical properties",2015,"10.1175/JAS-D-14-0368.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950349728&doi=10.1175%2fJAS-D-14-0368.1&partnerID=40&md5=450b95731a3819f827beec466a104701","Observed and modeled rainfall occurrence from shallow (warm) maritime clouds and their composite statistical relationships with cloud macrophysical properties are analyzed and directly compared. Rain falls from ~25% of warm, single-layered, maritime clouds observed by CloudSat and from ~27% of the analogous warm clouds simulated within a large-domain, fine-resolution radiative-convective equilibrium experiment performed using the Regional Atmospheric Modeling System (RAMS), with its sophisticated bin-emulating bulk microphysical scheme. While the fractional occurrence of observed and simulated warm rainfall is found to increase with both increasing column-integrated liquid water and cloud depth, calculations of rainfall occurrence as a joint function of these two macrophysical quantities suggest that the modeled bulk cloud-to-rainwater conversion process is more efficient than observations indicate-in agreement with previous research. Unexpectedly and in opposition to the model-derived relationship, deeper CloudSat-observed warm clouds with little column water mass are more likely to rain than their corresponding shallow counterparts, despite having lower cloud-mean water contents. Given that these composite relationships were derived from statically identified warm clouds, an attempt is made to quantitatively explore rainfall occurrence within the context of the warm cloud life cycle. Extending a previously established cloud-top buoyancy analysis technique, it is shown that rainfall likelihoods from positively buoyant RAMS-simulated clouds more closely resemble the surprising observed relationships than do those derived from negatively buoyant simulated clouds. This suggests that relative to the depiction of warm clouds within the RAMS output, CloudSat observes higher proportions of positively buoyant, developing warm clouds. © 2015 American Meteorological Society."
"25941200000;8397494800;7410070663;48661551300;7403931916;","Estimation of errors in two-stream approximations of the solar radiative transfer equation for cloudy-sky conditions",2015,"10.1175/JAS-D-15-0033.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950341918&doi=10.1175%2fJAS-D-15-0033.1&partnerID=40&md5=9ba257e4d58a16e5849de20ac0828645","Solar flux densities and heating rates predicted by a broadband, multilayer d-Eddington two-stream approximation are compared to estimates from a Monte Carlo model that uses detailed descriptions of cloud particle phase functions and facilitates locally nonzero net horizontal flux densities. Results are presented as domain averages for 256-km sections of cloudy atmospheres inferred from A-Train satellite data: 32 632 samples for January 2007 between 70°S and 70°N with total cloud fraction C &gt; 0.05. The domains are meant to represent grid cells of a conventional global climate model and consist of columns of infinite width across track and Δx ≈ 1 km along track. The δ-Eddington was applied in independent column approximation (ICA) mode, while the Monte Carlo was applied using both Δx → 8 (i.e., ICA) and Δx ≈ 1 km. Mean-bias errors due to the δ-Eddington's neglect of phase function details and horizontal transfer, as functions of cosine of solar zenith angle μ0, are comparable in magnitude and have the same signs. With minor dependence on cloud particle sizes, the δ-Eddington over- and underestimates top-of-atmosphere reflected flux density for the cloudy portion of domains by ~10 W m-2 for μ0 &gt; 0.9 and -3 W m-2 for μ0 &lt; 0.2; full domain averages are ~8 and -2 W m-2, respectively, given mean C &gt; 0.75 for all μ0. These errors are reversed in sign, but slightly larger, for net surface flux densities. The δ-Eddington underestimates total atmospheric absorption by ~2.5 W m-2 on average. Hence, δ-Eddington mean-bias errors for domain-averaged layer heating rates are usually negative but can be positive. Rarely do they exceed ±10% of the mean heating rate; the largest errors are when the sides of liquid clouds are irradiated by direct beams. © 2015 American Meteorological Society."
"54384879100;56735558200;24177399000;56736109500;36651002800;6602470952;","Will tropical mountaintop plant species survive climate change? Identifying key knowledge gaps using species distribution modelling in Australia",2015,"10.1016/j.biocon.2015.07.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937946474&doi=10.1016%2fj.biocon.2015.07.022&partnerID=40&md5=fd8e839e4daa8930d921800af6ca8b2b","Species inhabiting tropical mountaintops may be most at risk from the detrimental effects of climate change. Yet few regional assessments have critically assessed the degree of threat to species in these habitats. Here we model under three climate scenarios the current and future suitable climate niche of 19 plant species endemic to tropical mountaintops in northeast Queensland, Australia. The suitable climate niche for each of the 19 species is predicted to decline by a minimum of 17% and maximum of 100% by 2040 (mean for all species of 81%) and minimum of 46% (mean for all species of 95%) by 2080. Seven species are predicted to have some suitable climate niche space reductions (ranging from 1 to 54% of their current suitable area) by 2080 under all three climate scenarios. Three additional species are projected to retain between 0.1 and 9% of their current distribution under one or two of the climate scenarios. In addition to these declines, which are predicted to occur over the next 30. years in northeast Queensland, we discuss and outline pressing research priorities that may be relevant for the conservation of biodiversity on tropical mountaintop environments across the globe. Specifically, further research is needed on thermal tolerances, acclimation potentials, and physiological constraints of tropical mountaintop taxa as current species distributions are primarily determined by climatic factors. © 2015 Elsevier B.V.."
"36931958000;7401666571;6602075440;9434771700;","Influence of explicit Phaeocystis parameterizations on the global distribution of marine dimethyl sulfide",2015,"10.1002/2015JG003017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956579036&doi=10.1002%2f2015JG003017&partnerID=40&md5=1bb25073454f004e7106f9009025a2ba","Dimethyl sulfide (DMS) is a biogenic organosulfur compound which contributes strongly to marine aerosol mass and the determination of cloud condensation nuclei over the remote oceans. Since uncertainties in DMS flux to the atmosphere lead to large variations in climate forcing, the global DMS distribution has been the subject of increasingly complex dynamic simulations. DMS concentrations are directly controlled by marine ecosystems. Phaeocystis is a major DMS producer but is often omitted from global reduced sulfur mechanisms. Here we incorporate this phytoplankton group into the marine ecosystem-biogeochemical module of the Community Earth System Model. To examine its role in the ocean sulfur cycle, an earlier DMS model has been enhanced to include new knowledge gained over the last few years. Results from the baseline run show that simulated Phaeocystis biomass generally agrees with observations, with high concentrations near the Antarctic continent and between 50° and 60° north. Given the new explicit Phaeocystis representation, the DMS distribution shows significant improvements, especially regarding the amplitude and location of high-latitude peaks. The simulated global mean surface DMS value is 2.26 nM, comparable to an estimate of 2.34 nM from the latest climatology extrapolated based on observations. The total oceanic DMS source to the atmosphere is 20.4 Tg S/yr, on the low side of previous estimates. Comparisons with and without Phaeocystis show that the group dominates DMS distributions in temperate and cold waters, contributing 13% of the global flux. The proportion may increase as sea ice declines and should be considered in climate projections. Key Points A detailed DMS model is updated with explicit global Phaeocystis ecology Simulated distributions of DMS flux and concentration are improved The role of Phaeocystis in the global sulfur cycle is evaluated. © 2015. The Authors."
"56896953300;6603273568;7005257933;15729555500;","Temporal changes in climatic limitation of tree-growth at upper treeline forests: Contrasted responses along the west-to-east humidity gradient in Northern Patagonia",2015,"10.1016/j.dendro.2015.09.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943604642&doi=10.1016%2fj.dendro.2015.09.001&partnerID=40&md5=aa4a2354d16c82ea7ba21222c2b99824","Over the last decades, gradual changes in summer climate in the Southern Hemisphere have affected forest growth in contrasting ways in moist and dry regions. Here, we use correlation analysis and a forward process-based model (Vaganov-Shashkin-Lite) to investigate changes in climate limitation of the interannual tree-ring growth of Nothofagus pumilio at the upper treeline along a precipitation gradient in northern Patagonia. Patterns of climate limitation vary consistently along the gradient. At mesic and humid treelines, tree-ring growth is positively related to growing season temperature and negatively to precipitation. At xeric treelines, the opposite is observed. Moreover, the climate-growth relations are not stationary. In particular, according to the model, the step decrease in precipitation in 1952 induced an increase of the moisture limitation at the dry edge of the gradient. Correlation analyses evidence that the dependence of growth on moisture after 1952 has enhanced since 1976. While the model consistently reproduces tree-ring width variations over the 1931-1975 period, it does not capture the growth patterns in the following years. Some environmental parameters (cloudiness, snowpack, atmospheric CO2) affecting moisture, radiation and stomatal aperture may have reached thresholds beyond which the effect on tree-growth has become sizable. © 2015 Elsevier GmbH."
"6602124129;7103158725;57213015562;57194512642;","Evaluating the potential of database technology for documenting environmental change in China's deserts",2015,"10.1016/j.catena.2014.12.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938955191&doi=10.1016%2fj.catena.2014.12.025&partnerID=40&md5=84949b8e1d3eeab9030667d5b208f63e","Despite decades of research, fundamental questions remain about how China's deserts and desert margins function, how they interact with regional and global scale environmental systems, and how they have responded to recent natural and anthropogenic forced climate change. The predominant focus of desert research in China, and globally, has been site specific case studies within sub-disciplines. This highly focused view makes development of a comprehensive interdisciplinary understanding of these deserts difficult. The fields of database creation, data mining and modern statistics have advanced the analysis of complex real-world data, however these methods enjoy only a relatively modest penetration into the geosciences. We report herein on the application of these new technologies to desert environmental systems in China, and illustrate the potential value of well-constructed databases and tool-rich analysis environments at regional, local and site specific scales. Regional analysis suggests significant warm season decrease and cold season increase in cloudiness in China's deserts suggesting that contrasts between cold and warm season cloudiness may be increasing. At a local and site specific scale at central China's Tengger Desert/Helan Mountains climate transition we find a significant climate forced greening of the desert margin over the past decade which may be reversing desertification trends aiding China's remediation efforts. We note that this new approach provides a ""living"" archive that allows capture of changes currently occurring in China's deserts as well as allowing assessments of human efforts to modify desert and desert margin environments. © 2014 Elsevier B.V.."
"25724813400;7201471897;55513577400;35490828000;7003627515;56016514800;","Recent surface mass balance from Syowa Station to Dome F, East Antarctica: comparison of field observations, atmospheric reanalyses, and a regional atmospheric climate model",2015,"10.1007/s00382-015-2512-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946473162&doi=10.1007%2fs00382-015-2512-6&partnerID=40&md5=2290f7463841ac2f8980e84d6c57154f","Stake measurements at 2 km intervals are used to determine the spatial and temporal surface mass balance (SMB) in recent decades along the Japanese Antarctic Research Expedition traverse route from Syowa Station to Dome F. To determine SMB variability at regional scales, this traverse route is divided into four regions, i.e., coastal, lower katabatic, upper katabatic and inland plateau. We also perform a regional evaluation of large scale SMB simulated by the regional atmospheric climate model versions 2.1 and 2.3 (RACMO2.1 and RACMO2.3), and the four more recent global reanalyses. Large-scale spatial variability in the multi-year averaged SMB reveals robust relationships with continentality and surface elevation. In the katabatic regions, SMB variability is also highly associated with surface slope, which in turn is affected by bedrock topography. Stake observation records show large inter-annual variability in SMB, but did not indicate any significant trends over both the last 40 years for the coastal and lower katabatic regions, and the last 20 years record for the upper katabatic and inland plateau regions. The four reanalyses and the regional climate model reproduce the macro-scale spatial pattern well for the multi-year averaged SMB, but fail to capture the mesoscale SMB increase at the distance interval ~300 to ~400 km from Syowa station. Thanks to the updated scheme in the cloud microphysics, RACMO2.3 shows the best spatial agreement with stake measurements over the inland plateau region. ERA-interim, JRA-55 and MERRA exhibit high agreement with the inter-annual variability of observed SMB in the coastal, upper katabatic and inland plateau regions, and moderate agreement in the lower katabatic region, while NCEP2 and RACMO2.1 inter-annual variability shows no significant correlation with the observations for the inland plateau region. © 2015, Springer-Verlag Berlin Heidelberg."
"56511027300;8678477400;16177612700;6603129131;","Variability of West African monsoon patterns generated by a WRF multi-physics ensemble",2015,"10.1007/s00382-015-2505-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946479158&doi=10.1007%2fs00382-015-2505-5&partnerID=40&md5=ff1bb670f62aa58b2b91e11764c2139e","The credibility of regional climate simulations over West Africa stands and falls with the ability to reproduce the West African monsoon (WAM) whose precipitation plays a pivotal role for people’s livelihood. In this study, we simulate the WAM for the wet year 1999 with a 27-member multi-physics ensemble of the Weather Research and Forecasting (WRF) model. We investigate the inter-member differences in a process-based manner in order to extract generalizable information on the behavior of the tested cumulus (CU), microphysics (MP), and planetary boundary layer (PBL) schemes. Precipitation, temperature and atmospheric dynamics are analyzed in comparison to the Tropical Rainfall Measuring Mission (TRMM) rainfall estimates, the Global Precipitation Climatology Centre (GPCC) gridded gauge-analysis, the Global Historical Climatology Network (GHCN) gridded temperature product and the forcing data (ERA-Interim) to explore interdependencies of processes leading to a certain WAM regime. We find that MP and PBL schemes contribute most to the ensemble spread (147 mm month−1) for monsoon precipitation over the study region. Furthermore, PBL schemes have a strong influence on the movement of the WAM rainband because of their impact on the cloud fraction, that ranges from 8 to 20 % at 600 hPa during August. More low- and mid-level clouds result in less incoming radiation and a weaker monsoon. Ultimately, we identify the differing intensities of the moist Hadley-type meridional circulation that connects the monsoon winds to the Tropical Easterly Jet as the main source for inter-member differences. The ensemble spread of Sahel precipitation and associated dynamics for August 1999 is comparable to the observed inter-annual spread (1979–2010) between dry and wet years, emphasizing the strong potential impact of regional processes and the need for a careful selection of model parameterizations. © 2015, The Author(s)."
"35146762200;35235647600;56225504000;56382254300;7403028059;","Dynamics of land surface temperature in the central Tien Shan Mountains",2015,"10.1659/MRD-JOURNAL-D-14-00001.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954202226&doi=10.1659%2fMRD-JOURNAL-D-14-00001.1&partnerID=40&md5=91619ea3a049a320deab22b6ce264ebe","Permafrost conditions in mountain ranges are sensitive to regional land surface temperature (LST), among other factors. To explore that relationship, this study carried out 3 steps: (1) validated Moderate Resolution Imaging Spectroradiometer 1-km daily LST data using data measured in situ, (2) used the Harmonic Analysis of Time Series (HANTS) algorithm for fitting and removing the influence of clouds, and (3) analyzed the spatial and temporal characteristics of LST dynamics in the central Tien Shan mountain range based on remote-sensing data improved by covariance and empirical orthogonal function analysis. The results indicate that the in situ data present a basic reference for rebuilding invalid values in the retrieved data, and the data gap in daily LST products can be logically reconstructed with the HANTS algorithm. Major long-term and large-scale patterns can be well extracted with the reconstructed LST data. The most dynamic and sensitive LST areas occurred in the buffers around the periglacial areas. Areas above the periglacial line mainly exhibited a decrease in LST, while areas below it showed an increase. This suggests that the periglacial line of the central Tien Shan region has risen during the past decade. These findings can provide a reference for how periglacial areas respond to climate change and how this may affect hydrological and ecological processes. © International Mountain Society."
"57004863900;18433849900;","Spring migration of Falconiformes in the southern Baikal migratory corridor: Peculiarities of migration and its relation with landscape–climatic conditions",2015,"10.1134/S199542551506013X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949934416&doi=10.1134%2fS199542551506013X&partnerID=40&md5=b70ed169ba329925176a4638e0d679d2","Based on the results of studying the spring migration of Falconiformes in 2011 and 2013, we have found that the southern Baikal migratory corridor, being a zone of migratory soaring bird concentration in eastern Siberia, plays one of the key roles not only in autumn, but also in spring. Outcomes on the abundance, species composition, and features of migratory behavior of birds have been made. In the course of long-term observations of Falconiformes, three patterns of their migratory movement through the southernmost part of Lake Baikal have been determined which are implemented depending on the cloud, wind, and ice situation. A relation between the intensity of spring migration observed and meteorological conditions on the migratory route has been found. Based on the example of four common species of daytime raptors, it is shown that they have different responses to weather changes during spring migration. © 2015, Pleiades Publishing, Ltd."
"50661685500;36562562600;55917254800;55701524500;55876526300;","Performance improvement techniques for geospatial web services in a cyberinfrastructure environment - A case study with a disaster management portal",2015,"10.1016/j.compenvurbsys.2015.04.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949728205&doi=10.1016%2fj.compenvurbsys.2015.04.003&partnerID=40&md5=eaa0b843d8fa11db1a6de900e94988eb","High population growth, urbanization, and global climate change drive up the frequency of disasters, affecting the safety of people's lives and property worldwide. Because of the inherent big-data nature of this disaster-related information, the processes of data exchange and transfer among physically distributed locations are increasingly challenging. This paper presents our proposed efficient network transmission model for interoperating heterogeneous geospatial data in a cyberinfrastructure environment. This transmission model supports multiple data encoding methods, such as GML (Geography Markup Language) and GeoJSON, as well as data compression/decompression techniques, including LZMA and DEFLATE. Our goal is to tackle fundamental performance issues that impact efficient retrieval of remote data. Systematic experiments were conducted to demonstrate the superiority of the proposed transmission model over the traditional OGC Web Feature Service (WFS) transmission model. The experiments also identified the optimized configuration for data encoding and compression techniques in different network environments. To represent a real-world user request scenario, the Amazon EC2 cloud platform was utilized to deploy multiple client nodes for the experiments. A web portal was developed to integrate the real-time geospatial web services reporting with real-time earthquake related information for spatial policy analysis and collaborative decision-making. © 2015 Elsevier Ltd."
"7003782348;55823600500;","A 22 month record of surface meteorology and energy balance from the ablation zone of Brewster Glacier, New Zealand",2015,"10.3189/2015JoG15J004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948748856&doi=10.3189%2f2015JoG15J004&partnerID=40&md5=ec5245e6a1b3fcf31f5f49abb3189de5","Multi-annual records of glacier surface meteorology and energy balance are necessary to resolve glacier-climate interactions but remain sparse, especially in the Southern Hemisphere. To address this, we present a record from the ablation zone of Brewster Glacier, New Zealand, between October 2010 and September 2012. The mean air temperature was 1.2°C at 1760ma.s.l., with only a moderate temperature difference between the warmest and coldest months (?8°C). Long-term annual precipitation was estimated to exceed 6000mma-1, with the majority of precipitation falling within a few degrees of the freezing level. The main melt season was between November and March (83% of annual ablation), but melt events occurred during all months. Annually, net radiation was positive (a source of energy) and supplied 64% of the melt energy, driven primarily by net shortwave radiation. Net longwave radiation was often positive during cloudy conditions in summer, demonstrating the radiative importance of clouds during melt. Turbulent sensible and latent heat fluxes were directed towards the surface in the summer months, accounting for just over a third of the energy for melt (34%). The energy gain associated with rainfall was small except during heavy events in summer."
"14027937700;24173639400;56506597700;9249731200;","Role of upper ocean processes in the seasonal SST evolution over tropical Indian Ocean in climate forecasting system",2015,"10.1007/s00382-015-2478-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945475683&doi=10.1007%2fs00382-015-2478-4&partnerID=40&md5=26e80becf459c481b979bc9b8ff14428","In this study role of upper ocean processes in the evolution of sea surface temperature (SST) seasonal variations over the tropical Indian Ocean (TIO) is investigated in climate forecast system version1 (CFSv1) and version2 (CFSv2). Analysis reveals that CFSv2 could capture seasonal evolution of SST, wind speed and mixed layer depth better than CFSv1 with some biases. Discrepancy in reproducing the evolution of seasonal SST in coupled models leads to bias in the spatial and temporal distribution of precipitation. This has motivated to carry out mixed layer heat budget analysis in determining seasonal evolution of TIO SST. Spatial pattern of mixed layer heat budget from observations and models suggest that the processes responsible for SST tendency differ from region to region over the TIO. Further it is found that models underestimated SST tendency compared to the observations. Misrepresentation of advective processes and heat flux (HF) over the TIO is mainly responsible for the distortion of seasonal SST change in the coupled models. Sub-regional heat budget analysis reveals that CFSv1 is unable to reproduce the annual cycle of mixed layer temperature (MLT) tendency over the Arabian Sea, while CFSv2 captured the annual cycle of SST with systematic cold bias. Misrepresentation of the annual cycles of net HF and horizontal advection (Hadv) are accountable for the low rate of change of MLT during most of the year. Hadv during summer season is underestimated by 50 and 25 % respectively in CFSv1 and CFSv2. Further, CFSv1 fails to simulate MLT tendency due to improper evolution of HF annual cycle over the Bay of Bengal. Though annual cycle of HF in CFSv2 is well represented over the Bay of Bengal, its contribution to MLT change is underestimated compared to observations. Over the southern TIO region, MLT tendency is dominated by HF and Hadv terms in both observations and models. Contribution of HF to the annual cycle of MLT tendency is underestimated in CFSv1 whereas it is overestimated in CFSv2. Contribution of Hadv to MLT change is underestimated by about 50 % in CFSv1 and 10–20 % in CFSv2 over southern TIO. These errors in HF and Hadv are associated with biases in HF components and surface wind representation. Evolution of lead–lag relationship between HF and MLT/SST in both the observations and models suggest the importance of HF in SST evolution over the TIO region. Over all, CFSv2 produced better SST seasonal/annual cycle in spite of having cold bias. This improvement in CFSv2  may be attributed to better cloud–aerosol–radiation physics, which reduces radiation biases. Updated land-surface, ocean and sea ice processes and ocean component may be responsible for improved circulation and annual cycle of ocean–atmospheric components (winds and ocean circulation). However, there is a requirement for improved parameterization of turbulent HF and radiation estimates in CFSv2 to reduce the cold SST bias. © 2015, Springer-Verlag Berlin Heidelberg."
"22953929700;7401672948;7005489435;7004353965;34768438000;","Object-based detection of Arctic sea ice and melt ponds using high spatial resolution aerial photographs",2015,"10.1016/j.coldregions.2015.06.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941600234&doi=10.1016%2fj.coldregions.2015.06.014&partnerID=40&md5=bfc2503fb47ca232de81d64c5ddc0bf1","High resolution aerial photographs used to detect and classify sea ice features can provide accurate physical parameters to refine, validate, and improve climate models. However, manually delineating sea ice and melt ponds is time-consuming and labor-intensive. In this study, an object-based classification algorithm is developed to automatically extract sea ice and melt ponds efficiently from 163 aerial photographs taken during the Chinese National Arctic Research Expedition in summer 2010 (CHINARE 2010) in the Arctic Pacific Sector. The photographs are selected from 599 cloud-free photographs based on their image quality and representativeness in the marginal ice zone (MIZ). The algorithm includes three major steps: (1) the image segmentation groups the neighboring pixels into objects according to the similarity of spectral and textural information; (2) the random forest ensemble classifier distinguishes four general classes: water, general submerged ice (GSI, including melt ponds and submerged ice along ice edges), shadow, and ice/snow; and (3) the polygon neighbor analysis further separates melt ponds and submerged ice from the GSI according to their spatial relationships. The overall classification accuracy for the four general classes is 95.5% based on 178 ground reference objects. Furthermore, the producer's accuracy of 90.8% and user's accuracy of 91.8% are achieved for melt pond detection through 98 independent reference objects. For the 163 photos examined, a total of 19,438 melt ponds larger than 1m2 are detected, with a pond density of 867.2km-2, mean pond size of 32.6±0.03m2, and mean pond fraction of 0.06±0.006; a total of 42,468 ice floes are detected, with the mean floe size of 173.3±0.1m2 (majority in 1-30m2) and mean ice concentration of 46.1±0.5% (ranging from 18.6-98.6%). These results matched well with ship-based visual observations in the MIZ in the same area and time. The method presented in the paper can be applied to data sets of high spatial resolution Arctic sea ice photographs for deriving detailed sea ice concentration, floe size, and melt pond distributions over wider regions, and extracting sea ice physical parameters and their corresponding changes between years. © 2015 Elsevier B.V."
"36169164600;7402385366;7003494809;","Mapping rice paddy extent and intensification in the Vietnamese Mekong River Delta with dense time stacks of Landsat data",2015,"10.1016/j.rse.2015.08.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941562954&doi=10.1016%2fj.rse.2015.08.004&partnerID=40&md5=7fe14752caeec1476c32a9f17f841ff1","Rice is a staple food crop for the majority of the world's population, yet paddy fields are threatened by urban expansion, climate change, and degraded agricultural land. Vietnam, one of the largest exporters of rice globally, grows most of its rice in the Mekong River Delta, but this low-lying and heavily populated area is susceptible to major land cover changes. To properly monitor and manage rice crops in this region, remote sensing with satellite imagery has been particularly useful; however, most efforts to map regional paddy area utilize coarse resolution MODIS or AVHRR data due to their high temporal frequency. Because the average size of a rice paddy field in the region is smaller than a coarse resolution pixel, we map the Mekong study area using finer-scale Landsat data collected across multiple growing seasons. First, we exploit dense Landsat time stacks for circa 2000 and circa 2010 to map rice paddy extent using vegetation trajectories, then combine these pixel-based rice maps with image-based segments to generate a polygon-based rice map. The results show that this method can map rice paddies with over 90% overall accuracy (and errors of omission and commission ranging from 6 to 25%) at a finer spatial resolution than previous efforts. Next, we differentiate between single-, double-, and triple-cropped rice paddies in the delta using a supervised classification based on exemplars of these different cropping trends. From circa 2000 to circa 2010, we find that triple-cropped rice fields have nearly doubled in area from one-third to nearly two-thirds of paddy area. Our work also highlights the importance of scenes that capture flooded fields, and the utility of cloud-covered scenes within the dense time stacks of data, to achieve higher classification accuracies. Methods to map rice paddies are vital to understanding the sustainability of these agricultural systems, and the work presented here makes strides toward routine monitoring at a field-level resolution. © 2015 Elsevier Inc."
"57201089191;37096609400;","Global energy and water balances in the latest reanalyses",2015,"10.1007/s13143-015-0079-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948472054&doi=10.1007%2fs13143-015-0079-0&partnerID=40&md5=9d8b37320a5ab67ae3aaf3217fca8e1d","The recently released Japanese 55-year Reanalysis (JRA- 55) data are evaluated and compared with three other global reanalyses, namely Interim version of the next European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim), Modern Era Retrospective-Analysis for Research and Applications (MERRA) and Climate Forecast System Reanalysis (CFSR), in terms of global energy and water balances. All four reanalyses show an energy imbalance at TOA and surface. Especially, clouds in JRA-55 are optically weaker than those in the three other reanalyses, leading to excessive outgoing longwave radiation, which in turn causes negative net energy flux at TOA. Moreover, JRA-55 has a negative imbalance at surface and at TOA, which is attributed to systematic positive biases in latent heat flux over the ocean. As for the global water balance, all reanalyses present a similar spatial pattern of the difference between evaporation and precipitation (E-P). However, JRA-55 has a relatively strong negative (positive) E-P in the Intertropical Convergence Zone and South Pacific Convergence Zone (extratropical regions) due to overestimated precipitation (evaporation), in spite of the global net being close to zero. In time series analysis, especially in E-P, significant stepwise changes occur in MERRA, CFSR and ERA-Interim due to the changes in the satellite observing system used in the data assimilation. Both MERRA and CFSR show a strong downward E-P shift in 1998, simultaneously with the start of the assimilation of AMSU-A sounding radiances. ERA-Interim exhibits an upward E-P shift in 1992 due to changes in observations from the SSM/I of new DMSP satellites. On the contrary, JRA-55 exhibits less trends and remains stable over time, which may be caused by newly available, homogenized observations and advances in data assimilation technique. © 2015, Korean Meteorological Society and Springer Science+Business Media Dordrecht."
"6603308366;55945667800;55625600000;7801425389;","An analog ensemble for short-term probabilistic solar power forecast",2015,"10.1016/j.apenergy.2015.08.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939814087&doi=10.1016%2fj.apenergy.2015.08.011&partnerID=40&md5=d94d0c7cfd19361811e2b1944f7ad13d","The energy produced by photovoltaic farms has a variable nature depending on astronomical and meteorological factors. The former are the solar elevation and the solar azimuth, which are easily predictable without any uncertainty. The amount of liquid water met by the solar radiation within the troposphere is the main meteorological factor influencing the solar power production, as a fraction of short wave solar radiation is reflected by the water particles and cannot reach the earth surface. The total cloud cover is a meteorological variable often used to indicate the presence of liquid water in the troposphere and has a limited predictability, which is also reflected on the global horizontal irradiance and, as a consequence, on solar photovoltaic power prediction. This lack of predictability makes the solar energy integration into the grid challenging. A cost-effective utilization of solar energy over a grid strongly depends on the accuracy and reliability of the power forecasts available to the Transmission System Operators (TSOs). Furthermore, several countries have in place legislation requiring solar power producers to pay penalties proportional to the errors of day-ahead energy forecasts, which makes the accuracy of such predictions a determining factor for producers to reduce their economic losses. Probabilistic predictions can provide accurate deterministic forecasts along with a quantification of their uncertainty, as well as a reliable estimate of the probability to overcome a certain production threshold. In this paper we propose the application of an analog ensemble (AnEn) method to generate probabilistic solar power forecasts (SPF). The AnEn is based on an historical set of deterministic numerical weather prediction (NWP) model forecasts and observations of the solar power. For each forecast lead time and location, the ensemble prediction of solar power is constituted by a set of past production data. These measurements are those concurrent to past deterministic NWP forecasts for the same lead time and location, chosen based on their similarity to the current forecast and, in the current application, are represented by the one-hour average produced solar power.The AnEn performance for SPF is compared to a quantile regression (QR) technique and a persistence ensemble (PeEn) over three solar farms in Italy spanning different climatic conditions. The QR is a state-of-the-science method for probabilistic predictions that, similarly to AnEn, is based on a historical data set. The PeEn is a persistence model for probabilistic predictions, where the most recent 20 power measurements available at the same lead-time are used to form an ensemble. The performance assessment has been carried out evaluating important attributes of a probabilistic system such as statistical consistency, reliability, resolution and skill. The AnEn performs as well as QR for common events, by providing predictions with similar reliability, resolution and sharpness, while it exhibits more skill for rare events and during hours with a low solar elevation. © 2015 Elsevier Ltd."
"9940013500;6601967252;55915206300;6602377428;7201479825;","Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record",2015,"10.5194/amt-8-4561-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946595033&doi=10.5194%2famt-8-4561-2015&partnerID=40&md5=66b0f40730fc3d3f3b89899bb2ab3bf3","Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA) Climate Data Record (CDR) currently comprising up to 24 years (1982-2006) of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS) stability requirements for desert reference sites. The limitation in quality due to non-removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. The first step consists of the application of a robust and reliable cloud mask, taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers, some clouds can still remain undetected. A second step relies on a post-processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high-quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR release. © 2015 Author(s)."
"7401615907;7005170782;7006228584;6602282959;35331416200;7102689617;7103167530;55910010100;","Marine atmospheric boundary layer and low-level cloud responses to the Kuroshio Extension front in the early summer of 2012: three-vessel simultaneous observations and numerical simulations",2015,"10.1007/s10872-014-0266-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942504291&doi=10.1007%2fs10872-014-0266-0&partnerID=40&md5=d400912be7f7a67db8a778849ec8caff","Intensive atmospheric observations were carried out with five research vessels in total across the sea surface temperature (SST) front along the Kuroshio Extension in the early summer of 2012, to identify the effects of the front on the thermal structure and cloud formation in the marine atmospheric boundary layer (MABL). Three of the vessels were aligned together along the 143°E meridian with latitudinal separation of as small as 30′ or 45′, going back and forth across the SST front for in situ observations during 2–6 July. The SST front was quite sharp and moved northward by about 50 km in 3 days, which was not well represented in objectively analyzed SST data sets. The observations captured rapid changes of the mesoscale MABL structure across the SST front, which were particularly evident in cloud base height and downward longwave radiation (DLR) at the surface. The higher base of low-level clouds observed over the warmer water resulted from stronger turbulent mixing in the MABL, which became prominent under the northerlies. The most frequently measured DLR value was greater by 20 W m−2 to the south of the SST front than to the north. High-resolution atmospheric model experiments conducted with and without the frontal SST gradient have confirmed its critical importance for the MABL structure and low-level clouds. These imprints of the SST front simulated in the models are sensitive to SST data assigned at the lower boundary of the model. © 2014, The Oceanographic Society of Japan and Springer Japan."
"55577875600;7406500188;55717074000;","Seasonality in anthropogenic aerosol effects on East Asian climate simulated with CAM5",2015,"10.1002/2015JD023451","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954391203&doi=10.1002%2f2015JD023451&partnerID=40&md5=019f9095bec229e234e305fb100b357d","This study investigates the seasonality in anthropogenic aerosol optical depth (AOD) distributions and their effects on clouds and precipitation in East Asia with the Community Atmospheric Model version 5. The differences between the model experiments with and without anthropogenic emissions exhibit a northward shift of the maximal AOD change in East Asia from March to July and then a southward withdrawal from September to November, which are induced by East Asian monsoon circulation. Associated with the shift, the direct and semidirect effects of the anthropogenic aerosols are the most pronounced in spring and summer, with a maximum center in North China during summer and a secondary center in South China during spring. The cloud liquid water path and shortwave cloud forcing changes, however, are the weakest in North China during summer. The indirect effect is the strongest in South China during spring, which is related to the large amount of middle-low level clouds in cold seasons in East China. A positive feedback between aerosol induced surface cooling and low-level cloud increase is identified in East China, which acts to enforce the aerosol indirect effect in spring. Accordingly, the climate response to the anthropogenic aerosols is also characterized by a northward shift of reduced precipitation from spring to summer, leading to a spring drought in South China and a summer drought in North China. The spring drought is attributed to both direct and indirect effects of the anthropogenic aerosols, while the summer drought is primarily determined by the aerosols’ direct effect. © 2015. American Geophysical Union. All Rights Reserved."
"56989640500;21935606200;36915461700;7102913661;","Aerosol-cloud associations over gangetic basin during a typical monsoon depression event using WRF-Chem simulation",2015,"10.1002/2015JD023634","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954379322&doi=10.1002%2f2015JD023634&partnerID=40&md5=c7543a39936b98bff00cc24c24fc2ce7","To study aerosol-cloud interactions over the Gangetic Basin of India, the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) has been applied to a typical monsoon depression event prevalent between the 23 and 29 August 2009. This event was sampled during the Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) aircraft campaign, providing measurements of aerosol and cloud microphysical properties from two sorties. Comparison of the simulated meteorological, thermodynamical, and aerosol fields against satellite and in situ aircraft measurements illustrated that the westward propagation of the monsoon depression and the cloud, aerosol, and rainfall spatial distribution was simulated reasonably well using anthropogenic emission rates from Monitoring Atmospheric Composition and Climate project along with cityZEN projects (MACCity)+Intercontinental Chemical Transport Experiment Phase B anthropogenic emission rates. However,the magnitude of aerosol optical depth was underestimated by up to 50%. A simulation with aerosol emissions increased by a factor of 6 over the CAIPEEX campaign domain increased the simulated aerosol concentrations to values close to the observations, mainly within boundary layer. Comparison of the low-aerosol simulation and high-aerosol simulation for the two sorties illustrated that more anthropogenic aerosols increased the cloud condensing nuclei (CCN) and cloud droplet mass concentrations. The number of simulated cloud droplets increased while the cloud droplet effective radii decreased, highlighting the importance of CCN-cloud feedbacks over this region. The increase in simulated anthropogenic aerosols (including absorbing aerosols) also increased the temperature of air parcels below clouds and thus the convective available potential energy (CAPE). The increase in CAPE intensified the updraft and invigorated the cloud, inducing formation of deeper clouds with more ice-phase hydrometeors for both cases. These case studies provide evidence of aerosol-induced cloud invigoration over the Gangetic Basin. © 2015. American Geophysical Union. All Rights Reserved."
"35096299800;7004299063;55893823700;57203200427;37099944400;35975039100;7407104838;24458137900;7004079572;53878006900;57207008570;6506373162;36097570900;23101759100;13403622000;55688930000;9249627300;","The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): Simulation design and preliminary results",2015,"10.5194/gmd-8-3379-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946011029&doi=10.5194%2fgmd-8-3379-2015&partnerID=40&md5=64316f8a1c196d65f5b77b6fec24bc15","We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities. © 2015 Author(s)."
"57001643600;7403295159;7402359452;","Impacts of the triggering function of cumulus parameterization on warm-season diurnal rainfall cycles at the Atmospheric Radiation Measurement Southern Great Plains Site",2015,"10.1002/2015JD023337","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954404426&doi=10.1002%2f2015JD023337&partnerID=40&md5=1eeaef3a97ca61f7e050cf9ac85150e6","In this study, we investigated the impacts of the triggering function of the deep convection scheme on diurnal rainfall variation in the middle latitudes by using the single-column version of the Community Atmospheric Model (SCAM). Using the climate statistics of a long-term ensemble analysis of SCAM simulations, we quantified and validated the diurnal rainfall climatological regimes at the Atmospheric Radiation Measurement Southern Great Plains (SGP) site. The results showed that the averaged diurnal rainfall cycle simulated using the default Zhang-Mcfarlane (ZM) scheme of the SCAM peaks near noon, which is far earlier than the observed nighttime peak phase. This bias was due to the ZM scheme, which produced spurious daytime rainfall, even during days in which only light rainfall was observed. By contrast, using a weather-focused scheme, the Simplified Arakawa-Schubert (SAS) scheme, we successfully simulated the nocturnal peak of the diurnal cycle. Experiments conducted on the ZM and SAS schemes featuring different triggering functions revealed that the relaxation of launching parcels above the planetary boundary layer (PBL) and the inclusion of convective inhibition (CIN) were crucial designs for the model to capture the nocturnal rainfall events of the SGP. The inclusion of CIN reduces spurious weak convective events, and the allowance of launching parcels being above the PBL better captures convective cloud base. The results of this study highlight the modulatory effect of low-level inhomogeneity on the diurnal variation of convection over midlatitudes and the importance of the triggering function of the deep convection scheme in capturing those variations. © 2015. American Geophysical Union. All Rights Reserved."
"23974991500;57201809600;6603376209;24484904900;","An evaluation and regional error modeling methodology for near-real-time satellite rainfall data over Australia",2015,"10.1002/2015JD023512","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954387506&doi=10.1002%2f2015JD023512&partnerID=40&md5=64b150f1e07978ac01f61619c31c557a","In providing uniform spatial coverage, satellite-based rainfall estimates can potentially benefit hydrological modeling, particularly for flood prediction. Maximizing the value of information from such data requires knowledge of its error. The most recent Tropical Rainfall Measuring Mission (TRMM) 3B42RT (TRMM-RT) satellite product version 7 (v7) was used for examining evaluation procedures against in situ gauge data across mainland Australia at a daily time step, over a 9 year period. This provides insights into estimating uncertainty and informing quantitative error model development, with methodologies relevant to the recently operational Global Precipitation Measurement mission that builds upon the TRMM legacy. Important error characteristics highlighted for daily aggregated TRMM-RT v7 include increasing (negative) bias and error variance with increasing daily gauge totals and more reliability at detecting larger gauge totals with a probability of detection of <0.5 for rainfall<~3 mm/d. Additionally, pixel location within clusters of spatially contiguous TRMM-RT v7 rainfall pixels (representing individual rain cloud masses) has predictive ability for false alarms. Differences between TRMM-RT v7 and gauge data have increasing (positive) bias and error variance with increasing TRMM-RT estimates. Difference errors binned within 10 mm/d increments of TRMM-RT v7 estimates highlighted negatively skewed error distributions for all bins, suitably approximated by the generalized extreme value distribution. An error model based on this distribution enables bias correction and definition of quantitative uncertainty bounds, which are expected to be valuable for hydrological modeling and/or merging with other rainfall products. These error characteristics are also an important benchmark for assessing if/how future satellite rainfall products have improved. © 2015. American Geophysical Union. All Rights Reserved."
"36681847100;6701827140;23095038400;","Fog climatology in Latvia",2015,"10.1007/s00704-014-1270-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942365147&doi=10.1007%2fs00704-014-1270-4&partnerID=40&md5=e450ee0a7c1a5eb7c04f369088906d32","Fog has been recognised as a hazardous weather phenomenon that can cause accidents and affect urban air quality negatively. Therefore, assessing the characteristics of fog formation, as well as the changes in fog frequency and intensity as a result of climate change is of high importance. This study covers a 52-year period and contains an analysis of the frequency of fog occurring, long-term changes in fog frequency and atmospheric conditions that favour the occurrence of fog events in Latvia. During the analysis, two inter-annual maxima of fog frequency were identified in the spring and autumn; the seasonal differences in the formation of fog were also confirmed using satellite observations of low-level cloudiness. However, the long-term changes of fog frequency showed a decrease tendency of fog to form, which may be associated with improvements in air quality since industrialization and the observed increase of air temperature. © 2014, Springer-Verlag Wien."
"56612060700;6603576275;","Impact of physical parameterization schemes on track and intensity of severe cyclonic storms in Bay of Bengal",2015,"10.1007/s00703-015-0381-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941998016&doi=10.1007%2fs00703-015-0381-5&partnerID=40&md5=784856f39a4c9ae487347c31b259f140","The objective of the present study is to investigate in detail the impact of different physical parameterization schemes on track and intensity of two severe cyclonic storms, AILA and JAL, which formed over Bay of Bengal, using a WRF mesoscale model. Three 2-way interactive nested domains with horizontal resolutions of 60, 20 and 6.6 km are used with initial and boundary conditions from NCEP-FNL data. Three sets of experiments include sensitivity to cumulus, microphysics and planetary boundary layer parameterization schemes, respectively. From cumulus parameterization experiments, Betts–Miller–Janjic is found to be better in the group. The strength of mid-latitude trough and presence of southward wind surge for cyclone AILA, the strength of the cross-equatorial flow as well as stronger easterly wind fields in the mid-tropospheric levels for cyclone JAL, and the amount of potential vorticity for both cyclones are some of the factors, which affect the large-scale flow and, hence, the track of both storms. WSM6 Microphysics scheme is able to produce a realistic feature of the cyclones as compared to the other schemes. The realistic representation of mid-tropospheric heating contributed by snow and graupel hydrometeors may be one of the reasons for better intensity simulation by WSM6. The higher values of relative humidity in and above the boundary layer favor the deep vertical mixing in YSU and thus contribute towards the better intensity simulation. © 2015, Springer-Verlag Wien."
"56158622800;55789476300;55723065600;6602252422;","Detection of anthropogenic dust using CALIPSO lidar measurements",2015,"10.5194/acp-15-11653-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929478466&doi=10.5194%2facp-15-11653-2015&partnerID=40&md5=0a14e2e5691e41d17269145639b0b955","Anthropogenic dusts are those produced by human activities on disturbed soils, which are mainly cropland, pastureland, and urbanized regions, and are a subset of the total dust load which includes natural sources from desert regions. Our knowledge of anthropogenic dusts is still very limited due to a lack of data. To understand the contribution of anthropogenic dust to the total global dust load, it is important to identify it apart from total dust. In this study, a new technique for distinguishing anthropogenic dust from natural dust is proposed by using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) dust and planetary boundary layer (PBL) height retrievals along with a land use data set. Using this technique, the global distribution of dust is analyzed and the relative contribution of anthropogenic and natural dust sources to regional and global emissions are estimated. Results reveal that local anthropogenic dust aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25 % of the global continental dust load. Of these anthropogenic dust aerosols, more than 53 % come from semi-arid and semi-wet regions. Annual mean anthropogenic dust column burden (DCB) values range from 0.42 g m-2, with a maximum in India, to 0.12 g m-2, with a minimum in North America. A better understanding of anthropogenic dust emission will enable us to focus on human activities in these critical regions and with such knowledge we will be more able to improve global dust models and to explore the effects of anthropogenic emission on radiative forcing, climate change, and air quality in the future. © Author(s) 2015."
"55403720400;55928817500;36705143500;","Predicting the mineral composition of dust aerosols - Part 1: Representing key processes",2015,"10.5194/acp-15-11593-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945290081&doi=10.5194%2facp-15-11593-2015&partnerID=40&md5=b4ec8d94722d58ad73f0714334824421","Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to measurements from North Africa shows that the model extensions result in better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles. © Author(s) 2015."
"7006661408;7005923979;7101689290;6603942738;9234020200;7402053012;56924760700;","High Mercury Wet Deposition at a ""clean Air"" Site in Puerto Rico",2015,"10.1021/acs.est.5b02430","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945290028&doi=10.1021%2facs.est.5b02430&partnerID=40&md5=f45669e29f7967e72d5732bc60e8a21c","Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds, during two complete years the site averaged 27.9 μg m-2 yr-1 wet Hg deposition, or about 30% more than Florida and the Gulf Coast, the highest deposition areas within the U.S. These high Hg deposition rates are driven in part by high rainfall, which averaged 2855 mm yr-1. The volume-weighted mean Hg concentration was 9.8 ng L-1, and was highest during summer and lowest during the winter dry season. Rainout of Hg (decreasing concentration with increasing rainfall depth) was minimal. The high Hg deposition was not supported by gaseous oxidized mercury (GOM) at ground level, which remained near global background concentrations (&lt;10 pg m-3). Rather, a strong positive correlation between Hg concentrations and the maximum height of rain detected within clouds (echo tops) suggests that droplets in high convective cloud tops scavenge GOM from above the mixing layer. The high wet Hg deposition at this ""clean air"" site suggests that other tropical areas may be hotspots for Hg deposition as well. © 2015 American Chemical Society."
"55730541100;35345729700;56919576300;24537168200;37089603000;55783064400;36171732700;7201787800;35759254100;57195257572;7006377579;7006235542;7006837187;","The importance of Asia as a source of black carbon to the European Arctic during springtime 2013",2015,"10.5194/acp-15-11537-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945144124&doi=10.5194%2facp-15-11537-2015&partnerID=40&md5=32c35c008833dfb51b2a0fbf0306dbd2","Black carbon aerosol (BC) deposited to the Arctic sea ice or present in the free troposphere can significantly affect the Earth's radiation budget at high latitudes yet the BC burden in these regions and the regional source contributions are poorly constrained. Aircraft measurements of aerosol composition in the European Arctic were conducted during the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) campaign in March 2013. Pollutant plumes were encountered throughout the lower to upper Arctic troposphere featuring enhancements in CO and aerosol mass loadings, which were chemically speciated into BC and non-refractory sulphate and organic matter. FLEXPART-WRF simulations have been performed to evaluate the likely contribution to the pollutants from regional ground sources. By combining up-to-date anthropogenic and open fire biomass burning (OBB) inventories, we have been able to compare the contributions made to the observed pollution layers from the sources of eastern/northern Asia (AS), Europe (EU) and North America (NA). Over 90% of the contribution to the BC was shown to arise from non-OBB anthropogenic sources. AS sources were found to be the major contributor to the BC burden, increasing background BC loadings by a factor of 3-5 to 100.8±48.4 ng sm-3 (in standard air m3 at 273.15K and 1013.25 mbar) and 55.8±22.4 ng sm-3 in the middle and upper troposphere respectively. AS plumes close to the tropopause (about 7.5-8 km) were also observed, with BC concentrations ranging from 55 to 73 ng sm-3, which will potentially have a significant radiative impact. EU sources influenced the middle troposphere with a BC mean concentration of 70.8±39.1 ng sm-3 but made a minor contribution to the upper troposphere due to the relatively high latitude of the source region. The contribution of NA was shown to be much lower at all altitudes with BC mean concentration of 20 ng sm-3. The BC transported to the Arctic is mixed with a non-BC volume fraction representing between 90-95% of the mass, and has a relatively uniform core size distribution with mass median diameter 190-210 nm and geometric standard deviation σg 1.55-1.65 and this varied little across all source regions. It is estimated that 60-95% of BC is scavenged between emission and receptor based on BC/δCO comparisons between source inventories and measurement. We show that during the springtime of 2013, the anthropogenic pollution particularly from sources in Asia, contributed significantly to BC across the European Arctic free troposphere. In contrast to previous studies, the contribution from open wildfires was minimal. Given that Asian pollution is likely to continue to rise over the coming years, it is likely that the radiative forcing in the Arctic will also continue to increase. © 2015 Author(s)."
"56694153100;55377275100;6701427420;8934166100;","Carbon stocks of mangroves within the Zambezi River Delta, Mozambique",2015,"10.1016/j.foreco.2015.06.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945485343&doi=10.1016%2fj.foreco.2015.06.027&partnerID=40&md5=65d5b2879272ff03f1ed6264b36f86c2","Mangroves are well-known for their numerous ecosystem services, including storing a globally significant C pool. There is increasing interest in the inclusion of mangroves in national climate change mitigation and adaptation plans in developing nations as they become involved with incentive programs for climate change mitigation. The quality and precision of data required by these programs necessitates the use of an inventory approach that allows for quantification, rather than general characterization, of C stocks. In this study, we quantified the ecosystem C stock of the Zambezi River Delta mangroves utilizing a rigorous, yet operationally feasible approach. We applied a stratified random sampling inventory design, based on five forest canopy height classes, derived from Ice, Cloud, and Land Elevation Satellite/Geoscience Laser Altimeter System (ICE Sat/GLAS) and the Shuttle Radar Topography Mission (SRTM) data, and a Spatial Decision Support System to allocate inventory plots. Carbon content in above- and below-ground biomass pools in addition to soils to a depth of 200cm was measured. The average biomass C density for the height classes ranged from 99.2MgCha-1 to 341.3MgCha-1. Soil C density was the largest measured C pool, containing 274.6MgCha-1 to 314.1MgCha-1 and accounting for 45-73% of the height class ecosystem C densities, which ranged from 373.8MgCha-1 to 620.8MgCha-1. The ecosystem C density estimates for the five strata were weighted based on their spatial distribution across the landscape to yield a total C stock for the Zambezi River Delta mangroves of 1.4×107MgC. The error bounds from the 95% confidence interval are ±6% of our ecosystem C stock estimate, well within acceptable levels of uncertainty. © 2015."
"56830597000;35605772300;","Geospatial monitoring and prioritization of forest fire incidences in Andhra Pradesh, India",2015,"10.1007/s10661-015-4821-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941286708&doi=10.1007%2fs10661-015-4821-y&partnerID=40&md5=4433ff80664ab57ce323dd95890298ff","Forest fire has been identified as one of the key environmental issue for long-term conservation of biodiversity and has impact on global climate. Spatially multiple observations are necessary for monitoring of forest fires in tropics for understanding conservation efficacy and sustaining biodiversity in protected areas. The present work was carried out to estimate the spatial extent of forest burnt areas and fire frequency using Resourcesat Advanced Wide Field Sensor (AWiFS) data (2009, 2010, 2012, 2013 and 2014) in Andhra Pradesh, India. The spatio-temporal analysis shows that an area of 7514.10 km2 (29.22 % of total forest cover) has been affected by forest fires. Six major forest types are distributed in Andhra Pradesh, i.e. semi-evergreen, moist deciduous, dry deciduous, dry evergreen, thorn and mangroves. Of the total forest burnt area, dry deciduous forests account for >75 %. District-wise analysis shows that Kurnool, Prakasam and Cuddapah have shown >100 km2 of burnt area every year. The total forest burnt area estimate covering protected areas ranges between 6.9 and 22.3 % during the study period. Spatial burnt area analysis for protected areas in 2014 indicates 37.2 % of fire incidences in the Nagarjunasagar Srisailam Tiger Reserve followed by 20.2 % in the Sri Lankamalleswara Wildlife Sanctuary, 20.1 % in the Sri Venkateswara Wildlife Sanctuary and 17.4 % in the Gundla Brahmeswaram Wildlife Sanctuary. The analysis of cumulative fire occurrences from 2009 to 2014 has helped in delineation of conservation priority hotspots using a spatial grid cell approach. Conservation priority hotspots I and II are distributed in major parts of study area including protected areas of the Nagarjunasagar Srisailam Tiger Reserve and Gundla Brahmeswaram Wildlife Sanctuary. The spatial database generated will be useful in studies related to influence of fires on species adaptability, ecological damage assessment and conservation planning. © 2015, Springer International Publishing Switzerland."
"55684491100;7102604282;56898519400;55245030000;56244407700;","Dehydration effects from contrails in a coupled contrail-climate model",2015,"10.5194/acp-15-11179-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943810827&doi=10.5194%2facp-15-11179-2015&partnerID=40&md5=65ff08c7bfd5a940c168ec9e2c8f46a1","The uptake of water by contrails in ice-supersaturated air and the release of water after ice particle advection and sedimentation dehydrates the atmosphere at flight levels and redistributes humidity mainly to lower levels. The dehydration is investigated by coupling a plume-scale contrail model with a global aerosol-climate model. The contrail model simulates all the individual contrails forming from global air traffic for meteorological conditions as defined by the climate model. The computed contrail cirrus properties compare reasonably with theoretical concepts and observations. The mass of water in aged contrails may exceed 106 times the mass of water emitted from aircraft. Many of the ice particles sediment and release water in the troposphere, on average 700 m below the mean flight levels. Simulations with and without coupling are compared. The drying at contrail levels causes thinner and longer-lived contrails with about 15 % reduced contrail radiative forcing (RF). The reduced RF from contrails is on the order of 0.06 W m-2, slightly larger than estimated earlier because of higher soot emissions. For normal traffic, the RF from dehydration is small compared to interannual variability. A case with emissions increased by 100 times is used to overcome statistical uncertainty. The contrails impact the entire hydrological cycle in the atmosphere by reducing the total water column and the cover by high- and low-level clouds. For normal traffic, the dehydration changes contrail RF by positive shortwave and negative longwave contributions on the order of 0.04 W m-2, with a small negative net RF. The total net RF from contrails and dehydration remains within the range of previous estimates. © 2015 Author(s)."
"7404061081;36611965700;7006421484;24329947300;7004174939;7101984634;","Towards a long-term global aerosol optical depth record: Applying a consistent aerosol retrieval algorithm to MODIS and VIIRS-observed reflectance",2015,"10.5194/amt-8-4083-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943626355&doi=10.5194%2famt-8-4083-2015&partnerID=40&md5=1828751ade712939b68b9f99630a4d25","To answer fundamental questions about aerosols in our changing climate, we must quantify both the current state of aerosols and how they are changing. Although NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) sensors have provided quantitative information about global aerosol optical depth (AOD) for more than a decade, this period is still too short to create an aerosol climate data record (CDR). The Visible Infrared Imaging Radiometer Suite (VIIRS) was launched on the Suomi-NPP satellite in late 2011, with additional copies planned for future satellites. Can the MODIS aerosol data record be continued with VIIRS to create a consistent CDR? When compared to ground-based AERONET data, the VIIRS Environmental Data Record (V-EDR) has similar validation statistics as the MODIS Collection 6 (M-C6) product. However, the V-EDR and M-C6 are offset in regards to global AOD magnitudes, and tend to provide different maps of 0.55 Î1/4m AOD and 0.55/0.86 Î1/4m-based Ångström Exponent (AE). One reason is that the retrieval algorithms are different. Using the Intermediate File Format (IFF) for both MODIS and VIIRS data, we have tested whether we can apply a single MODIS-like (ML) dark-target algorithm on both sensors that leads to product convergence. Except for catering the radiative transfer and aerosol lookup tables to each sensor's specific wavelength bands, the ML algorithm is the same for both. We run the ML algorithm on both sensors between March 2012 and May 2014, and compare monthly mean AOD time series with each other and with M-C6 and V-EDR products. Focusing on the March-April-May (MAM) 2013 period, we compared additional statistics that include global and gridded 1° andtimes; 1° AOD and AE, histograms, sampling frequencies, and collocations with ground-based AERONET. Over land, use of the ML algorithm clearly reduces the differences between the MODIS and VIIRS-based AOD. However, although global offsets are near zero, some regional biases remain, especially in cloud fields and over brighter surface targets. Over ocean, use of the ML algorithm actually increases the offset between VIIRS and MODIS-based AOD (to ∼ 0.025), while reducing the differences between AE. We characterize algorithm retrievability through statistics of retrieval fraction. In spite of differences between retrieved AOD magnitudes, the ML algorithm will lead to similar decisions about ""whether to retrieve"" on each sensor. Finally, we discuss how issues of calibration, as well as instrument spatial resolution may be contributing to the statistics and the ability to create a consistent MODIS' VIIRS aerosol CDR. © 2015 Author(s)."
"45661986200;57203492395;7102128820;34976155900;13411455700;36637844900;9536598800;6507112497;","The representation of the West African monsoon vertical cloud structure in the Met Office Unified Model: An evaluation with CloudSat",2015,"10.1002/qj.2614","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84952299658&doi=10.1002%2fqj.2614&partnerID=40&md5=bf55312ce9cdda377fe6c47e7a2a7c24","Weather and climate model simulations of the West African Monsoon (WAM) have generally poor representation of the rainfall distribution and monsoon circulation because key processes, such as clouds and convection, are poorly characterized. The vertical distribution of cloud and precipitation during the WAM are evaluated in Met Office Unified Model simulations against CloudSat observations. Simulations were run at 40 and 12 km horizontal grid length using a convection parametrization scheme and at 12, 4, and 1.5 km grid length with the convection scheme effectively switched off, to study the impact of model resolution and convection parametrization scheme on the organisation of tropical convection. Radar reflectivity is forward-modelled from the model cloud fields using the CloudSat simulator to present a like-with-like comparison with the CloudSat radar observations. The representation of cloud and precipitation at 12 km horizontal grid length improves dramatically when the convection parametrization is switched off, primarily because of a reduction in daytime (moist) convection. Further improvement is obtained when reducing model grid length to 4 or 1.5 km, especially in the representation of thin anvil and mid-level cloud, but three issues remain in all model configurations. Firstly, all simulations underestimate the fraction of anvils with cloud-top height above 12 km, which can be attributed to too low ice water contents in the model compared to satellite retrievals. Secondly, the model consistently detrains mid-level cloud too close to the freezing level, compared to higher altitudes in CloudSat observations. Finally, there is too much low-level cloud cover in all simulations and this bias was not improved when adjusting the rainfall parameters in the microphysics scheme. To improve model simulations of the WAM, more detailed and insitu observations of the dynamics and microphysics targeting these non-precipitating cloud types are required. © 2015 Royal Meteorological Society."
"25926762100;14045744500;22635190100;7402064802;7003582587;","Using regime analysis to identify the contribution of clouds to surface temperature errors in weather and climate models",2015,"10.1002/qj.2603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84952300009&doi=10.1002%2fqj.2603&partnerID=40&md5=429740fd4f4c2b18cbc1ac998acfe495","Many global circulation models (GCMs) exhibit a persistent bias in the 2 m temperature over the midlatitude continents, present in short-range forecasts as well as long-term climate simulations. A number of hypotheses have been proposed, revolving around deficiencies in the soil-vegetation-atmosphere energy exchange, poorly resolved low-level boundary-layer clouds or misrepresentations of deep-convective storms. A common approach to evaluating model biases focuses on the model-mean state. However, this makes difficult an unambiguous interpretation of the origins of a bias, given that biases are the result of the superposition of impacts of clouds and land-surface deficiencies over multiple time steps. This article presents a new methodology to objectively detect the role of clouds in the creation of a surface warm bias. A unique feature of this study is its focus on temperature-error growth at the time-step level. It is shown that compositing the temperature-error growth by the coinciding bias in total downwelling radiation provides unambiguous evidence for the role that clouds play in the creation of the surface warm bias during certain portions of the day. Furthermore, the application of an objective cloud-regime classification allows for the detection of the specific cloud regimes that matter most for the creation of the bias. We applied this method to two state-of-the-art GCMs that exhibit a distinct warm bias over the Southern Great Plains of the USA. Our analysis highlights that, in one GCM, biases in deep-convective and low-level clouds contribute most to the temperature-error growth in the afternoon and evening respectively. In the second GCM, deep clouds persist too long in the evening, leading to a growth of the temperature bias. The reduction of the temperature bias in both models in the morning and the growth of the bias in the second GCM in the afternoon could not be assigned to a cloud issue, but are more likely caused by a land-surface deficiency. © 2015 Royal Meteorological Society."
"7004922359;55620131400;55937797300;55620328100;7409102487;","The influence of shelf-sea fronts on winter monsoon over East China Sea",2015,"10.1007/s00382-014-2455-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943820015&doi=10.1007%2fs00382-014-2455-3&partnerID=40&md5=a246a967ad2fde65b8ee5ddd01556b63","Strong sea surface temperature fronts in open seas are known to affect the atmosphere. Shelf-sea fronts in winter have comparable strengths, yet their impacts on winds have not been studied. In January of 2012, a persistent, narrow band of cloud stretching 600–1,000 km was observed along the front of East China Sea (ECS). Numerical and analytical models show that the cloud was formed atop a recirculating cell induced by the front and, more generally, that β-plumes of low and high pressures emanate and spread far from fronts. Consistent with the theory, observations show that in ECS at inter-annual time scales, strong fronts co-vary with on-shelf convergent wind, strong northeasterly monsoon, and alongshelf alignment of clouds with low clouds near the coast and higher clouds offshore. Our results suggest that shelf-sea fronts are potentially an important dynamic determinant of climate variability of East Asia. © 2015, Springer-Verlag Berlin Heidelberg."
"24178522800;6701659989;","Can metric-based approaches really improve multi-model climate projections? The case of summer temperature change in France",2015,"10.1007/s00382-014-2445-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943813555&doi=10.1007%2fs00382-014-2445-5&partnerID=40&md5=815bc8dcdf30a824777beecd61c51e58","The multi-model ensemble mean is generally used as a default approach to estimate climate change signals, based on the implicit hypothesis that all models provide equally credible projections. As this hypothesis is unlikely to be true, it is in theory possible to obtain more realistic projections by giving more weight to more realistic models according to a relevant metric, if such a metric exists. This alternative approach however raises many methodological issues. In this study, a methodological framework based on a perfect model approach is described. It is intended to provide some useful elements of answer to these methodological issues. The basic idea is to take a random climate model and treat it as if it were the truth (or “synthetic observations”). Then, all the other members from the multi-model ensemble are used to derive thanks to a metric-based approach a posterior estimate of the future change, based on the synthetic observation of the metric. This posterior estimate can be compared to the synthetic observation of future change to evaluate the skill of the approach. This general framework is applied to future summer temperature change in France. A process-based metric, related to cloud-temperature interactions is tested, with different simple statistical methods to combine multiple model results (e.g. weighted average, model selection, regression.) Except in presence of large observational errors in the metric, metric-based methods using the metric related to cloud temperature interactions generally lead to large reductions of errors compared to the ensemble mean, but the sensitivity to methodological choices is important. © 2015, Springer-Verlag Berlin Heidelberg."
"55872832900;7405816725;","A model for absorption of solar radiation by mineral dust within liquid cloud drops",2015,"10.1016/j.jastp.2015.08.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940739195&doi=10.1016%2fj.jastp.2015.08.013&partnerID=40&md5=cb23e188ebc5603c96830eca0f17e3fd","Models of light scattering and absorption that consider the effect of insoluble inclusions present within liquid cloud droplets may assume the inclusion occupies random locations within the droplet. In certain cases, external forces can lead to certain orientations or alignments that are strongly preferred. Within this modeling study, we consider one such case in which an insoluble mineral dust inclusion (ρ=2.6g/cm3) is placed within a liquid water drop (ρ=1.0g/cm3). Such an instance mimics mineral dust aerosols being incorporated within cloud drops in Earth's atmosphere. Model results suggest super-micron mineral dust settles to the bottom of cloud droplets. However, Brownian motion largely randomizes the position of sub-micron mineral dust within the droplet. The inherent organization of the particles that result has important consequences for light absorption by mineral dust when present within a cloud drop. Modeled results suggest light absorption efficiency may be enhanced by as much as 4-6 fold for an isolated droplet experiencing direct solar illumination at solar zenith angles of &lt;20°. For such an isolated droplet, the absorption efficiency enhancement falls rapidly with increasing solar zenith angle indicating a strong angle of incidence dependence. We also consider the more common case of droplets that contain dust inclusions deep within optically dense clouds. Absorption efficiency enhancements for these locales follow a dramatically different pattern compared to the optically isolated droplet due to the presence of diffuse rather than direct solar irradiation. In such cases, light absorption efficiency is decreased through including super-micron dust within water droplets. The study has important implications for modeling the absorption of sunlight by mineral dust aerosol within liquid water clouds. The angle of incidence dependence also reveals that experimental measurement of light absorption for cases in which particle alignment occurs may not always accurately reflect atmospheric absorption of sunlight. Therefore, care must be taken to extrapolate measurement data to climate models. © 2015 Elsevier Ltd."
"25031430500;7004214645;7102976560;","Impact of aerosol radiative effects on 2000–2010 surface temperatures",2015,"10.1007/s00382-014-2464-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943819596&doi=10.1007%2fs00382-014-2464-2&partnerID=40&md5=93d13d29a8717dcf966ae7a4e789eaa4","Aerosol radiative forcing from direct and indirect effects of aerosols is examined over the recent past (last 10–15 years) using updated sulfate aerosol emissions in two Earth System Models with very different surface temperature responses to aerosol forcing. The hypothesis is that aerosol forcing and in particular, the impact of indirect effects of aerosols on clouds (Aerosol–Cloud Interactions, or ACI), explains the recent ‘hiatus’ in global mean surface temperature increases. Sulfate aerosol emissions increase globally from 2000 to 2005, and then decrease slightly to 2010. Thus the change in anthropogenic sulfate induced net global radiative forcing is small over the period. Regionally, there are statistically significant forcings that are similar in both models, and consistent with changes in simulated emissions and aerosol optical depth. Coupled model simulations are performed to look at impacts of the forcing on recent surface temperatures. Temperature response patterns in the models are similar, and reflect the regional radiative forcing. Pattern correlations indicate significant correlations between observed decadal surface temperature changes and simulated surface temperature changes from recent sulfate aerosol forcing in an equilibrium framework. Sulfate ACI might be a contributor to the spatial patterns of recent temperature forcing, but not to the global mean ‘hiatus’ itself. © 2015, Springer-Verlag Berlin Heidelberg."
"7006493632;57208579037;26324818700;56443331100;","Understanding the systematic air temperature biases in a coupled climate system model through a process-based decomposition method",2015,"10.1007/s00382-014-2435-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943814414&doi=10.1007%2fs00382-014-2435-7&partnerID=40&md5=560cab593851fe7a267e9d28514f9dc9","A quantitative attribution analysis is performed on the systematic atmospheric temperature biases in a coupled climate system model (flexible global ocean–atmosphere–land system model, spectral version 2) in reference to the European Center for Medium-Range Weather Forecasts, Re-analysis Interim data during 1979–2005. By adopting the coupled surface–atmosphere climate feedback response analysis method, the model temperature biases are related to model biases in representing the radiative processes including water vapor, ozone, clouds and surface albedo, and the non-radiative processes including surface heat fluxes and other dynamic processes. The results show that the temperature biases due to biases in radiative and non-radiative processes tend to compensate one another. In general, the radiative biases tend to dominate in the summer hemisphere, whereas the non-radiative biases dominate in the winter hemisphere. The temperature biases associated with radiative processes due to biases in ozone and water vapor content are the main contributors to the total temperature bias in the tropical and summer stratosphere. The overestimated surface albedo in both polar regions always results in significant cold biases in the atmosphere above in the summer season. Apart from these radiative biases, the zonal-mean patterns of the temperature biases in both boreal winter and summer are largely determined by model biases in non-radiative processes. In particular, the stronger non-radiative process biases in the northern winter hemisphere are responsible for the relatively larger ‘cold pole’ bias in the northern winter polar stratosphere. © 2014, Springer-Verlag Berlin Heidelberg."
"49962867200;7003633932;6603135083;","Coralline algae as a globally significant pool of marine dimethylated sulfur",2015,"10.1002/2015GB005274","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946543722&doi=10.1002%2f2015GB005274&partnerID=40&md5=90bb703b6c0efa662762074e93d73d53","Marine algae are key sources of the biogenic sulfur compound dimethylsulphoniopropionate (DMSP), a vital component of the marine sulfur cycle. Autotrophic ecosystem engineers such as red coralline algae support highly diverse and biogeochemically active ecosystems and are known to be high DMSP producers, but their importance in the global marine sulfur cycle has not yet been appreciated. Using a global sampling approach, we show that red coralline algae are a globally significant pool of DMSP in the oceans, estimated to be ~110 × 1012 moles worldwide during the summer months. Latitude was a major driver of observed regional-scale variations, with peaks in polar and tropical climate regimes, reflecting the varied cellular functions for DMSP (e.g., as a cryoprotectant and antioxidant). A temperate coralline algal bed was investigated in more detail to also identify local-scale temporal variations. Here, water column DMSP was driven by water temperature, and to a lesser extent, cloud cover; two factors which are also vital in controlling coralline algal growth. This study demonstrates that coralline algae harbor a large pool of dimethylated sulfur, thereby playing a significant role in both the sulfur and carbon marine biogeochemical cycles. However, coralline algal habitats are severely threatened by projected climate change; a loss of this habitat may thus detrimentally impact oceanic sulfur and carbon biogeochemical cycling. ©2015. The Authors."
"57202041815;57190574460;","Investigation of temporal change in glacial extent of Chitral watershed using Landsat data: a critique",2015,"10.1007/s10661-016-5565-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984869360&doi=10.1007%2fs10661-016-5565-z&partnerID=40&md5=18f64212a07c0b5ef0805df0aaaefc68","Himalayan glaciers are showing consistent signs of recession similar to glaciers elsewhere in the world with the exception of slight mass gain or stability in Karakoram. Deficient knowledge regarding the processes controlling the glacier dynamics together with remoteness, rugged terrain, insufficient in situ measurements, unsuitable datasets, and scanty network of meteorological stations has always been a big challenge in projecting future glacier dynamics in the region. Here, we present a number of scientific concerns regarding the appropriateness of data sets and methods adopted by a study carried out by Naeem et al. (2016), published in the journal of Environmental Monitoring and Assessment to investigate and project glacier dynamics in Chitral watershed using Landsat data. The use of predominantly snow and cloud covered satellite images especially for 2006 and 2007 strongly questions the glacier fluctuation estimates put forth by the authors. The inferences from existing scientific literature suggesting robustness of semi-automatic methods for glacier mapping challenge the use of unsupervised classification approach for delineating glacier extents as adopted in Naeem et al. (2016). Considering the scientific concerns and loopholes in the study by Naeem et al. (2016), the glacier fluctuations in Chitral watershed need to be reassessed. © 2016, Springer International Publishing Switzerland."
"35461763400;6701836226;55539832600;7004864963;56879858000;7006790175;55683878900;23479194900;7006495018;55957434200;57193567609;7005734412;55585274300;24448185400;55893745600;6701458964;6603545563;7005902195;41561458500;7003854090;57192645486;56179392600;6507532116;7003461830;57202747671;57197127548;36955999600;36930720800;7402428134;41661879600;56880368900;7004139928;35774441900;55942083800;7003929943;7102830450;7003424343;56830588700;6701530776;56880287200;56879983900;56879816400;50562006500;6507398267;36462896300;36996953300;55075942300;24172248700;56712019900;26434039800;11240127200;7006334079;55835550200;56879845700;35369409100;15733160400;57202110733;55056323800;7005579717;56572131500;53980757300;","The Amazon Tall Tower Observatory (ATTO): Overview of pilot measurements on ecosystem ecology, meteorology, trace gases, and aerosols",2015,"10.5194/acp-15-10723-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942764996&doi=10.5194%2facp-15-10723-2015&partnerID=40&md5=7efd465d3fc0b90d6ab1109f37864908","The Amazon Basin plays key roles in the carbon and water cycles, climate change, atmospheric chemistry, and biodiversity. It has already been changed significantly by human activities, and more pervasive change is expected to occur in the coming decades. It is therefore essential to establish long-term measurement sites that provide a baseline record of present-day climatic, biogeochemical, and atmospheric conditions and that will be operated over coming decades to monitor change in the Amazon region, as human perturbations increase in the future. <br><br> The Amazon Tall Tower Observatory (ATTO) has been set up in a pristine rain forest region in the central Amazon Basin, about 150 km northeast of the city of Manaus. Two 80 m towers have been operated at the site since 2012, and a 325 m tower is nearing completion in mid-2015. An ecological survey including a biodiversity assessment has been conducted in the forest region surrounding the site. Measurements of micrometeorological and atmospheric chemical variables were initiated in 2012, and their range has continued to broaden over the last few years. The meteorological and micrometeorological measurements include temperature and wind profiles, precipitation, water and energy fluxes, turbulence components, soil temperature profiles and soil heat fluxes, radiation fluxes, and visibility. A tree has been instrumented to measure stem profiles of temperature, light intensity, and water content in cryptogamic covers. The trace gas measurements comprise continuous monitoring of carbon dioxide, carbon monoxide, methane, and ozone at five to eight different heights, complemented by a variety of additional species measured during intensive campaigns (e.g., VOC, NO, NO<inf>2</inf>, and OH reactivity). Aerosol optical, microphysical, and chemical measurements are being made above the canopy as well as in the canopy space. They include aerosol light scattering and absorption, fluorescence, number and volume size distributions, chemical composition, cloud condensation nuclei (CCN) concentrations, and hygroscopicity. In this paper, we discuss the scientific context of the ATTO observatory and present an overview of results from ecological, meteorological, and chemical pilot studies at the ATTO site. © Author(s) 2015."
"23988450000;6701365566;","ROCADA: a gridded daily climatic dataset over Romania (1961–2013) for nine meteorological variables",2015,"10.1007/s11069-015-1757-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938961605&doi=10.1007%2fs11069-015-1757-z&partnerID=40&md5=8c4f63986abeea55c078fa32d9a4b4cc","Daily records of nine meteorological variables covering the interval 1961–2013 were used in order to create a state-of-the-art homogenized climatic dataset over Romania at a spatial resolution of 0.1°. All meteorological stations with full data records, as well as stations with up to 30 % missing data, were used for the following variables: air pressure (150 stations); minimum, maximum, and average air temperature (150 stations); soil temperature (127 stations); precipitation (188 stations); sunshine hours (135 stations); cloud cover (104 stations); relative humidity (150 stations). For each parameter, the data series were first homogenized with the software MASH (Multiple Analysis of Series for Homogenization); then, the data series were gridded by means of the software MISH (Meteorological Interpolation based on Surface Homogenized Data). The datasets are freely available on request on the PANGAEA data portal (doi.pangaea.de/10.1594/PANGAEA.833627). © 2015, Springer Science+Business Media Dordrecht."
"56263736800;7406118506;36537522100;7404592426;55388912500;55729410500;","Evaluation of modeled surface ozone biases as a function of cloud cover fraction",2015,"10.5194/gmd-8-2959-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942594843&doi=10.5194%2fgmd-8-2959-2015&partnerID=40&md5=d97c55c99db9d03ff1597da7bc1760d1","A regional air-quality forecast system's model of surface ozone variability based on cloud coverage is evaluated using satellite-observed cloud fraction (CF) information and a surface air-quality monitoring system. We compared CF and daily maximum ozone from the National Oceanic and Atmospheric Administration's National Air Quality Forecast Capability (NOAA NAQFC) with CFs from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the US Environmental Protection Agency's AirNow surface ozone measurements during May to October 2014. We found that observed surface ozone shows a negative correlation with the MODIS CFs, showing around 1 ppb decrease for 10 % MODIS CF change over the contiguous United States, while the correlation of modeled surface ozone with the model CFs is much weaker, showing only g'0.5 ppb per 10 % NAQFC CF change. Further, daytime CF differences between MODIS and NAQFC are correlated with modeled surface-ozone biases between AirNow and NAQFC, showing g'1.05 ppb per 10 % CF change, implying that spatial and temporal misplacement of the modeled cloud field might have biased modeled surface ozone level. Current NAQFC cloud fields seem to have fewer CFs compared to MODIS cloud fields (mean NAQFC CF Combining double low line 0.38 and mean MODIS CF Combining double low line 0.55), contributing up to 35 % of surface-ozone bias in the current NAQFC system. © 2015. CC Attribution 3.0 License."
"25637650700;6602390932;37095221700;57219113417;7003861526;6602903407;8132538500;55502994400;","A global aerosol classification algorithm incorporating multiple satellite data sets of aerosol and trace gas abundances",2015,"10.5194/acp-15-10597-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942800379&doi=10.5194%2facp-15-10597-2015&partnerID=40&md5=e65e343f15b7a3ce0745193978da8373","Detecting the optical properties of aerosols using passive satellite-borne measurements alone is a difficult task due to the broadband effect of aerosols on the measured spectra and the influences of surface and cloud reflection. We present another approach to determine aerosol type, namely by studying the relationship of aerosol optical depth (AOD) with trace gas abundance, aerosol absorption, and mean aerosol size. Our new Global Aerosol Classification Algorithm, GACA, examines relationships between aerosol properties (AOD and extinction Ångström exponent from the Moderate Resolution Imaging Spectroradiometer (MODIS), UV Aerosol Index from the second Global Ozone Monitoring Experiment, GOME-2) and trace gas column densities (NO2, HCHO, SO2 from GOME-2, and CO from MOPITT, the Measurements of Pollution in the Troposphere instrument) on a monthly mean basis. First, aerosol types are separated based on size (Ångström exponent) and absorption (UV Aerosol Index), then the dominating sources are identified based on mean trace gas columns and their correlation with AOD. In this way, global maps of dominant aerosol type and main source type are constructed for each season and compared with maps of aerosol composition from the global MACC (Monitoring Atmospheric Composition and Climate) model. Although GACA cannot correctly characterize transported or mixed aerosols, GACA and MACC show good agreement regarding the global seasonal cycle, particularly for urban/industrial aerosols. The seasonal cycles of both aerosol type and source are also studied in more detail for selected 5° &times; 5° regions. Again, good agreement between GACA and MACC is found for all regions, but some systematic differences become apparent: the variability of aerosol composition (yearly and/or seasonal) is often not well captured by MACC, the amount of mineral dust outside of the dust belt appears to be overestimated, and the abundance of secondary organic aerosols is underestimated in comparison with GACA. Whereas the presented study is of exploratory nature, we show that the developed algorithm is well suited to evaluate climate and atmospheric composition models by including aerosol type and source obtained from measurements into the comparison, instead of focusing on a single parameter, e.g., AOD. The approach could be adapted to constrain the mix of aerosol types during the process of a combined data assimilation of aerosol and trace gas observations. © Author(s) 2015."
"55441652200;55790072300;","A hybrid LS-HE and LS-SVM model to predict time series of precipitable water vapor derived from GPS measurements",2015,"10.1007/s12517-014-1716-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940437908&doi=10.1007%2fs12517-014-1716-0&partnerID=40&md5=fcbadce9ad6bf630e9b070da6830298b","Precipitable water vapor (PWV) is one of the key parameters for the analysis of global climate systems, formation of clouds, and short-term forecasts of precipitation. Since water vapor is highly variable both spatially and temporally, it can be problematic, requiring modeling and efficient techniques in order to measure its quantity. Global Positioning System (GPS) stations provide total water column at high quality under all weather conditions with high temporal resolution. The technique used in this work is Precise Point Positioning (PPP) for single dual-frequency GPS receiver aided by precise orbit and clock product. Zenith wet delay (ZWD) is estimated through a stochastic process called random walk at 5-min intervals. The seasonal and diurnal variations of PWV for four GPS stations located in Europe are investigated. Latitude and station height are the most influential factors for the amount of water vapor when we compare their amplitudes and offsets to NASA Water Vapor Dataset-M (NVAP-M) and station heights. The area-averaged accumulated rain time series retrieved from Tropical Rainfall Measuring Mission (TRMM) product also shows that high PWV levels do not necessarily lead to rainfall. The amplitudes of diurnal and semi-diurnal variations are found to be of much lower amount than those of seasonal variations. In order to validate the capability of GPS-sensed PWV measurements, two episodes in wintertime and summertime are simulated using Weather Research Forecast (WRF) model. Both simulated PWV and observational PWV are consistent with each other. The main objective of this paper is to model and forecast the PWV time series which would be useful information on climatology and meteorology. Due to the distinct harmonic characteristics of PWV time series, the least squares harmonic estimation (LS-HE) is applied to time series of PWV derived from 4-year GPS station observations. Subsequently, least squares support vector machine (LS-SVM) optimized by cross-validation strategy is used to model non-harmonic components of the signal. The underlying motivation for using LS-SVM is the proficiency of this methodology to precisely model time series data when the underlying model is usually non-stationary, not defined a priori, and non-linear which are major characteristics of PWV data. The modeled time series shows that the hybrid approach (LS-HE and LS-SVM) can efficiently filter white noise in the observations and then perform forecasting. The bias (∼0.37 mm) and standard deviation (∼3 mm) of observed and predicted values presents the sound capability of the proposed model. © 2014, Saudi Society for Geosciences."
"46661485700;6507975139;55940639700;","A novel approach for the extraction of cloud motion vectors using airglow imager measurements",2015,"10.5194/amt-8-3893-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942455932&doi=10.5194%2famt-8-3893-2015&partnerID=40&md5=b17d65aca260b34fff7a85ef66ace6e7","The paper explores the possibility of implementing an advanced photogrammetric technique, generally employed for satellite measurements, on airglow imager, a ground-based remote sensing instrument primarily used for upper atmospheric studies, measurements of clouds for the extraction of cloud motion vectors (CMVs). The major steps involved in the algorithm remain the same, including image processing for better visualization of target elements and noise removal, identification of target cloud, setting a proper search window for target cloud tracking, estimation of cloud height, and employing 2-D cross-correlation to estimate the CMVs. Nevertheless, the implementation strategy at each step differs from that of satellite, mainly to suit airglow imager measurements. For instance, climatology of horizontal winds at the measured site has been used to fix the search window for target cloud tracking. The cloud height is estimated very accurately, as required by the algorithm, using simultaneous collocated lidar measurements. High-resolution, both in space and time (4 min), cloud imageries are employed to minimize the errors in retrieved CMVs. The derived winds are evaluated against MST radar-derived winds by considering it as a reference. A very good correspondence is seen between these two wind measurements, both showing similar wind variation. The agreement is also found to be good in both the zonal and meridional wind velocities with RMSEs &lt; 2.4 m s-1. Finally, the strengths and limitations of the algorithm are discussed, with possible solutions, wherever required."
"54895907100;57198706734;56870876200;","Improved simulation of precipitation in the tropics using a modified BMJ scheme in the WRF model",2015,"10.5194/gmd-8-2915-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942362035&doi=10.5194%2fgmd-8-2915-2015&partnerID=40&md5=8b04c8e24819fc5b4a026121bfeae39f","The successful modelling of the observed precipitation, a very important variable for a wide range of climate applications, continues to be one of the major challenges that climate scientists face today. When the Weather Research and Forecasting (WRF) model is used to dynamically downscale the Climate Forecast System Reanalysis (CFSR) over the Indo-Pacific region, with analysis (grid-point) nudging, it is found that the cumulus scheme used, Betts-Miller-Janjić (BMJ), produces excessive rainfall suggesting that it has to be modified for this region. Experimentation has shown that the cumulus precipitation is not very sensitive to changes in the cloud efficiency but varies greatly in response to modifications of the temperature and humidity reference profiles. A new version of the scheme, denoted ""modified BMJ"" scheme, where the humidity reference profile is more moist, was developed. In tropical belt simulations it was found to give a better estimate of the observed precipitation as given by the Tropical Rainfall Measuring Mission (TRMM) 3B42 data set than the default BMJ scheme for the whole tropics and both monsoon seasons. In fact, in some regions the model even outperforms CFSR. The advantage of modifying the BMJ scheme to produce better rainfall estimates lies in the final dynamical consistency of the rainfall with other dynamical and thermodynamical variables of the atmosphere. © Author(s) 2015."
"56871105000;7102082564;9239400200;6701313416;","The impact of oceanic heat transport on the atmospheric circulation",2015,"10.5194/esd-6-591-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942315356&doi=10.5194%2fesd-6-591-2015&partnerID=40&md5=a2b4ab253ba5fca4ea8b59ff030f2744","A general circulation model of intermediate complexity with an idealized Earth-like aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric circulation. Focus is on the atmospheric mean meridional circulation and global thermodynamic properties. <br><br> The atmosphere counterbalances to a large extent the imposed changes in the oceanic heat transport, but, nonetheless, significant modifications to the atmospheric general circulation are found. Increasing the strength of the oceanic heat transport up to 2.5 PW leads to an increase in the global mean near-surface temperature and to a decrease in its equator-to-pole gradient. For stronger transports, the gradient is reduced further, but the global mean remains approximately constant. This is linked to a cooling and a reversal of the temperature gradient in the tropics. <br><br> Additionally, a stronger oceanic heat transport leads to a decline in the intensity and a poleward shift of the maxima of both the Hadley and Ferrel cells. Changes in zonal mean diabatic heating and friction impact the properties of the Hadley cell, while the behavior of the Ferrel cell is mostly controlled by friction. <br><br> The efficiency of the climate machine, the intensity of the Lorenz energy cycle and the material entropy production of the system decline with increased oceanic heat transport. This suggests that the climate system becomes less efficient and turns into a state of reduced entropy production as the enhanced oceanic transport performs a stronger large-scale mixing between geophysical fluids with different temperatures, thus reducing the available energy in the climate system and bringing it closer to a state of thermal equilibrium. © 2015 Author(s)."
"7101723095;57200264463;26639803600;","Detection of Asian dust storms from geostationary satellite observations of the INSAT-3D imager",2015,"10.1080/01431161.2015.1084432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943411594&doi=10.1080%2f01431161.2015.1084432&partnerID=40&md5=e688183b69a3fce9795d11f2a7a55804","Asian dust storm outbreaks significantly influence air quality, weather, and climate. Therefore, it is desirable to have qualitative and quantitative information on the time, location, and coverage of these outbreaks at high spatial and temporal resolution. The imager on board the Indian metrological geostationary satellite INSAT-3D observes Asia at a temporal resolution of 30 min and a spatial resolution of 1, 4, 8, and 4 km in the visible, middle infrared (MIR), water vapour (WV), and thermal infrared (TIR) bands, respectively. In this article, an algorithm is described for detecting desert dust storms from INSAT-3D imager data. The algorithm described here is a combination of various pre-existing methods such as infrared split-window, MIR and TIR brightness temperature difference, and visible to MIR reflectance ratio, which are based on the fact that dust exhibits features of spectral dependence and contrast over the visible, MIR, and TIR spectrum that are different from clouds, surface, and clear-sky atmosphere. Using the Atmospheric Infrared Sounder (Aqua/AIRS) dust score as proxy, INSAT-3D dust storm products were tested under different scenarios such as dust storms and dust transport in Asia. TIR observations from the geostationary platform of INSAT-3D allows computation of the infrared difference dust index (IDDI), which gives a quantitative measure of dust loading relative to clear atmosphere. Moreover, due to the high temporal resolution (30 min) of INSAT-3D observations, INSAT-3D-derived dust products allow more precise monitoring of dust transportation as compared with dust products derived from polar satellite observations. © 2015 Taylor & Francis."
"8898737800;12645767500;7202899330;","Sensitivity analysis of polarimetric O2 A-band spectra for potential cloud retrievals using OCO-2/GOSAT measurements",2015,"10.5194/amt-8-3601-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941047431&doi=10.5194%2famt-8-3601-2015&partnerID=40&md5=0da88ccf7a8d6a537672774013e828c4","Clouds play a crucial role in Earth's radiative budget, yet their climate feedbacks are poorly understood. The advent of space-borne high resolution spectrometers probing the O2 A band, like GOSAT and OCO-2, could make it possible to simultaneously retrieve vertically resolved cloud parameters that play a vital role in Earth's radiative budget, thereby allowing a reduction of the corresponding uncertainty due to clouds. Such retrievals would also facilitate air mass bias reduction in corresponding measurements of CO2 columns. In this work, the hyperspectral, polarimetric response of the O2 A band to mainly three important cloud parameters, viz., optical thickness, top height and droplet size has been studied, revealing a different sensitivity to each for the varying atmospheric absorption strength within the A band. Cloud optical thickness finds greatest sensitivity in intensity measurements, the sensitivity of other Stokes parameters being limited to low cloud optical thicknesses. Cloud height had a negligible effect on intensity measurements at non-absorbing wavelengths but finds maximum sensitivity at an intermediate absorption strength, which increases with cloud height. The same is found to hold for cloud geometric thickness. The geometry-dependent sensitivity to droplet size is maximum at non-absorbing wavelengths and diminishes with increasing absorption strength. It has been shown that significantly more information on droplet size can be drawn from multi-angle measurements. We find that, in the absence of sunglint, the backscatter hemisphere (scattering angle larger than 90°) is richer in information on droplet size, especially in the glory and rainbow regions. It has been shown that I and Q generally have differing sensitivities to all cloud parameters. Thus, accurate measurements of two orthogonal components IP and IS (as in GOSAT) are expected to contain more information than measurements of only I, Ih or Iv (as in the case of OCO-2). © Author(s) 2015."
"6603198149;9639143500;7007049991;23028170700;7006712738;7404894686;7404104801;26643531100;35432672900;56711026200;6701329415;35357335300;7005973015;","Coordinated Hubble Space Telescope and Venus Express Observations of Venus' upper cloud deck",2015,"10.1016/j.icarus.2015.05.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84935445297&doi=10.1016%2fj.icarus.2015.05.027&partnerID=40&md5=1b66a7ce51ef30466302902a881241a7","Hubble Space Telescope Imaging Spectrograph (HST/STIS) UV observations of Venus' upper cloud tops were obtained between 20N and 40S latitude on December 28, 2010; January 22, 2011 and January 27, 2011 in coordination with the Venus Express (VEx) mission. The high spectral (0.27nm) and spatial (40-60km/pixel) resolution HST/STIS data provide the first direct and simultaneous record of the latitude and local time distribution of Venus' 70-80km SO and SO2 (SOx) gas density on Venus' morning quadrant. These data were obtained simultaneously with (a) VEx/SOIR occultation and/or ground-based James Clerk Maxwell Telescope sub-mm observations that record respectively, Venus' near-terminator SO2 and dayside SOx vertical profiles between ~75 and 100km; and (b) 0.36μm VEx/VMC images of Venus' cloud-tops. Updating the (Marcq, E. et al. [2011]. Icarus 211, 58-69) radiative transfer model SO2 gas column densities of ~2-10μm-atm and ~0.4-1.8μm-atm are retrieved from the December 2010 and January 2011 HST observations, respectively on Venus' dayside (i.e., at solar zenith angles (SZA)&lt;60°); SO gas column densities of 0.1-0.11μm-atm, 0.03-0.31μm-atm and 0.01-0.13μm-atm are also retrieved from the respective December 28, 2010, January 22, 2011 and January 27, 2011 HST observations. A decline in the observed low-latitude 0.24 and 0.36μm cloud top brightness paralleled the declining SOx gas densities. On December 28, 2010 SO2 VMR values ~280-290ppb are retrieved between 74 and 81km from the HST and SOIR data obtained near Venus' morning terminator (at SZAs equal to 70° and 90°, respectively); these values are 10× higher than the HST-retrieved January 2011 near terminator values. Thus, the cloud top SO2 gas abundance declined at all local times between the three HST observing dates. On all dates the average dayside SO2/SO ratio inferred from HST between 70 and 80km is higher than that inferred from the sub-mm the JCMT data above 84km confirming that SOx photolysis is more efficient at higher altitudes. The direct correlation of the SOx gases provides the first clear evidence that SOx photolysis is not the only source for Venus' 70-80km sulfur reservoir. The cloud top SO2 gas density is dependent in part on the vertical transport of the gas from the lower atmosphere; and the 0.24μm cloud top brightness levels are linked to the density of the sub-micron haze. Thus, the new results may suggest a correlation between Venus' cloud-top sub-micron haze density and the vertical transport rate. These new results must be considered in models designed to simulate and explore the relationship between Venus' sulfur chemistry cycle, H2SO4 cloud formation rate and climate evolution. Additionally, we present the first photochemical model that uniquely tracks the transition of the SO2 atmosphere from steady to non-steady state with increasing SZA, as function of altitude within Venus' mesosphere, showing the photochemical and dynamical basis for the factor of ~2 enhancements in the SOx gas densities observed by HST near the terminator above that observed at smaller SZA. These results must also be considered when modeling the long-term evolution of Venus' atmospheric chemistry and dynamics. © 2015 Elsevier Inc."
"55847411500;18438882300;37122239200;12040723700;","Spatial variability of tephra and carbon accumulation in a Holocene peatland",2015,"10.1016/j.quascirev.2015.07.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939147666&doi=10.1016%2fj.quascirev.2015.07.025&partnerID=40&md5=1e450ccd4800904cb9f8088759e79cc9","Microscopic tephra layers ('cryptotephras') represent important age-equivalent stratigraphic markers utilised in many palaeoenvironmental reconstructions. When used in conjunction with proximal records of volcanic activity they can also provide information about volcanic ash cloud fallout and frequency. However, the spatial distributions of tephra layers can be discontinuous even within the same region. Understanding the deposition and post-depositional redistribution of tephra is vital if we are to use cryptotephras as records of ash cloud occurrence and chronostratigraphic markers. The discrete nature of tephra layers also allows for detailed study into processes of deposition and reworking which affect many palaeoenvironmental proxy records.We undertook a multi-core study in order to examine the historical tephrostratigraphy of a raised peatland in Northern Ireland. Three tephra layers originating from Iceland (Hekla 1947, Hekla 1845 and Hekla 1510) are present in 14 of the 15 cores analysed. This suggests that in areas not influenced by snowfall or anthropogenic disturbance at the time of tephra delivery, the presence or absence of a tephra layer is generally consistent across a peatland of this type. However, tephra shard counts (per unit area) vary by an order of magnitude between cores. These intra-site differences may confound the interpretation of shard counts from single cores as records of regional ash cloud mass/density. Bootstrap resampling analysis suggests that total shard counts from multiple cores are required in order to make a reliable estimate of median shard counts for a site. The presence of three historical tephras in 14 cores enables a spatio-temporal analysis of the long-term apparent rate of carbon accumulation (LARCA) in the peatland. Substantial spatial and temporal variations in LARCA are identified over the last ~450 years. This high variability needs to be taken into account when designing studies of peatland carbon accumulation. © 2015 The Authors."
"26664385000;35205746400;","Stable isotopes reveal sources of precipitation in the Qinghai Lake Basin of the northeastern Tibetan Plateau",2015,"10.1016/j.scitotenv.2015.04.105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929492590&doi=10.1016%2fj.scitotenv.2015.04.105&partnerID=40&md5=02dfe1af2df45c3725539b717350da67","The use of isotopic tracers is an effective approach for characterizing the moisture sources of precipitation in cold and arid regions, especially in the Tibetan Plateau (TP), an area of sparse human habitation with few weather and hydrological stations. This study investigated stable isotope characteristics of precipitation in the Qinghai Lake Basin, analyzed moisture sources using data sets from NCEP-NCAR, and calculated vapor contributions from lake evaporation to the precipitation in the basin using a two-component mixing model. Results showed that the Local Meteoric Water Line (LMWL) was defined as δ2H=7.86 δ18O+15.01, with a slope of less than 8, indicating that some non-equilibrium evaporation processes occurred when the drops fell below the cloud base. Temperature effects controlled δ18O and δ2H in precipitation in the basin, with high values in summer season and low values in winter season. Moisture in the basin was derived predominantly from the Southeast Asian Monsoon (SEAM) from June to August and the Westerly Circulation (WC) from September through May. Meanwhile, the transition in atmospheric circulation took place in June and September. The SEAM strengthened gradually, while the WC weakened gradually in June, and inversely in September. However, the Southwest Asian Monsoon (SWAM) did not reach the Qinghai Lake Basin due to the barrier posed by Tanggula Mountain. High d-excess (>10‰) and significant altitude and lake effects of δ18O in precipitation suggested that the vapor evaporated from Qinghai Lake, strongly influenced annual precipitation, and affected the regional water cycle in the basin distinctly. The monthly contribution of lake evaporation to basin precipitation ranged from 3.03% to 37.93%, with an annual contribution of 23.42% or 90.54mm, the majority of which occurred in the summer season. The findings demonstrate that the contribution of evaporation from lakes to atmospheric vapor is fundamental to water cycling on the TP. © 2015 Elsevier B.V."
"54982705800;7006304904;7004713805;7006784145;24343173500;8657166100;25522357400;","A new chemistry option in WRF-Chem v. 3.4 for the simulation of direct and indirect aerosol effects using VBS: Evaluation against IMPACT-EUCAARI data",2015,"10.5194/gmd-8-2749-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924731478&doi=10.5194%2fgmd-8-2749-2015&partnerID=40&md5=d9ff3dbd31ebb9f698b3c8827304f9f4","A parameterization for secondary organic aerosol (SOA) production based on the volatility basis set (VBS) approach has been coupled with microphysics and radiative schemes in the Weather Research and Forecasting model with Chemistry (WRF-Chem) model. The new chemistry option called ""RACM-MADE-VBS-AQCHEM"" was evaluated on a cloud resolving scale against ground-based and aircraft measurements collected during the IMPACT-EUCAARI (Intensive Cloud Aerosol Measurement Campaign - European Integrated project on Aerosol Cloud Climate and Air quality interaction) campaign, and complemented with satellite data from MODIS. The day-to-day variability and the diurnal cycle of ozone (O3) and nitrogen oxides (NOx) at the surface are captured by the model. Surface aerosol mass concentrations of sulfate (SO4), nitrate (NO3), ammonium (NH4), and organic matter (OM) are simulated with correlations larger than 0.55. WRF-Chem captures the vertical profile of the aerosol mass concentration in both the planetary boundary layer (PBL) and free troposphere (FT) as a function of the synoptic condition, but the model does not capture the full range of the measured concentrations. Predicted OM concentration is at the lower end of the observed mass concentrations. The bias may be attributable to the missing aqueous chemistry processes of organic compounds and to uncertainties in meteorological fields. A key role could be played by assumptions on the VBS approach such as the SOA formation pathways, oxidation rate, and dry deposition velocity of organic condensable vapours. Another source of error in simulating SOA is the uncertainties in the anthropogenic emissions of primary organic carbon. Aerosol particle number concentration (condensation nuclei, CN) is overestimated by a factor of 1.4 and 1.7 within the PBL and FT, respectively. Model bias is most likely attributable to the uncertainties of primary particle emissions (mostly in the PBL) and to the nucleation rate. Simulated cloud condensation nuclei (CCN) are also overestimated, but the bias is more contained with respect to that of CN. The CCN efficiency, which is a characterization of the ability of aerosol particles to nucleate cloud droplets, is underestimated by a factor of 1.5 and 3.8 in the PBL and FT, respectively. The comparison with MODIS data shows that the model overestimates the aerosol optical thickness (AOT). The domain averages (for 1 day) are 0.38 ± 0.12 and 0.42 ± 0.10 for MODIS and WRF-Chem data, respectively. The droplet effective radius (Re) in liquid-phase clouds is underestimated by a factor of 1.5; the cloud liquid water path (LWP) is overestimated by a factor of 1.1-1.6. The consequence is the overestimation of average liquid cloud optical thickness (COT) from a few percent up to 42 %. The predicted cloud water path (CWP) in all phases displays a bias in the range +41-80 %, whereas the bias of COT is about 15 %. In sensitivity tests where we excluded SOA, the skills of the model in reproducing the observed patterns and average values of the microphysical and optical properties of liquid and all phase clouds decreases. Moreover, the run without SOA (NOSOA) shows convective clouds with an enhanced content of liquid and frozen hydrometers, and stronger updrafts and downdrafts. Considering that the previous version of WRF-Chem coupled with a modal aerosol module predicted very low SOA content (secondary organic aerosol model (SORGAM) mechanism) the new proposed option may lead to a better characterization of aerosol-cloud feedbacks. © Author(s) 2015."
"57188665106;55889593300;24172039900;7003627515;55634326100;","Improved GRACE regional mass balance estimates of the Greenland Ice Sheet cross-validated with the input-output method",2015,"10.5194/tcd-9-4661-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042575397&doi=10.5194%2ftcd-9-4661-2015&partnerID=40&md5=35ee85e9b94093041166a14c760d78d6","In this study, we use satellite gravimetry data from the Gravity Recovery and Climate Experiment (GRACE) to estimate regional mass changes of the Greenland ice sheet (GrIS) and neighbouring glaciated regions using a least-squares inversion approach. We also consider results from the input-output method (IOM) that quantifies the difference between mass input and output of the surface mass balance (SMB) components from the Regional Atmospheric Climate Model version 2 (RACMO2) and ice discharge (D) from 12 years of high-precision ice velocity and thickness surveys. We use a simulation model to quantify and correct for GRACE approximation errors in mass changes between different sub-regions of GrIS and investigate the reliability of pre-1990s ice discharge estimates based on modelled runoff. We find that the difference between IOM and our improved GRACE mass change estimates is reduced in terms of the long-term mass changes when using runoff-based discharge estimates in several sub-areas. In most regions our GRACE and IOM solutions are consistent with other studies, but differences remain in the northwestern GrIS. We verify the GRACE mass balance in that region by considering several different GIA models and mass change estimates derived from the Ice, Cloud and land Elevation satellite (ICEsat). We conclude that the remaining differences between GRACE and IOM are likely due to underestimated uncertainties in the IOM solutions. © Author(s) 2015."
"57161358100;56162305900;7003666669;7102010848;55688930000;56384704800;23095483400;57203053317;16444232500;7202079615;25031430500;7103158465;55588510300;7004214645;36171703500;57208121852;49861577800;7402803216;","On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models",2015,"10.5194/acpd-15-23683-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84993931925&doi=10.5194%2facpd-15-23683-2015&partnerID=40&md5=61c78ef8c06fc32ddd04771f78a7e775","Aerosol-cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (ω500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascend (ω500 &lt; -25 hPa d-1) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is as large as that in stratocumulus regimes, which indicates that regimes with strong large-scale ascend are as important as stratocumulus regimes in studying AIE. It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (&gt; 0.1 mm d-1) contributes the most to the total aerosol indirect forcing (from 64 to nearly 100 %). Results show that the uncertainty in AIE is even larger within specific dynamical regimes than that globally, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes. © Author(s) 2015."
"25521667800;7004942632;","Ice supersaturation and the potential for contrail formation in a changing climate",2015,"10.5194/esd-6-555-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941048808&doi=10.5194%2fesd-6-555-2015&partnerID=40&md5=bb70560a8aee900fa75431eebba13542","Ice supersaturation (ISS) in the upper troposphere and lower stratosphere is important for the formation of cirrus clouds and long-lived contrails. Cold ISS (CISS) regions (taken here to be ice-supersaturated regions with temperature below 233 K) are most relevant for contrail formation. We analyse projected changes to the 250 hPa distribution and frequency of CISS regions over the 21st century using data from the Representative Concentration Pathway 8.5 simulations for a selection of Coupled Model Intercomparison Project Phase 5 models. The models show a global-mean, annual-mean decrease in CISS frequency by about one-third, from 11 to 7% by the end of the 21st century, relative to the present-day period 1979-2005. Changes are analysed in further detail for three subregions where air traffic is already high and increasing (Northern Hemisphere mid-latitudes) or expected to increase (tropics and Northern Hemisphere polar regions). The largest change is seen in the tropics, where a reduction of around 9 percentage points in CISS frequency by the end of the century is driven by the strong warming of the upper troposphere. In the Northern Hemisphere mid-latitudes the multi-model-mean change is an increase in CISS frequency of 1 percentage point; however the sign of the change is dependent not only on the model but also on latitude and season. In the Northern Hemisphere polar regions there is an increase in CISS frequency of 5 percentage points in the annual mean. These results suggest that, over the 21st century, climate change may have large impacts on the potential for contrail formation; actual changes to contrail cover will also depend on changes to the volume of air traffic, aircraft technology and flight routing. © Author(s) 2015."
"57213551855;36538539800;8511991900;7202048112;55624488227;7202010686;","Application of an online-coupled regional climate model, WRF-CAM5, over East Asia for examination of ice nucleation schemes: Part I. comprehensive model evaluation and trend analysis for 2006 and 2011",2015,"10.3390/cli3030627","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007416601&doi=10.3390%2fcli3030627&partnerID=40&md5=c6ac4fdfe0d11304a0e905e1acdadce0","Online-coupled climate and chemistry models are necessary to realistically represent the interactions between climate variables and chemical species and accurately simulate aerosol direct and indirect effects on cloud, precipitation, and radiation. In this Part I of a two-part paper, simulations from the Weather Research and Forecasting model coupled with the physics package of Community Atmosphere Model (WRF-CAM5) are conducted with the default heterogeneous ice nucleation parameterization over East Asia for two full years: 2006 and 2011. A comprehensive model evaluation is performed using satellite and surface observations. The model shows an overall acceptable performance for major meteorological variables at the surface and in the boundary layer, as well as column variables (e.g., precipitation, cloud fraction, precipitating water vapor, downward longwave and shortwave radiation). Moderate to large biases exist for cloud condensation nuclei over oceanic areas, cloud variables (e.g., cloud droplet number concentration, cloud liquid and ice water paths, cloud optical depth, longwave and shortwave cloud forcing). These biases indicate a need to improve the model treatments for cloud processes, especially cloud droplets and ice nucleation, as well as to reduce uncertainty in the satellite retrievals. The model simulates well the column abundances of chemical species except for column SO2 but relatively poor for surface concentrations of several species such as CO, NO2, SO2, PM2.5, and PM10. Several reasons could contribute to the underestimation of major chemical species in East Asia including underestimations of anthropogenic emissions and natural dust emissions, uncertainties in the spatial and vertical distributions of the anthropogenic emissions, as well as biases in meteorological, radiative, and cloud predictions. Despite moderate to large biases in the chemical predictions, the model performance is generally consistent with or even better than that reported for East Asia with only a few exceptions. The model generally reproduces the observed seasonal variations and the difference between 2006 and 2011 for most variables or chemical species. Overall, these results demonstrate promising skills of WRF-CAM5 for long-term simulations at a regional scale and suggest several areas of potential improvements. © 2015 by the authors."
"36538539800;57213551855;8511991900;7202048112;","Application of an online-coupled regional climate model, WRF-CAM5, over East Asia for examination of ice nucleation schemes: PART II. sensitivity to heterogeneous ice nucleation parameterizations and dust emissions",2015,"10.3390/cli3030753","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85008412108&doi=10.3390%2fcli3030753&partnerID=40&md5=97b850a44936427d3386e5f552031d8b","Aerosol particles can affect cloud microphysical properties by serving as ice nuclei (IN). Large uncertainties exist in the ice nucleation parameterizations (INPs) used in current climate models. In this Part II paper, to examine the sensitivity of the model predictions to different heterogeneous INPs, WRF-CAM5 simulation using the INP of Niemand et al. (N12) [1] is conducted over East Asia for two full years, 2006 and 2011, and compared with simulation using the INP of Meyers et al. (M92) [2], which is the original INP used in CAM5. M92 calculates the nucleated ice particle concentration as a function of ice supersaturation, while N12 represents the nucleated ice particle concentration as a function of temperature and the number concentrations and surface areas of dust particles. Compared to M92, the WRF-CAM5 simulation with N12 produces significantly higher nucleated ice crystal number concentrations (ICNCs) in the northern domain where dust sources are located, leading to significantly higher cloud ice number and mass concentrations and ice water path, but the opposite is true in the southern domain where temperatures and moistures play a more important role in ice formation. Overall, the simulation with N12 gives lower downward shortwave radiation but higher downward longwave radiation, cloud liquid water path, cloud droplet number concentrations, and cloud optical depth. The increase in cloud optical depth and the decrease in downward solar flux result in a stronger shortwave and longwave cloud forcing, and decreases temperature at 2-m and precipitation. Changes in temperature and radiation lower surface concentrations of OH, O3, SO4 2-, and PM2.5, but increase surface concentrations of CO, NO2, and SO2 over most of the domain. By acting as cloud condensation nuclei (CCN) and IN, dust particles have different impacts on cloud water and ice number concentrations, radiation, and temperature at 2-m and precipitation depending on whether the dominant role of dust is CCN or IN. These results indicate the importance of the heterogeneous ice nucleation treatments and dust emissions in accurately simulating regional climate and air quality. © 2015 by the authors."
"24764483400;7801353107;23484340400;","How sensitive are aerosol-precipitation interactions to the warm rain representation?",2015,"10.1002/2014MS000422","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945490310&doi=10.1002%2f2014MS000422&partnerID=40&md5=7c60b1c34e83af04bbb867bc869f0dd5","It is widely acknowledged that aerosol-cloud interactions are a major uncertainty in climate and numerical weather prediction. One of the sources of uncertainty is the sensitivity of the cloud microphysics parameterization to changes in aerosol, in particular the response of precipitation. In this work, we conduct an idealized, dynamically consistent, intercomparison of warm rain microphysics schemes to understand this source of uncertainty. The aims of this investigation are: (i) investigate how sensitive precipitation susceptibility (S0) is to cloud microphysics representation and (ii) use S0 to determine the minimum complexity of microphysics required to produce a consistent precipitation response to changes in cloud drop number concentration (Nd). The main results from this work are: (i) over a large range of liquid water path and Nd, all the bulk schemes, but particularly the single moment schemes, artificially produce rain too rapidly. Relative to a reference bin microphysics scheme, this leads to a low in-cloud S0 and impacts the evolution of S0 over time. (ii) Rain evaporation causes surface S0 from all schemes to be larger than the cloud base S0. The magnitude of the change in S0 with altitude is dependent on the scheme and the representation of the rain drop size distribution. Overall, we show that single-moment schemes produce the largest range in the sensitivity of precipitation to changes in Nd. Modifying rain production parameterization alone does not reduce this spread. Instead, increasing the complexity of the rain representation to double-moment significantly improves this behavior and the overall consistency between schemes. © 2015. The Authors."
"8578246200;56537579400;7403625607;52264136000;6602682871;35777359400;","Sensitivity of Intercalibration Uncertainty of the CLARREO Reflected Solar Spectrometer Features",2015,"10.1109/TGRS.2015.2409030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027946959&doi=10.1109%2fTGRS.2015.2409030&partnerID=40&md5=5c6747063224f9518d432312e95b08d3","The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission was recommended by the National Research Council in 2007 to conduct highly accurate and International System of Unit-traceable decadal change observations and provide an on-orbit intercalibration standard with high accuracy for relevant Earth observing sensors. The goal of reference intercalibration is to enable rigorous observations of critical climate change variables, including reflected broadband radiation, cloud properties, and changes in surface albedo, including snow and ice albedo feedback, to be made consistently among different sensors. This requires the CLARREO Reflected Solar Spectrometer (RSS) to provide highly accurate spectral reflectance measurements to establish an on-orbit reference with a radiometric accuracy requirement better than 0.3% (k = 2) for existing sensors. In this paper, MODTRAN-simulated top-of-atmosphere spectral data and spectral measurements from the SCIAMACHY instrument on Envisat are used to determine sensitivity of intercalibration uncertainty on key design parameters of the CLARREO spectrometer: spectral range, sampling and resolution. Their impact on intercalibration uncertainty for MODIS and VIIRS imagers is estimated for various surface types (ocean, vegetation, desert, snow, deep convective clouds, clouds and all-sky). Results indicate that for the visible to near-infrared spectral region (465-856 nm), the RSS instrument under current design concept produces uncertainties of 0.16% for the spectral range and 0.3% for the sampling and resolution. However, for the water vapor absorption bands in the short wavelength infrared region (1242-1629 nm), the same requirement is not met for sampling and resolution due to their high sensitivity to the influence of atmospheric water vapor. © 1980-2012 IEEE."
"8219958200;7201504886;55614754800;35932420900;53980793000;6603247427;36917877800;","Large eddy simulation using the general circulation model ICON",2015,"10.1002/2015MS000431","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945482763&doi=10.1002%2f2015MS000431&partnerID=40&md5=ae6e9001357bb44b804ce4f82d3f12b8","ICON (ICOsahedral Nonhydrostatic) is a unified modeling system for global numerical weather prediction (NWP) and climate studies. Validation of its dynamical core against a test suite for numerical weather forecasting has been recently published by Zängl et al. (2014). In the present work, an extension of ICON is presented that enables it to perform as a large eddy simulation (LES) model. The details of the implementation of the LES turbulence scheme in ICON are explained and test cases are performed to validate it against two standard LES models. Despite the limitations that ICON inherits from being a unified modeling system, it performs well in capturing the mean flow characteristics and the turbulent statistics of two simulated flow configurations - one being a dry convective boundary layer and the other a cumulus-topped planetary boundary layer. © 2015. The Authors."
"55268661300;55461837700;35509639400;","The influence of atmospheric cloud radiative effects on the large-scale atmospheric circulation",2015,"10.1175/JCLI-D-14-00825.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945563501&doi=10.1175%2fJCLI-D-14-00825.1&partnerID=40&md5=f8e8257b7879365556e4ad3385969292","The influence of clouds on the large-scale atmospheric circulation is examined in numerical simulations from an atmospheric general circulation model run with and without atmospheric cloud radiative effects (ACRE). In the extratropics of both hemispheres, the primary impacts of ACRE on the circulation include 1) increases in the meridional temperature gradient and decreases in static stability in the midlatitude upper troposphere, 2) strengthening of the midlatitude jet, 3) increases in extratropical eddy kinetic energy by up to 30%, and 4) increases in precipitation at middle latitudes but decreases at subtropical latitudes. In the tropics, the primary impacts of ACRE include 1) eastward wind anomalies in the tropical upper troposphere-lower stratosphere (UTLS) and 2) reductions in tropical precipitation. The impacts of ACRE on the atmospheric circulation are interpreted in the context of a series of dynamical and physical processes. The changes in the extratropical circulation and precipitation are consistent with the influence of ACRE on the baroclinicity and eddy fluxes of momentum in the extratropical upper troposphere, the changes in the zonal wind in the UTLS with the influence of ACRE on the amplitude of the equatorial planetary waves, and the changes in the tropical precipitation with the energetic constraints on the tropical troposphere. The results make clear that ACRE have a pronounced influence on the atmospheric circulation not only at tropical latitudes, but at extratropical latitudes as well. They highlight the critical importance of correctly simulating ACRE in global climate models. © 2015 American Meteorological Society."
"36655445400;57203012011;35849722200;41362078500;","Characteristics of heat sources and clouds over eastern China and the Tibetan Plateau in boreal summer",2015,"10.1175/JCLI-D-14-00859.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979521676&doi=10.1175%2fJCLI-D-14-00859.1&partnerID=40&md5=92f7bb4c21e132700d4677bbc22ae0d6","In this study, the summer clouds and precipitation over eastern China and the Tibetan Plateau (TP) are examined by analyzing the satellite observations and the apparent heat source Q1 and moisture sink Q2 computed from the NCEP-NCAR reanalysis. The vertically integrated [Q1] and [Q2] and precipitation have similar interannual variations in eastern China, revealing the important contribution from the condensation process. This relationship is weakened in east TP (ETP) because of the contribution of the surface sensible heat flux. In west TP (WTP), [Q1] is negatively correlated with precipitation because the surface sensible heat flux can be sharply weakened by the decrease of ground-air temperature difference due to rainfall. High clouds and deep convection are closely related with [Q1] and [Q2] over eastern China and ETP, while middle clouds and nimbostratus are responsible for the condensation over WTP. During the rainy summer, more convective rains and stronger upward motion appear in eastern China. Greater Q1 and Q2 and stronger upward motion present over ETP, while weaker Q1 and upward motion are observed over WTP in the rainy summer when compared to the dry summer. The cloud-water path over eastern China positively correlates with [Q1] and [Q2] over ETP. The deep convection over eastern China also positively correlates with the convection over ETP. These correlations suggest that moisture due to the evaporation of cloud water in anvil clouds detrained from the deep convection over ETP can be transported downstream and benefit the development of convection over eastern China. © 2015 American Meteorological Society."
"57211236228;","Aerosols-cloud properties in dynamic atmosphere over Kedarnath Sub-Himalayan Region of India: A long term study from MODIS satellite",2015,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941621538&partnerID=40&md5=a3609064050197721c7a2825208a716d","The present long term study deals with the aerosol-cloud optical properties carried out during 2003-2012 over Kedarnath (30.73°N, 79.07°E) of the sub-Himalayan region of Uttarakhand, India with a resolution of 1°x1° grid in magnitude. The study was conducted using Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard NASA's Terra and Aqua satellites. Interannual and seasonal variations of Aerosol Optical Depth (AOD) are examined in the light of regional synoptic climatic meteorology. Aerosol optical depths have found to be increased >28 % across Kedarnath region of India during the study period of 2003-2012. Annual mean Terra/Aqua AOD values at 550 nm displayed an increasing trend at a rate of ∼0.0045/0.0089 per year respectively. Further, seasonal winter means Terra/Aqua AOD values exhibit an increasing trend at a rate of ∼0.013/0.006 per year respectively. The results extracted in the present study are compared with the earlier studies as well as with the AOD values over various other Indian regions. © 2015, Technoscience Publications. All rights reserved."
"54585176800;7004978125;7801642934;","Cloud-radiation feedback and atmosphere-ocean coupling in a stochastic multicloud model",2015,"10.1016/j.dynatmoce.2015.05.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931263082&doi=10.1016%2fj.dynatmoce.2015.05.003&partnerID=40&md5=07302337a5612e5f223ca1182b04767c","Despite recent advances in supercomputing, current general circulation models (GCMs) have significant problems in representing the variability associated with organized tropical convection. Furthermore, due to high sensitivity of the simulations to the cloud radiation feedback, the tropical convection remains a major source of uncertainty in long-term weather and climate forecasts. In a series of recent studies, it has been shown, in paradigm two-baroclinic-mode systems and in aquaplanet GCMs, that a stochastic multicloud convective parameterization based on three cloud types (congestus, deep and stratiform) can be used to improve the variability and the dynamical structure of tropical convection, including intermittent coherent structures such as synoptic and mesoscale convective systems. Here, the stochastic multicloud model is modified with a parameterized cloud radiation feedback mechanism and atmosphere-ocean coupling. The radiative convective feedback mechanism is shown to increase the mean and variability of the Walker circulation. The corresponding intensification of the circulation is associated with propagating synoptic scale systems originating inside of the enhanced sea surface temperature area. In column simulations, the atmosphere ocean coupling introduces pronounced low frequency convective features on the time scale associated with the depth of the mixed ocean layer. However, in the presence of the gravity wave mixing of spatially extended simulations, these features are not as prominent. This highlights the deficiency of the column model approach at predicting the behavior of multiscale spatially extended systems. Overall, the study develops a systematic framework for incorporating parameterized radiative cloud feedback and ocean coupling which may be used to improve representation of intraseasonal and seasonal variability in GCMs. © 2015 Elsevier B.V."
"56583515100;8922308700;15848674200;15755995900;","Evaluation of tropical channel refinement using MPAS-A aquaplanet simulations",2015,"10.1002/2015MS000470","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945464868&doi=10.1002%2f2015MS000470&partnerID=40&md5=da964f61366c173061ee6a0f6f552bd5","Climate models with variable-resolution grids offer a computationally less expensive way to provide more detailed information and increased accuracy by resolving processes that cannot be adequately represented by a coarser grid. This study uses the Model for Prediction Across Scales-Atmosphere (MPAS-A), consisting of a nonhydrostatic dynamical core and a subset of Weather Research and Forecasting (WRF) model physics, to investigate the potential benefits of using tropical channel refinement. The simulations are performed with an idealized aquaplanet configuration using 30 and 240 km global grid spacing, and two variable-resolution grids spanning the same grid spacing range; one with a narrow (20S-20N) and one with a wide (30S-30N) tropical channel refinement. Increasing resolution in the tropics impacts both the tropical and extratropical circulation. Compared to the 30 km global grid, both refined channel simulations exhibit slightly stronger updrafts inside the Hadley cell resulting in more resolved precipitation. Using a wider tropical refinement leads to a closer correspondence with the global high-resolution grid. While different grid spacings produce similar cloud size distributions that are consistent with observations, the dependence of precipitation rate on cloud size varies among simulations. The refined channel simulations show improved tropical and extratropical precipitation relative to the global coarse simulation. All simulations show a single precipitation peak centered on the equator. Although the results show that tropical refinement is an effective method for avoiding artifacts due to grid resolution sensitivities seen in earlier studies that only refined a portion of the tropics, some biases remain well inside of the refinement region. © 2015. The Authors."
"15841308100;6603944055;7401636555;7005165467;7003907406;57200082194;7201903057;7005123759;","On the measurability of change in Amazon vegetation from MODIS",2015,"10.1016/j.rse.2015.05.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937966430&doi=10.1016%2fj.rse.2015.05.020&partnerID=40&md5=a93fa7e5798965f9117a18bde9836370","The Amazon rainforest is a critical hotspot for bio-diversity, and plays an essential role in global carbon, water and energy fluxes and the earth's climate. Our ability to project the role of vegetation carbon feedbacks on future climate critically depends upon our understanding of this tropical ecosystem, its tolerance to climate extremes and tipping points of ecosystem collapse. Satellite remote sensing is the only practical approach to obtain observational evidence of trends and changes across large regions of the Amazon forest; however, inferring these trends in the presence of high cloud cover fraction and aerosol concentrations has led to widely varying conclusions. Our study provides a simple and direct statistical analysis of a measurable change in daily and composite surface reflectance obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) based on the noise level of data and the number of available observations. Depending on time frame and data product chosen for analysis, changes in leaf area need to exceed up to 2 units leaf area per unit ground area (expressed as m2m-2) across much of the basin before these changes can be detected at a 95% confidence level with conventional approaches, roughly corresponding to a change in NDVI and EVI of about 25%. A potential way forward may be provided by advanced multi-angular techniques, such as the Multi-Angle Implementation of Atmospheric Correction Algorithm (MAIAC), which allowed detection of changes of about 0.6-0.8units in leaf area (2-6% change in NDVI) at the same confidence level. In our analysis, the use of the Enhanced Vegetation Index (EVI) did not improve accuracy of detectable change in leaf area but added a complicating sensitivity to the bi-directional reflectance, or view geometry effects. © 2015 Elsevier Inc."
"55716995500;8855923200;35209683700;15756666000;26324818700;","Quantitative decomposition of radiative and non-radiative contributions to temperature anomalies related to siberian high variability",2015,"10.1007/s00382-014-2371-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940725838&doi=10.1007%2fs00382-014-2371-6&partnerID=40&md5=1772f59c0d17921fdeed04300efc80fd","In this study, we carried out an attribution analysis that quantitatively assessed relative contributions to the observed temperature anomalies associated with strong and weak Siberian High (SH). Relative contributions of radiative and non-radiative processes to the variation of surface temperature, in terms of both amplitude and spatial pattern, were analyzed. The strong SH activity leads to the continental-scale cold temperature anomalies covering eastern Siberia, Mongolia, East China, and Korea (i.e., SH domain). The decomposition of the observed temperature anomalies associated with the SH variation was achieved with the Coupled atmosphere–surface climate Feedback-Responses Analysis Method, in which the energy balance in the atmosphere–surface column and linearization of radiative energy perturbation are formulated. For the mean amplitude of −3.13 K of cold temperature anomaly over the SH domain, sensible heat flux is tightly connected with a cooling of −1.26 K. Atmospheric dynamics adds another −1.13 K through the large-scale cold advection originated from the high latitudes. The longwave effects of cloud and water vapor account for the remaining cold anomalies of −1.00 and −0.60 K, respectively, while surface dynamics (0.71 K) and latent heat flux (0.26 K) help to mitigate the cold temperature anomalies. Influences of ozone and albedo processes are found to be relatively weak. © 2014, Springer-Verlag Berlin Heidelberg."
"8213490600;57094698800;36953809700;","Daily forecasting of reference and strawberry crop evapotranspiration in greenhouses in a Mediterranean climate based on solar radiation estimates",2015,"10.1016/j.agwat.2015.06.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957020991&doi=10.1016%2fj.agwat.2015.06.012&partnerID=40&md5=ff9ad4e49f35c9877c9b9a7b6f05c936","This paper presents a method for carrying out daily forecasting of strawberry crop evapotranspiration (ETc), using forecasted greenhouse reference evapotranspiration values (ETo green) and crop coefficients. ETo green was estimated using two methods, the first based on incoming solar radiation and the second using the Makkink FAO-24 equation. In both cases, ETo green was estimated using daily meteorological variables forecasted by the Spanish Meteorology National Agency (AEMET) and then comparing it with the result obtained using measured meteorological data under greenhouse conditions. In addition, values of estimated ETc using measured and forecasted meteorological data were also compared. Lastly, these values were compared with ETc measurements using drainage lysimeters. Incoming solar radiation was estimated from forecasted temperatures and sky cloudiness conditions. Forecasted outdoor and indoor incoming solar radiation values were more accurate using the method based on temperatures. Small differences and high correlations were observed when comparing forecasted and weather measured ETo green and ETc. With respect to forecasted ETo green, the errors were smaller when incoming solar radiation was estimated from forecasted temperature data, especially when using the Makkink equation, with underestimations below 3%. Therefore, these results suggest that the latter method is best suited to the task. Also, the use of forecasted ETc, especially from Makkink FAO24 equation, provided more accurate estimates when compared with lysimeter-measured values. © 2015 Elsevier B.V."
"55805902000;55351830700;12752488600;7003404986;6602762273;","TerraSAR-X dual-pol time-series for mapping of wetland vegetation",2015,"10.1016/j.isprsjprs.2015.05.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938747913&doi=10.1016%2fj.isprsjprs.2015.05.001&partnerID=40&md5=76521acb29eaf201489f6e7305b660cb","Mapping vegetation formations at a fine scale is crucial for assessing wetland functions and for better landscape management. Identification and characterization of vegetation formations is generally conducted at a fine scale using ecological ground surveys, which are limited to small areas. While optical remotely sensed imagery is limited to cloud-free periods, SAR time-series are used more extensively for wetland mapping and characterization using the relationship between distribution of vegetation formations and flood duration. The aim of this study was to determine the optimal number and key dates of SAR images to be classified to map wetland vegetation formations at a 1:10,000 scale. A series of eight dual-polarization TerraSAR-X images (HH/VV) was acquired in 2013 during dry and wet seasons in temperate climate conditions. One polarimetric parameter was extracted first, the Shannon entropy, which varies with wetland flooding status and vegetation roughness. Classification runs of all the possible combinations of SAR images using different k (number of images) subsets were performed to determine the best combinations of the Shannon entropy images to identify wetland vegetation formations. The classification runs were performed using Support Vector Machine techniques and were then analyzed using the McNemar test to investigate significant differences in the accuracy of all classification runs based on the different image subsets. The results highlight the relevant periods (i.e. late winter, spring and beginning of summer) for mapping vegetation formations, in accordance with ecological studies. They also indicate that a relationship can be established between vegetation formations and hydrodynamic processes with a short time-series of satellite images (i.e. 5 dates). This study introduces a new approach for herbaceous wetland monitoring using SAR polarimetric imagery. This approach estimates the number and key dates required for wetland management (e.g. restoration) and biodiversity studies using remote sensing data. © 2015 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)."
"7410339976;55854024000;9239676900;8643559700;55710625500;36015780400;35489753100;55521311100;57077274600;57204845855;55744406100;57217563227;56158988200;","Improving the light use efficiency model for simulating terrestrial vegetation gross primary production by the inclusion of diffuse radiation across ecosystems in China",2015,"10.1016/j.ecocom.2015.04.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930636808&doi=10.1016%2fj.ecocom.2015.04.004&partnerID=40&md5=737830f71a5b3f6c2de3047dd63ec638","Qualification of gross primary production (GPP) of terrestrial ecosystem over large areas is important in understanding the response of terrestrial ecosystem to global climate change. While light use efficiency (LUE) models were widely used in regional carbon budget estimates, few studies consider the effect of diffuse radiation on LUE caused by clouds using a big leaf model. Here we developed a cloudiness index light use efficiency (CI-LUE) model based on the MOD17 model algorithm to estimate the terrestrial ecosystem GPP, in which the base light use efficiency encompassed the cloudiness index, maximum LUE and clear sky LUE. GPP measured at seven sites from 2003 to 2007 in China were used to calibrate and validate the CI-LUE model. The results showed that at forest sites and cropland site the CI-LUE model outperformed the Vegetation Photosynthesis Model (VPM), Terrestrial Ecosystem Carbon flux model (TEC), MOD17 model algorithm driven by in situ meteorological measurements and MODIS GPP products, especially the R2 of simulated GPP against flux measurements at Dinghushan forest site increased from 0.17 (MODIS GPP products) to 0.61 (CI-LUE). Instead, VPM model had the best agreement with GPP measurements followed by CI-LUE model and lastly TEC model at two grassland sites. Meanwhile, GPP calculated by CI-LUE model has less underestimation under cloudy skies in comparison with MOD17 model. This study demonstrated the potential of the CI-LUE model in improving GPP simulations resulting from the inclusion of diffuse radiation in regulating the base light use efficiency and maximum light use efficiency. © 2015 Elsevier B.V."
"57203439874;35849722200;7005632987;55879571100;14326501100;56145499000;55763374800;55007493900;","Aerosol climatology and discrimination of aerosol types retrieved from MODIS, MISR and OMI over Durban (29.88°S, 31.02°E), South Africa",2015,"10.1016/j.atmosenv.2015.06.058","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937026742&doi=10.1016%2fj.atmosenv.2015.06.058&partnerID=40&md5=70e8bb8e055a73f46911853857131df9","The present study represents the characteristics of aerosol optical depth (AOD) retrieved from multiple satellite sensors (MODerate resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging SpectroRadiometer (MISR), and Ozone Monitoring Instrument (OMI)) during 2003-2013 over an urban-coastal region, Durban (DBN; 29.88°S, 31.02°E, 46m°asl), situated on the east coast of South Africa. An intercomparison and validation of AOD is performed against the AOD measurements from ground-based AErosol RObotic NETwork (AERONET) Sunphotometer. The results revealed that MISR-AERONET comparison indicated strong correlation compared to MODIS-AERONET comparison. Also, the comparison between MODIS and MISR AODs noticed significant positive correlation over DBN with the overestimation of latter by former. Highest AOD characterizes during the spring (September-November) followed by summer (December-February) and autumn (March-May) with the lowest AOD observed during the winter (June-August) season. The Angstrom exponent (AE<inf>470-600</inf>) indicates predominance of fine-mode aerosols during spring and summer and dominance of coarse-mode aerosols in winter. A HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is used to locate the origin of airmass transport and understand the variability of aerosol source regions. Finally, the relationship between AOD and AE has been examined to classify different aerosol types and showed seasonal heterogeneity in their contribution depending upon variability in sources. This is the first ever attempt to classify aerosols over this environment. © 2015 Elsevier Ltd."
"55328973600;21935606200;7103390363;6701671840;6701620591;35395776600;","Contribution of Brown Carbon to Direct Radiative Forcing over the Indo-Gangetic Plain",2015,"10.1021/acs.est.5b03368","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940828971&doi=10.1021%2facs.est.5b03368&partnerID=40&md5=761cca127a82305514b320f0b2c34af0","The Indo-Gangetic Plain is a region of known high aerosol loading with substantial amounts of carbonaceous aerosols from a variety of sources, often dominated by biomass burning. Although black carbon has been shown to play an important role in the absorption of solar energy and hence direct radiative forcing (DRF), little is known regarding the influence of light absorbing brown carbon (BrC) on the radiative balance in the region. With this in mind, a study was conducted for a one month period during the winter-spring season of 2013 in Kanpur, India that measured aerosol chemical and physical properties that were used to estimate the sources of carbonaceous aerosols, as well as parameters necessary to estimate direct forcing by aerosols and the contribution of BrC absorption to the atmospheric energy balance. Positive matrix factorization analyses, based on aerosol mass spectrometer measurements, resolved organic carbon into four factors including low-volatile oxygenated organic aerosols, semivolatile oxygenated organic aerosols, biomass burning, and hydrocarbon like organic aerosols. Three-wavelength absorption and scattering coefficient measurements from a Photo Acoustic Soot Spectrometer were used to estimate aerosol optical properties and estimate the relative contribution of BrC to atmospheric absorption. Mean ± standard deviation values of short-wave cloud free clear sky DRF exerted by total aerosols at the top of atmosphere, surface and within the atmospheric column are -6.1 ± 3.2, -31.6 ± 11, and 25.5 ± 10.2 W/m2, respectively. During days dominated by biomass burning the absorption of solar energy by aerosols within the atmosphere increased by ∼35%, accompanied by a 25% increase in negative surface DRF. DRF at the top of atmosphere during biomass burning days decreased in negative magnitude by several W/m2 due to enhanced atmospheric absorption by biomass aerosols, including BrC. The contribution of BrC to atmospheric absorption is estimated to range from on average 2.6 W/m2 for typical ambient conditions to 3.6 W/m2 during biomass burning days. This suggests that BrC accounts for 10-15% of the total aerosol absorption in the atmosphere, indicating that BrC likely plays an important role in surface and boundary temperature as well as climate. (Graph Presented). © 2015 American Chemical Society."
"15072064200;57214957374;36016681500;7402504360;7102828379;7403218246;7202088827;8773116800;6603467357;7003798647;","Atmospheric black carbon and sulfate concentrations in Northeast Greenland",2015,"10.5194/acp-15-9681-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940178697&doi=10.5194%2facp-15-9681-2015&partnerID=40&md5=d8280ab215c09b72ce92296de94d2bc4","Measurements of equivalent black carbon (EBC) in aerosols at the high Arctic field site Villum Research Station (VRS) at Station Nord in North Greenland showed a seasonal variation in EBC concentrations with a maximum in winter and spring at ground level. Average measured concentrations were about 0.067 ± 0.071 for the winter and 0.011 ± 0.009 for the summer period. These data were obtained using a multi-angle absorption photometer (MAAP). A similar seasonal pattern was found for sulfate concentrations with a maximum level during winter and spring analyzed by ion chromatography. Here, measured average concentrations were about 0.485 ± 0.397 for the winter and 0.112 ± 0.072 for the summer period. A correlation between EBC and sulfate concentrations was observed over the years 2011 to 2013 stating a correlation coefficient of R2 Combining double low line 0.72. This finding gives the hint that most likely transport of primary emitted BC particles to the Arctic was accompanied by aging of the aerosols through condensational processes. BC and sulfate are known to have only partly similar sources with respect to their transport pathways when reaching the high Arctic. Aging processes may have led to the formation of secondary inorganic matter and further transport of BC particles as cloud processing and further washout of particles is less likely based on the typically observed transport patterns of air masses arriving at VRS. Additionally, concentrations of EC (elemental carbon) based on a thermo-optical method were determined and compared to EBC measurements. EBC measurements were generally higher, but a correlation between EC and EBC resulted in a correlation coefficient of R2 Combining double low line 0.64. Model estimates of the climate forcing due to BC in the Arctic are based on contributions of long-range transported BC during spring and summer. The measured concentrations were here compared with model results obtained by the Danish Eulerian Hemispheric Model, DEHM. Good agreement between measured and modeled concentrations of both EBC/BC and sulfate was observed. Also, the correlation between BC and sulfate concentrations was confirmed based on the model results observed over the years 2011 to 2013 stating a correlation coefficient of R2 Combining double low line 0.74. The dominant source is found to be combustion of fossil fuel with biomass burning as a minor, albeit significant source. © Author(s) 2015."
"8900058400;57204252724;7003480967;9332706900;13610168000;","Seasonal and diurnal trends in black carbon properties and co-pollutants in Mexico City",2015,"10.5194/acp-15-9693-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940661645&doi=10.5194%2facp-15-9693-2015&partnerID=40&md5=74601f13adb5f6c6f01d4a209cb866e9","The Mexico City metropolitan area (MCMA) is a region that continues to grow in population and vehicular traffic as well as being the largest source of short-lived climate pollutants (SLCP) in Latin America. The local city government has made significant progress in controlling some of these pollutants, i.e., ozone (O3) and carbon monoxide (CO), but particulate matter (PM2.5 and PM10) and black carbon (BC) have shown a less positive response to mitigation strategies that have been in place for almost 3 decades. For the first time, extended measurements of equivalent black carbon (eBC), derived from light absorption measurements, have been made using a Photoacoustic Extinctiometer (PAX) over a 13 month period from March 2013 through March 2014. The daily trends in workdays (Monday through Saturday) and Sunday eBC, PM2.5 and the co-pollutants CO, O3 and NOx are evaluated with respect to the three primary seasons in the MCMA: rainy, cold and dry and warm and dry. The maximum values in all of the particle and gas concentrations were significantly larger (Student's t test, P &lt; 0.05) during the dry periods than in the rainy season. The changes from rainy to dry seasons for eBC, PM2.5, CO, O3 and NOx were 8.8 to 13.1 μg m-3 (40 %), 49 to 73 μg m-3 (40 %), 2.5 to 3.8 ppm (40 %), 73 to 100 ppb (30 %) and 144 to 252 ppb (53 %), respectively. The primary factors that lead to these large changes between the wet and dry seasons are the accelerated vertical mixing of boundary layer and free tropospheric air by the formation of clouds that dilutes the concentration of the SLCPs, the decreased actinic flux that reduces the production of ozone by photochemical reactions and the heavy, almost daily rain that removes particulate matter. A significant ""weekend effect"" was also identified, particularly the decrease in BC due to fewer large transport vehicles that are fueled by diesel, which produces a large fraction of the BC. The other co-pollutant concentrations are also significantly less on weekends except for O3 that shows no change in maximum values from workdays to Sundays. This lack of change is a result of the balancing effects of lower precursor gases, i.e., VOCs, offset by lower concentrations of NOx, that is an O3 inhibitor. A comparison of the average maximum value of eBC measured during the 1 year period of the current study, with maximum values measured in shorter field campaigns in 2000 and 2006, shows no significant change in the eBC emissions over a 14 year period. This suggests that new methods may need to be developed that can decrease potentially toxic levels of this particulate pollutant. © Author(s) 2015."
"56818946700;57203200427;22958134600;6506373162;53878006900;35227762400;6602600408;","Climate extremes in multi-model simulations of stratospheric aerosol and marine cloud brightening climate engineering",2015,"10.5194/acp-15-9593-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940861845&doi=10.5194%2facp-15-9593-2015&partnerID=40&md5=f10e8ec2606894dfbb3747664e6d6113","Simulations from a multi-model ensemble for the RCP4.5 climate change scenario for the 21st century, and for two solar radiation management (SRM) schemes (stratospheric sulfate injection (G3), SULF and marine cloud brightening by sea salt emission SALT) have been analysed in terms of changes in the mean and extremes of surface air temperature and precipitation. The climate engineering and termination periods are investigated. During the climate engineering period, both schemes, as intended, offset temperature increases by about 60 % globally, but are more effective in the low latitudes and exhibit some residual warming in the Arctic (especially in the case of SALT which is only applied in the low latitudes). In both climate engineering scenarios, extreme temperature changes are similar to the mean temperature changes over much of the globe. The exceptions are the mid- and high latitudes in the Northern Hemisphere, where high temperatures (90th percentile of the distribution) of the climate engineering period compared to RCP4.5 control period rise less than the mean, and cold temperatures (10th percentile), much more than the mean. This aspect of the SRM schemes is also reflected in simulated reduction in the frost day frequency of occurrence for both schemes. However, summer day frequency of occurrence increases less in the SALT experiment than the SULF experiment, especially over the tropics. Precipitation extremes in the two SRM scenarios act differently - The SULF experiment more effectively mitigates extreme precipitation increases over land compared to the SALT experiment. A reduction in dry spell occurrence over land is observed in the SALT experiment. The SULF experiment has a slight increase in the length of dry spells. A strong termination effect is found for the two climate engineering schemes, with large temperature increases especially in the Arctic. Globally, SULF is more effective in reducing extreme temperature increases over land than SALT. Extreme precipitation increases over land is also more reduced in SULF than the SALT experiment. However, globally SALT decreases the frequency of dry spell length and reduces the occurrence of hot days compared to SULF. © Author(s) 2015."
"55373004600;57208346904;","Effects of cumulus parameterizations on predictions of summer flood in the Central United States",2015,"10.1007/s00382-014-2301-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028194511&doi=10.1007%2fs00382-014-2301-7&partnerID=40&md5=91a215629aee714f343c9d1cf25d227e","This study comprehensively evaluates the effects of twelve cumulus parameterization (CUP) schemes on simulations of 1993 and 2008 Central US summer floods using the regional climate-weather research and forecasting model. The CUP schemes have distinct skills in predicting the summer mean pattern, daily rainfall frequency and precipitation diurnal cycle. Most CUP schemes largely underestimate the magnitude of Central US floods, but three schemes including the ensemble cumulus parameterization (ECP), the Grell-3 ensemble cumulus parameterization (G3) and Zhang-McFarlane-Liang cumulus parameterization (ZML) show clear advantages over others in reproducing both floods location and amount. In particular, the ECP scheme with the moisture convergence closure over land and cloud-base vertical velocity closure over oceans not only reduces the wet biases in the G3 and ZML schemes along the US coastal oceans, but also accurately reproduces the Central US daily precipitation variation and frequency distribution. The Grell (GR) scheme shows superiority in reproducing the Central US nocturnal rainfall maxima, but others generally fail. This advantage of GR scheme is primarily due to its closure assumption in which the convection is determined by the tendency of large-scale instability. Future study will attempt to incorporate the large-scale tendency assumption as a trigger function in the ECP scheme to improve its prediction of Central US rainfall diurnal cycle. © 2014, Springer-Verlag Berlin Heidelberg."
"56708460400;34870277200;55751665200;6505762249;","The impact of revised simplified Arakawa–Schubert convection parameterization scheme in CFSv2 on the simulation of the Indian summer monsoon",2015,"10.1007/s00382-014-2320-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934983663&doi=10.1007%2fs00382-014-2320-4&partnerID=40&md5=3f40cfa40a4fd20bbe8c829b7f8b4a54","Keeping the systematic bias of the climate forecast system model version 2 (CFSv2) in mind, an attempt is made to improve the Indian summer monsoon (ISM) rainfall variability in the model from diurnal through daily to seasonal scale. Experiments with default simplified Arakawa–Schubert (SAS) and a revised SAS schemes are carried out to make 15 years climate run (free run) to evaluate the model fidelity with revised SAS as compared to default SAS. It is clearly seen that the revised SAS is able to reduce some of the biases of CFSv2 with default SAS. Improvement is seen in the annual seasonal cycle, onset and withdrawal but most importantly the rainfall probability distribution function (PDF) has improved significantly. To understand the reason behind the PDF improvement, the diurnal rainfall simulation is analysed and it is found that the PDF of diurnal rainfall has significantly improved with respect to even a high resolution CFSv2 T382 version. In the diurnal run with revised SAS, the PDF of rainfall over central India has remarkably improved. The improvement of diurnal cycle of total rainfall has actually been contributed by the improvement of diurnal cycle of convection and associated convective rainfall. This is reflected in outgoing longwave radiation and high cloud diurnal cycle. This improvement of convective cycle has resolved a long standing problem of dry bias by CFSv2 over Indian land mass and wet bias over equatorial Indian Ocean. Besides the improvement, there are some areas where there are still scopes for further development. The cold tropospheric temperature bias, low cloud fractions need further improvement. To check the role of shallow convection, another free run is made with revised SAS along with shallow convection (SC). The major difference between the new and old SC schemes lies in the heating and cooling behavior in lower-atmospheric layers above the planetary boundary layer. However, the inclusion of revised SC scheme could not show much improvement as compared to revised SAS with deep convection. Thus, it seems that revised SAS with deep convection can be a potentially better parameterization scheme for CFSv2 in simulating ISM rainfall variability. © 2014, Springer-Verlag Berlin Heidelberg."
"56125661000;16230139500;16426140700;8380252900;36486362800;","Exploiting the sensitivity of two satellite cloud height retrievals to cloud vertical distribution",2015,"10.5194/amt-8-3419-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940209939&doi=10.5194%2famt-8-3419-2015&partnerID=40&md5=93279d17a727ff3abb5a6e3e89ab7c48","This work presents a study on the sensitivity of two satellite cloud height retrievals to cloud vertical distribution. The difference in sensitivity is exploited by relating the difference in the retrieved cloud heights to cloud vertical extent. The two cloud height retrievals, performed within the Freie Universität Berlin AATSR MERIS Cloud (FAME-C) algorithm, are based on independent measurements and different retrieval techniques. First, cloud-top temperature (CTT) is retrieved from Advanced Along Track Scanning Radiometer (AATSR) measurements in the thermal infrared. Second, cloud-top pressure (CTP) is retrieved from Medium Resolution Imaging Spectrometer (MERIS) measurements in the oxygen-A absorption band and a nearby window channel. Both CTT and CTP are converted to cloud-top height (CTH) using atmospheric profiles from a numerical weather prediction model. First, a sensitivity study using radiative transfer simulations in the near-infrared and thermal infrared was performed to demonstrate, in a quantitative manner, the larger impact of the assumed cloud vertical extinction profile, described in terms of shape and vertical extent, on MERIS than on AATSR top-of-atmosphere measurements. Consequently, cloud vertical extinction profiles will have a larger influence on the MERIS than on the AATSR cloud height retrievals for most cloud types. Second, the difference in retrieved CTH (ΔCTH) from AATSR and MERIS are related to cloud vertical extent (CVE), as observed by ground-based lidar and radar at three ARM sites. To increase the impact of the cloud vertical extinction profile on the MERIS-CTP retrievals, single-layer and geometrically thin clouds are assumed in the forward model. Similarly to previous findings, the MERIS-CTP retrievals appear to be close to pressure levels in the middle of the cloud. Assuming a linear relationship, the ΔCTH multiplied by 2.5 gives an estimate on the CVE for single-layer clouds. The relationship is stronger for single-layer clouds than for multi-layer clouds. Due to large variations of cloud vertical extinction profiles occurring in nature, a quantitative estimate of the cloud vertical extent is accompanied with large uncertainties. Yet, estimates of the CVE provide an additional parameter, next to CTH, that can be obtained from passive imager measurements and can be used to further describe cloud vertical distribution, thus contributing to the characterization of a cloudy scene. To further demonstrate the plausibility of the approach, an estimate of the CVE was applied to a case study. In light of the follow-up mission Sentinel-3 with AATSR and MERIS like instruments, Sea and Land Surface Temperature Radiometer (SLSTR) and (Ocean and Land Colour Instrument) OLCI, respectively, for which the FAME-C algorithm can be easily adapted, a more accurate estimate of the CVE can be expected. OLCI will have three channels in the oxygen-A absorption band, possibly providing enhanced information on cloud vertical distributions. © Author(s) 2015."
"55746159100;35509639400;","Influence of low-cloud radiative effects on tropical circulation and precipitation",2015,"10.1002/2013MS000288","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937042731&doi=10.1002%2f2013MS000288&partnerID=40&md5=583f64411756f8aecd29ad91065e4221","Low-level clouds, which constitute the most prevalent cloud type over tropical oceans, exert a radiative cooling within the planetary boundary layer. By using an atmospheric general circulation model, we investigate the role that this cloud radiative cooling plays in the present-day climate. Low-cloud radiative effects are found to increase the tropics-wide precipitation, to strengthen the winds at the surface of the tropical oceans, and to amplify the atmospheric overturning circulation. An analysis of the water and energy budgets of the atmosphere reveals that most of these effects arises from the strong coupling of cloud-radiative cooling with turbulent fluxes at the ocean surface. The impact of cloud-radiative effects on atmospheric dynamics and precipitation is shown to occur on very short time scales (a few days). Therefore, short-term atmospheric forecasts constitute a valuable framework for evaluating the interactions between cloud processes and atmospheric dynamics, and for assessing their dependence on model physics. © 2014. The Authors."
"7007021059;8962699100;7202954964;7401945370;57212988186;7201485519;","High cloud increase in a perturbed SST experiment with a global nonhydrostatic model including explicit convective processes",2015,"10.1002/2013MS000301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907823728&doi=10.1002%2f2013MS000301&partnerID=40&md5=b23519623440f028e884b4e71759387d","Results are presented from a series of sensitivity tests in idealized global warming experiments using the global nonhydrostatic model, NICAM, in which convection at scales of 7-14 km is explicitly resolved. All have a strong positive longwave cloud feedback larger than that seen in conventional GCMs with parameterized convection. Consequently, the global mean net outgoing radiation decreases in response to increased sea surface temperatures. Large increases in high clouds with tops between 180 and 50 hPa are found, and these changes contribute the most to this longwave cloud feedback. Relative humidity and upper tropospheric temperature also increases strongly, again more so than typically seen in conventional GCMs. The magnitude of the response varies considerably between different versions of NICAM. Most of the NICAM control simulations show large overestimates in cloud fraction between 180 and 50 hPa compared to observations. The changes in cloud fraction in the upper troposphere are strongly correlated with their control values. Versions of NICAM with stronger cloud feedbacks have large positive biases in high-top cloud amount and temperature in the free troposphere in their control simulations. The version which has the best agreement with the observations in this regard has the weakest longwave cloud feedback; however, this is still more strongly positive than that typically seen in conventional GCMs. These results demonstrate the potential for stronger high cloud fraction feedbacks in climate warming scenarios than currently predicted by conventional GCMs and highlight the potential relevance of deep convective processes. Key Points Larger positive longwave feedback in NICAM than in conventional GCMs High cloud fraction increases in NICAM in increased SST experiments Possibility of larger high cloud fraction feedback in future models © 2014. The Authors."
"56612517400;36538539800;55462884000;7202418289;55915206300;36680583100;57204359029;","Decadal simulation and comprehensive evaluation of CESM/CAM5.1 with advanced chemistry, aerosol microphysics, and aerosol-cloud interactions",2015,"10.1002/2014MS000360","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928789260&doi=10.1002%2f2014MS000360&partnerID=40&md5=dad06294dc5400cf90478f3edd0a7ed2","Earth system models have been used for climate predictions in recent years due to their capabilities to include biogeochemical cycles, human impacts, as well as coupled and interactive representations of Earth system components (e.g., atmosphere, ocean, land, and sea ice). In this work, the Community Earth System Model (CESM) with advanced chemistry and aerosol treatments, referred to as CESM-NCSU, is applied for decadal (2001-2010) global climate predictions. A comprehensive evaluation is performed focusing on the atmospheric component - the Community Atmosphere Model version 5.1 (CAM5.1) by comparing simulation results with observations/reanalysis data and CESM ensemble simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5). The improved model can predict most meteorological and radiative variables relatively well with normalized mean biases (NMBs) of -14.1 to -9.7% and 0.7-10.8%, respectively, although temperature at 2 m (T2) is slightly underpredicted. Cloud variables such as cloud fraction (CF) and precipitating water vapor (PWV) are well predicted, with NMBs of -10.5 to 0.4%, whereas cloud condensation nuclei (CCN), cloud liquid water path (LWP), and cloud optical thickness (COT) are moderately-to-largely underpredicted, with NMBs of -82.2 to -31.2%, and cloud droplet number concentration (CDNC) is overpredictd by 26.7%. These biases indicate the limitations and uncertainties associated with cloud microphysics (e.g., resolved clouds and subgrid-scale cumulus clouds). Chemical concentrations over the continental U.S. (CONUS) (e.g., SO42-, Cl-, OC, and PM2.5) are reasonably well predicted with NMBs of -12.8 to -1.18%. Concentrations of SO2, SO42-, and PM10 are also reasonably well predicted over Europe with NMBs of -20.8 to -5.2%, so are predictions of SO2 concentrations over the East Asia with an NMB of -18.2%, and the tropospheric ozone residual (TOR) over the globe with an NMB of -3.5%. Most meteorological and radiative variables predicted by CESM-NCSU agree well overall with those predicted by CESM-CMIP5. The performance of LWP and AOD predicted by CESM-NCSU is better than that of CESM-CMIP5 in terms of model bias and correlation coefficients. Large biases for some chemical predictions can be attributed to uncertainties in the emissions of precursor gases (e.g., SO2, NH3, and NOx) and primary aerosols (black carbon and primary organic matter) as well as uncertainties in formulations of some model components (e.g., online dust and sea-salt emissions, secondary organic aerosol formation, and cloud microphysics). Comparisons of CESM simulation with baseline emissions and 20% of anthropogenic emissions from the baseline emissions indicate that anthropogenic gas and aerosol species can decrease downwelling shortwave radiation (FSDS) by 4.7 W m-2 (or by 2.9%) and increase SWCF by 3.2 W m-2 (or by 3.1%) in the global mean. © 2015. The Authors."
"56571063800;13403627400;43661479500;53879778800;7006728825;7004469744;","Evaluating uncertainty in convective cloud microphysics using statistical emulation",2015,"10.1002/2014MS000383","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928804697&doi=10.1002%2f2014MS000383&partnerID=40&md5=398c3b5f8c9d90505530e06c4a8eeb1d","The microphysical properties of convective clouds determine their radiative effects on climate, the amount and intensity of precipitation as well as dynamical features. Realistic simulation of these cloud properties presents a major challenge. In particular, because models are complex and slow to run, we have little understanding of how the considerable uncertainties in parameterized processes feed through to uncertainty in the cloud responses. Here we use statistical emulation to enable a Monte Carlo sampling of a convective cloud model to quantify the sensitivity of 12 cloud properties to aerosol concentrations and nine model parameters representing the main microphysical processes. We examine the response of liquid and ice-phase hydrometeor concentrations, precipitation, and cloud dynamics for a deep convective cloud in a continental environment. Across all cloud responses, the concentration of the Aitken and accumulation aerosol modes and the collection efficiency of droplets by graupel particles have the most influence on the uncertainty. However, except at very high aerosol concentrations, uncertainties in precipitation intensity and amount are affected more by interactions between drops and graupel than by large variations in aerosol. The uncertainties in ice crystal mass and number are controlled primarily by the shape of the crystals, ice nucleation rates, and aerosol concentrations. Overall, although aerosol particle concentrations are an important factor in deep convective clouds, uncertainties in several processes significantly affect the reliability of complex microphysical models. The results suggest that our understanding of aerosol-cloud interaction could be greatly advanced by extending the emulator approach to models of cloud systems. © 2015. The Authors."
"57202299549;7006705919;7406243250;15765007300;","Short-term time step convergence in a climate model",2015,"10.1002/2014MS000368","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928780295&doi=10.1002%2f2014MS000368&partnerID=40&md5=d8bcfe004e06807a91cab9cc18d281c8","This paper evaluates the numerical convergence of very short (1 h) simulations carried out with a spectral-element (SE) configuration of the Community Atmosphere Model version 5 (CAM5). While the horizontal grid spacing is fixed at approximately 110 km, the process-coupling time step is varied between 1800 and 1 s to reveal the convergence rate with respect to the temporal resolution. Special attention is paid to the behavior of the parameterized subgrid-scale physics. First, a dynamical core test with reduced dynamics time steps is presented. The results demonstrate that the experimental setup is able to correctly assess the convergence rate of the discrete solutions to the adiabatic equations of atmospheric motion. Second, results from full-physics CAM5 simulations with reduced physics and dynamics time steps are discussed. It is shown that the convergence rate is 0.4 - considerably slower than the expected rate of 1.0. Sensitivity experiments indicate that, among the various subgrid-scale physical parameterizations, the stratiform cloud schemes are associated with the largest time-stepping errors, and are the primary cause of slow time step convergence. While the details of our findings are model specific, the general test procedure is applicable to any atmospheric general circulation model. The need for more accurate numerical treatments of physical parameterizations, especially the representation of stratiform clouds, is likely common in many models. The suggested test technique can help quantify the time-stepping errors and identify the related model sensitivities. © 2015. The Authors."
"55519994900;23991212200;55411439700;","The response of US summer rainfall to quadrupled CO2 climate change in conventional and superparameterized versions of the NCAR community atmosphere model",2015,"10.1002/2014MS000306","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930677124&doi=10.1002%2f2014MS000306&partnerID=40&md5=232bc47ef7f3dc27c6012b6a2e7845a8","Observations and regional climate modeling (RCM) studies demonstrate that global climate models (GCMs) are unreliable for predicting changes in extreme precipitation. Yet RCM climate change simulations are subject to boundary conditions provided by GCMs and do not interact with large-scale dynamical feedbacks that may be critical to the overall regional response. Limitations of both global and regional modeling approaches contribute significant uncertainty to future rainfall projections. Progress requires a modeling framework capable of capturing the observed regional-scale variability of rainfall intensity without sacrificing planetary scales. Here the United States summer rainfall response to quadrupled CO2 climate change is investigated using conventional (CAM) and superparameterized (SPCAM) versions of the NCAR Community Atmosphere Model. The superparameterization approach, in which cloud-resolving model arrays are embedded in GCM grid columns, improves rainfall statistics and convective variability in global simulations. A set of 5 year time-slice simulations, with prescribed sea surface temperature and sea ice boundary conditions harvested from preindustrial and abrupt four times CO2 coupled Community Earth System Model (CESM/CAM) simulations, are compared for CAM and SPCAM. The two models produce very different changes in mean precipitation patterns, which develop from differences in large-scale circulation anomalies associated with the planetary-scale response to warming. CAM shows a small decrease in overall rainfall intensity, with an increased contribution from the weaker parameterized convection and a decrease from large-scale precipitation. SPCAM has the opposite response, a significant shift in rainfall occurrence toward higher precipitation rates including more intense propagating Central United States mesoscale convective systems in a four times CO2 climate. Key Points Large-scale dynamics are critical to regional rainfall climate change responses Superparameterization captures expected increases in rain and storm intensity Extreme rain may be decoupled from key climate change drivers in standard GCMs © 2014. American Geophysical Union. All Rights Reserved."
"15044268700;25637373000;6507492100;7004687638;35984036000;6602075440;7005814217;7102450474;7102696626;56725357800;","A spectral transform dynamical core option within the Community Atmosphere Model (CAM4)",2015,"10.1002/2014MS000329","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937202641&doi=10.1002%2f2014MS000329&partnerID=40&md5=4767cacb37c02808173cc7d572420618","An ensemble of simulations covering the present day observational period using forced sea surface temperatures and prescribed sea-ice extent is configured with an 85 truncation resolution spectral transform dynamical core (T85) within the Community Atmosphere Model (CAM), version 4 and is evaluated relative to observed and model derived data sets and the one degree finite volume (FV) dynamical core. The spectral option provides a well-known base within the climate model community to assess climate behavior and statistics, and its relative computational efficiency for smaller computing platforms allows it to be extended to perform high-resolution climate length simulations. Overall, the quality of the T85 ensemble is similar to FV. Analyzing specific features of the T85 simulations show notable improvements to the representation of wintertime Arctic sea level pressure and summer precipitation over the Western Indian subcontinent. The mean and spatial patterns of the land surface temperature trends over the AMIP period are generally well simulated with the T85 ensemble relative to observations, however the model is not able to capture the extent nor magnitude of changes in temperature extremes over the boreal summer, where the changes are most dramatic. Biases in the wintertime Arctic surface temperature and annual mean surface stress fields persist with T85 as with the CAM3 version of T85, as compared to FV. An experiment to identify the source of differences between dycores has revealed that the longwave cloud forcing is sensitive to the choice of dycore, which has implications for tuning strategies of the physics parameter settings. Key Points Longwave cloud forcing in T85 CAM4 is sensitive to the choice of dynamical core Improved precipitation over India does not translate to improved surface stress The increase in temperature extremes during NH summer is underestimated © 2014. The Authors."
"28268113000;35933524800;6602271599;54941109900;7003539477;8320132400;57194045072;35208465800;54996804200;7102890924;6602334969;","The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity",2015,"10.1002/2014MS000324","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937199156&doi=10.1002%2f2014MS000324&partnerID=40&md5=70ef93a393241138abef01cf358df764","This paper presents the NOW regional coupled ocean-atmosphere model built from the NEMO ocean and WRF atmospheric numerical models. This model is applied to the tropical Indian Ocean, with the oceanic and atmospheric components sharing a common °horizontal grid. Long experiments are performed over the 1990-2009 period using the Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) cumulus parameterizations. Both simulations produce a realistic distribution of seasonal rainfall and a realistic northward seasonal migration of monsoon rainfall over the Indian subcontinent. At subseasonal time scales, the model reasonably reproduces summer monsoon active and break phases, although with underestimated rainfall and surface wind signals. Its relatively high resolution results in realistic spatial and seasonal distributions of tropical cyclones, but it fails to reproduce the strongest observed cyclone categories. At interannual time scales, the model reproduces the observed variability associated with the Indian Ocean Dipole (IOD) and the delayed basin-wide warming/cooling induced by the El Niño Southern Oscillation (ENSO). The timing of IOD occurrence in the model generally matches that of the observed events, confirming the influence of ENSO on the IOD development (through the effect of lateral boundary conditions in our simulations). Although the KF and BMJ simulations share a lot in common, KF strongly overestimates rainfall at all time scales. KF also overestimates the number of simulated cyclones by a factor two, while simulating stronger events (up to 55 m s-1) compared to BMJ (up to 40 m s-1). These results could be related to an overly active cumulus parameterization in KF. Key Points Application of a new coupled regional climate model to the tropical Indian Ocean Sensitivity to convection schemes from intraseasonal to interannual time scales Role of ENSO for triggering the Indian Ocean Dipole © 2014. The Authors."
"36931129200;36141355100;57203053317;","Microphysical processing of aerosol particles in orographic clouds",2015,"10.5194/acp-15-9217-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939863197&doi=10.5194%2facp-15-9217-2015&partnerID=40&md5=bfdee94859fb5a092d91045e3d0002f7","An explicit and detailed treatment of cloud-borne particles allowing for the consideration of aerosol cycling in clouds has been implemented into COSMO-Model, the regional weather forecast and climate model of the Consortium for Small-scale Modeling (COSMO). The effects of aerosol scavenging, cloud microphysical processing and regeneration upon cloud evaporation on the aerosol population and on subsequent cloud formation are investigated. For this, two-dimensional idealized simulations of moist flow over two bell-shaped mountains were carried out varying the treatment of aerosol scavenging and regeneration processes for a warm-phase and a mixed-phase orographic cloud. The results allowed us to identify different aerosol cycling mechanisms. In the simulated non-precipitating warm-phase cloud, aerosol mass is incorporated into cloud droplets by activation scavenging and released back to the atmosphere upon cloud droplet evaporation. In the mixed-phase cloud, a first cycle comprises cloud droplet activation and evaporation via the Wegener-Bergeron-Findeisen (WBF) process. A second cycle includes below-cloud scavenging by precipitating snow particles and snow sublimation and is connected to the first cycle via the riming process which transfers aerosol mass from cloud droplets to snowflakes. In the simulated mixed-phase cloud, only a negligible part of the total aerosol mass is incorporated into ice crystals. Sedimenting snowflakes reaching the surface remove aerosol mass from the atmosphere. The results show that aerosol processing and regeneration lead to a vertical redistribution of aerosol mass and number. Thereby, the processes impact the total aerosol number and mass and additionally alter the shape of the aerosol size distributions by enhancing the internally mixed/soluble Aitken and accumulation mode and generating coarse-mode particles. Concerning subsequent cloud formation at the second mountain, accounting for aerosol processing and regeneration increases the cloud droplet number concentration with possible implications for the ice crystal number concentration. © Author(s) 2015."
"35868180800;7005477332;7004315232;6701416358;","Human-caused fires limit convection in tropical Africa: First temporal observations and attribution",2015,"10.1002/2015GL065063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940448515&doi=10.1002%2f2015GL065063&partnerID=40&md5=9ac628267e7a8697ebb976fe383a1244","It is well established that smoke particles modify clouds, which in turn affects climate. However, no study has quantified the temporal dynamics of aerosol-cloud interactions with direct observations. Here for the first time, we use temporally offset satellite observations from northern Africa between 2006 and 2010 to quantitatively measure the effect of fire aerosols on convective cloud dynamics. We attribute a reduction in cloud fraction during periods of high aerosol optical depths to a smoke-driven inhibition of convection. We find that higher smoke burdens limit upward vertical motion, increase surface pressure, and increase low-level divergence - meteorological indicators of convective suppression. These results are corroborated by climate simulations that show a smoke-driven increase in regionally averaged shortwave tropospheric heating and decrease in convective precipitation during the fire season. Our results suggest that in tropical regions, anthropogenic fire initiates a positive feedback loop where increased aerosol emissions limit convection, dry the surface, and enable increased fire activity via human ignition. ©2015. American Geophysical Union. All Rights Reserved."
"55729575400;55769580900;57191749372;","Modification of cumulus convection and planetary boundary layer schemes in the GRAPES global model",2015,"10.1007/s13351-015-5043-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007190395&doi=10.1007%2fs13351-015-5043-5&partnerID=40&md5=0954d8b4df966868d30595fa8e2b2f7a","Cumulus convection is a key linkage between hydrological cycle and large-scale atmospheric circulation. Cumulus parameterization scheme is an important component in numerical weather and climate modeling studies. In the Global/Regional Assimilation and Prediction Enhanced System (GRAPES), turbulent mixing and diffusion approach is applied in its shallow convection scheme. This method overestimates the vertical transport of heat and moisture fluxes but underestimates cloud water mixing ratio over the region of stratocumulus clouds. As a result, the simulated low stratocumulus clouds are less than observations. To overcome this problem, a mass flux method is employed in the shallow convection scheme to replace the original one. Meanwhile, the deep convection scheme is adjusted correspondingly. This modification is similar to that in the US NCEP Global Forecast System (GFS), which uses the simplified Arakawa Schubert Scheme (SAS). The planetary boundary layer scheme (PBL) is also revised by considering the coupling between the PBL and stratocumulus clouds. With the modification of both the cumulus and PBL schemes, the GRAPES simulation of shallow convective heating rate becomes more reasonable; total amounts of stratocumulus clouds simulated over the eastern Pacific and their vertical structure are more consistent with observations; the underestimation of stratocumulus clouds simulated by original schemes is less severe with the revised schemes. Precipitation distribution in the tropics becomes more reasonable and spurious precipitation is effectively suppressed. The westward extension and northward movement of the western Pacific subtropical high simulated with the revised schemes are more consistent with Final Operational Global Analysis (FNL) than that simulated with the original schemes. The statistical scores for the global GRAPES forecast are generally improved with the revised schemes, especially for the simulation of geopotential height in the Northern Hemisphere and winds in the tropics. Root mean square errors (RMSEs) decrease in the lower and upper troposphere with the revised schemes. The above results indicate that with the revised cumulus and PBL schemes, model biases in the tropics decrease and the global GRAPES performance is greatly improved. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2015."
"7005275092;","Photolysis rates in correlated overlapping cloud fields: Cloud-J 7.3c",2015,"10.5194/gmd-8-2587-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939155073&doi=10.5194%2fgmd-8-2587-2015&partnerID=40&md5=fe2d52149382a4dd93fd84e88f30e063","A new approach for modeling photolysis rates (J values) in atmospheres with fractional cloud cover has been developed and is implemented as Cloud-J - a multi-scattering eight-stream radiative transfer model for solar radiation based on Fast-J. Using observations of the vertical correlation of cloud layers, Cloud-J 7.3c provides a practical and accurate method for modeling atmospheric chemistry. The combination of the new maximum-correlated cloud groups with the integration over all cloud combinations by four quadrature atmospheres produces mean J values in an atmospheric column with root mean square (rms) errors of 4 % or less compared with 10-20 % errors using simpler approximations. Cloud-J is practical for chemistry-climate models, requiring only an average of 2.8 Fast-J calls per atmosphere vs. hundreds of calls with the correlated cloud groups, or 1 call with the simplest cloud approximations. Another improvement in modeling J values, the treatment of volatile organic compounds with pressure-dependent cross sections, is also incorporated into Cloud-J. © Author(s) 2015."
"55800291300;55915046600;56218731300;7801686786;6506846397;56781470400;","Three-dimensional dust aerosol distribution and extinction climatology over northern Africa simulated with the ALADIN numerical prediction model from 2006 to 2010",2015,"10.5194/acp-15-9063-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939226744&doi=10.5194%2facp-15-9063-2015&partnerID=40&md5=b331aef5a1af2dea5668fb449d1e90e3","The seasonal cycle and optical properties of mineral dust aerosols in northern Africa were simulated for the period from 2006 to 2010 using the numerical atmospheric model ALADIN (Aire Limitée Adaptation dynamique Développement InterNational) coupled to the surface scheme SURFEX (SURFace EXternalisée). The particularity of the simulations is that the major physical processes responsible for dust emission and transport, as well as radiative effects, are taken into account on short timescales and at mesoscale resolution. The aim of these simulations is to quantify the dust emission and deposition, locate the major areas of dust emission and establish a climatology of aerosol optical properties in northern Africa. The mean monthly aerosol optical thickness (AOT) simulated by ALADIN is compared with the AOTs derived from the standard Dark Target (DT) and Deep Blue (DB) algorithms of the Aqua-MODIS (MODerate resolution Imaging Spectroradiometer) products over northern Africa and with a set of sun photometer measurements located at Banizoumbou, Cinzana, Soroa, Mbour and Cape Verde. The vertical distribution of dust aerosol represented by extinction profiles is also analysed using CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) observations. The annual dust emission simulated by ALADIN over northern Africa is 878 Tg year-1. The Bodélé Depression appears to be the main area of dust emission in northern Africa, with an average estimate of about 21.6 Tg year-1. The simulated AOTs are in good agreement with satellite and sun photometer observations. The positions of the maxima of the modelled AOTs over northern Africa match the observed positions, and the ALADIN simulations satisfactorily reproduce the various dust events over the 2006-2010 period. The AOT climatology proposed in this paper provides a solid database of optical properties and consolidates the existing climatology over this region derived from satellites, the AERONET network and regional climate models. Moreover, the 3-D distribution of the simulated AOTs also provides information about the vertical structure of the dust aerosol extinction. © Author(s) 2015."
"56814942700;55493791400;56811010900;8968525800;7103357902;7402538754;7004288217;","Schneefernerhaus as a mountain research station for clouds and turbulence",2015,"10.5194/amt-8-3209-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939186571&doi=10.5194%2famt-8-3209-2015&partnerID=40&md5=5c676e6763098daa4b550fd2247ba696","Cloud measurements are usually carried out with airborne campaigns, which are expensive and are limited by temporal duration and weather conditions. Ground-based measurements at high-altitude research stations therefore play a complementary role in cloud study. Using the meteorological data (wind speed, direction, temperature, humidity, visibility, etc.) collected by the German Weather Service (DWD) from 2000 to 2012 and turbulence measurements recorded by multiple ultrasonic sensors (sampled at 10 Hz) in 2010, we show that the Umweltforschungsstation Schneefernerhaus (UFS) located just below the peak of Zugspitze in the German Alps, at a height of 2650 m, is a well-suited station for cloud-turbulence research. The wind at UFS is dominantly in the east-west direction and nearly horizontal. During the summertime (July and August) the UFS is immersed in warm clouds about 25 % of the time. The clouds are either from convection originating in the valley in the east, or associated with synoptic-scale weather systems typically advected from the west. Air turbulence, as measured from the second- and third-order velocity structure functions that exhibit well-developed inertial ranges, possesses Taylor microscale Reynolds numbers up to 104, with the most probable value at ∼ 3000. In spite of the complex topography, the turbulence appears to be nearly as isotropic as many laboratory flows when evaluated on the ""Lumley triangle"". © Author(s) 2015."
"6602087787;6603697954;40761587800;56579812000;7006238452;9943588200;36160514000;7004353965;35611456600;36846877900;6602357598;6701858573;","Melt pond fraction and spectral sea ice albedo retrieval from MERIS data - Part 1: Validation against in situ, aerial, and ship cruise data",2015,"10.5194/tc-9-1551-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939148708&doi=10.5194%2ftc-9-1551-2015&partnerID=40&md5=28b73a7e91709ae9eaff705429e8041f","The presence of melt ponds on the Arctic sea ice strongly affects the energy balance of the Arctic Ocean in summer. It affects albedo as well as transmittance through the sea ice, which has consequences for the heat balance and mass balance of sea ice. An algorithm to retrieve melt pond fraction and sea ice albedo from Medium Resolution Imaging Spectrometer (MERIS) data is validated against aerial, shipborne and in situ campaign data. The results show the best correlation for landfast and multiyear ice of high ice concentrations. For broadband albedo, R2 is equal to 0.85, with the RMS (root mean square) being equal to 0.068; for the melt pond fraction, R2 is equal to 0.36, with the RMS being equal to 0.065. The correlation for lower ice concentrations, subpixel ice floes, blue ice and wet ice is lower due to ice drift and challenging for the retrieval surface conditions. Combining all aerial observations gives a mean albedo RMS of 0.089 and a mean melt pond fraction RMS of 0.22. The in situ melt pond fraction correlation is R2 = 0.52 with an RMS = 0.14. Ship cruise data might be affected by documentation of varying accuracy within the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol, which may contribute to the discrepancy between the satellite value and the observed value: mean R2 = 0.044, mean RMS = 0.16. An additional dynamic spatial cloud filter for MERIS over snow and ice has been developed to assist with the validation on swath data. © Author(s) 2015."
"6602087787;6603697954;40761587800;56779685000;6602493816;35611456600;36846877900;6602357598;6701858573;","Melt pond fraction and spectral sea ice albedo retrieval from MERIS data - Part 2: Case studies and trends of sea ice albedo and melt ponds in the Arctic for years 2002-2011",2015,"10.5194/tc-9-1567-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939158015&doi=10.5194%2ftc-9-1567-2015&partnerID=40&md5=b8e59f35425660bc9cba352b1eff4d5c","The spatial and temporal dynamics of melt ponds and sea ice albedo contain information on the current state and the trend of the climate of the Arctic region. This publication presents a study on melt pond fraction (MPF) and sea ice albedo spatial and temporal dynamics obtained with the Melt Pond Detection (MPD) retrieval scheme for the Medium Resolution Imaging Spectrometer (MERIS) satellite data. This study compares sea ice albedo and MPF to surface air temperature reanalysis data, compares MPF retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS), and examines albedo and MPF trends. Weekly averages of MPF for 2007 and 2011 showed different MPF dynamics while summer sea ice minimum was similar for both years. The gridded MPF and albedo products compare well to independent reanalysis temperature data and show melt onset when the temperature gets above zero; however MPD shows an offset at low MPFs of about 10 % most probably due to unscreened high clouds. Weekly averaged trends show pronounced dynamics of both, MPF and albedo: a negative MPF trend in the East Siberian Sea and a positive MPF trend around the Queen Elizabeth Islands. The negative MPF trend appears due to a change of the absolute MPF value in its peak, whereas the positive MPF trend is created by the earlier melt onset, with the peak MPF values unchanged. The MPF dynamics in the East Siberian Sea could indicate a temporal change of ice type prevailing in the region, as opposed to the Queen Elizabeth Islands, where MPF dynamics react to an earlier seasonal onset of melt. © Author(s) 2015."
"7410069943;7501757094;55714712500;56240865700;","Past and future direct radiative forcing of nitrate aerosol in East Asia",2015,"10.1007/s00704-014-1249-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938739624&doi=10.1007%2fs00704-014-1249-1&partnerID=40&md5=0158f94e0157e14b8a24b4f9dc8174e0","Nitrate as a rapidly increasing aerosol species in recent years affects the present climate and potentially has large implications on the future climate. In this study, the long-term direct radiative forcing (DRF) of nitrate aerosol is investigated using State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) atmospheric general circulation model (AGCM) and the aerosol dataset simulated by a chemical transport model with focus on East Asia. The DRF due to other aerosols, especially sulfate, is also evaluated for comparisons. Although the chemical transport model underestimates the magnitudes of nitrate and sulfate aerosols when compared with Chinese site observations, some insights into the significances of nitrate climate effects still emerge. The present-day global annual mean all-sky DRF of nitrate is calculated to be −0.025 W m−2 relative to the preindustrial era, which is much weaker than −0.37 W m−2 for sulfate. However, nitrate DRF may become increasingly important in the future especially over East Asia, given the expectation that decreasing trend in global sulfate continues while the projected nitrate maintains at the present level for a mid-range forcing scenario and even be a factor of two larger by the end of the 21st century for high emission scenarios. For example, the anthropogenic nitrate DRF of −2.0 W m−2 over eastern China could persist until the 2050s, and nitrate is projected to account for over 60 % of total anthropogenic aerosol DRF over East Asia by 2100. In addition, we illustrate that the regional nitrate DRF and its seasonal variation are sensitive to meteorological parameters, in particular the relative humidity and cloud amount. It thus remains a need for climate models to include more realistically nitrate aerosol in projecting future climate changes. © 2014, Springer-Verlag Wien."
"36182467000;15019752400;55965624000;55976582900;7005219614;","Revision of the convective transport module CVTRANS 2.4 in the EMAC atmospheric chemistry-climate model",2015,"10.5194/gmd-8-2435-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938680511&doi=10.5194%2fgmd-8-2435-2015&partnerID=40&md5=eb6cc7ceb98412f448291b772fd40b0e","The convective transport module, CVTRANS, of the ECHAM/MESSy Atmospheric Chemistry (EMAC) model has been revised to better represent the physical flows and incorporate recent findings on the properties of the convective plumes. The modifications involve (i) applying intermediate time stepping based on a settable criterion, (ii) using an analytic expression to account for the intra-time-step mixing ratio evolution below cloud base, and (iii) implementing a novel expression for the mixing ratios of atmospheric compounds at the base of an updraft. Even when averaged over a year, the predicted mixing ratios of atmospheric compounds are affected considerably by the intermediate time stepping. For example, for an exponentially decaying atmospheric tracer with a lifetime of 1 day, the zonal averages can locally differ by more than a factor of 6 and the induced root mean square deviation from the original code is, weighted by the air mass, higher than 40% of the average mixing ratio. The other modifications result in smaller differences. However, since they do not require additional computational time, their application is also recommended. © Author(s) 2015."
"56682032300;55683727600;36026436300;55588510300;54402966300;6601941399;13405658600;","Uncertainties in global aerosols and climate effects due to biofuel emissions",2015,"10.5194/acp-15-8577-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938633742&doi=10.5194%2facp-15-8577-2015&partnerID=40&md5=4d83645e7b15ed79c881463098a18b78","Aerosol emissions from biofuel combustion impact both health and climate; however, while reducing emissions through improvements to combustion technologies will improve health, the net effect on climate is largely unconstrained. In this study, we examine sensitivities in global aerosol concentration, direct radiative climate effect, and cloud-albedo aerosol indirect climate effect to uncertainties in biofuel emission factors, optical mixing state, and model nucleation and background secondary organic aerosol (SOA). We use the Goddard Earth Observing System global chemical-transport model (GEOS-Chem) with TwO Moment Aerosol Sectional (TOMAS) microphysics. The emission factors include amount, composition, size, and hygroscopicity, as well as optical mixing-state properties. We also evaluate emissions from domestic coal use, which is not biofuel but is also frequently emitted from homes. We estimate the direct radiative effect assuming different mixing states (homogeneous, core-shell, and external) with and without absorptive organic aerosol (brown carbon). We find the global-mean direct radiative effect of biofuel emissions ranges from -0.02 to +0.06 W m-2 across all simulation/mixing-state combinations with regional effects in source regions ranging from -0.2 to +0.8 W m-2. The global-mean cloud-albedo aerosol indirect effect (AIE) ranges from +0.01 to -0.02 W m-2 with regional effects in source regions ranging from -1.0 to -0.05 W m-2. The direct radiative effect is strongly dependent on uncertainties in emissions mass, composition, emissions aerosol size distributions, and assumed optical mixing state, while the indirect effect is dependent on the emissions mass, emissions aerosol size distribution, and the choice of model nucleation and secondary organic aerosol schemes. The sign and magnitude of these effects have a strong regional dependence. We conclude that the climate effects of biofuel aerosols are largely unconstrained, and the overall sign of the aerosol effects is unclear due to uncertainties in model inputs. This uncertainty limits our ability to introduce mitigation strategies aimed at reducing biofuel black carbon emissions in order to counter warming effects from greenhouse gases. To better understand the climate impact of particle emissions from biofuel combustion, we recommend field/laboratory measurements to narrow constraints on (1) emissions mass, (2) emission size distribution, (3) mixing state, and (4) ratio of black carbon to organic aerosol. © Author(s) 2015."
"55973913400;7006434689;55999273500;56442378900;35751142400;14034301300;56533839200;55554016600;6701842515;7005069415;","The Ice Selective Inlet: A novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds",2015,"10.5194/amt-8-3087-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938635314&doi=10.5194%2famt-8-3087-2015&partnerID=40&md5=19e61d2e844854be5130b84fbd3fb9ef","Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol-cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs) via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of much more numerous liquid droplets. The Ice Selective Inlet (ISI), presented in this paper, is a novel inlet designed to selectively sample pristine ice crystals in mixed-phase clouds and extract the ice residual particles contained within the crystals for physical and chemical characterization. Using a modular setup composed of a cyclone impactor, droplet evaporation unit and pumped counterflow virtual impactor (PCVI), the ISI segregates particles based on their inertia and phase, exclusively extracting small ice particles between 5 and 20 andmu;m in diameter. The setup also includes optical particle spectrometers for analysis of the number size distribution and shape of the sampled hydrometeors. The novelty of the ISI is a droplet evaporation unit, which separates liquid droplets and ice crystals in the airborne state, thus avoiding physical impaction of the hydrometeors and limiting potential artefacts. The design and validation of the droplet evaporation unit is based on modelling studies of droplet evaporation rates and computational fluid dynamics simulations of gas and particle flows through the unit. Prior to deployment in the field, an inter-comparison of the optical particle size spectrometers and a characterization of the transmission efficiency of the PCVI was conducted in the laboratory. The ISI was subsequently deployed during the Cloud and Aerosol Characterization Experiment (CLACE) 2013 and 2014-two extensive international field campaigns encompassing comprehensive measurements of cloud microphysics, as well as bulk aerosol, ice residual and ice nuclei properties. The campaigns provided an important opportunity for a proof of concept of the inlet design. In this work we present the setup of the ISI, including the modelling and laboratory characterization of its components, as well as field measurements demonstrating the ISI performance and validating the working principle of the inlet. Finally, measurements of biological aerosol during a Saharan dust event (SDE) are presented, showing a first indication of enrichment of bio-material in sub-2 μm ice residuals. © 2015 Author(s)."
"55328699600;7003681353;55227462000;","Crop failure rates in a geoengineered climate: Impact of climate change and marine cloud brightening",2015,"10.1088/1748-9326/10/8/084003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938718660&doi=10.1088%2f1748-9326%2f10%2f8%2f084003&partnerID=40&md5=84c0b2a14acf226bb984b2f948d39e6a","The impact of geoengineering on crops has to date been studied by examining mean yields. We present the first work focusing on the rate of crop failures under a geoengineered climate. We investigate the impact of a future climate and a potential geoengineering scheme on the number of crop failures in two regions, Northeastern China and West Africa. Climate change associated with a doubling of atmospheric carbon dioxide increases the number of crop failures in Northeastern China while reducing the number of crop failures in West Africa. In both regions marine cloud brightening is likely to reduce the number crop failures, although it is more effective at reducing mild crop failure than severe crop failure. We find that water stress, rather than heat stress, is the main cause of crop failure in current, future and geoengineered climates. This demonstrates the importance of irrigation and breeding for tolerance to water stress as adaptation methods in all futures. Analysis of global rainfall under marine cloud brightening has the potential to significantly reduce the impact of climate change on global wheat and groundnut production. © 2015 IOP Publishing Ltd."
"6701519241;8071168700;","A simple scaling approach to produce climate scenarios of local precipitation extremes for the Netherlands",2015,"10.1088/1748-9326/10/8/085001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938813013&doi=10.1088%2f1748-9326%2f10%2f8%2f085001&partnerID=40&md5=f2389804fc5aefae532225ef7d1649cb","Scenarios of future changes in small scale precipitation extremes for the Netherlands are presented. These scenarios are based on a new approach whereby changes in precipitation extremes are set proportional to the change in water vapor amount near the surface as measured by the 2m dew point temperature. This simple scaling framework allows the integration of information derived from: (i) observations, (ii) a new unprecedentedly large 16 member ensemble of simulations with the regional climate model RACMO2 driven by EC-Earth, and (iii) short term integrations with a non-hydrostatic model Harmonie. Scaling constants are based on subjective weighting (expert judgement) of the three different information sources taking also into account previously published work. In all scenarios local precipitation extremes increase with warming, yet with broad uncertainty ranges expressing incomplete knowledge of how convective clouds and the atmospheric mesoscale circulation will react to climate change. © 2015 IOP Publishing Ltd."
"12242677000;6603282418;","Net surface shortwave radiation from GOES imagery-product evaluation using ground-based measurements from SURFRAD",2015,"10.3390/rs70810788","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962560207&doi=10.3390%2frs70810788&partnerID=40&md5=498f7f668ee1c38e817b0864ea13f6d9","The Earth's surface net radiation controls the energy and water exchanges between the Earth's surface and the atmosphere, and can be derived from satellite observations. The ability to monitor the net surface radiation over large areas at high spatial and temporal resolution is essential for many applications, such as weather forecasting, short-term climate prediction or water resources management. The objective of this paper is to derive the net surface radiation in the shortwave domain at high temporal (half-hourly) and spatial resolution (~1 km) using visible imagery from Geostationary Operational Environmental Satellite (GOES). The retrieval algorithm represents an adaptation to GOES data of a standard algorithm initially developed for the NASA-operated Clouds and Earth's Radiant Energy System (CERES) scanner. The methodology relies on: (1) the estimation of top of atmosphere shortwave radiation from GOES spectral measurements; and (2) the calculation of net surface shortwave (SW) radiation accounting for atmospheric effects. Comparison of GOES-retrieved net surface shortwave radiation with ground-measurements at the National Oceanic and Atmospheric Administration's (NOAA) Surface Radiation (SURFRAD) stations yields very good agreement with average bias lower than 5 W.m-2 and root mean square difference around 70 W.m-2. The algorithm performance is usually higher over areas characterized by low spatial variability in term of land cover type and surface biophysical properties. The technique does not involve retrieval and assessment of cloud properties and can be easily adapted to other meteorological satellites around the globe. © 2015 by the authors."
"55501554900;36538539800;56149492300;57206910481;7004713805;","Implementation and initial application of new chemistry-aerosol options in WRF/Chem for simulating secondary organic aerosols and aerosol indirect effects for regional air quality",2015,"10.1016/j.atmosenv.2014.12.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926161331&doi=10.1016%2fj.atmosenv.2014.12.007&partnerID=40&md5=9459085261737b902077c7bfef1c473e","Atmospheric aerosols play important roles in affecting regional meteorology and air quality through aerosol direct and indirect effects. Two new chemistry-aerosol options have been developed in WRF/Chem v3.4.1 by incorporating the 2005 Carbon Bond (CB05) mechanism and coupling it with the existing aerosol module MADE with SORGAM and VBS modules for simulating secondary organic aerosol (SOA), aqueous-phase chemistry in both large scale and convective clouds, and aerosol feedback processes (hereafter CB05-MADE/SORGAM and CB05-MADE/VBS). As part of the Air Quality Model Evaluation International Initiative (AQMEII) Phase II model intercomparison that focuses on online-coupled meteorology and chemistry models, WRF/Chem with the two new options is applied to an area over North America for July 2006 episode. The simulations with both options can reproduce reasonably well most of the observed meteorological variables, chemical concentrations, and aerosol/cloud properties. Compared to CB05-MADE/SORGAM, CB05-MADE/VBS greatly improves the model performance for organic carbon (OC) and PM2.5, reducing NMBs from -81.2% to -13.1% and from -26.1% to -15.6%, respectively. Sensitivity simulations show that the aerosol indirect effects (including aqueous-phase chemistry) can reduce the net surface solar radiation by up to 53 W m-2 with a domainwide mean of 12 W m-2 through affecting cloud formation and radiation scattering and reflection by increasing cloud cover, which in turn reduce the surface temperature, NO2 photolytic rate, and planetary boundary layer height by up to 0.3 °C, 3.7 min-1, and 64 m, respectively. The changes of those meteorological variables further impact the air quality through the complex chemistry-aerosol-cloud-radiation interactions by reducing O3 mixing ratios by up to 5.0 ppb. The results of this work demonstrate the importance of aerosol indirect effects on the regional climate and air quality. For comparison, the impacts of aerosol direct effects on both regional meteorology and air quality are much lower with the reduction on net surface solar radiation only by up to 17 W m-2 and O3 only by up to 1.4 ppb, which indicates the importance and necessity to accurately represent the aerosol indirect effects in the online-couple regional models. © 2014 Elsevier Ltd."
"56027890800;26639062900;37091783400;6602765265;7005773698;","Comparison of the mixing state of long-range transported Asian and African mineral dust",2015,"10.1016/j.atmosenv.2015.04.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930652770&doi=10.1016%2fj.atmosenv.2015.04.031&partnerID=40&md5=a37d862ccc5e4908e5ed8ea7cb5b352f","Mineral dust from arid regions represents the second largest global source of aerosols to the atmosphere. Dust strongly impacts the radiative balance of the earth's atmosphere by directly scattering solar radiation and acting as nuclei for the formation of liquid droplets and ice nuclei within clouds. The climate effects of mineral dust aerosols are poorly understood, however, due to their complex chemical and physical properties, which continuously evolve during atmospheric transport. This work focuses on characterizing atmospheric mineral dust from the two largest global dust sources: the Sahara Desert in Africa and the Gobi and Taklamakan Deserts in Asia. Measurements of individual aerosol particle size and chemical mixing state were made at El Yunque National Forest, Puerto Rico, downwind of the Sahara Desert, and Gosan, South Korea, downwind of the Gobi and Taklamakan Deserts. In general, the chemical characterization of the individual dust particles detected at these two sites reflected the dominant mineralogy of the source regions; aluminosilicate-rich dust was more common at El Yunque (~91% of El Yunque dust particles vs. ~69% of Gosan dust particles) and calcium-rich dust was more common at Gosan (~22% of Gosan dust particles vs. ~2% of El Yunque dust particles). Furthermore, dust particles from Africa and Asia were subjected to different transport conditions and atmospheric processing; African dust showed evidence of cloud processing, while Asian dust was modified via heterogeneous chemistry and direct condensation of secondary species. A larger fraction of dust detected at El Yunque contained the cloud-processing marker oxalate ion compared to dust detected at Gosan (~20% vs ~9%). Additionally, nearly 100% of dust detected at Gosan contained nitrate, showing it was aged via heterogeneous reactions with nitric acid, compared to only ~60% of African dust. Information on the distinct differences in the chemical composition of mineral dust particles, as well as the mechanisms and extent of atmospheric processing, is critical for assessing its impacts on the earth's radiative budget through scattering, absorption, and nucleating cloud droplets and ice crystals. © 2015 Elsevier Ltd."
"57218444105;7402146514;7102953444;35758658900;","Analysis of surface incident shortwave radiation from four satellite products",2015,"10.1016/j.rse.2015.05.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930197873&doi=10.1016%2fj.rse.2015.05.015&partnerID=40&md5=0b13249eeff79d515d67cf60d753c26d","Incident solar radiation (R<inf>s</inf>) over the Earth's surface is important for studying our climate and environment. Global observation networks have been established, but many land surfaces are under-represented. Satellite remote sensing is the only way to estimate R<inf>s</inf> at both global and regional scales. Many efforts have been made to evaluate the accuracy of current R<inf>s</inf> products generated from satellite observations, but only a limited amount of ground measurements was generally used and the individual satellite products were used for analyzing R<inf>s</inf> variability. In this study, four satellite estimates of R<inf>s</inf>, including the Global Energy and Water Cycle Experiment - Surface Radiation Budget (GEWEX-SRB V3.0), the International Satellite Cloud Climatology Project - Flux Data (ISCCP-FD), the University of Maryland (UMD)/Shortwave Radiation Budget (SRB) (UMD-SRB V3.3.3) product, and the Earth's Radiant Energy System (CERES) EBAF, were evaluated using comprehensive ground measurements at 1151 sites around the world from the Global Energy Balance Archive (GEBA) and the China Meteorological Administration (CMA). It was found that these satellite estimates of R<inf>s</inf> agree better with surface measurements at monthly than at daily time scale and can capture the seasonal variation of R<inf>s</inf> very well, but these satellite products overestimated R<inf>s</inf> by approximately 10wm-2. The mean bias and the root mean square error (RMSE) of the monthly mean estimates from these four data sets were 10.2wm-2 and 24.8wm-2 respectively. The global annual mean values of R<inf>s</inf> were 186.7wm-2, 185.4wm-2, and 188.6wm-2 for CERES-EBAF, ISCCP-FD, and GEWEX-SRB V3.0 respectively. The averaged global annual mean R<inf>s</inf> value from ground-measured-calibrated three satellite derived R<inf>s</inf> products was 180.6wm-2, which is smaller than that estimated from individual satellite-derived products. The CERES-EBAF product shows the best accuracy among these four data sets, which indicates that including more accurate cloud information from active instruments can improve the accuracy of R<inf>s</inf>. These satellite products show different temporal trends. Both GEWEX-SRB V3.0 and ISCCP-FD showed similar trends at the global scale but with different magnitudes. A significant dimming was found between 1984 and 1991, followed by brightening from 1992 to 2000, and then by a significant dimming over 2001-2007. The CERES-EBAF product showed a brightening trend, but not significantly since 2000. The variability from satellite estimates at pixel level was also analyzed. The results are comparable with previous studies based on observed R<inf>s</inf> at the surface for specific regions, although some inconsistencies still exist and the magnitudes of the variations should be further quantified. We also found that clouds contribute more to the long-term variations of R<inf>s</inf> derived from satellite observations than aerosols. © 2015 Elsevier Inc."
"6701463335;7202258620;7003498065;36538539800;7006304904;9738422100;9239331500;8625148400;54941580100;55938109300;6701342931;7202595372;55879681300;8067250600;13007286600;55807448700;56109007900;39361670300;56489746200;7403143315;14719880500;24767977600;22635720500;7003862871;54982705800;6505947323;55720332500;7003658498;","Feedbacks between air pollution and weather, part 2: Effects on chemistry",2015,"10.1016/j.atmosenv.2014.10.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937861018&doi=10.1016%2fj.atmosenv.2014.10.021&partnerID=40&md5=aa299d67d7f3fb35aea2fe091d152747","Fully-coupled air-quality models running in ""feedback"" and ""no-feedback"" configurations were compared against each other and observation network data as part of Phase 2 of the Air Quality Model Evaluation International Initiative. In the ""no-feedback"" mode, interactions between meteorology and chemistry through the aerosol direct and indirect effects were disabled, with the models reverting to climatologies of aerosol properties, or a no-aerosol weather simulation, while in the ""feedback"" mode, the model-generated aerosols were allowed to modify the models' radiative transfer and/or cloud formation processes. Annual simulations with and without feedbacks were conducted for domains in North America for the years 2006 and 2010, and for Europe for the year 2010. Comparisons against observations via annual statistics show model-to-model variation in performance is greater than the within-model variation associated with feedbacks. However, during the summer and during intense emission events such as the Russian forest fires of 2010, feedbacks have a significant impact on the chemical predictions of the models. The aerosol indirect effect was usually found to dominate feedbacks compared to the direct effect. The impacts of direct and indirect effects were often shown to be in competition, for predictions of ozone, particulate matter and other species. Feedbacks were shown to result in local and regional shifts of ozone-forming chemical regime, between NOx- and VOC-limited environments. Feedbacks were shown to have a substantial influence on biogenic hydrocarbon emissions and concentrations: North American simulations incorporating both feedbacks resulted in summer average isoprene concentration decreases of up to 10%, while European direct effect simulations during the Russian forest fire period resulted in grid average isoprene changes of -5 to +12.5%. The atmospheric transport and chemistry of large emitting sources such as plumes from forest fires and large cities were shown to be strongly impacted by the presence or absence of feedback mechanisms in the model simulations. Summertime model performance for ozone and other gases was improved through the inclusion of indirect effect feedbacks, while performance for particulate matter was degraded, suggesting that current parameterizations for in- and below cloud processes, once the cloud locations become more directly influenced by aerosols, may over- or under-predict the strength of these processes. Process parameterization-level comparisons of fully coupled feedback models are therefore recommended for future work, as well as further studies using these models for the simulations of large scale urban/industrial and/or forest fire plumes. © 2014."
"7003862871;24767977600;54941580100;55938109300;7006304904;55879681300;7003658498;7004713805;13007286600;55807448700;8625148400;39361670300;56489746200;22635720500;54982705800;6505947323;9738422100;","Sensitivity of feedback effects in CBMZ/MOSAIC chemical mechanism",2015,"10.1016/j.atmosenv.2015.04.030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937153690&doi=10.1016%2fj.atmosenv.2015.04.030&partnerID=40&md5=2b7e317d89189b64543360e52f8e8e16","To investigate the impact of the aerosol effects on meteorological variables and pollutant concentrations two simulations with the WRF-Chem model have been performed over Europe for year 2010. We have performed a baseline simulation without any feedback effects and a second simulation including the direct as well as the indirect aerosol effect. The paper describes the full configuration of the model, the simulation design, special impacts and evaluation. Although low aerosol particle concentrations are detected, the inclusion of the feedback effects results in an increase of solar radiation at the surface over cloudy areas (North-West, including the Atlantic) and decrease over more sunny locations (South-East). Aerosol effects produce an increase of the water vapor and decrease the planet boundary layer height over the whole domain except in the Sahara area, where the maximum particle concentrations are detected. Significant ozone concentrations are found over the Mediterranean area. Simulated feedback effects between aerosol concentrations and meteorological variables and on pollutant distributions strongly depend on the aerosol concentrations and the clouds. Further investigations are necessary with higher aerosol particle concentrations. WRF-Chem variables are evaluated using available hourly observations in terms of performance statistics. Standardized observations from the ENSEMBLE system web-interface were used. The research was developed under the second phase of Air Quality Model Evaluation International Initiative (AQMEII). WRF-Chem demonstrates its capability in capturing temporal and spatial variations of the major meteorological variables and pollutants, except the wind speed over complex terrain. The wind speed bias may affect the accuracy in the chemical predictions (NO2, SO2). The analysis of the correlations between simulated data sets and observational data sets indicates that the simulation with aerosol effects performs slightly better. These results indicate potential importance of the aerosol feedback effects and an urgent need to further improve the representations in current atmospheric models to reduce uncertainties at all scales. © 2015 Elsevier Ltd."
"55961513200;7403681878;37025370400;","Optimizing Total Energy-Mass Flux (TEMF) Planetary Boundary Layer Scheme for Intel's Many Integrated Core (MIC) Architecture",2015,"10.1109/JSTARS.2015.2438638","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027930779&doi=10.1109%2fJSTARS.2015.2438638&partnerID=40&md5=918531aaf85266016e7b78fa545b282d","In order to make use of the ever-improving microprocessor performance, the applications must be modified to take advantage of the parallelism of today's microprocessors. One such application that needs to be modernized is the weather research and forecasting (WRF) model, which is designed for numerical weather prediction and atmospheric research. The WRF software infrastructure consists of several components such as dynamic solvers and physics schemes. Numerical models are used to resolve the large-scale flow. However, subgrid-scale parameterizations are for an estimation of small-scale properties (e.g., boundary layer turbulence and convection, clouds, radiation). Those have a significant influence on the resolved scale due to the complex nonlinear nature of the atmosphere. For the cloudy planetary boundary layer (PBL), it is fundamental to parameterize vertical turbulent fluxes and subgrid-scale condensation in a realistic manner. A parameterization based on the total energy-mass flux (TEMF) that unifies turbulence and moist convection components produces a better result than other PBL schemes. Thus, we present our optimization results for the TEMF PBL scheme. Those optimizations included vectorization of the code to utilize multiple vector units inside each processor code. The optimizations improved the performance of the original TEMF code on Xeon Phi 7120P by a factor of bf 25 .bf 9 × . Furthermore, the same optimizations improved the performance of the TEMF on a dual socket configuration of eight-core Intel Xeon E5-2670 CPUs by a factor of bf 8}.bf 3 × compared to the original TEMF code. © 2015 IEEE."
"6602199405;43061093300;56522551600;57216468047;7102253065;23028170700;35357335300;6701329415;","Upper atmosphere temperature structure at the Venusian terminators: A comparison of SOIR and VTGCM results",2015,"10.1016/j.pss.2015.01.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927927061&doi=10.1016%2fj.pss.2015.01.012&partnerID=40&md5=293271107662e7162f3a66f353b3801a","Abstract Venus Express SOIR terminator profiles of CO2 densities and corresponding temperatures have been determined for 132 selected orbits obtained between 2006 and 2013. These recently recalibrated measurements provide temperature profiles at the Venusian terminator over approximately 70-160 km, revealing a striking permanent temperature minimum (at about 125 km) and a weaker temperature maximum (over 100-110 km). In addition, topside temperatures (above 140 km) reveal a warming trend consistent with a typical thermospheric structure. These features are reflected in the corresponding CO2 density profiles, and provide detailed constraints for global circulation models of the upper atmosphere. New Venus Thermospheric General Circulation Model (VTGCM) simulations are presented for conditions appropriate to these SOIR measurements. In particular, solar minimum to moderate fluxes are specified and mean values of eddy diffusion and wave drag parameters are utilized. Recent upgrades to the VTGCM code now include more realistic lower boundary conditions at ~70km near cloud tops. Model temperature profiles are extracted from the terminators that correspond to five latitude bins presently used in the SOIR data analysis. Averaging of VTGCM temperature profiles in each of these bins (at each terminator) is conducted to match SOIR sampling. Comparisons of these SOIR and VTGCM temperature profiles are shown. Most notably, the observed temperature minimum near 125 km and the weaker temperature maximum over 100-110 km are generally reproduced by the VTGCM at the correct pressure/altitude levels. However, magnitudes of simulated and measured temperatures are somewhat different as a function of latitude. In addition, VTGCM evening terminator (ET) temperatures are simulated to be modestly warmer than corresponding morning terminator (MT) values, a result of stronger ET than MT zonal winds at/above about 130 km. The SOIR terminator temperatures thus far do not reveal this consistent trend, suggesting the VTGCM climate based winds may not precisely represent the averaged conditions during SOIR sampling. Overall, these data-model comparisons reveal that both radiative and dynamical processes are responsible for maintaining averaged temperatures and driving significant variations in terminator temperature profiles. © 2015 Elsevier Ltd."
"6701463335;7202258620;9239331500;7003498065;36538539800;7006304904;9738422100;8625148400;54941580100;55938109300;6701342931;7202595372;55879681300;8067250600;13007286600;55807448700;56109007900;39361670300;56489746200;7403143315;14719880500;24767977600;22635720500;7003862871;54982705800;6505947323;55720332500;7003658498;","Feedbacks between air pollution and weather, Part 1: Effects on weather",2015,"10.1016/j.atmosenv.2014.12.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988241317&doi=10.1016%2fj.atmosenv.2014.12.003&partnerID=40&md5=0e15fe06ad1c57eeba71db7c06e9fa1e","The meteorological predictions of fully coupled air-quality models running in ""feedback"" versus ""no-feedback"" simulations were compared against each other and observations as part of Phase 2 of the Air Quality Model Evaluation International Initiative. In the ""no-feedback"" mode, the aerosol direct and indirect effects were disabled, with the models reverting to either climatologies of aerosol properties, or a no-aerosol weather simulation. In the ""feedback"" mode, the model-generated aerosols were allowed to modify the radiative transfer and/or cloud formation parameterizations of the respective models. Annual simulations with and without feedbacks were conducted on domains over North America for the years 2006 and 2010, and over Europe for the year 2010.The incorporation of feedbacks was found to result in systematic changes to forecast predictions of meteorological variables, both in time and space, with the largest impacts occurring in the summer and near large sources of pollution. Models incorporating only the aerosol direct effect predicted feedback-induced reductions in temperature, surface downward and upward shortwave radiation, precipitation and PBL height, and increased upward shortwave radiation, in both Europe and North America. The feedback response of models incorporating both the aerosol direct and indirect effects varied across models, suggesting the details of implementation of the indirect effect have a large impact on model results, and hence should be a focus for future research. The feedback response of models incorporating both direct and indirect effects was also consistently larger in magnitude to that of models incorporating the direct effect alone, implying that the indirect effect may be the dominant process. Comparisons across modelling platforms suggested that direct and indirect effect feedbacks may often act in competition: the sign of residual changes associated with feedbacks often changed between those models incorporating the direct effect alone versus those incorporating both feedback processes. Model comparisons to observations for no-feedback and feedback implementations of the same model showed that differences in performance between models were larger than the performance changes associated with implementing feedbacks within a given model. However, feedback implementation was shown to result in improved forecasts of meteorological parameters such as the 2 m surface temperature and precipitation. These findings suggest that meteorological forecasts may be improved through the use of fully coupled feedback models, or through incorporation of improved climatologies of aerosol properties, the latter designed to include spatial, temporal and aerosol size and/or speciation variations. © 2014 ."
"37056101400;7006252685;35551238800;55226243300;7006133602;7004171611;6602080205;9536598800;57203492395;7202803069;56414165400;55554531900;13205433800;12645353200;7003334425;35490341500;53871663500;6602087140;8633162900;55752793600;47160911200;41361010200;55619429300;24340667100;21933618400;56919576300;55232845800;7103197731;7201594914;55338801300;23019619200;56065138100;41361927700;25523100000;","Advances in understanding mineral dust and boundary layer processes over the Sahara from Fennec aircraft observations",2015,"10.5194/acp-15-8479-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938302579&doi=10.5194%2facp-15-8479-2015&partnerID=40&md5=aa82c3f9074fcb807da63689d9a58a08","The Fennec climate programme aims to improve understanding of the Saharan climate system through a synergy of observations and modelling. We present a description of the Fennec airborne observations during 2011 and 2012 over the remote Sahara (Mauritania and Mali) and the advances in the understanding of mineral dust and boundary layer processes they have provided. Aircraft instrumentation aboard the UK FAAM BAe146 and French SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) Falcon 20 is described, with specific focus on instrumentation specially developed for and relevant to Saharan meteorology and dust. Flight locations, aims and associated meteorology are described. Examples and applications of aircraft measurements from the Fennec flights are presented, highlighting new scientific results delivered using a synergy of different instruments and aircraft. These include (1) the first airborne measurement of dust particles sizes of up to 300 microns and associated dust fluxes in the Saharan atmospheric boundary layer (SABL), (2) dust uplift from the breakdown of the nocturnal low-level jet before becoming visible in SEVIRI (Spinning Enhanced Visible Infra-Red Imager) satellite imagery, (3) vertical profiles of the unique vertical structure of turbulent fluxes in the SABL, (4) in situ observations of processes in SABL clouds showing dust acting as cloud condensation nuclei (CCN) and ice nuclei (IN) at -15 °C, (5) dual-aircraft observations of the SABL dynamics, thermodynamics and composition in the Saharan heat low region (SHL), (6) airborne observations of a dust storm associated with a cold pool (haboob) issued from deep convection over the Atlas Mountains, (7) the first airborne chemical composition measurements of dust in the SHL region with differing composition, sources (determined using Lagrangian backward trajectory calculations) and absorption properties between 2011 and 2012, (8) coincident ozone and dust surface area measurements suggest coarser particles provide a route for ozone depletion, (9) discrepancies between airborne coarse-mode size distributions and AERONET (AERosol Robotic NETwork) sunphotometer retrievals under light dust loadings. These results provide insights into boundary layer and dust processes in the SHL region - a region of substantial global climatic importance. © Author(s) 2015."
"24777788700;55897485300;57191077667;16443826700;35569803200;36722293600;6603303046;6603848988;55947099700;","Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: Implications for long-range dispersal of volcanic clouds",2015,"10.5194/acp-15-8381-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938381597&doi=10.5194%2facp-15-8381-2015&partnerID=40&md5=f25f9ad2289df9a066a1d0d0849306b0","Sulfur-rich degassing, which is mostly composed of sulfur dioxide (SO2), plays a major role in the overall impact of volcanism on the atmosphere and climate. The accurate assessment of this impact is currently hampered by the poor knowledge of volcanic SO2 emissions. Here, using an inversion procedure, we show how assimilating snapshots of the volcanic SO2 load derived from the Infrared Atmospheric Sounding Interferometer (IASI) allows for reconstructing both the flux and altitude of the SO2 emissions with an hourly resolution. For this purpose, the regional chemistry-transport model CHIMERE is used to describe the dispersion of SO2 when released in the atmosphere. As proof of concept, we study the 10 April 2011 eruption of the Etna volcano (Italy), which represents one of the few volcanoes instrumented on the ground for the continuous monitoring of SO2 degassing. We find that the SO2 flux time-series retrieved from satellite imagery using the inverse scheme is in agreement with ground observations during ash-poor phases of the eruption. However, large discrepancies are observed during the ash-rich paroxysmal phase as a result of enhanced plume opacity affecting ground-based ultraviolet (UV) spectroscopic retrievals. As a consequence, the SO2 emission rate derived from the ground is underestimated by almost one order of magnitude. Altitudes of the SO2 emissions predicted by the inverse scheme are validated against an RGB image of the Moderate Resolution Imaging Spectroradiometer (MODIS) capturing the near-source atmospheric pathways followed by Etna plumes, in combination with forward trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. At a large distance from the source, modelled SO2 altitudes are compared with independent information on the volcanic cloud height. We find that the altitude predicted by the inverse scheme is in agreement with snapshots of the SO2 height retrieved from recent algorithms exploiting the high spectral resolution of IASI. The validity of the modelled SO2 altitude is further confirmed by the detection of a layer of particles at the same altitude by the spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Analysis of CALIOP colour and depolarization ratios suggests that these particles consist of sulfate aerosols formed from precursory volcanic SO2. The reconstruction of emission altitude, through inversion procedures which assimilate volcanic SO2 column amounts, requires specific meteorological conditions, especially sufficient wind shear so that gas parcels emitted at different altitudes follow distinct trajectories. We consequently explore the possibility and limits of assimilating in inverse schemes infrared (IR) imagery of the volcanic SO2 cloud altitude which will render the inversion procedure independent of the wind shear prerequisite. © Author(s) 2015."
"8687660300;56740959600;15128812000;56740593800;56740303200;55308556700;56740508700;","Black carbon emissions from Russian diesel sources: Case study of Murmansk",2015,"10.5194/acp-15-8349-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938149851&doi=10.5194%2facp-15-8349-2015&partnerID=40&md5=b473da8f3aa5e01f75f1f4319c8e057f","Black carbon (BC) is a potent pollutant because of its effects on climate change, ecosystems and human health. Black carbon has a particularly pronounced impact as a climate forcer in the Arctic because of its effect on snow albedo and cloud formation. We have estimated BC emissions from diesel sources in the Murmansk Region and Murmansk City, the largest city in the world above the Arctic Circle. In this study we developed a detailed inventory of diesel sources including on-road vehicles, off-road transport (mining, locomotives, construction and agriculture), ships and diesel generators. For on-road transport, we conducted several surveys to understand the vehicle fleet and driving patterns, and, for all sources, we also relied on publicly available local data sets and analysis. We calculated that BC emissions in the Murmansk Region were 0.40 Gg in 2012. The mining industry is the largest source of BC emissions in the region, emitting 69 % of all BC emissions because of its large diesel consumption and absence of emissions controls. On-road vehicles are the second largest source, emitting about 13 % of emissions. Old heavy duty trucks are the major source of emissions. Emission controls on new vehicles limit total emissions from on-road transportation. Vehicle traffic and fleet surveys show that many of the older cars on the registry are lightly or never used. We also estimated that total BC emissions from diesel sources in Russia were 50.8 Gg in 2010, and on-road transport contributed 49 % of diesel BC emissions. Agricultural machinery is also a significant source Russia-wide, in part because of the lack of controls on off-road vehicles. © Author(s) 2015."
"12808494200;57200530823;7003278104;55418990300;8969695400;7004740616;","Using joint probability distribution functions to evaluate simulations of precipitation, cloud fraction and insolation in the North America Regional Climate Change Assessment Program (NARCCAP)",2015,"10.1007/s00382-014-2253-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929703993&doi=10.1007%2fs00382-014-2253-y&partnerID=40&md5=1d03999a5da68f5db87b91bf2f63704d","This study evaluates model fidelity in simulating relationships between seasonally averaged precipitation, cloud fraction and surface insolation from the North American Regional Climate Change Assessment Project (NARCCAP) hindcast using observational data from ground stations and satellites. Model fidelity is measured in terms of the temporal correlation coefficients between these three variables and the similarity between the observed and simulated joint probability distribution functions (JPDFs) in 14 subregions over the conterminous United States. Observations exhibit strong negative correlations between precipitation/cloud fraction and surface insolation for all seasons, whereas the relationship between precipitation and cloud fraction varies according to regions and seasons. The skill in capturing these observed relationships varies widely among the NARCCAP regional climate models, especially in the Midwest and Southeast coast regions where observations show weak (or even negative) correlations between precipitation and cloud fraction in winter due to frequent non-precipitating stratiform clouds. Quantitative comparison of univariate and JPDFs indicates that model performance varies markedly between regions as well as seasons. This study also shows that comparison of JPDFs is useful for summarizing the performance of and highlighting problems with some models in simulating cloud fraction and surface insolation. Our quantitative metric may be useful in improving climate models by highlighting shortcomings in the formulations related with the physical processes involved in precipitation, clouds and radiation or other multivariate processes in the climate system. © 2014, Springer-Verlag Berlin Heidelberg."
"26867472700;7402105994;6602414959;24390528000;36894599500;7003777747;6602600408;","Climate responses to anthropogenic emissions of short-lived climate pollutants",2015,"10.5194/acp-15-8201-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937786790&doi=10.5194%2facp-15-8201-2015&partnerID=40&md5=69b8acd25ac95e60a397bec31c890673","Policies to control air quality focus on mitigating emissions of aerosols and their precursors, and other short-lived climate pollutants (SLCPs). On a local scale, these policies will have beneficial impacts on health and crop yields, by reducing particulate matter (PM) and surface ozone concentrations; however, the climate impacts of reducing emissions of SLCPs are less straightforward to predict. In this paper we consider a set of idealized, extreme mitigation strategies, in which the total anthropogenic emissions of individual SLCP emissions species are removed. This provides an upper bound on the potential climate impacts of such air quality strategies. We focus on evaluating the climate responses to changes in anthropogenic emissions of aerosol precursor species: black carbon (BC), organic carbon (OC) and sulphur dioxide (SO<inf>2</inf>). We perform climate integrations with four fully coupled atmosphere-ocean global climate models (AOGCMs), and examine the effects on global and regional climate of removing the total land-based anthropogenic emissions of each of the three aerosol precursor species. We find that the SO<inf>2</inf> emissions reductions lead to the strongest response, with all models showing an increase in surface temperature focussed in the Northern Hemisphere mid and (especially) high latitudes, and showing a corresponding increase in global mean precipitation. Changes in precipitation patterns are driven mostly by a northward shift in the ITCZ (Intertropical Convergence Zone), consistent with the hemispherically asymmetric warming pattern driven by the emissions changes. The BC and OC emissions reductions give a much weaker response, and there is some disagreement between models in the sign of the climate responses to these perturbations. These differences between models are due largely to natural variability in sea-ice extent, circulation patterns and cloud changes. This large natural variability component to the signal when the ocean circulation and sea-ice are free-running means that the BC and OC mitigation measures do not necessarily lead to a discernible climate response. © Author(s) 2015."
"55613230528;16025327700;55504032900;56734549500;26029334300;52364194000;57217371644;56130488100;","Brief Communication: Climatic, meteorological and topographical causes of the 16-17 June 2013 Kedarnath (India) natural disaster event",2015,"10.5194/nhess-15-1597-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937777818&doi=10.5194%2fnhess-15-1597-2015&partnerID=40&md5=eb414af0a1b2a044dc919c9b65335d55","The devastating flood episode (16-17 June 2013) at Kedarnath (Uttrakhand, India), caused a huge loss of lives and loss of physical/material wealth. To understand this catastrophic event, rainfall/convective data and associated climate meteorological parameters are investigated. A low-pressure zone with very high cloud cover (60-90 %) and relative humidity (70-100 %), associated with low (< 4 m s-1) wind velocity, are observed over the Kedarnath region during 15-17 June. The cause of this disaster seems to be heavy and continuous rainfall, associated with snowmelt and the overflooding/collapse of Chorabari Lake, located upstream. Monsoon advancement was much faster than usual, due to the presence of the convectively active phase of the Madden-Julian oscillation. © Author(s) 2015."
"55790072300;53867207000;","Dust storm detection using random forests and physical-based approaches over the Middle East",2015,"10.1007/s12040-015-0585-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937467983&doi=10.1007%2fs12040-015-0585-6&partnerID=40&md5=b19d8a9c1597fe639555761748ccec3a","Dust storms are important phenomena over large regions of the arid and semi-arid areas of the Middle East. Due to the influences of dust aerosols on climate and human daily activities, dust detection plays a crucial role in environmental and climatic studies. Detection of dust storms is critical to accurately understand dust, their properties and distribution. Currently, remotely sensed data such as MODIS (Moderate Resolution Imaging Spectroradiometer) with appropriate temporal and spectral resolutions have been widely used for this purpose. This paper investigates the capability of two physical-based methods, and random forests (RF) classifier, for the first time, to detect dust storms using MODIS imagery. Since the physical-based approaches are empirical, they suffer from certain drawbacks such as high variability of thresholds depending on the underlying surface. Therefore, classification-based approaches could be deployed as an alternative. In this paper, the most relevant bands are chosen based on the physical effects of the major classes, particularly dust, cloud and snow, on both emissive infrared and reflective bands. In order to verify the capability of the methods, OMAERUV AAOD (aerosol absorption optical depth) product from OMI (Ozone Monitoring Instrument) sensor is exploited. In addition, some small regions are selected manually to be considered as ground truth for measuring the probability of false detection (POFD) and probability of missing detection (POMD). The dust class generated by RF is consistent qualitatively with the location and extent of dust observed in OMERAUV and MODIS true colour images. Quantitatively, the dust classes generated for eight dust outbreaks in the Middle East are found to be accurate from 7% and 6% of POFD and POMD respectively. Moreover, results demonstrate the sound capability of RF in classifying dust plumes over both water and land simultaneously. The performance of the physical-based approaches is found weaker than RF due to empirical thresholds that are not always true. © Indian Academy of Sciences."
"55684491100;7102604282;56898519400;55245030000;56244407700;","Dehydration effects from contrails in a coupled contrail-climate model",2015,"10.5194/acpd-15-19553-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042582450&doi=10.5194%2facpd-15-19553-2015&partnerID=40&md5=f2796f55548ba6b2de8809e4744a1469","Uptake of water by contrails in ice-supersaturated air and release of water after ice particle advection and sedimentation dehydrates the atmosphere at flight levels and redistributes humidity mainly to lower levels. The dehydration is investigated by coupling a plume-scale contrail model with a global aerosol-climate model. The contrail model simulates all the individual contrails forming from global air traffic for meteorological conditions as defined by the climate model. The computed contrail-cirrus properties compare reasonably with theoretical concepts and observations. The mass of water in aged contrails may exceed 106 times the mass of water emitted from aircraft. Many of the ice particles sediment and release water in the troposphere, on average 700 m below the mean flight levels. Simulations with and without coupling are compared. The drying at contrail levels causes thinner and longer lived contrails with about 15 % reduced contrail radiative forcing (RF). The reduced RF from contrails is of the order 0.06 W m-2, slightly larger than estimated earlier because of higher soot emissions. For normal traffic, the RF from dehydration is small compared to interannual variability. A case with 100 times increased emissions is used to overcome statistical uncertainty. The contrails impact the entire hydrological cycle in the atmosphere by reducing the total water column and the cover of high and low-level clouds. For normal traffic, the dehydration changes contrail RF by positive shortwave and negative longwave contributions of order 0.04 W m-2, with a small negative net RF. The total net RF from contrails and dehydration remains within the range of previous estimates. © Author(s) 2015."
"7801371714;","Statistical Variability and Persistence Change in Daily Air Temperature Time Series from High Latitude Arctic Stations",2015,"10.1007/s00024-014-0878-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931287765&doi=10.1007%2fs00024-014-0878-8&partnerID=40&md5=15f7ae018dbf54add1d914bad35486b2","In the last decades, Arctic communities have been reporting that weather conditions are becoming less predictable. Most scientific studies have not been able to consistently confirm such a trend. The question regarding the possible increase in weather variability was addressed here based on daily minimum and maximum surface air temperature time series from 15 high latitude Arctic stations from Canada, Norway, and the Russian Federation. A range of analysis methods were applied, distinguished mainly by the way in which they treat time scale. Statistical L-moments were determined for temporal windows of different lengths. While the picture provided by L-scale and L-kurtosis is not consistent with an increasing variability, L-skewness was found to change towards more positive values, reflecting an enhancement of warm spells. Haar wavelet analysis was applied both to the entire time series and to running windows. Persistence diagrams were generated based on running windows advancing through time and on local slopes of Haar analysis graphs; they offer a more nuanced view on variability by reflecting its change over time on a range of temporal scales. Local increases in variability could be identified in some cases, but no consistent change was detected in any of the stations over the studied temporal scales. The possibility for other intervals of temporal scale (e.g., days, hours, minutes) to potentially reveal a different situation cannot be ruled out. However, in the light of the results presented here, explanations for the discrepancy between variability perception and results of pattern analysis might have to be explored using an integrative approach to weather variables such as air temperature, cloud cover, precipitation, wind, etc. © 2014, Springer Basel."
"42462407100;7004587644;55951225700;55777759900;56261301800;35775264900;7006441949;","Evaluation of the Australian Community Climate and Earth-System Simulator Chemistry-Climate Model",2015,"10.5194/acpd-15-19161-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042582602&doi=10.5194%2facpd-15-19161-2015&partnerID=40&md5=e5e196f753ce1b840c87ce0fe67bc996","Chemistry climate models are important tools for addressing interactions of composition and climate in the Earth System. In particular, they are used for assessing the combined roles of greenhouse gases and ozone in Southern Hemisphere climate and weather. Here we present an evaluation of the Australian Community Climate and Earth System Simulator-Chemistry Climate Model, focusing on the Southern Hemisphere and the Australian region. This model is used for the Australian contribution to the international Chemistry-Climate Model Initiative, which is soliciting hindcast, future projection and sensitivity simulations. The model simulates global total column ozone (TCO) distributions accurately, with a slight delay in the onset and recovery of springtime Antarctic ozone depletion, and consistently higher ozone values. However, October averaged Antarctic TCO from 1960 to 2010 show a similar amount of depletion compared to observations. A significant innovation is the evaluation of simulated vertical profiles of ozone and temperature with ozonesonde data from Australia, New Zealand and Antarctica from 38 to 90° S. Excess ozone concentrations (up to 26.4 % at Davis during winter) and stratospheric cold biases (up to 10.1 K at the South Pole) outside the period of perturbed springtime ozone depletion are seen during all seasons compared to ozonesondes. A disparity in the vertical location of ozone depletion is seen: centered around 100 hPa in ozonesonde data compared to above 50 hPa in the model. Analysis of vertical chlorine monoxide profiles indicates that colder Antarctic stratospheric temperatures (possibly due to reduced mid-latitude heat flux) are artificially enhancing polar stratospheric cloud formation at high altitudes. The models inability to explicitly simulated supercooled ternary solution may also explain the lack of depletion at lower altitudes. The simulated Southern Annular Mode (SAM) index compares well with ERA-Interim data. Accompanying these modulations of the SAM, 50 hPa zonal wind differences between 2001-2010 and 1979-1998 show increasing zonal wind strength southward of 60° S during December for both the model simulations and ERA-Interim data. These model diagnostics shows that the model reasonably captures the stratospheric ozone driven chemistry-climate interactions important for Australian climate and weather while highlighting areas for future model development. © Author(s) 2015."
"57190948518;8942525300;56757625500;6507564744;35810775100;8942524900;36659468200;36134816800;55831482700;12753162000;55683727600;55377690600;56377286600;","Impacts of aviation fuel sulfur content on climate and human health",2015,"10.5194/acpd-15-18921-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964558926&doi=10.5194%2facpd-15-18921-2015&partnerID=40&md5=cd3692cf2b4ea3fccef78a2547e7cb07","Aviation emissions impact both air quality and climate. Using a coupled tropospheric chemistry-aerosol microphysics model we investigate the effects of varying aviation fuel sulfur content (FSC) on premature mortality from long-term exposure to aviation-sourced PM2.5 (particulate matter with a dry diameter of &lt; 2.5 μm) and on the global radiation budget due to changes in aerosol and tropospheric ozone. We estimate that present-day non-CO2 aviation emissions with a typical FSC of 600 ppm result in 3597 (95 % CI: 1307-5888) annual mortalities globally due to increases in cases of cardiopulmonary disease and lung cancer, resulting from increased surface PM2.5 concentrations. We quantify the global annual mean combined radiative effect (REcomb) of non-CO2 aviation emissions as -13.3 mW m-2; from increases in aerosols (direct radiative effect and cloud albedo effect) and tropospheric ozone. Ultra-low sulfur jet fuel (ULSJ; FSC Combining double low line15 ppm) has been proposed as an option to reduce the adverse health impacts of aviation-induced PM2.5. We calculate that swapping the global aviation fleet to ULSJ fuel would reduce the global aviation-induced mortality rate by 624 (95 % CI: 227-1021) mortalities a-1 and increase REcomb by +7.0 mW m-2. We explore the impact of varying aviation FSC between 0-6000 ppm. Increasing FSC increases annual mortality, while enhancing climate cooling through increasing the aerosol cloud albedo effect (aCAE). We explore the relationship between the injection altitude of aviation emissions and the resulting climate and air quality impacts. Compared to the standard aviation emissions distribution, releasing aviation emissions at the ground increases global aviation-induced mortality and produces a net warming effect, primarily through a reduced aCAE. Aviation emissions injected at the surface are 5 times less effective at forming cloud condensation nuclei, reducing the aviation-induced aCAE by a factor of 10. Applying high FSCs at aviation cruise altitudes combined with ULSJ fuel at lower altitudes result in reduced aviation-induced mortality and increased negative RE compared to the baseline aviation scenario. © Author(s) 2015."
"57199171671;6603699060;8283063300;","THE INTERSTELLAR MEDIUM in the KEPLER SEARCH VOLUME",2015,"10.1088/0004-637X/807/2/162","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84936991213&doi=10.1088%2f0004-637X%2f807%2f2%2f162&partnerID=40&md5=05462b5f376a6002518565e19f9ad2e3","The properties of the interstellar medium (ISM) surrounding a planetary system can impact planetary climate through a number of mechanisms, including changing the size of the astrosphere (one of the major shields for cosmic rays) as well as direct deposition of material into planetary atmospheres. In order to constrain the ambient ISM conditions for exoplanetary systems, we present observations of interstellar Na i and K i absorption toward seventeen early type stars in the Kepler prime mission field of view (FOV). We identify 39 Na i and 8 K i velocity components, and attribute these to 11 ISM clouds. Six of these are detected toward more than one star, and for these clouds we put limits on the cloud properties, including distance and hydrogen number density. We identify one cloud with significant (1.5 cm-3) hydrogen number density located within the nominal ∼100 pc boundary of the Local Bubble. We identify systems with confirmed planets within the Kepler FOV that could lie within these ISM clouds, and estimate upper limits on the astrosphere sizes of these systems under the assumption that they do lie within these clouds. Under this condition, the Kepler-20, 42, and 445 multiplanet systems could have compressed astrospheres much smaller than the present-day heliosphere. Among the known habitable zone planet hosts, Kepler-186 could have an astrosphere somewhat smaller than the heliosphere, while Kepler-437 and KOI-4427 could have astrospheres much larger than the heliosphere. The thick disk star Kepler-444 may have an astrosphere just a few AU in radius. © 2015. The American Astronomical Society. All rights reserved."
"55263254000;23485087200;7006173230;","Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash",2015,"10.5194/acp-15-7523-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937035667&doi=10.5194%2facp-15-7523-2015&partnerID=40&md5=6fac41c097101fecbf22a713e782f1ab","Ice nucleation of volcanic ash controls both ash aggregation and cloud glaciation, which affect atmospheric transport and global climate. Previously, it has been suggested that there is one characteristic ice nucleation efficiency for all volcanic ash, regardless of its composition, when accounting for surface area; however, this claim is derived from data from only two volcanic eruptions. In this work, we have studied the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman microscopy coupled to an environmental cell. Ash from the Fuego (basaltic ash, Guatemala), Soufrière Hills (andesitic ash, Montserrat), and Taupo (Oruanui eruption, rhyolitic ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. In the present study, we find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice from 225 to 235 K at ice saturation ratios of 1.05 ± 0.01, comparable to the mineral dust proxy kaolinite. Since depositional ice nucleation will be more important at colder temperatures, fine volcanic ash may represent a global source of cold-cloud ice nuclei. For immersion freezing relevant to mixed-phase clouds, however, only the Oruanui ash exhibited appreciable heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode. © Author(s) 2015."
"22941100900;56721057800;6506773349;7006466341;56386270200;56050216000;41660987700;7801467546;26433082600;24545697300;6603180620;7101819382;56386261600;6506963976;56385216600;6603506032;7003750797;35579918200;7202387972;56721429100;56385967100;16444870500;6601991204;10340256300;7403488582;6603091692;7005182425;55476534400;6602482382;7003545995;6603729725;6602308680;9274551500;7005196695;6602966752;6603797956;56385261500;57210822816;56668474200;16833977600;37762496400;","ACTRIS non-methane hydrocarbon intercomparison experiment in Europe to support WMO GAW and EMEP observation networks",2015,"10.5194/amt-8-2715-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937054214&doi=10.5194%2famt-8-2715-2015&partnerID=40&md5=c002ea8497a22f624ba94dc2bc0b0694","The performance of 18 European institutions involved in long-term non-methane hydrocarbon (NMHC) measurements in ambient air within the framework of the Global Atmosphere Watch (GAW) and the European Monitoring and Evaluation Programme (EMEP) was assessed with respect to data quality objectives (DQOs) of ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) and GAW. Compared to previous intercomparison studies the DQOs define a novel approach to assess and ensure a high quality of the measurements. Having already been adopted by GAW, the ACTRIS DQOs are demanding with deviations to a reference value of less than 5% and a repeatability of better than 2% for NMHC mole fractions above 0.1 nmol mol -1 . The participants of the intercomparison analysed two dry gas mixtures in pressurised cylinders, a 30-component NMHC mixture in nitrogen (NMHC-N 2 ) at approximately 1 nmol mol -1 and a whole air sample (NMHC-air), following a standardised operation procedure including zero- and calibration gas measurements. Furthermore, participants had to report details on their instruments and assess their measurement uncertainties. The NMHCs were analysed either by gas chromatography-flame ionisation detection (GC-FID) or by gas chromatography-mass spectrometry (GC-MS). For the NMHC-N 2 measurements, 62% of the reported values were within the 5% deviation class corresponding to the ACTRIS DQOs. For NMHC-air, generally more frequent and larger deviations to the assigned values were observed, with 50 % of the reported values within the 5 % deviation class. Important contributors to the poorer performance in NMHC-air compared to NMHC-N 2 were a more complex matrix and a larger span of NMHC mole fractions (0.03-2.5 nmol mol -1 ). The performance of the participating laboratories were affected by the different measurement procedures such as the usage of a two-step vs. a one-step calibration, breakthroughs of C 2 -C 3 hydrocarbons in the focussing trap, blank values in zero-gas measurements (especially for those systems using a Nafion® Dryer), adsorptive losses of aromatic compounds, and insufficient chromatographic separation. © Author(s) 2015."
"16309079300;7102115699;8710626800;53163086500;7003807287;22979041700;14629833700;57203103268;7003659681;7202784101;8633399500;6701865456;35465341400;22980040900;7006481399;35270219700;","Characterizing transiting planet atmospheres through 2025",2015,"10.1086/680855","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930679963&doi=10.1086%2f680855&partnerID=40&md5=6a2442c665a946767d3b95e9a40b0ef3","The discovery of planets around other stars is revolutionizing our notions of planet formation and is poised to do the same for planetary climate. Studying transiting planets is complementary to eventual studies of directly imaged planets: (1) we can readily measure the mass and radius of transiting planets, linking atmospheric properties to bulk composition and formation, (2) many transiting planets are strongly irradiated and exhibit novel atmospheric physics, and (3) the most common temperate terrestrial planets orbit close to red dwarf stars and are difficult to image directly. We have only been able to comprehensively characterize the atmospheres of a handful of transiting planets, because most orbit faint stars. The Transiting Exoplanet Survey Satellite (TESS) will discover transiting planets orbiting the brightest stars, enabling, in principle, an atmospheric survey of 102–103 bright hot Jupiters and warm sub-Neptunes. Uniform observations of such a statistically significant sample would provide leverage to understand—and learn from—the diversity of short-period planets, and would identify the minority of truly special planets worthy of more intensive follow-up. We argue that the best way to maximize the scientific returns of TESS is to adopt a triage approach. A space mission consisting of a ∼1 m telescope with an optical–NIR spectrograph could measure molecular absorption for nonterrestrial planets discovered by TESS, as well as eclipses and phase variations for the hottest jovians. Such a mission could observe up to 103 transits per year, thus enabling it to survey a large fraction of the bright (J < 11) hot-Jupiters and warm sub-Neptunes TESS is expected to find. The James Webb Space Telescope (JWST) could be used to perform detailed atmospheric characterization of the most interesting transiting targets (transit, eclipse, and—when possible—phase-resolved spectroscopy). TESS is also expected to discover a few temperate terrestrial planets transiting nearby M-Dwarfs. Characterizing these worlds will be time-intensive: JWST will need months to provide tantalizing constraints on the presence of an atmosphere, planetary rotational state, clouds, and greenhouse gases. Future flagship missions should be designed to provide better constraints on the habitability of M-Dwarf temperate terrestrial planets. © 2015. The Astronomical Society of the Pacific. All rights reserved."
"6602560015;7402942478;16426275900;7402480218;6701416358;7005395283;","Saharan dust as a causal factor of hemispheric asymmetry in aerosols and cloud cover over the tropical Atlantic Ocean",2015,"10.1080/01431161.2015.1060646","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937115514&doi=10.1080%2f01431161.2015.1060646&partnerID=40&md5=2c260d198c29e9dc68e10ceebe9939ee","Previous studies showed that, over the global ocean, there is no noticeable hemispheric asymmetry in cloud fraction (CF). This contributes to the balance in solar radiation reaching the sea surface in the northern and southern hemispheres. In the current study, we focus on the tropical Atlantic (30° N–30° S), which is characterized by significant amounts of Saharan dust dominating other aerosol species over the North Atlantic. Our main point is that, over the tropical Atlantic, Saharan dust not only is responsible for the pronounced hemispheric aerosol asymmetry, but also contributes to significant cloud cover along the Saharan Air Layer (SAL). Over the tropical Atlantic in July, along the SAL, Moderate Resolution Imaging Spectroradiometer CF data showed significant cloud cover (up to 0.8–0.9). This significant CF along SAL together with clouds over the Atlantic Intertropical Convergence Zone contributes to the 20% hemispheric CF asymmetry. This leads to the imbalance in strong solar radiation, which reaches the sea surface between the tropical North and South Atlantic, and, consequently, affects climate formation in the tropical Atlantic. During the 10-year study period (July 2002–June 2012), NASA Aerosol Reanalysis (aka MERRAero) showed that, when the hemispheric asymmetry in dust aerosol optical thickness (AOT) was most pronounced (particularly in July), dust AOT averaged separately over the tropical North Atlantic was one order of magnitude higher than that averaged over the tropical South Atlantic. In the presence of such strong hemispheric asymmetry in dust AOT in July, CF averaged separately over the tropical North Atlantic exceeded that over the tropical South Atlantic by 20%. Both Multiangle Imaging Spectroradiometer measurements and MERRAero data were in agreement on seasonal variations in hemispheric aerosol asymmetry. Hemispheric asymmetry in total AOT over the Atlantic was most pronounced between March and July, when dust presence over the North Atlantic was maximal. In September and October, there was no noticeable hemispheric aerosol asymmetry between the tropical North and South Atlantic. During the season with no noticeable hemispheric aerosol asymmetry, we found no noticeable asymmetry in cloud cover. © 2015 The Author(s). Published by Taylor & Francis."
"57195574170;56520921400;56906772100;","Pan-spectral observing system simulation experiments of shortwave reflectance and long-wave radiance for climate model evaluation",2015,"10.5194/gmd-8-1943-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944460762&doi=10.5194%2fgmd-8-1943-2015&partnerID=40&md5=60b3505089515ccd64d8b0138102df50","Top-of-atmosphere (TOA) spectrally resolved shortwave reflectances and long-wave radiances describe the response of the Earth's surface and atmosphere to feedback processes and human-induced forcings. In order to evaluate proposed long-duration spectral measurements, we have projected 21st Century changes from the Community Climate System Model (CCSM3.0) conducted for the Intergovernmental Panel on Climate Change (IPCC) A2 Emissions Scenario onto shortwave reflectance spectra from 300 to 2500 nm and long-wave radiance spectra from 2000 to 200 cm-1 at 8 nm and 1 cm-1 resolution, respectively. The radiative transfer calculations have been rigorously validated against published standards and produce complementary signals describing the climate system forcings and feedbacks. Additional demonstration experiments were performed with the Model for Interdisciplinary Research on Climate (MIROC5) and Hadley Centre Global Environment Model version 2 Earth System (HadGEM2-ES) models for the Representative Concentration Pathway 8.5 (RCP8.5) scenario. The calculations contain readily distinguishable signatures of low clouds, snow/ice, aerosols, temperature gradients, and water vapour distributions. The goal of this effort is to understand both how climate change alters reflected solar and emitted infrared spectra of the Earth and determine whether spectral measurements enhance our detection and attribution of climate change. This effort also presents a path forward to understand the characteristics of hyperspectral observational records needed to confront models and inline instrument simulation. Such simulation will enable a diverse set of comparisons between model results from coupled model intercomparisons and existing and proposed satellite instrument measurement systems. © Author(s) 2015."
"24480463300;57093496500;8568391400;55682775100;23995325300;36719980500;36623061000;6701461735;6602753217;7003984086;6701764148;57094000100;6701481405;","Aerosol size distribution seasonal characteristics measured in Tiksi, Russian Arctic",2015,"10.5194/acpd-15-18109-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984875146&doi=10.5194%2facpd-15-18109-2015&partnerID=40&md5=cd0376b88052abe9d7265ad81c4e282d","Four years of continuous aerosol number size distribution measurements from an Arctic Climate Observatory in Tiksi Russia are analyzed. Source region effects on particle modal features, and number and mass concentrations are presented for different seasons. The monthly median total aerosol number concentration in Tiksi ranges from 184 cm-3 in November to 724 cm-3 in July with a local maximum in March of 481 cm-3. The total mass concentration has a distinct maximum in February-March of 1.72-2.38 μgm-3 and two minimums in June of 0.42 μg m-3 and in September-October of 0.36-0.57 μgm-3. These seasonal cycles in number and mass concentrations are related to isolated aerosol sources such as Arctic haze in early spring which increases accumulation and coarse mode numbers, and biogenic emissions in summer which affects the smaller, nucleation and Aitken mode particles. The impact of temperature dependent natural emissions on aerosol and cloud condensation nuclei numbers was significant. Therefore, in addition to the precursor emissions of biogenic volatile organic compounds, the frequent Siberian forest fires, although far are suggested to play a role in Arctic aerosol composition during the warmest months. During calm and cold months aerosol concentrations were occasionally increased by nearby aerosol sources in trapping inversions. These results provide valuable information on inter-annual cycles and sources of Arctic aerosols. © Author(s) 2015."
"6603020128;7006346740;","Investigation of weather anomalies in the low-latitude islands of the Indian Ocean in 1991",2015,"10.5194/angeo-33-789-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84936943948&doi=10.5194%2fangeo-33-789-2015&partnerID=40&md5=0de944fd250754435080deefef30d450","Temperature, precipitation and sunshine duration measurements at meteorological stations across the southern Indian Ocean have been analysed to try to differentiate the possible influence of the Mount Pinatubo volcanic eruption in the Philippines in June 1991 and the normal weather forcings. During December 1991, precipitation on the tropical islands Glorieuses (11.6° S) and Mayotte (12.8° S) was 4 and 3 times greater, respectively, than the climatological mean (precipitation is greater by more than than twice the standard deviation (SD)). Mean sunshine duration (expressed in sun hours per day) was only 6 h on Mayotte, although the sunshine duration is usually more than 7.5 ± 0.75 h, and on the Glorieuses it was only 5 h, although it is usually 8.5 ± 1 h. Mean and SD of sunshine duration are based on December (1964-2001 for Mayotte, 1966-1999 for the Glorieuses). The Madden-Julian Oscillation (MJO) is shown to correlate best with precipitation in this area. Variability controlling the warm zone on these two islands can be increased by the Indian Ocean Dipole (IOD), El Niño, the quasi-biennial oscillation (QBO) and/or solar activity (sunspot number, SSN). However, temperature records of these two islands show weak dependence on such forcings (temperatures are close to the climatological mean for December). This suggests that such weather forcings have an indirect effect on the precipitation. December 1991 was associated with unusually low values of the MJO index, which favours high rainfall, as well as with El Niño, eastern QBO and high SSN, which favour high variability. It is therefore not clear whether the Mount Pinatubo volcanic eruption had an effect. Since the precipitation anomalies at the Glorieuses and Mayotte are more or less local (Global Precipitation Climatology Project (GPCP) data) and the effect of the Pinatubo volcanic cloud should be more widespread, it seems unlikely that Pinatubo was the cause. Islands at higher southern latitudes (south of Tromelin at 15.5° S) were not affected by the Pinatubo eruption in terms of sunshine duration, precipitation or temperature. © The Author(s) 2015."
"10040054900;36097134700;","Dispelling clouds of uncertainty",2015,"10.1029/2015eo031303","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949558066&doi=10.1029%2f2015eo031303&partnerID=40&md5=a6ff2fbff8882bde43403943fb4df8e7",[No abstract available]
"35867442600;9536598800;7103016965;7004469744;24764483400;35810775100;7801353107;","Precipitation sensitivity to autoconversion rate in a numerical weather-prediction model",2015,"10.1002/qj.2497","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941121413&doi=10.1002%2fqj.2497&partnerID=40&md5=b98c60af6c404e566b13807cce967238","Aerosols are known to significantly affect cloud and precipitation patterns and intensity, but these interactions are ignored or very simplistically handled in climate and numerical weather-prediction (NWP) models. A suite of one-way nested Met Office Unified Model (UM) runs, with a single-moment bulk microphysics scheme was used to study two convective cases with contrasting characteristics observed in southern England. The autoconversion process that converts cloud water to rain is directly controlled by the assumed droplet number. The impact of changing cloud droplet number concentration (CDNC) on cloud and precipitation evolution can be inferred through changes to the autoconversion rate. This was done for a range of resolutions ranging from regional NWP (1 km) to high resolution (up to 100 m grid spacing) to evaluate the uncertainties due to changing CDNC as a function of horizontal grid resolution. The first case is characterised by moderately intense convective showers forming below an upper-level potential vorticity anomaly, with a low freezing level. The second case, characterised by one persistent stronger storm, is warmer with a deeper boundary layer. The colder case is almost insensitive to even large changes in CDNC, while in the warmer case a change of a factor of 3 in assumed CDNC affects total surface rain rate by ~17%. In both cases the sensitivity to CDNC is similar at all grid spacings <1 km. The contrasting sensitivities of these cases are induced by their contrasting ice-phase proportion. The ice processes in this model damp the precipitation sensitivity to CDNC. For this model the convection is sensitive to CDNC when the accretion process is more significant than the melting process and vice versa. © 2015 Royal Meteorological Society."
"36523706800;55613774900;57200370281;","Towards optimal aerosol information for the retrieval of solar surface radiation using Heliosat",2015,"10.3390/atmos6070863","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84998682055&doi=10.3390%2fatmos6070863&partnerID=40&md5=41906ab7c16472d5db5779b02ae73053","High quality data of surface radiation is a prerequisite for climate monitoring (Earth radiation budget) and solar energy applications. A very common method to derive solar surface irradiance is the Heliosat method, a one channel approach for the retrieval of the effective cloud albedo (CAL). This information is then used to derive the solar surface irradiance by application of a clear sky model. The results of this study are based on radiative transfer modelling, visual inspection of satellite images and evaluation of satellite based solar surface radiation with ground measurements. The respective results provide evidence that variations in Aerosol Optical depth induced by desert storms and biomass burning events lead to a significant increase of the effective cloud albedo, thus, that certain aerosol events are interpreted as clouds by the method. For the estimation of the solar surface radiation aerosol information is needed as input for the clear sky model. As the aerosol effect is partly considered by CAL, there is a need to modify external aerosol information for the use within the clear sky model, e.g.; by truncation of high aerosol loads. Indeed, it has been shown that a modified version of the Monitoring Atmospheric Composition and Climate (MACC) aerosol information leads to better accuracy of the retrieved solar surface radiation than the original MACC data for the investigated 9 sites and time period (2006-2009). Further, the assumption of a constant aerosol optical depth of 0.18 provides also better accuracies of the estimated solar surface radiation than the original MACC data for the investigated sites and period. It is concluded that this is partly due to the consideration of scattering aerosols by the effective cloud albedo. © 2015 by the authors; licensee MDPI, Basel, Switzerland."
"56536197100;6603256951;25932356800;25226581600;56108347500;8603242500;","A climate change projection for summer hydrologic conditions in a semiarid watershed of central Arizona",2015,"10.1016/j.jaridenv.2015.02.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924077058&doi=10.1016%2fj.jaridenv.2015.02.022&partnerID=40&md5=bb4017940692cb027ea4e1a350ff510a","Potential climate change impacts on summer precipitation and subsequent hydrologic responses in the southwestern U.S. are poorly constrained at present due to a lack of studies accounting for high resolution processes. In this investigation, we apply a distributed hydrologic model to the Beaver Creek watershed of central Arizona to explore its utility for climate change assessments. Manual model calibration and model validation were performed using radar-based precipitation data during three summers and compared to two alternative meteorological products to illustrate the sensitivity of the streamflow response. Using the calibrated and validated model, we investigated the watershed response during historical (1990-2000) and future (2031-2040) summer projections derived from a single realization of a mesoscale model forced with boundary conditions from a general circulation model under a high emissions scenario. Results indicate spatially-averaged changes across the two projections: an increase in air temperature of 1.2°C, a 2.4-fold increase in precipitation amount and a 3-fold increase in variability, and a 3.1-fold increase in streamflow amount and a 5.1-fold increase in variability. Nevertheless, relatively minor changes were obtained in spatially-averaged evapotranspiration. To explain this, we used the simulated hydroclimatological mechanisms to identify that higher precipitation limits radiation through cloud cover leading to lower evapotranspiration in regions with orographic effects. This challenges conventional wisdom on evapotranspiration trends and suggest that a more nuanced approach is needed to communicate hydrologic vulnerability to stakeholders and decision-makers in this semiarid region. © 2015 Elsevier Ltd."
"43961694900;55916925700;6602182223;57219113417;","Fire emission heights in the climate system - Part 2: Impact on transport, black carbon concentrations and radiation",2015,"10.5194/acp-15-7173-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934300482&doi=10.5194%2facp-15-7173-2015&partnerID=40&md5=7c4ad19ddfe4d7ad75c2051e055b6a57","Wildfires represent a major source for aerosols impacting atmospheric radiation, atmospheric chemistry and cloud micro-physical properties. Previous case studies indicated that the height of the aerosol-radiation interaction may crucially affect atmospheric radiation, but the sensitivity to emission heights has been examined with only a few models and is still uncertain. In this study we use the general circulation model ECHAM6 extended by the aerosol module HAM2 to investigate the impact of wildfire emission heights on atmospheric long-range transport, black carbon (BC) concentrations and atmospheric radiation. We simulate the wildfire aerosol release using either various versions of a semi-empirical plume height parametrization or prescribed standard emission heights in ECHAM6-HAM2. Extreme scenarios of near-surface or free-tropospheric-only injections provide lower and upper constraints on the emission height climate impact. We find relative changes in mean global atmospheric BC burden of up to 7.9±4.4 % caused by average changes in emission heights of 1.5-3.5 km. Regionally, changes in BC burden exceed 30-40 % in the major biomass burning regions. The model evaluation of aerosol optical thickness (AOT) against Moderate Resolution Imaging Spectroradiometer (MODIS), AErosol RObotic NETwork (AERONET) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations indicates that the implementation of a plume height parametrization slightly reduces the ECHAM6-HAM2 biases regionally, but on the global scale these improvements in model performance are small. For prescribed emission release at the surface, wildfire emissions entail a total sky top-of-atmosphere (TOA) radiative forcing (RF) of -0.16±0.06 W m-2. The application of a plume height parametrization which agrees reasonably well with observations introduces a slightly stronger negative TOA RF of -0.20±0.07 W m-2. The standard ECHAM6-HAM2 model in which 25 % of the wildfire emissions are injected into the free troposphere (FT) and 75 % into the planetary boundary layer (PBL), leads to a TOA RF of -0.24±0.06 W m-2. Overall, we conclude that simple plume height parametrizations provide sufficient representations of emission heights for global climate modeling. Significant improvements in aerosol wildfire modeling likely depend on better emission inventories and aerosol process modeling rather than on improved emission height parametrizations. © Author(s) 2015."
"7404764644;36895494300;30067702800;55102510300;36118201600;56486548700;","Comparison of satellite-derived LAI and precipitation anomalies over Brazil with a thermal infrared-based Evaporative Stress Index for 2003-2013",2015,"10.1016/j.jhydrol.2015.01.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84936348533&doi=10.1016%2fj.jhydrol.2015.01.005&partnerID=40&md5=1806521c649f27662da16a8c5db5ca6c","Shortwave vegetation index (VI) and leaf area index (LAI) remote sensing products yield inconsistent depictions of biophysical response to drought and pluvial events that have occurred in Brazil over the past decade. Conflicting reports of severity of drought impacts on vegetation health and functioning have been attributed to cloud and aerosol contamination of shortwave reflectance composites, particularly over the rainforested regions of the Amazon basin which are subject to prolonged periods of cloud cover and episodes of intense biomass burning. This study compares timeseries of satellite-derived maps of LAI from the Moderate Resolution Imaging Spectroradiometer (MODIS) and precipitation from the Tropical Rainfall Mapping Mission (TRMM) with a diagnostic Evaporative Stress Index (ESI) retrieved using thermal infrared remote sensing over South America for the period 2003-2013. This period includes several severe droughts and floods that occurred both over the Amazon and over unforested savanna and agricultural areas in Brazil. Cross-correlations between absolute values and standardized anomalies in monthly LAI and precipitation composites as well as the actual-to-reference evapotranspiration (ET) ratio used in the ESI were computed for representative forested and agricultural regions. The correlation analyses reveal strong apparent anticorrelation between MODIS LAI and TRMM precipitation anomalies over the Amazon, but better coupling over regions vegetated with shorter grass and crop canopies. The ESI was more consistently correlated with precipitation patterns over both landcover types. Temporal comparisons between ESI and TRMM anomalies suggest longer moisture buffering timescales in the deeper rooted rainforest systems. Diagnostic thermal-based retrievals of ET and ET anomalies, such as used in the ESI, provide independent information on the impacts of extreme hydrologic events on vegetation health in comparison with VI and precipitation-based drought indicators, and used in concert may provide a more reliable evaluation of natural and managed ecosystem response to variable climate regimes. © 2015."
"45760924500;7404087896;16199172000;7402942478;6603738005;","On the feasibility of monitoring carbon monoxide in the lower troposphere from a constellation of Northern Hemisphere geostationary satellites. (Part 1)",2015,"10.1016/j.atmosenv.2015.04.069","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929462616&doi=10.1016%2fj.atmosenv.2015.04.069&partnerID=40&md5=7e48452aade5ba40983ddaab1d3eef10","By the end of the current decade, there are plans to deploy several geostationary Earth orbit (GEO) satellite missions for atmospheric composition over North America, East Asia and Europe with additional missions proposed. Together, these present the possibility of a constellation of geostationary platforms to achieve continuous time-resolved high-density observations over continental domains for mapping pollutant sources and variability at diurnal and local scales. In this paper, we use a novel approach to sample a very high global resolution model (GEOS-5 at 7km horizontal resolution) to produce a dataset of synthetic carbon monoxide pollution observations representative of those potentially obtainable from a GEO satellite constellation with predicted measurement sensitivities based on current remote sensing capabilities. Part 1 of this study focuses on the production of simulated synthetic measurements for air quality OSSEs (Observing System Simulation Experiments). We simulate carbon monoxide nadir retrievals using a technique that provides realistic measurements with very low computational cost. We discuss the sampling methodology: the projection of footprints and areas of regard for geostationary geometries over each of the North America, East Asia and Europe regions; the regression method to simulate measurement sensitivity; and the measurement error simulation. A detailed analysis of the simulated observation sensitivity is performed, and limitations of the method are discussed. We also describe impacts from clouds, showing that the efficiency of an instrument making atmospheric composition measurements on a geostationary platform is dependent on the dominant weather regime over a given region and the pixel size resolution. These results demonstrate the viability of the ""instrument simulator"" step for an OSSE to assess the performance of a constellation of geostationary satellites for air quality measurements. We describe the OSSE results in a follow up paper (Part 2 of this study). © 2015 Elsevier Ltd."
"52363531000;7004425841;13613779300;8719649000;55777297100;55984680100;7102916495;","Estimating aboveground biomass and leaf area of low-stature Arctic shrubs with terrestrial LiDAR",2015,"10.1016/j.rse.2015.02.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924794738&doi=10.1016%2fj.rse.2015.02.023&partnerID=40&md5=bc790b74fe0733ae783c21a83a80d561","Arctic tundra ecosystems are responding to effects of climatic warming via shifts in vegetation composition and increased woody biomass. In this sensitive ecosystem, minor increases in woody plant biomass may induce significant changes in ecosystem structure and function. However, establishing methods for quantifying and potentially scaling woody plant biomass in low-stature biomes is challenging. In this study, we investigated the potential to use terrestrial laser scanning (TLS) to remotely estimate harvested biomass and leaf area of two dominant low-stature (<1.5m tall) Arctic shrub species in 0.64m2 subplots established in northern Alaskan tundra. We explored two biomass estimation approaches (volumetric surface differencing and voxel counting) applied to point clouds obtained from close-range (2m) and variable-range (<50m) terrestrial laser scans. Relationships between harvested biomass and TLS metrics were strong for all combinations of approaches, with voxel counting giving a marginally better result than surface differencing for close-range data (R2=0.94 vs 0.92; RMSE=102g vs 117g) and surface differencing proving stronger than voxel counting for variable-range data (R2=0.91 vs 0.82; RMSE=119g vs 169g). Strong relationships between total harvested biomass and total leaf dry mass (R2=0.93; RMSE=13.4g), and between leaf dry mass and leaf wet area (R2=0.99; RMSE=9.01cm2) justify estimation of shrub leaf area from TLS-derived shrub biomass. Our results show that rapidly acquired, repeatable terrestrial laser scans taken at multiple ranges can be processed using simple biomass estimation approaches to yield aboveground biomass and leaf area estimates for low-stature shrubs at fine spatial scales (sub-meter to ~50 meters) with the fidelity required to monitor small but ecologically meaningful changes in tundra structure. Further, these data may be employed as ground reference data for broader scale remote sensing data collection, such as airborne LiDAR scanning, that would enable shrub biomass and leaf-area estimates at fine spatial resolution over large spatial extents. © 2015 Elsevier Inc.."
"24332905600;55879739300;57207869145;6506718302;7006665163;8670472000;7005635934;9246517900;","Integration of prognostic aerosol-cloud interactions in a chemistry transport model coupled offline to a regional climate model",2015,"10.5194/gmd-8-1885-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933511408&doi=10.5194%2fgmd-8-1885-2015&partnerID=40&md5=47410bee693a740a51c95941ba1eb392","To reduce uncertainties and hence to obtain a better estimate of aerosol (direct and indirect) radiative forcing, next generation climate models aim for a tighter coupling between chemistry transport models and regional climate models and a better representation of aerosol-cloud interactions. In this study, this coupling is done by first forcing the Rossby Center regional climate model (RCA4) with ERA-Interim lateral boundaries and sea surface temperature (SST) using the standard cloud droplet number concentration (CDNC) formulation (hereafter, referred to as the ""stand-alone RCA4 version"" or ""CTRL"" simulation). In the stand-alone RCA4 version, CDNCs are constants distinguishing only between land and ocean surface. The meteorology from this simulation is then used to drive the chemistry transport model, Multiple-scale Atmospheric Transport and Chemistry (MATCH), which is coupled online with the aerosol dynamics model, Sectional Aerosol module for Large Scale Applications (SALSA). CDNC fields obtained from MATCH-SALSA are then fed back into a new RCA4 simulation. In this new simulation (referred to as ""MOD"" simulation), all parameters remain the same as in the first run except for the CDNCs provided by MATCH-SALSA. Simulations are carried out with this model setup for the period 2005-2012 over Europe, and the differences in cloud microphysical properties and radiative fluxes as a result of local CDNC changes and possible model responses are analysed. Our study shows substantial improvements in cloud microphysical properties with the input of the MATCH-SALSA derived 3-D CDNCs compared to the stand-alone RCA4 version. This model setup improves the spatial, seasonal and vertical distribution of CDNCs with a higher concentration observed over central Europe during boreal summer (JJA) and over eastern Europe and Russia during winter (DJF). Realistic cloud droplet radii (CD radii) values have been simulated with the maxima reaching 13 μm, whereas in the stand-alone version the values reached only 5 μm. A substantial improvement in the distribution of the cloud liquid-water paths (CLWP) was observed when compared to the satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the boreal summer months. The median and standard deviation values from the ""MOD"" simulation are closer to observations than those obtained using the stand-alone RCA4 version. These changes resulted in a significant decrease in the total annual mean net fluxes at the top of the atmosphere (TOA) by -5 W m-2 over the domain selected in the study. The TOA net fluxes from the ""MOD"" simulation show a better agreement with the retrievals from the Clouds and the Earth's Radiant Energy System (CERES) instrument. The aerosol indirect effects are estimated in the ""MOD"" simulation in comparison to the pre-industrial aerosol emissions (1900). Our simulations estimated the domain averaged annual mean total radiative forcing of -0.64 W m-2 with a larger contribution from the first indirect aerosol effect (-0.57 W m-2) than from the second indirect aerosol effect (-0.14 W m-2). © Author(s) 2015."
"6602611904;56276309900;7005908295;","CMIP5-predicted climate shifts over the East Mediterranean: Implications for the transition region between Mediterranean and semi-arid climates",2015,"10.1002/joc.4114","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939469299&doi=10.1002%2fjoc.4114&partnerID=40&md5=c59659da78304f13971e67e2d13d3edb","The effect of climate change on the Eastern Mediterranean (EM) region, a region that reflects a transition between Mediterranean and semi-arid climates, was examined. This transition region is affected by global changes such as the expansion of the Hadley cell, which leads to a poleward shift of the subtropical dry zone. The Hadley cell expansion forces the migration of jet streams and storm tracks poleward from their standard course, potentially increasing regional desertification. This article focuses on the northern coastline of Israel along the EM region where most wet synoptic systems (i.e. systems that may lead to precipitation) are generated. The current climate was compared to the predicted mid-21st century climate based on Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathway (RCP) RCP4.5 and RCP8.5 scenarios using four Coupled Model Intercomparison Project Phase 5 (CMIP5) models. A warming of 1.1-2.6°C was predicted for this region. The models predicted that rain in the region will become less frequent, with a reduction of 1.2-3.4% in 6-h intervals classified as wet synoptic systems and a 10-22% reduction in wet events. They further predicted that the maximum wet event duration in the mid-21st century would become shorter relative to the current climate, implying that extremely long wet systems will become less frequent. Three of the models predicted shrinking of the wet season length by up to 15%. All models predicted an increasing occurrence frequency of Active Red Sea Troughs (ARSTs) for the RCP8.5 scenario by up to 11% by the mid-21st century. For the RCP4.5 scenario, a similar increase of up to 6% was predicted by two of the models. © 2015 Royal Meteorological Society."
"7103202688;7005284577;7003390361;16834406100;6602221672;15080710300;7004176333;6506458269;36672804000;6508148129;7202050065;34570326800;57203776263;16032925200;35737484800;56704589000;36546474200;6603735912;6603178707;16480965400;18438062100;18134511700;7004643405;24477694300;7003710822;26424128800;6602356428;18134565600;7404062492;","In situ vertical profiles of aerosol extinction, mass, and composition over the southeast United States during SENEX and SEAC4RS: Observations of a modest aerosol enhancement aloft",2015,"10.5194/acp-15-7085-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934323918&doi=10.5194%2facp-15-7085-2015&partnerID=40&md5=21c33de097594baeebf8c468f6946c81","Vertical profiles of submicron aerosol from in situ aircraft-based measurements were used to construct aggregate profiles of chemical, microphysical, and optical properties. These vertical profiles were collected over the southeastern United States (SEUS) during the summer of 2013 as part of two separate field studies: the Southeast Nexus (SENEX) study and the Study of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS). Shallow cumulus convection was observed during many profiles. These conditions enhance vertical transport of trace gases and aerosol and create a cloudy transition layer on top of the sub-cloud mixed layer. The trace gas and aerosol concentrations in the transition layer were modeled as a mixture with contributions from the mixed layer below and the free troposphere above. The amount of vertical mixing, or entrainment of air from the free troposphere, was quantified using the observed mixing ratio of carbon monoxide (CO). Although the median aerosol mass, extinction, and volume decreased with altitude in the transition layer, they were ∼10 % larger than expected from vertical mixing alone. This enhancement was likely due to secondary aerosol formation in the transition layer. Although the transition layer enhancements of the particulate sulfate and organic aerosol (OA) were both similar in magnitude, only the enhancement of sulfate was statistically significant. The column integrated extinction, or aerosol optical depth (AOD), was calculated for each individual profile, and the transition layer enhancement of extinction typically contributed less than 10 % to the total AOD. Our measurements and analysis were motivated by two recent studies that have hypothesized an enhanced layer of secondary aerosol aloft to explain the summertime enhancement of AOD (2-3 times greater than winter) over the southeastern United States. The first study attributes the layer aloft to secondary organic aerosol (SOA) while the second study speculates that the layer aloft could be SOA or secondary particulate sulfate. In contrast to these hypotheses, the modest enhancement we observed in the transition layer was not dominated by OA and was not a large fraction of the summertime AOD. © Author(s) 2015."
"15755995900;7006705919;56162305900;55688930000;7003666669;7006270084;8922308700;55717074000;52464731300;22635190100;","How does increasing horizontal resolution in a global climate model improve the simulation of aerosol-cloud interactions?",2015,"10.1002/2015GL064183","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948711317&doi=10.1002%2f2015GL064183&partnerID=40&md5=969ff8f82b189d40e8245bf6f679da5f","The Community Atmosphere Model Version 5 is run at horizontal grid spacing of 2, 1, 0.5, and 0.25°, with the meteorology nudged toward the Year Of Tropical Convection analysis, and cloud simulators and the collocated A-Train satellite observations are used to explore the resolution dependence of aerosol-cloud interactions. The higher-resolution model produces results that agree better with observations, showing an increase of susceptibility of cloud droplet size, indicating a stronger first aerosol indirect forcing (AIF), and a decrease of susceptibility of precipitation probability, suggesting a weaker second AIF. The resolution sensitivities of AIF are attributed to those of droplet nucleation and precipitation parameterizations. The annual average AIF in the Northern Hemisphere midlatitudes (where most anthropogenic emissions occur) in the 0.25° model is reduced by about 1 W m-2 (-30%) compared to the 2° model, leading to a 0.26 W m-2 reduction (-15%) in the global annual average AIF. © 2015. American Geophysical Union. All Rights Reserved."
"7401693165;55828239000;36442544600;36643146900;","A New Detection Method of Volcanic Ash Cloud Based on MODIS Image",2015,"10.1007/s12524-014-0416-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929996961&doi=10.1007%2fs12524-014-0416-2&partnerID=40&md5=7c48b8836c37258bf2102e7f992853c8","The volcanic ash can affect the global climate changes and aviation safety, and has become a hot topic for public security research. The satellite remote sensing sensor can quickly and accurately obtain the volcanic ash cloud information. However, the satellite image has pretty strong inter-band correlation and data redundancy. Principal component analysis (PCA) can overcome the inter-band correlation and data redundancy of satellite images and compress a large number of complex information effectively into a few principal components. Taking the Eyjafjallajokull volcanic ash cloud formed on 19 April 2010 for example, in this paper, the PCA method is used to detect the volcanic ash cloud based on moderate resolution imaging spectroradiometer (MODIS) image. The results show that: the PCA method can obtain the volcanic ash cloud from MODIS image; it is much simpler and the detected volcanic ash cloud has a good consistency with the previous research on the basis of spatial distribution and SO<inf>2</inf> concentration. © 2014, Indian Society of Remote Sensing."
"57192409297;56979100500;57204542986;","Measurement of cloud optical depth using sunphotometer calibrated by pdm algorithm",2015,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063847911&partnerID=40&md5=f0ca2679fa1f1590db2dd6ab3112cc15","One of the useful information to predict earth climate change over a long time is the thin ice cloud microphysical properties such as cloud optical depth (COD). It is a measure of cloud transparency in atmosphere and it depends on the cloud thickness of vertical depth and moisture density. Many algorithms have been developed to measure cloud optical depth but development of calibration constant algorithm for ground based COD retrieval is still lacking. Previously, Langley calibration method was used to calibrate ground based instrument, but this calibration method have a few limitation for long time monitoring purpose. Therefore, combination of clear-sky detection model, Perez- Du Mortier (PDM) algorithm was developed for near sea level calibration purpose and this method have been successfully used to calibrate ground based spectrometer for Aerosol Optical Depth (AOD) retrieval. This paper reports the results of investigating the feasibility of PDM algorithm in calibrating instrument for COD retrievals at near sea level. Calibration constant obtained is then applied to cirrus cloud observed at University Malaysia Sabah, Kota Kinabalu, Sabah. It was found that the proposed calibration method can be used in calibrating ground instrument to measure cloud optical depth at low altitude. © 2015 AENSI Publisher. All rights reserved."
"14632189100;15726838100;6603858896;8526394600;35572640900;6603728352;","Equatorial Atlantic Ocean dynamics in a coupled ocean–atmosphere model simulation",2015,"10.1007/s10236-015-0836-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929838458&doi=10.1007%2fs10236-015-0836-8&partnerID=40&md5=49bbfdf14a5abe844806900bb43a5d8b","The ocean temperatures and zonal currents at the equatorial Atlantic simulated by an improved version of the Brazilian earth system model (BESM), with changes in the cloud cover scheme and optical properties of the atmospheric component, are analyzed and compared to those obtained from a previous version of BESM and also from other seven selected CMIP5 models. It is shown that this updated version of BESM, despite some persistent biases, more accurately represents the surface temperature variation at the Equator and the equatorial thermocline east–west slope. These improvements are associated to a more realistic seasonal cycle achieved for the Atlantic equatorial undercurrent, as well as sea surface temperatures and zonal wind stress. The better simulation of the equatorial undercurrent is, in its turn, credited to a more realistic representation of the surface wind position and strength at the tropical Atlantic by the coupled model. With many of the systematic errors noticed in the previous version of the model alleviated, this version of BESM can be considered as a useful tool for modelers involved in Atlantic variability studies. © 2015, The Author(s)."
"56210720700;57194852533;56703076700;23491184100;55350802700;55481275400;6602097544;7003855730;16308514000;","On the competition among aerosol number, size and composition in predicting CCN variability: A multi-annual field study in an urbanized desert",2015,"10.5194/acp-15-6943-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933557313&doi=10.5194%2facp-15-6943-2015&partnerID=40&md5=6614e8de29cfa5acb9b9083e9a6210ac","A 2-year data set of measured CCN (cloud condensation nuclei) concentrations at 0.2 % supersaturation is combined with aerosol size distribution and aerosol composition data to probe the effects of aerosol number concentrations, size distribution and composition on CCN patterns. Data were collected over a period of 2 years (2012-2014) in central Tucson, Arizona: a significant urban area surrounded by a sparsely populated desert. Average CCN concentrations are typically lowest in spring (233 cm-3), highest in winter (430 cm-3) and have a secondary peak during the North American monsoon season (July to September; 372 cm-3). There is significant variability outside of seasonal patterns, with extreme concentrations (1 and 99 % levels) ranging from 56 to 1945 cm-3 as measured during the winter, the season with highest variability. <br><br> Modeled CCN concentrations based on fixed chemical composition achieve better closure in winter, with size and number alone able to predict 82 % of the variance in CCN concentration. Changes in aerosol chemical composition are typically aligned with changes in size and aerosol number, such that hygroscopicity can be parameterized even though it is still variable. In summer, models based on fixed chemical composition explain at best only 41 % (pre-monsoon) and 36 % (monsoon) of the variance. This is attributed to the effects of secondary organic aerosol (SOA) production, the competition between new particle formation and condensational growth, the complex interaction of meteorology, regional and local emissions and multi-phase chemistry during the North American monsoon. Chemical composition is found to be an important factor for improving predictability in spring and on longer timescales in winter. <br><br> Parameterized models typically exhibit improved predictive skill when there are strong relationships between CCN concentrations and the prevailing meteorology and dominant aerosol physicochemical processes, suggesting that similar findings could be possible in other locations with comparable climates and geography. © Author(s) 2015."
"55704350200;56708137800;14020751800;","Reconstruction of cloud geometry using a scanning cloud radar",2015,"10.5194/amt-8-2491-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934927659&doi=10.5194%2famt-8-2491-2015&partnerID=40&md5=c0f995c5be620d5ec37bb769125ae0d8","Clouds are one of the main reasons of uncertainties in the forecasts of weather and climate. In part, this is due to limitations of remote sensing of cloud microphysics. Present approaches often use passive spectral measurements for the remote sensing of cloud microphysical parameters. Large uncertainties are introduced by three-dimensional (3-D) radiative transfer effects and cloud inhomogeneities. Such effects are largely caused by unknown orientation of cloud sides or by shadowed areas on the cloud. Passive ground-based remote sensing of cloud properties at high spatial resolution could be crucially improved with this kind of additional knowledge of cloud geometry. To this end, a method for the accurate reconstruction of 3-D cloud geometry from cloud radar measurements is developed in this work. Using a radar simulator and simulated passive measurements of model clouds based on a large eddy simulation (LES), the effects of different radar scan resolutions and varying interpolation methods are evaluated. In reality, a trade-off between scan resolution and scan duration has to be found as clouds change quickly. A reasonable choice is a scan resolution of 1 to 2\degree. The most suitable interpolation procedure identified is the barycentric interpolation method. The 3-D reconstruction method is demonstrated using radar scans of convective cloud cases with the Munich miraMACS, a 35 GHz scanning cloud radar. As a successful proof of concept, camera imagery collected at the radar location is reproduced for the observed cloud cases via 3-D volume reconstruction and 3-D radiative transfer simulation. Data sets provided by the presented reconstruction method will aid passive spectral ground-based measurements of cloud sides to retrieve microphysical parameters. © Author(s) 2015."
"55075228200;7102866124;8277424000;","Influence of biomass aerosol on precipitation over the Central Amazon: An observational study",2015,"10.5194/acp-15-6789-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934975984&doi=10.5194%2facp-15-6789-2015&partnerID=40&md5=558767960092a3bf41016f1c28705791","Understanding the influence of biomass burning aerosol on clouds and precipitation in the Amazon is key to reducing uncertainties in simulations of climate change scenarios with regard to deforestation fires. Here, we associate rainfall characteristics obtained from an S-band radar in the Amazon with in situ measurements of biomass burning aerosol for the entire year of 2009. The most important results were obtained during the dry season (July-December). The results indicate that the influence of aerosol on precipitating systems is modulated by the atmospheric degree of instability. For less unstable atmospheres, the higher the aerosol concentration is, the lower the precipitation is over the region. In contrast, for more unstable cases, higher concentrations of black carbon are associated with greater precipitation, increased ice content, and larger rain cells; this finding suggests an association with long-lived systems. The results presented are statistically significant. However, due to limitations imposed by the available data set, important features, such as the contribution of each mechanism to the rainfall suppression, need further investigation. Regional climate model simulations with aircraft and radar measurements would help clarify these questions. © Author(s) 2015."
"55068709500;57204495346;55399842300;57213268296;24511929800;56253852700;55710583000;56011231200;56517289900;6701581547;","Regional air pollution brightening reverses the greenhouse gases induced warming-elevation relationship",2015,"10.1002/2015GL064410","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934434556&doi=10.1002%2f2015GL064410&partnerID=40&md5=43ad68eeb2c5ae1a96f4de6d36ba04f4","Mountain waters, glaciers, hazards, and biodiversity are vulnerable to the impacts of global warming. Warming is projected to amplify over mountains by global climate models, yet meteorological records do not show a uniform acceleration of warming with elevation. Here we explore warming-elevation relationships using records from 2660 meteorological stations and determine that the vertical gradient of warming rate varies with location. The warming is faster at higher altitudes in Asia and western North America, but the opposite is observed over Central Europe and eastern North America which have received more short-wave radiation (brightening) associated with a decrease of aerosols and clouds since the 1980s. We found that altitudinal differences in air pollution (brightening), with observations showing more short-wave radiation received at low altitudes than at mountains, modulate the warming-elevation relationships. The advance in understanding of the drivers of regional climate change will contribute to the formulation of strategies for climate change mitigation at high elevations. © 2015. American Geophysical Union. All Rights Reserved."
"57217271893;","Detecting soil moisture impacts on convective initiation in Europe",2015,"10.1002/2015GL064030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934441377&doi=10.1002%2f2015GL064030&partnerID=40&md5=6380e2b4d09c39e69ea2326fb466ce9b","Feedbacks between soil moisture and precipitation are important for understanding hydroclimatic variability in many regions. However, much uncertainty remains about how land surface fluxes influence the initiation of deep convection locally. While some studies consider only atmospheric and soil profiles, in a one-dimensional sense, others have argued that horizontal variability in fluxes plays an important role in convective triggering, via mesoscale circulations. This paper presents the first comprehensive observational analysis over Europe linking convective initiation to soil moisture, based on satellite observations of cloud top and land surface temperature, and soil moisture. The results show that convective initiations are favored on the downwind side of dry surfaces, close to wetter areas. The signal is clearest following dry periods and under light winds, consistent with forcing by a mesoscale circulation. Overall, the detected signal in Europe is weaker than in previous Sahelian analysis, but key spatial characteristics are essentially the same. ©2015. The Authors."
"36105812700;6603711967;7004038301;55682653785;16315122000;6602741207;55366988900;7003563351;24168358300;7007061108;6602625048;35558816600;55964407600;26643608000;56250938500;7403552006;7006033826;14624363000;7102585350;6701853567;36926057000;56588914000;24345504800;6508089485;14619596900;7410371558;","Twelve thousand years of dust: The Holocene global dust cycle constrained by natural archives",2015,"10.5194/cp-11-869-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84935893874&doi=10.5194%2fcp-11-869-2015&partnerID=40&md5=c0bc70b6da95cf2bf3bdec4498618e84","Mineral dust plays an important role in the climate system by interacting with radiation, clouds, and biogeochemical cycles. In addition, natural archives show that the dust cycle experienced variability in the past in response to global and local climate change. The compilation of the DIRTMAP (Dust Indicators and Records from Terrestrial and MArine Palaeoenvironments) paleodust data sets in the last 2 decades provided a benchmark for paleoclimate models that include the dust cycle, following a time slice approach. We propose an innovative framework to organize a paleodust data set that builds on the positive experience of DIRTMAP and takes into account new scientific challenges by providing a concise and accessible data set of temporally resolved records of dust mass accumulation rates and particle grain size distributions. We consider data from ice cores, marine sediments, loess-paleosol sequences, lake sediments, and peat bogs for this compilation, with a temporal focus on the Holocene period. This global compilation allows the investigation of the potential, uncertainties, and confidence level of dust mass accumulation rate reconstructions and highlights the importance of dust particle size information for accurate and quantitative reconstructions of the dust cycle. After applying criteria that help to establish that the data considered represent changes in dust deposition, 45 paleodust records have been identified, with the highest density of dust deposition data occurring in the North Atlantic region. Although the temporal evolution of dust in the North Atlantic appears consistent across several cores and suggests that minimum dust fluxes are likely observed during the early to mid-Holocene period (6000-8000 years ago), the magnitude of dust fluxes in these observations is not fully consistent, suggesting that more work needs to be done to synthesize data sets for the Holocene. Based on the data compilation, we used the Community Earth System Model to estimate the mass balance of and variability in the global dust cycle during the Holocene, with dust loads ranging from 17.2 to 20.8 Tg between 2000 and 10 000 years ago and with a minimum in the early to mid-Holocene (6000-8000 years ago). © Author(s) 2015."
"55261195800;56724696200;6602080205;","Impacts of 20th century aerosol emissions on the South Asian monsoon in the CMIP5 models",2015,"10.5194/acp-15-6367-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84935839203&doi=10.5194%2facp-15-6367-2015&partnerID=40&md5=85904afe59dd6a36608a5b790b9d5429","Comparison of single-forcing varieties of 20th century historical experiments in a subset of models from the Fifth Coupled Model Intercomparison Project (CMIP5) reveals that South Asian summer monsoon rainfall increases towards the present day in Greenhouse Gas (GHG)-only experiments with respect to pre-industrial levels, while it decreases in anthropogenic aerosol-only experiments. Comparison of these single-forcing experiments with the all-forcings historical experiment suggests aerosol emissions have dominated South Asian monsoon rainfall trends in recent decades, especially during the 1950s to 1970s. The variations in South Asian monsoon rainfall in these experiments follows approximately the time evolution of inter-hemispheric temperature gradient over the same period, suggesting a contribution from the large-scale background state relating to the asymmetric distribution of aerosol emissions about the equator. By examining the 24 available all-forcings historical experiments, we show that models including aerosol indirect effects dominate the negative rainfall trend. Indeed, models including only the direct radiative effect of aerosol show an increase in monsoon rainfall, consistent with the dominance of increasing greenhouse gas emissions and planetary warming on monsoon rainfall in those models. For South Asia, reduced rainfall in the models with indirect effects is related to decreased evaporation at the land surface rather than from anomalies in horizontal moisture flux, suggesting the impact of indirect effects on local aerosol emissions. This is confirmed by examination of aerosol loading and cloud droplet number trends over the South Asia region. Thus, while remote aerosols and their asymmetric distribution about the equator play a role in setting the inter-hemispheric temperature distribution on which the South Asian monsoon, as one of the global monsoons, operates, the addition of indirect aerosol effects acting on very local aerosol emissions also plays a role in declining monsoon rainfall. The disparity between the response of monsoon rainfall to increasing aerosol emissions in models containing direct aerosol effects only and those also containing indirect effects needs to be urgently investigated since the suggested future decline in Asian anthropogenic aerosol emissions inherent to the representative concentration pathways (RCPs) used for future climate projection may turn out to be optimistic. In addition, both groups of models show declining rainfall over China, also relating to local aerosol mechanisms. We hypothesize that aerosol emissions over China are large enough, in the CMIP5 models, to cause declining monsoon rainfall even in the absence of indirect aerosol effects. The same is not true for India. © Author(s) 2015."
"24491752100;7404297096;6602115214;","Meridionally tilted ice cloud structures in the tropical upper troposphere as seen by CloudSat",2015,"10.5194/acp-15-6271-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931263458&doi=10.5194%2facp-15-6271-2015&partnerID=40&md5=f7cc8cb795d2b6838e44c55926bb58c3","It remains challenging to quantify global cloud properties and uncertainties associated with their impacts on climate change because of our poor understanding of cloud three-dimensional (3-D) structures from observations and unrealistic characterization of 3-D cloud effects in global climate models (GCMs). In this study we find cloud 3-D effects can cause significant error in cloud ice and radiation measurements if it is not taken into account appropriately. One of the cloud 3-D complexities, the slantwise tilt structure, has not received much attention in research and even less has been reported considering a global perspective. A novel approach is presented here to analyze the ice cloud water content (IWC) profiles retrieved from CloudSat and a joint radar-lidar product (DARDAR). By integrating IWC profiles along different tilt angles, we find that upper-troposphere (UT) ice cloud mass between 11 and 17 km is tilted poleward from active convection centers in the tropics [30° S, 30° N]. This systematic tilt in cloud mass structure is expected from the mass conservation principle of the Hadley circulation with the divergent flow of each individual convection/convective system from down below, and its existence is further confirmed from cloud-resolving-scale Weather Research and Forecasting (WRF) model simulations. Thus, additive effects of tilted cloud structures can introduce 5-20% variability by its nature or produce errors to satellite cloud/hydrometeor ice retrievals if simply converting it from slant to nadir column. A surprising finding is the equatorward tilt in middle tropospheric (5-11 km) ice clouds, which is also evident in high-resolution model simulations but not in coarse-resolution simulations with cumulus parameterization. The observed cloud tilt structures are intrinsic properties of tropical clouds, producing synoptic distributions around the Intertropical Convergence Zone (ITCZ). These findings imply that current interpretations based on over-simplified cloud vertical structures could lead to considerable cloud measurement errors and have a subsequent impact on understanding cloud radiative, dynamical and hydrological properties. © Author(s) 2015."
"7003440089;6603553760;55993369600;16443893300;57210222492;6603745481;17346981400;37123320600;56400886500;56681868600;56400768700;7102317973;","Characterization of the boundary layer at Dome C (East Antarctica) during the OPALE summer campaign",2015,"10.5194/acp-15-6225-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930938893&doi=10.5194%2facp-15-6225-2015&partnerID=40&md5=505a789cdc1f428b6c81bf2fb697a61c","Regional climate model MAR (Modèle Atmosphérique Régional) was run for the region of Dome C located on the East Antarctic plateau, during Antarctic summer 2011-2012, in order to refine our understanding of meteorological conditions during the OPALE tropospheric chemistry campaign. A very high vertical resolution is set up in the lower troposphere, with a grid spacing of roughly 2 m. Model output is compared with temperatures and winds observed near the surface and from a 45 m high tower as well as sodar and radiation data. MAR is generally in very good agreement with the observations, but sometimes underestimates cloud formation, leading to an underestimation of the simulated downward long-wave radiation. Absorbed short-wave radiation may also be slightly overestimated due to an underestimation of the snow albedo, and this influences the surface energy budget and atmospheric turbulence. Nevertheless, the model provides sufficiently reliable information about surface turbulent fluxes, vertical profiles of vertical diffusion coefficients and boundary layer height when discussing the representativeness of chemical measurements made nearby the ground surface during field campaigns conducted at Concordia station located at Dome C (3233 m above sea level). © Author(s) 2015."
"13405658600;8728433200;56682032300;55683891800;7501381728;","The importance of interstitial particle scavenging by cloud droplets in shaping the remote aerosol size distribution and global aerosol-climate effects",2015,"10.5194/acp-15-6147-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930959649&doi=10.5194%2facp-15-6147-2015&partnerID=40&md5=59be22da4edca63c2ffda224be02d802","In this paper, we investigate the coagulation of interstitial aerosol particles (particles too small to activate to cloud droplets) with cloud drops, a process often ignored in aerosol-climate models. We use the GEOS-Chem-TOMAS (Goddard Earth Observing System-Chemistry TwO-Moment Aerosol Sectional) global chemical transport model with aerosol microphysics to calculate the changes in the aerosol size distribution, cloud-albedo aerosol indirect effect, and direct aerosol effect due to the interstitial coagulation process. We find that inclusion of interstitial coagulation in clouds lowers total particle number concentrations by 15-21% globally, where the range is due to varying assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The interstitial coagulation process lowers the concentration of particles with dry diameters larger than 80 nm (a proxy for larger CCN) by 10-12%. These 80 nm particles are not directly removed by the interstitial coagulation but are reduced in concentration because fewer smaller particles grow to diameters larger than 80 nm. The global aerosol indirect effect of adding interstitial coagulation varies from +0.4 to +1.3 W m-2 where again the range depends on our cloud assumptions. Thus, the aerosol indirect effect of this process is significant, but the magnitude depends greatly on assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The aerosol direct effect of the interstitial coagulation process is minor (< 0.01 W m-2) due to the shift in the aerosol size distribution at sizes where scattering is most effective being small. We recommend that this interstitial scavenging process be considered in aerosol models when the size distribution and aerosol indirect effects are important."
"56580380600;7201903057;56580244700;","Change in the glacier extent in Turkey during the Landsat Era",2015,"10.1016/j.rse.2015.03.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937761713&doi=10.1016%2fj.rse.2015.03.002&partnerID=40&md5=dddc217df94b6b30ef11c974486ce449","We report the latest study for small glaciers, using Turkey as an example, and update previous studies of glaciers in Turkey from the 1970s to 2012-2013. We used seventy-two Landsat scenes from the Multispectral Scanner (MSS), Return Beam Vidicon-3 (RBV-3), Thematic Mapper (TM), Enhanced Thematic Mapper plus (ETM+), and Operational Land Imager (OLI); five Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images; and forty-one commercial satellite images. IKONOS, Quickbird-2, GeoEye-1, and WorldView-1 and -2 commercial satellite images were used to evaluate mapping accuracies, to understand debris-covered glacial margins, to map glacier margins in shadows, and to better determine the area of the smaller glaciers in Turkey. We also used nine Landsat-5 simultaneously acquired TM and MSS images to more accurately process MSS imagery from the 1970s. The area of the glaciers in Turkey decreased from 25km2 in the 1970s to 10.85km2 in 2012-2013. By 2012-2013, five glaciers had disappeared, six were less than 0.5km2, one was 0.8km2, and only two were 3.0km2 or larger. No trends in 1980 to 2012 annual precipitation, 1980 to 2012 winter precipitation, and 1980 to 2008 cloud cover extent were found, while surface temperatures increased, with summer minimum temperatures showing the greatest increases. We attribute glacier recession in Turkey from the 1970s to 2012-2013 to increasing summer minimum temperatures with no changes in precipitation or cloud cover over this time period. © 2015 Elsevier Inc."
"14033871500;15060929700;25926243900;7004461962;24448101200;","Assimilation of surface albedo and vegetation states from satellite observations and their impact on numerical weather prediction",2015,"10.1016/j.rse.2015.03.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937758023&doi=10.1016%2fj.rse.2015.03.009&partnerID=40&md5=eb9922cc06342870d7d3cc22ed5f7e43","The vegetation state can have a prominent influence on the global energy, water and carbon cycles. This has been particularly evident during extreme conditions in recent years (e.g. Europe 2003 and Russia 2010 heat waves, Horn of Africa 2010 drought, and Australia 2010 drought recovery). Weather parameters are sensitive to the vegetation state and particularly to albedo and Leaf Area Index (LAI) that controls the partitioning of the surface energy fluxes into latent and sensible fluxes, and the development of planetary boundary conditions and clouds. An optimal interpolation analysis of a satellite-based surface albedo and LAI is performed through the combination of satellite observations and derived climatologies, depending on their associated errors. The final analysis products have smoother temporal evolution than the direct observations, which makes them more appropriate for environmental and numerical weather prediction. The impact of assimilating these near-real-time (NRT) products within the land surface scheme of the European Centre of Medium-Range Weather Forecasts (ECMWF) is evaluated for anomalous years. It is shown that: (i) the assimilation of these products enables detecting/monitoring extreme climate conditions where the LAI anomaly could reach more than 50% and in wet years albedo anomaly could reach 10% , (ii) extreme NRT LAI anomalies have a strong impact on the surface fluxes, while for the albedo, which has a smaller inter-annual variability, the impact on surface fluxes is small, (iii) neutral to slightly better agreement with in-situ surface soil moisture observations and surface energy and CO2 fluxes from eddy-covariance towers is obtained, and (iv) in forecast using a land-atmosphere coupled system, the assimilation of NRT LAI reduces the near-surface air temperature and humidity errors both in wet and dry cases, while NRT albedo has a small impact, mainly in wet cases (when albedo anomalies are more noticeable). © 2015 Elsevier Inc."
"23492864500;8866821900;23768540500;13006055400;","The behavior of trade-wind cloudiness in observations and models: The major cloud components and their variability",2015,"10.1002/2014MS000390","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027925077&doi=10.1002%2f2014MS000390&partnerID=40&md5=6937f1fc0a73bc674d6ce78a5278c96c","Guided by ground-based radar and lidar profiling at the Barbados Cloud Observatory (BCO), this study evaluates trade-wind cloudiness in ECMWF's Integrated Forecast System (IFS) and nine CMIP5 models using their single-timestep output at selected grid points. The observed profile of cloudiness is relatively evenly distributed between two important height levels: the lifting condensation level (LCL) and the tops of the deepest cumuli near the trade-wind inversion (2-3 km). Cloudiness at the LCL dominates the total cloud cover, but is relatively invariant. Variance in cloudiness instead peaks at the inversion. The IFS reproduces the depth of the cloud field and its variability, but underestimates cloudiness at the LCL and the inversion. A few CMIP5 models produce a single stratocumulus-like layer near the LCL, but more than half of the CMIP5 models reproduce the observed cloud layer depth in long-term mean profiles. At single-time steps, however, half of the models do not produce cloudiness near cloud tops along with the (almost ever-present) cloudiness near the LCL. In seven models, cloudiness is zero at both levels 10 to 65% of the time, compared to 3% in the observations. Models therefore tend to overestimate variance in cloudiness near the LCL. This variance is associated with longer time scales than in observations, which suggests that modeled cloudiness is too sensitive to large-scale processes. To conclude, many models do not appear to capture the processes that underlie changes in cloudiness, which is relevant for cloud feedbacks and climate prediction. © 2015. The Authors."
"7401984344;7004617224;55388912500;7202970886;6603631763;7201472576;","Variability and trends in U.S. cloud cover: ISCCP, PATMOS-x, and CLARA-A1 compared to homogeneity-adjusted weather observations",2015,"10.1175/JCLI-D-14-00805.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962210258&doi=10.1175%2fJCLI-D-14-00805.1&partnerID=40&md5=5e68e7019df1e3455fed1c5900800036","Variability and trends in total cloud cover for 1982-2009 across the contiguous United States from the International Satellite Cloud Climatology Project (ISCCP), AVHRR Pathfinder Atmospheres-Extended (PATMOS-x), and EUMETSAT Satellite Application Facility on Climate Monitoring Clouds, Albedo and Radiation from AVHRR Data Edition 1 (CLARA-A1) satellite datasets are assessed using homogeneity-adjusted weather station data. The station data, considered as ""ground truth"" in the evaluation, are generally well correlated with the ISCCP and PATMOS-x data and with the physically related variables diurnal temperature range, precipitation, and surface solar radiation. Among the satellite products, overall, the PATMOS-x data have the highest interannual correlations with the weather station cloud data and those other physically related variables. The CLARA-A1 daytime dataset generally shows the lowest correlations, even after trends are removed. For the U.S. mean, the station dataset shows a negative but not statistically significant trend of -0.40% decade-1, and satellite products show larger downward trends ranging from -0.55% to -5.00% decade-1 for 1984-2007. PATMOS-x 1330 local time trends for U.S. mean cloud cover are closest to those in the station data, followed by the PATMOS-x diurnally corrected dataset and ISCCP, with CLARA-A1 having a large negative trend contrasting strongly with the station data. These results tend to validate the usefulness of weather station cloud data for monitoring changes in cloud cover, and they show that the long-term stability of satellite cloud datasets can be assessed by comparison to homogeneity-adjusted station data and other physically related variables. © 2015 American Meteorological Society."
"56230988400;56033466400;6603566335;6603606681;23484340400;36701462300;36187387300;49664027700;","A single-column model intercomparison on the stratocumulus representation in present-day and future climate",2015,"10.1002/2014MS000377","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027919200&doi=10.1002%2f2014MS000377&partnerID=40&md5=a6deccded1850060a65b829f6ecb8648","Six Single-Column Model (SCM) versions of climate models are evaluated on the basis of their representation of the dependence of the stratocumulus-topped boundary layer regime on the free tropospheric thermodynamic conditions. The study includes two idealized experiments corresponding to the present-day and future climate conditions in order to estimate the low-cloud feedback. Large-Eddy Simulation (LES) results are used as a benchmark and GCM outputs are included to assess whether the SCM results are representative of their 3-D counterparts. The SCMs present a variety of dependencies of the cloud regime on the free tropospheric conditions but, at the same time, several common biases. For all the SCMs the stratocumulus-topped boundary layer is too shallow, too cool, and too moist as compared to the LES results. Moreover, they present a lack of clouds and liquid water and an excess of precipitation. The disagreement among SCMs is even more distinct for the response to a climate perturbation. Even though the overall feedback is positive for all the models, in line with the LES results, the SCMs show a rather noisy behavior, which depends irregularly on the free tropospheric conditions. Finally, the comparison with the host GCM outputs demonstrates that the considered approach is promising but needs to be further generalized for the SCMs to fully capture the behavior of their 3-D counterparts. Key Points: The article presents a hierarchy of models: six SCMs, the corresponding GCMs, one LES SCM biases: too shallow, cool, moist, and precipitating ABL, lack of clouds Positive overall cloud feedback in line with LES but SCMs show a noisy behavior © 2015. The Authors."
"56033466400;6603606681;56030635600;6603566335;","An les model study of the influence of the free tropospheric thermodynamic conditions on the stratocumulus response to a climate perturbation",2015,"10.1002/2014MS000380","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84968594613&doi=10.1002%2f2014MS000380&partnerID=40&md5=b3218dfd5d4537f24b7f7660c2405cd8","Twenty-five large-eddy simulations are performed to study how free tropospheric thermodynamic conditions control equilibrium state solutions of stratocumulus-topped marine boundary layers. In particular, we systematically vary the lower tropospheric stability (LTS) and a similar measure for the bulk humidity difference between the 700 hPa level and the surface, ΔQ. For all simulations, a completely overcast boundary layer is obtained in which the turbulence is mainly driven by cloud top radiative cooling. The steady state liquid water path (LWP) is rather insensitive to the LTS, but increases significantly and almost linearly with the free tropospheric humidity. In a second suite of runs, the response of the stratocumulus layer to an idealized global warming scenario is assessed by applying a uniform warming of 2 K to the initial temperature profile including the sea surface while the initial relative humidity profile is kept identical to the control case. The warming of the sea surface acts to increase the latent heat flux, which invigorates turbulence in the boundary layer. The steady state inversion height therefore increases, despite the competing effect of a more humid free troposphere that increases the downwelling radiative flux and hence tends to decrease the entrainment rate. The stratocumulus layer nevertheless thins for all free tropospheric conditions as cloud base rises more than cloud top. This implies a positive stratocumulus cloud-climate feedback for this scenario as thinner clouds reflect less shortwave radiation back to space. The cloud thinning response to the climate perturbation is found to be mostly controlled by the change of ΔQ. © 2015. The Authors."
"56597778200;23028121100;24071230200;7201472576;55944611200;24802640400;9233045100;15840467900;57194628631;12801836100;6701410329;","The Clouds Climate Change Initiative: Assessment of state-of-the-art cloud property retrieval schemes applied to AVHRR heritage measurements",2015,"10.1016/j.rse.2013.10.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929061517&doi=10.1016%2fj.rse.2013.10.035&partnerID=40&md5=78258a75a7a331c5d023cf31df16aeb5","Cloud property retrievals from 3 decades of the Advanced Very High Resolution Radiometer (AVHRR) measurements provide a unique opportunity for a long-term analysis of clouds. In this study, the accuracy of AVHRR-derived cloud properties cloud mask, cloud-top height, cloud phase and cloud liquid water path is assessed using three state-of-the-art retrieval schemes. In addition, the same retrieval schemes are applied to the AVHRR heritage channels of the Moderate Resolution Imaging Spectroradiometer (MODIS) to create AVHRR-like retrievals with higher spatial resolution and based on presumably more accurate spectral calibration. The cloud property retrievals were collocated and inter-compared with observations from CloudSat, CALIPSO and AMSR-E The resulting comparison exhibited good agreement in general. The schemes provide correct cloud detection in 82 to 90% of all cloudy cases. With correct identification of clear-sky in 61 to 85% of all clear areas, the schemes are slightly biased towards cloudy conditions. The evaluation of the cloud phase classification shows correct identification of liquid clouds in 61 to 97% and a correct identification of ice clouds in 68 to 95%, demonstrating a large variability among the schemes. Cloud-top height (CTH) retrievals were of relatively similar quality with standard deviations ranging from 2.1km to 2.7km. Significant negative biases in these retrievals are found in particular for cirrus clouds. The biases decrease if optical depth thresholds are applied to determine the reference CTH measure. Cloud liquid water path (LWP) is also retrieved well with relative low standard deviations (20 to 28g/m2), negative bias and high correlations. Cloud ice water path (IWP) retrievals of AVHRR and MODIS exhibit a relative high uncertainty with standard deviations between 800 and 1400g/m2, which in relative terms exceed 100% when normalized with the mean IWP. However, the global histogram distributions of IWP were similar to the reference dataset. MODIS retrievals are for most comparisons of slightly better quality than AVHRR-based retrievals. Additionally, the choice of different near-infrared channels, 3.7. μm as opposed to 1.6. μm, can have a significant impact on the retrieval quality, most pronounced for IWP, with better accuracy for the 1.6. μm channel setup. This study presents a novel assessment of the quality of cloud properties derived from AVHRR channels, which quantifies the accuracy of the considered retrievals based on common approaches and validation data. Furthermore, it assesses the capabilities of AVHRR-like spectral information for retrieving cloud properties in the light of generating climate data records of cloud properties from three decades of AVHRR measurements. © 2013 Elsevier Inc."
"56483153400;56596353200;7404454238;10241250100;7402511803;24778875500;9249605700;","Climate change effects on the worst-case storm surge: A case study of Typhoon Haiyan",2015,"10.1088/1748-9326/10/6/064011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937468932&doi=10.1088%2f1748-9326%2f10%2f6%2f064011&partnerID=40&md5=48bae650a48f8af6bf08590cb4c9527d","Effects of climate change on the worst case scenario of a storm surge induced by a super typhoon in the present climate are investigated through the case study of Typhoon Haiyan. We present the results of our investigation on super-typhoon Haiyan by using a super high resolution (1 km grid) regional model that explicitly handles cloud microphysical processes. As the parent model, we adopted the operational weekly ensemble experiments (60 km grid) of the Japan Meteorological Agency, and compared experiments using sea surface temperatures and atmospheric environmental parameters from before the beginning of anthropogenic climate change (150 years ago) with those using observed values throughout the typhoon. We were able not only to represent the typhoon's intensity but also to evaluate the influences of climate change on worst case storm surges in the Gulf of Leyte due to a typhoon with high robustness. In 15 of 16 ensemble experiments, the intensity of the simulated worst case storm in the actual conditions was stronger than that in a hypothetical natural condition without historical anthropogenic forcing during the past 150 years. The intensity of the typhoon is translated to a disaster metric by simulating the storm surge height by using a shallow-water long-wave model. The result indicates that the worst case scenario of a storm surge in the Gulf of Leyte may be worse by 20%, though changes in frequency of such events are not accounted for here. © 2015 IOP Publishing Ltd."
"34881780600;6506328135;36868795400;37099564300;56583515100;8247122100;","Mechanisms of convective cloud organization by cold pools over tropical warm ocean during the AMIE/DYNAMO field campaign",2015,"10.1002/2014MS000384","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027952454&doi=10.1002%2f2014MS000384&partnerID=40&md5=8709ad51eeaf0dd28137b2ce2cb21759","This paper investigates the mechanisms of convective cloud organization by precipitation-driven cold pools over the warm tropical Indian Ocean during the 2011 Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation (MJO) Investigation Experiment/Dynamics of the MJO (AMIE/DYNAMO) field campaign. A high-resolution regional model simulation is performed using the Weather Research and Forecasting model during the transition from suppressed to active phases of the November 2011 MJO. The simulated cold pool lifetimes, spatial extent, and thermodynamic properties agree well with the radar and ship-borne observations from the field campaign. The thermodynamic and dynamic structures of the outflow boundaries of isolated and intersecting cold pools in the simulation and the associated secondary cloud populations are examined. Intersecting cold pools last more than twice as long, are twice as large, 41% more intense (measured with buoyancy), and 62% deeper than isolated cold pools. Consequently, intersecting cold pools trigger 73% more convection than do isolated ones. This is due to stronger outflows that enhance secondary updraft velocities by up to 45%. However, cold pool-triggered convective clouds grow into deep convection not because of the stronger secondary updrafts at cloud base, but rather due to closer spacing (aggregation) between clouds and larger cloud clusters that form along the cold pool boundaries when they intersect. The close spacing of large clouds moistens the local environment and reduces entrainment drying, increasing the probability that the clouds further develop into deep convection. Implications for the design of future convective parameterization with cold pool-modulated entrainment rates are discussed. Key Points: Intersecting cold pools trigger more clouds than isolated ones Intersecting cold pools produce larger clouds and closer spacing among them Larger clouds and closer spacing promote deeper convection © 2015. The Authors."
"23977679300;7006860287;14119516800;7004368198;7003303148;","The sea surface temperature climate change initiative: Alternative image classification algorithms for sea-ice affected oceans",2015,"10.1016/j.rse.2013.11.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929061634&doi=10.1016%2fj.rse.2013.11.022&partnerID=40&md5=e61e787e8a209ed2f71088bb1e0e45dd","We present a Bayesian image classification scheme for discriminating cloud, clear and sea-ice observations at high latitudes to improve identification of areas of clear-sky over ice-free ocean for SST retrieval. We validate the image classification against a manually classified dataset using Advanced Along Track Scanning Radiometer (AATSR) data. A three-way classification scheme using a near-infrared textural feature improves classifier accuracy by 9.9% over the nadir only version of the cloud clearing used in the ATSR Reprocessing for Climate (ARC) project in high latitude regions. The three-way classification gives similar numbers of cloud and ice scenes misclassified as clear but significantly more clear-sky cases are correctly identified (89.9% compared with 65% for ARC). We also demonstrate the potential of a Bayesian image classifier including information from the 0.6. μm channel to be used in sea-ice extent and ice surface temperature retrieval with 77.7% of ice scenes correctly identified and an overall classifier accuracy of 96%. © 2014 Elsevier Inc."
"7004368198;7006960661;57196612094;","Selecting algorithms for Earth observation of climate within the European Space Agency Climate Change Initiative: Introduction to a special issue",2015,"10.1016/j.rse.2015.02.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939978914&doi=10.1016%2fj.rse.2015.02.017&partnerID=40&md5=751e15f134ad6c75f366680d0a1d242b","This special issue is focused on the assessment of algorithms for the observation of Earth's climate from environmental satellites. Climate data records derived by remote sensing are increasingly a key source of insight into the workings of and changes in Earth's climate system. Producers of data sets must devote considerable effort and expertise to maximise the true climate signals in their products and minimise effects of data processing choices and changing sensors. A key choice is the selection of algorithm(s) for classification and/or retrieval of the climate variable. Within the European Space Agency Climate Change Initiative, science teams undertook systematic assessment of algorithms for a range of essential climate variables. The papers in the special issue report some of these exercises (for ocean colour, aerosol, ozone, greenhouse gases, clouds, soil moisture, sea surface temperature and glaciers). The contributions show that assessment exercises must be designed with care, considering issues such as the relative importance of different aspects of data quality (accuracy, precision, stability, sensitivity, coverage, etc.), the availability and degree of independence of validation data and the limitations of validation in characterising some important aspects of data (such as long-term stability or spatial coherence). As well as requiring a significant investment of expertise and effort, systematic comparisons are found to be highly valuable. They reveal the relative strengths and weaknesses of different algorithmic approaches under different observational contexts, and help ensure that scientific conclusions drawn from climate data records are not influenced by observational artifacts, but are robust. © 2015 Elsevier Inc."
"56428331200;35363185800;7405690800;","The cloud-radiative effect when simulating strength asymmetry in two types of El Niño events using CMIP5 models",2015,"10.1002/2014JC010683","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027939579&doi=10.1002%2f2014JC010683&partnerID=40&md5=206c098bcbfe671e4c22d5e2d4927c0d","It has been suggested that the strength asymmetry of the Bjerknes feedback is responsible for the pronounced amplitude asymmetry between eastern Pacific (EP) and central Pacific (CP) El Niño events. Detailed analyses have indicated that this strength asymmetry is mainly derived from the weaker sensitivity of the zonal sea level pressure (SLP) anomaly to that of the diabatic heating anomaly during the development phase of CP El Niño events, which mainly results from the large cancelation induced by the negative sea surface temperature (SST)-cloud thermodynamic feedback that negates the positive dynamical feedback. This study validates these conclusions by using historical runs of 20 models involved in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our results suggest that the CMIP5 models generally depict the asymmetry in amplitude between the two types of El Niño events well, which is consistent with successfully simulating the strength asymmetry of the Bjerknes feedback. As observed during both types of El Niño events, variations in the total cloud amount and shortwave radiation also indicated that the cloud-radiative effect is an important factor that causes amplitude asymmetry between CP and EP El Niño events. However, the CMIP5 models are severely biased when capturing realistic CP El Niño structures, namely few models can simulate the significantly weaker warming anomalies in the EP relative to the CP. © 2015. American Geophysical Union. All Rights Reserved."
"7501720647;36934610300;55220976100;55211425200;","Is the tropical atmosphere in convective quasi-equilibrium?",2015,"10.1175/JCLI-D-14-00681.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944929428&doi=10.1175%2fJCLI-D-14-00681.1&partnerID=40&md5=39f4ca442d3ce8d3e230586c113e0eaa","The hypothesis of convective quasi-equilibrium (CQE) has dominated thinking about the interaction between deep moist convection and the environment for at least two decades. In this view, deep convection develops or decays almost instantly to remove any changes of convective instability, making the tropospheric temperature always tied to the boundary layer moist static energy. The present study examines the validity of the CQE hypothesis at different vertical levels using long-term sounding data from tropical convection centers. The results show that the tropical atmosphere is far from the CQE with much weaker warming in the middle and upper troposphere associated with the increase of boundary layer moist static energy. This is true for all the time scales resolved by the observational data, ranging from hourly to interannual and decadal variability. It is possibly caused by the ubiquitous existence of shallow convection and stratiform precipitation, both leading to sign reversal of heating from lower to upper troposphere. The simulations by 42 global climate models from phases 3 and 5 of the Coupled Model Intercomparsion Project (CMIP3 and CMIP5) are also analyzed and compared with the observations. © 2015 American Meteorological Society."
"14920137300;","A strategy for representing the effects of convective momentum transport in multiscale models: Evaluation using a new superparameterized version of the Weather Research and Forecast model (SP-WRF)",2015,"10.1002/2014MS000417","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027921791&doi=10.1002%2f2014MS000417&partnerID=40&md5=d235b4b8f88330cd617b47890364ba66","This paper describes a general method for the treatment of convective momentum transport (CMT) in large-scale dynamical solvers that use a cyclic, two-dimensional (2-D) cloud-resolving model (CRM) as a ""superparameterization"" of convective-system-scale processes. The approach is similar in concept to traditional parameterizations of CMT, but with the distinction that both the scalar transport and diagnostic pressure gradient force are calculated using information provided by the 2-D CRM. No assumptions are therefore made concerning the role of convection-induced pressure gradient forces in producing up or down-gradient CMT. The proposed method is evaluated using a new superparameterized version of the Weather Research and Forecast model (SP-WRF) that is described herein for the first time. Results show that the net effect of the formulation is to modestly reduce the overall strength of the large-scale circulation, via ""cumulus friction."" This statement holds true for idealized simulations of two types of mesoscale convective systems, a squall line, and a tropical cyclone, in addition to real-world global simulations of seasonal (1 June to 31 August) climate. In the case of the latter, inclusion of the formulation is found to improve the depiction of key synoptic modes of tropical wave variability, in addition to some aspects of the simulated time-mean climate. The choice of CRM orientation is also found to importantly affect the simulated time-mean climate, apparently due to changes in the explicit representation of wide-spread shallow convective regions. © 2015. The Authors."
"56027708800;56024884500;55718857500;8718425100;55190998900;8963601100;57203321797;","Atmospheric brown clouds reach the Tibetan Plateau by crossing the Himalayas",2015,"10.5194/acp-15-6007-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930677345&doi=10.5194%2facp-15-6007-2015&partnerID=40&md5=42d5ad0e7e1d36bf488a7c2d9db1187b","The Himalayas and the Tibetan Plateau region (HTP), despite being a remote and sparsely populated area, is regularly exposed to polluted air masses with significant amounts of aerosols including black carbon. These dark, light-absorbing particles are known to exert a great melting potential on mountain cryospheric reservoirs through albedo reduction and radiative forcing. This study combines ground-based and satellite remote sensing data to identify a severe aerosol pollution episode observed simultaneously in central Tibet and on the southern side of the Himalayas during 13-19 March 2009 (pre-monsoon). Trajectory calculations based on the high-resolution numerical weather prediction model COSMO are used to locate the source regions and study the mechanisms of pollution transport in the complex topography of the HTP. We detail how polluted air masses from an atmospheric brown cloud (ABC) over South Asia reach the Tibetan Plateau within a few days. Lifting and advection of polluted air masses over the great mountain range is enabled by a combination of synoptic-scale and local meteorological processes. During the days prior to the event, winds over the Indo-Gangetic Plain (IGP) are generally weak at lower levels, allowing for accumulation of pollutants and thus the formation of ABCs. The subsequent passing of synoptic-scale troughs leads to southwesterly flow in the middle troposphere over northern and central India, carrying the polluted air masses across the Himalayas. As the IGP is known to be a hotspot of ABCs, the cross-Himalayan transport of polluted air masses may have serious implications for the cryosphere in the HTP and impact climate on regional to global scales. Since the current study focuses on one particularly strong pollution episode, quantifying the frequency and magnitude of similar events in a climatological study is required to assess the total impact. © Author(s) 2015."
"55876539600;23008936200;35725269400;7003401367;56733172800;6701670154;8605632400;7005587298;7401439650;7004883672;6701518060;7102275990;56078142500;7004793287;12645158100;55779976700;","The Ocean Colour Climate Change Initiative: II. Spatial and temporal homogeneity of satellite data retrieval due to systematic effects in atmospheric correction processors",2015,"10.1016/j.rse.2015.01.033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937762472&doi=10.1016%2fj.rse.2015.01.033&partnerID=40&md5=14179105ed66c32530fc8b9b864694eb","The established procedure to access the quality of atmospheric correction processors and their underlying algorithms is the comparison of satellite data products with related in-situ measurements. Although this approach addresses the accuracy of derived geophysical properties in a straight forward fashion, it is also limited in its ability to catch systematic sensor and processor dependent behaviour of satellite products along the scan-line, which might impair the usefulness of the data in spatial analyses. The Ocean Colour Climate Change Initiative (OC-CCI) aims to create an ocean colour dataset on a global scale to meet the demands of the ecosystem modelling community. The need for products with increasing spatial and temporal resolution that also show as little systematic and random errors as possible, increases. Due to cloud cover, even temporal means can be influenced by along-scanline artefacts if the observations are not balanced and effects cannot be cancelled out mutually. These effects can arise from a multitude of results which are not easily separated, if at all. Among the sources of artefacts, there are some sensor-specific calibration issues which should lead to similar responses in all processors, as well as processor-specific features which correspond with the individual choices in the algorithms. A set of methods is proposed and applied to MERIS data over two regions of interest in the North Atlantic and the South Pacific Gyre. The normalised water leaving reflectance products of four atmospheric correction processors, which have also been evaluated in match-up analysis, is analysed in order to find and interpret systematic effects across track. These results are summed up with a semi-objective ranking and are used as a complement to the match-up analysis in the decision for the best Atmospheric Correction (AC) processor. Although the need for discussion remains concerning the absolutes by which to judge an AC processor, this example demonstrates clearly, that relying on the match-up analysis alone can lead to misjudgement. © 2015 Elsevier Inc."
"57191652481;7403347501;56202683600;23027396200;56350344100;13003619600;","Improving InSAR elevation models in Antarctica using laser altimetry, accounting for ice motion, orbital errors and atmospheric delays",2015,"10.1016/j.rse.2015.01.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924535938&doi=10.1016%2fj.rse.2015.01.017&partnerID=40&md5=2ebfd49a75cc9fb05ed27c12da7b58cc","Ice dynamics is closely related to climate change. However, a lack of digital elevation models (DEMs) of sufficient horizontal resolution and vertical precision has been a major issue in dynamic studies for years. Existing Antarctic DEMs are derived from satellite radar and laser altimetry as well as limited terrestrial data; these sparse datasets result in poor spatial resolution (hundreds of metres to 1. km). In this paper, we propose a method for generating high-accuracy and high-resolution DEMs using interferometric synthetic aperture radar (InSAR) and Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry by reducing the influence of ice motion, satellite orbital errors and topographically correlated atmospheric delays. A case study in the Grove Mountains area shows that the InSAR DEM has a root-mean-square (RMS) error of 5.9. m, which is better than the Radarsat Antarctic Mapping Project (RAMP) (21.1. m) and Bamber (8.5. m) DEMs. The new DEM is used to calculate ice velocity over the Grove Mountains area where GPS measurements have been collected for comparison. Compared to the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) InSAR-Based Antarctica Ice Velocity Map, ice velocity estimates from long-baseline interferogram and the new DEM have a smaller RMS error; this suggests that with the new DEM, baseline length is no longer a limiting factor for the accuracy of InSAR-based ice velocity mapping. © 2015 Elsevier Inc."
"56004404700;6701789833;18634493700;15122563500;7202588796;56277503400;56240070800;","Rain events decrease boreal peatland net CO2 uptake through reduced light availability",2015,"10.1111/gcb.12864","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928370053&doi=10.1111%2fgcb.12864&partnerID=40&md5=2f322c209c612de20f07063c3bf5cf59","Boreal peatlands store large amounts of carbon, reflecting their important role in the global carbon cycle. The short-term exchange and the long-term storage of atmospheric carbon dioxide (CO2) in these ecosystems are closely associated with the permanently wet surface conditions and are susceptible to drought. Especially, the single most important peat forming plant genus, Sphagnum, depends heavily on surface wetness for its primary production. Changes in rainfall patterns are expected to affect surface wetness, but how this transient rewetting affects net ecosystem exchange of CO2 (NEE) remains unknown. This study explores how the timing and characteristics of rain events during photosynthetic active periods, that is daytime, affect peatland NEE and whether rain event associated changes in environmental conditions modify this response (e.g. water table, radiation, vapour pressure deficit, temperature). We analysed an 11-year time series of half-hourly eddy covariance and meteorological measurements from Degerö Stormyr, a boreal peatland in northern Sweden. Our results show that daytime rain events systematically decreased the sink strength of peatlands for atmospheric CO2. The decrease was best explained by rain associated reduction in light, rather than by rain characteristics or drought length. An average daytime growing season rain event reduced net ecosystem CO2 uptake by 0.23-0.54 gC m-2. On an annual basis, this reduction of net CO2 uptake corresponds to 24% of the annual net CO2 uptake (NEE) of the study site, equivalent to a 4.4% reduction of gross primary production (GPP) during the growing season. We conclude that reduced light availability associated with rain events is more important in explaining the NEE response to rain events than rain characteristics and changes in water availability. This suggests that peatland CO2 uptake is highly sensitive to changes in cloud cover formation and to altered rainfall regimes, a process hitherto largely ignored. © 2015 John Wiley & Sons Ltd."
"55869517400;35237112700;12786314100;8581743700;6701727687;6701389765;35433083100;7004168515;8514315800;25637389200;56102017200;6602481221;7004129856;7202489497;7401837283;56015123400;","The ozone climate change initiative: Comparison of four Level-2 processors for the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)",2015,"10.1016/j.rse.2014.12.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939974180&doi=10.1016%2fj.rse.2014.12.013&partnerID=40&md5=a5e92395d5364b5ab70c9cc209e8b327","The MIPAS spectrometer onboard the Envisat platform observed infrared emission from the Earth's limb between 2002 and 2012. It recorded high-resolution spectra during day and night, from pole to pole and between 6 and 70. km altitude in the nominal measurement mode or up to 170. km in special measurement modes, producing daily more than 1000 vertical profiles of various trace gases. The operational Level-2 data are processed by ESA/DLR but there exist three other, independent research Level-2 processors that are hosted by ISAC-CNR/University of Bologna, Oxford University, and KIT IMK/IAA. All four Level-2 processors rely on the same Level-1b data provided by ESA but their retrieval schemes differ. As part of ESA's Ozone Climate Change Initiative project, an intercomparison of the four MIPAS processors took place, in which vertical ozone profiles retrieved by these four processors from MIPAS nominal mode measurements were compared for 2007 and 2008. We present the results of this comparison exercise, which consisted of five parts: an information content study of the vertical averaging kernels, an intercomparison of zonal seasonal means and spreads, a determination of biases through comparison to ozonesonde and lidar measurements, a comparison to other satellite records (bias estimation and precision assessment with respect to ACE-FTS and Aura-MLS data), and a geophysical validation of the provided error bars using MIPAS-MIPAS collocations. The four processors demonstrate similar performance. All processors use the same Level-1b data from ESA, apply global fits, and use microwindows instead of the full spectrum. The main differences in the processing schemes include the choice of microwindows, the regularization approach, the treatment of negative retrieved values, and the cloud detection threshold. The different regularization schemes lead to a different trade-off between noise and resolution, but without a clear average advantage for any particular data set. The vertical resolution is typically 3-5. km and the single profile precision is about 2-3%. In the middle and upper stratosphere, at 25-45. km, all four MIPAS processors clearly show a high bias of 2 to 5% relative to all reference instruments. The similarity of the structure and magnitude of the bias among the MIPAS data sets indicates that the bias is most likely linked to the use of microwindows of the MIPAS AB band. The satellite intercomparisons show furthermore that for the KIT dataset, the onset of the high bias starts at a somewhat higher altitude (only above 35. km) than for the other three datasets. This is likely due to the more restrictive use of the AB band by the KIT processor, which comes at the cost of a coarser vertical resolution near the ozone volume mixing ratio (vmr) peak. In the troposphere, the Level-2 algorithms that suppress negative ozone values in the iterative retrieval process produce a larger positive bias than the algorithm that does not follow such a strategy. Our main conclusion is that the four MIPAS processors are more similar to each other than to any other reference instrument. This indicates that the observed biases are very likely instrument-related. © 2014 Elsevier Inc."
"36572335000;7102517130;56265041500;8045690700;55742914900;6506730508;14059827200;7202079615;7003705113;6507308842;22978151200;10139397300;","A multi-model evaluation of aerosols over South Asia: Common problems and possible causes",2015,"10.5194/acp-15-5903-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930630842&doi=10.5194%2facp-15-5903-2015&partnerID=40&md5=64d9d2f542590b9573eee94faf6a0559","Atmospheric pollution over South Asia attracts special attention due to its effects on regional climate, water cycle and human health. These effects are potentially growing owing to rising trends of anthropogenic aerosol emissions. In this study, the spatio-temporal aerosol distributions over South Asia from seven global aerosol models are evaluated against aerosol retrievals from NASA satellite sensors and ground-based measurements for the period of 2000-2007. Overall, substantial underestimations of aerosol loading over South Asia are found systematically in most model simulations. Averaged over the entire South Asia, the annual mean aerosol optical depth (AOD) is underestimated by a range 15 to 44% across models compared to MISR (Multi-angle Imaging SpectroRadiometer), which is the lowest bound among various satellite AOD retrievals (from MISR, SeaWiFS (Sea-Viewing Wide Field-of-View Sensor), MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua and Terra). In particular during the post-monsoon and wintertime periods (i.e., October-January), when agricultural waste burning and anthropogenic emissions dominate, models fail to capture AOD and aerosol absorption optical depth (AAOD) over the Indo-Gangetic Plain (IGP) compared to ground-based Aerosol Robotic Network (AERONET) sunphotometer measurements. The underestimations of aerosol loading in models generally occur in the lower troposphere (below 2 km) based on the comparisons of aerosol extinction profiles calculated by the models with those from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data. Furthermore, surface concentrations of all aerosol components (sulfate, nitrate, organic aerosol (OA) and black carbon (BC)) from the models are found much lower than in situ measurements in winter. Several possible causes for these common problems of underestimating aerosols in models during the post-monsoon and wintertime periods are identified: the aerosol hygroscopic growth and formation of secondary inorganic aerosol are suppressed in the models because relative humidity (RH) is biased far too low in the boundary layer and thus foggy conditions are poorly represented in current models, the nitrate aerosol is either missing or inadequately accounted for, and emissions from agricultural waste burning and biofuel usage are too low in the emission inventories. These common problems and possible causes found in multiple models point out directions for future model improvements in this important region. © Author(s) 2015."
"24537168200;37089603000;15726163700;8576496400;7201787800;55783064400;55730541100;56919576300;7102689176;16243859200;55520327700;56613191200;6603172418;","Iodine observed in new particle formation events in the Arctic atmosphere during ACCACIA",2015,"10.5194/acp-15-5599-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930226916&doi=10.5194%2facp-15-5599-2015&partnerID=40&md5=6f6d41c3304ef81e6fb5071ac6dfd0ef","Accurately accounting for new particle formation (NPF) is crucial to our ability to predict aerosol number concentrations in many environments and thus cloud properties, which is in turn vital in simulating radiative transfer and climate. Here we present an analysis of NPF events observed in the Greenland Sea during the summertime as part of the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) project. While NPF events have been reported in the Arctic before, we were able, for the first time, to detect iodine in the growing particles using an Aerosol Mass Spectrometer (AMS) during a persistent event in the region of the coastal sea-ice near Greenland. Given the potency of iodine as a nucleation precursor, the results imply that iodine was responsible for the initial NPF, a phenomenon that has been reported at lower latitudes and associated with molecular iodine emissions from coastal macroalgae. The initial source of iodine in this instance is not clear, but it was associated with air originating approximately 1 day previously over melting coastal sea-ice. These results show that atmospheric models must consider iodine as a source of new particles in addition to established precursors such as sulfur compounds. © Author(s) 2015."
"56448637100;6603478665;42662973900;23051160600;35459245100;56663244400;7007182077;6602917432;7006712143;23995325300;26643041500;","Impacts of emission reductions on aerosol radiative effects",2015,"10.5194/acp-15-5501-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930203348&doi=10.5194%2facp-15-5501-2015&partnerID=40&md5=50d255a983b3b0368a6b6a198e20573a","The global aerosol-climate model ECHAM-HAMMOZ was used to investigate changes in the aerosol burden and aerosol radiative effects in the coming decades. Four different emissions scenarios were applied for 2030 (two of them applied also for 2020) and the results were compared against the reference year 2005. Two of the scenarios are based on current legislation reductions: one shows the maximum potential of reductions that can be achieved by technical measures, and the other is targeted to short-lived climate forcers (SLCFs). We have analyzed the results in terms of global means and additionally focused on eight subregions. Based on our results, aerosol burdens show an overall decreasing trend as they basically follow the changes in primary and precursor emissions. However, in some locations, such as India, the burdens could increase significantly. The declining emissions have an impact on the clear-sky direct aerosol effect (DRE), i.e. the cooling effect. The DRE could decrease globally 0.06-0.4 W m-2 by 2030 with some regional increases, for example, over India (up to 0.84 W m-2). The global changes in the DRE depend on the scenario and are smallest in the targeted SLCF simulation. The aerosol indirect radiative effect could decline 0.25-0.82 W m-2 by 2030. This decrease takes place mostly over the oceans, whereas the DRE changes are greatest over the continents. Our results show that targeted emission reduction measures can be a much better choice for the climate than overall high reductions globally. Our simulations also suggest that more than half of the near-future forcing change is due to the radiative effects associated with aerosol-cloud interactions. © Author(s) 2015."
"22633429500;6701806265;37112248300;54383910700;55339822300;","Profiles of second- to fourth-order moments of turbulent temperature fluctuations in the convective boundary layer: First measurements with rotational Raman lidar",2015,"10.5194/acp-15-5485-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930221844&doi=10.5194%2facp-15-5485-2015&partnerID=40&md5=3dab9818272f3e9bd969ead6eda09dd8","The rotational Raman lidar (RRL) of the University of Hohenheim (UHOH) measures atmospheric temperature profiles with high resolution (10 s, 109 m). The data contain low-noise errors even in daytime due to the use of strong UV laser light (355 nm, 10 W, 50 Hz) and a very efficient interference-filter-based polychromator. In this paper, the first profiling of the second- to fourth-order moments of turbulent temperature fluctuations is presented. Furthermore, skewness profiles and kurtosis profiles in the convective planetary boundary layer (CBL) including the interfacial layer (IL) are discussed. The results demonstrate that the UHOH RRL resolves the vertical structure of these moments. The data set which is used for this case study was collected in western Germany (50°53'50.56'' N, 6°27'50.39'' E; 110 m a.s.l.) on 24 April 2013 during the Intensive Observations Period (IOP) 6 of the HD(CP)2 (High-Definition Clouds and Precipitation for advancing Climate Prediction) Observational Prototype Experiment (HOPE). We used the data between 11:00 and 12:00 UTC corresponding to 1 h around local noon (the highest position of the Sun was at 11:33 UTC). First, we investigated profiles of the total noise error of the temperature measurements and compared them with estimates of the temperature measurement uncertainty due to shot noise derived with Poisson statistics. The comparison confirms that the major contribution to the total statistical uncertainty of the temperature measurements originates from shot noise. The total statistical uncertainty of a 20 min temperature measurement is lower than 0.1 K up to 1050 m a.g.l. (above ground level) at noontime; even for single 10 s temperature profiles, it is smaller than 1 K up to 1020 m a.g.l. Autocovariance and spectral analyses of the atmospheric temperature fluctuations confirm that a temporal resolution of 10 s was sufficient to resolve the turbulence down to the inertial subrange. This is also indicated by the integral scale of the temperature fluctuations which had a mean value of about 80 s in the CBL with a tendency to decrease to smaller values towards the CBL top. Analyses of profiles of the second-, third-, and fourth-order moments show that all moments had peak values in the IL around the mean top of the CBL which was located at 1230 m a.g.l. The maximum of the variance profile in the IL was 0.39 K2 with 0.07 and 0.11 K2 for the sampling error and noise error, respectively. The third-order moment (TOM) was not significantly different from zero in the CBL but showed a negative peak in the IL with a minimum of -0.93 K3 and values of 0.05 and 0.16 K3 for the sampling and noise errors, respectively. The fourth-order moment (FOM) and kurtosis values throughout the CBL were not significantly different to those of a Gaussian distribution. Both showed also maxima in the IL but these were not statistically significant taking the measurement uncertainties into account. We conclude that these measurements permit the validation of large eddy simulation results and the direct investigation of turbulence parameterizations with respect to temperature. © Author(s) 2015."
"36150977900;25227357000;7102018821;7202048112;7402359452;","A global model simulation for 3-D radiative transfer impact on surface hydrology over the Sierra Nevada and Rocky Mountains",2015,"10.5194/acp-15-5405-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929630775&doi=10.5194%2facp-15-5405-2015&partnerID=40&md5=5d20a5ef88fb60c2cfc59544e388b6a7","We investigate 3-D mountain effects on solar flux distributions and their impact on surface hydrology over the western United States, specifically the Rocky Mountains and the Sierra Nevada, using the global CCSM4 (Community Climate System Model version 4; Community Atmosphere Model/Community Land Model - CAM4/CLM4) with a 0.23° × 0.31° resolution for simulations over 6 years. In a 3-D radiative transfer parameterization, we have updated surface topography data from a resolution of 1 km to 90 m to improve parameterization accuracy. In addition, we have also modified the upward-flux deviation (3-D-PP (plane-parallel)) adjustment to ensure that the energy balance at the surface is conserved in global climate simulations based on 3-D radiation parameterization. We show that deviations in the net surface fluxes are not only affected by 3-D mountains but also influenced by feedbacks of cloud and snow in association with the long-term simulations. Deviations in sensible heat and surface temperature generally follow the patterns of net surface solar flux. The monthly snow water equivalent (SWE) deviations show an increase in lower elevations due to reduced snowmelt, leading to a reduction in cumulative runoff. Over higher-elevation areas, negative SWE deviations are found because of increased solar radiation available at the surface. Simulated precipitation increases for lower elevations, while it decreases for higher elevations, with a minimum in April. Liquid runoff significantly decreases at higher elevations after April due to reduced SWE and precipitation. © Author(s) 2015. CC Attribution 3.0 License."
"6603371044;7103211168;35497573900;6701431208;","Development of the GEOS-5 atmospheric general circulation model: Evolution from MERRA to MERRA2",2015,"10.5194/gmd-8-1339-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929167850&doi=10.5194%2fgmd-8-1339-2015&partnerID=40&md5=06ba74a63aa4215ec9263449142457c4","The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) version of the Goddard Earth Observing System-5 (GEOS-5) atmospheric general circulation model (AGCM) is currently in use in the NASA Global Modeling and Assimilation Office (GMAO) at a wide range of resolutions for a variety of applications. Details of the changes in parameterizations subsequent to the version in the original MERRA reanalysis are presented here. Results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. The GEOS-5 AGCM presented here is the model used as part of the GMAO MERRA2 reanalysis, global mesoscale simulations at 10 km resolution through 1.5 km resolution, the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean-atmosphere and coupled atmosphere-chemistry simulations. The seasonal mean climate of the MERRA2 version of the GEOS-5 AGCM represents a substantial improvement over the simulated climate of the MERRA version at all resolutions and for all applications. Fundamental improvements in simulated climate are associated with the increased re-evaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. Improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. The series of resolution-aware parameters related to the moist physics was shown to result in improvements at higher resolutions and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications. © Author(s) 2015."
"16305360700;8404544300;15519503600;55934425600;35487911100;54936465600;55547119523;55802017200;7005211669;8274985300;","Ice nucleation by combustion ash particles at conditions relevant to mixed-phase clouds",2015,"10.5194/acp-15-5195-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929207839&doi=10.5194%2facp-15-5195-2015&partnerID=40&md5=3a447019d926f57b8261a1d553ad85cf","Ice-nucleating particles can modify cloud properties with implications for climate and the hydrological cycle; hence, it is important to understand which aerosol particle types nucleate ice and how efficiently they do so. It has been shown that aerosol particles such as natural dusts, volcanic ash, bacteria and pollen can act as ice-nucleating particles, but the ice-nucleating ability of combustion ashes has not been studied. Combustion ashes are major by-products released during the combustion of solid fuels and a significant amount of these ashes are emitted into the atmosphere either during combustion or via aerosolization of bottom ashes. Here, we show that combustion ashes (coal fly ash, wood bottom ash, domestic bottom ash, and coal bottom ash) nucleate ice in the immersion mode at conditions relevant to mixed-phase clouds. Hence, combustion ashes could play an important role in primary ice formation in mixed-phase clouds, especially in clouds that are formed near the emission source of these aerosol particles. In order to quantitatively assess the impact of combustion ashes on mixed-phase clouds, we propose that the atmospheric abundance of combustion ashes should be quantified since up to now they have mostly been classified together with mineral dust particles. Also, in reporting ice residue compositions, a distinction should be made between natural mineral dusts and combustion ashes in order to quantify the contribution of combustion ashes to atmospheric ice nucleation. © Author(s) 2015. CC Attribution 3.0 License."
"55365651300;57203078745;6506022279;","Future climate and surface mass balance of Svalbard glaciers in an RCP8.5 climate scenario: A study with the regional climate model MAR forced by MIROC5",2015,"10.5194/tc-9-945-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929087553&doi=10.5194%2ftc-9-945-2015&partnerID=40&md5=bb659870ca2511b319b99e17a5da7415","We have performed a future projection of the climate and surface mass balance (SMB) of Svalbard with the MAR (Modèle Atmosphérique Régional) regional climate model forced by MIROC5 (Model for Interdisciplinary Research on Climate), following the RCP8.5 scenario at a spatial resolution of 10 km. MAR predicts a similar evolution of increasing surface melt everywhere in Svalbard followed by a sudden acceleration of melt around 2050, with a larger melt increase in the south compared to the north of the archipelago. This melt acceleration around 2050 is mainly driven by the albedo-melt feedback associated with the expansion of the ablation/bare ice zone. This effect is dampened in part as the solar radiation itself is projected to decrease due to a cloudiness increase. The near-surface temperature is projected to increase more in winter than in summer as the temperature is already close to 0 °C in summer. The model also projects a stronger winter west-to-east temperature gradient, related to the large decrease of sea ice cover around Svalbard. By 2085, SMB is projected to become negative over all of Svalbard's glaciated regions, leading to the rapid degradation of the firn layer. © Author(s) 2015."
"57196510591;","Climate model biases in the eastern tropical oceans: Causes, impacts and ways forward",2015,"10.1002/wcc.338","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926525576&doi=10.1002%2fwcc.338&partnerID=40&md5=c09bdccceab8e02be2b8d9d962f0351b","The eastern boundaries of the tropical and subtropical oceans are regions of high biological productivity that support some of the world's largest fisheries. They also feature extensive stratocumulus cloud decks that play a pivotal role in the response of the climate system to greenhouse gas forcing. Global climate models experience great difficulties simulating eastern boundary regions, with one of the most notable shortcomings being warm sea-surface temperature biases that often exceed 5 K. These model biases are due to several reasons. (1) Weaker than observed alongshore winds lead to an underrepresentation of upwelling and alongshore currents and the cooling associated with them. (2) Stratocumulus decks and their effects on shortwave radiation are underpredicted in the models. (3) The offshore transport of cool waters by mesoscale eddies is not adequately represented by global models due to insufficient resolution. (4) The sharp vertical temperature gradient separating the warm upper ocean layer from the deep ocean is too diffuse in the models. More work will be required to assess the relative importance of these error sources and to find ways of mitigating them. Coordinated multi-model experiments are vital to achieve this goal, as are enhanced ocean and atmosphere observations of the eastern boundary regions. To what extent eastern ocean biases compromise the models' ability to produce accurate seasonal predictions, and climate change projections should be another focus of research efforts. © 2015 John Wiley & Sons, Ltd."
"55656926800;7404090918;7404240633;55656250400;","Trends of MSU brightness temperature in the middle troposphere simulated by CMIP5 models and their sensitivity to cloud liquid water",2015,"10.1175/JTECH-D-13-00250.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84980315249&doi=10.1175%2fJTECH-D-13-00250.1&partnerID=40&md5=3982b6ba5c3aa1defcdde8e4310307fa","Only a climate model that is able to simulate well the historical atmospheric temperature trend can be used for estimating the future atmospheric temperature trends on different emission scenarios. Satellite-based Microwave Sounding Unit (MSU) brightness temperature in the middle troposphere (T2) is an important analog of midtropospheric atmospheric temperature. So, there is the need to compare the atmospheric temperature trend simulated by the fifth phase of the Coupled Model Intercomparison Project (CMIP5) historical realizations and the observed MSU T2. There are two approaches for estimating modeled MSU T2: apply a global-mean static weighting function to generate the weighted average of the modeled temperature at all atmospheric layers and simulate satellite-view MSU T2 using the model's output as input into a radiative transfer model (RTM). In this paper, the two approaches for estimating modeled MSU T2 are evaluated. For each CMIP5, it is shown that there exists a model-simulated static weighting function, such that the MSU T2 trend using the weighting function is equivalent to that calculated by RTM. The effect of modeled cloud liquid water on MSU T2 trends in CMIP5 simulations is investigated by comparing the modeled cloud liquid water vertical profile and the weighting function. Moreover, it is found that warming trends of MSU T2 for CMIP5 simulations calculated by the RTM are about 15% less than those using the two traditional static weighting functions. By comparing the model-derived weighting function with the two traditional weighting functions, the reason for the systematical biases is revealed. © 2015 American Meteorological Society."
"57192188404;6701511321;23995566800;6507575165;57203078473;","Effects of injected ice particles in the lower stratosphere on the Antarctic ozone hole",2015,"10.1002/2014EF000266","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85000766227&doi=10.1002%2f2014EF000266&partnerID=40&md5=18155665dc6552db359472dec09c6066","The Antarctic ozone hole will continue to be observed in the next 35-50 years, although the emissions of chlorofluorocarbons (CFCs) have gradually been phased out during the last two decades. In this paper, we suggest a geo-engineering approach that will remove substantial amounts of hydrogen chloride (HCl) from the lower stratosphere in fall, and hence limit the formation of the Antarctic ozone hole in late winter and early spring. HCl will be removed by ice from the atmosphere at temperatures higher than the threshold under which polar stratospheric clouds (PSCs) are formed if sufficiently large amounts of ice are supplied to produce water saturation. A detailed chemical-climate numerical model is used to assess the expected efficiency of the proposed geo-engineering method, and specifically to calculate the removal of HCl by ice particles. The size of ice particles appears to be a key parameter: larger particles (with a radius between 10 and 100 μm) appear to be most efficient for removing HCl. Sensitivity studies lead to the conclusions that the ozone recovery is effective when ice particles are supplied during May and June in the latitude band ranging from 70°S to 90°S and in the altitude layer ranging from 10 to 26 km. It appears, therefore, that supplying ice particles to the Antarctic lower stratosphere could be effective in reducing the depth of the ozone hole. In addition, photodegradation of CFCs might be accelerated when ice is supplied due to enhanced vertical transport of this efficient greenhouse gas. © 2015 The Authors. Earth's Future published by Wiley on behalf of the American Geophysical Union."
"55624487819;56478409200;44861328200;57211219633;15119954300;","Spatiotemporal variations of pan evaporation in China during 1960-2005: Changing patterns and causes",2015,"10.1002/joc.4025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928548249&doi=10.1002%2fjoc.4025&partnerID=40&md5=4252663a1df188b959f3d7dd34e966d2","Observed pan evaporation data from 588 stations covering the entire territory of China are analysed using the modified Mann-Kendall trend test method. Fuzzy C-Means clustering is conducted for regionalization. Sensitivity analysis is performed to identify the principal influencing factors. Results indicate that: (1) the entire country can be categorized into three parts, i.e. A: southern, central and southwestern China; B: northwestern China and C: strip zone extending from northeastern to southwestern China; (2) significant decreasing pan evaporation can be identified in southern, central, southwestern, eastern and northwestern China. Stations with significant increasing pan evaporation seem to be scattered sporadically across China. Besides, the strip zone extending in the NE-SW direction is dominated by significant and also nonsignificant increasing trends of pan evaporation and (3) sensitivity analysis indicates that relative humidity is the principal influencing factor for pan evaporation, especially in northwestern, northern and northeastern China. Generally, in northwestern, northern and northeastern China, relative humidity has an adverse relation with pan evaporation, implying pan evaporation paradox and also intensifying hydrological cycle in these regions. In southeastern China, particularly the middle and lower Yangtze River basin and the Pearl River basin, relations between pan evaporation and relative humidity are relatively complex, showing that other factors in addition to relative humidity can have impacts on pan evaporation changes, such as cloud coverage, temperature and aerosol concentration. Local features of aerodynamic and radiative drivers of the hydrological cycle and their regional responses to climate changes, and also different features of ground surface may play considerable roles in pan evaporation changes. © 2014 Royal Meteorological Society."
"55555084100;56543788800;7003459101;25624725200;56422246700;7006415284;8550791300;35798085000;7201352328;7403200489;18536452000;7004061510;7003852865;","Characterization of airborne ice-nucleation-active bacteria and bacterial fragments",2015,"10.1016/j.atmosenv.2015.02.060","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924405751&doi=10.1016%2fj.atmosenv.2015.02.060&partnerID=40&md5=ddf099f15b9fc5697a1e2a98094133b0","Some bacteria have the unique capacity of synthesising ice-nucleation-active (INA) proteins and exposing them at their outer membrane surface. As INA bacteria enter the atmosphere, they may impact the formation of clouds and precipitation. We studied members of airborne bacterial communities for their capacity to catalyse ice formation and we report on the excretion of INA proteins by airborne Pseudomonas sp. We also observed for the first time that INA biological fragments <220nm were present in precipitation samples (199 and 482 INA fragments per L of precipitation), which confirms the presence of submicron INA biological fragments in the atmosphere. During 14 precipitation events, strains affiliated with the genus Pseudomonas, which are known to carry ina genes, were dominant. A screening for INA properties revealed that ~12% of the cultivable bacteria caused ice formation at ≤-7°C. They had likely been emitted to the atmosphere from terrestrial surfaces, e.g. by convective transport. We tested the ability of isolated INA strains to produce outer membrane vesicles and found that two isolates could do so. However, only very few INA vesicles were released per INA cell. Thus, the source of the submicron INA proteinaceous particles that we detected in the atmosphere remains to be elucidated. © 2015 Elsevier Ltd."
"53878006900;6506373162;7005955015;","Tropical rainforest response to marine sky brightening climate engineering",2015,"10.1002/2015GL063363","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929512953&doi=10.1002%2f2015GL063363&partnerID=40&md5=ad2c7a0f182f1b84fa1f4d034e18e337","Tropical forests represent a major atmospheric carbon dioxide sink. Here the gross primary productivity (GPP) response of tropical rainforests to climate engineering via marine sky brightening under a future scenario is investigated in three Earth system models. The model response is diverse, and in two of the three models, the tropical GPP shows a decrease from the marine sky brightening climate engineering. Partial correlation analysis indicates precipitation to be important in one of those models, while precipitation and temperature are limiting factors in the other. One model experiences a reversal of its Amazon dieback under marine sky brightening. There, the strongest partial correlation of GPP is to temperature and incoming solar radiation at the surface. Carbon fertilization provides a higher future tropical rainforest GPP overall, both with and without climate engineering. Salt damage to plants and soils could be an important aspect of marine sky brightening. ©2015. American Geophysical Union. All Rights Reserved."
"35570389600;8724963200;54416512600;56428830000;6506539438;","IGCM4: A fast, parallel and flexible intermediate climate model",2015,"10.5194/gmd-8-1157-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928753040&doi=10.5194%2fgmd-8-1157-2015&partnerID=40&md5=2527afab8e23162e8ea3b3da0b6c7c28","The IGCM4 (Intermediate Global Circulation Model version 4) is a global spectral primitive equation climate model whose predecessors have extensively been used in areas such as climate research, process modelling and atmospheric dynamics. The IGCM4's niche and utility lies in its speed and flexibility allied with the complexity of a primitive equation climate model. Moist processes such as clouds, evaporation, atmospheric radiation and soil moisture are simulated in the model, though in a simplified manner compared to state-of-the-art global circulation models (GCMs). IGCM4 is a parallelised model, enabling both very long integrations to be conducted and the effects of higher resolutions to be explored. It has also undergone changes such as alterations to the cloud and surface processes and the addition of gravity wave drag. These changes have resulted in a significant improvement to the IGCM's representation of the mean climate as well as its representation of stratospheric processes such as sudden stratospheric warmings. The IGCM4's physical changes and climatology are described in this paper. © 2015 Author(s). CC Attribution 3.0 License."
"56464971600;7004479957;15026371500;","Time scales of response to antisymmetric surface fluxes in an aquaplanet GCM",2015,"10.1002/2015GL063372","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928694587&doi=10.1002%2f2015GL063372&partnerID=40&md5=6af2104123b3d86499335c76e565f145","The intertropical convergence zone (ITCZ) shifts in response to hemispheric asymmetries in extratropical energy forcings. This study investigates the response time scale of this shift in an aquaplanet global climate model coupled to a slab ocean. A steady antisymmetric perturbation is abruptly added to the slab-ocean heat flux convergence in midlatitudes. The time scale of the ITCZ shift scales linearly with the heat capacity of the combined ocean-atmosphere system, and the shift is amplified by subtropical clear-sky radiation and cloud radiative feedbacks. Key Points ITCZ shift time scale increases linearly with model heat capacity Radiative feedbacks amplify ITCZ response to midlatitude heat flux forcing Equilibration time is 8 years for realistic slab-ocean mixed layer depth ©2015. American Geophysical Union. All Rights Reserved."
"7103246957;7102933062;7004461962;36895628100;","Observational study of land-surface-cloud-atmosphere coupling on daily timescales",2015,"10.3389/feart.2015.00013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006233287&doi=10.3389%2ffeart.2015.00013&partnerID=40&md5=154a652e06c844e42696c511a4e72d69","Our aim is to provide an observational reference for the evaluation of the surface and boundary layer parameterizations used in large-scale models using the remarkable long-term Canadian Prairie hourly dataset. First we use shortwave and longwave data from the Baseline Surface Radiation Network (BSRN) station at Bratt’s Lake, Saskatchewan, and clear sky radiative fluxes from ERA-Interim, to show the coupling between the diurnal cycle of temperature and relative humidity and effective cloud albedo and net longwave flux. Then we calibrate the nearby opaque cloud observations at Regina, Saskatchewan in terms of the BSRN radiation fluxes. We find that in the warm season, we can determine effective cloud albedo to ±0.08 from daytime opaque cloud, and net long-wave radiation to ±8W/m2 from daily mean opaque cloud and relative humidity. This enables us to extend our analysis to the 55 years of hourly observations of opaque cloud cover, temperature, relative humidity, and daily precipitation from 11 climate stations across the Canadian Prairies. We show the land-surface-atmosphere coupling on daily timescales in summer by stratifying the Prairie data by opaque cloud, relative humidity, surface wind, day-night cloud asymmetry and monthly weighted precipitation anomalies. The multiple linear regression fits relating key diurnal climate variables, the diurnal temperature range, afternoon relative humidity and lifting condensation level, to daily mean net longwave flux, windspeed and precipitation anomalies have R2 -values between 0.61 and 0.69. These fits will be a useful guide for evaluating the fully coupled system in models. © 2015 Betts, Desjardins, Beljaars and Tawfik."
"7801353107;","Revisiting Twomey's approximation for peak supersaturation",2015,"10.5194/acp-15-3803-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927617546&doi=10.5194%2facp-15-3803-2015&partnerID=40&md5=4fc3ed85a0d6fec3b6a9b0b9d5ae1b0b","Twomey's seminal 1959 paper provided lower and upper bound approximations to the estimation of peak supersaturation within an updraft and thus provides the first closed expression for the number of nucleated cloud droplets. The form of this approximation is simple, but provides a surprisingly good estimate and has subsequently been employed in more sophisticated treatments of nucleation parametrization. In the current paper, we revisit the lower bound approximation of Twomey and make a small adjustment that can be used to obtain a more accurate calculation of peak supersaturation under all potential aerosol loadings and thermodynamic conditions. In order to make full use of this improved approximation, the underlying integro-differential equation for supersaturation evolution and the condition for calculating peak supersaturation are examined. A simple rearrangement of the algebra allows for an expression to be written down that can then be solved with a single lookup table with only one independent variable for an underlying lognormal aerosol population. While multimodal aerosol with N different dispersion characteristics requires 2NC1 inputs to calculate the activation fraction, only N of these one-dimensional lookup tables are needed. No additional information is required in the lookup table to deal with additional chemical, physical or thermodynamic properties. The resulting implementation provides a relatively simple, yet computationally cheap, physically based parametrization of droplet nucleation for use in climate and Numerical Weather Prediction models. © Author(s) 2015."
"55783064400;24537168200;55730541100;7201787800;7403384594;57207320612;7004185679;50961266400;36469891700;7006837187;","Assessment of the sensitivity of core / shell parameters derived using the single-particle soot photometer to density and refractive index",2015,"10.5194/amt-8-1701-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927627471&doi=10.5194%2famt-8-1701-2015&partnerID=40&md5=49b0c0c934bd435316eff19c0743b9b5","Black carbon (BC) is the dominant absorbing aerosol in the atmosphere, and plays an important role in climate and human health. The optical properties and cloud condensation nuclei (CCN) activity of soot depend on the amounts (both relative and absolute) of BC and non-refractory material in the particles. Mixing between these two components is often represented in models by a core / shell coated sphere. The single-particle soot photometer (SP2) is one of, if not the only, instrument capable of reporting distributions of both core size and coating thickness. Most studies combine the SP2's incandescence and 1064 nm scattering data to report coating properties, but to date there is no consistency in the assumed values of density and refractive index of the core that are used in these calculations, which can greatly affect the reported parameters such as coating thickness. Given that such data are providing an important constraint for model comparisons and comparison between large data sets, it is important that this lack of consistency is addressed. In this study we explore the sensitivity of the reported coatings to these parameters. An assessment of the coating properties of freshly emitted, thermodenuded ambient particles demonstrated that a core density of 1.8 g cm-3 and refractive index of (2.26-1.26i) were the most appropriate to use with ambient soot in the Los Angeles area. Using these parameters generated a distribution with median shell / core ratio of 1.02 ± 0.11, corresponding to a median absolute coating thickness of 2 ± 8 nm. The main source of statistical error in the single-particle data was random variation in the incandescence signals. Other than the sensitivity to core refractive index, the incandescence calibration was the main source of uncertainty when optically determining the average coatings. The refractive index of coatings was found to have only a minor influence. This work demonstrates that using this technique the SP2 can accurately determine the average mixing state (externally or internally mixed) of ambient soot within the precision of the instrument calibration. Ambient coatings were measured up to a median shell / core ratio of 1.50 ± 0.11, meaning that this technique is able to resolve absolute changes in mixing state. However, when different core parameters were used, the core / shell ratio and the coating thickness were shown to be offset by amounts that could be larger than the atmospheric variability in these parameters, though the results have a similar precision. For comparison, using the core parameters that resulted in the thickest coatings, on the same thermodenuded fresh particles as before, generated a median shell / core ratio of 1.39 ± 0.11, corresponding to a median absolute coating thickness of 30 ± 8 nm. These results must be taken into account when comparing BC coatings measured using this technique, or if using these data for optical or CCN calculations. We have determined the most appropriate values of BC density and refractive index to use to measure mixing state at 1064 nm where particle morphology has only a minor effect, but appropriate values to use for optical calculations of nonspherical particles at visible wavelengths will also be subject to similar, significant uncertainties. Without similar constraints as those provided here, constraining the behaviour of BC particles in models using field data will be subject to large systematic measurement uncertainties. © Author(s) 2015."
"57189089842;7006235542;7006377579;21933618400;36465124400;7103197731;57195257572;57205787051;55629357900;6701802669;","Observations and comparisons of cloud microphysical properties in spring and summertime Arctic stratocumulus clouds during the ACCACIA campaign",2015,"10.5194/acp-15-3719-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926442230&doi=10.5194%2facp-15-3719-2015&partnerID=40&md5=60d955e9b0676b3a7b847bb5f1ef0b6f","Measurements from four case studies in spring and summer-time Arctic stratocumulus clouds during the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) campaign are presented. We compare microphysics observations between cases and with previous measurements made in the Arctic and Antarctic. During ACCACIA, stratocumulus clouds were observed to consist of liquid at cloud tops, often at distinct temperature inversions. The cloud top regions precipitated low concentrations of ice into the cloud below. During the spring cases median ice number concentrations (∼ 0.5 L-1) were found to be lower by about a factor of 5 than observations from the summer campaign (∼ 3 L-1). Cloud layers in the summer spanned a warmer temperature regime than in the spring and enhancement of ice concentrations in these cases was found to be due to secondary ice production through the Hallett-Mossop (H-M) process. Aerosol concentrations during spring ranged from ∼ 300-400 cm-3 in one case to lower values of ∼ 50-100 cm-3 in the other. The concentration of aerosol with sizes Dp > 0.5 μm was used in a primary ice nucleus (IN) prediction scheme (DeMott et al., 2010). Predicted IN values varied depending on aerosol measurement periods but were generally greater than maximum observed median values of ice crystal concentrations in the spring cases, and less than the observed ice concentrations in the summer due to the influence of secondary ice production. Comparison with recent cloud observations in the Antarctic summer (Grosvenor et al., 2012), reveals lower ice concentrations in Antarctic clouds in comparable seasons. An enhancement of ice crystal number concentrations (when compared with predicted IN numbers) was also found in Antarctic stratocumulus clouds spanning the H-M temperature zone; however, concentrations were about an order of magnitude lower than those observed in the Arctic summer cases but were similar to the peak values observed in the colder Arctic spring cases, where the H-M mechanism did not operate. © 2015 Author(s)."
"42263280300;55796506900;56068376200;","Simultaneous reductions in emissions of black carbon and co-emitted species will weaken the aerosol net cooling effect",2015,"10.5194/acp-15-3671-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926434273&doi=10.5194%2facp-15-3671-2015&partnerID=40&md5=b6a1bab1000845f4cef536d580f9d6c9","Black carbon (BC), a distinct type of carbonaceous material formed from the incomplete combustion of fossil and biomass based fuels under certain conditions, can interact with solar radiation and clouds through its strong light-absorption ability, thereby warming the Earth's climate system. Some studies have even suggested that global warming could be slowed down in the short term by eliminating BC emission due to its short lifetime. In this study, we estimate the influence of removing some sources of BC and other co-emitted species on the aerosol radiative effect by using an aerosol-climate atmosphere-only model BCC-AGCM2.0.1-CUACE/Aero with prescribed sea surface temperature and sea ice cover, in combination with the aerosol emissions from the Representative Concentration Pathways (RCPs) scenarios. We find that the global annual mean aerosol net cooling effect at the top of the atmosphere (TOA) will be enhanced by 0.12 W m-2 compared with recent past year 2000 levels if the emissions of only BC are reduced to the level projected for 2100 based on the RCP2.6 scenario. This will be beneficial∼for the mitigation of global warming. However, both aerosol negative direct and indirect radiative effects are weakened when BC and its co-emitted species (sulfur dioxide and organic carbon) are simultaneously reduced. Relative to year 2000 levels, the global annual mean aerosol net cooling effect at the TOA will be weakened by 1.7-2.0 W m-2 if the emissions of all these aerosols are decreased to the levels projected for 2100 in different ways based on the RCP2.6, RCP4.5, and RCP8.5 scenarios. Because there are no effective ways to remove the BC exclusively without influencing the other co-emitted components, our results therefore indicate that a reduction in BC emission can lead to an unexpected warming on the Earth's climate system in the future. © Author(s) 2015."
"25631411400;7005304841;7102495313;7003875148;","Large-eddy simulations of an Arctic mixed-phase stratiform cloud observed during ISDAC: Sensitivity to moisture aloft, surface fluxes and large-scale forcing",2015,"10.1002/qj.2425","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932154879&doi=10.1002%2fqj.2425&partnerID=40&md5=ae09f6f362183942796ffe38aefacd35","Large-eddy simulation (LES) is used to examine the complex interactions between cloud properties and boundary-layer structure in Arctic low-level mixed-phase clouds using idealised conditions based on the Indirect and Semi-Direct Aerosol Campaign (ISDAC, April 2008). The persistence of steady mixed-phase conditions depends mostly on a balance between ice vertical redistribution and ice growth by vapour deposition in such a way that ice crystals cannot accumulate within the cloud layer to consume the available liquid water. An external source of water vapour is necessary to balance the net sink of total water in the cloud layer. Two main local sources of moisture are present: the initial moist surface layer and the free troposphere. In the studied case, the surface layer is found to be the dominant source of vapour to the cloud, the temperature inversion preventing significant entrainment from above. In most of the cases, the simulated boundary layer becomes rapidly well-mixed despite the stabilising effect of ice sublimation and latent cooling close to the surface. The minor effect of near-surface latent cooling on stability is connected to the initially moist surface layer limiting ice sublimation. Water vapour supply in the sub-cloud layer, resulting from entrainment of moisture from aloft, reduces ice sublimation above the surface layer and contributes to the maintenance of some degree of boundary-layer decoupling. In contrast, moisture surface fluxes reduce sublimation in the surface layer and accelerate cloud-surface coupling. Overall, the persistence of cloud-surface decoupling remains mostly driven by large-scale heat and moisture advection. © 2014 Royal Meteorological Society."
"56490969800;56681764600;8701353900;6603868770;","How microphysical choices affect simulated infrared brightness temperatures",2015,"10.1016/j.atmosres.2014.12.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921475668&doi=10.1016%2fj.atmosres.2014.12.010&partnerID=40&md5=d652d00cbc6d341c49496e0727257267","Numerical weather prediction (NWP) today relies more and more on satellite data, both for assimilation and for evaluation. However, process-based analyses of the biases between observed and simulated satellite data, which go beyond a mere identification of the biases, are rare. The present study investigates a long-known bias (Böhme et al., 2011) between brightness temperatures (BTs) simulated from the regional NWP model COSMO-DE forecasts via RTTOV (Radiative Transfer for TOVS) and those observed by Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI). The pivotal question is whether a novel two-moment cloud ice scheme, developed by Köhler (2013) primarily to improve the representation of ice nucleation processes, exhibits an improved performance with respect to this bias and, if that is so, to provide a process-based analysis which identifies the reasons for the improved behaviour.It is shown that the new two-moment cloud ice scheme reduces the BT bias distinctly and can therefore be considered an improvement in comparison to two standard schemes, the two-category ice scheme and the three-category ice scheme. The improvement in simulated BTs is due to a vertical redistribution of cloud ice to lower model levels. Sensitivity studies identify two of the introduced changes in the two-moment cloud ice scheme to be hand-in-hand responsible for most of the improved performance: the choice of heterogeneous ice nucleation scheme and the consideration of cloud ice sedimentation. Including only cloud ice sedimentation without changing the heterogeneous ice nucleation scheme has no distinct effect on cloud ice. Further sensitivity studies with varying aerosol number densities reveal a comparably small sensitivity, indicating that the use of a physically reasonable heterogeneous ice nucleation scheme is far more important than the exact knowledge of the actual aerosol number densities. © 2015 Elsevier B.V.."
"55859441800;41362078500;53872142100;55859907800;","Observation and modeling analyses of the macro- and microphysical characteristics of a heavy rain storm in Beijing",2015,"10.1016/j.atmosres.2015.01.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921744885&doi=10.1016%2fj.atmosres.2015.01.007&partnerID=40&md5=faa1470d6ea19316cc9a31ad41aa9805","Beijing and its surrounding areas experienced a heavy rain event from 21 to 22 July 2012. The event can be divided into two phases: a warm-sector precipitation phase, ahead of the cold front, and a cold front precipitation phase. Observational analyses indicated that this rain event resulted from the cooperation of upper- and lower-level weather systems, and also the development and merging of mesoscale convective storm clusters in cumulus-embedded stratus. Simulation results showed that water vapor and hydrometeors transported into Beijing came mainly from the west and south and then exited from the north and east in general. All hydrometeors except ice crystals showed net inflow during the warm-sector phase, while all hydrometeors showed net outflow during the cold front phase overall. The interactions between cold and warm cloud microphysical processes generated the severe precipitation, with melting of graupel into rainwater contributing the most. Cold cloud processes contributed more to rain in the cold front phase compared to that in the warm-sector phase. The general precipitation and hydrometeor precipitation efficiencies were 67.0% and 86.3% in the warm-sector phase, while those in the cold front phase were 44.0% and 74.6%, respectively. © 2015 Elsevier B.V."
"53664696600;57208936945;9039487900;","Tree-ring δ18O in African mahogany (Entandrophragma utile) records regional precipitation and can be used for climate reconstructions",2015,"10.1016/j.gloplacha.2015.01.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922349725&doi=10.1016%2fj.gloplacha.2015.01.014&partnerID=40&md5=226c881fbd8a509203bf23c93aee1b85","The availability of instrumental climate data in West and Central Africa is very restricted, both in space and time. This limits the understanding of the regional climate system and the monitoring of climate change and causes a need for proxies that allow the reconstruction of paleoclimatic variability. Here we show that oxygen isotope values (δ18O) in tree rings of Entandrophragma utile from North-western Cameroon correlate to precipitation on a regional to sub-continental scale (1930-2009). All found correlations were negative, following the proposed recording of the 'amount effect' by trees in the tropics. The capacity of E. utile to record the variability of regional precipitation is also confirmed by the significant correlation of tree-ring δ18O with river discharge data (1944-1983), outgoing longwave radiation (a proxy for cloud cover; 1974-2011) and sea surface salinity in the Gulf of Guinea (1950-2011). Furthermore, the high values in the δ18O chronology from 1970 onwards coincide with the Sahel drought period. Given that E. utile presents clear annual growth rings, has a wide-spread distribution in tropical Africa and is long lived (&gt;250years), we argue that the analysis of oxygen isotopes in growth rings of this species is a promising tool for the study of paleoclimatic variability during the last centuries in West and Central Africa. © 2014 Elsevier B.V."
"56895370000;35849722200;42962694100;55355215900;","Numerical study of natural sea salt aerosol and its radiative effects on climate and sea surface temperature over East Asia",2015,"10.1016/j.atmosenv.2015.01.074","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922639337&doi=10.1016%2fj.atmosenv.2015.01.074&partnerID=40&md5=d39c62aa3ce17b47b0f6195c0b3be6c7","A regional climate model, RIEMS-POM, was used to study the direct radiative forcing (DRF) of sea salt on precipitation, sea surface temperature (SST) and summer circulation over East Asia with aerosol dataset from GOCART. The simulations predicted negative DRFs of-0.87Wm-2at the surface and-1.40Wm-2at the top of the atmosphere by sea salt. Results from the simulations suggest the forcing of sea salt produces a slight positive temperature anomaly and a reduction in precipitation over Southern China, accompanied by an opposite trend north of 40°N in Northern and Northeastern China. The tendency of wetting in North and drying in South by sea salt was mainly determined by the wind field, the vertical motion, as well as the local evaporation anomalies. The impacts of sea salt on SST suggest that the net surface shortwave radiative flux and the changes in convective cloud are important in forming the decreased SST throughout the year, while the northward oceanic heat transport anomaly and the other heat flux anomalies contribute relatively smaller. The feature by sea salt on SST imposes an extra force from the atmosphere to the ocean. The sea salt could also diminish the land-sea temperature contrast (LSTC) in summer and therefore the climatological summer circulation over East Asia, leading to reduced precipitation in Southern China. All these climatic feedbacks, such as LSTC and precipitation anomaly, will be attenuated when the SST is fixed. © 2015 Elsevier Ltd."
"6603809220;7101625995;8870038800;","Effects of declining aerosols on projections of zonally averaged tropical precipitation",2015,"10.1088/1748-9326/10/4/044018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928804623&doi=10.1088%2f1748-9326%2f10%2f4%2f044018&partnerID=40&md5=16b2db2dc3556c127bfc5fc49e9f2bf5","All of the representative concentration pathways (RCPs) assume that future emissions of aerosols and aerosol precursors will decline sharply. There is considerable evidence that historically increasing aerosols have substantially affected tropical precipitation, but the effects of projected aerosol declines have received little attention. We compare projections forced by the medium-low RCP4.5 pathway in two subsets of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5): one group (HiForc) includes treatments of indirect aerosol effects on cloud albedo and cloud lifetime as well as direct aerosol effects, while the other group (LoForc) only treats direct aerosol effects. In this scenario we find that models in the HiForc group consistently project larger increases in both the mean and inter-hemispheric (north minus south) asymmetry of tropical sea-surface temperature (SST) and precipitation than do models in the LoForc group. Earlier projections from CMIP3, in which future aerosol declines were assumed to be smaller, behave more like the CMIP5 LoForc group. These results show that projected tropical SST and precipitation changes are sensitive to assumptions about aerosol emissions and indirect aerosol effects. If the real world resembles the HiForc group, then future aerosol changes are likely to be an important (even dominant) driver of tropical precipitation changes under low to moderate forcing scenarios. © 2015 IOP Publishing Ltd."
"57210687618;7006184606;7103372949;","Island precipitation enhancement and the diurnal cycle in radiative-convective equilibrium",2015,"10.1002/qj.2443","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927623600&doi=10.1002%2fqj.2443&partnerID=40&md5=a2de1047a0ee08255e27d9cb7678101e","To understand why tropical islands are rainier than nearby ocean areas, we explore how a highly idealized island, which differs from the surrounding ocean only in heat capacity, might respond to the diurnal cycle and influence the tropical climate, especially the spatial distribution of rainfall and the thermal structure of the troposphere. We perform simulations of three-dimensional radiative-convective equilibrium with the System for Atmospheric Modeling (SAM) cloud-system-resolving model, with interactive surface temperature, where a highly idealized, low heat capacity circular island is embedded in a slab-ocean domain. The calculated precipitation rate over the island can be more than double the domain average value, with island rainfall occurring primarily in an intense, regular thunderstorm system that forms in the afternoon to early evening each day. Island size affects the magnitude of simulated island rainfall enhancement, the intensity of the convection, and the timing of the rainfall maximum relative to solar noon. A combination of dynamic and thermodynamic mechanisms leads to a monotonic enhancement of domain-averaged tropospheric temperature with increasing fraction of island surface, which may contribute to localization of ascent over the Maritime Continent and its relationship to the Walker Circulation. © 2014 Royal Meteorological Society."
"7005659017;6506180695;7801642681;36701716800;6701874937;55748076700;","First results of compact coherent Doppler wind lidar and its validation at IITM, Pune, India",2015,"10.1002/met.1428","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928582088&doi=10.1002%2fmet.1428&partnerID=40&md5=6ed887af5912bfd76be79641497956a7","A coherent Doppler wind lidar was installed in July2009 at the Indian Institute of Tropical Meteorology (IITM), Pune (18°43′N, 73°51′E, 559m AMSL), India, to map the daily three-dimensional wind fields in the atmospheric boundary layer (ABL). The aim was to provide a more in-depth understanding of weather, climate and air quality over Pune initially and later to be extended to other suitable sites in the country. The excellent performance of the system led to the deployment of next generation (extended) wind lidar with higher pulse power (∼100μJ) in July2010 to probe winds in clear-air (aerosol particles as tracers) as well as in cloud-air (cloud particles as tracers) up to about 12km AMSL. In this communication, a brief description of these two lidar versions together with some salient results, including comparison with co-located in situ techniques is presented. Sample data obtained on some typical experimental days with extended lidar and its calibration with co-located AWS and GPS Radiosonde are also presented. This comparison shows a reasonable agreement within the measurement accuracies. The spectral analysis of data reveals short-period, propagating-type gravity waves of about 5min periodicity, exchanging energy between lower and upper altitude levels. In addition to the ABL evolution and Low Level Jet (LLJ) features, the data can be used to establish cirrus cloud structures and associated circulation. © 2015 Royal Meteorological Society."
"57209908958;55986748500;18434662400;","Long-term simulation of large-scale urbanization effect on the East Asian monsoon",2015,"10.1007/s10584-013-0885-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926278564&doi=10.1007%2fs10584-013-0885-2&partnerID=40&md5=b40ded623d5c782e115e372d3d4c4670","The Weather Research and Forecasting (WRF) model is used to simulate the long-term effect of urbanization on regional climate, especially the East Asian monsoon. Besides land use change from urbanization, anthropogenic heat release is an important factor for the urban climate and environment, so these two factors are included in the simulation. Two experiments were designed and executed for the 10-year period. Urbanization is not considered in one experiment, and in the other, urban land use and anthropogenic heat release are comprehensively investigated. Comparison of the two runs shows that urbanization mainly decreases low-cloud cover across most of East China, and nearly all surface energy fluxes increase except those of latent heat and upward shortwave. Based on a multiyear average, the urbanization reduced summer precipitation in urban agglomerations, but the interannual variability is very large. Local upwelling airflow is strengthened by urbanization; however, additional precipitation was not produced because of a decline of surface moisture in urban agglomeration areas. From 850 hPa circulation change and the East Asian monsoon index, the summer monsoon is strengthened slightly and the winter monsoon is always weakened by large-scale urbanization. © 2013, Springer Science+Business Media Dordrecht."
"57090391300;6701800388;6603061242;55492126900;","Assessment of bioaerosol pollution over Indo-Gangetic plain",2015,"10.1007/s11356-014-3776-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938676556&doi=10.1007%2fs11356-014-3776-9&partnerID=40&md5=0cb067c6442133e0b2d194408dc80833","Aerosol plays a very important role in climate change and public health. It affects cloud condensation nuclei and causes a number of epidemic diseases. The correlations of aerosol with epidemic diseases are due to the biotic components of aerosol. The present study deals with the measurements and characterization of bioaerosol over Indo-Gangetic plain. The levels of PM10 and PM2.5 are much higher than the recommended value set by NAAQS in India. Bacterial and fungal concentrations are in the reported range. Bacterial concentration is higher than fungal concentration. Gram-positive bacteria contribute 75 % while gram-negative bacteria contribute 25 % only. A total seven types of fungi are identified in aerosols. Aspergillus niger is dominant. Meteorological parameters play important roles in growth and presence of microorganism in the air. Bacterial concentrations are governed mainly by temperature while fungal concentration is influenced by relative humidity. © 2014, Springer-Verlag Berlin Heidelberg."
"57203380630;57211729264;55492124900;7202310913;56760551400;6602106261;","Multifaceted application of crop residue biochar as a tool for sustainable agriculture: An ecological perspective",2015,"10.1016/j.ecoleng.2015.01.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922831018&doi=10.1016%2fj.ecoleng.2015.01.011&partnerID=40&md5=5215cff154152f36a96c237af31fda96","Lignocellulosic crop residue biomass, in surplus, is of vital importance due to its multifaceted utilization potential on- and off-site to agricultural systems; therefore, its management is essential for sustainable agriculture. The malpractice of open crop residue burning leading to the brown cloud phenomenon and contributing significantly to atmospheric heterogeneity through enhanced gaseous and particulate emissions is of greater off-late concern. Available traditional crop residue management (CRM) technologies have not achieved wider adaptation; therefore, recently thermochemical conversion has been foreseen as an interesting tool for potential CRM under changing climate scenario. Biochar, a by-product of thermochemical processes, has been evaluated as a potential soil ameliorant and C sequestration agent. As soil ameliorant, it improves soil basic properties directly along with subdued release of greenhouse gases from agroecosystems, provides adsorption surface to agrochemicals and improves essential nutrient dynamics. Since the potential benefits of biochar in soil are governed by initial pyrolysis conditions and soil types; therefore, its wider utilization potential as suitable tool in sustainable agriculture and climate change mitigation needs to be critically analyzed before its specific recommendation to an agroecosystem. The present review provides a critical insight on current research on various aspects, particularly ecological, of crop residue biochar starting from the feedstock sources, pyrolysis conditions and changes after application. Additionally, a brief account is given on the agronomic relevance and major constraints of biochar amendment as an ecological engineering tool for sustainable agriculture. After reviewing various aspects of crop residue as feedstock, we recommend its use as a blend, rather than sole use, along with several other lignocellulosic materials under pyrolysis process as well as ameliorating agent. © 2015 Elsevier B.V."
"6602443347;","Insolation patterns on eccentric exoplanets",2015,"10.1016/j.icarus.2014.12.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920913607&doi=10.1016%2fj.icarus.2014.12.017&partnerID=40&md5=3da2bfe4207b1bc3955eefdfd3d789e2","Several studies have found that synchronously-rotating Earth-like planets in the habitable zones of M-dwarf stars should exhibit an ""eyeball"" climate pattern, with a pupil of open ocean facing the parent star, and ice everywhere else. Recent work on eccentric exoplanets by Wang et al. (Wang, Y., Tian, F., Hu, Y. [2014b] Astrophys. J. 791, L12) has extended this conclusion to the 2:1 spin-orbit resonance as well, where the planet rotates twice during one orbital period. However, Wang et al. also found that the 3:2 and 5:2 half-odd resonances produce a zonally-striped climate pattern with polar icecaps instead. Unfortunately, they used incorrect insolation functions for the 3:2 and 5:2 resonances whose long-term time averages are essentially independent of longitude.This paper presents the correct insolation patterns for eccentric exoplanets with negligible obliquities in the 0:1, 1:2, 1:1, 3:2, 2:1, 5:2, 3:1, 7:2, and 4:1 spin-orbit resonances. I confirm that the mean insolation is distributed in an eyeball pattern for integer resonances; but for half-odd resonances, the mean insolation takes a ""double-eyeball"" pattern, identical over the ""eastern"" and ""western"" hemispheres. Presuming that liquids, ices, clouds, albedo, and thermal emission are similarly distributed, this has significant implications for the observation and interpretation of potentially habitable exoplanets.Finally, whether a striped ball, eyeball, or double-eyeball pattern emerges, the possibility exists that long-term build-up of ice (or liquid) away from the hot spots may alter the planet's inertia tensor and quadrupole moments enough to re-orient the planet, ultimately changing the distribution of liquid and ice. © 2014 Elsevier Inc.."
"56562594400;7005702722;56562157700;","Mechanisms for convection triggering by cold pools",2015,"10.1002/2015GL063227","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927797051&doi=10.1002%2f2015GL063227&partnerID=40&md5=8c1de084d387a1ac766855f1e032141d","Cold pools are fundamental ingredients of deep convection. They contribute to organizing the subcloud layer and are considered key elements in triggering convective cells. It was long known that this could happen mechanically, through lifting by the cold pools' fronts. More recently, it has been suggested that convection could also be triggered thermodynamically, by accumulation of moisture around the edges of cold pools. A method based on Lagrangian tracking is here proposed to disentangle the signatures of both forcings and quantify their importance in a given environment. Results from a simulation of radiative-convective equilibrium over the ocean show that parcels reach their level of free convection through a combination of both forcings, each being dominant at different stages of the ascent. Mechanical forcing is an important player in lifting parcels from the surface, whereas thermodynamic forcing reduces the inhibition encountered by parcels before they reach their level of free convection. Key Points Thermodynamic effect of cold pools crucial in the inhibition layer Gust front lifting is necessary for lifting parcels from the surface No forcing mechanism by cold pools is entirely dominant; cooperation is needed ©2015. American Geophysical Union. All Rights Reserved."
"53980213900;36856321600;","Aerosol specification in single-column Community Atmosphere Model version 5",2015,"10.5194/gmd-8-817-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926052111&doi=10.5194%2fgmd-8-817-2015&partnerID=40&md5=22cd8a4ef5f9025396fb3d1aeb8a62d8","Single-column model (SCM) capability is an important tool for general circulation model development. In this study, the SCM mode of version 5 of the Community Atmosphere Model (CAM5) is shown to handle aerosol initialization and advection improperly, resulting in aerosol, cloud-droplet, and ice crystal concentrations which are typically much lower than observed or simulated by CAM5 in global mode. This deficiency has a major impact on stratiform cloud simulations but has little impact on convective case studies because aerosol is currently not used by CAM5 convective schemes and convective cases are typically longer in duration (so initialization is less important). By imposing fixed aerosol or cloud-droplet and crystal number concentrations, the aerosol issues described above can be avoided. Sensitivity studies using these idealizations suggest that the Meyers et al. (1992) ice nucleation scheme prevents mixed-phase cloud from existing by producing too many ice crystals. Microphysics is shown to strongly deplete cloud water in stratiform cases, indicating problems with sequential splitting in CAM5 and the need for careful interpretation of output from sequentially split climate models. Droplet concentration in the general circulation model (GCM) version of CAM5 is also shown to be far too low (∼ 25 cm-3) at the southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site. © Author(s) 2015."
"57206379134;57203275224;","Diminished greenhouse warming from Archean methane due to solar absorption lines",2015,"10.5194/cp-11-559-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925983504&doi=10.5194%2fcp-11-559-2015&partnerID=40&md5=d2d09ccd562255ae67c8ae2ca5b1ced3","Previous research has shown that methane may have been sustained at high concentrations in the Archean atmosphere, helping to offset lower insolation and solve the faint young sun problem. However, recent updates to the HITRAN (High-Resolution Transmission) line database have significantly increased the shortwave absorption by CH<inf>4</inf> in comparison to older versions of the database (e.g. HITRAN 2000). Here we investigate the climatological implications of strong shortwave CH<inf>4</inf> absorption in an Archean atmosphere rich in CH<inf>4</inf>. We show that the surface warming at CH4 abundances >10-3 is diminished relative to the HITRAN 2000 line data. Strong shortwave absorption also results in a∼warm stratosphere and lower tropopause. We discuss these results in the context of contemporary research on the Archean climate and how these results could affect the formation of stratospheric clouds and an organic haze. © Author(s) 2015."
"55796057500;56260361400;6505856601;23466744600;24460392200;6603624776;6602176524;","Meso-scale modelling and radiative transfer simulations of a snowfall event over France at microwaves for passive and active modes and evaluation with satellite observations",2015,"10.5194/amt-8-1605-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944964430&doi=10.5194%2famt-8-1605-2015&partnerID=40&md5=f110171d1d0fdcc2270db7f814d10a9d","Microwave passive and active radiative transfer simulations are performed with the Atmospheric Radiative Transfer Simulator (ARTS) for a mid-latitude snowfall event, using outputs from the Meso-NH mesoscale cloud model. The results are compared to the corresponding microwave observations available from MHS and CloudSat. The spatial structures of the simulated and observed brightness temperatures show an overall agreement since the large-scale dynamical structure of the cloud system is reasonably well captured by Meso-NH. However, with the initial assumptions on the single-scattering properties of snow, there is an obvious underestimation of the strong scattering observed in regions with large frozen hydrometeor quantities. A sensitivity analysis of both active and passive simulations to the microphysical parametrizations is conducted. Simultaneous analysis of passive and active calculations provides strong constraints on the assumptions made to simulate the observations. Good agreements are obtained with both MHS and CloudSat observations when the single-scattering properties are calculated using the ""soft sphere"" parametrization from Liu (2004), along with the Meso-NH outputs. This is an important step toward building a robust data set of simulated measurements to train a statistically based retrieval scheme. © Author(s) 2015."
"55682751100;8084443000;24480463300;37067325200;14035386400;6603180620;11339750700;15724763500;6701853225;55603297400;23967608200;35461255500;","Major contribution of neutral clusters to new particle formation at the interface between the boundary layer and the free troposphere",2015,"10.5194/acp-15-3413-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926176027&doi=10.5194%2facp-15-3413-2015&partnerID=40&md5=071c9965f9cae8f812f962f90fb2cceb","The formation of new aerosol particles in the atmosphere is a key process influencing the aerosol number concentration as well as the climate, in particular at high altitude, where the newly formed particles directly influence cloud formation. However, free tropospheric new particle formation (NPF) is poorly documented due to logistic limitations and complex atmospheric dynamics around high-altitude stations that make the observation of this day-time process challenging. Recent improvements in measurement techniques make now possible the detection of neutral clusters down to ∼ 1 nm sizes, which opens new horizons in our understanding of the nucleation process. Indeed, only the charged fraction of clusters has been reported in the upper troposphere up to now. Here we report day-time concentrations of charged and neutral clusters (1 to 2.5 nm mobility diameter) recorded at the interface between the boundary layer (BL) and the FT as well as in the FT at the altitude site of Puy de Dôme (1465 m a.s.l.), central France, between 10 and 29 February 2012. Our findings demonstrate that in the FT, and especially at the interface between the BL and the FT, the formation of 1.5 nm neutral clusters significantly exceeds the one of ionic clusters during NPF events, clearly indicating that they dominate in the nucleation process. We also observe that the total cluster concentration significantly increases during NPF events compared to the other days, which was not clearly observed for the charged cluster population in the past. During the studied period, the nucleation process does not seem to be sulfuric acid-limited and could be promoted by the transport of pollutants to the upper troposphere, coupled with low temperatures. © 2015 Author(s)."
"55911904900;22635999400;57206332144;6603133611;7005399437;7004299722;","Cloud thermodynamic phase detection with polarimetrically sensitive passive sky radiometers",2015,"10.5194/amt-8-1537-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925638087&doi=10.5194%2famt-8-1537-2015&partnerID=40&md5=23edb0dabd23de8af64c988c2eceb3eb","The primary goal of this project has been to investigate if ground-based visible and near-infrared passive radiometers that have polarization sensitivity can determine the thermodynamic phase of overlying clouds, i.e., if they are comprised of liquid droplets or ice particles. While this knowledge is important by itself for our understanding of the global climate, it can also help improve cloud property retrieval algorithms that use total (unpolarized) radiance to determine cloud optical depth (COD). This is a potentially unexploited capability of some instruments in the NASA Aerosol Robotic Network (AERONET), which, if practical, could expand the products of that global instrument network at minimal additional cost. We performed simulations that found, for zenith observations, that cloud thermodynamic phase is often expressed in the sign of the Q component of the Stokes polarization vector. We chose our reference frame as the plane containing solar and observation vectors, so the sign of Q indicates the polarization direction, parallel (positive) or perpendicular (parallel) to that plane. Since the fraction of linearly polarized to total light is inversely proportional to COD, optically thin clouds are most likely to create a signal greater than instrument noise. Besides COD and instrument accuracy, other important factors for the determination of cloud thermodynamic phase are the solar and observation geometry (scattering angles between 40 and 60 are best), and the properties of ice particles (pristine particles may have halos or other features that make them difficult to distinguish from water droplets at specific scattering angles, while extreme ice crystal aspect ratios polarize more than compact particles). We tested the conclusions of our simulations using data from polarimetrically sensitive versions of the Cimel 318 sun photometer/radiometer that compose a portion of AERONET. Most algorithms that exploit Cimel polarized observations use the degree of linear polarization (DoLP), not the individual Stokes vector elements (such as Q). Ability to determine cloud thermodynamic phase depends on Q measurement accuracy, which has not been rigorously assessed for Cimel instruments. For this reason, we did not know if cloud phase could be determined from Cimel observations successfully. Indeed, comparisons to ceilometer observations with a single polarized spectral channel version of the Cimel at a site in the Netherlands showed little correlation. Comparisons to lidar observations with a more recently developed, multi-wavelength polarized Cimel in Maryland, USA, show more promise. The lack of well-characterized observations has prompted us to begin the development of a small test instrument called the Sky Polarization Radiometric Instrument for Test and Evaluation (SPRITE). This instrument is specifically devoted to the accurate observation of Q, and the testing of calibration and uncertainty assessment techniques, with the ultimate goal of understanding the practical feasibility of these measurements. © Author(s) 2015."
"54954644000;26533129200;7006760316;","Campanian Ignimbrite volcanism, climate, and the final decline of the Neanderthals",2015,"10.1130/G36514.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929465931&doi=10.1130%2fG36514.1&partnerID=40&md5=f366969e6e733800ea22d876317843a8","The eruption of the Campanian Ignimbrite at ca. 40 ka coincided with the final decline of Neanderthals in Europe. Environmental stress associated with the eruption of the Campanian Ignimbrite has been invoked as a potential driver for this extinction as well as broader upheaval in Paleolithic societies. To test the climatic importance of the Campanian eruption, we used a three-dimensional sectional aerosol model to simulate the global aerosol cloud after release of 50 Tg and 200 Tg SO2. We coupled aerosol properties to a comprehensive earth system model under last glacial conditions. We find that peak cooling and acid deposition lasted one to two years and that the most intense cooling sidestepped hominin population centers in Western Europe. We conclude that the environmental effects of the Campanian Ignimbrite eruption alone were insufficient to explain the ultimate demise of Neanderthals in Europe. Nonetheless, significant volcanic cooling during the years immediately following the eruption could have impacted the viability of already precarious populations and influenced many aspects of daily life for Neanderthals and anatomically modern humans. © 2015 Geological Society of America."
"56489062200;7404653593;36815705700;12040335900;","Retrieval of outgoing longwave radiation from COMS narrowband infrared imagery",2015,"10.1007/s00376-014-4013-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938299751&doi=10.1007%2fs00376-014-4013-7&partnerID=40&md5=264abfaa86613ca6f324e08ec27011d2","Hourly outgoing longwave radiation (OLR) from the geostationary satellite Communication Oceanography Meteorological Satellite (COMS) has been retrieved since June 2010. The COMS OLR retrieval algorithms are based on regression analyses of radiative transfer simulations for spectral functions of COMS infrared channels. This study documents the accuracies of OLRs for future climate applications by making an intercomparison of four OLRs from one single-channel algorithm (OLR<inf>12.0</inf> using the 12.0 μm channel) and three multiple-channel algorithms (OLR<inf>10.8+12.0</inf> using the 10.8 and 12.0 μm channels; OLR<inf>6.7+10.8</inf> using the 6.7 and 10.8 μm channels; and OLR<inf>All</inf> using the 6.7, 10.8, and 12.0 μm channels). The COMS OLRs from these algorithms were validated with direct measurements of OLR from a broadband radiometer of the Clouds and Earth’s Radiant Energy System (CERES) over the full COMS field of view [roughly (50°S–50°N, 70°–170°E)] during April 2011. Validation results show that the root-mean-square errors of COMS OLRs are 5–7 W m−2, which indicates good agreement with CERES OLR over the vast domain. OLR<inf>6.7+10.8</inf> and OLR<inf>All</inf> have much smaller errors (∼6 W m−2) than OLR<inf>12.0</inf> and OLR<inf>10.8+12.0</inf> (∼8 W m−2). Moreover, the small errors of OLR<inf>6.7+10.8</inf> and OLR<inf>All</inf> are systematic and can be readily reduced through additional mean bias correction and/or radiance calibration. These results indicate a noteworthy role of the 6.7 μm water vapor absorption channel in improving the accuracy of the OLRs. The dependence of the accuracy of COMS OLRs on various surface, atmospheric, and observational conditions is also discussed. © 2015, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"57206174471;35738058800;6603568514;7003531755;7201498373;35277762300;6506553716;7003483600;","Urbanization causes increased cloud base height and decreased fog in coastal Southern California",2015,"10.1002/2015GL063266","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925863139&doi=10.1002%2f2015GL063266&partnerID=40&md5=aaa6b65b9da65b0362e0248dddf71180","Subtropical marine stratus clouds regulate coastal and global climate, but future trends in these clouds are uncertain. In coastal Southern California (CSCA), interannual variations in summer stratus cloud occurrence are spatially coherent across 24 airfields and dictated by positive relationships with stability above the marine boundary layer (MBL) and MBL height. Trends, however, have been spatially variable since records began in the mid-1900s due to differences in nighttime warming. Among CSCA airfields, differences in nighttime warming, but not daytime warming, are strongly and positively related to fraction of nearby urban cover, consistent with an urban heat island effect. Nighttime warming raises the near-surface dew point depression, which lifts the altitude of condensation and cloud base height, thereby reducing fog frequency. Continued urban warming, rising cloud base heights, and associated effects on energy and water balance would profoundly impact ecological and human systems in highly populated and ecologically diverse CSCA. © 2015. American Geophysical Union. All Rights Reserved."
"18434033000;52463601100;56253852700;15849661500;6701363731;26434217100;57195769430;8697462600;57188751935;57203155960;55427631900;6602537415;57192833729;55636563800;7006091410;6505772245;26432415000;56557053600;55637266800;","Regional climate hindcast simulations within EURO-CORDEX: Evaluation of a WRF multi-physics ensemble",2015,"10.5194/gmd-8-603-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924976189&doi=10.5194%2fgmd-8-603-2015&partnerID=40&md5=e65b4a9e74db50ae4647139a5cc62bbc","In the current work we present six hindcast WRF (Weather Research and Forecasting model) simulations for the EURO-CORDEX (European Coordinated Regional Climate Downscaling Experiment) domain with different configurations in microphysics, convection and radiation for the time period 1990-2008. All regional model simulations are forced by the ERA-Interim reanalysis and have the same spatial resolution (0.44°). These simulations are evaluated for surface temperature, precipitation, short-and longwave downward radiation at the surface and total cloud cover. The analysis of the WRF ensemble indicates systematic temperature and precipitation biases, which are linked to different physical mechanisms in the summer and winter seasons. Overestimation of total cloud cover and underestimation of downward shortwave radiation at the surface, mostly linked to the Grell-Devenyi convection and CAM (Community Atmosphere Model) radiation schemes, intensifies the negative bias in summer temperatures over northern Europe (max-2.5 °C). Conversely, a strong positive bias in downward shortwave radiation in summer over central (40-60%) and southern Europe mitigates the systematic cold bias over these regions, signifying a typical case of error compensation. Maximum winter cold biases are over northeastern Europe (2.8 °C); this location suggests that land-atmosphere rather than cloud-radiation interactions are to blame. Precipitation is overestimated in summer by all model configurations, especially the higher quantiles which are associated with summertime deep cumulus convection. The largest precipitation biases are produced by the Kain-Fritsch convection scheme over the Mediterranean. Precipitation biases in winter are lower than those for summer in all model configurations (15-30%). The results of this study indicate the importance of evaluating not only the basic climatic parameters of interest for climate change applications (temperature and precipitation), but also other components of the energy and water cycle, in order to identify the sources of systematic biases, possible compensatory or masking mechanisms and suggest pathways for model improvement. © 2015 Author(s)."
"55746507000;7402333662;","Direct impacts of waves on tropical cold point tropopause temperature",2015,"10.1002/2014GL062737","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925878381&doi=10.1002%2f2014GL062737&partnerID=40&md5=5958a2c94125fc51e21a3ace68ebd017","Cold point tropopause temperature is a key regulator of cirrus clouds and stratospheric water vapor, which have significant impacts on the Earth's radiation budget and climate. Using tropical radiosonde observations, we show that waves in the tropical tropopause layer lower cold point temperature by 1.6 K on average relative to the seasonal mean. Furthermore, wave activity in the tropical tropopause layer has not been constant over the last 2.5 decades, altering the magnitude of the wave impacts on cold point temperature at a decadal scale. The change in the direct wave impact is partially (~20-30%) responsible for the sudden decrease in cold point temperature and stratospheric water vapor at the end of 2000, which has not been fully explained by changes in the Brewer-Dobson circulation. We further show that these wave impacts are not well represented in reanalysis data. © 2015. American Geophysical Union. All Rights Reserved."
"37112248300;22633429500;47761232800;6701806265;","Temperature profiling of the atmospheric boundary layer with rotational Raman lidar during the HD(CP)2 Observational Prototype Experiment",2015,"10.5194/acp-15-2867-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924589260&doi=10.5194%2facp-15-2867-2015&partnerID=40&md5=26516aa1fa2d62b5ef29ed645e85b82b","The temperature measurements of the rotational Raman lidar of the University of Hohenheim (UHOH RRL) during the High Definition of Clouds and Precipitation for advancing Climate Prediction (HD(CP)2) Observation Prototype Experiment (HOPE) in April and May 2013 are discussed. The lidar consists of a frequency-tripled Nd:YAG laser at 355 nm with 10 W average power at 50 Hz, a two-mirror scanner, a 40 cm receiving telescope, and a highly efficient polychromator with cascading interference filters for separating four signals: the elastic backscatter signal, two rotational Raman signals with different temperature dependence, and the vibrational Raman signal of water vapor. The main measurement variable of the UHOH RRL is temperature. For the HOPE campaign, the lidar receiver was optimized for high and low background levels, with a novel switch for the passband of the second rotational Raman channel. The instrument delivers atmospheric profiles of water vapor mixing ratio as well as particle backscatter coefficient and particle extinction coefficient as further products. As examples for the measurement performance, measurements of the temperature gradient and water vapor mixing ratio revealing the development of the atmospheric boundary layer within 25 h are presented. As expected from simulations, a reduction of the measurement uncertainty of 70% during nighttime was achieved with the new low-background setting. A two-mirror scanner allows for measurements in different directions. When pointing the scanner to low elevation, measurements close to the ground become possible which are otherwise impossible due to the non-total overlap of laser beam and receiving telescope field of view in the near range. An example of a low-level temperature measurement is presented which resolves the temperature gradient at the top of the stable nighttime boundary layer 100 m above the ground. © Author(s) 2015. CC Attribution 3.0 License."
"55575920100;56490969800;6603196991;8618154900;36339753800;7004881313;6603868770;","Assessment of small-scale integrated water vapour variability during HOPE",2015,"10.5194/acp-15-2675-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924401940&doi=10.5194%2facp-15-2675-2015&partnerID=40&md5=c15148ee198bc58031b825564d9672bc","The spatio-temporal variability of integrated water vapour (IWV) on small scales of less than 10 km and hours is assessed with data from the 2 months of the High Definition Clouds and Precipitation for advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE). The statistical intercomparison of the unique set of observations during HOPE (microwave radiometer (MWR), Global Positioning System (GPS), sun photometer, radiosondes, Raman lidar, infrared and near-infrared Moderate Resolution Imaging Spectroradiometer (MODIS) on the satellites Aqua and Terra) measuring close together reveals a good agreement in terms of random differences (standard deviation ≤1 kg m-2) and correlation coefficient (≥ 0.98). The exception is MODIS, which appears to suffer from insufficient cloud filtering. For a case study during HOPE featuring a typical boundary layer development, the IWV variability in time and space on scales of less than 10 km and less than 1 h is investigated in detail. For this purpose, the measurements are complemented by simulations with the novel ICOsahedral Nonhydrostatic modelling framework (ICON), which for this study has a horizontal resolution of 156 m. These runs show that differences in space of 3-4 km or time of 10-15 min induce IWV variabilities on the order of 0.4 kg m-2. This model finding is confirmed by observed time series from two MWRs approximately 3 km apart with a comparable temporal resolution of a few seconds. Standard deviations of IWV derived from MWR measurements reveal a high variability (&gt; 1 kg m-2) even at very short time scales of a few minutes. These cannot be captured by the temporally lower-resolved instruments and by operational numerical weather prediction models such as COSMO-DE (an application of the Consortium for Small-scale Modelling covering Germany) of Deutscher Wetterdienst, which is included in the comparison. However, for time scales larger than 1 h, a sampling resolution of 15 min is sufficient to capture the mean standard deviation of IWV. The present study shows that instrument sampling plays a major role when climatological information, in particular the mean diurnal cycle of IWV, is determined. © Author(s) 2015."
"57203386948;56990731400;8045690700;24081888700;7007020226;56239378700;7004174939;7003865921;12645612500;55147025100;56722821200;","Quantification of trans-Atlantic dust transport from seven-year (2007-2013) record of CALIPSO lidar measurements",2015,"10.1016/j.rse.2014.12.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027954478&doi=10.1016%2fj.rse.2014.12.010&partnerID=40&md5=79f62d72af89ff2463f83f3ece1bfced","The trans-Atlantic dust transport has important implications for human and ecosystem health, the terrestrial and oceanic biogeochemical cycle, weather systems, and climate. This study provides an observation-based multiyear estimate of trans-Atlantic dust transport using a 7-year (2007-2013) record of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements of the three dimensional distribution of aerosol backscatter, extinction and depolarization ratio in both cloud-free and above-cloud conditions. We estimate that on a basis of the 7-year average and integration over 10°S-30°N, 182Tga-1 dust leaves the coast of North Africa at 15°W, of which 132Tga-1 and 43Tga-1 reaches 35°W and 75°W, respectively. These flux estimates have an overall known uncertainty of ±(45-70)%. Because of lack of reliable observations, uncertainties associated with the diurnal variation of dust and the missing below-cloud dust cannot be quantified. Significant seasonal variations are observed in both the magnitude of total dust mass flux and its meridional and vertical distributions. The interannual variability of annual dust mass flux is highly anti-correlated with the prior-year Sahel Precipitation Index. Using only cloud-free aerosol observations to calculate dust mass flux could introduce a high bias when compared with all-sky conditions that include both cloud-free and above-cloud aerosol observations. The bias is about 20% at 35°W and 75°W in boreal winter and spring based on the 7-year average, as long as dust within and below low-level clouds is negligible. © 2014 Elsevier Inc."
"6506383700;55803773100;21935606200;6508260037;11539061800;","Seasonal inhomogeneity in cloud precursors over Gangetic Himalayan region during GVAX campaign",2015,"10.1016/j.atmosres.2014.11.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919935217&doi=10.1016%2fj.atmosres.2014.11.022&partnerID=40&md5=58eea05f25d6a7c6325a6a9ac02eca35","Atmospheric aerosols are key elements in cloud microphysics, the hydrological cycle and climate by serving as cloud condensation nuclei (CCN). The present work analyzes simultaneous measurements of number concentration of CCN (NCCN) and condensation nuclei (NCN) obtained at Nainital, in the Gangetic-Himalayan (GH) region, during the frameworks of Ganges Valley Aerosol Experiment (GVAX), June 2011 to March 2012. The NCCN, NCN and activation (AR=NCCN/NCN) at 0.31-0.33% S (supersaturation ratio), exhibit significant daily, monthly and seasonal variations within a range of 684-2065cm-3 for NCCN, 1606-4124cm-3 for NCN, and 0.38-0.60 for AR, suggesting large inhomogeneity in aerosol properties, types and sources, which control the degree of aerosol potential activation. Thus, transported aerosols from the Ganges valley and abroad, the boundary-layer dynamics and atmospheric modification processes play an important role in aerosol-cloud interactions over the GH region. The NCN and NCCN show monthly-dependent diurnal variations with afternoon maxima due to transported aerosols from the Ganges valley up to the Himalayan foothills, while the AR is lower during these hours implying lower hygroscopicities or smaller sizes of the transported aerosols. The dependence of NCCN on S is highest during Dec-Mar and lowest during monsoon (Jun-Sep), suggesting different aerosol chemical composition. Comparison between Nainital and Kanpur shows that NCN and NCCN are much lower at Nainital, while the similarity in AR suggests aerosols of similar type, source and chemical composition uplifted from the Ganges valley to the Himalayan foothills. © 2014 Elsevier B.V."
"57217323583;6603203838;6603023560;6701491265;6603407189;55502994400;6602390932;7402129369;","Total column water vapour measurements from GOME-2 MetOp-A and MetOp-B",2015,"10.5194/amt-8-1111-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938577785&doi=10.5194%2famt-8-1111-2015&partnerID=40&md5=31fc610584947a7c99c7ec27d79f0501","Knowledge of the total column water vapour (TCWV) global distribution is fundamental for climate analysis and weather monitoring. In this work, we present the retrieval algorithm used to derive the operational TCWV from the GOME-2 sensors aboard EUMETSAT's MetOp-A and MetOp-B satellites and perform an extensive inter-comparison in order to evaluate their consistency and temporal stability. For the analysis, the GOME-2 data sets are generated by DLR in the framework of the EUMETSAT O3M-SAF project using the GOME Data Processor (GDP) version 4.7. The retrieval algorithm is based on a classical Differential Optical Absorption Spectroscopy (DOAS) method and combines a H2O and O2 retrieval for the computation of the trace gas vertical column density. We introduce a further enhancement in the quality of the H2O total column by optimizing the cloud screening and developing an empirical correction in order to eliminate the instrument scan angle dependencies. The overall consistency between measurements from the newer GOME-2 instrument on board of the MetOp-B platform and the GOME-2/MetOp-A data is evaluated in the overlap period (December 2012-June 2014). Furthermore, we compare GOME-2 results with independent TCWV data from the ECMWF ERA-Interim reanalysis, with SSMIS satellite measurements during the full period January 2007-June 2014 and against the combined SSM/I + MERIS satellite data set developed in the framework of the ESA DUE GlobVapour project (January 2007-December 2008). Global mean biases as small as ±0.035 g cm-2 are found between GOME-2A and all other data sets. The combined SSM/I-MERIS sample and the ECMWF ERA-Interim data set are typically drier than the GOME-2 retrievals, while on average GOME-2 data overestimate the SSMIS measurements by only 0.006 g cm-2. However, the size of these biases is seasonally dependent. Monthly average differences can be as large as 0.1 g cm-2, based on the analysis against SSMIS measurements, which include only data over ocean. The seasonal behaviour is not as evident when comparing GOME-2 TCWV to the ECMWF ERA-Interim and the SSM/I+MERIS data sets, since the different biases over land and ocean surfaces partly compensate each other. Studying two exemplary months, we estimate regional differences and identify a very good agreement between GOME-2 total columns and all three data sets, especially for land areas, although some discrepancies (bias larger than ±0.5 g cm-2) over ocean and over land areas with high humidity or a relatively large surface albedo are observed."
"24076322200;56506690300;7003578759;","The sunshine state: Investigating external drivers of sky conditions",2015,"10.1080/02723646.2015.1004995","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925775134&doi=10.1080%2f02723646.2015.1004995&partnerID=40&md5=80e52e05f6cab0421c7296d7758d933b","Following rapid population growth and urbanization in Florida, there is an increased demand for energy. The state currently gets more than 50% of its electricity from burning imported natural gas. As the future of fossil fuels is uncertain and their impact on climate has proven negative, one could expect great potential and interest in further developing the solar industry, which utilizes the most prominent of renewable energy sources in Florida. Solar energy production is dependent on the supply of clear skies and plentiful insolation. This paper seeks to explain variations in the number of clear sunny days by identifying the months with clearest (cloudiest) sky conditions during the years 1950-2009 in relation to some of the most dominant low frequency climate patterns of variability in the Northern Hemisphere. The hypergeometric distribution is used to test for significant association between the phases of El Ninõ Southern Oscillation (ENSO), North Atlantic Oscillation, Pacific-North American, and Atlantic Multi-decadal Oscillation (AMO) and cloud cover in Florida. We find that ENSO and AMO significantly impact the occurrence of clear/cloudy skies with the warm phase of ENSO associated with cloudier conditions across much of the state and the warm phase of AMO bringing clearer conditions to northern stations. © 2015 Taylor and Francis."
"57213743966;6701511321;25629055800;","Ensemble simulations of the role of the stratosphere in the attribution of northern extratropical tropospheric ozone variability",2015,"10.5194/acp-15-2341-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923870111&doi=10.5194%2facp-15-2341-2015&partnerID=40&md5=fe93d10dbc7864d313431a3e6cf713c5","Despite the need to understand the impact of changes in emissions and climate on tropospheric ozone, the attribution of tropospheric interannual ozone variability to specific processes has proven difficult. Here, we analyze the stratospheric contribution to tropospheric ozone variability and trends from 1953 to 2005 in the Northern Hemisphere (NH) mid-latitudes using four ensemble simulations of the free running (FR) Whole Atmosphere Community Climate Model (WACCM). The simulations are externally forced with observed time-varying (1) sea-surface temperatures (SSTs), (2) greenhouse gases (GHGs), (3) ozone depleting substances (ODS), (4) quasi-biennial oscillation (QBO), (5) solar variability (SV) and (6) stratospheric sulfate surface area density (SAD). A detailed representation of stratospheric chemistry is simulated, including the ozone loss due to volcanic eruptions and polar stratospheric clouds. In the troposphere, ozone production is represented by CH4-NOx smog chemistry, where surface chemical emissions remain interannually constant. Despite the simplicity of its tropospheric chemistry, at many NH measurement locations, the interannual ozone variability in the FR WACCM simulations is significantly correlated with the measured interannual variability. This suggests the importance of the external forcing applied in these simulations in driving interannual ozone variability. The variability and trend in the simulated 1953-2005 tropospheric ozone from 30 to 90 N at background surface measurement sites, 500 hPa measurement sites and in the area average are largely explained on interannual timescales by changes in the 30-90°N area averaged flux of ozone across the 100 hPa surface and changes in tropospheric methane concentrations. The average sensitivity of tropospheric ozone to methane (percent change in ozone to a percent change in methane) from 30 to 90°N is 0.17 at 500 hPa and 0.21 at the surface; the average sensitivity of tropospheric ozone to the 100 hPa ozone flux (percent change in ozone to a percent change in the ozone flux) from 30 to 90°N is 0.19 at 500 hPa and 0.11 at the surface. The 30-90°N simulated downward residual velocity at 100 hPa increased by 15% between 1953 and 2005. However, the impact of this on the 30-90°N 100 hPa ozone flux is modulated by the long-term changes in stratospheric ozone. The ozone flux decreases from 1965 to 1990 due to stratospheric ozone depletion, but increases again by approximately 7% from 1990 to 2005. The first empirical orthogonal function of interannual ozone variability explains from 40% (at the surface) to over 80% (at 150 hPa) of the simulated ozone interannual variability from 30 to 90°N. This identified mode of ozone variability shows strong stratosphere-troposphere coupling, demonstrating the importance of the stratosphere in an attribution of tropospheric ozone variability. The simulations, with no change in emissions, capture almost 50% of the measured ozone change during the 1990s at a variety of locations. This suggests that a large portion of the measured change is not due to changes in emissions, but can be traced to changes in large-scale modes of ozone variability. This emphasizes the difficulty in the attribution of ozone changes, and the importance of natural variability in understanding the trends and variability of ozone. We find little relation between the El Niño-Southern Oscillation (ENSO) index and large-scale tropospheric ozone variability over the long-term record. © Author(s) 2015."
"55667068400;18038550600;7401472342;","Persistent after-effects of heavy rain on concentrations of ice nuclei and rainfall suggest a biological cause",2015,"10.5194/acp-15-2313-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923863045&doi=10.5194%2facp-15-2313-2015&partnerID=40&md5=027e20fa7c875afd40f3c50d7d3b29b3","Rainfall is one of the most important aspects of climate, but the extent to which atmospheric ice nuclei (IN) influence its formation, quantity, frequency, and location is not clear. Microorganisms and other biological particles are released following rainfall and have been shown to serve as efficient IN, in turn impacting cloud and precipitation formation. Here we investigated potential long-term effects of IN on rainfall frequency and quantity. Differences in IN concentrations and rainfall after and before days of large rainfall accumulation (i.e., key days) were calculated for measurements made over the past century in southeastern and southwestern Australia. Cumulative differences in IN concentrations and daily rainfall quantity and frequency as a function of days from a key day demonstrated statistically significant increasing logarithmic trends (R2 &gt; 0.97). Based on observations that cumulative effects of rainfall persisted for about 20 days, we calculated cumulative differences for the entire sequence of key days at each site to create a historical record of how the differences changed with time. Comparison of pre-1960 and post-1960 sequences most commonly showed smaller rainfall totals in the post-1960 sequences, particularly in regions downwind from coal-fired power stations. This led us to explore the hypothesis that the increased leaf surface populations of IN-active bacteria due to rain led to a sustained but slowly diminishing increase in atmospheric concentrations of IN that could potentially initiate or augment rainfall. This hypothesis is supported by previous research showing that leaf surface populations of the ice-nucleating bacterium Pseudomonas syringae increased by orders of magnitude after heavy rain and that microorganisms become airborne during and after rain in a forest ecosystem. At the sites studied in this work, aerosols that could have initiated rain from sources unrelated to previous rainfall events (such as power stations) would automatically have reduced the influences on rainfall of those whose concentrations were related to previous rain, thereby leading to inhibition of feedback. The analytical methods described here provide means to map and delimit regions where rainfall feedback mediated by microorganisms is suspected to occur or has occurred historically, thereby providing rational means to establish experimental set-ups for verification. © Author(s) 2015."
"55683891800;56229494700;36026436300;55683727600;12753162000;13403849600;8942525300;9235235300;13405658600;","Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation",2015,"10.5194/acp-15-2247-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923865363&doi=10.5194%2facp-15-2247-2015&partnerID=40&md5=c7ccf804ae0eb16a57bda76e2c77b567","Emissions of biogenic volatile organic compounds (BVOCs) have changed in the past millennium due to changes in land use, temperature, and CO2 concentrations. Recent reconstructions of BVOC emissions have predicted that global isoprene emissions have decreased, while monoterpene and sesquiterpene emissions have increased; however, all three show regional variability due to competition between the various influencing factors. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on secondary organic aerosol (SOA) formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS (Goddard Earth Observing System; TwO-Moment Aerosol Sectional) global aerosol microphysics model. With anthropogenic emissions (e.g., SO2, NOx, primary aerosols) turned off and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp &gt; 80 nm (N80) of &gt; 25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in the combined aerosol radiative effect (direct and indirect) of &gt; 0.5 W m-2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields, and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m-2 and the global mean cloud-albedo aerosol indirect effect of between -0.008 and -0.056 W m-2. This change in aerosols, and the associated radiative forcing, could be a largely overlooked and important anthropogenic aerosol effect on regional climates. © Author(s) 2015."
"9436114900;55663671600;54986194000;7005632987;13907628100;","Mineral dust aerosol distributions, its direct and semi-direct effects over South Africa based on regional climate model simulation",2015,"10.1016/j.jaridenv.2014.11.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910646375&doi=10.1016%2fj.jaridenv.2014.11.002&partnerID=40&md5=bf232ee37cf1065a4ef230d0b2ed52b5","The present contribution investigates the seasonal mean mass distributions, direct and semi-direct climatic effects of desert dust aerosols over South Africa, using the 12 year runs of Regional Climate Model (RegCM4). The results have shown that the desert dust particles which burden the western and southern regions of South Africa are mainly produced from the Kalahari and Namib Desert areas. At the surface and within the atmosphere, the short- and long-wave radiative forcing (RF) of dust showed contrasting effects. However, due to the dust short-wave RF dominant influence, the Net-RF of dust causes reduction on net radiation absorbed by the surface via enhancing radiative heating in the atmosphere. The radiative feedbacks of desert dust particles predominantly result in a positive response on net atmospheric radiative heating rate, Cloud Cover (CC) and cloud liquid water path. The CC enhancement and Net-RF of dust, cooperatively, induce reduction in surface temperature (up to-1.1K) and surface sensible heat flux (up to-24W/m2). The presence of desert dust aerosol also causes boundary layer height reduction, surface pressure enhancement and dynamical changes. Overall, the present contribution underscores the importance of including the effects of wind-eroded dust particles in climate change studies over South Africa. © 2014 Elsevier Ltd."
"36801729300;55315290600;6603926727;7005618829;","Radiative effect of dust aerosols on cloud microphysics and meso-scale dynamics during monsoon breaks over Arabian sea",2015,"10.1016/j.atmosenv.2015.01.037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922646127&doi=10.1016%2fj.atmosenv.2015.01.037&partnerID=40&md5=969fac44bd0a496dd1a0cdf01e501c30","During monsoon breaks (large scale rainfall below the long term normal), dry air laddened with dust aerosols intrude over central India through Arabian sea (AS) from West Asian desert regions. To understand the effect of these dust aerosols on marine clouds over AS during monsoon breaks, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Cloud and the Earth's Radiant Energy System (CERES) data have been analyzed for the period 2007 to 2013. The vertical profile of dust backscatter coefficient (DBS) showed an elevated layer between 2 and 5km and the maximum heating rate observed is 9K/Day which is higher by 3K/day as compared to the heating observed in June to September (JJAS) mean. Semi-direct effect due to the interaction of the long range transported dust with pristine cloud environment is observed in both warm and cold clouds. Significant differences in shortwave and longwave fluxes at the top of the atmosphere (TOA), cloud micro and macrophysical parameters are observed between the clouds with and without dust. Also, the percentage differences are more in cold clouds as compared to warm clouds. Dust induced semi-direct effect is found to be more pronounced in cold clouds, while indirect effect in warm clouds. Zonal anomalies of dynamical parameters due to dust induced heating, affect the circulation patterns in the immediate meso-scale environment, which strengthen/extend the monsoon break situation. © 2015 Elsevier Ltd."
"7201472576;57214023403;9246517900;","Advancing the uncertainty characterisation of cloud masking in passive satellite imagery: Probabilistic formulations for NOAA AVHRR data",2015,"10.1016/j.rse.2014.10.028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913596446&doi=10.1016%2fj.rse.2014.10.028&partnerID=40&md5=c4eae6e5756b3f69a384256db85d0981","Two alternative methods for probabilistic cloud masking of images from the Advanced Very High Resolution Radiometer (AVHRR) sensor have been examined. Both methods are based on Bayesian theory and were trained using data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. Results were evaluated by comparing to independent CALIPSO-CALIOP observations and to a one-year ground-based cloud dataset composed from five different remote sensing systems over the observation site in Cabauw in the Netherlands. In addition, results were compared to two different cloud masks; one derived from the geostationary Spinning Enhanced Visible and Infrared Imager (SEVIRI) sensor and one from the Climate Monitoring Satellite Application Facility Clouds (CMSAF), Albedo and Radiation dataset from AVHRR data (CLARA-A1). It was demonstrated that the probabilistic methods compare well with the referenced satellite datasets and for daytime conditions they provide even better performance than the reference methods. Among the two probabilistic approaches, it was found that the formulation based on a Naïve Bayesian formulation (denoted PPS-Prob Naïve) performed clearly superior to the formulation based on a linear summation of conditional cloud probabilities (denoted PPS-Prob SPARC) for daytime conditions. For the study based on the observations over the Cabauw site, the overall daytime Kuipers Skill Score for PPS-Prob Naïve was 0.84, for PPS-Prob SPARC 0.79, for CLARA-A1 0.74 and for SEVIRI 0.66. Corresponding results for night-time conditions were less favourable for the probabilistic formulations (Kuipers Skill Score 0.74 for PPS_Prob Naïve, 0.68 for PPS-Prob SPARC, 0.80 for CLARA-A1 and 0.79 for SEVIRI) but still relatively close to the reference dataset. The Cabauw distribution of cloudiness occurrences in different octa categories was reproduced very closely by all methods, including the probabilistic formulations. Results based on Cabauw observations were also largely in good agreement with results deduced from comparisons with the CALIPSO-CALIOP cloud mask.The PPS-Prob Naïve approach will be implemented in an upcoming version of the Polar Platform System (PPS) cloud software issued by the EUMETSAT Nowcasting Satellite Application Facility (NWC SAF). It will also be used in the second release of the CMSAF CLARA cloud climate data record based on historic AVHRR GAC data (to be denoted CLARA-A2). © 2014 The Authors."
"55653739600;7102309161;14067693600;22234191300;7202664004;","Hybrid fine scale climatology and microphysics of in-cloud icing: From 32km reanalysis to 5km mesoscale modeling",2015,"10.1016/j.atmosres.2014.11.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949116482&doi=10.1016%2fj.atmosres.2014.11.006&partnerID=40&md5=7432bd79cac733b690663a3430624d6b","In-cloud icing can impose safety concerns and economic challenges for various industries. Icing climate representations proved beneficial for optimal designs and careful planning. The current study investigates in-cloud icing, its related cloud microphysics and introduces a 15-year time period climatology of icing events. The model was initially driven by reanalysis data from North American Regional Reanalysis and downscaled through a two-level nesting of 10. km and 5. km, using a limited-area version of the Global Environment Multiscale Model of the Canadian Meteorological Center. In addition, a hybrid approach is used to reduce time consuming calculations. The simulation realized exclusively on significant icing days, was combined with non-significant icing days as represented by data from NARR. A proof of concept is presented here for a 1000. km area around Gaspé during January for those 15. years.An increase in the number and intensity of icing events has been identified during the last 15years. From GEM-LAM simulations and within the atmospheric layer between 10m and 200m AGL, supercooled liquid water contents indicated a maximum of 0.4gm-3, and 50% of the values are less than 0.05gm-3. All values of median volume diameters (MVD) are approximately capped by 70μm and the typical values are around 15μm. Supercooled Large Droplets represent approximately 5%. The vertical profile of icing climatology demonstrates a steady duration of icing events until the level of 60m. The altitudes of 60m and 100m indicate substantial icing intensification toward higher elevations. GEM-LAM demonstrated a substantial improvement in the calculation of in-cloud icing, reducing significantly the challenge posed by complex terrains. © 2014 Elsevier B.V."
"48661551300;7403931916;7003266014;7402942478;","Response of aerosol direct radiative effect to the East Asian summer monsoon",2015,"10.1109/LGRS.2014.2352630","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908010970&doi=10.1109%2fLGRS.2014.2352630&partnerID=40&md5=bc2557fb1612f3f35f7bfbbb33670ebd","Asian summer monsoon and atmospheric aerosol simultaneously influence the climate in the East Asian region. However, substantial uncertainties exist in the current understanding of the interactions between monsoon and aerosol and their combined effects. Previous studies have shown that aerosols influence the strength of monsoon and monsoon-related water cycles; however, monsoon strongly regulates the aerosol spatial distribution. This letter investigates the radiative flux response at the top of the atmosphere to the Asian summer monsoon by using observations made by the Clouds and Earth's Radiant Energy System and the Moderate Resolution Imaging Spectroradiometer. In comparison with the ten-year (2002-2011) mean climatology, the aerosol radiative effect is estimated over two eastern Asia regions for the months of July in 2002 and 2003, corresponding to a weak and a strong summer monsoon event, respectively. The dramatically different influences show the aerosol radiative forcing over land to be strongly responsive to Asian summer monsoon. Furthermore, the reanalysis-based estimate of the aerosol radiative effect is consistent with its observation-only counterpart. © 2014 IEEE."
"56203249800;35561911800;36705143500;55408944000;9242540400;6604021707;7401548835;9242539000;57191598636;22978151200;7004177660;7004409909;55339475000;6603552777;57193132723;12240390300;7404334532;7006224475;57191693467;56249704400;7006399110;8954866200;57191692422;12241892400;7201837768;6506806004;55403720400;8414341100;7006550762;12763470600;7405727977;7004214645;56528677800;6507308842;14829673100;22986631300;7403318365;57203378018;","Future climate change under RCP emission scenarios with GISS ModelE2",2015,"10.1002/2014MS000403","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928814435&doi=10.1002%2f2014MS000403&partnerID=40&md5=a09054e13edbe0b876d903beba94aabf","We examine the anthropogenically forced climate response for the 21st century representative concentration pathway (RCP) emission scenarios and their extensions for the period 2101-2500. The experiments were performed with ModelE2, a new version of the NASA Goddard Institute for Space Sciences (GISS) coupled general circulation model that includes three different versions for the atmospheric composition components: a noninteractive version (NINT) with prescribed composition and a tuned aerosol indirect effect (AIE), the TCAD version with fully interactive aerosols, whole-atmosphere chemistry, and the tuned AIE, and the TCADI version which further includes a parameterized first indirect aerosol effect on clouds. Each atmospheric version is coupled to two different ocean general circulation models: the Russell ocean model (GISS-E2-R) and HYCOM (GISS-E2-H). By 2100, global mean warming in the RCP scenarios ranges from 1.0 to 4.5°C relative to 1850-1860 mean temperature in the historical simulations. In the RCP2.6 scenario, the surface warming in all simulations stays below a 2°C threshold at the end of the 21st century. For RCP8.5, the range is 3.5-4.5°C at 2100. Decadally averaged sea ice area changes are highly correlated to global mean surface air temperature anomalies and show steep declines in both hemispheres, with a larger sensitivity during winter months. By the year 2500, there are complete recoveries of the globally averaged surface air temperature for all versions of the GISS climate model in the low-forcing scenario RCP2.6. TCADI simulations show enhanced warming due to greater sensitivity to CO<inf>2</inf>, aerosol effects, and greater methane feedbacks, and recovery is much slower in RCP2.6 than with the NINT and TCAD versions. All coupled models have decreases in the Atlantic overturning stream function by 2100. In RCP2.6, there is a complete recovery of the Atlantic overturning stream function by the year 2500 while with scenario RCP8.5, the E2-R climate model produces a complete shutdown of deep water formation in the North Atlantic. © 2015. The Authors."
"56471924500;8099715700;13607045000;56322939600;","A method to measure total atmospheric long-wave down-welling radiation using a low cost infrared thermometer tilted to the vertical",2015,"10.1016/j.energy.2014.12.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924903115&doi=10.1016%2fj.energy.2014.12.035&partnerID=40&md5=338ec995d732ed3ea362f95677f9e6dc","Atmospheric long-wave down-welling radiation is a fundamental element of climate change and of input to thermal simulation. Measuring long-wave radiation is needed to calculate locally total energy flows to the earth's surface and night cooling rates in urban precincts. It is an important parameter for the weather files used by energy building simulation software to calculate the thermal performance of buildings and their energy efficiency. Currently, atmospheric down-welling radiation is usually measured by a pyrgeometer, for radiation beyond 3μm. This is expensive and bulky. A simple methodology for measurement and calculation, with good accuracy, of average atmospheric long-wave down-welling radiation using a tilted, low-cost infrared thermometer is described. Tilt setting, comparison to data gathered by the pyrgeometer, and comparison of simulation studies with both data sets is described. A link of the magnitude of divergence between instant data pairs and radiant intensity is demonstrated and shown to depend on asymmetry in cloud density. © 2014 Elsevier Ltd."
"55681565300;26325911300;7004807312;","Atmospheric consequences of disruption of the ocean thermocline",2015,"10.1088/1748-9326/10/3/034016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925424021&doi=10.1088%2f1748-9326%2f10%2f3%2f034016&partnerID=40&md5=4e8726d62099bd4e3c75c96950ea8076","Technologies utilizing vertical ocean pipes have been proposed as a means to avoid global warming, either by providing a source of clean energy, increasing ocean carbon uptake, or storing thermal energy in the deep ocean. However, increased vertical transport of water has the capacity to drastically alter the ocean thermocline. To help bound potential climate consequences of these activities, we perform a set of simulations involving idealized disruption of the ocean thermocline by greatly increasing vertical mixing in the upper ocean. We use an Earth System Model (ESM) to evaluate the likely thermal and hydrological response of the atmosphere to this scenario. In our model, increased vertical transport in the upper ocean decreases upward shortwave and longwave radiation at the top-of-the-atmosphere due primarily to loss of clouds and sea-ice over the ocean. This extreme scenario causes an effective radiative forcing of ≈15.5-15.9 W m-2, with simulations behaving on multi-decadal time scales as if they are approaching an equilibrium temperature ≈8.6-8.8 °C higher than controls. Within a century, this produces higher global mean surface temperatures than would have occurred in the absence of increased vertical ocean transport. In our simulations, disruption of the thermocline strongly cools the lower atmosphere over the ocean, resulting in high pressure anomalies. The greater land-sea pressure contrast is found to increase water vapour transport from ocean to land in the lower atmosphere and therefore increase global mean precipitation minus evaporation (P-E) over land; however, many high latitude regions and some low latitude regions experience decreased P-E. Any real implementation of ocean pipe technologies would damage the thermal structure of the ocean to a lesser extent than simulated here; nevertheless, our simulations indicate the likely sign and character of unintended atmospheric consequences of such ocean technologies. Prolonged application of ocean pipe technologies, rather than avoiding global warming, could exacerbate long-term warming of the climate system. © 2015 IOP Publishing Ltd."
"26537088900;55598938800;8686475900;","Numerical simulation of the interaction between ammonium nitrate aerosol and convective boundary-layer dynamics",2015,"10.1016/j.atmosenv.2015.01.048","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921833140&doi=10.1016%2fj.atmosenv.2015.01.048&partnerID=40&md5=695a286f3b40e3b26f8dee09f04ce757","We investigate the interaction between the ammonium nitrate aerosol (NAO3) abundance and convective boundary-layer (CBL) dynamics by means of a large-eddy simulation (LES) framework. In our LES model the CBL dynamics is solved coupled with radiation, chemistry, and surface exchange. Concerning the aerosol coupling we assume a simplified representation that accounts for black carbon, aerosol water and inorganic aerosols, focusing on the semi-volatile ammonium nitrate aerosol within the CBL. The aerosol absorption and scattering of shortwave radiation is also taken into consideration. We use a data set of observations taken at the Cabauw Experimental Site for Atmospheric Research during the IMPACT/EUCAARI (European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions) campaign to successfully evaluate our LES approach. We highlight that our LES framework reproduces the observations of the ratio between gas-phase nitrate and total nitrate at the surface, with a diurnally-averaged overestimation of only ≈12%. We show that the dependence between gas-aerosol conversion of nitrate and CBL (thermo)dynamics produces highly non-linear concentration and turbulent flux vertical profiles. The flux profiles maximize at around 1/3 of the CBL. Close to the surface, we show that the outgassing of NAO3 affects the dry deposition of nitrate. This outgassing is responsible for the high deposition velocities obtained from the concentration and flux measurements during observational campaigns. To account for the influence of CBL (thermo)dynamics on gas-aerosol conversion we propose an effective turbulent exchange coefficient based on an analysis of the flux budget equation of aerosol nitrate calculated by our LES. The implementation of this effective turbulent exchange coefficient in a 1D model leads to a better agreement with the LES results and with surface observations. © 2015 Elsevier Ltd."
"37040691400;55218162500;16200107900;57205497099;25029309200;7402711358;57200319386;","Measurements of CH3O2NO2 in the upper troposphere",2015,"10.5194/amt-8-987-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924061077&doi=10.5194%2famt-8-987-2015&partnerID=40&md5=bb7fedbff45e2b07fb202feb44fbf329","Methyl peroxy nitrate (CH3O2NO2) is a non-acyl peroxy nitrate that is important for photochemistry at low temperatures characteristic of the upper troposphere. We report the first measurements of CH3O2NO2, which we achieved through a new aircraft inlet configuration, combined with thermal-dissociation laser-induced fluorescence (TD-LIF) detection of NO2, and describe the accuracy, specificity, and interferences to CH3O2NO2 measurements. CH3O2NO2 is predicted to be a ubiquitous interference to upper-tropospheric NO2 measurements. We describe an experimental strategy for obtaining NO2 observations free of the CH3O2NO2 interference. Using these new methods, we made observations during two recent aircraft campaigns: the Deep Convective Clouds and Chemistry (DC-3) and the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) experiments. The CH3O2NO2 measurements we report have a detection limit (S/N = 2) of 15 pptv at 1 min averaging on a background of 200 pptv NO2 and an accuracy of ±40%. Observations are used to constrain the interference of pernitric acid (HO2NO2) to the CH3O2NO2 measurements, as HO2NO2 partially decomposes (∼11%) along with CH3O2NO2 in the heated CH3O2NO2 channel used to detect CH3O2NO2. © Author(s) 2015."
"35334472800;7404247296;8280398300;57202099430;","Contribution of liquid, NAT and ice particles to chlorine activation and ozone depletion in Antarctic winter and spring",2015,"10.5194/acp-15-2019-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923531430&doi=10.5194%2facp-15-2019-2015&partnerID=40&md5=608f8840e40fdb057e01b3ed036a163f","Heterogeneous reactions in the Antarctic stratosphere are the cause of chlorine activation and ozone depletion, but the relative roles of different types of polar stratospheric clouds (PSCs) in chlorine activation is an open question. We use multi-year simulations of the chemistry-climate model ECHAM5/MESSy for Atmospheric Chemistry (EMAC) to investigate the impact that the various types of PSCs have on Antarctic chlorine activation and ozone loss. One standard and three sensitivity EMAC simulations have been performed. In all simulations a Newtonian relaxation technique using the ERA-Interim reanalysis was applied to simulate realistic synoptic conditions. In the three sensitivity simulations, we only changed the heterogeneous chemistry on PSC particles by switching the chemistry on liquid, nitric acid trihydrate (NAT) and ice particles on and off. The results of these simulations show that the significance of heterogeneous reactions on NAT and ice particles for chlorine activation and ozone depletion in Antarctic winter and spring is small in comparison to the significance of heterogeneous reactions on liquid particles. Liquid particles alone are sufficient to activate almost all of the available chlorine, with the exception of the upper PSC regions between 10 and 30 hPa, where temporarily ice particles show a relevant contribution. Shortly after the first PSC occurrence, NAT particles contribute a small fraction to chlorine activation. Heterogeneous chemistry on liquid particles is responsible for more than 90% of the ozone depletion in Antarctic spring in the model simulations. In high southern latitudes, heterogeneous chemistry on ice particles causes only up to 5 DU of additional ozone depletion in the column and heterogeneous chemistry on NAT particles less than 0.5 DU. The simulated HNO3, ClO and O3 results agree closely with observations from the Microwave Limb Sounder (MLS) onboard NASA's Aura satellite. © Author(s) 2015."
"56522768500;56522444900;56522882300;","Satellite-based climatology of low-level continental clouds in southern West Africa during the summer monsoon season",2015,"10.1002/2014JD022614","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923649637&doi=10.1002%2f2014JD022614&partnerID=40&md5=63a3f255460bf14180e3ce2754376a6d","Synoptic observations and various satellite products have been utilized for computing climatologies of low-level stratus over southern West Africa for the wet monsoon seasons July-September of 2006-2011. Previous studies found inconsistencies between satellite cloud products; climate models often fail to reproduce the extensive stratus decks. Therefore, a better observational reference and an understanding of its limitations are urgently needed to better validate models. Most detailed information of the spatiotemporal characteristics of low-level clouds was obtained from two Meteosat Second Generation (MSG) satellite-based data sets. However, CALIPSO and CloudSat cross sections of cloud occurrence frequency suggest that both MSG products underestimate the low-level cloudiness over Nigeria due to shielding by abundant upper level and midlevel clouds and reveal that the stratus is lower over the continent than over the ocean. The Terra Multiangle Imaging Spectroradiometer product appears to overestimate the morning extent of low-level clouds. The climatology presented here shows that the zone of abundant low-level stratiform clouds is at its diurnal minimum south of 6-7°N around sunset (~1800 UTC). Thereafter, it starts to spread inland and reaches its maximum northward extent of 10-11°N between 0900 and 1000 UTC. The maximum affected area is approximately 800,000 km2. After about 1000 UTC, the northern boundary gets fragmented due to the breakup of stratus decks into fair-weather cumuli. The stratus is most frequent around Cape Palmas, over Ivory Coast, and at the windward sides of the Mampong Range (Ghana) and Oshogbo Hills (Nigeria). © 2015. American Geophysical Union. All Rights Reserved."
"26645901500;7004468723;55325353200;23395171500;57203260074;","Projected increase in diurnal and interdiurnal variations of European summer temperatures",2015,"10.1002/2014GL062531","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925086424&doi=10.1002%2f2014GL062531&partnerID=40&md5=2333772aa09661e680cf67a25407998f","Beyond the mean warming, climate change may modify the temperature variability, with consequences on extreme events causing societal and environmental impacts. Here we assess future changes in both the interdiurnal variability (ITV) and diurnal range (DTR) of European summer temperatures based on Fifth Phase of the Coupled Model Intercomparison Project projections under three 21st century scenarios. Both indices are projected to increase, with a rather good model agreement on the sign, while uncertainties remain on the amplitude. Extremely high day-to-day and diurnal temperature variations are expected to occur more frequently. Across models and scenarios, ITV and DTR increases vary primarily as functions of the decrease in surface evapotranspiration linked to the European summer drying. They are also partly explained by changes in the atmospheric dynamics and the surface cloud radiative effect. Model-dependent degrees of control of (i) ITV and DTR by mean temperature and (ii) surface evapotranspiration by soil moisture appear as helpful metrics to reduce future uncertainties in ITV and DTR projections. © 2015 The Authors."
"28568055900;16550482700;7201483081;6602403713;6602784254;6603631763;7402942478;15047918700;6602137800;7102294773;","Central American biomass burning smoke can increase tornado severity in the U.S.",2015,"10.1002/2014GL062826","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925144120&doi=10.1002%2f2014GL062826&partnerID=40&md5=e2141355dab9ed9231a146d2d2a2fc4c","Tornadoes in the Southeast and central U.S. are episodically accompanied by smoke from biomass burning in central America. Analysis of the 27 April 2011 historical tornado outbreak shows that adding smoke to an environment already conducive to severe thunderstorm development can increase the likelihood of significant tornado occurrence. Numerical experiments indicate that the presence of smoke during this event leads to optical thickening of shallow clouds while soot within the smoke enhances the capping inversion through radiation absorption. The smoke effects are consistent with measurements of clouds and radiation before and during the outbreak. These effects result in lower cloud bases and stronger low-level wind shear in the warm sector of the extratropical cyclone generating the outbreak, two indicators of higher probability of tornadogenesis and tornado intensity and longevity. These mechanisms may contribute to tornado modulation by aerosols, highlighting the need to consider aerosol feedbacks in numerical severe weather forecasting. © 2015 The Authors."
"55670345400;7006698304;7101661890;","The consequences of a local approach in statistical models of convection on its large-scale coherence",2015,"10.1002/2014JD022680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923610633&doi=10.1002%2f2014JD022680&partnerID=40&md5=c0cfb41f92a391c36b97eb7133a56a58","Organized tropical convection is a crucial mechanism in the climate system, but its representation in climate models through parametrization schemes has numerous shortcomings. One of these shortcomings is that they are deterministic despite the statistical nature of the relationship they are representing. Several attempts at devising a stochastic parametrization scheme have been made, many of which assume a local approach, that is, one in which the convection in a grid box is determined without consideration of the previous time steps and the surrounding boxes. This study seeks to explore the effect of this assumption on the coherence of convection using cloud regimes, which represent various modes of tropical convection. First, we analyze the coherence of observed convection beyond the typical size of a model grid box and time step. Then, we evaluate the consequences of the local assumption on this coherence in simple statistical models. Cloud regimes in the real world show high degrees of coherence, manifesting in their lifetimes, areas, and inter-regime relationships. However, in a local statistical model, they are too small, too short-lived, and have incorrect relationships between each other. This can be improved by incorporating time memory and spatial dependence in the modeling. Our results imply that a local approach to a statistical representation of convection is not viable, and a statistical model must account for nonlocal influence in order to have large-scale convective coherence that more closely resembles the real world. © 2015. American Geophysical Union. All Rights Reserved."
"6603580448;7404291795;7102663296;35551376300;","Extending the long-term record of volcanic SO2 emissions with the Ozone Mapping and Profiler Suite nadir mapper",2015,"10.1002/2014GL062437","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925132320&doi=10.1002%2f2014GL062437&partnerID=40&md5=fded640b12d46298c6d909361ccc7fc4","Uninterrupted, global space-based monitoring of volcanic sulfur dioxide (SO2) emissions is critical for climate modeling and aviation hazard mitigation. We report the first volcanic SO2 measurements using ultraviolet (UV) Ozone Mapping and Profiler Suite (OMPS) nadir mapper data. OMPS was launched on the Suomi National Polar-orbiting Partnership satellite in October 2011. We demonstrate the sensitivity of OMPS SO2 measurements by quantifying SO2 emissions from the modest eruption of Paluweh volcano (Indonesia) in February 2013 and tracking the dispersion of the volcanic SO2 cloud. The OMPS SO2 retrievals are validated using Ozone Monitoring Instrument and Atmospheric Infrared Sounder measurements. The results confirm the ability of OMPS to extend the long-term record of volcanic SO2 emissions based on UV satellite observations. We also show that the Paluweh volcanic SO2 reached the lower stratosphere, further demonstrating the impact of small tropical volcanic eruptions on stratospheric aerosol optical depth and climate. © 2015 The Authors."
"55788217100;24537168200;7006837187;55783064400;6701796926;13405658600;","Aged boreal biomass-burning aerosol size distributions from BORTAS 2011",2015,"10.5194/acp-15-1633-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923078156&doi=10.5194%2facp-15-1633-2015&partnerID=40&md5=7f0eb573d69728aba1d833dc677ca58c","Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number-size distributions in climate model inventories lead to uncertainties in the CCN (cloud condensation nuclei) concentrations and forcing estimates derived from these models. <br><br> The BORTAS-B (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellite) measurement campaign was designed to sample boreal biomass-burning outflow over eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size distribution of aged biomass-burning emissions (aged ∼ 1-2 days) from boreal wildfires in northwestern Ontario. The composite median size distribution yields a single dominant accumulation mode with <i>D</i>pm Combining double low line 230 nm (number-median diameter) and &sigma; Combining double low line 1.5, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (Î""OA/Î""CO) along the path of Flight b622 show values of 0.09-0.17 Î1/4g mg'3 ppbvg'1 (parts per billion by volume) with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA (organic aerosol) production/evaporation within the aged plume over the sampling period (plume age: 1-2 days), though it does not preclude OA production/loss at earlier stages. <br><br> A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the δOA/δCO enhancement ratios. We estimate that the young-plume median diameter was in the range of 59-94 nm with modal widths in the range of 1.7-2.8 (the ranges are due to uncertainty in the entrainment rate). Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in the plume dilution rates. © 2015 Author (s)."
"37261023300;7404297096;6701823396;7004423756;","Verification of air/surface humidity differences from AIRS and ERA-Interim in support of turbulent flux estimation in the Arctic",2015,"10.1002/2014JD021666","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923558116&doi=10.1002%2f2014JD021666&partnerID=40&md5=28957fa1d5c7d9ab17fb25f5b3e9934f","Evaporation from the Arctic Ocean and its marginal seas is essential for air moisture, cloudiness, and precipitation, as well as for the associated feedbacks, which contribute to the Arctic amplification of climate warming. However, evaporation in the Arctic is still associated with large uncertainties. The Boisvert et al. (2013) moisture flux scheme (BMF13) is based on application of the Atmospheric Infrared Sounder (AIRS) data, which produces high-quality, global, daily atmospheric temperature and moisture profiles even in the presence of clouds. Comparing the results of BMF13 against the ERA-Interim reanalysis, we found differences up to 55Wm-2 in the surface latent heat flux in the Beaufort-East Siberian Seas (BESS). We found out that the quality of the input data for the BMF13 and ERA-Interim flux schemes was the main cause for the differences. Differences in the input data sets cause moisture flux estimates to differ up to 1.6 × 10-2gm-2 s-1 (40Wm-2 latent heat flux) in the BESS region, when both data sets were applied to the BMF13 scheme. Thus, the input data sets, AIRS version 6 and ERA-Interim reanalysis, were compared with a variety of in situ data. In skin temperature ERA-Interim had twice as large an error as AIRS version 6, but smaller errors in air specific humidity. The results suggested that AIRS data and the BMF13 scheme are a good option to estimate the moisture flux in the Arctic. However, the differences detected demonstrate a need for more in situ measurements of air temperature and humidity in the Arctic. © 2015. American Geophysical Union. All Rights Reserved."
"16642923700;55390996400;56421162500;56190565900;56189792300;56421494700;23995988300;57203073322;","Effects of cumulus clouds on microclimate and shoot-level photosynthetic gas exchange in Picea engelmannii and Abies lasiocarpa at treeline, Medicine Bow Mountains, Wyoming, USA",2015,"10.1016/j.agrformet.2014.10.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911403362&doi=10.1016%2fj.agrformet.2014.10.012&partnerID=40&md5=c98d839d8597111343486f4b9d9df37d","Here we describe the dynamic effects of cumulus clouds on microclimate and shoot-level photosynthetic gas exchange in saplings of two treeline conifer species-Picea engelmannii and Abies lasiocarpa. Measurements were made during both clear-sky and partly cloudy conditions (~10-70% cumulus cloud cover) throughout the 2012 growing season within an alpine-treeline ecotone. Cumulus clouds generated dynamic fluctuations in photosynthetically active radiation (PAR), higher maximum PAR (&gt;2500μmolm-2s-1), 2-4 fold increases in diffuse PAR, reduced daily mean and cumulative PAR, lower needle temperatures, and reduced leaf-to-air vapor pressure differences relative to clear-sky conditions. Onset of cloud-shade corresponded with declines in photosynthesis, needle temperatures, and evapotranspiration, which were proportional to cloud duration and opacity. Despite increased diffuse light and greater sunlight intensity during cloud-gaps, photosynthesis was never higher on partly cloudy days compared to clear days in either species, during cloud-gaps or cloud-shade. However, reduced transpiration paired with photosynthesis comparable with clear-sky levels during cloud-gaps resulted in greater instantaneous water use efficiency relative to clear-sky measurements. There was no apparent photoinhibition of photosynthesis reflected in gas exchange measurements in response to abrupt and dramatic changes in PAR levels caused by cumulus clouds. We conclude that cumulus clouds reduce instantaneous and daily carbon gain, although lower needle temperatures and associated reductions in transpirational water loss may alleviate daily and seasonal water stress, thereby enhancing carbon gain over the growing season. © 2014 Elsevier B.V."
"8891521600;55372257600;7801693068;7202069518;","Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: Methodology",2015,"10.5194/amt-8-611-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922453803&doi=10.5194%2famt-8-611-2015&partnerID=40&md5=506327c84dff79a59902a4266fae806d","The top-of-atmosphere (TOA) radiative fluxes are critical components to advancing our understanding of the Earth's radiative energy balance, radiative effects of clouds and aerosols, and climate feedback. The Clouds and the Earth's Radiant Energy System (CERES) instruments provide broadband shortwave and longwave radiance measurements. These radiances are converted to fluxes by using scene-type-dependent angular distribution models (ADMs). This paper describes the next-generation ADMs that are developed for Terra and Aqua using all available CERES rotating azimuth plane radiance measurements. Coincident cloud and aerosol retrievals, and radiance measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological parameters from Goddard Earth Observing System (GEOS) data assimilation version 5.4.1 are used to define scene type. CERES radiance measurements are stratified by scene type and by other parameters that are important for determining the anisotropy of the given scene type. Anisotropic factors are then defined either for discrete intervals of relevant parameters or as a continuous functions of combined parameters, depending on the scene type. Significant differences between the ADMs described in this paper and the existing ADMs are over clear-sky scene types and polar scene types. Over clear ocean, we developed a set of shortwave (SW) ADMs that explicitly account for aerosols. Over clear land, the SW ADMs are developed for every 1° latitude × 1° longitude region for every calendar month using a kernel-based bidirectional reflectance model. Over clear Antarctic scenes, SW ADMs are developed by accounting the effects of sastrugi on anisotropy. Over sea ice, a sea-ice brightness index is used to classify the scene type. Under cloudy conditions over all surface types, the longwave (LW) and window (WN) ADMs are developed by combining surface and cloud-top temperature, surface and cloud emissivity, cloud fraction, and precipitable water. Compared to the existing ADMs, the new ADMs change the monthly mean instantaneous fluxes by up to 5 W mg-2 on a regional scale of 1° latitude × 1° longitude, but the flux changes are less than 0.5 W mg-2 on a global scale. © Author(s) 2015."
"14030547700;57189186147;55233816400;57190125016;6603159386;","Summer drought and ENSO-related cloudiness distinctly drive Fagus sylvatica growth near the species rear-edge in northern Spain",2015,"10.1016/j.agrformet.2014.11.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911496106&doi=10.1016%2fj.agrformet.2014.11.012&partnerID=40&md5=edb87160fee242caab9f45c71e1de977","The ample distribution of common beech (Fagus sylvatica) across Europe implies that this key tree species occurs under a broad variety of climatic conditions despite its sensitivity to drought stress. Iberian beech rear-edge (southernmost) forests are located along the boundary between the Eurosiberian and Mediterranean biogeographical regions. Therefore, those forests are considered to be sensitive monitors of the effects of warming-induced drought stress on marginal tree populations. We evaluate if the radial growth of Iberian beech populations is mainly constrained by drought. Since previous findings indicated that El Niño-Southern Oscillation (ENSO) teleconnections may influence the rainfall regime in northern Spain, we also assessed if beech response to drought and water availability is modulated by this large-scale climatic pattern. We compared the recent growth patterns and responses to climate across a network of 30 tree-ring site chronologies established throughout northern Spain where beech forests are subjected to contrasting climatic conditions. Iberian beech populations located near or within the Mediterranean biogeographical region were the most sensitive to June water deficit. However, the dependency of beech growth on drought stress near the rear-edge of the species was mitigated where cloudy conditions prevail in summer, namely in mesic stands located in the Eurosiberian region. Drought stress in the latter populations was alleviated by cloudiness, which in turn depended on ENSO, and this effect on growth has been intensifying for the last decades. We prove that the sensitivity of rear-edge populations to drought, in terms of growth reduction, is greatly modulated by local or regional environmental gradients, but also by the influence of large-scale climatic variation. © 2014 Elsevier B.V."
"55509364700;35114996800;16426140700;8380252900;25928285500;36486362800;","Multichannel analysis of correlation length of SEVIRI images around ground-based cloud observatories to determine their representativeness",2015,"10.5194/amt-8-567-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922569141&doi=10.5194%2famt-8-567-2015&partnerID=40&md5=e860b05e0d791f50398ef92b66c62331","Images of measured radiance in different channels of the geostationary Meteosat-9 SEVIRI instrument are analysed with respect to the representativeness of the observations of eight cloud observatories in Europe (e.g. measurements from cloud radars or microwave radiometers). Cloudy situations are selected to get a time series for every pixel in a 300 km × 300 km area centred around each ground station. Then a cross correlation of each time series to the pixel nearest to the corresponding ground site is calculated. In the end a correlation length is calculated to define the representativeness. It is found that measurements in the visible and near infrared channels, which respond to cloud physical properties, are correlated in an area with a 1 to 4 km radius, while the thermal channels, that correspond to cloud top temperature, are correlated to a distance of about 20 km. This also points to a higher variability of the cloud microphysical properties inside a cloud than of the cloud top temperature. The correlation length even increases for the channels at 6.2, 7.3 and 9.7 μm. They respond to radiation from the upper atmospheric layers emitted by atmospheric gases and higher level clouds, which are more homogeneous than low-level clouds. Additionally, correlations at different distances, corresponding to the grid box sizes of forecast models, were compared. The results suggest the possibility of comparisons between instantaneous cloud observations from ground sites and regional forecast models and ground-based measurements. For larger distances typical for global models the correlations decrease, especially for short-wave measurements and corresponding cloud products. By comparing daily means, the correlation length of each station is increased to about 3 to 10 times the value of instantaneous measurements and also the comparability to models grows. © 2015 Author(s)."
"56531367400;55628589750;","How thermodynamic environments control stratocumulus microphysics and interactions with aerosols",2015,"10.1088/1748-9326/10/2/024004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923787514&doi=10.1088%2f1748-9326%2f10%2f2%2f024004&partnerID=40&md5=549e35ed195c5f3d04ced75c3aab66df","Aerosol-cloud interactions are central to climate system changes and depend on meteorological conditions. This study identifies distinct thermodynamic regimes and proposes a conceptual framework for interpreting aerosol effects. In the analysis, ten years (2003-2012) of daily satellite-derived aerosol and cloud products are combined with reanalysis data to identify factors controlling Southeast Atlantic stratocumulus microphysics. Considering the seasonal influence of aerosol input from biomass burning, thermodynamic environments that feature contrasting microphysical cloud properties and aerosol-cloud relations are classified. While aerosol impact is stronger in unstable environments, it is mostly confined to situations with low aerosol loading (aerosol index AI ≲ 0.15), implying a saturation of aerosol effects. Situations with high aerosol loading are associated with weaker, seasonally contrasting aerosol-droplet size relationships, likely caused by thermodynamically induced processes and aerosol swelling. © 2015 IOP Publishing Ltd."
"7402866430;56527094700;55871853200;57208685340;","Cloud climatology over the oceanic regions adjacent to the Indian Subcontinent: inter-comparison between passive and active sensors",2015,"10.1080/01431161.2014.1001082","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923354646&doi=10.1080%2f01431161.2014.1001082&partnerID=40&md5=1ed907d61a3f4cc75f6e4a019e0b1432","Understanding the cloud vertical structure and its variation in space and time is important to reduce the uncertainty in climate forcing. Here, we present the cloud climatology over the oceanic regions (Arabian Sea, Bay of Bengal, and South Indian Ocean) adjacent to the Indian subcontinent using data from the Multiangle Imaging Spectroradiometer (MISR), Moderate Resolution Imaging Spectroradiometer (MODIS), GCM-Oriented CALIPSO Cloud Product (GOCCP), and International Satellite Cloud Climatology Project (ISCCP). Fractional cloud cover (fc) shows stronger seasonal variations over the Arabian Sea (mean annual fc lies in the range 0.5–0.61) and Bay of Bengal (mean annual fc lies in the range 0.69–0.75) relative to the South Indian Ocean (mean annual fc lies in the range 0.64–0.71). Inter-comparison of statistics from passive (MISR, MODIS and ISCCP) and active (GOCCP) sensors reveals the challenges in interpreting satellite data for climate implications. While MISR detects more low clouds because of its stereo technique, MODIS and ISCCP detect more high clouds because of their radiometric techniques. Therefore, a combination of these two techniques in passive sensors may lead to more realistic understanding of the cloud vertical structure. GOCCP (active sensor) can detect multilayer cloud, but accuracy reduces if the high clouds are optically thick. A dominance of low and high clouds throughout the year is observed in these regions, where cumulus and cirrus dominate among low and high clouds, respectively. © 2015 Taylor & Francis."
"7005536590;","Evaluation of ISCCP cloud amount with MODIS observations",2015,"10.1016/j.atmosres.2014.09.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911378137&doi=10.1016%2fj.atmosres.2014.09.006&partnerID=40&md5=8982be974f11e8cc3e66bf82a8f3d95c","The goal of the International Satellite Cloud Climatology Project (ISCCP) is to provide global cloud amount statistics for atmospheric radiation flux modeling, which is a key element of climate change studies. However, ISCCP estimates rely on two spectral channels only, while the most advanced satellite sensors offer over 20 spectral bands, and thus a higher probability of correct cloud detection. We validated the accuracy of ISCCP mean monthly cloud amount statistics using the state-of-the-art, 36-spectral channel Moderate-resolution Imaging Spectroradiometer (MODIS) instrument aboard the Terra and Aqua satellites. Based on the MODIS Level 2 Cloud Mask we developed a dedicated Level 3 product for Central Europe (2004-2009). For the first time, MODIS swath data were projected onto an ISCCP equal-area grid, which guaranteed an exact geometrical agreement between both climatologies. Results showed that there was a close correlation between ISCCP and MODIS data (ρ = 0.872, α. = 0.99), especially at warmer part of the year (ρ ≥. 0.940, α. >. 0.99). However, ISCCP estimations were found to be unreliable in wintertime when surface was covered with snow. The presence of snow resulted in a significant underestimate of cloud amount by 0.45 for individual ISCCP grid boxes. Our results suggest that MODIS cloud climatology is more reliable when estimates of mean monthly cloud amount are required. © 2014 Elsevier B.V."
"55438009600;56448067500;55645567200;7201381456;57154891500;","Influence of regional climate change on meteorological characteristics and their subsequent effect on ozone dispersion in Taiwan",2015,"10.1016/j.atmosenv.2014.12.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84918508254&doi=10.1016%2fj.atmosenv.2014.12.020&partnerID=40&md5=4d600d8943e8945cb6b7a1221506f4e2","The objective of this study is to understand the influence of regional climate change on local meteorological conditions and their subsequent effect on local ozone (O3) dispersion in Taiwan. The 33-year NCEP-DOE Reanalysis 2 (NNR2) data set (1979-2011) was analyzed to understand the variations in regional-scale atmospheric conditions in East Asia and the western North Pacific. To save computational processing time, two scenarios representative of past (1979-86) and current (2004-11) atmospheric conditions were selected but only targeting the autumn season (September, October and November) when the O3 concentrations were at high levels. Numerical simulations were performed using weather research and forecasting (WRF) model and Community Multiscale Air Quality (CMAQ) model for the past and current scenarios individually but only for the month of October because of limited computational resources.Analysis of NNR2 data exhibited increased air temperature, weakened Asian continental anticyclone, enhanced northeasterly monsoonal flow, and a deepened low-pressure system forming near Taiwan. With enhanced evaporation from oceans along with a deepened low-pressure system, precipitation amounts increased in Taiwan in the current scenario. As demonstrated in the WRF simulation, the land surface physical process responded to the enhanced precipitation resulting in damper soil conditions, and reduced ground temperatures that in turn restricted the development of boundary layer height. The weakened land-sea breeze flow was simulated in the current scenario. With reduced dispersion capability, air pollutants would tend to accumulate near the emission source leading to a degradation of air quality in this region. The conditions would be even worse in southwestern Taiwan due to the fact that stagnant wind fields would occur more frequently in the current scenario. On the other hand, in northern Taiwan, the simulated O3 concentrations are lower during the day in the current scenario due to the enhanced cloud conditions and reduced solar radiation. © 2014 Elsevier Ltd."
"55355823000;23108890800;36562388300;55575063800;34882516100;57194964847;","Use of Landsat TM/ETM+ to monitor the spatial and temporal extent of spring breakup floods in the Lena River, Siberia",2015,"10.1080/01431161.2014.995271","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923339267&doi=10.1080%2f01431161.2014.995271&partnerID=40&md5=8776733ec161469a4fe1c7b2db27ae87","A warmer-than-normal air temperature enhances the probability of extreme hydrologic events. A spring breakup flood is among the most serious hydrologic events in high-latitude regions. This study examined the use of Landsat Thematic Mapper/Enhanced Thematic Mapper Plus (TM/ETM+) to monitor the spatial and temporal extent of spring breakup floods in the Lena River, Siberia. Although the 30 m spatial resolution of Landsat produced a detailed mapping of the floodplain, acquisition of Landsat images at short-term intervals was difficult because of the long revisit time of Landsat (16 days) and the frequent cloud cover over Siberia. However, information from two sensors (i.e. TM and ETM+) was combined to essentially halve the revisit time. Moreover, frequent Landsat images were acquired at higher latitudes by using information from overlap areas between neighbouring path images. Therefore, the average revisit time was determined to be 2.6 (= 16/3/2) days in the triple overlap area using two sensors. Updated data sets with a high temporal frequency enhanced the ability to monitor the spatial and temporal extent of the spring breakup floods, although the area was small. In addition, the neighbouring Landsat images themselves were used for large-scale monitoring of breakup floods, given that Landsat overpasses from west to east operating in a near-polar sun-synchronous orbit with a progression speed that is almost the same as the speed of a spring breakup flood. In 2007, spring breakup floods were successively monitored from Solyanka to Yakutsk. Reliable and timely information for large-area monitoring of floods was crucial to understand better the influence on regional hydrology and climate. The images from Landsat TM/ETM+ sensors were regarded as a suitable data source for operational use in flood monitoring due to the wide geographic coverage, high temporal resolution, adequate spatial resolution, and minimal cost. © 2015 Taylor & Francis."
"8856938500;36449157300;36921601500;55921861500;12804309300;7003871110;35775264900;6603871013;6603480361;","Inclusion of mountain-wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry-climate model",2015,"10.5194/acp-15-1071-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922010094&doi=10.5194%2facp-15-1071-2015&partnerID=40&md5=43a5088b4dab9beee3040457b6597a0d","An important source of polar stratospheric clouds (PSCs), which play a crucial role in controlling polar stratospheric ozone depletion, is from the temperature fluctuations induced by mountain waves. However, this formation mechanism is usually missing in chemistry-climate models because these temperature fluctuations are neither resolved nor parameterised. Here, we investigate the representation of stratospheric mountain-wave-induced temperature fluctuations by the UK Met Office Unified Model (UM) at climate scale and mesoscale against Atmospheric Infrared Sounder satellite observations for three case studies over the Antarctic Peninsula. At a high horizontal resolution (4 km) the regional mesoscale configuration of the UM correctly simulates the magnitude, timing, and location of the measured temperature fluctuations. By comparison, at a low horizontal resolution (2.5° &times; 3.75°) the global climate configuration fails to resolve such disturbances. However, it is demonstrated that the temperature fluctuations computed by a mountain wave parameterisation scheme inserted into the climate configuration (which computes the temperature fluctuations due to unresolved mountain waves) are in relatively good agreement with the mesoscale configuration responses for two of the three case studies. The parameterisation was used to include the simulation of mountain-wave-induced PSCs in the global chemistry-climate configuration of the UM. A subsequent sensitivity study demonstrated that regional PSCs increased by up to 50% during July over the Antarctic Peninsula following the inclusion of the local mountain-wave-induced cooling phase. © 2015 Author(s)."
"6603627233;35331416200;7201716828;56289106200;12143017100;57211224269;","Future increase of supertyphoon intensity associated with climate change",2015,"10.1002/2014GL061793","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923575201&doi=10.1002%2f2014GL061793&partnerID=40&md5=57eb0c97253dbe14ca2e2955824f405d","Increases of tropical cyclone intensity with global warming have been demonstrated by historical data studies and theory. This raises great concern regarding future changes in typhoon intensity. The present study addressed the problem to what extent supertyphoons will become intense in the global warming climate of the late 21st century. Very high resolution downscale experiments using a cloud-resolving model without convective parameterizations were performed for the 30 most intense typhoons obtained from the 20 km mesh global simulation of a warmer climate. Twelve supertyphoons occurred in the downscale experiments, and the most intense supertyphoon attained a central pressure of 857 hPa and a wind speed of 88 m s-1. The maximum intensity of the supertyphoon was little affected by uncertainties that arise from experimental settings. This study indicates that the most intense future supertyphoon could attain wind speeds of 85-90 m s-1 and minimum central pressures of 860 hPa. © 2015. American Geophysical Union. All Rights Reserved."
"7403564495;15032788000;","Effects of Arctic haze on surface cloud radiative forcing",2015,"10.1002/2014GL062015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923533017&doi=10.1002%2f2014GL062015&partnerID=40&md5=d5d741fe30b3267a66f1d2656864b9df","From 4years of observations from Barrow, Alaska, it is shown that the cloud radiative impact on the surface is a net warming effect between October and May and a net cooling in summer. During episodes of high surface haze aerosol concentrations and cloudy skies, both the net warming and net cooling are amplified, ranging from +12.2 Wm-2 in February to -11.8 Wm-2 in August. In liquid clouds, approximately 50%-70% of this change is caused by changes in cloud particle effective radius, with the remainder being caused by unknown atmospheric feedbacks that increase cloud water path. While the yearly averaged warming and cooling effects nearly cancel, the timing of the forcing may be a relevant control of the amplitude and timing of sea ice melt. © 2015. American Geophysical Union. All Rights Reserved."
"57217772325;7410041005;54783792600;55717074000;56119479900;7202708481;","Global dust distribution from improved thin dust layer detection using A-train satellite lidar observations",2015,"10.1002/2014GL062111","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923543866&doi=10.1002%2f2014GL062111&partnerID=40&md5=abb1088e773592433e1ba1cfc27fd764","A new dust detection algorithm was developed to take advantage of strong dust signals in the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) 532 nm perpendicular channel to more accurately identify optically thin dust layer boundaries. Layer mean particulate depolarization ratios and improved thin ice cloud detections by combining CALIPSO and CloudSat products were used to further refine the dust mask. Three year global mean results show that the new method detects dust occurrences total detected dust case numbertotal observation number of 0.12 and 0.028 below and above 4 km altitudes, while CALIPSO Level 2 products reported 0.07 and 0.012, respectively. The improvements are mainly in weak source and transporting regions, and the upper troposphere, where optically thin, but significant dust layers from the point of view of aerosol-cloud interactions are dominated. The results can help us to better understand global dust transportation and dust-cloud interactions and improve model simulations. © 2015. American Geophysical Union. All Rights Reserved."
"14044758700;7402445326;55898865500;35569458500;7103291287;6602087140;","Volcanic ash layer depth: Processes and mechanisms",2015,"10.1002/2014GL062454","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923549852&doi=10.1002%2f2014GL062454&partnerID=40&md5=2a7c3b69a96a4ebe479911122eda98f9","The long duration of the 2010 Eyjafjallajökull eruption provided a unique opportunity to measure a widely dispersed volcanic ash cloud. Layers of volcanic ash were observed by the European Aerosol Research Lidar Network with a mean depth of 1.2 km and standard deviation of 0.9 km. In this paper we evaluate the ability of the Met Office's Numerical Atmospheric-dispersion Modelling Environment (NAME) to simulate the observed ash layers and examine the processes controlling their depth. NAME simulates distal ash layer depths exceptionally well with a mean depth of 1.2 km and standard deviation of 0.7 km. The dominant process determining the depth of ash layers over Europe is the balance between the vertical wind shear (which acts to reduce the depth of the ash layers) and vertical turbulent mixing (which acts to deepen the layers). Interestingly, differential sedimentation of ash particles and the volcano vertical emission profile play relatively minor roles. © 2015. American Geophysical Union. All Rights Reserved."
"37116849700;7409074131;56611366900;8859530100;55745955800;37018824600;6701333444;55272477500;","Development of fine-resolution analyses and expanded large-scale forcing properties: 2. Scale awareness and application to single-column model experiments",2015,"10.1002/2014JD022254","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923207976&doi=10.1002%2f2014JD022254&partnerID=40&md5=3943c85c99a2c72fc5ad2371ce56eec2","Fine-resolution three-dimensional fields have been produced using the Community Gridpoint Statistical Interpolation (GSI) data assimilation system for the U.S. Department of Energy’s Atmospheric Radiation Measurement Program (ARM) Southern Great Plains region. The GSI system is implemented in a multiscale data assimilation framework using theWeather Research and Forecastingmodel at a cloud-resolving resolution of 2 km. From the fine-resolution three-dimensional fields, large-scale forcing is derived explicitly at grid-scale resolution; a subgrid-scale dynamic component is derived separately, representing subgrid-scale horizontal dynamic processes. Analyses show that the subgrid-scale dynamic component is often a major component over the large-scale forcing for grid scales larger than 200 km. The single-column model (SCM) of the Community AtmosphericModel version 5 is used to examine the impact of the grid-scale and subgrid-scale dynamic components on simulated precipitation and cloud fields associated with a mesoscale convective system. It is found that grid-scale size impacts simulated precipitation, resulting in an overestimation for grid scales of about 200 km but an underestimation for smaller grids. The subgrid-scale dynamic component has an appreciable impact on the simulations, suggesting that grid-scale and subgrid-scale dynamic components should be considered in the interpretation of SCM simulations. . © 2014. American Geophysical Union. All Rights Reserved."
"7409074131;37116849700;56611366900;8859530100;55745955800;37018824600;6701333444;55272477500;","Development of fine-resolution analyses and expanded large-scale forcing properties: 1. Methodology and evaluation",2015,"10.1002/2014JD022245","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923173815&doi=10.1002%2f2014JD022245&partnerID=40&md5=f2bb6e4cc2a97d3eef8ece548c7a935e","We produce fine-resolution, three-dimensional fields of meteorological and other variables for the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Southern Great Plains site. The Community Gridpoint Statistical Interpolation system is implemented in a multiscale data assimilation (MS-DA) framework that is used within the Weather Research and Forecasting model at a cloud-resolving resolution of 2 km. The MS-DA algorithm uses existing reanalysis products and constrains fine-scale atmospheric properties by assimilating high-resolution observations. A set of experiments show that the data assimilation analysis realistically reproduces the intensity, structure, and time evolution of clouds and precipitation associated with a mesoscale convective system. Evaluations also show that the large-scale forcing derived from the fine-resolution analysis has an overall accuracy comparable to the existing ARM operational product. For enhanced applications, the fine-resolution fields are used to characterize the contribution of subgrid variability to the large-scale forcing and to derive hydrometeor forcing, which are presented in companion papers. © 2014. American Geophysical Union. All Rights Reserved."
"55803773100;21935606200;","CCN closure study: Effects of aerosol chemical composition andmixing state",2015,"10.1002/2014JD021978","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923183581&doi=10.1002%2f2014JD021978&partnerID=40&md5=2b543f5bad29cf7fe4dd4fbb866e8206","This study presents a detailed cloud condensation nuclei (CCN) closure study that investigates the effects of chemical composition (bulk and size resolved) and mixing state (internal and external) on CCN activity of aerosols. Measurements of the chemical composition, aerosol size distribution, total number concentration, and CCN concentration at supersaturation (SS = 0.2-1.0%) were performed during the winter season in Kanpur, India. Among the two cases considered here, better closure results are obtained for case 1 (low total aerosol loading, 49.54 ± 26.42 µg m-3, and high O:C ratio, 0.61 ± 0.07) compared to case 2 (high total aerosol loading, 101.05 ± 18.73 µg m-3, and low O:C ratio, 0.42 ± 0.06), with a maximum reduction of 3-81% in CCN overprediction for all depleted SS values (0.18-0.60%). Including the assumption that less volatile oxidized organic aerosols represent the soluble organic fraction reduced the overprediction to at most 40% and 129% in the internal and external mixing scenarios, respectively. At higher depleted SS values (0.34-0.60%), size-resolved chemical composition with an internal mixing state performed well in CCN closure among all organic solubility scenarios. However, at a lower depleted SS value (0.18%), closure is found to be more sensitive to both the chemical composition and mixing state of aerosols. At higher SS values, information on the solubility of organics and size-resolved chemical composition is required for accurate CCN predictions, whereas at lower SS values, information on the mixing state in addition to the solubility of organics and size-resolved chemical composition is required. Overall, κtotal values are observed to be independent of the O:C ratio [κtotal = (0.36 ± 0.01) × O:C - (0.03 ± 0.01)] in the range of 0.2&lt;O:C&lt;0.81, which indicates that the variation in the chemical composition of aerosols is not well represented by the changes in the O:C ratio alone. © 2014. American Geophysical Union. All Rights Reserved."
"56494041500;55668192400;14008365900;55916752500;","Mass changes in Arctic ice caps and glaciers: Implications of regionalizing elevation changes",2015,"10.5194/tc-9-139-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921719465&doi=10.5194%2ftc-9-139-2015&partnerID=40&md5=d4d4d73b395c48afd48dd8c23bab856d","The mass balance of glaciers and ice caps is sensitive to changing climate conditions. The mass changes derived in this study are determined from elevation changes derived measured by the Ice, Cloud, and land Elevation Satellite (ICESat) for the time period 2003-2009. Four methods, based on interpolation and extrapolation, are used to regionalize these elevation changes to areas without satellite coverage. A constant density assumption is then applied to estimate the mass change by integrating over the entire glaciated region. The main purpose of this study is to investigate the sensitivity of the regional mass balance of Arctic ice caps and glaciers to different regionalization schemes. The sensitivity analysis is based on studying the spread of mass changes and their associated errors, and the suitability of the different regionalization techniques is assessed through cross-validation. The cross-validation results shows comparable accuracies for all regionalization methods, but the inferred mass change in individual regions, such as Svalbard and Iceland, can vary up to 4 Gt a'1, which exceeds the estimated errors by roughly 50% for these regions. This study further finds that this spread in mass balance is connected to the magnitude of the elevation change variability. This indicates that care should be taken when choosing a regionalization method, especially for areas which exhibit large variability in elevation change. © 2015 Author(s)."
"37051480000;35392584500;6701511324;","Explicit representation of subgrid variability in cloud microphysics yields weaker aerosol indirect effect in the ECHAM5-HAM2 climate model",2015,"10.5194/acp-15-703-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921348913&doi=10.5194%2facp-15-703-2015&partnerID=40&md5=33ba3e089306e150c92d06dfea71611d","The impacts of representing cloud microphysical processes in a stochastic subcolumn framework are investigated, with emphasis on estimating the aerosol indirect effect. It is shown that subgrid treatment of cloud activation and autoconversion of cloud water to rain reduce the impact of anthropogenic aerosols on cloud properties and thus reduce the global mean aerosol indirect effect by 19%, from g-1.59 to g-1.28 W mg-2. This difference is partly related to differences in the model basic state; in particular, the liquid water path (LWP) is smaller and the shortwave cloud radiative forcing weaker when autoconversion is computed separately for each subcolumn. However, when the model is retuned so that the differences in the basic state LWP and radiation balance are largely eliminated, the global-mean aerosol indirect effect is still 14% smaller (i.e. g-1.37 W mg-2) than for the model version without subgrid treatment of cloud activation and autoconversion. The results show the importance of considering subgrid variability in the treatment of autoconversion. Representation of several processes in a self-consistent subgrid framework is emphasized. This paper provides evidence that omitting subgrid variability in cloud microphysics contributes to the apparently chronic overestimation of the aerosol indirect effect by climate models, as compared to satellite-based estimates. © 2015 Author(s)."
"37089417300;7102988363;7004194999;","The global impact of the transport sectors on atmospheric aerosol in 2030-Part 1: Land transport and shipping",2015,"10.5194/acp-15-633-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921384008&doi=10.5194%2facp-15-633-2015&partnerID=40&md5=65b5cf3e4fa78625b6375c78314393eb","Using the EMAC (ECHAM/MESSy Atmospheric Chemistry) global climate-chemistry model coupled to the aerosol module MADE (Modal Aerosol Dynamics model for Europe, adapted for global applications), we simulate the impact of land transport and shipping emissions on global atmospheric aerosol and climate in 2030. Future emissions of short-lived gas and aerosol species follow the four Representative Concentration Pathways (RCPs) designed in support of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We compare the resulting 2030 land-transport-and shipping-induced aerosol concentrations to the ones obtained for the year 2000 in a previous study with the same model configuration. The simulations suggest that black carbon and aerosol nitrate are the most relevant pollutants from land transport in 2000 and 2030 and their impacts are characterized by very strong regional variations during this time period. Europe and North America experience a decrease in the land-transport-induced particle pollution, although in these regions this sector remains a major source of surface-level pollution in 2030 under all RCPs. In Southeast Asia, however, a significant increase is simulated, but in this region the surface-level pollution is still controlled by other sources than land transport. Shipping-induced air pollution is mostly due to aerosol sulfate and nitrate, which show opposite trends towards 2030. Sulfate is strongly reduced as a consequence of sulfur reduction policies in ship fuels in force since 2010, while nitrate tends to increase due to the excess of ammonia following the reduction in ammonium sulfate. The aerosol-induced climate impact of both sectors is dominated by aerosol-cloud effects and is projected to decrease between 2000 and 2030, nevertheless still contributing a significant radiative forcing to Earth's radiation budget. © Author(s) 2015."
"26423400900;56344421700;55872098800;35326039600;","Turbulent Structures and Coherence in the Atmospheric Surface Layer",2015,"10.1007/s10546-014-9967-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028194850&doi=10.1007%2fs10546-014-9967-6&partnerID=40&md5=38c869e6a1215396213f84fea0e3e180","Organized structures in turbulent flow fields are a well-known and still fascinating phenomenon. Although these so-called coherent structures are obvious from visual inspection, quantitative assessment is a challenge and many aspects e.g., formation mechanisms and contribution to turbulent fluxes, are discussed controversially. During the “High Definition Clouds and Precipitation for Advancing Climate Prediction” Observational Prototype Experiment (HOPE) from April to May 2013, an advanced dual Doppler lidar technique was used to image the horizontal wind field near the surface for approximately 300 h. A visual inspection method, as well as a two-dimensional integral length scale analysis, were performed to characterize the observations qualitatively and quantitatively. During situations with forcing due to shear, the wind fields showed characteristic patterns in the form of clearly bordered, elongated areas of enhanced or reduced wind speed, which can be associated with near-surface streaks. During calm situations with strong buoyancy forcing, open cell patterns in the horizontal divergence field were observed. The measurement technique used enables the calculation of integral length scales of both horizontal wind components in the streamwise and cross-stream directions. The individual length scales varied considerably during the observation period but were on average shorter during situations with $$z/L&lt;0$$z/L&lt;0 compared to strongly stable situations. During unstable situations, which were dominated by wind fields with structures, the streamwise length scales increased with increasing wind speed, whereas the cross-stream length scales decreased. Consequently, the anisotropy increased from 1 for calm situations to values of 2–3 for wind speeds of 8–10$$\,\hbox {m s}^{-1}$$ms-1. During neutral to stable situations, the eddies were on average quite isotropic in the horizontal plane. © 2014, The Author(s)."
"35222774700;55635713200;7003548068;55450672000;","Modeling atmospheric longwave radiation at the surface during overcast skies: The role of cloud base height",2015,"10.1002/2014JD022310","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921992787&doi=10.1002%2f2014JD022310&partnerID=40&md5=c8ca800b88ce4352da0c796d0f9eb708","The behavior of the atmospheric downward longwave radiation at the surface under overcast conditions is studied. For optically thick clouds, longwave radiation depends greatly on the cloud base height (CBH), besides temperature and water vapor profiles. The CBH determines the cloud emission temperature and the air layers contributing to the longwave radiation that reaches the surface. Overcast situations observed at Girona (NE Iberian Peninsula) were studied by using a radiative transfer model. The data set includes different seasons, and a large range of CBH (0–5000 m). The atmosphere profiles were taken from the European Center for Medium-Range Weather Forecast analysis. The CBH was determined from ceilometer measurements and also estimated by using a suitable method applied to the vertical profile of relative humidity. The agreement between calculations and pyrgeometer measurements is remarkably good (1.6 ± 6.2 W m−2) if the observed CBH is used; poorer results are obtained with the estimated CBH (4.3 ± 7.0 W m−2). These results are better than those obtained from a simple parameterization based upon ground-level data (1.1 ± 11.6 W m−2), which can be corrected by adding a term that takes into account the CBH (−0.1 ± 7.3 W m−2). At this site, the cloud radiative effect (CRE) at the surface lies in the range 50–80 W m−2, has a clear seasonal behavior (higher CRE in winter), and depends upon the CBH. For the cold and the warm seasons, CRE decreases with CBH at a rate of −5 and −4 W m−2/km, respectively. Results obtained for other climates (subarctic and tropical) are also presented. © 2014. American Geophysical Union. All Rights Reserved."
"55928112000;6603711967;7003666669;6603400519;23479921600;55717074000;39262899400;36105812700;","Modeling dust as component minerals in the Community Atmosphere Model: Development of framework and impact on radiative forcing",2015,"10.5194/acp-15-537-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921329740&doi=10.5194%2facp-15-537-2015&partnerID=40&md5=279e20aeb435e8ab82ae0c965286ee74","The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale, using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral components in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as + 0.05 Wm-2 for both CAM4 and CAM5 simulations with mineralogy. We compare this to the radiative forcing from simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 Wm-2) and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, -0.05 and -0.17 Wm-2, respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods. © Author(s) 2015."
"56493740900;7004364155;55942502100;7102651635;","Clouds and the earth’s radiant energy system (CERES) data products for climate research",2015,"10.2151/jmsj.2015-048","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954350508&doi=10.2151%2fjmsj.2015-048&partnerID=40&md5=eb5eafb41e9220f1a69155c3314426d0","NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project integrates CERES, Moderate Resolution Imaging Spectroradiometer (MODIS), and geostationary satellite observations to provide top-of-atmosphere (TOA) irradiances derived from broadband radiance observations by CERES instruments. It also uses snow cover and sea ice extent retrieved from microwave instruments as well as thermodynamic variables from reanalysis. In addition, these variables are used for surface and atmospheric irradiance computations. The CERES project provides TOA, surface, and atmospheric irradiances in various spatial and temporal resolutions. These data sets are for climate research and evaluation of climate models. Long-term observations are required to understand how the Earth system responds to radiative forcing. A simple model is used to estimate the time to detect trends in TOA reflected shortwave and emitted longwave irradiances. © 2015, Meteorological Society of Japan."
"36740698600;23392868000;56479186900;56477918600;56479176700;7005920812;56162305900;7006705919;","Parameterizing deep convection using the assumed probability density function method",2015,"10.5194/gmd-8-1-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920829259&doi=10.5194%2fgmd-8-1-2015&partnerID=40&md5=7defe35363dda3e0f06e6ae4b9ffb921","Due to their coarse horizontal resolution, present-day climate models must parameterize deep convection. This paper presents single-column simulations of deep convection using a probability density function (PDF) parameterization. The PDF parameterization predicts the PDF of subgrid variability of turbulence, clouds, and hydrometeors. That variability is interfaced to a prognostic microphysics scheme using a Monte Carlo sampling method. <br><br> The PDF parameterization is used to simulate tropical deep convection, the transition from shallow to deep convection over land, and midlatitude deep convection. These parameterized single-column simulations are compared with 3-D reference simulations. The agreement is satisfactory except when the convective forcing is weak. <br><br> The same PDF parameterization is also used to simulate shallow cumulus and stratocumulus layers. The PDF method is sufficiently general to adequately simulate these five deep, shallow, and stratiform cloud cases with a single equation set. This raises hopes that it may be possible in the future, with further refinements at coarse time step and grid spacing, to parameterize all cloud types in a large-scale model in a unified way. © 2015 Author(s)."
"57213294702;8670213100;6507681572;15841350300;24778445700;6603395511;6701796418;","Cloud effects on the solar and thermal radiation budgets of the Mediterranean basin",2015,"10.1016/j.atmosres.2013.11.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908206018&doi=10.1016%2fj.atmosres.2013.11.009&partnerID=40&md5=d033652a5549089a9b084f7d6cc227d4","The cloud effects on the shortwave (SW), longwave (LW) and net all-wave radiation budgets of the Mediterranean basin were computed using a detailed radiative transfer model together with satellite and reanalysis data for surface and atmospheric properties. The model radiation fluxes at TOA were validated against CERES and ERBE satellite data, while at the Earth's surface they were validated against ground-based GEBA and BSRN station measurements. The cloud radiative effects were obtained for low, middle, high-level clouds, and for total cloud cover. Overall for the basin, the effect on solar radiation is to produce radiative cooling at the top of atmosphere (TOA) and at the surface that more than balances the warming effects on terrestrial radiation. The result is a net radiative cooling at TOA and at the surface, equal to -18.8 and -15.9Wm-2, respectively. The low-level clouds are most important for the TOA budget through significant SW reflection and little LW emission to space. High clouds play an important role in net surface cooling (-9.8Wm-2) through the combination of SW reflection to space and a much reduced LW warming effect at the surface. The geographical patterns of the effects are mainly characterized by a strong south to north increasing gradient. The seasonal variation of net radiative effects is dominated by solar radiation with maxima in spring and minima in winter. © 2013 Elsevier B.V."
"23569888300;14008365900;55916752500;55668192400;","Reconciled freshwater flux into the Godthåbsfjord system from satellite and airborne remote sensing",2015,"10.1080/01431161.2014.995277","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920983092&doi=10.1080%2f01431161.2014.995277&partnerID=40&md5=6b4e9d7e9ff808cd7651569973e283de","As the rapid reduction in ice volume of the Greenland ice sheet (GrIS) continues, increased melt water flux from the GrIS enters the deep Greenlandic fjords. This increased freshwater flux may change the salinity and eventually the ecology of the fjords. Here, we present a case study in which we, from various remote-sensing data sets, estimate the freshwater flux from the GrIS into a specific fjord system, the Godthåbsfjord, in southwest Greenland. The area of the GrIS draining into Godthåbsfjord covers approximately 36,700 km2. The large areal extent and the multiple outlets from the GrIS hamper in situ observations. Here, we evaluate available data from remote sensing and find a drainage basin in rapid change. An analysis of data from the Gravity Recovery and Climate Experiment (GRACE) satellites shows a mean seasonal freshwater flux into Godthåbsfjord of 18.2 ± 1.2 Gt, in addition to an imbalance in the mass balance of the drainage basin from 2003 to 2013 of 14.4 ± 0.2 Gt year−1. Altimetry data from air and spaceborne missions also suggest rapid changes in the outlet glacier dynamics. We find that only applying data from the Ice, Cloud, and land Elevation Satellite (ICESat) mission the mass change of the Godthåbsfjord drainage basin is significantly underestimated. When including additional laser-altimetry surveys, to account for changes in the outlet glaciers elevation, not captured by ICESat, the altimetry data were able to reconcile the basin mass balance with the gravimetric estimate and provide a higher spatial resolution of the mass changes. © 2015, © 2015 Taylor & Francis."
"42662217100;6603422104;","Cloud regime variability over the Azores and its application to climate model evaluation",2015,"10.1175/JCLI-D-15-0066.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957716899&doi=10.1175%2fJCLI-D-15-0066.1&partnerID=40&md5=2e129666f98b4b52a3d555e34f4a8348","From its location on the subtropics-midlatitude boundary, the Azores is influenced by both the subtropical high pressure and the midlatitude baroclinic storm regimes and therefore experiences a wide range of cloud structures, from fair-weather scenes to stratocumulus sheets and deep convective systems. This work combines three types of datasets to study cloud variability in the Azores: A satellite analysis of cloud regimes, a reanalysis characterization of storminess, and a 19-month field campaign that occurred on Graciosa Island. Combined analysis of the three datasets provides a detailed picture of cloud variability and the respective dynamic influences, with emphasis on low clouds that constitute a major uncertainty source in climate model simulations. The satellite cloud regime analysis shows that the Azores cloud distribution is similar to the mean global distribution and can therefore be used to evaluate cloud simulation in global models. Regime analysis of low clouds shows that stratocumulus decks occur under the influence of the Azores high pressure system, while shallow cumulus clouds are sustained by cold-air outbreaks, as revealed by their preference for postfrontal environments and northwesterly flows. An evaluation of climate model cloud regimes from phase 5 of CMIP (CMIP5) over the Azores shows that all models severely underpredict shallow cumulus clouds, while most models also underpredict the occurrence of stratocumulus cloud decks. It is demonstrated that the regime analysis can assist in the selection of case studies representing specific climatological cloud distributions. With all the tools now in place, a methodology is suggested to better understand cloud-dynamics interactions and attempt to explain and correct climate model cloud deficiencies. © 2015 American Meteorological Society."
"56005080300;23082420800;8696069500;57197233116;7201504886;","The influence of cloud feedbacks on equatorial atlantic variability",2015,"10.1175/JCLI-D-14-00495.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944073510&doi=10.1175%2fJCLI-D-14-00495.1&partnerID=40&md5=25086a96ab8f046b4f017b004e7ccea1","Observations show that cloud feedback over the Namibian stratocumulus region is positive because cloud cover is anticorrelated with local sea surface temperature (SST) anomalies. Moreover, regressions of observed atmospheric fields on equatorial Atlantic SST anomalies indicate that cloud feedbacks over the Namibian stratocumulus region covary with Atlantic Niño. However, from observations alone, it is not possible to quantify the influence of regional cloud feedbacks on equatorial climate variability. To address this question, a set of sensitivity experiments are conducted using an atmospheric general circulation model (ECHAM6) coupled to a slab ocean in which the strength of positive cloud feedback is enhanced over several regions in the South Atlantic basin. Enhanced positive cloud feedback over the Namibian stratocumulus region increases local as well as equatorial SST variability, whereas enhanced cloud feedback over other regions in the South Atlantic increases local SST variability but exhibits negligible responses at the equator. The authors' results indicate that the Namibian region plays a central role in enhancing equatorial SST variability because it is located where the SST anomalies associated with the simulated Atlantic Niño in the slab-ocean model develop. These results highlight the important role of the regional coupling of cloud cover over the Namibian region with local SSTs and its effects on equatorial Atlantic climate variability. © 2015 American Meteorological Society."
"7201485519;7005056279;13402835300;35509639400;8397494800;8918407000;13405561000;55389942900;6701815637;36187387300;7201504886;","The diurnal cycle of marine cloud feedback in climate models",2015,"10.1007/s00382-014-2234-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939881418&doi=10.1007%2fs00382-014-2234-1&partnerID=40&md5=958f57206bd907351ce2acb586d5e57e","We examine the diurnal cycle of marine cloud feedback using high frequency outputs in CFMIP-2 idealised uniform +4 K SST perturbation experiments from seven CMIP5 models. Most of the inter-model spread in the diurnal mean marine shortwave cloud feedback can be explained by low cloud responses, although these do not explain the model responses at the neutral/weakly negative end of the feedback range, where changes in mid and high level cloud properties are more important. All of the models show reductions in marine low cloud fraction in the warmer climate, and these are in almost all cases largest in the mornings when more cloud is present in the control simulations. This results in shortwave cloud feedbacks being slightly stronger and having the largest inter-model spread at this time of day. The diurnal amplitudes of the responses of marine cloud properties to the warming climate are however small compared to the inter-model differences in their diurnally meaned responses. This indicates that the diurnal cycle of cloud feedback is not strongly relevant to understanding inter-model spread in overall cloud feedback and climate sensitivity. A number of unusual behaviours in individual models are highlighted for future investigation. © 2014, Crown Copyright."
"22959252400;7404829395;56537463000;","Long-term cloud change imprinted in seasonal cloud variation: More evidence of high climate sensitivity",2015,"10.1002/2015GL065911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946549097&doi=10.1002%2f2015GL065911&partnerID=40&md5=31e6ebf841ccbbb28a0da29b35c496f3","The large spread of model equilibrium climate sensitivity (ECS) is mainly caused by the differences in the simulated marine boundary layer cloud (MBLC) radiative feedback. We examine the variations of MBLC fraction in response to the changes of sea surface temperature (SST) at seasonal and centennial time scales for 27 climate models that participated in the Coupled Model Intercomparison Project phase 3 and phase 5. We find that the intermodel spread in the seasonal variation of MBLC fraction with SST is strongly correlated with the intermodel spread in the centennial MBLC fraction change per degree of SST warming and that both are well correlated with ECS. Seven models that are consistent with the observed seasonal variation of MBLC fraction with SST at a rate -1.28 ± 0.56%/K all have ECS higher than the multimodel mean of 3.3 K yielding an ensemble-mean ECS of 3.9 K and a standard deviation of 0.45 K. Key Points Boundary cloud variations at seasonal and centennial scales are correlated Boundary cloud seasonal response is correlated with sensitivity Observations suggest a higher climate sensitivity than multimodel mean © 2015. American Geophysical Union. All Rights Reserved."
"16245558300;7101610644;15065751600;7202010300;35957510700;7402475964;","The rainfall sensitivity of tropical net primary production in CMIP5 Twentieth- and Twenty-First-Century simulations",2015,"10.1175/JCLI-D-14-00675.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950150160&doi=10.1175%2fJCLI-D-14-00675.1&partnerID=40&md5=1154af3200b1f7dca4b3236c737a7765","Recent efforts to narrow the spread in equilibrium climate sensitivity (ECS) across global climate models have focused on identifying observationally based constraints, which are rooted in empirical correlations between ECS and biases in the models' present-day climate. This study reexamines one such constraint identified from CMIP3 models: the linkage between ECS and net top-of-the-atmosphere radiation biases in the Southern Hemisphere (SH). As previously documented, the intermodel spread in the ECS of CMIP3 models is linked to present-day cloud and net radiation biases over the midlatitude Southern Ocean, where higher cloud fraction in the present-day climate is associated with larger values of ECS. However, in this study, no physical explanation is found to support this relationship. Furthermore, it is shown here that this relationship disappears in CMIP5 models and is unique to a subset of CMIP models characterized by unrealistically bright present-day clouds in the SH subtropics. In view of this evidence, Southern Ocean cloud and net radiation biases appear inappropriate for providing observationally based constraints on ECS. Instead of the Southern Ocean, this study points to the stratocumulus-to-cumulus transition regions of the SH subtropical oceans as key to explaining the intermodel spread in the ECS of both CMIP3 and CMIP5 models. In these regions, ECS is linked to present-day cloud and net radiation biases with a plausible physical mechanism: models with brighter subtropical clouds in the present-day climate show greater ECS because 1) subtropical clouds dissipate with increasing CO2 concentrations in many models and 2) the dissipation of brighter clouds contributes to greater solar warming of the surface. © 2015 American Meteorological Society."
"35509639400;7201504886;15026371500;7006698304;7007181954;57205867148;7103294731;56014511300;6603566335;7102567936;55686667100;7201485519;","Clouds, circulation and climate sensitivity",2015,"10.1038/ngeo2398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926359595&doi=10.1038%2fngeo2398&partnerID=40&md5=3cc991046f3922dab00d63d9f51143a1","Fundamental puzzles of climate science remain unsolved because of our limited understanding of how clouds, circulation and climate interact. One example is our inability to provide robust assessments of future global and regional climate changes. However, ongoing advances in our capacity to observe, simulate and conceptualize the climate system now make it possible to fill gaps in our knowledge. We argue that progress can be accelerated by focusing research on a handful of important scientific questions that have become tractable as a result of recent advances. We propose four such questions below; they involve understanding the role of cloud feedbacks and convective organization in climate, and the factors that control the position, the strength and the variability of the tropical rain belts and the extratropical storm tracks."
"7102604282;55245030000;55717074000;","Can cirrus cloud seeding be used for geoengineering?",2015,"10.1002/2015GL065992","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946553399&doi=10.1002%2f2015GL065992&partnerID=40&md5=5d753d0b95f16854e78d51807e32ec32","Cirrus cloud seeding has been proposed as a possible technique that might thin cirrus clouds leading to reduced heating. The technique was shown to be viable in one model evaluation. Here we use an updated version of the Community Atmosphere Model version 5 (CAM5) and reevaluate whether seeding is a viable mechanism for cooling. We explore different model setups (with and without secondary organic aerosols acting as heterogeneous ice nuclei). None of the updated versions of the CAM5 lead to a significant amount of negative climate forcing and hence do not lead to cooling. We only calculate a net negative cloud forcing (-0.74 ± 0.25 W m-2) if we restrict the modeled subgrid-scale updraft velocity during nucleation to &lt;0.2 m s-1 and if the deposition of water vapor onto preexisting ice crystals during nucleation is not included. Hence, we do not find that cirrus cloud seeding is a viable climate intervention technique. Key Points Cirrus cloud seeding only works to cool climate for restricted model setup The most recent version of CAM5 predicts warming Mechanisms that attempt to restrict seeding to polar regions may not cool © 2015. American Geophysical Union. All Rights Reserved."
"56321122100;25640569400;16679271700;8877858700;6701754792;7006698304;","A hybrid cloud regime methodology used to evaluate Southern Ocean cloud and shortwave radiation errors in ACCESS",2015,"10.1175/JCLI-D-14-00846.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942904525&doi=10.1175%2fJCLI-D-14-00846.1&partnerID=40&md5=1384bee4061b809887c028db8ae7dbb6","A deficit of shortwave cloud forcing over the Southern Ocean is persistent in many global climate models. Cloud regimes have been widely used in model evaluation studies to make a process-oriented diagnosis of cloud parameterization errors, but cloud regimes have some limitations in resolving both observed and simulated cloud behavior. A hybrid methodology is developed for identifying cloud regimes from observed and simulated cloud simultaneously. Through this methodology, 11 hybrid cloud regimes are identified in the ACCESS1.3 model for the high-latitude Southern Ocean. The hybrid cloud regimes resolve the features of observed cloud and characterize cloud errors in the model. The simulated properties of the hybrid cloud regimes, and their occurrence over the Southern Ocean and in the context of extratropical cyclones, are evaluated, and their contributions to the shortwave radiation errors are quantified. Three errors are identified: an overall deficit of cloud fraction, a tendency toward optically thin low andmidtopped cloud, and an absence of a shallow frontal-type cloud at high latitudes and in the warmfronts of extratropical cyclones. To demonstrate the utility of the hybrid cloud regimes for the evaluation of changes to the model, the effects of selected changes to the model microphysics are investigated. © 2015 American Meteorological Society."
"28367935500;7201784177;","Circulation response to warming shaped by radiative changes of clouds and water vapour",2015,"10.1038/ngeo2345","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923262088&doi=10.1038%2fngeo2345&partnerID=40&md5=dacfb8af419501f5dfdb943e0d72c30a","The atmospheric circulation controls how global climate change will be expressed regionally. Substantial circulation changes are expected under global warming, including a narrowing of the intertropical convergence zone, a slow down and poleward expansion of the tropical circulation, and a poleward shift of mid-latitude stormtracks and jets. Yet, climate model projections of the circulation response to climate change remain uncertain. Here we present simulations with two different aquaplanet climate models and analyse these simulations using the cloud and water-vapour locking method. We find that radiative changes of clouds and water vapour are key to the regional response of precipitation and circulation to global warming. Model disagreement in the response of key characteristics of the atmospheric circulation - the intertropical convergence zone, the strength of the Hadley circulation, and the trade winds - arises from disagreement between the models in radiative changes of tropical ice clouds and their coupling to the circulation. We find that cloud changes amplify a poleward shift of the extratropical jet, whereas water vapour changes oppose such a shift, but the degree of compensation is model-dependent. We conclude that radiative changes of clouds and water vapour are not only integral to the magnitude of future global-mean warming but also determine patterns of regional climate change. © 2015 Macmillan Publishers Limited. All rights reserved"
"55894937000;7401776640;","On the relationships between subtropical clouds and meteorology in observations and CMIP3 and CMIP5 models",2015,"10.1175/JCLI-D-14-00475.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943809416&doi=10.1175%2fJCLI-D-14-00475.1&partnerID=40&md5=bf0e7fa28eac79f16b8bc5c23e0f2ce4","Climate models' simulation of clouds over the eastern subtropical oceans contributes to large uncertainties in projected cloud feedback to global warming. Here, interannual relationships of cloud radiative effect and cloud fraction to meteorological variables are examined in observations and in models participating in phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5, respectively). In observations, cooler sea surface temperature, a stronger estimated temperature inversion, and colder horizontal surface temperature advection are each associated with larger low-level cloud fraction and increased reflected shortwave radiation. A moister free troposphere and weaker subsidence are each associated with larger midand high-level cloud fraction and offsetting components of shortwave and longwave cloud radiative effect. It is found that a larger percentage of CMIP5 than CMIP3 models simulate the wrong sign or magnitude of the relationship of shortwave cloud radiative effect to sea surface temperature and estimated inversion strength. Furthermore,most models fail to produce the sign of the relationship between shortwave cloud radiative effect and temperature advection. These deficiencies are mostly, but not exclusively, attributable to errors in the relationship between low-level cloud fraction and meteorology. Poor model performance also arises due to errors in the response of mid- and high-level cloud fraction to variations in meteorology. Models exhibiting relationships closest to observations tend to project less solar reflection by clouds in the late twenty-first century and have higher climate sensitivities than poorer-performing models. Nevertheless, the intermodel spread of climate sensitivity is large even among these realistic models. © 2015 American Meteorological Society."
"16202694600;7004060399;6602098362;","Reexamining the relationship between climate sensitivity and the Southern Hemisphere radiation budget in CMIP models",2015,"10.1175/JCLI-D-15-0031.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950138463&doi=10.1175%2fJCLI-D-15-0031.1&partnerID=40&md5=b3b7a71d4eb235bc632670a60dddd5e0","Recent efforts to narrow the spread in equilibrium climate sensitivity (ECS) across global climate models have focused on identifying observationally based constraints, which are rooted in empirical correlations between ECS and biases in the models' present-day climate. This study reexamines one such constraint identified from CMIP3 models: the linkage between ECS and net top-of-the-atmosphere radiation biases in the Southern Hemisphere (SH). As previously documented, the intermodel spread in the ECS of CMIP3 models is linked to present-day cloud and net radiation biases over the midlatitude Southern Ocean, where higher cloud fraction in the present-day climate is associated with larger values of ECS. However, in this study, no physical explanation is found to support this relationship. Furthermore, it is shown here that this relationship disappears in CMIP5 models and is unique to a subset of CMIP models characterized by unrealistically bright present-day clouds in the SH subtropics. In view of this evidence, Southern Ocean cloud and net radiation biases appear inappropriate for providing observationally based constraints on ECS. Instead of the Southern Ocean, this study points to the stratocumulus-to-cumulus transition regions of the SH subtropical oceans as key to explaining the intermodel spread in the ECS of both CMIP3 and CMIP5 models. In these regions, ECS is linked to present-day cloud and net radiation biases with a plausible physical mechanism: models with brighter subtropical clouds in the present-day climate show greater ECS because 1) subtropical clouds dissipate with increasing CO2 concentrations in many models and 2) the dissipation of brighter clouds contributes to greater solar warming of the surface. © 2015 American Meteorological Society."
"7403906746;23668415500;6603236154;","On the microphysical effects of observed cloud edge charging",2015,"10.1002/qj.2554","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946472503&doi=10.1002%2fqj.2554&partnerID=40&md5=329341afbbe2ceaf5b9b8f82be90571b","Liquid layer clouds are abundant globally. Lacking strong convection, they do not become electrified by the usual thunderstorm mechanisms of collisional electrification between hydrometeors of different phases. Instead, the background global circuit current flow in fair weather is largely unaffected by the layer cloud's presence, and, if the layer cloud is extensive horizontally, the vertical fair weather conduction current passes through the cloud. A consequence of the vertical current flow is that, at the cloud-air boundary where there is a conductivity transition and droplets form or evaporate, droplet charging occurs. Charge can affect both droplet evaporation and droplet-droplet collisions. Using new radiosonde instrumentation, the charge observed at layer cloud edges is evaluated for both these microphysical droplet processes. This shows that the charging is more likely to affect collision processes than activation, for small droplets. Enhancing the collection efficiency of small droplets modifies their evolution and propagates through the size distribution to shorten the autoconversion time-scale to rain drops, and the cloud radiative properties. Because the conduction current density is influenced by both external (e.g. solar modulation of high-energy particles) and internal (e.g. El Niño-Southern Oscillation) factors, current flow leading to layer cloud edge charging provides a possible route for expressing solar influences on the climate system and a teleconnection mechanism for communicating internal climate variability. © 2015 Royal Meteorological Society."
"56230988400;6603566335;6603606681;","Evaluation of low-cloud climate feedback through single-column model equilibrium states",2015,"10.1002/qj.2398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928286280&doi=10.1002%2fqj.2398&partnerID=40&md5=acda455d43390b359cf49584964da882","The dependency of the boundary-layer cloud regime on the free tropospheric temperature and humidity is examined. Equilibrium state solutions obtained with the single-column model version of the climate model EC-EARTH are analysed in a phase space defined by the lower tropospheric stability (LTS) and a similar measure for humidity. The set-up comprises two experiments: one with large-scale subsidence which is constant in time and a second one with additional stochastic noise added to the subsidence. The dependency of the boundary-layer state on the free tropospheric conditions is qualitatively consistent between the two experiments. Well-mixed stratocumulus-topped boundary layers are found for high LTS and moist free tropospheric conditions. Cooler and dryer free tropospheric conditions favour the presence of shallow cumulus clouds. Subsequently the response to a sea surface warming of 2 K and a free atmospheric perturbation conserving both the LTS and the relative humidity is assessed. The model predicts an overall positive low-cloud feedback for both the constant subsidence experiment and the experiment with the additional stochastic noise. © 2014 Royal Meteorological Society."
"55732558900;7102859255;7202252296;54903097700;7102577095;7004198777;7003666669;55544607500;55317177900;7006705919;","Interannual to decadal climate variability of sea salt aerosols in the coupled climate model CESM1.0",2015,"10.1002/2014JD022888","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925131075&doi=10.1002%2f2014JD022888&partnerID=40&md5=e254eb7facd7b3161afddf427297ba09","This study examines multiyear climate variability associated with sea salt aerosols and their contribution to the variability of shortwave cloud forcing (SWCF) using a 150 year simulation for preindustrial conditions of the Community Earth System Model version 1.0. The results suggest that changes in sea salt and related cloud and radiative properties on interannual timescales are dominated by the El Niño-Southern Oscillation cycle. Sea salt variability on longer (interdecadal) timescales is associated with low-frequency variability in the Pacific Ocean similar to the Interdecadal Pacific Oscillation but does not show a statistically significant spectral peak. A multivariate regression suggests that sea salt aerosol variability may contribute to SWCF variability in the tropical Pacific, explaining up to 20-30% of the variance in that region. Elsewhere, there is only a small sea salt aerosol influence on SWCF through modifying cloud droplet number and liquid water path that contributes to the change of cloud effective radius and cloud optical depth (and hence cloud albedo), producing a multiyear aerosol-cloud-wind interaction. © 2015. American Geophysical Union. All Rights Reserved."
"56883885900;55544443300;36720934300;55823994500;","Sensitivity of the climate response to the altitude of black carbon in the Northern subtropics in an aquaplanet GCM",2015,"10.1175/JCLI-D-15-0037.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942848261&doi=10.1175%2fJCLI-D-15-0037.1&partnerID=40&md5=3315df77f4c10af671f84f5399d4560c","This study explores the dependence of the climate response on the altitude of black carbon in the northern subtropics by employing an atmospheric general circulation model coupled to an aquaplanet mixed layer ocean, with a focus on the pattern changes in the temperature, hydrological cycle, and large-scale circulation. Black carbon added below or within the subtropical low-level clouds tends to suppress convection, which reduces the low cloud amount, resulting in a positive cloud radiative forcing. The warmer northern subtropics then induce a northward shift of the intertropical convergence zone (ITCZ) and a poleward expansion of the descending branch of the northern Hadley cell. As the black carbon-induced local warming is amplified by clouds and is advected by the anomalous Hadley circulation, the entire globe gets warmer. In contrast, black carbon added near the surface increases the buoyancy of air parcels to enhance convection, leading to an increase in the subtropical low cloud amount and a negative cloud radiative forcing. The temperature increase remains local to where black carbon is added and elsewhere decreases, so that the ITCZ is shifted southward and the descending branch of the northern Hadley cell contracts equatorward. Consistent with previous studies, the authors demonstrate that the climate response to black carbon is highly sensitive to the vertical distribution of black carbon relative to clouds; hence, models have to accurately compute the vertical transport of black carbon to enhance their skill in simulating the climatic effects of black carbon. © 2015 American Meteorological Society."
"8067118800;7202899330;13402835300;56162305900;6701752471;10241462700;8918407000;","Evaluation of the warm rain formation process in global models with satellite observations",2015,"10.1175/JAS-D-14-0265.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944955162&doi=10.1175%2fJAS-D-14-0265.1&partnerID=40&md5=31519f73467ef714734722762e6f9a5d","This study examines the warm rain formation process over the global ocean in global climate models. Methodologies developed to analyze CloudSat and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations are employed to investigate the cloud-to-precipitation process of warm clouds and are applied to the model results to examine how the models represent the process for warm stratiform clouds. Despite a limitation of the present study that compares the statistics for stratiform clouds in climate models with those from satellite observations, including both stratiform and (shallow) convective clouds, the statistics constructed with the methodologies are compared between the models and satellite observations to expose their similarities and differences. A problem common to some models is that they tend to produce rain at a faster rate than is observed. These model characteristics are further examined in the context of cloud microphysics parameterizations using a simplified one-dimensional model of warm rain formation that isolates key microphysical processes from full interactions with other processes in global climate models. The one-dimensional model equivalent statistics reproduce key characteristics of the global model statistics when corresponding autoconversion schemes are assumed in the one-dimensional model. The global model characteristics depicted by the statistics are then interpreted as reflecting behaviors of the autoconversion parameterizations adopted in the models. Comparisons of the one-dimensional model with satellite observations hint at improvements to the formulation of the parameterization scheme, thus offering a novel way of constraining key parameters in autoconversion schemes of global models. © 2015 American Meteorological Society."
"9635764200;","Cloud responses in the AMIP simulations of CMIP5 models in the southeastern Pacific marine subsidence region",2015,"10.1002/joc.4181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938854585&doi=10.1002%2fjoc.4181&partnerID=40&md5=79fed06511b2d3f81cf183a02e4d2bc6","The sensitivity of regimes dominated by low clouds has been identified as the largest contributor to uncertainties in tropical cloud feedback estimates in climate models. The Atmospheric Model Intercomparison Project simulations of the low cloud response to sea surface temperature (SST) are compared with satellite observations in the southeastern Pacific subsidence region. The model ensemble annual average cloud fraction is only about 10% lower than Moderate Resolution Imaging Spectroradiometer observations; however, many models compensate by overestimating the cloud liquid water path (LWP), especially in areas typically associated with shallow cumulus. Analysis of the monthly distribution also shows that models have considerable difficulty in simulating the annual cycle in the cloud radiative effect (CRE), cloud fraction, and LWP likely due in part to underestimation of the strength of lower tropospheric stability and the depth of the boundary layer. The interannual sensitivity of CRE to SST agrees with observations in about half of the models, with the other half generally underestimating the cloud radiative forcing sensitivity. Model-observational differences are driven by the varying interannual responses in cloud fraction and LWP. Most models, including those that capture the mean interannual sensitivity of CRE to SST, have lower sensitivity in cloud fraction that is compensated by oversensitivity in the cloud LWP, especially in areas of more frequent shallow cumulus. Results presented here also highlight the possibility of using the vertical gradient of moist static energy (MSE) to test the fidelity of a model's representation of clouds and cloud sensitivity. Models that reproduce the observed distribution of cloud fraction with the lower tropospheric MSE gradient not only show better regional distribution and annual cycle in clouds and radiative forcing, but also demonstrate cloud and radiative sensitivities to SST that are more well correlated with the observed cloud sensitivities. © 2015 Royal Meteorological Society."
"56457851700;7202145115;26645289600;54897465300;16444006500;","Mixed-phase cloud physics and Southern Ocean cloud feedback in climate models",2015,"10.1002/2015JD023603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944930594&doi=10.1002%2f2015JD023603&partnerID=40&md5=8f6366391dfd3995997b51892cd95e0d","Increasing optical depth poleward of 45° is a robust response to warming in global climatemodels. Much of this cloud optical depth increase has been hypothesized to be due to transitions from ice-dominated to liquid-dominated mixed-phase cloud. In this study, the importance of liquid-ice partitioning for the optical depth feedback is quantified for 19 Coupled Model Intercomparison Project Phase 5models. Allmodels show a monotonic partitioning of ice and liquid as a function of temperature, but the temperature at which ice and liquid are equally mixed (the glaciation temperature) varies by as much as 40 K across models. Models that have a higher glaciation temperature are found to have a smaller climatological liquid water path (LWP) and condensedwater path and experience a larger increase in LWP as the climate warms. The ice-liquid partitioning curve of eachmodel may be used to calculate the response of LWP towarming. It is found that the repartitioning between ice and liquid in a warming climate contributes at least 20% to 80% of the increase in LWP as the climate warms, depending onmodel. Intermodel differences in the climatological partitioning between ice and liquid are estimated to contribute at least 20% to the intermodel spread in the high-latitude LWP response in themixed-phase region poleward of 45°S. It is hypothesized that a more thorough evaluation and constraint of global climate model mixed-phase cloud parameterizations and validation of the total condensate and ice-liquid apportionment against observations will yield a substantial reduction in model uncertainty in the high-latitude cloud response to warming. © 2015. American Geophysical Union. All Rights Reserved."
"8866821900;7201504886;35509639400;","Using aquaplanets to understand the robust responses of comprehensive climate models to forcing",2015,"10.1007/s00382-014-2138-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939873329&doi=10.1007%2fs00382-014-2138-0&partnerID=40&md5=69761b7cc5058381a2ff428415301b3f","Idealized climate change experiments using fixed sea-surface temperature are investigated to determine whether zonally symmetric aquaplanet configurations are useful for understanding climate feedbacks in more realistic configurations. The aquaplanets capture many of the robust responses of the large-scale circulation and hydrologic cycle to both warming the sea-surface temperature and quadrupling atmospheric CO<inf>2</inf>. The cloud response to both perturbations varies across models in both Earth-like and aquaplanet configurations, and this spread arises primarily from regions of large-scale subsidence. Most models produce a consistent cloud change across the subsidence regimes, and the feedback in trade-wind cumulus regions dominates the tropical response. It is shown that these trade-wind regions have similar cloud feedback in Earth-like and aquaplanet warming experiments. The tropical average cloud feedback of the Earth-like experiment is captured by five of eight aquaplanets, and the three outliers are investigated to understand the discrepancy. In two models, the discrepancy is due to warming induced dissipation of stratocumulus decks in the Earth-like configuration which are not represented in the aquaplanet. One model shows a circulation response in the aquaplanet experiment accompanied by a cloud response that differs from the Earth-like configuration. Quadrupling atmospheric CO<inf>2</inf> in aquaplanets produces slightly greater adjusted forcing than in Earth-like configurations, showing that land-surface effects dampen the adjusted forcing. The analysis demonstrates how aquaplanets, as part of a model hierarchy, help elucidate robust aspects of climate change and develop understanding of the processes underlying them. © 2014, The Author(s)."
"56032970700;22934904700;57212988186;7401945370;","Improvement in global cloud-system-resolving simulations by using a double-moment bulk cloud microphysics scheme",2015,"10.1175/JCLI-D-14-00241.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961288103&doi=10.1175%2fJCLI-D-14-00241.1&partnerID=40&md5=ad597cf154d88fb53d004953fd451c16","This study examines the impact of an alteration of a cloud microphysics scheme on the representation of longwave cloud radiative forcing (LWCRF) and its impact on the atmosphere in global cloud-system-resolving simulations. A new double-moment bulk cloud microphysics scheme is used, and the simulated results are compared with those of a previous study. It is demonstrated that improvements within the new cloud microphysics scheme have the potential to substantially improve climate simulations. The new cloud microphysics scheme represents a realistic spatial distribution of the cloud fraction and LWCRF, particularly near the tropopause. The improvement in the cirrus cloud-top height by the new cloud microphysics scheme substantially reduces the warm bias in atmospheric temperature from the previous simulation via LWCRF by the cirrus clouds. The conversion rate of cloud ice to snow and gravitational sedimentation of cloud ice are the most important parameters for determining the strength of the radiative heating near the tropopause and its impact on atmospheric temperature. © 2015 American Meteorological Society."
"37029434200;56875002400;8662096300;56704049300;","Building a better Urban picture: Combining day and night remote sensing imagery",2015,"10.3390/rs70911887","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942512520&doi=10.3390%2frs70911887&partnerID=40&md5=1a8926992faec930d870d3c1a84bb8ed","Urban areas play a very important role in global climate change. There is increasing need to understand global urban areas with sufficient spatial details for global climate change mitigation. Remote sensing imagery, such as medium resolution Landsat daytime multispectral imagery and coarse resolution Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light imagery, has provided a powerful tool for characterizing and mapping cities, with advantages and disadvantages. Here we propose a framework to merge cloud and cloud shadow-free Landsat Normalized Difference Vegetation Index (NDVI) composite and DMSP/OLS Night Time Light (NTL) to characterize global urban areas at a 30 m resolution, through a Normalized Difference Urban Index (NDUI) to make full use of them while minimizing their limitations. We modify the maximum NDVI value multi-date image compositing method to generate the cloud and cloud shadow-free Landsat NDVI composite, which is critical for generating a global NDUI. Evaluation results show the NDUI can effectively increase the separability between urban areas and bare lands as well as farmland, capturing large scale urban extents and, at the same time, providing sufficient spatial details inside urban areas. With advanced cloud computing facilities and the open Landsat data archives available, NDUI has the potential for global studies at the 30 m scale. © 2015 by the authors."
"24722339600;6602878057;7004479957;42662217100;6603431534;25640569400;56647964800;8247122100;35584010200;57201609270;6506537159;6603422104;25624545600;56647425100;7006146719;7102128820;7401796996;55740664200;14019399400;57200679067;7004057920;7006783796;6506234624;35473805400;19337612500;36876405100;25823927100;","Clouds, aerosols, and precipitation in the marine boundary layer: An arm mobile facility deployment",2015,"10.1175/BAMS-D-13-00180.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919704727&doi=10.1175%2fBAMS-D-13-00180.1&partnerID=40&md5=eecd3689256b7a0319e7063224d79e91","A 21-month deployment to Graciosa Island in the northeastern Atlantic Ocean is providing an unprecedented record of the clouds, aerosols, and meteorology in a poorly sampled remote marine environment. (CAP-MBL). CAP-MBL was designed to gather an extended record of high-quality data on clouds and aerosol properties in a remote marine environment needed to improve the treatment of clouds and aerosols in climate models. A feature of the CAP-MBL deployment is the ability to simultaneously observe clouds, aerosols, and precipitation and to understand how these variables interact with each other. Interactions are two way, with aerosols potentially impacting precipitation most likely via the suppression of warm rain but in turn aerosols are strongly scavenged by precipitation, even in the relatively weak drizzle from low clouds. The CAP-MBL deployment's continuous record allows for greater statistical reliability in the observed relationships between aerosols, clouds, and precipitation than is possible with aircraft but retains the advantages of in situ sampling of aerosol properties that are difficult to constrain with satellite data. Given the great variety of aerosol, cloud, and precipitation conditions, the data from CAP-MBL and from the permanent site will continue to challenge understanding and provide an unprecedented dataset for the evaluation and improvement of numerical models from cloud-resolving ones to global weather and climate models."
"56900293300;55386235300;","The characteristics of ice cloud properties derived from CloudSat and CALIPSO measurements",2015,"10.1175/JCLI-D-14-00666.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944104236&doi=10.1175%2fJCLI-D-14-00666.1&partnerID=40&md5=5948631b355d47f89a6d2ceff4f62f6f","The characteristics of ice clouds with a wide range of optical depths are studied based on satellite retrievals and radiative transfer modeling. Results show that the global-mean ice cloud optical depth, ice water path, and effective radius are approximately 2, 109 g m-2, and 48 μm, respectively. Ice cloud occurrence frequency varies depending not only on regions and seasons, but also on the types of ice clouds as defined by optical depth τ values. Ice clouds with different τ values show differently preferential locations on the planet; optically thinner ones (τ &lt; 3) are most frequently observed in the tropics around 15 km and in midlatitudes below 5 km, while thicker ones (τ &gt; 3) occur frequently in tropical convective areas and along midlatitude storm tracks. It is also found that ice water content and effective radius show different temperature dependence among the tropics, midlatitudes, and high latitudes. Based on analyzed ice cloud frequencies and microphysical properties, cloud radiative forcing is evaluated using a radiative transfer model. The results show that globally radiative forcing due to ice clouds introduces a net warming of the earth-atmosphere system. Those with τ &lt; 4.0 all have a positive (warming) net forcing with the largest contribution by ice clouds with τ ~ 1.2. Regionally, ice clouds in high latitudes show a warming effect throughout the year, while they cause cooling during warm seasons but warming during cold seasons in midlatitudes. Ice cloud properties revealed in this study enhance the understanding of ice cloud climatology and can be used for validating climate models. © 2015 American Meteorological Society."
"7202660824;7403288995;7402064802;55746365900;","Positive tropical marine low-cloud cover feedback inferred from cloud-controlling factors",2015,"10.1002/2015GL065627","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945241933&doi=10.1002%2f2015GL065627&partnerID=40&md5=9ee265d41edaadfa7785fad358cbfefa","Differences in simulations of tropical marine low-cloud cover (LCC) feedback are sources of significant spread in temperature responses of climate models to anthropogenic forcing. Here we show that in models the feedback is mainly driven by three large-scale changes - a strengthening tropical inversion, increasing surface latent heat flux, and an increasing vertical moisture gradient. Variations in the LCC response to these changes alone account for most of the spread in model-projected 21st century LCC changes. A methodology is devised to constrain the LCC response observationally using sea surface temperature (SST) as a surrogate for the latent heat flux and moisture gradient. In models where the current climate's LCC sensitivities to inversion strength and SST variations are consistent with observed, LCC decreases systematically, which would increase absorption of solar radiation. These results support a positive LCC feedback. Correcting biases in the sensitivities will be an important step toward more credible simulation of cloud feedbacks. © 2015 American Geophysical Union. All Rights Reserved."
"7004592415;7005513582;7201520140;55011796100;6701428682;","Latitudinal temperature gradients and high-latitude temperatures during the latest Cretaceous: Congruence of geologic data and climate models",2015,"10.1130/G36802.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942238538&doi=10.1130%2fG36802.1&partnerID=40&md5=4d6c761b17e729bbf53f32f68ee8505e","A major challenge in paleoclimatology is disagreement between data and models for periods of warm climate. Data generally indicate equable conditions and reduced latitudinal temperature gradients, while models generally produce colder conditions and steeper latitudinal gradients except when using very high CO<inf>2</inf>. Here we show congruence between temperature indicators and climate model output for the cool greenhouse interval of the latest Cretaceous (Maastrichtian) using a global database of terrestrial and marine indicators and fully coupled simulations with the Community Climate System Model version 3. In these simulations we explore potential roles of greenhouse gases and properties of pre-anthropogenic liquid clouds in creating warm conditions. Our model simulations successfully reproduce warm polar temperatures and the latitudinal temperature gradient without overheating the tropics. Best fits for mean annual temperature are simulations that use 6× preindustrial levels of atmospheric CO<inf>2</inf>, or 2× preindustrial levels of atmospheric CO<inf>2</inf> and liquid cloud properties that may reflect pre-anthropogenic levels of cloud condensation nuclei. The Siberian interior is problematic, but this may relate to reconstructed elevation and the presence of lakes. Data and models together indicate tropical sea-surface temperatures ~5 °C above modern, an equator-to-pole temperature difference of 25-30 °C, and a mid-latitudinal temperature gradient of ~0.4 °C per 1° latitude, similar to the Eocene. Modified liquid cloud properties allow successful simulation of Maastrichtian climate at the relatively low levels of atmospheric CO<inf>2</inf> indicated by proxies and carbon cycle modeling. This supports the suggestion that altered properties of liquid clouds may be an important mechanism of warming during past greenhouse intervals. © 2015 Geological Society of America."
"57202076497;57212803688;55697757300;","Forty-year (1971–2010) semiquantitative observations of visibilitycloud-precipitation in Korea and its implication for aerosol effects on regional climate",2015,"10.1080/10962247.2015.1016633","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944055964&doi=10.1080%2f10962247.2015.1016633&partnerID=40&md5=91286e3c019da7805f7a87952f77f0f0","Forty-year (1971–2010) observations of cloud cover and types have been analyzed, and implications on the effects of aerosol–cloud feedback were explored. Cloud cover and types have been observed over Korea on the basis of visible (human-eye) attributes without any change in official observing instructions. Visibility has been used as an ongoing proxy measure of aerosol concentrations, and observed meteorological variables such as sunshine duration and precipitation have been employed to analyze aerosol causes and implications for urban and regional climate. The analysis revealed persistent decade-long patterns in Korea: steadily reduced visibility (–0.37 km/yr), consistently decreasing sunshine duration (–0.06 %/hr), and declining occurrence of light precipitation. Spatial distributions of sunshine duration and visibility exhibited more localized variations in the early period (1971–1990), and tended to be more uniform throughout Korea over more recent years (1991–2010), implying the recent regional-scale impact of cloud change over northeast Asia. Cloud analysis results showed that the five most common types were stratocumulus (Sc), cirrus (Ci), altostratus (As), stratus (St), and nimbostratus (Ns), with occurrences of 33%, 17%, 17%, 9%, and 8%, respectively. Occurrence of rarely precipitating or nonprecipitating low-level Sc clouds showed an increasing (+0.34%/yr), but no (or only minor) effects of aerosols on heavy precipitation such as cumulus cloud types were found. Cloud cover in the range of 6/10 to 8/10 units has increased by 31.5 ± 6.5%, and occurrences of both cloud-free (~2/10 units) and overcast (~8/10 units) conditions have decreased. © 2015 A&WMA."
"57209630149;7201821692;7004540083;7006399110;7601318782;","An intercomparison of the spatiotemporal variability of satellite- and ground-based cloud datasets using spectral analysis techniques",2015,"10.1175/JCLI-D-14-00537.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942844424&doi=10.1175%2fJCLI-D-14-00537.1&partnerID=40&md5=8e6bb9c9bb213e2de17d1b75dced8450","Because of the importance of clouds in modulating Earth's energy budget, it is critical to understand their variability in space and time for climate and modeling studies. This study examines the consistency of the spatiotemporal variability of cloud amount (CA) and cloud-top pressure (CTP) represented by five 7-yr satellite datasets from the Global Energy and Water Cycle Experiment (GEWEX) cloud assessment project, and total cloud fraction observation from the Extended Edited Cloud Reports Archive (EECRA). Two spectral analysis techniques, namely combined maximum covariance analysis (CMCA) and combined principal component analysis (CPCA), are used to extract the dominant modes of variability from the combined datasets, and the resulting spatial patterns are compared in parallel. The results indicate that the datasets achieve overall excellent agreement on both seasonal and interannual scales of variability, with the correlations between the spatial patterns mostly above 0.6 and often above 0.8. For seasonal variability, the largest differences are found in the Northern Hemisphere high latitudes and near the South African coast forCAand in the Sahel region for CTP, where some differences in the phase and strength of the seasonal cycle are found. On interannual scales, global cloud variability is mostly associated with major climate modes, including El Niño-Southern Oscillation (ENSO), the Pacific decadal oscillation (PDO), and the Indian Ocean dipole mode (IODM), and the datasets also agree reasonably well. The good agreement across the datasets supportsthe conclusion that they are describing cloud variations with these climate modes. © 2015 American Meteorological Society."
"7501630594;56467606100;7501956187;56467654300;","Quantifying the effects of long-term climate change on tropical cyclone rainfall using a cloud-resolving model: Examples of two landfall typhoons in Taiwan",2015,"10.1175/JCLI-D-14-00044.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920276258&doi=10.1175%2fJCLI-D-14-00044.1&partnerID=40&md5=143b11521aa7a90ecea58b73eb6be90c","To quantify the effects of long-term climate change on typhoon rainfall near Taiwan, cloud-resolving simulations of Typhoon (TY) Sinlaku and TY Jangmi, both in September 2008, are performed and compared with sensitivity tests where these same typhoons are placed in the climate background of 1950-69, which is slightly cooler and drier compared to themodern climate of 1990-2009 computed using NCEP-NCAR reanalysis data. Using this strategy, largely consistent responses are found in themodel although only two cases are studied. In control experiments, bothmodern-day typhoons yield more rainfall than their counterpart in the sensitivity test using past climate, by about 5%-6% at 200-500km from the center for Sinlaku and roughly 4%-7% within 300 km of Jangmi, throughout much of the periods simulated. In both cases, the frequency of more-intense rainfall (20 to &gt;50mmh-1) also increases by about 5%-25%and the increase tends to be larger toward higher rain rates. Results fromthe water budget analysis, again quite consistent between the two cases, indicate that the increased rainfall from the typhoons in the modern climate is attributable to both a moister environment (by 2.5%-4%) as well as, on average, a more active secondary circulation of the storm. Thus, a changing climate may already have had a discernible impact on TC rainfall near Taiwan. While an overall increase in TC rainfall of roughly 5%may not seemlarge, it is certainly not insignificant considering that the long-termtrend observed in the past 40-50 yr, whatever the causes might be, may continue for many decades in the foreseeable future. © 2015 American Meteorological Society."
"7404829395;56537463000;22959252400;56901200600;7404815507;57211379123;8397494800;6603613067;7103271625;6603171355;57193132723;56203249800;7004714030;55686667100;14045744500;8918407000;13405561000;25031430500;54788178800;35550043200;6701525565;7102001105;7006165316;","Evaluating the diurnal cycle of upper-tropospheric ice clouds in climate models using SMILES observations",2015,"10.1175/JAS-D-14-0124.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932192199&doi=10.1175%2fJAS-D-14-0124.1&partnerID=40&md5=8979e5057dad82a83516361ab0b00a30","Upper-tropospheric ice cloud measurements from the Superconducting Submillimeter Limb Emission Sounder (SMILES) on the International Space Station (ISS) are used to study the diurnal cycle of upper-tropospheric ice cloud in the tropics and midlatitudes (40°S-40°N) and to quantitatively evaluate ice cloud diurnal variability simulated by 10 climate models. Over land, the SMILES-observed diurnal cycle has a maximum around 1800 local solar time (LST), while the model-simulated diurnal cycles have phases differing from the observed cycle by -4 to 12 h. Over ocean, the observations show much smaller diurnal cycle amplitudes than over land with a peak at 1200 LST, while the modeled diurnal cycle phases are widely distributed throughout the 24-h period. Most models show smaller diurnal cycle amplitudes over ocean than over land, which is in agreement with the observations. However, there is a large spread of modeled diurnal cycle amplitudes ranging from 20% to more than 300% of the observed over both land and ocean. Empirical orthogonal function (EOF) analysis on the observed and model-simulated variations of ice clouds finds that the first EOF modes over land from both observation and model simulations explain more than 70% of the ice cloud diurnal variations and they have similar spatial and temporal patterns. Over ocean, the first EOF from observation explains 26.4% of the variance, while the first EOF from most models explains more than 70%. The modeled spatial and temporal patterns of the leading EOFs over ocean show large differences from observations, indicating that the physical mechanisms governing the diurnal cycle of oceanic ice clouds are more complicated and not well simulated by the current climate models. © 2015 American Meteorological Society."
"57204886915;55823467500;7203062717;57193132723;","Role of longwave cloud-radiation feedback in the simulation of the Madden-Julian oscillation",2015,"10.1175/JCLI-D-14-00767.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942864304&doi=10.1175%2fJCLI-D-14-00767.1&partnerID=40&md5=aef722671f95632a043e02c665a96d69","The role of the cloud-radiation interaction in the simulation of the Madden-Julian oscillation (MJO) is investigated. A special focus is on the enhancement of column-integrated diabatic heating due to the greenhouse effects of clouds and moisture in the region of anomalous convection. The degree of this enhancement, the greenhouse enhancement factor (GEF), is measured at different precipitation anomaly regimes as the negative ratio of anomalous outgoing longwave radiation to anomalous precipitation. Observations show that the GEF varies significantly with precipitation anomaly and with the MJO cycle. The greenhouse enhancement is greater in weak precipitation anomaly regimes and its effectiveness decreases monotonically with increasing precipitation anomaly. The GEF also amplifies locally when convection is strengthened in association with the MJO, especially in the weak precipitation anomaly regime (&lt;5 mm day-1). A robust statistical relationship is found among CMIP5 climate model simulations between the GEF and the MJO simulation fidelity. Models that simulate a stronger MJO also simulate a greater GEF, especially in the weak precipitation anomaly regime (&lt;5 mm day-1). Models with a greater GEF in the strong precipitation anomaly regime (&gt;30 mm day-1) represent a slightly slower MJO propagation speed. Many models that lack the MJO underestimate the GEF in general and in particular in the weak precipitation anomaly regime. The results herein highlight that the cloud-radiation interaction is a crucial process for climate models to correctly represent the MJO. © 2015 American Meteorological Society."
"26659013400;14045744500;23484340400;","A regime-dependent parametrization of subgrid-scale cloud water content variability",2015,"10.1002/qj.2506","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941172126&doi=10.1002%2fqj.2506&partnerID=40&md5=d3ecd6d42477c979ca52e0448f7896b5","The subgrid-scale spatial variability in cloud water content can be described by a parameter f called the fractional standard deviation. This is equal to the standard deviation of the cloud water content divided by the mean. This parameter is an input to schemes that calculate the impact of subgrid-scale cloud inhomogeneity on gridbox-mean radiative fluxes and microphysical process rates. A new regime-dependent parametrization of the spatial variability of cloud water content is derived from CloudSat observations of ice clouds. In addition to the dependencies on horizontal and vertical resolution and cloud fraction included in previous parametrizations, the new parametrization includes an explicit dependence on cloud type. The new parametrization is then implemented in the Global Atmosphere 6 (GA6) configuration of the Met Office Unified Model and used to model the effects of subgrid variability of both ice and liquid water content on radiative fluxes and autoconversion and accretion rates in three 20-year atmosphere-only climate simulations. These simulations show the impact of the new regime-dependent parametrization on diagnostic radiation calculations, interactive radiation calculations and both interactive radiation calculations and in a new warm microphysics scheme. The control simulation uses a globally constant f value of 0.75 to model the effect of cloud water content variability on radiative fluxes. The use of the new regime-dependent parametrization in the model results in a global mean which is higher than the control's fixed value and a global distribution of f which is closer to CloudSat observations. When the new regime-dependent parametrization is used in radiative transfer calculations only, the magnitudes of short-wave and long-wave top of atmosphere cloud radiative forcing are reduced, increasing the existing global mean biases in the control. When also applied in a new warm microphysics scheme, the short-wave global mean bias is reduced. This article describes the development and impacts of a new cloud-type dependent parametrization of the variability of cloud water content. This image shows a snapshot from the CloudSat observations (courtesy of the CloudSat Data Processing Center) used to derive the parametrization together with the corresponding MODIS view and highlights the clear difference in variability between convective clouds to the centre and right of the image and non-convective clouds to the left. © 2015 Royal Meteorological Society."
"56533419900;24173130300;56533742600;35611334800;35227762400;36342881200;6602600408;","Analysis of diagnostic climate model cloud parametrizations using large-eddy simulations",2015,"10.1002/qj.2515","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941191226&doi=10.1002%2fqj.2515&partnerID=40&md5=8197490d909f3699dd93f95ec7318753","Current climate models often predict fractional cloud cover on the basis of a diagnostic probability density function (PDF) describing the subgrid-scale variability of the total water specific humidity, q<inf>t</inf>, favouring schemes with limited complexity. Standard shapes are uniform or triangular PDFs, the widths of which are assumed to scale with the grid-box mean q<inf>t</inf> or the grid-box mean saturation specific humidity, q<inf>s</inf>. In this study, the q<inf>t</inf> variability is analysed from large-eddy simulations for two stratocumulus, two shallow cumulus, and one deep convective cases. We find that, in most cases, triangles are a better approximation to the simulated PDFs than uniform distributions. In 2 of the 24 slices examined, the actual distributions were so strongly skewed that the simple symmetric shapes could not capture the PDF at all. The distribution width for either shape scales acceptably well with both the mean values of q<inf>t</inf> and q<inf>s</inf>, the former being a slightly better choice. The q<inf>t</inf> variance is underestimated by the fitted PDFs, but overestimated by the existing parametrizations. While the cloud fraction is in general relatively well diagnosed from fitted or parametrized uniform or triangular PDFs, it fails to capture cases with small partial cloudiness, and in 10-30% of the cases misdiagnoses clouds in clear skies or vice versa. The results suggest choosing a parametrization with a triangular shape, where the distribution width would scale with the grid-box mean q<inf>t</inf> using a scaling factor of 0.076. However, this is subject to the caveat that the reference simulations examined here were partly for rather small domains and driven by idealised boundary conditions. © 2015 Royal Meteorological Society."
"8859530100;56611366900;6701333444;6506545080;55272477500;57209854833;37116849700;37018824600;7409074131;55745955800;","RACORO continental boundary layer cloud investigations: 3. separation of parameterization biases single-column model CAM5 simulations of shallow cumulus",2015,"10.1002/2014JD022524","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955656931&doi=10.1002%2f2014JD022524&partnerID=40&md5=91efe5d8206ce98891a1a5a0227c2f52","Climatically important low-level clouds are commonly misrepresented in climate models. The FAst-physics System TEstbed and Research (FASTER) Project has constructed case studies from the Atmospheric Radiation Measurement Climate Research Facility’s Southern Great Plain site during the RACORO aircraft campaign to facilitate research on model representation of boundary-layer clouds. This paper focuses on using the single-column Community Atmosphere Model version 5 (SCAM5) simulations of a multi-day continental shallow cumulus case to identify specific parameterization causes of low-cloud biases. Consistent model biases among the simulations driven by a set of alternative forcings suggest that uncertainty in the forcing plays only a relatively minor role. In-depth analysis reveals that the model’s shallow cumulus convection scheme tends to significantly under-produce clouds during the times when shallow cumuli exist in the observations, while the deep convective and stratiform cloud schemes significantly over-produce low-level clouds throughout the day. The links between model biases and the underlying assumptions of the shallow cumulus scheme are further diagnosed with the aid of large-eddy simulations and aircraft measurements, and by suppressing the triggering of the deep convection scheme. It is found that the weak boundary layer turbulence simulated is directly responsible for the weak cumulus activity and the simulated boundary layer stratiform clouds. Increased vertical and temporal resolutions are shown to lead to stronger boundary layer turbulence and reduction of low-cloud biases. © 2015. American Geophysical Union. All Rights Reserved."
"23767277800;7401776640;55894937000;","How has subtropical stratocumulus and associated meteorology changed since the 1980s?",2015,"10.1175/JCLI-D-15-0120.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946227883&doi=10.1175%2fJCLI-D-15-0120.1&partnerID=40&md5=6810ad765e64a79db853bf40697e9470","The importance of low-level cloud feedbacks to climate sensitivity motivates an investigation of how low-level cloud amount and related meteorological conditions have changed in recent decades in subtropical stratocumulus regions. Using satellite cloud datasets corrected for inhomogeneities, it is found that during 1984-2009 low-level cloud amount substantially increased over the northeastern Pacific, southeastern Pacific, and southeastern Atlantic; decreased over the northeastern Atlantic; and weakly increased over the southeastern Indian Ocean subtropical stratocumulus regions. Examination of meteorological parameters from four reanalyses indicates that positive trends in low-level cloud amount are associated with cooler sea surface temperature, greater inversion strength, and enhanced cold-air advection. The converse holds for negative trends in low-level cloud amount. A multilinear regression model based on these three meteorological variables reproduces the sign and magnitude of observed cloud amount trends in all stratocumulus regions within the range of observational uncertainty. Changes in inversion strength have the largest independent effect on cloud trends, followed by changes in advection strength. Changes in sea surface temperature have the smallest independent effect on cloud trends. Differing signs of cloud trends and differing contributions from meteorological parameters suggest that observed changes in subtropical stratocumulus since the 1980s may be due to natural variability rather than a systematic response to climate change. © 2015 American Meteorological Society."
"36740698600;55738957800;16246205000;","Effects of convective microphysics parameterization on large-scale cloud hydrological cycle and radiative budget in tropical and midlatitude convective regions",2015,"10.1175/JCLI-D-15-0064.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950154509&doi=10.1175%2fJCLI-D-15-0064.1&partnerID=40&md5=2efbd5921a974cc430b33e11c0e4131a","A two-moment microphysics scheme for deep convection was previously implemented in the NCAR Community Atmosphere Model version 5 (CAM5) by Song et al. The new scheme improved hydrometeor profiles in deep convective clouds and increased deep convective detrainment, reducing the negative biases in low and midlevel cloud fraction and liquid water path compared to observations. Here, the authors examine in more detail the impacts of this improved microphysical representation on regional-scale water and radiation budgets. As a primary source of cloud water for stratiform clouds is detrainment from deep and shallow convection, the enhanced detrainment leads to larger stratiform cloud fractions, higher cloud water content, and more stratiform precipitation over the ocean, particularly in the subtropics where convective frequency is also increased. This leads to increased net cloud radiative forcing. Over land regions, cloud amounts are reduced as a result of lower relative humidity, leading to weaker cloud forcing and increasedOLR. Comparing the water budgets to cloud-resolving model simulations shows improvement in the partitioning between convective and stratiformprecipitation, though the deep convection is still too active in theGCM. The addition of convective microphysics leads to an overall improvement in the regional cloud water budgets. © 2015 American Meteorological Society."
"57044397100;35069282600;7005477332;7004315232;","Aerosol-cloud interactions in ship tracks using Terra MODIS/MISR",2015,"10.1002/2014JD022736","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928624091&doi=10.1002%2f2014JD022736&partnerID=40&md5=121a938e97e1445788aa70a867e68917","Simultaneous ship track observations fromTerra Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging Spectroradiometer (MISR) have been compiled to investigate how ship-injected aerosols affect marine warm boundary layer clouds for different cloud types and environmental conditions. By taking advantage of the high spatial resolution multiangle observations available from MISR, we utilized the retrieved cloud albedo, cloud top height, and cloudmotion vectors to examine cloud property responses in ship-polluted and nearby unpolluted clouds. The strength of the cloud albedo response to increased aerosol level is primarily dependent on cloud cell structure, dryness of the free troposphere, and boundary layer depth, corroborating a previous study by Chen et al. (2012) where A-Train satellite data were utilized. Under open cell cloud structure the cloud properties are more susceptible to aerosol perturbations as compared to closed cells. Aerosol plumes caused an increase in liquid water amount (+38%), cloud top height (+13%), and cloud albedo (+49%) for open cell clouds, whereas for closed cell clouds, little change in cloud properties was observed. Further capitalizing on MISR’s unique capabilities, the MISR cross-track cloud speed was used to derive cloud top divergence. Statistically averaging the results from the identified plume segments to reduce random noise, we found evidence of cloud top divergence in the ship-polluted clouds, whereas the nearby unpolluted clouds showed cloud top convergence, providing observational evidence of a change in local mesoscale circulation associated with enhanced aerosols. Furthermore, open cell polluted clouds revealed stronger cloud top divergence as compared to closed cell clouds, consistent with different dynamical mechanisms driving their responses. These results suggest that detailed cloud responses, classified by cloud type and environmental conditions, must be accounted for in global climate modeling studies to reduce uncertainties in calculations of aerosol indirect forcing. © 2015. American Geophysical Union. All Rights Reserved."
"13204619900;8891521600;","The ENSO effects on tropical clouds and top-of-atmosphere cloud radiative effects in CMIP5 models",2015,"10.1002/2014JD022337","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932195186&doi=10.1002%2f2014JD022337&partnerID=40&md5=7b8e0ccd43c4241d0c15fcd268fdeeea","The El Niño–Southern Oscillation (ENSO) effects on tropical clouds and top-of-atmosphere (TOA) cloud radiative effects (CREs) in Coupled Model Intercomparison Project Phase 5 (CMIP5) models are evaluated using satellite-based observations and International Satellite Cloud Climatology Project satellite simulator output. Climatologically, most CMIP5 models produce considerably less total cloud amount with higher cloud top and notably larger reflectivity than observations in tropical Indo-Pacific (60°E-200°E; 10°S-10°N). During ENSO, most CMIP5 models strongly underestimate TOA CRE and cloud changes over western tropical Pacific. Over central tropical Pacific, while themulti-modelmean resembles observations in TOA CRE and cloud amount anomalies, it notably overestimates cloud top pressure (CTP) decreases; there are also substantial inter-model variations. The relative effects of changes in cloud properties, temperature, and humidity on TOA CRE anomalies during ENSO in the CMIP5 models are assessed using cloud radiative kernels. The CMIP5 models agree with observations in that their TOA shortwave CRE anomalies are primarily contributed by total cloud amount changes, and their TOA longwave CRE anomalies are mostly contributed by changes in both total cloud amount and CTP. The model biases in TOA CRE anomalies particularly the strong underestimations over western tropical Pacific are, however, mainly explained by model biases in CTP and cloud optical thickness (τ) changes. Despite the distinct model climatological cloud biases particularly in τ regime, the TOA CRE anomalies from total cloud amount changes are comparable between the CMIP5 models and observations, because of the strong compensations between model underestimation of TOA CRE anomalies from thin clouds and overestimation from medium and thick clouds. © 2015. American Geophysical Union. All Rights Reserved."
"56075881200;55802246600;55476830600;55688930000;56162305900;55522498000;55717074000;55087038900;","A new approach to modeling aerosol effects on East Asian climate: Parametric uncertainties associated with emissions, cloud microphysics, and their interactions",2015,"10.1002/2015JD023442","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943457532&doi=10.1002%2f2015JD023442&partnerID=40&md5=349e540d984e83c88c34c057889dacf7","In this study, we adopt a parametric sensitivity analysis framework that integrates the quasi-Monte Carlo parameter sampling approach and a surrogate model to examine aerosol effects on the East Asian Monsoon climate simulated in the Community Atmosphere Model (CAM5). A total number of 256 CAM5 simulations are conducted to quantify the model responses to the uncertain parameters associated with cloud microphysics parameterizations and aerosol (e.g., sulfate, black carbon (BC), and dust) emission factors and their interactions. Results show that the interaction terms among parameters are important for quantifying the sensitivity of fields of interest, especially precipitation, to the parameters. The relative importance of cloud microphysics parameters and emission factors (strength) depends on evaluation metrics or the model fields we focused on, and the presence of uncertainty in cloud microphysics imposes an additional challenge in quantifying the impact of aerosols on cloud and climate. Due to their different optical and microphysical properties and spatial distributions, sulfate, BC, and dust aerosols have very different impacts on East Asian Monsoon through aerosol-cloud-radiation interactions. The climatic effects of aerosol do not always have a monotonic response to the change of emission factors. The spatial patterns of both sign and magnitude of aerosol-induced changes in radiative fluxes, cloud, and precipitation could be different, depending on the aerosol types, when parameters are sampled in different ranges of values. We also identify the different cloud microphysical parameters that show the most significant impact on climatic effect induced by sulfate, BC, and dust, respectively, in East Asia. © 2015. American Geophysical Union. All Rights Reserved."
"9249239700;36150977900;7501439334;6603126554;56130997600;23094149200;36991861900;","The impacts of cloud snow radiative effects on Pacific Ocean surface heat fluxes, surface wind stress, and ocean temperatures in coupled GCM simulations",2015,"10.1002/2014JD022538","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927697858&doi=10.1002%2f2014JD022538&partnerID=40&md5=fb28439499717c1cfc25fa2f53f95ad8","An accurate representation of the climatology of the coupled ocean-atmosphere system in global climate models has strong implications for the reliability of projected climate change inferred by these models. Our previous efforts have identified substantial biases of ocean surface wind stress that are fairly common in two generations of the Coupled Model Intercomparison Project (CMIP) models, relative to QuikSCAT climatology. One of the potential causes of the CMIP model biases is the missing representation of large frozen precipitating hydrometeors (i.e., cloud snow) in all CMIP3 and most CMIP5 models, which has not been investigated previously. We examine the impacts of cloud snow on the radiation and atmospheric circulation, air-sea fluxes, and explore the implications to common biases inCMIPmodels usingtheNational Center for Atmospheric Research coupled Community Earth SystemModel (CESM) to perform sensitivity experiments with and without cloud snow radiative effects. This study focuses on the impacts of cloud snow in CESM on ocean surface wind stress and air-sea heat fluxes, as well as their relationship with sea surface temperature (SST) and subsurface ocean temperatures in the Pacific sector. It is found that inclusion of the cloud snow parameterization in CESM reduces the surface wind stress and upper ocean temperature (including SST) biases in the tropical and midlatitude Pacific. The differences in the upper ocean temperature with and without the cloud snow parameterization are consistent with the effect of different strength of vertical mixing due to ocean surface wind stress differences but cannot be explained by the differences in net air-sea heat fluxes. © 2015. American Geophysical Union. All Rights Reserved."
"57207473157;25226875800;7401436524;","Simulations of stratus clouds over Eastern China in CAM5: Sources of errors",2015,"10.1175/JCLI-D-14-00350.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920268378&doi=10.1175%2fJCLI-D-14-00350.1&partnerID=40&md5=3f75794e2350324902686475af2a48f5","A previous study by Zhang et al. suggested two biases of the high-resolution configured Community Atmosphere Model, version 5 (CAM5), in simulating stratus clouds over eastern China, including an underestimation of stratus occurrence frequency and a spurious low stratus amount when present (AWP) value center over the Sichuan basin. In this study, the causes for these two problems are further explored. The underestimate of stratus occurrence frequency in the model is attributed to the bias in large-scale ambient environmental fields. This is confirmed by investigating the differences between two climate counterparts. Results suggest that when the environmental fields in the climate ensemble become more realistic, the simulations of stratus cloud radiative forcing and cloud fraction are enhanced, mainly caused by a corresponding increase in the stratus occurrence frequency. The specific sources of the cloud changes between these two ambient climates are then investigated. The presence of a low stratus AWP value center is found to be sensitive to the choice of dynamical core. This is confirmed by comparing the simulations from two dynamical core counterparts: a default finite-volume core and an alternative Eulerian spectral transform core. Experiments with these two cores suggest that the spectral CAM5 is able to alleviate this problem. Correspondingly, the subsiding motions when stratus clouds occur in the default core are largely suppressed in the spectral core. As a result, the spectral CAM5 has more midtopped nimbostratus cloud fraction than the default configuration over the Sichuan basin, especially in the lower levels of the cloud profiles. © 2015 American Meteorological Society."
"23485410200;23484340400;7004539332;6603821988;7201439545;7103016965;24168416900;26659116700;8982748700;14045744500;7004966070;7801353107;55628584418;24077600000;20435098200;7404142321;57193921169;56884778400;55921861500;35094424100;7004093651;24463029300;","Processes controlling tropical tropopause temperature and stratospheric water vapor in climate models",2015,"10.1175/JCLI-D-15-0075.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942855249&doi=10.1175%2fJCLI-D-15-0075.1&partnerID=40&md5=ee205b5b27dc658491a91cf5f130b847","A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations. © 2015 American Meteorological Society."
"8586682800;57199321052;","Revisiting ice nucleation from precipitation samples",2015,"10.1002/2015GL065733","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946605459&doi=10.1002%2f2015GL065733&partnerID=40&md5=8cad9fed6d30e264810fe5361324ac58","An emerging and unsolved question is the sensitivity of cloud processes, precipitation, and climate to the atmospheric ice nucleus spectrum. This work revisits estimation of atmospheric ice-nucleating particle concentration derived from cloud water and precipitation samples representing a wide range of geographical locations, seasons, storm systems, precipitation types, instruments, concentrations, and temperatures. Concentrations of ice-nucleating particles are shown to vary over 10 orders of magnitude. High variability is observed in the -5°C to -12°C range which is suggested to be biologically derived nuclei whose life cycle is associated with intermittent source and efficient sink processes. The highest ever observed nucleus concentrations at -8°C are 3 orders of magnitude lower than observed ice crystal concentrations in tropical cumuli at the same temperature. The observed upper and lower limits of the nucleus spectrum provide a possible constraint on minimum enhancement factors for secondary ice formation processes. Key Points New measurements of ice-nucleating particle in snow, sleet, and rainwater samples Nucleus concentration varies over 10 orders of magnitude between -5 and -38°C Ice nucleus spectrum shows high variability between -5 and -12°C © 2015. American Geophysical Union. All Rights Reserved."
"37099944400;25031430500;25927110300;","Arctic radiative fluxes: Present-day biases and future projections in CMIP5 models",2015,"10.1175/JCLI-D-14-00801.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942929138&doi=10.1175%2fJCLI-D-14-00801.1&partnerID=40&md5=9f83674f2050f5639cd6a202b67edcea","Radiative fluxes are critical for understanding the energy budget of the Arctic region, where the climate has been changing rapidly and is projected to continue to change. This work investigates causes of present-day biases and future projections of top-of-atmosphere (TOA) Arctic radiative fluxes in phase 5 of the Coupled Model Intercomparison Project (CMIP5). Compared to Clouds and the Earth's Radiant Energy System Energy Balanced and Filled (CERES-EBAF), CMIP5 net TOA downward shortwave (SW) flux biases are larger than outgoing longwave radiation (OLR) biases. The primary contributions to modeled TOA SW flux biases are biases in cloud amount and snow cover extent compared to the GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP) and the newly developed Making Earth System Data Records for Use in Research Environments (MEaSUREs) dataset, respectively (with most models predicting insufficient cloud amount and snow cover in the Arctic), and biases with sea ice albedo. Future projections (2081-90) with representative concentration pathway 8.5 (RCP8.5) simulations suggest increasing net TOA downward SW fluxes (+8 Wm-2) over the Arctic basin due to a decrease of surface albedo from melting snow and ice, and increasing OLR (+6 Wm-2) due to an increase in surface temperatures. The largest contribution to future Arctic net TOA downward SW flux increases is declining sea ice area, followed by declining snow cover area on land, reductions to sea ice albedo, and reductions to snow albedo on land. Cloud amount is not projected to change significantly. These results suggest the importance of accurately representing both the surface area and albedos of sea ice and snow cover as well as cloud amount in order to accurately represent TOA radiative fluxes for the present-day climate and future projections. © 2015 American Meteorological Society."
"56005080300;23082420800;","Evidence for weakening of the Walker circulation from cloud observations",2015,"10.1002/2015GL065463","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945208046&doi=10.1002%2f2015GL065463&partnerID=40&md5=b48c54674bcf10f418bca0deec26f65f","Climate models simulate a weakening of the Walker circulation in response to increased greenhouse gases, but it has not been possible to detect this weakening with observations because there are not direct measurements of atmospheric circulation strength. Indirect measurements, such as equatorial gradients in sea level pressure (SLP), exhibit trends of inconsistent sign. In this study we estimate the change in midtropospheric velocity (ω500) from observed change in cloud cover, which we argue is more closely tied to the overturning circulation than indirect measurements of SLP at the surface. Our estimates suggest a weakening and eastward shift of the Walker circulation over the last century. Because changes in cloud cover in Atmospheric Model Intercomparison Project simulations forced with increased sea surface temperature are remarkably similar in pattern, sign, and magnitude, we assert that the observed changes in cloud cover and the associated weakening of Walker circulation are at least in part externally forced. © 2015 American Geophysical Union. All Rights Reserved."
"8525144100;","Spread of model climate sensitivity linked to double-Intertropical Convergence Zone bias",2015,"10.1002/2015GL064119","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931568310&doi=10.1002%2f2015GL064119&partnerID=40&md5=b2011731bac1a6b0f33a1c2e071fffcf","Despite decades of climate research and model development, two outstanding problems still plague the latest global climate models (GCMs): the double-Intertropical Convergence Zone (ITCZ) bias and the 2-5°C spread of equilibrium climate sensitivity (ECS). Here we show that the double-ITCZ bias and ECS in 44 GCMs from Coupled Model Intercomparison Project Phases 3/5 are negatively correlated. The models with weak (strong) double-ITCZ biases have high (low)-ECS values of ∼4.1(2.2)°C. This indicates that the double-ITCZ bias is a new emergent constraint for ECS based on which ECS might be in the higher end of its range (∼4.0°C) and most models might have underestimated ECS. In addition, we argue that the double-ITCZ bias can physically affect both cloud and water vapor feedbacks (thus ECS) and is a more easily measured emergent constraint for ECS than previous ones. It can be used as a performance metric for evaluating and comparing different GCMs. ©2015. This article is a U.S. Government work and is in the public domain in the USA."
"56471281900;56014511300;24070588000;","An exploration of multivariate fluctuation dissipation operators and their response to sea surface temperature perturbations",2015,"10.1175/JAS-D-14-0077.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920610167&doi=10.1175%2fJAS-D-14-0077.1&partnerID=40&md5=60fd47665572b6122655ec6aada34591","The fluctuation-dissipation theorem (FDT) has been proposed as a method of calculating the mean response of the atmosphere to small external perturbations. This paper explores the application of the theory under time and space constraints that approximate realistic conditions. To date, most applications of the theory in the climate context used univariate, low-dimensional-state representations of the climate system and an arbitrarily long sample size. The authors explore high-dimensional multivariate FDT operators and the lower bounds of sample size needed to construct skillful operators. It is shown that the skill of the operator depends on the selection of variables and features representing the climate system and that these features change once memory (slab ocean) is added to the system. In addition, it is found that the FDT operator has skill in estimating the response to realistic sea surface temperature (SST) patterns, such as El Niño-Southern Oscillation (ENSO), despite the fact that these patterns were not part of the data used to produce the operator. The response of clouds is also studied; for variables that represent cloud properties, the decrease in skill in relation to decrease in sample size still maintains the key features of the response. © 2015 American Meteorological Society."
"7401776640;8542741400;","Empirical removal of artifacts from the ISCCP and PATMOS-x satellite cloud records",2015,"10.1175/JTECH-D-14-00058.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944042754&doi=10.1175%2fJTECH-D-14-00058.1&partnerID=40&md5=d0b4577ab09d59d2fa4b152466153117","The International Satellite Cloud Climatology Project (ISCCP) dataset and the Pathfinder Atmospheres-Extended (PATMOS-x) dataset are two commonly used multidecadal satellite cloud records. Because they are constructed from weather satellite measurements lacking long-term stability, ISCCP and PATMOS-x suffer from artifacts that inhibit their use for investigating cloud changes over recent decades. The present study describes and applies a post hoc method to empirically remove spurious variability from anomalies in total cloud fraction at each grid box. Spurious variability removed includes that associated with systematic changes in satellite zenith angle, drifts in satellite equatorial crossing time, and unrealistic large-scale spatially coherent anomalies associated with known and unidentified problems in instrument calibration and ancillary data. The basic method is to calculate for each grid box the least squares best-fit line between cloud anomalies and artifact factor anomalies, and to let the residuals from the best-fit line be the newly corrected data. After the correction procedure, the patterns of regional trends in ISCCP and PATMOS-x total cloud fraction appear much more natural. The corrected data cannot be used for studies of globally averaged cloud change, however, because the methods employed remove any real cloud variability occurring on global scales together with spurious variability. An examination of Moderate Resolution Imaging Spectroradiometer (MODIS) total cloud fraction data indicates that removing global-scale variability has little impact on regional patterns of cloud change. Corrected ISCCP and PATMOS-x data are available from the Research Data Archive at NCAR. © 2015 American Meteorological Society."
"25031430500;7103158465;","Advanced two-moment bulk microphysics for global models. Part I: Off-line tests and comparison with other schemes",2015,"10.1175/JCLI-D-14-00102.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923065772&doi=10.1175%2fJCLI-D-14-00102.1&partnerID=40&md5=15d7c8ed0066e0cc81395aabedb0883e","Prognostic precipitation is added to a cloud microphysical scheme for global climate models. Results indicate very similar performance to other commonly used mesoscale schemes in an offline driver for idealized warm rain cases, better than the previous version of the global model microphysics scheme with diagnostic precipitation. In the mixed phase regime, there is significantly more water and less ice, which may address a common bias seen with the scheme in climate simulations in the Arctic. For steady forcing cases, the scheme has limited sensitivity to time step out to the ~15-min time steps typical of global models. The scheme is similar to other schemes with moderate sensitivity to vertical resolution. The limited time step sensitivity bodes well for use of the scheme in multiscale models from the mesoscale to the large scale. The scheme is sensitive to idealized perturbations of cloud drop and crystal number. Precipitation decreases and condensate increases with increasing drop number, indicating substantial decreases in precipitation efficiency. The sensitivity is less than with the previous version of the scheme for low drop number concentrations (Nc &lt; 100 cm -3). Ice condensate increases with ice number, with large decreases in liquid condensate as well for a mixed phase case. As expected with prognostic precipitation, accretion is stronger than with diagnostic precipitation and the accretion to autoconversion ratio increases faster with liquid water path (LWP), in better agreement with idealized models and earlier studies than the previous version. © 2015 American Meteorological Society."
"7103232081;15125216700;55350230200;","Tropical gravity wave momentum fluxes and latent heating distributions",2015,"10.1175/JAS-D-15-0020.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943413628&doi=10.1175%2fJAS-D-15-0020.1&partnerID=40&md5=00dc4a01c3330ced9c956ff990c75950","Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations for GW momentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating. © 2015 American Meteorological Society."
"55253694900;7102084129;55389396600;6508061772;7004222436;","Effects of aerosol sources and chemical compositions on cloud drop sizes and glaciation temperatures",2015,"10.1002/2015JD023270","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944909397&doi=10.1002%2f2015JD023270&partnerID=40&md5=b2e5b542efdc31d8bdb7cc9607f53fba","The effect of aerosols on cloud properties, such as its droplet sizes and its glaciation temperatures, depends on their compositions and concentrations. In order to examine these effects,we collected rain samples in northern Israel during five winters (2008-2011 and 2013) and determined their chemical composition, which was later used to identify the aerosols’ sources. By combining the chemical data with satellite-retrieved cloud properties, we linked the aerosol types, sources, and concentrations with the cloud glaciation temperatures (Tg). The presence of dust increased Tg from -26°C to -12°C already at relatively low dust concentrations. This result is in agreement with the conventional wisdom that desert dust serves as good ice nuclei (INs). With higher dust concentrations, Tg saturated at -12°C, even though cloud droplet sizes decreased as a result of the cloud condensation nucleating (CCN) activity of the dust. Marine air masses also encouraged freezing, but in this case, freezing was enhanced by the larger cloud droplet sizes in the air masses (caused by low CCN concentrations) and not by IN concentrations or by aerosol type. An increased fraction of anthropogenic aerosols in marine air masses caused a decrease in Tg, indicating that these aerosols served as poor IN. Anthropogenic aerosols reduced cloud droplet sizes, which further decreased Tg. Our results could be useful in climate models for aerosol-cloud interactions, aswe investigated the effects of aerosols of different sources on cloud properties. Such parameterization can simplify these models substantially. © 2015. American Geophysical Union. All Rights Reserved."
"55575258400;26645289600;7402064802;16425142900;36856321600;6602963031;7004222705;57210518852;","External influences on modeled and observed cloud trends",2015,"10.1175/JCLI-D-14-00734.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942906591&doi=10.1175%2fJCLI-D-14-00734.1&partnerID=40&md5=93ce5f53080f69ee8d3935d6b0a56cc2","Understanding the cloud response to external forcing is a major challenge for climate science. This crucial goal is complicated by intermodel differences in simulating present and future cloud cover and by observational uncertainty. This is the first formal detection and attribution study of cloud changes over the satellite era. Presented herein areCMIP5 model-derived fingerprints of externally forced changes to three cloud properties: the latitudes at which the zonally averaged total cloud fraction (CLT) is maximized or minimized, the zonal average CLT at these latitudes, and the height of high clouds at these latitudes. By considering simultaneous changes in all three properties, the authors define a coherent multivariate fingerprint of cloud response to external forcing and use models from phase 5 of CMIP (CMIP5) to calculate the average time to detect these changes. It is found that given perfect satellite cloud observations beginning in 1983, the models indicate that a detectable multivariate signal should have already emerged. A search is then made for signals of external forcing in two observational datasets: ISCCP andPATMOS-x. The datasets are both found to show a poleward migration of the zonal CLT pattern that is incompatible with forcedCMIP5 models.Nevertheless, a detectable multivariate signal is predicted by models over the PATMOS-x time period and is indeed present in the dataset. Despite persistent observational uncertainties, these results present a strong case for continued efforts to improve these existing satellite observations, in addition to planning for new missions. © 2015 American Meteorological Society."
"56747419100;57214153361;56659005700;56588071900;26641079300;55578304300;48061112000;57202109092;8581523500;55743195000;7404864296;","Inter-annual variations of cloud and precipitation and their possible relationships with surface aerosols in Shanghai",2015,"10.4209/aaqr.2014.08.0179","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938297260&doi=10.4209%2faaqr.2014.08.0179&partnerID=40&md5=f30dd10015c0e02c46cbe075dcde7eee","Aerosol-cloud-precipitation interactions have attracted much more attention for decades, but there still remain many uncertainties in assessing global climate. Long-term ground-based measurements of aerosol, cloud and precipitation in Shanghai were used to examine their inter-annual variations and possible relationships. During 1990–2010, the yearly averaged total cloud cover (TCC) and low cloud cover (LCC) decrease on average by 0.58% and 2.49% per year. LCC correlates to surface aerosols (e.g., PM<inf>10</inf>), with a correlation coefficient (R) of 0.67. Aerosol optical depth (AOD), as an indicator of columnar aerosol loading, shows a non-significant correlation with cloud cover. The yearly-aggregated heavy and extreme rain days and their rainfall amount increase gradually. The moderate rain day enhances but its annual rainfall amount declines year by year, while the light rain exhibits an opposite pattern to the moderate rain. These results imply that local aerosols maybe exert somewhat enforcing on low cloud and light rain through possible entrainment or updraft that can bring up surface particles into free troposphere, whereas its influence to total cloud and precipitation is negligible at a small scale. Future studies are needed to ensure whether local aerosols to directly affect low cloud, and to explore how surface aerosols to enter into higher atmospheric layers and impact cloud and precipitation at larger scales. © Taiwan Association for Aerosol Research."
"55879571100;57203439874;35849722200;56145499000;14326501100;","Correlation analysis between AOD and cloud parameters to study their relationship over china using MODIS data (2003–2013): Impact on cloud formation and climate change",2015,"10.4209/aaqr.2014.08.0168","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929666720&doi=10.4209%2faaqr.2014.08.0168&partnerID=40&md5=0661f37d70dac1f288d89672ef4c9e6c","In the present study, we examined the spatial and temporal variations in aerosol optical depth (AOD) at 550 nm and its relationship with various cloud parameters derived from the Moderate resolution Imaging Spectroradiometer (MODIS) sensor onboard Terra satellite. The data have been analyzed for the period of 10-years between March 2003 and February 2013 over 12 major cities in China. The results revealed that high AOD noticed over low latitude regions influenced with high anthropogenic activities and the low AOD observed for the high altitude and mountainous areas, since AOD accounts for the slant path which reduces the aerosol emissions. In addition, the aerosol variations in the atmosphere are complicated by several factors in emissions (natural and anthropogenic) as well as stagnant synoptic meteorology. From the temporal studies, it is clear that the maximum AOD was found during summer followed by spring and autumn with a minimum AOD in winter season for all the regions of study in China. Furthermore, we studied the relationship between AOD versus water vapor (WV), cloud fraction (CF), cloud optical thickness (COT), cloud effective radius (CER), cloud top pressure (CTP), and cloud top temperature (CTT) for the selected regions in China. Additionally, regression analysis and one paired student’s t-Test were applied to represent the probability of data significant at 95% confidence for the derived AOD values and cloud parameters in order to provide a better understanding of aerosol-cloud interaction. © Taiwan Association for Aerosol Research."
"7404633868;7006698304;6701754792;7406215388;7202957110;","Mass-flux characteristics of tropical cumulus clouds from wind profiler observations at Darwin, Australia",2015,"10.1175/JAS-D-14-0259.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943805402&doi=10.1175%2fJAS-D-14-0259.1&partnerID=40&md5=8e1e85b92ac06fafa0a273a4775ca400","Cumulus parameterizations in weather and climate models frequently apply mass-flux schemes in their description of tropical convection. Mass flux constitutes the product of the fractional area covered by convection in a model grid box and the vertical velocity in cumulus clouds. However, vertical velocities are difficult to observe on GCM scales, making the evaluation of mass-flux schemes difficult. Here, the authors combine high-temporal-resolution observations of in-cloud vertical velocities derived from a pair of wind profilers over twowet seasons at Darwin with physical properties of precipitating clouds [cloud-top heights (CTH), convective-stratiform classification] derived from the Darwin C-band polarimetric radar to provide estimates of cumulus mass flux and its constituents. The length of this dataset allows for investigations of the contributions from different cumulus cloud types-namely, congestus, deep, and overshooting convection-to the overall mass flux and of the influence of large-scale conditions on mass flux. The authors found that mass flux was dominated by updrafts and, in particular, the updraft area fraction, with updraft vertical velocity playing a secondary role. The updraft vertical velocities peaked above 10 km where both the updraft area fractions and air densities were small, resulting in a marginal effect on mass-flux values. Downdraft area fractions are much smaller and velocities aremuch weaker than those in updrafts. The area fraction responded strongly to changes in midlevel large-scale vertical motion and convective inhibition (CIN). In contrast, changes in the lower-tropospheric relative humidity and convective available potential energy (CAPE) strongly modulate in-cloud vertical velocities but have moderate impacts on area fractions. Although average mass flux is found to increase with increasing CTH, it is the environmental conditions that seem to dictate the magnitude of mass flux produced by convection through a combination of effects on area fraction and velocity. © 2015 American Meteorological Society."
"36086191200;51863973800;35615593500;16480080500;6701492129;56250708000;36158029700;","A detailed cloud fraction climatology of the upper indus basin and its implications for near-surface air temperature",2015,"10.1175/JCLI-D-14-00505.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944080856&doi=10.1175%2fJCLI-D-14-00505.1&partnerID=40&md5=447783ff048524f24ae0b89dd467f051","Clouds play a key role in hydroclimatological variability by modulating the surface energy balance and air temperature. This study utilizes MODIS cloud cover data, with corroboration from global meteorological reanalysis (ERA-Interim) cloud estimates, to describe a cloud climatology for the upper Indus River basin. It has specific focus on tributary catchments in the northwest of the region, which contribute a large fraction of basin annual runoff, including 65% of flow originating above Besham, Pakistan or 50 km3 yr-1 in absolute terms. In this region there is substantial cloud cover throughout the year, with spatial means of 50%-80% depending on the season. The annual cycles of catchment spatial mean daytime and nighttime cloud cover fraction are very similar. This regional diurnal homogeneity belies substantial spatial variability, particularly along seasonally varying vertical profiles (based on surface elevation). Correlations between local near-surface air temperature observations and MODIS cloud cover fraction confirm the strong linkages between local atmospheric conditions and near-surface climate variability. These correlations are interpreted in terms of seasonal and diurnal variations in apparent cloud radiative effect and its influence on near-surface air temperature in the region. The potential role of cloud radiative effect in recognized seasonally and diurnally asymmetrical temperature trends over recent decades is also assessed by relating these locally observed trends to ERA-Interim-derived trends in cloud cover fraction. Specifically, reduction in nighttime cloud cover fraction relative to daytime conditions over recent decades appears to provide a plausible physical mechanismfor the observed nighttime cooling of surface air temperature in summermonths. © 2015 American Meteorological Society."
"8977001000;7403282069;","Improved low-cloud simulation from the community atmosphere model with an advanced third-order turbulence closure",2015,"10.1175/JCLI-D-14-00776.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934448553&doi=10.1175%2fJCLI-D-14-00776.1&partnerID=40&md5=10df0632cad6bc10ebfb82bdad6fad5f","In this study, a simplified intermediately prognostic higher-order turbulence closure (IPHOC) is implemented in the Community Atmosphere Model, version 5 (CAM5), to provide a consistent treatment of subgrid-scale cloud processes, except for deep convection. The planetary boundary layer (PBL) height is prognosticated to better resolve the discontinuity of temperature and moisture above the PBL top. Single-column model tests show that fluxes of liquid water potential temperature and total water, cloud fraction, and liquid water content are improved with this approach. The simplified IPHOC package replaces the boundary layer dry and moist turbulence parameterizations, the shallow convection parameterization, and the liquid-phase part of the cloud macrophysics parameterization in CAM5. CAM5-IPHOC improves the simulation of the low-level clouds off the west coasts of continents and the storm track region in the Southern Hemisphere (SH). The transition from stratocumulus to cumulus clouds is more gradual. There are also improvements on the cloud radiative forcing, especially shortwave, in the subsidence regime. The improvements in the relationships among low cloud amount, surface relative humidity, lower tropospheric stability, and PBL depth are seen in some stratocumulus regions. CAM5-IPHOC, however, produces weaker precipitation at the South Pacific convergence zone than CAM5 because of less energy flux into the SH atmosphere. The more downward surface shortwave radiative cooling and the less top-of-the-atmosphere longwave cloud radiative heating in the SH relative to the Northern Hemisphere explains the anomalous cooling and the lesser energy flux into the SH, which is related to the underestimate of extratropical middle/high clouds in the SH. © 2015 American Meteorological Society."
"56540693200;","Natural aerosols and climate: Understanding the unpolluted atmosphere to better understand the impacts of pollution",2015,"10.1002/wea.2540","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940952409&doi=10.1002%2fwea.2540&partnerID=40&md5=dbf774f2fee5bff451357c30ef7126ed","Natural aerosols define a pre-industrial baseline state from which the magnitude of anthropogenic aerosol effects on climate are calculated and are a major component of the large uncertainty in anthropogenic aerosol-cloud radiative forcing. This uncertainty would be reduced if aerosol environments unperturbed by air pollution could be studied in the present-day atmosphere, but the pervasiveness of air pollution makes identification of unperturbed regions difficult. This study uses global model simulations to show where aerosol concentrations have remained similar between 1750 and 2000. Four suitable measurement stations are then identified in regions with a pristine-like aerosol state. © 2015 Royal Meteorological Society."
"55628587967;55751665200;34870277200;6701346974;36006968000;","Simulation of the Indian Summer Monsoon in the superparameterized Climate Forecast System Version 2: Preliminary results",2015,"10.1175/JCLI-D-14-00607.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949995844&doi=10.1175%2fJCLI-D-14-00607.1&partnerID=40&md5=34e5ebb5685a3226b6cd9babd73e4125","An analysis of a 5-yr (from 1 January 2009 to 31 December 2013) free run of the superparameterized (SP) Climate Forecast System (CFS) version 2 (CFSv2) (SP-CFS), implemented for the first time at a spectral triangular truncation at wavenumber 62 (T62) atmospheric horizontal resolution, is presented. The SP-CFS simulations are evaluated against observations and traditional convection parameterized CFSv2 simulations at T62 resolution as well as at some higher resolutions. The metrics for evaluating the model performance are chosen in order to mainly address the improvement in systematic biases observed in the CFSv2 documented in earlier studies. While the primary focus of this work is on evaluating the improvement of the simulation of the Indian summer monsoon (ISM) by the SP-CFS model, some results are also presented within the context of the global climate. The SP-CFS significantly reduces the dry bias of precipitation over the Indian subcontinent and better captures the monsoon intraseasonal oscillation (MISO) modes. SP-CFS also improves the northward and eastward propagation of high- and low-frequency modes of ISM. Compared to CFSv2, the SP-CFS model simulates improved convectively coupled equatorial waves; better temperature structures both spatially and vertically, leading to a significantly improved relative distribution of variance for the synoptic disturbances and low-frequency tropical intraseasonal oscillations (ISOs). This analysis of the development of SP-CFS is particularly important as it shows promise for improving the cloud process representation through an SP framework and is able to improve the mean as well as intraseasonal characteristics of CFSv2 within the context of the ISM. © 2015 American Meteorological Society."
"57199180379;55745955800;","Scale-aware parameterization of liquid cloud inhomogeneity and its impact on simulated climate in CESM",2015,"10.1002/2015JD023565","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942197793&doi=10.1002%2f2015JD023565&partnerID=40&md5=62975e7fd1c91b1038cdbb1e51603ebb","Using long-term radar-based groundmeasurements fromthe Atmospheric RadiationMeasurement Program, we derive the inhomogeneity of cloud liquid water as represented by the shape parameter of a gamma distribution. The relationship between the inhomogeneity and the model grid size as well as atmospheric condition is presented. A larger grid scale and more unstable atmosphere are associated with larger inhomogeneity that is described by a smaller shape parameter. This relationship is implemented as a scale-aware parameterization of the liquid cloud inhomogeneity in the Community Earth System Model (CESM) in which the shape parameter impacts the cloud microphysical processes.When used in the default CESM1 with the finite-volume dynamic core where a constant liquid inhomogeneity parameter was assumed, it reduces the cloud inhomogeneity in high latitudes and increases it in low latitudes. This is due to both the smaller (larger) grid size in high (low) latitudes in the longitude-latitude grid setting of CESM and the more stable (unstable) atmosphere. The single-column model and general circulation model sensitivity experiments show that the new parameterization increases the cloud liquid water path in polar regions and decreases it in low latitudes. An advantage of the parameterization is that it can recognize the spatial resolutions of the CESM without special tuning of the cloud water inhomogeneity parameter. © 2015. The Authors."
"55942502100;56493740900;6603546080;7102651635;57208727319;55695451700;7004364155;","CERES synoptic product: Methodology and validation of surface radiant flux",2015,"10.1175/JTECH-D-14-00165.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942520520&doi=10.1175%2fJTECH-D-14-00165.1&partnerID=40&md5=c3def51172244e8ba08209d64ab7e426","The Clouds and the Earth's Radiant Energy System Synoptic (SYN1deg), edition 3, product provides climate-quality global 3-hourly 1° × 1° gridded top of atmosphere, in-atmosphere, and surface radiant fluxes. The in-atmosphere surface fluxes are computed hourly using a radiative transfer code based upon inputs from Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS), 3-hourly geostationary (GEO) data, and meteorological assimilation data from the Goddard Earth Observing System. The GEO visible and infrared imager calibration is tied to MODIS to ensure uniform MODIS-like cloud properties across all satellite cloud datasets. Computed surface radiant fluxes are compared to surface observations at 85 globally distributed land (37) and ocean buoy (48) sites as well as several other publicly available global surface radiant flux data products. Computed monthly mean downward fluxes from SYN1deg have a bias (standard deviation) of 3.0Wm-2 (5.7%) for shortwave and -4.0Wm-2 (2.9%) for longwave compared to surface observations. The standard deviation between surface downward shortwave flux calculations and observations at the 3-hourly time scale is reduced when the diurnal cycle of cloud changes is explicitly accounted for. The improvement is smaller for surface downward longwave flux owing to an additional sensitivity to boundary layer temperature/humidity, which has a weaker diurnal cycle compared to clouds. © 2015 American Meteorological Society."
"55366700000;7102084129;","Extensive closed cell marine stratocumulus downwind of europe—a large aerosol cloud mediated radiative effect or forcing?",2015,"10.1002/2015JD023176","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944882022&doi=10.1002%2f2015JD023176&partnerID=40&md5=ffd87193cf9d1031dde547c71c6aec7e","Marine stratocumulus clouds (MSC) cover large areas over the oceans and possess super sensitivity of their cloud radiative effect to changes in aerosol concentrations. Aerosols can cause transitions between regimes of fully cloudy closed cells and open cells. The possible role of aerosols in cloud cover has a big impact on the amount of reflected solar radiation from the clouds, thus potentially constitutes very large aerosol indirect radiative effect, which can exceed 100 Wm-2. It is hypothesized that continentally polluted clouds remain in closed cells regime for longer time from leaving continent and hence for longer distance away from land, thus occupying larger ocean areas with full cloud cover. Attributing this to anthropogenic aerosols would imply a very large negative radiative forcing with a significant climate impact. This possibility is confirmed by analyzing a detailed case study based on geostationary and polar-orbiting satellite observations of the microphysical and dynamical evolution of MSC. We show that large area of closed cells was formed over the northeast Atlantic Ocean downwind of Europe in a continentally polluted air mass. The closed cells undergo cleansing process that was tracked for 3.5 days that resulted with a rapid transition from closed to open cells once the clouds started drizzling heavily. The mechanism leading to the eventual breakup of the clouds due to both meteorological and aerosol considerations is elucidated. We termed this cleansing and cloud breakup process maritimization. Further study is needed to assess the climatological significance of such situations. © 2015. American Geophysical Union. All Rights Reserved."
"12787718700;55334859900;7202514351;","Tropical montane vegetation dynamics near the upper cloud belt strongly associated with a shifting ITCZ and fire",2015,"10.1111/1365-2745.12423","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931569932&doi=10.1111%2f1365-2745.12423&partnerID=40&md5=f3aa52a143b7eea36ea836c27da63ee4","Tropical montane forests house unusual and diverse biota and are considered highly vulnerable to climate change, particularly near the trade wind inversion (TWI) - the upper end of the cloud belt that defines tropical montane cloud forest (TMCF). The upper cloud belt has two possible futures: one hypothesis postulates a 'lifting cloud base', raising both the upper and lower ends of the cloud belt; the other expects the upper end of the cloud belt will change independently, with a 'shifting TWI'. We used a 5900-year-long palaeorecord of vegetation and fire from a small forest hollow at 2455 m in the Cordillera Central, Dominican Republic. The site sits near the upper limit of TMCF taxa and the TWI and allows us to evaluate the relationship between vegetation dynamics and two potential drivers of TWI elevation - the Intertropical Convergence Zone (ITCZ) and the El Niño/Southern Oscillation (ENSO). Vegetation changed from cloud forest (5900-5500 cal. years BP) to alpine grassland (4300-1300 cal. years BP), to pine savanna (1300-600 cal. years BP) and finally to closed pine forest (after 600 cal. years BP). Habitat distribution models for TMCF and pine forest taxa show that these state changes were strongly associated with position of the ITCZ (cloud forest xR2 = 0.63; pine forest xR2 = 0.53), providing support for the shifting TWI hypothesis. We find a negative relationship between fire and TMCF and a hump-shaped relationship between fire activity and pine. Synthesis. Shifts up- and downslope of the upper limit of the cloud belt over the last 5900 years produced major vegetation changes. Fire also played a significant role, in particular when pine occupied the site after 1300 years ago and from 1965 AD when fire suppression led to a rapid return of cloud forest taxa. Our results strongly suggest that latitudinal shifts in the ITCZ position have controlled the upper limit of cloud forest in the Caribbean and understanding how the ITCZ will respond to climate change will be critical for tropical montane conservation strategies. Shifts up- and downslope of the cloud belt's upper limit over the last 5900 years produced major vegetation changes on high mountains in the Caribbean. Habitat distribution models show that vegetation state changes were strongly linked to latitudinal position of the ITCZ, providing support for the shifting TWI hypothesis over a lifting cloud base hypothesis for tropical high elevations. © 2015 British Ecological Society."
"56899014600;7005126327;35364149600;7201888941;","Estimating the fraction of winter orographic precipitation produced under conditions meeting the seeding criteria for the Wyoming weather modification pilot project",2015,"10.1175/JAMC-D-14-0163.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944077014&doi=10.1175%2fJAMC-D-14-0163.1&partnerID=40&md5=75b763cc333de51bcf82cb848a507e15","Annual precipitation increases of 10% or more are often quoted for the impact of winter orographic cloud seeding; however, establishing the basis for such values is problematic for two reasons. First, the impact of glaciogenic seeding of candidate orographic storms has not been firmly established. Second, not all winter precipitation is produced by candidate ""seedable"" storms. Addressing the first question motivated the Wyoming state legislature to fund a multiyear, crossover, randomized cloud-seeding experiment in southeastern Wyoming to quantify the impact of glaciogenic seeding of wintertime orographic clouds. The crossover design requires two barriers, one randomly selected for seeding, for comparisons of seeded and nonseeded precipitation under relatively homogeneous atmospheric conditions. Addressing the second question motivated the work here. The seeding criteria-700-hPa temperatures ≤-8°C, 700-hPa winds between 210° and 315°, and the presence of supercooled liquid water-were applied to eight winters to determine the percent of winter precipitation that may fall under the seeding criteria. Since no observational datasets provide precipitation and all of the atmospheric variables required for this study, a regional climate model dynamical downscaling of historical data over 8 years was used. The accuracy of the model was tested against several measurements, and the small model biases were removed. On average, ~26% of the time between 15 November and 15 April atmospheric conditions were seedable over the barriers in southeastern Wyoming. These seedable conditions were accompanied by precipitation ~12%-14% of the time, indicating that ~27%-30% of the winter precipitation resulted from seedable clouds. © 2015 American Meteorological Society."
"6701775424;7003507706;","Ecosystem risk assessment for Gnarled Mossy Cloud Forest, Lord Howe Island, Australia",2015,"10.1111/aec.12202","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929851948&doi=10.1111%2faec.12202&partnerID=40&md5=050c2ad7965588d3b1d8635f3c16c3a6","Gnarled Mossy Cloud Forest is a globally unique ecosystem, combining floristic elements from Australia, New Zealand and New Caledonia. It is restricted to a very small area (28ha) at elevations above 750m on the summits of two mountains on Lord Howe Island in the Pacific Ocean, approximately 570km off the east coast of Australia. Moisture derived from clouds is a key feature of the ecosystem. We assessed the conservation status of this ecosystem using the International Union for the Conservation of Nature Red List criteria for ecosystems. There has been no historical clearing of the ecosystem, but declines (with large uncertainty bounds) were estimated for two abiotic variables that are important in maintaining the component species (cloud cover and rainfall). Overall, we found the ecosystem to be Critically Endangered based on a restricted geographic distribution combined with continuing decline (criterion B1aii, iii, B1b, B1c and B2aii, iii, B2b, B2c). Decline was inferred from: a loss of moisture from declining rainfall and cloud cover due to climate change (affecting disturbance regimes, gap formation and species survival and recruitment); ongoing exotic rat predation on seeds and seedlings of several sensitive species that are structural components of the ecosystem (affecting survival and recruitment); and the fact that the ecosystem is considered to exist at only one location. This mirrors similar threats from exotic species and climate change to other Pacific island cloud forests. Eradication of rats from Lord Howe Island will reduce the immediate risk to this ecosystem; however, only global mitigation of greenhouse gases could alleviate risk from declining cloud cover and moisture availability. © 2014 Ecological Society of Australia."
"55977336000;","Estimating errors in cloud amount and cloud optical thickness due to limited spatial sampling using a satellite imager as a proxy for nadir-view sensors",2015,"10.1002/2015JD023507","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939268806&doi=10.1002%2f2015JD023507&partnerID=40&md5=fa84b9374e6c7970e3ae1a4e834fee9c","Cloud climatologies from space-based active sensors have been used in climate and other studies without their uncertainties specified. This study quantifies the errors in monthly mean cloud amount and optical thickness due to the limited spatial sampling of space-based active sensors. Nadir-view observations from a satellite imager, the Moderate Resolution Imaging Spectroradiometer (MODIS), serve as a proxy for those active sensors and observations within 10° of the sensor’s nadir view serve as truth for data from 2003 to 2013 in the Arctic. June-July monthly mean cloud amount and liquid water and ice cloud optical thickness from MODIS for both observations are calculated and compared. Results show that errors increase with decreasing sample numbers for monthly means in cloud amount and cloud optical thickness. The root-mean-square error of monthly mean cloud amount from nadir-view observations increases with lower latitudes, with 0.7% (1.4%) at 80°N and 4.2% (11.2%) at 60°N using data from 2003 to 2013 (from 2012). For a 100 km resolution Equal-Area Scalable Earth Grid (EASE-Grid) cell of 1000 sample numbers, the absolute differences in these two monthly mean cloud amounts are less than 6.5% (9.0%, 11.5%) with an 80 (90, 95)%chance; such differences decrease to 4.0% (5.0%, 6.5%) with 5000 sample numbers. For a 100 kmresolution EASE-Grid of 1000 sample numbers, the absolute differences in these two monthly mean cloud optical thicknesses are less than 2.7 (3.8) with a 90% chance for liquid water cloud (ice cloud); such differences decrease to 1.3 (1.0) for 5000 sample numbers. The uncertainties in monthly mean cloud amount and optical thickness estimated in this study may provide useful information for applying cloud climatologies from active sensors in climate studies and suggest the need for future spaceborne active sensors with a wide swath. © 2015. American Geophysical Union. All Rights Reserved."
"24168416900;7103016965;9044746800;7102591209;","The sensitivity of simulated high clouds to ice crystal fall speed, shape and size distribution",2015,"10.1002/qj.2457","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939443127&doi=10.1002%2fqj.2457&partnerID=40&md5=f4550a87b6ec81d42d1b0e0c10834ca8","The sensitivity of an operational numerical weather prediction model to the parametrized microphysical properties of ice hydrometeors is examined. The effects of varying ice-particle size distribution, fall speed, mass and depositional capacitance are considered in kilometre-scale simulations of midlatitude cloud systems and 20 year global climate integrations. It is shown that the observed sensitivity can be obtained from steady-state arguments, whereby the vertical moisture flux is balanced by the hydrometeor sedimentation flux and supersaturation production is in equilibrium with depositional growth. The high-resolution simulations are compared with in situ measurements from the Constrain field campaign (Prestwick, UK). © 2015 Royal Meteorological Society."
"14520559400;6601927317;17436105100;35330742100;36970733200;7202779940;55683304700;24398842400;56518167000;7004142910;35422648700;","Ice nucleation by cellulose and its potential contribution to ice formation in clouds",2015,"10.1038/ngeo2374","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926380037&doi=10.1038%2fngeo2374&partnerID=40&md5=a6d0e80f4ce03baf86f69c17d032df85","Ice particles in the atmosphere influence clouds, precipitation and climate, and often form with help from aerosols that serve as ice-nucleating particles. Biological particles, including non-proteinaceous ones, contribute to the diverse spectrum of ice-nucleating particles. However, little is known about their atmospheric abundance and ice nucleation efficiency, and their role in clouds and the climate system is poorly constrained. One biological particle type, cellulose, has been shown to exist in an airborne form that is prevalent throughout the year even at remote and elevated locations. Here we report experiments in a cloud simulation chamber to demonstrate that microcrystalline cellulose particles can act as efficient ice-nucleating particles in simulated supercooled clouds. In six immersion mode freezing experiments, we measured the ice nucleation active surface-site densities of aerosolized cellulose across a range of temperatures. Using these active surface-site densities, we developed parameters describing the ice nucleation ability of these particles and applied them to observed atmospheric cellulose and plant debris concentrations in a global aerosol model. We find that ice nucleation by cellulose becomes significant (>0.1l -1) below about -21 °C, temperatures relevant to mixed-phase clouds. We conclude that the ability of cellulose to act as ice-nucleating particles requires a revised quantification of their role in cloud formation and precipitation."
"56471429200;7404732357;7003975505;","Initiation of a runaway greenhouse in a cloudy column",2015,"10.1175/JAS-D-13-047.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920576512&doi=10.1175%2fJAS-D-13-047.1&partnerID=40&md5=e97fda622966b0f61f1100284c07cfa3","Aone-dimensional radiative-convective equilibriummodel is used to investigate the influence of clouds on the onset of a runaway greenhouse under strong solar forcing. By comparing experiments with clear-sky conditions (clouds are transparent to radiation) to experiments with full-sky conditions (clouds are radiatively active), the authors find that the critical solar irradiance that is necessary to trigger a runaway greenhouse is increased from around 1.15-1.20 times the present-day total solar irradiance (TSI) on Earth S0 for clear-sky conditions to around 1.40-1.45S0 for full-sky conditions. Cloud thickness increases with TSI, leading to a substantially higher albedo, which in turn allows the climate to remain in equilibrium for markedly higher values of TSI. The results suggest that steady states with sea surface temperatures higher than 335K exist for a large range of TSI. The thickening clouds in these states do not reduce the outgoing longwave radiation any more, implying that the thickening of clouds increases only their shortwave effect. This mechanism allows the column to remain in balance even at high sea surface temperatures. The authors find double equilibria for both clear-sky and full-sky conditions, but the range for which they occur extends to considerably higher values of TSIs for full-sky conditions. Moreover, when clouds are included in the radiative transfer calculations, climate instabilities are no longer caused by longwave effects but by the cloud albedo effect. © 2015 American Meteorological Society."
"56808345800;7003467276;","Arctic energy budget in relation to sea ice variability on monthly-to-annual time scales",2015,"10.1175/JCLI-D-15-0002.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942919585&doi=10.1175%2fJCLI-D-15-0002.1&partnerID=40&md5=2474a0d47ac89897dda14593d2a7a23c","The large decrease in Arctic sea ice in recent years has triggered a strong interest in Arctic sea ice predictions on seasonal-to-decadal time scales. Hence, it is important to understand physical processes that provide enhanced predictability beyond persistence of sea ice anomalies. This study analyzes the natural variability of Arctic sea ice from an energy budget perspective, using 15 climate models from phase 5 of CMIP (CMIP5), and compares these results to reanalysis data. The authors quantify the persistence of sea ice anomalies and the cross correlation with the surface and top-of-atmosphere energy budget components. The Arctic energy balance components primarily indicate the important role of the seasonal ice-albedo feedback, through which sea ice anomalies in the melt season reemerge in the growth season. This is a robust anomaly reemergence mechanism among all 15 climate models. The role of the ocean lies mainly in storing heat content anomalies in spring and releasing them in autumn. Ocean heat flux variations play only a minor role. Confirming a previous (observational) study, the authors demonstrate that there is no direct atmospheric response of clouds to spring sea ice anomalies, but a delayed response is evident in autumn. Hence, there is no cloud-ice feedback in late spring and summer, but there is a cloud-ice feedback in autumn, which strengthens the ice-albedo feedback. Anomalies in insolation are positively correlated with sea ice variability. This is primarily a result of reduced multiple reflection of insolation due to an albedo decrease. This effect counteracts the ice-albedo effect up to 50%. ERA-Interim and Ocean Reanalysis System 4 (ORAS4) confirm the main findings from the climate models. © 2015 American Meteorological Society."
"56183904600;6701571700;8629086900;6603446872;","Regional climate model sensitivities to parametrizations of convection and non-precipitating subgrid-scale clouds over South America",2015,"10.1007/s00382-014-2199-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939879226&doi=10.1007%2fs00382-014-2199-0&partnerID=40&md5=4d66c0972a63682c9ddfa27f3a6a0ca0","This study provides a first thorough evaluation of the COnsortium for Small scale MOdeling weather prediction model in CLimate Mode (COSMO-CLM) over South America. Simulations are driven by ERA-Interim reanalysis data. Besides precipitation, we examine the surface radiation budget, cloud cover, 2 m temperatures, and the low level circulation. We evaluate against reanalysis data as well as observations from ground stations and satellites. Our analysis focuses on the sensitivity of results to the convective parametrization in comparison to their sensitivity to the representation of non-precipitating subgrid-scale clouds in the parametrization of radiation. Specifically, we compare simulations with a relative humidity versus a statistical subgrid-scale cloud scheme, in combination with convection schemes according to Tiedtke (Mon Weather Rev 117(8):1779–1800, 1989) and from the European Centre for Medium-Range Weather Forecasts Integrated Forecasting System (IFS) cycle 33r1. The sensitivity of simulated tropical precipitation to the parametrizations of convection and subgrid-scale clouds is of similar magnitude. We show that model runs with different subgrid-scale cloud schemes produce substantially different cloud ice and liquid water contents. This impacts surface radiation budgets, and in turn convection and precipitation. Considering all evaluated variables in synopsis, the model performs best with the (both non-default) IFS and statistical schemes for convection and subgrid-scale clouds, respectively. Despite several remaining deficiencies, such as a poor simulation of the diurnal cycle of precipitation or a substantial austral summer warm bias in northern Argentina, this new setup considerably reduces long-standing model biases, which have been a feature of COSMO-CLM across tropical domains. © 2014, Springer-Verlag Berlin Heidelberg."
"56477833000;23974441400;55544043300;56701251300;7202019251;","Toward improved daily cloud-free fractional snow cover mapping with multi-source remote sensing data in China",2015,"10.3390/rs70606986","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933575473&doi=10.3390%2frs70606986&partnerID=40&md5=a04da0688ddced09df23ebdbffa059b3","With the high resolution of optical data and the lack of weather effects of passive microwave data, we developed an algorithm to map daily cloud-free fractional snow cover (FSC) based on the Moderate Resolution Imaging Spectroradiometer (MODIS) standard daily FSC product, the Advanced Microwave Scanning Radiometer (AMSR2) snow water equivalent (SWE) product and digital elevation data. We then used the algorithm to produce a daily cloud-free FSC product with a resolution of 500 m for regions in China. In addition, we produced a high-resolution FSC map using a Landsat 8 Operational Land Imager (OLI) image as a true value to test the accuracy of the cloud-free FSC product developed in this study. The analysis results show that the daily cloud-free FSC product developed in this study can completely remove clouds and effectively improve the accuracy of snow area monitoring. Compared to the true value, the mean absolute error of our product is 0.20, and its root mean square error is 0.29. Thus, the synthesized product in this study can improve the accuracy of snow area monitoring, and the obtained snow area data can be used as reliable input parameters for hydrological and climate models. The land cover type and terrain factors are the main factors that limit the accuracy of the daily cloud-free FSC product developed in this study. These limitations can be further improved by improving the accuracy of the MODIS standard snow product for complicated underlying surfaces. © 2015 by the authors."
"36660793000;54787068100;56940462100;36438236100;57219146294;","Responses of vegetation activity to climate variation on the Qinghai-Tibetan Plateau (China) from 1982 to 2011",2015,"10.3354/cr01333","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946063654&doi=10.3354%2fcr01333&partnerID=40&md5=7a9443172991be29a9d7c6cf79299c5a","The response of vegetation activity to variations in cloud cover, temperature, and precipitation on the Qinghai-Tibetan Plateau from 1982-2011 was analysed using the third generation Normalized Difference Vegetation Index (NDVI-3g) and Climatic Research Unit (CRU) dataset. There was no significant correlation between growing season cloud cover and vegetation growth (p > 0.1) over the Plateau. However, both temperature and precipitation were positively and significantly correlated with vegetation growth (p < 0.1), although these correlations varied among the different sub-regions of the Plateau. For instance, in higher altitude and latitude regions (where temperatures are lower), there was a significant correlation between temperature and NDVI series during the growing season (p < 0.1), whereas the other climate factors were not significantly correlated with vegetation dynamics (p > 0.1). In sub-regions with lower altitude or latitude (where temperature is not the limiting climate factor), precipitation variations had an important influence on vegetation activity. The time lag between precipitation variations and changes in vegetation dynamics differed between those sub-regions of the Plateau with different plant species and soil properties. In the warm and humid region, vegetation activity was less sensitive to all of the climate factors compared with the other regions. © Inter-Research 2015."
"7401604360;55199339300;6701925357;55597088322;57188751935;52463601100;55555283600;","WRF multi-physics simulation of clouds in the African region",2015,"10.1002/qj.2560","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946482243&doi=10.1002%2fqj.2560&partnerID=40&md5=1793283a9da199c058a4fa0faef6cc50","The Weather Research and Forecasting (WRF) model has been used to simulate clouds, and their effects on precipitation and radiation, in Africa. The results have been compared with observational databases, mainly based on satellite measurements. The Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) has been used to consistently compare simulated clouds with satellite data, allowing us to evaluate not only the total cloud cover but also the cloud amount of different cloud types, classified according to their optical thickness and cloud-top pressure. Nine WRF simulations, for the 2002-2006 period, were carried out to evaluate the influence on cloud cover of different physical parametrizations and model configurations. In general, model simulations show similar results, underestimating total cloud cover in most of the studied region. In the tropical convective area, high clouds are underestimated, but the net effect on the radiation is partially compensated by the overestimation of cloud optical depth. Major differences appear over subtropical areas dominated by marine boundary-layer clouds, mainly off the coast of Namibia. In this area, simulations show too many thick clouds and too few clouds with lower optical thickness. The net result is an underestimation of low cloud cover. Also, the transition from stratocumulus to shallow cumulus away from the coast is not realistically modelled. © 2015 Royal Meteorological Society."
"6602805147;56192746700;6505932008;6701606453;","Impacts of cloud droplet-nucleating aerosols on shallow tropical convection",2015,"10.1175/JAS-D-14-0153.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943450624&doi=10.1175%2fJAS-D-14-0153.1&partnerID=40&md5=178881cf34629e3e27af3e23d1e00f3c","Low-level warm-phase clouds cover a substantial portion of Earth's oceans and play an important role in the global water and energy budgets. The characteristics of these clouds are controlled by the large-scale environment, boundary layer conditions, and cloud microphysics. Variability in the concentration of aerosols can alter cloud microphysical and precipitation processes that subsequently impact the system dynamics and thermodynamics and thereby create aerosol-cloud dynamic-thermodynamic feedback effects. In this study, three distinct cloud regimes were simulated, including stratocumulus, low-level cumulus (cumulus under stratocumulus), and deeper cumulus clouds. The simulations were conducted without environmental large-scale forcing, thereby allowing all three cloud types to freely interact with the environmental state in an undamped fashion. Increases in aerosol concentration in these unforced, warm-phase, tropical cloud simulations lead to the production of fewer low-level cumuli; thinning and erosion of the widespread stratocumulus layer; and the development of deeper, inversion-penetrating cumuli. The mechanisms for these changes are explored. Despite the development of deeper, more heavily precipitating cumuli, the reduction of the widespread moderately precipitating stratocumulus clouds leads to an overall reduction in domainwide accumulated precipitation when aerosol concentrations are enhanced. © 2015 American Meteorological Society."
"54787758100;","Investigating a solar influence on cloud cover using the North American Regional Reanalysis data",2015,"10.1051/swsc/2015012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930936758&doi=10.1051%2fswsc%2f2015012&partnerID=40&md5=ca3fe0334f98f3ecb101dee4109cead6","The controversial connection between cosmic rays, solar activity, and cloud cover is investigated using a climatological reconstructed reanalysis product: the North American Regional Reanalysis which provides high-resolution, low, mid-level, high, and total cloud cover data over a Lambert conformal conic projection permitting land/ocean discrimination. Pearson's product-moment regional correlations were obtained between monthly cloud cover data and solar variability indicators, cosmic ray neutron monitors, several climatological indices, including the Atlantic Multidecadal Oscillation (AMO), and between cloud layers. Regions of the mid-latitude oceans exhibited a positive correlation with cosmic ray flux. Additionally, this maritime low cloud cover exhibits the only failed correlation significance with other altitudes. The cross correlation reveals that cloud cover is positively correlated everywhere but for ocean low cloud cover, supporting the unique response of the marine layer. The results of this investigation suggest that with the assumption that solar forcing does impact cloud cover, measurements of solar activity exhibits a slightly higher correlation than GCRs. The only instance where GCRs exhibit a positive regional correlation with cloud cover is for maritime low clouds. The AMO exerts the greatest control of cloud cover in the NARR domain. © D.S. Krahenbuhl, Published by EDP Sciences 2015."
"55831774800;7401796996;8629713500;57193132723;7006783796;6603546080;7004364155;","Assessment of NASA GISS CMIP5 and post-CMIP5 simulated clouds and TOA radiation budgets using satellite observations. Part II: TOA radiation budget and CREs",2015,"10.1175/JCLI-D-14-00249.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961353263&doi=10.1175%2fJCLI-D-14-00249.1&partnerID=40&md5=5bdb21c24f42cc5f90295a026ca53aee","In Part I of this study, the NASA GISS Coupled Model Intercomparison Project (CMIP5) and post-CMIP5 (herein called C5 and P5, respectively) simulated cloud properties were assessed utilizing multiple satellite observations, with a particular focus on the southern midlatitudes (SMLs). This study applies the knowledge gained from Part I of this series to evaluate the modeled TOA radiation budgets and cloud radiative effects (CREs) globally using CERES EBAF (CE) satellite observations and the impact of regional cloud properties and water vapor on the TOA radiation budgets. Comparisons revealed that the P5- and C5-simulated global means of clear-sky and all-sky outgoing longwave radiation (OLR) match well with CE observations, while biases are observed regionally. Negative biases are found in both P5- and C5-simulated clear-sky OLR. P5-simulated all-sky albedo slightly increased over the SMLs due to the increase in low-level cloud fraction from the new planetary boundary layer (PBL) scheme. Shortwave, longwave, and net CRE are quantitatively analyzed as well. Regions of strong large-scale atmospheric upwelling/downwelling motion are also defined to compare regional differences across multiple cloud and radiative variables. In general, the P5 and C5 simulations agree with the observations better over the downwelling regime than over the upwelling regime. Comparing the results herein with the cloud property comparisons presented in Part I, the modeled TOA radiation budgets and CREs agree well with the CE observations. These results, combined with results in Part I, have quantitatively estimated how much improvement is found in the P5-simulated cloud and radiative properties, particularly over the SMLs and tropics, due to the implementation of the new PBL and convection schemes. © 2015 American Meteorological Society."
"57192668733;55726303300;57208847623;57190380835;","Super-parameterization in GRAPES: The construction of SP-GRAPES and associated preliminary results",2015,"10.1007/s13351-015-4074-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007247631&doi=10.1007%2fs13351-015-4074-2&partnerID=40&md5=7ec4cb93e7a50752900273bd62595223","Super-parameterization (SP) aims to explicitly represent deep convection within a coarse resolution global model by embedding a cloud resolving model (CRM) in each column of the mother model. For the first time, we implemented the SP in a mesoscale regional weather model, the Global/Regional Assimilation and PrEdiction System (GRAPES). The constructed SP-GRAPES uses a two-dimensional (2D) CRM in each grid column. A control and two SP simulations are conducted for the Beijing “7.21” heavy rainfall event to evaluate improvements in GRAPES using SP. The SP-run-I is a basic SP run delivering microphysics feedback only, whereas the SP-run-II delivers both microphysical and cloud fraction feedbacks. A comparison of the runs indicates that the SP-run-I has a slightly positive impact on the precipitation forecast than the control run. However, the inclusion of cloud fraction feedback leads to an evident overall improvement, particularly in terms of cloud fraction and 24-h cumulative precipitation. Although this is only a preliminary study using SP-GRAPES, we believe that it will provide considerable guidance for follow-up studies using SP in China. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2015."
"57144638800;8368714300;14124224600;55959710400;","Macroscopic cloud properties in the WRF NWP model: An assessment using sky camera and ceilometer data",2015,"10.1002/2015JD023502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991441277&doi=10.1002%2f2015JD023502&partnerID=40&md5=7c94cf6142299c98211c2c842bcb4c2c","The ability of six microphysical parameterizations included in the Weather Research and Forecasting (WRF) numerical weather prediction (NWP) model to represent various macroscopic cloud characteristics at multiple spatial and temporal resolutions is investigated. In particular, the model prediction skills of cloud occurrence, cloud base height, and cloud cover are assessed. When it is possible, the results are provided separately for low-, middle-, and high-level clouds. The microphysical parameterizations assessed are WRF single-moment six-class, Thompson, Milbrandt-Yau, Morrison, Stony Brook University, and National Severe Storms Laboratory double moment. The evaluated macroscopic cloud properties are determined based on the model cloud fractions. Two cloud fraction approaches, namely, a binary cloud fraction and a continuous cloud fraction, are investigated. Model cloud cover is determined by overlapping the vertically distributed cloud fractions following three different strategies. The evaluation is conducted based on observations gathered with a ceilometer and a sky camera located in Jaén (southern Spain). The results prove that the reliability of the WRF model mostly depends on the considered cloud parameter, cloud level, and spatiotemporal resolution. In our test bed, it is found that WRF model tends to (i) overpredict the occurrence of high-level clouds irrespectively of the spatial resolution, (ii) underestimate the cloud base height, and (iii) overestimate the cloud cover. Overall, the best cloud estimates are found for finer spatial resolutions (1.3 and 4 km with slight differences between them) and coarser temporal resolutions. The roles of the parameterization choice of the microphysics scheme and the cloud overlapping strategy are, in general, less relevant. © 2015. American Geophysical Union. All Rights Reserved."
"6701925357;55199339300;55597088322;7401604360;55555283600;","High-resolution future projections of temperature and precipitation in the Canary Islands",2015,"10.1175/JCLI-D-15-0030.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947770799&doi=10.1175%2fJCLI-D-15-0030.1&partnerID=40&md5=15efaafc3c87832fa461b2f40b65eff2","The complex orography of the Canary Islands favors the creation of microclimates, which cannot be studied using global climate models or regional models with moderate resolution. In this work, WRF is used to perform a dynamic climate regionalization in the archipelago, using the pseudo-global warming technique to compute the initial and boundary conditions from a reanalysis dataset and from results of 14 global climate models. The simulations were performed for three decades, one at present (1995-2004) and two in the future (2045-54 and 2090-99), and for two different greenhouse gas scenarios (RCP4.5 and RCP8.5), defined in phase 5 of the Coupled Model Intercomparison Project. The obtained results, at a 5-km horizontal resolution, show a clear dependence of temperature increase with height and a positive change in diurnal temperature range, which is mainly due to a reduction in soil moisture and a slight decrease in cloud cover. This negative change in soil moisture is mainly a consequence of a decrease in precipitation, although the evaluation of simulated reduction in precipitation does not show statistical significance in most of the Canary Islands for the analyzed periods and scenarios. © 2015 American Meteorological Society."
"55923546200;8942524900;43661479500;12753162000;55480654300;35810775100;36134816800;7004469744;8633783900;24463029300;","The climatic importance of uncertainties in regional aerosol-cloud radiative forcings over recent decades",2015,"10.1175/JCLI-D-15-0127.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945902497&doi=10.1175%2fJCLI-D-15-0127.1&partnerID=40&md5=76fc4e9212aebeaa907146c9fef528c2","Regional patterns of aerosol radiative forcing are important for understanding climate change on decadal time scales. Uncertainty in aerosol forcing is likely to vary regionally and seasonally because of the short aerosol lifetime and heterogeneous emissions. Here the sensitivity of regional aerosol cloud albedo effect (CAE) forcing to 31 aerosol process parameters and emission fluxes is quantified between 1978 and 2008. The effects of parametric uncertainties on calculations of the balance of incoming and outgoing radiation are found to be spatially and temporally dependent. Regional uncertainty contributions of opposite sign cancel in global-mean forcing calculations, masking the regional importance of some parameters. Parameters that contribute little to uncertainty in Earth's global energy balance during recent decades make significant contributions to regional forcing variance. Aerosol forcing sensitivities are quantified within 11 climatically important regions, where surface temperatures are thought to influence large-scale climate effects. Substantial simulated uncertainty in CAE forcing in the eastern Pacific leaves open the possibility that apparent shifts in the mean ENSO state may result from a forced aerosol signal on multidecadal time scales. A likely negative aerosol CAE forcing in the tropical North Atlantic calls into question the relationship between Northern Hemisphere aerosol emission reductions and CAE forcing of sea surface temperatures in the main Atlantic hurricane development region on decadal time scales. Simulated CAE forcing uncertainty is large in the North Pacific, suggesting that the role of the CAE in altering Pacific tropical storm frequency and intensity is also highly uncertain. © 2015 American Meteorological Society."
"6503855019;6507671561;7006452341;","Impact of anomalous northward oceanic heat transport on global climate in a slab ocean setting",2015,"10.1175/JCLI-D-14-00377.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944111704&doi=10.1175%2fJCLI-D-14-00377.1&partnerID=40&md5=3a63c4462b40cf5e0ea09f7cd400e4c7","This paper explores the impact of anomalous northward oceanic heat transport on global climate in a slab ocean setting. To that end, the GCM LMDZ5A of the Laboratoire de Météorologie Dynamique is coupled to a slab ocean, with realistic zonal asymmetries and seasonal cycle. Two simulations with different anomalous surface heating are imposed: 1) uniform heating over the North Atlantic basin and 2) concentrated heating in the Gulf Stream region, with a compensating uniform cooling in the Southern Ocean in both cases. The magnitudes of the heating and of the implied northward interhemispheric heat transport are within the range of current natural variability. Both simulations show global effects that are particularly strong in the tropics, with a northward shift of the intertropical convergence zone (ITCZ) toward the heating anomalies. This shift is accompanied by a northward shift of the storm tracks in both hemispheres. From the comparison between the two simulations with different anomalous surface heating in the North Atlantic, it emerges that the global climate response is nearly insensitive to the spatial distribution of the heating. The cloud response acts as a large positive feedback on the oceanic forcing, mainly because of the low-cloud-induced shortwave anomalies in the extratropics. While previous literature has speculated that the extratropical Q flux may impact the tropics by the way of the transient eddy fluxes, it is explicitly demonstrated here. In the midlatitudes, the authors find a systematic northward shift of the jets, as well as of the associated Ferrel cells, storm tracks, and precipitation bands. © 2015 American Meteorological Society."
"6603369413;7006185793;7003448155;8507259400;6701858531;57207137435;35222254500;","Variability of CONUS lightning in 2003-12 and associated impacts",2015,"10.1175/JAMC-D-14-0072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922984792&doi=10.1175%2fJAMC-D-14-0072.1&partnerID=40&md5=343c3dffeca21515606905012bb76a91","Changes in lightning characteristics over the conterminous United States (CONUS) are examined to support the National Climate Assessment (NCA) program. Details of the variability of cloud-to-ground (CG) lightning characteristics over the decade 2003-12 are provided using data from the National Lightning Detection Network (NLDN). Changes in total (CG1cloud flash) lightning across part of theCONUS during the decade are provided using satellite Lightning Imaging Sensor (LIS) data. The variations in NLDN-derived CG lightning are compared with available statistics on lightning-caused impacts to various U.S. economic sectors. Overall, a downward trend in total CG lightning count is found for the decadal period; the 5-yr mean NLDN CG count decreased by 12.8% from 25 204 345.8 (2003-07) to 21 986 578.8 (2008-12). There is a slow upward trend in the fraction and number of positive-polarity CG lightning, however. Associated lightningcaused fatalities and injuries, and the number of lightning-caused wildland fires and burn acreage also trended downward, but crop and personal-property damage costs increased. The 5-yr mean LIS total lightning changed little over the decadal period. Whereas the CONUS-averaged dry-bulb temperature trended upward during the analysis period, the CONUS-averaged wet-bulb temperature (a variable that is better correlated with lightning activity) trended downward. A simple linear model shows that climate-induced changes in CG lightning frequency would likely have a substantial and direct impact on humankind (e.g., a long-term upward trend of 1°C in wet-bulb temperature corresponds to approximately 14 fatalities and over $367 million in personal-property damage resulting from lightning). © 2015 American Meteorological Society."
"8668565900;55915387400;7006592026;6602844274;7102953444;","Evaluation of the radiation budget with a regional climate model over Europe and inspection of dimming and brightening",2015,"10.1002/2014JD022497","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925596407&doi=10.1002%2f2014JD022497&partnerID=40&md5=d82f875c6e397d1b75139a624f9eea2f","Shortwave (SW) and longwave (LW) components of the radiation budget at the surface and top of atmosphere (TOA) are evaluated in the regional climate model RegCM version 4 driven by European Centre for Medium-Range Weather Forecasts Reanalysis over Europe. The simulated radiative components were evaluated with those from satellite-based products and reanalysis. At the surface the model overestimated the absorbed solar radiation but was compensated by a greater loss of thermal energy while both SWand LW TOA net fluxes were underestimated representing too little solar energy absorbed and too little outgoing thermal energy. Averaged biases in radiative parameters were generally within 25 Wm-2, were dependent on differences by as much as 0.2 in cloud fraction, surface, and planetary albedo and less dependent on surface temperature associated with the surface longwave parameters, and are in line with other studies. Clear-sky fluxes showed better results when cloud cover differences had no influence. We also found a clear distinction between land versus water with smaller biases over land at the surface and over water at the TOA due to differences in cloud fraction and albedo. Finally, we inspected dimming and brightening for the period 1979-2010 with an indication for dimming early in the time series (i.e., 1979-1987) and brightening after, which agrees with surface-based observations. After 2000, however, a decrease in the brightening by more than 1 order of magnitude was evident which is in contrast to the continued brightening found in surface records and satellite-derived estimates. © 2015. American Geophysical Union. All Rights Reserved."
"6603196991;7801489438;56771374500;25928285500;42361350100;56771426500;9235244500;7003956042;8436589000;7006146719;7004167838;6701410575;6603868770;","JOYCE: Jülich Observatory for Cloud Evolution",2015,"10.1175/BAMS-D-14-00105.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938913436&doi=10.1175%2fBAMS-D-14-00105.1&partnerID=40&md5=46514ae52681e8fc97dea495926a6888","The Jülich Observatory for Cloud Evolution (JOYCE), located at Forschungszentrum Jülich in the most western part of Germany, is a recently established platform for cloud research. The main objective of JOYCE is to provide observations, which improve our understanding of the cloudy boundary layer in a midlatitude environment. Continuous and temporally highly resolved measurements that are specifically suited to characterize the diurnal cycle of water vapor, stability, and turbulence in the lower troposphere are performed with a special focus on atmosphere - surface interaction. In addition, instruments are set up to measure the micro- and macrophysical properties of clouds in detail and how they interact with different boundary layer processes and the large-scale synoptic situation. For this, JOYCE is equipped with an array of state-of-the-art active and passive remote sensing and in situ instruments, which are briefly described in this scientific overview. As an example, a 24-h time series of the evolution of a typical cumulus cloud-topped boundary layer is analyzed with respect to stability, turbulence, and cloud properties. Additionally, we present longer-term statistics, which can be used to elucidate the diurnal cycle of water vapor, drizzle formation through autoconversion, and warm versus cold rain precipitation formation. Both case studies and long-term observations are important for improving the representation of clouds in climate and numerical weather prediction models. ©2015 American Meteorological Society."
"55749340500;25629055800;7401936984;7403564495;","A variance-based decomposition and global sensitivity index method for uncertainty quantification: Application to retrieved ice cloud properties",2015,"10.1002/2014JD022750","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930380331&doi=10.1002%2f2014JD022750&partnerID=40&md5=040640ee3e01cd0823001fa518f94e8e","This study develops a novel uncertainty quantification (UQ) method for cloud microphysical property retrievals using variance-based decomposition and global sensitivity index. In this UQ framework, empirical orthogonal function (EOF) analysis is applied to the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) ground-based observations, which are the inputs for the cloud retrieval studied here. The principal components (PCs) in the EOF expansion are parameterized as random input variables, and hence, the input dimension is greatly reduced (up to a factor of 50), allowing large ensemble of random samplings. The EOF expansion improves the accuracy of the uncertainty estimation by taking into account the cross correlations in the input data profiles. This method enables a probabilistic representation of a retrieval process by adding normally distributed perturbations into PCs of sample means of input data profiles within a time window. Therefore, it effectively facilitates objective validation of climate models against cloud retrievals under a probabilistic framework for rigorous statistical inferences. Moreover, the variance-based global sensitivity index analysis, part of this method, attributes the output uncertainties to each individual source, thus providing directions for improving retrieval algorithms and observation strategies. For demonstration, we apply this method to quantify the uncertainties of the ARM program’s baseline cloud retrieval algorithm for an ice cloud case observed at the Southern Great Plains site on 9 March 2000. © 2015. American Geophysical Union. All Rights Reserved."
"7004647146;9246029600;36809017200;36720934300;15026371500;","The remote impacts of climate feedbacks on regional climate predictability",2015,"10.1038/ngeo2346","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923218714&doi=10.1038%2fngeo2346&partnerID=40&md5=7f777cc3dfacd84613099733b3a60a57","Uncertainty in the spatial pattern of climate change is dominated by divergent predictions among climate models. Model differences are closely linked to their representation of climate feedbacks, that is, the additional radiative fluxes that are caused by changes in clouds, water vapour, surface albedo, and other factors, in response to an external climate forcing. Progress in constraining this uncertainty is therefore predicated on understanding how patterns of individual climate feedbacks aggregate into a regional and global climate response. Here we present a simple, moist energy balance model that combines regional feedbacks and the diffusion of both latent and sensible heat. Our model emulates the relationship between regional feedbacks and temperature response in more comprehensive climate models; the model can therefore be used to understand how uncertainty in feedback patterns drives uncertainty in the patterns of temperature response. We find that whereas uncertainty in tropical feedbacks induces a global response, the impact of uncertainty in polar feedbacks remains predominantly regionally confined. © 2015 Macmillan Publishers Limited. All rights reserved"
"7003663305;7402934750;56899043400;56898950300;6602513845;6505818202;","Deriving arctic cloud microphysics at Barrow, Alaska: Algorithms, results, and radiative closure",2015,"10.1175/JAMC-D-15-0054.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943762047&doi=10.1175%2fJAMC-D-15-0054.1&partnerID=40&md5=c5a830ba8f6909f73a20689a18966593","Cloud phase and microphysical properties control the radiative effects of clouds in the climate system and are therefore crucial to characterize in a variety of conditions and locations. An Arctic-specific, ground-based, multisensor cloud retrieval system is described here and applied to 2 yr of observations from Barrow, Alaska. Over these 2 yr, clouds occurred 75% of the time, with cloud ice and liquid each occurring nearly 60% of the time. Liquid water occurred at least 25% of the time, even in winter, and existed up to heights of 8 km. The vertically integrated mass of liquid was typically larger than that of ice. While it is generally difficult to evaluate the overall uncertainty of a comprehensive cloud retrieval system of this type, radiative flux closure analyses were performed in which flux calculations using the derived microphysical properties were compared with measurements at the surface and the top of the atmosphere. Radiative closure biases were generally smaller for cloudy scenes relative to clear skies, while the variability of flux closure results was only moderately larger than under clear skies. The best closure at the surface was obtained for liquid-containing clouds. Radiative closure results were compared with those based on a similar, yet simpler, cloud retrieval system. These comparisons demonstrated the importance of accurate cloud-phase and cloud-type classification, and specifically the identification of liquid water, for determining radiative fluxes. Enhanced retrievals of liquid water path for thin clouds were also shown to improve radiative flux calculations. © 2015 American Meteorological Society."
"56735478500;55628589750;","Where Aerosols become clouds-potential for global analysis based on CALIPSO data",2015,"10.3390/rs70404178","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937819347&doi=10.3390%2frs70404178&partnerID=40&md5=bc4000e2160b9d7dc595cf401e8d0b7e","This study evaluates the potential to determine the global distribution of hydrated aerosols based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data products. Knowledge of hydrated aerosol global distribution is of high relevance in the study of the radiative impact of aerosol-cloud interactions on Earth's climate. The cloud-aerosol discrimination (CAD) score of the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) instrument on the CALIPSO satellite separates aerosols and clouds according to the probability density functions (PDFs) of attenuated backscatter, total color ratio, volume depolarization ratio, altitude and latitude. The pixels that CAD fails to identify as either cloud or aerosol are used here to pinpoint the occurrence of hydrated aerosols and to globally quantify their relative frequency using data of August from 2006 to 2013. Atmospheric features in this no-confidence range mostly match with aerosol PDFs and imply an early hydration state of aerosols. Their strong occurrence during August above the South-East Atlantic and below an altitude of 4 km coincides with the biomass burning season in southern Africa and South America. © 2015 by the authors."
"55232897900;24722339600;23094149200;","Satellite estimates of precipitation susceptibility in low-level marine stratiform clouds",2015,"10.1002/2015JD023319","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943370195&doi=10.1002%2f2015JD023319&partnerID=40&md5=0860524d068361d7d6bb1910c4dd3f47","Quantifying the sensitivity of warm rain to aerosols is important for constraining climate model estimates of aerosol indirect effects. In this study, the precipitation sensitivity to cloud droplet number concentration (Nd) in satellite retrievals is quantified by applying the precipitation susceptibility metric to a combined CloudSat/Moderate Resolution Imaging Spectroradiometer data set of stratus and stratocumulus clouds that cover the tropical and subtropical Pacific Ocean and Gulf of Mexico. Consistent with previous observational studies of marine stratocumulus, precipitation susceptibility decreases with increasing liquid water path (LWP), and the susceptibility of the mean precipitation rate R is nearly equal to the sum of the susceptibilities of precipitation intensity and of probability of precipitation. Consistent with previous modeling studies, the satellite retrievals reveal that precipitation susceptibility varies not only with LWP but also with Nd. Puzzlingly, negative values of precipitation susceptibility are found at low LWP and high Nd. There is marked regional variation in precipitation susceptibility values that cannot simply be explained by regional variations in LWP and Nd. This suggests other controls on precipitation apart from LWP and Nd and that precipitation susceptibility will need to be quantified and understood at the regional scale when relating to its role in controlling possible aerosol-induced cloud lifetime effects. © 2015. American Geophysical Union. All Rights Reserved."
"37099564300;7402480218;7006303509;","Quantifying diurnal cloud radiative effects by cloud type in the tropical Western Pacific",2015,"10.1175/JAMC-D-14-0288.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944040115&doi=10.1175%2fJAMC-D-14-0288.1&partnerID=40&md5=ce80ea0afdfc1410b814a2737920775b","Cloud radiative effects are examined using long-term datasets collected at the U.S. Department of Energy's three Atmospheric Radiation Measurement Program Climate Research Facilities in the tropical western Pacific Ocean. The surface radiation budget, cloud populations, and cloud radiative effects are quantified by partitioning the data by cloud type, time of day, and large-scale modes of variability such as El Niño-Southern Oscillation (ENSO) phase and wet/dry seasons at Darwin, Australia. The novel aspect of this analysis is the breakdown of aggregate cloud radiative effects by cloud type across the diurnal cycle. The Nauru Island (Republic of Nauru) cloud populations and subsequently the surface radiation budget are strongly impacted by ENSO variability, whereas the cloud populations over Manus Island (Papua New Guinea) shift only slightly in response to changes in ENSO phase. The Darwin site exhibits large seasonal monsoon-related variations. When present, deeper convective clouds have a strong influence on the amount of radiation that reaches the surface. Their limited frequency reduces their aggregate radiative impact, however. The largest source of shortwave cloud radiative effects at all three sites comes from low clouds. The observations are used to demonstrate that potential model biases in the amplitude of the diurnal cycle and mean cloud frequency would lead to larger errors in the surface energy budget when compared with biases in the timing of the diurnal cycle of cloud frequency. These results provide solid benchmarks to evaluate model simulations of cloud radiative effects in the tropics. © 2015 American Meteorological Society."
"57213753419;7403276033;6602859414;6602089079;55492414700;","Shortwave TOA cloud radiative forcing derived from a long-term (1980-Present) record of satellite UV reflectivity and CERES measurements",2015,"10.1175/JCLI-D-14-00551.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950153851&doi=10.1175%2fJCLI-D-14-00551.1&partnerID=40&md5=10b02305bc38285aa0026c40cfe3b2ab","A 34-yr record of shortwave top-of-atmosphere (TOA) radiative cloud forcing is derived from UV Lambertian equivalent reflectivity (LER) data constructed using measured upwelling radiances from the Nimbus-7 Solar Backscatter Ultraviolet (SBUV) and from seven NOAA SBUV/2 instruments on polar-orbiting satellites. The approach is to scale the dimensionless UV LER data to match the CERES shortwave cloud radiative forcing when they are concurrent (2000-13). The underlying trends of this new longer-term CERES-like data record are solely based on the UV LER record. The good agreement between trends and anomalies of the CERES-like and CERES shortwave cloud forcing records during the overlapping data period supports using this new dataset for extended climate studies. The estimated linear trend for the shortwave TOA radiative forcing due to clouds from 60°S to 60°N is +1.47 W m-2 with a 0.11 uncertainty at the 95% confidence level over the 34-yr period 1980-2013. © 2015 American Meteorological Society."
"56575686800;7201485519;55537426400;10241462700;","The cloud radiative effect on the atmospheric energy budget and global mean precipitation",2015,"10.1007/s00382-014-2174-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939876805&doi=10.1007%2fs00382-014-2174-9&partnerID=40&md5=5b1096b540d8a452490f7619b478c080","This study seeks to explain the effects of cloud on changes in atmospheric radiative absorption that largely balance changes in global mean precipitation under climate change. The partial radiative perturbations (PRPs) due to changes in cloud and due to the effects of the pre-existing climatological cloud distribution on non-cloud changes, known as “cloud masking”, are calculated when atmospheric CO2 concentration is doubled for the HadSM3 and MIROC models and for a large ensemble of parameter perturbed models based on HadSM3. Because the effect of cloud on changes in atmospheric shortwave absorption is almost negligible, longwave fluxes are analysed alone. We find that the net effects of cloud masking and cloud PRP on atmospheric absorption are both substantial. For the tropics, our results are reviewed in light of hypotheses put forward to explain cloud and radiative flux changes. We find that the major effects of clouds on radiation change are linked to known physical processes that are quite consistently simulated by models. Cloud top height changes are quite well described by the fixed anvil temperature hypothesis of Hartmann and Larson; cloud base heights change little, remaining near the same pressure. Changes in cloud geographical location and cloud amount are significant, but play a smaller role in driving radiative flux changes. Finally, because clouds are a large source of modelling uncertainty, we consider whether resolving errors in cloud simulation could reconcile modelled global mean precipitation trends of about 1–3 %(Formula Presented.) with some estimates of observed trends of 7 %(Formula Presented.) or more. This would require the radiative effect of clouds to change from one that increases atmospheric radiative absorption by about (Formula Presented.) to one that decreases it by (Formula Presented.). Based on our results, this seems difficult to achieve within our current rationale for the tropics at least. © 2014, Springer-Verlag Berlin Heidelberg."
"23008938100;56033135100;","How well do simulated last glacial maximum tropical temperatures constrain equilibrium climate sensitivity?",2015,"10.1002/2015GL064903","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938118156&doi=10.1002%2f2015GL064903&partnerID=40&md5=6474069232694aa11b21e10120de9f95","Previous work demonstrated a significant correlation between tropical surface air temperature and equilibrium climate sensitivity (ECS) in PMIP (Paleoclimate Modelling Intercomparison Project) phase 2 model simulations of the last glacial maximum (LGM). This implies that reconstructed LGM cooling in this region could provide information about the climate system ECS value. We analyze results from new simulations of the LGM performed as part of Coupled Model Intercomparison Project (CMIP5) and PMIP phase 3. These results show no consistent relationship between the LGM tropical cooling and ECS. A radiative forcing and feedback analysis shows that a number of factors are responsible for this decoupling, some of which are related to vegetation and aerosol feedbacks. While several of the processes identified are LGM specific and do not impact on elevated CO<inf>2</inf> simulations, this analysis demonstrates one area where the newer CMIP5 models behave in a qualitatively different manner compared with the older ensemble. The results imply that so-called Earth System components such as vegetation and aerosols can have a significant impact on the climate response in LGM simulations, and this should be taken into account in future analyses. Key Points New LGM simulations show no tropical temperature to climate sensitivity relation This is caused by a model complexity, especially due to Earth System components It is unclear how inferred ECS will change as more model components are included. © 2015. American Geophysical Union. All Rights Reserved."
"56681764600;8701353900;","Identifying sensitivities for cirrus modelling using a two-moment two-mode bulk microphysics scheme",2015,"10.3402/tellusb.v67.24494","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930959764&doi=10.3402%2ftellusb.v67.24494&partnerID=40&md5=1f71aa7408eec96f4907a85550ffaf92","Cirrus cloud genesis is an inherently multiscale and non-linear problem. The synoptic scale provides the environment, the mesoscale determines the forcing and the actual nucleation events occur on a microscopic scale. This makes the parameterisation in numerical weather prediction models a challenging task. In order to improve the prediction of cirrus clouds and ice supersaturation formation in the German Weather Service (DWD) model chain, the controlling physical processes are investigated and parameterised in a new cloud ice microphysics scheme. The new scheme is an extended version of the ice-microphysical scheme operational in the numerical weather prediction models of DWD. The developed two-moment two-mode cloud ice scheme includes state-of-the-art parameterisations for the two main processes for ice formation, namely homogeneous and heterogeneous nucleation. Homogeneous freezing of supercooled liquid aerosols is triggered in regions with high atmospheric ice supersaturations (145-160%) and high cooling rates. Atmospheric small-scale fluctuations are accounted for by use of the turbulent kinetic energy. Heterogeneous nucleation depends mostly on the existence of ice nuclei in the atmosphere and occurs primarily at lower ice supersaturations. Thus, heterogeneously nucleated ice crystals deplete ice supersaturation via depositional growth and can therefore inhibit subsequent homogeneous freezing. The new cloud ice scheme accounts for pre-existing ice crystals, contains a prognostic budget variable for activated ice nuclei and includes cloud ice sedimentation. Furthermore, a consistent treatment of the depositional growth of the two-ice particle modes and the larger snowflakes is applied by using a relaxation time scale method which ensures a physical representation for depleting ice supersaturation. The new cloud ice scheme is used to identify the relative roles of heterogeneous and homogeneous nucleation in the formation of cirrus clouds and ice supersaturation. A parcel model is used in order to investigate the differences between the operational and new cloud ice scheme. The time scales for the homogeneous nucleation event and for the depositional growth are emphasised. The importance of the new ice nucleation scheme is demonstrated by conducting idealised simulations of orographic cirrus in the COSMO (Consortium for Small-Scale Modeling) model environment. © 2015 C. G. Kö hler and A. Seifert."
"25031430500;7103158465;56479980800;6506848305;36856321600;","Advanced two-moment bulk microphysics for global models. Part II: Global model solutions and aerosol-cloud interactions",2015,"10.1175/JCLI-D-14-00103.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923025690&doi=10.1175%2fJCLI-D-14-00103.1&partnerID=40&md5=b14398b7928f561f2194b3c50f2d3f29","A modified microphysics scheme is implemented in the Community AtmosphereModel, version 5 (CAM5). The new scheme features prognostic precipitation. The coupling between the microphysics and the rest of the model is modified to make it more flexible. Single-column tests show the new microphysics can simulate a constrained drizzling stratocumulus case. Substepping the cloud condensation (macrophysics) within a time step improves single-column results. Simulations of mixed-phase cases are strongly sensitive to ice nucleation. The new microphysics alters process rates in both single-column and global simulations, even at low (200 km) horizontal resolution. Thus, prognostic precipitation can be important, even in low-resolution simulations where advection of precipitation is not important. Accretion dominates as liquid water path increases in agreement with cloud-resolving model simulations and estimates from observations. The new microphysics with prognostic precipitation increases the ratio of accretion over autoconversion. The change in process rates appears to significantly reduce aerosol-cloud interactions and indirect radiative effects of anthropogenic aerosols by up to 33% (depending on substepping) to below 1Wm-2 of cooling between simulations with preindustrial (1850) and present-day (2000) aerosol emissions. © 2015 American Meteorological Society."
"57218273453;56424145700;55738957800;","The role of moist processes in shortwave radiative feedback during ENSO in the CMIP5 models",2015,"10.1175/JCLI-D-15-0276.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957708153&doi=10.1175%2fJCLI-D-15-0276.1&partnerID=40&md5=2a2819c247618ca67665b719381a8c55","The weak negative shortwave (SW) radiative feedback αsw during El Niño-Southern Oscillation (ENSO) over the equatorial Pacific is a common problem in the models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5). In this study, the causes for the αsw biases are analyzed using three-dimensional cloud fraction and liquid water path (LWP) provided by the 17 CMIP5 models and the relative roles of convective and stratiform rainfall feedbacks in αsw are explored. Results show that the underestimate of SW feedback is primarily associated with too negative cloud fraction and LWP feedbacks in the boundary layers, together with insufficient middle and/or high cloud and dynamics feedbacks, in both the CMIP and Atmospheric Model Intercomparsion Project (AMIP) runs, the latter being somewhat better. The underestimations of SW feedbacks are due to both weak negative SW responses to El Niño, especially in the CMIP runs, and strong positive SW responses to La Niña, consistent with their biases in cloud fraction, LWP, and dynamics responses to El Niño and La Niña. The convective rainfall feedback, which is largely reduced owing to the excessive cold tongue in the CMIP runs compared with their AMIP counterparts, contributes more to the difference of SW feedback (mainly under El Niño conditions) between the CMIP and AMIP runs, while the stratiform rainfall plays a more important role in SW feedback during La Niña. © 2015 American Meteorological Society."
"36634069800;7405489798;7402064802;22635190100;","Low-cloud characteristics over the tropical western Pacific from ARM observations and CAM5 simulations",2015,"10.1002/2015JD023369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943453997&doi=10.1002%2f2015JD023369&partnerID=40&md5=f9dff08902cf67b438059fdd94365dce","This study evaluates the ability of the Community Atmospheric Model version 5 (CAM5) to reproduce low clouds observed by the Atmospheric Radiation Measurement (ARM) cloud radar at Manus Island of the tropical western Pacific during the Years of Tropical Convection. Here low clouds are defined as clouds with their tops below the freezing level and bases within the boundary layer. Low-cloud statistics in CAM5 simulations and ARM observations are compared in terms of their general occurrence, mean vertical profiles, fraction of precipitating versus nonprecipitating events, diurnal cycle, and monthly time series. Other types of clouds are included to put the comparison in a broader context. The comparison shows that the model overproduces total clouds and their precipitation fraction but underestimates low clouds in general. The model, however, produces excessive low clouds in a thin layer between 954 and 930 hPa, which coincides with excessive humidity near the top of the mixed layer. This suggests that the erroneously excessive low clouds stem from parameterization of both cloud and turbulence mixing. The model also fails to produce the observed diurnal cycle in low clouds, not exclusively due to the model coarse grid spacing that does not resolve Manus Island. This study demonstrates the utility of ARM long-term cloud observations in the tropical western Pacific in verifying low clouds simulated by global climate models, illustrates issues of using ARM observations in model validation, and provides an example of severe model biases in producing observed low clouds in the tropical western Pacific. © 2015. American Geophysical Union. All Rights Reserved."
"24823024400;6506887943;55832671000;23017945100;","Variability of mixed-phase clouds in the Arctic with a focus on the Svalbard region: A study based on spaceborne active remote sensing",2015,"10.5194/acp-15-2445-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924199028&doi=10.5194%2facp-15-2445-2015&partnerID=40&md5=7dcf89ef93ac0190b237e134f68361bd","The Arctic region is known to be very sensitive to climate change. Clouds and in particular mixed-phase clouds (MPCs) remain one of the greatest sources of uncertainties in the modelling of the Arctic response to climate change due to an inaccurate representation of their variability and their quantification. In this study, we present a characterisation of the vertical, spatial and seasonal variability of Arctic clouds and MPCs over the entire Arctic region based on satellite active remote sensing observations. MPC properties in the region of the Svalbard archipelago (78° N, 15° E) are also investigated. The occurrence frequency of clouds and MPCs are determined from CALIPSO/CLOUDSAT measurements processed with the DARDAR retrieval algorithm, which allow for a reliable cloud thermodynamic phase classification (warm liquid, supercooled liquid, ice, mixing of ice and supercooled liquid). Significant differences are observed between MPC properties over the entire Arctic region and over the Svalbard region. Results show that MPCs are encountered all year long, with a minimum occurrence of 30% in winter and 50% during the rest of the year on average over the entire Arctic. Over the Svalbard region, MPC occurrence is more constant with time with larger values (55%) compared to the average observed in the Arctic. MPCs are especially located at low altitudes, below 3000 m, where their frequency of occurrence reaches 90%, particularly during winter, spring and autumn. Moreover, results highlight that MPCs are statistically more frequent above open sea than land or sea ice. The temporal and spatial distribution of MPCs over the Svalbard region seems to be linked to the supply of moister air and warmer water from the North Atlantic Ocean, which contribute to the initiation of the liquid water phase. Over the whole Arctic, and particularly in western regions, the increase of MPC occurrence from spring to autumn could be connected to the sea ice melting. During this period, the open water transports some of the warm water from the North Atlantic Ocean to the rest of the Arctic region. This facilitates the vertical transfer of moisture and thus the persistence of the liquid phase. Particular attention is also paid to the measurement uncertainties and how they could affect our conclusions. © Author(s) 2015."
"14024070000;7404493635;6603837066;7004429912;","On the hydrometeorological changes of a tropical water basin in the caribbean and its sensitivity to midterm changes in regional climate",2015,"10.1175/JHM-D-14-0083.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941267503&doi=10.1175%2fJHM-D-14-0083.1&partnerID=40&md5=be9c0a929ff47bb40015f13d4614784a","Global climate change manifests in the Caribbean basin as increased SSTs, precipitation anomalies, and changes in atmospheric moisture content, among other effects. These regional climate changes have a profound impact on the local human, flora, and fauna populations. Such is the case of the Enriquillo basin, a highly sensitive ecosystem located in the southwestern region of the Caribbean island of Hispaniola. The major bodies of water in the basin, Lake Enriquillo and Lake Azuéi, show a shrinking and expanding pattern since the early 1980s. The surface area of Lake Enriquillo was observed to reach minimum values in 2004 (170 km2), shifting to a rapid expansion to its current levels (>350 km2 as of late 2013). Lake Azuéi is observed to grow at similar rates. This lake expansion could be attributed to regional climate change. Long-term regional climate data reflect increasing SSTs (~1°C), air temperatures (~0.37°C decade-1), dewpoint (~0.66°C decade-1), and precipitation (~30%); no reliable local precipitation records were found. Furthermore, local governments are being forced to issue evacuations, prompting one of the first cases of environmental refugees not caused by an extreme event (e.g., a hurricane or tsunami). The hypothesis of lake expansion in the Enriquillo basin as a regional response to climate change is further investigated with the use of an integrated regional atmospheric modeling system. Model results from simulations performed for years during the lakes' lowest water levels (2003-04) and during their continued growth (2012-13) show increased total accumulated surface precipitation, atmospheric liquid water content, and an enhanced positive feedback system that produces orographic cloud cover in the surrounding tropical montane cloud forests as a consequence of the changing atmospheric and oceanic conditions. © 2015 American Meteorological Society."
"7005035462;","A 17-yr climate record of environmental parameters derived from the Tropical Rainfall Measuring Mission (TRMM) microwave imager",2015,"10.1175/JCLI-D-15-0155.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945954382&doi=10.1175%2fJCLI-D-15-0155.1&partnerID=40&md5=f1a77c01b53b2f592aa1c71ba3490711","The Tropical Rainfall Measuring Mission (TRMM) satellite began operating in December 1997 and was shut down on 8 April 2015. Over the oceans, the microwave (MW) sensor aboard TRMM measures sea surface temperature, wind speed, and rain rate as well as atmospheric columnar water vapor and cloud liquid water. Improved calibration methods are applied to the TRMM Microwave Imager (TMI), and a 17-yr climate record of these environmental parameters is produced so as to be consistent with the climate records from 13 other MW sensors. These TMI retrievals are validated relative to in situ observations over its 17-yr mission life. All indications point to TMI being an extremely stable sensor capable of providing satellite climate records of unprecedented length and accuracy. © 2015 American Meteorological Society."
"55913183200;7402989545;","Seasonal variation and physical properties of the cloud system over southeastern China derived from CloudSat products",2015,"10.1007/s00376-014-4070-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924308124&doi=10.1007%2fs00376-014-4070-y&partnerID=40&md5=1d458263a2d637c290f37f58f1f863d4","Based on the National Centers for Environmental Prediction (NCEP) and Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) data and CloudSat products, the seasonal variations of the cloud properties, vertical occurrence frequency, and ice water content of clouds over southeastern China were investigated in this study. In the CloudSat data, a significant alternation in high or low cloud patterns was observed from winter to summer over southeastern China. It was found that the East Asian Summer Monsoon (EASM) circulation and its transport of moisture leads to a conditional instability, which benefits the local upward motion in summer, and thereby results in an increased amount of high cloud. The deep convective cloud centers were found to coincide well with the northward march of the EASM, while cirrus lagged slightly behind the convection center and coincided well with the outflow and meridional wind divergence of the EASM. Analysis of the radiative heating rates revealed that both the plentiful summer moisture and higher clouds are effective in destabilizing the atmosphere. Moreover, clouds heat the mid-troposphere and the cloud radiative heating is balanced by adiabatic cooling through upward motion, which causes meridional wind by the Sverdrup balance. The cloud heating-forced circulation was observed to coincide well with the EASM circulation, serving as a positive effect on EASM circulation. © 2015, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"23094149200;7202899330;12645767500;7005920812;6506848305;","Regional assessments of low clouds against large-scale stability in CAM5 and CAM-CLUBB using MODIS and ERA-Interim reanalysis data",2015,"10.1175/JCLI-D-14-00184.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922782271&doi=10.1175%2fJCLI-D-14-00184.1&partnerID=40&md5=3f6d11721f6be4ec6bd71182c0a2524a","Daily gridded cloud data from MODIS and ERA-Interim reanalysis have been assessed to examine variations of low cloud fraction (CF) and cloud-top height and their dependence on large-scale dynamics and a measure of stability. To assess the stratocumulus (Sc) to cumulus (Cu) transition (STCT), the observations are used to evaluate two versions of the NCAR Community Atmosphere Model version 5 (CAM5), both the base model and a version that has implemented a new subgrid low cloud parameterization, Cloud Layers Unified by Binormals (CLUBB). The ratio of moist static energy (MSE) at 700-1000 hPa (MSEtotal) is a skillful predictor of median CF of screened low cloud grids. Values of MSEtotal less than 1.00 represent either conditionally or absolutely unstable layers, and probability density functions of CF suggest a preponderance of either trade Cu (median CF&lt;0.4) or transitional Sc clouds (0.4&lt;CF&lt;0.9). With increased stability (MSEtotal&gt;1.00), an abundance of overcast or nearly overcast low clouds exists. While both MODIS and ERA-Interim indicate a fairly smooth transition between the low cloud regimes, CAM5-Base simulates an abrupt shift from trade Cu to Sc, with trade Cu covering both too much area and occurring over excessively strong stabilities. In contrast, CAM-CLUBB simulates a smoother trade Cu to Sc transition (CTST) as a function of MSEtotal, albeit with too extensive coverage of overcast Sc in the primary northeastern Pacific subsidence region. While the overall CF distribution in CAM-CLUBB is more realistic, too few transitional clouds are simulated for intermediate MSEtotal compared to observations. © 2015 American Meteorological Society."
"56502199700;7202079615;","Evaluation of autoconversion schemes in a single model framework with satellite observations",2015,"10.1002/2015JD023818","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027941930&doi=10.1002%2f2015JD023818&partnerID=40&md5=6599dfa4ffbded0463b9266bbc7b6281","We examined the performance of autoconversion (mass transfer from cloud water to rainwater by the coalescence of cloud droplets) schemes in warm rain, which are commonly used in general circulation models. To exclude biases in the different treatment of the aerosol-cloud-precipitation-radiation interaction other than that of the autoconversion process, sensitivity experiments were conducted within a single model framework using an aerosol-climate model, MIROC-SPRINTARS. The liquid water path (LWP) and cloud optical thickness have a particularly high sensitivity to the autoconversion schemes, and their sensitivity is of the same magnitude as model biases. In addition, the ratio of accretion to autoconversion (Acc/Aut ratio), a key parameter in the examination of the balance of microphysical conversion processes, also has a high sensitivity globally depending on the scheme used. Although the Acc/Aut ratio monotonically increases with increasing LWP, significantly lower ratio is observed in Kessler-type schemes. Compared to satellite observations, a poor representation of cloud macrophysical structure and optically thicker low cloud are found in simulations with any autoconversion scheme. As a result of the cloud-radiation interaction, the difference in the global mean net cloud radiative forcing (NetCRF) among the schemes reaches 10 Wm-2. The discrepancy between the observed and simulated NetCRF is especially large with a high LWP. The potential uncertainty in the parameterization of the autoconversion process is nonnegligible, and no formulation significantly improves the bias in the cloud radiative effect yet. This means that more fundamental errors are still left in other processes of the model. © 2015. American Geophysical Union. All Rights Reserved."
"57212781009;","Climate radiative feedbacks and adjustments at the Earth’s surface",2015,"10.1002/2014JD022896","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929709435&doi=10.1002%2f2014JD022896&partnerID=40&md5=b3abfe9cce5e90769c3d1cbfe9033697","Climate radiative feedbacks are traditionally defined at top of atmosphere (TOA); however, strong radiative feedbacks also occur at the surface, with profound effect on the surface heat budget and hydrological cycle. “Rapid responses” to radiative forcing also occur and may also be expected to affect the surface. This study evaluates surface radiation changes, using a combined Partial Radiative Perturbation-Gregory approach, under abrupt increases in CO2 in a climate model. We find significant surface rapid radiative response from changes in clouds, relative humidity, and latent heat flux. As surface temperature increases, strong water vapor feedback exceeds net cooling from atmospheric and surface temperature changes, resulting in increased surface evaporation. Feedbacks fromclouds are smaller, with complex horizontal and vertical structures. Surface longwave feedback structures differ widely from those of the TOA and are dominated by lower troposphere changes. Lapse rate, cloud, and albedo feedbacks are small equatorward of around 50° of latitude but stronger at high latitudes. The approach here allows precise evaluation of the rich structure of surface radiative feedbacks. © 2015. American Geophysical Union. All Rights Reserved."
"56256907500;6701823396;6701529949;","Atmospheric and oceanic conditions and the extremely low Bothnian Bay sea ice extent in 2014/2015",2015,"10.1002/2015GL064901","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945439378&doi=10.1002%2f2015GL064901&partnerID=40&md5=cbce327deaa6e50fbbc65d776ca16772","The winter of 2014/2015 was the first for which we can be certain that the northernmost embayment of the Baltic Sea, the Bothnian Bay, remained partially ice-free. We assess atmospheric and oceanic drivers responsible for this extreme event. In terms of atmospheric drivers, mild Bothnian Bay winters are characterized by positive North Atlantic Oscillation (NAO) associated with the advection of air from the North Atlantic. In winter 2014/2015, NAO was at a record high level and resulted in a northerly storm track associated with vigorous southwesterlies that drove ice toward the northeastern end of the bay. Furthermore, we found that the 1985-2015 Baltic Sea ice extent distribution differs from any other preceding 30 winter period since 1720 with a high confidence. Based on climate projections, it is very likely that in the next 50-years partially ice-free Bothnian Bay will go from being an extremely rare event to a new normal. © 2015 American Geophysical Union. All Rights Reserved."
"7201504886;","Rethinking the lower bound on aerosol radiative forcing",2015,"10.1175/JCLI-D-14-00656.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941121923&doi=10.1175%2fJCLI-D-14-00656.1&partnerID=40&md5=389902a1e913cfde4f2cfe38df888fb2","Based on research showing that in the case of a strong aerosol forcing, this forcing establishes itself early in the historical record, a simple model is constructed to explore the implications of a strongly negative aerosol forcing on the early (pre-1950) part of the instrumental record. This model, which contains terms representing both aerosol-radiation and aerosol-cloud interactions, well represents the known time history of aerosol radiative forcing as well as the effect of the natural state on the strength of aerosol forcing. Model parameters, randomly drawn to represent uncertainty in understanding, demonstrate that a forcing more negative than -1.0Wm-2 is implausible, as it implies that none of the approximately 0.3-K temperature rise between 1850 and 1950 can be attributed to Northern Hemisphere forcing. The individual terms of the model are interpreted in light of comprehensive modeling, constraints from observations, and physical understanding to provide further support for the less negative (-1.0Wm-2) lower bound. These findings suggest that aerosol radiative forcing is less negative and more certain than is commonly believed. © 2015 American Meteorological Society."
"44061090200;24528108000;24921742700;35547807400;","A comparison of temperature and precipitation responses to different earth radiation management geoengineering schemes",2015,"10.1002/2015JD023269","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944916849&doi=10.1002%2f2015JD023269&partnerID=40&md5=8ce2400a766af68c2f9de7cfa9323a62","Earth radiation management has been suggested as a way to rapidly counteract globalwarming in the face of a lack ofmitigation efforts, buying time and avoiding potentially catastrophic warming. We compare six different radiation management schemes that use surface, troposphere, and stratosphere interventions in a single climate model in which we projected future climate from 2020 to 2099 based on RCP4.5.We analyze the surface air temperature responses to determine how effective the schemes are at returning temperature to its 1986-2005 climatology and analyze precipitation responses to compare side effects. We find crop albedo enhancement is largely ineffective at returning temperature to its 1986-2005 climatology. Desert albedo enhancement causes excessive cooling in the deserts and severe shifts in tropical precipitation. Ocean albedo enhancement, sea-spray geoengineering, cirrus cloud thinning, and stratospheric SO2 injection have the potential to cool more uniformly, but cirrus cloud thinning may not be able to cool by much more than 1 K globally.We find that of the schemes potentially able to return surface air temperature to 1986-2005 climatology under future greenhouse gas warming, none has significantly less severe precipitation side effects than other schemes. Despite different forcing patterns, ocean albedo enhancement, sea-spray geoengineering, cirrus cloud thinning, and stratospheric SO2 injection all result in large scale tropical precipitation responses caused by Hadley cell changes and land precipitation changes largely driven by thermodynamic changes. Widespread regional scale changes in precipitation over land are significantly different from the 1986-2005 climatology and would likely necessitate significant adaptation despite geoengineering. © 2015. The Authors."
"7005578774;57207969036;6602098362;55542531000;","Climate variability and relationships between top-of-atmosphere radiation and temperatures on Earth",2015,"10.1002/2014JD022887","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930379494&doi=10.1002%2f2014JD022887&partnerID=40&md5=c978f032e4556f64ddef1eb807cd4e7d","The monthly global and regional variability in Earth’s radiation balance is examined using correlations and regressions between atmospheric temperatures and water vapor with top-of-atmosphere outgoing longwave (OLR), absorbed shortwave (ASR), and net radiation (RT = ASR-OLR). Anomalous global mean monthly variability in the net radiation is surprisingly large, often more than ±1Wm-2, and arises mainly from clouds and transient weather systems. Relationships are strongest and positive between OLR and temperatures, especially over land for tropospheric temperatures, except in the deep tropics where high sea surface temperatures are associated with deep convection, high cold cloud tops and thus less OLR but also less ASR. Tropospheric vertically averaged temperatures (surface = 150 hPa) are thus negatively correlated globally with net radiation (-0.57), implying 2.18 ± 0.10Wm-2 extra net radiation to space for 1°C increase in temperature. Water vapor is positively correlated with tropospheric temperatures and thus also negatively correlated with net radiation; however, when the temperature dependency of water vapor is statistically removed, a significant positive feedback between water vapor and net radiation is revealed globally with 0.87Wm-2 less OLR to space per millimeter of total column water vapor. The regression coefficient between global RT and tropospheric temperature becomes -2.98Wm-2 K-1 if water vapor effects are removed, slightly less than expected from blackbody radiation (-3.2Wm-2 K-1), suggesting a positive feedback from clouds and other processes. Robust regional structures provide additional physical insights. The observational record is too short, weather noise too great, and forcing too small to make reliable estimates of climate sensitivity. © 2015. American Geophysical Union. All Rights Reserved."
"9636267700;7401651197;12902788500;16527798200;7004346568;6603811829;","Pollen as atmospheric cloud condensation nuclei",2015,"10.1002/2015GL064060","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930485130&doi=10.1002%2f2015GL064060&partnerID=40&md5=29d8764288523d61d9b3a3fdc4d78c14","Anemophilous (wind-dispersed) pollen grains are emitted in large quantities by vegetation in the midlatitudes for reproduction. Pollen grains are coarse particles (5-150μm) that can rupture when wet to form submicron subpollen particles (SPP) that may have a climatic role. Laboratory CCN experiments of six fresh pollen samples show that SPP activate as CCN at a range of sizes, requiring supersaturations from 0.81 (±0.07)% for 50 nm particles, 0.26 (±0.03)% for 100nm particles, and 0.12 (±0.00)% for 200nm particles. Compositional analyses indicate that SPP contain carbohydrates and proteins. The SPP contribution to global CCN is uncertain but could be important depending on pollen concentrations outside the surface layer and the number of SPP generated from a single pollen grain. The production of hygroscopic SPP from pollen represents a novel, biologically driven cloud formation pathway that may influence cloud optical properties and lifetimes, thereby influencing climate. Key Points Pollen grains can rupture when wet to form submicron subpollen particles (SPP) Laboratory experiments show that SPP are hygroscopic and can act as CCN Pollen grains may contribute to CCN in northern midlatitudes ©2015. American Geophysical Union. All Rights Reserved."
"7201498373;35079444600;8414341100;56203249800;","Irrigation as an historical climate forcing",2015,"10.1007/s00382-014-2204-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939885377&doi=10.1007%2fs00382-014-2204-7&partnerID=40&md5=b4b23f8e75516434016242af8e57ab30","Irrigation is the single largest anthropogenic water use, a modification of the land surface that significantly affects surface energy budgets, the water cycle, and climate. Irrigation, however, is typically not included in standard historical general circulation model (GCM) simulations along with other anthropogenic and natural forcings. To investigate the importance of irrigation as an anthropogenic climate forcing, we conduct two 5-member ensemble GCM experiments. Both are setup identical to the historical forced (anthropogenic plus natural) scenario used in version 5 of the Coupled Model Intercomparison Project, but in one experiment we also add water to the land surface using a dataset of historically estimated irrigation rates. Irrigation has a negligible effect on the global average radiative balance at the top of the atmosphere, but causes significant cooling of global average surface air temperatures over land and dampens regional warming trends. This cooling is regionally focused and is especially strong in Western North America, the Mediterranean, the Middle East, and Asia. Irrigation enhances cloud cover and precipitation in these same regions, except for summer in parts of Monsoon Asia, where irrigation causes a reduction in monsoon season precipitation. Irrigation cools the surface, reducing upward fluxes of longwave radiation (increasing net longwave), and increases cloud cover, enhancing shortwave reflection (reducing net shortwave). The relative magnitude of these two processes causes regional increases (northern India) or decreases (Central Asia, China) in energy availability at the surface and top of the atmosphere. Despite these changes in net radiation, however, climate responses are due primarily to larger magnitude shifts in the Bowen ratio from sensible to latent heating. Irrigation impacts on temperature, precipitation, and other climate variables are regionally significant, even while other anthropogenic forcings (anthropogenic aerosols, greenhouse gases, etc.) dominate the long term climate evolution in the simulations. To better constrain the magnitude and uncertainties of irrigation-forced climate anomalies, irrigation should therefore be considered as another important anthropogenic climate forcing in the next generation of historical climate simulations and multi-model assessments. © 2014, Springer-Verlag (outside the USA)."
"8511991900;15765505200;7403282069;56611485900;36342344200;7401796996;55738957800;57189634238;6603431534;7003666669;","Improving representation of convective transport for scale-aware parameterization: 1. Convection and cloud properties simulated with spectral bin and bulk microphysics",2015,"10.1002/2014JD022142","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929707929&doi=10.1002%2f2014JD022142&partnerID=40&md5=5ef2a6fed42e276cb9a6303cec4f8c38","The ultimate goal of this study is to improve the representation of convective transport by cumulus parameterization for mesoscale and climate models. As Part 1 of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in midlatitude continent and tropical regions using the Weather Research and Forecasting model with spectral bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation and vertical velocity of convective cores than MOR and MY2 and therefore will be used for analysis of scale dependence of eddy transport in Part 2. The common features of the simulations for all convective systems are (1) themodel tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates Ze in convective cores, especially for the weak updraft velocity; and (3) the model performs better for midlatitude convective systems than the tropical system. The modeled mass fluxes of the midlatitude systems are not sensitive to microphysics schemes but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow, and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes. © 2015. American Geophysical Union. All Rights Reserved."
"55469523400;15124698700;","Increases in moist-convective updraught velocities with warming in radiative-convective equilibrium",2015,"10.1002/qj.2567","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946481565&doi=10.1002%2fqj.2567&partnerID=40&md5=83372d07eefe03c0d969806e198ce0d0","The scaling of updraught velocities over a wide range of surface temperatures is investigated in simulations of radiative-convective equilibrium with a cloud-system resolving model. The updraught velocities increase with warming, with the largest fractional increases occurring in the upper troposphere and for the highest percentile updraughts. A plume model approximately reproduces the increases in updraught velocities if the plume environment is prescribed as the mean profile in each simulation while holding the entrainment and microphysical assumptions fixed. Convective available potential energy (CAPE) also increases with warming in the simulations but at a much faster fractional rate when compared with the square of the updraught velocities. This discrepancy is investigated with a two-plume model in which a weakly entraining plume represents the most intense updraughts, and the environment is assumed to adjust so that a more strongly entraining plume has negligible buoyancy. The two-plume model suggests that updraught velocities increase with warming at a lower fractional rate than implied by the CAPE because of the influence of entrainment on both the mean stratification and the updraughts themselves. © 2015 Royal Meteorological Society."
"37088140000;","A new global climatology of annual land surface temperature",2015,"10.3390/rs70302850","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926338015&doi=10.3390%2frs70302850&partnerID=40&md5=251c692328595cb4b5543053edfe8250","Land surface temperature (LST) is an important parameter in various fields including hydrology, climatology, and geophysics. Its derivation by thermal infrared remote sensing has long tradition but despite substantial progress there remain limited data availability and challenges like emissivity estimation, atmospheric correction, and cloud contamination. The annual temperature cycle (ATC) is a promising approach to ease some of them. The basic idea to fit a model to the ATC and derive annual cycle parameters (ACP) has been proposed before but so far not been tested on larger scale. In this study, a new global climatology of annual LST based on daily 1 km MODIS/Terra observations was processed and evaluated. The derived global parameters were robust and free of missing data due to clouds. They allow estimating LST patterns under largely cloud-free conditions at different scales for every day of year and further deliver a measure for its accuracy respectively variability. The parameters generally showed low redundancy and mostly reflected real surface conditions. Important influencing factors included climate, land cover, vegetation phenology, anthropogenic effects, and geology which enable numerous potential applications. The datasets will be available at the CliSAP Integrated Climate Data Center pending additional processing. © 2015 by the authors."
"7402199436;7403058740;","Two regimes of cloud water over the Okhotsk Sea and the adjacent regions around Japan in summer",2015,"10.1002/2014JD022536","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927696512&doi=10.1002%2f2014JD022536&partnerID=40&md5=5f42940fd0e60dc13ef7fa106c3e85af","This study derived two regimes of cloud water with a dipole structure between over the Okhotsk Sea and over the adjacent regions around Japan in summer by using a climate index for cool summer. When the Okhotsk high develops, clouds are confined to a thin low-level layer owing to the enhanced stability in the lower atmosphere induced by the downward motion associated with the Okhotsk high. The resulting optically thin clouds allow more downward shortwave radiation to reach the surface of the Okhotsk Sea. In contrast, the low-level easterly winds blowing toward the Japanese Islands and the Eurasian continent enhance cloud formation. This is due to the convergence of the water vapor flux induced by the easterly winds associated with the Okhotsk high and the southerly winds associated with the Baiu frontal zone and the Pacific high and due to the orographic uplift of air mass. When a cyclonic circulation occurs over the Okhotsk Sea, a thick layer of low-level clouds extending close to the sea surface is formed. The convergence of the water vapor flux over the subarctic sea surface temperature (SST) frontal zone and the cool SST promote fog formation, and upward motion associated with the cyclonic circulation supports the high cloud water content from the lower to the upper troposphere. The resulting optically thick clouds reduce the downward shortwave radiation at the surface of the Okhotsk Sea. Over the regions around Japan, water vapor flux diverges owing to dry air originating from land and cloud water decreases. © 2015. American Geophysical Union. All Rights Reserved."
"7403717185;55841938900;7005281574;7403232646;56900166700;","Marine boundary layer heights and their longitudinal, diurnal, and interseasonal variability in the southeastern Pacific using COSMIC, CALIOP, and radiosonde data",2015,"10.1175/JCLI-D-14-00238.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944144875&doi=10.1175%2fJCLI-D-14-00238.1&partnerID=40&md5=45fd0d1697c2aec8dde42132e15b4789","The spatial and temporal variability of the marine boundary layer (MBL) over the southeastern Pacific is studied using high-resolution radiosonde data from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), lidar cloud measurements from the CALIOP instrument on the CALIPSO satellite, radio occultation (RO) data from the COSMIC satellites, and the ERA-Interim. The height of the MBL (MBLH) is estimated using three RO-derived parameters: the bending angle, refractivity, and water vapor pressure computed from the refractivity derived from a one-dimensional variational data inversion (1D-VAR) procedure. Two different diagnostic methods (minimum gradient and break point method) are compared. The results show that, although a negative bias in the refractivity exists as a result of superrefraction, the spatial and temporal variations of the MBLH determined from the RO observations are consistent with those from CALIOP and the radiosondes. The authors find that the minimum gradient in the RO bending angle gives the most accurate estimation of the MBL height. © 2015 American Meteorological Society."
"15074029300;6603353668;","Comparing environmental vulnerability in the montane cloud forest of eastern Mexico: A vulnerability index",2015,"10.1016/j.ecolind.2014.12.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920702815&doi=10.1016%2fj.ecolind.2014.12.019&partnerID=40&md5=9596cc979a23072bb1acc92b8c9083cd","The montane cloud forest (MCF) is one of the most threatened ecosystems, in spite of its high strategic value for sustainable development, the role it plays in the hydrological cycle maintenance, and as reservoir of endemic biodiversity. For Mexico, this forest is considered the most threatened terrestrial ecosystem at national level because of land-use changes and the effects of global climate change. To compare and assess the environmental vulnerability in the MCF we measured two physiological traits (stomatal conductance and leaf water potential), four climate variables (air temperature, photosynthetically active radiation, vapor pressure deficit, water availability) and the potential geographic distribution of eleven tree species from this forest. We evaluated stomatal conductance responses using the envelope function method (EFM), and after analyzing these responses we developed a vulnerability index that allowed us to compare the environmental vulnerability among species. We proposed the EFM as a useful tool to assess regional environmental vulnerability by comparing species. Our results showed differential species responses to all the studied variables; however, the vulnerability index allowed us to conclude that the most vulnerable species was Liquidambar styraciflua, and the least vulnerable Persea longipes. We also found that temperatures above 34 °C, and vapor pressure deficit above 2.9 kPa with relative humidity below 30% jeopardized the stomatal conductance performance of all species. We also found leaf water potential as the most influential variable over the studied species followed by vapor pressure deficit, showing that even in the MCF water is a determinant factor for species' development. ©2014 Elsevier Ltd. All rights reserved."
"36538539800;55802355600;56942554300;56612517400;7202048112;8511991900;6701378450;","Incorporating an advanced aerosol activation parameterization into WRF-CAM5: Model evaluation and parameterization intercomparison",2015,"10.1002/2014JD023051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939256583&doi=10.1002%2f2014JD023051&partnerID=40&md5=132e8f6b284723b341be37700e3e330f","Aerosol activation into cloud droplets is an important process that governs aerosol indirect effects. The advanced treatment of aerosol activation by Fountoukis and Nenes (2005) and its recent updates, collectively called the FN series, have been incorporated into a newly developed regional coupled climate-air quality model based on the Weather Research and Forecasting model with the physics package of the Community Atmosphere Model version 5 (WRF-CAM5) to simulate aerosol-cloud interactions in both resolved and convective clouds. The model is applied to East Asia for two full years of 2005 and 2010. A comprehensive model evaluation is performed for model predictions of meteorological, radiative, and cloud variables, chemical concentrations, and column mass abundances against satellite data and surface observations from air quality monitoring sites across East Asia. The model performs overall well for major meteorological variables including near-surface temperature, specific humidity, wind speed, precipitation, cloud fraction, precipitable water, downward shortwave and longwave radiation, and column mass abundances of CO, SO2, NO2, HCHO, and O3 in terms of both magnitudes and spatial distributions. Larger biases exist in the predictions of surface concentrations of CO and NOx at all sites and SO2, O3, PM2.5, and PM10 concentrations at some sites, aerosol optical depth, cloud condensation nuclei over ocean, cloud droplet number concentration (CDNC), cloud liquid and ice water path, and cloud optical thickness. Compared with the default Abdul-Razzack Ghan (2000) parameterization, simulations with the FN series produce ~107-113% higher CDNC, with half of the difference attributable to the higher aerosol activation fraction by the FN series and the remaining half due to feedbacks in subsequent cloud microphysical processes. With the higher CDNC, the FN series are more skillful in simulating cloud water path, cloud optical thickness, downward shortwave radiation, shortwave cloud forcing, and precipitation. The model evaluation identifies several areas of improvements including emissions and their vertical allocation as well as model formulations such as aerosol formation, cloud droplet nucleation, and ice nucleation. © 2015. American Geophysical Union. All Rights Reserved."
"7401796996;56702455000;8629713500;56457152000;","Investigation of the marine boundary layer cloud and CCN properties under coupled and decoupled conditions over the azores",2015,"10.1002/2014JD022939","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941082433&doi=10.1002%2f2014JD022939&partnerID=40&md5=59d883db45a06a421d77c3fe0cee0d5a","Six coupled and decoupled marine boundary layer (MBL) clouds were chosen from the 19 month Atmospheric Radiation Measurement Mobile Facility data set over the Azores. Thresholds of liquid water potential temperature difference ΔθL &lt; 0.5 K (&gt;0.5 K) and total water mixing ratio difference Δqt &lt; 0.5 g/kg (&gt;0.5 g/kg) below the cloud base were used for selecting the coupled (decoupled) cases. A schematic diagram was given to demonstrate the coupled and decoupled MBL vertical structures and how they associate with nondrizzle, virga, and rain drizzle events. Out of a total of 2676 5 min samples, 34.5% were classified as coupled and 65.5% as decoupled, 36.2% as nondrizzle and 63.8% as drizzle (47.7% as virga and 16.1% as rain), and 33.4% as daytime and 66.6% as nighttime. The decoupled cloud layer is deeper (0.406 km) than coupled cloud layer (0.304 km), and its liquid water path and cloud droplet effective radius (re) values (122.1 gm-2 and 13.0 μm) are higher than coupled ones (83.7 gm-2 and 10.4 μm). Conversely, decoupled stratocumuli have lower cloud droplet number concentration (Nd) and surface cloud condensation nucleus (CCN) concentration (NCCN) (74.5 cm-3 and 150.9 cm-3) than coupled stratocumuli (111.7 cm-3 and 216.4 cm-3). The linear regressions between re and Nd with NCCN have demonstrated that coupled re and Nd strongly depend on NCCN and have higher correlations (-0.56 and 0.59) with NCCN than decoupled results (-0.14 and 0.25). The MBL cloud properties under nondrizzle and virga drizzle conditions are similar to each other but significantly different to those of rain drizzle. © 2015. American Geophysical Union. All Rights Reserved."
"56014511300;35509639400;57203200427;7004479957;35547807400;57203049177;7201504886;","Adjustments in the forcing-feedback framework for understanding climate change",2015,"10.1175/BAMS-D-13-00167.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929458571&doi=10.1175%2fBAMS-D-13-00167.1&partnerID=40&md5=676781524cdccb8d2b0cb38a12798ec2","The traditional forcing-feedback framework has provided an indispensable basis for discussing global climate changes. However, as analysis of model behavior has become more detailed, shortcomings and ambiguities in the framework have become more evident, and physical effects unaccounted for by the traditional framework have become interesting. In particular, the new concept of adjustments, which are responses to forcings that are not mediated by the global-mean temperature, has emerged. This concept, related to the older ones of climate efficacy and stratospheric adjustment, is a more physical way of capturing unique responses to specific forcings. We present a pedagogical review of the adjustment concept, why it is important, and how it can be used. The concept is particularly useful for aerosols, where it helps to organize what has become a complex array of forcing mechanisms. It also helps clarify issues around cloud and hydrological response, transient versus equilibrium climate change, and geoengineering. ©American Meteorological Society."
"57212215393;6701835010;7005702722;7202208382;7004247643;","MJO intensification with warming in the superparameterized CESM",2015,"10.1175/JCLI-D-14-00494.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938953977&doi=10.1175%2fJCLI-D-14-00494.1&partnerID=40&md5=72f72750d35a434dc70b60100b3067a9","The Madden-Julian oscillation (MJO) is the dominant mode of tropical intraseasonal variability, characterized by an eastward-propagating envelope of convective anomalies with a 30-70-day time scale. Here, the authors report changes in MJO activity across coupled simulations with a superparameterized version of the NCAR Community Earth System Model. They find that intraseasonal OLR variance nearly doubles between a preindustrial control run and a run with 4×CO2. Intraseasonal precipitation increases at a rate of roughly 10% per 1 K of warming, and MJO events become 20%-30% more frequent. Moist static energy (MSE) budgets of composite MJO events are calculated for each scenario, and changes in budget terms are used to diagnose the physical processes responsible for changes in the MJO with warming. An increasingly positive contribution from vertical advection is identified as the most likely cause of the enhanced MJO activity. A decomposition links the changes in vertical advection to a steepening of the mean MSE profile, which is a robust thermodynamic consequence of warming. Surface latent heat flux anomalies are a significant sink of MJO MSE at 1×CO2, but this damping effect is reduced in the 4×CO2 case. This work has implications for organized tropical variability in past warm climates as well as future global warming scenarios. © 2015 American Meteorological Society."
"56000281400;","Mountain weather: Observation and modeling",2015,"10.1016/bs.agph.2015.01.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928215734&doi=10.1016%2fbs.agph.2015.01.001&partnerID=40&md5=fcd2cb47437528056a8e78d08bb22d1c","Mountains, through atmospheric processes, play an integrated role in weather systems and climate systems. In turn, weather and climate over and nearby mountains are modified depending on environmental conditions. Mountain size, shape, slope, aspect ratio, and orientation along the water sources affect the weather systems; they can intensify fronts, eddies, vortex, rotors and turbulence, visibility, and precipitation. Depending on their location and height, precipitation type as snow over the mountains contributes significantly to hydrometeorological cycle and ecosystem. Increasing temperatures because of a possible climate change can reduce river discharges during warm seasons. Therefore, accurate measurements of climate change impact on the mountains are required. On the other hand, obtaining measurements over the mountainous regions are extremely difficult because of strong winds, cold temperatures (<0°C), mountain slopes, and heavy snow precipitation as well as instrumental issues. New developments on measurement strategies and instruments, and developing multiscale numerical models with detailed cloud microphysical processes and boundary layer parameterizations can reduce uncertainties in the weather and climate prediction. In this review, the challenges related to collecting measurements, numerical model predictions, and climate change issues over and nearby mountains will be emphasized. © 2015 Elsevier Inc."
"55893616600;6602538849;23006934800;7005742190;","Lake-related cloud dynamics on the Tibetan Plateau: Spatial patterns and interannual variability",2015,"10.1175/JCLI-D-14-00698.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950109827&doi=10.1175%2fJCLI-D-14-00698.1&partnerID=40&md5=f21e31d41b50a4d11605e60196b88afa","The scarcity of meteorological observations has hitherto prevented spatially comprehensive and complete assessments on regional and local-scale atmospheric processes such as breeze systems on the Tibetan Plateau (TiP). Because of the high abundance of lakes, the steep topography, and the intense insolation of the TiP, lake breeze and land breeze systems might, however, contribute substantially to the local climatic and hydrological variability. The presented study aims at unveiling the influence of the lake effect over the whole TiP by using a novel high-mountain satellite cloud product, based on Meteosat Indian Ocean Data Coverage (IODC) data from 1999 to 2012, focusing on 70 lake systems larger than 72 km2. Of particular interest are the spatial and interannual variability of lake-related cloud dynamics during boreal summer and autumn. For both seasons, a significant effect of lakes on cloudiness is shown during the early morning. Its mean strength is mainly determined by each basin's temperature difference between lake and surroundings. For boreal summer the large-scale influences of tropical and extratropical circulation pattern on the interannual variability of the lake effect are also investigated. The results show that the Arctic and North Atlantic Oscillations (AO and NAO) inhibit convective activity above lakes in the northern and central-eastern domain. A positive polarity of the Southern Oscillation index (SOI), in contrast, is in phase with enhanced convective activity. The variability of the Indian summer monsoon circulation does not affect cloud dynamics at more than two locations. Case studies are employed to illustrate interactions between cloud activity and the SOI and NAO. For this purpose satellite data are combined with the modeled 10 km × 10 km High Asia Refined Analysis dataset on a daily basis. © 2015 American Meteorological Society."
"35829589800;56268922700;","Diurnal precipitation and high cloud frequency variability over the Gulf Stream and over the Kuroshio",2015,"10.1007/s00382-014-2245-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939894091&doi=10.1007%2fs00382-014-2245-y&partnerID=40&md5=54c09b320b4f5650c7ec2ebdd6c3c440","Recent studies show mid-latitude western boundary currents (WBCs) substantially influence the atmosphere aloft, and an important feature is enhanced rain band over the WBCs in climatological mean field. However, how such long-term, climate phenomena are related to shorter, weather timescale phenomena are generally remained to be explored. In this paper, diurnal precipitation and cloud variations are investigated global mid-latitude oceans with emphasis on air–sea interactions over WBCs using satellite-derived precipitation and outgoing longwave radiation (OLR) datasets. Strong 24-h period components of precipitations are found over the Gulf Stream in summer and over the Kuroshio in the East China Sea in early summer (Baiu–Meiyu season), respectively. Similar diurnal precipitations are not observed in WBCs in the Southern Hemisphere year around. The diurnal precipitation cycles over the Gulf Stream and the Kuroshio exhibit peak phases in the early to late morning for the Gulf Stream and late morning to early afternoon for the Kuroshio, with southeastward phase propagations. High cloud frequency derived from OLR data exhibit consistent diurnal cycles. A substantial difference of diurnal cycles between the Gulf Stream and the Kuroshio regions are associated with the large-scale Baiu–Meiyu rain and cloud bands for the latter region. Diurnal precipitation and high cloud variability is found in the vicinity of the Kuroshio itself, embedded in the Baiu–Meiyu rain and cloud bands distributing in a wider area without a strong diurnal component. The spatial and seasonal distributions of the diurnal variability over these WBCs strongly suggests that the diurnal precipitation and cloud cycles are essential aspects of deep heating mode of atmospheric response recently reported for these WBCs. These results indicate that these WBCs in the Northern Hemisphere play an important role in modulating short-term precipitation variations, and on the other hand diurnal variability can be a substantial agent for the mid-latitude air–sea interaction. © 2014, The Author(s)."
"26632168400;57206503877;55663817800;7401936984;52464731300;","Evaluation of cloud-resolvingmodel simulations of midlatitude cirrus with ARM and A-train observations",2015,"10.1002/2014JD022570","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938207557&doi=10.1002%2f2014JD022570&partnerID=40&md5=898da1e3960f7bcedaa665a505970f25","Cirrus clouds are ubiquitous in the upper troposphere and still constitute one of the largest uncertainties in climate predictions. This paper evaluates cloud-resolving model (CRM) and cloud system-resolving model (CSRM) simulations of a midlatitude cirrus case with comprehensive observations collected under the auspices of the Atmospheric Radiation Measurements (ARM) program and with spaceborne observations from the National Aeronautics and Space Administration A-train satellites. The CRM simulations are driven with periodic boundary conditions and ARM forcing data, whereas the CSRM simulations are driven by the ERA-Interim product. Vertical profiles of temperature, relative humidity, and wind speeds are reasonably well simulated by the CSRM and CRM, but there are remaining biases in the temperature, wind speeds, and relative humidity, which can be mitigated through nudging the model simulations toward the observed radiosonde profiles. Simulated vertical velocities are underestimated in all simulations except in the CRM simulations with grid spacings of 500 m or finer, which suggests that turbulent vertical air motions in cirrus clouds need to be parameterized in general circulation models and in CSRM simulations with horizontal grid spacings on the order of 1 km. The simulated ice water content and ice number concentrations agree with the observations in the CSRM but are underestimated in the CRM simulations. The underestimation of ice number concentrations is consistent with the overestimation of radar reflectivity in the CRM simulations and suggests that the model produces too many large ice particles especially toward the cloud base. Simulated cloud profiles are rather insensitive to perturbations in the initial conditions or the dimensionality of the model domain, but the treatment of the forcing data has a considerable effect on the outcome of the model simulations. Despite considerable progress in observations and microphysical parameterizations, simulating the microphysical, macrophysical, and radiative properties of cirrus remains challenging. Comparing model simulations with observations from multiple instruments and observational platforms is important for revealing model deficiencies and for providing rigorous benchmarks. However, there still is considerable need for reducing observational uncertainties and providing better observations especially for relative humidity and for the size distribution and chemical composition of aerosols in the upper troposphere. © 2015. The Authors."
"56518632100;7402146514;56518508500;35205101700;","Assessment of sea ice albedo radiative forcing and feedback over the Northern Hemisphere from 1982 to 2009 using satellite and reanalysis data",2015,"10.1175/JCLI-D-14-00389.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922989514&doi=10.1175%2fJCLI-D-14-00389.1&partnerID=40&md5=cb31be3ed244061625aacef26f95cff2","The decreasing surface albedo caused by continuously retreating sea ice over Arctic plays a critical role in Arctic warming amplification. However, the quantification of the change in radiative forcing at top of atmosphere (TOA) introduced by the decreasing sea ice albedo and its feedback to the climate remain uncertain. In this study, based on the satellite-retrieved long-term surface albedo product CLARA-A1 (Cloud, Albedo, and Radiation dataset, AVHRR-based, version 1) and the radiative kernel method, an estimated 0.206±0.05Wm-2 sea ice radiative forcing (SIRF) has decreased in the Northern Hemisphere (NH) owing to the loss of sea ice from 1982 to 2009, yielding a sea ice albedo feedback (SIAF) of 0.25Wm-2K-1 for the NH and 0.19Wm-2K-1 for the entire globe. These results are lower than the estimate from another method directly using the Clouds and the Earth's Radiant Energy System (CERES) broadband planetary albedo. Further data analysis indicates that kernel method is likely to underestimate the change in all-sky SIRF because all-sky radiative kernels mask too much of the effect of sea ice albedo on the variation of cloudy albedo. By applying an adjustment with CERES-based estimate, the change in all-sky SIRF over the NH was corrected to 0.33±0.09Wm-2, corresponding to a SIAF of 0.43Wm-2K-1 for NH and 0.31Wm-2K-1 for the entire globe. It is also determined that relative to satellite surface albedo product, two popular reanalysis products, ERA-Interim and MERRA, severely underestimate the changes in NHSIRF in melt season (May- August) from 1982 to 2009 and the sea ice albedo feedback to warming climate. © 2015 American Meteorological Society."
"55272477500;6506545080;8859530100;6701333444;37018824600;7203034123;7004242319;54397207800;7101846027;56611366900;","RACORO continental boundary layer cloud investigations: 2. large-eddy simulations of cumulus clouds and evaluation with in situ and ground-based observations",2015,"10.1002/2014JD022525","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955633916&doi=10.1002%2f2014JD022525&partnerID=40&md5=7e299c8039372fb2e789c58b43b94ee5","A 60 h case study of continental boundary layer cumulus clouds is examined using two large-eddy simulation (LES) models. The case is based on observations obtained during the RACORO Campaign (Routine Atmospheric Radiation Measurement (ARM) Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations) at the ARM Climate Research Facility’s Southern Great Plains site. The LES models are driven by continuous large-scale and surface forcings and are constrained by multimodal and temporally varying aerosol number size distribution profiles derived from aircraft observations. We compare simulated cloud macrophysical and microphysical properties with ground-based remote sensing and aircraft observations. The LES simulations capture the observed transitions of the evolving cumulus-topped boundary layers during the three daytime periods and generally reproduce variations of droplet number concentration with liquid water content (LWC), corresponding to the gradient between the cloud centers and cloud edges at given heights. The observed LWC values fall within the range of simulated values; the observed droplet number concentrations are commonly higher than simulated, but differences remain on par with potential estimation errors in the aircraft measurements. Sensitivity studies examine the influences of bin microphysics versus bulk microphysics, aerosol advection, supersaturation treatment, and aerosol hygroscopicity. Simulated macrophysical cloud properties are found to be insensitive in this nonprecipitating case, but microphysical properties are especially sensitive to bulk microphysics supersaturation treatment and aerosol hygroscopicity. © 2015. American Geophysical Union. All Rights Reserved."
"15726427000;6603126554;56219284300;24367209100;7007127402;7102171439;7005528388;35429251000;","Cloud-induced uncertainties in AIRS and ECMWF temperature and specific humidity",2015,"10.1002/2014JD022440","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925652268&doi=10.1002%2f2014JD022440&partnerID=40&md5=8ae55fc1dd4649cccd66d8f2b79a1175","The uncertainties of the Atmospheric Infrared Sounder (AIRS) Level 2 version 6 specific humidity (q) and temperature (T) retrievals are quantified as functions of cloud types by comparison against Integrated Global Radiosonde Archive radiosonde measurements. The cloud types contained in an AIRS/Advanced Microwave Sounding Unit footprint are identified by collocated Moderate Resolution Imaging Spectroradiometer retrieved cloud optical depth (COD) and cloud top pressure. We also report results of similar validation of q and T from European Centre for Medium-Range Weather Forecasts (ECMWF) forecasts (EC) and retrievals from the AIRS Neural Network (NNW), which are used as the initial state for AIRS V6 physical retrievals. Differences caused by the variation in the measurement locations and times are estimated using EC, and all the comparisons of data sets against radiosonde measurements are corrected by these estimated differences. We report in detail the validation results for AIRS GOOD quality control, which is used for the AIRS Level 3 climate products. AIRS GOOD quality q reduces the dry biases inherited from the NNW in the middle troposphere under thin clouds but enhances dry biases in thick clouds throughout the troposphere (reaching -30% at 850 hPa near deep convective clouds), likely because the information contained in AIRS retrievals is obtained in cloud-cleared areas or above clouds within the field of regard. EC has small moist biases (~5-10%), which are within the uncertainty of radiosonde measurements, in thin and high clouds. Temperature biases of all data are within ±1 K at altitudes above the 700 hPa level but increase with decreasing altitude. Cloud-cleared retrievals lead to large AIRS cold biases (reaching about-2 K) in the lower troposphere for large COD, enhancing the cold biases inherited from the NNW. Consequently, AIRS GOOD quality T root-mean-squared errors (RMSEs) are slightly smaller than the NNW errors in thin clouds (1.5-2.5 K) but slightly larger than the NNW errors for thick COD (reaching 3.5 K near the surface). The AIRS BEST quality control retains retrievals with uncertainties closer to those of the NNW. The AIRS error estimates reported in the L2 product tend to underestimate the precision (RMSE) implied by comparisons to the radiosonde measurements and do not reflect the observed cloud dependency of uncertainties. © 2015. American Geophysical Union. All Rights Reserved."
"41362078500;35849722200;14056120000;57189634238;36655445400;","Simulation of the effects of aerosol on mixed-phase orographic clouds using the WRF model with a detailed bin microphysics scheme",2015,"10.1002/2014JD022988","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942192556&doi=10.1002%2f2014JD022988&partnerID=40&md5=6200e42baf9e6ecb9bdd0d8486084018","TheWeather Research Forecast (WRF) mesoscale model coupled with a detailed bin microphysics scheme is used to investigate the impact of aerosol particles serving as cloud condensation nuclei and ice nuclei on orographic clouds and precipitation. A mixed-phase orographic cloud developed under two scenarios of aerosol (a typical continental background and a relatively polluted urban condition) and ice nuclei over an idealized mountain is simulated. The results show that, when the initial aerosol condition is changed from the relatively clean case to the polluted scenario, more droplets are activated, leading to a delay in precipitation, but the precipitation amount over the terrain is increased by about 10%. A detailed analysis of the microphysical processes indicates that ice-phase particles play an important role in cloud development, and their contribution to precipitation becomes more important with increasing aerosol particle concentrations. The growth of ice-phase particles through riming and Wegener-Bergeron-Findeisen regime is more effective under more polluted conditions, mainly due to the increased number of droplets with a diameter of 10-30 µm. Sensitivity tests also show that a tenfold increase in the concentration of ice crystals formed from ice nucleation leads to about 7% increase in precipitation, and the sensitivity of the precipitation to changes in the concentration and size distribution of aerosol particles is becoming less pronounced when the concentration of ice crystals is also increased. © 2015. American Geophysical Union. All rights reserved."
"35318594900;35241110500;6507349253;39961878800;35775269300;57201813408;55897795700;57213534151;56722640400;56096586900;57192214096;55683053000;36868818500;56219624100;6508160039;57201537465;35411016300;56197402000;6508040067;56197080800;6507295878;6701365566;23988450000;23011145300;43861632200;25821922200;6507587263;56667832400;56197394600;23396194300;56197311200;23397791900;57212246188;56196886900;56196733100;56196956100;21735248300;56097044600;35605404900;","Climate of the Carpathian Region in the period 1961-2010: Climatologies and trends of 10 variables",2015,"10.1002/joc.4059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930382323&doi=10.1002%2fjoc.4059&partnerID=40&md5=63087b60dee2b9e17d14400f0e464d52","The Carpathians are the longest mountain range in Europe and a geographic barrier between Central Europe, Eastern Europe, and the Balkans. To investigate the climate of the area, the CARPATCLIM project members collected, quality-checked, homogenized, harmonized, and interpolated daily data for 16 meteorological variables and many derived indicators related to the period 1961-2010. The principal outcome of the project is the Climate Atlas of the Carpathian Region, hosted on a dedicated website (www.carpatclim-eu.org) and made of high-resolution daily grids (0.1° × 0.1°) of all variables and indicators at different time steps. In this article, we analyze the spatial and temporal variability of 10 variables: minimum, mean, and maximum temperature, daily temperature range, precipitation, cloud cover, relative sunshine duration, relative humidity, surface air pressure, and wind speed at 2 m. For each variable, we present the gridded climatologies for the period 1961-2010 and discuss the linear trends both on an annual and seasonal basis. Temperature was found to increase in every season, in particular in the last three decades, confirming the trends occurring in Europe; wind speed decreased in every season; cloud cover and relative humidity decreased in spring, summer, and winter, and increased in autumn, while relative sunshine duration behaved in the opposite way; precipitation and surface air pressure showed no significant trend, though they increased slightly on an annual basis. We also discuss the correlation between the variables and we highlight that in the Carpathian Region positive and negative sunshine duration anomalies are highly correlated to the corresponding temperature anomalies during the global dimming (1960s and 1970s) and brightening (1990s and 2000s) periods. © 2014 Royal Meteorological Society."
"55795656900;6602080773;7201845221;","Representation of transport and scavenging of trace particlesin the Emanuel moist convection scheme",2015,"10.1002/qj.2431","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932085129&doi=10.1002%2fqj.2431&partnerID=40&md5=3034d0dcb5e70b48244d08360593f090","In the Tropics, cumulus convection has a major influence on precipitation and vertical transport of atmospheric particles, which are subject to scavenging by precipitation. A new parametrization of transport and scavenging of trace particles by convective clouds and precipitation has been developed and introduced in the Laboratoire de Météorologie Dynamique general circulation model (LMDz). This model uses the deep convection scheme of Emanuel, which is particularly suited for the Tropics. Our parametrization of transport and scavenging is closely linked to this scheme and our developments follow step-by-step the building of this convection representation. The purpose of this study is to understand better the influence of convection on the tracer vertical distribution and to assess the role of the convection parametrization. Short-term and long-term simulations have been performed focusing on the concentrations of the natural radionuclide 7Be, which is produced mainly in the stratosphere and upper troposphere and attaches to available aerosols. Single-column simulations forced by data from the Tropical Ocean-Global Atmosphere-Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE) show the high efficiency of in-cloud scavenging by convective and large-scale processes in the removal of the tracer. These simulations show that, in the LMDz model, convection does not affect radionuclide concentrations as much as stratiform clouds and associated precipitation. In the free troposphere and in the boundary layer, below-cloud evaporation of rain has a major effect on tracer distribution, unlike impaction, which has a negligible effect. Three-dimensional model simulation results are compared with surface data of a station belonging to the worldwide network of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). We show that this new parametrization is able to reproduce the observed yearly averaged concentrations of 7Be at the surface and decrease by a third the overestimation of radionuclides formerly simulated without convective scavenging. LMDz simulations have been also performed over the year 2007 on a global scale using the terragenic 210Pb and cosmogenic 7Be radionuclides. © 2014 Royal Meteorological Society."
"35329672300;56959736200;36152171200;7202079615;55918817700;49662076300;7004286908;7201350647;56517620100;57203180094;9248799600;","An evaluation of simulated particulate sulfate over East Asia through global model intercomparison",2015,"10.1002/2014JD021693","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955716875&doi=10.1002%2f2014JD021693&partnerID=40&md5=bfce9c320e1dc43c1b50648574583a20","Sulfate aerosols simulated by an aerosol module coupled to the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) at a spatial resolution (220 km) widely used by global climate models were evaluated by a comparison with in situ observations and the same aerosol module coupled to the Model for Interdisciplinary Research on Climate (MIROC) over East Asia for January, April, July, and October 2006. The results indicated that a horizontal gradient of sulfate from the source over China to the outflow over Korea-Japan was present in both the simulations and the observations. At the observation sites, the correlation coefficients of the sulfate concentrations between the simulations and the observations were high (NICAM: 0.49–0.89, MIROC: 0.61–0.77), whereas the simulated sulfate concentrations were lower than those obtained by the observation with the normalized mean bias of NICAM being -68 to -54% (all), -77 to -63% (source), and -67 to -30% (outflow) and that of MIROC being -61 to -28% (all), -77 to -63% (source), and -60 to +2% (outflow). Both NICAM and MIROC strongly underpredict surface SO2 over China source regions and Korea-Japan outflow regions, but the MIROC SO2 is much higher than NICAM SO2 over both regions. These differences between the models were mainly explained by differences in the sulfate formation within clouds and the dry deposition of SO2. These results indicated that the uncertainty of the meteorological and cloud fields as well as the vertical transport patterns between the different host climate models has a substantial impact on the simulated sulfate distribution. © 2015. American Geophysical Union. All Rights Reserved."
"9436114900;7005632987;54986194000;55663671600;15737545100;","Simulation of anthropogenic aerosols mass distributions and analysing their direct and semi-direct effects over South Africa using RegCM4",2015,"10.1002/joc.4225","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943368921&doi=10.1002%2fjoc.4225&partnerID=40&md5=34345aa048e0dd70442f7a072ca0e90c","This study examines the mass distributions and direct and semi-direct effects of different Anthropogenic Aerosols (AAs) [i.e. sulphate, Black Carbon (BC), Organic Carbon (OC) and all together (SBO)] over South Africa using the 12 year runs of the Regional Climate Model (RegCM4). The maximum burden and Surface Radiative Forcing (SRF) values are found over AA source regions: up to 9mg m-2 [-12W m-2] for sulphate and 12.1mg m-2 [-14W m-2] for SBO during austral summer, as well as, up to 0.85mg m-2 [-2W m-2] for BC and 2.2mg m-2 [-0.68W m-2] for OC during austral winter. Contrary to sulphate, both BC and OC aerosols reduce incoming solar radiation reaching the ground via enhancing shortwave radiative heating in the atmosphere. The climatic feedback caused by AAs resulted in changes in background aerosol concentrations. As a result of this and other processes of the climate system, the climatic effects of AAs were also found in remote areas away from the main AA loading zones. However, in terms of statistical significance, the climatic influences of AAs are more prominent in the vicinity of their source regions. The overall feedback of the climate system to the radiative effects of AAs resulted in both positive and negative changes to the Net Atmospheric radiative Heating Rate (NAHR). Areas that experience a reduction in NAHR exhibited an increase in Cloud Cover (CC). During the NAHR enhancement, CC over arid areas decreased; while CC over the wet/semi-wet regions increased. The changes in Surface Temperature (ST) and sensible heat flux are more closely correlated with the CC change than SRF of AAs. Furthermore, decreases or increases in ST, respectively, lead to reductions or enhancements in boundary layer height and the vice versa in surface pressure. Overall, the results suggest that the feedback of cloud fields has a far-reaching role in moderating other climatic anomalies. © 2014 Royal Meteorological Society."
"55639736800;7004099427;","Laypeople’s Risky Decisions in the Climate Change Context: Climate Engineering as a Risk-Defusing Strategy?",2015,"10.1080/10807039.2014.932203","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919873577&doi=10.1080%2f10807039.2014.932203&partnerID=40&md5=f2380b5ec93d63acb7c68d053e4c70a8","ABSTRACT: This study explores the development of laypeople's preferences for newly emerging climate engineering technology (CE). It examines whether laypeople perceive CE to be an acceptable back-up strategy (plan B) if current efforts to mitigate CO2 emissions were to fail. This idea is a common justification for CE research in the scientific debate and may significantly influence future public debates. Ninety-eight German participants chose their preferred climate policy strategy in a quasi-realistic scenario. Participants could chose between mitigation and three CE techniques as alternative options. We employed a think-aloud interview technique, which allowed us to trace participants’ informational needs and thought processes. Drawing on Huber's risk management decision theory, the study addressed whether specific CE options are more likely to be accepted if they are mentally represented as a back-up strategy. Results support this assumption, especially for cloud whitening. This result is especially relevant considering the high prevalence of the plan B framing in CE appraisal studies and its implications for public opinion-formation processes. © 2015, Copyright © Taylor & Francis Group, LLC."
"7006720957;7006235116;","Intraseasonal teleconnections between South America and South Africa",2015,"10.1175/JCLI-D-15-0116.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950150503&doi=10.1175%2fJCLI-D-15-0116.1&partnerID=40&md5=589bfbf0d60deb28e8bb22ad978f49cd","Teleconnection of climate anomalies between various parts of the tropics and extratropics is a well-established feature of the climate system. Building on previous work showing that a teleconnection exists between the South American monsoon system and interannual summer rainfall variability over southern Africa, this study considers intraseasonal variability over these landmasses. It is shown that strong teleconnections exist between South African daily rainfall and that over various areas of South America, with the latter leading by 4-5 days, for both winter and summer, involving regions with strong rainfall in these seasons. During the summer, the mechanisms involve both a modulation of the local Walker cell as well as extratropical Rossby wave trains. For winter, the latter mechanism is more important. While in summer tropical convective anomalies over South America play an important role, in winter the subtropics become more important. In both cases, these modulations lead to regional changes in circulation over southern Africa that are favorable for the dominant synoptic rainfall-producing weather systems such as cutofflows and tropical extratropical cloud bands. © 2015 American Meteorological Society."
"56708893500;7006050335;","Effect of clouds and dust storms on the sky radiation exchange for buildings located in hot–dry climates",2015,"10.1080/23744731.2014.1000781","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940375632&doi=10.1080%2f23744731.2014.1000781&partnerID=40&md5=378651670be5e80b77eaf26ef80c83b8","This article evaluates the impact of effective sky temperatures on building radiation exchange under clear, cloudy, and dusty conditions for extremely hot and dry climates. In part, a dusty sky temperature model has been introduced as a function of atmospheric aerosol optical depth. The sky radiative exchange was evaluated using a one-dimensional transient heat transfer model with numerical calculations performed using the fully implicit finite-difference method. The newly available ASHRAE 2013 clear sky model was evaluated and implemented to calculate the hourly incident solar radiation for a horizontal roof under the extremely hot–dry climate conditions of Riyadh, Saudi Arabia. Results showed that in clear sky conditions, sky longwave radiation contributes to a reduction of the total heat gain. A daily mean clear sky cooling around 2645 and 2385 W-hr/m2 was estimated for July and January, respectively. In contrast, cloud and dust covers increase effective sky temperature and diminish the role of sky radiative cooling. Depending on severity, the mean contributed sky cooling heat exchange was found to range between 436 and 1636 W-hr/m2 for dust storm and scattered cloudy sky conditions, respectively. Similarly, the ASHRAE 2013 clear sky model and the sky temperature models were shown for four other extremely hot–dry global sites. © 2015, ASHRAE."
"56017369900;","Acting locally to mitigate globally: climate action in the Anthropocene",2015,"10.1007/s13412-015-0225-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977134168&doi=10.1007%2fs13412-015-0225-0&partnerID=40&md5=f83dd1a7f37537130873e7fd2c064e7f","The idea that individual- or local-scale actions can combine to have global effects and relevance is of course not limited to the natural sciences. Slogans such as “think globally, act locally” have been used for many years in an effort to encourage individuals and locally anchored movements to see their place—and their actions—as part of a broader effort. What the message embedded in the term Anthropocene highlights, however, is the fact that a multitude of individuals acting locally influences global conditions whether or not we “think” globally. Nowhere is this more true than with climate change. In the Arctic, the consequences of climate change are more visible, yet the links between action and consequences appear more distant, and this illustrates a key challenge. Local action has often been pursued in the shadow of the global negotiations, yet many of the most important breakthroughs currently being made are arguably being accomplished at the local and regional levels. This is in fact the silver lining in that dark cloud surrounding the Anthropocene. It points to the critical importance of local level action on climate change, both from a governance perspective and for improving underlying the socio-technical conditions that influence what is possible in global efforts. © 2015, The Author(s)."
"36908840200;7202048112;55476830600;57188966058;57111001300;6506328135;57210180554;9845949200;6602858513;13406399300;","Exploring a multiresolution approach using AMIP simulations",2015,"10.1175/JCLI-D-14-00729.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942910911&doi=10.1175%2fJCLI-D-14-00729.1&partnerID=40&md5=c75909a1f6cffa8b79441ecc22cc6b1f","This study presents a diagnosis of a multiresolution approach using the Model for Prediction Across Scales-Atmosphere (MPAS-A) for simulating regional climate. Four Atmospheric Model Intercomparison Project (AMIP) experiments were conducted for 1999-2009. In the first two experiments, MPAS-A was configured using global quasi-uniform grids at 120- and 30-km grid spacing. In the other two experiments, MPAS-A was configured using variable-resolution (VR) mesh with local refinement at 30km over North America and South America and embedded in a quasi-uniform domain at 120km elsewhere. Precipitation and related fields in the four simulations are examined to determine how well the VRs reproduce the features simulated by the globally high-resolution model in the refined domain. In previous analyses of idealized aquaplanet simulations, characteristics of the global high-resolution simulation in moist processes developed only near the boundary of the refined region. In contrast, AMIP simulations with VR grids can reproduce high-resolution characteristics across the refined domain, particularly in South America. This finding indicates the importance of finely resolved lower boundary forcings such as topography and surface heterogeneity for regional climate and demonstrates the ability of the MPAS-A VR to replicate the large-scale moisture transport as simulated in the quasi-uniform high-resolution model. Upscale effects from the high-resolution regions on a large-scale circulation outside the refined domain are observed, but the effects are mainly limited to northeastern Asia during the warm season. Together, the results support the multiresolution approach as a computationally efficient and physically consistent method formodeling regional climate. © 2015 American Meteorological Society."
"20434940900;8629713500;56037559900;7201920350;7401796996;57191636820;57191636379;","Comparison of atmospheric profiles between microwave radiometer retrievals and radiosonde soundings",2015,"10.1002/2015JD023438","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84976426133&doi=10.1002%2f2015JD023438&partnerID=40&md5=aba7b552505de1b6c6d1bff428cbddf5","Atmospheric profiles of temperature (T), vapor density (ρv), and relative humidity (RH) retrieved from ground-based microwave radiometer (MWR) measurements are compared with radiosonde soundings at Wuhan, China. The MWR retrievals were averaged in the ±30 min period centered at sounding times of 00 and 12 UTC. A total of 403 and 760 profiles under clear and cloudy skies were selected. Based on the comparisons, temperature profiles have better consistency than the ρv and RH profiles, lower levels are better than upper levels, and the cloudy are better than the clear-sky profiles. Three cloud types (low, middle, and high) were identified by matching the infrared radiation thermometer-detected cloud base temperature to the MWR-retrieved temperature-height profiles. Temperature profile under high cloud has the highest correlation coefficient (R) and the lowest bias and RMS, but under low cloud is in the opposite direction. The ρv profile under middle cloud has the highest R and the lowest bias but under high cloud has the lowest R, the largest bias, and RMS. Based on the radiosonde soundings, both clear and cloudy wind speeds and drifting distances increase with height but increase much faster under clear than cloudy above 4 km. The increased wind speeds and drifting distances with height have resulted in decreased correlation coefficient and increased temperature biases and RMSs with height for both clear and cloudy skies. The differences in R, bias, and RMS between clear and cloudy skies are primarily resulted from their wind speeds and drifting distances. © 2015. American Geophysical Union. All Rights Reserved."
"22954523900;56715044400;24366038500;7003414581;55444637900;36705265400;8927405700;6701697023;7004864963;","Seasonal variability of heterogeneous ice formation in stratiform clouds over the Amazon Basin",2015,"10.1002/2015GL064068","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938205431&doi=10.1002%2f2015GL064068&partnerID=40&md5=b3c1276f07867c571259708ce66c8db2","Based on 11months of polarization lidar observations in the Amazon Basin near Manaus, Brazil (2.3°S, 60°W), the relationship between temperature and heterogeneous ice formation efficiency in stratiform clouds was evaluated in the cloud top temperature range between -40 and 0°C. Between -30 and 0°C, ice-containing clouds are a factor of 1.5 to 2 more frequent during the dry season. Free-tropospheric aerosol backscatter profiles revealed a twofold to tenfold increase in aerosol load during the dry season and a Monitoring Atmospheric Composition and Climate - Interim Implementation reanalysis data set implies that the aerosol composition during the dry season is strongly influenced by biomass burning aerosol, whereas other components such as mineral dust do not vary strongly between the seasons. The injection of smoke accompanied by the likely dispersion of biological material, soil dust, or ash particles was identified as a possible source for the increased ice formation efficiency during the dry season. Key Points A unique 1year stratiform cloud data set was obtained for the Amazon Basin During the dry season, ice forms more efficient than during the wet season Biomass burning aerosols must be the source of ice nuclei during the dry season. © 2015. American Geophysical Union. All Rights Reserved."
"56948669100;23974441400;56477833000;7401672948;7202019251;","Spatio-temporal change of snow cover and its response to climate over the tibetan plateau based on an improved daily cloud-free snow cover product",2015,"10.3390/rs7010169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987971113&doi=10.3390%2frs7010169&partnerID=40&md5=c312331162e36ba4130ca3e74b49925e","Using new, daily cloud-free snow-cover products, this study examines snow cover dynamics and their response to climate change. The results demonstrate that the daily cloud-free snow-cover products not only posses the advantages of the AMSR-E (unaffected by weather conditions) and MODIS (relatively higher resolution) products, but are also characterized by high snow and overall classification accuracies (~85% and ~98%, respectively), substantially greater than those of the existing daily snow-cover products for all sky conditions and very similar to, or even slightly greater than, those of the daily MODIS products for clear-sky conditions. Using the snow-cover products, we analyzed the snow cover dynamics over the Tibetan Plateau and determined that the maximum number of snow-covered days (SCD) in a year followed a decreasing tendency from 2003 to 2010, with a decrease in snow-covered area (SCA) equivalent to 55.3% of the total Tibetan Plateau area. There is also a slightly increasing tendency in the maximum snow cover area (SCA), and a slightly decreasing tendency in the persistent snow cover area (i.e., pixels of SCD > 350 days) was observed for the 8-year period, which was characterized by increases in temperature (0.09 °C/year) and in precipitation (0.26 mm/year). This suggests that, on the Tibetan Plateau, changes in temperature and precipitation exert a considerable influence on the regional SCD and SCA, as well as the distribution of persistent snow cover. © 2014 by the authors; licensee MDPI, Basel, Switzerland."
"56948669100;23974441400;56477833000;7401672948;7202019251;","Spatio-temporal change of snow cover and its response to climate over the Tibetan Plateau based on an improved daily cloud-free snow cover product",2015,"10.3390/rs70100169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920757058&doi=10.3390%2frs70100169&partnerID=40&md5=43da21aa8933fc5b497d3d7489ba409e","Using new, daily cloud-free snow-cover products, this study examines snow cover dynamics and their response to climate change. The results demonstrate that the daily cloud-free snow-cover products not only posses the advantages of the AMSR-E (unaffected by weather conditions) and MODIS (relatively higher resolution) products, but are also characterized by high snow and overall classification accuracies (~85% and ~98%, respectively), substantially greater than those of the existing daily snow-cover products for all sky conditions and very similar to, or even slightly greater than, those of the daily MODIS products for clear-sky conditions. Using the snow-cover products, we analyzed the snow cover dynamics over the Tibetan Plateau and determined that the maximum number of snow-covered days (SCD) in a year followed a decreasing tendency from 2003 to 2010, with a decrease in snow-covered area (SCA) equivalent to 55.3% of the total Tibetan Plateau area. There is also a slightly increasing tendency in the maximum snow cover area (SCA), and a slightly decreasing tendency in the persistent snow cover area (i.e., pixels of SCD > 350 days) was observed for the 8-year period, which was characterized by increases in temperature (0.09 °C/year) and in precipitation (0.26 mm/year). This suggests that, on the Tibetan Plateau, changes in temperature and precipitation exert a considerable influence on the regional SCD and SCA, as well as the distribution of persistent snow cover. © 2014 by the authors."
"56054435300;55720588700;7404395984;7004697990;36196693000;55790781000;57206377115;55720539800;7101677832;","Assimilation of thermodynamic information from advanced infrared sounders under partially cloudy skies for regional NWP",2015,"10.1002/2014JD022976","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933280390&doi=10.1002%2f2014JD022976&partnerID=40&md5=59509f84b052ffb8175d505255104a5b","Generally, only clear-infrared spectral radiances (not affected by clouds) are assimilated in weather analysis systems. This is due to difficulties in modeling cloudy radiances as well as in observing their vertical structure from space. To take full advantage of the thermodynamic information in advanced infrared (IR) sounder observations requires assimilating radiances from cloud-contaminated regions. An optimal imager/sounder cloud-clearing technique has been developed by the Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin-Madison. This technique can be used to retrieve clear column radiances through combining collocated multiband imager IR clear radiances and the sounder cloudy radiances; no background information is needed in this method. The imager/sounder cloud-clearing technique is similar to that of the microwave/IR cloud clearing in the derivation of the clear-sky equivalent radiances. However, it retains the original IR sounder resolution, which is critical for regional numerical weather prediction applications. In this study, we have investigated the assimilation of cloud-cleared IR sounder radiances using Atmospheric Infrared Sounder (AIRS)/Moderate Resolution Imaging Spectroradiometer for three hurricanes, Sandy (2012), Irene (2011), and Ike (2008). Results show that assimilating additional cloud-cleared AIRS radiances reduces the 48 and 72 h temperature forecast root-mean-square error by 0.1–0.3 K between 300 and 850 hPa. Substantial improvement in reducing track forecasts errors in the range of 10km to 50km was achieved. © 2015. American Geophysical Union. All Rights Reserved."
"6602999057;7006837187;25624545600;57217801354;56522444900;7003510880;6701679993;7006424590;7201443624;7201572145;16548895600;35551238800;6603932982;56032594900;9536598800;","The dacciwa project: Dynamics-aerosol-chemistry-cloud interactions in West Africa",2015,"10.1175/BAMS-D-14-00108.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939862773&doi=10.1175%2fBAMS-D-14-00108.1&partnerID=40&md5=11731e6c33eae46ebf3647984b832614","The DACCIWA project was undertaken jointly by a consortium to investigate the role of dynamic aerosol-chemistry-cloud interactions in environmental pollution in South Western Africa (SWA). The DACCIWA project was proposed to operate from December 1, 2013 till November 30, 2018, with financial support from the European Union worth €8.75M. The scope and logistics of the project demanded an international and multi-disciplinary approach. The consortium was composed of sixteen partners from four European and two West African countries and consisted of universities, research institutes, and operational weather and climate services."
"7006729638;","Climatic trends in Puerto Rico: Observed and projected since 1980",2015,"10.3354/cr01338","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946059102&doi=10.3354%2fcr01338&partnerID=40&md5=b4ba9bc03a729c2947692177ba589775","This study considers observed and CMIP5 (Coupled Model Intercomparison Project 5) projected climate trends in Puerto Rico, with a focus on change maps and time series since 1980. The Hadley circulation has accelerated and sinking motions have warmed the lower atmosphere faster (+0.03°C yr-1) than the underlying ocean (+0.01°C yr-1). Increased evaporation and northerly winds are generating upward trends in rainfall on the Atlantic side of Puerto Rico, while the Caribbean side is drying. Global warming appears to enhance shallow clouds and vegetation, and inhibit deep convection around the island. The impact on natural resources appears limited, but rising sea levels will necessitate pro-active coastal management. © Inter-Research 2015."
"22934904700;55471474500;57212988186;24492188100;8618000600;9535769800;7403059580;36653408700;55711668600;55706080300;6601963213;7401945370;57218120214;","A 20-Year climatology of a NICAM AMIP-type simulation",2015,"10.2151/jmsj.2015-024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942018143&doi=10.2151%2fjmsj.2015-024&partnerID=40&md5=aff90a72bb63da9810621b10bc49a793","A 20-year integration by the nonhydrostatic icosahedral atmospheric model (NICAM) with a 14 km mesh was conducted for the first time to obtain a climatological mean and diurnal to interannual variability of a simulated atmosphere. Clouds were explicitly calculated using a cloud microphysics scheme without cumulus convection scheme. The simulation was performed under the atmospheric model intercomparison project-type conditions, except that sea surface temperature was nudged toward observed historical values using the slab ocean model. The results are analyzed with a focus on tropical disturbances, including tropical cyclones (TCs) and the Madden- Julian oscillation (MJO). NICAM simulates many aspects of atmospheric climatological mean state and variability. The geographical distributions of precipitation, including interannual, seasonal, and diurnal variations, are well reproduced. Zonal mean basic states, clouds, and top-of-atmosphere radiation are qualitatively simulated, though some severe biases such as underestimated low clouds, shortwave reflection, warmer surface, and tropical upper troposphere exist. TCs and MJO are the main focus of the simulation. In the simulation, TCs are detected with the objective thresholds of maximum wind speed due to the realistic intensity of simulated TCs. The seasonal march of TC genesis in each ocean basin is well simulated. The statistical property of the MJO and tropical waves is well reproduced in the space-time power spectra, consistent with previous NICAM studies. This implies that the stratospheric variability is also reproduced, as partially revealed in this study. Asian monsoon analysis shows that climatological western North Pacific monsoon onset occurs near the observed onset, and that the Baiu front is reproduced to some extent. Some significant model biases still exist, which indicates a need for further model improvements. The results indicate that a high-resolution global nonhydrostatic model has the potential to reveal multiscale phenomena in the climate system. © 2015, Meteorological Society of Japan."
"24485369800;57193419761;56746839400;57207403865;57203714946;56395875900;56643794500;55074722200;14032147800;7404331038;57211569167;57188827110;36441407000;","Modelling the effect of aerosol feedbacks on the regional meteorology factors over China",2015,"10.4209/aaqr.2014.11.0272","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938347850&doi=10.4209%2faaqr.2014.11.0272&partnerID=40&md5=cdd490a1c17050b0520579ba19a03beb","The fully coupled online air quality model WRF/chem was used to investigate the aerosol-radiation interaction and aerosol-cloud interaction on the regional meteorological factors over China in 2006.The aerosol-radiation interaction and aerosol-cloud interaction of aerosols influence the various regional meteorological factors in the worst aerosol-polluted regions of China. Domain-wide monthly-mean over all day and night hours incoming solar radiation decreased by –11.03 W/m2, –9.84 W/m2, –5.84 W/m2 and –12.37 W/m2; temperature at 2 meters (T2) decreased by –0.22°C, –0.12°C, –0.06°C and –0.24°C; Planetary boundary layer (PBL) height decreased by –16.44 m, –15.90 m, –5.48 m and –31.59 m in January, April, July and October, respectively. The values of the monthly-mean incoming solar radiation, T2 and PBL height had greater decreases in east China. Due to aerosol feedbacks, a slight increase of the monthly-mean precipitation occurred in southern and south-eastern China. The aerosol-radiation interaction and aerosol-cloud interaction of aerosols were compared for the United States (U.S.) continent, Europe, India and this study. Due to the higher aerosol load in China, the monthly-mean incoming solar radiation, T2 and PBL height exhibited greater decreases in China than in the U.S. continent and in Europe. Aerosol extinction was the dominant effect on the incoming solar radiation for either cloudless or cloudy weather conditions in China, but aerosol extinction was only apparent during cloudless weather in Europe. In India, the incoming solar radiation decreased by –20 W/m2 or more in the most aerosol polluted area, which is close to the value of decrease determined in China. © Taiwan Association for Aerosol Research."
"55293421800;55479808100;24177361900;8633162900;6603954179;7003968166;","Isotope meteorology of cold front passages: A case study combining observations and modeling",2015,"10.1002/2015GL063988","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938203185&doi=10.1002%2f2015GL063988&partnerID=40&md5=7e691e7fd2f7f35bafe936fb909f752d","This study investigates the role of below-cloud evaporation and evapotranspiration for the short-term variability of stable isotopes in near-surface water vapor and precipitation associated with central European cold fronts. To this end, a combination of observations with high temporal resolution and numerical sensitivity experiments with the isotope-enabled regional weather prediction model COSMO<inf>iso</inf> is used. The representation of the interaction between rain droplets and ambient vapor below the cloud is fundamental for adequately simulating precipitation isotopes (δ<inf>p</inf>) and total rainfall amount. Neglecting these effects leads to depletion biases of 20-40‰ in δp2H and 5-10‰ in δp18O and to an increase of 74% in rainfall amount. Isotope fractionation during soil evaporation is of primary importance for correctly simulating the variability of continental low-level vapor δv2H and δv18O and particularly of the secondary isotope parameter deuterium excess (d<inf>v</inf>). Key Points Cold fronts leave characteristic imprint in water vapor and rain isotopes Below-cloud interaction affects rainfall amount and precipitation isotopes at short time scales Soil evaporation fractionation is crucial for isotopes in low-level water vapor. © 2015. American Geophysical Union. All Rights Reserved."
"8613647200;7102687667;14059243100;54400559100;54397987500;","Trends in the frequency of high relative humidity over China: 1979-2012",2015,"10.1175/JCLI-D-14-00840.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957653873&doi=10.1175%2fJCLI-D-14-00840.1&partnerID=40&md5=fca741a859748274bff0972e2a404341","High relative humidity (HRH) is defined as a relative humidity of at least 80%, which is often associated with the occurrence of cloud layers. Thus, the frequency of HRH and its changes in the troposphere may be related to the occurrence frequency of cloud layers and their changes. In this study, trends in the frequency of HRH (defined as days with relative humidity ≥ 80%) over China from the surface to the midtroposphere (≥ 400 hPa) from 1979 to 2012 were analyzed using a homogenized humidity dataset for spring (March-May), summer (June-August), autumn (September-November), and winter (December-February). The results for the ground level indicate decreasing trends at most stations in southeastern China in spring and in northern China in summer. In the lower troposphere (850 and 700 hPa), most stations over China exhibit positive trends in summer, autumn, and winter. For the midtroposphere (500-400 hPa), increasing trends dominate over China in spring, summer, and autumn. Finally, six reanalysis datasets, the NCEP-NCAR, NCEP-DOE, CFSR, ERA-Interim, MERRA, and JRA-55 datasets, were compared with the observed increasing trends in HRH frequency in the low-to-middle troposphere. Similar increasing trends in HRH frequency in the reanalysis datasets and the homogenized humidity data are observed in certain seasons and for certain regions. These results are consistent with the increasing low-to-middle cloud amounts in recent decades. © 2015 American Meteorological Society."
"57206508283;7404454238;8832995400;56966408000;55243246800;8558968300;43060893200;57190728534;56596353200;12143017100;36844777100;57190733131;","Projection of future climate change over Japan in ensemble simulations with a high-resolution regional climate model",2015,"10.2151/sola.2015-022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982671668&doi=10.2151%2fsola.2015-022&partnerID=40&md5=e3399ae75e8c15936cd87e90c318a9e9","Future changes in surface air temperature and precipitation over Japan by the end of the 21st century are projected by a well-developed non-hydrostatic regional climate model with a grid spacing of 5 km under the RCP8.5 scenario. Uncertainties in the projected temperature and precipitation are also evaluated with the results obtained from ensemble simulations using this high-resolution model. The projected future climate indicates robust increases in the annual-mean surface air temperature for all regions in Japan. In contrast, many regions do not exhibit statistically significant changes in annual precipitation. In some regions and months, however, monthly precipitation in a couple of members of the ensemble simulations has a statistically significant decrease or increase. Monthly precipitation over the eastern Japan Sea side (EJ) region in December has relatively robust decreases. These decreases are attributed to decreases or weakening of convection over the Japan Sea polar air-mass convergence zone, which is accounted for by the weakening of large-scale low-level northwesterly winds associated with the winter monsoon. The relationship between precipitation and convergence in the EJ region is consistent with the results above: Convective clouds are shallower in the future climate compared with those in the present climate. © 2015, the Meteorological Society of Japan."
"7003904922;55710671300;","Parameterization of aerosol scavenging due to atmospheric ionization",2015,"10.1002/2014JD023016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942162898&doi=10.1002%2f2014JD023016&partnerID=40&md5=d90daec6d83823d784f1e9be0c9d15ba","A new approach to parameterizing the modulation of aerosol scavenging by electric charges on particles and droplets gives improved accuracy and is applied over an extended range of droplet and particle radii relevant to cloud microphysical processes. The base level scavenging rates for small particles are dominated by diffusion and for large particles by intercept, weight, and flow effects. For charged particles encountering uncharged droplets, in all cases there is an increase in the scavenging rates, due to the image force. For dropletswith charges of opposite sign to those of the particle charge, the rates are further increased, due to the Coulomb force, whereas for droplet with charges of the same sign, the rates are decreased. Increases above the base level (electroscavenging) predominate for the larger particles and occur in the interior of clouds even when no space charge (net charge) is present. Decreases below the base level (electroantiscavenging) occur for same-sign charges with smaller particles. The rates for uncharged droplets are parameterized, and the effect of charges on the droplets then parameterized as a departure from those rates. The results are convenient for incorporation in models of clouds which include detailed microphysics, to model the electrically induced reductions and increases in cloud condensation nucleus and ice forming nucleus concentrations and size distributions and contact ice nucleation rates that affect coagulation and precipitation and cloud albedo. Implications for effects on weather and climate, due both to externally and internally induced variability in atmospheric ionization, are outlined. © 2015. American Geophysical Union. All rights reserved."
"30667558200;7003278104;24485218400;9249239700;","Multimodel evaluation of cloud phase transition using satellite and reanalysis data",2015,"10.1002/2014JD022932","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940459958&doi=10.1002%2f2014JD022932&partnerID=40&md5=b0da8367580cd2d885d482a72c459bdb","We take advantage of climate simulations from two multimodel experiments to characterize and evaluate the cloud phase partitioning in 16 general circulation models (GCMs), specifically the vertical structure of the transition between liquid and ice in clouds. We base our analysis on the ratio of ice condensates to the total condensates (phase ratio, PR). Its transition at 90% (PR90) and its links with other relevant variables are evaluated using the GCM-Oriented Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation Cloud Product climatology, reanalysis data, and other satellite observations. In 13 of 16 models, the PR90 transition height occurs too low (6 km to 8.4 km) and at temperatures too warm (-13.9°C to -32.5°C) compared to observations (8.6 km, -33.7°C); features consistent with a lack of supercooled liquid with respect to ice above 6.5 km. However, this bias would be slightly reduced by using the lidar simulator. In convective regimes (more humid air and precipitation), the observed cloud phase transition occurs at a warmer temperature than for subsidence regimes (less humid air and precipitation). Only few models manage to roughly replicate the observed correlations with humidity (5/16), vertical velocity (5/16), and precipitation (4/16); 3/16 perform well for all these parameters (MPI-ESM, NCAR-CAM5, and NCHU). Using an observation-based Clausius-Clapeyron phase diagram, we illustrate that the Bergeron-Findeisen process is a necessary condition for models to represent the observed features. Finally, the best models are those that include more complex microphysics. © 2015. American Geophysical Union. All Rights Reserved."
"6603571946;7102591209;7006007679;","A new ice cloud parameterization for infrared radiative transfer simulation of cloudy radiances: Evaluation and optimization with IIR observations and ice cloud profile retrieval products",2015,"10.1002/2015JD023462","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939265645&doi=10.1002%2f2015JD023462&partnerID=40&md5=2306612ae66365b335ec9d88b5794364","A new ice cloud optical property database in the thermal infrared has been parameterized for the RTTOV radiative transfermodel. The Self-Consistent ScatteringModel (SCSM) database is based on an ensemble model of ice crystals and a parameterization of the particle size distribution. This convolution can predict the radiative properties of cirrus without the need of a priori information on the ice particle shape and an estimate of the ice crystal effective dimension. The ice cloud optical properties are estimated through linear parameterizations of ambient temperature and ice water content. We evaluate the new parameterization against existing parameterizations used in RTTOV. We compare infrared observations from Imaging Infrared Radiometer, on board CALIPSO, against RTTOV simulations of the observations. The simulations are performed using two different products of ice cloud profiles, retrieved from the synergy between space-based radar and lidar observations. These are the 2C-ICE and DARDAR products. We optimized the parameterization by testing different SCSM databases, derived from different shapes of the particle size distribution, and weighting the volume extinction coefficient of the ensemble model. By selecting a large global data set of ice cloud profiles of visible optical depths between 0.03 and 4, we found that the simulations, based on the optimized SCSM database parameterization, reproduces the observations with a mean bias of only 0.43 K and a standard deviation of 6.85 K. The optimized SCSM database parameterization can also be applied to any other radiative transfer model. © 2015. American Geophysical Union. All Rights Reserved."
"56656056300;57211548819;7102725774;8622098900;","Species turnover of corticolous bryophyte assemblages over 15 years in an Australian subtropical cloud forest",2015,"10.1111/aec.12268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948085659&doi=10.1111%2faec.12268&partnerID=40&md5=a70f1ff8af103bdd7be85a67f283f25b","Montane forest ecosystem characterized by frequent cloud or mist inundation are considered highly vulnerable to climatic change. Despite this, there is a paucity of long-term studies assessing community change within these important ecosystems. We present the first comparative analysis of corticolous bryophyte diversity over 15 years in high elevation forests of the Gondwana Rainforests of Australia World Heritage Area, south-east Queensland, Australia. We found limited evidence of change in species richness across the five isolated stands of microphyll fern forest studied. However, we document considerable species turnover within corticolous bryophyte communities with a large and coherent pattern of change in the liverwort flora in particular (43-62% species turnover). Liverworts, but not mosses, also exhibited strong spatial patterns in species assemblages that likely correspond to varying exposure to orographic moisture associated with south-easterly winds. We postulate that microclimatic factors are stronger determinants of liverwort assemblages than moss assemblages in this system and that documented directional change in liverwort communities is a response to temporal fluctuation in moisture inputs from orographic cloud that are not discernible from precipitation records. © 2015 Ecological Society of Australia."
"7402031560;","Cold flow properties of biodiesel: A guide to getting an accurate analysis",2015,"10.1080/17597269.2015.1057791","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938693520&doi=10.1080%2f17597269.2015.1057791&partnerID=40&md5=64b3df0bc8b791ed03483d10e87158f1","Biodiesel has several advantages compared to conventional diesel fuel (petrodiesel). Nevertheless, biodiesel has poor cold flow properties that may restrict its use in moderate climates. It is essential that the cold flow properties of biodiesel and its blends with petrodiesel be measured as accurately as possible. This work provides an overview of the important cold flow properties and how they are analyzed. The utility of cloud point (CP), pour point (PP), and cold filter plugging point (CFPP) in evaluating biodiesel at low temperatures is discussed. Advantages and limitations of the experimental methods are evaluated. Finally, the use of sub-ambient differential scanning calorimetry (DSC) in the study of low temperature phase behavior of biodiesel is examined. Copyright © 2015 Taylor & Francis."
"56432943600;23389993800;37561143500;25630656700;","Detection of rapidly developing convection using rapid scan data from a geostationary satellite",2015,"10.1080/2150704X.2015.1062160","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938310342&doi=10.1080%2f2150704X.2015.1062160&partnerID=40&md5=adf75239ad8501208c24e929142dc2bc","Accurate rapidly developing convection (RDC) detection is an essential part of a severe weather warning. A novel algorithm called object track and identification (OTI) is proposed for detecting RDC using infrared image sequences from geostationary meteorology satellite. Convective cells are computed using extended maxima transform-based region growing algorithm. Firstly, a novel area overlap-based object tracking method is proposed to track convective cells in successive images. Secondly, the lowest 25% of overall brightness temperature of the same convective cloud is averaged in order to preserve the extremum information of evolution of cloud. Thirdly, a new identification criterion, which contains three subcriteria, is developed to detect RDC. Contingency table approach applied to various case studies over China shows that the OTI algorithm is efficient and accurate. © 2015 © 2015 Taylor & Francis."
"7403931916;7102018821;55737877800;56939103900;48661551300;7201826462;","On the radiative properties of ice clouds: Light scattering, remote sensing, and radiation parameterization",2015,"10.1007/s00376-014-0011-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913537558&doi=10.1007%2fs00376-014-0011-z&partnerID=40&md5=b97f8a8c35cebcaaccab2346f3d4f4be","Presented is a review of the radiative properties of ice clouds from three perspectives: light scattering simulations, remote sensing applications, and broadband radiation parameterizations appropriate for numerical models. On the subject of light scattering simulations, several classical computational approaches are reviewed, including the conventional geometric-optics method and its improved forms, the finite-difference time domain technique, the pseudo-spectral time domain technique, the discrete dipole approximation method, and the T-matrix method, with specific applications to the computation of the single-scattering properties of individual ice crystals. The strengths and weaknesses associated with each approach are discussed. With reference to remote sensing, operational retrieval algorithms are reviewed for retrieving cloud optical depth and effective particle size based on solar or thermal infrared (IR) bands. To illustrate the performance of the current solar- and IR-based retrievals, two case studies are presented based on spaceborne observations. The need for a more realistic ice cloud optical model to obtain spectrally consistent retrievals is demonstrated. Furthermore, to complement ice cloud property studies based on passive radiometric measurements, the advantage of incorporating lidar and/or polarimetric measurements is discussed. The performance of ice cloud models based on the use of different ice habits to represent ice particles is illustrated by comparing model results with satellite observations. A summary is provided of a number of parameterization schemes for ice cloud radiative properties that were developed for application to broadband radiative transfer submodels within general circulation models (GCMs). The availability of the single-scattering properties of complex ice habits has led to more accurate radiation parameterizations. In conclusion, the importance of using nonspherical ice particle models in GCM simulations for climate studies is proven. © 2015, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"6602809597;7102953444;","The effect of aerosols and sea surface temperature on China’s climate in the late twentieth century from ensembles of global climate simulations",2015,"10.1002/2014JD022851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927644020&doi=10.1002%2f2014JD022851&partnerID=40&md5=27323546326975ea0b587581b01c751d","Over the late twentieth century, China has seen a strong increase in aerosol emissions, whose quantitative role for observed changes in surface solar radiation (SSR), surface air temperature (SAT), and precipitation remains debated. We use ensembles of transient sensitivity experiments with the global climate model ECHAM5 from the Max Planck Institute for Meteorology, Hamburg, Germany, combined with the Hamburg Aerosol Module to examine the effect of aerosols and prescribed, observation-based sea surface temperatures (SSTs) on the above variables. Observations and control experiments agree reasonably well in eastern China in terms of SSR dimming (-6 ± 2 W/m2/decade, 1960-2000; stronger than in models of the Coupled Model Intercomparison Project Phase 5, CMIP5), statistically nonsignificant summer SAT trend (1950-2005), and drying in summer from 1950 to 1990 (-2.5% to -3.5% per decade, essentially via reduction of convective precipitation). Other observed features are not reproduced by the model, e.g., precipitation increase in the 1990s in the Yangtze River valley or, from the 1960s onward, the strong winter warming in northern China and Mongolia and SSR dimming in western China. Aerosol effects are stronger for sulfur dioxide than for black and organic carbon and are more pronounced at lower model resolution. Transient SSTs are crucial for decadal-scale SAT variability over land, especially the strong warming in the 1990s, and, via SST forced reduction of cloud cover, for the ceasing of SSR dimming around the year 2000. Unforced cloud variability leads to relevant scatter (up to ±2 W/m2/decade) of modeled SSR trends at individual observation sites. © 2015. American Geophysical Union. All Rights Reserved."
"10341067100;55805082800;6603002398;","Arctic climate change in an ensemble of regional CORDEX simulations",2015,"10.3402/polar.v34.24603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934779697&doi=10.3402%2fpolar.v34.24603&partnerID=40&md5=ebe970f1bae6df857e6deaa1f5405011","Fifth phase Climate Model Intercomparison Project historical and scenario simulations from four global climate models (GCMs) using the Representative Concentration Pathways greenhouse gas concentration trajectories RCP4.5 and RCP8.5 are downscaled over the Arctic with the regional Rossby Centre Atmosphere model (RCA). The regional model simulations largely reflect the circulation bias patterns of the driving global models in the historical period, indicating the importance of lateral and lower boundary conditions. However, local differences occur as a reduced winter 2-m air temperature bias over the Arctic Ocean and increased cold biases over land areas in RCA. The projected changes are dominated by a strong warming in the Arctic, exceeding 15°K in autumn and winter over the Arctic Ocean in RCP8.5, strongly increased precipitation and reduced sea-level pressure. Near-surface temperature and precipitation are linearly related in the Arctic. The wintertime inversion strength is reduced, leading to a less stable stratification of the Arctic atmosphere. The diurnal temperature range is reduced in all seasons. The large-scale change patterns are dominated by the surface and lateral boundary conditions so future response is similar in RCA and the driving global models. However, the warming over the Arctic Ocean is smaller in RCA; the warming over land is larger in winter and spring but smaller in summer. The future response of winter cloud cover is opposite in RCA and the GCMs. Precipitation changes in RCA are much larger during summer than in the global models and more small-scale change patterns occur. © 2015 T. Koenigk et al."
"56618531600;55738957800;","Evaluating convective parameterization closures using cloud-resolving model simulation of tropical deep convection",2015,"10.1002/2014JD022246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925100267&doi=10.1002%2f2014JD022246&partnerID=40&md5=645aa8168b19e8cc79eda6e93ebbf3a9","Closure is an important component of a mass flux-based convective parameterization scheme, and it determines the amount of convection with the aid of a large-scale variable (closure variable) that is sensitive to convection. In this study, we have evaluated and quantified the relationship between commonly used closure variables and convection for a range of global climate model (GCM) horizontal resolutions, taking convective precipitation and mass flux at 600 hPa as measures for deep convection. We have used cloud-resolving model simulation data to create domain averages representing GCM horizontal resolutions of 128km, 64 km, 32 km, 16 km, 8 km, and 4km. Lead-lag correlation analysis shows that except moisture convergence and turbulent kinetic energy, none of the other closure variables evaluated in this study show any relationship with convection for the six subdomain sizes. It is found that the correlation between moisture convergence and convective precipitation is largest when moisture convergence leads convection. This correlation weakens as the subdomain size decreases to 8km or smaller. Although convective precipitation and mass flux increase with moisture convergence at a given subdomain size, as the subdomain size increases, the rate at which they increase becomes smaller. This suggests that moisture convergence-based closure should scale down the predicted mass flux for a given moisture convergence as GCM resolution increases. © 2015. American Geophysical Union. All Rights Reserved."
"35095482200;7006783796;8723505700;","Aerosol variability, synoptic-scale processes, and their link to the cloud microphysics over the northeast pacific during MAGIC",2015,"10.1002/2015JD023175","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932147074&doi=10.1002%2f2015JD023175&partnerID=40&md5=ce527dba53d94a44072956fbdcea5724","Shipborne aerosol measurements collected from October 2012 to September 2013 along 36 transects between the port of Los Angeles, California (33.7°N, 118.2°), and Honolulu, Hawaii (21.3°N, 157.8°W), during the Marine ARM GPCI (Global Energy and Water Cycle Experiment (GEWEX)-Cloud System Study (GCSS)-Pacific Cross-section Intercomparison) Investigation of Clouds campaign are analyzed to determine the circulation patterns that modulate the synoptic and monthly variability of cloud condensation nuclei (CCN) in the boundary layer. Seasonal changes in CCN are evident, with low magnitudes during autumn/winter, and high CCN during spring/summer accompaniedwith a characteristic westward decrease. CCNmonthly evolution is consistent with satellite-derived cloud droplet number concentration Ndfrom the Moderate Resolution Imaging Spectroradiometer. One-point correlation (r) analysis between the 1000 hPa zonal wind time series over a region between 125°Wand 135°W, 35°N and 45°N, and the Ndfield yields a negative r (up to -0.55) over a domain that covers a zonal extent of at least 20° from the California shoreline, indicating that Nddecreases when the zonal wind intensifies. The negative r expands southwestward as the zonal wind precedes Ndby up to 3 days, suggesting a transport mechanism from the coast of North America mediated by the California low-coastal jet, which intensifies in summer when the aerosol concentration and Ndreach a maximum. A first assessment of aerosol-cloud interaction (ACI) is performed by combining CCN and satellite Ndvalues from the Fifteenth Geostationary Operational Environmental Satellite. The CCN-Ndcorrelation is 0.66–0.69, and the ACI metric defined as ACI= ∂ln(Nd)/∂ln(CCN) is high at 0.9, similar to other aircraft-based studies and substantially greater than those inferred from satellites and climate models. © 2015. American Geophysical Union. All rights reserved."
"55323972500;36020977200;24467994800;6701611146;55927784300;","Results of the Global WaterPack: A novel product to assess inland water body dynamics on a daily basis",2015,"10.1080/2150704X.2014.1002945","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922326578&doi=10.1080%2f2150704X.2014.1002945&partnerID=40&md5=65a50d71a127a4b5df0c463555c52299","The understanding and assessment of surface water variability of inland water bodies, for example, due to climate variability and human impact, requires steady and continuous information about its inter-and intra-annual dynamics. In this letter, we present an approach using dynamic threshold techniques and utilizing time series to generate a data set containing detected surface water bodies on a global scale with daily temporal resolution. Exemplary results for the year 2013 that were based on moderate resolution imaging spectroradiometer products are presented in this letter. The main input data sets for the presented product were MOD09GQ/MYD09GQ and MOD10A1/MYD10A1 with a spatial resolution of 250 m and 500 m, respectively. Using the static water mask MOD44W, we extracted training pixels to generate dynamic thresholds for individual data sets on daily basis. In a second processing step, the generated sequences of water masks were utilized to interpolate the results for any missing observations, either due to cloud coverage or missing data, as well as to reduce misclassification due to cloud shadow. The product provides an opportunity for further research and for assessing the drivers of changes of inland water bodies at a global scale. © 2015 Taylor and Francis."
"21740519000;36187387300;23981063100;54883121500;7801532509;35169960300;7006760857;7004854393;35737139200;7005246023;7003554893;19639722300;","Representation of daytime moist convection over the semi-arid Tropics by parametrizations used in climate and meteorological models",2015,"10.1002/qj.2517","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941189190&doi=10.1002%2fqj.2517&partnerID=40&md5=7ffe6fd23a5840898922acac18df4400","A case of daytime development of deep convection over tropical semi-arid land is used to evaluate the representation of convection in global and regional models. The case is based on observations collected during the African Monsoon Multidisciplinary Analysis (AMMA) field campaign and includes two distinct transition phases, from clear sky to shallow cumulus and from cumulus to deep convection. Different types of models, run with identical initial and boundary conditions, are intercompared: a reference large-eddy simulation (LES), single-column model (SCM) version of four different Earth system models that participated in the Coupled Model Intercomparison Project 5 exercise, the SCM version of the European Centre for Medium-range Weather Forecasts operational forecast model, the SCM version of a mesoscale model and a bulk model. Surface fluxes and radiative heating are prescribed preventing any atmosphere-surface and cloud-radiation coupling in order to simplify the analyses so that it focuses only on convective processes. New physics packages are also evaluated within this framework. As the LES correctly reproduces the observed growth of the boundary layer, the gradual development of shallow clouds, the initiation of deep convection and the development of cold pools, it provides a basis to evaluate in detail the representation of the diurnal cycle of convection by the other models and to test the hypotheses underlying convective parametrizations. Most SCMs have difficulty in representing the timing of convective initiation and rain intensity, although substantial modifications to boundary-layer and deep-convection parametrizations lead to improvements. The SCMs also fail to represent the mid-level troposphere moistening during the shallow convection phase, which we analyse further. Nevertheless, beyond differences in timing of deep convection, the SCM models reproduce the sensitivity to initial and boundary conditions simulated in the LES regarding boundary-layer characteristics, and often the timing of convection triggering. © 2015 Royal Meteorological Society."
"56182620500;7401796996;8629713500;7404829395;56537463000;","Evaluation of CMIP5 simulated clouds and TOA radiation budgets using NASA satellite observations",2015,"10.1007/s00382-014-2158-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939884974&doi=10.1007%2fs00382-014-2158-9&partnerID=40&md5=3ae53f3620765f9180f67a3f2d01f063","A large degree of uncertainty in global climate models (GCMs) can be attributed to the representation of clouds and how they interact with incoming solar and outgoing longwave radiation. In this study, the simulated total cloud fraction (CF), cloud water path (CWP), top of the atmosphere (TOA) radiation budgets and cloud radiative forcings (CRFs) from 28 CMIP5 AMIP models are evaluated and compared with multiple satellite observations from CERES, MODIS, ISCCP, CloudSat, and CALIPSO. The multimodel ensemble mean CF (57.6 %) is, on average, underestimated by nearly 8 % (between 65°N/S) when compared to CERES–MODIS (CM) and ISCCP results while an even larger negative bias (17.1 %) exists compared to the CloudSat/CALIPSO results. CWP bias is similar in comparison to the CF results, with a negative bias of 16.1 gm−2 compared to CM. The model simulated and CERES EBAF observed TOA reflected SW and OLR fluxes on average differ by 1.8 and −0.9 Wm−2, respectively. The averaged SW, LW, and net CRFs from CERES EBAF are −50.1, 27.6, and −22.5 Wm−2, respectively, indicating a net cooling effect of clouds on the TOA radiation budget. The differences in SW and LW CRFs between observations and the multimodel ensemble means are only −1.3 and −1.6 Wm−2, respectively, resulting in a larger net cooling effect of 2.9 Wm−2 in the model simulations. A further investigation of cloud properties and CRFs reveals that the GCM biases in atmospheric upwelling (15°S–15°N) regimes are much less than in their downwelling (15°–45°N/S) counterparts over the oceans. Sensitivity studies have shown that the magnitude of SW cloud radiative cooling increases significantly with increasing CF at similar rates (~−1.25 Wm−2 %−1) in both regimes. The LW cloud radiative warming increases with increasing CF but is regime dependent, suggested by the different slopes over the upwelling and downwelling regimes (0.81 and 0.22 Wm−2 %−1, respectively). Through a comprehensive error analysis, we found that CF is a primary modulator of warming (or cooling) in the atmosphere. The comparisons and statistical results from this study may provide helpful insight for improving GCM simulations of clouds and TOA radiation budgets in future versions of CMIP. © 2014, Springer-Verlag Berlin Heidelberg."
"35423527600;40461229800;56502000100;55612221800;56509096000;26639062900;","An in situ method for sizing insoluble residues in precipitation and other aqueous samples",2015,"10.1080/02786826.2014.991439","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922424395&doi=10.1080%2f02786826.2014.991439&partnerID=40&md5=94cbc687c28c6595a7fad526777b8b34","Particles are frequently incorporated into clouds or precipitation, influencing climate by acting as cloud condensation or ice nuclei, taking up coatings during cloud processing, and removing species through wet deposition. Many of these particles, particularly ice nuclei, can remain suspended within cloud droplets/crystals as insoluble residues. While previous studies have measured the soluble or bulk mass of species within clouds and precipitation, no studies to date have determined the number concentration and size distribution of insoluble residues in precipitation or cloud water using in situ methods. Herein, for the first time we demonstrate that nanoparticle tracking analysis (NTA) is a powerful in situ method for determining the total number concentration, number size distribution, and surface area distribution of insoluble residues in precipitation, both of rain and melted snow. The method uses 500 L or less of liquid sample and does not require sample modification. Number concentrations for the insoluble residues in aqueous precipitation samples ranged from 2.0-3.0 (±0.3) × 108 particles cm-3, while surface area ranged from 1.8 (±0.7)-3.2 (±1.0) × 107 m2 cm-3. Number size distributions peaked between 133 and 150 nm, with both single and multi-modal character, while surface area distributions peaked between 173 and 270 nm. Comparison with electron microscopy of particles up to 10 m show that, by number, &gt;97% residues are &lt;1 m in diameter, the upper limit of the NTA. The range of concentration and distribution properties indicates that insoluble residue properties vary with ambient aerosol concentrations, cloud microphysics, and meteorological dynamics. NTA has great potential for studying the role that insoluble residues play in critical atmospheric processes. © 2015 American Association for Aerosol Research."
"7401974644;7402064802;57197705845;22635190100;6508300972;7401936984;","The parametric sensitivity of CAM5‘s MJO",2015,"10.1002/2014JD022507","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925119164&doi=10.1002%2f2014JD022507&partnerID=40&md5=87281dfb86984fb4a451d8706adeaaef","We systematically explore the ability of the Community Atmospheric Model version 5 (CAM5) to simulate the Madden-Julian Oscillation (MJO), through an analysis of MJO metrics calculated from a 1100-member perturbed parameter ensemble of 5 year simulations with observed sea surface temperatures. Parameters fromthe deep convection scheme make the greatest contribution to the variance in MJO simulation quality with a much smaller contribution from parameters in the large-scale cloud, shallow convection, and boundary layer turbulence schemes. ImprovedMJO variability results froma larger lateral entrainment rate and a reduction in the precipitation efficiency of deep convection that was achieved by a smaller autoconversion of cloud to rainwater and a larger evaporation of convective precipitation. Unfortunately, simulations with an improved MJO also have a significant negative impact on the climatological values of low-level cloud and absorbed shortwave radiation, suggesting that structural in addition to parametric modifications to CAM5‘s parameterization suite are needed in order to simultaneously well simulate the MJO and mean-state climate. © 2015. American Geophysical Union. All Rights Reserved."
"57195597793;13607567200;36945025900;57092467500;6603710604;35614095500;15135280400;","Indian monsoon and the elevated-heat-pump mechanism in a coupled aerosol-climate model",2015,"10.1002/2015JD023346","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943411825&doi=10.1002%2f2015JD023346&partnerID=40&md5=9ccf57da32f6c56f3c27af60530f6973","A coupled aerosol-atmosphere-ocean-sea ice climate model is used to explore the interaction between aerosols and the Indian summer monsoon precipitation on seasonal-to-interannual time scales. Results show that when increased aerosol loading is found on the Himalayas slopes in the premonsoon period (April-May), intensification of early monsoon rainfall over India and increased low-level westerly flow follow, in agreement with the elevated-heat-pump mechanism. The increase in rainfall during the early monsoon season has a cooling effect on the land surface. In the same period, enhanced surface cooling may also be amplified through solar dimming by more cloudiness and aerosol loading, via increased dust transported by low-level westerly flow. The surface cooling causes subsequent reduction in monsoon rainfall in July-August over India. The time-lagged nature of the reasonably realistic response of the model to aerosol forcing suggests that absorbing aerosols, besides their potential key roles in impacting monsoon water cycle and climate, may influence the seasonal variability of the Indian summer monsoon. © 2015. American Geophysical Union. All Rights Reserved."
"57202055245;8877858700;6602725432;7003811754;55085483100;7005056279;16425609300;55777759900;","Evaluation of boundary-layer cloud forecasts over the Southern Ocean in a limited-area numerical weather prediction system usingin situ, space-borne and ground-based observations",2015,"10.1002/qj.2519","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941168010&doi=10.1002%2fqj.2519&partnerID=40&md5=1b6d99d5d54773ae67324a557080ed64","Near-synchronized in situ, space-borne (A-Train) and ground-based lidar observations are employed to evaluate the boundary-layer clouds (BLCs) over Tasmania and the adjacent Southern Ocean (SO) simulated by the limited-area version of Australian Community Climate and Earth System Simulator (ACCESS-C). Two winter cases featuring BLCs associated with a post-frontal environment and the leading side of a high-pressure ridge are studied. Previous studies showed that these synoptic conditions contribute to the largest reflected short-wave radiation biases simulated over the SO. Results of the simulations suggest that the ACCESS-C model demonstrates an appreciable level of skill in simulating the macrophysical properties of the BLCs over the SO, generally consistent with the in situ and remote-sensing observations. However, some notable challenges remain: the area cloud fraction of the marine BLCs is consistently underpredicted; the fine-scale structure of the marine cumuli is poorly represented in the 4 km grid-length simulations; the capping inversion over the marine boundary layer is generally too high, associated with the marine BLCs being predicted at the wrong altitude and temperature ranges; the liquid water content (LWC) of the BLCs is underestimated; and the model representation of drizzle production can be too efficient. Sensitivity studies are also conducted to test a newly developed autoconversion microphysics scheme and shear-dominated planetary boundary-level (PBL) scheme. These parametrizations show notable improvement in cloud prediction for CASE B (i.e. better area cloud fraction and better average and maximum values of LWC). However, none of these tests is able to improve the simulated marine PBL structure. Overall, the simulated cloud biases are jointly influenced by physical parametrizations, poor representations of large-scale advection, surface fluxes and subsidence. More substantial observations are needed to improve our understanding of the origins and development of these biases and the relative contribution of these errors to the radiation budget over the SO. © 2015 Royal Meteorological Society."
"22133985200;6602215448;7201423091;15926468600;","Towards an aerosol classification scheme for future EarthCARE lidar observations and implications for research needs",2015,"10.1002/asl2.524","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921334097&doi=10.1002%2fasl2.524&partnerID=40&md5=a77cb77df7befe69bfa7339490818f46","Owing to the high variability of aerosols, and their different impact on the Earth's climate system, aerosol type classification from satellite measurements is of high importance. Polarization sensitive lidar measurements on board the future Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) satellite mission will provide information to distinguish different aerosol types. We analyze whether former classification schemes based on lidar measurements at 532nm are applicable to EarthCARE measurements at 355nm. We compare coordinated lidar measurements at both wavelengths performed during five field experiments; adapt thresholds for aerosol classification with future spaceborne lidar measurements and identify limitations of the current state of knowledge. © 2015 Royal Meteorological Society."
"24329376600;57203049177;7201485519;","The dependence of radiative forcing and feedback on evolving patterns of surface temperature change in climate models",2015,"10.1175/JCLI-D-14-00545.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922774244&doi=10.1175%2fJCLI-D-14-00545.1&partnerID=40&md5=b91b98cac39ae8dd2637668ad0564bfc","Experiments with CO2 instantaneously quadrupled and then held constant are used to show that the relationship between the global-mean net heat input to the climate system and the global-mean surface air temperature change is nonlinear in phase 5 of the Coupled Model Intercomparison Project (CMIP5) atmosphere-ocean general circulation models (AOGCMs). The nonlinearity is shown to arise from a change in strength of climate feedbacks driven by an evolving pattern of surface warming. In 23 out of the 27 AOGCMs examined, the climate feedback parameter becomes significantly (95% confidence) less negative (i.e., the effective climate sensitivity increases) as time passes. Cloud feedback parameters show the largest changes. In the AOGCM mean, approximately 60% of the change in feedback parameter comes from the tropics (30°N-30°S). An important region involved is the tropical Pacific, where the surface warming intensifies in the east after a few decades. The dependence of climate feedbacks on an evolving pattern of surface warming is confirmed using the HadGEM2 and HadCM3 atmosphere GCMs (AGCMs). With monthly evolving sea surface temperatures and sea ice prescribed from its AOGCM counter part, each AGCM reproduces the timevarying feedbacks, but when a fixed pattern of warming is prescribed the radiative response is linear with global temperature change or nearly so. It is also demonstrated that the regression and fixed-SST methods for evaluating effective radiative forcing are in principle different, because rapid SST adjustment when CO2 is changed can produce a pattern of surface temperature change with zero global mean but nonzero change in net radiation at the top of the atmosphere (~-0.5W m-2 in HadCM3). © 2015 American Meteorological Society."
"57189634238;8511991900;6506328135;8922308700;7102266120;","Roles of wind shear at different vertical levels: Cloud system organization and properties",2015,"10.1002/2015JD023253","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938208199&doi=10.1002%2f2015JD023253&partnerID=40&md5=ab0156397a52488dd521e3bc2a528196","Understanding critical processes that contribute to the organization of mesoscale convective systems (MCSs) is important for accurate weather forecasts and climate predictions. In this study, we investigate the effects of wind shear at different vertical levels on the organization and properties of convective systems using the Weather Research and Forecasting model with spectral bin microphysics. Based on a control run for a MCS with weak wind shear (Ctrl), we find that increasing wind shear at the lower troposphere (L-shear) leads to a more organized quasi-line convective system. Strong wind shear in the middle troposphere (M-shear) tends to produce large vorticity and form a mesocyclone circulation and an isolated strong storm that leans toward supercellular structure. By increasing wind shear at the upper vertical levels only (U-shear), the organization of the convection is not changed much, but the convective intensity is weakened. Increasing wind shear in the middle troposphere for the selected case results in a significant drying, and the drying is more significant when conserving moisture advection at the lateral boundaries, contributing to the suppressed convective strength and precipitation relative to Ctrl. Precipitation in the L-shear and U-shear does not change much from Ctrl. Evident changes of cloud macrophysical and microphysical properties in the strong wind shear cases are mainly due to large changes in convective organization and water vapor. The insights obtained from this study help us better understand the major factors contributing to convective organization and precipitation. © 2015. American Geophysical Union. All Rights Reserved."
"56954720900;57202121637;6602715868;6701742258;55325353200;","Influence of large offshore wind farms on North German climate",2015,"10.1127/metz/2015/0652","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946743039&doi=10.1127%2fmetz%2f2015%2f0652&partnerID=40&md5=f7e9ae510fd11f2b545a8500c58e219d","Wind farms impact the local meteorology by taking up kinetic energy from the wind field and by creating a large wake. The wake influences mean flow, turbulent fluxes and vertical mixing. In the present study, the influences of large offshore wind farms on the local summer climate are investigated by employing the mesoscale numerical model METRAS with and without wind farm scenarios. For this purpose, a parametrisation for wind turbines is implemented in METRAS. Simulations are done for a domain covering the northern part of Germany with focus on the urban summer climate of Hamburg. A statistical-dynamical downscaling is applied using a skill score to determine the required number of days to simulate the climate and the influence of large wind farms situated in the German Bight, about 100 km away from Hamburg. Depending on the weather situation, the impact of large offshore wind farms varies from nearly no influence up to cloud cover changes over land. The decrease in the wind speed is most pronounced in the local areas in and around the wind farms. Inside the wind farms, the sensible heat flux is reduced. This results in cooling of the climate summer mean for a large area in the northern part of Germany. Due to smaller momentum fluxes the latent heat flux is also reduced. Therefore, the specific humidity is lower but because of the cooling, the relative humidity has no clear signal. The changes in temperature and relative humidity are more wide spread than the decrease of wind speed. Hamburg is located in the margins of the influenced region. Even if the influences are small, the urban effects of Hamburg become more relevant than in the present and the off-shore wind farms slightly intensify the summer urban heat island. © 2015 The authors."
"57199117424;55262499900;6602636483;35413553600;","AIRS, IASI, and CrIS retrieval records at climate scales: An investigation into the propagation of systematic uncertainty",2015,"10.1175/JAMC-D-14-0299.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943738349&doi=10.1175%2fJAMC-D-14-0299.1&partnerID=40&md5=ff51a5f5ddcd24273be51c195cd1ea62","Uncertainty requirements for climate observations are more stringent than for weather observations because of the scale dependency of natural variation. At present there is no space-based climate observing system, so weather observations have to be aggregated for the study of large-scale change. The management and minimization of uncertainty sources in weather observations are, therefore, a high priority. This work is a first attempt at investigating if a single long-term record can be assembled with temperature retrievals from three hyperspectral satellite sounders in polar orbit: the Atmospheric Infrared Sounder (AIRS) on Aqua in afternoon orbit since 2002, the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp-A in morning orbit since 2006, and the Cross-track Infrared Sounder (CrIS) on board the Suomi National Polar-Orbiting Partnership in afternoon orbit since 2011. These instruments measure not only the vertical atmospheric structure but also atmospheric composition, thus providing coincident observations of many essential climate variables. Two main sources of known systematic differences, namely local sampling time (LST) and instrument type (i.e., interferometer vs grating spectrometer), are characterized. For a 5-yr record it is shown that differences among these temperature soundings are height dependent; a multi-instrument data record could be assembled from measurements of the stratosphere but this is not yet possible for the troposphere, where cloud effects are shown to be dominant and dependent on instrument type. Moreover, LST differences are limited to regional systematic effects in the lower troposphere and boundary layer. This research is a step toward the development of transparent and geophysically consistent methods with which to assemble weather measurements into climate observations. © 2015 American Meteorological Society."
"56203684400;6602506659;","Analysis of the results of thunderstorm forecasting based on atmospheric instability indices using the WRF-ARW numerical model data",2015,"10.3103/S1068373915010033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923046182&doi=10.3103%2fS1068373915010033&partnerID=40&md5=f323cec5adf14123b90a66c10cb77220","Presented are the statistical estimates of 26 indices of atmospheric instability widely used in the world practice for the thunderstorm prediction. Proposed is a new index for the thunderstorm forecasting that takes account of the vertical component of wind speed. The computation of indices is based on the data of forecasts obtained with the WRF-ARW hydrodynamic mesoscale model. The verification of thunderstorm forecasts is carried out using the observational data from weather stations and the data of the World Wide Lightning Location Network. © 2015, Allerton Press, Inc."
"55431666500;16029674800;","Simulation of the South American climate by a coupled model with super-parameterized convection",2015,"10.1007/s00382-015-2476-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925538543&doi=10.1007%2fs00382-015-2476-6&partnerID=40&md5=98d6761e5edad197db0e31ce0b3e6d5c","The simulation of the climate over South America by a coupled ocean–atmosphere model with embedded cloud resolving model is studied on different time scales. The mean climate and the variability over South America as simulated by the superparameterized Community Climate System Model version 3 (SP-CCSM) are compared with those in the observation and in the control simulation of the CCSM3 (CT-CCSM) which employs conventional scheme of convection parameterization. The CT-CCSM is able to simulate only the longer period seasonal oscillation (SO) while the SP-CCSM is successful in simulating both the SO and the intraseasonal oscillation (ISO). The spatial structure and the propagation of the oscillations are better in the SP-CCSM. Both models are able to simulate the observed low-frequency modes of variability related to El Niño-Southern oscillation (ENSO) and Pacific decadal oscillation (PDO). While the ENSO mode in the CT-CCSM has more regular variability with a biennial time scale, the SP-CCSM simulates the ENSO mode with more irregular variability and time scale closer to the observation. The spatial structure, the relation with the Pacific and the regional variations of the observed PDO mode are better simulated by the SP-CCSM than the CT-CCSM. © 2015, Springer-Verlag Berlin Heidelberg."
"56209169300;7203047398;35234290400;12788802100;","A multi-tier hazard: Part II—meteorological analysis",2015,"10.1007/s11069-014-1486-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925489616&doi=10.1007%2fs11069-014-1486-8&partnerID=40&md5=570326cbf6a218c156c3d4149cb285b6","In Part I, we have described in detail a multi-tier hazard that occurred in the State of Uttarakhand in India in June 2013. Due to some unusual meteorological situation, a cloud burst happened which was followed by river flooding and this led to significant landslides in the mountainous region. In Part II, we describe the results of an analysis of various meteorological parameters that clearly support the occurrence of this event. The approach we have used is the identification of anomalies in long-term climatic datasets. Anomaly is a pattern in the data that is unusual from the expected behavior. Anomalous events in the global climate system occur relatively infrequently but their consequences can be disastrous. Climate data contain multiple variables (e.g., temperature, pressure, wind speed, humidity, and precipitation). Each variable has its own type of distribution, trend, and seasonal variability. This analysis of identifying anomalies has successfully identified the synoptic situation that led to the multi-tier disaster. © 2014, Springer Science+Business Media Dordrecht."
"6701382162;8069865100;36198252400;6602645956;56898633200;35220798500;","Probabilistic 0-1-h convective initiation nowcasts that combine geostationary satellite observations and numerical weather prediction model data",2015,"10.1175/JAMC-D-14-0129.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943743955&doi=10.1175%2fJAMC-D-14-0129.1&partnerID=40&md5=8ff6df2faf92fa03e0c1891dd2d35bca","The Geostationary Operational Environmental Satellite (GOES)-R convective initiation (CI) algorithm predicts CI in real time over the next 0-60 min. While GOES-R CI has been very successful in tracking nascent clouds and obtaining cloud-top growth and height characteristics relevant to CI in an object-tracking framework, its performance has been hindered by elevated false-alarm rates, and it has not optimally combined satellite observations with other valuable data sources. Presented here are two statistical learning approaches that incorporate numerical weather prediction (NWP) input within the established GOES-R CI framework to produce probabilistic forecasts: logistic regression (LR) and an artificial-intelligence approach known as random forest (RF). Both of these techniques are used to build models that are based on an extensive database of CI events and nonevents and are evaluated via cross validation and on independent case studies. With the proper choice of probability thresholds, both the LR and RF techniques incorporating NWP data produce substantially fewer false alarms than when only GOES data are used. The NWP information identifies environmental conditions (as favorable or unfavorable) for the development of convective storms and improves the skill of the CI nowcasts that operate on GOES-based cloud objects, as compared with when the satellite IR fields are used alone. The LR procedure performs slightly better overall when 14 skill measures are used to quantify the results and notably better on independent case study days. © 2015 American Meteorological Society."
"56721283500;6602649973;7003482472;","Atmospheric circulation characteristics associated with daytime extreme static instability over Athens, Greece",2015,"10.3354/cr01305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937040805&doi=10.3354%2fcr01305&partnerID=40&md5=d44fc764d8f04be174711bb3404d2fba","The main atmospheric circulation characteristics associated with extreme static instability conditions over the Athens region were examined for the period 1974-2012. The data used consist of daily values of: (1) upper air temperature and dew point, precipitation and cloud cover in Athens and (2) 2.5° x 2.5° 1000 and 500 hPa geopotential heights (GH) and sea level pressure (SLP) over the Mediterranean region, for the period 1974-2012. The stability index K (K-index) was calculated from upper air measurements, and the 5% of the days with the highest K values were selected for both the cold and the warm periods of the year. These days were classified into clusters according to the corresponding GH patterns, using factor analysis and K-means cluster analysis. Results show 9 and 5 clusters for the cold and the warm periods, respectively. The mean 500 hPa GH and SLP patterns were constructed and the cloud cover and precipitation characteristics were investigated for the days classified under each cluster. For the cold period, the main atmospheric circulation factors that are responsible for extreme instability levels are the cyclonic activity in the central Mediterranean, and the warm and humid southeasterly surface flow over Athens; extreme instability is associated with high values of cloud cover, as well as of precipitation amount and frequency of precipitation events. For the warm period, upper air disturbances and the presence of corresponding cold air masses are the main factors leading to extreme instability conditions, while cloud cover and precipitation are relatively lower than during the cold period. © Inter-Research 2015."
"55220091300;7501760109;55716700200;57203378018;","Improving arctic sea ice prediction using PIOMAS initial sea ice thickness in a coupled ocean-atmosphere model",2015,"10.1175/MWR-D-15-0097.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949843987&doi=10.1175%2fMWR-D-15-0097.1&partnerID=40&md5=3f39cccc9ea9198487b31e96caf29b38","Because sea ice thickness is known to influence future patterns of sea ice concentration, it is likely that an improved initialization of sea ice thickness in a coupled ocean-atmosphere model would improve Arctic sea ice cover forecasts. Here, two sea ice thickness datasets as possible candidates for forecast initialization were investigated: the Climate Forecast System Reanalysis (CFSR) and the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS). Using Ice, Cloud, and Land Elevation Satellite (ICESat) data, it was shown that the PIOMAS dataset had a more realistic representation of sea ice thickness than CFSR. Subsequently, both March CFSR and PIOMAS sea ice thicknesses were used to initialize hindcasts using the Climate Forecast System, version 2 (CFSv2), model. A second set of model runs was also done in which the original model physics were modified tomore physically reasonable settings-namely, increasing the number of marine stratus clouds in the Arctic region and enabling realistic representation of the ice-ocean heat flux. Hindcasts were evaluated using sea ice concentration observations from the National Aeronautics and Space Administration (NASA) Team and Bootstrap algorithms. Results show that using PIOMAS initial sea ice thickness in addition to the physics modifications yielded significant improvement in the prediction of September Arctic sea ice extent along with increased interannual predictive skill. Significant local improvements in sea ice concentration were also seen in distinct regions for the change to PIOMAS initial thickness or the physics adjustments, with the most improvement occurring when these changes were applied concurrently. © 2015 American Meteorological Society."
"57151771800;8542741400;8633783900;","Interhemispheric aerosol radiative forcing and tropical precipitation shifts during the late Twentieth Century",2015,"10.1175/JCLI-D-15-0148.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945474745&doi=10.1175%2fJCLI-D-15-0148.1&partnerID=40&md5=dcff66163ff42aef2965a788781e53ee","Through the latter half of the twentieth century, meridional shifts in tropical precipitation have been associated with severe droughts. Although linked to a variety of causes, the origin of these shifts remains elusive. Here, it is shown that they are unlikely to arise from internal variability of the climate system alone, as simulated by coupled ocean-atmosphere climate models. Similar to previous work, the authors find that anthropogenic and volcanic aerosols are the dominant drivers of simulated twentieth-century tropical precipitation shifts. Models that include the cloud-albedo and lifetime aerosol indirect effects yield significantly larger shifts than models that lack aerosol indirect effects and also reproduce most of the southward tropical precipitation shift in the Pacific. However, all models significantly underestimate the magnitude of the observed shifts in the Atlantic sector, unless driven by observed SSTs. Mechanistically, tropical precipitation shifts are driven by interhemispheric sea surface temperature variations, which are associated with hemispherically asymmetric changes in low-latitude surface pressure, winds, and low clouds, as well as the strength, location, and cross-equatorial energy transport of the Hadley cells. Models with a larger hemispheric aerosol radiative forcing gradient yield larger hemispheric temperature contrasts and, in turn, larger meridional precipitation shifts. The authors conclude that aerosols are likely the dominant driver of the observed southward tropical precipitation shift in the Pacific. Aerosols are also significant drivers of the Atlantic shifts, although one cannot rule out a contribution from natural variability to account for the magnitude of the observed shifts. © 2015 American Meteorological Society."
"6602988199;7003777747;","Climate response to externally mixed black carbon as a function of altitude",2015,"10.1002/2014JD022849","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928603536&doi=10.1002%2f2014JD022849&partnerID=40&md5=9c6bc14317fe93671257289a72f4acec","The climate response to the presence of black carbon (BC) aerosol at a given altitude in the atmosphere is investigated using a global circulation model. The vertical dependence of the efficiency with which BC exerts radiative forcing (RF) through the direct aerosol effect has previously been extensively studied. Here we use the Community Atmosphere Model version 4 atmospheric component of the National Center for Atmospheric Research Community Earth System model version 1.03 to calculate the three-dimensional response to a BC layer inserted at various altitudes. Simulations have been performed both for fixed sea surface temperatures and using a slab ocean setup to include the surface temperature response. We investigate the vertical profiles of RF exerted per gram of externally mixed BC due to both the direct and semidirect aerosol effects. Associated changes in cloud cover, relative humidity, and precipitation are discussed. The precipitation response to BC is decomposed into a fast, stability-related change and a slow, temperature-driven component. We find that while the efficiency of BC to exert positive RF due to the direct effect strengthens with altitude, as in previous studies, it is strongly offset by a negative semidirect effect. The net radiative perturbation of BC at top of atmosphere is found to be positive everywhere below the tropopause and negative above. The global, annual mean precipitation response to BC, after equilibration of a slab ocean, is found to be positive between the surface and 900 hPa but negative at all other altitudes. © 2015. American Geophysical Union. All Rights Reserved."
"57205867148;6602513845;6603081424;7203034123;22940460400;35101612400;7003696273;6507906800;8397494800;7004714030;9242540400;7410070663;26659116700;23486734100;36187387300;36722732500;6508175197;","Radiative flux and forcing parameterization error in aerosol-free clear skies",2015,"10.1002/2015GL064291","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938209037&doi=10.1002%2f2015GL064291&partnerID=40&md5=b39c9038396856749122d4b4499a3290","This article reports on the accuracy in aerosol- and cloud-free conditions of the radiation parameterizations used in climate models. Accuracy is assessed relative to observationally validated reference models for fluxes under present-day conditions and forcing (flux changes) from quadrupled concentrations of carbon dioxide. Agreement among reference models is typically within 1 W/m2, while parameterized calculations are roughly half as accurate in the longwave and even less accurate, and more variable, in the shortwave. Absorption of shortwave radiation is underestimated by most parameterizations in the present day and has relatively large errors in forcing. Error in present-day conditions is essentially unrelated to error in forcing calculations. Recent revisions to parameterizations have reduced error in most cases. A dependence on atmospheric conditions, including integrated water vapor, means that global estimates of parameterization error relevant for the radiative forcing of climate change will require much more ambitious calculations. Key Points Radiation parameterizations in GCMs are more accurate than their predecessors Errors in estimates of 4 ×CO<inf>2</inf> forcing are large, especially for solar radiation Errors depend on atmospheric state, so global mean error is unknown. © 2015. American Geophysical Union. All Rights Reserved."
"55582924900;55707280000;56918994000;56247186000;23481546200;","Sensitivity of tropical cyclone track simulation over the Western North Pacific to different heating/drying rates in the Betts-Miller-Janjić Scheme",2015,"10.1175/MWR-D-14-00340.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945162618&doi=10.1175%2fMWR-D-14-00340.1&partnerID=40&md5=4887a1f171521a66558469efb32583f9","The Weather Research and Forecasting Model is employed to examine the sensitivity of simulated tropical cyclone (TC) motion and associated intensity of the western Pacific subtropical high (WSPH) to different heating and drying rates in the Betts-Miller-Janjić (BMJ) cumulus parameterization (CP) scheme. A case study of Tropical Cyclone Megi (2010) is performed. Results indicate that the simulated WPSH strengthens as the heating/drying effects of the BMJ decrease. A strong WPSH subsequently leads to changes in the large-scale steering flow in its southern edge and delays the northward turning of the simulated storm. The associated physical mechanism is revealed. As the heating/drying is overestimated in the BMJ, the model produces unrealistic drying below 500 hPa whereas the atmosphere becomes moist above 500 hPa. Drying in the lower troposphere hinders the activation of the microphysics while moistening in the upper troposphere facilitates the microphysics. As a result, the model generates extensive anvil clouds that extend far away from the TC center and reach the upper troposphere over the WPSH. This leads to a warming in the upper troposphere due to condensation in the anvil clouds, and a cooling in the lower troposphere due to precipitation evaporation below the anvil clouds. Subsequently, the WPSH weakens and the large-scale steering flow becomes anomalously northward, leading to an early recurvature of TC Megi. Results of this study emphasize the importance of a correct representation of anvil clouds in simulating the WPSH and TC track. This study also implies that correcting the heating/drying can be an effective way to reduce errors in simulating the WPSH and TC motion. � 2015 American Meteorological Society."
"55582924900;55707280000;56576766700;","Sensitivity of tropical cyclone feedback on the intensity of the Western Pacific subtropical high to microphysics schemes",2015,"10.1175/JAS-D-14-0051.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944067917&doi=10.1175%2fJAS-D-14-0051.1&partnerID=40&md5=a90cae41d4b839ed706125b522876ca7","The Advanced Research version of Weather Research and Forecasting (WRF-ARW) Model is used to examine the sensitivity of a simulated tropical cyclone (TC) track and the associated intensity of the western Pacific subtropical high (WPSH) to microphysical parameterization (MP) schemes. It is found that the simulated WPSH is sensitive to MP schemes only when TCs are active over the western North Pacific. WRF fails to capture TC tracks because of errors in the simulation of the WPSH intensity. The failed simulation of WPSH intensity and TC track can be attributed to the overestimated convection in the TC eyewall region, which is caused by inappropriate MP schemes. In other words, the MP affects the simulation of the TC activity, which influences the simulation of WPSH intensity and, thus, TC track. The feedback of the TC to WPSH plays a critical role in the model behavior of the simulation. Further analysis suggests that the overestimated convection in the TC eyewall results in excessive anvil clouds and showers in the middle and upper troposphere. As the simulated TC approaches the WPSH, the excessive anvil clouds extend far away from the TC center and reach the area of the WPSH. Because of the condensation of the anvil clouds' outflows and showers, a huge amount of latent heat is released into the atmosphere and warms the air above the freezing level at about 500 hPa. Meanwhile, the evaporative (melting) process of hydrometers in the descending flow takes place below the freezing level and cools the air in the lower and middle troposphere. As a result, the simulated WPSH intensity is weakened, and the TC turns northward earlier than in observations. © 2015 American Meteorological Society."
"25226837900;","Climate impacts of large-scale wind farms as parameterized in a global climate model",2015,"10.1175/JCLI-D-14-00245.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942851867&doi=10.1175%2fJCLI-D-14-00245.1&partnerID=40&md5=886c565f13f31adbec49455c81d67ede","The local, regional, and global climate impacts of a large-scale global deployment of wind power in regionally high densities over land are investigated for a 60-yr period. Wind farms are represented as elevated momentum sinks as well as enhanced turbulence to represent turbine blade mixing in the Community Atmosphere Model, version 5 (CAM5), a global climate model. For a total installed capacity of 2.5TW, to provide 16% of the world's projected electricity demand in 2050, minimal impacts are found both regionally and globally on temperature, sensible and latent heat fluxes, cloud, and precipitation. A mean near-surface warming of 0.12 ± 0.07K is seen within the wind farms, with a global-mean temperature change of -0.013 ± 0.015 K. Impacts on wind speed and turbulence are more pronounced but largely confined within the wind farm areas. Increasing the wind farm areas to provide an installed capacity of 10TW, or 65% of the 2050 electricity demand, causes further impacts; however, they remain slight overall. Maximum temperature changes are less than 0.5K in the wind farm areas. To provide 20 TW of installed capacity, or 130% of the 2050 electricity demand, impacts both within the wind farms and beyond become more pronounced, with a doubling in turbine density. However, maximum temperature changes remain less than 0.7 K. Representing wind farms instead as an increase in surface roughness generally produces similar mean results; however, maximum changes increase, and influences on wind and turbulence are exaggerated. Overall, wind farm impacts are much weaker than those expected from greenhouse gas emissions, with very slight global-mean climate impacts. © 2015 American Meteorological Society."
"55922039700;7005211669;7004402705;8383395800;","The near-global mesospheric potassium layer: Observations and modeling",2015,"10.1002/2015JD023212","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940460647&doi=10.1002%2f2015JD023212&partnerID=40&md5=16600f15baf3c5be3ad3013ca9c45373","Themeteoricmetal layers act as unique tracers of chemistry and dynamics in the upper atmosphere. Existing lidar studies from a few locations show that K exhibits a semiannual seasonality (winter and summer maxima), quite unlike the annual seasonality (winter maximum and summerminimum) seen with Na and Fe. This work uses spaceborne observations made with the Optical Spectrograph and InfraRed Imager System instrument on the Odin satellite to retrieve the near-global K layer for the first time. The satellite data (2004 to mid-2013) are used to validate the implementation of a recently proposed potassium chemistry scheme in a whole atmosphere chemistry climate model, which provides a chemical basis for this semiannual seasonal behavior. The satellite and model data show that this semiannual seasonality is near global in extent, with the strongest variation at middle and high latitudes. The column abundance, centroid layer height, and root-mean-square width of the K layer are consistent with the limited available lidar record. The K data set is then used to investigate the impact of polar mesospheric clouds on the metal layers at high latitudes during summer. Finally, the occurrence frequency of sporadic K layers and their possible link to sporadic E layers are examined. © 2015. The Authors."
"57194347408;36482110100;57218518385;56158245500;","Evapotranspiration estimated by using datasets from the Chinese FengYun-2D geostationary meteorological satellite over the Yellow River source area",2015,"10.1016/j.asr.2014.09.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84916897322&doi=10.1016%2fj.asr.2014.09.018&partnerID=40&md5=b14cb6e825a072fdd634ddd257cf6309","In this paper, we developed algorithms to estimate hourly evapotranspiration (ET) during a day under clear and cloud cover conditions using data from the Chinese FengYun-2D (FY-2D) geostationary meteorological satellite over the Yellow River source area. For cloud-free conditions, the Surface Energy Balance System (SEBS) methodology and FY-2D data were used to derive the hourly ET. For cloudy cover conditions, the transmission coefficient was calculated using top of atmosphere (TOA) reflectance and the attenuation of solar radiation in the atmosphere. Heat fluxes and ET under different atmospheric and cloud cover conditions were then calculated. Compared with ground-based measurements from eddy covariance systems deployed in the Maqu Climate and Environment Comprehensive Observation Station, the average relative error was 15.20% during the experimental period. The proposed methodology can rely exclusively on remote sensing data in the absence of ancillary ground observations. Thus, the proposed method can potentially estimate the regional surface energy budget. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved."
"56525006400;6603699044;","Impact of microphysics parameterizations on simulations of the 27 october 2010 great Salt Lake-effect snowstorm",2015,"10.1175/WAF-D-14-00060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923312087&doi=10.1175%2fWAF-D-14-00060.1&partnerID=40&md5=8ed92d217c32f41c9b9a2b5f1044d15f","Simulations of moist convection at cloud-permitting grid spacings are sensitive to the parameterization of microphysical processes, posing a challenge for operational weather prediction. Here, the Weather Research and Forecasting (WRF) Model is used to examine the sensitivity of simulations of the Great Salt Lake-effect snowstorm of 27 October 2010 to the choice of microphysics parameterization (MP). It is found that the simulated precipitation from fourMP schemes varies in areal coverage, amount, and position. The Thompson scheme (THOM) verifies best against radar-derived precipitation estimates and gauge observations. The Goddard, Morrison, and WRF double-moment 6-class microphysics schemes (WDM6) produce more precipitation than THOM, with WDM6 producing the largest overprediction relative to radar-derived precipitation estimates and gauge observations. Analyses of hydrometeor mass tendencies show that WDM6 creates more graupel, less snow, and more total precipitation than the other schemes. These results indicate that the rate of graupel and snow production can strongly influence the precipitation efficiency in simulations of lake-effect storms, but further work is needed to evaluate MP-scheme accuracy across a wider range of events, including the use of aircraft- and ground-based hydrometeor sampling to validate MP hydrometeor categorization. © 2015 American Meteorological Society."
"7005578774;57207969036;6602098362;","Relationships among top-of-atmosphere radiation and atmospheric state variables in observations and CESM",2015,"10.1002/2015JD023381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945453810&doi=10.1002%2f2015JD023381&partnerID=40&md5=c3c299fa055dff84c238f7c50a2a97f1","A detailed examination is made in both observations and the Community Earth System Model (CESM) of relationships among top-of-atmosphere radiation, water vapor, temperatures, and precipitation for 2000–2014 to assess the origins of radiative perturbations and climate feedbacks empirically. The 30-member large ensemble coupled runs are analyzed along with one run with specified sea surface temperatures for 1994 to 2005 (to avoid volcanic eruptions). The vertical structure of the CESM temperature profile tends to be top heavy in the model, with too much deep convection and not enough lower stratospheric cooling as part of the response to tropospheric heating. There is too much absorbed solar radiation (ASR) over the Southern Oceans and not enough in the tropics, and El Niño–Southern Oscillation (ENSO) is too large in amplitude in this version of the model. However, the covariability of monthly mean anomalies produces remarkably good replication of most of the observed relationships. There is a lot more high-frequency variability in radiative fluxes than in temperature, highlighting the role of clouds and transient weather systems in the radiation statistics. Over the Warm Pool in the tropical western Pacific and Indian Oceans, where nonlocal effects from the Walker circulation driven by the ENSO events are important, several related biases emerge: in response to high SST anomalies there is more precipitation, water vapor, and cloud and less ASR and outgoing longwave radiation in the model than observed. Different model global mean trends are evident, however, possibly hinting at too much positive cloud feedback in the model. © 2015. American Geophysical Union. All rights reserved."
"12143654900;49061276900;10939346700;","The Atacama surface solar maximum",2015,"10.1175/BAMS-D-13-00175.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929460098&doi=10.1175%2fBAMS-D-13-00175.1&partnerID=40&md5=515d0476a54d77347e134784cbdca63a","We have presented a descriptive analysis showing a suite of different global products that combine information from models and satellites to provide the global distribution of surface total solar radiation as well as the distribution of the main substances that explain the atmospheric extinction of solar radiation reaching the surface. Latitude, elevation, cloud fraction, water vapor, and aerosols have a first-order influence on the distribution of surface solar radiation over the planet, and no single factor explains the combined distribution. The most likely location of the total solar radiation over the surface of the planet is on the pre-Andean Domeyko Cordillera, a mountain range with elevations between 3,500 and 5,000 m. The regional climate of the Atacama is such that extremely low values of water vapor, cloud cover, ozone, and aerosols concur in this region. The atmospheric transparency in the visible and infrared provided by these conditions, together with a relatively high elevation and low latitude, conspire to produce a region where mean total radiation values exceed 300 W m-2. According to a semiempirical model for surface solar radiation that takes into account extinction by gases, clouds, aerosols, and the effect of topography, the maximum is about 310 ± 15 W m-2, although for individual years, especially those with dry summertime Altiplano conditions, the solar maximum should be located in the Altiplano region near to the Chajnantor Plateau. The delicate combination of elements that concurs in the Atacama region still justifies the increase in observational capabilities of solar radiation and atmospheric composition as it was first devised and executed by the pioneers of solar research in Mount Montezuma in the early twentieth century. © 2015 American Meteorological Society."
"55175065800;7003656857;6603566335;6603815281;","A year-long large-eddy simulation of the weather over Cabauw: An overview",2015,"10.1175/MWR-D-14-00293.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925004362&doi=10.1175%2fMWR-D-14-00293.1&partnerID=40&md5=b978b60b5582637fea140d8b10195b66","Results are presented of two large-eddy simulation (LES) runs of the entire year 2012 centered at the Cabauw observational supersite in the Netherlands. The LES is coupled to a regional weather model that provides the large-scale information. The simulations provide three-dimensional continuous time series of LES-generated turbulence and clouds, which can be compared in detail to the extensive observational dataset of Cabauw. The LES dataset is available from the authors on request. This type of LES setup has a number of advantages. First, it can provide a more statistical approach to the study of turbulent atmospheric flow than the more common case studies, since a diverse but representative set of conditions is covered, including numerous transitions. This has advantages in the design and evaluation of parameterizations. Second, the setup can provide valuable information on the quality of the LES model when applied to such a wide range of conditions. Last, it also provides the possibility to emulate observation techniques. This might help detect limitations and potential problems of a variety of measurement techniques. The LES runs are validated through a comparison with observations from the observational supersite and with results from the ""parent"" large-scale model. The long time series that are generated, in combination with information on the spatial structure, provide a novel opportunity to study time scales ranging from seconds to seasons. This facilitates a study of the power spectrum of horizontal and vertical wind speed variance to identify the dominant variance-containing time scales. © 2015 American Meteorological Society."
"14020325100;7005565819;","On the impact of additive noise in storm-scale EnKF experiments",2015,"10.1175/MWR-D-14-00323.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943421955&doi=10.1175%2fMWR-D-14-00323.1&partnerID=40&md5=339ca50b8cb5fb344e2c006d0caba611","Storm-scale ensemble Kalman filter (EnKF) studies routinely use methods to accelerate the spinup of convective structures when assimilating convective-scale radar observations. This typically involves adding coherent perturbations into analyses at regular intervals in regions where radar observations indicate convection is ongoing. Significant uncertainty remains as to the most effective use of these perturbations, including appropriate perturbation magnitudes, spatial scales, fields, and smoothing kernels, as well as flexible strategies that can be applied across a spectrum of convective events with negligible a priori tuning. Here, several idealized experiments were performed to elucidate the impact and sensitivity of adding coherent perturbations into storm-scale analyses of convection. Through the use of toy experiments, it is demonstrated that various factors exhibit substantial influence on the postsmoothed perturbation magnitudes, making tuning challenging. Several OSSEs were performed to document the impact of these perturbations on the analyses, particularly thermodynamic analyses within convection. The repeated addition of coherent perturbations produced temperature and moisture biases that are most pronounced in analyses of the surface cold pool and aloft near the tropopause, and eventually lead to biases in the dynamic fields. In an attempt to reduce these biases and make the noise procedure more adaptive, reflectivity innovations were used to restrict the addition of noise to areas where these innovations are large. This produced analyses with reduced thermodynamic biases and RMSE values comparable to the best-performing experiment where the noise magnitudes were manually adjusted. The impact of these findings on previous and future convective-scale EnKF analyses and forecasts are discussed."
"35305397000;35618134000;24332905600;7003705113;57211862504;36629318500;11940634500;7102111067;","Quantifying the impacts of an updated global dimethyl sulfide climatology on cloud microphysics and aerosol radiative forcing",2015,"10.1002/2014JD022687","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927692872&doi=10.1002%2f2014JD022687&partnerID=40&md5=2a5c90f3a46f878336187e1a5eaeb386","One of the critical parameters in assessing the global impacts of dimethyl sulfide (DMS) on cloud properties and the radiation budget is the estimation of phytoplankton-induced ocean emissions, which are derived from prescribed, climatological surface seawater DMS concentrations. The most widely used global ocean DMS climatology was published 15 years ago and has recently been updated using a much larger database of observations. The updated climatology displays significant differences in terms of the global distribution and regional monthly averages of sea surface DMS. In this study, we use the ECHAM5-HAMMOZ aerosol-chemistry-climate general circulation model to quantify the influence of the updated DMS climatology in computed atmospheric properties, namely, the spatial and temporal distributions of atmospheric DMS concentration, sulfuric acid concentration, sulfate aerosols, number of activated aerosols, cloud droplet number concentration, and the aerosol radiative forcing at the top of the atmosphere. Significant differences are observed for all the modeled variables. Comparison with observations of atmospheric DMS and total sulfate also shows that in places with large DMS emissions, the updated climatology shows a better match with the observations. This highlights the importance of using the updated climatology for projecting future impacts of oceanic DMS emissions, especially considering that the relative importance of the natural sulfur fluxes is likely to increase due to legislation to “clean up” anthropogenic emissions. The largest estimated differences are in the Southern Ocean, Indian Ocean, and parts of the Pacific Ocean, where the climatologies differ in seasonal concentrations over large geographical areas. The model results also indicate that the former DMS climatology underestimated the effect of DMS on the globally averaged annual aerosol radiative forcing at the top of the atmosphere by about 20%. © 2015. American Geophysical Union. All Rights Reserved."
"25924727700;23493268700;6603581315;","Precipitation efficiency derived from isotope ratios in water vapor distinguishes dynamical and microphysical influences on subtropical atmospheric constituents",2015,"10.1002/2015JD023403","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944937165&doi=10.1002%2f2015JD023403&partnerID=40&md5=7921091dca5c23e1e7422f571a7aa45a","With water vapor and clouds expected to effect significant feedbacks on climate, moisture transport through convective processes has important implications for future temperature change. The precipitation efficiency—the ratio of the rates at which precipitation and condensation form (e = P/C)—is useful for characterizing how much boundary layer moisture recycles through precipitation versus mixes into the free troposphere through cloud detrainment. Yet it is a difficult metric to constrain with traditional observational techniques. This analysis characterizes the precipitation efficiency of convection near the Big Island of Hawaii, USA, using a novel tracer: isotope ratios in water vapor. The synoptic circulation patterns associated with high and low precipitation efficiency are identified, and the importance of large-scale dynamics and local convective processes in regulating vertical distributions of atmospheric constituents important for climate is evaluated. The results suggest that high e days are correlated with plume-like transport originating from the relatively clean tropics, while low e days are associated with westerly transport, generated by a branching of the jet stream. Differences in transport pathway clearly modify background concentrations of water vapor and other trace gases measured at Mauna Loa Observatory; however, local convective processes appear to regulate aerosols there. Indeed, differences between observed and simulated diurnal cycles of particle number concentration indicate that precipitation scavenges aerosols and possibly facilitates new particle formation when e is high. As measurements of isotope ratios in water vapor expand across the subtropics, the techniques presented here can further our understanding of how synoptic weather, precipitation processes, and climate feedbacks interrelate. © 2015. American Geophysical Union. All Rights Reserved."
"55522498000;14920052300;55802246600;7404815507;16312351300;55375994400;","Parametric sensitivity analysis for the Asian summer monsoon precipitation simulation in the Beijing Climate Center AGCM, version 2.1",2015,"10.1175/JCLI-D-14-00655.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942854183&doi=10.1175%2fJCLI-D-14-00655.1&partnerID=40&md5=c3b8660c5db956288fd1b9094191983e","In this study, the authors apply an efficient sampling approach and conduct a large number of simulations to explore the sensitivity of the simulated Asian summer monsoon (ASM) precipitation, including the climatological state and interannual variability, to eight parameters related to the cloud and precipitation processes in the Beijing Climate Center AGCM, version 2.1 (BCC_AGCM2.1). The results herein show that BCC_AGCM2.1 has large biases in simulating theASMprecipitation. The precipitation efficiency and evaporation coefficient for deep convection are the most sensitive parameters in simulating the ASM precipitation. With optimal parameter values, the simulated precipitation climatology could be remarkably improved, including increased precipitation over the equatorial Indian Ocean, suppressed precipitation over the Philippine Sea, and more realistic mei-yu distribution over eastern China. The ASM precipitation interannual variability is further analyzed, with a focus on the ENSO impacts. It is shown that simulations with betterASM precipitation climatology can also producemore realistic precipitation anomalies during El Niño-decaying summer. In the low-skill experiments for precipitation climatology, the ENSO-induced precipitation anomalies are most significant over continents (vs over ocean in observations) in the South Asian monsoon region. More realistic results are derived from the higher-skill experiments with stronger anomalies over the Indian Ocean and weaker anomalies over India and the western Pacific Ocean, favoring more evident easterly anomalies forced by the tropical Indian Ocean warming and stronger Indian Ocean-western Pacific teleconnection as observed. Themodel results reveal a strong connection between the simulatedASMprecipitation climatological state and interannual variability in BCC_AGCM2.1 when key parameters are perturbed. © 2015 American Meteorological Society."
"7004171611;6506051565;7404209127;55466977400;56516947200;14819069200;7103010852;","Spectral signatures of Earth's climate variability over 5 years from IASI",2015,"10.1175/JCLI-D-14-00431.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922790299&doi=10.1175%2fJCLI-D-14-00431.1&partnerID=40&md5=235330c163ec5261342513be9af26f22","Interannual variability in spectrally resolved longwave radiances is quantified at a variety of spatial scales using 5 yr of IASI observations. Maximum variability is seen at the smallest scales investigated (10° zonal means) at northern and southern high latitudes across the center of the 15-μm CO2 band. As the spatial scale increases, the overall magnitude of interannual variability is reduced across the spectrum and the spectral shape of the variability changes. In spectral regions sensitive to conditions in the upper troposphere, the effect of increasing spatial scale is relatively small and at the global scale these parts of the spectrum show the greatest year-to-year variability. Conversely, the atmospheric window (8-12 μm), which is sensitive to variations in surface temperature and cloud, shows a marked reduction in interannual variability with increasing spatial scale. Over the 5 yr studied, at global scales the standard deviation in annual mean brightness temperature is less than 0.17K across the spectrum, dropping to less than 0.05K across the window. Spectrally integrating the IASI measurements to create pseudobroadband and window channels indicates a variation about the mean that is higher for the broadband channel than for the window channel at the global and quasiglobal scales and over the Southern Hemisphere. These findings are in agreement with observations from CERES Terra over the same period and imply that at the largest spatial scales, over the period considered here, fluctuations in mid- to upper-tropospheric temperatures and water vapor, and not cloud or surface temperature, play the dominant role in determining the level of interannual variability in all-sky outgoing longwave radiation. © 2015 American Meteorological Society."
"36020971200;","MODIS Terra Collection 6 fractional snow cover validation in mountainous terrain during spring snowmelt using Landsat TM and ETM+",2015,"10.1002/hyp.10134","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892750705&doi=10.1002%2fhyp.10134&partnerID=40&md5=42ac0631a5d66138f68d9e17a66dea24","Daily swath MODIS Terra Collection 6 fractional snow cover (MOD10_L2) estimates were validated with two-day Landsat TM/ETM + snow-covered area estimates across central Idaho and southwestern Montana, USA. Snow cover maps during spring snowmelt for 2000, 2001, 2002, 2003, 2005, 2007, and 2009 were compared between MODIS Terra and Landsat TM/ETM + using least-squared regression. Strong spatial and temporal map agreement was found between MODIS Terra fractional snow cover and Landsat TM/ETM + snow-covered area, although map disagreement was observed for two validation dates. High-altitude cirrus cloud contamination during low snow conditions as well as late season transient snowfall resulted in map disagreement. MODIS Terra's spatial resolution limits retrieval of thin-patchy snow cover, especially during partially cloudy conditions. Landsat's image acquisition frequency can introduce difficulty when discriminating between transient and resident mountain snow cover. Furthermore, transient snowfall later in the snowmelt season, which is a stochastic accumulation event that does not usually persist beyond the daily timescale, will skew decadal snow-covered area variability if bi-monthly climate data record development is the objective. As a quality control step, ground-based daily snow telemetry snow-water-equivalent measurements can be used to verify transient snowfall events. Users of daily MODIS Terra fractional snow products should be aware that local solar illumination and sensor viewing geometry might influence fractional snow cover estimation in mountainous terrain. Cross-sensor interoperability has been confirmed between MODIS Terra and Landsat TM/ETM + when mapping snow from the visible/infrared spectrum. This relationship is strong and supports operational multi-sensor snow cover mapping, specifically climate data record development to expand cryosphere, climate, and hydrological science applications. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd."
"36992744000;8866821900;6701431208;13406399300;","Global radiative-convective equilibrium in the community atmosphere model, version 5",2015,"10.1175/JAS-D-14-0268.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943780744&doi=10.1175%2fJAS-D-14-0268.1&partnerID=40&md5=b1caebeeb1da43b155080226d51adf78","In the continued effort to understand the climate system and improve its representation in atmospheric general circulation models (AGCMs), it is crucial to develop reduced-complexity frameworks to evaluate these models. This is especially true as the AGCM community advances toward high horizontal resolutions (i.e., grid spacing less than 50 km), which will require interpreting and improving the performance of many model components.A simplified global radiative-convective equilibrium (RCE) configuration is proposed to explore the implication of horizontal resolution on equilibrium climate. RCE is the statistical equilibrium in which the radiative cooling of the atmosphere is balanced by heating due to convection. In this work, the Community Atmosphere Model, version 5 (CAM5), is configured in RCE to better understand tropical climate and extremes. The RCE setup consists of an ocean-covered Earth with diurnally varying, spatially uniform insolation and no rotation effects. CAM5 is run at two horizontal resolutions: a standard resolution of approximately 100-km grid spacing and a high resolution of approximately 25-km spacing. Surface temperature effects are considered by comparing simulations using fixed, uniform sea surface temperature with simulations using an interactive slab-ocean model. The various CAM5 configurations provide useful insights into the simulation of tropical climate as well as the model's ability to simulate extreme precipitation events. In particular, the manner in which convection organizes is shown to be dependent on model resolution and the surface configuration (including surface temperature), as evident by differences in cloud structure, circulation, and precipitation intensity. © 2015 American Meteorological Society."
"24074386100;57204297539;7404441387;6701623059;57202245193;7102707599;6603760227;7201903057;15319527800;36679171400;7004154240;55680480300;57203378018;7801678853;","Climate drivers linked to changing seasonality of Alaska Coastal tundra vegetation productivity",2015,"10.1175/EI-D-15-0013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949895066&doi=10.1175%2fEI-D-15-0013.1&partnerID=40&md5=8d85e49f05d8e7714a2d04d789abf5d8","The mechanisms driving trends and variability of the normalized difference vegetation index (NDVI) for tundra in Alaska along the Beaufort, east Chukchi, and east Bering Seas for 1982–2013 are evaluated in the context of remote sensing, reanalysis, and meteorological station data as well as regional modeling. Over the entire season the tundra vegetation continues to green; however, biweekly NDVI has declined during the early part of the growing season in all of the Alaskan tundra domains. These springtime declines coincide with increased snow depth in spring documented in northern Alaska. The tundra region generally has warmed over the summer but intraseasonal analysis shows a decline in midsummer land surface temperatures. The midsummer cooling is consistent with recent large-scale circulation changes characterized by lower sea level pressures, which favor increased cloud cover. In northern Alaska, the sea-breeze circulation is strengthened with an increase in atmospheric moisture/cloudiness inland when the land surface is warmed in a regional model, suggesting the potential for increased vegetation to feedback onto the atmospheric circulation that could reduce midsummer temperatures. This study shows that both large- and local-scale climate drivers likely play a role in the observed seasonality of NDVI trends. © 2015."
"56875115500;7404476158;56063950500;8308418400;","Interannual variations in growing-season NDVI and its correlation with climate variables in the southwestern karst region of China",2015,"10.3390/rs70911105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942540737&doi=10.3390%2frs70911105&partnerID=40&md5=d0c13ce2814711ded208767ef89528b4","In this study, the updated Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) dataset for growing season (April to October), which can better reflect the vegetation vigor, was used to investigate the interannual variations in NDVI and its relationship with climatic factors, in order to preliminarily understand the climate impact on vegetation and provide theoretical basis for the response of ecosystem to climate change. Multivariate linear regression models, including the Ordinary Least Squares (OLS) and Geographically Weighted Regression (GWR), were adopted to analyze the correlation between NDVI and climatic factors (temperature and precipitation) together. Average growing-season NDVI significantly increased at a rate of 0.0015/year from 1982 to 2013, larger than several regions in China. On the whole, its relationship with temperature is positive and also stronger than precipitation, which indicated that temperature may be a limiting factor for the vegetation growth in the Karst region. Moreover, the correlation coefficients between grassland NDVI and climatic factors are the largest. Under the background of NDVI increasing trend from 1982 to 2013, the period of 2009-2012 was chosen to investigate the influencing factors of a sharp decline in NDVI. It can be found that the reduced temperature and solar radiation, caused by the increase in cloud cover and precipitation, may play important roles in the vegetation cover change. All in all, the systematic research on the interannual variations of growing-season NDVI and its relationship with climate revealed the heterogeneity and variability in the complicated climate change in the Karst ecosystem for the study area. It is the Karst characteristics that hinder obtaining more representative conclusions and tendencies in this region. Hence, more attention should be paid to promoting Karst research in the future. © 2015 by the authors."
"56135632400;8953662800;55574865800;55805773500;26661481400;57203386948;56722821200;","CALIPSO inferred most probable heights of global dust and smoke layers",2015,"10.1002/2014JD022898","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932198817&doi=10.1002%2f2014JD022898&partnerID=40&md5=d4fecaa130169235db17fc617bbb7257","The vertical location of aerosol layers is critical for determining predominance of aerosol radiative and microphysical effects in aerosol-cloud-precipitation-climate interaction. The spaceborne lidar system, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), provides an unprecedented opportunity to observe vertical distributions of global aerosol layers. In this study we examine the most probable height (MPH) of dust and smoke layers, which are calculated either fromaerosol occurrence frequency (OF) in vertical feature mask or aerosol extinction profile. The study focuses on six high-aerosol-loading regions where aerosols are of great interest in a range of scientific topics: Saharan Air Layer (SAL) over Tropical Atlantic, West African Monsoon region (WAM), Southeast Atlantic Ocean (SAO), Southeast Asia (SEA) and South China Sea, Amazon (AMZ), and Northwestern Pacific (NWP). The analysis revealed interesting spatial and seasonal variability of different vertical mixture features over these regions: seasonal migration of dust layers over SAL, separation andmixture of dust and smoke layers overWAM and NWP, and smoke layer above clouds over SAO, SEA, and AMZ. Results also indicated that the OF-based MPH tends to be much higher than the aerosol optical depth (AOD)-basedMPH, owing to the predominating near-surface sources. Within the same vertical resolution grid of CALIPSO, aerosols are found with higher OF at higher levels but AOD tends to increase toward lower levels, because most aerosol sources are near the surface and the aerosol layers transported to high altitudes are generally much more diluted over larger spatial domain than those near the surface. © 2015. American Geophysical Union. All rights reserved."
"8846887600;56655654500;7004060399;","How well do the CMIP5 models simulate the antarctic atmospheric energy budget?",2015,"10.1175/JCLI-D-15-0027.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947552066&doi=10.1175%2fJCLI-D-15-0027.1&partnerID=40&md5=a838f731b2c626cb2bde0970a6bb4bf1","The authors evaluate 23 coupled atmosphere-ocean general circulation models from phase 5 of CMIP (CMIP5) in terms of their ability to simulate the observed climatological mean energy budget of the Antarctic atmosphere. While the models are shown to capture the gross features of the energy budget well [e.g., the observed two-way balance between the top-of-atmosphere (TOA) net radiation and horizontal convergence of atmospheric energy transport], the simulated TOA absorbed shortwave (SW) radiation is too large during austral summer. In the multimodel mean, this excessive absorption reaches approximately 10 W m-2, with even larger biases (up to 25-30 W m-2) in individual models. Previous studies have identified similar climate model biases in the TOA net SW radiation at Southern Hemisphere midlatitudes and have attributed these biases to errors in the simulated cloud cover. Over the Antarctic, though, model cloud errors are of secondary importance, and biases in the simulated TOA net SW flux are instead driven mainly by biases in the clear-sky SW reflection. The latter are likely related in part to the models' underestimation of the observed annual minimum in Antarctic sea ice extent, thus underscoring the importance of sea ice in the Antarctic energy budget. Finally, substantial differences in the climatological surface energy fluxes between existing observational datasets preclude any meaningful assessment of model skill in simulating these fluxes. © 2015 American Meteorological Society."
"12242677000;26643440200;","Intercomparison of independent calibration techniques applied to the visible channel of the ISCCP B1 data",2015,"10.1175/JTECH-D-14-00040.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942523342&doi=10.1175%2fJTECH-D-14-00040.1&partnerID=40&md5=4aec247c8a62207f389235062ccc3ba5","The International Satellite Cloud Climatology Project (ISCCP) B1 data, which were recently rescued at the National Oceanic and Atmospheric Administration's National Climatic Data Center (NOAA/NCDC), are a resource for the study of the earth's climate. The ISCCP B1 data represent geostationary satellite imagery for all channels, including the infrared (IR), visible, and IR water vapor sensors. These are global 3-hourly snapshots from satellites around the world, covering the time period from 1979 to present at approximately 10-km spatial resolution. ISCCP B1 data will be used in the reprocessing of the cloud products, resulting in a higher-resolution ISCCP cloud climatology, surface radiation budget (SRB), etc. To realize the promise of a higher-resolution cloud climatology from the B1 data, an independent assessment of the calibration of the visible band was performed. The present study aims to accomplish this by cross-calibrating with the intercalibrated Advanced Very High Resolution Radiometer (AVHRR) reflectance data from the AVHRR Pathfinder Atmospheres-Extended (PATMOS-x) dataset. Since the reflectance calibration approach followed in the PATMOS-x dataset is radiometrically tied to the absolute calibration of the National Aeronautics and Space Administration's (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) imager instrument, the present intercalibration scheme yields calibration coefficients consistent with MODIS. Results from this study show that the two independent sets (this study and the ISCCP) of results agree to within their mutual uncertainties. An independent approach to calibration based on multiyear observations over spatially and temporally invariant desert sites has also been used for validation. Results reveal that for most of the geostationary satellites, the mean differencewith ISCCP calibration is less than 3%with the randomerrors under2%.Another result is that this extends the intercalibrated record to beyond what ISCCP provides (prior to 1983 and beyond 2009). © 2015 American Meteorological Society."
"57217109580;7402866430;57191294058;7102006474;55915387400;","Dust aerosol feedback on the Indian summer monsoon: Sensitivity to absorption property",2015,"10.1002/2015JD023589","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944937879&doi=10.1002%2f2015JD023589&partnerID=40&md5=922725d8b1d0867d027811bebb3d3c80","We examine the sensitivity of dust radiative feedback to the dust absorption property during the Indian summer monsoon (June-September) season from 2005 to 2010 using the Regional Climate Model version 4.1. The dust direct radiative forcing at top of atmosphere switches from cooling to warming for absorbing dust over the Indian subcontinent. The dust-induced low pressure anomaly plays a crucial role in building up large-scale convergence particularly over the Arabian Peninsula, which strengthens the monsoon circulation leading to enhanced precipitation over India. The intensity of precipitation and wind field at 850 hPa increases over India by considering more absorbing dust. Air temperature and cloud fraction change by 20-50% in the lower to middle troposphere as a result of dynamic response due to modification in dust absorptive characteristics. Our results demonstrate that the response of monsoon circulation to dust radiative feedback is highly sensitive to dust absorption; and hence, it should be accurately represented in the models for improved simulation of monsoon precipitation. The results have important implications in case of break-to-active transition within the Indian summer monsoon season. © 2015. American Geophysical Union. All Rights Reserved."
"56604618200;6701511321;55505135400;7403263977;","Simulation of polar ozone depletion: An update",2015,"10.1002/2015JD023365","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940461707&doi=10.1002%2f2015JD023365&partnerID=40&md5=843acecd2a442e5e2724fc96a177f247","We evaluate polar ozone depletion chemistry using the specified dynamics version of the Whole Atmosphere Community Climate Model for the year 2011. We find that total ozone depletion in both hemispheres is dependent on cold temperatures (below 192 K) and associated heterogeneous chemistry on polar stratospheric cloud particles. Reactions limited to warmer temperatures above 192 K, or on binary liquid aerosols, yield little modeled polar ozone depletion in either hemisphere. An imposed factor of three enhancement in stratospheric sulfate increases ozone loss by up to 20 Dobson unit (DU) in the Antarctic and 15 DU in the Arctic in this model. Such enhanced sulfate loads are similar to those observed following recent relatively small volcanic eruptions since 2005 and imply impacts on the search for polar ozone recovery. Ozone losses are strongly sensitive to temperature, with a test case cooler by 2 K producing as much as 30 DU additional ozone loss in the Antarctic and 40 DU in the Arctic. A new finding of this paper is the use of the temporal behavior and variability of ClONO2 and HCl as indicators of the efficacy of heterogeneous chemistry. Transport of ClONO2 from the southern subpolar regions near 55-65°S to higher latitudes near 65-75°S provides a flux of NOx from more sunlit latitudes to the edge of the vortex and is important for ozone loss in this model. Comparisons between modeled and observed total column and profile ozone perturbations, ClONO2 abundances, and the rate of change of HCl bolster confidence in these conclusions. © 2015. American Geophysical Union. All Rights Reserved."
"55795506000;56996271000;7102953444;","Impact of geolocations of validation data on the evaluation of surface incident shortwave radiation from earth system models",2015,"10.1002/2014JD022572","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939266129&doi=10.1002%2f2014JD022572&partnerID=40&md5=85b94e10265497494c7641a587c438ef","Ground-based observations of surface incident solar radiation (Rs) have been used to evaluate simulations of global climate models. Existing studies have shown that biases in simulated clouds have a significant spatial pattern, which may be transferred to the simulated Rs. Therefore, the evaluation results of Rs simulations may depend on the locations of the ground-based observations. In this study, Rs simulations of 48 models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) were first evaluated with ground-based observations from different networks (446 stations in total) from 2000 to 2005. The global mean biases of the CMIP5 Rs simulations were found to vary from 4.8 to 11.9Wm-2 when Rs observations from different networks were used as reference data. To reduce the location impact on the evaluation results, CMIP5 simulated Rs was then evaluated with the latest satellite Rs retrieval at 1° × 1° spatial resolution by the Clouds and the Earth’s Radiant Energy System, Energy Balanced and Filled (CERES EBAF). It was found that the CMIP5 simulated multimodel mean Rs has a small bias of 2.6Wm-2 compared with CERES EBAF over the globe, 4.7Wm-2 and 1.7Wm-2 over land and oceans, respectively. CERES EBAF Rs was found to have a positive bias of 1.3Wm-2 compared with ground-based observations. After removing this bias of CERES EBAF Rs, global mean Rs was estimated to be 185Wm-2. © 2015. The Authors."
"56521954400;55703823500;7401919308;37022493200;56044343900;","Atmospheric responses to oceanic eddies in the Kuroshio Extension region",2015,"10.1002/2014JD022930","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938202550&doi=10.1002%2f2014JD022930&partnerID=40&md5=46efda70192d9459d24420b6b6470c47","We examined atmospheric responses to 35,000+ oceanic eddies in the Kuroshio Extension region during the period of 2006-2009. Using satellite data, we showed that cold (warm) eddies cause surface winds to decelerate (accelerate) and reduce (increase) latent and sensible heat fluxes, cloud liquid water, water vapor content, and rain rate; all of these changes are quantified. Both the linear correlation between wind divergence and downwind sea surface temperature (SST) gradient and the correspondence between vorticity and crosswind SST gradient support the vertical momentum mixing mechanism, which indicates that SST perturbations modify surface winds by changing the vertical turbulent mixing in the marine atmospheric boundary layer (MABL). High-resolution National Centers for Environmental Prediction Climate Forecast System Reanalysis (CFSR) data can reproduce the atmospheric responses to the oceanic eddies in the MABL albeit with some differences in intensity. In addition, the CFSR data reveal that the atmospheric responses to these oceanic eddies are not confined in the MABL. MABL deepens (shoals) over the warm (cold) eddies; enhanced (reduced) vertical transport of transient zonal momentum occurs over the warm (cold) eddies from the sea surface to about 850 hPa level; vertical velocity anomalies over oceanic eddies penetrate beyond the MABL into free atmosphere; there exists a positive correlated relationship between SST and convective rain rate anomalies, indicative of ocean eddies’ impact on the free troposphere. However, the composites of cloud liquid water and rain rate are different from the results based on the satellite data. © 2015. American Geophysical Union. All Rights Reserved."
"57213268296;55068709500;57092782300;6701581547;","Spatial patterns of climatological temperature lapse rate in mainland China: A multi-time scale investigation",2015,"10.1002/2014JD022978","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928591781&doi=10.1002%2f2014JD022978&partnerID=40&md5=3d049f1719218a5bbb146ce727d5c40f","Quantitative evaluation of how mountain ecosystems respond to climate change requires accurate estimates of temperature at high elevations. One approach to estimating highland temperature is to extrapolate temperatures from low elevations based on previous observations of the environmental temperature lapse rate (γlocal). However, our understanding of γlocal is still very limited. Here we use daily mean, maximum, and minimum temperature (Tmean, Tmax, and Tmin) data from 523 meteorological stations in mainland China to estimate the spatiotemporal patterns of the climatological γlocal (γlocal(Tmean), γlocal(Tmax), and γlocal(Tmin)). The patterns of all γlocal display (1) a significant (P&lt;0.05) spatial difference between southern China (4 to 6 K km-1) and northern China (including the Qinghai-Tibetan Plateau, &gt;6Kkm-1) and (2) a distinct seasonal variation, with higher γlocal occurring in summer and lower in winter (except for the Qinghai-Tibetan Plateau where the seasonality is reversed). In addition, the seasonal amplitude of γlocal(Tmax) exceeds that of γlocal(Tmin). Physically, γlocal(Tmax) is significantly influenced by cloud cover (partial correlation coefficients: R =-0.25, P&lt;0.001) and regulated by precipitation, with γlocal (Tmax) increasing with Tmax in humid regions while decreasing in drier regions. At night, the spatial pattern of γlocal (Tmin) is determined by Tmin (R =-0.51, P&lt;0.001) due to temperature control on the saturated adiabatic lapse rate. Our results demonstrate that the magnitude of γlocal obviously differs in regional distributions and seasonal variations and may be a result of the interactions among the climatic factors. To improve the accuracy of the extrapolation method requires spatial patterns of γlocal rather than just a constant universal value. © 2015. American Geophysical Union. All Rights Reserved."
"25625606300;6603463220;","Sequence-based mapping approach to spatio-temporal snow patterns from MODIS time-series applied to Scotland",2015,"10.1016/j.jag.2014.08.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920647956&doi=10.1016%2fj.jag.2014.08.005&partnerID=40&md5=53a799e831797dc2abbaccc903fc7306","Snow cover and its monitoring are important because of the impact on important environmental variables, hydrological circulation and ecosystem services. For regional snow cover mapping and monitoring, the MODIS satellite sensors are particularly appealing. However cloud presence is an important limiting factor. This study addressed the problem of cloud cover for time-series in a boreal-Atlantic region where melting and recovering of snow often do not follow the usual alpine-like patterns. A key requirement in this context was to apply improved methods to deal with the high cloud cover and the irregular spatio-temporal snow occurrence, through exploitation of space-time correlation of pixel values. The information contained in snow presence sequences was then used to derive summary indices to describe the time series patterns. Finally it was tested whether the derived indices can be considered an accurate summary of the snow presence data by establishing and evaluating their statistical relations with mor-phology and the landscape. The proposed cloud filling method had a good agreement (between 80 and 99%) with validation data even with a large number of pixels missing. The sequence analysis algorithm proposed takes into account the position of the states to fully consider the temporal dimension, i.e. the order in which a certain state appears in an image sequence compared to its neighbourhoods. The indices that were derived from the sequence of snow presence proved useful for describing the general spatio-temporal patterns of snow in Scotland as they were well related (more than 60% of explained deviance)with environmental information such as morphology supporting their use as a summary of snow patterns over time. The use of the derived indices is an advantage because of data reduction, easier interpretability and capture of sequence position-wise information (e.g. importance of short term fall/melt cycles). The derived seven clusters took into account the temporal patterns of the snow presence and they were well separated both spatially and according to the snow patterns and the environmental information. In conclusion, the use of sequences proved useful for analysing different spatio-temporal patterns of snow that could be related to other environmental information to characterize snow regimes regions in Scot-land and to be integrated with ground measures for further hydrological and climatological analysis as baseline data for climate change models. © 2014 Elsevier B.V."
"7006729638;","Passive suppression of South African rainfall by the Agulhas Current",2015,"10.1175/EI-D-15-0017.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947125048&doi=10.1175%2fEI-D-15-0017.1&partnerID=40&md5=f101a2dc604ed21094e085e680c5b867","This study reconsiders the role of the Agulhas Current in South African climate variability. Here, the Agulhas Current is delimited by its anticyclonic looping flow and cluster analysis of detrended SST anomalies that lead to an area 28°–37°S, 18°–35°E, poleward of South Africa. Regression of detrended Agulhas SST with rainfall anomaly fields in the years 1950–2012 yields a surprising negative influence over the interior. In summer, the negative regression exhibits a northwest axis consistent with reduced cloud band activity. Positive influence is confined to the eastern escarpment in the September–November season when cutoff lows are prevalent. The overall negative influence of the Agulhas SST is confirmed by regression with the vegetation fraction and latent heat flux in the satellite era. Mechanisms of South African rainfall suppression were investigated. The Agulhas SST index is positively related to the multivariate ENSO index at the 1–3-month lead time. Hence, warm years in the Agulhas Current follow Pacific El Niño. Composite ocean analysis shows enhanced westerly winds offshore and a westward extension of warm salty water from the anticyclonic south Indian Ocean gyre. Composite atmospheric analysis exhibits moist uplifted air over the Agulhas Current folding into an equatorward circulation that sinks over the interior plateau. Because Agulhas SST partially follows ENSO, its suppression of interior rainfall is concluded to be passive. © 2015."
"36179077700;15765007300;56900961900;7406243250;","Effects of localized grid refinement on the general circulation and climatology in the community atmosphere model",2015,"10.1175/JCLI-D-14-00599.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944088518&doi=10.1175%2fJCLI-D-14-00599.1&partnerID=40&md5=9c453b2ad6c8787ce41d8d0473a9552d","Using the spectral element (SE) dynamical core within the National Center for Atmospheric Research-Department of Energy Community Atmosphere Model (CAM), a regionally refined nest at 0.25° (~28 km) horizontal resolution located over the North Atlantic is embedded within a global 1° (~111 km) grid. A 23-yr simulation using Atmospheric Model Intercomparison Project (AMIP) protocols and default CAM, version 5, physics is compared to an identically forced run using the global 1° (~111 km) grid without refinement. The addition of a refined patch over the Atlantic basin does not noticeably affect the global circulation. In the area where the refinement is located, large-scale precipitation increases with the higher resolution. This increase is partly offset by a decrease in precipitation resulting from convective parameterizations, although total precipitation is also slightly higher at finer resolutions. Equatorial waves are not significantly impacted when traversing multiple grid spacings. Despite the grid transition region bisecting northern Africa, local zonal jets and African easterly wave activity are highly similar in both simulations. The frequency of extreme precipitation events increases with resolution, although this increase is restricted to the refined patch. Topography is better resolved in the nest as a result of finer grid spacing. The spatial patterns of variables with strong orographic forcing (such as precipitation, cloud, and precipitable water) are improved with local refinement. Additionally, dynamical features, such as wind patterns, associated with steep terrain are improved in the variable-resolution simulation when compared to the uniform coarser run. © 2015 American Meteorological Society."
"24485218400;7003278104;16445293700;7003582587;22134875500;6507112497;57203043665;12761291000;35605362100;6507017020;36876405100;55622148300;54398596200;57204886915;6506423324;7402820442;22635190100;25924499900;6601992858;7103116704;6603561402;7201839229;53871956100;16246205000;16029674800;56098638700;7501760109;7404815507;57203012011;6602178158;55738957800;55717881500;","Vertical structure and physical processes of the madden-julian oscillation: Exploring key model physics in climate simulations",2015,"10.1002/2014JD022375","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932193909&doi=10.1002%2f2014JD022375&partnerID=40&md5=5202b558b542dd51264cb19ab936aa8c","Aimed at reducing deficiencies in representing the Madden-Julian oscillation (MJO) in general circulation models (GCMs), a global model evaluation project on vertical structure and physical processes of the MJO was coordinated. In this paper, results from the climate simulation component of this project are reported. It is shown that the MJO remains a great challenge in these latest generation GCMs. The systematic eastward propagation of the MJO is only well simulated in about one fourth of the total participating models. The observed vertical westward tilt with altitude of the MJO is well simulated in good MJO models but not in the poor ones. Damped Kelvin wave responses to the east of convection in the lower troposphere could be responsible for the missing MJO preconditioning process in these poor MJO models. Several process-oriented diagnostics were conducted to discriminate key processes for realistic MJO simulations. While large-scale rainfall partition and low-level mean zonal winds over the Indo-Pacific in a model are not found to be closely associated with its MJO skill, two metrics, including the low-level relative humidity difference between high- and low-rain events and seasonal mean gross moist stability, exhibit statistically significant correlations with the MJO performance. It is further indicated that increased cloud-radiative feedback tends to be associated with reduced amplitude of intraseasonal variability, which is incompatible with the radiative instability theory previously proposed for the MJO. Results in this study confirm that inclusion of air-sea interaction can lead to significant improvement in simulating the MJO. © 2015. The Authors."
"16834715500;7103201242;7102609908;24451351900;12144461400;15726586900;","Observation of moisture tendencies related to shallow convection",2015,"10.1175/JAS-D-14-0042.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923106975&doi=10.1175%2fJAS-D-14-0042.1&partnerID=40&md5=c74c5e6d9c819b8893b38e652078e928","Tropospheric moisture is a key factor controlling the global climate and its variability. For instance, moistening of the lower troposphere is necessary to trigger the convective phase of a Madden-Julian oscillation (MJO). However, the relative importance of the processes controlling this moistening has yet to be quantified. Among these processes, the importance of themoistening by shallowconvection is still debated. The authors use high-frequency observations of humidity and convection fromthe Research Vessel (R/V) Mirai that was located in the Indian Ocean ITCZ during the Cooperative Indian Ocean Experiment on Intraseasonal Variability/Dynamics of the MJO (CINDY/DYNAMO) campaign. This study is an initial attempt to directly link shallow convection to moisture variations within the lowest 4km of the atmosphere from the convective scale to the mesoscale.Within a few tens of minutes and near shallow convection occurrences, moisture anomalies of 0.25-0.5g kg-1 that correspond to tendencies on the order of 10-20 g kg-1 day-1 between 1 and 4km are observed and are attributed to shallow convective clouds. On the scale of a few hours, shallow convection is associated with anomalies of 0.5-1 g kg-1 that correspond to tendencies on the order of 1-4 g kg-1 day-1 according to two independent datasets: lidar and soundings. This can be interpreted as the resultant mesoscale effect of the population of shallow convective clouds. Large-scale advective tendencies can be stronger than the moistening by shallow convection; however, the latter is a steady moisture supply whose importance can increase with the time scale. This evaluation of the moistening tendency related to shallow convection is ultimately important to develop and constrain numerical models. © 2015 American Meteorological Society."
"7004239939;7404577357;","Updated PMC trends derived from SBUV data",2015,"10.1002/2014JD022253","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925670391&doi=10.1002%2f2014JD022253&partnerID=40&md5=a441225ab1eb328b5af0f40add6a1035","Previous analysis of polar mesospheric clouds (PMCs) observed by Solar Backscatter Ultraviolet (SBUV) instruments found that long-term variations in PMC brightness and occurrence frequency were anticorrelated with solar activity and that an increasing secular trend was present at most latitudes. In this paper, long-term PMC variations are presented in terms of ice water content (IWC), a physically based variable which is easier to interpret than previously reported UV albedo values. This model-based conversion from albedo to IWC removes most scattering angle effects. The derived long-term PMC variations in the SBUV data set are qualitatively the same using either an empirically derived adjustment for local time effects or no adjustment (i.e., assuming cancelation of interannual variations in tidally induced amplitude and/or phase). When we use stratospheric ozone variations as a proxy for mesospheric temperature changes, as suggested by recent model studies, we can explain more of the long-term IWC variability than if we use a linear trend. These results show that PMC ice water content in bright clouds increased rapidly from 1979 through the late 1990s and has been approximately constant fromthe late 1990s through 2013. The numerical value and sign of this trend during the last 15 years depend on the choice of end points and latitude band. Simultaneously, the solar response of IWC observed by SBUV has weakened during the most recent cycle in the Northern Hemisphere, but increased in the Southern Hemisphere. © 2015. American Geophysical Union. All Rights Reserved."
"51061006300;57213743966;55271575700;","On the capabilities and limitations of GCCM simulations of summertime regional air quality: A diagnostic analysis of ozone and temperature simulations in the US using CESM CAM-Chem",2015,"10.1016/j.atmosenv.2014.11.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922947204&doi=10.1016%2fj.atmosenv.2014.11.001&partnerID=40&md5=489835a10dd5eee34f42f0251d6773a9","We conduct a diagnostic analysis of ozone chemistry simulated by four different configurations of a Global Climate-Chemistry Model (GCCM), the Community Earth System Model (CESM) with detailed tropospheric chemistry. The purpose of this study is to evaluate the ability of GCCMs to simulate future ozone chemistry by evaluating their ability to simulate present-day chemistry. To address this we chose four configurations of the CESM that differ in their meteorology (analyzed versus simulated meteorological fields), number of vertical levels, and the coupling of the ice and ocean models. We apply mixed model statistics to evaluate these different configurations against CASTNET ozone observations within different regions of the US by using various performance metrics relevant to evaluating future ozone changes. These include: mean biases and interannual variability, the ozone response to emission changes, the ozone response to temperature changes and ozone extreme values. Using these metrics, we find that although the configuration using analyzed meteorology best simulates temperatures it does not outperform a configuration with simulated meteorology in other metrics. All configurations are unable to capture observed ozone decreases and the ozone north-south gradient over the eastern US during 1995-2005. We find that the configuration with simulated meteorology with 56 vertical levels is markedly better in capturing observed ozone-temperature relationships and extreme values than a configuration that is identical except that it contains 26 vertical levels. We recommend caution in the use of GCCMs in simulating surface chemistry as differences in a variety of model parameters have a significant impact on the resulting chemical and climate variables. Isoprene emissions depend strongly on surface temperature and the resulting ozone chemistry is dependent on isoprene emissions but also on cloud cover, photolysis, the number of vertical levels, and the choice of meteorology. These dependencies must be accounted for in the interpretation of GCCM results. © 2014."
"55802246600;12240491800;7005007661;8570871900;7402933297;22635042200;55688930000;8870579400;7401491382;36657850900;","Light-absorbing particles in snow and ice: Measurement and modeling of climatic and hydrological impact",2015,"10.1007/s00376-014-0010-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913536012&doi=10.1007%2fs00376-014-0010-0&partnerID=40&md5=cf9e64573dd03257fb734b1accc27197","Light absorbing particles (LAP, e.g., black carbon, brown carbon, and dust) influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance (a.k.a., surface darkening), which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice (LAPSI) has been identified as one of major forcings affecting climate change, e.g. in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this review paper, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the mass concentrations, albedo reduction, radiative forcing, and climatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle. © 2015, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"7201920350;55352172500;57199068971;7401796996;55615078100;47962453900;20434940900;56067551900;16426559500;56924084300;56923937200;55352411500;55352577600;56037559900;57207212444;56924767100;56439778100;55392517600;","The mesoscale heavy rainfall observing system (MHROS) over the middle region of the Yangtze river in China",2015,"10.1002/2015JD023341","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945246951&doi=10.1002%2f2015JD023341&partnerID=40&md5=9753a24e445413961e69dd3049f57c25","The Mesoscale Heavy Rainfall Observing System (MHROS), supported by the Institute of Heavy Rain (IHR), Chinese Meteorology Administration, is one of the major systems to observe mesoscale convective systems (MCSs) over the middle region of the Yangtze River in China. The IHR MHROS consists of mobile C-POL and X-POL precipitation radars, millimeter wavelength cloud radar, fixed S-band precipitation radars, GPS network, microwave radiometers, radio soundings, wind profiler radars, and disdrometers. The atmospheric variables observed or retrieved by these instruments include the profiles of atmospheric temperature, moisture, wind speed and direction, vertical structures of MCS clouds and precipitation, atmospheric water vapor, and cloud liquid water. These quality-controlled observations and retrievals have been used in mesoscale numerical weather prediction to improve the accuracy of weather forecasting and MCS research since 2007. These long-term observations have provided the most comprehensive data sets for researchers to investigate the formation-dissipation processes of MCSs and for modelers to improve their simulations of MCSs. As the first paper of a series, we briefly introduce the IHR MHROS and describe the specifications of its major instruments. Then, we provide an integrative analysis of the IHR MHROS observations for a heavy rain case on 3-5 July 2014 as well as the application of IHR MHROS observations in improving the model simulations. In a series of papers, we will tentatively answer several key scientific questions related to the MCS and Meiyu frontal systems over the middle region of the Yangtze River using the IHR MHROS observations. © 2015. American Geophysical Union. All Rights Reserved."
"57200702127;7404829395;56537463000;","Atmospheric responses to the redistribution of anthropogenic aerosols",2015,"10.1002/2015JD023665","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944907910&doi=10.1002%2f2015JD023665&partnerID=40&md5=142ca91428058514e0f36b51d7b4bf3f","The geographical shift of global anthropogenic aerosols fromthe developed countries to the Asian continent since the 1980s could potentially perturb the regional and global climate due to aerosol-cloud-radiation interactions. We use an atmospheric general circulation model with different aerosol scenarios to investigate the radiative and microphysical effects of anthropogenic aerosols from different regions on the radiation budget, precipitation, and large-scale circulations. An experiment contrasting anthropogenic aerosol scenarios in 1970 and 2010 shows that the altered cloud reflectivity and solar extinction by aerosols results in regional surface temperature cooling in East and South Asia, and warming in the US and Europe, respectively. These aerosol-induced temperature changes are consistent with the relative temperature trends from 1980 to 2010 over different regions in the reanalysis data. A reduced meridional streamfunction and zonal winds over the tropics as well as a poleward shift of the jet stream suggest weakened and expanded tropical circulations, which are induced by the redistributed aerosols through a relaxing of the meridional temperature gradient. Consequently, precipitation is suppressed in the deep tropics and enhanced in the subtropics. Our assessments of the aerosol effects over the different regions suggest that the increasing Asian pollution accounts for the weakening of the tropics circulation, while the decreasing pollution in Europe and US tends to shift the circulation systems southward. Moreover, the aerosol indirect forcing is predominant over the total aerosol forcing in magnitude, while aerosol radiative and microphysical effects jointly shape the meridional energy distributions and modulate the circulation systems. © 2015. American Geophysical Union. All Rights Reserved."
"7003704096;55361310000;57213414254;7005453346;","Multiple regimes of wind, stratification, and turbulence in the stable boundary layer",2015,"10.1175/JAS-D-14-0311.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943393566&doi=10.1175%2fJAS-D-14-0311.1&partnerID=40&md5=8fe4605b14d32a6af16ae01611c73775","A long time series of temporally high-resolution wind and potential temperature data from the 213-m tower at Cabauw in the Netherlands demonstrates the existence of two distinct regimes of the stably stratified nocturnal boundary layer at this location. Hidden Markov model (HMM) analysis is used to objectively characterize these regimes and classify individual observed states. The first regime is characterized by strongly stable stratification, large wind speed differences between 10 and 200 m, and relatively weak turbulence. The second is associated with near-neutral stratification, weaker wind speed differences between 10 and 200 m, and relatively strong turbulence. In this second regime, the state of the boundary layer is similar to that during the day. The occupation statistics of these regimes are shown to covary with the large-scale pressure gradient force and cloud cover such that the first regime predominates under clear skies with weak geostrophic wind speed and the second regime predominates under conditions of extensive cloud cover or large geostrophic wind speed. These regimes are not distinguished by standard measures of stability, such as the Obukhov length or the bulk Richardson number. Evidence is presented that the mechanism generating these distinct regimes is associated with a previously documented feedback resulting from the existence of an upper limit on the maximum downward heat flux that can be sustained for a given near-surface wind speed. © 2015 American Meteorological Society."
"7402379980;7102080550;9239331500;35351704600;","Sensitivity of real-data simulations of the 3 May 1999 Oklahoma City tornadic supercell and associated tornadoes to multimoment microphysics. Part I: Storm- and tornado-scale numerical forecasts",2015,"10.1175/MWR-D-14-00279.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943424715&doi=10.1175%2fMWR-D-14-00279.1&partnerID=40&md5=1bc8d5f87e808570702d7dfd404d3e5c","Numerical predictions of the 3 May 1999 Oklahoma City, Oklahoma, tornadic supercell are performed within a real-data framework utilizing telescoping nested grids of 3-km, 1-km, and 250-m horizontal spacing. Radar reflectivity and radial velocity from the Oklahoma City WSR-88D are assimilated using a cloud analysis procedure coupled with a cycled 3DVAR system to analyze storms on the 1-km grid for subsequent forecast periods. Single-, double-, and triple-moment configurations of a multimoment bulk microphysics scheme are used in several experiments on the 1-km and 250-m grids to assess the impact of varying the complexity of the microphysics scheme on the storm structure, behavior, and tornadic activity (on the 250-m grid). This appears to be the first study of its type to investigate single- versus multimoment microphysics within a real-data context. It is found that the triple-moment scheme overall performs the best, producing the smallest track errors for the mesocyclone on the 1-km grid, and stronger and longer-lived tornado-like vortices (TLVs) on the 250-m grid, closest to the observed tornado. In contrast, the single-moment scheme with the default Marshall-Palmer rain intercept parameter performs poorly, producing a cold pool that is too strong, and only weak and short-lived TLVs. The results in the context of differences in latent cooling from evaporation and melting between the schemes, as well as implications for numerical prediction of tornadoes, are discussed. More generally, the feedbacks to storm thermodynamics and dynamics from increasing the prognostic detail of the hydrometeor size distributions are found to be important for improving the simulation and prediction of tornadic thunderstorms. © 2015 American Meteorological Society."
"54410091100;57190285908;55721897500;55994910100;36610012200;57190407334;","Long-term time series of vegetation variations and its relationship with climate factors by integrating AVHRR GIMMS and Terra MODIS data",2015,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957812737&partnerID=40&md5=ad2f7f7ebe2e1d4a3c33352eb765b0d4","Long-term time series of Normalized Difference Vegetation Index datasets is key for the monitoring of land surface dynamics and vegetation change. We evaluated the Advanced Very High Resolution Radiometer (AVHRR) Global Inventory Modeling and Mapping Studies (GIMMS) NDVI and the Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI for the same time period from 2000 to 2006 for a comparative analysis. Prior to use, both datasets have been processed using the Savitzky-Golay filter to reduce the effects of clouds, atmosphere, sensor properties and behaviour and the surface Bidirectional Distribution Reflectance Function (BDRF). The average Normalized Difference Vegetation Index, monthly Coefficient of Variation and trends of GIMMS and MODIS datasets are typically in alignment. A high correlation of 98.1% pixels (r≥0.9, P<0.05) are observed between the GIMMS and MODIS datasets. The correlation coefficient, intercept and slope parameters using the two datasets have been calculated to derive a new GIMMS dataset (1982-2006). A long-term series dataset (1982 to 2013) was subsequently produced at 8 km spatial resolution for the Northeast of China by integrating the new GIMMS (1982-2000) and MODIS (2001-2013) datasets. The expanded Normalized Difference Vegetation Index dataset passed consistency tests based on the linear regression for each pixel and was utilized for the 1982-2013 long-term series analysis. Significant correlations were detected between the monthly Normalized Difference Vegetation Index trends and regional climatic change."
"7004022660;7102653983;","Ultrafine particles over Eastern Australia: An airborne survey",2015,"10.3402/tellusb.v67.25308","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930966094&doi=10.3402%2ftellusb.v67.25308&partnerID=40&md5=41714f8afe53be80d7caca47ebdc858a","Ultrafine particles (UFP) in the atmosphere may have significant impacts on the regional water and radiation budgets through secondary effects on cloud microphysics. Yet, as these particles are invisible for current remote sensing techniques, knowledge about their three-dimensional distribution, source strengths and budgets is limited. Building on a 40-yr-old Australia-wide airborne survey which provides a reference case study of aerosol sources and budgets, this study presents results from a new airborne survey over Eastern Australia, northern New South Wales and Queensland. Observations identified apparent changes in the number and distribution of major anthropogenic aerosol sources since the early 1970s, which might relate to the simultaneously observed changes in rainfall patterns over eastern Queensland. Coal-fired power stations in the inland areas between Brisbane and Rockhampton were clearly identified as the major sources for ultrafine particulate matter. Sugar mills, smelters and shipping along the coast close to the Ports of Townsville and Rockhampton were comparable minor sources. Airborne Lagrangian plume studies were applied to investigate source strength and ageing properties within power station plumes. Significant changes observed, compared to the measurements in the 1970s, included a significant increase in the number concentration of UFP related to coal-fired power station emissions in the sparsely populated Queensland hinterland coincident with the area with the most pronounced reduction in rainfall. © 2015 W. Junkermann and J. M. Hacker."
"57151771800;","A 21st century northward tropical precipitation shift caused by future anthropogenic aerosol reductions",2015,"10.1002/2015JD023623","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945459346&doi=10.1002%2f2015JD023623&partnerID=40&md5=fe2f648c02edf4204248b5ccb2ee52f5","The tropical rain belt is a narrow band of clouds near the equator, where the most intense rainfall on the planet occurs. On seasonal timescales, the rain moves across the equator following the Sun, resulting in wet and dry seasons in the tropics. The position of the tropical rain belt also varies on longer timescales. Through the latter half of the twentieth century, for example, shifts in tropical rainfall have been associated with severe droughts, including the African Sahel and Amazon droughts. Here I show that climate models project a northward migration of the tropical rain belt through the 21st century, with future anthropogenic aerosol reductions driving the bulk of the shift. Models that include both aerosol indirect effects yield significantly larger northward shifts than models that lack aerosol indirect effects. Moreover, the rate of the shift corresponds to the rate of the decrease of anthropogenic aerosol emissions across different time periods and future emission scenarios. This response is consistent with relative warming of the Northern Hemisphere, a decrease in northward cross-equatorial moist static energy transport, and a northward shift of the Hadley circulation, including the tropical rain belt. The shift is relatively weak in the Atlantic sector, consistent with both a smaller decrease in aerosol emissions and a larger reduction in northward cross-equatorial ocean heat flux. Although aerosol effects remain uncertain, I conclude that future reductions in anthropogenic aerosol emissions may be the dominant driver of a 21st century northward shift of the tropical rain belt. © 2015. American Geophysical Union. All Rights Reserved."
"35739529800;6603263640;","What is the representation of the moisture-tropopause relationship in CMIP5 models?",2015,"10.1175/JCLI-D-14-00543.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942910650&doi=10.1175%2fJCLI-D-14-00543.1&partnerID=40&md5=2d2ed62b789612a727e11c50e1273211","A dynamical relationship that connects the extratropical tropopause potential temperature and the near-surface distribution of equivalent potential temperature was proposed in a previous study and was found to work successfully in capturing the annual cycle of the extratropical tropopause in reanalyses. This study extends the diagnosis of the moisture-tropopause relationship to an ensemble of CMIP5 models. It is found that, in general, CMIP5 multimodel averages are able to produce the one-to-one moisture-tropopause relationship. However, a few biases are observed as compared to reanalyses. First of all, ""cold biases"" are seen at both the upper and lower levels of the troposphere, which are universal for all seasons, both hemispheres, and almost all CMIP5 models. This has been known as the ""general coldness of climate models"" since 1990 but the mechanisms remain elusive. It is shown that, for Northern Hemisphere annual averages, the upper- and lower-level ""cold"" biases are, in fact, correlated across CMIP5 models, which supports the dynamical linkage. Second, a large intermodel spread is found and nearly half of the models underestimate the annual cycle of the tropopause potential temperature as compared to that of the near-surface equivalent potential temperature fluctuation. This implies the incapability of the models to propagate the surface seasonal cycle to the upper levels. Finally, while reanalyses exhibit a pronounced asymmetry in tropopause potential temperature between the northern and southern summers, only a few CMIP5 models are able to capture this aspect of the seasonal cycle because of the too dry specific humidity in northern summer. © 2015 American Meteorological Society."
"24177361900;7801370642;22633257000;24331602600;7003968166;","Importance of latent heat release in ascending air streams for atmospheric blocking",2015,"10.1038/ngeo2487","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938581560&doi=10.1038%2fngeo2487&partnerID=40&md5=39db52305c7da840ce36645c790fb787","Atmospheric blocking is a key component of extratropical weather variability and can contribute to various types of extreme weather events. Changes in blocking frequencies due to Arctic amplification and sea ice loss may enhance extreme events, but the mechanisms potentially involved in such changes are under discussion. Current theories for blocking are essentially based on dry dynamics and do not directly take moist processes into account. Here we analyse a 21-year climatology of blocking from reanalysis data with a Lagrangian approach, to quantify the release of latent heat in clouds along the trajectories that enter the blocking systems. We show that 30 to 45% of the air masses involved in Northern Hemisphere blocking are heated by more than 2 K - with a median heating of more than 7 K - in the three days before their arrival in the blocking system. This number increases to 60 to 70% when considering a seven-day period. Our analysis reveals that, in addition to quasi-horizontal advection of air with low potential vorticity, ascent from lower levels associated with latent heating in clouds is of first-order importance for the formation and maintenance of blocking. We suggest that this process should be accounted for when investigating future changes in atmospheric blocking. © 2015 Macmillan Publishers Limited."
"23989037500;6603060770;","Atmospheric dynamics of hot exoplanets",2015,"10.1146/annurev-earth-060614-105146","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930401787&doi=10.1146%2fannurev-earth-060614-105146&partnerID=40&md5=12963bd13c1ce88ae0a5c8c016da0d9c","The characterization of exoplanetary atmospheres has come of age in the past decade, as astronomical techniques now allow for albedos, chemical abundances, temperature profiles and maps, rotation periods, and even wind speeds to be measured. Atmospheric dynamics sets the background state of density, temperature, and velocity that determines or influences the spectral and temporal appearance of an exoplanetary atmosphere. Hot exoplanets are most amenable to these characterization techniques. In this review, we focus on highly irradiated, large exoplanets (the hot Jupiters), as astronomical data begin to confront theoretical questions. We summarize the basic atmospheric quantities inferred from the astronomical observations. We review the state of the art by addressing a series of current questions, and look toward the future by considering a separate set of exploratory questions. Attaining the next level of understanding requires a concerted effort of constructing multifaceted, multiwavelength datasets for benchmark objects. Understanding clouds presents a formidable obstacle, as they introduce degeneracies into the interpretation of spectra, yet their properties and existence are directly influenced by atmospheric dynamics. Confronting general circulation models with these multifaceted, multiwavelength datasets will help us understand these and other degeneracies. Copyright © 2015 by Annual Reviews. All rights reserved."
"14020649100;6507215763;7005565819;","Impacts of a storm merger on the 24 May 2011 El Reno, Oklahoma, tornadic supercell",2015,"10.1175/WAF-D-14-00164.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942802702&doi=10.1175%2fWAF-D-14-00164.1&partnerID=40&md5=50cbeb5088cd529cc93dd67f52a25be0","On 24 May 2011, a tornadic supercell (the El Reno, Oklahoma, storm) produced tornadoes rated as category 3 and 5 events on the enhanced Fujita scale (EF3 and EF5, respectively) during a severe weather outbreak. The transition (""handoff"") between the two tornadoes occurred as the El Reno storm merged with a weaker, ancillary storm. To examine the impacts of the merger on the dynamics of these storms, a series of three-dimensional cloud-scale analyses are created by assimilating 1-min volumetric observations from the National Weather Radar Testbed's phased array radar into a numerical cloud model using the local ensemble transform Kalman filter technique. The El Reno storm, its updrafts, and vortices in the analyzed fields are objectively identified, and the changes in these objects before, during, and after the merger are examined. It is found that the merger did not cause the tornado handoff, which preceded the updraft merger by about 5 min. Instead, the handoff likely resulted from midlevel mesocyclone occlusion, in which the midlevel mesocyclone split and a portion is shed rearward with respect to storm motion. During the merger process, the midlevel mesocyclone and updraft structure in the El Reno storm became relatively disorganized. New updraft pulses that formed above colliding outflow boundaries between the two storms tilted environmental vorticity from low levels to generate an additional midlevel vortex that later merged with the El Reno storm's midlevel mesocyclone. Once the ~10-min merger process was complete, the El Reno storm and its mesocyclone rapidly reintensified, as access to buoyant inflow sector air was restored. © 2015 American Meteorological Society."
"6603369413;6602352355;","A method for retrieving the ground flash fraction and flash type from satellite lightning mapper observations",2015,"10.1175/JTECH-D-14-00085.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921677493&doi=10.1175%2fJTECH-D-14-00085.1&partnerID=40&md5=a719bdccdc03b063b27971497ad88a57","An analytic perturbation method is introduced for retrieving the lightning ground flash fraction in a set of N lightning flashes observed by a satellite lightning mapper. The value of N must be large, typically in the thousands, and the satellite lightning optical observations consist of the maximum group area (MGA) produced by each flash. Moreover, the method subsequently determines the flash type (ground or cloud) of each of the N flashes. Performance tests of the method were conducted using simulated observations that were based on Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) data. It is found that the mean ground flash fraction retrieval errors are below 0.04 across the full range 0-1 under the nominal conditions defined. In general, it is demonstrated that the retrieval errors depend on many factors (i.e., the number N of satellite observations, the magnitude of random and systematic instrument measurement errors, the ground flash fraction itself, and the number of samples used to form certain climate distributions employed in the method). The fraction of flashes accurately flash typed by the method averaged better than 78%. Overall, the accuracy of ground flash fraction and flash-typing retrievals degrade as the simulated population ground and cloud flashMGA distributions become more identical. Finally, because the analytic perturbation method was found to be quite robust (i.e., it performed well for several arbitrary underlying MGA distributions), it is not restricted to the lightning problem studied here but can be applied to any inverse problem having a similar problem statement. © 2015 American Meteorological Society."
"57188548240;6603583923;6603820600;10639674700;7202906456;12752627000;7403513732;","Holocene land–sea climatic links on the equatorial Pacific coast (Bay of Guayaquil, Ecuador)",2015,"10.1177/0959683615612566","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961620652&doi=10.1177%2f0959683615612566&partnerID=40&md5=7d36de304b6483a43f8f579dcb5e0223","We analyzed the pollen content of a marine core located near the Bay of Guayaquil in Ecuador to document the link between sea surface temperatures (SSTs) and changes in rainfall regimes on the adjacent continent during the Holocene. Based on the expansion/regression of five vegetation types, we observe three successive climatic patterns. In the first phase, between 11,700 and 7700 cal. yr BP, the presence of a cloud (Andean) forest in the mid altitudes and mangroves in the estuary of the Guayas basin, were associated with a maximum in boreal summer insolation, a northernmost position of the Intertropical Convergence Zone (ITCZ), a land–sea thermal contrast, cloud dripping, and dry edaphic conditions. Between 7700 and 2850 cal. yr BP, the expansion of the coastal vegetation and the regression of the mangrove indicate a drier climate with weak ITCZ and low El Niño Southern Oscillation (ENSO) variability while austral summer insolation gradually increased. The interval between 4200 and 2850 cal. yr BP was marked by the coolest and driest climatic conditions of the Holocene because of the weak influence of the ITCZ and a strengthening of the Humboldt Current. After 2850 cal. yr BP, high variability and amplitude of the Andean forest changes occurred when ENSO frequency and amplitude increased, indicating high variability in land–sea connections. The ITCZ reached the latitude of Guayaquil only after 2500 cal. yr BP inducing the bimodal precipitation regime we observe today. Our study shows that besides insolation, the ITCZ position, and ENSO frequency, changes in eastern equatorial Pacific SSTs play a major role in determining the composition of the ecosystems and the hydrological cycle of the Ecuadorian Pacific coast and the Western Cordillera in Ecuador. © 2015, © The Author(s) 2015."
"7003561239;35577008300;","A possible link between wildfire aerosol and North American Monsoon precipitation in Arizona-New Mexico",2015,"10.1002/joc.4195","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938902098&doi=10.1002%2fjoc.4195&partnerID=40&md5=00fad6a17dc8a1390b9c3fe3aceb3409","Previous research highlights the dominant role of Pacific sea surface temperatures (SSTs) and their associated large-scale teleconnections in modulating the North American monsoon (NAM). At the regional scale, feedbacks associated with land-surface boundary conditions have been shown to provide 'memory' in the system. Here, a previously unexplored second-order linkage between aerosol generated by late-spring wildfires and subsequent summer precipitation delivered by the NAM in the Arizona-New Mexico (AZNM) region is proposed. Correlations between June/July organic carbon and elemental carbon (OC/EC) in Inter-agency Monitoring of Protected Visual Environments (IMPROVE) aerosol data (Gila Wilderness and Bandelier) and NAM precipitation in southern AZNM over the period 1994-2012 are shown to be negative (r=-0.4), suggesting that active antecedent wildfire seasons tend to be immediately followed by a weak late summer monsoon. This result is consistent with a previous study linking precipitation and area burned in wildfires in AZNM. A survey of extant literature suggests a sound basis for potential mechanisms related to convective processes and cloud microphysics, and furthermore suggests that this forcing could be of similar magnitude to well-documented land-based second-order NAM forcings (antecedent snowpack and soil moisture, vegetation, and mineral dust). Based on these results, we believe that the role of aerosols in modulating summer precipitation deserves further investigation both observationally and in modeling studies. If indeed wildfire smoke does contribute to the modulation of NAM intensity, by virtue of its close temporal association with NAM season, it may well represent a factor that could contribute effectively to improved seasonal prediction of summer precipitation in the NAM region. © 2015 Royal Meteorological Society."
"57204308417;57198900588;7409077047;57215437146;56734752800;","Toward the estimation of surface soil moisture content using geostationary satellite data over sparsely vegetated area",2015,"10.3390/rs70404112","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937957636&doi=10.3390%2frs70404112&partnerID=40&md5=6faa40a4a330148407974e3402c0ff8c","Based on a novel bare surface soil moisture (SSM) retrieval model developed from the synergistic use of the diurnal cycles of land surface temperature (LST) and net surface shortwave radiation (NSSR) (Leng et al. 2014. ""Bare Surface Soil Moisture Retrieval from the Synergistic Use of Optical and Thermal Infrared Data"". International Journal of Remote Sensing 35: 988-1003.), this paper mainly investigated the model's capability to estimate SSM using geostationary satellite observations over vegetated area. Results from the simulated data primarily indicated that the previous bare SSM retrieval model is capable of estimating SSM in the low vegetation cover condition with fractional vegetation cover (FVC) ranging from 0 to 0.3. In total, the simulated data from the Common Land Model (CoLM) on 151 cloud-free days at three FLUXNET sites that with different climate patterns were used to describe SSM estimates with different underlying surfaces. The results showed a strong correlation between the estimated SSM and the simulated values, with a mean Root Mean Square Error (RMSE) of 0.028 m3·m-3 and a coefficient of determination (R2) of 0.869. Moreover, diurnal cycles of LST and NSSR derived from the Meteosat Second Generation (MSG) satellite data on 59 cloud-free days were utilized to estimate SSM in the REMEDHUS soil moisture network (Spain). In particular, determination of the model coefficients synchronously using satellite observations and SSM measurements was explored in detail in the cases where meteorological data were not available. A preliminary validation was implemented to verify the MSG pixel average SSM in the REMEDHUS area with the average SSM calculated from the site measurements. The results revealed a significant R2 of 0.595 and an RMSE of 0.021 m3·m-3. © 2015 by the authors; licensee MDPI, Basel, Switzerland."
"26028456800;54886100100;54885574700;57216310373;7403254320;57203049963;7003811754;7403429025;57193305330;6602549564;57209178100;37090740300;6507992360;54886494000;12759748000;7006521322;","Trends in extreme daily rainfall and temperature indices over South Asia",2015,"10.1002/joc.4081","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930381081&doi=10.1002%2fjoc.4081&partnerID=40&md5=8c7e5ea8fd834cd67fe2df46d77a8c77","Over the last few decades, weather and climate extremes have become a major focus of researchers, the media and general public due to their damaging effects on human society and infrastructure. Trends in indices of climate extremes are studied for the South Asian region using high-quality records of daily temperature and precipitation observations. Data records from 210 (265) temperature (precipitation) observation stations are analysed over the period 1971-2000 (1961-2000). Spatial maps of station trends, time series of regional averages and frequency distribution analysis form the basis of this study. Due to the highly diverse geography of the South Asian region, the results are also described for some specific regions, such as the island of Sri Lanka; the tropical region (excluding Sri Lanka); the Greater Himalayas above 35°N, the Eastern Himalayas (Nepal) and the Thar Desert. Generally, changes in the frequency of temperature extremes over South Asia are what one would expect in a warming world; warm extremes have become more common and cold extremes less common. The warming influence is greater in the Eastern Himalayas compared with that in the Greater Himalayas. The Thar Desert also shows enhanced warming, but increases are mostly less than in the Eastern Himalayas. Changes in the indices of extreme precipitation are more mixed than those of temperature, with spatially coherent changes evident only at relatively small scales. Nevertheless, most extreme precipitation indices show increases in the South Asia average, consistent with globally averaged results. The indices trends are further studied in the context of Atmospheric Brown Clouds (ABCs) over the region. Countries falling within the ABC hotspot namely Indo-Gangetic Plain (IGP) have shown a different behaviour on the trends of extreme indices compared with the parts outside this hotspot. IGP has increased temperature and decreased rainfall and tally closely with the actual trends. © 2014 Royal Meteorological Society."
"55346507200;15044457500;7409074131;7402865879;56158622800;","Variable characteristics of the wintertime net heat flux along the Kuroshio system and its association with climate in China",2015,"10.1002/joc.4055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928591281&doi=10.1002%2fjoc.4055&partnerID=40&md5=f10c3eafc6dc535eb933a3a240589947","On the basis of the datasets obtained for the monthly turbulent heat flux (1984-2009) from the Objectively Analyzed Air-Sea Heat Flux (OAFlux), the radiation flux from the International Satellite Cloud Climatology Project (ISCCP), the variability characteristics of the net heat flux (Qnet) over the Kuroshio System (KS) and its relationship with the climate in China were studied. The results reveal that except for a steady enhancement in the period 1984-2009, the boreal winter Qnet over the KS is characterized by obvious interannual variation of the period quasi-5 year as well as decadal variability shifting from negative to positive anomalies in the mid-1990s. In the wintertime, the increasing KS Qnet is primarily responsible for the intensification of the East Asia winter monsoon (EAWM) via a deepening of the Aleutian low and an enhancement of the Siberia high and has a correlation coefficient of 0.72 with a 1-month delay. The enhanced-EAWM induces colder winters in Northeast China and higher Qnet over the KS by carrying significantly greater amounts of cold air mass. During the low Qnet winter, the EAWM is weakened, and the southwesterly wind that contains abundant water vapour enhances and pushes toward southern China, thereby bringing heavier rainfall. The anomalous Qnet over the KS in the wintertime lasts until the following spring with a weaker relative intensity. In the spring after the low KS Qnet winter, the anomalous easterly wind transfers colder air masses from the Sea of Japan to the North China and Yellow-Huaihe regions and then cools these regions. The warmer and wetter southwesterlies along the northwestern flank of the anomalous anticyclone east of Taiwan Island meet these colder easterlies accompanied by an anomalous upward motion, thereby inducing an anomalous northwest-southeast precipitation band in the central and eastern region of China, especially in the Yangtze-Huaihe region. © 2014 Royal Meteorological Society."
"56172609700;16029674800;","Projection of Summer Precipitation over the Southeastern United States in the Superparameterized CCSM4",2015,"10.1175/JCLI-D-14-00765.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947595467&doi=10.1175%2fJCLI-D-14-00765.1&partnerID=40&md5=72308882100340e263591ec39c1ac58c","Projections of the hydrological cycle over the southeastern United States are compared between CCSM4 and the superparameterized model (SP-CCSM4). Under the extreme forcing of the representative concentration pathway 8.5 (RCP8.5) climate change scenario, in Virginia, North Carolina, South Carolina, and Kentucky, SP-CCSM4 projects a decrease in summer precipitation, whereas the conventionally parameterized CCSM4 projects an increase in summer rainfall. The projected reduction in summer precipitation in SP-CCSM4 is due to the remote influence from the northwest intrusion of the North Atlantic subtropical high, as well as the local decrease of soil moisture content. Both models show that summer precipitation over the southern United States is characterized by a positive feedback with soil moisture. However, in CCSM4 rainfall increases with increasing soil moisture and in SP-CCSM4 rainfall decreases with decreasing soil moisture. The different representation of cloud processes in the two models yields different responses of precipitation to the latent heat flux changes over the southeastern United States. Moreover, multivariate EOF analyses in the two models suggest that the local land-atmosphere interactions have a stronger influence on the projected changes of precipitation over the southeastern United States than does the North Atlantic subtropical high. © 2015 American Meteorological Society."
"36523706800;55613774900;41961756000;15069732800;56702309200;","Digging the METEOSAT treasure-3 decades of solar surface radiation",2015,"10.3390/rs70608067","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933564225&doi=10.3390%2frs70608067&partnerID=40&md5=64f15836994dd683d2a6ad38b8eb28fd","Solar surface radiation data of high quality is essential for the appropriate monitoring and analysis of the Earth's radiation budget and the climate system. Further, they are crucial for the efficient planning and operation of solar energy systems. However, well maintained surface measurements are rare in many regions of the world and over the oceans. There, satellite derived information is the exclusive observational source. This emphasizes the important role of satellite based surface radiation data. Within this scope, the new satellite based CM-SAF SARAH (Solar surfAce RAdiation Heliosat) data record is discussed as well as the retrieval method used. The SARAH data are retrieved with the sophisticated SPECMAGIC method, which is based on radiative transfer modeling. The resulting climate data of solar surface irradiance, direct irradiance (horizontal and direct normal) and clear sky irradiance are covering 3 decades. The SARAH data set is validated with surface measurements of the Baseline Surface Radiation Network (BSRN) and of the Global Energy and Balance Archive (GEBA). Comparison with BSRN data is performed in order to estimate the accuracy and precision of the monthly and daily means of solar surface irradiance. The SARAH solar surface irradiance shows a bias of 1.3 W/m2 and a mean absolute bias (MAB) of 5.5 W/m2 for monthly means. For direct irradiance the bias and MAB is 1W/m2 and 8.2 W/m2 respectively. Thus, the uncertainty of the SARAH data is in the range of the uncertainty of ground based measurements. In order to evaluate the uncertainty of SARAH based trend analysis the time series of SARAH monthly means are compared to GEBA. It has been found that SARAH enables the analysis of trends with an uncertainty of 1W/m2/dec; a remarkable good result for a satellite based climate data record. SARAH has been also compared to its legacy version, the satellite based CM-SAF MVIRI climate data record. Overall, SARAH shows a significant higher accuracy and homogeneity than its legacy version. With its high accuracy and temporal and spatial resolution SARAH is well suited for regional climate monitoring and analysis as well as for solar energy applications. © 2015 by the authors."
"57034558300;6602725432;6507719789;7003811754;57202055245;","A climatology of the precipitation over the Southern Ocean as observed at Macquarie Island",2015,"10.1175/JAMC-D-14-0211.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84952924591&doi=10.1175%2fJAMC-D-14-0211.1&partnerID=40&md5=5524317d37098b4146530e2a4a5f2d24","Macquarie Island (54.50°S, 158.94°E) is an isolated island with modest orography in the midst of the Southern Ocean with precipitation records dating back to 1948.These records (referred to asMAC) are of particular interest because of the relatively large biases in the energy and water budgets commonly found in climate simulations and reanalysis products over the region. A basic climatology of the surface precipitation P is presented and compared with the ERA-Interim (ERA-I) reanalysis. The annual ERA-I precipitation (953 mm) is found to underestimate the annual MAC precipitation (1023 mm) by 6.8% from 1979 to 2011.The frequency of 3-h surface precipitation atMAC is 36.4% from 2003 to 2011. Light precipitation (0.066 ≤ P &lt; 0.5mm h-1) dominates this dataset (29.7%), and heavy precipitation (P ≥ 1.5 mm h-1) is rare (1.1%). Drizzle (0 &lt; P &lt; 0.066 mm h-1) is commonly produced by ERA-I (43.9%) but is weaker than the detectable threshold of MAC. Warm rain intensity and frequency from CloudSat products were compared with those from MAC. These CloudSat products also recorded considerable drizzle (16%-30%) but were not significantly different from MAC when P ≥ 0.5 mm h-1. Heavy precipitation events were, in general, more commonly associated with fronts and cyclonic lows. Some heavy precipitation events were found to arise from weaker fronts and lows that were not adequately represented in the reanalysis products. Yet other heavy precipitation events were observed at points/times not associated with either fronts or cyclonic lows. Two case studies are employed to further examine this finding. © 2015 American Meteorological Society."
"6505921592;56271414600;53864302900;51763878300;7005776035;56872456700;56495373200;7003771738;","River inundation suggests ice-sheet runoff retention",2015,"10.3189/2015JoG15J012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942419685&doi=10.3189%2f2015JoG15J012&partnerID=40&md5=0b1a3ac71cd78a260d75cb672ff3b5fe","The Greenland ice sheet is experiencing dramatic melt that is likely to continue with rapid Arctic warming. However, the proportion of meltwater stored before reaching the global ocean remains difficult to quantify. We use NASA MODIS surface reflectance data to estimate river discharge from two West Greenland rivers - the Watson River near Kangerlussuaq and the Naujat Kuat River near Nuuk - over the summers of 2000-12. By comparison with in situ river discharge observations, 'inundation-discharge' relations were constructed for both rivers. MODIS-based total annual discharges agree well with total discharge estimated from in situ observations (86% of summer discharge in 2009 to 96% in 2011 at the Watson River, and 106% of total discharge in 2011 to 104% in 2012 at the Naujat Kuat River). We find, however, that a time-lapse camera, deployed at the Watson River in summer 2012, better captures the variations in observed discharge, benefiting from fewer data gaps due to clouds. The MODIS-derived estimates indicate that summer discharge has not significantly increased over the last decade, despite a strong warming trend. Also, meltwater runoff estimates derived from the regional climate model RACMO2/GR for the drainage basins are higher than our reconstructions of river discharge. These results provide indirect evidence for a considerable component of water storage within the glacio-hydrological system."
"34979885900;7102587442;6602208685;8349521000;6602888227;23398538400;56609273300;17135301400;","Methane storms as a driver of Titan's dune orientation",2015,"10.1038/ngeo2406","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928595636&doi=10.1038%2fngeo2406&partnerID=40&md5=46ce268f69b3193671ec5dcee36d2268","The equatorial regions of Saturn's moon Titan are covered by linear dunes that propagate eastwards. Global climate models (GCMs), however, predict westward mean surface winds at low latitudes on Titan, similar to the trade winds on Earth. This apparent contradiction has been attributed to Saturn's gravitational tides, large-scale topography and wind statistics, but none of these hypotheses fully explains the global eastward propagation of dunes in Titan's equatorial band. However, above altitudes of about 5 km, Titan's atmosphere is in eastward super-rotation, suggesting that this momentum may be delivered to the surface. Here we assess the influence of equatorial tropical methane storms - which develop at high altitudes during the equinox - on Titan's dune orientation, using mesoscale simulations of convective methane clouds with a GCM wind profile that includes super-rotation. We find that these storms produce fast eastward gust fronts above the surface that exceed the normal westward surface winds. These episodic gusts generated by tropical storms are expected to dominate aeolian transport, leading to eastward propagation of dunes. We therefore suggest a coupling between super-rotation, tropical methane storms and dune formation on Titan. This framework, applied to GCM predictions and analogies to some terrestrial dune fields, explains the linear shape, eastward propagation and poleward divergence of Titan's dunes, and implies an equatorial origin of dune sand. © 2015 Macmillan Publishers Limited. All rights reserved."
"46761421300;55816347300;57211649819;57190093136;55218452200;","Towards farm-oriented open data in Europe: The scope and pilots of the European project ""foodie""",2015,"10.7160/aol.2015.070106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928389007&doi=10.7160%2faol.2015.070106&partnerID=40&md5=cddf4e5e89b93fae2da75c0a30afc515","The different groups of stakeholders involved in the agricultural activities have to manage many different and heterogeneous sources of information that need to be combined in order to make economically and environmentally sound decisions, which include (among others) the definition of policies (subsidies, standardisation and regulation, national strategies for rural development, climate change), development of sustainable agriculture, harvest timing and yield estimation, crop damages detection, etc. The European project called ""Farm-Oriented Open Data in Europe"" with abbreviation ""FOODIE"", funded between years 2014 and 2017 addresses the above mentioned issues. This paper describes the scope of the project with emphasis on its pilots. The Czech pilot is then analysed in detail including its three scenarios: Improving efficiency of transport in agriculture, Telematics of farm machinery and Monitoring of in-field variability for site specific crop management."
"56503442700;56502753000;14048914300;6602798575;","Land use intensity trajectories on Amazonian pastures derived from Landsat time series",2015,"10.1016/j.jag.2015.04.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939641248&doi=10.1016%2fj.jag.2015.04.010&partnerID=40&md5=95c6122762408043ee33cff3247e708b","Monitoring changes in land use intensity of grazing systems in the Amazon is an important prerequisite to study the complex political and socio-economic forces driving Amazonian deforestation. Remote sensing offers the potential to map pasture vegetation over large areas, but mapping pasture conditions consistently through time is not a trivial task because of seasonal changes associated with phenology and data gaps from clouds and cloud shadows. In this study, we tested spectral-temporal metrics derived from intra-annual Landsat time series to distinguish between grass-dominated and woody pastures. The abundance of woody vegetation on pastures is an indicator for management intensity, since the duration and intensity of land use steer secondary succession rates, apart from climate and soil conditions. We used the developed Landsat-based metrics to analyze pasture intensity trajectories between 1985 and 2012 in Novo Progresso, Brazil, finding that woody vegetation cover generally decreased after four to ten years of grazing activity. Pastures established in the 80s and early 90s showed a higher fraction of woody vegetation during their initial land use history than pastures established in the early 2000s. Historic intensity trajectories suggested a trend towards more intensive land use in the last decade, which aligns well with regional environmental policies and market dynamics. This study demonstrates the potential of dense Landsat time series to monitor land-use intensification on Amazonian pastures. © 2015 Elsevier B.V."
"57196538727;6603729296;","Neotectonically triggered instability around the palaeolake regime in Central Kumaun Himalaya, India",2015,"10.1016/j.quaint.2014.10.033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930277416&doi=10.1016%2fj.quaint.2014.10.033&partnerID=40&md5=ff9a9e76a743e73502c31a6618075ffe","Mass wasting often results from the combined effect of tectonic and climate processes. It has not only resulted in human casualties on large scale but has also ruined agricultural land and disrupted hydro power projects and other governmental as well as private property. Despite the belief that prevention is inevitably better than cure, decrease in future hazards requires proper dissemination of knowledge to the Himalayan inhabitants. Considering this, we investigated a part of Kumaun Himalaya to understand the cause of cloud burst induced mass movements along the Saryu River that took place on 18th August 2010 and subsequently on 12-14th September, 2012. A number of Quaternary faults, e.g., Dulam fault (DF), Dulam Gadhera Fault (DGF) and Vongarh-Gason Fault (VGF) in the zone of a major thrust (Berinag Thrust) in the studied sector are invariably active as evident by various geomorphic features, e.g., saw cutting of host rocks, immature topography, deflecting river courses, ponding of ancient drainage, development of cascades, formation of unpaired fluvial terraces, and series of triangular fault facets. The fragile lithology, deep V shaped valleys, accelerating erosion and incision with higher uplift due to tectonic upheaval along the active faults are also responsible for rainfall induced catastrophes in the region. Additionally, morphometric analysis reveals that the Saryu basin is elongated and tilted. Further, the tectonic tilting and moderate to coarse drainage density may possibly be responsible for quicker runoff, amplified erosion, and subsequently increased flooding around the study area. We infer that the area is not only controlled by topography but may also have been affected by the hydraulic factors such as climate. In addition, the drainage is dominated mostly by first order streams which seem to be indicative of higher chances of flooding, as most of the water is concentrated in a single channel during monsoon season. We believe that the similar studies done in the other sectors will be helpful in reducing not only the huge loss of life but may also help in protecting ongoing and huge hydropower and other developmental projects in this newly born state. © 2014 Elsevier Ltd and INQUA."
"35425197200;7402765035;55366898500;6504500313;7401448505;7103391609;7202408732;55803523500;35319762400;6503892591;6601955756;","Observing system simulation experiments (OSSEs) to evaluate the potential impact of an optical autocovariance wind lidar (OAWL) on numerical weather prediction",2015,"10.1175/JTECH-D-15-0038.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946571630&doi=10.1175%2fJTECH-D-15-0038.1&partnerID=40&md5=16488ead09fe8e5a67ab99bcf7e5baf3","The potential impact of Doppler wind lidar (DWL) observations from a proposed optical autocovariance wind lidar (OAWL) instrument is quantified in observing system simulation experiments (OSSEs). The OAWL design would provide profiles of useful wind vectors along a ground track to the left of the International Space Station (ISS), which is in a 51.6° inclination low-Earth orbit (LEO). These observations are simulated realistically, accounting for cloud and aerosol distributions inferred from the OSSE nature runs (NRs), and measurement and sampling error sources. The impact of the simulated observations is determined in both global and regional OSSE frameworks. The global OSSE uses the ECMWF T511 NR and the NCEP operational Global Data Assimilation System at T382 resolution. The regional OSSE uses an embedded hurricane NR and the NCEP operational HWRF data assimilation system with outer and inner domains of 9- and 3-km resolution, respectively. The global OSSE results show improved analyses and forecasts of tropical winds and extratropical geopotential heights. The tropical wind RMSEs are significantly reduced in the analyses and in short-term forecasts. The tropical wind improvement decays as the forecasts lengthen. The regional OSSEs are limited but show some improvements in hurricane track and intensity forecasts. © 2015 American Meteorological Society."
"25421717700;7003525439;","Initial conditions for convective-scale ensemble forecasting provided by ensemble data assimilation",2015,"10.1175/MWR-D-14-00209.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944050906&doi=10.1175%2fMWR-D-14-00209.1&partnerID=40&md5=e71a1c3f51a82d29921387dbc31cccfe","A kilometer-scale ensemble data assimilation system (KENDA) based on a local ensemble transform Kalman filter (LETKF) has been developed for the Consortium for Small-Scale Modeling (COSMO) limited-area model. The data assimilation system provides an analysis ensemble that can be used to initialize ensemble forecasts at a horizontal grid resolution of 2.8 km. Convective-scale ensemble forecasts over Germany using ensemble initial conditions derived by the KENDA system are evaluated and compared to operational forecasts with downscaled initial conditions for a short summer period during June 2012. The choice of the inflation method applied in the LETKF significantly affects the ensemble analysis and forecast. Using a multiplicative background covariance inflation does not produce enough spread in the analysis ensemble leading to a degradation of the ensemble forecasts. Inflating the analysis ensemble instead by either multiplicative analysis covariance inflation or relaxation inflation methods enhances the analysis spread and is able to provide initial conditions that produce more consistent ensemble forecasts. The forecast quality for short forecast lead times up to 3 h is improved, and 21-h forecasts also benefit from the increased spread. Doubling the ensemble size has not only a clear positive impact on the analysis but also on the short-term ensemble forecasts, while a simple representation of model error perturbing parameters of the model physics has only a small impact. Precipitation and surface wind speed ensemble forecasts using the high-resolution KENDA-derived initial conditions are competitive compared to the operationally used downscaled initial conditions. © 2015 American Meteorological Society."
"6701783232;","Response of a simulated hurricane to misalignment forcing compared to the predictions of a simple theory",2015,"10.1175/JAS-D-14-0149.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943809864&doi=10.1175%2fJAS-D-14-0149.1&partnerID=40&md5=e219c3dea99ae7be774ec006fca0c1bd","This paper compares the tilt dynamics of a mature tropical cyclone simulated with a conventional cloud model to reduced modeling results and theoretical predictions. The primary experiment involves a tropical cyclone of hurricane strength on the f plane exposed to a finite period of idealized misalignment forcing. A complementary experiment shows how the vortex responds to the same forcing when moisture and symmetric secondary circulation (SSC) are removed from the initial condition. It is found that the applied forcing excites a much stronger tilt mode in the dry nonconvective vortex than in the moist convective hurricane. The evolution of tilt in both experiments agrees reasonably well with a simple linear response theory that neglects the SSC and assumes moisture merely reduces static stability in the vortex core. An additional experiment with suspended cloud water but no substantial SSC supports the theoretical notion that reduction of static stability is sufficient to inhibit the excitation of a tilt mode. However, there is some discrepancy between theory and details of asymmetric convection in the eyewall region of the simulated hurricane. Moreover, a final experiment without moisture but with an artificially maintained secondary circulation suggests that the SSC has a nonnegligible role in reducing tilt. Diagnosis of the primary hurricane simulation further illustrates how the SSC has discernible influence over misalignment at least in the eyewall. Sensitivity of tilt dynamics to the azimuthally averaged vortex structure is briefly addressed. © 2015 American Meteorological Society."
"36924613900;6602515776;8954406100;","Long-term analysis of clear sky at astronomical sites: A comparison between polar and geostationary satellites",2015,"10.1093/mnras/stv1319","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940112255&doi=10.1093%2fmnras%2fstv1319&partnerID=40&md5=2ded1bc011455327a7e51b75a960d224","In this paper, we analyse three sites of great astronomical importance: Mt Graham, Paranal and La Silla. In recent years, with the development of new telescopes, the study of cloud cover is getting more and more important for the selection of new sites as well as for the development of existing telescopes. At the moment there is discussion on the techniques used to study climatic conditions. We have mainly two large data sets: satellite data and ground data. The two sets have advantages and disadvantages. We study in detail the various data available and we compare these data and analyse the correlations between them. In particular, we focus on the long-term statistics for the trends in climate change. We use two satellites: GOES (Geostationary Operational Environmental Satellite) and Aqua. In particular, we use the GOES camera data and MODIS (Moderate Resolution Imaging Spectroradiometer) data, which is a key instrument aboard the Aqua satellite. Finally, we use the heliograph ground data of the Columbine weather station to validate the two families of satellite data. The use of such data allows a mutual validation of the results, which allows the analysis to be extended to other sites. We obtained a mean night cloud cover for the 10 yr analysed (2003-2012) of 12 per cent at Paranal, 22 per cent at La Silla and 37 per cent at Mt Graham. We also get a punctual correlation of 96 per cent between the two satellites and of 92 per cent between the satellite and the heliograph data at Mt Graham for 2009. © 2015 The Authors."
"7003871110;8945984800;8055301200;7201400583;11940634500;35305397000;35746915400;7102578937;8581789300;","Particles and iodine compounds in coastal Antarctica",2015,"10.1002/2015JD023301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939260144&doi=10.1002%2f2015JD023301&partnerID=40&md5=c3f284ffe696488c747091fc0c7f2fc1","Aerosol particle number concentrations have been measured at Halley and Neumayer on the Antarctic coast, since 2004 and 1984, respectively. Sulphur compounds known to be implicated in particle formation and growth were independently measured: sulphate ions and methane sulphonic acid in filtered aerosol samples and gas phase dimethyl sulphide for limited periods. Iodine oxide, IO, was determined by a satellite sensor from 2003 to 2009 and by different ground-based sensors at Halley in 2004 and 2007. Previous model results and midlatitude observations show that iodine compounds consistent with the large values of IO observed may be responsible for an increase in number concentrations of small particles. Coastal Antarctica is useful for investigating correlations between particles, sulphur, and iodine compounds, because of their large annual cycles and the source of iodine compounds in sea ice. After smoothing all the measured data by several days, the shapes of the annual cycles in particle concentration at Halley and Neumayer are approximated by linear combinations of the shapes of sulphur compounds and IO but not by sulphur compounds alone. However, there is no short-term correlation between IO and particle concentration. The apparent correlation by eye after smoothing but not in the short term suggests that iodine compounds and particles are sourced some distance offshore. This suggests that new particles formed from iodine compounds are viable, i.e., they can last long enough to grow to the larger particles that contribute to cloud condensation nuclei, rather than being simply collected by existing particles. If so, there is significant potential for climate feedback near the sea ice zone via the aerosol indirect effect. © 2015. The Authors."
"57192222103;12762440500;36020828900;55740539300;56267743000;","Relationship between lightning activity and tropical cyclone intensity over the northwest Pacific",2015,"10.1002/2014JD022334","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930325921&doi=10.1002%2f2014JD022334&partnerID=40&md5=cd3b06ad4a26015d8b0991c58d5c6e7e","Lightning data from the World Wide Lightning Location Network along with tropical cyclone (TC) track and intensity data from the China Meteorological Administration are used to study lightning activity in TCs over the northwest Pacific from 2005 to 2009 and to investigate the relationship between inner core lightning and TC intensity changes. Lightning in TCs over the northwest Pacific is more likely to occur in weak storms at tropical depression (10.8-17.1ms-1) and tropical storm (17.2-24.4ms-1) intensity levels, in agreement with past studies of Atlantic hurricanes. The greatest lightning density (LD) in the inner core appears in storms undergoing an intensity change of 15-25ms-1 during the next 24 h. Lightning is observed in all storm intensity change categories: rapid intensification (RI), average intensity change (AIC), and rapid weakening (RW). The differences in LD between RI and RW are largest in the inner core, and the LD for RI cases is larger than for RW cases in the inner core (0-100 km). Lightning activity there, rather than in the outer rainbands, may be a better indicator for RI prediction in northwest Pacific storms. There was a marked increase in the lightning density of inner core during the RI stage for Super Typhoon Rammasun (2008). Satellite data for this storm show that the RI stage had the highest cloud top height and coldest cloud top temperatures, with all the minimum black body temperature values being below 200 K in the inner core. © 2015. American Geophysical Union. All Rights Reserved."
"35737484800;6602890253;7404062492;6602252175;48661588600;7006497590;14048087800;8261329600;6602356428;6603178707;57203776263;6602221672;15080710300;55797926900;7004643405;36616603800;16480965400;35396858200;18134565600;8359591200;6603775815;6506458269;","Airborne measurements of organosulfates over the continental U.S.",2015,"10.1002/2014JD022378","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928622720&doi=10.1002%2f2014JD022378&partnerID=40&md5=5024cf23aa396fa2855663dbad945a43","Organosulfates are important secondary organic aerosol (SOA) components and good tracers for aerosol heterogeneous reactions. However, the knowledge of their spatial distribution, formation conditions, and environmental impact is limited. In this study, we report two organosulfates, an isoprene-derived isoprene epoxydiols (IEPOX) (2,3-epoxy-2-methyl-1,4-butanediol) sulfate and a glycolic acid (GA) sulfate, measured using the NOAA Particle Analysis Laser Mass Spectrometer (PALMS) on board the NASA DC8 aircraft over the continental U.S. during the Deep Convective Clouds and Chemistry Experiment (DC3) and the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS). During these campaigns, IEPOX sulfate was estimated to account for 1.4% of submicron aerosol mass (or 2.2% of organic aerosol mass) on average near the ground in the southeast U.S., with lower concentrations in the western U.S. (0.2-0.4%) and at high altitudes (&lt;0.2%). Compared to IEPOX sulfate, GA sulfate was more uniformly distributed, accounting for about 0.5% aerosolmass on average, andmay bemore abundant globally. A number of other organosulfates were detected; nonewere as abundant as these two. Ambientmeasurements confirmed that IEPOX sulfate is formed from isoprene oxidation and is a tracer for isoprene SOA formation. The organic precursors of GA sulfatemay include glycolic acid and likely have both biogenic and anthropogenic sources. Higher aerosol acidity as measured by PALMS and relative humidity tend to promote IEPOX sulfate formation, and aerosol acidity largely drives in situ GA sulfate formation at high altitudes. This study suggests that the formation of aerosol organosulfates depends not only on the appropriate organic precursors but also on emissions of anthropogenic sulfur dioxide (SO2), which contributes to aerosol acidity. © 2015. The Authors."
"56033677700;55671920100;7005396385;7201754973;7403584142;","A study of multiple tropopause structures caused by inertia-gravity waves in the antarctic",2015,"10.1175/JAS-D-14-0228.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943747069&doi=10.1175%2fJAS-D-14-0228.1&partnerID=40&md5=8fdaad25feeb9ed0828142732aa1aa7a","Multiple tropopauses (MTs) defined by the World Meteorological Organization are frequently detected from autumn to spring at Syowa Station (69.0°S, 39.6°E). The dynamical mechanism of MT events was examined by observations of the first mesosphere-stratosphere-troposphere (MST) radar in the Antarctic, the Program of the Antarctic Syowa MST/Incoherent Scatter (IS) Radar (PANSY), and of radiosondes on 8-11 April 2013. The MT structure above the first tropopause is composed of strong temperature fluctuations. By a detailed analysis of observed three-dimensional wind and temperature fluctuation components, it is shown that the phase and amplitude relations between these components are consistent with the theoretical characteristics of linear inertia-gravity waves (IGWs). Numerical simulations were performed by using a nonhydrostatic model. The simulated MT structures and IGW parameters agree well with the observation. In the analysis using the numerical simulation data, it is seen that IGWs were generated around 65°S, 15°E and around 70°S, 15°E, propagated eastward, and reached the region above Syowa Station when the MT event was observed. These IGWs were likely radiated spontaneously from the upper-tropospheric flow around 65°S, 15°E and were forced by strong southerly surface winds over steep topography (70°S, 15°E). The MT occurrence is attributable to strong IGWs and the low mean static stability in the polar winter lower stratosphere. It is also shown that nonorographic gravity waves associated with the tropopause folding event contribute to 40% of the momentum fluxes, as shown by a gravity wave-resolving general circulation model in the lower stratosphere around 65°S. This result indicates that they are one of the key components for solving the coldbias problem found in most climate models. © 2015 American Meteorological Society."
"56469821600;10641207200;56469654100;","Desertification risk in Kakheti Region, East Georgia",2015,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920466974&partnerID=40&md5=e70ea5e98702798040600a4c6fae359f","Desertification or land degradation in drylands is caused by various factors. The most important of these is climate change, a significant global ecological problem. Desertification, like erosion, as an environmental process of ecosystem degradation, is often caused by human activity. It is a common misconception that droughts cause desertification. Well-managed lands can recover from drought if the rains return. These practices help to control erosion and maintain productivity during periods when moisture is available. Traditionally, the most vulnerable territories considered under the threat of desertification in Georgia is Kakheti region (East Georgia), which has been selected as one of the priority investigation area. In Eastern Georgia, intervals of atmospheric precipitation do not coincide with the phases of water demand of plants. In recent decades as a result of more frequent droughts in Kakheti, the region has already lost hundreds, thousands of hectares of fertile land. Based on the contemporary climate warming projections, the temperature is expected to increase and precipitation to decrease. This will lead to an increase in evaporation and reduction of river flow. Under such conditions the danger of desertification is evident. To mitigate the negative effects of desertification, it is recommended to put forward set of adaptation activities through rehabilitation of water use systems, prevention of loss of water, reconstruction and expansion of irrigation canals, accumulation of unused autumn-winter river water and spring floods in reservoirs, developing an optimal scheme of distributing water resources among water users, device windbreaks and work on breeding of drought resistant varieties, preparation of water volume forecasts of rivers and their role in planning of water use; application of apply drip and sprinkler irrigation, using artificial precipitation following increase as a result of active influence on clouds. All these activities will provide means for suspending desertification process, create ecological safety for the environment and improve the economic wellbeing of population."
"26430995400;56850959100;","Diagnosing the vertical structure of the eddy diffusivity in real and idealized atmospheres",2015,"10.1002/qj.2387","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924538794&doi=10.1002%2fqj.2387&partnerID=40&md5=8eda030de337230b5f1e0b6dbbeae06a","The Earth's extratropical troposphere is equilibrated by turbulent eddy fluxes of potential temperature and momentum. The equilibrated state has the remarkable characteristic that isentropic slopes leaving the surface in the subtropics reach the tropopause near the Poles. It has been speculated that turbulent eddy fluxes maintain this state for a wide range of radiative forcing and planetary parameters. In a previous study, the authors showed that this state needs to be associated with an eddy diffusivity of Ertel potential vorticity that is largest at the surface and decays through the troposphere to approximately zero at the tropopause. This result is confirmed in this study using atmospheric reanalysis and idealized numerical simulations. However, it is also shown that the vertical profile of the eddy diffusivity can change, resulting in different isentropic slopes and climates. This is illustrated with a series of idealized numerical simulations with varying planetary scales and rotation rates. © 2014 Royal Meteorological Society."
"45961453200;56152346800;45961133700;","Heterogeneous change patterns of water level for inland lakes in High Mountain Asia derived from multi-mission satellite altimetry",2015,"10.1002/hyp.10399","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930377357&doi=10.1002%2fhyp.10399&partnerID=40&md5=cd24fddfdc082539405ff598c9a3627c","High-altitude inland lakes in High Mountain Asia (HMA) are key indicators to climate change and variability as a result of mostly closed watersheds and minimal disturbance by human activities. However, examination of the spatial and temporal pattern of lake changes, especially for water-level variations, is usually limited by poor accessibility of most lakes. Recently, satellite altimeters have demonstrated their potential to monitor water level changes of terrestrial water bodies including lakes and rivers. By combining multiple satellite altimetry data provided by the Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (LEGOS) and Geoscience Laser Altimeter System (GLAS) instrument on the NASA Ice, Cloud and land Elevation satellite (ICESat), this study examined water level changes of typical lakes in HMA at a longer timescale (in the 1990s and 2000s) compared with earlier studies on Tibetan lakes. Cross-evaluation of the radar altimetry data from LEGOS and laser altimetry data from ICESat/GLAS shows that they were in good agreement in depicting inter-annual, seasonal and abrupt changes of lake level. The long-term altimetry measurements reveal that water-level changes of the 18 lakes showed remarkable spatial and temporal patterns that were characterized by different trends, onsets of rapid rises and magnitudes of inter-annual variations for different lakes. During the study period, lakes in the central and northern HMA (15 lakes) showed a general growth tendency, while lakes in South Tibet (three lakes) showed significant shrinking tendency. Lakes in Central Tibet experienced rapid and stable water-level rises around mid-1990s followed by slowing growth rates after 2006. In contrast, the water-level rises of lakes in the northern and north-eastern Tibetan Plateau were characterized by abrupt increases in specific years rather than gradual growth. Meteorological data based on station observations indicate that the annual changes of water level showed strongly correlated with precipitation and evaporation but may not evidently related to the glacier melting induced by global warming. © 2014 John Wiley & Sons, Ltd."
"57217109580;7402866430;57191294058;","Impacts of aerosols on dynamics of Indian summer monsoon using a regional climate model",2015,"10.1007/s00382-014-2284-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933278478&doi=10.1007%2fs00382-014-2284-4&partnerID=40&md5=c10cc060019eee9a417bf5cfe8a37f2f","A regional climate model, RegCM has been utilized to examine the dynamic impacts of large aerosol radiative forcing on the atmospheric temperature and circulation in India during the monsoon (Jun–Sep) seasons of 2009 and 2010. Surface shortwave radiative forcing at the aerosol hot spots is in the range −25 to −60 W m−2 with the larger values observed during the summer monsoon season of 2010 (due to larger dust load) relative to that in 2009. It is important to note that the summer monsoon rainfall in 2010 was declared to be a normal monsoon as against the deficit rain in 2009. Changes in near surface air temperature show a spatial dipole pattern with the aerosol effect dampening out above 500 hPa with a larger change observed for natural aerosols relative to anthropogenic aerosols. The dipole pattern is characteristics of aerosol-induced change. Aerosols tend to strengthen the summer monsoon zonal mean wind at 850 hPa over the hotspots (larger effect in 2009 than in 2010) whereas there is negligible impact on the corresponding mean meridional wind component. This has resulted in a southward shift of the monsoon circulation during 2010 summer, leading to an increase in upward motion over the core monsoon region and thereby increasing the cloud fraction. This may also be facilitated by the aerosol induced heating in the lower troposphere. In 2009, the upward motion is enhanced to the south of the core monsoon region. The dynamic effects imply a positive feedback of the aerosol direct radiative forcing on the summer monsoon circulation over India. © 2014, Springer-Verlag Berlin Heidelberg."
"7801373292;","Drive for resilience requires greater engagement",2015,"10.5942/jawwa.2015.107.0170","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946740587&doi=10.5942%2fjawwa.2015.107.0170&partnerID=40&md5=a12d0eff527216cdd267592b09d663b9","The 2015 Black & Veatch Strategic Directions: U.S. Water Industry Report revealed their most pressing concerns and their approaches to addressing them. The report also made recommendations for meeting the water industry's top challenges and securing a strategy of resilience. The strategic benefits of sustainable and environmentally aware business practices also play a role in fostering resilience. According to the survey, the most significant sustainability issue for water utilities was maintaining or expanding asset life. Respondents also felt customer water rates, long-term financial viability, and energy efficiency were important sustainability issues. The most significant climate issue for nearly two-thirds of water utilities participating in the survey was water supply and scarcity. Among utilities actively using data analytics, nearly half of the respondents said they use dashboards that display consumption, equipment data, and other metrics. Performance monitoring, service reliability, asset management, and treatment were seen as areas that would gain the most from an analytics strategy. Cloud-based systems with greater cost efficiencies are making analytics available to smaller utilities."
"57210337677;56658923100;8376749100;7005884117;25624178100;56381923500;35756335100;","Geostationary satellite observation of precipitable water vapor using an Empirical Orthogonal Function (EOF) based reconstruction technique over eastern China",2015,"10.3390/rs70505879","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930021123&doi=10.3390%2frs70505879&partnerID=40&md5=1ef24dbaa4407186103844838126d439","Water vapor, as one of the most important greenhouse gases, is crucial for both climate and atmospheric studies. Considering the high spatial and temporal variations of water vapor, a timely and accurate retrieval of precipitable water vapor (PWV) is urgently needed, but has long been constrained by data availability. Our study derived the vertically integrated precipitable water vapor over eastern China using Multi-functional Transport Satellite (MTSAT) data, which is in geostationary orbit with high temporal resolution. The missing pixels caused by cloud contamination were reconstructed using an Empirical Orthogonal Function (EOF) decomposition method over both spatial and temporal dimensions. GPS meteorology data were used to validate the retrieval and the reconstructed results. The diurnal variation of PWV over eastern China was analyzed using harmonic analysis, which indicates that the reconstructed PWV data can depict the diurnal cycle of PWV caused by evapotranspiration and local thermal circulation. © 2015 by the authors."
"55837451900;36988863300;22333823900;7801372905;","High-resolution digital 3D models of algar do Penico Chamber: Limitations, challenges, and potential",2015,"10.5038/1827-806X.44.1.3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912095265&doi=10.5038%2f1827-806X.44.1.3&partnerID=40&md5=726b999ab634a24ea078812028735527","The study of karst and its geomorphological structures is important for understanding the relationships between hydrology and climate over geological time. In that context, we conducted a terrestrial laser-scan survey to map geomorphological structures in the karst cave of Algar do Penico in southern Portugal. The point cloud data set obtained was used to generate 3D meshes with different levels of detail, allowing the limitations of mapping capabilities to be explored. In addition to cave mapping, the study focuses on 3D-mesh analysis, including the development of two algorithms for determination of stalactite extremities and contour lines, and on the interactive visualization of 3D meshes on the Web. Data processing and analysis were performed using freely available open-source software. For interactive visualization, we adopted a framework based on Web standards X3D, WebGL, and X3DOM. This solution gives both the general public and researchers access to 3D models and to additional data produced from map tools analyses through a web browser, without the need for plug-ins. © 2015, Societa Speleologica Italiana. All rights reserved."
"7006850123;7201820022;","On the estimation of boreal forest biomass from TanDEM-X data without training samples",2015,"10.1109/LGRS.2014.2361393","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910038278&doi=10.1109%2fLGRS.2014.2361393&partnerID=40&md5=e125da9c0cc54fb5c65b479d66242d61","Boreal forests play an important part in the climate system, and estimates of the biomass are important also from an economic point of view. In this letter, forest aboveground biomass is estimated from bistatic TanDEM-X data, a Lidar digital elevation model (DEM), and the interferometric water cloud model, without using training samples to calibrate the model. The forest was characterized by allometric relations for area fill (vegetation fraction) and height versus stem volume, and stem volume versus biomass. Biomass was estimated for 202 forest stands at least 1 ha large at the forest test site of Remningstorp, Sweden, from 18 bistatic TanDEM-X acquisitions with a relative root-mean-square error (RMSE) of 16%-32%. TanDEM-X acquisitions with a height of ambiguity around 80 m resulted in the best results. A multitemporal combination resulted in a relative RMSE of 17%. This result is comparable with the retrieval error obtained in a previous study when training the model using a set of known forest stands. © 2004-2012 IEEE."
"57198945375;57203579757;37861012100;7005565819;36598393700;","A comparison of multiscale GSI-based EnKF and 3DVar data assimilation using radar and conventional observations for midlatitude convective-scale precipitation forecasts",2015,"10.1175/MWR-D-14-00345.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943413562&doi=10.1175%2fMWR-D-14-00345.1&partnerID=40&md5=3b0fc00762284f509303e9a81b23e39f","A GSI-based data assimilation (DA) system, including three-dimensional variational assimilation (3DVar) and ensemble Kalman filter (EnKF), is extended to the multiscale assimilation of both meso- and synoptic-scale observation networks and convective-scale radar reflectivity and velocity observations. EnKF and 3DVar are systematically compared in this multiscale context to better understand the impacts of differences between the DA techniques on the analyses at multiple scales and the subsequent convective-scale precipitation forecasts. Averaged over 10 diverse cases, 8-h precipitation forecasts initialized using GSI-based EnKF are more skillful than those using GSI-based 3DVar, both with and without storm-scale radar DA. The advantage from radar DA persists for ~5 h using EnKF, but only ~1 h using 3DVar. A case study of an upscale growing MCS is also examined. The better EnKF-initialized forecast is attributed to more accurate analyses of both the mesoscale environment and the storm-scale features. The mesoscale location and structure of a warm front is more accurately analyzed using EnKF than 3DVar. Furthermore, storms in the EnKF multiscale analysis are maintained during the subsequent forecast period. However, storms in the 3DVar multiscale analysis are not maintained and generate excessive cold pools. Therefore, while the EnKF forecast with radar DA remains better than the forecast without radar DA throughout the forecast period, the 3DVar forecast quality is degraded by radar DA after the first hour. Diagnostics revealed that the inferior analysis at mesoscales and storm scales for the 3DVar is primarily attributed to the lack of flow dependence and cross-variable correlation, respectively, in the 3DVar static background error covariance."
"56763174500;55745955800;","Three-dimensional constrained variational analysis: Approach and application to analysis of atmospheric diabatic heating and derivative fields during an ARM SGP intensive observational period",2015,"10.1002/2015JD023621","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940461323&doi=10.1002%2f2015JD023621&partnerID=40&md5=2f42934eea44eceb7fbf01bf145843ec","Atmospheric vertical velocities and advective tendencies are essential large-scale forcing data to drive single-column models (SCMs), cloud-resolving models (CRMs), and large-eddy simulations (LESs). However, they cannot be directly measured from field measurements or easily calculated with great accuracy. In the Atmospheric Radiation Measurement Program (ARM), a constrained variational algorithm (1-D constrained variational analysis (1DCVA)) has been used to derive large-scale forcing data over a sounding network domain with the aid of flux measurements at the surface and top of the atmosphere (TOA). The 1DCVA algorithmis now extended into three dimensions (3DCVA) along with other improvements to calculate gridded large-scale forcing data, diabatic heating sources (Q1), and moisture sinks (Q2). Results are presented for a midlatitude cyclone case study on 3 March 2000 at the ARM Southern Great Plains site. These results are used to evaluate the diabatic heating fields in the available products such as Rapid Update Cycle, ERA-Interim, National Centers for Environmental Prediction Climate Forecast System Reanalysis, Modern-Era Retrospective Analysis for Research and Applications, Japanese 55-year Reanalysis, and North American Regional Reanalysis. We show that although the analysis/reanalysis generally captures the atmospheric state of the cyclone, their biases in the derivative terms (Q1 and Q2) at regional scale of a few hundred kilometers are large and all analyses/reanalyses tend to underestimate the subgrid-scale upward transport of moist static energy in the lower troposphere. The 3DCVA-gridded large-scale forcing data are physically consistent with the spatial distribution of surface and TOA measurements of radiation, precipitation, latent and sensible heat fluxes, and clouds that are better suited to force SCMs, CRMs, and LESs. Possible applications of the 3DCVA are discussed. © 2015. The Authors."
"7005123385;56514898500;22956414100;6603767711;13608035400;6506948406;","A data assimilation technique to account for the nonlinear dependence of scatteringmicrowave observations of precipitation",2015,"10.1002/2015JD023107","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933278673&doi=10.1002%2f2015JD023107&partnerID=40&md5=16d15acb26c30af0f0012837cefca93f","Satellite microwave observations of rain, whether from radar or passive radiometers, depend in a very crucial way on the vertical distribution of the condensed water mass and on the types and sizes of the hydrometeors in the volume resolved by the instrument. This crucial dependence is nonlinear, with different types and orders of nonlinearity that are due to differences in the absorption/emission and scattering signatures at the different instrument frequencies. Because it is not monotone as a function of the underlying condensed water mass, the nonlinearity requires great care in its representation in the observation operator, as the inevitable uncertainties in the numerous precipitation variables are not directly convertible into an additive white uncertainty in the forward calculated observations. In particular, when attempting to assimilate such data into a cloud-permitting model, special care needs to be applied to describe and quantify the expected uncertainty in the observations operator in order not to turn the implicit white additive uncertainty on the input values into complicated biases in the calculated radiances. One approach would be to calculate the means and covariances of the nonlinearly calculated radiances given an a priori joint distribution for the input variables. This would be a very resource-intensive proposal if performed in real time. We propose a representation of the observation operator based on performing this moment calculation off line, with a dimensionality reduction step to allow for the effective calculation of the observation operator and the associated covariance in real time during the assimilation. The approach is applicable to other remotely sensed observations that depend nonlinearly on model variables, including wind vector fields. The approach has been successfully applied to the case of tropical cyclones, where the organization of the system helps in identifying the dimensionality-reducing variables. © 2015. American Geophysical Union. All Rights Reserved."
"57203104770;56829615200;56893370900;57214407959;7006971656;7004862277;","The influence of marine microbial activities on aerosol production: A laboratory mesocosm study",2015,"10.1002/2015JD023469","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943385025&doi=10.1002%2f2015JD023469&partnerID=40&md5=2ff7636a8edb9f59b7b9572df15d19bb","The oceans cover most of the Earth’s surface, contain nearly half the total global primary biomass productivity, and are a major source of atmospheric aerosol particles. Here we experimentally investigate links between biological activity in seawater and sea spray aerosol (SSA) flux, a relationship of potential significance for organic aerosol loading and cloud formation over the oceans and thus for climate globally. Bubbles were generated in laboratory mesocosm experiments either by recirculating impinging water jets or glass frits. Experiments were conducted with Atlantic Ocean seawater collected off the eastern end of Long Island, NY, and with artificial seawater containing cultures of bacteria and phytoplankton Thalassiosira pseudonana, Emiliania huxleyi, and Nannochloris atomus. Changes in SSA size distributions occurred during all phases of bacterial and phytoplankton growth, as characterized by cell concentrations, dissolved organic carbon, total particulate carbon, and transparent exopolymer particles (gel-forming polysaccharides representing a major component of biogenic exudate material). Over a 2 week growth period, SSA particle concentrations increased by a factor of less than 2 when only bacteria were present and by a factor of about 3 when bacteria and phytoplankton were present. Production of jet-generated SSA particles of diameter less than 200 nm increased with time, while production of all particle diameters increased with time when frits were used. The implications of a marine biological activity dependent SSA flux are discussed. © 2015. American Geophysical Union. All Rights Reserved."
"6602371262;54925973300;7003663939;","Quantifying the land-atmosphere coupling behavior in modern reanalysis products over the U.S. southern great plains",2015,"10.1175/JCLI-D-14-00680.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942843891&doi=10.1175%2fJCLI-D-14-00680.1&partnerID=40&md5=8541f62e36134edeb61907675d48b870","The coupling of the land with the planetary boundary layer (PBL) on diurnal time scales is critical to regulating the strength of the connection between soil moisture and precipitation. To improve understanding of land-atmosphere (L-A) interactions, recent studies have focused on the development of diagnostics to quantify the strength and accuracy of the land-PBL coupling at the process level. In this paper, the authors apply a suite of local land-atmosphere coupling (LoCo) metrics to modern reanalysis (RA) products and observations during a 17-yr period over the U.S. southern Great Plains. Specifically, a range of diagnostics exploring the links between soil moisture, evaporation, PBL height, temperature, humidity, and precipitation is applied to the summertime monthlymean diurnal cycles of the NorthAmerican Regional Reanalysis (NARR),Modern-Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR). Results showthatCFSRis the driest andMERRAthewettest of the threeRAs in terms of overall surface-PBLcoupling. When compared against observations, CFSR has a significant dry bias that impacts all components of the land-PBL system. CFSR and NARR are more similar in terms of PBL dynamics and response to dry and wet extremes, while MERRA is more constrained in terms of evaporation and PBL variability. Each RA has a unique land-PBL coupling that has implications for downstream impacts on the diurnal cycle of PBL evolution, clouds, convection, and precipitation as well as representation of extremes and drought. As a result, caution should be used when treating RAs as truth in terms of their water and energy cycle processes. © 2015 American Meteorological Society."
"57208579037;7006493632;26324818700;56443331100;","Attributing analysis on the model bias in surface temperature in the climate system model FGOALS-s2 through a process-based decomposition method",2015,"10.1007/s00376-014-4061-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922455211&doi=10.1007%2fs00376-014-4061-z&partnerID=40&md5=3f222c66b3baac1572d36a1aa215ac6a","This study uses the coupled atmosphere-surface climate feedback-response analysis method (CFRAM) to analyze the surface temperature biases in the Flexible Global Ocean-Atmosphere-Land System model, spectral version 2 (FGOALS-s2) in January and July. The process-based decomposition of the surface temperature biases, defined as the difference between the model and ERA-Interim during 1979–2005, enables us to attribute the model surface temperature biases to individual radiative processes including ozone, water vapor, cloud, and surface albedo; and non-radiative processes including surface sensible and latent heat fluxes, and dynamic processes at the surface and in the atmosphere. The results show that significant model surface temperature biases are almost globally present, are generally larger over land than over oceans, and are relatively larger in summer than in winter. Relative to the model biases in non-radiative processes, which tend to dominate the surface temperature biases in most parts of the world, biases in radiative processes are much smaller, except in the sub-polar Antarctic region where the cold biases from the much overestimated surface albedo are compensated for by the warm biases from nonradiative processes. The larger biases in non-radiative processes mainly lie in surface heat fluxes and in surface dynamics, which are twice as large in the Southern Hemisphere as in the Northern Hemisphere and always tend to compensate for each other. In particular, the upward/downward heat fluxes are systematically underestimated/overestimated in most parts of the world, and are mainly compensated for by surface dynamic processes including the increased heat storage in deep oceans across the globe. © 2015, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"55991322300;55164722000;","Influence of cosmic-ray variability on the monsoon rainfall and temperature",2015,"10.1016/j.jastp.2014.11.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912142400&doi=10.1016%2fj.jastp.2014.11.005&partnerID=40&md5=b063042fb53c9014bcc0b22398c73ecc","We study the role of galactic cosmic ray (GCR) variability in influencing the rainfall variability in Indian Summer Monsoon Rainfall (ISMR) season. We find that on an average during 'drought' (low ISMR) periods in India, GCR flux is decreasing, and during 'flood' (high ISMR) periods, GCR flux is increasing. The results of our analysis suggest for a possibility that the decreasing GCR flux during the summer monsoon season in India may suppress the rainfall. On the other hand, increasing GCR flux may enhance the rainfall. We suspect that in addition to real environmental conditions, significant levitation/dispersion of low clouds and hence reduced possibility of collision/coalescence to form raindrops suppresses the rainfall during decreasing GCR flux in monsoon season. On the other hand, enhanced collision/coalescence efficiency during increasing GCR flux due to electrical effects may contribute to enhancing the rainfall. Based on the observations, we put forward the idea that, under suitable environmental conditions, changing GCR flux may influence precipitation by suppressing/enhancing it, depending upon the decreasing/increasing nature of GCR flux variability during monsoon season in India, at least. We further note that the rainfall variability is inversely related to the temperature variation during ISMR season. We suggest an explanation, although speculative, how a decreasing/increasing GCR flux can influence the rainfall and the temperature. We speculate that the proposed hypothesis, based on the Indian climate data can be extended to whole tropical and sub-tropical belt, and that it may contribute to global temperature in a significant way. If correct, our hypothesis has important implication for the sun - climate link. © 2014 Elsevier Ltd."
"7003991093;6507253177;55789008200;14029905100;","Response of the large-scale structure of the atmosphere to global warming",2015,"10.1002/qj.2456","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939444860&doi=10.1002%2fqj.2456&partnerID=40&md5=5a262d3960e7a36b378dd5378b39b297","This article discusses the possible response of the large-scale atmospheric structure to a warmer climate. Using integrations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) in conjunction with physical arguments, we try to identify what changes are likely to be robust and what the underlying mechanisms might be. We focus on the large-scale zonally averaged circulation, in particular on height of the tropopause, the strength and position of the surface westerlies and the strength and extent of the Hadley Cell. We present analytic arguments and numerical calculations which suggest that under global warming the height of the tropopause will increase in both the transient response and final equilibrium state, and an increase is clearly found in all the comprehensive models in CMIP5. Upper stratospheric cooling is also found in the comprehensive models, and this too can be explained by a radiative argument. Regarding the circulation, most models show a slight expansion and weakening of the Hadley Cell, depending on season and hemisphere. The expansion is small and largely confined to winter but with some expansion in Southern Hemisphere summer. The weakening occurs principally in the Northern Hemisphere but the intermodel scatter is large. There is also a general polewards shift in surface westerlies, but the changes are small and again are little larger than the intermodel variability in the change. This shift is positively correlated with the Hadley Cell expansion to a degree that depends somewhat on the metric chosen for the latter. There is a robust strengthening in the Southern Hemisphere surface winds across seasons. In the Northern Hemisphere there is a slight strengthening in the westerlies in most models in winter but a consistent weakening of the westerlies in summer. We present various physical arguments concerning these circulation changes but none that are both demonstrably correct and that account for the model results. We conclude that the above-mentioned large-scale thermodynamic/radiative changes in the large-scale atmospheric structure are generally robust, in the sense of being both well understood and consistently reproduced by comprehensive models. In that sense the dynamical changes are less robust given the current state of knowledge and simulation, although one cannot conclude that they are, in principle, unknowable or less predictable. © 2015 Royal Meteorological Society."
"6505809593;7004314335;","Satellite observations of land surface temperature patterns induced by synoptic circulation",2015,"10.1002/joc.3971","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922825924&doi=10.1002%2fjoc.3971&partnerID=40&md5=9d975dd9594d17497e0c3843087542a8","Land surface temperature (LST) controls physical, chemical and biological processes on earth, and is used for assessing climatic changes. The seasonal and diurnal cycles, cloud cover, surface properties and atmospheric processes at several scales govern the LST, leading to its high spatial and temporal variability. In this study, a first attempt to assess the contribution of the synoptic scale circulation on LST is carried over using 2000-2012 MODIS data over the East Mediterranean (EM). This is demonstrated for 6 out of 19 synoptic circulation patterns characterizing the EM in the winter, summer and spring. Mean LST data calculated for each synoptic category (LSTsyn_cat) showed mainly the seasonality, i.e. climatological signal (LSTclim). In order to remove the seasonality, we used the LST anomaly (LSTsyn_cat-LSTclim), which 'cleaned' also the effects of vegetation and mineralogy, revealing the effects of circulation. Surface air temperature anomalies (at 995 sigma level) retrieved from NCEP/NCAR reanalysis calculated for the same synoptic categories were consistent with those of LST. This confirms the ability of remote sensing to detect the effect of the synoptic scale circulation on the spatial distribution of LST. © 2014 Royal Meteorological Society."
"55359866000;55342744700;6506696085;55145289900;56105220000;","Coupled atmospheric-ice load model for evaluation of wind plant power loss",2015,"10.1175/JAMC-D-14-0125.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944072777&doi=10.1175%2fJAMC-D-14-0125.1&partnerID=40&md5=49df8d819187b623910d7cbe23ef00f2","Icing is a weather phenomenon that is typical of cold climates. It impacts human activities through ice accretion on tower structures, transmission lines, and the blades of wind turbines. Icing on turbine blades, in particular, results in wind turbine performance degradation and/or safety shutdowns. The objective of this study is to explore the feasibility of using a coupled atmospheric and ice load model to simulate icing start-up, duration, and amount while also quantitatively evaluating power loss in wind plants related to icing events and mechanisms. Eight of 27 icing episodes identified for a wind plant in the Gaspé region of Québec (Canada) during the period 2008-10 were simulated using a mesoscale model (the Global Environmental Multiscale Limited-Area Model, or GEM-LAM). The simulations were verified using near-surface temperature, relative humidity, and wind speed, all of which compared well to in situ observations. Simulated wind speed, precipitation, cloud liquid water content, and median volume diameter of the droplets were used to drive ice load models to simulate the total ice load on a cylindrical structure. The three ice load models accounted for freezing rain, wet snow, and in-cloud icing, respectively, and in all three cases a sink term was added to account for melting due to radiation. The start-up and duration of ice were well captured by the coupled model, and a positive correlation was found between icing episodes and wind power reduction. This study demonstrates the improvements of the icing forecasts by using three ice load models, and provides a framework for both qualitative and quantitative evaluation of icing impact on wind turbine operations. © 2015 American Meteorological Society."
"7102266120;15751598400;55802246600;56075881200;8042408300;","The low-level jet over the southern great plains determined from observations and reanalyses and its impact on moisture transport",2015,"10.1175/JCLI-D-14-00719.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945903076&doi=10.1175%2fJCLI-D-14-00719.1&partnerID=40&md5=1549ad6f3370d4673057102ec417798b","This study utilizes six commonly used reanalysis products, including the NCEP-Department of Energy Reanalysis 2 (NCEP2), NCEP Climate Forecast System Reanalysis (CFSR), ECMWF interim reanalysis (ERA-Interim), Japanese 25-year Reanalysis Project (JRA-25), Modern-Era Retrospective Analysis for Research and Applications (MERRA), and North American Regional Reanalysis (NARR), to evaluate features of the southern Great Plains low-level jet (LLJ) above the U.S. Department of Energy's Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) Southern Great Plains site. Two sets of radiosonde data are utilized: the six-week Midlatitude Continental Convective Clouds Experiment (MC3E) and a 10-yr period spanning 2001 through 2010. All six reanalyses are compared to MC3E data, while only the NARR, MERRA, and CFSR are compared to the 10-yr data. The reanalyses are able to represent most aspects of the composite LLJ profile, although there is a tendency for each reanalysis to overestimate the wind speed between the nose of the LLJ (at approximately 900 mb) and a pressure level of 700 mb. There are large discrepancies in the number of LLJs observed and derived from the reanalysis, particularly for strong LLJs, leading to an underestimate of the moisture transport associated with LLJs. When the 10-yr period is considered, the NARR and CFSR overestimate and MERRA underestimates the total moisture transport, but all three underestimate the transport associated with strong LLJs by factors of 1.4, 2.0, and 2.7 for CFSR, NARR, and MERRA, respectively. During MC3E there were differences in the patterns of moisture convergence and divergence, but the patterns are more consistent during the 10-yr period. © 2015 American Meteorological Society."
"56372296600;7102811204;9233178200;57193072346;56875345100;37013011200;48661217200;","Multi-temporal landsat images and ancillary data for land use/cover change (LULCC) detection in the Southwest of Burkina Faso, West Africa",2015,"10.3390/rs70912076","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942521959&doi=10.3390%2frs70912076&partnerID=40&md5=3b0a6ec1f5af39853f0a2deb3a80bc4d","Accurate quantification of land use/cover change (LULCC) is important for efficient environmental management, especially in regions that are extremely affected by climate variability and continuous population growth such as West Africa. In this context, accurate LULC classification and statistically sound change area estimates are essential for a better understanding of LULCC processes. This study aimed at comparing mono-temporal and multi-temporal LULC classifications as well as their combination with ancillary data and to determine LULCC across the heterogeneous landscape of southwest Burkina Faso using accurate classification results. Landsat data (1999, 2006 and 2011) and ancillary data served as input features for the random forest classifier algorithm. Five LULC classes were identified: woodland, mixed vegetation, bare surface, water and agricultural area. A reference database was established using different sources including high-resolution images, aerial photo and field data. LULCC and LULC classification accuracies, area and area uncertainty were computed based on the method of adjusted error matrices. The results revealed that multi-temporal classification significantly outperformed those solely based on mono-temporal data in the study area. However, combining mono-temporal imagery and ancillary data for LULC classification had the same accuracy level as multi-temporal classification which is an indication that this combination is an efficient alternative to multi-temporal classification in the study region, where cloud free images are rare. The LULCC map obtained had an overall accuracy of 92%. Natural vegetation loss was estimated to be 17.9% ± 2.5% between 1999 and 2011. The study area experienced an increase in agricultural area and bare surface at the expense of woodland and mixed vegetation, which attests to the ongoing deforestation. These results can serve as means of regional and global land cover products validation, as they provide a new validated data set with uncertainty estimates in heterogeneous ecosystems prone to classification errors. © 2015 by the authors."
"26023029400;55737886800;6602925483;7103396041;","A GIS-based assessment of the suitability of SCIAMACHY satellite sensor measurements for estimating reliable CO concentrations in a low-latitude climate",2015,"10.1007/s10661-014-4227-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921900266&doi=10.1007%2fs10661-014-4227-2&partnerID=40&md5=482a13fe8b0ca7c1846e502bbb9c6b3a","An assessment of the reliability of the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) satellite sensor measurements to interpolate tropospheric concentrations of carbon monoxide considering the low-latitude climate of the Niger Delta region in Nigeria was conducted. Monthly SCIAMACHY carbon monoxide (CO) column measurements from January 2,003 to December 2005 were interpolated using ordinary kriging technique. The spatio-temporal variations observed in the reliability were based on proximity to the Atlantic Ocean, seasonal variations in the intensities of rainfall and relative humidity, the presence of dust particles from the Sahara desert, industrialization in Southwest Nigeria and biomass burning during the dry season in Northern Nigeria. Spatial reliabilities of 74 and 42 % are observed for the inland and coastal areas, respectively. Temporally, average reliability of 61 and 55 % occur during the dry and wet seasons, respectively. Reliability in the inland and coastal areas was 72 and 38 % during the wet season, and 75 and 46 % during the dry season, respectively. Based on the results, the WFM-DOAS SCIAMACHY CO data product used for this study is therefore relevant in the assessment of CO concentrations in developing countries within the low latitudes that could not afford monitoring infrastructure due to the required high costs. Although the SCIAMACHY sensor is no longer available, it provided cost-effective, reliable and accessible data that could support air quality assessment in developing countries. © 2015, Springer International Publishing Switzerland."
"56505654900;6603533228;7003480967;57204252724;","Changes in intense precipitation events in Mexico City",2015,"10.1175/JHM-D-14-0081.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941312981&doi=10.1175%2fJHM-D-14-0081.1&partnerID=40&md5=d248b91fd0d362a36bda9d5f48f3b678","The authors analyzed an extensive precipitation dataset available for the Mexico City basin that included hourly precipitation in various sectors of the city from 1993 to 2007. Observations indicated that significant changes occurred in the timing and number of intense events (precipitation rate < 20mm h-1) over this time period. Alternative hypotheses that changes in the emission of aerosol pollutants or in the land use can result in the observed variations are tested. The Weather Research and Forecasting Model was used to simulate September precipitation from 2002 to 2011 at the peak of the wet season. Changes were introduced to the microphysical scheme as a proxy for differences in the aerosol population and the droplet activation spectra. Simulations were also performed with the land use of the urban areas set up to represent older and more current conditions. Results indicate that increased pollution (decreased urban area) led to an average precipitation decrease over the mountain areas of 20%-40% (10%-20%) and an increase of 20% (30%) to the east of Mexico City. The timing of intense precipitation shifts from 1900 to 1600 LT for the polluted and decreased urban area cases when compared to a control experiment. These results add valuable information about how precipitation is modified by complex terrain and surface exchange processes in large urban areas under wet conditions."
"55946400800;6602371262;6507498114;55999844600;","Impact of irrigation methods on land surface model spinup and initialization of WRF forecasts",2015,"10.1175/JHM-D-14-0203.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941273996&doi=10.1175%2fJHM-D-14-0203.1&partnerID=40&md5=7f965542ad864b1c46424020006fbde4","In the United States, irrigation represents the largest consumptive use of freshwater and accounts for approximately one-third of total water usage. Irrigation impacts soil moisture and can ultimately influence clouds and precipitation through land-planetary boundary layer (PBL) coupling processes. This study utilizesNASA's Land Information System(LIS) and theNASAUnified Weather Research and ForecastingModel (NU-WRF) framework to investigate the effects of drip, flood, and sprinkler irrigation methods on land-atmosphere interactions, including land-PBL coupling and feedbacks at the local scale. To initialize 2-day, 1-km WRF forecasts over the centralGreat Plains in a drier-than-normal (2006) and a wetter-than-normal year (2008), 5-yr irrigated LIS spinupswere used. The offline and coupled simulation results show that regional irrigation impacts are sensitive to time, space, andmethod and that irrigation cools andmoistens the surface over and downwind of irrigated areas, ultimately resulting in both positive and negative feedbacks on the PBL depending on the time of day and background climate conditions. Furthermore, the results portray the importance of both irrigation method physics and correct representation of several key components of land surfacemodels, including accurate and timely land-cover and crop-type classification, phenology (greenness), and soilmoisture anomalies (through a land surface model spinup) in coupled prediction models. © 2015 American Meteorological Society."
"57144839900;14065573800;","Observational evidence of frontal-scale atmospheric responses to Kuroshio extension variability",2015,"10.1175/JCLI-D-14-00829.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950149572&doi=10.1175%2fJCLI-D-14-00829.1&partnerID=40&md5=0bfe29d2fc6dd8c81caebbd2a7a03a87","This study investigates the regional atmospheric response to the Kuroshio Extension (KE) using a combination of multiple satellite observations and reanalysis data from boreal winter over a period of at least a decade. The goal is to understand the relationship between KE variations and atmospheric responses at low frequencies. A climate index is used to measure the interannual to decadal KE variability, which leaves remarkable imprints on the mesoscale sea surface temperature (SST). Clear spatial coherence between the SST signals and frontal-scale atmospheric variables, including surface wind convergence, vertical velocity, precipitation, and clouds, is identified by linear regression analysis. Consistent with previous studies, the penetrating effect of the KE variability on the free atmosphere is found. The westward tilt of the atmospheric response above the KE near 500 hPa is revealed. The difference in the associations of frontal-scale air temperature and geopotential height with the KE variability between the satellite observations and the reanalysis data suggests an imperfect interpretation of frontal-scale oceanic forcing on the overlying atmosphere in the reanalysis assimilation system. © 2015 American Meteorological Society."
"56897063400;24576967300;6701660199;56897131600;","Spectral indicators of forage quality in West Africa's tropical savannas",2015,"10.1016/j.jag.2015.04.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943646558&doi=10.1016%2fj.jag.2015.04.019&partnerID=40&md5=c2aeaa62e9c40927e106f1cf6dedb9d1","Forage is among the essential ecosystem services provided by tropical savannas. Expected changes in climate and land usemaycause a strong decline in herbaceous forage provision and thus make it advisable to monitor its dynamics. Spectroscopy offers promising tools for fast and non-destructive estimations of forage variables, yet suffers from unfavourable measurement conditions during the tropical growing period such as frequent cloud cover and high humidity. This study aims to test whether spatio-temporal information on the quality (metabolisable energy content, ME) and quantity (green biomass, BM) of West African forage resources can be correlated to in situ measured reflectance data. We could establish robust and independent models via partial least squares regression, when spectra were preprocessed using second derivative transformation (ME: max. adjusted R2 in validation (adjR2 VAL) = 0.83, min. normalised root mean square error (nRMSE) = 7.3%; BM: max. adjR2 VAL = 0.75, min. nRMSE = 9.4%). Reflectance data with a reduced spectral range (350-1075 nm) still rendered satisfactory accuracy. Our results confirm that a strong correlation between forage characteristics and reflectance of tropical savanna vegetation can be found. For the first time in field spectroscopy studies, forage quality is modelled as ME content based on 24-h in vitro gas production in the Hohenheim gas test system and crude protein concentration of BM. Established spectral models could help to monitor forage provision in space and time, which is of great importance for an adaptive livestock management. © 2015 Elsevier B.V."
"7101667328;","Correction of excessive precipitation over steep and high mountains in a GCM: A simple method of parameterizing the thermal effects of subgrid topographic variation",2015,"10.1175/JAS-D-14-0336.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941251022&doi=10.1175%2fJAS-D-14-0336.1&partnerID=40&md5=f4c714f5b37c96d086bda6d4037c1a84","The excessive precipitation over steep and high mountains (EPSM) in GCMs and mesoscale models is due to a lack of parameterization of the thermal effects of subgrid-scale topographic variation. These thermal effects drive subgrid-scale heated-slope-induced vertical circulations (SHVC). SHVC provide a ventilation effect of removing heat from the boundary layer of resolvable-scale mountain slopes and depositing it higher up. The lack of SHVC parameterization is the cause of EPSM. The author has previously proposed a method of parameterizing SHVC, here termed SHVC.1. Although this has been successful in avoiding EPSM, the drawback is that it suppresses convective-type precipitation in the regions where it is applied. In this article, the author proposes a new method of parameterizing SHVC, here termed SHVC.2. In SHVC.2, the potential temperature and mixing ratio of the boundary layer are changed when used as input to the cumulus parameterization scheme over mountainous regions. This allows the cumulus parameterization to assume the additional function of SHVC parameterization. SHVC.2 has been tested in NASA Goddard's GEOS-5 GCM. It achieves the primary goal of avoiding EPSM while also avoiding the suppression of convective-type precipitation in the regions where it is applied. © 2015 American Meteorological Society."
"57203102974;6506612036;","An analysis of global aerosol type as retrieved by MISR",2015,"10.1002/2015JD023322","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930377103&doi=10.1002%2f2015JD023322&partnerID=40&md5=e9b24203876f5ce570dd97c49c46a703","In addition to aerosol optical depth (AOD), aerosol type is required globally for climate forcing calculations, constraining aerosol transport models and other applications. However, validating satellite aerosol-type retrievals is more challenging than testing AOD results, because aerosol type is a more complex quantity, and ground truth data are far less numerous and generally not as robust. We evaluate the Multiangle Imaging Spectroradiometer (MISR) Version 22 aerosol-type retrievals by assessing product self-consistency on a regional basis and by making comparisons with general expectation and with the Aerosol Robotic Network aerosol-type climatology, as available. The results confirm and add detail to the observation that aerosol-type discrimination improves dramatically where midvisible AOD exceeds about 0.15 or 0.2. When the aerosol-type information content of the observations is relatively low, increased scattering-angle range improves particle-type sensitivity. The MISR standard, operational product discriminates among small, medium, and large particles and exhibits qualitative sensitivity to single-scattering albedo (SSA) under good aerosol-type retrieval conditions, providing a categorical aerosol-type classification. MISR Ångström exponent deviates systematically from ground truth where particle types missing from the algorithm climatology are present, or where cloud contamination is likely to occur, and SSA tends to be overestimated where absorbing particles are found. We determined that the number of mixtures passing the algorithm acceptance criteria (#SuccMix) represents aerosol-type retrieval quality effectively, providing a useful aerosol-type quality flag. © 2015. American Geophysical Union. All Rights Reserved."
"55344397300;7006306835;7005808242;","Mechanisms of forced tropical meridional energy flux change",2015,"10.1175/JCLI-D-14-00165.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926059668&doi=10.1175%2fJCLI-D-14-00165.1&partnerID=40&md5=872f56d7b9ab5f94dc3cea8fed71d4eb","Anthropogenically forced changes to the mean and spatial pattern of sea surface temperatures (SSTs) alter tropical atmospheric meridional energy transport throughout the seasonal cycle-in total, its partitioning between the Hadley cells and eddies and, for the Hadley cells, the relative roles of the mass flux and the gross moist stability (GMS). The authors investigate this behavior using an atmospheric general circulation model forced with SST anomalies caused by either historical greenhouse gas or aerosol forcing, dividing the SST anomalies into two components: the tropicalmean SST anomaly applied uniformly and the full SST anomalies minus the tropical mean. For greenhouse gases, the polar-amplified SST spatial pattern partially negates enhanced eddy poleward energy transport driven by mean warming. Both SST components weaken winter Hadley cell circulation and alter GMS. The Northern Hemisphere-focused aerosol cooling induces northward energy flux anomalies in the deep tropics, which manifest partially via strengthened northern and weakened southern Hadley cell overturning. Aerosol-induced GMS changes also contribute to the northward energy fluxes. A simple thermodynamic scaling qualitatively captures these changes, although it performs less well for the greenhouse gas simulations. The scaling provides an explanation for the tight correlation demonstrated in previous studies between shifts in the intertropical convergence zone and crossequatorial energy fluxes. © 2015 American Meteorological Society."
"16234359000;24467994800;7102811204;24070648400;35168189000;6701611146;","Modelling the Gross Primary Productivity of West Africa with the Regional Biomass Model RBM+, using optimized 250 m MODIS FPAR and fractional vegetation cover information",2015,"10.1016/j.jag.2015.04.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943622131&doi=10.1016%2fj.jag.2015.04.007&partnerID=40&md5=eea259f5ad6e264ae6f894d5cc86a2d7","Global warming associated with climate change is one of the greatest challenges of today's world. Increasing emissions of the greenhouse gas CO2 are considered as a major contributing factor to global warming. One regulating factor of CO2 exchange between atmosphere and land surface is vegetation. Measurements of land cover changes in combination with modelling the Gross Primary Productivity (GPP) can contribute to determine important sources and sinks of CO2. The aim of this study is to accurately model the GPP for a region in West Africa with a spatial resolution of 250 m, and the differentiation of GPP based on woody and herbaceous vegetation. For this purpose, the Regional Biomass Model (RBM) was applied, which is based on a Light Use Efficiency (LUE) approach. The focus was on the spatial enhancement of the RBM from the original 1000-250 m spatial resolution (RBM+). The adaptation to the 250 m scale included the modification of two main input parameters: (1) the fraction of absorbed Photosynthetically Active Radiation (FPAR) based on the 1000 m MODIS MOD15A2 FPAR product which was downscaled to 250 m using MODIS NDVI time series; (2) the fractional cover of woody and herbaceous vegetation, which was improved by using a multi-scale approach. For validation and regional adjustments of GPP and the input parameters, in situ data from a climate station and eddy covariance measurements were integrated. The results of this approach show that the input parameters could be improved significantly: downscaling considerably reduces data gaps of the original FPAR product and the improved dataset differed less than 5.0% from the original data for cloud free regions. The RMSE of the fractional vegetation cover varied between 5.1 and 12.7%. Modelled GPP showed a slight overestimation in comparison to eddy covariance measurements. The in situ data was exceeded by 8.8% for 2005 and by 2.0% for 2006. The model results were converted to NPP and also agreed well with previous NPP measurements reported from different studies. Altogether a high accuracy and suitability of the regionally adjusted and downscaled model RBM+ can be concluded. The differentiation between vegetation growth forms allows a separation of long-term and short-term carbon storage based on woody and herbaceous vegetation, respectively. © 2015 Elsevier B.V."
"56048117600;57213081821;54179678200;56457817300;6603868770;6603499076;6701527592;56412846600;36458602300;35203870600;55481995500;55575920100;","Towards a high-resolution regional reanalysis for the european CORDEX domain",2015,"10.1002/qj.2486","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922793888&doi=10.1002%2fqj.2486&partnerID=40&md5=19b5f31a249d3a5bb08192191b4d303c","Atmospheric reanalyses covering the European region are mainly available as part of relatively coarse global reanalyses. The aim of this article is to present the development and evaluation of a next generation regional reanalysis for the European CORDEX EUR-11 domain with a horizontal grid spacing of approximately 6 km. In this context, a reanalysis is understood to be an assimilation of heterogeneous observations with a physical model such as a numerical weather prediction (NWP) model. The reanalysis system presented here is based on the NWP model COSMO by the German Meteorological Service (Deutscher Wetterdienst) using a continuous nudging scheme. In order to assess the added value of data assimilation, a dynamical downscaling experiment has been conducted, i.e. an identical model set-up but without data assimilation. Both systems have been evaluated for a 1 year test period, employing standard measures such as analysis increments, biases, or log-odds ratios, as well as tests for distributional characteristics. An important aspect is the evaluation from different perspectives and with independent measurements such as satellite infrared brightness temperatures using forward operators, integrated water vapour from GPS stations, and ceilometer cloud cover. It can be shown that the reanalysis better resolves local extreme events; this is basically an effect of the higher spatio-temporal resolution, as known from dynamical downscaling approaches. However, an important criterion for regional reanalyses is the coherence with independent observations of high temporal and spatial resolution, resulting in significant improvement over dynamical downscaling. The system is intended to become operational within a year, continuously reprocessing and evaluating longer time periods. The reanalysis data are planned to become available to the research community within a year. Synthetic satellite image for 24 August 2011 at 1200 UTC overlayed (in ascending sequence) with 1-hour precipitation sums and contour plots of wind speed and zonal temperature anomalies at 8 km height from the high-resolution regional reanalysis (left). The corresponding MSG satellite image is shown on the right. The article describes setup and details of a regional reanalysis for CORDEX-Europe at 6 km horizontal resolution. The performance of the model is evaluated and the reanalysis is compared to independent observations as well as ERA-Interim and a dynamical downscaling run. © 2015 Royal Meteorological Society 141 686 January 2015 Part A 10.1002/qj.2486 Featured Research Article Featured Research Article © 2014 Royal Meteorological Society."
"36866503400;36138641800;7004233526;","The North American Cordillera-An impediment to growing the continent-wide laurentide ice sheet",2015,"10.1175/JCLI-D-15-0044.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950117585&doi=10.1175%2fJCLI-D-15-0044.1&partnerID=40&md5=b9cdb0a99224187728bbe947879c17b1","This study examines the evolution of a continental-scale ice sheet on a triangular representation of North America, with and without the influence of the Cordilleran region. Simulations are conducted using a comprehensive atmospheric general circulation model asynchronously coupled to a three-dimensional thermomechanical ice-sheet model. The atmospheric state is updated for every 2 × 106 km3 increase in ice volume, and the coupled model is integrated to steady state. In the first experiment a flat continent with no background topography is used. The ice sheet evolves fairly zonally symmetric, and the equilibriumstate is continent-wide and has the highest point in the center of the continent. This equilibrium ice sheet forces an anticyclonic circulation that results in relatively warmer (cooler) summer surface temperatures in the northwest (southeast), owing to warm (cold) air advection and radiative heating due to reduced cloudiness. The second experiment includes a simplified representation of the Cordilleran region. The ice sheet's equilibrium state is here structurally different from the flat continent case; the center of mass is strongly shifted to the east and the interior of the continent remains ice free-an outline broadly resembling the geologically determined ice margin in Marine Isotope Stage 4. The limited glaciation in the continental interior is the result of warm summer surface temperatures primarily due to stationary waves and radiative feedbacks. © 2015 American Meteorological Society."
"55717347500;56962915800;7203062717;","Roles of barotropic convective momentum transport in the intraseasonal oscillation",2015,"10.1175/JCLI-D-14-00575.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942928215&doi=10.1175%2fJCLI-D-14-00575.1&partnerID=40&md5=8d26458617af248bd0d65cab91e45078","Both observational data analysis and model simulations suggest that convective momentum transport (CMT) by cumulus convection may play a significant role in the intraseasonal oscillations (ISO) by redistributing atmospheric momentum vertically through fast convective mixing process. The authors present a simple theoretical model for the ISO by parameterizing the cumulus momentum transport process in which the CMT tends to produce barotropic wind anomalies that will affect the frictional planetary boundary layer (PBL). In the model with equatorial easterly vertical wind shear (VWS), it is found that the barotropic CMT tends to select most unstable planetary-scale waves because CMT suppresses the equatorial Ekman pumping of short waves, which reduces the shortwave instability from the PBL moisture convergence and accelerates the shortwave propagation. The model with subtropical easterly VWS has behavior that can be qualitatively different from the model with equatorial easterly VWS and has robust northward propagation. The basic mechanism of this northward propagation is that the CMT accelerates the barotropic cyclonic wind to the north of ISO, which will enhance the precipitation by PBL Ekman pumping and favor the northward propagation. The simulated northward propagation is sensitive to the strength and location of the seasonal-mean easterly VWS. These results suggest that accurate simulation of the climatological-mean state is critical for reproducing the realistic ISO in general circulation models. © 2015 American Meteorological Society."
"37261023300;7404297096;6701681018;","Increasing evaporation amounts seen in the Arctic between 2003 and 2013 from AIRS data",2015,"10.1002/2015JD023258","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939252987&doi=10.1002%2f2015JD023258&partnerID=40&md5=cce3327b5e1aaad01701b28c24e9666b","The vertical moisture flux (i.e., evaporation) plays an important role in the Arctic energy budget, the water vapor feedback, and Arctic amplification. It is one of the most uncertain variables, especially in this “new Arctic” climate system, which is dominated by large ice-free ocean areas for a longer portion of the year. Moisture flux rates, produced using Atmospheric Infrared Sounder (AIRS) data, from the Arctic Ocean and surrounding seas were found to have increased between 2003 and 2013 by 7.2 × 10-4gm-2 s-1 per year (equivalent to 1.79Wm-2 per year in latent heat). This is a 7% increase in the average moisture flux each year and a 0.12% increase in the yearly global ocean latent heat flux, with some months increasing more than others. The largest increases seen are in the Arctic coastal seas during the spring and fall where there has been a reduction in sea ice cover and an increase in sea surface temperatures. Increases in the moisture flux from the surface also correspond to increases in total atmospheric column water vapor and low-level clouds, especially in the central Arctic regions. Changes in the atmospheric water vapor in the surrounding seas (e.g., East Greenland) are most likely due to lower latitude transport of moisture rather than from the surface. Yearly, the moisture flux from the surface supplies about 10% of the total column atmosphere water vapor. © 2015. American Geophysical Union. All Rights Reserved."
"56647766300;56648063100;56647799000;","Motivation for and development of a standardized introductory meteorology assessment exam",2015,"10.1175/BAMS-D-13-00157.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929455079&doi=10.1175%2fBAMS-D-13-00157.1&partnerID=40&md5=878f1df9c94571a1deb95ac2f432caa6","Education research has shown that there is often a disconnect between what instructors teach and what students actually comprehend. Much of this disconnect stems from students' previous conceptions of the subject that often remain steadfast despite instruction. The field of meteorology is particularly susceptible to misconceptions as a result of the years of personal experience students have with weather before instruction. Consequently, it is often challenging for students to accurately integrate course material with their observations and personal explanations. A longitudinal assessment exam of the meteorology program at the U.S. Air Force Academy revealed that misconceptions of fundamental, introductory content can propagate through years of instruction, potentially impeding deeper understanding of advanced topics and hindering attainment of professional certifications. Thus, it is clear that such misconceptions must be identified and corrected early. This manuscript describes the development of the Fundamentals in Meteorology Inventory (FMI), a multiple-choice assessment exam designed to identify the common misconceptions of fundamental topics covered in introductory meteorology courses. In developing the FMI, care was taken to avoid complex vocabulary and to include plausible distractors identified by meteorology faculty members. Question topics include clouds and precipitation, wind, fronts and air masses, temperature, stability, severe weather, and climate. Applications of the exam for the meteorology community are discussed, including identifying common meteorology misconceptions, assessing student understanding, measuring teaching effectiveness, and diagnosing areas for improvement in introductory meteorology courses. Future work to be completed to ensure the efficacy of the FMI will also be acknowledged. © 2015 American Meteorological Society."
"7202081585;35459699300;23978675000;7202048299;6701511321;","Investigation of the transport processes controlling the geographic distribution of carbon monoxide at the tropical tropopause",2015,"10.1002/2014JD022661","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925629770&doi=10.1002%2f2014JD022661&partnerID=40&md5=c9f9cafb3de0743c96a6a6a6a8cd2d9c","Convectively influenced trajectory calculations are used to investigate the impact of different Tropical Tropopause Layer (TTL) transport pathways for establishing the distribution of carbon monoxide (CO) at 100 hPa as observed by the Microwave Limb Sounder (MLS) on board the Aura satellite. Carbon monoxide is a useful tracer for investigating TTL transport and convective influence because the CO lifetime (≃1-2 months) is comparable to the time required for slow ascent through the TTL. MERRA horizontal winds are used for the diabatic trajectories, and off-line calculations of TTL radiative heating are used to determine the vertical motion field. The locations and times of convective influence events along the trajectories are determined from 3-hourly, geostationary satellite measurements of convective clouds. The trajectory model reproduces most of the prominent features in the 100 hPa CO geographic distribution indicated by the MLS observations for the winter and summer 2007 periods simulated. CO concentrations and tendencies simulated with the Whole Atmosphere Climate Chemistry Model (WACCM) are used to specify boundary-layer concentrations for convective influence and CO loss rates resulting from reaction with OH. The broad maximum in CO concentration over the Pacific during Boreal winter is primarily a result of the strong radiative heating (corresponding to upward vertical motion) associated with the abundant TTL cirrus in this region. Convection over the Pacific brings clean maritime air to the tropopause region and actually decreases the 100 hPa CO. The relative abundance of CO over the continental convective regions during wintertime is sensitive to small variations in convective cloud-top height. Both the simulated and the observed summertime 100 hPa CO distributions are dominated by the maximum co-located with the upper level anticyclone forced by the Asian monsoon convection. Sensitivity tests indicate that the summertime Asian monsoon anticyclone 100 hPa CO maximum is dominated by extreme convective systems with detrainment of polluted air above about 360-365 K potential temperature. This result stems directly from the fact that the heating rates are negative (downward motion) below 360-365 K during summertime through most of the tropics; therefore, air detrained from convection at lower levels will generally just sink back down into the middle troposphere. We find that most of the CO feeding into the Asian monsoon anticyclone comes from convection over the Tibetan Plateau and India, with relatively minor contributions from southeast Asia and eastern China. © 2015. American Geophysical Union. All Rights Reserved."
"15766838300;25421717700;55602947100;36705265400;","Characterisation and predictability of a strong and a weak forcing severe convective event - A multi-data approach",2015,"10.1127/metz/2015/0625","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937547034&doi=10.1127%2fmetz%2f2015%2f0625&partnerID=40&md5=499daad2b28b52c2cad305b082eda9e3","Two severe summer-time convective events in Germany are investigated which can be classified by the prevailing synoptic conditions into a strong and a weak forcing case. The strong forcing case exhibits a larger scale precipitation pattern caused by frontal ascent whereas scattered convection is dominating the convective activity in the weak forcing case. Other distinguished differences between the cases are faster movement of convective cells and larger regions with significant loss mainly due to severe gusts in the strong forcing case. A comprehensive set of various observations is used to characterise the two different events. The observations include measurements from a lightning detection network, precipitation radar, geostationary satellite and weather stations, as well as information from an automated cell detection algorithm based on radar reflectivity which is combined with severe weather reports, and damage data from insurances. Forecast performance at various time scales is analysed ranging from nowcasting and warning to shortrange forecasting. Various methods and models are examined, including human warnings, observation-based nowcasting algorithms and high-resolution ensemble prediction systems. The analysis shows the advantages of a multi-sensor and multi-source approach in characterising convective events and their impacts. Using data from various sources allows to combine the different strengths of observational data sets, especially in terms of spatial coverage or data accuracy, e.g. damage data from insurances provide good spatial coverage with little meteorological information while measurements at weather stations provide accurate but pointwise observations. Furthermore, using data from multiple sources allow for a better understanding of the convective life cycle. Several parameters from different instruments are shown to have a predictive skill for convective development, these include satellite-based cloud-top cooling rates as measure for intensive convective growth, 3D-radar reflectivity, mesocyclone detection from doppler radar, overshooting top detection or lightning jumps to evaluate storm intensification and formation of severe weather. This synergetic approach can help to improve nowcasting algorihtms and thus the warning process. The predictability of the analysed severe convective events differs with different types of forcing which is reflected in both, convective-scale ensemble prediction system forecasts and human weather warnings. Human warnings show larger false alarm rates in the weak forcing case. Ensemble predictions are able to capture the characteristics of the convective precipitation. The forecast skill is connected strongly to the synoptic situation and the presence of large-scale forcing increases the forecast skill. This has to be considered for potential future warn-on-forecast strategies. © 2015 The authors."
"56336485600;36795110800;7403209556;","The life cycle assessment of a UK data centre",2015,"10.1007/s11367-014-0838-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961289760&doi=10.1007%2fs11367-014-0838-7&partnerID=40&md5=15618b4c8d3457b532b790e9a2b8fca2","Purpose: Data centres are high-energy consumers, and historical assessment of their environmental impact has focused largely on energy consumption. Widely adopted assessment methods consider either single issues or do not comprehensively assess links between issues. One exception is the CLEER Model, which compares life cycle energy and greenhouse gas (GHG) emissions of Cloud-based and present-day services. However, there remains the need to verify components for inclusion in a data centre life cycle assessment (LCA), assess quality and quantity of secondary data, benchmark an existing data centre LCA, assess non-Cloud-based services for multiple impacts, and establish facility areas that are sensitive to change. Methods: A hybrid approach, combining process-based and economic input output (EIO) data, was used to perform the screening LCA of an existing UK data centre. The study includes the definition of the goal and scope, modelling assumptions, a life cycle inventory, results and interpretation and a sensitivity check. Results and discussion: The dominance of the information technology (IT) operational phase to the overall impact and the severity of the impact on human health are concluded. Due to the use of free cooling, the IT-embodied impact is greater than the combined mechanical and electrical operational impact. Electricity production dominates the total life cycle impact; however, the second most significant impact derives from the disposal of metal refining waste products during the manufacture of IT components and electricity distribution networks. The release of carcinogens is one of the largest contributors to the whole life cycle impact and is almost equal in value between the embodied and operational phases. Finally, a sensitivity check found that a Swedish facility optimised for operational energy efficiency with a 1.25-year server refresh resulted in an embodied impact almost double the operational. Conclusions: It was concluded that current LCI data, software packages and project data allow for a sufficiently accurate data centre LCA model. The results support the need to broaden environmental impact reduction to beyond operational energy consumption for cooling and that building environmental assessment methods (BEAMs) should consider more embodied impacts. It is concluded also that three parameters are sensitive to design changes that influence the overall impact: operational energy for the IT equipment, cooling and power delivery; the energy mix; and the amount of IT equipment across the facility’s lifetime. The results present a clear need to monitor life cycle impact, develop further tools to compare different design/operation options and functional units, improve data and develop an LCA-based BEAM. © 2015, Springer-Verlag Berlin Heidelberg."
"55914512600;56375050900;57214142405;","Analysis of optical and physical properties of aerosols during crop residue burning event of October 2010 over Lahore, Pakistan",2015,"10.1016/j.apr.2015.05.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954560323&doi=10.1016%2fj.apr.2015.05.002&partnerID=40&md5=49aa5e5df0c4960595d5c12eb2462542","Aerosols released from biomass burning affect the tropospheric chemistry, radiation budget and cloud processes and hence can cause significant climate modifications. Due to certain economical reasons, the open burning of crop residue has become popular in Pakistan. In the present work we have analyzed the optical and physical properties of aerosols during crop residue burning over Lahore, a central location of Pakistan. The data from ground based Aerosol Robotic Network (AERONET), satellite based MODIS and CALIPSO remote sensing instruments have been used for the characterization of aerosols during crop residue burning event of October 2010. The maximum value (2.75) of daily mean AOD was observed on 20 October 2010 and the next highest value of 2.64 was observed on 19 October 2010, indicating heavy aerosol loading over Lahore on both days due to intense crop residue burning. The fine mode AOD values ranged from 0.14 to 2.68 (on 20 October 2010) with average value of 0.87 during October 2010 over Lahore. It was found that fine mode aerosols have greater contribution than coarse mode aerosols towards total aerosol burden indicating the presence of fine mode (crop residue burning) aerosols over Lahore. Cluster analysis showed that the mixed aerosols (biomass burning and urban-industrial) were present during the heavy aerosol loading period over Lahore. The highest volume concentration of fine mode occurred on 19 and 20 October 2010 representing the dominance of fine mode aerosols. Due to scattering of incoming solar radiation by intense smoke observed on 19 and 20 October 2010 high values of SSA (~0.95) were found. HYSPLIT model backward trajectories showed that the winds transported aerosols from southeast and northwest directions. © 2015 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V. All rights reserved."
"26536715700;13407050600;7103008628;14020325100;56441562600;7005717609;6701538799;","A real-time convection-allowing ensemble prediction system initialized by mesoscale ensemble Kalman filter analyses",2015,"10.1175/WAF-D-15-0013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944590333&doi=10.1175%2fWAF-D-15-0013.1&partnerID=40&md5=6d02fa5e9d85bf0878e68d532e651102","In May and June 2013, the National Center for Atmospheric Research produced real-time 48-h convection-allowing ensemble forecasts at 3-km horizontal grid spacing using the Weather Research and Forecasting (WRF) Model in support of the Mesoscale Predictability Experiment field program. The ensemble forecasts were initialized twice daily at 0000 and 1200 UTC from analysis members of a continuously cycling, limited-area, mesoscale (15 km) ensemble Kalman filter (EnKF) data assimilation system and evaluated with a focus on precipitation and severe weather guidance. Deterministic WRF Model forecasts initialized from GFS analyses were also examined. Subjectively, the ensemble forecasts often produced areas of intense convection over regions where severe weather was observed. Objective statistics confirmed these subjective impressions and indicated that the ensemble was skillful at predicting precipitation and severe weather events. Forecasts initialized at 1200 UTC were more skillful regarding precipitation and severe weather placement than forecasts initialized 12 h earlier at 0000 UTC, and the ensemble forecasts were typically more skillful than GFS-initialized forecasts. At times, 0000 UTC GFS-initialized forecasts had temporal distributions of domain-average rainfall closer to observations than EnKF-initialized forecasts. However, particularly when GFS analyses initialized WRF Model forecasts, 1200 UTC forecasts produced more rainfall during the first diurnal maximum than 0000 UTC forecasts. This behavior was mostly attributed to WRF Model initialization of clouds and moist physical processes. The success of these real-time ensemble forecasts demonstrates the feasibility of using limited-area continuously cycling EnKFs as a method to initialize convection-allowing ensemble forecasts, and future real-time high-resolution ensemble development leveraging EnKFs seems justified. � 2015 American Meteorological Society."
"8622374000;56284582200;","A diabatically generated potential vorticity structure near the extratropical tropopause in three simulated extratropical cyclones",2015,"10.1175/MWR-D-14-00092.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943425086&doi=10.1175%2fMWR-D-14-00092.1&partnerID=40&md5=aa4a1a17ad1356bb60c3b7011a33f6e1","The structure of near-tropopause potential vorticity (PV) acts as a primary control on the evolution of extratropical cyclones. Diabatic processes such as the latent heating found in ascending moist warm conveyor belts modify PV. A dipole in diabatically generated PV (hereafter diabatic PV) straddling the extratropical tropopause, with the positive pole above the negative pole, was diagnosed in a recently published analysis of a simulated extratropical cyclone. This PV dipole has the potential to significantly modify the propagation of Rossby waves and the growth of baroclinically unstable waves. This previous analysis was based on a single case study simulated with 12-km horizontal grid spacing and parameterized convection. Here the dipole is investigated in three additional cold-season extratropical cyclones simulated in both convection-parameterizing and convection-permitting model configurations. A diabatic PV dipole across the extratropical tropopause is diagnosed in all three cases. The amplitude of the dipole saturates approximately 36 h from the time diabatic PV is accumulated. The node elevation of the dipole varies between 2 and 4 PVU (1 PVU = 106 K kg-1 m2 s-1) in the three cases, and the amplitude of the system-averaged dipole varies between 0.2 and 0.4 PVU. The amplitude of the negative pole is similar in the convection-parameterizing and convection-permitting simulations. The positive pole, which is generated by longwave radiative cooling, is weak in the convection-permitting simulations due to the small domain size, which limits the accumulation of diabatic tendencies within the interior of the domain. The possible correspondence between the diabatic PV dipole and the extratropical tropopause inversion layer is discussed. © 2015 American Meteorological Society."
"6507400558;7006095466;","Organized convection parameterization for the ITCZ",2015,"10.1175/JAS-D-15-0006.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943413782&doi=10.1175%2fJAS-D-15-0006.1&partnerID=40&md5=d86ad59013f3890445b6f4f42d476e55","Mesoscale convective systems (MCSs) are of fundamental importance in the dynamics of the atmospheric circulation and the climate system. They are often observed to develop over significant terrain in ambient shear flows in midlatitudes and embedded within the Madden-Julian oscillation (MJO) and convectively coupled equatorial wave (CCEW) envelopes, as well as in the intertropical convergence zone (ITCZ). Yet general circulation models (GCMs) fail to resolve these systems, and their underlying convective parameterizations are not directed to represent organized circulations. Shear-parallel MCSs, which are common in the ITCZ, have a three-dimensional structure and, as such, present a serious modeling challenge. Here, a previously developed multicloud model (MCM) is modified to parameterize MCSs. One of the main modifications is the parameterization of stratiform condensation to capture extended stratiform outflows, which characterize MCSs, resulting from strong upper-level jets. Linear analysis shows that, under the influence of a typical double African and equatorial jet shear flow, this modification results in an additional new scale-selective instability peaking at the mesoalpha scale of roughly 400 km. Nonlinear simulations conducted with the modified MCM on a 400 km × 400 km doubly periodic domain, without rotation, resulted in the spontaneous transition from a quasi-two-dimensional shear-perpendicular convective system, consistent with linear theory, to a fully three-dimensional flow structure. The simulation is characterized by shear-parallel bands of convection, moving slowly eastward, embedded in stratiform systems that expand perpendicularly and propagate westward with the upper-level jet. The mean circulation and the implications for the domain-averaged vertical transport of momentum and potential temperature are discussed. © 2015 American Meteorological Society."
"6506756436;7004115548;","An alternative cell-averaged departure point reconstruction for pointwise semi-Lagrangian transport schemes",2015,"10.1002/qj.2509","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941192119&doi=10.1002%2fqj.2509&partnerID=40&md5=d148164e56d0e7ef187309813006a2bc","Convection-permitting limited-area models based on the same spectral semi-implicit semi-Lagrangian (SL) techniques which are used in the ECMWF global model, are run operationally in several countries of the ALADIN/HIRLAM consortium. Forecasters have reported a general tendency for these models to produce overestimated precipitation and unrealistic divergent winds at the edges of the cold outflows generated by the precipitation evaporation in the vicinity of convective clouds. These grid-point storms have been associated with a spurious behaviour of the pointwise interpolation used in the SL scheme, where grid-scale buoyant updraughts create strong small-scale convergence near the surface. A modification of the interpolation weights in the SL transport scheme introduces the concept of cell-averaging into the traditional pointwise SL scheme which improves the conservation property of the scheme and eliminates the spurious mode. The COMAD (COntinuous Mapping about Departure points) correction applied to the standard interpolation weights takes into account the deformation of the air parcels along each direction of interpolation in order to improve the continuity and the conservative property of the re-mapping between the model grid points and the origin points of the backward trajectories. The method has been validated with the small planet configuration of the Integrated Forecast System at ECMWF and with the limited-area version of the same dynamics used for the AROME (Météo-France) and HARMONIE (HIRLAM) models. The pathological behaviour of grid-scale buoyant flows permitted by these dynamical cores is corrected by the COMAD interpolations. The precipitation forecasts in the convection-permitting models AROME/HARMONIE which show an overestimation of intense convective precipitation are systematically improved by the new weights. © 2015 Royal Meteorological Society."
"56024049900;7004154626;","Inter-annual variability of aerosols and its relationship with regional climate over Indian subcontinent",2015,"10.1002/joc.4037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928588237&doi=10.1002%2fjoc.4037&partnerID=40&md5=f1911b1742bd1c4f8ee739a44c5bb0e8","The spatio-temporal variability of aerosols over Indian subcontinent is mainly due to transported dust from adjacent deserts (Thar and Middle East deserts), local emission due to anthropogenic activities and prevailing meteorological conditions. On large scale, the quantification of transported and locally emitted aerosol from these regions is complicated. Here, we used empirical orthogonal function (EOF) analysis to identify these regions and their variability by using 33 years of Total Ozone Monitoring Spectrometer (TOMS) satellite data. The maximum variability in aerosol is explained by first two EOF modes (70.31 and 20.57%) over Indian subcontinent. The major aerosol, i.e. transported dust from adjacent deserts confined to NW India and Pakistan, is observed in first leading mode, whereas biomass burning, industrial and dense populated region of southeast and eastern region of the Indo-Gangetic Plain (IGP) are revealed in the second dominant mode. The EOF analysis is carried out specifically for the pre-monsoon and monsoon seasons over Indian subcontinent as maximum aerosol loading is observed during this period. The region of NW India, IGP, Pakistan and northern Arabian Sea explains maximum variability in both seasons. The first three leading modes and their relationship with different atmospheric and surface variables are carried out for pre-monsoon and monsoon seasons. This study explains the potential role of aerosols on reduction in cloudiness, increased shortwave at the ground, land-surface tropospheric warming and its feedback to other related processes. This study strongly suggests that there is a need for further appropriate observational as well as modelling study on the role of semi-direct aerosol effect over Indian subcontinent. © 2014 Royal Meteorological Society."
"35731251200;24495045400;6602311240;6603980201;57208639946;35556656200;7005773698;","Direct night-time ejection of particle-phase reduced biogenic sulfur compounds from the ocean to the atmosphere",2015,"10.1021/es506177s","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928389843&doi=10.1021%2fes506177s&partnerID=40&md5=631521390c4384e19138305e1840a958","The influence of oceanic biological activity on sea spray aerosol composition, clouds, and climate remains poorly understood. The emission of organic material and gaseous dimethyl sulfide (DMS) from the ocean represents well-documented biogenic processes that influence particle chemistry in marine environments. However, the direct emission of particle-phase biogenic sulfur from the ocean remains largely unexplored. Here we present measurements of ocean-derived particles containing reduced sulfur, detected as elemental sulfur ions (e.g., 32S+, 64S<inf>2</inf>+), in seven different marine environments using real-time, single particle mass spectrometry; these particles have not been detected outside of the marine environment. These reduced sulfur compounds were associated with primary marine particle types and wind speeds typically between 5 and 10 m/s suggesting that these particles themselves are a primary emission. In studies with measurements of seawater properties, chlorophyll-a and atmospheric DMS concentrations were typically elevated in these same locations suggesting a biogenic source for these sulfur-containing particles. Interestingly, these sulfur-containing particles only appeared at night, likely due to rapid photochemical destruction during the daytime, and comprised up to ∼67% of the aerosol number fraction, particularly in the supermicrometer size range. These sulfur-containing particles were detected along the California coast, across the Pacific Ocean, and in the southern Indian Ocean suggesting that these particles represent a globally significant biogenic contribution to the marine aerosol burden. © 2015 American Chemical Society."
"54398596200;55754495900;7404976222;","Impact of subdaily air-sea interaction on simulating intraseasonal oscillations over the tropical Asian monsoon region",2015,"10.1175/JCLI-D-14-00407.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923039962&doi=10.1175%2fJCLI-D-14-00407.1&partnerID=40&md5=ac98de7176c5def691075260f138e21b","The off-equatorial boreal summer intraseasonal oscillation (ISO) is closely linked to the onset, active, and break phases of the tropical Asian monsoon, but the accurate simulation of the eastward-propagating lowfrequency ISO by current models remains a challenge. In this study, an atmospheric general circulation model (AGCM)-ocean mixed layer coupled model with high (10 min) coupling frequency (DC_10m) shows improved skill in simulating the ISO signal in terms of period, intensity, and propagation direction, compared with the coupled runs with low (1 and 12 h) coupling frequency and a stand-alone AGCM driven by the daily sea surface temperature (SST) fields. In particular, only the DC_10m is able to recreate the observed lead-lag phase relationship between SST (SST tendency) and precipitation at intraseasonal time scales, indicating that the ISO signal is closely linked to the subdaily air-sea interaction. During the ISO life cycle, air-sea interaction reduces the SST underlying the convection via wind-evaporation and cloud-radiation feedbacks, as well as wind-induced oceanic mixing, which in turn restrains convection. However, to the east of the convection, the heat-induced atmospheric Gill-type response leads to downward motion and a reduced surface westerly background flow because of the easterly anomalies. The resultant decreased oceanic mixing, together with the increased shortwave flux, tends to warm the SST and subsequently trigger convection. Therefore, the eastward-propagating ISO may result from an asymmetric east-west change in SST induced mainly by multiscale air-sea interactions. © 2015 American Meteorological Society."
"18536452000;24332557200;7003712840;7201352328;56268837500;56268579900;57206129983;6602496630;","A new approach for assimilation of 2D radar precipitation in a high-resolution NWP model",2015,"10.1002/met.1466","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921680549&doi=10.1002%2fmet.1466&partnerID=40&md5=1e486b1477f7b13593f047bd02ec1306","A new approach for assimilation of 2D precipitation in numerical weather prediction models is presented and tested in a case with convective, heavy precipitation. In the scheme a nudging term is added to the horizontal velocity divergence tendency equation. In case of underproduction of precipitation, the strength of the nudging is proportional to the offset between observed and modelled precipitation, leading to increased moisture convergence. If the model over-predicts precipitation, the low level moisture source is reduced, and in-cloud moisture is nudged towards environmental values. The method was implemented in the Danish Meteorological Institute numerical weather prediction (DMI NWP) nowcasting system, running with hourly cycles, performing a surface analysis and 3D variational analysis for upper air assimilation at each cycle restart, followed by nudging assimilation of precipitation and then a free forecast. The precipitation fields are based on a 2D composite CAPPI (constant altitude plan position indicator) field made from observations with the DMI weather radars, and have a 10 min time resolution. The results obtained in this study indicate that the new method implies fast adjustment of the dynamical state of the model to facilitate precipitation release when the model precipitation intensity is too low. Removal of precipitation is shown to be of importance and the position of the model precipitation cells becomes skilful even at the smallest scales (∼3km). Bias is reduced for low and extreme precipitation rates. In this meteorological case, the usage of the nudging procedure has been shown to improve the prediction of heavy precipitation substantially. © 2014 Royal Meteorological Society."
"55331697200;7005650812;","Two heavy rainfall types over the Korean Peninsula in the humid East Asian summer environment: A satellite observation study",2015,"10.1175/MWR-D-14-00184.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921457682&doi=10.1175%2fMWR-D-14-00184.1&partnerID=40&md5=49da13a2448c74c4bb4dcd846a4af2d8","A total of 10 years (2002-11) of Tropical Rainfall MeasuringMission (TRMM) Precipitation Radar (PR) reflectivities, signaling heavy rainfall (&gt;10mmh-1), were objectively classified by applying the K-means clustering method in order to obtain typical reflectivity profiles associated with heavy rainfall over East Asia. Two types of heavy rainfall emerged as the most important rain processes over East Asia: type 1 (cold type) characterized by high storm height and abundant ice water under convectively unstable conditions, developing mostly over inland China; and type 2 (warmtype) associated with a lower stormheight and lower ice water content, developing mostly over the ocean. These two types also show sharp contrasts in relation to their seasonal changes and in the diurnal variation of frequency maxima, in addition to other contrasting meteorological parameters. The PR-derived heavy rain events were observed over the Korean peninsula and their spatiotemporal evolution was examined using 10-yr composites of 11-μm brightness temperature from geostationary satellites and Interim ECMWF Re-Analysis (ERA-Interim) data. Cold-type heavy rainfall over Korea is characterized by an eastward moving cloud system with an oval shape while the warm type shows a comparatively wide spatial distribution over an area extending from the southwest to northeast. Overall the warm-type process appears to link the low-level moisture convergence area to the vertically aligned divergence area formed over the jet stream level. This setup continuously pushes air upward under moist-adiabatically near-neutral conditions and thus yields heavy rainfall. As warm-type heavy rainfall persists longer, it is considered to be more responsible for flood events occurring over the Korean peninsula. © 2015 American Meteorological Society."
"8958009400;7006432091;","Extreme convection of the near-equatorial Americas, Africa, and adjoining oceans as seen by TRMM",2015,"10.1175/MWR-D-14-00109.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921454687&doi=10.1175%2fMWR-D-14-00109.1&partnerID=40&md5=873de0dac163d980c9f3efc63bc1ab5d","This study documents the preferred location and diurnal cycle of extreme convective storms that occur in the tropical band containing the east Pacific Ocean, Central and South America, the Atlantic Ocean, and northern Africa. Data from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar show three types of convective-stratiform structures that constitute extreme convective events: deep convective cores (DCCs), wide convective cores (WCCs), and broad stratiform regions (BSRs). Interim ECMWF Re- Analysis (ERA-Interim) data show the associated synoptic environmental factors associated with the occurrence of extreme convective features. The DCC, WCC, and BSR echoes are associated with early, middle, and late stages of convective system development, respectively, and the statistics and timing of their occurrence are related to topography and life cycle behavior of the convection. Storms containing DCC occur primarily over the Sudanian savannas of Africa and near the mountains in northern South America, being diurnally controlled. Storms with WCC manifest over land, in the same regions as the DCC, but also over oceanic regions. They appear around the clock but with maximum frequency at night. They are favored in regions of midlevel synoptic-scale low pressure systems, which over the sub-Sahara are the troughs of easterly waves. Storms containing BSR maximize over oceanic regions west of Africa and South America, where they exhibit a weak diurnal cycle with a slight midmorning maximum. Off the west coast of South America, the storms with WCC and BSR have longer lifetimes enhanced by orographic lifting over the Andes. The storms with BSR in the east Pacific Ocean often develop into tropical cyclones. © 2015 American Meteorological Society."
"36054921000;7102567936;7404970050;56086015900;57187656400;56576680000;","Regional simulation of the october and november MJO events observed during the CINDY/DYNAMO field campaign at gray zone resolution",2015,"10.1175/JCLI-D-14-00294.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961292171&doi=10.1175%2fJCLI-D-14-00294.1&partnerID=40&md5=f4de6f3dbf09f092b16c0b0ee9bcf224","This study investigates the October and November MJO events observed during the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY)/Dynamics of the MJO (DYNAMO) field campaign through cloud-permitting numerical simulations. The simulations are compared to multiple observational datasets. The control simulation at 9-km horizontal grid spacing captures the slow eastward progression of both the October and November MJO events in surface precipitation, outgoing longwave radiation, zonal wind, humidity, and large-scale vertical motion. The vertical motion shows weak ascent in the leading edge of the MJO envelope, followed by deep ascent during the peak precipitation stage and trailed by a broad second baroclinic mode structure with ascent in the upper troposphere and descent in the lower troposphere. Both the simulation and the observations also show slow northward propagation components and tropical cyclone-like vortices after the passage of the MJO active phase. Comparison with synthesized observations from the northern sounding array shows that the model simulates the passage of the two MJO events over the sounding array region well. Sensitivity experiments to SST indicate that daily SST plays an important role for the November MJO event, but much less so for the October event. Analysis of the moist static energy (MSE) budget shows that both advection and diabatic processes (i.e., surface fluxes and radiation) contribute to the development of the positive MSE anomaly in the active phase, but their contributions differ by how much they lead the precipitation peak. In comparison to the observational datasets used here, the model simulation may have a stronger surface flux feedback and a weaker radiative feedback. The normalized gross moist stability in the simulations shows an increase from near-zero values to ~0.8 during the active phase, similar to what is found in the observational datasets. © 2015 American Meteorological Society."
"35998927000;6602399492;6604094122;7004732931;7004276549;57195257572;7102188656;6507937756;6603738264;55906535100;57193341821;55800670000;7102781936;8525148200;7006104157;6701410575;6701781257;55879878800;55726268900;8395782400;23048728700;57189406481;56522764000;6507803913;8252840100;57215122815;57215120496;6507787465;55832972600;7003836948;7402328256;57215115804;12545383800;57190741622;15926052500;15050204600;35579025600;56355289400;55237678900;56075676700;57190742602;57190739746;23011365100;55807218700;6603108295;6506731012;6508079704;7004239300;11139844700;37096246200;18133721300;35737707800;7103322260;7201350279;35757011300;6602842789;6602532206;7003768642;8623052000;30067950800;56780325800;15724233200;55730602600;7409579664;7006926073;55805741300;57190735534;57215119590;57215116125;57215128973;57215141705;11339735300;57209138042;56490784200;45061083300;26323948700;56195655500;8083685800;57215130385;56879845700;7801500046;55693313200;16444514600;57215112614;57215118167;6506585969;57215129978;57215137798;7006050100;7202800932;57190736439;23494021100;57204252724;6701801931;57215117896;57215113734;","Global-scale atmosphere monitoring by in-service aircraft - current achievements and future prospects of the European Research Infrastructure IAGOS",2015,"10.3402/tellusb.v67.28452","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982797855&doi=10.3402%2ftellusb.v67.28452&partnerID=40&md5=e2ffd0b222453d28e39f511680c22b12","The European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System) operates a global-scale monitoring system for atmospheric trace gases, aerosols and clouds utilising the existing global civil aircraft. This new monitoring infrastructure builds on the heritage of the former research projects MOZAIC (Measurement of Ozone and Water Vapour on Airbus In-service Aircraft) and CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container). CARIBIC continues within IAGOS and acts as an important airborne measurement reference standard within the wider IAGOS fleet. IAGOS is a major contributor to the in-situ component of the Copernicus Atmosphere Monitoring Service (CAMS), the successor to the Global Monitoring for the Environment and Security ± Atmospheric Service, and is providing data for users in science, weather services and atmospherically relevant policy. IAGOS is unique in collecting regular in-situ observations of reactive gases, greenhouse gases and aerosol concentrations in the upper troposphere and lowermost stratosphere (UTLS) at high spatial resolution. It also provides routine vertical profiles of these species in the troposphere over continental sites or regions, many of which are undersampled by other networks or sampling studies, particularly in Africa, Southeast Asia and South America. In combination with MOZAIC and CARIBIC, IAGOS has provided long-term observations of atmospheric chemical composition in the UTLS since 1994. The longest time series are 20 yr of temperature, H2O and O3, and 9-15 yr of aerosols, CO, NOy, CO2, CH4, N2O, SF6, Hg, acetone, ~30 HFCs and ~20 non-methane hydrocarbons. Among the scientific highlights which have emerged from these data sets are observations of extreme concentrations of O3 and CO over the Pacific basin that have never or rarely been recorded over the Atlantic region for the past 12 yr; detailed information on the temporal and regional distributions of O3, CO,H2O, NOy and aerosol particles in the UTLS, including the impacts of cross-tropopause transport, deep convection and lightning on the distribution of these species; characterisation of ice-supersaturated regions in the UTLS; and finally, improved understanding of the spatial distribution of upper tropospheric humidity including the finding that the UTLS is much more humid than previously assumed. © 2015 A. Petzold et al."
"51360903200;56005684100;","A physical analysis of the severe 2013/2014 cold winter in North America",2015,"10.1002/2015JD023116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945438655&doi=10.1002%2f2015JD023116&partnerID=40&md5=54477d4f57b673e04fc9e5c0b8937e54","The severe 2013/2014 cold winter has been examined in the context of the previous 55 winters using the National Centers for Environmental Prediction reanalysis data for the period 1960–2014. North America is dominated by pronounced cold anomalies over the Great Plains and Great Lakes in December 2013 and February 2014 but exhibits an east-west contrast pattern with warm anomalies over most of the North American West in January 2014. A relevant temperature index, defined as land surface temperature anomalies averaged over (40°–60°N, 105°–80°W), reveals a warming trend as well as interannual variability with a significant power peak of 6.0 years. While 2013/2014 was the second coldest winter during 1960–2014, it is the coldest one in the linearly detrended series, with a negative anomaly of 2.63 standard deviations. This indicates that the long-term warming has made the 2013/2014 winter less severe than it could have been. The temperature and circulation variability in association with the zonally symmetric variability of the polar vortex projects weakly on the corresponding anomalies in the 2013/2014 winter, whereas the variability associated with the principal mode of North American surface temperature projects strongly on the corresponding anomalies in the winter. This mode is associated with a sea surface temperature (SST) pattern of significant anomalies over the North Pacific and North Atlantic middle and high latitudes. The anomalous atmospheric circulation shows an anticyclonic anomaly over the Gulf of Alaska-Bering Sea and a cyclonic anomaly downstream over North America. It bears resemblance to the North Pacific Oscillation/Western Pacific pattern and drives the SST in the North Pacific. Over western-central Canada and the northern U.S., below-average heights are associated with above-normal precipitation, implying enhanced upward vertical motion and variation of local cloud forcing, leading to a variation of the surface energy budget dominated by surface longwave radiation anomalies. Over North America, there is less downwelling longwave radiation at the surface when the atmosphere is cold, which is offset by the corresponding reduction in outgoing longwave radiation. © 2015. Her Majesty the Queen in Right of Canada."
"55970956300;6506339394;55782803000;55489902700;54416866200;56469654300;54896322800;","Determination of seasonal changes in wetlands using CHRIS/Proba Hyperspectral satellite images: A case study from Acigöl (Denizli), Turkey",2015,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920374704&partnerID=40&md5=2ad3f90360589653770a174559f94807","The changes in wetlands that occur through natural processes, as well as through industrialization and agricultural activities, are decreasing and even annihilating the living spaces of endemic species. Acigol (Denizli, Turkey), which is a suitable habitatfor flamingos (Phoenicopterus ruber), is a lake that is affected by seasonal anomalies as a result of being shallow. Acigol, which is fed by precipitation, groundwater and the springs that occur along tectonic faults, has no water output other than evaporation and industrial activities. In addition to natural factors, it is important to determine the changes in the wetlands of Acigol, where industrial salt is produced, in order to reveal the micro-ecological equilibrium, the relationship between climate and natural life, and regulation of industrial activities. Remote sensing tools are frequently used in determination of changes in wetlands. Changes in coastlines, water level and area covered by water are parameters that can be examined by remote sensing while investigating wetlands. In this study, the water-covered area was examined using remote sensing. Within the scope of this study, CHRIS/Proba Mode 2 (water bandset) hyperspectral satellite images, acquired on 9/17/2011 for the season and on 6/18/2012 - 6/19/2012 for wet season, were used in order to present the seasonal changes in Acigol, during one hydrogeological period. The processes of noise reduction, cloud screening, atmospheric correction, geometric correction, and identification of wetlands have been implemented on the CHRIS/Proba images. In determining the water-covered areas, the Normalized Difference Water Index (NDWI) was used. It was determined that W6 (560 nm) and W18 (1015 nm) and W2 (447 nm) and W18 (1015 nm) band combinations were most appropriate to be used in NDWI to demonstrate the water-land separation. Using Proba-NDWI image, itwas established thatan area of 27.4 km2 was covered with water during dry season, and 61.2 km2 was covered during wet season. The results indicated that; since the lake water area is directly affected by seasonal and annual climatic anomalies, water used by industrial facilities has to be drawn out of the lake in reasonable amount."
"55332348600;7003266014;26645289600;7403931916;55802031900;","Cirrus feedback on interannual climate fluctuations",2014,"10.1002/2014GL062095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921831180&doi=10.1002%2f2014GL062095&partnerID=40&md5=1b90534c8808c33d4f6918e6cd314eca","Cirrus clouds are not only important in determining the current climate but also play an important role in climate change and variability. Analysis of satellite observations shows that the amount and altitude of cirrus clouds (cloud optical depth &lt; 3.6, cloud top pressure &lt; 440 hPa) increase in response to interannual surface warming. Using cirrus cloud radiative kernels, the magnitude of the interannual cirrus feedback is estimated to be 0.20 ± 0.21 W/m2/°C, which represents an important component of the cloud feedback. Thus, cirrus clouds are likely to act as a positive feedback on interannual climate fluctuations, by reducing the Earth's ability to radiate longwave radiation to space in response to planetary surface warming. Most of the cirrus feedback comes from increasing cloud amount in the tropical tropopause layer (TTL) and subtropical upper troposphere. Key Points Cirrus clouds likely contribute a positive feedback on climate fluctuationsCirrus cloud amount and altitude increase in response to surface warmingCirrus clouds represent an important component of the cloud feedback ©2014. American Geophysical Union. All Rights Reserved."
"55923546200;8942524900;8633783900;43661479500;35810775100;55480654300;24463029300;12753162000;36134816800;7004469744;","Uncertainty in the magnitude of aerosol-cloud radiative forcing over recent decades",2014,"10.1002/2014GL062029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921790880&doi=10.1002%2f2014GL062029&partnerID=40&md5=40ba027986211b72331273f6acce10e1","Aerosols and their effect on the radiative properties of clouds are one of the largest sources of uncertainty in calculations of the Earth's energy budget. Here the sensitivity of aerosol-cloud albedo effect forcing to 31 aerosol parameters is quantified. Sensitivities are compared over three periods; 1850-2008, 1978-2008, and 1998-2008. Despite declining global anthropogenic SO2 emissions during 1978-2008, a cancelation of regional positive and negative forcings leads to a near-zero global mean cloud albedo effect forcing. In contrast to existing negative estimates, our results suggest that the aerosol-cloud albedo effect was likely positive (0.006 to 0.028Wm-2) in the recent decade, making it harder to explain the temperature hiatus as a forced response. Proportional contributions to forcing variance from aerosol processes and natural and anthropogenic emissions are found to be period dependent. To better constrain forcing estimates, the processes that dominate uncertainty on the timescale of interest must be better understood. Key Points Forcing sensitivity to aerosol parameters is strongly period dependentUnderstanding near-future climate is limited if a single period is consideredIn recent decades, parametric uncertainty is smaller than model diversity ©2014. The Authors."
"7801642934;55541170400;","The Walker circulation, diabatic heating, and outgoing longwave radiation",2014,"10.1002/2014GL062257","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921814876&doi=10.1002%2f2014GL062257&partnerID=40&md5=b2e257a9444a3ec078b19667246f18e8","For the tropical atmosphere on planetary scales, it is common to model the circulation using strong damping. Here with new data analysis techniques, evidence suggests that damping can actually be neglected. Specifically, near the equator, the east-west overturning circulation is in agreement with the undamped wave response to atmospheric heating. To estimate the heating, satellite observations of outgoing longwave radiation (OLR) are used. Frequently, OLR is used as a heuristic indicator of cloudiness. Here the results further suggest that OLR variations are actually proportional to diabatic heating variations, with a proportionality constant of 18 W m-2 (K d-1)-1. While the agreement holds best over long time averages of years or decades, it also holds over shorter periods of one season or 1 month. Consequently, it is suggested that the strength of the Walker circulation - and its evolution in time - could be estimated using satellite data. Key Points The Walker circulation can be modeled without dampingDiabatic heating is proportional to outgoing longwave radiation (OLR)The strength of the Walker circulation can be estimated from satellite data ©2014. American Geophysical Union. All Rights Reserved."
"7402284525;7005275092;","Is the residual vertical velocity a good proxy for stratosphere-troposphere exchange of ozone?",2014,"10.1002/2014GL061994","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921790748&doi=10.1002%2f2014GL061994&partnerID=40&md5=6c17424198ddf97b4102dad8e2623272","Stratosphere-troposphere exchange (STE) of ozone (O<inf>3</inf>) is key in the budget of tropospheric O<inf>3</inf>, in turn affecting climate forcing and global air quality. We compare three commonly used diagnostics meant to quantify cross-tropopause O<inf>3</inf> fluxes with a Chemistry-Transport Model driven by two distinct European Centre forecast fields. Our reference case calculates accurate, geographically resolved net transport across an isosurface in artificial tracer e90 representing the tropopause. Hemispheric fluxes derived from the ozone mass budget of the lowermost stratosphere yield similar results. Use of the Brewer-Dobson residual vertical velocity as a scaled proxy for ozone flux, however, fails to capture the interannual variability. Thus, the common notion that the strength of stratospheric overturning circulation is a good measure for global STE does not apply to O<inf>3</inf>. Climatic variability in the modeled O<inf>3</inf> flux needs to be diagnosed directly rather than indirectly through the overturning circulation. Key Points O<inf>3</inf> residual flux by BDC does not sync with cross-tropopause O<inf>3</inf> fluxesMore accurate diagnostics of ozone STE are needed in climate-chemistry modelsTC and LS methods are suitable for diagnosing STE of ozone ©2014. American Geophysical Union. All Rights Reserved."
"35606965700;7003532926;","Variation of the global electric circuit and Ionospheric potential in a general circulation model",2014,"10.1002/2014GL062352","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921834748&doi=10.1002%2f2014GL062352&partnerID=40&md5=d2a554763560d8ff93d91a0fed3d9105","A general circulation model of the atmosphere and ocean INMCM4.0 (Institute of Numerical Mathematics Coupled Model) is used for modeling the global electric circuit short-time variability and long-term evolution. The ionospheric potential parameterization is proposed which takes into account quasi-stationary currents of electrified clouds (including thunderstorms) as principal contributors into the DC global circuit. The diurnal, seasonal, and interannual variations of the ionospheric potential (IP) are modeled and compared with available data. Numerical simulations suggest that the IP decreases in the mean with the global warming due to increasing greenhouse gas emission (by about 10% during the 21st century if the Representative Concentration Pathway 8.5 Wm-2 scenario is assumed). At the same time the lightning flash rate increases with global warming by about 5 fl/s per degree. Interannual IP variability is low and does not exceed 1% of the mean value, being tightly correlated with the mean sea surface temperature in the Pacific Ocean (El Niño area). Key Points A novel parameterization of the ionospheric potential is suggestedDiurnal and seasonal variations are simulated in a global circulation modelLong-term trends of ionospheric potential are predicted for changing climate ©2014. American Geophysical Union. All Rights Reserved."
"28568055900;9233714800;7403252833;56493777900;15724233200;7102294773;","Assimilation of next generation geostationary aerosol optical depth retrievals to improve air quality simulations",2014,"10.1002/2014GL062089","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921812352&doi=10.1002%2f2014GL062089&partnerID=40&md5=bba9677e162d9cff54576e836e81fb91","Planned geostationary satellites will provide aerosol optical depth (AOD) retrievals at high temporal and spatial resolution which will be incorporated into current assimilation systems that use low-Earth orbiting (e.g., Moderate Resolution Imaging Spectroradiometer (MODIS)) AOD. The impacts of such additions are explored in a real case scenario using AOD from the Geostationary Ocean Color Imager (GOCI) on board of the Communication, Ocean, and Meteorology Satellite, a geostationary satellite observing northeast Asia. The addition of GOCI AOD into the assimilation system generated positive impacts, which were found to be substantial in comparison to only assimilating MODIS AOD. We found that GOCI AOD can help significantly to improve surface air quality simulations in Korea for dust, biomass burning smoke, and anthropogenic pollution episodes when the model represents the extent of the pollution episodes and retrievals are not contaminated by clouds. We anticipate future geostationary missions to considerably contribute to air quality forecasting and provide better reanalyses for health assessments and climate studies. Key Points Geostationary AOD data improves skill of current air quality predictionsImprovements are found for multiple types of pollution events on Northeast AsiaIt serves as a real case scenario support for planned geostationary missions ©2014. American Geophysical Union. All Rights Reserved."
"56151545200;35265216700;55476830600;53981601100;36021733300;55624488227;56068376200;","Pathways of sulfate enhancement by natural and anthropogenic mineral aerosols in china",2014,"10.1002/2014JD022301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921341944&doi=10.1002%2f2014JD022301&partnerID=40&md5=8bf11df7106abb7de3c07b3aee93d9fc","China, the world’s largest consumer of coal, emits approximately 30 million tons of sulfur dioxide (SO2) per year. SO2 is subsequently oxidized to sulfate in the atmosphere. However, large gaps exist between model-predicted and measured sulfate levels in China. Long-term field observations and numerical simulations were integrated to investigate the effect of mineral aerosols on sulfate formation. We found that mineral aerosols contributed a nationwide average of approximately 22% to sulfate production in 2006. The increased sulfate concentration was approximately 2 μgm3 in the entire China. In East China and the Sichuan Basin, the increments reached 6.3 μgm3 and 7.3 μgm3, respectively. Mineral aerosols led to faster SO2 oxidation through three pathways. First, more SO2 was dissolved as cloud water alkalinity increased due to water-soluble mineral cations. Sulfate production was then enhanced through the aqueous-phase oxidation of S(IV) (dissolved sulfur in oxidation state +4). The contribution to the national sulfate production was 5%. Second, sulfate was enhanced through S(IV) catalyzed oxidation by transition metals. The contribution to the annual sulfate production was 8%, with 19% during the winter that decreased to 2% during the summer. Third, SO2 reacts on the surface of mineral aerosols to produce sulfate. The contribution to the national average sulfate concentration was 9% with 16% during the winter and a negligible effect during the summer. The inclusion of mineral aerosols does resolve model discrepancies with sulfate observations in China, especially during the winter. These three pathways, which are not fully considered in most current chemistry-climate models, will significantly impact assessments regarding the effects of aerosol on climate change in China. © 2014. American Geophysical Union. All Rights Reserved."
"55921861500;6603480361;35775264900;7003871110;7006532784;","The impact of polar stratospheric ozone loss on southern Hemisphere stratospheric circulation and climate",2014,"10.5194/acp-14-13705-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919608111&doi=10.5194%2facp-14-13705-2014&partnerID=40&md5=3f72571d0bdd5eb08b893d53e60c5272","The impact of polar stratospheric ozone loss resulting from chlorine activation on polar stratospheric clouds is examined using a pair of model integrations run with the fully coupled chemistry climate model UM-UKCA. Suppressing chlorine activation through heterogeneous reactions is found to produce modelled ozone differences consistent with observed ozone differences between the present and pre-ozone hole period. Statistically significant high-latitude Southern Hemisphere (SH) ozone loss begins in August and peaks in October-November, with > 75% of ozone destroyed at 50 hPa. Associated with this ozone destruction is a > 12 K decrease of the lower polar stratospheric temperatures and an increase of > 6 K in the upper stratosphere. The heating components of this temperature change are diagnosed and it is found that the temperature dipole is the result of decreased short-wave heating in the lower stratosphere and increased dynamical heating in the upper stratosphere. The cooling of the polar lower stratosphere leads, through thermal wind balance, to an acceleration of the polar vortex and delays its breakdown by ∼ 2 weeks. A link between lower stratospheric zonal wind speed, the vertical component of the Eliassen-Palm (EP) flux, <i>F</i><i>z</i> and the residual mean vertical circulation, <span styleCombining double low line""border-top: 1px solid #000; color: #000;""><i>w</i></span>∗, is identified. In November and December, increased westerly winds and a delay in the breakup of the polar vortex lead to increases in <i>F</i><i>z</i>, indicating increased wave activity entering the stratosphere and propagating to higher altitudes. The resulting increase in wave breaking, diagnosed by decreases to the EP flux divergence, drives enhanced downwelling over the polar cap. Many of the stratospheric signals modelled in this study propagate down to the troposphere, and lead to significant surface changes in December. © 2014 Author."
"55783064400;24537168200;8684037700;7006837187;37089603000;7201787800;55520002300;8574701200;7004438457;7005733107;14522372400;8760535800;7003815387;36869143400;7202628826;","Size-dependent wet removal of black carbon in Canadian biomass burning plumes",2014,"10.5194/acp-14-13755-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906543632&doi=10.5194%2facp-14-13755-2014&partnerID=40&md5=881b54a28a9a267370780a093c40c2be","Wet deposition is the dominant mechanism for removing black carbon (BC) from the atmosphere and is key in determining its atmospheric lifetime, vertical gradient and global transport. Despite the importance of BC in the climate system, especially in terms of its ability to modulate the radiative energy budget, there are few quantitative case studies of wet removal in ambient environments. We present a case study of BC wet removal by examining aerosol size distributions and BC coating properties sampled in three Canadian boreal biomass burning plumes, one of which passed through a precipitating cloud. This depleted the majority of the plume's BC mass, and the largest and most coated BC-containing particles were found to be preferentially removed, suggesting that nucleation scavenging was likely the dominant mechanism. Calculated single-scattering albedo (SSA) showed little variation, as a large number of non-BC particles were also present in the precipitation-affected plume. The remaining BC cores were smaller than those observed in previous studies of BC in post-precipitation outflow over Asia, possibly due to the thick coating by hydrophilic compounds associated with the Canadian biomass burning particles. This study provides measurements of BC size, mixing state and removal efficiency to constrain model parameterisations of BC wet removal in biomass burning regions, which will help to reduce uncertainty in radiative forcing calculations. © Author(s) 2014."
"7007078966;15519671300;6506718302;35459245100;","A global process-based study of marine CCN trends and variability",2014,"10.5194/acp-14-13631-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919684043&doi=10.5194%2facp-14-13631-2014&partnerID=40&md5=aac609a0c8fe1acb1c1d122b485b82aa","Low-level clouds have a strong climate-cooling effect in oceanic regions due to the much lower albedo of the underlying sea surface. Marine clouds typically have low droplet concentrations, making their radiative properties susceptible to changes in cloud condensation nucleus (CCN) concentrations. Here, we use the global aerosol model GLOMAP to investigate the processes that determine variations in marine CCN concentrations, and focus especially on the effects of previously identified wind speed trends in recent decades. Although earlier studies have found a link between linear wind speed trends and CCN concentration, we find that the effects of wind speed trends identified using a dynamic linear model in the Northern Equatorial Pacific (0.56 m s-1 per decade in the period 1990-2004) and the North Atlantic (g-0.21 m s-1 per decade) are largely dampened by other processes controlling the CCN concentration, namely nucleation scavenging and transport of continental pollution. A CCN signal from wind speed change is seen only in the most pristine of the studied regions, i.e. over the Southern Ocean, where we simulate 3.4 cm-3 and 0.17 m s-1 increases over the 15-year period in the statistical mean levels of CCN and wind speed, respectively. Our results suggest that future changes in wind-speed-driven aerosol emissions from the oceans can probably have a climate feedback via clouds only in the most pristine regions. On the other hand, a feedback mechanism via changing precipitation patterns and intensities could take place over most oceanic regions, as we have shown that nucleation scavenging has by far the largest absolute effect on CCN concentrations. © 2014 Author(s)."
"22953153500;56910091600;36128620700;7202252296;7006705919;7401666571;","A physically based framework for modeling the organic fractionation of sea spray aerosol from bubble film Langmuir equilibria",2014,"10.5194/acp-14-13601-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919627367&doi=10.5194%2facp-14-13601-2014&partnerID=40&md5=f50c5a87af2e14c7c6f140d8556bc75a","The presence of a large fraction of organic matter in primary sea spray aerosol (SSA) can strongly affect its cloud condensation nuclei activity and interactions with marine clouds. Global climate models require new parameterizations of the SSA composition in order to improve the representation of these processes. Existing proposals for such a parameterization use remotely sensed chlorophyll a concentrations as a proxy for the biogenic contribution to the aerosol. However, both observations and theoretical considerations suggest that existing relationships with chlorophyll a, derived from observations at only a few locations, may not be representative for all ocean regions. We introduce a novel framework for parameterizing the fractionation of marine organic matter into SSA based on a competitive Langmuir adsorption equilibrium at bubble surfaces. Marine organic matter is partitioned into classes with differing molecular weights, surface excesses, and Langmuir adsorption parameters. The classes include a lipid-like mixture associated with labile dissolved organic carbon (DOC), a polysaccharide-like mixture associated primarily with semilabile DOC, a protein-like mixture with concentrations intermediate between lipids and polysaccharides, a processed mixture associated with recalcitrant surface DOC, and a deep abyssal humic-like mixture. Box model calculations have been performed for several cases of organic adsorption to illustrate the underlying concepts. We then apply the framework to output from a global marine biogeochemistry model, by partitioning total dissolved organic carbon into several classes of macromolecules. Each class is represented by model compounds with physical and chemical properties based on existing laboratory data. This allows us to globally map the predicted organic mass fraction of the nascent submicron sea spray aerosol. Predicted relationships between chlorophyll a and organic fraction are similar to existing empirical parameterizations, but can vary between biologically productive and nonproductive regions, and seasonally within a given region. Major uncertainties include the bubble film thickness at bursting, and the variability of organic surfactant activity in the ocean, which is poorly constrained. In addition, polysaccharides may enter the aerosol more efficiently than Langmuir adsorption would suggest. Potential mechanisms for enrichment of polysaccharides in sea spray include the formation of marine colloidal particles that may be more efficiently swept up by rising bubbles, and cooperative adsorption of polysaccharides with proteins or lipids. These processes may make important contributions to the aerosol, but are not included here. This organic fractionation framework is an initial step towards a closer linking of ocean biogeochemistry and aerosol chemical composition in Earth system models. Future work should focus on improving constraints on model parameters through new laboratory experiments or through empirical fitting to observed relationships in the real ocean and atmosphere, as well as on atmospheric implications of the variable composition of organic matter in sea spray. © 2014 Author(s)."
"36183122600;36056017400;55405013100;7004005379;7004607037;8953514400;24281186100;7006005916;","Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula",2014,"10.5194/acp-14-13497-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919460699&doi=10.5194%2facp-14-13497-2014&partnerID=40&md5=9fe29455199258fb51f123cf7b974383","A better understanding of aerosol radiative properties is a crucial challenge for climate change studies. This study aims at providing a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, long-term data sets of aerosol properties from six AERONET stations located in the Iberian Peninsula (southwestern Europe) have been analyzed in terms of climatological characterization and inter-annual changes. Aerosol information was used as input for the libRadtran model in order to determine the aerosol radiative effect (ARE) at the surface in the ultraviolet (AREUV), visible (AREVIS), near-infrared (ARENIR), and the entire SW range (ARESW) under cloud-free conditions. Over the whole Iberian Peninsula, yearly aerosol radiative effects in the different spectral ranges were found to be-1.1 < AREUV <-0.7,-5.7 < AREVIS <-3.5,-2.6 < ARENIR <-1.6, and-8.8 < ARESW <-5.7 (in W m&minus;2). Monthly means of ARE showed a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE), ARE per unit of aerosol optical depth, has also been evaluated in the four spectral ranges. AFE exhibited a dependence on single scattering albedo as well as a weaker one on the Ångström exponent. AFE is larger (in absolute value) for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency varied with the aerosol types. The predominant aerosol size determined the fractions AFEVIS/AFESW and AFENIR/AFESW. The AFEVIS was the dominant contributor for all aerosol types, although non-absorbing large particles caused more even contribution of VIS and NIR intervals. The AFEUV/AFESW ratio showed a higher value in the case of absorbing fine particles. © 2014 Author(s)."
"6603925960;57207507108;7003865921;6507495053;","Where and when will we observe cloud changes due to climate warming'",2014,"10.1002/2014GL061792","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921602172&doi=10.1002%2f2014GL061792&partnerID=40&md5=c5e9cbcf2b82aa7e23054ac0e37675fc","Climate models predict that the geographic distribution of clouds will change in response to anthropogenic warming, though uncertainties in the existing satellite record are larger than the magnitude of the predicted effects. Here we argue that cloud vertical distribution, observable by active spaceborne sensors, is a more robust signature of climate change. Comparison of Atmospheric Model Intercomparison Project present day and +4 K runs from Coupled Model Intercomparison Project Phase 5 shows that cloud radiative effect and total cloud cover do not represent robust signatures of climate change, as predicted changes fall within the range of variability in the current observational record. However, the predicted forced changes in cloud vertical distribution (directly measurable by spaceborne active sensors) are much larger than the currently observed variability and are expected to first appear at a statistically significant level in the upper troposphere, at all latitudes. © 2014. American Geophysical Union. All Rights Reserved."
"7103246957;7102933062;15830822000;6602469213;","Climate coupling between temperature, humidity, precipitation, and cloud cover over the Canadian prairies",2014,"10.1002/2014JD022511","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919608064&doi=10.1002%2f2014JD022511&partnerID=40&md5=0091ed632c156b1a5063b54c89891ebf","This analysis uses over 50 years of hourly observations of temperature, relative humidity, and opaque cloud cover and daily precipitation from 11 climate stations across the Canadian Prairies to analyze the monthly, seasonal, and long-term climate coupling in the warm season. On climate time scales, temperature depends on cloud forcing, while relative humidity depends on precipitation. The monthly climate depends on both opaque cloud cover for the current month and precipitation for both the present and past 2 months in summer. Multiple linear regression shows that anomalies of opaque cloud and precipitation explain 60–80% of the variance in the diurnal temperature range, afternoon relative humidity, and lifting condensation level on monthly time scales. We analyze the internal coupling of diurnal climate observables as a further guide to evaluating models. We couple the statistics to simplified energy and water budgets for the Prairies in the growing season. The opaque cloud observations have been calibrated against the incoming shortwave and longwave fluxes. We estimate that the drydown of total water storage on the landscape damps 56% of precipitation anomalies for the growing season on large spatial scales, although this drydown increases evapotranspiration. This couples the climatological surface fluxes to four key observables: cloud forcing, precipitation, temperature, and humidity. We estimate a climatological evaporative fraction of 0.61 for the Prairies. The observational relationships of the coupled Prairie climate system across time scale will be useful for evaluating these coupled processes in models for weather and seasonal forecasting and climate simulation. © 2014. American Geophysical Union. All rights reserved."
"57211986156;7402989545;57131609600;","Changes of Pacific decadal variability in the twentieth century driven by internal variability, greenhouse gases, and aerosols",2014,"10.1002/2014GL062269","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921602358&doi=10.1002%2f2014GL062269&partnerID=40&md5=d1cc81539ee48b0ca874507d80cf4ad7","This paper explores the contributions of internal variability, greenhouse gases (GHGs), and anthropogenic aerosols (AAs) in driving the magnitude and evolution of Pacific Decadal Variability (PDV) during the twentieth century by analyzing 129 Coupled Model Intercomparison Project Phase 5 model realizations. Evidence shows that PDV phase transition is dominated by internal variability, but it is also significantly affected by external forcing agents such as GHGs and aerosols. The combined effects of GHGs and AAs favor the positive phase of PDV with stronger ocean warming in the tropics than the extratropical Pacific. The GHG forcing induces the increased surface downward longwave radiation, especially over the tropical Pacific, and results in stronger warming in that area. The AA forcing results in a stronger cooling in the North Pacific region, due to the reduced surface downward shortwave radiation via cloud-aerosol interaction: this offsets the substantial warming caused by GHG forcing. © 2014. American Geophysical Union. All Rights Reserved."
"7005729142;16642567800;56470189200;","Terminal velocities and kinetic energies of natural hailstones",2014,"10.1002/2014GL062324","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921540977&doi=10.1002%2f2014GL062324&partnerID=40&md5=9acf350aafc9ddcc85e0c784fa4caece","The physical properties of 2295 hailstones that developed in Great Plains (US) storms were measured, including their maximum dimension, mass, and cross-sectional area. Using these data, size-dependent relationships for their terminal velocities and kinetic energies are developed. These relationships can be used in weather forecast modeling and hail damage prediction and assessment. When hailstones are assumed to be spherical, their terminal velocities and kinetic energies are in agreement with what has been reported in previous studies. When non-sphericity is considered, which is the case for natural hail, the terminal velocities and kinetic energies are, on average, lower than those of spheres of the same maximum diameter, but can be larger. © 2014. American Geophysical Union. All Rights Reserved."
"56243460400;24578134500;8636921300;56442593500;49261252100;57204294964;8705999100;55293780600;6603385683;56442610900;6602003804;","Glacier topography and elevation changes derived from Pléiades sub-meter stereo images",2014,"10.5194/tc-8-2275-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84916614182&doi=10.5194%2ftc-8-2275-2014&partnerID=40&md5=62c45648833cb7020d416f74b9cef6e3","In response to climate change, most glaciers are losing mass and hence contribute to sea-level rise. Repeated and accurate mapping of their surface topography is required to estimate their mass balance and to extrapolate/calibrate sparse field glaciological measurements. In this study we evaluate the potential of sub-meter stereo imagery from the recently launched Pléiades satellites to derive digital elevation models (DEMs) of glaciers and their elevation changes. Our five evaluation sites, where nearly simultaneous field measurements were collected, are located in Iceland, the European Alps, the central Andes, Nepal and Antarctica. For Iceland, the Pléiades DEM is also compared to a lidar DEM. The vertical biases of the Pléiades DEMs are less than 1m if ground control points (GCPs) are used, but reach up to 7m without GCPs. Even without GCPs, vertical biases can be reduced to a few decimetres by horizontal and vertical co-registration of the DEMs to reference altimetric data on ice-free terrain. Around these biases, the vertical precision of the Pléiades DEMs is ±1m and even ±0.5m on the flat glacier tongues (1σ confidence level). Similar precision levels are obtained in the accumulation areas of glaciers and in Antarctica. We also demonstrate the high potential of Pléiades DEMs for measuring seasonal, annual and multiannual elevation changes with an accuracy of 1m or better if cloud-free images are available. The negative region-wide mass balances of glaciers in the Mont-Blanc area (-1.04 ± 0.23ma-1 water equivalent, w.e.) are revealed by differencing Satellite pour l'Observation de la Terre 5 (SPOT 5) and Pléiades DEMs acquired in August 2003 and 2012, confirming the accelerated glacial wastage in the European Alps. © Author(s) 2014."
"55505265100;7102913661;7004347243;7102294773;15723554700;6506321617;24172779500;","Effect of different emission inventories on modeled ozone and carbon monoxide in Southeast Asia",2014,"10.5194/acp-14-12983-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906747194&doi=10.5194%2facp-14-12983-2014&partnerID=40&md5=b0aa53ad9dafe72d0dbe84c4223bf007","In order to improve our understanding of air quality in Southeast Asia, the anthropogenic emissions inventory must be well represented. In this work, we apply different anthropogenic emission inventories in the Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.3 using Model for Ozone and Related Chemical Tracers (MOZART) gas-phase chemistry and Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) aerosols to examine the differences in predicted carbon monoxide (CO) and ozone (O3) surface mixing ratios for Southeast Asia in March and December 2008. The anthropogenic emission inventories include the Reanalysis of the TROpospheric chemical composition (RETRO), the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), the MACCity emissions (adapted from the Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment projects), the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS) emissions, and a combination of MACCity and SEAC4RS emissions. Biomass-burning emissions are from the Fire Inventory from the National Center for Atmospheric Research (NCAR) (FINNv1) model. WRF-Chem reasonably predicts the 2 m temperature, 10 m wind, and precipitation. In general, surface CO is underpredicted by WRF-Chem while surface O3 is overpredicted. The NO2 tropospheric column predicted by WRF-Chem has the same magnitude as observations, but tends to underpredict the NO2 column over the equatorial ocean and near Indonesia. Simulations using different anthropogenic emissions produce only a slight variability of O3 and CO mixing ratios, while biomass-burning emissions add more variability. The different anthropogenic emissions differ by up to 30% in CO emissions, but O3 and CO mixing ratios averaged over the land areas of the model domain differ by ∼4.5% and ∼8%, respectively, among the simulations. Biomass-burning emissions create a substantial increase for both O3 and CO by ∼29% and ∼16%, respectively, when comparing the March biomass-burning period to the December period with low biomass-burning emissions. The simulations show that none of the anthropogenic emission inventories are better than the others for predicting O3 surface mixing ratios. However, the simulations with different anthropogenic emission inventories do differ in their predictions of CO surface mixing ratios producing variations of ∼30% for March and 10-20% for December at Thai surface monitoring sites. © Author(s) 2014."
"56439201600;24765842200;6701636816;6602743250;6701834461;7006728825;","Using cloud ice flux to parametrise large-scale lightning",2014,"10.5194/acp-14-12665-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84915749860&doi=10.5194%2facp-14-12665-2014&partnerID=40&md5=9294a3da74e5f8f228c55f8bafd44414","Lightning is an important natural source of nitrogen oxide especially in the middle and upper troposphere. Hence, it is essential to represent lightning in chemistry transport and coupled chemistry-climate models. Using ERA-Interim meteorological reanalysis data we compare the lightning flash density distributions produced using several existing lightning parametrisations, as well as a new parametrisation developed on the basis of upward cloud ice flux at 440 hPa. The use of ice flux forms a link to the non-inductive charging mechanism of thunderstorms. Spatial and temporal distributions of lightning flash density are compared to tropical and subtropical observations for 2007-2011 from the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite. The well-used lightning flash parametrisation based on cloud-top height has large biases but the derived annual total flash density has a better spatial correlation with the LIS observations than other existing parametrisations. A comparison of flash density simulated by the different schemes shows that the cloud-top height parametrisation has many more instances of moderate flash densities and fewer low and high extremes compared to the other parametrisations. Other studies in the literature have shown that this feature of the cloud-top height parametrisation is in contrast to lightning observations over certain regions. Our new ice flux parametrisation shows a clear improvement over all the existing parametrisations with lower root mean square errors (RMSEs) and better spatial correlations with the observations for distributions of annual total, and seasonal and interannual variations. The greatest improvement with the new parametrisation is a more realistic representation of the zonal distribution with a better balance between tropical and subtropical lightning flash estimates. The new parametrisation is appropriate for testing in chemistry transport and chemistry-climate models that use a lightning parametrisation."
"24067291600;36552457100;55290896600;55683214500;57202707841;56401230900;35146408200;57212332473;7402805784;","Usability of noise-free daily satellite-observed green–red vegetation index values for monitoring ecosystem changes in Borneo",2014,"10.1080/01431161.2014.978039","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912017527&doi=10.1080%2f01431161.2014.978039&partnerID=40&md5=445833da32d4856450562f9ccfac27ed","We examined the usability of daily green–red vegetation index (GRVI) observations from the Terra and Aqua Moderate Resolution Imaging Spectroradiometer satellite on cloud-free days for monitoring ecosystem changes in Bornean tropical forests at a 500 m spatial resolution over 11 years (2003–2013). The number of observational days of cloud-free GRVI data in the southwest monsoon period (May–October; 1–5 days/month) was greater than that in the northeast monsoon period (November–April; 0–2 days/month). Spatial variation in the observation frequency was noticed, with Terra (morning) and Aqua (afternoon) data showing different geographic distribution patterns of cloud-free data. The observation frequency in the western Kalimantan mountains (Sarawak and Sabah) was 1–2 days/month greater than that in the eastern mountains (Kalimantan). The quality of cloud-free GRVI data was validated by using sky images taken at the same time as the satellite observations and canopy surface images in a tropical rainforest. In oil palm and acacia plantations and peatlands, which were mainly distributed in coastal regions of Sarawak and West and Central Kalimantan, the cloud-free daily GRVI value fell below zero owing to deforestation and forest degradation caused by forest fire and increased with replanting and vegetation recovery. These results indicate that daily cloud-free GRVI data from multiple satellites collected at different times of the day are required for accurate monitoring of intra- and interannual phenological variation and forest degradation attributed to changes in climatic conditions and deforestation caused by human activities in tropical ecosystems. © 2014, © 2014 Taylor & Francis."
"54681868200;35292968200;55794904400;14031886500;","Reconstruction of MODIS land-surface temperature in a flat terrain and fragmented landscape",2014,"10.1080/01431161.2014.978036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912050704&doi=10.1080%2f01431161.2014.978036&partnerID=40&md5=ed02103f54a9f3e959a636bbb754e56d","Moderate Resolution Imaging Spectroradiometer (MODIS) land-surface temperature (LST) products provide important and reliable time-series data for the examination of global climate change, water cycling, and ecological evolution. In particular, in recently developed remote-sensing evapotranspiration models, such as the Surface Energy Balance Algorithm for Land and the Surface Energy Balance System, LST is a critical parameter that can directly influence the accuracy and integrity of final results. However, clouds and other atmospheric disturbances, which cover a large area throughout most of the year, are read as blank values by these programs, creating a problem. To solve this, a number of algorithms have been proposed to reconstruct LST data, but few can be used to evaluate flat and relatively fragmented landscape regions, such as the Yellow River Delta in China. Here, we conducted an analysis where we considered the LST of a flat area to be mainly influenced by land cover and other environmental elements (e.g. soil moisture). We used maps such as land cover, normalized difference vegetation index, and MODIS band 7 as additional data in the reconstruction model. All of the LST pixels we used were randomly divided into two parts: one part was used to train the model, and the other part was used to validate the calculated results. Three different methods have been developed to reconstruct LST data – linear regression, regression tree (RT) analysis, and artificial neural networks. In comparing these methods, we found that the RT method is able to estimate the LST of MODIS pixels with the greatest accuracy, and that it is both convenient and useful for reconstructing the LST map in flat and fragmented regions. © 2014, © 2014 Taylor & Francis."
"36702554300;55169224000;6602644862;6603581221;53878565500;56440269600;56020041300;55173498100;56453386700;56440296000;52564574500;55504871600;6602400272;57205923198;48661958200;36981391200;57211170882;7405295215;56099749900;55511109800;57205648153;7404700567;56246020600;35592560600;7003504656;7003982216;55549790500;7003781032;6603755619;","Pasture degradation modifies the water and carbon cycles of the Tibetan highlands",2014,"10.5194/bg-11-6633-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919363203&doi=10.5194%2fbg-11-6633-2014&partnerID=40&md5=56542c4b9e67a03eca71e72fb61e1514","The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments investigating changes of surface properties and processes together with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan Plateau. We connected measurements of micro-lysimeter, chamber, 13C labelling, and eddy covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyse how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while a change in the sum of evapotranspiration over a longer period cannot be confirmed. The results show an earlier onset of convection and cloud generation, likely triggered by a shift in evapotranspiration timing when dominated by evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a significant influence on larger scales. © Author(s) 2014."
"55389942900;6701815637;6603566335;","Impact of changes in the formulation of cloud-related processes on model biases and climate feedbacks",2014,"10.1002/2014MS000341","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027918346&doi=10.1002%2f2014MS000341&partnerID=40&md5=91d78f6fedae273aff1a8a79996dce81","To test the impact of modeling uncertainties and biases on the simulation of cloud feedbacks, several configurations of the EC-Earth climate model are built altering physical parameterizations. An overview of the various radiative feedbacks diagnosed from the reference EC-Earth configuration is documented for the first time. The cloud feedback is positive and small. While the total feedback parameter is almost insensitive to model configuration, the cloud feedback, in particular its shortwave (SW) component, can vary considerably depending on the model settings. The lateral mass exchange rate of penetrative convection and the conversion rate from condensed water to precipitation are leading uncertain parameters affecting the radiative feedbacks diagnosed. Consistent with other studies, we find a strong correlation between low-cloud model fidelity and low-cloud response under global warming. It is shown that this relationship holds only for stratocumulus regimes and is contributed by low-cloud cover, rather than low-cloud optical thickness. Model configurations simulating higher stratocumulus cover, which is closer to the observations, exhibit a stronger positive SW cloud feedback. This feedback is likely underestimated in the reference EC-Earth configuration, over the eastern basins of the tropical oceans. In addition, connections between simulated high-cloud top altitude in present-day climate and longwave cloud feedback are discussed. © 2014. The Authors."
"56119479900;55717074000;","Immersion freezing by natural dust based on a soccer ball model with the Community Atmospheric Model version 5: Climate effects",2014,"10.1088/1748-9326/9/12/124020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919667757&doi=10.1088%2f1748-9326%2f9%2f12%2f124020&partnerID=40&md5=0410c7e918d47a268c2577a01a502785","We introduce a simplified version of the soccer ball model (SBM) developed by Niedermeier et al (2014 Geophys. Res. Lett. 41 736-741) into the Community Atmospheric Model version 5 (CAM5). It is the first time that SBM is used in an atmospheric model to parameterize the heterogeneous ice nucleation. The SBM, which was simplified for its suitable application in atmospheric models, uses the classical nucleation theory to describe the immersion/condensation freezing by dust in the mixed-phase cloud regime. Uncertain parameters (mean contact angle, standard deviation of contact angle probability distribution, and number of surface sites) in the SBM are constrained by fitting them to recent natural dust (Saharan dust) datasets. With the SBM in CAM5, we investigate the sensitivity of modeled cloud properties to the SBM parameters, and find significant seasonal and regional differences in the sensitivity among the three SBM parameters. Changes of mean contact angle and the number of surface sites lead to changes of cloud properties in Arctic in spring, which could be attributed to the transport of dust ice nuclei to this region. In winter, significant changes of cloud properties induced by these two parameters mainly occur in northern hemispheric mid-latitudes (e.g., East Asia). In comparison, no obvious changes of cloud properties caused by changes of standard deviation can be found in all the seasons. These results are valuable for understanding the heterogeneous ice nucleation behavior, and useful for guiding the future model developments. © 2014 IOP Publishing Ltd."
"56278161100;56457990000;26324818700;35209683700;","Feedback attribution of the land-sea warming contrast in a global warming simulation of the NCAR CCSM4",2014,"10.1088/1748-9326/9/12/124005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919665363&doi=10.1088%2f1748-9326%2f9%2f12%2f124005&partnerID=40&md5=3c8b9e1281718e4836efb9206ca7d582","One of the salient features in both observations and climate simulations is a stronger land warming than sea. This paper provides a quantitative understanding of the main processes that contribute to the land-sea warming asymmetry in a global warming simulation of the NCAR CCSM4. The CO2 forcing alone warms the surface nearly the same for both land and sea, suggesting that feedbacks are responsible for the warming contrast. Our analysis on one hand confirms that the principal contributor to the above-unity land-to-sea warming ratio is the evaporation feedback; on the other hand the results indicate that the sensible heat flux feedback has the largest land-sea warming difference that favors a greater ocean than land warming. Therefore, the results uniquely highlight the importance of other feedbacks in establishing the above-unity land-to-sea warming ratio. Particularly, the SW cloud feedback and the ocean heat storage in the transient response are key contributors to the greater warming over land than sea. © 2014 IOP Publishing Ltd."
"55422916100;7403136998;36668278600;55826694700;55135832200;54683496300;35501268200;35572232000;","The parallel system for integrating impact models and sectors (pSIMS)",2014,"10.1016/j.envsoft.2014.04.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912115472&doi=10.1016%2fj.envsoft.2014.04.008&partnerID=40&md5=c96fc880a0fb0d95db8223d8012080d4","We present a framework for massively parallel climate impact simulations: the parallel System for Integrating Impact Models and Sectors (pSIMS). This framework comprises a) tools for ingesting and converting large amounts of data to a versatile datatype based on a common geospatial grid; b) tools for translating this datatype into custom formats for site-based models; c) a scalable parallel framework for performing large ensemble simulations, using any one of a number of different impacts models, on clusters, supercomputers, distributed grids, or clouds; d) tools and data standards for reformatting outputs to common datatypes for analysis and visualization; and e) methodologies for aggregating these datatypes to arbitrary spatial scales such as administrative and environmental demarcations. By automating many time-consuming and error-prone aspects of large-scale climate impacts studies, pSIMS accelerates computational research, encourages model intercomparison, and enhances reproducibility of simulation results. We present the pSIMS design and use example assessments to demonstrate its multi-model, multi-scale, and multi-sector versatility. © 2014 Elsevier Ltd."
"36816703000;8437626600;7201634517;7601556245;56643277200;55452292200;57212611731;","Formation process of the widespread extreme haze pollution over northern China in January 2013: Implications for regional air quality and climate",2014,"10.1016/j.atmosenv.2014.09.026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907080650&doi=10.1016%2fj.atmosenv.2014.09.026&partnerID=40&md5=0a8e2600e2823a78b72e0074288fe9f9","In this study, we present a regional insight into characteristics and formation process of the widespread extreme haze pollution in northern China during January of 2013 using integrated satellite observations and ground measurements. Different from common regional pollution, dense haze clouds during the most polluted period not only wandered over northern China for more than one week, but also exhibited large spatial variations with some abrupt peak values in Beijing. High UV Aerosol Index (UVAI) values &gt;2.5 indicate prevalent absorbing aerosols in upper part of the haze clouds. CALIPSO vertical detection shows that the haze layers were more than 3 km thick, with strong extinction within 1 km near surface and elevated dust layers above. Top of the more than 2 km thick dust plumes can reach 5 km, having a substantial contribution to the haze clouds. Movement of high aerosol loading regions with aerosol optical depth (AOD) exceeding 2.0 shows a notable superposition of different pollution processes within boundary layer, which largely enhanced the haze pollution. Peak value of PM10 in industrial cities of Hebei was around 1000 μg/m3, almost twice of that in usual pollution. Subsequent peak values of PM10 from south to north confirm the intense regional transport, which could be the main cause of sudden record-breaking particle concentration in Beijing. Anomalous weather conditions facilitated the unusual heavy pollution became extremely severe. Our results indicate close connections between variation of atmospheric circulation and the regional heavy pollution over northern China. © 2014 Elsevier Ltd."
"36132314500;57203540849;35115649600;27168081700;","Remote effect of the model cold bias in the tropical North Atlantic on the warm bias in the tropical southeastern Pacific",2014,"10.1002/2014MS000338","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923093845&doi=10.1002%2f2014MS000338&partnerID=40&md5=70f6df6bd8247e5f0a57f6a462cd7471","Most state-of-the-art climate models show significant systematic biases in the tropical southeastern Pacific (SEP) and tropical North Atlantic (TNA). These biases manifest themselves as the sea surface temperature (SST) in the SEP being too warm and the SST in the TNA being too cold. That is, as the cold SST biases appear in the TNA, the warm SST biases also occur in the SEP. This indicates that if climate models cannot succeed in simulating the TNA variability, they will also fail at least partially in the SEP. Our coupled model experiments show that the cold SST bias in the TNA results in a weakening of the Hadley-type circulation from the TNA to the SEP. This meridional circulation reduces the South Pacific subtropical anticyclone and the associated subsidence, which in turn leads to a reduction of low clouds, a weakening of the easterly trade wind, and thus an increase of the warm SST bias in the SEP. © 2014. The Authors."
"35105938900;56397706700;7005966519;6701578292;26645057800;","Nine thousand years of upper montane soil/vegetation dynamics from the summit of Caratuva Peak, Southern Brazil",2014,"10.1016/j.jsames.2014.09.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908329141&doi=10.1016%2fj.jsames.2014.09.019&partnerID=40&md5=70fcf1af55fc34c967a9df8a9e3016a2","Biodiversity loss, climate change, and increased freshwater consumption are some of the main environmental problems on Earth. Mountain ecosystems can reduce these threats by providing several positive influences, such as the maintenance of biodiversity, water regulation, and carbon storage, amongst others. The knowledge of the history of these environments and their response to climate change is very important for management, conservation, and environmental monitoring programs. The genesis of the soil organic matter of the current upper montane vegetation remains unclear and seems to be quite variable depending on location. Some upper montane sites in the very extensive coastal Sea Mountain Range present considerable organic matter from the late Pleistocene and other from only the Holocene. Our study was carried out on three soil profiles (two cores in grassland and one in forest) on the Caratuva Peak of the Serra do Ibitiraquire (a sub-range of Sea Mountain Range - Serra do Mar) in Southern Brazil. The δ13C isotopic analyses of organic matter in soil horizons were conducted to detect whether C3 or C4 plants dominated the past communities. Complementarily, we performed a pollen analysis and 14C dating of the humin fraction to obtain the age of the studied horizons. Except for a short and probably drier period (between 6000 and 4500calyrBP), C3 plants, including ombrophilous grasses and trees, have dominated the highlands of the Caratuva Peak (Pico Caratuva), as well as the other uppermost summits of the Serra do Ibitiraquire, since around 9000calyrBP. The Caratuva region represents a landscape of high altitude grasslands (campos de altitude altomontanos or campos altomontanos) and upper montane rain/cloud forests with soils that most likely contain some organic matter from the late Pleistocene, as has been reported in Southern and Southeastern Brazil for other sites. However, our results indicate that the studied deposits (near the summit) are from the early to late Holocene, when somewhat wetter and warmer conditions (since around 9000calyrBP) enabled a stronger colonization of the ridge of Pico Caratuva by mainly C3 plants, especially grassland species. However, at the same time, even near the summit, the soil core from the forest site already presented the current physiognomy (or a shrubby/elfin or successional forest), indicating that the colonization of the neighboring uppermost saddles and valleys were probably populated mainly by upper montane forest species. © 2014 Elsevier Ltd."
"54916510500;16246405500;35308103700;","A new snow and ice load map for mechanical design of power lines in great britain",2014,"10.1016/j.coldregions.2014.09.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908021546&doi=10.1016%2fj.coldregions.2014.09.001&partnerID=40&md5=21234cc2b11ef92d01293d589cef4323","A new high resolution map of extreme snow and ice loads has been produced. Wet snow accumulations on overhead power lines are estimated using observations from a network of surface synoptic weather stations, while areas of severe in-cloud icing (rime icing) are identified from high resolution numerical weather prediction model simulations. Ice loads at 50. year return period were estimated using the ""Peaks-Over-Threshold"" (POT) method and interpolated to a high resolution map using regression kriging. The results indicate a significant variation with elevation and latitude, with the highest loads expected in the wettest parts of the Scottish Highlands. In-cloud icing occurs mainly above 300-400. m and is the dominant icing type above 400-600. m depending on the location. The final icing map demonstrates how state of the art atmospheric icing models can be successfully utilized to estimate the icing climate even when only very limited measurements of actual icing are available. © 2014 Elsevier B.V."
"6603606681;6603566335;56030635600;7003656857;55175065800;57195449014;","A mixed-layer model study of the stratocumulus response to changes in large-scale conditions",2014,"10.1002/2014MS000347","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027920985&doi=10.1002%2f2014MS000347&partnerID=40&md5=08c929813328262ac4107b982a3cdcb2","A mixed-layer model is used to study the response of stratocumulus equilibrium state solutions to perturbations of cloud controlling factors which include the sea surface temperature, the specific humidity and temperature in the free troposphere, as well as the large-scale divergence and horizontal wind speed. In the first set of experiments, we assess the effect of a change in a single forcing condition while keeping the entrainment rate fixed, while in the second set, the entrainment rate is allowed to respond. The role of the entrainment rate is exemplified from an experiment in which the sea surface temperature is increased. An analysis of the budget equation for heat and moisture demonstrates that for a fixed entrainment rate, the stratocumulus liquid water path (LWP) will increase since the moistening from the surface evaporation dominates the warming effect. By contrast, if the response of the entrainment rate to the change in the surface forcing is sufficiently strong, enhanced mixing of dry and warm inversion air will cause a thinning of the cloud layer. If the entrainment warming effect is sufficiently strong, the surface sensible heat flux will decrease, as opposed to an increase which will occur for a fixed entrainment rate. It is argued that the surface evaporation will always increase for an increase in the sea surface temperature, and this change will be enlarged if the entrainment rate increases. These experiments aid the interpretation of results of similar simulations with single-column model versions of climate models carried out in the framework of the CFMIP-GCSS Intercomparison of Large-Eddy and Single-Column Models (CGILS) project. Because in a large-scale models, the entrainment response to changes in the large-scale forcing conditions depends on the details of the parameterization of turbulent and convective transport, intermodel differences in the sign of the LWP response may be well attributable to differences in the entrainment response. © 2014. The Authors."
"6506534909;6507948271;7005112315;6602499341;6701757355;7004490499;35263691500;56118787100;56194633100;7101723095;56194445800;56194956200;56118696000;","Tropical tropopause dynamics (TTD) campaigns over Indian region: An overview",2014,"10.1016/j.jastp.2014.05.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911454081&doi=10.1016%2fj.jastp.2014.05.007&partnerID=40&md5=d8850a3064ad83c258b7af6323d47be2","It is widely accepted that the tropical tropopause is closely linked to climate change. Several campaigns have already been conducted and also are being planned to address various issues related to the tropical tropopause layer (TTL). Despite many campaigns, several scientific issues still remain unexplained including Indian summer monsoon dynamics, cirrus clouds and the trace gas distribution across the tropopause etc. In order to address some of the issues, particularly over the Indian region, intensive observational campaigns called 'tropical tropopause dynamics (TTD)' are being conducted since December 2010 at two stations namely Gadanki (13.5°N, 79.2°E) and Trivandrum (8.5°N, 76.9°E) under CAWSES India Phase-II programme. This overview article aims to bring out the current understanding on the tropical tropopause, issues addressed through the TTD campaigns and the details of the data collected in these campaigns using collocated instruments as well as complementary satellite data. So far 32 campaigns have been completed successfully and in this paper main focus is given for describing the systematic data collected using various techniques (MST radar, Mie lidar, Radiosonde, ozonesonde) simultaneously in each month. In general, over the study region affected by the monsoon, a prominent updraft prevails in the middle and upper troposphere regions covering TTL affecting the transport of minor species across the tropopause. The behavior of the cold point tropopause (CPT) at Gadanki and Trivandrum reveals that there are significant differences in the CPT characteristics even within the monsoon region. Cold point tropopause shows stronger sub-daily scale variation over Trivandrum than Gadanki though no indication of deep convection is present at the former location particularly in winter. © 2014 Elsevier Ltd."
"24460392200;15835468800;24740735800;36088530800;7102001105;","Overview and sample applications of SMILES and Odin-SMR retrievals of upper tropospheric humidity and cloud ice mass",2014,"10.5194/acp-14-12613-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84915747396&doi=10.5194%2facp-14-12613-2014&partnerID=40&md5=fbffb51961649fb2152d9623592ceb92","Retrievals of cloud ice mass and humidity from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) and the Odin-SMR (Sub-Millimetre Radiometer) limb sounder are presented and example applications of the data are given. SMILES data give an unprecedented view of the diurnal variation of cloud ice mass. Mean regional diurnal cycles are reported and compared to some global climate models. Some improvements in the models regarding diurnal timing and relative amplitude were noted, but the models' mean ice mass around 250 hPa is still low compared to the observations. The influence of the ENSO (El Niño-Southern Oscillation) state on the upper troposphere is demonstrated using 12 years of Odin-SMR data. <br><br> The same retrieval scheme is applied for both sensors, and gives low systematic differences between the two data sets. A special feature of this Bayesian retrieval scheme, of Monte Carlo integration type, is that values are produced for all measurements but for some atmospheric states retrieved values only reflect a priori assumptions. However, this ""all-weather"" capability allows a direct statistical comparison to model data, in contrast to many other satellite data sets. Another strength of the retrievals is the detailed treatment of ""beam filling"" that otherwise would cause large systematic biases for these passive cloud ice mass retrievals. <br><br> The main retrieval inputs are spectra around 635/525 GHz from tangent altitudes below 8/9 km for SMILES/Odin-SMR, respectively. For both sensors, the data cover the upper troposphere between 30° S and 30° N. Humidity is reported as both relative humidity and volume mixing ratio. The vertical coverage of SMILES is restricted to a single layer, while Odin-SMR gives some profiling capability between 300 and 150 hPa. Ice mass is given as the partial ice water path above 260 hPa, but for Odin-SMR ice water content, estimates are also provided. Besides a smaller contrast between most dry and wet cases, the agreement with Aura MLS (Microwave Limb Sounder) humidity data is good. In terms of tropical mean humidity, all three data sets agree within 3.5 %RHi. Mean ice mass is about a factor of 2 lower compared to CloudSat. This deviation is caused by the fact that different particle size distributions are assumed, combined with saturation and a priori influences in the SMILES and Odin-SMR data."
"7005766987;7005659017;7801642681;","Type-segregated aerosol effects on regional monsoon activity: A study using ground-based experiments and model simulations",2014,"10.1016/j.atmosenv.2014.10.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908399872&doi=10.1016%2fj.atmosenv.2014.10.022&partnerID=40&md5=ee4e1a608e8251203292e2eb40b5ef49","Classification of observed aerosols into key types [e.g., clean-maritime (CM), desert-dust (DD), urban-industrial/biomass-burning (UI/BB), black carbon (BC), organic carbon (OC) and mixed-type aerosols (MA)] would facilitate to infer aerosol sources, effects, and feedback mechanisms, not only to improve the accuracy of satellite retrievals but also to quantify the assessment of aerosol radiative impacts on climate. In this paper, we report the results of a study conducted in this direction, employing a Cimel Sun-sky radiometer at the Indian Institute of Tropical Meteorology (IITM), Pune, India during 2008 and 2009, which represent two successive contrasting monsoon years. The study provided an observational evidence to show that the local sources are subject to heavy loading of absorbing aerosols (dust and black carbon), with strong seasonality closely linked to the monsoon annual rainfall cycle over Pune, a tropical urban station in India. The results revealed the absence of CM aerosols in the pre-monsoon as well as in the monsoon seasons of 2009 as opposed to 2008. Higher loading of dust aerosols is observed in the pre-monsoon and monsoon seasons of 2009; majority may be coated with fine BC aerosols from local emissions, leading to reduction in regional rainfall. Further, significant decrease in coarse-mode AOD and presence of carbonaceous aerosols, affecting the aerosol-cloud interaction and monsoon-rain processes via microphysics and dynamics, is considered responsible for the reduction in rainfall during 2009. Additionally, we discuss how optical depth, contributed by different types of aerosols, influences the distribution of monsoon rainfall over an urban region using the Monitoring Atmospheric Composition and Climate (MACC) aerosol reanalysis. Furthermore, predictions of the Dust REgional Atmospheric Model (DREAM) simulations combined with HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) cluster model are also discussed in support of the observed features. © 2014 Elsevier Ltd."
"56323835800;13404819100;27171906700;56443344600;57203523035;7102419371;7403735217;7402530272;","Comparative analysis of new particle formation events in less and severely polluted urban atmosphere",2014,"10.1016/j.atmosenv.2014.09.043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927776918&doi=10.1016%2fj.atmosenv.2014.09.043&partnerID=40&md5=1ae5a7c1cede11d523e050cef6cb5d2d","In this paper, we conducted a comparative study of new particle formation (NPF) events occurring between Qingdao and Toronto during spring. The extent of air pollution in Qingdao was much severer than that in Toronto, but the occurrence frequency of NPF events in Qingdao (41%) was almost same as that (42%) in Toronto. The geometric median diameter of new particles (D<inf>pg,1</inf>) increased up to >40nm in 15 days out of the total 16 NPF days in Qingdao, the D<inf>pg,1</inf> at least in eight days increased up to >60nm and even reached >80nm in two days. Two-stage growth was generally observed in these eight NPF events. The first-stage growth occurred in daytime and it was likely associated with formation of secondary organic aerosol (SOA) on basis of the modeling results. The second-stage growth was generally observed at nighttime when the modeling results showed increases of NH<inf>4</inf>+ and NO<inf>3</inf>- in concentration together with SOA, implying that NH<inf>4</inf>NO<inf>3</inf> possibly played a role in the growth. In Toronto, the maximum D<inf>pg,1</inf> of the observed new particles in all 13 NPF events was less than 50nm. A slight second-stage growth of new particles was observed only in four days when either the increase of NH<inf>4</inf>+ and NO<inf>3</inf>- in concentration or the increase of relative humidity occurred. The NPF events in Toronto less likely had a significant contribution to cloud condensation nuclei due to the small size of the observed new particles. © 2014 Elsevier Ltd."
"35263301100;23990979700;8973238600;56414208900;24775093700;16402681800;7201939972;36834624800;6603275172;","Kinetic and metabolic isotope effects in coral skeletal carbon isotopes: A re-evaluation using experimental coral bleaching as a case study",2014,"10.1016/j.gca.2014.09.033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910023860&doi=10.1016%2fj.gca.2014.09.033&partnerID=40&md5=6bdea58d376e79af7c680250cb5a5b70","Coral skeletal δ13C can be a paleo-climate proxy for light levels (i.e., cloud cover and seasonality) and for photosynthesis to respiration (P/R) ratios. The usefulness of coral δ13C as a proxy depends on metabolic isotope effects (related to changes in photosynthesis) being the dominant influence on skeletal δ13C. However, it is also influenced by kinetic isotope effects (related to calcification rate) which can overpower metabolic isotope effects and thus compromise the use of coral skeletal δ13C as a proxy. Heikoop et al. (2000) proposed a simple data correction to remove kinetic isotope effects from coral skeletal δ13C, as well as an equation to calculate P/R ratios from coral isotopes. However, despite having been used by other researchers, the data correction has never been directly tested, and isotope-based P/R ratios have never been compared to P/R ratios measured using respirometry. Experimental coral bleaching represents a unique environmental scenario to test this because bleaching produces large physiological responses that influence both metabolic and kinetic isotope effects in corals. Here, we tested the δ13C correction and the P/R calculation using three Pacific and three Caribbean coral species from controlled temperature-induced bleaching experiments where both the stable isotopes and the physiological variables that cause isotopic fractionation (i.e., photosynthesis, respiration, and calcification) were simultaneously measured. We show for the first time that the data correction proposed by Heikoop et al. (2000) does not effectively remove kinetic effects in the coral species studied here, and did not improve the metabolic signal of bleached and non-bleached corals. In addition, isotope-based P/R ratios were in poor agreement with measured P/R ratios, even when the data correction was applied. This suggests that additional factors influence δ13C and δ18O, which are not accounted for by the data correction. We therefore recommend that the data correction not be routinely applied for paleo-climate reconstruction, and that P/R ratios should only be obtained by direct measurement by respirometry. © 2014 Elsevier Ltd."
"56267893800;55438125800;56510471700;","Characteristics of the seasonal variation of the global tropopause revealed by COSMIC/GPS data",2014,"10.1016/j.asr.2014.08.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922544634&doi=10.1016%2fj.asr.2014.08.020&partnerID=40&md5=89efe15af62994cb6b58b0bb18937041","Using the Global Navigation Satellite System (GNSS) radio occultation observations from Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) from 2007 to 2012, the climatological characteristics of the global tropopause was studied, with the following features identified. The overall results generally agree with previous studies. The tropopause has an obvious zonal structure, with more zonal characteristics in the Southern Hemisphere than the Northern Hemisphere. The vertical shape of the tropopause is sharp in the tropics and broad in the sub-tropical latitudes, with the sharpest latitudinal gradient in the mid-latitudes of both hemispheres. The global tropopause exists in a large range between 8 km and 17 km (or between 100 hPa and 340 hPa). The highest tropopause is over the South Asian monsoon regions for the entire year. The spatial structure of the tropopause in the polar region is of concentric structure, with an altitude between 7.5 km and 10 km. It is more symmetric in the Antarctic than the Arctic. Differing from other places, the height of the tropopause in the Antarctic is higher in winter as opposed to summer. The tropopause has distinct seasonal variability, especially in polar regions. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved."
"23101280300;35409457600;35473149000;55576078700;56132957600;54414914800;","Evaluation of ALOS PALSAR sensitivity for characterizing natural forest cover in wider tropical areas",2014,"10.1016/j.rse.2013.04.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909633770&doi=10.1016%2fj.rse.2013.04.025&partnerID=40&md5=c88d7538b24ed0f2ac287f39e77be77d","The transformation of natural forest to non-forest cover is a dominant phenomenon in tropical regions; this creates unprecedented pressure to climate, biodiversity, and ecosystem services. Owing to persistent clouds and other atmospheric effects in the region, forest managers are facing difficulties in mapping and monitoring the forest cover changes consistently. This article presents an automated mapping method and examines the potentials of ALOS PALSAR data for characterizing natural forest cover in the tropics. Several scenes of high-resolution PALSAR data with HH and HV polarizations were processed to cover Sumatra Island. The mapping method applied image segmentation and threshold techniques to discriminate land covers. Non-forest land covers were separated using HH backscatter thresholds, while forest cover was based on HV thresholds. Twenty-two thematic maps derived at different HV backscatter thresholds were evaluated by comparing the land cover classes of the reference data. Sampling theory was used to determine the required sample size and geographic locations of the reference data. Among the resulting maps, a map with a threshold of -. 11.5. dB HV backscatter was found to be more sensitive for portraying the spatial patterns of land covers in the study area. The overall mapping accuracy at this threshold was 79.34%. Regardless of the data size, this automated mapping approach yielded decent spatial patterns of land covers and proved to be applicable for high-resolution wall-to-wall mapping and monitoring of natural forest cover in wider tropical areas. © 2014 Elsevier Inc."
"35205101700;7402146514;55713316500;50661916400;57190309014;","Estimation of high-resolution land surface shortwave albedo from AVIRIS data",2014,"10.1109/JSTARS.2014.2302234","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027926661&doi=10.1109%2fJSTARS.2014.2302234&partnerID=40&md5=8ea8543b65bdbc945bb23af51008a36d","Hyperspectral remote sensing data offer unique opportunities for the characterization of the land surface and atmosphere in the spectral domain. However, few studies have been conducted to estimate albedo from such hyperspectral data. In this study, we propose a novel approach to estimate surface shortwave albedo from data provided by the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). Our proposed method is based on the empirical relationship between apparent directional reflectance and surface shortwave broadband albedo established by extensive radiative transfer simulations. We considered the use of two algorithms to reduce data redundancy in the establishment of the empirical relationship including stepwise regression and principle component analysis (PCA). Results showed that these two algorithms were able to produce albedos with similar accuracies. Analysis was carried out to evaluate the effects of surface anisotropy on the direct estimation of broadband albedo. We found that the Lambertian assumption we made in this study did not lead to significant errors in the estimation of broadband albedo from simulated AVIRIS data over snow-free surfaces. Cloud detection was carried out on the AVIRIS images using a Gaussian distribution matching method. Preliminary evaluation of the proposed method was made using AmeriFlux ground measurements and Landsat data, showing that our albedo estimation can satisfy the accuracy requirements for climate and agricultural studies, with respective root-mean-square-errors (RMSEs) of 0.027, when compared with AmeriFlux, and 0.032, when compared with Landsat. Further efforts will focus on the extension and refinement of our algorithm for application to satellite hyperspectral data. © 2014 IEEE."
"56184706600;7003495982;7405489798;","Sensitivity of the water cycle over the Indian Ocean and Maritime Continent to parameterized physics in a regional model",2014,"10.1002/2014MS000313","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027925622&doi=10.1002%2f2014MS000313&partnerID=40&md5=3e80d690f55f9ab6d99ccc7e00c90c0c","A regional model was used to simulate the water cycle over the Indian Ocean (IO) and Maritime Continent (MC). Sixteen 92 day simulations were performed using different combinations of eight cumulus parameterization schemes and three planetary boundary-layer (PBL) parameterization schemes. The strength of the water cycle in the IO and MC, measured by its domain mean precipitation and precipitable water, differs substantially among the simulations. The large spread of water cycle strength is mainly toward dry biases in comparison to global data assimilation products. The simulated water cycle, its spread, and biases differ between the IO and MC. Influences of PBL schemes can penetrate into the upper troposphere and those by cumulus schemes into the boundary layer. Dry biases in the simulations are produced mainly because of feedbacks among erroneously low diabatic heating peaks, shallow moisture convergence layers, dry lower troposphere, and weak surface evaporation. There is no single type of parameterization scheme that can be identified to be the main sources of the dry biases. It is the combination of errors from three types of parameterization schemes, namely, cumulus, PBL, and microphysics, that makes the simulated water cycle unrealistic. The lesson learned is that the tropical water cycle can be better simulated only by improving parameterization schemes of different processes all together as a package. Key Points: The water cycle can be better simulated only by improving model physics Biases produced by a PBL scheme can penetrate into the middle troposphere Biases produced by cumulus schemes can penetrate into the boundary layer © 2014. The Authors."
"36675355500;7101605237;7006513495;","Projection of red spruce (Picea rubens Sargent) habitat suitability and distribution in the Southern Appalachian Mountains, USA",2014,"10.1016/j.ecolmodel.2014.06.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910683890&doi=10.1016%2fj.ecolmodel.2014.06.005&partnerID=40&md5=d99f4c8adbefea5fafceda66a652de35","Red spruce (. Picea rubens Sargent) has exhibited widespread growth decline and high mortality for the last half century in the eastern United States. Good prediction of this species' distribution in relation to environmental conditions is critical for effective management. This study projects red spruce distribution in response to multiple causal mechanisms in the Great Smoky Mountains National Park (GSMNP) of the Southern Appalachian Mountains by coupling a temporal simulation model of tree growth (ARIM.SIM) to a species distribution model (ARIM.HAB). ARIM.HAB computed habitat suitability, estimated from ARIM.SIM-generated red spruce growth, for every spatial 30. m grid cell in GSMNP. ARIM.SIM showed that different factors were responsible for habitat suitability and growth at higher vs. lower elevations. The air pollution variables (acid rain and cloud immersion frequency) caused low habitat suitability at higher elevations (1800-2028. m). Reduced air pollution but greater stress from climatic variables (high temperatures, reduced precipitation) caused medium suitability at lower elevations (1400-1600. m). And less stress from air pollution and climate variables combined with ample water to produce highest suitability at intermediate elevations (1600-1800. m). The projected range was verified with an existing geospatial database for red spruce and showed excellent correspondence with present-day distribution (AUC. =. 0.99, kappa. =. 0.87 and TSS. =. 0.88). This research shows that species distribution models coupled with a process-based temporal simulation models can improve the precision and accuracy of, respectively, habitat suitability and range projections for species at local scales. © 2014 Elsevier B.V."
"8922308700;15755995900;55544607500;","Precipitation characteristics of CAM5 physics at mesoscale resolution during MC3E and the impact of convective timescale choice",2014,"10.1002/2014MS000334","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027941201&doi=10.1002%2f2014MS000334&partnerID=40&md5=2aef96d26e147c55af2c6947d3f33791","The physics suite of the Community Atmosphere Model version 5 (CAM5) has recently been implemented in the Weather Research and Forecasting (WRF) model to explore the behavior of the parameterization suite at high resolution and within the controlled setting of a limited area model. The initial paper documenting this capability characterized the behavior for a northern high-latitude region. This paper characterizes the precipitation characteristics for continental, midlatitude, springtime conditions during the Midlatitude Continental Convective Clouds Experiment (MC3E) over the central United States. This period exhibited a range of convective conditions from those driven strongly by large-scale synoptic regimes to more locally driven convection. The study focuses on the precipitation behavior at 32 km grid spacing to better anticipate how the physics will behave in a global model when used at similar grid spacing in the coming years. Importantly, one change to the Zhang-McFarlane deep convective parameterization when implemented in WRF was to make the convective timescale parameter an explicit function of grid spacing. This study examines the sensitivity of the precipitation to the default value of the convective timescale in WRF, which is 600 s for 32 km grid spacing, to the value of 3600 s used for 2° grid spacing in CAM5. For comparison, a 1200 s and an infinite convective timescale are also used. The results show that the 600 s timescale gives the most accurate precipitation amount over the central United States. However, this setting has the worst precipitation diurnal cycle, with the convection too tightly linked to the daytime surface heating. Longer timescales greatly improve the diurnal cycle but result in less precipitation and produce a low bias. An analysis of rain rates shows the accurate precipitation amount with the shorter timescale is assembled from an over abundance of drizzle combined with too few heavy rain events. With longer timescales, one can improve the frequency distribution, particularly for the extreme rain rates. Ultimately, without changing other aspects of the physics, one must decide between accurate diurnal timing and rain amount when choosing an appropriate convective timescale. © 2014. The Authors."
"23028121100;55339298600;7004419968;7201479825;","Comparison of decadal global water vapor changes derived from independent satellite time series",2014,"10.1002/2014JD021588","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84918591101&doi=10.1002%2f2014JD021588&partnerID=40&md5=846422f989a36d3be3f74cdd4aea3740","We analyze trends in total column water vapor (TCWV) retrieved from independent satellite observations and retrieval schemes. GOME-SCIAMACHY (Global Ozone Monitoring Experiment-SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) measurements are carried out in the visible part of the solar spectrum and present a partly cloud-corrected climatology that is available over land and ocean. The HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data) product, provided by EUMETSAT's Satellite Application Facility on Climate Monitoring is based on passive microwave observations from the Special Sensor Microwave/Imager. It also includes the TCWV from cloudy pixels but is only available over oceans. The common observation time period is between 1996 and 2005. Due to the relatively short length of the period, the strong interannual variability with strong contributions from El Niño and La Niña events and the strong anomaly at the start of the common period, caused by the 1997/1998 El Niño, the observed trends should not be interpreted as long-term climate trends. After subtraction of average seasonality from monthly gridded data, a linear model and a level shift model have been fitted to the HOAPS and GOME-SCIAMACHY data, respectively. Autocorrelation and cross correlation of fit residuals are accounted for in assessing uncertainties in trends. The trends observed in both time series agree within uncertainty margins. This agreement holds true for spatial patterns, magnitudes, and global averages. The consistency increases confidence in the reliability of the trends because the methods, spectral range, and observation technique as well as the satellites and their orbits are completely independent of each other. The similarity of the trends in both data sets is an indication of sufficient stability in the observations for the time period of ≈ 10 years. ©2014. American Geophysical Union. All Rights Reserved."
"24779895300;21739916500;6603579524;6603812137;16064239500;","Bidirectional leader development in sprite-producing positive cloud-to-ground flashes: Origins and characteristics of positive and negative leaders",2014,"10.1002/2013JD021291","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84918514762&doi=10.1002%2f2013JD021291&partnerID=40&md5=5cad9dfb67542036e9b1f5a2f61bf752","Thirty-five sprite-producing lightning flashes were recorded in nine nights in different seasons at the east coast of Spain with a 3D Lightning Mapping Array (LMA) since July 2011. A low-frequency time-of-arrival network provided data on emissions from return strokes and intracloud processes and a very-high-frequency interferometer network produced complementary lightning data. This study analyzes the bidirectional development of flashes in order to understand the positioning and timing of the positive cloud-to-ground stroke (+CG) and its consequences for charge neutralization by negative leaders, affecting sprite morphology. A summary of negative leader extents, altitudes, and speeds before and after the + CG stroke is provided, as well as positive leader origins and inferred speeds. Negative leader speeds exhibited modes at 105 and 5 × 105 m s-1. Five examples with different evolutions are discussed: (1) Slow bidirectional development with negative leader termination before the + CG stroke; (2) Fast bidirectional development with the negative leader continuing after the + CG stroke. (3) Slow-fast bidirectional development with a negative leader exhibiting a sudden lowering and speed increase; (4) Fast secondary bidirectional development from an in-cloud horizontal positive leader. Negative leaders propagated rapidly into the upper positive charge layer, continuing after the + CG stroke; (5) Slow bidirectional development with a long negative leader (50 km) subject to cutoff while the original positive leader remained trapped inside negative charge. A + CG stroke subsequently occurred under the old negative leader channel. Carrot sprites tended to be associated with fast extending leaders after the stroke, columniform/mixed sprites with slower side branches. ©2014. American Geophysical Union. All Rights Reserved."
"37560912800;6701753599;55942083800;7004142910;","Competition between water uptake and ice nucleation by glassy organic aerosol particles",2014,"10.5194/acp-14-12513-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906842530&doi=10.5194%2facp-14-12513-2014&partnerID=40&md5=4ac47a01424189b517db0c9ddc55522b","Organic aerosol particles play a key role in climate by serving as nuclei for clouds and precipitation. Their sources and composition are highly variable, and their phase state ranges from liquid to solid under atmospheric conditions, affecting the pathway of activation to cloud droplets and ice crystals. Due to slow diffusion of water in the particle phase, organic particles may deviate in phase and morphology from their thermodynamic equilibrium state, hampering the prediction of their influence on cloud formation. We overcome this problem by combining a novel semi-empirical method for estimation of water diffusivity with a kinetic flux model that explicitly treats water diffusion. We estimate timescales for particle deliquescence as well as various ice nucleation pathways for a wide variety of organic substances, including secondary organic aerosol (SOA) from the oxidation of isoprene, α-pinene, naphthalene, and dodecane. The simulations show that, in typical atmospheric updrafts, glassy states and solid/liquid core-shell morphologies can persist for long enough that heterogeneous ice nucleation in the deposition and immersion mode can dominate over homogeneous ice nucleation. Such competition depends strongly on ambient temperature and relative humidity as well as humidification rate and particle size. Due to differences in glass transition temperature, hygroscopicity and atomic O/C ratio of the different SOA, naphthalene SOA particles have the highest potential to act as heterogeneous ice nuclei. Our findings demonstrate that kinetic limitations of water diffusion into organic aerosol particles are likely to be encountered under atmospheric conditions and can strongly affect ice nucleation pathways. For the incorporation of ice nucleation by organic aerosol particles into atmospheric models, our results demonstrate a demand for model formalisms that account for the effects of molecular diffusion and not only describe ice nucleation onsets as a function of temperature and relative humidity but also include updraft velocity, particle size and composition. © Author(s) 2014."
"56151545200;35265216700;55476830600;53981601100;36021733300;55624488227;56068376200;","Pathways of sulfate enhancement by natural and anthropogenic mineral aerosols in China",2014,"10.1002/2014JD022301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018787356&doi=10.1002%2f2014JD022301&partnerID=40&md5=05ad7b7a87087884ef51a1cb795aa162","China, the world’s largest consumer of coal, emits approximately 30 million tons of sulfur dioxide (SO2) per year. SO2 is subsequently oxidized to sulfate in the atmosphere. However, large gaps exist between model-predicted and measured sulfate levels in China. Long-term field observations and numerical simulations were integrated to investigate the effect of mineral aerosols on sulfate formation. We found that mineral aerosols contributed a nationwide average of approximately 22% to sulfate production in 2006. The increased sulfate concentration was approximately 2 μgm3 in the entire China. In East China and the Sichuan Basin, the increments reached 6.3 μgm3 and 7.3 μgm3, respectively. Mineral aerosols led to faster SO2 oxidation through three pathways. First, more SO2 was dissolved as cloud water alkalinity increased due to water-soluble mineral cations. Sulfate production was then enhanced through the aqueous-phase oxidation of S(IV) (dissolved sulfur in oxidation state +4). The contribution to the national sulfate production was 5%. Second, sulfate was enhanced through S(IV) catalyzed oxidation by transition metals. The contribution to the annual sulfate production was 8%, with 19% during the winter that decreased to 2% during the summer. Third, SO2 reacts on the surface of mineral aerosols to produce sulfate. The contribution to the national average sulfate concentration was 9% with 16% during the winter and a negligible effect during the summer. The inclusion of mineral aerosols does resolve model discrepancies with sulfate observations in China, especially during the winter. These three pathways, which are not fully considered in most current chemistry-climate models, will significantly impact assessments regarding the effects of aerosol on climate change in China. © 2014. American Geophysical Union. All Rights Reserved."
"26664901700;7004205208;55332040400;55331928800;","Electromagnetic activity before initial breakdown pulses of lightning",2014,"10.1002/2014JD022155","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84918516277&doi=10.1002%2f2014JD022155&partnerID=40&md5=23ee1083055c6add80aaecd4efe1565e","Lightning flash initiation is studied using electric field change (E-change) measurements made in Florida. An initial E-change (IEC) was found immediately before the first initial breakdown (IB) pulse in both cloud-to-ground (CG) and intracloud (IC) flashes if the E-change sensor was within 80% of the reversal distance of the IEC. For 18 CG flashes, the IECs had an average point dipole moment of 23 C m and an average duration of 0.18 ms; these parameters for 18 IC flashes were -170 C m and 1.53 ms. The IECs of CG flashes began with a change in the slope of the E-change (with respect to time) from zero slope to a positive slope, consistent with downward motion of negative charge and/or upward motion of positive charge. For IECs of IC flashes, the beginning slope change was from zero to negative slope, consistent with upward motion of negative charge and/or downward motion of positive charge. During an IEC, the E-change monotonically increased for CG flashes and monotonically decreased for IC flashes. In 14 of 36 cases, the IEC beginning was coincident with a discrete, impulsive source of VHF radiation; another 13 cases had at least one VHF source during the IEC or the first IB pulse. Before the IECs, there were no preliminary variations detected in the 36 flashes. It is hypothesized that lightning initiation begins with an ionizing event that causes the IEC and that the IEC enhances the ambient electric field to produce the first IB pulse. ©2014. American Geophysical Union. All Rights Reserved."
"56125661000;16426140700;8380252900;36486362800;","FAME-C: Cloud property retrieval using synergistic AATSR and MERIS observations",2014,"10.5194/amt-7-3873-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84914674873&doi=10.5194%2famt-7-3873-2014&partnerID=40&md5=7fc0b7c9179ba81f6b85e5200c27b227","A newly developed daytime cloud property retrieval algorithm, FAME-C (Freie Universität Berlin AATSR MERIS Cloud), is presented. Synergistic observations from the Advanced Along-Track Scanning Radiometer (AATSR) and the Medium Resolution Imaging Spectrometer (MERIS), both mounted on the polar-orbiting Environmental Satellite (Envisat), are used for cloud screening. For cloudy pixels two main steps are carried out in a sequential form. First, a cloud optical and microphysical property retrieval is performed using an AATSR near-infrared and visible channel. Cloud phase, cloud optical thickness, and effective radius are retrieved, and subsequently cloud water path is computed. Second, two cloud top height products are retrieved based on independent techniques. For cloud top temperature, measurements in the AATSR infrared channels are used, while for cloud top pressure, measurements in the MERIS oxygen- A absorption channel are used. Results from the cloud optical and microphysical property retrieval serve as input for the two cloud top height retrievals. Introduced here are the AATSR and MERIS forward models and auxiliary data needed in FAME-C. Also, the optimal estimation method, which provides uncertainty estimates of the retrieved property on a pixel basis, is presented. Within the frame of the European Space Agency (ESA) Climate Change Initiative (CCI) project, the first global cloud property retrievals have been conducted for the years 2007-2009. For this time period, verification efforts are presented, comparing, for four selected regions around the globe, FAME-C cloud optical and microphysical properties to cloud optical and microphysical properties derived from measurements of the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite. The results show a reasonable agreement between the cloud optical and microphysical property retrievals. Biases are generally smallest for marine stratocumulus clouds: -0.28, 0.41 μm and -0.18 gm-2 for cloud optical thickness, effective radius and cloud water path, respectively. This is also true for the root-mean-square deviation. Furthermore, both cloud top height products are compared to cloud top heights derived from ground-based cloud radars located at several Atmospheric Radiation Measurement (ARM) sites. FAME-C mostly shows an underestimation of cloud top heights when compared to radar observations. The lowest bias of -0.3 km is found for AATSR cloud top heights for single-layer clouds, while the highest bias of -3.0 km is found for AATSR cloud top heights for multilayer clouds. Variability is low for MERIS cloud top heights for low-level clouds, and high for MERIS cloud top heights for mid-level and high-level single-layer clouds, as well as for both AATSR and MERIS cloud top heights for multilayer clouds. © Author(s) 2014."
"56267893800;56452346100;","Humidity sensor failure: A problem that should not be neglected",2014,"10.5194/amt-7-3909-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919392351&doi=10.5194%2famt-7-3909-2014&partnerID=40&md5=559f7aac0bad3f6b92c78413f6160cab","The problem of abnormally dry bias induced by radiosonde humidity sensor failure in the low and mid-troposphere is studied based on the global operational radiosonde relative humidity observations from December 2008 to November 2009. The concurrent humidity retrievals from the FORMOSAT-3/COSMIC radio occultation mission are also used to assess the quality of the radiosonde humidity observations. It is found that extremely dry relative humidity are common in the low and mid-troposphere, with an annual globally averaged occurrence of 4.2%. These low-humidity observations usually exist between 20 and 40° latitude in both the Northern Hemisphere and Southern Hemisphere, and from heights of 700 to 450 hPa. Winter and spring are the favored seasons for their occurrence, with a maximum fraction of 9.53 % in the Northern Hemisphere and 16.82% in the Southern Hemisphere. The phenomenon does not result from natural atmospheric variability, but rather humidity sensor failure. If the performance of humidity sensors is not good, low-humidity observations occur easily, particularly when the radiosonde ascends through stratiform clouds with high moisture content. The humidity sensor cannot adapt to the huge change of the atmospheric environment inside and outside stratiform clouds, resulting in sensor failure and no response to atmospheric change. These extremely dry relative humidity observations are erroneous. However, they have been archived as formal data and applied in many research studies. This may seriously undermine the reliability of numerical weather prediction and the analysis of weather and climate if quality control is not applied before using these data. © Author(s) 2014."
"56386678000;14052002000;7103197356;7005456532;","Improving HelioClim-3 estimates of surface solar irradiance using the McClear clear-sky model and recent advances in atmosphere composition",2014,"10.5194/amt-7-3927-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913580913&doi=10.5194%2famt-7-3927-2014&partnerID=40&md5=911eadd05631ee93d690b29c569997d2","The HelioClim-3 database (HC3v3) provides records of surface solar irradiation every 15 min, estimated by processing images from the geostationary meteorological Meteosat satellites using climatological data sets of the atmospheric Linke turbidity factor. This technical note proposes a method to improve a posteriori HC3v3 by combining it with data records of the irradiation under clear skies from the new McClear clear-sky model, whose inputs are the advanced global aerosol property forecasts and physically consistent total column content in water vapour and ozone produced by the MACC (Monitoring Atmosphere Composition and Climate) projects. The method is validated by comparison with a series of ground measurements for 15 min and 1 h for 6 stations and for daily irradiation for 23 stations. The correlation coefficient is large, greater than respectively 0.92, 0.94, and 0.97, for 15 min, 1 h and daily irradiation. The bias ranges from g'4 to 4% of the mean observed irradiation for most sites. The relative root mean square difference (RMSD) varies between 14 and 38% for 15 min, 12 and 33% for 1 h irradiation, and 6 and 20% for daily irradiation. As a rule of thumb, the farther from the nadir of the Meteosat satellite located at latitude 0° and longitude 0°, and the greater the occurrence of fragmented cloud cover, the greater the relative RMSD. The method improves HC3v3 in most cases, and with no degradation in the others. A systematic correction of HC3v3 with McClear is recommended. © Author(s) 2014."
"55935471700;51663627700;7006204597;9843579700;16068495600;7003430284;55683314900;56179033200;6602504147;55480868800;7004027519;","CCN activity of size-selected aerosol at a Pacific coastal location",2014,"10.5194/acp-14-12307-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913556456&doi=10.5194%2facp-14-12307-2014&partnerID=40&md5=59df9cfc8f168e918e8ff5c517fa1743","As one aspect of the NETwork on Climate and Aerosols: addressing key uncertainties in Remote Canadian Environments (NETCARE), measurements of the cloud condensation nucleation properties of 50 and 100 nm aerosol particles were conducted at Ucluelet on the west coast of Vancouver Island in August 2013. The overall hygroscopicity parameter of the aerosol (κambient) exhibited a wide variation, ranging from 0.14 ± 0.05 to 1.08 ± 0.40 (where the uncertainty represents the systematic error). The highest ΰ values arose when the organic-to-sulfate ratio of the aerosol was lowest and when winds arrived from the west after transport through the marine boundary layer. The average κambient during this time was 0.57 ± 0.16, where the uncertainty represents the standard deviation. At most other times, the air was predominantly influenced by both marine and continental emissions, which had lower average PM1 κambient values (max value, 0.41 ± 0.08). The two-day average aerosol ionic composition also showed variation, but was consistently acidic and dominated by ammonium (18-56% by mole) and sulfate (19-41% by mole), with only minor levels of sodium or chloride. Average κorg (hygroscopicity parameter for the aerosol's organic component) values were estimated using PM1 aerosol composition data and by assuming that the ratio of aerosol organic to sulfate mass is related directly to the composition of the size-selected particles. © 2014 Author(s)."
"6504688501;9333422400;35810775100;10139397300;7004469744;7004402705;8669968400;35775264900;56232242500;6603480361;12806941900;7405666962;7004966070;7004587644;7006532784;7005126327;56634572800;7006717176;","Aerosol microphysics simulations of the Mt.∼Pinatubo eruption with the UM-UKCA composition-climate model",2014,"10.5194/acp-14-11221-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908346820&doi=10.5194%2facp-14-11221-2014&partnerID=40&md5=1800523d331fed638f733adef2c8c7cf","We use a stratosphere-troposphere composition-climate model with interactive sulfur chemistry and aerosol microphysics, to investigate the effect of the 1991 Mount Pinatubo eruption on stratospheric aerosol properties. Satellite measurements indicate that shortly after the eruption, between 14 and 23 Tg of SO2 (7 to 11.5 Tg of sulfur) was present in the tropical stratosphere. Best estimates of the peak global stratospheric aerosol burden are in the range 19 to 26 Tg, or 3.7 to 6.7 Tg of sulfur assuming a composition of between 59 and 77 % H2SO4. In light of this large uncertainty range, we performed two main simulations with 10 and 20 Tg of SO2 injected into the tropical lower stratosphere. Simulated stratospheric aerosol properties through the 1991 to 1995 period are compared against a range of available satellite and in situ measurements. Stratospheric aerosol optical depth (sAOD) and effective radius from both simulations show good qualitative agreement with the observations, with the timing of peak sAOD and decay timescale matching well with the observations in the tropics and mid-latitudes. However, injecting 20 Tg gives a factor of 2 too high stratospheric aerosol mass burden compared to the satellite data, with consequent strong high biases in simulated sAOD and surface area density, with the 10 Tg injection in much better agreement. Our model cannot explain the large fraction of the injected sulfur that the satellite-derived SO2 and aerosol burdens indicate was removed within the first few months after the eruption. We suggest that either there is an additional alternative loss pathway for the SO2 not included in our model (e.g. via accommodation into ash or ice in the volcanic cloud) or that a larger proportion of the injected sulfur was removed via cross-tropopause transport than in our simulations. <br><br> We also critically evaluate the simulated evolution of the particle size distribution, comparing in detail to balloon-borne optical particle counter (OPC) measurements from Laramie, Wyoming, USA (41° N). Overall, the model captures remarkably well the complex variations in particle concentration profiles across the different OPC size channels. However, for the 19 to 27 km injection height-range used here, both runs have a modest high bias in the lowermost stratosphere for the finest particles (radii less than 250 nm), and the decay timescale is longer in the model for these particles, with a much later return to background conditions. Also, whereas the 10 Tg run compared best to the satellite measurements, a significant low bias is apparent in the coarser size channels in the volcanically perturbed lower stratosphere. Overall, our results suggest that, with appropriate calibration, aerosol microphysics models are capable of capturing the observed variation in particle size distribution in the stratosphere across both volcanically perturbed and quiescent conditions. Furthermore, additional sensitivity simulations suggest that predictions with the models are robust to uncertainties in sub-grid particle formation and nucleation rates in the stratosphere. © 2014 Author(s)."
"36720994100;49161131000;35454141800;9838847000;","Improvement of CALIOP cloud masking algorithms for better estimation of dust extinction profiles",2014,"10.2151/jmsj.2014-502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911995398&doi=10.2151%2fjmsj.2014-502&partnerID=40&md5=efd844e43062fbefbdde825da636f43d","Mineral dust suspended in the atmosphere affects the Earth’s radiation budget. To accurately predict the effect of dust on the climate system, information regarding its extinction profiles is needed. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite has enabled the global observation of the vertical distributions of aerosols and clouds since June 2006. To correctly retrieve extinction coefficients from CALIOP signals, the lidar-observed layers must be classified into aerosols or clouds. The cloud masking algorithms of CALIOP should be improved since the cloud mask products occasionally misclassify dense dust as clouds. This study attempts to discriminate misclassified clouds from the CALIOP cloud mask with a discriminant analysis. The training data are collected by tests with the CloudSat cloud mask, the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask, and relative humidity. Discrimination of dust from clouds is successful in cases over land and water surfaces during the daytime and nighttime. In contrast, the discrimination model of previous studies was inadequate during the nighttime since training data were not collected during the nighttime. The accuracy rate of the linear discriminant function classification is 91.7 % for misclassified clouds. The cloud mask is most frequently misclassified in the Taklimakan Desert. The proportion of misclassified clouds to the observed dust is ~34.6 % (below 2 km) in the desert. Comparison of our results with CALIOP level 3 products indicates that the extinction profile using the improved cloud mask is at most twice larger than that of CALIOP level 3 products. This study suggests that the smaller extinction coefficients of CALIOP level 3 products are mainly caused by misclassification of dust as clouds in the vertical feature mask. © 2014, Meteorological Society of Japan."
"8919299300;10139397300;6602903407;7102805852;7003861526;","Aerosol direct radiative effect of smoke over clouds over the southeast Atlantic Ocean from 2006 to 2009",2014,"10.1002/2014GL061103","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912059025&doi=10.1002%2f2014GL061103&partnerID=40&md5=0ea20a79ae6bb9a673d5b641982f3b90","The aerosol direct radiative effect (DRE) of African smoke was analyzed in cloud scenes over the southeast Atlantic Ocean, using Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite observations and Hadley Centre Global Environmental Model version 2 (HadGEM2) climate model simulations. The observed mean DRE was about 30-35 W m-2 in August and September 2006-2009. In some years, short episodes of high-aerosol DRE can be observed, due to high-aerosol loadings, while in other years the loadings are lower but more prolonged. Climate models that use evenly distributed monthly averaged emission fields will not reproduce these high-aerosol loadings. Furthermore, the simulated monthly mean aerosol DRE in HadGEM2 is only about 6 W m-2 in August. The difference with SCIAMACHY mean observations can be partly explained by an underestimation of the aerosol absorption Ångström exponent in the ultraviolet. However, the subsequent increase of aerosol DRE simulation by about 20% is not enough to explain the observed discrepancy between simulations and observations. Key PointsNew aerosol radiative effects above clouds are presentedClimate models do not reproduce these details wellAerosol and cloud properties need to be measured to understand the differences ©2014. American Geophysical Union. All Rights Reserved."
"56151374100;56227666500;7006954443;7403441497;7404614089;7006393267;","Cloud mask over snow-/ice-covered areas for the GCOM-C1/SGLI cryosphere mission: Validations over Greenland",2014,"10.1002/2014JD022017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913573217&doi=10.1002%2f2014JD022017&partnerID=40&md5=735b51a2c9073411780118173696b579","Cloud detection is a critically important first step required to derive many satellite data products. A novel cloud detection algorithm designed for the cryosphere mission of Global Climate Observation Mission First Climate satellite/Second Generation Global Imager (GCOM-C1/SGLI) is presented. This reflectance-based cloud detection scheme mainly utilizes only two short wavelength infrared channels with dynamic thresholds that depend on Sun-satellite viewing geometry to perform accurate cloud detection over snow/ice surfaces in high latitude as well as high-elevation regions. Profiles of atmospheric absorbing and scattering molecules as well as surface elevation are considered in the determination of the thresholds for the resulting snow/ice cloud mask (SCM) algorithm. Image-based tests and statistical results have been used to validate the performance of the SCM over the Greenland plateau. Statistics using collocated Cloud-Aerosol Lidar with Orthogonal Polarization and Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua observations over Greenland in 2007 show that over snow/ice surfaces the performance of the SCM is generally better than that of the MODIS cloud mask. © 2014. American Geophysical Union. All Rights Reserved."
"57212988186;7401945370;","Intermodel variances of subtropical stratocumulus environments simulated in CMIP5 models",2014,"10.1002/2014GL061812","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912074677&doi=10.1002%2f2014GL061812&partnerID=40&md5=af769273fc3a6cbb29a7dd744d3b20a6","This paper investigates simulation biases associated with the large-scale environments of subtropical marine stratocumulus (Sc) in present climate simulations from the Coupled Model Intercomparison Project Phase 5 models. Comparison of eight major variables that strongly control the Sc clouds, including jumps of temperature and vapor across the inversion layer, indicates that these models all have similar shortcomings, such as overestimation of sensible and latent surface fluxes. The differences among the biases of these major variables between the Sc regions were also evaluated. Of all Sc regions, the Namibian Sc region showed the largest biases. The modeled simulation skill of the annual variation of low cloud cover (LCC) increases when the correlation coefficient between LCC and lower atmospheric stability is higher. This paper reemphasizes the importance, suggested in previous studies, of an improved relationship between lower tropospheric stability and LCC if we are to better predict annual variations in subtropical LCC. Key Points Detailed intermodel variability in marine stratocumulus environmentsHigh-geographical universality in skill of stratocumulus simulationImportant relationship between low cloud cover and stability of lower atmosphere ©2014. American Geophysical Union. All Rights Reserved."
"21735380100;6701820543;56219012200;35203929500;","Greenhouse gas profiling by infrared-laser and microwave occultation in cloudy air: Results from end-to-end simulations",2014,"10.1002/2014JD021938","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913558295&doi=10.1002%2f2014JD021938&partnerID=40&md5=6033ea49e1ad7695f2b8122cc858f9c4","The new mission concept of microwave and infrared-laser occultation between Low Earth Orbit satellites (LMIO) is capable to provide accurate, consistent, and long-term stable measurements of many essential climate variables. These include temperature, humidity, key greenhouse gases (GHGs) such as carbon dioxide and methane, and line of sight wind speed, all with focus on profiling the upper troposphere and lower stratosphere. The GHG retrieval performance from LMIO data was so far analyzed under clear-air conditions only, without clouds and scintillations from turbulence. Here we present and evaluate an algorithm, built into an already published clear-air algorithm, which copes with cloud and scintillation influences on the infrared-laser transmission profiles used for GHG retrieval. We find that very thin ice clouds fractionally extinct the infrared-laser signals, thicker but broken ice clouds block them over limited altitude ranges, and liquid water clouds generally block them so that their cloud top altitudes typically constitute the limit to tropospheric penetration of profiles. The advanced algorithm penetrates through broken cloudiness. It achieves this by producing a cloud flagging profile from cloud-perturbed infrared-laser signals, which then enables bridging of transmission profile gaps via interpolation. Evaluating the retrieval performance with quasi-realistic end-to-end simulations, including high-resolution cloud data and scintillations from turbulence, we find a small increase only of GHG retrieval RMS errors due to broken-cloud scenes and the profiles remain essentially unbiased as in clear air. These results are encouraging for future LMIO implementation, indicating that GHG profiles can be retrieved through broken cloudiness, maximizing upper troposphere coverage. © 2014. American Geophysical Union. All Rights Reserved."
"54946259400;7102317626;55355179800;7103100591;7101686436;7006823846;","Biological ice nucleation initiates hailstone formation",2014,"10.1002/2014JD022004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913529218&doi=10.1002%2f2014JD022004&partnerID=40&md5=2ea76ffd30fe57e10c3f606c18592d95","Cloud condensation and ice nuclei in the troposphere are required precursors to cloud and precipitation formation, both of which influence the radiative balance of Earth. The initial stage of hailstone formation (i.e., the embryo) and the subsequent layered growth allow hail to be used as a model for the study of nucleation processes in precipitation. By virtue of the preserved particle and isotopic record captured by hailstones, they represent a unique form of precipitation that allows direct characterization of the particles present during atmospheric ice nucleation. Despite the ecological and economic consequences of hail storms, the dynamics of hailstone nucleation, and thus their formation, are not well understood. Our experiments show that hailstone embryos from three Rocky Mountain storms contained biological ice nuclei capable of freezing water at warm, subzero (°C) temperatures, indicating that biological particles can act as nucleation sites for hailstone formation. These results are corroborated by analysis of δD and δ18 O from melted hailstone embryos, which show that the hailstones formed at similarly warm temperatures in situ. Low densities of ice nucleation active abiotic particles were also present in hailstone embryos, but their low concentration indicates they were not likely to have catalyzed ice formation at the warm temperatures determined from water stable isotope analysis. Our study provides new data on ice nucleation occurring at the bottom of clouds, an atmospheric region whose processes are critical to global climate models but which has challenged instrument-based measurements. © 2014. American Geophysical Union. All Rights Reserved."
"6506328135;34881780600;37099564300;36059595100;7402480218;57211676851;7403077486;","Evaluation of convection-permitting model simulations of cloud populations associated with the madden-julian oscillation using data collected during the AMIE/DYNAMO field campaign",2014,"10.1002/2014JD022143","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913534082&doi=10.1002%2f2014JD022143&partnerID=40&md5=a9a1a4bdda97a77e5221e57493d31d3c","Regional convection-permitting model simulations of cloud populations observed during the 2011 Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation Investigation Experiment/Dynamics of the Madden-Julian Oscillation Experiment (AMIE/DYNAMO) field campaign are evaluated against ground-based radar and ship-based observations. Sensitivity of model simulated reflectivity, surface rain rate, and cold pool statistics to variations of raindrop breakup/self-collection parameters in four state-of-the-art two-moment bulk microphysics schemes in the Weather Research and Forecasting (WRF) model is examined. The model simulations generally overestimate reflectivity from large and deep convective cells, and underestimate stratiform rain and the frequency of cold pools. In the sensitivity experiments, introduction of more aggressive raindrop breakup or decreasing the self-collection efficiency increases the cold pool occurrence frequency in all of the simulations, and slightly reduces the reflectivity and precipitation statistics bias in some schemes but has little effect on the overall mean surface precipitation. Both the radar observations and model simulations of cloud populations show an approximate power law relationship between convective echo-top height and equivalent convective cell radius. © 2014. American Geophysical Union. All Rights Reserved."
"24779089500;35595682100;8255698000;55605771904;","The roles of deep convection and extratropical mixing in the tropical tropopause layer: An in situ measurement perspective",2014,"10.1002/2014JD022157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913580581&doi=10.1002%2f2014JD022157&partnerID=40&md5=71a8a03aa76fbea3c1dc9b9b121d07e2","The majority of air which enters the stratosphere passes through the tropical tropopause layer (TTL), where the temperature profile and amount of deep convection set the entry level for stratospheric water vapor. We use simultaneous in situ measurements of ozone, carbon monoxide, carbon dioxide, water vapor, and heavy water vapor (HDO) from the 2006 Costa Rica Aura Validation Experiment and 2007 Tropical Composition, Cloud, and Climate Coupling campaigns in a one-dimensional mixing model to investigate how different transport pathways in the TTL impact the amount of water vapor which enters the stratosphere. We focused on four main pathways: (1) slow upward ascent, (2) isentropic transport from the midlatitude lowermost stratosphere, (3) convective injection, and (4) descent within the TTL coupled to convection. Each pathway brings air into the TTL with a specific chemical signature, such that anomalies in simultaneously measured tracer concentrations can be used to identify the source of the air mass. We found that isentropic transport from the midlatitude lowermost stratosphere accounted for 20–60% of the air in the lower TTL and 20–40% of air above the tropopause, bringing elevated ozone concentrations which radiatively warm the TTL, impacting the amount of dehydration which takes place. Convective input accounted for on average ~30% of the air measured below 370 K potential temperature, and ~10% of air above the tropopause in both summer and winter, increasing water vapor concentrations above the tropopause by 0.3 ppmv on average and by up to 1.6 ppmv in some air masses. © 2014. American Geophysical Union. All Rights Reserved."
"35114996800;36486362800;23481991200;","A comparison of solar radiative flux above clouds from MODIS with BALTIMOS regional climate model simulations",2014,"10.1007/s00704-010-0253-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911991234&doi=10.1007%2fs00704-010-0253-3&partnerID=40&md5=a017968d57af87680d96c40c0b7ddd5c","A comparison study for the solar radiative flux above clouds is presented between the regional climate model system BALTEX integrated model system (BALTIMOS) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. For MODIS, an algorithm has been developed to retrieve reflected shortwave fluxes over clouds. The study area is the Baltic Sea catchment area during an 11-month period from February to December 2002. The intercomparison focuses on the variations of the daily and seasonal cycle and the spatial distributions. We found good agreement between the observed and the simulated data with a bias of the temporal mean of 13.6 W/m2 and a bias of the spatial mean of 35.5 W/m2. For summer months, BALTIMOS overestimates the solar flux with up to 90 W/m2 (20%). This might be explained by the insufficient representation of cirrus clouds in the regional climate model. © 2010, The Author(s)."
"7003848718;6508240165;57184817500;","The atmospheric boundary layer structure over the open and ice-covered Baltic Sea: In situ measurements compared to simulations with the regional model REMO",2014,"10.1007/s00704-009-0177-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911990479&doi=10.1007%2fs00704-009-0177-y&partnerID=40&md5=c269bab414904e0442a06fa17438558b","The regional model REMO, which is the atmospheric component of the coupled atmosphere–ice–ocean–land climate model system BALTIMOS, is tested with respect to its ability to simulate the atmospheric boundary layer over the open and ice-covered Baltic Sea. REMO simulations are compared to ship, radiosonde, and aircraft observations taken during eight field experiments. The main results of the comparisons are: (1) The sharpness and strength of the temperature inversion are underestimated by REMO. Over open water, this is connected with an overestimation of cloud coverage and moisture content above the inversion. (2) The vertical temperature stratification in the lowest 200 m over sea ice is too stable. (3) The horizontal inhomogeneity of sea ice concentration as observed by aircraft could not be properly represented by the prescribed ice concentration in REMO; large differences in the surface heat fluxes arise especially under cold-air advection conditions. The results of the comparisons suggest a reconsideration of the parameterization of subgrid-scale vertical exchange both under unstable und stable conditions. © 2009, Springer-Verlag."
"55915206300;23481991200;55637266800;","A comparison of the BALTIMOS coupled climate model with atmospheric and sea surface parameters derived from AMSR-E",2014,"10.1007/s00704-009-0178-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911988658&doi=10.1007%2fs00704-009-0178-x&partnerID=40&md5=30b847ba23430f5e8af1f0d32e06423f","The BALTEX Integrated Model System (BALTIMOS) coupled atmosphere ocean model was compared to passive microwave observations of the Advanced Microwave Scanning Radiometer (AMSR-E). Emphasis was put on quantifying the uncertainties associated with the different variables based on data screening both in the model and observations. Monthly means of three atmospheric parameters, as well as sea surface temperature, were compared for a period of 1 year. Sea ice extent was also derived from AMSR-E and compared to the model data on a daily basis. It is shown that the accuracy of the comparisons on a monthly mean basis is limited by precipitation screening. Out of the three atmospheric parameters, surface wind speed and water vapor column amount agree with the model data to within the accuracy of the comparison. The vertically integrated cloud liquid water content diagnosed from BALTIMOS is systematically higher than the liquid water content derived from satellite, even if potential systematic errors are accounted for. In terms of coupling, the two most relevant variables discussed are sea surface temperature and sea ice extent. The temporal extent of sea ice in the investigation area is well represented, as are the periods of the main growing and decay periods. The total sea ice cover appears to be underestimated by BALTIMOS, especially in the peak season between January and the beginning of March. The amplitude of the annual cycle of sea surface temperature in BALTIMOS appears to be too weak compared to the observations, leading to too cold sea surface temperatures in summer and too warm sea surface temperatures in winter. This might also partially explain the underestimation of sea ice cover by BALTIMOS. © 2009, Springer-Verlag."
"23095483400;57203053317;24398842400;16401192300;","Impact of the representation of marine stratocumulus clouds on the anthropogenic aerosol effect",2014,"10.5194/acp-14-11997-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911392721&doi=10.5194%2facp-14-11997-2014&partnerID=40&md5=fed9120d0b2d53ddf9327a1fcf70747b","Stratocumulus clouds are important for climate as they reflect large amounts of solar radiation back into space. However they are difficult to simulate in global climate models because they form under a sharp inversion and are thin. A comparison of model simulations with the ECHAM6-HAM2 global aerosol climate model to observations, reanalysis and literature data revealed too strong turbulent mixing at the top of stratocumulus clouds and a lack of vertical resolution. Further reasons for cloud biases in stratocumulus regions are the too ""active"" shallow convection scheme, the cloud cover scheme and possibly too low subsidence rates. To address some of these issues and improve the representation of stratocumulus clouds, we made three distinct changes to ECHAM6-HAM2. With a ""sharp"" stability function in the turbulent mixing scheme we have observed, similar to previous studies, increases in stratocumulus cloud cover and liquid water path. With an increased vertical resolution in the lower troposphere in ECHAM6-HAM2 the stratocumulus clouds form higher up in the atmosphere and their vertical extent agrees better with reanalysis data. The recently implemented in-cloud aerosol processing in stratiform clouds is used to improve the aerosol representation in the model. Including the improvements also affects the anthropogenic aerosol effect. In-cloud aerosol processing in ECHAM6-HAM2 leads to a decrease in the anthropogenic aerosol effect in the global annual mean from -1.19 Wm-2 in the reference simulation to -1.08 Wm-2, while using a ""sharp"" stability function leads to an increase to -1.34 Wm-2. The results from the simulations with increased vertical resolution are diverse but increase the anthropogenic aerosol effect to -2.08 Wm-2 at 47 levels and -2.30 Wm-2 at 95 levels. © Author(s) 2014. CC Attribution 3.0 License."
"24450860900;7003591311;","On the relationship between responses in cloud water and precipitation to changes in aerosol",2014,"10.5194/acp-14-11817-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961291304&doi=10.5194%2facp-14-11817-2014&partnerID=40&md5=e64f2c86adab0e6597bbbbfe1f376fe9","Climate models continue to exhibit strong sensitivity to the representation of aerosol effects on cloud reflectance and cloud amount. This paper evaluates a proposed method to constrain modeled cloud liquid water path (LWP) adjustments in response to changes in aerosol concentration Na using observations of precipitation susceptibility. Recent climate modeling has suggested a linear relationship between relative LWP responses to relative changes in Na, i.e., dlnLWP/dln Na, and the precipitation frequency susceptibility Spop, which is defined as the relative change in the probability of precipitation for a relative change in Na. Using large-eddy simulations (LES) of marine stratocumulus and trade wind cumulus clouds, we show that these two cloud regimes exhibit qualitatively different relationships between λ and Spop; in stratocumulus clouds, λ increases with Spop, while in trade wind cumulus, λ decreases with Spop. The LES-derived relationship for marine stratocumulus is qualitatively similar but quantitatively different than that derived from climate model simulations of oceanic clouds aggregated over much larger spatial scales. We explore possible reasons for variability in these relationships, including the selected precipitation threshold and the various definitions of precipitation susceptibility that are currently in use. Because aerosol-cloud-precipitation interactions are inherently small-scale processes, we recommend that when deriving the relationship between λ and Spop, careful attention be given to the cloud regime, the scale, and the extent of aggregation of the model output or the observed data. © Author(s) 2014."
"56448637100;15519671300;9276570300;16028575500;7004047498;35461255500;7006712143;","Analysis of nucleation events in the European boundary layer using the regional aerosol-climate model REMO-HAM with a solar radiation-driven OH-proxy",2014,"10.5194/acp-14-11711-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911374974&doi=10.5194%2facp-14-11711-2014&partnerID=40&md5=3c0a5a7858f6dbfa372d0510340df4f1","This work describes improvements in the regional aerosol-climate model REMO-HAM in order to simulate more realistically the process of atmospheric new particle formation (NPF). A new scheme was implemented to simulate OH radical concentrations using a proxy approach based on observations and also accounting for the effects of clouds upon OH concentrations. Second, the nucleation rate calculation was modified to directly simulate the formation rates of 3 nm particles, which removes some unnecessary steps in the formation rate calculations used earlier in the model. Using the updated model version, NPF over Europe was simulated for the periods 2003-2004 and 2008-2009. The statistics of the simulated particle formation events were subsequently compared to observations from 13 ground-based measurement sites. The new model shows improved agreement with the observed NPF rates compared to former versions and can simulate the event statistics realistically for most parts of Europe."
"23052016900;7007078966;17345303300;55359575700;6506718302;8657171200;6504793116;56369730100;17341189400;23027982900;7006708207;7006960661;35459245100;","Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state",2014,"10.5194/acp-14-11731-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908667979&doi=10.5194%2facp-14-11731-2014&partnerID=40&md5=a40e7eb37b3c6c01f623098fb0bf4b6b","Recently developed parameterizations for the sea spray aerosol source flux, encapsulating wave state, and its organic fraction were incorporated into the aerosol-climate model ECHAM-HAMMOZ to investigate the direct and indirect radiative effects of sea spray aerosol particles. Our simulated global sea salt emission of 805 Tg yr-1 (uncertainty range 378-1233 Tg yr-1) was much lower than typically found in previous studies. Modelled sea salt and sodium ion concentrations agreed relatively well with measurements in the smaller size ranges at Mace Head (annual normalized mean model bias -13% for particles with vacuum aerodynamic diameter Dva &lt; 1 μm), Point Reyes (-29% for particles with aerodynamic diameter Da &lt; 2.5 μm) and Amsterdam Island (-52% for particles with Da &lt; 1 μm) but the larger sizes were overestimated (899% for particles with 2.5 μm &lt; Da &lt; 10 μm) at Amsterdam Island. This suggests that at least the high end of the previous estimates of sea spray mass emissions is unrealistic. On the other hand, the model clearly underestimated the observed concentrations of organic or total carbonaceous aerosol at Mace Head (-82%) and Amsterdam Island (-68%). The large overestimation (212%) of organic matter at Point Reyes was due to the contribution of continental sources. At the remote Amsterdam Island site, the organic concentration was underestimated especially in the biologically active months, suggesting a need to improve the parameterization of the organic sea spray fraction. Globally, the satellite-retrieved AOD over the oceans, using PARASOL data, was underestimated by the model (means over ocean 0.16 and 0.10, respectively); however, in the pristine region around Amsterdam Island the measured AOD fell well within the simulated uncertainty range. The simulated sea spray aerosol contribution to the indirect radiative effect was positive (0.3 W m-2), in contrast to previous studies. This positive effect was ascribed to the tendency of sea salt aerosol to suppress both the in-cloud supersaturation and the formation of cloud condensation nuclei from sulfate. These effects can be accounted for only in models with sufficiently detailed aerosol microphysics and physics-based parameterizations of cloud activation. However, due to a strong negative direct effect, the simulated effective radiative forcing (total radiative) effect was -0.2 W m-2. The simulated radiative effects of the primary marine organic emissions were small, with a direct effect of 0.03 W m-2 and an indirect effect of -0.07 W m-2."
"24376166200;55806758800;55547129338;","Role of snow-albedo feedback in higher elevation warming over the Himalayas, Tibetan Plateau and Central Asia",2014,"10.1088/1748-9326/9/11/114008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928957126&doi=10.1088%2f1748-9326%2f9%2f11%2f114008&partnerID=40&md5=4e01682337719c99a48d8e217fdff77c","Recent literature has shown that surface air temperature (SAT) in many high elevation regions, including the Tibetan Plateau (TP) has been increasing at a faster rate than at their lower elevation counterparts. We investigate projected future changes in SAT in the TP and the surrounding high elevation regions (between 25°-45°N and 50°-120°E) and the potential role snow-albedo feedback may have on amplified warming there. We use the Community Climate System Model version 4 (CCSM4) and Geophysical Fluid Dynamics Laboratory (GFDL) model which have different spatial resolutions as well as different climate sensitivities. We find that surface albedo (SA) decreases more at higher elevations than at lower elevations owing to the retreat of the 0 °C isotherm and the associated retreat of the snow line. Both models clearly show amplified warming over Central Asian mountains, the Himalayas, the Karakoram and Pamir during spring. Our results suggest that the decrease of SA and the associated increase in absorbed solar radiation (ASR) owing to the loss of snowpack play a significant role in triggering the warming over the same regions. Decreasing cloud cover in spring also contributes to an increase in ASR over some of these regions in CCSM4. Although the increase in SAT and the decrease in SA are greater in GFDL than CCSM4, the sensitivity of SAT to changes in SA is the same at the highest elevations for both models during spring; this suggests that the climate sensitivity between models may differ, in part, owing to their corresponding treatments of snow cover, snow melt and the associated snow/albedo feedback. © 2014 IOP Publishing Ltd."
"56080932300;42661306000;12041200900;12040992000;55352089200;8609238900;7102780088;","Assessing the Current Evolution of the Greenland Ice Sheet by Means of Satellite and Ground-Based Observations",2014,"10.1007/s10712-014-9287-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927123656&doi=10.1007%2fs10712-014-9287-x&partnerID=40&md5=c9c20988a5596b68014176e9e3bd277d","The present study utilises different satellite and ground-based geodetic observations in order to assess the current evolution of the Greenland Ice Sheet (GIS). Satellite gravimetry data acquired by the Gravity Recovery and Climate Experiment are used to derive ice-mass changes for the period from 2003 to 2012. The inferred time series are investigated regarding long-term, seasonal and interannual variations. Laser altimetry data acquired by the Ice, Cloud, and land Elevation Satellite (ICESat) are utilised to solve for linear and seasonal changes in the ice-surface height and to infer independent mass-change estimates for the entire GIS and its major drainage basins. We demonstrate that common signals can be identified in the results of both sensors. Moreover, the analysis of a Global Positioning System (GPS) campaign network in West Greenland for the period 1995–2007 allows us to derive crustal deformation caused by glacial isostatic adjustment (GIA) and by present-day ice-mass changes. ICESat-derived elastic crustal deformations are evaluated comparing them with GPS-observed uplift rates which were corrected for the GIA effect inferred by model predictions. Existing differences can be related to the limited resolution of ICESat. Such differences are mostly evident in dynamical regions such as the Disko Bay region including the rapidly changing Jakobshavn Isbræ, which is investigated in more detail. Glacier flow velocities are inferred from satellite imagery yielding an accelerated flow from 1999 to 2012. Since our GPS observations cover a period of more than a decade, changes in the vertical uplift rates can also be investigated. It turns out that the increased mass loss of the glacier is also reflected by an accelerated vertical uplift. © 2014, Springer Science+Business Media Dordrecht."
"56080932300;42661306000;55352089200;25626008100;56591911900;6507664989;54407975900;55220226400;6602546962;7003895114;55903760300;7102780088;","Mass, Volume and Velocity of the Antarctic Ice Sheet: Present-Day Changes and Error Effects",2014,"10.1007/s10712-014-9286-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927123280&doi=10.1007%2fs10712-014-9286-y&partnerID=40&md5=0f3441838afc098b51ea0bd92c0f1796","This study examines present-day changes of the Antarctic ice sheet (AIS) by means of different data sets. We make use of monthly gravity field solutions acquired by the Gravity Recovery and Climate Experiment (GRACE) to study mass changes of the AIS for a 10-year period. In addition to ‘standard’ solutions of release 05, solutions based on radial base functions were used. Both solutions reveal an increased mass loss in recent years. For a 6-year period surface-height changes were inferred from laser altimetry data provided by the Ice, Cloud, and land Elevation Satellite (ICESat). The basin-scale volume trends were converted into mass changes and were compared with the GRACE estimates for the same period. Focussing on the Thwaites Glacier, Landsat optical imagery was utilised to determine ice-flow velocities for a period of more than two decades. This data set was extended by means of high-resolution synthetic aperture radar (SAR) data from the TerraSAR-X mission, revealing an accelerated ice flow of all parts of the glacier. ICESat data over the Thwaites Glacier were complemented by digital elevation models inferred from TanDEM-X data. This extended data set exhibits an increased surface lowering in recent times. Passive microwave remote sensing data prove the long-term stability of the accumulation rates in a low accumulation zone in East Antarctica over several decades. Finally, we discuss the main error sources of present-day mass-balance estimates: the glacial isostatic adjustment effect for GRACE as well as the biases between laser operational periods and the volume–mass conversion for ICESat. © 2014, Springer Science+Business Media Dordrecht."
"56246458800;6602516156;8378887500;36515307600;7005941217;55480930900;35490380800;6507256381;24587715900;8256598400;6603293852;56273253000;","Denitrification by large NAT particles: The impact of reduced settling velocities and hints on particle characteristics",2014,"10.5194/acp-14-11525-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908018868&doi=10.5194%2facp-14-11525-2014&partnerID=40&md5=eb8227b88858be6c763ee6218f0378a2","Vertical redistribution of HNO3 through large HNO3-containing particles associated with polar stratospheric clouds (PSCs) plays an important role in the chemistry of the Arctic winter stratosphere. During the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) campaign, apparently very large NAT (nitric acid trihydrate) particles were observed by the airborne in situ probe FSSP-100 (Molleker et al., 2014). Our analysis shows that the FSSP-100 observations associated with the flight on 25 January 2010 cannot easily be explained assuming compact spherical NAT particles due to much too short growing time at temperatures below the existence temperature of NAT (<i>T</i>NAT). State-of-the-art simulations using CLaMS (Chemical Lagrangian Model of the Stratosphere; Grooß et al., 2014) suggest considerably smaller particles. We consider the hypothesis that the simulation reproduces the NAT particle masses in a realistic way, but that real NAT particles may have larger apparent sizes compared to compact spherical particles, e.g. due to non-compact morphology or aspheric shape. Our study focuses on the consequence that such particles would have reduced settling velocities compared to compact spheres, altering the vertical redistribution of HNO3. Utilising CLaMS simulations, we investigate the impact of reduced settling velocities of NAT particles on vertical HNO3 redistribution and compare the results with observations of gas-phase HNO3 by the airborne Fourier transform spectrometer MIPAS-STR associated with two RECONCILE flights. The MIPAS-STR observations confirm conditions consistent with denitrification by NAT particles for the flight on 25 January 2010 and show good agreement with the simulations within the limitations of the comparison. Best agreement is found if settling velocities between 100 and 50% relative to compact spherical particles are considered (slight preference for the 70% scenario). In contrast, relative settling velocities of 30% result in too weak vertical HNO3 redistribution. Sensitivity simulations considering temperature biases of ±1 K and multiplying the simulated nucleation rates by factors of 0.5 and 2.0 affect the comparisons to a similar extent, but result in no effective improvement compared to the reference scenario. Our results show that an accurate knowledge of the settling velocities of NAT particles is important for quantitative simulations of vertical HNO3 redistribution. © 2014 Author(s)."
"54783792600;57217772325;56978385600;7410041005;","Spatial scales of altocumulus clouds observed with collocated CALIPSO and CloudSat measurements",2014,"10.1016/j.atmosres.2014.05.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902459340&doi=10.1016%2fj.atmosres.2014.05.023&partnerID=40&md5=f303c965524f58aa5ea0aa626e46b68d","Altocumulus (Ac) clouds are important, yet climate models have difficulties in simulating and predicting these clouds, due to their small horizontal scales and thin vertical extensions. In this research, 4. years of collocated Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar and CloudSat radar measurements is analyzed to study the along-track horizontal scales and vertical depths of Ac clouds. Methodology to calculate Ac along-track horizontal scale and vertical depth using collocated CALIPSO and CloudSat measurements is introduced firstly. The global mean Ac along-track horizontal scale is 40.2. km, with a standard deviation of 52.3. km. Approximately 93.6% of Ac cannot be resolved by climate models with a grid resolution of 1°. The global mean mixed-phase Ac vertical depth is 1.96. km, with a standard deviation of 1.10. km. Global distributions of the Ac along-track horizontal scales and vertical depths are presented and possible factors contributing to their geographical differences are analyzed. The result from this study can be used to improve Ac parameterizations in climate models and validate the model simulations. © 2014."
"6507761647;9640480500;6602463657;6602841758;24399292500;55188724900;57210628914;56421979300;6506718750;36614659600;56421758700;6701709684;27868213600;53881216100;7201710877;","Mapping atmospheric aerosols with a citizen science network of smartphone spectropolarimeters",2014,"10.1002/2014GL061462","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911453217&doi=10.1002%2f2014GL061462&partnerID=40&md5=fed0701af7e6b16bec57682a3269f967","To assess the impact of atmospheric aerosols on health, climate, and air traffic, aerosol properties must be measured with fine spatial and temporal sampling. This can be achieved by actively involving citizens and the technology they own to form an atmospheric measurement network. We establish this new measurement strategy by developing and deploying iSPEX, a low-cost, mass-producible optical add-on for smartphones with a corresponding app. The aerosol optical thickness (AOT) maps derived from iSPEX spectropolarimetric measurements of the daytime cloud-free sky by thousands of citizen scientists throughout the Netherlands are in good agreement with the spatial AOT structure derived from satellite imagery and temporal AOT variations derived from ground-based precision photometry. These maps show structures at scales of kilometers that are typical for urban air pollution, indicating the potential of iSPEX to provide information about aerosol properties at locations and at times that are not covered by current monitoring efforts. Key Points The iSPEX add-on turns smartphones into aerosol measurement devicesThousands of iSPEX measurements across the Netherlands form AOT mapsThe iSPEX AOT data match MODIS and AERONET data and have 2 km resolution ©2014. The Authors."
"56188688000;7005830548;7005302245;7005751636;","Improving the representation of clouds, radiation, and precipitation using spectral nudging in the weather research and forecasting model",2014,"10.1002/2014JD022173","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214541&doi=10.1002%2f2014JD022173&partnerID=40&md5=625419784de7bbdd0344dbc888f6b0c0","Spectral nudging—a scale-selective interior constraint technique—is commonly used in regional climate models to maintain consistency with large-scale forcing while permitting mesoscale features to develop in the downscaled simulations. Several studies have demonstrated that spectral nudging improves the representation of regional climate in reanalysis-forced simulations compared with not using nudging in the interior of the domain. However, in the Weather Research and Forecasting (WRF) model, spectral nudging tends to produce degraded precipitation simulations when compared to analysis nudging—an interior constraint technique that is scale indiscriminate but also operates on moisture fields which until now could not be altered directly by spectral nudging. Since analysis nudging is less desirable for regional climate modeling because it dampens fine-scale variability, changes are proposed to the spectral nudging methodology to capitalize on differences between the nudging techniques and aim to improve the representation of clouds, radiation, and precipitation without compromising other fields. These changes include adding spectral nudging toward moisture, limiting nudging to below the tropopause, and increasing the nudging time scale for potential temperature, all of which collectively improve the representation of mean and extreme precipitation, 2 m temperature, clouds, and radiation, as demonstrated using a model-simulated 20 year historical period. Such improvements to WRF may increase the fidelity of regional climate data used to assess the potential impacts of climate change on human health and the environment and aid in climate change mitigation and adaptation studies. ©2014. American Geophysical Union. All Rights Reserved."
"26647270000;7202967741;36559769700;26653350000;57193840197;7801595201;7202252296;56227525700;13406672500;7006978226;","Source-diagnostic dual-isotope composition and optical properties of water-soluble organic carbon and elemental carbon in the South Asian outflow intercepted over the Indian Ocean",2014,"10.1002/2014JD022127","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018215065&doi=10.1002%2f2014JD022127&partnerID=40&md5=7786de3ff109c9224b5293ebe4cfb5eb","The dual carbon isotope signatures and optical properties of carbonaceous aerosols have been investigated simultaneously for the first time in the South Asian outflow during an intensive campaign at the Maldives Climate Observatory on Hanimaadhoo (MCOH) (February and March 2012). As one component of the Cloud Aerosol Radiative Forcing Dynamics Experiment, this paper reports on the sources and the atmospheric processing of elemental carbon (EC) and water-soluble organic carbon (WSOC) as examined by a dual carbon isotope approach. The radiocarbon (Δ14C) data show that WSOC has a significantly higher biomass/biogenic contribution (86 ± 5%) compared to EC (59 ± 4%). The more13C-enriched signature of MCOH-WSOC (20.8 ± 0.7‰) compared to MCOH-EC (25.8 ± 0.3‰) and megacity Delhi WSOC (24.1 ± 0.9‰) suggests that WSOC is significantly more affected by aging during long-range transport than EC. The δ13 C-Δ14 C signal suggests that the wintertime WSOC intercepted over the Indian Ocean largely represents aged primary biomass burning aerosols. Since light-absorbing organic carbon aerosols (Brown Carbon (BrC)) have recently been identified as potential contributors to positive radiative forcing, optical properties of WSOC were also investigated. The mass absorption cross section of WSOC (MAC365) was 0.5 ± 0.2 m2 g1 which is lower than what has been observed at near-source sites, indicating a net decrease of WSOC light-absorption character during long-range transport. Near-surface WSOC at MCOH accounted for ~1% of the total direct solar absorbance relative to EC, which is lower than the BrC absorption inferred from solar spectral observations of ambient aerosols, suggesting that a significant portion of BrC might be included in the water-insoluble portion of organic aerosols. ©2014. American Geophysical Union. All Rights Reserved."
"7405728922;7202180152;6701497749;36932594300;6603262263;6701562113;55476830600;55717074000;","Aerosol indirect effect on the grid-scale clouds in the two-way coupled WRF-CMAQ: Model description, development, evaluation and regional analysis",2014,"10.5194/acp-14-11247-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908410171&doi=10.5194%2facp-14-11247-2014&partnerID=40&md5=c0f357a4b6dcf716ac04683bc90dbae3","This study implemented first, second and glaciation aerosol indirect effects (AIE) on resolved clouds in the two-way coupled Weather Research and Forecasting Community Multiscale Air Quality (WRF-CMAQ) modeling system by including parameterizations for both cloud drop and ice number concentrations on the basis of CMAQpredicted aerosol distributions and WRF meteorological conditions. The performance of the newly developed WRF- CMAQ model, with alternate Community Atmospheric Model (CAM) and Rapid Radiative Transfer Model for GCMs (RRTMG) radiation schemes, was evaluated with observations from the Clouds and the See http://ceres.larc. nasa.gov/. Earth's Radiant Energy System (CERES) satellite and surface monitoring networks (AQS, IMPROVE, CASTNET, STN, and PRISM) over the continental US (CONUS) (12 km resolution) and eastern Texas (4 km resolution) during August and September of 2006. The results at the Air Quality System (AQS) surface sites show that in August, the normalized mean bias (NMB) values for PM2.5 over the eastern US (EUS) and the western US (WUS) are 5.3% (-0.1 %) and 0.4% (-5.2 %) for WRF-CMAQ/CAM (WRF-CMAQ/RRTMG), respectively. The evaluation of PM2.5 chemical composition reveals that in August, WRF-CMAQ/CAM (WRF-CMAQ/RRTMG) consistently underestimated the observed SO2-4 by -23.0% (-27.7 %), -12.5% (-18.9 %) and -7.9% (-14.8 %) over the EUS at the Clean Air Status Trends Network (CASTNET), Interagency Monitoring of Protected Visual Environments (IMPROVE) and Speciated Trends Network (STN) sites, respectively. Both configurations (WRF-CMAQ/CAM, WRF-CMAQ/RRTMG) overestimated the observed mean organic carbon (OC), elemental carbon (EC) and and total carbon (TC) concentrations over the EUS in August at the IMPROVE sites. Both configurations generally underestimated the cloud field (shortwave cloud forcing, SWCF) over the CONUS in August due to the fact that the AIE on the subgrid convective clouds was not considered when the model simulations were run at the 12 km resolution. This is in agreement with the fact that both configurations captured SWCF and longwave cloud forcing (LWCF) very well for the 4 km simulation over eastern Texas, when all clouds were resolved by the finer resolution domain. The simulations of WRF-CMAQ/CAM and WRF-CMAQ/RRTMG show dramatic improvements for SWCF, LWCF, cloud optical depth (COD), cloud fractions and precipitation over the ocean relative to those of WRF default cases in August. The model performance in September is similar to that in August, except for a greater overestimation of PM2.5 due to the overestimations of SO2-4 , NH+4 , NO-3 , and TC over the EUS, less underestimation of clouds (SWCF) over the land areas due to the lower SWCF values, and fewer convective clouds in September. This work shows that inclusion of indirect aerosol effect treatments in WRF-CMAQ represents a significant advancement and milestone in air quality modeling and the development of integrated emissions control strategies for air quality management and climate change mitigation. © 2014 Author(s)."
"55332412000;35285676700;7410177774;36661206400;16480175700;49662076300;26022467200;6701775319;10640192200;15922221400;","Modeling ultrafine particle growth at a pine forest site influenced by anthropogenic pollution during BEACHON-RoMBAS 2011",2014,"10.5194/acp-14-11011-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903301083&doi=10.5194%2facp-14-11011-2014&partnerID=40&md5=90b447842a587b39f7a1bff392e9d70c","Formation and growth of ultrafine particles is crudely represented in chemistry-climate models, contributing to uncertainties in aerosol composition, size distribution, and aerosol effects on cloud condensation nuclei (CCN) concentrations. Measurements of ultrafine particles, their precursor gases, and meteorological parameters were performed in a ponderosa pine forest in the Colorado Front Range in July-August 2011, and were analyzed to study processes leading to small particle burst events (PBEs) which were characterized by an increase in the number concentrations of ultrafine 4-30 nm diameter size particles. These measurements suggest that PBEs were associated with the arrival at the site of anthropogenic pollution plumes midday to early afternoon. During PBEs, number concentrations of 4-30 nm diameter particles typically exceeded 104 cm3, and these elevated concentrations coincided with increased SO2 and monoterpene concentrations, and led to a factor-of-2 increase in CCN concentrations at 0.5% supersaturation. The PBEs were simulated using the regional WRF-Chem model, which was extended to account for ultrafine particle sizes starting at 1 nm in diameter, to include an empirical activation nucleation scheme in the planetary boundary layer, and to explicitly simulate the subsequent growth of Aitken particles (10-100 nm) by condensation of organic and inorganic vapors. The updated model reasonably captured measured aerosol number concentrations and size distribution during PBEs, as well as ground-level CCN concentrations. Model results suggest that sulfuric acid originating from anthropogenic SO2 triggered PBEs, and that the condensation of monoterpene oxidation products onto freshly nucleated particles contributes to their growth. The simulated growth rate of ∼ 3.4 nm h1 for 4-40 nm diameter particles was comparable to the measured average value of 2.3 nm h1. Results also suggest that the presence of PBEs tends to modify the composition of sub-20 nm diameter particles, leading to a higher mass fraction of sulfate aerosols. Sensitivity simulations suggest that the representation of nucleation processes in the model largely influences the predicted number concentrations and thus CCN concentrations. We estimate that nucleation contributes 67% of surface CCN at 0.5% supersaturation in this pine forest environment. © 2014 Author(s)."
"35069282600;8067118800;56418532300;7202899330;","Ship track observations of a reduced shortwave aerosol indirect effect in mixed-phase clouds",2014,"10.1002/2014GL061320","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911426422&doi=10.1002%2f2014GL061320&partnerID=40&md5=8b6824ac42c69b4b411b37c435ca994e","Aerosol influences on clouds are a major source of uncertainty to our understanding of forced climate change. Increased aerosol can enhance solar reflection from clouds countering greenhouse gas warming. Recently, this indirect effect has been extended from water droplet clouds to other types including mixed-phase clouds. Aerosol effects on mixed-phase clouds are important because of their fundamental role on sea ice loss and polar climate change, but very little is known about aerosol effects on these clouds. Here we provide the first analysis of the effects of aerosol emitted from ship stacks into mixed-phase clouds. Satellite observations of solar reflection in numerous ship tracks reveal that cloud albedo increases 5 times more in liquid clouds when polluted and persist 2 h longer than in mixed-phase clouds. These results suggest that seeding mixed-phase clouds via shipping aerosol is unlikely to provide any significant counterbalancing solar radiative cooling effects in warming polar regions. Key Points Ship tracks discovered in ice clouds reveal a reduced aerosol indirect effectShip emissions enhance ice production in low-level clouds ©2014. American Geophysical Union. All Rights Reserved."
"12040335900;36015299300;24597299800;8906055900;56662561200;7404653593;","Connecting early summer cloud-controlled sunlight and late summer sea ice in the arctic",2014,"10.1002/2014JD022013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945282365&doi=10.1002%2f2014JD022013&partnerID=40&md5=d028959f8bb5b3a8ef3fa10381d0296f","This study demonstrates that absorbed solar radiation (ASR) at the top of the atmosphere in early summer (May–July) plays a precursory role in determining the Arctic sea ice concentration (SIC) in late summer (August–October). The monthly ASR anomalies are obtained over the Arctic Ocean (65°N–90°N) from the Clouds and the Earth’s Radiant Energy System during 2000–2013. The ASR changes primarily with cloud variation. We found that the ASR anomaly in early summer is significantly correlated with the SIC anomaly in late summer (correlation coefficient, r ≈ 0.8 with a lag of 1 to 4 months). The region exhibiting high (low) ASR anomalies and low (high) SIC anomalies varies yearly. The possible reason is that the solar heat input to ice is most effectively affected by the cloud shielding effect under the maximum TOA solar radiation in June and amplified by the ice-albedo feedback. This intimate delayed ASR-SIC relationship is not represented in most of current climate models. Rather, the models tend to over-emphasize internal sea ice processes in summer. © 2014. American Geophysical Union. All Rights Reserved."
"9249239700;36150977900;7003278104;16507851200;6603126554;15726427000;7005528388;","Characterizing tropical pacific water vapor and radiative biases in CMIP5 GCMs: Observation-based analyses and a snow and radiation interaction sensitivity experiment",2014,"10.1002/2014JD021924","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945303496&doi=10.1002%2f2014JD021924&partnerID=40&md5=2c018687b42d04f407db26a934985177","Significant systematic biases in the moisture fields within the tropical Pacific trade wind regions are found in the Coupled Model Intercomparison Project (CMIP3/CMIP5) against profile and total column water vapor (TotWV) estimates from the Atmospheric Infrared Sounder and TotWV from the Special Sensor Microwave/Imager. Positive moisture biases occur in conjunction with significant biases of eastward low-level moisture convergence north of the South Pacific Convergence Zone and south of the Intertropical Convergence Zone—the V-shaped regions. The excessive moisture there is associated with overestimates of reflected upward shortwave (RSUT), underestimates of outgoing longwave radiation (RLUT) at the top of atmosphere (TOA), and underestimates of downward shortwave flux at the surface (RSDS) compared to Clouds and the Earth’s Energy System, Energy Balance and Filled data. We characterize the impacts of falling snow and its radiation interaction, which are not included in most CMIP5 models, on the moisture fields using the National Center for Atmospheric Research-coupled global climate model (GCM). A number of differences in the model simulation without snow-radiation interactions are consistent with biases in the CMIP5 simulations. These include effective low-level eastward/southeastward wind and surface wind stress anomalies, and an increase in TotWV, vertical profile of moisture, and cloud amounts in the V-shaped region. The anomalous water vapor and cloud amount might be associated with the model increase of RSUT and decrease of RLUT at TOA and decreased RSDS in clear and all sky in these regions. These findings hint at the importance of water vapor-radiation interactions in the CMIPS/CMIP5 model simulations that exclude the radiative effect of snow. © 2014. American Geophysical Union. All Rights Reserved."
"55245030000;7102604282;","Aircraft soot indirect effect on large-scale cirrus clouds: Is the indirect forcing by aircraft soot positive or negative?",2014,"10.1002/2014JD021914","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943752866&doi=10.1002%2f2014JD021914&partnerID=40&md5=3eafd32fce4df39f3dc8fea6c627b74a","The indirect effect of aircraft soot on cirrus clouds is subject to large uncertainties due to uncertainty in the effectiveness of aircraft soot acting as heterogeneous ice nuclei (IN) and the complexity caused by background ice nucleation, which introduces two major competing ice nucleation mechanisms: homogeneous freezing that generally produces more abundant ice particles and heterogeneous nucleation that generally produces fewer ice particles. In this paper, we used the coupled Community Atmosphere Model version 5.2 (CAM5)/IMPACT model to estimate the climate impacts of aircraft soot acting as IN in large-scale cirrus clouds. We assume that only the aircraft soot particles that are preactivated in persistent contrail cirrus clouds are efficient IN. Further, we assume that these particles lose their ability to act as efficient IN when they become coated with three monolayers of sulfate. We varied the background number concentration of sulfate aerosols allowed to act as homogeneous ice nucleation sites as well as the dust concentrations that act as heterogeneous ice nuclei to examine the sensitivity of the forcing by aircraft soot to the background atmosphere. The global average effect can range from a high negative (cooling) rate, 0.35 W m−2, for the high sulfate/low dust case to a positive (warming) rate, +0.09 W m−2, for the low sulfate/low dust case (default CAM5 setup) when approximately 0.6% of total aviation soot acts as IN. The net negative forcing is caused by the addition of IN to a background atmosphere that is dominated by homogeneous nucleation (mainly in the tropic Indian Ocean, Central America, and North Atlantic Ocean). The forcings can be all positive, about +0.11 to +0.21 W m−2, when the background atmosphere is dominated by pure heterogeneous ice nucleation. © 2014. American Geophysical Union. All Rights Reserved."
"36515307600;7005941217;56187256200;7202607188;35490380800;54393349200;57189215242;55857180100;7005433221;57204302411;56246458800;8378887500;55895104800;56195655500;6602516156;7004557737;57214302151;7404247296;7402838215;36106191000;7003620360;","Microphysical properties of synoptic-scale polar stratospheric clouds: In situ measurements of unexpectedly large HNO3-containing particles in the arctic vortex",2014,"10.5194/acp-14-10785-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908053250&doi=10.5194%2facp-14-10785-2014&partnerID=40&md5=dbb7a5f5f877a770f73cd6ec697d79a4","In January 2010 and December 2011, synoptic-scale polar stratospheric cloud (PSC) fields were probed during seven flights of the high-altitude research aircraft M-55 Geophysica within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interaction) and the ESSenCe (ESSenCe: ESA Sounder Campaign) projects. Particle size distributions in a diameter range between 0.46 and 401/4m were recorded by four different optical in situ instruments. Three of these particle instruments are based on the detection of forward-scattered light by single particles. The fourth instrument is a grayscale optical array imaging probe. Optical particle diameters of up to 351/4m were detected with particle number densities and total particle volumes exceeding previous Arctic measurements. Also, gas-phase and particle-bound NOy was measured, as well as water vapor concentrations. The optical characteristics of the clouds were measured by the remote sensing lidar MAL (Miniature Aerosol Lidar) and by the in situ backscatter sonde MAS (Multiwavelength Aerosol Scatterometer), showing the synoptic scale of the encountered PSCs. The particle mode below 21/4m in size diameter has been identified as supercooled ternary solution (STS) droplets. The PSC particles in the size range above 21/4m in diameter are considered to consist of nitric acid hydrates, and the particles' high HNO3 content was confirmed by the NOy instrument. Assuming a particle composition of nitric acid trihydrate (NAT), the optically measured size distributions result in particle-phase HNO3 mixing ratios exceeding available stratospheric values. Therefore the measurement uncertainties concerning probable overestimations of measured particle sizes and volumes are discussed in detail. We hypothesize that either a strong asphericity or an alternate particle composition (e.g., water ice coated with NAT) could explain our observations. In particular, with respect to the denitrification by sedimentation of large HNO3-containing particles, generally considered to be NAT, our new measurements raise questions concerning composition, shape and nucleation pathways. Answering these would improve the numerical simulation of PSC microphysical processes like cloud particle formation, growth and denitrification, which is necessary for better predictions of future polar ozone losses, especially under changing global climate conditions. Generally, it seems that the occurrence of large NAT particles-sometimes termed ""NAT rocks""-are a regular feature of synoptic-scale PSCs in the Arctic. © 2014 Author(s)."
"55574051300;57200172055;57202930095;7201360038;7006781962;","Climate-relevant physical properties of molecular constituents for isoprene-derived secondary organic aerosol material",2014,"10.5194/acp-14-10731-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907943701&doi=10.5194%2facp-14-10731-2014&partnerID=40&md5=d8261f38e3dfef86875dfb33cb2bd630","Secondary organic aerosol (SOA) particles, formed from gas-phase biogenic volatile organic compounds (BVOCs), contribute large uncertainties to the radiative forcing that is associated with aerosols in the climate system. Reactive uptake of surface-active organic oxidation products of BVOCs at the gas-aerosol interface can potentially decrease the overall aerosol surface tension and therefore influence their propensity to act as cloud condensation nuclei (CCN). Here, we synthesize and measure some climate-relevant physical properties of SOA particle constituents consisting of the isoprene oxidation products ±-and-2-IEPOX (isoprene epoxide), as well as-and-2-methyltetraol. Following viscosity measurements, we use octanol-water partition coefficients to quantify the relative hydrophobicity of the oxidation products while dynamic surface tension measurements indicate that aqueous solutions of ±-and2-IEPOX exhibit significant surface tension depression. We hypothesize that the surface activity of these compounds may enhance aerosol CCN activity, and that 2-IEPOX may be highly relevant for surface chemistry of aerosol particles relative to other IEPOX isomers. © 2014 Author(s)."
"8920681600;57203053066;","Simulating Pliocene warmth and a permanent El Niño-like state: The role of cloud albedo",2014,"10.1002/2014PA002644","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910645321&doi=10.1002%2f2014PA002644&partnerID=40&md5=d819b7a690f76bb4a54bf3953f1241e0","Available evidence suggests that during the early Pliocene (4-5 Ma) the mean east-west sea surface temperature (SST) gradient in the equatorial Pacific Ocean was significantly smaller than today, possibly reaching only 1-2C. The meridional SST gradients were also substantially weaker, implying an expanded ocean warm pool in low latitudes. Subsequent global cooling led to the establishment of the stronger, modern temperature gradients. Given our understanding of the physical processes that maintain the present-day cold tongue in the east, warm pool in the west and hence sharp temperature contrasts, determining the key factors that maintained early Pliocene climate still presents a challenge for climate theories and models. This study demonstrates how different cloud properties could provide a solution. We show that a reduction in the meridional gradient in cloud albedo can sustain reduced meridional and zonal SST gradients, an expanded warm pool and warmer thermal stratification in the ocean, and weaker Hadley and Walker circulations in the atmosphere. Having conducted a range of hypothetical modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows good agreement with proxy SST data from major equatorial and coastal upwelling regions, the tropical warm pool, middle and high latitudes, and available subsurface temperature data. As suggested by the observations, the simulated Pliocene-like climate sustains a robust El Niño-Southern Oscillation despite the reduced mean east-west SST gradient. Our results demonstrate that cloud albedo changes may be a critical element of Pliocene climate and that simulating the meridional SST gradient correctly is central to replicating the geographical patterns of Pliocene warmth. Key PointsCloud albedo changes may be a critical element of Pliocene climateMeridional SST gradient is a key in replicating the patterns of Pliocene warmthA robust ENSO despite the reduced mean east-west SST gradient ©2014. American Geophysical Union. All Rights Reserved."
"8846887600;7004060399;","Climate system response to stratospheric ozone depletion and recovery",2014,"10.1002/qj.2330","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922846122&doi=10.1002%2fqj.2330&partnerID=40&md5=acfe9b4a426ba3d526ff2a472b2fb495","We review what is presently known about the climate system response to stratospheric ozone depletion and its projected recovery, focusing on the responses of the atmosphere, ocean and cryosphere. Compared with well-mixed greenhouse gases (GHGs), the radiative forcing of climate due to observed stratospheric ozone loss is very small: in spite of this, recent trends in stratospheric ozone have caused profound changes in the Southern Hemisphere (SH) climate system, primarily by altering the tropospheric midlatitude jet, which is commonly described as a change in the Southern Annular Mode. Ozone depletion in the late twentieth century was the primary driver of the observed poleward shift of the jet during summer, which has been linked to changes in tropospheric and surface temperatures, clouds and cloud radiative effects, and precipitation at both middle and low latitudes. It is emphasized, however, that not all aspects of the SH climate response to stratospheric ozone forcing can be understood in terms of changes in the midlatitude jet. The response of the Southern Ocean and sea ice to ozone depletion is currently a matter of debate. For the former, the debate is centred on the role of ocean eddies in possibly opposing wind-driven changes in the mean circulation. For the latter, the issue is reconciling the observed expansion of Antarctic sea-ice extent during the satellite era with robust modelling evidence that the ice should melt as a result of stratospheric ozone depletion (and increases in GHGs). Despite lingering uncertainties, it has become clear that ozone depletion has been instrumental in driving SH climate change in recent decades. Similarly, ozone recovery will figure prominently in future climate change, with its impacts expected to largely cancel the impacts of increasing GHGs during the next half-century. © 2014 Royal Meteorological Society."
"6701754792;7404514776;6602929454;55782381000;","Evaluation of hydrometeor frequency of occurrence in a limited-area numerical weather prediction system using near real-time CloudSat-CALIPSO observations",2014,"10.1002/qj.2308","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922838179&doi=10.1002%2fqj.2308&partnerID=40&md5=343fbb0cd4c9de11cf831e7ce4c7a81b","Near real-time measurements from the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission are used to evaluate the representation of the hydrometeor frequency of occurrence (HFO) in the limited-area version of the Australian Community Climate and Earth-System Simulator (ACCESS-A), using 1 year of collocated satellite data and model forecasts. The ACCESS-A is found to overpredict the HFO below 12 km height (primarily over the Southern Ocean), and largely underpredict the HFO above 12 km height (primarily in the Tropics). The seasonal variability of these biases was found to be small suggesting that these model problems can be investigated with short-term simulations. This implies that faster model improvement should be achievable using the technique proposed in this study. Selected skill scores were then analysed as a function of lead time, hydrometeor height in the troposphere and season. The highest forecast skill was found in the subtropics, mostly owing to a low incidence of false positives. Overall the ACCESS-A forecast skill at the Southern Hemisphere mid-latitudes is comparable to that of the North Atlantic/European version of the UK Met Office Unified Model at Northern Hemisphere mid-latitudes. It is also found that mid-latitude low-level hydrometeors and tropical low-level and high-level hydrometeors during the Southern Hemisphere summer are the most challenging hydrometeors to simulate in the domain. © 2013 Royal Meteorological Society."
"25926762100;26031982400;6507121473;36676894700;25647575500;7801592570;6602472532;","Comparison of one-moment and two-moment bulk microphysics for high-resolution climate simulations of intense precipitation",2014,"10.1016/j.atmosres.2014.05.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901987080&doi=10.1016%2fj.atmosres.2014.05.012&partnerID=40&md5=c689ff5ee651ecc010993de860c70acd","As high-resolution climate models become increasingly complex, it should be carefully assessed to what extent the improved physics in such models justifies the large computational cost that the complexity imposes. This paper presents a detailed sensitivity study of convective precipitation characteristics to the number of prognostic moments in bulk microphysics schemes using a high-resolution convection-resolving climate model.It is shown that 1-moment and 2-moment microphysics schemes produce more similar surface precipitation characteristics for a composite of 20 real-case convective simulations in Belgium than for many idealized studies conducted before. In the baseline 2-moment scheme, size sorting of particles is counteracted by collisional drop breakup to produce mean drop sizes that are similar to those in the 1-moment version of the scheme. Hence, fallout, evaporation and surface rain rates are very similar between the two versions of the scheme.Conversely, larger sensitivities of precipitation extremes were found to the treatment of drop breakup and the shape of the particle size distributions. Consistent with previous studies, domain-averaged and peak precipitation increased monotonically with increasing breakup equilibrium diameter Deq. Further, it is shown that a negative exponential size distribution results in excessive radar reflectivities for light rain rates. Surface precipitation and the joint distribution of reflectivity and rain rate are best reproduced by a 2-moment version of the scheme that applies gamma distributions with a diagnostic shape parameter for all particles and a large Deq. However, given the large sensitivities and uncertainties associated with collisional drop breakup and size sorting, it is likely that the full potential of improved physics in a 2-moment scheme will remain underexposed as long as these processes are not better understood. © 2014 Elsevier B.V."
"56303781300;55341341000;10144208300;35745167300;6701619700;","Radiation and energy balance dynamics over young chir pine (Pinus roxburghii) system in Doon of western Himalayas",2014,"10.1007/s12040-014-0480-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912140131&doi=10.1007%2fs12040-014-0480-6&partnerID=40&md5=caf4e5020f614f11693f27fc284a90d3","The regional impacts of future climate changes are principally driven by changes in energy fluxes. In this study, measurements on micrometeorological and biophysical variables along with surface energy exchange were made over a coniferous subtropical chir pine (Pinus roxburghii) plantation ecosystem at Forest Research Institute, Doon valley, India. The energy balance components were analyzed for two years to understand the variability of surface energy fluxes, their drivers, and closure pattern. The period covered two growth cycles of pine in the years 2010 and 2011 without and with understory growth. Net short wave and long wave radiative fluxes substantially varied with cloud dynamics, season, rainfall induced surface wetness, and green growth. The study clearly brought out the intimate link of albedo dynamics in chir pine system with dynamics of leaf area index (LAI), soil moisture, and changes in understory background. Rainfall was found to have tight linear coupling with latent heat fluxes. Latent heat flux during monsoon period was found to be higher in higher rainfall year (2010) than in lower rainfall year (2011). Higher or lower pre-monsoon sensible heat fluxes were succeeded by noticeably higher or lower monsoon rainfall respectively. Proportion of latent heat flux to net radiation typically followed the growth curve of green vegetation fraction, but with time lag. The analysis of energy balance closure (EBC) showed that the residual energy varied largely within ±30% of net available energy and the non-closure periods were marked by higher rainspells or forced clearance of understory growths. © Indian Academy of Sciences."
"36094524600;6602600493;57113345900;12042092500;55897144500;7006592026;","Sensitivity of the regional climate model RegCM4.2 to planetary boundary layer parameterisation",2014,"10.1007/s00382-013-2003-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957958191&doi=10.1007%2fs00382-013-2003-6&partnerID=40&md5=ec9bc3c9729fd097d71cfc63548ac1af","This study investigates the performance of two planetary boundary layer (PBL) parameterisations in the regional climate model RegCM4.2 with specific focus on the recently implemented prognostic turbulent kinetic energy parameterisation scheme: the University of Washington (UW) scheme. When compared with the default Holtslag scheme, the UW scheme, in the 10-year experiments over the European domain, shows a substantial cooling. It reduces winter warm bias over the north-eastern Europe by 2 °C and reduces summer warm bias over central Europe by 3 °C. A part of the detected cooling is ascribed to a general reduction in lower tropospheric eddy heat diffusivity with the UW scheme. While differences in temperature tendency due to PBL schemes are mostly localized to the lower troposphere, the schemes show a much higher diversity in how vertical turbulent mixing of the water vapour mixing ratio is governed. Differences in the water vapour mixing ratio tendency due to the PBL scheme are present almost throughout the troposphere. However, they alone cannot explain the overall water vapour mixing ratio profiles, suggesting strong interaction between the PBL and other model parameterisations. An additional 18-member ensemble with the UW scheme is made, where two formulations of the master turbulent length scale in unstable conditions are tested and unconstrained parameters associated with (a) the evaporative enhancement of the cloud-top entrainment and (b) the formulation of the master turbulent length scale in stable conditions are systematically perturbed. These experiments suggest that the master turbulent length scale in the UW scheme could be further refined in the current implementation in the RegCM model. It was also found that the UW scheme is less sensitive to the variations of the other two selected unconstrained parameters, supporting the choice of these parameters in the default formulation of the UW scheme. © 2013, Springer-Verlag Berlin Heidelberg."
"56119479900;55717074000;24398842400;56424145700;","Different contact angle distributions for heterogeneous ice nucleation in the community atmospheric model version 5",2014,"10.5194/acp-14-10411-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907936517&doi=10.5194%2facp-14-10411-2014&partnerID=40&md5=f0bdde44d0de8184ddcd8538d90dea87","In order to investigate the impact of different treatments for the contact angle (&alpha;) in heterogeneous ice nucleating properties of natural dust and black carbon (BC) particles, we implement the classical-nucleation-theory-based parameterization of heterogeneous ice nucleation (Hoose et al., 2010) in the Community Atmospheric Model version 5 (CAM5) and then improve it by replacing the original single-contact-angle model with the probability-density-function-of-(-PDF) model to better represent the ice nucleation behavior of natural dust found in observations. We refit the classical nucleation theory (CNT) to constrain the uncertain parameters (i.e., onset and activation energy in the single-model; mean contact angle and standard deviation in the-PDF model) using recent observation data sets for Saharan natural dust and BC (soot). We investigate the impact of the time dependence of droplet freezing on mixed-phase clouds and climate in CAM5 as well as the roles of natural dust and soot in different nucleation mechanisms. Our results show that, when compared with observations, the potential ice nuclei (IN) calculated by the-PDF model show better agreement than those calculated by the single-model at warm temperatures (T &minus;20 °C). More ice crystals can form at low altitudes (with warm temperatures) simulated by the-PDF model than compared to the single-model in CAM5. All of these can be attributed to different ice nucleation efficiencies among aerosol particles, with some particles having smaller contact angles (higher efficiencies) in the-PDF model. In the sensitivity tests with the-PDF model, we find that the change in mean contact angle has a larger impact on the active fraction at a given temperature than a change in standard deviation, even though the change in standard deviation can lead to a change in freezing behavior. Both the single-and the-PDF model indicate that the immersion freezing of natural dust plays a more important role in the heterogeneous nucleation than that of soot in mixed-phase clouds. The new parameterizations implemented in CAM5 induce more significant aerosol indirect effects than the default parameterization. © 2014 Author(s)."
"6603451699;57203029315;7101871222;26642916300;","Sulfur isotope mass-independent fractionation in impact deposits of the 3.2billion-year-old Mapepe Formation, Barberton Greenstone Belt, South Africa",2014,"10.1016/j.gca.2014.07.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908448983&doi=10.1016%2fj.gca.2014.07.018&partnerID=40&md5=6dc55e80b971e800f5c324e988d290f2","Theoretical and experimental studies have shown that atmospheric SO2 isotopologue self-shielding effects in the 190-220nm region of the solar spectrum are the likely cause for mass independent fractionation of sulfur isotopes (S-MIF). The main products of this photochemical reaction - SO3 and S0 - typically define a compositional array of ca. δ33S/δ34S=0.06-0.14. This is at odds with the generally observed trend in Archean sulfides, which broadly defines an array of ca. δ33S/δ34S=0.9. Various explanations have been proposed, including a diminution of δ34S caused by chemical and biogenic mass-dependent fractionation of sulfur isotopes (S-MDF), mixing with photolytic products produced during felsic volcanic events, or partial blocking of the low-wavelength part of the spectrum due to the presence of reduced atmospheric gases or an organic haze. Early in Earth history large meteorite impacts would have ejected dust and gas clouds into the atmosphere that shielded solar radiation and affected global climate. It is thus likely that at certain time intervals of high meteorite flux the atmosphere was significantly perturbed, having an effect on atmospheric photochemistry and possibly leaving anomalous sulfur isotopic signatures in the rock record. Here we describe the sulfur isotopic signatures in sulfides of spherule beds S2, S3 and S4 of the Barberton Greenstone Belt, South Africa. In particular, in spherule bed S3 - and to a lesser extent S4 - a trend of ca. δ33S/δ34S=0.23 is observed that closely follows the expected trend for SO2-photolysis in the 190-220nm spectral range. This suggests that an impact dust cloud (deposited as spherule beds), which sampled the higher region of the atmosphere, specifically incorporated products of SO2 photolysis in the 190-220nm range, and blocked photochemical reactions at higher wavelengths (250-330nm band). By implication, the generally observed Archean trend appears to be the result of mixing of different MIF-S sources arising from a variety of photochemical reactions that took place in the lower part of the atmosphere. © 2014 Elsevier Ltd."
"7005232598;57195353975;57212417536;","Effect of some climatic parameters on tropospheric and total ozone column over Alipore (22.52◦N, 88.33◦E), India",2014,"10.1007/s12040-014-0490-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912081035&doi=10.1007%2fs12040-014-0490-4&partnerID=40&md5=3e1f32345635c2dbcef3e8089e47f4d0","The paper presents the nature of variations of tropospheric and total ozone column retrieved from the Convective Cloud Differential (CCD) technique, Ozone Monitoring Instrument (OMI), and Total Ozone Mapping Spectrometer (TOMS) data, National Aeronautics and Space Administrations (NASA), USA, respectively; surface temperature, relative humidity, total rainfall, ozone precursors (non-methane hydrocarbon, carbon monoxide, nitrogen dioxide, and sulphur dioxide) that are collected from India Meteorological Department (IMD), Alipore, Kolkata; solar insolation obtained from Solar Geophysical Data Book and El-Niño index collected from National Climatic Data Center, US Department of Commerce, National Oceanic and Atmospheric Administration, USA. The effect of these climatic parameters and ozone precursors on ozone variations is critically analyzed and explained on the basis of linear regression and correlation. It has been observed that the maximum, minimum and mean temperature, relative humidity, solar insolation, tropospheric, and total ozone column (TOC) showed slight increasing tendencies from October 2004 to December 2011, while total rainfall and El-Niño index showed little decreasing tendencies for the same period. Amongst selected climatic parameters and ozone precursors, the solar insolation and the average temperature had a significant influence on both, the tropospheric ozone and total ozone column formation. The solar insolation had contributed more in tropospheric ozone than in total ozone column; while El-Niño index had played a more significant role in total ozone column build up than in tropospheric ozone. Negative correlation was observed between almost all ozone precursors with the tropospheric and total ozone. The tropospheric ozone and total ozone column were also significantly correlated. The level of significance and contribution of different climatic parameters are determined from correlation technique and Multiple Linear Regression (MLR) method. The related chemical kinetics for ozone production processes has been critically described. © Indian Academy of Sciences."
"6602504047;7004714030;6701735773;6603433697;","Role of clouds and land-atmosphere coupling in midlatitude continental summer warm biases and climate change amplification in CMIP5 simulations",2014,"10.1002/2014GL061145","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911165066&doi=10.1002%2f2014GL061145&partnerID=40&md5=485c7ba67266a20aed231967b3344844","Over land, most state-of-the-art climate models contributing to Coupled Model Intercomparison Project Phase 5 (CMIP5) share a strong summertime warm bias in midlatitude areas, especially in regions where the coupling between soil moisture and atmosphere is effective. The most biased models overestimate solar incoming radiation, because of cloud deficit and have difficulty to sustain evaporation. These deficiencies are also involved in the spread of the summer temperature projections among models in the midlatitude; the models which simulate a higher-than-average warming overestimate the present climate net shortwave radiation which increases more-than-average in the future, in link with a decrease of cloudiness. They also show a higher-than-average reduction of evaporative fraction in areas with soil moisture-limited evaporation regimes. Over these areas, the most biased models in the present climate simulate a larger warming in response to climate change which is likely to be overestimated. Key Points Systematic summer warm biases in regions of strong soil-atmosphere couplingMost biased models underestimate evaporative fraction and cloudsMost biased models show a stronger warming in climate change projections ©2014. American Geophysical Union. All Rights Reserved."
"16645127300;8953038700;8570871900;","Sensitivity of modeled far-IR radiation budgets in polar continents to treatments of snow surface and ice cloud radiative properties",2014,"10.1002/2014GL061216","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911433885&doi=10.1002%2f2014GL061216&partnerID=40&md5=50e8223e9311e4e18752965345c72130","While most general circulation models assume spectrally independent surface emissivity and nonscattering clouds in their longwave radiation treatment, spectral variation of the index of refraction of ice indicates that in the far IR, snow surface emissivity can vary considerably and ice clouds can cause nonnegligible scattering. These effects are more important for high-elevation polar continents where the dry and cold atmosphere is not opaque in the far IR. We carry out sensitivity studies to show that in a winter month over the Antarctic Plateau including snow surface spectral emissivity and ice cloud scattering in radiative transfer calculation reduces net upward far-IR flux at both top of atmosphere and surface. The magnitudes of such reductions in monthly mean all-sky far-IR flux range from 0.72 to 1.47 Wm-2, with comparable contributions from the cloud scattering and the surface spectral emissivity. The reduction is also sensitive to sizes of both snow grains and cloud particles. Key Points Ice cloud and snow surface radiative properties vary considerably in the far IRSnow surface emissivity and cloud scattering affect far IR comparablyEven for far-IR radiation alone, the impact is nonnegligible ©2014. American Geophysical Union. All Rights Reserved."
"56643836400;57212524847;","Light Absorption by Charge Transfer Complexes in Brown Carbon Aerosols",2014,"10.1021/ez500263j","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84969257379&doi=10.1021%2fez500263j&partnerID=40&md5=3fa26ef0556b48b84beaeab35cd7ed66","Recently, it has become apparent that a fraction of the organic species in ambient aerosols absorbs ultraviolet-visible light with a potential impact on climate. It is believed that this light-absorbing, sometimes called ""brown"", carbon originates from biomass and biofuel burning and could be formed through secondary processes in particles or clouds. Here, we identify for the first time charge transfer (CT) complexes as a significant source of light absorption by organic compounds in aerosols. A dense manifold of these complexes, formed from interactions between alcohol and carbonyl moieties, accounts for approximately 50% of the absorption (300-600 nm) observed for water-extracted ambient particulate matter collected in Athens, GA. Corresponding fluorescence emission spectra with broad, overlapping long-wavelength tails are consistent with efficient energy transfer among a near continuum of such coupled excited states. We postulate that a wide variety of CT complexes are formed as a result of a supramolecular association of self-assembling, smaller molecules, just as they are in natural humic substances, and that this gives rise to absorption that extends to red wavelengths. These findings imply that light absorption by organic aerosols is governed by a combination of independent as well as interacting chromophores and that both must be included in an accurate representation of aerosol optical properties. © 2014 American Chemical Society."
"14019100300;35068194500;22978151200;55915206300;55717074000;56384704800;7006306835;50261552200;7404829395;","Evaluating clouds, aerosols, and their interactions in three global climate models using satellite simulators and observations",2014,"10.1002/2014JD021722","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214798&doi=10.1002%2f2014JD021722&partnerID=40&md5=12e3540e32a99b594282f463a7c16e07","Accurately representing aerosol-cloud interactions in global climate models is challenging. As parameterizations evolve, it is important to evaluate their performance with appropriate use of observations. In this investigation we compare aerosols, clouds, and their interactions in three global climate models (Geophysical Fluid Dynamics Laboratory-Atmosphere Model 3 (AM3), National Center for Atmospheric Research-Community Atmosphere Model 5 (CAM5), and Goddard Institute for Space Studies-ModelE2) to Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. Modeled cloud properties are diagnosed using a MODIS simulator. Cloud droplet number concentrations (N) are computed identically from satellite-simulated and MODIS-observed values of liquid cloud optical depth and droplet effective radius. We find that aerosol optical depth (τa) simulated by models is similar to observations in many regions around the globe. For N, AM3 and CAM5 capture the observed spatial pattern of higher values in coastal marine stratocumulus versus remote ocean regions, though modeled values, in general, are higher than observed. Aerosol-cloud interactions were computed as the sensitivity of ln(N) to ln(τa) for coastal marine liquid clouds near South Africa (SAF) and Southeast Asia where τa varies in time. AM3 and CAM5 are more sensitive than observations, while the sensitivity for ModelE2 is statistically insignificant. This widely used sensitivity could be subject to misinterpretation due to the confounding influence of meteorology on both aerosols and clouds. A simple framework for assessing the sensitivity of ln(N) to ln(τa) at constant meteorology illustrates that observed sensitivity can change from positive to statistically insignificant when including the confounding influence of relative humidity. Satellite-simulated versus standard model values of N are compared; for CAM5 in SAF, standard model values are significantly lower than satellite-simulated values with a bias of 83 cm3. © 2014. American Geophysical Union. All rights reserved."
"6701791841;56507504100;54391679700;57193098631;","The cause of solar dimming and brightening at the earth’s surface during the last half century: Evidence from measurements of sunshine duration",2014,"10.1002/2013JD021308","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018574642&doi=10.1002%2f2013JD021308&partnerID=40&md5=72a7298c0131a824b5d193713dd0b3d3","Analysis of the Angstrom-Prescott relationship between normalized values of global radiation and sunshine duration measured during the last 50 years made at five sites with a wide range of climate and aerosol emissions showed few significant differences in atmospheric transmissivity under clear or cloud-covered skies between years when global dimming occurred and years when global brightening was measured, nor in most cases were there any significant changes in the parameters or in their relationships to annual rates of fossil fuel combustion in the surrounding 1° cells. It is concluded that at the sites studied changes in cloud cover rather than anthropogenic aerosols emissions played the major role in determining solar dimming and brightening during the last half century and that there are reasons to suppose that these findings may have wider relevance. © 2014. American Geophysical Union. All rights reserved."
"17135286400;56611366900;","Statistical characteristics of cloud variability. Part 2: Implication for parameterizations of microphysical and radiative transfer processes in climate models",2014,"10.1002/2014JD022003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214830&doi=10.1002%2f2014JD022003&partnerID=40&md5=094df3af74cda81b26743af46b0a333a","The effects of subgrid cloud variability on grid-average microphysical rates and radiative fluxes are examined by use of long-term retrieval products at the Tropical West Pacific, Southern Great Plains, and North Slope of Alaska sites of the Department of Energy’s Atmospheric Radiation Measurement program. Four commonly used distribution functions, the truncated Gaussian, Gamma, lognormal, and Weibull distributions, are constrained to have the same mean and standard deviation as observed cloud liquid water content. The probability density functions are then used to upscale relevant physical processes to obtain grid-average process rates. It is found that the truncated Gaussian representation results in up to 30% mean bias in autoconversion rate, whereas the mean bias for the lognormal representation is about 10%. The Gamma and Weibull distribution function performs the best for the grid-average autoconversion rate with the mean relative bias less than 5%. For radiative fluxes, the lognormal and truncated Gaussian representations perform better than the Gamma and Weibull representations. The results show that the optimal choice of subgrid cloud distribution function depends on the nonlinearity of the process of interest, and thus, there is no single distribution function that works best for all parameterizations. Examination of the scale (window size) dependence of the mean bias indicates that the bias in grid-average process rates monotonically increases with increasing window sizes, suggesting the increasing importance of subgrid variability with increasing grid sizes. © 2014. American Geophysical Union. All rights reserved."
"25647334300;7103158465;6506385754;25031430500;7005729142;","Comparison of ice cloud properties simulated by the Community Atmosphere Model (CAM5) with in-situ observations",2014,"10.5194/acp-14-10103-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907432729&doi=10.5194%2facp-14-10103-2014&partnerID=40&md5=57fcbc199304f878de832769ec47b9f2","Detailed measurements of ice crystals in cirrus clouds were used to compare with results from the Community Atmospheric Model Version 5 (CAM5) global climate model. The observations are from two different field campaigns with contrasting conditions: Atmospheric Radiation Measurements Spring Cloud Intensive Operational Period in 2000 (ARM-IOP), which was characterized primarily by midlatitude frontal clouds and cirrus, and Tropical Composition, Cloud and Climate Coupling (TC4), which was dominated by anvil cirrus. Results show that the model typically overestimates the slope parameter of the exponential size distributions of cloud ice and snow, while the variation with temperature (height) is comparable. The model also overestimates the ice/snow number concentration (0th moment of the size distribution) and underestimates higher moments (2nd through 5th), but compares well with observations for the 1st moment. Overall the model shows better agreement with observations for TC4 than for ARM-IOP in regards to the moments. The mass-weighted terminal fall speed is lower in the model compared to observations for both ARM-IOP and TC4, which is partly due to the overestimation of the size distribution slope parameter. Sensitivity tests with modification of the threshold size for cloud ice to snow autoconversion (Dcs) do not show noticeable improvement in modeled moments, slope parameter and mass weighed fall speed compared to observations. Further, there is considerable sensitivity of the cloud radiative forcing to Dcs, consistent with previous studies, but no value of Dcs improves modeled cloud radiative forcing compared to measurements. Since the autoconversion of cloud ice to snow using the threshold size Dcs has little physical basis, future improvement to combine cloud ice and snow into a single category, eliminating the need for autoconversion, is suggested. © Author(s) 2014."
"25640569400;7004479957;34772240500;14018770700;7406442958;","Improving subtropical boundary layer cloudiness in the 2011 NCEP GFS",2014,"10.5194/gmd-7-2107-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907388402&doi=10.5194%2fgmd-7-2107-2014&partnerID=40&md5=bf12de990909b317c0b9b980c904eb94","The current operational version of National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) shows significant low cloud bias. These biases also appear in the Coupled Forecast System (CFS), which is developed from the GFS. These low cloud biases degrade seasonal and longer climate forecasts, particularly of short-wave cloud radiative forcing, and affect predicted sea surface temperature. Reducing this bias in the GFS will aid the development of future CFS versions and contributes to NCEP's goal of unified weather and climate modelling. Changes are made to the shallow convection and planetary boundary layer parameterisations to make them more consistent with current knowledge of these processes and to reduce the low cloud bias. These changes are tested in a singlecolumn version of GFS and in global simulations with GFS coupled to a dynamical ocean model. In the single-column model, we focus on changing parameters that set the following: the strength of shallow cumulus lateral entrainment, the conversion of updraught liquid water to precipitation and grid-scale condensate, shallow cumulus cloud top, and the effect of shallow convection in stratocumulus environments. Results show that these changes improve the single-column simulations when compared to large eddy simulations, in particular through decreasing the precipitation efficiency of boundary layer clouds. These changes, combined with a few other model improvements, also reduce boundary layer cloud and albedo biases in global coupled simulations. © Author(s) 2014."
"55597863700;55644722700;8212745200;55740020200;7402280263;6603031730;55900277600;6602186158;22234742000;","A biophysically based and objective satellite seasonality observation method for applications over the Arctic",2014,"10.1080/01431161.2014.963897","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910130203&doi=10.1080%2f01431161.2014.963897&partnerID=40&md5=e86d96161b11e689e4b75c5dbb24799a","Despite wide applications of remote-sensing data with high temporal resolution for monitoring phenology, two persistent problems have prevented the realization of their full potential. The first is the subjectivity in defining thresholds for a phenological event (e.g. the start or end of growing season − SOS or EOS). The second is the use of various arbitrarily selected filtering and smoothing algorithms for constructing vegetation index seasonal profiles in order to reduce the noise caused by residue cloud contamination and aerosol variations. In this study, we addressed both problems by developing a biophysically based and objective satellite seasonality observation method (BLOSSOM) for application over Canada’s Arctic. Application of the BLOSSOM method to three northern Canadian national parks (Ivvavik, Wapusk, and Sirmilik) proved that the method is operational. Using the uncertainties in the vegetation index and its threshold, we estimated the overall mean uncertainties as being −5.3 to 3.4 days, −4.2 to 5.2 days, and −6.2 to 8.4 days, respectively, for SOS, EOS, and growing season length (GSL). Further independent tests against SOS, determined using records of snow cover at nearby climate stations (as ‘truth’), indicate that the mean absolute error is less than 3.6 ± 0.2 days. © 2014, © 2014 Taylor & Francis."
"37261525600;55893823700;35273334200;56382798500;7006630889;7102976560;57200319057;","Aviation 2006 NOx-induced effects on atmospheric ozone and HOx in Community Earth System Model (CESM)",2014,"10.5194/acp-14-9925-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907907887&doi=10.5194%2facp-14-9925-2014&partnerID=40&md5=3c37d9020317ecec8fd8935ed7481ffa","The interaction between atmospheric chemistry and ozone (O3) in the upper troposphere-lower stratosphere (UTLS) presents a major uncertainty in understanding the effects of aviation on climate. In this study, two configurations of the atmospheric model from the Community Earth System Model (CESM), Community Atmosphere Model with Chemistry, Version 4 (CAM4) and Version 5 (CAM5), are used to evaluate the effects of aircraft nitrogen oxide (NOx Combining double low line NO + NO2) emissions on ozone and the background chemistry in the UTLS. CAM4 and CAM5 simulations were both performed with extensive tropospheric and stratospheric chemistry including 133 species and 330 photochemical reactions. CAM5 includes direct and indirect aerosol effects on clouds using a modal aerosol module (MAM), whereby CAM4 uses a bulk aerosol module, which can only simulate the direct effect. To examine the accuracy of the aviation NOx-induced ozone distribution in the two models, results from the CAM5 and CAM4 simulations are compared to ozonesonde data. Aviation NOx emissions for 2006 were obtained from the AEDT (Aviation Environmental Design Tool) global commercial aircraft emissions inventory. Differences between simulated O3concentrations and ozonesonde measurements averaged at representative levels in the troposphere and different regions are 13% in CAM5 and 18% in CAM4. Results show a localized increase in aviation-induced O3concentrations at aviation cruise altitudes that stretches from 40° N to the North Pole. The results indicate a greater and more disperse production of aviation NOx-induced ozone in CAM5, with the annual tropospheric mean O3perturbation of 1.2 ppb (2.4%) for CAM5 and 1.0 ppb (1.9%) for CAM4. The annual mean O3perturbation peaks at about 8.2 ppb (6.4%) and 8.8 ppb (5.2%) in CAM5 and CAM4, respectively. Aviation emissions also result in increased hydroxyl radical (OH) concentrations and methane (CH4) loss rates, reducing the tropospheric methane lifetime in CAM5 and CAM4 by 1.69 and 1.40%, respectively. Aviation NOx emissions are associated with an instantaneous change in global mean short-term O3radiative forcing (RF) of 40.3 and 36.5 mWm-2in CAM5 and CAM4, respectively."
"55789354000;57214957748;57214957751;57215075653;26029605900;55770069100;56213440200;7005287667;6603898548;57214957433;","Cloud droplet activity changes of soot aerosol upon smog chamber ageing",2014,"10.5194/acp-14-9831-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901948343&doi=10.5194%2facp-14-9831-2014&partnerID=40&md5=9cffb82d83f27baf08f50a44efe22ca6","Particles containing soot, or black carbon, are generally considered to contribute to global warming. However, large uncertainties remain in the net climate forcing resulting from anthropogenic emissions of black carbon (BC), to a large extent due to the fact that BC is co-emitted with gases and primary particles, both organic and inorganic, and subject to atmospheric ageing processes. In this study, diesel exhaust particles and particles from a flame soot generator spiked with light aromatic secondary organic aerosol (SOA) precursors were processed by UV radiation in a 6 m3Teflon chamber in the presence of NOx. The time-dependent changes of the soot nanoparticle properties were characterised using a Cloud Condensation Nuclei Counter, an Aerosol Particle Mass Analyzer and a Soot Particle Aerosol Mass Spectrometer. The results show that freshly emitted soot particles do not activate into cloud droplets at supersaturations ≤2%, i.e. the BC core coated with primary organic aerosol (POA) from the exhaust is limited in hygroscopicity. Before the onset of UV radiation it is unlikely that any substantial SOA formation is taking place. An immediate change in cloud-activation properties occurs at the onset of UV exposure. This change in hygroscopicity is likely attributed to SOA formed from intermediate volatility organic compounds (IVOCs) in the diesel engine exhaust. The change of cloud condensation nuclei (CCN) properties at the onset of UV radiation implies that the lifetime of soot particles in the atmosphere is affected by the access to sunlight, which differs between latitudes. The ageing of soot particles progressively enhances their ability to act as cloud condensation nuclei, due to changes in: (I) organic fraction of the particle, (II) chemical properties of this fraction (e.g. primary or secondary organic aerosol), (III) particle size, and (IV) particle morphology. Applying κ-Köhler theory, using a κSOA value of 0.13 (derived from independent input parameters describing the organic material), showed good agreement with cloud droplet activation measurements for particles with a SOA mass fraction ≥0.12 (slightly aged particles). The activation properties are enhanced with only a slight increase in organic material coating the soot particles (SOA mass fraction &lt; 0.12), however not as much as predicted by Köhler theory. The discrepancy between theory and experiments during the early stages of ageing might be due to solubility limitations, unevenly distributed organic material or hindering particle morphology. The change in properties of soot nanoparticles upon photochemical processing clearly increases their hygroscopicity, which affects their behaviour both in the atmosphere and in the human respiratory system. © 2014 Author(s)."
"54983414800;57193999542;6505932008;","A cloudsat cloud object partitioning technique and assessment and integration of deep convective anvil sensitivities to sea surface temperature",2014,"10.1002/2014JD021717","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214568&doi=10.1002%2f2014JD021717&partnerID=40&md5=abcc7577c8a32c20a1ea80358269a770","A cloud object partitioning algorithm is developed to provide a widely useful database of deep convective clouds. It takes contiguous CloudSat cloudy regions and identifies various length scales of clouds from a tropical, oceanic subset of data. The methodology identifies a level above which anvil characteristics become important by analyzing the cloud object shape. Below this level in what is termed the pedestal region, convective cores are identified based on reflectivity maxima. Identifying these regions allows for the assessment of length scales of the anvil and pedestal of deep convective clouds. Cloud objects are also appended with certain environmental quantities from European Centre for Medium-Range Weather Forecasts. Simple geospatial and temporal assessments show that the cloud object technique agrees with standard observations of local frequency of deep convective cloudiness. Deep convective clouds over tropical oceans play important roles in Earth’s climate system. The newly developed data set is used to evaluate the response of tropical, deep convective clouds to sea surface temperature (SST). Several previously proposed responses are examined: the Fixed Anvil Temperature Hypothesis, the Iris Hypothesis, and the Thermostat Hypothesis. When the data are analyzed per cloud object, increasing SST is found to be associated with increased anvil thickness, decreased anvil width, and cooler cloud top temperatures. Implications for the corresponding hypotheses are discussed. A new response suggesting that the base temperature of deep convective anvils remains approximately constant with increasing SSTs is introduced. These cloud dependencies on SST are integrated to form a more comprehensive theory for deep convective anvil responses to SST. © 2014. American Geophysical Union. All Rights Reserved."
"25823927100;","Humidity variability revealed by a sounding array and its implications for cloud representation in GCMs",2014,"10.1002/2014JD021837","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214651&doi=10.1002%2f2014JD021837&partnerID=40&md5=f5c000ad8c84cae887e9727985bf84f9","Subgrid-scale humidity variability is critical for statistical cloud schemes. The Atmospheric Radiation Measurement (ARM) sounding array, covering a comparable size to a grid box of current global climate models (GCMs), provides estimates of subgrid-scale humidity variability. Using radiosonde measurements from ARM sounding arrays, humidity variabilities at a tropical and a midlatitude site are analyzed. Normalized moisture variance is small in the lower troposphere but tends to be large in the middle troposphere. Moisture variability dominates relative humidity (RH) variability at the tropical site, but the contribution by temperature variability cannot be ignored at the midlatitude site. Based on the analysis, a simple linear relationship between RH variance and mean is proposed. Cloud schemes assuming Gaussian distributions give comparable cloudiness as those assuming a beta distribution considering both moisture variance and skewness. A probability distribution function scheme assuming a Gaussian distribution of RH has more flexibility than a RH threshold scheme, which tends to overestimate cloudiness in the moist boundary layer over the tropics. Supersaturation with respect to ice needs to be allowed in the upper troposphere over the tropics to reduce the persistent overestimated cloudiness there. Similar comparison results are found from analysis of cloud resolving model simulations. The study suggests that measurements from sounding arrays would be valuable for statistical cloud scheme evaluation and development. © 2014. American Geophysical Union. All Rights Reserved."
"35205101700;7402146514;55361434900;","Analysis of global land surface albedo climatology and spatial-temporal variation during 1981–2010 from multiple satellite products",2014,"10.1002/2014JD021667","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027957350&doi=10.1002%2f2014JD021667&partnerID=40&md5=7c9b8b7881c4e6f058fb36db3a9624cc","For several decades, long-term time series data sets of multiple global land surface albedo products have been generated from satellite observations. These data sets have been used as one of the key variables in climate change studies. This study aims to assess the surface albedo climatology and to analyze long-term albedo changes, from nine satellite-based data sets for the period 1981–2010, on a global basis. Results show that climatological surface albedo data sets derived from satellite observations can be used to validate, calibrate, and further improve surface albedo simulations and parameterizations in current climate models. However, the albedo products derived from the International Satellite Cloud Climatology Project and the Global Energy and Water Exchanges Project have large seasonal biases. At latitudes higher than 50°, the maximal difference in winter zonal albedo ranges from 0.1 to 0.4 among the nine satellite data sets. Satellite-based albedo data sets agree relatively well during the summer at high latitudes, with a standard deviation of 0.04 for the 70°–80° zone in both hemispheres. The fine-resolution (0.05°) data sets agree well with each other for all the land cover types in middle to low latitudes; however, large spread was identified for their albedos at middle to high latitudes over land covers with mixed snow and sparse vegetation. By analyzing the time series of satellite-based albedo products over the past three decades, albedo of the Northern Hemisphere was found to be decreasing in July, likely due to the shrinking snow cover. Meanwhile, albedo in January was found to be increasing, likely because of the expansion of snow cover in northern winter. However, to improve the albedo estimation at high latitudes, and ultimately the climate models used for long-term climate change studies, a still better understanding of differences between satellite-based albedo data sets is required. © 2014. American Geophysical Union. All Rights Reserved."
"54788302000;6603800142;57195574170;6602584093;56520921400;","Temporal variability of observed and simulated hyperspectral reflectance",2014,"10.1002/2014JD021566","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214790&doi=10.1002%2f2014JD021566&partnerID=40&md5=50c8830f59530d0679ca4678e5aede61","Multivariate analysis techniques were used to quantify and compare the spectral and temporal variability of observed and simulated shortwave hyperspectral Earth reflectance. The observed reflectances were measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument between 2002 and 2010. The simulated reflectances were calculated using climate Observing System Simulation Experiments (OSSEs), which used two Intergovernmental Panel on Climate Change AR4 scenarios (constant CO2 and A2 emission) to drive Moderate Resolution Atmospheric Transmission simulations. Principal component (PC) spectral shapes and time series exhibited evidence of physical variables including cloud reflectance, vegetation and desert albedo, and water vapor absorption. Comparing the temporal variability of the OSSE-simulated and SCIAMACHY-measured hyperspectral reflectance showed that their Intertropical Convergence Zone-like Southern Hemisphere (SH) tropical PC1 ocean time series had a 90◦ phase difference. The observed and simulated PC intersection quantified their similarity and directly compared their temporal variability. The intersection showed that despite the similar spectral variability, the temporal variability of the dominant PCs differed as in, for example, the 90◦ phase difference between the SH tropical intersection PC1s. Principal component analysis of OSSE reflectance demonstrated that the spectral and centennial variability of the two cases differed. The A2 PC time series, unlike the constant CO2 time series, exhibited centennial secular trends. Singular spectrum analysis isolated the A2 secular trends. The A2 OSSE PC1 and PC4 secular trends matched those in aerosol optical depth and total column precipitable water, respectively. This illustrates that time series of hyperspectral reflectance may be used to identify and attribute secular climate trends with a sufficiently long measurement record and high instrument accuracy. © 2014. American Geophysical Union. All Rights Reserved."
"56369737200;56173394600;6507260843;7003933929;35567619000;","Observations of a stratospheric aerosol veil from a tropical volcanic eruption in December 1808: Is this the Unknown ∼ 1809 eruption?",2014,"10.5194/cp-10-1707-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907395020&doi=10.5194%2fcp-10-1707-2014&partnerID=40&md5=4ce962465a703e13687e969553f12b7f","The Unknown eruption of 1808/1809 was the second most explosive SO2-rich volcanic eruption in the last two centuries, eclipsed only by the cataclysmic VEI 7 Tambora eruption in April 1815. However, no eyewitness accounts of the event, and therefore its location, or the atmospheric optical effects associated with its aerosols have been documented from historical records. Here we report on two meteorological observations dating from the end of 1808 that describe phenomena we attribute to volcanic-induced atmospheric effects caused by the Unknown eruption. The observations were made by two highly respected Latin American scientists. The first, Francisco José de Caldas, describes a stratospheric aerosol haze, a ""transparent cloud that obstructs the sun's brilliance"", that was visible over the city of Bogotá, Colombia, from 11 December 1808 to at least mid-February 1809. The second, made by physician José Hipólito Unanue in Lima, Peru, describes sunset after-glows (akin to well-documented examples known to be caused by stratospheric volcanic aerosols) from mid-December 1808 to February 1809. These two accounts provide direct evidence of a persistent stratospheric aerosol veil that spanned at least 2600 km into both Northern and Southern Hemispheres and establish that the source was a tropical volcano. Moreover, these observations confirm that the Unknown eruption, previously identified and tentatively assigned to February 1809 (±4 months) from analysis of ice core sulfate records, occurred in late November or early December 1808 (4 December 1808 ±7 days). This date has important implications for the associated hemispheric climate impacts and temporal pattern of aerosol dispersal. © Author(s) 2014. CC Attribution 3.0 License."
"55620143100;7004715270;6603385031;26022467200;9332706900;7202865036;57211681908;35503801600;7005848261;7005968859;","Characteristics of atmospheric ice nucleating particles associated with biomass burning in the US: Prescribed burns and wildfires",2014,"10.1002/2014JD021980","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214760&doi=10.1002%2f2014JD021980&partnerID=40&md5=5778c9b19f4185ec60779b01345bad30","An improved understanding of atmospheric ice nucleating particles (INP), including sources and atmospheric abundance, is needed to advance our understanding of aerosol-cloud-climate interactions. This study examines diverse biomass burning events to better constrain our understanding of how fires impact populations of INP. Sampling of prescribed burns and wildfires in Colorado and Georgia, U.S.A., revealed that biomass burning leads to the release of particles that are active as condensation/immersion freezing INP at temperatures from 32 to 12°C. During prescribed burning of wiregrass, up to 64% of INP collected during smoke-impacted periods were identified as soot particles via electron microscopy analyses. Other carbonaceous types and mineral-like particles dominated INP collected during wildfires of ponderosa pine forest in Colorado. Total measured nINP and the excess nINP associated with smoke-impacted periods were higher during two wildfires compared to the prescribed burns. Interferences from non-smoke sources of INP, including long-range transported mineral dust and local contributions of soils and plant materials lofted from the wildfires themselves, presented challenges in using the observations to develop a smoke-specific nINP parameterization. Nevertheless, these field observations suggest that biomass burning may serve as an important source of INP on a regional scale, particularly during time periods that lack other robust sources of INP such as long-range transported mineral dust. © 2014. American Geophysical Union. All Rights Reserved."
"16444006500;55636317280;7006235542;6701802669;","Downslope föhn winds over the antarctic peninsula and their effect on the larsen ice shelves",2014,"10.5194/acp-14-9481-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907190395&doi=10.5194%2facp-14-9481-2014&partnerID=40&md5=4b7ef2693e6b23fa2ff17710ccb5c54a","Mesoscale model simulations are presented of a westerly föhn event over the Antarctic Peninsula mountain ridge and onto the Larsen C ice shelf, just south of the recently collapsed Larsen B ice shelf. Aircraft observations showed the presence of föhn jets descending near the ice shelf surface with maximum wind speeds at 250-350 m in height. Surface flux measurements suggested that melting was occurring. Simulated profiles of wind speed, temperature and wind direction were very similar to the observations. However, the good match only occurred at a model time corresponding to ∼9 h before the aircraft observations were made since the model föhn jets died down after this. This was despite the fact that the model was nudged towards analysis for heights greater than ∼1.15 km above the surface. <br><br> Timing issues aside, the otherwise good comparison between the model and observations gave confidence that the model flow structure was similar to that in reality. Details of the model jet structure are explored and discussed and are found to have ramifications for the placement of automatic weather station (AWS) stations on the ice shelf in order to detect föhn flow. Cross sections of the flow are also examined and were found to compare well to the aircraft measurements. Gravity wave breaking above the mountain crest likely created a∼situation similar to hydraulic flow and allowed föhn flow and ice shelf surface warming to occur despite strong upwind blocking, which in previous studies of this region has generally not been considered. Our results therefore suggest that reduced upwind blocking, due to wind speed increases or stability decreases, might not result in an increased likelihood of föhn events over the Antarctic Peninsula, as previously suggested. <br><br> The surface energy budget of the model during the melting periods showed that the net downwelling short-wave surface flux was the largest contributor to the melting energy, indicating that the cloud clearing effect of föhn events is likely to be the most important factor for increased melting relative to non-föhn days. The results also indicate that the warmth of the föhn jets through sensible heat flux (""SH"") may not be critical in causing melting beyond boundary layer stabilisation effects (which may help to prevent cloud cover and suppress loss of heat by convection) and are actually cancelled by latent heat flux (""LH"") effects (snow ablation). It was found that ground heat flux (""GRD"") was likely to be an important factor when considering the changing surface energy budget for the southern regions of the ice shelf as the climate warms. © 2014 Author(s)."
"7404587604;8229909100;","Diurnal variation in the initiation of rainfall over the Indian subcontinent during two different monsoon seasons of 2008 and 2009",2014,"10.1007/s00704-013-1006-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84951046120&doi=10.1007%2fs00704-013-1006-x&partnerID=40&md5=81a01572417c8ae6cd73dbb10369d467","In the present study, the diurnal variations in the time of initiation of rainfall, during two contrasting monsoon seasons of 2008 (below normal) and 2009 (normal) over the Indian subcontinent and surrounding oceanic areas has been analyzed. Harmonic analysis was used to detect the spatial variation of the diurnal cycle of the time of initiation of rainfall, as obtained at half-hourly intervals from the Kalpana 1 satellite. In general, the diurnal cycle in the time of initiation is strongest in regions where convective clouds are predominant, while it is weaker in regions where the clouds are predominantly stratiform with long-lived medium to high cloud cover. In the interior of the subcontinent, the time of maximum mainly occurred in the afternoon to evening hours, with a distinct southeast to northwest gradation. Substantial spatial variations were detected in the diurnal patterns between a normal and below normal monsoon years. Spatially, rainfall is initiated later in 2009 compared to 2008 over most of the interior of the Indian subcontinent. The most distinct difference was observed over the core monsoon region in central India, where the diurnal patterns were stronger in 2009 compared to 2008. On the other hand, over the oceans surrounding the Indian subcontinent, the initiation times are generally earlier in 2009. © Springer-Verlag Wien 2013."
"24823024400;6506887943;55832671000;23017945100;","Variability of the mixed phase in the Arctic with a focus on the Svalbard region: A study based on spaceborne active remote sensing",2014,"10.5194/acpd-14-23453-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042902250&doi=10.5194%2facpd-14-23453-2014&partnerID=40&md5=4edd0fac61e2a8cd8aea1c25124eb11e","The Arctic region is known to be very sensitive to climate change. Clouds and in particular mixed phase clouds (MPC) remain one of the greatest sources of uncertainties in the modeling of the Arctic response to climate change due to an inaccurate representation of their variability and their quantification. In this study, we present a characterization of the vertical, spatial and seasonal variability of Arctic clouds and MPC over the whole Arctic region based on satellite active remote sensing observations. MPC properties in the region of Svalbard archipelago (78° N, 15° E) are also investigated. The occurrence frequency of clouds and MPC are determined from CALIPSO/CLOUDSAT measurements processed with the DARDAR retrieval algorithm which allows for a reliable cloud thermodynamic phase classification (warm liquid, supercooled liquid, ice, mixing of ice and supercooled liquid). Significant differences are observed between MPC variability over the whole Arctic region and over the Svalbard region. Results show that MPC are ubiquitous all along the year, with a minimum occurrence of 30% in winter and 50% during the rest of the year, in average over the whole Arctic. Over the Svalbard region, MPC occurrence is more constant with time with larger values (55 %) compared to the average observed in the Arctic. MPC are especially located at low altitudes, below 3000 m, where their frequency of occurrence reaches 90 %, in particular during winter, spring and autumn. Moreover, results highlight that MPC statistically prevail over sea. The temporal and spatial distribution of MPC over the Svalbard region seems to be linked to the contribution of moister air and warmer water from the North Atlantic Ocean which contribute to the initiation of the liquid water phase. Over the whole Arctic, and particularly in western regions, the increase of MPC occurrence from spring to autumn could be connected to the sea ice melting. During this period, the open water transports a part of the warm water from the Svalbard region to the rest of the Arctic region. This facilitates the vertical transfer of moisture and thus the persistence of the liquid phase. A particular attention is also paid on the measurements uncertainties and how they could affect our results. © 2014 Author(s)."
"23134745300;7003597653;55788845400;35794572100;6507136276;55191507700;7004101496;55669656100;7202746102;","Evaluation of IASI-derived dust aerosol characteristics over the tropical belt",2014,"10.5194/acp-14-9343-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907280023&doi=10.5194%2facp-14-9343-2014&partnerID=40&md5=74280551a1c6d7adb066054815358183","IASI (Infrared Atmospheric Sounder Interferometer)-derived monthly mean infrared (10 Î1/4m) dust aerosol optical depth (AOD) and altitude are evaluated against ground-based Aerosol RObotic NETwork of sun photometers (AERONET) measurements of the 500 nm coarse-mode AOD and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) measurements of altitude at 38 AERONET sites (sea and land) within the tropical belt (30° N-30° S). The period covered extends from July 2007 to June 2013. The evaluation goes through the analysis of Taylor diagrams and box-and-whiskers plots, separating situations over oceanic regions and over land. For the AOD, such an evaluation raises the problem of the difference between the two spectral domains used: infrared for IASI and visible for AERONET. Consequently, the two measurements do not share the same metrics. For that reason, AERONET coarse-mode AOD is first ""translated"" into IASI-equivalent infrared AOD. This is done by the determination, site by site, of an infrared to visible AOD ratio. Because translating visible coarse-mode AOD into infrared AOD requires accurate knowledge of variables, such as the infrared refractive index or the particle size distribution, quantifying the bias between these two sources of AOD is not straightforward. This problem is detailed in this paper, in particular in Appendix A. For the sites over oceanic regions, the overall AOD temporal correlation comes to 0.86 for 786 items (IASI and AERONET monthly mean bins). The overall normalized standard deviation (i.e. ratio of the standard deviation of the test data (IASI) to that of the reference data (AERONET)) is 0.93, close to the desired value of 1. Over land, essentially desert, correlation is 0.74 for 619 items and the normalized standard deviation is 0.86. This slight but significant degradation over land most probably results from the greater complexity of the surface (heterogeneity, elevation) and, to a lesser extent, to the episodic presence of dust within the boundary layer (particularly for sites close to active sources) to which IASI, as any thermal infrared sounder, is poorly sensitive, unlike AERONET. Site by site, disparities appear that are principally due to either the insufficient number of AERONET observations throughout the period considered, to the complexity of the location leading to the mixing of several aerosol types (in the case of the Persian Gulf, for example), to surface heterogeneities (elevation, emissivity, etc.), or to the use of a single aerosol model (called ""MITR""). Results using another aerosol model, with a different refractive index, are presented and discussed. Concerning altitude over oceanic regions, correlation is 0.70 for 853 items and the normalized standard deviation is 0.92. A systematic bias of 0.4 km (IASI-CALIOP) is observed, with a standard deviation of 0.48 km. This result is satisfactory, considering the important differences between the two instruments (space-time coverage, definition of the altitude). Altitude results over land, essentially over deserts, are not satisfactory for a majority of sites. The smaller sensitivity of IASI to altitude compared to its sensitivity to AOD, added to the difficulties met for the determination of the AOD over land (surface heterogeneities), explain this result. Work is in progress to solve this difficulty. We conclude that the present results demonstrate the usefulness of IASI data, which are planned to cover a long period of time, as an additional constraint to a better knowledge of the impact of aerosols on the climate system."
"55672593500;12801836100;7201826462;55915206300;6506606807;7003711370;7202154370;6603631763;36739372100;6506286986;7801448355;26635422600;26659897600;9233045100;7006783796;6506234624;15726335100;6603043158;57208765879;7102122493;24538154100;","Remote sensing of cloud top pressure/height from SEVIRI: Analysis of ten current retrieval algorithms",2014,"10.5194/amt-7-2839-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907009887&doi=10.5194%2famt-7-2839-2014&partnerID=40&md5=99d5798075110d9ddecb811498637167","The role of clouds remains the largest uncertainty in climate projections. They influence solar and thermal radiative transfer and the earth's water cycle. Therefore, there is an urgent need for accurate cloud observations to validate climate models and to monitor climate change. Passive satellite imagers measuring radiation at visible to thermal infrared (IR) wavelengths provide a wealth of information on cloud properties. Among others, the cloud top height (CTH) - a crucial parameter to estimate the thermal cloud radiative forcing - can be retrieved. In this paper we investigate the skill of ten current retrieval algorithms to estimate the CTH using observations from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard Meteosat Second Generation (MSG). In the first part we compare ten SEVIRI cloud top pressure (CTP) data sets with each other. The SEVIRI algorithms catch the latitudinal variation of the CTP in a similar way. The agreement is better in the extratropics than in the tropics. In the tropics multi-layer clouds and thin cirrus layers complicate the CTP retrieval, whereas a good agreement among the algorithms is found for trade wind cumulus, marine stratocumulus and the optically thick cores of the deep convective system. <br><br> In the second part of the paper the SEVIRI retrievals are compared to CTH observations from the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR) instruments. It is important to note that the different measurement techniques cause differences in the retrieved CTH data. SEVIRI measures a radiatively effective CTH, while the CTH of the active instruments is derived from the return time of the emitted radar or lidar signal. Therefore, some systematic differences are expected. On average the CTHs detected by the SEVIRI algorithms are 1.0 to 2.5 km lower than CALIOP observations, and the correlation coefficients between the SEVIRI and the CALIOP data sets range between 0.77 and 0.90. The average CTHs derived by the SEVIRI algorithms are closer to the CPR measurements than to CALIOP measurements. The biases between SEVIRI and CPR retrievals range from -0.8 km to 0.6 km. The correlation coefficients of CPR and SEVIRI observations vary between 0.82 and 0.89. To discuss the origin of the CTH deviation, we investigate three cloud categories: optically thin and thick single layer as well as multi-layer clouds. For optically thick clouds the correlation coefficients between the SEVIRI and the reference data sets are usually above 0.95. For optically thin single layer clouds the correlation coefficients are still above 0.92. For this cloud category the SEVIRI algorithms yield CTHs that are lower than CALIOP and similar to CPR observations. Most challenging are the multi-layer clouds, where the correlation coefficients are for most algorithms between 0.6 and 0.8. Finally, we evaluate the performance of the SEVIRI retrievals for boundary layer clouds. While the CTH retrieval for this cloud type is relatively accurate, there are still considerable differences between the algorithms. These are related to the uncertainties and limited vertical resolution of the assumed temperature profiles in combination with the presence of temperature inversions, which lead to ambiguities in the CTH retrieval. Alternative approaches for the CTH retrieval of low clouds are discussed."
"56612517400;36538539800;","Improvement and further development in CESM/CAM5: Gas-phase chemistry and inorganic aerosol treatments",2014,"10.5194/acp-14-9171-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907010428&doi=10.5194%2facp-14-9171-2014&partnerID=40&md5=072ef2a52fb4f0bf958efea72c77f89f","Gas-phase chemistry and subsequent gas-to-particle conversion processes such as new particle formation, condensation, and thermodynamic partitioning have large impacts on air quality, climate, and public health through influencing the amounts and distributions of gaseous precursors and secondary aerosols. Their roles in global air quality and climate are examined in this work using the Community Earth System Model version 1.0.5 (CESM1.0.5) with the Community Atmosphere Model version 5.1 (CAM5.1) (referred to as CESM1.0.5/CAM5.1). CAM5.1 includes a simple chemistry that is coupled with a 7-mode prognostic Modal Aerosol Model (MAM7). MAM7 includes classical homogenous nucleation (binary and ternary) and activation nucleation (empirical first-order power law) parameterizations, and a highly simplified inorganic aerosol thermodynamics treatment that only simulates particulate-phase sulfate and ammonium. In this work, a new gas-phase chemistry mechanism based on the 2005 Carbon Bond Mechanism for Global Extension (CB05-GE) and several advanced inorganic aerosol treatments for condensation of volatile species, ion-mediated nucleation (IMN), and explicit inorganic aerosol thermodynamics for sulfate, ammonium, nitrate, sodium, and chloride have been incorporated into CESM/CAM5.1-MAM7. Compared to the simple gas-phase chemistry, CB05-GE can predict many more gaseous species, and thus could improve model performance for PM2.5, PM10, PM components, and some PM gaseous precursors such as SO2 and NH3 in several regions as well as aerosol optical depth (AOD) and cloud properties (e.g., cloud fraction (CF), cloud droplet number concentration (CDNC), and shortwave cloud forcing, SWCF) on the global scale. The modified condensation and aqueous-phase chemistry could further improve the prediction of additional variables such as HNO3, NO2, and O3 in some regions, and new particle formation rate (&lt;i&gt;J&lt;/i&gt;) and AOD on the global scale. IMN can improve the prediction of secondary PM2.5 components, PM2.5, and PM10 over Europe as well as AOD and CDNC on the global scale. The explicit inorganic aerosol thermodynamics using the ISORROPIA II model improves the prediction of all major PM2.5 components and their gaseous precursors in some regions as well as downwelling shortwave radiation, SWCF, and cloud condensation nuclei at a supersaturation of 0.5% on the global scale. For simulations of 2001-2005 with all the modified and new treatments, the improved model predicts that on global average, SWCF increases by 2.7 W m-2, reducing the normalized mean bias (NMB) of SWCF from -5.4 to 1.2%. Uncertainties in emissions can largely explain the inaccurate prediction of precursor gases (e.g., SO2, NH3, and NO) and primary aerosols (e.g., black carbon and primary organic matter). Additional factors leading to the discrepancies between model predictions and observations include assumptions associated with equilibrium partitioning for fine particles assumed in ISORROPIA II, irreversible gas/particle mass transfer treatment for coarse particles, uncertainties in model treatments such as dust emissions, secondary organic aerosol formation, multi-phase chemistry, cloud microphysics, aerosol-cloud interaction, dry and wet deposition, and model parameters (e.g., accommodation coefficients and prefactors of the nucleation power law) as well as uncertainties in model configuration such as the use of a coarse-grid resolution."
"8942525300;7004063850;","The contribution of fungal spores and bacteria to regional and global aerosol number and ice nucleation immersion freezing rates",2014,"10.5194/acp-14-9051-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906872160&doi=10.5194%2facp-14-9051-2014&partnerID=40&md5=31087ada56eb895027ea607691f6a638","Primary biological aerosol particles (PBAPs) may play an important role in aerosol-climate interactions, in particular by affecting ice formation in mixed phase clouds. However, the role of PBAPs is poorly understood because the sources and distribution of PBAPs in the atmosphere are not well quantified. Here we include emissions of fungal spores and bacteria in a global aerosol microphysics model and explore their contribution to concentrations of supermicron particle number, cloud condensation nuclei (CCN) and immersion freezing rates. Simulated surface annual mean concentrations of fungal spores are ∼ 2.5 × 104 mg-3 over continental midlatitudes and 1 × 105 mg-3 over tropical forests. Simulated surface concentrations of bacteria are 2.5 × 104 mg-3 over most continental regions and 5 × 104 mg-3 over grasslands of central Asia and North America. These simulated surface number concentrations of fungal spores and bacteria are broadly in agreement with the limited available observations. We find that fungal spores and bacteria contribute 8 and 5% respectively to simulated continental surface mean supermicron number concentrations, but have very limited impact on CCN concentrations, altering regional concentrations by less than 1%. In agreement with previous global modelling studies, we find that fungal spores and bacteria contribute very little (3 × 10g-3%, even when we assume upper limits for ice nucleation activity) to global average immersion freezing ice nucleation rates, which are dominated by soot and dust. However, at lower altitudes (400 to 600 hPa), where warmer temperatures mean that soot and dust may not nucleate ice, we find that PBAP controls the immersion freezing ice nucleation rate. This demonstrates that PBAPs can be of regional importance for IN formation, in agreement with case study observations."
"55885039800;35887706900;20435752700;7004174939;","On the signature of the cirrus twilight zone",2014,"10.1088/1748-9326/9/9/094010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907706560&doi=10.1088%2f1748-9326%2f9%2f9%2f094010&partnerID=40&md5=8abdee22a699f26cb8d15514dbae0377","Cirrus clouds are known to play a key role in the climate system, but their overall effect on Earth's radiation budget is not yet fully quantified. The uncertainties are, in part, due to ambiguities in cirrus extent or coverage. Here we show that despite careful filtering of cloudy pixels, cirrus clouds have a clear statistical signature. This signature can be estimated by the proximity to detectable cirrus clouds. Such a residual signature can affect retrievals that rely on a cloud-free atmosphere, such as aerosol optical depth (AOD) or sea surface temperature. Analyzing MODIS raw-data and products, we show a clear increase in the reflectance when approaching detectable cirrus clouds. We estimated a mean increase in AOD of 0.03 ± 0.01 and a decrease in the Angstrom-exponent of -0.22 ± 0.20 in the first kilometer around detectable cirrus. The effect decays tenfold at a typical distance of 5.5 ± 1.8 km. Such trends confirm the contribution of large particles that are likely to be ice crystals to the so-called cloud-free atmosphere near detectable cirrus clouds. © 2014 IOP Publishing Ltd."
"35461255500;56127300900;7007162501;7005755464;8758100000;17433787100;55950593000;55889182700;11339750700;22633932300;6508032361;56015132600;23967608200;22934624000;56370907100;8871497700;6506323836;7102915729;9274551500;6701853225;6603488837;6701574983;7006593624;26643041500;7006712143;7003984086;7004296127;55682775100;23995325300;6701514223;7102513363;23980457200;6602414538;6507755223;7006599647;57202562775;57193897383;57207261095;","Finnish centre of excellence in physics, chemistry, biology and meteorology of atmospheric composition and climate change: Summary and outlook",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906982708&partnerID=40&md5=183ac75ad31b995f87e5c8080e3023e5","The Finnish Centre of Excellence (FCoE) in “Physics, Chemistry, Biology and Meteorology of Atmospheric Composition and Climate Change” (2008–2013) completed its research activity at the end of 2013. The FCoE research was originally focused on enhanced process-level understanding of various couplings between atmospheric CO2concentrations, photosynthesis, biogenic volatile organic compounds (BVOC), aerosol particles and clouds. During the FCoE period, the scientific scope moved gradually towards the so-called all-scale concept. In this paper we summarize its main scientific achievements, and give an outlook for future scientific activities and focus. © 2014 Finnish Environment Institute. All rights reserved."
"56421304300;55994084500;15073608800;","Sea ice surface temperature estimation using MODIS and AMSR-E data within a guided variational model along the Labrador coast",2014,"10.1109/JSTARS.2013.2292795","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910079010&doi=10.1109%2fJSTARS.2013.2292795&partnerID=40&md5=82c3db9c85e7dae14e1514118cd60ddb","In this study, a new method, entitled as the multi-modality guided variational (MGV) method, is proposed, in which the data from a passive microwave sensor is used jointly with the data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to estimate the sea ice surface temperature (IST). The method augments existing sea IST values from the MODIS IST map, while filling in areas in the MODIS image that may be sparsely sampled due to the cloud cover, or due to increased spacing between the pixels at the swath edges. The former issue is particularly problematic in the marginal ice zone, where the atmospheric conditions often lead to persistent cloud cover. The sea IST is of interest because it can be used to estimate the sea ice thickness, an important parameter for shipping, climate change, and weather forecasting applications. The impact of the MGV method is checked through a comparison between the sea ice thickness calculated using the swath surface temperature and that calculated using the surface temperature from MGV. Using the operational ice charts as a guideline, it is found that the sea ice thickness values calculated using the MGV surface temperature are realistic, and there is a 16% increase in the number of sea ice thickness data points available when the MGV method is used as compared to when the swath data are used. © 2008-2012 IEEE."
"55636624100;6603419302;6603056511;36637396200;6602334854;18134711700;26426079600;8421669500;6603712978;6603070692;55789555200;55921121100;55961872100;23099630400;36990114300;54583993900;36614378300;6507614547;7004485925;6701793410;6602183432;","Ground-based measurements of the solar diameter during the rising phase of solar cycle 24",2014,"10.1051/0004-6361/201423598","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907270628&doi=10.1051%2f0004-6361%2f201423598&partnerID=40&md5=03276c3847b6f72e156577bce741aa06","Context. For the past thirty years, modern ground-based time-series of the solar radius have shown different apparent variations according to different instruments. The origins of these variations may result from the observer, the instrument, the atmosphere, or the Sun. Solar radius measurements have been made for a very long time and in different ways. Yet we see inconsistencies in the measurements. Numerous studies of solar radius variation appear in the literature, but with conflicting results. These measurement differences are certainly related to instrumental effects or atmospheric effects. Use of different methods (determination of the solar radius), instruments, and effects of Earth's atmosphere could explain the lack of consistency on the past measurements. A survey of the solar radius has been initiated in 1975 by Francis Laclare, at the Calern site of the Observatoire de la Côte d'Azur (OCA). Several efforts are currently made from space missions to obtain accurate solar astrometric measurements, for example, to probe the long-term variations of solar radius, their link with solar irradiance variations, and their influence on the Earth climate. Aims. The Picard program includes a ground-based observatory consisting of different instruments based at the Calern site (OCA, France). This set of instruments has been named ""Picard Sol"" and consists of a Ritchey-Chrétien telescope providing full-disk images of the Sun in five narrow-wavelength bandpasses (centered on 393.37, 535.7, 607.1, 782.2, and 1025.0 nm), a Sun-photometer that measures the properties of atmospheric aerosol, a pyranometer for estimating a global sky-quality index, a wide-field camera that detects the location of clouds, and a generalized daytime seeing monitor allowing us to measure the spatio-temporal parameters of the local turbulence. Picard Sol is meant to perpetuate valuable historical series of the solar radius and to initiate new time-series, in particular during solar cycle 24. Methods. We defined the solar radius by the inflection-point position of the solar-limb profiles taken at different angular positions of the image. Our results were corrected for the effects of refraction and turbulence by numerical methods. Results. From a dataset of more than 20000 observations carried out between 2011 and 2013, we find a solar radius of 959.78 ± 0.19 arcsec (696 113 ± 138 km) at 535.7 nm after making all necessary corrections. For the other wavelengths in the solar continuum, we derive very similar results. The solar radius observed with the Solar Diameter Imager and Surface Mapper II during the period 2011-2013 shows variations shorter than 50 milli-arcsec that are out of phase with solar activity. © 2014 ESO."
"9249239700;7102425008;7003278104;7202899330;8560603600;","Characterizing the radiative impacts of precipitating snow in the ECMWF Integrated Forecast System global model",2014,"10.1002/2014JD021450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937517861&doi=10.1002%2f2014JD021450&partnerID=40&md5=776cdc5a62e4a0ba232c95f797a2bc8b","Global weather and climate models often exclude the effects of precipitating hydrometeors and convective core mass on radiative fluxes. In particular, many models split the ice phase into separate “cloud ice” and “snow” categories representing the smaller and larger ice particles, respectively; a separation that is generally not well defined in observations. A version of the European Centre for Medium-Range Weather Forecasts (ECMWF) global numerical weather prediction model which includes the radiative effects of cloud liquid, cloud ice, and precipitating snow is used to investigate the impact of including and excluding the radiative effects of the precipitating snow category. The results show that exclusion of precipitating snow in the radiation calculations leads to differences in the shortwave and longwave radiative fluxes of 5–15 W m−2 in strongly precipitating and convective areas. These differences are of the same order of magnitude as the systematic errors in the model compared to satellite observations. Corresponding biases in the radiative heating profiles are on the order of 0.15 K d−1. The results imply that precipitating snow should be included in the radiative calculations in all weather and climate models in the context of improving model fidelity and reducing compensating errors. ©2014. American Geophysical Union. All Rights Reserved."
"55635713200;7003548068;55450672000;7402480218;","Comparing the cloud vertical structure derived from several methods based on radiosonde profiles and ground-based remote sensing measurements",2014,"10.5194/amt-7-2757-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921984903&doi=10.5194%2famt-7-2757-2014&partnerID=40&md5=4f6e05bea562136fbbbf4f79ad0150e9","The cloud vertical distribution and especially the cloud base height, which is linked to cloud type, are important characteristics in order to describe the impact of clouds on climate. In this work, several methods for estimating the cloud vertical structure (CVS) based on atmospheric sounding profiles are compared, considering the number and position of cloud layers, with a ground-based system that is taken as a reference: the Active Remote Sensing of Clouds (ARSCL). All methods establish some conditions on the relative humidity, and differ in the use of other variables, the thresholds applied, or the vertical resolution of the profile. In this study, these methods are applied to 193 radiosonde profiles acquired at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site during all seasons of the year 2009 and endorsed by Geostationary Operational Environmental Satellite (GOES) images, to confirm that the cloudiness conditions are homogeneous enough across their trajectory. The perfect agreement (i.e., when the whole CVS is estimated correctly) for the methods ranges between 26 and 64%; the methods show additional approximate agreement (i.e., when at least one cloud layer is assessed correctly) from 15 to 41%. Further tests and improvements are applied to one of these methods. In addition, we attempt to make this method suitable for low-resolution vertical profiles, like those from the outputs of reanalysis methods or from the World Meteorological Organization's (WMO) Global Telecommunication System. The perfect agreement, even when using low-resolution profiles, can be improved by up to 67% (plus 25% of the approximate agreement) if the thresholds for a moist layer to become a cloud layer are modified to minimize false negatives with the current data set, thus improving overall agreement. © Author(s) 2014."
"56384704800;57202299549;55717074000;7003666669;55519994900;15755995900;7006705919;23095483400;57203053317;","Technical note: On the use of nudging for aerosol-climate model intercomparison studies",2014,"10.5194/acp-14-8631-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906657160&doi=10.5194%2facp-14-8631-2014&partnerID=40&md5=b1b10d7c8b595b25f2b26a170c014dd4","Nudging as an assimilation technique has seen increased use in recent years in the development and evaluation of climate models. Constraining the simulated wind and temperature fields using global weather reanalysis facilitates more straightforward comparison between simulation and observation, and reduces uncertainties associated with natural variabilities of the large-scale circulation. On the other hand, the forcing introduced by nudging can be strong enough to change the basic characteristics of the model climate. In the paper we show that for the Community Atmosphere Model version 5 (CAM5), due to the systematic temperature bias in the standard model and the sensitivity of simulated ice formation to anthropogenic aerosol concentration, nudging towards reanalysis results in substantial reductions in the ice cloud amount and the impact of anthropogenic aerosols on long-wave cloud forcing. In order to reduce discrepancies between the nudged and unconstrained simulations, and meanwhile take the advantages of nudging, two alternative experimentation methods are evaluated. The first one constrains only the horizontal winds. The second method nudges both winds and temperature, but replaces the long-term climatology of the reanalysis by that of the model. Results show that both methods lead to substantially improved agreement with the free-running model in terms of the top-of-atmosphere radiation budget and cloud ice amount. The wind-only nudging is more convenient to apply, and provides higher correlations of the wind fields, geopotential height and specific humidity between simulation and reanalysis. Results from both CAM5 and a second aerosol-climate model ECHAM6-HAM2 also indicate that compared to the wind-and-temperature nudging, constraining only winds leads to better agreement with the free-running model in terms of the estimated shortwave cloud forcing and the simulated convective activities. This suggests nudging the horizontal winds but not temperature is a good strategy for the investigation of aerosol indirect effects since it provides well-constrained meteorology without strongly perturbing the model's mean climate. © 2014 Author(s)."
"36088530800;36052878000;24460392200;7102425008;25031430500;6701511324;26645289600;","Diagnosing the average spatio-temporal impact of convective systems-part 2:A model intercomparison using satellite data",2014,"10.5194/acp-14-8701-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906708306&doi=10.5194%2facp-14-8701-2014&partnerID=40&md5=344b2dd9b1f8cdbbd75da7d1f03550e8","The representation of the effect of tropical deep convective (DC) systems on upper-tropospheric moist processes and outgoing longwave radiation is evaluated in the EC-Earth3, ECHAM6, and CAM5 (Community Atmosphere Model) climate models using satellite-retrieved data. A composite technique is applied to thousands of deep convective systems that are identified using local rain rate maxima in order to focus on the temporal evolution of the deep convective processes in the model and satellite-retrieved data. The models tend to over-predict the occurrence of rain rates that are less than 3 mm 1 compared to Tropical Rainfall Measurement Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA). While the diurnal distribution of oceanic rain rate maxima in the models is similar to the satellite-retrieved data, the land-based maxima are out of phase. Despite having a larger climatological mean upper-tropospheric relative humidity, models closely capture the satellite-derived moistening of the upper troposphere following the peak rain rate in the deep convective systems. Simulated cloud fractions near the tropopause are larger than in the satellite data, but the ice water contents are smaller compared with the satellite-retrieved ice data. The models capture the evolution of ocean-based deep convective systems fairly well, but the land-based systems show significant discrepancies. Over land, the diurnal cycle of rain is too intense, with deep convective systems occurring at the same position on subsequent days, while the satellite-retrieved data vary more in timing and geographical location. Finally, simulated outgoing longwave radiation anomalies associated with deep convection are in reasonable agreement with the satellite data, as well as with each other. Given the fact that there are strong disagreements with, for example, cloud ice water content, and cloud fraction, between the models, this study supports the hypothesis that such agreement with satellite-retrieved data is achieved in the three models due to different representations of deep convection processes and compensating errors. © 2014 Author(s)."
"13405658600;36969949500;55241984000;57203084853;7003430284;","New-particle formation, growth and climate-relevant particle production in egbert, canada: Analysis from 1 year of size-distribution observations",2014,"10.5194/acp-14-8647-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906706168&doi=10.5194%2facp-14-8647-2014&partnerID=40&md5=4f41eaa9bbf0715f3e87c06031088d8d","Aerosol particle nucleation, or new-particle formation, is the dominant contributor to particle number in the atmosphere. However, these particles must grow through condensation of low-volatility vapors without coagulating with the larger, preexisting particles in order to reach climate-relevant sizes (diameters larger than 50-100 nm), where the particles may affect clouds and radiation. In this paper, we use 1 year of size-distribution measurements from Egbert, Ontario, Canada to calculate the frequency of regional-scale new-particle-formation events, new-particle-formation rates, growth rates and the fraction of new particles that survive to reach climate-relevant sizes. Regional-scale new-particle-formation events occur on 14-31% of the days (depending on the stringency of the classification criteria), with event frequency peaking in the spring and fall. New-particle-formation rates and growth rates are similar to those measured at other midlatitude continental sites. We calculate that roughly half of the climate-relevant particles (with diameters larger than 50-100 nm) at Egbert are formed through new-particle-formation events. With the addition of meteorological and SO2 measurements, we find that new-particle formation at Egbert often occurs under synoptic conditions associated with high surface pressure and large-scale subsidence that cause sunny conditions and clean-air flow from the north and west. However, new-particle formation also occurs when air flows from the polluted regions to the south and southwest of Egbert. The new-particle- formation rates tend to be faster during events under the polluted south/southwest flow conditions. © 2014 Author(s)."
"55806832000;22953153500;6604063209;55801194500;55683314900;57218344117;7006089413;55942083800;7006204597;","Ice nucleation by fungal spores from the classes agaricomycetes, ustilaginomycetes, and eurotiomycetes, and the effect on the atmospheric transport of these spores",2014,"10.5194/acp-14-8611-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906675409&doi=10.5194%2facp-14-8611-2014&partnerID=40&md5=394683aa8ee4c8a256cfa98cc0469d3b","We studied the ice nucleation properties of 12 different species of fungal spores chosen from three classes:Agaricomycetes, Ustilaginomycetes, and Eurotiomycetes.Agaricomycetes include many types of mushroom species and are widely distributed over the globe. Ustilaginomycetes are agricultural pathogens and have caused widespread damage to crops. Eurotiomycetes are found on all types of decaying material and include important human allergens. We focused on these classes because they are thought to be abundant in the atmosphere and because there is very little information on the ice nucleation ability of these classes of spores in the literature. All of the fungal spores investigated contained some fraction of spores that serve as ice nuclei at temperatures warmer than homogeneous freezing. The cumulative number of ice nuclei per spore was 0.001 at temperatures between-19 °C and-29 °C, 0.01 between-25.5 °C and-31 °C, and 0.1 between-26 °C and-31.5 °C. On average,the order of ice nucleating ability for these spores is Ustilaginomycetes Agaricomycetes'Eurotiomycetes. The freezing data also suggests that, at temperatures ranging from-20 °C to-25 °C, all of the fungal spores studied here are less efficient ice nuclei compared to Asian mineral dust on a per surface area basis. We used our new freezing results together with data in the literature to compare the freezing temperatures of spores from the phyla Basidiomycota and Ascomycota, which together make up 98% of known fungal species found on Earth. The data show that within both phyla (Ascomycota and Basidiomycota), there is a wide range of freezing properties, and also that the variation within a phylum is greater than the variation between the average freezing properties of the phyla. Using a global chemistry-climate transport model, we investigated whether ice nucleation on the studied spores, followed by precipitation, can influence the transport and global distributions of these spores in the atmosphere. Simulations suggest that inclusion of ice nucleation scavenging of these fungal spores in mixed-phase clouds can decrease the annual mean concentrations of fungal spores in near-surface air over the oceans and polar regions,and decrease annual mean concentrations in the upper troposphere. © 2014 Author(s)."
"9738329300;56372089100;7102314226;55332061900;","On the role of clouds in the fair weather part of the global electric circuit",2014,"10.5194/acp-14-8599-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906706167&doi=10.5194%2facp-14-8599-2014&partnerID=40&md5=afe80e1ef8b48d1d584127ed8d8aad49","Clouds in the fair weather return path of the global electric circuit (GEC) reduce conductivity because of the limited mobility of charge due to attachment to cloud water droplets, effectively leading to a loss of ions. A high-resolution GEC model, which numerically solves the current continuity equation in combination with Ohm's law, is used to show that return currents partially flow around clouds, with current divergence above the cloud and convergence below the cloud. An analysis of this effect is presented for various types of clouds, i.e. for different altitude extents and for different horizontal dimensions, finding that the effect is most pronounced for high clouds with a diameter below 100 km. Based on these results, a method to calculate column and global resistance is developed that can account for all cloud sizes and altitudes. The CESM1(WACCM) (Community Earth System Model-Whole Atmosphere Community Climate Model) as well as ISCCP (International Satellite Cloud Climatology Project) cloud data are used to calculate the effect of this phenomenon on global resistance. From CESM1(WACCM), it is found that when including clouds in the estimate of resistance the global resistance increases by up to 73%, depending on the parameters used. Using ISCCP cloud cover leads to an even larger increase, which is likely to be overestimated because of time averaging of cloud cover. Neglecting current divergence/convergence around small clouds overestimates global resistance by up to 20% whereas the method introduced by previous studies underestimates global resistance by up to 40%. For global GEC models, a conductivity parameterization is developed to account for the current divergence/convergence phenomenon around clouds. Conductivity simulations from CESM1(WACCM) using this parameterization are presented. © 2014 Author(s)."
"25624545600;56337203000;7102128820;7006146719;","The interdependence of continental warm cloud properties derived from unexploited solar background signals in ground-based lidar measurements",2014,"10.5194/acp-14-8389-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906545451&doi=10.5194%2facp-14-8389-2014&partnerID=40&md5=31dd7ced65ab9fe310fea245fa32187b","We have extensively analysed the interdependence between cloud optical depth, droplet effective radius, liquid water path (LWP) and geometric thickness for stratiform warm clouds using ground-based observations. In particular, this analysis uses cloud optical depths retrieved from untapped solar background signals that are previously unwanted and need to be removed in most lidar applications. Combining these new optical depth retrievals with radar and microwave observations at the Atmospheric Radiation Measurement (ARM) Climate Research Facility in Oklahoma during 2005-2007, we have found that LWP and geometric thickness increase and follow a power-law relationship with cloud optical depth regardless of the presence of drizzle; LWP and geometric thickness in drizzling clouds can be generally 20-40% and at least 10% higher than those in non-drizzling clouds, respectively. In contrast, droplet effective radius shows a negative correlation with optical depth in drizzling clouds and a positive correlation in non-drizzling clouds, where, for large optical depths, it asymptotes to 10 μm. This asymptotic behaviour in non-drizzling clouds is found in both the droplet effective radius and optical depth, making it possible to use simple thresholds of optical depth, droplet size, or a combination of these two variables for drizzle delineation. This paper demonstrates a new way to enhance ground-based cloud observations and drizzle delineations using existing lidar networks. © Author(s) 2014."
"56805240800;6701823396;55636317262;","Surface energy budget on Larsen and Wilkins ice shelves in the Antarctic Peninsula: Results based on reanalyses in 1989-2010",2014,"10.5194/tc-8-1519-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924962603&doi=10.5194%2ftc-8-1519-2014&partnerID=40&md5=bcbe6cbe2194a632daff8089e824f0b7","Ice shelves in the Antarctic Peninsula have significantly disintegrated during recent decades. To better understand the atmospheric contribution in the process, we have analysed the inter-annual variations in radiative and turbulent surface fluxes and weather conditions over Larsen C Ice Shelf (LCIS) and Wilkins Ice Shelf (WIS) in the Antarctic Peninsula in 1989-2010. Three atmospheric reanalyses were applied: ERA-Interim by ECMWF, Climate Forecast System Reanalysis (CFSR) by NCEP, and JRA-25/JCDAS by the Japan Meteorological Agency. In addition, in situ observations from an automatic weather station (AWS) on LCIS were applied, mainly for validation of the reanalyses. The AWS observations on LCIS did not show any significant temperature trend, and the reanalyses showed warming trends only over WIS: ERA-Interim in winter (0.23 °C yrĝ̂'1) and JRA-25/JCDAS in autumn (0.13 °C yrĝ̂'1). In LCIS from December through August and in WIS from March through August, the variations of surface net flux were partly explained by the combined effects of atmospheric pressure, wind and cloud fraction. The explained variance was much higher in LCIS (up to 80%) than in WIS (26-27%). Summer melting on LCIS varied between 11 and 58 cm water equivalent (w.e.), which is comparable to previous results. The mean amount of melt days per summer on LCIS was 69. The high values of melting in summer 2001-2002 presented in previous studies on the basis of simple calculations were not supported by our study. Instead, our calculations based on ERA-Interim yielded strongest melting in summer 1992-1993 on both ice shelves. On WIS the summer melting ranged between 10 and 23 cm w.e., and the peak values coincided with the largest disintegrations of the ice shelf. The amount of melt on WIS may, however, be underestimated by ERA-Interim, as previously published satellite observations suggest that it suffers from a significant bias over WIS. © Author(s) 2014."
"6603818654;7006577245;35794936300;35345729700;8388968100;57208121047;8657166100;","Transport of aerosol to the Arctic: Analysis of CALIOP and French aircraft data during the spring 2008 POLARCAT campaign",2014,"10.5194/acp-14-8235-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906247884&doi=10.5194%2facp-14-8235-2014&partnerID=40&md5=d243aa8e3897df30b6e9f095aa836bcd","Lidar and in situ observations performed during the Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, Climate, Chemistry, Aerosols and Transport (POLARCAT) campaign are reported here in terms of statistics to characterize aerosol properties over northern Europe using daily airborne measurements conducted between Svalbard and Scandinavia from 30 March to 11 April 2008. It is shown that during this period a rather large number of aerosol layers was observed in the troposphere, with a backscatter ratio at 532 nm of 1.2 (1.5 below 2 km, 1.2 between 5 and 7 km and a minimum in between). Their sources were identified using multispectral backscatter and depolarization airborne lidar measurements after careful calibration analysis. Transport analysis and comparisons between in situ and airborne lidar observations are also provided to assess the quality of this identification. Comparison with level 1 backscatter observations of the spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) were carried out to adjust CALIOP multispectral observations to airborne observations on a statistical basis. Recalibration for CALIOP daytime 1064 nm signals leads to a decrease of their values by about 30%, possibly related to the use of the version 3.0 calibration procedure. No recalibration is made at 532 nm even though 532 nm scattering ratios appear to be biased low (-8%) because there are also significant differences in air mass sampling between airborne and CALIOP observations. Recalibration of the 1064 nm signal or correction of -5% negative bias in the 532 nm signal both could improve the CALIOP aerosol colour ratio expected for this campaign. The first hypothesis was retained in this work. Regional analyses in the European Arctic performed as a test emphasize the potential of the CALIOP spaceborne lidar for further monitoring in-depth properties of the aerosol layers over Arctic using infrared and depolarization observations. The CALIOP April 2008 global distribution of the aerosol backscatter reveal two regions with large backscatter below 2 km: the northern Atlantic between Greenland and Norway, and northern Siberia. The aerosol colour ratio increases between the source regions and the observations at latitudes above 70° N are consistent with a growth of the aerosol size once transported to the Arctic. The distribution of the aerosol optical properties in the mid-troposphere supports the known main transport pathways between the mid-latitudes and the Arctic."
"55795535700;35494005000;","Cloud properties and radiative effects of the Asian summer monsoon derived from A-Train data",2014,"10.1002/2014JD021458","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906674784&doi=10.1002%2f2014JD021458&partnerID=40&md5=770abe6596dea10f7f9e5645e5624232","Using A-Train satellite data, we investigate the distribution of clouds and their microphysical and radiative properties in Southeast Asia during the summer monsoon. We find an approximate balance in the top of the atmosphere (TOA) cloud radiative effect, which is largely due to commonly occurring cirrus layers that warm the atmosphere, and less frequent deep layers, which produce a strong cooling at the surface. The distribution of ice water path (IWP) in these layers, obtained from the 2C-ICE CloudSat data product, is highly skewed with a mean value of 440 g m-2 and a median of 24 g m-2. We evaluate the fraction of the total IWP observed by CloudSat and CALIPSO individually and find that both instruments are necessary for describing the overall IWP statistics and particularly the values that are most important to cirrus radiative impact. In examining how cloud radiative effects at the TOA vary as a function of IWP, we find that cirrus with IWP less than 200 g m-2 produce a net warming in the study region. Weighting the distribution of radiative effect by the frequency of occurrence of IWP values, we determine that cirrus with IWP around 20 g m-2 contribute most to heating at the TOA. We conclude that the mean IWP is a poor diagnostic of radiative impact. We suggest that climate model intercomparisons with data should focus on the median IWP because that statistic is more descriptive of the cirrus that contribute most to the radiative impacts of tropical ice clouds. © 2014. American Geophysical Union. All Rights Reserved."
"35221443100;56312778700;57208121852;23020321400;","Rainfall-aerosol relationships explained by wet scavenging and humidity",2014,"10.1002/2014GL060958","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905609539&doi=10.1002%2f2014GL060958&partnerID=40&md5=4defa7a6daa153f184af0fe5b42cbdf3","Relationships between precipitation rate and aerosol optical depth, the extinction of light by aerosol in an atmospheric column, have been observed in satellite-retrieved data. What are the reasons for these precipitation-aerosol relationships? We investigate relationships between convective precipitation rate (Rconv) and aerosol optical depth (τtot) using the ECHAM5-HAM aerosol-climate model. We show that negative R conv-τtot relationships arise due to wet scavenging of aerosol. The apparent lack of negative Rconv-τtot relationships in satellite-retrieved data is likely because the satellite data do not sample wet scavenging events. When convective wet scavenging is excluded in the model, we find positive Rconv-τtot relationships in regions where convective precipitation is the dominant form of model precipitation. The spatial distribution of these relationships is in good agreement with satellite-based results. We further demonstrate that a substantial component of these positive relationships arises due to covariation with large-scale relative humidity. Although the interpretation of precipitation-aerosol relationships remains a challenging question, we suggest that progress can be made through a synergy between observations and models. Key Points Negative precipitation-aerosol relationships arise due to wet scavenging Satellites poorly sample aerosol populations depleted by wet scavenging Positive precipitation-aerosol relationships arise due to humidification effects © 2014. American Geophysical Union. All Rights Reserved."
"6507495053;8669401600;57203260074;6602137606;12645700600;55030182900;","European heatwave in July 2006: Observations and modeling showing how local processes amplify conducive large-scale conditions",2014,"10.1002/2014GL060205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905303249&doi=10.1002%2f2014GL060205&partnerID=40&md5=2e509bfc596fe8a062b74634add1edd8","July 2006 was particularly warm in Europe. The consistency of this kind of anomaly with large-scale circulation conditions or local processes is a key issue for regional climate evolution. Using observations from space and ground-based observatory, together with simulations from regional model, shows that two concomitant but disconnected drivers explain this heatwave. The first driver corresponds to large-scale conditions (specific atmospheric condition with advection of continental air favoring clear sky). The second condition relates to local processes (dry soil, amplifying surface temperature in heatwave for first 5days, and making this event warm enough to induce a monthly mean anomaly). This large-scale event is studied at a site in northern France, where comprehensive observation data carefully reanalyzed are available. A regional model is able to produce the amplitude of the event, for both temperature and cloud large-scale anomalies. Coupling model and observations allow discriminating the surface contribution to the temperature anomaly. Key Point Heatwave can be studied in a precise location © 2014. American Geophysical Union. All Rights Reserved."
"8570871900;22937577900;7102944401;7006107059;35180334400;","Aerosol radiative forcing from the 2010 Eyjafjallajökull volcanic eruptions",2014,"10.1002/2014JD021977","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906692373&doi=10.1002%2f2014JD021977&partnerID=40&md5=59a4d56bf65265772f59322fa1e4910e","Although the 2010 volcanic eruptions of Eyjafjallajökull did not exert a large climate forcing, several features of their emissions favored weaker aerosol cooling or stronger warming than commonly attributed to volcanic events. These features include a high ratio of fine ash to SO2, occurrence near reflective surfaces exposed to strong insolation, and the production of very little stratospheric sulfate. We derive plausible ranges of optical properties and top-of-atmosphere direct radiative forcing for aerosol emissions from these events and find that shortwave cooling from sulfate was largely offset by warming from ash deposition to cryospheric surfaces and longwave warming from atmospheric ash and sulfate. Shortwave forcing from atmospheric ash was slightly negative in the global mean under central estimates of optical properties, though this forcing term was uniquely sensitive to the simulated distribution of clouds. The forcing components sum to near climate-neutral global mean 2010 instantaneous (−1.9 mW m−2) and effective (−0.5 mW m−2) radiative forcing, where the latter is elevated by high efficacy of snow-deposited ash. Ranges in net instantaneous (−7.3 to +2.8 mW m−2) and effective (−7.2 to +4.9 mW m−2) forcing derived from sensitivity studies are dominated by uncertainty in ash shortwave absorptivity. Forcing from airborne ash decayed quickly, while sulfate forcing persisted for several weeks and ash deposits continued to darken snow and sea ice surfaces for months following the eruption. Despite small global forcing, monthly averaged net forcing exceeded 1 W m−2 in some regions. These findings indicate that ash can be an important component of climate forcing from high-latitude volcanic eruptions and in some circumstances may exceed sulfate forcing. © 2014. American Geophysical Union. All Rights Reserved."
"6504750541;6507400558;7004978125;","Simulation of monsoon intraseasonal oscillations in a coarse-resolution aquaplanet GCM",2014,"10.1002/2014GL060662","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905316152&doi=10.1002%2f2014GL060662&partnerID=40&md5=021b51be4d759ab891006e807e710a31","The skill of the global climate models (GCMs) to realistically simulate the monsoon intraseasonal oscillations (MISOs) is related to the sensitivity of their convective parameterization schemes. Here we show that by coupling a simple multicloud parameterization to a coarse-resolution aquaplanet GCM, realistic MISOs can be simulated. We conduct three different simulations with a fixed nonhomogeneous sea surface temperature mimicking the Indian Ocean/western Pacific warm pool (WP) centered at the three latitudes 5°N, 10°N, and 15°N, respectively, to replicate the seasonal migration of the Tropical Convergence Zone (TCZ). This results in the generation of mean circulation resembling the monsoonal flow pattern in boreal summer. Succession of eastward propagating Madden-Julian Oscillation (MJO) disturbances with phase speed, amplitude, and structure similar to summer MJOs are simulated when the WP is at 5°N. When the WP is located over 10°N, northward and eastward propagating MISOs are simulated. This case captures the meridional seesaw of convection between continental and oceanic TCZ observed during boreal summer over South Asia. Westward propagating Rossby wave-like disturbances are simulated when the WP is over 15°N congruous with the synoptic disturbances seen over the monsoon trough. The initiation of intraseasonal oscillations in the model can occur internally through organization of convective events above the WP associated with internal dynamics. Key Points Monsoon ISO simulated using multicloud model Three-cloud structure, key for Monsoon ISOs A more realistic parameterization scheme for monsoon ISOs © 2014. American Geophysical Union. All Rights Reserved."
"57216427721;57194516481;","Structural geology mapping using PALSAR data in the Bau gold mining district, Sarawak, Malaysia",2014,"10.1016/j.asr.2014.02.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904055666&doi=10.1016%2fj.asr.2014.02.012&partnerID=40&md5=b7ee0544679a7be455c9233cad774a11","The application of optical remote sensing data for geological mapping is difficult in the tropical environment. The persistent cloud coverage, dominated vegetation in the landscape and limited bedrock exposures are constraints imposed by the tropical climate. Structural geology investigations that are searching for epithermal or polymetallic vein-type ore deposits can be developed using Synthetic Aperture Radar (SAR) remote sensing data in tropical/sub-tropical regions. The Bau gold mining district in the State of Sarawak, East Malaysia, on the island of Borneo has been selected for this study. The Bau is a gold field similar to Carlin style gold deposits, but gold mineralization at Bau is much more structurally controlled. Geological analyses coupled with the Phased Array type L-band Synthetic Aperture Radar (PALSAR) remote sensing data were used to detect structural elements associated with gold mineralization. The PALSAR data were used to perform lithological-structural mapping of mineralized zones in the study area and surrounding terrain. Structural elements were detected along the SSW to NNE trend of the Tuban fault zone and Tai Parit fault that corresponds to the areas of occurrence of the gold mineralization in the Bau Limestone. Most of quartz-gold bearing veins occur in high-angle faults, fractures and joints within massive units of the Bau Limestone. The results show that four deformation events (D1-D4) in the structures of the Bau district and structurally controlled gold mineralization indicators, including faults, joints and fractures are detectable using PALSAR data at both regional and district scales. The approach used in this study can be more broadly applicable to provide preliminary information for exploration potentially interesting areas of epithermal or polymetallic vein-type mineralization using the PALSAR data in the tropical/sub-tropical regions. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved."
"55607528700;8594309800;8853393600;36812255500;24398842400;7005628166;","Quantification of ice nuclei active at near 0 °c temperatures in low-altitude clouds at the Puy de Dôme atmospheric station",2014,"10.5194/acp-14-8185-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910067977&doi=10.5194%2facp-14-8185-2014&partnerID=40&md5=3096264964622022fbbe1b11858db4d2","The distribution, abundance and nature of ice nucleation active particles in the atmosphere are major sources of uncertainty in the prediction of cloud coverage, precipitation patterns and climate. Some biological ice nuclei (IN) induce freezing at temperatures at which most other atmospheric particles exhibit no detectable activity (> -10 °C). Their actual contribution to the pool of IN in clouds remains poorly known, but numerical studies have suggested a probable significance of biological IN in atmospheric processes. In this study, cloud water was collected aseptically from the summit of Puy de Dôme (1465 m a.s.l., France) within contrasted meteorological and physico-chemical situations. Total and biological (i.e. heat-sensitive) IN were quantified by droplet-freezing assay between -5 °C and -14 °C. We observed that freezing was systematically induced by biological material, between -6 °C and -8 °C in 92% of the samples. Its removal by heat treatment consistently led to a decrease of the onset freezing temperature, by 3 °C or more in most samples. At -10 °C, 0 to ∼ 220 biological IN mL-1 of cloud water were measured (i.e. 0 to ∼ 22 m-3 of cloud air based on cloud liquid water content estimates), and these represented 65% to 100% of the total IN. Based on back-trajectories and on physico-chemical analyses, the high variability observed resulted probably from a source effect, with IN originating mostly from continental sources. Assuming that biological IN were all bacteria, at maximum 0.6% of the bacterial cells present in cloud water samples could have acted as IN at -8 °C, 1.5% at -10 °C, and 3.1% at -12 °C. The data set generated here will help elucidate the role of biological and bacterial IN on cloud microphysics by numeric modelling, and their impact on precipitation at local scale. © Author(s) 2014."
"6603203838;26430632200;13006169700;6603023560;55919935700;15127430500;8544882500;","Tropical tropospheric ozone column retrieval for GOME-2",2014,"10.5194/amt-7-2513-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921525658&doi=10.5194%2famt-7-2513-2014&partnerID=40&md5=996a132facedff7ab6d018fb8056e122","This paper presents the operational retrieval of tropical tropospheric ozone columns (TOCs) from the Second Global Ozone Monitoring Experiment (GOME-2) instruments using the convective-cloud-differential (CCD) method. The retrieval is based on total ozone and cloud property data provided by the GOME Data Processor (GDP) 4.7, and uses above-cloud and clear-sky ozone column measurements to derive a monthly mean TOC between 20° N and 20° S. Validation of the GOME-2 TOC with several tropical ozonesonde sites shows good agreement, with a high correlation between the GOME-2 and sonde measurements, and small biases within ~ 3 DU. The TOC data have been used in combination with tropospheric NO<inf>2</inf> measurements from GOME-2 to analyse the effect of the 2009-2010 El Niño-Southern Oscillation (ENSO) on the tropospheric ozone distribution in the tropics. El Niño induced dry conditions in September-October 2009 resulted in relatively high tropospheric ozone columns over the southern Indian Ocean and northern Australia, while La Niña conditions in September-October 2010 resulted in a strong increase in tropospheric NO<inf>2</inf> in South America, and enhanced ozone in the eastern Pacific and South America. Comparisons of the GOME-2 tropospheric ozone data with simulations of the ECHAM/MESSy Atmospheric Chemistry (EMAC) model for 2009 El Niño conditions illustrate the usefulness of the GOME-2 TOC measurements in evaluating chemistry climate models (CCMs). Evaluation of CCMs with appropriate satellite observations helps to identify strengths and weaknesses of the model systems, providing a better understanding of driving mechanisms and adequate relations and feedbacks in the Earth atmosphere, and finally leading to improved models. © Author(s) 2014."
"57210559570;55258950300;25630924500;55487543500;","Aerosol hygroscopicity parameter derived from the light scattering enhancement factor measurements in the North China Plain",2014,"10.5194/acp-14-8105-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925399906&doi=10.5194%2facp-14-8105-2014&partnerID=40&md5=cd4ef168f28faca246493edd512f6802","The relative humidity (RH) dependence of aerosol light scattering is an essential parameter for accurate estimation of the direct radiative forcing induced by aerosol particles. Because of insufficient information on aerosol hygroscopicity in climate models, a more detailed parameterization of hygroscopic growth factors and resulting optical properties with respect to location, time, sources, aerosol chemistry and meteorology are urgently required. In this paper, a retrieval method to calculate the aerosol hygroscopicity parameter, κ, is proposed based on the in situ measured aerosol light scattering enhancement factor, namely f(RH), and particle number size distribution (PNSD) obtained from the HaChi (Haze in China) campaign. Measurements show that f(RH) increases sharply with increasing RH, and that the time variance of f(RH) is much greater at higher RH. A sensitivity analysis reveals that the f(RH) is more sensitive to the aerosol hygroscopicity than PNSD. f(RH) for polluted cases is distinctly higher than that for clean periods at a specific RH. The derived equivalent κ, combined with the PNSD measurements, is applied in the prediction of the cloud condensation nuclei (CCN) number concentration. The predicted CCN number concentration with the derived equivalent κ agrees well with the measured ones, especially at high supersaturations. The proposed calculation algorithm of κ with the f(RH) measurements is demonstrated to be reasonable and can be widely applied."
"6603375387;15755536700;8732108800;6602390932;24080501600;8385562400;55502994400;6603695169;7801358011;","A multi-site intercomparison of integrated water vapour observations for climate change analysis",2014,"10.5194/amt-7-2487-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906061891&doi=10.5194%2famt-7-2487-2014&partnerID=40&md5=974dd73be465ad1a7641be37ae5eaf39","Water vapour plays a dominant role in the climate change debate. However, observing water vapour over a climatological time period in a consistent and homogeneous manner is challenging. On one hand, networks of ground-based instruments able to retrieve homogeneous integrated water vapour (IWV) data sets are being set up. Typical examples are Global Navigation Satellite System (GNSS) observation networks such as the International GNSS Service (IGS), with continuous GPS (Global Positioning System) observations spanning over the last 15+ years, and the AErosol RObotic NETwork (AERONET), providing long-term observations performed with standardized and well-calibrated sun photometers. On the other hand, satellite-based measurements of IWV already have a time span of over 10 years (e.g. AIRS) or are being merged to create long-term time series (e.g. GOME, SCIAMACHY, and GOME-2). This study performs an intercomparison of IWV measurements from satellite devices (in the visible, GOME/SCIAMACHY/GOME-2, and in the thermal infrared, AIRS), in situ measurements (radiosondes) and ground-based instruments (GPS, sun photometer), to assess their use in water vapour trends analysis. To this end, we selected 28 sites world-wide for which GPS observations can directly be compared with coincident satellite IWV observations, together with sun photometer and/or radiosonde measurements. The mean biases of the different techniques compared to the GPS estimates vary only between -0.3 to 0.5 mm of IWV. Nevertheless these small biases are accompanied by large standard deviations (SD), especially for the satellite instruments. In particular, we analysed the impact of clouds on the IWV agreement. The influence of specific issues for each instrument on the intercomparison is also investigated (e.g. the distance between the satellite ground pixel centre and the co-located ground-based station, the satellite scan angle, daytime/nighttime differences). Furthermore, we checked if the properties of the IWV scatter plots between these different instruments are dependent on the geography and/or altitude of the station. For all considered instruments, the only dependency clearly detected is with latitude: the SD of the IWV observations with respect to the GPS IWV retrievals decreases with increasing latitude and decreasing mean IWV. © Author(s) 2014."
"30967521200;9843579700;57217869945;35774441900;55942083800;16481745400;","Ambient measurements of biological aerosol particles near Killarney, Ireland: A comparison between real-time fluorescence and microscopy techniques",2014,"10.5194/acp-14-8055-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906070923&doi=10.5194%2facp-14-8055-2014&partnerID=40&md5=2f118b4278eabdc7310cd8537fd62e75","Primary biological aerosol particles (PBAPs) can contribute significantly to the coarse particle burden in many environments. PBAPs can thus influence climate and precipitation systems as cloud nuclei and can spread disease to humans, animals, and plants. Measurement data and techniques for PBAPs in natural environments at high time-and size resolution are, however, sparse, and so large uncertainties remain in the role that biological particles play in the Earth system. In this study two commercial real-time fluorescence particle sensors and a Sporewatch single-stage particle impactor were operated continuously from 2 August to 2 September 2010 at a rural sampling location in Killarney National Park in southwestern Ireland. A cascade impactor was operated periodically to collect size-resolved particles during exemplary periods. Here we report the first ambient comparison of a waveband integrated bioaerosol sensor (WIBS-4) with a ultraviolet aerodynamic particle sizer (UV-APS) and also compare these real-time fluorescence techniques with results of fluorescence and optical microscopy of impacted samples. Both real-time instruments showed qualitatively similar behavior, with increased fluorescent bioparticle concentrations at night, when relative humidity was highest and temperature was lowest. <br><br> The fluorescent particle number from the FL3 channel of the WIBS-4 and from the UV-APS were strongly correlated and dominated by a 3 Î1/4m mode in the particle size distribution. The WIBS FL2 channel exhibited particle modes at approx. 1 and 3 Î1/4m, and each was correlated with the concentration of fungal spores commonly observed in air samples collected at the site (ascospores, basidiospores,Ganoderma< /i> spp.). The WIBS FL1 channel exhibited variable multimodal distributions turning into a broad featureless single mode after averaging, and exhibited poor correlation with fungal spore concentrations, which may be due to the detection of bacterial and non-biological fluorescent particles.Cladosporiumspp., which are among the most abundant fungal spores in many terrestrial environments, were not correlated with any of the real-time fluorescence channels, suggesting that the real-time fluorescence instruments are relatively insensitive to PBAP classes with dark, highly absorptive cell walls. <br><br> Fluorescence microscopy images of cascade impactor plates showed large numbers of coarse-mode particles consistent with the morphology and weak fluorescence expected of sea salt. Some of these particles were attached to biological cells, suggesting that a marine source influenced the PBAPs observed at the site and that the ocean may be an important contributor to PBAP loadings in coastal environments. © 2014 Author(s)."
"36810868100;55258950300;36810195000;55314120800;55487543500;55706247100;","SO2 noontime-peak phenomenon in the North China Plain",2014,"10.5194/acp-14-7757-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905665746&doi=10.5194%2facp-14-7757-2014&partnerID=40&md5=2c85f0e66f9d222b116912f5e1d47ead","A phenomenon of frequent noontime SO2 concentration peaks was discovered in a detailed analysis of the SO2 concentrations in the North China Plain (NCP). The possible causes and their contributions are analyzed. The impacts of such a phenomenon on the sulphur cycle were studied and the implications of the phenomenon for atmospheric chemistry, cloud physics, and climate were discussed. Different from the more common SO2 diurnal patterns with high nighttime concentrations, NCP witnessed high frequencies of noontime SO2 peaks, with an occurrence frequency of 50 to 72% at four stations. Down mixing of elevated pollution layers, plume transport processes, mountain-valley winds, and fog/high RH haze events were the possible causes. The contribution of each process varies from day to day and from station to station, however, none of those four processes can be neglected. SO2 peaks occurring during noontime instead of nighttime will lead to a 13 to 35% increase in sulphur dry deposition, a 9 to 23% increase in gas phase oxidation, and an 8 to 33% increase in aqueous phase conversions, which will increase the hygroscopicity and the light scattering of aerosols, thus having important impacts on atmospheric chemistry, cloud physics, and climate. © Author(s) 2014."
"12546184200;7401798754;26643508500;26635486800;","The magnitude and impact of the Youngest Toba Tuff super-eruption",2014,"10.3389/feart.2014.00016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009652352&doi=10.3389%2ffeart.2014.00016&partnerID=40&md5=9299812d665749aec48232fb64885b93","Super-eruptions, orders of magnitude larger than biggest eruptions experienced in historic times, have devastated wide areas by pyroclastic flows, covered continent-size areas by ash fallout, and injected large quantities of aerosols into the stratosphere affecting global climate. The Youngest Toba Tuff (YTT) is the largest known super-eruption in the Quaternary. Here we reconstructed the ultra-distal volcanic ash dispersal during this super-eruption using a computational ash dispersal model, which provides insights into the eruption dynamics and the impact of the event. The method uses a 3D time-dependent tephra dispersion model, a set of wind fields, and several tens of thickness measurements of the YTT tephra deposit. Results reveal that the YTT eruption dispersed ~8600 km3 (~3800 km3 dense rock equivalent, DRE) of ash, covering ~40 million km2 with more than 5mm of ash. These new fallout volume estimations indicate that the total volume of the material erupted (including the massive pyroclastic density current (PDC), 1500km3 DRE, deposits on Sumatra) was ~5300 km3 DRE. Simulation results indicate that the eruption had a very large mass flow rate and that the umbrella cloud, associated with the eruption plume, spread as an enormous gravity current around the neutral buoyancy level. The YTT tephra forms a key chronostratigraphic marker in the sedimentary sequences, and is particularly useful for constraining the age of the palaeoenvironmental and archeological records, and synchronizing these archives to investigate temporal relationships. These new constraints on the extent of the YTT deposit are therefore particularly useful for cryptotephra studies that aim to find nonvisible tephra layers for these chronological purposes. This method used to constrain volcanological parameters of eruptions in the past provides insights into the dispersal processes, and allows the amount of volatiles released to be estimated which is crucial to assessing the impact of such events. © 2014 Costa, Smith, Macedonio and Matthews."
"7202594386;12041044800;57216728845;","Index of thermal stress for cows (ITSC) under high solar radiation in tropical environments",2014,"10.1007/s00484-014-0868-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939871406&doi=10.1007%2fs00484-014-0868-7&partnerID=40&md5=265835b667357ff8e6133c921f36d702","This paper presents a new thermal stress index for dairy cows in inter-tropical regions, with special mention to the semi-arid ones. Holstein cows were measured for rectal temperature (T<inf>R</inf>), respiratory rate (F<inf>R</inf>) and rates of heat exchange by convection (C), radiation (R), skin surface evaporation (E<inf>S</inf>) and respiratory evaporation (E<inf>R</inf>) in the north eastern region of Brazil, after exposure to sun for several hours. Average environmental measurements during the observations were air temperature (T<inf>A</inf>) 32.4 °C (24.4–38.9°), wind speed (U) 1.8 m.s−1 (0.01–11.0), relative humidity 63.6 % (36.8–81.5) and short-wave solar radiation 701.3 W m−2 (116–1,295). The effective radiant heat load (ERHL) was 838.5 ± 4.9 W m−2. Values for the atmospheric transmittance (τ) were also determined for tropical regions, in order to permit adequate estimates of the solar radiation. The average value was τ = 0.611 ± 0.004 for clear days with some small moving clouds, with a range of 0.32 to 0.91 in the day period from 1000 to 1300 hours. Observed τ values were higher (0.62–0.66) for locations near the seacoast and in those regions well-provided with green fields. Effects of month, location and time of the day were all statistically significant (P < 0.01). A total of 1,092 data were obtained for cows exposed for 1 to 8 h to sun during the day; in 7 months (February, March, April, July, August, September and November), 4 days per month on the average. A principal component analysis summarised the T<inf>R</inf>, F<inf>R</inf>, C, R, E<inf>S</inf> and E<inf>R</inf> measurements into just one synthetic variable (y<inf>1</inf>); several indexes were then obtained by multiple regression of y<inf>1</inf> on the four environmental variables and its combinations, by using Origin 8.1 software (OriginLab Corp.). The chosen equation was the index of thermal stress for cows, ITSC = 77.1747 + 4.8327 T<inf>A</inf> − 34.8189 U + 1.111 U2 + 118.6981 P<inf>V</inf> − 14.7956 P<inf>V</inf> 2 − 0.1059 ERHL with r2 = 0.812. The correlations of ITSC with T<inf>R</inf>, F<inf>R</inf>, C, E<inf>S</inf>, R and E<inf>R</inf> were 0.275, 0.255, −0.493, −0.647, −0.818 and 0.075, respectively. Correlations of the index with the physiological variables are presented, and ITSC is compared to three other indexes. © 2014, ISB."
"22939192200;56224155200;36118090300;","Examinations of cloud variability and future change in the coupled model intercomparison project phase 3 simulations",2014,"10.1007/s13143-014-0038-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957441921&doi=10.1007%2fs13143-014-0038-1&partnerID=40&md5=bb1cea51be0798503f9df0e463992d32","Low-level cloud variability is critical to the radiation balance of Earth due to its wide spatial coverage. Using the adjusted International Satellite Cloud Climatology Project (ISCCP) observations of Clement et al. (2009), and the Coupled Model Intercomparison Project Phase 3 (CMIP3) model simulations, this study examines the observed and the simulated low-cloud variations and their relationships with large-scale environmental variables. From the observational analysis, significant correlations are found between low clouds and those of sea surface temperature (SST), lower tropospheric stability (LTS), and sea level pressure (SLP) over tropical marine areas of low cloud prevailing regions during most of the year. Increase of SST coincides with the reduction of LTS and increased vertical motion, which tends to reduce low-level clouds in subtropical oceans. Among the 14 models investigated, CGCM3 and HadGEM1 exhibit more realistic representation of the observed relationship between low-level clouds and large-scale environments. In future climate projection, these two models show a good agreement in the reduction of low-cloud throughout much of the global oceans in response to greenhouse gas forcing, suggesting a positive low-cloud feedback in a climate change context. © 2014, Korean Meteorological Society and Springer Science+Business Media Dordrecht."
"56624047500;57201696235;6602360081;23568163400;7401472342;","Bacterial ice nuclei impact cloud lifetime and radiative properties and reduce atmospheric heat loss in the BRAMS simulation model",2014,"10.1088/1748-9326/9/8/084020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928979022&doi=10.1088%2f1748-9326%2f9%2f8%2f084020&partnerID=40&md5=5f273d831a37b9b3c21def98e6d58846","This study examines the effect of the bacterial species Pseudomonas syringae acting as ice nuclei (IN) on cloud properties to understand its impact on local radiative budget and heating rates. These bacteria may become active IN at temperatures as warm as -2°C. Numerical simulations were developed using the Brazilian Regional Atmospheric Model System (BRAMS). To investigate the isolated effect of bacterial IN, four scenarios were created considering only homogeneous and bacterial ice nucleation, with 1, 10 and 100 IN per cubic meter of cloud volume and one with no bacteria. Moreover, two other scenarios were generated: the BRAMS default parameterization and its combination with bacterial IN. The model reproduced a strong convective cell over São Paulo on 3 March 2003. Results showed that bacterial IN may change cloud evolution as well as its microphysical properties, which in turn influence cloud radiative properties. For example, the reflected shortwave irradiance over an averaged domain in a scenario considering bacterial IN added to the BRAMS default parameterization was 14% lower than if bacteria were not considered. Heating rates can also be impacted, especially due to differences in cloud lifetime. Results suggest that the omission of bacterial IN in numerical models, including global cloud models, could neglect relevant ice nucleation processes that potentially influence cloud radiative properties. © 2014 IOP Publishing Ltd."
"7003836546;24437444900;36621776000;6507607421;22635944500;56059425100;55765335000;","Natural and anthropogenic aerosols in the Eastern Mediterranean and Middle East: Possible impacts",2014,"10.1016/j.scitotenv.2014.02.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901654332&doi=10.1016%2fj.scitotenv.2014.02.035&partnerID=40&md5=5ec65c38e48961a72a6f217bd40d7581","The physical and chemical properties of airborne particles have significant implications on the microphysical cloud processes. Maritime clouds have different properties than polluted ones and the final amounts and types of precipitation are different. Mixed phase aerosols that contain soluble matter are efficient cloud condensation nuclei (CCN) and enhance the liquid condensate spectrum in warm and mixed phase clouds. Insoluble particles such as mineral dust and black carbon are also important because of their ability to act as efficient ice nuclei (IN) through heterogeneous ice nucleation mechanisms. The relative contribution of aerosol concentrations, size distributions and chemical compositions on cloud structure and precipitation is discussed in the framework of RAMS/ICLAMS model. Analysis of model results and comparison with measurements reveals the complexity of the above links. Taking into account anthropogenic emissions and all available aerosol-cloud interactions the model precipitation bias was reduced by 50% for a storm simulation over eastern Mediterranean. © 2014 Elsevier B.V."
"56044817200;7005902717;","Andean elevation control on tropical Pacific climate and ENSO",2014,"10.1002/2014PA002640","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85000040135&doi=10.1002%2f2014PA002640&partnerID=40&md5=c8b1c32afabd844f3cf53f76e96f6eba","Late Cenozoic marine proxy data record a long-term transition in the tropical Pacific from El Niño-like conditions with reduced zonal sea surface temperature (SST) gradient, deepened thermocline, and reduced upwelling in the eastern equatorial Pacific (EEP) to conditions similar to modern. This transition coincides with kilometer-scale uplift of the central Andes. To understand whether the rise of the Andes contributed to tropical Pacific climate evolution, we performed experiments with the National Center for Atmospheric Research's Community Climate System Model version 4 to quantify changes in tropical Pacific climate and El Niño-Southern Oscillation as a function of Andean elevations. Our results demonstrate that uplift increases the equatorial east-west SST gradient and Walker circulation. The rise of the Andes from 1 to 3 km increases the SST gradient by 0.8°C and Walker circulation by 60% due to strengthened radiative cooling by enhanced low-cloud formation in the EEP. This cooling effect is largest in the southeastern tropical Pacific and accounts for about one half of the reconstructed SST cooling along the Peru coast. The uplift also strengthens upwelling north of the EEP, consistent with documented increases in biological productivity in this region, and decreases the frequency of El Niño-Southern Oscillation and the number of strong El Niño events. Simulated responses to Andean uplift are generally consistent with the late Cenozoic proxy records, but too small in magnitude. Taken together, our results indicate that Andean uplift was likely one of the multiple factors that contributed to the long-term evolution of both the mean climate state and the interannual variability in the tropical Pacific. Key Points CCSM4 is used to study responses of tropical Pacific climate to Andean upliftAndean uplift invokes a La Niña-like SST responseAndean uplift reduces the ENSO frequency and strong El Niño events ©2014. American Geophysical Union. All Rights Reserved."
"54909969100;7007018426;7004021287;6701824742;57210095254;15020631200;","Mapping Asian cropping intensity with MODIS",2014,"10.1109/JSTARS.2014.2344630","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027932562&doi=10.1109%2fJSTARS.2014.2344630&partnerID=40&md5=0b4498a3377e9179664c641316aa25f9","Agricultural systems are geographically extensive, have profound significance to society, and affect regional energy, climate, and water cycles. Since most suitable lands worldwide have been cultivated, there is a growing pressure to increase yields on existing agricultural lands. In tropical and subtropical regions, multicropping is widely used to increase food production, but regional-to-global information related to multicropping practices is poor. The high temporal resolution and moderate spatial resolution of the MODIS sensors provide an ideal source of information for characterizing cropping practices over large areas. Relative to studies that document agricultural extensification, however, systematic assessment of agricultural intensification via multicropping has received relatively little attention. The goal of this work was to help close this information gap by developing methods that use multitemporal remote sensing to map multicropping systems in Asia. Image time-series analysis is especially challenging in this part of the world because atmospheric conditions including clouds and aerosols lead to high frequencies of missing or low-quality observations, especially during the Asian Monsoon. The methodology that we developed builds upon the algorithm used to produce the MODIS Land Cover Dynamics product (MCD12Q2), but uses an improved methodology optimized for crops. We assessed our results at the aggregate scale using state, district, and provincial level inventory statistics reporting total cropped and harvested areas, and at the field scale using survey results for 191 field sites in Bangladesh. While the algorithm highlighted the dominant continental-scale patterns in agricultural practices throughout Asia, and produced reasonable estimates of state and provincial level total harvested areas, field-scale assessment revealed significant challenges in mapping high cropping intensity due to abundant missing data. © 2014 IEEE."
"55251638900;7006646563;36828871200;55465944900;","Snow cover estimation using blended MODIS and AMSR-E data for improved watershed-scale spring streamflow simulation in Quebec, Canada",2014,"10.1002/hyp.10123","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904436395&doi=10.1002%2fhyp.10123&partnerID=40&md5=85c34753294c5795c90076c030d3e51e","Estimation of the amount of water stored in snow is a principal source of error for spring streamflow simulations in snow-dominant regions. Measuring this variable throughout large and often remote areas using snow surveys is an expensive task since they are practically point measurements. Remote sensing is an alternative method, which can cover much larger areas in little time, but further research is required to reduce uncertainties on snow water equivalent (SWE) estimations, especially during the melting period. However, optical-near infrared (NIR) and passive microwave remote sensing can detect snow cover area (SCA) with greater certainty, which can be used as a proxy for SWE. The two datasets work in complementary ways considering their spatial resolutions and cloud cover limitations. This study developed an SCA product from blended passive microwave (Advanced Microwave Scanning Radiometer - Earth Observing System: AMSR-E) and optical-NIR (Moderate Resolution Imaging Spectroradiometer: MODIS) remote sensing data to improve estimates of streamflow caused by snowmelt during the spring period. The blended product was assimilated in a snowmelt model (SPH-AV) coupled with the MOHYSE hydrological model through a modified direct insertion method. SCA estimated from AMSR-E data was first compared with in situ snow-depth measurements and SCA estimated with MODIS. Results showed an agreement of over 95% between AMSR-E-derived and cloud-free MODIS-derived SCA products in the spring. Comparison with ground stations confirmed the underestimation of snow cover by AMSR-E. Assimilation of the blended snow product in SPH-AV coupled with MOHYSE yielded an overall improvement of the Nash-Sutcliffe coefficient comparable with simulations with no updates, which is comparable to results driven by biweekly snow surveys. Assimilation of remotely sensed passive microwave data was also found to have little positive impact on streamflow simulation due to the difficulty of differentiating melting snow from snow-free surfaces. © 2013 The Authors. Hydrological Processes published by John Wiley & Sons Ltd."
"55480654300;7004469744;35810775100;34976155900;56757625500;7003740015;","The complex response of Arctic aerosol to sea-ice retreat",2014,"10.5194/acp-14-7543-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905179525&doi=10.5194%2facp-14-7543-2014&partnerID=40&md5=973cb3a95b25029ddc63f4d613c5ca16","Loss of summertime Arctic sea ice will lead to a large increase in the emission of aerosols and precursor gases from the ocean surface. It has been suggested that these enhanced emissions will exert substantial aerosol radiative forcings, dominated by the indirect effect of aerosol on clouds. Here, we investigate the potential for these indirect forcings using a global aerosol microphysics model evaluated against aerosol observations from the Arctic Summer Cloud Ocean Study (ASCOS) campaign to examine the response of Arctic cloud condensation nuclei (CCN) to sea-ice retreat. In response to a complete loss of summer ice, we find that north of 70° N emission fluxes of sea salt, marine primary organic aerosol (OA) and dimethyl sulfide increase by a factor of ∼ 10, ∼ 4 and ∼ 15 respectively. However, the CCN response is weak, with negative changes over the central Arctic Ocean. The weak response is due to the efficient scavenging of aerosol by extensive drizzling stratocumulus clouds. In the scavenging-dominated Arctic environment, the production of condensable vapour from oxidation of dimethyl sulfide grows particles to sizes where they can be scavenged. This loss is not sufficiently compensated by new particle formation, due to the suppression of nucleation by the large condensation sink resulting from sea-salt and primary OA emissions. Thus, our results suggest that increased aerosol emissions will not cause a climate feedback through changes in cloud microphysical and radiative properties. © Author(s) 2014."
"36637673700;16029936600;56679340600;","The fate of NOx emissions due to nocturnal oxidation at high latitudes: 1-D simulations and sensitivity experiments",2014,"10.5194/acp-14-7601-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905176639&doi=10.5194%2facp-14-7601-2014&partnerID=40&md5=6da4b73e5f6314526f1f91583fcf4fe2","The fate of nitrogen oxide pollution during high-latitude winter is controlled by reactions of dinitrogen pentoxide (N2O5) and is highly affected by the competition between heterogeneous atmospheric reactions and deposition to the snowpack. MISTRA (MIcrophysical STRAtus), a 1-D photochemical model, simulated an urban pollution plume from Fairbanks, Alaska to investigate this competition of N2O5 reactions and explore sensitivity to model parameters. It was found that dry deposition of N2O5 made up a significant fraction of N2O5 loss near the snowpack, but reactions on aerosol particles dominated loss of N2O5 over the integrated atmospheric column. Sensitivity experiments found the fate of NOx emissions were most sensitive to NO emission flux, photolysis rates, and ambient temperature. The results indicate a strong sensitivity to urban area density, season and clouds, and temperature, implying a strong sensitivity of the results to urban planning and climate change. Results suggest that secondary formation of particulate (PM2.5) nitrate in the Fairbanks downtown area does not contribute significant mass to the total PM2.5 concentration, but appreciable amounts are formed downwind of downtown due to nocturnal NOx oxidation and subsequent reaction with ammonia on aerosol particles."
"7201839229;15026371500;55285921200;","A mechanism for future changes in Hadley circulation strength in CMIP5 climate change simulations",2014,"10.1002/2014GL060868","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906355742&doi=10.1002%2f2014GL060868&partnerID=40&md5=1217c9fa166cc9ad686b6d6c816d39f9","The Coupled Model Intercomparison Project Phase 5 (CMIP5) 21st century climate change simulations exhibit a robust (slight) weakening of the Hadley cell (HC) during the boreal winter (summer, respectively) season in the future climate. Using 30 different coupled model simulations, we investigate the main mechanisms for both the multimodel ensemble mean changes in the HC strength and its intermodel changes in response to global warming during these seasons. A simple scaling analysis relates the strength of the HC to three factors: the meridional potential temperature gradient, gross static stability, and tropopause height. We found that changes in the meridional potential temperature gradients across the subtropics in a warming climate play a crucial role in the ensemble mean changes and model-to-model variations in the HC strength for both seasons. A larger reduction in the meridional temperature gradient in the Northern Hemisphere in boreal winter leads to the larger reduction of the HC strength in that season. © 2014. American Geophysical Union. All Rights Reserved."
"57212270042;57200055610;36623540900;36537129600;57218357221;7005902263;7006901405;","Surface and free tropospheric sources of methanesulfonic acid over the tropical Pacific Ocean",2014,"10.1002/2014GL060934","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904273532&doi=10.1002%2f2014GL060934&partnerID=40&md5=29ceb7bccf128f2057761f1ab24b956b","The production of sulfate aerosols through sulfur chemistry in marine environments is critical to the tropical climate system. However, not all sulfur compounds have been studied in detail. One such compound is methanesulfonic acid (MSA). In this study, we use a one-dimensional chemical transport model to analyze the observed vertical profiles of gas phase MSA during the Pacific Atmospheric Sulfur Experiment. The observed sharp decrease in MSA from the surface to 600 m implies a surface source of 4.0 × 107 molecules/cm2/s. Evidence suggests that this source is photolytically enhanced in daytime. We also find that the observed large increase of MSA from the boundary layer into the lower free troposphere (1000-2000 m) results mainly from the degassing of MSA from dehydrated aerosols. We estimate a source of 1.2 × 107 molecules/cm2/s to the free troposphere through this pathway. This source of soluble MSA could potentially provide an important precursor for new particle formation in the free troposphere over the tropics, affecting the climate system through aerosol-cloud interactions. © 2014. American Geophysical Union. All Rights Reserved."
"55113736500;","Effects of biomass burning on climate, accounting for heat and moisture fluxes, black and brown carbon, and cloud absorption effects",2014,"10.1002/2014JD021861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911871617&doi=10.1002%2f2014JD021861&partnerID=40&md5=1b0e37a143fb8c34e991759eb0b07306","This paper examines the effects on climate and air pollution of open biomass burning (BB) when heat and moisture fluxes, gases and aerosols (including black and brown carbon, tar balls, and reflective particles), cloud absorption effects (CAEs) I and II, and aerosol semidirect and indirect effects on clouds are treated. It also examines the climate impacts of most anthropogenic heat and moisture fluxes (AHFs and AMFs). Transient 20 year simulations indicate BB may cause a net global warming of ~0.4 K because CAE I (~32% of BB warming), CAE II, semidirect effects, AHFs (~7%), AMFs, and aerosol absorption outweigh direct aerosol cooling and indirect effects, contrary to previous BB studies that did not treat CAEs, AHFs, AMFs, or brown carbon. Some BB warming can be understood in terms of the anticorrelation between instantaneous direct radiative forcing (DRF) changes and surface temperature changes in clouds containing absorbing aerosols. BB may cause ~250,000 (73,000–435,000) premature mortalities/yr, with &gt;90% from particles. AHFs from all sources and AMFs + AHFs from power plants and electricity use each may cause a statistically significant +0.03 K global warming. Solar plus thermal-IR DRFs were +0.033 (+0.027) W/m2 for all AHFs globally without (with) evaporating cooling water, +0.009 W/m2 for AMFs globally, +0.52 W/m2 (94.3% solar) for all-source BC outside of clouds plus interstitially between cloud drops at the cloud relative humidity, and +0.06 W/m2 (99.7% solar) for BC inclusions in cloud hydrometeor particles. Modeled post-1850 biomass, biofuel, and fossil fuel burning, AHFs, AMFs, and urban surfaces accounted for most observed global warming. © 2014. American Geophysical Union. All Rights Reserved."
"55331928800;26664901700;7004205208;55332040400;","Modeling initial breakdown pulses of CG lightning flashes",2014,"10.1002/2014JD021553","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913578051&doi=10.1002%2f2014JD021553&partnerID=40&md5=9e185eb9b3fc957d7c38b1db7896ab8c","Electric field change waveforms of initial breakdown pulses (IBPs) in cloud-to-ground (CG) lightning flashes were recorded at ten sites at Kennedy Space center, Florida, in 2011. Six “classic” IBPs were modeled using three modified transmission line (MTL) models called MTLL, MTLE, and MTLK. The locations of the six IBPs were obtained using a time-of-arrival method and used as inputs for the models; the recorded IBP waveforms from six to eight sites were used as model constraints. All three models were able to reasonably fit the measured IBP waveforms; the best fit was most often given by the MTLE model. For each individual IBP, there was good agreement between the three models on several physical parameters of the IBPs: current risetime, current falltime, current shape factor, current propagation speed, and the total charge moment change. For the six IBPs modeled, the ranges, mean values, and standard deviations of these quantities are as follows: current risetime [4.8–25, (12 ±6)] μs, current falltime [15–37, (25 ±6)] μs, current speed [0.78–1.8, (1.3 ±0.3)]×108 m/s, and charge moment change [0.015–0.30, (0.12 ±0.10)] C km. Currents in the MTLL and MTLE models moved a negative charge −Q downward and deposited an equivalent positive charge +Q along their paths; the mean Q values were 0.35 C for MTLL and 0.71 C for MTLE. MTLK model deposited negative charge along its lower path and positive charge along its upper path with mean values of 0.27 C. © 2014. American Geophysical Union. All Rights Reserved."
"34876658200;56612517400;55802355600;36538539800;6701378450;","Incorporation of advanced aerosol activation treatments into CESM/CAM5: Model evaluation and impacts on aerosol indirect effects",2014,"10.5194/acp-14-7485-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904891921&doi=10.5194%2facp-14-7485-2014&partnerID=40&md5=cf68fa67da60214d366044044360d8b8","One of the greatest sources of uncertainty in the science of anthropogenic climate change is from aerosol-cloud interactions. The activation of aerosols into cloud droplets is a direct microphysical linkage between aerosols and clouds; parameterizations of this process link aerosol with cloud condensation nuclei (CCN) and the resulting indirect effects. Small differences between parameterizations can have a large impact on the spatiotemporal distributions of activated aerosols and the resulting cloud properties. In this work, we incorporate a series of aerosol activation schemes into the Community Atmosphere Model version 5.1.1 within the Community Earth System Model version 1.0.5 (CESM/CAM5) which include factors such as insoluble aerosol adsorption and giant cloud condensation nuclei (CCN) activation kinetics to understand their individual impacts on global-scale cloud droplet number concentration (CDNC). Compared to the existing activation scheme in CESM/CAM5, this series of activation schemes increase the computation time by ∼10% but leads to predicted CDNC in better agreement with satellite-derived/in situ values in many regions with high CDNC but in worse agreement for some regions with low CDNC. Large percentage changes in predicted CDNC occur over desert and oceanic regions, owing to the enhanced activation of dust from insoluble aerosol adsorption and reduced activation of sea spray aerosol after accounting for giant CCN activation kinetics. Comparison of CESM/CAM5 predictions against satellite-derived cloud optical thickness and liquid water path shows that the updated activation schemes generally improve the low biases. Globally, the incorporation of all updated schemes leads to an average increase in column CDNC of 150% and an increase (more negative) in shortwave cloud forcing of 12%. With the improvement of model-predicted CDNCs and better agreement with most satellite-derived cloud properties in many regions, the inclusion of these aerosol activation processes should result in better predictions of radiative forcing from aerosol-cloud interactions. © Author(s) 2014. CC Attribution 3.0 License."
"56294231100;9043417100;6603172418;","An investigation into the performance of four cloud droplet activation parameterisations",2014,"10.5194/gmd-7-1535-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904886728&doi=10.5194%2fgmd-7-1535-2014&partnerID=40&md5=8e7a591dbd8948593bc9688373448ba6","Cloud droplet number concentration prediction is central to large-scale weather and climate modelling. The benchmark cloud parcel model calculation of aerosol particle growth and activation, by diffusion of vapour to aerosol particles in a rising parcel of air experiencing adiabatic expansion, is too computationally expensive for use in large-scale global models. Therefore the process of activation of aerosol particles into cloud droplets is parameterised with an aim to strike the optimum balance between numerical expense and accuracy. We present a detailed systematic evaluation of three cloud droplet activation parameterisations that are widely used in large-scale models and one recent update. In all cases, it is found that there is a tendency to overestimate the fraction of activated aerosol particles when the aerosol particle ""median diameter"" is large (between 250 and 2000 nm) in a single lognormal mode simulation. This is due to an infinite ""effective simulation time"" of the parameterisations compared to a prescribed simulation time in the parcel model. This problem arises in the parameterisations because it is assumed that a parcel of air rises to the altitu. © Author(s) 2014. CC Attribution 3.0 License."
"36058435800;7202607188;37661167800;6701772538;7005274759;7003314595;6507447151;55813419700;6506622371;13008018200;6603789748;55905970100;55905504600;6603315547;7102011023;","Balloon-borne match measurements of midlatitude cirrus clouds",2014,"10.5194/acp-14-7341-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904578010&doi=10.5194%2facp-14-7341-2014&partnerID=40&md5=2e96af061b08ff51ee036438329f3d8a","Observations of high supersaturations with respect to ice inside cirrus clouds with high ice water content (> 0.01 g kg&minus;1) and high crystal number densities (> 1 cm&minus;3) are challenging our understanding of cloud microphysics and of climate feedback processes in the upper troposphere. However, single measurements of a cloudy air mass provide only a snapshot from which the persistence of ice supersaturation cannot be judged. We introduce here the ""cirrus match technique"" to obtain information about the evolution of clouds and their saturation ratio. The aim of these coordinated balloon soundings is to analyze the same air mass twice. To this end the standard radiosonde equipment is complemented by a frost point hygrometer, ""SnowWhite"", and a particle backscatter detector, ""COBALD"" (Compact Optical Backscatter AerosoL Detector). Extensive trajectory calculations based on regional weather model COSMO (Consortium for Small-Scale Modeling) forecasts are performed for flight planning, and COSMO analyses are used as a basis for comprehensive microphysical box modeling (with grid scale of 2 and 7 km, respectively). Here we present the results of matching a cirrus cloud to within 2-15 km, realized on 8 June 2010 over Payerne, Switzerland, and a location 120 km downstream close to Zurich. A thick cirrus cloud was detected over both measurement sites. We show that in order to quantitatively reproduce the measured particle backscatter ratios, the small-scale temperature fluctuations not resolved by COSMO must be superimposed on the trajectories. The stochastic nature of the fluctuations is captured by ensemble calculations. Possibilities for further improvements in the agreement with the measured backscatter data are investigated by assuming a very slow mass accommodation of water on ice, the presence of heterogeneous ice nuclei, or a wide span of (spheroidal) particle shapes. However, the resulting improvements from these microphysical refinements are moderate and comparable in magnitude with changes caused by assuming different regimes of temperature fluctuations for clear-sky or cloudy-sky conditions, highlighting the importance of proper treatment of subscale fluctuations. The model yields good agreement with the measured backscatter over both sites and reproduces the measured saturation ratios with respect to ice over Payerne. Conversely, the 30% in-cloud supersaturation measured in a massive 4 km thick cloud layer over Zurich cannot be reproduced, irrespective of the choice of meteorological or microphysical model parameters. The measured supersaturation can only be explained by either resorting to an unknown physical process, which prevents the ice particles from consuming the excess humidity, or - much more likely - by a measurement error, such as a contamination of the sensor housing of the SnowWhite hygrometer by a precipitation drop from a mixed-phase cloud just below the cirrus layer or from some very slight rain in the boundary layer. This uncertainty calls for in-flight checks or calibrations of hygrometers under the special humidity conditions in the upper troposphere. © Author(s) 2014. CC Attribution 3.0 License."
"35779366300;8680433600;7004678728;7003865921;55545601500;","Study of global cloud droplet number concentration with A-Train satellites",2014,"10.5194/acp-14-7125-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904338996&doi=10.5194%2facp-14-7125-2014&partnerID=40&md5=253a47ed472301141c5057d3645e55b4","Cloud droplet number concentration (CDNC) is an important microphysical property of liquid clouds that impacts radiative forcing, precipitation and is pivotal for understanding cloud-aerosol interactions. Current studies of this parameter at global scales with satellite observations are still challenging, especially because retrieval algorithms developed for passive sensors (i.e., MODerate Resolution Imaging Spectroradiometer (MODIS)/Aqua) have to rely on the assumption of cloud adiabatic growth. The active sensor component of the A-Train constellation (i.e., Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)/CALIPSO) allows retrievals of CDNC from depolarization measurements at 532 nm. For such a case, the retrieval does not rely on the adiabatic assumption but instead must use a priori information on effective radius (re), which can be obtained from other passive sensors. In this paper, re values obtained from MODIS/Aqua and Polarization and Directionality of the Earth Reflectance (POLDER)/PARASOL (two passive sensors, components of the A-Train) are used to constrain CDNC retrievals from CALIOP. Intercomparison of CDNC products retrieved from MODIS and CALIOP sensors is performed, and the impacts of cloud entrainment, drizzling, horizontal heterogeneity and effective radius are discussed. By analyzing the strengths and weaknesses of different retrieval techniques, this study aims to better understand global CDNC distribution and eventually determine cloud structure and atmospheric conditions in which they develop. The improved understanding of CDNC can contribute to future studies of global cloud-aerosol-precipitation interaction and parameterization of clouds in global climate models (GCMs). © Author(s) 2014."
"42263280300;55796506900;36628695400;","Improvement of cloud microphysics in the aerosolclimate model BCC_AGCM2.0.1_CUACE/AERO, evaluation against observations, and updated aerosol indirect effect",2014,"10.1002/2014JD021886","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921332525&doi=10.1002%2f2014JD021886&partnerID=40&md5=4c8338e7c0ff5f691c3d459670299595","A two-moment cloud microphysical scheme, to predict both the mass and number concentrations of cloud droplets and ice crystals, is implemented into the aerosol-climate model BCC_AGCM2.0.1_CUACE/Aero. The model results for aerosols, cloud properties, and meteorological fields are evaluated, and the anthropogenic aerosol indirect effect (AIE) is estimated. The new model simulates more realistic aerosol mass concentrations and optical depth compared with the original version using a one-moment bulk cloud microphysical scheme. The global annual mean column cloud droplet number concentration (CDNC) from the new model is 3.3 × 1010 m-2, which is comparable to the 4.0 × 1010 m-2 from satellite retrieval. The global annual mean cloud droplet effective radius at the cloud top from the new model is 8.1 μm, which is smaller than the 10.5 μm from observation. The simulated liquid water path (LWP) in the new model is significantly lower than that in the original model. In particular, the annual mean LWP is lower in the new model by more than 100 g m-2 in some midlatitude regions and hence much more consistent with satellite retrievals. Cloud radiative forcing and precipitation are improved to some extent in the new model. The global annual mean radiation budget at the top of the atmosphere is 0.6 W m-2, which is considerably different from the value of 1.8 W m-2 in the original model. The global annual mean anthropogenic AIE is estimated to be 1.9 W m-2 without imposing a lower bound of CDNC, whereas it is reduced significantly when a higher lower bound of CDNC is prescribed. © 2014. American Geophysical Union. All rights reserved."
"55796430300;7003666669;55544607500;54903097700;7005265210;7202252296;7102577095;","Semidirect dynamical and radiative effect of north african dust transport on lower tropospheric clouds over the subtropical north atlantic in CESM 1.0",2014,"10.1002/2013JD020997","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925438658&doi=10.1002%2f2013JD020997&partnerID=40&md5=0786c9988d9d79061eb190615e3060e1","This study uses a century length preindustrial climate simulation by the Community Earth System Model (CESM 1.0) to explore statistical relationships between dust, clouds, and atmospheric circulation and to suggest a semidirect dynamical mechanism linking subtropical North Atlantic lower tropospheric cloud cover with North African dust transport. The length of the run allows us to account for interannual variability of North African dust emissions and transport in the model. CESM’s monthly climatology of both aerosol optical depth and surface dust concentration at Cape Verde and Barbados, respectively, agree well with available observations, as does the aerosol size distribution at Cape Verde. In addition, CESM shows strong seasonal cycles of dust burden and lower tropospheric cloud fraction, with maximum values occurring during boreal summer, when a strong correlation between these two variables exists over the subtropical North Atlantic. Calculations of Estimated Inversion Strength (EIS) and composites of EIS on high and low downstream North African dust months during boreal summer reveal that dust is likely increasing inversion strength over this region due to both solar absorption and reflection. We find no evidence for a microphysical link between dust and lower tropospheric clouds in this region. These results yield new insight over an extensive period of time into the complex relationship between North African dust and North Atlantic lower tropospheric clouds, which has previously been hindered by spatiotemporal constraints of observations. Our findings lay a framework for future analyses using different climate models and submonthly data over regions with different underlying dynamics. © 2014. American Geophysical Union. All rights reserved."
"56524152600;7005131869;7003748648;","Evaluation of the convection-resolving regional climate modeling approach in decade-long simulations",2014,"10.1002/2014JD021478","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924854959&doi=10.1002%2f2014JD021478&partnerID=40&md5=d0878a1b20558f74edf1d973df106512","The uncertainties in current global and regional climate model integrations are partly related to the representation of clouds, moist convection, and complex topography, thus motivating the use of convection-resolving models. On climate time scales, convection-resolving methods have been used for process studies, but application to long-term scenario simulations has been very limited. Here we present a convection-resolving simulation for a 10 yearlong period (1998–2007) integrated with the Consortium for Small-Scale Modeling in Climate Mode model. Two one-way nested grids are used with horizontal resolutions of 2.2 km for a convection-resolving model (CRM2) on an extended Alpine domain (1100 km × 1100 km) and 12 km for a convection-parametrizing model (CPM12) covering Europe. CPM12 is driven by lateral boundary conditions from the ERA-Interim reanalysis. Validation is conducted against high-resolution surface data. The CRM2 model strongly improves the simulation of the diurnal cycles of precipitation and temperature, despite an enhanced warm bias and a tendency for the overestimation of precipitation over the Alps. The CPM12 model has a poor diurnal cycle associated with the use of parameterized convection. The assessment of extreme precipitation events reveals that both models adequately represent the frequency-intensity distributions for daylong events in summer, but large differences occur for hourly precipitation. The CPM12 model underestimates the frequency of heavy hourly events, while CRM2 shows good agreement with observations in the summer season. We also present results on the scaling of precipitation extremes with local daily mean temperatures. In accordance with observations, CRM2 exhibits adiabatic scaling for intermediate hourly events (90th percentile) and superadiabatic scaling for extreme hourly events (99th and 99.9th percentiles) during the summer season. The CPM12 model partly reproduces this scaling as well. The excellent performance of CRM2 in representing hourly precipitation events in terms of intensity and scaling is highly encouraging, as this addresses a previously untested (and untuned) model capability. © 2014. American Geophysical Union. All rights reserved."
"36611965700;16402575500;","Separation of the lapse rate and the cold point tropopauses in the tropics and the resulting impact on cloud top-tropopause relationships",2014,"10.1002/2013JD021189","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925387698&doi=10.1002%2f2013JD021189&partnerID=40&md5=9246672b3828b4a35121335a58c816db","Four years of temperature profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate GPS satellite retrievals are used to examine the difference between the World Meteorological Organization lapse rate definition and the cold point definition of the tropopause in the tropics. The separation between the cold point tropopause (CPT) and lapse rate tropopause (LRT) heights is quantified in seasonal averages and with the frequency of occurrence. In seasonal averages, small separations, <0.5 km, are found in the deep tropics, increasing to ~1 km toward higher latitudes and maximizing at ~1.5 km near the jet streams. The seasonal average separations show significant longitudinal structures in the December-January-February (DJF) and June-July-August (JJA) seasons. Case studies indicate that breaking Rossby waves and their effects extending into the equatorial region are responsible for the longitudinal structure in the DJF season. The seasonal average CPT-LRT separation therefore identifies the regions of the tropical upper troposphere-lower stratosphere that are controlled by extratropical forcing. Examination of individual profiles shows that a small yet significant fraction (~12%) of temperature profiles has CPT-LRT separations of 1 km or larger in the region of small seasonal average separation. These large separations are produced by wave perturbations of the upper tropospheric temperature structure. The impact of tropopause separation on the cloud top-tropopause relationship is examined using colocated CALIPSO cloud top data. We find that the frequency of clouds above the tropopause is reduced by approximately 50% if the CPT is used instead of LRT. The occurrence of clouds above the CPT is nevertheless significant, especially over the western Pacific in the DJF season and over the Asian monsoon region in the JJA season. © 2014. American Geophysical Union. All rights reserved."
"8874791900;54383118700;11939861600;","Radiation sensitivity tests of the HARMONIE 37h1 NWP model",2014,"10.5194/gmd-7-1433-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904468012&doi=10.5194%2fgmd-7-1433-2014&partnerID=40&md5=f602f1ff62845369724c69ad27e99e4b","When short-wave (SW) radiation fluxes modelled with a numerical weather prediction (NWP) model or climate model do not match observed SW fluxes it can be challenging to find the cause of the differences. Several elements in the model affect SW fluxes. This necessitates individual testing of each of the physical processes in the NWP model. Here we present a focused study of the SW radiation schemes in the HIRLAM (HIgh Resolution Limited Area Model) Aladin Regional Mesoscale Operational NWP In Europe (HARMONIE) model, which is the primary NWP model used and developed by several National Weather Services in Europe. Detailed calculations have been made with the DISORT model run in the libRadtran framework, which is a collection of state-of-the-art radiative transfer software and data sets. These are used to test the NWP radiation calculations. Both models are given the same atmospheric properties as input. We also perform a separate test of cloud liquid optical property parameterisations with Mie calculations. This leads us to introduce a new parameterisation for calculating these properties. In addition, we show that the results of a simpler radiation scheme, introduced into HARMONIE, compare well with those of the comprehensive default parameterisations. The methodology applied here may be used for testing radiation schemes in other NWP or climate models. © Author(s) 2014. CC Attribution 3.0 License."
"6603134359;55505978200;6701718644;6603727335;35072736500;7004029258;7006762240;6506827783;23096334600;7202588796;","The Full Annual Carbon Balance of Boreal Forests Is Highly Sensitive to Precipitation",2014,"10.1021/ez500169j","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84969138526&doi=10.1021%2fez500169j&partnerID=40&md5=021c97a87c9f8630dbb36abf96c16fef","The boreal forest carbon balance is predicted to be particularly sensitive to climate change. Carbon balance estimates of these biomes stem mainly from eddy-covariance measurements of net ecosystem exchange (NEE). However, a full net ecosystem carbon balance (NECB) must include the lateral carbon export (LCE) through discharge. We show that annual LCE at a boreal forest site ranged from 4 to 28%, averaging 11% (standard deviation of 8%), of annual NEE over 13 years. Annual LCE and NEE are strongly anticorrelated; years with weak NEE coincide with high LCE. The decreased NEE in response to increased precipitation is caused by a reduction in the amount of incoming radiation caused by clouds. If our finding is also valid for other sites, it implies that increased precipitation at high latitudes may shift forest NECB in large areas of the boreal biome. Our results call for future analysis of this dual effect of precipitation on NEE and LCE. © 2014 American Chemical Society."
"22635081500;7004160106;6603081424;7409322518;7402933297;7203062717;","Modeling the influences of aerosols on pre-monsoon circulation and rainfall over Southeast Asia",2014,"10.5194/acp-14-6853-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903849552&doi=10.5194%2facp-14-6853-2014&partnerID=40&md5=101776cb7500d9d4a8357c732f7ffaab","We conduct several sets of simulations with a version of NASA's Goddard Earth Observing System, version 5, (GEOS-5) Atmospheric Global Climate Model (AGCM) equipped with a two-moment cloud microphysical scheme to understand the role of biomass burning aerosol (BBA) emissions in Southeast Asia (SEA) in the pre-monsoon period of February-May. Our experiments are designed so that both direct and indirect aerosol effects can be evaluated. For climatologically prescribed monthly sea surface temperatures, we conduct sets of model integrations with and without biomass burning emissions in the area of peak burning activity, and with direct aerosol radiative effects either active or inactive. Taking appropriate differences between AGCM experiment sets, we find that BBA affects liquid clouds in statistically significantly ways, increasing cloud droplet number concentrations, decreasing droplet effective radii (i.e., a classic aerosol indirect effect), and locally suppressing precipitation due to a deceleration of the autoconversion process, with the latter effect apparently also leading to cloud condensate increases. Geographical re-arrangements of precipitation patterns, with precipitation increases downwind of aerosol sources are also seen, most likely because of advection of weakly precipitating cloud fields. Somewhat unexpectedly, the change in cloud radiative effect (cloud forcing) at surface is in the direction of lesser cooling because of decreases in cloud fraction. Overall, however, because of direct radiative effect contributions, aerosols exert a net negative forcing at both the top of the atmosphere and, perhaps most importantly, the surface, where decreased evaporation triggers feedbacks that further reduce precipitation. Invoking the approximation that direct and indirect aerosol effects are additive, we estimate that the overall precipitation reduction is about 40% due to the direct effects of absorbing aerosols, which stabilize the atmosphere and reduce surface latent heat fluxes via cooler land surface temperatures. Further refinements of our two-moment cloud microphysics scheme are needed for a more complete examination of the role of aerosol-convection interactions in the seasonal development of the SEA monsoon. © 2014 Author(s)."
"55460555300;7102578937;7801561771;7003613864;55940397300;57210538699;36504218000;","Changes in atmospheric aerosol loading retrieved from space-based measurements during the past decade",2014,"10.5194/acp-14-6881-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903974015&doi=10.5194%2facp-14-6881-2014&partnerID=40&md5=248477cfa352daad66a2b405fb367c57","The role and potential management of short-lived atmospheric pollutants such as aerosols are currently a topic of scientific and public debates. Our limited knowledge of atmospheric aerosol and its influence on the Earth's radiation balance has a significant impact on the accuracy and error of current predictions of future climate change. In the last few years, there have been several accounts of the changes in atmospheric aerosol derived from satellite observations, but no study considering the uncertainty caused by different/limited temporal sampling of polar-orbiting satellites and cloud disturbance in the trend estimates of cloud-free aerosol optical thickness (AOT). This study presents an approach to minimize the uncertainties by use of weighted least-squares regression and multiple satellite-derived AOTs from the space-born instruments, MODIS (onboard Terra from 2000 to 2009 and Aqua form 2003 to 2008), MISR (Terra from 2000 to 2010), and SeaWiFS (OrbView-2 from 1998 to 2007) and thereby provides more convincing trend estimates for atmospheric aerosols during the past decade. The AOT decreases over western Europe (i.e., by up to about-40% from 2003 to 2008). In contrast, a statistically significant increase (about +34% in the same period) over eastern China is observed and can be attributed to the increase in both industrial output and Asian desert dust. © 2014 Author(s)."
"56216562700;8378887500;6603936414;56651119900;6602489117;8256598200;57202099430;55050158700;8791306500;8058018000;56767589600;56273253000;56010548600;7003341789;55502590800;43462093500;57214302151;56246458800;","Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) scientific objectives",2014,"10.5194/amt-7-1915-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891847456&doi=10.5194%2famt-7-1915-2014&partnerID=40&md5=71e6ad151b4f27efb8b091d9816f48f7","The upper troposphere/lower stratosphere (UTLS) represents an important part of the climate system. Even small changes in the composition and dynamic structure of this region have significant radiative effects. Quantifying the underlying physical and chemical processes therefore represents a crucial task. Currently, there is a lack of UTLS observations with sufficient three-dimensional resolution. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) aircraft instrument addresses this observational lack by providing observations of numerous trace constituents as well as temperature and cloud structures with an unprecedented combination of vertical resolution (up to 300 m) and horizontal resolution (about 30 km × 30 km). As a result, important scientific questions concerning stratosphere-troposphere exchange, the occurrence of subvisible cirrus clouds in the lowermost stratosphere (LMS), polar chemistry, and gravity wave p. © Author(s) 2014."
"36094524600;6602600493;9233146000;10045102700;","The impact of boundary forcing on RegCM4.2 surface energy budget",2014,"10.1007/s10584-013-0995-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937928614&doi=10.1007%2fs10584-013-0995-x&partnerID=40&md5=c3bd9fc115d9aceddb6de102425ecab2","The surface energy budget components from two simulations of the regional climate model RegCM4.2 over the European/North African domain during the period 1989–2005 are analysed. The simulations differ in specified boundary forcings which were obtained from ERA-Interim reanalysis and the HadGEM2-ES Earth system model. Surface radiative and turbulent fluxes are compared against ERA-Interim. Errors in surface radiative fluxes are derived with respect to the Global Energy and Water Cycle Experiment/Surface Radiation Budget satellite-based products. In both space and time, we find a high degree of realism in the RegCM surface energy budget components, but some substantial errors and differences between the two simulations are also present. The most prominent error is an overestimation of the net surface shortwave radiation flux of more than 50 W/m2 over central and southeastern Europe during summer months. This error strongly correlates with errors in the representation of total cloud cover, and less strongly with errors in surface albedo. During other seasons, the amplitude of the surface energy budget components is more in line with reference datasets. The errors may limit the usefulness of RegCM simulations in applications (e.g. high-quality simulation-driven impact studies). However, by using a simple diagnostic model for error interpretation, we suggest potential sensitivity studies aiming to reduce the underestimation of cloud cover and overestimation of shortwave radiation flux. © 2013, Springer Science+Business Media Dordrecht."
"55613112200;8691681600;35228711600;7004864963;","The effect of atmospheric aerosol particles and clouds on net ecosystem exchange in the Amazon",2014,"10.5194/acp-14-6523-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903790936&doi=10.5194%2facp-14-6523-2014&partnerID=40&md5=ce02883d2b1c4755e1365d94ecbc325f","Carbon cycling in the Amazon is closely linked to atmospheric processes and climate in the region as a consequence of the strong coupling between the atmosphere and biosphere. This work examines the effects of changes in net radiation due to atmospheric aerosol particles and clouds on the net ecosystem exchange (NEE) of CO2 in the Amazon region. Some of the major environmental factors affecting the photosynthetic activity of plants, such as air temperature and relative humidity, were also examined. An algorithm for clear-sky irradiance was developed and used to determine the relative irradiance, f, which quantifies the percentage of solar radiation absorbed and scattered due to atmospheric aerosol particles and clouds. Aerosol optical depth (AOD) was calculated from irradiances measured with the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, onboard the Terra and Aqua satellites, and was validated with ground-based AOD measurements from AERONET (Aerosol Robotic Network) sun photometers. Carbon fluxes were measured using eddy covariance technique at the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) flux towers. Two sites were studied: the Jaru Biological Reserve (RBJ), located in Rondonia, and the Cuieiras Biological Reserve at the K34 LBA tower (located in a preserved region in the central Amazon). Analysis was performed continuously from 1999 to 2009 at K34 and from 1999 to 2002 at RBJ, and includes wet, dry and transition seasons. In the Jaru Biological Reserve, a 29% increase in carbon uptake (NEE) was observed when the AOD ranged from 0.10 to 1.5 at 550 nm. In the Cuieiras Biological Reserve, the aerosol effect on NEE was smaller, accounting for an approximate 20% increase in NEE. High aerosol loading (AOD above 3 at 550 nm) or high cloud cover leads to reductions in solar flux and strong decreases in photosynthesis up to the point where NEE approaches zero. The observed increase in NEE is attributed to an enhancement (∼50%) in the diffuse fraction of photosynthetic active radiation (PAR). The enhancement in diffuse PAR can be done through increases in aerosols and/or clouds. In the present study, it was not possible to separate these two components. Significant changes in air temperature and relative humidity resulting from changes in solar radiation fluxes under high aerosol loading were also observed at both sites. Considering the long-range transport of aerosols in the Amazon, the observed changes in NEE for these two sites may occur over large areas in the Amazon, significantly altering the carbon balance in the largest rainforest in the world. © Author(s) 2014. CC Attribution 3.0 License."
"22982141200;55904436200;55904510600;7201920155;57203321797;7103325318;55033235700;","Comparison of NCEP/NCAR and ERA-40 total cloud cover with surface observations over the Tibetan Plateau",2014,"10.1002/joc.3852","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902650833&doi=10.1002%2fjoc.3852&partnerID=40&md5=8885046c0105590e3ff0ff9af8942491","The annual and seasonal total cloud cover (TCC) variations in the eastern and central Tibetan Plateau (TP) during 1961-2005 are analysed using 71 surface observational stations. The mean TCC decreases from the southeastern to the northwestern TP, consistent with the patterns of atmospheric moisture in the region. The annual mean TCC shows a significant decreasing trend of -0.09 percentdecade-1, mainly contributed by winter. About 65% of the stations show significant downward trends on the annual basis with large trend magnitudes occurring in the central TP. The seasonal patterns confirm the annual patterns in most cases. Compared with the surface observations, both National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis (NCEP/NCAR) (1961-2005) and ERA-40 (1961-2001) can reproduce the decreasing TCC trends. The shift of TCC before and after the mid-1980s is obvious in observations and both reanalyses, reflecting the changes of large-scale atmospheric circulation. However, NCEP/NCAR underestimates and ERA-40 overestimates observations on the annual and seasonal basis, presumably caused by the different cloud parameterization schemes. A Taylor diagram diagnose summarizes the discrepancies between observations and reanalyses. © 2013 Royal Meteorological Society."
"55939921400;55939987900;55706776600;7409875726;55939659300;55322972500;26029601100;","Three-dimensional point cloud based sky view factor analysis in complex urban settings",2014,"10.1002/joc.3868","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902658594&doi=10.1002%2fjoc.3868&partnerID=40&md5=ff05eb4ec4882da15b4a218b30d27d4d","Quantitatively describing effects caused by trees is a challenging issue for sky view factor (SVF) studies. The complex geometrical shapes of trees and the seasonally changing canopy volume caused by leaf growth and defoliation have forced SVF users to disregard trees in their analyses or to apply a simple geometric object, such as a rectangular pole or vertically elongated ellipsoid. The three-dimensional point cloud (3DPC) method is useful for quantitative analysis of urban settings by describing the structured spatial complex in detail, not only by shape itself but also with many meaningful indices such as SVF. We here proposed a new SVF analysis method based on 3DPC. Stereoscopic projection was applied to project 3DPC on the virtual hemisphere. From intensive analysis of 3DPC SVF in a normal urban complex area, we discerned the effects caused by trees. The results showed that the tree effect derived from 3DPC SVF in an urban complex is clearly described by a comparison between two cases (trees and no trees). Trees with topography play an important role and contribute to the heat balance in an urban complex. © 2013 Royal Meteorological Society."
"26645289600;24329376600;35547807400;57210518852;","Quantifying components of aerosol-cloud-radiation interactions in climate models",2014,"10.1002/2014JD021710","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904727875&doi=10.1002%2f2014JD021710&partnerID=40&md5=8aecd7d7dac5eb65c857a78b365a2e94","The interaction of anthropogenic aerosols with radiation and clouds is the largest source of uncertainty in the radiative forcing of the climate during the industrial period. Here we apply novel techniques to diagnose the contributors to the shortwave (SW) effective radiative forcing (ERF) from aerosol-radiation-interaction (ERFari) and from aerosol cloud interaction (ERFaci) in experiments performed in phase 5 of the Coupled Model Intercomparison Project. We find that the ensemble mean SW ERFari+aci of -1.40±0.56 W m-2 comes roughly 25% from ERFari (-0.35±0.20 W m-2) and 75% from ERFaci (-1.04±0.67 W m-2). ERFari is made up of -0.62±0.30 W m-2 due to aerosol scattering opposed by +0.26 ± 0.12 W m-2 due to aerosol absorption and is largest near emission sources. The ERFari from nonsulfate aerosols is +0.13 ± 0.09 W m-2, consisting of -0.15±0.11 W m-2 of scattering and +0.29 ± 0.15 W m-2 of absorption. The change in clear-sky flux is a negatively biased measure of ERFari, as the presence of clouds reduces the magnitude and intermodel spread of ERFari by 40-50%. ERFaci, which is large both near and downwind of emission sources, is composed of -0.99±0.54 W m-2 from enhanced cloud scattering, with much smaller contributions from increased cloud amount and absorption. In models that allow aerosols to affect ice clouds, large increases in the optical depth of high clouds cause substantial longwave and shortwave radiative anomalies. Intermodel spread in ERFaci is dominated by differences in how aerosols increase cloud scattering, but even if all models agreed on this effect, over a fifth of the spread in ERFaci would remain due solely to differences in total cloud amount. Key Points We compute effective forcings from aerosol-cloud-radiation interactions in GCMs Total aerosol forcing is 25% direct effect and 75% indirect effect Indirect effect comes mostly from enhanced cloud scattering ©2014. American Geophysical Union. All Rights Reserved."
"55726160100;55519994900;23991212200;7202252296;7102577095;","Investigating impacts of forest fires in Alaska and western Canada on regional weather over the northeastern United States using CAM5 global simulations to constrain transport to a WRF-Chem regional domain",2014,"10.1002/2013JD020973","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904767793&doi=10.1002%2f2013JD020973&partnerID=40&md5=35da1d5f4773a92b6c62f915f4017277","An aerosol-enabled globally driven regional modeling system has been developed by coupling the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5) with the Weather Research and Forecasting model with chemistry (WRF-Chem). In this modeling system, aerosol-enabled CAM5, a state-of-the-art global climate model is downscaled to provide coherent meteorological and chemical boundary conditions for regional WRF-Chem simulations. Aerosol particle emissions originating outside the WRF-Chem domain can be a potentially important nonlocal aerosol source. As a test case, the potential impacts of nonlocal forest fire aerosols on regional precipitation and radiation were investigated over the northeastern United States during the summer of 2004. During this period, forest fires in Alaska and western Canada lofted aerosol particles into the midtroposphere, which were advected across the United States. WRF-Chem simulations that included nonlocal biomass burning aerosols had domain-mean aerosol optical depths that were nearly three times higher than those without, which reduced peak downwelling domain-mean shortwave radiation at the surface by ~25 W m-2. In this classic twin experiment design, adding nonlocal fire plume led to near-surface cooling and changes in cloud vertical distribution, while variations in domain-mean cloud liquid water path were negligible. The higher aerosol concentrations in the simulation with the fire plume resulted in a ~10% reduction in domain-mean precipitation coincident with an ~8% decrease in domain-mean CAPE. A suite of simulations was also conducted to explore sensitivities of meteorological feedbacks to the ratio of black carbon to total plume aerosols, as well as to overall plume concentrations. Results from this ensemble revealed that plume-induced near-surface cooling and CAPE reduction occur in a wide range of conditions. The response of moist convection was very complex because of strong thermodynamic internal variability. Key Points Nonlocal fire emissions resulted in ~10% precipitation reduction Nonlocal fire emissions reduced peak surface shortwave radiation at by 25 W m-2 An aerosol-enabled globally driven regional modeling system is developed ©2014. American Geophysical Union. All Rights Reserved."
"55726160100;55519994900;23991212200;7202252296;7102577095;","Investigating impacts of forest fires in Alaska and western Canada on regional weather over the northeastern United States using CAM5 global simulations to constrain transport to a WRF-Chem regional domain",2014,"10.1002/2013JD020973.","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018750745&doi=10.1002%2f2013JD020973.&partnerID=40&md5=e8639b92f9ca5b032cdd8363fa8d3f3e","An aerosol-enabled globally driven regional modeling system has been developed by coupling the National Center for Atmospheric Research’s Community Atmosphere Model version 5 (CAM5) with the Weather Research and Forecasting model with chemistry (WRF-Chem). In this modeling system, aerosol-enabled CAM5, a state-of-the-art global climate model is downscaled to provide coherent meteorological and chemical boundary conditions for regional WRF-Chem simulations. Aerosol particle emissions originating outside the WRF-Chem domain can be a potentially important nonlocal aerosol source. As a test case, the potential impacts of nonlocal forest fire aerosols on regional precipitation and radiation were investigated over the northeastern United States during the summer of 2004. During this period, forest fires in Alaska and western Canada lofted aerosol particles into the midtroposphere, which were advected across the United States. WRF-Chem simulations that included nonlocal biomass burning aerosols had domain-mean aerosol optical depths that were nearly three times higher than those without, which reduced peak downwelling domain-mean shortwave radiation at the surface by ~25 W m-2. In this classic twin experiment design, adding nonlocal fire plume led to near-surface cooling and changes in cloud vertical distribution, while variations in domain-mean cloud liquid water path were negligible. The higher aerosol concentrations in the simulation with the fire plume resulted in a ~10%reduction in domain-mean precipitation coincident with an ~8%decrease in domain-mean CAPE. A suite of simulations was also conducted to explore sensitivities of meteorological feedbacks to the ratio of black carbon to total plume aerosols, as well as to overall plume concentrations. Results from this ensemble revealed that plume-induced near-surface cooling and CAPE reduction occur in a wide range of conditions. The response of moist convection was very complex because of strong thermodynamic internal variability. © 2014. American Geophysical Union. All Rights Reserved."
"55606974300;7102604282;8570871900;7003519472;55732558900;55245030000;","Radiative forcing of organic aerosol in the atmosphere and on snow: Effects of SOA and brown carbon",2014,"10.1002/2013JD021186","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904747009&doi=10.1002%2f2013JD021186&partnerID=40&md5=92e7519d60f5cc44bba2fcdf79e7dfae","Organic aerosols (OA) play an important role in climate change. However, very few calculations of global OA radiative forcing include secondary organic aerosol (SOA) or the light-absorbing part of OA (brown carbon). Here we use a global model to assess the radiative forcing associated with the change in primary organic aerosol (POA) and SOA between present-day and preindustrial conditions in both the atmosphere and the land snow/sea ice. Anthropogenic emissions are shown to substantially influence the SOA formation rate, causing it to increase by 29 Tg/yr (93%) since preindustrial times. We examine the effects of varying the refractive indices, size distributions for POA and SOA, and brown carbon fraction in SOA. The increase of SOA exerts a direct forcing ranging from -0.12 to -0.31 W m-2 and a first indirect forcing in warm-phase clouds ranging from 0.22 to 0.29 W m-2, with the range due to different assumed SOA size distributions and refractive indices. The increase of POA since preindustrial times causes a direct forcing varying from -0.06 to -0.11 W m-2, when strongly and weakly absorbing refractive indices for brown carbon are used. The change in the total OA exerts a direct forcing ranging from -0.14 to -0.40 W m-2. The atmospheric absorption from brown carbon ranges from +0.22 to +0.57 W m-2, which corresponds to 27%~70% of the black carbon (BC) absorption predicted in the model. The radiative forcing of OA deposited in land snow and sea ice ranges from +0.0011 to +0.0031 W m-2 or as large as 24%of the forcing caused by BC in snow and ice simulated by the model. © 2014. American Geophysical Union. All Rights Reserved."
"35073084900;7003263504;7003780337;","Assessing the performance of GPS radio occultation measurements in retrieving tropospheric humidity in cloudiness: A comparison study with radiosondes, ERA-interim, and AIRS data sets",2014,"10.1002/2013JD021398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904719967&doi=10.1002%2f2013JD021398&partnerID=40&md5=3b97f33c1d4c2b3bb5e21c99fba0f89f","We assess the impact that the Global Positioning System radio occultations (GPSRO) measurements have on complementing different data sets in characterizing the lower-to-middle tropospheric humidity in cloudy conditions over both land and oceans using data from 1 August 2006 to 31 October 2006. We use observations from rawinsondes, Global Positioning System radio occultations (GPSRO), Atmospheric Infrared Sounder (AIRS), and the European Center for Medium-Range Weather Forecasts Reanalysis Interim (ERA-Interim). During the selected time period, Constellation Observing System for Meteorology, Ionosphere, and Climate data were not assimilated in ERA-Interim. From each data set, we estimate a zonally averaged tropospheric specific humidity profile at tropical, middle, and high latitudes. Over land, we use rawinsondes as the ground truth and quantify the specific humidity differences and root-mean-square-errors (RMSEs) of the GPSRO, AIRS, and ERA-Interim profiles. GPSRO are beneficial in retrieving lower tropospheric humidity than upper tropospheric profiles, due to their loss of sensitivity at high altitudes. Blending GPSRO with ERA-Interim produces profiles with smaller humidity biases outside the tropics, but GPSRO data do not improve the humidity RMSE when compared to rawinsondes. Combining GPSRO with AIRS leads to smaller humidity bias at the tropics and high latitudes, while reducing humidity’s RMSEs. Over oceans, no rawinsonde information is available, and we use ERA-Interim as a reference. Combining GPSRO with AIRS leads to smaller humidity RMSEs than AIRS. We conclude that cross-comparisons and synergies among multi-instrument observations are promising in advancing our knowledge of the tropospheric humidity in cloudy conditions. GPSRO data can contribute to improving humidity retrievals over cloud-covered regions, especially over land and within the boundary layer. © 2014. American Geophysical Union. All Rights Reserved."
"56246506700;8568391400;6603850285;6603563152;23995325300;","Growth of sulphuric acid nanoparticles under wet and dry conditions",2014,"10.5194/acp-14-6461-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903774486&doi=10.5194%2facp-14-6461-2014&partnerID=40&md5=00a8c0259de7183f9d959d44cafa28f8","New particle formation, which greatly influences the number concentrations and size distributions of an atmospheric aerosol, is often followed by a rapid growth of freshly formed particles. The initial growth of newly formed aerosol is the crucial process determining the fraction of nucleated particles growing to cloud condensation nuclei sizes, which have a significant influence on climate. In this study, we report the laboratory observations of the growth of nanoparticles produced by nucleation of H2SO4 and water in a laminar flow tube at temperatures of 283, 293 and 303 K, under dry (a relative humidity of 1%) and wet conditions (relative humidity of 30%) and residence times of 30, 45, 60 and 90 s. The initial H2SO4 concentration spans the range from 2 × 108 to 1.4 × 1010 molecule cm-3 and the calculated wall losses of H2SO4 were assumed to be diffusion limited. The detected particle number concentrations, measured by the Ultrafine Condensation Particle Counter (UCPC) and Differential Mobility Particle Sizer (DMPS), were found to depend strongly on the residence time. Hygroscopic particle growth, presented by growth factors, was found to be in good agreement with the previously reported studies. The experimental growth rates ranged from 20 nm h-1 to 890 nm h-1 at relative humidity (RH) 1% and from 7 nm h-1 to 980 nm h-1 at RH 30% and were found to increase significantly with the increasing concentration of H2SO4. Increases in the nucleation temperature had a slight enhancing effect on the growth rates under dry conditions. The influence of relative humidity on growth was not consistent - at lower H2SO4 concentrations, the growth rates were higher under dry conditions while at H2SO4 concentrations greater than 1 × 1010 molecule cm-3, the growth rates were higher under wet conditions. The growth rates show only a weak dependence on the residence time. The experimental observations were compared with predictions made using a numerical model, which investigates the growth of particles with three different extents of neutralization by ammonia, NH3: (1) pure H2SO4 - H2O particles; (2) particles formed by ammonium bisulphate, (NH4)HSO4; (3) particles formed by ammonium sulphate, (NH4)2SO4. The highest growth rates were found for ammonium sulphate particles. Since the model accounting for the initial H2SO4 concentration predicted the experimental growth rates correctly, our results suggest that the commonly presumed diffusional wall losses of H2SO4 in case of long-lasting experiments are not so significant. We therefore assume that there are not only losses of H2SO4 on the wall, but also a flux of H2SO4 molecules from the wall into the flow tube, the effect being more profound under dry conditions and at higher temperatures of the tube wall. Based on a comparison with the atmospheric observations, our results indicate that sulphuric acid alone cannot explain the growth rates of particles formed in the atmosphere. © Author(s) 2014. CC Attribution 3.0 License."
"24491752100;7404297096;","CloudSat-constrained cloud ice water path and cloud top height retrievals from MHS 157 and 183.3 GHz radiances",2014,"10.5194/amt-7-1873-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903769540&doi=10.5194%2famt-7-1873-2014&partnerID=40&md5=137edc9493a10160002cd13a625b94ce","Ice water path (IWP) and cloud top height (ht) are two of the key variables in determining cloud radiative and thermodynamical properties in climate models. Large uncertainty remains among IWP measurements from satellite sensors, in large part due to the assumptions made for cloud microphysics in these retrievals. In this study, we develop a fast algorithm to retrieve IWP from the 157, 183.3 ± 3 and 190.3 GHz radiances of the Microwave Humidity Sounder (MHS) such that the MHS cloud ice retrieval is consistent with CloudSat IWP measurements. This retrieval is obtained by constraining the empirical forward models between collocated and coincident measurements of CloudSat IWP and MHS cloud-induced radiance depression (Tcir) at these channels. The empirical forward model is represented by a look-up table (LUT) ofTcir-IWP relationships as a function ofht and the frequency channel. Withht simultaneously retrieved, the IWP is found to be more accurate. The useful range of the MHS IWP retrieval is between 0.5 and 10 kg mĝ̂'2, and agrees well with CloudSat in terms of the normalized probability density function (PDF). Compared to the empirical model, current operational radiative transfer models (RTMs) still have significant uncertainties in characterizing the observedTcir-IWP relationships. Therefore, the empirical LUT method developed here remains an effective approach to retrieving ice cloud properties from the MHS-like microwave channels. © Author(s) 2014. CC Attribution 3.0 License."
"37099552800;53876886100;16233350800;46461233500;24537168200;23479194900;26027431900;10739566100;6506258154;15080710300;6602496366;17433787100;57214957748;14035386400;14420077300;24311471900;57203776263;11339750700;16833315000;34868441100;35461255500;7006712143;25522357400;36647693000;7003545995;7006708207;8657171200;56472932500;8871497700;9432343100;9235257000;8084443000;7005287667;6603135449;7006593624;7005069415;7006387246;","Organic aerosol components derived from 25 AMS data sets across Europe using a consistent ME-2 based source apportionment approach",2014,"10.5194/acp-14-6159-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903207744&doi=10.5194%2facp-14-6159-2014&partnerID=40&md5=aa9687f555bd00f6640edf1d6dc4b582","Organic aerosols (OA) represent one of the major constituents of submicron particulate matter (PM1) and comprise a huge variety of compounds emitted by different sources. Three intensive measurement field campaigns to investigate the aerosol chemical composition all over Europe were carried out within the framework of the European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) and the intensive campaigns of European Monitoring and Evaluation Programme (EMEP) during 2008 (May-June and September-October) and 2009 (February-March). In this paper we focus on the identification of the main organic aerosol sources and we define a standardized methodology to perform source apportionment using positive matrix factorization (PMF) with the multilinear engine (ME-2) on Aerodyne aerosol mass spectrometer (AMS) data. Our source apportionment procedure is tested and applied on 25 data sets accounting for two urban, several rural and remote and two high altitude sites; therefore it is likely suitable for the treatment of AMS-related ambient data sets. For most of the sites, four organic components are retrieved, improving significantly previous source apportionment results where only a separation in primary and secondary OA sources was possible. Generally, our solutions include two primary OA sources, i.e. hydrocarbon-like OA (HOA) and biomass burning OA (BBOA) and two secondary OA components, i.e. semi-volatile oxygenated OA (SV-OOA) and low-volatility oxygenated OA (LV-OOA). For specific sites cooking-related (COA) and marine-related sources (MSA) are also separated. Finally, our work provides a large overview of organic aerosol sources in Europe and an interesting set of highly time resolved data for modeling purposes. © Author(s) 2014."
"7003494403;56032639200;23975565200;6602997651;12774262800;7003431919;","Retrospective analysis of a nonforecasted rain-on-snow flood in the Alps-A matter of model limitations or unpredictable nature?",2014,"10.5194/hess-18-2265-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902836122&doi=10.5194%2fhess-18-2265-2014&partnerID=40&md5=143bb6ec61b1c5a9ef566aedd6ee2ff3","A rain-on-snow flood occurred in the Bernese Alps, Switzerland, on 10 October 2011, and caused significant damage. As the flood peak was unpredicted by the flood forecast system, questions were raised concerning the causes and the predictability of the event. Here, we aimed to reconstruct the anatomy of this rain-on-snow flood in the Lötschen Valley (160 km2) by analyzing meteorological data from the synoptic to the local scale and by reproducing the flood peak with the hydrological model WaSiM-ETH (Water Flow and Balance Simulation Model). This in order to gain process understanding and to evaluate the predictability. The atmospheric drivers of this rain-on-snow flood were (i) sustained snowfall followed by (ii) the passage of an atmospheric river bringing warm and moist air towards the Alps. As a result, intensive rainfall (average of 100 mm day-1) was accompanied by a temperature increase that shifted the 0° line from 1500 to 3200 m a.s.l. (meters above sea level) in 24 h with a maximum increase of 9 K in 9 h. The south-facing slope of the valley received significantly more precipitation than the north-facing slope, leading to flooding only in tributaries along the south-facing slope. We hypothesized that the reason for this very local rainfall distribution was a cavity circulation combined with a seeder-feeder-cloud system enhancing local rainfall and snowmelt along the south-facing slope. By applying and considerably recalibrating the standard hydrological model setup, we proved that both latent and sensible heat fluxes were needed to reconstruct the snow cover dynamic, and that locally high-precipitation sums (160 mm in 12 h) were required to produce the estimated flood peak. However, to reproduce the rapid runoff responses during the event, we conceptually represent likely lateral flow dynamics within the snow cover causing the model to react ""oversensitively"" to meltwater. Driving the optimized model with COSMO (Consortium for Small-scale Modeling)-2 forecast data, we still failed to simulate the flood because COSMO-2 forecast data underestimated both the local precipitation peak and the temperature increase. Thus we conclude that this rain-on-snow flood was, in general, predictable, but requires a special hydrological model setup and extensive and locally precise meteorological input data. Although, this data quality may not be achieved with forecast data, an additional model with a specific rain-on-snow configuration can provide useful information when rain-on-snow events are likely to occur. © 2014 Author(s)."
"54381716300;7006698304;36131108000;","The relationship between clouds and dynamics in Southern Hemisphere extratropical cyclones in the real world and a climate model",2014,"10.1002/2013JD020699","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903280980&doi=10.1002%2f2013JD020699&partnerID=40&md5=72866ede2cc969b307dddb4a9e3ed782","The representation of clouds over the Southern Ocean in contemporary climate models remains a major challenge. A major dynamical influence on the structure of clouds is the passage of extratropical cyclones. They exert significant dynamical influences on the clouds in the dynamically active frontal regions as well as in the dynamically suppressed regions ahead and behind the cyclones. A cyclone compositing methodology is applied to a reanalysis and vertical profiles of cloudiness from CloudSat/CALIPSO to quantify the relationship between clouds and dynamics in extratropical cyclones over the Southern Ocean. It is found that the range of cloud fraction, vertical motion, and relative humidity changes considerably with height. There is a strong quasi-linear relationship between the three variables which changes with altitude. After establishing the observed relationships, the methodology is applied to the Australian Community Climate and Earth System Simulator to evaluate the model’s ability to simulate the identified cloud-dynamics relationships. While the model is able to qualitatively reproduce the overall cloud structure, the circulation around the cyclone is generally too weak. As a result, the model fails to represent the observed cloud to dynamics relationship. This wrong relationship in the model leads to a misrepresentation of the cloud field manifested as either an error in the cloud fraction or as simulating the “right” clouds for the “wrong” reason. The result underscores the importance of relationship-oriented model evaluation techniques over simple right or wrong assessments. © 2014. American Geophysical Union. All Rights Reserved."
"55683910600;13403622000;12040335900;","Spaceborne lidar observations of the ice-nucleating potential of dust, polluted dust, and smoke aerosols in mixed-phase clouds",2014,"10.1002/2013JD021333","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903289260&doi=10.1002%2f2013JD021333&partnerID=40&md5=0ad34eb45ee2e84f4db06a7277c233c2","Previous laboratory studies and in situ measurements have shown that dust particles possess the ability to nucleate ice crystals, and smoke particles to some extent as well. Even with coatings of pollutants such as sulphate and nitrate on the surface of dust particles, it has been shown that polluted dust particles are still able to nucleate ice in the immersion, deposition, condensation, and contact freezing modes, albeit less efficiently than unpolluted dust. The ability of these aerosols to act as ice nuclei in the Earth’s atmosphere has important implications for the Earth’s radiative budget and hence global climate change. Here we determine the relationship between cloud thermodynamic phase and dust, polluted dust, and smoke aerosols individually by analyzing their vertical profiles over a ∼5 year period obtained by NASA’s spaceborne lidar, Cloud-Aerosol Lidar with Orthogonal Polarization. We found that when comparing the effects of temperature and aerosols, temperature appears to have the dominant influence on supercooled liquid cloud fraction. Nonetheless, we found that aerosols still appear to exert a strong influence on supercooled liquid cloud fraction as suggested by the existence of negative temporal and spatial correlations between supercooled liquid cloud fraction and frequencies of dust aerosols from around the world, at the −10°C, −15°C, −20°C, and −25°C isotherms. Although smoke aerosol frequencies were also found to be negatively correlated with supercooled liquid cloud fraction, their correlations are weaker in comparison to those between dust frequencies and supercooled liquid cloud fraction. For the first time, we show this based on observations from space, which lends support to previous studies that dust and potentially smoke aerosols can globally alter supercooled liquid cloud fraction. Our results suggest that the ice-nucleating ability of these aerosols may have an indirect climatic impact that goes beyond the regional scale, by influencing cloud thermodynamic phase globally. © 2014. American Geophysical Union. All Rights Reserved."
"7102253788;6602976712;7004091067;7003663305;","Continental heat anomalies and the extreme melting of the Greenland ice surface in 2012 and 1889",2014,"10.1002/2014JD021470","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903280965&doi=10.1002%2f2014JD021470&partnerID=40&md5=fb33c5e7bee23bfe89d6acf3041ec752","Recent decades have seen increased melting of the Greenland ice sheet. On 11 July 2012, nearly the entire surface of the ice sheet melted; such rare events last occurred in 1889 and, prior to that, during the Medieval Climate Anomaly. Studies of the 2012 event associated the presence of a thin, warm elevated liquid cloud layer with surface temperatures rising above the melting point at Summit Station, some 3212 m above sea level. Here we explore other potential factors in July 2012 associated with this unusual melting. These include (1) warm air originating from a record North American heat wave, (2) transitions in the Arctic Oscillation, (3) transport of water vapor via an Atmospheric River over the Atlantic to Greenland, and (4) the presence of warm ocean waters south of Greenland. For the 1889 episode, the Twentieth Century Reanalysis and historical records showed similar factors at work. However, markers of biomass burning were evident in ice cores from 1889 which may reflect another possible factor in these rare events. We suggest that extreme Greenland summer melt episodes, such as those recorded recently and in the late Holocene, could have involved a similar combination of slow climate processes, including prolonged North American droughts/heat waves and North Atlantic warm oceanic temperature anomalies, together with fast processes, such as excursions of the Arctic Oscillation, and transport of warm, humid air in Atmospheric Rivers to Greenland. It is the fast processes that underlie the rarity of such events and influence their predictability. © 2014. American Geophysical Union. All Rights Reserved."
"56229926400;57204253860;9635764200;","Radar observations of MJO and Kelvin wave interactions during DYNAMO/ CINDY2011/AMIE",2014,"10.1002/2013JD021031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903287579&doi=10.1002%2f2013JD021031&partnerID=40&md5=f3646759172e9f062c661de2ff43ce15","Radar and sounding data collected during the Dynamics of the Madden-Julian Oscillation (DYNAMO), the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011), and the Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation Investigation Experiment (AMIE) field campaigns in the equatorial Indian Ocean to study the initiation of the Madden-Julian Oscillation (MJO) are used to examine the precipitation, cloud, and moisture characteristics during the MJO and convectively coupled Kelvin waves (KWs). Three MJO events and 10 KWs were identified from satellite data using different wave number frequency filters, although event identification varied based on the chosen range of latitude, frequency, and outgoing longwave radiation threshold. Radar and sounding data were composited for the three MJO events, four KWs during the active MJO, five KWs during the suppressed MJO, and one KW during the developing MJO. The MJO composite was generally consistent with past studies, although an increase in convective rain appeared to precede relative humidity increases at low- to middle-levels. The active and developing MJO KWs produced more rain and cloud than suppressed MJO KWs and had a secondary peak in stratiform rain potentially associated with subsynoptic-scale cloud clusters. The suppressed MJO KW composite displayed previously documented structure of vertical moisture buildup prior to the KW passage, whereas the developing MJO KW did not. The KW moisture signature during the active MJO was somewhat overwhelmed by the moist environment associated with the active MJO. Upper level moisture was enhanced after KW passage, regardless of MJO phase. However, upper level moisture was most enhanced after the developing MJO KW passage, providing deep tropospheric moisture that may have assisted MJO onset. Nonprecipitating upper level cloud and midlevel altocumulus/altostratus also persisted after most KW passages. © 2014. American Geophysical Union. All Rights Reserved."
"6602847465;36237711800;55917341900;55476786400;7005703744;14014252200;","Suomi NPP VIIRS imagery evaluation",2014,"10.1002/2013JD021170","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903289279&doi=10.1002%2f2013JD021170&partnerID=40&md5=4b52b11efc9f0ded5ef00665302c08a4","The Visible Infrared Imaging Radiometer Suite (VIIRS) combines the best aspects of both civilian and military heritage instrumentation. VIIRS has improved capabilities over its predecessors: a wider swath width and much higher spatial resolution at swath edge. The VIIRS day-night band (DNB) is sensitive to very low levels of visible light and is capable of detecting low clouds, land surface features, and sea ice at night, in addition to light emissions from both man-made and natural sources. Imagery from the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite has been in the checkout process since its launch on 28 October 2011. The ongoing evaluation of VIIRS Imagery helped resolve several imagery-related issues, including missing radiance measurements. In particular, near-constant contrast imagery, derived from the DNB, had a large number of issues to overcome, including numerous missing or blank-fill images and a stray light leakage problem that was only recently resolved via software fixes. In spite of various sensor issues, the VIIRS DNB has added tremendous operational and research value to Suomi NPP. Remarkably, it has been discovered to be sensitive enough to identify clouds even in very low light new moon conditions, using reflected light from the Earth’s airglow layer. Impressive examples of the multispectral imaging capabilities are shown to demonstrate its applications for a wide range of operational users. Future members of the Joint Polar Satellite System constellation will also carry and extend the use of VIIRS. Imagery evaluation will continue with these satellites to ensure the quality of imagery for end users. © 2014. American Geophysical Union. All Rights Reserved."
"55768583400;6507868235;6602194980;","Winter-responding proxy temperature reconstructions and the North Atlantic Oscillation",2014,"10.1002/2014JD021561","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903288929&doi=10.1002%2f2014JD021561&partnerID=40&md5=8b33ceb40d145b2b6e24bc09a9f6f74d","Instrumental temperature data for the Northern Hemisphere (30°–90°N) clearly indicate that winter season variability is larger than equivalent measures for summer. This should not be surprising as temperatures in winter are dominated by variability caused by changes in atmospheric circulation features, whereas in summer variability is more dominated by local changes in cloudiness. Here we consider most of the few winter-responding annually resolved proxy reconstructions of temperature from the northern North Atlantic and northwestern European regions. We find the expected out-of-phase relationship between northwest Europe and Greenland due to the North Atlantic Oscillation (NAO), which is stronger when the series from the two locations are formed from more than one series. On 30 year time scales this relationship between the two locations shows no century-scale variations since 1250 CE (Common Era), the start of our reconstructions, in contrast to the strong positive NAO values before 1400 CE implied by the study of Trouet et al. (2009). © 2014. American Geophysical Union. All Rights Reserved."
"7403183564;55807147600;7005294787;8433156200;7402767628;35237545900;7202299505;55743195000;","Ammonium deficiency caused by heterogeneous reactions during a super Asian dust episode",2014,"10.1002/2013JD021096","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903287590&doi=10.1002%2f2013JD021096&partnerID=40&md5=1522aaa6f9227362668d62087e9977f9","Mineral dust particles exert profound impacts on air quality, visibility, and ocean biogeochemistry. Interactions between dust particles and other anthropogenic pollutants modify not only the size spectrum and morphology but also physicochemical properties of dust particles, thereby affecting their radiative properties and ability to act as cloud condensation nuclei and in turn their impact on climate. Here we report field observations on the surface chemical transformations in a super Asian dust plume captured in coastal areas of China and the adjacent marginal seas. The dust plume showed enhanced concentrations of sulfate, nitrate, and calcium along with a decrease in ammonium. The percentages of total Ca in water-soluble form increased from an intrinsic value of ~5% to 25–40% at four stations along the path of the dust plume. From these increases, we estimated the extent to which carbonate was modified by heterogeneous reactions and calculated that the enhanced sulfate and nitrate could account for 40–60% of the observed concentrations. Our observation suggests that the formation of ammonium sulfate via the H2SO4-NH3-H2Oternary system was impeded by heterogeneous reactions in the marine boundary layer when dust loads exceeded a certain threshold. A conceptual model is proposed to elucidate the heterogeneous reactions during the super Asian dust event and their impacts on atmospheric chemistry. © 2014. American Geophysical Union. All Rights Reserved."
"56206619200;56996271000;","Estimation of atmospheric mixing layer height from radiosonde data",2014,"10.5194/amt-7-1701-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902468362&doi=10.5194%2famt-7-1701-2014&partnerID=40&md5=f0d9a868058b9066a8ca75059f49398e","Mixing layer height (h) is an important parameter for understanding the transport process in the troposphere, air pollution, weather and climate change. Many methods have been proposed to determine h by identifying the turning point of the radiosonde profile. However, substantial differences have been observed in the existing methods (e.g. the potential temperature (θ), relative humidity (RH), specific humidity (q) and atmospheric refractivity (N) methods). These differences are associated with the inconsistency of the temperature and humidity profiles in a boundary layer that is not well mixed, the changing measurability of the specific humidity and refractivity with height, the measurement error of humidity instruments within clouds, and the general existence of clouds. This study proposes a method to integrate the information of temperature, humidity and cloud to generate a consistent estimate of h. We apply this method to high vertical resolution (∼ 30 m) radiosonde data that were collected at 79 stations over North America during the period from 1998 to 2008. The data are obtained from the Stratospheric Processes and their Role in Climate Data Center (SPARC). The results show good agreement with those from N method as the information of temperature and humidity contained in N; however, cloud effects that are included in our method increased the reliability of our estimated h. From 1988 to 2008, the climatological h over North America was 1675 ± 303 m with a strong east-west gradient: higher values (generally greater than 1800 m) occurred over the Midwest US, and lower values (usually less than 1400 m) occurred over Alaska and the US West Coast. © 2014 Author(s) CC Attribution 3.0 License."
"50661916400;7402146514;","Surface-sensible and latent heat fluxes over the Tibetan Plateau from ground measurements, reanalysis, and satellite data",2014,"10.5194/acp-14-5659-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902089763&doi=10.5194%2facp-14-5659-2014&partnerID=40&md5=1e266df11b0d5e1fdbdeee63b0d22271","Estimations from meteorological stations over the Tibetan Plateau (TP) indicate that since the 1980s the surface-sensible heat flux has been decreasing continuously, and modeling studies suggest that such changes are likely linked to the weakening of the East Asian Monsoon through exciting Rossby wave trains. However, the spatial and temporal variations in the surface-sensible and latent heat fluxes over the entire TP remain unknown. This study aims to characterize the spatial and seasonal variability of the surface-sensible and latent heat fluxes at 0.5° over the TP from 1984 to 2007 by synthesizing multiple data sources including ground measurements, reanalysis products, and remote-sensing products. The root mean square errors (RMSEs) from cross validation are 14.3 Wmĝ̂'2 and 10.3 Wmĝ̂'2 for the monthly fused sensible and latent heat fluxes, respectively. The fused sensible and latent heat-flux anomalies are consistent with those estimated from meteorological stations, and the uncertainties of the fused data are also discussed. The associations among the fused sensible and latent heat fluxes and the related surface anomalies such as mean temperature, temperature range, snow cover, and normalized difference vegetation index (NDVI) in addition to atmospheric anomalies such as cloud cover and water vapor show seasonal dependence, suggest that the land-biosphere- atmosphere interactions over the TP could display nonuniform feedbacks to the climate changes. It would be interesting to disentangle the drivers and responses of the surface-sensible and latent heat-flux anomalies over the TP in future research from evidences of modeling results. © Author(s) 2014. CC Attribution 3.0 License."
"56195261100;55976582900;","Uncertainties in future climate predictions due to convection parameterisations",2014,"10.5194/acp-14-5561-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901930022&doi=10.5194%2facp-14-5561-2014&partnerID=40&md5=7abe7569ce921a007d0b5169eb8bdedc","In the last decades several convection parameterisations have been developed to consider the impact of small-scale unresolved processes in Earth System Models associated with convective clouds. Global model simulations, which have been performed under current climate conditions with different convection schemes, significantly differ among each other in the simulated transport of trace gases and precipitation patterns due to the parameterisation assumptions and formulations, e.g. the computation of convective rainfall rates, calculation of entrainment and detrainment rates etc. Here we address sensitivity studies comparing four different convection schemes under alternative climate conditions (with doubling of the CO2 concentrations) to identify uncertainties related to convective processes. The increase in surface temperature reveals regional differences up to 4 K dependent on the chosen convection parameterisation. These differences are statistically significant almost everywhere in the troposphere of the intertropical convergence zone. The increase in upper tropospheric temperature affects the amount of water vapour transported to the lower stratosphere, leading to enhanced water vapour contents between 40% and 60% at the cold point temperature in the Tropics. Furthermore, the change in transporting short-lived pollutants within the atmosphere is highly ambiguous for the lower and upper troposphere. These results reflect that different approaches to compute mass fluxes, detrainment levels or trigger functions determine the transport of short-lived trace gases from the planetary boundary layer to lower, middle or upper tropospheric levels. Finally, cloud radiative effects have been analysed, uncovering a shift in different cloud types in the Tropics, especially for cirrus and deep convective clouds. These cloud types induce a change in net cloud radiative forcing varying from 0.5 W m-2 to 2.0 W m-2.©Author(s) 2014."
"36969949500;13405658600;57211106013;","Analysis of feedbacks between nucleation rate, survival probability and cloud condensation nuclei formation",2014,"10.5194/acp-14-5577-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902108631&doi=10.5194%2facp-14-5577-2014&partnerID=40&md5=b3533bfa511bdec5efacacc5a1b52183","Aerosol nucleation is an important source of particle number in the atmosphere. However, in order to become cloud condensation nuclei (CCN), freshly nucleated particles must undergo significant condensational growth while avoiding coagulational scavenging. In an effort to quantify the contribution of nucleation to CCN, this work uses the GEOS-Chem-TOMAS global aerosol model to calculate changes in CCN concentrations against a broad range of nucleation rates and mechanisms. We then quantify the factors that control CCN formation from nucleation, including daily nucleation rates, growth rates, coagulation sinks, condensation sinks, survival probabilities, and CCN formation rates, in order to examine feedbacks that may limit growth of nucleated particles to CCN. Nucleation rate parameterizations tested in GEOS-Chem-TOMAS include ternary nucleation (with multiple tuning factors), activation nucleation (with two pre-factors), binary nucleation, and ion-mediated nucleation. We find that nucleation makes a significant contribution to boundary layer CCN(0.2%), but this contribution is only modestly sensitive to the choice of nucleation scheme, ranging from 49 to 78% increase in concentrations over a control simulation with no nucleation. Moreover, a two order-of-magnitude increase in the globally averaged nucleation rate (via changes to tuning factors) results in small changes (less than 10%) to global CCN(0.2%) concentrations. To explain this, we present a simple theory showing that survival probability has an exponentially decreasing dependence on the square of the condensation sink. This functional form stems from a negative correlation between condensation sink and growth rate and a positive correlation between condensation sink and coagulational scavenging. Conceptually, with a fixed condensable vapor budget (sulfuric acid and organics), any increase in CCN concentrations due to higher nucleation rates necessarily entails an increased aerosol surface area in the accumulation mode, resulting in a higher condensation sink, which lowers vapor concentrations and growth rates. As a result, slowly growing nuclei are exposed to a higher frequency of coagulational scavenging for a longer period of time, thus reducing their survival probabilities and closing a negative feedback loop that dampens the impact of nucleation on CCN. We confirm quantitatively that the decreases in survival probability predicted by GEOS-Chem-TOMAS due to higher nucleation rates are in accordance with this simple theory of survival probability. © Author(s) 2014. CC Attribution 3.0 License."
"57193903298;6603156461;36867775200;55056560000;56187256200;35998927000;","Modeling the evolution of aerosol particles in a ship plume using PartMC-MOSAIC",2014,"10.5194/acp-14-5327-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901853838&doi=10.5194%2facp-14-5327-2014&partnerID=40&md5=8a9602eee8c854453ec3b1f669eba7a1","This study investigates the evolution of ship-emitted aerosol particles using the stochastic particle-resolved model PartMC-MOSAIC (Particle Monte Carlo model-Model for Simulating Aerosol Interactions and Chemistry). Comparisons of our results with observations from the QUANTIFY (Quantifying the Climate Impact of Global and European Transport Systems) study in 2007 in the English Channel and the Gulf of Biscay showed that the model was able to reproduce the observed evolution of total number concentration and the vanishing of the nucleation mode consisting of sulfate particles. Further process analysis revealed that during the first hour after emission, dilution reduced the total number concentration by four orders of magnitude, while coagulation reduced it by an additional order of magnitude. Neglecting coagulation resulted in an overprediction of more than one order of magnitude in the number concentration of particles smaller than 40 nm at a plume age of 100 s. Coagulation also significantly altered the mixing state of the particles, leading to a continuum of internal mixtures of sulfate and black carbon. The impact on cloud condensation nuclei (CCN) concentrations depended on the supersaturation thresholdSat which CCN activity was evaluated. For the base case conditions, characterized by a low formation rate of secondary aerosol species, neglecting coagulation, but simulating condensation, led to an underestimation of CCN concentrations of about 37% forSCombining double low line 0.3% at the end of the 14-h simulation. In contrast, for supersaturations higher than 0.7%, neglecting coagulation resulted in an overestimation of CCN concentration, about 75% forSCombining double low line 1%. ForSlower than 0.2% the differences between simulations including coagulation and neglecting coagulation were negligible. Neglecting condensation, but simulating coagulation did not impact the CCN concentrations below 0.2% and resulted in an underestimation of CCN concentrations for larger supersaturations, e.g., 18% forSCombining double low line 0.6%. We also explored the role of nucleation for the CCN concentrations in the ship plume. For the base case the impact of nucleation on CCN concentrations was limited, but for a sensitivity case with higher formation rates of secondary aerosol over several hours, the CCN concentrations increased by an order of magnitude for supersaturation thresholds above 0.3%. © 2014 Author(s)."
"9537045600;7102354961;36458602300;6603431534;36697778900;6603196991;16242417100;7005777274;","G band atmospheric radars: New frontiers in cloud physics",2014,"10.5194/amt-7-1527-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902162758&doi=10.5194%2famt-7-1527-2014&partnerID=40&md5=473c572f7069ff6e1c6a7975b4038f0b","Clouds and associated precipitation are the largest source of uncertainty in current weather and future climate simulations. Observations of the microphysical, dynamical and radiative processes that act at cloud scales are needed to improve our understanding of clouds. The rapid expansion of ground-based super-sites and the availability of continuous profiling and scanning multi-frequency radar observations at 35 and 94 GHz have significantly improved our ability to probe the internal structure of clouds in high temporal-spatial resolution, and to retrieve quantitative cloud and precipitation properties. However, there are still gaps in our ability to probe clouds due to large uncertainties in the retrievals. <br><br> The present work discusses the potential of G band (frequency between 110 and 300 GHz) Doppler radars in combination with lower frequencies to further improve the retrievals of microphysical properties. Our results show that, thanks to a larger dynamic range in dual-wavelength reflectivity, dual-wavelength attenuation and dual-wavelength Doppler velocity (with respect to a Rayleigh reference), the inclusion of frequencies in the G band can significantly improve current profiling capabilities in three key areas: boundary layer clouds, cirrus and mid-level ice clouds, and precipitating snow. © 2014 Author(s)."
"56062773600;7404358451;","A moist pseudo-incompressible model",2014,"10.1016/j.atmosres.2013.08.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895876938&doi=10.1016%2fj.atmosres.2013.08.004&partnerID=40&md5=aa0b926cb40bf8236f473d3d0300f399","A pseudo-incompressible model for moist atmospheric flows is presented. The equation set is derived from a fully compressible system by assuming that the pressure perturbations are small. Unlike the standard dry pseudo-incompressible approximation the hydrostatic background state is allowed to vary in time and a set of equations dictating the evolution of the background state are derived. Changes of the background state are the result of net accumulation of diabatic processes and latent heat conversion. Their governing equations emerge in the theory from a consistency condition for the velocity divergence constraint. The model is validated by comparing its results for a well-established benchmark test with those from a fully compressible model. © 2013 Elsevier B.V."
"7404330190;15755362800;55682998500;55930571700;","A case study of aerosol impacts on summer convective clouds and precipitation over northern China",2014,"10.1016/j.atmosres.2013.10.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895861163&doi=10.1016%2fj.atmosres.2013.10.006&partnerID=40&md5=bf2de7c4526267be5a6bb06c486d5cfc","The emissions such as greenhouse gases, precursor gases and particulate matters may directly alter the Earth radiative budget or indirectly modify cloud and precipitation processes, and possibly induce changes in climate and the hydrological cycle at the regional to global scale. The previous publications reported a few quantitative assessments and inconsistent results on the effects of the emissions on cloud and precipitation. The aerosol properties and possible impacts on a convective precipitation case on 4 July 2008 over the urban region of northern China are investigated based on the Moderate Resolution Imaging Spectroradiometer (MODIS) data and the Weather Research and Forecast (WRF) model coupled with Chemistry (WRF-Chem). Results show that the Aerosol Optical Depth (AOD) is over 0.9 in the study area, indicating a high concentration of aerosol pollution. The value of Angstrom exponent in the study area is larger than 1.0, indicating that the main particles in the area are industrial and biomass burning pollution aerosols with radii less than 0.25-0.5. μm. The modeling results show that the domain-averaged precipitation amount under polluted conditions can be increased up to 17% during the whole cloud lifetime. However, the maximum rainfall rate above 30. mm/h is enhanced, whereas that below 30. mm/h is suppressed in most cloud lifetime. The differences of cloud microphysics and dynamics between polluted and clean conditions indicate that both warm and ice microphysics and updraft are suppressed at the storm's initial and dissipating stages, whereas those at the storm's mature stage are obviously enhanced under polluted conditions. © 2013 Elsevier B.V."
"47962218600;57203475350;57206506609;35490217800;34771409300;9635846500;55863085500;7102799692;6506656962;7005133082;6603711612;55485239400;12773907600;","Correlating remote sensing data with the abundance of pupae of the dengue virus mosquito vector, Aedes aegypti, in central Mexico",2014,"10.3390/ijgi3020732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948980327&doi=10.3390%2fijgi3020732&partnerID=40&md5=44af6c2194a3d4777ad8e2169e0c7d50","Using a geographic transect in Central Mexico, with an elevation/climate gradient, but uniformity in socio-economic conditions among study sites, this study evaluates the applicability of three widely-used remote sensing (RS) products to link weather conditions with the local abundance of the dengue virus mosquito vector, Aedes aegypti (Ae. aegypti). Field-derived entomological measures included estimates for the percentage of premises with the presence of Ae. aegypti pupae and the abundance of Ae. aegypti pupae per premises. Data on mosquito abundance from field surveys were matched with RS data and analyzed for correlation. Daily daytime and nighttime land surface temperature (LST) values were obtained from Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua cloud-free images within the four weeks preceding the field survey. Tropical Rainfall Measuring Mission (TRMM)-estimated rainfall accumulation was calculated for the four weeks preceding the field survey. Elevation was estimated through a digital elevation model (DEM). Strong correlations were found between mosquito abundance and RS-derived night LST, elevation and rainfall along the elevation/climate gradient. These findings show that RS data can be used to predict Ae. aegypti abundance, but further studies are needed to define the climatic and socio-economic conditions under which the correlations observed herein can be assumed to apply.. © 2014 by the authors; licensee MDPI, Basel, Switzerland."
"48161289200;55990731900;15070397200;","Reconstructing glacier retreat since the Little Ice Age in SE Tibet by glacier mapping and equilibrium line altitude calculation",2014,"10.1016/j.geomorph.2014.03.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897428669&doi=10.1016%2fj.geomorph.2014.03.018&partnerID=40&md5=54f910c598c3e8edfd9b96fa2a1839fb","Temperate glaciers in the eastern Nyainqêntanglha Range, southeastern Tibet, are highly sensitive to climate change and therefore of particular high interest for research on late Holocene changes of the monsoonal climate in High Asia. However, because of the remoteness of the area, the scarcity of empirical data, and the challenges to remote sensing work posed by cloud and snow cover, knowledge about the glacier dynamics and changes in this region is still very limited. In this study, we applied a remote sensing approach in which 1964 glaciers were mapped from a Landsat ETM+ scene and subsequently parameterized by DEM-supported measurements. Geomorphological evidence, i.e., trimlines and latero-frontal moraines, were used to obtain quantitative data on the glaciers' morphological characteristics and the changes since the Little Ice Age (LIA) maximum glacier advance. Statistical analysis of glacier length change revealed an average retreat of ~. 27% and a trend toward stronger retreat for smaller glaciers. An evaluation of different methods to calculate equilibrium line altitudes (ELAs) indicates that an optimized toe-to-ridge altitude method (TRAM) is more suitable than other methods in settings with complex topography and a lack of mass balance measurements. A large number of glacier measurements are crucial for high quality of TRAM results, and special attention has to be paid to different glacier characteristics. In order to determine the best-fitting TRAM ratio value and to test the quality of the calculated ELAs, a remote sensing approach was applied: for each investigated glacier, the altitudes of transient snowlines visible in the late summer Landsat scene were measured from the DEM and compared to TRAM results. The interpolated ELA results show a SE-NW gradient ranging from 4400 to 5600. m asl and an average ELA rise of ~. 136. m since the LIA. Because of the high spatial resolution of measurements, the ELA distribution reveals topographic effects down to the catchment scale, specifically orographic rainfall and leeward shielding. The interpretation of these patterns reveals that the eastern Nyainqêntanglha Range is influenced by both, the Indian (ISM) and East Asian summer monsoon (EASM). However, the EASM does not reach the western part of the study area. The results indicate that the monsoonal temperate glaciers' high sensitivity to climate change is driven by two double forcings owing to the coincidence of accumulation and ablation phases. © 2014 Elsevier B.V."
"57194006071;57203176082;26531622800;56520903100;","High abundances of oxalic, azelaic, and glyoxylic acids and methylglyoxal in the open ocean with high biological activity: Implication for secondary OA formation from isoprene",2014,"10.1002/2014GL059913","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902296898&doi=10.1002%2f2014GL059913&partnerID=40&md5=358ee41b7725c472549f5a2159fc7dfc","Atmospheric dicarboxylic acids (DCA) are a ubiquitous water-soluble component of secondary organic aerosols (SOA), which can act as cloud condensation nuclei (CCN), affecting the Earth's climate. Despite the high abundances of oxalic acid and related compounds in the marine aerosols, there is no consensus on what controls their distributions over the open ocean. Marine biological productivity could play a role in the production of DCA, but there is no substantial evidence to support this hypothesis. Here we present latitudinal distributions of DCA, oxoacids and α-dicarbonyls in the marine aerosols from the remote Pacific. Their concentrations were found several times higher in more biologically influenced aerosols (MBA) than less biologically influenced aerosols. We propose isoprene and unsaturated fatty acids as sources of DCA as inferred from significantly higher abundances of isoprene-SOA tracers and azelaic acid in MBA. These results have implications toward the reassessment of climate forcing feedbacks of marine-derived SOA. © 2014. American Geophysical Union. All Rights Reserved."
"7201606127;7402064802;","Low-cloud optical depth feedback in climate models",2014,"10.1002/2013JD021052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902815940&doi=10.1002%2f2013JD021052&partnerID=40&md5=093a0a4a7706a80527033818d3e7ffbe","The relationship between low-level cloud optical depth and atmospheric and surface air temperature is examined in the control climate of 13 climate models to determine if cloud optical depth-temperature relationships found in observations are replicated in climate models and if climate model behavior found in control climate simulations provides information about the optical depth feedback in climate warming simulations forced by increasing carbon dioxide. A positive relationship between cloud optical depth and cloud temperature exists in allmodels for low clouds with relatively cold temperatures atmiddle and high latitudes, whereas a negative relationship exists for warmer low clouds in the tropics and subtropics. This relationship is qualitatively similar to that in an earlier analysis of satellite observations, although modeled regression slopes tend to be too positive and their intermodel spread is large. In the models, the cold cloud response comes from increases in cloud water content with increasing temperature, while the warm cloud response comes from decreases in physical thickness with increasing cloud temperature. The intermodel and interregional spread of low-cloud optical depth feedback in climate warming simulations is well predicted by the corresponding spread in the relationships between optical depth and temperature for the current climate, suggesting that this aspect of cloud feedback may be constrained by observations. Because models have a positive bias relative to observations in the optical depth-temperature relationship, shortwave cloud feedback for climate changes may be more positive than climate models currently simulate. © 2014. American Geophysical Union. All Rights Reserved"
"56537463000;7404829395;22959252400;16553368000;7006417494;7202899330;7005973015;","Weakening and strengthening structures in the Hadley Circulation change under global warming and implications for cloud response and climate sensitivity",2014,"10.1002/2014JD021642","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902839438&doi=10.1002%2f2014JD021642&partnerID=40&md5=b1bb998c9545aaddedfbd0fd3fdddd6f","It has long been recognized that differences in climate model-simulated cloud feedbacks are a primary source of uncertainties for the model-predicted surface temperature change induced by increasing greenhouse gases such as CO2. Large-scale circulation broadly determines when and where clouds form and how they evolve. However, the linkage between large-scale circulation change and cloud radiative effect (CRE) change under global warming has not been thoroughly studied. By analyzing 15 climate models, we show that the change of the Hadley Circulation exhibits meridionally varying weakening and strengthening structures, physically consistent with the cloud changes in distinct cloud regimes. The regions that experience a weakening (strengthening) of the zonal-mean circulation account for 54% (46%) of the multimodel-mean top-of-atmosphere (TOA) CRE change integrated over 45°S-40°N. The simulated Hadley Circulation structure changes per degree of surface warming differ greatly between the models, and the intermodel spread in the Hadley Circulation change is well correlated with the intermodel spread in the TOA CRE change. This correlation underscores the close interactions between large-scale circulation and clouds and suggests that the uncertainties of cloud feedbacks and climate sensitivity reside in the intimate coupling between large-scale circulation and clouds. New model performance metrics proposed in this work, which emphasize how models reproduce satellite-observed spatial variations of zonal-mean cloud fraction and relative humidity associated with the Hadley Circulation, indicate that the models closer to the satellite observations tend to have equilibrium climate sensitivity higher than the multimodel mean. © 2014. American Geophysical Union. All Rights Reserved."
"26537088900;8686475900;36182467000;35206950500;7102410621;55598938800;","Aerosols in the convective boundary layer: Shortwave radiation effects on the coupled land-atmosphere system",2014,"10.1002/2013JD021237","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902839117&doi=10.1002%2f2013JD021237&partnerID=40&md5=35e6791b07862b6dfa9a4662fb5a05a5","By combining observations and numerical simulations, we investigated the responses of the surface energy budget and the convective boundary layer (CBL) dynamics to the presence of aerosols. A detailed data set containing (thermo)dynamic observations at CESAR (Cabauw Experimental Site for Atmospheric Research) and aerosol information from the European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions was employed to design numerical experiments reproducing two typical clear-sky days, each characterized by contrasting thermodynamic initial profiles: (i) residual layer above a strong surface inversion and (ii) well-mixed CBL connected to the free troposphere by a capping inversion, without the residual layer in between. A large-eddy simulation (LES) model and a mixed-layer (MXL) model, coupled to a broadband radiative transfer code and a land surface model, were used to study the impacts of aerosols on shortwave radiation. Both the LES model and the MXL model results reproduced satisfactorily the observations for both days. A sensitivity analysis on a wide range of aerosol properties was conducted. Our results showed that higher lo of aerosols decreased irradiance imposing an energy restriction at the surface, delaying the morning onset of the CBL and advancing its afternoon collapse. Moderately to strongly absorbing aerosols increased the heating rate contributing positively to increase the afternoon CBL height and potential temperature and to decrease Bowen ratio. In contrast, scattering aerosols were associated with smaller heating rates and cooler and shallower CBLs. Our findings advocate the need for accounting for the aerosol influence in analyzing surface and CBL dynamics. ©2014. American Geophysical Union. All Rights Reserved."
"37072984700;57203029613;","Effects of aerosols on precipitation in north-eastern North America",2014,"10.5194/acp-14-5111-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901453434&doi=10.5194%2facp-14-5111-2014&partnerID=40&md5=83f3cdac4fa3cd79414cb06c46ccb88c","The changes in precipitation in north-eastern North America caused by chemistry-and particularly anthropogenic aerosols-are investigated using the Weather Research Forecasting with Chemistry (WRF/Chem v3.2) model. The simulations were carried out for a five-month period from April to August 2009. The model results show that non-negligible changes in both convective and cloud-resolved (non-convective) precipitation are caused by chemistry and/or aerosols over most parts of the domain. The changes can be attributed to both radiative and microphysical interactions with the meteorology. A chemistry-induced change of approximately 15% is found in the five-month mean daily convective precipitation over areas with high convective rain; most of this can be traced to radiative effects. Total convective rain is greater than total non-convective rain in the domain, but a chemistry-induced increase of about 30% is evident in the five-month mean daily non-convective precipitation over the heavily urbanized parts of the Atlantic coast. The effects of aerosols on cloud microphysics and precipitation were examined for two particle size ranges, 0.039-0.1 Î1/4m and 1-2.5 Î1/4m, representing the nucleation and accumulation modes respectively. Strongly positive spatial correlation between cloud droplet number and non-convective rain are found for activated (cloud-borne) aerosols in both size ranges. Non-activated (interstitial) aerosols have a positive correlation with cloud droplet number and non-convective rain when they are small and an inverse correlation for larger sizes. © 2014 Author(s)."
"7004587891;35573513700;7005780974;","Early evaluation of the VIIRS calibration, cloud mask and surface reflectance Earth data records",2014,"10.1016/j.rse.2014.03.028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898625152&doi=10.1016%2fj.rse.2014.03.028&partnerID=40&md5=a78b905efc99f1894d1205c2848d2924","Surface reflectance is one of the key products from VIIRS and as with MODIS, is used in developing several higher-order land products. The VIIRS Surface Reflectance (SR) Intermediate Product (IP) is based on the heritage MODIS Collection 5 product (Vermote, El Saleous, & Justice, 2002). The quality and character of surface reflectance depend on the accuracy of the VIIRS Cloud Mask (VCM), the aerosol algorithms and the adequate calibration of the sensor. The focus of this paper is the early evaluation of the VIIRS SR product in the context of the maturity of the operational processing system, the Interface Data Processing System (IDPS). After a brief introduction, the paper presents the calibration performance and the role of the surface reflectance in calibration monitoring. The analysis of the performance of the cloud mask with a focus on vegetation monitoring (no snow conditions) shows typical problems over bright surfaces and high elevation sites. Also discussed is the performance of the aerosol input used in the atmospheric correction and in particular the artifacts generated by the use of the Navy Aerosol Analysis and Prediction System. Early quantitative results of the performance of the SR product over the AERONET sites show that with the few adjustments recommended, the accuracy is within the threshold specifications. The analysis of the adequacy of the SR product (Land PEATE adjusted version) in applications of societal benefits is then presented. We conclude with a set of recommendations to ensure consistency and continuity of the JPSS mission with the MODIS Land Climate Data Record. © 2014 ."
"7004239300;57204252724;57195257572;55879878800;55800670000;11139844700;8309699900;","The backscatter cloud probe-a compact low-profile autonomous optical spectrometer",2014,"10.5194/amt-7-1443-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901593368&doi=10.5194%2famt-7-1443-2014&partnerID=40&md5=c476914b905fc88aa9bd77743985cc22","A compact (500 cm3), lightweight (500 g), near-field, single particle backscattering optical spectrometer is described that mounts flush with the skin of an aircraft and measures the concentration and optical equivalent diameter of particles from 5 to 75 Î1/4m. The backscatter cloud probe (BCP) was designed as a real-time qualitative cloud detector primarily for data quality control of trace gas instruments developed for the climate monitoring instrument packages that are being installed on commercial passenger aircraft as part of the European Union In-Service Aircraft for a Global Observing System (IAGOS) program (<a hrefCombining double low line""http://www.iagos.org/ ""targetCombining double low line""-blank"">http://www.iagos.org/ </a>). Subsequent evaluations of the BCP measurements on a number of research aircraft, however, have revealed it capable of delivering quantitative particle data products including size distributions, liquid-water content and other information on cloud properties. We demonstrate the instrument's capability for delivering useful long-term climatological, as well as aviation performance information, across a wide range of environmental conditions. The BCP has been evaluated by comparing its measurements with those from other cloud particle spectrometers on research aircraft and several BCPs are currently flying on commercial A340/A330 Airbus passenger airliners. The design and calibration of the BCP is described in this article, along with an evaluation of measurements made on the research and commercial aircraft. Preliminary results from more than 7000 h of airborne measurements by the BCP on two Airbus A340s operating on routine global traffic routes (one Lufthansa, the other China Airlines) show that more than 340 h of cloud data have been recorded at normal cruise altitudes (> 10 km) and more than 40% of the > 1200 flights were through clouds at some point between takeoff and landing. These data are a valuable contribution to databases of cloud properties, including sub-visible cirrus, in the upper troposphere and useful for validating satellite retrievals of cloud water and effective radius; in addition, providing a broader, geographically and climatologically relevant view of cloud microphysical variability that is useful for improving parameterizations of clouds in climate models. Moreover, they are also useful for monitoring the vertical climatology of clouds over airports, especially those over megacities where pollution emissions may be impacting local and regional climate. © 2014 Author(s)."
"38863214100;15065091300;8226785300;6507224579;","Strong dependence of the inner edge of the habitable zone on planetary rotation rate",2014,"10.1088/2041-8205/787/1/L2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900461276&doi=10.1088%2f2041-8205%2f787%2f1%2fL2&partnerID=40&md5=38637c21512506d6e627c5828a33265d","Planetary rotation rate is a key parameter in determining atmospheric circulation and hence the spatial pattern of clouds. Since clouds can exert a dominant control on planetary radiation balance, rotation rate could be critical for determining the mean planetary climate. Here we investigate this idea using a three-dimensional general circulation model with a sophisticated cloud scheme. We find that slowly rotating planets (like Venus) can maintain an Earth-like climate at nearly twice the stellar flux as rapidly rotating planets (like Earth). This suggests that many exoplanets previously believed to be too hot may actually be habitable, depending on their rotation rate. The explanation for this behavior is that slowly rotating planets have a weak Coriolis force and long daytime illumination, which promotes strong convergence and convection in the substellar region. This produces a large area of optically thick clouds, which greatly increases the planetary albedo. In contrast, on rapidly rotating planets a much narrower belt of clouds form in the deep tropics, leading to a relatively low albedo. A particularly striking example of the importance of rotation rate suggested by our simulations is that a planet with modern Earth's atmosphere, in Venus' orbit, and with modern Venus' (slow) rotation rate would be habitable. This would imply that if Venus went through a runaway greenhouse, it had a higher rotation rate at that time. © 2014. The American Astronomical Society. All rights reserved.."
"57211094015;7003861526;","Evaluation of SCIAMACHY Oxygen A band cloud heights using Cloudnet measurements",2014,"10.5194/amt-7-1331-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901276107&doi=10.5194%2famt-7-1331-2014&partnerID=40&md5=c747464b40d1ee32835bacd8d484f646","Two SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) O2 A band cloud height products are evaluated using ground-based radar/lidar measurements between January 2003 and December 2011. The products are the ESA (European Space Agency) Level 2 (L2) version 5.02 cloud top height and the FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A band) version 6 cloud height. The radar/lidar profiles are obtained at the Cloudnet sites of Cabauw and Lindenberg, and are averaged for 1 h centered at the SCIAMACHY overpass time. In total we have 217 cases of single-layer clouds and 204 cases of multilayer clouds. We find that the ESA L2 cloud top height has a better agreement with the Cloudnet cloud top height than the Cloudnet cloud middle height. The ESA L2 cloud top height is on average 0.4 km higher than the Cloudnet cloud top height, with a standard deviation of 3.1 km. The FRESCO cloud height is closer to the Cloudnet cloud middle height than the Cloudnet cloud top height. The mean difference between the FRESCO cloud height and the Cloudnet cloud middle height is 0.1 km with a standard deviation of 1.9 km. The ESA L2 cloud top height is higher than the FRESCO cloud height. The differences between the SCIAMACHY cloud (top) height and the Cloudnet cloud top height are linked to cloud optical thickness. The SCIAMACHY cloud height products are further compared to the Cloudnet cloud top height and the Cloudnet cloud middle height in 1 km bins. For single-layer clouds, the difference between the ESA L2 cloud top height and the Cloudnet cloud top height is less than 1 km for each cloud bin at 3-7 km. The difference between the FRESCO cloud height and the Cloudnet cloud middle height is less than 1 km for each cloud bin at 0-6 km. The results are similar for multilayer clouds, but the percentage of cases having a bias within 1 km is smaller than for single-layer clouds. We may conclude that the FRESCO cloud height is accurate for low and middle level clouds, whereas the ESA L2 cloud top height is more accurate for middle level clouds. Both products are less accurate for high clouds. © 2014 Author(s)."
"9235244500;7006146719;8705440100;36802109600;55967530700;17433789100;12760330000;56176938900;36761569700;55991656800;56177254900;26536205100;7004863773;6602515941;24480463300;8131956400;36930812200;8326989900;23995325300;7006712143;7007039218;55682775100;8871497700;35461255500;7003984086;","Observing wind, aerosol particles, cloud and precipitation: Finland's new ground-based remote-sensing network",2014,"10.5194/amt-7-1351-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901275433&doi=10.5194%2famt-7-1351-2014&partnerID=40&md5=9d0e69ca328487f1d51964a28197b362","The Finnish Meteorological Institute, in collaboration with the University of Helsinki, has established a new ground-based remote-sensing network in Finland. The network consists of five topographically, ecologically and climatically different sites distributed from southern to northern Finland. The main goal of the network is to monitor air pollution and boundary layer properties in near real time, with a Doppler lidar and ceilometer at each site. In addition to these operational tasks, two sites are members of the Aerosols, Clouds and Trace gases Research InfraStructure Network (ACTRIS); a K/a band cloud radar at Sodankylä will provide cloud retrievals within CloudNet, and a multi-wavelength Raman lidar, PollyXT (POrtabLe Lidar sYstem eXTended), in Kuopio provides optical and microphysical aerosol properties through EARLINET (the European Aerosol Research Lidar Network). Three C-band weather radars are located in the Helsinki metropolitan area and are deployed for operational and research applications. We performed two inter-comparison campaigns to investigate the Doppler lidar performance, compare the backscatter signal and wind profiles, and to optimize the lidar sensitivity through adjusting the telescope focus length and data-integration time to ensure sufficient signal-to-noise ratio (SNR) in low-aerosol-content environments. In terms of statistical characterization, the wind-profile comparison showed good agreement between different lidars. Initially, there was a discrepancy in the SNR and attenuated backscatter coefficient profiles which arose from an incorrectly reported telescope focus setting from one instrument, together with the need to calibrate. After diagnosing the true telescope focus length, calculating a new attenuated backscatter coefficient profile with the new telescope function and taking into account calibration, the resulting attenuated backscatter profiles all showed good agreement with each other. It was thought that harsh Finnish winters could pose problems, but, due to the built-in heating systems, low ambient temperatures had no, or only a minor, impact on the lidar operation-including scanning-head motion. However, accumulation of snow and ice on the lens has been observed, which can lead to the formation of a water/ice layer thus attenuating the signal inconsistently. Thus, care must be taken to ensure continuous snow removal. © 2014 Author(s)."
"8631239200;6701562113;56188688000;7005751636;","Increasing the credibility of regional climate simulations by introducing subgrid-scale cloud-radiation interactions",2014,"10.1002/2014JD021504","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901725235&doi=10.1002%2f2014JD021504&partnerID=40&md5=97854ffe4b40325f3c5745d07fc6f0e9","The radiation schemes in the Weather Research and Forecasting (WRF) model have previously not accounted for the presence of subgrid-scale cumulus clouds, thereby resulting in unattenuated shortwave radiation, which can lead to overly energetic convection and overpredicted surface precipitation. This deficiency can become problematic when applying WRF as a regional climate model (RCM). Therefore, modifications were made to the WRF model to allow the Kain-Fritsch (KF) convective parameterization to provide subgrid-scale cloud fraction and condensate feedback to the rapid radiative transfer model-global (RRTMG) shortwave and longwave radiation schemes. The effects of these changes are analyzed via 3 year simulations using the standard and modified versions of WRF, comparing the modeled results with the North American Regional Reanalysis (NARR) and Climate Forecast System Reanalysis data, as well as with available data from the Surface Radiation Network and Clouds and Earth’s Radiant Energy System. During the summer period, including subgrid cloudiness estimated by KF in the RRTMG reduces the surface shortwave radiation, leading to less buoyant energy, which is reflected in a smaller diabatic convective available potential energy, thereby alleviating the overly energetic convection. Overall, these changes have reduced the overprediction of monthly, regionally averaged precipitation during summer for this RCM application, e.g., by as much as 49mm for the southeastern U.S., to within 0.7% of the NARR value of 221mm. These code modifications have been incorporated as an option available in the latest version of WRF (v3.6). © 2014. American Geophysical Union. All Rights Reserved."
"7403564495;7401936984;55749340500;57198616562;15065375800;","Quantifying uncertainties of cloud microphysical property retrievals with a perturbation method",2014,"10.1002/2013JD021112","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901718835&doi=10.1002%2f2013JD021112&partnerID=40&md5=591dfecca7fc50fad1025e0a7ef18715","Quantifying the uncertainty of cloud retrievals is an emerging topic important for both cloud process studies and modeling studies. This paper presents a general approach to estimate uncertainties in ground-based retrievals of cloud properties. This approach, called the perturbation method, quantifies the cloud retrieval uncertainties by perturbing the cloud retrieval influential factors (like inputs and parameters) within their error ranges. The error ranges for the cloud retrieval inputs and parameters are determined by either instrument limitations or comparisons against aircraft observations. With the knowledge from observations and the retrieval algorithms, the perturbation method can provide an estimate of the cloud retrieval uncertainties, regardless of the complexity (like nonlinearity) of the retrieval algorithm. The relative contribution to the uncertainties of retrieved cloud properties from the inputs, assumptions, and parameterizations can also be assessed with this perturbation method. As an example, we apply this approach to the Atmospheric Radiation Measurement Program baseline retrieval, MICROBASE. Only nonprecipitating single-phase (liquid or ice) clouds have been examined in this study. Results reveal that different influential factors play the dominant contributing role to the uncertainties of different cloud properties. To reduce uncertainties in cloud retrievals, future efforts should be emphasized on the major contributing factors for considered cloud properties. This study also shows high sensitivity of cloud retrieval uncertainties to different cloud types, with the largest uncertainties for deep convective clouds. Limitations and further efforts for this uncertainty quantification method are discussed. © 2014. American Geophysical Union. All Rights Reserved."
"54897465300;26645289600;7202145115;","The response of the Southern Hemispheric eddy-driven jet to future changes in shortwave radiation in CMIP5",2014,"10.1002/2014GL060043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901933770&doi=10.1002%2f2014GL060043&partnerID=40&md5=2b70595a74f0b00f7fa685e4bbae045a","A strong relationship is found between changes in the meridional gradient of absorbed shortwave radiation (ASR) and Southern Hemispheric jet shifts in 21st century climate simulations of CMIP5 (Coupled Model Intercomparison Project phase 5) coupled models. The relationship is such that models with increases in the meridional ASR gradient around the southern midlatitudes, and therefore increases in midlatitude baroclinicity, tend to produce a larger poleward jet shift. The ASR changes are shown to be dominated by changes in cloud properties, with sea ice declines playing a secondary role. We demonstrate that the ASR changes are the cause, and not the result, of the intermodel differences in jet response by comparing coupled simulations with experiments in which sea surface temperature increases are prescribed. Our results highlight the importance of reducing the uncertainty in cloud feedbacks in order to constrain future circulation changes. Key Points Large intermodel spread in SW radiation response to global warming in CMIP5 Spread in SW changes causes spread in SH jet response to global warming Different SW changes cause different changes in midlatitude baroclinicity © 2014. American Geophysical Union. All Rights Reserved."
"15751598400;7402480218;","Spatial variability of surface irradiance measurements at the Manus ARM site",2014,"10.1002/2013JD021187","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901708454&doi=10.1002%2f2013JD021187&partnerID=40&md5=7b8e2f6484ca131f018ea9e284bfb751","The location of the Atmospheric Radiation Measurement (ARM) site on Manus island was chosen because it is very close to the coast, in a flat, near-sea level area of the island, hopefully minimizing the impact of local island effects on the meteorology of the measurements. In this study, we confirm that the Manus site is indeed less impacted by the island meteorology than slightly inland by comparing over a year of broadband surface irradiance and ceilometer measurements and derived quantities at the standard Manus site and a second location 7 km away as part of the ARM Madden Julian Oscillation Investigation Experiment (AMIE)-Manus campaign. The two sites show statistically similar distributions of irradiance and other derived quantities for all wind directions except easterly winds, when the inland site is downwind from the standard Manus site. Under easterly wind conditions, which occur 17% of the time, there is a higher occurrence of cloudiness at the downwind site likely due to land heating and orographic effects. This increased cloudiness is caused by scattered clouds often with bases around 700 m in altitude. While the central Manus site consistently measures a frequency of occurrence of low clouds (cloud base height less than 1200 m) about 25% of the time regardless of wind direction, the AMIE site has higher frequencies of low clouds (38%) when winds are from the east. This increase in low, locally produced clouds causes an additional -20 W/m2 shortwave surface cloud radiative effect at the AMIE site than the Manus site. © 2014. American Geophysical Union. All Rights Reserved."
"35738058800;6701580874;6603568514;7005265210;","North American west coast summer low cloudiness: Broadscale variability associated with sea surface temperature",2014,"10.1002/2014GL059825","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901932524&doi=10.1002%2f2014GL059825&partnerID=40&md5=0dcd375fb89daff138bc7332da343edf","Six decades of observations at 20 coastal airports, from Alaska to southern California, reveal coherent interannual to interdecadal variation of coastal low cloudiness (CLC) from summer to summer over this broad region. The leading mode of CLC variability represents coherent variation, accounting for nearly 40% of the total CLC variance spanning 1950-2012. This leading mode and the majority of individual airports exhibit decreased low cloudiness from the earlier to the later part of the record. Exploring climatic controls on CLC, we identify North Pacific Sea Surface Temperature anomalies, largely in the form of the Pacific Decadal Oscillation (PDO) as well correlated with, and evidently helping to organize, the coherent patterns of summer coastal cloud variability. Links from the PDO to summer CLC appear a few months in advance of the summer. These associations hold up consistently in interannual and interdecadal frequencies. Key Points Coastal low cloudiness from California to Alaska varies coherently over 63 years Variability in cloudiness is organized by sea surface temperature variability Links from SST to summer cloudiness appear a few months in advance of the summer © 2014. American Geophysical Union. All Rights Reserved."
"8312732800;7004572420;55918817700;7401635168;","Mixing state of regionally transported soot particles and the coating effect on their size and shape at a mountain site in Japan",2014,"10.1002/2013JD020880","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901705794&doi=10.1002%2f2013JD020880&partnerID=40&md5=f5ff3f8fce9093074fa4b5459653969d","Soot particles influence the global climate through interactions with sunlight. A coating on soot particles increases their light absorption by increasing their absorption cross section and cloud condensation nuclei activity when mixed with other hygroscopic aerosol components. Therefore, it is important to understand how soot internally mixes with other materials to accurately simulate its effects in climate models. In this study, we used a transmission electron microscope (TEM) with an auto particle analysis system, which enables more particles to be analyzed than a conventional TEM. Using the TEM, soot particle size and shape (shape factor) were determined with and without coating from samples collected at a remote mountain site in Japan. The results indicate that ~10% of aerosol particles between 60 and 350 nm in aerodynamic diameters contain or consist of soot particles and ~75% of soot particles were internally mixed with nonvolatile ammonium sulfate or other materials. In contrast to an assumption that coatings change soot shape, both internally and externally mixed soot particles had similar shape and size distributions. Larger aerosol particles had higher soot mixing ratios, i.e., more than 40% of aerosol particles with diameters >1 µm had soot inclusions, whereas <20% of aerosol particles with diameters <1 µm included soot. Our results suggest that climate models may use the same size distributions and shapes for both internally and externally mixed soot; however, changing the soot mixing ratios in the different aerosol size bins is necessary. © 2014. American Geophysical Union. All Rights Reserved."
"23978675000;7202081585;35459699300;6506458269;35430463900;6506886910;","Dehydration in the tropical tropopause layer: A case study for model evaluation using aircraft observations",2014,"10.1002/2013JD021381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901702037&doi=10.1002%2f2013JD021381&partnerID=40&md5=2036d25d447fa48db6c7e5a7db931984","The dynamical and microphysical processes that influence water vapor concentrations in the tropical tropopause layer (TTL) are investigated in simulations of ice clouds along backward trajectories of air parcels sampled during three flights of the Airborne Tropical Tropopause Experiment over the central to eastern tropical Pacific in boreal fall 2011. ERA-Interim reanalysis temperatures interpolated onto the flight tracks have a negligible (-0.09 K) cold bias compared to aircraft measurements of tropical cold point temperature thus permitting case study simulations of TTL dehydration. When the effects of subgrid-scale waves, cloud microphysical processes, and convection are considered, the simulated water vapor mixing ratios on the final day of 40 day backward trajectories exhibit a mean profile that is within 20-30% of the mean of the aircraft measurements collected during vertical profiling maneuvers between the 350 and 410 K potential temperature levels. Averaged over the three flights, temperature variability driven by subgrid-scale waves dehydrated the 360-390 K layer by approximately -0.5 ppmv, whereas including homogeneous freezing of aqueous aerosols and subsequent sublimation and rehydration of ice crystals increased water vapor below the 380 K level by about +1 ppmv. The predominant impact of convection was to moisten the TTL, resulting in an average enhancement below the 370 K level by +1 to 5 ppmv. Accurate (to within 0.5-1 ppmv) predictions of TTL water vapor using trajectory models require proper representations of waves, in situ ice cloud formation, and convective influence, which together determine the saturation history of air parcels. © 2014. American Geophysical Union. All Rights Reserved."
"24329085500;7003620360;35614095500;6601922531;6505768455;7005126327;7003431244;","Observation of polar stratospheric clouds over McMurdo (77.85°S, 166.67°E) (2006-2010)",2014,"10.1002/2013JD019892","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901707487&doi=10.1002%2f2013JD019892&partnerID=40&md5=7505ca16f7caf65168017a7b8ed1befc","Polar stratospheric clouds (PSCs) have been observed in the Antarctic winter from2006 to 2010 at the Antarctic base of McMurdo Station using a newly developed Rayleigh lidar. Total backscatter ratio and volume depolarization at 532 nm have been measured from 9 km up to 30 km with an average of 90 measurements per winter season. The data set was analyzed in order to evaluate the occurrence of PSCs based on their altitude, seasonal variability, geometrical thickness, and cloud typology derived from observed optical parameters. We have adopted the latest version of the scheme used to classify PSCs detected by the CALIPSO satellite-based lidar in order to facilitate comparison of ground-based and satellite-borne lidars. This allowed us to approximately identify how processes acting at different spatial scales might affect the formation of different PSC particles. The McMurdo lidar observations are dominated by PSC layers during the Antarctic winter. A clear difference between the different type of PSCs classified according to the observed optical parameters and their geometrical thickness was observed. Ice and supercooled ternary solution PSCs are observed predominantly as thin layers, while thicker layers are associated with nitric acid trihydrate particles. The same classification scheme has been adopted to reanalyze the 1995-2001 McMurdo lidar data in order to compare both data sets (1995-2001 versus 2006-2010). © 2014. American Geophysical Union. All Rights Reserved."
"16177084000;57203200427;36600036800;8397494800;7101672097;37037519900;7407104838;35096299800;7005955015;57207008570;53878006900;6506373162;7006705919;7004299063;55544607500;7404732357;57205638870;55893823700;9249627300;55317177900;","Forcings and feedbacks in the geomip ensemble for a reduction in solar irradiance and increase in CO2",2014,"10.1002/2013JD021110","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901723947&doi=10.1002%2f2013JD021110&partnerID=40&md5=f98cb7a2b2a4be357da362528f091d4f","The effective radiative forcings (including rapid adjustments) and feedbacks associated with an instantaneous quadrupling of the preindustrial CO2 concentration and a counterbalancing reduction of the solar constant are investigated in the context of the Geoengineering Model Intercomparison Project (GeoMIP). The forcing and feedback parameters of the net energy flux, as well as its different components at the top-of-atmosphere (TOA) and surface, were examined in 10 Earth System Models to better understand the impact of solar radiation management on the energy budget. In spite of their very different nature, the feedback parameter and its components at the TOA and surface are almost identical for the two forcing mechanisms, not only in the global mean but also in their geographical distributions. This conclusion holds for each of the individual models despite intermodel differences in how feedbacks affect the energy budget. This indicates that the climate sensitivity parameter is independent of the forcing (when measured as an effective radiative forcing). We also show the existence of a large contribution of the cloudy-sky component to the shortwave effective radiative forcing at the TOA suggesting rapid cloud adjustments to a change in solar irradiance. In addition, the models present significant diversity in the spatial distribution of the shortwave feedback parameter in cloudy regions, indicating persistent uncertainties in cloud feedback mechanisms. © 2014. American Geophysical Union. All Rights Reserved."
"35573324500;15724736600;6602667330;7004233804;","Characterization of an unexpected snowfall event in iqaluit, nunavut, and surrounding area during the Storm Studies in the Arctic field project",2014,"10.1002/2013JD021176","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901698368&doi=10.1002%2f2013JD021176&partnerID=40&md5=b0e52e7de4a85f6a146b4618dfcb59a2","Small accumulation precipitation events are critical for the high-latitude hydrological cycle. They contribute to more than 50% of total accumulation in the area and occur at a greater frequency than high-accumulation events. Despite their importance, the processes controlling them have not been investigated in sufficient detail. This study characterizes an unexpected high-latitude snowfall event at Iqaluit, Nunavut, and surrounding area during the Storm Studies in the Arctic field project. High-resolution data collected, from both ground based and airborne Doppler radar, along with upper air and surface observations, provided the basis for analysis of the conditions that led to the event and offer some insight as to why it was not well forecast by the Canadian operational model. Several factors worked in concert to produce this event. Low-level convection and upslope processes were important in cloud and precipitation generation over the orography upstream. When combined with additional lift from the passing of a weak trough, cloud and precipitation production were enhanced, allowing these features to penetrate over the terrain and resulted in precipitation at Iqaluit. Analysis of the global environmental multiscale limited area model (2.5 km resolution) suggests that upstream convection and upslope processes were affected by model errors. As a consequence, precipitation onset was delayed, and the total accumulation was 50% lower than the observations. Results indicate that the complexity of precipitation events in the region represents a significant challenge for predicting and modeling and understanding their role in the region’s hydrological cycle. © 2014. American Geophysical Union. All Rights Reserved."
"32067667700;8321475300;55391692700;7003406178;7005973748;","The effect of total grain-size distribution on the dynamics of turbulent volcanic plumes",2014,"10.1016/j.epsl.2014.03.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897398131&doi=10.1016%2fj.epsl.2014.03.021&partnerID=40&md5=f5df57941e2a91e8fd2607f7fa12c1be","The impact of explosive volcanic plumes on climate and on air traffic strongly depends on the concentration and grain-size distribution (GSD) of pyroclastic fragments injected into the atmosphere. Accurate and robust modelling of the evolution of GSD during pyroclast transport from the vent to the ash cloud is therefore crucial for the assessment of major volcanic hazards. Analysis of field deposits from various recent Plinian eruptions shows that their total GSD is well described by a power law, as expected from the physics of magma fragmentation, with an exponent (D) ranging from 3.0 to 3.9. By incorporating these measured GSD into the initial conditions of a steady-state 1D model of explosive eruption columns, we show that they have a first-order impact on the dynamical behaviour of explosive eruption columns. Starting from an initial value of D, the model tracks the evolution of GSD in the column and calculates the dynamical consequences of particle sedimentation. The maximum height reached by the column, one of the first-order results relevant to aircraft safety, changes by 30% for mass fluxes of 107kgs -1 or larger, and by 45-85% for mass fluxes between 105 and 107kgs -1, depending on exponent D. We compare our predictions to a specially assembled set of geologic field data and remote sensing observations from 10 Plinian eruptions for which maximum column height and mass flux are known independently. The incorporation of realistic power-law GSD in the model greatly improves the predictions, which opens new perspectives for estimation of ash load and GSD in volcanic clouds from near real-time measurements available from satellite payloads. Our results also contribute to the improvement of volcanic source term characterization that is required input for meteorological dispersion models. © 2014 Elsevier B.V."
"57206273805;6701378450;","Understanding the contributions of aerosol properties and parameterization discrepancies to droplet number variability in a global climate model",2014,"10.5194/acp-14-4809-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900819346&doi=10.5194%2facp-14-4809-2014&partnerID=40&md5=a5a26cbfae03877735c97f25b337be4b","Aerosol indirect effects in climate models strongly depend on the representation of the aerosol activation process. In this study, we assess the process-level differences across activation parameterizations that contribute to droplet number uncertainty by using the adjoints of the Abdul-Razzak and Ghan (2000) and Fountoukis and Nenes (2005) droplet activation parameterizations in the framework of the Community Atmospheric Model version 5.1 (CAM5.1). The adjoint sensitivities ofNd to relevant input parameters are used to (i) unravel the spatially resolved contribution of aerosol number, mass, and chemical composition to changes inNd between present-day and pre-industrial simulations and (ii) identify the key variables responsible for the differences inNd fields and aerosol indirect effect estimates when different activation schemes are used within the same modeling framework. The sensitivities are computed online at minimal computational cost. Changes in aerosol number and aerosol mass concentrations were found to contribute toNd differences much more strongly than chemical composition effects. The main sources of discrepancy between the activation parameterizations considered were the treatment of the water uptake by coarse mode particles, and the sensitivity of the parameterizedNd accumulation mode aerosol geometric mean diameter. These two factors explain the different predictions ofNd over land and over oceans when these parameterizations are employed. Discrepancies in the sensitivity to aerosol size are responsible for an exaggerated response to aerosol volume changes over heavily polluted regions. Because these regions are collocated with areas of deep clouds, their impact on shortwave cloud forcing is amplified through liquid water path changes. The same framework is also utilized to efficiently explore droplet number uncertainty attributable to hygroscopicity parameter of organic aerosol (primary and secondary). Comparisons between the parameterization-derived sensitivities of droplet number against predictions with detailed numerical simulations of the activation process were performed to validate the physical consistency of the adjoint sensitivities. © 2014 Author(s)."
"35810775100;7004469744;36134816800;8942524900;57205638870;6602506226;8942525300;7102795549;24463029300;43661479500;56384704800;7003666669;7006270084;55717074000;57208121852;55588510300;57211106013;55976582900;7005219614;22978151200;6507308842;55885662200;16643812900;56370934200;10139397300;12806941900;7405666962;17345303300;6506718302;6603613067;38762392200;9275665400;35998927000;7005228425;7403682442;7006634316;7103135455;7005069415;55984791900;35449990500;7006708207;36041280100;6602571316;35461255500;7003984086;7004686011;7006058570;6603563152;7102708429;7102496779;7005287667;6506810759;","Intercomparison and evaluation of global aerosol microphysical properties among AeroCom models of a range of complexity",2014,"10.5194/acp-14-4679-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900843983&doi=10.5194%2facp-14-4679-2014&partnerID=40&md5=750193a41be6ced7805d8061b814b05f","Many of the next generation of global climate models will include aerosol schemes which explicitly simulate the microphysical processes that determine the particle size distribution. These models enable aerosol optical properties and cloud condensation nuclei (CCN) concentrations to be determined by fundamental aerosol processes, which should lead to a more physically based simulation of aerosol direct and indirect radiative forcings. This study examines the global variation in particle size distribution simulated by 12 global aerosol microphysics models to quantify model diversity and to identify any common biases against observations. Evaluation against size distribution measurements from a new European network of aerosol supersites shows that the mean model agrees quite well with the observations at many sites on the annual mean, but there are some seasonal biases common to many sites. In particular, at many of these European sites, the accumulation mode number concentration is biased low during winter and Aitken mode concentrations tend to be overestimated in winter and underestimated in summer. At high northern latitudes, the models strongly underpredict Aitken and accumulation particle concentrations compared to the measurements, consistent with previous studies that have highlighted the poor performance of global aerosol models in the Arctic. In the marine boundary layer, the models capture the observed meridional variation in the size distribution, which is dominated by the Aitken mode at high latitudes, with an increasing concentration of accumulation particles with decreasing latitude. Considering vertical profiles, the models reproduce the observed peak in total particle concentrations in the upper troposphere due to new particle formation, although modelled peak concentrations tend to be biased high over Europe. Overall, the multi-model-mean data set simulates the global variation of the particle size distribution with a good degree of skill, suggesting that most of the individual global aerosol microphysics models are performing well, although the large model diversity indicates that some models are in poor agreement with the observations. Further work is required to better constrain size-resolved primary and secondary particle number sources, and an improved understanding of nucleation and growth (e.g. the role of nitrate and secondary organics) will improve the fidelity of simulated particle size distributions. © 2014 Author(s)."
"55796506900;55355176000;7410070663;","Application and evaluation of a new radiation code under McICA scheme in BCC-AGCM2.0.1",2014,"10.5194/gmd-7-737-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900008409&doi=10.5194%2fgmd-7-737-2014&partnerID=40&md5=31a8bdfc962f6daf3b1b6c7c697c6474","This research incorporates the correlated k distribution BCC-RAD radiation model into the climate model BCC-AGCM2.0.1 and examines the change in climate simulation by implementation of the new radiation algorithm. It is shown that both clear-sky radiation fluxes and cloud radiative forcings (CRFs) are improved. The modeled atmospheric temperature and specific humidity are also improved due to changes in radiative heating rates, which most likely stem from the revised treatment of gaseous absorption. Subgrid cloud variability, including vertical overlap of fractional clouds and horizontal inhomogeneity in cloud condensate, is addressed by using the Monte Carlo Independent Column Approximation (McICA) method. In McICA, a cloud-type-dependent function for cloud fraction decorrelation length, which gives zonal mean results very close to the observations of CloudSat/CALIPSO, is developed. Compared to utilizing a globally constant decorrelation length, the maximum changes in seasonal CRFs by the new scheme can be as large as 10 and 20Wm-2 for longwave (LW) and shortwave (SW) CRFs, respectively, mostly located in the tropics. The inclusion of an observation-based horizontal inhomogeneity of cloud condensate has also a significant impact on CRFs, with global means of ~1.5Wm-2 and ~3.7 Wm-2 for LW and SW CRFs at the top of atmosphere (TOA), respectively. Generally, incorporating McICA and horizontal inhomogeneity of cloud condensate in the BCC-RAD model reduces global mean TOA and surface SW and LW flux biases in BCC-AGCM2.0.1. These results demonstrate the feasibility of the new model configuration to be used in BCC-AGCM2.0.1 for climate simulations, and also indicate that more detailed real-world information on cloud structures should be obtained to constrain cloud settings in McICA in the future. © Author(s) 2014."
"15755995900;7006705919;57193213111;7006270084;8922308700;55717074000;7003666669;55544607500;","Assessing the CAM5 physics suite in the WRF-Chem model: Implementation, resolution sensitivity, and a first evaluation for a regional case study",2014,"10.5194/gmd-7-755-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900454585&doi=10.5194%2fgmd-7-755-2014&partnerID=40&md5=d18429ea581589e4b1d825e873ccc3a2","A suite of physical parameterizations (deep and shallow convection, turbulent boundary layer, aerosols, cloud microphysics, and cloud fraction) from the global climate model Community Atmosphere Model version 5.1 (CAM5) has been implemented in the regional model Weather Research and Forecasting with chemistry (WRF-Chem). A downscaling modeling framework with consistent physics has also been established in which both global and regional simulations use the same emissions and surface fluxes. The WRF-Chem model with the CAM5 physics suite is run at multiple horizontal resolutions over a domain encompassing the northern Pacific Ocean, northeast Asia, and northwest North America for April 2008 when the ARCTAS, ARCPAC, and ISDAC field campaigns took place. These simulations are evaluated against field campaign measurements, satellite retrievals, and ground-based observations, and are compared with simulations that use a set of common WRF-Chem parameterizations. This manuscript describes the implementation of the CAM5 physics suite in WRF-Chem, provides an overview of the modeling framework and an initial evaluation of the simulated meteorology, clouds, and aerosols, and quantifies the resolution dependence of the cloud and aerosol parameterizations. We demonstrate that some of the CAM5 biases, such as high estimates of cloud susceptibility to aerosols and the underestimation of aerosol concentrations in the Arctic, can be reduced simply by increasing horizontal resolution. We also show that the CAM5 physics suite performs similarly to a set of parameterizations commonly used in WRF-Chem, but produces higher ice and liquid water condensate amounts and near-surface black carbon concentration. Further evaluations that use other mesoscale model parameterizations and perform other case studies are needed to infer whether one parameterization consistently produces results more consistent with observations. © Author(s) 2014. CC Attribution 3.0 License."
"23995988300;36158667700;57203073322;","Dynamic cloud regimes, incident sunlight, and leaf temperatures in espeletia grandiflora and Chusquea tessellata, two representative species of the Andean Páramo, Colombia",2014,"10.1657/1938-4246-46.2.371","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902194634&doi=10.1657%2f1938-4246-46.2.371&partnerID=40&md5=c50c6fecea2ddea3f9a0a332cb24daa1","The alpine páramo of Chingaza National Park, Colombia, has a highly variable cloud regime typical of many tropical alpine areas. Yet, little information is available regarding the effects of such dynamic sunlight regimes on alpine temperatures. A close association between changes in incident sunlight and corresponding air (Ta) and leaf (Tl) temperatures occurred in two dominant species with strongly contrasting leaf form and whole-plant architecture. Spikes in sunlight incidence of &gt;3000 μmol m-2 s-1 occurred during cloud cover and corresponded to increases in Tl of 4-5 °C in a 1-min-interval in both species. Although Tl was predominately above Ta, during the day, depressions below Ta of over 6 °C occurred during cloudy conditions when photosynthetic photon flux density (PFDs) was &lt;400 μmol m-2 s-1. The greatest frequency (69%) of changes in incident sunlight (PFDs; over 2-min intervals) was less than 100 μmol m-2 s-1, although changes &gt;1000 μmol m-2 s-1 occurred for 2.4% of the day, including a maximum change of 1512 μmol m-2 s-1. These data may be valuable for predicting the ecophysiological impact of climate warming and associated changes in future cloud regimes experienced by tropical alpine species."
"56597778200;6506286986;9233045100;26635422600;55670345400;6701410329;","CLAAS: The CM SAF cloud property data set using SEVIRI",2014,"10.5194/acp-14-4297-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899748847&doi=10.5194%2facp-14-4297-2014&partnerID=40&md5=a67ede035f7b33f32487d1d442ca98b3","An 8-year record of satellite-based cloud properties named CLAAS (CLoud property dAtAset using SEVIRI) is presented, which was derived within the EUMETSAT Satellite Application Facility on Climate Monitoring. The data set is based on SEVIRI measurements of the Meteosat Second Generation satellites, of which the visible and near-infrared channels were intercalibrated with MODIS. Applying two state-of-the-art retrieval schemes ensures high accuracy in cloud detection, cloud vertical placement and microphysical cloud properties. These properties were further processed to provide daily to monthly averaged quantities, mean diurnal cycles and monthly histograms. In particular, the per-month histogram information enhances the insight in spatio-temporal variability of clouds and their properties. Due to the underlying intercalibrated measurement record, the stability of the derived cloud properties is ensured, which is exemplarily demonstrated for three selected cloud variables for the entire SEVIRI disc and a European subregion. All data products and processing levels are introduced and validation results indicated. The sampling uncertainty of the averaged products in CLAAS is minimized due to the high temporal resolution of SEVIRI. This is emphasized by studying the impact of reduced temporal sampling rates taken at typical overpass times of polar-orbiting instruments. In particular, cloud optical thickness and cloud water path are very sensitive to the sampling rate, which in our study amounted to systematic deviations of over 10% if only sampled once a day. The CLAAS data set facilitates many cloud related applications at small spatial scales of a few kilometres and short temporal scales of a few hours. Beyond this, the spatiotemporal characteristics of clouds on diurnal to seasonal, but also on multi-annual scales, can be studied. © 2014 Author(s)."
"8394117100;55804227100;7006711866;44461541300;35490828000;26643595600;7003627515;7006515772;","Empirical estimation of present-day Antarctic glacial isostatic adjustment and ice mass change",2014,"10.5194/tc-8-743-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899564285&doi=10.5194%2ftc-8-743-2014&partnerID=40&md5=c3456628bdb1838560069de8e77a3667","This study explores an approach that simultaneously estimates Antarctic mass balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating a firn densification model to account for firn compaction and surface processes as well as reprocessed data sets over a slightly longer period of time. A range of different Gravity Recovery and Climate Experiment (GRACE) gravity models were evaluated and a new Ice, Cloud, and Land Elevation Satellite (ICESat) surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than recent conventional GIA models. The new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea sector in West Antarctica (WA) and the Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica (EA). The total GIA-related mass change estimates for the entire Antarctic ice sheet ranged from 53 to 103 Gt yr-1, depending on the GRACE solution used, with an estimated uncertainty of ±40 Gt yr -1. Over the time frame February 2003-October 2009, the corresponding ice mass change showed an average value of -100 ± 44 Gt yr-1 (EA: 5 ± 38, WA: -105 ± 22), consistent with other recent estimates in the literature, with regional mass loss mostly concentrated in WA. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present-day GIA and ice mass change, particularly with respect to determining more reliable uncertainties. © Author(s) 2014."
"34976155900;7007099717;8588658600;","Wave-cloud lines over the Arabian Sea",2014,"10.1002/2013JD021347","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900556794&doi=10.1002%2f2013JD021347&partnerID=40&md5=2fe2bd02bc7a47a3e43eba7a78e92c6d","Meteosat visible satellite images between 2006 and 2011 show wave-cloud lines over the Arabian Sea in all months outside the summer monsoon (June-September). These lines are most frequent between January and May (2-3 per month in a given year). All wave-cloud lines in the region propagate offshore. As these wave-cloud lines are associated with coherent convergence lines, the objective technique described by Berry and Reeder is applied to the ERA-Interim reanalysis and a climatology of convergence lines at 850 hPa developed. Despite the coarse resolution of the ERA-Interim reanalysis, the statistical properties of these lines are broadly constant with those deduced from the Meteosat visible satellite images. The generation mechanism is investigated in a simulation with the Met Office Unified Model of a particular wave-cloud line (12 March 2011). The process appears to be similar to that over northwestern Australia, which has been documented previously. During the day, a synoptic-scale northeasterly flow opposes the inland advection of the sea breeze on the west coast of India. However, as the daytime turbulence decays and the boundary layer stabilizes, the northeasterly flow accelerates, pushing offshore the leading edge of the sea breeze during the late evening and early hours of the morning. A wave is generated as the northeasterlies penetrate the marine boundary layer, and this wave propagates westward, producing cloud at its leading edge where there is strong ascent. © 2014. American Geophysical Union. All Rights Reserved."
"57203378050;55470017900;6603652793;7404548584;7004371379;57219896501;","Evaluating the impact of multisensor data assimilation on a global aerosol particle transport model",2014,"10.1002/2013JD020975","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900546159&doi=10.1002%2f2013JD020975&partnerID=40&md5=e9a7a9652da22b6c05b15016ff6af787","By evaluating quality-assured Moderate Resolution Imaging Spectroradiometer (MODIS) Dark Target (DT), MODIS Deep Blue (DB), Multiangle Imaging Spectroradiometer (MISR), and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol products assimilated into the U. S. Navy Aerosol Analysis and Prediction System (NAAPS), the impact of single-sensor and multisensor data assimilation on aerosol optical depth (AOD) analysis and forecast skill is characterized using ground-based Level 2 Aerosol Robotic Network (AERONET) data sets during the 2007 boreal summer (June-August 2007). The single-sensor assimilation experiment suggests that all products tested can improve NAAPS performance on a regional or a global scale. The multisensor assimilation experiment suggests that model improvement is greatest with the combined use of Terra and Aqua MODIS DT products, largely due to data density. Incremental improvements are identified, as a function of data density, over regions such as the Saharan desert when adding MISR and MODIS DB products. The inclusion of CALIOP data is mass-neutral by definition and has an insignificant impact on the NAAPS 00 h analysis. CALIOP assimilation does improve the 48 h forecast from NAAPS due to more accurate 00 h vertical distribution and hence forecasted advection. Root-mean-square errors exceeding 0.1 are found over East Asia and North Africa for both the NAAPS analysis and satellite AOD data, indicating that satellite aerosol products in these two regions need improvement. Similarly, low correlation is found between NAAPS and AERONET over Australia, even with the use of all available satellite aerosol products, suggesting that more detailed examination of some critical regions is necessary. © 2014. American Geophysical Union. All Rights Reserved."
"55795506000;56996271000;7102953444;","Evaluations of atmospheric downward longwave radiation from 44 coupled general circulation models of CMIP5",2014,"10.1002/2013JD021427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900541917&doi=10.1002%2f2013JD021427&partnerID=40&md5=9d2c0cf6343b530376bd5178cd2b1d50","Atmospheric downward longwave radiation at the surface (Ld) quantifies the atmospheric greenhouse effect. This study evaluated Ld simulations from 44 general circulation models (GCMs) in the Coupled Model Intercomparison Project Phase 5 (CMIP5) with a comprehensive data set of Ld observations at 156 global-distributed sites from 1992 to 2005. Compared with the Baseline Surface Radiation Network data that are of the highest quality among the available Ld data sets, CMIP5 GCM Ld has a negligible bias, much better than CMIP3 GCMs, likely because of the improvement of low cloud simulations in CMIP5 models. However, the selection of validation data has an important impact on the evaluation results. The global mean Ld inferred from different bias-removing methods are nearly the same, approximately 341Wm-2 globally averaged from 1992 to 2005. CMIP5 GCMs showed that global Ld increased at a rate of 1.54Wm-2 per decade (p&lt;0.01) from 1979 to 2005, which is consistent with available reanalyses. This good agreement in long-term trends of Ld is likely because both reanalyses and CMIP5 models reproduced the observed warming and the associated increase of water vapor content in the lower atmosphere. However, CMIP5 GCMs are still poor in producing monthly anomalies of Ld. © 2014. American Geophysical Union. All Rights Reserved."
"57151771800;20734542100;","The vertical distribution of black carbon in CMIP5 models: Comparison to observations and the importance of convective transport",2014,"10.1002/2014JD021595","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900561253&doi=10.1002%2f2014JD021595&partnerID=40&md5=f9c9e71531c806762959fffbae5e4dc2","Large uncertainty in the direct radiative forcing of black carbon (BC) exists, with published estimates ranging from 0.25 to 0.9 W m-2. A significant source of this uncertainty relates to the vertical distribution of BC, particularly relative to cloud layers. We first compare the vertical distribution of BC in Coupled Model Intercomparison Project Phase 5 (CMIP5) models to aircraft measurements and find that models tend to overestimate upper tropospheric/lower stratospheric (UT/LS) BC, particularly over the central Pacific from Hiaper Pole-to-Pole Observations Flight 1 (HIPPO1). However, CMIP5 generally underestimates Arctic BC from the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign, implying a geographically dependent bias. Factors controlling the vertical distribution of BC in CMIP5 models, such as wet and dry deposition, precipitation, and convective mass flux (MC), are subsequently investigated. We also perform a series of sensitivity experiments with the Community Atmosphere Model version 5, including prescribed meteorology, enhanced vertical resolution, and altered convective wet scavenging efficiency and deep convection. We find that convective mass flux has opposing effects on the amount of black carbon in the atmosphere. More MC is associated with more convective precipitation, enhanced wet removal, and less BC below 500 hPa. However, more MC, particularly above 500 hPa, yield more BC aloft due to enhanced convective lofting. These relationships-particularly MC versus BC below 500 hPa-are generally stronger in the tropics. Compared to the Modern-Era Retrospective Analysis for Research and Applications, most CMIP5 models overestimate MC, with all models overestimating MC above 500 hPa. Our results suggest that excessive convective transport is one of the reasons for CMIP5 overestimation of UT/LS BC. © 2014. American Geophysical Union. All Rights Reserved."
"7005461772;7003993113;55940118700;6602861814;47761439400;7003354633;6506199476;12239121500;","Combining model and geostationary satellite data to reconstruct hourly SST field over the Mediterranean Sea",2014,"10.1016/j.rse.2013.11.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899451070&doi=10.1016%2fj.rse.2013.11.001&partnerID=40&md5=c964597be2e93cc2e38e88acd8a9dbfb","This work focuses on the reconstruction of Sea Surface Temperature (SST) diurnal cycle through combination of numerical model analyses and geostationary satellite measurements. The approach takes advantage of geostationary satellite observations as the diurnal signal source to produce gap-free optimally interpolated (OI) hourly SST fields using model analyses as first-guess. The resulting SST anomaly field (satellite-model) is free, or nearly free, of any diurnal cycle, thus allowing one to interpolate SST anomalies using satellite data acquired at different times of the day.The method is applied to reconstruct the hourly Mediterranean SST field during summer 2011 using SEVIRI data and Mediterranean Forecasting System analyses. A synthetic cloud reconstruction experiment demonstrated that the OI SST method is able to reconstruct an unbiased SST field with a RMS. = 0.16. °C with respect to SEVIRI observations. The OI interpolation estimate, the model first guess and the SEVIRI data are evaluated using drifter and mooring measurements. Special attention is devoted to the analysis of diurnal warming (DW) events that are particularly frequent in the Mediterranean Sea. The model reproduces quite well the Mediterranean SST diurnal cycle, except for the DW events. Due to the thickness of the model surface layer, the amplitude of the model diurnal cycle is often less intense than the corresponding SEVIRI and drifter observations. The Diurnal OI SST (DOISST) field, resulting from the blending of model and SEVIRI data via optimal interpolation, reproduces well the diurnal cycle including extreme DW events. The evaluation of DOISST products against drifter measurements results in a mean bias of -. 0.07. °C and a RMS of 0.56. °C over interpolated pixels. These values are very close to the corresponding statistical parameters estimated from SEVIRI data (bias. = -. 0.16. °C, RMS. = 0.47. °C). Results also confirm that part of the mean bias between temperature measured by moorings at 1. m depth and the satellite observations can be ascribed to the different nature of the measurements (bulk versus skin). © 2013 Elsevier Inc."
"53878006900;7005955015;13403622000;12779071400;","The climatic effects of modifying cirrus clouds in a climate engineering framework",2014,"10.1002/2013JD021063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910664400&doi=10.1002%2f2013JD021063&partnerID=40&md5=50efb2cde837710df867a2a737be8106","The climatic effects of climate engineering—or geoengineering—via cirrus cloud thinning are examined. Thinner cirrus clouds can allow more outgoing longwave radiation to escape to space, potentially cooling the climate. The cloud properties and climatic effects due to perturbing the ice crystal fall speed are investigated in a set of hemispheric scale sensitivity experiments with the Community Earth System Model. It is found that increasing the ice crystal fall speed, as an analog to cirrus cloud seeding, depletes high-level clouds and reduces the longwave cloud forcing. Deliberate depletion of cirrus clouds increases outgoing longwave radiation, reduces the upper tropospheric water vapor, and cools the climate. Global cirrus cloud thinning gave a net cloud forcing change of −1.55 Wm−2 and a global annual mean temperature change of −0.94 K. Though there is negligible change in the global annual mean precipitation (−0.001 mm/d), the spatially nonhomogeneous forcing induces circulation changes and hence remote climate changes. Climate engineering the Southern Hemisphere only results in a northward shift of the Intertropical Convergence Zone and possible Sahelian drought alleviation, while targeting the Northern Hemisphere alone causes a greater cooling. It was found that targeting cirrus clouds everywhere outside of the tropics results in changes to the circulation and precipitation even in the nonclimate engineered regions, underscoring the risks of remote side effects and indeed the complexity of the climate system. © 2014. American Geophysical Union. All Rights Reserved."
"12040335900;7404653593;45661599100;13403622000;55683910600;","Influence of cloud phase composition on climate feedbacks",2014,"10.1002/2013JD020582","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924161128&doi=10.1002%2f2013JD020582&partnerID=40&md5=fe7dafc6a40716960c619ed9ed26c22d","The ratio of liquid water to ice in a cloud, largely controlled by the presence of ice nuclei and cloud temperature, alters cloud radiative effects. This study quantitatively examines how the liquid fraction of clouds influences various climate feedbacks using the NCAR Community Atmosphere Model (CAM). Climate feedback parameters were calculated using equilibrated temperature changes in response to increases in the atmospheric concentration of carbon dioxide in CAM Version 3.0 with a slab ocean model. Two sets of model experiments are designed such that cloud liquid fraction linearly decreases with a decrease in temperature down to -20°C (Experiment “C20”) and -40°C (Experiment “C40”). Thus, at the same subzero temperature, C20 yields fewer liquid droplets (and more ice crystals) than C40. Comparison of the results of experiments C20 and C40 reveals that experiment C20 is characterized by stronger cloud and temperature feedbacks in the tropics (30°N–30°S) (by 0.25 and -0.28 W m-2 K-1, respectively) but weaker cloud, temperature, and albedo feedbacks (by -0.20, 0.11, and -0.07 W m-2 K-1) in the extratropics. Compensation of these climate feedback changes leads to a net climate feedback change of ~7.28% of that of C40 in the model. These results suggest that adjustment of the cloud phase function affects all types of feedbacks (with the smallest effect on water vapor feedback). Although the net change in total climate feedback is small due to the cancellation of positive and negative individual feedback changes, some of the individual changes are relatively large. This illustrates the importance of the influence of cloud phase partitioning for all major climate feedbacks, and by extension, for future climate change predictions. © 2014. American Geophysical Union. All Rights Reserved."
"34772240500;8922308700;55688930000;","Impact of subgrid-scale radiative heating variability on the stratocumulus-to-trade cumulus transition in climate models",2014,"10.1002/2013JD020999","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942456071&doi=10.1002%2f2013JD020999&partnerID=40&md5=adbbb2fc51384039b886989f69cae287","Subgrid-scale interactions between turbulence and radiation are potentially important for accurately simulating marine low clouds in climate models. To better understand the impact of these interactions, the Weather Research and Forecasting model is configured for large eddy simulation to study the stratocumulus to trade cumulus (Sc-to-Cu) transition. Using the Global Energy and Water Cycle Experiment Atmospheric System Studies composite Lagrangian transition case and the Atlantic Trade Wind Experiment case, it is shown that the lack of subgrid-scale turbulence-radiation interaction, as is the case in current generation climate models, accelerates the Sc-to-Cu transition. Our analysis suggests that subgrid-scale turbulence-radiation interactions in cloud-topped boundary layers contribute to stronger production of temperature variance, which in turn leads to stronger buoyancy production of turbulent kinetic energy and helps to maintain the Sc cover. © 2014. American Geophysical Union. All Rights Reserved."
"9249239700;36150977900;7003278104;7006417494;16507851200;7501439334;","Cloud-precipitation-radiation-dynamics interaction in global climate models: A snow and radiation interaction sensitivity experiment",2014,"10.1002/2013JD021038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927696828&doi=10.1002%2f2013JD021038&partnerID=40&md5=1fdbb2cdd51e344bdedd4fdceccb123b","Conventional global climate models (GCMs) often consider radiation interactions only with small-particle/suspended cloud mass, ignoring large-particle/falling and convective core cloud mass. We characterize the radiation and atmospheric circulation impacts of frozen precipitating hydrometeors (i.e., snow), using the National Center for Atmospheric Research coupled GCM, by conducting sensitivity experiments that turn off the radiation interaction with snow. The changes associated with the exclusion of precipitating hydrometeors exhibit a number differences consistent with biases in CMIP3 and CMIP5 (Coupled Model Intercomparison Project Phase 3 and Phase 5), including more outgoing longwave flux at the top of atmosphere and downward shortwave flux at the surface in the heavily precipitating regions. Neglecting the radiation interaction of snow increases the net radiative cooling near the cloud top with the resulting increased instability triggering more convection in the heavily precipitating regions of the tropics. In addition, the increased differential vertical heating leads to a weakening of the low-level mean flow and an apparent low-level eastward advection from the warm pool resulting in moisture convergence south of the Intertropical Convergence Zone and north of the South Pacific Convergence Zone (SPCZ). This westerly bias, with effective warm and moist air transport, might be a contributing factor in the model’s northeastward overextension of the SPCZ and the concomitant changes in sea surface temperatures, upward motion, and precipitation. Broader dynamical impacts include a stronger local meridional overturning circulation over the middle and east Pacific and commensurate changes in low and upper level winds, large-scale ascending motion, with a notable similarity to the systematic bias in this region in CMIP5 upper level zonal winds. © 2014. American Geophysical Union. All Rights Reserved."
"55268661300;55461837700;7202899330;35509639400;","A global survey of the instantaneous linkages between cloud vertical structure and large-scale climate",2014,"10.1002/2013JD020669","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897582126&doi=10.1002%2f2013JD020669&partnerID=40&md5=56f3005e5d63f220c2dc148bc6aca886","The instantaneous linkages between cloud vertical structure and various large-scale meteorological parameters are investigated using 5 years of data from the CloudSat/CALIPSO instruments. The linkages are systemically explored and quantified at all vertical levels and throughout the global ocean in both the long-term mean and on month-to-month timescales. A number of novel large-scale meteorological parameters are used in the analysis, including tropopause temperatures, upper tropospheric stability, and storm track activity. The results provide a baseline for evaluating physical parameterizations of clouds in GCMs and a reference for interpreting the signatures of large-scale atmospheric phenomena in cloud vertical structure. In the long-term mean, upper tropospheric cloud incidence throughout the globe increases with (1) decreasing tropopause temperature (at a rate of ∼2–4% K−1), (2) decreasing upper tropospheric stability (∼5–10% per K km−1), and (3) increasing large-scale vertical motion (∼1–4% per 10 hPa d−1). In contrast, lower tropospheric cloud incidence increases with (1) increasing lower tropospheric stability (10% per K km−1) and descending motion (1% per 10 hPa d−1) in regions of subtropical regime but (2) decreasing lower tropospheric stability (4% per K km−1) and ascending motion (2% per 10 hPa d−1) over the Arctic region. Variations in static stability and vertical motion account for ∼20–35% of the month-to-month variance in upper tropospheric cloudiness but less than 10% of the variance in lower tropospheric clouds. Upper tropospheric cloud incidence in the storm track regions is strongly linked to the variance of large-scale vertical motion and thus the amplitude of baroclinic waves. © 2014. American Geophysical Union. All Rights Reserved."
"56647425100;25624545600;7102128820;57201793920;36161790500;45661986200;57200679067;","Aerosol impacts on drizzle properties in warm clouds from ARM mobile facility maritime and continental deployments",2014,"10.1002/2013JD021339","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906533824&doi=10.1002%2f2013JD021339&partnerID=40&md5=102fc02d20f25d19815a265f67f98f5c","We have extensively evaluated the response of cloud base drizzle rate (Rcb; mmd1) in warm clouds to liquid water path (LWP; g m2) and to cloud condensation nuclei (CCN) number concentration (NCCN; cm3), an aerosol proxy. This evaluation is based on a 19 month long data set of Doppler radar, lidar, microwave radiometers, and aerosol observing systems from the Atmospheric Radiation Measurement (ARM) Mobile Facility deployments at the Azores and in Germany. Assuming 0.55% supersaturation to calculate NCCN, we found a power law Rcb = (0:0015±0:0009).LWP(1:68±0:05) NCCN(0:66±0:08), indicating that Rcb decreases by a factor of 2–3 as NCCN increases from 200 to 1000 cm3 for fixed LWP. Additionally, the precipitation susceptibility to NCCN ranges between 0.5 and 0.9, in agreement with values from simulations and aircraft measurements. Surprisingly, the susceptibility of the probability of precipitation from our analysis is much higher than that from CloudSat estimates but agrees well with simulations from a multiscale high-resolution aerosol-climate model. Although scale issues are not completely resolved in the intercomparisons, our results are encouraging, suggesting that it is possible for multiscale models to accurately simulate the response of LWP to aerosol perturbations. © 2014. American Geophysical Union. All Rights Reserved."
"9838847000;35454141800;36907291300;","Joint analysis of cloud top heights from cloudsat and CALIPSO: New insights into cloud top microphysics",2014,"10.1002/2013JD020919","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904746708&doi=10.1002%2f2013JD020919&partnerID=40&md5=8284103dd95a1d944f4c032f30b10ee2","We examined the differences in the cloud top heights (CTHs) detected by the CloudSat radar and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar. Theoretical estimates have shown that CloudSat has higher sensitivity than CALIPSO does when large particles exist. In such case it might be possible that CloudSat-determined CTHs are larger than CALIPSO-determined CTHs. We compared the global distribution of CTHs detected by CloudSat and CALIPSO (version 3, V3) using our cloud mask schemes after carefully selecting data during September–November 2006. The global mean fraction of clouds where CloudSat-determined CTHs were larger than CALIPSO-determined CTHs turned out to be unexpectedly large. The fractions were 26% and 39% at low level and midlevel, and the corresponding CTH differences were 0.56 km and 0.86 km, respectively. On the western coasts of continents, these clouds occurred within temperature inversions. Accounting for the differences in sensitivity to particle size between CloudSat and CALIPSO, the existence of such clouds indicates that the cloud tops consist of large particles with small number concentration. The discovery of such clouds was revealed by our joint analysis of CloudSat and CALIPSO. When the standard vertical feature mask (VFM) V3 was used, these clouds were also found but the fractions were less pronounced. The differences were partly attributed to the overestimation of cloud fraction in the VFM V3, although the degree of misidentification in V3 was reduced compared with that of V2. © 2013. American Geophysical Union. All Rights Reserved."
"55463274000;23065650200;7402934750;55663817800;","Parameterization of ice fall speeds in midlatitude cirrus: Results from SPartICus",2014,"10.1002/2013JD020602","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938216440&doi=10.1002%2f2013JD020602&partnerID=40&md5=7ef0460b16d957a854a372330b1739f3","The climate sensitivity predicted in general circulation models can be sensitive to the treatment of the ice particle fall velocity. In this study, the mass-weighted ice fall speed (Vm) and the number concentration ice fall speed (Vn) in midlatitude cirrus clouds are computed from in situ measurements of ice particle area and number concentration made by the two-dimensional stereo probe during the Small Particles In Cirrus field campaign. For single-moment ice microphysical schemes, Vm and the ice particle size distribution effective diameter De were parameterized in terms of cloud temperature (T) and ice water content (IWC). For two-moment schemes, Vm and Vn were related to De and the mean maximum dimension ‾D, respectively. For single-moment schemes, although the correlations of Vm and De with T were higher than the correlations of Vm and De with IWC, it is demonstrated that Vm and De are better predicted by using both T and IWC. The parameterization relating Vm to T and IWC is compared with another scheme relating Vm to T and IWC, with the latter based on millimeter cloud radar measurements. Regarding two-moment ice microphysical schemes, a strong correlation was found between De and Vm and between ‾D and Vn owing to their similar weightings by ice particle mass and number concentration, respectively. Estimating Vm from De makes Vm a function of IWC and projected area, realistically coupling Vm with both the cloud microphysics and radiative properties. © 2014. American Geophysical Union. All Rights Reserved."
"35794588800;7102805852;7103016965;24764483400;8724962900;7005056279;7801353107;55630942000;","A method to represent subgrid-scale updraft velocity in kilometer-scale models: Implication for aerosol activation",2014,"10.1002/2013JD021218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942419022&doi=10.1002%2f2013JD021218&partnerID=40&md5=d3f6f274e8710c0225f5ce7ad06dfcd7","Updraft velocities strongly control the activation of aerosol particles or that component that act as cloud condensation nuclei (CCN). For kilometer-scale models, vertical motions are partially resolved but the subgrid-scale (SGS) contribution needs to be parametrized or constrained to properly represent the activation of CCNs. This study presents a method to estimate the missing SGS (or unresolved) contribution to vertical velocity variability in models with horizontal grid sizes up to ∼2 km. A framework based on Large Eddy Simulations (LES) and high-resolution aircraft observations of stratocumulus and shallow cumulus clouds has been developed and applied to output from the United Kingdom Met Office Unified Model (UM) operating at kilometer-scale resolutions in numerical weather prediction configuration. For a stratocumulus deck simulation, we show that the UM 1 km model underestimates significantly the variability of updraft velocity with an averaged cloud base standard deviation between 0.04 and 0.05 m s−1 compared to LES and aircraft estimates of 0.38 and 0.54 m s−1, respectively. Once the SGS variability is considered, the UM corrected averages are between 0.34 and 0.44 m s−1. Off-line calculations of CCN-activated fraction using an activation scheme have been performed to illustrate the implication of including the SGS vertical velocity. It suggests increased CCN-activated fraction from 0.52 to 0.89 (respectively, 0.10 to 0.54) for a clean (respectively, polluted) aerosol environment for simulations with a 1 km horizontal grid size. Our results highlight the importance of representing the SGS vertical velocity in kilometer-scale simulations of aerosol-cloud interactions. © 2014. American Geophysical Union. All Rights Reserved."
"36623061000;26643041500;6602136905;6603135449;15047358600;35221661700;57200562779;55683038000;7006593624;35461255500;7006182491;","Rapid changes in biomass burning aerosols by atmospheric oxidation",2014,"10.1002/2014GL059396","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899040439&doi=10.1002%2f2014GL059396&partnerID=40&md5=4e6972b279c84575099522f92af08125","Primary and secondary aerosol particles originating from biomass burning contribute significantly to the atmospheric aerosol budget and thereby to both direct and indirect radiative forcing. Based on detailed measurements of a large number of biomass burning plumes of variable age in southern Africa, we show that the size distribution, chemical composition, single-scattering albedo, and hygroscopicity of biomass burning particles change considerably during the first 2-4 h of their atmospheric transport these changes, driven by atmospheric oxidation and subsequent secondary aerosol formation, may reach a factor of 6 for the aerosol scattering coefficient and a factor >10 for the cloud condensation nuclei concentration. Since the observed changes take place over the spatial and temporal scales that are neither covered by emission inventories nor captured by large-scale model simulations, the findings reported here point out a significant gap in our understanding on the climatic effects of biomass burning aerosols. Key Points A large number of biomass burning plumes were observed in southern Africa Cloud activating and optical properties change rapidly during plume transport The changes in climatically relevant properties depend on atmospheric oxidation © 2014 the Authors."
"6701518904;35448324200;8416469500;7006510465;","Performance simulations for a spaceborne methane lidar mission",2014,"10.1002/2013JD021253","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921906445&doi=10.1002%2f2013JD021253&partnerID=40&md5=438ac6f1ffa61f106c7144a40cbf0add","Future spaceborne lidar measurements of key anthropogenic greenhouse gases are expected to close current observational gaps particularly over remote, polar, and aerosol-contaminated regions, where actual in situ and passive remote sensing observation techniques have difficulties. For methane, a “Methane Remote Lidar Mission” was proposed by Deutsches Zentrum für Luft- und Raumfahrt and Centre National d’Etudes Spatiales in the frame of a German-French climate monitoring initiative. Simulations assess the performance of this mission with the help of Moderate Resolution Imaging Spectroradiometer and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations of the earth’s surface albedo and atmospheric optical depth. These are key environmental parameters for integrated path differential absorption lidar which uses the surface backscatter to measure the total atmospheric methane column. Results show that a lidar with an average optical power of 0.45 W at 1.6 μm wavelength and a telescope diameter of 0.55 m, installed on a low Earth orbit platform (506 km), will measure methane columns at precisions of 1.2%, 1.7%, and 2.1% over land, water, and snow or ice surfaces, respectively, for monthly aggregated measurement samples within areas of 50 × 50 km2. Globally, the mean precision for the simulated year 2007 is 1.6%, with a standard deviation of 0.7%. At high latitudes, a lower reflectance due to snow and ice is compensated by denser measurements, owing to the orbital pattern. Over key methane source regions such as densely populated areas, boreal and tropical wetlands, or permafrost, our simulations show that the measurement precision will be between 1 and 2%. © 2014. American Geophysical Union. All Rights Reserved."
"57209630149;7201821692;7006399110;","Application of spectral analysis techniques in the intercomparison of aerosol data: Part iii. using combined PCA to compare spatiotemporal variability of MODIS, MISR, and OMI aerosol optical depth",2014,"10.1002/2013JD020538","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84916915099&doi=10.1002%2f2013JD020538&partnerID=40&md5=c198db8c12f59cb25d0fc4b2635bc72a","Satellite measurements of global aerosol properties are very useful in constraining aerosol parameterization in climate models. The reliability of different data sets in representing global and regional aerosol variability becomes an essential question. In this study, we present the results of a comparison using combined principal component analysis (CPCA), applied to monthly mean, mapped (Level 3) aerosol optical depth (AOD) product from Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Ozone Monitoring Instrument (OMI). This technique effectively finds the common space-time variability in the multiple data sets by decomposing the combined AOD field. The results suggest that all of the sensors capture the globally important aerosol regimes, including dust, biomass burning, pollution, and mixed aerosol types. Nonetheless, differences are also noted. Specifically, compared with MISR and OMI, MODIS variability is significantly higher over South America, India, and the Sahel. MODIS deep blue AOD has a lower seasonal variability in North Africa, accompanied by a decreasing trend that is not found in either MISR or OMI AOD data. The narrow swath of MISR results in an underestimation of dust variability over the Taklamakan Desert. The MISR AOD data also exhibit overall lower variability in South America and the Sahel. OMI does not capture the Russian wild fire in 2010 nor the phase shift in biomass burning over East South America compared to Central South America, likely due to cloud contamination and the OMI row anomaly. OMI also indicates a much stronger (boreal) winter peak in South Africa compared with MODIS and MISR. © 2013. American Geophysical Union. All Rights Reserved."
"56537827700;6603546080;8578246200;7201634460;48662824200;55916098100;7006495234;","Initial stability assessment of S-NPP VIIRS reflective solar band calibration using invariant desert and deep convective cloud targets",2014,"10.3390/rs6042809","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898064221&doi=10.3390%2frs6042809&partnerID=40&md5=508704b0d8b1c35bf2fb75259f3ed283","The latest CERES FM-5 instrument launched onboard the S-NPP spacecraft will use the VIIRS visible radiances from the NASA Land Product Evaluation and Analysis Tool Elements (PEATE) product for retrieving the cloud properties associated with its TOA flux measurement. In order for CERES to provide climate quality TOA flux datasets, the retrieved cloud properties must be consistent throughout the record, which is dependent on the calibration stability of the VIIRS imager. This paper assesses the NASA calibration stability of the VIIRS reflective solar bands using the Libya-4 desert and deep convective clouds (DCC). The invariant targets are first evaluated for temporal natural variability. It is found for visible (VIS) bands that DCC targets have half of the variability of Libya-4. For the shortwave infrared (SWIR) bands, the desert has less variability. The brief VIIRS record and target variability inhibits high confidence in identifying any trends that are less than ±0.6%/yr for most VIS bands, and ±2.5%/yr for SWIR bands. None of the observed invariant target reflective solar band trends exceeded these trend thresholds. Initial assessment results show that the VIIRS data have been consistently calibrated and that the VIIRS instrument stability is similar to or better than the MODIS instrument. © 2014 by the authors; licensee MDPI, Basel, Switzerland."
"55622717600;7403931916;7201826462;8680433600;57205355972;","Ice particle habit and surface roughness derived from PARASOL polarization measurements",2014,"10.5194/acp-14-3739-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898413052&doi=10.5194%2facp-14-3739-2014&partnerID=40&md5=b1e4ac7fc31a9d8075a0f2d7a895285b","Ice clouds are an important element in the radiative balance of the earth's climate system, but their microphysical and optical properties still are not well constrained, especially ice particle habit and the degree of particle surface roughness. In situ observations have revealed common ice particle habits and evidence for surface roughness, but these observations are limited. An alternative is to infer the ice particle shape and surface roughness from satellite observations of polarized reflectivity since they are sensitive to both particle shape and degree of surface roughness. In this study an adding-doubling radiative transfer code is used to simulate polarized reflectivity for nine different ice habits and one habit mixture, along with 17 distinct levels of the surface roughness. A lookup table (LUT) is constructed from the simulation results and used to infer shape and surface roughness from PARASOL satellite polarized reflectivity data over the ocean. Globally, the retrievals yield a compact aggregate of columns as the most commonly retrieved ice habit. Analysis of PARASOL data from the tropics results in slightly more aggregates than in midlatitude or polar regions. Some level of surface roughness is inferred in nearly 70% of PARASOL data, with mean and median roughness near Ï Combining double low line 0.2 and 0.15, respectively. Tropical region analyses have 20% more pixels retrieved with particle surface roughness than in midlatitude or polar regions. The global asymmetry parameter inferred at a wavelength of 0.865 Î1/4m has a mean value of 0.77 and a median value of 0.75. © 2014 Author(s)."
"36629266300;6602558284;6602412939;35570389600;35185383500;","Spectrum-driven planetary deglaciation due to increases in stellar luminosity",2014,"10.1088/2041-8205/785/1/L9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897425543&doi=10.1088%2f2041-8205%2f785%2f1%2fL9&partnerID=40&md5=92866f247710321d207cf2cec206e7f2","Distant planets in globally ice-covered, ""snowball,"" states may depend on increases in their host stars' luminosity to become hospitable for surface life. Using a general circulation model, we simulated the equilibrium climate response of a planet to a range of instellations from an F-, G-, or M-dwarf star. The range of instellation that permits both complete ice cover and at least partially ice-free climate states is a measure of the climate hysteresis that a planet can exhibit. An ice-covered planet with high climate hysteresis would show a higher resistance to the initial loss of surface ice coverage with increases in instellation, and abrupt, extreme ice loss once deglaciation begins. Our simulations indicate that the climate hysteresis depends sensitively on the host star spectral energy distribution. Under fixed CO2 conditions, a planet orbiting an M-dwarf star exhibits a smaller climate hysteresis, requiring smaller instellation to initiate deglaciation than planets orbiting hotter, brighter stars. This is due to the higher absorption of near-infrared radiation by ice on the surfaces and greenhouse gases and clouds in the atmosphere of an M-dwarf planet. Increases in atmospheric CO 2 further lower the climate hysteresis, as M-dwarf snowball planets exhibit a larger radiative response than G-dwarf snowball planets for the same increase in CO2. For a smaller hysteresis, planets near the outer edge of the habitable zone will thaw earlier in their evolutionary history, and will experience a less abrupt transition out of global ice cover. © 2014. The American Astronomical Society. All rights reserved.."
"7402439028;57208357584;7003846526;35577912900;35551859000;7404764644;7003713591;7004413402;57203598625;7402555282;7003916945;7004208584;7103177588;7202843160;7004587891;7003399430;7005989723;57203081487;56486548700;6701580854;6602798575;7006544303;35573513700;55694391900;34880359800;7102838745;26659474400;7101963685;10139694400;6602598233;10439597500;7004089691;7006200031;56031375100;","Landsat-8: Science and product vision for terrestrial global change research",2014,"10.1016/j.rse.2014.02.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896818071&doi=10.1016%2fj.rse.2014.02.001&partnerID=40&md5=405e2a949f1c030d5c927f76fe5198d7","Landsat 8, a NASA and USGS collaboration, acquires global moderate-resolution measurements of the Earth's terrestrial and polar regions in the visible, near-infrared, short wave, and thermal infrared. Landsat 8 extends the remarkable 40. year Landsat record and has enhanced capabilities including new spectral bands in the blue and cirrus cloud-detection portion of the spectrum, two thermal bands, improved sensor signal-to-noise performance and associated improvements in radiometric resolution, and an improved duty cycle that allows collection of a significantly greater number of images per day. This paper introduces the current (2012-2017) Landsat Science Team's efforts to establish an initial understanding of Landsat 8 capabilities and the steps ahead in support of priorities identified by the team. Preliminary evaluation of Landsat 8 capabilities and identification of new science and applications opportunities are described with respect to calibration and radiometric characterization; surface reflectance; surface albedo; surface temperature, evapotranspiration and drought; agriculture; land cover, condition, disturbance and change; fresh and coastal water; and snow and ice. Insights into the development of derived 'higher-level' Landsat products are provided in recognition of the growing need for consistently processed, moderate spatial resolution, large area, long-term terrestrial data records for resource management and for climate and global change studies. The paper concludes with future prospects, emphasizing the opportunities for land imaging constellations by combining Landsat data with data collected from other international sensing systems, and consideration of successor Landsat mission requirements. © 2014."
"36023718600;7005413744;17434022100;55767074400;26654147000;7004690545;7201502185;8598454000;","Representation of climate extreme indices in the ACCESS1.3b coupled atmosphere-land surface model",2014,"10.5194/gmd-7-545-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907388831&doi=10.5194%2fgmd-7-545-2014&partnerID=40&md5=07f74ca37cd434fcc35c73dc4d5b09a0","Climate extremes, such as heat waves and heavy precipitation events, have large impacts on ecosystems and societies. Climate models provide useful tools for studying underlying processes and amplifying effects associated with extremes. The Australian Community Climate and Earth System Simulator (ACCESS) has recently been coupled to the Community Atmosphere Biosphere Land Exchange (CABLE) model. We examine how this model represents climate extremes derived by the Expert Team on Climate Change Detection and Indices (ETCCDI) and compare them to observational data sets using the AMIP framework. We find that the patterns of extreme indices are generally well represented. Indices based on percentiles are particularly well represented and capture the trends over the last 60 years shown by the observations remarkably well. The diurnal temperature range is underestimated, minimum temperatures (TMIN) during nights are generally too warm and daily maximum temperatures (TMAX) too low in the model. The number of consecutive wet days is overestimated, while consecutive dry days are underestimated. The maximum consecutive 1-day precipitation amount is underestimated on the global scale. Biases in TMIN correlate well with biases in incoming longwave radiation, suggesting a relationship with biases in cloud cover. Biases in TMAX depend on biases in net shortwave radiation as well as evapotranspiration. The regions and season where the bias in evapotranspiration plays a role for the TMAX bias correspond to regions and seasons where soil moisture availability is limited. Our analysis provides the foundation for future experiments that will examine how land-surface processes contribute to these systematic biases in the ACCESS modelling system. © Author(s) 2014.."
"6506286986;56597778200;26635422600;55915206300;6701410329;","Characteristics of cloud liquid water path from SEVIRI onboard the meteosat second generation 2 satellite for several cloud types",2014,"10.5194/amt-7-887-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898753197&doi=10.5194%2famt-7-887-2014&partnerID=40&md5=d3124d39cabb1d55e35c06eb505aab6d","In this study the temporal and spatial characteristics of the liquid water path (LWP) of low, middle and high level clouds are analysed using space-based observations from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument onboard the Meteosat Second Generation 2 (MSG 2) satellite. Both geophysical quantities are part of the CLAAS (CLoud property dAtAset using SEVIRI) data set and are generated by EUMETSAT's Satellite Application Facility on Climate Monitoring (CM SAF). In this article we focus on the statistical properties of LWP, retrieved during daylight conditions, associated with individual cloud types. We analysed the intrinsic variability of LWP, that is, the variability in only cloudy regions and the variations driven by cloud amount. The relative amplitude of the intrinsic diurnal cycle exceeded the cloud amount driven amplitude in our analysed cases. Our results reveal that each cloud type possesses a characteristic intrinsic LWP distribution. These frequency distributions are constant with time in the entire SEVIRI field of view, but vary for smaller regions like Central Europe. Generally the average LWP is higher over land than over sea; in the case of low clouds this amounts to 15-27% in 2009. The variance of the frequency distributions is enhanced as well. Also, the average diurnal cycle of LWP is related to cloud type with the most pronounced relative diurnal variations being detected for low and middle level clouds. Maps of the relative amplitude and the local time of maximum LWP show the variation throughout the SEVIRI field of view. © 2014 Author(s)."
"16678944000;35096760500;55897579400;6603144464;57203029315;","The faint young Sun problem revisited with a 3-D climate-carbon model &ndash; Part 1",2014,"10.5194/cp-10-697-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923068619&doi=10.5194%2fcp-10-697-2014&partnerID=40&md5=32468308524a959ec3dfdc7f0302d31a","During the Archaean, the Sun's luminosity was 18 to 25% lower than the present day. One-dimensional radiative convective models (RCM) generally infer that high concentrations of greenhouse gases (CO<inf>2</inf>, CH4) are required to prevent the early Earth's surface temperature from dropping below the freezing point of liquid water and satisfying the faint young Sun paradox (FYSP, an Earth temperature at least as warm as today). Using a one-dimensional (1-D) model, it was proposed in 2010 that the association of a reduced albedo and less reflective clouds may have been responsible for the maintenance of a warm climate during the Archaean without requiring high concentrations of atmospheric CO<inf>2</inf> (pCO<inf>2</inf>). More recently, 3-D climate simulations have been performed using atmospheric general circulation models (AGCM) and Earth system models of intermediate complexity (EMIC). These studies were able to solve the FYSP through a large range of carbon dioxide concentrations, from 0.6 bar with an EMIC to several millibars with AGCMs. To better understand this wide range in pCO<inf>2</inf>, we investigated the early Earth climate using an atmospheric GCM coupled to a slab ocean. Our simulations include the ice-albedo feedback and specific Archaean climatic factors such as a faster Earth rotation rate, high atmospheric concentrations of CO<inf>2</inf> and/or CH4, a reduced continental surface, a saltier ocean, and different cloudiness. We estimated full glaciation thresholds for the early Archaean and quantified positive radiative forcing required to solve the FYSP. We also demonstrated why RCM and EMIC tend to overestimate greenhouse gas concentrations required to avoid full glaciations or solve the FYSP. Carbon cycle-climate interplays and conditions for sustaining pCO<inf>2</inf> will be discussed in a companion paper. © Author(s) 2014."
"37661167800;7202607188;24587715900;6701772538;6603955469;6603604042;17434636400;6602516156;7005453641;7102011023;","Arctic stratospheric dehydration - Part 2: Microphysical modeling",2014,"10.5194/acp-14-3231-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897474802&doi=10.5194%2facp-14-3231-2014&partnerID=40&md5=205e16a314828bcebbf645d9778def5e","Large areas of synoptic-scale ice PSCs (polar stratospheric clouds) distinguished the Arctic winter 2009/2010 from other years and revealed unprecedented evidence of water redistribution in the stratosphere. A unique snapshot of water vapor repartitioning into ice particles was obtained under extremely cold Arctic conditions with temperatures around 183 K. Balloon-borne, aircraft and satellite-based measurements suggest that synoptic-scale ice PSCs and concurrent reductions and enhancements in water vapor are tightly linked with the observed de- and rehydration signatures, respectively. In a companion paper (Part 1), water vapor and aerosol backscatter measurements from the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) and LAPBIAT-II (Lapland Atmosphere-Biosphere Facility) field campaigns have been analyzed in detail. This paper uses a column version of the Zurich Optical and Microphysical box Model (ZOMM) including newly developed NAT (nitric acid trihydrate) and ice nucleation parameterizations. Particle sedimentation is calculated in order to simulate the vertical redistribution of chemical species such as water and nitric acid. Despite limitations given by wind shear and uncertainties in the initial water vapor profile, the column modeling unequivocally shows that (1) accounting for small-scale temperature fluctuations along the trajectories is essential in order to reach agreement between simulated optical cloud properties and observations, and (2) the use of recently developed heterogeneous ice nucleation parameterizations allows the reproduction of the observed signatures of de- and rehydration. Conversely, the vertical redistribution of water measured cannot be explained in terms of homogeneous nucleation of ice clouds, whose particle radii remain too small to cause significant dehydration. © Author(s) 2014."
"7004502105;7004863760;6505908568;","Influence of relative humidity and clouds on the global mean surface temperature",2014,"10.1260/0958-305X.25.2.389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898968201&doi=10.1260%2f0958-305X.25.2.389&partnerID=40&md5=9b66216772ef36cf13f18efa47fe4f8e","The explanation for climate change is still searching for an experimental proof and the most important question is whether climate change is anthropogenic. According to the Intergovernmental Panel on Climate Change IPCC global warming is mostly man made due to the increasing CO2 concentration. In this work we study the contributions of humidity and clouds to the surface temperature. We will show that changes of relative humidity or low cloud cover explain the major changes in the global mean temperature. We will present the evidence of this argument using the observed relative humidity between years 1970 and 2011 and the observed low cloud cover between years 1983 and 2008. One percent increase in relative humidity or in low cloud cover decreases the temperature by 0.15 °C and 0.11 °C, respectively. In the time periods mentioned before the contribution of the CO2 increase was less than 10% to the total temperature change."
"38863214100;6507224579;","A low-order model of water vapor, clouds, and thermal emission for tidally locked terrestrial planets",2014,"10.1088/0004-637X/784/2/155","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896450885&doi=10.1088%2f0004-637X%2f784%2f2%2f155&partnerID=40&md5=d251579188373d6cedd42e696ba28061","In the spirit of minimal modeling of complex systems, we develop an idealized two-column model to investigate the climate of tidally locked terrestrial planets with Earth-like atmospheres in the habitable zone of M-dwarf stars. The model is able to approximate the fundamental features of the climate obtained from three-dimensional (3D) atmospheric general circulation model (GCM) simulations. One important reason for the two-column model's success is that it reproduces the high cloud albedo of the GCM simulations, which reduces the planet's temperature and delays the onset of a runaway greenhouse state. The two-column model also clearly illustrates a secondary mechanism for determining the climate: the nightside acts as a ""radiator fin"" through which infrared energy can be lost to space easily. This radiator fin is maintained by a temperature inversion and dry air on the nightside, and plays a similar role to the subtropics on modern Earth. Since one-dimensional radiative-convective models cannot capture the effects of the cloud albedo and radiator fin, they are systematically biased toward a narrower habitable zone. We also show that cloud parameters are the most important in the two-column model for determining the day-night thermal emission contrast, which decreases and eventually reverses as the stellar flux increases. This reversal is important because it could be detected by future extrasolar planet characterization missions, which would suggest that the planet has Earth-like water clouds and is potentially habitable. © 2014. The American Astronomical Society. All rights reserved.."
"57201201895;55880075900;6603708768;","Wildland fire emissions, carbon, and climate: Wildfire-climate interactions",2014,"10.1016/j.foreco.2013.02.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895925568&doi=10.1016%2fj.foreco.2013.02.020&partnerID=40&md5=2378c5c445b012ec7dcfc73f4fdf81d1","Increasing wildfire activity in recent decades, partially related to extended droughts, along with concern over potential impacts of future climate change on fire activity has resulted in increased attention on fire-climate interactions. Findings from studies published in recent years have remarkably increased our understanding of fire-climate interactions and improved our capacity to delineate probable future climate change and impacts. Fires are projected to increase in many regions of the globe under a changing climate due to the greenhouse effect. Burned areas in the western US could increase by more than 50% by the middle of this century. Increased fire activity is not simply an outcome of the changing climate, but also a participant in the change. Smoke particles reduce overall solar radiation absorbed by the Earth's atmosphere during individual fire events and fire seasons, leading to regional climate effects including reduction in surface temperature, suppression of cloud and precipitation, and enhancement of climate anomalies such as droughts. Black carbon (BC) in smoke particles displays some different radiation and climate effects by warming the middle and lower atmosphere, leading to a more stable atmosphere. BC also plays a key role in the smoke-snow feedback mechanism. Fire emissions of CO2, on the other hand, are an important atmospheric CO2 source and contribute substantially to the global greenhouse effect. Future studies should generate a global picture of all aspects of radiative forcing by smoke particles. Better knowledge is needed in space and time variability of smoke particles, evolution of smoke optical properties, estimation of smoke plume height and vertical profiles and their impacts on locations of warming layers, stability structure, clouds and smoke transport, quantification of BC emission factors and optical properties from different forest fuels, and BC's individual and combined roles with organic carbon. Finally, understanding the short- and long-term greenhouse effect of fire CO2 emissions, increased capacity to project future fire trends (especially mega-fires), with consideration of climate-fuel-human interactions, and improved fire weather and climate prediction skills (including exploring the SST-fire relations) remain central knowledge needs. © 2013."
"16443990500;56017066000;55557545200;8588223400;","Water adsorption constrained Frenkel-Halsey-Hill adsorption activation theory: Montmorillonite and illite",2014,"10.1016/j.atmosenv.2013.12.040","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893129852&doi=10.1016%2fj.atmosenv.2013.12.040&partnerID=40&md5=4c59095334801a62a0e43af8447ef998","Fresh mineral aerosol has recently been found to be effective cloud condensation nuclei (CCN) and contribute to the number of cloud droplets in the atmosphere due to the effect of water adsorption on CCN activation. The work described here uses experimental water adsorption measurements on Na-montmorillonite and illite clay to determine empirical adsorption parameters that can be used in a recently derived theoretical framework (Frenkel-Halsey-Hill Activation Theory, FHH-AT) that accounts for the effect of water adsorption on CCN activation. Upon fitting the Frenkel-Halsey-Hill (FHH) adsorption model to water adsorption measurements, we find FHH adsorption parameters, AFHH and BFHH, to be 98±22 and 1.79±0.11 for montmorillonite and 75±17 and 1.77±0.11 for illite, respectively. The AFHH and BFHH values obtained from water adsorption measurements differ from values reported previously determined by applying FHH-AT to CCN activation measurements. Differences in FHH adsorption parameters were attributed to different methods used to obtain them and the hydratable nature of the clays. FHH adsorption parameters determined from water adsorption measurements were then used to calculate the critical super-saturation (sc) for CCN activation using FHH-AT. The relationship between sc and the dry particle diameter (Ddry) gave CCN activation curve exponents (xFHH) of-0.61 and-0.64 for montmorillonite and illite, respectively. The xFHH values were slightly lower than reported previously for mineral aerosol. The lower exponent suggests that the CCN activity of hydratable clays is less sensitive to changes in Ddry and the hygroscopicity parameter exhibits a broader variability with Ddry compared to more soluble aerosols. Despite the differences in AFHH, BFHH and xFHH, the FHH-AT derived CCN activities of montmorillonite and illite are quite similar to each other and in excellent agreement with experimental CCN measurements resulting from wet-generated clay aerosol. This study illustrates that FHH-AT using adsorption parameters constrained by water adsorption is a simple, valid method for predicting CCN activation of fresh clay minerals and provides parameters that can be used in atmospheric models to study the effect of mineral dust aerosol on cloud formation and climate. © 2014 Elsevier Ltd."
"10239531200;55650183600;7202158002;23490082500;57200842213;55567227700;7402874543;","The Nebula Winter: The united view of the snowball Earth, mass extinctions, and explosive evolution in the late Neoproterozoic and Cambrian periods",2014,"10.1016/j.gr.2013.05.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893801843&doi=10.1016%2fj.gr.2013.05.003&partnerID=40&md5=597aeb284c66741cbd309ae87a204fc2","Encounters with nebulae, such as supernova remnants and dark clouds in the galaxy, can lead to an environmental catastrophe on the Earth through the negative climate forcings and destruction of the ozone layer by enhanced fluxes of cosmic rays and cosmic dust particles. A resultant reduction in primary productivity leads to mass extinctions through depletion of oxygen and food starvations as well as anoxia in the ocean. The model shows three levels of hierarchical time variations caused by supernova encounters (1-10kyrs), dark cloud encounters (0.1-10Myrs), and starbursts (~100Myrs), respectively. This ""Nebula Winter"" model can explain the catastrophic phenomena such as snowball Earth events, repeated mass extinctions, and Cambrian explosion of biodiversities which took place in the late Proterozoic era through the Cambrian period. The Late Neoproterozoic snowball Earth event covers a time range of ca. 200Myrs long spanning from 770Ma to the end of Cambrian period (488Ma) with two snowball states called Sturtian and Marinoan events. Mass extinctions occurred at least eight times in this period, synchronized with large fluctuations in δ13C of carbonates in the sediment. Each event is likely to correspond to each nebula encounter. In other words, the late Neoproterozoic snowball Earth and Cambrian explosion are possibly driven by a starburst, which took place around 0.6Ga in the Milky Way Galaxy. The evidences for a Nebula Winter can be obtained from geological records in sediment in the deep oceans at those times. © 2013 International Association for Gondwana Research."
"57188569785;57014174300;56258240400;35172156300;56335853900;56045326900;56179074200;55713806600;","Estimation of monthly-mean global solar radiation using MODIS atmospheric product over China",2014,"10.1016/j.jastp.2014.01.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894499445&doi=10.1016%2fj.jastp.2014.01.017&partnerID=40&md5=4879f9152068717c1f12ec34ab4ccefe","This paper investigated the potential of MOD08-M3 atmospheric product in estimation of monthly-mean solar radiation. 8 models were developed using cloud fraction (CF), cloud optical thickness (COT), precipitable water vapor (PWV) and aerosol optical thickness (AOT) at 50 stations across China. All the models give reasonable results with average RMSE of 1.247MJm-2 and MAPE of 9.9%. Models have lower RMSE in cool temperature (CT) and warm temperate (WT) zones. In terms of MAPE, models perform better in Qinghai-Tibet plateau climate (QT) zone. Model accuracy can be significantly improved by introducing COT and PWV. The improvements by introducing COT are more pronounced in summer for CT, WT and ST regions. While inclusion of PWV is more effective in summer, autumn, and winter for CT, QT, and ST regions, respectively. However, introducing AOT does not contribute to the improvement in estimation accuracy. The performances of models show seasonal behavior. In terms of MAPE, models perform best in summer for CT and WT regions, and in autumn for ST region. Lowest RMSE are observed in autumn and winter for CT and QT regions, respectively. Models have lower RMSE in both autumn and winter for WT and ST regions. © 2014."
"24390528000;6602600408;35611334800;7102953444;","Pollution trends over Europe constrain global aerosol forcing as simulated by climate models",2014,"10.1002/2013GL058715","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896406949&doi=10.1002%2f2013GL058715&partnerID=40&md5=2202db9b6f8fb2e3d500f48f8705d9cf","An increasing trend in surface solar radiation (solar brightening) has been observed over Europe since the 1990s, linked to economic developments and air pollution regulations and their direct as well as cloud-mediated effects on radiation. Here, we find that the all-sky solar brightening trend (1990-2005) over Europe from seven out of eight models (historical simulations in the Fifth Coupled Model Intercomparison Project) scales well with the regional and global mean effective forcing by anthropogenic aerosols (idealized ""present- day"" minus ""preindustrial"" runs). The reason for this relationship is that models that simulate stronger forcing efficiencies and stronger radiative effects by aerosol-cloud interactions show both a stronger aerosol forcing and a stronger solar brightening. The all-sky solar brightening is the observable from measurements (4.06±0.60 W m-2 decade-1), which then allows to infer a global mean total aerosol effective forcing at about -1.30 W m-2 with standard deviation ±0.40 W m-2. © 2014. American Geophysical Union. All Rights Reserved."
"9246029600;15026371500;7004647146;","The influence of regional feedbacks on circulation sensitivity",2014,"10.1002/2014GL059336","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896551772&doi=10.1002%2f2014GL059336&partnerID=40&md5=ca26da995697862b06626fe7a6871e87","Weakening of the tropical overturning circulation in a warmer world is a robust feature in climate models. Here an idealized representation of ocean heat flux drives a Walker cell in an aquaplanet simulation. A goal of the study is to assess the influence of the Walker circulation on the magnitude and structure of climate feedbacks, as well as to global sensitivity. We compare two CO 2 perturbation experiments, one with and one without a Walker circulation, to isolate the differences attributable to tropical circulation and associated zonal asymmetries. For an imposed Walker circulation, the subtropical shortwave cloud feedback is reduced, which manifests as a weaker tropical-subtropical anomalous energy gradient and consequently a weaker slow down of the Hadley circulation, relative to the case without a Walker circulation. By focusing on the coupled feedback circulation system, these results offer insights into understanding changes in atmospheric circulation and hence the hydrological cycle under global warming. © 2014. American Geophysical Union. All Rights Reserved."
"36124786200;7201845221;","Tropical deep convection and density current signature in surface pressure: Comparison between WRF model simulations and infrasound measurements",2014,"10.5194/acp-14-3113-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897432316&doi=10.5194%2facp-14-3113-2014&partnerID=40&md5=6b09caef9f424c069ae0f14d168033e4","Deep convection is a major atmospheric transport process in the tropics, affecting the global weather and the climate system. In the framework of the ARISE (Atmospheric dynamics Research InfraStructure in Europe) project, we combine model simulations of tropical deep convection with in situ ground measurements from an IMS (International Monitoring System) infrasound station in the Ivory Coast to analyze the effects of density current propagation. The WRF (Weather Research and Forecasting) model is firstly run in a simplified (referred to as ""idealized case"") and highly resolved configuration to explicitly account for convective dynamics. Then, a coarser three-dimensional simulation (referred to as ""real"") is nudged towards meteorological reanalysis data in order to compare the real case with the idealized model and in situ observations.In the 2-D run, the evolution of a deep convective cloud generates a density current that moves outward up to 30 km away from storm center. The increase in surface density (up to 18 g mg-3 larger than surrounding air) is mostly due to the sudden temperature decrease (down to -2 °C, with respect to the domain-averaged value) from diabatic cooling by rain evaporation near ground level. It is accompanied by a dramatic decrease in relative humidity (down to -50%), buoyancy (down to -0.08 m s-2), equivalent potential temperature (25 °C lower than the planetary boundary layer (PBL)) and the rapid enhancement of horizontal wind speed (up to 15 m s-2). If temperature and density changes are strong enough, surface pressure becomes largely affected and high-frequency disturbances (up to several tens of Pa) can be detected at the leading edges of density current. The moister and warmer air of subcloud layer is lifted up and replaced by a more stable flow. The resulting thermodynamical instabilities are shown to play a key role in triggering new convection. If the initial environment is sufficiently unstable, they can give rise to continuous updrafts that may lead to the transition from single-cell to multicell cloud systems, even without the presence of an initial wind shear.The overall consistence and similarity between idealized and real simulation, and the good agreement of the real case with in situ retrievals of temperature, pressure, wind speed and direction, seem to confirm the ability of 2-D and 3-D models to well reproduce convective dynamics. Surface pressure disturbances, simulated in both the idealized and real cases as a consequence of cold pool propagation, are very similar to those recorded in the Ivory Coast. Present results stress the direct link between mesoscale convective system activity and high-frequency surface pressure variations, suggesting the possibility of developing a new method for real-time rainstorm tracking based on the ground-based infrasound monitoring of pressure field.© Author(s) 2014. CC Attribution 3.0 License."
"55682762600;13403622000;55683910600;57203053317;55184057600;7102604282;56119479900;55717074000;7202079615;","Intercomparison of the cloud water phase among global climate models",2014,"10.1002/2013JD021119","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898805462&doi=10.1002%2f2013JD021119&partnerID=40&md5=b8b8b94e69c78e7d3dfe50fb569259bc","Mixed-phase clouds (clouds that consist of both cloud droplets and ice crystals) are frequently present in the Earth’s atmosphere and influence the Earth’s energy budget through their radiative properties, which are highly dependent on the cloud water phase. In this study, the phase partitioning of cloud water is compared among six global climate models (GCMs) and with Cloud and Aerosol Lidar with Orthogonal Polarization retrievals. It is found that the GCMs predict vastly different distributions of cloud phase for a given temperature, and none of them are capable of reproducing the spatial distribution or magnitude of the observed phase partitioning. While some GCMs produced liquid water paths comparable to satellite observations, they all failed to preserve sufficient liquid water at mixed-phase cloud temperatures. Our results suggest that validating GCMs using only the vertically integrated water contents could lead to amplified differences in cloud radiative feedback. The sensitivity of the simulated cloud phase in GCMs to the choice of heterogeneous ice nucleation parameterization is also investigated. The response to a change in ice nucleation is quite different for each GCM, and the implementation of the same ice nucleation parameterization in all models does not reduce the spread in simulated phase among GCMs. The results suggest that processes subsequent to ice nucleation are at least as important in determining phase and should be the focus of future studies aimed at understanding and reducing differences among the models. © 2014. American Geophysical Union. All Rights Reserved."
"55642592500;8987692000;7005133082;57201215091;6603863372;","How can we use MODIS land surface temperature to validate long-term urban model simulations?",2014,"10.1002/2013JD021101","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898832171&doi=10.1002%2f2013JD021101&partnerID=40&md5=03c218aff6e5c5c0983a4ae521176d04","High spatial resolution urban climate modeling is essential for understanding urban climatology and predicting the human health impacts under climate change. Satellite thermal remote-sensing data are potential observational sources for urban climate model validation with comparable spatial scales, temporal consistency, broad coverage, and long-term archives. However, sensor view angle, cloud distribution, and cloud-contaminated pixels can confound comparisons between satellite land surface temperature (LST) and modeled surface radiometric temperature. The impacts of sensor view angles on urban LST values are investigated and addressed. Three methods to minimize the confounding factors of clouds are proposed and evaluated using 10 years of Moderate Resolution Imaging Spectroradiometer (MODIS) data and simulations from the High-Resolution Land Data Assimilation System (HRLDAS) over Greater Houston, Texas, U.S. For the satellite cloud mask (SCM) method, prior to comparison, the cloud mask for each MODIS scene is applied to its concurrent HRLDAS simulation. For the max/min temperature (MMT) method, the 50 warmest days and coolest nights for each data set are selected and compared to avoid cloud impacts. For the high clear-sky fraction (HCF) method, only those MODIS scenes that have a high percentage of clear-sky pixels are compared. The SCM method is recommended for validation of long-term simulations because it provides the largest sample size as well as temporal consistency with the simulations. The MMT method is best for comparison at the extremes. And the HCF method gives the best absolute temperature comparison due to the spatial and temporal consistency between simulations and observations. © 2014. American Geophysical Union. All Rights Reserved."
"55707488500;56611366900;57198616562;37018824600;7202970886;7402480218;","A comparison of multiscale variations of decade-long cloud fractions from six different platforms over the southern great plains in the United States",2014,"10.1002/2013JD019813","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898827530&doi=10.1002%2f2013JD019813&partnerID=40&md5=bfc5e7385b90b0e7db3b1d86625c905c","This study compares 1997–2011 observationally based cloud fraction estimates from six different platforms (three ground-based estimates and three satellite-based estimates) over the Southern Great Plains, United States. The comparisons are performed at multiple temporal and spatial scales. The results show that 1997–2011 mean cloud fractions from the Active Remote Sensing of CLouds (ARSCL) and from the International Satellite Cloud Climatology Project (ISCCP) are significantly (at a 2% significance level, two-sided t test) larger than the others, having 0.08 and 0.15 larger mean diurnal variations, 0.08 and 0.13 larger mean annual variations, and 0.08 and 0.14 larger interannual variations, respectively. Although more high (low) clouds are likely a reason for larger ARSCL (ISCCP) cloud fractions, other mechanisms cannot be ruled out and require further investigations. Furthermore, half of the estimates exhibit a significant (at a 1% significance level, one-sided t test) overall increase of 0.08–0.10 in the annually averaged cloud fractions from 1998 to 2009; another half of the estimates exhibit little tendency of increase in this decade. Monthly cloud fractions from all the estimates exhibit quasi-Gaussian frequency distributions while the distributions of daily cloud fractions are found dependent on spatial scales. Cloud fractions from all the estimates show much larger seasonal variations than diurnal variations. Findings from this study suggest caution when using observationally based cloud fraction estimates for climate studies such as evaluating model performance and reinforce the need of consistency in defining and retrieving cloud fractions. © 2014. American Geophysical Union. All Rights Reserved."
"55706019000;55021377200;12754012000;56537880300;","Increasing bioenergy production on arable land: Does the regional and local climate respond? Germany as a case study",2014,"10.1002/2013JD020877","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898790974&doi=10.1002%2f2013JD020877&partnerID=40&md5=b91f96dac84598218f8e4bc4b2331b35","The extent and magnitude of land cover change effect on local and regional future climate during the vegetation period due to different forms of bioenergy plants are quantified for extreme temperatures and energy fluxes. Furthermore, we vary the spatial extent of plant allocation on arable land and simulate alternative availability of transpiration water to mimic both rainfed agriculture and irrigation. We perform climate simulations down to 1 km scale for 1970-1975 C20 and 2070-2075 A1B over Germany with Consortium for Small-Scale Modeling in Climate Mode. Here an impact analysis indicates a strong local influence due to land cover changes. The regional effect is decreased by two thirds of the magnitude of the local-scale impact. The changes are largest locally for irrigated poplar with decreasing maximum temperatures by 1◦C in summer months and increasing specific humidity by 0.15 g kg−1. The increased evapotranspiration may result in more precipitation. The increase of surface radiative fluxes Rnet due to changes in latent and sensible heat is estimated by 5 W m−2 locally. Moreover, increases in the surface latent heat flux cause strong local evaporative cooling in the summer months, whereas the associated regional cooling effect is pronounced by increases in cloud cover. The changes on a regional scale are marginal and not significant. Increasing bioenergy production on arable land may result in local temperature changes but not in substantial regional climate change in Germany. We show the effect of agricultural practices during climate transitions in spring and fall. © 2014. American Geophysical Union. All Rights Reserved."
"6506423324;57204253860;","The role of tilted heating in the evolution of the MJO",2014,"10.1002/2013JD020638","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898816693&doi=10.1002%2f2013JD020638&partnerID=40&md5=74441ad4877b809e2f2240c8dcee8104","There has been much discussion about the role of tilted heating in the evolution of the MJO. It is believed that the inability of many general circulation models to produce a robust MJO is directly related to deficiencies in the model-produced tropical heating distributions. Given the MJO’s importance in tropical climate, we need to better understand what heating distributions are required in climate models to produce strong MJOs. This study addresses the role of tilted heating in the Community Atmospheric Model version 4 (CAM4). Idealized and observed heating distributions are added to the tropical atmosphere in CAM4. These include heating that tilts westward with height in the lower and upper atmosphere, as well as various tilted and untilted heating in the form of either idealized blobs or observations derived from the Tropical Rainfall Measuring Mission Precipitation Radar and the International Satellite Cloud Climatology Project. We find that low-level heating ahead of the MJO convective center is critical for the initial strengthening and later maintenance of the MJO. However, tilted heating is not necessary to simulate a realistic MJO. In addition, excess upper level heating, whether tilted or not, appears to degrade the MJO signal, although Rossby wave modes are evident only in runs with additional upper level heating. Kelvin waves are evident during strong MJOs for all simulations but are only visible over the central Pacific. Results suggest that accurate shallow convective parameterizations may be more important than deep convective ones in the evolution of the MJO. © 2014. American Geophysical Union. All Rights Reserved."
"19934555300;56024884500;7005274759;7003968166;56027675700;7005219614;","On the linkage between the asian summer monsoon and tropopause fold activity over the eastern mediterranean and the middle east",2014,"10.1002/2013JD021113","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898806731&doi=10.1002%2f2013JD021113&partnerID=40&md5=9681731bb5c357297706a4a2b324667f","A climatology of tropopause folds occurring over the Eastern Mediterranean and the Middle East (EMME) has been established using the ERA-Interim reanalyses for the years 1979–2012. The methodology employs an algorithm that detects folds at grid points where the vertical profile features multiple crossings of the dynamical tropopause and allows their classification according to their vertical extent. Our results confirm the findings of an earlier 1 year climatology that recognized a global “hot spot” of summertime fold activity between the eastern Mediterranean and central Asia, in the vicinity of the subtropical jet. Two distinct maxima of activity are identified over Turkey and Iran-Afghanistan where fold frequency exceeds 25%. Occasionally, medium and deep folds form over the two regions at surprisingly low latitudes. This summertime peak in fold activity diverges from the zonal mean seasonal cycle over the subtropics and is driven by the South Asian Monsoon. Starting in late spring, the EMME is gradually brought under the influence of the zonally asymmetric background state induced by the monsoon. As areas of sharply sloping isentropes develop especially over the eastern Mediterranean and Iran-Afghanistan, subsidence and fold formation are favored. Further investigation of the reanalysis data provided empirical evidence that the monsoon also drives the interannual variability of EMME fold activity. An upward trend in fold activity is identified, especially in May, attributed to the recent advanced monsoon onset and the deepening convective activity throughout summer, which promotes upper-level baroclinicity over the EMME and favors folding. © 2014. American Geophysical Union. All Rights Reserved."
"55512941600;57203053317;7102988363;26643250500;","Dust ice nuclei effects on cirrus clouds",2014,"10.5194/acp-14-3027-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897419824&doi=10.5194%2facp-14-3027-2014&partnerID=40&md5=e92b0cec80f3ad7e871083889e6c163a","In order to study aerosol-cloud interactions in cirrus clouds, we apply a new multiple-mode ice microphysical scheme to the general circulation model ECHAM5-HAM. The multiple-mode ice microphysical scheme allows for analysis of the competition between homogeneous freezing of solution droplets, deposition nucleation of pure dust particles, and immersion freezing of coated dust particles and pre-existing ice. We base the freezing efficiencies of coated and pure dust particles on the most recent laboratory data. The effect of pre-existing ice, which has been neglected in previous ice nucleation parameterizations, is to deplete water vapour by depositional growth and thus prevent homogeneous and heterogeneous freezing from occurring. As a first step, we extensively tested the model and validated the results against in situ measurements from various aircraft campaigns. The results compare well with observations; properties such as ice crystal size and number concentration as well as supersaturation are predicted within the observational spread. We find that heterogeneous nucleation on mineral dust particles and the consideration of pre-existing ice in the nucleation process may lead to significant effects: globally, ice crystal number and mass are reduced by 10 and 5%, whereas the ice crystals' size is increased by 3%. The reductions in ice crystal number are most pronounced in the tropics and mid-latitudes in the Northern Hemisphere. While changes in the microphysical and radiative properties of cirrus clouds in the tropics are mostly driven by considering pre-existing ice, changes in the northern hemispheric mid-latitudes mainly result from heterogeneous nucleation. The so-called negative Twomey effect in cirrus clouds is represented in ECHAM5-HAM. The net change in the radiation budget is-0.94 W mg-2, implying that both heterogeneous nucleation on dust and pre-existing ice have the potential to modulate cirrus properties in climate simulations and thus should be considered in future studies. ©Author(s) 2014."
"13403622000;56111858700;","Cirrus cloud susceptibility to the injection of ice nuclei in the upper troposphere",2014,"10.1002/2013JD020816","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898435021&doi=10.1002%2f2013JD020816&partnerID=40&md5=be02d82bc79ad77eb1a786497c93eeee","Due to their net warming effect, cirrus clouds play a crucial role in the climate system. A recently proposed climate engineering mechanism (CEM) intends to reduce high cloud cover by seeding cirrus clouds with efficient ice nuclei (IN) and therefore cool climate. Here, the susceptibility of cirrus clouds to the injection of ice nuclei in the upper troposphere is investigated in the extended Community Atmospheric Model version 5 (CAM5). Due to large uncertainties associated with the dominant ice nucleation mechanism in cirrus clouds, different control cases were simulated. In addition to pure homogeneous and heterogeneous nucleation, cases with competition between homogeneous and heterogeneous nucleation and different fractions of mineral dust active as IN were considered. Whereas seeding in the pure heterogeneous case leads to a strong warming due to overseeding, an optimal seeding IN concentration of approximately 18 l−1 was found for the other cases. For the optimal seeding concentration, a reduction in the net cloud forcing (NCF) of up to 2 W m−2 was simulated, corresponding to a strong cooling effect. To optimize the cooling and minimize the amount of seeding material, globally nonuniform seeding strategies were tested, with minimal seeding in the summer hemisphere and in the tropics. With seeding applied to less than half the globe, an even stronger reduction in the NCF was achieved. This suggests that the CEM could work for an atmosphere even with considerable heterogeneous ice nucleation and that the desired cooling could be obtained without seeding the entire globe. © 2014. American Geophysical Union. All rights reserved."
"55268661300;55461837700;57196143493;57195636034;","Observed linkages between the northern annular mode/North Atlantic Oscillation, cloud incidence, and cloud radiative forcing",2014,"10.1002/2013GL059113","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895078879&doi=10.1002%2f2013GL059113&partnerID=40&md5=e29cb50624503a13ab32e26fd741b7ee","The signature of the northern annular mode/North Atlantic Oscillation (NAM/NAO) in the vertical and horizontal distribution of tropospheric cloudiness is investigated in CloudSat and CALIPSO data from June 2006 to April 2011. During the Northern Hemisphere winter, the positive polarity of the NAM/NAO is marked by increases in zonally averaged cloud incidence north of ~60°N, decreases between ~25 and 50°N, and increases in the subtropics. The tripolar-like anomalies in cloud incidence associated with the NAM/NAO are largest over the North Atlantic Ocean basin/Middle East and are physically consistent with the NAM/NAO-related anomalies in vertical motion. Importantly, the NAM/NAO-related anomalies in tropospheric cloud incidence lead to significant top of atmosphere cloud radiative forcing anomalies that are comparable in amplitude to those associated with the NAM/NAO-related temperature anomalies. The results provide observational evidence that the most prominent pattern of Northern Hemisphere climate variability is significantly linked to variations in cloud radiative forcing. Implications for two-way feedback between extratropical dynamics and cloud radiative forcing are discussed. Key Points NAM/NAO is marked by a meridional dipole in upper tropospheric clouds NAM/NAO-related cloud anomalies lead to marked cloud radiative forcing (CRF) anomalies The CRF anomalies act to shorten the timescale of the NAM/NAO-related temperature anomalies ©2014. American Geophysical Union. All Rights Reserved."
"56054435300;55720588700;55720539800;55790781000;7004697990;37046755400;","Advanced infrared sounder subpixel cloud detection with imagers and its impact on radiance assimilation in NWP",2014,"10.1002/2013GL059067","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895155606&doi=10.1002%2f2013GL059067&partnerID=40&md5=5fab97f5a5a4edfca698273fccf1bd1a","Accurate cloud detection is very important for infrared (IR) radiance assimilation; improved cloud detection could reduce cloud contamination and hence improve the assimilation. Although operational numerical weather prediction (NWP) centers are using IR sounder radiance data for cloud detection, collocated high spatial resolution imager data could help sounder subpixel cloud detection and characterization. IR sounder radiances with improved cloud detection using Atmospheric Infrared Sounder (AIRS)/Moderate Resolution Imaging Spectroradiometer (MODIS) were assimilated for Hurricane Sandy (2012). Forecast experiments were run with Weather Research and Forecasting (WRF) as the forecast model and the Three-Dimensional Variational Assimilation (3DVAR)-based Gridpoint Statistical Interpolation (GSI) as the analysis system. Results indicate that forecasts of both hurricane track and intensity are substantially improved when the collocated high spatial resolution MODIS cloud mask is used for AIRS subpixel cloud detection for assimilating radiances. This methodology can be applied to process Crosstrack Infrared Sounder (CRIS)/Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi-NPOESS Preparatory Project (NPP)/Joint Polar Satellite System (JPSS) and Infrared Atmospheric Sounding Interferometer (IASI)/Advanced Very High Resolution Radiometer (AVHRR) onboard the Metop series for improved radiance assimilation in NWP. Key Points The application of AIRS subpixel cloud detection with 1 km MODIS cloud The analysis fields with assimilation of accurate clear radiances are improved The forecasts are substantially improved with the AIRS subpixel cloud detection ©2014. American Geophysical Union. All Rights Reserved."
"8977001000;7403282069;","An explicit representation of vertical momentum transport in a multiscale modeling framework through its 2-d cloud-resolving model component",2014,"10.1002/2013JD021078","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898465921&doi=10.1002%2f2013JD021078&partnerID=40&md5=cd88028dd366b12a697aa43df0d4a8cd","In this study, an explicit representation of vertical momentum transport by convective cloud systems, including mesoscale convective systems (MCSs), is proposed and tested in a multiscale modeling framework (MMF). The embedded cloud-resolving model (CRM) provides vertical momentum transport in one horizontal direction. The vertical momentum transport in the other direction is assumed to be proportional to the vertical mass flux diagnosed from the CRM in addition to the effects of entrainment and detrainment. In order to represent both upgradient and downgradient vertical momentum transports, the orientation of the embedded CRM must change with time instead of being stationary typically in MMFs. The orientation is determined by the stratification of the lower troposphere and environmental wind shear. Introducing the variation of the orientations of the embedded CRM is responsible for reducing the stationary anomalous precipitation and many improvements. Improvements are strengthened when the CRM simulated vertical momentum transport is allowed to modify the large-scale circulation simulated by the host general circulation model. These include an improved spatial distribution, amplitude, and intraseasonal variability of the surface precipitation in the tropics, more realistic zonal mean diabatic heating and drying patterns, more reasonable zonal mean large-scale circulations and the East Asian summer monsoon circulation, and an improved, annual mean implied meridional ocean transport in the Southern Hemisphere. Further tests of this convective momentum transport parameterization scheme will be performed with a higher-resolution MMF to further understand its roles in the intraseasonal oscillation and tropical waves, monsoon circulation, and zonal mean large-scale circulations. © 2014. American Geophysical Union. All rights reserved."
"6701368631;24173681800;13405658600;","A simple way to improve the diurnal cycle in convective rainfall over land in climate models",2014,"10.1002/2013JD020149","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898475785&doi=10.1002%2f2013JD020149&partnerID=40&md5=6bbac06d45acc6649e67986750eb1159","Within the tropics, and during the summer months in midlatitudes, most of the rainfall reaching the surface is generated by moist convection. Over land, the diurnal cycle in moist convective rainfall usually peaks in the late afternoon. In most climate models, the diurnal peak in convective rainfall occurs several hours too early and is often near local solar noon. We argue that this bias partly originates from the methods used in convective parameterizations to calculate the cloud base mass flux. In most convective parameterizations, the initial convective mass flux is determined from the convective available potential energy (CAPE) of an updraft parcel originating from the model layer closest to the surface. In models, the rapid increase in the CAPE of this near-surface layer following sunrise contributes to a rapid increase in convective precipitation. However, the mass-weighted CAPE of the boundary layer as a whole responds much more slowly to the increase in downward solar radiation at the surface. Using a recently developed convective parameterization in version 4 of the Community Atmosphere Model (CAM4), we show that the overall accuracy in the diurnal simulation of convective precipitation increases as the number of near-surface layers from which convective air parcels are permitted to originate increases from one to four. We also show that the simulation of the diurnal cycle in convective precipitation over land can be improved through the introduction of variables which attempt to represent the persistence of subgrid-scale convective organization within a grid column across model time steps. © 2014. American Geophysical Union. All rights reserved."
"57196143493;57195636034;","The implication of radiative forcing and feedback for meridional energy transport",2014,"10.1002/2013GL059079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894752824&doi=10.1002%2f2013GL059079&partnerID=40&md5=c15eedfc76e2907f847e0e8fa2cc34ad","The distributions of radiative forcing and feedback in the Coupled Model Intercomparison Project phase 5 abrupt4xCO2 and Historical experiments are diagnosed, with a focus on their effects on the zonal mean structure of the top-of-the-atmosphere radiation anomalies and implications for the meridional energy transport. It is found that because the greenhouse gas longwave forcing peaks in the low latitudes, it reinforces the equator-to-pole net radiation gradient and accounts for the increase in the poleward energy transport in both hemispheres under global warming. The shortwave forcing by aerosol, ozone, etc. peaks in the Northern Hemisphere and instead implies an interhemispheric energy transport. Although the water vapor feedback also reinforces the equator-to-pole gradient of the net radiation, the temperature and albedo feedback act against it. The feedback tend to offset the zonal mean radiation anomaly caused by the forcing, although the overall feedback effect on the energy transport is rather uncertain, mainly due to the uncertainty in the cloud feedback. Key Points CO2 forcing increases meridional gradient in net radiation Forcing, rather than feedback, accounts for enhanced poleward energy transport Aerosol forcing accounts for an inter-hemispheric transport anomaly ©2014. American Geophysical Union. All Rights Reserved."
"55883034700;55788882600;12544791500;56112745700;55788634100;38861027800;36088544000;","Future arctic temperature and ozone: The role of stratospheric composition changes",2014,"10.1002/2013JD021100","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898414439&doi=10.1002%2f2013JD021100&partnerID=40&md5=1d4f1759f3bcb2c59a802504a2206766","Using multidecadal simulations with the European Centre/Hamburg–Modular Earth Submodel System Atmospheric Chemistry (EMAC) model, the role of changing concentrations of ozone-depleting substances (ODSs) and greenhouse gases (GHGs) on Arctic springtime ozone was examined. The focus is on potential changes in the meteorological conditions relevant for Arctic ozone depletion. It is found that with rising GHG levels the lower Arctic stratosphere will cool significantly in early winter, while no significant temperature signal is identified later in winter or spring. A seasonal shift of the lowest polar minimum temperatures from late to early winter in the second part of the 21st century occurs. However, Arctic lower stratosphere temperatures do not seem to decline to new record minima. The future Arctic lower stratosphere vortex will have a longer lifetime, as a result of an earlier formation in autumn. No extended vortex persistence is found in spring due to enhanced dynamical warming by tropospheric wave forcing. Because of the dominant early winter cooling, largest accumulated polar stratospheric cloud (PSC) areas (APSC) are projected for the middle of the 21st century. A further increase of APSC toward the end of the 21st century is prevented by increased dynamical polar warming. EMAC suggests that in the near future, there is a chance of low Arctic springtime ozone in individual years; however, there is no indication of a formation of regular Arctic ozone holes. Toward the end of the 21st century, when ODSs will be close to the 1960 levels, further rising GHG levels will cause increased Arctic springtime ozone. © 2014. American Geophysical Union. All rights reserved."
"52264873100;55576500100;8331328200;56025906100;","An investigation into the relationship between liquid water content and cloud number concentration in the stratiform clouds over north China",2014,"10.1016/j.atmosres.2013.12.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893468895&doi=10.1016%2fj.atmosres.2013.12.004&partnerID=40&md5=fb6881c072159dadb2bd3cc85b7d5816","The determination of the relationship between liquid water content (LWC) and cloud number concentration (Nc) is significant in the cloud microphysical parameterization. A statistical analysis of cloud microphysical properties has been performed based on the in-situ observations from the North China Cloud Physics Detection Project (NCCPDP) during the period from 1980 to 1982. From the statistical results, the relationship between LWC and Nc was investigated. The results show that: (1) LWC of 34.2% of the clouds is quite low (less than 0.100gm-3), and only about 25.7% of the observations show LWC greater than 0.500gm-3; LWC varies widely from 0.0012 to 4.940gm-3, with an overall average of 0.462gm-3; (2) Nc of more than 42.9% of these cases is less than 250.0cm-3 with only about 15.1% of the cases having Nc larger than 2000.0cm-3, and the percentiles of 25%, 50%, 75%, and 90% of the values of Nc are 93.0cm-3, 395.0cm-3, 1444.0cm-3, and 4672.0cm-3, respectively; and (3) the relationship between LWC and Nc can be expressed as log10Nc=0.7941*log10LWC+3.1820. These results are expected to be useful for improving the microphysical parameterizations in climate and weather forecasting models. © 2013 Elsevier B.V."
"47461006200;6506644040;8782763500;26643193500;56702490400;","Suppression of transpiration due to cloud immersion in a seasonally dry Mexican weeping pine plantation",2014,"10.1016/j.agrformet.2013.11.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889690861&doi=10.1016%2fj.agrformet.2013.11.002&partnerID=40&md5=18f2327ca8aaeb0c3551ff67f8264a7e","Cloud immersion affects the water budget of fog-affected forests not only by introducing an additional source of water (via cloud water interception by the canopy), but also by suppressing plant transpiration. The latter effect is often overlooked and not routinely quantified, restricting a complete understanding of the net hydrological effect of cloud immersion and the possible consequences of projected reductions in cloud immersion under drier and warmer climates in tropical montane regions in the coming decades. This paper describes an approach to quantify the suppression of stand-level tree transpiration (Et) due to cloud immersion using measurements of sapflow, fog occurrence (visibility), leaf wetness, and near-surface climate. Estimates of fog-induced Et suppression in a 10-year-old Pinus patula plantation in the montane cloud belt of central Veracruz, Mexico, are presented for two contrasting dry seasons and a wet season. Fog occurred for 32% of the total study period, although showing pronounced seasonal variation (e.g. 44% during the second dry season). When fog occurred it was accompanied by rainfall during three quarters of the total time. Although the canopy was wet for almost a third of the time, fog-induced canopy wetness constituted only a very small portion of this total (2%). Relative to sunny conditions, Et was suppressed by 90±7% under conditions of dense fog versus 83±7% under light fog and 78±10% during overcast conditions. Quantification of the potential change in annual Et associated with two scenarios for future cloud immersion at the study site revealed that: (i) when all fog occurrence is replaced by overcast conditions, mean annual Et (645±50mm) is likely to increase by only 2±1%; and (ii) when sunny conditions replace all foggy conditions, the likely increase in annual Et is 17±3%. As the rise in the regional lifting condensation level is likely to be on the order of only a couple of hundred meters and will probably result in a shift to overcast rather than clear-sky conditions, the present results suggest that the corresponding impact on Et may be relatively small. Consequently, a climate change-related reduction in dry-season precipitation, through the associated potential reductions in soil water reserves, presents a more worrisome prospect for plant-water relations and water yield from headwater catchments than diminishing cloud immersion alone. The present results highlight the need for better projections of climate change-related alterations in cloud cover and immersion, as well as rainfall patterns for tropical montane regions. © 2013 Elsevier B.V."
"55717075800;55726314800;15070397200;35093720000;46761494200;55207477400;55598023100;55664298600;","A shift in cloud cover over the southeastern tibetan plateau since 1600: Evidence from regional tree-ring δ18O and its linkages to tropical oceans",2014,"10.1016/j.quascirev.2014.01.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893728572&doi=10.1016%2fj.quascirev.2014.01.009&partnerID=40&md5=37130592d84fd6fe9b040d05d718e790","We studied the climatic significance and potential forcing of regional tree-ring δ18O across the southeastern Tibetan Plateau from 1600 to 2009. Three normalized tree-ring δ18O time series showed high signal coherence at both low and high frequencies. A 400 years composite tree-ring δ18O chronology in southeastern Tibetan Plateau was established by averaging Z-score method. The composite δ18O chronology showed that climate changed since 1860, causing a shift in the hydroclimatic regime and in the influence of regional atmospheric circulation. Spatial correlation analysis revealed that tree-ring δ18O was significantly negatively correlated with moisture conditions, and especially with cloud cover during wet summers; the strongest correlation was found for the June to August period. Our regional cloud cover reconstruction for June-August period between 26°N and 34°N and between 89°E and 103°E explained 37.6% of the variation from 1953 to 2009. The climate conditions from 1600 to 1860 (the Little Ice Age) were cold and cloudy, but thereafter became sunnier and warmer. Hydroclimatic variations in this region are primarily affected by atmospheric processes in the tropical Indian Ocean and in the East Pacific Ocean, linked to the El Niño-Southern Oscillation (ENSO). The cloud cover over the southeastern Tibetan Plateau is modulated more strongly by sea surface temperatures in the Indian Ocean than over the Pacific Ocean, suggesting low-frequency responses to anomalous ocean warming. The impact of ENSO on regional tree-ring δ18O series was temporally unstable. Our comparisons among different proxies highlight that a tree-ring δ18O network has great potential to reveal common low-frequency climatic signals in monsoon Asia over long time scales. © 2014."
"7202355164;55768583400;7103033688;7006889553;","Updated high-resolution grids of monthly climatic observations - the CRU TS3.10 Dataset",2014,"10.1002/joc.3711","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896707401&doi=10.1002%2fjoc.3711&partnerID=40&md5=b382b20d925bc803e5f6ffb2e878d7c8","This paper describes the construction of an updated gridded climate dataset (referred to as CRU TS3.10) from monthly observations at meteorological stations across the world's land areas. Station anomalies (from 1961 to 1990 means) were interpolated into 0.5° latitude/longitude grid cells covering the global land surface (excluding Antarctica), and combined with an existing climatology to obtain absolute monthly values. The dataset includes six mostly independent climate variables (mean temperature, diurnal temperature range, precipitation, wet-day frequency, vapour pressure and cloud cover). Maximum and minimum temperatures have been arithmetically derived from these. Secondary variables (frost day frequency and potential evapotranspiration) have been estimated from the six primary variables using well-known formulae. Time series for hemispheric averages and 20 large sub-continental scale regions were calculated (for mean, maximum and minimum temperature and precipitation totals) and compared to a number of similar gridded products. The new dataset compares very favourably, with the major deviations mostly in regions and/or time periods with sparser observational data. CRU TS3.10 includes diagnostics associated with each interpolated value that indicates the number of stations used in the interpolation, allowing determination of the reliability of values in an objective way. This gridded product will be publicly available, including the input station series (http://www.cru.uea.ac.uk/ and http://badc.nerc.ac.uk/data/cru/). © 2013 Royal Meteorological Society."
"7006609519;36472923300;36673016000;","Nordic Lightning Information System: Thunderstorm climate of Northern Europe for the period 2002-2011",2014,"10.1016/j.atmosres.2014.01.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893128168&doi=10.1016%2fj.atmosres.2014.01.008&partnerID=40&md5=e665058d0aa7bcd6ae67cd166362b7f2","A 10-year statistics (2002-2011) of the Nordic Lightning Information System (NORDLIS) are presented. NORDLIS is a joined lightning location network between Norway, Sweden, Finland, and Estonia, comprising in 2011 of 32 lightning location sensors. Our data set contains a total of 4,121,649 cloud-to-ground (CG) flashes. We show the regional and temporal distribution of lightning in Northern Europe during the study period. Our results indicate that the average annual ground flash density values are greatest in Southern Sweden, Baltic countries and Western Finland. The average number of thunderstorm days is largest in the Baltic countries and Southwestern Sweden, and the annual number of ground flashes has varied during the study period from 250,000 to 620,000. The largest observed daily number of ground flashes is 51,500, and the largest daily ground flash density is about 5CGskm-2; this has occurred in southern Sweden in July 2003. The average daily number of ground flashes peaks in mid-July-early-August. Cold season (October-April) thunderstorms occur frequently over the North Sea west of Norway and in the west coast of Denmark. Our results also show that an intense thunderstorm may occur practically anywhere in the Northern Europe except for certain maritime and mountain areas. © 2014 Elsevier B.V."
"55569635300;7003875148;7005634455;7006041988;7005304841;7201957405;7410338331;","The Arctic summer atmosphere: An evaluation of reanalyses using ASCOS data",2014,"10.5194/acp-14-2605-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896497414&doi=10.5194%2facp-14-2605-2014&partnerID=40&md5=78b91666389c0ea602685bb916e99249","The Arctic has experienced large climate changes over recent decades, the largest for any region on Earth. To understand the underlying reasons for this climate sensitivity, reanalysis is an invaluable tool. The Arctic System Reanalysis (ASR) is a regional reanalysis, forced by ERA-Interim at the lateral boundaries and incorporating model physics adapted to Arctic conditions, developed to serve as a state-of-the-art, high-resolution synthesis tool for assessing Arctic climate variability and monitoring Arctic climate change. We use data from Arctic Summer Cloud-Ocean Study (ASCOS) to evaluate the performance of ASR and ERA-Interim for the Arctic Ocean. The ASCOS field experiment was deployed on the Swedish icebreaker Oden north of 87° N in the Atlantic sector of the Arctic during August and early September 2008. Data were collected during the transits from and to Longyearbyen and the 3-week ice drift with Oden moored to a drifting multiyear ice floe. These data are independent and detailed enough to evaluate process descriptions. The reanalyses captures basic meteorological variations coupled to the synoptic-scale systems, but have difficulties in estimating clouds and atmospheric moisture. While ERA-Interim has a systematic warm bias in the lowest troposphere, ASR has a cold bias of about the same magnitude on average. The results also indicate that more sophisticated descriptions of cloud microphysics in ASR did not significantly improve the modeling of cloud properties compared to ERA-Interim. This has consequences for the radiation balance, and hence the surface temperature, and illustrate how a modeling problem in one aspect of the atmosphere, here the clouds, feeds back to other parameters, especially near the surface and in the boundary layer."
"55675283100;55926866400;7005729142;7003763119;7003438077;14021294500;7004165697;7402049334;","Cloud-scale ice-supersaturated regions spatially correlate with high water vapor heterogeneities",2014,"10.5194/acp-14-2639-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896356075&doi=10.5194%2facp-14-2639-2014&partnerID=40&md5=5af4cd2f5ef5c7febde578e0e73e550a","Cirrus clouds have large yet uncertain impacts on Earth's climate. Ice supersaturation (ISS)-where the relative humidity with respect to ice (RHi) is greater than 100%-is the prerequisite condition of ice nucleation. Here we use 1 Hz (∼230 m) in situ, aircraft-based observations from 87 N to 67 S to analyze the spatial characteristics of ice-supersaturated regions (ISSRs). The median length of 1-D horizontal ISSR segments is found to be very small (∼1 km), which is 2 orders of magnitude smaller than previously reported. To understand the conditions of these small-scale ISSRs, we compare individual ISSRs with their horizontally adjacent subsaturated surroundings and show that 99% and 73% of the ISSRs are moister and colder, respectively. When quantifying the contributions of water vapor (H2O) and temperature (T) individually, the magnitudes of the differences between the maximum RHi values inside ISSRs (RHimax) and the RHi in subsaturated surroundings are largely derived from the H2O spatial variabilities (by 88%) than from those of T (by 9%). These features hold for both ISSRs with and without ice crystals present. Similar analyses for all RHi horizontal variabilities (including ISS and non-ISS) show strong contributions from H2O variabilities at various T, H2O, pressure (P) and various horizontal scales (∼1-100 km). Our results provide a new observational constraint on ISSRs on the microscale (∼100 m) and point to the importance of understanding how these fine-scale features originate and impact cirrus cloud formation and the RHi field in the upper troposphere (UT). © 2014 Author(s)."
"54940625500;8068419200;7201708378;","Investigating vegetation-climate feedbacks during the early Eocene",2014,"10.5194/cp-10-419-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896775080&doi=10.5194%2fcp-10-419-2014&partnerID=40&md5=7274d142d8787ad2e81747e7e839d647","Evidence suggests that the early Eocene was a time of extreme global warmth. However, there are discrepancies between the results of many previous modelling studies and the proxy data at high latitudes, with models struggling to simulate the shallow temperature gradients of this time period to the same extent as the proxies indicate. Vegetation-climate feedbacks play an important role in the present day, but are often neglected in these palaeoclimate modelling studies, and this may be a contributing factor to resolving the model-data discrepancy. Here we investigate these vegetation-climate feedbacks by carrying out simulations of the early Eocene climate at 2 × and 4 × pre-industrial atmospheric CO2 with fixed vegetation (homogeneous shrubs everywhere) and dynamic vegetation. The results show that the simulations with dynamic vegetation are warmer in the global annual mean than the simulations with fixed shrubs by 0.9 °C at 2 × and 1.8 °C at 4 &amp;times;. Consequently, the warming when CO2 is doubled from 2 × to 4 × is 1 °C higher (in the global annual mean) with dynamic vegetation than with fixed shrubs. This corresponds to an increase in climate sensitivity of 26%. This difference in warming is enhanced at high latitudes, with temperatures increasing by over 50% in some regions of Antarctica. In the Arctic, ice-albedo feedbacks are responsible for the majority of this warming. On a global scale, energy balance analysis shows that the enhanced warming with dynamic vegetation is mainly associated with an increase in atmospheric water vapour but changes in clouds also contribute to the temperature increase. It is likely that changes in surface albedo due to changes in vegetation cover resulted in an initial warming which triggered these water vapour feedbacks. In conclusion, dynamic vegetation goes some way to resolving the discrepancy, but our modelled temperatures cannot reach the same warmth as the data suggest in the Arctic. This suggests that there are additional mechanisms, not included in this modelling framework, behind the polar warmth or that the proxies have been misinterpreted. © Author(s) 2014."
"55574711000;7403476075;7404495164;57192697907;34882294600;36005104100;","Monitoring snow cover using Chinese meteorological satellite data over China",2014,"10.1016/j.rse.2013.12.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893173480&doi=10.1016%2fj.rse.2013.12.022&partnerID=40&md5=8bc4fda2add30817b20fd0a0a2bcd232","Snow cover plays an important role in hydrological processes and global climate change research. Geostationary satellites with high temporal resolution provide multiple observations in one day, which highlights their potential for monitoring real-time snow-cover information. In this paper, data from the Chinese meteorological satellites Fengyun-2D (FY-2D), Fengyun-2E (FY-2E) and Fengyun-3B (FY-3B) was used for snow-cover mapping over China. A new method of detecting snow-cover information is proposed, that combines the Visible and Infrared Spin Scan-Radiometer (VISSR) on board the geostationary satellites FY-2D and FY-2E and the Microwave Radiation Imager (MWRI) on board the polar orbiting satellite FY-3B. The snow cover estimated from Fengyun satellites was compared by the Moderate Resolution Imaging Spectroradiometer (MODIS) snow-cover products (MOD10A1 and MYD10A1), and Interactive Multisensor Snow and Ice Mapping System (IMS) snow-cover products. The Fengyun satellite snow-cover images and IMS snow-cover products were validated with meteorological station observations for the 2010-2011 and 2011-2012 winter seasons. The influence of elevation and land-cover types on the accuracy of snow retrievals was also analyzed. The results showed that the combined use of FY-2D and FY-2E VISSR data reduced cloud obscuration by 30.47% compared to the MODIS products. The validation demonstrated that the accuracy of the final multi-sensor snow-cover images was 91.28%, which is similar to that for IMS snow-cover products. This work indicates that combined data from geostationary satellites and passive microwave remote sensing monitored snow cover over China to a high level of accuracy. © 2014 Elsevier Inc."
"57205787051;57202567768;35794588800;6603172418;","A parameterisation for the activation of cloud drops including the effects of semi-volatile organics",2014,"10.5194/acp-14-2289-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895809731&doi=10.5194%2facp-14-2289-2014&partnerID=40&md5=e3a9759f4a6a8bd462fd271183f2a811","We present a parameterisation of aerosol activation, including co-condensation of semi-volatile organics, for warm clouds that has applications in large-scale numerical models. The scheme is based on previously developed parameterisations that are in the literature, but has two main modifications. The first is that the total aerosol mass is modified by the condensation of organic vapours entering cloud base, whereas the second is that this addition of mass acts to modify the median diameter and the geometric standard deviation of the aerosol size distribution. It is found that the scheme is consistent with parcel model calculations of co-condensation under different regimes. Such a parameterisation may find use in evaluating important feedbacks in climate models. © Author(s) 2014."
"55286185400;","An investigation of the connections among convection, clouds, and climate sensitivity in a global climate model",2014,"10.1175/JCLI-D-13-00145.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897635713&doi=10.1175%2fJCLI-D-13-00145.1&partnerID=40&md5=3dd5992de7ee02a6fa9aeda8808d35e9","This study explores connections between process-level modeling of convection and global climate model (GCM) simulated clouds and cloud feedback to global warming through a set of perturbed-physics and perturbed sea surface temperature experiments. A bulk diagnostic approach is constructed, and a set of variables is derived and demonstrated to be useful in understanding the simulated relationship. In particular, a novel bulk quantity, the convective precipitation efficiency or equivalently the convective detrainment efficiency, is proposed as a simple measure of the aggregated properties of parameterized convection important to the GCM simulated clouds. As the convective precipitation efficiency increases in the perturbedphysics experiments, both liquid and ice water path decrease, with low and middle cloud fractions diminishing at a faster rate than high cloud fractions. This asymmetry results in a large sensitivity of top-of-atmosphere net cloud radiative forcing to changes in convective precipitation efficiency in this limited set of models. For global warming experiments, intermodel variations in the response of cloud condensate, low cloud fraction, and total cloud radiative forcing are well explained by model variations in response to total precipitation (or detrainment) efficiency. Despite significant variability, all of the perturbed-physics models produce a sizable increase in precipitation efficiency to warming. A substantial fraction of the increase is due to its convective component, which depends on the parameterization of cumulus mixing and convective microphysical processes. The increase in convective precipitation efficiency and associated change in convective cloud height distribution owing to warming explains the increased cloud feedback and climate sensitivity in recently developed Geophysical Fluid Dynamics Laboratory GCMs. The results imply that a cumulus scheme using fractional removal of condensate for precipitation and inverse calculation of the entrainment rate tends to produce a lower climate sensitivity than a scheme using threshold removal for precipitation and the entrainment rate formulated inversely dependent on convective depth. © 2014 American Meteorological Society."
"7004479957;8882641700;","Low cloud reduction in a greenhouse-warmed climate: Results from Lagrangian les of a subtropical marine cloudiness transition",2014,"10.1002/2013MS000250","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899096387&doi=10.1002%2f2013MS000250&partnerID=40&md5=fac647578cd997136a7a7715847debc9","Lagrangian large-eddy simulations of a composite stratocumulus to cumulus transition case over the subtropical northeast Pacific Ocean are subject to perturbed forcings that isolate the cloud response to CO<inf>2</inf>, to overall tropical warming, and to increased inversion stability over the subtropical subsidence regions. These simulations show that a tropical surface warming of 4 K induces substantial stratocumulus thinning via a thermodynamic mechanism: increased cloud layer humidity flux in a warmer climate induces an entrainment liquid-flux adjustment that dries the stratocumulus cloud layer, whether well mixed or cumulus coupled. A radiative mechanism amplifies this response: increased emissivity of the free troposphere due to increased CO<inf>2</inf> and water vapor reduces radiative driving of turbulence in a stratocumulus-capped boundary layer; a thinner stratocumulus layer accompanies less turbulence. In combination, a 4 K warming and CO<inf>2</inf> quadrupling greatly reduce low cloud and weaken the simulated shortwave cloud radiative effect by over 50%. Large increases in inversion stability in the stratocumulus regions could counter much of this cloudiness reduction. Key Points LES isolates radiative and thermodynamic positive low cloud feedback mechanisms Thermodynamic cloud thinning due to entrainment liquid-flux adjustment ELF thinning mechanism affects all subtropical Sc-topped cloud regimes © 2014. American Geophysical Union. All Rights Reserved."
"36241005100;7006329853;","Controls on the archean climate system investigated with a global climate model",2014,"10.1089/ast.2013.1112","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896339894&doi=10.1089%2fast.2013.1112&partnerID=40&md5=b6bdb5539f643741ed30a9bddbd229ae","The most obvious means of resolving the faint young Sun paradox is to invoke large quantities of greenhouse gases, namely, CO2 and CH 4. However, numerous changes to the Archean climate system have been suggested that may have yielded additional warming, thus easing the required greenhouse gas burden. Here, we use a three-dimensional climate model to examine some of the factors that controlled Archean climate. We examine changes to Earth's rotation rate, surface albedo, cloud properties, and total atmospheric pressure following proposals from the recent literature. While the effects of increased planetary rotation rate on surface temperature are insignificant, plausible changes to the surface albedo, cloud droplet number concentrations, and atmospheric nitrogen inventory may each impart global mean warming of 3-7 K. While none of these changes present a singular solution to the faint young Sun paradox, a combination can have a large impact on climate. Global mean surface temperatures at or above 288 K could easily have been maintained throughout the entirety of the Archean if plausible changes to clouds, surface albedo, and nitrogen content occurred. © Mary Ann Liebert, Inc. 2014."
"7005968838;57208455286;7005871193;57203474131;7003663939;7003420718;7007026915;14050275600;6601996486;6505685792;36824281400;7003633691;6701787831;57193800572;8206721000;7003854772;6603274519;7006508549;15131276100;","Land cover changes and their biogeophysical effects on climate",2014,"10.1002/joc.3736","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900587683&doi=10.1002%2fjoc.3736&partnerID=40&md5=e52175cd03a8c18656e5c0e33ff06af1","Land cover changes (LCCs) play an important role in the climate system. Research over recent decades highlights the impacts of these changes on atmospheric temperature, humidity, cloud cover, circulation, and precipitation. These impacts range from the local- and regional-scale to sub-continental and global-scale. It has been found that the impacts of regional-scale LCC in one area may also be manifested in other parts of the world as a climatic teleconnection. In light of these findings, this article provides an overview and synthesis of some of the most notable types of LCC and their impacts on climate. These LCC types include agriculture, deforestation and afforestation, desertification, and urbanization. In addition, this article provides a discussion on challenges to, and future research directions in, assessing the climatic impacts of LCC. © 2013 Royal Meteorological Society."
"55582924900;55707280000;56576766700;23481546200;","Why are tropical cyclone tracks over the western North Pacific sensitive to the cumulus parameterization scheme in regional climate modeling? A case study for megi (2010)",2014,"10.1175/MWR-D-13-00232.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896784115&doi=10.1175%2fMWR-D-13-00232.1&partnerID=40&md5=05ae0663dc9780dda9c2892bed2af5ac","The Weather Research and Forecasting Model is employed to simulate Tropical Cyclone (TC) Megi (2010) using the Grell-Devenyi (GD) and Betts-Miller-Janjić (BMJ) cumulus parameterization schemes, respectively. The TC track can be well reproduced with the GD scheme, whereas it turns earlier than observations with the BMJ scheme. The physical mechanism behind different performances of the two cumulus parameterization schemes in the TC simulation is revealed. The failure in the simulation of the TC track with the BMJ scheme is attributed to the overestimation of anvil clouds, which extend far away from the TC center and reach the area of the western Pacific subtropical high (WPSH). Such extensive anvil clouds, which result from the excessively deep convection in the eyewall, eventually lead to a large bias in microphysics latent heating. The warming of the upper troposphere due to the condensation in anvil clouds coupled with the cooling of the lower troposphere due to precipitation evaporation cause a weakening of the WPSH, which in turn is favorable for the early recurvature of Megi. © 2014 American Meteorological Society."
"56100447800;7004114883;25924878400;","A lagrangian analysis of deep convective systems and their local environmental effects",2014,"10.1175/JCLI-D-13-00285.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897630576&doi=10.1175%2fJCLI-D-13-00285.1&partnerID=40&md5=328a5646da4f2a3e6d5b5b8c7eebb832","Life cycles of deep convective raining systems are documented through use of a Lagrangian tracking algorithm applied to high-resolution Climate Prediction Center morphing technique (CMORPH) rainfall data, permitting collocation with related environmental ancillary fields and the International Satellite Cloud Climatology Project (ISCCP) cloud states (Rossow et al. 2005). System life cycles are described in terms of propagation speed, duration, and dominant cloud structures. Tracked systems are usually associated with the ISCCP weather state 1 (WS1) deep convection cloud state and an independent, microwave-based deep convective precipitation regime developed here. The distribution and characteristics of tracked systems are found to be similar between ocean basins in terms of system speed and duration, with westward-propagating systems predominant in every basin. The effects that these systems have on environmental parameters are assessed, stratified according to their average propagation speed and by ocean basin. Regardless of system speed the net effect on the environment is similar, with the largest difference being how quickly changes occur, with net surface radiation decreasing about 150 W m-2 and total precipitable water perturbed by 5-7 kg m-2; sea surface temperature (SST) drops 0.2°-0.3°C over 24 h, with system speed affecting how long SSTs remain depressed. The observed drop in SST is partly caused by the presence of widespread, optically thick clouds that greatly decrease the net surface radiative flux. Quick changes in SSTs caused by tracked systems are captured by buoys but not represented well in gridded SST products, as these regions remain largely under the precipitating cloud cover associated with these systems. © 2014 American Meteorological Society."
"35561911800;9242540400;56203249800;6604021707;7401548835;9242539000;57191598636;22978151200;24538369000;7004177660;7004409909;36851768400;55339475000;6603552777;57193132723;6505881672;12240390300;7404334532;7006224475;57191693467;56249704400;7006399110;8954866200;57191692422;12241892400;7102967367;7201837768;36705143500;6506806004;35094442700;55403720400;8414341100;8687063000;7006550762;12763470600;7405727977;7004214645;56528677800;56126782200;55408944000;6507308842;14829673100;22986631300;7403318365;57203378018;","Configuration and assessment of the GISS ModelE2 contributions to the CMIP5 archive",2014,"10.1002/2013MS000265","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893558445&doi=10.1002%2f2013MS000265&partnerID=40&md5=e1b1350cc5695cd9ae8b4eec93742aec","We present a description of the ModelE2 version of the Goddard Institute for Space Studies (GISS) General Circulation Model (GCM) and the configurations used in the simulations performed for the Coupled Model Intercomparison Project Phase 5 (CMIP5). We use six variations related to the treatment of the atmospheric composition, the calculation of aerosol indirect effects, and ocean model component. Specifically, we test the difference between atmospheric models that have noninteractive composition, where radiatively important aerosols and ozone are prescribed from precomputed decadal averages, and interactive versions where atmospheric chemistry and aerosols are calculated given decadally varying emissions. The impact of the first aerosol indirect effect on clouds is either specified using a simple tuning, or parameterized using a cloud microphysics scheme. We also use two dynamic ocean components: the Russell and HYbrid Coordinate Ocean Model (HYCOM) which differ significantly in their basic formulations and grid. Results are presented for the climatological means over the satellite era (1980-2004) taken from transient simulations starting from the preindustrial (1850) driven by estimates of appropriate forcings over the 20th Century. Differences in base climate and variability related to the choice of ocean model are large, indicating an important structural uncertainty. The impact of interactive atmospheric composition on the climatology is relatively small except in regions such as the lower stratosphere, where ozone plays an important role, and the tropics, where aerosol changes affect the hydrological cycle and cloud cover. While key improvements over previous versions of the model are evident, these are not uniform across all metrics. Key Points Description of the GISS ModelE2 contribution to CMIP5 Impact on evaluation of structural changes in composition and ocean treatment Ocean model choice is an important structural uncertainty © 2014. American Geophysical Union. All Rights Reserved."
"50261552200;6701752471;7103271625;57208462871;6701618837;","Multivariate probability density functions with dynamics in the GFDL atmospheric general circulation Model: Global tests",2014,"10.1175/JCLI-D-13-00347.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897589380&doi=10.1175%2fJCLI-D-13-00347.1&partnerID=40&md5=8fb957e1d2cb58f1a98ce2b784607551","A unified turbulence and cloud parameterization based on multivariate probability density functions (PDFs) has been incorporated into the GFDL atmospheric general circulation model (AM3). This PDFbased parameterization not only predicts subgrid variations in vertical velocity, temperature, and total water, which bridge subgrid-scale processes (e.g., aerosol activation and cloud microphysics) and grid-scale dynamic and thermodynamic fields, but also unifies the treatment of planetary boundary layer (PBL), shallow convection, and cloud macrophysics. This parameterization is called the Cloud Layers Unified by Binormals (CLUBB) parameterization. With the incorporation of CLUBB in AM3, coupled with a two-moment cloud microphysical scheme, AM3-CLUBB allows for a more physically based and self-consistent treatment of aerosol activation, cloud micro- and macrophysics, PBL, and shallow convection. The configuration and performance of AM3-CLUBB are described. Cloud and radiation fields, as well as most basic climate features, are modeled realistically. Relative to AM3, AM3-CLUBB improves the simulation of coastal stratocumulus, a longstanding deficiency in GFDL models, and their seasonal cycle, especially at higher horizontal resolution, but global skill scores deteriorate slightly. Through sensitivity experiments, it is shown that 1) the two-moment cloud microphysics helps relieve the deficiency of coastal stratocumulus, 2) using the CLUBB subgrid cloud water variability in the cloud microphysics has a considerable positive impact on global cloudiness, and 3) the impact of adjusting CLUBB parameters is to improve the overall agreement between model and observations. © 2014 American Meteorological Society."
"36987319800;57203054708;","Modeling the moist-convective atmosphere with a Quasi-3-D Multiscale Modeling Framework (Q3D MMF)",2014,"10.1002/2013MS000295","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899097139&doi=10.1002%2f2013MS000295&partnerID=40&md5=32af3488746bda2b187dc71defa525a0","The Q3D MMF (Quasi-Three-Dimensional Multiscale Modeling Framework) is a new generation of MMF that replaces the conventional subgrid-scale parameterizations in general circulation models (GCMs) with explicit simulations of cloud and associated processes by cloud-resolving models (CRMs). In the Q3D MMF, 3-D CRMs are applied to the channel domains that extend over GCM grid cells. To avoid ""double counting"" of the large-scale effects, only the eddy effects simulated by the CRMs are implemented into the GCM as far as the transports are concerned, while the total effects are implemented for diabatic processes. The CRMs recognize the large-scale horizontal inhomogeneity through the lateral boundary conditions obtained from the GCM through interpolation. To maintain compatibility between the GCM and CRMs, the averages of CRM variables over the GCM grid spacing are relaxed to the corresponding GCM variables with the advective time scale. To evaluate the Q3D MMF, a transition from a wave to strong vortices is simulated in an idealized horizontal domain. Comparison with a fully 3-D benchmark simulation shows that the Q3D MMF successfully predicts the evolution of the vortices. It also captures important statistics such as the domain-averaged surface precipitation rate, turbulent fluxes and subgrid-scale (co)variances. From tests with 3-D and 2-D CRMs, respectively, it is concluded that the ability to recognize large-scale inhomogeneities is primarily responsible for the successful performance of the Q3D MMF. It is also demonstrated that the use of two perpendicular sets of CRMs has positive impacts on the simulation. Key Points Q3D MMF, a new generation of superparameterization, has been developed It is evaluated with simulations of tropical cyclone in an idealized domain Encouraging results suggest its potential for future NWP and climate models © 2014. American Geophysical Union. All Rights Reserved."
"57203288317;7004479957;8882641700;","Fast stratocumulus time scale in mixed layer model and large eddy simulation",2014,"10.1002/2013MS000289","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899057740&doi=10.1002%2f2013MS000289&partnerID=40&md5=aaa83b8ebe1e9245cb87bc73cdb6f83d","A mixed layer model (MLM) and large eddy simulation (LES) are used to analyze the internal response time scales of a stratocumulus-topped boundary layer (STBL). Three separate time scales are identified: a slow time scale associated with boundary layer deepening (several days), an intermediate thermodynamic time scale (approximately 1 day), and a fast time scale (6-12 h) for cloud water path adjustment associated with an internal entrainment-liquid flux (ELF) feedback. The nocturnal DYCOMSII-RF01 case study is used to establish and interpret the previously unidentified fast STBL adjustment time scale with the MLM. The role of the entrainment closure is investigated by repeating the analysis with several different closures. Nearly every closure considered exhibits a fast time scale. Perturbations are applied to the well-mixed CGILS stratocumulus case in both MLM and LES in order to elicit a short time scale response. Purely radiative perturbations do not project strongly onto the fast scale, while perturbations to the free tropospheric humidity do. A 2K surface and atmospheric temperature perturbation also projects strongly onto the fast scale. We show that the ELF adjustment mechanism behind the fast time scale is responsible for much of the steady state liquid water path response in the perturbed case, acting as a cloud-thinning feedback mechanism in a uniformly warmed climate. Key Points We identify a fast Sc time scale due to entrainment-liquid flux (ELF) feedback Fast time scale is corroborated by MLM, LES, and physical reasoning ELF adjustment acts as a cloud-thinning feedback in uniformly warmed climate © 2014. American Geophysical Union. All Rights Reserved."
"23013520400;7402966758;","Observations of temperature, wind, cirrus, and trace gases in the tropical tropopause transition layer during the MJO",2014,"10.1175/JAS-D-13-0178.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896741245&doi=10.1175%2fJAS-D-13-0178.1&partnerID=40&md5=cced80a046e26aba9db38e748887851d","Satellite observations of temperature, optically thin cirrus clouds, and trace gases derived from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and the Microwave Limb Sounder (MLS) are analyzed in combination with Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) wind and humidity fields in the tropical tropopause transition layer (TTL), using the Madden-Julian oscillation (MJO) as a carrier signal. MJO-related deep convection induces planetary-scale Kelvin and Rossby waves in the stably stratified TTL. Regions of ascent in these waves are associated with anomalously low temperatures, high radiative heating rates, enhanced cirrus occurrence, and high carbon monoxide and low ozone concentrations. Low water vapor mixing ratio anomalies lag the low temperature anomalies by about 1-2 weeks. The anomalies in all fields propagate eastward, circumnavigating the tropical belt over a roughly 40-day interval. Equatorial cross sections reveal that the anomalies tilt eastward with height in the TTL and propagate downward from the lower stratosphere into the upper troposphere. As MJO-related convection moves into the western Pacific and dissipates, a fast-moving Kelvin wave flanked by Rossby waves propagates eastward across South America and Africa into the western Indian Ocean. The region of equatorial westerly wind anomalies behind the Kelvin wave front lengthens until it encompasses most of the tropics at the 150-hPa level, giving rise to equatorially symmetric, anomalously low zonal-mean temperature and water vapor mixing ratio and enhanced cirrus above about 100 hPa. © 2014 American Meteorological Society."
"7102743829;6506537159;","A PDF-based microphysics parameterization for shallow cumulus clouds",2014,"10.1175/JAS-D-13-0193.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896782736&doi=10.1175%2fJAS-D-13-0193.1&partnerID=40&md5=fd841c267127ba8b0e8401cf62bc9d53","Unbiased calculations of microphysical process rates such as autoconversion and accretion in mesoscale numerical weather prediction models require that subgrid-scale (SGS) variability over the model grid volume be taken into account. This variability can be expressed as probability distribution functions (PDFs) of microphysical variables.Using dynamically balanced large-eddy simulation (LES)model results froma case ofmarine trade cumulus, the authors develop PDFs of the cloud water, droplet concentration, and rainwater variables (qc, Nc, and qr). Both 1Dand 2Djoint PDFs (JPDFs) are presented. The authors demonstrate that accounting for the JPDFs results inmore accurate process rates for a regional-model grid size. Bias in autoconversion and accretion rates are presented, assuming different formulations of the JPDFs. Approximating the 2D PDF using a product of individual 1D PDFs overestimates the autoconversion rates by an order of magnitude, whereas neglecting the SGS variability altogether results in a drastic underestimate of the grid-mean autoconversion rate. PDF assumptions have a much smaller impact on accretion, largely because of the near-linear dependence of the variables in the accretion rate formula and the relatively weak correlation between qc and qr over the small LES grid volumes. The latter is attributed to the spatial decorrelation in the vertical between the two fields. Although the full PDFs are both height and time dependent, results suggest that fixed-in-time and fixed-in-height PDFs give an acceptable level of accuracy, especially for the crucial autoconversion calculation. © 2014 American Meteorological Society."
"57204318146;","Impact of cloud microphysics and cumulus parameterization on simulation of heavy rainfall event during 7-9 October 2007 over Bangladesh",2014,"10.1007/s12040-013-0401-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898747042&doi=10.1007%2fs12040-013-0401-0&partnerID=40&md5=60010c983beb7a18aaee664c5d5e33eb","In the present study, the Advanced Research WRF (ARW) version 3.2.1 has been used to simulate the heavy rainfall event that occurred between 7 and 9 October 2007 in the southern part of Bangladesh. Weather Research and Forecast (WRF-ARW version) modelling system with six different microphysics (MP) schemes and two different cumulus parameterization (CP) schemes in a nested configuration was chosen for simulating the event. The model domains consist of outer and inner domains having 9 and 3 km horizontal resolution, respectively with 28 vertical sigma levels. The impacts of cloud microphysical processes by means of precipitation, wind and reflectivity, kinematic and thermodynamic characteristics of the event have been studied. Sensitivity experiments have been conducted with the WRF model to test the impact of microphysical and cumulus parameterization schemes in capturing the extreme weather event. NCEP FNL data were used for the initial and boundary condition. The model ran for 72 h using initial data at 0000 UTC of 7 October 2007. The simulated rainfall shows that WSM6-KF combination gives better results for all combinations and after that Lin-KF combination. WSM3-KF has simulated, less area average rainfall out of all MP schemes that were coupled with KF scheme. The sharp peak of relative humidity up to 300 hPa has been simulated along the vertical line where maximum updraft has been found for all MPs coupled with KF and BMJ schemes. The simulated rain water and cloud water mixing ratio were maximum at the position where the vertical velocity and reflectivity has also been maximum. The production of rain water mixing ratio depends on MP schemes as well as CP schemes. Rainfall depends on rain water mixing ratio between 950 and 500 hPa. Rain water mixing ratio above 500 hPa level has no effect on surface rain. © Indian Academy of Sciences."
"7006184606;16644246500;54995785000;","Radiative-convective instability",2014,"10.1002/2013MS000270","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899097230&doi=10.1002%2f2013MS000270&partnerID=40&md5=d4ca3891ff2a63b723f9fe326d72bf2a","Radiative-moist-convective equilibrium (RCE) is a simple paradigm for the statistical equilibrium the earth's climate would exhibit in the absence of lateral energy transport. It has generally been assumed that for a given solar forcing and long-lived greenhouse gas concentration, such a state would be unique, but recent work suggests that more than one stable equilibrium may be possible. Here we show that above a critical specified sea surface temperature, the ordinary RCE state becomes linearly unstable to large-scale overturning circulations. The instability migrates the RCE state toward one of the two stable equilibria first found by Raymond and Zeng (2000). It occurs when the clear-sky infrared opacity of the lower troposphere becomes so large, owing to high water vapor concentration, that variations of the radiative cooling of the lower troposphere are governed principally by variations in upper tropospheric water vapor. We show that the instability represents a subcritical bifurcation of the ordinary RCE state, leading to either a dry state with large-scale descent, or to a moist state with mean ascent; these states may be accessed by finite amplitude perturbations to ordinary RCE in the subcritical state, or spontaneously in the supercritical state. As first suggested by Raymond (2000) and Sobel et al. (2007), the latter corresponds to the phenomenon of self-aggregation of moist convection, taking the form of cloud clusters or tropical cyclones. We argue that the nonrobustness of self-aggregation in cloud system resolving models may be an artifact of running such models close to the critical temperature for instability. Key Points Radiative-convective equilibrium becomes unstable at high temperature ©2013. American Geophysical Union. All Rights Reserved."
"35739529800;6603263640;","Midlatitude tropopause and low-level moisture",2014,"10.1175/JAS-D-13-0154.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896790479&doi=10.1175%2fJAS-D-13-0154.1&partnerID=40&md5=5211b3c19d6ed2b38217de4c8335d64b","A new relationship between the surface distribution of equivalent potential temperature and the potential temperature at the tropopause is proposed. Using a Gaussian approximation for the distribution of equivalent potential temperature, the authors argue that the tropopause potential temperature is approximately given by the mean equivalent potential temperature at the surface plus twice its standard derivation. This relationship is motivated by the comparison of the meridional circulation on dry and moist isentropes. It is further tested using four reanalysis datasets: the Interim ECMWF Re-Analysis (ERA-Interim); the NCEP-Department of Energy (DOE) Reanalysis II; the NCEP Climate Forecast System Reanalysis; and the Twentieth-Century Reanalysis (20CR), version 2. The proposed relationship successfully captures the annual cycle of the tropopause for both hemispheres. The results are robust among different reanalysis datasets, albeit the 20CR tends to overestimate the tropopause potential temperature. Furthermore, the proposed mechanism also works well in obtaining the interannual variability (with climatological annual cycle removed) for Northern Hemisphere summer with an above-0.6 correlation across different reanalyses. On the contrary, this mechanism is rather weak in explaining the interannual variability in the Southern Hemisphere and no longer works for Northern Hemisphere wintertime. This work suggests the important role of the moist dynamics in determining the midlatitude tropopause. © 2014 American Meteorological Society."
"55030182900;35546188200;7005246023;25958614700;8669401600;","Soil moisture-temperature feedbacks at meso-scale during summer heat waves over Western Europe",2014,"10.1007/s00382-013-1794-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885935998&doi=10.1007%2fs00382-013-1794-9&partnerID=40&md5=c6b385ccd53b0ed7de94fd544cf7db2b","This paper investigates the impact of soil moisture-temperature feedback during heatwaves occurring over France between 1989 and 2008. Two simulations of the weather research and forecasting regional model have been analysed, with two different land-surface models. One resolves the hydrology and is able to simulate summer dryness, while the other prescribes constant and high soil moisture and hence no soil moisture deficit. The sensitivity analysis conducted for all heatwave episodes highlights different soil moisture-temperature responses (1) over low-elevation plains, (2) over mountains and (3) over coastal regions. In the plains, soil moisture deficit induces less evapotranspiration and higher sensible heat flux. This has the effect of heating the planetary boundary layer and at the same time of creating a general condition of higher convective instability and a slight increase of shallow cloud cover. A positive feedback is created which increases the temperature anomaly during the heatwaves. In mountainous regions, enhanced heat fluxes over dry soil reinforce upslope winds producing strong vertical motion over the mountain slope, first triggered by thermal convection. This, jointly to the instability conditions, favors convection triggering and produces clouds and precipitation over the mountains, reducing the temperature anomaly. In coastal regions, dry soil enhances land/sea thermal contrast, strengthening sea-breeze circulation and moist cold marine air advection. This damps the magnitude of the heatwave temperature anomaly in coastal areas, expecially near the Mediterranean coast. Hence, along with heating in the plains, soil dryness can also have a significant cooling effect over mountains and coastal regions due to meso-scale circulations. © 2013 Springer-Verlag Berlin Heidelberg."
"55344913800;6602524412;36615513300;23570158900;","The atmospheric general circulation in thermodynamical coordinates",2014,"10.1175/JAS-D-13-0173.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896777269&doi=10.1175%2fJAS-D-13-0173.1&partnerID=40&md5=502f6752a59db08c69d00219cb0e09b2","The zonal and meridional components of the atmospheric general circulation are used to define a global thermodynamic streamfunction in dry static energy versus latent heat coordinates. Diabatic motions in the tropical circulations and fluxes driven by midlatitude eddies are found to form a single, global thermodynamic cycle. Calculations based on the Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) dataset indicate that the cycle has a peak transport of 428 Sv (Sv ≡ [109 kgs-1). The thermodynamic cycle encapsulates a globally interconnected heat and water cycle comprising ascent of moist air where latent heat is converted into dry static energy, radiative cooling where dry air loses dry static energy, and a moistening branch where air is warmed and moistened. It approximately follows a tropical moist adiabat and is bounded by the Clausius-Clapeyron relationship for near-surface air. The variability of the atmospheric general circulation is related to ENSO events using reanalysis data from recent years (1979- 2009) and historical simulations from the EC-Earth Consortium (EC-Earth) coupled climate model (1850- 2005). The thermodynamic cycle in both EC-Earth and ERA-Interim widens and weakens with positive ENSO phases and narrows and strengthens during negative ENSO phases with a high correlation coefficient. Weakening in amplitude suggests a weakening of the large-scale circulation, while widening suggests an increase in mean tropical near-surface moist static energy. © 2014 American Meteorological Society."
"37110553500;35207500900;7402585191;","Influence of Indian Ocean subtropical dipole on spring rainfall over China",2014,"10.1002/joc.3732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900667724&doi=10.1002%2fjoc.3732&partnerID=40&md5=508f6e2f6bd99779e9fd822009bec504","This study investigates the influence of the South Indian Ocean subtropical dipole (IOSD) on spring (March-April-May; MAM) rainfall over central-eastern China (CEC) and its dynamic processes by using station observations of China, Met Office Hadley Centre SST data for the period 1951-2012 and European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data for the period 1958-2012. It is found that the IOSD event which peaks in the boreal winter can persist to the following spring, with strength slightly weakening. Boreal spring rainfall over CEC, i.e. the middle-lower reaches of Yangtze River, the Yellow River valley as well as regions between them, has a significant correlation with the IOSD event. When the positive (negative) IOSD event occurs in the previous winter, the CEC is dry (wet) in the spring. One of possible mechanisms that the IOSD affects the China spring rainfall is the modulation of the meridional circulation, especially the Hadley cell in the tropic along 100-120°E. In the positive IOSD years, associated with the cold sea surface temperature anomalies (SSTA) and warm SSTA in the southeastern Indian Ocean (SEIO) and southwestern Indian Ocean, there is anomalous ascent over the equatorial Indian Ocean, whereas downward flows over the SEIO and CEC. The Hadley cell over this region intensifies. Anomalous northerly wind at 850 hPa prevails, preventing wet and warm air flow from the low latitudes, which in turn transports less moisture into CEC and favours decreased rainfall. Meanwhile, the CEC is located at the sinking region of the Hadley cell. The atmosphere is fed by low moisture content over this area, also unfavourable for the occurrence of precipitation. This paper suggests that the SSTA in the southern Indian Ocean can be a good predictor for the China spring precipitation and proposes a possible mechanism for the connection of the mid-latitude climate variations of both hemispheres induced by air-sea interaction. © 2013 Royal Meteorological Society."
"35229110700;42861284000;13404087800;55933439400;7003346742;6602948135;6603768446;35568218100;","Analysis and hindcast simulations of an extreme rainfall event in the Mediterranean area: The Genoa 2011 case",2014,"10.1016/j.atmosres.2013.10.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887919544&doi=10.1016%2fj.atmosres.2013.10.007&partnerID=40&md5=98714e982feb8c4d840d74001235e87d","The city of Genoa, which places between the Tyrrhenian Sea and the Apennine mountains (Liguria, Italy) was rocked by severe flash floods on the 4th of November, 2011. Nearly 500. mm of rain, a third of the average annual rainfall, fell in six hours. Six people perished and millions of Euros in damages occurred. The synoptic-scale meteorological system moved across the Atlantic Ocean and into the Mediterranean generating floods that killed 5 people in Southern France, before moving over the Ligurian Sea and Genoa producing the extreme event studied here.Cloud-permitting simulations (1. km) of the finger-like convective system responsible for the torrential event over Genoa have been performed using Advanced Research Weather and Forecasting Model (ARW-WRF, version 3.3).Two different microphysics (WSM6 and Thompson) as well as three different convection closures (explicit, Kain-Fritsch, and Betts-Miller-Janjic) were evaluated to gain a deeper understanding of the physical processes underlying the observed heavy rain event and the model's capability to predict, in hindcast mode, its structure and evolution. The impact of forecast initialization and of model vertical discretization on hindcast results is also examined. Comparison between model hindcasts and observed fields provided by raingauge data, satellite data, and radar data show that this particular event is strongly sensitive to the details of the mesoscale initialization despite being evolved from a relatively large scale weather system. Only meso-γ details of the event were not well captured by the best setting of the ARW-WRF model and so peak hourly rainfalls were not exceptionally well reproduced. The results also show that specification of microphysical parameters suitable to these events have a positive impact on the prediction of heavy precipitation intensity values. © 2013."
"6503862357;55963198600;6508260037;7006499081;","Investigating aerosol properties in Peninsular Malaysia via the synergy of satellite remote sensing and ground-based measurements",2014,"10.1016/j.atmosres.2013.11.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890275428&doi=10.1016%2fj.atmosres.2013.11.018&partnerID=40&md5=5e668cd5ed2900bc6ca5855f76de84a4","Spatio-temporal variation and trends in atmospheric aerosols as well as their impact on solar radiation and clouds are crucial for regional and global climate change assessment. These topics are not so well-documented over Malaysia, the fact that it receives considerable amounts of pollutants from both local and trans-boundary sources. The present study aims to analyse the spatio-temporal evolution and decadal trend of Aerosol Optical Depth (AOD) from Terra and Aqua MODIS sensors, to identify different types and origin of aerosols and explore the link between aerosols and solar radiation. AOD and fine-mode fraction (FMF) products from MODIS, AOD and Ångström Exponent (AE) values from AERONET stations along with ground-based PM10 measurements and solar radiation recordings at selected sites in Peninsular Malaysia are used for this scope. The MODIS AODs exhibit a wide spatio-temporal variation over Peninsular Malaysia, while Aqua AOD is consistently lower than that from Terra. The AOD shows a neutral-to-declining trend during the 2000s (Terra satellite), while that from Aqua exhibits an increasing trend (~0.01 per year). AERONET AODs exhibit either insignificant diurnal variation or higher values during the afternoon, while their short-term availability does not allow for a trend analysis. Moreover, the PM10 concentrations exhibit a general increasing trend over the examined locations. The sources and destination of aerosols are identified via the HYSPLIT trajectory model, revealing that aerosols during the dry season (June to September) are mainly originated from the west and southwest (Sumatra, Indonesia), while in the wet season (November to March) they are mostly associated with the northeast monsoon winds from the southern China Sea. Different aerosol types are identified via the relationship of AOD with FMF, revealing that the urban and biomass-burning aerosols are the most abundant over the region contributing to a significant reduction (~-0.21MJm-2) of the solar radiation. © 2013 Elsevier B.V."
"7202057166;7005729142;","Observational quantification of the separation of simple and complex atmospheric ice particles",2014,"10.1002/2013GL058781","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893870452&doi=10.1002%2f2013GL058781&partnerID=40&md5=635883eea1351edd589a04fc56b995bf","The impact of ice clouds on weather and climate is a function of ice particle shape through light scattering properties and cloud lifetime through ice particle sedimentation rates. Many weather forecast and climate models use two categories to represent ice cloud particles: cloud ice and snow, though the distinction between particle categories is generally without observational justification. Improved characterization of cloud ice and snow as well as the transition between them will make models more realistic. An analysis of particle imagery data from high-resolution aircraft particle imaging probes indicates that atmospheric ice particles can easily be separated by particle complexity. In this work, a technique is described which enables the clear separation of vapor grown particles from aggregates of particles. When applied to two example data sets, the technique shows that the separation between these categories occurs at 150 and 250 microns, for two example data sets. Key Points Cloud ice and snow are separated based on observations ©2014. American Geophysical Union. All Rights Reserved."
"37032042300;7005287667;7005712238;35461255500;","A long-term satellite study of aerosol effects on convective clouds in Nordic background air",2014,"10.5194/acp-14-2203-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896832628&doi=10.5194%2facp-14-2203-2014&partnerID=40&md5=7f3cf43557be6b0bc726180c92f474f3","Aerosol-cloud interactions constitute a major uncertainty in future climate predictions. This study combines 10 years of ground-based aerosol particle measurements from two Nordic background stations (Vavihill and Hyytiälä) with MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data of convective clouds. The merged data are used to examine how aerosols affect cloud droplet sizes and precipitation from convective clouds over the Nordic countries. From the satellite scenes, vertical profiles of cloud droplet effective radius (re) are created by plotting retrieved cloud top re against cloud top temperature for the clouds in a given satellite scene. The profiles have been divided according to aerosol number concentrations but also meteorological reanalysis parameters from the ECMWF (European Centre for Medium-Range Forecasts). Furthermore, weather radar data from the BALTEX (Baltic Sea Experiment) and precipitation data from several ground-based meteorological measurement stations have been investigated to determine whether aerosols affect precipitation intensity and amount. Small re throughout the entire cloud profiles is associated with high aerosol number concentrations at both stations. However, aerosol number concentrations seem to affect neither the cloud optical thickness nor the vertical extent of the clouds in this study. Cloud profiles with no or little precipitation have smaller droplets than those with more precipitation. Moreover, the amount of precipitation that reaches the ground is affected by meteorological conditions such as the vertical extent of the clouds, the atmospheric instability and the relative humidity in the lower atmosphere rather than the aerosol number concentration. However, lower precipitation rates are associated with higher aerosol number concentrations for clouds with similar vertical extent. The combination of these ground-based and remote-sensing datasets provides a unique long-term study of the effects of aerosols on convective clouds over the Nordic countries."
"7003663939;56045376000;53363967500;56045237300;","Intensified land surface control on boundary layer growth in a changing climate",2014,"10.1002/2013GL058826","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894470543&doi=10.1002%2f2013GL058826&partnerID=40&md5=a7ff26e704932575d950070d62ea4456","Data from the Coupled Model Intercomparison Project Phase 5 for historical and future climate scenarios are examined for changes in the energy cycle component of land surface feedback on the atmosphere, namely, through the linkages from soil moisture to sensible heat flux to the height of the lifting condensation level marking the cloud base. Climate models project heightened sensitivity in both of these segments of the feedback pathway over most of the globe. This is in agreement with studies showing similar increases in land-atmosphere feedback through the water cycle, despite different physical processes, and may contribute to prevalent droughts and floods found in most climate change forecasts. Key Points Land-atmosphere feedback goes from soil moisture to sensible heat to PBL growth This feedback pathway is likely to strengthen in a warming climate Sensitivity to land use change and climate extremes may amplify in the future ©2014. American Geophysical Union. All Rights Reserved."
"36138641800;26635011200;7006206130;6507952158;","The impact of climate-vegetation interactions on the onset of the Antarctic ice sheet",2014,"10.1002/2013GL058994","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894256417&doi=10.1002%2f2013GL058994&partnerID=40&md5=49a2e24a62092cdacb0f41520da6019d","A global coupled atmosphere/vegetation model and a dynamic ice sheet model were employed to study the impact of climate-vegetation interactions on the onset of the Antarctic ice sheet during the Eocene-Oligocene transition. We found that the CO2 threshold for Antarctic glaciation is highly sensitive to the prevailing vegetation. In our experiments, the CO2 threshold is less than 280 ppm if the Antarctic vegetation is dominated by forests and between 560 and 1120 ppm for tundra and bare ground conditions. The large impact of vegetation on inception is attributed to the ability of canopies to shade the snow-covered ground, which leads to a weaker snow albedo feedback and higher summer temperatures. However, the overall effect of canopy shading on the Antarctic climate also depends on features like local cloudiness and atmospheric meridional heat transport. Our results suggest that vegetation feedbacks on climate are crucial for the timing of the Antarctic glaciation. Key Points The CO2 threshold for Antarctic glaciation is highly sensitive to vegetation Vegetation increases the surface temperature by shading the snow-covered ground The vegetation effect on the local climate is sensitive to the local cloudiness ©2014. American Geophysical Union. All Rights Reserved."
"7404471029;7005702722;8882641700;","A moisture budget perspective of the amount effect",2014,"10.1002/2013GL058302","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894257904&doi=10.1002%2f2013GL058302&partnerID=40&md5=48e5e3cc5155d46f4319c642eea7a56b","A stable water isotopologue-enabled cloud-resolving model was used to investigate the cause of the amount effect on the seasonal (or longer) time scales. When the total water (vapor and condensed phase) budget of the precipitating column of air is considered, our results indicate that as convection becomes stronger and the precipitation rate increases, the δD of precipitation (δDp) depends on the isotopic composition of the converged vapor more than that of surface evaporation. Tests with disabled fractionation from rain evaporation demonstrate that this mechanism does not account for the amount effect as has been previously suggested. If the isotopic content of converged vapor is made uniform with height with a value characteristic of surface evaporation, the amount effect largely disappears, further supporting the dominance of converged vapor in changes to the δDp signal with increasing precipitation. δDp values were compared to the water budget term EP, where P is precipitation and E is evaporation. Results from this comparison support the overall conclusion that moisture convergence is central in determining the value of δD p and the strength of the amount effect in steady state. Key Points Amount effect in tropics results from isotopic content of converged vapor Previous mechanisms are not as responsible for the rain signal as was thought Knowledge of the water budget and changes how isotopes are addressed in climate ©2013. American Geophysical Union. All Rights Reserved."
"54783781000;7004057920;","Climatology of aerosol and cloud optical properties at the atmospheric radiation measurements climate research facility barrow and atqasuk sites",2014,"10.1002/2013JD020296","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896948748&doi=10.1002%2f2013JD020296&partnerID=40&md5=a9a77e268e794bd2d6361b1dacd807c2","The long-term measurements at the Barrow and Atqasuk sites have been processed to develop the climatology of aerosol and cloud properties at interannual, seasonal, and diurnal temporal scales. At the Barrow site, the surface temperature exhibits an increasing trend in both thawed and frozen seasons over the period studied here, about one decade. Corresponding to the warming, the snow melting day arrives earlier, and the non-snow-cover duration increases. Aerosol optical depth increased during 2001–2003 and 2005–2009 and decreased during 2003–2005. The liquid water path (LWP), cloud optical depth (COD), and cloud fraction exhibit apparently decreasing trends from 2002 to 2007 and increased significantly after 2008. In the frozen season, the arctic haze and ice clouds are dominant, while in the thawed season, the oceanic biogenic aerosols and liquid water clouds or mixed-phase clouds are dominant. The cloud droplet effective radius during the thawed season is larger than that during the frozen season. The diurnal variations of aerosol and cloud-related atmospheric properties are not obvious at these two sites. During the sunshine periods, the aerosol has a cooling effect on the surface through direct aerosol radiative forcing. In the frozen season, clouds have a positive impact on the net surface radiation, and the water vapor path, LWP, and COD have good positive correlations with the surface temperature, suggesting that the cloud radiation feedback is positive. In the thawed season, clouds have a negative impact on the net surface radiation. © 2014. American Geophysical Union. All rights reserved."
"16639418500;36523706800;15069732800;57206531303;7004200407;","A surface radiation climatology across two Meteosat satellite generations",2014,"10.1016/j.rse.2013.11.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890284057&doi=10.1016%2fj.rse.2013.11.007&partnerID=40&md5=64d5e14587e5ea12bdb8e788a337c47f","Long-term observations of the surface radiation budget are essential for climate monitoring, climate model evaluation and solar energy applications. The Satellite Application Facility on Climate Monitoring (CM SAF) released a climate data record (CDR) of global and direct surface irradiance as well as effective cloud albedo derived from observations of the Meteosat First Generation satellites (MFG, 1983-2005). This study presents an extension of this CDR using measurements from the Meteosat Second Generation satellites (MSG, 2004-present). This extended surface radiation dataset spans nearly 30. years of data and, therefore, is in its uniquely high temporal and spatial resolution a valuable contribution to the climate community.In order to enable climatological consistency and homogeneity, the retrieval algorithm had to be modified for MSG: 1. The two narrowband visible channels of the MSG satellites are combined to simulate the MFG broadband visible channel; 2. The maximum cloud reflectance is empirically adjusted to account for the differences in the dynamic range of MSG compared to MFG.The extended dataset is tested for homogeneity and no significant breaks are detected during the overlap period of 2004-2005. Validation of the extended global radiation dataset against ground based observations from the Baseline Surface Radiation Network yields a mean monthly absolute bias of 8.15Wm-2. This complies with the target accuracy threshold of 15Wm-2 defined by the Global Climate Observing System.Global radiation has an overall positive, and significant, trend over the Meteosat disk which is mainly due to a negative trend in the effective cloud albedo, i.e., a decrease in cloudiness. Trends due to changes in the clear sky radiation are small and only induced by trends in the water vapor fields. Trends caused by changes in the direct effects of atmospheric aerosol are not represented because an aerosol climatology is used. © 2013."
"55823544000;57189595246;35365381300;","Severe cloud contamination of MODIS Land Surface Temperatures over an Arctic ice cap, Svalbard",2014,"10.1016/j.rse.2013.11.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890290162&doi=10.1016%2fj.rse.2013.11.005&partnerID=40&md5=e805bab95d850dc1a0d547c39aa6f630","Land Surface Temperature (LST) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) is among today's major tools for climate monitoring. After more than a decade of operation, there still remains considerable uncertainty about its performance in polar regions. We compare MODIS LST to eight years of in situ observations of surface and air temperatures on Austfonna, an Arctic ice cap located on Svalbard. From measurements of longwave radiation and air temperature, an in situ cloud index is derived to quantify the cloudiness at the study site and assess the possibility for LST being affected by erroneous cloud detection. According to this cloud index, only 26% of satellite-derived LST values are acquired under clear-sky conditions. In situations, when the cloud index indicates clouds, about 40% of the scenes are classified as clear-sky by MODIS during winter, while it is only about 20% in the summer period. The shortcomings of the MODIS cloud detection are reflected by a Root Mean Square Error (RMSE) of LST compared to in situ surface temperatures of 7.0. K under actual cloudy conditions, in contrast to 3.0. K under actual clear-sky conditions. The overall RMSEs of LST compared to surface and air temperatures are 5.3. K and 6.2. K, respectively. The bias under actual clear-sky conditions displays a clear seasonality, with MODIS LST being strongly cold-biased during winter and slightly warm-biased during summer. The study exemplifies the challenges of thermal remote sensing over snow and ice surface in areas with frequent cloudiness, especially during polar night. Nevertheless, remotely sensed LST offers a great, but hitherto largely unexploited opportunity for environmental monitoring in regions with sparse observations, in particular if the cloud detection can be improved. © 2013 Elsevier Inc."
"6603494167;6603037832;7103333830;","Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties",2014,"10.5194/amt-7-637-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896828536&doi=10.5194%2famt-7-637-2014&partnerID=40&md5=3f508c16c2e659597619727533abe0c1","This paper describes the All Sky Infrared Visible Analyzer (ASIVA), a multi-purpose visible and infrared sky imaging and analysis instrument whose primary function is to provide radiometrically calibrated imagery in the mid-infrared (mid-IR) atmospheric window. This functionality enables the determination of diurnal fractional sky cover and estimates of sky/cloud temperature from which one can derive estimates of sky/cloud emissivity and cloud height. This paper describes the calibration methods and performance of the ASIVA instrument with particular emphasis on data products being developed for the meteorological community. Data presented here were collected during the Solmirus' ASIVA campaign conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Climate Research Facility from 21 May to 27 July 2009. The purpose of this campaign was to determine the efficacy of IR technology in providing reliable nighttime sky cover data. Significant progress has been made in the analysis of the campaign data over the past several years and the ASIVA has proven to be an excellent instrument for determining sky cover as well as the potential for determining sky/cloud temperature, sky/cloud emissivity, precipitable water vapor (PWV), and ultimately cloud height.©Author(s) 2014."
"36816004800;7101800802;","TopoSCALE v.1.0: Downscaling gridded climate data in complex terrain",2014,"10.5194/gmd-7-387-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896873312&doi=10.5194%2fgmd-7-387-2014&partnerID=40&md5=0ec8c4470e1d2d358f49a69092f3d2a4","Simulation of land surface processes is problematic in heterogeneous terrain due to the the high resolution required of model grids to capture strong lateral variability caused by, for example, topography, and the lack of accurate meteorological forcing data at the site or scale it is required. Gridded data products produced by atmospheric models can fill this gap, however, often not at an appropriate spatial resolution to drive land-surface simulations. In this study we describe a method that uses the well-resolved description of the atmospheric column provided by climate models, together with high-resolution digital elevation models (DEMs), to downscale coarse-grid climate variables to a fine-scale subgrid. The main aim of this approach is to provide high-resolution driving data for a land-surface model (LSM). The method makes use of an interpolation of pressure-level data according to topographic height of the subgrid. An elevation and topography correction is used to downscale short-wave radiation. Long-wave radiation is downscaled by deriving a cloud-component of all-sky emissivity at grid level and using downscaled temperature and relative humidity fields to describe variability with elevation. Precipitation is downscaled with a simple non-linear lapse and optionally disaggregated using a climatology approach. We test the method in comparison with unscaled grid-level data and a set of reference methods, against a large evaluation dataset (up to 210 stations per variable) in the Swiss Alps. We demonstrate that the method can be used to derive meteorological inputs in complex terrain, with most significant improvements (with respect to reference methods) seen in variables derived from pressure levels: air temperature, relative humidity, wind speed and incoming long-wave radiation. This method may be of use in improving inputs to numerical simulations in heterogeneous and/or remote terrain, especially when statistical methods are not possible, due to lack of observations (i.e. remote areas or future periods)."
"55765742100;24400381400;6701823396;","Characteristics of arctic low-tropospheric humidity inversions based on radio soundings",2014,"10.5194/acp-14-1959-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894424304&doi=10.5194%2facp-14-1959-2014&partnerID=40&md5=f16ca81cbfbe67eba5599f0c5d5fe766","Humidity inversions have a high potential importance in the Arctic climate system, especially for cloud formation and maintenance, in wide spatial and temporal scales. Here we investigate the climatology and characteristics of humidity inversions in the Arctic, including their spatial and temporal variability, sensitivity to the methodology applied and differences from the Antarctic humidity inversions. The study is based on data of the Integrated Global Radiosonde Archive (IGRA) from 36 Arctic stations between the years 2000 and 2009. The results indicate that humidity inversions are present on multiple levels nearly all the time in the Arctic atmosphere. Almost half (48%) of the humidity inversions were found at least partly within the same vertical layer with temperature inversions, whereas the existence of the other half may, at least partly, be linked to uneven vertical distribution of horizontal moisture transport. A high atmospheric surface pressure was found to increase the humidity inversion occurrence, whereas relationships between humidity inversion properties and cloud cover were generally relatively weak, although for some inversion properties they were systematic. For example, humidity inversions occurred slightly more often and were deeper under clear sky than in overcast conditions for almost all stations. The statistics of Arctic humidity inversion properties, especially inversion strength, depth and base height, proved to be very sensitive to the instruments and methodology applied. For example, the median strength of the strongest inversion in a profile was twice as large as the median of all Arctic inversions. The most striking difference between the Arctic and Antarctic humidity inversions was the much larger range of the seasonal cycle of inversion properties in the Arctic. Our results offer a baseline for validation of weather prediction and climate models and also encourage further studies on humidity inversions due to the vital, but so far poorly understood, role of humidity inversions in Arctic cloud processes. © 2014 Author (s)."
"7103246957;7102933062;15830822000;7410340979;37661669600;","Coupling of winter climate transitions to snow and clouds over the Prairies",2014,"10.1002/2013JD021168","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898975134&doi=10.1002%2f2013JD021168&partnerID=40&md5=cf4d5328e16c2ffd7e36c73f1c88bb4a","Using data from 13 climate stations on the Canadian Prairies, together with opaque cloud cover and daily snow depth, to analyze the winter climate transitions with snow, we find that a snow cover acts as a fast climate switch. Surface temperature falls by about 10 K with fresh snowfall and rises by a similar amount with snowmelt, while the daily range of relative humidity falls to around 5–15% with snow cover. These are robust climate signals. For every 10% decrease in days with snow cover over the Canadian Prairies, the mean October to April climate is warmer by about 1.4 K. Stratifying by daily mean opaque cloud cover across snow transitions shows the rapid shift within 5 days from a diurnal cycle dominated by shortwave cloud forcing to one dominated by longwave cloud forcing. We calculate the change in the surface radiative budget with snow using surface albedo data from the Moderate Resolution Imaging Spectroradiometer and station longwave data. We find that with the fall-winter snow transitions, the surface radiative heating is reduced by 50 Wm-2, with 69% coming from the reduced net shortwave flux, resulting from the increased surface albedo and a small increase in effective cloud albedo, and 31% from a reduced incoming longwave flux. This drop in surface radiative heating is sufficient to produce a drop in the surface radiometric skin temperature of 11 K. We find that in winter, the monthly mean diurnal climate is more closely coupled to the diurnal shortwave forcing than the mean diurnal climate. © 2014. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"55742914900;7501627905;7005304841;7102913661;55510783800;","The responses of cloudiness to the direct radiative effect of sulfate and carbonaceous aerosols",2014,"10.1002/2013JD020529","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898965794&doi=10.1002%2f2013JD020529&partnerID=40&md5=a087e3fb9ec604c438922f5d5acb16fb","This study investigates the responses of the direct radiative effect of light absorbing and scattering carbonaceous and sulfate aerosols on cloudiness and associated radiative fluxes using an interactive aerosol-climate model coupled with a slab ocean model. We find that without including the impact of aerosols on cloud microphysics in the model (indirect effect), the direct radiative effect of aerosols alone can cause a change in cloud coverage and thus in cloud flux change which is consistent with several previous studies. More notably, our result indicates that the direct radiative effect of absorbing aerosols can cause changes in both low-level and high-level clouds with opposite signs. As a result, the global mean cloud radiation response to absorbing aerosols has a rather small value. The change of cloud solar radiative response (all-sky effect minus clear-sky effect) at the top of the atmosphere due to the existence of direct radiative effect of scattering, absorbing, and both types of aerosols is 0.72, 0.08, and 0.81 Wm2, respectively, all are comparable in quantity to the current estimation of aerosol direct radiative forcing. The cloud response due to the longwave radiative effect is 0.09, 0.18, and 0.27 Wm2, respectively. The global means of the radiative flux and cloud radiative responses appear to be linearly additive; however, this is definitely not the case for the zonal mean or at the regional scale. © 2014. American Geophysical Union. All Rights Reserved."
"55723061900;35849722200;","Can we modify stratospheric water vapor by deliberate cloud seeding?",2014,"10.1002/2013JD020707","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898995553&doi=10.1002%2f2013JD020707&partnerID=40&md5=991e130260583470ea5de443343b3789","Stratospheric water vapor has an important effect on Earth’s climate. Considering the significance of overshooting deep convection in modulating the water vapor content (WVC) of the lower stratosphere (LS), we use a three-dimensional convective cloud model to simulate the effects of various silver iodide (AgI) seeding scenarios on tropical overshooting deep convection that occurred on 30 November 2005 in Darwin, Australia. The primary motivation for this study is to investigate whether the WVC in the LS can be artificially modified by deliberate cloud seeding. It is found that AgI seeding done at the early stages of clouds produces significant effects on cloud microphysical and dynamical properties, and that further affects the WVC in the LS, while seeding at the mature stages of clouds has only a slight impact. The response of stratospheric water vapor to changes in the amount of seeding agent is nonlinear. The seeding with a small (large) amount of AgI increases (decreases) the WVC in the LS, due to enhanced (reduced) production and vertical transport of cloud ice from the troposphere and subsequent sublimation in the stratosphere. The results show that stratospheric water vapor can be artificially altered by deliberate cloud seeding with proper amount of seeding agent. This study also shows an important role of graupel in regulating cloud microphysics and dynamics and in modifying the WVC in the LS. © 2014. American Geophysical Union. All Rights Reserved."
"55893823700;26431001200;57203030873;57202754759;7102976560;","Can regional climate engineering save the summer Arctic sea ice?",2014,"10.1002/2013GL058731","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893169522&doi=10.1002%2f2013GL058731&partnerID=40&md5=4cb2be24f24f4d17ddfb9c79379b5007","Rapid declines in summer Arctic sea ice extent are projected under high-forcing future climate scenarios. Regional Arctic climate engineering has been suggested as an emergency strategy to save the sea ice. Model simulations of idealized regional dimming experiments compared to a business-as-usual greenhouse gas emission simulation demonstrate the importance of both local and remote feedback mechanisms to the surface energy budget in high latitudes. With increasing artificial reduction in incoming shortwave radiation, the positive surface albedo feedback from Arctic sea ice loss is reduced. However, changes in Arctic clouds and the strongly increasing northward heat transport both counteract the direct dimming effects. A 4 times stronger local reduction in solar radiation compared to a global experiment is required to preserve summer Arctic sea ice area. Even with regional Arctic dimming, a reduction in the strength of the oceanic meridional overturning circulation and a shut down of Labrador Sea deep convection are possible. Key Points A large amount of solar dimming of 13% is required to save the sea ice Compensating changes in local and remote energy fluxes are important Meridional Overturning Circulation would be still reduced ©2014. The Authors."
"7102875574;36809017200;7003971889;9246029600;37861539400;","The dependence of transient climate sensitivity and radiative feedbacks on the spatial pattern of ocean heat uptake",2014,"10.1002/2013GL058955","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893852494&doi=10.1002%2f2013GL058955&partnerID=40&md5=56ea0b2b85224cefce8ab62c1205da93","The effect of ocean heat uptake (OHU) on transient global warming is studied in a multimodel framework. Simple heat sinks are prescribed in shallow aquaplanet ocean mixed layers underlying atmospheric general circulation models independently and combined with CO2 forcing. Sinks are localized to either tropical or high latitudes, representing distinct modes of OHU found in coupled simulations. Tropical OHU produces modest cooling at all latitudes, offsetting only a fraction of CO2 warming. High-latitude OHU produces three times more global mean cooling in a strongly polar-amplified pattern. Global sensitivities in each scenario are set primarily by large differences in local shortwave cloud feedbacks, robust across models. Differences in atmospheric energy transport set the pattern of temperature change. Results imply that global and regional warming rates depend sensitively on regional ocean processes setting the OHU pattern, and that equilibrium climate sensitivity cannot be reliably estimated from transient observations. Key Points Climate response depends strongly on spatial pattern of ocean heat uptake Different radiative feedbacks govern transient and equilibrium CO2 warming Results are robust across an ensemble of aquaplanet climate models ©2014. American Geophysical Union. All Rights Reserved."
"36621776000;7003836546;8372868700;24437444900;22635944500;6507607421;7005219614;","Impact of natural aerosols on atmospheric radiation and consequent feedbacks with the meteorological and photochemical state of the atmosphere",2014,"10.1002/2013JD020714","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899017647&doi=10.1002%2f2013JD020714&partnerID=40&md5=fb46e8ff75a96d6c49d20c532048e4d8","This paper addresses the aerosol effects on radiation and the feedback on meteorology and photochemical activity, applying the online model RAMS/ICLAMS. The model treats meteorology and chemical pollutants on an interactive way. Cloud condensation nuclei (CCN), giant cloud condensation nuclei, and ice nuclei are treated as predictive quantities. The calculation of the aerosol optical properties accounts for size-resolved mineral dust and size- and humidity-dependent optical properties of sea salt. The simulations with and without aerosol impacts reveal the complex direct and indirect mechanisms through which the alteration of radiation fluxes influences meteorology and photochemical processes. For the specific dust event, the reduction in the surface shortwave radiation over cloudless regions affected by dust averages at ~ -75 W m-2 at 12:00 UTC per unit dust loading (1 g m-2). The increase on downwelling longwave radiation over the same areas and time averages at ~ 40 W m-2 per unit dust loading (1 g m-2). Surface upwelling longwave radiation over Mediterranean exhibits a complex daytime behavior. During midnight, the inclusion of dust leads to larger upwelling longwave radiation fluxes over the African continent. The net downward longwave radiation over cloudless areas exhibits an increase both during noon and midnight with the inclusion of dust. The results show that the vertical structure of the dust layer governs the magnitude of the feedback on radiation. The activation of natural particles as CCN causes small changes in radiation fluxes and temperature. Precipitation is influenced more by the indirect rather than the direct and semidirect effects. © 2013. American Geophysical Union. All Rights Reserved."
"35180334400;8570871900;57203030873;","Diagnosing shortwave cryosphere radiative effect and its 21st century evolution in CESM",2014,"10.1002/2013JD021139","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899001981&doi=10.1002%2f2013JD021139&partnerID=40&md5=cfed351dd01199bf08cea852a694cb06","We incorporate a new diagnostic called the cryosphere radiative effect (CrRE), the instantaneous influence of surface snow and sea ice on the top-of-model solar energy budget, into two released versions of the Community Earth System Model (CESM1 and CCSM4). CrRE offers a more climatically relevant metric of the cryospheric state than snow and sea ice extent and is influenced by factors such as the seasonal cycle of insolation, cloud masking, and vegetation cover. We evaluate CrRE during the late 20th century and over the 21st century, specifically diagnosing the nature of CrRE contributions from terrestrial and marine sources. The radiative influence of ice sheets and glaciers is not considered, but snow on top of them is accounted for. Present-day global CrRE in both models is -3.8 W m2, with a boreal component (-4.2 to -4.6 W m-2) that compares well with observationally derived estimates (-3.9 to -4.6 W m-2). Similar present-day CrRE in the two model versions results from compensating differences in cloud masking and sea ice extent. Over the 21st century, radiative forcing in the Representative Concentration Pathway (RCP) 8.5 scenario causes reduced boreal sea ice cover, austral sea ice cover, and boreal snow cover, which all contribute roughly equally to enhancing global absorbed shortwave radiation by 1.4–1.8 Wm-2. Twenty-first century RCP8.5 global cryospheric albedo feedback are +0.41 and +0.45 W/m-2/K, indicating that the two models exhibit similar temperature-normalized CrRE change. © 2014. American Geophysical Union. All Rights Reserved."
"26533129200;57205479655;56122121300;7006329853;7202043942;56604618200;7402938522;","The contribution of anthropogenic SO2 emissions to the Asian tropopause aerosol layer",2014,"10.1002/2013JD020578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898979944&doi=10.1002%2f2013JD020578&partnerID=40&md5=27c864ceab94d6b93127869e5f3f3bc5","Recent observations reveal a seasonally occurring layer of aerosol located from 0° to 100° E, 20° to 45° N and extending vertically from about 13 km to 18 km; this has been termed the Asian tropopause aerosol layer (ATAL), and its existence is closely associated with the Asian summer monsoon circulation. Observational studies argue that the ATAL is a recent phenomenon, as the layer is not observed in the satellite record prior to 1998. This suggests that the ATAL may be of anthropogenic origin associated with a shift in the dominant regional emission of sulfur dioxide (SO2) to China and India in the late 1990s. Here we test the hypothesis that SO2 emitted from Asia led to the formation of the ATAL using an aerosol microphysical model coupled to a global chemistry climate model. This is the first modeling study to specifically examine the ATAL and its possible origin. From our results, we conclude that the ATAL is most likely due to anthropogenic emissions, but its source cannot solely be attributed to emissions from Asia. Specifically, the results indicate that Chinese and Indian emissions contribute ∼30% of the sulfate aerosol extinction in the ATAL during volcanically quiescent periods. We also show that even small volcanic eruptions preclude our ability to make any conclusions about the existence of the ATAL before 1998 with observations alone. © 2014. American Geophysical Union. All Rights Reserved."
"6602081215;7102603429;7101653556;6603107733;9044746800;56218570500;56037464300;","Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements",2014,"10.5194/acp-14-1649-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894088628&doi=10.5194%2facp-14-1649-2014&partnerID=40&md5=566a3689ec7a3aad2d1f13e843717cc2","The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed-phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light-scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed-phase and cirrus clouds. The patterns are analysed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light-scattering properties and also similar causes. Overall, the in situ data are consistent, with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic air masses than in a continental, polluted one. Overall, the roughness and complexity are expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity. © 2014 Author(s). CC Attribution 3.0 License."
"36559769700;7202967741;55634652600;7409117673;7006978226;","Sources and light absorption of water-soluble organic carbon aerosols in the outflow from northern China",2014,"10.5194/acp-14-1413-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893864853&doi=10.5194%2facp-14-1413-2014&partnerID=40&md5=53adc36000b8b67dc579e420547393e9","High loadings of anthropogenic carbonaceous aerosols in Chinese air influence the air quality for over one billion people and impact the regional climate. A large fraction (17-80%) of this aerosol carbon is water-soluble, promoting cloud formation and thus climate cooling. Recent findings, however, suggest that water-soluble carbonaceous aerosols also absorb sunlight, bringing additional direct and indirect climate warming effects, yet the extent and nature of light absorption by this water-soluble ""brown carbon"" and its relation to sources is poorly understood. Here, we combine source estimates constrained by dual carbon isotopes with light-absorption measurements of water-soluble organic carbon (WSOC) for a March 2011 campaign at the Korea Climate Observatory at Gosan (KCOG), a receptor station in SE Yellow Sea for the outflow from northern China. The mass absorption cross section at 365 nm (MAC365) of WSOC for air masses from N. China were in general higher (0.8-1.1 m2 g-1), than from other source regions (0.3-0.8 m2 g-1). However, this effect corresponds to only 2-10% of the radiative forcing caused by light absorption by elemental carbon. Radiocarbon constraints show that the WSOC in Chinese outflow had significantly higher fraction fossil sources (30-50%) compared to previous findings in S. Asia, N. America and Europe. Stable carbon (δ13C) measurements were consistent with aging during long-range air mass transport for this large fraction of carbonaceous aerosols. © 2014 Author(s)."
"24576706500;7005449794;","Regional climate modeling over the maritime continent. Part I: New parameterization for convective cloud fraction",2014,"10.1175/JCLI-D-13-00127.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893867008&doi=10.1175%2fJCLI-D-13-00127.1&partnerID=40&md5=953eecb577dfa42ee5015864fd27cb88","This paper describes a new method for parameterizing convective cloud fraction that can be used within large-scale climate models, and evaluates the new method using the Regional Climate Model, version 3 (RegCM3), coupled to the land surface scheme Integrated Biosphere Simulator (IBIS). The horizontal extent of convective cloud cover is calculated by utilizing a relationship between the simulated amount of convective cloud water and typical observations of convective cloud water density. This formulation not only provides a physically meaningful basis for the simulation of convective cloud cover, but it is also spatially and temporally variable and independent of model resolution, rendering it generally applicable for large-scale climate models. Simulations over the Maritime Continent show that the new method allows for simulation of an essential convective-radiative feedback, which was absent in the existing version of RegCM3-IBIS, such that moist convection not only responds to diurnal variability at the earth's surface but also impacts the solar radiation received at the surface via cumulus cloud production. The impact on model performance was mixed, but it is considered that appropriate representation of the convective-radiative feedback and improved physical realism resulting from the new cloud fraction parameterization will likely have positive benefits elsewhere. The role of convective rainfall production in the convective-radiative feedback and a new parameterization for convective autoconversion are addressed in Part II of this paper series. © 2014 American Meteorological Society."
"28367935500;7201504886;7201627869;8696069500;","Compensation of hemispheric albedo asymmetries by shifts of the ITCZ and tropical clouds",2014,"10.1175/JCLI-D-13-00205.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893189880&doi=10.1175%2fJCLI-D-13-00205.1&partnerID=40&md5=7f484d657901761985076718bb0ef55c","Despite a substantial hemispheric asymmetry in clear-sky albedo, observations of Earth's radiation budget reveal that the two hemispheres have the same all-sky albedo. Here, aquaplanet simulations with the atmosphere general circulation model ECHAM6 coupled to a slab ocean are performed to study to what extent and by which mechanisms clouds compensate hemispheric asymmetries in clear-sky albedo. Clouds adapt to compensate the imposed asymmetries because the intertropical convergence zone (ITCZ) shifts into the dark surface hemisphere. The strength of this tropical compensation mechanism is linked to the magnitude of the ITCZ shift. In some cases the ITCZ shift is so strong as to overcompensate the hemispheric asymmetry in clear-sky albedo, yielding a range of climates for which the hemisphere with lower clear-sky albedo has a higher all-sky albedo. The ITCZ shift is sensitive to the convection scheme and the depth of the slab ocean. Cloud-radiative feedbacks explain part of the sensitivity to the convection scheme as they amplify the ITCZ shift in the Tiedtke (TTT) scheme but have a neutral effect in the Nordeng (TNT) scheme. A shallower slab ocean depth, and thereby reduced thermal inertia of the underlying surface and increased seasonal cycle, stabilizes the ITCZ against annual-mean shifts. The results lend support to the idea that the climate system adjusts so as to minimize hemispheric albedo asymmetries, although there is no indication that the hemispheres must have exactly the same albedo. © 2014 American Meteorological Society."
"24178522800;6701659989;","Land-sea contrast, soil-atmosphere and cloud-temperature interactions: Interplays and roles in future summer European climate change",2014,"10.1007/s00382-013-1868-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895045422&doi=10.1007%2fs00382-013-1868-8&partnerID=40&md5=3694e04ace992dd63ca15e6afc303ac5","Europe and in particular its southern part are expected to undergo serious climate changes during summer in response to anthropogenic forcing, with large surface warming and decrease in precipitation. Yet, serious uncertainties remain, especially over central and western Europe. Several mechanisms have been suggested to be important in that context but their relative importance and possible interplays are still not well understood. In this paper, the role of soil-atmosphere interactions, cloud-temperature interactions and land-sea warming contrast in summer European climate change and how they interact are analyzed. Models for which evapotranspiration is strongly limited by soil moisture in the present climate are found to tend to simulate larger future decrease in evapotranspiration. Models characterized by stronger present-day anti-correlation between cloud cover and temperature over land tend to simulate larger future decrease in cloud cover. Large model-to-model differences regarding land-sea warming contrast and its impacts are also found. Warming over land is expected to be larger than warming over sea, leading to a decrease in continental relative humidity and precipitation because of the discrepancy between the change in atmospheric moisture capacity over land and the change in specific humidity. Yet, it is not true for all the models over our domain of interest. Models in which evapotranspiration is not limited by soil moisture and with a weak present-day anti-correlation between cloud cover and temperature tend to simulate smaller land surface warming. In these models, change in specific humidity over land is therefore able to match the continental increase in moisture capacity, which leads to virtually no change in continental relative humidity and smaller precipitation change. Because of the physical links that exist between the response to anthropogenic forcing of important impact-related climate variables and the way some mechanisms are simulated in the context of present-day variability, this study suggests some potentially useful metrics to reduce summer European climate change uncertainties. © 2013 Springer-Verlag Berlin Heidelberg."
"24576706500;7005449794;","Regional climate modeling over the maritime continent. Part II: New parameterization for autoconversion of convective rainfall",2014,"10.1175/JCLI-D-13-00171.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893862913&doi=10.1175%2fJCLI-D-13-00171.1&partnerID=40&md5=9f6dac99cb941ff6df03b32c1f2f8b6a","This paper describes a new method for parameterizing the conversion ofconvective cloud liquid water to rainfall (""autoconversion"") that can be used within large-scale climate models, and evaluates the new method using the Regional Climate Model, version 3 (RegCM3), coupled to the land surfacescheme Integrated Biosphere Simulator (IBIS). The new method is derived from observed distributions of cloud water content and is constrained by observations of cloud droplet characteristics and climatological rainfall intensity. This new method explicitly accounts for subgrid variability with respect to cloud water density and is independent of model resolution, making itgenerally applicable for large-scale climate models. This work builds on the development of a new parameterization method for convective cloud fraction, which was described in Part I. Simulations over the Maritime Continent using the Emanuel convection scheme show significant improvement in model performance, not only with respect to convective rainfall but also in shortwave radiation, net radiation, and turbulent surface fluxes of latent and sensible heat, without any additional modifications made to the simulation of those variables. Model improvements are demonstrated over a 19-yr validation period as well as a shorter 4-yr evaluation. Model performance with the Grell convection scheme is not similarly improved and reasons for this outcome are discussed. This work illustrates the importance of representing observed subgrid-scale variability in diurnally varying convective processes for simulations of the Maritime Continent region. © 2014 American Meteorological Society."
"7006550762;7004935827;16304488000;","The impact of different absolute solar irradiance values on current climate model simulations",2014,"10.1175/JCLI-D-13-00136.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893184752&doi=10.1175%2fJCLI-D-13-00136.1&partnerID=40&md5=cbbb5012be7f2967a445979752200ec5","Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.4°C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model's depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value. © 2014 American Meteorological Society."
"55431666500;16029674800;7202208382;36011145800;6601970557;","Simulation of the South Asian monsoon in a coupled model with an embedded cloud-resolving model",2014,"10.1175/JCLI-D-13-00257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893185906&doi=10.1175%2fJCLI-D-13-00257.1&partnerID=40&md5=795a80ea30305728dc07a785dcbda96c","The simulation of the South Asian monsoon by a coupled ocean-atmosphere model with an embedded cloud-resolving model is analyzed on intraseasonal and interannual time scales. The daily modes of variability in the superparameterized Community Climate System Model, version 3 (SP-CCSM), are compared with those in observation, the superparameterized Community Atmospheric Model, version 3 (SP-CAM3), and the control simulation of CCSM (CT-CCSM) with conventional parameterization of convection. The CT-CCSM fails to simulate the observed intraseasonal oscillations but is able to generate the atmospheric El Niño-Southern Oscillation (ENSO) mode, although with regular biennial variability. The dominant modes of variability extracted from daily anomalies of outgoing longwave radiation, precipitation, and low-level horizontal wind in SP-CCSM consist of two intraseasonal oscillations and two seasonally persisting modes, in good agreement with observation. The most significant observed features of the intraseasonal oscillations correctly simulated by the SP-CCSM are the northward propagation of convection, precipitation, and circulation as well as the eastward and westward propagations. The observed spatial structure and the periods of the oscillations are also well captured by the SP-CCSM, although with lesser magnitude. The SP-CCSM is able to simulate the chaotic variability and spatial structure of the seasonally persisting atmospheric ENSO mode,while the evidence for the Indian Ocean dipole mode is inconclusive. The SP-CAM3 simulates two intraseasonal oscillations and the atmospheric ENSO mode.However, the intraseasonal oscillations in SP-CAM3 do not show northward propagation while their periods and spatial structures are not comparable to observation. The results of this study indicate the necessity of coupled models with sufficiently realistic cloud parameterizations. © 2014 American Meteorological Society."
"7005729142;7003865921;26028515700;7202016984;6506458269;26643615000;7005433221;57204302411;","Relationships between ice water content and volume extinction coefficient from in situ observations for temperatures from 0° to -86°C: Implications for spaceborne lidar retrievals",2014,"10.1175/JAMC-D-13-087.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897584981&doi=10.1175%2fJAMC-D-13-087.1&partnerID=40&md5=b1d3407b28847109991cb2ecb2119126","An examination of 2 yr of Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) lidar observations and CloudSat cloud radar observations shows that ice clouds at temperatures below about -45°C frequently fall below the CloudSat radar's detection threshold yet are readily detectable by the lidar. The CALIPSO ice water content (IWC) detection threshold is about 0.1 versus 5mg m-3 for CloudSat. This comparison emphasizes the need for developing a lidar-only IWC retrieval method that is reliable for high-altitude ice clouds at these temperatures in this climatically important zone of the upper troposphere. Microphysical measurements from 10 aircraft field programs, spanning latitudes from the Arctic to the tropics and temperatures from -86° to 0°C, are used to develop relationships between the IWC and volume extinction coefficient s in visible wavelengths. Relationships used to derive a radiatively important ice cloud property, the ice effective diameter De, from σ are also developed. Particle size distributions (PSDs) and direct IWC measurements, together with evaluations of the ice particle shapes and comparisons with semidirect extinction measurements, are used in this analysis. Temperature-dependent De(σ) and IWC-σ relationships developed empirically facilitate the retrieval of IWC from lidar-derived σ and De values and for comparison with other IWC observations. This suite of empirically derived relationships can be expressed analytically. These relationships can be used to derive IWC and De from σ and are developed for use in climate models to derive σ from prognosed values of IWC and specified PSD properties. © 2014 American Meteorological Society."
"56032511300;55522563200;23035769400;7003842561;6701718281;","Effect of aerosol pollution on clouds and its dependence on precipitation intensity",2014,"10.1007/s00382-013-1898-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894997589&doi=10.1007%2fs00382-013-1898-2&partnerID=40&md5=634e11ba6ba2a8062ed20f44ccf021f4","In this study, simulations performed with a large-eddy resolving numerical model are used to examine the effect of aerosol on cumulus clouds, and how this effect varies with precipitation intensity. By systematically varying the surface moisture fluxes, the modeled precipitation rate is forced to change from weak to strong intensity. For each of these intensities, simulations of a high-aerosol case (a polluted case with a higher aerosol concentration) and a low-aerosol case (a clean case with a lower aerosol concentration) are performed. Whether or not precipitation and associated sub-cloud evaporation and convective available potential energy (CAPE) are large, liquid-water path (LWP) is larger in the high-aerosol case than in the low-aerosol case over the first two-thirds of the entire simulation period. In weak precipitation cases, reduction in aerosol content leads to changes in CAPE in the middle parts of cloud layers, which in turn induces larger LWP in the low-aerosol case over the last third of the simulation period. With strong precipitation, stronger stabilization of the sub-cloud layers in the low-aerosol case counters the CAPE changes in the middle parts of cloud layers, inducing smaller LWP in the low-aerosol case over the last third of the simulation period. The results highlight an interaction between aerosol effects on CAPE above cloud base and those in sub-cloud layers, and indicate the importance of a consideration of aerosol effects on CAPE above cloud base as well as those in sub-cloud layers. In the high-aerosol case, near the beginning of the simulation period, larger environmental CAPE does not necessarily lead to larger in-cloud CAPE and associated larger cloud intensity because aerosol-induced increase in cloud population enhances competition among clouds for the environmental CAPE. This demonstrates the importance of the consideration of cloud population for an improved parameterization of convective clouds in climate models. © 2013 Springer-Verlag Berlin Heidelberg."
"7401559092;6701741264;56083793400;","A quantitative evaluation of the public response to climate engineering",2014,"10.1038/nclimate2087","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896869033&doi=10.1038%2fnclimate2087&partnerID=40&md5=ca371eac2a896a3a1cdda9bdc96aa347","Atmospheric greenhouse gas concentrations continue to increase, with CO 2 passing 400 parts per million in May 2013. To avoid severe climate change and the attendant economic and social dislocation, existing energy efficiency and emissions control initiatives may need support from some form of climate engineering. As climate engineering will be controversial, there is a pressing need to inform the public and understand their concerns before policy decisions are taken. So far, engagement has been exploratory, small-scale or technique-specific. We depart from past research to draw on the associative methods used by corporations to evaluate brands. A systematic, quantitative and comparative approach for evaluating public reaction to climate engineering is developed. Its application reveals that the overall public evaluation of climate engineering is negative. Where there are positive associations they favour carbon dioxide removal (CDR) over solar radiation management (SRM) techniques. Therefore, as SRM techniques become more widely known they are more likely to elicit negative reactions. Two climate engineering techniques, enhanced weathering and cloud brightening, have indistinct concept images and so are less likely to draw public attention than other CDR or SRM techniques. © 2014 Macmillan Publishers Limited."
"24329376600;7003976079;","Cloud feedbacks, rapid adjustments, and the forcing-response relationship in a transient CO2 reversibility scenario",2014,"10.1175/JCLI-D-13-00421.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893829965&doi=10.1175%2fJCLI-D-13-00421.1&partnerID=40&md5=b6d40fd0aae4b5d842401acd14f81e0b","The Hadley Centre Global Environment Model, version 2-Earth System (HadGEM2-ES) climate model is forced by a 1%yr-1 compound increase in atmospheric CO2 for 140 years, followed by a 1%yr-1 CO2 decrease back to the starting level. Analogous atmosphere-only simulations are performed to diagnose the component of change associated with the effective radiative forcing and rapid adjustments. The residual change is associated with radiative feedbacks that are shown to be linearly related to changes in global-mean surface air temperature and are found to be reversible under this experimental design, even for regional cloud feedback changes. The cloud adjustment is related to changes in cloud amount, with little indication of any large-scale changes in cloud optical depth. Plant physiological forcing plays a significant role in determining the cloud adjustment in this model and is the dominant contribution to the low-level cloud changes over land. Low-level cloud adjustments are associated with changes in surface turbulent fluxes and lower tropospheric stability, with significant adjustments in boundary layer cloud types and in the depth of the boundary layer itself. The linearity of simple forcing-response frameworks are examined and found to be generally applicable. Small regional departures from linearity occur during the early part of the ramp-down phase, where the Southern Ocean and eastern tropical Pacific continue to warm for a few decades, despite the reversal in radiative forcing and global temperatures. The importance of considering time-varying patterns of warming and regional phenomena when diagnosing and understanding feedbacks in a coupled atmosphere-ocean framework is highlighted."
"16246205000;55738957800;26324818700;","Quantifying contributions of climate feedbacks to tropospheric warming in the NCAR CCSM3.0",2014,"10.1007/s00382-013-1805-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895046534&doi=10.1007%2fs00382-013-1805-x&partnerID=40&md5=4d461d171d00f78643e4682cd5f036ab","In this study, a coupled atmosphere-surface ""climate feedback-response analysis method"" (CFRAM) was applied to the slab ocean model version of the NCAR CCSM3.0 to understand the tropospheric warming due to a doubling of CO2 concentration through quantifying the contributions of each climate feedback process. It is shown that the tropospheric warming displays distinct meridional and vertical patterns that are in a good agreement with the multi-model mean projection from the IPCC AR4. In the tropics, the warming in the upper troposphere is stronger than in the lower troposphere, leading to a decrease in temperature lapse rate, whereas in high latitudes the opposite it true. In terms of meridional contrast, the lower tropospheric warming in the tropics is weaker than that in high latitudes, resulting in a weakened meridional temperature gradient. In the upper troposphere the meridional temperature gradient is enhanced due to much stronger warming in the tropics than in high latitudes. Using the CFRAM method, we analyzed both radiative feedbacks, which have been emphasized in previous climate feedback analysis, and non-radiative feedbacks. It is shown that non-radiative (radiative) feedbacks are the major contributors to the temperature lapse rate decrease (increase) in the tropical (polar) region. Atmospheric convection is the leading contributor to temperature lapse rate decrease in the tropics. The cloud feedback also has non-negligible contributions. In the polar region, water vapor feedback is the main contributor to the temperature lapse rate increase, followed by albedo feedback and CO2 forcing. The decrease of meridional temperature gradient in the lower troposphere is mainly due to strong cooling from convection and cloud feedback in the tropics and the strong warming from albedo feedback in the polar region. The strengthening of meridional temperature gradient in the upper troposphere can be attributed to the warming associated with convection and cloud feedback in the tropics. Since convection is the leading contributor to the warming differences between tropical lower and upper troposphere, and between the tropical and polar regions, this study indicates that tropical convection plays a critical role in determining the climate sensitivity. In addition, the CFRAM analysis shows that convective process and water vapor feedback are the two major contributors to the tropical upper troposphere temperature change, indicating that the excessive upper tropospheric warming in the IPCC AR4 models may be due to overestimated warming from convective process or underestimated cooling due to water vapor feedback. © 2013 Springer-Verlag Berlin Heidelberg."
"22635190100;7401936984;7402064802;7404142321;7401974644;35509639400;7004468723;55746159100;8866821900;12242312400;55686667100;7402435469;","On the correspondence between mean forecast errors and climate errors in CMIP5 models",2014,"10.1175/JCLI-D-13-00474.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893853114&doi=10.1175%2fJCLI-D-13-00474.1&partnerID=40&md5=8843ef5089848d05f353e552496d0728","The present study examines the correspondence between short- and long-term systematic errors in five atmospheric models by comparing the 16 five-day hindcast ensembles from the Transpose Atmospheric Model Intercomparison Project II (Transpose-AMIP II) for July-August 2009 (short term) to the climate simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and AMIP for the June- August mean conditions of the years of 1979-2008 (long term). Because the short-term hindcasts were conducted with identical climate models used in the CMIP5/AMIP simulations, one can diagnose over what time scale systematic errors in these climate simulations develop, thus yielding insights into their origin through a seamless modeling approach. The analysis suggests that most systematic errors of precipitation, clouds, and radiation processes in the long-term climate runs are present by day 5 in ensemble average hindcasts in all models. Errors typically saturate after few days of hindcasts with amplitudes comparable to the climate errors, and the impacts of initial conditions on the simulated ensemble mean errors are relatively small. This robust bias correspondence suggests that these systematic errors across different models likely are initiated by model parameterizations since the atmospheric large-scale states remain close to observations in the first 2-3 days. However, biases associated with model physics can have impacts on the large-scale states by day 5, such as zonal winds, 2-m temperature, and sea level pressure, and the analysis further indicates a good correspondence between shortand long-term biases for these large-scale states. Therefore, improving individual model parameterizations in the hindcast mode could lead to the improvement of most climate models in simulating their climate mean state and potentially their future projections. © 2014 American Meteorological Society."
"12902788500;7401651197;11440916900;16527798200;","Using raman microspectroscopy to determine chemical composition and mixing state of airborne marine aerosols over the pacific ocean",2014,"10.1080/02786826.2013.867297","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891472333&doi=10.1080%2f02786826.2013.867297&partnerID=40&md5=25b17159d45bf62b25183722236ff2c0","Chemical composition and mixing state of aerosols collected over an 11,000 km latitudinal cruise in the Pacific Ocean are reported here as determined by a new application of Raman spectroscopy. The Raman microspectroscopy technique employs a Raman spectrometer coupled to an optical microscope to identify the chemical composition and internal mixing state of single particles. By analyzing multiple particles in a collected ensemble, the degree of external mixing of particles was also determined. To lend context to the Pacific aerosol population sampled, atmospheric aerosol concentration, and the critical supersaturation required for the aerosols to activate as cloud condensation nuclei, and chlorophyll a concentration in the underlying water (a metric for phytoplankton biomass in the ocean) were also obtained. Our results indicate that long chain organic molecules were prevalent in the marine aerosol samples throughout the cruise, including during coastal and open ocean locations, in both hemispheres, and in the seasons of autumn and spring. Long chain organic compounds tended to be present in internal mixtures with other organic and inorganic components. Although variations in the fraction of aerosols activated as CCN were observed, no simple correlation between organics and CCN activation was found. According to our measurements, marine aerosol in the Pacific Ocean may be generally characterized as multicomponent aerosol containing and often dominated by a high organic fraction. Our results suggest that the prevalence of organics and the high degree of internal mixing of aerosol must be accounted for in accurate modeling of the role of marine aerosols in cloud formation and climate. Copyright © American Association for Aerosol Research."
"35090272500;6701847229;7006206130;","Analysis of the West African Monsoon system in the regional climate model COSMO-CLM",2014,"10.1002/joc.3702","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887829940&doi=10.1002%2fjoc.3702&partnerID=40&md5=12649ae58199dfee9b14b00f2da8ecb9","The West African Monsoon (WAM) is a major component of the global monsoon system. The contrast between land surface temperature (LST) (in the Sahel and Sahara) and sea surface temperature (SST) dominates the WAM formation. This study investigated the WAM representation, and the impact of surface temperature uncertainties in three regional climate simulations with the model COnsortium for Small-scale MOdelling-Climate Limited-area Model (COSMO-CLM) (grid-spacing: 0.44°). The regional simulations were driven by present-day climate simulations with the global climate model ECHAM5 (grid-spacing: ∼1.9°), and by the re-analysis data ERA-Interim (∼0.7°). The WAM dynamics were quantified using the WAM wind shear index (WAMI). In addition, indices for outgoing long-wave radiation (OLR) (an indicator for convective clouds), and total precipitation were used to assess monsoon characteristics. The large-scale patterns of precipitation were adequately reproduced by COSMO-CLM compared to observations, but there were significant uncertainties at regional scales, such as a strong overestimation of precipitation in the Sahel. The model also significantly overestimated convective activity and simulated a too intense monsoon circulation as indicated by WAMI. The impact of bare soil albedo on LST was investigated by implementing an MODIS-observation based bare-soil albedo parameterization, which led to a reduction of the simulated warm bias in the Sahara region during the monsoon season by up to 3K, and an improvement of simulated Sahel precipitation. However, the simulated monsoon circulation was not improved. Using either ERA-Interim or ECHAM5 at the lateral boundaries showed that the COSMO-CLM results were very sensitive to the driving data. And, on coarse grid-scales (of the order of the grid-spacing of the driving datasets) the regional climate model was not able to perform substantially better than the forcing data. The differently driven COSMO-CLM simulations also indicated that the land-sea temperature gradient, and its impact on WAM, is dominated by SST and less by LST (in Sahara and Sahel). © 2013 Royal Meteorological Society."
"35857960400;6507107974;7003375121;7006313933;6701427386;","Simulation of the PDO effect on the North America summer climate with emphasis on Mexico",2014,"10.1016/j.atmosres.2013.10.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887237049&doi=10.1016%2fj.atmosres.2013.10.010&partnerID=40&md5=a9e4e8bc0b60893e570cb81bf4aef37a","Five composite anomaly fields (CAF) are built for the summer of each Pacific decadal oscillation (PDO) phase: skin temperature; air temperature (T7), zonal (u7) and meridional (v7) wind at the 700mb level; and precipitation (R).An energy balance model, named thermodynamic climate model (TCM), is integrated on the NH to compute the summer anomalies (sub-index A) of the land surface temperature (LST),T7, u7, v7, R and cloudiness (ε). To study the effect of the PDO phases on Mexico's climate, the CAF of the sea surface temperature (SST) is used in the TCM as an input. The output fields are objectively compared with their respective CAF (except SSTA) using an index of agreement, and the six variables are mainly discussed on the north Pacific and adjacent continents (NPAC), with emphasis on Mexico.The TCM generates a kind of atmospheric bridge by which the SSTA produces a T7A, the consequent condensation of water vapour anomaly and the corresponding εA over the continent, affecting the planetary albedo and therefore the LST.The u7A forms a large meridional wave train over the NPAC centre, which is part of the Pacific/North American pattern in both PDO phases and is more intense in winter than in summer. In the PDO warm phase and over the eastern half of the NPAC, the v7A is positive, so that the moisture flux from the Pacific Ocean toward North America (NA) increases the precipitation during NA monsoons. These results have an acceptable agreement with the CAF.We also analysed the combined effect of cloudiness and evaporation according to the soil moisture, over the eastern NA and the Gobi Desert for both PDO phases, showing its thermal moderator effect. © 2013 Elsevier B.V."
"55801763300;55862061100;36070982500;7404742641;","Diurnal temperature range variation and its causes in a semiarid region from 1957 to 2006",2014,"10.1002/joc.3690","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893637238&doi=10.1002%2fjoc.3690&partnerID=40&md5=8eaee86db724a98fdd42a60f7fc927b1","ABSTRACT: The diurnal temperature range (DTR) is an important indicator of climate change, and it has decreased worldwide since the 1950s, particularly over arid and semiarid regions. This study analyses the effect of meteorological and anthropogenic factors on DTR variation to investigate the possible causes of DTR decreases in semiarid climates. The study region is located in northeast China, and the study period is from 1957 to 2006. There are three main results. First, the rate of decrease in the DTR is -1.24K per 50years. This decrease is mainly attributed to the increasing daily minimum temperature rate (Tmin, 2.24K per 50years), which is greater than the change in the daily maximum temperature (Tmax, 1.00K per 50years). Second, sunshine duration (SD) appears to be the most significant meteorological factor that determines the DTR through downward shortwave radiation (Rsw,d) and surface soil moisture (SM). The effect of Rsw,d is larger for Tmax than for Tmin; therefore, the decrease in Rsw,d results in a smaller increase in Tmax than in Tmin. On the other hand, the increase in SM can strengthen daytime latent heat release, and the increase in Tmax is then slowed because of the cooling effect of evaporation. The precipitation values and the leaf area index show a negative correlation with the DTR, whereas the cloud amount and the relative humidity appear not to be main causes of the DTR decrease in this region. Finally, atmospheric aerosols can reduce the SD by 0.27hyear-1 by decreasing atmospheric transparency, as indicated by an analysis of the Total Ozone Mapping Spectrometer Aerosol Index from 1979 to 2005. The decrease in direct solar radiation is the main cause of decreases in Rsw,d. These findings will provide references for DTR variation studies in similar climates. © 2013 Royal Meteorological Society."
"16025327700;26029334300;57217371644;7102102724;57189333357;35791966000;","Lightning and convective rain study in different parts of India",2014,"10.1016/j.atmosres.2013.09.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886259064&doi=10.1016%2fj.atmosres.2013.09.018&partnerID=40&md5=877868708a3a28879a3be68d58e28327","The effect of solar variability parameters (solar flux (F10.7cm), cosmic ray flux, sunspot numbers) and meteorological parameters on convective rainfall and lightning flashes in four different Indian regions of equal area is studied. Regions are selected having different topological, vegetation, proximity with ocean and habitat features. Solar variability shows statistically insignificant effect on lightning flash and convective rainfall. The seasonal variation of lightning flashes and convective rainfall in each region could be explained considering the variation of CAPE and surface temperature in that region. The dependence of lightning flashes and convective rainfall on meteorological parameters varies from region to region, as is evident from correlation studies. Lightning flashes is well correlated (R=0.81) with CAPE in region R1 and barely correlated (R=0.23, 0.24) in region R3 and R4 whereas rainfall is well correlated (R&gt;0.68) in all the regions. Lightning flashes are better correlated (R&gt;0.57) with temperature in R1, R2 and R4 and moderately correlated in R3 (R=0.44). Rainfall in R3 is very well correlated (R=0.91) with surface temperature and there is insignificant correlation in R1 (R=0.09). There is very good positive correlation (R&gt;0.59) between cloud cover and convective rainfall in the entire region and well negative correlation (-0.83&lt;R&lt;-0.61) between OLR and convective rainfall. OLR and cloud cover show little impact on lightning flashes. Lightning flashes and convective rainfall show average positive correlation (0.48&lt;R&lt;0.53). Aerosol concentration is the largest in region R4 and showed an increasing trend between 2007 and 2011. Lightning flashes and convective rainfall are positively correlated (0.10&lt;R&lt;0.58) with aerosol concentration. © 2013 Elsevier B.V."
"55512618700;57202301596;","Tropical biases in CMIP5 multimodel ensemble: The excessive equatorial pacific cold tongue and double ITCZ problems",2014,"10.1175/JCLI-D-13-00337.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893830438&doi=10.1175%2fJCLI-D-13-00337.1&partnerID=40&md5=afedbbc53616e220c7c4432faf4df5da","Errors of coupled general circulation models (CGCMs) limit their utility for climate prediction and projection. Origins of and feedback for tropical biases are investigated in the historical climate simulations of 18 CGCMs from phase 5 of the Coupled Model Intercomparison Project (CMIP5), together with the available Atmospheric Model Intercomparison Project (AMIP) simulations. Based on an intermodel empirical orthogonal function (EOF) analysis of tropical Pacific precipitation, the excessive equatorial Pacific cold tongue and double intertropical convergence zone (ITCZ) stand out as the most prominent errors of the current generation of CGCMs. The comparison of CMIP-AMIP pairs enables us to identify whether a given type of errors originates from atmospheric models. The equatorial Pacific cold tongue bias is associated with deficient precipitation and surface easterly wind biases in the western half of the basin in CGCMs, but these errors are absent in atmosphere-only models, indicating that the errors arise from the interaction with the ocean via Bjerknes feedback. For the double ITCZ problem, excessive precipitation south of the equator correlates well with excessive downward solar radiation in the Southern Hemisphere (SH) midlatitudes, an error traced back to atmospheric model simulations of cloud during austral spring and summer. This extratropical forcing of the ITCZ displacements is mediated by tropical ocean-atmosphere interaction and is consistent with recent studies of ocean-atmospheric energy transport balance. © 2014 American Meteorological Society."
"15841308100;55965146700;7102650724;6603944055;57200082194;","Satellite observed widespread decline in Mongolian grasslands largely due to overgrazing",2014,"10.1111/gcb.12365","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891661601&doi=10.1111%2fgcb.12365&partnerID=40&md5=521d8713ed2067e250a6b194af92a83b","The Mongolian Steppe is one of the largest remaining grassland ecosystems. Recent studies have reported widespread decline of vegetation across the steppe and about 70% of this ecosystem is now considered degraded. Among the scientific community there has been an active debate about whether the observed degradation is related to climate, or over-grazing, or both. Here, we employ a new atmospheric correction and cloud screening algorithm (MAIAC) to investigate trends in satellite observed vegetation phenology. We relate these trends to changes in climate and domestic animal populations. A series of harmonic functions is fitted to Moderate Resolution Imaging Spectroradiometer (MODIS) observed phenological curves to quantify seasonal and inter-annual changes in vegetation. Our results show a widespread decline (of about 12% on average) in MODIS observed normalized difference vegetation index (NDVI) across the country but particularly in the transition zone between grassland and the Gobi desert, where recent decline was as much as 40% below the 2002 mean NDVI. While we found considerable regional differences in the causes of landscape degradation, about 80% of the decline in NDVI could be attributed to increase in livestock. Changes in precipitation were able to explain about 30% of degradation across the country as a whole but up to 50% in areas with denser vegetation cover (P &lt; 0.05). Temperature changes, while significant, played only a minor role (r2 = 0.10, P &lt; 0.05). Our results suggest that the cumulative effect of overgrazing is a primary contributor to the degradation of the Mongolian steppe and is at least partially responsible for desertification reported in previous studies. © 2013 John Wiley &amp; Sons Ltd."
"6701757748;55938062400;","Model sensitivity analysis study for western disturbances over the Himalayas",2014,"10.1007/s00703-013-0302-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895070412&doi=10.1007%2fs00703-013-0302-4&partnerID=40&md5=b0f8397760949c35aab779443ecce574","Western disturbances (WDs) are extratropical synoptic scale weather systems which cause significant precipitation over the Himalayas and surrounding areas during winter (December, January and February, DJF). Three intense WDs, 13-17 January 2002, 05-08 February 2002, and 11-13 February 2002, are chosen as two of the WDs are extensively studied by Hatwar et al. (Curr Sci 88:913-920, 2005) and one independent WD (Indian Meteorological Department, Delhi, Mausam 54(1):346-347, 2003) is considered. Firstly, it is planned to study model sensitivity with these WD cases, which are simulated with different combinations of cloud microphysics, planetary boundary layer and cumulus parameterization schemes in weather research and forecasting model to assess a better suite for the WD simulations. Sensitivity and error analyses carried out with different observations, show that the combination of Eta Ferrier or Eta Grid-scale cloud and precipitation microphysics scheme, Yonsei University scheme and Kain-Fritsch scheme has shown consistently lower error values. Further, the results suggest, that the model simulations of a WD capture the spatial distribution of precipitation, locations of low pressure region and the circulation patterns very well. It is observed that the WD system comprises of low pressure region in the vertical atmospheric column in form of a stationary surface low and a depression in the subtropical westerly jet moving eastwards. Further, the growth of convective cyclonic systems over the steep topographical region of the Himalayas is depicted by the increased positive vorticity and high values of CAPE, alluding to the propensity of WDs to cause orographically forced precipitation. WDs and associated precipitation show varied but significant impacts on the Indian winter climate such as snow cover variation and cold wave or fog conditions along with impact on winter crop production. © 2013 Springer-Verlag Wien."
"12769875100;","Variability of monthly diurnal cycle composites of TOA radiative fluxes in the tropics",2014,"10.1175/JAS-D-13-0112.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893855294&doi=10.1175%2fJAS-D-13-0112.1&partnerID=40&md5=786cae5e72ea5ec04e898beb30f8e19e","Earth system variability is generated by a number of different sources and time scales. Understanding sources of atmospheric variability is critical to reducing the uncertainty in climate models and to understanding the impacts of sampling on observational datasets. The diurnal cycle is a fundamental variability evident in many geophysical variables-including top-of-the-atmosphere (TOA) radiative fluxes. This study considers aspects of the TOA flux diurnal cycle not previously analyzed: namely, deseasonalized variations in the monthly diurnal cycle composites, termed monthly diurnal cycle variability. Significant variability in the monthly diurnal cycle composites is found in both outgoing longwave radiation (OLR) and reflected shortwave (RSW). OLR and RSW monthly diurnal cycle variability exhibits a regional structure that follows traditional, climatological diurnal cycle categorization by prevailing cloud and surface types. The results attribute monthly TOA flux diurnal cycle variability to variations in the diurnal cloud evolution, which is sensitive to monthly atmospheric dynamic-and thermodynamic-state anomalies. The results also suggest that monthly diurnal cycle variability can amplify or buffer monthly TOA flux anomalies, depending on the region. Considering the impact of monthly diurnal cycle variability on monthly TOA flux anomalies, the results suggest that monthly TOA flux diurnal cycle variability must be considered when constructing a TOA flux dataset from sun-synchronous orbit. The magnitude of monthly diurnal composite variability in OLR and RSW is regionally dependent-1-7 Wm -2 and 10%-80% relative to interannual TOA flux variability. The largest (4-7 Wm-2 40%-80%) and smallest (1-3Wm-2 10%-30%) TOA flux uncertainties occur in convective and nonconvective regions, respectively, over both land and ocean. © 2014 American Meteorological Society."
"39261772800;6603414854;55940557800;8870849300;57199924863;","Impact of aerosol on surface reaching solar irradiance over Mohal in the northwestern Himalaya, India",2014,"10.1016/j.jastp.2013.12.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891654802&doi=10.1016%2fj.jastp.2013.12.002&partnerID=40&md5=15d805410b2b448e217d5f592d05534e","The present study, for the first time during 2007, is focused to examine the impact of aerosols on surface reaching solar irradiance over Mohal (31.9°N, 77.12°E, 1154m amsl) in the northwestern part of the Indian Himalaya. The study also aims to estimate shortwave aerosol radiative forcing (SWARF) and its effect on regional climate. The multi-wavelength solar radiometer (MWR) is used to measure aerosol optical depth (AOD) over a wider spectrum, i.e. ultraviolet, visible and near-infrared. The AOD is obtained by analyzing the data from MWR following the Langley technique. The radiative transfer model is used along with Optical Properties of Aerosols and Clouds model to estimate the SWARF. Aerosol shows a great efficiency to reduce substantial fraction of energy from the surface reaching direct solar beam, i.e. 154Wm-2μm-1 per unit AOD at 0.5μm. The SWARF at the surface, top of the atmosphere and the atmosphere is estimated to be -18.5±1.7, +0.6±3.7 and +19.1±3.1Wm-2, respectively. The large SWARF at the surface stood during the summer (April-July), while small during the monsoon (August-September). Moderate SWARF is obtained in the autumn (October-November) and winter (December-March). The study estimates a notable extinction in incoming solar radiation relatively with lower atmospheric heating from 0.41 to 0.73Kday-1. The potential effect of aerosol is found relatively higher on high aerosol loading days. On these days, the lower atmospheric heating increases by a factor 1.8 (during dust events) and 1.7 (during biomass burning). This study concludes that aerosols produce significant reduction in incoming solar radiation with substantial increase in lower atmospheric heating, leading to a remarkable effect on the atmospheric stability. In addition, as a subject of future interest, the present study has also important implications on the atmospheric circulation and regional climate. © 2013 Elsevier Ltd."
"55567359600;55323908500;","Simulating water temperatures and stratification of a pre-alpine lake with a hydrodynamic model: Calibration and sensitivity analysis of climatic input parameters",2014,"10.1002/hyp.9687","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891738996&doi=10.1002%2fhyp.9687&partnerID=40&md5=0688d9776d10ee9ce75435e28ba8dada","We report on the calibration of the one-dimensional hydrodynamic lake model Dynamic Reservoir Simulation Model to simulate the water temperature conditions of the pre-alpine Lake Ammersee (southeast Germany) that is a representative of deep and large lakes in this region. Special focus is given to the calibration in order to reproduce the correct thermal distribution and stratification including the time of onset and duration of summer stratification. To ensure the application of the model to investigate the impact of climate change on lakes, an analysis of the model sensitivity under stepwise modification of meteorological input parameters (air temperature, wind speed, precipitation, global radiation, cloud cover, vapour pressure and tributary water temperature) was conducted. The total mean error of the calibration results is -0.23°C, the root mean square error amounts to 1.012°C. All characteristics of the annual stratification cycle were reproduced accurately by the model. Additionally, the simulated deviations for all applied modifications of the input parameters for the sensitivity analysis can be differentiated in the high temporal resolution of monthly values for each specific depth. The smallest applied alteration to each modified input parameter caused a maximum deviation in the simulation results of at least 0.26°C. The most sensitive reactions of the model can be observed through modifications of the input parameters air temperature and wind speed. Hence, the results show that further investigations at Lake Ammersee, such as coupling the hydrodynamic model with chemo-dynamic models to assess the impact of changing climate on biochemical conditions within lakes, can be carried out using Dynamic Reservoir Simulation Model. © 2012 John Wiley & Sons, Ltd."
"36551674900;7701313284;55577486600;57199131919;57216667773;","Combining MODIS and AMSR-E observations to improve MCD43A3 short-time snow-covered Albedo estimation",2014,"10.1002/hyp.9570","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891695516&doi=10.1002%2fhyp.9570&partnerID=40&md5=b3d061cda252c2ad2712876346c5092a","Land surface albedo plays an important role in the radiation budget and global climate models. NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) provide 16-day albedo product with 500-m resolution every 8 days (MCD43A3). Some in-situ albedo measurements were used as the true surface albedo values to validate the MCD43A3 product. As the 16-day MODIS albedo retrievals do not include snow observations when there is ephemeral snow on the ground surface in a 16-day period, comparisons between MCD43A3 and 16 day averages of field data do not agree well. Another reason is that the MODIS cannot detect the snow when the area is covered by clouds. The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) data are not affected by weather conditions and are a good supplement for optical remote sensing in cloudy weather. When the surface is covered by ephemeral snow, the AMSR-E data can be used as the additional information to retrieve the snow albedo. In this study, we developed an improved method by using the MODIS products and the AMSR-E snow water equivalent (SWE) product to improve the MCD43A3 short-time snow-covered albedo estimation. The MODIS daily snow products MOD10A1 and MYD10A1 both provide snow and cloud information from observations. In our study region, we updated the MODIS daily snow product by combining MOD10A1 and MYD10A1. Then, the product was combined with the AMSR-E SWE product to generate new daily snow-cover and SWE products at a spatial resolution of 500 m. New SWE datasets were integrated into the Noah Land Surface Model snow model to calculate the albedo above a snow surface, and these values were then utilized to improve the MODIS 16-day albedo product. After comparison of the results with in-situ albedo measurements, we found that the new corrected 16-day albedo can show the albedo changes during the short snowfall season. For example, from January 25 to March 14, 2007 at the BJ site, the albedo retrieved from snow-free observations does not indicate the albedo changes affected by snow; the improved albedo conforms well to the in-situ measurements. The correlation coefficient of the original MODIS albedo and the in-situ albedo is 0.42 during the ephemeral snow season, but the correlation coefficient of the improved MODIS albedo and the in-situ albedo is 0.64. It is concluded that the new method is capable of capturing the snow information from AMSR-E SWE to improve the short-time snow-covered albedo estimation. © 2012 John Wiley & Sons, Ltd."
"55800936800;7801565183;14034301300;35195849700;17434636400;36776963300;7005069415;7006434689;","Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)",2014,"10.5194/acp-14-1123-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893311414&doi=10.5194%2facp-14-1123-2014&partnerID=40&md5=d70b7083ba1c4188ff4a8d22f3984740","Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN) number concentrations at eight different supersaturations (SS) from 0.24% to 1.18% were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SSpeak, as a measure of the SS at which ambient clouds are formed. A 17-month CCN climatology was then used to retrieve the SSpeak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were available. The SSpeak values varied between 0.01% and 2.0% during all campaigns. An overall median SSpeak of 0.35% and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier) generally experience lower SSpeak values than air masses coming from the northwest (steep slope). The observed overall median values were 0.41% and 0.22% for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and shallow-layer clouds. These cloud types are consistent with weather observations routinely performed at the JFJ. © 2014 Author(s)."
"57203030873;8866821900;36720934300;25031430500;35180334400;8570871900;","Processes controlling Southern Ocean shortwave climate feedbacks in CESM",2014,"10.1002/2013GL058315","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892665927&doi=10.1002%2f2013GL058315&partnerID=40&md5=4d9c5ed1ba351e00b9bfaaa01cf34c08","A climate model (Community Earth System Model with the Community Atmosphere Model version 5 (CESM-CAM5)) is used to identify processes controlling Southern Ocean (30-70°S) absorbed shortwave radiation (ASR). In response to 21st century Representative Concentration Pathway 8.5 forcing, both sea ice loss (2.6 W m-2) and cloud changes (1.2 W m-2) enhance ASR, but their relative importance depends on location and season. Poleward of ∼55°S, surface albedo reductions and increased cloud liquid water content (LWC) have competing effects on ASR changes. Equatorward of ∼55°S, decreased LWC enhances ASR. The 21st century cloud LWC changes result from warming and near-surface stability changes but appear unrelated to a small (1°) poleward shift in the eddy-driven jet. In fact, the 21st century ASR changes are 5 times greater than ASR changes resulting from large (5°) naturally occurring jet latitude variability. More broadly, these results suggest that thermodynamics (warming and near-surface stability), not poleward jet shifts, control 21st century Southern Ocean shortwave climate feedbacks. ©2013. American Geophysical Union. All Rights Reserved."
"55683899300;6506718302;35459245100;7006712143;7007039218;6507755223;","Reallocation in modal aerosol models: Impacts on predicting aerosol radiative effects",2014,"10.5194/gmd-7-161-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893233113&doi=10.5194%2fgmd-7-161-2014&partnerID=40&md5=18697277ce09b730cc9d9bd203c490a9","Atmospheric models often represent the aerosol particle size distribution with a modal approach, in which particles are described with log-normal modes within predetermined size ranges. This approach reallocates particles numerically from one mode to another for example during particle growth, potentially leading to artificial changes in the aerosol size distribution. In this study we analysed how the modal reallocation affects climate-relevant variables: cloud droplet number concentration (CDNC), aerosol-cloud interaction parameter (ACI) and light extinction coefficient (<i>q</i>ext). The ACI parameter gives the response of CDNC to a change in total aerosol number concentration. We compared these variables between a modal model (with and without reallocation routines) and a high resolution sectional model, which was considered a reference model. We analysed the relative differences in the chosen variables in four experiments designed to assess the influence of atmospheric aerosol processes. We find that limiting the allowed size ranges of the modes, and subsequent remapping of the distribution, leads almost always to an underestimation of cloud droplet number concentrations (by up to 100%) and an overestimation of light extinction (by up to 20%). On the other hand, the aerosol-cloud interaction parameter can be either over- or underestimated by the reallocating model, depending on the conditions. For example, in the case of atmospheric new particle formation events followed by rapid particle growth, the reallocation can cause on average a 10% overestimation of the ACI parameter. Thus it is shown that the reallocation affects the ability of a model to estimate aerosol climate effects accurately, and this should be taken into account when using and developing aerosol models. © Author(s) 2014."
"22635898800;57211106013;","Does the POA-SOA split matter for global CCN formation?",2014,"10.5194/acp-14-995-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893347531&doi=10.5194%2facp-14-995-2014&partnerID=40&md5=071e8b396f1736ee85bbce2090fb3a6c","A model of carbonaceous aerosols has been implemented in the TwO-Moment Aerosol Sectional (TOMAS) microphysics module in the GEOS-Chem chemical transport model (CTM), a model driven by assimilated meteorology. Inclusion of carbonaceous emissions alongside pre-existing treatments of sulfate and sea-salt aerosols increases the number of emitted primary aerosol particles by a factor of 2.5 and raises annual-average global cloud condensation nuclei at 0.2% supersaturation (CCN(0.2%)) concentrations by a factor of two. Compared to the prior model without carbonaceous aerosols, this development improves the model prediction of condensation nuclei with dry diameter larger than 10 nm (CN10) number concentrations significantly from -45% to -7% bias when compared to long-term observations. Inclusion of carbonaceous particles also largely eliminates a tendency for the model to underpredict higher cloud condensation nuclei (CCN) concentrations. Similar to other carbonaceous models, the model underpredicts organic carbon (OC) and elemental carbon (EC) mass concentrations by a factor of 2 when compared to EMEP and IMPROVE observations. Because primary organic aerosol (POA) and secondary organic aerosol (SOA) affect aerosol number size distributions via different microphysical processes, we assess the sensitivity of CCN production, for a fixed source of organic aerosol (OA) mass, to the assumed POA-SOA split in the model. For a fixed OA budget, we found that CCN(0.2%) decreases nearly everywhere as the model changes from a world dominated by POA emissions to one dominated by SOA condensation. POA is about twice as effective per unit mass at CCN production compared to SOA. Changing from a 100% POA scenario to a 100% SOA scenario, CCN(0.2%) concentrations in the lowest model layer decrease by about 20%. In any scenario, carbonaceous aerosols contribute significantly to global CCN. The SOA-POA split has a significant effect on global CCN, and the microphysical implications of POA emissions versus SOA condensation appear to be at least as important as differences in chemical composition as expressed by the hygroscopicity of OA. These findings stress the need to better understand carbonaceous aerosols loadings, the global SOA budget, microphysical pathways of OA formation (emissions versus condensation) as well as chemical composition to improve climate modeling. © Author(s) 2014."
"55221454700;35270436100;","China's dimming and brightening: Evidence, causes and hydrological implications",2014,"10.5194/angeo-32-41-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893289030&doi=10.5194%2fangeo-32-41-2014&partnerID=40&md5=4a79d981e0fd8a89ce291cdef55ad00f","There is growing evidence that, corresponding to global dimming and brightening, surface solar radiation and sunshine hours over China have undergone decadal fluctuations during the 1960s-2000s. The results of a number of these analyses are, however, very different. In this study, we synthesize reliable results and conclusively address recent advances and insufficiencies in studies on dimming and brightening in China. A temporally and spatially prevalent dimming trend is noted in surface solar radiation, direct solar radiation and sunshine hours since the 1960s. Meanwhile, the changing trend in diffuse solar radiation is less pronounced. Increasing anthropogenic aerosol loading is regarded as the most plausible explanation for China's dimming. The brightening trend since 1990, which mainly occurs in southeastern China and in the spring season, is weak and insignificant. The reverse in the solar radiation trend is associated with climate change by cloud suppression and slowdown in anthropogenic emissions. The future solar radiation trend in China could largely depend on the development of air quality control. Other potential driving factors such as wind speed, water vapor and surface albedo are also non-negligible in specific regions of China. Hydrological implications of dimming and brightening in China lack systematic investigation. However, the fact that solar radiation and pan evaporation trends in China track a similar curve in 1990 further suggests that the pan evaporation paradox could be partly resolved by changes in solar radiation. © 2014 Author(s)."
"56022498200;57205984068;","Influence of microphysical schemes on atmospheric water in the Weather Research and Forecasting model",2014,"10.5194/gmd-7-147-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893310195&doi=10.5194%2fgmd-7-147-2014&partnerID=40&md5=9ee082673ce0e7ffccbf86c7725e75aa","This study examines how different microphysical parameterization schemes influence orographically induced precipitation and the distributions of hydrometeors and water vapour for midlatitude summer conditions in the Weather Research and Forecasting (WRF) model. A high-resolution two-dimensional idealized simulation is used to assess the differences between the schemes in which a moist air flow is interacting with a bell-shaped 2 km high mountain. Periodic lateral boundary conditions are chosen to recirculate atmospheric water in the domain. It is found that the 13 selected microphysical schemes conserve the water in the model domain. The gain or loss of water is less than 0.81% over a simulation time interval of 61 days. The differences of the microphysical schemes in terms of the distributions of water vapour, hydrometeors and accumulated precipitation are presented and discussed. The Kessler scheme, the only scheme without ice-phase processes, shows final values of cloud liquid water 14 times greater than the other schemes. The differences among the other schemes are not as extreme, but still they differ up to 79% in water vapour, up to 10 times in hydrometeors and up to 64% in accumulated precipitation at the end of the simulation. The microphysical schemes also differ in the surface evaporation rate. The WRF single-moment 3-class scheme has the highest surface evaporation rate compensated by the highest precipitation rate. The different distributions of hydrometeors and water vapour of the microphysical schemes induce differences up to 49 W m&minus;2 in the downwelling shortwave radiation and up to 33 W m&minus;2 in the downwelling longwave radiation. © Author(s) 2014."
"36059595100;8511991900;7202048112;15755995900;55544607500;55476830600;36538539800;57207176515;16246205000;","Investigation of aerosol indirect effects using a cumulus microphysics parameterization in a regional climate model",2014,"10.1002/2013JD020958","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900620563&doi=10.1002%2f2013JD020958&partnerID=40&md5=a264bc5e18113673404179e0061b28d5","A new Zhang and McFarlane (ZM) cumulus scheme includes a two-moment cloud microphysics parameterization for convective clouds. This allows aerosol effects to be investigated more comprehensively by linking aerosols with microphysical processes in both stratiform clouds that are explicitly resolved and convective clouds that are parameterized in climate models. This new scheme is implemented in the Weather Research and Forecasting model, coupled with the physics and aerosol packages from the Community Atmospheric Model version 5. A case of July 2008 during the East Asian summer monsoon is selected to evaluate the performance of the new ZM and to investigate aerosol effects on monsoon precipitation. The precipitation and radiative fluxes simulated by the new ZM show a better agreement with observations compared to simulations with the original ZM that does not include convective cloud microphysics and aerosol-convective cloud interactions. Detailed analysis suggests that an increase in detrained cloud water and ice mass by the new ZM is responsible for this improvement. Aerosol impacts on cloud properties, precipitation, and radiation are examined by reducing the primary aerosols and anthropogenic emissions to 30% of those in the present (polluted) condition. The simulated surface precipitation is reduced by 9.8% from clean to polluted environment, and the reduction is less significant when microphysics processes are excluded from the cumulus clouds. Cloud fraction is reduced by the increased aerosols due to suppressed convection, except during some heavy precipitation periods when cloud fraction, cloud top height, and rain rate are increased due to enhanced convection. © 2013. American Geophysical Union. All Rights Reserved."
"56985140700;7402064802;","Land-atmosphere coupling manifested in warm-season observations on the U.S. southern great plains",2014,"10.1002/2013JD020492","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900635485&doi=10.1002%2f2013JD020492&partnerID=40&md5=91763f5eeb14df9f006e7f71cc4fb706","This study examines several observational aspects of land-atmosphere coupling on daily average time scales during warm seasons of the years 1997 to 2008 at the Department of Energy Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) Central Facility site near Lamont, Oklahoma. Characteristics of the local land-atmosphere coupling are inferred by analyzing the covariability of selected land and atmospheric variables that include precipitation and soil moisture, surface air temperature, relative humidity, radiant and turbulent fluxes, as well as low-level cloud base height and fractional coverage. For both the energetic and hydrological aspects of this coupling, it is found that large-scale atmospheric forcings predominate, with local feedbacks of the land on the atmosphere being comparatively small much of the time. The relatively weak land feedbacks are manifested especially by (1) the inability of soil moisture to comprehensively impact the coupled land-atmosphere energetics and (2) the limited recycling of local surface moisture under conditions where most of the rainfall derives from convective cells that originate at remote locations. There is some evidence, nevertheless, that the local land feedback becomes stronger as the soil dries out in the aftermath of precipitation events, or on days when the local boundary layer clouds are influenced by thermal updrafts associated with convection that originates at the surface. Potential implications of these results for climate-model representation of regional land-atmosphere coupling also are discussed. Key Points Statistically significant SGP land-atmosphere interactions occur Atmospheric forcings predominate over land feedbacks Land feedbacks grow stronger as the soil becomes drier ©2013. The Authors."
"7005304841;","Do sophisticated parameterizations of aerosol-cloud interactions in CMIP5 models improve the representation of recent observed temperature trends?",2014,"10.1002/2013JD020511","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900605777&doi=10.1002%2f2013JD020511&partnerID=40&md5=9d819c2fb059935f76d1529bca29df0d","Model output from the Coupled Model Inter comparison Project phase 5 (CMIP5) archive was compared with the observed latitudinal distribution of surface temperature trends between the years 1965 and 2004. By comparing model simulations that only consider changes in greenhouse gas forcing (GHG) with simulations that also consider the time evolution of anthropogenic aerosol emissions (GHGAERO), the influence of aerosol forcing on modeled surface temperature trends, and the dependence of the forcing on the model representation of aerosols and aerosol indirect effects, was evaluated. One group of models include sophisticated parameterizations of aerosol activation into cloud droplets; viz., the cloud droplet number concentration (CDNC) is a function of the modeled supersaturation as well as the aerosol concentration. In these models, the temperature trend bias was reduced in GHGAERO compared to GHG in more regions than in the other models. The ratio between high- and low-latitude warming also improved compared to observations. In a second group of models, the CDNC is diagnosed using an empirical relationship between the CDNC and the aerosol concentration. In this group, the temperature trend bias was reduced in more regions than in the model group where no aerosol indirect effects are considered. No clear difference could be found between models that include an explicit aerosol module and the ones that utilize prescribed aerosol. There was also no clear difference between models that include aerosol effects on the precipitation formation rate and the ones that do not. The results indicate that the best representation of recent observed surface temperature trends is obtained if the modeled CDNC is a function of both the aerosol concentration and the supersaturation. © 2013. American Geophysical Union. All Rights Reserved."
"56985140700;7402064802;","Land-atmosphere coupling manifested in warm-season observations on the U.S. southern great plains",2014,"10.1002/2013JD020492.","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018734137&doi=10.1002%2f2013JD020492.&partnerID=40&md5=2efd5b258e5463194f2d2b3520287f6e","This study examines several observational aspects of land-atmosphere coupling on daily average time scales during warm seasons of the years 1997 to 2008 at the Department of Energy Atmospheric Radiation Measurement Program’s Southern Great Plains (SGP) Central Facility site near Lamont, Oklahoma. Characteristics of the local land-atmosphere coupling are inferred by analyzing the covariability of selected land and atmospheric variables that include precipitation and soil moisture, surface air temperature, relative humidity, radiant and turbulent fluxes, as well as low-level cloud base height and fractional coverage. For both the energetic and hydrological aspects of this coupling, it is found that large-scale atmospheric forcings predominate, with local feedbacks of the land on the atmosphere being comparatively small much of the time. The relatively weak land feedbacks are manifested especially by (1) the inability of soil moisture to comprehensively impact the coupled land-atmosphere energetics and (2) the limited recycling of local surface moisture under conditions where most of the rainfall derives from convective cells that originate at remote locations. There is some evidence, nevertheless, that the local land feedback becomes stronger as the soil dries out in the aftermath of precipitation events, or on days when the local boundary layer clouds are influenced by thermal updrafts associated with convection that originates at the surface. Potential implications of these results for climate-model representation of regional land-atmosphere coupling also are discussed. © 2013. American Geophysical Union. All Rights Reserved."
"30767842400;57205638870;6701597468;7202079615;","A new method for evaluating the impact of vertical distribution on aerosol radiative forcing in general circulation models",2014,"10.5194/acp-14-877-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893077064&doi=10.5194%2facp-14-877-2014&partnerID=40&md5=45ed125182ceadca1b5f5ca72c2ff344","The quantification and understanding of direct aerosol forcing is essential in the study of climate. One of the main issues that makes its quantification difficult is the lack of a complete understanding of the role of the vertical distribution of aerosols and clouds. This work aims at reducing the uncertainty of aerosol top-of-the-atmosphere (TOA) forcing due to the vertical superposition of several short-lived atmospheric components, in particular different aerosol species and clouds. We propose a method to quantify the contribution of different parts of the atmospheric column to the TOA forcing as well as to evaluate the contribution to model differences that is exclusively due to different spatial distributions of aerosols and clouds. We investigate the contribution of aerosol above, below and in clouds by using added diagnostics in the aerosol-climate model LMDz. We also compute the difference between the TOA forcing of the ensemble of the aerosols and the sum of the forcings from individual species in clear sky. This difference is found to be moderate for the global average (14%) but can reach high values regionally (up to 100%). Nonlinear effects are even more important when superposing aerosols and clouds. Four forcing computations are performed: one where the full aerosol 3-D distribution is used, and then three where aerosols are confined to regions above, inside and below clouds, respectively. We find that the TOA forcing of aerosols depends crucially on the presence of clouds and on their position relative to that of the aerosol, in particular for black carbon (BC). We observe a strong enhancement of the TOA forcing of BC above clouds, attenuation for BC below clouds, and a moderate enhancement when BC is found within clouds. BC above clouds accounts for only about 30% of the total BC optical depth but for 55% of the forcing, while forcing efficiency increases by a factor of 7.5 when passing from below to above clouds. <br><br> The different behaviour of forcing nonlinearities for these three components of the atmospheric column encouraged us to develop the method for application to inter-model variability studies by reading 3-D aerosol and cloud fields from different general circulation models (GCMs) into the same model. We apply the method to the comparison of forcing due to the aerosols and clouds distributions of the general circulation models LMDz and SPRINTARS. The different amount of BC above but also within clouds is revealed to play a major role on the differences of cloudy-sky forcings between the two models, which can exceed 100% regionally. © 2014 Author(s)."
"56016514800;6602598448;35490828000;12767251100;7003627515;6603873829;","Updated cloud physics in a regional atmospheric climate model improves the modelled surface energy balance of Antarctica",2014,"10.5194/tc-8-125-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893094548&doi=10.5194%2ftc-8-125-2014&partnerID=40&md5=56967d60dffe28f3f81d7ac4f3ddac35","In this study the effects of changes in the physics package of the regional atmospheric climate model RACMO2 on the modelled surface energy balance, near-surface temperature and wind speed of Antarctica are presented. The physics package update primarily consists of an improved turbulent and radiative flux scheme and a revised cloud scheme that includes a parameterisation for ice cloud super-saturation. The ice cloud super-saturation has led to more moisture being transported onto the continent, resulting in more and optically thicker clouds and more downward long-wave radiation. Overall, the updated model better represents the surface energy balance, based on a comparison with >750 months of data from nine automatic weather stations located in East Antarctica. Especially the representation of the turbulent sensible heat flux and net long-wave radiative flux has improved with a decrease in biases of up to 40%. As a result, modelled surface temperatures have increased and the bias, when compared to 10 m snow temperatures from 64 ice-core observations, has decreased from-2.3 K to-1.3 K. The weaker surface temperature inversion consequently improves the representation of the sensible heat flux, whereas wind speed biases remain unchanged. However, significant model biases remain, partly because RACMO2 at a resolution of 27 km is unable to resolve steep topography. © Author(s) 2014."
"7408063586;55268321000;57097535500;57212209888;55356965000;7102862273;","Mixing state of size-selected submicrometer particles in the arctic in May and September 2012",2014,"10.1021/es404622n","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892751673&doi=10.1021%2fes404622n&partnerID=40&md5=a6f1a0dc46845845bb697d49423b25c5","Aerosols have been associated with large uncertainties in estimates of the radiation budget and cloud formation processes in the Arctic. This paper reports the results of a study of in situ measurements of hygroscopicity, fraction of volatile species, mixing state, and off-line morphological and elemental analysis of Aitken and accumulation mode particles in the Arctic (Ny-Ålesund, Svalbard) in May and September 2012. The accumulation mode particles were more abundant in May than in September. This difference was due to more air mass flow from lower latitude continental areas, weaker vertical mixing, and less wet scavenging in May than in September, which may have led to a higher amount of long-range transport aerosols entering the Arctic in the spring. The Aitken mode particles observed intermittently in May were produced by nucleation, absent significant external mixing, whereas the accumulation mode particles displayed significant external mixing. The occurrence of an external mixing state was observed more often in May than in September and more often in accumulation mode particles than in Aitken mode particles, and it was associated more with continental air masses (Siberian) than with other air masses. The external mixing of the accumulation mode particles in May may have been caused by multiple sources (i.e., long-range transport aerosols with aging and marine aerosols). These groups of externally mixed particles were subdivided into different mixing structures (internal mixtures of predominantly sulfates and volatile organics without nonvolatile species and internal mixtures of sulfates and nonvolatile components, such as sea salts, minerals, and soot). The variations in the mixing states and chemical species of the Arctic aerosols in terms of their sizes, air masses, and seasons suggest that the continuous size-dependent measurements observed in this study are useful for obtaining better estimates of the effects of these aerosols on climate change. © 2013 American Chemical Society."
"36241005100;7006329853;","Delayed onset of runaway and moist greenhouse climates for Earth",2014,"10.1002/2013GL058376","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896691850&doi=10.1002%2f2013GL058376&partnerID=40&md5=4ae07fbf0451a9581e29d4e12e1b9dbd","As the Sun slowly grows brighter over its main sequence lifetime, habitability on Earth's surface will eventually become threatened probably leading to moist and then runaway greenhouse climates. One-dimensional climate models predict that a catastrophic thermal runaway will be triggered by a 6% increase in the solar constant above its present level. However, here simulations using a three-dimensional climate model with fixed carbon dioxide and methane indicate that surface habitability may be maintained at significantly larger solar constants. A 15.5% increase in the solar constant yields global mean surface temperatures of 312.9 K, well short of moist and runaway greenhouse states. Numerical limitations prevent simulation of climates much warmer than this. Nonetheless, our results imply that Earth's climate may remain safe against both water loss and thermal runaway limits for at least another 1.5 billion years and probably for much longer. Key Points Earth remains habitable with at minimum 15.5% increase in the solar constant Subsaturation, clouds, and dynamics responsible for extending habitability Clouds may dissipate in hot climates due to large saturation vapor pressures ©2013. American Geophysical Union. All Rights Reserved."
"35503830800;56253793500;7004060399;7102167757;57198719030;16029719200;7202400272;","Seasonal ventilation of the stratosphere: Robust diagnostics from one-way flux distributions",2014,"10.1002/2013JD020213","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893984771&doi=10.1002%2f2013JD020213&partnerID=40&md5=cf31df34b293672ed3d3c3134755c99c","We present an analysis of the seasonally varying ventilation of the stratosphere using one-way flux distributions. Robust transport diagnostics are computed using GEOSCCM subject to fixed present-day climate forcings. From the one-way flux, we determine the mass of the stratosphere that is in transit since entry through the tropical tropopause to its exit back into the troposphere, partitioned according to stratospheric residence time and exit location. The seasonalities of all diagnostics are quantified with respect to the month of year (a) when air enters the stratosphere, (b) when the mass of the stratosphere is partitioned, and (c) when air exits back into the troposphere. We find that the return flux, within 3 months since entry, depends strongly on when entry occurred: (34˙10)% more of the air entering the stratosphere in July leaves poleward of 45ı N compared to air that enters in January. The month of year when the air mass is partitioned is also found to be important: The stratosphere contains about six times more air of tropical origin during late summer and early fall that will leave poleward of 45ı within 6 months since entering the stratosphere compared to during late winter to late spring. When the entire mass of the air that entered the stratosphere at the tropics regardless of its residence time is considered, we find that (51˙1)% and (39˙2)% will leave poleward of 10ı in the Nothern Hemisphere (NH) and Southern Hemisphere (SH), respectively. © 2013. American Geophysical Union. All rights reserved."
"25521667800;7101630970;7004942632;","A Lagrangian analysis of ice-supersaturated air over the North Atlantic",2014,"10.1002/2013JD020251","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893932255&doi=10.1002%2f2013JD020251&partnerID=40&md5=3bb10421f38cff1ef3dfc7a7d9dd0fa0","Understanding the nature of air parcels that exhibit ice supersaturation is important because they are the regions of potential formation of both cirrus and aircraft contrails, which affect the radiation balance. Ice-supersaturated air parcels in the upper troposphere and lower stratosphere over the North Atlantic are investigated using Lagrangian trajectories. The trajectory calculations use European Centre for Medium-Range Weather Forecasts Interim reanalysis data for three winter and three summer seasons, resulting in approximately 200,000 trajectories with ice supersaturation for each season. For both summer and winter, the median duration of ice supersaturation along a trajectory is less than 6 h. Five percent of air which becomes ice supersaturated in the troposphere and 23% of air which becomes ice supersaturated in the stratosphere will remain ice supersaturated for at least 24 h. Weighting the ice-supersaturation duration with the observed frequency indicates the likely overall importance of the longer duration ice-supersaturated trajectories. Ice-supersaturated air parcels typically experience a decrease in moisture content while ice supersaturated, suggesting that cirrus clouds eventually form in the majority of such air. A comparison is made between short-lived (less than 24 h) and long-lived (greater than 24 h) ice-supersaturated air flows. For both air flows, ice supersaturation occurs around the northernmost part of the trajectory. Short-lived ice-supersaturated air flows show no significant differences in speed or direction of movement to subsaturated air parcels. However, long-lived ice-supersaturated air occurs in slower-moving air flows, which implies that they are not associated with the fastest moving air through a jet stream. © 2013. American Geophysical Union. All rights reserved."
"35224467200;36131817700;56006167800;36058718900;16679273900;51664948800;55261403000;55376151400;42861975100;9243515100;","Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments",2014,"10.5194/cp-10-91-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892604510&doi=10.5194%2fcp-10-91-2014&partnerID=40&md5=ab907830e9041a19f866bb03c00b1a84","Grain-size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy, this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain-size end-member modelling analysis. Between three and five robust grain-size end-member subpopulations were distinguished at different sites from similarly-likely end-member model runs. Their main modes were grouped and linked to common sediment transport and depositional processes that can be associated with contemporary Tibetan climate (precipitation patterns and lake ice phenology, gridded wind and shear stress data from the High Asia Reanalysis) and local catchment configurations. The coarse sands and clays with grain-size modes >250 μm and <2 μm were probably transported by fluvial processes. Aeolian sands (∼200 μm) and coarse local dust (∼60 μm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ∼25 μm may derive from near-by sources that keep in longer term suspension. The continuous background dust is differentiated into two robust end members (modes: 5-10 and 2-5 μm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upper-level westerly and episodic northerly wind transport. According to this study grain-size end members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19± 5%), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14% and 51 ± 11%). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history. © 2014 Author(s)."
"6701643061;","Electrostatic modeling of intracloud stepped leader electric fields and mechanisms of terrestrial gamma ray flashes",2014,"10.1002/2013GL058983","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896719137&doi=10.1002%2f2013GL058983&partnerID=40&md5=ff2ed3b40038efb923202fd9a9fadd23","Understanding of electric field configurations created by long intracloud (IC) stepped leaders is of significant interest for understanding how these events produce bursts of high-energy photons in the Earth's atmosphere, commonly referred to as terrestrial gamma ray flashes (TGFs). In the present work modeling results using the electrostatic moment method solutions are used for quantitative interpretation of electric fields observed at close ∼200 m and long ∼30 km ranges from IC stepped leaders. The modeling results are consistent with the existence and continuous advancement of VHF-dark positive leaders at the positive end of the bidirectional leader system. It is demonstrated that the electric dipole moment of the entire leader system is a quadratic function of the leader length, and the dipole moment changes due to the leader steps increase proportionally to the overall leader length (i.e., even when step length remains constant), in good agreement with observations. The results indicate that the dipole moment changes on the order of tens of C km and current moment changes on the order of tens of kA km, that have been associated with TGFs, are essential attributes of long IC stepped leaders and directly follow from their intrinsic large-scale charge dynamics. Key Points Results provide evidence of VHF-dark positive leaders in bidirectional system Dipole moment of the leader system is a quadratic function of the leader length Current moment changes tens of kA km in TGFs are attributes of IC leaders ©2013. American Geophysical Union. All Rights Reserved."
"55321814200;10244893900;56962763800;7004005379;8619735800;24529026200;6603892355;","Solar radiation measurements compared to simulations at the BSRN Izaña station. Mineral dust radiative forcing and efficiency study",2014,"10.1002/2013JD020301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893977982&doi=10.1002%2f2013JD020301&partnerID=40&md5=2827ce3154042c5b7e52284446cb57ff","This paper presents a comparative study of shortwave downward radiation (SDR) measurements and simulations, obtained with the radiative transfer model LibRadtran, at the Baseline Surface Radiation Network (BSRN) site of Izaña Atmospheric Observatory (IZA, Spain). The analysis is based on cloud-free days between March 2009 and August 2012 (386 days), including aerosol-free and Saharan mostly pure mineral dust conditions and comparing the day-to-day, annual, and interannual variability. The observed agreement between simulations and measurements is excellent: the variance of daily measurements overall agrees within 99% with the variance of daily simulations, and the mean bias (simulations–measurements) is –0.30 ˙ 0.24 MJm–2 (–1.1 ˙ 0.9%) for global, –0.16 ˙ 0.34 MJm–2 (–0.4 ˙ 0.9%) for direct, and +0.02 ˙ 0.25 MJm–2 (+0.9 ˙ 9.2%) for diffuse SDR. Furthermore, the diurnally averaged aerosol radiative forcing (∆DF) and radiative forcing efficiency (∆DFeff) due to Saharan mostly pure mineral dust events has been computed at Izaña Observatory. The mean ∆DF values are –7 ˙ 1, –96 ˙ 5, and 44 ˙ 2 Wm–2 for global, direct, and diffuse BSRN SDR, respectively (mean aerosol optical depth, AOD, at 500 nm of 0.18 ˙ 0.01), whereas the mean ∆DFeff values are –59 ˙ 6, –495 ˙ 11, and 230 ˙ 8 Wm–2 per unit of AOD at 500 nm for global, direct, and diffuse BSRN SDR, respectively. These values highlight the importance of scattering processes for mineral dust aerosols: the ratio between ∆DF and the corresponding SDR without aerosols is ~ 2.5% for diffuse SDR versus 0.2% for direct SDR. This illustrates the significant potential of mineral dust particles to cool the Earth-atmosphere system. © 2013. American Geophysical Union. All rights reserved."
"7006453728;55596824500;","A comparative evaluation of impact of domain size and parameterization scheme on simulation of tropical cyclones in the Bay of Bengal",2014,"10.1002/2013JD020592","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893952443&doi=10.1002%2f2013JD020592&partnerID=40&md5=f73892711026029ead04b11fde1cf8b7","A large number of processes and factors control the quality of simulations with a numerical weather prediction model and especially with mesoscale models; identification and optimization of these processes are critical for improving forecast skill. The importance of cumulus parameterization schemes in simulation of tropical cyclones was recognized early, and a large number of studies have addressed this issue. However, certain other aspects have received relatively less attention. In particular, unlike simulation with a global circulation model, a mesoscale simulation is characterized by a limited domain and hence inhomogeneous lateral boundary conditions that strongly affect the quality of the simulation. In this work, we investigate the relative impact of size of the model domain and the cumulus parameterization scheme on simulation of 10 cyclones over the Bay of Bengal during the period 1999–2009. For five domains with different spatial extents, simulations were carried out for three different cumulus parameterization schemes (Anthes-Kuo, Grell, and Kain-Fritsch2) for each of the 10 events (using the mesoscale model MM5). Our results show that the size of the domain also plays an equally critical role as the parameterization scheme in simulation of maximum intensity, track, and spatial structure of the cyclones. The impact of domain size is not linear; while each domain chosen is large enough, neither the largest nor the smallest domain provides the best simulation. However, there is consistency in the sense that a single domain emerges as best for intensity and track among the five considered. While the specific conclusions may depend on the ocean basin, the methodology is generic and can be applied to any ocean basin of cyclogenesis. © 2013. American Geophysical Union. All rights reserved."
"7404303923;7004500706;8068419200;36655855100;55199580500;55578889300;54279670400;8401913500;6508089485;55199710600;36701462300;13410099900;6603196127;7102886537;8657988300;7005978899;6701853567;7004828383;36728564200;","Evaluating the dominant components of warming in Pliocene climate simulations",2014,"10.5194/cp-10-79-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892608937&doi=10.5194%2fcp-10-79-2014&partnerID=40&md5=7bbfb52c58a777d2bbd0c20c026c0bb1","The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 °C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean-atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with the cloud component of planetary albedo enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere midlatitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo, only partially offset by the increases in the cooling impact of cloud albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with clouds in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that albedo feedbacks, particularly those of sea ice and ice sheets, provide the most significant enhancements to high latitude warming in the Pliocene. © 2014 Author(s)."
"8750834400;55918124000;55918374200;35460698500;13605209800;56105932800;35168359400;","Inverse insolation dependence of Venus' cloud-level convection",2014,"10.1016/j.icarus.2013.10.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887209200&doi=10.1016%2fj.icarus.2013.10.012&partnerID=40&md5=66da94ac4fa0ef7b9b5f4095d7f856c8","It is generally accepted that convection in planetary atmospheres is enhanced in low latitudes and in the daytime where incoming solar radiation is intense. Here we demonstrate, using a local convection model, that this tendency is reversed for Venus' cloud-level convection, which is driven by heating of the cloud base by upwelling infrared radiation. The dense lower atmosphere of Venus serves as a heat reservoir, whose temperature is horizontally well homogenized by large-scale dynamics, and thus upwelling infrared flux heats the cloud base almost equally over the entire planet. Since solar radiation preferentially heats the upper part of the cloud and has a stabilizing influence on the atmosphere, convection is relatively suppressed in low latitudes and in the daytime. The inverse insolation dependence seen in the numerical model explains observations of the latitudinal dependence of the convective layer depth and the gravity wave activity. The mechanism suggested in this study should be taken into account in climate modeling of Venus and cloudy exoplanets. How the combination of the opposite effects of the infrared heating and the solar heating determines the global distribution of the convective activity is an issue of universal importance. A long-lifetime Venus balloon floating at cloud heights would be useful for understanding these dynamical processes and the associated material transport. © 2013 Elsevier Inc."
"55875842200;7409080503;","Estimation of cloud condensation nuclei concentration from aerosol optical quantities: Influential factors and uncertainties",2014,"10.5194/acp-14-471-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892615220&doi=10.5194%2facp-14-471-2014&partnerID=40&md5=82b7bde04d712c1ce8a226e95289eb87","Large-scale measurements of cloud condensation nuclei (CCN) are difficult to obtain on a routine basis, whereas aerosol optical quantities are more readily available. This study investigates the relationship between CCN and aerosol optical quantities for some distinct aerosol types using extensive observational data collected at multiple Atmospheric Radiation Measurement (ARM) Climate Research Facility (CRF) sites around the world. The influences of relative humidity (RH), aerosol hygroscopicity (fRH) and single scattering albedo (SSA) on the relationship are analyzed. Better relationships are found between aerosol optical depth (AOD) and CCN at the Southern Great Plains (US), Ganges Valley (India) and Black Forest sites (Germany) than those at the Graciosa Island (the Azores) and Niamey (Niger) sites, where sea salt and dust aerosols dominate, respectively. In general, the correlation between AOD and CCN decreases as the wavelength of the AOD measurement increases, suggesting that AOD at a shorter wavelength is a better proxy for CCN. The correlation is significantly improved if aerosol index (AI) is used together with AOD. The highest correlation exists between CCN and aerosol scattering coefficients (σsp) and scattering AI measured in situ. The CCN-AOD (AI) relationship deteriorates with increasing RH. If RH exceeds 75%, the relationship where AOD is used as a proxy for CCN becomes invalid, whereas a tight σsp-CCN relationship exists for dry particles. Aerosol hygroscopicity has a weak impact on the σsp-CCN relationship. Particles with low SSA are generally associated with higher CCN concentrations, suggesting that SSA affects the relationship between CCN concentration and aerosol optical quantities. It may thus be used as a constraint to reduce uncertainties in the relationship. A significant increase in σsp and decrease in CCN with increasing SSA is observed, leading to a significant decrease in their ratio (CCN/σsp) with increasing SSA. Parameterized relationships are developed for estimating CCN, which account for RH, particle size, and SSA."
"57217352376;24757981500;57193840197;","Boundary layer aerosol characteristics at Mahabubnagar during CAIPEEX-IGOC: Modeling the optical and radiative properties",2014,"10.1016/j.scitotenv.2013.09.039","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885084826&doi=10.1016%2fj.scitotenv.2013.09.039&partnerID=40&md5=966d18f4122acd7c13fb3bbacdd3e25b","An Integrated Ground Observational Campaign (IGOC) was conducted at Mahabubnagar - a tropical rural station in the southern peninsular India, under the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) program during the period from July to November 2011. Measured chemical composition and carbonaceous aerosols from PM2.5 samples were used in an aerosol optical model to deduce crucial aerosol optical properties, which were then used in a radiative transfer model for radiative forcing estimations. The model derived aerosol optical depth (AOD at 500nm), varied from 0.13 to 0.76 (mean of 0.40±0.18) whereas Ångström exponent (AE) between 0.10 and 0.65 (mean of 0.33±0.17) suggests relative dominance of coarse particles over the station. On the other hand, single scattering albedo (SSA at 500nm) was found to vary from 0.78 to 0.92 (mean of 0.87±0.04) during the measurement period. The magnitude of absorption Ångström exponent (AAE), varied from 0.83 to 1.33 (mean of 1.10±0.15), suggests mixed type aerosols over the station. Aerosol direct radiative forcing was estimated and found to vary from -8.9 to -49.3Wm-2 (mean of -27.4±11.8Wm-2) at the surface and +9.7 to +44.5Wm-2 (mean of +21.3±9.4Wm-2) in the atmosphere during the course of measurements. The atmospheric forcing was observed to be ~30% higher during October (+29±9Wm-2) as compared to August (+21±7Wm-2) when the station is mostly influenced by continental polluted aerosols. The result suggests an additional atmospheric heating rate of 0.24Kday-1 during October, which may be crucial for various boundary layer processes in favorable atmospheric conditions. © 2013."
"6602909313;55851533800;24537421700;55851487700;8836278700;35577097300;","Temporal variation of aerosol optical depth and associated shortwave radiative forcing over a coastal site along the west coast of India",2014,"10.1016/j.scitotenv.2013.08.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883757138&doi=10.1016%2fj.scitotenv.2013.08.013&partnerID=40&md5=ee070cfcf6be88c431dd30b15e44ea14","Optical characterization of aerosol was performed by assessing the columnar aerosol optical depth (AOD) and angstrom wavelength exponent (α) using data from the Microtops II Sunphotometer. The data were collected on cloud free days over Goa, a coastal site along the west coast of India, from January to December 2008. Along with the composite aerosol, the black carbon (BC) mass concentration from the Aethalometer was also analyzed. The AOD0.500μm and angstrom wavelength exponent (α) were in the range of 0.26 to 0.7 and 0.52 to 1.33, respectively, indicative of a significant seasonal shift in aerosol characteristics during the study period. The monthly mean AOD0.500μm exhibited a bi-modal distribution, with a primary peak in April (0.7) and a secondary peak in October (0.54), whereas the minimum of 0.26 was observed in May. The monthly mean BC mass concentration varied between 0.31μg/m3 and 4.5μg/m3, and the single scattering albedo (SSA), estimated using the OPAC model, ranged from 0.87 to 0.97. Modeled aerosol optical properties were used to estimate the direct aerosol shortwave radiative forcing (DASRF) in the wavelength range 0.25μm4.0μm. The monthly mean forcing at the surface, at the top of the atmosphere (TOA) and in the atmosphere varied between -14.1Wm-2 and -35.6Wm-2, -6.7Wm-2 and -13.4Wm-2 and 5.5Wm-2 to 22.5Wm-2, respectively. These results indicate that the annual SSA cycle in the atmosphere is regulated by BC (absorbing aerosol), resulting in a positive forcing; however, the surface forcing was governed by the natural aerosol scattering, which yielded a negative forcing. These two conditions neutralized, resulting in a negative forcing at the TOA that remains nearly constant throughout the year. © 2013 Elsevier B.V."
"7006041988;7003663305;36856321600;22978151200;56835353400;7401974644;9242540400;7402064802;7003875148;","Near-surface meteorology during the Arctic Summer Cloud Ocean Study (ASCOS): Evaluation of reanalyses and global climate models",2014,"10.5194/acp-14-427-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892567478&doi=10.5194%2facp-14-427-2014&partnerID=40&md5=3038314d7cdbf390cd93ce634676653c","Atmospheric measurements from the Arctic Summer Cloud Ocean Study (ASCOS) are used to evaluate the performance of three atmospheric reanalyses (European Centre for Medium Range Weather Forecasting (ECMWF)-Interim reanalysis, National Center for Environmental Prediction (NCEP)-National Center for Atmospheric Research (NCAR) reanalysis, and NCEP-DOE (Department of Energy) reanalysis) and two global climate models (CAM5 (Community Atmosphere Model 5) and NASA GISS (Goddard Institute for Space Studies) ModelE2) in simulation of the high Arctic environment. Quantities analyzed include near surface meteorological variables such as temperature, pressure, humidity and winds, surface-based estimates of cloud and precipitation properties, the surface energy budget, and lower atmospheric temperature structure. In general, the models perform well in simulating large-scale dynamical quantities such as pressure and winds. Near-surface temperature and lower atmospheric stability, along with surface energy budget terms, are not as well represented due largely to errors in simulation of cloud occurrence, phase and altitude. Additionally, a development version of CAM5, which features improved handling of cloud macro physics, has demonstrated to improve simulation of cloud properties and liquid water amount. The ASCOS period additionally provides an excellent example of the benefits gained by evaluating individual budget terms, rather than simply evaluating the net end product, with large compensating errors between individual surface energy budget terms that result in the best net energy budget."
"55200342600;6701712459;11940707700;37461808200;6602438071;","A satellite-based snow cover climatology (1985-2011) for the European Alps derived from AVHRR data",2014,"10.5194/tc-8-73-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892771593&doi=10.5194%2ftc-8-73-2014&partnerID=40&md5=7391391bf553be1c62aa1fefcde78f2d","Seasonal snow cover is of great environmental and socio-economic importance for the European Alps. Therefore a high priority has been assigned to quantifying its temporal and spatial variability. Complementary to land-based monitoring networks, optical satellite observations can be used to derive spatially comprehensive information on snow cover extent. For understanding long-term changes in alpine snow cover extent, the data acquired by the Advanced Very High Resolution Radiometer (AVHRR) sensors mounted onboard the National Oceanic and Atmospheric Association (NOAA) and Meteorological Operational satellite (MetOp) platforms offer a unique source of information. In this paper, we present the first space-borne 1 km snow extent climatology for the Alpine region derived from AVHRR data over the period 1985-2011. The objective of this study is twofold: first, to generate a new set of cloud-free satellite snow products using a specific cloud gap-filling technique and second, to examine the spatiotemporal distribution of snow cover in the European Alps over the last 27 yr from the satellite perspective. For this purpose, snow parameters such as snow onset day, snow cover duration (SCD), melt-out date and the snow cover area percentage (SCA) were employed to analyze spatiotemporal variability of snow cover over the course of three decades. On the regional scale, significant trends were found toward a shorter SCD at lower elevations in the south-east and south-west. However, our results do not show any significant trends in the monthly mean SCA over the last 27 yr. This is in agreement with other research findings and may indicate a deceleration of the decreasing snow trend in the Alpine region. Furthermore, such data may provide spatially and temporally homogeneous snow information for comprehensive use in related research fields (i.e., hydrologic and economic applications) or can serve as a reference for climate models. © 2014 Author(s). CC Attribution 3.0 License."
"6701363731;6505791231;15019752400;19934555300;55987577800;7006058570;7005219614;","Summertime free-tropospheric ozone pool over the eastern Mediterranean/middle east",2014,"10.5194/acp-14-115-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891699219&doi=10.5194%2facp-14-115-2014&partnerID=40&md5=9a30f89a6d22334718f408c3e33b14c5","Observations show that the Mediterranean troposphere is characterized by a marked enhancement in summertime ozone, with a maximum over the eastern Mediterranean. This has been linked to enhanced photochemical ozone production and subsidence under cloud-free anticyclonic conditions. The eastern Mediterranean is among the regions with the highest levels of background tropospheric ozone worldwide. A 12 yr climatological analysis (1998-2009) of free-tropospheric ozone was carried out over the region based on the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data and simulations with the EMAC (ECHAM5-MESSy) atmospheric chemistry-climate model. EMAC is nudged towards the ECMWF analysis data and includes a stratospheric ozone tracer. A characteristic summertime pool with high ozone concentrations is found in the middle troposphere over the eastern Mediterranean-Middle East (EMME) in the ERA-Interim ozone data, Tropospheric Emission Spectrometer (TES) satellite ozone data and simulations with EMAC. The enhanced ozone over the EMME during summer is a robust feature, extending down to lower free-tropospheric levels. The investigation of ozone in relation to potential vorticity and water vapour and the stratospheric ozone tracer indicates that the dominant mechanism causing the free-tropospheric ozone pool is the downward transport from the upper troposphere and lower stratosphere, in association with the enhanced subsidence and the limited horizontal divergence observed over the region. The implications of these high free-tropospheric ozone levels on the seasonal cycle of near-surface ozone over the Mediterranean are discussed. © 2014 Author(s) ."
"7004479957;8882641700;16029674800;","Cloud feedbacks on greenhouse warming in the superparameterized climate model SP-CCSM4",2014,"10.1002/2014MS000355","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027950951&doi=10.1002%2f2014MS000355&partnerID=40&md5=b7bb164ae9e2a943183ac3504e7f6c63","Cloud feedbacks on greenhouse warming are studied in a superparameterized version of the Community Climate System Model (SP-CCSM4) in an atmospheric component SP-CAM4 that explicitly simulates cumulus convection. A 150 year simulation in an abrupt quadrupling of CO2 is branched from a control run. It develops moderate positive global cloud feedback and an implied climate sensitivity of 2.8 K comparable to the conventionally parameterized CCSM4 and the median of other modern climate models. All of SP-CCSM4's positive shortwave cloud feedback is due to a striking decrease in low cloud over land, which is much more pronounced than in most other climate models, including CCSM4. Four other cloud responses - decreased midlevel cloud, more Arctic water and ice cloud, a slight poleward shift of midlatitude storm track cloud, and an upward shift of high clouds - are also typical of conventional global climate models. SP-CCSM4 does not simulate the large warming-induced decrease in Southern Ocean cloud found in CCSM4. Two companion uncoupled SP-CAM4 simulations, one with a uniform 4 K sea-surface temperature increase and one with quadrupled CO2 but fixed SST, suggest that SP-CCSM4's global-scale cloud changes are primarily mediated by the warming, rather than by rapid adjustments to increased CO2. SP-CAM4 show spatial patterns of cloud response qualitatively similar to the previous-generation superparameterized SP-CAM3, but with systematically more positive low cloud feedbacks over low-latitude land and ocean. Key Points: The superparameterized SP-CCSM4 has moderate positive cloud feedbacks It simulates less low cloud over land as climate warms SP-CCSM4 rapid cloud adjustments associated with abrupt CO2 increase are weak © 2014. The Authors."
"56005080300;23082420800;8696069500;57197233116;7201504886;","Simulating the role of subtropical stratocumulus clouds in driving Pacific climate variability",2014,"10.1175/JCLI-D-13-00548.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903398794&doi=10.1175%2fJCLI-D-13-00548.1&partnerID=40&md5=1e6ff096dc77f31888a28513f9f059d4","This study examines the influence of the northeast and southeast Pacific subtropical stratocumulus cloud regions on the modes of Pacific climate variability simulated by an atmospheric general circulation model (ECHAM6) coupled to a slab ocean. The sensitivity of cloud liquid water to underlying SST is changed in the radiation module of the atmospheric model to increase the strength of positive low-cloud feedback in the two regions. Enhanced low-cloud feedback increases the persistence and variance of the leading modes of climate variability at decadal and longer time scales. Additional integrations show that the southeast Pacific influences climate variability in the equatorial ENSO region, whereas the effects of the northeast Pacific remain confined to the North Pacific. The results herein suggest that a positive feedback among SST, cloud cover, and large-scale atmospheric circulation can explain decadal climate variability in the Pacific Ocean. In particular, cloud feedbacks over the subtropical stratocumulus regions set the time scale of climate variability. A proper representation of low-level cloud feedbacks in the subtropical stratocumulus regions could therefore improve the simulation of Pacific climate variability. © 2014 American Meteorological Society."
"56457851700;7202145115;16444006500;","Observed Southern Ocean cloud properties and shortwave reflection. Part II: Phase changes and low cloud feedback",2014,"10.1175/JCLI-D-14-00288.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919629576&doi=10.1175%2fJCLI-D-14-00288.1&partnerID=40&md5=34081536e75c4dd8659c46a209a561fb","Climate models produce an increase in cloud optical depth in midlatitudes associated with climate warming, but the magnitude of this increase and its impact on reflected solar radiation vary from model to model. Transition from ice to liquid in midlatitude clouds is thought to be one mechanism for producing increased cloud optical depth. Here observations of cloud properties are used from a suite of remote sensing instruments to estimate the effect of conversion of ice to liquid associated with warming on reflected solar radiation in the latitude band from 40° to 60°S. The calculated increase in upwelling shortwave radiation (SW↑) is found to be important and of comparable magnitude to the increase in SW↑ associated with warming-induced increases of optical depth in climate models. The region where the authors' estimate increases SW↑ extends farther equatorward than the region where optical depth increases with warming in models. This difference is likely caused by other mechanisms at work in the models but is also sensitive to the amount of ice present in climate models and its susceptibility to warming. © 2014 American Meteorological Society."
"7501720647;36934610300;55220976100;","Stratocumulus clouds in Southeastern pacific simulated by eight CMIP5-CFMIP global climate models",2014,"10.1175/JCLI-D-13-00376.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898020225&doi=10.1175%2fJCLI-D-13-00376.1&partnerID=40&md5=1ad15a4c5095cfbc6b70e22dfb33955c","This study examines the stratocumulus clouds and associated cloud feedback in the southeast Pacific (SEP) simulated by eight global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) and Cloud Feedback Model Intercomparison Project (CFMIP) using long-term observations of clouds, radiative fluxes, cloud radiative forcing (CRF), sea surface temperature (SST), and large-scale atmosphere environment. The results show that the state-of-the-art global climate models still have significant difficulty in simulating the SEP stratocumulus clouds and associated cloud feedback. Comparing with observations, the models tend to simulate significantly less cloud cover, higher cloud top, and a variety of unrealistic cloud albedo. The insufficient cloud cover leads to overly weak shortwave CRF and net CRF. Only two of the eight models capture the observed positive cloud feedback at subannual to decadal time scales. The cloud and radiation biases in the models are associated with 1) model biases in large-scale temperature structure including the lack of temperature inversion, insufficient lower troposphere stability (LTS), and insufficient reduction of LTS with local SST warming, and 2) improper model physics, especially insufficient increase of low cloud cover associated with larger LTS. The two models that arguably do best at simulating the stratocumulus clouds and associated cloud feedback are the only ones using cloud-top radiative cooling to drive boundary layer turbulence. © 2014 American Meteorological Society."
"7202970886;6603631763;","Entering the era of 130-year satellite cloud climatologies: A North American case study",2014,"10.1175/JCLI-D-14-00068.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906871572&doi=10.1175%2fJCLI-D-14-00068.1&partnerID=40&md5=bf90c510747fd952039415f1c614b8ad","The emergence of satellite-based cloud records of climate length and quality hold tremendous potential for climate model development, climate monitoring, and studies on global water cycling and its subsequent energetics. This article examines the more than 30-yr Pathfinder Atmospheres-Extended (PATMOS-x) Advanced Very High Resolution Radiometer (AVHRR) cloudiness record over North America and assesses its suitability as a climate-quality data record. A loss of ̃4.2% total cloudiness is observed between 1982 and 2012 over a North American domain centered over the contiguous United States. While ENSO can explain some of the observed change, a weather state clustering analysis identifies shifts in weather patterns that result in loss of water cloud over the Great Lakes and cirrus over southern portions of the United States. The radiative properties of the shifting weather states are characterized, and the results suggest that extended cloud satellite records may prove useful tools for increasing knowledge of cloud feedbacks, a long-standing issue in the climate change community. © 2014 American Meteorological Society."
"16202694600;7004060399;","Southern hemisphere cloud-dynamics biases in CMIP5 models and their implications for climate projections",2014,"10.1175/JCLI-D-14-00113.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905177906&doi=10.1175%2fJCLI-D-14-00113.1&partnerID=40&md5=df67aa7a7f968525a8c8cab21adcac7a","This study quantifies cloud-radiative anomalies associated with interannual variability in the latitude of the Southern Hemisphere (SH) midlatitude eddy-driven jet, in 20 global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Two distinct model types are found. In the first class of models (type I models), total cloud fraction is reduced at SH midlatitudes as the jet moves poleward, contributing to enhanced shortwave radiative warming. In the second class of models (type II models), this dynamically induced cloud radiative warming effect is largely absent. Type I and type II models have distinct deficiencies in their representation of observed Southern Ocean clouds, but comparison with two independent satellite datasets indicates that the cloud-dynamics behavior of type II models is more realistic. Because the SH midlatitude jet shifts poleward in response to CO2 forcing, the cloud-dynamics biases uncovered from interannual variability are directly relevant for climate change projections. In CMIP5 model experiments with abruptly quadrupled atmospheric CO2 concentrations, the global-mean surface temperature initially warms more in type I models, even though their equilibrium climate sensitivity is not significantly larger. In type I models, this larger initial warming is linked to the rapid adjustment of the circulation and clouds to CO2 forcing in the SH, where a nearly instantaneous poleward shift of the midlatitude jet is accompanied by a reduction in the reflection of solar radiation by clouds. In type II models, the SH jet also shifts rapidly poleward with CO2 quadrupling, but it is not accompanied by cloud radiative warming anomalies, resulting in a smaller initial global-mean surface temperature warming. © 2014 American Meteorological Society."
"57198208348;12801992200;57219951382;","Improved representation of marine stratocumulus cloud shortwave radiative properties in the CMIP5 climate models",2014,"10.1175/JCLI-D-13-00755.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905915164&doi=10.1175%2fJCLI-D-13-00755.1&partnerID=40&md5=0317b1a8c99513c14d9140326519a02f","The radiative properties of subtropical marine stratocumulus clouds are investigated in an ensemble of current-generation global climate models from phase 5 of the Climate Model Intercomparison Project (CMIP5). Using a previously documented method for determining regional mean cloud albedo, the authors find a closer agreement with observations in the CMIP5 models as compared to the previous generation of models (phase 3 of CMIP). The multimodel average indicates regional mean, monthly mean cloud albedos ranging from 0.32 to 0.5 among 26 models and five regions, to be compared with satellite observations that indicate a range from 0.32 to 0.39 for the same five regions. The intermodel spread in cloud fraction gives rise to a spread in albedo. Within models, there is a tendency for large cloud fraction to be related to low cloud albedo and vice versa, a relationship that dampens the intermodel variability in total albedo. The intramodel variability in albedo, for a given cloud fraction, is found to be up to twice as large in magnitude in models as in satellite observations. The reason for this larger variability in models is not settled, but possible contributing factors may be imperfect representation in the models of cloud type distribution or of sensitivity to meteorological variability or aerosols. Changes in aerosol loading are found to be the likely cause of an increase in cloud albedo over time. The radiative effect of such a scene brightening in marine stratocumulus cloud regions, from preindustrial times to present day, is estimated to be up to -1 W m-2 for the global ocean, but there are no observations to verify this number. © 2014 American Meteorological Society."
"13402835300;7404142321;7003976079;6603853280;8397494800;7004714030;8918407000;7201504886;22137065500;10241462700;","Origins of the solar radiation biases over the Southern Ocean in CFMIP2 models",2014,"10.1175/JCLI-D-13-00169.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892601126&doi=10.1175%2fJCLI-D-13-00169.1&partnerID=40&md5=ca00241e76b8053c42ff0d3de593e441","Current climate models generally reflect too little solar radiation over the Southern Ocean, which may be the leading cause of the prevalent sea surface temperature biases in climate models. The authors study the role of clouds on the radiation biases in atmosphere-only simulations of the Cloud Feedback Model Intercomparison Project phase 2 (CFMIP2), as clouds have a leading role in controlling the solar radiation absorbed at those latitudes. The authors composite daily data around cyclone centers in the latitude band between 40° and 70°S during the summer. They use cloud property estimates from satellite to classify clouds into different regimes, which allow them to relate the cloud regimes and their associated radiative biases to themeteorological conditions in which they occur. The cloud regimes are defined using cloud properties retrieved using passive sensors and may suffer from the errors associated with this type of retrievals. The authors use information from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar to investigate inmore detail the properties of the ""midlevel"" cloud regime.Most of the model biases occur in the cold-air side of the cyclone composite, and the cyclone composite accounts formost of the climatological error in that latitudinal band. The midlevel regime is themain contributor to reflected shortwave radiation biases. CALIPSO data show that themidlevel cloud regime is dominated by two main cloud types: cloud with tops actually at midlevel and low-level cloud. Improving the simulation of these cloud types should help reduce the biases in the simulation of the solar radiation budget in the Southern Ocean in climate models. © 2014 American Meteorological Society."
"8262131200;7103172539;55738125200;21735966500;57202482489;56355463900;","Application of satellite data for evaluating the cold climate performance of the Canadian regional climate model over Québec, Canada",2014,"10.1175/JHM-D-13-086.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897971928&doi=10.1175%2fJHM-D-13-086.1&partnerID=40&md5=dcb378209252846b4d4ab14ad8d5c1b3","This study evaluates key aspects of the snow cover, cloud cover, and radiation budget simulated by the Canadian Regional Climate Model, version 4 (CRCM4), coupled with two versions of the Canadian Land Surface Scheme (CLASS). CRCM4 coupled with CLASS version 2.7 has been used operationally at Ouranos since 2006, while, more recently, CRCM4 has been coupled experimentally with CLASS 3.5, which includes a number of improvements to the representation of snow cover processes. The simulations showed evidence of a systematic cold temperature bias. Evaluation of cloud cover and radiation fluxes with satellite data suggests this bias is related to insufficient cloud radiative forcing from a combination of underestimated cloud cover, excessive cloud albedo, and too low cloud emissivity in the model. This cold bias is reinforced by a positive snow albedo feedback manifest through earlier snow cover onset in the fall and early winter period. Snow albedo was found to be very sensitive to the treatment of albedo refresh but insignificantly influenced by the partitioning of solid precipitation in CLASS. This study demonstrates that atmospheric forcing can exert a significant impact on the simulation of snow cover and surface albedo. The results highlight the need to evaluate parameterizations in land surface models designed for climate models in fully coupled mode."
"6602611139;6602786888;","Effect of cloudiness on long-term variability in air temperature in Krakow",2014,"10.1002/joc.3672","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891741811&doi=10.1002%2fjoc.3672&partnerID=40&md5=60d7c65d8d70d31bf3d3a461951a1b3b","The purpose of this article is to describe the effect of cloudiness on long-term changes in air temperature. The article attempts to assess the role of clouds in contemporary climate change. The article is based on archived air temperature and cloudiness data obtained from the Jagiellonian University in Krakow. The analyses include mean daily air temperature and cloud cover data for years 1863-2010 and noontime cloud genus observations for years 1906-2010. It was concluded that the increase in air temperature in Krakow is more strongly associated with changes in the structure of cloudiness than changes in the amount of cloudiness. The relationship between these two types of changes is more apparent during the second half of the 20th century, in an era of accelerating climate warming. © 2013 Royal Meteorological Society."
"10241250100;55686667100;10243650000;10241462700;7102857642;","Multi-parameter multi-physics ensemble (MPMPE): A new approach exploring the uncertainties of climate sensitivity",2014,"10.1002/asl2.472","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905919525&doi=10.1002%2fasl2.472&partnerID=40&md5=156651b7584295bbc05e320f6d3eb0c9","To explore both the parametric and structural uncertainties of climate sensitivity (CS), we have proposed a new general circulation model (GCM) ensemble termed the multi-parameter multi-physics ensemble (MPMPE). We used eight multi-physics ensemble (MPE) models in which the MIROC5 physics schemes were replaced by those of MIROC3. MPMPE consisted of perturbed-physics ensembles in which the parameter values were swept for each MPE model. MPMPE resulted in a wide range of CS, which was related to the shortwave cloud feedback (SWcld). Coupling between low- and mid-level clouds controlled the differences in the parametric spread of SWcld among the MPE models. © 2014 Royal Meteorological Society."
"37099944400;57203030873;25031430500;55717074000;56119479900;52464731300;6603925960;","Contributions of clouds, surface albedos, and mixed-phase ice nucleation schemes to Arctic radiation biases in CAM5",2014,"10.1175/JCLI-D-13-00608.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903386100&doi=10.1175%2fJCLI-D-13-00608.1&partnerID=40&md5=afc90bd55fa42c8dad01b909d60665a2","The Arctic radiation balance is strongly affected by clouds and surface albedo. Prior work has identified Arctic cloud liquid water path (LWP) and surface radiative flux biases in the Community Atmosphere Model, version 5 (CAM5), and reductions to these biases with improved mixed-phase ice nucleation schemes. Here, CAM5 net top-of-atmosphere (TOA) Arctic radiative flux biases are quantified along with the contributions of clouds, surface albedos, and new mixed-phase ice nucleation schemes to these biases. CAM5 net TOA allsky shortwave (SW) and outgoing longwave radiation (OLR) fluxes are generally within 10Wm-2 of Clouds and the Earth's Radiant Energy System Energy Balanced and Filled (CERES-EBAF) observations. However, CAM5 has compensating SW errors: Surface albedos over snow are too high while cloud amount and LWP are too low. Use of a new CAM5 Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar simulator that corrects an error in the treatment of snow crystal size confirms insufficient cloud amount in CAM5 year-round. CAM5 OLR is too low because of low surface temperature in winter, excessive atmospheric water vapor in summer, and excessive cloud heights year-round. Simulations with two new mixed-phase ice nucleation schemes-one based on an empirical fit to ice nuclei observations and one based on classical nucleation theory with prognostic ice nuclei-improve surface climate in winter by increasing cloud amount and LWP. However, netTOAand surface radiation biases remain because of increases in midlevel clouds and a persistent deficit in cloud LWP. These findings highlight challenges with evaluating and modeling Arctic cloud, radiation, and climate processes. © 2014 American Meteorological Society."
"36608763800;8866821900;8696069500;","Mixed-phase clouds cause climate model biases in Arctic wintertime temperature inversions",2014,"10.1007/s00382-013-1964-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903394459&doi=10.1007%2fs00382-013-1964-9&partnerID=40&md5=44a780ab4eb869e00680f3dae49bc12e","Temperature inversions are a common feature of the Arctic wintertime boundary layer. They have important impacts on both radiative and turbulent heat fluxes and partly determine local climate-change feedbacks. Understanding the spread in inversion strength modelled by current global climate models is therefore an important step in better understanding Arctic climate and its present and future changes. Here, we show how the formation of Arctic air masses leads to the emergence of a cloudy and a clear state of the Arctic winter boundary layer. In the cloudy state, cloud liquid water is present, little to no surface radiative cooling occurs and inversions are elevated and relatively weak, whereas surface radiative cooling leads to strong surface-based temperature inversions in the clear state. Comparing model output to observations, we find that most climate models lack a realistic representation of the cloudy state. An idealised single-column model experiment of the formation of Arctic air reveals that this bias is linked to inadequate mixed-phase cloud microphysics, whereas turbulent and conductive heat fluxes control the strength of inversions within the clear state. © 2013 Springer-Verlag Berlin Heidelberg."
"7402786837;6602600408;57208121852;7006689276;","Processes limiting the emergence of detectable aerosol indirect effects on tropical warm clouds in global aerosol-climate model and satellite data",2014,"10.3402/tellusb.v66.24054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901999818&doi=10.3402%2ftellusb.v66.24054&partnerID=40&md5=9135cb87ecf763961778aa343cc3eb46","We use data from simulations performed with the global aerosol-climate model ECHAM5-HAM to test the proposition that shipping emissions do not have a statistically significant effect on water clouds over tropical oceans on climate scales put forward in earlier satellite based work. We analyse a total of four sensitivity experiments, three of which employ global shipping emissions and one simulation which only employs shipping emissions in the mid-Atlantic Ocean. To ensure comparability to earlier results from observations, we sample the model data using a method previously applied to satellite data aimed at separating 'clean' from 'polluted' oceanic regions based on i) the location of main shipping routes and ii) wind direction at 10 mabove sea level. The model simulations run with realistic present-day shipping emissions show changes in the lower tropospheric aerosol population attributable to shipping emissions across major shipping corridors over tropical oceans. However, we find the resulting effect on cloud properties to be non-distinguishable from natural gradients and variability, that is, gradients of cloud properties sampled across major shipping corridors over tropical oceans are very similar among those simulations. Our results therefore compare well to the earlier findings from satellite observations. Substantial changes of the aerosol population and cloud properties only occur when shipping emissions are increased 10-fold. We find that aerosol advection and rapid aerosol removal from the atmosphere play an important role in determining the non-significant response in i) column integrated aerosol properties and ii) cloud microphysical properties in the realistic simulations. Additionally, high variability and infrequent occurrence of simulated low-level clouds over tropical oceans in ECHAM5-HAM limit the development of aerosol indirect effects because i) in-cloud production of sulphate from ship-emitted sulphuric species via aqueous oxidation pathways is very low and ii) a possible observational signal is blurred out by high variability in simulated clouds. Our results highlight i) the importance of adequately accounting for atmospheric background conditions when determining climate forcings from observations and ii) the effectiveness of buffering mechanisms on micro-and macroscopic scales which limit the emergence of such climate forcings. © 2014 K. Peters et al."
"16246205000;55738957800;26324818700;","Characterizing the climate feedback pattern in the NCAR CCSM3-SOM using hourly data",2014,"10.1175/JCLI-D-13-00567.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898026917&doi=10.1175%2fJCLI-D-13-00567.1&partnerID=40&md5=8e2349233ed35cb19b864425f56685de","The climate feedback-response analysis method (CFRAM) was applied to 10-yr hourly output of the NCAR Community Climate System Model, version 3, using the slab ocean model (CCSM3-SOM), to analyze the strength and spatial distribution of climate feedbacks and to characterize their contributions to the global and regional surface temperature Ts changes in response to a doubling of CO2. The global mean bias in the sum of partial Ts changes associated with the CO2 forcing, and each feedback derived with the CFRAM analysis is about 2% of Ts change obtained directly from the CCSM3-SOM simulations. The pattern correlation between the two is 0.94, indicating that the CFRAManalysis using hourlymodel output is accurate and thus is appropriate for quantifying the contributions of climate feedback to the formation of global and regional warming patterns. For global mean Ts, the largest contributor to the warming is water vapor feedback, followed by the direct CO2 forcing and albedo feedback. The albedo feedback exhibits the largest spatial variation, followed by shortwave cloud feedback. In terms of pattern correlation and RMS difference with the modeled global surface warming, longwave cloud feedback contributes the most. On zonal average, albedo feedback is the largest contributor to the stronger warming in high latitudes than in the tropics. The longwave cloud feedback further amplifies the latitudinal warming contrast. Both the land-ocean warming difference and contributions of climate feedbacks to it vary with latitude. Equatorward of 50°, shortwave cloud feedback and dynamical advection are the two largest contributors. The land-ocean warming difference on the hemispheric scale is mainly attributable to longwave cloud feedback and convection. © 2014 American Meteorological Society."
"56321122100;7006698304;6701754792;23017945100;","Characterizing observed midtopped cloud regimes associated with Southern Ocean shortwave radiation biases",2014,"10.1175/JCLI-D-14-00139.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905898101&doi=10.1175%2fJCLI-D-14-00139.1&partnerID=40&md5=68ab7b61ea87b193fb468f45b86e0d72","Clouds strongly affect the absorption and reflection of shortwave and longwave radiation in the atmosphere. A key bias in climate models is related to excess absorbed shortwave radiation in the high-latitude Southern Ocean. Model evaluation studies attribute these biases in part to midtopped clouds, and observations confirm significant midtopped clouds in the zone of interest. However, it is not yet clear what cloud properties can be attributed to the deficit in modeled clouds. Present approaches using observed cloud regimes do not sufficiently differentiate between potentially distinct types of midtopped clouds and their meteorological contexts. This study presents a refined set of midtopped cloud subregimes for the high-latitude Southern Ocean, which are distinct in their dynamical and thermodynamic background states. Active satellite observations from CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) are used to study the macrophysical structure and microphysical properties of the new cloud regimes. The subgrid-scale variability of cloud structure and microphysics is quantified within the cloud regimes by identifying representative physical cloud profiles at high resolution from the radar-lidar (DARDAR) cloud classification mask. The midtopped cloud subregimes distinguish between stratiform clouds under a high inversion and moderate subsidence; an optically thin cold-air advection cloud regime occurring under weak subsidence and including altostratus over low clouds; optically thick clouds with frequent deep structures under weak ascent and warm midlevel anomalies; and a midlevel convective cloud regime associated with strong ascent and warm advection. The new midtopped cloud regimes for the high-latitude Southern Ocean will provide a refined tool for model evaluation and the attribution of shortwave radiation biases to distinct cloud processes and properties. © 2014 American Meteorological Society."
"36131978400;7202208382;16029674800;","Simulations of the West African monsoon with a superparameterized climate model. Part II: African easterly waves",2014,"10.1175/JCLI-D-13-00677.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909619790&doi=10.1175%2fJCLI-D-13-00677.1&partnerID=40&md5=ffaf17993c8b1c4ab3ab5c1956ac805c","The relationship between African easterly waves and convection is examined in two coupled general circulation models: the Community Climate System Model (CCSM) and the ''superparameterized'' CCSM (SP-CCSM). In the CCSM, the easterly waves are much weaker than observed. In the SP-CCSM, a twodimensional cloud-resolving model replaces the conventional cloud parameterizations of CCSM. Results show that this allows for the simulation of easterly waves with realistic horizontal and vertical structures, although the model exaggerates the intensity of easterly wave activity over West Africa. The simulated waves of SP-CCSM are generated in East Africa and propagate westward at similar (although slightly slower) phase speeds to observations. The vertical structure of the waves resembles the first baroclinicmode. The coupling of the waves with convection is realistic. Evidence is provided herein that the diabatic heating associated with deep convection provides energy to the waves simulated in SP-CCSM. In contrast, horizontal and vertical structures of the weak waves in CCSM are unrealistic, and the simulated convection is decoupled from the circulation. © 2014 American Meteorological Society."
"7004544454;24722339600;57201235812;7004479957;7403682442;7006837187;22975069200;55300573400;7003591311;6701404949;18935008000;8285351400;8247122100;35584010200;7005035762;","Ocean-cloud-atmosphere-land interactions in the southeastern pacific",2014,"10.1175/BAMS-D-11-00246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900314869&doi=10.1175%2fBAMS-D-11-00246.1&partnerID=40&md5=d945bc11717ecb7eb8b29b7e7e0207e5","The Variability of American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere- Land Study (VOCALS) is an international research program focused upon improved understanding and modeling of the southeast Pacific (SEP) climate system on diurnal to inter annual time scales. The SEP is characterized by strong coastal ocean upwelling, the coldest sea surface temperatures (SST) at comparable latitudes, the planet's most extensive subtropical stratocumulus deck, and a high and steep cordillera to the east. The VOCALS program is built on several research activities in SEP climate research (Mechoso and Wood 2010). The preceding Eastern Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC) provided important insight on the intertropical convergence zone (ITCZ)/cold-tongue complex and marine boundary layer (MBL) clouds over the SEP."
"56030635600;6603566335;6603606681;56016514800;","A mixed-layer model perspective on stratocumulus steady states in a perturbed climate",2014,"10.1002/qj.2282","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922897105&doi=10.1002%2fqj.2282&partnerID=40&md5=383bae1df727a5f2d3ae6e7c6c95d219","Equilibrium states of stratocumulus are evaluated for a range of free tropospheric conditions in a mixed-layer model framework using a number of different entrainment formulations. The equilibrium states show that a reduced lower tropospheric stability (LTS) and a drier free troposphere support a thicker cloud layer. Furthermore, cooler and drier free-tropospheric conditions promote decoupling which is the first stage of stratocumulus break-up into cumulus. The qualitative results hold for all the considered entrainment formulations, although the precise quantitative details of the boundary-layer state do vary with the choice of entrainment parametrization. Perturbations of the equilibrium states by increasing the sea-surface temperature while keeping the LTS and the free-tropospheric relative humidity constant leads to cloud thinning and an increased occurrence of decoupling regime. These results are in line with recent large-eddy simulation studies and increase the confidence in them by showing their validity for a large range of free tropospheric conditions. © 2013 Royal Meteorological Society."
"6507224579;","Resolved snowball earth clouds",2014,"10.1175/JCLI-D-13-00738.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902089848&doi=10.1175%2fJCLI-D-13-00738.1&partnerID=40&md5=7004063d44d0c8936f2cb3d96eda9c1f","Recent general circulation model (GCM) simulations have challenged the idea that a snowball Earth would be nearly entirely cloudless. This is important because clouds would provide a strong warming to a highalbedo snowball Earth. GCM results suggest that clouds could lower the threshold CO2 needed to deglaciate a snowball by a factor of 10-100, enough to allow consistency with geochemical data. Here a cloud-resolving model is used to investigate cloud and convection behavior in a snowball Earth climate. The model produces convection that extends vertically to a similar temperature as modern tropical convection. This convection produces clouds that resemble stratocumulus clouds under an inversion on modern Earth, which slowly dissipate by sedimentation of cloud ice. There is enough cloud ice for the clouds to be optically thick in the longwave, and the resulting cloud radiative forcing is similar to that produced in GCMs run in snowball conditions. This result is robust to large changes in the cloud microphysics scheme because the cloud longwave forcing, which dominates the total forcing, is relatively insensitive to cloud amount and particle size. The cloud-resolving model results are therefore consistent with the idea that clouds would provide a large warming to a snowball Earth, helping to allow snowball deglaciation. © 2014 American Meteorological Society."
"8969695400;7003278104;57200530823;45961120000;27567747000;8891491000;7003271327;45961715700;55786282000;55786718600;55418990300;13406365400;22947314100;6602999938;","Cloud computing and virtualization within the regional climate model and evaluation system",2014,"10.1007/s12145-013-0126-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894311212&doi=10.1007%2fs12145-013-0126-2&partnerID=40&md5=1f76288872db597b26c823966017fc68","The Regional Climate Model Evaluation System (RCMES) facilitates the rapid, flexible inclusion of NASA observations into climate model evaluations. RCMES provides two fundamental components. A database (RCMED) is a scalable point-oriented cloud database used to elastically store remote sensing observations and to make them available using a space time query interface. The analysis toolkit (RCMET) is a Python-based toolkit that can be delivered as a cloud virtual machine, or as an installer package deployed using Python Buildout to users in order to allow for temporal and spatial regridding, metrics calculation (RMSE, bias, PDFs, etc.) and end-user visualization. RCMET is available to users in an ""offline"", lone scientist mode based on a virtual machine dynamically constructed with model outputs and observations to evaluate; or on an institution's computational cluster seated close to the observations and model outputs. We have leveraged RCMES within the content of the Coordinated Regional Downscaling Experiment (CORDEX) project, working with the University of Cape Town and other institutions to compare the model output to NASA remote sensing data; in addition we are also working with the North American Regional Climate Change Assessment Program (NARCCAP). In this paper we explain the contribution of cloud computing to RCMES's specifically describing studies of various cloud databases we evaluated for RCMED, and virtualization toolkits for RCMET, and their potential strengths in delivering user-created dynamic regional climate model evaluation virtual machines for our users. © 2013 Springer-Verlag Berlin Heidelberg."
"7003976079;24329376600;7201485519;","Global-mean radiative feedbacks and forcing in atmosphere-only and coupled atmosphere-ocean climate change experiments",2014,"10.1002/2014GL060347","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902040526&doi=10.1002%2f2014GL060347&partnerID=40&md5=7b62e99cf8de54508f07309b72d4a910","Analysis of the available Coupled Model Intercomparison Project Phase 5 models suggests that sea surface temperature-forced, atmosphere-only global warming experiments (""amip4K,"" ""amipFuture,"" and ""aqua4K"") are a good guide to the global cloud feedbacks determined from coupled atmosphere-ocean CO2-forced simulations, including the intermodel spread. Differences in the total climate feedback parameter between the experiments arise primarily from differences in the clear-sky feedbacks which can largely be anticipated from the nature of the experimental design. The effective CO2 radiative forcing is anticorrelated with the total feedback in the coupled simulations. This anticorrelation strengthens as the experimental design becomes simpler, the number of potential degrees of freedom of the system's response reduces, and the relevant physical processes can be identified. In the aquaplanet simulations the anticorrelation is primarily driven by opposing changes in the rapid cloud adjustment to CO2 and the net cloud response to increased surface warming. Establishing a physical explanation for this behavior is important future work. © 2014. American Geophysical Union. All Rights Reserved."
"7404433688;","Cloud parameters retrieved by the bispectral reflectance algorithm and associated applications",2014,"10.1007/s13351-014-3292-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921381802&doi=10.1007%2fs13351-014-3292-3&partnerID=40&md5=7d1ed3639f0ab23826f213c0f7b44f55","Retrieval of cloud parameters is fundamental for descriptions of the cloud process in weather and cloud models, and is also the base for theoretical and applicational investigations on weather modification, aerosol-cloud-precipitation interaction, cloud-radiative climate effects, and so on. However, it is still difficult to obtain full information of cloud parameters over a wide area under the current level of science and technology. Luckily, parameters at the top of clouds can be retrieved with the satellite spectrum remote sensing, which is useful in obtaining global cloud properties. In this paper, cloud parameters retrieved by the bispectral reflectance (BSR) method and other methods developed on the basis of the BSR are briefly summarized. Recent advances in studies on the indirect effects of aerosol on cloud parameters are reviewed. The relationships among cloud parameters and precipitation intensity, type, and structure are elaborated on, based upon the pixel-level merged datasets derived from daily measurements of precipitation radar and visible and infrared scanner, together with cloud parameters retrieved by the BSR. It is revealed that cloud particle effective radius and liquid water path near cloud tops are effective to identify the thickness and intensity of convective precipitating clouds. Furthermore, the differences in cloud parameters and precipitation intensity for precipitating and non-precipitating clouds over land and ocean are compared in this paper. ©The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2014."
"8953038700;16645127300;7102268722;6603081424;8397494800;22635081500;7004364155;","A global climatology of outgoing Longwave spectral cloud radiative effect and associated effective cloud properties",2014,"10.1175/JCLI-D-13-00663.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907573450&doi=10.1175%2fJCLI-D-13-00663.1&partnerID=40&md5=7bbeb0da3af4ab65abb4dd3398eaee9e","Longwave (LW) spectral flux and cloud radiative effect (CRE) are important for understanding the earth's radiation budget and cloud-radiation interaction. Here, the authors extend their previous algorithms to collocated Atmospheric Infrared Sounder (AIRS) and Cloud and the Earth's Radiant Energy System (CERES) observations over the entire globe and show that the algorithms yield consistently good performances for measurements over both land and ocean. As a result, the authors are able to derive spectral flux and CRE at 10-cm-1 intervals over the entire LW spectrum from all currently available collocated AIRS and CERES observations. Using this multiyear dataset, they delineate the climatology of spectral CRE, including the far IR, over the entire globe as well as in different climate zones. Furthermore, the authors define two quantities, IR-effective cloud-top height (CTHeff) and cloud amount (CAeff), based on the monthly-mean spectral (or band by band) CRE. Comparisons with cloud fields retrieved by the CERES-Moderate Resolution Imaging Spectroradiometer (MODIS) algorithm indicate that, under many circumstances, the CTHeff and CAeff can be related to the physical retrievals of CTH and CA and thus can enhance understandings of model deficiencies in LW radiation budgets and cloud fields. Using simulations from the GFDL global atmosphere model, version 2 (AM2); NASA's Goddard Earth Observing System, version 5 (GEOS-5); and Environment Canada's Canadian Centre for Climate Modelling and Analysis (CCCma) Fourth Generation Canadian Atmospheric General Circulation Model (CanAM4) as case studies, the authors further demonstrate the merits of the CTHeff and CAeff concepts in providing insights on global climate model evaluations that cannot be obtained solely from broadband LW flux and CRE comparisons. © 2014 American Meteorological Society."
"16029674800;57199907553;","Climate simulations and projections with a super-parameterized climate model",2014,"10.1016/j.envsoft.2014.06.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903700780&doi=10.1016%2fj.envsoft.2014.06.013&partnerID=40&md5=450e8664ca9416d95a4ba2c4e4236d3b","The mean climate and its variability are analyzed in a suite of numerical experiments with a fully coupled general circulation model in which subgrid-scale moist convection is explicitly represented through embedded 2D cloud-system resolving models. Control simulations forced by the present day, fixed atmospheric carbon dioxide concentration are conducted using two horizontal resolutions and validated against observations and reanalyses. The mean state simulated by the higher resolution configuration has smaller biases. Climate variability also shows some sensitivity to resolution but not as uniform as in the case of mean state. The interannual and seasonal variability are better represented in the simulation at lower resolution whereas the subseasonal variability is more accurate in the higher resolution simulation. The equilibrium climate sensitivity of the model is estimated from a simulation forced by an abrupt quadrupling of the atmospheric carbon dioxide concentration. The equilibrium climate sensitivity temperature of the model is 2.77. °C, and this value is slightly smaller than the mean value (3.37. °C) of contemporary models using conventional representation of cloud processes. The climate change simulation forced by the representative concentration pathway 8.5 scenario projects an increase in the frequency of severe droughts over most of the North America. © 2014 The Authors."
"14325218600;24576706500;7005449794;","Improving the simulation of the West African monsoon using the MIT regional climate model",2014,"10.1175/JCLI-D-13-00188.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896077818&doi=10.1175%2fJCLI-D-13-00188.1&partnerID=40&md5=8483ca384a06f012416392874a14284b","This paper presents an evaluation of the performance of the Massachusetts Institute of Technology (MIT) regional climate model (MRCM) in simulating the West African monsoon. The MRCM is built on the Regional Climate Model, version 3 (RegCM3), but with several improvements, including coupling of Integrated Biosphere Simulator (IBIS) land surface scheme, a new surface albedo assignment method, new convective cloud and convective rainfall autoconversion schemes, and a modified scheme for simulating boundary layer height and boundary layer clouds. To investigate the impact of these more physically realistic representations when incorporated into MRCM, a series of experiments were carried out implementing two land surface schemes [IBIS with a new albedo assignment, and the Biosphere-Atmosphere Transfer Scheme (BATS)] and two convection schemes (Grell with the Fritsch-Chappell closure, and Emanuel in both the default form and modified with the new convective cloud cover and a rainfall autoconversion scheme). The analysis primarily focuses on comparing the rainfall characteristics, surface energy balance, and large-scale circulations against various observations. This work documents significant sensitivity in simulation of the West African monsoon to the choices of the land surface and convection schemes. Despite several deficiencies, the simulation with the combination of IBIS and the modified Emanuel scheme with the new convective cloud cover and a rainfall autoconversion scheme shows the best performance with respect to the spatial distribution of rainfall and the dynamics of the monsoon. The coupling of IBIS leads to representations of the surface energy balance and partitioning that show better agreement with observations compared to BATS. The IBIS simulations also reasonably reproduce the dynamical structures of the West African monsoon circulation. © 2014 American Meteorological Society."
"57131609600;7402989545;55913183200;","Climate sensitivities of two versions of FGOALS model to idealized radiative forcing",2014,"10.1007/s11430-013-4692-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901255008&doi=10.1007%2fs11430-013-4692-4&partnerID=40&md5=7ff3fc0177e4d21c9ee310a014a27118","Projections of future climate change by climate system models depend on the sensitivities of models to specified greenhouse gases. To reveal and understand the different climate sensitivities of two versions of LASG/IAP climate system model FGOALS-g2 and FGOALS-s2, we investigate the global mean surface air temperature responses to idealized CO2 forcing by using the output of abruptly quadrupling CO2 experiments. The Gregory-style regression method is used to estimate the ""radiative forcing"" of quadrupled CO2 and equilibrium sensitivity. The model response is separated into a fast-response stage associated with the CO2 forcing during the first 20 years, and a slow-response stage post the first 20 years. The results show that the radiative forcing of CO2 is overestimated due to the positive water-vapor feedback and underestimated due to the fast cloud processes. The rapid response of water vapor in FGOALS-s2 is responsible for the stronger radiative forcing of CO2. The climate sensitivity, defined as the equilibrium temperature change under doubled CO2 forcing, is about 3.7 K in FGOALS-g2 and 4.5 K in FGOALS-s2. The larger sensitivity of FGOALS-s2 is due mainly to the weaker negative longwave clear-sky feedback and stronger positive shortwave clear-sky feedback at the fast-response stage, because of the more rapid response of water vapor increase and sea-ice decrease in FGOALS-s2 than in FGOALS-g2. At the slow-response stage, similar to the fast-response stage, net negative clear-sky feedback is weaker in FGOALS-s2. Nevertheless, the total negative feedback is larger in FGOALS-s2 due to a larger negative shortwave cloud feedback that involves a larger response of total cloud fraction and condensed water path increase. The uncertainties of estimated forcing and net feedback mainly come from the shortwave cloud processes. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg."
"57198208348;57219951382;7102495313;","The importance of representing mixed-phase clouds for simulating distinctive atmospheric states in the Arctic",2014,"10.1175/JCLI-D-13-00271.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892467999&doi=10.1175%2fJCLI-D-13-00271.1&partnerID=40&md5=8cd12959921466b099b81ff1d8132bb4","Observations from the Surface Heat Budget of the Arctic Ocean experiment (SHEBA) suggest that the Arctic Basin is characterized by two distinctly different preferred atmospheric states during wintertime. These states appear as two peaks in the frequency distribution of surface downwelling longwave radiation (LWD), representing radiatively clear and opaque conditions. Here, the authors have investigated the occurrence and representation of these states in the widely used ECMWF Interim Re-Analysis (ERA-Interim) dataset. An interannually recurring bimodal distribution of LWDvalues is not a clearly observable feature in the reanalysis data. However, large differences in the simulated liquid water content of clouds in ERA-Interim compared to observations are identified and these are linked to the lack of a radiatively opaque peak in the reanalysis. Using a single-column model, dynamically controlled by data fromERA-Interim, the authors show that, by tuning the glaciation speed of supercooled liquid clouds, it is possible to reach a very good agreement between the model and observations from the SHEBA campaign in terms of LWD. The results suggest that the presence of two preferred Arctic states, as observed during SHEBA, is a recurring feature of the Arctic climate system during winter [December-March (DJFM)]. The mean increase in LWD during the Arctic winter compared to ERAInterim is 15Wm-2. This has a substantial bearing on climate model evaluation in the Arctic as it indicates the importance of representing Arctic states in climate models and reanalysis data and that doing so could have a significant impact on winter ice thickness and surface temperatures in the Arctic. © 2014 American Meteorological Society."
"24485218400;23094149200;15726427000;57211301037;7003278104;","Modulation of marine low clouds associated with the tropical intraseasonal variability over the eastern Pacific",2014,"10.1175/JCLI-D-13-00569.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904497817&doi=10.1175%2fJCLI-D-13-00569.1&partnerID=40&md5=137b5937a3ba6f83dec1beada022657e","Owing to its profound influences on global energy balance, accurate representation of low cloud variability in climatemodels is an urgent need for future climate projection. In the present study, marine lowcloud variability on intraseasonal time scales is characterized, with a particular focus over the Pacific basin during boreal summer and its association with the dominant mode of tropical intraseasonal variability (TISV) over the eastern Pacific (EPAC) intertropical convergence zone (ITCZ). Analyses indicate that, when anomalous TISV convection is enhanced over the elongatedEPACITCZ, reduction of low cloud fraction (LCF) is evident over a vast area of the central North Pacific. Subsequently, when the enhanced TISV convection migrates to the northern part of the EPAC warm pool, a ''comma shaped'' pattern of reduced LCF prevails over the subtropical North Pacific, along with a pronounced reduction of LCF present over the southeast Pacific (SEPAC). Further analyses indicate that surface latent heat fluxes and boundary heights induced by anomalous low-level circulation through temperature advection and changes of total wind speed, as well as midlevel vertical velocity associated with the EPAC TISV, could be the most prominent factors in regulating the intraseasonal variability of LCF over the North Pacific. For the SEPAC, temperature anomalies at the top of the boundary inversion layer between 850 and 800 hPa play a critical role in the local LCFintraseasonal variations. Results presented in this study provide not only improved understanding of variability of marine low clouds and the underlying physics, but also a prominent benchmark in constraining and evaluating the representation of low clouds in climate models. © 2014 American Meteorological Society."
"7007047895;7004003763;7203025601;35473805400;7402787638;12766815800;7006669087;57206164665;7004730494;57203466193;35584010200;7407084420;7006429360;7406998136;6604020335;7201534142;6701469150;","Radar in atmospheric sciences and related research: Current systems, emerging technology, and future needs",2014,"10.1175/BAMS-D-13-00079.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922435806&doi=10.1175%2fBAMS-D-13-00079.1&partnerID=40&md5=a3418298f9318613056a4b4f19c25956","Emerging radar technologies best suited to addressing key scientific questions and future problems are identified and discussed. Future research with radar will involve multiplatform, multi-model investigations. There will be four major research themes involving radar. To address these scientific problems, radars will be needed on diverse platforms including ships, aircraft, and stationary and mobile ground-based platforms. Some of the latter platforms may be quasi mobile: able to move the radar to a fixed location for an extended period. Radar will be needed to study, for example, tropical cloud systems, oceanic tropical convection and its impact on climate, the effects of aerosols on cloud microphysics, and global and regional orographic precipitation as a source of water supply. Dr. Rauber suggests that during the next two decades global climate change impacts are likely to drive research more and more."
"54983414800;6505932008;7202899330;6701718281;","Convective-scale responses of a large-domain, modelled tropical environment to surface warming",2014,"10.1002/qj.2230","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902247274&doi=10.1002%2fqj.2230&partnerID=40&md5=59099410db4272a028cbb16d05bc63db","This article explores the response of convective-scale atmospheric characteristics to surface temperature through the lens of large-domain, cloud-system-resolving model experiments run at radiative convective equilibrium. We note several features reminiscent of the response to surface warming in atmospheric general circulation models. These include an increase in the rain rate that is smaller than the modelled increase in precipitable water, a systematic decrease in sensible heating and an increase in clear-sky cooling. However, in contrast to climate models, we note that tropospheric relative humidity increases and column-integrated water vapour increases at the rate anticipated from the Clausius-Clapeyron relationship, but only when compared with the troposphere mean temperature rather than surface temperature. Also shown are results elucidating the changes in the vertically integrated water budget and the distribution of high precipitation rates shifting toward higher rates. Moist static energy distributions are analyzed and, from these, clouds are implicated in effecting the final equilibrium state of the atmosphere. The results indicate that, while there are aspects of the tropical equilibrium that are represented realistically in current general circulation model climate-change experiments, there are potentially influential local interactions that are sufficiently important as to alter the mean response of the tropical water and energy balance to changes in sea-surface temperature. Convection is shown to dictate the equilibrium state across all scales, including those unresolved in climate models, rather than only responding to surface-induced changes. © 2013 Royal Meteorological Society."
"56172609700;57199907553;16029674800;","Projections of the tropical Atlantic vertical wind shear and its relationship with ENSO in SP-CCSM4",2014,"10.1175/JCLI-D-14-00002.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909606178&doi=10.1175%2fJCLI-D-14-00002.1&partnerID=40&md5=8e6360aaf66f9307fc513026e40d94c2","The vertical wind shear over the tropical Atlantic Ocean and its relationship with ENSO are analyzed in the superparameterized Community Climate System Model, version 4 (SP-CCSM4) and in the conventional CCSM4. The climatology of vertical wind shear over the tropical Atlantic and the ENSO-shear relationship are well simulated in the control runs of SP-CCSM4 and CCSM4. However, because of different representations of cloud processes, in a warmer climate such as the representative concentration pathway 8.5 (RCP8.5) scenario, SP-CCSM4 projects increased mean westerlies at 200 hPa during July through October (JASO), whereas CCSM4 projects decreased mean westerlies at 200 hPa over the equatorial Atlantic. The different changes in the upper-level wind further contribute to different projection of JASO mean vertical wind shear over the equatorial Atlantic. In the RCP8.5 scenario, when excluding the linear trend, projection of the ENSO-shear relationships by SP-CCSM4 retains similar features as in the observed current climate, whereas the ENSO-shear relationship projected by CCSM4indicates an increase in the vertical wind shear dominating the tropical Atlantic during El Niño events. The difference in projection of ENSO-shear relationship is, to a certain extent, related to the different response of the tropical Atlantic SST to ENSO. Analysis of the climate change projection of Walker circulation, cloud cover, and convective activity illustrates that superparameterization simulates a stronger suppression of African convection than the conventional parameterization of moist processes. The weak convective activity diminishes the divergent wind associated with the vertical motion, which contributes to increased westerlies projected in SP-CCSM4. © 2014 American Meteorological Society."
"7004617224;7401984344;","Trends in U.S. total cloud cover from a homogeneity-adjusted dataset",2014,"10.1175/JCLI-D-13-00722.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903386105&doi=10.1175%2fJCLI-D-13-00722.1&partnerID=40&md5=e10a27f18af9fc98e5e6eddda758a41e","Cloud cover data from ground-based weather observers can be an important source of climate information, but the record of such observations in the United States is disrupted by the introduction of automated observing systems and other artificial shifts that interfere with our ability to assess changes in cloudiness at climate time scales. A new dataset using 54 National Weather Service (NWS) and 101 military stations that continued to make human-augmented cloud observations after the 1990s has been adjusted using statistical changepoint detection and visual scrutiny. The adjustments substantially reduce the trends in U.S. mean total cloud cover while increasing the agreement between the cloud cover time series and those of physically related climate variables. For 1949-2009, the adjusted time series give a trend in U.S. mean total cloud of 0.11% ± 0.22% decade-1 for the military data, 0.55% ± 0.24% decade-1 for the NWS data, and 0.31% ± 0.22% decade-1 for the combined dataset. These trends are less than one-half of those in the original data. For 1976-2004, the original data give a significant increase but the adjusted data show an insignificant trend from -0.17% decade-1 (military stations) to 0.66% decade-1 (NWS stations). Trends have notable regional variability, with the northwest United States showing declining total cloud cover for all time periods examined, while trends for most other regions are positive. Differences between trends in the adjusted datasets from military stations and NWS stations may be rooted in the difference in data source and reflect the uncertainties in the homogeneity adjustment process. © 2014 American Meteorological Society."
"7005246023;19639722300;7103246957;35612769500;","Triggering deep convection with a probabilistic plume model",2014,"10.1175/JAS-D-13-0340.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910149156&doi=10.1175%2fJAS-D-13-0340.1&partnerID=40&md5=2e7fb3cff0931bef1c3a33b736f128d0","Amodel unifying the representation of the planetary boundary layer and dry, shallow, and deep convection, the probabilistic plume model (PPM), is presented. Its capacity to reproduce the triggering of deep convection over land is analyzed in detail. The model accurately reproduces the timing of shallow convection and of deep convection onset over land, which is a major issue in many current general climate models. PPM is based on a distribution of plumes with varying thermodynamic states (potential temperature and specific humidity) induced by surface-layer turbulence. Precipitation is computed by a simple ice microphysics, and with the onset of precipitation, downdrafts are initiated and lateral entrainment of environmental air into updrafts is reduced. The most buoyant updrafts are responsible for the triggering of moist convection, causing the rapid growth of clouds and precipitation. Organization of turbulence in the subcloud layer is induced by unsaturated downdrafts, and the effect of density currents is modeled through a reduction of the lateral entrainment. The reduction of entrainment induces further development from the precipitating congestus phase to full deep cumulonimbus. Model validation is performed by comparing cloud base, cloud-top heights, timing of precipitation, and environmental profiles against cloud-resolving models and large-eddy simulations for two test cases. These comparisons demonstrate that PPM triggers deep convection at the proper time in the diurnal cycle and produces reasonable precipitation. On the other hand, PPM underestimates cloud-top height. © 2014 American Meteorological Society."
"55713076400;57203054708;","A unified representation of deep moist convection in numerical modeling of the atmosphere. Part II",2014,"10.1175/JAS-D-13-0382.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901751645&doi=10.1175%2fJAS-D-13-0382.1&partnerID=40&md5=74604c3a0ad774aeb50394ebc6171daa","In Part I of this paper, a generalized modeling framework for representing deep moist convection was presented. The framework, called unified parameterization, effectively unifies the parameterizations in general circulation models (GCMs) and cloud-resolving models (CRMs) and thus is applicable to any horizontal resolution between those typically used in those models. The key parameter in the unification is the fractional convective cloudiness s, which is the fractional area covered by convective updrafts in the grid cell. The central issue of Part I is to formulate the σ dependence of vertical eddy transports of thermodynamic variables and to determine σ for each realization of grid-scale processes. The present paper completes the formulation through further analysis of the simulated data. The analyzed fields include the vertical structure of the σ dependence of vertical and horizontal eddy transports of moist static energy and horizontal momentum and that of cloud microphysical sources. For the momentum transport, the analysis results clearly show the limits of the traditional approach of parameterization based on an effectively one-dimensional model. For cloud microphysical conversions, it is shown that those taking place primarily inside and outside the updrafts are roughly proportional to σ and 1 - σ, respectively. © 2014 American Meteorological Society."
"36442544600;56026687200;36643146900;7401693165;36060594300;56026560000;","Diffusion Source Detection of Volcanic Ash Cloud Using MODIS Satellite Data",2014,"10.1007/s12524-013-0360-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893462070&doi=10.1007%2fs12524-013-0360-6&partnerID=40&md5=7de4ead0ef0597f1fe3d0cf5fc0528cf","The massive volcanic ash cloud not only causes obvious global climate and environmental changes, but also threatens aviation safety under the background of globalization. The diffusion source detection is a key factor in the volcanic ash cloud monitoring and the diffusion research. Taking the Eyjafjallajokull's volcanic ash cloud on April 19, 2010 in Iceland as an example, based on the analysis of the absorption spectrum characteristics in the thermal infrared spectral range, in this paper, a new diffusion source detection algorithm of volcanic ash cloud combining split window algorithm with SO2 concentration distribution is proposed from the moderate resolution imaging spectroradiometer (MODIS) satellite remote sensing images; subsequently the ash radiance index (ARI) and absorbing aerosol index (AAI) are applied as contrast to the detection results. The results show that the proposed algorithm can effectively detect the diffusion source of volcanic ash cloud, and has high consistency with the ARI and AAI distributions, and has certain potential applications in improving the detection effect of volcanic ash cloud and prediction accuracy of diffusion model. © 2014 Indian Society of Remote Sensing."
"23568239000;","Analysis of aerosol-cloud-interactions over semi-arid and arid subtropical land regions from three different satellite datasets (MODIS, AATSR/ENVISAT, IASI)",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905486007&partnerID=40&md5=270d3c7d2a0186414ebc3e6191bd4df8","Indirect aerosol effects, i.e. the change of cloud physical properties by aerosol interactions, have been identified as one of the largest uncertainties in the current understanding of the climate system. Despite the uncertainties of the representations of aerosol-cloud interactions in current climate projections, they have large impact on the climate system itself - in terms of the radiation balance, but also in terms of precipitation, and thus vegetation cover, and re-distribution of water throughout the atmosphere. Nevertheless, so far only very few studies of large-scale statistics of aerosol-cloud interactions over land are available. Moreover most studies on the topic cover liquid water clouds only. Aerosol cloud interactions over arid and semi-arid land regions have been analysed from three different satellite datasets with respect to aerosol type and cloud phase. The regions of the analysis cover Southern Africa, the Sahel domain with the influence of the West African monsoon circulation, the North-Western African Maghreb region and the Arabian Peninsula. These regions have been chosen as they are dominated by one (Maghreb, Arabia) or two (Sahel, Southern Africa) aerosol types and as mineral dust is one of the dominating aerosol types in all of them. The second dominating aerosol type is biomass burning in the Sahel and Southern Africa. These aerosol types can be discriminated by separating the aerosol information into fine mode (biomass burning) and coarse mode (desert dust) aerosol. Thus they can generally also be discriminated from satellite, although these capabilities are limited over land. Over land the diurnal cycle of convection is much stronger and aerosol interactions with deep convective cloud systems over land have been identified to be of great importance not only for precipitation in regions under pressure of desertification, but also with respect to climate change. For liquid water clouds the well-known first indirect aerosol effect (""Twomey effect""), i.e. higher cloud albedo due to smaller droplet sizes, could be confirmed for all regions, if liquid water path is held constant. Nevertheless, liquid water path has been found to be affected by aerosol presence and the aerosol effect on liquid water path dominates the net effect of aerosols on cloud optical depth. For ice phase clouds the same effects are observed with ice water path controlling the net aerosol effect on optical depth. From thermal infrared retrievals of mineral dust and ice clouds an increase of ice particle size with respect to background conditions has been detected. Together with observations at solar wavelengths the differences can be interpreted as indications for an increase of optically thicker clouds at the cost of cirrus coverage. Although the Twomey effect has been identified to be active in all cases, cloud water path and cloud phase transitions could be identified to be of predominant importance for resulting cloud propertiy changes due to aerosol presence. The second indirect aerosol effect (""Albrecht effect"") could not be identified from the statistical analysis. Although cloud cover distributions as functions of aerosol optical depth (AOD) indicate an increase of cloud cover with AOD, these could not be related to any other cloud properties including cloud droplet size. Thus the satellite observations do not support the relatively simple formulation of the second indirect aerosol effect (longer cloud lifetime due to drizzle suppression as a consequence of smaller droplets). An aerosol effect on cloud phase has been identified with respect to cloud water path. It could not be confirmed in terms of cloud coverage. The statistical analysis of cloud macro- and microphysical properties has been performed after the observations have been projected all to the same cloud top temperature distribution. This method allows correcting for effects of the temperature and moisture fields (meteorological conditions), which otherwise would dominate the statistical results. It has been shown that aerosol type is important for aerosol cloud interactions in subtropical land regions. Moreover the cloud water path (liquid and ice) has been identified to be a strong constraint on indirect aerosol effects, outweighing e.g. the optical depth increase by droplet size reduction (""Twomey-effect""). It could moreover be shown that aerosol-cloud interactions are also important for ice cloud properties in subtropical land regions, which have yet not fully been addressed in statistical analyses of indirect aerosol effects and consequently in climate projections. Nevertheless, by means of the large-scale statistical analysis, also some deficits of current satellite datasets have been identified, which have to be solved in order to furthermore reduce the uncertainties of indirect aerosol effects. It has been the first attempt to quantify aerosol-cloud interactions focussed on semiarid and arid land regions, performing the same kind of analysis to liquid water and ice clouds at the same time with the same methods, comparing results from three different independent satellite datasets, using advanced statistical descriptions of the observed deviations from background in order to account for non-linearity and multimodal or non-Gaussian probability distributions of cloud properties, applying a newly developed method to account for variations in cloud top temperature affecting cloud property observations statistically and also introducing a newly developed dataset from IASI which is sensitive to desert dust and ice clouds only, adding information about aerosol type sensitivity of aerosol-cloud interactions."
"55892807200;7006280684;","Using longwave HIRS radiances to test climate models",2014,"10.1007/s00382-013-1959-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905080643&doi=10.1007%2fs00382-013-1959-6&partnerID=40&md5=a5664e7ae3259359f5eadfce2ccbb444","A 'model-to-radiance' comparison of simulated brightness temperatures from the Hadley Centre Global Environmental Model 2 with measurements from the High Resolution Infrared Radiation Sounder/4 (HIRS/4) instrument onboard the MetOp-A satellite is presented. For the all-sky, the model overestimates brightness temperatures in the atmospheric window region with the greatest biases over areas associated with deep convective cloud. In contrast to many global climate models, much smaller clear-sky biases are found indicating that model clouds are the dominating source of error. Simulated values in upper atmospheric CO2 channels approximate observations better as a result of compensating cold biases at the poles and warm biases at lower latitudes, due to a poor representation of the Brewer Dobson circulation in the 38 level 'low-top' configuration of the model. Simulated all and clear-sky outgoing longwave radiation (OLR) evaluated against the Clouds and the Earth's Radiant Energy System (CERES) and HIRS OLR products reveal good agreement, in part due to cancellation of positive and negative biases. Through physical arguments relating to the spectral energy balance within a cloud, it is suggested that broadband agreement could be the result of a balance between positive window biases and unseen negative biases originating from the water vapour rotational band in the far infrared (not sampled by HIRS). © 2013 Springer-Verlag Berlin Heidelberg."
"16024614000;7401491382;","Diurnal cycles of cumulus, cumulonimbus, stratus, stratocumulus, and fog from surface observations over land and ocean",2014,"10.1175/JCLI-D-13-00352.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896092753&doi=10.1175%2fJCLI-D-13-00352.1&partnerID=40&md5=85f3e2852b8c026dc1aa6a73f187e15d","A worldwide climatology of the diurnal cycles of low clouds is obtained from surface observations made eight or four times daily at 3-or 6-h intervals from weather stations and ships. Harmonic fits to the daily cycle are made for 5388 weather stations with long periods of record, and for gridded data on a 5° × 5° or 10° × 10° latitude-longitude grid over land and ocean areas separately. For all cloud types, the diurnal cycle has larger amplitude over land than over ocean, on average by a factor of 2. Diurnal cycles of cloud amount appear to be proprietary to each low cloud type, showing the same cycle regardless of whether that type dominates the diurnal cycle of cloud cover. Stratiform cloud amounts tend to peak near sunrise, while cumuliform amounts peak in the afternoon; however, cumulonimbus amounts peak in the early morning over the ocean. Small latitudinal and seasonal variation is apparent in the phase and amplitude of the diurnal cycles of each type. Land areas show more seasonality compared to ocean areas with respect to which type dominates the diurnal cycle. Multidecadal trends in low cloud cover are small and agree between day and night regardless of the local climate. Diurnal cycles of base height are much larger over land than over the ocean. For most cloud types, the bases are highest in the midafternoon or early evening. © 2014 American Meteorological Society."
"56278161100;26324818700;7202699757;7006518289;7005965757;12769875100;","Individual feedback contributions to the seasonality of surface warming",2014,"10.1175/JCLI-D-13-00658.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904479647&doi=10.1175%2fJCLI-D-13-00658.1&partnerID=40&md5=f3a0a6b4223ad37e68b95874ef69a7bb","Using the climate feedback response analysis method, the authors examine the individual contributions of the CO2 radiative forcing and climate feedbacks to the magnitude, spatial pattern, and seasonality of the transient surface warming response in a 1%yr-1 CO2 increase simulation of the NCAR Community Climate System Model, version 4 (CCSM4). The CO2 forcing and water vapor feedback warm the surface everywhere throughout the year. The tropical warming is predominantly caused by the CO2 forcing and water vapor feedback, while the evaporation feedback reduces the warming. Most feedbacks exhibit noticeable seasonal variations; however, their net effect has little seasonal variation due to compensating effects, which keeps the tropical warming relatively invariant all year long. The polar warming has a pronounced seasonal cycle, with maximum warming in fall/winter and minimum warming in summer. In summer, the large cancelations between the shortwave and longwave cloud feedbacks and between the surface albedo feedback warming and the cooling from the ocean heat storage/dynamics feedback lead to a warming minimum. In polar winter, surface albedo and shortwave cloud feedbacks are nearly absent due to a lack of insolation. However, the ocean heat storage feedback relays the polar warming due to the surface albedo feedback from summer to winter, and the longwave cloud feedback warms the polar surface. Therefore, the seasonal variations in the cloud feedback, surface albedo feedback, and ocean heat storage/dynamics feedback, directly caused by the strong annual cycle of insolation, contribute primarily to the large seasonal variation of polar warming. Furthermore, the CO2 forcing and water vapor and atmospheric dynamics feedbacks add to the maximum polar warming in fall/winter. © 2014 American Meteorological Society."
"7202660824;7403288995;7402064802;36856321600;","On the spread of changes in marine low cloud cover in climate model simulations of the 21st century",2014,"10.1007/s00382-013-1945-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897579481&doi=10.1007%2fs00382-013-1945-z&partnerID=40&md5=dd51ebf12b2a2e48793b3124376bbcce","In 36 climate change simulations associated with phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5), changes in marine low cloud cover (LCC) exhibit a large spread, and may be either positive or negative. Here we develop a heuristic model to understand the source of the spread. The model's premise is that simulated LCC changes can be interpreted as a linear combination of contributions from factors shaping the clouds' large-scale environment. We focus primarily on two factors-the strength of the inversion capping the atmospheric boundary layer (measured by the estimated inversion strength, EIS) and sea surface temperature (SST). For a given global model, the respective contributions of EIS and SST are computed. This is done by multiplying (1) the current-climate's sensitivity of LCC to EIS or SST variations, by (2) the climate-change signal in EIS or SST. The remaining LCC changes are then attributed to changes in greenhouse gas and aerosol concentrations, and other environmental factors. The heuristic model is remarkably skillful. Its SST term dominates, accounting for nearly two-thirds of the intermodel variance of LCC changes in CMIP3 models, and about half in CMIP5 models. Of the two factors governing the SST term (the SST increase and the sensitivity of LCC to SST perturbations), the SST sensitivity drives the spread in the SST term and hence the spread in the overall LCC changes. This sensitivity varies a great deal from model to model and is strongly linked to the types of cloud and boundary layer parameterizations used in the models. EIS and SST sensitivities are also estimated using observational cloud and meteorological data. The observed sensitivities are generally consistent with the majority of models as well as expectations from prior research. Based on the observed sensitivities and the relative magnitudes of simulated EIS and SST changes (which we argue are also physically reasonable), the heuristic model predicts LCC will decrease over the 21st-century. However, to place a strong constraint, for example on the magnitude of the LCC decrease, will require longer observational records and a careful assessment of other environmental factors producing LCC changes. Meanwhile, addressing biases in simulated EIS and SST sensitivities will clearly be an important step towards reducing intermodel spread in simulated LCC changes. © 2013 Springer-Verlag Berlin Heidelberg."
"56707664800;6603596462;","Assessment of contribution of greenhouse gases, water vapor, and cloudiness to the variations of global surface air temperature",2014,"10.3103/S1068373914030029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898605850&doi=10.3103%2fS1068373914030029&partnerID=40&md5=b852834e14b2b9198b16fae610908ee5","Considered are the possible reasons for variations of global surface air temperature as an indicator of the climate change. Analyzed are the variations of air temperature, concentration of greenhouse gases and water vapor, and cloudiness observed in recent decades, A role of greenhouse effect components in the variations of global surface air temperature is assessed using the parameterization developed. © 2014 Allerton Press, Inc."
"36057442400;7103158465;7202784114;","Dynamical and microphysical evolution during mixed-phase cloud glaciation simulated using the bulk adaptive habit prediction model",2014,"10.1175/JAS-D-14-0070.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910148466&doi=10.1175%2fJAS-D-14-0070.1&partnerID=40&md5=c735f60a0d44b76d31c80438e1fe2f08","A bulk microphysics scheme predicting ice particle habit evolution has been implemented in the Weather Research and Forecasting Model. Large-eddy simulations are analyzed to study the effects of ice habit and number concentration on the bulk ice and liquid masses, dynamics, and lifetime of Arctic mixed-phase boundary layer clouds. The microphysical and dynamical evolution simulated using the adaptive habit scheme is compared with that assuming spherical particles with a density of bulk ice or a reduced density and with mass-dimensional parameterizations. It is found that the adaptive habit method returns an increased (decreased) ice (liquid) mass as compared to spheres and provides a more accurate simulation as compared to dendrite mass-size relations. Using the adaptive habit method, simulations are then completed to understand the microphysical and dynamical interactions within a single-layer mixed-phase stratocumulus cloud observed during flight 31 of the Indirect and Semi-Direct Aerosol Campaign. With cloud-top longwave radiative cooling as a function of liquid mass acting as the primary dynamic driver of turbulent eddies within these clouds, the consumption of liquid at the expense of ice growth and subsequent sedimentation holds a strong control on the cloud lifetime. Ice concentrations ≥4L-1 collapse the liquid layer without any externalmaintaining sources. Layermaintenance is possible at 4L-1 when a constant cloud-top cooling rate or the watermass lost due to sedimentation is supplied. Larger concentrations require a more substantial source of latent or sensible heat for mixed-phase persistence. © 2014 American Meteorological Society."
"56016514800;6602598448;36239282800;16203322900;7005939834;55762874000;26643300800;22836772900;53871288800;7005776035;35490828000;12767251100;7003627515;6603873829;","Improved representation of East Antarctic surface mass balance in a regional atmospheric climate model",2014,"10.3189/2014JoG14J051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909986649&doi=10.3189%2f2014JoG14J051&partnerID=40&md5=28b512d847f67cd79ea8896570c532d0","This study evaluates the impact of a recent upgrade in the physics package of the regional atmospheric climate model RACMO2 on the simulated surface mass balance (SMB) of the Antarctic ice sheet. The modelled SMB increases, in particular over the grounded ice sheet of East Antarctica (+44Gt a-1), with a small change in West Antarctica. This mainly results from an increase in precipitation, which is explained by changes in the cloud microphysics, including a new parameterization for ice cloud supersaturation, and changes in large-scale circulation patterns, which alter topographically forced precipitation. The spatial changes in SMB are evaluated using 3234 in situ SMB observations and ice-balance velocities, and the temporal variability using GRACE satellite retrievals. The in situ observations and balance velocities show a clear improvement of the spatial representation of the SMB in the interior of East Antarctica, which has become considerably wetter. No improvements are seen for West Antarctica and the coastal regions. A comparison of model SMB temporal variability with GRACE satellite retrievals shows no significant change in performance."
"55537426400;6603196127;55686667100;35762238200;10243650000;","Robust seasonality of arctic warming processes in two different versions of the MIROC GCM",2014,"10.1175/JCLI-D-14-00086.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905921024&doi=10.1175%2fJCLI-D-14-00086.1&partnerID=40&md5=bf97410c3e4afdb235be16f76e0711bb","It is one of the most robust projected responses of climate models to the increase of atmospheric CO2 concentration that the Arctic experiences a rapid warming with a magnitude larger than the rest of the world. Whilemany processes are proposed as important, the relative contribution of individual processes to the Arctic warming is not often investigated systematically. Feedbacks are quantified in two different versions of an atmosphere-ocean GCM under idealized transient experiments based on an energy balance analysis that extends from the surface to the top of the atmosphere. The emphasis is placed on the largest warming from late autumn to early winter (October-December) and the difference fromother seasons. It is confirmed that dominating processes vary with season. In autumn, the largest contribution to the Arctic surface warming is made by a reduction of ocean heat storage and cloud radiative feedback. In the annual mean, on the other hand, it is the albedo feedback that contributes the most, with increasing ocean heat uptake to the deeper layers working as a negative feedback. While the qualitative results are robust between the two models, they differ quantitatively, indicating the need for further constraint on each process. Ocean heat uptake, lower tropospheric stability, and low-level cloud response probably require special attention. © 2014 American Meteorological Society."
"7202145115;54897465300;","Trends in the CERES dataset, 2000-13: The effects of sea ice and jet shifts and comparison to climate models",2014,"10.1175/JCLI-D-13-00411.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896071856&doi=10.1175%2fJCLI-D-13-00411.1&partnerID=40&md5=bd82b98f33d83b6711c3706e94486604","The Clouds and the Earth's Radiant Energy System (CERES) observations of global top-of-atmosphere radiative energy fluxes for the period March 2000-February 2013 are examined for robust trends and variability. The trend in Arctic ice is clearly evident in the time series of reflected shortwave radiation, which closely follows the record of ice extent. The data indicate that, for every 106km2 decrease in September sea ice extent, annual-mean absorbed solar radiation averaged over 75°-908° increases by 2.5Wm-2, or about 6Wm-2 between 2000 and 2012. CMIP5 models generally show a much smaller change in sea ice extent over the 1970-2012 period, but the relationship of sea ice extent to reflected shortwave is in good agreement with recent observations. Another robust trend during this period is an increase in reflected shortwave radiation in the zonal belt from 45° to 65°S. This trend is mostly related to increases in sea ice concentrations in the Southern Ocean and less directly related to cloudiness trends associated with the annular variability of the Southern Hemisphere. Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) produce a scaling of cloud reflection to zonal wind increase that is similar to trend observations in regions separated from the direct effects of sea ice. Atmospheric Model Intercomparison Project (AMIP) model responses over the Southern Ocean are not consistent with each other or with the observed shortwave trends in regions removed from the direct effect of sea ice. © 2014 American Meteorological Society."
"57212988186;7401945370;55471474500;22934904700;56032970700;","Responses of tropical and subtropical high-cloud statistics to global warming",2014,"10.1175/JCLI-D-14-00179.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907821758&doi=10.1175%2fJCLI-D-14-00179.1&partnerID=40&md5=048941ca613d37f641f93ea9a55b8e20","Data from global high-resolution, nonhydrostatic simulations, covering a 1-yr period and with horizontal grid sizes of 7 and 14 km, were analyzed to evaluate the response of high cloud to global warming. The results indicate that, in a warmer atmosphere, high-cloud cover increases robustly and associated longwave (LW) cloud radiative forcing (CRF) increases on average. To develop a better understanding of high-cloud responses to climate change, the geographical distribution of high-cloud size obtained from the model was analyzed and compared with observations. In warmer atmospheres, the contribution per cloud to CRF decreases for both the LWand shortwave (SW) components. However, because of significant increases in the numbers of high clouds in almost all cloud size categories, the magnitude of both LW and SW CRF increases in the simulations. In particular, the contribution from an increase in the number of smaller clouds has more effect on the CRF change. It was also found that the ice and liquid water paths decrease in smaller clouds and that particularly the former contributes to reduced LW CRF per high cloud. © 2014 American Meteorological Society."
"7003532926;","Possible reasons for low climate-model sensitivity to increased carbon dioxide concentrations",2014,"10.1134/S0001433814040239","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905459845&doi=10.1134%2fS0001433814040239&partnerID=40&md5=7242df22c48cc184533a1d466a169217","The sensitivities of two climate-model versions-INMCM4 which participated in the Coupled Model Intercomparison Project, Phase 5 (CMIP5), and a new INMCM5 version with increased vertical and horizontal resolutions in its atmospheric block-to the quadrupled concentration of CO2 are studied. When the CO2 concentration is quadrupled, the equilibrium increase in surface temperature amounts to about 4.2 K for INMCM4, which is lower than that for other models that participated in the CMIP5. When the CO2 concentration increases, the cloud radiative forcing in the model decreases; in this case, one portion of this decrease occurs during the first year after the concentration of CO2 is quadrupled and the other portion almost linearly depends on the value of global warming. The results of additional numerical experiments with the model show that a rapid decrease in cloud-radiative forcing results from variations in stratification in the atmospheric surface boundary layer and associated increased cloudiness. The portion of a linear decrease in cloud-radiative forcing with increased temperature is associated with an increase in the water content of model clouds at higher temperatures. The elimination of these two mechanisms allows one to increase the model sensitivity to the quadrupled concentration of CO2 up to 5.2 K. © 2014 Pleiades Publishing, Ltd."
"23492864500;12753020100;57206156792;54881971400;7201504886;","The distribution and variability of low-level cloud in the North Atlantic trades",2014,"10.1002/qj.2307","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922948890&doi=10.1002%2fqj.2307&partnerID=40&md5=efe1b55b16f2f42a66603ead49b5ae83","In the North Atlantic trades, variations in the distribution of low-level cloud are rich. Using two years of observations from a remote-sensing site located on the east coast of Barbados, the vertical distribution of cloud and its contribution to low-level cloud amount are explored. The vertical distribution of first-detected cloud-base heights is marked by a strong peak near the lifting condensation level (LCL) from passive optically thin shallow cumuli. Cloud with a base near this level dominates the total cloud cover with a contribution of about two-thirds. The other one-third comes from cloud with its cloud base further aloft at heights > 1 km, such as cumulus edges or stratiform cloud below the trade inversion. Cloud found aloft, regardless of where its base is located, contains more variance, in particular near the inversion and on time-scales longer than a day. In turn, cloud near the LCL is surprisingly invariant on longer time-scales, although consistent with existing theories. Because this component does not systematically vary, changes in cloud cover in response to changes in meteorology or climate may be limited to changes in its contribution from cloud aloft. © 2013 Royal Meteorological Society."
"57213177124;7406372329;","A simple analytical model for understanding the formation of sea surface temperature patterns under global warming",2014,"10.1175/JCLI-D-14-00346.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909619231&doi=10.1175%2fJCLI-D-14-00346.1&partnerID=40&md5=d269d09976430aa516d4db289b73f6fa","How sea surface temperature (SST) changes under global warming is critical for future climate projection because SST change affects atmospheric circulation and rainfall. Robust features derived from 17 models of phase 5 of the Coupled Model Intercomparison Project (CMIP5) include a much greater warming in high latitudes than in the tropics, an El Niño-like warming over the tropical Pacific and Atlantic, and a dipole pattern in the Indian Ocean. However, the physical mechanism responsible for formation of such warming patterns remains open. A simple theoretical model is constructed to reveal the cause of the future warming patterns. The result shows that a much greater polar, rather than tropical, warming depends primarily on present-day mean SST and surface latent heat flux fields, and atmospheric longwave radiation feedback associated with cloud change further enhances this warming contrast. In the tropics, an El Niño-like warming over the Pacific and Atlantic arises from a similar process, while cloud feedback resulting from different cloud regimes between east and west ocean basins also plays a role. A dipole warming over the equatorial Indian Ocean is a response to weakened Walker circulation in the tropical Pacific. © 2014 American Meteorological Society."
"57209854833;8859530100;25823927100;7403174207;7103271625;57193132723;6602364115;55272477500;56611366900;","Evaluation of cloud fraction simulated by seven SCMs against the ARM observations at the SGP site",2014,"10.1175/JCLI-D-13-00555.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906860932&doi=10.1175%2fJCLI-D-13-00555.1&partnerID=40&md5=faeff3bcb82357a8f55d4ca390c192e7","This study evaluates the performances of seven single-column models (SCMs) by comparing simulated cloud fraction with observations at theAtmospheric RadiationMeasurement Program(ARM) SouthernGreat Plains (SGP) site fromJanuary 1999 toDecember 2001.Comparedwith the 3-yrmean observational cloud fraction, the ECMWF SCM underestimates cloud fraction at all levels and the GISS SCM underestimates cloud fraction at levels below 200 hPa. The two GFDL SCMs underestimate lower-to-middle level cloud fraction but overestimate upper-level cloud fraction. The three Community Atmosphere Model (CAM) SCMs overestimate upper-level cloud fraction and produce lower-level cloud fraction similar to the observations but as a result of compensating overproduction of convective cloud fraction and underproduction of stratiform cloud fraction. Besides, the CAM3 and CAM5 SCMs both overestimate midlevel cloud fraction, whereas the CAM4 SCM underestimates. The frequency and partitioning analyses show a large discrepancy among the seven SCMs: Contributions of nonstratiform processes to cloud fraction production are mainly in upper-level cloudy events over the cloud cover range 10%-80%in SCMs with prognostic cloud fraction schemes and in lower-level cloudy events over the cloud cover range 15%-50%in SCMs with diagnostic cloud fraction schemes. Further analysis reveals different relationships between cloud fraction and relative humidity (RH) in the models and observations. The underestimation of lower-level cloud fraction inmost SCMs ismainly due to the larger threshold RH used in models. The overestimation of upper-level cloud fraction in the threeCAMSCMs and twoGFDL SCMs is primarily due to the overestimation of RH and larger mean cloud fraction of cloudy events plus more occurrences of RH around 40%-80%, respectively. © 2014 American Meteorological Society."
"55972773600;55718857500;23161713000;","Observation of new particle formation and growth under cloudy conditions at Gosan Climate Observatory, Korea",2014,"10.1007/s00703-014-0336-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939886790&doi=10.1007%2fs00703-014-0336-2&partnerID=40&md5=62a9602829d2a7e77e2fdc38ad0cd219","Under cloudy conditions at the Gosan Climate Observatory (GCO), Korea, we observed distinct new particle formation and growth (NPF) events from simultaneous co-located measurements of aerosol and cloud profiles, cloud cover, shortwave radiation, and the number concentration and size distribution of aerosols. The high frequency of NPF was observed at GCO under decreased downwelling solar radiation caused by clouds. Although we observed about 15 and 40 % decreases in downwelling surface shortwave radiations, in the presence of thick mid-level (low-level) clouds, on January 28 and 30, 2012, respectively, distinct NPFs with a growth rate of 3.3 (3.9) nm h−1 were observed. We examined a 4-year series (May 2008 to April 2012) of continuous measurements of the size distribution of aerosol numbers and visually observed cloud cover. We found that approximately 13 % (i.e., 35 days out of 280 days) of total NPF events were observed under cloud-free conditions (i.e., cloud cover of 0/10). About 20 % (i.e., 57 days out of 280 days) of total NPF events occurred under mostly overcast conditions (i.e., cloud cover of 9/10–10/10). Although NPF events occurring under cloudy conditions were also found elsewhere, the frequency of NPF occurring at GCO seems much higher. The average value of relative humidity for the strong-NPF event days is lower than that of the weak and non-NPF event days for all cloud categories. No significant difference in the condensation sink was found among strong-, weak-, and non-NPF days, but the condensation sink showed a slight decreasing tendency with increasing cloudiness. Further investigations on precursor gases and preexisting aerosols under cloudy conditions are needed. © 2014, Springer-Verlag Wien."
"35335123900;6701589295;","Changes in the distribution of cloud forests during the last glacial predict the patterns of genetic diversity and demographic history of the tree fern Alsophila firma (Cyatheaceae)",2014,"10.1111/jbi.12396","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939263005&doi=10.1111%2fjbi.12396&partnerID=40&md5=0590054d8f5318beb336d72c5aa77a6b","Aim: We investigated changes in distribution of cloud forests during the last 130 kyr, and tested whether these changes explain the spatial patterns of genetic diversity of the tree fern Alsophila firma (Cyatheaceae), a species restricted to this habitat. Location: Mexican cloud forests. Methods: We sampled 204 individuals from 16 localities. Genetic data consisted of DNA sequences for five chloroplast microsatellites and one nuclear gene. We used distribution modelling to predict the historical distribution of cloud forests during the last glacial period, using two palaeoclimate models: the Model for Interdisciplinary Research on Climate (MIROC) and the Community Climate System Model (CCSM). We tested the correlation between temporal cloud forest stability and genetic diversity and used an approximate Bayesian computation (ABC) framework to test two plausible demographic scenarios. Results: The range fluctuations observed for cloud forests during the last 130 kyr are key factors affecting the distribution of genetic variation in A. firma. Increased genetic diversity in areas with high temporal environmental suitability is probably the result of increased population sizes and higher interpopulation connectivity. In accordance with the expansion of cloud forests predicted by CCSM, the genetic data supported the scenario of a population expansion occurring c. 110 ka, followed by population divergence c. 20 ka. However, population dynamics involving expansion of suitable microclimates could reconcile the stability of cloud forests predicted by MIROC and the observed genetic patterns. Main conclusions: The predicted changes in the distribution of cloud forests were congruent with the population genetics of A. firma. However, the choice of palaeoclimate model has a substantial impact on the inferences drawn from the observed genetic and demographic patterns. The use of alternative palaeoclimate hypotheses and biome modelling can provide a common analytical framework for evaluating the historical cohesiveness of forest communities. © 2014 John Wiley & Sons Ltd."
"7003908632;55935942400;","Relative importance of acid coating on ice nuclei in the deposition and contact modes for wintertime Arctic clouds and radiation",2014,"10.1007/s00703-013-0298-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891664940&doi=10.1007%2fs00703-013-0298-9&partnerID=40&md5=0191d52f5ad874e2829f3840bd459adb","Aerosols emitted from volcanic activities and polluted mid-latitudes regions are efficiently transported over the Arctic during winter by the large-scale atmospheric circulation. These aerosols are highly acidic. The acid coating on ice nuclei, which are present among these aerosols, alters their ability to nucleate ice crystals. In this research, the effect of acid coating on deposition and contact ice nuclei on the Arctic cloud and radiation is evaluated for January 2007 using a regional climate model. Results show that the suppression of contact freezing by acid coating on ice nuclei leads to small changes of the cloud microstructure and has no significant effect on the cloud radiative forcing (CRF) at the top of the atmosphere when compared with the effect of the alteration of deposition ice nucleation by acid coating on deposition ice nuclei. There is a negative feedback by which the suppression of contact freezing leads to an increase of the ice crystal nucleation rate by deposition ice nucleation. As a result, the suppression of contact freezing leads to an increase of the cloud ice crystal concentration. Changes in the cloud liquid and ice water contents remain small and the CRF is not significantly modified. The alteration of deposition ice nucleation by acid coating on ice nuclei is dominant over the alteration of contact freezing. © 2013 The Author(s)."
"26767443700;7402064802;7401974644;","On the contribution of longwave radiation to global climate model biases in arctic lower tropospheric stability",2014,"10.1175/JCLI-D-14-00126.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907584697&doi=10.1175%2fJCLI-D-14-00126.1&partnerID=40&md5=52fdd776269fa36521b9baf35bd86220","Previous research has found that global climate models (GCMs) usually simulate greater lower tropospheric stabilities compared to reanalysis data. To understand the origins of this bias, the authors examine hindcast simulations initialized with reanalysis data of six GCMs and find that four of the six models simulate within five days a positive bias in Arctic lower tropospheric stability during the Arctic polar night over sea ice regions. These biases in lower tropospheric stability are mainly due to cold biases in surface temperature, as very small potential temperature biases exist aloft. Similar to previous research, polar night surface temperature biases in the hindcast runs relate to all-sky downwelling longwave radiation in the models, which very much relates to the cloud liquid water. Also found herein are clear-sky longwave radiation biases and a fairly large clear-sky longwave radiation bias in the day one hindcast. This clear-sky longwave bias is analyzed by running the same radiation transfer model for each model's temperature and moisture profile, and the model spread in clear-sky downwelling longwave radiation with the same radiative transfer model is found to be much less, suggesting that model differences other than temperature and moisture are aiding in the spread in downwelling longwave radiation. The six models were also analyzed in Atmospheric Model Intercomparison Project (AMIP) mode to determine if hindcast simulations are analogous to free-running simulations. Similar winter lower tropospheric stability biases occur in four of the six models with surface temperature biases relating to the winter lower tropospheric stability values. © 2014 American Meteorological Society."
"55457676600;56195429100;7410213546;57190774365;","Automatic cloud detection for high spatial resolution multi-temporal images",2014,"10.1080/2150704X.2014.942921","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907899873&doi=10.1080%2f2150704X.2014.942921&partnerID=40&md5=2717c0c105b6b1adaccd79175880a6dc","In this article, we propose an automatic cloud detection process for images with high spatial resolution. First, thick cloud regions are detected by applying a simple threshold method to the target image (an image that includes a cloud-covered region). Next, a reference image (another image that was acquired at a different time and includes the region with relatively little or no cloud-cover) is transformed to the coordinates of the target image by a modified scale-invariant feature transform (SIFT) method. The difference between the target image and transformed reference image is used to extract the peripheral cloud regions. The thick and peripheral cloud regions are then merged based on their relative locations and areas to detect the final cloud regions. Multi-temporal Korea Multi-Purpose Satellite-2 (KOMPSAT-2) images are used to construct study sites to evaluate the proposed method for a range of cloud-cover cases. From the proposed method, a large number of correctly matched points were extracted for this generation of the transformation model, and cloud-covered regions were effectively detected for all sites without manual intervention. © 2014 Taylor & Francis."
"7005858663;57212542665;22952171900;","Engineering ideas for brighter clouds",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910596465&partnerID=40&md5=1aab301e3212c782810fe2372b0cd04b","It may be possible to reduce global warming by increasing the reflectivity of marine stratocumulus clouds thereby reducing the amount of solar energy that is absorbed. Quite a small change to the reflectivity could stop further temperature rise or even produce a reversion towards pre-industrial values. This paper gives a brief account of the physics behind the Twomey effect and its application for marine cloud brightening by the release of sub-micron drops of sea water into the marine boundary layer using a fleet of mobile spray vessels. We argue that the mobility of spray vessels and the short life of spray are advantageous by allowing rapid tactical control in response to local conditions. We identify the main engineering problem as spray production, which in turn requires ultra-filtration of plankton-rich seawater. The proposed engineering solutions involving Rayleigh nozzles etched in silicon and piezo-electric excitation are illustrated with drawings. The results of a COMSOL Multiphysics simulation of drop generation are given, with nozzle diameter, drive pressure, excitation frequency and power requirement as functions of drop diameter. The predicted power requirement is higher than initially hoped for and this has led to a modified vessel design with active hydrofoils giving much lower drag than displacement hulls and turbines. The active control of hydrofoil pitch angle can be used for power generation, roll stabilizing and may also reduce hull loading similarly to the suspension systems of road vehicles. The need to identify unwanted side effects of marine cloud brightening has led to a method for using climate models to give an everywhere-to-everywhere transfer function of the effects of spray in each region on weather records at all observing stations. The technique uses individual coded modulation of the concentration of cloud-condensation nuclei separately in each of many spray regions and is based on methods used for small-signal detection in electronic systems. The first use in a climate model shows very accurate measurement of changes to a temperature record and that that marine cloud brightening can affect precipitation in both directions. Replication with other climate models will be necessary. The paper ends with tentative estimates for the cost of mass production spray vessels based on actual quotations for parts of the spray generation hardware and on the cost of Flower-class corvettes used by the Royal Navy in World War II which were built in similar numbers. © The Royal Society of Chemistry 2014."
"55544443300;57202301596;","Dependence of climate response on meridional structure of external thermal forcing",2014,"10.1175/JCLI-D-13-00622.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904490458&doi=10.1175%2fJCLI-D-13-00622.1&partnerID=40&md5=18395512398ef7b6d9e911b465ad0cbf","This study shows that the magnitude of global surface warming greatly depends on the meridional distribution of surface thermal forcing. An atmospheric model coupled to an aquaplanet slab mixed layer ocean is perturbed by prescribing heating to the ocean mixed layer. The heating is distributed uniformly globally or confined to narrow tropical or polar bands, and the amplitude is adjusted to ensure that the global mean remains the same for all cases. Since the tropical temperature is close to a moist adiabat, the prescribed heating leads to a maximized warming near the tropopause, whereas the polar warming is trapped near the surface because of strong atmospheric stability. Hence, the surface warming is more effectively damped by radiation in the tropics than in the polar region. As a result, the global surface temperature increase is weak (strong) when the given amount of heating is confined to the tropical (polar) band. The degree of this contrast is shown to depend on water vapor-and cloud-radiative feedbacks that alter the effective strength of prescribed thermal forcing. © 2014 American Meteorological Society."
"36655445400;35849722200;41362078500;25652997700;","A numerical investigation of the impacts of anthropogenic sulfate aerosol on regional climate in East Asia",2014,"10.1007/s13143-014-0026-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904253009&doi=10.1007%2fs13143-014-0026-5&partnerID=40&md5=4e5c2104404d9a3eb90e0d63b15af20d","Aerosol and its effects, especially its indirect effects, on climate have drawn more and more attention in recent years. In this study, the first indirect radiative forcing (RF) of sulfate aerosol and its impacts on the regional climate in East Asia during the period from December 2008 to November 2009 were investigated. Affected by the general circulation and the conversion efficiency from SO2 to SO42-? in aqueous phase, a remarkable seasonal variation of sulfate was found. The results show that the highest sulfate concentration as large as 24 g m-2 appears in the summer. The indirect RF due to sulfate aerosol at the top of atmosphere (TOA) and the surface is negative, which leads to a cooling effect on the surface by 0.12°C and a reduction of precipitation by 0.01 mm d-1. The tendencies of temperature and rainfall have significant diversity in space and time. The cloud feedback, associated with the hydrologic cycle and energy budget, is responsible for this discordant distribution. The variation of low cloud dominates the change of surface temperature. The subsidence due to the cooling effect in the mid atmosphere restrained and reduced the low clouds, leading to an apparent warm effect on the surface in Northeast Mongolia. © 2014 The Korean Meteorological Society and Springer."
"57044397100;35069282600;7202899330;57196499374;","Satellite-based estimate of global aerosol-cloud radiative forcing by marine warm clouds",2014,"10.1038/ngeo2214","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906825012&doi=10.1038%2fngeo2214&partnerID=40&md5=6771a50c507722b25aa9dc15a296dc0c","Changes in aerosol concentrations affect cloud albedo and Earth's radiative balance. Aerosol radiative forcing from pre-industrial time to the present due to the effect of atmospheric aerosol levels on the micro- and macrophysics of clouds bears the largest uncertainty among external influences on climate change. Of all cloud forms, low-level marine clouds exert the largest impact on the planet's albedo. For example, a 6% increase in the albedo of global marine stratiform clouds could offset the warming that would result from a doubling of atmospheric CO 2 concentrations. Marine warm cloud properties are thought to depend on aerosol levels and large-scale dynamic or thermodynamic states. Here we present a comprehensive analysis of multiple measurements from the A-Train constellation of Earth-observing satellites, to quantify the radiative forcing exerted by aerosols interacting with marine clouds. Specifically, we analyse observations of co-located aerosols and clouds over the world's oceans for the period August 2006-April 2011, comprising over 7.3 million CloudSat single-layer marine warm cloud pixels. We find that thermodynamic conditions - that is, tropospheric stability and humidity in the free troposphere - and the state of precipitation act together to govern the cloud liquid water responses to the presence of aerosols and the strength of aerosol-cloud radiative forcing. © 2014 Macmillan Publishers Limited. All rights reserved."
"26026749200;22037157600;6603478504;7202899330;","What does CloudSat reveal about global land precipitation detection by other spaceborne sensors?",2014,"10.1002/2013WR014566","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902236354&doi=10.1002%2f2013WR014566&partnerID=40&md5=0b0e449d204ae11f3fc863d90fea300a","Current orbital land precipitation products have serious shortcomings in detecting light rain and snowfall, the most frequent types of global precipitation. The missed precipitation is then propagated into the merged precipitation products that are widely used. Precipitation characteristics such as frequency and intensity and their regional distribution are expected to change in a warming climate. It is important to accurately capture those characteristics to understand and model the current state of the Earth's climate and predict future changes. In this work, the precipitation detection performance of a suite of precipitation sensors, commonly used in generating the merged precipitation products, are investigated. The high sensitivity of CloudSat Cloud Profiling Radar (CPR) to liquid and frozen hydrometeors enables superior estimates of light rainfall and snowfall within 80S-80N. Three years (2007-2009) of CloudSat precipitation data were collected to construct a climatology reference for guiding our analysis. In addition, auxiliary data such as infrared brightness temperature, surface air temperature, and cloud types were used for a more detailed assessment. The analysis shows that no more than 50% of the tropical (40S-40N) precipitation occurrence is captured by the current suite of precipitation measuring sensors. Poleward of 50 latitude, a combination of various factors such as an abundance of light rainfall, snowfall, shallow precipitation-bearing clouds, and frozen surfaces reduces the space-based precipitation detection rate to less than 20%. This shows that for a better understanding of precipitation from space, especially at higher latitudes, there is a critical need to improve current precipitation retrieval techniques and sensors. © 2014. American Geophysical Union. All Rights Reserved."
"26325744400;13105366200;7103393418;","Cloud cover, cloud liquid water and cloud attenuation at Ka and V bands over equatorial climate",2014,"10.1002/met.1417","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904728734&doi=10.1002%2fmet.1417&partnerID=40&md5=13a41b40614c7bd8fb70cc6f499dc4f7","Cloud cover statistics and their diurnal variation have been obtained from in situ and satellite measurements for three equatorial locations. Cloud liquid water content, 0 °C isotherm height and cloud attenuation have also been obtained from radiosonde measurement using the so-called Salonen model at Kuala Lumpur (Malaysia). The results show a strong seasonal variation of cloud cover and cloud liquid water content on the two monsoon seasons. The Liquid Water Content (LWC) obtained from radiosonde and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) is higher during the Northeast Monsoon season, which corresponds to the period of higher percentage cloud cover and high rainfall accumulation. The International Telecommunication Union-Region (ITU-R) model underestimates the cumulative distribution of LWC values at the present station. The relationship of the cloud attenuation, derived from the profiles of liquid water density and temperature within the cloud, shows an underestimate by the data obtained from the ITU-R model. The cloud attenuation at Kuala Lumpur is somewhat underestimated by the ITU-R model up to about 1.2 dB at Ka (30 GHz) and 3.4 dB at V (50 GHz) bands. The results of the specific attenuation can be used for the estimation of cloud attenuation at microwave and millimetre wave over earth-space paths. The present data are important for planning and design of satellite communications at Ka and V bands on the Earth-space path in the equatorial region. © 2014 Royal Meteorological Society."
"57217772325;7202708481;7410041005;","Lidar-based remote sensing of atmospheric boundary layer height over land and ocean",2014,"10.5194/amt-7-173-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006052060&doi=10.5194%2famt-7-173-2014&partnerID=40&md5=6031ca698a6fdfbb9a41577e929e6317","Atmospheric boundary layer (ABL) processes are important in climate, weather and air quality. A better understanding of the structure and the behavior of the ABL is required for understanding and modeling of the chemistry and dynamics of the atmosphere on all scales. Based on the systematic variations of the ABL structures over different surfaces, different lidar-based methods were developed and evaluated to determine the boundary layer height and mixing layer height over land and ocean. With Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) micropulse lidar (MPL) and radiosonde measurements, diurnal and season cycles of atmospheric boundary layer depth and the ABL vertical structure over ocean and land are analyzed. The new methods are then applied to satellite lidar measurements. The aerosol-derived global marine boundary layer heights are evaluated with marine ABL stratiform cloud top heights and results show a good agreement between them. © Author(s) 2014. CC Attribution 3.0 License."
"54783792600;7410041005;7005729142;8511991900;57217772325;","Ice concentration retrieval in stratiform mixed-phase clouds using cloud radar reflectivity measurements and 1D ice growth model simulations",2014,"10.1175/JAS-D-13-0354.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907916579&doi=10.1175%2fJAS-D-13-0354.1&partnerID=40&md5=e16418fdd414531319be2b6caa10aee5","Measurements of ice number concentration in clouds are important but still pose problems. The pattern of ice development in stratiform mixed-phase clouds (SMCs) offers an opportunity to use cloud radar reflectivity (Ze) measurements and other cloud properties to retrieve ice number concentrations. To quantify the strong temperature dependencies of ice crystal habits and growth rates, a one-dimensional (1D) ice growth model has been developed to calculate ice diffusional growth and riming growth along ice particle fallout trajectories in SMCs. The radar reflectivity and fallout velocity profiles of ice crystals calculated from the 1D ice growth model are evaluated with the Atmospheric Radiation Measurements (ARM) Climate Research Facility (ACRF) ground-based high-vertical-resolution radar measurements. A method has been developed to retrieve ice number concentrations in SMCs at a specific cloud-top temperature (CTT) and liquid water path (LWP) by combining Ze measurements and 1D ice growth model simulations. The retrieved ice number concentrations in SMCs are evaluated using integrated airborne in situ and remote sensing measurements and three-dimensional cloud-resolving model simulations with a bin microphysical scheme. The statistical evaluations show that the retrieved ice number concentrations in the SMCs are within an uncertainty of a factor of 2. © 2014 American Meteorological Society."
"36706881700;7409080503;57138743300;55388912500;8839875600;","Cloud vertical distribution from radiosonde, remote sensing, and model simulations",2014,"10.1007/s00382-014-2142-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905117045&doi=10.1007%2fs00382-014-2142-4&partnerID=40&md5=047f1cb667d8915672196b8ab337d262","Knowledge of cloud vertical structure is important for meteorological and climate studies due to the impact of clouds on both the Earth's radiation budget and atmospheric adiabatic heating. Yet it is among the most difficult quantities to observe. In this study, we develop a long-term (10 years) radiosonde-based cloud profile product over the Southern Great Plains and along with ground-based and space-borne remote sensing products, use it to evaluate cloud layer distributions simulated by the National Centers for Environmental Prediction global forecast system (GFS) model. The primary objective of this study is to identify advantages and limitations associated with different cloud layer detection methods and model simulations. Cloud occurrence frequencies are evaluated on monthly, annual, and seasonal scales. Cloud vertical distributions from all datasets are bimodal with a lower peak located in the boundary layer and an upper peak located in the high troposphere. In general, radiosonde low-level cloud retrievals bear close resemblance to the ground-based remote sensing product in terms of their variability and gross spatial patterns. The ground-based remote sensing approach tends to underestimate high clouds relative to the radiosonde-based estimation and satellite products which tend to underestimate low clouds. As such, caution must be exercised to use any single product. Overall, the GFS model simulates less low-level and more high-level clouds than observations. In terms of total cloud cover, GFS model simulations agree fairly well with the ground-based remote sensing product. A large wet bias is revealed in GFS-simulated relative humidity fields at high levels in the atmosphere. © 2014 Springer-Verlag Berlin Heidelberg."
"56005080300;23082420800;7401776640;7003543851;","Observational and model estimates of cloud amount feedback over the Indian and Pacific oceans",2014,"10.1175/JCLI-D-13-00165.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892526467&doi=10.1175%2fJCLI-D-13-00165.1&partnerID=40&md5=d715a20a07be32eb4530bf7c6509a6a6","Constraining intermodel spread in cloud feedback with observations is problematic because available cloud datasets are affected by spurious behavior in long-term variability. This problem is addressed by examining cloud amount in three independent ship-based [Extended Edited Cloud Reports Archive (EECRA)] and satellite-based [International SatelliteCloudClimatology Project (ISCCP) andAdvancedVeryHighResolution Radiometer Pathfinder Atmosphere-Extended (PATMOS-X)] observational datasets, and models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). The three observational datasets show consistent cloud variability in the overlapping years of coverage (1984-2007). The long-term cloud amount change from 1954 to 2005 in ship-based observations shares many of the same features with the multimodel mean cloud amount change of 42 CMIP5 historical simulations, although the magnitude of the multimodel mean is smaller. The radiative impact of cloud changes is estimated by computing an observationally derived estimate of cloud amount feedback. The observational estimates of cloud amount feedback are statistically significant over four regions: the northeast Pacific subtropical stratocumulus region and equatorial western Pacific, where cloud amount feedback is found to be positive, and the southern central Pacific and western Indian Ocean, where cloud amount feedback is found to be negative. Multimodel mean cloud amount feedback is consistent in sign but smaller in magnitude than in observations over these four regions because models simulate weaker cloud changes. Individual models, however, can simulate cloud amount feedback of the same magnitude if not larger than observed. Focusing on the regions where models and observations agree can lead to improved understanding of the mechanisms of cloud amount changes and associated radiative impact. © 2014 American Meteorological Society."
"56120949400;55916925700;10240213900;6602300399;","The sensitivity of global wildfires to simulated past, present, and future lightning frequency",2014,"10.1002/2013JG002502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898874590&doi=10.1002%2f2013JG002502&partnerID=40&md5=4c6f289768637b3f2f154a7a6ca3d368","In this study, components of the Max Planck Institute Earth System Model were used to explore how changes in lightning induced by climate change alter wildfire activity. To investigate how climate change alters global flash frequency, simulations with the atmospheric general circulation model ECHAM6 were performed for the time periods preindustrial, present-day, and three future scenarios. The effect of changes in lightning activity on fire occurrence was derived from simulations with the land surface vegetation model JSBACH. Global cloud-to-ground lightning activity decreased by 3.3% under preindustrial climate and increased by up to 21.3% for the RCP85 projection at the end of the century when compared to present-day, respectively. Relative changes were most pronounced in North America and northeastern Asia. Global burned area was little affected by these changes and only increased by up to 3.3% for RCP85. However, on the regional scale, significant changes occurred. For instance, burned area increases of over 100% were found in high-latitude regions, while also several regions were identified where burned area declined, such as parts of South America and Africa. ©2014. American Geophysical Union. All Rights Reserved."
"57211236228;","Long term (2003-2012) spatio-temporal MODIS (Terra/Aqua level 3) derived climatic variations of aerosol optical depth and cloud properties over a semi arid urban tropical region of Northern India",2014,"10.1016/j.atmosenv.2013.10.030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890106250&doi=10.1016%2fj.atmosenv.2013.10.030&partnerID=40&md5=8434dfd036003a922fc5035b10559d39","Aerosol optical depth (AOD) values at 550nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard NASA's Terra and Aqua satellites, for the 10 years period of 2003-2012 have been analyzed in the present study. The retrieved satellite data (Terra/Aqua) has been used to investigate the temporal heterogeneity in columnar aerosol characteristics over a semi arid urban tropical Delhi zone (28° 34', 77° 07', 233m ASL) of Northern India with a resolution of 1°×1° grid in magnitude. Aerosol optical depths have found to be increased >25% across Delhi region of India during the study period of 2003-2012. Yearly mean Terra/Aqua AOD values have shown an increasing trend at a rate of 0.005/0.009 per year respectively. However, seasonally winter means Terra/Aqua AOD values exhibit an increasing trend at a rate of ~0.012/0.007 per year respectively. In order to provide a better understanding of aerosol-cloud interaction, a single paired one tailed distribution student's t-Test has been applied to the Terra AOD values and cloud parameters. The results extracted in the present study are compared with the earlier studies as well as with the AOD values over various other Indian regions. © 2013 Elsevier Ltd."
"56266792700;55703823500;57216579009;55731174900;","Numerical study of the effect of anthropogenic aerosols on spring persistent rain over Eastern China",2014,"10.1007/s13351-014-3198-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904162185&doi=10.1007%2fs13351-014-3198-0&partnerID=40&md5=462b6fc8ff4d737856f5678d4540bd43","The effect of anthropogenic aerosols on the spring persistent rain (SPR) over eastern China is investigated by using a high-resolution Community Atmosphere Model version 5.1 (CAM5.1). The results show that the SPR starts later due to anthropogenic aerosols, with a shortened duration and reduced rainfall amount. A reduction in air temperature over the low latitudes in East Asia is linked to anthropogenic aerosols; so is a weakened southwesterly on the north side of the subtropical high. Meanwhile, air temperature increases significantly over the high latitudes. This north-south asymmetrical thermal effect acts to reduce the meridional temperature gradient, weakening the upper-level westerly jet over East Asia and the vertical motion over southeastern China. As a result, the SPR is reduced and has a much shorter duration. The indirect effect of anthropogenic aerosols also plays an important role in changing the SPR. Cloud droplet number concentration increases due to anthropogenic aerosols acting as cloud condensation nuclei, leading to a reduction in cloud effective radius over eastern China and a reduced precipitation efficiency there. © 2014 The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg."
"57213950832;12645767500;36097134700;","Observational boundary layer energy and water budgets of the stratocumulus-to-cumulus transition",2014,"10.1175/JCLI-D-14-00242.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919774906&doi=10.1175%2fJCLI-D-14-00242.1&partnerID=40&md5=b9da7736c5c752f25eeaaf464a2366c4","The authors estimate summer mean boundary layer water and energy budgets along a northeast Pacific transect from 35° to 15°N, which includes the transition from marine stratocumulus to trade cumulus clouds. Observational data is used from three A-Train satellites, Aqua, CloudSat, and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO); data derived from GPS signals intercepted by microsatellites of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC); and the container-ship-based Marine Atmospheric Radiation Measurement Program (ARM) Global Energy and Water Cycle Experiment Cloud System Study/Working Group on Numerical Experimentation (GCSS/WGNE) Pacific Cross-Section Intercomparison (GPCI) Investigation of Clouds (MAGIC) campaign. These are unique satellite and shipborne observations providing the first global-scale observations of light precipitation, new vertically resolved radiation budget products derived from the active sensors, and well-sampled radiosonde data near the transect. In addition to the observations, the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) fields are utilized to estimate the budgets. Both budgets approach within 3Wm-2 averaged along the transect, although uncertainty estimates from the study are much larger than this residual. A mean entrainment rate along the transect of 3:4+1.2-1.1 mm s-1 is also estimated. A gradual transition is observed in the climatological mean from the stratocumulus regime to the cumulus regime characterized by an increase in boundary layer height, latent heat flux, rain, and the horizontal advection of dry air and a decrease in entrainment of warm dry air. © 2014 American Meteorological Society."
"36131978400;7202208382;16029674800;","Simulations of the West African monsoon with a superparameterized climate model. Part I: The seasonal cycle",2014,"10.1175/JCLI-D-13-00676.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909606587&doi=10.1175%2fJCLI-D-13-00676.1&partnerID=40&md5=eeb818fb950327f8d2831e45870c81ea","The West African monsoon seasonal cycle is simulated with two coupled general circulation models: the Community Climate System Model (CCSM), which uses traditional convective parameterizations, and the ""superparameterized"" CCSM (SP-CCSM), in which the atmospheric parameterizations have been replaced with an embedded cloud-resolving model. Compared to CCSM, SP-CCSM better represents the magnitude and spatial patterns of summer monsoon precipitation over West Africa. Most importantly, the region of maximum precipitation is shifted from the Gulf of Guinea in CCSM (not realistic) to over the continent in SPCCSM. SP-CCSM also develops its own biases-namely, excessive rainfall along the Guinean coast in summer. Biases in rainfall from both models are linked to a misrepresentation of the equatorial Atlantic cold tongue. Warm sea surface temperature (SST) biases are linked to westerly trade wind biases and convection within the intertropical convergence zone. Improved SST biases in SP-CCSM are linked to increased tropospheric warming associated with convection. A weaker-than-observed Saharan heat low is found in both models, which explains why the main band of precipitation does not penetrate as far northward as observed. The latitude-height position of the African easterly jet (AEJ) is comparable to observations in both models, but the meridional temperature and moisture gradients and the strength of the jet are too weak in SP-CCSM and too strong in CCSM. Differences in the AEJ are hypothesized to be influenced by the contrasting representation of African easterly waves in both models; no wave activity is found in CCSM, and strong waves are found in SP-CCSM. © 2014 American Meteorological Society."
"16228699500;","Water replacement in the Cape Town City Bowl",2014,"10.1080/00207233.2014.897469","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899966400&doi=10.1080%2f00207233.2014.897469&partnerID=40&md5=7d4f0e9e4ad02c48b3cc70976537df7d","The Cape Town City Bowl is fed by a number of perennial springs that rise on the slopes of Table Mountain, thus given the name 'Camissa' the Place of Sweet Waters by the Khoi who inhabited the area before European settlement in 1652. Much of this water is piped to Table Bay where it is discharged, unused. Despite its Mediterranean climate of dry summers, there is not much fluctuation in flow rate from these springs. Condensation from the cloud cover on the mountain crest, caused by the prevailing S-E wind during the season is thought to be a significant agent for recharging the Table Mountain aquifers. © 2014 © 2014 Taylor & Francis."
"56450100300;7201504886;","Climate and climate sensitivity to changing CO2 on an idealized land planet",2014,"10.1002/2014MS000369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027939481&doi=10.1002%2f2014MS000369&partnerID=40&md5=47d46b7709de128768f2c825bdb3b92d","The comprehensive general circulation model ECHAM6 is used in a radiative-convective equilibrium configuration. It is coupled to a perfectly conducting slab. To understand the local impact of thermodynamic surface properties on the land-ocean warming contrast, the surface latent heat flux and surface heat capacity are reduced stepwise, aiming for a land-like climate. Both ocean-like and land-like RCE simulation reproduce the tropical atmosphere over ocean and land in a satisfactory manner and lead to reasonable land-ocean warming ratios. A small surface heat capacity induces a high diurnal surface temperature range which triggers precipitation during the day and decouples the free troposphere from the diurnal mean temperature. With increasing evaporation resistance, the net atmospheric cooling rate decreases because cloud base height rises, causing a reduction of precipitation. Climate sensitivity depends more on changes in evaporation resistance than on changes in surface heat capacity. A feedback analysis with the partial radiation perturbation method shows that amplified warming over idealized land can be associated with disproportional changes in the lapse rate versus the water vapor feedback. Cloud feedbacks, convective aggregation, and changes in global mean surface temperature confuse the picture. © 2014. The Authors."
"57204886915;16445293700;7006198994;7403128993;7003278104;7006127310;7003545639;7405489798;7102696626;36720934300;35364699800;","Process-oriented MJO simulation diagnostic: Moisture sensitivity of simulated convection",2014,"10.1175/JCLI-D-13-00497.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904488716&doi=10.1175%2fJCLI-D-13-00497.1&partnerID=40&md5=ae4ca9d6dfd60254e344740b2999e7dc","Process-oriented diagnostics for Madden-Julian oscillation (MJO) simulations are being developed to facilitate improvements in the representation of the MJO in weather and climate models. These processoriented diagnostics are intended to provide insights into how parameterizations of physical processes in climate models should be improved for a better MJO simulation. This paper proposes one such processoriented diagnostic, which is designed to represent sensitivity of simulated convection to environmental moisture: composites of a relative humidity (RH) profile based on precipitation percentiles. The ability of the RH composite diagnostic to represent the diversity of MJO simulation skill is demonstrated using a group of climate model simulations participating in phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). A set of scalar process metrics that captures the key physical attributes of the RH diagnostic is derived and their statistical relationship with indices that quantify the fidelity of the MJO simulation is tested. It is found that a process metric that represents the amount of lower-tropospheric humidity increase required for a transition from weak to strong rain regimes has a robust statistical relationship with MJO simulation skill. The results herein suggest that moisture sensitivity of convection is closely related to a GCM's ability to simulate the MJO. © 2014 American Meteorological Society."
"7102425008;13006055400;","On the representation of high-latitude boundary layer mixed-phase cloud in the ECMWF global model",2014,"10.1175/MWR-D-13-00325.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906875566&doi=10.1175%2fMWR-D-13-00325.1&partnerID=40&md5=1943cf894bea4e7f280ed7dc77ad2b2c","Supercooled liquid water (SLW) layers in boundary layer clouds are abundantly observed in the atmosphere at high latitudes, but remain a challenge to represent in numerical weather prediction (NWP) and climate models. Unresolved processes such as small-scale turbulence and mixed-phase microphysics act to maintain the liquid layer at cloud top, directly affecting cloud radiative properties and prolonging cloud lifetimes. This paper describes the representation of supercooled liquid water in boundary layer clouds in the European Centre for Medium-Range Weather Forecasts (ECMWF) global NWP model and in particular the change from a diagnostic temperature-dependent mixed phase to a prognostic representation with separate cloud liquid and ice variables. Data from the Atmospheric Radiation Measurement site in Alaska and from the CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite missions are used to evaluate the model parameterizations. The prognostic scheme shows a more realistic cloud structure, with an SLW layer at cloud top and ice falling out below. However, because of the limited vertical and horizontal resolution and uncertainties in the parameterization of physical processes near cloud top, the change leads to an overall reduction in SLW water with a detrimental impact on shortwave and longwave radiative fluxes, and increased 2-m temperature errors over land. A reduction in the ice deposition rate at cloud top significantly improves the SLW occurrence and radiative impacts, and highlights the need for improved understanding and parameterization of physical processes for mixed-phase cloud in large-scale models. © 2014 American Meteorological Society."
"8920681600;57203053066;","What controls the mean east-west sea surface temperature gradient in the equatorial pacific: The role of cloud albedo",2014,"10.1175/JCLI-D-13-00255.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896917979&doi=10.1175%2fJCLI-D-13-00255.1&partnerID=40&md5=5fc2e56ff16d32eee6b5ddaef4477149","The mean east-west sea surface temperature gradient along the equator is a key feature of tropical climate. Tightly coupled to the atmospheric Walker circulation and the oceanic east-west thermocline tilt, it effectively defines tropical climate conditions. In the Pacific, its presence permits the El Niño-Southern Oscillation phenomenon.What determines this temperature gradient within the fully coupled ocean-atmosphere system is therefore a central question in climate dynamics, critical for understanding past and future climates. Using a comprehensive coupled model [Community Earth System Model (CESM)], the authors demonstrate how the meridional gradient in cloud albedo between the tropics and midlatitudes (Δα) sets the mean east-west sea surface temperature gradient in the equatorial Pacific. To change Δα in the numerical experiments, the authors change the optical properties of clouds by modifying the atmospheric water path, but only in the shortwave radiation scheme of the model. When Δα is varied from approximately20.15 to 0.1, the east-west SST contrast in the equatorial Pacific reduces from 7.58° to less than 18° and the Walker circulation nearly collapses. These experiments reveal a near-linear dependence between Δα and the zonal temperature gradient, which generally agrees with results from the Coupled Model Intercomparison Project phase 5 (CMIP5) preindustrial control simulations. The authors explain the close relation between the two variables using an energy balance model incorporating the essential dynamics of the warm pool, cold tongue, and Walker circulation complex. © 2014 American Meteorological Society."
"55716181900;6602403713;7003668116;","Evaluating the accuracy of a high-resolution model simulation through comparison with MODIS observations",2014,"10.1175/JAMC-D-13-0140.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897990862&doi=10.1175%2fJAMC-D-13-0140.1&partnerID=40&md5=c3c6598d6ad7a9f22a5768417ad5072f","Synthetic infrared brightness temperatures (BTs) derived from a high-resolution Weather Research and Forecasting (WRF) model simulation over the contiguous United States are compared with Moderate Resolution Imaging Spectroradiometer (MODIS) observations to assess the accuracy of the model-simulated cloud field.Asophisticated forward radiative transfer model (RTM) is used to compute the synthetic MODIS observations. A detailed comparison of synthetic and real MODIS 11-μm BTs revealed that the model simulation realistically depicts the spatial characteristics of the observed cloud features. Brightness temperature differences (BTDs) computed for 8.5-11 and 11-12μm indicate that the combined numerical model-RTM system realistically treats the radiative properties associated with optically thin cirrus clouds. For instance, much larger 11-12-μm BTDs occurred within thin clouds surrounding optically thicker, mesoscale cloud features. Although the simulated and observed BTD probability distributions for optically thin cirrus clouds had a similar range of positive values, the synthetic 11-μmBTs were much colder than observed. Previous studies have shown that MODIS cloud optical thickness values tend to be too large for thin cirrus clouds, which contributed to the apparent cold BT bias in the simulated thin cirrus clouds. Errors are substantially reduced after accounting for the observed optical thickness bias, which indicates that the thin cirrus clouds are realistically depicted during the model simulation. © 2014 American Meteorological Society."
"56493740900;7102651635;55717441600;7004325649;7003854810;","Retrieval of atmospheric and cloud property anomalies and their trend from temporally and spatially averaged infrared spectra observed from space",2014,"10.1175/JCLI-D-13-00566.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902095902&doi=10.1175%2fJCLI-D-13-00566.1&partnerID=40&md5=cab80e2ed74ba98be650dca4f6a02e4a","A surface, atmospheric, and cloud (fraction, height, optical thickness, and particle size) property anomaly retrieval from highly averaged longwave spectral radiances is simulated using 28 years of reanalysis. Instantaneous nadir-view spectral radiances observed from an instrument on a 908 inclination polar orbit are computed. Spectral radiance changes caused by surface, atmospheric, and cloud property perturbations are also computed and used for the retrieval. This study's objectives are 1) to investigate whether or not separating clear sky from cloudy sky reduces the retrieval error and 2) to estimate the error in a trend of retrieved properties. This simulation differs from earlier studies in that annual 108 latitude zonal cloud and atmospheric property anomalies defined as the deviation from 28-yr climatological means are retrieved instead of the difference of these properties from two time periods. The root-mean-square (RMS) difference of temperature and humidity anomalies retrieved from all-sky radiance anomalies is similar to the RMS difference derived from clear-sky radiance anomalies computed by removing clouds. This indicates that the cloud property anomaly retrieval error does not affect the retrieved temperature and humidity anomalies. When retrieval errors are nearly random, the error in the trend of retrieved properties is small. Approximately 30% of 108 latitude zones meet conditions that the true temperature and water vapor amount trends are within a 95% confidence interval of retrieved trends, and that the standard deviation of retrieved anomalies sret is within 20% of the standard deviation of true anomalies σn. If σret/σn - 1 is within ± 0.2, 91% of the true trends fall within the 95% confidence interval of the corresponding retrieved trend. © 2014 American Meteorological Society."
"7004853382;7203047936;36456423100;","Uncertainty of AMSU-A derived temperature trends in relationship with clouds and precipitation over ocean",2014,"10.1007/s00382-013-1958-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906726600&doi=10.1007%2fs00382-013-1958-7&partnerID=40&md5=58fd4b232e46074473e746251b4f5619","Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit-A (AMSU-A) observations from a series of National Oceanic and Atmospheric Administration satellites have been extensively utilized for estimating the atmospheric temperature trend. For a given atmospheric temperature condition, the emission and scattering of clouds and precipitation modulate MSU and AMSU-A brightness temperatures. In this study, the effects of the radiation from clouds and precipitation on AMSU-A derived atmospheric temperature trend are assessed using the information from AMSU-A window channels. It is shown that the global mean temperature in the low and middle troposphere has a larger warming rate (about 20-30 % higher) when the cloud-affected radiances are removed from AMSU-A data. It is also shown that the inclusion of cloud-affected radiances in the trend analysis can significantly offset the stratospheric cooling represented by AMSU-A channel 9 over the middle and high latitudes of Northern Hemisphere. © 2013 Springer-Verlag (outside the USA)."
"6603631763;7202970886;12801836100;56999327800;","The pathfinder atmospheres-extended avhrr climate dataset",2014,"10.1175/BAMS-D-12-00246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905687083&doi=10.1175%2fBAMS-D-12-00246.1&partnerID=40&md5=79b50f529767f5ae04bae7105c424259","The Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres-Extended (PATMOS-x) dataset offers over three decades of global observations from the NOAA Polar-orbiting Operational Environmental Satellite (POES) project and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) [Meteorological Operational (MetOp)] satellite series. The AVHRR PATMOS-x data provide calibrated AVHRR observations in addition to properties about tropospheric clouds and aerosols, Earth's surface, Earth's radiation budget, and relevant ancillary data. To provide three decades of data in a convenient format, PATMOS-x generates mapped and sampled results with a spatial resolution of 0.1° on a global latitude-longitude grid. AVHRR PATMOS-x is composed of data from 17 different sensors. An examination of cloud amount and total-sky time series demonstrates that intersatellite biases are less than 2%. AVHRR PATMOS-x data are hosted by the National Climatic Data Center (NCDC)."
"56991036700;6506939784;16025322100;14825561100;","Estimation of regional snowline elevation (RSLE) from MODIS images for seasonally snow covered mountain basins",2014,"10.1016/j.jhydrol.2014.08.064","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949115755&doi=10.1016%2fj.jhydrol.2014.08.064&partnerID=40&md5=56f7a957f7b161a5a158b338ac3a12bd","We present a method for estimation of regional snowline elevation (RSLE) from satellite data for seasonally snow covered mountain basins. The methodology is based on finding an elevation for which the sum of snow covered pixels below and land pixels above the RSLE is minimized for each day. The methodology is tested with MODIS daily snow cover product in the period 2000-2013 in the upper Váh basin (Slovakia). The accuracy is evaluated by daily snow depth measurements at seven climate stations and additional snow course measurements at 16 profiles in the period 2000-2013. The results show that RSLE allows accurate estimation of snowline elevation. For the RSLE estimation, two thresholds need to be considered. The thresholds of maximum cloud coverage and minimum number of snow pixels considerably affect the number of days (images) available for estimation. The sensitivity evaluation indicates that the cloud threshold has less effect on the accuracy than the minimum snow threshold. Setting cloud and minimum snow thresholds to 70% and 5% respectively, results in an average RSLE estimation accuracy of 86% at climate stations. The accuracy in the forest is 92% in the winter months and drops to 70% in April. The main factors that control the accuracy and scatter around the snowline are vegetation cover and shading of terrain. The results show that spatial patterns of misclassification correspond well with forest cover and potential insolation duration in winter. The developed RSLE method is more accurate than the previously used methods of snowline elevation estimation, it decreases the scatter around the snowline and can be potentially applied in an improved cloud reduction in MODIS products as well. © 2014 Elsevier B.V."
"36570526700;7401796996;8629713500;","Cloud fraction at the ARM SGP site: Instrument and sampling considerations from 14 years of ARSCL",2014,"10.1007/s00704-013-0853-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891663975&doi=10.1007%2fs00704-013-0853-9&partnerID=40&md5=8f8ea66b7eb47d0730ac0681de32bfec","The Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) site has a rich history of actively sensed cloud observations. Fourteen years (1997-2010) of observations from the Millimeter Cloud Radar (MMCR), Micropulse Lidar (MPL), and Belfort/Vaisala Ceilometers are used to understand how instrument selection and sampling impacts estimates of Cloud Fraction (CF) at this location. Although all instruments should be used in combination for the best estimates of CF, instrument downtime limits available samples and increases observational errors, demanding that users make sacrifices when calculating CF at longer intervals relevant to climate studies. Selection of MMCR or MMCR + MPL cloud masks changes very little in the overall understanding of total CF. Addition of the MPL increases the 14-year average CF by 9 %, mainly through an increase in optically thin high clouds year-round, and mid-level clouds during the summer months. Splitting the period into two equal 7-year periods reveals negligible change in MMCR + MPL CF. For the MMCR, however, CF deceases by 6.1 %. This sudden change in CF occurs around the time the radar was upgraded, suggesting that this decrease is tied to hardware sensitivity or scanning strategy changes. Users must be cognizant of this and other issues when calculating CF from the variety of observations available at the ARM SGP site. © 2013 Springer-Verlag Wien."
"26536569500;","An analytical model for tropical relative humidity",2014,"10.1175/JCLI-D-14-00255.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907584686&doi=10.1175%2fJCLI-D-14-00255.1&partnerID=40&md5=3b9c4f36381e430cce64e4b2fe9a7e4f","An analytical model is derived for tropical relative humidity using only the Clausius-Clapeyron relation, hydrostatic balance, and a bulk-plume water budget. This theory is constructed for radiative-convective equilibriumand compared against a cloud-resolving model. With some reinterpretation of variables, it can be applied more generally to the entire tropics. Given four variables-pressure, temperature, and the fractional entrainment and detrainment rates-the equations predict the relative humidity (RH) andthe temperature lapse rate analytically.TheRHis a simple ratio involving the fractional detrainment rate and the water-vapor lapse rate. When integrated upward in height, the equations give profiles of RH and temperature for a convecting atmosphere. The theory explains the magnitude of RH and the ""C"" shape of the tropospheric RH profile. It also predicts that RH is an invariant function of temperature as the atmosphere warms, and this behavior matches what has been seen in global climate models and what is demonstrated here with cloud-resolving simulations. Extending the theory to include the evaporation of hydrometeors, a lower bound is derived for the precipitation efficiency (PE) at each height: PE > 1 - RH. In a cloud-resolving simulation, this constraint is obeyed with the PE profile taking the shape of an inverted C shape. © 2014 American Meteorological Society."
"7006495789;41261181900;55318318400;","Space-based geoengineering solutions",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937405110&partnerID=40&md5=ad2d61c776652627493b5e77425a5e21","This chapter provides an overview of space-based geoengineering as a tool to modulate solar insolation and offset the impacts of humandriven climate change. A range of schemes are considered including static and orbiting occulting disks and artificial dust clouds at the interior Sun-Earth Lagrange point, the gravitational balance point between the Sun and Earth. It is demonstrated that, in principle, a dust cloud can be gravitationally anchored at the interior Lagrange point to reduce solar insolation and that orbiting disks can provide a uniform reduction of solar insolation with latitude, potentially offsetting the regional impacts of a static disk. While clearly speculative, the investigation of space-based geoengineering schemes provides insights into the long-term prospects for large-scale, active control of solar insolation. © The Royal Society of Chemistry 2014."
"40462246800;7003330218;","Recent sea surface temperature trends and future scenarios for the Mediterranean Sea",2014,"10.5697/oc.56-3.411","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902159940&doi=10.5697%2foc.56-3.411&partnerID=40&md5=b18e12942b497ea6c4b2eebfa3fd10c9","We analyse recent Mediterranean Sea surface temperatures (SSTs) and their response to global change using 1/4-degree gridded advanced very-high-resolution radiometer (AVHRR) daily SST data, 1982-2012. These data indicate significant annual warming (from 0.24°C decade-1 west of the Strait of Gibraltar to 0.51°C decade-1 over the Black Sea) and significant spatial variation in annual average SST (from 15°C over the Black Sea to 21°C over the Levantine sub-basin). Ensemble mean scenarios indicate that the study area SST may experience significant warming, peaking at 2.6°C century-1 in the Representative Concentration Pathways 85 (RCP85) scenario. © Polish Academy of Sciences, Institute of Oceanology, 2014."
"55353781900;7404433688;55386235300;15756666000;55969140000;7202708481;56161349600;56126562300;","A study of the distribution and variability of cloud water using ISCCP, SSM/I cloud product, and reanalysis datasets",2014,"10.1175/JCLI-D-13-00031.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899081857&doi=10.1175%2fJCLI-D-13-00031.1&partnerID=40&md5=1457be7ebf90cf9e57d338b6b1bf496c","In this paper, the global distribution of cloud water based on International Satellite Cloud Climatology Project (ISCCP), Moderate Resolution Imaging Spectroradiometer (MODIS), CloudSat Cloud Profiling Radar (CPR), European Center for Medium-Range Weather Forecasts Interim Re-Analysis (ERAInterim), and Climate Forecast System Reanalysis (CFSR) datasets is presented, and the variability of cloud water from ISCCP, the Special Sensor Microwave Imager (SSM/I), ERA-Interim, and CFSR data over the time period of 1995 through 2009 is discussed. The results show noticeable differences in cloud water over land and over ocean, as well as latitudinal variations. Large values of cloud water are mainly distributed over the North Pacific and Atlantic Oceans, eastern ITCZ, regions off the west coast of the continents as well as tropical rain forest. Cloud water path (CWP), liquid water path (LWP), and ice water path (IWP) from these datasets show a relatively good agreement in distributions and zonal means. The results of trend analyzing show an increasing trend in CWP, and also a significant increasing trend of LWP can be found in the dataset of ISCCP, ERA-Interim, and CFSR over the ocean. Besides the long-term variation trend, rises of cloud water are found when temperature and water vapor exhibit a positive anomaly. EOF analyses are also applied to the anomalies of cloud water, the first dominate mode of CWP and IWP are similar, and a phase change can be found in the LWP time coefficient around 1999 in ISCCP and CFSR and around 2002 in ERA-Interim. © 2014 American Meteorological Society."
"37087012900;7402934750;12144198300;7003663305;6701729202;","Cloud microphysical properties retrieved from downwelling infrared radiance measurements made at Eureka, Nunavut, Canada (2006-09)",2014,"10.1175/JAMC-D-13-0113.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896519519&doi=10.1175%2fJAMC-D-13-0113.1&partnerID=40&md5=8c27b3d4334e6cc9593ac27e01fea254","The radiative properties of clouds are related to cloud microphysical and optical properties, including water path, optical depth, particle size, and thermodynamic phase. Ground-based observations from remote sensors provide high-quality, long-term, continuous measurements that can be used to obtain these properties. In the Arctic, a more comprehensive understanding of cloud microphysics is important because of the sensitivity of the Arctic climate to changes in radiation. Eureka, Nunavut (80°N, 86°25'W, 10 m), Canada, is a research station located on Ellesmere Island. A large suite of ground-based remote sensors at Eureka provides the opportunity to make measurements of cloud microphysics using multiple instruments and methodologies. In this paper, cloud microphysical properties are presented using a retrieval method that utilizes infrared radiances obtained from an infrared spectrometer at Eureka between March 2006 and April 2009. These retrievals provide a characterization of the microphysics of ice and liquid in clouds with visible optical depths between 0.25 and 6, which are a class of clouds whose radiative properties depend greatly on their microphysical properties. The results are compared with other studies that use different methodologies at Eureka, providing context for multimethod perspectives. The authors' findings are supportive of previous studies, including seasonal cycles in phase and liquid particle size, weak temperature-phase dependencies, and frequent occurrences of supercooled water. Differences in microphysics are found between mixed-phase and single-phase clouds for both ice and liquid. The Eureka results are compared with those obtained using a similar retrieval technique during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. © 2014 American Meteorological Society."
"55717244800;","A unified convection scheme (UNICON). Part II: Simulation",2014,"10.1175/JAS-D-13-0234.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907050617&doi=10.1175%2fJAS-D-13-0234.1&partnerID=40&md5=03c77488583f05e1251811efda470482","Aunified convection scheme (UNICON) is implemented into the Community Atmosphere Model, version 5 (CAM5), and tested in single-column and global simulations forced by observed sea surface temperature. Compared to CAM5, UNICON substantially improves the single-column simulations of stratocumulus-tocumulus transition and shallow and deep convection cases. The global performance of UNICON is similar to CAM5 with a relative spatiotemporal root-mean-square error (RMSE) of 0.777 (0.755 in CAM5) against the earlier version of the model (CCSM3.5). The notable improvements in the UNICON-simulated climatologies over CAM5 are seasonal precipitation patterns (i.e., monsoon) over the western Pacific and South Asia, reduced biases of cloud radiative forcing in the tropical deep convection regions, aerosol optical depth in the tropical and subtropical regions, and cumulus fraction and in-cumulus condensate. One notable degradation is that UNICON simulates warmer near-surface air temperature over the United States during summer. In addition to the climatology, UNICON significantly improves the simulation of the diurnal cycle of precipitation and the Madden-Julian oscillation (MJO). The surface precipitation simulated by UNICON is a maximum in the late afternoon (early afternoon in CAM5) over the summer continents and in the early morning (predawn in CAM5) over the ocean with a fairly realistic amplitude of the diurnal cycle. Sensitivity simulations indicate that the key for successfulMJOsimulation in UNICONis a seamless parameterization of the updraft plume dilution rate as convection evolves from shallow to deep convection. The mesoscale perturbation of the vertical velocity and the thermodynamic scalars of convective updrafts is an additional requirement for simulating the observed diurnal cycle of precipitation. © 2014 American Meteorological Society."
"6602845217;56020871100;55330583500;36537081500;","Analysis of the Slab Ocean El Nino atmospheric feedbacks in observed and simulated ENSO dynamics",2014,"10.1007/s00382-014-2057-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901987382&doi=10.1007%2fs00382-014-2057-0&partnerID=40&md5=be9d6462c9b94b33b25ddd835f2f846e","In a recent study it was illustrated that the El Nino Southern Oscillation (ENSO) mode can exist in the absence of any ocean dynamics. This oscillating mode exists just due to the interaction between atmospheric heat fluxes and ocean heat capacity. The primary purpose of this study is to further explore these atmospheric Slab Ocean ENSO dynamics and therefore the role of positive atmospheric feedbacks in model simulations and observations. The positive solar radiation feedback to sea surface temperature (SST), due to reduced cloud cover for anomalous warm SSTs, is the main positive feedback in the Slab Ocean El Nino dynamics. The strength of this positive cloud feedback is strongly related to the strength of the equatorial cold tongue. The combination of positive latent and sensible heat fluxes to the west and negative ones to the east of positive anomalies leads to the westward propagation of the SST anomalies, which allows for oscillating behavior with a preferred period of 6-7 years. Several indications are found that parts of these dynamics are indeed observed and simulated in other atmospheric or coupled general circulation models (AGCMs or CGCMs). The CMIP3 AGCM-slab ensemble of 13 different AGCM simulations shows unstable ocean-atmosphere interactions along the equatorial Pacific related to stronger cold tongues. In observations and in the CMIP3 and CMIP5 CGCM model ensemble the strength and sign of the cloud feedback is a function of the strength of the cold tongue. In summary, this indicates that the Slab Ocean El Nino dynamics are indeed a characteristic of the equatorial Pacific climate that is only dominant or significantly contributing to the ENSO dynamics if the SST cold tongue is sufficiently strong. In the observations this is only the case during strong La Nina conditions. The presence of the Slab Ocean ENSO atmospheric feedbacks in observations and CGCM model simulations implies that the family of physical ENSO modes does have another member, which is entirely driven by atmospheric processes and does not need to have the same spatial pattern nor the same time scales as the main ENSO dynamics. © 2014 Springer-Verlag Berlin Heidelberg."
"56100422000;7102866124;6603497730;","Inner convective system cloud-top wind estimation using multichannel infrared satellite images",2014,"10.1080/01431161.2013.871391","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892986516&doi=10.1080%2f01431161.2013.871391&partnerID=40&md5=21537a7125dee76663f43eb3d1c84754","Knowledge of deep convective system cloud processes and dynamic structures is a key feature in climate change and nowcasting. However, the horizontal inner structures at the cloud tops of deep convective systems are not well understood due to lack of measurements and the complex processes linked to dynamics and thermodynamics. This study describes a new technique to extract inner cloud-top dynamics using brightness temperature differences. This new information could help clarify ring and U or V shape structures in deep convection and be potentially useful in nowcasting applications. Indeed, the use of high-resolution numerical weather prediction (NWP) models, which now include explicit microphysical processes, requires data assimilation at very high resolution as well. A standard atmospheric motion vector tracking algorithm was applied to a pair of images composed of combinations of Spinning Enhanced Visible and Infra-red Imager (SEVIRI) channels. Several ranges of channel differences were used in the tracking process, such intervals being expected to correspond to specific cloud-top microphysics structures. Various consistent flows of motion vectors with different speeds and/or directions were extracted at the same location depending on the channel difference intervals used. These differences in speed/direction can illustrate local wind shear situations, or correspond to expansion or dissipation of cloud regions that contain high concentrations of specific kinds of ice crystals or droplets. The results from this technique were compared to models and ancillary data to advance our discussion and inter-comparisons. Also, the technique proposed here was evaluated using SEVIRI images simulated by the radiative transfer model RTTOV with input data from the UK Met Office Unified Model. A future application of the new data is exemplified by showing the relationship between wind divergence calculated from the new atmospheric motion vector and convective cloud top intensification. © 2014 © Taylor & Francis."
"7103313899;7202444684;7004692414;57208867310;","Case study on microphysical properties of boundary layer mixed-phase cloud observed at Ny-Ålesund, Svalbard: Observed cloud microphysics and calculated optical properties on 9 June 2011",2014,"10.1016/j.polar.2013.11.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901471475&doi=10.1016%2fj.polar.2013.11.001&partnerID=40&md5=508663c4662f6d957539b375e8ae684e","Cloud radiation interactions are important in the global climate system. However, an understanding of mixed-phase boundary layer clouds in the Arctic remains poor. During May-June 2011, ground-based in situ measurements were made at Zeppelin Station, operated by the Norwegian Polar Institute (altitude 474 m) in Ny-Ålesund (78.9°N, 11.9°E), Svalbard. The instruments used comprised a Cloud, Aerosol and Precipitation Spectrometer (CAPS), and a Cloud Particle Microscope imager. The CAPS incorporated a Cloud and Aerosol Spectrometer and Cloud Imaging Probe (CIP). During the observation period, clouds associated with cyclonic disturbances and those associated with outbreaks of westerly cold air masses from the sea were observed. Atmospheric temperature during all measurements ranged from 0 to -5 °C. In every case, columns were the major type of ice particle measured by the CAPS-CIP. Cloud microphysical properties were observed continuously on 9 June 2011. Size spectra, liquid/ice water content, and particle effective size changed depending on progress stages. Based on the observed microphysics, optical properties were calculated and investigated. Optical properties were determined mainly by those of liquid water particles, even during periods when the relative contribution of ice particles to total water content was at the maximum. It was confirmed that the wavelength region of 1.6 and 2.2 μm can be used in remote sensing. This study shows that it is possible to measure detailed changes of cloud properties in the Arctic region by using instruments installed at a ground-based mountain station. © 2013 Elsevier B.V. and NIPR."
"56342804700;7402333662;","Summer season squall-line simulations: Sensitivity of gravity waves to physics parameterization and implications for their parameterization in global climate models",2014,"10.1175/JAS-D-13-0380.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906739407&doi=10.1175%2fJAS-D-13-0380.1&partnerID=40&md5=5d687189d9ce5729af0dee4f2958f299","Gravity waves have important effects on the middle atmosphere circulation, and those generated by convection are prevalent in the tropics and summer midlatitudes. Numerous case studies have been carried out to investigate their characteristics in high-resolution simulations. Here, the impact of the choice of physics parameterizations on the generation and spectral properties of these waves in models is investigated. Using the Weather Research and Forecasting Model (WRF) a summertime squall line over the Great Plains is simulated in a three-dimensional, nonlinear, and nonhydrostatic mesoscale framework. The distributions of precipitation strength and echo tops in the simulations are compared with radar data. Unsurprisingly, those storm features are most sensitive to the microphysics scheme. However, it is found that these variations in storm morphology have little influence on the simulated stratospheric momentum flux spectra. These results support the fundamental idea behind climate model parameterizations: that the large-scale storm conditions can be used to predict the spectrum of gravity wave momentum flux above the storm irrespective of the convective details that coarse-resolution models cannot capture. The simulated spectra are then contrasted with those obtained from a parameterization used in global climate models. The parameterization reproduces the shape of the spectra reasonably well but their magnitudes remain highly sensitive to the peak heating rate within the convective cells. © 2014 American Meteorological Society."
"56676874900;6602230939;","The role of ENSO in global ocean temperature changes during 1955-2011 simulated with a 1D climate model",2014,"10.1007/s13143-014-0011-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896111691&doi=10.1007%2fs13143-014-0011-z&partnerID=40&md5=7b71f43d2bfd175048e0e21035f880e0","Global average ocean temperature variations to 2,000 m depth during 1955-2011 are simulated with a 40 layer 1D forcingfeedback- mixing model for three forcing cases. The first case uses standard anthropogenic and volcanic external radiative forcings. The second adds non-radiative internal forcing (ocean mixing changes initiated in the top 200 m) proportional to the Multivariate ENSO Index (MEI) to represent an internal mode of natural variability. The third case further adds ENSO-related radiative forcing proportional to MEI as a possible natural cloud forcing mechanism associated with atmospheric circulation changes. The model adjustable parameters are net radiative feedback, effective diffusivities, and internal radiative (e.g., cloud) and non-radiative (ocean mixing) forcing coefficients at adjustable time lags. Model output is compared to Levitus ocean temperature changes in 50 m layers during 1955-2011 to 700 m depth, and to lag regression coefficients between satellite radiative flux variations and sea surface temperature between 2000 and 2010. A net feedback parameter of 1.7Wm-2 K-1 with only anthropogenic and volcanic forcings increases to 2.8Wm-2 K-1 when all ENSO forcings (which are one-third radiative) are included, along with better agreement between model and observations. The results suggest ENSO can influence multi-decadal temperature trends, and that internal radiative forcing of the climate system affects the diagnosis of feedbacks. Also, the relatively small differences in model ocean warming associated with the three cases suggests that the observed levels of ocean warming since the 1950s is not a very strong constraint on our estimates of climate sensitivity. © The Korean Meteorological Society and Springer 2014."
"14051038900;57203199846;7202641466;57194275819;7003494572;","Improved representation of tropical Pacific Ocean-atmosphere dynamics in an intermediate complexity climate model",2014,"10.1175/JCLI-D-12-00849.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892607640&doi=10.1175%2fJCLI-D-12-00849.1&partnerID=40&md5=40c38f8a17fdd304f6329c2753c8f696","A new anomaly coupling technique is introduced into a coarse-resolution dynamic climate model [the Liège Ocean Carbon Heteronomous model (LOCH)-Vegetation Continuous Description model (VECODE)-Earth System Models of Intermediate Complexity Climate deBilt (ECBILT)-Coupled Large-Scale Ice-Ocean model (CLIO)-Antarctic andGreenland Ice SheetModel (AGISM) ensemble (LOVECLIM)], improving themodel's representation of eastern equatorial Pacific surface temperature variability. The anomaly coupling amplifies the surface diabatic atmospheric forcing within a Gaussian-shaped patch applied in the tropical Pacific Ocean. It is implemented with an improved predictive cloud scheme based on empirical relationships between cloud cover and key state variables. Results are presented from a perturbed physics ensemble systematically varying the parameters controlling the anomaly coupling patch size, location, and amplitude. The model's optimal parameter combination is chosen through calibration against the observed power spectrum of monthly-mean surface temperature anomalies in the Niño-3 region. The calibrated model exhibits substantial improvement in equatorial Pacific interannual surface temperature variability and robustly reproduces El Niño-SouthernOscillation (ENSO)-like variability. The authors diagnose some of the key atmospheric and oceanic feedbacks in themodel important for simulating ENSO-like variability, such as the positive Bjerknes feedback and the negative heat flux feedback, and analyze the recharge-discharge of the equatorial Pacific ocean heat content. They findLOVECLIM robustly captures important ocean dynamics related to thermocline adjustment and equatorial Kelvin waves. The calibrated model demonstrates some improvement in simulating atmospheric feedbacks, but the coupling between ocean and atmosphere is relatively weak. Because of the tractability of LOVECLIM and its consequent utility in exploring long-term climate variability and large ensemble perturbed physics experiments, improved representation of tropical Pacific ocean-atmosphere dynamics in the model may more readily allow for the investigation of the role of tropical Pacific ocean-atmosphere dynamics in past climate changes. © 2014 American Meteorological Society."
"55844779300;57203073322;","Experimental cloud immersion and foliar water uptake in saplings of Abies fraseri and Picea rubens",2014,"10.1007/s00468-013-0934-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892836698&doi=10.1007%2fs00468-013-0934-5&partnerID=40&md5=8009e0fdcaf934a4d8430a27e2884be2","Key message: Frequent cloud immersion events result in direct uptake of cloud water and improve plant water potentials during daylight hours in saplings of two dominant cloud forest species. In ecosystems with frequent cloud immersion, the influence on plant water balance can be important. While cloud immersion can reduce plant water loss via transpiration, recent advances in methodology have suggested that many species also absorb water directly into leaves (foliar water uptake). The current study examines foliar water uptake and its influence on daily plant water balance in tree species of the endangered spruce-fir forest of the southern Appalachian Mountains, USA. These mountain-top communities are considered relic, boreal forests that may have persisted because of the benefits of frequent cloud immersion. We examined changes in needle water content, xylem water potentials, and stable isotope values in saplings of the two dominant tree species, Abies fraseri and Picea rubens before and after a 24 h period of experimental cloud immersion. Both species exhibited foliar water uptake following immersion, evidenced by substantial changes in stable isotope values of extracted needle water that reflected the composition of the fog water. In addition, total needle water content improved 3.7-6.4 % following experimental submersion and xylem water potentials were significantly greater (up to 0.33 MPa) in cloud-immersed plants over control plants. These results indicate that foliar water uptake may be an adaptive strategy for utilizing cloud water and improving overall tree vigor in these most southerly distributed boreal species. © 2013 Springer-Verlag Berlin Heidelberg."
"38762392200;9275665400;","Effect of solar variations on particle formation and cloud condensation nuclei",2014,"10.1088/1748-9326/9/4/045004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928096609&doi=10.1088%2f1748-9326%2f9%2f4%2f045004&partnerID=40&md5=ea6d7c00ededb0c074411766a46b6205","The impact of solar variations on particle formation and cloud condensation nuclei (CCN), a critical step for one of the possible solar indirect climate forcing pathways, is studied here with a global aerosol model optimized for simulating detailed particle formation and growth processes. The effect of temperature change in enhancing the solar cycle CCN signal is investigated for the first time. Our global simulations indicate that a decrease in ionization rate associated with galactic cosmic ray flux change from solar minimum to solar maximum reduces annual mean nucleation rates, number concentration of condensation nuclei larger than 10nm (CN10), and number concentrations of CCN at water supersaturation ratio of 0.8% (CCN0.8) and 0.2% (CCN0.2) in the lower troposphere by 6.8%, 1.36%, 0.74%, and 0.43%, respectively. The inclusion of 0.2 C temperature increase enhances the CCN solar cycle signals by around 50%. The annual mean solar cycle CCN signals have large spatial and seasonal variations: (1) stronger in the lower troposphere where warm clouds are formed, (2) about 50% larger in the northern hemisphere than in the southern hemisphere, and (3) about a factor of two larger during the corresponding hemispheric summer seasons. The effect of solar cycle perturbation on CCN0.2 based on present study is generally higher than those reported in several previous studies, up to around one order of magnitude. © 2014 IOP Publishing Ltd."
"42962520400;8268390600;35271743000;57202110203;6506796994;","A class of cloud detection algorithms based on a map-mrf approach in space and time",2014,"10.1109/TGRS.2013.2286834","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896319722&doi=10.1109%2fTGRS.2013.2286834&partnerID=40&md5=b57e9ae19846f6776072b75359eba3b0","A recurrent concern in cloud detection approaches is the high misclassification rate for pixels close to cloud edges. We tackle this problem by introducing a novel penalty term within the classical maximum a posteriori probability-Markov random field (MAP-MRF) approach. To improve the classification rate, such term, for which we suggest two different functional forms, accounts for the predictable motion of cloud volumes across images. Two mass tracking techniques are proposed. The first one is an effective and efficient implementation of the probability hypothesis density (PHD) filter, which is based on Gaussian mixtures (GMs) and relies on finite set statistics (FISST). The second one is a region matching procedure based on a maximum cross-correlation (MCC) that is characterized by low computational load. Through extensive tests on simulated images and real data, acquired by the SEVIRI sensor, both methods show a clear performance gain in comparison with classical spatial MRF-based algorithms. © 1980-2012 IEEE."
"49561281500;55978079800;","Conservational use of remote sensing techniques for a novel rainwater harvesting in arid environment",2014,"10.1007/s12665-014-3367-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912101185&doi=10.1007%2fs12665-014-3367-6&partnerID=40&md5=df3e611f40a15a62781c36174e3896bb","Remote sensing applications in water resources management are becoming an essential asset in all different levels of integrated water rational use. Due to remote sensing data availability and different acquisition sensors of satellite images, a wide variability of benchmarks could be conducted under the same theme. Rainwater harvesting is the branch of science where the rainwater is the main target to improve groundwater recharge, stratocumulus clouds are the main source of rain in arid regions. Cloud detection using remote sensing techniques proved to be efficient recently but the general uses of different cloud detection techniques are to precisely omit clouds from satellite images. The use of cloud detection scheme described herein is designed for the MERIS Level1B data; therefore, total set of 60 MERIS images was collected on monthly basis for 5 years started from January 2008. The use of the cloud detection algorithm is to find proper land cover suitable for rainwater harvesting mostly covered with cloud all over the year. Evaluation of land use for rainwater harvesting in terms of groundwater recharge is considered, several factors were taken into consideration and NDWI is one of the most important factors involved. Results pointed out that some regions in southern Saudi Arabia are qualified enough to be considered as potential sites for better rainwater harvesting. © 2014, Springer-Verlag Berlin Heidelberg."
"55454408200;15069126500;7004194999;","CO2 equivalences for short-lived climate forcers",2014,"10.1007/s10584-013-1014-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898029766&doi=10.1007%2fs10584-013-1014-y&partnerID=40&md5=702a9209d3fd1fa977a52d9c343f94be","With advancing climate change there is a growing need to include short-lived climate forcings in cost-efficient mitigation strategies to achieve international climate policy targets. Tools are required to compare the climate impact of perturbations with distinctively different atmospheric lifetimes and atmospheric properties. We present a generic approach for relating the climate effect of short-lived climate forcers (SLCF) to that of CO2 emissions. We distinguish between three alternative types of metric-based factors that can be used to derive CO2 equivalences for SLCF: based on forcing, activity and fossil fuel consumption. We derive numerical values for a wide range of parameter assumptions and apply the resulting generalised approach to the practical example of aviation-induced cloudiness. The evaluation of CO2 equivalences for SLCF tends to be more sensitive to SLCF specific physical uncertainties and the normative choice of a discount rate than to the choice of a physical or economic metric approach. The ability of physical metrics to approximate economic-based metrics alters with changing atmospheric concentration levels and trends. Under reference conditions, physical CO2 equivalences for SLCF provide sufficient proxies for economic ones. The latter, however, allow detailed insight into structural uncertainties. They provide CO2 equivalences for SLCF in short term strategies in the face of failing climate policies, and a temporal evolution of CO2 equivalences over time that is noticeably better in line with cost-efficient climate stabilisation. © 2013 Springer Science+Business Media Dordrecht."
"23979324300;14619799100;55663720200;6602829165;15727794100;","Climate change scenarios of surface solar radiation in data sparse regions: A Case study in Malaprabha river basin, India",2014,"10.3354/cr01180","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900417090&doi=10.3354%2fcr01180&partnerID=40&md5=c623d61c60e0edf652d6d96adef9516b","A variety of methods are available to estimate future solar radiation (SR) scenarios at spatial scales that are appropriate for local climate change impact assessment. However, there are no clear guidelines available in the literature to decide which methodologies are most suitable for different applications. Three methodologies to guide the estimation of SR are discussed in this study, namely: Case 1: SR is measured, Case 2: SR is measured but sparse and Case 3: SR is not measured. In Case 1, future SR scenarios are derived using several downscaling methodologies that transfer the simulated large-scale information of global climate models to a local scale (measurements). In Case 2, the SR was first estimated at the local scale for a longer time period using sparse measured records, and then future scenarios were derived using several downscaling methodologies. In Case 3: the SR was first estimated at a regional scale for a longer time period using complete or sparse measured records of SR from which SR at the local scale was estimated. Finally, the future scenarios were derived using several downscaling methodologies. The lack of observed SR data, especially in developing countries, has hindered various climate change impact studies. Hence, this was further elaborated by applying the Case 3 methodology to a semi-arid Malaprabha reservoir catchment in southern India. A support vector machine was used in down-scaling SR. Future monthly scenarios of SR were estimated from simulations of third-generation Canadian General Circulation Model (CGCM3) for various SRES emission scenarios (A1B, A2, B1, and COMMIT). Results indicated a projected decrease of 0.4 to 12.2 W m-2 yr-1 in SR during the period 2001-2100 across the 4 scenarios. SR was calculated using the modified Hargreaves method. The decreasing trends for the future were in agreement with the simulations of SR from the CGCM3 model directly obtained for the 4 scenarios. © Inter-Research 2014."
"56047842600;13204426200;55386900400;","The effect of aerosol optical depth on rainfall with reference to meteorology over metro cities in India",2014,"10.1007/s11356-014-2711-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902546891&doi=10.1007%2fs11356-014-2711-4&partnerID=40&md5=8f105284ce89baa4b0fe84939fb41e10","Rainfall is a key link in the global water cycle and a proxy for changing climate; therefore, proper assessment of the urban environment's impact on rainfall will be increasingly important in ongoing climate diagnostics and prediction. Aerosol optical depth (AOD) measurements on the monsoon seasons of the years 2008 to 2010 were made over four metro regional hotspots in India. The highest average of AOD was in the months of June and July for the four cities during 3 years and lowest was in September. Comparing the four regions, Kolkata was in the peak of aerosol contamination and Chennai was in least. Pearson correlation was made between AOD with climatic parameters. Some changes in the parameters were found during drought year. Temperature, cloud parameters, and humidity play an important role for the drought conditions. The role of aerosols, meteorological parameters, and their impacts towards the precipitation during the monsoon was studied. © 2014 Springer-Verlag Berlin Heidelberg."
"55334859900;35502101300;","Mesoclimatic patterns shape the striking vegetation mosaic in the Cordillera Central, Dominican Republic",2014,"10.1657/1938-4246-46.4.755","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913532797&doi=10.1657%2f1938-4246-46.4.755&partnerID=40&md5=184d48583a681ca7a2096b63920ae72c","A relationship between forest vegetation patterns and climate has been proposed for Caribbean mountains, but mesoscale temperature, precipitation (PPT), humidity, and cloud formation patterns are poorly documented. Half-hourly temperature and humidity observations were obtained from 2001 to 2011 from a network of 10 data-logging instruments ranging in elevation from 1500 to 2800 m on the windward slopes of the Cordillera Central, Dominican Republic. We report diurnal, seasonal, and annual patterns in temperature, PPT, humidity, and the trade wind inversion (TWI) along the elevation gradient. The elevational gradient in mean air temperature was non-linear during the dry season, with lapse rates decreasing to -0.5 °C km-1 between 1500 and 1900 m and -0.8 °C km-1 between 2100 and 2400 m. Relative humidity reached a maximum at 2100 m (mean of 91%), but remains above 85% over the entire gradient until 2600 m, above which it drops steeply. Relative humidity also showed marked seasonality but only at the highest elevations, dropping markedly above 2400 m and especially above 2600 m in the dry season, while remaining high at lower elevations throughout the year. PPT declined only slightly with elevation on windward slopes, but was markedly lower in leeward areas. Dry season PPT was lower on windward and leeward slopes at all elevations, except at ∼2400 m on windward slopes where it remained nearly as high as the rest of the year. Sub-zero temperatures occurred at elevations ≥2325 m and increased markedly in frequency ≥2600 m. These observations support the hypothesis that the discrete vegetation ecotone between the cloud forest and subalpine pine forest at ∼2200 m on windward slopes results from climatic discontinuities, especially during the dry season. In particular, the TWI effect on mesoclimatic patterns (especially moisture) regulates the elevational maximum of cloud forest flora and likely will represent a strong barrier to the future migration of cloud forest flora to higher elevations in response to warmer temperatures. Together with increased moisture stress due to higher temperatures, climate change in the high elevations of tropical mountains is therefore likely to disrupt the dynamics and distributions of tropical montane forests. © 2014 Regents of the University of Colorado."
"12040335900;36815705700;7404653593;7005548544;7501828935;55671946600;","Influence of non-feedback variations of radiation on the determination of climate feedback",2014,"10.1007/s00704-013-0998-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891654516&doi=10.1007%2fs00704-013-0998-6&partnerID=40&md5=56a8c4948fb287e470656d82048f155b","Recent studies have estimated the magnitude of climate feedback based on the correlation between time variations in outgoing radiation flux and sea surface temperature (SST). This study investigates the influence of the natural non-feedback variation (noise) of the flux occurring independently of SST on the determination of climate feedback. The observed global monthly radiation flux is used from the Clouds and the Earth's Radiant Energy System (CERES) for the period 2000-2008. In the observations, the time lag correlation of radiation and SST shows a distorted curve with low statistical significance for shortwave radiation while a significant maximum at zero lag for longwave radiation over the tropics. This observational feature is explained by simulations with an idealized energy balance model where we see that the non-feedback variation plays the most significant role in distorting the curve in the lagged correlation graph, thus obscuring the exact value of climate feedback. We also demonstrate that the climate feedback from the tropical longwave radiation in the CERES data is not significantly affected by the noise. We further estimate the standard deviation of radiative forcings (mainly from the noise) relative to that of the non-radiative forcings, i.e., the noise level from the observations and atmosphere-ocean coupled climate model simulations in the framework of the simple model. The estimated noise levels in both CERES (>13 %) and climate models (11-28 %) are found to be far above the critical level (~5 %) that begins to misrepresent climate feedback. © 2013 Springer-Verlag Wien."
"57218273453;56424145700;55738957800;","The role of nonconvective condensation processes in response of surface shortwave cloud radiative forcing to El Niño warming",2014,"10.1175/JCLI-D-13-00632.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906861471&doi=10.1175%2fJCLI-D-13-00632.1&partnerID=40&md5=aa80468765c9906c3603313ed22ec358","The weak response of surface shortwave cloud radiative forcing (SWCF) to El Niño over the equatorial Pacific remains a common problem in many contemporary climate models. This study shows that two versions of the Grid-Point Atmospheric Model of the Institute of Atmospheric Physics (IAP)/State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) (GAMIL) produce distinctly different surface SWCF response to El Niño. The earlier version, GAMIL1, underestimates this response, whereas the latest version, GAMIL2, simulates it well. To understand the causes for the different SWCF responses between the two simulations, the authors analyze the underlying physical mechanisms. Results indicate the enhanced stratiform condensation and evaporation in GAMIL2 play a key role in improving the simulations of multiyear annual mean water vapor (or relative humidity), cloud fraction, and incloud liquid water path (ICLWP) and hence in reducing the biases of SWCF and rainfall responses to El Niño due to all of the improved dynamical (vertical velocity at 500 hPa), cloud amount, and liquid water path (LWP) responses. The largest contribution to the SWCF response improvement in GAMIL2 is from LWP in the Niño-4 region and from low-cloud cover and LWP in the Niño-3 region. Furthermore, as a crucial factor in the low-cloud response, the atmospheric stability change in the lower layers is significantly influenced by the nonconvective heating variation during La Niña. © 2014 American Meteorological Society."
"55445972400;56744278700;7006306835;","Contrasting climate responses to the scattering and absorbing features of anthropogenic aerosol forcings",2014,"10.1175/JCLI-D-13-00401.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904511882&doi=10.1175%2fJCLI-D-13-00401.1&partnerID=40&md5=440e77b32dd78f20f0c7c3417d31a3a4","Anthropogenic aerosols comprise optically scattering and absorbing particles, with the principal concentrations being in the Northern Hemisphere, yielding negative and positive global mean radiative forcings, respectively. Aerosols also influence cloud albedo, yielding additional negative radiative forcings. Climate responses to a comprehensive set of isolated aerosol forcing simulations are investigated in a coupled atmosphere- ocean framework, forced by preindustrial to present-day aerosol-induced radiative perturbations. Atmospheric and oceanic climate responses (including precipitation, atmospheric circulation, atmospheric and oceanic heat transport, sea surface temperature, and salinity) to negative and positive particulate forcings are consistently anticorrelated. The striking effects include distinct patterns of changes north and south of the equator that are governed by the sign of the aerosol forcing and its initiation of an interhemispheric forcing asymmetry. The presence of opposing signs of the forcings between the aerosol scatterers and absorbers, and the resulting contrast in climate responses, thus dilutes the individual effects of aerosol types on influencing global and regional climate conditions. The aerosol-induced changes in the variables also have a distinct fingerprint when compared to the responses of the more globally uniform and interhemispherically symmetric well-mixed greenhouse gas forcing. The significance of employing a full ocean model is demonstrated in this study by the ability to partition how individual aerosols influence atmospheric and oceanic conditions separately. © 2014 American Meteorological Society."
"24757696000;7004154626;24329545900;7102797196;55510783800;55742914900;","Assessment and validation of i-skyradiometer retrievals using broadband flux and MODIS data",2014,"10.1155/2014/849279","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896380105&doi=10.1155%2f2014%2f849279&partnerID=40&md5=40f911605ce3bcdf0533746fad873900","Ground-based network of cloud measurements is presently limited and there exists uncertainty in the cloud microphysical parameters derived from ground-based measurements. Bias in the i-skyradiometer derived cloud optical depth (τ c) and droplet effective radius (R eff) and the importance of these parameters in the parameterization of clouds in climate models have made us intend to develop a possible method for improving these parameters. A new combination method, which uses zenith sky transmittance and surface radiation measurements, has been proposed in the present study to improve the retrievals. The i-skyradiometer derived parameters τ c and R eff have been provided as a first guess to a radiative transfer model (SBDART) and a new retrieval algorithm has been implemented to obtain the best combination of τ c and R eff having minimum bias (-0.09 and -2.5) between the simulated global and diffuse fluxes at the surface with the collocated surface radiation measurements. The new retrieval method has improved τ c and R eff values compared to those derived using the transmittance only method and are in good agreement with the MODIS satellite retrievals. The study therefore suggests a possible improvement of the i-skyradiometer derived cloud parameters using observed radiation fluxes and a radiative transfer model. © 2014 S. Dipu et al."
"23991212200;7004479957;6507017020;","Restricting 32-128 km horizontal scales hardly affects the MJO in the Superparameterized Community Atmosphere Model v.3.0 but the number of cloud-resolving grid columns constrains vertical mixing",2014,"10.1002/2014MS000340","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932199444&doi=10.1002%2f2014MS000340&partnerID=40&md5=4b5ba6f0720cd6fd63979db9a1efdea3","The effects of artificially restricting the 32-128 km horizontal scale regime on MJO dynamics in the Superparameterized Community Atmosphere Model v.3.0 have been explored through reducing the extent of its embedded cloud resolving model (CRM) arrays. Two and four-fold reductions in CRM extent (from 128 to 64 km and 32 km) produce statistical composite MJO signatures with spatial scale, zonal phase speed, and intrinsic wind-convection anomaly structure that are all remarkably similar to the standard SPCAM's MJO. This suggests that the physics of mesoscale convective organization on 32-128 km scales are not critical to MJO dynamics in SPCAM and that reducing CRM extent may be a viable strategy for 400% more computationally efficient analysis of superparameterized MJO dynamics. However several unexpected basic state responses caution that extreme CRM domain reduction can lead to systematic mean state issues in superparameterized models. We hypothesize that an artificial limit on the efficiency of vertical updraft mixing is set by the number of grid columns available for compensating subsidence in the embedded CRM arrays. This can lead to reduced moisture ventilation supporting too much liquid cloud and thus an overly strong cloud shortwave radiative forcing, particularly in regions of deep convection. Key Points Physics of MMF MJO are insensitive to near elimination of meso-beta-scale The efficiency of deep convective mixing in MMFs is limited by CRM extent 4x speedup of superparameterized models possible for MJO analysis © 2014. The Authors."
"55717244800;","A unified convection scheme (UNICON). Part I: Formulation",2014,"10.1175/JAS-D-13-0233.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910107295&doi=10.1175%2fJAS-D-13-0233.1&partnerID=40&md5=e36fa47740bfb1ca0c179e495d24e323","The author develops a unified convection scheme (UNICON) that parameterizes relative (i.e., with respect to the grid-mean vertical flow) subgrid vertical transport by nonlocal asymmetric turbulent eddies. UNICON is a process-based model of subgrid convective plumes and mesoscale organized flow without relying on any quasi-equilibrium assumptions such as convective available potential energy (CAPE) or convective inhibition (CIN) closures. In combination with a relative subgrid vertical transport scheme by local symmetric turbulent eddies and a grid-scale advection scheme, UNICON simulates vertical transport of water species and conservative scalars without double counting at any horizontal resolution. UNICONsimulates all dry-moist, forced-free, and shallow-deep convection within a single framework in a seamless, consistent, and unified way. It diagnoses the vertical profiles of the macrophysics (fractional area, plume radius, and number density) as well as the microphysics (production and evaporation rates of convective precipitation) and the dynamics (mass flux and vertical velocity) of multiple convective updraft and downdraft plumes. UNICON also prognoses subgrid cold pool and mesoscale organized flow within the planetary boundary layer (PBL) that is forced by evaporation of convective precipitation and accompanying convective downdrafts but damped by surface flux and entrainment at the PBL top. The combined subgrid parameterization of diagnostic convective updraft and downdraft plumes, prognostic subgrid mesoscale organized flow, and the feedback among them remedies the weakness of conventional quasi-steady diagnostic plume models-the lack of plume memory across the time step-allowing UNICON to successfully simulate various transitional phenomena associated with convection (e.g., the diurnal cycle of precipitation and the Madden-Julian oscillation). © 2014 American Meteorological Society."
"14066725300;7005202019;","The radiative environment of the Tibetan Plateau",2014,"10.1002/joc.3824","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901822635&doi=10.1002%2fjoc.3824&partnerID=40&md5=e86bca07f5bf44d5a5a36f816a1782b8","The Tibetan Plateau, also known as the Qinghai-Tibetan Plateau, is a vast elevated plateau in Central Asia. It occupies an area of around 2.3 millionkm2 and has an average elevation of over 4500m. The plateau is interspersed with mountain ranges, has a strong thermal effect on its atmospheric environment, and influences regional and global climate. As the depth of the atmosphere over the plateau is much smaller than its surroundings, the impact of solar radiation on heating the plateau is magnified. At present, observations of shortwave (SW) fluxes over the plateau are very meager and satellite estimates are very coarse. Therefore, estimating the role of radiation in the total heat budget of the plateau is difficult. We use an updated version of the University of Maryland Surface Radiation Budget model driven with observations from Meteosat-5 to characterize clouds and surface SW radiative fluxes at high-temporal and spatial resolution (hourly at 0.125°). Results are presented for a period of 5years in terms of means and variability in space, time, and the context of the regional monsoon regimes. Maximum monthly mean values of SW flux near 360Wm-2 occur in May and June, mainly in the western plateau. Minimum values of 120-150Wm-2 are most widespread in December and January. An anomaly in clouds and SW fluxes in the plateau during the Indian monsoon drought year of 2002 is discovered and discussed. The objective of this study is to provide improved estimates of cloud amounts and radiative fluxes over the plateau in unprecedented detail and with consideration of the plateau conditions. It is anticipated that this information will be useful as a benchmark for the evaluation of numerical models that are known to have difficulties in this complex region and for hydrological modelling. © 2013 Royal Meteorological Society."
"12761052200;36849508000;6701431208;","Effects of vertical resolution and nonorographic gravity wave drag on the simulated climate in the Community Atmosphere Model, version 5",2014,"10.1002/2013MS000303","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904860175&doi=10.1002%2f2013MS000303&partnerID=40&md5=d261e065d1922332edfa3a50ff473c53","Horizontal resolution of general circulation models (GCMs) has significantly increased during the last decade, however these changes were not accompanied by similar changes in vertical resolution. In our study, the Community Atmosphere Model, version 5 (CAM5) is used to study the sensitivity of climate to vertical resolution and nonorographic gravity wave drag. Nonorographic gravity wave drag is typically omitted from low-top GCMs, however as we show, its influence on climate can be seen all the way to the surface. We show that an increase in vertical resolution from 1200 to 500 m in the free troposphere and lower stratosphere in CAM5 improves the representation of near-tropopause temperatures, lower stratospheric temperatures, and surface wind stresses. In combination with nonorographic gravity waves, CAM5 with increased vertical resolution produces a realistic Quasi-Biennial Oscillation (QBO), has an improved seasonal cycle of temperature in the extratropics, and represents better the coupling between the stratosphere and the troposphere. Key Points Vertical resolution has a significant impact on the mean simulated climate Increased vertical resolution causes warming near the tropopause Vertical resolution and gravity waves impact surface stresses © 2014. The Authors."
"7201472576;57214023403;","Multi-sensor calibration studies of AVHRR-heritage channel radiances using the simultaneous nadir observation approach",2014,"10.3390/rs6031845","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896949789&doi=10.3390%2frs6031845&partnerID=40&md5=585a611318f5fde0c32e86153cf143ce","The European Space Agency project for studies of cloud properties in the Climate Change Initiative programme (ESA-CLOUD-CCI) aims at compiling the longest possible time series of cloud products from one single multispectral sensor-The five-channel Advanced Very High Resolution Radiometer (AVHRR) instrument. A particular aspect here is to include corresponding products based on other existing (Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Along-Track Scanning Radiometer (AATSR), MEdium Resolution Imaging Spectrometer (MERIS), Visible and Infrared Radiometer Suite (VIIRS)) and future Sea and Land Surface Temperature Radiometer (SLSTR) sensors measuring in similar (AVHRR-heritage) spectral channels. Initial inter-comparisons of the involved AVHRR-heritage channel radiances over a short demonstration period (2007-2009) were performed. Using Aqua-MODIS as reference, AVHRR (NOAA-18), AATSR, and MERIS channel radiances were evaluated using the simultaneous nadir (SNO) approach. Results show generally agreeing radiances within approximately 3% for channels at 0.6 μm and 0.8 μm. Larger deviations (+5%) were found for the corresponding AATSR channel at 0.6 μm. Excessive deviations but with opposite sign were also indicated for AATSR 1.6 μm and MERIS 0.8 μm radiances. Observed differences may largely be attributed to residual temporal and spatial matching differences while excessive AATSR and MERIS deviations are likely partly attributed to incomplete compensation for spectrally varying surface and atmospheric conditions. However, very good agreement was found for all infrared channels among all the studied sensors. Here, deviations were generally less than 0.2% for the measured brightness temperatures with the exception of some remaining non-linear deviations at extreme low and high temperatures. © 2014 by the authors; licensee MDPI, Basel, Switzerland."
"54974135900;7004940683;7101632548;7103305526;","Swansong biospheres II: The final signs of life on terrestrial planets near the end of their habitable lifetimes",2014,"10.1017/S1473550413000426","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903137645&doi=10.1017%2fS1473550413000426&partnerID=40&md5=94894e63427bb16244a556de737e6ddd","The biosignatures of life on Earth do not remain static, but change considerably over the planet's habitable lifetime. Earth's future biosphere, much like that of the early Earth, will consist of predominantly unicellular microorganisms due to the increased hostility of environmental conditions caused by the Sun as it enters the late stage of its main sequence evolution. Building on previous work, the productivity of the biosphere is evaluated during different stages of biosphere decline between 1 and 2.8Gyr from present. A simple atmosphere-biosphere interaction model is used to estimate the atmospheric biomarker gas abundances at each stage and to assess the likelihood of remotely detecting the presence of life in low-productivity, microbial biospheres, putting an upper limit on the lifetime of Earth's remotely detectable biosignatures. Other potential biosignatures such as leaf reflectance and cloud cover are discussed. © 2014 Cambridge University Press."
"7202485447;18635289400;16551540700;23012437100;24344262300;7003377766;7103294028;7101899854;24172779500;","Interactions between biomass-burning aerosols and clouds over Southeast Asia: Current status, challenges, and perspectives",2014,"10.1016/j.envpol.2014.06.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908622881&doi=10.1016%2fj.envpol.2014.06.036&partnerID=40&md5=68e277eb4a6ca2e1e53230ed3e00de81","The interactions between aerosols, clouds, and precipitation remain among the largest sources of uncertainty in the Earth's energy budget. Biomass-burning aerosols are a key feature of the global aerosol system, with significant annually-repeating fires in several parts of the world, including Southeast Asia (SEA). SEA in particular provides a ”natural laboratory” for these studies, as smoke travels from source regions downwind in which it is coupled to persistent stratocumulus decks. However, SEA has been under-exploited for these studies. This review summarizes previous related field campaigns in SEA, with a focus on the ongoing Seven South East Asian Studies (7-SEAS) and results from the most recent BASELInE deployment. Progress from remote sensing and modeling studies, along with the challenges faced for these studies, are also discussed. We suggest that improvements to our knowledge of these aerosol/cloud effects require the synergistic use of field measurements with remote sensing and modeling tools. © 2014 Elsevier Ltd. All rights reserved."
"34772240500;7004544454;14018770700;7406442958;7403295159;55717244800;36876405100;7004479957;36097134700;","Diagnosis of the marine low cloud simulation in the NCAR community earth system model (CESM) and the NCEP global forecast system (GFS)-modular ocean model v4 (MOM4) coupled model",2014,"10.1007/s00382-014-2067-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905112207&doi=10.1007%2fs00382-014-2067-y&partnerID=40&md5=708dcd8bfe2312ffec45500e6f0f0187","We present a diagnostic analysis of the marine low cloud climatology simulated by two state-of-the-art coupled atmosphere-ocean models: the National Center for Atmospheric Research community earth system model version 1 (CESM1) and the National Center for Environmental Predictions global forecasting system-modular ocean model version 4 (GFS-MOM4) coupled model. In the CESM1, the coastal stratocumulus (Sc)-topped planetary boundary layers (PBLs) in the subtropical Eastern Pacific are well-simulated but the climatological transition from Sc to shallow cumulus (Cu) is too abrupt and occurs too close to the coast. By contrast, in the GFS-MOM4 the coastal Sc amount and PBL depth are severely underestimated while the transition from Sc to shallow Cu is ""delayed"" and offshore Sc cover is too extensive in the subtropical Eastern Pacific. We discuss the possible connections between these differences in the simulations and differences in the parameterizations of shallow convection and boundary layer turbulence in the two models. © 2014 Springer-Verlag Berlin Heidelberg."
"57212988186;57202909501;7403058740;7401945370;","Responses of subtropical marine stratocumulus cloud to perturbed lower atmospheres",2014,"10.2151/sola.2014-008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907816014&doi=10.2151%2fsola.2014-008&partnerID=40&md5=1fbd0501b5cc8768ace7d8cc9325fc71","Most global climate models (GCMs) suffer from prediction biases in their dynamic and thermodynamic structures in and around the boundary layer (BL). It remains unclear which of these biases within the large-scale conditions are crucial to the accurate reproduction of BL clouds. To develop a better understanding of the effects of variations in the simulated large-scale conditions, this paper uses large-eddy simulations to evaluate the effects of the fluctuation based on the latest GCM ensemble data on the prediction of a Californian stratocumulus under perturbed environments. The result indicates the relative importance of each component, and the most important factors controlling cloud behavior are the amplitudes of jumps in vapor and temperature across a BL top. The given variations in wind velocity and its vertical shear, largescale subsidence, and surface heat fluxes have a lesser effect. This suggests that to reduce model biases predicted in GCMs, greater attention should be paid to the stratification structure across the BL top. © 2014, the Meteorological Society of Japan."
"35745037500;6602986914;7004006601;7403362745;35609878300;24511929800;17135775200;7003351590;55828969900;55637266800;","The surface radiation budget over South America in a set of regional climate models from the CLARIS-LPB project",2014,"10.1007/s00382-013-1916-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906941453&doi=10.1007%2fs00382-013-1916-4&partnerID=40&md5=694940870f175b9e933a3522604e80a5","The performance of seven regional climate models in simulating the radiation and heat fluxes at the surface over South America (SA) is evaluated. Sources of uncertainty and errors are identified. All simulations have been performed in the context of the CLARIS-LPB Project for the period 1990-2008 and are compared with the GEWEX-SRB, CRU, and GLDAS2 dataset and NCEP-NOAA reanalysis. Results showed that most of the models overestimate the net surface short-wave radiation over tropical SA and La Plata Basin and underestimate it over oceanic regions. Errors in the short-wave radiation are mainly associated with uncertainties in the representation of surface albedo and cloud fraction. For the net surface long-wave radiation, model biases are diverse. However, the ensemble mean showed a good agreement with the GEWEX-SRB dataset due to the compensation of individual model biases. Errors in the net surface long-wave radiation can be explained, in a large proportion, by errors in cloud fraction. For some particular models, errors in temperature also contribute to errors in the net long-wave radiation. Analysis of the annual cycle of each component of the energy budget indicates that the RCMs reproduce generally well the main characteristics of the short- and long-wave radiations in terms of timing and amplitude. However, a large spread among models over tropical SA is apparent. The annual cycle of the sensible heat flux showed a strong overestimation in comparison with the reanalysis and GLDAS2 dataset. For the latent heat flux, strong differences between the reanalysis and GLDAS2 are calculated particularly over tropical SA. © 2013 Springer-Verlag Berlin Heidelberg."
"7402199436;57211976266;7403058740;","Indices of cool summer climate in northern Japan: Yamase indices",2014,"10.2151/jmsj.2014-102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896337986&doi=10.2151%2fjmsj.2014-102&partnerID=40&md5=50a604273727c614bca7da31dee781bb","This study examined seven indices of the cool summer climate in northern Japan in terms of spatial representativeness and interannual variability using weather observation station data and reanalysis data from the Japanese 25-year Reanalysis/Japan Meteorological Agency Climate Data Assimilation System in June-August for 1979-2010. The indices are constructed using sea level pressure (SLP) and surface air temperature (SAT): area-average SLP over the Okhotsk Sea; north-south SLP difference in northern Japan; east-west SLP difference along the Tsugaru Strait; east-west SLP difference along the Soya Strait; SAT anomaly from climatology at a location along the coasts of the Pacific and the Okhotsk Sea; diurnal variance of SAT at a location along the coasts of the Pacific and the Okhotsk Sea; and time coefficient of the east-west oscillation mode of SAT in northern Japan. The last two are newly proposed. The atmospheric fields represented by the indices commonly show the following features: the developed Okhotsk high at the surface and a mid-troposphere ridge to its northwest; southward extensions of low SAT, high SLP, low specific humidity, and high cloud water content along the Pacific coast of northern Japan and along the Japan Sea coast of the Eurasian continent; and strong easterly/northeasterly winds to the east and west of northern Japan. Furthermore, these indices show consistent interannual variabilities and clearly detect cool summers in northern Japan in the past. Meanwhile, differences between the indices lie in the location of the ridge in the mid-troposphere and the vertical structure of the Okhotsk high, the center locations of low SAT and enhanced easterly/northeasterly surface winds, and the degree of the southward extensions of the cool air along the Pacific coast of northern Japan and along the Japan Sea coast of the Eurasian continent. Based on these characteristics, we can choose a suitable index for the intended use. © 2014, Meteorological Society of Japan."
"16246205000;55738957800;","Role of climate feedback in El Niño-like SST response to global warming",2014,"10.1175/JCLI-D-14-00072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907572369&doi=10.1175%2fJCLI-D-14-00072.1&partnerID=40&md5=1575d9a7cf62f897e0a8f45b09c4de3f","Under global warming from the doubling of CO2, the equatorial Pacific experiences an El Niño-like warming, as simulated by most global climate models. A new climate feedback and response analysis method (CFRAM) is applied to 10 years of hourly output of the slab ocean model (SOM) version of the NCAR Community Climate System Model, version 3.0, (CCSM3-SOM) to determine the processes responsible for this warming. Unlike the traditional surface heat budget analysis, the CFRAM can explicitly quantify the contributions of each radiative climate feedback and of each physical and dynamical process of a GCM to temperature changes. The mean bias in the sum of partial SST changes due to each feedback derived with CFRAMin the tropical Pacific is negligible (0.5%) compared to the mean SST change from the CCSM3-SOM simulations, with a spatial pattern correlation of 0.97 between the two. The analysis shows that the factors contributing to the El Niño-like SST warming in the central Pacific are different from those in the eastern Pacific. In the central Pacific, the largest contributor to El Niño-like SST warming is dynamical advection, followed by PBL diffusion, water vapor feedback, and surface evaporation. In contrast, in the eastern Pacific the dominant contributor to El Niño-like SST warming is cloud feedback, with water vapor feedback further amplifying the warming. © 2014 American Meteorological Society."
"6508194789;56493740900;7004325649;12769875100;7003854810;","A comparison of climate signal trend detection uncertainty analysis methods",2014,"10.1175/JCLI-D-13-00400.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899059732&doi=10.1175%2fJCLI-D-13-00400.1&partnerID=40&md5=4c9cbce95e3d8f1f0b4254cd19b9aa90","Two climate signal trend analysis methods are the focus of this paper. The uncertainty of trend estimate from these two methods is investigated using Monte Carlo simulation. Several theoretically and randomly generated series of white noise, first-order autoregressive and second-order autoregressive, are explored. The choice of method that is most appropriate for the time series of interest depends upon the autocorrelation structure of the series. If the structure has its autocorrelation coefficients decreased with increasing lags (i.e., an exponential decay pattern), then the method of Weatherhead et al. is adequate. If the structure exhibits a decreasing sinusoid pattern of coefficient with lags (or a damped sinusoid pattern) or a mixture of both exponential decay and damped sinusoid patterns, then the method of Leroy et al. is recommended. The two methods are then applied to the time series of monthly and globally averaged top-of-the-atmosphere (TOA) irradiances for the reflected solar shortwave and emitted longwave regions, using radiance observations made by Clouds and the Earth's Radiant Energy System (CERES) instruments during March 2000 through June 2011. Examination of the autocorrelation structures indicates that the reflected shortwave region has an exponential decay pattern, while the longwave region has a mixture of exponential decay and damped sinusoid patterns. Therefore, it is recommended that the method ofWeatherhead et al. is used for the series of reflected shortwave irradiances and that the method of Leroy et al. is used for the series of emitted longwave irradiances."
"55489412200;36625213300;15725009000;56940082700;55857543900;16314082800;56053847500;9279986800;35491696900;24399478800;55856751000;55857029000;55856873300;55857096100;47961004800;24764834600;36626171700;6602205640;6602529747;7004035832;","Seasonal production, allocation and cycling of carbon in two mid-elevation tropical montane forest plots in the Peruvian Andes",2014,"10.1080/17550874.2013.819042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893301874&doi=10.1080%2f17550874.2013.819042&partnerID=40&md5=c64b292fd77e56ba56e4f48ad6dbd1ce","Background: Tropical montane cloud forests (TMCF) are unique ecosystems with high biodiversity and large carbon reservoirs. To date there have been limited descriptions of the carbon cycle of TMCF. Aims: We present results on the production, allocation and cycling of carbon for two mid-elevation (1500-1750 m) tropical montane cloud forest plots in San Pedro, Kosñipata Valley, Peru. Methods: We repeatedly recorded the components of net primary productivity (NPP) using biometric measurements, and autotrophic (R a) and heterotrophic (R h) respiration, using gas exchange measurements. From these we estimated gross primary productivity (GPP) and carbon use efficiency (CUE) at the plot level. Results: The plot at 1500 m was found very productive, with our results comparable with the most productive lowland Amazonian forests. The plot at 1750 m had significantly lower productivity, possibly because of greater cloud immersion. Both plots had similar patterns of NPP allocation, a substantial seasonality in NPP components and little seasonality in Ra. Conclusions: These two plots lie within the ecotone between lower and upper montane forests, near the level of the cloud base. Climate change is likely to increase elevation of the cloud base, resulting in shifts in forest functioning. Longer-term surveillance of the carbon cycle at these sites would yield valuable insights into the response of TMCFs to a shifting cloud base. © 2014 Copyright 2013 Botanical Society of Scotland and Taylor &amp; Francis."
"36608763800;8696069500;","Arctic amplification dominated by temperature feedbacks in contemporary climate models",2014,"10.1038/ngeo2071","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895461097&doi=10.1038%2fngeo2071&partnerID=40&md5=bb023bf70922574008d83487e9a2ec38","Climate change is amplified in the Arctic region. Arctic amplification has been found in past warm and glacial periods, as well as in historical observations and climate model experiments. Feedback effects associated with temperature, water vapour and clouds have been suggested to contribute to amplified warming in the Arctic, but the surface albedo feedback - the increase in surface absorption of solar radiation when snow and ice retreat - is often cited as the main contributor. However, Arctic amplification is also found in models without changes in snow and ice cover. Here we analyse climate model simulations from the Coupled Model Intercomparison Project Phase 5 archive to quantify the contributions of the various feedbacks. We find that in the simulations, the largest contribution to Arctic amplification comes from a temperature feedbacks: as the surface warms, more energy is radiated back to space in low latitudes, compared with the Arctic. This effect can be attributed to both the different vertical structure of the warming in high and low latitudes, and a smaller increase in emitted blackbody radiation per unit warming at colder temperatures. We find that the surface albedo feedback is the second main contributor to Arctic amplification and that other contributions are substantially smaller or even opposeArctic amplification. © 2014 Macmillan Publishers Limited."
"7004977068;6701397189;6603759926;6506102131;","Spatial and temporal variability in the onset of the growing season on svalbard, arctic Norway - Measured by MODIS-NDVI satellite data",2014,"10.3390/rs6098088","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907452438&doi=10.3390%2frs6098088&partnerID=40&md5=e1370e6c227cea507ba29e188018e5a8","The Arctic is among the regions with the most rapid changes in climate and has the expected highest increase in temperature. Changes in the timing of phenological phases, such as onset of the growing season observed from remote sensing, are among the most sensitive bio-indicators of climate change. The study area here is the High Arctic archipelago of Svalbard, located between 76°30' and 80°50'N. The goal of this study was to use MODIS Terra data (the MOD09Q1 and MOD09A1 surface reflectance products, both with 8-day temporal composites) to map the onset of the growing season on Svalbard for the 2000-2013 period interpreted from field observations. Due to a short and intense period with greening-up and frequent cloud cover, all the cloud free data is needed, which requires reliable cloud masks. We used a combination of three cloud removing methods (State QA values, own algorithms, and manual removal). This worked well, but is time-consuming as it requires manual interpretation of cloud cover. The onset of the growing season was then mapped by a NDVI threshold method, which showed high correlation (r2 = 0.60, n = 25, p &lt; 0.001) with field observations of flowering of Salix polaris (polar willow). However, large bias was found between NDVI-based mapped onset and field observations in bryophyte-dominated areas, which indicates that the results in these parts must be interpreted with care. On average for the 14-year period, the onset of the growing season occurs after July 1st in 68.4% of the vegetated areas of Svalbard. The mapping revealed large variability between years. The years 2000 and 2008 were extreme in terms of late onset of the growing season, and 2002 and 2013 had early onset. Overall, no clear trend in onset of the growing season for the 2000-2013 period was found. © 2014 by the authors."
"57211094015;6505778090;6603957672;7003861526;6602115068;","Evaluation of broadband surface solar irradiance derived from the Ozone Monitoring Instrument",2014,"10.1016/j.rse.2014.03.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899703404&doi=10.1016%2fj.rse.2014.03.036&partnerID=40&md5=498ad8861583da2c0d0c3fb14f1f3409","Surface solar irradiance (SSI) data are important for planning and estimating the production of solar power plants. Long-term high quality surface solar radiation data are needed for monitoring climate change. This paper presents a new surface solar irradiance dataset, the broadband (0.2-4μm) surface solar irradiance product derived from the Ozone Monitoring Instrument (OMI). The OMI SSI algorithm is based on the Heliosat method and uses the OMI O2-O2 cloud product as main input. The OMI SSI data are validated against the globally distributed Baseline Surface Radiation Network (BSRN) measurements at 19 stations for the year 2008. Furthermore, the monthly mean OMI SSI data are compared to independent surface solar irradiance products from International Satellite Cloud Climatology Project Flux Data (ISCCP-FD) and Clouds and the Earth's Radiant Energy System (CERES) data for the year 2005. The mean difference between OMI SSI and BSRN global (direct+diffuse) irradiances is -1.2Wm-2 (-0.2%), the root mean square error is 100.1Wm-2 (18.1%), and the mean absolute error is 67.8Wm-2 (12.2%). The differences between OMI SSI and BSRN global irradiances are smaller over continental and coastal sites and larger over deserts and islands. OMI SSI has a good agreement with the CERES shortwave (SW) model B surface downward flux (SDF) product. The correlation coefficient and index of agreement between monthly mean 1-degree gridded OMI SSI and CERES SW SDF are &gt;0.99. OMI SSI is lower than CERES SW SDF which is partly due to the solar zenith angle. On average, OMI SSI is 13.5Wm-2 (2.5%) lower than the ISCCP-FD SW surface downward flux and the correlation coefficient and index of agreement are &gt;0.98 for every month. © 2014."
"55953785300;55817600100;56975691100;37030925300;56382111000;","Statistical modeling of sea ice concentration using satellite imagery and climate reanalysis data in the barents and Kara seas, 1979-2012",2014,"10.3390/rs6065520","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84986907166&doi=10.3390%2frs6065520&partnerID=40&md5=a36e1f324655213ccd6ea2eb3505438e","Extensive sea ice over Arctic regions is largely involved in heat, moisture, and momentum exchanges between the atmosphere and ocean. Some previous studies have been conducted to develop statistical models for the status of Arctic sea ice and showed considerable possibilities to explain the impacts of climate changes on the sea ice extent. However, the statistical models require improvements to achieve better predictions by incorporating techniques that can deal with temporal variation of the relationships between sea ice concentration and climate factors. In this paper, we describe the statistical approaches by ordinary least squares (OLS) regression and a time-series method for modeling sea ice concentration using satellite imagery and climate reanalysis data for the Barents and Kara Seas during 1979-2012. The OLS regression model could summarize the overall climatological characteristics in the relationships between sea ice concentration and climate variables. We also introduced autoregressive integrated moving average (ARIMA) models because the sea ice concentration is such a long-range dataset that the relationships may not be explained by a single equation of the OLS regression. Temporally varying relationships between sea ice concentration and the climate factors such as skin temperature, sea surface temperature, total column liquid water, total column water vapor, instantaneous moisture flux, and low cloud cover were modeled by the ARIMA method, which considerably improved the prediction accuracies. Our method may also be worth consideration when forecasting future sea ice concentration by using the climate data provided by general circulation models (GCM). © 2014 by the authors."
"55462884000;36538539800;7004046707;7006461606;","Will the role of intercontinental transport change in a changing climate?",2014,"10.5194/acp-14-9379-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84976649265&doi=10.5194%2facp-14-9379-2014&partnerID=40&md5=566b91c57de17b482483e99148e448df","Intercontinental transport of atmospheric pollution (ITAP) can offset the impact of local emission control efforts, impact human and ecosystem health, and play a role in climate forcing. This study aims to determine the role of ITAP caused by East Asian anthropogenic emissions (EAAEs) under current and future emission and climate scenarios. The contribution from EAAEs is determined using a ""brute force method"" in which results from simulations with and without EAAEs are compared. ITAP from East Asia is enhanced in the future due to faster wind speeds aloft and a stronger low pressure center near eastern Russia that facilitate enhanced westerly export in the free troposphere and stronger southerly transport near the surface, increased gaseous precursor emissions, and increased temperatures. As a result, the contribution of ozone (O3) generated by EAAEs to the global average O3 mixing ratio increases by ∼0.8 ppb from 1.2 ppb in 2001 to 2.0 ppb in 2050. The contribution of PM2.5 generated by EAAEs to the global PM2.5 level increases by ∼0.07 μgm-3 from 0.32 μgm-3 in 2001 to 0.39 μgm-3 in 2050, despite a non-homogenous response in PM2.5 resulting from cloud and radiative feedbacks. EAAEs can increase East Asian biogenic secondary organic aerosol by 10-81 %, indicating that it is largely controllable. EAAEs also increase the deposition of nitrogen, black carbon, and mercury both locally and downwind, implying that they may play a role in climate feedbacks and ecosystem health of these regions. These results show that EAAEs have a large impact on global air quality and climate, especially on downwind regions. Such impacts may be enhanced under future climate and emission scenarios, demonstrating a need to synergize global pollution control and climate mitigation efforts. © Author(s) 2014."
"55913339000;56780996700;36152171200;55913917200;38362385200;","A review of aerosol optical properties and radiative effects",2014,"10.1007/s13351-014-4045-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939225932&doi=10.1007%2fs13351-014-4045-z&partnerID=40&md5=334195d5ab1cf96753778760855aed11","Atmospheric aerosols influence the earth’s radiative balance directly through scattering and absorbing solar radiation, and indirectly through affecting cloud properties. An understanding of aerosol optical properties is fundamental to studies of aerosol effects on climate. Although many such studies have been undertaken, large uncertainties in describing aerosol optical characteristics remain, especially regarding the absorption properties of different aerosols. Aerosol radiative effects are considered as either positive or negative perturbations to the radiation balance, and they include direct, indirect (albedo effect and cloud lifetime effect), and semi-direct effects. The total direct effect of anthropogenic aerosols is negative (cooling), although some components may contribute a positive effect (warming). Both the albedo effect and cloud lifetime effect cool the atmosphere by increasing cloud optical depth and cloud cover, respectively. Absorbing aerosols, such as carbonaceous aerosols and dust, exert a positive forcing at the top of atmosphere and a negative forcing at the surface, and they can directly warm the atmosphere. Internally mixed black carbon aerosols produce a stronger warming effect than externally mixed black carbon particles do. The semidirect effect of absorbing aerosols could amplify this warming effect. Based on observational (ground- and satellite-based) and simulation studies, this paper reviews current progress in research regarding the optical properties and radiative effects of aerosols and also discusses several important issues to be addressed in future studies. ©The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2014"
"6701450462;7103294731;7003287025;7005723936;7004942632;","The climate impact of past changes in halocarbons and CO2 in the tropical UTLS region",2014,"10.1175/JCLI-D-14-00232.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919683648&doi=10.1175%2fJCLI-D-14-00232.1&partnerID=40&md5=77459b0a8140e8d03a3e48521387d150","Achemistry-climate model coupled to an ocean model is used to compare the climate impact of past (1960-2010) changes in concentrations of halocarbons with those of CO2 in the tropical upper troposphere and lower stratosphere (UTLS). The halocarbon contribution to both upper troposphere warming and the associated increase in lower stratospheric upwelling is about 40% as large as that due to CO2. Trends in cold-point temperature and lower stratosphere water vapor are positive for both halocarbons and CO2, and are of about the same magnitude. Trends in lower stratosphere ozone are negative, due to the increased upwelling. These increases in water vapor and decreases in lower stratosphere ozone feed back onto lower stratosphere temperature through radiative cooling. The radiative cooling from ozone is about a factor of 2 larger than that from water vapor in the vicinity of the cold-point tropopause, while water vapor dominates at heights above 50 hPa. For halocarbons this indirect radiative cooling more than offsets the direct radiative warming, and together with the adiabatic cooling accounts for the lack of a halocarbon-induced warming of the lower stratosphere. For CO2 the indirect cooling from increased water vapor and decreased ozone is of comparable magnitude to the direct warming from CO2 in the vicinity of the cold-point tropopause, and (together with the increased upwelling) lowers the height at which CO2 increases induce stratospheric cooling, thus explaining the relatively weak increase in cold-point temperature due to the CO2 increases. © 2014 American Meteorological Society."
"6506827279;7006783796;57211010680;56493740900;8833356300;8668585900;6603809758;56108764300;","Regional apparent boundary layer lapse rates determined from CALIPSO and MODIS data for cloud-height determination",2014,"10.1175/JAMC-D-13-081.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897980418&doi=10.1175%2fJAMC-D-13-081.1&partnerID=40&md5=ca2e61a795e6871e1141ce821d022498","Reliably determining low-cloud heights using a cloud-top temperature from satellite infrared imagery is often challenging because of difficulties in characterizing the local thermal structure of the lower troposphere with the necessary precision and accuracy. To improve low-cloud-top height estimates over water surfaces, various methods have employed lapse rates anchored to the sea surface temperature to replace the boundary layer temperature profiles that relate temperature to altitude. To further improve low-cloud-top height retrievals, collocated Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data taken from July 2006 to June 2007 and from June 2009 to May 2010 (2 yr) for single-layer low clouds are used here with numerical weather model analyses to develop regional mean boundary apparent lapse rates. These parameters are designated as apparent lapse rates because they are defined using the cloud-top temperatures from satellite retrievals and surface skin temperatures; they do not represent true lapse rates. Separate day and night, seasonal mean lapse rates are determined for 10'-resolution snow-free land, water, and coastal regions, while zonally dependent lapse rates are developed for snow/ice-covered areas for use in the Clouds and the Earth's Radiant Energy System (CERES) Edition 4 cloud property retrieval system (CCPRS-4). The derived apparent lapse rates over ice-free water range from 5 to 9Kkm-1 with mean values of about 6.9 and 7.2Kkm-1 during the day and night, respectively. Over land, the regional values vary from 3 to 8Kkm-1, with day and night means of 5.5 and 6.2Kkm-1, respectively. The zonal-mean apparent lapse rates over snow and ice surfaces generally decrease with increasing latitude, ranging from 4 to 8Kkm-1. All of the CCPRS-4 lapse rates were used along with five other lapse rate techniques to retrieve cloud-top heights for 2 months of independent Aqua MODIS data. When compared with coincident CALIPSO data for October 2007, the mean cloud-top height differences between CCPRS-4 and CALIPSO during the daytime (nighttime) are 0.04±0.61km(0.10±0.62 km) over ice-free water, -0.0±0.85km (-0.01± 0.83 km) over snow-free land, and 0.38 ± 0.95km (0.03 6 0.92 km) over snow-covered areas. The CCPRS-4 regional monthly means are generally unbiased and lack spatial error gradients seen in the comparisons for most of the other techniques. Over snow-free land, the regional monthly-mean errors range from -0.28 ± 0.74km during daytime to 0.04± 0.78km at night. The water regional monthlymeans are, on average, 0.04 ± 0.44km less than the CALIPSO values during day and night. Greater errors are realized for snow-covered regions. Overall, the CCPRS-4 lapse rates yield the smallest RMS differences for all times of day over all areas both for individual retrievals andmonthly means. These new regional apparent lapse rates, used in processingCERESEdition 4 data, should provide more accurate low-cloud-type heights than previously possible using satellite imager data. © 2014 American Meteorological Society."
"26026749200;7202899330;7202640224;7101600167;6603478504;12645767500;","An update on the oceanic precipitation rate and its zonal distribution in light of advanced observations from space",2014,"10.1175/JCLI-D-13-00679.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901830214&doi=10.1175%2fJCLI-D-13-00679.1&partnerID=40&md5=4c38233304ff5009f034429d2dd8896d","This study contributes to the estimation of the global mean and zonal distribution of oceanic precipitation rate using complementary information from advanced precipitation measuring sensors and provides an independent reference to assess current precipitation products. Precipitation estimates from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and CloudSat cloud profiling radar (CPR) were merged, as the two complementary sensors yield an unprecedented range of sensitivity to quantify rainfall from drizzle through the most intense rates. At higher latitudes, where TRMM PR does not exist, precipitation estimates from Aqua's Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) complemented CloudSat CPR to capture intense precipitation rates. The high sensitivity of CPR allows estimation of snow rate, an important type of precipitation at high latitudes, not directly observed in current merged precipitation products. Using the merged precipitation estimate from the CloudSat, TRMM, and Aqua platforms (this estimate is abbreviated to MCTA), the authors' estimate for 3-yr (2007-09) nearglobal (80°S-80°N) oceanic mean precipitation rate is ̃2.94 mm day-1. This new estimate of mean global ocean precipitation is about 9% higher than that of the corresponding Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) value (2.68 mm day-1) and about 4% higher than that of the Global Precipitation Climatology Project (GPCP; 2.82 mm day-1). Furthermore, MCTA suggests distinct differences in the zonal distribution of precipitation rate from that depicted in GPCPand CMAP, especially in the Southern Hemisphere. © 2014 American Meteorological Society."
"57210687618;","On the choice of average solar zenith angle",2014,"10.1175/JAS-D-13-0392.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904861612&doi=10.1175%2fJAS-D-13-0392.1&partnerID=40&md5=5011efde4630ebc76266fd0e43a2d7d7","Idealized climate modeling studies often choose to neglect spatiotemporal variations in solar radiation, but doing so comes with an important decision about how to average solar radiation in space and time. Since both clear-sky and cloud albedo are increasing functions of the solar zenith angle, one can choose an absorptionweighted zenith angle that reproduces the spatial-or time-mean absorbed solar radiation. Calculations are performed for a pure scattering atmosphere and with a more detailed radiative transfer model and show that the absorption-weighted zenith angle is usually between the daytime-weighted and insolation-weighted zenith angles but much closer to the insolation-weighted zenith angle in most cases, especially if clouds are responsible for much of the shortwave reflection. Use of daytime-average zenith angle may lead to a high bias in planetary albedo of approximately 3%, equivalent to a deficit in shortwave absorption of approximately 10Wm-2 in the global energy budget (comparable to the radiative forcing of a roughly sixfold change in CO2 concentration). Other studies that have used general circulation models with spatially constant insolation have underestimated the global-mean zenith angle, with a consequent low bias in planetary albedo of approximately 2%-6% or a surplus in shortwave absorption of approximately 7-20Wm-2 in the global energy budget. © 2014 American Meteorological Society."
"54982477100;6504435747;15126996400;","Perceived community-based flood adaptation strategies under climate change in Nepal",2014,"10.1504/IJGW.2014.058758","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904724090&doi=10.1504%2fIJGW.2014.058758&partnerID=40&md5=e38fb693ab33d33bf5bbe712fcdaa2a0","Climate induced natural disasters and extreme events are escalating with the increased variability of climatic parameters due to climate change. This study assesses the flood adaptation strategies that are applicable at the community level in two Terai districts of Nepal. The data were collected through three focus group discussions and 210 household surveys. The study revealed that flood forecasting practices at community level included monitoring the extent of rainfall in upper catchments and identifying the position of clouds. 'Initiate communication', 'take care the affected people', and 'select the appropriate location to stay' were most preferred strategies during the flood. Similarly, 'exchanging helps with each other', 'preparing temporary settlement plan' and 'co-ordinating with government and other agencies' are most preferred post-flood adaptation strategies. Identification and assessment of locally-relevant flood adaptation strategies will help governments to choose adaptation strategies that are both effective and preferred by local people in vulnerable communities. © 2014 Inderscience Enterprises Ltd."
"57195198884;24780687700;41562304600;36004971000;56223675500;56900065000;","Dust Identification over Arid and Semiarid Regions of Asia Using AIRS Thermal Infrared Channels",2014,"10.1155/2014/847432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934949318&doi=10.1155%2f2014%2f847432&partnerID=40&md5=59aeda2043072aef49b27944f5afb5e3","Asia dust generated in northern China exerts significant influences on regional air quality, weather, and climate. In this study, a dust identification algorithm over arid and semiarid regions of Asia was proposed based on the thermal observations of atmospheric infrared sounder (AIRS). Firstly, a combination of the line-by-line (LBL) and discrete ordinates radiative transfer (DISORT) model was utilized to investigate the thermal infrared signatures of dust and cloud in 800-1250 cm-1 region. Secondly, six channels in the thermal infrared region were selected from AIRS to monitor dust from space, and a further sensitivity analysis for dust and cloud under different conditions was also performed. Then, the description of the detailed identification method was provided based on distinct thermal infrared signature of dust. At last, several dust events that observed in northern China between the period of 2008 and 2012 were analyzed, and the usefulness of monitoring the outbreaks of Asian dust was emphasized through the comparison with moderate resolution imaging spectroradiometer (MODIS) visible observations and cloud aerosol lidar with orthogonal polarization (CALIOP) data in this study. © 2014 Hui Xu et al."
"22136979800;","Central antarctic climate response to the solar cycle",2014,"10.1007/s00382-013-1925-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899910217&doi=10.1007%2fs00382-013-1925-3&partnerID=40&md5=a3926714a86a3d57dade4862cecb8389","Antarctic ""Vostok"" station works most closely to the center of the ice cap among permanent year-around stations. Climate conditions are exclusively stable: low precipitation level, cloudiness and wind velocity. These conditions can be considered as an ideal model laboratory to study the surface temperature response on solar irradiance variability during 11-year cycle of solar activity. Here we solve an inverse heat conductivity problem: calculate the boundary heat flux density (HFD) from known evolution of temperature. Using meteorological temperature record during (1958-2011) we calculated the HFD variation about 0.2-0.3 W/m2 in phase with solar activity cycle. This HFD variation is derived from 0.5 to 1 °C temperature variation and shows relatively high climate sensitivity per 0.1 % of solar radiation change. This effect can be due to the polar amplification phenomenon, which predicts a similar response 0.3-0.8 °C/0.1 % (Gal-Chen and Schneider in Tellus 28:108-121, 1975). The solar forcing (TSI) is disturbed by volcanic forcing (VF), so that their linear combination TSI + 0.5VF empirically provides higher correlation with HFD (r = 0.63 ± 0.22) than TSI (r = 0.50 ± 0.24) and VF (r = 0.41 ± 0.25) separately. TSI shows higher wavelet coherence and phase agreement with HFD than VF. © 2013 Springer-Verlag Berlin Heidelberg."
"25941200000;8397494800;7101815213;","Estimation of errors associated with the EarthCARE 3D scene construction algorithm",2014,"10.1002/qj.2294","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922839584&doi=10.1002%2fqj.2294&partnerID=40&md5=deacc541e991cdb719fca6eb69a72227","The EarthCARE satellite mission plans to perform a continuous closure experiment to assess the quality of retrieved cloud and aerosol properties. It will do so by comparing top-of-atmosphere (TOA) broad-band (BB) fluxes with simulated values produced by three-dimensional (3D) radiative transfer models that act on the two-dimensional (2D) retrieved cross-section and a 3D atmosphere around it produced by a scene construction algorithm (SCA). This study proposes and tests a method for estimating errors in simulated TOA BB fluxes due to the SCA. Two methods for estimating SCA-related errors for TOA fluxes are presented. The primary one relies on computation of errors for reconstructed narrow-band imager nadir radiances. A-train satellite data were used to show that for constructed domains measuring (11 km)2, approximately the size of the EarthCARE assessment domains, with total cloud fractions &gt; 0.2, errors for reflected BB short-wave fluxes due to the SCA are smaller than ±4.2 and ±11.5 W m-2 for 66 and 90% of the domains, respectively. Corresponding values for outgoing long-wave fluxes are ±1.2 and ±3.0 W m-2. The largest and smallest errors are associated with fields of broken convective cloud and overcast stratiform cloud, respectively. The SCA was applied to simulated measurements for a (153 km)2 field of deep convective clouds produced by a cloud-system-resolving model. Actual and estimated TOA BB short-wave flux errors due to the SCA agree well and are smaller than ±22 and ±40 W m-2 for 66 and 90% of the (11 km)2 sampled subdomains. Assuming that errors due to the SCA are purely bias errors, they were subtracted from fluxes estimated for the constructed domains. This resulted in TOA BB short-wave flux errors smaller than ±7 and ±25 W m-2 for 66 and 90% of the sampled subdomains. This suggests that estimated errors due to the SCA should be removed directly from simulated TOA BB fluxes before executing a closure assessment. © 2013 RoyalMeteorological Society."
"9436114900;9436114900;54986194000;7005632987;7005632987;55663671600;","Simulation of biomass burning aerosols mass distributions and their direct and semi-direct effects over south africa using a regional climate model",2014,"10.1007/s00703-014-0328-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027930285&doi=10.1007%2fs00703-014-0328-2&partnerID=40&md5=6ba53104abf1255902bf9ee4fa70f1a2","In this study, we examine the mass distributions, direct and semi-direct effects of different biomass burning aerosols (BBAs) over South Africa using the 12-year runs of the Regional Climate Model (RegCM4). The results were analyzed and presented for the main BB season (July-October). The results show that Mpumalanga, KwaZulu Natal and the eastern parts of Limpopo are the main local source areas of BBAs in South Africa. In comparison to carbonaceous aerosols, BB-induced sulfate aerosol mass loading and climatic effects were found to be negligible. All carbonaceous aerosols reduce solar radiation at the surface by enhancing local atmospheric radiative heating. The climatic feedback caused by BBAs, resulted in changes in background aerosol concentrations. Thus, on a regional scale, climatic effects of BBAs were also found in areas far away from the BBA loading zones. The feed- back mechanisms of the climate system to the aerosol radiative effects resulted in both positive and negative changes to the low-level columnar averaged net atmospheric radiative heating rate (NAHR). Areas that experienced an NAHR reduction showed an increase in cloud cover (CC). During the NAHR enhancement, CC over arid areas decreased; whereas CC over the wet/semi-wet regions increased. The changes in surface temperature (ST) and surface sensible heat flux are more closely correlated with BBA semi-direct effects induced CC alteration than their direct radiative forcing. Furthermore, decreases (or increases) in ST, respectively, lead to the reductions (and enhancements) in boundary layer height and the vice versa on surface pressure. The direct and semi-direct effects of BBAs also jointly promoted a reduction and rise in surface wind speed that was spatially highly variable. Overall, the results suggest that the CC change induced by the presence of radiatively interactive BBAs is important to determine alterations in other climatic variables. © Springer-Verlag Wien 2014"
"56166275800;7401711350;57203258256;","Nonlinear feedbacks associated with the indian ocean dipole and their response to global warming in the GFDL-ESM2M coupled climate model",2014,"10.1175/JCLI-D-13-00527.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901825007&doi=10.1175%2fJCLI-D-13-00527.1&partnerID=40&md5=1d528655bb92211183c02c9be0351225","A feature of the Indian Ocean dipole (IOD) is its positive skewness, with cold IOD east pole (IODE) sea surface temperature anomalies (SSTAs) exhibiting larger amplitudes than warm SSTAs. Using the coupled Geophysical Fluid Dynamics Laboratory Earth System Model with Modular Ocean Model version 4 (MOM4) component (GFDL-ESM2M), the role of nonlinear feedbacks in generating this positive skewness is investigated and their response to global warming examined. These feedbacks are a nonlinear dynamic heating process, the Bjerknes feedback, wind-evaporation-SST feedback, and SST-cloud-radiation feedback. Nonlinear dynamic heating assists IOD skewness by strongly damping warm IODE SSTAs and reinforcing cold IODE anomalies. In a warmer climate, the damping strengthens while the reinforcement weakens. The SST-thermocline relationship is part of the positive Bjerknes feedback and contributes strongly to IOD skewness as it is weak during the development of warm IODE SSTAs, but strong during the development of cold IODE SSTAs. In response to global warming, this relationship displays weaker asymmetry associated with weaker westerly winds over the central equatorial Indian Ocean. The negative SST-cloud- radiation feedback is also asymmetric with cold IODE SSTAs less damped by incoming shortwave radiation. Under global warming, the damping of cold IODE SSTAs shows little change but warm IODE SSTAs become more damped. This stronger damping is a symptom of negative IODs becoming stronger in amplitude due to the mean IODE thermocline shoaling. The wind-evaporation-SST feedback does not contribute to IOD asymmetry with cold IODE SSTAs decreasing evaporation, which in turn warms the surface. However, as this study focuses on one model, the response of these feedbacks to global warming is uncertain. © 2014 American Meteorological Society."
"36179077700;55687302500;15765007300;8339569900;7406243250;31067496800;","Aquaplanet experiments using CAM's variable-resolution dynamical core",2014,"10.1175/JCLI-D-14-00004.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904479646&doi=10.1175%2fJCLI-D-14-00004.1&partnerID=40&md5=626df4106645d2372b197700a59f8061","A variable-resolution option has been added within the spectral element (SE) dynamical core of the U.S. Department of Energy (DOE)-NCAR Community Atmosphere Model (CAM). CAM-SE allows for static refinement via conforming quadrilateral meshes on the cubed sphere. This paper investigates the effect of mesh refinement in a climate model by running variable-resolution (var-res) simulations on an aquaplanet. The variable-resolution grid is a 2° (∼222 km) grid with a refined patch of 0.25° (∼28 km) resolution centered at the equator. Climatology statistics from these simulations are compared to globally uniform runs of 2° and 0.25°. A significant resolution dependence exists when using the CAM version 4 (CAM4) subgrid physical parameterization package across scales. Global cloud fraction decreases and equatorial precipitation increases with finer horizontal resolution, resulting in drastically different climates between the uniform grid runs and a physics-induced grid imprinting in the var-res simulation. Using CAM version 5 (CAM5) physics significantly improves cloud scaling at different grid resolutions. Additional precipitation at the equator in the highresolution mesh results in collocated zonally anomalous divergence in both var-res simulations, although this feature is much weaker in CAM5 than CAM4. The equilibriumsolution at each grid spacing within the var-res simulations captures the majority of the resolution signal of the corresponding globally uniform grids. The var-res simulation exhibits good performance with respect to wave propagation, including equatorial regions where waves pass through grid transitions. In addition, the increased frequency of high-precipitation events in the refined 0.258 area within the var-res simulations matches that observed in the global 0.25° simulations. © 2014 American Meteorological Society."
"57205420032;56415384100;57208284748;57211488930;","Ecosystem assessment in the Tonle Sap Lake region of Cambodia using RADARSAT-2 Wide Fine-mode SAR data",2014,"10.1080/01431161.2014.890301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897508229&doi=10.1080%2f01431161.2014.890301&partnerID=40&md5=a9c34053b16b0890330591affa8ef91b","The Tonle Sap Lake (TSL), located in Cambodia, is the largest freshwater lake in Southeast Asia and has significant ecological, economic, and sociocultural value. The TSL's ecosystems have been affected by climate change and an increasing amount of human activity in recent years. Considering that the TSL area is often covered by clouds, particularly in the rainy season, synthetic aperture radar (SAR) data are suitable for assessing the ecosystems in this great lake, as SAR enables weather- and cloud-independent observations. In this study, we investigated the capability of the RADARSAT-2 Wide Fine (WF) mode dual-polarization SAR data with a scene size of 170 × 150 km (azimuth × range) and a resolution of 7.6 × 5.2 m to study TSL's ecosystem, by analysing the usefulness of backscattering coefficients and scattering mechanism-related parameters in identifying artificial targets and different land-cover types. The results of this study demonstrate the applicability of RADARSAT-2 WF-mode SAR data in the study of TSL's ecosystems. © 2014 Taylor & Francis."
"56000854300;6602800357;6603668522;39962003300;8562793700;","Significance of remnant cloud forest fragments as reservoirs of tree and epiphytic bromeliad diversity",2014,"10.1177/194008291400700205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902503955&doi=10.1177%2f194008291400700205&partnerID=40&md5=2a5432403ecc84807393f0bac8ddd58c","Tropical Montane Cloud Forests (TMCF) support exceptional concentrations of biodiversity but are severely threatened by deforestation. In Mexico, 60% of TMCF tree species has been reported as threatened, and the epiphytic plants characteristic of these forests are particularly vulnerable to disturbance and climate change. We evaluated the role of remnant TMCF fragments as reservoirs of tree and epiphytic bromeliad biodiversity in southeastern Mexico. In four cloud forest fragments of varying size (1.2, 4.1, 6.6 and 9.8 ha), we recorded all trees ≥ 10 cm dbh in six 20 × 10 m plots and sampled eight trees at each site to measure bromeliad diversity. The assessment revealed that even very small forest fragments can host significant tree and epiphytic bromeliad diversity. In total, 45 tree and 18 bromeliad species were recorded among all the sites. These forest fragments are an important reservoir of both endemic tree species (seven species) and those with conservation status (nine tree species and one bromeliad species). Important variation in tree and bromeliad composition was found among fragments. This high heterogeneity among forest sites means that maintenance of even small fragments can play a strategic role in the conservation of biodiversity in the severely transformed landscape of the region. Such maintenance merits full consideration in the design of forest management policies and TMCF restoration initiatives."
"37088899300;56350198800;55741517200;38762557600;55691665700;55440359400;7202079615;57211223914;","Regional climatic effects according to different estimations of biogenic volatile organic compounds during the asian summer monsoon",2014,"10.1007/s13143-014-0033-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906891267&doi=10.1007%2fs13143-014-0033-6&partnerID=40&md5=fa49547eef70b435f34dc1bbd88c1f13","A series of 60-year numerical experiments starting from 1851 was conducted using a global climate model coupled with an aerosol-cloud-radiation model to investigate the response of the Asian summer monsoon to variations in the secondary organic aerosol (SOA) flux induced by two different estimations of biogenic volatile organic compound (BVOC) emissions. One estimation was obtained from a pre-existing archive and the other was generated by a next-generation model (the Model of Emissions of Gases and Aerosols from Nature, MEGAN). The use of MEGAN resulted in an overall increase of the SOA production through a higher rate of gasto-particle conversion of BVOCs. Consequently, the atmospheric loading of organic carbon (OC) increased due to the contribution of SOA to OC aerosol. The increase of atmospheric OC aerosols was prominent in particular in the Indian subcontinent and Indochina Peninsula (IP) during the pre- and early-monsoon periods because the terrestrial biosphere is the major source of BVOC emissions and the atmospheric aerosol concentration diminishes rapidly with the arrival of monsoon rainfall. As the number of atmospheric OC particles increased, the number concentrations of cloud droplets increased, but their size decreased. These changes represent a combination of aerosol-cloud interactions that were favorable to rainfall suppression. However, the modeled precipitation was slightly enhanced in May over the oceans that surround the Indian subcontinent and IP. Further analysis revealed that a compensating updraft in the surrounding oceans was induced by the thermally-driven downdraft in the IP, which was a result of surface cooling associated with direct OC aerosol radiative forcing, and was able to surpass the aerosolcloud interactions. The co-existence of oceanic ascending motion with the maximum convective available potential energy was also found to be crucial for rainfall formation. Although the model produced statistically significant rainfall changes with locally organized patterns, the suggested pathways should be considered guardedly because in the simulation results, 1) the BVOC-induced aerosol direct effect was marginal; 2) cloud-aerosol interactions were modeldependent; and 3) Asian summer monsoons were biased to a nonnegligible extent. © 2014 Korean Meteorological Society and Springer Science+Business Media Dordrecht."
"8558370300;9244992800;","Quantifying the summertime response of the Austral jet stream and hadley cell to stratospheric ozone and greenhouse gases",2014,"10.1175/JCLI-D-13-00539.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904497229&doi=10.1175%2fJCLI-D-13-00539.1&partnerID=40&md5=512b740f183e54c59825844f128fa3a1","The impact of anthropogenic forcing on the summertime austral circulation is assessed across three climate model datasets: the Chemistry-Climate Model Validation activity 2 and phases 3 and 5 of the Coupled Model Intercomparison Project. Changes in stratospheric ozone and greenhouse gases impact the Southern Hemisphere in this season, and a simple framework based on temperature trends in the lower polar stratosphere and upper tropical troposphere is developed to separate their effects. It suggests that shifts in the jet stream and Hadley cell are driven by changes in the upper-troposphere-lower-stratosphere temperature gradient. The mean response is comparable in the three datasets; ozone has chiefly caused the poleward shift observed in recent decades, while ozone and greenhouse gases largely offset each other in the future. The multimodel mean perspective, however, masks considerable spread in individual models' circulation projections. Spread resulting from differences in temperature trends is separated from differences in the circulation response to a given temperature change; both contribute equally to uncertainty in future circulation trends. Spread in temperature trends is most associated with differences in polar stratospheric temperatures, and could be narrowed by reducing uncertainty in future ozone changes. Differences in tropical temperatures are also important, and arise from both uncertainty in future emissions and differences in models' climate sensitivity. Differences in climate sensitivity, however, only matter significantly in a high emissions future. Even if temperature trends were known, however, differences in the dynamical response to temperature changes must be addressed to substantially narrow spread in circulation projections. © 2014 American Meteorological Society."
"8625649800;25227335300;6701341272;7103266655;55478675400;35475623000;57205899909;","Cloud-resolving 4D-var assimilation of doppler wind lidar data on a meso-gamma-scale convective system",2014,"10.1175/MWR-D-13-00362.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84916204353&doi=10.1175%2fMWR-D-13-00362.1&partnerID=40&md5=4e172193cd33e78248a6dfb82ddfe337","The authors evaluated the effects of assimilating three-dimensional Doppler wind lidar (DWL) data on the forecast of the heavy rainfall event of 5 July 2010 in Japan, produced by an isolated mesoscale convective system (MCS) at a meso-gamma scale in a system consisting of only warm rain clouds. Several impact experiments using the nonhydrostatic four-dimensional variational data assimilation system (NHM-4DVAR) and the Japan Meteorological Agency nonhydrostatic model with a 2-km horizontal grid spacing were conducted in which 1) no observations were assimilated (NODA), 2) radar reflectivity and radial velocity determined by Doppler radar and precipitable water vapor determined by GPS satellite observations were assimilated (CTL), and 3) radial velocity determined byDWLwere added to the CTL experiment (LDR) and five data denial and two observational error sensitivity experiments. Although both NODA and CTL simulated an MCS, only LDR captured the intensity, location, and horizontal scale of the observed MCS. Assimilating DWL data improved the wind direction and speed of low-level airflows, thus improving the accuracy of the simulated water vapor flux. The examination of the impacts of specific assimilations and assigned observation errors showed that assimilation of all data types is important for forecasting intense MCSs. The investigation of the MCS structure showed that large amounts of water vapor were supplied to the rainfall event by southerly flow. A midlevel inversion layer led to the production of exclusively liquid water particles in the MCS, and in combination with the humid airflow into the MCS, this inversion layer may be another important factor in its development. © 2014 American Meteorological Society."
"12769875100;","Variability of regional TOA flux diurnal cycle composites at the monthly time scale",2014,"10.1175/JAS-D-13-0336.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906771332&doi=10.1175%2fJAS-D-13-0336.1&partnerID=40&md5=cd52e79fa108dd86aa5ea9da55bc8088","Diurnal variability is a fundamental component of Earth's climate system. Clouds, temperature, and precipitation exhibit robust responses to the daily cycle of solar insolation. Recent work indicates significant variability in the top-of-the-atmosphere (TOA) flux diurnal cycle in the tropics associated with monthly changes in the cloud diurnal cycle evolution. It has been proposed that the observedmonth-to-month variations in the TOA flux diurnal cycle are caused by anomalies in the atmospheric dynamic and thermodynamic state. This hypothesis is tested using a regression analysis to quantify the relationship between diurnal cycle shape and the atmospheric dynamic and thermodynamic state. TOA radiative fluxes are obtained from Clouds and the Earth's Radiant Energy System (CERES) Edition 3 data and the atmospheric dynamic and thermodynamic state is taken from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis. Four regions representing traditional diurnal cycle regimes are used in this analysis: North Africa (land nonconvective), central South America (land convective), Peru marine stratocumulus (ocean nonconvective), and Indian Ocean (ocean convective). The results show a statistically significant diurnal cycle shape change and cloud response related to monthly atmospheric state anomalies. Using the single-variable regression relationships to predict monthly diurnal cycle variability shows improvements of 1%-18%over assuming a climatological diurnal cycle shape; the most significant gains are found in North Africa. The proposed hypothesis, therefore, contributes to diurnal cycle variability explaining at least 10%-20% of the total monthly-mean diurnal cycle variability."
"56108769500;25953950400;","The effect of pollution aerosol on wintertime orographic precipitation in the colorado rockies using a simplified emissions scheme to predict CCN concentrations",2014,"10.1175/JAMC-D-13-0166.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897987566&doi=10.1175%2fJAMC-D-13-0166.1&partnerID=40&md5=24548357cf5be2c3496c26d53cab4eb1","The impacts of enhanced CCN concentrations on various cloud and precipitation systems are potentially significant both to the large-scale climate system and local precipitation patterns. Precipitating stable orographic cloud systems are particularly susceptible to increases in CCN as parcel lifetimes within these clouds are typically short compared to clouds of similar depth. As such, even small perturbations to the precipitation efficiency within these clouds can have substantial impacts. In the mountainous regions of the western United States, where water resources are derived primarily from orographic precipitation during the cold season, this effect is of particular interest. The aims of this study are twofold. The first part is focused on the implementation of a simplified aerosol emissions scheme into the Regional Atmospheric Modeling System (RAMS). This scheme uses aerosol output from the Weather Research and Forecast Chemistry model (WRF-Chem) to initialize aerosol sources in RAMS. The second part of this study uses this scheme in the simulation of an orographic snow case that occurred in northwest Colorado during February 2007. The result of this study suggests that atmospheric CCN concentrations can be reasonably simulated using a simplified parameterization of aerosol emissions, despite a lack of explicit secondary aerosol (SA)within the model. Furthermore, the spatial and temporal variations inCCNpredicted by this scheme produced a complicated response in the surface distribution of precipitation from the orographic snowstorm, a result not seen in studies where CCN concentrations are set to be horizontally homogenous. © 2014 American Meteorological Society."
"36458602300;55481995500;16480992300;6603196991;6701592014;7402934750;57137032900;","Absorption properties of supercooled liquid water between 31 and 225 GHz: Evaluation of absorption models using ground-based observations",2014,"10.1175/JAMC-D-13-0214.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897985706&doi=10.1175%2fJAMC-D-13-0214.1&partnerID=40&md5=3dcadc4ffea3bd92d1c6912b8a4f4cd4","Microwave radiometers (MWR) are commonly used to quantify the amount of supercooled liquid water (SLW) in clouds; however, the accuracy of the SLW retrievals is limited by the poor knowledge of the SLW dielectric properties at microwave frequencies. Six liquid water permittivity models were compared with ground-based MWR observations between 31 and 225GHz from sites in Greenland, the German Alps, and a low-mountain site; average cloud temperatures of observed thin cloud layers range from 0° to 233°C. A recently published method to derive ratios of liquid water opacity from different frequencies was employed in this analysis. These ratios are independent of liquid water path and equal to the ratio of αL at those frequencies that can be directly compared with the permittivity model predictions. The observed opacity ratios from all sites show highly consistent results that are generally within the range of model predictions; however, none of the models are able to approximate the observations over the entire frequency and temperature range. Findings in earlier published studies were used to select one specific model as a reference model for αL at 90 GHz; together with the observed opacity ratios, the temperature dependence of αL at 31.4, 52.28, 150, and 225 GHz was derived. The results reveal that two models fit the opacity ratio data better than the other four models, with one of the two models fitting the data better for frequencies below 90GHz and the other for higher frequencies. These findings are relevant for SLW retrievals and radiative transfer in the 31-225-GHz frequency region. © 2014 American Meteorological Society."
"6603434295;57126848900;7005002831;6507308842;55885662200;","Model-based estimation of sampling-caused uncertainty in aerosol remote sensing for climate research applications",2014,"10.1002/qj.2305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922895903&doi=10.1002%2fqj.2305&partnerID=40&md5=38151741433cf5c3be88b38fe75a92fa","To evaluate the effect of sampling frequency on the global monthly mean aerosol optical thickness (AOT), we use 6 years of geographical coordinates of Moderate Resolution Imaging Spectroradiometer (MODIS) L2 aerosol data, daily global aerosol fields generated by the Goddard Institute for Space Studies General Circulation Model and the chemical transport models Global Ozone Chemistry Aerosol Radiation and Transport, Spectral Radiation-transport Model for Aerosol Species and Transport Model 5, at a spatial resolution between 1.125°× 1.125° and 2°× 3°: the analysis is restricted to 60°S-60°N geographical latitude. We found that, in general, the MODIS coverage causes an underestimate of the global mean AOT over the ocean. The long-term mean absolute monthly difference between all and dark target (DT) pixels was 0.01-0.02 over the ocean and 0.03-0.09 over the land, depending on the model dataset. Negative DT biases peak during boreal summers, reaching 0.07-0.12 (30-45% of the global long-term mean AOT). Addition of the Deep Blue pixels tempers the seasonal dependence of the DT biases and reduces the mean AOT difference over land by 0.01-0.02. These results provide a quantitative measure of the effect the pixel exclusion due to cloud contamination, ocean sun-glint and land type has on the MODIS estimates of the global monthly mean AOT. We also simulate global monthly mean AOT estimates from measurements provided by pixel-wide along-track instruments such as the Aerosol Polarimetry Sensor and the Cloud-Aerosol LiDAR with Orthogonal Polarization. We estimate the probable range of the global AOT standard error for an along-track sensor to be 0.0005-0.0015 (ocean) and 0.0029-0.01 (land) or 0.5-1.2% and 1.1-4% of the corresponding global means. These estimates represent errors due to sampling only and do not include potential retrieval errors. They are smaller than or comparable to the published estimate of 0.01 as being a climatologically significant change in the global mean AOT, suggesting that sampling density is unlikely to limit the use of such instruments for climate applications at least on a global, monthly scale © 2013 Royal Meteorological Society."
"55802221900;23478660100;57205842560;23478519800;8668565900;7102953444;","Direct and semi-direct aerosol radiative effect on the Mediterranean climate variability using a coupled regional climate system model",2014,"10.1007/s00382-014-2205-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925614859&doi=10.1007%2fs00382-014-2205-6&partnerID=40&md5=ed7cb160c9eb9b9c12f1ac3ece44976e","A fully coupled regional climate system model (CNRM-RCSM4) has been used over the Mediterranean region to investigate the direct and semi-direct effects of aerosols, but also their role in the radiation–atmosphere–ocean interactions through multi-annual ensemble simulations (2003–2009) with and without aerosols and ocean–atmosphere coupling. Aerosols have been taken into account in CNRM-RCSM4 through realistic interannual monthly AOD climatologies. An evaluation of the model has been achieved, against various observations for meteorological parameters, and has shown the ability of CNRM-RCSM4 to reproduce the main patterns of the Mediterranean climate despite some biases in sea surface temperature (SST), radiation and cloud cover. The results concerning the aerosol radiative effects show a negative surface forcing on average because of the absorption and scattering of the incident radiation. The SW surface direct effect is on average −20.9 Wm−2 over the Mediterranean Sea, −14.7 Wm−2 over Europe and −19.7 Wm−2 over northern Africa. The LW surface direct effect is weaker as only dust aerosols contribute (+4.8 Wm−2 over northern Africa). This direct effect is partly counterbalanced by a positive semi-direct radiative effect over the Mediterranean Sea (+5.7 Wm−2 on average) and Europe (+5.0 Wm−2) due to changes in cloud cover and atmospheric circulation. The total aerosol effect is consequently negative at the surface and responsible for a decrease in land (on average −0.4 °C over Europe, and −0.5 °C over northern Africa) and sea surface temperature (on average −0.5 °C for the Mediterranean SST). In addition, the latent heat loss is shown to be weaker (−11.0 Wm−2) in the presence of aerosols, resulting in a decrease in specific humidity in the lower troposphere, and a reduction in cloud cover and precipitation. Simulations also indicate that dust aerosols warm the troposphere by absorbing solar radiation, and prevent radiation from reaching the surface, thus stabilizing the troposphere. The comparison with the model response in atmosphere-only simulations shows that these feedbacks are attenuated if SST cannot be modified by aerosols, highlighting the importance of using coupled regional models over the Mediterranean. Oceanic convection is also strengthened by aerosols, which tends to reinforce the Mediterranean thermohaline circulation. In parallel, two case studies are presented to illustrate positive feedbacks between dust aerosols and regional climate. First, the eastern Mediterranean was subject to high dust aerosol loads in June 2007 which reduce land and sea surface temperature, as well as air–sea humidity fluxes. Because of northern wind over the eastern Mediterranean, drier and cooler air has been consequently advected from the sea to the African continent, reinforcing the direct dust effect over land. On the contrary, during the western European heat wave in June 2006, dust aerosols have contributed to reinforcing an important ridge responsible for dry and warm air advection over western Europe, and thus to increasing lower troposphere (+0.8 °C) and surface temperature (+0.5 °C), namely about 15 % of this heat wave. © 2014, The Author(s)."
"34976900400;8105442200;57210240500;36544937700;56449398300;56449414100;55290356700;35318562800;6506534909;7401511851;57202637284;","Lidar investigations on the optical and dynamical properties of cirrus clouds in the upper troposphere and lower stratosphere regions at a tropical station, Gadanki, India (13.5°N, 79.2°E)",2014,"10.1117/1.JRS.8.083659","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897134711&doi=10.1117%2f1.JRS.8.083659&partnerID=40&md5=50194461bf9ea98ded8a4d10e44c9a45","High altitude cirrus clouds are composed mainly of ice crystals with a variety of sizes and shapes. They have a large influence on Earth's energy balance and global climate. Recent studies indicate that the formation, dissipation, life time, optical, and micro-physical properties are influenced by the dynamical conditions of the surrounding atmosphere like background aerosol, turbulence, etc. In this work, an attempt has been made to quantify some of these characteristics by using lidar and mesosphere-stratosphere-troposphere (MST) radar. Mie lidar and 53 MHz MST radar measurements made over 41 nights during the period 2009 to 2010 from the tropical station, Gadanki, India (13.5N, 79.2E). The optical and microphysical properties along with the structure and dynamics of the cirrus are presented as observed under different atmospheric conditions. The study reveals the manifestation of different forms of cirrus with a preferred altitude of formation in the 13 to 14 km altitude. There are considerable differences in the properties obtained among 2009 and 2010 showing significant anomalous behavior in 2010. The clouds observed during 2010 show relatively high asymmetry and large multiple scattering effects. The anomalies found during 2010 may be attributed to the turbulence noticed in the surrounding atmosphere. The results show a clear correlation between the crystal morphology in the clouds and the dynamical conditions of the prevailing atmosphere during the observational period. © Society of Photo-Optical Instrumentation Engineers."
"56315540600;56820509800;56058520000;36110342400;7403315325;36070629400;21735592100;56329651900;","Airborne Lidar-derived volume metrics for aboveground biomass estimation: A comparative assessment for conifer stands",2014,"10.1016/j.agrformet.2014.07.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905695911&doi=10.1016%2fj.agrformet.2014.07.008&partnerID=40&md5=37b47c58b3a208c0ffbd325ea257279e","Estimating aboveground biomass (AGB) is essential to quantify the carbon balance of terrestrial ecosystems, and becomes increasingly important under changing global climate. Volume metrics of individual trees, for example stem volume, have been proven to be strongly correlated to AGB. In this paper, we compared a range of airborne Lidar-derived volume metrics (i.e. stem volume, crown volume under convex hull, and crown volume under Canopy Height Model (CHM)) to estimate AGB. In addition, we evaluated the effect of horizontal crown overlap (which is often neglected in Lidar literature) on the accuracy of AGB estimation by using a hybrid method that combined marker-controlled watershed segmentation and point cloud segmentation algorithms. Our results show that: (1) when the horizontal crown overlap issue was not addressed, models based on point cloud segmentation outperformed models based on marker-controlled watershed segmentation; models using stem volume estimated AGB more accurately than models using crown volume under convex hull and crown volume under CHM. (2) Once the horizontal crown overlap issue was taken into consideration, the model using crown volume under CHM yielded a more accurate estimation of AGB. Our study provides a comprehensive evaluation of the use of airborne Lidar-derived volume metrics for AGB estimation and could help researchers choose the appropriate airborne Lidar-derived volume metric. Moreover, the results also indicate that horizontal crown overlap should be addressed when the airborne Lidar-derived forest crown volume is used for estimating AGB. © 2014 Elsevier B.V."
"35249319600;56034947700;","Long-term high-frequency validation of MODIS LST products in a Mediterranean mountain environment",2014,"10.1080/01431161.2013.873148","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893954479&doi=10.1080%2f01431161.2013.873148&partnerID=40&md5=f0934b0873c8988c7d4638b4466bf65d","The accuracy of Moderate-resolution Imaging Spectroradiometer (MODIS) level 3 1 km land surface temperature (LST) products was assessed through long-term validation carried out in a mountainous site in Sierra Nevada, southeast Spain. A total of 1458 day and night thermal images, acquired by Terra and Aqua satellites during 2008, were processed and compared to ground-truth data recorded at the meteorological station of Robledal de Cañar with a frequency of one measurement every 10 min. The purpose of this investigation was to understand whether MODIS LST data can be used as input for climate models to be constructed for mountainous environments. Several trends in the MODIS LST data were observed, including the underestimation of daytime values and the overestimation of night-time values. Although all the data sets (Terra and Aqua, diurnal and nocturnal) showed high correlation coefficients with ground measurements, only night values maintained a relatively high accuracy of approximately 2°C of annual average error. Factors that may cause errors in the MODIS LST data, like acquisition angle, cloud, and snow cover, were analysed without conclusive results. High accuracy levels, i.e. close to 1°C, similar to other validation studies carried out over simpler and much more homogenous land-cover types such as cultivated fields, have been achieved for night images acquired during the summer months, thus making these datasets reliable for their use in climatic models over mountainous regions. © 2014 © 2014 Taylor & Francis."
"25421495700;56072222400;56423917100;55386911300;23395726200;6603764342;8621261100;","Different growth sensitivity to climate of the conifer Juniperus thurifera on both sides of the Mediterranean Sea",2014,"10.1007/s00484-014-0811-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911812041&doi=10.1007%2fs00484-014-0811-y&partnerID=40&md5=1f6ebabb05d9193e3f7bcbbbae95df9f","Mediterranean plants cope with cold wet winters and dry hot summers, with a drought gradient from northwest to southeast. Limiting climatic conditions have become more pronounced in the last decades due to the warming trend and rainfall decrease. Juniperus thurifera L., a long-lived conifer tree endemic to the western Mediterranean region, has a disjunct distribution in Europe and Africa, making it a suitable species to study sensitivity to climate in both sides of the Mediterranean Basin. Tree-ring width chronologies were built for three J. thurifera stands at Spain (Europe) and three in Morocco (Africa) and correlated with monthly temperature and precipitation. The temporal stability of climate-growth relationships was assessed using moving correlations; the drought effect on growth was calculated using the monthly standardized precipitation-evapotranspiration index (SPEI) at different temporal scales. In the wettest stands, increasing spring temperature and summer precipitation enhanced growth, while in the driest stands, growth was enhanced by higher spring precipitation and lower summer temperature. The climate-growth correlations shifted during the twentieth century, especially since the 1970s. Particularly noticeable is the recent negative correlation with previous autumn and winter precipitation in the wettest stands of J. thurifera, probably related with an effect of cloud cover or flooding on carbon storage depletion for next year growth. The driest stands were affected by drought at long time scales, while the wettest stands respond to drought at short time scales. This reveals a different strategy to cope with drought conditions, with populations from drier sites able to cope with short periods of water deficit. © 2014, ISB."
"55287000900;7404925844;55781984100;55781880600;49061563400;55782210200;55781439000;","The dramatic climate warming in the Qaidam Basin, northeastern Tibetan Plateau, during 1961-2010",2014,"10.1002/joc.3781","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897913789&doi=10.1002%2fjoc.3781&partnerID=40&md5=c6e0218758f619f15ce73cd5b36a4443","On the basis of meteorological station records during 1961-2010, we investigate the variations of temperature and precipitation in the Qaidam Basin. Results show that climate warming is significant in the region of Qaidam Basin over the past 50years, with an average warming rate of 0.53°C10a-1. The largest and smallest warming rate happened at Mangya station (0.89°C10a-1) and Lenghu station (0.24°C10a-1), respectively. Seasonal warming was greatest in winter at eight meteorological stations, ranging from 0.43°C10a-1 (Lenghu station) to 1.01°C10a-1 (Delingha station). Since 1961, the annual precipitation has increased with a rate of 7.38mm10a-1. Seasonal precipitation mainly increased in summer (4.02mm10a-1). The maximum precipitation increase occurred at Delingha station (25.09mm10a-1) and the minimum at Lenghu station (0.10mm10a-1). The elevation dependency of warming trends is unremarkable because most of the stations are located at lower altitudes. It is suggested that sunshine duration is related to the tendencies of temperature increase at different stations. Pollution emissions from industrial processes (i.e. brown clouds) and urbanization are the main factors contributing to the warming climate. Furthermore, the predominant weakening of zonal wind speed over the Tibetan Plateau resulted from the global warming also contributes to the climate warming in the Qaidam Basin. Consequently, the warming rate in the Qaidam Basin is much higher than in other regions over the Tibetan Plateau. The Qaidam Basin is thus considered to be the most susceptible region with the most significant warming in the Tibetan Plateau. © 2013 Royal Meteorological Society."
"56005630600;23082420800;56005518700;","The south pacific meridional mode: A mechanism for ENSO-like variability",2014,"10.1175/JCLI-D-13-00082.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892516499&doi=10.1175%2fJCLI-D-13-00082.1&partnerID=40&md5=e0de8ef47396886181c9ba7fe9bac874","In this study, the authors investigate the connection between the South Pacific atmospheric variability and the tropical Pacific climate in models of different degrees of coupling between the atmosphere and ocean. A robust mode of variability, defined as the South Pacific meridional mode (SPMM), is identified in a multimodel ensemble of climate model experiments where the atmosphere is only thermodynamically coupled to a slab ocean mixed layer. The physical interpretation of the SPMM is nearly identical to the North Pacific meridional mode (NPMM) with the off-equatorial southeast trade wind variability altering the latent heat flux and sea surface temperature (SST) and initiating a wind-evaporation-SST feedback that propagates signals into the tropics. The authors also show that a positive cloud feedback plays a role in the development of this mode, but this effect is model dependent. While physically analogous to the NPMM, theSPMMhas a stronger expression in the equatorial Pacific and directly perturbs the zonal gradients of SST and sea level pressure (SLP) on the equator, thus leading to ENSO-like variability despite the lack of ocean-atmosphere dynamical coupling. Further analysis suggests that the SPMM is also active in fully coupled climate models and observations. This study highlights the important role of the Southern Hemisphere in tropical climate variability and suggests that including observations from the data-poor South Pacific could improve the ENSO predictability. © 2014 American Meteorological Society."
"56109268200;55544443300;15026371500;","Sensitivity of intertropical convergence zone movement to the latitudinal position of thermal forcing",2014,"10.1175/JCLI-D-13-00691.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898039411&doi=10.1175%2fJCLI-D-13-00691.1&partnerID=40&md5=e15e72e6926ceb0d09a15998b1913644","A variety of recent studies have shown that extratropical heating anomalies can be remarkably effective at causing meridional shifts in the intertropical convergence zone (ITCZ). But what latitudinal location of forcing ismost effective at shifting the ITCZ? In a series of aquaplanet simulationswith theGFDLAtmosphericModel, version 2 (AM2), coupled to a slab mixed layer ocean, it is shown that high-latitude forcing actually causes a larger shift in the ITCZ than when equivalent surface forcing is applied in the tropics. Equivalent simulations are run with an idealized general circulation model (GCM) without cloud and water vapor feedbacks, also coupled to an aquaplanet slab ocean, where the ITCZ response instead becomes weaker the farther the forcing is from the equator, indicating that radiative feedbacks must be important in AM2. In the absence of radiative feedbacks, the tendency for anomalies to decrease in importance the farther away they are from the equator is due to the quasi-diffusive nature of energy transports. Cloud shortwave responses in AM2 act to strengthen the ITCZ response to extratropical forcing, amplifying the response as it propagates toward the equator. These results emphasize the great importance of the extratropics in determining the position of the ITCZ. © 2014 American Meteorological Society."
"34770243200;","Coal renaissance? [Renaissance der Kohle?]",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904102659&partnerID=40&md5=4f7008cbe115bbc0f655df86107505cb","Coal is among the energy sources experiencing a rapidly growing demand. This is being driven particularly by the large amounts of coal used for electricity generation, and by the fact that some countries have turned away from nuclear power. The fact that coal prices have been falling for the last few years has also had an influence. However, there are also dark clouds on the horizon. For one thing, the burning of coal causes a rapid increase in the emission of CO2 and therefore results in global warming. The climate target of limiting global warming to 2 °C is already considered unachievable. And another negative aspect is the decreasing revenues achieved by coal producers, which has already caused some companies to run into financial difficulties, and has led to additional consolidation in the coal sector."
"18835391900;36504416300;24604939500;35184909500;17344986000;57213386315;57190928502;24297881400;57203805202;55445678400;52263498000;57206696888;6602415577;7005592751;26535998300;57217745412;35190595700;56675196500;35446475800;7203056909;6603406338;57190927165;26646794300;8204540500;55812599300;7202501354;56063297500;56525484400;7006630889;","Toward enhanced understanding and projections of climate extremes using physics-guided data mining techniques",2014,"10.5194/npg-21-777-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984410731&doi=10.5194%2fnpg-21-777-2014&partnerID=40&md5=59da3dafa9dc097bca94d9ac4894c84a","Extreme events such as heat waves, cold spells, floods, droughts, tropical cyclones, and tornadoes have potentially devastating impacts on natural and engineered systems and human communities worldwide. Stakeholder decisions about critical infrastructures, natural resources, emergency preparedness and humanitarian aid typically need to be made at local to regional scales over seasonal to decadal planning horizons. However, credible climate change attribution and reliable projections at more localized and shorter time scales remain grand challenges. Long-standing gaps include inadequate understanding of processes such as cloud physics and ocean-land-atmosphere interactions, limitations of physics-based computer models, and the importance of intrinsic climate system variability at decadal horizons. Meanwhile, the growing size and complexity of climate data from model simulations and remote sensors increases opportunities to address these scientific gaps. This perspectives article explores the possibility that physically cognizant mining of massive climate data may lead to significant advances in generating credible predictive insights about climate extremes and in turn translating them to actionable metrics and information for adaptation and policy. Specifically, we propose that data mining techniques geared towards extremes can help tackle the grand challenges in the development of interpretable climate projections, predictability, and uncertainty assessments. To be successful, scalable methods will need to handle what has been called “big data” to tease out elusive but robust statistics of extremes and change from what is ultimately small data. Physically based relationships (where available) and conceptual understanding (where appropriate) are needed to guide methods development and interpretation of results. Such approaches may be especially relevant in situations where computer models may not be able to fully encapsulate current process understanding, yet the wealth of data may offer additional insights. Large-scale interdisciplinary team efforts, involving domain experts and individual researchers who span disciplines, will be necessary to address the challenge. © Author(s) 2014."
"6701823396;","Effects of Arctic Sea Ice Decline on Weather and Climate: A Review",2014,"10.1007/s10712-014-9284-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907663485&doi=10.1007%2fs10712-014-9284-0&partnerID=40&md5=5178fbe0f8ffaa1f3e680ad43154259e","The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia. © 2014, The Author(s)."
"35090272500;6603327055;7006206130;","Analysis of the radiation budget in regional climate simulations with COSMO-CLM for Africa",2014,"10.1127/0941-2948/2014/0527","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925447936&doi=10.1127%2f0941-2948%2f2014%2f0527&partnerID=40&md5=cf0495fd76efe5f8a3558f405627a5a8","This study analysed two regional climate simulations for Africa regarding the radiation budgets with particular focus on the contribution of potentially influential parameters on uncertainties in the radiation components. The ERA-Interim driven simulations have been performed with the COSMO-CLM (gridspacings of 0.44 ° or 0.22 °). The simulated budgets were compared to the satellite-based Global Energy and Water Cycle Experiment Surface Radiation Budget and ERA-Interim data sets. The COSMO-CLM tended to underestimate the net solar radiation and the outgoing long-wave radiation, and showed a regionally varying over- or underestimation in all budget components. An increase in horizontal resolution from 0.44 ° to 0.22 ° slightly reduced the mean errors by up to 5 %. Especially over sea regions, uncertainties in cloud fraction were the main influencing parameter on errors in the simulated radiation fluxes. Compared to former simulations the introduction of a new bare soil albedo treatment reduced the influence of uncertainties in surface albedo significantly. Over the African continent errors in aerosol optical depth and skin temperature were regionally important sources for the discrepancies within the simulated radiation. In a sensitivity test it was shown that the use of aerosol optical depth values from the MACC reanalysis product improved the simulated surface radiation substantially. © 2014 The authors."
"6508063123;7006705919;55688930000;55317177900;15755995900;42661692800;55544607500;","Short-term modulation of Indian summer monsoon rainfall by West Asian dust",2014,"10.1038/ngeo2107","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897144207&doi=10.1038%2fngeo2107&partnerID=40&md5=f120a12c0649d24bf7eb5067787e0327","The Indian summer monsoon is influenced by numerous factors, including aerosol-induced changes to clouds, surface and atmospheric heating, and atmospheric circulation. Most previous studies assessing the effect of aerosols on monsoon rainfall have focussed on the local impact of aerosols on precipitation on monthly to seasonal timescales. Here, we show that desert dust aerosol levels over the Arabian Sea, West Asia and the Arabian Peninsula are positively correlated with the intensity of the Indian summer monsoon, using satellite data and models; a lead-lag analysis indicates that dust and precipitation vary in concert over timescales of about a week. Our analysis of global climate model simulations indicates that by heating the atmosphere, dust aerosols induce large-scale convergence over North Africa and the Arabian Peninsula, increasing the flow of moisture over India within a week. According to these simulations, dust-induced heating of the atmosphere over North Africa and West Asia rapidly modulates monsoon rainfall over central India. © 2014 Macmillan Publishers Limited. All rights reserved."
"24538127000;6602574802;","Seasonality of the urban heat island effect in Madison, Wisconsin",2014,"10.1175/JAMC-D-14-0107.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907934337&doi=10.1175%2fJAMC-D-14-0107.1&partnerID=40&md5=61195bc6b646360cf6de53bab49a9a72","Spatial and temporal variation in the urban heat island (UHI) effect from March 2012 through October 2013 was characterized using continuous temperature measurements from an array of up to 151 fixed sensors in and around Madison, Wisconsin, an urban area of population 407 000 surrounded by lakes and a rural landscape of agriculture, forests, wetlands, and grasslands. Spatially, the density of the built environment was the primary driver of temperature patterns, with local modifying effects of lake proximity and topographic relief. Temporally, wind speed, cloud cover, relative humidity, soil moisture, and snow all influenced UHI intensity, although the magnitude and significance of their effects varied by season and time of day. Seasonally, UHI intensities tended to be higher during the warmer summer months and lower during the colder months. Seasonal trends in monthly average wind speed and cloud cover tracked annual trends in UHI intensity, with clearer, calmer conditions that are conducive to the stronger UHIs being more common during the summer. However, clear, calm summer nights still had higher UHI intensities than clear, calm winter nights, indicating that some background factor, such as vegetation, shifted baseline UHI intensities throughout the year. The authors propose that regional vegetation and snow-cover conditions set seasonal baselines forUHI intensity and that factors like wind and clouds modified daily UHI intensity around that baseline. © 2014 American Meteorological Society."
"55687436600;55545601500;7004678728;35779366300;7004656200;","Ocean subsurface studies with the CALIPSO spaceborne lidar",2014,"10.1002/2014JC009970","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906098279&doi=10.1002%2f2014JC009970&partnerID=40&md5=ad206a403f99b2c8cb829e86019e2c7f","The primary objective of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission is to study the climate impact of clouds and aerosols in the atmosphere. However, recent studies have demonstrated that CALIPSO also collects information about the ocean subsurface. The objective of this study is to estimate the ocean subsurface backscatter from CALIPSO lidar measurements. The effects of the lidar receiver's transient response on the attenuated backscatter were first removed in order to obtain the correct attenuated backscatter profile. The empirical relationship between sea surface lidar backscatter and wind speed was used to estimate the theoretical ocean surface backscatter. Then the two-way atmospheric transmittance was estimated as the ratio between the corrected ocean surface backscatter and the theoretical one. The ocean subsurface backscatter was finally derived from the subsurface attenuated backscatter divided by the two-way atmospheric transmittance. Significant relationships between integrated subsurface backscatter and chlorophyll-a concentration and between integrated subsurface backscatter and particulate organic carbon were found, which indicate a potential use of CALIPSO lidar to estimate global chlorophyll-a and particulate organic carbon concentrations. Key Points Ocean subsurface backscatter was estimated from CALIPSO lidar measurements The receiver's transient response on the attenuated backscatter was removed A relationship between subsurface backscatter and chlorophyll-a was found © 2014. American Geophysical Union. All Rights Reserved."
"7004890737;7402896938;55992280400;6602458644;8687046600;","Improving tropospheric and stratospheric moisture analysis with hyperspectral infrared radiances",2014,"10.22499/2.6404.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939552099&doi=10.22499%2f2.6404.004&partnerID=40&md5=9313bf6b7420e02c7cbeddb2137c65c3","The accurate analysis of humidity fields on a global scale is essential in numerical weather prediction to forecast extreme weather and for monitoring and predicting climate. Tropospheric humidity is not well observed by the conventional observing system where radiosonde and aircraft based observations still leave large volumes unobserved, particularly over the southern oceans and in the tropics. As a result, use of satellite remote sensing is essential to produce accurate humidity fields. Through use of hyperspectral infrared radiances and a nine month Observing System Experiment (OSE) from 1 March to 30 November 2010, we show results demonstrating considerably improved analysis and short-term forecast humidity fields when verified against radiosonde data. This improvement of analysed moisture fields is potentially an important precursor to improved modeling of moisture fields and, as a result, improved prediction of severe weather, rainfall and cloud cover in a number of circumstances. © 2014 Australian Meteorological and Oceanographic Journal."
"6603359788;7402074810;","Stratocumulus-topped marine boundary layer processes revealed by the absence of profiler reflectivity",2014,"10.1175/JAMC-D-12-0308.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905122791&doi=10.1175%2fJAMC-D-12-0308.1&partnerID=40&md5=9ad4ec0b54b515cc44f1cee8e20cd9b9","Stratocumulus (Sc) clouds occur frequently over the cold waters of the southeastern Pacific Ocean. Data collected during two Pan American Climate Study research cruises in the tropical eastern Pacific illuminate many aspects of this Sc-topped marine boundary layer (MBL). Here the focus is on understanding gaps in detectable wind-profiler reflectivities during two boreal autumn cruises. After rigorous quality control that included applying the Riddle threshold of minimum signal-to-noise ratio (SNR) detectability, there are many instances with no measurable atmospheric signals through a depth of up to several hundred meters, often lasting for an hour or more. Rain gauge data from the autumn 2004 cruise are used to calibrate the profiler, which allows SNR to be converted to both equivalent reflectivity and the structure-function parameter of the index of refraction C2n. Profiles of C2n statistics from the two profiler modes (resolutions) highlight the wide range of C2n during a 24-h period and bound the atmosphere's C2n when low-mode gaps are not mirrored in the high-mode data. Considering the gaps in terms of C2n allows them to be understood as indications of reduced ""top down"" buoyancy processes and/or reduced turbulent intensity, both of which have been demonstrated by previous researchers to be associated with decoupling within the Sc-topped MBL. A decoupling index calculated from surface and ceilometer data strongly suggests that decoupled conditions were common and that the MBL was coupled when gaps in profiler reflectivity were unlikely. Further study of data from other cruises may lead to a method of using profiler reflectivity as an indicator of decoupled conditions. © 2014 American Meteorological Society."
"25654041600;7403429025;56067770900;55861207600;","Clouds gather in the sky, but no rain falls. Vulnerability to rainfall variability and food insecurity in Northern Bangladesh and its effects on migration",2014,"10.1080/17565529.2013.833078","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896134444&doi=10.1080%2f17565529.2013.833078&partnerID=40&md5=d91fe2532498e1d637dd6e99fc173c84","This article presents empirical evidence on changing rainfall patterns in Kurigram district in northern Bangladesh, on the local people's perception of these changes, and on their decision to migrate, or not, in order to cope with rainfall variability and food insecurity. Our study was conducted as one of eight case studies within the 'Where the Rain Falls' Project. Taking on a social vulnerability perspective, we show that migration from the region is not driven by climatic changes, but rather by the existing livelihood and labour migration systems. First, there is a distinct seasonality and thus rainfall dependency of rural livelihoods, which makes the rural population sensitive to changing rainfall patterns. Second, rainfall variability and food security are closely intertwined. Third, the distinct rhythm in the labour migration system is largely structured by seasonal hunger (Monga) in northern Bangladesh and by the demand for agricultural labourers and informal workers at the respective destinations. Fourth, persisting local patterns of social inequality shape both people's condition of food security and their decision to migrate for work or not. We conclude that, instead of climate change, social inequality and food insecurity as well as structural economic differences are the strongest drivers of migration inside Bangladesh. © 2013 © 2013 The Author(s). Published by Taylor & Francis."
"56429444900;7401797554;","Carbon conundrum, climate change, CO2 capture and consumptions",2014,"10.1016/j.jcou.2014.06.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912534268&doi=10.1016%2fj.jcou.2014.06.005&partnerID=40&md5=35bdb787936a39f1937dea1eec8febee","Carbon dioxide (CO2) emission and absorption components consist of biosphere, hydrosphere, atmosphere, lithosphere and fossil fuels. CO2 flow rates are governed by large scale fluid dynamic, thermodynamic and radio-active transfer processes. This results in dynamic flow of CO2 over land and oceans affecting regional climates. Convective uptake of CO2 from Asia flows at high altitude to America and then returns sweeping the local emissions back to Asia. In this process the bulk clouds of CO2 are absorbed in cold Pacific Ocean surface waters near America, causing regional cooling effect. Dynamic thermohaline circulations take away the dissolved carbon to warmer Asian waters maintaining the global carbon balance. Monsoon winds sweep Himalayan valley smoke and CO2 to Arabian Sea causing regional warming. Atmospheric CO2 and dissolved water carbon concentrations cause regional warming and cooling effects. Global carbon circuit may cause regional warming and cooling, irrespective of local emissions. In this study, nature's response to higher concentration of CO2 and its direct removal from atmosphere or sequestration at source is presented. This paper describes global carbon balance, regional climate changes and carbon fix alternatives by developing industrial use of CO2. ASHREA has envisioned 11 new future refrigerants for evacuated glass tube solar water heaters. Our simulation results show that supercritical CO2 is an optimum natural refrigerant in terms of thermodynamic and heat transfer properties in the range of -20 to 30 and 30-70 °C. We demonstrated the utilization of captured CO2 as mediating fluid for refrigeration and solar water heating applications. © 2014 Elsevier Ltd. All rights reserved."
"6603685334;6602844274;55495155800;6603585313;15058058100;35799889800;","The fast longwave and shortwave flux (FLASHFlux) data product: Single-scanner footprint fluxes",2014,"10.1175/JAMC-D-13-061.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897997889&doi=10.1175%2fJAMC-D-13-061.1&partnerID=40&md5=40122fa86fe18e9e4f74613f36c27bb6","The Clouds and the Earth's Radiant Energy Systems (CERES) project utilizes radiometric measurements taken aboard the Terra and Aqua spacecrafts to derive the world-class data products needed for climate research. Achieving the exceptional fidelity of the CERES data products, however, requires a considerable amount of processing to assure quality and to verify accuracy and precision, which results in the CERES data being released more than 6 months after the satellite observations. For most climate studies such delays are of little consequence; however, there are a significant number of near-real time uses for CERES data products. The Fast Longwave and Shortwave Radiative Flux (FLASHFlux) data product was therefore developed to provide a rapid release version of the CERES results, which could be made available to the research and applications communities within 1 week of the satellite observations by exchanging some accuracy for speed. FLASHFlux has both achieved this 1-week processing objective and demonstrated the ability to provide remarkably good agreement when compared with the CERES data products for both the instantaneous single-scanner footprint (SSF) fluxes and the time- and space-averaged (TISA) fluxes. This paper describes the methods used to expedite the production of the FLASHFlux SSF fluxes by utilizing data from the CERES and Moderate Resolution Imaging Spectroradiometer instruments, as well as other meteorological sources. This paper also reports on the validation of the FLASHFlux SSF results against ground-truth measurements and the intercomparison of FLASHFlux and CERES SSF results. A complementary paper will discuss the production and validation of the FLASHFlux TISA fluxes."
"18839257600;14036133800;7006134584;6603748992;57212850701;","Maritime climate influence on chaparral composition and diversity in the coast range of central California",2014,"10.1002/ece3.1211","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921971749&doi=10.1002%2fece3.1211&partnerID=40&md5=fcb21edc590cf131fea4624c2cad3f14","We investigated the hypothesis that maritime climatic factors associated with summer fog and low cloud stratus (summer marine layer) help explain the compositional diversity of chaparral in the coast range of central California. We randomly sampled chaparral species composition in 0.1-hectare plots along a coast-to-interior gradient. For each plot, climatic variables were estimated and soil samples were analyzed. We used Cluster Analysis and Principle Components Analysis to objectively categorize plots into climate zone groups. Climate variables, vegetation composition and various diversity measures were compared across climate zone groups using ANOVA and nonmetric multidimensional scaling. Differences in climatic variables that relate to summer moisture availability and winter freeze events explained the majority of variance in measured conditions and coincided with three chaparral assemblages: maritime (lowland coast where the summer marine layer was strongest), transition (upland coast with mild summer marine layer influence and greater winter precipitation), and interior sites that generally lacked late summer water availability from either source. Species turnover (β-diversity) was higher among maritime and transition sites than interior sites. Coastal chaparral differs from interior chaparral in having a higher obligate seeder to facultative seeder (resprouter) ratio and by being dominated by various Arctostaphylos species as opposed to the interior dominant, Adenostoma fasciculatum. The maritime climate influence along the California central coast is associated with patterns of woody plant composition and β-diversity among sites. Summer fog in coastal lowlands and higher winter precipitation in coastal uplands combine to lower late dry season water deficit in coastal chaparral and contribute to longer fire return intervals that are associated with obligate seeders and more local endemism. Soil nutrients are comparatively less important in explaining plant community composition, but heterogeneous azonal soils contribute to local endemism and promote isolated chaparral patches within the dominant forest vegetation along the coast. © 2014 The Authors."
"8562505600;7404589013;55960819100;55710865800;55994631200;55500618200;36807214200;57217416783;","Validation of China-wide interpolated daily climate variables from 1960 to 2011",2014,"10.1007/s00704-014-1140-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897124131&doi=10.1007%2fs00704-014-1140-0&partnerID=40&md5=cbd42214ce9d2e60119d2c16c4223d50","Temporally and spatially continuous meteorological variables are increasingly in demand to support many different types of applications related to climate studies. Using measurements from 600 climate stations, a thin-plate spline method was applied to generate daily gridded climate datasets for mean air temperature, maximum temperature, minimum temperature, relative humidity, sunshine duration, wind speed, atmospheric pressure, and precipitation over China for the period 1961–2011. A comprehensive evaluation of interpolated climate was conducted at 150 independent validation sites. The results showed superior performance for most of the estimated variables. Except for wind speed, determination coefficients (R2) varied from 0.65 to 0.90, and interpolations showed high consistency with observations. Most of the estimated climate variables showed relatively consistent accuracy among all seasons according to the root mean square error, R2, and relative predictive error. The interpolated data correctly predicted the occurrence of daily precipitation at validation sites with an accuracy of 83 %. Moreover, the interpolation data successfully explained the interannual variability trend for the eight meteorological variables at most validation sites. Consistent interannual variability trends were observed at 66–95 % of the sites for the eight meteorological variables. Accuracy in distinguishing extreme weather events differed substantially among the meteorological variables. The interpolated data identified extreme events for the three temperature variables, relative humidity, and sunshine duration with an accuracy ranging from 63 to 77 %. However, for wind speed, air pressure, and precipitation, the interpolation model correctly identified only 41, 48, and 58 % of extreme events, respectively. The validation indicates that the interpolations can be applied with high confidence for the three temperatures variables, as well as relative humidity and sunshine duration based on the performance of these variables in estimating daily variations, interannual variability, and extreme events. Although longitude, latitude, and elevation data are included in the model, additional information, such as topography and cloud cover, should be integrated into the interpolation algorithm to improve performance in estimating wind speed, atmospheric pressure, and precipitation. © 2014, Springer-Verlag Wien."
"7005578774;6602098362;6603752634;","Earth's energy imbalance",2014,"10.1175/JCLI-D-13-00294.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896700588&doi=10.1175%2fJCLI-D-13-00294.1&partnerID=40&md5=80524ce66cc3be01c9a6782adba99d56","Climate change from increased greenhouse gases arises from a global energy imbalance at the top of the atmosphere (TOA). TOA measurements of radiation from space can track changes over time but lack absolute accuracy. An inventory of energy storage changes shows that over 90% of the imbalance is manifested as a rise in ocean heat content (OHC). Data from the Ocean Reanalysis System, version 4 (ORAS4), and other OHC-estimated rates of change are used to compare with model-based estimates of TOA energy imbalance [from the Community Climate System Model, version 4 (CCSM4)] and with TOA satellite measurements for the year 2000 onward. Most ocean-only OHC analyses extend to only 700-m depth, have large discrepancies among the rates of change of OHC, and do not resolve interannual variability adequately to capture ENSO and volcanic eruption effects, all aspects that are improved with assimilation of multivariate data. ORAS4 rates of change of OHC quantitatively agree with the radiative forcing estimates of impacts of the three major volcanic eruptions since 1960 (Mt. Agung, 1963; El Chichón, 1982; and Mt. Pinatubo, 1991). The natural variability of the energy imbalance is substantial from month to month, associated with cloud and weather variations, and interannually mainly associated with ENSO, while the sun affects 15% of the climate change signal on decadal time scales. All estimates (OHC and TOA) show that over the past decade the energy imbalance ranges between about 0.5 and 1Wm-2. By using the full-depth ocean, there is a better overall accounting for energy, but discrepancies remain at interannual time scales between OHC- and TOA-based estimates, notably in 2008/09. © 2014 American Meteorological Society."
"45261451700;57213054025;","Multi-Physics ensemble prediction of tropical cyclone movement over Bay of Bengal",2014,"10.1007/s11069-013-0852-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891037778&doi=10.1007%2fs11069-013-0852-2&partnerID=40&md5=4035be3675b8ac1d1c457bd31632eded","Ensemble prediction methodology based on variations in physical process parameterizations in tropical cyclone track prediction has been assessed. Advanced Research Weather Research and Forecasting model with 30-km resolution was used to make 5-day simulation of the movement of Orissa super cyclone (1999), one of the most intense tropical cyclones over the North Indian Ocean. Altogether 36 ensemble members with all possible combinations of three cumulus convection, two planetary boundary layer and six cloud microphysics parameterization schemes were produced. A comparison of individual members indicated that Kain-Fritsch cumulus convection scheme, Mellor-Yamada-Janjic planetary boundary layer scheme and Purdue Lin cloud microphysics scheme showed better performance. The best possible ensemble formulation is identified based on SPREAD and root mean square error (RMSE). While the individual members had track errors ranging from 96-240 km at 24 h to 50-803 km at 120 h, most of the ensemble predictions show significant betterment with mean errors less than 130 km up to 120 h. The convection ensembles had large spread of the cluster, and boundary layer ensembles had significant error disparity, indicating their important roles in the movement of tropical cyclones. Six-member ensemble predictions with cloud microphysics schemes of LIN, WSM5, and WSM6 produce the best predictions with least of RMSE, and large SPREAD indicates the need for inclusion of all possible hydrometeors in the simulation and that six-member ensemble is sufficient to produce the best ensemble prediction of tropical cyclone tracks over Bay of Bengal. © 2013 Springer Science+Business Media Dordrecht."
"57212017731;57212026619;","Highly Biased Hygroscopicity Derived from Size-Resolved Cloud Condensation Nuclei Activation Ratios without Data Inversion",2014,"10.3878/j.issn.1674-2834.13.0116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057718900&doi=10.3878%2fj.issn.1674-2834.13.0116&partnerID=40&md5=af72b5680d70f54c2cf6aeddb371f222","The impact of aerosols on the climate and atmospheric environment depends on the water uptake ability of particles; namely, hygroscopic growth and activation into cloud condensation nuclei (CCN). The size-resolved activation ratios (SRAR), characterizing the fraction of aerosol particles that act as CCN at different particle sizes and supersaturations, can be measured using a combination of differential mobility analyzers (DMA) and particle counters. DMA-based measurements are influenced by the multiply charged particles and the quasi-mono-dispersed particles (effect of DMA transfer function) selected for each prescribed particle size. A theoretical study, assuming different particle number size distributions and hygroscopicity of aerosols, is performed to study the effects of the DMA transfer function and multiple charging on the measured SRAR and the derived hygroscopicity. Results show that the raw SRAR can be significantly skewed and hygroscopicity may be highly biased from the true value if the data are not corrected. The effect of the transfer function is relatively small and depends on the sample to sheath flow ratio. Multiply charged particles, however, can lead to large biases of the SRAR. These results emphasize that the inversion algorithm, which is used to correct the effects of the DMA transfer function and multiple charging, is necessary for accurate measurement of the SRAR. © 2014, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"55964332500;6701365566;56374719300;23988450000;34870189000;56374581100;","An overview of annual climatic changes in Romania: Trends in air temperature, precipitation, sunshine hours, cloud cover, relative humidity and wind speed during the 1961-2013 period",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908409613&partnerID=40&md5=3b61ac30a7ac8ffa40b7459e9974af71","Six meteorological variables from all available Romanian weather stations were tested for trends at annual scale over the 1961-2013 period. Changes in annual air temperature, precipitation, sunshine hours, nebulosity, relative humidity and wind speed were investigated. The Mann-Kendall nonparametric trend test was used in order to find statistically-significant trends, whilst the magnitude of trends was estimated using the Kendall-Theil method. The results point to significant climatic changes at annual scale in Romania. The most drastic change regards the air temperature, which is increasing at all stations. The number of sunshine hours follows a similar pattern, increasing at most stations - except in the mountainous regions of Meridional and Curvature Carpathians. The wind speed presents a significant decreasing signal at the majority of the locations, in agreement with the overall tendency of terrestrial stilling. The annual precipitation amount is rather stable, with increasing trends North-Western Romania and decreasing trends in the Danube Delta (South-East). Cloud cover is generally decreasing, and the relative humidity shows mixed trends. Our findings are in good agreement with previous studies on climatic variability in Romania."
"57217999869;7007014370;","Surface tensions of solutions containing dicarboxylic acid mixtures",2014,"10.1016/j.atmosenv.2014.02.049","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896824304&doi=10.1016%2fj.atmosenv.2014.02.049&partnerID=40&md5=68e5dd91a62107016305554f8e9531a5","Organic solutes tend to lower the surface tension of cloud condensation nuclei, allowing them to more readily activate. The surface tension of various dicarboxylic acid aerosol mixtures was measured at 20°C using the Wilhelmy plate method. At lower concentrations, the surface tension of a solution with equi-molar mixtures of dicarboxylic acids closely followed that of a solution with the most surface-active organic component alone. Measurements of surface tension for these mixtures were lower than predictions using Henning's model and the modified Szyszkowski equation, by ~1-2%. The calculated maximum surface excess (Γmax) and inverse Langmuir adsorption coefficient (β) from the modified Szyszkowski equation were both larger than measured values for 6 of the 7 mixtures tested. Accounting for the reduction in surface tension in the Köhler equation reduced the critical saturation ratio for these multi-component mixtures - changes were negligible for dry diameters of 0.1 and 0.5μm, but a reduction from 1.0068 to 1.0063 was seen for the 4-dicarboxylic acid mixture with a dry diameter of 0.05μm. © 2014 Elsevier Ltd."
"42961385000;56276813400;8915901800;6603335688;6603555567;26323963700;35365981100;56874843300;6507717732;","A 520 year record of summer sunshine for the eastern European Alps based on stable carbon isotopes in larch tree rings",2014,"10.1007/s00382-013-1864-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905085178&doi=10.1007%2fs00382-013-1864-z&partnerID=40&md5=f5c5e0bfd695d5a6959ba08c744f4f08","A 520-year stable carbon isotope chronology from tree ring cellulose in high altitude larch trees (Larix decidua Mill.), from the eastern European Alps, correlates more strongly with summer temperature than with summer sunshine hours. However, when instrumental records of temperature and sunshine diverge after AD1980, the tree ring time series does not follow warming summer temperatures but more closely tracks summer sunshine trends. When the tree ring stable carbon isotope record is used to reconstruct summer temperature the reconstruction is not robust. Reconstructed temperatures prior to the twentieth century are higher than regional instrumental records, and the evolution of temperature conflicts with other regional temperature reconstructions. It is concluded that sunshine is the dominant control on carbon isotope fractionation in these trees, via the influence of photosynthetic rate on the internal partial pressure of CO2, and that high summer (July-August) sunshine hours is a suitable target for climate reconstruction. We thus present the first reconstruction of summer sunshine for the eastern Alps and compare it with the regional temperature evolution. © 2013 Springer-Verlag Berlin Heidelberg."
"55916895500;52264136000;36680955200;7005450157;7006460453;7004325649;7404150761;","CLARREO approach for reference intercalibration of reflected solar sensors: On-orbit data matching and sampling",2014,"10.1109/TGRS.2014.2302397","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901818388&doi=10.1109%2fTGRS.2014.2302397&partnerID=40&md5=5c602893166fa5607d64adfd2e24917c","The implementation of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission was recommended by the National Research Council in 2007 to provide an on-orbit intercalibration standard with accuracy of 0.3% (k = 2) for relevant Earth observing sensors. The goal of reference intercalibration, as established in the Decadal Survey, is to enable rigorous high-accuracy observations of critical climate change parameters, including reflected broadband radiation [Clouds and Earth's Radiant Energy System (CERES)], cloud properties [Visible Infrared Imaging Radiometer Suite (VIIRS)], and changes in surface albedo, including snow and ice albedo feedback. In this paper, we describe the CLARREO approach for performing intercalibration on orbit in the reflected solar (RS) wavelength domain. It is based on providing highly accurate spectral reflectance and reflected radiance measurements from the CLARREO Reflected Solar Spectrometer (RSS) to establish an on-orbit reference for existing sensors, namely, CERES and VIIRS on Joint Polar Satellite System satellites, Advanced Very High Resolution Radiometer and follow-on imagers on MetOp, Landsat imagers, and imagers on geostationary platforms. One of two fundamental CLARREO mission goals is to provide sufficient sampling of high-accuracy observations that are matched in time, space, and viewing angles with measurements made by existing instruments, to a degree that overcomes the random error sources from imperfect data matching and instrument noise. The data matching is achieved through CLARREO RSS pointing operations on orbit that align its line of sight with the intercalibrated sensor. These operations must be planned in advance; therefore, intercalibration events must be predicted by orbital modeling. If two competing opportunities are identified, one target sensor must be given priority over the other. The intercalibration method is to monitor changes in targeted sensor response function parameters: effective offset, gain, nonlinearity, optics spectral response, and sensitivity to polarization. In this paper, we use existing satellite data and orbital simulation methods to determine mission requirements for CLARREO, its instrument pointing ability, methodology, and needed intercalibration sampling and data matching for accurate intercalibration of RS radiation sensors on orbit. We conclude that with the CLARREO RSS in a polar 90 ^{\circ} inclination orbit at a 609-km altitude, estimated intercalibration sampling will limit the uncertainty contribution from data matching noise to 0.3% (k = 2) over the climate autocorrelation time period. The developed orbital modeling and intercalibration event prediction will serve as a framework for future mission operations. © 1980-2012 IEEE."
"55571119000;7102495313;","The diurnal temperature range in the CMIP5 models",2014,"10.1007/s00382-014-2144-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939896407&doi=10.1007%2fs00382-014-2144-2&partnerID=40&md5=5477c3f1a2b12bc8475021b16cfa9151","This paper analyzes the diurnal temperature range (DTR) over land in simulations of the recent past and in future projections by 20 models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5). The annually averaged DTR is evaluated for the present-day climate using two gridded datasets (HadGHCND and CRU). The DTR varies substantially between different CMIP5 models, particularly in the subtropics, and is generally underestimated. In future projections of the high emission scenario RCP8.5, the models disagree on both the sign and the magnitude of the change in DTR. Still, a majority of the models project a globally averaged reduction in the DTR, with an increase over Europe, a decrease over the Sahara desert and a substantial decrease in DTR at high latitudes in winter. The general DTR reduction is partly linked to the enhancement of the downwelling clear sky longwave radiation due to greenhouse gases. At high latitudes in winter, the decrease in DTR seems to be enforced by an increase in cloudiness, but in most other regions counteracted by decreases in cloud fraction. Changes in the hydrological cycle and in the clear sky shortwave radiation also impact the DTR. The DTR integrates many processes and neither the model differences in the DTR nor in the change in DTR can be attributed to a single parameter. Which variables that impact the model discrepancies vary both regionally and seasonally. However, clouds seem to matter in most regions and seasons and the evaporative fraction is important in summer. © 2014, Springer-Verlag Berlin Heidelberg."
"24485235300;55511366500;36173886200;7102196528;6602293483;","On the influence of physical parameterisations and domains configuration in the simulation of an extreme precipitation event",2014,"10.1016/j.dynatmoce.2014.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906672113&doi=10.1016%2fj.dynatmoce.2014.08.001&partnerID=40&md5=35edded6f4d31e3dcbcf3ba84ee1ea24","At daybreak and late morning of 18th of February 2008 Lisbon and Setúbal have been under the influence of a heavy rain event. This period was simulated by two operational WRF model set ups running for Portugal at the University of Aveiro in two different horizontal and vertical resolution and physical parameterisations. These two model configurations were tested for the described precipitation event in terms of microphysics and cumulus parameterisation and also in their domain configuration setup. Results suggest that the combination of cumulus and microphysics schemes is very important in the prediction of the amounts of precipitation. A small change in domain resolution has more impact in the spatial patterns of precipitation rather than in the amounts predicted. © 2014 Elsevier B.V."
"36060938100;55802246600;7402989545;55522498000;","Parameter tuning and calibration of RegCM3 with MIT-emanuel cumulus parameterization scheme over CORDEX East Asia domain",2014,"10.1175/JCLI-D-14-00229.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907833472&doi=10.1175%2fJCLI-D-14-00229.1&partnerID=40&md5=aaec232ef4ea7d20d709af1e5abb3477","In this study, the authors calibrated the performance of the Regional Climate Model, version 3 (RegCM3), with the Massachusetts Institute of Technology (MIT)-Emanuel cumulus parameterization scheme over the Coordinated Regional Climate Downscaling Experiment (CORDEX) East Asia domain by tuning seven selected parameters based on the multiple very fast simulated annealing (MVFSA) approach. The seven parameters were selected based on previous studies using RegCM3 with the MIT-Emanuel convection scheme. The results show the simulated spatial pattern of rainfall, and the probability density function distribution of daily rainfall rates is significantly improved in the optimal simulation. Sensitivity analysis suggests that the parameter relative humidity criteria (RHC) has the largest effect on the model results. Followed by an increase of RHC, an increase of total rainfall is found over the northern equatorial western Pacific, mainly contributed by the increase of explicit rainfall. The increases of the convergence of low-level water vapor transport and the associated increases in cloud water favor the increase of explicit rainfall. The identified optimal parameters constrained by total rainfall have positive effects on the low-level circulation and surface air temperature. Furthermore, the optimized parameters based on the chosen extreme case are transferable to a normal case and the model's new version with a mixed convection scheme. © 2014 American Meteorological Society."
"55535166800;56493740900;7403531523;55942502100;7406061582;7102651635;7406741310;8719703500;7006783796;55455053000;","Unfiltering earth radiation budget experiment (ERBE) scanner radiances using the CERES algorithm and its evaluation with nonscanner observations",2014,"10.1175/JTECH-D-13-00072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898917684&doi=10.1175%2fJTECH-D-13-00072.1&partnerID=40&md5=ee3538c813821b7ce4ef3979c6a33dad","The NOAA-9 Earth Radiation Budget Experiment (ERBE) scanner measured broadband shortwave, longwave, and total radiances from February 1985 through January 1987. These scanner radiances are reprocessed using the more recent Clouds and the Earth's Radiant Energy System (CERES) unfiltering algorithm. The scene information, including cloud properties, required for reprocessing is derived using Advanced Very High Resolution Radiometer (AVHRR) data on board NOAA-9, while no imager data were used in the original ERBE unfiltering. The reprocessing increases the NOAA-9 ERBE scanner unfiltered longwave radiances by 1.4%-2.0% during daytime and 0.2%-0.3% during nighttime relative to those derived from the ERBE unfiltering algorithm. Similarly, the scanner unfiltered shortwave radiances increase by ̃1% for clear ocean and land and decrease for all-sky ocean, land, and snow/ice by ̃1%. The resulting NOAA-9 ERBE scanner unfiltered radiances are then compared with NOAA-9 nonscanner irradiances by integrating the ERBE scanner radiance over the nonscanner field of view. The comparison indicates that the integrated scanner radiances are larger by 0.9% for shortwave and 0.7% smaller for longwave.A sensitivity study shows that the one-standard-deviation uncertainties in the agreement are ±2.5%, ±1.2%, and ±1.8% for the shortwave, nighttime longwave, and daytime longwave irradiances, respectively. The NOAA-9 and ERBS nonscanner irradiances are also compared using 2 years of data. The comparison indicates that the NOAA-9 nonscanner shortwave, nighttime longwave, and daytime longwave irradiances are 0.3% larger, 0.6% smaller, and 0.4% larger, respectively. The longer observational record provided by the ERBS nonscanner plays a critical role in tying the CERES-like NOAA-9ERBEscanner dataset from the mid-1980s to the present-day CERES scanner data record. © 2014 American Meteorological Society."
"55235064100;55560463400;35722808700;55446625600;35192263300;35721814200;","Recent climate changes over the Tibetan Plateau and their impacts on energy and water cycle: A review",2014,"10.1016/j.gloplacha.2013.12.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890489538&doi=10.1016%2fj.gloplacha.2013.12.001&partnerID=40&md5=5c24d61d6684f00ab26686ea7a52ac22","The Tibetan Plateau (TP) exerts strong thermal forcing on the atmosphere over Asian monsoon region and supplies water resources to adjacent river basins. Recently, the Plateau experienced evident climate changes, which have changed atmospheric and hydrological cycles and thus reshaped the local environment. This study reviewed recent research progress in the climate changes and explored their impacts on the Plateau energy and water cycle, based on which a conceptual model to synthesize these changes was proposed and urgent issues to be explored were summarized. The TP has experienced an overall surface air warming and moistening, solar dimming, and wind stilling since the beginning of the 1980s. The surface warming depends on elevation and its horizontal pattern is consistent with the one of the glacier change. Accompanying the warming was air moistening, and both facilitated the trigger of more deep-clouds, which resulted in solar dimming. Surface wind speed declined from the 1970s, as a result of atmospheric circulation adjustment caused by the differential surface warming between the Asian high-latitude and low-latitude. The climate changes had weakened the thermal forcing over the TP. The warming and wind stilling lowered the Bowen ratio and led to less surface sensible heating. Atmospheric radiative cooling was enhanced, mainly by outgoing longwave emission from the warming planetary system and slightly by solar radiation reflection. Both processes contributed to the thermal forcing weakening over the Plateau. The water cycle was also altered by the climate changes. The wind stilling may have weakened water vapor exchange between the Asia monsoon region and the Plateau and thus led to less precipitation in the monsoon-impacted southern and eastern Plateau, but the warming enhanced land evaporation. Their overlap resulted in runoff reduction in the southern and eastern Plateau regions. By contrast, more convective precipitation over the central TP was triggered under the warmer and moister condition and yielded more runoff; meanwhile, the solar dimming weakened lake evaporation. The two together with enhanced glacier melts contributed to the lake expansion in the central TP. © 2013 Elsevier B.V."
"55622642400;36634859600;6603581315;","Analysis of low-frequency precipitation variability in CMIP5 historical simulations for southwestern North America",2014,"10.1175/JCLI-D-13-00317.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896982861&doi=10.1175%2fJCLI-D-13-00317.1&partnerID=40&md5=c80866ff564c6dc0e31cc0f4dfb6be93","Drier future conditions are projected for the arid southwest of North America, increasing the chances of the region experiencing severe and prolonged drought. To examine the mechanisms of decadal variability, 47 global climate model historical simulations performed for phase 5 of the Coupled Model Intercomparison Project (CMIP5) were assessed. On average, the CMIP5 models have higher climatological precipitation over the past century in southwestern North America than current instrumental or reanalysis products. The timing of the winter peak in climatological precipitation over California and Nevada is accurately represented. Models with resolutions coarser than 2° show a larger spread in the location and strength of the North American monsoon ridge and subsequent summer precipitation, in comparison with the higher-resolution models. Less than 20% of decadal variability in wintertime precipitation over California is associated with North Pacific sea surface temperature anomalies, a larger proportion than is associated with the tropical forcing but not sufficient for making decadal drought predictions. North American monsoon precipitation is strongly associated with local land temperatures on interannual-to-decadal time scales attributable to evaporative cooling and radiation changes driven by varying cloud cover. Soil moisture in Texas and Oklahoma in April is shown to be positively correlated with monsoon precipitation for the following summer, indicating a potential source of nonoceanic interseasonal persistence in southwestern North American hydroclimate. To make meaningful decadal predictions in the future, it is likely that forecasting will move away fromsea surface temperature-driven anomaly patterns, and focus on land surface processes, which can allow persistence of precipitation anomalies via feedbacks. © 2014 American Meteorological Society."
"35350641800;56019178600;7202157381;7006069664;36801320800;7402866430;36867063100;","Sensitivity Studies of Convective Schemes and Model Resolutions in Simulations of Wintertime Circulation and Precipitation over the Western Himalayas",2014,"10.1007/s00024-014-0935-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921978457&doi=10.1007%2fs00024-014-0935-3&partnerID=40&md5=a04e29e8533377e3cd082152fbe6cbc2","The present study examines the performance of convective parameterization schemes at two different horizontal resolutions (90 and 30 km) in simulating winter (December–February; DJF) circulation and associated precipitation over the Western Himalayas using the regional climate model RegCM4. The model integrations are carried out in a one-way nested mode for three distinct precipitation years (excess, normal and deficit) using four combinations of cumulus schemes. The National Center for Environment Prediction—Department of Energy Reanalysis-2 project utilized gridded data, observed precipitation data from the India Meteorological Department and station data from the Snow and Avalanche Study Establishment were used to evaluate model performance. The seasonal mean circulation patterns and precipitation distribution are well demonstrated by all of the cumulus convection schemes. However, model performance varies using different schemes. Statistical analysis confirms that the root mean square error is reduced by about 2–3 times and the correlation coefficient (CC) increases in the fine resolution (30 km) simulations compared to coarse resolution (90 km) simulations. A statistically significant CC (at a 10 % significance level) is found only in the fine resolution simulations. The Grell cumulus model with a Fritsch–Chappell closure (Grell-FC) is better at simulating seasonal mean patterns and inter-annual variability of two contrasting winter seasons than the other scheme combinations. © 2014, Springer Basel."
"55630942000;","The use of aircraft for meteorological research in the United Kingdom",2014,"10.1002/met.1448","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892472781&doi=10.1002%2fmet.1448&partnerID=40&md5=6697657f48ed6d3f4be36478002f1711","Atmospheric observations from aircraft have played an important role in meteorological research for many years; this paper presents an overview of meteorological research done with research aircraft in the United Kingdom. Key developments from throughout the history of meteorological research flying in the United Kingdom are presented, along with highlights of UK atmospheric research flying done in the last decade using the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft. The work presented includes research into thermodynamics, cloud processes, atmospheric aerosol, radiative transfer and atmospheric chemistry. Research aircraft provide a unique platform for the observation of atmospheric processes, allowing targeted measurement of specific parameters at a range of altitudes throughout the atmosphere. These measurements have improved greatly the understanding of the Earth's atmosphere, and the impact of these measurements has been seen through improvements in the representation of physical processes within numerical weather prediction (NWP) and climate models. Research aircraft have also been used extensively for the calibration and validation of remote sensing measurements, providing a unique test-bed for satellite observations. This research has led to improved use of satellite observations that have enhanced greatly how the atmosphere is viewed. Many developments in atmospheric research would not have been possible without the use of aircraft measurements, and these measurements will continue to play a key role in future developments of meteorological observation and prediction, as the complexity and resolution of weather and climate models increases. © 2014 Royal Meteorological Society."
"24329947300;7005135473;","Assessment of smoke shortwave radiative forcing using empirical angular distribution models",2014,"10.1016/j.rse.2013.08.034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884681637&doi=10.1016%2fj.rse.2013.08.034&partnerID=40&md5=af1bc1f1772f041d244aa15897015d73","The Clouds and the Earth's Radiant Energy System (CERES) data has been used by several studies to calculate the top of atmosphere (TOA) shortwave aerosol radiative forcing (SWARF) of biomass burning aerosols over land. However, the current CERES angular distribution models that are used to convert measured TOA radiances to fluxes are not characterized by aerosols. Using our newly developed empirical angular models for smoke aerosols we calculate the SWARF over South America for eight years (2000-2008) during the biomass burning season. Our results indicate that when compared to our new angular distribution model-derived values, the instantaneous SWARF is underestimated by the CERES data by nearly 3.3Wm-2. Our studies indicate that it is feasible to develop angular models using empirical methods that can then be used to reduce uncertainties in aerosol radiative forcing calculations. More importantly, empirically-based methods for calculating radiative forcing can serve as a benchmark for modeling studies. © 2013 Elsevier Inc."
"26643615000;6603431534;34881780600;7405489798;7402480218;36243762400;36634069800;7404633868;6701754792;","Stratiform and convective precipitation observed by multiple radars during the DYNAMO/AMIE experiment",2014,"10.1175/JAMC-D-13-0311.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910672368&doi=10.1175%2fJAMC-D-13-0311.1&partnerID=40&md5=1a6ec966b6ebd31bb5d487e7ef967f57","In this study, methods of convective/stratiform precipitation classification and surface rain-rate estimation based on the Atmospheric Radiation Measurement Program (ARM) cloud radar measurements were developed and evaluated. Simultaneous and collocated observations of the Ka-band ARM zenith radar (KAZR), two scanning precipitation radars [NCAR S-band/Ka-band Dual Polarization, Dual Wavelength Doppler Radar (S-PolKa) and Texas A&amp;M University Shared Mobile Atmospheric Research and Teaching Radar (SMART-R)], and surface precipitation during the Dynamics of the Madden-Julian Oscillation/ARM MJOInvestigation Experiment (DYNAMO/AMIE) field campaign were used. The motivation of this study is to apply the unique long-term ARM cloud radar observations without accompanying precipitation radars to the study of cloud life cycle and precipitation features under different weather and climate regimes. The resulting convective/stratiform classification from KAZR was evaluated against precipitation radars. Precipitation occurrence and classified convective/stratiform rain fractions from KAZR compared favorably to the collocated SMART-R and S-PolKa observations. Both KAZR and S-PolKa radars observed about 5% precipitation occurrence. The convective (stratiform) precipitation fraction is about 18% (82%). Collocated disdrometer observations of two days showed an increased number concentration of small and large raindrops in convective rain relative to dominant small raindrops in stratiform rain. The composite distributions of KAZR reflectivity and Doppler velocity also showed distinct structures for convective and stratiform rain. These evidences indicate that the method produces physically consistent results for the two types of rain. A new KAZR-based, two-parameter [the gradient of accumulative radar reflectivity Ze (GAZ) below 1 km and near-surface Ze] rain-rate estimation procedure was developed for both convective and stratiform rain. This estimate was compared with the exponential Z-R (reflectivity-rain rate) relation. The relative difference between the estimated and surface-measured rainfall rates showed that the two-parameter relation can improve rainfall estimation relative to the Z-R relation. © 2014 American Meteorological Society."
"55521274000;55904369100;55901447400;6602375690;","Glacier mass changes on the Tibetan Plateau 2003-2009 derived from ICESat laser altimetry measurements",2014,"10.1088/1748-9326/9/1/014009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928096185&doi=10.1088%2f1748-9326%2f9%2f1%2f014009&partnerID=40&md5=3519ddfe1428e43a2564a39f960212de","Glacier mass changes are a valuable indicator of climate variability and monsoon oscillation on the underexplored Tibetan Plateau. In this study data from the Ice Cloud and Elevation Satellite (ICESat) is employed to estimate elevation and mass changes of glaciers on the Tibetan Plateau between 2003 and 2009. In order to get a representative sample size of ICESat measurements, glaciers on the Tibetan Plateau were grouped into eight climatically homogeneous sub-regions. Most negative mass budgets of - 0.77 ± 0.35 m w.e. a -1 were found for the Qilian Mountains and eastern Kunlun Mountains while a mass gain of + 0.37 ± 0.25 m w.e. a-1 was found in the westerly-dominated north-central part of the Tibetan Plateau. A total annual mass budget of - 15.6 ± 10.1 Gt a-1 was estimated for the eight sub-regions sufficiently covered by ICESat data which represents ∼80% of the glacier area on the Tibetan Plateau. 13.9 ± 8.9 Gt a-1 (or 0.04 ± 0.02 mm a-1 sea-level equivalent) of the total mass budget contributed 'directly' to the global sea-level rise while 1.7 ± 1.9 Gt a-1 drained into endorheic basins on the plateau. © 2014 IOP Publishing Ltd."
"26026749200;12042086300;7404016992;8665263500;35431772700;7005140533;18633549200;","Satellite-based precipitation estimation and its application for streamflow prediction over mountainous western U.S. basins",2014,"10.1175/JAMC-D-14-0056.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928314792&doi=10.1175%2fJAMC-D-14-0056.1&partnerID=40&md5=96aa811a63db371a46ad3f20bdf74b43","Recognizing the importance and challenges inherent to the remote sensing of precipitation in mountainous areas, this study investigates the performance of the commonly used satellite-based high-resolution precipitation products (HRPPs) over several basins in the mountainous western United States. Five HRPPs [Tropical Rainfall Measuring Mission 3B42 and 3B42-RT algorithms, the Climate Prediction Center morphing technique (CMORPH), Precipitation Estimation from Remotely Sensed Imagery Using Artificial Neural Networks (PERSIANN), and the PERSIANN Cloud Classification System (PERSIANN-CCS)] are analyzed in the present work using ground gauge, gauge-adjusted radar, and CloudSat precipitation products. Using ground observation of precipitation and streamflow, the skill of HRPPs and the resulting streamflow simulations from the Variable Infiltration Capacity hydrological model are cross-compared. HRPPs often capture major precipitation events but seldom capture the observed magnitude of precipitation over the studied region and period (2003-09). Bias adjustment is found to be effective in enhancing the HRPPs and resulting streamflow simulations. However, if not bias adjusted using gauges, errors are typically large as in the lower-level precipitation inputs to HRPPs. The results using collocated Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) and CloudSat precipitation data show that missing data, often over frozen land, and limitations in retrieving precipitation from systems that lack frozen hydrometeors contribute to the observed microwave-based precipitation errors transferred to HRPPs. Over frozen land, precipitation retrievals from infrared sensors and microwave sounders show some skill in capturing the observed precipitation climatology maps. However, infrared techniques often show poor detection skill, and microwave sounding in dry atmosphere remains challenging. By recognizing the sources of precipitation error and in light of the operation of the Global Precipitation Measurement mission, further opportunity for enhancing the current status of precipitation retrievals and the hydrology of cold and mountainous regions becomes available. © 2014 American Meteorological Society."
"55715297700;54958151600;55706213200;","Variations of the tropopause over different latitude bands observed using COSMIC radio occultation Bending Angles",2014,"10.1109/TGRS.2013.2259632","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896291074&doi=10.1109%2fTGRS.2013.2259632&partnerID=40&md5=9eb85c79959cdae1eee302240fbe9738","The tropopause is a transition layer between the troposphere and the stratosphere. The exchange of air, water vapor, trace gases, and energy between the troposphere and the stratosphere occurs in this layer. Accurate and continuous observations of the tropopause on a global scale are crucial for monitoring stratosphere-Troposphere exchange and understanding the properties of atmosphere in the upper troposphere and lower stratosphere. In this paper, the tropopause heights are identified from Global Positioning System radio occultation (RO) bending angle profiles using the covariance transform method. Temporal variations of the tropopause parameters, including the tropopause height, temperature, and pressure at different latitude bands are investigated using the RO observations from the Constellation Observing System for Meteorology, Ionosphere and Climate mission during the period from January 2007 to December 2011. We divide the Earth into 18 nonoverlapping latitude bands 10\circ wide. Monthly averages of the tropopause parameters weighted by area are calculated at each latitude band and the temporal variations of these tropopause parameters are analyzed. The results indicate that the latitudinal variation patterns of the tropopause parameters in the Northern Hemisphere are different than those in the Southern Hemisphere. The relationship between the variations of different tropopause parameters is studied. The results show that the variation of the tropopause temperature and pressure is negatively correlated with that of the tropopause height in most of the latitude bands. In addition, the trend of the variation of the tropopause height in each latitude band is calculated with the median of pairwise slopes regression method. We find that the overall trend in the tropopause height varies in different latitude bands. The global average tropopause height decreases © 1980-2012 IEEE."
"6603463248;","A strategy for verifying near-convection-resolving model forecasts at observing sites",2014,"10.1175/WAF-D-12-00075.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921631514&doi=10.1175%2fWAF-D-12-00075.1&partnerID=40&md5=837d5467a66ba38c72b1419ab7819007","Routine verification of deterministic numerical weather prediction (NWP) forecasts fromthe convectionpermitting 4-km (UK4) and near-convection-resolving 1.5-km (UKV) configurations of the Met Office Unified Model (MetUM) has shown that it is hard to consistently demonstrate an improvement in skill from the higher-resolution model, even though subjective comparison suggests that it performs better. In this paper the use of conventional metrics and precise matching (through extracting the nearest grid point to an observing site) of the forecast to conventional synoptic observations in space and time is replaced with the use of inherently probabilistic metrics such as the Brier score, ranked probability, and continuous ranked probability scores applied to neighborhoods of forecast grid points. Three neighborhood sizes were used: ~4, ~12, and ~25 km, which match the sizes of the grid elements currently used operationally. Six surface variables were considered: 2-m temperature, 10-m wind speed, total cloud amount (TCA), cloud-base height (CBH), visibility, and hourly precipitation. Any neighborhood has a positive impact on skill, either in reducing the skill deficit or enhancing the skillfulness over and above the single grid point. This is true for all variables. An optimal neighborhood appears to depend on the variable and threshold. Adopting this probabilistic approach enables easy comparison to future near-convection-resolving ensemble prediction systems (EPS) and also enables the optimization of postprocessing to maximize the skill of forecast products."
"36754104400;","Entropic balance theory and variational field Lagrangian formalism: Tornadogenesis",2014,"10.1175/JAS-D-13-0211.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901791558&doi=10.1175%2fJAS-D-13-0211.1&partnerID=40&md5=9bba518e3f3b17fe836f282bb2edd0aa","The entropic balance theory has been applied with outstanding results to explain many important aspects of tornadic phenomena. The theory was originally developed in variational (probabilistic) field Lagrangian formalism, or in short, variational formalism, with Lagrangian density and action appropriate for supercell-storm and tornadic phenomena. The variational formalism is broadly used in in modern physics, not only in classical mechanics, with Lagrangian density and action designed for each physical problem properly. The Clebsch transformation (equation) was derived in the classical variational formalism but has not been used because of the unobservable and nonmeteorological Lagrange multiplier. The entropic balance condition is thus developed from the Clebsch transformation, changing the unobservable nonmeteorological Lagrange multiplier to observable meteorological rotational flow velocity with entropy and making it applicable to tornadic phenomena. Theoretical details of the entropic balance are presented such as the entropic right-hand rule, entropic dipole, source and sink, overshooting mechanism of hydrometeors against westerlies and the existence of single and multiple vortices and their relation to tornadogenesis. These results are in reasonable agreement with the many observations and data analysis publications. The Clebsch transformation and entropic balance are the new balance conditions, different from the known other balance conditions such as hydrostatic, (quasi-)geostrophic, cyclostrophic, Boussinesq, and anelastic balance. The variations in calculus of variations and in the classical variational formalism are hypothetical. However, this article suggests that the hypothetical variations could be physical, relating to quantum variations and their interaction with the classical systems. © 2014 American Meteorological Society."
"10243650000;7201485519;55686667100;56575686800;7007021059;36722732500;","Importance of instantaneous radiative forcing for rapid tropospheric adjustment",2014,"10.1007/s00382-013-1955-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906725328&doi=10.1007%2fs00382-013-1955-x&partnerID=40&md5=ba887e7cf85a593766964c321ce61fca","To better understand CFMIP/CMIP inter-model differences in rapid low cloud responses to CO2 increases and their associated effective radiative forcings, we examined the tropospheric adjustment of the lower tropospheric stability (LTS) in three general circulation models (GCMs): HadGEM2-A, MIROC3.2 medres, and MIROC5. MIROC3.2 medres showed a reduction in LTS over the sub-tropical ocean, in contrast to the other two models. This reduction was consistent with a temperature decrease in the mid-troposphere. The temperature decrease was mainly driven by instantaneous radiative forcing (RF) caused by an increase in CO2. Reductions in radiative and latent heating, due to clouds, and in adiabatic and advective heating, also contribute to the temperature decrease. The instantaneous RF in the mid-troposphere in MIROC3.2 medres is inconsistent with the results of line-by-line (LBL) calculations, and thus it is considered questionable. These results illustrate the importance of evaluating the vertical profile of instantaneous RF with LBL calculations; improved future model performance in this regard should help to increase our confidence in the tropospheric adjustment in GCMs. © 2013 Springer-Verlag Berlin Heidelberg."
"55349777400;57200534631;36071585400;","Seasonal effects of impervious surface estimation in subtropical monsoon regions",2014,"10.1080/17538947.2013.781241","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902969401&doi=10.1080%2f17538947.2013.781241&partnerID=40&md5=260fb966234165c65dad86f593539d28","Accurate impervious surface estimation (ISE) is challenging due to the diversity of land covers and the vegetation phenology and climate. This study investigates the variation of impervious surfaces estimated from different seasons of satellite images and the seasonal sensitivity of different methods. Four Landsat ETM+images of four different seasons and two popular methods (i.e. artificial neural network (ANN) and support vector machine (SVM)) are employed to estimate the impervious surface on the pixel level. Results indicate that winter (dry season) is the best season to estimate impervious surface even though plants are not in their growing season. Less cloud and less variable source areas (VSA) (seasonal water body) become the major advantages of winter for the ISE, as cloud is easily confused with bright impervious surfaces, and water in VSA is confused with dark impervious surfaces due to their similar spectral reflectance. For the seasonal sensitivity of methods, ANN appears more stable as its accuracy varied less than that obtained with SVM. However, both the methods showed a general consistency of the seasonal changes of the accuracy, indicating that winter time is the best season for impervious surfaces estimation with optical satellite images in subtropical monsoon regions. © 2013 © 2013 Taylor & Francis."
"56082097700;6603866486;26534695200;26321297900;36626171700;7004543198;6602529747;7006372295;","Microbial community composition explains soil respiration responses to changing carbon inputs along an Andes-to-Amazon elevation gradient",2014,"10.1111/1365-2745.12247","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903178944&doi=10.1111%2f1365-2745.12247&partnerID=40&md5=9dd350516a6fdeee9ae0422e6db300f4","Summary: The Andes are predicted to warm by 3-5 °C this century with the potential to alter the processes regulating carbon (C) cycling in these tropical forest soils. This rapid warming is expected to stimulate soil microbial respiration and change plant species distributions, thereby affecting the quantity and quality of C inputs to the soil and influencing the quantity of soil-derived CO2 released to the atmosphere. We studied tropical lowland, premontane and montane forest soils taken from along a 3200-m elevation gradient located in south-east Andean Peru. We determined how soil microbial communities and abiotic soil properties differed with elevation. We then examined how these differences in microbial composition and soil abiotic properties affected soil C-cycling processes, by amending soils with C substrates varying in complexity and measuring soil heterotrophic respiration (RH). Our results show that there were consistent patterns of change in soil biotic and abiotic properties with elevation. Microbial biomass and the abundance of fungi relative to bacteria increased significantly with elevation, and these differences in microbial community composition were strongly correlated with greater soil C content and C:N (nitrogen) ratios. We also found that RH increased with added C substrate quality and quantity and was positively related to microbial biomass and fungal abundance. Statistical modelling revealed that RH responses to changing C inputs were best predicted by soil pH and microbial community composition, with the abundance of fungi relative to bacteria, and abundance of gram-positive relative to gram-negative bacteria explaining much of the model variance. Synthesis. Our results show that the relative abundance of microbial functional groups is an important determinant of RH responses to changing C inputs along an extensive tropical elevation gradient in Andean Peru. Although we do not make an experimental test of the effects of climate change on soil, these results challenge the assumption that different soil microbial communities will be 'functionally equivalent' as climate change progresses, and they emphasize the need for better ecological metrics of soil microbial communities to help predict C cycle responses to climate change in tropical biomes. Using a 3200-m tropical forest elevation gradient in south-east Andean Peru, we demonstrated that the relative abundance of microbial functional groups is an important determinant of heterotrophic respiration responses to changing above-ground carbon inputs. These findings emphasize that better ecological metrics of soil microbial communities are needed to help predict carbon cycle responses to climate change in tropical biomes. © 2014 NERC Centre for Ecology and Hydrology. Journal of Ecology published by John Wiley &amp; Sons Ltd on behalf of British Ecological Society."
"22982141200;7006550959;7201920155;57203321797;55919261400;6602164207;57207388638;","Observed surface wind speed in the Tibetan Plateau since 1980 and its physical causes",2014,"10.1002/joc.3807","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899479799&doi=10.1002%2fjoc.3807&partnerID=40&md5=8219601c5a4c24d3f3157fd2b9f20f06","Climate warming on the Tibetan Plateau (TP) potentially influences many climate parameters other than temperature including wind speed, cloudiness and precipitation. Temporal trends of surface wind speed at 71 stations above 2000 m above sea level in the TP are examined during 1980-2005. To uncover causes of observed trends in wind speed, relationships with surface temperature, a TP index and sunshine duration are also analysed. The TP index is calculated as the accumulated 500 hPa geopotential height above 5000 m over the region of 30°N-40°N, 75°E-105°E from NCEP/NCAR reanalysis. The annual mean wind speed patterns during 1980-2005 are similar to those in different seasons, with higher wind speeds in the northern and western parts of the TP. Highest mean wind speeds occur in spring and lowest in autumn. During 1980-2005, annual and seasonal mean wind speeds show statistically decreasing trends at most stations. The mean trend magnitude for annual mean wind speed is -0.24ms-1decade-1, with the maximum decline in spring (-0.29ms-1decade-1) and minimum in autumn (-0.19ms-1decade-1). Both annually and in different seasons, wind speed is significantly negatively correlated with mean temperature, minimum temperature, maximum temperature, and the TP index, but significantly positively correlated with sunshine duration. Wind speed trends fail to show a simple elevation dependency but speeds are positively correlated with meridional surface temperature/pressure gradients. Warming in the TP may weaken the latitudinal gradients of both regional temperature and surface pressure, thus altering the regional atmospheric circulation and accounting in part for the observed decline of wind speed. © 2013 Royal Meteorological Society."
"6602118778;16745169400;24168358300;","Upland glaciation in tropical pangaea: Geologic evidence and implications for late paleozoic climate modeling",2014,"10.1086/675255","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897423974&doi=10.1086%2f675255&partnerID=40&md5=221cd7c8cbc9a51f5131a6c3087523d0","The late Paleozoic archives a prolonged icehouse, long recognized by means of Gondwanan continental glaciation. In contrast, the paleotropics have long been considered warm. Here we present the hypothesis of upland glaciation in the Ancestral Rocky Mountains (ARM) of western equatorial Pangaea, a region located within 11° of the paleoequator. The data to support this hypothesis include (a) a Permo-Pennsylvanian valley with glacial attributes and diamictite exhibiting rare striated clasts; (b) coarse-grained lacustrine strata onlapping the valley and preserving lonestones in Gilbert-type deltaic deposits proximally, along with (c) coarse-grained fluvial siliciclastic strata with microstriae and evidence for widespread flood deposition; (d) polygonally cracked paleosurfaces inferred to reflect frozen ground; and (e) voluminous paleoloess. Tropical glaciation occurs today at altitudes &gt;4500 m and descended to 2100-3000 m at the last glacial maximum (LGM). However, ARM depositional systems terminating at sea level and emanating from inferred ice-contact facies indicate that ice-terminus elevations were lower (&lt;1200-1600 m) than those of the LGM. If valid, tropical temperatures were ~15°C cooler than today during intervals recording hypothesized tropical glacial conditions. This implies at least episodic cold within western tropical Pangaea, which conflicts with inferences from oxygen isotope paleothermometry. Furthermore, climate models for the late Paleozoic cannot reproduce tropical upland glaciation except under prohibitively low Pco2, implying the need to consider other forcings, such as cloud and aerosol behavior. Upland glaciation in the Permo-Pennsylvanian tropics was potentially widespread, given the global orogenesis accompanying Pangaean assembly. However, testing this hypothesis requires identification of pro- and periglacial indicators, owing to widespread erosion of upland (glaciated) regions. Midlatitude glaciation in both hemispheres also was likely, challenging climate models and paleogeographic consensus for this period. © 2014 by The University of Chicago. All rights reserved."
"8934032500;57209596880;7404587604;","Simulation of the annual and diurnal cycles of rainfall over South Africa by a regional climate model",2014,"10.1007/s00382-013-2046-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891695317&doi=10.1007%2fs00382-013-2046-8&partnerID=40&md5=e485222ab9127ce08b5d59509b932a3a","The capability of a current state-of-the-art regional climate model for simulating the diurnal and annual cycles of rainfall over a complex subtropical region is documented here. Hourly rainfall is simulated over Southern Africa for 1998–2006 by the non-hydrostatic model weather research and forecasting (WRF), and compared to a network of 103 stations covering South Africa. We used five simulations, four of which consist of different parameterizations for atmospheric convection at a 0.5 × 0.5° resolution, performed to test the physic-dependency of the results. The fifth experiment uses explicit convection over tropical South Africa at a 1/30° resolution. WRF simulates realistic mean rainfall fields, albeit wet biases over tropical Africa. The model mean biases are strongly modulated by the convective scheme used for the simulations. The annual cycle of rainfall is well simulated over South Africa, mostly influenced by tropical summer rainfall except in the Western Cape region experiencing winter rainfall. The diurnal cycle shows a timing bias, with atmospheric convection occurring too early in the afternoon, and causing too abundant rainfall. This result, particularly true in summer over the northeastern part of the country, is weakly physic-dependent. Cloud-resolving simulations do not clearly reduce the diurnal cycle biases. In the end, the rainfall overestimations appear to be mostly imputable to the afternoon hours of the austral summer rainy season, i.e., the periods during which convective activity is intense over the region. © 2014, Springer-Verlag Berlin Heidelberg."
"7401796996;55172258800;8629713500;55831774800;35209683700;57203326554;7403508241;7402480218;","Critical mechanisms for the formation of extreme arctic sea-ice extent in the summers of 2007 and 1996",2014,"10.1007/s00382-013-1920-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906091466&doi=10.1007%2fs00382-013-1920-8&partnerID=40&md5=984683fc5cb627200857df7a8b6de634","Along with significant changes in the Arctic climate system, the largest year-to-year variation in sea-ice extent (SIE) has occurred in the Laptev, East Siberian, and Chukchi seas (defined here as the area of focus, AOF), among which the two highly contrasting extreme events were observed in the summers of 2007 and 1996 during the period 1979-2012. Although most efforts have been devoted to understanding the 2007 low, a contrasting high September SIE in 1996 might share some related but opposing forcing mechanisms. In this study, we investigate the mechanisms for the formation of these two extremes and quantitatively estimate the cloud-radiation-water vapor feedback to the sea-ice-concentration (SIC) variation utilizing satellite-observed sea-ice products and the NASA MERRA reanalysis. The low SIE in 2007 was associated with a persistent anticyclone over the Beaufort Sea coupled with low pressure over Eurasia, which induced anomalous southerly winds. Ample warm and moist air from the North Pacific was transported to the AOF and resulted in positive anomalies of cloud fraction (CF), precipitable water vapor (PWV), surface LWnet (down-up), total surface energy and temperature. In contrast, the high SIE event in 1996 was associated with a persistent low pressure over the central Arctic coupled with high pressure along the Eastern Arctic coasts, which generated anomalous northerly winds and resulted in negative anomalies of above mentioned atmospheric parameters. In addition to their immediate impacts on sea ice reduction, CF, PWV and radiation can interplay to lead to a positive feedback loop among them, which plays a critical role in reinforcing sea ice to a great low value in 2007. During the summer of 2007, the minimum SIC is 31 % below the climatic mean, while the maximum CF, LWnet and PWV can be up to 15 %, 20 Wm-2, and 4 kg m-3 above. The high anti-correlations (-0.79, -0.61, -0.61) between the SIC and CF, PWV, and LWnet indicate that CF, PWV and LW radiation are indeed having significant impacts on the SIC variation. A new record low occurred in the summer of 2012 was mainly triggered by a super storm over the central Arctic Ocean in early August that caused substantial mechanical ice deformation on top of the long-term thinning of an Arctic ice pack that had become more dominated by seasonal ice. © 2013 The Author(s)."
"24822250800;36523706800;7402543833;","Retrieving daily global solar radiation from routine climate variables",2014,"10.1007/s00704-013-0979-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899898455&doi=10.1007%2fs00704-013-0979-9&partnerID=40&md5=a085f167f24a6bbebee94b5d4d5047c3","Solar radiation is an important variable for studies related to solar energy applications, meteorology, climatology, hydrology, and agricultural meteorology. However, solar radiation is not routinely measured at meteorological stations; therefore, it is often required to estimate it using other techniques such as retrieving from satellite data or estimating using other geophysical variables. Over the years, many models have been developed to estimate solar radiation from other geophysical variables such as temperature, rainfall, and sunshine duration. The aim of this study was to evaluate six of these models using data measured at four independent worldwide networks. The dataset included 13 stations from Australia, 25 stations from Germany, 12 stations from Saudi Arabia, and 48 stations from the USA. The models require either sunshine duration hours (Ångstrom) or daily range of air temperature (Bristow and Campbell, Donatelli and Bellocchi, Donatelli and Campbell, Hargreaves, and Hargreaves and Samani) as input. According to the statistical parameters, Ångstrom and Bristow and Campbell indicated a better performance than the other models. The bias and root mean square error for the Ångstrom model were less than 0.25 MJ m2 day-1 and 2.25 MJ m2 day-1, respectively, and the correlation coefficient was always greater than 95 %. Statistical analysis using Student's t test indicated that the residuals for Ångstrom, Bristow and Campbell, Hargreaves, and Hargreaves and Samani are not statistically significant at the 5 % level. In other words, the estimated values by these models are statistically consistent with the measured data. Overall, given the simplicity and performance, the Ångstrom model is the best choice for estimating solar radiation when sunshine duration measurements are available; otherwise, Bristow and Campbell can be used to estimate solar radiation using daily range of air temperature. © 2013 Springer-Verlag Wien."
"55506372600;6603795286;8633783900;","The multidecadal atlantic SST-sahel rainfall teleconnection in CMIP5 simulations",2014,"10.1175/JCLI-D-13-00242.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890451545&doi=10.1175%2fJCLI-D-13-00242.1&partnerID=40&md5=88631576d35d12cdb9cf918fdc590d3c","This study uses models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to evaluate and investigate Sahel rainfall multidecadal variability and teleconnections with global sea surface temperatures (SSTs). Multidecadal variability is lower than observed in all historical simulations evaluated. Focus is on teleconnections with North Atlantic SST [Atlantic multidecadal variability (AMV)] as it is more successfully simulated than the Indian Ocean teleconnection. To investigate why some models successfully simulated this teleconnection and others did not, despite having similarly large AMV, two groups of models were selected. Models with large AMV were highlighted as good (or poor) by their ability to simulate relatively high (low) Sahel multidecadal variability and have significant (not significant) correlation between multidecadal Sahel rainfall and an AMV index. Poor models fail to capture the teleconnection between the AMV and Sahel rainfall because the spatial distribution of SST multidecadal variability across the North Atlantic is incorrect. A lack of SST signal in the tropical North Atlantic and Mediterranean reduces the interhemispheric SST gradient and, through circulation changes, the rainfall variability in the Sahel. This pattern was also evident in the control simulations, where SST and Sahel rainfall variability were significantly weaker than historical simulations. Errors in SST variability were suggested to result from a combination of weak wind-evaporation-SST feedbacks, poorly simulated cloud amounts and feedbacks in the stratocumulus regions of the eastern Atlantic, dust-SST-rainfall feedbacks, and sulfate aerosol interactions with clouds. By understanding the deficits and successes of CMIP5 historical simulations, future projections and decadal hindcasts can be examined with additional confidence. © 2014 American Meteorological Society."
"7101689290;7402778680;","Precipitation isotopes link regional climate patterns to water supply in a tropical mountain forest, eastern Puerto Rico",2014,"10.1002/2013WR014413","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902367884&doi=10.1002%2f2013WR014413&partnerID=40&md5=98a89154cb18946277782dd2dc007f9a","Like many mountainous areas in the tropics, watersheds in the Luquillo Mountains of eastern Puerto Rico have abundant rainfall and stream discharge and provide much of the water supply for the densely populated metropolitan areas nearby. Projected changes in regional temperature and atmospheric dynamics as a result of global warming suggest that water availability will be affected by changes in rainfall patterns. It is essential to understand the relative importance of different weather systems to water supply to determine how changes in rainfall patterns, interacting with geology and vegetation, will affect the water balance. To help determine the links between climate and water availability, stable isotope signatures of precipitation from different weather systems were established to identify those that are most important in maintaining streamflow and groundwater recharge. Precipitation stable isotope values in the Luquillo Mountains had a large range, from fog/cloud water with δ2H, δ18O values as high as +12 ‰, -0.73 ‰ to tropical storm rain with values as low as -127 ‰, -16.8 ‰. Temporal isotope values exhibit a reverse seasonality from those observed in higher latitude continental watersheds, with higher isotopic values in the winter and lower values in the summer. Despite the higher volume of convective and low-pressure system rainfall, stable isotope analyses indicated that under the current rainfall regime, frequent trade -wind orographic showers contribute much of the groundwater recharge and stream base flow. Analysis of rain events using 20 years of 15 -minute resolution data at a mountain station (643 m) showed an increasing trend in rainfall amount, in agreement with increased precipitable water in the atmosphere, but differing from climate model projections of drying in the region. The mean intensity of rain events also showed an increasing trend. The determination of recharge sources from stable isotope tracers indicates that water supply will be affected if regional atmospheric dynamics change trade- wind orographic rainfall patterns in the Caribbean. Key Points Stable isotopes correlate weather patterns to recharge source Frequent, low-intensity orographic precipitation provides much of water supply Precipitation observations are evaluated considering regional climate change © 2014. American Geophysical Union. All Rights Reserved."
"56486349300;55588578400;47561454500;55483744300;56486753800;47561000100;56486433600;56486240500;","Track of super typhoon haiyan predicted by a typhoon model for the South China Sea",2014,"10.1007/s13351-014-3269-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921329329&doi=10.1007%2fs13351-014-3269-2&partnerID=40&md5=821ff61b36342f369bb393dbee6fdb6b","Super Typhoon Haiyan was the most notable typhoon in 2013. In this study, results from the operational prediction of Haiyan by a tropical regional typhoon model for the South China Sea are analyzed. It is shown that the model has successfully reproduced Haiyan’s rapid passage through the Philippines and its northward deflection after its second landfall in Vietnam. However, the predicted intensity of Haiyan is weaker than the observed. An analysis of higher-resolution model simulations indicates that the storm is characterized by an upper-level warm core during its mature stage and a deep layer of easterly flow. Sensitivity experiments are conducted to study the impact of certain physical processes such as the interaction between stratus and cumulus clouds on the improvement of the typhoon intensity forecast. It is found that appropriate boundary layer and cumulus convective parameterizations, and orographic gravity-wave parameterization, as well as improved initial conditions and increased horizontal grid resolution, all help to improve the intensity forecast of Haiyan. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2014."
"55877246300;7004114481;","The effect of aerosols on long wave radiation and global warming",2014,"10.1016/j.atmosres.2013.08.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885199131&doi=10.1016%2fj.atmosres.2013.08.009&partnerID=40&md5=0c31ed6cf3ae5cdb2a83d94a9d6d6676","The effect of aerosols on long wave (LW) radiation was studied based on narrowband LW calculations in a reference mid-latitude summer atmosphere with and without aerosols. Aerosols were added to the narrowband LW scheme based on their typical schematic observed spectral and vertical behaviour over European land areas. This was found to agree also with the spectral aerosol data from the Lan Zhou University Semi-Arid Climate Observatory and Laboratory measurement stations in the north-western China.A volcanic stratospheric aerosol load was found to induce local LW warming and a stronger column ""greenhouse effect"" than a doubled CO2 concentration. A heavy near-surface aerosol load was found to increase the downwelling LW radiation to the surface and to reduce the outgoing LW radiation, acting very much like a thin low cloud in increasing the LW greenhouse effect of the atmosphere. The short wave reflection of white aerosol has, however, stronger impact in general, but the aerosol LW greenhouse effect is non-negligible under heavy aerosol loads. © 2013 Elsevier B.V."
"7004299063;","Stratospheric aerosol geoengineering",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937430699&partnerID=40&md5=04ed754b40afdde485ecfd27f2f2ec2c","In response to global warming, one suggested geoengineering response involves creating a cloud of particles in the stratosphere to reflect some sunlight and cool Earth. While volcanic eruptions show that stratospheric aerosols cool the planet, the volcano analog also warns against geoengineering because of responses such as ozone depletion, regional hydrologic responses, whitening of the skies, reduction of solar power, and impacts of diffuse radiation. No technology to conduct geoengineering now exists, but using airplanes or tethered balloons to put sulfur gases into the stratosphere may be feasible. Nevertheless, it may be very difficult to create stratospheric sulfate particles with a desirable size distribution. The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, has found that insolation reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. Temperature changes would also not be uniform; the tropics would cool, but high latitudes would warm, with continuing, but reduced sea ice and ice sheet melting. Temperature extremes would still increase, but not as much as without geoengineering. If geoengineering were halted all at once, there would be rapid temperature and precipitation increases at 5-10 times the rates from gradual global warming. The prospect of geoengineering working may reduce the current drive toward reducing greenhouse gas emissions, and there are concerns about commercial or military control. Because geoengineering cannot safely address climate change, global efforts to reduce greenhouse gas emissions and to adapt are crucial to address anthropogenic global warming. © The Royal Society of Chemistry 2014."
"56316680600;35581315600;56317120900;","Radiometric quality and performance of TIMESAT for smoothing moderate resolution imaging spectroradiometer enhanced vegetation index time series from western Bahia State, Brazil",2014,"10.1117/1.JRS.8.083580","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905750183&doi=10.1117%2f1.JRS.8.083580&partnerID=40&md5=ddc9804fbbd3a70895f1636c62efa0fc","The launch of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor aboard the Terra and Aqua platforms in 1999 and 2002, respectively, with temporal resolutions of 1 to 2 days opened the possibility of using a longtime series of satellite images to map land use and land cover classes from different regions of the Earth, to study vegetation phenology, and to monitor regional and global climate change, among other applications. The main objectives of this study were twofold: to analyze the radiometric quality of the time series of enhanced vegetation index (EVI) products derived from the Terra MODIS sensor in western Bahia State, Brazil, and to identify the most appropriate filter to smooth MODIS EVI time series of the study area among those available in the public domain, the TIMESAT algorithm. The 2000 to 2011 time period was considered (a total of 276 scenes). The radiometric quality was analyzed based on the pixel reliability data set available in the MOD13Q1 product. The performances of the three smoothing filters available within TIMESAT (double logistic, Savitzky-Golay, and asymmetric Gaussian) were analyzed using the Graybill's F test and Willmott statistics. Five percent of the MODIS pixels from the study area were cloud-affected, almost all of which were from the rainy season. The double logistic filter presented the best performance. © 2014 SPIE."
"57200130699;8266754800;23104422600;8680306800;7101869647;","Tropical connections to climatic change in the extratropical Southern Hemisphere: The role of atlantic SST trends",2014,"10.1175/JCLI-D-13-00615.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903398792&doi=10.1175%2fJCLI-D-13-00615.1&partnerID=40&md5=db0eb0a469601f1e6cc07e51dace4509","The austral spring relationships between sea surface temperature (SST) trends and the Southern Hemisphere (SH) extratropical atmospheric circulation are investigated using an atmospheric general circulation model (AGCM). A suite of simulations are analyzed wherein the AGCM is forced by underlying SST conditions in which recent trends are constrained to individual ocean basins (Pacific, Indian, and Atlantic), allowing the impact of each region to be assessed in isolation. When forced with observed global SST, the model broadly replicates the spatial pattern of extratropical SHgeopotential height trends seen in reanalyses. However, when forcing by each ocean basin separately, similar structures arise only when Atlantic SST trends are included. It is further shown that teleconnections from the Atlantic are associated with perturbations to the zonal Walker circulation and the corresponding intensification of the local Hadley cell, the impact of which results in the development of atmospheric Rossby waves. Thus, increased Rossby waves, forced by positive Atlantic SST trends, may have played a role in driving geopotential height trends in the SH extratropics. Furthermore, these atmospheric circulation changes promote warming throughout the Antarctic Peninsula and much of West Antarctica, with a pattern that closely matches recent observational records. This suggests that Atlantic SST trends, via a teleconnection to the SH extratropics, may have contributed to springtime climatic change in the SH extratropics over the past three decades. © 2014 American Meteorological Society."
"49862613500;36752370400;26642900400;","Is Eurasian snow cover in October a reliable statistical predictor for the wintertime climate on the Iberian Peninsula?",2014,"10.1002/joc.3788","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897912072&doi=10.1002%2fjoc.3788&partnerID=40&md5=b946753ad9f4e204f285bf6ce8153425","In this study, the recently found lead-lag relationship between Eurasian snow cover increase in October and wintertime precipitation totals on the Iberian Peninsula is re-visited and generalized to a broad range of atmospheric variables on the synoptic and local scale. To this aim, a robust (resistant to outliers) method for calculating the index value for Eurasian snow cover increase in October is proposed. This 'Robust Snow Advance Index' (RSAI) is positively correlated with the wintertime (DJF) frequency of cyclonic and westerly flow circulation types over the Iberian Peninsula, while the corresponding relationship with anticyclonic and easterly flow types is negative. For both cases, an explained variance of approximately 60% indicates a strong and highly significant statistical link on the synoptic scale. Consistent with these findings, it is then shown that the lead-lag relationship equally holds for the DJF-mean conditions of (1) precipitation amount, (2) diurnal temperature range, (3) sun hours, (4) cloud cover and (5) wind speed on the local scale. To assess if these target variables can be skillfully hindcast, simple linear regression is applied as a statistical forecasting method, using the October RSAI as the only predictor variable. One-year out cross-validation yields locally significant hindcast correlations of up to approximately 0.8, obtaining field significance for any of the five target variables mentioned above. The validity for a wide range of atmospheric variables and the consistency of the local- and synoptic-scale results affirm the question posed in the title. © 2013 Royal Meteorological Society."
"7202501354;6603406338;","The simulated atmospheric response to expansion of the Arctic boreal forest biome",2014,"10.1007/s00382-013-1746-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891624782&doi=10.1007%2fs00382-013-1746-4&partnerID=40&md5=7e04abdbde2a3a1e4ac1a51cd2285b7b","Over the last century, the Arctic has warmed at twice the rate of the planet as a whole. Observational evidence indicates that this rapid warming is affecting the tundra and boreal forest biomes by changing their structure and geographic distribution. A global climate model (GCM) was used to explore the atmospheric response to boreal forest expansion by applying a one-grid cell shift of the forest into tundra. This subtle shift is meant to represent the expansion that would occur this century rather than more extreme scenarios predicted by dynamic vegetation models. Results show that this shift causes an average annual warming of 0.3 °C over the region because of a reduction in the surface albedo and an increase in net radiation. A warming of ~1.0 °C occurs in spring when the forest masks the higher albedo snow-covered surface and results in snowmelt and a reduction in cloud cover. Results fail to show a larger-scale dynamical response although some warming of the lower and mid troposphere occurs in July. No changes were found in the position or strength of the Arctic frontal zone as some studies have indicated will occur with a shift in the boreal forest-tundra boundary. These findings suggest that coupled model simulations that predict larger changes in vegetation distribution are likely overemphasizing the amount of Arctic warming that will occur this century. These findings also indicate that a realistic dynamical response to subtle land cover change might not be correctly simulated by GCMs run at coarse spatial resolutions. © 2013 Springer-Verlag Berlin Heidelberg."
"55710586900;8336962200;37026834700;6602273139;56352637700;35461255500;8758100000;57199017174;37026834700;","SOSAA — a new model to simulate the concentrations of organic vapours, sulphuric acid and aerosols inside the ABL — Part 2: Aerosol dynamics and one case study at a boreal forest site",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906978293&partnerID=40&md5=4ac2a4960f28ab0c4ba80079e7fd13a7","Natural and anthropogenic aerosols may have a great impact on climate as they directly interact with solar radiation and indirectly affect the Earth’s radiation balance and precipitation by modifying clouds. In order to quantify the direct and indirect effects, it is essential to understand the complex processes that connect aerosol particles to cloud droplets. Modern measurement techniques are able to detect particle sizes down to 1 nm in diameter, from ground to the stratosphere. However, the data are not sufficient in order to fully understand the processes. Here we demonstrate how the newly developed one-dimensional column model SOSAA was used to investigate the complex processes of aerosols at a boreal forest site for a six-month period during the spring and summer of 2010. Two nucleation mechanisms (kinetic and organic) were tested in this study, and both mechanisms produced a good prediction of the particle number concentrations in spring. However, overestimation of the particle number concentration in summer by the organic mechanism suggests that the OH oxidation products from monoterpenes may not be the essential compounds in atmospheric nucleation. In general, SOSAA was correct in predicting new particle formation events for 35% of the time and partly correct for 45% of the time. © 2014 Finnish Environment Institute. All rights reserved."
"24464437300;12765807300;57210198318;7003627515;","Surface energy balance in the ablation zone of Langfjordjøkelen, an arctic, maritime glacier in northern Norway",2014,"10.3189/2014JoG13J063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897133042&doi=10.3189%2f2014JoG13J063&partnerID=40&md5=d2ea9888deb6a6170833d1bad36b0ac2","Glaciers in northern and southern Norway are subject to different daily and seasonal cycles of incoming solar radiation, which is presumably reflected in the importance of net solar radiation in their surface energy balance. We present a 3 year continuous record from an automatic weather station in the ablation zone of the ice cap Langfjordjøkelen, one of the most northerly glaciers of mainland Norway. Despite its location at 70° N, Langfjordjøkelen was found to have a maritime climate, with an annual mean air temperature of -1.08°C, frequent cloud cover and end-of-winter snow depths over 3m in all three years. The main melt season was May-October, but occasional melt events occurred on warm, cloudy winter days. Net solar and longwave radiation together accounted for 58% of the melt energy, with a positive contribution by net longwave radiation (7%). The sensible and latent heat fluxes supplied the remainder of the melt energy. Cloud optical thickness over Langfjordjøkelen was larger than on two glaciers in southern Norway, especially in the summer months. This resulted in a smaller contribution of net solar radiation to surface melt on Langfjordjøkelen; the effect of the higher latitude on net solar radiation was found to be small. © 2014 Publishing Technology."
"7102591209;9044746800;24168416900;6603735878;6602350870;6602087140;57214307732;7004028051;","A self-consistent scattering model for cirrus. II: The high and low frequencies",2014,"10.1002/qj.2193","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899474616&doi=10.1002%2fqj.2193&partnerID=40&md5=a05e1e1b246e2802a1bcf563c3ab93d1","The predictive quality of an ensemble model of cirrus ice crystals to model passive and active measurements of ice cloud, from the ultraviolet (UV) to the microwave, is tested. The ensemble model predicts m ∝ D2, where D is the maximum dimension of the ice crystal, and m is its mass. This predicted m-D relationship is applied to a moment estimation parametrization of the particle size distribution (PSD), to estimate the PSD shape, given ice water content (IWC) and in-cloud temperature. The same microphysics is applied across the electromagnetic spectrum to model UV, infrared, microwave and radar observations. The short-wave measurements consist of airborne UV backscatter lidar (light detection and ranging) estimates of the volume extinction coefficient, total solar optical depth, and space-based multi-directional spherical albedo retrievals, at 0.865 μm, between the scattering angles 85° and 125°. The airborne long-wave measurements consist of high-resolution interferometer upwelling brightness temperatures, obtained between the wavelengths of about 3.45 μm and 4.1 μm, and 8.0 μm to 12.0 μm. The low-frequency measurements consist of ground-based Chilbolton 35 GHz radar reflectivity measurements and space-based upwelling 190 GHz brightness temperature measurements. The predictive quality of the ensemble model is demonstrated to be generally within the experimental uncertainty of the lidar backscatter estimates of the volume extinction coefficient and total solar optical depth. The ensemble model prediction of the high-resolution brightness temperature measurements is generally within ±2 K and ±1 K at solar and infrared wavelengths, respectively. The 35 GHz radar reflectivity and 190 GHz brightness temperatures are generally simulated to within ±2 dBZe, and ±2 K, respectively. The directional spherical albedo observations suggest that the scattering phase function of the most randomized ensemble model gives the best fit to the measurements (generally within ±3%). This article demonstrates that the ensemble model, assuming the same microphysics, is physically consistent across the electromagnetic spectrum. © 2013 Royal Meteorological Society."
"56070346000;8888621200;35224480500;18437757900;","Investigating the sensitivity of surface-level nitrate seasonality in Antarctica to primary sources using a global model",2014,"10.1016/j.atmosenv.2014.03.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896279613&doi=10.1016%2fj.atmosenv.2014.03.003&partnerID=40&md5=6f84ffb890dc171e1174754157a4bfca","Determining the sources of total nitrate (TNIT≡NO3-+HNO3) reaching Antarctica is a long-standing challenge. Here we analyze the monthly sensitivity of surface-level TNIT in Antarctica to primary sources using a global 3-D chemical transport model, GEOS-Chem, and its adjoint. Modeled seasonal variation of TNIT concentrations shows good agreement with several measurement studies, given that the lack of post-depositional processing in the model leads to an expected underestimate of maximum values in November through January. Remote NOx sources have the greatest impact May-July, during when the model background concentrations are sensitive to NOx emissions from fossil fuel combustion, soil, and lightning originating from 25°S to 65°S. In this season, NOx is transported to Antarctica as TNIT, which is formed above continental source regions at an altitude of 5-11km. In other seasons, more NOx is transported as a reservoir species (e.g., peroxyacetyl nitrate, PAN) through the free troposphere, transforming into TNIT within a cone of influence that extends to 35°S and above 4km altitude. Photolysis of PAN over Antarctica is the main driver of modeled NOx seasonality. Stratospheric production and loss of tracers are relatively unimportant in monthly sensitivities in GEOS-Chem, driving only a few percent of surface level variability of TNIT. A small peak concentration in August is captured by the model, although some measured values in August fall outside the range of simulated concentrations. Modifications to the model to represent sedimentation of polar stratospheric clouds (PSCs) lead to increased surface level August TNIT concentrations. However, this simple representation does not explicitly account for PSC particle deposition or disappearance of the tropopause in the middle of winter, and thus the influence of stratospheric nitrate sources estimated in this study is likely a lower bound. © 2014 Elsevier Ltd."
"6603377859;36552332100;7004370563;10540631700;","Rain drop size distribution over the Tibetan Plateau",2014,"10.1016/j.atmosres.2014.07.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905215816&doi=10.1016%2fj.atmosres.2014.07.005&partnerID=40&md5=4de93cb0a5c144ef8ce051f5a94f807d","Over the last decade, interest in measuring and studying rain drop size distribution (DSD) has grown due to applications in cloud physics, in calibration of space-borne and ground-based microwave active precipitation sensors and in soil science and agriculture. Such studies are of particular interest over remote areas, where knowledge of clouds and precipitation processes is lacking while the need for remote sensing based precipitation estimates is growing in global water cycle and climate trend studies.Disdrometric data over the Tibetan Plateau were collected during the 2010 monsoon season using the Pludix disdrometer, a vertically pointing, continuous wave, X-band, low power radar. Three experimental sites were set up at altitudes greater than 3300. m a.s.l., and a total number of 37 rain events were measured at two of the three sites.The analysis focuses on 2-min and 5-min DSD data for selected convective and stratiform events and the results are discussed in comparison with previous studies performed at lower altitudes. The time evolution of DSDs shows a regular behavior with respect to rain intensity: they change concavity and show a breakup signature in cases of the highest rain rates. Collisional breakup takes place for relatively lower rain rates, compared to the low-altitude measurements, and the size of the largest drops is also relatively smaller. An overall rainfall characteristic evaluation is also performed on the whole data set, deriving DSD integral parameters in order to compute a relationship between reflectivity and rain rate, resulting in A=. 214 (. A=. 247) and b=. 1.25 (. b=. 1.15) for convective (stratiform) precipitation. © 2014 Elsevier B.V."
"55748076700;6603265463;7005659017;","Lidar profiling of aerosol scavenging parameters at a tropical station, Pune, India",2014,"10.1080/01431161.2014.882527","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896870838&doi=10.1080%2f01431161.2014.882527&partnerID=40&md5=239353cd4f8da941493b58a85af54373","In this study, we deal with observations of aerosol column content (height integration of vertical distribution of aerosol number density) that have been carried out using an Ar+ lidar for three different measurement cycles (each cycle consisting of three experimental days associated with non-rain, rain, and non-rain, respectively) of weekly spaced observations for pre-monsoon (March/April 1994), monsoon (September 1991), and post-monsoon (October 1998). Based on these observed profiles of aerosol number concentration on rainy days with respect to those on non-rainy days, vertical distributions of scavenging collection efficiencies (SCEs) are computed and discussed in this article. The SCE is found to decrease from 0.3 to 0.01 between the heights, 100 and 800 m for thunderstorm rain in April 1994, and during monsoon, it increases from 0.1 to 0.7. In the October 1998 episode, SCE was found to increase initially from 0.35 to 0.75 for heights between 40 and 200 m and thereafter decrease to 0.35 in the height interval of 200-800 m. For the rainfall intensity increase from 1 to 10 mm hour-1, the corresponding scavenging coefficient (SC) for atmospheric layer 50-100 m varies from 4 × 10-6 to 4 × 10-5 s-1 for thunderstorm in April 1994 and between 5 × 10-6 and 5 × 10-5 s-1 in October 1998, respectively. During monsoon, these values vary from 3 × 10-5 to 5 × 10-4 s-1. They lie in the range of those observed in the earlier field studies. The results are found useful to establish links between aerosols and cloud properties, and the influence of such interactions on weather and climate. © 2014 Taylor &amp; Francis."
"55597088322;7401604360;55199339300;57212479545;16302232000;55555283600;","Evaluation of WRF Parameterizations for dynamical downscaling in the Canary Islands",2014,"10.1175/JCLI-D-13-00458.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904480040&doi=10.1175%2fJCLI-D-13-00458.1&partnerID=40&md5=9dd6d6792c9cfddae8df24af5fed8b33","The ability of the Weather Research and Forecasting (WRF) Model simulations to perform climate regionalization studies in an orographically complex region, the Canary Islands, is analyzed. Six different 5-yr simulations were carried out to investigate the sensitivity to several parameterization schemes and to uncertainties in sea surface temperature (SST). The simulated maximum and minimum temperatures, together with the daily rainfall, were compared with observational data. To take into account the climatic differences in this archipelago, observational sites were grouped using a geographical regionalization based on principal component analysis and a clustering technique to group the stations according to their climatic characteristics The analysis showed that both the microphysics and the boundary layer schemes have a large impact on the simulated precipitation. However, the largest differences were observed when the cumulus parameterization, in the coarser domains, was changed. An analysis of the vertical profiles of the simulated hydrometeors was performed to study the differences revealed by the different simulations. Although the cumulus scheme was not applied in the innermost domain, the total amount of water available in the atmospheric column is modified. Moreover, an average increase of 0.7°C in SST, estimated from phase 5 of the Coupled Model Intercomparison Project (CMIP5) variability, produces changes of the same order as those those obtained with different parameterizations. Temperatures are similarly simulated by the different configurations, except for the case in which an SST increment was introduced. Two configurations (CTRL and LSM-PX) were able to correctly reproduce the studied variables in the Canary Islands, improving the Interim ECMWF Re-Analysis (ERA-Interim) data and showing their abilities for regional-scale climate studies in this archipelago. © 2014 American Meteorological Society."
"16041047000;57210230785;7003465505;7003627515;","Greenland surface mass balance as simulated by the community earth system model. part II: Twenty-first-century changes",2014,"10.1175/JCLI-D-12-00588.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892455947&doi=10.1175%2fJCLI-D-12-00588.1&partnerID=40&md5=9e5d153a07c220485f47225884fcaf37","This study presents the first twenty-first-century projections of surface mass balance (SMB) changes for the Greenland Ice Sheet (GIS) with the Community Earth System Model (CESM), which includes a new ice sheet component. For glaciated surfaces, CESM includes a sophisticated calculation of energy fluxes, surface albedo, and snowpack hydrology (melt, percolation, refreezing, etc.). To efficiently resolve the high SMB gradients at the ice sheet margins and provide surface forcing at the scale needed by ice sheet models, the SMB is calculated at multiple elevations and interpolated to a finer 5-km ice sheet grid. During a twenty-firstcentury simulation driven by representative concentration pathway 8.5 (RCP8.5) forcing, the SMB decreases from 372±100 Gt yr-1 in 1980-99 to -78 ±143 Gt yr-1 in 2080-99. The 2080-99 near-surface temperatures over the GIS increase by 4.7K (annual mean) with respect to 1980-99, only 1.3 times the global increase (+3.7 K). Snowfall increases by 18%, while surface melt doubles. The ablation area increases from 9% of the GIS in 1980-99 to 28% in 2080-99. Over the ablation areas, summer downward longwave radiation and turbulent fluxes increase, while incoming shortwave radiation decreases owing to increased cloud cover. The reduction in GIS-averaged July albedo from 0.78 in 1980-99 to 0.75 in 2080-99 increases the absorbed solar radiation in this month by 12%. Summer warming is strongest in the north and east of Greenland owing to reduced sea ice cover. In the ablation area, summer temperature increases are smaller due to frequent periods of surface melt. © 2014 American Meteorological Society."
"12244212300;56424145700;8718425100;55029613600;8930075400;","Upper tropospheric warming intensifies sea surface warming",2014,"10.1007/s00382-013-1928-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906095652&doi=10.1007%2fs00382-013-1928-0&partnerID=40&md5=319c88887b12cfe3baa8c43725116337","One of the robust features in the future projections made by the state-of-the-art climate models is that the highest warming rate occurs in the upper-troposphere especially in the tropics. It has been suggested that more warming in the upper-troposphere than the lower-troposphere should exert a dampening effect on the sea surface warming associated with the negative lapse rate feedback. This study, however, demonstrates that the tropical upper-tropospheric warming (UTW) tends to trap more moisture in the lower troposphere and weaken the surface wind speed, both contributing to reduce the upward surface latent heat flux so as to trigger the initial sea surface warming. We refer to this as a 'top-down' warming mechanism. The rise of tropospheric moisture together with the positive water vapor feedback enhance the downward longwave radiation to the surface and facilitate strengthening the initial sea surface warming. Meanwhile, the rise of sea surface temperature (SST) can feed back to intensify the initial UTW through the moist adiabatic adjustment, completing a positive UTW-SST warming feedback. The proposed 'top-down' warming mechanism and the associated positive UTW-SST warming feedback together affect the surface global warming rate and also have important implications for understanding the past and future changes of precipitation, clouds and atmospheric circulations. © 2013 Springer-Verlag Berlin Heidelberg."
"7202928871;7003298801;56344001900;","A comparison of atmospheric reanalysis products for the Arctic Ocean and implications for uncertainties in air-sea fluxes",2014,"10.1175/JCLI-D-13-00424.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904490452&doi=10.1175%2fJCLI-D-13-00424.1&partnerID=40&md5=aaa0ec4a454f6ecd6fb18d2d19b43648","The uncertainties related to atmospheric fields in the Arctic Ocean from commonly used and recently available reanalysis products are investigated. Fields from the 1) ECMWF Interim Re-Analysis (ERAInterim), 2) Common Ocean-Ice Reference Experiment version 2 (CORE2), 3) Japanese 25-yr Reanalysis Project (JRA-25), 4) NCEP-NCAR reanalysis, 5) NCEP Climate Forecast System Reanalysis (CFSR), and 6) Modern-Era Retrospective Analysis for Research and Applications (MERRA) are evaluated against satellite-derived and in situ observations for zonal and meridional winds, precipitation, specific humidity, surface air temperature, and downwelling longwave and shortwave radiation fluxes. Comparison to reference observations shows that for variables such as air temperature and humidity, all reanalysis products have similar solutions. However, other variables such as winds, precipitation, and radiation show large spreads. The magnitude of uncertainties in all fields is large when compared to the signal. Biases in Arctic cloud parameterizations and predicted temperature and humidity profiles in reanalyses as discussed in other studies are likely common sources of error that affect surface downwelling radiation, air temperature, humidity, and precipitation. © 2014 American Meteorological Society."
"7404678955;","Quantifying and Reducing Uncertainty in the Large-Scale Response of the Water Cycle",2014,"10.1007/s10712-012-9203-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897459417&doi=10.1007%2fs10712-012-9203-1&partnerID=40&md5=c945307670de52f2d6f60887e9b5fdc1","Despite their obvious environmental, societal and economic importance, our understanding of the causes and magnitude of the variations in the global water cycle is still unsatisfactory. Uncertainties in hydrological predictions from the current generation of models pose a serious challenge to the reliability of forecasts and projections across time and space scales. This paper provides an overview of the current issues and challenges in modelling various aspects of the Earth's hydrological cycle. These include: the global water budget and water conservation, the role of model resolution and parametrisation of precipitation-generating processes on the representation of the global and regional hydrological cycle, representation of clouds and microphysical processes, rainfall variability, the influence of land-atmosphere coupling on rainfall patterns and their variability, monsoon processes and teleconnections, and ocean and cryosphere modelling. We conclude that continued collaborative activity in the areas of model development across timescales, process studies and climate change studies will provide better understanding of how and why the hydrological cycle may change, and better estimation of uncertainty in model projections of changes in the global water cycle. © 2012 Her Majesty the Queen in Right of United Kingdom 2012."
"26537644500;7402637536;","Holocene storminess inferred from sediments of two lakes on Adak Island, Alaska",2014,"10.1016/j.yqres.2014.02.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904071650&doi=10.1016%2fj.yqres.2014.02.007&partnerID=40&md5=abd2f591af0b7ed6a9bb383aecde540a","The abundance of sedimentary organic material from two lakes was used to infer past Holocene storminess on Adak Island where frequent storms generate abundant rainfall and extensive cloud cover. Andrew and Heart Lakes are located 10 km apart; their contrasting physical characteristics cause the sedimentary organic matter to respond differently to storms. Their records were synchronized using correlated tephra beds. Sedimentation rates increased between 4.0 and 3.5 ka in both lakes. Over the instrumental period, Andrew Lake biogenic-silica content (BSi) is most strongly correlated with winter sunlight availability, which influences photosynthetic production, and river input, which influences the dilution of BSi by mineral matter. Heart Lake BSi is likely affected by wind-driven remobilization of sediment, as suggested by correlations among BSi, the North Pacific Index, and winter storminess. The results indicate relatively stormy conditions from 9.6 to 4.0 ka, followed by drying between 4.0 and 2.7 ka, with the driest conditions from 2.7 to 1.5 ka. The stormiest period was between AD 500 and 1200, then drying from 1150 to 1500 and more variable until 1850. This record of Holocene storminess fills a major gap at the center of action for North Pacific wintertime climate. © 2014 University of Washington."
"36608836600;23568612700;26635393200;7202980469;7003706805;","Downscaling regional climate data to calculate the radiative index of dryness in complex terrain",2014,"10.22499/2.6402.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922250643&doi=10.22499%2f2.6402.003&partnerID=40&md5=da2cce938f944c00d454f84b58b5c45c","The radiative index of dryness (or aridity index) is a non-dimensional measure of the long-term balance between rainfall and net radiation. Quantifying aridity requires spatially distributed information on net radiation and rainfall. The variability in net radiation in complex terrain can be modelled at high spatial resolution by combining point data with equations that incorporate the effects of elevation, surface geometry and atmospheric attenuation of incoming radiation. At large spatial scales and over long time periods, however, the combination of seasonality, year to year variations and spatial variability in climate result in complex spatial-temporal patterns of incoming radiation, which are more effectively captured in satellite-based measurements. This study uses a high resolution model of shortwave radiation as a tool for downscaling satellite-derived data on incoming radiation. The aim was to incorporate topographic effects on net radiation in complex terrain while retaining information on regional and seasonal trends captured in satellite data. The method relies on satellite-based measures of incoming radiation from the Australian Bureau of Meteorology (BoM) to provide the spatial coverage and long-term data that represent the average incoming radiation across the state of Victoria in southeast Australia. These long-term data were coupled with a topographic downscaling algorithm to produce estimates of net radiation and aridity at the resolution of a 20 m digital elevation model. Results show that annual precipitation (and cloud fraction) gradients drive the variability in aridity at large scales (10-100 km) while topography (e.g. slope aspect and slope angle) are the main drivers at small scales (e.g. 1 km). The aridity index varied between 0.24 and 10.95 across the state of Victoria. The effect of aridity on vegetation was apparent at local scales through systematic variations in tree-height along rainfall gradients and across aspects with different levels of exposure to solar radiation."
"34969469300;7404574877;56181882400;7003351590;56323780400;25823648900;","Assessment of RegCM4.3 over the CORDEX South America domain: Sensitivity analysis for physical parameterization schemes",2014,"10.3354/cr01239","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905988612&doi=10.3354%2fcr01239&partnerID=40&md5=a8258905c474e5e0d5c52705d7138307","In mid-2012, the Abdus Salam International Centre for Theoretical Physics (ICTP) released version 4.3 of the Regional Climate Model (RegCM4.3). This version includes a new surface scheme, the Common Land Model (CLM); a new planetary boundary layer (PBL) scheme, the University of Washington PBL (UW-PBL); and new convection schemes including Tiedtke, and Mixed1 and Mixed2-with Grell (MIT) over the land and MIT (Grell) over the ocean for Mixed1 (Mixed2). These implementations suggest the necessity of an evaluation study to determine the best configuration of RegCM4.3 for simulating the climate of South America (SA). The main motivation is to come up with the best configurations of RegCM4.3 over the SA domain for use in the Coordinated Regional Downscaling Experiment (CORDEX) project. We analyzed 7 simulations for the period 1990-2000. The control simulation used the Biosphere-Atmosphere Transfer Scheme (BATS), Holtslag for the PBL and Mixed1 for cumulus convection. In the other simulations we changed these schemes using the new RegCM4.3 options. The evaluation of the simulations was carried out in 3 groups: (1) sensitivity to convection (Mixed1, MIT and Tiedtke), (2) sensitivity to the PBL (Holtslag and UW-PBL) and (3) sensitivity to surface processes (BATS and CLM). Considering all of SA, the results show that precipitation is better simulated with the schemes of the control simulation, while for air temperature, better results were obtained using the MIT cumulus scheme together with the CLM scheme. In summary, we recommend 2 configurations for the CORDEX project over SA: (1) the schemes used in the control simulation and (2) the MIT scheme for cumulus convection, Holtslag for the PBL, and CLM for surface interaction processes. © Inter-Research 2014."
"55003524100;7003510377;","Estimation of satellite rainfall error variance using readily available geophysical features",2014,"10.1109/TGRS.2013.2238636","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890426166&doi=10.1109%2fTGRS.2013.2238636&partnerID=40&md5=7b9627332aa4c51cf8df2622ecb09e0a","The present study addresses the estimation of error variance (mean square error, MSE) of three satellite rainfall products: i) Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) product of 3B42RT; ii) Climate Prediction Center (CPC) Morph (CMORPH); and iii) Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS). Nonlinear regression model is used to fit the response variable (satellite rainfall error variance) with explanatory variable (satellite rainfall rate) by grouping them as function of three key geophysical features: topography, climate, and season. The results of the study suggest that the error variance of a rainfall product is strongly correlated with rainfall rate and can be expressed as a power-law function. The geophysical feature based error classification analysis helps in achieving superior accuracy for prognostic error variance quantification in the absence of ground truth data. The multiple correlation coefficients between the estimated and observed error variance over an independent validation region (Upper Mississippi River basin) and time period (2007-2010) are found to be 0.75, 0.86, and 0.87 for 3B42RT, CMORPH, and PERSIANN-CCS products, respectively. In another validation region (Arkansas-Red River basin), the correlation coefficients are 0.59, 0.89, and 0.92 for the same products, respectively. Results of the assessment of error variance models reveal that the type of error component present in a satellite rainfall product directly impacts the accuracy of estimated error variance. The model estimates the error variance more accurately when the precipitation error components are mostly hit bias or false precipitation, while for a product with extensive missed precipitation, the accuracy of estimated error variance is significantly compromised. The study clearly demonstrates the feasibility of quantifying the error variance of satellite rainfall products in a spatially and temporally varying manner using readily available geophysical features and rainfall rate. The study is a path finder to a globally applicable and operationally feasible methodology for error variance estimation at high spatial and temporal scales for advancing satellite rainfall applications in ungauged basins. © 1980-2012 IEEE."
"23012263800;7004587891;55939316400;24467868900;","Retrieval of surface albedo on a daily basis: Application to MODIS data",2014,"10.1109/TGRS.2014.2313842","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903276310&doi=10.1109%2fTGRS.2014.2313842&partnerID=40&md5=5919c8c055c1fb1aeca45b47385e3129","In this paper, we will evaluate the Vermote et al. method, hereafter referred to as VJB, in comparison to the MCD43 MODerate Resolution Imaging Spectroradiometer (MODIS) product, focusing on the white sky albedo parameter. We also present and study three different methods based on the VJB assumption, the 4param, 5param Rsqr, and 5param Vsqr. We use daily MODIS Climate Modeling Grid data both from Terra and Aqua platforms from 2002 to 2011 for all the pixels over Europe. We obtain an overall root-mean-square error of 5% when using the VJB method and 6.1%, 5.1%, and 5.3% for the 4param, 5param Rsqr, and 5param Vsqr methods, respectively. The main differences between the methods are located in areas where only few cloud-free snow-free samples were available that correspond mainly to mountainous areas during the winter. We finally conclude that the VJB method has an equivalent performance in deriving the white sky albedo results to the MODIS product with the advantage of daily temporal resolution. Additionally, we propose the 5param Rsqr method as an alternative to the VJB method due to its decreased data processing time. © 2014 IEEE."
"7004003763;56413066900;35330541400;56146550200;7004242319;6701546267;57210590791;26656668800;","Finescale radar and airmass structure of the comma head of a continental winter cyclone: The role of three airstreams",2014,"10.1175/MWR-D-14-00057.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910010406&doi=10.1175%2fMWR-D-14-00057.1&partnerID=40&md5=84ad20c8ef3912065caa151b4bbe28ef","Data from airborne W-band radar, thermodynamic fields from the Weather Research and Forecasting (WRF) Model, and air parcel back trajectories from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model are used to investigate the finescale reflectivity, vertical motion, and airmass structure of the comma head of a winter cyclone that produced 15-25 cm of snow across the U.S. Midwest on 29-30 January 2010. The comma head consisted of three vertically stacked air masses: from bottom to top, an arctic air mass of Canadian origin, a moist cloud-bearing air mass of Gulf of Mexico origin, and a drier air mass originating mostly at low altitudes over Baja California and the Mexican Plateau. The drier air mass capped the entire comma head and significantly influenced precipitation distribution and type across the storm, limiting cloud depth on the warm side, and creating instability with respect to ice-saturated ascent, cloud-top generating cells, and a seeder-feeder process on the cold side. Convective generating cells with depths of 1.5-3.0km and vertical air velocities of 1-3ms-1 were ubiquitous atop the cold side of the comma head. The airmass boundaries within the comma head lacked the thermal contrast commonly observed along fronts in other sectors of extratropical cyclones. The boundary between the Gulf and Canadian air masses, although quite distinct in terms of precipitation distribution, wind, and moisture, was marked by almost no horizontal thermal contrast at the time of observation. The higher-altitude airmass boundary between the Gulf of Mexico and Baja air masses also lacked thermal contrast, with the less-stable Baja air mass overriding the stable Gulf of Mexico air. © 2014 American Meteorological Society."
"55004877800;7006200031;15123538900;25421141300;6603608525;","On-the-fly massively multitemporal change detection using statistical quality control charts and landsat data",2014,"10.1109/TGRS.2013.2272545","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896391610&doi=10.1109%2fTGRS.2013.2272545&partnerID=40&md5=e19f4ba61c78de5750c0513676d461f6","One challenge to implementing spectral change detection algorithms using multitemporal Landsat data is that key dates and periods are often missing from the record due to weather disturbances and lapses in continuous coverage. This paper presents a method that utilizes residuals from harmonic regression over years of Landsat data, in conjunction with statistical quality control charts, to signal subtle disturbances in vegetative cover. These charts are able to detect changes from both deforestation and subtler forest degradation and thinning. First, harmonic regression residuals are computed after fitting models to interannual training data. These residual time series are then subjected to Shewhart X-bar control charts and exponentially weighted moving average charts. The Shewhart X-bar charts are also utilized in the algorithm to generate a data-driven cloud filter, effectively removing clouds and cloud shadows on a location-specific basis. Disturbed pixels are indicated when the charts signal a deviation from data-driven control limits. The methods are applied to a collection of loblolly pine ( Pinus taeda) stands in Alabama, USA. The results are compared with stands for which known thinning has occurred at known times. The method yielded an overall accuracy of 85%, with the particular result that it provided afforestation/deforestation maps on a per-image basis, producing new maps with each successive incorporated image. These maps matched very well with observed changes in aerial photography over the test period. Accordingly, the method is highly recommended for on-the-fly change detection, for changes in both land use and land management within a given land use. © 2013 IEEE."
"55821191900;7005026236;6603879118;","Accuracy assessment of MODIS/Terra snow cover product for parts of Indian Himalayas",2014,"10.1080/10106049.2013.819041","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904542842&doi=10.1080%2f10106049.2013.819041&partnerID=40&md5=a91a94a5d3f46808943cbed4e8d09ff6","Snow cover mapping is important for snow and glacier-related research. The spatial and temporal distribution of snow cover area is a fundamental input to the atmospheric models, snowmelt runoff models and climate models, as well as other applications. Daily snow cover maps from Moderate Resolution Imaging Spectroradiometer (MODIS) Terra satellite were retrieved for the period between 2004 and 2007, and pixels in these images were classified as cloud, snow or snow-free. These images have then been compared with ground snow depth (SD) measurements from the four observatories located at different parts of Himalayas. Comparison of snow maps with in situ data showed good agreement with overall accuracies in between 78.15 and 95.60%. When snow cover was less, MODIS data were found to be less accurate in mapping snow cover region. As the SD increases, the accuracy of MODIS snow cover maps also increases. © 2013 © 2013 Taylor & Francis."
"14019431100;7102074443;55946190800;","A multiple-vortex tornado in Southeastern Brazil",2014,"10.1175/MWR-D-13-00319.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906875565&doi=10.1175%2fMWR-D-13-00319.1&partnerID=40&md5=1b9ce012b4519f833248a0e805339311","During the late afternoon hours of 24May 2005 a severe weather outbreak occurred in the state of São Paulo, southeastern Brazil. Severe thunderstorms were observed ahead of a surface cold front, including a (Southern Hemisphere) cyclonic left-moving supercell that produced a multiple-vortex tornado in the outskirts of the town of Indaiatuba, Brazil (23.18°S, 47.28°W). A documentation of the multivortex structure of the tornado and of the cloud-base features is performed using still images from a video that recorded the event. Characteristics of the tornadic thunderstorm and the synoptic-scale environment in which it developed are examined using Doppler radar data, geostationary satellite imagery, surface and upper-air observations, and data from the National Centers for Environmental Prediction's Climate Forecast System Reanalysis. The cloud base of the thunderstorm displayed morphological features associated with midlatitude tornadic supercells, including a low-level mesocyclone and a ""clear slot"" however, the rear-flank downdraft did not obscure the view of the tornado from the western flank of the storm. The tornadic stormdeveloped in amoist prefrontal environmentwith a low-level jet. Limitedmesoscale observations hampered the quantitative analysis of the local thermodynamic forcing, but the available data suggest that the supercell developed undermoderate conditional instability. Strong speed and directional vertical wind shear were observed, while the local boundary layer displayed very high relative humidity and low surface-based lifting condensation level. © 2014 American Meteorological Society."
"25822334900;7403225300;15842539500;","Spatio-temporal variation and monsoon effect on the temperature lapse rate of a subtropical Island",2014,"10.3319/TAO.2013.11.08.01(A)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897096333&doi=10.3319%2fTAO.2013.11.08.01%28A%29&partnerID=40&md5=997df2a8c9127e18fb9b811af2a31cab","Temperature lapse rate (TLR) has been widely used in the prediction of mountain climate and vegetation and in many ecological models. The aims of this paper are to explore the spatio-temporal variations and monsoon effects on the TLR in the subtropical island of Taiwan with its steep Central Mountain Region (CMR). A TLR analysis using the 32-year monthly mean air temperatures and elevations from 219 weather stations (sea level to 3852 m a.s.l.) was performed based on different geographical regions and monsoon exposures. The results revealed that the average TLR for all of Taiwan is -5.17°C km-1, with a general tendency to be steeper in summer and shallower in winter. The results are also shallower than the typical or global average TLR of -6.5°C km-1. During the prevailing northeast monsoon season (winter), the TLR exhibits a contrast between the windward side (steeper, -5.97°C km -1) and the leeward side (shallower, -4.51°C km-1). From the diagnosis on spatial characteristics of monthly cloud amount and vertical atmospheric profiles, this contrasting phenomenon may be explained by the warming effect of onshore stratus clouds (500 - 2500 m depth) on cold and dry Siberian monsoon air on the windward side of the CMR. On the southwestern leeward side of the CMR, the low-level (1500 m), the weak ventilation atmosphere and temperature inversion make the TLR shallower than on the windward side."
"55897614800;6701751100;8361740900;7006861646;","High-resolution prediction of a major convective period over West Africa",2014,"10.1002/qj.2225","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905024800&doi=10.1002%2fqj.2225&partnerID=40&md5=774837c2bac6924789da8033a182df12","In this article, we evaluate the predictions of the French cloud-resolving model AROME using a set of high-resolution (5 km) simulations that focus on the well documented African Monsoon Multidisciplinary Analysis (AMMA) period of 23-28 July 2006 over a large domain (0-22°N, 15°W-20°E). The model skill is assessed against independent Global Positioning System observations of precipitable water and in terms of quantitative precipitation forecasts. As the rain-gauge network is sparse over West Africa, the simulated precipitation fields were compared with data from satellite-based precipitation products (TRMM-3B42). We show that initial and boundary conditions significantly improve the AROME forecasts when the large-scale forcing model (ARPEGE) assimilates surface-sensitive observations from microwave remote-sensing sensors over land surface. The daily mean AROME precipitation shows a spatial distribution in good agreement with the satellite precipitation estimates. The intertropical convergence zone is correctly reproduced in terms of shape and location but its intensity is broadly overestimated by about 25%. The AROME model is shown to be able to reproduce all regimes, from light rain to the biggest Mesoscale Convective Systems (MCSs). The observations made at the Niamey AMMA supersite allow a detailed evaluation. Near the Niamey AMMA supersite, we show that AROME is able to represent most of the key features of the West African monsoon from the diurnal to synoptic scales. The life cycle of two successive sequences of MCSs associated with an African easterly wave and a deep monsoon burst are well captured by AROME. Finally, a tracking approach based on the 1 h accumulated precipitation is applied to both Global Satellite Mapping of Precipitation (GSMaP) satellite estimates and to AROME and ARPEGE forecasts, allowing a good characterization of each MCS and statistics. Contrary to ARPEGE, the AROME MCSs trajectories and lifetimes, and the diurnal cycles of their initiation and dissipation, are in agreement with the GSMaP tracking and previous MCS statistics. © 2013 Royal Meteorological Society."
"34979885900;6701751765;22949402700;57203083372;23096635200;","Titan's past and future: 3D modeling of a pure nitrogen atmosphere and geological implications",2014,"10.1016/j.icarus.2014.07.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905454757&doi=10.1016%2fj.icarus.2014.07.009&partnerID=40&md5=32e2c235aebded4082f9b7d0bfe9e783","Several clues indicate that Titan's atmosphere has been depleted in methane during some period of its history, possibly as recently as 0.5-1 billion years ago. It could also happen in the future. Under these conditions, the atmosphere becomes only composed of nitrogen with a range of temperature and pressure allowing liquid or solid nitrogen to condense. Here, we explore these exotic climates throughout Titan's history with a 3D Global Climate Model (GCM) including the nitrogen cycle and the radiative effect of nitrogen clouds. We show that for the last billion years, only small polar nitrogen lakes should have formed. Yet, before 1. Ga, a significant part of the atmosphere could have condensed, forming deep nitrogen polar seas, which could have flowed and flooded the equatorial regions. Alternatively, nitrogen could be frozen on the surface like on Triton, but this would require an initial surface albedo higher than 0.65 at 4. Ga. Such a state could be stable even today if nitrogen ice albedo is higher than this value. According to our model, nitrogen flows and rain may have been efficient to erode the surface. Thus, we can speculate that a paleo-nitrogen cycle may explain the erosion and the age of Titan's surface, and may have produced some of the present valley networks and shorelines. Moreover, by diffusion of liquid nitrogen in the crust, a paleo-nitrogen cycle could be responsible of the flattening of the polar regions and be at the origin of the methane outgassing on Titan. © 2014 Elsevier Inc."
"26039315200;9842163500;37078305200;7007042259;","Season-dependence of remote sensing indicators of tree species diversity",2014,"10.1080/2150704X.2014.912767","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902662206&doi=10.1080%2f2150704X.2014.912767&partnerID=40&md5=d51091d7b11ea7a1caa3aeb1a04191b2","During recent years, many studies have been undertaken to investigate how spectral characteristics of forests can provide information on spatial patterns of tree species diversity (TSD). Important advances have been made, and significant relationships between TSD and remotely sensed indicators of net primary productivity and environmental heterogeneity have been reported. However, the season-dependence of these relationships has not yet been fully investigated, and the influence of phenology remains poorly understood. In this study, we aim to assess how the relationships between remote sensing indicators and TSD depend on the season of the year. TSD measures, including species richness, Shannon's diversity and Simpson's diversity, were determined for 82 field plots in the Afromontane cloud forests of Taita Hills, Kenya. A time series of 15 Landsat images were used to calculate a set of spectral and heterogeneity metrics. The relationship between remote-sensing metrics and TSD measures was analysed by simple and multivariate regression analysis. We conclude that the relationships between remote-sensing metrics and TSD are season-dependent. Hence, it is demonstrated the date of image acquisition is an important aspect to be considered in biodiversity studies. Given that the dependence of the relationships is closely linked to climate seasonality defining vegetation phenology, the relationships may also vary according to geographical conditions. © 2014 Taylor & Francis."
"56505349400;55317091800;","Environmental dependence and seasonal variation of diffuse solar radiation in tropical peatland",2014,"10.2480/agrmet.D-14-00028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922336033&doi=10.2480%2fagrmet.D-14-00028&partnerID=40&md5=36c2ded970c124b385733fd446501fd0","Changes in cloud cover and atmospheric aerosol loading strongly affect the diffuse proportion of solar radiation (Rd/Rg). It has been reported that plant photosynthesis is more efficient under diffuse light conditions, but diffuse radiation (Rd) regimes in tropical peatland frequently subjected to largescale fires are poorly described, and there are few or no site-based datasets to date. Therefore, we continuously measured Rd for more than three years at a burnt ex-forest on tropical peatland in Central Kalimantan, Indonesia. Daily Rd/Rg was significantly related to the clearness index (Rg/Ro) with a linear threshold model. The model parameters showed that Rd/Rg under a clear sky is larger in tropical peatland with a humid climate than in Australia. Using the model, long-term variation in Rd/Rg for more than 12 years was estimated from Rg measured above a nearby forest. As a result, Rd/Rg showed a seasonal variation with its minimum of 0.51 in June (the transition between the wet and dry seasons) and its maximum of 0.68 in October (the late dry season) on a monthly basis. The decreasing pattern from the late wet season to the early dry season corresponded to decreasing precipitation due to fewer clouds. In contrast, the increasing pattern through the latter half of the dry season was due to shading by smoke emitted through burning biomass and peat fires. In particular, during the El Niño droughts in 2002, 2006 and 2009, the monthly mean Rd/Rg rose above 0.72, because the ground was densely covered with smoke from large-scale fires. © 2014, Society of Agricultural Meteorology of Japan. All rights reserved."
"23985484100;34976574800;","Large-eddy simulation of stratified turbulence. Part II: Application of the stretched-vortex model to the atmospheric boundary layer",2014,"10.1175/JAS-D-13-0306.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84916203014&doi=10.1175%2fJAS-D-13-0306.1&partnerID=40&md5=b0a2c2a370c4d9be959a07afe87d5f49","The buoyancy-adjusted stretched-vortex subgrid-scale (SGS) model is assessed for a number of large-eddy simulations (LESs) corresponding to diverse atmospheric boundary layer conditions. The cases considered are free convection, a moderately stable boundary layer [first Global Energy and Water Exchanges (GEWEX) Atmospheric Boundary Layer Study (GABLS)] case, shallow cumulus [Barbados Oceanographic and Meteorological Experiment (BOMEX)], shallow precipitating cumulus [Rain in Cumulus over the Ocean (RICO)] and nocturnal stratocumulus [Second Dynamics and Chemistry of the Marine Stratocumulus (DYCOMS-II) field study RF01]. An identical LES setup, including advection discretization and SGS model parameters, is used for all cases, which is a stringent test on the ability of LES to accurately capture diverse conditions without any flow-adjustable parameters. The LES predictions agree well with observations and previously reported model results. A grid-resolution convergence study is carried out, and for all cases the mean profiles exhibit good grid-resolution independence, even for resolutions that are typically considered coarse. Second-order statistics, for example, variances, converge at finer resolutions compared to domain means. The simulations show that 90% of the turbulent kinetic energy (at each level) must be resolved to obtain sufficiently converged mean profiles. This empirical convergence criterion can be used as a guide in designing future LES runs. © 2014 American Meteorological Society."
"56438509000;56438382300;25624545600;54401423900;13608035400;","Investigation of discrepancies in satellite rainfall estimates over Ethiopia",2014,"10.1175/JHM-D-13-0111.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84915793262&doi=10.1175%2fJHM-D-13-0111.1&partnerID=40&md5=d96624ede9278fe88bf9e3ae02d7a115","Tropical Applications of Meteorology Using Satellite and Ground-Based Observations (TAMSAT) rainfall estimates are used extensively across Africa for operational rainfall monitoring and food security applications; thus, regional evaluations ofTAMSAT are essential to ensure its reliability.This study assesses the performance of TAMSAT rainfall estimates, along with the African Rainfall Climatology (ARC), version 2; the Tropical Rainfall Measuring Mission (TRMM) 3B42 product; and the Climate Prediction Center morphing technique (CMORPH), against a dense rain gauge network over a mountainous region of Ethiopia. Overall, TAMSAT exhibits good skill in detecting rainy events but underestimates rainfall amount, while ARC underestimates both rainfall amount and rainy event frequency. Meanwhile, TRMM consistently performs best in detecting rainy events and capturing themean rainfall and seasonal variability, while CMORPHtends to overdetect rainy events. Moreover, the mean difference in daily rainfall between the products and rain gauges shows increasing underestimation with increasing elevation. However, the distribution in satellite-gauge differences demon-strates that although 75% of retrievals underestimate rainfall, up to 25% overestimate rainfall over all elevations. Case studies using high-resolution simulations suggest underestimation in the satellite algorithms is likely due to shallow convection with warm cloud-top temperatures in addition to beam-lling effects in microwave-based retrievals from localized convective cells. The overestimation by IR-based algorithms is attributed to nonraining cirrus with cold cloud-top temperatures. These results stress the importance of understanding regional precipitation systems causing uncertainties in satellite rainfall estimates with a view toward using this knowledge to improve rainfall algorithms. © 2014 American Meteorological Society."
"56380621100;8043701900;","Estimating vertical motion profile shape within tropical weather states over the oceans",2014,"10.1175/JCLI-D-13-00602.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907433694&doi=10.1175%2fJCLI-D-13-00602.1&partnerID=40&md5=4e2f09ced9fd46b967d64ce299613eb6","The vertical structure of tropical deep convection strongly influences interactions with larger-scale circulations and climate. This paper focuses on investigating this vertical structure and its relationship with mesoscale tropical weather states. The authors test the hypothesis that latent heating plus turbulent flux convergence varies (in space and time) in association with weather state type. The authors estimate mean-state vertical motion profile shape and latent heating plus turbulent flux convergence for six weather states defined using cloud-top pressure and optical depth properties from the International Satellite Cloud Climatology Project (ISCCP) dataset. Assuming two modes of vertical motion profile variability, these modes are statistically extracted from reanalysis data using a principal component analysis. Using these modes and the relationship between vertical motion, the dry static energy budget, and mass continuity, the authors estimate vertical motion profile shape. In these estimates, the authors use Global Precipitation Climatology Project (GPCP) [and Tropical Rainfall Measuring Mission (TRMM) 3B42] precipitation and Quick Scatterometer (QuikSCAT) surface convergence data in the ITCZ region from 2001 to 2006. Finally, these profile shapes are categorized by weather state type and spatiotemporally averaged to generate mean-state vertical motion profiles and latent heating plus turbulent flux convergence. The authors find that vertical motion profile shape varies by weather state. The isolated systems convective regime exhibits more ""bottom heaviness""than the other convectively active regimes, with maximum upward vertical motion occurring in the lower troposphere rather than the middle to upper troposphere. The variability observed does not coincide with the conventional profile variability based on stratiform rain fraction. © 2014 American Meteorological Society."
"32367837300;26867472700;56284582200;56726831900;7005446873;","Distinguishing the cold conveyor belt and sting jet airstreams in an intense extratropical cyclone",2014,"10.1175/MWR-D-13-00348.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905715422&doi=10.1175%2fMWR-D-13-00348.1&partnerID=40&md5=968bbf5b0297d07ab8686d949abfb1cc","Strong winds equatorward and rearward of a cyclone core have often been associated with two phenomena: the cold conveyor belt (CCB) jet and sting jets. Here, detailed observations of the mesoscale structure in this region of an intense cyclone are analyzed. The in situ and dropsonde observations were obtained during two research flights through the cyclone during the Diabatic Influences on Mesoscale Structures in Extratropical Storms (DIAMET) field campaign. A numerical weather prediction model is used to link the strong wind regions with three types of ""airstreams"" or coherent ensembles of trajectories: two types are identified with the CCB, hooking around the cyclone center, while the third is identified with a sting jet, descending from the cloud head to the west of the cyclone. Chemical tracer observations show for the first time that the CCB and sting jet airstreams are distinct air masses even when the associated low-level wind maxima are not spatially distinct. In the model, the CCBexperiences slow latent heating through weak-resolved ascent and convection, while the sting jet experiences weak cooling associated with microphysics during its subsaturated descent. Diagnosis of mesoscale instabilities in the model shows that the CCB passes through largely stable regions, while the sting jet spends relatively long periods in locations characterized by conditional symmetric instability (CSI). The relation of CSI to the observed mesoscale structure of the bent-back front and its possible role in the cloud banding is discussed."
"35337041800;15926418500;15047161300;23003259600;7601490850;","Clear-sky aerosol optical depth over East China estimated from visibility measurements and chemical transport modeling",2014,"10.1016/j.atmosenv.2014.06.044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903387529&doi=10.1016%2fj.atmosenv.2014.06.044&partnerID=40&md5=5772a51d78ea690c04a5dbd6a2dc6b8e","Horizontal visibility measured at ground meteorological stations provides an under-exploited source of information for studying the interdecadal variation of aerosols and their climatic impacts. Here we propose to use a 3-hourly visibility dataset to infer aerosol optical depth (AOD) over East China, using the nested GEOS-Chem chemical transport model to interpret the spatiotemporally varying relations between columnar and near-surface aerosols. Our analysis is focused in 2006 under cloud-free conditions. We evaluate the visibility-inferred AOD using MODIS/Terra and MODIS/Aqua AOD datasets, after validating MODIS data against three ground AOD measurement networks (AERONET, CARSNET and CSHNET). We find that the two MODIS datasets agree with ground-based AOD measurements, with negative mean biases of 0.05-0.08 and Reduced Major Axis regression slopes around unity. Visibility-inferred AOD roughly capture the general spatiotemporal patterns of the two MODIS datasets with negligible mean differences. The inferred AOD reproduce the seasonal variability (correlation exceeds 0.9) and the slight AOD growth from the late morning to early afternoon shown in the MODIS datasets, suggesting the validity of our AOD inference method. Future research will extend the visibility-based AOD inference to study the long-term variability of AOD. © 2014 The Authors."
"35331050000;7102653996;","The potential for mesoscale visibility predictions with a multimodel ensemble",2014,"10.1175/WAF-D-13-00067.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902204862&doi=10.1175%2fWAF-D-13-00067.1&partnerID=40&md5=629da4e971da534c6abdec53608447af","This work examines the viability of producing short-range (,20 h) probabilistic fog predictions in remote locations, absent an observational history, using an uncalibrated 4-km, 10-member Weather Research and Forecasting Model (WRF) ensemble configured to closely match the Air Force Weather Agency Mesoscale Ensemble Forecast Suite. Three distinct sources of error in the final predictions are considered separately to facilitate a better understanding of the total error and appropriate mitigation strategies. These include initial condition error, parameterization of subgrid-scale processes, and error in the visibility parameterization used to convert NWP model output variables to visibility. The raw WRF predictions are generally not skillful in valley and coastal regions, where they produce a shortage of light fog predictions with visibilities of 1-7 mi (1.6-11.3 km) in favor of excessive forecasts of zero cloud water, corresponding to no fog. Initial condition error and visibility parameterization error are shown to play a relatively minor role compared to error in the parameterization of subgrid-scale processes. This deficiency is caused by a negative relative humidity bias, which results from a warm overnight bias. A second-order source of error arises from an inconsistent delineation of fog and haze in the NWP model compared to the verifying observations. Results show that under most conditions it is necessary to deviate from the perfect-prog assumption, and to introduce some method of statistical postprocessing to obtain skillful visibility predictions from the ensemble."
"55043271500;9279986800;35491696900;55489412200;47961004800;15725009000;55857096100;16314082800;56940082700;6602205640;7004035832;","Assessing above-ground woody debris dynamics along a gradient of elevation in Amazonian cloud forests in Peru: Balancing above-ground inputs and respiration outputs",2014,"10.1080/17550874.2013.818073","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893215827&doi=10.1080%2f17550874.2013.818073&partnerID=40&md5=c5a52139d2212c6c3357980f4bf3b19f","Background: Dead biomass, including woody debris (WD), is an important component of the carbon cycle in tropical forests. Aims: This study analyses WD (&gt;2 cm) and other above-ground fluxes in mature tropical forest plots along an elevational gradient (210-3025 m above sea level) in southern Peru. Methods: This work was based on inventories of fine and coarse WD (FWD and CWD, respectively), above-ground biomass, and field-based and experimental respiration measurements. Results: Total WD stocks ranged from 6.26 Mg C ha-1 at 3025 m to 11.48 Mg C ha-1 at 2720 m. WD respiration was significantly correlated with moisture content (P &lt; 0.001; R 2 = 0.25), temperature (P &lt; 0.001; R 2 = 0.12) and wood density (P &lt; 0.001; R 2 = 0.16). Controlled experiments showed that both water content and temperature increased respiration rates of individual WD samples. The full breadth of the temperature sensitivity coefficient, or Q 10, estimates, ranging from 1.14-2.13, was low compared to other studies. In addition, temperature sensitivity of WD respiration was greater for higher elevations. Conclusions: Carbon stocks, mortality and turnover of above-ground biomass varied widely and were not significantly related with elevation or slope. This study demonstrates that some forests may be a carbon source due to legacies of disturbance and increasing temperatures, which may cause additional, short-term carbon efflux from WD. Predictions of tropical forest carbon cycles under future climate should incorporate WD dynamics and related feedback.s © 2014 Copyright 2013 Botanical Society of Scotland and Taylor &amp; Francis."
"55736537200;22934530000;8880094700;","Coupled climate impacts of the Drake Passage and the Panama Seaway",2014,"10.1007/s00382-013-1809-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906100912&doi=10.1007%2fs00382-013-1809-6&partnerID=40&md5=8a4624828b199ece9a67d3c1a3b0569c","Tectonically-active gateways between ocean basins have modified ocean circulation over Earth history. Today, the Atlantic and Pacific are directly connected via the Drake Passage, which forms a barrier to the time-mean geostrophic transport between the subtropics and Antarctica. In contrast, during the warm early Cenozoic era, when Antarctica was ice-free, the Drake Passage was closed. Instead, at that time, the separation of North and South America provided a tropical seaway between the Atlantic and Pacific that remained open until the Isthmus of Panama formed in the relatively recent geological past. Ocean circulation models have previously been used to explore the individual impacts of the Drake Passage and the Panama Seaway, but rarely have the two gateways been considered together, and most explorations have used very simple atmospheric models. Here we use a coupled ocean-ice-atmosphere model (GFDL's CM2Mc), to simulate the impacts of a closed Drake Passage both with and without a Panama Seaway. We find that the climate response to a closed Drake Passage is relatively small when the Panama Seaway is absent, similar to prior studies, although the coupling to a dynamical atmosphere does increase the temperature change. However, with a Panama Seaway, closing Drake Passage has a much larger effect, due to the cessation of deep water formation in the northern hemisphere. Both gateways alter the transport of salt by ocean circulation, with the Panama Seaway allowing fresh Pacific water to be imported to the North Atlantic, and the Drake Passage preventing the flow of saline subtropical water to the circum-Antarctic, a flow that is particularly strong when the Panama Seaway is open. Thus, with a Panama Seaway and a closed Drake Passage, the Southern Ocean tends to be relatively salty, while the North Atlantic tends to be relatively fresh, such that the deep ocean is ventilated from the circum-Antarctic. Ensuing changes in the ocean heat transport drive a bi-polar shift of surface ocean temperatures, and the Intertropical Convergence Zone migrates toward the warmer southern hemisphere. The response of clouds to changes in surface ocean temperatures amplifies the climate response, resulting in temperature changes of up to 9 °C over Antarctica, even in the absence of land-ice feedbacks. These results emphasize the importance of tectonic gateways to the climate history of the Cenozoic, and support a role for ocean circulation changes in the glaciation of Antarctica. © 2013 Springer-Verlag Berlin Heidelberg."
"56020125200;6507206337;6603035763;7003627515;56599183200;54787305500;","Evaluating Greenland glacial isostatic adjustment corrections using GRACE, altimetry and surface mass balance data",2014,"10.1088/1748-9326/9/1/014004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928096380&doi=10.1088%2f1748-9326%2f9%2f1%2f014004&partnerID=40&md5=de7d62bec162f4253250ba14d29c3e3f","Glacial isostatic adjustment (GIA) represents a source of uncertainty for ice sheet mass balance estimates from the Gravity Recovery and Climate Experiment (GRACE) time-variable gravity measurements. We evaluate Greenland GIA corrections from Simpson et al (2009 Quat. Sci. Rev. 28 1631-57), A et al (2013 Geophys. J. Int. 192 557-72) and Wu et al (2010 Nature Geosci. 3 642-6) by comparing the spatial patterns of GRACE-derived ice mass trends calculated using the three corrections with volume changes from ICESat (Ice, Cloud, and land Elevation Satellite) and OIB (Operation IceBridge) altimetry missions, and surface mass balance products from the Regional Atmospheric Climate Model (RACMO). During the period September 2003-August 2011, GRACE ice mass changes obtained using the Simpson et al (2009 Quat. Sci. Rev. 28 1631-57) and A et al (2013 Geophys. J. Int. 192 557-72) GIA corrections yield similar spatial patterns and amplitudes, and are consistent with altimetry observations and surface mass balance data. The two GRACE estimates agree within 2% on average over the entire ice sheet, and better than 15% in four subdivisions of Greenland. The third GRACE estimate corrected using the (Wu et al 2010 Nature Geosci. 3 642-6)) GIA shows similar spatial patterns, but produces an average ice mass loss for the entire ice sheet that is 64 - 67 Gt yr-1 smaller. In the Northeast the recovered ice mass change is 46-49 Gt yr -1 (245-270%) more positive than that deduced from the other two corrections. By comparing the spatial and temporal variability of the GRACE estimates with trends of volume changes from altimetry and surface mass balance from RACMO, we show that the Wu et al (2010 Nature Geosci. 3 642-6) correction leads to a large mass increase in the Northeast that is inconsistent with independent observations. © 2014 IOP Publishing Ltd."
"56070169600;24462161500;7102111356;","Improvements in the estimation of daily minimum air temperature in peninsular Spain using MODIS land surface temperature",2014,"10.1080/01431161.2014.935831","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905093640&doi=10.1080%2f01431161.2014.935831&partnerID=40&md5=584915df3e055702e781f4449c4d7add","Air temperature (Ta) is a key variable in many environmental risk models and plays a very important role in climate change research. In previous studies we developed models for estimating the daily maximum (Tmax), mean (Tmean), and minimum air temperature (Tmin) in peninsular Spain over cloud-free land areas using Moderate Resolution Imaging Spectroradiometer (MODIS) data. Those models were obtained empirically through linear regressions between daily Ta and daytime Terra-MODIS land surface temperature (LST), and then optimized by including spatio-temporal variables. The best Tmean and Tmax models were satisfactory (coefficient of determination (R2) of 0.91-0.93; and residual standard error (RSE) of 1.88-2.25 K), but not the Tmin models (R2 = 0.80-0.81 and RSE = 2.83-3.00 K). In this article Tmin models are improved using night-time Aqua LST instead of daytime Terra LST, and then refined including total precipitable water (W) retrieved from daytime Terra-MODIS data and the spatio-temporal variables curvature (c), longitude (λ), Julian day of the year (JD) and elevation (h). The best Tmin models are based on the National Aeronautics and Space Administration (NASA) standard product MYD11 LST; and on the direct broadcast version of this product, the International MODIS/AIRS Processing Package (IMAPP) LST product. Models based on Sobrino's LST1 algorithm were also tested, with worse results. The improved Tmin models yield R2 = 0.91-0.92 and RSE = 1.75 K and model validations obtain similar R2 and RSE values, root mean square error of the differences (RMSD) of 1.87-1.88 K and bias = 0.11 K. The main advantage of the Tmin models based on the IMAPP LST product is that they can be generated in nearly real-time using the MODIS direct broadcast system at the University of Oviedo. © 2014 © 2014 Taylor &amp; Francis."
"12242885800;8986947000;","Hadley cell influence on 7Be activity concentrations at Australian mainland IMS radionuclide particulate stations",2014,"10.1016/j.jenvrad.2013.10.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886607380&doi=10.1016%2fj.jenvrad.2013.10.011&partnerID=40&md5=cedd6e320a59fd539e63f8dc5f4010fb","Beryllium-7 (7Be) daily data from the four International Monitoring System (IMS) radionuclide particulate stations on mainland Australia are analysed over the period 2001 to 2011. The analysis indicates that levels of 7Be in surface air at the stations follow annual cycles, with yearly peak activity concentrations occurring later at stations further south. The yearly peak migrates north-south at a rate of approximately 4.4° latitude per month. The change in phase of the 7Be annual cycle between the stations corresponds with the seasonal migration of the Southern Hemisphere Hadley cell across mainland Australia. The implication is that the changing position of the downward limb of the Southern Hemisphere Hadley cell regulates the phase of the annual cycle in 7Be activity concentrations in surface air in the Australian region. © 2013 Elsevier Ltd."
"16425292000;55927784300;","Land-surface temperature dynamics in the Upper Mekong Basin derived from MODIS time series",2014,"10.1080/01431161.2014.890304","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897476607&doi=10.1080%2f01431161.2014.890304&partnerID=40&md5=f8133cd5318e883c0104b97cec4ff86f","Land surface temperature (LST) is an important indicator for climate variability and can be sensed remotely by satellites with a high temporal resolution on a broad spatial scale. In this research, Moderate Resolution Imaging Spectroradiometer (MODIS) LST is used to derive a 13 year time series on the Upper Mekong Basin (UMB), belonging to the People's Republic of China and the Republic of the Union of Myanmar, to analyse the spatial pattern and temporal development of LST. The data set shows the regular annual curve of surface temperatures with maximum values in summer and minimum values in winter. Average temperatures in the southern parts of the basin are higher than in the northern part. Spatial gradients between maximum and minimum LST as well as gradients between daytime and night-time LST are much lower in the southern parts than in the northern parts, which are characterized by a strong topography. The pixel-wise variability of monthly means was found to be in the range of ±4°C for most pixels in the daytime scenes, whereas the night-time scenes show a lower variability with most pixels in the range of ±1°C. The variability of LST in the northern areas clearly exceeds that in the southern areas. Some inter-annual variations occur, mainly during summer: in some years a two-peak distribution is found, which is explained by the generally low number of observations in the respective months. A primary challenge of optical satellite data in the UMB is cloud contamination in the summer months, where peak rainfall occurs. In the Mekong Highlands for instance, the average number of available daytime observations of MODIS LST in July is one observation per month only. It can be assumed that climate statistics calculated from such data is biased. In this context, two gap-filling algorithms were applied to two test areas for the year 2002 and results are discussed in the article. Another issue with MODIS LST data are day-to-day differences in the acquisition time. A temporal homogenization was applied to selected LST data, converting them to one fixed acquisition time. The converted data were compared to the original data set. No significant influence could be found. © 2014 Taylor & Francis."
"57094306300;8072265400;55797749000;","An efficient method of estimating downward solar radiation based on the MODIS observations for the use of land surface modeling",2014,"10.3390/rs6087136","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84997174238&doi=10.3390%2frs6087136&partnerID=40&md5=be50ee838735ac9da1e8134a62ade490","Solar radiation is a critical variable in global change sciences. While most of the current global datasets provide only the total downward solar radiation, we aim to develop a method to estimate the downward global land surface solar radiation and its partitioned direct and diffuse components, which provide the necessary key meteorological inputs for most land surface models. We developed a simple satellite-based computing scheme to enable fast and reliable estimation of these variables. The global Moderate Resolution Imaging Spectroradiometer (MODIS) products at 1° spatial resolution for the period 2003-2011 were used as the forcing data. Evaluations at Baseline Surface Radiation Network (BSRN) sites show good agreement between the estimated radiation and ground-based observations. At all the 48 BSRN sites, the RMSE between the observations and estimations are 34.59, 41.98 and 28.06 W·m-2 for total, direct and diffuse solar radiation, respectively. Our estimations tend to slightly overestimate the total and diffuse but underestimate the direct solar radiation. The errors may be related to the simple model structure and error of the input data. Our estimation is also comparable to the Clouds and Earth's Radiant Energy System (CERES) data while shows notable improvement over the widely used National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) Reanalysis data. Using our MODIS-based datasets of total solar radiation and its partitioned components to drive land surface models should improve simulations of global dynamics of water, carbon and climate. © 2014 by the authors."
"55706438900;7004098794;36704834200;7006003656;56428745800;6602132337;56429508600;54782488100;6601967743;56410554700;7102215529;7404040259;56146108800;55573647400;6701583174;56429019700;53871641200;","Reef-scale thermal stress monitoring of coral ecosystems: New 5-km global products from NOAA coral reef watch",2014,"10.3390/rs61111579","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84912101441&doi=10.3390%2frs61111579&partnerID=40&md5=6128e1df95fadeb26dbc01c2cfe2e1b6","The U.S. National Oceanic and Atmospheric Administration (NOAA) Coral Reef Watch (CRW) program has developed a daily global 5-km product suite based on satellite observations to monitor thermal stress on coral reefs. These products fulfill requests from coral reef managers and researchers for higher resolution products by taking advantage of new satellites, sensors and algorithms. Improvements of the 5-km products over CRW's heritage global 50-km products are derived from: (1) the higher resolution and greater data density of NOAA's next-generation operational daily global 5-km geo-polar blended sea surface temperature (SST) analysis; and (2) implementation of a new SST climatology derived from the Pathfinder SST climate data record. The new products increase near-shore coverage and now allow direct monitoring of 95% of coral reefs and significantly reduce data gaps caused by cloud cover. The 5-km product suite includes SST Anomaly, Coral Bleaching HotSpots, Degree Heating Weeks and Bleaching Alert Area, matching existing CRW products. When compared with the 50-km products and in situ bleaching observations for 2013-2014, the 5-km products identified known thermal stress events and matched bleaching observations. These near reef-scale products significantly advance the ability of coral reef researchers and managers to monitor coral thermal stress in near-real-time. © 2014 by the authors."
"55620467200;7005387538;","Alaska tidewater glacier terminus positions, 1948-2012",2014,"10.1002/2013JF002915","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896510722&doi=10.1002%2f2013JF002915&partnerID=40&md5=10fac8e317b9a7cd63db512bc215b42d","A significant portion of the world's glacier ice drains through tidewater outlets, though much remains unknown about the response to recent climate change of tidewater glaciers. We present a 64 year record of length change for 50 Alaska tidewater glaciers. We use U.S. Geological Survey topographic maps to provide a base length for glaciers before 1970. Using all available cloud-free Landsat images, we manually digitize calving front outlines for each glacier between 1972 and 2012, resulting in a total of more than 10,000 outlines. Tidewater glacier lengths vary seasonally; focusing on the 36 glaciers terminating in tidewater throughout the study period, we find a mean (± standard deviation) seasonal variation of 60± 85 m a-1. We use these oscillations to determine the significance of interannual changes in glacier length. All 36 glaciers underwent at least one period (≥1 year) of significant advance or retreat; 28 glaciers underwent at least one period of both significant advance and retreat. Over the entire period 1948-2012, 24 of these glaciers retreated a total (± uncertainty) of 107.95±0.29 km, 11 advanced a total of 7.71±0.20, and one (Chenega Glacier) did not change significantly. Retreats and advances are highly variable in time; several glaciers underwent rapid, short-term retreats of a few years duration. These retreats occurred after large changes in summer sea surface temperature anomalies; further study is needed to determine what triggered these retreats. No coherent regional behavior signal is apparent in the length record, although two subregions show a coherence similar to recent observations in Greenland. ©2014. American Geophysical Union. All Rights Reserved."
"55363002500;9240820800;7403968786;6507949344;57209045965;57210718719;","Evaluation of 10 year AQUA/MODIS land surface temperature with SURFRAD observations",2014,"10.1080/01431161.2013.873149","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893949135&doi=10.1080%2f01431161.2013.873149&partnerID=40&md5=fb15f05feb27f48ce15648efaaa5fe70","As the 10 year Moderate Resolution Imaging Spectroradiometer Land Surface Temperature MODIS LST becomes available, it is significant to perform a comprehensive evaluation on the long-term product before downstream users use it for climate studies and atmospheric models. In this study, a validation is carried out using observations from the US Surface Radiation budget (SURFRAD) network. Strict quality control removes cloud-contaminated samples from MODIS LST collection and decreases noise information from SURFRAD measurements, thereby making the validation more persuasive. With analysis on 19,735 valid samples, Aqua/MODIS LST from a split-window algorithm shows retrieval errors from -14 K to 17 K with a bias of -0.93 K, an RMSE of 2.65 K, and a standard deviation of 2.48 K. The errors also show strong seasonal signals. With correlation tests between LST errors and several other factors, it is disclosed that LST retrieval errors mainly come from atmospheric effects and surface emissivity uncertainties, which are closely related to relative air humidity, absolute air humidity, sensor zenith angle, wind speed, normalized difference vegetation index (NDVI), and soil moisture. In addition, the impacts from these factors may not be independent. These impact factors suggest a deficiency of the split-window algorithm in dealing with atmospheric and surface complexity and variety. © 2014 © 2014 Taylor & Francis."
"24337553400;35735005100;55913917200;55913339000;7102797196;16313088100;","Dust aerosol characteristics and shortwave radiative impact at a gobi desert of northwest China during the spring of 2012",2014,"10.2151/jmsj.2014-A03","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909990975&doi=10.2151%2fjmsj.2014-A03&partnerID=40&md5=b0bb3fdc9fe73ee1f7797901ca254dc0","The Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) project initiated an intensive field experiment on dust aerosols in Dunhuang from April 1 to June 12, 2012. Using sky radiometer measurements and conducting model simulations, we investigated the dust aerosol characteristics and its shortwave radiative impact on the regional climate. The daily averaged optical features of the aerosols markedly varied throughout the study period. High aerosol loading and predominantly coarse particulates were observed in the spring of 2012 ascribed to the influence of prevalent dust storm. The single scattering albedo at 500 nm (SSA500) varied from 0.91 to 0.97 on dusty days and from 0.86 to 0.91 on dust-free days, indicating that the dust aerosols sourced from northwest China were not strongly absorbing. Surface radiation quantities estimated by the radiative transfer model excellently agreed with ground-based and satellite observations, with correlation coefficients exceeding 0.990 and mean differences ranging from −3.9 to 17.0 W m−2. The daily mean aerosol shortwave direct radiative forcing (ARF) values were largely negative at the surface (−79.4 to −3.2 W m−2) and moderately positive in the atmosphere (2.2–25.1 W m−2), indicating strong cooling at the surface and moderate atmospheric warming. The monthly averaged ARFEs (ARFs per unit aerosol optical depth at 500 nm (AOD500)) at the surface were (−73.9 ± 11.6) W m−2, (−67.4 ± 8.3) W m−2, and (−74.4 ± 5.4) W m−2 in April, May, and June, respectively (overall average of (−70.8 ± 7.9) W m−2), comparable to previously obtained values in East Asia and India domains. The relations between the diurnal ARFs at the surface and top of the atmosphere (TOA) and the AOD500 indicate that aerosol composition remained relatively stable at Dunhuang during the spring of 2012. The ARF at the TOA was positive for SSA500 less than 0.85 or when the imaginary part at 500 nm exceeded 0.015. © 2014, Meteorological Society of Japan."
"55325157500;57203142176;6507501796;57194045072;6507112497;","A systematic approach to identify the sources of tropical SST errors in coupled models using the adjustment of initialised experiments",2014,"10.1007/s00382-014-2051-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892897418&doi=10.1007%2fs00382-014-2051-6&partnerID=40&md5=7dab2777c6975c74f2d85c9cd31a00fb","Understanding the sources of systematic errors in climate models is challenging because of coupled feedbacks and errors compensation. The developing seamless approach proposes that the identification and the correction of short term climate model errors have the potential to improve the modeled climate on longer time scales. In previous studies, initialised atmospheric simulations of a few days have been used to compare fast physics processes (convection, cloud processes) among models. The present study explores how initialised seasonal to decadal hindcasts (re-forecasts) relate transient week-to-month errors of the ocean and atmospheric components to the coupled model long-term pervasive SST errors. A protocol is designed to attribute the SST biases to the source processes. It includes five steps: (1) identify and describe biases in a coupled stabilized simulation, (2) determine the time scale of the advent of the bias and its propagation, (3) find the geographical origin of the bias, (4) evaluate the degree of coupling in the development of the bias, (5) find the field responsible for the bias. This strategy has been implemented with a set of experiments based on the initial adjustment of initialised simulations and exploring various degrees of coupling. In particular, hindcasts give the time scale of biases advent, regionally restored experiments show the geographical origin and ocean-only simulations isolate the field responsible for the bias and evaluate the degree of coupling in the bias development. This strategy is applied to four prominent SST biases of the IPSLCM5A-LR coupled model in the tropical Pacific, that are largely shared by other coupled models, including the Southeast Pacific warm bias and the equatorial cold tongue bias. Using the proposed protocol, we demonstrate that the East Pacific warm bias appears in a few months and is caused by a lack of upwelling due to too weak meridional coastal winds off Peru. The cold equatorial bias, which surprisingly takes 30 years to develop, is the result of an equatorward advection of midlatitude cold SST errors. Despite large development efforts, the current generation of coupled models shows only little improvement. The strategy proposed in this study is a further step to move from the current random ad hoc approach, to a bias-targeted, priority setting, systematic model development approach. © 2014, Springer-Verlag Berlin Heidelberg."
"36668812400;55188785600;","Energy exchange in a dense urban environment - Part I: Temporal variability of long-term observations in central London",2014,"10.1016/j.uclim.2013.10.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922689715&doi=10.1016%2fj.uclim.2013.10.002&partnerID=40&md5=8f2ca253f889866b5d2fd4b7ce1ada92","Though anthropogenic impacts on boundary layer climates are expected to be large in dense urban areas, to date very few studies of energy flux observations are available. We report on 3.5. years of measurements gathered in central London, UK. Radiometer and eddy covariance observations at two adjacent sites, at different heights, were analysed at various temporal scales and with respect to meteorological conditions, such as cloud cover. Although the evaporative flux is generally small due to low moisture availability and a predominately impervious surface, the enhancement following rainfall usually lasts for 12-18. h. As both the latent and sensible heat fluxes are larger in the afternoon, they maintain a relatively consistent Bowen ratio throughout the middle of the day. Strong storage and anthropogenic heat fluxes sustain high and persistently positive sensible heat fluxes. At the monthly time scale, the urban surface often loses more energy by this turbulent heat flux than is gained from net all-wave radiation. Auxiliary anthropogenic heat flux information suggest human activities in the study area are sufficient to provide this energy. © 2013 Elsevier B.V."
"7403073436;7202484739;7404458295;7403326970;","An evaluation of the impact of horizontal resolution on tropical cyclone predictions using COAMPS-TC",2014,"10.1175/WAF-D-13-00054.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940223718&doi=10.1175%2fWAF-D-13-00054.1&partnerID=40&md5=625c218c8a75d185e8c3d67ad941f2d0","A series of experiments have been conducted using the Coupled Ocean-Atmosphere Mesoscale Prediction System-Tropical Cyclone (COAMPS-TC) to assess the impact of horizontal resolution on hurricane intensity prediction for 10 Atlantic storms during the 2005 and 2007 hurricane seasons. The results of this study from the Hurricane Katrina (2005) simulations indicate that the hurricane intensity and structure are very sensitive to the horizontal grid spacing (9 and 3 km) and underscore the need for cloud microphysics to capture the structure, especially for strong storms with small-diameter eyes and large pressure gradients. The high resolution simulates stronger vertical motions, a more distinct upper-level warm core, stronger upper-level outflow, and greater finescale structure associated with deep convection, including spiral rainbands and the secondary circulation. A vortex Rossby wave (VRW) spectrum analysis is performed on the simulated 10-m winds and the NOAA/Hurricane Research Division (HRD) Real-Time Hurricane Wind Analysis System (H*Wind) to evaluate the impact of horizontal resolution. The degree to which the VRWs are adequately resolved near the TC inner core is addressed and the associated resolvable wave energy is explored at different grid resolutions. The fine resolution is necessary to resolve higher-wavenumber modes of VRWs to preserve more wave energy and, hence, to attain a more detailed eyewall structure. The wind-pressure relationship from the high-resolution simulations is in better agreement with the observations than are the coarse-resolution simulations for the strong storms. Two case studies are analyzed and overall the statistical analyses indicate that high resolution is beneficial for TC intensity and structure forecasts, while it has little impact on track forecasts."
"55942502100;56114842800;7403531523;","Diurnal variations of albedo retrieved from earth radiation budget experiment measurements",2014,"10.1175/JAMC-D-13-0119.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928341046&doi=10.1175%2fJAMC-D-13-0119.1&partnerID=40&md5=2e8f21b05f1545b654290bea1b833e93","Five years of measurements from the Earth Radiation Budget Satellite (ERBS) have been analyzed to define the diurnal cycle of albedo from 55°N to 55°S. The ERBS precesses through all local times every 72 days so as to provide data regarding the diurnal cycles for Earth radiation. Albedo together with insolation at the top of the atmosphere is used to compute the heating of the Earth-atmosphere system; thus its diurnal cycle is important in the energetics of the climate system. A principal component (PC) analysis of the diurnal variation of top-of-atmosphere albedo using these data is presented. The analysis is done separately for ocean and land because of the marked differences of cloud behavior over ocean and over land. For ocean, 90%-92% of the variance in the diurnal cycle is described by a single component; for land, the first PC accounts for 83%-89% of the variance. Some of the variation is due to the increase of albedo with increasing solar zenith angle, which is taken into account in the ERBS data processing by a directional model, and some is due to the diurnal cycle of cloudiness. The second PC describes 2%-4% of the variance for ocean and 5% for land, and it is primarily due to variations of cloudiness throughout the day, which are asymmetric about noon. These terms show the response of the atmosphere to the cycle of solar heating. The third PC for ocean is a two-peaked curve, and the associated map shows high values in cloudy regions."
"55243352000;35588263000;6507478686;","A global satellite view of the seasonal distribution of mineral dust and its correlation with atmospheric circulation",2014,"10.1016/j.dynatmoce.2014.07.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906668893&doi=10.1016%2fj.dynatmoce.2014.07.002&partnerID=40&md5=b570db014bcc671e07e3593c17666c35","Aerosols make a considerable contribution to the climate system through their radiative and cloud condensation nuclei effects, which underlines the need for understanding the origin of aerosols and their transport pathways. Seasonal distribution of mineral dust around the globe and its correlation with atmospheric circulation is investigated using satellite data, and meteorological data from ECMWF. The most important sources of dust are located in North Africa, the Middle East and Southwest Asia with an observed summer maximum, and East Asia with a spring peak. Maximum dust activity over North Africa and the Middle East in summer is attributed to dry convection associated with the summertime low-pressure system, while unstable weather and dry conditions are responsible for the spring peak in dust emission in East Asia. Intercontinental transport of mineral dust by atmospheric circulation has been observed, including trans-Atlantic transport of North African dust, trans-Pacific transport of Asian dust, and transport of dust from the Middle East across the Indian Ocean. The extent of African dust over the Atlantic Ocean and its latitudinal variation with season is related to the large-scale atmospheric circulation, including seasonal changes in the position of the intertropical convergence zone (ITCZ) and variation of wind patterns. North African aerosols extend over longer distances across the North Atlantic in summer because of greater dust emission, an intensified easterly low level jet (LLJ) and strengthening of the Azores-Bermuda anticyclonic circulation. Transport of East Asian aerosol is facilitated by the existence of a LLJ that extends from East Asia to the west coast of North America. © 2014 Elsevier B.V."
"22940851800;6603458409;7004657713;23491895700;7004960144;7202972418;25926056300;7003698344;","Surface energy budget of landfast sea ice during the transitions from winter to snowmelt and melt pond onset: The importance of net longwave radiation and cyclone forcings",2014,"10.1002/2013JC009672","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904536775&doi=10.1002%2f2013JC009672&partnerID=40&md5=2d00fb38260883978603a60617773490","Relatively few sea ice energy balance studies have successfully captured the transition season of warming, snowmelt, and melt pond formation. In this paper, we report a surface energy budget for landfast sea ice that captures this important period. The study was conducted in the Canadian Arctic Archipelago from 10 May to 20 June 2010. Over the first 20 days of the study, we found that short periods (1-3 days) of increased net radiation associated with low longwave loss provided most of the energy required to warm the snowpack from winter conditions. An extended period of low longwave loss (5 days) combined with the seasonal increase in incoming shortwave radiation then triggered snowmelt onset. Melt progressed with a rapid reduction in albedo and attendant increases in shortwave energy absorption, resulting in melt pond formation 8 days later. The key role of longwave radiation in initiating melt onset supports past findings, and confirms the importance of clouds and water vapor associated with synoptic weather systems. However, we also observed a period of strong turbulent energy exchange associated with the passage of a cyclone. The cyclone event occurred shortly after melt pond formation, but it delivered enough energy to significantly hasten melt onset had it occurred earlier in the season. Changes in the frequency, duration, and timing of synoptic-scale weather events that deliver clouds and/or strong turbulent heat fluxes may be important in explaining observed changes in sea ice melt onset timing. © 2014. American Geophysical Union. All Rights Reserved."
"56003822100;7003352529;7402578968;6701751679;","Aboveground total and green biomass of dryland shrub derived from terrestrial laser scanning",2014,"10.1016/j.isprsjprs.2013.12.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892470397&doi=10.1016%2fj.isprsjprs.2013.12.006&partnerID=40&md5=6b1f35a5ea4e27b38862c6037f6e2a77","Sagebrush (Artemisia tridentata), a dominant shrub species in the sagebrush-steppe ecosystem of the western US, is declining from its historical distribution due to feedbacks between climate and land use change, fire, and invasive species. Quantifying aboveground biomass of sagebrush is important for assessing carbon storage and monitoring the presence and distribution of this rapidly changing dryland ecosystem. Models of shrub canopy volume, derived from terrestrial laser scanning (TLS) point clouds, were used to accurately estimate aboveground sagebrush biomass. Ninety-one sagebrush plants were scanned and sampled across three study sites in the Great Basin, USA. Half of the plants were scanned and destructively sampled in the spring (n=46), while the other half were scanned again in the fall before destructive sampling (n=45). The latter set of sagebrush plants was scanned during both spring and fall to further test the ability of the TLS to quantify seasonal changes in green biomass. Sagebrush biomass was estimated using both a voxel and a 3-D convex hull approach applied to TLS point cloud data. The 3-D convex hull model estimated total and green biomass more accurately (R2=0.92 and R2=0.83, respectively) than the voxel-based method (R2=0.86 and R2=0.73, respectively). Seasonal differences in TLS-predicted green biomass were detected at two of the sites (p&lt;0.001 and p=0.029), elucidating the amount of ephemeral leaf loss in the face of summer drought. The methods presented herein are directly transferable to other dryland shrubs, and implementation of the convex hull model with similar sagebrush species is straightforward. © 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)."
"55821966900;7403573190;57196510591;56268753200;36466972400;","Diagnosing southeast tropical Atlantic SST and ocean circulation biases in the CMIP5 ensemble",2014,"10.1007/s00382-014-2247-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939872321&doi=10.1007%2fs00382-014-2247-9&partnerID=40&md5=e10ef0103592b30077b97531fda047cc","Warm sea-surface temperature (SST) biases in the southeastern tropical Atlantic (SETA), which is defined by a region from 5°E to the west coast of southern Africa and from 10°S to 30°S, are a common problem in many current and previous generation climate models. The Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble provides a useful framework to tackle the complex issues concerning causes of the SST bias. In this study, we tested a number of previously proposed mechanisms responsible for the SETA SST bias and found the following results. First, the multi-model ensemble mean shows a positive shortwave radiation bias of ~20 W m−2, consistent with models’ deficiency in simulating low-level clouds. This shortwave radiation error, however, is overwhelmed by larger errors in the simulated surface turbulent heat and longwave radiation fluxes, resulting in excessive heat loss from the ocean. The result holds for atmosphere-only model simulations from the same multi-model ensemble, where the effect of SST biases on surface heat fluxes is removed, and is not sensitive to whether the analysis region is chosen to coincide with the maximum warm SST bias along the coast or with the main SETA stratocumulus deck away from the coast. This combined with the fact that there is no statistically significant relationship between simulated SST biases and surface heat flux biases among CMIP5 models suggests that the shortwave radiation bias caused by poorly simulated low-level clouds is not the leading cause of the warm SST bias. Second, the majority of CMIP5 models underestimate upwelling strength along the Benguela coast, which is linked to the unrealistically weak alongshore wind stress simulated by the models. However, a correlation analysis between the model simulated vertical velocities and SST biases does not reveal a statistically significant relationship between the two, suggesting that the deficient coastal upwelling in the models is not simply related to the warm SST bias via vertical heat advection. Third, SETA SST biases in CMIP5 models are correlated with surface and subsurface ocean temperature biases in the equatorial region, suggesting that the equatorial temperature bias remotely contributes to the SETA SST bias. Finally, we found that all CMIP5 models simulate a southward displaced Angola–Benguela front (ABF), which in many models is more than 10° south of its observed location. Furthermore, SETA SST biases are most significantly correlated with ABF latitude, which suggests that the inability of CMIP5 models to accurately simulate the ABF is a leading cause of the SETA SST bias. This is supported by simulations with the oceanic component of one of the CMIP5 models, which is forced with observationally derived surface fluxes. The results show that even with the observationally derived surface atmospheric forcing, the ocean model generates a significant warm SST bias near the ABF, underlining the important role of ocean dynamics in SETA SST bias problem. Further model simulations were conducted to address the impact of the SETA SST biases. The results indicate a significant remote influence of the SETA SST bias on global model simulations of tropical climate, underscoring the importance and urgency to reduce the SETA SST bias in global climate models. © 2014, Springer-Verlag Berlin Heidelberg."
"7005659017;55444254800;7005766987;7004154626;","Sun-Sky Radiometer Synthesis of Interplay Between Aerosols and Monsoon Activity Over Pune, India",2014,"10.1007/s00024-014-0828-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908123005&doi=10.1007%2fs00024-014-0828-5&partnerID=40&md5=862251612bb1f5a1e430f98d11ccd8a7","Besides several thematic campaigns, utilizing a variety of platforms including satellites, ground-based networks have been established to improve our understanding of the role of aerosols in the changing monsoon climate. Two such widely known networks over the globe are ‘SKYNET’ and ‘AERONET’ with sun-sky radiometers as the principal equipment that characterizes aerosols and gases over different geographical locations under varied air mass conditions. Pune (18°43′N, 73°51′E, 559 m above mean sea level), a fast growing low-latitude, urban city in India, is one of the sites where Prede (POM-01L, SKYNET) and Cimel (CE-318, AERONET) Sun-sky radiometers have been in operation since 2004. These radiometers have been extensively used in several studies related to stand-alone and coupled aerosol-cloud-climate processes. The Prede instrument at this site is being augmented for the network of the Global Atmospheric Watch program of the World Meteorological Organization to facilitate data coordination through the World Data Center for Aerosols. The present study envisages understanding the response of atmospheric constituents, through simultaneous operation of the radiometers amongst others, for the rainfall activity over Pune during two contrasting monsoon years of 2008 (active, 98 % of long period average (LPA) rainfall over the whole country) and 2009 (weak, 78 % of LPA). The synthesis of data indicates that, apart from excellent agreement between the direct Sun observations, both radiometers capture well the monsoon features within the instrument density and efficacy of data retrieval algorithms involved. The meteorological fields from the ECMWF re-analysis and NOAA-HYSPLIT air-mass back-trajectory analysis during the study period have been utilized to explain the variations observed in the radiometer products. © 2014, Springer Basel."
"56085373500;57034458200;16025236700;","Genesis of hurricane Julia (2010) within an African easterly wave: Developing and nondeveloping members from WRF-LETKF ensemble forecasts",2014,"10.1175/JAS-D-13-0187.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903892653&doi=10.1175%2fJAS-D-13-0187.1&partnerID=40&md5=bb1a4b65dd2894b3b56bf2fc3b262487","In this study, the predictability of and parametric differences in the genesis of Hurricane Julia (2010) are investigated using 20 mesoscale ensemble forecasts with the finest resolution of 1km. Results show that the genesis of Julia is highly predictable, with all but two members undergoing genesis. Despite the high predictability, substantial parametric differences exist between the stronger and weaker members. Notably, the strongest-developing member exhibits large upper-tropospheric warming within a storm-scale outflow during genesis. In contrast, the nondeveloping member has weak and more localized warming due to inhibited convective development and a lack of a storm-scale outflow.A reduction in the Rossby radius of deformation in the strongest member aids in the accumulation of the warmth, while little contraction takes place in the nondeveloping member. The warming in the upper troposphere is responsible for the development of mesoα-scale surface pressure falls and a meso-β surface low in the strongest-developing member. Such features fail to form in the nondeveloping member as weak upper-tropospheric warming is unable to induce meaningful surface pressure falls. Cloud ice content is nearly doubled in the strongest member as compared to its nondeveloping counterparts, suggesting the importance of depositional heating of the upper troposphere. It is found that the stronger member undergoes genesis faster due to the lack of convective inhibition near the African easterly wave (AEW) pouch center prior to genesis. This allows for the faster development of a mesoscale convective system and storm-scale outflow, given the already favorable larger-scale conditions. © 2014 American Meteorological Society."
"55207477400;55717075800;46761494200;55726314800;35093720000;55598023100;","No altitude-dependent effects of climatic signals are recorded in Smith fir tree-ring δ18O on the southeastern Tibetan Plateau, despite a shift in tree growth",2014,"10.1111/bor.12053","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901952138&doi=10.1111%2fbor.12053&partnerID=40&md5=266fe17336eb485a9fe04333f1dd74aa","To reveal the influence of current warming on tree growth and δ18O in a sensitive high-latitude region that is undergoing rapid climate change, we examined tree width and the earlywood and latewood δ18O at two sites with a 400-m elevation difference in the Sygera Mountains of the southeastern Tibetan Plateau. The study period was from 1950 to 2011. The mean tree-ring index at the low site was higher than that at the high site during the study period. The climatic responses of earlywood and latewood δ18O at both sites were similar. Earlywood δ18O was mainly influenced by the June to August temperature and total cloud cover, whereas latewood δ18O was mainly controlled by relative humidity from July to August. Spatial correlations with CRU TS 3.1 regional data suggest that our δ18O chronologies can represent climatic changes over large regions. The high offset between earlywood δ18O at the two sites (2.3‰ higher at the low site) was mainly influenced by the high temperature lapse rate as a function of altitude during the earlywood growing season. Furthermore, meltwater with lower δ18O values might have affected earlywood δ18O at the high site, and thereby increased the earlywood δ18O offset between two sites. The low latewood δ18O offset between the two sites (0.4‰ higher at the low site) was not significant, but appears to have been primarily influenced by the low precipitation δ18O lapse rate as a function of altitude during the latewood growing season. Earlywood δ18O of Smith fir suitable for reconstructing past temperatures and latewood δ18O suitable for reconstructing past relative humidity on the southeastern Tibetan Plateau were identified. © 2013 Collegium Boreas. Published by John Wiley &amp; Sons Ltd."
"8579580700;56582801100;7403162140;6507091483;","Temporal variations in the linkage between the net ecosystem exchange of water vapour and CO2 over boreal forests in eastern Siberia",2014,"10.1002/eco.1449","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897507259&doi=10.1002%2feco.1449&partnerID=40&md5=833547dbae5ce3c1d38b4fd588642686","This study investigated evapotranspiration and CO2 exchange, observed by the eddy covariance method, over two larch-dominated forests, in the middle part of the Lena basin, eastern Siberia. Compared with the Spasskaya Pad (SP) forest, the Elgeeii (EG) forest had more plant biomass and a soil texture that allowed for larger water retention. Observations in three growing seasons revealed that the two sites had similar seasonal patterns of meteorological conditions and almost the same total evapotranspiration; however, the net and gross uptakes of CO2 at the EG forest were 1·61 and 1·31 times those at the SP forest, respectively. The difference in aboveground biomass was probably responsible for the higher productivity at EG. Less aboveground biomass would result in less transpiration by trees at SP, which would be compensated for in total evapotranspiration by soil evaporation and transpiration by the forest floor vegetation. It is likely that forest transpiration is commonly optimized to the same level of evapotranspiration under similar meteorological conditions through differences in the contributions of evapotranspiration from the forest floor vegetation and the soil water availability. Water use efficiency (WUE) displayed different patterns, reflecting the seasonal variations in each flux. Seasonal sequences in the WUE at EG indicated a midsummer depletion, which is commonly observed in forest ecosystems under a broad climate. Daily variation corresponding to the vapour pressure deficit and the cloud cover conditions (reduced solar radiation) was also observed. In contrast, WUE was relatively invariable at the seasonal and daily scales at SP. © 2013 John Wiley &amp; Sons, Ltd."
"42661692800;7202048112;6506328135;6508063123;57210180554;6602858513;7406243250;","The dependence of ITCZ structure on model resolution and dynamical core in aquaplanet simulations",2014,"10.1175/JCLI-D-13-00269.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896075417&doi=10.1175%2fJCLI-D-13-00269.1&partnerID=40&md5=b9529dbe1094c5f5a0091b3aec8fddc0","Aquaplanet simulations using the Community Atmosphere Model, version 4 (CAM4), with the Model for Prediction Across Scales-Atmosphere (MPAS-A) and High-Order Method Modeling Environment (HOMME) dynamical cores and using zonally symmetric sea surface temperature (SST) structure are studied to understand the dependence of the intertropical convergence zone (ITCZ) structure on resolution and dynamical core. While all resolutions in HOMME and the low-resolution MPAS-A simulations give a single equatorial peak in zonal mean precipitation, the high-resolution MPAS-A simulations give a double ITCZ with precipitation peaking around 28-38 on either side of the equator. This study reveals that the structure of ITCZ is dependent on the feedbacks between convection and large-scale circulation. It is shown that the difference in specific humidity betweenHOMMEandMPAS-A can lead to different latitudinal distributions of the convective available potential energy (CAPE) by influencing latent heat release by clouds and the upper-tropospheric temperature. With lower specific humidity, the high-resolution MPAS-A simulation has CAPE increasing away from the equator that enhances convection away from the equator and, through a positive feedback on the circulation, results in a double ITCZ structure. In addition, it is shown that the dominance of antisymmetric waves in the model is not enough to cause double ITCZ, and the lateral extent of equatorial waves does not play an important role in determining the width of the ITCZ but rather the latter may influence the former. © 2014 American Meteorological Society."
"6506322102;26641045500;6603943978;6603049815;24777891700;55053446300;6507327642;6603898368;7003272339;7004499360;23667124700;6701558984;","Observations of surface radiation and stratospheric processes at Thule air base, Greenland, during the IPY",2014,"10.4401/ag-6382","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902987602&doi=10.4401%2fag-6382&partnerID=40&md5=0b6956edf87c38b44329c6f4ec3ee1d4","Ground-based measurements of atmospheric parameters have been carried out for more than 20 years at the Network for the Detection of Atmospheric Composition Change (NDACC) station at Thule Air Base (76.5°N, 68.8°W), on the north-western coast of Greenland. Various instruments dedicated to the study of the lower and middle polar atmosphere are installed at Thule in the framework of a long standing collaboration among Danish, Italian, and US research institutes and universities. This effort aims at monitoring the composition, structure and dynamics of the polar stratosphere, and at studying the Arctic energy budget and the role played by different factors, such as aerosols, water vapour, and surface albedo. During the International Polar Year (IPY), in winter 2008-2009, an intensive measurement campaign was conducted at Thule within the framework of the IPY project ""Ozone layer and UV radiation in a changing climate evaluated during IPY"" (ORACLE-O3) which sought to improve our understanding of the complex mechanisms that lead to the Arctic stratospheric O3 depletion. The campaign involved a lidar system, measuring aerosol backscatter and depolarization ratios up to 35 km and atmospheric temperature profiles from 25 to 70 km altitude, a ground-based millimeter-wave spectrometer (GBMS) used to derive stratospheric mixing ratio profiles of different chemical species involved in the stratospheric ozone depletion cycle, and then ground-based radiometers and a Cimel sunphotometer to study the Arctic radiative budget at the surface. The observations show that the surface radiation budget is mainly regulated by the longwave component throughout most of the year. Clouds have a significant impact contributing to enhance the role of longwave radiation. Besides clouds, water vapour seasonal changes produce the largest modification in the shortwave component at the surface, followed by changes in surface albedo and in aerosol amounts. For what concerns the middle atmosphere, during the first part of winter 2008-2009 the cold polar vortex allowed for the formation of polar stratospheric clouds (PSCs) which were observed above Thule by means of the lidar. This period was also characterized by GBMS measurements of low values of O3 due to the catalytic reactions prompted by the PSCs. In midJanuary, as the most intense Sudden Stratospheric Warming event ever observed in the Arctic occurred, GBMS and lidar measurements of O3, N2O, CO and temperature described its evolution as it propagated from the upper atmosphere to the lower stratosphere. © 2014 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved."
"56158429100;35090697300;56142344000;49361390400;","Variations in water level and glacier mass balance in Nam Co lake, Nyainqentanglha range, Tibetan Plateau, based on ICESat data for 2003-09",2014,"10.3189/2014AoG66A100","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903121957&doi=10.3189%2f2014AoG66A100&partnerID=40&md5=4535ca8b1a7afc6570550b7862c3e556","Water level fluctuations of inland lakes are related to regional-scale climate changes, and reflect variations in evaporation, precipitation and glacier meltwater flowing into the lake area in its catchment. In this paper, Ice, Cloud and land Elevation Satellite (ICESat) altimeter data and Landsat imagery (2002-09) are used to estimate Nam Co lake (Nyainqentanglha range, Tibetan Plateau) water elevation changes during 2002-09. In 2003 Nam Co lake covered an area of ~1998.8±4.2km2 and was situated at 4723ma.s.l. Over such inland water bodies, ICESat altimeter data offer both wide coverage and spatial and temporal accuracy. We combine remote-sensing and GIS technology to map and reconstruct lake area and increased volume changes during a 7 year time series. Nam Co lake water level increased by 2.4±0.12m (0.33ma-1) between 23 February 2003 and 1 October 2009, and lake volume increased by 4.9±0.5km3. In the past 7 years, Nam Co lake area has increased from 1998.78±5.4 to 2023.8±3.4km 2, the glacier-covered area has decreased from 832.34 to 821.0km 2 and the drainage basin area has decreased from 201.1±4.2 to 196.1±2.3km2. However, the most spectacular feature is the continual water level rise from 2003 to 2009 without an obvious associated increase in precipitation. Based on digital elevation models (DEMs) from Shuttle Radar Topography Mission (SRTM) DEM data and corrected ICESat elevation data, significant changes to glacier mass balance in the western Nyainqentanglha mountains are indicated. Nyainqentanglha mountain glacier surface elevations decreased by 8.39±0.45m during 2003-09. Over the same period, at least 1.01km3 of glacial meltwater flowed into Nam Co lake, assuming a glacial runoff coefficient of 0.6. The mean glacier mass-balance value is -490mmw.e. over the corresponding period, indicating that glacier meltwater in the catchment contributes to lake level rise. The contribution rate of glacial meltwater to lake water volume rise is 20.75%. The temporal lake level fluctuation correlates with temperature variations over the same time span."
"56986615100;6506365550;56985470700;24598096400;14051672300;7102927027;","Design of a GIS-based web application for simulating biofuel feedstock yields",2014,"10.3390/ijgi3030929","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940653065&doi=10.3390%2fijgi3030929&partnerID=40&md5=97780c233b0230de78ef51ad1c583a9c","Short rotation woody crops (SRWC), such as hybrid poplar, have the potential to serve as a valuable feedstock for cellulosic biofuels. Spatial estimates of biomass yields under different management regimes are required for assisting stakeholders in making better management decisions and to establish viable woody cropping systems for biofuel production. To support stakeholders in their management decisions, we have developed a GIS-based web interface using a modified 3PG model for spatially predicting poplar biomass yields under different management and climate conditions in the U.S. Pacific Northwest region. The application is implemented with standard HTML5 components, allowing its use in a modern browser and dynamically adjusting to the client screen size and device. In addition, cloud storage of the results makes them accessible on any Internet-enabled device. The web interface appears simple, but is powerful in parameter manipulation and in visualizing and sharing the results. Overall, this application comprises dynamic features that enable users to run SRWC crop growth simulations based on GIS information and contributes significantly to choosing appropriate feedstock growing locations, anticipating the desired physiological properties of the feedstock and incorporating the management and policy analysis needed for growing hybrid poplar plantations. © 2014 by the authors; licensee MDPI, Basel, Switzerland."
"14038701400;57218315684;54420865700;","Multi annual variability and climatic signal analysis of sunshine duration at a large urban area of Mediterranean (Athens)",2014,"10.1016/j.uclim.2014.09.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927016517&doi=10.1016%2fj.uclim.2014.09.008&partnerID=40&md5=03f1c95e6421a993f274f3016b9c836c","This study analyses the interannual variability of sunshine duration (SDU) at the urban area of Athens from 1897 to 2011. Observations of total cloud cover (TCC) are also used for a better interpretation of SDU variations. The annual SDU in Athens has increased by +8% (+19 h/decade) over the past century, mainly due to increase in the summer and spring SDU, however, distinct sub periods with decreasing and increasing trends are also discerned. SDU in Athens has undergone an abrupt increase during 1940s with early 1950s being the brightest period of the record. For long periods the course of SDU mirrors TCC, indicating a strong negative correlation between the two variables, nevertheless during the last three decades, both variables reveal trends of the same sign (more evident in spring). Under all-sky conditions, annual SDU decreased by approximately 7% from 1950s to 1980s and increased by 3% thereafter. Under clear sky conditions, the increase of SDU after 1980s is larger, amounting to 9%. Singular spectrum analysis and Continuous Wavelet Transform indicated significant non-linear trends of SDU and an intermittent oscillation, centered at 2.9-3.0 yrs. © 2014 Elsevier B.V."
"29367509500;","Observations of stratospheric O3 intrusions in air quality monitoring data in Ontario, Canada",2014,"10.1016/j.atmosenv.2014.08.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906768928&doi=10.1016%2fj.atmosenv.2014.08.024&partnerID=40&md5=9fe4f4c315001e1773507c64dfaaa017","Intrusions of stratospheric ozone (O3) to the troposphere at tropopause fold events are one mechanism of stratosphere-troposphere exchange, which is known to be a significant component of the tropospheric O3 budget. Although these intrusions rarely extend downward to the surface and are not observed directly, air quality measurements of ground-level O3 in Ontario have shown brief anomalous spikes in O3 concentrations coinciding with the weather conditions associated with tropopause fold events. Several events are documented in this article that occurred over southern Ontario during December 28, 2008; February 11-12, 2009; January 20, 2013; and January 31, 2013. Each case presents several examples of sudden increases in O3 concentrations (generally about 10-20ppb above a background of about 30-40ppb) along with the related synoptic weather factors associated with tropopause folds and stratospheric O3 intrusions. © 2014."
"7006681376;7004047492;24280225800;","High temporal resolution estimations of the Arctic sea ice albedo during the melting and refreezing periods of the years 2011",2014,"10.1016/j.rse.2013.10.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886304044&doi=10.1016%2fj.rse.2013.10.001&partnerID=40&md5=f188aa94263cd44de5a8f6317ccbab2c","Methods for estimating seasonal and long term trends of the Arctic sea ice albedo are of growing importance to cryosphere and climate studies. Remote sensing of the sea ice albedo has hitherto been carried out using optical satellite instruments. However, the measured data is often insufficient in late summer and fall because of clouds and low solar elevations. Therefore, new methods are a prerequisite for realistic estimations for the global sea ice albedo over the whole melting-refreezing period. Here, we show that a new microwave based sea ice albedo estimation method alleviates problems of optical instruments, offering new albedo data especially during the refreezing periods even on a daily basis. In this study we present detailed weekly and daily albedo progress over the whole Arctic sea ice area from June to September for the period of 2003-2011, estimated using the microwave method. © 2013 Elsevier Inc."
"24081949800;7005449794;7003659713;57207288506;","Local feedback mechanisms of the shallow water region around the Maritime Continent",2014,"10.1002/2013JC009700","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84915747470&doi=10.1002%2f2013JC009700&partnerID=40&md5=8de88d11e99af9ef4844c250758eaba1","The focus of this study is the local-scale air-sea feedback mechanisms over the shallow shelf water region (water depth 200 m) of the Maritime Continent (MC). MC was selected as a pilot study site for its extensive shallow water coverage, geographic complexity, and importance in the global climate system. To identify the local-scale air-sea feedback processes, we ran numerical experiments with perturbed surface layer water temperature using a coupled ocean-atmosphere model and an uncoupled ocean model. By examining the responses of the coupled and uncoupled models to the water temperature perturbation, we identify that, at a local-scale, a negative feedback process through the coupled dynamics that tends to restore the SST from its perturbation could dominate the shallow water region of the MC at a short time scale of several days. The energy budget shows that 38% of initial perturbation-induced heat energy was adjusted through the air-sea feedback mechanisms within 2 weeks, of which 58% is directly trnsferred into the atmosphere by the adjustment of latent heat flux due to the evaporative cooling mechanism. The increased inputs of heat and moisture into the lower atmosphere then modifies its thermal structure and increases the formation of low-level clouds, which act as a shield preventing incoming solar radiation from reaching the sea surface, accounts for 38% of the total adjustment of surface heat fluxes, serving as the second mechanism for the negative feedback process. The adjustment of sensible heat flux and net longwave radiation play a secondary role. The response of the coupled system to the SST perturbation suggests a response time scale of the coupled feedback process of about 3-5 days. The two-way air-sea feedback tightly links the surface heat fluxes, clouds and SST, and can play an important role in regulating the shortterm variability of the SST over the shallow shelf water regions."
"23991074400;54581786900;34973234300;57139379600;55731334900;56937504400;55237867300;","Effect of land surface processes on the Tibetan Plateau's past and its predicted response to global warming: An analytical investigation based on simulation results from the CMIP5 model",2014,"10.1007/s12665-013-3034-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905190457&doi=10.1007%2fs12665-013-3034-3&partnerID=40&md5=9ccef46478df2e23b175de2f106ac79d","Complex interactions between the land surface and atmosphere and the exchange of water and energy have a significant impact on climate. The Tibetan Plateau is the highest plateau in the world and is known as ""Earth's third pole"". Because of its unique natural geographical and climatic characteristics, it directly affects China's climate, as well as the world's climate, through its thermal and dynamic roles. In this study, the BCCCSM1.1 model for the simulation results of CMIP5 is used to analyze the variation of the land surface processes of the Tibetan Plateau and the possible linkages with temperature change. The analysis showed that, from 1850 to 2005, as temperature increases, the model shows surface downward short-wave radiation, upward short-wave radiation, and net radiation to decrease, and long-wave radiation to increase. Meanwhile, latent heat flux increases, whereas sensible heat flux decreases. Except for sensible heat flux, the correlation coefficients of land surface fluxes with surface air temperature are all significant at the 99 % significance level. The model results indicate rising temperature to cause the ablation of ice (or snow) cover and increasing leaf area index, with reduced snowfall, together with a series of other changes, resulting in increasing upward and downward long-wave radiation and changes in soil moisture, evaporation, latent heat flux, and water vapor in the air. However, rising temperature also reduces the difference between the surface and air temperature and the surface albedo, which lead to further reductions of downward and upward short-wave radiation. The surface air temperature in winter increases by 0.93 °C/100 years, whereas the change is at a minimum (0.66 °C/100 years) during the summer. Downward short-wave and net radiation demonstrate the largest decline in the summer, whereas upward short-wave radiation demonstrates its largest decline during the spring. Downward short-wave radiation is predominantly affected by air humidity, followed by the impact of total cloud fraction. The average downward short-wave and net radiation attain their maxima in May, whereas for upward short-wave radiation the maximum is in March. The model predicts surface temperature to increase under all the different representative concentration pathway (RCP) scenarios, with the rise under RCP8.5 reaching 5.1 °C/100 years. Long-wave radiation increases under the different emission scenarios, while downward short-wave radiation increases under the low- and medium-emission concentration pathways, but decreases under RCP8.5. Upward short-wave radiation reduces under the various emission scenarios, and the marginal growth decreases as the emission concentration increases. © 2014 Springer-Verlag Berlin Heidelberg."
"7404240633;57189084438;8213069900;55742840200;7410070663;","Parametrization of instantaneous global horizontal irradiance: Clear-sky component",2014,"10.1002/qj.2126","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927581644&doi=10.1002%2fqj.2126&partnerID=40&md5=4d2968fd2512710095e8a95ea882f07e","Based on an accurate atmospheric radiative transfer scheme, a parametrization of instantaneous global horizontal irradiance (GHI) at the Earth's surface has been developed. The scheme is named SUNFLUX and this article describes the development of the scheme for clear-sky conditions. The work dealing with clouds has been published in a separate article. Unlike traditional methods, this study applies the band model idea used in radiative transfer theory to the development of the surface radiation scheme and, importantly, includes absorption and scattering in the parametrization. Thus the scheme is more accurate compared with those using simple empirical approaches and may be applied to any site without being tuned for local conditions. The parametrization of aerosol transmittance and albedo developed by Kokhanovsky et al. is adopted to account for the effects of aerosols. All variables used in the scheme are available in climate models or from satellite observations. Therefore, the parametrization can be used to determine the GHI at the surface under clear-sky conditions The scheme is evaluated using observations obtained from three US Atmospheric Radiation Measurement (ARM) stations and three stations on the Tibetan Plateau, and the results demonstrate that the scheme is accurate. The relative mean bias difference is less than 4.3% and the relative root-mean-squared difference is less than 0.09%. © 2013 Royal Meteorological Society."
"56494067400;56448868700;35323821500;","Climatological classification of available potential energy for convection in the city of belém-pa [Classificação climatológica da energia potencial disponível para a convecção na cidade de belém-pa]",2014,"10.1590/0102-778620130040","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921763756&doi=10.1590%2f0102-778620130040&partnerID=40&md5=69d99d8643ababa1bcfc35cf6232271a","The climatological classification of the Convection Available Potential Energy (CAPE) was studied in order to verify both the possibility of convection to start and the organizational type, in Belém (Pará - PA, Brazil), associating it to extreme precipitation events (EEPRP). For the CAPE analysis, DTCEA’s radiosonde data and precipitation measurements from the INMET’s stations, in the period from 1987 to 2011, we used. It was observed that the local atmosphere presented favorable conditions for the development of deep convection, because the most frequent CAPE values were higher than 1000 J/Kg, representing 61% of all radiosonde measurements. According to some authors, a CAPE value of 1000J/Kg is the deep convection limit. The CAPE 2 and 3 classifications presented significant increasing tendencies along the years, whereas CAPE 1 showed a decrease. This is probably due to the air temperature increased at the city, impacting the CAPE value. A low correlation between CAPE and EEPRP, as well as between CAPE and Pacific Ocean Index and the Atlantic Interhemispheric Gradient. was also shown. Therefore CAPE is not sufficient condition for the formation of clouds and precipitation, since meso and large scale dynamical forcing are relevant contributors to the climate modulation on the city. © 2014, Sociedade Brasileira de Meteorologia. All rights reserved."
"57203025941;6603171056;7003408430;56372966800;","Calendar-year dating of the Greenland Ice Sheet Project 2 (GISP2) ice core from the early sixth century using historical, ion, and particulate data",2014,"10.1130/2014.2505(22)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907546595&doi=10.1130%2f2014.2505%2822%29&partnerID=40&md5=5c738aac19858f1260d3f6c3a2dc171b","We use the occurrence of unusual or out-of-season dust storms and dissolved ion data as proxies for dust to propose a calendar-year chronology for a portion of the Greenland Ice Sheet Project 2 (GISP2) ice core during the early sixth century A.D. Our new time scale moves a small sulfate peak to early 537 A.D., which is more consistent with recent fi ndings of a 6 mo to 18 mo time lag between volcanic eruptions and atmospheric fallout of their sulfate aerosols. Our new time scale is consistent with a small volcanic input to the A.D. 536-537 climate downturn. We use the time range of Ni-rich fragments and cosmic spherules to provide an independent test of the chronology. The time range of Ni-rich fragments and cosmic spherules matches historical observations of ""dancing stars"" starting in the summer of A.D. 533 and lasting until A.D. 539 or 540. These dancing stars have been previously attributed to cosmogenic dust loading of Earth's atmosphere. The time scale cannot be shifted to be either younger or older by 1 yr without destroying the match to historical accounts of dancing stars. © 2014 The Geological Society of America. All rights reserved."
"7005533072;25422236800;34873483200;24069675400;26667053600;","Sea and Land Surface Temperature Radiometer detection assembly design and performance",2014,"10.1117/1.JRS.8.084979","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905727891&doi=10.1117%2f1.JRS.8.084979&partnerID=40&md5=574d41a4ee37160d23f19fb53a3bd8a8","The Sea and Land Surface Temperature Radiometers (SLSTRs) are high-accuracy radiometers selected for the Copernicus mission Sentinel-3 space component to provide sea surface temperature (SST) data continuity with respect to previous (Advanced) Along Track Scanning Radiometers [(A)ATSRs] for climatology. Many satellites are foreseen over a 20-year period, each with a 7.5-year lifetime. Sentinel-3A will be launched in 2015 and Sentinel-3B at least six months later, implying that two identical satellites will be maintained in the same orbit with a 180-deg phase delay. Each SLSTR has an improved design with respect to AATSR affording wider near-nadir and oblique view swaths (1400 and 740 km) for SST/land surface temperature global coverage at a 1-km spatial resolution (at SSP) with a daily revisit time (with two satellites), appropriate for both climate and meteorology. Cloud screening and other products are obtained with 0.5 km spatial resolution [at sub-satellite point (SSP)] in visible and short wave infrared (SWIR) bands, while two additional channels are included to monitor high temperature events such as forest fires. The two swaths are obtained with two conical scans and telescopes combined optically at a common focus, representing the input of a cooled focal plane assembly, where nine channels are separated with dichroic and are focalized on detectors with appropriate optical relays. IR and SWIR optics/detectors are cooled to 85 K by an active mechanical cryo-cooler with vibration compensation, while the VIS ones are maintained at a stable temperature. The opto-mechanical design and the expected electro-optical performance of the focal plane assembly are described and the model predictions at system level are compared with experimental data acquired in the vacuum chamber in flight representative thermal conditions or in the laboratory. © 2014 SPIE."
"6603549099;55856811000;39362296200;7201718045;","On the estimation of melt pond fraction on the arctic sea ice with ENVISAT WSM images",2014,"10.1109/TGRS.2014.2311476","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902076202&doi=10.1109%2fTGRS.2014.2311476&partnerID=40&md5=4998ad27fd5b9f2fa41dbd7f8ac82abb","The accuracy of microwave radiometer ice concentration (IC) retrievals in the Arctic is degraded by melt ponds on sea ice during the melting season. For the development of IC retrieval algorithms and for the quantification of their uncertainties, data sets on the area fraction of melt ponds (fmp) are needed. fmp retrieval with optical satellite data is limited by clouds. Thus, we have studied fmp retrieval with ENVISAT wide swath mode (WSM) synthetic aperture radar (SAR) images which have large daily coverage over the Arctic Sea ice in 2007-2012. The WSM images used here were acquired north of the Fram Strait in June-August 2009. Data on fmp were available from the Integrated Climate Data Center's daily Moderate Resolution Imaging Spectroradiometer (MODIS) fmp product in a 12.5-km grid. Relationships between SAR σ° and MODIS fmp were studied visually by comparing daily SAR mosaics and fmp charts and by analyzing fmp and σ° time series and spatially and temporally coincident fmp and σ° data. The correspondence between the changes of fmp and the σ° statistics is too low to suggest fmp estimation from theWSM images. In some cases, there was a 2-3-dB σ° increase during the ponding period. It is assumed that the variation of snow and sea ice characteristics diminishes σ° changes due to the melt ponding and drainage. Good correlation between σ° and fmp has only been observed for smooth landfast first-year ice in previous studies. A very interesting observation was the large temporal σ° variations during the late melting season, which are likely linked to the atmospherically forced freezing-melting events. These events may also influence radiometer IC retrievals. © 1980-2012 IEEE."
"7007035776;35621245100;55004028300;16044004800;56123970600;8290336100;7404087101;","Optimizing carbon storage and biodiversity protection in tropical agricultural landscapes",2014,"10.1111/gcb.12482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901934416&doi=10.1111%2fgcb.12482&partnerID=40&md5=52a91887cb16761e348b7c94005bbb42","With the rapidly expanding ecological footprint of agriculture, the design of farmed landscapes will play an increasingly important role for both carbon storage and biodiversity protection. Carbon and biodiversity can be enhanced by integrating natural habitats into agricultural lands, but a key question is whether benefits are maximized by including many small features throughout the landscape ('land-sharing' agriculture) or a few large contiguous blocks alongside intensive farmland ('land-sparing' agriculture). In this study, we are the first to integrate carbon storage alongside multi-taxa biodiversity assessments to compare land-sparing and land-sharing frameworks. We do so by sampling carbon stocks and biodiversity (birds and dung beetles) in landscapes containing agriculture and forest within the Colombian Chocó-Andes, a zone of high global conservation priority. We show that woodland fragments embedded within a matrix of cattle pasture hold less carbon per unit area than contiguous primary or advanced secondary forests (>15 years). Farmland sites also support less diverse bird and dung beetle communities than contiguous forests, even when farmland retains high levels of woodland habitat cover. Landscape simulations based on these data suggest that land-sparing strategies would be more beneficial for both carbon storage and biodiversity than land-sharing strategies across a range of production levels. Biodiversity benefits of land-sparing are predicted to be similar whether spared lands protect primary or advanced secondary forests, owing to the close similarity of bird and dung beetle communities between the two forest classes. Land-sparing schemes that encourage the protection and regeneration of natural forest blocks thus provide a synergy between carbon and biodiversity conservation, and represent a promising strategy for reducing the negative impacts of agriculture on tropical ecosystems. However, further studies examining a wider range of ecosystem services will be necessary to fully understand the links between land-allocation strategies and long-term ecosystem service provision. © 2014 John Wiley & Sons Ltd."
"7004051458;","Galactic cosmic rays, total solar irradiance, sunspots, earth surface air temperature: Correlations",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901421204&partnerID=40&md5=2cf8ebe7a1ad7d10c49603ee43c23831","The variation in the annual mean Earth surface air temperature is a key indicator of the climate change. An empirical search explores the connection among the long-term surface air temperature change (δT), the ionization caused by the galactic cosmic rays (GCRs) in the upper atmosphere, the interplanetary magnetic field (IMF) intensity (B) at the Earth orbit, the total solar irradiance (TSI) and the sunspot numbers (SSNs). Several scenarios are investigated with the world's longest and robust GCR data string for the instrumental era (1937-2013) covering eight SSN cycles (17-24). The data are further extended to 1900 to include three additional cycles (14-16). For δT comparisons, three datasets used are: the US surface air temperature (UST), the global surface air temperature (GST), and the land ocean temperature (LOT). For 1900-1955 and 1968-1987, an inverse correlation between GCR and GST is obtained. For 1956-1967, GCR intensity changes significantly (~18%) with little change in GST. A positive correlation is obtained between GCR and GST for 1988-2008, implying that GCRs contribute to global warming. These results lead to infer that there is no sustained GCR-GST relationship, i.e. changes in GCR flux does not affect GST. Recent results from the CLOUD experiment are consistent with this inference. A comparison between the amplitude of the solar wind electric field and GST leads to an inconclusive result as well. It is also noted that TSI does not contribute to δT either. The historic evidence and the predicted trend for peak activity [Ahluwalia H S & Jackiewicz J, Sunspot cycle 23 descent to an unusual minimum and forecasts for cycle 24 activity, Adv Space Res (UK), 50 (2012) pp 662-668, doi:10.1016/j.asr.2011.04.023, 2012] for future cycles (25 and 26) suggests that Earth may cool in the next three decades, in contrast to IPCC [IPCC, Climate change 2007: The physical basis, Eds: S Solomon et al. (Cambridge Press, New York), 2007] consensus that GST will rise 4°C ± 2°C in the year 2100."
"56079254300;56079305100;7005886789;","Concentrated solar drying of tomatoes",2014,"10.1016/j.esd.2013.11.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896739205&doi=10.1016%2fj.esd.2013.11.006&partnerID=40&md5=dbfcf39f33d9e44eca628e7d1a47b2ae","Fruits and vegetables are an integral part of the human diet. Many developing countries such as Tanzania experience post-harvest losses of 40%, and there is little ability to preserve and store foods for off-season consumption due to expensive or unreliable energy and a lack of access to refrigeration. Alternatively, fruits and vegetables can be dehydrated using solar crop dryers. Because many developing countries are in tropical regions, properly dehydrating fruits and vegetables to moisture levels appropriate for storage and off-season consumption can be difficult. In an attempt to overcome the challenges of the high humidity, intermittent clouds, and haze often present in tropical climates, this paper investigates the effectiveness of adding a concave solar concentrator built from low-cost, locally available materials to a typical Tanzanian solar crop dryer. Two identical solar crop dryers were constructed, with one serving as the control and the other for testing the solar concentrator. Drying trials using Roma tomatoes with initial moisture content of approximately 90% were conducted in Davis, California (38° 32' 42″ N/121° 44' 21″ W) in various climatic conditions throughout the summer and fall. Tomatoes were considered dried at 10% moisture content. Temperature, relative humidity, and solar radiation were measured outside as well as within each of the dryers to determine how the addition of a solar concentrator can affect the drying rate of tomatoes in solar crop dryers. The concentrator proved to be effective, reducing drying time by 21% in addition to increasing internal dryer temperature and reducing relative humidity. An additional study on the quality of the fresh and dried tomatoes found that the pH, titratable acidity, color, Brix, lycopene, and vitamin C determined there was no significant difference in quality between tomatoes dried with and without the concentrator. © 2013 Elsevier Ltd."
"55293130300;7201897043;","Thirty-two-year ocean–atmosphere coupled downscaling of global reanalysis over the Intra-American Seas",2014,"10.1007/s00382-014-2069-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893203424&doi=10.1007%2fs00382-014-2069-9&partnerID=40&md5=586cdc011d8e8f4961ee0df9ee8a3e93","This study examines the oceanic and atmospheric variability over the Intra-American Seas (IAS) from a 32-year integration of a 15-km coupled regional climate model consisting of the Regional Spectral Model (RSM) for the atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean. It is forced at the lateral boundaries by National Centers for Environmental Prediction-Department of Energy (NCEP-DOE R-2) atmospheric global reanalysis and Simplified Ocean Data Assimilation global oceanic reanalysis. This coupled downscaling integration is a free run without any heat flux correction and is referred as the Regional Ocean–Atmosphere coupled downscaling of global Reanalysis over the Intra-American Seas (ROARS). The paper examines the fidelity of ROARS with respect to independent observations that are both satellite based and in situ. In order to provide a perspective on the fidelity of the ROARS simulation, we also compare it with the Climate Forecast System Reanalysis (CFSR), a modern global ocean–atmosphere reanalysis product. Our analysis reveals that ROARS exhibits reasonable climatology and interannual variability over the IAS region, with climatological SST errors less than 1 °C except along the coastlines. The anomaly correlation of the monthly SST and precipitation anomalies in ROARS are well over 0.5 over the Gulf of Mexico, Caribbean Sea, Western Atlantic and Eastern Pacific Oceans. A highlight of the ROARS simulation is its resolution of the loop current and the episodic eddy events off of it. This is rather poorly simulated in the CFSR. This is also reflected in the simulated, albeit, higher variance of the sea surface height in ROARS and the lack of any variability in the sea surface height of the CFSR over the IAS. However the anomaly correlations of the monthly heat content anomalies of ROARS are comparatively lower, especially over the Gulf of Mexico and the Caribbean Sea. This is a result of ROARS exhibiting a bias of underestimation (overestimation) of high (low) clouds. ROARS like CFSR is also able to capture the Caribbean Low Level Jet and its seasonal variability reasonably well. © 2014, Springer-Verlag Berlin Heidelberg."
"56342393700;15830057200;56161483400;36936951100;","Agro-ecological zoning of Chhattisgarh",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947284809&partnerID=40&md5=0a24b2ebf435561879749b44569256d1","The study was carried out entitled, ""Agro-ecological zoning of Chhattisgarh"" to characterize the agro-climatic and agro-ecological parameters. The characterization was based on screening of distinct agro-climatic parameters apart with agro-ecological parameters and preparation of data base for the said zones of Chhattisgarh. The study reaveled that agro-climatic factors viz temperature, rainfall, humidity, cloud cover, radiation intensity, rainy days, wind speed, and potential transpiration varied during annual duration including Rabi and kharif season from one region to another region of Chhattisgarh. The purpose of zoning, as carried out for rural land-use planning, is to separate areas with similar sets of potentials and constraints for development. Specific programmes can then be formulated to provide the most effective support to each zone. Agro-ecological zoning (AEZ), as applied in FAO studies, defines zones on the basis of combinations of soil, landform and climatic characteristics. The particular parameters used in the definition focus attention on the climatic and edaphic requirements of crops and on the management systems under which the crops are grown. The Agro-ecological zone map gives an idea of a soil type and climatic condition of a particular place. The classes of 63 Agro-ecological zone map help the scientist and farmer to grow a crop according to climatic condition and soil type of Chhattisgarh."
"55709068100;56014821400;52464842700;55994328200;","Object-based approach to national land cover mapping using HJ satellite imagery",2014,"10.1117/1.JRS.8.083686","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897775628&doi=10.1117%2f1.JRS.8.083686&partnerID=40&md5=a299d7a245ed807b25f692e31abaae27","To meet the carbon storage estimate in ecosystems for a national carbon strategy, we introduce a consistent database of China land cover. The Chinese Huan Jing (HJ) satellite is proven efficient in the cloud-free acquisition of seasonal image series in a monsoon region and in vegetation identification for mesoscale land cover mapping. Thirty-eight classes of level II land cover are generated based on the Land Cover Classification System of the United Nations Food and Agriculture Organization that follows a standard and quantitative definition. Twenty-four layers of derivative spectral, environmental, and spatial features compose the classification database. Object-based approach characterizing additional nonspectral features is conducted through mapping, and multiscale segmentations are applied on object boundary match to target real-world conditions. This method sufficiently employs spatial information, in addition to spectral characteristics, to improve classification accuracy. The algorithm of hierarchical classification is employed to follow step-by-step procedures that effectively control classification quality. This algorithm divides the dual structures of universal and local trees. Consistent universal trees suitable to most regions are performed first, followed by local trees that depend on specific features of nine climate stratifications. The independent validation indicates the overall accuracy reaches 86%. © 2014 Society of Photo-Optical Instrumentation Engineers."
"7003498065;6602378790;7202180152;7404179087;7003658498;","Space-time analysis of the Air Quality Model Evaluation International Initiative (AQMEII) Phase 1 air quality simulations",2014,"10.1080/10962247.2013.811127","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897826995&doi=10.1080%2f10962247.2013.811127&partnerID=40&md5=d8d30a750b1a92fb591be3a3799e06df","This study presents an evaluation of summertime ozone concentrations over North America (NA) and Europe (EU) using the database generated from Phase 1 of the Air Quality Model Evaluation International Initiative (AQMEII). The analysis focuses on identifying temporal and spatial features that can be used to stratify operational model evaluation metrics and to test the extent to which the various modeling systems can replicate the features seen in the observations. Using a synoptic map typing approach, it is demonstrated that model performance varies with meteorological conditions associated with specific synoptic-scale flow patterns over both eastern NA and EU. For example, the root mean square error of simulated daily maximum 8-hr ozone was twice as high when cloud fractions were high compared with when cloud fractions were low over eastern NA. Furthermore, results show that over both NA and EU the regional models participating in AQMEII were able to better reproduce the observed variance in ambient ozone levels than the global model used to specify chemical boundary conditions, although the variance simulated by almost all regional models is still less that the observed variance on all spatiotemporal scales. In addition, all modeling systems showed poor correlations with observed fluctuations on the intraday time scale over both NA and EU. Furthermore, a methodology is introduced to distinguish between locally influenced and regionally representative sites for the purpose of model evaluation. Results reveal that all models have worse model performance at locally influenced sites. Overall, the analyses presented in this paper show how observed temporal and spatial information can be used to stratify operational model performance statistics and to test the modeling systems' ability to replicate observed temporal and spatial features, especially at scales the modeling systems are designed to capture. The analyses presented in this paper demonstrate how observed temporal and spatial information can be used to stratify operational model performance and to test the modeling systems' ability to replicate observed temporal and spatial features. Decisions for the improvement of regional air quality models should be based on the information derived from only regionally representative sites. © 2014 Copyright © 2014 A&WMA."
"55715614000;57202301596;55483667500;7406372329;55762732700;55437594700;36657972500;","Indian Ocean variability in the CMIP5 multi-model ensemble: The zonal dipole mode",2014,"10.1007/s00382-013-2000-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906761970&doi=10.1007%2fs00382-013-2000-9&partnerID=40&md5=f7bbb5406241019c14befe06338c94c4","The performance of 21 Coupled Model Intercomparison Project Phase 5 (CMIP5) models in the simulation of the Indian Ocean Dipole (IOD) mode is evaluated. Compared to CMIP3, CMIP5 models exhibit a similar spread in IOD intensity. A detailed diagnosis was carried out to understand whether CMIP5 models have shown improvement in their representation of the important dynamical and thermodynamical feedbacks in the tropical Indian Ocean. These include the Bjerknes dynamic air-sea feedback, which includes the equatorial zonal wind response to sea surface temperature (SST) anomaly, the thermocline response to equatorial zonal wind forcing, the ocean subsurface temperature response to the thermocline variations, and the thermodynamic air-sea coupling that includes the wind-evaporation-SST and cloud-radiation-SST feedback. Compared to CMIP3, the CMIP5 ensemble produces a more realistic positive wind-evaporation-SST feedback during the IOD developing phase, while the simulation of Bjerknes dynamic feedback is more unrealistic especially with regard to the wind response to SST forcing and the thermocline response to surface wind forcing. The overall CMIP5 performance in the IOD simulation does not show remarkable improvements compared to CMIP3. It is further noted that the El Niño-Southern Oscillation (ENSO) and IOD amplitudes are closely related, if a model generates a strong ENSO, it is likely that this model also simulates a strong IOD. © 2013 Springer-Verlag Berlin Heidelberg."
"56067551900;7201920350;57190045008;56067530400;","Modes of mesoscale convective system organization during Meiyu season over the Yangtze River basin",2014,"10.1007/s13351-014-0108-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896072162&doi=10.1007%2fs13351-014-0108-4&partnerID=40&md5=33e8ef5646d7f41c9964b65c88b738b7","Mesoscale convective systems (MCSs) are classified and investigated through a statistical analysis of composite radar reflectivity data and station observations during June and July 2010-2012. The number of linear-mode MCSs is slightly larger than the number of nonlinear-mode MCSs. Eight types of linear-mode MCSs are identified: trailing stratiform MCSs (TS), leading stratiform MCSs (LS), training line/adjoining stratiform MCSs (TL/AS), back-building/quasi-stationary MCSs (BB), parallel stratiform MCSs (PS), broken line MCSs (BL), embedded line MCSs (EL), and long line MCSs (LL). Six of these types have been identified in previous studies, but EL and LL MCSs are described for the first time by this study. TS, LS, PS, and BL MCSs are all moving systems, while TL/AS, BB, EL, and LL MCSs are quasi-stationary. The average duration of linear-mode MCSs is more than 7 h. TL/AS and TS MCSs typically have the longest durations. Linear-mode MCSs often develop close to the Yangtze River, especially over low-lying areas and river valleys. The diurnal cycle of MCS initiation over the Yangtze River valley contains multiple peaks. The vertical distribution of environmental wind is decomposed into storm-relative perpendicular and parallel wind components. The environmental wind field is a key factor in determining the organizational mode of a linear-mode MCS. © 2014 The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg."
"55647163997;56318517100;18037213400;","Abundance, biomass and diversity of ground-beetles (Col. Carabidae) as indicators of climatic change effects over elevation strata in Tenerife (Canary Islands)",2014,"10.1016/j.ecolind.2014.07.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905869267&doi=10.1016%2fj.ecolind.2014.07.025&partnerID=40&md5=cc2ecd56206c8d0f6f2c7df684b9a1ad","Species relative importance distribution pattern changes of the ground-beetle assemblages were analyzed along elevation strata of Tenerife Island. The species importance estimates were expressed in terms of (i) activity density, as total catching of ground-beetle adults obtained with pitfall traps over each elevation stratum for one year, and (ii) biomass, as the total number of specimens caught multiplied by a mean dry weight in milligrams for the species. The K-dominance curves indicated moderate or insignificant perturbances, and patterns were sigmoidal following a truncated log-normal slightly skewed to the right, by using the Kolmogoroff-Smirnov test. The results also showed perceptible deviations from the truncated log-normal pattern (p < 0.05) mainly with biomass data. The disturbance through successional progress and perturbances by environmental warming and cooling could be assumed by deviations from the log-normal distribution among species. Thus, assuming that the assemblages of strata exhibited generally low similarity, the results will be arranged around the following four tracks: (1) the assemblage progressed toward highest abundances, dominance and a low-diversity equilibrium state in the cloud montane stratum, (2) the assemblage was subject to severe warming and dryness, lowest abundances with dominance in biomass, such that log-normal pattern was not shown in the basal stratum, (3) a non-equilibrium state in summer-xeric montane stratum maintained the highest diversity and an archetypical log-normal pattern was described for assemblage, and (4) assemblage stressed by cold semi-arid climate showed a certain tendency to log-normality and decrease in the diversity for the summit stratum. These results indicate that variation in ground-beetle assemblages by way of advanced evolutionary and adaptive trade-offs can best be understood as consequences of selective pressures by adverse climatic changes - perturbances - or seasonal climatic fluctuations and population dynamics - disturbances - according to the elevation stratum, which can generate different deviations from the log-normal pattern; these are more directly related to magnitude and frequency of local natural disturbance regimes and the productivity of the ecosystem. © 2014 Elsevier Ltd."
"55911415100;24491912000;7003398142;","Validation of remotely sensed rainfall over major climatic regions in Northeast Tanzania",2014,"10.1016/j.pce.2013.09.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901696503&doi=10.1016%2fj.pce.2013.09.013&partnerID=40&md5=4cc1c751351dc5f79709ec545a66413b","Increase in population has resulted in pressure for more land and water use for food security in Northeast Tanzania. This calls for proper understanding of spatial-temporal variations of quality and quantity of water to ensure sustainable management. The number of hydro-meteorological stations such as rainfall stations and flow measuring stations has not increased and even the functioning of the existing ones is deteriorating. Satellite rainfall estimates (SRE) are being used widely in place of gauge observations or to supplement gauge observations. However, rigorous validation is necessary to have some level of confidence in using the satellite products for different applications. This paper discusses the results of application of SRE over a data scarce tropical complex region in Northeast Tanzania. We selected river catchments found in two different climatological zones: the inland region mountains (i.e. Kikuletwa and Ruvu basins) and the coastal region mountains (i.e. Mkomazi, Luengera and Zigi basins), characterized by semi arid, sub-humid to humid tropical climate. Thus, the validation sites were ideal for testing the different SRE products. In this study, we evaluated two gauge corrected high resolution SRE products which combine both infrared and passive-microwave estimates; the National Oceanographic and Atmospheric Administration Climate Prediction Center (NOAA-CPC) African Rainfall Estimation (RFE2) and the Tropical Rainfall Measuring Mission product 3B42 (TRMM-3B42) using station network.The accuracy of the products was evaluated through a comparison with available gauge data. The comparison was made on pair-wise (point to pixel) and sub-basin level with the reproduction of rainfall volume, rainfall intensity and consistency of rain and no-rain days. The SRE products performed reasonably well over both regions in detecting the occurrence of rainfall. The underestimation was mainly ascribed to topology and the coastal effect. Whereas, the overestimation was mainly ascribed to evaporation of rainfall in the dry atmosphere under the cloud base. Local calibration of satellite-derived rainfall estimates and merging of satellite estimates with locally available rain-gauge observations are some of the approaches that could be employed to alleviate these problems. Although, the products did not show strong correlation to the observed rainfall over the complex tropical mountainous catchments considered, they have high potential to augment gauge observations in data sparse basins. © 2013 Elsevier Ltd."
"55357667300;15051249600;37013451200;22236141200;","Analysis of photosynthetically active radiation in Northwest China from observation and estimation",2014,"10.1007/s00484-014-0835-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929575779&doi=10.1007%2fs00484-014-0835-3&partnerID=40&md5=8398df51bca9dec563d2f51b28718f87","Photosynthetically active radiation (PAR) observed at Fukang, China from 2005 to 2012 was used to investigate PAR variability and its relationship with global solar radiation (G) under various sky conditions in Northwest China. Clearness index (K<inf>t</inf>) was used for characterizing the sky conditions and model development; it was discovered that daily PAR/G (F<inf>p</inf>) generally increased from 1.79 ± 0.016 mol MJ−1 in November to 1.95 ± 0.004 mol MJ−1 in July with annual average being about 1.89 mol MJ−1; F<inf>p</inf> generally decreased with sky conditions changing from overcast skies to clear skies in each month. Meanwhile, an efficient all-sky PAR model under any sky conditions has been proposed by investigating the dependence of hourly PAR on K<inf>t</inf> and cosine of solar zenith angle μ. The model was assessed through the statistical indices: mean bias error (MBE), mean absolute error (MAE), and root-mean-square error (RMSE) whose values were only −0.34 % (−1.75 %), 3.62 % (3.47 %), and 5.52 % (4.79 %), respectively, at hourly (daily) basis. The model has also been tested at three other four sites with distinctly different climates in China. Finally, PAR values during 1961–2012 in Northwest China were reconstructed and annual mean daily PAR was 29.25 mol m−2 d−1. PAR decreased at 0.18 mol m−2 d−1 per decade during 1961–2012, and the decreases were sharpest in spring (0.63 mol m−2 d−1 per decade). The possible reasons for the long-term variability have also been analyzed, which will lay foundations for cloud effect study in the near future. © 2014, ISB."
"36523706800;41961756000;","Brief accuracy assessment of aerosol climatologies for the retrieval of solar surface radiation",2014,"10.3390/atmos5040959","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919771123&doi=10.3390%2fatmos5040959&partnerID=40&md5=7b816e20f6dfc69763f3e574e01dd073","Solar surface irradiance is an important variable in many different fields, e.g., climate monitoring and solar energy. Remote sensing data are nowadays well established and the only observational data source in many regions of the world. Aerosols significantly affect the clear sky radiation and hence also the all sky radiation. In order to achieve the optimal accuracy for surface radiation, information of aerosols with low uncertainty is needed. In this study, the effect of four different aerosol climatologies on the solar surface radiation have been evaluated for the period 2006-2009 at nine BSRN stations. The use of the aerosol climatology from the European Center of Medium Weather Forecast (MACC) leads to the highest accuracy of solar radiation. The mean absolute bias is 6.8 Watt per square meter for global irradiance and 11.3 for direct irradiance. With the Max-Planck climatology (MAC-v1) 9.4 and 14.8 Watt per square meter and with GADS/OPAC (Global Aerosol Data Set/Optical Properties of Aerosols and Clouds) 10.0 and 14.6 Watt per square meter have been achieved, respectively. The improvement in the accuracy of solar radiation by using the MACC climatology is relatively large. Also remarkable is that the new MAC-v1 climatology and the older GADS/OPAC climatology performs on the same level with respect to the achieved accuracy in radiation. The effect of interannual variations of Aerosol Optical Depth (AOD) on the global irradiance is rather low for the investigated sites and period. © 2014 by the authors; licensee MDPI, Basel, Switzerland."
"7006406683;35546736600;7801566289;6507409536;6506474525;","Comparison of near-surface air temperatures and MODIS ice-surface temperatures at summit, Greenland (2008-13)",2014,"10.1175/JAMC-D-14-0023.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907063212&doi=10.1175%2fJAMC-D-14-0023.1&partnerID=40&md5=a9ed67c912d0e2872ab3d382917b6eba","The stability of the Moderate Resolution Imaging Spectroradiometer (MODIS) ice-surface temperature (IST) product from Terra was investigated for use as a climate-quality data record. The availability of climatequality air temperature data TA from a NOAA observatory at Greenland's Summit Station has enabled this high-temporal-resolution study of MODIS ISTs. During a &gt;5-yr period (July 2008-August 2013), more than 2500 IST values were compared with ±3-min-average TA values from NOAA's primary 2-m temperature sensor. This enabled an expected small offset between air and ice-sheet surface temperatures (TA &gt; IST) to be investigated over multiple annual cycles. The principal findings of this study show 1) that IST values are slightly colder than the TA values near freezing but that this offset increases as temperature decreases and 2) that there is a pattern in IST-TA differences as the solar zenith angle (SoZA) varies annually. This latter result largely explains the progressive offset from the in situ data at colder temperatures but also indicates that the MODIS cloudmask is less accurate approaching and during the polar night. The consistency of the results over each year in this study indicates thatMODIS provides a platformfor remotely deriving surface temperature data, with the resulting IST data being most compatible with in situ TA data when the sky is clear and the SoZA is less than ~85°. The ongoing development of the IST dataset should benefit from improved cloud filtering as well as algorithm modifications to account for the progressive offset from TA at colder temperatures. © 2014 American Meteorological Society."
"25225587000;7101867299;7003525439;","Aspects of short-term probabilistic blending in different weather regimes",2014,"10.1002/qj.2220","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902252030&doi=10.1002%2fqj.2220&partnerID=40&md5=f96bc910d980f91bc8dc60f16bf12264","This study explores the potential of regime-dependent approaches to improve short-range precipitation forecasts. Probabilistic forecasts have been generated from the radar nowcaster Radar Tracking and Monitoring (Rad-TRAM) and the convection-permitting weather prediction model of the Consortium for Small-scale Modeling, Deutscher Wetterdienst (COSMO-DE) using the neighbourhood method for a 99 day period during summer 2009. The convective adjustment time-scale was used to classify the days of the investigated period into stratiform, equilibrium and non-equilibrium convection regimes. The COSMO-DE forecasts were calibrated using the reliability diagram method and blended with the nowcasts using an additive weighting, where the weighting function varies with lead time according to the time evolution of the conditional square root of ranked probability score (CSRR). The examination of two case studies showed large differences in the calibration and weighting functions for different regimes. Over the entire period, regime-dependent calibration was found to produce large improvements in reliability in comparison with the uncalibrated forecasts; however, the results were only modestly better than with a single calibration function. The blending procedure successfully combined the nowcast and forecast information, in the sense that the blended forecast was as good as either of the two components, but there was no further gain expected from regime-dependent weighting if regime-dependent calibration had already been performed. © 2013 Royal Meteorological Society."
"35995806700;24780734700;7202821735;","Interpreting bryophyte stable carbon isotope composition: Plants as temporal and spatial climate recorders",2014,"10.1002/2013GC005169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901365932&doi=10.1002%2f2013GC005169&partnerID=40&md5=9cbeb04acee5b2e5d9b76d140dff08c0","Bryophytes are unable to control tissue water content although physiological adaptations allow growth in a wide range of habitats. Carbon isotope signals in two mosses (Syntrichia ruralis and Chorisodontium aciphyllum) and two liverworts (Conocephalum conicum and Marchantia polymorpha), whether instantaneous (real time, Δ13C), or organic matter (as δ13COM), provide an assimilation-weighted summary of bryophyte environmental adaptations. In mosses, δ13C OM is within the measured range of Δ13C values, which suggests that other proxies, such as compound-specific organic signals, will be representative of historical photosynthetic and growth conditions. The liverworts were photosynthetically active over a wider range of relative water contents (RWC) than the mosses. There was a consistent 5‰ offset between Δ13C values in C. conicum and M. polymorpha, suggestive of greater diffusion limitation in the latter. Analysis of a C. aciphyllum moss-peat core showed the isotopic composition over the past 200 years reflects recent anthropogenic CO2 emissions. Once corrected for source-CO 2 inputs, the seasonally integrated Δ13C OM between 1350 and 2000 A.D. varied by 1.5‰ compared with potential range of the 12‰ measured experimentally, demonstrating the relatively narrow range of conditions under which the majority of net assimilation takes place. Carbon isotope discrimination also varies spatially, with a 4‰ shift in epiphytic bryophyte organic matter found between lowland Amazonia and upper montane tropical cloud forest in the Peruvian Andes, associated with increased diffusion limitation. © 2014. The Authors."
"31267503200;57208464149;7003658685;36008168500;7004015298;57215223917;36892703600;6506129917;24484158900;7004399781;","Synoptic-scale dust transport events in the southern Himalaya",2014,"10.1016/j.aeolia.2014.03.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898678801&doi=10.1016%2fj.aeolia.2014.03.008&partnerID=40&md5=a916cb48326bb2e222bf2ff97df8f9e0","The variability of long-range dust transport events observed in the southern Himalaya and its relation with source areas have been studied thanks to five years' continuous measurements which were carried out at the ""Nepal Climate Observatory-Pyramid"" (NCO-P, 27°57'N, 86°48'E), the highest Northern Hemisphere GAW-WMO global station sited at 5079. m. a.s.l. in the high Khumbu valley (Nepal) on the southern Himalaya. During the period March 2006-February 2011, the analyses of the aerosol particle concentrations and LAGRANTO three-dimensional backward trajectories indicated the occurrence of 275. days affected by synoptic-scale dust transport, which account for 22.2% of the investigated period. The frequency of dust transport days (DTDs) showed a clear seasonal cycle, with the highest seasonal value observed during pre-monsoon season (33.5% of the pre-monsoon's days are DTDs).Large enhancements in coarse aerosol number concentration N1-10 (average: +689%) and mass PM1-10 (average: +1086%) were observed during the dust transport events as compared to the days without dust (dust-free days, DFDs). In addition, the single scattering albedo (SSA) also showed higher values, ranging from 0.87 to 0.90, during DTDs with respect to DFDs (0.80-0.87).The predominant source of mineral dust reaching the measurement site was identified in the arid regions of the north-western Indian subcontinent (Thar desert), which accounted for 41.6% of the trajectories points associated with DTDs. Seasonal analysis also indicated that the winter season was significantly influenced by far western desert regions, such as North Africa and the Arabic Peninsula. © 2014."
"7004412006;55081286200;","Trends in precipitation, runoff, and evapotranspiration for rivers draining to the gulf of Maine in the United States",2014,"10.1175/JHM-D-13-018.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897985702&doi=10.1175%2fJHM-D-13-018.1&partnerID=40&md5=e362ac39f998704528e119c5dc187d37","Climate warming is projected to result in increases in total annual precipitation in northeastern North America. The response of runoff to increases in precipitation is likely to be more complex because increasingevapotranspiration (ET) could counteract increasing precipitation. This study was conducted to examine these competing trends in the historical record for 22 rivers having &gt; 70 yr of runoff data. Annual (water year)average precipitation increased in all basins, with increases ranging from 0.9 to 3.12mm yr -1. Runoff increasedin all basins with increases ranging from 0.67 to 2.58mm yr -1. The ET was calculated by using a water balance approach in which changes in terrestrial water storage were considered negligible. ET increased in 16 basins and decreased in 6 basins. Temporal trends in temperature, precipitation, runoff, and ET were also calculated for each basin over their respective periods of record for runoff and for the consistent period (1927- 2011) for the area-weighted average of the nine largest non-nested basins. From 1927 through 2011, precipitation and runoff increased at average rates of 1.6 and 1.7mm yr -1, respectively, and ET increased slightly at a rate of 0.18mm yr -1. For the more recent period (1970-2011), there was a positive trend in ET of 1.9mm yr -1. The lack of a more consistent increase in ET, compared with the increases in precipitation and runoff, for the full periods of record, was unexpected, but may be explained by various factors including decreasing wind speed, increasing cloudiness, decreasing vapor pressure deficit, and patterns of forest growth. © 2014 American Meteorological Society."
"57189997349;10240999000;","Trends in monthly tropopause characteristics observed over Taipei, Taiwan",2014,"10.1175/JAS-D-13-0230.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897470183&doi=10.1175%2fJAS-D-13-0230.1&partnerID=40&md5=22ca4e3d6f3b316da56f5c40d4cb7183","This study presents monthly trends in the cold-point tropopause (CPT), calculated using three decades of radiosonde data from 1981 to 2010 over Taipei, Taiwan (25°01'N, 121°27'E). Multivariate regression analysis has been used to suppress the effect of natural variations, such as quasi-biennial oscillation (QBO), ENSO, solar cycle, and volcanic eruptions. From the continuous time series, statistically insignificant heating and a decrease in the height of CPT are observed. However, the trends estimated using individual monthly time series revealed new features with statistically significant increasing trends in CPT temperature at a rate of approximately 0.03°Cyr-1 and statistically significant decreasing trends inCPTheight at a rate of approximately 4.7m yr-1 during summer months. An enhanced heating rate in the upper troposphere along with a suppressed cooling rate in the lower stratosphere observed over Taipei might have caused the tropopause heating trend during summer. The possible relationship between tropopause trends and lower-stratospheric ozone is also examined. The seasonal and spatial variations in trends estimated using NCEP-Climate Forecast System Reanalysis (CFSR) data reveal the spatial heterogeneity in CPT temperature trends. Initial inspection of monthly trends in tropopause characteristics suggests that the estimation of tropopause trends using the continuous time series may not exactly represent the long-term variability of individual months or seasons. © 2014 American Meteorological Society."
"7006652175;55489807200;7006010452;6602987195;","Change-point analysis of polar zone radiosonde temperature data",2014,"10.1175/JAMC-D-13-084.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896513445&doi=10.1175%2fJAMC-D-13-084.1&partnerID=40&md5=62bd74c5a0f49e2eb30c026ed4b1ebbf","A comprehensive change-point analysis of annual radiosonde temperature measurements collected at the surface, troposphere, tropopause, and lower-stratosphere levels at both the South and North Polar zones has been done. The data from each zone are modeled as a multivariate Gaussian series with a possible change point in both the mean vector as well as the covariance matrix. Prior to carrying out an analysis of the data, a methodology for computing the large sample distribution of the maximum likelihood estimator of the change point is first developed. The Bayesian approach for change-point estimation under conjugate priors is also developed. A simulation study is carried out to compare the maximum likelihood estimator and various Bayesian estimates. Then, a comprehensive change-point analysis under a multivariate framework is carried out on the temperature data for the period 1958-2008. Change detection is based on the likelihood ratio procedure, and change-point estimation is based on the maximum likelihood principle and other Bayesian procedures. The analysis showed strong evidence of change in the correlation between tropopause and lowerstratosphere layers at the South Polar zone subsequent to 1981. The analysis also showed evidence of a cooling effect at the tropopause and lower-stratosphere layers, as well as a warming effect at the surface and troposphere layers at both the South and North Polar zones. © 2014 American Meteorological Society."
"23978405300;7007182077;6602753217;6602978326;36011801900;55463048400;23995325300;","The effect of boundary layer dynamics on aerosol properties at the Indo-Gangetic plains and at the foothills of the Himalayas",2014,"10.1016/j.atmosenv.2014.02.058","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895939625&doi=10.1016%2fj.atmosenv.2014.02.058&partnerID=40&md5=6b38d55537aac06ae2283c6c61928f1e","Previous studies have noted that aerosols originating from the polluted Indo-Gangetic plains can reach high altitudes at the Indian Himalayas and thereby have an effect on the south Asian monsoon. Here we examine the transport of pollutions by comparing aerosol properties from a Himalayan foothill measurement site and a site at the Indo-Gangetic plains. Gual Pahari is a polluted semi-urban background measurement site at the Indo-Gangetic plains close to New Delhi and Mukteshwar is a relatively clean background measurement site at the foothills of the Himalayas about 270km NE from Gual Pahari and about 2km above the nearby plains. The data set has more than two years of simultaneous measurements including meteorological parameters and aerosol mass concentrations. Modeled backward trajectories and Planetary Boundary Layer (PBL) heights are also used to examine the origin or air masses and the extent of the vertical mixing. The comparison shows that aerosol concentrations at the foothill site are correlated with the average PBL height. Together with the favorable synoptic scale circulation, this suggests a contribution of air mass transport from the plains. © 2014 Elsevier Ltd."
"56048942300;7201425334;35232873900;16025402200;","Atmospheric teleconnection mechanisms of extratropical North Atlantic SST influence on Sahel rainfall",2014,"10.1007/s00382-014-2094-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894543687&doi=10.1007%2fs00382-014-2094-8&partnerID=40&md5=9897135f526e90927c4fe568e23bacd1","Extratropical North Atlantic cooling has been tied to droughts over the Sahel in both paleoclimate observations and modeling studies. This study, which uses an atmospheric general circulation model (GCM) coupled to a slab ocean model that simulates this connection, explores the hypothesis that the extratropical North Atlantic cooling causes the Sahel droughts via an atmospheric teleconnection mediated by tropospheric cooling. The drying is also produced in a regional climate model simulation of the Sahel when reductions in air temperature (and associated geopotential height and humidity changes) from the GCM simulation are imposed as the lateral boundary conditions. This latter simulation explicitly demonstrates the central role of tropospheric cooling in mediating the atmospheric teleconnection from extratropical North Atlantic cooling. Diagnostic analyses are applied to the GCM simulation to infer teleconnection mechanisms. An analysis of top of atmosphere radiative flux changes diagnosed with a radiative kernel technique shows that extratropical North Atlantic cooling is augmented by a positive low cloud feedback and advected downstream, cooling Europe and North Africa. The cooling over North Africa is further amplified by a reduced greenhouse effect from decreased atmospheric specific humidity. A moisture budget analysis shows that the direct moisture effect and monsoon weakening, both tied to the ambient cooling and resulting circulation changes, and feedbacks by vertical circulation and evaporation augment the rainfall reduction. Cooling over the Tropical North Atlantic in response to the prescribed extratropical cooling also augments the Sahel drying. Taken together, they suggest a thermodynamic pathway for the teleconnection. The teleconnection may also be applicable to understanding the North Atlantic influence on Sahel rainfall over the twentieth century. © 2014, Springer-Verlag Berlin Heidelberg."
"55192195500;6602866771;36926418400;7201594415;","Daily and seasonal courses of gas exchange and niche partitioning among coexisting tree species in a tropical montane forest",2014,"10.1016/j.flora.2014.02.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898058086&doi=10.1016%2fj.flora.2014.02.005&partnerID=40&md5=b68a99950b175e1a2411f04f2b23dfb7","We investigated the seasonal gas exchange patterns of three different functional types of tropical afromontane trees, namely Podocarpus falcatus (Thunb.) Mirb. (evergreen gymnosperm), Prunus africana (Hook. f.) Kalkm. (broad-leaf evergreen), and Croton macrostachyus Hochst. ex Del. (broad-leaf deciduous) which grow side-by-side in the Munessa forest, southern Central Ethiopia. The hypothesis is that the trees can make different use of the environmental conditions which change seasonally and also from year to year. These changes can be understood as fluctuating niches, the utilization of which allows coexistence through balanced carbon gain. In this study, light and moisture were considered the two main fluctuating niches. Porometry was used to measure the daily and seasonal responses of the leaves to environmental variables under dry and wet season conditions in the course of the climatically differing years 2009 and 2010. Correlations of the patterns of these responses were analyzed by regression analysis. From daily integrated rates of irradiation, photosynthesis and transpiration, light and water use efficiencies of photosynthetic carbon gain and their mutual interdependences were determined. Except an extended dry season in 2009 when C. macrostachyus had shed its foliage, all three species continued photosynthetic net CO2 uptake concomitant with transpiration at all seasons, although at varying rates. Ecophysiological performance of P. falcatus leaves is mainly light-driven and responds relatively little to a change in moisture conditions. Its carbon and water relations are striving for stability rather than flexibility. As of a typically subdominant species of the forest, P. africana leaves can efficiently use low light intensities but suffer from photoinhibition at full light. Their performance, showing more dynamic response to the environment than P. falcatus, P. africana appears driven more by moisture than by light. Compared to the two evergreens C. macrostachyus exhibited the highest flexibility in its leaves' physiological responses to environmental conditions, in particular to the light climate which is additionally potentiated by the fast turnover of its foliage. This species optimizes its carbon gain during the wet season and during the early dry period when cloud cover is minimal. Our findings thus reveal that elasticity of the response to fluctuating environmental conditions is an additional aspect in the assessment of the utilization of temporally fluctuating niches by adult tree individuals. © 2014 Elsevier GmbH."
"56098410300;55185085100;29068067200;7102556773;","Combining airborne laser scanning data and optical satellite data for classification of alpine vegetation",2014,"10.1016/j.jag.2013.05.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897572445&doi=10.1016%2fj.jag.2013.05.003&partnerID=40&md5=59e56fda0f6bd7aac5fbb06d26ac2e79","Climate change and outdated vegetation maps are among the reasons for renewed interest in mapping sensitive alpine and subalpine vegetation. Satellite data combined with elevation derivatives have been shown to be useful for mapping alpine vegetation, however, there is room for improvement. The inclusion of airborne laser scanning data metrics has not been widely investigated for alpine vegetation. This study has combined SPOT 5 satellite data, elevation derivatives, and laser data metrics for a 25 km × 31 km study area in Abisko, Sweden. Nine detailed vegetation classes defined by height, density and species composition in addition to snow/ice, water, and bare rock were classified using a supervised Random Forest classifier. Several of the classes consisted of shrub and grass species with a maximum height of 0.4 m or less. Laser data metrics were calculated from the nDSM based on a 10 m × 10 m grid, and after variable selection, the metrics used in the classification were the 95th and 99th height percentiles, a vertical canopy density metric, the mean and standard deviation of height, a vegetation ratio based on the raw laser data point cloud with a variable height threshold (from 0.1 to 1.0 m with 0.1 m intervals), and standard deviation of these vegetation ratios. The satellite data used in classification was all SPOT bands plus NDVI and NDII, while the elevation derivatives consisted of elevation, slope and the Saga Wetness Index. Overall accuracy when using the combination of laser data metrics, elevation derivatives and SPOT 5 data increased by 6% as compared to classification of SPOT and elevation derivatives only, and increased by 14.2% compared to SPOT 5 data alone. The classes which benefitted most from inclusion of laser data metrics were mountain birch and alpine willow. The producer's accuracy for willow increased from 18% (SPOT alone) to 41% (SPOT + elevation derivatives) and then to 55% (SPOT + elevation derivatives + laser data) when laser data were included, with the 95th height percentile and Saga Wetness Index contributing most to willow's improved classification. Addition of laser data metrics did not increase the classification accuracy of spectrally similar dry heath (<0.3 m height) and mesic heath (0.3-1.0 m height), which may have been a result of laser data penetration of sparse shrub canopy or laser data processing choices. The final results show that laser data metrics combined with satellite data and elevation derivatives contributed overall to a better classification of alpine and subalpine vegetation. © 2013 Elsevier B.V."
"7103180783;7402401574;6602080205;53880473700;","The impacts of European and Asian anthropogenic sulfur dioxide emissions on Sahel rainfall",2014,"10.1175/JCLI-D-13-00769.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907048188&doi=10.1175%2fJCLI-D-13-00769.1&partnerID=40&md5=c0133ce077f0baf94bdddd3e07d8fdd9","In this study, the atmospheric component of a state-of-the-art climate model [the Hadley Centre Global Environment Model, version 2-Earth System (HadGEM2-ES)] has been used to investigate the impacts of regional anthropogenic sulfur dioxide emissions on boreal summer Sahel rainfall. The study focuses on the transient response of the West African monsoon (WAM) to a sudden change in regional anthropogenic sulfur dioxide emissions, including land surface feedbacks but without sea surface temperature (SST) feedbacks. The response occurs in two distinct phases: 1) fast adjustment of the atmosphere on a time scale of days to weeks (up to 3 weeks) through aerosol-radiation and aerosol-cloud interactions with weak hydrological cycle changes and surface feedbacks and 2) adjustment of the atmosphere and land surface with significant local hydrological cycle changes and changes in atmospheric circulation (beyond 3 weeks). European emissions lead to an increase in shortwave (SW) scattering by increased sulfate burden, leading to a decrease in surface downwardSWradiation that causes surface cooling over North Africa, a weakening of the Saharan heat low and WAM, and a decrease in Sahel precipitation. In contrast, Asian emissions lead to very little change in sulfate burden over North Africa, but they induce an adjustment of the Walker circulation, which leads again to a weakening of theWAMand a decrease in Sahel precipitation. The responses to European and Asian emissions during the second phase exhibit similar large-scale patterns of anomalous atmospheric circulation and hydrological variables, suggesting a preferred response. The results support the idea that sulfate aerosol emissions contributed to the observed decline in Sahel precipitation in the second half of the twentieth century. © 2014 American Meteorological Society."
"55556626900;7403079681;19638530300;","Simulation of the stratosphere-troposphere exchange process in a typical cold vortex over Northeast China",2014,"10.1007/s11430-014-4864-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903121357&doi=10.1007%2fs11430-014-4864-x&partnerID=40&md5=c95eae3059d202273f9a4e3f54acd03a","A mesoscale weather research and forecasting (WRF) model was used to simulate a cold vortex that developed over Northeast China during June 19-23, 2010. The simulation used high vertical resolution to reproduce the key features of the cold vortex development. Characteristics of the associated stratosphere-troposphere exchange (STE), specifically the spatiotemporal distribution of the cross-tropopause mass flux (CTF), were investigated using the Wei formula. The simulation results showed that the net mass exchange induced by the cold vortex was controlled by stratosphere-to-troposphere transport (STT) processes. In the pre-formation stage of the cold vortex (i.e., the development of the trough and ridge), active exchange was evident. Over the lifecycle of the cold vortex, STT processes prevailed at the rear of the trough and moving vortex, whereas troposphere-to-stratosphere transport (TST) processes prevailed at the front end. This spatial pattern was caused by temporal fluctuations of the tropopause. However, because of the cancellation of the upward flux by the downward flux, the contribution of the tropopause fluctuation term to the net mass exchange was only minor. In this case, horizontal motion dominated the net mass exchange. The time evolution of the CTF exhibited three characteristics: (1) the predominance of the STT during the pre-formation stage; (2) the formation and development of the cold vortex, in which the CTF varied in a fluctuating pattern from TST to STT to TST; and (3) the prevalence of the STT during the decay stage. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg."
"30967646900;7202145115;","The atmospheric energy constraint on global-mean precipitation change",2014,"10.1175/JCLI-D-13-00163.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892510739&doi=10.1175%2fJCLI-D-13-00163.1&partnerID=40&md5=b5b8d60256e2f46b2fcc824360a03d19","Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) robustly predict that the rate of increase in global-mean precipitation with global-mean surface temperature increase is much less than the rate of increase of water vapor. The goal of this paper is to explain in detail the mechanisms by which precipitation increase is constrained by radiative cooling. Changes in clear-sky atmospheric radiative cooling resulting from changes in temperature and humidity in global warming simulations are in good agreement with the multimodel, global-mean precipitation increase projected by GCMs (~1.1Wm-2K-1). In an atmosphere with fixed specific humidity, radiative cooling from the top of the atmosphere (TOA) increases in response to a uniform temperature increase of the surface and atmosphere, while atmospheric cooling by exchange with the surface decreases because the upward emission of longwave radiation from the surface increases more than the downward longwave radiation from the atmosphere. When a fixed relative humidity (RH) assumption is made, however, uniform warming causes a much smaller increase of cooling at the TOA, and the surface contribution reverses to an increase in net cooling rate due to increased downward emission from water vapor. Sensitivity of precipitation changes to lapse rate changes is modest when RH is fixed. Carbon dioxide reduces TOA emission with only weak effects on surface fluxes, and thus suppresses precipitation. The net atmospheric cooling response and thereby the precipitation response to CO2-induced warming at fixed RH are mostly contributed by changes in surface fluxes. The role of clouds is discussed. Intermodel spread in the rate of precipitation increase across the CMIP5 simulations is attributed to differences in the atmospheric cooling. © 2014 American Meteorological Society."
"56612539800;8439180500;57191108061;","Assessment of surface urban heat islands over three megacities in east asia using land surface temperature data retrieved from COMS",2014,"10.3390/rs6065852","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84986888969&doi=10.3390%2frs6065852&partnerID=40&md5=1071a76055a089633e0cb2969388ef2b","Surface urban heat island (SUHI) impacts control the exchange of sensible heat and latent heat between land and atmosphere and can worsen extreme climate events, such as heat waves. This study assessed SUHIs over three megacities (Seoul, Tokyo, Beijing) in East Asia using one-year (April 2011-March 2012) land surface temperature (LST) data retrieved from the Communication, Ocean and Meteorological Satellite (COMS). The spatio-temporal variations of SUHI and the relationship between SUHI and vegetation activity were analyzed using hourly cloud-free LST data. In general, the LST was higher in low latitudes, low altitudes, urban areas and dry regions compared to high latitudes, high altitudes, rural areas and vegetated areas. In particular, the LST over the three megacities was always higher than that in the surrounding rural areas. The SUHI showed a maximum intensity (10-13 °C) at noon during the summer, irrespective of the geographic location of the city, but weak intensities (4-7 °C) were observed during other times and seasons. In general, the SUHI intensity over the three megacities showed strong seasonal (diurnal) variations during the daytime (summer) and weak seasonal (diurnal) variations during the nighttime (other seasons). As a result, the temporal variation pattern of SUHIs was quite different from that of urban heat islands, and the SUHIs showed a distinct maximum at noon of the summer months and weak intensities during the nighttime of all seasons. The patterns of seasonal and diurnal variations of the SUHIs were clearly dependent on the geographic environment of cities. In addition, the intensity of SUHIs showed a strong negative relationship with vegetation activity during the daytime, but no such relationship was observed during the nighttime. This suggests that the SUHI intensity is mainly controlled by differences in evapotranspiration (or the Bowen ratio) between urban and rural areas during the daytime. © 2014 by the authors."
"54882858600;54896503000;9236113800;","Limits to Understory Plant Restoration Following Fuel-Reduction Treatments in a Piñon–Juniper Woodland",2014,"10.1007/s00267-014-0338-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919877150&doi=10.1007%2fs00267-014-0338-3&partnerID=40&md5=6b218889a4fa290058847a8cb388a967","National fuel-reduction programs aim to reduce the risk of wildland fires to human communities and to restore forest and rangeland ecosystems to resemble their historical structure, function, and diversity. There are a number of factors, such as seed bank dynamics, post-treatment climate, and herbivory, which determine whether this latter goal may be achieved. Here, we examine the short-term (2 years) vegetation response to fuel-reduction treatments (mechanical mastication, broadcast burn, and pile burn) and seeding of native grasses on understory vegetation in an upland piñon–juniper woodland in southeast Utah. We also examine how wildlife herbivory affects the success of fuel-reduction treatments. Herbaceous cover increased in response to fuel-reduction treatments in all seeded treatments, with the broadcast burn and mastication having greater increases (234 and 160 %, respectively) in herbaceous cover than the pile burn (32 %). In the absence of seeding, herbaceous cover only increased in the broadcast burn (32 %). Notably, fuel-reduction treatments, but not seeding, strongly affected herbaceous plant composition. All fuel-reduction treatments increased the relative density of invasive species, especially in the broadcast burn, which shifted the plant community composition from one dominated by perennial graminoids to one dominated by annual forbs. Herbivory by wildlife reduced understory plant cover by over 40 % and altered plant community composition. If the primary management goal is to enhance understory cover while promoting native species abundance, our study suggests that mastication may be the most effective treatment strategy in these upland piñon–juniper woodlands. Seed applications and wildlife exclosures further enhanced herbaceous cover following fuel-reduction treatments. © 2014, Springer Science+Business Media New York."
"55816939900;16403549400;56230206700;7004392319;35409457600;35473149000;26428503000;25029116500;56229764300;55377275100;14218970700;57194068533;56229830800;","Contribution of L-band SAR to systematic global mangrove monitoring",2014,"10.1071/MF13177","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903312678&doi=10.1071%2fMF13177&partnerID=40&md5=6551fa901f4900fdc4f12e3cd2a6c128","Information on the status of and changes in mangroves is required for national and international policy development, implementation and evaluation. To support these requirements, a component of the Japan Aerospace Exploration Agency's (JAXA) Kyoto and Carbon (K&C) initiative has been to design and develop capability for a Global Mangrove Watch (GMW) that routinely monitors and reports on local to global changes in the extent of mangroves, primarily on the basis of observations by Japanese L-band synthetic aperture radar (SAR). The GMW aims are as follows: (1) to map progression of change within or from existing (e.g. Landsat-derived) global baselines of the extent of mangroves by comparing advanced land-observing satellite 2 (ALOS-2) phased array L-band SAR 2 (PALSAR-2) data from 2014 with that acquired by the Japanese earth resources satellite (JERS-1) SAR (1992-1998) and ALOS PALSAR (2006-2011); (2) to quantify changes in the structure and associated losses and gains of carbon on the basis of canopy height and above-ground biomass (AGB) estimated from the shuttle radar topographic mission (SRTM; acquired 2000), the ice, cloud and land-elevation satellite (ICESAT) geoscience laser altimeter system (GLAS; 2003-2010) and L-band backscatter data; (3) to determine likely losses and gains of tree species diversity through reference to International Union for the Conservation of Nature (IUCN) global thematic layers on the distribution of mangrove species; and (4) to validate maps of changes in the extent of mangroves, primarily through comparison with dense time-series of Landsat sensor data and to use these same data to describe the causes and consequences of change. The paper outlines and justifies the techniques being implemented and the role that the GMW might play in supporting national and international policies that relate specifically to the long-term conservation of mangrove ecosystems and the services they provide to society. © CSIRO 2014."
"6604028763;16063202700;6506950229;49861272400;56646077000;","Delving into the variations in tree species composition and richness across South American subtropical Atlantic and Pampean forests",2014,"10.1093/jpe/rtt058","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937002731&doi=10.1093%2fjpe%2frtt058&partnerID=40&md5=51b00ae344957fd8a879827967d5dce4","Aims: We analyse here the variations in species composition and richness and the geographic ranges of the tree species occurring in South American subtropical Atlantic and Pampean forests. Our goals were to assess (i) the floristic consistency of usual classifications based on vegetation physiognomy, climate and elevation; (ii) the leading role of temperature-related variables on the variations in species composition and richness; (iii) the predominance of species with tropical-subtropical ranges, possibly as a result of forest expansion over grasslands after the Last Glacial Maximum (LGM); (iv) the restriction of most subtropical endemics to stressful habitats as a possible result of past forest refuges during the LGM. Methods: The region was defined by the Tropic of Capricorn to the north, the Rio de la Plata to the south, the Atlantic shoreline to the east and the catchment areas of the upper Paraná and Uruguay Rivers to the west. Multivariate analyses, multiple regression modelling and variance partition analyses were performed on a database containing 63 994 occurrence records of 1555 tree species in 491 forest sites and 48 environmental variables. All species were also classified according to their known geographic range. Important Findings: A main differentiation in species composition and richness was observed between the eastern windward coastlands (rain and cloud forests) and western leeward hinterlands (Araucaria and semi-deciduous forests). Pre-defined forest types on both sides were consistent with variations in tree species composition, which were significantly related to both environmental variables and spatial proximity, with extremes of low temperature playing a chief role. Tree species richness declined substantially towards the south and also from rain to seasonal forests and towards the highland summits and sandy shores. Species richness was significantly correlated with both minimum temperature and actual evapotranspiration. About 91% of the subtropical flora is shared with the much richer tropical flora, probably extracting species that can cope with frost outbreaks. The 145 subtropical endemics were not concentrated in harsher habitats. © The Author 2013. Published by Oxford University Press on behalf of the Institute of Botany, Chinese Academy of Sciences and the Botanical Society of China. All rights reserved."
"7401829462;6603321168;7003487155;8579929300;55846028600;55845766100;6507397711;6603454479;15758090100;6603851915;","Iron oxide minerals in dust of the Red Dawn event in eastern Australia, September 2009",2014,"10.1016/j.aeolia.2014.02.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908270552&doi=10.1016%2fj.aeolia.2014.02.003&partnerID=40&md5=6b805194f0c4a14b436df24c83fa0529","Iron oxide minerals typically compose only a few weight percent of bulk atmospheric dust but are important for potential roles in forcing climate, affecting cloud properties, influencing rates of snow and ice melt, and fertilizing marine phytoplankton. Dust samples collected from locations across eastern Australia (Lake Cowal, Orange, Hornsby, and Sydney) following the spectacular ""Red Dawn"" dust storm on 23 September 2009 enabled study of the dust iron oxide assemblage using a combination of magnetic measurements, Mössbauer spectroscopy, reflectance spectroscopy, and scanning electron microscopy. Red Dawn was the worst dust storm to have hit the city of Sydney in more than 60years, and it also deposited dust into the Tasman Sea and onto snow cover in New Zealand. Magnetization measurements from 20 to 400K reveal that hematite, goethite, and trace amounts of magnetite are present in all samples. Magnetite concentrations (as much as 0.29wt%) were much higher in eastern, urban sites than in western, agricultural sites in central New South Wales (0.01wt%), strongly suggesting addition of magnetite from local urban sources. Variable temperature Mössbauer spectroscopy (300 and 4.2K) indicates that goethite and hematite compose approximately 25-45% of the Fe-bearing phases in samples from the inland sites of Orange and Lake Cowal. Hematite was observed at both temperatures but goethite only at 4.2K, thereby revealing the presence of nanogoethite (less than about 20nm). Similarly, hematite particulate matter is very small (some of it d&lt;100nm) on the basis of magnetic results and Mössbauer spectra. The degree to which ferric oxide in these samples might absorb solar radiation is estimated by comparing reflectance values with a magnetic parameter (hard isothermal remanent magnetization, HIRM) for ferric oxide abundance. Average visible reflectance and HIRM are correlated as a group (r2=0.24), indicating that Red Dawn ferric oxides have capacity to absorb solar radiation. Much of this ferric oxide occurs as nanohematite and nanogoethite particles on surfaces of other particulate matter, thereby providing high surface area to enhance absorption of solar radiation. Leaching of the sample from Orange in simulated human-lung fluid revealed low bioaccessibility for most metals. © 2014 Elsevier B.V.."
"56663417400;7402989545;","How does el niño affect the interannual variability of the boreal summer hadley circulation?",2014,"10.1175/JCLI-D-13-00277.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896993042&doi=10.1175%2fJCLI-D-13-00277.1&partnerID=40&md5=5eb8100b4258af830c557c638d5faf19","Analyses of 30-yr four reanalysis datasets [NCEP-NCAR reanalysis (NCEP1), NCEP-Department of Energy reanalysis (NCEP2), Japanese 25-year Reanalysis Project (JRA-25), and Interim ECMWF Re-Analysis (ERA-Interim)] reveal remarkably interannual variability of the Hadley circulation (HC) in boreal summer (June-August). The two leading modes of interannual variability of boreal summer HC are obtained by performing empirical orthogonal function (EOF) analysis on the mass streamfunction. A general intensification of boreal summer HC is seen in EOF-1 mode among NCEP1, NCEP2, and JRA-25 but the corresponding EOF-2 mode in ERA-Interim, while a weakened northern Hadley cell and remarkable regional variation of a southern Hadley cell are captured by the EOF-2 mode (from NCEP1, NCEP2, and JRA-25) and EOF-1 mode (from ERA-Interim), as evidenced by the enhanced (decreased) southern Hadley cell in the southern tropics (the northern tropics and southern subtropics). Both modes are driven by El Nĩno-like SST forcing in boreal summer, but are relevant to different phases of El Nĩno events. The EOF-1 (or EOF-2 derived from ERA-Interim) [EOF-2 (or EOF-1 derived from ERA-Interim)] mode is driven by SST anomalies in developing (decaying) El Nĩno summers. The interannual variations of the northern Hadley cell in both modes are driven by El Niño through modulating the interannual variations of the East Asian summer monsoon, while anomalous local Hadley circulation (LHC) in the regions 30°S-20°N, 110°E-180° and 30°S-20°N, 160°E-120°W in response to El Niño forcing largely determine the interannual variations of southern Hadley cell in both modes, respectively. The different behaviors of the southern Hadley cell between two leading modes can be well explained by the southward shift of the tropical heating center from north of 10°N in developing El Niño summers to south of 10°N in decaying El Niño summers.© 2014 American Meteorological Society."
"36069754700;7102301113;","Assimilation of Doppler Weather Radar Data in WRF Model for Simulation of Tropical Cyclone Aila",2014,"10.1007/s00024-013-0723-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908110311&doi=10.1007%2fs00024-013-0723-5&partnerID=40&md5=95b7ea09264813d9d8fd5cae54ddcb4f","For the accurate and effective forecasting of a cyclone, it is critical to have accurate initial structure of the cyclone in numerical models. In this study, Kolkata Doppler weather radar (DWR) data were assimilated for the numerical simulation of a land-falling Tropical Cyclone Aila (2009) in the Bay of Bengal. To study the impact of radar data on very short-range forecasting of a cyclone's path, intensity and precipitation, both reflectivity and radial velocity were assimilated into the weather research and forecasting (WRF) model through the ARPS data assimilation system (ADAS) and cloud analysis procedure. Numerical experiment results indicated that radar data assimilation significantly improved the simulated structure of Cyclone Aila. Strong influences on hydrometeor structures of the initial vortex and precipitation pattern were observed when radar reflectivity data was assimilated, but a relatively small impact was observed on the wind fields at all height levels. The assimilation of radar wind data significantly improved the prediction of divergence/convergence conditions over the cyclone's inner-core area, as well as its wind field in the low-to-middle troposphere (600–900 hPa), but relatively less impact was observed on analyzed moisture field. Maximum surface wind speed produced from DWR–Vr and DWR–ZVr data assimilation experiments were very close to real-time values. The impact of radar data, after final analysis, on minimum sea level pressure was relatively less because the ADAS system does not adjust for pressure due to the lack of pressure observations, and from not using a 3DVAR balance condition that includes pressure. The greatest impact of radar data on forecasting was realized when both reflectivity and wind data (DWR–ZVr and DWR–ZVr00 experiment) were assimilated. It is concluded that after final analysis, the center of the cyclone was relocated very close to the observed position, and simulated cyclone maintained its intensity for a longer duration. Using this analysis, different stages of the cyclone are better captured, and cyclone structure, intensification, direction of movement, speed and location are significantly improved when both radar reflectivity and wind data are assimilated. As compared to other experiments, the maximum reduction in track error was noticed in the DWR–ZVr and DWR–ZVr00 experiments, and the predicted track in these experiments was very close to the observed track. In the DWR–ZVr and DWR–ZVr00 experiments, rainfall pattern and amount of rainfall forecasts were remarkably improved and were similar to the observation over West Bengal, Orissa and Jharkhand; however, the rainfall over Meghalaya and Bangladesh was missed in all the experiments. The influence of radar data reduces beyond a 12-h forecast, due to the dominance of the flow from large-scale, global forecast system models. This study also demonstrates successful coupling of the data assimilation package ADAS with the WRF model for Indian DWR data. © 2013, Springer Basel."
"35369409100;55545335600;55716266100;56374442600;35735614000;55366522200;55999590500;55974472800;15724233200;7006595513;","Characteristics of regional new particle formation in urban and regional background environments in the North China Plain",2013,"10.5194/acp-13-12495-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885831076&doi=10.5194%2facp-13-12495-2013&partnerID=40&md5=665a0597e9b0691c6b9673009b4e5522","Long-term measurements of particle number size distributions were carried out both at an urban background site (Peking University, PKU) and a regional Global Atmospheric Watch station (Shangdianzi, SDZ) from March to November in 2008. In total, 52 new particle formation (NPF) events were observed simultaneously at both sites, indicating that this is a regional phenomenon in the North China Plain. On average, the mean condensation sink value before the nucleation events started was 0.025 s-1 in the urban environment, which was 1.6 times higher than that at regional site. However, higher particle formation and growth rates were observed at PKU (10.8 cm-3 s-1 and 5.2 nm h-1) compared with those at SDZ (4.9 cm-3 s-1 and 4.0 nm h-1). These results implied that precursors were much more abundant in the polluted urban environment. Different from the observations in cleaner environments, the background conditions of the observed particle homogeneous nucleation events in the North China Plain could be characterized as the co-existing of a stronger source of precursor gases and a higher condensational sink of pre-existing aerosol particles. Secondary aerosol formation following nucleation events results in an increase of particle mass concentration, particle light scattering coefficient, and cloud condensation nuclei (CCN) number concentration, with consequences on visibility, radiative effects, and air quality. Typical regional NPF events with significant particle nucleation rates and subsequent particle growth over a sufficiently long time period at both sites were chosen to investigate the influence of NPF on the number concentration of ""potential"" CCN. As a result, the NPF and the subsequent condensable growth increased the CCN number concentration in the North China Plain by factors in the range from 5.6 to 8.7. Moreover, the potential contribution of anthropogenic emissions to the CCN number concentration was more than 50%, to which more attention should be drawn in regional and global climate modeling, especially in the polluted urban areas. © Author(s) 2013."
"16687162300;7003819791;55589460800;36903932800;7202442681;7004273155;7103024868;6602795803;","A novel methodological approach for δ18O analysis of sugars using gas chromatography-pyrolysis-isotope ratio mass spectrometry",2013,"10.1080/10256016.2013.824875","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890237761&doi=10.1080%2f10256016.2013.824875&partnerID=40&md5=faa9704cbeb38066180e63893e9b0c64","Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific δ18O analysis has been commercially available for more than a decade, this method has been hardly applied so far. Here we present the first GC-Py-IRMS δ18O results for trimethylsilyl-derivatives of plant sap-relevant sugars and a polyalcohol (glucose, fructose, sucrose, raffinose and pinitol). Particularly, we focus on sucrose, which is assimilated in leaves and which is the most important transport sugar in plants and hence of utmost relevance in plant physiology and paleoclimate studies. Replication measurements of sucrose standards and concentration series indicate that the GC-Py-IRMS δ18O measurements are not stable over time and that they are amount (area) dependent. We, therefore, suggest running sample batch replication measurements in alternation with standard concentration series of reference material. This allows for carrying out (i) a drift correction, (ii) a calibration against reference material and (iii) an amount (area) correction. Tests with 18O-enriched water do not provide any evidence for oxygen isotope exchange reactions affecting sucrose and raffinose. We present the first application of GC-Py-IRMS δ18O analysis for sucrose from needle extract (soluble carbohydrate) samples. The obtained δ18Osucrose/ Vienna Standard Mean Ocean Water (VSMOW) values are more positive and vary in a wider range (32.1-40.1 ‰) than the δ18Obulk/ VSMOW values (24.6-27.2 ‰). Furthermore, they are shown to depend on the climate parameters maximum day temperature, relative air humidity and cloud cover. These findings suggest that δ18Osucrose of the investigated needles very sensitively reflects the climatically controlled evaporative 18O enrichment of leaf water and thus highlights the great potential of GC-Py-IRMS δ18Osucrose analysis for plant physiology and paleoclimate studies. © 2013 Taylor &amp; Francis."
"12801836100;6603631763;55476786400;","The expected performance of cloud optical and microphysical properties derived from Suomi NPP VIIRS day/night band lunar reflectance",2013,"10.1002/2013JD020478","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891274035&doi=10.1002%2f2013JD020478&partnerID=40&md5=97a554405d1cba2ad2d0cd619aa6712b","The day/night band channel of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on board Suomi-National Polar Partnership (S-NPP) is a visible/near-infrared sensor (500-900 nm band pass) capable of measuring extremely low magnitudes of light, down to the levels of reflected moonlight and beyond. Whereas similar measurement capabilities have existed on predecessor sensors (principally, the Defense Meteorological Satellite Program), the day/night band offers the first calibrated radiance measurements, and as a result, it is the first opportunity to apply moonlight measurements to the problem of retrieving nocturnal cloud optical properties. Daytime retrievals of cloud properties such as top height, optical thickness, cloud top particle size, and water content, have been conducted routinely from an assortment of operational and research grade optical sensors for decades. These observations are providing a satellite-based global data record of increasing relevance to climate change monitoring (where clouds are thought to play an integral feedback role). The lack of a complete diurnal record of such key parameters presents an important shortfall of these records. Here we present the adaption of the daytime cloud optical and microphysical properties algorithm, which derives cloud optical thickness and effective radius from reflected sunlight to lunar reflectance. The new algorithm is referred to nighttime lunar cloud optical and microphysical properties. Day/night consistency of optical depth is shown through global analysis for one complete day of VIIRS data. Limitations of the retrieval of effective radius are discussed. Key Points Retrieval to derive nighttime cloud properties from lunar reflectance Use of Day/Night band of VIIRS instrument ©2013. American Geophysical Union. All Rights Reserved."
"35096299800;7004299063;35547807400;7102805852;24458137900;7404732357;","An overview of the Geoengineering Model Intercomparison Project (GeoMIP)",2013,"10.1002/2013JD020569","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891276726&doi=10.1002%2f2013JD020569&partnerID=40&md5=bf7858bc1bd87ac682bc8f1b67123e02","The Geoengineering Model Intercomparison Project (GeoMIP) was designed to determine robust climate system model responses to solar geoengineering. GeoMIP currently consists of four standardized simulations involving reduction of insolation or increased amounts of stratospheric sulfate aerosols. Three more experiments involving marine cloud brightening are planned. This project has improved confidence in the expected climate effects of geoengineering in several key areas, such as the effects of geoengineering on spatial patterns of temperature and the spatial distribution of precipitation, especially extreme precipitation events. However, GeoMIP has also highlighted several important research gaps, such as the effects on terrestrial net primary productivity and the importance of the CO2 physiological effect in determining the hydrologic cycle response to geoengineering. Future efforts will endeavor to address these gaps, as well as encourage cooperation with the chemistry modeling communities, the impact assessment communities, and other groups interested in model output. Key Points GeoMIP has been quite successful with 13 models participating Three new experiments on marine cloud brightening are planned GeoMIP has improved understanding and highlighted research gaps ©2013. American Geophysical Union. All Rights Reserved."
"36994120200;7006039508;47962387700;14060756100;","Recent variability of the tropical tropopause inversion layer",2013,"10.1002/2013GL058350","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889595275&doi=10.1002%2f2013GL058350&partnerID=40&md5=bd5635e76c83d6f8cdd1a9fd2010287d","The recent variability of the tropopause temperature and the tropopause inversion layer (TIL) are investigated with Global Positioning System Radio Occultation data and simulations with the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model (WACCM). Over the past decade (2001-2011) the data show an increase of 0.8 K in the tropopause temperature and a decrease of 0.4 K in the strength of the tropopause inversion layer in the tropics, meaning that the vertical temperature gradient has declined, and therefore that the stability above the tropopause has weakened. WACCM simulations with finer vertical resolution show a more realistic TIL structure and variability. Model simulations show that the increased tropopause temperature and the weaker tropopause inversion layer are related to weakened upwelling in the tropics. Such changes in the thermal structure of the upper troposphere and lower stratosphere may have important implications for climate, such as a possible rise in water vapor in the lower stratosphere. Key Points Tropical tropopause temp. increase, strength of TIL decrease over last decade Radiative cooling and dynamical warming contribute to TIL variability WACCM with finer vertical resolution captures TIL variability better ©2013. American Geophysical Union. All Rights Reserved."
"7202699757;7006518289;7401900092;55701363700;6701581880;","Energy balance in a warm world without the ocean conveyor belt and sea ice",2013,"10.1002/2013GL058123","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889005245&doi=10.1002%2f2013GL058123&partnerID=40&md5=7037036e73667b1021cd52cc14394df9","Under a strong global warming scenario, the global mean temperature could rise up to 10°C, causing the global ocean conveyor belt to collapse and the summer sea ice to disappear. This will lead to profound changes in our climate system and to impact drastically the living conditions of the globe. Here we study how the global heat redistribution and regional heat balance will respond to these changes using the National Center for Atmospheric Research Community Climate System Model version 4. Results show that the collapsed ocean conveyor belt reduces the oceanic northward meridional heat transport (MHT) by nearly 60% with a minor increase in the atmospheric MHT. The polar amplified warming is primarily caused by the increased absorption of longwave radiation due to the increased greenhouse gases and cloudiness and by the increased absorption of shortwave radiation due to a lower albedo associated with the disappeared summer sea ice. Key Points Collapsed AMOC under RCP8.5 will reduce oceanic heat transport Reduced oceanic heat transport is partly compensated by atmosphere Reduced sea ice lowers the albedo and increases absorption of solar radiation ©2013. American Geophysical Union. All Rights Reserved."
"7003780337;55949038600;","Monitoring the width of the tropical belt with GPS radio occultation measurements",2013,"10.1002/2013GL058203","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889032550&doi=10.1002%2f2013GL058203&partnerID=40&md5=e69d1baa05c32154cde2f1d0e0b5c2f1","GPS radio occultation data collected over the period 2002-2011 were analyzed to examine the possible expansion of the tropical belt due to climate change. By the use of high vertical-resolution temperature profiles, monthly averages of the lapse rate tropopause were obtained and used to derive a decade-long time series of the tropical edge latitude (TEL) in each hemisphere and its linear trends. Two different TEL criteria were examined. Our analysis shows that a statistically significant widening trend of ≈1° latitude/decade was found in the Northern Hemisphere (NH) by either criterion. This contrasts strongly with the Southern Hemisphere (SH), where no statistically significant trends were found. Comparison with ECMWF reanalysis shows good agreement, but the agreement is worse over SH. Substantial differences in seasonal trends were found between NH and SH, with the latter showing strong widening in the austral summer countered by contraction over the austral winter and spring. Key Points A decade of tropopause height data was used to study changes in tropical width Widening rates are sensitive to the definition of the tropical boundaries Significant widening trend was observed in NH but not SH for the past decade © Published 2013. This article is a U.S. Government work and is in the public domain in the USA."
"6504750541;6507400558;7004978125;","Realistic initiation and dynamics of the Madden-Julian Oscillation in a coarse resolution aquaplanet GCM",2013,"10.1002/2013GL058187","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889826764&doi=10.1002%2f2013GL058187&partnerID=40&md5=f8ea1c047a7e87b933bff718b55815d2","The main mechanisms for the initiation and propagation of the Madden-Julian Oscillation (MJO) are still widely debated. The capacity of operational global climate models (GCMs) to correctly simulate the MJO is hindered by the inadequacy of the underlying cumulus parameterizations. Here we show that a coarse resolution GCM, coupled to a simple multicloud model parameterization mimicking the observed dynamics and physical structure of organized tropical convection, simulates the MJO in an idealized setting of an aquaplanet without ocean dynamics. We impose a fixed nonhomogeneous sea-surface temperature replicating the Indian Ocean/Western Pacific warm pool. This results in a succession of MJOs with realistic phase speed, amplitude, and physical structure. Each MJO event is initiated at a somewhat random location over the warm pool and dies sometimes near the eastern boundary of the warm pool and sometimes at a random location way beyond the warm pool. Also occasionally the MJO events stall at the center of maximum heating. This is reminiscent of the fact that in nature some MJOs stall over the maritime continent while others reach the central Pacific Ocean and beyond. The initiation mechanism in the model is believed to be a combination of persistent intermittent convective events interacting with observed large-scale flow patterns and internal tropical dynamics. The large-scale flow patterns are associated with planetary-scale dry Kelvin waves that are triggered by preceding MJO events and circle the globe, while congestus cloud decks on the flanks of the warm pool are believed to force Rossby gyres which then funnel moisture toward the equatorial region. Key Points Realistic MJO initiation and dynamics in a GCM Used a simple three layer multicloud convection scheme in the simulation A different initiation mechanism for the MJO as opposed to the existing theory ©2013. American Geophysical Union. All Rights Reserved."
"35368540100;56746732000;55276378300;56585184400;56813208900;57189939159;7405765177;","Monitoring daily evapotranspiration in Northeast Asia using MODIS and a regional Land Data Assimilation System",2013,"10.1002/2013JD020639","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891275548&doi=10.1002%2f2013JD020639&partnerID=40&md5=854e8c1dfcdcc9a023e3c3a998cd32d1","We applied an approach for daily estimation and monitoring of evapotranspiration (ET) over the Northeast Asia monsoon region using satellite remote sensing observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). Frequent cloud cover results in a substantial loss of remote sensing information, limiting the capability of continuous ET monitoring for the monsoon region. Accordingly, we applied and evaluated a stand-alone MODIS ET algorithm for representative regional ecosystem types and an alternative algorithm to facilitate continuous regional ET estimates using surface meteorological inputs from the Korea Land Data Assimilation System (KLDAS) in addition to MODIS land products. The resulting ET calculations showed generally favorable agreement (root-mean-square error &lt; 1.3 mm d -1) with respect to in situ measurements from eight regional flux tower sites. The estimated mean annual ET for 3 years (2006 to 2008) was approximately 362.0 ± 161.5 mm yr-1 over the Northeast Asia domain. In general, the MODIS and KLDAS-based ET (MODIS-KLDAS ET) results showed favorable performance when compared to tower observations, though the results were overestimated for a forest site by approximately 39.5% and underestimated for a cropland site in South Korea by 0.8%. The MODIS-KLDAS ET data were generally underestimated relative to the MODIS (MOD16) operational global terrestrial ET product for various biome types, excluding cropland; however, MODIS-KLDAS ET showed better agreement than MOD16 ET for forest and cropland sites in South Korea. Our results indicate that MODIS ET estimates are feasible but are limited by satellite optical-infrared remote sensing constraints over cloudy regions, whereas alternative ET estimates using continuous meteorological inputs from operational regional climate systems (e.g., KLDAS) provide accurate ET results and continuous monitoring capability under all-sky conditions. Key Points Stand-alone clear-sky ET estimate using MODIS products was implemented at 1 km Cloudy-sky ET was estimated by combining MODIS and Korean LDAS (KLDAS) MODIS-KLDAS ET showed better performance than MOD16 ET in Northeast Asia ©2013. American Geophysical Union. All Rights Reserved."
"49864573500;13405658600;","A parameterization of sub-grid particle formation in sulfur-rich plumes for global- and regional-scale models",2013,"10.5194/acp-13-12117-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890370273&doi=10.5194%2facp-13-12117-2013&partnerID=40&md5=e1570914c7db6acfe523d5677105fe21","New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulfur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are tens of kilometres and larger. Based on the results of the System for Atmospheric Modelling (SAM), a large-eddy simulation/cloud-resolving model (LES/CRM) with online two-moment aerosol sectional (TOMAS) microphysics, we have developed a computationally efficient, but physically based, parameterization that predicts the characteristics of aerosol formed within sulfur-rich plumes based on parameters commonly available in global- and regional-scale models. Given large-scale mean meteorological parameters ((1) wind speed, (2) boundary-layer height and (3) downward shortwave radiative flux), (4) emissions of SO2 and (5) NOx from the source, (6) mean background condensation sink, (7) background SO2 and (8) NOx concentrations, and (9) the desired distance from the source, the parameterization will predict (1) the fraction of the emitted SO2 that is oxidized to H2SO4, (2) the fraction of that H2SO4 that forms new particles instead of condensing onto pre-existing particles, (3) the mean mass per particle of the newly formed particles, and (4) the number of newly formed particles per kilogram SO2 emitted. The parameterization we describe here should allow for more accurate predictions of aerosol size distributions and a greater confidence in the effects of aerosols in climate and health studies."
"55955309500;6603955973;14720154900;","A new perspective on the infrared brightness temperature distribution of the deep convective clouds",2013,"10.1007/s12040-013-0345-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889661999&doi=10.1007%2fs12040-013-0345-4&partnerID=40&md5=d0a76860f5befe333e0164265eafff65","We are proposing a statistical technique to analyze the best fit of the histogram of infrared brightness temperature of convective cloud pixels. For this we have utilized the infrared brightness temperatures (IRTB) of Kalpana-1 (8 km resolution) and globally merged infrared brightness temperatures of Climate Prediction Centre NCEP/NWS (4 km resolution, merged from all the available geostationary satellites GOES-8/10, METEOSAT-7/5 and GMS), for both deep convective and non-deep convective (shallow cloud) cases. It is observed that Johnson SB function is the best continuous distribution function in explaining the histogram of infrared brightness temperatures of the convective clouds. The best fit is confirmed by Kolmogorov-Smirnov statistic. Johnson SB's distribution of histogram of infrared brightness temperatures clearly discriminates the cloud pixels of deep convective and non-deep convective cases. It also captures the asymmetric nature in histogram of infrared brightness temperatures. We also observed that Johnson SB distribution of infrared brightness temperatures for deep convective systems is different in each of the pre-monsoon, monsoon and post-monsoon seasons. And Johnson SB parameters are observed to be best in discriminating the Johnson SB distribution of infrared brightness temperatures of deep convective systems for each season. Due to these properties of Johnson SB function, it can be utilized in the modelling of the histogram of infrared brightness temperature of deep convective and non-deep convective systems. It focuses a new perspective on the infrared brightness temperature that will be helpful in cloud detection, classification and modelling. © Indian Academy of Sciences."
"36088530800;36052878000;24460392200;7102425008;6602178158;26645289600;","Diagnosing the average spatio-temporal impact of convective systems -Part 1: A methodology for evaluating climate models",2013,"10.5194/acp-13-12043-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890523211&doi=10.5194%2facp-13-12043-2013&partnerID=40&md5=a7769a731e25cce6662662da8bb310ce","An earlier method to determine the mean response of upper-tropospheric water to localised deep convective systems (DC systems) is improved and applied to the EC-Earth climate model. Following Zelinka and Hartmann (2009), several fields related to moist processes and radiation from various satellites are composited with respect to the local maxima in rain rate to determine their spatio-temporal evolution with deep convection in the central Pacific Ocean. Major improvements to the earlier study are the isolation of DC systems in time so as to prevent multiple sampling of the same event, and a revised definition of the mean background state that allows for better characterisation of the DC-system-induced anomalies. The observed DC systems in this study propagate westward at ~ 4 ms -1. Both the upper-tropospheric relative humidity and the outgoing longwave radiation are substantially perturbed over a broad horizontal extent and for periods &gt;30 h. The cloud fraction anomaly is fairly constant with height but small maximum can be seen around 200 hPa. The cloud ice water content anomaly is mostly confined to pressures greater than 150 hPa and reaches its maximum around 450 hPa, a few hours after the peak convection. Consistent with the large increase in upper-tropospheric cloud ice water content, albedo increases dramatically and persists about 30 h after peak convection. Applying the compositing technique to EC-Earth allows an assessment of the model representation of DC systems. The model captures the large-scale responses, most notably for outgoing longwave radiation, but there are a number of important differences. DC systems appear to propagate eastward in the model, suggesting a strong link to Kelvin waves instead of equatorial Rossby waves. The diurnal cycle in the model is more pronounced and appears to trigger new convection further to the west each time. Finally, the modelled ice water content anomaly peaks at pressures greater than 500 hPa and in the upper troposphere between 250 hPa and 500 hPa, there is less ice than the observations and it does not persist as long after peak convection. The modelled upper-tropospheric cloud fraction anomaly, however, is of a comparable magnitude and exhibits a similar longevity as the observations. © Author(s) 2013. CC Attribution 3.0 License."
"36105949100;7004944088;55684491100;22981551200;56187256200;55966258500;35998927000;35183991500;7006211890;","Aircraft type influence on contrail properties",2013,"10.5194/acp-13-11965-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879983933&doi=10.5194%2facp-13-11965-2013&partnerID=40&md5=b35a5b0a15986907bad0ca058b89c3dc","The investigation of the impact of aircraft parameters on contrail properties helps to better understand the climate impact from aviation. Yet, in observations, it is a challenge to separate aircraft and meteorological influences on contrail formation. During the CONCERT campaign in November 2008, contrails from 3 Airbus passenger aircraft of types A319-111, A340-311 and A380-841 were probed at cruise under similar meteorological conditions with in situ instruments on board DLR research aircraft Falcon. Within the 2 min-old contrails detected near ice saturation, we find similar effective diameters Deff (5.2-5.9 μm), but differences in particle number densities nice (162-235 cm-3) and in vertical contrail extensions (120-290 m), resulting in large differences in contrail optical depths τ at 550 nm (0.25-0.94). Hence larger aircraft produce optically thicker contrails. Based on the observations, we apply the EULAG-LCM model with explicit ice microphysics and, in addition, the Contrail and Cirrus Prediction (CoCiP) model to calculate the aircraft type impact on young contrails under identical meteorological conditions. The observed increase in τ for heavier aircraft is confirmed by the models, yet for generally smaller τ. CoCiP model results suggest that the aircraft dependence of climate-relevant contrail properties persists during contrail lifetime, adding importance to aircraft-dependent model initialization. We finally derive an analytical relationship between contrail, aircraft and meteorological parameters. Near ice saturation, contrail width × τ scales linearly with the fuel flow rate, as confirmed by observations. For higher relative humidity with respect to ice (RHI), the analytical relationship suggests a non-linear increase in the form (RHI-1) 2/3. Summarized, our combined results could help to more accurately assess the climate impact from aviation using an aircraft-dependent contrail parameterization. © Author(s) 2013."
"12144198300;57205397413;6701729202;","Radiative consequences of low-temperature infrared refractive indices for supercooled water clouds",2013,"10.5194/acp-13-11925-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890098734&doi=10.5194%2facp-13-11925-2013&partnerID=40&md5=2d2ed0734c4891d60d465fd802527dad","Simulations of cloud radiative properties for climate modeling and remote sensing rely on accurate knowledge of the complex refractive index (CRI) of water. Although conventional algorithms employ a temperature-independent assumption (TIA), recent infrared measurements of supercooled water have demonstrated that the CRI becomes increasingly ice-like at lower temperatures. Here, we assess biases that result from ignoring this temperature dependence. We show that TIA-based cloud retrievals introduce spurious ice into pure, supercooled clouds, or underestimate cloud optical thickness and droplet size. TIA-based downwelling radiative fluxes are lower than those for the temperature-dependent CRI by as much as 1.7 W m&minus;2 (in cold regions), while top-of-atmosphere fluxes are higher by as much as 3.4 W m&minus;2 (in warm regions). Proper accounting of the temperature dependence of the CRI, therefore, leads to significantly greater local greenhouse warming due to supercooled clouds than previously predicted. The current experimental uncertainty in the CRI at low temperatures must be reduced to account for supercooled clouds properly in both climate models and cloud-property retrievals. © 2013 Author(s)."
"55940667800;24177361900;7003968166;","An online trajectory module (version 1.0) for the nonhydrostatic numerical weather prediction model COSMO",2013,"10.5194/gmd-6-1989-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888383707&doi=10.5194%2fgmd-6-1989-2013&partnerID=40&md5=77ea32323f064529ab6172cb4608d207","A module to calculate online trajectories has been implemented into the nonhydrostatic limited-area weather prediction and climate model COSMO. Whereas offline trajectories are calculated with wind fields from model output, which is typically available every one to six hours, online trajectories use the simulated resolved wind field at every model time step (typically less than a minute) to solve the trajectory equation. As a consequence, online trajectories much better capture the short-term temporal fluctuations of the wind field, which is particularly important for mesoscale flows near topography and convective clouds, and they do not suffer from temporal interpolation errors between model output times. The numerical implementation of online trajectories in the COSMO-model is based upon an established offline trajectory tool and takes full account of the horizontal domain decomposition that is used for parallelization of the COSMO-model. Although a perfect workload balance cannot be achieved for the trajectory module (due to the fact that trajectory positions are not necessarily equally distributed over the model domain), the additional computational costs are found to be fairly small for the high-resolution simulations described in this paper. The computational costs may, however, vary strongly depending on the number of trajectories and trace variables. Various options have been implemented to initialize online trajectories at different locations and times during the model simulation. As a first application of the new COSMO-model module, an Alpine north foehn event in summer 1987 has been simulated with horizontal resolutions of 2.2, 7 and 14 km. It is shown that low-tropospheric trajectories calculated offline with one- to six-hourly wind fields can significantly deviate from trajectories calculated online. Deviations increase with decreasing model grid spacing and are particularly large in regions of deep convection and strong orographic flow distortion. On average, for this particular case study, horizontal and vertical positions between online and offline trajectories differed by 50-190 km and 150-750 m, respectively, after 24 h. This first application illustrates the potential for Lagrangian studies of mesoscale flows in high-resolution convection-resolving simulations using online trajectories."
"24485834000;57112070700;7004714030;6505465237;13607567200;55581675600;8696069500;6603247427;6602600408;","The respective roles of surface temperature driven feedbacks and tropospheric adjustment to CO2 in CMIP5 transient climate simulations",2013,"10.1007/s00382-013-1682-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888029321&doi=10.1007%2fs00382-013-1682-3&partnerID=40&md5=c9a7ff64419303cf21e46a093c5e3074","An overview of radiative climate feedbacks and ocean heat uptake efficiency diagnosed from idealized transient climate change experiments of 14 CMIP5 models is presented. Feedbacks explain about two times more variance in transient climate response across the models than ocean heat uptake efficiency. Cloud feedbacks can clearly be identified as the main source of inter-model spread. Models with strong longwave feedbacks in the tropics feature substantial increases in cloud ice around the tropopause suggestive of changes in cloud-top heights. The lifting of the tropical tropopause goes together with a general weakening of the tropical circulation. Distinctive inter-model differences in cloud shortwave feedbacks occur in the subtropics including the equatorward flanks of the storm-tracks. Related cloud fraction changes are not confined to low clouds but comprise middle level clouds as well. A reduction in relative humidity through the lower and mid troposphere can be identified as being the main associated large-scale feature. Experiments with prescribed sea surface temperatures are analyzed in order to investigate whether the diagnosed feedbacks from the transient climate simulations contain a tropospheric adjustment component that is not conveyed through the surface temperature response. The strengths of the climate feedbacks computed from atmosphere-only experiments with prescribed increases in sea surface temperatures, but fixed CO2 concentrations, are close to the ones derived from the transient experiment. Only the cloud shortwave feedback exhibits discernible differences which, however, can not unequivocally be attributed to tropospheric adjustment to CO2. Although for some models a tropospheric adjustment component is present in the global mean shortwave cloud feedback, an analysis of spatial patterns does not lend support to the view that cloud feedbacks are dominated by their tropospheric adjustment part. Nevertheless, there is positive correlation between the strength of tropospheric adjustment processes and cloud feedbacks across different climate models. © 2013 Springer-Verlag Berlin Heidelberg."
"49664027700;7004714030;35509639400;","On the interpretation of inter-model spread in CMIP5 climate sensitivity estimates",2013,"10.1007/s00382-013-1725-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888055218&doi=10.1007%2fs00382-013-1725-9&partnerID=40&md5=4ceccac16b19a865d199754e9f6dbaf4","This study diagnoses the climate sensitivity, radiative forcing and climate feedback estimates from eleven general circulation models participating in the Fifth Phase of the Coupled Model Intercomparison Project (CMIP5), and analyzes inter-model differences. This is done by taking into account the fact that the climate response to increased carbon dioxide (CO2) is not necessarily only mediated by surface temperature changes, but can also result from fast land warming and tropospheric adjustments to the CO2 radiative forcing. By considering tropospheric adjustments to CO2 as part of the forcing rather than as feedbacks, and by using the radiative kernels approach, we decompose climate sensitivity estimates in terms of feedbacks and adjustments associated with water vapor, temperature lapse rate, surface albedo and clouds. Cloud adjustment to CO2 is, with one exception, generally positive, and is associated with a reduced strength of the cloud feedback; the multi-model mean cloud feedback is about 33 % weaker. Non-cloud adjustments associated with temperature, water vapor and albedo seem, however, to be better understood as responses to land surface warming. Separating out the tropospheric adjustments does not significantly affect the spread in climate sensitivity estimates, which primarily results from differing climate feedbacks. About 70 % of the spread stems from the cloud feedback, which remains the major source of inter-model spread in climate sensitivity, with a large contribution from the tropics. Differences in tropical cloud feedbacks between low-sensitivity and high-sensitivity models occur over a large range of dynamical regimes, but primarily arise from the regimes associated with a predominance of shallow cumulus and stratocumulus clouds. The combined water vapor plus lapse rate feedback also contributes to the spread of climate sensitivity estimates, with inter-model differences arising primarily from the relative humidity responses throughout the troposphere. Finally, this study points to a substantial role of nonlinearities in the calculation of adjustments and feedbacks for the interpretation of inter-model spread in climate sensitivity estimates. We show that in climate model simulations with large forcing (e.g., 4 × CO2), nonlinearities cannot be assumed minor nor neglected. Having said that, most results presented here are consistent with a number of previous feedback studies, despite the very different nature of the methodologies and all the uncertainties associated with them. © 2013 Springer-Verlag Berlin Heidelberg."
"6506848305;25031430500;7103158465;7005920812;7102239370;23393856300;","Higher-order turbulence closure and its impact on climate simulations in the community atmosphere model",2013,"10.1175/JCLI-D-13-00075.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887298740&doi=10.1175%2fJCLI-D-13-00075.1&partnerID=40&md5=adce92ad80ea2541ac9b4fd3a6b274d8","This paper describes climate simulations of the Community Atmosphere Model, version 5 (CAM5), coupled with a higher-order turbulence closure known as Cloud Layers Unified by Binormals (CLUBB). CLUBB is a unified parameterization of the planetary boundary layer (PBL) and shallow convection that is centered around a trivariate probability density function (PDF) and replaces the conventional PBL, shallow convection, and cloud macrophysics schemes in CAM5. CAM-CLUBB improves many aspects of the base state climate compared to CAM5. Chief among them is the transition of stratocumulus to trade wind cumulus regions in the subtropical oceans. In these regions, CAM-CLUBB provides a much more gradual transition that is in better agreement with observational analysis compared to CAM5, which is too abrupt. The improvement seen in CAM-CLUBB can be largely attributed to the gradual evolution of the simulated turbulence, which is in part a result of the unified nature of the parameterization, and to the general improved representation of shallow cumulus clouds compared to CAM5. In addition, there are large differences in the representation and structure of marine boundary layer clouds between CAM-CLUBB and CAM5. CAM-CLUBB is also shown to be more robust, in terms of boundary layer clouds, to changes in vertical resolution for global simulations in a preliminary test. © 2013 American Meteorological Society."
"55745955800;7004479957;8882641700;7101795549;6701431208;35509639400;54893098900;57195644113;8977001000;57193132723;6603606681;55272477500;8877858700;6701752471;36876405100;24173130300;25927181300;7004714030;7203062717;13405561000;56865378100;7005920812;56611366900;7005056279;57203053317;6701346974;6603371044;6602364115;7006705919;23768540500;55536607600;6603566335;56039057300;7201504886;35497573900;7403282069;6603613067;7201485519;7403174207;55286185400;","CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models",2013,"10.1002/2013MS000246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006568652&doi=10.1002%2f2013MS000246&partnerID=40&md5=b171fa23582f1967fe02b0e35904ae26","CGILS-the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)-investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: in a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as the ""NESTS"" negative cloud feedback and the ""SCOPE"" positive cloud feedback (Negative feedback from Surface Turbulence under weaker Subsidence-Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations. © American Geophysical Union."
"55471474500;7401945370;","Response of ice and liquid water paths of tropical cyclones to global warming simulated by a global nonhydrostatic model with explicit cloud microphysics",2013,"10.1175/JCLI-D-13-00182.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890216284&doi=10.1175%2fJCLI-D-13-00182.1&partnerID=40&md5=06cb31a4fac213b13a1a173c8c94f3c2","Cloud feedback plays a key role in the future climate projection. Using global nonhydrostatic model (GNHM) simulation data for a present-day [control (CTL)] and a warmer [global warming (GW)] experiment, the authors estimate the contribution of tropical cyclones (TCs) to ice water paths (IWP) and liquid water paths (LWP) associated with TCs and their changes between CTL and GW experiments. They use GNHM with a 14-km horizontal mesh for explicitly calculating cloud microphysics without cumulus parameterization. This dataset shows that the cyclogenesis underGWconditions reduces to approximately 70% of that under CTL conditions, as shown in a previous study, and the tropical averaged IWP (LWP) is reduced by approximately 2.76% (0.86%). Horizontal distributions of IWP and LWP changes seem to be closely related to TC track changes. To isolate the contributions of IWP/LWP associated with TCs, the authors first examine the radial distributions of IWP/LWP from the TC center at their mature stages and find that they generally increase for more intense TCs. As the intense TC in GW increases, the IWP and LWP around the TC center in GW becomes larger than that in CTL. The authors next define the TC area as the region within 500km from the TC center at its mature stages. They find that the TC's contribution to the total tropical IWP (LWP) is 4.93% (3.00%) in CTL and 5.84% (3.69%) in GW. Although this indicates that the TC's contributions to the tropical IWP/LWP are small, IWP/LWP changes in each basin behave in a manner similar to those of the cyclogenesis and track changes under GW. © 2013 Park-media, Ltd."
"15848674200;24492014600;56520921400;57210180554;6602858513;7406243250;6506328135;7202048112;","Observed scaling in clouds and precipitation and scale incognizance in regional to global atmospheric models",2013,"10.1175/JCLI-D-13-00005.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888064298&doi=10.1175%2fJCLI-D-13-00005.1&partnerID=40&md5=267fb0b4675b5eae6c326e7a6c526db2","Observations of robust scaling behavior in clouds and precipitation are used to derive constraints on how partitioning of precipitation should change with model resolution. Analysis indicates that 90%-99% of stratiform precipitation should occur in clouds that are resolvable by contemporary climate models (e.g., with 200-km or finer grid spacing). Furthermore, this resolved fraction of stratiform precipitation should increase sharply with resolution, such that effectively all stratiform precipitation should be resolvable above scales of ~50 km. It is shown that the Community Atmosphere Model (CAM) and the Weather Research and Forecasting model (WRF) also exhibit the robust cloud and precipitation scaling behavior that is present in observations, yet the resolved fraction of stratiform precipitation actually decreases with increasing model resolution. A suite of experiments with multiple dynamical cores provides strong evidence that this ""scale-incognizant"" behavior originates in one of the CAM4 parameterizations. An additional set of sensitivity experiments rules out both convection parameterizations, and by a process of elimination these results implicate the stratiform cloud and precipitation parameterization. Tests with the CAM5 physics package show improvements in the resolution dependence of resolved cloud fraction and resolved stratiform precipitation fraction. © 2013 American Meteorological Society."
"7101677832;6603631763;7202970886;24802640400;","Satellite Regional Cloud Climatology over the Great Lakes",2013,"10.3390/rs5126223","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891383370&doi=10.3390%2frs5126223&partnerID=40&md5=8f8e03bc6d442b0ec39f282848a7e065","Thirty-one years of imager data from polar orbiting satellites are composited to produce a satellite climate data set of cloud amount for the Great Lakes region. A trend analysis indicates a slight decreasing trend in cloud cover over the region during this time period. The trend is significant and largest (~2% per decade) over the water bodies. A strong seasonal cycle of cloud cover is observed over both land and water surfaces. Winter cloud amounts are greater over the water bodies than land due to heat and moisture flux into the atmosphere. Late spring through early autumn cloud amounts are lower over the water bodies than land due to stabilization of the boundary layer by relatively cooler lake waters. The influence of the lakes on cloud cover also extends beyond their shores, affecting cloud cover and properties far down wind. Cloud amount composited by wind direction demonstrate that the increasing cloud amounts downwind of the lakes is greatest during autumn and winter. Cold air flows over relatively warm lakes in autumn and winter generate wind parallel convective cloud bands. The cloud properties of these wind parallel cloud bands over the lakes during winter are presented © 2013 by the authors."
"7006280684;6602415539;25959962200;55170561300;55935371700;","Can top-of-atmosphere radiation measurements constrain climate predictions? Part I: Tuning",2013,"10.1175/JCLI-D-12-00595.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888049675&doi=10.1175%2fJCLI-D-12-00595.1&partnerID=40&md5=f88b69a56b678f15360fe0eadc23762d","Perturbed physics configurations of version 3 of the Hadley Centre Atmosphere Model (HadAM3) driven with observed sea surface temperatures (SST) and sea ice were tuned to outgoing radiation observations using a Gauss-Newton line search optimization algorithm to adjust the model parameters. Four key parameters that previous research found affected climate sensitivity were adjusted to several different target values including two sets of observations. The observations used were the global average reflected shortwave radiation (RSR) and outgoing longwave radiation (OLR) from the Clouds and the Earth's Radiant Energy System instruments combined with observations of ocean heat content. Using the same method, configurations were also generated that were consistent with the earlier Earth Radiation Budget Experiment results. Many, though not all, tuning experiments were successful, with about 2500 configurations being generated and the changes in simulated outgoing radiation largely due to changes in clouds. Clear-sky radiation changes were small, largely due to a cancellation between changes in upper-tropospheric relative humidity and temperature. Changes in other climate variables are strongly related to changes in OLR and RSR particularly on large scales. There appears to be some equifinality with different parameter configurations producing OLR and RSR values close to observed values. These models have small differences in their climatology with the one group being similar to the standard configuration and the other group drier in the tropics and warmer everywhere. © 2013 American Meteorological Society."
"7006280684;55170561300;6602415539;25959962200;","Can top-of-atmosphere radiation measurements constrain climate predictions? Part II: Climate sensitivity",2013,"10.1175/JCLI-D-12-00596.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888067432&doi=10.1175%2fJCLI-D-12-00596.1&partnerID=40&md5=6e03352579b0ab0acf92c1fde52c979d","A large number of perturbed-physics simulations of version 3 of the Hadley Centre Atmosphere Model (HadAM3) were compared with the Clouds and the Earth's Radiant Energy System (CERES) estimates of outgoing longwave radiation (OLR) and reflected shortwave radiation (RSR) as well as OLR and RSR from the earlier Earth Radiation Budget Experiment (ERBE) estimates. The model configurations were produced from several independent optimization experiments in which four parameters were adjusted. Model-observation uncertainty was estimated by combining uncertainty arising from satellite measurements, observational radiation imbalance, total solar irradiance, radiative forcing, natural aerosol, internal climate variability, and sea surface temperature and that arising from parameters that were not varied. Using an emulator built from 14 001 ""slab"" model evaluations carried out using the climateprediction.net ensemble, the climate sensitivity for each configuration was estimated. Combining different prior probabilities for model configurations with the likelihood for each configuration and taking account of uncertainty in the emulated climate sensitivity gives, for the HadAM3 model, a 2.5%-97.5% range for climate sensitivity of 2.7-4.2 K if the CERES observations are correct. If the ERBE observations are correct, then they suggest a larger range, for HadAM3, of 2.8-5.6 K. Amplifying the CERES observational covariance estimate by a factor of 20 brings CERES and ERBE estimates into agreement. In this case the climate sensitivity range is 2.7-5.4 K. The results rule out, at the 2.5% level for HadAM3 and several different prior assumptions, climate sensitivities greater than 5.6 K. © 2013 American Meteorological Society."
"7406319763;55365584100;","Influences of circulation and climate change on European summer heat extremes",2013,"10.1175/JCLI-D-12-00740.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888043289&doi=10.1175%2fJCLI-D-12-00740.1&partnerID=40&md5=3045a91be4a397002d1745d8945459f6","Atmospheric circulation patterns occurring on the warmest 10% of summer days for a region of Europe severely impacted by the 2003 heatwave have been identified using a perturbed parameter ensemble of regional high-resolution climate model simulations for the recent past. Changes in the frequency and duration of these circulation types, driven by the simulations following a moderate transient pathway of anthropogenic emissions, are then shown for the period 2070 to 2100. Increases in the future probability of hot days are then attributed separately to changes in the frequency and temperature intensity of the circulation types. Changes in temperature intensity are found to have an effect 2 to 3 times larger than in frequency. The authors then consider how model uncertainty in changes of future temperature within circulation patterns compares to the uncertainty irrespective of circulation, in an attempt to exclude contributions to the overall uncertainty arising from changes in circulation. Within individual patterns, the range of meteorological physical processes may be narrower. However, no reduction in uncertainty was found when single patterns were considered. Contributions to the lack of narrowing from circulation-type duration, model vegetation root depth and changes in cloud cover, pressure gradient, and continental-scale warming are subsequently examined using relationships between changes in surface latent heat and temperature. Vegetation root depth is found to be the greatest contributor to the temperature uncertainty. © 2013 American Meteorological Society."
"26325744400;13105366200;7103393418;","Cloud attenuation studies of the six major climatic zones of Africa for Ka and V satellite system design",2013,"10.4401/ag-6342","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892622577&doi=10.4401%2fag-6342&partnerID=40&md5=34cc3f7650af7227411587e8562ca06a","Cloud cover statistics, cloud base and top height, cloud temperature, frequency of precipitation, freezing height, total cloud liquid water content (TCLWC) and cloud attenuation data have been obtained for the six major climatic zones of Africa. The present results reveal a strong positive correlation between the monthly distribution of low cloud cover, cloud top height, cloud temperature, and frequency of precipitation in the six zones. The cumulative distribution of the TCLWC derived from radiosonde measurement in each climatic zone shows a departure from the TCLWC recommended by the ITU Study Group 3 data, with an exceedance percentage difference of 32% to 90% occurring 0.01% to 10% of the time. The underestimation of the TCLWC is greatest in the tropical rain forest. A comparison of the cloud attenuation cumulative distribution in the Ka and V bands reveals that the International Telecommunication Union - Region (ITU-R) is an intergovernmental organization that develops rain model based on collected data around the world. This model underestimates the cloud attenuation in all of the six climatic zones by 2.0 dB and 4.7 dB for the arid Sahara desert, 1.3 dB and 3.0 dB in semi-arid North Africa, 1.3 dB and 1.5 dB in savannah North Africa, 2.0 dB and 3.6 dB in the tropical rain forest, 1.3 dB and 2.9 dB in savannah South Africa and 0.9 dB and 2.6 dB in semi-arid South Africa, respectively, at 30 and 50 GHz. Overall, the cloud attenuation in the tropical rain-forest zone is very high because of the high annual total cloud cover (98%), high annual frequency of precipitation (4.5), low annual clear sky amount (8%), high cloud depth (10,937 m), high 0°C isotherm height (4.7 km), high TCLWC (4.0 kg/m2 at 0.01%) and low seasonal cloud base height (356 m). © 2013 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved."
"26431037300;26645901500;7004468723;","Evaluation and response of winter cold spells over Western Europe in CMIP5 models",2013,"10.1007/s00382-012-1565-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888072587&doi=10.1007%2fs00382-012-1565-z&partnerID=40&md5=15c70a2ebe1f5a2c19bd71173f8074f5","This paper is dedicated to the analysis of winter cold spells over Western Europe in the simulations of the 5th phase of the Coupled Model Intercomparison Project (CMIP5). Both model biases and responses in a warming climate are discussed using historical simulations and the 8.5 W/m2 Representative Concentration Pathway (RCP8.5) scenario, respectively on the 1979-2008 and 2070-2099 periods. A percentile-based index (10th percentile of daily minimum temperature, Q10) with duration and spatial extent criteria is used to define cold spells. Related diagnostics (intensity, duration, extent, and severity as a combination of the former three statistics) of 13 models are compared to observations and suggest that models biases on severity are mainly due to the intensity parameter rather than to duration and extent. Some hypotheses are proposed to explain these biases, that involve large-scale dynamics and/or radiative fluxes related to clouds. Evolution of cold spells characteristics by the end of the century is then discussed by comparing RCP8.5 and historical simulations. In line with the projected rise of mean temperature, ""present-climate"" cold spells (computed with the 1979-2008 10th percentile, Q10P) are projected to be much less frequent and, except in one model, less severe. When cold spells are defined from the future 10th percentile threshold (""future-climate"" cold spells, Q10F), all models simulate a decrease of their intensity linearly related to the seasonal mean warming. Some insights are given to explain the inter-model diversity in the magnitude of the cold spells response. In particular, the snow-albedo feedback is suggested to play an important role, while for some models changes in large-scale dynamics are also not negligible. © 2012 Springer-Verlag Berlin Heidelberg."
"57199732322;9237189600;15034092500;7404516111;55718000700;8418271700;","Changes of meteorological parameters and lightning current during water impounded in Three Gorges area",2013,"10.1016/j.atmosres.2013.06.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883529052&doi=10.1016%2fj.atmosres.2013.06.004&partnerID=40&md5=94fd63fbb782152a3a4b3842670c506d","With the completion of Three Gorges Project and its water impoundment started from 2003, a big reservoir with water area of 1.08×109m2 and volume of 3.93×1010m3 has been formed, which causes the surrounding microclimate changed. This paper compared the changes of meteorological parameters and Cloud-to-Groundare one of the reasons that lead to lighting activity enhancing. © 2013."
"12143017100;35273743200;7102731541;","Future changes in structures of extremely intense tropical cyclones using a 2-km mesh nonhydrostatic model",2013,"10.1175/JCLI-D-12-00477.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890206668&doi=10.1175%2fJCLI-D-12-00477.1&partnerID=40&md5=cb56b900705bd9659bcbf78f88da7b4d","Recent studies have projected that global warming may lead to an increase in the number of extremely intense tropical cyclones. However, how global warming affects the structure of extremely intense tropical cyclones has not been thoroughly examined. This study defines extremely intense tropical cyclones as having a minimum central pressure below 900 hPa and investigates structural changes in the inner core and thereby changes in the intensity in the future climate. A 2-km mesh nonhydrostatic model (NHM2) is used to downscale the 20-km mesh atmospheric general circulation model projection forced with a control scenario and a scenario of twenty-first-century climate change. The eyewall region of extremely intense tropical cyclones simulated by NHM2 becomes relatively smaller and taller in the future climate. The intense nearsurface inflow intrudes more inward toward the eye. The heights and the radii of the maximum wind speed significantly decrease and an intense updraft area extends from the lower level around the leading edge of thinner near-surface inflows, where the equivalent potential temperature substantially increases in the future climate. Emanuel's potential intensity theory suggests that about half of the intensification (increase in central pressure fall) is explained by the changes in the atmospheric environments and sea surface temperature, while the remaining half needs to be explained by other processes. It is suggested that the structural change projected by NHM2, which is significant within a radius of 50 km, is playing an important role in the intensification of extremely intense tropical cyclones in simulations of the future climate. © 2013 American Meteorological Society."
"7404011080;55941105400;7202485447;","Numerical simulations of asian dust-aerosols and regional impact on weather and climate- part I: Control case-prcm simulation without dust-aerosols",2013,"10.4209/aaqr.2013.06.0207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888396791&doi=10.4209%2faaqr.2013.06.0207&partnerID=40&md5=73a2ea2ca2bac8b955cfa62852ffb8e1","Aerosol particles affect atmospheric radiation and cloud microphysics, and are considered a major uncertainty in climate forcing. At the same time, accurate simulation and prediction of meteorological conditions are necessary to simulate the distribution and chemical reaction of the aerosols. Distribution of pollutions can also be used to validate meteorological models. This paper consists of two parts: Part I: Numerical simulation of weather and soil conditions from the Purdue Regional Climate Model (PRCM); and Part II: Numerical modeling of online interaction between dust and weather/ climate. Both parts were integrated continuously from April 08 to 24, 1998 without nudging or restarting. The detailed treatment of soil and the planetary boundary layer (PBL), using the semi-conserved ice-potential temperature and total water substance as prognostic variables, a local reference to calculate the pressure gradient, and the accurate advection scheme, allowed the PRCM to well reproduce the movements of the fronts/cyclones, downslope wind, upper/mid-level-jet, vertical mixing, and the low-level convergence over a complex terrain. They are crucial to the lift, dispersion, and transport of dusts over the Gobi Desert, the Taklimakan Desert, and the downstream regions. The dust model in Part II calculated the production, mixing, transport/removal, and radiative property of the dusts using the meteorology generated by the PRCM. The radiative effects of the dusts calculated from the dust model were then fed back to the PRCM. Because no nudging or restarting was applied during 17 continuous days of integration, the conservation laws of momentum, energy, and mass (including dry air, water substances and dusts) are valid. Hence, the PRCM provides data that are consistent for studying the movement of aerosols and the interactions among the aerosols, weather, and soil. © Taiwan Association for Aerosol Research."
"36701462300;55686667100;","Tropospheric adjustment to increasing CO2: Its timescale and the role of land-sea contrast",2013,"10.1007/s00382-012-1555-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888025348&doi=10.1007%2fs00382-012-1555-1&partnerID=40&md5=5a23f9c5b9ea60ec2f1ecebde3054ae1","Physical processes responsible for tropospheric adjustment to increasing carbon dioxide concentration are investigated using abrupt CO2 quadrupling experiments of a general circulation model (GCM) called the model for interdisciplinary research on climate version 5 with several configurations including a coupled atmosphere-ocean GCM, atmospheric GCM, and aqua-planet model. A similar experiment was performed in weather forecast mode to explore timescales of the tropospheric adjustment. We found that the shortwave component of the cloud radiative effect (SWcld) reaches its equilibrium within 2 days of the abrupt CO2 increase. The change in SWcld is positive, associated with reduced clouds in the lower troposphere due to warming and drying by instantaneous radiative forcing. A reduction in surface turbulent heat fluxes and increase of the near-surface stability result in shoaling of the marine boundary layer, which shifts the cloud layer downward. These changes are common to all experiments regardless of model configuration, indicating that the cloud adjustment is primarily independent of air-sea coupling and land-sea thermal contrast. The role of land in cloud adjustment is further examined by a series of idealized aqua-planet experiments, with a rectangular continent of varying width. Land surface warming from quadrupled CO2 induces anomalous upward motion, which increases high cloud and associated negative SWcld over land. The geographic distribution of continents regulates the spatial pattern of the cloud adjustment. A larger continent produces more negative SWcld, which partly compensates for a positive SWcld over the ocean. The land-induced negative adjustment is a factor but not necessary requirement for the tropospheric adjustment. © 2012 The Author(s)."
"35368622800;57203052274;36524063800;36602176800;36476153900;7006461606;56097800400;6601992794;7003919219;","Factors driving mercury variability in the Arctic atmosphere and ocean over the past 30 years",2013,"10.1002/2013GB004689","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888804825&doi=10.1002%2f2013GB004689&partnerID=40&md5=9f18c53021c825bcbc47b456848477fc","Long-term observations at Arctic sites (Alert and Zeppelin) show large interannual variability (IAV) in atmospheric mercury (Hg), implying a strong sensitivity of Hg to environmental factors and potentially to climate change. We use the GEOS-Chem global biogeochemical Hg model to interpret these observations and identify the principal drivers of spring and summer IAV in the Arctic atmosphere and surface ocean from 1979-2008. The model has moderate skill in simulating the observed atmospheric IAV at the two sites (r ~ 0.4) and successfully reproduces a long-term shift at Alert in the timing of the spring minimum from May to April (r = 0.7). Principal component analysis indicates that much of the IAV in the model can be explained by a single climate mode with high temperatures, low sea ice fraction, low cloudiness, and shallow boundary layer. This mode drives decreased bromine-driven deposition in spring and increased ocean evasion in summer. In the Arctic surface ocean, we find that the IAV for modeled total Hg is dominated by the meltwater flux of Hg previously deposited to sea ice, which is largest in years with high solar radiation (clear skies) and cold spring air temperature. Climate change in the Arctic is projected to result in increased cloudiness and strong warming in spring, which may thus lead to decreased Hg inputs to the Arctic Ocean. The effect of climate change on Hg discharges from Arctic rivers remains a major source of uncertainty. Key Points Arctic mercury (Hg) is simulated using a global biogeochemical model Atmospheric Hg is enhanced by high temperatures, low sea ice, and clear skies Ocean Hg is high under clear skies and cold spring air temperature ©2013. American Geophysical Union. All Rights Reserved."
"6603631763;26643408200;11940251300;6507949344;","Using SURFRAD to verify the NOAA single-channel land surface temperature algorithm",2013,"10.1175/JTECH-D-13-00051.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891650656&doi=10.1175%2fJTECH-D-13-00051.1&partnerID=40&md5=eccc2741ccc1637ec95a089716e48b1f","Because of spectral shifts from instrument to instrument in the operational NOAA satellite imager longwave infrared channels, the NOAA/National Environmental Satellite, Data, and Information Service (NESDIS) has developed a single-channel land surface temperature (LST) algorithm based on the observed 11-mm radiances, numerical weather prediction data, and radiative transfer modeling that allows for consistent results from the Geostationary Operational Environmental Satellite-I/L (GOES-I/L), GOES-M-P, and Advanced Very High Resolution Radiometer (AVHRR)/1 through 3 sensor versions. This approach is implemented in the real-time NESDIS processing systems [GOES Surface and Insolation Products (GSIP) and Clouds fromAVHRR Extended (CLAVR-x)], and in the Pathfinder Atmospheres-Extended (PATMOS-x) climate dataset.An analysis of the PATMOS-x LST against that derived fromthe upwelling broadband longwave flux at each Surface RadiationNetwork (SURFRAD) site showed that biases in PATMOS-x were approximately 1Kor less. The standard deviations of the PATMOS-xminusSURFRADLST biases are generally 2.5Kor less at all sites for all sensors. Using the PATMOS-x minus SURFRAD LST distributions to validate the PATMOS-x cloud detection, the PATMOS-x cloud probability of correct detection values were shown to meet the GOES-R specifications for all sites. © 2013 American Meteorological Society."
"12144041700;","The effects of imposed stratospheric cooling on the maximum intensity of tropical cyclones in axisymmetric radiative-convective equilibrium",2013,"10.1175/JCLI-D-13-00195.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890211818&doi=10.1175%2fJCLI-D-13-00195.1&partnerID=40&md5=f638d6fff26e7e952406dc8423af4e0f","The effects of stratospheric cooling and sea surface warming on tropical cyclone (TC) potential intensity (PI) are explored using an axisymmetric cloud-resolving model run to radiative-convective equilibrium (RCE). Almost all observationally constrained datasets show that the tropical lower stratosphere has cooled over the past few decades. Such cooling may affect PI by modifying the storm's outflow temperature, which together with the sea surface temperature (SST) determines the thermal efficiency in PI theory. Results show that cooling near and above the model tropopause (̃90 hPa), with fixed SST, increases the PI at a rate of 1ms-1 per degree of cooling. Most of this trend comes from a large increase in the thermal efficiency component of PI as the stratosphere cools. Sea surface warming (with fixed stratospheric temperature) increases the PI by roughly twice as much per degree, at a rate of about 2ms-1K-1. Under increasing SST, most of the PI trend comes from large changes in the air-sea thermodynamic disequilibrium. The predicted outflow temperature shows no trend in response to SST increase; However, the outflow height increases substantially. Under stratospheric cooling, the outflow temperature decreases and at the same rate as the imposed cooling. These results have considerable implications for global PI trends in response to climate change. Tropical oceans have warmed by about 0.15Kdecade-1 since the 1970s, but the stratosphere has cooled anywhere from 0.3 to over 1Kdecade-1, depending on the dataset. Therefore, global PI trends in recent decades appear to have been driven more by stratospheric cooling than by surface warming. © 2013 American Meteorological Society."
"26645901500;7004468723;26431037300;","European temperatures in CMIP5: Origins of present-day biases and future uncertainties",2013,"10.1007/s00382-013-1731-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888021902&doi=10.1007%2fs00382-013-1731-y&partnerID=40&md5=79b88e48c533a2a6bfc707e294255816","European temperatures and their projected changes under the 8.5 W/m2 Representative Concentration Pathway scenario are evaluated in an ensemble of 33 global climate models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Respective contributions of large-scale dynamics and local processes to both biases and changes in temperatures, and to the inter-model spread, are then investigated from a recently proposed methodology based on weather regimes. On average, CMIP5 models exhibit a cold bias in winter, especially in Northern Europe. They overestimate summer temperatures in Central Europe, in association with a greater diurnal range than observed. The projected temperature increase is stronger in summer than in winter, with the highest summer warming occurring over Mediterranean regions. Links between biases and sensitivities are evidenced in winter, suggesting a potential influence of snow cover biases on the projected surface warming. A brief analysis of daily temperature extremes suggests that the intra-seasonal variability is projected to decrease (slightly increase) in winter (summer). Then, in order to understand model discrepancies in both present-day and future climates, we disentangle effects of large-scale atmospheric dynamics and regional physical processes. In particular, in winter, CMIP5 models simulate a stronger North-Atlantic jet stream than observed and, in contrast with CMIP3 results, the majority of them suggests an increased frequency of the negative phase of the North-Atlantic Oscillation under future warming. While large-scale circulation only has a minor contribution to ensemble-mean biases or changes, which are primarily dominated by non-dynamical processes, it substantially affects the inter-model spread. Finally, other sources of uncertainties, including the North-Atlantic warming and local radiative feedbacks related to snow cover and clouds, are briefly discussed. © 2013 Springer-Verlag Berlin Heidelberg."
"55312908900;7201882869;","Changes in snow mass balance in the Canadian Rocky Mountains caused by CO2 rise: Regional atmosphere model results",2013,"10.1080/07055900.2013.852964","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888376492&doi=10.1080%2f07055900.2013.852964&partnerID=40&md5=8a64a47208b14612bacc0436432e09d6","This study investigates snow mass balance in the Canadian Rockies under a relatively conservative Intergovernmental Panel on Climate Change emission scenario for the twenty-first century through the use of regional atmosphere modelling. We dynamically downscale results from five 10-year subsets of general circulation model integrations to 6 km resolution to produce a physically consistent representation of the atmosphere at high elevations. Regional model results make evident greater warming with increasing elevation at low to mid-levels of the atmosphere, and a simple thermodynamic explanation of this process is presented. Simulated increases in atmospheric water vapour result in increases in cloud cover and precipitation at high elevations, which temporarily offset the effects of rising temperatures, but by 2100 all model elevations experience reductions in snow mass balance. A simple energy balance model produces reasonable estimates of changes in the elevation of equilibrium net snow accumulation, with increases between 185 and 197 m under an approximate 1.5°C rise in surface temperatures by 2100. © 2013 Taylor & Francis."
"9737845400;36697726500;7004047492;9246472600;8545284000;","Snow surface roughness from mobile laser scanning data",2013,"10.1016/j.coldregions.2013.09.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884918668&doi=10.1016%2fj.coldregions.2013.09.001&partnerID=40&md5=159781695226e08d36388d981110a206","Mobile laser scanning is a rapid and flexible method for acquisition of high resolution three-dimensional topographic data. Lidar based mobile mapping system produces three-dimensional point cloud from the surrounding objects. Typically, a two-dimensional profiling scanner is mounted on the system and the third dimension is achieved by the movement of the vehicle. The characteristics of the obtained point cloud depend largely on the sensor arrangement and the sensor properties.In this paper we discuss an application of mobile laser scanning for producing snow surface roughness information for climate data validation. The ROAMER, a single-scanner mobile laser scanning system, was deployed for the survey of three dimensional snow surface data.Relatively large areas could be reached with mobile laser scanning, which improves the output of surface roughness measurements and increases the statistical validity.The accuracy and precision of the mobile scanning system used in the study are almost at the same level as those of terrestrial laser scanners. The relative point precision for the system is estimated to be a few millimetres with centimetre level absolute positioning. The results show that the roughness produced from the data is in agreement with the validation data obtained from the plate photography process. This means that mobile laser scanning can be successfully used in snow surface roughness determination from large areas. The major challenge is related to direct georeferencing of mapping sensor data with global satellite navigation and inertial positioning. However, computation of surface roughness is a local operation, where the absolute accuracy is of little significance, but good relative precision is essential. The dense sampling of the surface enabled us to study multi-scale approach for surface roughness modelling, which is discussed more in this paper.We believe that even in the near future, mobile laser scanning will be considerably exploited in many applications in the environmental modelling and monitoring e.g. in forestry, hydrology, glaciology and climate sciences. © 2013 Elsevier B.V."
"55934848500;7005902717;","Dehumidification over tropical continents reduces climate sensitivity and inhibits snowball earth initiation",2013,"10.1175/JCLI-D-12-00820.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888048390&doi=10.1175%2fJCLI-D-12-00820.1&partnerID=40&md5=ac5373f9cf451d74005fc00c3b224faf","The enigmatic Neoproterozoic geological record suggests the potential for a fully glaciated ""snowball Earth."" Low-latitude continental position has been invoked as a potential snowball Earth trigger by increasing surface albedo and decreasing atmospheric CO2 concentrations through increased silicate weathering. Herein, climate response to the reduction of total solar irradiance (TSI) and CO2 concentration is tested using four different land configurations (aquaplanet, modern, Neoproterozoic, and low-latitude supercontinent) with uniform topography in the NCAR Community Atmosphere Model, version 3.1 (CAM3.1), GCM with a mixed layer ocean. Despite a lower surface albedo at 100% TSI, the threshold for global glaciation decreases from 92% TSI in the aquaplanet configuration to 85% TSI with a low-latitude supercontinent. The difference in thresholds is principally because of the partitioning of local longwave cooling relative to poleward energy transport. Additionally, dehumidification of the troposphere over large tropical continents in CAM3.1 increases direct heating by decreasing cloud cover. Continental heating intensifies the Walker circulation, enhancing surface evaporation and moistening the marine troposphere. Topography also provides an important control on snowball Earth initiation. Modern topography in the modern continental arrangement eases snowball initiation, requiring a 2% smaller reduction in TSI relative to a modern continental arrangement without topography. In the absence of potential silicate weathering feedbacks, large tropical landmasses raise the barrier to initiation of snowball events. More generally, these simulations demonstrate the substantial influence of geography on climate sensitivity and challenge the notion that the reduced continental area early in Earth history might provide a solution to the faint young Sun paradox. © 2013 American Meteorological Society."
"7004299063;6701588531;7003412405;35069282600;","Studying geoengineering with natural and anthropogenic analogs",2013,"10.1007/s10584-013-0777-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888135763&doi=10.1007%2fs10584-013-0777-5&partnerID=40&md5=d62432266a064fb86918327f30eed3e7","Solar radiation management (SRM) has been proposed as a possible option for offsetting some anthropogenic radiative forcing, with the goal of reducing some of the associated climatic changes. There are clearly significant uncertainties associated with SRM, and even small-scale experiments that might reduce uncertainty would carry some risk. However, there are also natural and anthropogenic analogs to SRM, such as volcanic eruptions in the case of stratospheric aerosol injection and ship tracks in the case of marine cloud albedo modification. It is essential to understand what we can learn from these analogs in order to validate models, particularly because of the problematic nature of outdoor experiments. It is also important to understand what we cannot learn, as this might better focus attention on what risks would need to be solely examined by numerical models. Stratospheric conditions following a major volcanic eruption, for example, are not the same as those to be expected from intentional geoengineering, both because of confounding effects of volcanic ash and the differences between continuous and impulsive injection of material into the stratosphere. Nonetheless, better data would help validate models; we thus recommend an appropriate plan be developed to better monitor the next large volcanic eruption. Similarly, more could be learned about cloud albedo modification from careful study not only of ship tracks, but of ship and other aerosol emission sources in cloud regimes beyond the narrow conditions under which ship tracks form; this would benefit from improved satellite observing capabilities. © 2013 Springer Science+Business Media Dordrecht."
"10242193100;","A multi-attribute model for wind farm location combining cloud and utility theories",2013,"10.1007/978-1-4471-5143-2_5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892535506&doi=10.1007%2f978-1-4471-5143-2_5&partnerID=40&md5=c477fa36d0416786dd8291fe282be7de","Nowadays sustainable development is a major focus of national and international economic, social, and environmental agendas, so that a good quality of life can be enjoyed by current and future generations. The problem of climate change has caused great concerns at all levels, from the general public to national governments and international agencies. Renewable energies can be an important remedy to many environmental problems that the world faces today. In this context, some new governmental policies have been adopted to encourage the introduction of renewable energies. But the energy planning scenario has completely changed over the past two decades from and almost exclusively concern with cost minimization of supply-side options to the need of explicitly multiple and conflicting objectives. Different and numerous groups of actors, such as institutions and administration authorities, potential investors, environmental groups, get involved in the process of fossil fuel energy substitution by renewable energies. This complex environment indicates the multi-criteria character of the problem. In this chapter multi-attribute decision-making method combining cloud and utility theory is proposed in order to evaluate different locations for a wind farm in the north of Spain. Whereas utility theory allows us to use different utility curves describing different attitudes toward risk, cloud theory provides a model that facilitates transformation of uncertainty contained in both quantitative and qualitative concepts to a uniform presentation in a numerical domain. Six locations are candidate to place the wind farm according to their topography, infrastructure, land use, safety, and number of days with wind speed [=70 km/h. The results show that the location with the highest number of days with wind speed[=70 km/ h and the best land use attribute is the best place to locate the wind farm for both a risk aversion decision-maker and a risk-seeking decision-maker. © Springer-Verlag London 2013."
"7004371983;8859027300;7102266405;6508340903;7006359209;7404416268;","Trajectory of the Arctic as an integrated system",2013,"10.1890/11-1498.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891299305&doi=10.1890%2f11-1498.1&partnerID=40&md5=ff8fd49b16c1fe0e495ebe1d2cda61ec","Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic system and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, seaice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content.© 2013 by the Ecological Society of America."
"55488728300;55878640000;7408519295;7202977282;","Influence of springtime North Atlantic Oscillation on crops yields in Northeast China",2013,"10.1007/s00382-012-1597-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888070734&doi=10.1007%2fs00382-012-1597-4&partnerID=40&md5=25a3f0f5d97069e98cfb06395d7fe677","Forecasting grain production is of strategic importance in considerations of climate change and growing population. Here we show that the springtime North Atlantic Oscillation (NAO) is significantly correlated to the year-to-year increment of maize and rice yield in Northeast China (NEC). The physical mechanism for this relationship was investigated. Springtime NAO can induce sea surface temperature anomalies (SSTAs) in the North Atlantic, which display a tripole pattern and are similar to the empirical mode pattern in spring. The spring Atlantic SSTA pattern that could persists to summer, can trigger a high-level tropospheric Rossby wave response in the Eurasia continent, resulting in atmospheric circulation anomalies over the Siberia-Mongolia region, which is unfavorable (favorable) for cold surges that affect NEC. Weaker (stronger) cold surges can accordingly reduce (increase) cloud amount, resulting in an increase (a decrease) in daily maximum temperature and a decrease (an increase) in daily minimum temperature, thereby leading to an increase (a decrease) in diurnal temperature range. And summer-mean daily minimum temperature and diurnal temperature range are most significantly related to the NEC crop yields. © 2012 Springer-Verlag Berlin Heidelberg."
"35885220000;23973663100;","Use of DEM data to monitor height changes due to deforestation",2013,"10.1007/s12517-012-0768-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886789209&doi=10.1007%2fs12517-012-0768-2&partnerID=40&md5=3d986d1d6a6c1282ec1fe6201547d79d","Deforestation has been a major cause of climate change and other environmental problems. An accurate estimation of the volume of deforested area is needed for United Nations Reducing Emissions from Deforestation and Forest Degradation (UN-REDD+) policies implementation and global carbon accounting. Accurate information about three-dimensional (3-D) structure of forests is required to quantify forest carbon stock. This study demonstrates the use of different digital elevation models (DEMs) to monitor changes in height due to deforestation in Cambodia to support climate change mitigation policies of UN-REDD+. The Shuttle Radar Topographic Mission-DEM (SRTM-DEM), Advanced Spaceborne Thermal Emission and Reflection Radiometer Global DEM (ASTER-GDEM) and Panchromatic Remote sensing Instrument for Stereo Mapping-Digital Surface Model (PRISM-DSM) data were calibrated using Ice Cloud and land Elevation Satellite Geoscience Laser Altimeter System (ICESat-GLAS) data. The results obtained from this study clearly indicate the changes in the height of forests due to deforestation activity. The height of cutover forest generated from the PRISM-DSM and SRTM-DEM is more reliable than that from the PRISM-DSM and ASTER-GDEM data. Field data has also been used to validate the height of the cutover forests, which shows ±5 m uncertainties in the estimation. © 2012 Saudi Society for Geosciences."
"54580693200;55802117400;6601988043;6507487648;25521451000;7003362098;7004204248;7801629474;","Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles",2013,"10.1016/j.atmosenv.2013.09.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885809501&doi=10.1016%2fj.atmosenv.2013.09.036&partnerID=40&md5=7a708d3cbb11a5ecbfaf55c58b8524d6","In addition to direct photolysis, degradation of organic compounds by solar light can also occur by indirect photolysis or photo-sensitised processes. These reactions are important because they are involved in, among others, direct and indirect climate changes, adverse health effects from inhaled particles, effects on cloud chemistry and ozone production. In this work, the importance of atmospheric photo-sensitisation is evaluated in bulk aqueous solution and on the surface of aerosol deliquescent particles. Irradiation experiments in aqueous solution indicate that 4-carboxybenzophenone (CBP) is able to photosensitise the degradation of 4-phenoxyphenol (4PP). The process takes place via the CBP triplet state (3CBP*), which has an oxidising nature. 4PP is fluorescent, unlike the photosensitiser CBP, with two emission bands at ~320 and ~380nm. However, addition of CBP to a 4PP solution considerably decreases the intensity of 4PP fluorescence bands and causes a very intense new band to appear at ~420nm. This behaviour suggests a possible interaction between CBP and 4PP in solution, which could favour further light-induced processes. Moreover, the new band overlaps with the fluorescence spectrum of atmospheric HULIS (HUmic-LIke Substances), suggesting that supramolecular photosensitiser-substrate interactions may have a role in HULIS fluorescence properties. The interaction between CBP and 4PP coated on silica particles (gas-solid system) was also investigated under simulated sunlight, and in the presence of variable relative humidity. The water molecules inhibit the degradation of 4PP, induced by 3CBP* on the surface of aerosol particles, indicating that the process could be even faster on particles than in solution. We demonstrate that phenol substances adsorbed on aerosol surfaces and in bulk solution are substantially altered upon photosensitised processes. © 2013 Elsevier Ltd."
"55227140300;7006630889;","Chemical competition in nitrate and sulfate formations and its effect on air quality",2013,"10.1016/j.atmosenv.2013.08.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884154880&doi=10.1016%2fj.atmosenv.2013.08.036&partnerID=40&md5=8dab71f1dd9ebedb4df209b62bbdd813","The competition for bases in nitrate and sulfate aerosol formations significantly affects the concentration of nitrate aerosols. Sensitivity experiments with reduced sulfate precursor emissions, achieved through the use of the CAM-Chem model, show that nitrate concentration is particularly affected by sulfate precursor emissions in winter when their changes are linearly correlated. As a result, the nitrate concentration in the atmosphere is less affected by its own precursor emissions. The concentration-precursor emission relationship for sulfate is not significantly affected by the competition. The future air quality projection following the IPCC A1B emission change scenario shows that the decrease in sulfate precursor emissions and increase in ammonia emissions by 2050 will lead to adverse changes in nitrate concentrations. This will be in response to the reduction in its precursor emissions over the major industrial region of the United States. Due to the difference between nitrate and sulfate aerosols in physical properties and efficiency in cloud condensation, the visibility reduction caused by sulfate emission control occurs over industrial regions in winter. The resulting adverse changes in visibility to emission control will further increase the uncertainty in assessing air quality change. The nonlinear relationship between precursor emissions and changes in pollution levels will increase the difficulty in making effective air quality control strategies. © 2013 Elsevier Ltd."
"7201911396;56821526700;36873346600;24339847400;","Land atmosphere feedbacks and their role in the water resources of the Ganges basin",2013,"10.1016/j.scitotenv.2013.03.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891747605&doi=10.1016%2fj.scitotenv.2013.03.016&partnerID=40&md5=2b381c29adf3783134b2f831bb7217d5","The northern Indian subcontinent has frequently been identified as a hotspot for land atmosphere interactions. It is also a region with the highest concentration of irrigated land and highest (and increasing) population density in the world. The available water in the region with which to grow food depends on the Asian monsoon, groundwater and melt from Himalayan snows. Any changes or disruptions to these sources of water could threaten the food supply. It is therefore essential to understand how the land surface, and in particular irrigated land, interacts with the atmosphere. It is anticipated that the interactions will occur on many scales. To an extent the magnitude and form of these will depend on the depth of the atmosphere which is affected. Thus at the local, or micro, scale it is the surface layer (some 10s m deep) which is cooled and moistened by the evaporation of irrigated water, at the meso-scale the Planetary boundary layer (up to 1 or 2. km) will be modified - with possible atmospheric moistening, increased cloud and rain formation and at very large scales the whole dynamics of the south Asian Monsoon will be affected. This illustrates a strong interaction between the Asian monsoon and the regional topography. Of considerable significance is the finding in this paper that up to 60% of the evaporation from irrigated areas in the summer months is ultimately recycled to Himalayan rainfall and so feedbacks to river flows in the Ganges. © 2013."
"13606626700;55961887800;57212663824;14819302400;55961845900;7402820128;8943453100;","An integrated optical remote sensing system for environmental perturbation research",2013,"10.1109/JSTARS.2013.2250489","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890124081&doi=10.1109%2fJSTARS.2013.2250489&partnerID=40&md5=600089efaa4c2f585ab13c3f1cf1680d","Remote sensing is the only technology that can systematically monitor physical properties of the biosphere over a vast region. However, it is still a challenge to make these measures meaningful for assessing the impacts of environmental perturbation. Here, we integrate an optical remote sensing system termed EcoiRS (Ecosystem observation by an integrated Remote Sensing system) specifically for this purpose. EcoiRS consists of three subsystems: an off-the-shelf atmospheric correction model (ACORN), a cloud/shadow removal model, and an advanced spectral mixture analysis model (AutoMCU). The core of ACORN is a set of radiative transfer codes that can be used to remove the effects of molecular/aerosol scatterings and water vapor absorption from remotely sensed data, and to convert these digital signals to surface reflectance. Shadow and cloud cover that would obscure the reflective properties of land surfaces in an image can be minimized by referring to their optical and thermal spectral profiles. AutoMCU executes iterative unmixing for each pixel using selected spectral endmembers based upon the rule of Monte Carlo simulation. The main outcomes of EcoiRS include cover fractions of green vegetation, non-photosynthetically active vegetation and bare soils, along with uncertainty measures for each pixel. The dynamics of these derived products are significant indicators for monitoring the change of states of terrestrial environments, and they can be used for investigating different environmental perturbations. Here, we demonstrate studies of implementing EcoiRS to map three major but relatively less studied cases in a western Pacific island (Taiwan): typhoons, tree diseases and alien plant invasion. © 2008-2012 IEEE."
"55102510300;7006501049;","Melt patterns and dynamics in Alaska and Patagonia derived from passive microwave brightness temperatures.",2013,"10.3390/rs6010603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893380826&doi=10.3390%2frs6010603&partnerID=40&md5=6d1656ae6bcd0b6ecf3ba7a630c4b37e","Glaciers and icefields are critical components of Earth's cryosphere to study and monitor for understanding the effects of a changing climate. To provide a regional perspective of glacier melt dynamics for the past several decades, brightness temperatures (Tb) from the passive microwave sensor Special Sensor Microwave Imager (SSM/I) were used to characterize melt regime patterns over large glacierized areas in Alaska and Patagonia. The distinctness of the melt signal at 37V-GHz and the ability to acquire daily data regardless of clouds or darkness make the dataset ideal for studying melt dynamics in both hemispheres. A 24-year (1988-2011) time series of annual Tb histograms was constructed to (1) characterize and assess temporal and spatial trends in melt patterns, (2) determine years of anomalous Tb distribution, and (3) investigate potential contributing factors. Distance from coast and temperature were key factors influencing melt. Years of high percentage of positive Tb anomalies were associated with relatively higher stream discharge (e.g., Copper and Mendenhall Rivers, Alaska, USA and Rio Baker, Chile). The characterization of melt over broad spatial domains and a multi-decadal time period offers a more comprehensive picture of the changing cryosphere and provides a baseline from which to assess future change. © 2014 by the authors."
"6603266501;6603472552;7003687430;6503960759;","Influence of Meteorological Elements on Changes in Active-Layer Thickness in the Bellsund region, Svalbard",2013,"10.1002/ppp.1790","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888871578&doi=10.1002%2fppp.1790&partnerID=40&md5=7be12d97fcacd42ccf3050d345924162","Measurements of active-layer thickness (ALT) at seven locations on Calypsostranda, Svalbard (CALM Site P1), over 1986-2009, are used to estimate the influence of cloudiness, precipitation, air temperature, the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO). Between 1986 and 2002, ALT amounted to 118±14 cm and did not show any significant trend. During 2002-06, ALT increased rapidly (12.6 cm yr-1) to a maximum of~174 cm in 2006 and 2007. In 2008 and 2009, ALT decreased. No statistically significant correlations were determined between ALT and monthly precipitation and cloudiness at Barentsburg, Hornsund and Svalbard Airport stations. There were, however, very strong and highly significant (p&lt;0.001) relationships with air temperatures in May and June (the strongest association being with Svalbard Airport). The influence of air temperature in May and June on ALT is indirect; it regulates the time of the melt of snow cover, which determines the duration of the ground-warming period. Using statistical relationships between ALT and air temperature at Svalbard Airport, the time series of ALT at Calypsostranda is reconstructed from 1911 to 2010. It was also found that the AO and the NAO did not significantly affect ALT and air temperature on western Spitsbergen. © 2013 John Wiley &amp; Sons, Ltd."
"55841594900;6602142837;","Disaggregating convective and stratiform precipitation from station weather data",2013,"10.1016/j.atmosres.2013.07.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883291936&doi=10.1016%2fj.atmosres.2013.07.015&partnerID=40&md5=026c3b77da43ce2703761e5d09162d3d","We propose an alternative algorithm for disaggregating precipitation amounts into predominantly convective and stratiform based on station weather data. The algorithm is tested at 11 stations in the Czech Republic over 1982-2010, and climatological characteristics and trends of convective and stratiform precipitation are analysed. The results show that, while convective precipitation has a sharp annual cycle, stratiform precipitation is relatively constant throughout the year and does not contribute to the annual cycle of total precipitation. Dependence of precipitation amounts on altitude is stronger for stratiform than convective precipitation consistently across all seasons. The proportion of convective precipitation sharply increases with rising daily temperature in summer, but an analogous relationship is much weaker at the seasonal time scale. Trends in convective precipitation were rising over 1982-2010 in all three seasons in which convective precipitation is important (spring, summer and autumn) and they are stronger than are trends in stratiform precipitation in each season. This shows that the observed increases in total precipitation are mainly due to increases in convective precipitation, and this effect may also be related to an observed warming of surface air temperatures that may enhance instability and support conditions for stronger convection. The resulting time series of convective and stratiform precipitation may have several further applications, including for analysing probability distributions of extremes and evaluating climate models that simulate convective and stratiform precipitation through different parameterizations. © 2013 Elsevier B.V."
"35146091500;55910943000;57207153359;","Distribution of actual evapotranspiration over Qaidam basin, an Arid area in China",2013,"10.3390/rs5126976","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891438686&doi=10.3390%2frs5126976&partnerID=40&md5=6f8aebc0779788de605a322eb693926f","Evapotranspiration is a major loss flux of the water balance in arid and semi-arid areas. The estimation of actual evapotranspiration has significance for hydrological and environmental purposes. The Surface Energy Balance System (SEBS) algorithm was applied to estimate actual evapotranspiration in the Qaidam Basin and its eight hydrological sub-regions, Northwest China. There were 3,036 cloud-free and atmospherically corrected MODIS satellite images from 2001 to 2011 used in the SEBS algorithm to determine the actual evapotranspiration. The result indicated that the estimated annual actual evapotranspiration of the basin increased with time and the value varied from 72.7 to 182.3 mm. SEBS estimates were 7.5% and 14.1% of observed pan evaporation over the western and eastern areas, respectively. The variation of SEBS actual evapotranspiration is influenced by climate factors, vegetation, net radiation, land cover type and water table depth. The analysis of the evaporative behavior of different land cover types in the basin presented that water bodies, marsh, and farmland had relatively higher mean actual evapotranspiration though these land cover types make up less than 3.5% of the total basin. Bare soil has very low evapotranspiration and covered almost 60% of the study area. The actual evapotranspiration was observed to be decreased with an increase of water table depth. Overall, the SEBS algorithm proved to be useful and has potential for estimating spatial actual evapotranspiration on a regional scale. © 2013 by the authors."
"23096635200;7005137442;","Water loss from terrestrial planets with CO2-rich atmospheres",2013,"10.1088/0004-637X/778/2/154","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887940593&doi=10.1088%2f0004-637X%2f778%2f2%2f154&partnerID=40&md5=d21684500c2d44b087c1331c8b4cf489","Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study the dependence of water loss rates from terrestrial planets on a range of atmospheric and external parameters. We show that CO2 can only cause significant water loss by increasing surface temperatures over a narrow range of conditions, with cooling of the middle and upper atmosphere acting as a bottleneck on escape in other circumstances. Around G-stars, efficient loss only occurs on planets with intermediate CO2 atmospheric partial pressures (0.1-1 bar) that receive a net flux close to the critical runaway greenhouse limit. Because G-star total luminosity increases with time but X-ray and ultraviolet/ultravoilet luminosity decreases, this places strong limits on water loss for planets like Earth. In contrast, for a CO2-rich early Venus, diffusion limits on water loss are only important if clouds caused strong cooling, implying that scenarios where the planet never had surface liquid water are indeed plausible. Around M-stars, water loss is primarily a function of orbital distance, with planets that absorb less flux than ∼270 W m-2 (global mean) unlikely to lose more than one Earth ocean of H2O over their lifetimes unless they lose all their atmospheric N2/CO2 early on. Because of the variability of H2O delivery during accretion, our results suggest that many ""Earth-like"" exoplanets in the habitable zone may have ocean-covered surfaces, stable CO2/H2O-rich atmospheres, and high mean surface temperatures. © 2013. The American Astronomical Society. All rights reserved.."
"24177231700;57209757800;","A smoke-free kitchen: Initiating community based co-production for cleaner cooking and cuts in carbon emissions",2013,"10.1016/j.jclepro.2012.09.026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885430822&doi=10.1016%2fj.jclepro.2012.09.026&partnerID=40&md5=f5589d5c8957ba66351ff841b8e1841f","Cooking over open fire with solid fuels results in incomplete combustion and indoor air pollution (IAP) causing respiratory and other diseases leading to nearly two million premature deaths per year. In urban areas, IAP interacts with outdoor pollutants in toxic chemical mixtures affecting also other citizens and damaging regional air quality in terms of 'brown clouds'. Deaths result mainly in women, children and infants, who are directly exposed to smoke in unventilated kitchens, thus reflecting differentiated and unequal impacts across population groups. Despite the heavy health burden and discomfort, IAP has only recently been recognised as associated with neglected diseases. In search of synergies between adaptation and mitigation, we seek gender sensitive social innovations to halt smoke, soot and early death while reducing deforestation and carbon emissions. Using transition arenas as a participatory method for experiments and social learning we engaged with local entrepreneurs and peasant farmers in sub- Saharan Africa to initiate co-production of efficient flue-piped stoves that save energy, labour and lives. Findings indicate that successful design, production and adoption of improved cooking stoves is possible, but the structural challenges of poverty, inequality and distrust may inhibit further diffusion and more profound processes of social learning. Insights from local studies must therefore be contextualised into broader understandings, as attempted here, while local adoption must be combined with wider initiatives and government policies into complex micro-to-macro solutions that provide forceful effects against IAP and its drivers. © 2012 Elsevier Ltd. All rights reserved."
"55929555000;12774262800;7005274759;6603315547;6602809597;7003968166;","Tropopause level Rossby wave breaking in the Northern Hemisphere: A feature-based validation of the ECHAM5-HAM climate model",2013,"10.1002/joc.3631","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887617960&doi=10.1002%2fjoc.3631&partnerID=40&md5=93b4deed60a6a7f655928e3bbe99060a","Breaking synoptic-scale Rossby waves (RWB) at the tropopause level are central to the daily weather evolution in the extratropics and the subtropics. RWB leads to pronounced meridional transport of heat, moisture, momentum, and chemical constituents. RWB events are manifest as elongated and narrow structures in the tropopause-level potential vorticity (PV) field. A feature-based validation approach is used to assess the representation of Northern Hemisphere RWB in present-day climate simulations carried out with the ECHAM5-HAM climate model at three different resolutions (T42L19, T63L31, and T106L31) against the ERA-40 reanalysis data set. An objective identification algorithm extracts RWB events from the isentropic PV field and allows quantifying the frequency of occurrence of RWB. The biases in the frequency of RWB are then compared to biases in the time mean tropopause-level jet wind speeds. The ECHAM5-HAM model captures the location of the RWB frequency maxima in the Northern Hemisphere at all three resolutions. However, at coarse resolution (T42L19) the overall frequency of RWB, i.e. the frequency averaged over all seasons and the entire hemisphere, is underestimated by 28%.The higher-resolution simulations capture the overall frequency of RWB much better, with a minor difference between T63L31 and T106L31 (frequency errors of -3.5 and 6%, respectively). The number of large-size RWB events is significantly underestimated by the T42L19 experiment and well represented in the T106L31 simulation. On the local scale, however, significant differences to ERA-40 are found in the higher-resolution simulations. These differences are regionally confined and vary with the season. The most striking difference between T106L31 and ERA-40 is that ECHAM5-HAM overestimates the frequency of RWB in the subtropical Atlantic in all seasons except for spring. This bias maximum is accompanied by an equatorward extension of the subtropical westerlies. © 2012 Royal Meteorological Society."
"57196489468;56520921400;","A case study of subdaily simulated and observed continental convective precipitation: CMIP5 and multiscale global climate models comparison",2013,"10.1002/2013GL057987","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890528398&doi=10.1002%2f2013GL057987&partnerID=40&md5=aad45c8689c9c6205dc5b3ff05bbf84e","We analyze subdaily continental convective precipitation data relative to the Southeastern U.S. from gridded rain gauge measurements, conventional global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive, and a multiscale GCM. GCMs react too quickly to local convective instability and, therefore, overestimate the incidence of middle rainfall events and underestimate the incidence of no, little, and heavy rainfall events. Moreover, GCMs overestimate the persistence of heavy precipitation and underestimate the persistence of no and light precipitation. In general, GCMs with suppression mechanisms in the treatments of convective precipitation compare best with rain gauge derived data and should be trusted more than the others when assessing the risk from extreme precipitation events. The multiscale GCM has the best estimate of the diurnal cycle and a good estimate of heavy rainfall persistence. ©2013. American Geophysical Union. All Rights Reserved."
"24587715900;37661167800;6603955469;57212958836;6603604042;15033928900;7402838215;7005078521;55957806700;6507542556;7005453641;6701581258;15726759700;6701772538;7003765782;7102011023;","Arctic stratospheric dehydration - Part 1: Unprecedented observation of vertical redistribution of water",2013,"10.5194/acp-13-11503-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884247991&doi=10.5194%2facp-13-11503-2013&partnerID=40&md5=f11aef2391de7404164e86ee658c4972","We present high-resolution measurements of water vapour, aerosols and clouds in the Arctic stratosphere in January and February 2010 carried out by in situ instrumentation on balloon sondes and high-altitude aircraft combined with satellite observations. The measurements provide unparalleled evidence of dehydration and rehydration due to gravitational settling of ice particles. An extreme cooling of the Arctic stratospheric vortex during the second half of January 2010 resulted in a rare synoptic-scale outbreak of ice polar stratospheric clouds (PSCs) remotely detected by the lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite. The widespread occurrence of ice clouds was followed by sedimentation and consequent sublimation of ice particles, leading to vertical redistribution of water inside the vortex. A sequence of balloon and aircraft soundings with chilled mirror and Lyman- α hygrometers (Cryogenic Frostpoint Hygrometer, CFH; Fast In Situ Stratospheric Hygrometer, FISH; Fluorescent Airborne Stratospheric Hygrometer, FLASH) and backscatter sondes (Compact Optical Backscatter Aerosol Detector, COBALD) conducted in January 2010 within the LAPBIAT (Lapland Atmosphere-Biosphere Facility) and RECONCILE (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Loss and its Climate Interactions) campaigns captured various phases of this phenomenon: ice formation, irreversible dehydration and rehydration. Consistent observations of water vapour by these independent measurement techniques show clear signatures of irreversible dehydration of the vortex air by up to 1.6 ppmv in the 20-24 km altitude range and rehydration by up to 0.9 ppmv in a 1 km thick layer below. Comparison with space-borne Aura MLS (Microwave Limb Sounder) water vapour observations allow the spatiotemporal evolution of dehydrated air masses within the Arctic vortex to be derived and upscaled. © Author(s) 2013."
"56817949600;7402844661;57216598250;55968567100;","An initial assessment of Suomi NPP VIIRS vegetation index EDR",2013,"10.1002/2013JD020439","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890461141&doi=10.1002%2f2013JD020439&partnerID=40&md5=b25762cda42af52a1f5101b0b764e5d8","The Suomi National Polar-orbiting Partnership (S-NPP) satellite with Visible/Infrared Imager/Radiometer Suite (VIIRS) onboard was launched in October 2011. VIIRS is the primary instrument for a suite of Environmental Data Records (EDR), including Vegetation Index (VI) EDR, for weather forecasting and climate research. The VIIRS VI EDR operational product consists of the Top of the Atmosphere (TOA) Normalized Difference Vegetation Index (NDVI), the Top of the Canopy (TOC) Enhanced Vegetation Index (EVI), and per-pixel product quality information. In this paper, we report results of our assessment of the early VIIRS VI EDR (beta quality) using Aqua MODIS and NOAA-18 AVHRR/3 as a reference for May 2012 to March 2013. We conducted two types of analyses focused on an assessment of physical (global scale) and radiometric (regional scale) performances of VIIRS VI EDR. Both TOA NDVI and TOC EVI of VIIRS showed spatial and temporal trends consistent with the MODIS counterparts, whereas VIIRS TOA NDVI was systematically higher than that of AVHRR. Performance of the early VIIRS VI EDR was limited by a lack of adequate per-pixel quality information, commission/omission errors of the cloud mask, and uncertainties associated with the surface reflectance retrievals. A number of enhancements to the VI EDR are planned, including: (1) implementation of a TOC EVI back-up algorithm, (2) addition of more detailed quality flags on aerosols, clouds, and snow cover, and (3) implementation of gridding and temporal compositing. A web-based, product quality monitoring tool has been developed and automated product validation protocols are being prototyped. Key Points Present initial results of assessment of the VIIRS VI EDR product after launch VI showed good product integrity and was found radiometrically performing well VI is beta quality and users are warned that the product still contains errors ©2013. American Geophysical Union. All Rights Reserved."
"55968129100;7401795483;57190854861;","Analysis of the vertical structure of the atmospheric heating process and its seasonal variation over the Tibetan Plateau using a land data assimilation system",2013,"10.1002/2013JD020072","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890503146&doi=10.1002%2f2013JD020072&partnerID=40&md5=1e929ae51d25d6735958425290becfbe","The atmospheric heating process over the Tibetan Plateau (TP) in the premonsoon and mature monsoon seasons of 2008 and 2009 was investigated using radiosonde data and a land data assimilation system coupled with a mesoscale model (LDAS-A), which assimilates microwave brightness temperature and accurately reproduces land and atmospheric states. Focusing on the temperature observed below 200 hPa, we found that there were warming and cooling periods alternately in the premonsoon season within a general warming trend, and the profiles of heating in the two seasons were reversed. Then we identified the vertical structure of each heating component: sensible heat (SH), latent heat (LH), and horizontal advection (Hadv), using the LDAS-A in each season. The troposphere over the TP in warming periods was divided into three vertical layers in terms of the major heating process: SH transport below 450 hPa, LH from 450 to 250 hPa, and Hadv above 250 hPa. The SH and LH are transported by local convections. In contrast, the heat source for Hadv originated in the southwest of the plateau, related to synoptic-scale circulations. Latent cooling with cloud evaporation and adiabatic cooling with convection negatively contributed to heating in the upper troposphere. In cooling periods, the vertical structure of each heating component was similar to that in warming periods, but net heating was reversed because of the influence of synoptic-scale disturbances. In the mature monsoon season, warm Hadv in the upper troposphere rapidly weakened in response to the initial formation of the Tibetan High. Key Points Atmospheric heating over the Tibetan Plateau is examined using new data The profile of heat processes develops a three-layered structure in premonsoon Heating profile varies seasonally and is affected by synoptic-scale disturbance ©2013. American Geophysical Union. All Rights Reserved."
"55968364300;7005485117;7402933297;","Absorbing aerosol-induced change in the early monsoon Arabian Sea low-level jet: Modeled transfer from anomalous heating to nondivergent kinetic energy",2013,"10.1002/2013JD019808","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890461275&doi=10.1002%2f2013JD019808&partnerID=40&md5=8709c47327a99c3b9aab1a0da7e6a67b","This study examines the impact of anomalous differential generation of available potential energy by absorbing aerosols on the transition and early active phases of the South Asian summer monsoon. Aerosol direct and indirect radiative forcings can modify tropospheric temperature profiles through direct absorption, scattering, and extended cloud lifetimes. Recent studies have suggested that over monthly and seasonal time scales, these effects can lead to modified flow and rainfall regimes in the South Asian monsoon region. Of special interest is the covariance of heating and temperature prior to active monsoon onset. It can be shown that anomalous generation of available potential energy due to absorption of shortwave radiation by aerosols can impact the cascade of energy from the local Hadley circulation to the monsoon nondivergent flow. In order to quantify the potential impact of aerosol radiative forcing and the resulting changes in monsoon onset timing and intensity, an ensemble of Weather Research and Forecasting with Chemistry regional weather and chemistry model forecasts are created for the South Asian summer monsoon region during May, June, and July. The forecasts including shortwave absorption by aerosol are compared to control forecasts in which aerosols only scatter shortwave radiation. The evolution of irrotational and nondivergent kinetic energy, generation of available potential energy and rainfall are presented. It is found that the ensemble with aerosol shortwave absorption contains on average a more intense dynamical onset over South India which is statistically significant compared to the ensemble variability. The more intense monsoon onset is related to a more intense Arabian Sea low-level jet. In the ensemble with shortwave absorption by aerosol, the early season monsoon rainfall is diminished over South India and enhanced over the Northeastern Indian states. Key Points Springtime aerosol heating is anomalously high over the Indo-Gangetic Plain. Non-linear dynamics causes excess heating to impact early monsoon flow. The altered flow regime alters modeled early monsoon rainfall patterns. ©2013. American Geophysical Union. All Rights Reserved."
"25925912500;24074820100;6603297533;35203328900;6602420251;56265106600;","Towards an automatic lidar cirrus cloud retrieval for climate studies",2013,"10.5194/amt-6-3197-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890037737&doi=10.5194%2famt-6-3197-2013&partnerID=40&md5=34ee34d612a4b8f4bd7adb1e7e1e2314","This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has been developed and implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing aims to consider a large cloud variability and cirrus cloud monitoring through a robust retrieval process. Among cirrus features estimates for complex scenes that lidar systems can provide, we highlight cloud geometrical information and extinction-to- backscatter ratio (known as lidar ratio or LR). In general, direct information on cirrus cloud microphysics is difficult to derive because LR depends on the presence of ice crystals and their properties such as shape, size, composition and orientation of particles. An iterative process to derive a stable LR value has been proposed. One of the keys is to restrict the analysis to conditions allowing accurate multilayer events. This method uses nonparametric statistical approaches to identify stationary periods according to cloud features and variability. Measurements performed in the region of the metropolitan city of São Paulo (MSP) have been used to implement and test the methodology developed for cirrus cloud characterization. Good results are represented by examining specific cases with multilayer cirrus cloud occurrence. In addition to the geometrical parameters obtained, cirrus LR values were calculated for a single day ranging from 19 ± 01 sr to 74 ± 13 sr for 2 observed layers. This large difference in LR can indicate a mixture of ice crystal particles with different sizes and shapes in both layers of the cirrus clouds. Trajectory analyses indicate that both of these cloud layers can be associated with different air mass and should be considered as 2 distinct clouds in climatology. © 2013 Author(s).f 0."
"6603156461;36867775200;","Quantifying aerosol mixing state with entropy and diversity measures",2013,"10.5194/acp-13-11423-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889770749&doi=10.5194%2facp-13-11423-2013&partnerID=40&md5=7260cb0cb6e72a70f3200318c57683f9","This paper presents the first quantitative metric for aerosol population mixing state, defined as the distribution of per-particle chemical species composition. This new metric, the mixing state index χ, is an affine ratio of the average per-particle species diversity Dα and the bulk population species diversity Dγ, both of which are based on information-theoretic entropy measures. The mixing state index χ enables the first rigorous definition of the spectrum of mixing states from so-called external mixture to internal mixture, which is significant for aerosol climate impacts, including aerosol optical properties and cloud condensation nuclei activity. We illustrate the usefulness of this new mixing state framework with model results from the stochastic particle-resolved model PartMC-MOSAIC. These results demonstrate how the mixing state metrics evolve with time for several archetypal cases, each of which isolates a specific process such as coagulation, emission, or condensation. Further, we present an analysis of the mixing state evolution for a complex urban plume case, for which these processes occur simultaneously. We additionally derive theoretical properties of the mixing state index and present a family of generalized mixing state indexes that vary in the importance assigned to low-mass-fraction species. © Author(s) 2013."
"55742229800;7102011703;38863214100;6507253351;","The initiation of Neoproterozoic ""snowball"" climates in CCSM3: The influence of paleocontinental configuration",2013,"10.5194/cp-9-2555-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887765361&doi=10.5194%2fcp-9-2555-2013&partnerID=40&md5=b12478638b34c8f39e03ba15032816b1","We identify the ""hard snowball"" bifurcation point at which total sea-ice cover of the oceans is expected by employing the comprehensive coupled climate model CCSM3 (Community Climate System Model version 3) for two realistic Neoproterozoic continental configurations, namely a low-latitude configuration appropriate for the 720 Ma Sturtian glaciation and a higher southern latitude configuration reconstructed for 570 Ma but which has often been employed in the past to study the later 635 Ma Marinoan glaciation. Contrary to previous suggestions, we find that for the same total solar insolation (TSI) and atmospheric CO2 concentration (pCO2), the 570 Ma continental configuration is characterized by colder climate than the 720 Ma continental configuration and enters the hard snowball state more easily on account of the following three factors: the higher effective albedo of the snow-covered land compared to that of sea ice, the more negative net cloud forcing near the ice front in the Northern Hemisphere (NH), and, more importantly, the more efficient sea-ice transport towards the Equator in the NH due to the absence of blockage by continents. Beside the paleogeography, we also find the optical depth of aerosol to have a significant influence on this important bifurcation point. When the high value (recommended by CCSM3 but demonstrated to be a significant overestimate) is employed, the critical values of pCO2, beyond which a hard snowball will be realized, are between 80 and 90 ppmv (sea-ice fraction 55%) and between 140 and 150 ppmv (sea-ice fraction 50%) for the Sturtian and Marinoan continental configurations, respectively. However, if a lower value is employed that enables the model to approximately reproduce the present-day climate, then the critical values of pCO2 become 50-60 ppmv (sea-ice fraction 57%) and 100-110 ppmv (sea-ice fraction 48%) for the two continental configurations, respectively. All of these values are higher than previously obtained for the present-day geography (17-35 ppmv) using the same model, primarily due to the absence of vegetation, which increases the surface albedo, but are much lower than that obtained previously for the Marinoan continental configuration using the ECHAM5/MPI-OM model in its standard configuration (∼500 ppmv). However, when the sea-ice albedo in that model was reduced from 0.75 to a more appropriate value of 0.45, the critical pCO2 becomes ∼204 ppmv, closer to the values obtained here. Our results are similar to those obtained with the present-day geography (70-100 ppmv) when the most recent version of the NCAR model, CCSM4, was employed.©Author(s) 2013."
"55446470200;8701353900;7003968166;","A bulk parametrization of melting snowflakes with explicit liquid water fraction for the COSMO model",2013,"10.5194/gmd-6-1925-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887695127&doi=10.5194%2fgmd-6-1925-2013&partnerID=40&md5=bc46fdc822e3b2c69a094dc077c1ba34","A new snow melting parametrization is presented for the non-hydrostatic limited-area COSMO (""consortium for small-scale modelling"") model. In contrast to the standard cloud microphysics of the COSMO model, which instantaneously transfers the meltwater from the snow to the rain category, the new scheme explicitly considers the liquid water fraction of the melting snowflakes. These semi-melted hydrometeors have characteristics (e.g., shape and fall speed) that differ from those of dry snow and rain droplets. Where possible, theoretical considerations and results from vertical wind tunnel laboratory experiments of melting snowflakes are used as the basis for characterising the melting snow as a function of its liquid water fraction. These characteristics include the capacitance, the ventilation coefficient, and the terminal fall speed. For the bulk parametrization, a critical diameter is introduced. It is assumed that particles smaller than this diameter, which increases during the melting process, have completely melted, i.e., they are converted to the rain category. The values of the bulk integrals are calculated with a finite difference method and approximately represented by polynomial functions, which allows an efficient implementation of the parametrization. Two case studies of (wet) snowfall in Germany are presented to illustrate the potential of the new snow melting parametrization. It is shown that the new scheme (i) produces wet snow instead of rain in some regions with surface temperatures slightly above the freezing point, (ii) simulates realistic atmospheric melting layers with a gradual transition from dry snow to melting snow to rain, and (iii) leads to a slower snow melting process. In the future, it will be important to thoroughly validate the scheme, also with radar data and to further explore its potential for improved surface precipitation forecasts for various meteorological conditions. © 2013 Author(s)."
"7003535176;55925090100;","A climatology of formation conditions for aerodynamic contrails",2013,"10.5194/acp-13-10847-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887464328&doi=10.5194%2facp-13-10847-2013&partnerID=40&md5=2b681c6db6f962423f8e2d8ee12af061","Aircraft at cruise levels can cause two kinds of contrails, the well known exhaust contrails and the less well-known aerodynamic contrails. While the possible climate impact of exhaust contrails has been studied for many years, research on aerodynamic contrails began only a few years ago and nothing is known about a possible contribution of these ice clouds to climate impact. In order to make progress in this respect, we first need a climatology of their formation conditions and this is given in the present paper. <br><br> Aerodynamic contrails are defined here as line shaped ice clouds caused by aerodynamically triggered cooling over the wings of an aircraft in cruise which become visible immediately at the trailing edge of the wing or close to it. Effects at low altitudes like condensation to liquid droplets and their potential heterogeneous freezing are excluded from our definition. We study atmospheric conditions that allow formation of aerodynamic contrails. These conditions are stated and then applied to atmospheric data: first to a special case where an aerodynamic contrail was actually observed and then to a full year of global reanalysis data. We show where, when (seasonal variation), and how frequently (probability) aerodynamic contrails can form, and how this relates to actual patterns of air traffic. We study the formation of persistent aerodynamic contrails as well. Furthermore, we check whether aerodynamic and exhaust contrails can coexist in the atmosphere. We show that visible aerodynamic contrails are possible only in an altitude range between roughly 540 and 250 hPa, and that the ambient temperature is the most important parameter, not the relative humidity. Finally, we argue that currently aerodynamic contrails have a much smaller climate effect than exhaust contrails, which may however change in future with more air traffic in the tropics. © 2013 Author(s)."
"7004932211;7004050581;","Frequency of deep convective clouds in the tropical zone from 10 years of AIRS data",2013,"10.5194/acp-13-10795-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887414086&doi=10.5194%2facp-13-10795-2013&partnerID=40&md5=f28446941458024336c2ab6e46028127","Deep convective clouds (DCCs) have been widely studied because of their association with heavy precipitation and severe weather events. Changes in the properties of DCCs are likely in a changing climate. Ten years of data collected by Atmospheric Infrared Sounder (AIRS) allow us to identify decadal trends in frequency of occurrence of DCCs over land and ocean. In the past, DCCs have been identified in the thermal infrared by three methods: (1) thresholds based on the absolute value of an atmospheric window channel brightness temperature; (2) thresholds based on the difference between the brightness temperature in an atmospheric window channel and the brightness temperature centered on a strong water vapor absorption line; and (3) a threshold using the difference between the window channel brightness temperature and the tropopause temperature based on climatology. Simultaneous observations of these infrared identified DCCs with the Advanced Microwave Sounding Unit-Humidity Sounder for Brazil (AMSU-HSB) using 183 GHz water channels provide a statistical correlation with microwave deep convection and overshooting convection. In the past 10 years, the frequency of occurrence of DCCs has decreased for the tropical ocean, while it has increased for tropical land. The area of the tropical zone associated with DCCs is typically much less than 1%. We find that the least frequent, more extreme DCCs show the largest trend in frequency of occurrence, increasing over land and decreasing over ocean. The trends for land and ocean closely balance, such that the DCC frequency changed at an insignificant rate for the entire tropical zone. This pattern of essentially zero trend for the tropical zone, but opposite land/ocean trends, is consistent with measurements of global precipitation. The changes in frequency of occurrence of the DCCs are correlated with the Niño34 index, which defines the sea surface temperature (SST) anomaly in the east-central Pacific. This is also consistent with patterns seen in global precipitation. This suggests that the observed changes in the frequency are part of a decadal variability characterized by shifts in the main tropical circulation patterns, which does not fully balance in the 10-year AIRS data record. The regional correlations and anti-correlations of the DCC frequency anomaly with the Multivariate ENSO Index (MEI) provide a new perspective for the regional analysis of past events, since the SST anomaly in the Nino34 region is available in the form of the extended MEI from 1871. © 2013 Author(s)."
"35069282600;7202899330;12645767500;","Exposing biases in retrieved low cloud properties from CloudSat: A guide for evaluating observations and climate data",2013,"10.1002/2013JD020224","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889827911&doi=10.1002%2f2013JD020224&partnerID=40&md5=4007c92b2a42d20cc6bddd3d8414ac62","This study provides an assessment of low cloud properties retrieved from CloudSat, MODIS (Moderate Resolution Imaging Spectroradiometer), and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation with the goal of exposing biases that hinder meaningful comparisons with the simulated cloud properties in global climate models (GCMs). Being pertinent to GCM comparisons, CloudSat is the only satellite that can provide the vertical structure of cloud water and ice content from space. Biases in CloudSat low cloud properties are found to be tied to problems involving cloud detection and algorithm retrieval failures related to precipitation and strict cloud screening procedures. We show that MODIS and CloudSat cloud liquid water path (LWP) data agree when carefully screened for lack of precipitation but significantly depart in precipitating clouds due to rain water contamination of LWP in the CloudSat retrieval algorithm. The presence of drizzle and rain (occurring about 20% of the time) is associated with different mean LWP, mean particle sizes, and optical depths of all low clouds and therefore the radiative properties of the oceanic low clouds. Another more significant source of the LWP bias stems from the apparent lack of cloud detection. On average, the Cloud Profiling Radar misses clouds with adequate liquid and ice water retrievals as detected by MODIS in approximately 45% of warm clouds with the bulk of the bias occurring in clouds below 1 km in the so-called ""ground clutter zone."" By incorporating additional sensors such as MODIS, the following results suggest that this LWP bias can be greatly reduced. Key Points Liquid water path biases are exposed and quantified from CloudSat retrievals. Largest LWP bias is related to instrument capabilities. Other biases are related to algorithm retrieval failures. ©2013. American Geophysical Union. All Rights Reserved."
"7401548835;7006399110;7006550762;36026612000;24501035200;","Fast atmosphere-ocean model runs with large changes in CO2",2013,"10.1002/2013GL056755","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887283259&doi=10.1002%2f2013GL056755&partnerID=40&md5=112b39ea16f1096cd64e01277776d5d1","How does climate sensitivity vary with the magnitude of climate forcing? This question was investigated with the use of a modified coupled atmosphere-ocean model, whose stability was improved so that the model would accommodate large radiative forcings yet be fast enough to reach rapid equilibrium. Experiments were performed in which atmospheric CO2 was multiplied by powers of 2, from 1/64 to 256 times the 1950 value. From 8 to 32 times, the 1950 CO2, climate sensitivity for doubling CO2 reaches 8°C due to increases in water vapor absorption and cloud top height and to reductions in low level cloud cover. As CO2 amount increases further, sensitivity drops as cloud cover and planetary albedo stabilize. No water vapor-induced runaway greenhouse caused by increased CO2 was found for the range of CO2 examined. With CO2 at or below 1/8 of the 1950 value, runaway sea ice does occur as the planet cascades to a snowball Earth climate with fully ice covered oceans and global mean surface temperatures near -30°C. Key Points Atmospheric CO2 controls the Earth's climate Water vapor feedback magnifies the greenhouse effect Climate sensitivity is presently at a local minimum ©2013. American Geophysical Union. All Rights Reserved."
"8615886200;55927053800;6603303046;35569803200;57208765879;8680433600;55947099700;36722293600;","Global analysis of aerosol properties above clouds",2013,"10.1002/2013GL057482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887521298&doi=10.1002%2f2013GL057482&partnerID=40&md5=4671b3c141cc800b16aaea52b042f21a","The seasonal and spatial variability of Aerosol Above Cloud (AAC) properties are derived from passive satellite data for the year 2008. A significant amount of aerosols are transported above liquid water clouds on the global scale. For particles in the fine mode (i.e., radius smaller than 0.3 μm), including both clear-sky and AAC, retrievals increase the global mean aerosol optical thickness by 25(±6)%. The two main regions of originated anthropogenic AAC are the tropical Southeast Atlantic, for biomass-burning aerosols, and the North Pacific, mainly for pollutants. Man-made AAC are also detected over the Arctic during the spring. Mineral dust particles are detected above clouds within the so-called ""dust belt"" region (5-40° N). AAC may cause a warming effect and bias the retrieval of the cloud properties. This study will then help to better quantify the impacts of aerosols on clouds and climate. Key Points The Aerosol Above Cloud properties are derived from passive satellite data A significant amount of aerosols are transported above liquid water clouds ©2013. American Geophysical Union. All Rights Reserved."
"7103246957;7102933062;15830822000;55557550200;","Impact of land use change on the diurnal cycle climate of the Canadian Prairies",2013,"10.1002/2013JD020717","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889781447&doi=10.1002%2f2013JD020717&partnerID=40&md5=4af2bbab49c7e61901a535d12d383390","This paper uses hourly observations from 1953 to 2011 of temperature, relative humidity, and opaque cloud cover from 14 climate stations across the Canadian Prairies to analyze the impact of agricultural land use change on the diurnal cycle climate, represented by the mean temperature and relative humidity and their diurnal ranges. We show the difference between the years 1953-1991 and 1992-2011. The land use changes have been largest in Saskatchewan where 15-20% of the land area has been converted in the past four decades from summer fallow (where the land was left bare for 1 year) to annual cropping. During the growing season from 20 May to 28 August, relative humidity has increased by about 7%. During the first 2 months, 20 May to 19 July, maximum temperatures and the diurnal range of temperature have fallen by 1.2°C and 0.6°C, respectively, cloud cover has increased by about 4%, reducing surface net radiation by 6 W m-2, and precipitation has increased. We use the dry-downs after precipitation to separate the impact of cloud cover and show the coupling between evapotranspiration and relative humidity. We estimate, using reanalysis data from ERA-Interim, that increased transpiration from the larger area of cropland has reduced the surface Bowen ratio by 0.14-0.2. For the month on either side of the growing season, cloud cover has fallen slightly; maximum temperatures have increased, increasing the diurnal temperature range and the diurnal range of humidity. Key Points Increased annual cropping has cooled and moistened the summer climate More transpiration has increased precipitation and lowered cloud base Changing seasonal diurnal temperature and humidity ranges ©2013. Her Majesty the Queen in Right of Canada. American Geophysical Union. Reproduced with permission of the Minister of Agriculture and Agri-Food Canada."
"6506373162;7404732357;36600036800;7005955015;","Solar irradiance reduction via climate engineering: Impact of different techniques on the energy balance and the hydrological cycle",2013,"10.1002/2013JD020445","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889788935&doi=10.1002%2f2013JD020445&partnerID=40&md5=af6c89b8beea1d95e59abfb212eaa9d3","Different techniques of solar radiation management (SRM) have been suggested to counteract global warming, among them the injection of sulfur into the stratosphere, mirrors in space, and marine cloud brightening through artificial emissions of sea salt. This study focuses on to what extent climate impacts of these three methods would be different. We present results from simulations with an Earth system model where the forcing from the increase of greenhouse gases in a transient scenario (RCP4.5) was balanced over 50 years by SRM. While global mean temperature increases slightly due to the inertia of the climate system and evolves similar with time for the different SRM methods, responses of global mean precipitation differ considerably among the methods. The hydrological sensitivity is decreased by SRM, most prominently for aerosol-based techniques, sea salt emissions, and injection of sulfate into the stratosphere. Reasons for these differences are discussed through an analysis of the surface energy budget. Furthermore, effects on large-scale tropical dynamics and on regional climate are discussed. Key Points First comparison of climate impacts of three climate engineering techniques Global precipitation decreases with all CE methods but differs between methods Impact on tropical dynamics depends on SRM method ©2013. American Geophysical Union. All Rights Reserved."
"39361670300;35177669200;6508026916;6603764342;","Uncertainties in future ozone and PM10 projections over Europe from a regional climate multiphysics ensemble",2013,"10.1002/2013GL057403","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887291493&doi=10.1002%2f2013GL057403&partnerID=40&md5=e06a35fab9a5d7aa9e79d000301eaaa4","Due to the computational time required for modeling air quality climatologies, the characterization of processes introducing the largest uncertainty in air quality-climate projections is a sound field of research. Here an air quality ensemble is assessed over Europe for present (1971-2000) and future (2071-2100, SRES A2) periods to characterize the sensitivity of regional air quality projections to the physics of the regional climate model driving the simulations. The ensemble comprises eight members resulting from combining two options of parameterization schemes for the planetary boundary layer, cumulus, and microphysics. The differences in the ensemble members (spread) for the concentration of tropospheric ozone and particulate matter (PM10) are strongly affected by the physics selected and could be considered as a matter of uncertainty in the change signals. Also, the leading processes causing the largest uncertainties in air quality projections have been identified and are mainly related to the election of the cumulus schemes. Key Points Characterization of the mean change and spreads of air quality projections Leading process causing uncertainties in air quality projections is identified The influence of several key processes grows for future projections ©2013. American Geophysical Union. All Rights Reserved."
"36600036800;7005955015;57203200427;53878006900;6506373162;7404732357;57205638870;55957189000;","Sea-salt injections into the low-latitude marine boundary layer: The transient response in three Earth system models",2013,"10.1002/2013JD020432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889780865&doi=10.1002%2f2013JD020432&partnerID=40&md5=665f04ff5fe7ab64cc2e6db405222f4d","Among proposed mechanisms for counteracting global warming through solar radiation management is the deliberate injection of sea salt acting via marine cloud brightening and the direct effect of sea-salt aerosols. In this study, we show results from multidecadal simulations of such sea-salt climate engineering (SSCE) on top of the RCP4.5 emission scenario using three Earth system models. As in the proposed ""G3"" experiment of the Geoengineering Model Intercomparison Project, SSCE is designed to keep the top-of-atmosphere radiative forcing at the 2020 level for 50 years. SSCE is then turned off and the models run for another 20 years, enabling an investigation of the abrupt warming associated with a termination of climate engineering (""termination effect""). As in former idealized studies, the climate engineering in all three models leads to a significant suppression of evaporation from low-latitude oceans and reduced precipitation over low-latitude oceans as well as in the storm-track regions. Unlike those studies, however, we find in all models enhanced evaporation, cloud formation, and precipitation over low-latitude land regions. This is a response to the localized cooling over the low-latitude oceans imposed by the SSCE design. As a result, the models obtain reduced aridity in many low-latitude land regions as well as in southern Europe. Terminating the SSCE leads to a rapid near-surface temperature increase, which, in the Arctic, exceeds 2 K in all three models within 20 years after SSCE has ceased. In the same period September Arctic sea ice cover shrinks by over 25%. Key Points This is the first multi-ESM study of sea salt climate engineering Over the low-latitude continents all models find a reduction in aridity Terminating climate engineering leads to Arctic warming exceeding 1 K / decade ©2013 The Authors. Journal of Geophysical Research: Atmospheres published by Wiley on behalf of the American Geophysical Union."
"55716597600;57192695511;7003397919;6603652793;55638979500;","Mesoscale modeling and satellite observation of transport and mixing of smoke and dust particles over northern sub-Saharan African region",2013,"10.1002/2013JD020644","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889869764&doi=10.1002%2f2013JD020644&partnerID=40&md5=e81d05f3425e9cdb4026d7d44d67439c","The transport and vertical distribution of smoke and dust aerosols over the northern sub-Saharan African region are simulated in the Weather Research and Forecasting model with Chemistry (WRF-Chem), which uses hourly dynamic smoke emissions from the Fire Locating and Modeling of Burning Emissions database derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) fire products. Model performance for February 2008 is evaluated using MODIS true color images, aerosol optical depth (AOD) measurements from the Aerosol Robotic Network, MODIS AOD retrievals, and the Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIOP) atmospheric backscattering and extinction products. Specification of smoke injection height of 650 m in WRF-Chem yields aerosol vertical profiles that are most consistent with CALIOP observations of aerosol layer height. Between the equator and 10°N, Saharan dust is often mixed with smoke near the surface, and their transport patterns manifest the interplay of trade winds, subtropical highs, precipitation associated with the Intertropical Convergence Zone, and the high mountains located near the Great Rift Valley region. At the 700 hPa level and above, smoke layers spread farther to the north and south and are often above the dust layers over the Sahel region. In some cases, transported smoke can also be mixed with dust over the Saharan region. Statistically, 5% of the CALIOP valid measurements in February 2007-2011 show aerosol layers either above or between the clouds, reinforcing the importance of the aerosol vertical distribution for quantifying aerosol impact on climate in the Sahel region. Key Points Mesoscale modeling of smoke and dust transport and mixing over the Sahel region Constrain smoke injection and model evaluation with CALIOP, MODIS, and AERONET data Smoke often over the dust/cloud layer in Sahel and can mix with dust over Sahara ©2013. American Geophysical Union. All Rights Reserved."
"6603480361;55921861500;56189039500;7004168515;8667824800;35775264900;23476421000;56232242500;7006532784;","Circulation anomalies in the Southern Hemisphere and ozone changes",2013,"10.5194/acp-13-10677-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887295789&doi=10.5194%2facp-13-10677-2013&partnerID=40&md5=cb39641627fb1dc2645ca9e940511dfc","We report results from two pairs of chemistry-climate model simulations using the same climate model but different chemical perturbations. In each pair of experiments an ozone change was triggered by a simple change in the chemistry. One pair of model experiments looked at the impact of polar stratospheric clouds (PSCs) and the other pair at the impact of short-lived halogenated species on composition and circulation. The model response is complex with both positive and negative changes in ozone concentration, depending on location. These changes result from coupling between composition, temperature and circulation. Even though the causes of the modelled ozone changes are different, the high latitude Southern Hemisphere response in the lower stratosphere is similar. In both pairs of experiments the high-latitude circulation changes, as evidenced by N2O differences, are suggesting a slightly longer-lasting/stronger stratospheric descent in runs with higher ozone destruction (a manifestation of a seasonal shift in the circulation). We contrast the idealised model behaviour with interannual variability in ozone and N2O as observed by the MIPAS instrument on ENVISAT, highlighting similarities of the modelled climate equilibrium changes to the year 2006&ndash;2007 in observations. We conclude that the climate system can respond quite sensitively in its seasonal evolution to small chemical perturbations, that circulation adjustments seen in the model can occur in reality, and that coupled chemistry-climate models allow a better assessment of future ozone and climate change than recent CMIP-type models with prescribed ozone fields. © Author(s) 2013."
"7005920812;23393856300;","The subgrid importance latin hypercube sampler (SILHS): A multivariate subcolumn generator",2013,"10.5194/gmd-6-1813-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887309630&doi=10.5194%2fgmd-6-1813-2013&partnerID=40&md5=2e7597561480a6e0ced8f16b749f3a31","Coarse-resolution climate and weather forecast models cannot accurately parameterize small-scale, nonlinear processes without accounting for subgrid-scale variability. To do so, some models integrate over the subgrid variability analytically. Although analytic integration methods are attractive, they can be used only with physical parameterizations that have a sufficiently simple functional form. Instead, this paper introduces a method to integrate subgrid variability using a type of Monte Carlo integration. The method generates subcolumns with suitable vertical correlations and feeds them into a microphysics parameterization. The subcolumn methodology requires little change to the parameterization source code and can be used with a wide variety of physical parameterizations. Our subcolumn generator is multivariate, which is important for physical processes that involve two or more hydrometeor species, such as accretion of cloud droplets by rain drops. In order to reduce sampling noise in the integrations, our subcolumn generator employs two variance-reduction methods, namely importance and stratified (Latin hypercube) sampling. For this reason, we name the subcolumn generator the Subgrid Importance Latin Hypercube Sampler (SILHS). This paper tests SILHS in interactive, single-column simulations of a marine stratocumulus case and a shallow cumulus case. The paper then compares simulations that use SILHS with those that use analytic integration. Although the SILHS solutions exhibit considerable noise from time step to time step, the noise is greatly damped in most of the time-averaged profiles.©Author(s) 2013."
"7004372110;25027021800;8533581200;55916149100;55641786300;","Scheme for calculation of multi-layer cloudiness and precipitation for climate models of intermediate complexity",2013,"10.5194/gmd-6-1745-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887119636&doi=10.5194%2fgmd-6-1745-2013&partnerID=40&md5=eb3b6d8789f2dfd622a53c0dbeae3fb0","In this study we present a scheme for calculating the characteristics of multi-layer cloudiness and precipitation for Earth system models of intermediate complexity (EMICs). This scheme considers three-layer stratiform cloudiness and single-column convective clouds. It distinguishes between ice and droplet clouds as well. Precipitation is calculated by using cloud lifetime, which depends on cloud type and phase as well as on statistics of synoptic and convective disturbances. The scheme is tuned to observations by using an ensemble simulation forced by the ERA-40-derived climatology for 1979-2001. Upon calibration, the scheme realistically reproduces basic features of fields of cloud fractions, cloud water path, and precipitation. The simulated globally and annually averaged total cloud fraction is 0.59, and the simulated globally averaged annual precipitation is 100 cm yr?1. Both values agree with empirically derived values. The simulated cloud water path is too small, probably because the simulated vertical extent of stratiform clouds is too small. Geographical distribution and seasonal changes of calculated cloud fraction and precipitation are broadly realistic as well. However, some important regional biases still remain in the scheme, e.g. too little precipitation in the tropics. We discuss possibilities for future improvements in the scheme. © Author(s) 2013. CC Attribution 3.0 License."
"35221443100;57208121852;7103353990;23020321400;","The contribution of the strength and structure of extratropical cyclones to observed cloud-aerosol relationships",2013,"10.5194/acp-13-10689-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887028194&doi=10.5194%2facp-13-10689-2013&partnerID=40&md5=5c5570cf622b787fb609895af19ef4e5","Meteorological conditions may drive relationships between aerosol and cloud-related properties. It is important to account for the meteorological contribution to observed cloud-aerosol relationships in order to improve understanding of aerosol-cloud-climate interactions. A new method of investigating the contribution of meteorological covariation to observed cloud-aerosol relationships is introduced. Other studies have investigated the contribution of local meteorology to cloud-aerosol relationships. In this paper, a complimentary large-scale view is presented. Extratropical cyclones have been previously shown to affect satellite-retrieved aerosol optical depth (τ), due to enhanced emission of sea salt and sea surface brightness artefacts in regions of higher wind speed. Extratropical cyclones have also been shown to affect cloud-related properties such as cloud fraction (fc) and cloud top temperature (Ttop). Therefore, it seems plausible to hypothesise that extratropical cyclones may drive relationships between cloud-related properties and τ. In this paper, this hypothesis is investigated for extratropical cyclones, henceforth referred to as storms, over the Atlantic Ocean. MODerate resolution Imaging Spectroradiometer (MODIS) retrieved τ, fc and T top data are analysed using a storm-centric coordinate system centred on extratropical cyclones which have been tracked using European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis 850 hPa relative vorticity data. The tracked relative vorticity (ω) is used as a measure of storm strength, while position in the storm-centric domain is used to account for storm structure. Relationships between the cloud-related properties and τ are measured by calculating regression slopes and correlations. The fc-τ relationships are positive, while the Ttop-τ relationships are negative. By shuffling the pairing of the cloud and τ data at each location in the storm-centric domain and within narrow ω bins, the contribution of storm strength and storm structure to the observed relationships can be investigated. It is found that storm strength and storm structure can explain only a small component of the relationships observed in the MODIS data. The primary causes for observed cloud-aerosol relationships are likely to be other factors such as retrieval errors, local meteorology or aerosol-cloud interactions. © 2013 Author(s)."
"7102010848;7402803216;7406500188;55917306900;8871497700;26643041500;57131535300;56500974300;9846154100;55917847100;8438057200;56997768500;22942638300;35461255500;","Intense atmospheric pollution modifies weather: A case of mixed biomass burning with fossil fuel combustion pollution in eastern China",2013,"10.5194/acp-13-10545-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887055645&doi=10.5194%2facp-13-10545-2013&partnerID=40&md5=1138845fe34e3c2f371581c865f9ed9c","The influence of air pollutants, especially aerosols, on regional and global climate has been widely investigated, but only a very limited number of studies report their impacts on everyday weather. In this work, we present for the first time direct (observational) evidence of a clear effect of how a mixed atmospheric pollution changes the weather with a substantial modification in the air temperature and rainfall. By using comprehensive measurements in Nanjing, China, we found that mixed agricultural burning plumes with fossil fuel combustion pollution resulted in a decrease in the solar radiation intensity by more than 70 %, a decrease in the sensible heat by more than 85 %, a temperature drop by almost 10 K, and a change in rainfall during both daytime and nighttime. Our results show clear air pollution-weather interactions, and quantify how air pollution affects weather via air pollution-boundary layer dynamics and aerosol-radiation-cloud feedbacks. This study highlights cross-disciplinary needs to investigate the environmental, weather and climate impacts of the mixed biomass burning and fossil fuel combustion sources in East China. © Author(s) 2013. CC Attribution 3.0 License."
"56917398600;","A model-based approach to adjust microwave observations for operational applications: Results of a campaign at Munich Airport in winter 2011/2012",2013,"10.5194/amt-6-2879-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887003599&doi=10.5194%2famt-6-2879-2013&partnerID=40&md5=9aa1a05db1e59b7e4fda71cb1fc925af","In the frame of the project ""LuFo iPort VIS"" which focuses on the implementation of a site-specific visibility forecast, a field campaign was organised to offer detailed information to a numerical fog model. As part of additional observing activities, a 22-channel microwave radiometer profiler (MWRP) was operating at the Munich Airport site in Germany from October 2011 to February 2012 in order to provide vertical temperature and humidity profiles as well as cloud liquid water information. Independently from the model-related aims of the campaign, the MWRP observations were used to study their capabilities to work in operational meteorological networks. Over the past decade a growing quantity of MWRP has been introduced and a user community (MWRnet) was established to encourage activities directed at the set up of an operational network. On that account, the comparability of observations from different network sites plays a fundamental role for any applications in climatology and numerical weather forecast. <br><br> In practice, however, systematic temperature and humidity differences (bias) between MWRP retrievals and co-located radiosonde profiles were observed and reported by several authors. This bias can be caused by instrumental offsets and by the absorption model used in the retrieval algorithms as well as by applying a non-representative training data set. At the Lindenberg observatory, besides a neural network provided by the manufacturer, a measurement-based regression method was developed to reduce the bias. These regression operators are calculated on the basis of coincident radiosonde observations and MWRP brightness temperature (TB) measurements. However, MWRP applications in a network require comparable results at just any site, even if no radiosondes are available. <br><br> The motivation of this work is directed to a verification of the suitability of the operational local forecast model COSMO-EU of the Deutscher Wetterdienst (DWD) for the calculation of model-based regression operators in order to provide unbiased vertical profiles during the campaign at Munich Airport. The results of this algorithm and the retrievals of a neural network, specially developed for the site, are compared with radiosondes from Oberschleißheim located about 10 km apart from the MWRP site. Outstanding deviations for the lowest levels between 50 and 100 m are discussed. Analogously to the airport experiment, a model-based regression operator was calculated for Lindenberg and compared with both radiosondes and operational results of observation-based methods. <br><br> The bias of the retrievals could be considerably reduced and the accuracy, which has been assessed for the airport site, is quite similar to those of the operational radiometer site at Lindenberg above 1 km height. Additional investigations are made to determine the length of the training period necessary for generating best estimates. Thereby three months have proven to be adequate. The results of the study show that on the basis of numerical weather prediction (NWP) model data, available everywhere at any time, the model-based regression method is capable of providing comparable results at a multitude of sites. Furthermore, the approach offers auspicious conditions for automation and continuous updating. © 2013 Author(s)."
"56842476100;49864573500;23052016900;57197325620;35459245100;35547807400;8942525300;13405658600;","Reduced efficacy of marine cloud brightening geoengineering due to in-plume aerosol coagulation: Parameterization and global implications",2013,"10.5194/acp-13-10385-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886828367&doi=10.5194%2facp-13-10385-2013&partnerID=40&md5=11b7b35b6d40617ef50ebcf390d55065","The intentional enhancement of cloud albedo via controlled sea-spray injection from ships (marine cloud brightening) has been proposed as a possible method to control anthropogenic global warming; however, there remains significant uncertainty in the efficacy of this method due to, amongst other factors, uncertainties in aerosol and cloud microphysics. A major assumption used in recent cloud- and climate-modeling studies is that all sea spray was emitted uniformly into some oceanic grid boxes, and thus these studies did not account for subgrid aerosol coagulation within the sea-spray plumes. We explore the evolution of these sea-salt plumes using a multi-shelled Gaussian plume model with size-resolved aerosol coagulation. We determine how the final number of particles depends on meteorological conditions, including wind speed and boundary-layer stability, as well as the emission rate and size distribution of aerosol emitted. Under previously proposed injection rates and typical marine conditions, we find that the number of aerosol particles is reduced by over 50%, but this reduction varies from under 10% to over 90% depending on the conditions. We provide a computationally efficient parameterization for cloud-resolving and global-scale models to account for subgrid-scale coagulation, and we implement this parameterization in a global-scale aerosol-climate model. While designed to address subgrid-scale coagulation of sea-salt particles, the parameterization is generally applicable for coagulation of subgrid-scale aerosol from point sources. We find that accounting for this subgrid-scale coagulation reduces cloud droplet number concentrations by 46% over emission regions, and reduces the global mean radiative flux perturbation from -1.5 W m-2 to -0.8 W m-2. © 2013 Author(s)."
"7103413199;7402435469;55712683400;55910202200;37071745600;55712772000;55910010100;6701782816;17341093800;6504089753;55910431900;7201841885;7003554893;8255473900;7202954964;7401945370;55286185400;7005808242;35497573900;56224155200;55686667100;7102857642;24468389200;22137065500;6603371044;8539422800;57211224269;7006263720;","The aqua-planet experiment (APE): CONTROL SST simulation",2013,"10.2151/jmsj.2013-A02","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886797645&doi=10.2151%2fjmsj.2013-A02&partnerID=40&md5=5391c468dca1a27b4c52b8a38b8e8e32","Climate simulations by 16 atmospheric general circulation models (AGCMs) are compared on an aqua-planet, a water-covered Earth with prescribed sea surface temperature varying only in latitude. The idealised configuration is designed to expose differences in the circulation simulated by different models. Basic features of the aqua-planet climate are characterised by comparison with Earth. The models display a wide range of behaviour. The balanced component of the tropospheric mean flow, and mid-latitude eddy covariances subject to budget constraints, vary relatively little among the models. In contrast, differences in damping in the dynamical core strongly influence transient eddy amplitudes. Historical uncertainty in modelled lower stratospheric temperatures persists in APE. Aspects of the circulation generated more directly by interactions between the resolved fluid dynamics and parameterized moist processes vary greatly. The tropical Hadley circulation forms either a single or double inter-tropical convergence zone (ITCZ) at the equator, with large variations in mean precipitation. The equatorial wave spectrum shows a wide range of precipitation intensity and propagation characteristics. Kelvin mode-like eastward propagation with remarkably constant phase speed dominates in most models. Westward propagation, less dispersive than the equatorial Rossby modes, dominates in a few models or occurs within an eastward propagating envelope in others. The mean structure of the ITCZ is related to precipitation variability, consistent with previous studies. The aqua-planet global energy balance is unknown but the models produce a surprisingly large range of top of atmosphere global net flux, dominated by differences in shortwave reflection by clouds. A number of newly developed models, not optimised for Earth climate, contribute to this. Possible reasons for differences in the optimised models are discussed. The aqua-planet configuration is intended as one component of an experimental hierarchy used to evaluate AGCMs. This comparison does suggest that the range of model behaviour could be better understood and reduced in conjunction with Earth climate simulations. Controlled experimentation is required to explore individual model behaviour and investigate convergence of the aqua-planet climate with increasing resolution. © 2013, Meteorological Society of Japan."
"7402435469;","Dependence of APE simulations on vertical resolution with the community atmospheric model, version 3",2013,"10.2151/jmsj.2013-A08","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880671824&doi=10.2151%2fjmsj.2013-A08&partnerID=40&md5=eb27c43e7e8fb627268642f54280538e","The convergence of the zonal averaged equatorial precipitation with increasing vertical resolution in simulations with Community Atmosphere Model (CAM3) Eulerian spectral transform and finite volume dynamical cores is considered. The cores are both coupled to the standard CAM3 parameterization package. With the standard CAM3 26 level grid, the two versions converge to different states when the horizontal resolution alone is refined; the spectral transform to a single precipitation maximum and the finite volume to a double. With increasing vertical resolution both converge to a double structure. However, in the subsidence regions the high vertical resolution simulations have a very different climate balance and parameterized forcing than the lower resolution simulations and thus they do not represent the expected climate associated with the lower resolution dynamical cores. The cause of the different parameterized forcing is studied by considering the evolution of the 60-level model starting from a state created by the 26-level model. The cause is shown to be the discrete approximations in the shallow convection. When the 60-level model is presented with an initial state interpolated from a 26-level model state, the columns are stable by the discrete test in the shallow convection, even though they are unstable when the discrete calculation is based on the coarser 26-level grid. The Planetary Boundary Layer parameterization pumps water vapor into the lower troposphere, low clouds increase to unrealistic levels and force strong longwave radiative cooling. This destabilizes the column until the discrete test is satisfied on the 60-level grid and the shallow convection becomes active again. However the simulated state is by then very different and unlike the earth's atmosphere. Similar unrealistic behavior has been seen in earth-like simulations. © 2013, Meteorological Society of Japan."
"36017183900;55686667100;7102857642;","Superrotation and nonlinear hadley circulation response to zonally asymmetric sea surface temperature in an aquaplanet GCM",2013,"10.2151/jmsj.2013-A10","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886785286&doi=10.2151%2fjmsj.2013-A10&partnerID=40&md5=c224eac4dfb55d77bbd8133b3a7aba5d","The responses of the equatorial zonal wind and the Hadley circulation to the equatorial zonal wavenumber one sea surface temperature (SST) anomaly, Ts*, are examined in an atmospheric general circulation model (AGCM) with an aquaplanet condition. The Hadley cell is weakened as the magnitude of Ts* increases, balancing with a decrease in the zonal-mean diabatic heating over the tropics. The decrease of heating reflects a nonlinear relationship between precipitation and SST; deep convection, such as a super cloud cluster, is significantly suppressed over cold Ts*, whereas is slightly enhanced over warm Ts*. The effective suppression of deep convection is accomplished by the stable boundary layer and the dry subsidence anomaly associated with the Walker cell which is excited by the SST anomaly. And the decreased convection acts to further reinforce the subsidence via thermodynamic balance. Therefore, this positive feedback between large-scale circulation and deep convection determines the nonlinear relationship and controls the strength of the Hadley cell. In terms of the energetics of the tropical circulation, the Hadley cell has to be weakened to compensate for the lack of energy supply caused by an increase of tropical radiative cooling due to the effective suppression of deep convection over cold Ts*. We compared the results of our AGCM with that of other 15 aquaplanet AGCMs integrated with the same SST distribution. While the Hadley cell is weakened in all AGCMs when Ts* is added to the zonal uniform SST, there is a large diversity in the strength. This suggests that the difference in the physical parameterization causes a different sensitivity of the Hadley cell response to zonally asymmetric SST. The magnitude of weakening is approximately proportional to the decreased (increased) amount of the deep convective precipitation (the radiative cooling) over the tropics. This strong relationship suggests that the positive feedback also works in other AGCMs. It is considered that the feedback is also important for understanding the formation of a real tropical climate. © 2013, Meteorological Society of Japan."
"8696069500;6506738607;36339753800;8315173500;7201504886;24485834000;","Climate feedback efficiency and synergy",2013,"10.1007/s00382-013-1808-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886721511&doi=10.1007%2fs00382-013-1808-7&partnerID=40&md5=34912af8a22458ed2e7ab2a734322c0c","Earth's climate sensitivity to radiative forcing induced by a doubling of the atmospheric CO2 is determined by feedback mechanisms, including changes in atmospheric water vapor, clouds and surface albedo, that act to either amplify or dampen the response. The climate system is frequently interpreted in terms of a simple energy balance model, in which it is assumed that individual feedback mechanisms are additive and act independently. Here we test these assumptions by systematically controlling, or locking, the radiative feedbacks in a state-of-the-art climate model. The method is shown to yield a near-perfect decomposition of change into partial temperature contributions pertaining to forcing and each of the feedbacks. In the studied model water vapor feedback stands for about half the temperature change, CO2-forcing about one third, while cloud and surface albedo feedback contributions are relatively small. We find a close correspondence between forcing, feedback and partial surface temperature response for the water vapor and surface albedo feedbacks, while the cloud feedback is inefficient in inducing surface temperature change. Analysis suggests that cloud-induced warming in the upper tropical troposphere, consistent with rising convective cloud anvils in a warming climate enhances the negative lapse-rate feedback, thereby offsetting some of the warming that would otherwise be attributable to this positive cloud feedback. By subsequently combining feedback mechanisms we find a positive synergy acting between the water vapor feedback and the cloud feedback; that is, the combined cloud and water vapor feedback is greater than the sum of its parts. Negative synergies surround the surface albedo feedback, as associated cloud and water vapor changes dampen the anticipated climate change induced by retreating snow and ice. Our results highlight the importance of treating the coupling between clouds, water vapor and temperature in a deepening troposphere. © 2013 The Author(s)."
"7007021059;7003976079;7201485519;7404142321;","Quantitative evaluation of the seasonal variations in climate model cloud regimes",2013,"10.1007/s00382-012-1609-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886721481&doi=10.1007%2fs00382-012-1609-4&partnerID=40&md5=feea8c2aebc663a73cde443a1d2d53c4","An extended cloud-clustering method to assess the seasonal variation of clouds is applied to five CMIP5 models. The seasonal variation of the total cloud radiative effect (CRE) is dominated by variations in the relative frequency of occurrence of the different cloud regimes. Seasonal variations of the CRE within the individual regimes contribute much less. This is the case for both observations, models and model errors. The error in the seasonal variation of cloud regimes, and its breakdown into mean amplitude and time varying components, are quantified with a new metric. The seasonal variation of the CRE of the cloud regimes is relatively well simulated by the models in the tropics, but less well in the extra-tropics. The stratocumulus regime has the largest seasonal variation of shortwave CRE in the tropics, despite having a small magnitude in the climatological mean. Most of the models capture the temporal variation of the CRE reasonably well, with the main differences between models coming from the variation in amplitude. In the extra-tropics, most models fail to correctly represent both the amplitude and time variation of the CRE of congestus, frontal and stratocumulus regimes. The annual mean climatology of the CRE and its amplitude in the seasonal variation are both underestimated for the anvil regime in the tropics, the cirrus regime and the congestus regime in the extra-tropics. The models in this study that best capture the seasonal variation of the cloud regimes tend to have higher climate sensitivities. © 2012 Crown Copyright."
"55913183200;7402989545;","Why does FGOALS-gl reproduce a weak Medieval Warm Period but a reasonable Little Ice Age and 20th century warming?",2013,"10.1007/s00376-013-2227-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886872259&doi=10.1007%2fs00376-013-2227-8&partnerID=40&md5=aa81fbbaa7170150542c51b0139627cf","To understand the strengths and limitations of a low-resolution version of Flexible Global Ocean-Atmosphere-Land-Sea-ice (FGOALS-gl) to simulate the climate of the last millennium, the energy balance, climate sensitivity and absorption feedback of the model are analyzed. Simulation of last-millennium climate was carried out by driving the model with natural (solar radiation and volcanic eruptions) and anthropogenic (greenhouse gases and aerosols) forcing agents. The model feedback factors for (model sensitivity to) different forcings were calculated. The results show that the system feedback factor is about 2.5 (W m-2) K-1 in the pre-industrial period, while 1.9 (W m-2) K-1 in the industrial era. Thus, the model's sensitivity to natural forcing is weak, which explains why it reproduces a weak Medieval Warm Period. The relatively reasonable simulation of the Little Ice Age is caused by both the specified radiative forcing and unforced linear cold drift. The model sensitivity in the industrial era is higher than that of the pre-industrial period. A negative net cloud radiative feedback operates during whole-millennial simulation and reduces the model's sensitivity to specified forcing. The negative net cloud radiative forcing feedback under natural forcing in the period prior to 1850 is due to the underestimation (overestimation) of the response of cloudiness (in-cloud water path). In the industrial era, the strong tropospheric temperature response enlarges the effective radius of ice clouds and reduces the fractional ice content within cloud, resulting in a weak negative net cloud feedback in the industrial period. The water vapor feedback in the industrial era is also stronger than that in the pre-industrial period. Both are in favor of higher model sensitivity and thus a reasonable simulation of the 20th century global warming. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"7005528388;6603126554;7102171439;15726427000;24367209100;21742642500;35265576100;","Cloud-state-dependent sampling in airs observations based on cloudsat cloud classification",2013,"10.1175/JCLI-D-13-00065.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886239379&doi=10.1175%2fJCLI-D-13-00065.1&partnerID=40&md5=d6c5356644db9eff6f6eb89acf0813e6","The precision, accuracy, and potential sampling biases of temperature T and water vapor q vertical profiles obtained by satellite infrared sounding instruments are highly cloud-state dependent and poorly quantified. The authors describe progress toward a comprehensive T and q climatology derived from the Atmospheric Infrared Sounder (AIRS) suite that is a function of cloud state based on collocated CloudSat observations. The AIRS sampling rates, biases, and center root-mean-square differences (CRMSD) are determined through comparisons of pixel-scale collocated ECMWF model analysis data. The results show that AIRS provides a realistic representation of most meteorological regimes in most geographical regions, including those dominated by high thin cirrus and shallow boundary layer clouds. The mean AIRS observational biases relative to the ECMWF analysis between the surface and 200 hPa are within±1K in T and from -1 to +0.5 g kg-1 in q. Biases because of cloud-state-dependent sampling dominate the total biases in the AIRS data and are largest in the presence of deep convective (DC) and nimbostratus (Ns) clouds. Systematic cold and dry biases are found throughout the free troposphere for DC and Ns. Somewhat larger biases are found over land and in the midlatitudes than over the oceans and in the tropics, respectively. Tropical and oceanic regions generally have a smaller CRMSD than the midlatitudes and over land, suggesting agreement of T and q variability between AIRS andECMWFin these regions. The magnitude ofCRMSDis also strongly dependent on cloud type. © 2013 American Meteorological Society."
"7403076976;","Lightning Applications in Weather and Climate Research",2013,"10.1007/s10712-012-9218-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886751156&doi=10.1007%2fs10712-012-9218-7&partnerID=40&md5=639600ef58de4fb5076fb1cc3426940a","Thunderstorms, and lightning in particular, are a major natural hazard to the public, aviation, power companies, and wildfire managers. Lightning causes great damage and death every year but also tells us about the inner working of storms. Since lightning can be monitored from great distances from the storms themselves, lightning may allow us to provide early warnings for severe weather phenomena such as hail storms, flash floods, tornadoes, and even hurricanes. Lightning itself may impact the climate of the Earth by producing nitrogen oxides (NOx), a precursor of tropospheric ozone, which is a powerful greenhouse gas. Thunderstorms themselves influence the climate system by the redistribution of heat, moisture, and momentum in the atmosphere. What about future changes in lightning and thunderstorm activity? Many studies show that higher surface temperatures produce more lightning, but future changes will depend on what happens to the vertical temperature profile in the troposphere, as well as changes in water balance, and even aerosol loading of the atmosphere. Finally, lightning itself may provide a useful tool for tracking climate change in the future, due to the nonlinear link between lightning, temperature, upper tropospheric water vapor, and cloud cover. © 2013 Springer Science+Business Media Dordrecht."
"55489352600;8900751100;7406671641;12345271600;57201201895;","Simulated impacts of afforestation in East China monsoon region as modulated by ocean variability",2013,"10.1007/s00382-012-1592-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886728564&doi=10.1007%2fs00382-012-1592-9&partnerID=40&md5=57e8d452f9cb9dea970846b6dc433253","Using the National Center for Atmospheric Research Community Climate System Model Version 3.5, this paper examines the climatic effects of afforestation in the East China monsoon region with a focus on land-atmosphere interactions and the modulating influence of ocean variability. In response to afforestation, the local surface air temperature significantly decreases in summer and increases in winter. The summer cooling is attributed to enhanced evapotranspiration from increased tree cover. During winter, afforestation induces greater roughness and weaker winds over the adjacent coastal ocean, leading to diminished latent heat flux and increased sea-surface temperature (SST). The enhanced SST supports greater atmospheric water vapor, which is accompanied by anomalous wind, and transported into the East China monsoon region. The increase in atmospheric water vapor favors more cloud cover and precipitation, especially in the eastern afforestation region. Furthermore, the increase in atmospheric water vapor and cloud cover produce a greenhouse effect, raising the wintertime surface air temperature. By comparing simulations in which ocean temperature are either fixed or variable, we demonstrate that a significant hydrologic response in East China to afforestation only occurs if ocean temperatures are allowed to vary and the oceanic source of moisture to the continent is enhanced. © 2012 Springer-Verlag Berlin Heidelberg."
"57200400501;55951225700;","Evaluation of historical diurnal temperature range trends in CMIP5 models",2013,"10.1175/JCLI-D-13-00032.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888035918&doi=10.1175%2fJCLI-D-13-00032.1&partnerID=40&md5=c8dc00c49239cde45945862db99758a7","Diurnal temperature range (DTR) is a useful index of climatic change in addition to mean temperature changes. Observational records indicate that DTR has decreased over the last 50 yr because of differential changes in minimum and maximum temperatures. However, modeled changes in DTR in previous climate model simulations of this period are smaller than those observed, primarily because of an overestimate of changes in maximum temperatures. This present study examines DTR trends using the latest generation of global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) and utilizes the novel CMIP5 detection and attribution experimental design of variously forced historical simulations (natural-only, greenhouse gas-only, and all anthropogenic and natural forcings). Comparison of observed and modeled changes in DTR over the period of 1951-2005 again reveals that global DTR trends are lower in model simulations than observed across the 27-member multimodel ensemble analyzed here. Modeled DTR trends are similar for both experiments incorporating all forcings and for the historical experiment with greenhouse gases only, while no DTR trend is discernible in the naturally forced historical experiment. The persistent underestimate of DTR changes in this latest multimodel evaluation appears to be related to ubiquitous model deficiencies in cloud cover and land surface processes that impact the accurate simulation of regional minimum or maximum temperatures changes observed during this period. Different model processes are likely responsible for subdued simulated DTR trends over the various analyzed regions. © 2013 American Meteorological Society."
"7103158465;57193882808;","Response of tropical deep convection to localized heating perturbations: Implications for aerosol-induced convective invigoration",2013,"10.1175/JAS-D-13-027.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888021288&doi=10.1175%2fJAS-D-13-027.1&partnerID=40&md5=39665fe820e4e2d616922ff9d58c2d7b","A cloud-system-resolving model is used to investigate the effects of localized heating/cooling perturbations on tropical deep convection, in the context of the aerosol ""invigoration effect."" This effect supposes that a reduction of droplet collision-coalescence in polluted conditions leads to lofting of cloud water in convective updrafts and enhanced freezing, latent heating, and buoyancy. To specifically isolate and test this mechanism, heating perturbations were applied to updrafts with corresponding cooling applied in downdrafts. Ensemble simulations were run with either perturbed or unperturbed conditions and large-scale forcing from a 7.5-day period of active monsoon conditions during the 2006 Tropical Warm Pool-International Cloud Experiment. In the perturbed simulations there was an initial invigoration of convective updrafts and surface precipitation, but convection returned to its unperturbed state after about 24 h because of feedback with the larger-scale environment. This feedback led to an increase in the horizontally averaged mid-/upper-tropospheric temperature of about 1 K relative to unperturbed simulations. When perturbed conditions were applied to only part of the domain, gravity waves rapidly dispersed buoyancy anomalies in the perturbed region to the rest of the domain, allowing convective invigoration from the heating perturbations to be sustained over the entire simulation period. This was associated with a mean mesoscale circulation consisting of ascent (descent) at mid-/upper levels in the perturbed (unperturbed) region. In contrast to recent studies, it is concluded that the invigoration effect is intimately coupled with larger-scale dynamics through a two-way feedback, and in the absence of alterations in the larger-scale circulation there is limited invigoration beyond the convective adjustment time scale. © 2013 American Meteorological Society."
"35191486300;36494729400;8720083500;36468318400;55710051100;57214056158;55542116900;","Direct radiative forcing and climate effects of anthropogenic aerosols with different mixing states over China",2013,"10.1016/j.atmosenv.2013.07.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880938399&doi=10.1016%2fj.atmosenv.2013.07.004&partnerID=40&md5=1aa98e4e26e53a1f79ca2dc28b2e9f8f","An online coupled regional climate and chemistry model was used to investigate the direct effects of anthropogenic aerosols (sulfate, nitrate, black carbon BC and organic carbon OC) with different mixing states over China. Three mixing assumptions were considered, including external (EM), internal (IM, BC-core surrounded by well mixed scattering-shells) and partially internal (PIM, 32.2% of sulfate and nitrate, 35.5% of BC and 48.5% of OC were internally mixed) mixtures. Results indicated that high levels of anthropogenic aerosols were found in Southwest and Central to East China. Regional mean surface loadings of sulfate, nitrate, BC, primary OC over China were 9.56, 3.64, 2.30, and 2.99μgm-3, respectively. PIM-aerosol optical depth and single scattering albedo, which were consistent with AERONET and satellite observations, were 0.51±0.37 and 0.95±0.02 in Central to East China, implying that proportions of internally mixed aerosols in PIM were reasonable to some degrees. Both aerosol direct radiative forcing (DRF) and corresponding climate responses were sensitive to aerosol mixing states and BC/OC hygroscopicities. The more BC was internally mixed or hydrophilic, the more solar radiation was absorbed, thus leading to more decreases in cloud amount (CA) and subsequently less surface cooling. Combining with the uncertainties of BC/OC hygroscopicities, regional mean PIM-aerosol DRF at the top of atmosphere ranged from-0.78 to-0.61Wm-2 in all-sky and from-5.24 to-4.95Wm-2 in clear-sky. Additionally, responses of cloud amount and water path, total column absorbed solar radiation (TCASR), surface air temperature and precipitation (TP) to PIM-aerosol DRFs over China were about-0.45~-0.37%,-0.44~-0.32gm-2,+0.69~+0.72Wm-2,-0.13~-0.11K and-4.56~-4.29%, respectively. These responses were also sensitive to the lateral boundary condition perturbations especially for CA, TCASR and TP, while DRFs themselves were not. © 2013 The Authors."
"55751750800;20733898400;9334234800;6701574871;6602084752;","Multiscale performance of the ALARO-0 model for simulating extreme summer precipitation climatology in Belgium",2013,"10.1175/JCLI-D-12-00844.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888050926&doi=10.1175%2fJCLI-D-12-00844.1&partnerID=40&md5=7e0c2b8d2305fb4a5b34bdc7731e3ff9","Daily summer precipitation over Belgium from the Aire Limitée Adaptation Dynamique Développement International (ALADIN) model and a version of the model that has been updated with physical parameterizations, the so-called ALARO-0 model [ALADIN and AROME (Application de la Recherche à l'Opérationnel à Meso-Echelle) combined model, first baseline version released in 1998], are compared with respect to station observations for the period 1961-90. The 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) is dynamically downscaled using both models on a horizontal resolution of 40 km, followed by a one-way nesting on high spatial resolutions of 10 and 4 km. This setup allows us to explore the relative importance of spatial resolution versus parameterization formulation on the model skill to correctly simulate extreme daily precipitation. Model performances are assessed through standard statistical errors and density, frequency, and quantile distributions as well as extreme value analysis, using the peak-over-threshold method and generalized Pareto distribution. The 40-km simulations of ALADIN and ALARO-0 show similar results, both reproducing the observations reasonably well. For the high-resolution simulations, ALARO-0 at both 10 and 4 km is in better agreement with the observations than ALADIN. The ALADIN model consistently produces too high precipitation rates. The findings demonstrate that the new parameterizations within the ALARO-0 model are responsible for a correct simulation of extreme summer precipitation at various horizontal resolutions. Moreover, this study shows that ALARO-0 is a good candidate model for regional climate modeling. © 2013 American Meteorological Society."
"17436659500;52464814200;9743044300;","Improved historical solar radiation gridded data for Australia",2013,"10.1016/j.envsoft.2013.06.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883142023&doi=10.1016%2fj.envsoft.2013.06.013&partnerID=40&md5=758d8b42c5a89598412c75fb781d4fd7","An improved blended data method was developed for preparation and generation of solar radiation gridded datasets for SILO; Queensland Government database containing point and gridded daily climate data for Australia from 1890 till present designed for crop and pasture modelling. The new blended data method incorporates three sources of solar radiation data: radiometer measurements, sunshine duration, and cloud-cover observations. The new method converts all data sources to the percentage extra-terrestrial radiation using new conversion equations derived from the experimental data and thus the conversion tables previously used are now redundant. Comparison with satellite derived estimates shows that the blended data method has reduced bias compared to the previous method. The blended data method addresses the need for historical pre-satellite solar radiation gridded datasets for climate and agricultural modelling, model calibration, and computation of synthetic evaporation rates. © 2013 Elsevier Ltd."
"22635190100;7004544454;7402270607;34772240500;7006417494;55935070900;","On the connection between continental-scale land surface processes and the tropical climate in a coupled ocean-atmosphere-land system",2013,"10.1175/JCLI-D-12-00819.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888050855&doi=10.1175%2fJCLI-D-12-00819.1&partnerID=40&md5=82929a294c535ee239b24efc8a666cb0","An evaluation is presented of the impact on tropical climate of continental-scale perturbations given by different representations of land surface processes (LSPs) in a general circulation model that includes atmosphere-ocean interactions. One representation is a simple land scheme, which specifies climatological albedos and soil moisture availability. The other representation is the more comprehensive Simplified Simple Biosphere Model, which allows for interactive soil moisture and vegetation biophysical processes. The results demonstrate that such perturbations have strong impacts on the seasonal mean states and seasonal cycles of global precipitation, clouds, and surface air temperature. The impact is especially significant over the tropical Pacific Ocean. To explore the mechanisms for such impact, model experiments are performed with different LSP representations confined to selected continental-scale regions where strong interactions of climate-vegetation biophysical processes are present. The largest impact found over the tropical Pacific is mainly from perturbations in the tropical African continent where convective heating anomalies associated with perturbed surface heat fluxes trigger global teleconnections through equatorial wave dynamics. In the equatorial Pacific, the remote impacts of the convection anomalies are further enhanced by strong air-sea coupling between surface wind stress and upwelling, as well as by the effects of ocean memory. LSP perturbations over South America and Asia-Australia have much weaker global impacts. The results further suggest that correct representations of LSP, land use change, and associated changes in the deep convection over tropical Africa are crucial to reducing the uncertainty of future climate projections with global climate models under various climate change scenarios. © 2013 American Meteorological Society."
"54400070900;25226620200;6602829165;","Role of the cloud adjustment time scale in simulation of the interannual variability of Indian summer monsoon",2013,"10.1007/s00703-013-0282-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887527101&doi=10.1007%2fs00703-013-0282-4&partnerID=40&md5=ab6e65b141d0375208cf068a95bd6beb","The simulation of precipitation in a general circulation model relying on relaxed mass flux cumulus parameterization scheme is sensitive to cloud adjustment time scale (CATS). In this study, the frequency of the dominant intra-seasonal mode and interannual variability of Indian summer monsoon rainfall (ISMR) simulated by an atmospheric general circulation model is shown to be sensitive to the CATS. It has been shown that a longer CATS of about 5 h simulates the spatial distribution of the ISMR better. El Niño Southern Oscillation-ISMR relationship is also sensitive to CATS. The equatorial Indian Ocean rainfall and ISMR coupling is sensitive to CATS. Our study suggests that a careful choice of CATS is necessary for adequate simulation of spatial pattern as well as interannual variation of Indian summer monsoon precipitation. © 2013 Springer-Verlag Wien."
"6701846706;36945637600;7003557623;6602205640;35551380400;","Compositional shifts in costa rican forests due to climate-driven species migrations",2013,"10.1111/gcb.12300","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885419243&doi=10.1111%2fgcb.12300&partnerID=40&md5=d0c8dc2eaf4d6f65615ed7d22b2fc1f7","Species are predicted to shift their distributions upslope or poleward in response to global warming. This prediction is supported by a growing number of studies documenting species migrations in temperate systems but remains poorly tested for tropical species, and especially for tropical plant species. We analyzed changes in tree species composition in a network of 10 annually censused 1-ha plots spanning an altitudinal gradient of 70-2800 m elevation in Costa Rica. Specifically, we combined plot data with herbarium records (accessed through GBIF) to test if the plots' community temperature scores (CTS, average thermal mean of constituent species weighted by basal area) have increased over the past decade as is predicted by climate-driven species migrations. In addition, we quantified the contributions of stem growth, recruitment, and mortality to the observed patterns. Supporting our a priori hypothesis of upward species migrations, we found that there have been consistent directional shifts in the composition of the plots, such that the relative abundance of lowland species, and hence CTS, increased in 90% of plots. The rate of the observed compositional shifts corresponds to a mean thermal migration rate (TMR) of 0.0065 °C yr-1 (95% CI = 0.0005-0.0132 °C yr-1). While the overall TMR is slower than predicted based on concurrent regional warming of 0.0167 °C yr-1, migrations were on pace with warming in 4 of the 10 plots. The observed shifts in composition were driven primarily by mortality events (i.e., the disproportionate death of highland vs. lowland species), suggesting that individuals of many tropical tree species will not be able to tolerate future warming and thus their persistence in the face of climate change will depend on successful migrations. Unfortunately, in Costa Rica and elsewhere, land area inevitably decreases at higher elevations; hence, even species that are able to migrate successfully will face heightened risks of extinction. © 2013 John Wiley &amp; Sons Ltd."
"55934587900;6701519241;6603606681;6603566335;","Understanding convective extreme precipitation scaling using observations and an entraining plume model",2013,"10.1175/JAS-D-12-0317.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888071769&doi=10.1175%2fJAS-D-12-0317.1&partnerID=40&md5=593eb1d75a2644e96ebf50e05fa13b77","Previously observed twice-Clausius-Clapeyron (2CC) scaling for extreme precipitation at hourly time scales has led to discussions about its origin. The robustness of this scaling is assessed by analyzing a subhourly dataset of 10-min resolution over the Netherlands. The results confirm the validity of the previously found 2CC scaling for extreme convective precipitation. Using a simple entraining plume model, an idealized deep convective environmental temperature profile is perturbed to analyze extreme precipitation scaling from a frequently used relation based on the column condensation rate. The plume model simulates a steady precipitation increase that is greater than Clausius-Clapeyron scaling (super-CC scaling). Precipitation intensity increase is shown to be controlled by a flux of moisture through the cloud base and in-cloud lateral moisture convergence. Decomposition of this scaling relation into a dominant thermodynamic and additional dynamic component allows for better understanding of the scaling and demonstrates the importance of vertical velocity in both dynamic and thermodynamic scaling. Furthermore, systematically increasing the environmental stability by adjusting the temperature perturbations from constant to moist adiabatic increase reveals a dependence of the scaling on the change in environmental stability. As the perturbations become increasingly close to moist adiabatic, the scaling found by the entraining plume model decreases to CC scaling. Thus, atmospheric stability changes, which are expected to be dependent on the latitude, may well play a key role in the behavior of precipitation extremes in the future climate. © 2013 American Meteorological Society."
"8925509300;6602854186;7402121365;6603699075;25627238300;47861623900;6602185381;10840477200;57194045072;23477978100;7004693503;34881212700;","Role of sea ice in global biogeochemical cycles: Emerging views and challenges",2013,"10.1016/j.quascirev.2013.04.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885952221&doi=10.1016%2fj.quascirev.2013.04.011&partnerID=40&md5=b01afe315af1747119238277e1488e8c","Observations from the last decade suggest an important role of sea ice in the global biogeochemical cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas exchanges at the sea ice interface through an often permeable sea ice cover; and (iii) tight physical, biological and chemical interactions between the sea ice, the ocean and the atmosphere. Photosynthetic micro-organisms in sea ice thrive in liquid brine inclusions encased in a pure ice matrix, where they find suitable light and nutrient levels. They extend the production season, provide a winter and early spring food source, and contribute to organic carbon export to depth. Under-ice and ice edge phytoplankton blooms occur when ice retreats, favoured by increasing light, stratification, and by the release of material into the water column. In particular, the release of iron - highly concentrated in sea ice - could have large effects in the iron-limited Southern Ocean. The export of inorganic carbon transport by brine sinking below the mixed layer, calcium carbonate precipitation in sea ice, as well as active ice-atmosphere carbon dioxide (CO2) fluxes, could play a central role in the marine carbon cycle. Sea ice processes could also significantly contribute to the sulphur cycle through the large production by ice algae of dimethylsulfoniopropionate (DMSP), the precursor of sulphate aerosols, which as cloud condensation nuclei have a potential cooling effect on the planet. Finally, the sea ice zone supports significant ocean-atmosphere methane (CH4) fluxes, while saline ice surfaces activate springtime atmospheric bromine chemistry, setting ground for tropospheric ozone depletion events observed near both poles. All these mechanisms are generally known, but neither precisely understood nor quantified at large scales. As polar regions are rapidly changing, understanding the large-scale polar marine biogeochemical processes and their future evolution is of high priority. Earth system models should in this context prove essential, but they currently represent sea ice as biologically and chemically inert. Palaeoclimatic proxies are also relevant, in particular the sea ice proxies, inferring past sea ice conditions from glacial and marine sediment core records and providing analogues for future changes. Being highly constrained by marine biogeochemistry, sea ice proxies would not only contribute to but also benefit from a better understanding of polar marine biogeochemical cycles. © 2013 Elsevier Ltd."
"51864808600;7006319477;","Increased rainfall frequency triggers an increase in litter fall rates of reproductive structures in an arid eucalypt woodland",2013,"10.1111/aec.12055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885908980&doi=10.1111%2faec.12055&partnerID=40&md5=0ad8cac277f40285ac61e57cf517a9e3","Abstract: The diversity of responses to episodic rainfall events among perennial plant species is critical for the maintenance of ecosystem functions in arid systems. We use a litter fall study to capture the responses of three species to shifts in environmental conditions. We examined the effects of landform, rainfall and other meteorological variables (temperature, evaporation, relative humidity, solar exposure, wind speed and cloud cover) on the mass of reproductive structures falling from two shrubs (Senna artemisioides ssp. filifolia, Acacia burkittii) and one tree (Eucalyptus gracilis) species in a eucalypt mallee woodland in semi-arid eastern Australia. Data were collected over three years. The first year received below-average rainfall and the following years received about twice the average annual rainfall. We assessed the relative importance of our explanatory variables, for each species separately, comparing the results using two methods: (1) multi-model inference of a zero-inflated negative binomial generalized linear model, and (2) structural equation modelling. Multi-model inference showed rainfall frequency, at species-specific lag intervals, to be of highest relative importance for all three species. Wind speed was also relatively important for all three species. Structural equation modelling supported these results, with strong, direct path coefficients for the number of days of rainfall in the past 12 months. There was, however, no strong effect of the average rainfall event size. Our analyses demonstrate the strong, direct and positive effect of rainfall, and highlight the importance of rainfall frequency rather than rainfall event size. Furthermore, we found species-specific responses to environmental variables associated with wind, solar exposure and landform, further driving the litter fall of reproductive structures in perennial plants in semi-arid environments. Understanding how different species respond to rainfall and other meteorological conditions can give us greater insights into the capacity of these systems to adapt, which will be important in a changing climate. © 2013 Ecological Society of Australia."
"6508260037;36987542300;6508063123;36796935700;21935606200;39762535100;57202867102;57202327051;","Aerosol properties and radiative forcing over Kanpur during severe aerosol loading conditions",2013,"10.1016/j.atmosenv.2013.06.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880179266&doi=10.1016%2fj.atmosenv.2013.06.020&partnerID=40&md5=1c974c9f5f1306ee0e4ffdd242b41913","The present work analyzes the aerosol episode (AE) days and examines the modification in aerosol properties and radiative forcing during the period 2001-2010 based on Kanpur-AERONET data. AEs are defined as the days having daily-mean aerosol optical depth (AOD) above the decadal mean+1 STD (standard deviation); the threshold value is defined at 0.93. The analysis identifies 277 out of 2095 days (13.2%) of AEs over Kanpur, which are most frequently observed during post-monsoon (78 cases, 18.6%) and monsoon (76, 14.7%) seasons due to biomass-burning episodes and dust influence, respectively. On the other hand, the AEs during winter and pre-monsoon are lesser in both absolute and percentage values (65, 12.5% and 58, 9.1%, respectively). The modification in aerosol properties on the AE days is strongly dependent on season; during post-monsoon and winter, the AEs are associated with enhanced presence of fine-mode aerosols from anthropogenic emissions and/or biomass burning, while during pre-monsoon and monsoon seasons, they are mostly associated with dust. Aerosol radiative forcing (ARF) calculated using SBDART shows much more surface (~-69 to-97Wm-2) and Top of Atmosphere cooling (-20 to-30Wm-2) as well as atmospheric heating (~43 to 71Wm-2) during the AE days as compared to seasonal means. These forcing values are mainly controlled by the higher AODs and the modified aerosol characteristics (Angstrom Exponent α, single scattering albedo SSA) during the AE days in each season. Furthermore, the vertical profiles of aerosols and atmospheric radiative heating exhibit significant increase in lower and mid troposphere during the AE days. This may cause serious climate implications over Ganges Basin and surrounding regions with further consequences on cloud microphysics, monsoon rainfall and melting of Himalayan glaciers. © 2013 Elsevier Ltd."
"6602079010;57153656200;14032501300;7004208584;11939351200;","Re-evaluation of MODIS MCD43 greenland albedo accuracy and trends",2013,"10.1016/j.rse.2013.07.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882951354&doi=10.1016%2fj.rse.2013.07.023&partnerID=40&md5=0d4ec049a59f3085af92796195821c3f","In this study, the accuracy of the MODerate resolution Imaging Spectroradiometer (MODIS) combined Terra (MOD) and Aqua (MYD) 16-day albedo product (MCD43) is evaluated through comparisons with eleven years of in situ measurements at 17 automatic weather stations on the Greenland Ice Sheet. Taking into consideration accuracy issues with in situ observations, results show that utilizing all high-quality, cloud-free MODIS retrievals gives physically realistic ice sheet albedo values for solar zenith angles less than 75°, with a root-mean-square error of 0.067 (RMSE) and an overall mean bias of +. 0.022 (with the MODIS data biased slightly high relative to the in situ data). Using this data set, changes in ice sheet albedo from 2000 to 2012 are documented. Analysis reveals negative trends in ice sheet albedo during summer over the 13-year data record, with persistent negative albedo anomalies in recent years over western Greenland. During summer 2012, extensive surface melt resulted in a Greenland area-averaged albedo anomaly for June, July August relative to 2000-2009 of -. 0.044 that significantly increased the amount of total absorbed solar radiation and surface melt. © 2013 Elsevier Inc."
"7005561047;","Upper-bound general circulation of coupled ocean-atmosphere: Part 1. Atmosphere",2013,"10.1016/j.dynatmoce.2013.09.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886995732&doi=10.1016%2fj.dynatmoce.2013.09.001&partnerID=40&md5=eaf419fc155c9493b62613b3f89b5588","We consider the general atmospheric circulation within the deductive framework of our climate theory. The preceding three parts of this theory have reduced the troposphere to the tropical and polar air masses and determined their temperature and the surface latitude of their dividing boundary, which provide the prior thermal constraint for the present dynamical derivation. Drawing upon its similar material conservation as the thermal property, the (columnar) potential vorticity (PV) is assumed homogenized as well in air masses, which moreover has a zero tropical value owing to the hemispheric symmetry. Inverting this PV field produces an upper-bound zonal wind that resembles the prevailing wind, suggesting that the latter may be explained as the maximum macroscopic motion extractable by random eddies - within the confine of the thermal differentiation. With the polar front determined in conjunction with the zonal wind, the approximate leveling of the isobars at the surface and high aloft specifies the tropopause, which is colder and higher in the tropics than in the polar region. The zonal wind drives the meridional circulation via the Ekman dynamics, and the preeminence of the Hadley cell stems from the singular Ekman convergence at the equator that allows it to supply the upward mass flux in the ITCZ demanded by the global energy balance. © 2013 Elsevier B.V."
"35175400200;7409077047;57214289652;","Temporal upscaling of instantaneous evapotranspiration: An intercomparison of four methods using eddy covariance measurements and MODIS data",2013,"10.1016/j.rse.2013.07.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882711297&doi=10.1016%2fj.rse.2013.07.001&partnerID=40&md5=70311b2d927c2d902c3de1749e3515f1","The quantification of land surface evapotranspiration (ET) at daily or longer time scales is of great significance in modeling the global hydrological cycle, studying climate change, and managing water resources. However, current remote sensing-based ET models can generally only provide snapshots of ET at the time of a satellite overpass and do not satisfy the expectations of hydrologists, irrigation engineers, or water resource managers concerned with practical applications. Four commonly used ET upscaling schemes, namely, the constant reference evaporative fraction (EFr) method, the constant evaporative fraction (EF) method, the constant extraterrestrial solar radiation ratio (Rp) method, and the constant observed global solar radiation ratio (Rg) method, were evaluated in this study using ground-based eddy covariance (EC) measurements and the Moderate Resolution Imaging Spectroradiometer (MODIS) derived estimates from a two-source energy balance model. Analysis was made of both closed and un-closed surface fluxes and of different assumed satellite overpass times from mid-morning to mid-afternoon. Data for the analysis were collected at the Yucheng comprehensive experimental station in Northern China, spanning the period from late April 2009 to late October 2011. The results show that all four upscaling factors from noon to mid-afternoon had a better agreement with their corresponding daily averages. Overall, the EFr (Rg) method had the best (second best) performance of the four upscaling methods. The EF method was found to significantly underestimate the daily latent heat flux (LE) and performed the worst of the four upscaling methods. With the correction of the energy imbalance of EC measurements, the Rg method's performance was improved and outperformed the EFr method in the morning. The presence of clouds either increased or decreased the BIAS but generally increased the root mean square error (RMSE) for all four upscaling methods. When the upscaling methods were applied to convert the instantaneous MODIS remote sensing estimates of ET to daily values, the accuracy of the extrapolated daily ET was controlled by the accuracy of both the remote sensing ET estimates and the upscaling methods themselves. With the insignificantly biased estimates of the instantaneous LE from the N95 model at 101 MODIS overpass times in this study, using the EF method underestimated the daily ET by 11%, while all the remaining three factors overestimated the daily ET by a range of 5%-18%. This study was conducted to provide a scientific basis for developing an operational and more accurate ET-upscaling method with easy access to data in future studies. © 2013 Elsevier Inc."
"55812797600;7409080503;","Detection, variations and intercomparison of the planetary boundary layer depth from radiosonde, lidar and infrared spectrometer",2013,"10.1016/j.atmosenv.2013.07.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881085908&doi=10.1016%2fj.atmosenv.2013.07.019&partnerID=40&md5=e1e14e1d27c3f2f46ea54ef9b4916743","The depth of the planetary boundary layer (PBL) and its temporal evolution have important effects on weather, air quality and climate. While there are methods to detect the PBL depth from atmospheric profiles, few can be applied to different types of measurements and cope with changing atmospheric conditions. Many require supporting information from other instruments. In this study, two common methods for PBL depth detection (wavelet covariance and iterative curve-fitting) are combined, modified and applied to long-term time series of radiosonde profiles, micropulse lidar (MPL) measured backscatter and atmospheric emitted radiance interferometer (AERI) data collected at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site. Intercomparison among the three PBL retrieval products shows the robustness of the algorithm. The comparisons were made for different times of day, four seasons, and variable sky conditions. While considerable uncertainties exist in PBL detection using all three types of measurements, the agreement among the PBL products is promising under certain conditions, and the different measurements have complementary advantages. The best agreement in the seasonal cycle occurs in winter, and the best agreement in the diurnal cycle when the boundary-layer regime is mature and changes slowly. PBL depths from instruments with higher temporal resolution (MPL and AERI) are of comparable accuracy to radiosonde-derived PBL depths; AERI excels for shallow PBLs, MPL for cloudy conditions. The new continuous PBL data set can be used to improve model parameterizations of PBL and our understanding of atmospheric transport of pollutants which affect clouds, air quality and human health. © 2013 Elsevier Ltd."
"25031430500;7103158465;55232897900;24722339600;","Microphysical process rates and global aerosol-cloud interactions",2013,"10.5194/acp-13-9855-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885998549&doi=10.5194%2facp-13-9855-2013&partnerID=40&md5=ff3965e5b44b2440da7f050ce293ac98","Cloud microphysical process rates control the amount of condensed water in clouds and impact the susceptibility of precipitation to cloud-drop number and aerosols. The relative importance of different microphysical processes in a climate model is analyzed, and the autoconversion and accretion processes are found to be critical to the condensate budget in most regions. A simple steady-state model of warm rain formation is used to illustrate that the diagnostic rain formulations typical of climate models may result in excessive contributions from autoconversion, compared to observations and large eddy simulation models with explicit bin-resolved microphysics and rain formation processes. The behavior does not appear to be caused by the bulk process rate formulations themselves, because the steady-state model with the same bulk accretion and autoconversion has reduced contributions from autoconversion. Sensitivity tests are conducted to analyze how perturbations to the precipitation microphysics for stratiform clouds impact process rates, precipitation susceptibility and aerosol-cloud interactions (ACI). With similar liquid water path, corrections for the diagnostic rain assumptions in the GCM based on the steady-state model to boost accretion indicate that the radiative effects of ACI may decrease by 20% in the GCM. Links between process rates, susceptibility and ACI are not always clear in the GCM. Better representation of the precipitation process, for example by prognosticating precipitation mass and number, may help better constrain these effects in global models with bulk microphysics schemes. © Author(s) 2013."
"26638618800;16642666900;17433905200;56472932500;9235235300;","Particle number concentrations over Europe in 2030: The role of emissions and new particle formation",2013,"10.5194/acp-13-10271-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886233037&doi=10.5194%2facp-13-10271-2013&partnerID=40&md5=a84b1b9ec125e092b2e15536f9a3407a","The aerosol particle number concentration is a key parameter when estimating impacts of aerosol particles on climate and human health.We use a three-dimensional chemical transport model with detailed microphysics, PMCAMx-UF, to simulate particle number concentrations over Europe in the year 2030, by applying emission scenarios for trace gases and primary aerosols. The scenarios are based on expected changes in anthropogenic emissions of sulfur dioxide, ammonia, nitrogen oxides, and primary aerosol particles with a diameter less than 2.5 ?m (PM2.5) focusing on a photochemically active period, and the implications for other seasons are discussed. For the baseline scenario, which represents a best estimate of the evolution of anthropogenic emissions in Europe, PMCAMx-UF predicts that the total particle number concentration (Ntot) will decrease by 30-70% between 2008 and 2030. The number concentration of particles larger than 100 nm (N100), a proxy for cloud condensation nuclei (CCN) concentration, is predicted to decrease by 40-70%during the same period. The predicted decrease in Ntot is mainly a result of reduced new particle formation due to the expected reduction in SO2 emissions, whereas the predicted decrease in N100 is a result of both decreasing condensational growth and reduced primary aerosol emissions. For larger emission reductions, PMCAMx-UF predicts reductions of 60-80% in both Ntot and N100 over Europe. Sensitivity tests reveal that a reduction in SO2 emissions is far more efficient than any other emission reduction investigated, in reducing Ntot. For N100, emission reductions of both SO2 and PM2.5 contribute significantly to the reduced concentration, even though SO2 plays the dominant role once more. The impact of SO2 for both new particle formation and growth over Europe may be expected to be somewhat higher during the simulated period with high photochemical activity than during times of the year with less incoming solar radiation. The predicted reductions in both Ntot and N100 between 2008 and 2030 in this study will likely reduce both the aerosol direct and indirect effects, and limit the damaging effects of aerosol particles on human health in Europe. © Author(s) 2013."
"16027966800;25031430500;7202081585;7005729142;15724543600;23017945100;26643615000;7006329853;","Improved cirrus simulations in a general circulation model using CARMA sectional microphysics",2013,"10.1002/2013JD020193","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888147186&doi=10.1002%2f2013JD020193&partnerID=40&md5=6b063b9db967722165fc59d258b47b48","We have developed a new cirrus model incorporating sectional ice microphysics from the Community Aerosol and Radiation Model for Atmospheres (CARMA) in the latest version of NCAR's Community Atmosphere Model (CAM5). Comparisons with DARDAR and 2C-ICE show that CAM5/CARMA improves cloud fraction, ice water content, and ice water path compared to the standard CAM5. Prognostic snow in CAM5/CARMA increases overall ice mass and results in a melting layer at ~4 km in the tropics that is largely absent in CAM5. Subgrid scale supersaturation following Wilson and Ballard (1999) improves ice mass and relative humidity. Increased middle and upper tropospheric condensate in CAM5/CARMA requires a reduction in low-level cloud for energy balance, resulting in a 3.1 W m-2 improvement in shortwave cloud forcing and a 3.8 W m-2 improvement in downwelling shortwave flux at the surface compared to CAM5 and Clouds and Earth's Radiant Energy Systems (CERES). Total and clear-sky longwave upwelling flux at the top are improved in CAM5/CARMA by 1.0 and 2.6 W m-2, respectively. CAM has a 2-3 K cold bias at the tropical tropopause mostly from the prescribed ozone file. Correction of the prescribed ozone or nudging the CAM5/CARMA model to GEOS5-DAS meteorology yields tropical tropopause temperatures and water vapor that agree with the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) and the Microwave Limb Sounder (MLS). CAM5 relative humidity appears to be too large resulting in a +1.5 ppmv water vapor bias at the tropical tropopause when using GEOS5-DAS meteorology. In CAM5/CARMA, 75% of the cloud ice mass originates from ice particles detrained from convection compared to 25% from in situ nucleation. Key Points Improved cirrus simulations in CAM compared to DARDAR, 2C-ICE, COSMIC, and MLS Prognostic snow improves simulated IWC and representation of melting layer Simulations indicate 75% of cirrus from detrainment and 25% formed in situ ©2013. American Geophysical Union. All Rights Reserved."
"15319529200;7406925763;6507168651;7006691931;6603627233;7201716828;7601492669;32668049400;55936559500;7801600522;6603471237;","A comparison between the effects of artificial land cover and anthropogenic heat on a localized heavy rain event in 2008 in Zoshigaya, Tokyo, Japan",2013,"10.1002/jgrd.50850","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888160777&doi=10.1002%2fjgrd.50850&partnerID=40&md5=faaca62f6786a13341f71397196a7fa6","On 5 August 2008, a localized heavy rainfall event caused a rapid increase in drainpipe discharge, which killed five people working in a drainpipe near Zoshigaya, Tokyo. This study compared the effects of artificial land cover and anthropogenic heat on this localized heavy rainfall event based on three ensemble experiments using a cloud-resolving model that includes realistic urban features. The first experiment CTRL (control) considered realistic land cover and urban features, including artificial land cover, anthropogenic heat, and urban geometry. In the second experiment NOAH (no anthropogenic heat), anthropogenic heat was ignored. In the third experiment NOLC (no land cover), urban heating from artificial land cover was reduced by keeping the urban geometry but with roofs, walls, and roads of artificial land cover replaced by shallow water. The results indicated that both anthropogenic heat and artificial land cover increased the amount of precipitation and that the effect of artificial land cover was larger than that of anthropogenic heat. However, in the middle stage of the precipitation event, the difference between the two effects became small. Weak surface heating in NOAH and NOLC reduced the near-surface air temperature and weakened the convergence of horizontal wind and updraft over the urban areas, resulting in a reduced rainfall amount compared with that in CTRL. Key Points Effects of land cover and anthropogenic heat on a rainfall were investigated Overall, land cover effect exceeded anthropogenic heat effect in this rainfall In the middle of rainfall, the difference between the two effects became small ©2013. American Geophysical Union. All Rights Reserved."
"49662076300;7202463361;8986277400;26643054400;7004286908;7102797196;23161713000;55718857500;55432775500;57193213111;","Spatial and temporal variations of new particle formation in East Asia using an NPF-explicit WRF-chem model: North-south contrast in new particle formation frequency",2013,"10.1002/jgrd.50821","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888142986&doi=10.1002%2fjgrd.50821&partnerID=40&md5=6f4c78c01071313d4756540ca5b577e5","A recently developed new particle formation (NPF)-explicit version of the Weather Research and Forecasting Chemistry (WRF-chem) model can explicitly calculate the growth and sink of nucleated clusters with 20 aerosol size bins from 1 nm to 10 μm in diameter. In this study, the model was used to investigate spatial and temporal variations in NPF event frequency and the concentrations of aerosols (condensation nuclei, CN) and cloud condensation nuclei (CCN) within the boundary layer in East Asia in spring 2009. We found a distinct north-south contrast in the NPF frequency and mechanism in East Asia. NPF occurred mainly during limited periods over certain regions between 30° and 45°N (northeast China, Korea, and Japan, including regions around the active volcanoes Miyakejima and Sakurajima). In these latitudes, NPF was suppressed by high concentrations of preexisting particles under stagnant air conditions associated with high-pressure systems, although nucleation occurred more extensively during most of the simulation period. In contrast, south of 30°N, nucleation and NPF were both infrequent because of low SO2 emissions and H2SO4 concentrations. The period-averaged NPF frequency at 30°-45°N was three times that at 20°-30°N. This north-south contrast in NPF frequency was validated by surface measurements in outflow regions of East Asia. The simulated period- and domain-averaged contribution of secondary particles was estimated to be 44% for CN (&gt;10 nm) and 26% for CCN at a supersaturation of 1.0%, though the contribution was highly sensitive to the amount and size distribution of primary aerosol emissions and the rate coefficient of the nucleation parameterization. Key Points Simulation of NPF, CN, and CCN in East Asia using the NPF-explicit WRF-chem Distinct north-south contrast in the frequency and mechanism of NPF in East Asia Estimation of the contribution of primary and secondary particles to CN and CCN ©2013. American Geophysical Union. All Rights Reserved."
"35069282600;6507731482;7202899330;25953950400;","Radiative impacts of free-tropospheric clouds on the properties of marine stratocumulus",2013,"10.1175/JAS-D-12-0287.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885939468&doi=10.1175%2fJAS-D-12-0287.1&partnerID=40&md5=c922972b7f0bebea3b2beb3e1966621f","Observations from multiple satellites and large-eddy simulations (LESs) from the Regional Atmospheric Modeling System (RAMS) are used to determine the extent to which free-tropospheric clouds (FTCs) affect the properties of stratocumulus. Overlying FTCs decrease the cloud-top radiative cooling in stratocumulus by an amount that depends on the upper-cloud base altitude, cloud optical thickness, and abundance of moisture between the cloud layers. On average, FTCs increase the downward longwave radiative flux above stratocumulus clouds (at 3.5 km) by approximately 30Wm-2. As a consequence, this forcing translates to a relative decrease in stratocumulus cooling rates by about 20%. Overall, the reduced cloud-top radiative cooling decreases the turbulent mixing, vertical development, and precipitation rate in stratocumulus clouds at night. During the day these effects are greatly reduced because the overlying clouds shade the stratocumulus from strong solar radiation, thus reducing the net radiative effect by the upper cloud. Differences in liquid water path are also observed in stratocumulus; however, the response is tied to the diurnal cycle and the time scale of interaction between the FTCs and the stratocumulus. Radiative effects by FTCs tend to be largest in the midlatitudes where the clouds overlying stratocumulus tend to be more frequent, lower, and thicker on average. In conclusion, changes in net radiation and moisture brought about by FTCs can significantly affect the dynamics of marine stratocumulus and these processes should be considered when evaluating cloud feedbacks in the climate system. © 2013 American Meteorological Society."
"56263595100;7410070663;","Doubling-adding method for delta-four-stream spherical harmonic expansion approximation in radiative transfer parameterization",2013,"10.1175/JAS-D-12-0334.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877012462&doi=10.1175%2fJAS-D-12-0334.1&partnerID=40&md5=3e2b509a477cdd366d3353e052da600b","Though the single-layer solutions have been found for the δ-four-stream spherical harmonic expansion method (SHM) in radiative transfer, there is lack of a corresponding doubling-adding method (4SDA), which enables the calculation of radiative transfer through a vertically inhomogeneous atmosphere with multilayers. The doubling-adding method is based on Chandrasekhar's invariance principle, which was originally developed for discrete ordinates approximation. It is shown that the invariance principle can also be applied to SHM and δ-four-stream spherical harmonic expansion doubling-adding method (δ-4SDA) is proposed in this paper. The δ-4SDA method has been systematically compared to the δ-Eddington doubling-adding method (δ-2SDA), the δ-two-stream discrete ordinates doubling-adding method (δ-2DDA), and δ-four-stream discrete ordinates doubling-adding method (δ-4DDA). By applying δ-4SDA to a realistic atmospheric profile with gaseous transmission considered, it is found that the accuracy of δ-4SDA is superior to δ-2SDA or δ-2DDA, especially for the cloudy/aerosol conditions. It is shown that the relative errors of δ-4SDA are generally less than 1%in both heating rate and flux, while the relative errors of both δ-2SDA and δ-2DDA can be over 6%. Though δ-4DDA is slightly more accurate than δ-4SDA in heating rates, both of them are accurate enough to obtain the cloud-top solar heating. Here δ-4SDA is superior to δ-4DDAin computational efficiency. It is found that the error of aerosol radiative forcing can be up to 3Wm-2 by using δ-2SDA at the top of the atmosphere (TOA); such error is substantially reduced by applying δ-4SDA. In view of the overall accuracy and computational efficiency, δ-4SDA is suitable for application in climate models. © 2013 American Meteorological Society."
"57205067933;8937949500;56140027500;8722794800;","How representative are instantaneous evaporative fraction measurements of daytime fluxes?",2013,"10.5194/hess-17-3913-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885784536&doi=10.5194%2fhess-17-3913-2013&partnerID=40&md5=96fadcbb7ac9e901f3e8a1a15767b778","Sun-synchronous optical and thermal remote sensing is a promising technique to provide instantaneous ET (evapotranspiration) estimates during satellite overpass. The common approach to extrapolate the instantaneous estimates to values for daily or longer periods relies on the assumption that the EF (evaporative fraction, defined as the ratio of latent heat flux to surface available energy) remains nearly constant during daytime. However, there is still no consensus on the validity of the self-preservation of the EF. We use FLUXNET (a global network of eddy covariance stations) measurements to examine this self-preservation, and the conditions under which it can hold. It is found that the instantaneous EF could represent daytime EF under clear sky conditions, especially between 11:00 and 14:00 LT (local time) for all stations. However, the results show that the EF is more variable during cloudy sky conditions, so that an increase in cloud cover results in an increase in the variability of the EF during daytime. © Author(s) 2013. CC Attribution 3.0 License."
"36920234100;16834406100;54583461800;18134565600;6603548530;6603372665;23029627900;55883717800;15050345900;55401575900;35396858200;6701865015;","Laboratory and modeling studies on the effects of water and soot emissions and ambient conditions on the properties of contrail ice particles in the jet regime",2013,"10.5194/acp-13-10049-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885648471&doi=10.5194%2facp-13-10049-2013&partnerID=40&md5=21e9bfaa4f97009148baa5a685f8013e","Contrails and contrail-induced cirrus clouds are identified as the most uncertain components in determining aviation impacts on global climate change. Parameters affecting contrail ice particle formation immediately after the engine exit plane (< 5 s in plume age) may be critical to ice particle properties used in large-scale models predicting contrail radiative forcing. Despite this, detailed understanding of these parametric effects is still limited. In this paper, we present results from recent laboratory and modeling studies conducted to investigate the effects of water and soot emissions and ambient conditions on near-field formation of contrail ice particles and ice particle properties. The Particle Aerosol Laboratory (PAL) at the NASA Glenn Research Center and the Aerodyne microphysical parcel model for contrail ice particle formation were employed. Our studies show that exhaust water concentration has a significant impact on contrail ice particle formation and properties. When soot particles were introduced, ice particle formation was observed only when exhaust water concentration was above a critical level. When no soot or sulfuric acid was introduced, no ice particle formation was observed, suggesting that ice particle formation from homogeneous nucleation followed by homogeneous freezing of liquid water was unfavorable. Soot particles were found to compete for water vapor condensation, and higher soot concentrations emitted into the chamber resulted in smaller ice particles being formed. Chamber conditions corresponding to higher cruising altitudes were found to favor ice particle formation. The microphysical model captures trends of particle extinction measurements well, but discrepancies between the model and the optical particle counter measurements exist as the model predicts narrower ice particle size distributions and ice particle sizes nearly a factor of two larger than measured. These discrepancies are likely due to particle loss and scatter during the experimental sampling process and the lack of treatment of turbulent mixing in the model. Our combined experimental and modeling work demonstrates that formation of contrail ice particles can be reproduced in the NASA PAL facility, and the parametric understanding of the ice particle properties from the model and experiments can potentially be used in large-scale models to provide better estimates of the impact of aviation contrails on climate change. © Author(s) 2013."
"7202258620;7203001286;55720332500;6701463335;7403143315;7005361537;7003430284;6603260116;","Impact of Aerosol Activation on Modelled Regional Particulate Matter Mass and Size Distribution Due to Cloud Processing",2013,"10.1007/978-94-007-5577-2_23","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885416078&doi=10.1007%2f978-94-007-5577-2_23&partnerID=40&md5=f511a1b7810794ce3ca92c60c2addc72","Aerosol activation is a key process in aerosol-AQ cloud interaction. Although it is widely studied within the climate modeling community it has not been attracting significant attention within the air quality modeling community. In this study an off-line, sectional, chemically-speciated regional air quality model, AURAMS, has been used to assess the impact of aerosol activation on the modelled regional particulate matter (PM) mass concentration and size distribution. Asimple activation scheme based on an empirical relationship between cloud droplet number density and aerosol number density is compared to a more physically-based activation scheme. Model simulations were compared to aircraft observations obtained during the 2004 ICARTT field campaign. Modelled aerosol light extinction and column aerosol optical depth (AOD) were computed in three different ways in the current study. Two of them based on Mie calculations and one empirical reconstructed mass extinction method. The magnitude of the modeled AOD varies significantly depending on the approach. The impact of different aerosol activation schemes on the modelled AOD in this case is generally in the range of 20-30 % for the two Mie methods. As the empirical reconstructed mass extinction method is not size dependent, it is less sensitive to aerosol activation. © Springer Science+Business Media Dordrecht 2014."
"37089417300;7102988363;7004194999;","The global impact of the transport sectors on atmospheric aerosol: Simulations for year 2000 emissions",2013,"10.5194/acp-13-9939-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880593754&doi=10.5194%2facp-13-9939-2013&partnerID=40&md5=0f231417520e99a7bec874e79c628ad1","We use the EMAC (ECHAM/MESSy Atmospheric Chemistry) global model with the aerosol module MADE (Modal Aerosol Dynamics model for Europe, adapted for global applications) to quantify the impact of transport emissions (land transport, shipping and aviation) on the global aerosol. We consider a present-day (2000) scenario according to the CMIP5 (Climate Model Intercomparison Project Phase 5) emission data set developed in support of the IPCC (Intergovernmental Panel on Climate Change) Fifth Assessment Report. The model takes into account particle mass and number emissions: The latter are derived from mass emissions under different assumptions on the size distribution of particles emitted by the three transport sectors. Additional sensitivity experiments are performed to quantify the effects of the uncertainties behind such assumptions. The model simulations show that the impact of the transport sectors closely matches the emission patterns. Land transport is the most important source of black carbon (BC) pollution in the USA, Europe and the Arabian Peninsula, contributing up to 60-70% of the total surface-level BC concentration in these regions. Shipping contributes about 40-60% of the total aerosol sulfate surface-level concentration along the most-traveled routes of the northern Atlantic and northern Pacific oceans, with a significant impact (∼ 10-20%) along the coastlines. Aviation mostly affects aerosol number, contributing about 30-40% of the particle number concentration in the northern midlatitudes' upper troposphere (7-12 km), although significant effects are also simulated at the ground, due to the emissions from landing and take-off cycles. The transport-induced perturbations to the particle number concentrations are very sensitive to the assumptions on the size distribution of emitted particles, with the largest uncertainties (about one order of magnitude) obtained for the land transport sector. The simulated climate impacts, due to aerosol direct and indirect effects, are strongest for the shipping sector, in the range of-222.0 to-153.3 mW m&minus;2, as a consequence of the large impact of sulfate aerosol on low marine clouds and their optical properties. © 2013 Author(s)."
"7404179087;7202180152;7003498065;16835423100;7003658498;7006127815;","Air Quality Model Evaluation International Initiative (AQMEII): A Two-Continent Effort for the Evaluation of Regional Air Quality Models",2013,"10.1007/978-94-007-5577-2_77","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885397015&doi=10.1007%2f978-94-007-5577-2_77&partnerID=40&md5=3e1dd8ba860c653c6f4679626e0c1b3a","With the endorsement and support from the U.S. Environmental Protection Agency, European Commission, and Environment Canada, a project entitled Air Quality Model Evaluation International Initiative (AQMEII) was launched in 2009 by bringing together scientists from Europe and North America (Rao ST, Galmarini S, Puckett K, Bull Am Meteorol Soc 92:23-30, 2011). Several regional-scale numerical photochemical models were applied over the North American and European domains with 2006 emissions inventory. Several papers resulting from this international collaborative effort were accepted for publication in the AQMEII special issue of Atmospheric Environment. Also, a large 4-D database, assembled by EU Joint Research Centre for the AQMEII project, is now available to all scientists interested in developing innovative model evaluation techniques (Galmarini S, Rao ST, Atmos Environ 45(14):2464, 2011). Having successfully completed the first phase of AQMEII, Phase 2 of AQMEII was launched at the 2011 AQMEII workshop in Chapel Hill, NC, USA to focus on the interactions of air quality and climate change. In Phase 2, coupled meteorology-atmospheric chemistry models will be exercised over the two continents with a common emissions database to assess how well the current generation of coupled regional-scale air quality models can simulate the spatio-temporal variability in the optical and radiative characteristics of atmospheric aerosols and associated feedbacks among aerosols, radiations, clouds, and precipitation. The results from AQMEII Phase 2 would be useful to policy makers for developing effective policies to deal with air pollution and climate change. © Springer Science+Business Media Dordrecht 2014."
"35096299800;35547807400;7407104838;7004299063;36600036800;57203200427;57197325620;35459245100;7005955015;53878006900;6506373162;23052016900;7006705919;55688930000;9249627300;","Sea spray geoengineering experiments in the geoengineering model intercomparison project (GeoMIP): Experimental design and preliminary results",2013,"10.1002/jgrd.50856","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887193183&doi=10.1002%2fjgrd.50856&partnerID=40&md5=5a7484b98771130196bf0dac0634afd5","Marine cloud brightening through sea spray injection has been proposed as a method of temporarily alleviating some of the impacts of anthropogenic climate change, as part of a set of technologies called geoengineering. We outline here a proposal for three coordinated climate modeling experiments to test aspects of sea spray geoengineering, to be conducted under the auspices of the Geoengineering Model Intercomparison Project (GeoMIP). The first, highly idealized, experiment (G1ocean-albedo) involves a uniform increase in ocean albedo to offset an instantaneous quadrupling of CO2 concentrations from preindustrial levels. Results from a single climate model show an increased land-sea temperature contrast, Arctic warming, and large shifts in annual mean precipitation patterns. The second experiment (G4cdnc) involves increasing cloud droplet number concentration in all low-level marine clouds to offset some of the radiative forcing of an RCP4.5 scenario. This experiment will test the robustness of models in simulating geographically heterogeneous radiative flux changes and their effects on climate. The third experiment (G4sea-salt) involves injection of sea spray aerosols into the marine boundary layer between 30°S and 30°N to offset 2 W m-2 of the effective radiative forcing of an RCP4.5 scenario. A single model study shows that the induced effective radiative forcing is largely confined to the latitudes in which injection occurs. In this single model simulation, the forcing due to aerosol-radiation interactions is stronger than the forcing due to aerosol-cloud interactions. Key Points Outline of three marine cloud brightening experiments Land-sea contrast is an important feature of marine cloud brightening Direct effect of sea salt injection may be greater than indirect effect ©2013. American Geophysical Union. All Rights Reserved."
"8942525300;12753162000;","Natural aerosol-climate feedbacks suppressed by anthropogenic aerosol",2013,"10.1002/2013GL057966","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885562447&doi=10.1002%2f2013GL057966&partnerID=40&md5=1686b5b6979cbe85f3f34454da7b9875","The natural environment is an important source of atmospheric aerosol such as dust, sea spray, and wildfire smoke. Climate controls many of these natural aerosol sources, which, in turn, can alter climate through changing the properties of clouds and the Earth's radiative balance. However, the Earth's atmosphere is now heavily modified by anthropogenic pollution aerosol, but how this pollution may alter these natural aerosol-climate feedbacks has not been previously explored. Here we use a global aerosol microphysics model to analyze how anthropogenic aerosol alters one link within these feedbacks, namely, the sensitivity of cloud albedo to changes in natural aerosol. We demonstrate that anthropogenic aerosol in the Northern Hemisphere has halved the hemispheric mean cloud albedo radiative effect that occurs due to changes in natural aerosol emissions. Such a suppression has not occurred in the more pristine Southern Hemisphere. Key Points Cloud droplet number concentrations have increased in NH due to pollution Aerosol indirect effect due to natural aerosol is suppressed by pollution Natural aerosol-climate feedbacks more important before pollution aerosol ©2013. American Geophysical Union. All Rights Reserved."
"55878055300;23476370700;","Investigation of cosmic ray-cloud connections using MISR",2013,"10.1002/grl.50996","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885349326&doi=10.1002%2fgrl.50996&partnerID=40&md5=68c3dd34ae050a50c6b54d7191d6148d","Numerous empirical studies have analyzed International Satellite Cloud Climatology Project data and reached contradictory conclusions regarding the influence of solar-modulated galactic cosmic rays on cloud fraction and cloud properties. The Multiangle Imaging Spectroradiometer (MISR) instrument on the Terra satellite has been in continuous operation for 13 years and thus provides an independent (and previously unutilized) cloud data set to investigate purported solar-cloud links. Furthermore, unlike many previous solar-climate studies that report cloud fraction MISR measures albedo, which has clearer climatological relevance. Our long-term analysis of MISR data finds no statistically significant correlations between cosmic rays and global albedo or globally averaged cloud height, and no evidence for any regional or lagged correlations. Moreover, epoch superposition analysis of Forbush decreases reveals no detectable albedo response to cosmic ray decreases, thereby placing an upper limit on the possible influence of cosmic ray variations on global albedo of 0.0029 per 5% decrease. The implications for recent global warming are discussed. Key Points MISR provides independent check of purported cosmic ray-climate correlations No statistically significant correlation between cosmic rays and global albedo Forbush decrease analysis constrains max effect of cosmic rays on global albedo ©2013. American Geophysical Union. All Rights Reserved."
"55871853200;7402866430;57207721059;","Structural evolution of monsoon clouds in the Indian CTCZ",2013,"10.1002/grl.50970","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884951769&doi=10.1002%2fgrl.50970&partnerID=40&md5=c9246333e79d644d731707f6fa5f3d75","Structural evolution of monsoon clouds in the core monsoon region of India has been examined using multisensor data. Invigoration of warm clouds above 4.5 km (occurring in only 15.4% days of the last 11 monsoon seasons) is associated with a transition from negative to positive normalized rainfall anomaly. Cloud top pressure reduces with an increase in aerosol optical depth at a higher rate of invigoration in drier condition (characterized by large fraction of absorbing aerosols) than wet condition. Cloud effective radius for warm clouds does not show any significant change with an increase in aerosol concentration in the presence of high liquid water path, probably due to strong buffering role of meteorology. The structural evolution of monsoon clouds is influenced by both dynamic and microphysical processes that prolong the cloud lifetime, resulting in infrequent rainfall. Our results call for improved representation of aerosol and cloud vertical structures in the climate models to resolve this issue. Key Points Transition to positive rainfall anomaly for cloud invigoration above 4.5 km Higher rate of invigoration in response to aerosols in drier condition At high liquid water path, cloud effective radius is insensitive to aerosols ©2013. American Geophysical Union. All Rights Reserved."
"25637373000;15044268700;7005814217;7801492228;","Linearity of climate response to increases in black carbon aerosols",2013,"10.1175/JCLI-D-12-00715.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885343961&doi=10.1175%2fJCLI-D-12-00715.1&partnerID=40&md5=f2ef96c39dddc22d762a9749e24b081f","The impacts of absorbing aerosols on global climate are not completely understood. This paper presents the results of idealized experiments conducted with the Community Atmosphere Model, version 4 (CAM4), coupled to a slab ocean model (CAM4-SOM) to simulate the climate response to increases in tropospheric black carbon aerosols (BC) by direct and semidirect effects. CAM4-SOMwas forced with 0, 13, 23, 53, and 103 an estimate of the present day concentration of BC while maintaining the estimated present day global spatial and vertical distribution. The top-of-atmosphere (TOA) radiative forcing of BC in these experiments is positive (warming) and increases linearly as the BC burden increases. The total semidirect effect for the 1 3 BC experiment is positive but becomes increasingly negative for higher BC concentrations. The globalaverage surface temperature response is found to be a linear function of the TOA radiative forcing. The climate sensitivity to BC from these experiments is estimated to be 0.42KW-1m2 when the semidirect effects are accounted for and 0.22KW-1m2 with only the direct effects considered. Global-average precipitation decreases linearly as BC increases, with a precipitation sensitivity to atmospheric absorption of 0.4%W-1 m2. The hemispheric asymmetry of BC also causes an increase in southward cross-equatorial heat transport and a resulting northward shift of the intertropical convergence zone in the simulations at a rate of 4° PW-1. Global-average mid-and high-level clouds decrease, whereas the low-level clouds increase linearly with BC. The increase in marine stratocumulus cloud fraction over the southern tropical Atlantic is caused by increased BC-induced diabatic heating of the free troposphere."
"24081888700;6603081424;","On the global character of overlap between low and high clouds",2013,"10.1002/grl.50871","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884787253&doi=10.1002%2fgrl.50871&partnerID=40&md5=563bdbd91fd206514daeca7c8182fb54","The global character of overlap between low and high clouds is examined using active satellite sensors. Low-cloud fraction has a strong land-ocean contrast with oceanic values double those over land. Major low-cloud regimes include not only the eastern ocean boundary stratocumulus and shallow cumulus but also those associated with cold air outbreaks downwind of wintertime continents and land stratus over particular geographic areas. Globally, about 30% of low clouds are overlapped by high clouds. The overlap rate exhibits strong spatial variability ranging from higher than 90% in the tropics to less than 5% in subsidence areas and is anticorrelated with subsidence rate and low-cloud fraction. The zonal mean of vertical separation between cloud layers is never smaller than 5 km and its zonal variation closely follows that of tropopause height, implying a tight connection with tropopause dynamics. Possible impacts of cloud overlap on low clouds are discussed. Key Points The overlap occurs about 12% time and 30% for low clouds The overlap rate is tightly controlled by large-scale dynamics Vertical separation is large and its variability follows tropopause dynamics ©2013. American Geophysical Union. All Rights Reserved."
"55085483100;7404521962;6602725432;7003811754;","In situ observations of supercooled liquid clouds over the Southern Ocean during the HIAPER Pole-to-Pole Observation campaigns",2013,"10.1002/grl.50986","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884867223&doi=10.1002%2fgrl.50986&partnerID=40&md5=ecfcf6700bbe072d6102a6be69b48c53","Clouds over the Southern Ocean exist in a pristine environment that results in unique microphysical properties. However, in situ observations of these clouds are rare, and the dominant precipitation processes are unknown. Uncertainties in their life cycles and radiative properties make them interesting from a weather and climate perspective. Data from the standard cloud physics payload during the High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations global transects provide a unique snapshot the nature of low-level clouds in the Southern Ocean. High quantities of supercooled liquid water (up to 0.47gm-3) were observed in clouds as cold as -22°C during two flights in different seasons and different meteorological conditions, supporting climatologies inferred from satellite observations. Cloud droplet concentrations were calculated from mean droplet size and liquid water concentrations, and were in the range of 30-120cm-3, which is fairly typical for the pristine Southern Ocean environment. Ice in nonprecipitating or lightly precipitating clouds was found to be rare, while drizzle drops with diameter greater than 100μm formed through warm rain processes were widespread. Large, pristine crystals were commonly seen in very low concentrations below cloud base. Key Points SLW observed in all low-level cloud profiles in HIPPO RF2.06 and RF3.06 Very low ice concentrations observed, in spite of very cold temperatures Frequent large drops indicate that warm rain process is important for the SO ©2013. American Geophysical Union. All Rights Reserved."
"7005578774;6602098362;","Regional energy and water cycles: Transports from ocean to land",2013,"10.1175/JCLI-D-13-00008.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885365593&doi=10.1175%2fJCLI-D-13-00008.1&partnerID=40&md5=d1cef162bfd7f97c396b6a8bcb63f3c3","The flows of energy and water from ocean to land are examined in the context of the land energy and water budgets, for land as a whole and for continents. Most atmospheric reanalyses have large errors of up to 15W m-2 in the top-of-atmosphere (TOA) energy imbalance, and none include volcanic eruptions. The flow of energy from ocean to land is more reliable as it relies on analyzed wind, temperature, and moisture fields. It is examined for transports of the total, latent energy (LE), and dry static energy (DSE) to land as a whole and as zonal means. The net convergence of energy onto land is balanced by the loss of energy at TOA, measured by Clouds and the Earth's Radiant Energy System (CERES), and again there are notable discrepancies. Only the ECMWF Interim Re-Analysis (ERA-I) is stable and plausible. Strong compensation between variations in LE and DSE transports onto land means that their sum is more stable over time, and the net transport of energy onto land is largely that associated with the hydrological cycle (LE). A more detailed examination is given of the energy and water budgets for Eurasia, North and South America, Australia, and Africa, making use of Gravity Recovery and Climate Experiment (GRACE) data for water storage on land and data on river discharge into the ocean. With ERA-I, the new land estimates for both water and energy are closer to achieving balances than in previous studies. As well as the annual means, the mean annual cycles are examined in detail along with uncertainty sampling estimates, but the main test used here is that of closure. © 2013 American Meteorological Society."
"36179218000;56209367000;55476830600;7202048112;","Estimating the radiative forcing of carbonaceous aerosols over California based on satellite and ground observations",2013,"10.1002/jgrd.50835","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887196636&doi=10.1002%2fjgrd.50835&partnerID=40&md5=55b62600ffd44af49e0c27081b624ee4","Carbonaceous aerosols have the potential to impact climate directly through absorption of incoming solar radiation and indirectly by affecting cloud and precipitation. Recent modeling studies have made great efforts to simulate both the spatial and temporal distributions of carbonaceous aerosol's optical properties and radiative forcing. This study makes the first observationally constrained assessment of the direct radiative forcing of carbonaceous aerosols over California. By exploiting multiple observations (including ground sites and satellites), we constructed the distribution of aerosol optical depths and aerosol absorption optical depths (AAOD) over California for a 10 year period (2000-2010). We partitioned the total solar absorption into individual contributions from elemental carbon (EC), organic carbon (OC), and dust aerosols, using a newly developed scheme. Our results show that AAOD due to carbonaceous aerosols (EC and OC) at 440 nm was 50%-200% larger than natural dust, with EC contributing the bulk (70%-90%). Observationally constrained EC absorption agrees reasonably well with estimates from global and regional chemical transport models, but the models underestimate the OC AAOD by at least 50%. We estimated that the top of the atmosphere (TOA) forcing from carbonaceous aerosols was 0.7 W/m2 and the TOA forcing due to OC was close to zero. The atmospheric heating of carbonaceous aerosol was 2.2-2.9 W/m 2, of which EC contributed about 80-90%. We estimated the atmospheric heating of OC at 0.1-0.4 W/m2, larger than model simulations. EC reduction over the last two decades may have caused a surface brightening of 1.5-3.5 W/m2. Key Points The solar absorption was partitioned into contributions from EC, OC and dust. Observed and modeled EC AAOD agrees but models underestimate OC AAOD by 50%. TOA warming of carbonaceous aerosols is 0.7 W/m2 and that of OC is near zero. ©2013. American Geophysical Union. All Rights Reserved."
"26664901700;7004205208;55331928800;7004282880;12781228700;26028756400;26643499600;7004252789;26659311700;","Initial breakdown pulses in intracloud lightning flashes and their relation to terrestrial gamma ray flashes",2013,"10.1002/jgrd.50866","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887202941&doi=10.1002%2fjgrd.50866&partnerID=40&md5=0f380b526ce80cf0313206fe5c481518","The initial breakdown stage of 10 intracloud lightning flashes that may have produced terrestrial gamma ray flashes (TGFs) is studied with wideband E-change, multiband B-change, and VHF lightning mapping data; these flashes fit published criteria known to be associated with TGFs. The (x, y, z, t) locations of fast initial breakdown pulses (IBPs) were determined with E-change data using a time-of-arrival (TOA) technique. Each IBP includes one or more fast-rising subpulses. Previous research has shown that a typical intracloud flash initiates just above the main negative cloud charge (MNCC), then an initial negative leader propagates upward in 1-20 ms to the bottom of the upper positive cloud charge (UPCC), thereby establishing a conducting path between the MNCC and UPCC. TOA locations indicate that IBPs are directly related to the initial negative leader. The IBPs primarily occur in short (<750 μs) bursts of two to five pulses, and each burst produces a slow, monotonic E-change. Typically, one to three IBP bursts are needed to span the vertical gap from the MNCC to the UPCC, with successive bursts separated by 1-5 ms. In the B-change data, each IBP burst has an associated ULF pulse and several LF pulses, and these are caused by the same physical events that produce the slow, monotonic E-change and fast-rising IBP subpulses, respectively. Based on similarities with known TGF-associated signals, we speculate that a relativistic electron avalanche causes each LF pulse/IBP subpulse pair; thus, each pair has the potential to cause a TGF. Key Points Initial breakdown pulses (IBPs) of IC flashes move upward as the initial leader Initial leaders develop with a few IBP bursts separated by a few milliseconds IBPs and slow E-changes are causally connected to LF and slow ULF pulses of TGFs ©2013. American Geophysical Union. All Rights Reserved."
"57189255539;56962763800;","Characteristics of the subtropical tropopause region based on long-term highly resolved sonde records over Tenerife",2013,"10.1002/jgrd.50839","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887188070&doi=10.1002%2fjgrd.50839&partnerID=40&md5=d0cccdf4f7e40d3c494b05f3b01f4c35","This study examines the structure of the subtropical tropopause region over Tenerife (the Canary Islands, Spain; 28°N, 16°W) based on a 20 year (1992-2011) ozonesonde data and European Center for Medium-Range Weather Forecasts ERA-Interim potential vorticity (PV) and zonal wind speed reanalysis. High-resolution vertical profiles allowed a detailed description of the subtropical tropopause break and the associated subtropical jet stream (STJ), where models fail to properly simulate the upper troposphere-lower stratosphere (UTLS). The subtropical UTLS is revealed as a complex atmospheric region with a thickness ∼8 km, which is examined through the analysis and evaluation of four different tropopause definitions: thermal (TT), cold point, ozone (OT), and dynamical (DT) tropopauses. A novel method to determine the DT based on the vertical gradient of Lait's modified PV is presented and the concept of a second DT has been introduced for the first time. Monthly climatologies of tropopause height and potential temperature are calculated for double and single tropopause events. The 14.3 km height level is used to differentiate between tropical and extratropical UTLS regimes, intimately linked to the position of the STJ. There is fairly good consistency between all the defined tropopauses under the double tropopause scheme, except in spring, when the OT is observed at lower levels due to frequent baroclinic instabilities in the upper troposphere. As concerns to single tropopause events, the same pattern is found from April to June, reflecting the influence of analogous processes during these months. In winter, altitude differences between OT, DT, and TT resulted from poleward STJ excursions forced by blocking systems over the North Atlantic. Analysis of the tropopause inversion layer showed distinctive features for tropical and midlatitude tropopauses. Key Points The subtropical tropopause region is thoroughly characterized Several PV values are possible to define an isentropic barrier in the subtropics Distinctive features for midlatitude and tropical tropopauses are revealed ©2013. American Geophysical Union. All Rights Reserved."
"55598469400;6504118722;8629285200;55599076400;55599190600;7004125528;","Rainfall estimation over a Mediterranean region using a method based on various spectral parameters of SEVIRI-MSG",2013,"10.1016/j.asr.2013.07.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884288953&doi=10.1016%2fj.asr.2013.07.036&partnerID=40&md5=f2570c141886c2267e11144cde9071dc","The ultimate objective of this paper is the estimation of rainfall over an area in Algeria using data from the SEVIRI radiometer (Spinning Enhanced Visible and Infrared Imager). To achieve this aim, we use a new Convective/Stratiform Rain Area Delineation Technique (CS-RADT). The satellite rainfall retrieval technique is based on various spectral parameters of SEVIRI that express microphysical and optical cloud properties. It uses a multispectral thresholding technique to distinguish between stratiform and convective clouds. This technique (CS-RADT) is applied to the complex situation of the Mediterranean climate of this region. The tests have been conducted during the rainy seasons of 2006/2007 and 2010/2011 where stratiform and convective precipitation is recorded. The developed scheme (CS-RADT) is calibrated by instantaneous meteorological radar data to determine thresholds, and then rain rates are assigned to each cloud type by using radar and rain gauge data. These calibration data are collocated with SEVIRI data in time and space. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved."
"7403567126;7402539875;6701477370;7004206957;18438882300;","Influence of the Pacific Decadal Oscillation, El Niño-Southern Oscillation and solar forcing on climate and primary productivity changes in the northeast Pacific",2013,"10.1016/j.quaint.2013.02.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884414331&doi=10.1016%2fj.quaint.2013.02.001&partnerID=40&md5=4dc89ca73e4d874d7148598774e63190","Evidence of 11-year Schwabe solar sunspot cycles, El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) were detected in an annual record of diatomaceous laminated sediments from anoxic Effingham Inlet, Vancouver Island, British Columbia. Radiometric dating and counting of annual varves dates the sediments from AD 1947-1993. Intact sediment slabs were X-rayed for sediment structure (lamina thickness and composition based on gray-scale), and subsamples were examined for diatom abundances and for grain size. Wavelet analysis reveals the presence of ~2-3, ~4.5, ~7 and ~9-12-year cycles in the diatom record and an ~11-13 year record in the sedimentary varve thickness record. These cycle lengths suggest that both ENSO and the sunspot cycle had an influence on primary productivity and sedimentation patterns. Sediment grain size could not be correlated to the sunspot cycle although a peak in the grain size data centered around the mid-1970s may be related to the 1976-1977 Pacific climate shift, which occurred when the PDO index shifted from negative (cool conditions) to positive (warm conditions). Additional evidence of the PDO regime shift is found in wavelet and cross-wavelet results for Skeletonema costatum, a weakly silicified variant of S.costatum, annual precipitation and April to June precipitation. Higher spring (April/May) values of the North Pacific High pressure index during sunspot minima suggest that during this time, increased cloud cover and concomitant suppression of the Aleutian Low (AL) pressure system led to strengthened coastal upwelling and enhanced diatom production earlier in the year. These results suggest that the 11-year solar cycle, amplified by cloud cover and upwelling changes, as well as ENSO, exert significant influence on marine primary productivity in the northeast Pacific. The expression of these cyclic phenomena in the sedimentary record were in turn modulated by the phase of PDO, as indicated by the change in period of ENSO and suppression of the solar signal in the record after the 1976-1977 regime shift. © 2013 Elsevier Ltd and INQUA."
"24759068600;10639570300;7801654745;15769236000;26433171500;","Meteorological drivers of ablation processes on a cold glacier in the semi-arid Andes of Chile",2013,"10.5194/tc-7-1513-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885142541&doi=10.5194%2ftc-7-1513-2013&partnerID=40&md5=a11009dde4550fff432280351cb8adda","Meteorological and surface change measurements collected during a 2.5 yr period are used to calculate surface mass and energy balances at 5324 m a.s.l. on Guanaco Glacier, a cold-based glacier in the semi-arid Andes of Chile. Meteorological conditions are marked by extremely low vapour pressures (annual mean of 1.1 hPa), strong winds (annual mean of 10 m s-1), shortwave radiation receipt persistently close to the theoretical site maximum during cloud-free days (mean annual 295 W m-2; summer hourly maximum 1354 W m-2) and low precipitation rates (mean annual 45 mm w.e.). Snowfall occurs sporadically throughout the year and is related to frontal events in the winter and convective storms during the summer months. Net shortwave radiation provides the greatest source of energy to the glacier surface, and net longwave radiation dominates energy losses. The turbulent latent heat flux is always negative, which means that the surface is always losing mass via sublimation, which is the main form of ablation at the site. Sublimation rates are most strongly correlated with net shortwave radiation, incoming shortwave radiation, albedo and vapour pressure. Low glacier surface temperatures restrict melting for much of the period, however episodic melting occurs during the austral summer, when warm, humid, calm and high pressure conditions restrict sublimation and make more energy available for melting. Low accumulation (131 mm w.e. over the period) and relatively high ablation (1435 mm w.e.) means that mass change over the period was negative (-1304 mm w.e.), which continued the negative trend recorded in the region over the last few decades. © 2013 Authors(s)."
"57196143493;","On the longwave climate feedbacks",2013,"10.1175/JCLI-D-13-00025.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884952414&doi=10.1175%2fJCLI-D-13-00025.1&partnerID=40&md5=782f8cdbe2c1b7e37801953795f63c94","This paper mainly addresses two issues that concern the longwave climate feedbacks. First, it is recognized that the radiative forcing of greenhouse gases, as measured by their impact on the outgoing longwave radiation (OLR), may vary across different climate models even when the concentrations of these gases are identically prescribed. This forcing variation contributes to the discrepancy in these models' projections of surface warming.Amethod is proposed to account for this effect in diagnosing the sensitivity and feedbacks in the models. Second, it is shown that the stratosphere is an important factor that affects the OLR in transient climate change. Stratospheric water vapor and temperature changes may both act as a positive feedback mechanism during global warming and cannot be fully accounted as a ""stratospheric adjustment"" of radiative forcing. Neglecting these two issues may cause a bias in the longwave cloud feedback diagnosed as a residual term in the decomposition of OLR variations. There is no consensus among the climate models on the sign of the longwave cloud feedback after accounting for both issues. © 2013 American Meteorological Society."
"6603422104;7004540083;7601318782;55366637500;","Global weather states and their properties from passive and active satellite cloud retrievals",2013,"10.1175/JCLI-D-13-00024.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884916054&doi=10.1175%2fJCLI-D-13-00024.1&partnerID=40&md5=41c66f60a4daa3cc04447f6e0f167efb","In this study, the authors apply a clustering algorithm to International Satellite Cloud Climatology Project (ISCCP) cloud optical thickness-cloud top pressure histograms in order to derive weather states (WSs) for the global domain. The cloud property distribution within each WS is examined and the geographical variability of eachWSis mapped. Once the global WSs are derived, a combination of CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) vertical cloud structure retrievals is used to derive the vertical distribution of the cloud field within each WS. Finally, the dynamic environment and the radiative signature of the WSs are derived and their variability is examined. The cluster analysis produces a comprehensive description of global atmospheric conditions through the derivation of 11 WSs, each representing a distinct cloud structure characterized by the horizontal distribution of cloud optical depth and cloud top pressure. Matching those distinct WSs with cloud vertical profiles derived from CloudSat and CALIPSO retrievals shows that the ISCCP WSs exhibit unique distributions of vertical layering that correspond well to the horizontal structure of cloud properties. Matching the derived WSs with vertical velocity measurements shows a normal progression in dynamic regime when moving from the most convective to the least convective WS. Time trend analysis of the WSs shows a sharp increase of the fair-weatherWS in the 1990s and a flattening of that increase in the 2000s. The fact that the fair-weather WS is the one with the lowest cloud radiative cooling capability implies that this behavior has contributed excess radiative warming to the global radiative budget during the 1990s. © 2013 American Meteorological Society."
"48661551300;7403931916;7201826462;6701606453;6603081424;6602513845;7005729142;7102018821;","Influence of ice particle surface roughening on the global cloud radiative effect",2013,"10.1175/JAS-D-13-020.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884940988&doi=10.1175%2fJAS-D-13-020.1&partnerID=40&md5=7af5e18f0ff4ba4d72f83f5a62960936","Ice clouds influence the climate system by changing the radiation budget and large-scale circulation. Therefore, climate models need to have an accurate representation of ice clouds and their radiative effects. In this paper, new broadband parameterizations for ice cloud bulk scattering properties are developed for severely roughened ice particles. The parameterizations are based on a general habit mixture that includes nine habits (droxtals, hollow/solid columns, plates, solid/hollow bullet rosettes, aggregate of solid columns, and small/large aggregates of plates). The scattering properties for these individual habits incorporate recent advances in light-scattering computations. The influence of ice particle surface roughness on the ice cloud radiative effect is determined through simulations with the Fu-Liou and the GCM version of the Rapid Radiative Transfer Model (RRTMG) codes and the National Center for Atmospheric Research Community Atmosphere Model (CAM, version 5.1). The differences in shortwave (SW) and longwave (LW) radiative effect at both the top of the atmosphere and the surface are determined for smooth and severely roughened ice particles. While the influence of particle roughening on the single-scattering properties is negligible in the LW, the results indicate that ice crystal roughness can change the SW forcing locally by more than 10Wm-2 over a range of effective diameters. The global-averaged SW cloud radiative effect due to ice particle surface roughness is estimated to be roughly 1-2Wm-22. The CAM results indicate that ice particle roughening can result in a large regional SW radiative effect and a small but nonnegligible increase in the global LW cloud radiative effect. © 2013 American Meteorological Society."
"7003663939;55820874100;55872274100;55871758100;","Evolving land-atmosphere interactions over North America from CMIP5 simulations",2013,"10.1175/JCLI-D-12-00454.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884962983&doi=10.1175%2fJCLI-D-12-00454.1&partnerID=40&md5=eb1089391f2b2f57dbec06cde7e12aef","Long-term changes in land-atmosphere interactions during spring and summer are examined over North America. A suite of models from phase 5 of the Coupled Model Intercomparison Project simulating preindustrial, historical, and severe future climate change scenarios are examined for changes in soil moisture, surface fluxes, atmospheric boundary layer characteristics, and metrics of land-atmosphere coupling. Simulations of changes from preindustrial to modern conditions show warming brings stronger surface fluxes at high latitudes, while subtropical regions of North America respond with drier conditions. There is a clear anthropogenic aerosol response in midlatitudes that reduces surface radiation and heat fluxes, leading to shallower boundary layers and lower cloud base. Over the Great Plains, the signal does not reflect a purely radiatively forced response, showing evidence that the expansion of agriculture may have offset the aerosol impacts on the surface energy and water cycle. Future changes show soils are projected to dry across North America, even though precipitation increases north of a line that retreats poleward from spring to summer. Latent heat flux also has a north-south dipole of change, increasing north and decreasing south of a line that also moves northward with the changing season. Metrics of land-atmosphere feedback increase over most of the continent but are strongest where latent heat flux increases in the same location and season where precipitation decreases. Combined with broadly elevated cloud bases and deeper boundary layers, land-atmosphere interactions are projected to become more important in the future with possible consequences for seasonal climate prediction. © 2013 American Meteorological Society."
"57198945375;57203579757;57205302128;7102080550;","Object-based evaluation of the impact of horizontal grid spacing on convection-allowing forecasts",2013,"10.1175/MWR-D-13-00027.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884949876&doi=10.1175%2fMWR-D-13-00027.1&partnerID=40&md5=cb963351482a9c23212953ad0b7825ae","Forecasts generated by the Center for Analysis and Prediction of Storms with 1- and 4-km grid spacing using the Advanced Research Weather Research and Forecasting Model (ARW-WRF; ARW1 and ARW4, respectively) for the 2009-11 NOAA Hazardous Weather Testbed Spring Experiments are compared and verified. Object-based measures, including average values of object attributes, the object-based threat score (OTS), and the median of maximum interest (MMI) are used for the verification. Verification was first performed against observations at scales resolvable by each forecast model and then performed at scales resolvable by both models by remapping ARW1 to the ARW4 grid (ARW1to4). Thirty-hour forecasts of 1-h accumulated precipitation initialized at 0000 UTC on 22, 36, and 33 days during the spring of 2009, 2010, and 2011, respectively, are evaluated over a domain covering most of the central and eastern United States. ARW1, ARW1to4, and ARW4 all significantly overforecasted the number of objects during diurnal convection maxima. The overforecasts by ARW1 and ARW1to4 were more pronounced than ARW4 during the first convection maximum at 1-h lead time. The average object area and aspect ratio were closer to observations for ARW1 and ARW1to4 than for ARW4. None of the models showed a significant advantage over the others for average orientation angle and centroid location. Increased accuracy for ARW1, compared to ARW4, was statistically significant for the MMI but not the OTS. However, ARW1to4 had similar MMI and OTS as ARW4 at most lead times. These results are consistent with subjective evaluations that the greatest impact of grid spacing is on the smallest resolvable objects. © 2013 American Meteorological Society."
"55889449500;8266492600;6603760227;6701344775;","Evaluating and quantifying the climate-driven interannual variability in global inventory modeling and mapping studies (GIMMS) normalized difference vegetation index (NDVI3g) at global scales",2013,"10.3390/rs5083918","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884775910&doi=10.3390%2frs5083918&partnerID=40&md5=352a8e9e3835dc77c22b65d449d32f08","Satellite observations of surface reflected solar radiation contain information about variability in the absorption of solar radiation by vegetation. Understanding the causes of variability is important for models that use these data to drive land surface fluxes or for benchmarking prognostic vegetation models. Here we evaluated the interannual variability in the new 30.5-year long global satellite-derived surface reflectance index data, Global Inventory Modeling and Mapping Studies normalized difference vegetation index (GIMMS NDVI3g). Pearson's correlation and multiple linear stepwise regression analyses were applied to quantify the NDVI interannual variability driven by climate anomalies, and to evaluate the effects of potential interference (snow, aerosols and clouds) on the NDVI signal. We found ecologically plausible strong controls on NDVI variability by antecedent precipitation and current monthly temperature with distinct spatial patterns. Precipitation correlations were strongest for temperate to tropical water limited herbaceous systems where in some regions and seasons > 40% of the NDVI variance could be explained by precipitation anomalies. Temperature correlations were strongest in northern mid- to high-latitudes in the spring and early summer where up to 70% of the NDVI variance was explained by temperature anomalies. We find that, in western and central North America, winter-spring precipitation determines early summer growth while more recent precipitation controls NDVI variability in late summer. In contrast, current or prior wet season precipitation anomalies were correlated with all months of NDVI in sub-tropical herbaceous vegetation. Snow, aerosols and clouds as well as unexplained phenomena still account for part of the NDVI variance despite corrections. Nevertheless, this study demonstrates that GIMMS NDVI3g represents real responses of vegetation to climate variability that are useful for global models. © 2013 by the authors."
"55234835700;6506539438;","Large differences in reanalyses of diabatic heating in the tropical upper troposphere and lower stratosphere",2013,"10.5194/acp-13-9565-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884738171&doi=10.5194%2facp-13-9565-2013&partnerID=40&md5=a33624decfe9c7c2b046c34fa2483a72","We present the time mean heat budgets of the tropical upper troposphere (UT) and lower stratosphere (LS) as simulated by five reanalysis models: the Modern-Era Retrospective Analysis for Research and Applications (MERRA), European Reanalysis (ERA-Interim), Climate Forecast System Reanalysis (CFSR), Japanese 25-yr Reanalysis and Japan Meteorological Agency Climate Data Assimilation System (JRA-25/JCDAS), and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1. The simulated diabatic heat budget in the tropical UTLS differs significantly from model to model, with substantial implications for representations of transport and mixing. Large differences are apparent both in the net heat budget and in all comparable individual components, including latent heating, heating due to radiative transfer, and heating due to parameterised vertical mixing. We describe and discuss the most pronounced differences. Discrepancies in latent heating reflect continuing difficulties in representing moist convection in models. Although these discrepancies may be expected, their magnitude is still disturbing. We pay particular attention to discrepancies in radiative heating (which may be surprising given the strength of observational constraints on temperature and tropospheric water vapour) and discrepancies in heating due to turbulent mixing (which have received comparatively little attention). The largest differences in radiative heating in the tropical UTLS are attributable to differences in cloud radiative heating, but important systematic differences are present even in the absence of clouds. Local maxima in heating and cooling due to parameterised turbulent mixing occur in the vicinity of the tropical tropopause. © Author(s) 2013."
"6506316395;53463999600;8318179400;57203053544;","Evaluating satellite products for precipitation estimation in mountain regions: A case study for Nepal",2013,"10.3390/rs5084107","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884781772&doi=10.3390%2frs5084107&partnerID=40&md5=0765cd3d73e8b10cdd816f87ed71ac2f","Precipitation in mountain regions is often highly variable and poorly observed, limiting abilities to manage water resource challenges. Here, we evaluate remote sensing and ground station-based gridded precipitation products over Nepal against weather station precipitation observations on a monthly timescale. We find that the Tropical Rainfall Measuring Mission (TRMM) 3B-43 precipitation product exhibits little mean bias and reasonable skill in giving precipitation over Nepal. Compared to station observations, the TRMM precipitation product showed an overall Nash-Sutcliffe efficiency of 0.49, which is similar to the skill of the gridded station-based product Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation ofWater Resources (APHRODITE). The other satellite precipitation products considered (Global Satellite Mapping of Precipitation (GSMaP), the Climate Prediction Center Morphing technique (CMORPH), Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS)) were less skillful, as judged by Nash-Sutcliffe efficiency, and, on average, substantially underestimated precipitation compared to station observations, despite their, in some cases, higher nominal spatial resolution compared to TRMM. None of the products fully captured the dependence of mean precipitation on elevation seen in the station observations. Overall, the TRMM product is promising for use in water resources applications. © 2013 by the authors."
"7201472576;24280225800;36523706800;9233045100;24472110700;56597778200;26635422600;15069732800;6701681289;6701410329;24340241400;","CLARA-A1: A cloud, albedo, and radiation dataset from 28 yr of global AVHRR data",2013,"10.5194/acp-13-5351-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884413083&doi=10.5194%2facp-13-5351-2013&partnerID=40&md5=6b6f1f1cb8b00d64fa76a89c14b1d3f4","A new satellite-derived climate dataset - denoted CLARA-A1 (""The CM SAF cLoud, Albedo and RAdiation dataset from AVHRR data"") - is described. The dataset covers the 28 yr period from 1982 until 2009 and consists of cloud, surface albedo, and radiation budget products derived from the AVHRR (Advanced Very High Resolution Radiometer) sensor carried by polar-orbiting operational meteorological satellites. Its content, anticipated accuracies, limitations, and potential applications are described. The dataset is produced by the EUMETSAT Climate Monitoring Satellite Application Facility (CM SAF) project. The dataset has its strengths in the long duration, its foundation upon a homogenized AVHRR radiance data record, and in some unique features, e.g. the availability of 28 yr of summer surface albedo and cloudiness parameters over the polar regions. Quality characteristics are also well investigated and particularly useful results can be found over the tropics, mid to high latitudes and over nearly all oceanic areas. Being the first CM SAF dataset of its kind, an intensive evaluation of the quality of the datasets was performed and major findings with regard to merits and shortcomings of the datasets are reported. However, the CM SAF's long-term commitment to perform two additional reprocessing events within the time frame 2013-2018 will allow proper handling of limitations as well as upgrading the dataset with new features (e.g. uncertainty estimates) and extension of the temporal coverage. © Author(s) 2013."
"7004741583;9841756200;7101899588;6602638842;55613234903;7005900836;7003272339;6603604042;6603102974;57192202375;9233141200;","Why unprecedented ozone loss in the Arctic in 2011? Is it related to climate change?",2013,"10.5194/acp-13-5299-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884271110&doi=10.5194%2facp-13-5299-2013&partnerID=40&md5=3f7a9db6de780ac4a1ce07287861be22","An unprecedented ozone loss occurred in the Arctic in spring 2011. The details of the event are revisited from the twice-daily total ozone and NO 2 column measurements of the eight SAOZ/NDACC (Système d'Analyse par Observation Zénithale/Network for Detection of Atmospheric Composition Changes) stations in the Arctic. It is shown that the total ozone depletion in the polar vortex reached 38% (approx. 170 DU) by the end of March, which is larger than the 30% of the previous record in 1996. Aside from the long extension of the cold stratospheric NAT PSC period, the amplitude of the event is shown to be resulting from a record daily total ozone loss rate of 0.7%d -1 after mid-February, never seen before in the Arctic but similar to that observed in the Antarctic over the last 20 yr. This high loss rate is attributed to the absence of NOx in the vortex until the final warming, in contrast to all previous winters where, as shown by the early increase of NO2 diurnal increase, partial renoxification occurs by import of NOx or HNO3 from the outside after minor warming episodes, leading to partial chlorine deactivation. The cause of the absence of renoxification and thus of high loss rate, is attributed to a vortex strength similar to that of the Antarctic but never seen before in the Arctic. The total ozone reduction on 20 March was identical to that of the 2002 Antarctic winter, which ended around 20 September, and a 15-day extension of the cold period would have been enough to reach the mean yearly amplitude of the Antarctic ozone hole. However there is no sign of trend since 1994, either in PSC (polar stratospheric cloud) volume (volume of air cold enough to allow formation of PSCs), early winter denitrification, late vortex renoxification, and vortex strength or in total ozone loss. The unprecedented large Arctic ozone loss in 2011 appears to result from an extreme meteorological event and there is no indication of possible strengthening related to climate change. © Author(s) 2013."
"57204297539;7404441387;6701623059;24074386100;7102707599;57202245193;6603760227;7201903057;7006359209;","Recent declines in warming and vegetation greening trends over pan-arctic tundra",2013,"10.3390/rs5094229","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884690956&doi=10.3390%2frs5094229&partnerID=40&md5=d37f1167da59cf9b9c695a913ca8ad08","Vegetation productivity trends for the Arctic tundra are updated for the 1982-2011 period and examined in the context of land surface temperatures and coastal sea ice. Understanding mechanistic links between vegetation and climate parameters contributes to model advancements that are necessary for improving climate projections. This study employs remote sensing data: Global Inventory Modeling and Mapping Studies (GIMMS) Maximum Normalized Difference Vegetation Index (MaxNDVI), Special Sensor Microwave Imager (SSM/I) sea-ice concentrations, and Advanced Very High Resolution Radiometer (AVHRR) radiometric surface temperatures. Spring sea ice is declining everywhere except in the Bering Sea, while summer open water area is increasing throughout the Arctic. Summer Warmth Index (SWI-sum of degree months above freezing) trends from 1982 to 2011 are positive around Beringia but are negative over Eurasia from the Barents to the Laptev Seas and in parts of northern Canada. Eastern North America continues to show increased summer warmth and a corresponding steady increase in MaxNDVI. Positive MaxNDVI trends from 1982 to 2011 are generally weaker compared to trends from 1982-2008. So to better understand the changing trends, break points in the time series were quantified using the Breakfit algorithm. The most notable break points identify declines in SWI since 2003 in Eurasia and 1998 in Western North America. The Time Integrated NDVI (TI-NDVI, sum of the biweekly growing season values of MaxNDVI) has declined since 2005 in Eurasia, consistent with SWI declines. Summer (June-August) sea level pressure (slp) averages from 1999-2011 were compared to those from 1982-1998 to reveal higher slp over Greenland and the western Arctic and generally lower pressure over the continental Arctic in the recent period. This suggests that the large-scale circulation is likely a key contributor to the cooler temperatures over Eurasia through increased summer cloud cover and warming in Eastern North America from more cloud-free skies. © 2013 by the authors; licensee MDPI, Basel, Switzerland."
"55383124200;7004315232;7201463831;55880364500;","Stereoscopic height and wind retrievals for aerosol plumes with the MISR INteractive eXplorer (MINX)",2013,"10.3390/rs5094593","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884679984&doi=10.3390%2frs5094593&partnerID=40&md5=47dbc1a8eaf82acc2040c37888f377ef","The Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the Terra satellite acquires imagery at 275-m resolution at nine angles ranging from 0° (nadir) to 70° off-nadir. This multi-angle capability facilitates the stereoscopic retrieval of heights and motion vectors for clouds and aerosol plumes. MISR's operational stereo product uses this capability to retrieve cloud heights and winds for every satellite orbit, yielding global coverage every nine days. The MISR INteractive eXplorer (MINX) visualization and analysis tool complements the operational stereo product by providing users the ability to retrieve heights and winds locally for detailed studies of smoke, dust and volcanic ash plumes, as well as clouds, at higher spatial resolution and with greater precision than is possible with the operational product or with other space-based, passive, remote sensing instruments. This ability to investigate plume geometry and dynamics is becoming increasingly important as climate and air quality studies require greater knowledge about the injection of aerosols and the location of clouds within the atmosphere. MINX incorporates features that allow users to customize their stereo retrievals for optimum results under varying aerosol and underlying surface conditions. This paper discusses the stereo retrieval algorithms and retrieval options in MINX, and provides appropriate examples to explain how the program can be used to achieve the best results. © 2013 by the authors; licensee MDPI, Basel, Switzerland."
"7201485519;7005056279;","Coupling between subtropical cloud feedback and the local hydrological cycle in a climate model",2013,"10.1007/s00382-012-1608-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884703264&doi=10.1007%2fs00382-012-1608-5&partnerID=40&md5=5f179f1a730f7c8248480832cf35cd81","In HadGEM2-A, AMIP experiments forced with observed sea surface temperatures respond to uniform and patterned +4 K SST perturbations with strong positive cloud feedbacks in the subtropical stratocumulus/trade cumulus transition regions. Over the subtropical Northeast Pacific at 137°W/26°N, the boundary layer cloud fraction reduces considerably in the AMIP +4 K patterned SST experiment. The near-surface wind speed and the air-sea temperature difference reduces, while the near-surface relative humidity increases. These changes limit the local increase in surface evaporation to just 3 W/m2 or 0.6 %/K. Previous studies have suggested that increases in surface evaporation may be required to maintain maritime boundary layer cloud in a warmer climate. This suggests that the supply of water vapour from surface evaporation may not be increasing enough to maintain the low level cloud fraction in the warmer climate in HadGEM2-A. Sensitivity tests which force the surface evaporation to increase substantially in the +4 K patterned SST experiment result in smaller changes in boundary layer cloud and a weaker cloud feedback in HadGEM2-A, supporting this idea. Although global mean surface evaporation in climate models increases robustly with global temperature (and the resulting increase in atmospheric radiative cooling), local values may increase much less, having a significant impact on cloud feedback. These results suggest a coupling between cloud feedback and the hydrological cycle via changes in the patterns of surface evaporation. A better understanding of both the factors controlling local changes in surface evaporation and the sensitivity of clouds to such changes may be required to understand the reasons for inter-model differences in subtropical cloud feedback. © 2012 Crown Copyright."
"57197187873;23988281600;57190732418;7003481980;56157920300;","Statistical-dynamical modeling of the cloud-to-ground lightning activity in Portugal",2013,"10.1016/j.atmosres.2013.04.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878383432&doi=10.1016%2fj.atmosres.2013.04.010&partnerID=40&md5=e61a357d9bb9b6374569b23829071a0d","The present study employs a dataset of cloud-to-ground discharges over Portugal, collected by the Portuguese lightning detection network in the period of 2003-2009, to identify dynamically coherent lightning regimes in Portugal and to implement a statistical-dynamical modeling of the daily discharges over the country. For this purpose, the high-resolution MERRA reanalysis is used. Three lightning regimes are then identified for Portugal: WREG, WREM and SREG. WREG is a typical cold-core cut-off low. WREM is connected to strong frontal systems driven by remote low pressure systems at higher latitudes over the North Atlantic. SREG is a combination of an inverted trough and a mid-tropospheric cold-core nearby Portugal. The statistical-dynamical modeling is based on logistic regressions (statistical component) developed for each regime separately (dynamical component). It is shown that the strength of the lightning activity (either strong or weak) for each regime is consistently modeled by a set of suitable dynamical predictors (65-70% of efficiency). The difference of the equivalent potential temperature in the 700-500. hPa layer is the best predictor for the three regimes, while the best 4-layer lifted index is still important for all regimes, but with much weaker significance. Six other predictors are more suitable for a specific regime. For the purpose of validating the modeling approach, a regional-scale climate model simulation is carried out under a very intense lightning episode. © 2013 Elsevier B.V."
"36701716800;7005659017;26535270500;","Lidar investigation of tropical nocturnal boundary layer aerosols and cloud macrophysics",2013,"10.1016/j.atmosres.2013.05.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879179922&doi=10.1016%2fj.atmosres.2013.05.007&partnerID=40&md5=bf82ca26b4c885ba22632b5d53ded0d2","Observational evidence of two-way association between nocturnal boundary layer aerosols and cloud macrophysical properties over a tropical urban site is reported in this paper. The study has been conducted during 2008-09 employing a high space-time resolution polarimetric micro-pulse lidar over a tropical urban station in India. Firstly, the study highlights the crucial role of boundary layer aerosols and background meteorology on the formation and structure of low-level stratiform clouds in the backdrop of different atmospheric stability conditions. Turbulent mixing induced by the wind shear at the station, which is associated with a complex terrain, is found to play a pivotal role in the formation and structural evolution of nocturnal boundary layer clouds. Secondly, it is shown that the trapping of energy in the form of outgoing terrestrial radiation by the overlying low-level clouds can enhance the aerosol mixing height associated with the nocturnal boundary layer. To substantiate this, the long-wave heating associated with cloud capping has been quantitatively estimated in an indirect way by employing an Advanced Research Weather Research and Forecasting (WRF-ARW) model developed by National Center for Atmospheric Research (NCAR), Colorado, USA, and supplementary data sets; and differentiated against other heating mechanisms. The present investigation as well establishes the potential of lidar remote-sensing technique in exploring some of the intriguing aspects of the cloud-environment relationship. © 2013 Elsevier B.V."
"24344645000;57217455138;55580855300;","Estimation of global radiation in China and comparison with satellite product",2013,"10.1007/s12665-013-2255-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884903721&doi=10.1007%2fs12665-013-2255-9&partnerID=40&md5=98a5c9bf7394ec2e1a14d504a4b6041f","A modified solar radiation model, incorporating into several satellites remote sensing information such as NCEP/NCAR data, EOS-AURA satellite data, and Chinese FY-2C geo-stationary meteorological satellite data, is presented. The model is an attempt to modify Chen's radiation model and examine its estimation accuracy at various places in six different climatic zones of China. The verification of model is also carried out by comparing between calculated radiation value using modified model and radiation product of FY-2C satellites. According to the NSE values, the adaptability of model is reasonably high in Mid-Temperate Zone (MTZ), Warm Temperate Zone (WTZ), Tibetan Plateau Zone (TPZ), and Cold Temperature Zone (CTZ) climate regimes and slightly low in Subtropical Zone (SZ) and Tropical Zone (TZ) climate regimes. The comparison between modeled radiation values and FY-2C radiation product values shows that the radiation product of FY-2C satellites is superior to the modified model in SZ and TZ climate regimes. © 2013 Springer-Verlag Berlin Heidelberg."
"55898865500;7102128820;14044758700;","A method to diagnose boundary-layer type using doppler lidar",2013,"10.1002/qj.2068","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886306748&doi=10.1002%2fqj.2068&partnerID=40&md5=bf84f7515bb3095f6fbaada867ad1780","A new technique for objective classification of boundary layers is applied to ground-based vertically pointing Doppler lidar and sonic anemometer data. The observed boundary layer has been classified into nine different types based on those in the Met Office 'Lock' scheme, using vertical velocity variance and skewness, along with attenuated backscatter coefficient and surface sensible heat flux. This new probabilistic method has been applied to three years of data from Chilbolton Observatory in southern England and a climatology of boundary-layer type has been created. A clear diurnal cycle is present in all seasons. The most common boundary-layer type is stable with no cloud (30.0% of the dataset). The most common unstable type is well mixed with no cloud (15.4%). Decoupled stratocumulus is the third most common boundary-layer type (10.3%) and cumulus under stratocumulus occurs 1.0% of the time. The occurrence of stable boundary-layer types is much higher in the winter than the summer and boundary-layer types capped with cumulus cloud are more prevalent in the warm seasons. The most common diurnal evolution of boundary-layer types, occurring on 52 days of our three-year dataset, is that of no cloud with the stability changing from stable to unstable during daylight hours. These results are based on 16393 hours, 62.4% of the three-year dataset, of diagnosed boundary-layer type. This new method is ideally suited to long-term evaluation of boundary-layer type parametrisations in weather forecast and climate models. © 2013 Royal Meteorological Society."
"7101899854;7103294028;7402933297;57209178256;7004899626;35203432500;7005399437;55555383300;55330758500;6602406924;7202485447;7404548584;6507884489;57213358341;7004775578;8452628000;7003928082;18635289400;56265041500;16551540700;38461113600;24344796300;7006453841;23012437100;56135632400;36013189400;26661481400;55053404100;","From BASE-ASIA toward 7-SEAS: A satellite-surface perspective of boreal spring biomass-burning aerosols and clouds in Southeast Asia",2013,"10.1016/j.atmosenv.2012.12.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882679419&doi=10.1016%2fj.atmosenv.2012.12.013&partnerID=40&md5=3c4e838f681c256225a4e5202549d7a8","In this paper, we present recent field studies conducted by NASA's SMART-COMMIT (and ACHIEVE, to be operated in 2013) mobile laboratories, jointly with distributed ground-based networks (e.g., AERONET, http://aeronet.gsfc.nasa.gov/ and MPLNET, http://mplnet.gsfc.nasa.gov/) and other contributing instruments over northern Southeast Asia. These three mobile laboratories, collectively called SMARTLabs (cf. http://smartlabs.gsfc.nasa.gov/, Surface-based Mobile Atmospheric Research & Testbed Laboratorie. s) comprise a suite of surface remote sensing and in-situ instruments that are pivotal in providing high spectral and temporal measurements, complementing the collocated spatial observations from various Earth Observing System (EOS) satellites. A satellite-surface perspective and scientific findings, drawn from the BASE-ASIA (2006) field deployment as well as a series of ongoing 7-SEAS (2010-13) field activities over northern Southeast Asia are summarized, concerning (i) regional properties of aerosols from satellite and in-situ measurements, (ii) cloud properties from remote sensing and surface observations, (iii) vertical distribution of aerosols and clouds, and (iv) regional aerosol radiative effects and impact assessment. The aerosol burden over Southeast Asia in boreal spring, attributed to biomass burning, exhibits highly consistent spatial and temporal distribution patterns, with major variability arising from changes in the magnitude of the aerosol loading mediated by processes ranging from large-scale climate factors to diurnal meteorological events. Downwind from the source regions, the tightly coupled-aerosol-cloud system provides a unique, natural laboratory forfurther exploring the micro- and macro-scale relationships of the complex interactions. The climatic significance is presented through large-scale anti-correlations between aerosol and precipitation anomalies, showing spatial and seasonal variability, but their precise cause-and-effect relationships remain an open-ended question. To facilitate an improved understanding of the regional aerosol radiative effects, which continue to be one of the largest uncertainties in climate forcing, a joint international effort is required and anticipated to commence in springtime 2013 in northern SoutheastAsia. © 2012."
"35570389600;56575686800;7201485519;","An explanation for the difference between twentieth and twenty-first century land-sea warming ratio in climate models",2013,"10.1007/s00382-013-1664-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884704730&doi=10.1007%2fs00382-013-1664-5&partnerID=40&md5=47cd923a2366d33436480f2c071bc783","A land-sea surface warming ratio (or φ) that exceeds unity is a robust feature of both observed and modelled climate change. Interestingly, though climate models have differing values for φ, it remains almost time-invariant for a wide range of twenty-first century climate transient warming scenarios, while varying in simulations of the twentieth century. Here, we present an explanation for time-invariant land-sea warming ratio that applies if three conditions on radiative forcing are met: first, spatial variations in the climate forcing must be sufficiently small that the lower free troposphere warms evenly over land and ocean; second, the temperature response must not be large enough to change the global circulation to zeroth order; third, the temperature response must not be large enough to modify the boundary layer amplification mechanisms that contribute to making φ exceed unity. Projected temperature changes over this century are too small to breach the latter two conditions. Hence, the mechanism appears to show why both twenty-first century and time-invariant CO2 forcing lead to similar values of φ in climate models despite the presence of transient ocean heat uptake, whereas twentieth century forcing-which has a significant spatially confined anthropogenic tropospheric aerosol component that breaches the first condition-leads to modelled values of φ that vary widely amongst models and in time. Our results suggest an explanation for the behaviour of φ when climate is forced by other regionally confined forcing scenarios such as geo-engineered changes to oceanic clouds. Our results show how land-sea contrasts in surface and boundary layer characteristics act in tandem to produce the land-sea surface warming contrast. © 2013 Springer-Verlag Berlin Heidelberg."
"35177669200;6508026916;36457573700;36661106500;36457432800;39361670300;","A multi-physics ensemble of regional climate change projections over the Iberian Peninsula",2013,"10.1007/s00382-012-1551-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884698670&doi=10.1007%2fs00382-012-1551-5&partnerID=40&md5=5556e9247f24b3cfca467b5aab1fc3c6","This study illustrates the sensitivity of regional climate change projections to the model physics. A single-model (MM5) multi-physics ensemble of regional climate simulations over the Iberian Peninsula for present (1970-1999) and future (2070-2099 under the A2 scenario) periods is assessed. The ensemble comprises eight members resulting from the combination of two options of parameterization schemes for the planetary boundary layer, cumulus and microphysics. All the considered combinations were previously evaluated by comparing hindcasted simulations to observations, none of them providing clearly outlying climates. Thus, the differences among the various ensemble members (spread) in the future projections could be considered as a matter of uncertainty in the change signals (as similarly assumed in multi-model studies). The results highlight the great dependence of the spread on the synoptic conditions driving the regional model. In particular, the spread generally amplifies under the future scenario leading to a large spread accompanying the mean change signals, as large as the magnitude of the mean projected changes and analogous to the spread obtained in multi-model ensembles. Moreover, the sign of the projected change varies depending on the choice of the model physics in many cases. This, together with the fact that the key mechanisms identified for the simulation of the climatology of a given period (either present or future) and those introducing the largest spread in the projected changes differ significantly, make further claims for efforts to better understand and model the parameterized subgrid processes. © 2012 Springer-Verlag Berlin Heidelberg."
"55233965300;7403013913;36162966700;13406764900;7006234839;37019252000;55171972400;","History matching for exploring and reducing climate model parameter space using observations and a large perturbed physics ensemble",2013,"10.1007/s00382-013-1896-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884702226&doi=10.1007%2fs00382-013-1896-4&partnerID=40&md5=cfa6a2fb00cb2b91f3c06d97074d77ed","We apply an established statistical methodology called history matching to constrain the parameter space of a coupled non-flux-adjusted climate model (the third Hadley Centre Climate Model; HadCM3) by using a 10,000-member perturbed physics ensemble and observational metrics. History matching uses emulators (fast statistical representations of climate models that include a measure of uncertainty in the prediction of climate model output) to rule out regions of the parameter space of the climate model that are inconsistent with physical observations given the relevant uncertainties. Our methods rule out about half of the parameter space of the climate model even though we only use a small number of historical observations. We explore 2 dimensional projections of the remaining space and observe a region whose shape mainly depends on parameters controlling cloud processes and one ocean mixing parameter. We find that global mean surface air temperature (SAT) is the dominant constraint of those used, and that the others provide little further constraint after matching to SAT. The Atlantic meridional overturning circulation (AMOC) has a non linear relationship with SAT and is not a good proxy for the meridional heat transport in the unconstrained parameter space, but these relationships are linear in our reduced space. We find that the transient response of the AMOC to idealised CO2 forcing at 1 and 2 % per year shows a greater average reduction in strength in the constrained parameter space than in the unconstrained space. We test extended ranges of a number of parameters of HadCM3 and discover that no part of the extended ranges can by ruled out using any of our constraints. Constraining parameter space using easy to emulate observational metrics prior to analysis of more complex processes is an important and powerful tool. It can remove complex and irrelevant behaviour in unrealistic parts of parameter space, allowing the processes in question to be more easily studied or emulated, perhaps as a precursor to the application of further relevant constraints. © 2013 Springer-Verlag Berlin Heidelberg."
"9044746800;7103016965;6602081215;7102603429;7101653556;6603107733;22834248200;21933618400;7103197731;","The effective density of small ice particles obtained from in situ aircraft observations of mid-latitude cirrus",2013,"10.1002/qj.2058","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886239042&doi=10.1002%2fqj.2058&partnerID=40&md5=7dfaeb15fa9e3e304e2dbaf2edb85306","The effective ice-particle density, parametrized through a mass-dimension relation, is widely used in ice microphysical schemes for weather and climate models. In this study, we use aircraft-based observations in mid-latitude cirrus taken during the Constrain field programme in 2010. The low temperatures and a humidity often close to ice saturation meant that the typical ice particles observed were small (maximum dimension 20-800 μm) and ice water contents were low (0.001-0.05 g m-3). Two new instruments are included in this study: the Small Ice Detector Mark-2 (SID-2) and the deep-cone Nevzorov Total Water Content probe. SID-2 is a new single-particle light-scattering instrument and was used to identify and size small ice particles (10-150 μm). The deep-cone Nevzorov probe is shown to be able to collect small ice masses with sufficient sensitivity. The focus of this article is on the effective density of small ice particles (both pristine ice crystals and small aggregates up to 600 μm maximum dimension). Due to instrument limitations in previous studies, the effective density of small ice particles is questionable. Aircraft flights in six cirrus cases provided ice-particle measurements throughout the depth of the cirrus. The particle size distribution (PSD) was mostly bimodal. The smaller ice-crystal mode dominated the PSD near cloud top and the larger ice-aggregate mode dominated near cloud base. A mass-dimension relation valid for both ice crystals and aggregates was found that provided a best fit to the observations. For small ice particles (less than 70 μm diameter) the density is constant (700 kg m-3), while for larger ice crystals or aggregates the mass-dimension relation is m(D) = 0.0257D2.0. These measurements allow testing of the diagnostic split between ice crystals and aggregates used in the Met Office Unified Model. © 2012 Royal Meteorological Society and British Crown Copyright, the Met Office."
"57216427721;57194516481;7003791000;","Detection of hydrothermal alteration zones in a tropical region using satellite remote sensing data: Bau goldfield, Sarawak, Malaysia",2013,"10.1016/j.oregeorev.2013.03.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877876513&doi=10.1016%2fj.oregeorev.2013.03.010&partnerID=40&md5=96096993faaa0aefebc74ab8df4c7ef3","Remote sensing for geology in tropical environments is very challenging, because of the dense vegetation cover and the problem of persistent cloud cover. In this research paper, we have investigated and demonstrated the detection of hydrothermal alteration zones and structural elements associated with intrusion-related gold mineralization using various types of remote sensing data in the Bau gold mining district in the State of Sarawak, East Malaysia, on the island of Borneo. The climate of Bau is tropical with persistent cloud cover and very dense vegetation ground. Geological analyses coupled with remote sensing data were used to detect hydrothermally altered rocks and structural elements associated with gold mineralization in the Bau area. Landsat Enhanced Thematic Mapper+ (ETM+), Hyperion and Phased Array type L-band Synthetic Aperture Radar (PALSAR) data were used to carry out lithological-structural mapping of the mineralized zones in the study area and surrounding terrain. Hydrothermal alteration zones were detected along the SSW to NNE structural trend of the Tai Parit fault that corresponds with the occurrence of other gold mineralization in the Bau Limestone. The results show that the known gold prospects and potential areas of mineralization are recognizable by the methods used, despite limited bedrock exposure. The approach used in this study is broadly applicable to the detection of gold mineralization using ETM+, Hyperion and PALSAR data in tropical/sub-tropical regions. © 2013 Elsevier B.V."
"7202485447;7101899854;56016057500;7201381456;7003377766;16551540700;7102221568;13104873000;34969663100;8452628000;7404548584;35092526000;57218650887;57154893200;7103294028;18635289400;7005399437;49662784300;55781534800;6505894650;7410255240;55273729800;57154891500;7404967662;7401797911;24308208100;7101933764;7407038710;7403967484;7402628473;8080680100;13608654700;55936005100;36672614700;55781688500;7404861364;7501460689;","An overview of regional experiments on biomass burning aerosols and related pollutants in Southeast Asia: From BASE-ASIA and the Dongsha Experiment to 7-SEAS",2013,"10.1016/j.atmosenv.2013.04.066","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882628507&doi=10.1016%2fj.atmosenv.2013.04.066&partnerID=40&md5=ca57d2a950a08669d29e0b11f7aec65d","By modulating the Earth-atmosphere energy, hydrological and biogeochemical cycles, and affecting regional-to-global weather and climate, biomass burning is recognized as one of the major factors affecting the global carbon cycle. However, few comprehensive and wide-ranging experiments have been conducted to characterize biomass-burning pollutants in Southeast Asia (SEA) or assess their regional impact on meteorology, the hydrological cycle, the radiative budget, or climate change. Recently, BASE-ASIA (Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment) and the 7-SEAS (7-South-East Asian Studies)/Dongsha Experiment were conducted during the spring seasons of 2006 and 2010 in northern SEA, respectively, to characterize the chemical, physical, and radiative properties of biomass-burning emissions near the source regions, and assess their effects. This paper provides an overview of results from these two campaigns and related studies collected in this special issue, entitled ""Observation, modeling and impact studies of biomass burning and pollution in the SE Asian Environment"". This volume includes 28 papers, which provide a synopsis of the experiments, regional weather/climate, chemical characterization of biomass-burning aerosols and related pollutants in source and sink regions, the spatial distribution of air toxics (atmospheric mercury and dioxins) in source and remote areas, a characterization of aerosol physical, optical, and radiative properties, as well as modeling and impact studies. These studies, taken together, provide the first relatively complete dataset of aerosol chemistry and physical observations conducted in the source/sink region in the northern SEA, with particular emphasis on the marine boundary layer and lower free troposphere (LFT). The data, analysis and modeling included in these papers advance our present knowledge of source characterization of biomass-burning pollutants near the source regions as well as the physical and chemical processes along transport pathways. In addition, we raise key questions to be addressed by a coming deployment during springtime 2013 in northern SEA, named 7-SEAS/BASELInE (Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles and Interactions Experiment). This campaign will include a synergistic approach for further exploring many key atmospheric processes (e.g., complex aerosol-cloud interactions) and impacts of biomass burning on the surface-atmosphere energy budgets during the lifecycles of biomass-burning emissions. © 2013 The Authors."
"55372862700;6701846706;","Forest patches and the upward migration of timberline in the southern Peruvian Andes",2013,"10.1016/j.foreco.2013.05.041","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879727606&doi=10.1016%2fj.foreco.2013.05.041&partnerID=40&md5=c90c540b21d99968c53aab072bd2662d","Montane plant species around the globe are predicted to shift their distributions upslope in response to increasing temperatures associated with climate change. In the tropical Andes, which are one of the most diverse and threatened of all biodiversity hotspots, many plant and animal species have already started to shift their distributions to higher elevations in response to warming. However, a variety of biotic and abiotic factors may stabilize Andean timberlines and halt further upslope migrations into the high elevation grasslands (referred to as ""puna"" in southern Peru) above the forest. One possibility is that small forest patches that occur above-timberline throughout the Andes may facilitate forest expansion into newly suitable areas in the puna, yet little is known about the ecology or function of these patches. In this study, we examined seedling recruitment patterns, seed dispersal, and microclimate at the timberline, in and around above-timberline forest patches, and in the puna. The above-timberline forest patches had similar patterns of seed dispersal as the timberline but overal <1% of captured seeds were dispersed 10. m into the puna. At both the patch edges and the forest timberline, seedling abundances were lower in the puna relative to the adjacent forest and forest-puna ecotone. This reduction may be a result of reduced seed dispersal across the forest-puna ecotone and/or decreased germination of dispersed seeds due to the harsh microclimatic conditions occurring in the puna (daily temperature fluctuations are greatly elevated in the puna relative to the forest and frost events are more frequent and severe). While increasing temperatures associated with climate change may ameliorate some of the severe climatic conditions occurring in the puna, it will not directly affect other potential recruitment limitations such as reduced seed dispersal, high levels of UV radiation, and anthropogenic activities (cattle grazing and fires) in the puna. With the reduction of anthropogenic activities, above-timberline forest patches may serve as nucleating foci for future forest expansion into the puna. However, our results indicate that any upslope migration of the timberline into the puna will likely occur at a rate that is slower than what is required to keep pace with warming because recruitment is restricted to a narrow strip along the forest-puna borders. Slowed forest expansion into the puna could act as a barrier to the upslope migration of Andean cloud forest species leading to extreme losses of Andean biodiversity. © 2013 Elsevier B.V."
"6603773088;7003456370;6603141907;57203106385;7005413462;55832272900;55318043400;7005752023;","A Last Glacial Maximum through middle Holocene stalagmite record of coastal Western Australia climate",2013,"10.1016/j.quascirev.2013.07.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882783593&doi=10.1016%2fj.quascirev.2013.07.002&partnerID=40&md5=3d696477bd5225d164f6aec9b0091b8c","Stable isotope profiles of 230Th-dated stalagmites from cave C126, Cape Range Peninsula, Western Australia, provide the first high-resolution, continental paleoclimate record spanning the Last Glacial Maximum, deglaciation, and early to middle Holocene from the Indian Ocean sector of Australia. Today, rainfall at Cape Range is sparse, highly variable, and is divided more or less equally between winter and summer rains, with winter precipitation linked to northwest cloud bands and cold fronts derived from the southern mid- to high-latitudes, and summer precipitation due primarily to tropical cyclone activity. Influences of the Indo-Australian summer monsoon at Cape Range are minimal as this region lies south of the modern monsoon margin. The interaction of these atmospheric systems helps shape the environment at Cape Range, and thus C126 stalagmite-based paleoclimatic reconstructions should reflect variability in moisture source driven by changing ocean and atmospheric conditions.The C126 record reveals slow stalagmite growth and isotopically heavy oxygen isotope values during the Last Glacial Maximum, followed by increased growth rates and decreased oxygen isotopic ratios at 19ka, reaching a δ18O minimum from 17.5 to 16.0ka, coincident with Heinrich Stadial 1. The origin of this oxygen isotopic shift may reflect enhanced moisture and lower oxygen isotopic ratios due to amount effect-driven changes in rainfall δ18O values from an increase in rainfall derived from tropical cyclones or changes in northwest cloud band activity, although the controls on both systems are poorly constrained for this time period. Alternatively, lower C126 stalagmite δ18O values may have been driven by more frequent or more intense frontal systems associated with southerly-derived moisture sources, possibly in relation to meridional shifts in positioning of the southern westerlies which have been linked to southern Australia megalake highstands at this time. Finally, we also consider the possibility of contributions of tropical moisture derived from the Indo-Australian summer monsoon. The Intertropical Convergence Zone and associated monsoon trough shifted southward during Heinrich events and other periods of high northern latitude cooling, and although clearly weakened during glacial periods, rainfall with low δ18O values associated with the monsoon today suggests that even small contributions from this moisture source could have accounted for some of the observed oxygen isotopic decrease. Despite a pronounced isotopic excursion coincident with Heinrich Stadial 1, no identifiable anomaly is associated with Heinrich Stadial 2.The Holocene is also characterized by overall low δ18O values and rapid growth rates, with decreasing oxygen isotopic values during the earliest Holocene and at ~6.5ka, roughly coincident with southern Australia megalake highstands. The origins of these stalagmite oxygen isotopic shifts do not appear to reflect increases in mean annual temperature but are tied here largely to changes in the δ18O values of precipitation and may reflect a more southerly influence of the Indo-Australian summer monsoon at this time.C126 stalagmite carbon isotopic ratios offer an important complement to the oxygen isotopic time series. Stalagmite δ13C values averaged-5‰ during the Last Glacial Maximum and early deglaciation, and reached a plateau during the oxygen isotopic minimum at 17.5ka. However, δ13C values decreased sharply to-12‰ between 11 and 8ka, a shift interpreted to reflect increases in plant density in response to the onset of interglacial conditions. Stalagmite δ13C values at 6ka are lower than expected for the modern C4-dominated vegetation and thin soils of Cape Range, suggesting that a more C3-rich environment was present during elevated rainfall conditions of the early and middle Holocene. The Cape Range stalagmite time series thus reveals for the first time the millennial-scale sensitivity of the moisture source variations in northwestern Australia, a result that has implications for precipitation dynamics across much of the continent. © 2013 Elsevier Ltd."
"34979885900;6701751765;23096635200;6603150451;26323026900;6507671561;22936054800;","Exploring the faint young Sun problem and the possible climates of the Archean Earth with a 3-D GCM",2013,"10.1002/jgrd.50808","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886065268&doi=10.1002%2fjgrd.50808&partnerID=40&md5=148d9105ec48a418c20547896c1ed9ea","Different solutions have been proposed to solve the ""faint young Sun problem,"" defined by the fact that the Earth was not fully frozen during the Archean despite the fainter Sun. Most previous studies were performed with simple 1-D radiative convective models and did not account well for the clouds and ice-albedo feedback or the atmospheric and oceanic transport of energy. We apply a global climate model (GCM) to test the different solutions to the faint young Sun problem. We explore the effect of greenhouse gases (CO2 and CH4), atmospheric pressure, cloud droplet size, land distribution, and Earth's rotation rate. We show that neglecting organic haze, 100 mbar of CO2 with 2 mbar of CH4 at 3.8 Ga and 10 mbar of CO 2 with 2 mbar of CH4 at 2.5 Ga allow a temperate climate (mean surface temperature between 10°C and 20°C). Such amounts of greenhouse gases remain consistent with the geological data. Removing continents produces a warming lower than +4°C. The effect of rotation rate is even more limited. Larger droplets (radii of 17 μm versus 12 μm) and a doubling of the atmospheric pressure produce a similar warming of around +7°C. In our model, ice-free water belts can be maintained up to 25°N/S with less than 1 mbar of CO2 and no methane. An interesting cloud feedback appears above cold oceans, stopping the glaciation. Such a resistance against full glaciation tends to strongly mitigate the faint young Sun problem. Key PointsNew constraints on the amount of greenhouse gases to get a temperate climateWaterbelt can be maintained with less than 1 mbar of CO2 and no methaneThe effects of larger cloud droplets and a higher pressure are quantified ©2013. American Geophysical Union. All Rights Reserved."
"7003591311;14035836100;7102084129;16308514000;","On the relationship between cloud contact time and precipitation susceptibility to aerosol",2013,"10.1002/jgrd.50819","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886017985&doi=10.1002%2fjgrd.50819&partnerID=40&md5=f3f9a6a5b5395566e9a00b21bc449bee","The extent to which the rain rate from shallow, liquid-phase clouds is microphysically influenced by aerosol, and therefore drop concentration N d perturbations, is addressed through analysis of the precipitation susceptibility, So. Previously published work, based on both models and observations, disagrees on the qualitative behavior of So with respect to variables such as liquid water path L or the ratio between accretion and autoconversion rates. Two primary responses have emerged: (i) So decreases monotonically with increasing L and (ii) So increases with L, reaches a maximum, and decreases thereafter. Here we use a variety of modeling frameworks ranging from box models of (size-resolved) collision-coalescence, to trajectory ensembles based on large eddy simulation to explore the role of time available for collision-coalescence tc in determining the So response. The analysis shows that an increase in tc shifts the balance of rain production from autoconversion (a Nd-dependent process) to accretion (roughly independent of N d), all else (e.g., L) equal. Thus, with increasing cloud contact time, warm rain production becomes progressively less sensitive to aerosol, all else equal. When the time available for collision-coalescence is a limiting factor, So increases with increasing L whereas when there is ample time available, So decreases with increasing L. The analysis therefore explains the differences between extant studies in terms of an important precipitation-controlling parameter, namely the integrated liquid water history over the course of an air parcel's contact with a cloud. Key PointsTime-integrated liquid water determines precipitation susceptibility to aerosolRain susceptibility to aerosol is a non-monotonic function of liquid water ©2013. American Geophysical Union. All Rights Reserved."
"57213804976;7005339628;7402107243;7003775081;","Skin and bulk temperature difference at Lake Tahoe: A case study on lake skin effect",2013,"10.1002/jgrd.50786","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885982260&doi=10.1002%2fjgrd.50786&partnerID=40&md5=c8faae8153edfccaaa64433e42b0658e","Over water, infrared radiometers on satellites measure radiation leaving from the surface skin layer and therefore the retrieved temperature is representative of the skin layer. This is slightly different from the bulk layer deeper in the water where various floating thermometers take temperature measurements to validate satellite measurements. The difference between the bulk and skin temperature (skin effect) must be understood to properly validate schemes that use surface skin temperature to infer bulk temperatures. Further skin temperatures retrieved over inland waters may show different patterns to those retrieved over oceans due to differences in conditions such as wind speed, aerosols, and elevation. We have analyzed the differences between the skin and bulk temperatures at four permanent monitoring stations (buoys) located on Lake Tahoe since 1999 and compared the results with similar studies over the ocean typically obtained from boat cruises. Skin effect distributions were found to be consistent across the buoys; however, the diurnal behavior of the skin effect was slightly different and shown to be related to wind speed measured at an individual buoy. When wind speed was less than 2 m s-1, the skin temperature osclillated and greatly increased the uncertainty in the skin effect reported over Lake Tahoe. When downwelling sky radiation was increased from clouds or high humidity, this led to nighttime skin temperatures that were warmer than bulk temperatures by as much as 0.5 K. The size of the warm skin effect is larger than other ocean studies that observed warm nighttime skin values around 0.1 K. The nighttime skin effect was seen to be more consistent with a smaller standard deviation compared to the daytime skin effect. The nighttime skin behavior had a mean and standard deviation that ranged between 0.3 and 0.5 K and between 0.3 and 0.4 K, respectively. In contrast, daytime skin effect was strongly influenced by direct solar illumination and typically had a mean of 0.5 K in the morning that decreased to 0.1 K by midday. The standard deviation of the daytime skin effect ranged from 0.3 in the morning to 0.8 by midday. As the solar heating reduces later in the day the skin effect increases to a 0.3 K mean with a standard deviation of 0.4 K. The results for Lake Tahoe clearly demonstrate that validating satellite-derived skin measurements or merging multiple satellites data sets together would be most successful when using nighttime data at wind speeds greater than 2 m s-1 with greater uncertainties expected when using daytime measurements. Further, the assumptions used for the skin effect behavior over oceans may not be appropriate over lakes because of the greater range of environmental conditions that affect lakes. Key Points Daytime skin effect is driven by sunlight and local terrain-driven wind flowsNighttime skin temperatures can be used to study climate changeLake skin effect is more variable than ocean skin effect ©2013. American Geophysical Union. All Rights Reserved."
"6701592014;6603954927;7402934750;","The atmospheric radiation measurement (ARM) program network of microwave radiometers: Instrumentation, data, and retrievals",2013,"10.5194/amt-6-2359-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884470343&doi=10.5194%2famt-6-2359-2013&partnerID=40&md5=c3b1368f5858c46c51c0442121821682","The Climate Research Facility of the US Department of Energy's Atmospheric Radiation Measurement (ARM) Program operates a network of ground-based microwave radiometers. Data and retrievals from these instruments have been available to the scientific community for almost 20 yr. In the past five years the network has expanded to include a total of 22 microwave radiometers deployed in various locations around the world. The new instruments cover a frequency range between 22 and 197 GHz and are consistently and automatically calibrated. The latest addition to the network is a new generation of three-channel radiometers, currently in the early stage of deployment at all ARM sites. The network has been specifically designed to achieve increased accuracy in the retrieval of precipitable water vapor (PWV) and cloud liquid water path (LWP) with the long-term goal of providing the scientific community with reliable, calibrated radiometric data and retrievals of important geophysical quantities with well-characterized uncertainties. The radiometers provide high-quality, continuous datasets that can be utilized in a wealth of applications and scientific studies. This paper presents an overview of the microwave instrumentation, calibration procedures, data, and retrievals that are available for download from the ARM data archive. © 2013 Author(s)."
"37861539400;6507224579;","Why tropical sea surface temperature is insensitive to ocean heat transport changes",2013,"10.1175/JCLI-D-13-00192.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884221915&doi=10.1175%2fJCLI-D-13-00192.1&partnerID=40&md5=b07e5c3136f745311f3319aecce78291","Previous studies have shown that increases in poleward ocean heat transport (OHT) do not strongly affect tropical SST. The goal of this paper is to explain this observation. To do so, the authors force two atmospheric global climate models (GCMs) in aquaplanet configuration with a variety of prescribed OHTs. It is found that increased OHT weakens the Hadley circulation, which decreases equatorial cloud cover and shortwave reflection, as well as reduces surface winds and evaporation, which both limit changes in tropical SST. The authors also modify one of the GCMs by alternatively setting the radiative effect of clouds to zero and disabling wind-driven evaporation changes to show that the cloud feedback is more important than the wind-evaporation feedback for maintaining constant equatorial SST as OHT changes. This work highlights the fact that OHT can reduce the meridional SST gradient without affecting tropical SST and could therefore serve as an additional degree of freedom for explaining past warm climates. © 2013 American Meteorological Society."
"7005902717;26538420000;","Sensitivity of arctic climate variability to mean state: Insights from the cretaceous",2013,"10.1175/JCLI-D-12-00825.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884256227&doi=10.1175%2fJCLI-D-12-00825.1&partnerID=40&md5=b06abc781a710093c24dbe3cfd74f73a","This study investigates Arctic climate variability during a period of extreme warmth using the Community Climate System Model, version 3 (CCSM3) coupled ocean-atmosphere general circulation model. Four mid- Cretaceous simulations were completed with different CO2 levels (1, 10, and 16 times preindustrial levels with dynamic vegetation) and vegetation treatments (10 times with specified uniform bare ground). The magnitude and frequency of Arctic temperature variability is highly sensitive to the mean state and high-latitude upperocean static stability. As stability increases with a rise in CO2 levels from 1 to 10 times preindustrial levels, the frequency of temperature variability increases fromdecades (1x) to centuries (10x with bare ground) and longer (10x) and the peak-to-peakmagnitude increases from ~1° (for 1x) to~2°C (for 10x). In the 16x simulation with a highly stratified ocean, Arctic temperature variability is low with peak-to-peak magnitudes &lt;0.5°C. Under low CO2, Arctic climate variability is tied to sensible heat release from the ocean during movement of the sea ice margin. In absence of substantial sea ice, variability is driven by mass transport and upper-ocean salinity advection into the Arctic. In both cases, destruction of low-level clouds acts as an important feedback on lowlevel warming. The authors also report a link between unforced Arctic climate variability and North Pacific meridional overturning with warming events leading intensification. These results suggest that the nature of Arctic climate variability was likely much different in past climates and is likely to be so in the future. © 2013 American Meteorological Society."
"12769875100;26324818700;7202699757;7006518289;7005965757;55738957800;","A decomposition of feedback contributions to polar warming amplification",2013,"10.1175/JCLI-D-12-00696.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884252126&doi=10.1175%2fJCLI-D-12-00696.1&partnerID=40&md5=402313b582945f3f4bbcc6c18640a366","Polar surface temperatures are expected to warm 2-3 times faster than the global-mean surface temperature: a phenomenon referred to as polar warming amplification. Therefore, understanding the individual process contributions to the polar warming is critical to understanding global climate sensitivity. The Coupled Feedback Response Analysis Method (CFRAM) is applied to decompose the annual-and zonal-mean vertical temperature response within a transient 1% yr21 CO2 increase simulation of the NCAR Community Climate System Model, version 4 (CCSM4), into individual radiative and nonradiative climate feedback process contributions. The total transient annual-mean polar warming amplification (amplification factor) at the time of CO2 doubling is 12.12 (2.3) and 10.94K (1.6) in the Northern and Southern Hemisphere, respectively. Surface albedo feedback is the largest contributor to the annual-mean polar warming amplification accounting for 11.82 and 11.04K in the Northern and Southern Hemisphere, respectively. Net cloud feedback is found to be the second largest contributor to polar warming amplification (about 10.38K in both hemispheres) and is driven by the enhanced downward longwave radiation to the surface resulting from increases in low polar water cloud. The external forcing and atmospheric dynamic transport also contribute positively to polar warming amplification:10.29 and10.32 K, respectively. Water vapor feedback contributes negatively to polar warming amplification because its induced surface warming is stronger in low latitudes. Ocean heat transport storage and surface turbulent flux feedbacks also contribute negatively to polar warming amplification. Ocean heat transport and storage terms play an important role in reducing the warming over the Southern Ocean and Northern Atlantic Ocean. © 2013 American Meteorological Society."
"8401004800;56259852000;7005941217;7003620360;7005594499;6601922531;55895104800;55480930900;55857180100;56219012200;37661167800;6602489117;35490380800;55857038800;55479763800;6602516156;6507256381;7004557737;45061039100;36921601500;36767438100;17434636400;7003927831;34770453800;7004714883;57203513475;22979686100;48261287600;57196676725;24587715900;6603287639;6603604042;57193752496;23995745300;7101899588;7202174228;26024303900;7202607188;7102059695;36106191000;7005433221;36515307600;7404247296;8378887500;9840502200;7003355879;7102011023;56249134600;6603293852;7005453641;35472747700;7005272495;6701774457;56283402900;56216562700;7003501766;6603204132;8442084800;55469200300;6701581258;13408545500;7006471143;56187256200;27968097600;6603213300;6504028729;7003341789;15726759700;7003614389;55502590800;35867639900;43462093500;6601988288;7005124488;55857009400;36829694300;7202489497;57172205400;57189215242;55984419100;7007168548;6701772538;8586435700;56246458800;47562469600;7003765782;13607461800;55914429700;","Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions (RECONCILE): Activities and results",2013,"10.5194/acp-13-9233-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884220077&doi=10.5194%2facp-13-9233-2013&partnerID=40&md5=e145cd5d6edfc414c39ccf697e92a81b","The international research project RECONCILE has addressed central questions regarding polar ozone depletion, with the objective to quantify some of the most relevant yet still uncertain physical and chemical processes and thereby improve prognostic modelling capabilities to realistically predict the response of the ozone layer to climate change. This overview paper outlines the scope and the general approach of RECONCILE, and it provides a summary of observations and modelling in 2010 and 2011 that have generated an in many respects unprecedented dataset to study processes in the Arctic winter stratosphere. Principally, it summarises important outcomes of RECONCILE including (i) better constraints and enhanced consistency on the set of parameters governing catalytic ozone destruction cycles, (ii) a better understanding of the role of cold binary aerosols in heterogeneous chlorine activation, (iii) an improved scheme of polar stratospheric cloud (PSC) processes that includes heterogeneous nucleation of nitric acid trihydrate (NAT) and ice on non-volatile background aerosol leading to better model parameterisations with respect to denitrification, and (iv) long transient simulations with a chemistry-climate model (CCM) updated based on the results of RECONCILE that better reproduce past ozone trends in Antarctica and are deemed to produce more reliable predictions of future ozone trends. The process studies and the global simulations conducted in RECONCILE show that in the Arctic, ozone depletion uncertainties in the chemical and microphysical processes are now clearly smaller than the sensitivity to dynamic variability. © Author(s) 2013. CC Attribution 3.0 License."
"6508287655;7102797196;6603930943;55857028300;15725375400;35330367300;","Validation of Two MODIS aerosols algorithms with SKYNET and prospects for future climate satellites such as the GCOM-C/SGLI",2013,"10.1155/2013/508064","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884269016&doi=10.1155%2f2013%2f508064&partnerID=40&md5=11ca2f7b811441853a92a5053c45e395","Potential improvements of aerosols algorithms for future climate-oriented satellites such as the coming Global Change Observation Mission Climate/Second generation Global Imager (GCOM-C/SGLI) are discussed based on a validation study of three years' (2008-2010) daily aerosols properties, that is, the aerosol optical thickness (AOT) and the Ångström exponent (AE) retrieved from two MODIS algorithms. The ground-truth data used for this validation study are aerosols measurements from 3 SKYNET ground sites. The results obtained show a good agreement between the ground-truth data AOT and that of one of the satellites' algorithms, then a systematic overestimation (around 0.2) by the other satellites' algorithm. The examination of the AE shows a clear underestimation (by around 0.2-0.3) by both satellites' algorithms. The uncertainties explaining these ground-satellites' algorithms discrepancies are examined: the cloud contamination affects differently the aerosols properties (AOT and AE) of both satellites' algorithms due to the retrieval scale differences between these algorithms. The deviation of the real part of the refractive index values assumed by the satellites' algorithms from that of the ground tends to decrease the accuracy of the AOT of both satellites' algorithms. The asymmetry factor (AF) of the ground tends to increase the AE ground-satellites discrepancies as well. © 2013 Jules R. Dim et al."
"35262555900;36605450500;7005523706;7004011998;8632797000;35741822600;","Investigating the applicability of error correction ensembles of satellite rainfall products in river flow simulations",2013,"10.1175/JHM-D-12-074.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884184498&doi=10.1175%2fJHM-D-12-074.1&partnerID=40&md5=e9e4549133a217b1a706077552624c0b","This study uses a stochastic ensemble-based representation of satellite rainfall error to predict the propagation in flood simulation of three quasi-global-scale satellite rainfall products across a range of basin scales. The study is conducted on the Tar-Pamlico River basin in the southeastern United States based on 2 years of data (2004 and 2006). The NWS Multisensor Precipitation Estimator (MPE) dataset is used as the reference for evaluating three satellite rainfall products: the Tropical Rainfall Measuring Mission (TRMM) real-time 3B42 product (3B42RT), the Climate Prediction Center morphing technique (CMORPH), and the Precipitation Estimation from Remotely Sensed Imagery Using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS). Both ground-measured runoff and streamflow simulations, derived from the NWS Research Distributed Hydrologic Model forced with the MPE dataset, are used as benchmarks to evaluate ensemble streamflow simulations obtained by forcing the model with satellite rainfall corrected using stochastic error simulations from a two-dimensional satellite rainfall error model (SREM2D). The ability of the SREM2D ensemble error corrections to improve satellite rainfall-driven runoff simulations and to characterize the error variability of those simulations is evaluated. It is shown that by applying the SREM2D error ensemble to satellite rainfall, the simulated runoff ensemble is able to envelope both the reference runoff simulation and observed streamflow. The best (uncorrected) product is 3B42RT, but after applying SREM2D, CMORPH becomes the most accurate of the three products in the prediction of runoff variability. The impact of spatial resolution on the rainfall-to-runoff error propagation is also evaluated for a cascade of basin scales (500-5000km2). Results show a doubling in the bias from rainfall to runoff at all basin scales. Significant dependency to catchment area is exhibited for the random error propagation component © 2013 American Meteorological Society."
"54421076700;56522444900;6602999057;","Formation and maintenance of nocturnal low-level stratus over the southern west african monsoon region during amma 2006",2013,"10.1175/JAS-D-12-0241.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883816905&doi=10.1175%2fJAS-D-12-0241.1&partnerID=40&md5=7695d48227a68c74bfe66f698204a986","The southern parts of West Africa are frequently covered by an extensive deck of shallow, low (200-400m AGL) stratus or stratocumulus clouds during the summer monsoon. These clouds usually form at night in association with a nocturnal low-level jet (NLLJ) and can persist into the early afternoon hours. Recent work suggests that the stratus deck is unsatisfactorily represented in standard satellite retrievals and stateof- the-art climate models. Here the authors use high-resolution regional simulations with the Weather Research and Forecasting Model (WRF) and observations from the African Monsoon Multidisciplinary Analysis (AMMA) 2006 campaign to investigate (i) the spatiotemporal distribution, (ii) the influence on the shortwave radiation balance, and (iii) the detailed formation and maintenance mechanisms of the stratiform clouds. At least some configurations of WRF satisfactorily reproduce the diurnal cycle of the lowcloud evolution, yielding the following main conclusions: (i) The simulated stratus deck forms after sunset along the coast, spreads inland during the course of the night, and dissipates in the early afternoon. (ii) The average surface net shortwave radiation balance in stratus-dominated regions is about 35Wm22 lower than in those with fewer clouds. (iii) The cloud formation is related to a subtle balance between ''stratogenic'' upward (downward) fluxes of latent (sensible) heat caused by shear-driven turbulence below the NLLJ, cold advection, orographic lifting, and radiative cooling on one hand, and ''stratolytic'' dry advection and latent heating on the other hand. © 2013 American Meteorological Society."
"43661479500;8942524900;36134816800;35810775100;57208121852;8942525300;13405658600;7004469744;","The magnitude and causes of uncertainty in global model simulations of cloud condensation nuclei",2013,"10.5194/acp-13-8879-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876930346&doi=10.5194%2facp-13-8879-2013&partnerID=40&md5=431b083226b8dd68b6e21bc3507fcb45","Aerosol-cloud interaction effects are a major source of uncertainty in climate models so it is important to quantify the sources of uncertainty and thereby direct research efforts. However, the computational expense of global aerosol models has prevented a full statistical analysis of their outputs. Here we perform a variance-based analysis of a global 3-D aerosol microphysics model to quantify the magnitude and leading causes of parametric uncertainty in model-estimated present-day concentrations of cloud condensation nuclei (CCN). Twenty-eight model parameters covering essentially all important aerosol processes, emissions and representation of aerosol size distributions were defined based on expert elicitation. An uncertainty analysis was then performed based on a Monte Carlo-type sampling of an emulator built for each model grid cell. The standard deviation around the mean CCN varies globally between about ±30% over some marine regions to ±40-100% over most land areas and high latitudes, implying that aerosol processes and emissions are likely to be a significant source of uncertainty in model simulations of aerosol-cloud effects on climate. Among the most important contributors to CCN uncertainty are the sizes of emitted primary particles, including carbonaceous combustion particles from wildfires, biomass burning and fossil fuel use, as well as sulfate particles formed on sub-grid scales. Emissions of carbonaceous combustion particles affect CCN uncertainty more than sulfur emissions. Aerosol emission-related parameters dominate the uncertainty close to sources, while uncertainty in aerosol microphysical processes becomes increasingly important in remote regions, being dominated by deposition and aerosol sulfate formation during cloud-processing. The results lead to several recommendations for research that would result in improved modelling of cloud-active aerosol on a global scale. © Author(s) 2013. CC Attribution 3.0 License."
"6602403713;7404764644;30067702800;26641949400;6602428005;7101818864;","Examining rapid onset drought development using the thermal infrared-based evaporative stress index",2013,"10.1175/JHM-D-12-0144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883763732&doi=10.1175%2fJHM-D-12-0144.1&partnerID=40&md5=3380212be45a7e1e85f4da2902bfbcbf","Reliable indicators of rapid drought onset can help to improve the effectiveness of drought early warning systems. In this study, the evaporative stress index (ESI), which uses remotely sensed thermal infrared imagery to estimate evapotranspiration (ET), is compared to drought classifications in the U.S. Drought Monitor (USDM) and standard precipitation-based drought indicators for several cases of rapid drought development that have occurred across the United States in recent years. Analysis of meteorological time series from the North American Regional Reanalysis indicates that these events are typically characterized by warm air temperature and low cloud cover anomalies, often with high winds and dewpoint depressions that serve to hasten evaporative depletion of soil moisture reserves. Standardized change anomalies depicting the rate at which various multiweek ESI composites changed over different time intervals are computed to more easily identify areas experiencing rapid changes in ET. Overall, the results demonstrate that ESI change anomalies can provide early warning of incipient drought impacts on agricultural systems, as indicated in crop condition reports collected by the National Agricultural Statistics Service. In each case examined, large negative change anomalies indicative of rapidly drying conditions were either coincident with the introduction of drought in theUSDM or lead the USDM drought depiction by several weeks, depending on which ESI composite and time-differencing interval was used. Incorporation of the ESI as a data layer used in the construction of the USDM may improve timely depictions of moisture conditions and vegetation stress associated with flash drought events. © 2013 American Meteorological Society."
"50661916400;7402146514;","Characterizing the surface radiation budget over the Tibetan Plateau with ground-measured, reanalysis, and remote sensing data sets: 1. Methodology",2013,"10.1002/jgrd.50720","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886083731&doi=10.1002%2fjgrd.50720&partnerID=40&md5=3ad9e8e984b096d6b415f38e5478c76f","The surface radiation budget (SRB) over the Tibetan Plateau (TP) greatly influences local climate, climate extremes (e.g., drought, flood) in China, and the East Asian monsoon. However, current estimates of SRB from models and satellite data are subject to large errors, and ground-measured data sets within this region are rather limited over the TP. Our objective is to determine the SRB over the TP by integrating information from three sources: (1) four ground-measured data sets from AsiaFlux, ChinaFLUX, GAME/Tibet, and CAMP/Tibet; (2) four reanalysis data sets from Climate Forecast System Reanalysis, Modern-Era Retrospective Analysis for Research and Applications, ERA-Interim, and Japanese 25-year Reanalysis; and (3) two remote sensing data sets, Global Energy and Water Cycle Experiment Surface Radiation Budget and International Satellite Cloud Climatology Project FD. This study, the first of a two-paper series, presents the methodology. Individual radiation components of reanalysis and remote sensing data set were first validated using ground-measured data from 1997 to 2007; then, a linear regression method was applied to generate the fused data from July 1983 to December 2007. The cross-validation results indicate that the monthly mean root-mean-square errors (RMSEs) of fused downward shortwave irradiance and albedo are 15.1 W m-2 and 0.05, respectively; the RMSEs of the downward and upward longwave fluxes are 13.3 and 8.4 W m-2, respectively; and the RMSE of all-wave net radiation is as low as 18.9 W m-2. Compared to nine sites with long-term observation of downward shortwave irradiance, the fused data represent the decadal variations with higher correlation than using individual products, suggesting the potential for application of the fused data sets in climatic and environmental research. Key Points The surface radiation budget over the Tibetan Plateau is validatedA multiple linear regression method is applied to integrate multiple datasetsThe fused data insolation agreed well with that of other stations ©2013. American Geophysical Union. All Rights Reserved."
"7201634517;6602458644;8687046600;7004866567;47861260200;7006103811;","Mid-upper tropospheric methane retrieval from IASI and its validation",2013,"10.5194/amt-6-2255-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883624233&doi=10.5194%2famt-6-2255-2013&partnerID=40&md5=e82b960e9581ecf04fb9c6fa249d7288","Mid-upper tropospheric methane (CH4), as an operational product at NOAA's (National Oceanic and Atmospheric Administration) Comprehensive Large Array-data Stewardship System (CLASS), has been retrieved from the Infrared Atmospheric Sounding Interferometer (IASI) since 2008. This paper provides a description of the retrieval method and the validation using 596 CH4 vertical profiles from aircraft measurements by the HIAPER Pole-to-Pole Observations (HIPPO) program over the Pacific Ocean. The number of degrees of freedom for the CH4 retrieval is mostly less than 1.5, and it decreases under cloudy conditions. The retrievals show greatest sensitivity between 100-600 hPa in the tropics and 200-750 hPa in the mid-to high latitude. Validation is accomplished using aircraft measurements (convolved by applying the monthly mean averaging kernels) collocated with all the retrieved profiles within 200 km and on the same day, and the results show that, on average, a larger error of CH4 occurs at 300-500 hPa. The bias in the trapezoid of 374-477 hPa is-1.74% with a residual standard deviation of 1.20%, and at layer 596-753 hPa the bias is-0.69% with a residual standard deviation of 1.07%. The retrieval error is relatively larger in the high northern latitude regions and/or under cloudy conditions. The main reasons for this negative bias include the uncertainty in the spectroscopy near the methane branch and/or the empirical bias correction, plus residual cloud contamination in the cloud-cleared radiances. It is expected for NOAA to generate the CH4 product for 20 + years using a similar algorithm from three similar thermal infrared sensors: Atmospheric Infrared Sounder (AIRS), IASI and the Cross-track Infrared Sounder (CrIS). Such a unique product will provide a supplementary to the current ground-based observation network, particularly in the Arctic, for monitoring the CH4 cycle, its transport and trend associated with climate change. © 2013 Author(s)."
"6602354484;6603212184;55533371800;57207261095;26421139200;16833315000;7003897194;55533979000;6602443410;57217976765;6701410575;20735974900;","Secondary aerosol formation from stress-induced biogenic emissions and possible climate feedbacks",2013,"10.5194/acp-13-8755-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883531698&doi=10.5194%2facp-13-8755-2013&partnerID=40&md5=c4ec64f54e7a78adbd43a128dbfb66c8","Atmospheric aerosols impact climate by scattering and absorbing solar radiation and by acting as ice and cloud condensation nuclei. Biogenic secondary organic aerosols (BSOAs) comprise an important component of atmospheric aerosols. Biogenic volatile organic compounds (BVOCs) emitted by vegetation are the source of BSOAs. Pathogens and insect attacks, heat waves and droughts can induce stress to plants that may impact their BVOC emissions, and hence the yield and type of formed BSOAs, and possibly their climatic effects. This raises questions of whether stress-induced changes in BSOA formation may attenuate or amplify effects of climate change. In this study we assess the potential impact of stress-induced BVOC emissions on BSOA formation for tree species typical for mixed deciduous and Boreal Eurasian forests. We studied the photochemical BSOA formation for plants infested by aphids in a laboratory setup under well-controlled conditions and applied in addition heat and drought stress. The results indicate that stress conditions substantially modify BSOA formation and yield. Stress-induced emissions of sesquiterpenes, methyl salicylate, and C17-BVOCs increase BSOA yields. Mixtures including these compounds exhibit BSOA yields between 17 and 33%, significantly higher than mixtures containing mainly monoterpenes (4-6% yield). Green leaf volatiles suppress SOA formation, presumably by scavenging OH, similar to isoprene. By classifying emission types, stressors and BSOA formation potential, we discuss possible climatic feedbacks regarding aerosol effects. We conclude that stress situations for plants due to climate change should be considered in climate-vegetation feedback mechanisms. © 2013 Author(s)."
"55446037800;6603879924;23012388900;36627288300;8649404400;24921885300;57202119596;","Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars: II. Thermal emission spectra influenced by clouds",2013,"10.1051/0004-6361/201220566","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883362974&doi=10.1051%2f0004-6361%2f201220566&partnerID=40&md5=3ed9ab49b41512aab8d46217bcffc21d","Context. Clouds play an important role in the radiative transfer of planetary atmospheres because of the influence they have on the different molecular signatures through scattering and absorption processes. Furthermore, they are important modulators of the radiative energy budget affecting surface and atmospheric temperatures. Aims. We present a detailed study of the thermal emission of cloud-covered planets orbiting F-, G-, K-, and M-type stars. These Earth-like planets include planets with the same gravity and total irradiation as Earth, but can differ significantly in the upper atmosphere. The impact of single-layered clouds is analyzed to determine what information on the atmosphere may be lost or gained. The planetary spectra are studied at different instrument resolutions and compared to previously calculated low-resolution spectra. Methods. A line-by-line molecular absorption model coupled with a multiple scattering radiative transfer solver was used to calculate the spectra of cloud-covered planets. The atmospheric profiles used in the radiation calculations were obtained with a radiative-convective climate model combined with a parametric cloud description. Results. In the high-resolution flux spectra, clouds changed the intensities and shapes of the bands of CO 2, N2O, H2O, CH4, and O3. Some of these bands turned out to be highly reduced by the presence of clouds, which causes difficulties for their detection. The most affected spectral bands resulted for the planet orbiting the F-type star. Clouds could lead to false negative interpretations for the different molecular species investigated. However, at low resolution, clouds were found to be crucial for detecting some of the molecular bands that could not be distinguished in the cloud-free atmospheres. The CO2 bands were found to be less affected by clouds. Radiation sources were visualized with weighting functions at high resolution. Conclusions. Knowledge of the atmospheric temperature profile is essential for estimating the composition and important for avoiding false negative detection of biomarkers, in both cloudy and clear-sky conditions. In particular, a pronounced temperature contrast between the ozone layer and surface or cloud is needed to detect the molecule. Fortunately, the CO2 bands allow temperature estimation from the upper stratosphere down to the troposphere even in the presence of clouds. © 2013 ESO,."
"7403276033;7004239939;55492414700;6602859414;6602089079;7202190731;7402727750;7201596633;57213753419;","A net decrease in the Earth's cloud, aerosol, and surface 340 nm reflectivity during the past 33 yr (1979-2011)",2013,"10.5194/acp-13-8505-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883253964&doi=10.5194%2facp-13-8505-2013&partnerID=40&md5=739234d0485c8568d3fcea6cae5c3cf0","Measured upwelling radiances from Nimbus-7 SBUV (Solar Backscatter Ultraviolet) and seven NOAA SBUV/2 instruments have been used to calculate the 340 nm Lambertian equivalent reflectivity (LER) of the Earth from 1979 to 2011 after applying a common calibration. The 340 nm LER is highly correlated with cloud and aerosol cover because of the low surface reflectivity of the land and oceans (typically 2 to 6 RU, reflectivity units, where 1 RU Combining double low line 0.01 Combining double low line 1.0%) relative to the much higher reflectivity of clouds plus nonabsorbing aerosols (typically 10 to 90 RU). Because of the nearly constant seasonal and long-term 340 nm surface reflectivity in areas without snow and ice, the 340 nm LER can be used to estimate changes in cloud plus aerosol amount associated with seasonal and interannual variability and decadal climate change. The annual motion of the Intertropical Convergence Zone (ITCZ), episodic El Niño Southern Oscillation (ENSO), and latitude-dependent seasonal cycles are apparent in the LER time series. LER trend estimates from 5 zonal average and from 2 × 5 , latitude × longitude, time series show that there has been a global net decrease in 340 nm cloud plus aerosol reflectivity. The decrease in cos2(latitude) weighted average LER from 60 S to 60 N is 0.79 ± 0.03 RU over 33 yr, corresponding to a 3.6 ± 0.2% decrease in LER. Applying a 3.6% cloud reflectivity perturbation to the shortwave energy balance partitioning given by Trenberth et al. (2009) corresponds to an increase of 2.7 W m-2 of solar energy reaching the Earth's surface and an increase of 1.4% or 2.3 W m-2 absorbed by the surface, which is partially offset by increased longwave cooling to space. Most of the decreases in LER occur over land, with the largest decreases occurring over the US (-0.97 RU decade-1), Brazil (-0.9 RU decade-1), and central Europe (-1.35 RU decade-1). There are reflectivity increases near the west coast of Peru and Chile (0.8 ± 0.1 RU decade-1), over parts of India, China, and Indochina, and almost no change over Australia. The largest Pacific Ocean change is -2 ± 0.1 RU decade-1 over the central equatorial region associated with ENSO. There has been little observed change in LER over central Greenland, but there has been a significant decrease over a portion of the west coast of Greenland. Similar significant decreases in LER are observed over a portion of the coast of Antarctica for longitudes -160 to -60 and 80 to 150. © Author(s) 2013."
"57208346904;56263595100;","The cloud-aerosol-radiation (CAR) ensemble modeling system",2013,"10.5194/acp-13-8335-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882755953&doi=10.5194%2facp-13-8335-2013&partnerID=40&md5=a533963265cccba9813166212e459999","A cloud-aerosol-radiation (CAR) ensemble modeling system has been developed to incorporate the largest choices of alternate parameterizations for cloud properties (cover, water, radius, optics, geometry), aerosol properties (type, profile, optics), radiation transfers (solar, infrared), and their interactions. These schemes form the most comprehensive collection currently available in the literature, including those used by the world's leading general circulation models (GCMs). CAR provides a unique framework to determine (via intercomparison across all schemes), reduce (via optimized ensemble simulations), and attribute specific key factors for (via physical process sensitivity analyses) the model discrepancies and uncertainties in representing greenhouse gas, aerosol, and cloud radiative forcing effects. This study presents a general description of the CAR system and illustrates its capabilities for climate modeling applications, especially in the context of estimating climate sensitivity and uncertainty range caused by cloud-aerosol-radiation interactions. For demonstration purposes, the evaluation is based on several CAR standalone and coupled climate model experiments, each comparing a limited subset of the full system ensemble with up to 896 members. It is shown that the quantification of radiative forcings and climate impacts strongly depends on the choices of the cloud, aerosol, and radiation schemes. The prevailing schemes used in current GCMs are likely insufficient in variety and physically biased in a significant way. There exists large room for improvement by optimally combining radiation transfer with cloud property schemes. © 2013 Author(s)."
"57195574170;57212972452;56520921400;","On the usage of spectral and broadband satellite instrument measurements to differentiate climate models with different cloud feedback strengths",2013,"10.1175/JCLI-D-12-00378.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883182441&doi=10.1175%2fJCLI-D-12-00378.1&partnerID=40&md5=0b1151d6c92345d2c3bafa97e2fe1b6c","Top-of-atmosphere radiometric signals associated with different high- and low-cloud-radiative feedbacks have been examined through the use of an observing system simulation experiment (OSSE). The OSSE simulates variations in the spectrally resolved and spectrally integrated signals that are due to a range of plausible feedbacks of the climate system when forced withCO2 concentrations that increase at1% yr21. This initial version of the OSSE is based on the Community Climate System Model, version 3 (CCSM3), and exploits the fact that CCSM3 exhibits different cloud feedback strengths for different model horizontal resolutions. In addition to the conventional broadband shortwave albedos and outgoing longwave fluxes, a dataset of shortwave spectral reflectance and longwave spectral radiance has been created. These data have been analyzed to determine simulated satellite instrument signals of poorly constrained cloud feedbacks for three plausible realizations of Earth's climate system produced by CCSM3. These data have been analyzed to estimate the observational record length of albedo, outgoing longwave radiation, shortwave reflectance, or longwave radiance required to differentiate these dissimilar Earth system realizations. Shortwave spectral measurements in visible and near-infrared water vapor overtone lines are best suited to differentiate model results, and a 33% difference in shortwave-cloud feedbacks can be detected with 20 years of continuous measurements. Nevertheless, at most latitudes and with most wavelengths, the difference detection time is more than 30 years. This suggests that observing systems of sufficiently stable calibration would be useful in addressing the contribution of low clouds to the spread of climate sensitivities currently exhibited by the models that report to the Intergovernmental Panel on Climate Change (IPCC). © 2013 American Meteorological Society."
"6602364115;6603566335;","Constraining a system of interacting parameterizations through multiple-parameter evaluation: Tracing a compensating error between cloud vertical structure and cloud overlap",2013,"10.1175/JCLI-D-12-00779.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883183544&doi=10.1175%2fJCLI-D-12-00779.1&partnerID=40&md5=30ae7098ceee76826b81bd4114b56e11","This study explores the opportunities created by subjecting a system of interacting fast-acting parameterizations to long-term single-column model evaluation against multiple independent measurements at a permanent meteorological site. It is argued that constraining the system at multiple key points facilitates the tracing and identification of compensating errors between individual parametric components. The extended time range of the evaluation helps to enhance the statistical significance and representativeness of the singlecolumn model result, which facilitates the attribution of model behavior as diagnosed in a general circulation model to its subgrid parameterizations. At the same time, the high model transparency and computational efficiency typical of single-column modeling is preserved. The method is illustrated by investigating the impact of a model change in the Regional Atmospheric Climate Model (RACMO) on the representation of the coupled boundary layer-soil system at the Cabauw meteorological site in the Netherlands. A set of 12 relevant variables is defined that covers all involved processes, including cloud structure and amplitude, radiative transfer, the surface energy budget, and the thermodynamic state of the soil and various heights of the lower atmosphere. These variables are either routinely measured at the Cabauw site or are obtained from continuous large-eddy simulation at that site. This 12-point check proves effective in revealing the existence of a compensating error between cloud structure and radiative transfer, residing in the cloud overlap assumption. In this exercise, the application of conditional sampling proves a valuable tool in establishing which cloud regime exhibits the biggest impact. © 2013 American Meteorological Society."
"36243762400;6603431534;","Climatology of high cloud dynamics using profiling arm doppler radar observations",2013,"10.1175/JCLI-D-12-00695.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883173984&doi=10.1175%2fJCLI-D-12-00695.1&partnerID=40&md5=55bd77cc414d3322a2a4d1f7c1691b23","Ice cloud properties are influenced by cloud-scale vertical air motion. Dynamical properties of ice clouds can be determined via Doppler measurements from ground-based, profiling cloud radars. Here, the decomposition of the Doppler velocities into reflectivity-weighted particle velocity Vt and vertical air motion w is described. The methodology is applied to high clouds observations from 35-GHz profiling millimeter wavelength radars at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) climate research facility in Oklahoma (January 1997-December 2010) and theARMTropical Western Pacific (TWP) site in Manus (July 1999-December 2010). The Doppler velocity measurements are used to detect gravity waves (GW), whose correlation with high cloud macrophysical properties is investigated. Cloud turbulence is studied in the absence and presence of GW. High clouds are less turbulent when GW are observed. Probability density functions of Vt, w, and high cloud macrophysical properties for the two cloud subsets (with and without GW) are presented. Air-density-corrected Vt for high clouds for which GW (no GW)were detected amounted to hourly means and standard deviations of 0.8960.52ms21 (0.860.48ms21) and 1.03 6 0.41ms21 (0.86 6 0.49ms21) at SGP and Manus, respectively. The error of w at one standard deviation was estimated as 0.15ms21. Hourly means of waveraged around 0ms21 with standard deviations of 60.27 (SGP) and 60.29ms21 (Manus) for high clouds without GW and 60.22ms21 (both sites) for high clouds with GW. The midlatitude site showed stronger seasonality in detected high cloud properties. © 2013 American Meteorological Society."
"36187387300;6506416572;7004854393;6701735773;7004160585;","The present and future of the west african monsoon: A process-oriented assessment of CMIP5 simulations along the AMMA transect",2013,"10.1175/JCLI-D-12-00505.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883151474&doi=10.1175%2fJCLI-D-12-00505.1&partnerID=40&md5=7990fae3e3220d038ad8c81382439019","The present assessment of the West African monsoon in the models of the Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) indicates little evolution since the third phase of CMIP (CMIP3) in terms of both biases in present-day climate and climate projections. The outlook for precipitation in twenty-first-century coupled simulations exhibits opposite responses between the westernmost and eastern Sahel. The spread in the trend amplitude, however, remains large in both regions. Besides, although all models predict a spring and summer warming of the Sahel that is 10%-50% larger than the global warming, their temperature response ranges from 0 to 7 K. CMIP5 coupled models underestimate the monsoon decadal variability, but SST-imposed simulations succeed in capturing the recent partial recovery of monsoon rainfall. Coupled models still display major SST biases in the equatorial Atlantic, inducing a systematic southward shift of the monsoon. Because of these strong biases, the monsoon is further evaluated in SST-imposed simulations along the 108W-108E African Monsoon Multidisciplinary Analysis(AMMA)transect, across a range of time scales ranging from seasonal to intraseasonal and diurnal fluctuations. The comprehensive set of observational data now available allows an in-depth evaluation of the monsoon across those scales, especially through the use of high-frequency outputs provided by some CMIP5models at selected sites along the AMMA transect. Most models capture many features of the African monsoon with varying degrees of accuracy. In particular, the simulation of the top-of-atmosphere and surface energy balances, in relation with the cloud cover, and the intermittence and diurnal cycle of precipitation demand further work to achieve a reasonable realism. © 2013 American Meteorological Society."
"8846887600;56655654500;7004060399;","The antarctic atmospheric energy budget. part 1: Climatology and intraseasonal-to-interannual variability",2013,"10.1175/JCLI-D-12-00640.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883205427&doi=10.1175%2fJCLI-D-12-00640.1&partnerID=40&md5=ad48c53d89e508b6c031afa4e60debac","The authors present a new, observationally based estimate of the atmospheric energy budget for the Antarctic polar cap (the region poleward of 708S). This energy budget is constructed using state-of-the-art reanalysis products from ECMWF [the ECMWF Interim Re-Analysis (ERA-Interim)] and Clouds and the Earth's Radiant Energy System (CERES) top-of-atmosphere (TOA) radiative fluxes for the period 2001-10. The climatological mean Antarctic energy budget is characterized by an approximate balance between the TOA net outgoing radiation and the horizontal convergence of atmospheric energy transport, with the net surface energy flux and atmospheric energy storage generally being small in comparison. Variability in the energy budget on intraseasonal-to-interannual time scales bears a strong signature of the southern annular mode (SAM), with El Niño-Southern Oscillation (ENSO) having a smaller impact. The energy budget framework is shown to be a useful alternative to the SAM for interpreting surface climate variability in the Antarctic region. © 2013 American Meteorological Society."
"36339753800;6602600408;7201504886;","Assessment of different metrics for physical climate feedbacks",2013,"10.1007/s00382-013-1757-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884704176&doi=10.1007%2fs00382-013-1757-1&partnerID=40&md5=ecc4436a64d5cd5eb339af60d1352e96","We quantify the feedbacks from the physical climate system on the radiative forcing for idealized climate simulations using four different methods. The results differ between the methods and differences are largest for the cloud feedback. The spatial and temporal variability of each feedback is used to estimate the averaging scale necessary to satisfy the feedback concept of one constant global mean value. We find that the year-to-year variability, combined with the methodological differences, in estimates of the feedback strength from a single model is comparable to the model-to-model spread in feedback strength of the CMIP3 ensemble. The strongest spatial and temporal variability is in the short-wave component of the cloud feedback. In our simulations, where many sources of natural variability are neglected, long-term averages are necessary to get reliable feedback estimates. Considering the large natural variability and relatively small forcing present in the real world, as compared to the forcing imposed by doubling CO2 concentrations in the simulations, implies that using observations to constrain feedbacks is a challenging task and requires reliable long-term measurements. © 2013 The Author(s)."
"55793449600;21935606200;7103243257;57217352376;7403906746;","Quantifying the importance of galactic cosmic rays in cloud microphysical processes",2013,"10.1016/j.jastp.2013.05.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880142703&doi=10.1016%2fj.jastp.2013.05.017&partnerID=40&md5=fd5f987e675d14c9e0c64082fadfdf8e","Galactic Cosmic Rays are one of the major sources of ion production in the troposphere and stratosphere. Recent studies have shown that ions form electrically charged clusters which may grow to become cloud droplets. Aerosol particles charge by the attachment of ions and electrons. The collision efficiency between a particle and a water droplet increases, if the particle is electrically charged, and thus aerosol-cloud interactions can be enhanced. Because these microphysical processes may change radiative properties of cloud and impact Earth's climate it is important to evaluate these processes' quantitative effects. Five different models developed independently have been coupled to investigate this. The first model estimates cloud height from dew point temperature and the temperature profile. The second model simulates the cloud droplet growth from aerosol particles using the cloud parcel concept. In the third model, the scavenging rate of the aerosol particles is calculated using the collision efficiency between charged particles and droplets. The fourth model calculates electric field and charge distribution on water droplets and aerosols within cloud. The fifth model simulates the global electric circuit (GEC), which computes the conductivity and ionic concentration in the atmosphere in altitude range 0-45. km. The first four models are initially coupled to calculate the height of cloud, boundary condition of cloud, followed by growth of droplets, charge distribution calculation on aerosols and cloud droplets and finally scavenging. These models are incorporated with the GEC model. The simulations are verified with experimental data of charged aerosol for various altitudes. Our calculations showed an effect of aerosol charging on the CCN concentration within the cloud, due to charging of aerosols increase the scavenging of particles in the size range 0.1μm to 1μm. © 2013 Elsevier Ltd."
"22982270700;56228672600;","Analytical studies of the cloud droplet spectral dispersion influence on the first indirect aerosol effect",2013,"10.1007/s00376-012-2141-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881608102&doi=10.1007%2fs00376-012-2141-5&partnerID=40&md5=84bbbb18316cb9ef86dbd88f4c169707","Atmospheric aerosols (acting as cloud condensation nuclei) can enhance the cloud droplet number concentration and reduce the cloud droplet size, and in turn affect the cloud optical depth, as well as the cloud albedo, and thereby exert a radiative influence on climate (the first indirect aerosol effect). In this paper, based on various relationships between cloud droplet spectral dispersion (e{open}) and cloud droplet number concentration (N c), we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration. Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different e{open}-N c relationships varies from -29.1% to 25.2%, compared to the case without considering spectral dispersion (e{open} = 0). Our results suggest that an accurate description of e{open} - N c relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"26433746100;8618866300;7201498373;55535867400;16043525600;7401859637;7404005339;","Clouds and temperature drive dynamic changes in tropical flower production",2013,"10.1038/nclimate1934","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883399367&doi=10.1038%2fnclimate1934&partnerID=40&md5=fbeff90ebb5c7fc6dd06c6cb2ca2c302","Tropical forests are incredibly dynamic, showing rapid and longer-term changes in growth, mortality and net primary productivity. Tropical species may be highly sensitive to temperature increases associated with climate change because of their narrow thermal tolerances. However, at the ecosystem scale the competing effects of temperature, light and precipitation on tropical forest productivity have been difficult to assess. Here we quantify cloudiness over the past several decades to investigate how clouds, together with temperature and precipitation, affect flower production in two contrasting tropical forests. Our results show that temperature, rather than clouds, is critically important to tropical forest flower production. Warmer temperatures increased flower production over seasonal, interannual and longer timescales, contrary to recent evidence that some tropical forests are already near their temperature threshold. Clouds were primarily important seasonally, and limited production in a seasonally dry forest but enhanced production in an ever-wet forest. A long-term increase in flower production at the seasonally dry forest is not driven by clouds and instead may be tied to increasing temperatures. These relationships show that tropical forest productivity, which is not widely thought to be controlled by temperature, is indeed sensitive to small temperature changes (1-4 C) across multiple timescales. © 2013 Macmillan Publishers Limited. All rights reserved."
"7007020226;6602765265;","Understanding the transport and impact of African dust on the Caribbean Basin",2013,"10.1175/BAMS-D-12-00142.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884237704&doi=10.1175%2fBAMS-D-12-00142.1&partnerID=40&md5=98d6ba205734327b8fd14624c864c345","The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) dust product shows a strong link to the seasonal migration of the intertropical convergence zone over West Africa and monsoon dynamics. All these processes could play a fundamental role in dust emissions; the relative importance of these processes could change with season and with changing climate. Improved model performance will require a more accurate description of all processes controlling dust mobilization and distribution including the evolution and persistence of the strong stratification of dust layers. Models are essential to the development of an understanding of the entire dust cycle. However, dust models are in an early stage of development. A recent intercomparison of 15 global models in the Aerosol Comparisons between Observations and Models (AEROCOM) project shows large disparities."
"55388912500;7409080503;8636990400;57212385412;7004853382;25941200000;","Diagnosis and testing of low-level cloud parameterizations for the NCEP/GFS model using satellite and ground-based measurements",2013,"10.1007/s00382-013-1884-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884699540&doi=10.1007%2fs00382-013-1884-8&partnerID=40&md5=e669840015f25903f80b8551f29c5da4","The objective of this study is to investigate the quality of clouds simulated by the National Centers for Environmental Prediction global forecast system (GFS) model and to examine the causes for some systematic errors seen in the simulations through use of satellite and ground-based measurements. In general, clouds simulated by the GFS model had similar spatial patterns and seasonal trends as those retrieved from passive and active satellite sensors, but large systematic biases exist for certain cloud regimes especially underestimation of low-level marine stratocumulus clouds in the eastern Pacific and Atlantic oceans. This led to the overestimation (underestimation) of outgoing longwave (shortwave) fluxes at the top-of-atmosphere. While temperature profiles from the GFS model were comparable to those obtained from different observational sources, the GFS model overestimated the relative humidity field in the upper and lower troposphere. The cloud condensed water mixing ratio, which is a key input variable in the current GFS cloud scheme, was largely underestimated due presumably to excessive removal of cloud condensate water through strong turbulent diffusion and/or an improper boundary layer scheme. To circumvent the problem associated with modeled cloud mixing ratios, we tested an alternative cloud parameterization scheme that requires inputs of atmospheric dynamic and thermodynamic variables. Much closer agreements were reached in cloud amounts, especially for marine stratocumulus clouds. We also evaluate the impact of cloud overlap on cloud fraction by applying a linear combination of maximum and random overlap assumptions with a de-correlation length determined from satellite products. Significantly better improvements were found for high-level clouds than for low-level clouds, due to differences in the dominant cloud geometry between these two distinct cloud types. © 2013 Springer-Verlag Berlin Heidelberg."
"15833700100;57212238716;55801946000;57199775129;","GPU acceleration of the WSM6 cloud microphysics scheme in GRAPES model",2013,"10.1016/j.cageo.2013.06.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880611643&doi=10.1016%2fj.cageo.2013.06.016&partnerID=40&md5=46728c31630e4cee9edf8ce66c3b05a1","The microphysical process that leads to cloud and precipitation formation is one of the most important physical processes in numerical weather prediction (NWP) and climate models. The Weather Research Forecast (WRF) Single Moment 6-class (WSM6) microphysics scheme in the Global/Regional Assimilation and Prediction System (GRAPES) includes predictive variables of water vapor, cloud water, cloud ice, rain, snow and graupel. The computation of WSM6 is the most time-consuming portion among that of the entire GRAPES model. In recent years, with the advent of the Compute Unified Device Architecture (CUDA), modern graphics processing units (GPUs) with the advantage of low-power, low-cost, and high-performance computing capacity have been exploited to accomplish the arithmetic operations in scientific and engineering simulations. In this paper, we present an implementation of the WSM6 scheme in GRAPES using GPU to accelerate the computation. After a brief introduction to the WSM6 scheme, the data dependence for the GPU implementation of the WSM6 scheme is discussed. The data parallel method is employed to exploit the massive fine-grained parallelism. The CUDA programming model is used to convert the original WSM6 module into GPU programs. To achieve high computational performance, mapping horizontal domain onto an optimal block size is proposed. The experimental results demonstrate that the GPU version obtains over 140× speedup compared with the CPU serial version, and is an efficient parallel implementation. © 2013 Elsevier Ltd."
"35239053700;55386235300;55417853000;7404433688;","Liquid water in snowing clouds: Implications for satellite remote sensing of snowfall",2013,"10.1016/j.atmosres.2012.06.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882837959&doi=10.1016%2fj.atmosres.2012.06.008&partnerID=40&md5=8d8226bc21cd43ad7cd120dd88c68855","To study the impact of cloud liquid water on passive microwave snowfall remote sensing, we analyzed 4years of liquid water path data retrieved from microwave radiometer on Aqua satellite that are collocated with CloudSat snowfall observations. Results showed that cloud liquid water commonly occurs in snowing clouds (2-m air temperature lower than 2°C); about 72% of these clouds have a retrieved liquid water path greater than 0. The mean liquid water path for all snowing clouds is about 74gm-2, higher for horizontally extended clouds (70-100gm-2) and lower for isolated (~50gm-2). There is a clear tendency that snowing clouds are less likely to contain liquid water as 2-m air temperature decreases. However, the variation of the mode values of liquid water path with 2-m air temperature seems to be cloud type dependent, particularly for colder environment with 2-m air temperature lower than 263K. On average, larger values of liquid water path occur when near-surface radar reflectivity ranges from -10 to 0dBZ, corresponding to relatively weak snowfall of 0.02 to 0.15mmh-1, rather than to the heaviest snowfall observed. The impact of cloud liquid water on passive microwave satellite remote sensing of snowfall has been investigated using radiative transfer simulations. It is concluded that for frequencies higher than 80GHz the brightness temperature warming caused by cloud liquid water emission has a similar magnitude to the brightness temperature cooling caused by snowflakes' scattering. Therefore, while ice scattering is the primary signature for retrieving snowfall, it is equally important to take into account the impact by cloud liquid water when developing snowfall retrieval algorithms using high-frequency satellite observations. © 2012 Elsevier B.V."
"55628587967;34870277200;6701346974;36006968000;","Simulation of Indian summer monsoon intraseasonal oscillations in a superparameterized coupled climate model: Need to improve the embedded cloud resolving model",2013,"10.1007/s00382-012-1563-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884704781&doi=10.1007%2fs00382-012-1563-1&partnerID=40&md5=3a478441340c727e8cc37bde72a9c0ff","The characteristic features of Indian summer monsoon (ISM) and monsoon intraseasonal oscillations (MISO) are analyzed in the 25 year simulation by the superparameterized Community Climate System Model (SP-CCSM). The observations indicate the low frequency oscillation with a period of 30-60 day to have the highest power with a dominant northward propagation, while the faster mode of MISO with a period of 10-20 day shows a stationary pattern with no northward propagation. SP-CCSM simulates two dominant quasi-periodic oscillations with periods 15-30 day and 40-70 day indicating a systematic low frequency bias in simulating the observed modes. Further, contrary to the observation, the SP-CCSM 15-30 day mode has a significant northward propagation; while the 40-70 day mode does not show prominent northward propagation. The inability of the SP-CCSM to reproduce the observed modes correctly is shown to be linked with inability of the cloud resolving model (CRM) to reproduce the characteristic heating associated with the barotropic and baroclinic vertical structures of the high-frequency and the low-frequency modes. It appears that the superparameterization in the General Circulation Model (GCM) certainly improves seasonal mean model bias significantly. There is a need to improve the CRM through which the barotropic and baroclinic modes are simulated with proper space and time distribution. © 2012 Springer-Verlag Berlin Heidelberg."
"55512611100;36187987100;16318422000;55786907400;7004435460;38561453500;55787105600;","How will renewable power generation be affected by climate change? The case of a metropolitan region in Northwest Germany",2013,"10.1016/j.energy.2013.06.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881091829&doi=10.1016%2fj.energy.2013.06.035&partnerID=40&md5=c7929b4b7f12f29006e3346ccb385dfb","Energy systems that primarily use wind and solar power production are in need of long-term storage of electricity and fully developed transmission grids. Moreover, renewables-based energy systems may be strongly affected by climate change. We present two models that assess the impacts of climate change on solar and wind power generation and use these models to evaluate climate projections based on the A1B scenario for Germany's Northwest Metropolitan Region. For these projections the seasonal profile of solar power production is not affected despite less cloud cover during the summer, while the seasonal profile of wind power production has a more pronounced seasonal peak during the winter due to slightly increasing wind speeds. We compare the obtained seasonal profiles to different scenarios for electricity demand. For each scenario we identify the ratio of wind and solar power generation that minimizes thevariance of the residual load at the monthly time scale under the premise of a full supply by wind andsolar power. Our results suggest that the need for long-term storage of electricity and the need for extensions of the transmission grid will on the one hand decrease but on the other hand become more volatile because of climate change impacts in the Northwest Metropolitan Region over the next century. © 2013 Elsevier Ltd."
"57219220333;7006235116;6506647236;","Cloud bands over southern Africa: Seasonality, contribution to rainfall variability and modulation by the MJO",2013,"10.1007/s00382-012-1589-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884700014&doi=10.1007%2fs00382-012-1589-4&partnerID=40&md5=9249036ef42dfca8af37e0ce5456bf8e","Tropical-extratropical cloud band systems over southern Africa, known as tropical temperate troughs (TTTs), are known to contribute substantially to South African summer rainfall. This study performs a comprehensive assessment of the seasonal cycle and rainfall contribution of TTTs by using a novel object-based strategy that explicitly tracks these systems for their full life cycle. The methodology incorporates a simple assignment of station rainfall data to each event, thereby creating a database containing detailed rainfall characteristics for each TTT. This is used to explore the importance of TTTs for rain days and climatological rainfall totals in October-March. Average contributions range from 30 to 60 % with substantial spatial heterogeneity observed. TTT rainfall contributions over the Highveld and eastern escarpment are lower than expected. A short analysis of TTT rainfall variability indicates TTTs provide substantial, but not dominant, intraseasonal and interannual variability in station rainfall totals. TTTs are however responsible for a high proportion of heavy rainfall days. Of 52 extreme rainfall events in the 1979-1999 period, 30 are associated with these tropical-extratropical interactions. Cut-off lows were included in the evolution of 6 of these TTTs. The study concludes with an analysis of the question: does the Madden-Julian Oscillation influence the intensity of TTT rainfall over South Africa? Results suggest a weak but significant suppression (enhancement) of intensity during phase 1(6). © 2012 Springer-Verlag Berlin Heidelberg."
"24179143700;7201839229;","Boreal summer intraseasonal variability simulated in the NCEP climate forecast system: Insights from moist static energy budget and sensitivity to convective moistening",2013,"10.1007/s00382-012-1631-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884701089&doi=10.1007%2fs00382-012-1631-6&partnerID=40&md5=ebc4a1dfefa6f1345c065c426c353d0c","The NCEP Climate Forecast System (CFS) with the relaxed Arakawa Schubert (RAS, hereafter referred to as CTRL) convection scheme of Moorthi and Suarez exhibits better performance in representing boreal summer tropical intraseasonal variability as compared with a simulation using simplified Arakawa-Schubert scheme. The intraseasonal moist static energy (MSE) budget is analyzed in this version of the CFS model (CTRL), which produces realistic eastward and northward propagation characteristics. The moist and thermodynamic processes involved in the maintenance and propagation of the poleward moving intraseasonal oscillation (ISO) disturbances are examined here. Budget diagnostics show that horizontal MSE advection is the principal component of the budget, contributing to the poleward movement of the convection. The injection of MSE moistens the atmosphere north of the convective area causing the poleward movement of convection by destabilization of the atmosphere. The moistening process is mainly contributed by the climatological wind acting on the anomalous moisture gradient as confirmed from the examination of moisture advection equation. While surface enthalpy fluxes (consisting of radiative and surface turbulent heat fluxes) maintain the ISO anomalies, they oppose the MSE tendency due to horizontal advection thus regulating the poleward propagation characteristics. In addition, the model results show that wind-evaporation feedback dominates over cloud-radiation feedback for ISO propagation; this is in contrast to our estimates using the newly available European Centre for Medium Range Weather Forecasts Interim reanalysis. Sensitivity experiments suggest that intraseasonal variability in the CFS model with the RAS scheme is highly sensitive to the parameterization of both the shallow convection and the convective rain evaporation and downdrafts. Removal of these components adversely affects the propagation characteristics and greatly reduces the amplitude of intraseasonal variability. Our results support the primary importance of the moisture preconditioning ahead of the ISO and the physical relationship between moisture and precipitation. For realistic ISO simulations, models need to represent these features appropriately. © 2012 Springer-Verlag Berlin Heidelberg."
"55903859700;7006745049;55904167100;","Patterns of moisture and temperature in canopy and terrestrial soils in a temperate rainforest, Washington",2013,"10.1139/cjb-2013-0153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886550179&doi=10.1139%2fcjb-2013-0153&partnerID=40&md5=bb7be4c18f8d9b1859977587cc591601","The temperate rainforest on the Olympic Peninsula represents a biome that is characterized by unusually high epiphyte biomass and accompanying canopy soils. These canopy communities form thick mats that play important ecological roles: increasing ecosystem nutrient capital, fostering abundant invertebrates, and enhancing moisture retention. Little is known about the physical properties and microenvironmental conditions of these mats. We investigated seasonal patterns in temperature and moisture of canopy soils and compared them to O- and A-horizon terrestrial soils. Temperature tended to fluctuate more in canopy soils than in terrestrial soils. During the 4 months of highest precipitation, canopy soils also showed higher maximum saturation levels than terrestrial soils. Both soil types displayed sharp ""dry-downs"" during the summer dry season, which contrasts with results from similar research in a tropical cloud forest, where only canopy soils dried significantly during the dry season. In the late summer in the Olympic Rainforest, canopy soils remained dry until the first rainfall, whereas terrestrial soils began to rehydrate a month earlier, possibly through hydraulic redistribution. Regional climate models predict increased winter precipitation but drier summers for this area. Our results suggest that extended summer droughts may increase canopy drying, which may have negative impacts on epiphyte communities."
"8709358200;6507492100;35119974800;36021951400;55463767400;57217692852;36719997000;57207499057;","A Linked Science investigation: Enhancing climate change data discovery with semantic technologies",2013,"10.1007/s12145-013-0118-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882871673&doi=10.1007%2fs12145-013-0118-2&partnerID=40&md5=c6c930a67b4a0a6fad22c018e309d852","Linked Science is the practice of inter-connecting scientific assets by publishing, sharing and linking scientific data and processes in end-to-end loosely coupled workflows that allow the sharing and re-use of scientific data. Much of this data does not live in the cloud or on the Web, but rather in multi-institutional data centers that provide tools and add value through quality assurance, validation, curation, dissemination, and analysis of the data. In this paper, we make the case for the use of scientific scenarios in Linked Science. We propose a scenario in river-channel transport that requires biogeochemical experimental data and global climate-simulation model data from many sources. We focus on the use of ontologies-formal machine-readable descriptions of the domain-to facilitate search and discovery of this data. Mercury, developed at Oak Ridge National Laboratory, is a tool for distributed metadata harvesting, search and retrieval. Mercury currently provides uniform access to more than 100,000 metadata records; 30,000 scientists use it each month. We augmented search in Mercury with ontologies, such as the ontologies in the Semantic Web for Earth and Environmental Terminology (SWEET) collection by prototyping a component that provides access to the ontology terms from Mercury. We evaluate the coverage of SWEET for the ORNL Distributed Active Archive Center (ORNL DAAC). © 2013 # Springer-Verlag Berlin Heidelberg (outside the USA)."
"55854323600;7005395591;","Rates of shoreline change along the coast of Bangladesh",2013,"10.1007/s11852-013-0251-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883864847&doi=10.1007%2fs11852-013-0251-6&partnerID=40&md5=edc4ba5fbd4797ecb1f8bda7a9780402","Bangladesh, at the confluence of the sediment-laden Ganges and Brahmaputra Rivers, supports an enormous and rapidly growing population (&gt;140 million in 2011), across low-lying alluvial and delta plains that have accumulated over the past few thousand years. It has been identified as one of the most vulnerable places in the world to the impacts of climate change and sea-level rise. Although abundant sediment supply has resulted in accretion on some parts of the coast of Bangladesh, others are experiencing rapid erosion. We report a systematic assessment of rates of shoreline change over a 20-year period from 1989 to 2009, using Landsat satellite images with pixel resolution of 30 m on the ground. A Band ratio approach, using Band-5 divided by Band-2, discriminated the water line on images that were largely cloud-free, adequately registered, and at comparable tidal stages. Rates of shoreline change were calculated for &gt;16,000 transects generated at 50 m intervals along the entire mainland coastline (&gt;1,100 km) and major islands, using the End Point Rate (EPR) method in the Digital Shoreline Analysis System (DSAS) extension in ArcGIS®. Erosion characterises most of the seaward margin of the Sundarbans in western Bangladesh. Retreat rates of up to 20 m/yr are typical, with little evidence that local devastation of the mangrove fringe by Cyclone Sidr in November 2007 had resulted in uncharacteristic long-term rates of retreat where it made landfall. Erosion exceeded accretion in the Barguna Patuakhali coastal zone, most of which eroded at up to 20 m/yr, but with truncation of the southern tip of the Patharghata Upazila at up to 100 m/yr. In Bhola, erosion at rates of up to 120 m/yr were observed along much of the coast, but in the Noakhali Feni coastal zone, similar rates of erosion were balanced by rapid accretion of the main promontory by more than 600 m/yr. Rates of change were more subdued in the Chittagong and Cox's Bazar coastal zones of southeast Bangladesh. Islands in the Meghna estuary were especially dynamic; Hatiya Island accreted along some of its shoreline by 50 km2 between 1989 and 2009, but lost 65 km2 through erosion elsewhere, resulting in the island moving south. Similar trends were observed on adjacent islands. The overall area changed relatively little across the entire coastline over the 20-year period with accretion of up to 315 km2, countered by erosion of about 307 km2. © 2013 Springer Science+Business Media Dordrecht."
"6602300916;55968508800;","The link between from day to day change of weather types and synoptic situations in KrakóW during the period 1961-2010",2013,"10.2478/quageo-2013-0023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890504541&doi=10.2478%2fquageo-2013-0023&partnerID=40&md5=8cf5679946c900e75e5412479b1ce947","This paper analyses day-to-day changes of weather types and links these with synoptic situations, i.e. circulation types, air masses and weather fronts. The weather types were classified according to Woś (1999), while a calendar proposed by Niedźwiedź (2013) was used for synoptic situations. Weather records from Kraków were used covering the period 1961-2010. The frequency of all combinations of day-to-day weather type changes was calculated, identified using specific values of air temperature, cloudiness and precipitation. The analysis of the succession and frequency of the day-to-day changes was linked with the synoptic situations accompanying the change. It was found that the thermal weather types were relatively very stable and remained unchanged on the following day in 61.3% of cases, and that the synoptic situation also remained similar. Weather subtypes, identified with just cloudiness and precipitation, but not temperature, displayed much more day-to-day change in terms of frequency and scale. Synoptically it was the air mass change and/or the occurrence of atmospheric fronts, which tended to cause day-to-day weather type changes, while the impact of circulation was not always clear. Particular attention was devoted to sudden weather type changes caused primarily by dramatic air temperature fluctuations."
"25958628300;35898715500;36138073500;7202948585;7401491382;","Effects of bubbles, cracks, and volcanic tephra on the spectral albedo of bare ice near the Transantarctic Mountains: Implications for sea glaciers on Snowball Earth",2013,"10.1002/jgrf.20098","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887852293&doi=10.1002%2fjgrf.20098&partnerID=40&md5=d5047e3315a644e3b9092540fb99189b","Spectral albedo was measured along a 6 km transect near the Allan Hills in East Antarctica. The transect traversed the sequence from new snow through old snow, firn, and white ice, to blue ice, showing a systematic progression of decreasing albedo at all wavelengths, as well as decreasing specific surface area (SSA) and increasing density. Broadband albedos under clear-sky range from 0.80 for snow to 0.57 for blue ice, and from 0.87 to 0.65 under cloud. Both air bubbles and cracks scatter sunlight; their contributions to SSA were determined by microcomputed tomography on core samples of the ice. Although albedo is governed primarily by the SSA (and secondarily by the shape) of bubbles or snow grains, albedo also correlates highly with porosity, which, as a proxy variable, would be easier for ice sheet models to predict than bubble sizes. Albedo parameterizations are therefore developed as a function of density for three broad wavelength bands commonly used in general circulation models: visible, near-infrared, and total solar. Relevance to Snowball Earth events derives from the likelihood that sublimation of equatorward-flowing sea glaciers during those events progressively exposed the same sequence of surface materials that we measured at Allan Hills, with our short 6 km transect representing a transect across many degrees of latitude on the Snowball ocean. At the equator of Snowball Earth, climate models predict thick ice, or thin ice, or open water, depending largely on their albedo parameterizations; our measured albedos appear to be within the range that favors ice hundreds of meters thick. ©2013. American Geophysical Union. All Rights Reserved."
"55326237100;6602350870;6701422868;6506887943;7006577245;7006525200;","A variational approach for retrieving ice cloud properties from infrared measurements: Application in the context of two IIR validation campaigns",2013,"10.5194/acp-13-8229-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883027702&doi=10.5194%2facp-13-8229-2013&partnerID=40&md5=14a204100e379e71b54f256eee230673","Cirrus are cloud types that are recognized to have a strong impact on the Earth-atmosphere radiation balance. This impact is however still poorly understood, due to the difficulties in describing the large variability of their properties in global climate models. Consequently, numerous airborne and space-borne missions have been dedicated to their study in the last decades. The satellite constellation A-Train has for instance proven to be particularly helpful for the study of cirrus. More particularly, the Infrared Imaging Radiometer (IIR) carried onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite shows a great sensitivity to the radiative and microphysical properties of these clouds. Our study presents a novel methodology that uses the thermal infrared measurements of IIR to retrieve the ice crystal effective size and optical thickness of cirrus. This methodology is based on an optimal estimation scheme, which possesses the advantage of attributing precise uncertainties to the retrieved parameters. Two IIR airborne validation campaigns have been chosen as case studies for illustrating the results of our retrieval method. It is observed that optical thicknesses could be accurately retrieved but that large uncertainties may occur on the effective diameters. Strong agreements have also been found between the products of our method when separately applied to the measurements of IIR and of the airborne radiometer CLIMAT-AV, which consolidates the results of previous validation studies of IIR level-1 measurements. Comparisons with in situ observations and with operational products of IIR are also discussed and appear to be coherent with our results. However, we have found that the quality of our retrievals can be strongly impacted by uncertainties related to the choice of a pristine crystal model and by poor constraints on the properties of possible liquid cloud layers underneath cirrus. Simultaneous retrievals of liquid clouds radiative and microphysical properties and/or the use of different ice crystal models should therefore be considered in order to improve the quality of the results. © 2013 Author(s)."
"7004159166;","A steady-state analysis of the temperature responses of water vapor and aerosol lifetimes",2013,"10.5194/acp-13-8245-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882965924&doi=10.5194%2facp-13-8245-2013&partnerID=40&md5=6d103480a6c234e60879ead2d6086b7a","The dominant removal mechanism of soluble aerosol is wet deposition. The atmospheric lifetime of aerosol, relevant for aerosol radiative forcing, is therefore coupled to the atmospheric cycling time of water vapor. This study investigates the coupling between water vapor and aerosol lifetimes in a well-mixed atmosphere. Based on a steady-state study by Pruppacher and Jaenicke (1995) we describe the coupling in terms of the processing efficiency of air by clouds and the efficiencies of water vapor condensation, of aerosol activation, and of the transfer from cloud water to precipitation. We extend this to expressions for the temperature responses of the water vapor and aerosol lifetimes. Previous climate model results (Held and Soden, 2006) suggest a water vapor lifetime temperature response of +5.3 ± 2.0% K-1. This can be used as a first guess for the aerosol lifetime temperature response, but temperature sensitivities of the aerosol lifetime simulated in recent aerosol-climate model studies extend beyond this range and include negative values. This indicates that other influences probably have a larger impact on the computed aerosol lifetime than its temperature response, more specifically changes in the spatial distributions of aerosol (precursor) emissions and precipitation patterns, and changes in the activation efficiency of aerosol. These are not quantitatively evaluated in this study but we present suggestions for model experiments that may help to understand and quantify the different factors that determine the aerosol atmospheric lifetime. © Author(s) 2013."
"8067118800;6701752471;7202899330;","Evaluating cloud tuning in a climate model with satellite observations",2013,"10.1002/grl.50874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883197442&doi=10.1002%2fgrl.50874&partnerID=40&md5=5f00ce00d8f0ea1974ce56828cdd34c6","This study examines the validity of a tunable cloud parameter, the threshold particle radius triggering the warm rain formation, in a climate model. Alternate values of the model's particular parameter within uncertainty have been shown to produce severely different historical temperature trends due to differing magnitude of aerosol indirect forcing. Three different threshold radii are evaluated against satellite observations in terms of the statistics depicting microphysical process signatures of the warm rain formation. The results show that the simulated temperature trend best matches to observed trend when the model adopts the threshold radius that worst reproduces satellite-observed microphysical statistics and vice versa. This inconsistency between the ""bottom-up"" process-based constraint and the ""top-down"" temperature trend constraint implies the presence of compensating errors in the model. Key Points Evaluating a tunable cloud parameter in a climate model Exposing inconsistency between process-based and temperature-based constraints Implying compensating errors in the climate model. © 2013. American Geophysical Union. All Rights Reserved."
"35766719400;7004060399;","Are recent Arctic ozone losses caused by increasing greenhouse gases?",2013,"10.1002/grl.50835","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883116789&doi=10.1002%2fgrl.50835&partnerID=40&md5=cab141307037a22c86f30158e4da6e9a","It has been suggested that the Arctic ozone losses observed in recent years might be a manifestation of climate change due to increasing greenhouse gases. We here offer evidence to the contrary, by focusing on the volume of polar stratospheric clouds (VPSC), a convenient proxy for polar ozone loss whose simplicity allows for easily reproducible results. First, we analyze the time series of VPSC in three reanalysis data sets and find no statistically significant trends in VPSC-nor changes in their probability density functions-over the period 1979-2011. Second, we analyze VPSC in a stratosphere-resolving chemistry-climate model forced uniquely with increasing greenhouse gases following the A1B scenario: here too, we find no significant changes in VPSC over the entire 21st century. Taken together, these results strongly suggest that the sporadic high ozone losses in recent years have not been caused by increasing greenhouse gases. Key Points Reanalyses show no significant trends in Arctic polar stratospheric cloud volume Models forced solely with increasing greenhouse gases show no trends from 1960 to 2100 Recent Arctic ozone losses have not been caused by increasing greenhouse gases. © 2013. American Geophysical Union. All Rights Reserved."
"57219951382;7102495313;","Consequences of poor representation of Arctic sea-ice albedo and cloud-radiation interactions in the CMIP5 model ensemble",2013,"10.1002/grl.50768","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881644011&doi=10.1002%2fgrl.50768&partnerID=40&md5=a2233bdd2052eeb1b0b6a9d6a0b8277e","Clouds significantly influence the Arctic surface energy budget and a realistic representation of this impact is a key for proper simulation of the present-day and future climate. Considerable across-model spread in cloud variables remains in the fifth phase of Coupled Model Intercomparison Project ensemble and partly explains the substantial across-model spread in the surface radiative effect of the clouds. In summer, the extensive model differences in sea-ice albedo, which sets the potential of the cloud-albedo effect, are strongly positively correlated to their cloud radiative effect. This indicates that the model's sea-ice albedo not only determines the amount, but also the sign of its cloud radiative effect. The analysis further suggests that the present-day annual amplitude of sea-ice cover depends inversely on the model's sea-ice albedo. Given the present-day across-model spread in sea-ice albedo and coverage, a transition to a summer ice-free Arctic ocean translates to a model-span of increased surface shortwave absorption of about 75 W m -2. Key Points Sea-ice albedo is poorly constrained in the CMIP5 model ensemble Models with low sea-ice albedo have a more pronounced annual cycle of sea-ice Model's sea-ice albedo sets sign of its surface cloud radiative effect. © 2013. American Geophysical Union. All Rights Reserved."
"7201472576;57214023403;","On the optimal method for evaluating cloud products from passive satellite imagery using CALIPSO-CALIOP data: Example investigating the CM SAF CLARA-A1 dataset",2013,"10.5194/amt-6-1271-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882758547&doi=10.5194%2famt-6-1271-2013&partnerID=40&md5=81be56a7ce7de18c1d1cb5427b983223","A method for detailed evaluation of a new satellite-derived global 28 yr cloud and radiation climatology (Climate Monitoring SAF Clouds, Albedo and Radiation from AVHRR data, named CLARA-A1) from polar-orbiting NOAA and Metop satellites is presented. The method combines 1 km and 5 km resolution cloud datasets from the CALIPSO-CALIOP (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation - Cloud-Aerosol Lidar with Orthogonal Polarization) cloud lidar for estimating cloud detection limitations and the accuracy of cloud top height estimations. Cloud detection is shown to work efficiently for clouds with optical thicknesses above 0.30 except for at twilight conditions when this value increases to 0.45. Some misclassifications of cloud-free surfaces during daytime were revealed for semi-arid land areas in the sub-tropical and tropical regions leading to up to 20% overestimated cloud amounts. In addition, a substantial fraction (at least 20-30%) of all clouds remains undetected in the polar regions during the polar winter season due to the lack of or an inverted temperature contrast between Earth surfaces and clouds. Subsequent cloud top height evaluation took into account the derived information about the cloud detection limits. It was shown that this has fundamental importance for the achieved results. An overall bias of -274 m was achieved compared to a bias of -2762 m when no measures were taken to compensate for cloud detection limitations. Despite this improvement it was concluded that high-level clouds still suffer from substantial height underestimations, while the opposite is true for low-level (boundary layer) clouds. The validation method and the specifically collected satellite dataset with optimal matching in time and space are suggested for a wider use in the future for evaluation of other cloud retrieval methods based on passive satellite imagery. © Author(s) 2013."
"6602571042;55659788300;8602890000;6508390183;55832356200;","A new simplified approach for simultaneous retrieval of so2and ash content of tropospheric volcanic clouds: An application Climate to the Mt Etna volcano",2013,"10.5194/amt-6-1315-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882739322&doi=10.5194%2famt-6-1315-2013&partnerID=40&md5=904f4b39c0d2ea637cc9cd7c222d694a","A new procedure is presented for simultaneous estimation of SO2 and ash abundance in a volcanic plume, using thermal infrared (TIR) MODIS data. Plume altitude and temperature are the only two input parameters required to run the procedure, while surface emissivity, temperature, atmospheric profiles, ash optical properties, and radiative transfer models are not necessary to perform the atmospheric corrections. The procedure gives the most reliable results when the surface under the plume is uniform, for example above the ocean, but still produces fairly good estimates in more challenging and not easily modelled conditions, such as above land or meteorological cloud layers. The developed approach was tested on the Etna volcano. By linearly interpolating the radiances surrounding a detected volcanic plume, the volcanic plume removal (VPR) procedure described here computes the radiances that would have been measured by the sensor in the absence of a plume, and reconstructs a new image without plume. The new image and the original data allow computation of plume transmittance in the TIR-MODIS bands 29, 31, and 32 (8.6, 11.0 and 12.0 μm) by applying a simplified model consisting of a uniform plume at a fixed altitude and temperature. The transmittances are then refined with a polynomial relationship obtained by means of MODTRAN simulations adapted for the geographical region, ash type, and atmospheric profiles. Bands 31 and 32 are SO2 transparent and, from their transmittances, the effective ash particle radius (Re), and aerosol optical depth at 550 nm (AOD550) are computed. A simple relation between the ash transmittances of bands 31 and 29 Data Systems is demonstrated and used for SO2 columnar content (cs) estimation. Comparing the results of the VPR procedure with MODTRAN simulations for more than 200 000 different cases, the frequency distribution of the differences shows the following: the Re error is less than ±0.5 μm in more than 60% of cases; the AOD550 error is less than ±0.125 in 80% of cases; the cs error is less than ±0.5 gm-2 in more than 60% of considered cases. The VPR procedure was applied in two case studies of recent eruptions occurring at the Mt Etna volcano, Italy, and successfully compared with the results obtained from the established SO2 and ash assessments based on look-up tables (LUTs). Assessment of the sensitivity to the plume altitude uncertainty is also made. The VPR procedure is simple, extremely fast, and can be adapted to other ash types and different volcanoes. © Author(s) 2013."
"7103246957;7102933062;15830822000;","Cloud radiative forcing of the diurnal cycle climate of the Canadian Prairies",2013,"10.1002/jgrd.50593","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885133365&doi=10.1002%2fjgrd.50593&partnerID=40&md5=4a128432b0808679c5d289d3c24856a7","This analysis uses 40 years of hourly observations of temperature (T), relative humidity (RH), and opaque cloud cover from 14 climate stations across the Canadian Prairies to analyze the diurnal cycle climate, represented by the mean T and RH and their diurnal ranges. From April to October, when incoming shortwave radiation dominates over longwave cooling, maximum temperature and the diurnal ranges of T and RH increase with decreasing opaque cloud cover, while minimum temperature is almost independent of cloud. During the winter period, both maximum and minimum temperatures fall with decreasing cloud, as longwave cooling dominates over the net shortwave flux, which is reduced by the high solar zenith angle and surface reflection by snow. We relate the daily mean opaque cloud cover to the longwave and shortwave cloud forcing and the effective cloud albedo, using multiyear measurements of downward shortwave and longwave fluxes, and longwave fluxes under clear skies from historical weather reanalysis. We provide quadratic fits to compute effective cloud albedo and net longwave fluxes from opaque cloud cover. During the warm season, the daytime rise of temperature is related to the net radiation, and the nighttime fall is related to the net longwave cooling. The diurnal range of T, RH, and all the net radiative fluxes have a quasi-linear dependence on the effective cloud albedo. This gives a seasonal climate perspective on the coupled land-surface system of T, RH, and cloud cover over the Canadian Prairies, and the winter transitions in snowy climates. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"8922308700;15755995900;34772240500;55544607500;7006705919;57193213111;","The Separate Physics and Dynamics Experiment (SPADE) framework for determining resolution awareness: A case study of microphysics",2013,"10.1002/jgrd.50711","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885132718&doi=10.1002%2fjgrd.50711&partnerID=40&md5=81b9c7328149643138efa88c2470dc0c","Multiresolution dynamical cores for weather and climate modeling are pushing the atmospheric community toward developing scale aware or, more specifically, resolution aware parameterizations that function properly across a range of grid spacings. Determining resolution dependence of specific model parameterizations is difficult due to resolution dependencies in many model components. This study presents the Separate Physics and Dynamics Experiment (SPADE) framework for isolating resolution dependent behavior of specific parameterizations without conflating resolution dependencies from other portions of the model. To demonstrate SPADE, the resolution dependence of theMorrison microphysics, from the Weather Research and Forecasting model, and the Morrison-Gettelman microphysics, from the Community Atmosphere Model, are compared for grid spacings spanning the cloud modeling gray zone. It is shown that the Morrison scheme has stronger resolution dependence than Morrison-Gettelman, and the partial cloud fraction capability of Morrison-Gettelman is not the primary reason for this difference. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"42862769000;55720588700;6602636483;6603631763;24071119300;","Evaluation of single field-of-view cloud top height retrievals from hyperspectral infrared sounder radiances with CloudSat and CALIPSO measurements",2013,"10.1002/jgrd.50681","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885146670&doi=10.1002%2fjgrd.50681&partnerID=40&md5=72c29a446ea9041d10c7ae6dc8d3b9c2","Accurate cloud top height retrievals from hyperspectral infrared (IR) sounder radiances are needed for weather and climate prediction. To account for the nonlinearity of the cloud parameters with respect to the IR radiances, a one-dimensional variational retrieval algorithm is used to derive the cloud top heights (CTHs) from the Atmospheric Infrared Sounder (AIRS) radiances on a single field-of-view basis. The CTHs are evaluated by comparison with the measurements from radar and lidar instruments onboard the Earth Observing System (EOS) CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. Using the retrievals from a global 3 day dataset, it is found that the variational algorithm compared with the regression algorithm could reduce the variability of the difference between the AIRS and active measurements by 1 km. And the biases of AIRS CTHs range from +1.5 to -1.4 km and from +1.6 to -3.8 km, depending on the Cloud Profiling Radar (CPR) and CALIPSO CTHs between 3 and 18 km, respectively. Globally, the AIRS CTH is overestimated (underestimated) when the CTH from active measurements is below (above) 5 km. The bias decreases from -1.9 to -0.8 km, and the variability decreases from 2.8 to about 1.6 km with the increase of the CALIPSO cloud optical thickness from 0.1 to 2.5. It also reveals that the AIRS CTHs agree better with the CPR than the CALIPSO. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"29467691000;7005135473;7404747615;","Multiplatform analysis of the radiative effects and heating rates for an intense dust storm on 21 June 2007",2013,"10.1002/jgrd.50713","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885088469&doi=10.1002%2fjgrd.50713&partnerID=40&md5=0973cc4a1798c4e09f9414613ccff302","Dust radiative effects and atmospheric heating rates are investigated for a Saharan dust storm on 21 June 2007 using a combination of multiple satellite data sets and ground and aircraft observations as input into a delta-four stream radiative transfer model (RTM). This combines the strengths of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations and CloudSat satellites and in situ aircraft data to characterize the vertical structure of the dust layers (5 km in height with optical depths between 1.5 and 2.0) and underlying low-level water clouds. These observations were used, along with Aerosol Robotic Network retrievals of aerosol optical properties, as input to the RTM to assess the surface, atmosphere, and top of atmosphere (TOA) shortwave aerosol radiative effects (SWAREs). Our results show that the dust TOA SWARE per unit aerosol optical depth was -56 W m-2 in cloud-free conditions over ocean and +74 W m-2 where the dust overlay low-level clouds, and show heating rates greater than 10 K/d. Additional case studies also confirm the results of the 21 June case. This study shows the importance of identifying clouds beneath dust as they can have a significant impact on the radiative effects of dust, and hence assessments of the role of dust aerosol on the energy budget and climate. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"36637539100;16202694600;9244992800;","Thermal characteristics of the cold-point tropopause region in CMIP5 models",2013,"10.1002/jgrd.50649","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885123297&doi=10.1002%2fjgrd.50649&partnerID=40&md5=72123eccd21ac4264530f52ab528f4c8","The climatology, seasonality, and intraseasonal to interannual variability of the temperature field near the cold-point tropopause (CPT) are examined using the state-of-the-art climate models that participated in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Both historical simulations and future projections based on the Representative Concentration Pathway (RCP) 8.5 scenario are used to evaluate model performance and to identify potential changes at the CPT focusing on the 100 hPa and zero-lapse-rate (ZLR) temperatures. It is found that historical simulations successfully reproduce the large-scale spatial structure and seasonality of observed temperature and reasonably capture variability associated with El Niño-Southern Oscillation and equatorial waves near the CPT. However, the models show nonnegligible biases in several aspects: (1) most models have a warm bias around the CPT, (2) large intermodel differences occur in the amplitude of the seasonal cycle in 100 hPa temperature, (3) several models overestimate lower stratospheric warming in response to volcanic aerosols, (4) temperature variability associated with the quasi-biennial oscillation and Madden-Julian oscillation is absent in most models, and (5) equatorial waves near the CPT exhibit a wide range of variations among the models. In the RCP 8.5 scenario, the models predict robust warming both at the 100 hPa and ZLR levels, but cooling at the 70 hPa level. A weakened seasonal cycle in the temperature is also predicted in most models at both the 100 and 70 hPa levels. These findings may have important implications for cross-tropopause water vapor transport and related global climate change and variability. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"35073084900;7003263504;56537463000;","A validation study for GPS radio occultation data with moist thermodynamic structure of tropical cyclones",2013,"10.1002/jgrd.50698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885145746&doi=10.1002%2fjgrd.50698&partnerID=40&md5=931bd9b75d17943da8cec9973074ca06","We exploit the cloud-penetrating capability and insensitivity to precipitation of the Global Positioning System radio occultation (GPSRO) technique to study the humidity environment of tropical cyclones (TCs). We focus in regions within and around the vicinity of TCs' eye, where infrared and microwave observations are difficult to acquire due to cloudiness and heavy precipitation. We use data from the National Hurricane Center TC Best Tracks to identify the location of North Atlantic TCs. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center provides concurrent refractivity, temperature, and humidity measurements from the Challenging Minisatellite Payload and COSMIC missions and the European Centre for Medium-Range Weather Forecasts (ECMWF). The distribution of GPSRO-derived humidity profiles as functions of altitude and distance from the storms' center identifies a pronounced low-level inflow, characteristic of mature TCs, at distances between 50 and 90 km, which coincide with the area where the eyewall of TCs forms. We also capture wavelike structures resembling spiral rainbands beyond the eyewall. The distribution of water vapor as functions of altitude and TC intensity shows a decrease at all altitudes when a tropical system matures from a tropical depression to a Category 1 (Cat 1) hurricane. The water vapor gradually increases from Cat 2 to Cat 5 hurricanes - a result that is also identified in ECMWF data sets and Atmospheric Infrared Sounder observations. We conclude that GPSRO data can contribute significantly to the understanding and modeling of the vertical structures of TCs. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"9738329300;7102314226;26533129200;56372089100;","Toward a comprehensive global electric circuit model: Atmospheric conductivity and its variability in CESM1(WACCM) model simulations",2013,"10.1002/jgrd.50725","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885130064&doi=10.1002%2fjgrd.50725&partnerID=40&md5=91505b45333e5c434c85f830183bd5cd","As an important step in further modeling and understanding the global electric circuit, the Community Earth System Model (CESM1) has been extended to provide a calculation of conductivity in the troposphere and stratosphere. Conductivity depends on ion mobility and ion concentration, the latter being controlled by a number of ion production and loss processes. This leads to a complex dependency of conductivity on most importantly galactic cosmic ray flux, radon emissions from the Earth's surface, aerosol number concentrations, clouds, and temperature. To cover this variety in parameters for calculating and evaluating conductivity, an Earth system model is extremely useful. Here the extension of CESM1 to calculate conductivity is described, and the results are discussed with a focus on their spatial and temporal variabilities. The results are also compared to balloon and aircraft measurements, and good agreement is found for undisturbed conditions and during a solar proton event. The conductivity model implementation is a significant improvement to previous studies because of the high-quality, high-resolution model data input. Notably, the aerosol representation provided by off-line calculations of tropospheric and stratospheric aerosol using the Community Aerosol and Radiation Model for Atmospheres as part of CESM1(WACCM) (Whole Atmosphere Community Climate Model) provides a realistic computation of the impact of the background aerosol distribution for the first time. In addition to the novel high-resolution information on conductivity, it is found that an intra-annual cycle exists in the total global resistance, varying between 220 and 245 Ω. The model shows that this cycle is driven equally by seasonal aerosol and cloud variations. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"7402284525;7005275092;7004352797;9434771700;","Sensitivity of stratospheric dynamics to uncertainty in O3 production",2013,"10.1002/jgrd.50689","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885092795&doi=10.1002%2fjgrd.50689&partnerID=40&md5=1c4109776da3427e336ea4201273a0de","Some key photochemical uncertainties that cannot be readily eliminated by current observations translate into a range of stratospheric O3 abundances in the tens of percent. The uncertainty in O3 production due to that in the cross sections for O2 in the Hertzberg continuum is studied here with the NCAR Community Atmosphere Model, which allows for interactive climate and ozone chemistry. A min-max range in the O2 cross sections of 30%, consistent with current uncertainties, changes O 3 abundances in the lower tropical stratosphere by up to 30%, with a relatively smaller and opposite change above 30 hPa. Here we have systematically examined the changes in the time-mean state, the seasonal cycle, and the interannual variability of the temperature and circulation associated with the 30% change in O2 cross sections. This study points to the important role of O3 in the lower tropical stratosphere in determining the physical characteristics of the tropical tropopause layer. Reducing O 2 cross sections by 30% increases ozone abundances which warms the lower stratosphere (60iS -60iN; 2 K maximum at equator) and lowers the tropopause height by 100-200 m (30iS -30iN). The large-scale warming leads to enhanced stratification near the tropopause which reduces upward wave propagation everywhere except for high latitudes. The lowermost tropical stratosphere is better ventilated during austral winter. The annual cycle of ozone is amplified. The interannual variability of the winter stratospheric polar vortices also increases, but the mechanism involves wave-mean flow interaction, and the exact role of ozone in it needs further investigation. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"55243352000;6507478686;35588263000;","Simulation of the spatial distribution of mineral dust and its direct radiative forcing over Australia",2013,"10.3402/tellusb.v65i0.19856","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882591077&doi=10.3402%2ftellusb.v65i0.19856&partnerID=40&md5=b98c0a977a70adbff9196857bc98e8f2","Direct radiative forcing by mineral dust is important as it significantly affects the climate system by scattering and absorbing short-wave and long-wave radiation. The multi-angle imaging spectro radiometer (MISR) and cloud-aerosol lidar with orthogonal polarisation (CALIOP) aerosol data are used to observe mineral dust distribution over Australia. In addition, the weather research and forecasting with chemistry (WRF/Chem) model is used to estimate direct radiative forcing by dust. At the surface, the model domain clear-sky shortwave and long-wave direct radiative forcing by dust averaged for a 6-month period (austral spring and summer) was estimated to be -0.67 W m-2 and 0.13 W m-2, respectively. The long-wave warming effect of dust therefore offsets 19.4% of its short-wave cooling effect. However, over Lake Eyre Basin where coarse particles are more abundant, the long-wave warming effect of dust offsets 60.9% of the short-wave cooling effect. At the top of the atmosphere (TOA), clear-sky short-wave and long-wave direct radiative forcing was estimated to be -0.26 W m-2 and -0.01 W m-2, respectively. This leads to a net negative direct radiative forcing of dust at the TOA, indicating cooling of the atmosphere by an increase in outgoing radiation. Shortwave and long-wave direct radiative forcing by dust is shown to have a diurnal variation due to changes in solar zenith angle and in the intensity of infrared radiation. Atmospheric heating due to absorption of shortwave radiation was simulated, while the interaction of dust with long-wave radiation was associated with atmospheric cooling. The net effect was cooling of the atmosphere near the surface (below 0.2 km), with warming of the atmosphere at higher altitudes. © 2013 O. Alizadeh Choobari et al."
"56333106800;56265106600;35203328900;16444950900;6602074056;","Cirrus crystal fall velocity estimates using the Match method with ground-based lidars: First investigation through a case study",2013,"10.5194/amt-6-457-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882623331&doi=10.5194%2famt-6-457-2013&partnerID=40&md5=a1e4cf7adc118d6893381444da14d083","Cirrus ice particle sedimentation velocity (vs) is one of the critical variables for the parameterization of cirrus properties in a global climate model (GCM). In this study a methodology to estimate cirrus properties, such as crystal mean fall speed, through successive lidar measurements is evaluated. This ""Match"" technique has been applied on cirrus cloud observations and then tested with measurements from two ground-based lidars located in the Mediterranean area. These systems, with similar instrumental characteristics, are installed at the Observatory of Haute Provence (OHP, 43.9° N, 5.7° E) in France and at Rome Tor Vergata (RTV, 41.8° N, 12.6° E) in Italy. At a distance of approximately 600 km, the two lidar stations have provided systematic measurements for several years and are along a typical direction of an air path. A test case of an upper tropospheric cirrus, observed over both sites during the night between 13 and 14 March 2008, has been selected and the feasibility of the Match-cirrus approach investigated through this case. The analysis through lidar principal parameters (vertical location, geometrical thickness and optical depth) reveals a case of a thin sub-visible cirrus (SVC) located around the tropopause. A first range of values for v s (1.4-1.9 cm s-1, consistent with simple-shaped small crystals) has been retrieved with a simplified approach (adiabatic transport and ""frozen"" microphysical conditions inside the cirrus). The backward trajectory analysis suggests a type of cirrus formed by large-scale transport processes (adiabatic cooling of moist air masses coming from the subtropical area around Mexico gulf), which is characterized by a long atmospheric lifetime and horizontal extension of several hundred km. The analysis of this case study reveals that many uncertainties reduce the confidence of the retrieved estimates of the crystal fall velocity. However, this paper allows for assessing the technique feasibility by identifying the main critical issues for future similar investigations. This study shows that such approach is feasible; however, the methodology should be improved and some directions have been suggested for future campaigns. © Author(s) 2013. CC Attribution 3.0 License."
"7801344746;55339298600;57206531303;16639418500;","HelioFTH: Combining cloud index principles and aggregated rating for cloud masking using infrared observations from geostationary satellites",2013,"10.5194/amt-6-1883-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882378249&doi=10.5194%2famt-6-1883-2013&partnerID=40&md5=38bdc95b10cb99f762a60620279b13b9","In this paper a cloud mask and cloud fractional coverage (CFC) retrieval scheme called HelioFTH is presented. The algorithm is self-calibrating and relies on infrared (IR) window-channel observations only. It needs no input from numerical weather prediction (NWP) or radiative transfer models, nor from other satellite platforms. The scheme is applicable to the full temporal and spatial resolution of the Meteosat Visible and InfraRed Imager (MVIRI) and the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) sensors. The main focus is laid on the separation of middle- and high-level cloud coverage (HCC) from low-level clouds based on an internal cloud-top pressure (CTP) product. CFC retrieval employs a IR-only cloud mask based on an aggregated rating scheme. CTP retrieval is based on a Heliosat-like cloud index for the MVIRI IR channel. CFC from HelioFTH, the International Satellite Cloud Climatology Project (ISCCP) DX and the Satellite Application Facility on Climate Monitoring (CM SAF) were validated with CFC from the Baseline Surface Radiation Network (BSRN) and the Alpine Surface Radiation Budget (ASRB) network. HelioFTH CFC differs by not more than 5-10% from CM SAF CFC but it is higher than ISCCP-DX CFC. In particular the conditional probability to detect cloud-free pixels with HelioFTH is raised by about 35% compared to ISCCP-DX. The HelioFTH CFC is able to reproduce the day-to-day variability observed at the surface. Also, the HelioFTH HCC was inter-compared to CM SAF and ISCCP-DX over different regions and stations. The probability of false detection of cloud-free HCC pixels is in the same order as ISCCP-DX compared to the CM SAF HCC product over the full-disk area. HelioFTH could be used for generating an independent climate data record of cloud physical properties once its consistency and homogeneity is validated for the full Meteosat time series. © Author(s) 2013."
"55917711400;7006960661;14051743300;23568640600;23568239000;22936667100;35263614500;6603303046;7003769662;55827123800;12243975700;14820094400;55826210400;7003299547;7006430057;15840467900;7005216212;57194628631;6504793116;55947099700;56920790500;7801561771;6603100667;14051743300;7003363359;57205638870;6601950693;","Aerosol retrieval experiments in the ESA Aerosol-cci project",2013,"10.5194/amt-6-1919-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880881831&doi=10.5194%2famt-6-1919-2013&partnerID=40&md5=d2aa910e4ae995d9923b594a054ac4f6","Within the ESA Climate Change Initiative (CCI) project Aerosol-cci (2010-2013), algorithms for the production of long-term total column aerosol optical depth (AOD) datasets from European Earth Observation sensors are developed. Starting with eight existing pre-cursor algorithms three analysis steps are conducted to improve and qualify the algorithms: (1) a series of experiments applied to one month of global data to understand several major sensitivities to assumptions needed due to the ill-posed nature of the underlying inversion problem, (2) a round robin exercise of ""best"" versions of each of these algorithms (defined using the step 1 outcome) applied to four months of global data to identify mature algorithms, and (3) a comprehensive validation exercise applied to one complete year of global data produced by the algorithms selected as mature based on the round robin exercise. The algorithms tested included four using AATSR, three using MERIS and one using PARASOL. This paper summarizes the first step. Three experiments were conducted to assess the potential impact of major assumptions in the various aerosol retrieval algorithms. In the first experiment a common set of four aerosol components was used to provide all algorithms with the same assumptions. The second experiment introduced an aerosol property climatology, derived from a combination of model and sun photometer observations, as a priori information in the retrievals on the occurrence of the common aerosol components. The third experiment assessed the impact of using a common nadir cloud mask for AATSR and MERIS algorithms in order to characterize the sensitivity to remaining cloud contamination in the retrievals against the baseline dataset versions. The impact of the algorithm changes was assessed for one month (September 2008) of data: qualitatively by inspection of monthly mean AOD maps and quantitatively by comparing daily gridded satellite data against daily averaged AERONET sun photometer observations for the different versions of each algorithm globally (land and coastal) and for three regions with different aerosol regimes. The analysis allowed for an assessment of sensitivities of all algorithms, which helped define the best algorithm versions for the subsequent round robin exercise; all algorithms (except for MERIS) showed some, in parts significant, improvement. In particular, using common aerosol components and partly also a priori aerosol-type climatology is beneficial. On the other hand the use of an AATSR-based common cloud mask meant a clear improvement (though with significant reduction of coverage) for the MERIS standard product, but not for the algorithms using AATSR. It is noted that all these observations are mostly consistent for all five analyses (global land, global coastal, three regional), which can be understood well, since the set of aerosol components defined in Sect. 3.1 was explicitly designed to cover different global aerosol regimes (with low and high absorption fine mode, sea salt and dust). © Author(s) 2013."
"57206204252;8349977900;","Atmospheric dissolved iron deposition to the global oceans: Effects of oxalate-promoted Fe dissolution, photochemical redox cycling, and dust mineralogy",2013,"10.5194/gmd-6-1137-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882316676&doi=10.5194%2fgmd-6-1137-2013&partnerID=40&md5=87c7c06a3ff6436223dae5ceb4e9acf6","Mineral dust deposition is suggested to be a significant atmospheric supply pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this study, mineral dust and dissolved Fe (Fed) deposition rates are predicted for March 2009 to February 2010 using the 3-D chemical transport model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme. The model simulates Fed production during the atmospheric transport of mineral dust, taking into account inorganic and organic (oxalate)-promoted Fe dissolution processes, photochemical redox cycling between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of three different Fe-containing minerals (hematite, goethite, and aluminosilicates), and detailed mineralogy of wind-blown dust from the major desert regions. Our calculations suggest that during the year-long simulation ∼0.26 Tg (1 Tg Combining double low line 1012 g) of Fed was deposited to global oceanic regions. Compared to simulations only taking into account proton-promoted Fe dissolution, the addition of oxalate and Fe(II)/Fe(III) redox cycling to the dust-Fe mobilization scheme increased total annual model-predicted Fed deposition to global oceanic regions by ∼75%. The implementation of Fe(II)/Fe(III) photochemical redox cycling in the model also allows for the distinction between different oxidation states of deposited Fed. Our calculations suggest that during the daytime, large fractions of Fed deposited to the global oceans is likely to be in Fe(II) form, while nocturnal fluxes of Fed are largely in Fe(III) form. Model sensitivity simulations suggest Fed fluxes to the oceans can range from ∼50% reduction to ∼150% increase associated with the uncertainty in Fe-containing minerals commonly found in dust particles. This study indicates that Fe d deposition to the oceans is controlled by total dust-Fe mass concentrations, mineralogy, the surface area of dust particles, atmospheric chemical composition, cloud processing, and meteorological parameters and exhibits complex and spatiotemporally variable patterns. Our study suggests that the explicit model representation of individual processes leading to Fe d production within mineral dust are needed to improve the understanding of the atmospheric Fe cycle, and quantify the effect of dust-Fe on ocean biological productivity, carbon cycle, and climate. © Author(s) 2013."
"36627288300;6603618077;24921885300;","Clouds in the atmospheres of extrasolar planets: IV. on the scattering greenhouse effect of CO2 ice particles: Numerical radiative transfer studies",2013,"10.1051/0004-6361/201220025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881650572&doi=10.1051%2f0004-6361%2f201220025&partnerID=40&md5=4fe8dc1d4bc3dc47db52285c12367140","Context. Owing to their wavelength-dependent absorption and scattering properties, clouds have a strong impact on the climate of planetary atmospheres. The potential greenhouse effect of CO2 ice clouds in the atmospheres of terrestrial extrasolar planets is of particular interest because it might influence the position and thus the extension of the outer boundary of the classic habitable zone around main sequence stars. Such a greenhouse effect, however, is a complicated function of the CO2 ice particles' optical properties. Aims. We study the radiative effects of CO2 ice particles obtained by different numerical treatments to solve the radiative transfer equation. To determine the effectiveness of the scattering greenhouse effect caused by CO2 ice clouds, the radiative transfer calculations are performed over the relevant wide range of particle sizes and optical depths, employing different numerical methods. Methods. We used Mie theory to calculate the optical properties of particle polydispersion. The radiative transfer calculations were done with a high-order discrete ordinate method (DISORT). Two-stream radiative transfer methods were used for comparison with previous studies. Results. The comparison between the results of a high-order discrete ordinate method and simpler two-stream approaches reveals large deviations in terms of a potential scattering efficiency of the greenhouse effect. The two-stream methods overestimate the transmitted and reflected radiation, thereby yielding a higher scattering greenhouse effect. For the particular case of a cool M-type dwarf, the CO2 ice particles show no strong effective scattering greenhouse effect by using the high-order discrete ordinate method, whereas a positive net greenhouse effect was found for the two-stream radiative transfer schemes. As a result, previous studies of the effects of CO2 ice clouds using two-stream approximations overrated the atmospheric warming caused by the scattering greenhouse effect. Consequently, the scattering greenhouse effect of CO2 ice particles seems to be less effective than previously estimated. In general, higher order radiative transfer methods are needed to describe the effects of CO2 ice clouds accurately as indicated by our numerical radiative transfer studies. © 2013 ESO."
"55802246600;8042408300;55522498000;7102266120;","A modeling study of irrigation effects on surface fluxes and land-air-cloud interactions in the southern great plains",2013,"10.1175/JHM-D-12-0134.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881501315&doi=10.1175%2fJHM-D-12-0134.1&partnerID=40&md5=afa50ea9f58aebbc2308c3bc9abfd181","In this study, the authors incorporate an operational-like irrigation scheme into the Noah land surface model as part of the Weather Research and Forecasting Model (WRF). A series of simulations, with and without irrigation, is conducted over the Southern Great Plains (SGP) for an extremely dry (2006) and wet (2007) year. The results show that including irrigation reduces model bias in soil moisture and surface latent heat (LH) and sensible heat (SH) fluxes, especially during a dry year. Irrigation adds additional water to the surface, leading to changes in the planetary boundary layer. The increase in soil moisture leads to increases in the surface evapotranspiration and near-surface specific humidity but decreases in the SH and surface temperature. Those changes are local and occur during daytime. There is an irrigation-induced decrease in both the lifting condensation level (ZLCL) and mixed-layer depth. The decrease in ZLCL is larger than the decrease in mixed-layer depth, suggesting an increasing probability of shallow clouds. The simulated changes in precipitation induced by irrigation are highly variable in space, and the average precipitation over the SGP region only slightly increases. A high correlation is found among soil moisture, SH, and ZLCL. Larger values of soil moisture in the irrigated simulation due to irrigation in late spring and summer persist into the early fall, suggesting that irrigation-induced soil memory could last a few weeks to months. The results demonstrate the importance of irrigation parameterization for climate studies and improve the process-level understanding on the role of human activity in modulating land-air-cloud interactions. © 2013 American Meteorological Society."
"55660994800;56520921400;56048942300;7201425334;6701681018;7004807312;35301550500;","Climate response due to carbonaceous aerosols and aerosol-induced SST effects in NCAR community atmospheric model CAM3.5",2013,"10.5194/acp-13-7489-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881426748&doi=10.5194%2facp-13-7489-2013&partnerID=40&md5=2dba0a12d37387e10aca740ec7924a8e","This study used the Community Atmospheric Model 3.5 (CAM3.5) to investigate the effects of carbonaceous aerosols on climate. The simulations include control runs with 3 times the mass of carbonaceous aerosols as compared to the model's default carbonaceous aerosol mass, as well as no-carbon runs in which carbonaceous aerosols were removed. The slab ocean model (SOM) and the fixed sea surface temperature (SST) were used to examine effects of ocean boundary conditions. Throughout this study, climate response induced by aerosol forcing was mainly analyzed in the following three terms: (1) aerosol radiative effects under fixed SST, (2) effects of aerosol-induced SST feedbacks, and (3) total effects including effects of aerosol forcing and SST feedbacks. The change of SST induced by aerosols has large impacts on distribution of climate response; the magnitudes in response patterns such as temperature, precipitation, zonal winds, mean meridional circulation, radiative fluxes, and cloud coverage are different between the SOM and fixed SST runs. Moreover, different spatial responses between the SOM and fixed SST runs can also be seen in some local areas. This implies the importance of SST feedbacks on simulated climate response. The aerosol dimming effects cause a cooling predicted at low layers near the surface in most carbonaceous aerosol source regions. The temperature response shows a warming (cooling) predicted in the north (south) high latitudes, suggesting that aerosol forcing can cause climate change in regions far away from its origins. Our simulation results show that direct and semidirect radiative forcing due to carbonaceous aerosols decreases rainfall in the tropics. This implies that carbonaceous aerosols have possibly strong influence on weakening of the tropical circulation. Most changes in precipitation are negatively correlated with changes of radiative fluxes at the top of model. The changes in radiative fluxes at top of model are physically consistent with the response patterns in cloud fields. On global average, low-level cloud coverage increases, and mid- and high-level cloud coverage decreases in response to changes in radiative energy induced by aerosol forcing. An approximated moisture budget equation was analyzed in order to understand physical mechanism of precipitation changes induced by carbonaceous aerosols. Our results show that changes in tropical precipitation are mainly dominated are mainly dominated by the dynamic effect (i.e., vertical moisture transport carried by the perturbed flow). © Author(s) 2013."
"55444446000;6603150490;22733483400;7005168193;6507842550;6603950837;","Characterizing floods in the poorly gauged wetlands of the Tana River Delta, Kenya, using a water balance model and satellite data",2013,"10.5194/hess-17-3059-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881428495&doi=10.5194%2fhess-17-3059-2013&partnerID=40&md5=0bc220756573e5f84da95e7cb1227c97","Wetlands, such as those of the Tana River Delta in Kenya, are vital but threatened ecosystems. The flooding characteristics of wetlands largely determine their physical, chemical and biological properties, so their quantification is crucial for wetland management. This quantification can be achieved through hydrological modelling. In addition, the analysis of satellite imagery provides essential hydrological data to monitor floods in poorly gauged zones. The objective of this study was to quantify the main water fluxes and flooding characteristics (extent, duration and number of floods) in the poorly gauged Tana River Delta in East Africa during 2002-2011. To do so, we constructed a lumped hydrological model (the Tana Inundation Model, TIM) that was calibrated and validated with MODIS data. Further analysis of the MYD09A1 500 m composite product provided a map of the empirical probability of flooded state. In non-extreme years and for the current topology of the delta, the flood extent exceeded 300 km2. Floods over 200 km2 occurred on average once a year, with a mean duration of 18 days. River discharge from the upper basin counted for over 95% of the total water inflow. The results are discussed in the light of possible improvements of the models and wetland management issues. This study provides the first known quantification of spatial and temporal flooding characteristics in the Tana River Delta. As such, it is essential for the water and natural resource management of the Tana River basin. The water balance approach was pertinent to the study of this system, for which information on its internal properties and processes is limited. The methodology, a combination of hydrological modelling and flood mapping using MODIS products, should be applicable to other areas, including those for which data are scarce and cloud cover may be high, and where a medium spatial resolution is required. © Author(s) 2013."
"55268661300;55461837700;","The signature of the stratospheric Brewer-Dobson circulation in tropospheric clouds",2013,"10.1002/jgrd.503392013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881105162&doi=10.1002%2fjgrd.503392013&partnerID=40&md5=7d130ab48fc43238f3d7c13aec2b4669","The signature of the stratospheric Brewer-Dobson circulation (BDC) in tropospheric cloudiness is investigated in CloudSat and CALIPSO data from June 2006 through April 2011. During the Northern Hemisphere winter, periods of enhanced stratospheric wave driving are associated with increased cloud incidence in the tropical tropopause transition layer (TTL) juxtaposed against decreased cloud incidence in the Arctic troposphere. The results are consistent with the physical linkages between (1) the BDC and near-tropopause temperature and (2) near-tropopause temperature and upper tropospheric cloud incidence. The key finding of the work is that changes in the stratospheric circulation not only influence cloud amounts in the troposphere but also that they do so in a coupled manner that links climate variability in the Arctic and upper tropical troposphere. The results provide a pathway through which stratospheric processes influence tropospheric climate that is in addition to stratosphere/troposphere dynamical coupling. © 2013. American Geophysical Union. All Rights Reserved."
"19639722300;7201459977;7006904374;","Diagnosing evaporative fraction over land from boundary-layer clouds",2013,"10.1002/jgrd.50416","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884166514&doi=10.1002%2fjgrd.50416&partnerID=40&md5=4e69ad76d8b157b2f546ac3228d7569e","The potential use of continental fair-weather shallow cumuli as a way to retrieve the daily surface evaporative fraction over land is evaluated in convective conditions. The proposed method utilizes the fact that both the timing of cloud occurrence and the cloud-base height at the time of occurrence provide strong constraints on the surface energy balance and evaporative fraction. The retrieval is especially reliable in the presence of relatively stable and humid-free troposphere profiles. The advantage of the method is that it provides a more direct estimate of the surface evaporative fraction than indirect estimation based on inversion of a highly parameterized land-surface model. In addition, the evaporative fraction is obtained at a scale of a few kilometers, which is more pertinent for weather and climate studies. The retrieval strategy is tested and validated for three contrasting climates: the U.S. southern Great Plains, West Africa, and the Netherlands. We suggest that the use of satellite observations of shallow cumuli can help constrain the retrieval of the surface evaporative fraction within a data assimilation scheme/reanalysis. Key Points Onset of cumulus provides indicator of evaporative fraction. Cumulus are direct observables of surface energy partitioning Strategy requires less parameterization than inversion of land surface model. ©2013. American Geophysical Union. All Rights Reserved."
"42263280300;55796506900;7410070663;55355176000;36628695400;","Radiative forcing and climate response due to the presence of black carbon in cloud droplets",2013,"10.1002/jgrd.503122013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881089234&doi=10.1002%2fjgrd.503122013&partnerID=40&md5=e2d82e506a65823e04896edbb115a2ca","Optical properties of clouds containing black carbon (BC) particles in their water droplets are calculated by using the Maxwell Garnett mixing rule and Mie theory. The obtained cloud optical properties were then applied to an interactive system by coupling an aerosol model with a General Circulation Model. This system is used to investigate the radiative forcing and the equilibrium climate response due to BC in cloud droplets. The simulated global annual mean radiative forcing at the top of the atmosphere due to the BC in cloud droplets is found to be 0.086Wm2. Positive radiative forcing can be seen in Africa, South America, East and South Asia, and West Europe, with a maximum value of 1.5Wm2 being observed in these regions. The enhanced cloud absorption is shown to increase the global annual mean values of solar heating rate, water vapor, and temperature, but to decrease the global annual mean cloud fraction. Finally, the global annual mean surface temperature is shown to increase by +0.08 K. The local maximum changes are found to be as low as 1.5K and as high as +0.6 K. We show there has been a significant difference in surface temperature change in the Southern and Northern Hemisphere (+0.19K and 0.04 K, respectively). Our results show that this interhemispheric asymmetry in surface temperature change could cause a corresponding change in atmospheric dynamics and precipitation. It is also found that the northern trade winds are enhanced in the Intertropical Convergence Zone (ITCZ). This results in northerly surface wind anomalies which cross the equator to converge with the enhanced southern trade winds in the tropics of Southern Hemisphere. This is shown to lead to an increase (a decrease) of vertical ascending motion and precipitation on the south (north) side of the equator, which could induce a southward shift in the tropical rainfall maximum related to the ITCZ. © 2013. American Geophysical Union. All Rights Reserved."
"55683113200;26639062900;8899985400;55683299900;14828772800;24468213900;7005858285;13608200200;14067215000;6507224602;7006960329;7403401100;7006347751;7005773698;","Impact of marine biogeochemistry on the chemical mixing state and cloud forming ability of nascent sea spray aerosol",2013,"10.1002/jgrd.50598","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884125324&doi=10.1002%2fjgrd.50598&partnerID=40&md5=321f52fcec54e73c3f7da652e7c4234b","The composition and properties of sea spray aerosol, a major component of the atmosphere, are often controlled by marine biological activity; however, the scope of impacts that ocean chemistry has on the ability for sea spray aerosol to act as cloud condensation nuclei (CCN) is not well understood. In this study, we utilize a mesocosm experiment to investigate the impact of marine biogeochemical processes on the composition and mixing state of sea spray aerosol particles with diameters < 0.2 μm produced by controlled breaking waves in a unique ocean-atmosphere facility. An increase in relative abundance of a distinct, insoluble organic particle type was observed after concentrations of heterotrophic bacteria increased in the seawater, leading to an 86 ± 5% reduction in the hygroscopicity parameter (κ) at 0.2% supersaturation. Aerosol size distributions showed very little change and the submicron organic mass fraction increased by less than 15% throughout the experiment; as such, neither of these typical metrics can explain the observed reduction in hygroscopicity. Predictions of the hygroscopicity parameter that make the common assumption that all particles have the same bulk organic volume fractions lead to overpredictions of CCN concentrations by 25% in these experiments. Importantly, key changes in sea spray aerosol mixing state that ultimately influenced CCN activity were driven by bacteria-mediated alterations to the organic composition of seawater. Key Points Sea spray aerosol mixing state can strongly control its cloud forming ability Marine bacteria influence seawater composition and sea spray composition Organic species in sea spray can change independently of chlorophyll-a ©2013. American Geophysical Union. All Rights Reserved."
"55184057600;7102604282;","An evaluation of the potential radiative forcing and climatic impact of marine organic aerosols as heterogeneous ice nuclei",2013,"10.1002/grl.50794","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881288044&doi=10.1002%2fgrl.50794&partnerID=40&md5=33052f114b444b9f3c63c02fb5145c64","Observational evidence demonstrates that marine organic aerosols (MOA) are able to act as ice nuclei. MOA explains a substantial portion of the submicron marine aerosol, so that they have the potential to effectively influence marine cloud microphysics and cloud radiative forcing. This study provides the first evaluation of the radiative forcing and climatic impact of marine organic aerosols as ice nuclei on a global scale. MOA is implemented into a coupled aerosol and general circulation model. It is found that MOA contributes to more ice formation than dust or black carbon/organic matter in mixed-phase clouds. They also have a significant impact on the ice water path in the Southern Hemisphere and therefore could be an important missing source of ice nuclei in current models. The addition of MOA as natural heterogeneous ice nuclei reduces the magnitude of the total top-of-atmosphere anthropogenic aerosol forcing by as much as 0.3 W/m2. © 2013. American Geophysical Union. All Rights Reserved."
"23034148100;14035492400;16029719200;7102167757;","Contrasting Effects of Central Pacific and Eastern Pacific El Niño on stratospheric water vapor",2013,"10.1002/grl.50677","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881149277&doi=10.1002%2fgrl.50677&partnerID=40&md5=e6b265514d00efcac3d65f005606386e","Targeted experiments with a comprehensive chemistry-climate model are used to demonstrate that seasonality and the location of the peak warming of sea surface temperatures dictate the response of stratospheric water vapor to El Niño. In boreal spring, El Niño events in which sea surface temperature anomalies peak in the eastern Pacific lead to a warming at the tropopause above the warm pool region, and subsequently to more stratospheric water vapor (consistent with previous work). However, in fall and in early winter, and also during El Niño events in which the sea surface temperature anomaly is found mainly in the central Pacific, the response is qualitatively different: temperature changes in the warm pool region and specifically over the cold point region are nonuniform, and less water vapor enters the stratosphere. The difference in water vapor in the lower stratosphere between the two variants of El Niño approaches 0.3 ppmv, while the difference between the winter and spring responses exceeds 0.5 ppmv. © 2013. American Geophysical Union. All Rights Reserved."
"55812101900;7004299063;","Baffin Island snow extent sensitivity: Insights from a regional climate model",2013,"10.1002/jgrd.502492013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881108859&doi=10.1002%2fjgrd.502492013&partnerID=40&md5=f002458a643dfe6ee8ad4ccaa80c623f","Recent modeling efforts suggest that the Little Ice Age (LIA) onset could be explained by a series of four large decadally-spaced volcanic eruptions. At that time, glaciers on Baffin Island advanced and did not retreat until the past century, perhaps due to Arctic and North Atlantic Ocean sea ice feedbacks. To try to determine what parameters sustain snow cover, we investigate the relative impacts of changes in radiation and advection on minimum summer snow extent over Baffin Island. We used the Weather Research and Forecasting (WRF) model to run eight 6month long (April-September), 10 km resolution simulations, in which we varied boundary condition temperatures, solar radiation, and sea ice cover. Although the Control Run underestimated cloud cover and thus produced an exaggerated diurnal 2m temperature cycle, the relative changes of snow extent show that WRF accurately simulates snow expansion into the same regions as during the LIA. With an average temperature decrease from current temperatures by 3.91.1 K, it only requires one season for the model to lower the snowline by comparable elevation changes seen during the descent into the LIA. WRF's maximum snow line sensitivity is 7 K/km, within the range of the typically assumed lapse rate of 5-7 K/km in the Canadian Arctic. Thus, if a shift in the Arctic climate greatly expanded sea ice coverage following large volcanic eruptions, this would have been enough to perpetuate an ice sheet on Baffin Island throughout the LIA. © 2013. American Geophysical Union. All Rights Reserved."
"7202803069;55752793600;41361010200;55855413200;55855436100;7201572145;55619429300;55855243300;55855209200;57212388764;13205433800;35551238800;35490341500;55752674500;55556242500;55227743300;53871663500;13906443400;9536598800;7201798916;7006252685;25228665000;57203492395;16242453900;55855256400;16744797500;57193017893;7006133602;","Meteorological and dust aerosol conditions over the western Saharan region observed at Fennec Supersite-2 during the intensive observation period in June 2011",2013,"10.1002/jgrd.50470","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880854370&doi=10.1002%2fjgrd.50470&partnerID=40&md5=c906f11f987c9ab749f8fb74b9464dd1","The climate of the Sahara is relatively poorly observed and understood, leading to errors in forecast model simulations. We describe observations from the Fennec Supersite-2 (SS2) at Zouerate, Mauritania during the June 2011 Fennec Intensive Observation Period. These provide an improved basis for understanding and evaluating processes, models, and remote sensing. Conditions during June 2011 show a marked distinction between: (i) a ""Maritime phase"" during the early part of the month when the western sector of the Sahara experienced cool northwesterly maritime flow throughout the lower troposphere with shallow daytime boundary layers, very little dust uplift/transport or cloud cover. (ii) A subsequent ""heat low"" phase which coincided with a marked and rapid westward shift in the Saharan heat low towards its mid-summer climatological position and advection of a deep hot, dusty air layer from the central Sahara (the ""Saharan residual layer""). This transition affected the entire western-central Sahara. Dust advected over SS2 was primarily from episodic low-level jet (LLJ)-generated emission in the northeasterly flow around surface troughs. Unlike Fennec SS1, SS2 does not often experience cold pools from moist convection and associated dust emissions. The diurnal evolution at SS2 is strongly influenced by the Atlantic inflow (AI), a northwesterly flow of shallow, cool and moist air propagating overnight from coastal West Africa to reach SS2 in the early hours. The AI cools and moistens the western Saharan and weakens the nocturnal LLJ, limiting its dust-raising potential. We quantify the ventilation and moistening of the western flank of the Sahara by (i) the large-scale flow and (ii) the regular nocturnal AI and LLJ mesoscale processes. Key Points First detailed observations from western Sahara sector Intraseasonal shift in Saharan heat low drives meteorological/aerosol conditions Atlantic Inflow interaction with low level jet ©2013. American Geophysical Union. All Rights Reserved."
"26536932900;7402934750;7102266120;7103119050;","Ground-based remote retrievals of cumulus entrainment rates",2013,"10.1175/JTECH-D-12-00187.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881342252&doi=10.1175%2fJTECH-D-12-00187.1&partnerID=40&md5=773237bca36e127cd93b1a2af8a2255a","While fractional entrainment rates for cumulus clouds have typically been derived from airborne observations, this limits the size and scope of available datasets. To increase the number of continental cumulus entrainment rate observations available for study, an algorithm for retrieving them from ground-based remote sensing observations has been developed. This algorithm, called the Entrainment Rate In Cumulus Algorithm (ERICA), uses the suite of instruments at the Southern Great Plains (SGP) site of the U.S. Department of Energy's Atmospheric Radiation Measurement Program (ARM) Climate Research Facility as inputs into a Gauss-Newton optimal estimation scheme, in which an assumed guess of the entrainment rate is iteratively adjusted through intercomparison of modeled cloud attributes to their observed counterparts. The forward model in this algorithm is the explicit mixing parcel model (EMPM), a cloud parcel model that treats entrainment as a series of discrete entrainment events. A quantified value for the uncertainty in the retrieved entrainment rate is also returned as part of the retrieval. Sensitivity testing and information content analysis demonstrate the robust nature of this method for retrieving accurate observations of the entrainment rate without the drawbacks of airborne sampling. Results from a test of ERICA on 3 months of shallow cumulus cloud events show significant variability of the entrainment rate of clouds in a single day and from one day to the next. The mean value of 1.06km21 for the entrainment rate in this dataset corresponds well with prior observations and simulations of the entrainment rate in cumulus clouds. © 2013 American Meteorological Society."
"15050523700;36006968000;55667257200;","Role of interactions between aerosol radiative effect, dynamics, and cloud microphysics on transitions of monsoon intraseasonal oscillations",2013,"10.1175/JAS-D-12-0179.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880436653&doi=10.1175%2fJAS-D-12-0179.1&partnerID=40&md5=5407b73e6920f64a1917dca0720c486d","Extended-range prediction of monsoon intraseasonal oscillations (MISOs), crucial for agriculture and water management, is limited by their event-to-event variability. Here, the authors propose a hypothesis supported by a number of model simulations involving detailed cloud microphysical processes indicating that aerosols contribute significantly to the transitions from ""break"" to ""active"" phases of MISO. The role of aerosol indirect effect in the process of invi oration of precipitation is demonstrated with a high-resolution regional model for Indian summer monsoon breaks that are followed by an active condition (BFA) and contrasted with breaks that are not followed by an active condition (BNFA). The BFA are characterized by higher concentrations of absorbing aerosols that lead to a stronger north-south low-level temperature gradient and strong moisture convergence. Forced uplift beyond the freezing level initiates the cold-rain process involving mixed-phase microphysics and latent heat release at higher levels, thereby invigorating convection, enhancing precipitation, and resulting in an active condition. While more aerosols tend to reduce the cloud drop size and delay the warm rain, it is overcome by the higher moisture convergence during BFA and invigoration by cold-rain processes. The net production of rainfall is sensitive to cloud structure as it depends on the relative strength of the warm-and cold-rain initiation processes. The results indicate the importance of aerosols on transitions of MISO and a pathway by which they influence the transitions involving complex interactions between direct radiative forcing, large-scale dynamics, and cloud microphysics. Broader implications of these results in event-to-event variability of MISO and its predictability are also highlighted. © 2013 American Meteorological Society."
"57030797300;57111001300;26532085500;","Delineating the eddy-zonal flow interaction in the atmospheric circulation response to climate forcing: Uniform sst warming in an idealized aquaplanet model",2013,"10.1175/JAS-D-12-0248.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880693705&doi=10.1175%2fJAS-D-12-0248.1&partnerID=40&md5=af051128c5abc80a3713f48cf45a100c","The mechanisms of the atmospheric response to climate forcing are analyzed using an example of uniform SST warming in an idealized aquaplanet model.A200-member ensemble of experiments is conducted with an instantaneous uniform SST warming. The zonal mean circulation changes display a rapid poleward shift in the midlatitude eddy-driven westerlies and the edge of the Hadley cell circulation and a slow equatorward contraction of the circulation in the deep tropics. The shift of the poleward edge of the Hadley cell is predominantly controlled by the eddy momentumflux. It also shifts the eddy-driven westerlies against the surface friction, at a rate much faster than the expectation from the natural variability of the eddy-driven jet (i.e., the e-folding time scale of the annular mode), with much less feedback between the eddies and zonal flow. The transient eddy-zonal flow interactions are delineated using a newly developed finite-amplitude wave activity diagnostic of Nakamura. Applying it to the transient ensemble response to uniform SST warming reveals that the eddy-driven westerlies are shifted poleward by permitting more upward wave propagation in the middle and upper troposphere rather than reducing the lower-tropospheric baroclinicity. The increased upward wave propagation is attributed to a reduction in eddy dissipation of wave activity as a result of a weaker meridional potential vorticity (PV) gradient. The reduction allows more waves to propagate away from the latitudes of baroclinic generation, which, in turn, leads to more poleward momentum flux and a poleward shift of eddy-driven winds and Hadley cell edge. © 2013 American Meteorological Society."
"25926762100;","Impact of environmental instability on convective precipitation uncertainty associated with the nature of the rimed ice species in a bulk microphysics scheme",2013,"10.1175/MWR-D-13-00036.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881301417&doi=10.1175%2fMWR-D-13-00036.1&partnerID=40&md5=069ceed60141e4c42a665f495779dda2","Despite a number of studies dedicated to the sensitivity of deep convection simulations to the properties of the rimed ice species in microphysics schemes, no consensus has been achieved on the nature of the impact. Considering the need for improved quantitative precipitation forecasts, it is crucial that the cloud modeling community better understands the reasons for these differing conclusions and knows the relevance of these sensitivities for the numerical weather prediction. This study examines the role of environmental conditions and storm type on the sensitivity of precipitation simulations to the nature of the rimed ice species (graupel or hail). Idealized 3D simulations of supercells/multicells and squall lines have been performed in varying thermodynamic environments. It has been shown that for simulation periods of sufficient length (.2 h), graupel-containing and hail-containing storms produce domain-averaged surface precipitation that is more similar than many earlier studies suggest. While graupel is lofted to higher altitudes and has a longer residence time aloft than hail, these simulations suggest that most of this graupel eventually reaches the surface and the surface precipitation rates of hail- and graupel-containing storms converge. However, environmental conditions play an important role in the magnitude of this sensitivity. Storms in large-CAPE environments (typical of storms in the U.S. Midwest) are more sensitive than their low-CAPE counterparts (typical of storms in Europe) to the nature of the rimed ice species in terms of domain-average surface precipitation. Supercells/multicells are more sensitive than squall lines to the nature of the rimed ice species in terms of spatial precipitation distribution and peak precipitation, disregarding of the amount of CAPE. © 2013 American Meteorological Society."
"57199478598;6507386197;35345503300;","The sensitivity of the Arctic sea ice to orbitally induced insolation changes: A study of the mid-holocene paleoclimate modeling intercomparison project 2 and 3 simulations",2013,"10.5194/cp-9-969-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881159363&doi=10.5194%2fcp-9-969-2013&partnerID=40&md5=cff673cd7672af570f03831a3bffafc5","In the present work the Arctic sea ice in the mid-Holocene and the pre-industrial climates are analysed and compared on the basis of climate-model results from the Paleoclimate Modelling Intercomparison Project phase 2 (PMIP2) and phase 3 (PMIP3). The PMIP3 models generally simulate smaller and thinner sea-ice extents than the PMIP2 models both for the pre-industrial and the mid-Holocene climate. Further, the PMIP2 and PMIP3 models all simulate a smaller and thinner Arctic summer sea-ice cover in the mid-Holocene than in the pre-industrial control climate. The PMIP3 models also simulate thinner winter sea ice than the PMIP2 models. The winter sea-ice extent response, i.e. the difference between the mid-Holocene and the pre-industrial climate, varies among both PMIP2 and PMIP3 models. Approximately one half of the models simulate a decrease in winter sea-ice extent and one half simulates an increase. The model-mean summer sea-ice extent is 11% (21 %) smaller in the mid-Holocene than in the pre-industrial climate simulations in the PMIP2 (PMIP3). In accordance with the simple model of Thorndike (1992), the sea-ice thickness response to the insolation change from the pre-industrial to the mid-Holocene is stronger in models with thicker ice in the pre-industrial climate simulation. Further, the analyses show that climate models for which the Arctic sea-ice responses to increasing atmospheric CO2 concentrations are similar may simulate rather different sea-ice responses to the change in solar forcing between the mid-Holocene and the pre-industrial. For two specific models, which are analysed in detail, this difference is found to be associated with differences in the simulated cloud fractions in the summer Arctic; in the model with a larger cloud fraction the effect of insolation change is muted. A sub-set of the mid-Holocene simulations in the PMIP ensemble exhibit open water off the north-eastern coast of Greenland in summer, which can provide a fetch for surface waves. This is in broad agreement with recent analyses of sea-ice proxies, indicating that beachridges formed on the north-eastern coast of Greenland during the early- to mid-Holocene.© 2013 Author(s)."
"55807268100;7004647963;55807450200;55807401700;55807339100;8700431500;7006182764;","LiDAR derived ecological integrity indicators for riparian zones: Application to the Houille river in Southern Belgium/Northern France",2013,"10.1016/j.ecolind.2013.06.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880896996&doi=10.1016%2fj.ecolind.2013.06.024&partnerID=40&md5=1ad5b143dc9c4edaf2d29c4e3636ce49","Riparian zones are central landscape features providing several ecosystem services and are exceptionally rich in biodiversity. Despite their relatively low area coverage, riparian zones consequently represent a major concern for land and water resource managers confirmed within several European directives. These directives involve effective multi-scale monitoring to assess their conditions and their ability to carry out their functions. The objective of this research was to develop automated tools to provide from a single aerial LiDAR dataset new mapping tools and keystone riparian zone attributes assessing the ecological integrity of the riparian zone at a network scale (24 km). Different metrics were extracted from the original LiDAR point cloud, notably the Digital Terrain Model and Canopy Height Model rasters, allowing the extraction of riparian zones attributes such as the wetted channel (0.89 m; mean residual) and floodplain extents (6.02 m; mean residual). Different riparian forest characteristics were directly extracted from these layers (patch extent, overhanging character, longitudinal continuity, relative water level, mean and relative standard deviation of tree height). Within the riparian forest, the coniferous stands were distinguished from deciduous and isolated trees, with high accuracy (87.3%, Kappa index). Going further the mapping of the indicators, our study proposed an original approach to study the riparian zone attributes within different buffer width, from local scale (50 m long channel axis reach) to a network scale (ca. 2 km long reaches), using a disaggregation/re- agraggation process. This novel approach, combined to graphical presentations of the results allow natural resource managers to visualise the variation of upstream-downstream attributes and to identify priority action areas. In the case study, results showed a general decrease of the riparian forests when the river crosses built-up areas. They also highlighted the lower flooding frequency of riparian forest patches in habitats areas. Those results showed that LiDAR data can be used to extract indicators of ecological integrity of riparian zones in temperate climate zone. They will enable the assessment of the ecological integrity of riparian zones to be undertaken at the regional scale (13,000 km, completely covered by an aerial LIDAR survey in 2014). © 2013 Elsevier Ltd. All rights reserved."
"36941575300;8549269500;","CloudSat observations of cloud-type distribution over the Indian summer monsoon region",2013,"10.5194/angeo-31-1155-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880789452&doi=10.5194%2fangeo-31-1155-2013&partnerID=40&md5=d0da13999fe6d0dfbcbeb4414dabcbc6","The three-dimensional distribution of various cloud types over the Indian summer monsoon (ISM) region using five years (2006-2010) of CloudSat observations during June-July-August-September months is discussed for the first time. As the radiative properties, latent heat released and microphysical properties of clouds differ largely depending on the cloud type, it becomes important to know what types of clouds occur over which region. In this regard, the present analysis establishes the three-dimensional distribution of frequency of occurrence of stratus (St), stratocumulus (Sc), nimbostratus (Ns), cumulus (Cu), altocumulus (Ac), altostratus (As), cirrus (Ci) and deep convective (DC) clouds over the ISM region. The results show that the various cloud types preferentially occur over some regions of the ISM, which are consistent during all the years of observations. It is found that the DC clouds frequently occur over northeast of Bay of Bengal (BoB), Ci clouds over a wide region of south BoB-Indian peninsula-equatorial Indian Ocean, and Sc clouds over the north Arabian Sea. Ac clouds preferentially occur over land, and a large amount of As clouds are found over BoB. The occurrence of both St and Ns clouds over the study region is much lower than all other cloud types.The interannual variability of all these clouds including their vertical distribution is discussed. It is envisaged that the present study opens up possibilities to quantify the feedback of individual cloud type in the maintenance of the ISM through radiative forcing and latent heat release. © Author(s) 2013."
"36611965700;7404061081;7006421484;7004174939;7005399437;35501613900;7004166136;7003729315;","MODIS 3 km aerosol product: Applications over land in an urban/suburban region",2013,"10.5194/amt-6-1747-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880850114&doi=10.5194%2famt-6-1747-2013&partnerID=40&md5=6d8a44e35d01e195ef8e6a4ccaef569f","MODerate resolution Imaging Spectroradiometer (MODIS) instruments aboard the Terra and Aqua satellites have provided a rich dataset of aerosol information at a 10 km spatial scale. Although originally intended for climate applications, the air quality community quickly became interested in using the MODIS aerosol data. However, 10 km resolution is not sufficient to resolve local scale aerosol features. With this in mind, MODIS Collection 6 includes a global aerosol product with a 3 km resolution. Here, we evaluate the 3 km product over the Baltimore-Washington D.C., USA, corridor during the summer of 2011 by comparing with spatially dense aerosol data measured by airborne High Spectral Resolution Lidar (HSRL) and a network of 44 sun photometers (SP) spaced approximately 10 km apart, collected as part of the DISCOVER-AQ field campaign. The HSRL instrument shows that AOD can vary by over 0.2 within a single 10 km MODIS pixel, meaning that higher resolution satellite retrievals may help to better characterize aerosol spatial distributions in this region. Different techniques for validating a high-resolution aerosol product against SP measurements are considered. Although the 10 km product is more statistically reliable than the 3 km product, the 3 km product still performs acceptably with nearly two-thirds of MODIS/SP collocations falling within an expected error envelope with high correlation (R 0.90), although with a high bias of ∼ 0.06. The 3 km product can better resolve aerosol gradients and retrieve closer to clouds and shorelines than the 10 km product, but tends to show more noise, especially in urban areas. This urban degradation is quantified using ancillary land cover data. Overall, we show that the MODIS 3 km product adds new information to the existing set of satellite derived aerosol products and validates well over the region, but due to noise and problems in urban areas, should be treated with some degree of caution. © 2012 Author(s)."
"7005601387;7004912890;7005063377;","A review of the relevance of the 'CLOUD' results and other recent observations to the possible effect of cosmic rays on the terrestrial climate",2013,"10.1007/s00703-013-0260-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880639781&doi=10.1007%2fs00703-013-0260-x&partnerID=40&md5=f201fe81c8a523ec429726aac6b1a80d","The problem of the contribution of cosmic rays to climate change is a continuing one and one of importance. In principle, at least, the recent results from the CLOUD project at CERN provide information about the role of ionizing particles in 'sensitizing' atmospheric aerosols which might, later, give rise to cloud droplets. Our analysis shows that, although important in cloud physics the results do not lead to the conclusion that cosmic rays affect atmospheric clouds significantly, at least if H2SO4 is the dominant source of aerosols in the atmosphere. An analysis of the very recent studies of stratospheric aerosol changes following a giant solar energetic particles event shows a similar negligible effect. Recent measurements of the cosmic ray intensity show that a former decrease with time has been reversed. Thus, even if cosmic rays enhanced cloud production, there would be a small global cooling, not warming. © 2013 Springer-Verlag Wien."
"7007026915;7005050002;","Aviation-Contrail Impacts on Climate and Climate Change: A Ready-to-Wear Research Mantle for Geographers",2013,"10.1080/00330124.2012.697795","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879132322&doi=10.1080%2f00330124.2012.697795&partnerID=40&md5=c6ec02126eeb936afcddcdcbcc9e1028","Although geographers are highly visible in research into contemporary climate changes accompanying greenhouse gas increases (""global warming""), a relatively little explored component by them is the impact of aviation. This contrasts with the atmospheric science community of cloud physicists, chemists, and numerical modelers, who use geographic tools of trade. Geographers are well positioned to investigate aviation-climate impacts, especially related to contrail clouds, given geographic traditions of environment, spatial variation, regionalization, generalization, and the integrative approach to studying physical and human systems (here, climate, transportation, and energy). We highlight the role played by geographers in contrail-climate studies and advocate for a broader involvement in aviation policy formulation. © 2013 Copyright Taylor and Francis Group, LLC."
"42661269900;7003922138;23082420800;","The contribution of radiative feedbacks to orbitally driven climate change",2013,"10.1175/JCLI-D-12-00419.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881635656&doi=10.1175%2fJCLI-D-12-00419.1&partnerID=40&md5=7a7cef489860b5ee9d7eaffc78964296","Radiative feedbacks influence Earth's climate response to orbital forcing, amplifying some aspects of the response while damping others. To better understand this relationship, the GFDL Climate Model, version 2.1 (CM2.1), is used to perform idealized simulations in which only orbital parameters are altered while ice sheets, atmospheric composition, and other climate forcings are prescribed at preindustrial levels. These idealized simulations isolate the climate response and radiative feedbacks to changes in obliquity and longitude of the perihelion alone. Analysis shows that, despite being forced only by a redistribution of insolation with no global annual-mean component, feedbacks induce significant global-mean climate change, resulting in mean temperature changes of 20.5K in a lowered obliquity experiment and 10.6K in a NH winter solstice perihelion minus NH summer solstice perihelion experiment. In the obliquity experiment, some global-mean temperature response may be attributable to vertical variations in the transport of moist static energy anomalies, which can affect radiative feedbacks in remote regions by altering atmospheric stability. In the precession experiment, cloud feedbacks alter the Arctic radiation balance with possible implications for glaciation. At times when the orbital configuration favors glaciation, reductions in cloud water content and low-cloud fraction partially counteract changes in summer insolation, posing an additional challenge to understanding glacial inception.Additionally, several systems, such as the Hadley circulation and monsoons, influence climate feedbacks in ways that would not be anticipated from analysis of feedbacks in the more familiar case of anthropogenic forcing, emphasizing the complexity of feedback responses. © 2013 American Meteorological Society."
"57204041349;7203047936;","Temperature profiles and lapse rate climatology in altostratus and nimbostratus clouds derived from GPS RO data",2013,"10.1175/JCLI-D-12-00646.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881625445&doi=10.1175%2fJCLI-D-12-00646.1&partnerID=40&md5=276dfbec15a4fbd200bd1cc0d099d11f","Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) radio occultation (RO) refractivity profiles in altostratus and nimbostratus clouds from 2007 to 2010 are first identified based on collocated CloudSat data. Vertical temperature profiles in these clouds are then retrieved from cloudy refractivity profiles. Contributions of cloud liquid water content and ice water content are also included in the retrieval algorithm. The temperature profiles and their lapse rates are compared with those from a standard GPSROwet retrieval without including cloud effects. On average, the temperatures from cloudy retrieval are about 0.5-1.0K warmer than the GPS RO wet retrieval, except for the altitudes near the nimbostratus base. The differences of temperature between the two methods are largest in summer and smallest in winter. The lapse rate in altostratus clouds is around 6.58-7.58Ckm21 and does not vary greatly with height. On the contrary, the lapse rate increases significantly with height in nimbostratus clouds, from about 2.58-3.58Ckm21 near the cloud base to about 5.08-6.08Ckm21 at cloud center and 6.58-7.58Ckm21 below the cloud top. Seasonal variability of lapse rate derived from the cloudy retrieval is larger than that derived from the wet retrieval. The lapse rate within clouds is smaller in summer and larger in winter. The mean lapse rate decreases with temperature in all seasons. © 2013 American Meteorological Society."
"55823047900;8977001000;","Evaluating low-cloud simulation from an upgraded multiscale modeling framework model. Part I: Sensitivity to spatial resolution and climatology",2013,"10.1175/JCLI-D-12-00200.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881630278&doi=10.1175%2fJCLI-D-12-00200.1&partnerID=40&md5=307a655812d4ae3b02c6c60a6ad1ac6a","The multiscale modeling framework, which replaces traditional cloud parameterizations with a 2D cloudresolving model (CRM) in each atmospheric column, is a promising approach to climate modeling. TheCRM component contains an advanced third-order turbulence closure, helping it to better simulate low-level clouds. In this study, two simulations are performed with 1.98 3 2.58 grid spacing but they differ in the vertical resolution. The number of model layers below 700 hPa increases from 6 in one simulation (IP-6L) to 12 in another (IP-12L) to better resolve the boundary layer. The low-cloud horizontal distribution and vertical structures in IP-12L are more realistic and its global mean is higher than in IP-6L and closer to that of CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) observations. The spatial patterns of tropical precipitation are significantly improved; for example, a single intertropical convergence zone (ITCZ) in the Pacific, instead of double ITCZs in an earlier study that used coarser horizontal resolution and a different dynamical core in its host general circulation model (GCM), and the intensity of the South Pacific convergence zone (SPCZ), and the ITCZ in the Atlantic is more realistic. Many aspects of the global seasonal climatology agree well with observations except for excessive precipitation in the tropics. In terms of spatial correlations and patterns in the tropical/subtropical regions, most surface/vertically integrated properties show greater improvement over the earlier simulation than that with lower vertical resolution. The relationships between low-cloud amount and several large-scale properties are consistent with those observed in five low-cloud regions. There is an imbalance in the surface energy budget, which is an aspect of the model that needs to be improved in the future. © 2013 American Meteorological Society."
"25823927100;55286185400;7006306835;6701752471;7103271625;7402064802;56744278700;7401936984;","Precipitation partitioning, tropical clouds, and intraseasonal variability in GFDL AM2",2013,"10.1175/JCLI-D-12-00442.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881247845&doi=10.1175%2fJCLI-D-12-00442.1&partnerID=40&md5=df2be044187ad5c584bd8252e182d653","A set of Geophysical Fluid Dynamics Laboratory (GFDL) Atmospheric Model version 2 (AM2) sensitivity simulations by varying an entrainment threshold rate to control deep convection occurrence are used to investigate how cumulus parameterization impacts tropical cloud and precipitation characteristics. In the tropics, model convective precipitation (CP) is frequent and light, while large-scale precipitation (LSP) is intermittent and strong. With deep convection inhibited, CP decreases significantly over land and LSP increases prominently over ocean. This results in an overall redistribution of precipitation from land to ocean. A composite analysis reveals that cloud fraction (low and middle) and cloud condensate associated with LSP are substantially larger than those associated with CP. With about the same total precipitation and precipitation frequency distribution over the tropics, simulations having greater LSP fraction tend to have larger cloud condensate and low and middle cloud fraction. Simulations having a greater LSP fraction tend to be drier and colder in the upper troposphere. The induced unstable stratification supports strong transient wind perturbations and LSP. Greater LSP also contributes to greater intraseasonal (20-100 days) precipitation variability. Model LSP has a close connection to the low-level convergence via the resolved grid-scale dynamics and, thus, a close coupling with the surface heat flux. Such wind-evaporation feedback is essential to the development and maintenance of LSP and enhances model precipitation variability. LSP has stronger dependence and sensitivity on column moisture than CP. The moisture-convection feedback, critical to tropical intraseasonal variability, is enhanced in simulations with large LSP. Strong precipitation variability accompanied by a worse mean state implies that an optimal precipitation partitioning is critical to model tropical climate simulation. © 2013 American Meteorological Society."
"25634105600;57203540849;27168081700;7004029924;","Atlantic warm pool variability in the CMIP5 simulations",2013,"10.1175/JCLI-D-12-00556.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881263957&doi=10.1175%2fJCLI-D-12-00556.1&partnerID=40&md5=ebf93bb176b4b204eb247cf1012f5425","This study investigates Atlantic warm pool (AWP) variability in the historical run of 19 coupled general circulation models (CGCMs) submitted to phase 5 of the Coupled Model Intercomparison Project (CMIP5). As with the CGCMs in phase 3 (CMIP3), most models suffer from the cold SST bias in the AWP region and also show very weak AWP variability as represented by the AWP area index. However, for the seasonal cycle the AWP SST bias of model ensemble and model sensitivities are decreased compared with CMIP3, indicating that the CGCMs are improved. The origin of the cold SST bias in the AWP region remains unknown, but among the CGCMs in CMIP5 excess (insufficient) high-level cloud simulation decreases (enhances) the cold SST bias in the AWP region through the warming effect of the high-level cloud radiative forcing. Thus, the AWP SST bias in CMIP5 is more modulated by an erroneous radiation balance due to misrepresentation of high-level clouds rather than low-level clouds as in CMIP3. AWP variability is assessed as in the authors' previous study in the aspects of spectral analysis, interannual variability, multidecadal variability, and comparison of the remote connections with ENSO and the North Atlantic Oscillation (NAO) against observations. In observations the maximum influences of the NAO and ENSO on the AWP take place in boreal spring. For some CGCMs these influences erroneously last to late summer. The effect of this overestimated remote forcing can be seen in the variability statistics as shown in the rotated EOF patterns from the models. It is concluded that the NCAR Community Climate System Model, version 4 (CCSM4), the Goddard Institute for Space Studies (GISS) Model E, version 2, coupled with the Hybrid Coordinate Ocean Model (HYCOM) ocean model (GISS-E2H), and the GISS Model E, version 2, coupled with the Russell ocean model (GISS-E2R) are the best three models of CMIP5 in simulating AWP variability. © 2013 American Meteorological Society."
"7402130148;6602096831;7006728825;6701732679;","Modelling isolated deep convection: A case study from COPS",2013,"10.1127/0941-2948/2013/0408","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890900205&doi=10.1127%2f0941-2948%2f2013%2f0408&partnerID=40&md5=3e8c7619afb14c17bfabdd2b34b0e0ec","This study aims to determine the important physical processes which need to be well represented in a model simulation of the deep convective cloud which occurred on the 15th July 2007 during the Convective and Orographically-induced Precipitation Study (COPS). During the afternoon of 15th July 2007, an isolated, deep convective cloud developed, reaching heights of 12 km above ground level. Previous studies have shown that numerical weather prediction models struggle to simulate realistically this particular cloud. In the present study, it is found that a reservoir of moist air developed, providing necessary energy ready to be released via a suitable trigger (the arrival of a convergence line). A series of tests of the Weather Research and Forecasting (WRF) model is employed to find the modelled sensitivities to boundary-layer and land-surface specification, and the combinations of these necessary to provide the reservoir of moist air. © by Gebruder Borntraeger 2013."
"36020971200;9638473600;7401779240;35546736600;","Multitemporal snow cover mapping in mountainous terrain for Landsat climate data record development",2013,"10.1016/j.rse.2013.04.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877322081&doi=10.1016%2fj.rse.2013.04.004&partnerID=40&md5=fd529cd5a28a07d9df5f6a86180af9ec","A multitemporal method to map snow cover in mountainous terrain is proposed to guide Landsat climate data record (CDR) development. The Landsat image archive including MSS, TM, and ETM. + imagery was used to construct a prototype Landsat snow cover CDR for the interior northwestern United States. Landsat snow cover CDRs are designed to capture snow-covered area (SCA) variability at discrete bi-monthly intervals that correspond to ground-based snow telemetry (SNOTEL) snow-water-equivalent (SWE) measurements. The June 1 bi-monthly interval was selected for initial CDR development, and was based on peak snowmelt timing for this mountainous region. Fifty-four Landsat images from 1975 to 2011 were pre-processed that included image registration, top-of-the-atmosphere (TOA) reflectance conversion, cloud and shadow masking, and topographic normalization. Snow covered pixels were retrieved using the normalized difference snow index (NDSI) and unsupervised classification, and pixels having greater (less) than 50% snow cover were classified presence (absence). A normalized SCA equation was derived to independently estimate SCA given missing image coverage and cloud-shadow contamination. Relative frequency maps of missing pixels were assembled to assess whether systematic biases were embedded within this Landsat CDR. Our results suggest that it is possible to confidently estimate historical bi-monthly SCA from partially cloudy Landsat images. This multitemporal method is intended to guide Landsat CDR development for freshwater-scarce regions of the western US to monitor climate-driven changes in mountain snowpack extent. © 2013 Elsevier Inc."
"7102842636;24511929800;7003489918;8670213100;6701607011;56283400100;","Winter weather regimes over the Mediterranean region: Their role for the regional climate and projected changes in the twenty-first century",2013,"10.1007/s00382-013-1823-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881025723&doi=10.1007%2fs00382-013-1823-8&partnerID=40&md5=613641557e436f0e747bf287f1f4992e","The winter time weather variability over the Mediterranean is studied in relation to the prevailing weather regimes (WRs) over the region. Using daily geopotential heights at 700 hPa from the ECMWF ERA40 Reanalysis Project and Cluster Analysis, four WRs are identified, in increasing order of frequency of occurrence, as cyclonic (22.0 %), zonal (24.8 %), meridional (25.2 %) and anticyclonic (28.0 %). The surface climate, cloud distribution and radiation patterns associated with these winter WRs are deduced from satellite (ISCCP) and other observational (E-OBS, ERA40) datasets. The LMDz atmosphere-ocean regional climate model is able to simulate successfully the same four Mediterranean weather regimes and reproduce the associated surface and atmospheric conditions for the present climate (1961-1990). Both observational- and LMDz-based computations show that the four Mediterranean weather regimes control the region's weather and climate conditions during winter, exhibiting significant differences between them as for temperature, precipitation, cloudiness and radiation distributions within the region. Projections (2021-2050) of the winter Mediterranean weather and climate are obtained using the LMDz model and analysed in relation to the simulated changes in the four WRs. According to the SRES A1B emission scenario, a significant warming (between 2 and 4 °C) is projected to occur in the region, along with a precipitation decrease by 10-20 % in southern Europe, Mediterranean Sea and North Africa, against a 10 % precipitation increase in northern European areas. The projected changes in temperature and precipitation in the Mediterranean are explained by the model-predicted changes in the frequency of occurrence as well as in the intra-seasonal variability of the regional weather regimes. The anticyclonic configuration is projected to become more recurrent, contributing to the decreased precipitation over most of the basin, while the cyclonic and zonal ones become more sporadic, resulting in more days with below normal precipitation over most of the basin, and on the eastern part of the region, respectively. The changes in frequency and intra-seasonal variability highlights the usefulness of dynamics versus statistical downscaling techniques for climate change studies. © 2013 Springer-Verlag Berlin Heidelberg."
"55823047900;8977001000;","Evaluating low-cloud simulation from an upgraded multiscale modeling framework model. Part II: Seasonal variations over the eastern pacific",2013,"10.1175/JCLI-D-12-00276.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880779500&doi=10.1175%2fJCLI-D-12-00276.1&partnerID=40&md5=2fd4dd71baf85fbee1ae301bf38573ce","The eastern Pacific is a climatologically important region. Conventional coupled atmosphere-ocean general circulation models produce positive sea surface temperature biases of 2-5 K in this region because of insufficient stratocumulus clouds. In this study, a global multiscale modeling framework (MMF), which replaces traditional cloud parameterizations with a 2D cloud-resolving model (CRM) in each atmospheric column, is used to examine the seasonal variations of this Pacific region. The CRM component contains an advanced third-order turbulence closure, helping it to better simulate boundary layer turbulence and lowlevel clouds. Compared to available satellite observations of cloud amount, liquid water path, cloud radiative effects, and precipitation, this MMF produces realistic seasonal variations of the eastern Pacific region, although there are some disagreements in the exact location of maximum cloudiness centers in the Peruvian region and the intensity of ITCZ precipitation. Analyses of profile- and subcloud-based decoupling measures reveal very small amplitudes of seasonal variations in the decoupling strength in the subtropics except for those regions off the subtropical coasts where the decoupling measures suggest that the boundary layers should be well coupled in all four seasons. In the Peruvian and Californian regions, the seasonal variations of low clouds are related to those in the boundary layer height and the strength of inversion. Factors that influence the boundary layer and the inversion, such as solar incident radiation, subcloud-layer turbulent mixing, and large-scale subsidence, can collectively explain the seasonal variations of low clouds rather than the deepening-warming mechanism of Bretherton and Wyant cited in earlier studies. © 2013 American Meteorological Society."
"55342815900;6506738607;7003875148;","Springtime atmospheric energy transport and the control of Arctic summer sea-ice extent",2013,"10.1038/nclimate1884","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880855692&doi=10.1038%2fnclimate1884&partnerID=40&md5=369ada903611a22f7733ebd10b3d754a","The summer sea-ice extent in the Arctic has decreased in recent decades, a feature that has become one of the most distinct signals of the continuing climate change. However, the inter-annual variability is large - the ice extent by the end of the summer varies by several million square kilometres from year to year. The underlying processes driving this year-to-year variability are not well understood. Here we demonstrate that the greenhouse effect associated with clouds and water vapour in spring is crucial for the development of the sea ice during the subsequent months. In years where the end-of-summer sea-ice extent is well below normal, a significantly enhanced transport of humid air is evident during spring into the region where the ice retreat is encountered. This enhanced transport of humid air leads to an anomalous convergence of humidity, and to an increase of the cloudiness. The increase of the cloudiness and humidity results in an enhancement of the greenhouse effect. As a result, downward long-wave radiation at the surface is larger than usual in spring, which enhances the ice melt. In addition, the increase of clouds causes an increase of the reflection of incoming solar radiation. This leads to the counter-intuitive effect: for years with little sea ice in September, the downwelling short-wave radiation at the surface is smaller than usual. That is, the downwelling short-wave radiation is not responsible for the initiation of the ice anomaly but acts as an amplifying feedback once the melt is started. © 2013 Macmillan Publishers Limited. All rights reserved."
"57200530823;7003278104;8969695400;57202826644;45961120000;27567747000;7003271327;7004740616;12808494200;55418990300;55786282000;","Evaluation of the surface climatology over the conterminous united states in the north american regional climate change assessment program hindcast experiment using a regional climate model evaluation system",2013,"10.1175/JCLI-D-12-00452.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881226318&doi=10.1175%2fJCLI-D-12-00452.1&partnerID=40&md5=16343bbe6567ee099c12881a26c2ac75","Surface air temperature, precipitation, and insolation over the conterminous United States region from the North American Regional Climate Change Assessment Program (NARCCAP) regional climate model (RCM) hindcast study are evaluated using the Jet Propulsion Laboratory (JPL) Regional Climate Model Evaluation System (RCMES). All RCMs reasonably simulate the observed climatology of these variables. RCM skill varies more widely for the magnitude of spatial variability than the pattern. The multimodel ensemble is among the best performers for all these variables. Systematic biases occur across these RCMs for the annual means, with warm biases over the Great Plains (GP) and cold biases in the Atlantic and the Gulf of Mexico (GM) coastal regions. Wet biases in the Pacific Northwest and dry biases in the GM/southern Great Plains also occur inmost RCMs. All RCMs suffer problems in simulating summer rainfallin the Arizona-New Mexico region. RCMs generally overestimate surface insolation, especially in the eastern United States. Negative correlation between the biases in insolation and precipitation suggest that these two fields are related, likely via clouds. Systematic variations in biases for regions, seasons, variables, and metrics suggest that the bias correction in applying climate model data to assess the climate impact on various sectors must be performed accordingly. Precipitation evaluation with multiple observations reveals that observational data can be an important source of uncertainties in model evaluation; thus, cross examination of observational data is important for model evaluation. © 2013 American Meteorological Society."
"8977001000;55823047900;","Evaluating low-cloud simulation from an upgraded multiscale modeling framework model. Part III: Tropical and subtropical cloud transitions over the Northern Pacific",2013,"10.1175/JCLI-D-12-00650.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881628575&doi=10.1175%2fJCLI-D-12-00650.1&partnerID=40&md5=a3785d34dffc8a51af669091a1843c9c","An analysis of simulated cloud regime transitions along a transect from the subtropical California coast to the tropics for the northern summer season (June-August) is presented in this study. The Community Atmosphere Model, version 5 (CAM5), superparameterized CAM (SPCAM), and an upgraded SPCAM with intermediately prognostic higher-order closure (SPCAM-IPHOC) are used to perform global simulations by imposing climatological sea surface temperature and sea ice distributions. The seasonal-mean properties are compared with recent observations of clouds, radiation, and precipitation and with multimodel intercomparison results. There are qualitative agreements in the characteristics of cloud regimes along the transect among the three models. CAM5 simulates precipitation and shortwave radiative fluxes well but the stratocumulus-to-cumulus transition occurs too close to the coast of California. SPCAM-IPHOC simulates longwave radiative fluxes and precipitable water well, but with systematic biases in shortwave radiative fluxes. The broad, stronger ascending band in SPCAM is related to the large biases in the convective region but the characteristics of the stratocumulus region are still more realistic and the transition occurs slightly farther away from the coast than in CAM5. Even though SPCAM-IPHOC produces the most realistic seasonal-mean transition, it underestimates the mean gradient in low-cloud cover (LCC) across the mean transition location because of an overestimate of LCC in the transition and convective regions that shifts the transition locations farther from the coast. Analysis of two decoupling measures shows consistency in the mean location and the histogram of decoupling locations with those of LCC transition. CAM5, however, lacks such a consistency, suggesting a need for further refinement of its boundary layer cloud parameterization. © 2013 American Meteorological Society."
"13006774400;55353885700;6603313656;57201570597;6701742258;","Modelling the impact of urbanisation on regional climate in the Greater London Area",2013,"10.1002/joc.3589","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880849062&doi=10.1002%2fjoc.3589&partnerID=40&md5=dc9ad784e26d9814aea2c4c91659cd67","Urban areas have well-documented effects on climate, such as the urban heat island (UHI) effect, reduction of wind speeds, enhanced turbulence and boundary layer heights, and changes in cloud cover and precipitation. The aim of this study is to quantify the impact of the urban area of London on local and regional climate. This is achieved through the coupling of the non-hydrostatic mesoscale model METRAS with the sophisticated urban canopy scheme BEP. The model is configured for case studies of the London region, for typical UHI conditions, and the model results are evaluated using data from meteorological monitoring sites. This study develops a methodology to quantify the regional impact of urbanisation from numerical model results. The urban area, in its current form, is found to affect near surface temperature, the diurnal temperature range, the UHI, and the near surface wind speed and direction. For the selected cases, peak UHI intensities of up to 2.5 K are found during night time hours, with the timing and magnitude of the peak showing good agreement with previous experimental studies for London. The timing of the UHI peak intensity for the current urban land cover for London shows a good agreement with the results of measurements. A significant reduction in wind speed over the urban area was also simulated during both daytime and night time, due to the higher roughness of the city compared to the rural domain. The effect is shown to have a regional character, with both urban and surrounding rural areas demonstrating a significant impact. Thus, the UHI can not only be understood when focussing on local data, but the interaction with the surrounding needs to be considered. © 2012 Royal Meteorological Society."
"56628141500;55803635100;6603196127;36522733500;9249627300;37088899300;56283016300;6603378233;","Can an Earth System Model simulate better climate change at mid-Holocene than an AOGCM? A comparison study of MIROC-ESM and MIROC3",2013,"10.5194/cp-9-1519-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880761321&doi=10.5194%2fcp-9-1519-2013&partnerID=40&md5=7161a85eea08b9ff82e79d53b44c3bdd","The importance of evaluating models through paleoclimate simulations is becoming more recognized in efforts to improve climate projection. To evaluate an integrated Earth System Model, MIROC-ESM, we performed simulations in time-slice experiments for the mid-Holocene (6000 yr before present, 6 ka) and preindustrial (1850 AD, 0 ka) periods under the protocol of the Coupled Model Intercomparison Project 5/Paleoclimate Modelling Intercomparison Project 3. We first give an overview of the simulated global climates by comparing with simulations using a previous version of the MIROC model (MIROC3), which is an atmosphere-ocean coupled general circulation model. We then comprehensively discuss various aspects of climate change with 6 ka forcing and how the differences in the models can affect the results. We also discuss the representation of the precipitation enhancement at 6 ka over northern Africa. The precipitation enhancement at 6 ka over northern Africa according to MIROC-ESM does not differ greatly from that obtained with MIROC3, which means that newly developed components such as dynamic vegetation and improvements in the atmospheric processes do not have significant impacts on the representation of the 6 ka monsoon change suggested by proxy records. Although there is no drastic difference between the African monsoon representations of the two models, there are small but significant differences in the precipitation enhancement over the Sahara in early summer, which can be related to the representation of the sea surface temperature rather than the vegetation coupling in MIROC-ESM. Because the oceanic parts of the two models are identical, the difference in the sea surface temperature change is ultimately attributed to the difference in the atmospheric and/or land modules, and possibly the difference in the representation of low-level clouds. © Author(s) 2013."
"6603546080;7004364155;8555710700;8723505700;26666977800;55804461200;7004325649;7404150761;7403180902;","Geostationary enhanced temporal interpolation for ceres flux products",2013,"10.1175/JTECH-D-12-00136.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880719356&doi=10.1175%2fJTECH-D-12-00136.1&partnerID=40&md5=22ae2c04e34e66f06c4f848036143486","The Clouds and the Earth's Radiant Energy System (CERES) instruments on board the Terra and Aqua spacecraft continue to provide an unprecedented global climate record of the earth's top-of-atmosphere (TOA) energy budget since March 2000. A critical step in determining accurate daily averaged flux involves estimating the flux between CERES Terra or Aqua overpass times. CERES employs the CERES-only (CO) and the CERES geostationary (CG) temporal interpolation methods. The COmethod assumes that the cloud properties at the time of the CERES observation remain constant and that it only accounts for changes in albedo with solar zenith angle and diurnal land heating, by assuming a shape for unresolved changes in the diurnal cycle. The CG method enhances the CERES data by explicitly accounting for changes in cloud and radiation between CERES observation times using 3-hourly imager data from five geostationary (GEO) satellites. To maintain calibration traceability, GEO radiances are calibrated against Moderate Resolution Imaging Spectroradiometer (MODIS) and the derived GEO fluxes are normalized to the CERES measurements. While the regional (1° latitude 3 1° longitude) monthly-mean difference between the CG and CO methods can exceed 25 W m-2 over marine stratus and land convection, these regional biases nearly cancel in the global mean. The regional monthly CG shortwave (SW) and longwave (LW) flux uncertainty is reduced by 20%, whereas the daily uncertainty is reduced by 50% and 20%, respectively, over the CO method, based on comparisons with 15-min Geostationary Earth Radiation Budget (GERB) data. © 2013 American Meteorological Society."
"55149724600;9248887100;22941802900;7003975505;","The transient versus the equilibrium response of sea ice to global warming",2013,"10.1175/JCLI-D-12-00492.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880834152&doi=10.1175%2fJCLI-D-12-00492.1&partnerID=40&md5=ad533417b04d935bda276a45ed33e47c","To examine the long-term stability of Arctic and Antarctic sea ice, idealized simulations are carried out with the climate model ECHAM5/Max Planck Institute Ocean Model (MPI-OM). Atmospheric CO2 concentration is increased over 2000 years from preindustrial levels to quadrupling, is then kept constant for 5940 years, is afterward decreased over 2000 years to preindustrial levels, and is finally kept constant for 3940 years. Despite these very slow changes, the sea ice response significantly lags behind the CO2 concentration change. This lag, which is caused by the ocean's thermal inertia, implies that the sea ice equilibrium response to increasing CO2 concentration is substantially underestimated by transient simulations. The sea ice response to CO2 concentration change is not truly hysteretic and is in principle reversible. The authors find no lag in the evolution of Arctic sea ice relative to changes in annual-mean Northern Hemisphere surface temperature. The summer sea ice cover changes linearly with respect to both CO2 concentration and temperature, while the Arctic winter sea ice cover shows a rapid transition to a very low sea ice coverage. This rapid transition of winter sea ice is associated with a sharply enhanced ice-albedo feedback and a sudden onset of convective-cloud feedback in the Arctic. The Antarctic sea ice cover retreats continuously without any rapid transition during the warming. Compared to Arctic sea ice, Antarctic sea ice shows a much more strongly lagged response to changes in CO2 concentration. It even lags behind the surface temperature change, which is caused by a different response of ocean deep convection during the warming and the cooling periods. © 2013 American Meteorological Society."
"56001448100;35185383500;7003928455;7006970286;","Low simulated radiation limit for runaway greenhouse climates",2013,"10.1038/ngeo1892","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881345924&doi=10.1038%2fngeo1892&partnerID=40&md5=0bb8033471f10e33f1c3ad4618a0669d","The atmospheres of terrestrial planets are expected to be in long-term radiation balance: an increase in the absorption of solar radiation warms the surface and troposphere, which leads to a matching increase in the emission of thermal radiation. Warming a wet planet such as Earth would make the atmosphere moist and optically thick such that only thermal radiation emitted from the upper troposphere can escape to space. Hence, for a hot moist atmosphere, there is an upper limit on the thermal emission that is unrelated to surface temperature. If the solar radiation absorbed exceeds this limit, the planet will heat uncontrollably and the entire ocean will evaporate - the so-called runaway greenhouse. Here we model the solar and thermal radiative transfer in incipient and complete runaway greenhouse atmospheres at line-by-line spectral resolution using a modern spectral database. We find a thermal radiation limit of 282 W m -2 (lower than previously reported) and that 294 W m -2 of solar radiation is absorbed (higher than previously reported). Therefore, a steam atmosphere induced by such a runaway greenhouse may be a stable state for a planet receiving a similar amount of solar radiation as Earth today. Avoiding a runaway greenhouse on Earth requires that the atmosphere is subsaturated with water, and that the albedo effect of clouds exceeds their greenhouse effect. A runaway greenhouse could in theory be triggered by increased greenhouse forcing, but anthropogenic emissions are probably insufficient."
"18134578100;55789884400;13608960900;36080026700;8941441100;35756335100;55643726900;35849722200;","Design and application of an unattended multifunctional H-TDMA system",2013,"10.1175/JTECH-D-12-00129.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880003088&doi=10.1175%2fJTECH-D-12-00129.1&partnerID=40&md5=d91768e8705ffeb9f0a2ff5def07a5b2","The hygroscopic properties of aerosols have a significant impact on aerosol particle number size distributions (PNSD), formation of cloud condensation nuclei, climate forcing, and atmospheric visibility, as well as human health. To allow for the observation of the hygroscopic growth of aerosols with long-term accuracy, an unattended multifunctional hygroscopicity-tandem differential mobility analyzer (H-TDMA) system was designed and built by the Institute of Tropical and Marine Meteorology (ITMM), China Meteorological Administration (CMA), in Guangzhou, China. The system is capable of measuring dry and wet PNSD, hygroscopic growth factor by particle size, and mixing states. This article describes in detail the working principles, components, and calibration methods of the system. Standard polystyrene latex (PSL) spheres with five different diameters were chosen to test the system's precision and accuracy of particle size measurement. Ammonium sulfate was used to test the hygroscopic response of the system for accurate growth factor measurement. The test results show that the deviation of the growth factor measured by the systemis within a scope of -0.01 to -0.03 compared to Köhler theoretical curves. Results of temperature and humidity control performance tests indicate that the systemis robust.An internal temperature gradient of less than 0.2 Kfor a second differential mobility analyzer (DMA2) makes it possible to reach a set-point relative humidity (RH) value of 90% and with a standard deviation of ±0.44%, sufficient for unattended field observation. © 2013 American Meteorological Society."
"35867442600;7003708056;7003880283;26634569400;37026400000;6602177985;","Small scale topography influence on the formation of three convective systems observed during COPS over the Vosges Mountains",2013,"10.1127/0941-2948/2013/0402","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890941322&doi=10.1127%2f0941-2948%2f2013%2f0402&partnerID=40&md5=5300ca7134201bc3e1c0832690fc67fe","Numerical modelling of the airflow and precipitating convective systems are performed to better understand the role of topography for the triggering of convection over a moderate mountain region during the Convective and Orographically induced Precipitation Study (COPS) campaign. A non-hydrostatic cloud scale model with two nested domains is used which permits to zoom from the mesoscale environment of south-western Germany/eastern France, into the Vosges Mountains and finally into the small-terrain of the field experiment, increasing the grid resolution to well represent the orography of the region. Using radar observations, a classification of the location of the convection initiation was established during the COPS project, which considers that the convective systems form either on the mountain ridges or on the lee side of the massif. The three simulated cases of this study, corresponding to either position of convection initiation, compare well with available observations of local thermo-dynamical conditions, high resolution X-band radar reflectivity, Vienna Enhanced Resolution Analysis (VERA) of the surface horizontal wind and water vapour retrieval through GPS integrated water vapour 3D tomography. It was found that the convection generation is largely influenced by the Vosges topography. Even for a quite similar synoptic horizontal wind field, the relief acts differently for the studied cases. However, the convective systems are not formed solely by the mountains, but require inputs of moisture, proper stability, and some supportive mesoscale environment. Therefore, their representation in the model requires also a detailed knowledge of the local atmospheric conditions. © by Gebruder Borntraeger 2013."
"55801231800;7003763119;36106191000;55469200300;7402838215;","Ice water content of Arctic, midlatitude, and tropical cirrus - Part 2: Extension of the database and new statistical analysis",2013,"10.5194/acp-13-6447-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880621356&doi=10.5194%2facp-13-6447-2013&partnerID=40&md5=18d9a3c3acdf78266649af3c3423f79b","Ice clouds are known to be major contributors to radiative forcing in the Earth's atmosphere, yet describing their microphysical properties in climate models remains challenging. Among these properties, the ice water content (IWC) of cirrus clouds is of particular interest both because it is measurable and because it can be directly related to a number of other radiatively important variables such as extinction and effective radius. This study expands upon the work of Schiller et al. (2008), extending a climatology of IWC by combining datasets from several European and US airborne campaigns and ground-based lidar measurements over Jülich, Germany. The relationship between IWC and temperature is further investigated using the new merged dataset and probability distribution functions (PDFs). A PDF-based formulation allows for representation of not only the mean values of IWC, but also the variability of IWC within a temperature band. The IWC-PDFs are observed to be bimodal over the whole cirrus temperature range. This bimodality is also found in ice crystal number PDFs and might be attributed to different cirrus formation mechanisms such as heterogeneous and homogeneous freezing. © Author(s) 2013."
"57189940273;","Spatial models of dynamics of vegetation in scenerios of climatic change in «Timberline» cloud forest - Paramo of north slope of the Sierra Nevada of Mérida - Venezuela; scenario B1 and constant situation [Modelos espaciales de la dinámica de la vegetación en escenarios de cambio climático en el «Timberline» selva nublada - Paramo de la vertiente norte de la Sierra Nevada de Mérida (Venezuela); escenario B1 y situacion constante]",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880639541&partnerID=40&md5=cc892b13161f5dfd334c062d14f57203","In recent decades, the human has changed the concentrations of greenhouse gases, generating increasing global temperature, causing changes in the structure and distribution of animals and plants. Modeling was raised vegetation dynamics under scenarios of the Special Report on Emissions of greenhouse gases SRES Intergovernmental Panel on Climate Change IPCC. The methodology was based on spatial statistical analysis of the rate of normalized difference vegetation index (NDVI) calculated from SPOT 5 satellite images and their relationship with the gradient thermal in the limit of continuous cloud forest tree growth - Páramo «Timberline». Was determined autocorrelation decreased and increased the variance of NDVI as it rises above the gradient. There were statistical differences between the mean values of NDVI (p &lt; 0.01) of the vegetation units, and applying probabilistic analysis were determined NDVI ranges for them; cloud forest, pre (before) paramero forest, preparamero Shrub and páramo, can model changes of vegetation along the gradient. We found a strong correlation between NDVI and temperature (r2 = 90.45), allowing to generate an equation to model the response of vegetation to global warming. The models generated under different scenarios show a decrease in the Páramo tending towards extinction, being colonized by preparamero shrub and preparamero forest, which subsequently evolve the climax stage of cloud forest. Models show that there will be developmental processes and recolonization with the change reflected in the structure of plants."
"35195849700;23994595000;14034301300;24331763700;7403401100;7005069415;7006434689;","Hygroscopic mixing state of urban aerosol derived from size-resolved cloud condensation nuclei measurements during the MEGAPOLI campaign in Paris",2013,"10.5194/acp-13-6431-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880641175&doi=10.5194%2facp-13-6431-2013&partnerID=40&md5=a002670e601877f07a891a3ed2f3862b","Ambient aerosols are a complex mixture of particles with different physical and chemical properties and consequently distinct hygroscopic behaviour. The hygroscopicity of a particle determines its water uptake at subsaturated relative humidity (RH) and its ability to form a cloud droplet at supersaturated RH. These processes influence Earth's climate and the atmospheric lifetime of the particles. Cloud condensation nuclei (CCN) number size distributions (i.e. CCN number concentrations as a function of dry particle diameter) were measured close to Paris during the MEGAPOLI campaign in January-February 2010, covering 10 different supersaturations (SS =0.1-1.0%). The time-resolved hygroscopic mixing state with respect to CCN activation was also derived from these measurements. Simultaneously, a hygroscopicity tandem differential mobility analyser (HTDMA) was used to measure the hygroscopic growth factor (ratio of wet to dry mobility diameter) distributions at RH =90%. The aerosol was highly externally mixed and its mixing state showed significant temporal variability. The average particle hygroscopicity was relatively low at subsaturation (RH =90%; mean hygroscopicity parameter κ =0.12-0.27) and increased with increasing dry diameter in the range 35-265 nm. The mean κ value, derived from the CCN measurements at supersaturation, ranged from 0.08 to 0.24 at SS =1.0-0.1%. Two types of mixing-state resolved hygroscopicity closure studies were performed, comparing the water uptake ability measured below and above saturation. In the first type the CCN counter was connected in series with the HTDMA and and closure was achieved over the whole range of probed dry diameters, growth factors and supersaturations using the κ-parametrization for the water activity and assuming surface tension of pure water in the Köhler theory. In the second closure type we compared hygroscopicity distributions derived from parallel monodisperse CCN measurements and HTDMA measurements. Very good agreement was found at all supersaturations, which shows that monodisperse CCN measurements are a reliable alternative to determine the hygroscopic mixing state of ambient aerosols. © Author(s) 2013."
"25223276500;7004260140;23970956600;","Measurement of snow depth using a low-cost mobile laser scanner",2013,"10.1109/LGRS.2013.2271861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880773415&doi=10.1109%2fLGRS.2013.2271861&partnerID=40&md5=025fef3b6939433d88c9089cbb7d9567","In this letter, we demonstrate the potential of a small, robust, and low-cost mobile scanner for snow-depth studies. Snow-surface model and depth data are needed for purposes such as flood forecasting, agriculture, optimal management of water resources, and in formulating global climate-change scenarios. Traditionally, manual snow-depth measurements are laborious, time-consuming, and costly. A mobile mapping system comprised of an Ibeo Lux laser scanner, operating at a wavelength of 905 nm, and a NovAtel SPAN-CPT inertial navigation system was used to produce geo-referenced point clouds. The data were acquired first in the fall when the ground was free of snow and then a second time in winter when there was snow on the ground. Reference values from a total of 94 locations were collected with an RTK GPS pole. The maximum reference snow depth was 80 cm. The obtained snow-depth bias was 0.3 cm, which indicated that the proposed data-processing approach was capable of avoiding errors due to laser penetration into the snow, and the root-mean-squared error was 5.5 cm. Mobile laser scanning appears to be a promising technology for cryospheric studies having potential, e.g., to calibrate gravimetric measurements and earth observation satellite data, especially when reference data are needed for areas that are too large for terrestrial laser scanning. © 2013 IEEE."
"36538539800;57204359029;57206910481;57204206835;","Application of WRF/Chem-MADRID and WRF/Polyphemus in Europe - Part 1: Model description, evaluation of meteorological predictions, and aerosol-meteorology interactions",2013,"10.5194/acp-13-6807-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880642509&doi=10.5194%2facp-13-6807-2013&partnerID=40&md5=9f354cd25d3a06b3c4f3069f26a420e4","Comprehensive model evaluation and comparison of two 3-D air quality modeling systems (i.e., the Weather Research and Forecast model (WRF)/Polyphemus and WRF with chemistry and the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (MADRID) (WRF/Chem-MADRID)) are conducted over Western Europe. Part 1 describes the background information for the model comparison and simulation design, the application of WRF for January and July 2001 over triple-nested domains in Western Europe at three horizontal grid resolutions: 0.5&deg;, 0.125&deg;, and 0.025&deg;, and the effect of aerosol/meteorology interactions on meteorological predictions. Nine simulated meteorological variables (i.e., downward shortwave and longwave radiation fluxes (SWDOWN and LWDOWN), outgoing longwave radiation flux (OLR), temperature at 2 m (T2), specific humidity at 2 m (Q2), relative humidity at 2 m (RH2), wind speed at 10 m (WS10), wind direction at 10 m (WD10), and precipitation (Precip)) are evaluated using available observations in terms of spatial distribution, domainwide daily and site-specific hourly variations, and domainwide performance statistics. The vertical profiles of temperature, dew points, and wind speed/direction are also evaluated using sounding data. WRF demonstrates its capability in capturing diurnal/seasonal variations and spatial gradients and vertical profiles of major meteorological variables. While the domainwide performance of LWDOWN, OLR, T2, Q2, and RH2 at all three grid resolutions is satisfactory overall, large positive or negative biases occur in SWDOWN, WS10, and Precip even at 0.125&deg; or 0.025&deg; in both months and in WD10 in January. In addition, discrepancies between simulations and observations exist in T2, Q2, WS10, and Precip at mountain/high altitude sites and large urban center sites in both months, in particular, during snow events or thunderstorms. These results indicate the model's difficulty in capturing meteorological variables in complex terrain and subgrid-scale meteorological phenomena, due to inaccuracies in model initialization parameterization (e.g., lack of soil temperature and moisture nudging), limitations in the physical parameterizations (e.g., shortwave radiation, cloud microphysics, cumulus parameterizations, and ice nucleation treatments) as well as limitations in surface heat and moisture budget parameterizations (e.g., snow-related processes, subgrid-scale surface roughness elements, and urban canopy/heat island treatments and CO2 domes). While the use of finer grid resolutions of 0.125&deg; and 0.025&deg; shows some improvements for WS10, WD10, Precip, and some mesoscale events (e.g., strong forced convection and heavy precipitation), it does not significantly improve the overall statistical performance for all meteorological variables except for Precip. The WRF/Chem simulations with and without aerosols show that aerosols lead to reduced net shortwave radiation fluxes, 2 m temperature, 10 m wind speed, planetary boundary layer (PBL) height, and precipitation and increase aerosol optical depth, cloud condensation nuclei, cloud optical depth, and cloud droplet number concentrations over most of the domain. These results indicate a need to further improve the model representations of the above parameterizations as well as aerosol-meteorology interactions at all scales. © Author(s) 2013."
"36076994600;7005263785;24491934500;","Growth of atmospheric nano-particles by heterogeneous nucleation of organic vapor",2013,"10.5194/acp-13-6523-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880616793&doi=10.5194%2facp-13-6523-2013&partnerID=40&md5=63b8c6d7c823f65c7d476d58f225390e","Atmospheric aerosols play critical roles in air quality, public health, and visibility. In addition, they strongly influence climate by scattering solar radiation and by changing the reflectivity and lifetime of clouds. One major but still poorly understood source of atmospheric aerosols is new particle formation, which consists of the formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation) followed by growth of these clusters to a detectable size (∼3 nm). Because freshly nucleated clusters are most susceptible to loss due to high rate of coagulation with pre-existing aerosol population, the initial growth rate strongly influences the rate of new particle formation and ambient aerosol population. Whereas many field observations and modeling studies indicate that organics enhance the initial growth of the clusters and therefore new particle formation, thermodynamic considerations would suggest that the strong increase of equilibrium vapor concentration due to cluster surface curvature (Kelvin effect) may prevent ambient organics from condensing on these small clusters. Here, the contribution of organics to the initial cluster growth is described as heterogeneous nucleation of organic molecules onto these clusters. We find that the strong gradient in cluster population with respect to its size leads to positive cluster number flux. This positive flux drives the growth of clusters substantially smaller than the Kelvin diameter, conventionally considered the minimum particle size that can be grown through condensation. The conventional approach neglects the contribution from the cluster concentration gradient, and underestimates the cluster survival probabilities by a factor of up to 60 if early growth of clusters is due to both condensation of sulfuric acid and heterogeneous nucleation of organic vapors. © Author(s) 2013."
"41461226600;7004862277;","Photosensitised heterogeneous oxidation kinetics of biomass burning aerosol surrogates by ozone using an irradiated rectangular channel flow reactor",2013,"10.5194/acp-13-6507-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880578561&doi=10.5194%2facp-13-6507-2013&partnerID=40&md5=1c3ce3731f3e934986c19181549d709b","Heterogeneous reaction kinetics involving organic aerosol and atmospheric oxidants such as ozone can be enhanced under visible or UV irradiation in the presence of a photosensitiser, with subsequent implications for the climate, cloud radiative properties, air quality, and source appointment. In this study we report the steady-state reactive uptake coefficient, γ, of O 3 by levoglucosan and 5-nitroguaiacol acting as surrogates for biomass burning aerosol particles, with and without the presence of Pahokee peat acting as a photosensitiser. The reactive uptake has been determined in the dark and as a function of visible and UV-A irradiation and ozone concentration. In addition, γ was determined for 1: 1, 1: 10, and 1: 100 by mass mixtures of Pahokee peat and 5-nitroguaiacol, and for a 10:1:3 mixture of levoglucosan, Pahokee peat, and 5-nitroguaiacol. We developed a novel irradiated rectangular channel flow reactor (I-RCFR) that was operated under low pressures of about 2-4 hPa, and allowed for uniform irradiation of the organic substrates. The I-RCFR was coupled to a chemical ionisation mass spectrometer and has been successfully validated by measuring the kinetics between various organic species and oxidants. γ of O3 and levoglucosan in the dark and under visible and UV-A irradiation was determined to be in the range of (2-11) × 10-6 and did not change in the presence of Pahokee peat. The determined γ of O3 and 5-nitroguaiacol in the dark was 5.7 × 10-6 and was only enhanced under UV-A irradiation, yielding a value of 3.6 × 10-5. γ of the 1:1 Pahokee peat/5-nitroguaiacol substrate was enhanced under visible and UV-A irradiation to 2.4 × 10-5 and 2.8 × 10-5, respectively. Decreasing the amount of Pahokee peat in the 5-nitroguaiacol/Pahokee peat substrate resulted in lower values of γ under visible irradiation, however, γ was consistent under UV-A irradiation regardless of the amount of Pahokee peat. The 10:1:3 mixture by mass of levoglucosan, Pahokee peat, and 5-nitroguaiacol, under both visible and UV-A irradiation yielded γ values of 2.8 × 10-5 and 1.4 × 10-5, respectively. γ was determined as a function of photon flux for O3 with the 1:1 Pahokee peat/5-nitroguaiacol substrate, yielding a linear relationship under both visible and UV-A irradiation. γ of O3 with the 1:1 Pahokee peat/5-nitroguaiacol substrate was determined as a function of ozone concentration and exhibited an inverse dependence of γ on ozone concentration, commonly interpreted as a Langmuir-Hinshelwood mechanism. The reactive uptake data have been represented by a Langmuir-type isotherm. From the O3 uptake data under visible irradiation, the following fit parameters have been derived: ks = (5.5 ± 2.7) × 10 -19 cm2 s-1 molecule-1 and K O3 = (2.3 ± 2.0) × 10-12 cm-3 molecule-1; and under UV-A irradiation: ks = (8.1 ± 2.0) × 10-12 cm2 s-1 molecule -1 and KO3 = (1.7 ± 0.7) × 10-12 cm3molecule-1. The oxidative power, or the product of γ and [O3], was determined for O3 with the 1:1 Pahokee peat/5-nitroguaiacol substrate and was in the range of (1.2-26) × 106 molecule cm-3. Atmospheric particle lifetimes were estimated for a 0.4 μm 5-nitroguaiacol particle as a function of visible and UV-A irradiation and ozone concentration. © Author(s) 2013."
"57202299549;7006705919;56384704800;6506152198;7202048112;","Numerical issues associated with compensating and competing processes in climate models: An example from ECHAM-HAM",2013,"10.5194/gmd-6-861-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880560166&doi=10.5194%2fgmd-6-861-2013&partnerID=40&md5=9f8cec76a219f8c3531603343b392af7","The purpose of this paper is to draw attention to the need for appropriate numerical techniques to represent process interactions in climate models. In two versions of the ECHAM-HAM model, different time integration methods are used to solve the sulfuric acid (H2SO4) gas evolution equation, which lead to substantially different results in the H2SO4 gas concentration and the aerosol nucleation rate. Using convergence tests and sensitivity simulations performed with various time stepping schemes, it is confirmed that numerical errors in the second model version are significantly smaller than those in version one. The use of sequential operator splitting in combination with a long time step is identified as the main reason for the large systematic biases in the old model. The remaining errors of nucleation rate in version two, related to the competition between condensation and nucleation, have a clear impact on the simulated concentration of cloud condensation nuclei (CCN) in the lower troposphere. These errors can be significantly reduced by employing solvers that handle production, condensation and nucleation at the same time. Lessons learned in this work underline the need for more caution when treating multi-timescale problems involving compensating and competing processes, a common occurrence in current climate models. © 2013 Author(s). CC Attribution 3.0 License."
"16202694600;7004060399;6603422104;35739529800;26645289600;","The ozone hole indirect effect: Cloud-radiative anomalies accompanying the poleward shift of the eddy-driven jet in the Southern Hemisphere",2013,"10.1002/grl.50675","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880216867&doi=10.1002%2fgrl.50675&partnerID=40&md5=c1dc1769ddf4062f66d2bc6cd43e28ce","This study quantifies the response of the clouds and the radiative budget of the Southern Hemisphere (SH) to the poleward shift in the tropospheric circulation induced by the development of the Antarctic ozone hole. Single forcing climate model integrations, in which only stratospheric ozone depletion is specified, indicate that (1) high-level and midlevel clouds closely follow the poleward shift in the SH midlatitude jet and that (2) low-level clouds decrease across most of the Southern Ocean. Similar cloud anomalies are found in satellite observations during periods when the jet is anomalously poleward. The hemispheric annual mean radiation response to the cloud anomalies is calculated to be approximately +0.25 W m-2, arising largely from the reduction of the total cloud fraction at SH midlatitudes during austral summer. While these dynamically induced cloud and radiation anomalies are considerable and are supported by observational evidence, quantitative uncertainties remain from model biases in mean-state cloud-radiative processes. © 2013. American Geophysical Union. All Rights Reserved."
"30667558200;6603925960;","Evaluation of the cloud thermodynamic phase in a climate model using CALIPSO-GOCCP",2013,"10.1002/jgrd.50376","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882745774&doi=10.1002%2fjgrd.50376&partnerID=40&md5=7427d05eba35e04c9ea8e6db131e215c","Level 1 measurements, including cross-polarized backscatter, from the Cloud-Aerosol Lidar with Orthogonal Polarization lidar, have been used to document the vertical structure of the cloud thermodynamic phase at global scale. We built a cloud phase identification (liquid, ice, or undefined) in the Global Climate Model (GCM)-oriented Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud Product (GOCCP) and analyzed the spatial distribution of liquid and ice clouds in five January, February, March (JFM) seasons of global-scale observations (2007-2011). We developed a cloud phase diagnosis in the Cloud Feedback Model Intercomparison Program Observation Simulator Package to evaluate the cloud phase description in the LMDZ5B climate model. The diagnosis in the simulator is fully consistent with the CALIPSO-GOCCP observations to ensure that differences between the observations and the ""model + simulator"" ensemble outputs can be attributed to model biases. We compared the liquid and ice cloud vertical distributions simulated by the model with and without the simulator to quantify the impact of the simulator. The model does not produce liquid clouds above 3 km and produces ice instead of liquid at low and middle altitudes in polar regions, as well as along the Intertropical Convergence Zone. The model is unable to replicate the observed coexistence of liquid and ice cloud between 0°C and -40°C. Liquid clouds dominate T > -21°C in the observations, T > -12°C in the model + simulator, and T > -7.5°C in the model parameterization. Even if the simulator shifts the model cloud phase parameterization to colder temperature because of the lidar instrument peculiarities, the cloud phase transition remains too warm compared to the observations. Key Points To document the partition of liquid and ice phase within clouds at global scale To evaluate the description of liquid and ice clouds in a climate model To build a new cloud thermodynamic phase climatology vertically resolved ©2013. American Geophysical Union. All Rights Reserved."
"56263595100;57208346904;7410070663;7401806579;","Dominant roles of subgrid-scale cloud structures in model diversity of cloud radiative effects",2013,"10.1002/jgrd.50604","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882760269&doi=10.1002%2fjgrd.50604&partnerID=40&md5=0c1bbc42cc7e72827afc5c420088985c","Today, large model discrepancies exist in estimated cloud radiative effects (CREs) and irradiances across 1-D radiative transfer schemes aimed for climate models. The primary purpose of this study is to understand physical causes of such model discrepancies, especially in CREs under partly cloudy sky. To achieve this goal, the unique Cloud-Aerosol-Radiation (CAR) ensemble modeling system was employed, offline driven by the ERA-Interim global data for July 2004 with no feedback considered. For evaluating each individual contribution from the existing scheme diversity of cloud horizontal inhomogeneity, cloud optical properties, cloud vertical overlap, and gas absorptions, several sets of numerical experiments were conducted. It is the first time to explicitly demonstrate that after removing most of the disagreement in cloud fields, model spreads of CREs among the CAR's seven major radiation schemes, as well as those of radiative fluxes, dramatically diminish. Taking global mean CREs for example, their current model ranges can decrease to <4 W m-2 from about 10 W m-2 for shortwave and also to <4 W m-2 from 5-8 W m-2 for longwave. Dominant roles of subgrid-scale cloud structures (including vertical overlap and horizontal variability) were proven in general, explaining about 40-75% of the total model spreads. We have also found that model spreads of CREs are very sensitive to cloud cover fractions. Such nonlinear sensitivity can be largely reduced after removing the model difference in the treatments of cloud vertical overlap. Key Points Current model spreads of CREs and radiative fluxes can be dramatically reduced We demonstrated dominant roles of cloud subgrid structure in model diversities We reduced current nonlinear sensitivity of model spreads to cloud fractions ©2013. American Geophysical Union. All Rights Reserved."
"56244473600;7103206141;7102447698;57208462871;24481931900;16027961900;7201665727;","Impact of preindustrial to present-day changes in short-lived pollutant emissions on atmospheric composition and climate forcing",2013,"10.1002/jgrd.50608","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882769517&doi=10.1002%2fjgrd.50608&partnerID=40&md5=2c0b37899dbbe1303c5f9e02446a0339","We describe and evaluate atmospheric chemistry in the newly developed Geophysical Fluid Dynamics Laboratory chemistry-climate model (GFDL AM3) and apply it to investigate the net impact of preindustrial (PI) to present (PD) changes in short-lived pollutant emissions (ozone precursors, sulfur dioxide, and carbonaceous aerosols) and methane concentration on atmospheric composition and climate forcing. The inclusion of online troposphere-stratosphere interactions, gas-aerosol chemistry, and aerosol-cloud interactions (including direct and indirect aerosol radiative effects) in AM3 enables a more complete representation of interactions among short-lived species, and thus their net climate impact, than was considered in previous climate assessments. The base AM3 simulation, driven with observed sea surface temperature (SST) and sea ice cover (SIC) over the period 1981-2007, generally reproduces the observed mean magnitude, spatial distribution, and seasonal cycle of tropospheric ozone and carbon monoxide. The global mean aerosol optical depth in our base simulation is within 5% of satellite measurements over the 1982-2006 time period. We conduct a pair of simulations in which only the short-lived pollutant emissions and methane concentrations are changed from PI (1860) to PD (2000) levels (i.e., SST, SIC, greenhouse gases, and ozone-depleting substances are held at PD levels). From the PI to PD, we find that changes in short-lived pollutant emissions and methane have caused the tropospheric ozone burden to increase by 39% and the global burdens of sulfate, black carbon, and organic carbon to increase by factors of 3, 2.4, and 1.4, respectively. Tropospheric hydroxyl concentration decreases by 7%, showing that increases in OH sinks (methane, carbon monoxide, nonmethane volatile organic compounds, and sulfur dioxide) dominate over sources (ozone and nitrogen oxides) in the model. Combined changes in tropospheric ozone and aerosols cause a net negative top-of-the-atmosphere radiative forcing perturbation (-1.05 W m-2) indicating that the negative forcing (direct plus indirect) from aerosol changes dominates over the positive forcing due to ozone increases, thus masking nearly half of the PI to PD positive forcing from long-lived greenhouse gases globally, consistent with other current generation chemistry-climate models. Key Points Document and evaluate atmospheric chemistry in GFDL-AM3 Net forcing from PI to PD short-lived pollutant emission changes is -1.05 Wm-2 ©2013. American Geophysical Union. All Rights Reserved."
"24376166200;55547129338;","Implications for Arctic amplification of changes in the strength of the water vapor feedback",2013,"10.1002/jgrd.50578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882801972&doi=10.1002%2fjgrd.50578&partnerID=40&md5=e1a58b0b2a6c7ab324d476b1079fa646","One of the major climatic changes apparent over the Arctic Ocean has been the amplified rate at which air temperature has been increasing relative to the global mean. There are multiple factors which play roles in this amplification, including changes in sea ice/albedo, atmospheric circulation, clouds, and water vapor. We investigate the positive feedback on temperature caused by increasing downward longwave radiation flux (DLF) associated with increasing atmospheric precipitable water (PW). The Japanese 25-year Reanalysis and ERA-Interim reanalysis are used to examine the role of the DLF/PW component of the water vapor feedback loop on the enhanced warming in the Arctic between 1979 and 2011. We find a nonlinear relationship between DLF and PW, which suggests that the sensitivity of DLF to changes in PW varies by season, with the highest in winter and the lowest in summer. The positive trends in DLF and PW are widespread over the Arctic during autumn and spring but are centered mainly over the Atlantic sector in winter. The strength of the PW feedback loop depends on both the sensitivity of DLF to changes in PW and the change in PW during 1979-2011. If, in the future, PW were to increase significantly during winter in the central and Pacific sectors of the Arctic, there could be an expansion of Arctic amplification during winter. We also examine the effect of changes in cloud cover and find that such changes account for a much smaller proportion of the changes in DLF than does PW. Key Points Arctic amplification may expand during winter due to DLF/PW feedback Relative importance of PW on changes in DLF varies spatially and seasonally Role of cloud cover in contributing to the changes in DLF is small ©2013. American Geophysical Union. All Rights Reserved."
"29067574800;15724418700;","Seasonal to multidecadal variability of the width of the tropical belt",2013,"10.1002/jgrd.50610","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882754217&doi=10.1002%2fjgrd.50610&partnerID=40&md5=9d0f508b308b34431d5a203d6cf079b1","An expansion of the tropical belt has been extensively reported in observations, reanalyses, and climate model simulations, but there is a great deal of uncertainty in estimates of the rate of widening as different diagnostics give a wide range of results. This study critically examines robust diagnostics for the width of the tropical belt to explore their seasonality, interannual variability, and multidecadal trends. The width based on the latitudes of the maximum tropospheric dry bulk static stability, measuring the difference in potential temperature between the tropopause and the surface, is found to be closely coupled to the width based on the subtropical jet cores on all time scales. In contrast, the tropical belt width and Northern Hemisphere edge latitudes based on the latitudes at which the vertically averaged stream function vanishes, a measure of the Hadley circulation's poleward edges, lag those of the other diagnostics by approximately 1month. The tropical belt width varies by up to 10°latitude among the diagnostics, with trends in the tropical belt width ranging from -0.5 to 2.0°per decade over the 1979-2012 period. Nevertheless, in agreement with previous studies, nearly all diagnostics exhibit a widening trend, although the stream function diagnostic exhibits a significantly stronger widening than either the jet or dry bulk stability diagnostics. Finally, GPS radio occultation observations are used to assess the ability of the reanalyses to reproduce the tropical belt width, finding that they better situate the latitudes of maximum bulk stability versus those of the subtropical jets. Key Points Objective diagnostics exhibit a bi-annual seasonal cycle, significant expansion Hadley cell diagnostic lags other objective diagnostics by one month Reanalyses reproduce tropical belt widths observed from GPS-RO observations ©2013. American Geophysical Union. All Rights Reserved."
"14424178600;9433663600;9335272400;57203219128;55732462200;13409542900;6602349166;24565089800;6701380217;","Soil humic-like organic compounds in prescribed fire emissions using nuclear magnetic resonance spectroscopy",2013,"10.1016/j.envpol.2013.06.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880374756&doi=10.1016%2fj.envpol.2013.06.008&partnerID=40&md5=3873bf2e6d12b1d94f6636e07ce08720","Here we present the chemical characterization of the water-soluble organic carbon fraction of atmospheric aerosol collected during a prescribed fire burn in relation to soil organic matter and biomass combustion. Using nuclear magnetic resonance spectroscopy, we observed that humic-like substances in fire emissions have been associated with soil organic matter rather than biomass. Using a chemical mass balance model, we estimated that soil organic matter may contribute up to 41% of organic hydrogen and up to 27% of water-soluble organic carbon in fire emissions. Dust particles, when mixed with fresh combustion emissions, substantially enhances the atmospheric oxidative capacity, particle formation and microphysical properties of clouds influencing the climatic responses of atmospheric aeroso. Owing to the large emissions of combustion aerosol during fires, the release of dust particles from soil surfaces that are subjected to intense heating and shear stress has, so far, been lacking. © 2013 Elsevier Ltd. All rights reserved."
"55795535700;35494005000;","Cirrus cloud properties and the large-Scale meteorological environment: Relationships derived from A-Train and NCEP-NCAR reanalysis data",2013,"10.1175/JAMC-D-12-0102.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880297231&doi=10.1175%2fJAMC-D-12-0102.1&partnerID=40&md5=72ba05f7f430fb0dbce47b66c8d6bd19","Empirical knowledge of how cirrus cloud properties are coupled with the large-scale meteorological environment is a prerequisite for understanding the role of microphysical processes in the life cycle of cirrus cloud systems. Using active and passive remote sensing data from the A-Train, relationships between cirrus cloud properties and the large-scale dynamics are examined.Mesoscale cirrus events from along the A-Train track from 1 yr of data are sorted on the basis of vertical distributions of radar reflectivity and on large-scale meteorological parameters derived from the NCEP-NCAR reanalysis using a K-means cluster-analysis algorithm. With these defined regimes, the authors examine two questions: Given a cirrus cloud type defined by cloud properties, what are the large-scale dynamics? Vice versa, what cirrus cloud properties tend to emerge from large-scale dynamics regimes that tend to form cirrus? From the answers to these questions, the links between the large-scale dynamics regimes and the genre of cirrus that evolve within these regimes are identified. It is found that, to a considerable extent, the large-scale environment determines the bulk cirrus properties and that, within the dynamics regimes, cirrus cloud systems tend to evolve through life cycles, the details of which are not necessarily explained by the large-scale motions alone. These results suggest that, while simple relationships may be used to parameterize the gross properties of cirrus, more sophisticated parameterizations are required for representing the detailed structure and radiative feedbacks of these clouds. © 2013 American Meteorological Society."
"8658858500;15319530000;7102963655;","HIRS channel 12 brightness temperature dataset and its correlations with major climate indices",2013,"10.5194/acp-13-6907-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908414665&doi=10.5194%2facp-13-6907-2013&partnerID=40&md5=115db3c4f2a86286d01196383c48c834","A new version of the High-Resolution Infrared Radiation Sounder (HIRS) upper tropospheric water vapor channel (channel 12) brightness temperature dataset is developed using intersatellite calibrated data. In this dataset, only those pixels affected by upper tropospheric clouds are discarded. Compared to the previous version that was based on column-clear-sky data, the new version has much better daily spatial coverage. The HIRS observation patterns are compared to microwave sounder measurements. The differences between the two types of sounders vary with respect to brightness temperature with larger differences for higher (dry) values. Correlations between the HIRS upper tropospheric water vapor channel brightness temperatures and several major climate indices show strong signals during cold seasons. The selected climate indices track climate variation signals covering regions from the tropics to the poles. Qualitatively, moist signals are correlated with troughs and ascending branches of the circulation, while dry signals occur with ridges and descent. These correlations show the potential of using the upper tropospheric water vapor channel brightness temperature dataset together with a suite of many atmospheric variables to monitor regional climate changes and locate global teleconnection patterns. © Author(s) 2013."
"34874775800;35434835300;35215221100;36171552900;55496186000;","Observational occurrence of tropical cyclone ducts from GPS dropsonde data",2013,"10.1175/JAMC-D-11-0256.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880253551&doi=10.1175%2fJAMC-D-11-0256.1&partnerID=40&md5=54c90780e98f6024a27b6a3b4d7fd1e3","On the basis of global positioning system dropsonde data, Japan Meteorology Agency Regional Spectral Model analysis data, National Centers for Environmental Prediction reanalysis data, satellite products from the Naval Research Laboratory, and best-track tropical-cyclone (TC) datasets from the Shanghai Typhoon Institute, the statistical characteristics of the ducts induced by TCs (TC ducts) over the western North Pacific Ocean were analyzed for the period from September 2003 to September 2006, and two typical strong-duct cases with remarkable differences in formation cause were analyzed and compared. Of the total of 357 dropsondes, there are 212 cases that show ducting conditions, with an occurrence percentage of ∼59%.Of the 212 TC-duct events, profiles with multiple ducting layers make up nearly one-half, with the main type of ducts being elevated ducts; in contrast, weak ducts make up over one-half, resulting in a weak median duct strength and thickness. Ducts formed in the transition zone, especially on the left side of TC tracks, tend to be much stronger and thicker than those formed inside TCs. The former are induced by the interaction between TCs and their surrounding systems, such as the inrush of dry and cold air from the north on the left side of TC tracks. The latter are associated with successive subsidence in the gaps between spiral cloud bands. With increasing TC intensities, the associated ducts inside TCs tend to be much stronger and thicker and to appear at higher altitudes. © 2013 American Meteorological Society."
"55793507700;7003718864;","Variability and predictability of a three-dimensional hurricane in statistical equilibrium",2013,"10.1175/JAS-D-12-0112.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877644081&doi=10.1175%2fJAS-D-12-0112.1&partnerID=40&md5=4ff1d8c18b623a62a690ac55a7483191","The internal variability and predictability of idealized three-dimensional hurricanes is investigated using 100-day-long, statistically steady simulations in a compressible, nonhydrostatic, cloud-resolving model. The equilibrium solution is free of the confounding effects of initial conditions and environmental variability in order to isolate the ""intrinsic"" characteristics of the hurricane. The variance of the axisymmetric tangential velocity is dominated by two patterns: one characterized by a radial shift of the maximum wind, and the other by intensity modulation at the radius of maximum wind. These patterns are associated with convectively coupled bands of anomalous wind speed that propagate inward from large radii with a period of roughly 5 days, the strongest of which is associated with an eyewall replacement cycle. The asymmetric tangential wind is strongest radially inward of the radius of maximum wind. On average, asymmetries decelerate the azimuthal-mean tangential wind at the radius of maximum wind and accelerate it along the inner edge of eyewall. Predictability of axisymmetric storm structure is measured through the autocorrelation e-folding time and linear inverse modeling. Results from both methods reveal an intrinsic predictability time scale of about 2 days. The predictability and variability of the axisymmetric storm structure are consistent with recently obtained results from idealized axisymmetric hurricane modeling. © 2013 American Meteorological Society."
"16645127300;8953038700;55717441600;","Non-negligible effects of cloud vertical overlapping assumptions on longwave spectral fingerprinting studies",2013,"10.1002/jgrd.50562","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880869389&doi=10.1002%2fjgrd.50562&partnerID=40&md5=92031d340b0d94cedc9917e4bb0397a5","In order to monitor and attribute secular changes from outgoing spectral radiances, spectral fingerprints need to be constructed first. Large-scale model outputs are usually used to derive such spectral fingerprints. Different models make different assumptions on vertical overlapping of subgrid clouds. We explore the extent to which the spectral fingerprints constructed under different cloud vertical overlapping assumptions can affect such spectral fingerprinting studies. Utilizing a principal component-based radiative transfer model with high computational efficiency, we build an OSSE (Observing System Simulation Experiment) with full treatment of subgrid cloud variability to study this issue. We first show that the OLR (outgoing longwave radiation) computed from this OSSE is consistent with the OLR directly output from the parent large-scale models. We then examine the differences in spectral fingerprints due to cloud overlapping assumptions alone. Different cloud overlapping assumptions have little effect on the spectral fingerprints of temperature and humidity. However, the amplitude of the spectral fingerprints due to the same amount of cloud fraction change can differ as much as a factor of two between maximum random versus random overlap assumptions, especially for middle and low clouds. We further examine the impact of cloud overlapping assumptions on the results of linear regression of spectral differences with respect to predefined spectral fingerprints. Cloud-relevant regression coefficients are affected more by different cloud overlapping assumptions than regression coefficients of other geophysical variables. These findings highlight the challenges in constructing realistic longwave spectral fingerprints and in detecting climate change using all-sky observations. Key Points Build a Climate OSSE with full treatment of sub-grid cloud variability. Use the OSSE to study effect of cloud overlapping assumption on fingerprinting. Cloud overlapping assumptions affect amplitudes of spectral fingerprints most. ©2013. American Geophysical Union. All Rights Reserved."
"55807960100;7401795483;","Land-lake breezes at low latitudes: The case of Tonle Sap Lake in Cambodia",2013,"10.1002/jgrd.50547","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880863753&doi=10.1002%2fjgrd.50547&partnerID=40&md5=78daa0f3cac94fe9653838368176e8f5","Tonle Sap Lake is the largest freshwater lake in Southeast Asia. During the postmonsoon season, a small linear cloud system has been observed over this lake in early morning, while the sky above the surrounding land is clear. Although this cloud system is apparently generated by land breezes, previous studies on land-lake (sea) circulation have suggested that environmental factors at low latitudes inhibit development of nocturnal land breezes. In this study, we investigate the mechanism of these early morning clouds through numerical simulation. The simulations show a linear updraft system over the lake, forming along the southwest lakeshore around 22:00 and moving northeast to the middle of the lake. The heavier air mass from the land meets the extraordinarily warm and humid air mass over the lake, triggering updrafts under the conditionally convective instability. The characteristic high surface water temperature was favorable for generation of the land breeze and updraft systems. That high surface water temperature of the lake is produced by the tropical climate along with efficient energy absorption because of the shallowness of the water body. This unique feature can generate a clear nocturnal land breeze circulation accompanying a migrating updraft system over the lake despite its low latitude. Key Points Land-breeze develops even though this lake is located in the low-latitudes. A lined-up cloud is formed at night over the lake by the very hot lake water. The convection migrates over the lake by the katabatic wind. ©2013. American Geophysical Union. All Rights Reserved."
"57144865500;7202660188;7402767628;10240999000;7003601734;14819302400;14055495600;7501960798;57154985900;13102893800;7402541651;7102882068;36165586100;24338413500;8544421400;","A super Asian dust storm over the East and South China Seas: Disproportionate dust deposition",2013,"10.1002/jgrd.50405","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880857752&doi=10.1002%2fjgrd.50405&partnerID=40&md5=35f0ebc12aeafb268ce9d942038122d4","A super Asian dust (SAD) storm that originated from North China has affected East Asia since 20 March 2010. The tempo-spatial and size distributions of aerosol Al, a tracer of wind-blown dust, were measured on a regional aerosol network in March 2010. Two dust events were recorded: the SAD and a relatively moderate AD event. The SAD clouds raised Al concentrations to ~50 μg/m 3 on 21 and 22 March over the East China Sea (ECS) and occupied there for ~5 days. The SAD plume also stretched toward the South China Sea (SCS) on 21 March however, it caused a maximum Al concentration of ~8.5 μg/m 3 only, much lower than that observed in the ECS. In comparison, a weaker dust plume on 16 March caused Al maximum of ~4 μg/m3 over the ECS, and comparably, ~3 μg/m3 in the SCS. Dry dust deposition was measured during the peak phase of the SAD at 178 mg/m2/d, which corresponded to dry deposition velocities of 0.2-0.6 cm/s only, much lower than the commonly adopted one (1-2 cm/s). The corresponding increase in dust deposition by the SAD was up to a factor of ~12, which was, however, considerably disproportionate to the increase in dust concentration (i.e., the factor of over 100). In certain cases, synoptic atmospheric conditions appear to be more important in regulating dust contribution to the SCS than the strength of AD storms. Key Points A super Asian dust observed on a regional aerosol network over the ocean Increase in dust deposition is disproportionate to that in dust concentration Synoptic weather conditions play a critical role in AD transport to the SCS ©2013. American Geophysical Union. All Rights Reserved."
"57163475200;","Impact of climate change on agriculture over Mandya in Karnataka",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879937972&partnerID=40&md5=2cfd4bb67fe44b537f98fd77ae1e35e7","The role of aerosol effects on weather and climate has gained attention in the last few decades since they change the radiation balance of earth's atmosphere by reflecting and absorbing solar radiation and reducing the amount of solar radiation reaching the ground. The spatial and vertical distribution of aerosols and their absorptive properties influence local weather and atmospheric circulation patterns, cloud formation and hydrological processes. Therefore, monitoring of aerosols and their properties is critical for agricultural and climate research. By making use of the data from MODIS on AOT, influence of meteorological parameters on AOT and their influence on agriculture in terms of crop yield were observed and analyzed. © Research India Publications."
"38863214100;16309079300;6507224579;","Stabilizing cloud feedback dramatically expands the habitable zone of tidally locked planets",2013,"10.1088/2041-8205/771/2/L45","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879671188&doi=10.1088%2f2041-8205%2f771%2f2%2fL45&partnerID=40&md5=c0575f8a27381d0ec386a61e76ebdeea","The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phenomenon a stabilizing climate feedback. Substellar clouds also effectively block outgoing radiation from the surface, reducing or even completely reversing the thermal emission contrast between dayside and nightside. The presence of substellar water clouds and the resulting clement surface conditions will therefore be detectable with the James Webb Space Telescope. © 2013. The American Astronomical Society. All rights reserved.."
"6603613067;6603561402;7005453346;7410070663;8397494800;7005723936;7004207682;7003287025;55607020000;15763329000;7003365490;","The Canadian fourth generation atmospheric global climate model (CanAM4). Part I: Representation of physical processes",2013,"10.1080/07055900.2012.755610","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877335208&doi=10.1080%2f07055900.2012.755610&partnerID=40&md5=83d3df306ea66da5dc59d79fba663c73","The Canadian Centre for Climate Modelling and Analysis (CCCma) has developed the fourth generation of the Canadian Atmospheric Global Climate Model (CanAM4). The new model includes substantially modified physical parameterizations compared to its predecessor. In particular, the treatment of clouds, cloud radiative effects, and precipitation has been modified. Aerosol direct and indirect effects are calculated based on a bulk aerosol scheme. Simulation results for present-day global climate are analyzed, with a focus on cloud radiative effects and precipitation. Good overall agreement is found between climatological mean short- and longwave cloud radiative effects and observations from the Clouds and Earth's Radiant Energy System (CERES) experiment. An analysis of the responses of cloud radiative effects to variations in climate will be presented in a companion paper."
"26645289600;7402064802;57210518852;24329376600;7201485519;57203049177;35547807400;","Contributions of different cloud types to feedbacks and rapid adjustments in CMIP5",2013,"10.1175/JCLI-D-12-00555.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879994254&doi=10.1175%2fJCLI-D-12-00555.1&partnerID=40&md5=6dffacc57679602073af10c7645bcba2","Using five climate model simulations of the response to an abrupt quadrupling of CO2, the authors perform the first simultaneous model intercomparison of cloud feedbacks and rapid radiative adjustments with cloud masking effects removed, partitioned among changes in cloud types and gross cloud properties. Upon CO2 quadrupling, clouds exhibit a rapid reduction in fractional coverage, cloud-top pressure, and optical depth, with each contributing equally to a 1.1 W m22 net cloud radiative adjustment, primarily from shortwave radiation. Rapid reductions in midlevel clouds and optically thick clouds are important in reducing planetary albedo in every model. As the planet warms, clouds become fewer, higher, and thicker, and global mean net cloud feedback is positive in all but onemodel and results primarily fromincreased trapping of longwave radiation. As was true for earliermodels, high cloud changes are the largest contributor to intermodel spread in longwave and shortwave cloud feedbacks, but low cloud changes are the largest contributor to the mean and spread in net cloud feedback. The importance of the negative optical depth feedback relative to the amount feedback at high latitudes is even more marked than in earlier models. The authors show that the negative longwave cloud adjustment inferred in previous studies is primarily caused by a 1.3 W m22 cloud masking of CO2 forcing. Properly accounting for cloudmasking increases net cloud feedback by 0.3 W m22 K21,whereas accounting for rapid adjustments reduces by 0.14 W m22 K21 the ensemble mean net cloud feedback through a combination of smaller positive cloud amount and altitude feedbacks and larger negative optical depth feedbacks. ©2013 American Meteorological Society."
"55332348600;26645289600;7003266014;7403931916;","An analysis of the short-term cloud feedback using MODIS data",2013,"10.1175/JCLI-D-12-00547.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880678553&doi=10.1175%2fJCLI-D-12-00547.1&partnerID=40&md5=7b2bf5a7aa9998ea496361a03a5108b6","The cloud feedback in response to short-term climate variations is estimated from cloud measurements combined with offline radiative transfer calculations. The cloud measurements are made by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite and cover the period 2000-10. Low clouds provide a strong negative cloud feedback, mainly because of their impact in the shortwave (SW) portion of the spectrum. Midlevel clouds provide a positive net cloud feedback that is a combination of a positive SW feedback partially canceled by a negative feedback in the longwave (LW). High clouds have only a small impact on the net cloud feedback because of a close cancellation between largeLWandSWcloud feedbacks. Segregating the clouds by optical depth, it is found that the net cloud feedback is set by a positive cloud feedback due to reductions in the thickest clouds (mainly in the SW) and a cancelling negative feedback from increases in clouds with moderate optical depths (also mainly in the SW). The global average SW, LW, and net cloud feedbacks are 10.30 61.10, 20.46 60.74, and 20.16 60.83 W m-2 K-1, respectively. The SW feedback is consistent with previous work; the MODIS LW feedback is lower than previous calculations and there are reasons to suspect it may be biased low. Finally, it is shown that the apparently small control that global mean surface temperature exerts on clouds, which leads to the large uncertainty in the short-term cloud feedback, arises from statistically significant but offsetting relationships between individual cloud types and global mean surface temperature. ©2013 American Meteorological Society."
"7102696626;12761052200;55717244800;13406399300;57202891769;7006705919;55745955800;","The Mean Climate of the Community Atmosphere Model (CAM4) in Forced SST and Fully Coupled Experiments",2013,"10.1175/JCLI-D-12-00236.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874797242&doi=10.1175%2fJCLI-D-12-00236.1&partnerID=40&md5=b7c08680526e9b5d4dce6828cb0f00ed","The Community Atmosphere Model, version 4 (CAM4), was released as part of the Community Climate System Model, version 4 (CCSM4). The finite volume (FV) dynamical core is now the default because of its superior transport and conservation properties. Deep convection parameterization changes include a dilute plume calculation of convective available potential energy (CAPE) and the introduction of convective momentum transport (CMT). An additional cloud fraction calculation is now performed following macrophysical state updates to provide improved thermodynamic consistency. A freeze-drying modification is further made to the cloud fraction calculation in very dry environments (e.g., the Arctic), where cloud fraction and cloud water values were often inconsistent in CAM3. In CAM4 the FV dynamical core further degrades the excessive trade-wind simulation, but reduces zonal stress errors at higher latitudes. Plume dilution alleviates much of the midtropospheric tropical dry biases and reduces the persistent monsoon precipitation biases over the Arabian Peninsula and the southern Indian Ocean. CMT reduces much of the excessive tradewind biases in eastern ocean basins. CAM4 shows a global reduction in cloud fraction compared to CAM3, primarily as a result of the freeze-drying and improved cloud fraction equilibrium modifications. Regional climate feature improvements include the propagation of stationary waves from the Pacific into midlatitudes and the seasonal frequency of Northern Hemisphere blocking events. A 18 versus 28 horizontal resolution of the FV dynamical core exhibits superior improvements in regional climate features of precipitation and surface stress. Improvements in the fully coupled mean climate between CAM3 and CAM4 are also more substantial than in forced sea surface temperature (SST) simulations.©2013 American Meteorological Society."
"57001165400;55803043300;7403968239;","Cloud and water vapor feedbacks to the El Niño warming: Are they still biased in CMIP5 models?",2013,"10.1175/JCLI-D-12-00575.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876438721&doi=10.1175%2fJCLI-D-12-00575.1&partnerID=40&md5=e52bca17aac459ae1591997e0c7c6a9b","Previous evaluations of model simulations of the cloud and water vapor feedbacks in response to El Niño warming have singled out two common biases in models from phase 3 of the Coupled Model Intercomparison Project (CMIP3): an underestimate of the negative feedback from the shortwave cloud radiative forcing (SWCRF) and an overestimate of the positive feedback from the greenhouse effect of water vapor. Here, the authors check whether these two biases are alleviated in the CMIP5 models. While encouraging improvements are found, particularly in the simulation of the negative SWCRF feedback, the biases in the simulation of these two feedbacks remain prevalent and significant. It is shown that bias in the SWCRF feedback correlates well with biases in the corresponding feedbacks from precipitation, large-scale circulation, and longwave radiative forcing of clouds (LWCRF). By dividing CMIP5 models into two categories-high score models (HSM) and low score models (LSM)-based on their individual skills of simulating the SWCRF feedback, the authors further find that ocean-atmosphere coupling generally lowers the score of the simulated feedbacks of water vapor and clouds but that the LSM is more affected by the coupling than the HSM. They also find that the SWCRF feedback is simulated better in the models that have a more realistic zonal extent of the equatorial cold tongue, suggesting that the continuing existence of an excessive cold tongue is a key factor behind the persistence of the feedback biases in models. ©2013 American Meteorological Society."
"7004384155;7004540083;56270311300;7101677832;30667558200;6603925960;6602111828;35319507500;35867172500;6603631763;24802640400;7102063963;7006783796;8633248700;57208765879;15840467900;8680433600;6506827279;12801836100;7003865921;55704704700;7403296946;","Assessment of global cloud datasets from satellites: Project and database initiated by the GEWEX radiation panel",2013,"10.1175/BAMS-D-12-00117.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880884170&doi=10.1175%2fBAMS-D-12-00117.1&partnerID=40&md5=d429aa0a5d992e7a723ca1c8edd667aa","The Global Energy and Water Cycle Experiment (GEWEX) Radiation Panel initiated the GEWEX Cloud Assessment in 2005 to compare available, global, long-term cloud data products with the International Satellite Cloud Climatology Project (ISCCP). The GEWEX Cloud Assessment database included cloud properties retrieved from different satellite sensor measurements, taken at various local times and over various time periods. The relevant passive satellite sensors measured radiation scattered or emitted by Earth's surface and by its atmosphere including clouds. Specific spectral domains were exploited for particular retrieval methods to maximize the sensitivity to the presence of clouds and to determine key cloud properties. ISCCP also emphasized on temporal resolution over spectral resolution to resolve the diurnal cycle of clouds the GEWEX cloud climate record."
"57200241494;35621385000;55334838600;7006507564;6603647965;9234412200;","A daytime over land algorithm for computing AVHRR convective cloud climatologies for the Iberian Peninsula and the Balearic Islands",2013,"10.1002/joc.3572","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879602676&doi=10.1002%2fjoc.3572&partnerID=40&md5=99153c52952cfabec36fd5a0ceac1a2b","A daytime over land multispectral cloud detection algorithm is presented to derive accurate convective cloud climatologies with high spatial resolution (1.1 km) over the Iberian Peninsula (IP) and the Balearic Islands (BI). The cloud detection scheme was designed to process Advanced Very High Resolution Radiometer (AVHRR) HRPT data and is tested here on NOAA-17 morning (0900-1200 UTC) and NOAA-16 afternoon (1200-1500 UTC) overpasses for the warm 6-month study period May-October. The algorithm consists of four spectral threshold tests applied to each pixel. Test 1 corresponds to the snow-ice removal, test 2 is the thermal infrared test, test 3 is the albedo or visible test and test 4 is the ratio between near-infrared and visible channels. The algorithm discretizes all AVHRR data into four groups called cloud-filled, cloud-free, snow-ice and snow-free radiances. The high-resolution convective cloud masks are obtained by subtracting snow-ice pixels from cloudy ones. In this article, a detailed description of the convective cloud detection scheme and the sources of error detected for each test are given, and the first seasonal and monthly regional convective cloud frequency composites are presented. Future applications of the newly proposed threshold algorithm in climate and meteorology are also discussed in this article, particularly the production of convective cloud composites for climate monitoring of storms over the IP and BI. © 2012 Royal Meteorological Society."
"24171369600;55635267300;11241983900;57198384395;6508201898;","Intercomparison of satellite- and ground-based cloud fraction over Switzerland (2000-2012)",2013,"10.1016/j.atmosres.2013.01.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875615302&doi=10.1016%2fj.atmosres.2013.01.013&partnerID=40&md5=8fa0e584273acef67657121110e8aca8","Satellite data provide the opportunity for systematic and continuous observation of cloud cover over large spatial scales. In this paper, we describe the generation of two new high spatial resolution (0.05°) daytime cloud fraction data sets over Switzerland. The data sets are based on the Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask products. The data sets cover the period from March 1, 2000 to February 29, 2012 (Terra/MODIS) and July 1, 2002 to February 29, 2012 (Aqua/MODIS) and represent mid-morning and early-afternoon cloud cover over Switzerland. Time series clearly reflected seasonal variations in cloud fraction over Switzerland. A comparison with cloud fraction observations at four Synop stations (Chur, Locarno/Monti, Payerne, Zurich/Kloten) revealed an agreement of monthly mean mid-morning cloud fraction (MMCF) within ± 1 octa (i.e., 12.5%). Relative to Synop observations, MMCF was positively biased by 0.3-5.0%, except at Payerne (-2.5%). Linear correlation coefficients ranged from 0.878 to 0.972. Results were similar for monthly mean early-afternoon cloud fraction (MACF). Cloud fraction was found to be higher in the early-afternoon when compared to mid-morning, except at Payerne and Zurich/Kloten in fall, which is explained by typical daytime cloud cover patterns in Switzerland. Analysis of daily mid-morning cloud fraction showed that largest discrepancies were observed in partly cloudy conditions, which is mainly explained by differences in observation times and observation geometry. Our results demonstrate that the newly processed cloud fraction data sets from the MODIS sensor can play an important role in complementing traditional Synop observations in support of systematic cloud cover monitoring within the National Climate Observing System (GCOS Switzerland). © 2013 Elsevier B.V."
"56263595100;57208346904;7401806579;25227357000;55371795600;","Cloud-Aerosol-Radiation (CAR) ensemble modeling system: Overall accuracy and efficiency",2013,"10.1007/s00376-012-2171-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874531904&doi=10.1007%2fs00376-012-2171-z&partnerID=40&md5=4baf653f98908b6fe08689cf4bd96634","The Cloud-Aerosol-Radiation (CAR) ensemble modeling system has recently been built to better understand cloud/aerosol/radiation processes and determine the uncertainties caused by different treatments of cloud/aerosol/radiation in climate models. The CAR system comprises a large scheme collection of cloud, aerosol, and radiation processes available in the literature, including those commonly used by the world's leading GCMs. In this study, detailed analyses of the overall accuracy and efficiency of the CAR system were performed. Despite the different observations used, the overall accuracies of the CAR ensemble means were found to be very good for both shortwave (SW) and longwave (LW) radiation calculations. Taking the percentage errors for July 2004 compared to ISCCP (International Satellite Cloud Climatology Project) data over (60°N, 60°S) as an example, even among the 448 CAR members selected here, those errors of the CAR ensemble means were only about -0.67% (-0.6 W m-2) and -0.82% (-2.0 W m-2) for SW and LW upward fluxes at the top of atmosphere, and 0.06% (0.1 W m-2) and -2.12% (-7.8 W m-2) for SW and LW downward fluxes at the surface, respectively. Furthermore, model SW frequency distributions in July 2004 covered the observational ranges entirely, with ensemble means located in the middle of the ranges. Moreover, it was found that the accuracy of radiative transfer calculations can be significantly enhanced by using certain combinations of cloud schemes for the cloud cover fraction, particle effective size, water path, and optical properties, along with better explicit treatments for unresolved cloud structures. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"36060938100;7402989545;","Improve the simulation of western North Pacific summer monsoon in RegCM3 by suppressing convection",2013,"10.1007/s00703-013-0255-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879147489&doi=10.1007%2fs00703-013-0255-7&partnerID=40&md5=395652572002a11c2c6d3fc534f22042","Regional climate models, such as RegCM3, generally show large biases in the simulation of western North Pacific (WNP) summer monsoon (WNPSM). In this study, the authors improved the simulation of WNPSM by applying the convection suppression criterion based on the averaged relative humidity from cloud base to cloud top. The simulated rainfall and monsoon circulation are significantly improved. The suppressed convective heating associated with the decrease in convective rainfall simulates a low-level anomalous anticyclone to its north. The anomalous anticyclone reduces the intensity of low-level southwesterly flow and the wind speed at 10 m. The reduction in wind speed at 10 m decreases the evaporation at sea surface. The less supply of water vapor from underlying ocean in turn favors less convective rainfall. The overestimation of simulated convective percentages and the cold bias of 2 m air temperature are also reduced. The different effects of convection suppression criterion in stand-alone RegCM3 and corresponding regional air-sea coupled model are also discussed. © 2013 Springer-Verlag Wien."
"36914858100;7004657713;55322252400;35502847300;7202972418;","A validation of cloudsat and CALIPSO's temperature, humidity, cloud detection, and cloud base height over the arctic marine cryosphere",2013,"10.1080/07055900.2013.798582","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880204627&doi=10.1080%2f07055900.2013.798582&partnerID=40&md5=15f6a829985673d0f27cd43481c4fec9","The reliability of the data products from the European Centre for Medium-range Weather Forecasts fields mapped to CloudSat profiles (ECMWF-aux) and the Cloud Geometrical Profile from combined Cloud Profiling Radar (CPR) and Cloud Aerosol and Lidar Infrared Pathfinder Satellite Observations (CALIPSO) (GeoProf-lidar) was determined in a polar marine environment by comparing the satellite products with data from ship-based instrumentation. Simultaneous microwave radiometer profiler (MWRP) measurements were compared with CloudSat's ECMWF-aux temperature and absolute humidity profiles from the surface to 10 km. Cloud-base heights from the ceilometer and radiometer were compared with the GeoProf-lidar cloud-base heights which are derived from a combination of CloudSat and CALIPSO data. Temperatures from ECMWF-aux were generally warmer than those measured by the MWRP during all seasons (negative bias). The root mean square (RMS) differences for temperature were greater than one standard deviation of the MWRP and thus greater than the expected range of the climate. The ECMWF-aux absolute humidity profiles had relatively large RMS differences from the surface to 2 km when compared with the MWRP data during spring and summer. The correlation coefficients between both ECMWF-aux and MWRP temperature and absolute humidity were generally greater than 0.8, indicating a strong agreement between the profile lapse rates. However, negative biases indicated systematic differences in the actual values at all levels. The GeoProf-lidar cloud-base height was compared with the MWRP and ceilometer cloud-base heights. There were fifteen occurrences when both ship-based instruments indicated clear skies but the GeoProf-lidar product indicated clouds. For six of these occurrences no clouds were detectable by visual observation of the radar's reflectivity profile or from the lidar's backscatter profile; five of the occurrences were over mixed ice conditions. This is an indication that the constraints used by the GeoProf-lidar product for cloud detection need to be refined for the Arctic, specifically over mixed ice conditions. Further investigations should include comparisons of GeoProf-lidar cloud heights with the backscatter and reflectivity profiles and with optical depth over mixed ice conditions to help determine the sources of these issues."
"35209683700;55716995500;26324818700;","Radiative and dynamical forcing of the surface and atmospheric temperature anomalies associated with the northern annular mode",2013,"10.1175/JCLI-D-12-00431.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880695643&doi=10.1175%2fJCLI-D-12-00431.1&partnerID=40&md5=accda1c3b6bbbfd90a3d6c514dca9d9f","On the basis of the total energy balance within an atmosphere-surface column, an attribution analysis is conducted for the Northern Hemisphere (NH) atmospheric and surface temperature response to the northern annular mode (NAM) in boreal winter. The local temperature anomaly in the European Centre for Medium- Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) is decomposed into partial temperature anomalies because of changes in atmospheric dynamics, water vapor, clouds, ozone, surface albedo, and surface dynamics with the coupled atmosphere-surface climate feedback-response analysis method (CFRAM). Large-scale ascent/descent as part of the NAM-related mean meridional circulation anomaly adiabatically drives the main portion of the observed zonally averaged atmospheric temperature response, particularly the tropospheric cooling/warming over northern extratropics. Contributions from diabatic processes are generally small but could be locally important, especially at lower latitudes where radiatively active substances such as clouds and water vapor are more abundant. For example, in the tropical upper troposphere and stratosphere, both cloud and ozone forcings are critical in leading to the observed NAM-related temperature anomalies. Radiative forcing due to changes in water vapor acts as the main driver of the surface warming of southern North America during a positive phase of NAM, with atmospheric dynamics providing additional warming. In the negative phase of NAM, surface albedo change drives the surface cooling of southern North America, with atmospheric dynamics providing additional cooling. Over the subpolar North Atlantic and northern Eurasia, atmospheric dynamical processes again become the largest contributor to the NAM-related surface temperature anomalies, although changes in water vapor and clouds also contribute positively to the observed surface temperature anomalies while change in surface dynamics contributes negatively to the observed temperature anomalies.©2013 American Meteorological Society."
"36241005100;7006329853;","Hospitable archean climates simulated by a general circulation model",2013,"10.1089/ast.2012.0936","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880402282&doi=10.1089%2fast.2012.0936&partnerID=40&md5=7e24398a95dbc1d992152e90323731fb","Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO 2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model. © 2013 Mary Ann Liebert, Inc. 2013."
"13407895800;35090272500;6603327055;7006206130;","Evaluation of daily maximum and minimum 2-m temperatures as simulated with the regional climate model COSMO-CLM over Africa",2013,"10.1127/0941-2948/2013/0468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887836806&doi=10.1127%2f0941-2948%2f2013%2f0468&partnerID=40&md5=26157cba36a53b1d71e3742b42d09b58","The representation of the diurnal 2-m temperature cycle is challenging because of the many processes involved, particularly land-atmosphere interactions. This study examines the ability of the regional climate model COSMO-CLM (version 4.8) to capture the statistics of daily maximum and minimum 2-m temperatures (Tmin/Tmax) over Africa. The simulations are carried out at two different horizontal gridspacings (0.22° and 0.44°), and are driven by ECMWF ERA-Interim reanalyses as near-perfect lateral boundary conditions. As evaluation reference, a high-resolution gridded dataset of daily maximum and minimum temperatures (Tmin/Tmax) for Africa (covering the period 2008-2010) is created using the regression-kriging-regression-kriging (RKRK) algorithm. RKRK applies, among other predictors, the remotely sensed predictors land surface temperature and cloud cover to compensate for the missing information about the temperature pattern due to the low station density over Africa. This dataset allows the evaluation of temperature characteristics like the frequencies of Tmin/Tmax, the diurnal temperature range, and the 90th percentile of Tmax. Although the large-scale patterns of temperature are reproduced well, COSMO-CLM shows significant under- and overestimation of temperature at regional scales. The hemispheric summers are generally too warm and the day-to-day temperature variability is overestimated over northern and southern extra-tropical Africa. The average diurnal temperature range is underestimated by about 2°C across arid areas, yet overestimated by around 2°C over the African tropics. An evaluation based on frequency distributions shows good model performance for simulated Tmin (the simulated frequency distributions capture more than 80% of the observed ones), but less well performance for Tmax (capture below 70%). Further, over wide parts of Africa a too large fraction of daily Tmax values exceeds the observed 90th percentile of Tmax, particularly across the African tropics. Thus, the representation of processes controlling Tmax including cloud-solar interaction, radiation processes, and ground heat fluxes should be improved by further model developments. The higher-resolution simulation (0.22°) is on average about 0.5°C warmer with a more pronounced overestimation of the higher percentiles of Tmax, and yields no clear benefit over the lower-resolution simulation. © by Gebrüder Borntraeger 2013."
"55352969400;7102422542;23036934200;7003475150;35392584500;","NWP model forecast skill optimization via closure parameter variations",2013,"10.1002/qj.2044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884210439&doi=10.1002%2fqj.2044&partnerID=40&md5=e7920f69c2bb4c9681539c7f44671085","We apply a recently developed method, the Ensemble Prediction and Parameter Estimation System (EPPES), to demonstrate how numerical weather prediction (NWP) model closure parameters can be optimized. As proof of concept, we tune the medium-range forecast skill of the ECMWF model HAMburg version (ECHAM5) atmospheric general circulation model using an ensemble prediction system (EPS) emulator. Initial state uncertainty is represented in the EPS emulator by applying the initial state perturbations generated at the European Centre for Medium-range Weather Forecasts (ECMWF). Model uncertainty is represented in the emulator via parameter variations at the initial time. We vary four closure parameters related to parametrizations of subgrid-scale physical processes of clouds and precipitation. With this set-up, we generate ensembles of 10-day global forecasts with the ECHAM5 model at T42L31 resolution twice a day over a period of three months. The cost function in the optimization is formulated in terms of standard forecast skill scores, verified against the ECMWF operational analyses. A summarizing conclusion of the experiments is that the EPPES method is able to find ECHAM5 model closure parameter values that correspond to smaller values of the cost function. The forecast skill score improvements verify positively in dependent and independent samples. The main reason is the reduced temperature bias in the tropical lower troposphere. Moreover, the optimization improved the top-of-atmosphere radiation flux climatology of the ECHAM5 model, as verified against the Clouds and the Earth's Radiant Energy System (CERES) radiation data over a 6-year period, while the simulated tropical cloud cover was reduced, thereby increasing a negative bias as verified against the International Satellite Cloud Climatology Project (ISCCP) data. © 2012 Royal Meteorological Society."
"49961003000;","Adapting to a new reality - Strategies for building energy design in a changing climate",2013,"10.1080/10485236.2013.10750245","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885001075&doi=10.1080%2f10485236.2013.10750245&partnerID=40&md5=b8ca049355572ab50ca1b6004eb582ea","Building energy design is traditionally performed using retrogressive data sets (e.g., the past 30 years of weather data). The implied presumption has always been that this data will cycle back and forth around relatively static baseline averages. With increasing evidence that some level of climate change may be occurring, it is natural for building owners, developers, designers, and managers to question whether (and to what extent) these fundamental climate assumptions may be altered in future years. Depending on a building's locality, this could take the form of increasing or decreasing trends in seasonal average temperatures, daily maximum and minimum temperatures, relative humidity, barometric pressure, wind speed and direction, cloud cover, and total precipitation. These assumptions are crucial, because a typical building must remain habitable for 30 to 50 years (or longer) and provide its owner with the maximum possible return on a sizeable capital investment.This article will demonstrate how building owners and developers can employ intelligent strategies to maximize energy efficiency while concurrently meeting building energy requirements and retaining significant flexibility to cope with potential variations in local climate. Data from existing buildings that currently exhibit outstanding energy performance (e.g., net zero energy buildings, Leadership in Energy and Environmental Design [LEED®] Gold- and Platinum-certified buildings, buildings with ENERGY STAR® ratings above 90) will be utilized to identify energy efficiency and renewable energy production technologies that can further improve energy performance and reduce risk. This article will demonstrate that, by implementing these types of adaptive strategies, the building sector can more nimbly respond to potential climate variations."
"7006422317;15844751000;7202304406;7103352790;55550388400;36006968000;","Influence of convective parameterization on the systematic errors of Climate Forecast System (CFS) model over the Indian monsoon region from an extended range forecast perspective",2013,"10.1007/s00382-013-1662-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879553509&doi=10.1007%2fs00382-013-1662-7&partnerID=40&md5=b89ebd8e7ebfcec0141a67999f7c572e","This study investigates the influence of Simplified Arakawa Schubert (SAS) and Relax Arakawa Schubert (RAS) cumulus parameterization schemes on coupled Climate Forecast System version.1 (CFS-1, T62L64) retrospective forecasts over Indian monsoon region from an extended range forecast perspective. The forecast data sets comprise 45 days of model integrations based on 31 different initial conditions at pentad intervals starting from 1 May to 28 September for the years 2001 to 2007. It is found that mean climatological features of Indian summer monsoon months (JJAS) are reasonably simulated by both the versions (i.e. SAS and RAS) of the model; however strong cross equatorial flow and excess stratiform rainfall are noted in RAS compared to SAS. Both the versions of the model overestimated apparent heat source and moisture sink compared to NCEP/NCAR reanalysis. The prognosis evaluation of daily forecast climatology reveals robust systematic warming (moistening) in RAS and cooling (drying) biases in SAS particularly at the middle and upper troposphere of the model respectively. Using error energy/variance and root mean square error methodology it is also established that major contribution to the model total error is coming from the systematic component of the model error. It is also found that the forecast error growth of temperature in RAS is less than that of SAS; however, the scenario is reversed for moisture errors, although the difference of moisture errors between these two forecasts is not very large compared to that of temperature errors. Broadly, it is found that both the versions of the model are underestimating (overestimating) the rainfall area and amount over the Indian land region (and neighborhood oceanic region). The rainfall forecast results at pentad interval exhibited that, SAS and RAS have good prediction skills over the Indian monsoon core zone and Arabian Sea. There is less excess rainfall particularly over oceanic region in RAS up to 30 days of forecast duration compared to SAS. It is also evident that systematic errors in the coverage area of excess rainfall over the eastern foothills of the Himalayas remains unchanged irrespective of cumulus parameterization and initial conditions. It is revealed that due to stronger moisture transport in RAS there is a robust amplification of moist static energy facilitating intense convective instability within the model and boosting the moisture supply from surface to the upper levels through convergence. Concurrently, moisture detrainment from cloud to environment at multiple levels from the spectrum of clouds in the RAS, leads to a large accumulation of moisture in the middle and upper troposphere of the model. This abundant moisture leads to large scale condensational heating through a simple cloud microphysics scheme. This intense upper level heating contributes to the warm bias and considerably increases in stratiform rainfall in RAS compared to SAS. In a nutshell, concerted and sustained support of moisture supply from the bottom as well as from the top in RAS is the crucial factor for having a warm temperature bias in RAS. © 2013 Springer-Verlag Berlin Heidelberg."
"24376860700;36470046100;55482393700;7007152823;7401962278;","Variability of the climatic mass balance of Vestfonna ice cap, northeastern Svalbard, 1979-2011",2013,"10.3189/2013AoG63A407","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881644001&doi=10.3189%2f2013AoG63A407&partnerID=40&md5=294d6bb7a4bd9cb0004548d8aaccd89c","Vestfonna ice cap, northeastern Svalbard, is one of the largest ice bodies in the European Arctic, but little is known about the evolution of its mass balance. This study presents a reconstruction of the climatic mass balance of the ice cap for the period 1979/80-2010/11. The reconstruction is based on calculations using a mass-balance model that combines a surface-elevation- dependent accumulation scheme with a spatially distributed temperature-index ablation model that includes net shortwave radiation. Refreezing is included, based on the basic Pmax approach. The model accounts for cloud-cover effects and surface albedo variations that are calculated by a statistical albedo model. ERAInterim derived air temperature, precipitation and total cloud-cover data are used as input. Results reveal a mean climatic mass-balance rate of +0.09±0.15mw.e. a-1 for the study period. Annual balances show a slight, insignificant trend towards less positive values over the study period. Refreezing is estimated to contribute about one-third to annual accumulation, and a significant positive trend in refreezing is present over the study period. The modelling results reveal a significant steepening of the climatic mass-balance gradient and indicate a lengthening of the characteristic 3 month ablation period in recent years. © 2013 Publishing Technology."
"10239531200;55650183600;7202158002;7402874543;","Snowball Earth events driven by starbursts of the Milky Way Galaxy",2013,"10.1016/j.newast.2012.11.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007557730&doi=10.1016%2fj.newast.2012.11.005&partnerID=40&md5=3f4761584a67cb8569b30bd206003882","The trigger mechanism of the Snowball Earth events at 2.2–2.4 Ga and 0.55–0.77 Ga in the Proterozoic eon remains unknown despite intensive study over the last decade. We present the starburst model of the Snowball Earth. During a starburst of the Milky Way Galaxy, frequent and prolonged encounters with dark clouds and supernova remnants occur. The increased flux of cosmic dust particles and cosmic rays during the nebula encounters lead to a global super-cool climate, a Snowball Earth event. The individual nebula encounters may correspond to the substructures of super-cool/super-warm cycles in a Snowball Earth event. The starburst periods deduced from the ages of stars and star clusters coincide well with the Snowball Earth events reconstructed from geological records. We comprehensively evaluate the effects of cosmic rays, UV radiation, and cosmic dust particles during nebula encounters for the first time, and found that the starburst model of Snowball Earth events can adequately explain the triggering and occurrence pattern of Snowball Earth events. The direct evidence of nebula encounters can be obtained from deep-sea sediments deposited during the Snowball Earth events. © 2012 Elsevier B.V."
"26665643500;23082420800;7006256622;7003922138;42661269900;","Precessional cycles and their influence on the north pacific and north atlantic summer anticyclones",2013,"10.1175/JCLI-D-12-00343.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880664044&doi=10.1175%2fJCLI-D-12-00343.1&partnerID=40&md5=c5aeee2c4e4172f6421e1f903f9d336e","The response of the Northern Hemisphere summer anticyclones to a change in the timing of perihelion is investigated using the GFDL Climate Model version 2.1 (CM2.1). The orbital forcing consists of changes in the seasonal cycle of the top-of-atmosphere insolation as the perihelion shifts from the Northern Hemisphere winter to the Northern Hemisphere summer solstice. The North Pacific summer anticyclone experiences a large strengthening as well as a northward and westward expansion. The North Atlantic subtropical high experiences a smaller change that consists of a slight westward expansion but little change in strength. Experiments with a primitive equation atmospheric model show that these changes represent the circulation response to changes in the diabatic heating, both local and remotely. The remote diabatic forcing is associated with changes in the Southeast Asian and African summer monsoons, and the local forcing is dominated by a combined effect of a change in low clouds and local precipitation. © 2013 American Meteorological Society."
"7201498373;7003531755;36705143500;7403552006;","Intensification of north american megadroughts through surface and dust aerosol forcing",2013,"10.1175/JCLI-D-12-00022.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880685274&doi=10.1175%2fJCLI-D-12-00022.1&partnerID=40&md5=a6a07c167595d627b82560296606c381","Tree-ring-based reconstructions of the Palmer drought severity index (PDSI) indicate that, during the Medieval Climate Anomaly (MCA), the central plains of North America experienced recurrent periods of drought spanning decades or longer. These megadroughts had exceptional persistence compared to more recent events, but the causes remain uncertain. The authors conducted a suite of general circulation model experiments to test the impact of sea surface temperature (SST) and land surface forcing on the MCA megadroughts over the central plains. The land surface forcing is represented as a set of dune mobilization boundary conditions, derived from available geomorphological evidence and modeled as increased bare soil area and a dust aerosol source (328-448N, 1058-958W). In the experiments, cold tropical Pacific SST forcing suppresses precipitation over the central plains but cannot reproduce the overall drying or persistence seen in the PDSI reconstruction. Droughts in the scenario with dust aerosols, however, are amplified and have significantly longer persistence than in other model experiments, more closely matching the reconstructed PDSI. This additional drying occurs because the dust increases the shortwave planetary albedo, reducing energy inputs to the surface and boundary layer. The energy deficit increases atmospheric stability, inhibiting convection and reducing cloud cover and precipitation over the central plains. Results from this study provide the first model-based evidence that dust aerosol forcing and land surface changes could have contributed to the intensity and persistence of the central plains megadroughts, although uncertainties remain in the formulation of the boundary conditions and the future importance of these feedbacks."
"7005485117;55968364300;7003366215;14070768100;7403882699;56391331800;","Impacts of enhanced CCN on the organization of convection and recent reduced counts of monsoon depressions",2013,"10.1007/s00382-012-1638-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879499929&doi=10.1007%2fs00382-012-1638-z&partnerID=40&md5=ba38531cb041ced64ed27ac806854fb6","Monsoon depressions, that form during the Indian summer monsoon season (June to September) are known to be baroclinic disturbances (horizontal scale 2,000-3,000 km) and are driven by deep convection that carries a very large vertical slope towards cold air aloft in the upper troposphere. Deep convection is nearly always organized around the scale of these depressions. In the maintenance of the monsoon depression the generation of eddy kinetic energy on the scale of the monsoon depression is largely governed by the ""in scale"" covariance of heating and temperature and of vertical velocity and temperature over the region of the monsoon depression. There are normally about 6-8 monsoon depressions during a summer monsoon season. Recent years 2009, 2010 and 2011 saw very few (around 1, 0 and 1 per season respectively). The best numerical models such as those from ECMWF and US (GFS) carried many false alarms in their 3-5 day forecasts, more like 6-8 disturbances. Even in recent years with fewer observed monsoon depressions a much larger number of depressions is noted in ECMWF forecasts. These are fairly comprehensive models that carry vast data sets (surface and satellite based), detailed data assimilation, and are run at very high resolutions. The monsoon depression is well resolved by these respective horizontal resolutions in these models (at 15 and 35 km). These models carry complete and detailed physical parameterizations. The false alarms in their forecasts leads us to suggest that some additional important ingredient may be missing in these current best state of the art models. This paper addresses the effects of pollution for the enhancement of cloud condensation nuclei and the resulting disruption of the organization of convection in monsoon depressions. Our specific studies make use of a high resolution mesoscale model (WRF/CHEM) to explore the impacts of the first and second aerosol indirect effects proposed by Twomey and Albrecht. We have conducted preliminary studies including examination of the evolution of radar reflectivity (computed inversely from the model hydrometeors) for normal and enhanced CCN effects (arising from enhanced monsoon pollution). The time lapse histories show a major disruption in the organization of convection of the monsoon depressions on the time scale of a week to 10 days in these enhanced CCN scenarios. © 2012 Springer-Verlag Berlin Heidelberg."
"54883972100;6506749486;55922675100;15077749600;23008223800;","Multi-Criteria Decision Analysis integrated with GIS and remote sensing for astronomical observatory site selection in Antalya province, Turkey",2013,"10.1016/j.asr.2013.03.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878330987&doi=10.1016%2fj.asr.2013.03.001&partnerID=40&md5=d61b8c75200152bbe51245c62ea0b68c","Astronomical observatory site selection is a complex problem that involves evaluation of multiple factors from different sources. The aim of this study is to select the best possible candidates for astronomical observations sites using Multi-Criteria Decision Analysis integrated with Geographical Information Systems and remote sensing technologies. The study was implemented in the Antalya province of Turkey, which is convenient for astronomical site observatory facilities with its appropriate climate properties and weather conditions. Eleven factors (cloud cover, precipitable water, earthquake zones, geology, landslide inventory, active fault lines, Digital Elevation Model, city lights, mining activities, settlement areas, roads) were determined, splitting into three categories; meteorological, geographical and anthropogenic criteria. These factors were evaluated using Analytical Hierarchy Process method and the weights of criteria layers were determined. As a result, the most suitable areas were located extensively in western and eastern part of Antalya. This study offers a robust, accurate, cost and time effective procedure for preliminary site selection for astronomical observatory. However, for a final decision of the best location of astronomical observatory, site testing measurements and atmospheric seeing observations will be further required in these preliminary areas. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved."
"55765742100;24400381400;6701823396;","Antarctic low-tropospheric humidity inversions: 10-yr climatology",2013,"10.1175/JCLI-D-12-00671.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880695550&doi=10.1175%2fJCLI-D-12-00671.1&partnerID=40&md5=d5003237b74c3754193f7472f1c6e25c","Humidity inversions are nearly permanently present in the coastal Antarctic atmosphere. This is shown based on an investigation of statistical characteristics of humidity inversions at 11 Antarctic coastal stations using radiosonde data from the Integrated Global Radiosonde Archive (IGRA) from 2000 to 2009. The humidity inversion occurrence was highest in winter and spring, and high atmospheric pressure and cloud-free conditions generally increased the occurrence. A typical humidity inversion was less than 200 m deep and 0.2 g kg21 strong, and a typical humidity profile contained several separate inversion layers. The inversion base height had notable seasonal variations, but generally the humidity inversions were located at higher altitudes than temperature inversions. Roughly half of the humidity inversions were associated with temperature inversions, especially near the surface, and humidity and temperature inversion strengths as well as depths correlated at several stations. On the other hand, approximately 60% of the humidity inversions were accompanied by horizontal advection of water vapor increasing with height, which is also a probable factor supporting humidity inversions. The spatial variability of humidity inversions was linked to the topography and the water vapor content of the air. Compared to previous results for the Arctic, the most striking differences in humidity inversions in the Antarctic were a much higher frequency of occurrence in summer, at least under clear skies, and a reverse seasonal cycle of the inversion height. The results can be used as a baseline for validation of weather prediction and climate models and for studies addressing changes in atmospheric moisture budget in the Antarctic. ©2013 American Meteorological Society."
"55653739600;22234191300;7102309161;14067693600;7202664004;","Atmospheric icing severity: Quantification and mapping",2013,"10.1016/j.atmosres.2013.03.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876299436&doi=10.1016%2fj.atmosres.2013.03.005&partnerID=40&md5=f917753d194bee3d09c43c868e438c02","Atmospheric icing became a primary concern due to the significant impact and hazardous conditions of its accretion on structures. The objective of this study is to provide a map of icing events over 32. years (1979 to 2010) that describes the severity of winter icing. This information will prove useful to prevent damages and economical losses due to icing events by documenting the risk factor. To validate the icing climatology method, two case studies involving two topographically contrasting sites were selected: a simple terrain site which is the airport of Bagotville, near Saguenay (Canada) and a complex terrain site located in Mt Bélair, near Quebec City (Canada). Ice accumulation calculated by the use of reanalysis data was quantified using ice accretion on a cylinder model. Comparison between measurement and the model over Bagotville revealed insignificant differences in ice accumulation less than 0.3. mm, and in duration of icing events less than 0.2. day. On the other hand, during winter months, the calculation that showed a maximum of 60. mm in January 1999 over Mt Bélair site also had an underestimation of ice accumulation that varies from 5. mm to 16. mm. The horizontal resolution of NARR imposes a challenge on the calculation of icing events over complex terrains, especially during the months of November and March when air temperature is near freezing point. Taking into account the liquid water content, the duration of icing events and the classes of icing events as weighting factors, the icing severity index based on reanalysis data was introduced to assess the severity level of icing events, covering the north-east of Quebec including Quebec City, Sept-Iles, the east of Saguenay, the lower St Lawrence River and the Gaspe region. Consequently, an icing severity index mapping that represents the climatology of in-cloud atmospheric icing was produced. © 2013 Elsevier B.V."
"55334146100;6602164207;57191567671;","High latitude local scale temperature complexity: The example of Kevo Valley, Finnish Lapland",2013,"10.1002/joc.3573","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879247588&doi=10.1002%2fjoc.3573&partnerID=40&md5=509646eb9eb91ba56b12a4a200652ec5","Subarctic Scandinavia is expected to experience significant temperature increases over the next century. How this increase will influence local scale climate is largely unknown. This study examines local scale temperature variability in the subarctic where the unusual solar geometry means that the classic diurnal cycle of mid-latitudes has limited application. Near surface air temperature data were collected from a high density network of 60 temperature data loggers covering approximately 20 km2 in the valley system around Kevo Subarctic Research Station (69°45′N, 27°1′E). Temperature data was collected at 30 min intervals from September 2007 to March 2010, along with additional temperature and cloud cover data from the Kevo station. NCEP/NCAR reanalysis data was used to reconstruct synoptic conditions for the area at 6-h intervals. Lapse rates and regression of surface temperatures on free air temperatures are used to investigate local temperature variability. Median absolute yearly deviation analysis of the site temperatures was used to assess the representativeness of Kevo Station. The results show intense (up to + 80 °C km-1) and persistent inversion events during the winter months (NDJ) which are broken up by mechanical effects. In the transition from winter into spring (FMA) these inversions still occur but increasing radiation imposes a diurnal pattern on their formation and destruction. As snow cover peaks in spring the interaction between surface albedo, land cover and radiation serves to amplify the diurnal cycle in lapse rates. Summer lapse rates are modified by the presence of open water at low elevations. These results suggest that expected land cover and synoptic changes due to regional warming will act to decrease the frequency and intensity of inversion formation, steepening mean lapse rates and therefore increasing the relative amount of warming in valley floor locations. © 2012 Royal Meteorological Society."
"55628190300;7007010459;","Dynamic simulation of rainfall kinetic energy flux in a cloud resolving model",2013,"10.1002/grl.50622","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880533607&doi=10.1002%2fgrl.50622&partnerID=40&md5=57328a02b8df20cfd75c5311912c86d1","We present the first simulation of rainfall kinetic energy flux in a cloud resolving model. This demonstrates the potential for conducting erosion prediction studies using a regional climate model. Soil erosion is already a major global problem, and there is growing pressure on our land to deliver food and stability. Rainfall kinetic energy flux is an important variable in erosion prediction but is generally parameterized from intensity due to measurement difficulties. We show that a cloud resolving model can be used to dynamically simulate the kinetic energy of rain from basic physics, using four microphysics schemes. Results are within the range of observations and also capture the observed variability in kinetic energy for a given intensity. Large drops are shown to contribute disproportionately to total kinetic energy compared with their number, suggesting that several existing relations between terminal velocity and size of raindrops are poorly suited for kinetic energy modeling. Key Points Microphysics schemes can model rain kinetic energy flux close to observations This captures observed variability in kinetic energy, where current methods fail Large raindrops are more important for rain and kinetic energy than supposed ©2013. American Geophysical Union. All Rights Reserved."
"7006783796;12141789600;7006518279;8719703500;55747131500;8280879000;6506234624;7003475277;36842724800;55747560500;","Linear contrail and contrail cirrus properties determined from satellite data",2013,"10.1002/grl.50569","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880531513&doi=10.1002%2fgrl.50569&partnerID=40&md5=9e44f5e84abb79d9846ce59a25a364a2","The properties of contrail cirrus clouds are retrieved through analysis of Terra and Aqua Moderate Resolution Imaging Spectroradiometer data for 21 cases of spreading linear contrails. For these cases, contrail cirrus enhanced the linear contrail coverage by factors of 2.4-7.6 depending on the contrail mask sensitivity. In dense air traffic areas, linear contrail detection sensitivity is apparently reduced when older contrails overlap and thus is likely diminished during the afternoon. The mean optical depths and effective particle sizes of the contrail cirrus were 2-3 times and 20% greater, respectively, than the corresponding values retrieved for the adjacent linear contrails. When contrails form below, in, or above existing cirrus clouds, the column cloud optical depth is increased and particle size is decreased. Thus, even without increased cirrus coverage, contrails will affect the radiation balance. These results should be valuable for refining model characterizations of contrail cirrus needed to fully assess the climate impacts of contrails. Key Points Contrail cirrus and linear contrail properties are determined from satellite data Contrail cirrus optical depth and particle size exceed those for linear contrails Contrails increase thin cirrus optical depth and decrease cirrus particle size ©2013. American Geophysical Union. All Rights Reserved."
"7004657713;35502847300;6603458409;36914858100;23491895700;22940851800;7202972418;","All-sky downwelling longwave radiation and atmospheric-column water vapour and temperature over the Western Maritime Arctic",2013,"10.1080/07055900.2012.760441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879321307&doi=10.1080%2f07055900.2012.760441&partnerID=40&md5=da6273ccc158a46743438237899202b9","Measurements of downwelling longwave radiation and atmospheric-column variables (precipitable water, mean vapour pressure, and mean temperature) derived from microwave radiometric profiles were collected over a composite year at various locations in the Beaufort Sea-Amundsen Gulf region of the Canadian Arctic. Cloud cover was specified by a temporal fractional cloud cover derived from ceilometer measurements. A logarithmic relationship was found between downwelling longwave radiation and atmospheric-column water vapour expressed as precipitable water or mean vapour pressure. This relationship explained about 84% of the variance with a standard error of around 9%. Downwelling longwave radiation was not as well correlated with mean atmospheric temperature. The parameterization of downwelling longwave radiation as a function of atmospheric-column variables, which can be analyzed more accurately than surface variables in data sparse regions, may contribute to improved climate modelling of the western maritime Arctic region. It was shown that both the annual cycle of monthly median precipitable water and water vapour intrusions influenced the magnitude of downwelling longwave radiation, and the impact was enhanced by cloud cover."
"55519994900;23991212200;55411439700;","Robustness and sensitivities of central U.S. summer convection in the super-parameterized CAM: Multi-model intercomparison with a new regional EOF index",2013,"10.1002/grl.50597","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880549828&doi=10.1002%2fgrl.50597&partnerID=40&md5=0224148b803b7fd434913140c72f528d","Mesoscale convective systems (MCSs) can bring up to 60% of summer rainfall to the central United States but are not simulated by most global climate models. In this study, a new empirical orthogonal function based index is developed to isolate the MCS activity, similar to that developed by Wheeler and Hendon (2004) for the Madden-Julian Oscillation. The index is applied to compactly compare three conventional- and super-parameterized (SP) versions (3.0, 3.5, and 5.0) of the National Center for Atmospheric Research Community Atmosphere Model (CAM). Results show that nocturnal, eastward propagating convection is a robust effect of super-parameterization but is sensitive to its specific implementation. MCS composites based on the index show that in SP-CAM3.5, convective MCS anomalies are unrealistically large scale and concentrated, while surface precipitation is too weak. These aspects of the MCS signal are improved in the latest version (SP-CAM5.0), which uses high-order microphysics. Key Points A new EOF based index compactly evaluates the mid-latitude MCS signal in GCMs Central US summer MCS physics is a robust effect of cloud super-parameterization The MCS signal is most realistic in SP-CAM5.0 that uses high-order microphysics ©2013. American Geophysical Union. All Rights Reserved."
"7006041988;22978151200;37018824600;7201837768;6701333444;","Evaluation of aerosol-cloud interaction in the GISS ModelE using ARM observations",2013,"10.1002/jgrd.50460","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880907890&doi=10.1002%2fjgrd.50460&partnerID=40&md5=a725b4a1cb8e391ee127e23ca59926c6","Observations from the US Department of Energy's Atmospheric Radiation Measurement (ARM) program are used to evaluate the ability of the NASA GISS ModelE global climate model in reproducing observed interactions between aerosols and clouds. Included in the evaluation are comparisons of basic meteorology and aerosol properties, droplet activation, effective radius parameterizations, and surface-based evaluations of aerosol-cloud interactions (ACI). Differences between the simulated and observed ACI are generally large, but these differences may result partially from vertical distribution of aerosol in the model, rather than the representation of physical processes governing the interactions between aerosols and clouds. Compared to the current observations, the ModelE often features elevated droplet concentrations for a given aerosol concentration, indicating that the activation parameterizations used may be too aggressive. Additionally, parameterizations for effective radius commonly used in models were tested using ARM observations, and there was no clear superior parameterization for the cases reviewed here. This lack of consensus is demonstrated to result in potentially large, statistically significant differences to surface radiative budgets, should one parameterization be chosen over another. Key Points The GISS ModelE struggles to correctly simulate aerosol-cloud interactions Effective Radius parameterization has a significant impact on simulated climate Long-term atmospheric measurements help in evaluating model performance © 2013. American Geophysical Union. All Rights Reserved."
"54788178800;35550043200;7102001105;7202198678;6701525565;16643314500;24740735800;7402240717;7006165316;7404297096;","SMILES ice cloud products",2013,"10.1002/jgrd.50322","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880888147&doi=10.1002%2fjgrd.50322&partnerID=40&md5=9b239eda76514d68b5411e6b9bf52b0a","Upper tropospheric water vapor and clouds play an important role in Earth's climate, but knowledge of them, in particular diurnal variation in deep convective clouds, is limited. An essential variable to understand them is cloud ice water content. The Japanese Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on board the International Space Station (ISS) samples the atmosphere at different local times allowing the study of diurnal variability of atmospheric parameters. We describe a new ice cloud data set consisting of partial Ice Water Path and Ice Water Content. Preliminary comparisons with EOS-MLS, CloudSat-CPR and CALIOP-CALIPSO are presented. Then, the diurnal variation over land and over open ocean for partial ice water path is reported. Over land, a pronounced diurnal variation peaking strongly in the afternoon/early evening was found. Over the open ocean, little temporal dependence was encountered. This data set is publicly available for download in HDF5 format. Key Points Clouds play an important role in Earth's climate SMILES samples the atmosphere at different local times We present IWC and pIWP derived from SMILES © 2013. American Geophysical Union. All Rights Reserved."
"36899513900;55713076400;22635190100;7003597952;","The response of coastal stratocumulus clouds to agricultural irrigation in California",2013,"10.1002/jgrd.50516","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880861238&doi=10.1002%2fjgrd.50516&partnerID=40&md5=3e2a6c5ae5c4121e86107d046617d222","Stratocumulus clouds (SC) often exist over the eastern subtropical oceans during the summer and have significant impacts on the surface radiation budget. Both atmospheric subsidence and lower troposphere stability (LTS) have been found to play important roles in maintaining SC. Using global climate model simulations, we find that irrigation in California's Central Valley results in a decrease of land surface temperature, leading to a smaller land-sea heat contrast, and a corresponding reduction in sea breeze, subsidence, and LTS over the near-coastal region. The decrease in LTS directly drives a reduction in modeled SC coverage, and it would arguably do so in reality because of the well-known link between LTS and SC coverage. Consequently, simulated absorbed surface solar radiation over this region increases by 8 W/m2 (3.7%) due to the reduction in SC cover, resulting in the warming at the Earth's surface. This study has important implications for how SC can change with regard to future climate. In contrast to the general effects of climate change on the formation of SC, our results suggest that irrigation practices in the Central Valley may drive a decrease in nearby SC coverage. Key Points Irrigation causes land temperature decrease and smaller land-sea heat contrast. Absorbed surface solar radiation nearby California increased by 7.8 W/m2. It suggests that SC occurrences may decrease due to California irrigation. © 2013. American Geophysical Union. All Rights Reserved."
"55389942900;6701815637;","A novel diagnostic technique to investigate cloud-controlling factors",2013,"10.1002/jgrd.50511","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880870884&doi=10.1002%2fjgrd.50511&partnerID=40&md5=f4eef641c19af0c3223da44b29b5f9e9","Cloud properties depend on the local meteorological conditions. This relation is quantified using a simple framework which expands on previous methodologies. This novel diagnostic technique is applied in order to understand and assess the relative contribution of various environmental factors to the observed interannual and seasonal variations in cloud properties. In this analysis framework, sea surface temperature, sea level pressure, and, to a lesser extent, the humidity field are the largest contributors to the interannual cloud anomalies in the equatorial Pacific. In addition, in contrast to previous studies, we find that the interannual variability of the ratio of shortwave to longwave cloud radiative effect (N) is independent of the tropopause temperature. Finally, we quantify the role of different factors which are thought to influence the seasonal cycle of the stratocumulus in the subtropics. Off the California coast, the lower tropospheric stability (LTS) better describes the seasonal low-cloud amount changes than the estimated inversion strength (EIS). When the spatial variation in LTS (or EIS) and low-cloud amount is considered within a season, a different relationship is found that depends on the season. The nonlinear relationships between environmental factors and cloud properties can, to a certain extent, be described within the novel framework proposed. Key Points Novel diagnostic technique to analyse cloud-controlling factors and model bias Ratio of SW to LW CRE (N) is independent of tropopause temperature LTS (or EIS) and low-cloud amount relationships changes according to the season © 2013. American Geophysical Union. All Rights Reserved."
"8877858700;7404240633;7006744538;7006577693;55806795100;13402835300;","Evaluation of clouds in ACCESS using the satellite simulator package COSP: Regime-sorted tropical cloud properties",2013,"10.1002/jgrd.50496","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880878375&doi=10.1002%2fjgrd.50496&partnerID=40&md5=61f2b9a5eb9b2e4919f1e4cdd46e96ed","This study uses a regime sorting technique to explore the relationships that ACCESS1.3 clouds have with the large-scale environment. Satellite simulator output is used to demonstrate that the modeled clouds have similar sensitivity to the large-scale dynamic and thermodynamic conditions as shown by CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The high cloud cover and longwave cloud radiative effect is represented very well in the model across all regimes. The cloud types that the model simulates the most poorly are stratocumulus over cool sea surface temperatures (SSTs) and the deep convective regimes associated with strong upward midtropospheric vertical velocity and weak lower tropospheric stabilities. The reflectance of the deep convective regimes shows a stronger sensitivity to SST and less dependence on the large-scale dynamics than the observations. Many of the model errors identified occur across all regimes, such as the underestimate of clouds with large scattering ratios (SR) and the too frequent occurrence of drizzle and rain. A sensitivity test in which a different warm rain scheme was used shows that the modelled frequency of occurrence of nonprecipitating low cloud is quite sensitive to the autoconversion parameterization. The new scheme produced more cloud with large SR and higher cloud tops in better agreement with the observations. The thermodynamic regime analysis shows that the transition of shallow to deeper convection in the model requires a warmer SST and weaker LTS than the observations. The significant underestimate of cumulus congestus is likely to contribute to this delay due to the role these clouds have in preconditioning the midtroposphere for the onset of deep convection. Key Points High cloud cover and longwave cloud forcing is represented well across regimes Non-precipitating cloud and cloud top heights are sensitive to autoconversion Modeled transition from shallow to deeper convection requires warmer SST © 2013. American Geophysical Union. All Rights Reserved."
"7003666669;57193073844;56162305900;56384704800;8942524900;7004469744;13405658600;22978151200;57211106013;","A simple model of global aerosol indirect effects",2013,"10.1002/jgrd.50567","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880882329&doi=10.1002%2fjgrd.50567&partnerID=40&md5=44498e396d270ae107db9718920e930f","Most estimates of the global mean indirect effect of anthropogenic aerosol on the Earth's energy balance are from simulations by global models of the aerosol lifecycle coupled with global models of clouds and the hydrologic cycle. Extremely simple models have been developed for integrated assessment models, but lack the flexibility to distinguish between primary and secondary sources of aerosol. Here a simple but more physically based model expresses the aerosol indirect effect (AIE) using analytic representations of cloud and aerosol distributions and processes. Although the simple model is able to produce estimates of AIEs that are comparable to those from some global aerosol models using the same global mean aerosol properties, the estimates by the simple model are sensitive to preindustrial cloud condensation nuclei concentration, preindustrial accumulation mode radius, width of the accumulation mode, size of primary particles, cloud thickness, primary and secondary anthropogenic emissions, the fraction of the secondary anthropogenic emissions that accumulates on the coarse mode, the fraction of the secondary mass that forms new particles, and the sensitivity of liquid water path to droplet number concentration. Estimates of present-day AIEs as low as -5 W m-2 and as high as -0.3 W m-2 are obtained for plausible sets of parameter values. Estimates are surprisingly linear in emissions. The estimates depend on parameter values in ways that are consistent with results from detailed global aerosol-climate simulation models, which adds to understanding of the dependence on AIE uncertainty on uncertainty in parameter values. Key Points A simple physically-based model represents aerosol indirect effects The model estimates depend on parameters in ways like detailed global models The aerosol indirect effect is surprisingly linear in emissions © 2013. American Geophysical Union. All Rights Reserved."
"55746931700;7006698304;57204958234;57193132723;24764483400;8614138600;35435487400;35169960300;7005920812;25823927100;55717074000;55202282600;7003582587;7005446873;55469523400;57208626554;16246205000;7501760109;55806956100;7403174207;7401936984;55738957800;","A single-column model ensemble approach applied to the TWP-ICE experiment",2013,"10.1002/jgrd.50450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880871616&doi=10.1002%2fjgrd.50450&partnerID=40&md5=8d344e011a11a44af3a8394c76c8467d","Single-column models (SCM) are useful test beds for investigating the parameterization schemes of numerical weather prediction and climate models. The usefulness of SCM simulations are limited, however, by the accuracy of the best estimate large-scale observations prescribed. Errors estimating the observations will result in uncertainty in modeled simulations. One method to address the modeled uncertainty is to simulate an ensemble where the ensemble members span observational uncertainty. This study first derives an ensemble of large-scale data for the Tropical Warm Pool International Cloud Experiment (TWP-ICE) based on an estimate of a possible source of error in the best estimate product. These data are then used to carry out simulations with 11 SCM and two cloud-resolving models (CRM). Best estimate simulations are also performed. All models show that moisture-related variables are close to observations and there are limited differences between the best estimate and ensemble mean values. The models, however, show different sensitivities to changes in the forcing particularly when weakly forced. The ensemble simulations highlight important differences in the surface evaporation term of the moisture budget between the SCM and CRM. Differences are also apparent between the models in the ensemble mean vertical structure of cloud variables, while for each model, cloud properties are relatively insensitive to forcing. The ensemble is further used to investigate cloud variables and precipitation and identifies differences between CRM and SCM particularly for relationships involving ice. This study highlights the additional analysis that can be performed using ensemble simulations and hence enables a more complete model investigation compared to using the more traditional single best estimate simulation only. Key Points An ensemble of large-scale atmospheric states is derived for TWP-ICE. Single Column Models and Cloud-Resolving Models successfully simulate ensemble. Comparison with best estimate simulations further elucidate model behavior. © 2013. American Geophysical Union. All Rights Reserved."
"36054921000;7102567936;7005702722;","Cloud-resolving simulation of TOGA-COARE using parameterized large-scale dynamics",2013,"10.1002/jgrd.50510","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880872061&doi=10.1002%2fjgrd.50510&partnerID=40&md5=2e3ab90a963bc796385f40c60028ee0b","Variations in deep convective activity during the 4 month Tropical Ocean Global Atmosphere-Coupled Ocean Atmosphere Response Experiment (TOGA-COARE) field campaign are simulated using a cloud-resolving model (CRM). Convection in the model is coupled to large-scale vertical velocities that are parameterized using one of two different methods: the damped gravity wave (Damped-wave) method and the weak temperature gradient (WTG) method. The reference temperature profiles against which temperature anomalies are computed are taken either from observations or from a model integration with no large-scale vertical motion (but other forcings taken from observations); the parameterized large-scale vertical velocities are coupled to those temperature (or virtual temperature) anomalies. Sea surface temperature, radiative fluxes, and relaxation of the horizontal mean horizontal wind field are also imposed. Simulations with large-scale vertical velocity imposed from the observations are performed for reference. The primary finding is that the CRM with parameterized large-scale vertical motion can capture the intraseasonal variations in rainfall to some degree. Experiments in which one of several observation-derived forcings is set to its time-mean value suggest that those which influence direct forcings on the moist static energy budget - surface wind speed and sea surface temperature (which together influence surface evaporation) and radiative cooling - play the most important roles in controlling convection, particularly when the Damped-wave method is used. The parameterized large-scale vertical velocity has a vertical profile that is too bottom-heavy compared to observations when the Damped-wave method is used with vertically uniform Rayleigh damping on horizontal wind, but is too top-heavy when the WTG method is used. Key Points CRM with parameterized large-scale W captures part of intraseasonal variations Both surface turbulent fluxes and radiative cooling control convection Parameterized W is too top-heavy with WTG and too bottom-heavy with Damped-wave © 2013. American Geophysical Union. All Rights Reserved."
"57151771800;7401776640;7102953444;","Evaluation of multidecadal variability in CMIP5 surface solar radiation and inferred underestimation of aerosol direct effects over Europe, China, Japan, and India",2013,"10.1002/jgrd.50426","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880896083&doi=10.1002%2fjgrd.50426&partnerID=40&md5=765c056bfd5e617ec3cadeed8c430318","Observations from the Global Energy Balance Archive indicate regional decreases in all sky surface solar radiation from ∼1950s to 1980s, followed by an increase during the 1990s. These periods are popularly called dimming and brightening, respectively. Removal of the radiative effects of cloud cover variability from all sky surface solar radiation results in a quantity called ""clear sky proxy"" radiation, in which multidecadal trends can be seen more distinctly, suggesting aerosol radiative forcing as a likely cause. Prior work has shown climate models from the Coupled Model Intercomparison Project 3 (CMIP3) generally underestimate the magnitude of these trends, particularly over China and India. Here we perform a similar analysis with 173 simulations from 42 climate models participating in the new CMIP5. Results show negligible improvement over CMIP3, as CMIP5 dimming trends over four regions - Europe, China, India, and Japan - are all underestimated. This bias is largest for both India and China, where the multimodel mean yields a decrease in clear sky proxy radiation of -1.3±0.3 and -1.2±0.2 W m-2decade -1, respectively, compared to observed decreases of -6.5±0.9 and -8.2±1.3 W m-2decade-1. Similar underestimation of the observed dimming over Japan exists, with the CMIP5 mean dimming ∼20% as large as observed. Moreover, not a single simulation reproduces the magnitude of the observed dimming trend for these three regions. Relative to dimming, CMIP5 models better simulate the observed brightening, but significant underestimation exists for both China and Japan. Overall, no individual model performs particularly well for all four regions. Model biases do not appear to be related to the use of prescribed versus prognostic aerosols or to aerosol indirect effects. However, models exhibit significant correlations between clear sky proxy radiation and several aerosol-related fields, most notably aerosol optical depth (AOD) and absorption AOD. This suggests model underestimation of the observed trends is related to underestimation of aerosol direct radiative forcing and/or deficient aerosol emission inventories. Key Points CMIP5 models underestimate the magnitude of observed dimming and brightening Models exhibit correlations between solar radiation and several aerosol fields Underestimation is related to aerosol direct forcing and/or emissions © 2013. American Geophysical Union. All Rights Reserved."
"6603860837;7408612236;7003553324;6701366594;40661020000;7102432430;35095461100;6602865544;40661753400;","CDRD and PNPR satellite passive microwave precipitation retrieval algorithms: EuroTRMM/EURAINSAT origins and H-SAF operations",2013,"10.5194/nhess-13-887-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879243235&doi=10.5194%2fnhess-13-887-2013&partnerID=40&md5=41018b0552d0a2506c8f10db597c97e7","Satellite Application Facility on Support to Operational Hydrology and Water Management (H-SAF) is a EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites) program, designed to deliver satellite products of hydrological interest (precipitation, soil moisture and snow parameters) over the European and Mediterranean region to research and operations users worldwide. Six satellite precipitation algorithms and concomitant precipitation products are the responsibility of various agencies in Italy. Two of these algorithms have been designed for maximum accuracy by restricting their inputs to measurements from conical and cross-track scanning passive microwave (PMW) radiometers mounted on various low Earth orbiting satellites. They have been developed at the Italian National Research Council/Institute of Atmospheric Sciences and Climate in Rome (CNR/ISAC-Rome), and are providing operational retrievals of surface rain rate and its phase properties. Each of these algorithms is physically based, however, the first of these, referred to as the Cloud Dynamics and Radiation Database (CDRD) algorithm, uses a Bayesian-based solution solver, while the second, referred to as the PMW Neural-net Precipitation Retrieval (PNPR) algorithm, uses a neural network-based solution solver. Herein we first provide an overview of the two initial EU research and applications programs that motivated their initial development, EuroTRMM and EURAINSAT (European Satellite Rainfall Analysis and Monitoring at the Geostationary Scale), and the current H-SAF program that provides the framework for their operational use and continued development. We stress the relevance of the CDRD and PNPR algorithms and their precipitation products in helping secure the goals of H-SAF's scientific and operations agenda, the former helpful as a secondary calibration reference to other algorithms in H-SAF's complete mix of algorithms. Descriptions of the algorithms' designs are provided including a few examples of their performance. This aspect of the development of the two algorithms is placed in the context of what we refer to as the TRMM era, which is the era denoting the active and ongoing period of the Tropical Rainfall Measuring Mission (TRMM) that helped inspire their original development. In 2015, the ISAC-Rome precipitation algorithms will undergo a transformation beginning with the upcoming Global Precipitation Measurement (GPM) mission, particularly the GPM Core Satellite technologies. A few years afterward, the first pair of imaging and sounding Meteosat Third Generation (MTG) satellites will be launched, providing additional technological advances. Various of the opportunities presented by the GPM Core and MTG satellites for improving the current CDRD and PNPR precipitation retrieval algorithms, as well as extending their product capability, are discussed. © 2013 Author(s)."
"6603746516;57199894357;","Derivation of RCM-driven potential evapotranspiration for hydrological climate change impact analysis in Great Britain: A comparison of methods and associated uncertainty in future projections",2013,"10.5194/hess-17-1365-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879120636&doi=10.5194%2fhess-17-1365-2013&partnerID=40&md5=10c3539ef7c8a5f0d5d5d5988f258e1b","Potential evapotranspiration (PET) is the water that would be lost by plants through evaporation and transpiration if water was not limited in the soil, and it is commonly used in conceptual hydrological modelling in the calculation of runoff production and hence river discharge. Future changes of PET are likely to be as important as changes in precipitation patterns in determining changes in river flows. However PET is not calculated routinely by climate models so it must be derived independently when the impact of climate change on river flow is to be assessed. This paper compares PET estimates from 12 equations of different complexity, driven by the Hadley Centre's HadRM3-Q0 model outputs representative of 1961-1990, with MORECS PET, a product used as reference PET in Great Britain. The results show that the FAO56 version of the Penman-Monteith equations reproduces best the spatial and seasonal variability of MORECS PET across GB when driven by HadRM3-Q0 estimates of relative humidity, total cloud, wind speed and linearly bias-corrected mean surface temperature. This suggests that potential biases in HadRM3-Q0 climate do not result in significant biases when the physically based FAO56 equations are used. Percentage changes in PET between the 1961-1990 and 2041-2070 time slices were also calculated for each of the 12 PET equations from HadRM3-Q0. Results show a large variation in the magnitude (and sometimes direction) of changes estimated from different PET equations, with Turc, Jensen-Haise and calibrated Blaney-Criddle methods systematically projecting the largest increases across GB for all months and Priestley-Taylor, Makkink, and Thornthwaite showing the smallest changes. We recommend the use of the FAO56 equation as, when driven by HadRM3-Q0 climate data, this best reproduces the reference MORECS PET across Great Britain for the reference period of 1961-1990. Further, the future changes of PET estimated by FAO56 are within the range of uncertainty defined by the ensemble of 12 PET equations. The changes show a clear northwest-southeast gradient of PET increase with largest (smallest) changes in the northwest in January (July and October) respectively. However, the range in magnitude of PET changes due to the choice of PET method shown in this study for Great Britain suggests that PET uncertainty is a challenge facing the assessment of climate change impact on hydrology mostly ignored up to now. © 2013 Author(s)."
"22953153500;56640963500;10144486700;24458137900;","Estimating bacteria emissions from inversion of atmospheric transport: Sensitivity to modelled particle characteristics",2013,"10.5194/acp-13-5473-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879021331&doi=10.5194%2facp-13-5473-2013&partnerID=40&md5=db55969ed3018a8163096dcdd5271c71","Model-simulated transport of atmospheric trace components can be combined with observed concentrations to obtain estimates of ground-based sources using various inversion techniques. These approaches have been applied in the past primarily to obtain source estimates for long-lived trace gases such as CO2. We consider the application of similar techniques to source estimation for atmospheric aerosols, using as a case study the estimation of bacteria emissions from different ecosystem regions in the global atmospheric chemistry and climate model ECHAM5/MESSy-Atmospheric Chemistry (EMAC). <br><br> Source estimation via Markov Chain Monte Carlo is applied to a suite of sensitivity simulations, and the global mean emissions are estimated for the example problem of bacteria-containing aerosol particles. We present an analysis of the uncertainties in the global mean emissions, and a partitioning of the uncertainties that are attributable to particle size, activity as cloud condensation nuclei (CCN), the ice nucleation scavenging ratios for mixed-phase and cold clouds, and measurement error. <br><br> For this example, uncertainty due to CCN activity or to a 1 &mu;m error in particle size is typically between 10% and 40% of the uncertainty due to observation uncertainty, as measured by the 5-95th percentile range of the Monte Carlo ensemble. Uncertainty attributable to the ice nucleation scavenging ratio in mixed-phase clouds is as high as 10-20% of that attributable to observation uncertainty. Taken together, the four model parameters examined contribute about half as much to the uncertainty in the estimated emissions as do the observations. This was a surprisingly large contribution from model uncertainty in light of the substantial observation uncertainty, which ranges from 81-870% of the mean for each of ten ecosystems for this case study. The effects of these and other model parameters in contributing to the uncertainties in the transport of atmospheric aerosol particles should be treated explicitly and systematically in both forward and inverse modelling studies. © 2013 Author(s)."
"7202208382;6701835010;56162305900;7003666669;7102239370;25031430500;57199181531;","A community atmosphere model with superparameterized clouds",2013,"10.1002/2013EO250001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911878461&doi=10.1002%2f2013EO250001&partnerID=40&md5=5b62c9f293cac7e9e48c65d59705f2f9",[No abstract available]
"25031430500;57200319057;","The climate impact of aviation aerosols",2013,"10.1002/grl.50520","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879961526&doi=10.1002%2fgrl.50520&partnerID=40&md5=84c9588c2b10d531d22a3480f35574fa","A comprehensive general circulation model (GCM) is used to estimate the climate impact of aviation emissions of black carbon (BC) and sulfate (SO 4) aerosols. Aviation BC is found not to exert significant radiative forcing impacts, when BC nucleating efficiencies in line with observations are used. Sulfate emissions from aircraft are found to alter liquid clouds at altitudes below emission (∼200 hPa); contributing to shortwave cloud brightening through enhanced liquid water path and drop number concentration in major flight corridors, particularly in the N. Atlantic. Global averaged sulfate direct and indirect effects on liquid clouds of 46 mWm-2are larger than the warming effect of aviation induced cloudiness of 16 mWm-2. The net result of including contrail cirrus and aerosol effects is a global averaged cooling of -21 ± 11 mWm-2. These aerosol forcings should be considered with contrails in evaluating the total global impact of aviation on climate. ©2013 American Geophysical Union. All Rights Reserved."
"57200702127;8511991900;7404865816;7202048112;8877858700;","Improving bulk microphysics parameterizations in simulations of aerosol effects",2013,"10.1002/jgrd.50432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880304412&doi=10.1002%2fjgrd.50432&partnerID=40&md5=8fc1e9d3b39a15227ef1edc10e845e2d","To improve the microphysical parameterizations for simulations of the aerosol effects in regional and global climate models, the Morrison double-moment bulk microphysical scheme presently implemented in the Weather Research and Forecasting model is modified by replacing the prescribed aerosols in the original bulk scheme (Bulk-OR) with a prognostic double-moment aerosol representation to predict both aerosol number concentration and mass mixing ratio (Bulk-2M). Sensitivity modeling experiments are performed for two distinct cloud regimes: maritime warm stratocumulus clouds (Sc) over southeast Pacific Ocean from the VOCALS project and continental deep convective clouds in the southeast of China. The results from Bulk-OR and Bulk-2M are compared against atmospheric observations and simulations produced by a spectral bin microphysical scheme (SBM). The prescribed aerosol approach (Bulk-OR) produces unreliable aerosol and cloud properties throughout the simulation period, when compared to the results from those using Bulk-2M and SBM, although all of the model simulations are initiated by the same initial aerosol concentration on the basis of the field observations. The impacts of the parameterizations of diffusional growth and autoconversion of cloud droplets and the selection of the embryonic raindrop radius on the performance of the bulk microphysical scheme are also evaluated by comparing the results from the modified Bulk-2M with those from SBM simulations. Sensitivity experiments using four different types of autoconversion schemes reveal that the autoconversion parameterization is crucial in determining the raindrop number, mass concentration, and drizzle formation for warm stratocumulus clouds. An embryonic raindrop size of 40 μm is determined as a more realistic setting in the autoconversion parameterization. The saturation adjustment employed in calculating condensation/evaporation in the bulk scheme is identified as the main factor responsible for the large discrepancies in predicting cloud water in the Sc case, suggesting that an explicit calculation of diffusion growth with predicted supersaturation is necessary to improve the bulk microphysics scheme. Lastly, a larger rain evaporation rate below clouds is found in the bulk scheme in comparison to the SBM simulation, which may contribute to a lower surface precipitation in the bulk scheme. © 2013. American Geophysical Union. All Rights Reserved."
"7005809959;7005007661;7006212411;35547807400;6603749963;8767874100;8570871900;7003666669;26643250500;56249704400;56270311300;26643054400;7202429440;57194234454;7202779585;57205638870;7005129538;55796506900;56939401900;10139397300;56920788800;36047973900;55113736500;57219113417;42662973900;57203053317;24477694300;7004214645;13403622000;7401491382;6603400519;","Bounding the role of black carbon in the climate system: A scientific assessment",2013,"10.1002/jgrd.50171","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875359259&doi=10.1002%2fjgrd.50171&partnerID=40&md5=8cc9f6b598e2dff051c409563781337f","Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr-1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m-2 with 90% uncertainty bounds of (+0.08, +1.27) W m-2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m-2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m-2 with 90% uncertainty bounds of +0.17 to +2.1 W m-2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m-2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (-0.50 to +1.08) W m-2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (-0.06 W m-2 with 90% uncertainty bounds of -1.45 to +1.29 W m-2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates. ©2013 The Authors. Journal of Geophysical Research: Atmospheres published by Wiley on behalf of the American Geophysical Union."
"36720934300;15026371500;55544443300;","Anthropogenic sulfate aerosol and the southward shift of tropical precipitation in the late 20th century",2013,"10.1002/grl.50502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879911980&doi=10.1002%2fgrl.50502&partnerID=40&md5=86d46fe5aa9f15a1ce3b270e2105a1b0","In this paper, we demonstrate a global scale southward shift of the tropical rain belt during the latter half of the 20th century in observations and global climate models (GCMs). In rain gauge data, the southward shift maximizes in the 1980s and is associated with signals in Africa, Asia, and South America. A southward shift exists at a similar time in nearly all CMIP3 and CMIP5 historical simulations, and occurs on both land and ocean, although in most models the shifts are significantly less than in observations. Utilizing a theoretical framework based on atmospheric energetics, we perform an attribution of the zonal mean southward shift of precipitation across a large suite of CMIP3 and CMIP5 GCMs. Our results suggest that anthropogenic aerosol cooling of the Northern Hemisphere is the primary cause of the consistent southward shift across GCMs, although other processes affecting the atmospheric energy budget also contribute to the model-to-model spread. © 2013 American Geophysical Union. All Rights Reserved."
"7004643405;7202958190;7003390361;7201432984;7005284577;57126848900;57200319386;6603872903;7004176333;7005206572;7003729315;7402919163;7006572336;7403063262;7005891596;7103289129;7004166136;57203776263;7006664349;35109521000;7004008609;7103333752;6701378450;7006086673;7102736773;35109656700;7201483081;7005773698;7202429440;57196499374;6603547710;16308514000;7004664603;6603497236;22949331500;57206166579;7403996091;7006103811;","The 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study",2013,"10.1002/jgrd.50331","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875876234&doi=10.1002%2fjgrd.50331&partnerID=40&md5=b25361e19a83959725ef3bff89a1c0bf","The California Research at the Nexus of Air Quality and Climate Change (CalNex) field study was conducted throughout California in May, June, and July of 2010. The study was organized to address issues simultaneously relevant to atmospheric pollution and climate change, including (1) emission inventory assessment, (2) atmospheric transport and dispersion, (3) atmospheric chemical processing, and (4) cloud-aerosol interactions and aerosol radiative effects. Measurements from networks of ground sites, a research ship, tall towers, balloon-borne ozonesondes, multiple aircraft, and satellites provided in situ and remotely sensed data on trace pollutant and greenhouse gas concentrations, aerosol chemical composition and microphysical properties, cloud microphysics, and meteorological parameters. This overview report provides operational information for the variety of sites, platforms, and measurements, their joint deployment strategy, and summarizes findings that have resulted from the collaborative analyses of the CalNex field study. Climate-relevant findings from CalNex include that leakage from natural gas infrastructure may account for the excess of observed methane over emission estimates in Los Angeles. Air-quality relevant findings include the following: mobile fleet VOC significantly declines, and NO<inf>x</inf> emissions continue to have an impact on ozone in the Los Angeles basin; the relative contributions of diesel and gasoline emission to secondary organic aerosol are not fully understood; and nighttime NO<inf>3</inf> chemistry contributes significantly to secondary organic aerosol mass in the San Joaquin Valley. Findings simultaneously relevant to climate and air quality include the following: marine vessel emissions changes due to fuel sulfur and speed controls result in a net warming effect but have substantial positive impacts on local air quality. © 2013. American Geophysical Union. All Rights Reserved."
"23092821200;7401501923;7801682328;","Intersatellite calibration of NOAA HIRS CO2 channels for climate studies",2013,"10.1002/jgrd.50447","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880252514&doi=10.1002%2fjgrd.50447&partnerID=40&md5=deddf69b1a96a5584f04c27ed982fa93","The 30 years of observations from the High-Resolution Infrared Radiation Sounder (HIRS) longwave CO2 channels aboard the NOAA series of satellites are being used to detect climatological changes of cloud. However, the intersatellite radiance discrepancies in the channels need to be removed for the development of a consistent cloud series using HIRS data. By analyzing the intersatellite radiance comparisons at simultaneous-nadir-overpass locations for HIRS longwave CO2 channels onboard the NOAA and MetOp series of satellites, this study optimizes the spectral response functions (SRF) for each HIRS to generate a more consistent long-term set of observations. Intersatellite radiance biases as large as 5% are found for these channels; the spectral differences and spectral uncertainties are shown to be the main causes. To estimate the radiance change for a specific channel due to SRF difference and uncertainty, a linear model is developed to correlate the radiance change for the channel being analyzed with the spectral radiances in the eight selected HIRS channels. The hyperspectral measurements from the Infrared Atmospheric Sounding Interferometer on the MetOp satellite are used to simulate HIRS observations and estimate the parameters of the linear models. The linear models are applied to the NOAA and MetOp HIRS data at simultaneous-nadir-overpass locations to estimate the intersatellite radiance differences due to the SRF differences and uncertainties. The intersatellite mean radiance biases are minimized toward zero with residual maximum uncertainty less than 1% after the SRF differences and uncertainties are mitigated. Using the MetOp Infrared Atmospheric Sounding Interferometer as a reference, the optimized SRFs for every NOAA HIRS are found by effectively minimizing the root-mean-square values of the intersatellite radiance differences. The optimized shifts of the SRF can be as large as 3 cm-1.© 2013. American Geophysical Union. All Rights Reserved."
"36871608300;6506539438;","The importance of the tropical tropopause layer for equatorial Kelvin wave propagation",2013,"10.1002/jgrd.50418","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880251845&doi=10.1002%2fjgrd.50418&partnerID=40&md5=8e61dd50d1723b8a68aee47046b5ab00","We analyze the propagation of equatorial Kelvin waves from the troposphere to the stratosphere using a new filtering technique applied to ERA-Interim data (very similar results for Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) temperatures) that allows separation of wave activity into number of waves and wave amplitude. The phase speed of Kelvin waves (order 20 m/s) is similar to the magnitude of zonal wind in the tropical tropopause layer (TTL), and correspondingly, we find that the seasonal and interannual variability of Kelvin wave propagation is dominated by the variability in the wind field and less by tropospheric convectively coupled wave activity. We show that local relations between wave activity and zonal wind are ambiguous, and only full ray tracing calculations can explain the observed patterns of wave activity. Easterlies amplify and deflect the eastward traveling waves upward. Westerlies have the opposite effect. During boreal winter, the strong dipole of zonal winds in the TTL centered at the dateline confines wave propagation into the stratosphere to a window over the Atlantic-Indian Ocean sector (30°W to 90°E), which casts a lasting ""shadow"" into the lower stratosphere that explains the remarkable zonal asymmetry in wave activity there. During boreal summer, the upper level monsoon circulation leads to maximum easterlies, and wave amplitude (but not number of waves) maximizes over the Indian Ocean sector (30°E to 90°E). Interannual variability in wave propagation due to El-Niño/Southern Oscillation, for example, is well explained by its modification of the zonal wind field. © 2013. American Geophysical Union. All Rights Reserved."
"36880439600;7006525719;7102194844;","Retrieving cirrus microphysical properties from stellar aureoles",2013,"10.1002/jgrd.50440","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880300677&doi=10.1002%2fjgrd.50440&partnerID=40&md5=43db8a37be4764beb8be62082a87698b","The aureoles around stars caused by thin cirrus limit nighttime measurement opportunities for ground-based astronomy, but can provide information on high-altitude ice crystals for climate research. In this paper we attempt to demonstrate quantitatively how this works. Aureole profiles can be followed out to ∼0.2°from stars and ∼0.5°from Jupiter. Interpretation of diffracted starlight is similar to that for sunlight, but emphasizes larger particles. Stellar diffraction profiles are very distinctive, typically being approximately flat out to a critical angle followed by gradually steepening power-law falloff with slope less steep than -3. Using the relationship between the phase function for diffraction and the average Fourier transform of the projected area of complex ice crystals, we show that defining particle size in terms of average projected area normal to the propagation direction of the starlight leads to a simple, analytic approximation representing large-particle diffraction that is nearly independent of crystal habit. A similar analytic approximation for the diffraction aureole allows it to be separated from the point spread function and the sky background. Multiple scattering is deconvolved using the Hankel transform leading to the diffraction phase function. Application of constrained numerical inversion to the phase function then yields a solution for the particle size distribution in the range between ∼50 μm and ∼400 μm. Stellar aureole measurements can provide one of the very few, as well as least expensive, methods for retrieving cirrus microphysical properties from ground-based observations. © 2013. American Geophysical Union. All Rights Reserved."
"36573345200;6603007049;","Palaeoglacial and palaeoclimatic conditions in the NW Pacific, as revealed by a morphometric analysis of cirques upon the Kamchatka Peninsula",2013,"10.1016/j.geomorph.2013.03.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876968824&doi=10.1016%2fj.geomorph.2013.03.011&partnerID=40&md5=30a45fa1aaec7a319a1824965451e6e6","The distribution of glacial cirques upon the Kamchatka peninsula, Far Eastern Russia, is systematically mapped from satellite images and digital elevation model data. A total of 3758 cirques are identified, 238 of which are occupied by active glaciers. The morphometry of the remaining 3520 cirques is analysed. These cirques are found to show a very strong N bias in their azimuth (orientation), likely resulting from aspect-related variations in insolation. The strength of this N bias is considered to indicate that former glaciation upon the peninsula was often 'marginal', and mainly of cirque-type, with peaks extending little above regional equilibrium-line altitudes. This is supported by the fact that S and SE-facing cirques are the highest in the dataset, suggesting that glacier-cover was rarely sufficient to allow S and SE-facing glaciers to develop at low altitudes. The strength of these azimuth-related variations in cirque altitude is thought to reflect comparatively cloud-free conditions during former periods of glaciation. It is suggested that these characteristics, of marginal glaciation and comparatively cloud-free conditions, reflect the region's former aridity, which was likely intensified at the global Last Glacial Maximum, and during earlier periods of ice advance, as a result of the development of negative pressure anomalies over the North Pacific (driven by the growth of the Laurentide Ice Sheet), combined with other factors, including an increase in the extent and duration of sea ice, a reduction in global sea levels, cooler sea surface temperatures, and the localised growth of mountain glaciers. There is published evidence to suggest extensive glaciation of the Kamchatka Peninsula at times during the Late Quaternary, yet the data presented here appear to suggest that such phases were comparatively short-lived, and that smaller cirque-type glaciers were generally more characteristic of the period. © 2013 Elsevier B.V."
"55750595000;55749603200;55749524300;","Defending the forest in the clouds: Public interest law in Solomon Islands",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878269536&partnerID=40&md5=ac396128b616e5fb602abebfc5565f3d","Solomon Islands' forests have high levels of biodiversity and are an important component of the country's culture and custom. The forests are under threat due to decades of unsustainable logging. Under Solomon Islands' law, logging companies need approval from the government and the customary landowners before commencing logging. This case note summarises two cases in the Solomon Islands High Court brought by an association of landowners to protect the 'cloud forest' of Kolombangara Island. In the first case, the High Court held that the association had standing to seek an injunction to prevent a company from logging without obtaining the necessary government approvals. The second case, which has not yet been finally determined by the Court, challenges the legality of the approvals subsequently granted by the government. These cases potentially pave the way for further public interest environmental litigation in Solomon Islands. © Australian Centre for Climate and Environmental Law 2013."
"7004479957;8882641700;57203288317;","Mechanisms of marine low cloud sensitivity to idealized climate perturbations: A single-LES exploration extending the CGILS cases",2013,"10.1002/jame.20019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880790152&doi=10.1002%2fjame.20019&partnerID=40&md5=0a0a7afaf8fd67c8c22e8978d4bb1577","Climate change sensitivities of subtropical cloud-topped marine boundary layers are analyzed using large-eddy simulation (LES) of three CGILS cases of well-mixed stratocumulus, cumulus under stratocumulus, and shallow cumulus cloud regimes, respectively. For each case, a steadily forced control simulation on a small horizontally doubly periodic domain is run 10-20 days into quasi-steady state. The LES is rerun to steady state with forcings perturbed by changes in temperature, free-tropospheric relative humidity (RH), CO<inf>2</inf> concentration, subsidence, inversion stability, and wind speed; cloud responses to combined forcings superpose approximately linearly. For all three cloud regimes and 2× CO<inf>2</inf> forcing perturbations estimated from the CMIP3 multimodel mean, the LES predicts positive shortwave cloud feedback, like most CMIP3 global climate models. At both stratocumulus locations, the cloud remains overcast but thins in the warmer, moister, CO<inf>2</inf>-enhanced climate, due to the combined effects of an increased lower-tropospheric vertical humidity gradient and an enhanced free-tropospheric greenhouse effect that reduces the radiative driving of turbulence. Reduced subsidence due to weakening of tropical overturning circulations partly counteracts these two factors by raising the inversion and allowing the cloud layer to deepen. These compensating mechanisms may explain the large scatter in low cloud feedbacks predicted by climate models. CMIP3-predicted changes in wind speed, inversion stability, and free-tropospheric RH have lesser impacts on the cloud thickness. In the shallow cumulus regime, precipitation regulates the simulated boundary-layer depth and vertical structure. Cloud-droplet (aerosol) concentration limits the boundary-layer depth and affects the simulated cloud feedbacks. Key Points LES low-cloud feedbacks positive due to enhanced vertical humidity gradients Less subsidence in warmer climate counteracts positive low cloud feedbacks Precipitation and cloud droplet number affect cumulus depth, climate feedbacks ©2013. American Geophysical Union. All Rights Reserved."
"8882641700;7004479957;55745955800;8977001000;55272477500;24173130300;56611366900;7005056279;6603606681;7403282069;","Marine low cloud sensitivity to an idealized climate change: The CGILS les intercomparison",2013,"10.1002/jame.20025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880812843&doi=10.1002%2fjame.20025&partnerID=40&md5=4a00dc8fca01a79f4c3c556826e4d4e0","Subtropical marine low cloud sensitivity to an idealized climate change is compared in six large-eddy simulation (LES) models as part of CGILS. July cloud cover is simulated at three locations over the subtropical northeast Pacific Ocean, which are typified by cold sea surface temperatures (SSTs) under well-mixed stratocumulus, cool SSTs under decoupled stratocumulus, and shallow cumulus clouds overlying warmer SSTs. The idealized climate change includes a uniform 2 K SST increase with corresponding moist-adiabatic warming aloft and subsidence changes, but no change in free-tropospheric relative humidity, surface wind speed, or CO<inf>2</inf>. For each case, realistic advective forcings and boundary conditions are generated for the control and perturbed states which each LES runs for 10 days into a quasi-steady state. For the control climate, the LESs correctly produce the expected cloud type at all three locations. With the perturbed forcings, all models simulate boundary-layer deepening due to reduced subsidence in the warmer climate, with less deepening at the warm-SST location due to regulation by precipitation. The models do not show a consistent response of liquid water path and albedo in the perturbed climate, though the majority predict cloud thickening (negative cloud feedback) at the cold-SST location and slight cloud thinning (positive cloud feedback) at the cool-SST and warm-SST locations. In perturbed climate simulations at the cold-SST location without the subsidence decrease, cloud albedo consistently decreases across the models. Thus, boundary-layer cloud feedback on climate change involves compensating thermodynamic and dynamic effects of warming and may interact with patterns of subsidence change. ©2013. American Geophysical Union. All Rights Reserved."
"8718425100;7103060756;","Simulating clouds with global climate models: A comparison of CMIP5 results with CMIP3 and satellite data",2013,"10.1175/JCLI-D-12-00451.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878987256&doi=10.1175%2fJCLI-D-12-00451.1&partnerID=40&md5=abe8c393cd3fd2fa1e008c647077d067","Clouds are a key component of the climate system affecting radiative balances and the hydrological cycle. Previous studies from the Coupled Model Intercomparison Project phase 3 (CMIP3) showed quite large biases in the simulated cloud climatology affecting all GCMs as well as a remarkable degree of variation among the models that represented the state of the art circa 2005. Here the progress that has been made in recent years is measured by comparing mean cloud properties, interannual variability, and the climatological seasonal cycle from the CMIP5 models with satellite observations and with results from comparable CMIP3 experiments. The focus is on three climate-relevant cloud parameters: cloud amount, liquid water path, and cloud radiative forcing. The comparison shows that intermodel differences are still large in the Coupled Model Intercomparison Project phase 5 (CMIP5) simulations, and reveals some small improvements of particular cloud properties in some regions in the CMIP5 ensemble over CMIP3. In CMIP5 there is an improved agreement of the modeled interannual variability of liquid water path and of the modeled longwave cloud forcing over mid- and high-latitude oceans with observations. However, the differences in the simulated cloud climatology from CMIP3 and CMIP5 are generally small,and there is very little to no improvement apparent in the tropical and subtropical regions in CMIP5. Comparisons of the results from the coupled CMIP5 models with their atmosphere-only versions run with observed SSTs show remarkably similarbiases in the simulated cloud climatologies. This suggests the treatments of subgrid-scale cloud and boundary layer processes are directly implicated in the poor performance of current GCMs in simulating realistic cloud fields. © 2013 American Meteorological Society."
"55635713200;7003548068;55450672000;6603857794;","Behavior of cloud base height from ceilometer measurements",2013,"10.1016/j.atmosres.2013.02.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875588969&doi=10.1016%2fj.atmosres.2013.02.005&partnerID=40&md5=000fae0008b01c054639c4e9ec2e8f40","Given the importance of clouds in the climate, and the difficulty in determining their behavior and their contribution to climate change, there is a need for improvement of methods for automatic and continuous description of cloud characteristics. Ceilometers constitute a priori a reliable instrumental method for sounding the atmosphere and describing cloudiness, specifically cloud base height (CBH), cloud cover, and even cloud vertical structure. In the present study, the behavior of CBH at different time scales has been investigated at Girona (Spain) including a statistical analysis of the frequency distributions of CBH. The study covers four years (2007-2010) of high resolution (both in time and in the vertical direction) ceilometer measurements. At this location, ceilometer measurements reveal a seasonal cycle, with important differences between ""extreme"" seasons (winter and summer) and the ""transition"" seasons (spring and autumn). Summer months in general and July in particular behave quite differently than other periods in the year, both regarding the presence of clouds (with a minimum cloud occurrence of about 20-30%) and the distribution of CBH (with more than 25% of clouds having CBH around 1400. m and 80% of clouds with CBH lower than 3000. m). The distributions of CBH are explained on the basis of some atmospheric situations that generate clouds, in particular conditions that produce the large number of low level clouds found. © 2013 Elsevier B.V."
"36445544500;","Impact of aerosols on climate sensitivity of CO2 as implemented in climate models",2013,"10.1260/0958-305X.24.3-4.421","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880300695&doi=10.1260%2f0958-305X.24.3-4.421&partnerID=40&md5=9917a06f71fbf831c45319342f26847c","There are indications that the cooling effect of anthropogenic aerosols is overestimated. This has fundamental consequences for estimates of the climate sensitivity of CO2 and thus for temperature forecasts. Current climate models reflect this uncertainty by a wide range of "" projections"". Apart from cloud feedback, the largest uncertainty in these models is the effect of anthropogenic aerosols. The way current climate models implement the effect of different forcings is analyzed. This analysis is qualitative only, as there are major uncertainties in the quantity and effect of aerosol emissions and for confounding factors, such as ocean currents, which influence global heat distribution."
"10739072200;6602506226;8871497700;16444870500;46461233500;11339750700;7006762521;7004027519;6701820813;7004047498;57204496157;9276570300;7102692123;7006182491;7006712143;12806862100;55941661200;7006219023;6701511324;7005287667;7006595513;7006593624;26643041500;35461255500;","Warming-induced increase in aerosol number concentration likely to moderate climate change",2013,"10.1038/ngeo1800","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878680174&doi=10.1038%2fngeo1800&partnerID=40&md5=111ca48d52f6ceb4ce48b2690ea7f30a","Atmospheric aerosol particles influence the climate system directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. Apart from black carbon aerosol, aerosols cause a negative radiative forcing at the top of the atmosphere and substantially mitigate the warming caused by greenhouse gases. In the future, tightening of controls on anthropogenic aerosol and precursor vapour emissions to achieve higher air quality may weaken this beneficial effect. Natural aerosols, too, might affect future warming. Here we analyse long-term observations of concentrations and compositions of aerosol particles and their biogenic precursor vapours in continental mid- and high-latitude environments. We use measurements of particle number size distribution together with boundary layer heights derived from reanalysis data to show that the boundary layer burden of cloud condensation nuclei increases exponentially with temperature. Our results confirm a negative feedback mechanism between the continental biosphere, aerosols and climate: aerosol cooling effects are strengthened by rising biogenic organic vapour emissions in response to warming, which in turn enhance condensation on particles and their growth to the size of cloud condensation nuclei. This natural growth mechanism produces roughly 50% of particles at the size of cloud condensation nuclei across Europe. We conclude that biosphere-atmosphere interactions are crucial for aerosol climate effects and can significantly influence the effects of anthropogenic aerosol emission controls, both on climate and air quality. © 2013 Macmillan Publishers Limited. All rights reserved."
"8715232900;9043417100;6603172418;","Cloud droplet number enhanced by co-condensation of organic vapours",2013,"10.1038/ngeo1809","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878706936&doi=10.1038%2fngeo1809&partnerID=40&md5=a3e77aea89914170440f1e10061f5bc3","Clouds profoundly influence weather and climate. The brightness and lifetime of clouds is determined by cloud droplet number concentration, in turn dictated by the number of available seed particles. The formation of cloud droplets on non-volatile atmospheric particles is well understood. However, fine particulate matter in the atmosphere ranges widely in volatility. Co-condensation of semi-volatile compounds with water increases a particle's propensity for cloud droplet formation, with potential consequences for feedbacks between the terrestrial biosphere and climate. Here we systematically study cloud droplet formation, using a cloud parcel model extended to include co-condensation of semi-volatile organic compounds under a broad variety of realistic conditions. As an air parcel rises and cools, the concentration of organic vapour that it can hold declines. Thus, the simulated organic vapours become increasingly saturated as they ascend, and so condense on growing particles as they swell into cloud droplets. We show that condensation of increasingly volatile material adds to the soluble mass of these droplets and facilitates the uptake of additional water, which leads, in turn, to a substantial increase in the number of viable cloud droplets. We suggest that the co-condensation of semi-volatile organic compounds with water vapour has a substantial impact on the radiative properties of clouds. © 2013 Macmillan Publishers Limited. All rights reserved."
"55389942900;6701815637;","Changes in the cloud properties in response to El Niño: A bivariate approach",2013,"10.1007/s00382-012-1645-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878112547&doi=10.1007%2fs00382-012-1645-0&partnerID=40&md5=a513a2518589fe60f6bc4594c00221e7","We analyse the dependence of the cloud radiative effect (CRE) and cloud amount on mid-tropospheric pressure velocity (ω 500) and sea surface temperature (SST) and point out the shortcomings of using these two proxies separately as means to separate cloud regimes. A bivariate approach is proposed to overcome these shortcomings and it is used to systematically investigate marine cloud properties at different spatial and time scales in the present-day (1985-2001) tropical climate. During the 1997-1998 El Niño, the greatest regional change in CRE and cloud cover coincides with the greatest local change in circulation and SST. In addition, we find that the cooling effect of the stratiform low clouds reduces at the rate of approximately 1 W/m2 per percent of cloudiness reduction in the subsident cold pools of the Pacific ocean. During El Niño, the transition between different cloud regimes gives rise to opposing cloud feedbacks. The sign of the total feedback is controlled by the cloud optical thickness. More generally, we find that the largest part of the cloud response to El Niño, when averaged over the tropical Pacific, is not directly associated with ω 500 and SST changes, so other factors must play a role as well. © 2013 Springer-Verlag Berlin Heidelberg."
"7201504886;6603247427;6701689939;8696069500;35605362100;56154540200;35611334800;7404732357;7201627869;55581675600;14622350200;12775722600;56270311300;10241177500;57203053317;57205867148;6506238357;7003979342;","Atmospheric component of the MPI-M earth system model: ECHAM6",2013,"10.1002/jame.20015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876732870&doi=10.1002%2fjame.20015&partnerID=40&md5=4edb115fcc07396143dcadedf56c25dc","ECHAM6, the sixth generation of the atmospheric general circulation model ECHAM, is described. Major changes with respect to its predecessor affect the representation of shortwave radiative transfer, the height of the model top. Minor changes have been made to model tuning and convective triggering. Several model configurations, differing in horizontal and vertical resolution, are compared. As horizontal resolution is increased beyond T63, the simulated climate improves but changes are incremental; major biases appear to be limited by the parameterization of small-scale physical processes, such as clouds and convection. Higher vertical resolution in the middle atmosphere leads to a systematic reduction in temperature biases in the upper troposphere, and a better representation of the middle atmosphere and its modes of variability. ECHAM6 represents the present climate as well as, or better than, its predecessor. The most marked improvements are evident in the circulation of the extratropics. ECHAM6 continues to have a good representation of tropical variability. A number of biases, however, remain. These include a poor representation of low-level clouds, systematic shifts in major precipitation features, biases in the partitioning of precipitation between land and sea (particularly in the tropics), and midlatitude jets that appear to be insufficiently poleward. The response of ECHAM6 to increasing concentrations of greenhouse gases is similar to that of ECHAM5. The equilibrium climate sensitivity of the mixed-resolution (T63L95) configuration is between 2.9 and 3.4 K and is somewhat larger for the 47 level model. Cloud feedbacks and adjustments contribute positively to warming from increasing greenhouse gases. ©2013. American Geophysical Union. All Rights Reserved."
"6506848305;7103119050;","A simplified PDF parameterization of subgrid-scale clouds and turbulence for cloud-resolving models",2013,"10.1002/jame.20018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880803350&doi=10.1002%2fjame.20018&partnerID=40&md5=dd61e48e72450a624125d98ed46049d4","Over the past decade a new type of global climate model (GCM) has emerged, which is known as a multiscale modeling framework (MMF). Colorado State University's MMF represents a coupling between the Community Atmosphere Model and the System for Atmospheric Modeling (SAM) to serve as the cloud-resolving model (CRM) that replaces traditionally parameterized convection in GCMs. However, due to the high computational expense of the MMF, the grid size of the embedded CRM is typically limited to 4 km for long-term climate simulations. With grid sizes this coarse, shallow convective processes and turbulence cannot be resolved and must still be parameterized within the context of the embedded CRM. This paper describes a computationally efficient closure that aims to better represent turbulence and shallow convective processes in coarse-grid CRMs. The closure is based on the assumed probability density function (PDF) technique to serve as the subgrid-scale (SGS) condensation scheme and turbulence closure that employs a diagnostic method to determine the needed input moments. This paper describes the scheme, as well as the formulation of the eddy length which is empirically determined from large eddy simulation (LES) data. CRM tests utilizing the closure yields good results when compared to LESs for two trade-wind cumulus cases, a transition from stratocumulus to cumulus, and continental cumulus. This new closure improves the representation of clouds through the use of SGS condensation scheme and turbulence due to better representation of the buoyancy flux and dissipation rates. In addition, the scheme reduces the sensitivity of CRM simulations to horizontal grid spacing. The improvement when compared to the standard low-order closure configuration of the SAM is especially striking. ©2013. American Geophysical Union. All Rights Reserved."
"8542741400;57151771800;55915206300;6505921698;","The modification of sea surface temperature anomaly linear damping time scales by stratocumulus clouds",2013,"10.1175/JCLI-D-12-00370.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878975558&doi=10.1175%2fJCLI-D-12-00370.1&partnerID=40&md5=700c2fe7dcb890e1319ced074d0df0d7","Stratocumulus (Sc) cloud cover is a persistent feature of the subtropical North and South Atlantic. It is well known that Sc cloud cover increases with decreasing temperatures of the underlying sea surface and that an increase in cloudcover will cool the surface temperatures via increasing the local albedo, otherwise known as the Sc feedback. In this study observations are used to quantify the magnitude and spatial structure of the Sc feedback in the tropical-extratropical Atlantic Ocean and investigate the role of the Sc feedback in shaping the evolution of coupled modes of variability there. The authors show that in the Atlantic the Sc feedback increases the time scales of Newtonian cooling by 40% and in an idealized linear model of the tropical Atlantic the dominant mode of coupled variability (the Atlantic meridional mode or dipole mode) would experience no transient growth without the influence of the Sc feedback on the surface temperature damping time scales. This study also investigates Atlantic Sc clouds and the Sc feedback in phase 3 of the Coupled Model Intercomparison Project (CMIP3) models. The authors find that most models have negative biases in the mean state of Sc cloud cover and do not reproduce the observed spatial structure of Atlantic Sc clouds. This study also shows that while the majority of models exhibit some agreement with observations in the meridional structure of the Sc feedback, the vast majority of models underestimate the dependence of Sc cloud cover on the underlying SST. © 2013 American Meteorological Society."
"15848674200;7005310521;7004885872;6602514643;35746376000;","Multidecadal simulation of coastal fog with a regional climate model",2013,"10.1007/s00382-012-1486-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878110635&doi=10.1007%2fs00382-012-1486-x&partnerID=40&md5=6b7b74ad29dbff942102148e28f6c494","In order to model stratocumulus clouds and coastal fog, we have coupled the University of Washington boundary layer model to the regional climate model, RegCM (RegCM-UW). By comparing fog occurrences observed at various coastal airports in the western United States, we show that RegCM-UW has success at modeling the spatial and temporal (diurnal, seasonal, and interannual) climatology of northern California coastal fog. The quality of the modeled fog estimate depends on whether coast-adjacent ocean or land grid cells are used; for the model runs shown here, the oceanic grid cells seem to be most appropriate. The interannual variability of oceanic northern California summertime fog, from a multi-decadal simulation, has a high and statistically significant correlation with the observed interannual variability (r = 0.72), which indicates that RegCM-UW is capable of investigating the response of fog to long-term climatological forcing. While RegCM-UW has a number of aspects that would benefit from further investigation and development, RegCM-UW is a new tool for investigating the climatology of coastal fog and the physical processes that govern it. We expect that with appropriate physical parameterizations and moderate horizontal resolution, other climate models should be capable of simulating coastal fog. The source code for RegCM-UW is publicly available, under the GNU license, through the International Centre for Theoretical Physics. © 2012 Springer-Verlag."
"35090272500;36655586300;27067942000;7006206130;55798653600;","Satellite-based sunshine duration for Europe",2013,"10.3390/rs5062943","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880409429&doi=10.3390%2frs5062943&partnerID=40&md5=4b083809079ebf370c68e472129e22a6","In this study, two different methods were applied to derive daily and monthly sunshine duration based on high-resolution satellite products provided by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility on Climate Monitoring using data from Meteosat Second Generation (MSG) SEVIRI (Spinning Enhanced Visible and Infrared Imager). The satellite products were either hourly cloud type or hourly surface incoming direct radiation. The satellite sunshine duration estimates were not found to be significantly different using the native 15-minute temporal resolution of SEVIRI. The satellite-based sunshine duration products give additional spatial information over the European continent compared with equivalent in situ-based products. An evaluation of the satellite sunshine duration by product intercomparison and against station measurements was carried out to determine their accuracy. The satellite data were found to be within ±1 h/day compared to high-quality Baseline Surface Radiation Network or surface synoptic observations (SYNOP) station measurements. The satellite-based products differ more over the oceans than over land, mainly because of the treatment of fractional clouds in the cloud type-based sunshine duration product. This paper presents the methods used to derive the satellite sunshine duration products and the performance of the different retrievals. The main benefits and disadvantages compared to station-based products are also discussed. © 2013 by the authors."
"7006241374;7101754471;","IPCC underestimates the sun's role in climate change",2013,"10.1260/0958-305X.24.3-4.431","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880285535&doi=10.1260%2f0958-305X.24.3-4.431&partnerID=40&md5=422880c6943163cccc0ab81a50d1e3c5","For the understanding of current and future climate change it is a basic pre requisite to properly understand the mechanisms, which controlled climate change after the Last Ice Age. According to the IPCC 5th assessment report (in prep.) the Sun has not been a major driver of climate change during the post-Little Ice Age slow warming, and particularly not during the last 40 years. This statement requires critical review as the IPCC neglects strong paleo-climatologic evidence for the high sensitivity of the climate system to changes in solar activity. This high climate sensitivity is not alone due to variations in total solar irradiance-related direct solar forcing, but also due to additional, so-called indirect solar forcings. These include solar-related chemical-based UV irradiance-related variations in stratospheric temperatures and galactic cosmic ray-related changes in cloud cover and surface temperatures, as well as ocean oscillations, such as the Pacific Decadal Oscillation and the North Atlantic Oscillation that significant affect the climate. As it is still difficult to quantify the relative contribution of combined direct and indirect solar forcing and of increased atmospheric CO2 concentrations to the slow warming of the last 40 years, predictions about future global warming based exclusively on anthropogenic CO2 emission scenarios are premature. Nevertheless, the cyclical temperature increase of the 20th century coincided with the buildup and culmination of the Grand Solar Maximum that commenced in 1924 and ended in 2008. The anticipated phase of declining solar activity of the coming decades will be a welcome 'natural laboratory' to clarify and quantify the present and future role of solar variation in climate change."
"6701455548;","Consistent differences in climate feedbacks between Atmosphere-ocean GCMs and atmospheric GCMs with slab-ocean models",2013,"10.1175/JCLI-D-12-00519.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880261516&doi=10.1175%2fJCLI-D-12-00519.1&partnerID=40&md5=36419942f17be33f2e207e67e3326b62","Climate sensitivity is generally studied using two types of models. Atmosphere-ocean general circulation models (AOGCMs) include interactive ocean dynamics and detailed heat uptake. Atmospheric GCMs (AGCMs) with slab ocean models (SOMs) cannot fully simulate the ocean's response to and influence on climate. However, AGCMs are computationally cheaper and thus are often used to quantify and understand climate feedbacks and sensitivity. Here, physical climate feedbacks are compared between AOGCMs and SOM-AGCMs from the Coupled Model Intercomparison Project phase 3 (CMIP3) using the radiative kernel technique. Both the global-average (positive) water vapor and (negative) lapse-rate feedbacks are consistently stronger in AOGCMs. Water vapor feedback differences result from an essentially constant relative humidity and peak in the tropics, where temperature changes are larger for AOGCMs. Differences in lapserate feedbacks extend to midlatitudes and correspond to a larger ratio of tropical- to global-average temperature changes. Global-average surface albedo feedbacks are similar between models types because of a near cancellation of Arctic and Antarctic differences. In AOGCMs, the northern high latitudes warm faster than the southern latitudes, resulting in interhemispheric differences in albedo, water vapor, and lapse-rate feedbacks lacking in the SOM-AGCMs. Meridional heat transport changes also depend on the model type, although there is a large intermodel spread. However, there are no consistent global or zonal differences in cloud feedbacks. Effects of the forcing scenario [Special Report on Emissions Scenarios A1B (SRESa1b) or the 1% CO2 increase per year to doubling (1%to2x) experiments] on feedbacks are model dependent and generally of lesser importance than the model type. Care should be taken when using SOM-AGCMs to understand AOGCM feedback behavior. © 2013 American Meteorological Society."
"10341067100;35190076500;6506738607;57219951382;7102495313;7003875148;6603341831;6602178158;","Arctic climate change in 21st century CMIP5 simulations with EC-Earth",2013,"10.1007/s00382-012-1505-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878113362&doi=10.1007%2fs00382-012-1505-y&partnerID=40&md5=8da5ab18fadb26eecbb0c161f7a851fd","The Arctic climate change is analyzed in an ensemble of future projection simulations performed with the global coupled climate model EC-Earth2.3. EC-Earth simulates the twentieth century Arctic climate relatively well but the Arctic is about 2 K too cold and the sea ice thickness and extent are overestimated. In the twenty-first century, the results show a continuation and strengthening of the Arctic trends observed over the recent decades, which leads to a dramatically changed Arctic climate, especially in the high emission scenario RCP8.5. The annually averaged Arctic mean near-surface temperature increases by 12 K in RCP8.5, with largest warming in the Barents Sea region. The warming is most pronounced in winter and autumn and in the lower atmosphere. The Arctic winter temperature inversion is reduced in all scenarios and disappears in RCP8.5. The Arctic becomes ice free in September in all RCP8.5 simulations after a rapid reduction event without recovery around year 2060. Taking into account the overestimation of ice in the twentieth century, our model results indicate a likely ice-free Arctic in September around 2040. Sea ice reductions are most pronounced in the Barents Sea in all RCPs, which lead to the most dramatic changes in this region. Here, surface heat fluxes are strongly enhanced and the cloudiness is substantially decreased. The meridional heat flux into the Arctic is reduced in the atmosphere but increases in the ocean. This oceanic increase is dominated by an enhanced heat flux into the Barents Sea, which strongly contributes to the large sea ice reduction and surface-air warming in this region. Increased precipitation and river runoff lead to more freshwater input into the Arctic Ocean. However, most of the additional freshwater is stored in the Arctic Ocean while the total Arctic freshwater export only slightly increases. © 2012 The Author(s)."
"8839623400;23391698100;","Super-eruptions - Not quite so super?",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880219038&partnerID=40&md5=75b88e6aa9c1d9c936ab873bdbc60d47","Darren Mark and Ben Ellis report on how their work in Yellowstone could radically change researchers' understanding of explosive volcanic events taking place on Earth, with implications not just for those living nearby but also for the global climate. Globally, millions of people live in regions that could be devastated by the eruption of a super-volcano - for example, Yellowstone in North America, Campi Flegrei in southern Italy, and Toba in Indonesia. These eruptions can produce hundreds or even thousands of cubic kilometers of magma over days or weeks. Yet their most widespread effects do not come from locally-devastating pyroclastic flows of superheated gas and rock, but from ash clouds that can circle the globe. Sulfur injected into the stratosphere oxidizes to form small droplets of sulfuric acid. These stop sunlight reaching the planet's surface, cooling the climate."
"35177669200;6508026916;39361670300;36457573700;36661106500;6701344406;","A multi-physics ensemble of present-day climate regional simulations over the Iberian Peninsula",2013,"10.1007/s00382-012-1539-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878113861&doi=10.1007%2fs00382-012-1539-1&partnerID=40&md5=657c583d8fc9eea04007e2acdf7450b0","This work assesses the influence of the model physics in present-day regional climate simulations. It is based on a multi-phyiscs ensemble of 30-year long MM5 hindcasted simulations performed over a complex and climatically heterogeneous domain as the Iberian Peninsula. The ensemble consists of eight members that results from combining different parametrization schemes for modeling the Planetary Boundary Layer, the cumulus and the microphysics processes. The analysis is made at the seasonal time scale and focuses on mean values and interannual variability of temperature and precipitation. The objectives are (1) to evaluate and characterize differences among the simulations attributable to changes in the physical options of the regional model, and (2) to identify the most suitable parametrization schemes and understand the underlying mechanisms causing that some schemes perform better than others. The results confirm the paramount importance of the model physics, showing that the spread among the various simulations is of comparable magnitude to the spread obtained in similar multi-model ensembles. This suggests that most of the spread obtained in multi-model ensembles could be attributable to the different physical configurations employed in the various models. Second, we obtain that no single ensemble member outperforms the others in every situation. Nevertheless, some particular schemes display a better performance. On the one hand, the non-local MRF PBL scheme reduces the cold bias of the simulations throughout the year compared to the local Eta model. The reason is that the former simulates deeper mixing layers. On the other hand, the Grell parametrization scheme for cumulus produces smaller amount of precipitation in the summer season compared to the more complex Kain-Fritsch scheme by reducing the overestimation in the simulated frequency of the convective precipitation events. Consequently, the interannual variability of precipitation (temperature) diminishes (increases), which implies a better agreement with the observations in both cases. Although these features improve in general the accuracy of the simulations, controversial nuances are also highlighted. © 2012 Springer-Verlag Berlin Heidelberg."
"55623048200;35109882500;25926092000;","Comparisons of tropopause derived from COSMIC measurements at Nanjing since August 2006",2013,"10.1016/j.jastp.2013.03.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876303233&doi=10.1016%2fj.jastp.2013.03.013&partnerID=40&md5=c9d54553487d26a225e429b4e1ac466e","Tropopause temperature (T t) and pressure (p t) at Nanjing are derived from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) from August 2006 to December 2011. We compareT tandp tamong the COSMIC, radiosonde provided by the Earth System Research Laboratory (ESRL) and reanalysis data sets from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) Reanalysis (NNR) on 10-day, seasonal and annual timescales. Ten-day meanT t andp tof the COSMIC data are higher than that of radiosonde by 0.2°C and 5.3hPa and reanalysis by 1.0°C and 17.5hPa, respectively. Results of multiple comparisons demonstrate a significant difference forp tbetween the NNR and COSMIC data. Systematic biases are more significant in low-pressure level than in high-pressure level for reanalysis and radiosonde in terms of seasonal average differences. As for annual mean difference pressure, the COSMIC is higher than ESRL and NNR data by 3.4hPa-6.5hPa and 10hPa, respectively. Besides, the COSMIC and other two data sets are in the best agreement forT tandp twith maximum number of occultation events in 2008. Lastly, quasi-biennial period of correlation coefficients between the ESRL and NNR data sets from 2007 to 2011 requests further verification. © 2013 Elsevier Ltd."
"55399935700;8558370300;7102567936;7004060399;","Understanding hadley cell expansion versus contraction: Insights from simplified models and implications for recent observations",2013,"10.1175/JCLI-D-12-00598.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880301193&doi=10.1175%2fJCLI-D-12-00598.1&partnerID=40&md5=4f869aa3cc5cef29f1556e06f4ee6f46","This study seeks a deeper understanding of the causes of Hadley Cell (HC) expansion, as projected under global warming, and HC contraction, as observed under El Niño. Using an idealized general circulation model, the authors show that a thermal forcing applied to a narrow region around the equator produces ""El Niño-like"" HC contraction, while a forcing with wider meridional extent produces ""global warming-like"" HC expansion. These circulation responses are sensitive primarily to the thermal forcing's meridional structure and are less sensitive to its vertical structure. If the thermal forcing is confined to the midlatitudes, the amount of HC expansion is more than three times that of a forcing of comparable amplitude that is spread over the tropics. This finding may be relevant to recently observed trends of rapid tropical widening. The shift of the HC edge is explained using a very simple model in which the transformed Eulerian mean (TEM) circulation acts to diffuse heat meridionally. In this context, the HC edge is defined as the downward maximum of residual vertical velocity in the upper troposphere ω̄max* ; this corresponds well with the conventional Eulerian definition of the HC edge. In response to a positive thermal forcing, there is anomalous diabatic cooling, and henceanomalous TEM descent, on the poleward flank of the thermal forcing. This causes the HC edge (ω̄max* ) to shift toward the descending anomaly, so that a narrow forcing causes HC contraction and a wide forcing causes HC expansion. © 2013 American Meteorological Society."
"54981446800;7004540083;","Contributions of individual atmospheric diabatic heating processes to the generation of available potential energy",2013,"10.1175/JCLI-D-12-00457.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880264239&doi=10.1175%2fJCLI-D-12-00457.1&partnerID=40&md5=1750e7d345aba041b9670caa5941d846","The generation of zonal and eddy available potential energy (Gz and Ge) as formulated by Lorenz are computed on a global-, daily-, and synoptic-scale basis to consider the contribution of each diabatic heating component separately and in combination. Using global, mostly satellite-derived datasets for the diabatic heating components and the temperature enables us to obtainGz and, especially,Ge from observations for the first time and at higher temporal and spatial resolution than previously possible. The role of clouds in maintaining G is investigated. The global annual mean Gz is 1.52 W m-2. Values reach a minimum of 0.63 W m-2 in the Northern Hemisphere during spring and a maximum of 2.27 W m-2 in the Southern Hemisphere during winter. The largest contributors to Gz are latent heating in the tropical upper troposphere, associated with the intertropical convergence zone in the summer hemisphere and surface sensible heat fluxes in the winter pole. Diabatic cooling by radiative fluxes (mostly longwave) generally destroys Gz. The value of Ge is negative and is about an order of magnitude smaller than Gz, with a global annual mean of -0.29 W m-2. However, the small value of Ge results from the cancellation of the contributions from the individual diabatic heating terms, which are actually roughly similar in magnitude to their Gz contributions. The results presented herein suggest that the large-scale dynamics of the atmosphere organize the spatial and temporal distribution of clouds and precipitation in such a way as to increase the energy available to drive the circulation, a kind of positive feedback. © 2013 American Meteorological Society."
"7403079192;7202577511;7006850787;7202835111;55437655600;","Numerical simulation for a wind dust event in the US/Mexico border region",2013,"10.1007/s11869-012-0174-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878168876&doi=10.1007%2fs11869-012-0174-7&partnerID=40&md5=a9ca61d1c759fd0d124d01c3f5d5ee3f","Soil-derived dust represents one of the major components of the natural atmospheric aerosols. Arid and semiarid areas with unpaved and non-vegetated land cover are particularly vulnerable to windblown dust, which results in high particulate matter pollution. To understand, predict, and mitigate the impact of dust aerosol on air quality and climate, it is necessary to parameterize the emission rate of dust particles from the wind erosion processes accurately. However, windblown dust emission is poorly represented in existing air quality models. In this paper, a windblown dust emission model has been developed based on a parameterization of threshold wind friction velocity depending on the roughness of surface, vegetation type, soil type, soil moisture content, and on the size distribution of aerosols. The proposed dust model incorporates into a region air quality modeling system to simulate a North American dust storm episode occurring near the border of southwestern USA and northwestern region of Mexico on 23 February 2007. It is shown that the implementation of a windblown dust model in an air quality model can significantly improve the model capability for capturing the dust episode. The simulation of the model is in good agreement with the evolution of dust distribution. The modeled dust spatial patterns matched dust cloud patterns appearing on satellite images. Implementation of the windblown dust model successfully captured the time of peak particulate matter (PM) concentrations for both PM10 and PM2.5, as well as the peak value of the PM2.5 concentration. The modeled results clearly demonstrate an improved ability to predict PM events by applying the windblown dust emission scheme. © 2012 Springer Science+Business Media B.V."
"57200237025;57194681246;55746654700;55746859600;","Examinations on the meteorological factors of urban heat island development in small and medium-sized towns in Hungary",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878205364&partnerID=40&md5=5deb18050661e63188dacd023ce091a7","The thermal difference between the settlements and their environment is called urban heat island (UHI). Potential UHI intensities are determined by the size, population and built-up structure of settlements, while meteorological conditions have a determinant impact on the development of the heat island at a certain moment. However, not much attention is paid to medium-sized and small towns from this aspect in International and Hungarian studies. Consequently, this study has been focused on the development of UHI in such an environment in Hungary. Settlements, located near the city of Debrecen (cca. 220000 inhabitants) in East Hungary, with population of about 30000, 20000 10000 and 1000 were chosen for the research. Data were collected in two one-year-long mobile measurement campaigns. Spatial characteristics of UHI have been described. Results have proved the existence of UHI even in the smallest settlement under suitable weather conditions. Effects of cloudiness and wind speed have been revealed as well. Stratus clouds have proved to be the most effective in preventing the formation of UHI. Wind speed had a strong impact on the strength of the heat island, while wind directions affected its shape merely."
"7007026915;55745815100;55746147200;54889736700;7005050002;22946263800;","Mid-season climate diagnostics of jet contrail 'outbreaks' and implications for eastern US sky-cover trends",2013,"10.3354/cr01148","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878150613&doi=10.3354%2fcr01148&partnerID=40&md5=3ae2a1e3a821ab49c46cebed074d0998","The cirrus-level 'condensation trails' (contrails) produced by jet aircraft often occur as sub-regional-scale 'outbreaks' of multiple contrails, suggested as contributing to post ~1965 climate trends in parts of the US and Europe. Several previously-developed, satellite-image based contrail spatial inventories for the conterminous US (CONUS) revealed regional-scale differences in frequency. However, the use of such geographically-fixed regions was not ideal for climate studies. As a first step towards determining the potential climate impacts of contrail outbreaks for the CONUS, we develop maps of overlapping (in time, space) outbreak occurrences-'overlaps'- by applying GIS to a recent period (2000-2002) satellite-image derived inventory for mid-season months. The higher-frequency outbreak overlap regions undergo substantial between-season variations in magnitude and extent that reflect an association with upper-tropospheric temperature gradients and winds. Overlap maps generated for additional mid-season months in 2008-2009 indicate the inter-annual variability of the outbreak regionalization. To clarify the role of uppertroposphere synoptic meteorological conditions in contrail outbreak occurrence, we form compo - sites-multi-case averages-for the sub-region of maximum overlap frequency in each midseason month. Regional and seasonal variations in the relative roles of 'thermo-dynamic' (here, temperature, humidity) and 'dynamic' (vertical motion of air, horizontal wind) controls in outbreaks are identified. Last, we demonstrate potential utility of the spatial overlap method by deriving fallseason surface station trends (1951-1993) of sky cover variables for contrasting high versus low contrail and overlap frequency grid cells in the eastern CONUS. These suggest a contrail contribution to recent high-cloud increases, notably for the Midwest. © Inter-Research 2013."
"57190893918;6701752471;7201665727;","Cloud tuning in a coupled climate model: Impact on 20th century warming",2013,"10.1002/grl.50232","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879987149&doi=10.1002%2fgrl.50232&partnerID=40&md5=5cf8ec85018e6af16ae56b17ebde518e","Climate models incorporate a number of adjustable parameters in their cloud formulations. They arise from uncertainties in cloud processes. These parameters are tuned to achieve a desired radiation balance and to best reproduce the observed climate. A given radiation balance can be achieved by multiple combinations of parameters. We investigate the impact of cloud tuning in the CMIP5 GFDL CM3 coupled climate model by constructing two alternate configurations. They achieve the desired radiation balance using different, but plausible, combinations of parameters. The present-day climate is nearly indistinguishable among all configurations. However, the magnitude of the aerosol indirect effects differs by as much as 1.2 Wm -2, resulting in significantly different temperature evolution over the 20th century. © 2013 American Geophysical Union. All Rights Reserved."
"55788929500;55686667100;36701462300;","Mechanism of tropical low-cloud response to surface warming using weather and climate simulations",2013,"10.1002/grl.50474","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879936850&doi=10.1002%2fgrl.50474&partnerID=40&md5=c5b52c54497c13a883b6ec3459833b27","To understand mechanisms of shortwave cloud-radiative feedback to global warming in a general circulation model (GCM), we analyzed the response of tropical clouds to uniform increase of sea surface temperature in an atmospheric GCM with two different experimental designs: a single Atmospheric Model Intercomparison Project (AMIP) run for 30 years and a series of 10 day weather hindcasts following the Transpose AMIP II (TAMIP). Given the fast time scale of cloud processes, the hindcast ensemble can capture initial transient responses toward equilibrium obtained in the AMIP experiment, which shows a reduction of low clouds over tropical subsidence regions. The reduction of clouds occurs in the first 10 days in TAMIP when the marine boundary layer (MBL) is destabilized because of contrast between fast and slow warming in the MBL and aloft. Enhanced evaporation from the sea surface that should moisten the MBL through turbulent mixing is suppressed by a reduced surface wind speed associated with a slowdown of the Walker circulation. The sign of the low-cloud change over the subsidence regime is thus determined roughly by competition between convective drying and turbulent moistening of the MBL. © 2013 American Geophysical Union. All Rights Reserved."
"9042826200;7007163910;7004047546;","Lightning and fire weather in eastern coastal fynbos shrublands: Seasonality and long-term trends",2013,"10.1071/WF11167","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878039170&doi=10.1071%2fWF11167&partnerID=40&md5=ab8f4f157837fafb917333c5056b6181","Daily weather data (since 1939) from four localities in the south-eastern, coastal part of the Cape Floral Kingdom ('south-eastern-CFK') were used to calculate daily fire danger indices (FDIs). Cloud-to-ground lightning strike distributions (2006-10) were explored for geographical and temporal trends. Low or moderate fire danger conditions were the norm year round, and even large fires occurred under these conditions. Lightning occurred throughout the landscape at fairly low densities (mean≤0.4 strikes km-2 year-1) and in all seasons, increasing somewhat during summer. Lightning presence increased with increasing rainfall, relative humidity, temperature and wind speed. Lightning seasonality in the south-eastern-CFK did not differ from that in the south-western-CFK. Our results provide evidence of a largely aseasonal fire regime in eastern coastal fynbos shrublands: FDIs peaked in winter (due to low rainfall and hot, dry katabatic winds) but were not associated with a winter fire regime; lightning and the co-occurrence of lightning and elevated FDIs were aseasonal and were correlated with the incidence of lightning-ignited fires throughout the year. The implication for management is that season of burn is largely unimportant. Mean annual FDI increased significantly over the study period, a trend which is likely to manifest in increased frequency and severity of fire, some of which has already been observed. © 2013 IAWF."
"14029905100;55789008200;55789279200;","Variability in the width of the tropics and the annular modes",2013,"10.1029/2012GL054165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879930593&doi=10.1029%2f2012GL054165&partnerID=40&md5=a2347242d21c747a874e3703fe25700c","The correlation between unforced variability in the latitude of the edge of the Hadley cell (ΦHC) and latitude of the surface westerlies (ΦEDJ) is examined using a simplified moist general circulation model (GCM) and a suite of state of the art GCMs. The correlation can be determined by the time-mean separation of the two features. When the separation is small, there is a positive correlation, and as the separation between them increases, the correlation reduces. In the simplified model, a weak negative correlation emerges at large separations.The location of the anomalous meridional mass flux associated with variations in the latitude of ΦEDJ, relative to the climatological Hadley cell position, determines the extent to which ΦHC is influenced by changes in ΦEDJ. Changes in the latitude of ΦEDJ are driven by anomalous eddy momentum flux convergence, and these are approximately balanced by the Coriolis torque on the meridional flow, as expected under quasi-geostrophic scaling. Under changing time-mean climates, the anomalous flow associated with ΦEDJ variability translates location so that it is approximately fixed relative to the time-mean ΦEDJ. This means that the influence of ΦEDJ variability on ΦHC varies as a function of the time-mean separation of the features.Initial indications are that the same causal relationship holds in a suite of state of the art GCMs and that this explains the seasonal variation in the correlation between ΦHC and ΦEDJ. © 2013 American Geophysical Union. All Rights Reserved."
"7410070663;6603613067;19638935200;55796506900;57208346904;","Evaluation of black carbon semi-direct radiative effect in a climate model",2013,"10.1002/jgrd.50327","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881114295&doi=10.1002%2fjgrd.50327&partnerID=40&md5=3a387e53011d2264e5cc7a85c596cdb0","The semi-direct effect of black carbon (BC) is studied by using a newly proposed optical property parameterization for cloud droplets with BC inclusions. Based on Atmospheric Model Intercomparison Project-type climate model simulations, it is found that the cloud amount can be either enhanced or reduced when BC is included in clouds. The decrease of the global annual mean total cloud amount is only about 0.023%. The 3-D cloud fraction distribution, however, shows larger changes which vary with latitude. A correlation between the changes of the cloud fraction and the vertical velocity is found. The cloud water path is mainly affected by low clouds and so the impact of BC on the cloud water path is particularly strong. It is shown that the BC above clouds tends to stabilize the atmosphere and enhance the cloud amount in the boundary layer. This can be used to explain the relationship between aerosol optical depth and cloud amount according to satellite data. For BC in clouds and above, the global annual mean enhancement of solar absorption is about 0.049 W m-2 and 0.57 W m-2, respectively. The BC semi-direct radiative forcing is estimated by subtracting the BC direct forcing from the BC total radiative forcing. The global annual mean of BC direct forcing and semi-direct forcing at the top of the atmosphere are 0.264 W m-2 and 0.213 W m-2, respectively. Key PointsBC inclusion in cloud dropletsrelationship between BC and cloudRe-investigate the BC semi-direct forcing ©2013. American Geophysical Union. All Rights Reserved."
"57172205400;6701511321;7403263977;56604618200;","Simulation of polar stratospheric clouds in the specified dynamics version of the whole atmosphere community climate model",2013,"10.1002/jgrd.50415","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881126019&doi=10.1002%2fjgrd.50415&partnerID=40&md5=44ab1070b40755a4eb715071615a9413","We evaluate the simulation of polar stratospheric clouds (PSCs) in the Specified Dynamics version of the Whole Atmosphere Community Climate Model for the Antarctic winter 2005. In this model, PSCs are assumed to form instantaneously at a prescribed supersaturation, with a prescribed size distribution and number density. We use satellite observations of the Antarctic winter 2005 of nitric acid, water vapor, and PSCs to test and improve this PSC parameterization. Cloud-Aerosol Lidar with Orthogonal Polarization observations since 2006 show that in both hemispheres, the dominant PSC type throughout the entire polar winter is a mixture of Nitric Acid Trihydrate (NAT) and Supercooled Ternary Solutions droplets, but typical assumptions about PSC formation in the model at a given supersaturation do not produce such a population of particles and lead to earlier removal of HNO<inf>3</inf> from the gas phase compared to observations. In our new PSC scheme, the formation of mixed PSCs is forced by only allowing a fraction of total available HNO<inf>3</inf> to freeze to NAT and the remaining part to form STS. With this approach, a mixture of both is present throughout the winter, in agreement with observations. This approach yields good agreement with observations in terms of temperature-dependent removal of gas-phase HNO<inf>3</inf> and irreversible denitrification. In addition to nitric acid containing PSCs, we also investigate ice PSCs. We show that the choice of required saturation ratio of water vapor for ice formation can significantly improve the calculated vertical distribution of water vapor and is required to produce good agreement with observations. Key PointsRemoval of gas-phase HNO3 follows the STS equilibrium functionIce PSCs form at temperatures around the frost pointDenitrification and dehydration are in good agreement with observations ©2013. American Geophysical Union. All Rights Reserved."
"57202922977;7401844779;7101886364;25648525300;6602137800;7201826462;","Retrieval of cirrus properties by Sun photometry: A new perspective on an old issue",2013,"10.1002/jgrd.50185","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881157562&doi=10.1002%2fjgrd.50185&partnerID=40&md5=922d6e97fa0a3e65eff83ccac30a4b97","Cirrus clouds are important modulators of the Earth radiation budget and continue to be one of the most uncertain components in weather and climate modeling. Sun photometers are widely accepted as one of the most accurate platforms for measuring clear sky aerosol optical depth (AOD). However, interpretation of their measurements is ambiguous in the presence of cirrus. Derivation of a valid AOD under cirrus conditions was focused previously on correction factors, rather than on derivation of cirrus cloud optical thickness (COT). In the present work, we propose a new approach that uses the total measured irradiance to derive cirrus COT and ice particle effective diameter (D<inf>eff</inf>). For this approach, we generate lookup tables (LUTs) of total transmittance for the Sun photometer field of view (FOV) due to the direct and scattered irradiance over the spectral range of 400-2200 nm, for a range of cirrus COT (0-4), and a range of ice cloud effective diameters (10-120 μm) by using explicit cirrus optical property models for (a) cirrus only and (b) a two-component model including cirrus and aerosols. The new approach is tested on two cases (airborne and ground-based) using measured transmittances from the 14-channel NASA Ames Airborne Tracking Sun photometer. We find that relative uncertainties in COT are much smaller than those for D<inf>eff</inf>. This study shows that for optically thin cirrus cases (COT < 1.0), the aerosol layer between the instrument and the cloud plays an important role, especially in derivation of D<inf>eff</inf>. Additionally, the choice of the cirrus model may introduce large differences in derived D<inf>eff</inf>. Key Points New approach to retrieve cirrus properties from sunphotometersUtilization and comparison of several explicit cirrus optical properties modelsInvestigating the effect of aerosol below cloud on cirrus property retrievals ©2013. American Geophysical Union. All Rights Reserved."
"7201665727;7103206141;35514163500;7006306835;6701752471;56244473600;56744278700;","The roles of aerosol direct and indirect effects in past and future climate change",2013,"10.1002/jgrd.50192","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879936647&doi=10.1002%2fjgrd.50192&partnerID=40&md5=1c1e2af93c699f10e6bda452eac8de9c","Using the Geophysical Fluid Dynamics Laboratory's (GFDL's) fully coupled chemistry-climate (ocean/atmosphere/land/sea ice) model (CM3) with an explicit physical representation of aerosol indirect effects (cloud-water droplet activation), we find that the dramatic emission reductions (35%-80%) in anthropogenic aerosols and their precursors projected by Representative Concentration Pathway (RCP) 4.5 result in ~1 °C of additional warming and ~0.1 mm day-1 of additional precipitation, both globally averaged, by the end of the 21st century. The impact of these reductions in aerosol emissions on simulated global mean surface temperature and precipitation becomes apparent by mid-21st century. Furthermore, we find that the aerosol emission reductions cause precipitation to increase in East and South Asia by ~1.0 mm day-1 through the second half of the 21st century. Both the temperature and the precipitation responses simulated by CM3 are significantly stronger than the responses previously simulated by our earlier climate model (CM2.1) that only considered direct radiative forcing by aerosols. We conclude that the indirect effects of sulfate aerosol greatly enhance the impacts of aerosols on surface temperature in CM3; both direct and indirect effects from sulfate aerosols dominate the strong precipitation response, possibly with a small contribution from carbonaceous aerosols. Just as we found with the previous GFDL model, CM3 produces surface warming patterns that are uncorrelated with the spatial distribution of 21st century changes in aerosol loading. However, the largest precipitation increases in CM3 are colocated with the region of greatest aerosol decrease, in and downwind of Asia. Key Points Aerosol reductions (RCP4.5) cause 1K warming and +0.1 mm/day of precipitation.Sulfate indirect effects greatly enhance aerosol impacts on surface temperature.Aerosol reductions increase precipitation in Asia by 0.5-1.0 mm/day by 2100. ©2013. American Geophysical Union. All Rights Reserved."
"7401984344;7103267885;35362690800;7202226478;6507050339;","Toward improved corrections for radiation-induced biases in radiosonde temperature observations",2013,"10.1002/jgrd.50369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881140333&doi=10.1002%2fjgrd.50369&partnerID=40&md5=da504cfc2682023eb463e93f55354135","Radiation-induced biases in global operational radiosonde temperature data from May 2008 to August 2011 are examined by using spatially and temporally collocated Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) data as estimates of the truth. The data on average from most radiosonde types show a nighttime cold bias and a daytime warm bias relative to COSMIC. Most daytime biases increase with altitude and solar elevation angle (SEA). The global average biases in the 15-70 hPa layer are -0.05 ± 1.89 K standard deviation (~52,000 profiles) at night and 0.39 ± 1.80 K standard deviation (~64,500 profiles) in daytime (SEA > 7.5°). Daytime warm biases associated with clouds are smaller than those under clear conditions. Newer sondes (post-2000) have smaller biases and appear to be less sensitive to effects of clouds. Biases at night show greater seasonal and zonal variations than those for daytime. In general, warm night biases are associated with warm climate regimes and less warm or cold night biases with cold climate regimes. Bias characteristics for 13 major radiosonde types are provided, as a basis for updating radiosonde corrections used in numerical weather predictions, for validating satellite retrievals, and for adjusting archived radiosonde data to create consistent climate records. Key Points The analysis aims to facilitate improvements in radiosonde bias corrections ©2013. American Geophysical Union. All Rights Reserved."
"16425023500;55691911100;7202887068;6602158404;56042198600;35225302600;","Investigation of the complex dynamics and structure of the 2010 Eyjafjallajökull volcanic ash cloud using multispectral images and numerical simulations",2013,"10.1002/jgrd.50328","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881192557&doi=10.1002%2fjgrd.50328&partnerID=40&md5=dad8038ffd2f3cc9163247d7597fb7c7","We investigated the structure and evolution of the 2010 Eyjafjallajökull volcanic cloud and its dispersal over Iceland and Europe integrating satellite multispectral images and numerical simulations. Data acquired by Medium Resolution Imaging Spectrometer (MERIS) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) have been analyzed to quantify the cloud extent and composition. The VOL-CALPUFF dispersal code was applied to reconstruct the transient and 3-D evolution of the cloud. Source parameters estimated on the base of available a posteriori volcanological data sets have been used. Quantitative comparisons between satellite retrievals and modeling results were performed for two selected instants of time during the first and third eruptive phases on a regional scale. Sensitivity of the model to initial volcanological conditions has been analyzed at continental scale. Several complex non intuitive features of cloud dynamics have been highlighted and strengths and limitations of the adopted methods identified. The main findings are: the level of quantitative agreement between satellite observations and numerical results depends on ash cloud composition (particle sizes and concentration) with better agreement for smaller particles and higher concentrations; the agreement between observations and modeling outcomes also depends on the temporal stability of volcanological conditions and the complexity of the meteorological wind field; the irregular dispersion of ash, as reconstructed from satellite data and numerical modeling, can be well explained by the different response of particle sizes to strong vertical wind-shear, and by resuspension processes acting at ground level; eruptive source conditions are the main source of uncertainty in modeling, especially during an ongoing crisis and at long-range scales. Key Points A new methodological approach for investigating volcanic ash cloudIntegration of satellite observations and numerical simulationsModel sensitivity to initial volcanological conditions ©2013. American Geophysical Union. All Rights Reserved."
"6603503532;8632802100;25122294100;","Future changes in summertime precipitation amounts associated with topography in the Japanese islands",2013,"10.1002/jgrd.50383","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881135870&doi=10.1002%2fjgrd.50383&partnerID=40&md5=9734d937d63163a6aec1be5cccafb71f","This study investigates future changes in summertime precipitation amounts over the Japanese islands and their relations to the topographical heights by analyzing data from 20 km resolution regional climate model downscalings of MIROC3.2(hires) 20C3M and Special Report on Emission Scenarios A1B scenario data for the periods of 1981-2000 and 2081-2100. Results of the analyses indicate that future increases in June-July-August mean daily precipitation amounts are noticeable in the west and south sides (windward sides) of the mountainous regions, especially in western Japan where heavy rainfall is frequently observed in the recent climate. The large precipitation increases are likely to occur not only in high altitude areas but also at low altitudes where many urban areas are located. In such areas, the occurrence frequencies of precipitation amounts greater than 100 mm d-1 would also increase under the future climate scenario (A1B). One of the main causes of these precipitation changes appears to be the intensification of southwesterly moist air flows in the lower troposphere, which is likely to be associated with future increases in the north-south atmospheric pressure gradient, especially at latitudes south of 35°N. The intensified southwesterly moist air flows that impinge on the western and southern slopes of the mountains can generate stronger upslope flows and well-developed clouds, leading to increased precipitation. In contrast, future precipitation changes in the lee sides of the mountainous regions would be comparatively small. These results indicate that future precipitation changes strongly depend on the topography and prevailing wind direction. Key Points Relationship between future changes in summertime precipitation and topographyAnalyses of data from the three different regional climate modelsFinding as to the large influence of topography on future precipitation changes ©2013. American Geophysical Union. All Rights Reserved."
"35731251200;7202429440;7201432984;7103183855;36551105100;7005451983;7005773698;","The impact of shipping, agricultural, and urban emissions on single particle chemistry observed aboard the R/V Atlantis during CalNex",2013,"10.1002/jgrd.50427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881190921&doi=10.1002%2fjgrd.50427&partnerID=40&md5=3051dd38e23e75df2a5ac4c5cd66d6d2","The Research at the Nexus of Air Quality and Climate Change (CalNex) field campaign was undertaken to obtain a better understanding of the regional impacts of different pollution sources in California. As part of this study, real-time shipboard measurements were made of the size-resolved, single-particle mixing state of submicron and supermicron particles (0.2-3.0 μm aerodynamic diameter) along the California coast where major differences were noted between Southern and Northern California. In Southern California, particles containing soot made up the largest fraction of submicron particles (~38% on average and up to ~89% by number), whereas organic carbon particles comprised the largest fraction of submicron number concentrations (~29% on average and up to ~78% by number) in Northern California including the Sacramento area. The mixing state of these carbonaceous particle types varied during the cruise with sulfate being more prevalent on soot-containing particles in Southern California due to the influence of fresh shipping and port emissions in addition to contributions from marine biogenic emissions. Contributions from secondary organic aerosol species, including amines, and nitrate were more prevalent in Northern California, as well as during time periods impacted by agricultural emissions (e.g., from the inland Riverside and Central Valley regions). These regional differences and changes in the mixing state and sources of particles have implications for heterogeneous reactivity, water uptake, and cloud-nucleating abilities for aerosols in California. Key PointsSouthern California was dominated by soot containing particlesNorthern California was dominated by organic carbon particlesParticle mixing-state was heavily influenced by meteorological conditions ©2013. American Geophysical Union. All Rights Reserved."
"36816593400;57204180893;55884957400;","Retrieval and analysis of Arctic albedo from NOAA/AVHRR data",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885677790&partnerID=40&md5=23be9202e2aa246c515a68f01bbcdd58","Surface albedo in the Arctic is one of the most important factors influencing the polar heat budget. The impact of variations of the Arctic sea ice albedo on the heat budget of the earth-atmosphere system and on global climate change is significant. In this paper, the surface albedo in the Arctic was derived using the Level-IB (LIB) data from the advanced very high resolution radiometer (AVHRR) onboard the National Oceanic and Atmospheric Administration (NOAA) polar-orbiting satellites. We applied narrow-to-broadband conversion, anisotropic correction, atmospheric correction, and cloud detection to the satellite data, and obtained broadband surface albedo products in clear conditions with a 4 km spatial resolution. Comparisons between the AVHRR albedo products and in situ measurements collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) project showed a bias of -0.07 and a standard deviation of 0.05 during the spring-winter season. Monthly averaged NOAA/AVHRR surface albedo data from 2008 to 2010, combined with in situ measurements from the fourth Chinese Arctic research expedition, were used to study the variation of the Arctic sea ice albedo. The influence of snowfall and ice ridges on the variation of surface albedo was analyzed. The albedo decreased significantly and rapidly by about 03 when the snow was melting. Comparing between the albedo variations in the rough multi-year ice area and smooth first-year ice area shows an albedo difference of 0.2 during the melting season. The results indicate that the melting of snow and ice was the dominant factor for the variation of the Arctic albedo."
"55486290300;35593636200;7102862273;56037741700;7005304841;34771961300;7003827051;35600074800;","Comparison between summertime and wintertime Arctic Ocean primary marine aerosol properties",2013,"10.5194/acp-13-4783-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877870679&doi=10.5194%2facp-13-4783-2013&partnerID=40&md5=bb7b75841b05a2d2b8db502a55fdf24a","Primary marine aerosols (PMAs) are an important source of cloud condensation nuclei, and one of the key elements of the remote marine radiative budget. Changes occurring in the rapidly warming Arctic, most importantly the decreasing sea ice extent, will alter PMA production and hence the Arctic climate through a set of feedback processes. In light of this, laboratory experiments with Arctic Ocean water during both Arctic winter and summer were conducted and focused on PMA emissions as a function of season and water properties. Total particle number concentrations and particle number size distributions were used to characterize the PMA population. A comprehensive data set from the Arctic summer and winter showed a decrease in PMA concentrations for the covered water temperature (Tw) range between -1 and 15 °C. A sharp decrease in PMA emissions for a Tw increase from -1°C to 4 °C was followed by a lower rate of change in PMA emissions for Tw up to about 6 °C. Near constant number concentrations for water temperatures between 6 °C to 10 °C and higher were recorded. Even though the total particle number concentration changes for overlapping Tw ranges were consistent between the summer and winter measurements, the distribution of particle number concentrations among the different sizes varied between the seasons. Median particle number concentrations for a dry diameter (Dp) &lt; 0.125μm measured during winter conditions were similar (deviation of up to 3 %), or lower (up to 70 %) than the ones measured during summer conditions (for the same water temperature range). ForDp &gt; 0.125μm, the particle number concentrations during winter were mostly higher than in summer (up to 50 %). The normalized particle number size distribution as a function of water temperature was examined for both winter and summer measurements. An increase in Tw from -1°C to 10 °C during winter measurements showed a decrease in the peak of relative particle number concentration at about a Dp of 0.180 μm, while an increase was observed for particles with Dp &gt; 1μm. Summer measurements exhibited a relative shift to smaller particle sizes for an increase of Tw in the range 7-11 °C. The differences in the shape of the number size distributions between winter and summer may be caused by different production of organic material in water, different local processes modifying the water masses within the fjord (for example sea ice production in winter and increased glacial meltwater inflow during summer) and different origin of the dominant sea water mass. Further research is needed regarding the contribution of these factors to the PMA production. © Author(s) 2013."
"35098801000;6701455548;23486332900;6602688130;","Climate Feedbacks in CCSM3 under Changing CO2 Forcing. Part II: Variation of Climate Feedbacks and Sensitivity with Forcing",2013,"10.1175/JCLI-D-12-00479.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877642216&doi=10.1175%2fJCLI-D-12-00479.1&partnerID=40&md5=7d6aba9c9f1824297a59c51bb4b029d3","Are equilibrium climate sensitivity and the associated radiative feedbacks a constant property of the climate system, or do they change with forcing magnitude and base climate? Using the radiative kernel technique, feedbacks and climate sensitivity are evaluated in a fully coupled general circulation model (GCM) for three successive doublings of carbon dioxide starting from present-day concentrations. Climate sensitivity increases by 23% between the first and third CO2 doublings. Increases in the positive water vapor and cloud feedbacks are partially balanced by a decrease in the positive surface albedo feedback and an increase in the negative lapse rate feedback. Feedbacks can be decomposed into a radiative flux change and a climate variable response to temperature change. The changes in water vapor and Planck feedbacks are due largely to changes in the radiative response with climate state. Higher concentrations of greenhouse gases and higher temperatures lead to more absorption and emission of longwave radiation. Changes in cloud feedbacks are dominated by the climate response to temperature change, while the lapse rate and albedo feedbacks combine elements of both. Simulations with a slab ocean model (SOM) version of the GCMare used to verify whether an SOM-GCM accurately reproduces the behavior of the fully coupled model. Although feedbacks differ in magnitude between model configurations (with differences as large as those between CO2 doublings for some feedbacks), changes in feedbacks between CO2 doublings are consistent in sign andmagnitude in the SOM-GCM and the fully coupled model. © 2013 American Meteorological Society."
"7401711350;35290774700;","An observation-based assessment of nonlinear feedback processes associated with the indian ocean dipole",2013,"10.1175/JCLI-D-12-00483.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876906040&doi=10.1175%2fJCLI-D-12-00483.1&partnerID=40&md5=0ff90a702bea9a276451625ad6b3afd3","A well-known feature of the Indian Ocean dipole (IOD) is its positive skewness, with cold sea surface temperature (SST) anomalies over the east pole (IODE) exhibiting a larger amplitude than warm SST anomalies. Several mechanisms have been proposed for this asymmetry, but because of a lack of observations the role of various processes remains contentious. Using Argo profiles and other newly available data, the authors provide an observation-based assessment of the IOD skewness. First, the role of a nonlinear dynamical heating process is reaffirmed, which reinforces IODE cold anomalies but damps IODE warm anomalies. This reinforcing effect is greater than the damping effect, further contributing to the skewness. Second, the existence of a thermocline-temperature feedback asymmetry, whereby IODE cold anomalies induced by a shoaling thermocline are greater than warm anomalies associated with a deepening thermocline, is the primary forcing of the IOD skewness. This thermocline-temperature feedback asymmetry is a part of the nonlinear Bjerknes-like positive feedback loop involving winds, SST, and the thermocline, all displaying a consistent asymmetry with a stronger response when IODE SST is anomalously cold. The asymmetry is enhanced by a nonlinear barrier layer response, with a greater thinning associated with IODE cold anomalies than a thickening associated with IODE warm anomalies. Finally, in response to IODE cool anomalies, rainfall and evaporative heat loss diminish and incoming shortwave radiation increases, which results in damping the cool SST anomalies. The damping increases with IODE cold anomalies. Thus, the IOD skewness is generated in spite of a greater damping effect of the SST-cloud-radiation feedback process. © 2013 American Meteorological Society."
"8135796400;15827760700;8602071600;6602546166;8594721700;56083112000;7103297632;7006728329;7005744555;","Improving the performance of infrared reflective night curtains for warming field plots",2013,"10.1016/j.agrformet.2013.01.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875114412&doi=10.1016%2fj.agrformet.2013.01.004&partnerID=40&md5=b74a91edaeb9f5433bfb46af7640d641","Infrared reflective (IR) curtains have been widely used to obtain passive nighttime warming in field ecosystem experiments in order to simulate and study climate warming effects on ecosystems. For any field installation with IR-reflective curtains in an ecosystem the achieved heating effect depends on the heat gain determined by the stored energy during daytime (incoming radiation can be used as a proxy) the heat conservation determined by the IR-reflective effect of the curtains (cloudiness can be used as a proxy) and the heat loss determined by convectional heat loss (wind speed can be used as a proxy). In this study, we demonstrate some feasible avenues for improving the achieved temperature increase (Δ. T) when using IR-reflective curtains at field scale by attacking the three main factors determining the efficiency of the curtains: (i) improving the long wave IR reflection by the curtains, (ii) insulating the curtains and (iii) reducing the lateral wind speed. We provide experimentally based replies to the major concerns raised in the literature about the passive nighttime warming method. We show (a) that using IR-reflective curtains during night does in fact not result in nighttime warming only as there is a small carryover (<0.5. °C) into the following daytime, and (b) although the employment of IR-reflective curtains at nighttime may alter the RH, it is a small change and not always in the same direction. © 2013 Elsevier B.V."
"56384704800;55717074000;56162305900;7006303509;23065650200;55463274000;35494005000;","Evaluating and constraining ice cloud parameterizations in CAM5 using aircraft measurements from the SPARTICUS campaign",2013,"10.5194/acp-13-4963-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896755723&doi=10.5194%2facp-13-4963-2013&partnerID=40&md5=bb0bbe5c474c01eee002b09a184fe2ef","This study uses aircraft measurements of relative humidity and ice crystal size distribution collected during the SPARTICUS (Small PARTicles In CirrUS) field campaign to evaluate and constrain ice cloud parameterizations in the Community Atmosphere Model version 5. About 200h of data were collected during the campaign between January and June 2010, providing the longest aircraft measurements available so far for cirrus clouds in the midlatitudes. The probability density function (PDF) of ice crystal number concentration (N i) derived from the high-frequency (1 Hz) measurements features a strong dependence on ambient temperature. As temperature decreases from -35 °C to -62 °C, the peak in the PDF shifts from 10-20 L-1 to 200-1000 L-1, while Ni shows a factor of 6-7 increase. Model simulations are performed with two different ice nucleation schemes for pure ice-phase clouds. One of the schemes can reproduce a clear increase of Ni with decreasing temperature by using either an observation-based ice nuclei spectrum or a classical-theory-based spectrum with a relatively low (5-10%) maximum freezing ratio for dust aerosols. The simulation with the other scheme, which assumes a high maximum freezing ratio (100%), shows much weaker temperature dependence of Ni. Simulations are also performed to test empirical parameters related to water vapor deposition and the autoconversion of ice crystals to snow. Results show that a value between 0.05 and 0.1 for the water vapor deposition coefficient, and 250 μm for the critical diameter that distinguishes ice crystals from snow, can produce good agreement between model simulation and the SPARTI-CUS measurements in terms of Ni and effective radius. The climate impact of perturbing these parameters is also discussed. © Author(s) 2013."
"24343173500;8657166100;21741206300;8084443000;15833742800;7006107059;7103337730;35345729700;7403401100;57189215242;57050508600;7006808794;6505637161;7004015298;","Overview of aerosol properties associated with air masses sampled by the ATR-42 during the EUCAARI campaign (2008)",2013,"10.5194/acp-13-4877-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896694140&doi=10.5194%2facp-13-4877-2013&partnerID=40&md5=92ff74a717aa5c0222140c05259f125d","Within the frame of the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Météo-France aircraft ATR-42 performed 22 research flights over central Europe and the North Sea during the intensive observation period in May 2008. For the campaign, the ATR-42 was equipped to study the aerosol physical, chemical, hygroscopic and optical properties, as well as cloud microphysics. For the 22 research flights, retroplume analyses along the flight tracks were performed with FLEX-PART in order to classify air masses into five sectors of origin, allowing for a qualitative evaluation of emission influence on the respective air parcel. This study shows that the extensive aerosol parameters (aerosol mass and number concentrations) show vertical decreasing gradients and in some air masses maximum mass concentrations (mainly organics) in an intermediate layer (1-3 km). The observed mass concentrations (in the boundary layer (BL): between 10 and 30 μg m-3; lower free troposphere (LFT): 0.8 and 14μg m -3) are high especially in comparison with the 2015 European norms for PM2.5 (25 μg m-3) and with previous airborne studies performed over England (Morgan et al., 2009; McMeeking et al., 2012). Particle number size distributions show a larger fraction of particles in the accumulation size range in the LFT compared to BL. The chemical composition of submicron aerosol particles is dominated by organics in the BL, while ammonium sulphate dominates the submicron aerosols io n n the LFT, especially in the aerosol particles originated from north-eastern Europe (∼ 80%), also experiencing nucleation events along the transport. As a consequence, first the particle CCN acting ability, shown by the CCN/CN ratio, and second the average values of the scattering cross sections of optically active particles (i.e. scattering coefficiG e ent divided by the optical active particle concentration) are increased in thm e e LFT compared to BL. © Author(s) 2013."
"55939316400;24467868900;6602905171;","Phenology estimation from meteosat second generation data",2013,"10.1109/JSTARS.2013.2259577","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880284645&doi=10.1109%2fJSTARS.2013.2259577&partnerID=40&md5=56f901a8e20385cbd3e28e9dc8229a75","Many studies have focused on land surface phenology, for example as a means to characterize both water and carbon cycles for climate model inputs. However, the Spinning Enhanced Visible Infra-Red Imager (SEVIRI) sensor onboard Meteosat Second Generation (MSG) geostationary satellite has never been used for this goal. Here, five years of MSG-SEVIRI data have been processed to retrieve Normalized Difference Vegetation Index (NDVI) daily time series. Due to existing gaps as well as atmospheric and cloud contamination in the time series, an algorithm based on the iterative Interpolation for Data Reconstruction (IDR) has been developed and applied to SEVIRI NDVI time series, from which phenological parameters have been retrieved. The modified IDR (M-IDR) algorithm shows results of a similar quality to the original method, while dealing more efficiently with increased temporal resolution. The retrieved phenological phases were then analyzed and compared with an independent MODIS (Moderate resolution Imaging Spectrometer) dataset. Comparison of SEVIRI and MODIS-derived phenology with a pan-European ground phenology record shows a high accuracy of the SEVIRI-retrieved green-up and brown-down dates (within days) for most of the selected European validation sites, while differences with MODIS product are higher although this can be explained by differences in methodology. This confirms the potential of MSG data for phenological studies, with the advantage of a quicker availability of the data. © 2013 IEEE."
"8443691700;50162813600;36350395000;11940377800;","Characterizing spatiotemporal non-stationarity in vegetation dynamics in China using MODIS EVI dataset",2013,"10.1007/s10661-013-3231-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885482059&doi=10.1007%2fs10661-013-3231-2&partnerID=40&md5=6b0dbe002ca9c4fb8d46edcd47b70613","This paper evaluated the spatiotemporal non-stationarity in the vegetation dynamic based on 1-km resolution 16-day composite Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) datasets in China during 2001-2011 through a wavelet transform method. First, it revealed from selected pixels that agricultural crops, natural forests, and meadows were characterized by their distinct intra-annual temporal variation patterns in different climate regions. The amplitude of intra-annual variability generally increased with latitude. Second, parameters calculated using a per-pixel strategy indicated that the natural forests had the strongest variation pattern from seasonal to semiannual scales, and the multiple-cropping croplands typically showed almost equal variances distributed at monthly, seasonal, and semiannual scales. Third, spatiotemporal non-stationarity induced from cloud cover was also evaluated. It revealed that the EVI temporal profiles were significantly distorted with regular summer cloud cover in tropical and subtropical regions. Nevertheless, no significant differences were observed from those statistical parameters related to the interannual and interannual components between the de-clouded and the original MODIS EVI datasets across the whole country. Finally, 12 vegetation zones were proposed based on spatiotemporal variability, as indicated by the magnitude of interannual and intra-annual dynamic components, normalized wavelet variances of detailed components from monthly to semiannual scale, and proportion of cloud cover in summer. This paper provides insightful solutions for addressing spatiotemporal non-stationarity by evaluating the magnitude and frequency of vegetation variability using monthly, seasonal, semiannual to interannual scales across the whole study area. © 2013 Springer Science+Business Media Dordrecht."
"56180537800;7403959475;","Investigating coupled impacts of climate change and socioeconomic transformation on desertification by using multitemporal landsat images: A case study in central Xilingol, China",2013,"10.1109/LGRS.2013.2257158","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879915701&doi=10.1109%2fLGRS.2013.2257158&partnerID=40&md5=cf172ff920663eee007b94177064e697","A case study is conducted in Xilingol Rangeland, Inner Mongolia, China, to investigate the driving factors of temporal dynamics of desertification by using time-series Landsat images. The spectral characters of sand dunes and urban lands in the arid and semiarid grassland environments are very similar, and thus, it is hard to discriminate them with traditional image classifiers. Nine available scenes of Landsat images without cloud cover from 1985 to 2010 are chosen for the case study. An object-oriented image classification (OOIC) is developed to classify sand dunes. The classification results are assessed with the ground reference points in 1985, 2004, and 2010, the land-cover maps produced from other classifiers in literature, and Google Earth historical aerial photo archives. Second, the areas of sand dunes derived from OOIC at the nine times are extrapolated into a 26-year time-series data set from 1985 to 2010 by applying several extrapolation techniques commonly used in regional geographic studies. Afterward, six climate factors and nine socioeconomic variables during the same study period along with the sand dune area are composed into a completed data set to investigate the coupled impacts of climate change and socioeconomic transformation on the temporal dynamics of desertification. Three types of regression models (climate model, economic model, and the coupled model) are explored, respectively, to examine which factors contribute more to the desertification dynamics. The findings confirm that the desertification process in Xilingol Rangeland is very complicated although it shows a strong causal relationship with several socioeconomic factors. © 2004-2012 IEEE."
"23487049000;9043417100;56442378900;6604015058;6601927317;57141453800;34768718200;7004740995;6701834052;","The accommodation coefficient of water molecules on ice -cirrus cloud studies at the AIDA simulation chamber",2013,"10.5194/acp-13-4451-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876951466&doi=10.5194%2facp-13-4451-2013&partnerID=40&md5=b681937163cd85cac058c302392b7d0a","Cirrus clouds and their impact on the Earth's radiative budget are subjects of current research. The processes governing the growth of cirrus ice particles are central to the radiative properties of cirrus clouds. At temperatures relevant to cirrus clouds, the growth of ice crystals smaller than a few microns in size is strongly influenced by the accommodation coefficient of water molecules on ice, αice, making this parameter relevant for cirrus cloud modeling. However, the experimentally determined magnitude of αice for cirrus temperatures is afflicted with uncertainties of almost three orders of magnitude, and values for αice derived from cirrus cloud data lack significance so far. This has motivated dedicated experiments at the cloud chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) to determine αice in the cirrus-relevant temperature interval between 190K and 235K under realistic cirrus ice particle growth conditions. The experimental data sets have been evaluated independently with two model approaches: the first relying on the newly developed model SIGMA (Simple Ice Growth Model for determining Alpha), the second one on an established model, ACPIM (Aerosol-Cloud-Precipitation Interaction Model). Within both approaches a careful uncertainty analysis of the obtained αice values has been carried out for each AIDA experiment. The results show no significant dependence of αice on temperature between 190K and 235 K. In addition, we find no evidence for a dependence of αice on ice particle size or on water vapor supersaturation for ice particles smaller than 20 μm and supersaturations of up to 70 %. The temperature-averaged and combined result from both models is αice = 0.7+0.3 -0.5, which implies that αice may only exert a minor impact on cirrus clouds and their characteristics when compared to the assumption of αice = 1. Impact on prior calculations of cirrus cloud properties, e.g., in climate models, with αice typically chosen in the range 0.2-1 is thus expected to be negligible. In any case, we provide a well-constrained αice which future cirrus model studies can rely on. © Author(s) 2013."
"55192481900;6602511330;6701751351;23488276300;6602069539;35274451400;8918265400;16309022200;35599167600;7005625573;15819409900;35601505500;8583900200;9133990200;6603609485;7003395962;6602256545;6507078612;","Evaluation of the potential of MODIS satellite data to predict vegetation phenology in different biomes: An investigation using ground-based NDVI measurements",2013,"10.1016/j.rse.2013.01.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873595818&doi=10.1016%2fj.rse.2013.01.010&partnerID=40&md5=2a5f58d043d6dffccbd40c8d2e8b752e","Vegetation phenology is the study of the timing of seasonal events that are considered to be the result of adaptive responses to climate variations on short and long time scales. In the field of remote sensing of vegetation phenology, phenological metrics are derived from time series of optical data. For that purpose, considerable effort has been specifically focused on developing noise reduction and cloud-contaminated data removal techniques to improve the quality of remotely-sensed time series. Comparative studies between time series composed of satellite data acquired under clear and cloudy conditions and from radiometric data obtained with high accuracy from ground-based measurements constitute a direct and effective way to assess the operational use and limitations of remote sensing for predicting the main plant phenological events. In the present paper, we sought to explicitly evaluate the potential use of MODerate resolution Imaging Spectroradiometer (MODIS) remote sensing data for monitoring the seasonal dynamics of different types of vegetation cover that are representative of the major terrestrial biomes, including temperate deciduous forests, evergreen forests, African savannah, and crops. After cloud screening and filtering, we compared the temporal patterns and phenological metrics derived from in situ NDVI time series and from MODIS daily and 16-composite products. We also evaluated the effects of residual noise and the influence of data gaps in MODIS NDVI time series on the identification of the most relevant metrics for vegetation phenology monitoring. The results show that the inflexion points of a model fitted to a MODIS NDVI time series allow accurate estimates of the onset of greenness in the spring and the onset of yellowing in the autumn in deciduous forests (RMSE ≤ one week). Phenological metrics identical to those provided with the MODIS Global Vegetation Phenology product (MDC12Q2) are less robust to data gaps, and they can be subject to large biases of approximately two weeks or more during the autumn phenological transitions. In the evergreen forests, in situ NDVI time series describe the phenology with high fidelity despite small temporal changes in the canopy foliage. However, MODIS is unable to provide consistent phenological patterns. In crops and savannah, MODIS NDVI time series reproduce the general temporal patterns of phenology, but significant discrepancies appear between MODIS and ground-based NDVI time series during very localized periods of time depending on the weather conditions and spatial heterogeneity within the MODIS pixel. In the rainforest, the temporal pattern exhibited by a MODIS 16-day composite NDVI time series is more likely due to a pattern of noise in the NDVI data structure according to both rainy and dry seasons rather than to phenological changes. More investigations are needed, but in all cases, this result leads us to conclude that MODIS time series in tropical rainforests should be interpreted with great caution. © 2013 Elsevier Inc."
"6701540733;57207137435;7102084129;7402955395;7404369915;15019520200;55758342200;35461763400;6602545588;6701858531;6701709428;8372115100;7005697875;55758582200;6602638061;57204303593;8953038700;7005742394;56270311300;24298924900;7102604282;55942083800;6602600408;55947921200;7201504886;55757897400;55502994400;","An innovative satellite mission concept to measure the effects of aerosols on clouds and climate",2013,"10.1175/BAMS-D-11-00239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878714796&doi=10.1175%2fBAMS-D-11-00239.1&partnerID=40&md5=3e5cbdc5c0f97dd8244a5fec46ab34cd","The Clouds, Hazards, and Aerosols Survey for Earth Researchers (CHASER) satellite mission concept responds to the IPCC and Decadal Survey concerns by studying the activation of CCN and their interactions with clouds and storms. The CHASER satellite mission was developed to remotely sense quantities necessary for determining the interactions of aerosols with clouds and storms. CHASER will make the first global survey of Na, the activated CCN spectrum, and the vertical profiles of cloud properties directly affecting climate. CHASER will complement and transcend current National Aeronautics and Space Administration (NASA) Earth Science Missions studying aerosols, clouds, and thunderstorms. CHASER will determine vertical profiles of cloud parameters and lightning flashes pointing 30° off track toward sun-illuminated cloud surfaces, which minimizes shadowing. CHASER will use a high-heritage Cloud Profiler Suite (CPS) consisting of two instruments pointing 30° off nadir across track toward sun-illuminated surfaces on the east."
"7404142321;13402835300;7003332823;55746159100;8866821900;55686667100;7006698304;7402064802;7004764167;7402435469;","The transpose-AMIP II experiment and its application to the understanding of southern ocean cloud biases in climate models",2013,"10.1175/JCLI-D-12-00429.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874810896&doi=10.1175%2fJCLI-D-12-00429.1&partnerID=40&md5=d449e22db7645b13f43d3ff37ff11080","The Transpose-Atmospheric Model Intercomparison Project (AMIP) is an international model intercomparison project in which climate models are run in ""weather forecast mode.""The Transpose-AMIP II experiment is run alongside phase 5 of the Coupled Model Intercomparison Project (CMIP5) and allows processes operating in climate models to be evaluated, and the origin of climatological biases to be explored, by examining the evolution of the model from a state in which the large-scale dynamics, temperature, and humidity structures are constrained through use of common analyses. The Transpose-AMIP II experimental design is presented. The project requests participants to submit a comprehensive set of diagnostics to enable detailed investigation of the models to be performed. An example of the type of analysis that may be undertaken using these diagnostics is illustrated through a study of the development of cloud biases over the Southern Ocean, a region that is problematic for many models. Several models share a climatological bias for too little reflected shortwave radiation from cloud across the region. This is found to mainly occur behind cold fronts and/or on the leading side of transient ridges and to be associated with more stable lower-tropospheric profiles. Investigation of a case study that is typical of the bias and associated meteorological conditions reveals the models to typically simulate cloud that is too optically and physically thin with an inversion that is too low. The evolution of the models within the first few hours suggests that these conditions are particularly sensitive and a positive feedback can develop between the thinning of the cloud layer and boundary layer structure. © 2013 American Meteorological Society."
"57196263581;15032788000;","A simple framework for the dynamic response of cirrus clouds to local diabatic radiative heating",2013,"10.1175/JAS-D-12-056.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877324416&doi=10.1175%2fJAS-D-12-056.1&partnerID=40&md5=af41a0f571eb3c8379ebaadec48aebae","This paper presents a simple analytical framework for the dynamic response of cirrus to a local radiative flux convergence, expressible in terms of three independent modes of cloud evolution. Horizontally narrow and tenuous clouds within a stable environment adjust to radiative heating by ascending gradually across isentropes while spreading sufficiently fast that isentropic surfaces stay nearly flat. Alternatively, optically dense clouds experience very concentrated heating, and if they are also very broad, they develop a convecting mixed layer. Along-isentropic spreading still occurs, but in the form of turbulent density currents rather than laminar flows. A third adjustment mode relates to evaporation, which erodes cloudy air as it lofts, regardless of its optical density. The dominant mode is determined from two dimensionless numbers, whose predictive power is shown in comparisons with high-resolution numerical cloud simulations. The power and simplicity of the approach hints that fast, subgrid-scale radiative-dynamic atmospheric interactions might be efficiently parameterized within slower, coarse-grid climate models. © 2013 American Meteorological Society."
"57188557549;25227905500;9942293700;14520880100;22979219200;16052866300;","CloudSat-CALIPSO characterizations of cloud during the active and the break periods of Indian summer monsoon",2013,"10.1016/j.jastp.2013.02.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875871976&doi=10.1016%2fj.jastp.2013.02.016&partnerID=40&md5=95103f6d5e35be0efbdb0b374ea104ac","Here we report cloud macrophysical (cloud top height (CTH), cloud base height (CBH), cloud geometrical depth), microphysical (liquid and ice water contents, water paths, effective radii and number concentration) and radiative (heating rate) properties over the North Central India (18-28°N, 65-88°E) region (core monsoon zone) during the active and the break periods (2006-2010) of the Indian summer monsoon (ISM). Synergetic data from the CloudSat radar and the CALIPSO lidar are used. Analysis shows that the CTH and CBH have bimodal distributions during both the phases of monsoon. We have classified clouds into four type's viz., high-, mid-, low- and vertically extended deep clouds. The low-level clouds and optically thick cirrus are more dominant of the total observations and they occur more frequently during the active period compared to that of the break period. In contrast, the high-level clouds and optically thin cirrus are more frequent during the break phase of monsoon. The integrated depolarization ratio of high-level cloud exhibits bimodal distribution. It is observed that there is a significant variation in macrophysical, microphysical, optical and radiative properties of all the four types of clouds during the active and the break periods. As little observational evidence exists in the vertical structure of clouds during the active and the break periods of the ISM, the current results would be useful in understanding the characteristics of monsoon clouds, which have implications in the Earth's radiation budget and global climate models. © 2013 Elsevier Ltd."
"55577875600;55717074000;7406500188;56162305900;","A numerical study of the effect of different aerosol types on East Asian summer clouds and precipitation",2013,"10.1016/j.atmosenv.2012.12.039","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873250755&doi=10.1016%2fj.atmosenv.2012.12.039&partnerID=40&md5=b00e80f6b30d86347a40cc89e7b87327","In this study, the anthropogenic aerosol impact on the summer monsoon clouds and precipitation in East Asia is investigated using the NCAR Community Atmospheric Model version 5 (CAM5), a state-of-the-art climate model considering aerosol direct, semi-direct and indirect effects. The effects of all anthropogenic aerosols, and anthropogenic black carbon (BC), sulfate, and primary organic matter (POM) are decomposed from different sensitivity simulations. Anthropogenic sulfate and POM reduce the solar flux reaching the surface directly by scattering the solar radiation, and indirectly by increasing the cloud droplet number concentration and cloud liquid water path over East China. The surface air temperature over land is reduced, and the precipitation in North China is suppressed. Unlike anthropogenic sulfate and POM, anthropogenic BC does not have a significant effect on the air temperature at the surface, because of the reduction of the cloud liquid water path and the weakening of shortwave cloud forcing by its semi-direct effect. The anthropogenic BC strengthens the southwesterly wind over South China and leads to stronger deep convection at the 25°N-30°N latitudinal band. The effect of all anthropogenic aerosols on air temperature, clouds, and precipitation is not a linear summation of effects from individual anthropogenic sulfate, BC and POM. Overall all anthropogenic aerosols suppress the precipitation in North China and enhance the precipitation in South China and adjacent ocean regions. © 2013 Elsevier Ltd."
"7102403008;7006019301;37102073800;24479033900;6507612700;","The changing energy balance of the polar regions in a warmer climate",2013,"10.1175/JCLI-D-12-00233.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878155033&doi=10.1175%2fJCLI-D-12-00233.1&partnerID=40&md5=f1aa2949fc38b236abff57af9c2f142e","Energy fluxes for polar regions are examined for two 30-yr periods, representing the end of the twentieth and twenty-first centuries, using data from high-resolution simulations with the ECHAM5 climate model. The net radiation to space for the present climate agrees well with data from the Clouds and the Earth's Radiant Energy System (CERES) over the northern polar region but shows an underestimation in planetary albedo for the southern polar region. This suggests there are systematic errors in the atmospheric circulation or in the net surface energy fluxes in the southern polar region. The simulation of the future climate is based on the Intergovernmental Panel on Climate Change (IPCC)A1B scenario. The total energy transport is broadly the same for the two 30-yr periods, but there is an increase in the moist energy transport on the order of 6 W m-2 and a corresponding reduction in the dry static energy. For the southern polar region the proportion of moist energy transport is larger and the dry static energy correspondingly smaller for both periods. The results suggest a possible mechanism for the warming of the Arctic that is discussed. Changes between the twentieth and twenty-first centuries in the northern polar region show the net ocean surface radiation flux in summer increases~18 W m-2 (24%). For the southern polar region the response is different as there is a decrease in surface solar radiation. It is suggested that this is caused by changes in cloudiness associated with the poleward migration of the storm tracks. © 2013 American Meteorological Society."
"6602137554;50162103900;6602780143;","Modeling the effect of temperature, solar radiation and salinity on Bolboschoenus maritimus sequestration of mercury",2013,"10.1016/j.ecolmodel.2013.02.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875307249&doi=10.1016%2fj.ecolmodel.2013.02.013&partnerID=40&md5=d37e30646c803c0c11715be40ca862b4","Some tidal wetland halophytes are extremely important for pollution control but due to global climate change, wetlands and their ecosystem services may suffer considerable modifications. In this context we modeled the growth and mercury (Hg) sequestration by Bolboschoenus maritimus on the most contaminated area of a temperate shallow coastal lagoon historically subjected to heavy Hg load, under gradients of climate driven variables. For calibration purposes we used field data on temperature, salinity, solar radiation, plant biomass, plant decomposition and mercury concentration in the plants. Ten different methods evaluated model performance. We then simulated B. maritimus mercury sequestration under different environmental scenarios involving increases and decreases in temperature, salinity and cloud cover. The largest effects were related to high salinity scenarios but all variables presented an inverse relation with Hg-sequestration. Our results point to a progressive decrease on Hg-sequestration until the end of the century. © 2013 Elsevier B.V."
"57190227631;55745955800;7401806579;","Sensitivity of simulated climate to two atmospheric models: Interpretation of differences between dry models and moist models",2013,"10.1175/MWR-D-11-00367.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878199629&doi=10.1175%2fMWR-D-11-00367.1&partnerID=40&md5=54d4041202a6b196858988e355875f95","The dynamical core of the Institute of Atmospheric Physics of theChinese Academy of SciencesAtmospheric General Circulation Model (IAP AGCM) and the Eulerian spectral transform dynamical core of the CommunityAtmosphereModel, version 3.1 (CAM3.1), developed at theNational Center forAtmosphericResearch (NCAR) are used to study the sensitivity of simulated climate. The authors report thatwhen the dynamical cores are used with the same CAM3.1 physical parameterizations of comparable resolutions, the model with the IAP dynamical core simulated a colder troposphere than that from the CAM3.1 core, reducing the CAM3.1 warm bias in the tropical and midlatitude troposphere. However, when the two dynamical cores are used in the idealized Held-Suarez tests without moisture physics, the IAP AGCM core simulated a warmer troposphere than that in CAM3.1. The causes of the differences in the full models and in the dry models are then investigated. The authors show that the IAP dynamical core simulated weaker eddies in both the full physics and the dry models than those in the CAM due to different numerical approximations. In the dry IAP model, the weaker eddies cause smaller heat loss from poleward dynamical transport and thus warmer troposphere in the tropics and midlatitudes. When moist physics is included, however, weaker eddies also lead to weaker transport of water vapor and reduction of high clouds in the IAP model, which then causes a colder troposphere due to reduced greenhouse warming of these clouds. These results show how interactive physical processes can change the effect of a dynamical core on climate simulations between two models. © 2013 American Meteorological Society."
"55717075800;55207477400;7004960339;46761494200;35093720000;55726314800;55783129300;57203768638;55664298600;35254633000;","A 400-year tree-ring δ18O chronology for the southeastern Tibetan Plateau: Implications for inferring variations of the regional hydroclimate",2013,"10.1016/j.gloplacha.2013.02.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875275711&doi=10.1016%2fj.gloplacha.2013.02.005&partnerID=40&md5=4004114e8c53016e1754210ab1f94334","We developed a new tree-ring cellulose δ18O chronology for the southeastern Tibetan Plateau from Balfour spruce (Picea likiangensis var. balfouriana [Rehd. et Wils.]) that covered the period from 1600 to 2008, and compared the results with a previous study to explore climatic variations in the Nyingchi-Bomi area. Our tree-ring δ18O chronology correlated significantly with the previous study (Shi et al., 2012; Climate of the Past 8, 205-213) during the common period from 1781 to 2005, and provided new insights into long-term regional hydroclimatic variations. Besides the significant positive correlations between tree-ring δ18O and the temperature and sunshine duration during the growing season, tree-ring δ18O was strongly negatively correlated with regional cloud cover, relative humidity, and precipitation in July and August. The correlations with cloud cover data were stronger than in previous research, but the correlations with precipitation and relative humidity in July and August were weaker. When Indian summer monsoon conditions prevail, regional hydroclimate variations (and especially cloud cover) have the dominant influence on tree-ring δ18O in the study area. Based on the regional data, δ18O in tree rings can be an effective proxy to infer the temporal variations in regional hydroclimatic conditions and the strength of the Indian Summer Monsoon. Our results reveal that the Indian Summer Monsoon weakened from 1600 to 1650, followed by continuous strengthening until 1740 and a slight weakening from 1740 to present. The temporal variations in the cellulose δ18O chronology generally corresponded well to the δ18O and glacier snow accumulation records found in ice cores from the middle Himalaya. © 2013 Elsevier B.V."
"7003679645;7003569006;","Climate change simulated by full and mixed-layer ocean versions of CSIRO Mk3.5 and Mk3.0: Large-scale sensitivity",2013,"10.1007/s13143-013-0035-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880013217&doi=10.1007%2fs13143-013-0035-9&partnerID=40&md5=a0fab9afcd58b26108a7b81f9be725a2","The CSIRO Mk3.5 coupled atmosphere-ocean model includes upgrades to atmospheric and oceanic processes that remove a cold bias of the earlier Mk3.0. The global mean warming over the 21st century from Mk3.5 is 3.1 K under the CMIP3 A1B scenario, some 25% larger than that from Mk3.0. Two mixed-layer ocean versions of Mk3.5 were constructed, and these are also more sensitive than Mk3.0. To elucidate these differences, a simple feedback analysis is extended to Mk3.5, using changes for doubled CO2 in each model version. The net feedback for the low-mid latitude region is the main driver of the sensitivity contrast. The clear-sky component is consistently larger in Mk3.5, as is the increase in specific humidity, even after standardizing by the global warming. Cloud forcing provides a small positive feedback, which is stronger in cases that had larger declines in low-layer cloud. The net positive feedback for the higher-latitude region is larger in the coupled Mk3.5 than Mk3.0, which had more stable Arctic sea ice. However, some contrasts differed among the versions. As for Mk3.0, the surface warming in the coupled Mk3.5 is suppressed over that from the MLO case. Over the ocean, the pattern of suppression is similar to the change in energy flux into the surface in the coupled model. There is also a gradient of equatorial warming in the Asia-Pacific region that relates to the change in net convergence of heat transport by ocean currents. The effect of this pattern on regional rainfall is a focus of Part 2 of the study. © 2013 Korean Meteorological Society and Springer Science+Business Media Dordrecht."
"54897465300;7202145115;","On the speed of the eddy-driven jet and the width of the hadley cell in the southern hemisphere",2013,"10.1175/JCLI-D-12-00414.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878159039&doi=10.1175%2fJCLI-D-12-00414.1&partnerID=40&md5=9a225c67d3b1e9e16c496c48f7c762a3","A strong correlation between the speed of the eddy-driven jet and the width of the Hadley cell is found to exist in the Southern Hemisphere, both in reanalysis data and in twenty-first-century integrations from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report multimodel archive. Analysis of the space-time spectra of eddy momentum flux reveals that variations in eddy-driven jet speed are related to changes in the mean phase speed of midlatitude eddies. An increase in eddy phase speeds induces a poleward shift of the critical latitudes and a poleward expansion of the region of subtropical wave breaking. The associated changes in eddy momentum flux convergence are balanced by anomalous meridional winds consistent with a wider Hadley cell. At the same time, faster eddies are also associated with a strengthened poleward eddy momentum flux, sustaining a stronger westerly jet in midlatitudes. The proposed mechanism is consistent with the seasonal dependence of the interannual variability of the Hadley cell width and appears to explain at least part of the projected twenty-first-century trends. © 2013 American Meteorological Society."
"55577260000;55081428900;55969563500;35228858900;45661228900;55493237300;36909370500;7402196015;55969360800;55969439400;55661410200;55969561300;57191720827;","How do extreme wet events affect rice quality in a changing climate?",2013,"10.1016/j.agee.2013.03.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876704466&doi=10.1016%2fj.agee.2013.03.006&partnerID=40&md5=8ea0b7cc6cefbb84860427ed671faad4","Despite the growing body of evidence that ongoing warming modifies the cereal quality of several crop species, little is known about how it interacts with other climate change drivers. Here, we examined how elevated [CO2], warming, and extreme wet events (EWEs) would affect the grain quality of a temperate rice (Oryza sativa L.). In 2009 and 2010, plants were grown at two levels of [CO2] (c. 390 and 650μll-1) and three levels of warming (ambient, +1.2°C and +2.2/2.4°C) over the seasons in six independent temperature gradient field chambers (three each for ambient and elevated [CO2]). From 20 days after heading, plants were exposed to EWE with a simulated rainfall of 30mm a day and cloud cover by shading (c. 18% of full sunlight) for 10 consecutive days. There were also control plots, which were non-treated (NT) in terms of EWE. We found that warming and EWE, both independently and in their interaction, lead to a significant reduction in the percentages of sound grains, whereas elevated [CO2] does not seem to do so. Not only warming and EWE, but also elevated [CO2] resulted in a significant increase of immature chalky grains (ICGs), which mostly consisted of milky-white chalky grains, degrading the grain quality. In addition, warming interacted positively with elevated [CO2] on ICGs, whereas the warming sensitivity of IGCs was moderated in EWEs: e.g., on average, the % of ICGs in ambient vs. elevated [CO2] were 8.5% vs. 9.4%, 10.7% vs. 18.1% and 17.8% vs. 29.8% at ambient (24.7°C), +1.2°C and +2.4°C, respectively, whereas they in NT vs. EWE were 1.2% vs. 16.6%, 7.7% vs. 21.1% and 19.4% vs. 28.2%. Our results tightly confirmed that elevated [CO2] leads to a significant reduction in rice grain protein content (PC). While warming had little effect on the PC, EWE had a significant positive effect, and the EWE-induced increase in PC was smaller in elevated (+3.3%) than in ambient [CO2] (+10.9%). Given the rice quality predictor of ICGs and PC, our findings imply that expected climate change and weather extremes have a great potential to degrade the quality of rice, in terms of its milling, cooking, eating, and nutritional quality, as well as market value. © 2013 Elsevier B.V."
"7004617145;6701812159;36948127000;56246028600;","Range size and climatic niche correlate with the vulnerability of epiphytes to human land use in the tropics",2013,"10.1111/jbi.12050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876451979&doi=10.1111%2fjbi.12050&partnerID=40&md5=393544f78285227479bb55d4ba68edb8","Aim: Range-restricted species account for a large proportion of global biodiversity, and many such species are highly threatened by deforestation and intensifying land use in the tropics. The effects of land use on the diversity of range-restricted species have rarely been studied and remain unknown for vascular epiphytes - diverse and important elements of tropical forests. This study analyses the vulnerability of range-restricted epiphyte species to human land use, compared to that of widespread species. Location: Western Ecuador (Chocó ecoregion): lowland rain forest (Bilsa, 0°21′ N 79°44′ W, 450-650 m a.s.l.) and Andean cloud forest (Otonga, 0°25′ S 79°01′ W, 1650-2250 m a.s.l.). Methods: The epiphytic vegetation of 220 study plots was surveyed. Distribution data based on herbarium specimens were compiled for all identified species in order to estimate their geographical and elevational ranges as well as the climatic conditions within the species' ranges. These range characteristics were compared for species found in contiguous primary forests, primary forest fragments, secondary forests, and for isolated remnant trees in pastures. Results: Of the 587 identified epiphyte species, 252 were endemic to the Chocó ecoregion (42.9%). Chocó endemics were not more strongly affected by human land use than non-endemics. However, small geographical ranges and narrow climatic niches were associated with higher vulnerability to habitat changes caused by land use. Epiphyte assemblages in young secondary forests had the lowest proportions of range-restricted species and were dominated by species with broad elevational ranges. Species in secondary forests occupied the broadest ranges of mean annual temperature and precipitation; species on isolated remnant trees at the lowland site inhabited on average warmer and drier geographical ranges than species in the primary forest. Main conclusions: Epiphyte species with restricted geographical distributions and narrow climatic tolerances are particularly vulnerable to human-induced habitat changes, but endemism to national or biogeographical entities alone is a poor indicator of vulnerability. Instead, narrower ecological niches correlate with lower plasticity towards changes in microclimatic habitat conditions. Besides a higher extinction risk due to their small range sizes, many range-restricted species might be threatened by their lower tolerance to the impacts of human land use. © 2012 Blackwell Publishing Ltd."
"35435195400;7405489798;","Diabatic heating profiles in recent global reanalyses",2013,"10.1175/JCLI-D-12-00384.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878155319&doi=10.1175%2fJCLI-D-12-00384.1&partnerID=40&md5=bbb9d8d13b003aee15d0fc2924310d9c","Diabatic heating profiles are extremely important to the atmospheric circulation in the tropics and therefore to the earth's energy and hydrological cycles. However, their global structures are poorly known because of limited information from in situ observations. Some modern global reanalyses provide the temperature tendency from the physical processes. Their proper applications require an assessment of their accuracy and uncertainties. In this study, diabatic heating profiles from three recent global reanalyses [ECMWF Interim Re-Analysis (ERA-Interim), Climate Forecast System Reanalysis (CFSR), and Modern Era Retrospective Analysis for Research and Applications (MERRA)] are compared to those derived from currently available sounding observations in the tropics and to each other in the absence of the observations. Diabatic heating profiles produced by the reanalyses match well with those based on sounding observations only at some locations. The three reanalyses agree with each other better in the extratropics, where large-scale condensation dominates the precipitation process in data assimilation models, than in the tropics, where cumulus parameterization dominates. In the tropics, they only agree with each other in gross features, such as the contrast between the ITCZs over different oceans. Their largest disagreement is the number and level of heating peaks in the tropics. They may produce a single, double, or triple heating peak at a given location. It is argued that cumulus parameterization cannot be the sole source of the disagreement. Implications of such disagreement are discussed. © 2013 American Meteorological Society."
"36135669900;","Sea fog by southerly warm air over cool sea waters of the Southward North Korea cold current along the Korean East coast under cyclogenesis in the yellow sea",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878158630&partnerID=40&md5=1b446fdbe9bbfc4ed4e6a33f58e73426","Sea fog in the southeastern coastal sea of Korea was investigated on February 21 ̃ 23, 2005 by WRF 3.3 meteorological model, GOES-9 and NOAA-MCSST satellite images. On February 21, as a high pressure covers whole Korean peninsula, northwesterly in the Korean eastern coast caused moderate southwestward wind driven currents, resulting in southward littoral currents due to its coastal configuration. These currents caused further the intrusion of the North Korea Cold Current (NKCC) toward the south. Although air of 3 ̃ 70C by cold northwesterly wind from the northern China moved over a cool pool area off the Pohang coast and it was in the easy condition of evaporation of water droplets from the sea and condensation of water vapour to form fogs under the air and sea surface temperature differences of - 3 ̃ - 80C, strong marine surface dissipated fog droplet, resulting in 65% relative humidity (RH) with no formation of fog. However, as low pressure showing an anti-clockwise wind pattern on February 22 became more intensified in the Korean northwestern coast (cyclogenesis), southwesterly wind in the Korea northern coastal sea could cause southeastward wind driven currents, which induce upwelling of deep cold waters toward the sea surface and simultaneously these currents caused further the intrusion of the NKCC toward the southeastern open sea in about 100km away from Pohang city (a cool pool of 70C cold waters). As much warmer air of 7 ̃ 90C by strong southwesterly wind of 6 ̃ 11m/s moved over the cool pool in the open sea away from Pohang city, air and sea surface temperature difference was about 20C. So, the air over the cold sea must cool down to be saturated and water vapor in air to be condensed by salty condensation nuclei, resulting in the formation of sea fog or stratus cloud with 80% RH near the sea surface and vertically extended toward 1 km height."
"24341507700;16032479400;36598281300;8691336700;55667384900;24921885300;6603879924;6603035923;57202119596;","Spectral features of Earth-like planets and their detectability at different orbital distances around F, G, and K-type stars",2013,"10.1051/0004-6361/201117723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876571097&doi=10.1051%2f0004-6361%2f201117723&partnerID=40&md5=7110f3c47430c085c8bd6e0584ff4ee6","Context. In recent years, more and more transiting terrestrial extrasolar planets have been found. Spectroscopy already yielded the detection of molecular absorption bands in the atmospheres of Jupiter and Neptune-sized exoplanets. Detecting spectral features in the atmosphere of terrestrial planets is the next great challenge for exoplanet characterization. Aims. We investigate the spectral appearance of Earth-like exoplanets in the habitable zone (HZ) of different main sequence (F, G, and K-type) stars at different orbital distances. We furthermore discuss for which of these scenarios biomarker absorption bands and related compounds may be detected during primary or secondary transit with near-future telescopes and instruments. Methods. Atmospheric profiles from a 1D cloud-free atmospheric climate-photochemistry model were used to compute primary and secondary eclipse infrared spectra. The spectra were analyzed taking into account different filter bandpasses of two photometric instruments planned to be mounted to the James Webb Space Telescope (JWST). We analyzed in which filters and for which scenarios molecular absorption bands are detectable when using the space-borne JWST or the ground-based European Extremely Large Telescope (E-ELT). Results. Absorption bands of carbon dioxide (CO2), water (H2O), methane (CH4) and ozone (O3) are clearly visible in both high-resolution spectra as well as in the filters of photometric instruments. However, only during primary eclipse absorption bands of CO2, H2O and O3 are detectable for all scenarios when using photometric instruments and an E-ELT-like telescope setup. CH4 is only detectable at the outer HZ of the K-type star since here the atmospheric modeling results in very high abundances. Since the detectable CO2 and H2O absorption bands overlap, separate bands need to be observed to prove their existence in the planetary atmosphere. In order to detect H2O in a separate band, a ratio S/N &gt; 7 needs to be achieved for E-ELT observations, e.g. by co-adding at least 10 transit observations. Using a space-borne telescope like the JWST enables the detection of CO2 at 4.3 μm, which is not possible for ground-based observations due to the Earth's atmospheric absorption. Hence combining observations of space-borne and ground-based telescopes might allow to detect the presence of the biomarker molecule O3 and the related compounds H2O and CO2 in a planetary atmosphere. Other absorption bands using the JWST can only be detected for much higher S/Ns, which is not achievable by just co-adding transit observations since this would be far beyond the planned mission time of JWST. © 2013 ESO."
"57211379123;24511929800;7402989545;14059214300;","Variation of surface temperature during the last millennium in a simulation with the FGOALS-gl climate system model",2013,"10.1007/s00376-013-2178-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876435694&doi=10.1007%2fs00376-013-2178-0&partnerID=40&md5=4f2633e32489253a90d4ac5bf7098252","A reasonable past millennial climate simulation relies heavily on the specified external forcings, including both natural and anthropogenic forcing agents. In this paper, we examine the surface temperature responses to specified external forcing agents in a millennium-scale transient climate simulation with the fast version of LASG IAP Flexible Global Ocean-Atmosphere-Land System model (FGOALS-gl) developed in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP). The model presents a reasonable performance in comparison with reconstructions of surface temperature. Differentiated from significant changes in the 20th century at the global scale, changes during the natural-forcing-dominant period are mainly manifested in the Northern Hemisphere. Seasonally, modeled significant changes are more pronounced during the wintertime at higher latitudes. This may be a manifestation of polar amplification associated with sea-ice-temperature positive feedback. The climate responses to total external forcings can explain about half of the climate variance during the whole millennium period, especially at decadal timescales. Surface temperature in the Antarctic shows heterogeneous and insignificant changes during the preindustrial period and the climate response to external forcings is undetectable due to the strong internal variability. The model response to specified external forcings is modulated by cloud radiative forcing (CRF). The CRF acts against the fluctuations of external forcings. Effects of clouds are manifested in shortwave radiation by changes in cloud water during the natural-forcing-dominant period, but mainly in longwave radiation by a decrease in cloud amount in the anthropogenic-forcing-dominant period. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"57207473157;55899884100;","Shortwave cloud radiative forcing on major stratus cloud regions in AMIP-type simulations of CMIP3 and CMIP5 models",2013,"10.1007/s00376-013-2153-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876423455&doi=10.1007%2fs00376-013-2153-9&partnerID=40&md5=cb3e4a72be708b7a1a112cb731950ced","Cloud and its radiative effects are major sources of uncertainty that lead to simulation discrepancies in climate models. In this study, shortwave cloud radiative forcing (SWCF) over major stratus regions is evaluated for Atmospheric Models Intercomparison Project (AMIP)-type simulations of models involved in the third and fifth phases of the Coupled Models Intercomparison Project (CMIP3 and CMIP5). Over stratus regions, large deviations in both climatological mean and seasonal cycle of SWCF are found among the models. An ambient field sorted by dynamic (vertical motion) and thermodynamic (inversion strength or stability) regimes is constructed and used to measure the response of SWCF to large-scale controls. In marine boundary layer regions, despite both CMIP3 and CMIP5 models being able to capture well the center and range of occurrence frequency for the ambient field, most of the models fail to simulate the dependence of SWCF on boundary layer inversion and the insensitivity of SWCF to vertical motion. For eastern China, there are large differences even in the simulated ambient fields. Moreover, almost no model can reproduce intense SWCF in rising motion and high stability regimes. It is also found that models with a finer grid resolution have no evident superiority than their lower resolution versions. The uncertainties relating to SWCF in state-of-the-art models may limit their performance in IPCC experiments. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"57218273453;37022493200;7406250414;56424145700;7402989545;56003637600;57203367163;15830929400;7404438747;55656437900;25634562200;55656493400;55272861800;55656620500;24468389200;55656752500;55656321600;55656353100;55542833500;35119887100;7403590757;37105010900;35201784100;55715215300;7404976222;7103165085;8905764300;8684892000;35115649600;9845350200;","The flexible global ocean-atmosphere-land system model, Grid-point Version 2: FGOALS-g2",2013,"10.1007/s00376-012-2140-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874455373&doi=10.1007%2fs00376-012-2140-6&partnerID=40&md5=e55aeb3a399e234c6ead353a4aebc7af","This study mainly introduces the development of the Flexible Global Ocean-Atmosphere-Land System Model: Grid-point Version 2 (FGOALS-g2) and the preliminary evaluations of its performances based on results from the pre-industrial control run and four members of historical runs according to the fifth phase of the Coupled Model Intercomparison Project (CMIP5) experiment design. The results suggest that many obvious improvements have been achieved by the FGOALS-g2 compared with the previous version,FGOALS-g1, including its climatological mean states, climate variability, and 20th century surface temperature evolution. For example,FGOALS-g2 better simulates the frequency of tropical land precipitation, East Asian Monsoon precipitation and its seasonal cycle, MJO and ENSO, which are closely related to the updated cumulus parameterization scheme, as well as the alleviation of uncertainties in some key parameters in shallow and deep convection schemes, cloud fraction, cloud macro/microphysical processes and the boundary layer scheme in its atmospheric model. The annual cycle of sea surface temperature along the equator in the Pacific is significantly improved in the new version. The sea ice salinity simulation is one of the unique characteristics of FGOALS-g2, although it is somehow inconsistent with empirical observations in the Antarctic. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"14059214300;55487667200;57188863342;7404815507;57211379123;","Asymmetry of surface climate change under RCP2.6 projections from the CMIP5 models",2013,"10.1007/s00376-012-2151-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876453004&doi=10.1007%2fs00376-012-2151-3&partnerID=40&md5=3a4e6addc67dbdb34adef78e8778e1ca","The multi-model ensemble (MME) of 20 models from the Coupled Model Intercomparison Project Phase Five (CMIP5) was used to analyze surface climate change in the 21st century under the representative concentration pathway RCP2. 6, to reflect emission mitigation efforts. The maximum increase of surface air temperature (SAT) is 1. 86°C relative to the pre-industrial level, achieving the target to limit the global warming to 2°C. Associated with the ""increase-peak-decline"" greenhouse gases (GHGs) concentration pathway of RCP2. 6, the global mean SAT of MME shows opposite trends during two time periods: warming during 2006-55 and cooling during 2056-2100. Our results indicate that spatial distribution of the linear trend of SAT during the warming period exhibited asymmetrical features compared to that during the cooling period. The warming during 2006-55 is distributed globally, while the cooling during 2056-2100 mainly occurred in the NH, the South Indian Ocean, and the tropical South Atlantic Ocean. Different dominant roles of heat flux in the two time periods partly explain the asymmetry. During the warming period, the latent heat flux and shortwave radiation both play major roles in heating the surface air. During the cooling period, the increase of net longwave radiation partly explains the cooling in the tropics and subtropics, which is associated with the decrease of total cloud amount. The decrease of the shortwave radiation accounts for the prominent cooling in the high latitudes of the NH. The surface sensible heat flux, latent heat flux, and shortwave radiation collectively contribute to the especial warming phenomenon in the high-latitude of the SH during the cooling period. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"24468389200;57195423016;55220443400;15830929400;55754495900;7404976222;","Seasonal evolution of subtropical anticyclones in the climate system model FGOALS-s2",2013,"10.1007/s00376-012-2154-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876422479&doi=10.1007%2fs00376-012-2154-0&partnerID=40&md5=9f900cc2c4cf2ab45504559d6607f5f3","The simulation characteristics of the seasonal evolution of subtropical anticyclones in the Northern Hemisphere are documented for the Flexible Global Ocean-Atmosphere-Land Systemmodel, Spectral Version 2 (FGOALS-s2), developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, the Institute of Atmospheric Physics. An understanding of the seasonal evolution of the subtropical anticyclones is also addressed. Compared with the global analysis established by the European Centre for Medium-Range Forecasts, the ERA-40 global reanalysis data, the general features of subtropical anticyclones and their evolution are simulated well in both winter and summer, while in spring a pronounced bias in the generation of the South Asia Anticyclone(SAA) exists. Its main deviation in geopotential height from the reanalysis is consistent with the bias of temperature in the troposphere. It is found that condensation heating (CO) plays a dominant role in the seasonal development of the SAA and the subtropical anticyclone over the western Pacific (SAWP) in the middle troposphere. The CO biases in the model account for the biases in the establishment of the SAA in spring and the weaker strength of the SAA and the SAWP from spring to summer. CO is persistently overestimated in the central-east tropical Pacific from winter to summer, while it is underestimated over the area from the South China Sea to the western Pacific from spring to summer. Such biases generate an illusive anticyclonic gyre in the upper troposphere above the middle Pacific and delay the generation of the SAA over South Asia in April. In midsummer, the simulated SAA is located farther north than in the ERA-40 data owing to excessively strong surface sensible heating (SE) to the north of the Tibetan Plateau. Whereas, the two surface subtropical anticyclones in the eastern oceans during spring to summer are controlled mainly by the surface SE over the two continents in the Northern Hemisphere, which are simulated reasonably well, albeit with their centers shifted westwards owing to the weaker longwave radiation cooling in the simulation associated with much weaker local stratiform cloud. Further improvements in the related parameterization of physical processes are therefore identified. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"6701346974;56590724100;","Cloud-resolving modelling of aerosol indirect effects in idealised radiative-convective equilibrium with interactive and fixed sea surface temperature",2013,"10.5194/acp-13-4133-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882787274&doi=10.5194%2facp-13-4133-2013&partnerID=40&md5=12e03ea47bcc2245c6db13cf2253828f","The study attempts to evaluate the aerosol indirect effects over tropical oceans in regions of deep convection applying a three-dimensional cloud-resolving model run over a doubly-periodic domain. The Tropics are modelled using a radiative-convective equilibrium idealisation when the radiation, turbulence, cloud microphysics and surface fluxes are explicitly represented while the effects of large-scale circulation are ignored. The aerosol effects are modelled by varying the number concentration of cloud condensation nuclei (CCN) at 1% supersaturation, which serves as a proxy for the aerosol amount in the environment, over a wide range, from pristine maritime (50 cm-3) to polluted (1000 cm-3) conditions. No direct effects of aerosol on radiation are included. Two sets of simulations have been run: fixed (noninteractive) sea surface temperature (SST) and interactive SST as predicted by a simple slab-ocean model responding to the surface radiative fluxes and surface enthalpy flux. Both sets of experiments agree on the tendency of increased aerosol concentrations to make the shortwave cloud forcing more negative and reduce the longwave cloud forcing in response to increasing CCN concentration. These, in turn, tend to cool the SST in interactive-SST case. It is interesting that the absolute change of the SST and most other bulk quantities depends only on relative change of CCN concentration; that is, same SST change can be the result of doubling CCN concentration regardless of clean or polluted conditions. It is found that the 10-fold increase of CCN concentration can cool the SST by as much as 1.5 K. This is quite comparable to 2.1-2.3K SST warming obtained in a simulation for clean maritime conditions, but doubled CO2 concentration. Assuming the aerosol concentration has increased from preindustrial time by 30 %, the radiative forcing due to indirect aerosol effects is estimated to be -0.3Wm-2. It is found that the indirect aerosol effect is dominated by the first (Twomey) effect. Qualitative differences between the interactive and fixed SST cases have been found in sensitivity of the hydrological cycle to the increase in CCN concentration; namely, the precipitation rate shows some tendency to increase in fixed SST case, but robust tendency to decrease in interactive SST case. © Author(s) 2013."
"35405449400;56241176500;56223555000;7006993412;","An empirical model of global climate-Part 1: A critical evaluation of volcanic cooling",2013,"10.5194/acp-13-3997-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887147386&doi=10.5194%2facp-13-3997-2013&partnerID=40&md5=8f2b6a4291e6968a34274210c1f835a5","Observed reductions in Earth's surface temperature following explosive volcanic eruptions have been used as a proxy for geoengineering of climate by the artificial enhancement of stratospheric sulfate. Earth cools following major eruptions due to an increase in the reflection of sunlight caused by a dramatic enhancement of the stratospheric sulfate aerosol burden. Significant global cooling has been observed following the four major eruptions since 1900: Santa María, Mount Agung, El Chichón and Mt. Pinatubo, leading IPCC (2007) to state ""major volcanic eruptions can, thus, cause a drop in global mean surface temperature of about half a degree Celsius that can last for months and even years"". We use a multiple linear regression model applied to the global surface temperature anomaly to suggest that exchange of heat between the atmosphere and ocean, driven by variations in the strength of the Atlantic Meridional Overturning Circulation (AMOC), has been a factor in the decline of global temperature following these eruptions. The veracity of this suggestion depends on whether sea surface temperature (SST) in the North Atlantic, sometimes called the Atlantic Multidecadal Oscillation, but here referred to as Atlantic Multidecadal Variability (AMV), truly represents a proxy for the strength of the AMOC. Also, precise quantification of global cooling due to volcanoes depends on how the AMV index is detrended. If the AMV index is detrended using anthropogenic radiative forcing of climate, we find that surface cooling attributed to Mt. Pinatubo, using the Hadley Centre/University of East Anglia surface temperature record, maximises at 0.14 °C globally and 0.32 °C over land. These values are about a factor of 2 less than found when the AMV index is neglected in the model and quite a bit lower than the canonical 0.5 °C cooling usually attributed to Pinatubo. This result is driven by the high amplitude, low frequency component of the AMV index, demonstrating that reduced impact of volcanic cooling upon consideration of the AMV index is driven by variations in North Atlantic SST that occur over time periods much longer than those commonly associated with major volcanic eruptions. The satellite record of atmospheric temperature from 1978 to present and other century-long surface temperature records are also consistent with the suggestion that volcanic cooling may have been over estimated by about a factor of 2 due to prior neglect of ocean circulation. Our study suggests a recalibration may be needed for the proper use of Mt. Pinatubo as a proxy for geoengineering of climate. Finally, we highlight possible shortcomings in simulations of volcanic cooling by general circulation models, which are also being used to assess the impact of geoengineering of climate via stratospheric sulfate injection. © Author(s) 2013."
"7004908853;7003683808;7003495004;56684259500;7004469267;","Montreal protocol benefits simulated with CCM SOCOL",2013,"10.5194/acp-13-3811-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876116786&doi=10.5194%2facp-13-3811-2013&partnerID=40&md5=6936859e46c463901b28b02e49bd7d9b","Ozone depletion is caused by the anthropogenic increase of halogen-containing species in the atmosphere, which results in the enhancement of the concentration of reactive chlorine and bromine in the stratosphere. To reduce the influence of anthropogenic ozone-depleting substances (ODS), the Montreal Protocol was agreed by Governments in 1987, with several Amendments and Adjustments adopted later. In order to assess the benefits of the Montreal Protocol and its Amendments and Adjustments (MPA) on ozone and UV radiation, two different runs of the chemistry-climate model (CCM) SOCOL have been carried out. The first run was driven by the emission of ozone depleting substances (ODS) prescribed according to the restrictions of the MPA. For the second run we allow the ODS to grow by 3% annually. We find that the MPA would have saved up to 80% of the global annual total ozone by the end of the 21st century. Our calculations also show substantial changes of the stratospheric circulation pattern as well as in surface temperature and precipitations that could occur in the world without MPA implementations. To illustrate the changes in UV radiation at the surface and to emphasise certain features, which can only be seen for some particular regions if the influence of the cloud cover changes is accounted for, we calculate geographical distribution of the erythemally weighted irradiance (Eery). For the no Montreal Protocol simulation Eery increases by factor of 4 to 16 between the 1970s and 2100. For the scenario including the Montreal Protocol it is found that UV radiation starts to decrease in 2000, with continuous decline of 5% to 10% at middle latitudes in the both Northern and Southern Hemispheres. © 2013 Author(s)."
"7003266014;7004364155;","Impact of dataset choice on calculations of the short-term cloud feedback",2013,"10.1002/jgrd.50199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880672717&doi=10.1002%2fjgrd.50199&partnerID=40&md5=a55c29c9af3ec0df8370ee75163eebd5","Dessler [2010, hereafter D10] estimated the magnitude of the cloud feedback in response to short-term climate variations and concluded that it was likely positive, with an average magnitude of +0.50±0.75 W/m2/K. This paper investigates the sensitivity of D10's results to the choice of clear-sky top-of-atmosphere flux (ΔR<inf>clear-sky</inf>), surface temperature (ΔT<inf>s</inf>), and reanalysis data sets. Most of the alternative ΔR<inf>clear-sky</inf> data sets produce cloud feedbacks that are close to D10, differing by 0.2-0.3 W/m2/K. An exception is the Terra SSF1deg ΔR<inf>clear-sky</inf> product, which produces an overall negative cloud feedback. However, a critical examination of those data leads us to conclude that that result is due to problems in the Terra ΔR<inf>clear-sky</inf> arising from issues with cloud clearing prior to July 2001. Eliminating the problematic early portion yields a cloud feedback in good agreement with D10. We also present an alternative calculation of the cloud feedback that does not require an estimate of ΔR<inf>clear-sky</inf>, and this calculation also produces a positive cloud feedback in agreement with D10. The various ΔT<inf>s</inf> data sets produce cloud feedbacks that differ by as much as 0.8 W/m2/K. The choice of reanalysis, used as a source of ΔR<inf>clear-sky</inf> or as adjustments for the cloud radiative forcing, has a small impact on the inferred cloud feedback. Overall, these results confirm the robustness of D10's estimate of a likely positive feedback. © 2013. American Geophysical Union. All Rights Reserved."
"56537463000;7404829395;22959252400;8781752600;55446298200;57193132723;56203249800;7103271625;7103206141;6603171355;14045744500;7003582587;7003976079;8397494800;6603613067;24080737200;56250250300;7005955015;25031430500;6603809220;15736075100;7004714030;55686667100;13405561000;8918407000;7404815507;7003532926;6701606453;36097134700;7202899330;","Diagnosis of regime-dependent cloud simulation errors in CMIP5 models using ""a-Train"" satellite observations and reanalysis data",2013,"10.1029/2012JD018575","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881651440&doi=10.1029%2f2012JD018575&partnerID=40&md5=fe54862d795dd8907522b73879a8fece","The vertical distributions of cloud water content (CWC) and cloud fraction (CF) over the tropical oceans, produced by 13 coupled atmosphere-ocean models submitted to the Phase 5 of Coupled Model Intercomparison Project (CMIP5), are evaluated against CloudSat/CALIPSO observations as a function of large-scale parameters. Available CALIPSO simulator CF outputs are also examined. A diagnostic framework is developed to decompose the cloud simulation errors into large-scale errors, cloud parameterization errors and covariation errors. We find that the cloud parameterization errors contribute predominantly to the total errors for allmodels. The errors associated with large-scale temperature and moisture structures are relatively greater than those associated with large-scale midtropospheric vertical velocity and lower-level divergence. All models capture the separation of deep and shallow clouds in distinct large-scale regimes; however, the vertical structures of high/low clouds and their variations with large-scale parameters differ significantly from the observations. The CWCs associated with deep convective clouds simulated in most models do not reach as high in altitude as observed, and their magnitudes are generally weaker than CloudSat total CWC, which includes the contribution of precipitating condensates, but are close to CloudSat nonprecipitating CWC. All models reproduce maximum CF associated with convective detrainment, but CALIPSO simulator CFs generally agree better with CloudSat/CALIPSO combined retrieval than the model CFs, especially in the midtroposphere. Model simulated low clouds tend to have little variation with large-scale parameters except lower-troposphere stability, while the observed low cloud CWC, CF, and cloud top height vary consistently in all large-scale regimes. © 2012. American Geophysical Union. All Rights Reserved."
"6603453147;57206332144;57198593283;","Multi-satellite aerosol observations in the vicinity of clouds",2013,"10.5194/acp-13-3899-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899009280&doi=10.5194%2facp-13-3899-2013&partnerID=40&md5=580ed95a1770bbea83ce906c4cdf07d5","Improved characterization of aerosol properties in the vicinity of clouds is important for better understanding two critical aspects of climate: aerosol-cloud interactions and the direct radiative effect of aerosols. Satellite measurements have provided important insights into aerosol properties near clouds, but also suggested that the observations can be affected by 3-D radiative processes and instrument blurring not considered in current data interpretation methods. This study examines systematic cloud-related changes in particle properties and radiation fields that influence satellite measurements of aerosols in the vicinity of low-level maritime clouds. For this, the paper presents a statistical analysis of a yearlong global dataset of co-located MODIS and CALIOP observations and theoretical simulations. The results reveal that CALIOP-observed aerosol particle size and optical thickness, and MODIS-observed solar reflectance increase systematically in a wide transition zone around clouds. It is estimated that near-cloud changes in particle populations - including both aerosols and undetected cloud particles - are responsible for roughly two thirds of the observed increase in 0.55 μm MODIS reflectance. The results also indicate that 3-D radiative processes significantly contribute to near-cloud reflectance enhancements, while instrument blurring contributes significantly only within 1 km from clouds and then quickly diminishes with distance from clouds. © Author(s) 2013."
"57034458200;35226466500;57145869600;14834409800;55670772600;21740012000;7404136779;","The Beijing extreme rainfall of 21 July 2012: Right results but for wrong reasons",2013,"10.1002/grl.50304","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876928481&doi=10.1002%2fgrl.50304&partnerID=40&md5=023c0adf0ce6a0f9ecd2f6789aa97eb6","The heaviest rainfall in 6 decades fell in Beijing on 21 July 2012 with a record-breaking amount of 460 mm in 18 h and hourly rainfall rates exceeding 85 mm. This extreme rainfall event appeared to be reasonably well predicted by current operational models, albeit with notable timing and location errors. However, our analysis reveals that the model-predicted rainfall results mainly from topographical lifting and the passage of a cold front, whereas the observed rainfall was mostly generated by convective cells that were triggered by local topography and then propagated along a quasi-stationary linear convective system into Beijing. In particular, most of the extreme rainfall occurred in the warm sector far ahead of the cold front. Evidence from a cloud-permitting simulation indicates the importance of using high-resolution cloud-permitting models to reproduce the above-mentioned rainfall-production mechanisms in order to more accurately predict the timing, distribution, and intensity of such an extreme event. Key Points Local terrain and echo-training are the causes for the extreme rainfall event High resolution cloud resolving models can predict this extreme rainfall event Operational models provided right guidance but for wrong reasons ©2013 American Geophysical Union. All Rights Reserved."
"8068314800;7403497924;6603631763;","A global survey of the effect of cloud contamination on the aerosol optical thickness and its long-term trend derived from operational AVHRR satellite observations",2013,"10.1002/jgrd.50278","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882380928&doi=10.1002%2fjgrd.50278&partnerID=40&md5=c06f9f5479f2c2865ca251b4c1ab6d2d","Subpixel cloud contamination is one of the major issues plaguing passive satellite aerosol remote sensing. Its impact on the aerosol optical thickness (AOT) retrieval has been analyzed/evaluated by many studies. However, the question of how it influences the AOT trend remains to be answered. In this paper, four long-term advanced very high resolution radiometer (AVHRR) AOT data sets from 1981 to 2009 over global oceans for four different definitions of clear sky, respectively, are produced by applying a two-channel aerosol retrieval algorithm to the AVHRR clear-sky reflectances derived by combining NOAA Pathfinder Atmosphere's Extended AVHRR climate data record level-2b all-sky reflectances with the cloud probability parameter determined from the Bayesian probabilistic cloud detection technique. A global analysis of the effect of cloud contamination on the AVHRR AOT retrieval as well as on its long-term trend is then performed by comparing the results from the four data sets. It was found that cloud contamination imposes not only a positive bias on AOT values but also a positive bias on its long-term trend such that negative trends become less negative and positive trends become more positive. A cloud probability value of ≤1% has been identified as an optimal criterion for clear-sky definition to minimize the cloud contamination in the AVHRR aerosol retrieval while still retaining strong aerosol signals. In order for a satellite aerosol product to be useful and reliable in aerosol trend detection, the cloud contamination effect on aerosol trends needs to be studied/evaluated carefully along with the effects of calibration error, surface disturbance, and aerosol model assumptions. © 2013. American Geophysical Union. All Rights Reserved."
"57192273006;9244992800;","Multimodel attribution of the Southern Hemisphere Hadley cell widening: Major role of ozone depletion",2013,"10.1002/jgrd.50232","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882300753&doi=10.1002%2fjgrd.50232&partnerID=40&md5=d1906477d7b31a0e81dcb20c0ecb1a66","It has been suggested that the Hadley cell has been widening during the past three decades in both hemispheres, but attribution of its cause(s) remains challenging. By applying an optimal fingerprinting technique to 7 modern reanalyses and 49 coupled climate models participating in the CMIP3 and CMIP5, here we detect an influence of human-induced stratospheric ozone depletion on the observed expansion of the Hadley cell in the Southern Hemisphere (SH) summer. The detected signal is found to be separable from other external forcings that include greenhouse gases (GHGs), confirming a dominant role of stratospheric ozone in the SH summer climate change. Our results are largely insensitive to observational and model uncertainties, providing additional evidence for a human contribution to the atmospheric circulation changes. © 2013. American Geophysical Union. All Rights Reserved."
"55670345400;7006698304;","A three-hourly data set of the state of tropical convection based on cloud regimes",2013,"10.1002/grl.50294","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876907745&doi=10.1002%2fgrl.50294&partnerID=40&md5=9b009f9e67263f8a70627f479008c2b0","Tropical convection is a key driver in the climate system and is often identified using infrared satellite information or precipitation. Satellite-derived cloud regimes offer an alternative with potentially more informative distinctions between different types of convection. However, current ISCCP cloud regime data sets require visible satellite information and are therefore only available during daytime. We develop a convective regime data set for all three-hour intervals of the day using ISCCP infrared-only retrievals. We show that regimes derived in this way capture the essential properties of the original regimes, in particular, when identifying the state of tropical convection. We give examples for potential applications by illustrating the well-known Madden-Julian Oscillation and the diurnal cycle of convection in the framework of the newly derived regimes. The high temporal resolution, long record and global coverage of the regimes makes them a suitable tool for large-scale studies of tropical convection. Key Points Cloud regimes representing convection are extended to three-hour resolution These new regimes can identify different stages of convection like the original Applications to MJO and diurnal cycle show greater detail over original regimes ©2013. American Geophysical Union. All Rights Reserved."
"35219969500;57205479513;7003495982;24166464100;14023953700;","The representation of the TTL in a tropical channel version of the WRF model",2013,"10.1002/jgrd.50288","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882292324&doi=10.1002%2fjgrd.50288&partnerID=40&md5=08c8c3b02cb135626ffa969575a1af19","In this study, the Weather Research Forecast (WRF) model is used to investigate key physical processes controlling the Tropical Tropopause Layer (TTL) temperature and water vapor distributions in December 2005 to January-February 2006. The model domain is configured as a tropical channel with a horizontal grid spacing of 36 km, a vertical grid spacing of 500 m, and a top at 0.1 hPa. Initial and boundary conditions are set using the ERA-Interim reanalysis data set. An ozone distribution computed from satellite and ozonesonde measurements is used for radiative forcing calculations. The model's ability to replicate observed TTL temperatures is evaluated via comparisons with radiosonde data and reanalyses (MERRA and ERA-Interim). The Microwave Limb Sounder (MLS) water vapor measurements are used to evaluate WRF-simulated water vapor in the TTL. Results of the simulations show that the model reproduces the mean temperature and its variability above 50 hPa as well as the tropical tropopause height. However, the model cold point tropopause temperature is colder than the reanalyses by ∼1.2 K. The model captures the location of TTL water vapor minimum in the Western Pacific but is drier than the MLS observations in the TTL. To assess possible reasons for the tropopause temperature discrepancy, an additional WRF experiment was conducted using analysis nudging for water vapor. This experiment produces more tropical cirrus clouds in the upper troposphere and a warming of ∼1.5 K of the cold point tropopause. This suggests that the radiative effects of cirrus clouds and water vapor must be considered for accurate temperature simulations in the TTL. © 2013. American Geophysical Union. All Rights Reserved."
"24390528000;7005129538;6602600408;25648525300;","GCM simulations of anthropogenic aerosol-induced changes in aerosol extinction, atmospheric heating and precipitation over India",2013,"10.1002/jgrd.50298","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882374599&doi=10.1002%2fjgrd.50298&partnerID=40&md5=faf426c44e1a53b614711b6f9560fec8","The influence of anthropogenic emissions on aerosol distributions and the hydrological cycle are examined with a focus on monsoon precipitation over the Indian subcontinent, during January 2001 to December 2005, using the European Centre for Medium-Range Weather Forecasts-Hamburg (ECHAM5.5) general circulation model extended by the Hamburg Aerosol Module (HAM). The seasonal variability of aerosol optical depth (AOD) retrieved from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellite is broadly well simulated (R≈0.6-0.85) by the model. The spatial distribution and seasonal cycle of the precipitation observed over the Indian region are reasonably well simulated (R≈0.5 to 0.8) by the model, while in terms of absolute magnitude, the model underestimates precipitation, in particular in the south-west (SW) monsoon season. The model simulates significant anthropogenic aerosol-induced changes in clear-sky net surface solar radiation (dimming greater than -7 W m-2), which agrees well with the observed trends over the Indian region. A statistically significant decreasing precipitation trend is simulated only for the SWmonsoon season over the central-north Indian region, which is consistent with the observed seasonal trend over the Indian region. In the model, this decrease results from a reduction in convective precipitation, where there is an increase in stratiform cloud droplet number concentration (CDNC) and solar dimming that resulted from increased stability and reduced evaporation. Similarities in spatial patterns suggest that surface cooling, mainly by the aerosol indirect effect, is responsible for this reduction in convective activity. When changes in large-scale dynamics are allowed by slightly disturbing the initial state of the atmosphere, aerosol absorption in addition leads to a further stabilization of the lower troposphere, further reducing convective precipitation. © 2013. American Geophysical Union. All Rights Reserved."
"24463029300;35810775100;7004469744;57203200427;","Sensitivity of cloud condensation nuclei to regional changes in dimethyl-sulphide emissions",2013,"10.5194/acp-13-2723-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875887411&doi=10.5194%2facp-13-2723-2013&partnerID=40&md5=127ae7f06bcfdea29c9a488a9663942f","The atmospheric oxidation of dimethyl-sulphide (DMS) derived from marine phytoplankton is a significant source of marine sulphate aerosol. DMS has been proposed to regulate climate via changes in cloud properties, though recent studies have shown that present-day global cloud condensation nuclei (CCN) concentrations have only a weak dependence on the total emission flux of DMS. Here, we use a global aerosol microphysics model to examine how efficiently CCN are produced when DMS emissions are changed in different marine regions. We find that global CCN production per unit mass of sulphur emitted varies by more than a factor of 20 depending on where the change in oceanic DMS emission flux is applied. The variation in CCN production efficiency depends upon where CCN production processes (DMS oxidation, SO2 oxidation, nucleation and growth) are most efficient and removal processes (deposition) least efficient. The analysis shows that the production of aerosol sulphate through aqueous-phase oxidation of SO2 limits the amount of H2SO4 available for nucleation and condensational growth and therefore suppresses CCN formation, leading to the weak response of CCN to changes in DMS emission. Our results show that past and future changes in the spatial distribution of DMS emissions (through changes in the phytoplankton population or wind speed patterns) could exert a stronger control on climate than net increases in biological productivity. © 2013 Author(s)."
"35085155700;26643041500;7004713188;57207261095;22939204200;7004580878;9248574900;56370907100;7006821210;7005704570;35461255500;","Antarctic new particle formation from continental biogenic precursors",2013,"10.5194/acp-13-3527-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875911991&doi=10.5194%2facp-13-3527-2013&partnerID=40&md5=e4dd34d67c0210d194bde17bfd6ba5a7","Over Antarctica, aerosol particles originate almost entirely from marine areas, with minor contribution from long-range transported dust or anthropogenic material. The Antarctic continent itself, unlike all other continental areas, has been thought to be practically free of aerosol sources. Here we present evidence of local aerosol production associated with melt-water ponds in continental Antarctica. We show that in air masses passing such ponds, new aerosol particles are efficiently formed and these particles grow up to sizes where they may act as cloud condensation nuclei (CCN). The precursor vapours responsible for aerosol formation and growth originate very likely from highly abundant cyanobacteria Nostoc commune (Vaucher) communities of local ponds. This is the first time freshwater vegetation has been identified as an aerosol precursor source. The influence of the new source on clouds and climate may increase in future Antarctica, and possibly elsewhere undergoing accelerating summer melting of semi-permanent snow cover. © 2013 Author(s)."
"22952478000;7410120472;","Spatial and temporal variability of cloud-to-ground lightning over the continental U.S. during the period 1995-2010",2013,"10.1016/j.atmosres.2012.12.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873531458&doi=10.1016%2fj.atmosres.2012.12.017&partnerID=40&md5=63dc7bad700b0562766429bb962dfefa","We use 16. years (1995-2010) of data from the National Lightning Detection Network (NLDN) to examine the spatial and temporal variability of major cloud-to-ground (CG) lightning days (defined as the 80. days with the largest lightning activity) over the continental United States. Extreme lightning activity is concentrated over the central U.S. and west of the Appalachian Mountains. The largest frequency of major lightning days is concentrated during the summertime, with a tendency for these major days to have occurred in recent years. We also examine the presence of monotonic patterns over time in CG lightning flashes over the continental United States. Analyses are performed at the monthly scale (from April to September) and for total, negative-only, and positive-only flashes. The non-parametric Mann-Kendall test is used to examine the presence of monotonic patterns. The upgrades in NLDN during the study period complicate the separation between cloud-to-cloud flashes (CC) and the targeted CG lightning flashes. The results of the trend analyses are sensitive to the threshold used to discriminate between CC and CG flashes, in particular for positive-only flashes. The central U.S. is an area that exhibits statistically significant increasing trends independently of the selected threshold, while there is a general tendency towards decreasing trends over the Rocky Mountains. These results raise the question of whether the observed changes in lightning activity during the recent years are related to natural or human-induced changes in the climate system, and/or to inhomogeneities in the observational network. © 2013 Elsevier B.V."
"6603925960;55752626400;7003865921;35319507500;7202016984;55805773500;","Comparison of two different cloud climatologies derived from CALIOP-attenuated backscattered measurements (Level 1): The CALIPSO-ST and the CALIPSO-GOCCP",2013,"10.1175/JTECH-D-12-00057.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878390530&doi=10.1175%2fJTECH-D-12-00057.1&partnerID=40&md5=ff395729eb38eb9b8e744dce71d964cc","Two different cloud climatologies have been derived from the same NASA-Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)-measured attenuated backscattered profile (level 1, version 3 dataset). The first climatology, named Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations-Science Team (CALIPSO-ST), is based on the standard CALIOP cloud mask (level 2 product, version 3), with the aim to document clouds with the highest possible spatiotemporal resolution, taking full advantage of the CALIOP capabilities and sensitivity for a wide range of cloud scientific studies. The second climatology, named GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP), is aimed at a single goal: evaluating GCM prediction of cloudiness. For this specific purpose, it has been designed to be fully consistent with the CALIPSO simulator included in the Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) used within version 2 of the CFMIP (CFMIP-2) experiment and phase 5 of the Coupled Model Intercomparison Project (CMIP5). The differences between the two datasets in the global cloud cover maps-total, low level (P > 680 hPa), midlevel (680 < P < 440 hPa), and high level (P < 440 hPa)-are frequently larger than 10% and vary with region. The two climatologies show significant differences in the zonal cloud fraction profile (which differ by a factor of almost 2 in some regions), which are due to the differences in the horizontal and vertical averaging of the measured attenuated backscattered profile CALIOP profile before the cloud detection and to the threshold used to detect clouds (this threshold depends on the resolution and the signal-to-noise ratio). © 2013 American Meteorological Society."
"8321475300;57203259838;","Particle sedimentation and diffusive convection in volcanic ash-clouds",2013,"10.1002/jgrb.50155","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880724369&doi=10.1002%2fjgrb.50155&partnerID=40&md5=9b5b9b71dc76bc2d1635c3603a5e1b74","Understanding the longevity of volcanic ash-clouds generated by powerful explosive eruptions is a long standing problem for assessing volcanic hazards and the nature and time scale of volcanic forcings on climate change. It is well known that the lateral spreading and longevity of these clouds is influenced by stratospheric winds, particle settling and turbulent diffusion. Observations of the recent 2010 Eyjafjallajökull and 2011 Grimsvötn umbrella clouds, as well as the structure of atmospheric aerosol clouds from the 1991 Mt Pinatubo event, suggest that an additional key process governing the cloud dynamics is the production of internal layering. Here, we use analog experiments on turbulent particle-laden umbrella clouds to show that this layering occurs where natural convection driven by particle sedimentation and the differential diffusion of primarily heat and fine particles give rise to a large scale instability. Where umbrella clouds are particularly enriched in fine ash, this ""particle diffusive convection"" strongly influences the cloud longevity. More generally, cloud residence time will depend on fluxes due to both individual settling and diffusive convection. We develop a new sedimentation model that includes both sedimentation processes, and which is found to capture real-time measurements of the rate of change of particle concentration in the 1982 El Chichon, 1991 Mt Pinatubo and 1992 Mt Spurr ash-clouds. A key result is that these combined sedimentation processes enhance the fallout of fine particles relative to expectations from individual settling suggesting that particle aggregation is not the only mechanism required to explain volcanic umbrella longevity. ©2013. American Geophysical Union. All Rights Reserved."
"35770703500;7003740015;56309978600;7201525750;56109615300;","A theoretical study revealing the promotion of light-absorbing carbon particles solubilization by natural surfactants in nanosized water droplets",2013,"10.1002/asl2.421","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876437736&doi=10.1002%2fasl2.421&partnerID=40&md5=b5dc40362012ed475fd485ae73cd89b1","Many identified effects of atmospheric aerosol particles on climate come from pollutants. The effects of light-absorbing carbon particles (soot) are amongst the most uncertain and they are also considered to cause climate warming on the same order of magnitude as anthropogenic carbon dioxide. This study contributes to the understanding of the potential for transformation of the surface character of soot from hydrophobic to hydrophilic, which in clouds promotes a build-up of water-soluble material. We use molecular dynamics simulations to show how natural surfactants facilitate solubilization of fluoranthene, which we use as a model compound for soot in nanoaerosol water clusters. © 2013 Royal Meteorological Society."
"49961003000;","Adapting to a new reality-strategies for building energy design in a changing climate",2013,"10.1080/10485236.2013.10677560","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879763207&doi=10.1080%2f10485236.2013.10677560&partnerID=40&md5=fca836c4d6f77bc70b6c397d814cee8d","Building energy design is traditionally performed using retrogressive data sets (e.g., the past 30 years of weather data). The implied presumption has always been that this data will cycle back and forth around relatively static baseline averages. With increasing evidence that some level of climate change may be occurring, it is natural for building owners, developers, designers, and managers to question whether and to what extent these fundamental climate assumptions may be altered in future years. Depending on a building's locality, these could take the form of increasing or decreasing trends in seasonal average temperatures, daily maximum and minimum temperatures, relative humidity, barometric pressure, wind speed and direction, cloud cover, and total precipitation. These assumptions are crucial, because a typical building must remain habitable for 30-50 years (or longer) and provide its owner(s) with the maximum possible return on a sizeable capital investment.This article will demonstrate how building owners and developers can employ intelligent strategies to maximize energy efficiency while concurrently meeting building energy requirements and retaining significant flexibility to cope with potential variations in local climate. Data from existing buildings that currently exhibit outstanding energy performance (e.g., net zero energy buildings, Leadership in Energy and Environmental Design [LEED®] Gold-and Platinum-certified buildings, buildings with ENERGY STAR® ratings above 90) will be utilized to identify energy efficiency and renewable energy production technologies that can further improve energy performance and reduce risk. This article will demonstrate that, by implementing these types of adaptive strategies, the building sector can more nimbly respond to potential climate variations."
"12769875100;7004364155;","Impact of sun-synchronous diurnal sampling on tropical TOA flux interannual variability and trends",2013,"10.1175/JCLI-D-12-00416.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876076211&doi=10.1175%2fJCLI-D-12-00416.1&partnerID=40&md5=4c51d4f4b42f521d6c6fbcaf24514c03","Satellite observations of the earth's radiation budget (ERB) are a critical component of the climate observing system. Recent observations have been made from sun-synchronous orbits, which provide excellent spatial coverage with global measurements twice daily but do not resolve the full diurnal cycle. Previous investigations show that significant errors can occur in time-averaged energy budgets from sun-synchronous orbits if diurnal variations are ignored. However, the impact of incomplete diurnal sampling on top-ofatmosphere (TOA) flux variability and trends has received less attention. A total of 68 months of 3-hourly tropical outgoing longwave radiation (OLR) and reflected shortwave radiation (RSW) fluxes from the Clouds and the Earth's Radiant Energy System (CERES) synoptic (SYN) data product is used to examine the impact of incomplete diurnal sampling on TOA flux variability. Tropical OLR and RSW interannual variability and trends derived from sun-synchronous time sampling consistent with the Terra satelite from 2000 to 2005 show no statistically significant differences at the 95% confidence level with those obtained at 3-hourly time sampling at both 1° × 1° and 10° × 10° regional scales, as well as for tropical means. Monthly, 3-hourly OLR composite anomalies are decomposed into diurnally uniform and diurnal cycle shape change contributions to explain the impact of sampling on observed TOA flux variability. Diurnally uniform contributions to OLR variability account for more than 80% of interannual OLR variability at 1° × 1° spatial scales. Diurnal cycle shape variations are most important in equatorial land regions, contributing up to 50% to OLR variability over Africa. At spatial scales of 10° × 10° or larger, OLR variance contributions from diurnal cycle shape changes remain smaller than 20%."
"24801829100;7401895830;","Effects of the meteorological variability on regional air quality in East Asia",2013,"10.1016/j.atmosenv.2012.11.061","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872011036&doi=10.1016%2fj.atmosenv.2012.11.061&partnerID=40&md5=1f6f7a1cef46bf8cc1f85ea28d10cc7f","We examine the effects of the meteorological variability on O3 and SO42--NO3--NH4+ aerosol concentrations in East Asia using 3-D chemical transport model (GEOS-Chem) simulations for the period of 1985-2006. The model was driven by the GEOS assimilated meteorology with the emission estimates from the Streets et al. inventory with annual scale factors of Regional Emission inventory in Asia (REAS). Over the past two decades precursor emissions have been dramatically increased. Our model simulations however show strong non-linear responses of oxidation products to the increases of those precursors. The analysis of simulated results shows significant effects of meteorological variability on O3 and SO42--NO3--NH4+ concentrations. Springtime O3 concentration has been generally increased over the past two decades mainly due to increases in anthropogenic precursors emissions but concurrent changes in meteorology including decreases of cloud covers and increases of temperature further enhance O3 increases in East Asia. Our analysis reveals that changes in meteorology account for 30% of total O3 increases in East Asia over the past two decades. On the contrary, increases in mixing depth suppress increases of (NH4)2SO4 concentrations in summer but decreases in mixing depth in winter result in enhancement of NH4NO3 aerosols concentrations up to 4 μg m-3 in eastern China. Effects of meteorological variability on SO42--NO3--NH4+ aerosol concentrations are thus seasonally dependent such as a decrease in summer by 4% but an increase by 7% in winter over the past two decades. This result indicates that the meteorological conditions have changed more favorable for the PM air quality degradation in winter. © 2012 Elsevier Ltd."
"55667690300;35599000500;6602593134;","Solar activity and regional climate over short time scales at Thiruvananthapuram, South Kerala, India",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876806086&partnerID=40&md5=3869e43d4c897d68f64d9fbaf897fa8c","Possible correlation between solar activity and surface air temperature, however, small yet statistically significant that could exist over very small time scales at a particular station, is presented during a period in which the sunspot number exhibit a rising trend. The correlation between the variability of the daily and monthly average surface air temperature and solar irradiance at Trivandrum with sunspot number from January 2008 to March 2011 was investigated. The year 2008 was a solar minima year marking the end of 23rd solar cycle from May 1996 to December 2008 with duration of 12.6 years, while year 2009 was the beginning of the 24th solar cycle with the sunspot number showing a gradual rise during 2009-2010. The correlation between sunspot number, solar irradiance and surface air temperature were estimated during winter and pre-monsoon seasons when the effect of clouds was minimum. No statistically significant correlation was obtained between the surface air temperature or solar irradiance and sunspot number over small time scales unlike the small yet statistically significant correlation reported for studies over longer time scales."
"7403364247;7402244920;6603449464;6603929905;8700250600;7005401169;7007032760;","Assessing the seasonal dynamics of inundation, turbidity, and aquatic vegetation in the Australian wet-dry tropics using optical remote sensing",2013,"10.1002/eco.1270","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876328576&doi=10.1002%2feco.1270&partnerID=40&md5=f9221d0ce26afc758aec36e4999e3e79","Floodplain wetlands in the wet-dry tropics are under increasing pressure from water resource development, and there is a need for methods to assess the biophysical dynamics of these extensive and often remote ecosystems. This study assessed the capacity of optical remote sensing methods to monitor the seasonal dynamics of inundation, turbidity, and aquatic vegetation cover for a northern Australian savanna catchment. MODIS data were used to map seasonal flood inundation patterns, and Landsat 5 TM data were used to map dry-season waterbody dynamics. A network of water-depth loggers and temperature sensors provided ground observations of surface inundation dynamics, and was used to validate the inundation mapping. Post-flood waterbody surface area declined by 89% over the dry season, with 70% of the decline occurring for Palustrine (floodplain) waterbodies. All aquatic systems became increasingly disconnected as the dry season progressed. Statistical relationships were developed between seasonal measurements of turbidity, aquatic vegetation cover, and Landsat spectral data. Catchment wide predictions showed that turbidity increased and macrophyte cover decreased for the Palustrine and Lacustrine (lake) systems, while the Riverine systems became less turbid over the dry season. These results show that, for open savanna landscapes where cloud cover does not limit waterbody detection, optical remote sensing methods can be effectively applied to assess seasonal patterns of inundation and accompanying biophysical dynamics. This provides an effective tool to evaluate the impact of river flow regime changes from water resource use or climate change in these regions. © 2012 John Wiley & Sons, Ltd."
"7404062492;","Little net clear-sky radiative forcing from recent regional redistribution of aerosols",2013,"10.1038/ngeo1740","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875789154&doi=10.1038%2fngeo1740&partnerID=40&md5=dad83fd25a422bc91c2ae7e7dbeb432f","Aerosols both scatter and absorb incoming solar radiation, with consequences for the energy balance of the atmosphere. Unlike greenhouse gases, atmospheric aerosols are distributed non-uniformly around the Earth. Therefore, regional shifts in aerosol abundance could alter radiative forcing of the climate. Here, I use multi-angle imaging spectroradiometer (MISR) satellite data and the Atmospheric and Environmental Research radiative transfer model to assess the radiative effect of the spatial redistribution of aerosols over the past decade. Unexpectedly, the radiative transfer model shows that the movement of aerosols from high latitudes towards the Equator, as might happen if pollution shifts from Europe to southeast Asia, has little effect on clear-sky radiative forcing. Shorter slant paths and smaller upscatter fractions near the Equator compensate for more total sunlight there. Overall, there has been an almost exact cancellation in the clear-sky radiative forcing from aerosol increases and decreases in different parts of the world, whereas MISR should have been able to easily detect a change of 0.1 W m-2 per decade due to changing patterns. Long-term changes in global mean aerosol optical depth or indirect aerosol forcing of clouds are difficult to measure from satellites. However, the satellite data show that the regional redistribution of aerosols had little direct net effect on global average clear-sky radiative forcing from 2000 to 2012. © 2013 Macmillan Publishers Limited. All rights reserved."
"55555546400;6506117571;35227954100;","Interacting effects of ocean acidification and warming on growth and DMS-production in the haptophyte coccolithophore Emiliania huxleyi",2013,"10.1111/gcb.12105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874700633&doi=10.1111%2fgcb.12105&partnerID=40&md5=04d81c610807b738d957befcd1d75344","The production of the marine trace gas dimethyl sulfide (DMS) provides 90% of the marine biogenic sulfur in the atmosphere where it affects cloud formation and climate. The effects of increasing anthropogenic CO2 and the resulting warming and ocean acidification on trace gas production in the oceans are poorly understood. Here we report the first measurements of DMS-production and data on growth, DMSP and DMS concentrations in pH-stated cultures of the phytoplankton haptophyte Emiliania huxleyi. Four different environmental conditions were tested: ambient, elevated CO2 (+CO2), elevated temperature (+T) and elevated temperature and CO2 (+TCO2). In comparison to the ambient treatment, average DMS production was about 50% lower in the +CO2 treatment. Importantly, temperature had a strong effect on DMS production and the impacts outweighed the effects of a decrease in pH. As a result, the +T and +TCO2 treatments showed significantly higher DMS production of 36.2 ± 2.58 and 31.5 ± 4.66 μmol L-1 cell volume (CV) h-1 in comparison with the +CO2 treatment (14.9 ± 4.20 μmol L-1 CV h-1). As the cultures were aerated with an air/CO2 mixture, DMS was effectively removed from the incubation bottles so that concentration remained relatively low (3.6-6.1 mmol L-1 CV). Intracellular DMSP has been shown to increase in E. huxleyi as a result of elevated temperature and/or elevated CO2 and our results are in agreement with this finding: the ambient and +CO2 treatments showed 125 ± 20.4 and 162 ± 27.7 mmol L-1 CV, whereas +T and +TCO2 showed significantly increased intracellular DMSP concentrations of 195 ± 15.8 and 211 ± 28.2 mmol L-1 CV respectively. Growth was unaffected by the treatments, but cell diameter decreased significantly under elevated temperature. These results indicate that DMS production is sensitive to CO2 and temperature in E. huxleyi. Hence, global environmental change that manifests in ocean acidification and warming may not result in decreased DMS as suggested by earlier studies investigating the effect of elevated CO2 in isolation. © 2012 Blackwell Publishing Ltd."
"41261181900;41261844500;16052232100;55318318400;7006495789;","Heliotropic dust rings for Earth climate engineering",2013,"10.1016/j.asr.2012.10.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875215335&doi=10.1016%2fj.asr.2012.10.024&partnerID=40&md5=68100d0bd1d38415e246d836460af664","This paper examines the concept of a Sun-pointing elliptical Earth ring comprised of dust grains to offset global warming. A new family of non-Keplerian periodic orbits, under the effects of solar radiation pressure and the Earth's J 2 oblateness perturbation, is used to increase the lifetime of the passive cloud of particles and, thus, increase the efficiency of this geoengineering strategy. An analytical model is used to predict the orbit evolution of the dust ring due to solar-radiation pressure and the J 2 effect. The attenuation of the solar radiation can then be calculated from the ring model. In comparison to circular orbits, eccentric orbits yield a more stable environment for small grain sizes and therefore achieve higher efficiencies when the orbit decay of the material is considered. Moreover, the novel orbital dynamics experienced by high area-to-mass ratio objects, influenced by solar radiation pressure and the J 2 effect, ensure the ring will maintain a permanent heliotropic shape, with dust spending the largest portion of time on the Sun facing side of the orbit. It is envisaged that small dust grains can be released from a circular generator orbit with an initial impulse to enter an eccentric orbit with Sun-facing apogee. Finally, a lowest estimate of 1 × 10 12 kg of material is computed as the total mass required to offset the effects of global warming. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved."
"8629257200;57203492395;57217271893;35490341500;7403635969;9536598800;7004910963;25523100000;","The effect of background wind on mesoscale circulations above variable soil moisture in the Sahel",2013,"10.1002/qj.2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879225528&doi=10.1002%2fqj.2012&partnerID=40&md5=0cc6ccc206c7af27d17add82c6a964fd","Observational data are presented from several low-level flights carried out during the afternoon over areas of the Sahel that had been previously wetted by rain. The measurements are used to quantify the response of boundary-layer circulations to surface heterogeneity over a range of ambient conditions. Satellite observations of surface temperature anomalies show that soil moisture is significantly correlated with the surface heterogeneity in a majority of flights. By analysing the flight data in frequency space, consistently high levels of coherence are found between surface and flight-level measurements at length-scales around 25 km, indicating the presence of mesoscale circulations induced by the surface variability. The circulations are detectable in all of the nine flights where the mean sensible heat flux is high enough and they persist in a range of background wind speeds up to 5 m s-1. Further analysis confirms that the spatial phase-difference between surface and flight-level variables increases with the strength of the mean wind along the flight track. The boundary-layer thermal anomalies and circulations are advected downstream by the mean wind, and lead to convergent uplift on the order of 0.25 m s-1 at the 25 km scale. These results compare well with those from a cloud-resolving model and are broadly consistent with an analytical, linear model of a heated boundary layer. By demonstrating the significance of soil moisture in driving the circulations, the study shows that soil moisture is a likely cause of the negative precipitation feedback seen in recent remote sensing studies over the region. © 2012 Royal Meteorological Society."
"57202296507;32667855200;55825953800;","Energy budget change in the tropics according to the SRES A1B scenario in the IPCC AR4 models",2013,"10.1002/jgrd.50240","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882266161&doi=10.1002%2fjgrd.50240&partnerID=40&md5=53dda2077029043b0c4b3d8c8dec65d5","[1] The IPCC AR4 model data sets were investigated in order to address how the energy balance will change in the tropics (30°S-30°N) under the SRES A1B scenario. A climate change signal with a well-defined trend was extracted using cyclostationary empirical orthogonal function analysis; this signal depicts near-linear warming in the tropics. This ""warming"" signal, together with the seasonal cycle, explains most of the variance (91.32-94.86%) in the AR4 model datasets. In addition to the warming of the atmospheric column and the surface, the cloud fraction decreased over most of the tropics, except over the equatorial Pacific. Specific humidity generally increased over the entire troposphere. The decreased cloud fraction and the increased specific humidity resulted in a net increase in shortwave radiation (by ∼3.58 (±1.92) W m-2) in the atmospheric column. Simultaneously, the increased atmospheric and surface temperatures (resulting from positive water vapor feedback) caused enhanced longwave radiation exchange between the surface and the atmospheric column; net downward longwave radiation increased by ∼19.22 (±3.85) W m-2, and net upward longwave radiation increased by ∼14.50 (±3.04) W m-2 over 100 years. The second largest change was found in the heat flux leaving the surface, which amounted to ∼4.55 (±1.72)W m-2. As a result of the radiation budget change associated with warming and meridional energy transport by the atmosphere and the ocean, net energy gains were found for both the tropical atmosphere (∼5.82 (±3.23)W m-2) and the tropical surface (∼0.48 (±0.30) W m-2). © 2013. American Geophysical Union. All Rights Reserved."
"22953816800;55740282100;","Production rate and climate influences on the variability of 10Be deposition simulated by ECHAM5-HAM: Globally, in Greenland, and in Antarctica",2013,"10.1002/jgrd.50217","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882288456&doi=10.1002%2fjgrd.50217&partnerID=40&md5=77ba64d6bf646be1e70faf0904664d00","[1] Ice core concentrations of 10Be are used as a proxy for solar activity, but they might be affected by atmospheric transport and deposition and their changes. During the Holocene, the influence is likely to be small, but during glacials it has to be accounted for. First, the climate influence has to be understood during the present climate. This study uses an ECHAM5-HAM 30-year climatological simulation of 10Be to investigate the production and climate-related influences on 10Be deposition with focus on Greenland and Antarctica. We examine the climate modes driving snow accumulation and hence potentially 10Be deposition over a climatologically relevant period. The North Atlantic Oscillation (NAO) is found to be the main driver of changes in precipitation and 10Be deposition in Greenland, in agreement with previous studies. In Antarctica, the picture is more complex as precipitation and 10Be deposition are only weakly correlated with the Southern Annular Mode (SAM), El Niño-Southern Oscillation (ENSO), or Zonal Wave 3 pattern (ZW3). The results suggest that on seasonal scale, 10Be deposition is linked with both precipitation rate and tropopause height, mainly due to the similar seasonal cycle. However, the correlation with tropopause height persists on the annual time scale. All in all, 10Be variability in Antarctica is an interplay of several processes whose contribution varies in time and space. When interpreting 10Be ice core records for solar activity, the time scale is essentially important. On seasonal scale, the 10Be signal is dominated by weather influences, but on multiannual scales, the production rate is the main driver. On multidecadal scale, large long-term trends in climatic factors have the potential to distort the signal again as is seen in 10Be records during glacials. This study shows how climate modes connect to 10Be variability and how this connection could be used to correct for the climate impact. The established connections during present climatic conditions can be used as a basis to investigate these connections during glacial climate in a glacial model simulation. © 2013. American Geophysical Union. All Rights Reserved."
"8729013400;57203231357;12241438600;56152671900;55736987700;56152702100;36926764400;56152497900;","Changes in climate factors and extreme climate events in South China during 1961-2010",2013,"10.3724/SP.J.1248.2013.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900036778&doi=10.3724%2fSP.J.1248.2013.001&partnerID=40&md5=cdc3457c57e44537fe378310a4b3fea0","Daily climate data at 110 stations during 1961-2010 were selected to examine the changing characteristics of climate factors and extreme climate events in South China. The annual mean surface air temperature has increased significantly by 0.16°C per decade, most notably in the Pearl River Delta and in winter. The increase rate of the annual extreme minimum temperature (0.48°C per decade) is over twice that of the annual extreme maximum temperature (0.20°C per decade), and the increase of the mean temperature is mainly the result of the increase of the extreme minimum temperature. The increase rate of high-temperature days (1.1 d per decade) is close to the decrease rate of low-temperature days (-1.3 d per decade). The rainfall has not shown any significant trend, but the number of rainy days has decreased and the rain intensity has increased. The regional mean sunshine duration has a significant decreasing trend of -40.9 h per decade, and the number of hazy days has a significant increasing trend of 6.3 d per decade. The decrease of sunshine duration is mainly caused by the increase of total cloud, not by the increase of hazy days in South China. Both the regional mean pan evaporation and mean wind speed have significant decreasing trends of -65.9 mm per decade and -0.11 m s-1 per decade, respectively. The decrease of both sunshine duration and mean wind speed plays an important role in the decrease of pan evaporation. The number of landing tropical cyclones has an insignificant decreasing trend of -0.6 per decade, but their intensities show a weak increasing trend. The formation location of tropical cyclones landing in South China has converged towards 10-19°N, and the landing position has shown a northward trend. The date of the first landfall tropical cyclone postpones 1.8 d per decade, and the date of the last landfall advances 3.6 d per decade, resulting in reduction of the typhoon season by 5.4 d per decade."
"35512561700;15070481300;","Ground-based measurements of local cloud cover",2013,"10.1007/s00703-013-0245-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876818896&doi=10.1007%2fs00703-013-0245-9&partnerID=40&md5=b81efb8db53779534d927172ffea14d1","Clouds are believed to reflect temporal climate changes through variations in their amounts, characteristics, and occurrence. In addition, they reflect both weather and climate in a region. In this work, a methodology to determine the local cloud cover (LCC) is proposed using sky images obtained from a ground-based instrument. Three years of sky images from an urban, tropical site were obtained and analyzed through that methodology. Monthly average LCC varied from 3 to 96 %, while seasonal average values were 68 % for summer, 54 % for spring, 46 % for fall, and 23 % for winter. LCC results show a clear seasonal dependence and a fair agreement (r2 = 0. 72) with satellite data, which typically underestimate the cloud cover in relation to LCC. Our analysis also suggests the possibility of a measurable link between LCC and natural events like the El Niño Southern Oscillation. © 2013 Springer-Verlag Wien."
"35221443100;57208121852;23020321400;","Investigating relationships between aerosol optical depth and cloud fraction using satellite, aerosol reanalysis and general circulation model data",2013,"10.5194/acp-13-3177-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887069490&doi=10.5194%2facp-13-3177-2013&partnerID=40&md5=75f486bb3486e8f06e596ecaf38d1e7f","Strong positive relationships between cloud fraction (fc) and aerosol optical depth (τ) have been reported. Data retrieved from the MODerate resolution Imaging Spectroradiometer (MODIS) instrument show positive fc-τ relationships across most of the globe. A global mean f c increase of approximately 0.2 between low and high τ conditions is found for both ocean and land. However, these relationships are not necessarily due to cloud-aerosol interactions. Using state-of-the-art Monitoring Atmospheric Composition and Climate (MACC) reanalysis-forecast τ data, which should be less affected by retrieval artefacts, it is demonstrated that a large part of the observed fc-τ signal may be due to cloud contamination of satellite-retrieved τ. For longer MACC forecast time steps of 24 h, which likely contain less cloud contamination, some negative f c-τ relationships are found. The global mean fc increase between low and high τ conditions is reduced to 0.1, suggesting that cloud contamination may account for approximately one half of the satellite retrieved increase in fc. ECHAM5-HAM general circulation model (GCM) simulations further demonstrate that positive fc-τ relationships may arise due to covariation with relative humidity. Widespread negative simulated fc-τ relationships in the tropics are shown to arise due to scavenging of aerosol by convective precipitation. Wet scavenging events are likely poorly sampled in satellite-retrieved data, because the properties of aerosol below clouds cannot be retrieved. Quantifying the role of wet scavenging, and assessing GCM representations of this important process, remains a challenge for future observational studies of aerosol-cloud-precipitation interactions. © Author(s) 2013."
"22635999400;57126848900;6506545080;7203034123;15032788000;","Remote sensing of ice crystal asymmetry parameter using multi-directional polarization measurements - Part 2: Application to the Research Scanning Polarimeter",2013,"10.5194/acp-13-3185-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898462170&doi=10.5194%2facp-13-3185-2013&partnerID=40&md5=aab0bb1a343bdfea5867b472f7663163","A new method to retrieve ice cloud asymmetry parameters from multi-directional polarized reflectance measurements is applied to measurements of the airborne Research Scanning Polarimeter (RSP) obtained during the CRYSTAL-FACE campaign in 2002. The method assumes individual hexagonal ice columns and plates serve as proxies for more complex shapes and aggregates. The closest fit is searched in a look-up table of simulated polarized reflectances computed for cloud layers that contain individual, randomly oriented hexagonal columns and plates with a virtually continuous selection of aspect ratios and distortion. The asymmetry parameter, aspect ratio and distortion of the hexagonal particle that leads to the best fit with the measurements are considered the retrieved values. Two cases of thick convective clouds and two cases of thinner anvil cloud layers are analyzed. Median asymmetry parameters retrieved by the RSP range from 0.76 to 0.78, and are generally smaller than those currently assumed in most climate models and satellite retrievals. In all cases the measurements indicate roughened or distorted ice crystals, which is consistent with previous findings. Retrieved aspect ratios in three of the cases range from 0.9 to 1.6, indicating compact particles dominate the cloud-top shortwave radiation. Retrievals for the remaining case indicate plate-like ice crystals with aspect ratios around 0.3. The RSP retrievals are qualitatively consistent with the CPI images obtained in the same cloud layers. Retrieved asymmetry parameters are compared to those determined in situ by the Cloud Integrating Nephelometer (CIN). For two cases, the median values of asymmetry parameter retrieved by CIN and RSP agree within 0.01, while for the two other cases RSP asymmetry parameters are about 0.03- 0.05 greater than those obtained by the CIN. Part of this bias might be explained by vertical variation of the asymmetry parameter or ice shattering on the CIN probe, or both. © Author(s) 2013."
"55684491100;56244407700;","Aviation-induced cirrus and radiation changes at diurnal timescales",2013,"10.1002/jgrd.50184","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878130091&doi=10.1002%2fjgrd.50184&partnerID=40&md5=030c3abf8f4f9ec736d010637c77a38b","The radiative forcing from aviation-induced cirrus is derived from observations and models. The annual mean diurnal cycle of airtraffic in the North Atlantic region exhibits two peaks in early morning and afternoon with different peak times in the western and eastern parts of the North Atlantic region. The same ""aviation fingerprint"" is found in 8 years (2004-2011) of Meteosat observations of cirrus cover and OLR. The observations are related to airtraffic data with linear response models assuming the background atmosphere without aviation to be similar to that observed in the South Atlantic. The change in OLR is interpreted as aviation-induced longwave radiative forcing (LW RF). The data analysis suggests an LW RF of about 600-900 mW m-2 regionally. A detailed contrail cirrus model for given global meteorology and airtraffic in 2006 gives similar results. The global RF is estimated from the ratio of global and regional RF as derived from three models. The extrapolation implies about 100-160 mW m-2 global LW RF. The models show large differences in the shortwave/longwave RF-magnitude ratio. One model computes a ratio of 0.6, implying an estimate of global net RF of about 50 mW m-2 (40-80 mW m-2). Other models suggest smaller ratios, with less cooling during day, which would imply considerably larger net effects. The sensitivity of the results to the accuracy of the observations, traffic data, and models and the estimated background is discussed. © 2013. American Geophysical Union. All Rights Reserved."
"7003908632;55082035300;12764954600;7006204597;","Assessment of the effects of acid-coated ice nuclei on the Arctic cloud microstructure, atmospheric dehydration, radiation and temperature during winter",2013,"10.1002/joc.3454","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873527043&doi=10.1002%2fjoc.3454&partnerID=40&md5=2070d764e1fd00f1eb84d54ca4fa5c46","Owing to the large-scale transport of pollution-derived aerosols from the mid-latitudes to the Arctic, most of the aerosols are coated with acidic sulfate during winter in the Arctic. Recent laboratory experiments have shown that acid coating on dust particles substantially reduces the ability of these particles to nucleate ice crystals. Simulations performed using the Limited Area version of the Global Multiscale Environmental Model (GEM-LAM) are used to assess the potential effect of acid-coated ice nuclei on the Arctic cloud and radiation processes during January and February 2007. Ice nucleation is treated using a new parameterization based on laboratory experiments of ice nucleation on sulphuric acid-coated and uncoated kaolinite particles. Results show that acid coating on dust particles has an important effect on cloud microstructure, atmospheric dehydration, radiation and temperature over the Central Arctic, which is the coldest part of the Arctic. Mid and upper ice clouds are optically thinner while low-level mixed-phase clouds are more frequent and persistent. These changes in the cloud microstructures affect the radiation at the top of the atmosphere with longwave negative cloud forcing values ranging between 0 and - 6 W m-2 over the region covered by the Arctic air mass. © 2012 Royal Meteorological Society."
"7004198777;57202521210;7003789044;6507274020;57212809215;6603415946;36183151300;24722339600;28568055900;16550482700;7005035762;57210590791;","Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean",2013,"10.5194/acp-13-2541-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874901633&doi=10.5194%2facp-13-2541-2013&partnerID=40&md5=08632489f231339b99f10b01ce1a2ddf","The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics, including their significance, from eight flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number that influence droplet concentration. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were smaller in regions of enhanced particles near shore. However, physically thinner clouds, and not just higher droplet number concentrations from pollution, both contributed to the smaller droplets. Satellite measurements were used to show that cloud albedo was highest 500-1000 km offshore, and actually slightly lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles. © Author(s) 2013."
"54788302000;6603800142;6602584093;57195574170;56520921400;","Quantitative comparison of the variability in observed and simulated shortwave reflectance",2013,"10.5194/acp-13-3133-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900529990&doi=10.5194%2facp-13-3133-2013&partnerID=40&md5=df6793abed6a96c65a279f5a44b0a7b4","The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system that has been designed to monitor the Earth's climate with unprecedented absolute radiometric accuracy and SI traceability. Climate Observation System Simulation Experiments (OSSEs) have been generated to simulate CLARREO hyperspectral shortwave imager measurements to help define the measurement characteristics needed for CLARREO to achieve its objectives. To evaluate how well the OSSE-simulated reflectance spectra reproduce the Earth's climate variability at the beginning of the 21st century, we compared the variability of the OSSE reflectance spectra to that of the reflectance spectra measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY). Principal component analysis (PCA) is a multivariate decomposition technique used to represent and study the variability of hyperspectral radiation measurements. Using PCA, between 99.7%and 99.9%of the total variance the OSSE and SCIAMACHY data sets can be explained by subspaces defined by six principal components (PCs). To quantify how much information is shared between the simulated and observed data sets, we spectrally decomposed the intersection of the two data set subspaces. The results from four cases in 2004 showed that the two data sets share eight (January and October) and seven (April and July) dimensions, which correspond to about 99.9% of the total SCIAMACHY variance for each month. The spectral nature of these shared spaces, understood by examining the transformed eigenvectors calculated from the subspace intersections, exhibit similar physical characteristics to the original PCs calculated from each data set, such as water vapor absorption, vegetation reflectance, and cloud reflectance. © Author(s) 2013."
"10139397300;35810775100;24463029300;7405666962;7004469744;12806941900;","Impact of the modal aerosol scheme GLOMAP-mode on aerosol forcing in the hadley centre global environmental model",2013,"10.5194/acp-13-3027-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880534397&doi=10.5194%2facp-13-3027-2013&partnerID=40&md5=e2efc3bbcf9778017599d6e4c3a7ce1f","The Hadley Centre Global Environmental Model (HadGEM) includes two aerosol schemes: the Coupled Large-scale Aerosol Simulator for Studies in Climate (CLASSIC), and the new Global Model of Aerosol Processes (GLOMAP-mode). GLOMAP-mode is a modal aerosol microphysics scheme that simulates not only aerosol mass but also aerosol number, represents internally-mixed particles, and includes aerosol microphysical processes such as nucleation. In this study, both schemes provide hindcast simulations of natural and anthropogenic aerosol species for the period 2000-2006. HadGEM simulations of the aerosol optical depth using GLOMAP-mode compare better than CLASSIC against a data-assimilated aerosol re-analysis and aerosol ground-based observations. Because of differences in wet deposition rates, GLOMAP-mode sulphate aerosol residence time is two days longer than CLASSIC sulphate aerosols, whereas black carbon residence time is much shorter. As a result, CLASSIC underestimates aerosol optical depths in continental regions of the Northern Hemisphere and likely overestimates absorption in remote regions. Aerosol direct and first indirect radiative forcings are computed from simulations of aerosols with emissions for the year 1850 and 2000. In 1850, GLOMAP-mode predicts lower aerosol optical depths and higher cloud droplet number concentrations than CLASSIC. Consequently, simulated clouds are much less susceptible to natural and anthropogenic aerosol changes when the microphysical scheme is used. In particular, the response of cloud condensation nuclei to an increase in dimethyl sulphide emissions becomes a factor of four smaller. The combined effect of different 1850 baselines, residence times, and abilities to affect cloud droplet number, leads to substantial differences in the aerosol forcings simulated by the two schemes. GLOMAP-mode finds a presentday direct aerosol forcing of -0.49Wm-2 on a global average, 72% stronger than the corresponding forcing from CLASSIC. This difference is compensated by changes in first indirect aerosol forcing: the forcing of -1.17Wm-2 obtained with GLOMAP-mode is 20% weaker than with CLASSIC. Results suggest that mass-based schemes such as CLASSIC lack the necessary sophistication to provide realistic input to aerosol-cloud interaction schemes. Furthermore, the importance of the 1850 baseline highlights how model skill in predicting present-day aerosol does not guarantee reliable forcing estimates. Those findings suggest that the more complex representation of aerosol processes in microphysical schemes improves the fidelity of simulated aerosol forcings. © Author(s) 2013."
"7004214645;7102976560;57205638870;8570871900;55235148400;7102517130;25927718600;55588510300;6603809220;6603711967;18437654000;12240390300;6701597468;7402105994;15724543600;8354057400;7006270084;7003666669;7103206141;55717074000;7003777747;55242994500;56244473600;23968109800;11940188700;55183670500;15726660300;7202079615;22986631300;55317177900;56177637000;","Radiative forcing in the ACCMIP historical and future climate simulations",2013,"10.5194/acp-13-2939-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876185282&doi=10.5194%2facp-13-2939-2013&partnerID=40&md5=64a7873934c9477e989c388e63e03228","The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) examined the short-lived drivers of climate change in current climate models. Here we evaluate the 10 ACCMIP models that included aerosols, 8 of which also participated in the Coupled Model Intercomparison Project phase 5 (CMIP5). The models reproduce present-day total aerosol optical depth (AOD) relatively well, though many are biased low. Contributions from individual aerosol components are quite different, however, and most models underestimate east Asian AOD. The models capture most 1980-2000 AOD trends well, but underpredict increases over the Yellow/Eastern Sea. They strongly underestimate absorbing AOD in many regions. We examine both the direct radiative forcing (RF) and the forcing including rapid adjustments (effective radiative forcing; ERF, including direct and indirect effects). The models' all-sky 1850 to 2000 global mean annual average total aerosol RF is (mean; range) -0.26Wm-2; -0.06 to -0.49Wm-2. Screening based on model skill in capturing observed AOD yields a best estimate of -0.42Wm-2; -0.33 to -0.50Wm-2, including adjustment for missing aerosol components in some models. Many ACCMIP and CMIP5 models appear to produce substantially smaller aerosol RF than this best estimate. Climate feedbacks contribute substantially (35 to -58 %) to modeled historical aerosol RF. The 1850 to 2000 aerosol ERF is -1.17Wm -2; -0.71 to -1.44Wm-2. Thus adjustments, including clouds, typically cause greater forcing than direct RF. Despite this, the multi-model spread relative to the mean is typically the same for ERF as it is for RF, or even smaller, over areas with substantial forcing. The largest 1850 to 2000 negative aerosol RF and ERF values are over and near Europe, south and east Asia and North America. ERF, however, is positive over the Sahara, the Karakoram, high Southern latitudes and especially the Arctic. Global aerosol RF peaks in most models around 1980, declining thereafter with only weak sensitivity to the Representative Concentration Pathway (RCP). One model, however, projects approximately stable RF levels, while two show increasingly negative RF due to nitrate (not included in most models). Aerosol ERF, in contrast, becomes more negative during 1980 to 2000. During this period, increased Asian emissions appear to have a larger impact on aerosol ERF than European and North American decreases due to their being upwind of the large, relatively pristine Pacific Ocean. There is no clear relationship between historical aerosol ERF and climate sensitivity in the CMIP5 subset of ACCMIP models. In the ACCMIP/CMIP5 models, historical aerosol ERF of about -0.8 to -1.5Wm-2 is most consistent with observed historical warming. Aerosol ERF masks a large portion of greenhouse forcing during the late 20th and early 21st century at the global scale. Regionally, aerosol ERF is so large that net forcing is negative over most industrialized and biomass burning regions through 1980, but remains strongly negative only over east and southeast Asia by 2000. Net forcing is strongly positive by 1980 over most deserts, the Arctic, Australia, and most tropical oceans. Both the magnitude of and area covered by positive forcing expand steadily thereafter. © Author(s) 2013."
"36970250700;8908558200;6508003688;6701394069;13610836500;","Variability of the ocean heat content during the last millennium - An assessment with the ECHO-g Model",2013,"10.5194/cp-9-547-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874682583&doi=10.5194%2fcp-9-547-2013&partnerID=40&md5=697b9ed42afcd3bd9723faddde7781f5","Studies addressing climate variability during the last millennium generally focus on variables with a direct influence on climate variability, like the fast thermal response to varying radiative forcing, or the large-scale changes in atmospheric dynamics (e.g. North Atlantic Oscillation). The ocean responds to these variations by slowly integrating in depth the upper heat flux changes, thus producing a delayed influence on ocean heat content (OHC) that can later impact low frequency SST (sea surface temperature) variability through reemergence processes. In this study, both the externally and internally driven variations of the OHC during the last millennium are investigated using a set of fully coupled simulations with the ECHO-G (coupled climate model ECHAMA4 and ocean model HOPE-G) atmosphere-ocean general circulation model (AOGCM). When compared to observations for the last 55 yr, the model tends to overestimate the global trends and underestimate the decadal OHC variability. Extending the analysis back to the last one thousand years, the main impact of the radiative forcing is an OHC increase at high latitudes, explained to some extent by a reduction in cloud cover and the subsequent increase of short-wave radiation at the surface. This OHC response is dominated by the effect of volcanism in the preindustrial era, and by the fast increase of GHGs during the last 150 yr. Likewise, salient impacts from internal climate variability are observed at regional scales. For instance, upper temperature in the equatorial Pacific is controlled by ENSO (El Niño Southern Oscillation) variability from interannual to multidecadal timescales. Also, both the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) modulate intermittently the interdecadal OHC variability in the North Pacific and Mid Atlantic, respectively. The NAO, through its influence on North Atlantic surface heat fluxes and convection, also plays an important role on the OHC at multiple timescales, leading first to a cooling in the Labrador and Irminger seas, and later on to a North Atlantic warming, associated with a delayed impact on the AMO.© Author(s) 2013."
"35237179700;55611264400;7006432040;6507421222;35185383500;7102521078;36638394000;14051882200;6602412939;14522369600;","Habitable zones around main-sequence stars: New estimates",2013,"10.1088/0004-637X/765/2/131","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874490266&doi=10.1088%2f0004-637X%2f765%2f2%2f131&partnerID=40&md5=9842d45b1f1b92811a695ceaf570cab7","Identifying terrestrial planets in the habitable zones (HZs) of other stars is one of the primary goals of ongoing radial velocity (RV) and transit exoplanet surveys and proposed future space missions. Most current estimates of the boundaries of the HZ are based on one-dimensional (1D), cloud-free, climate model calculations by Kasting et al. However, this model used band models that were based on older HITRAN and HITEMP line-by-line databases. The inner edge of the HZ in the Kasting et al. model was determined by loss of water, and the outer edge was determined by the maximum greenhouse provided by a CO2 atmosphere. A conservative estimate for the width of the HZ from this model in our solar system is 0.95-1.67 AU. Here an updated 1D radiative-convective, cloud-free climate model is used to obtain new estimates for HZ widths around F, G, K, and M stars. New H2O and CO2 absorption coefficients, derived from the HITRAN 2008 and HITEMP 2010 line-by-line databases, are important improvements to the climate model. According to the new model, the water-loss (inner HZ) and maximum greenhouse (outer HZ) limits for our solar system are at 0.99 and 1.70 AU, respectively, suggesting that the present Earth lies near the inner edge. Additional calculations are performed for stars with effective temperatures between 2600 and 7200 K, and the results are presented in parametric form, making them easy to apply to actual stars. The new model indicates that, near the inner edge of the HZ, there is no clear distinction between runaway greenhouse and water-loss limits for stars with T eff ≲ 5000 K, which has implications for ongoing planet searches around K and M stars. To assess the potential habitability of extrasolar terrestrial planets, we propose using stellar flux incident on a planet rather than equilibrium temperature. This removes the dependence on planetary (Bond) albedo, which varies depending on the host star's spectral type. We suggest that conservative estimates of the HZ (water-loss and maximum greenhouse limits) should be used for current RV surveys and Kepler mission to obtain a lower limit on η⊕, so that future flagship missions like TPF-C and Darwin are not undersized. Our model does not include the radiative effects of clouds; thus, the actual HZ boundaries may extend further in both directions than the estimates just given. © 2013. The American Astronomical Society. All rights reserved."
"16302424800;50661784500;7101740729;6603041072;35459535800;","Collision dynamics and uptake of water on alcohol-covered ice",2013,"10.5194/acp-13-2223-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874482040&doi=10.5194%2facp-13-2223-2013&partnerID=40&md5=0a88f1dde923a6d8e711c136da18c260","Molecular scattering experiments are used to investigate water interactions with methanol and n-butanol covered ice between 155 K and 200 K. The inelastically scattered and desorbed products of an incident molecular beam are measured and analyzed to illuminate molecular scale processes. The residence time and uptake coefficients of water impinging on alcohol-covered ice are calculated. The surfactant molecules are observed to affect water transport to and from the ice surface in a manner that is related to the number of carbon atoms they contain. Butanol films on ice are observed to reduce water uptake by 20%, whereas methanol monolayers pose no significant barrier to water transport. Water colliding with methanol covered ice rapidly permeates the alcohol layer, but on butanol water molecules have mean surface lifetimes of ≲ 0.6 ms, enabling some molecules to thermally desorb before reaching the water ice underlying the butanol. These observations are put into the context of cloud and atmospheric scale processes, where such surfactant layers may affect a range of aerosol processes, and thus have implications for cloud evolution, the global water cycle, and long term climate. © 2013 Author(s)."
"6603550849;55258548500;40661878900;55207753100;7403253796;7404865816;","Role of OH-initiated oxidation of isoprene in aging of combustion soot",2013,"10.1021/es3045339","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874591421&doi=10.1021%2fes3045339&partnerID=40&md5=27e1756e1427bf767f26d18aeabcedeb","We have investigated the contribution of OH-initiated oxidation of isoprene to the atmospheric aging of combustion soot. The experiments were conducted in a fluoropolymer chamber on size-classified soot aerosols in the presence of isoprene, photolytically generated OH, and nitrogen oxides. The evolution in the mixing state of soot was monitored from simultaneous measurements of the particle size and mass, which were used to calculate the particle effective density, dynamic shape factor, mass fractal dimension, and coating thickness. When soot particles age, the increase in mass is accompanied by a decrease in particle mobility diameter and an increase in effective density. Coating material not only fills in void spaces, but also causes partial restructuring of fractal soot aggregates. For thinly coated aggregates, the single scattering albedo increases weakly because of the decreased light absorption and practically unchanged scattering. Upon humidification, coated particles absorb water, leading to an additional compaction. Aging transforms initially hydrophobic soot particles into efficient cloud condensation nuclei at a rate that increases in the presence of nitrogen oxides. Our results suggest that ubiquitous biogenic isoprene plays an important role in aging of anthropogenic soot, shortening its atmospheric lifetime and considerably altering its impacts on air quality and climate. © 2013 American Chemical Society."
"10139397300;6602600408;24322005900;57203200427;","Estimates of aerosol radiative forcing from the MACC re-analysis",2013,"10.5194/acp-13-2045-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874413447&doi=10.5194%2facp-13-2045-2013&partnerID=40&md5=5fc6fe5ec9559d984d7be3930700806e","The European Centre for Medium-range Weather Forecast (ECMWF) provides an aerosol re-analysis starting from year 2003 for the Monitoring Atmospheric Composition and Climate (MACC) project. The re-analysis assimilates total aerosol optical depth retrieved by the Moderate Resolution Imaging Spectroradiometer (MODIS) to correct for model departures from observed aerosols. The re-analysis therefore combines satellite retrievals with the full spatial coverage of a numerical model. Re-analysed products are used here to estimate the shortwave direct and first indirect radiative forcing of anthropogenic aerosols over the period 2003-2010, using methods previously applied to satellite retrievals of aerosols and clouds. The best estimate of globally-averaged, all-sky direct radiative forcing is-0.7 ± 0.3 Wm&minus;2. The standard deviation is obtained by a Monte-Carlo analysis of uncertainties, which accounts for uncertainties in the aerosol anthropogenic fraction, aerosol absorption, and cloudy-sky effects. Further accounting for differences between the present-day natural and pre-industrial aerosols provides a direct radiative forcing estimate of-0.4 ± 0.3 Wm&minus;2. The best estimate of globally-averaged, all-sky first indirect radiative forcing is-0.6 ± 0.4 Wm&minus;2. Its standard deviation accounts for uncertainties in the aerosol anthropogenic fraction, and in cloud albedo and cloud droplet number concentration susceptibilities to aerosol changes. The distribution of first indirect radiative forcing is asymmetric and is bounded by-0.1 and-2.0 Wm-2. In order to decrease uncertainty ranges, better observational constraints on aerosol absorption and sensitivity of cloud droplet number concentrations to aerosol changes are required. © 2013 Author(s)."
"7402283598;55705948900;7004091561;7402677913;7103206141;7201665727;7202041928;","Evaluation of factors controlling global secondary organic aerosol production from cloud processes",2013,"10.5194/acp-13-1913-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874357576&doi=10.5194%2facp-13-1913-2013&partnerID=40&md5=e301fb47f20d34492e7cf82c582059c7","Secondary organic aerosols (SOA) exert a significant influence on ambient air quality and regional climate. Recent field, laboratorial and modeling studies have confirmed that in-cloud processes contribute to a large fraction of SOA production with large space-time heterogeneity. This study evaluates the key factors that govern the production of cloud-process SOA (SOAcld) on a global scale based on the GFDL coupled chemistry-climate model AM3 in which full cloud chemistry is employed. The association between SOAcld production rate and six factors (i.e., liquid water content (LWC), total carbon chemical loss rate (TCloss), temperature, VOC/NOx, OH, and O 3) is examined. We find that LWC alone determines the spatial pattern of SOAcld production, particularly over the tropical, subtropical and temperate forest regions, and is strongly correlated with SOAcld production. TCloss ranks the second and mainly represents the seasonal variability of vegetation growth. Other individual factors are essentially uncorrelated spatiotemporally to SOAcld production. We find that the rate of SOAcld production is simultaneously determined by both LWC and TCloss, but responds linearly to LWC and nonlinearly (or concavely) to TCloss. A parameterization based on LWC and TCloss can capture well the spatial and temporal variability of the process-based SOAcld formation (R 2 Combining double low line 0.5) and can be easily applied to global three dimensional models to represent the SOA production from cloud processes. © Author(s) 2013."
"36856321600;9132948500;7402064802;","CMIP3 subtropical stratocumulus cloud feedback interpreted through a mixed-layer model",2013,"10.1175/JCLI-D-12-00188.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874810144&doi=10.1175%2fJCLI-D-12-00188.1&partnerID=40&md5=db656569dba4aaf794d7c16be6925961","Large-scale conditions over subtropical marine stratocumulus areas are extracted from global climate models (GCMs) participating in phase 3 of the Coupled Model Intercomparison Project (CMIP3) and used to drive an atmospheric mixed-layer model (MLM) for current and future climate scenarios. Cloud fraction is computed as the fraction of days whereGCMforcings produce a cloudy equilibriumMLMstate. This model is a good predictor of cloud fraction and its temporal variations on time scales longer than 1 week but overpredicts liquid water path and entrainment. GCM cloud fraction compares poorly with observations of mean state, variability, and correlation with estimated inversion strength (EIS). MLM cloud fraction driven by these same GCMs, however, agrees well with observations, suggesting that poor GCM low cloud fraction is due to deficiencies in cloud parameterizations rather than large-scale conditions. However, replacing the various GCM cloud parameterizations with a single physics package (the MLM) does not reduce intermodel spread in low-cloud feedback because theMLMismore sensitive than the GCMs to existent intermodel variations in large-scale forcing. This suggests that improving GCM low cloud physics will not by itself reduce intermodel spread in predicted stratocumulus cloud feedback. Differences in EIS and EIS change between GCMs are found to be a good predictor of current-climate MLM cloud amount and future cloud change. CMIP3 GCMs predict a robust increase of 0.5-1 K in EIS over the next century, resulting in a 2.3%-4.5% increase in MLM cloudiness. If EIS increases are real, subtropical stratocumulus may damp global warming in a way not captured by the GCMs studied. © 2013 American Meteorological Society."
"55660926800;7201504886;28367935500;","Climate and climate change in a radiative-convective equilibrium version of ECHAM6",2013,"10.1029/2012MS000191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876725239&doi=10.1029%2f2012MS000191&partnerID=40&md5=ed1ca72bf5ee40c74531b6324cf3683b","A radiative-convective equilibrium (RCE) configuration of a comprehensive atmospheric general circulation model, ECHAM6, is coupled to a mixed-layer ocean for the purpose of advancing understanding of climate and climate change. This configuration differs from a standard configuration only through the removal of land-surface processes, spatial gradients in solar insolation, and the effects of rotation. Nonetheless, the model produces a climate that resembles the tropical climate in a control simulation of Earth's atmosphere. In the RCE configuration, regional inhomogeneities in surface temperature develop. These inhomogeneities are transient in time but sufficiently long-lived to establish large-scale overturning circulations with a distribution similar to the preindustrial tropics in the standard configuration. The vertical structure of the atmosphere, including profiles of clouds and condensate conditioned on the strength of overturning, also resembles those produced by a control simulation of Earth's tropical atmosphere. The equilibrium climate sensitivity of the RCE atmosphere can explain 50% of the global climate sensitivity of a realistic configuration of ECHAM6. Part of the difference is attributed to the lack of polar amplification in RCE. The remainder appears to be related to a less positive cloud shortwave feedback, which results from an increase in low cloudiness with increasing surface temperatures in the RCE configuration. The RCE configuration shows an increase of climate sensitivity in a warmer climate. The increase in climate sensitivity scales with the degree to which the upper-troposphere temperature departs from a moist adiabat. © 2012. American Geophysical Union. All Rights Reserved."
"55255661500;6507004152;7202100400;35584506900;","Evaluating the bio-hydrological impact of a cloud forest in Central America using a semi-distributed water balance model",2013,"10.2478/jhh-2013-0003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875440050&doi=10.2478%2fjhh-2013-0003&partnerID=40&md5=da5744f4fbc0fe2d4da4b89d64feead4","Water scarcity poses a major threat to food security and human health in Central America and is increasingly recognized as a pressing regional issues caused primarily by deforestation and population pressure. Tools that can reliably simulate the major components of the water balance with the limited data available and needed to drive management decision and protect water supplies in this region. Four adjacent forested headwater catchments in La Tigra National Park, Honduras, ranging in size from 70 to 635 ha were instrumented and discharge measured over a one year period. A semi-distributed water balance model was developed to characterize the bio-hydrology of the four catchments, one of which is primarily cloud forest cover. The water balance model simulated daily stream discharges well, with Nash Sutcliffe model efficiency (E) values ranging from 0.67 to 0.90. Analysis of calibrated model parameters showed that despite all watersheds having similar geologic substrata, the bio-hydrological response the cloud forest indicated less plantavailable water in the root zone and greater groundwater recharge than the non cloud forest cover catchments. This resulted in watershed discharge on a per area basis four times greater from the cloud forest than the other watersheds despite only relatively minor differences in annual rainfall. These results highlight the importance of biological factors (cloud forests in this case) for sustained provision of clean, potable water, and the need to protect the cloud forest areas from destruction, particularly in the populated areas of Central America."
"35605362100;11939918300;7202153399;","Tropical precipitation and convection changes in the Max Planck Institute Earth system model (MPI-ESM) in response to CO2 forcing",2013,"10.1002/jame.20012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876713930&doi=10.1002%2fjame.20012&partnerID=40&md5=d327e8da723c8c8ca795b8ff59f3acba","In this study, the sensitivity of tropical precipitation and convection to CO2 forcing is examined. In order to test the robustness of the response, two simulations with idealized CO2 forcings following CMIP5, one with a smooth and one with an abrupt CO2 increase, are analyzed. The simulations are performed with the Max Planck Institute Earth system model (MPI-ESM). Beyond investigating the mean precipitation response, high-frequency (30 min) direct output of the convection scheme is considered to better assess the ability of the convection scheme to reproduce results from cloud-resolving simulations or physical argumentation. Over the tropics, precipitation increases by 1.7% K-1 almost independently of the CO2 forcing. Over land, the response under transient CO2 forcing is also positive, but negative under an abrupt CO2 increase. In both cases precipitation tends to follow evaporation, but the latter reacts differently due to land surface processes. The Madden-Julian oscillation also shows different sensitivities for the two CO2 forced climates. As the climate warms, deep convection gets more intense, less frequent, and deeper. The cloud top temperatures remain constant, whereas cumulus congestus and shallow clouds warm. As such, the MPI-ESM and its convection scheme hold for the fixed-anvil temperature hypothesis. This implies an enhancement of the deep convective cloud height by 3-4% K-1. Changes in precipitation intensity and convective cloud base properties scale with the Clausius-Clapeyron equation, whereas the energy constraint determines changes in precipitation frequency. This is true over the tropics considered as a whole and over the tropical oceans, but breaks down over land. ©2013. American Geophysical Union. All Rights Reserved."
"36604588400;35758381900;23006934800;26643251000;55918993800;","An evaluation of a semi-analytical cloud property retrieval using MSG SEVIRI, MODIS and CloudSat",2013,"10.1016/j.atmosres.2012.10.029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871159490&doi=10.1016%2fj.atmosres.2012.10.029&partnerID=40&md5=f825d2ea4ce564634cd11a10c0e01ed5","Knowledge of cloud properties such as cloud effective radius (aef) and optical thickness (τ) is essential to understand their role in the dynamic radiation budget and climate change. The Spinning Enhanced Visible and Infrared Instrument (SEVIRI) on board Meteosat Second Generation (MSG) with its high temporal resolution (15min), permits a quasi-continuous monitoring of the evolution of cloud properties. This has motivated the adaptation of the SLALOM (SimpLe Approximations for cLOudy Media) algorithm, a semi-analytical cloud property retrieval technique to MSG SEVIRI. The optical properties retrieved by SLALOM are compared against the well known and validated NASA MODIS cloud property product (MODIS 06) as well as the cloud optical depth product (2B-TAU) of CloudSat. The results are shown over the North Atlantic and over the European continent with the intention of determine the relative accuracy between SLALOM and the other retrievals. Over the North Atlantic, SLALOM-based cloud properties retrieved from SEVIRI datasets show a good agreement with the MODIS 06 product with correlation coefficients of 0.93 (τ) and 0.82 (aef). The largest deviations were found in less homogeneous cloud areas that are characterized by broken clouds and toward the cloud borders. Moreover, SLALOM optical thickness values are well within the range of corresponding CloudSat 2B-TAU optical thickness values which can be found within a SEVIRI pixel, except for τ&lt;5 where SLALOM tends to overestimate τ. Despite the different sensor characteristics and viewing geometries, the retrieved cloud properties compare very well. Over Europe, the evaluation between SLALOM and MODIS 06 showed larger differences. We attribute this to (a) uncertainties related to the surface albedo which is treated differently in the algorithms and is based on different albedo maps and (b) inhomogeneities of clouds which exhibit quite complex structures particularly over land. The latter are detected on different scales by MODIS and SEVIRI because of their different spatial resolutions. Given the demonstrated accuracy of SLALOM using MSG SEVIRI data there is a wide spread of potential applications. © 2012 Elsevier B.V."
"14024070000;7404493635;6602545330;7005837895;7102947372;","Climate impacts of land-cover and land-use changes in tropical islands under conditions of global climate change",2013,"10.1175/JCLI-D-12-00087.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874792089&doi=10.1175%2fJCLI-D-12-00087.1&partnerID=40&md5=117fe10a44603626ff7086e82914bdc5","Land-cover and land-use (LCLU) changes have significant climate impacts in tropical coastal regions with the added complexity of occurring within the context of a warming climate. The individual and combined effects of these two factors in tropical islands are investigated by use of an integrated mesoscale atmospheric modeling approach, taking the northeastern region of Puerto Rico as the test case. To achieve this goal, an ensemble of climate simulations is performed, combining two LCLU and global warming scenarios. Reconstructed agricultural maps and sea surface temperatures form the past (59-1955) scenario, while the present (2000-04) scenario is supported with high-resolution remote sensing LCLU data. Here, the authors show that LCLU changes produced the largest near-surface (2-m AGL) air temperature differences over heavily urbanized regions and that these changes do not penetrate the boundary layer. The influence of the global warming signal induces a positive inland gradient of maximum temperature, possibly because of increased trade winds in the present climatology. These increased winds also generate convergence zones and convection that transport heat and moisture into the boundary layer. In terms of minimum temperatures, the global warming signal induces temperature increases along the coastal plains and inland lowlands. © 2013 American Meteorological Society."
"56002706500;22133412000;14028759700;57203051832;","Effects of altitude and climate in determining elevational plant species richness patterns: A case study from Los Tuxtlas, Mexico",2013,"10.1016/j.flora.2013.03.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876737336&doi=10.1016%2fj.flora.2013.03.003&partnerID=40&md5=2445e66a656b18a6dd77bffffc913d3d","Altitudinal changes of composition and richness of montane plant assemblages are complex, depending on the taxonomic group and gradient conditions, with different factors involved that are directly altitude-dependent (e.g., temperatures, air pressure) and altitude-independent (e.g., precipitation, cloud cover, area). In order to assess the relative impacts of temperature, precipitation, air humidity, and area of altitudinal belts on plant diversity, we analyzed diversity patterns of five species-rich groups, mostly herbaceous plants, in 74 forest plots along three climatically contrasting elevational transects from humid tropical lowland vegetation up to cloud forests at Los Tuxtlas, Mexico. We recorded 278 plant species, with ferns being the most species-rich group followed by orchids, bromeliads, aroids, and piperoids. The most striking results were the contrasting patterns and model results for terrestrial and epiphytic taxa. Whereas the richness of all terrestrial species taken together did not change significantly with elevation, vascular epiphytes showed increasing species numbers with altitude. However, a number of individual terrestrial taxa showed also significant elevation-related changes: aroids showed a marked decline with hight, orchids and piperoids increased, and ferns displayed a hump-shaped pattern with highest richness in mid-altitudes. Among the epiphytes, aroids declined while most other groups increased with altitude. This distinction is relevant for projections of responses of plant communities to climate change, which will lead to increased temperatures and to changing precipitation and cloud condensation regimes and thus will likely affect terrestrial and epiphytic species in different ways. © 2013 Elsevier GmbH."
"55600705100;6601982331;","Implications of security mechanisms and Service Level Agreements (SLAs) of Platform as a Service (PaaS) clouds for geoprocessing services",2013,"10.1007/s12518-012-0083-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874094209&doi=10.1007%2fs12518-012-0083-3&partnerID=40&md5=2fb54dbca679eb59cde19e135f42e6e1","Cloud computing is an emerging computing paradigm aimed at running services over the internet to provide scalability and flexibility. The advantages in using the cloud for start-up and small businesses that lack infrastructure have been shown to far outweigh the disadvantages. Cloud platform services, also known as Platform as a Service (PaaS), provide a computing platform or solution stack on which software can be developed for later deployment in a cloud. However, there are a number of security challenges because users of the cloud have to rely on third-party companies to provide confidentiality, integrity and availability. Geoprocessing is the manipulation of geographic information, ranging from simple feature overlays and geocoding to raster processing and advanced climate modelling. The Open Geospatial Consortium's Web Processing Service defines a standardized interface that facilitates the publishing of geospatial processes. Parallelization and distribution of geoprocessing services have received much attention lately, including running them in a cloud. However, work on the security aspects of geoprocessing in a cloud is limited. In this paper, we analyse security mechanisms and Service Level Agreements of PaaS clouds and present results of experiments run in PaaS clouds. The implications of these results for the development of geoprocessing services in a PaaS cloud are discussed. Finally, recommendations for future work are presented. © 2012 Società Italiana di Fotogrammetria e Topografia (SIFET)."
"24577868100;6701520921;6701489606;7004925451;16444554900;","Evaluating cloud contamination in clear-sky MODIS Terra daytime land surface temperatures using ground-based meteorology station observations",2013,"10.1175/JCLI-D-12-00250.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874798044&doi=10.1175%2fJCLI-D-12-00250.1&partnerID=40&md5=7cf465fd21f8efa74c285db3bc7d7fdd","Environment Canada meteorological station hourly sampled air temperatures Tair at four stations in the southwest Yukon were used to identify cloud contamination in the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra clear-sky daytime land surface temperature (LST) and emissivity daily level-3 global 1-km grid product (MOD11A1, Collection 5) that is not flagged by the MODIS quality algorithm as contaminated. The additional cloudmasking used qualitative ground-based sky condition observations, collected at two of the four stations, and coincident MODIS quality flag information. The results indicate that air temperature observed at a variety of discrete spatial locations having different land cover is highly correlated with MODIS LST collected at 1-km grid spacing. Quadratic relationships between LST and air temperature, constrained by ground observations of ""clear"" sky conditions, show less variability than relationships found under ""mainly clear"" and ""mostly cloudy"" sky conditions, and themore clouds observed in the sky coincides with a decreasing y intercept.Analysis ofMODISLST and its associated quality flags showa cold bias (&lt;0°C) in the assignment of the ≤3-K-average LST error, indicating MODIS LST has a maximum average error of ≤2 K over a warm surface (&gt;0°C).Analysis of two observation stations shows that unidentified clouds inMODIS LST are between 13%and 17%, a result that agrees well with previous studies. Analysis of daytime values is important because many processes are dependent on daylight and maximum temperature. The daytime clear-sky LST-Tair relationship observed for the good-quality confirmed cloud-free-sky MODIS LST quality flag can be used to discriminate cloud-contaminated grid cells beyond the standard MODIS cloud mask. © 2013 American Meteorological Society."
"14523673200;55073323400;","Changes in cloud cover, precipitation, and summer temperature in north america from 1982 to 2009",2013,"10.1175/JCLI-D-12-00225.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874805534&doi=10.1175%2fJCLI-D-12-00225.1&partnerID=40&md5=cdeb333b9a874a7229cb65e5a33f0c53","In North America (NA), trends in summer surface air temperatures vary on decadal time scales, and some regions have temperature trends that exhibit a lack of warming in 1982-2009. From a surface energy balance perspective, the summer mean daily maximum temperature change can be affected by changes in solar heating that are associated with cloud cover change and changes in surface evaporative cooling caused by different precipitation and land surface wetness, but little is known about regional cloud cover and precipitation feedbacks to decadal temperature trends. Changes in cloudiness and precipitation and their connections with summer mean daily maximum temperature variations in NA were investigated using observation-based products of temperature and precipitation and satellite-derived cloud cover and radiation products. Results show that summer mean daily maximum temperature variance is largely explained by changes in cloud cover and precipitation. Cloud cover effect dominates at the high and middle latitudes of NA, and precipitation is a more dominant factor in the southern United States. The results indicate that cloud cover is either the major indicator of the summer mean daily maximum temperature changes (the effect) or the important local factor influencing the changes (the cause). Cloud cover is negatively correlated with mean daily maximum temperature variation in spring and autumn at the middle latitudes of NA but not at the high latitudes. © 2013 American Meteorological Society."
"55637607600;6602239759;57217977324;7004013739;6603328138;8669498200;12646180100;7102312611;","A spectral aging model for the meteosat-7 visible band",2013,"10.1175/JTECH-D-12-00124.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875650484&doi=10.1175%2fJTECH-D-12-00124.1&partnerID=40&md5=348a5bf4d1cbefb56a2ab0619711d559","For more than 30 years, the Meteosat satellites have been in a geostationary orbit around the earth. Because of the high temporal frequency of the data and the long time period, this database is an excellent candidate for fundamental climate data records (FCDRs). One of the prerequisites to create FCDRs is an accurate and stable calibration over the full data period. Because of the presence of contamination on the instrument in space, a degradation of the visible band of the instruments has been observed. Previous work on the Meteosat First Generation satellites, together with results from other spaceborne instruments, led to the idea that there is a spectral component to this degradation. This paper describes the model that was created to correct the Meteosat-7 visible (VIS) channel for these spectral aging effects. The model assumes an exponential temporal decay for the gray part of the degradation and a linear temporal decay for the wavelength-dependent part. The effect of these two parts of the model is tuned according to three parameters; 253 clear-sky stable earth targets with different surface types are used together with deep convective cloud measurements to fit these parameters. The validation of the model leads to an overall stability of the Meteosat-7 reflected solar radiation data record of about 0.66 W m-2 decade-1. © 2013 American Meteorological Society."
"7103373860;55652126100;","The arm climate research facility: A review of structure and capabilities",2013,"10.1175/BAMS-D-11-00218.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876264431&doi=10.1175%2fBAMS-D-11-00218.1&partnerID=40&md5=3472b6c086368e81ee77d138d1d15086","The Department of Energy (DOE) created the Atmospheric Radiation Measurement (ARM) has added instruments to expand its capabilities for the study of clouds, aerosol, and precipitation. The ARM sites provide a broad array of measurements covering cloud properties aerosol properties, surface properties, atmospheric thermodynamic properties, and radiative fluxes. These measurements are provided continuously with high temporal resolution despite the resolution of some of the remote sensing instruments being short to capture variability in cloud properties. The ARM Facility is managed and operated by nine DOE National Laboratories, located at Argonne, Berkeley, Brookhaven, Livermore, Los Alamos, Oak Ridge, National Renewable Energy, Pacific Northwest, and Sandia. It has developed and deployed its first ARM Mobile Facility (AMF) to improve its performance."
"35335123900;6701589295;","The role of glacial cycles in promoting genetic diversity in the Neotropics: The case of cloud forests during the Last Glacial Maximum",2013,"10.1002/ece3.483","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884492004&doi=10.1002%2fece3.483&partnerID=40&md5=70132d6b4d4151ceed8c7a1ce378e925","The increasing aridity during the Last Glacial Maximum (LGM) has been proposed as a major factor affecting Neotropical species. The character and intensity of this change, however, remains the subject of ongoing debate. This review proposes an approach to test contrasting paleoecological hypotheses by way of their expected demographic and genetic effects on Neotropical cloud forest species. We reviewed 48 paleoecological records encompassing the LGM in the Neotropics. The records show contrasting evidence regarding the changes in precipitation during this period. Some regions remained fairly moist and others had a significantly reduced precipitation. Many paleoecological records within the same region show apparently conflicting evidence on precipitation and forest stability. From these data, we propose and outline two demographic/genetic scenarios for cloud forests species based on opposite precipitation regimes: the dry refugia and the moist forests hypotheses. We searched for studies dealing with the population genetic structure of cloud forest and other montane taxa and compared their results with the proposed models. To date, the few available molecular studies show insufficient genetic evidence on the predominance of glacial aridity in the Neotropics. In order to disentangle the climatic history of the Neotropics, the present study calls for a general multi-disciplinary approach to conduct future phylogeographic studies. Given the contradictory paleoecological information, population genetic data on Neotropical cloud forest species should be used to explicitly test the genetic consequences of competing paleoecological models. © 2013 The Authors. Ecology and Evolution published by Blackwell Publishing Ltd."
"7006399667;7202081585;","Physical processes in the tropical tropopause layer and their roles in a changing climate",2013,"10.1038/ngeo1733","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874602847&doi=10.1038%2fngeo1733&partnerID=40&md5=55de7d7788f38777b60b6da8ea2cb4f4","Tropical climate and the composition of the global upper atmosphere are affected by the tropical tropopause layer - the atmospheric transition zone between the well-mixed, convective troposphere (up to altitudes of 12-14 km) and the highly stratified stratosphere (above about 18 km). Featuring chemical and dynamical properties that are midway between those of the troposphere and stratosphere, the tropopause layer is maintained by a complex interplay between large- and small-scale circulation patterns, deep convection, clouds and radiation. Tropospheric air enters the stratosphere primarily in the tropics. Ozone- and aerosol-related constituents of the global stratosphere, as well as water vapour content, are therefore largely determined by the composition of the air near the tropical tropopause. Over the past years, it has emerged that both slow ascent and rapid deep convection contribute to the composition and thermal structure of the tropical tropopause layer. Ice formation processes at low temperatures affect the efficacy of freeze drying as air passes through the cold tropopause region. Transport and mixing in the tropopause region has been found to be closely linked with the Asian monsoon and other tropical circulation systems. Given these connections, climate change is expected to influence the tropopause layer, for example through enhanced large-scale upwelling of air and potential changes in tropical convection, air temperature, chemical composition and cirrus. Copyright © 2013 Macmillan Publishers Limited."
"7005435915;6602494687;","Russian investigations in the field of atmospheric radiation in 2007-2010",2013,"10.1134/S000143381301009X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874298483&doi=10.1134%2fS000143381301009X&partnerID=40&md5=b1af46aa4199552210d105c792e09015","A short survey prepared by the Russian Commission on Atmospheric Radiation contains the most significant results of works in the field of atmospheric-radiation studies performed in 2007-2010. It is part of the Russian National Report on Meteorology and Atmospheric Sciences prepared for the International Association on Meteorology and Atmospheric Sciences (IAMAS). During this period, the Russian Commission on Atmospheric Radiation, jointly with concerned departments and organizations, ran the conference ""Physics and Education,"" dedicated to the 75th anniversary of the Department of Physics at St. Petersburg State University (2007); the International Symposium of CIS Countries ""Atmospheric Radiation and Dynamics"" (2009); and the 5th International Conference ""Atmospheric Physics, Climate, and Environment"" (2010). At the conferences, central problems in modern atmosphere physics were discussed: radiative transfer and atmospheric optics; greenhouse gases, clouds, and aerosols; remote methods of measurements; and new measurement data. This survey presents five directions covering the whole spectrum of investigations performed in the field of atmospheric radiation. © 2013 Pleiades Publishing, Ltd."
"6506685074;57214526980;","Changes in temperature and precipitation extremes observed in Modena, Italy",2013,"10.1016/j.atmosres.2012.10.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871128154&doi=10.1016%2fj.atmosres.2012.10.022&partnerID=40&md5=989f0e13f2e763f5e612e7ad5c2b6bc8","Climate changes has become one of the most analysed subjects from researchers community, mainly because of the numerous extreme events that hit the globe. To have a better view of climate changes and trends, long observations time series are needed.During last decade a lot of Italian time series, concerning several surface meteorological variables, have been analysed and published. No one of them includes one of the longest record in Italy, the time series of the Geophysical Observatory of the University of Modena and Reggio Emilia. Measurements, collected since early 19th century, always in the same position, except for some months during the second world war, embrace daily temperature, precipitation amount, relative humidity, pressure, cloudiness and other variables.In this work we concentrated on the analysis of yearly and seasonal trends and climate extremes of temperature, both minimum and maximum, and precipitation time series, for the periods 1861-2010 and 1831-2010 respectively, in which continuous measurements are available.In general, our results confirm quite well those reported by IPCC and in many other studies over Mediterranean area. In particular, we found that minimum temperature has a non significant positive trend of +. 0.1 °C per decade considering all the period, the value increases to 0.9 °C per decade for 1981-2010. For maximum temperature we observed a non significant +. 0.1 °C trend for all the period, while +. 0.8 °C for the last thirty years.On the other hand precipitation is decreasing, -6.3. mm per decade, considering all the analysed period, while the last thirty years are characterised by a great increment of 74.8. mm per decade.For both variables several climate indices have been analysed and they confirm what has been found for minimum and maximum temperatures and precipitation. In particular, during last 30. years frost days and ice days are decreasing, whereas summer days are increasing. During the last 30-year tropical nights and warm spell duration indices are characterised by a particular strong increment, if compared to the ones of the entire period.Finally, a cursory comparison between winter precipitation and NAO index was done, showing a high anti-correlation, especially since the second half of 20th century. © 2012 Elsevier B.V."
"24333241700;36842724800;55942502100;56493740900;","A supplementary clear-sky snow and ice recognition technique for CERES level 2 products",2013,"10.1175/JTECH-D-12-00100.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875641865&doi=10.1175%2fJTECH-D-12-00100.1&partnerID=40&md5=5cf3d3b4e82f3bee69b6e6dbce1d51d1","Identification of clear-sky snow and ice is an important step in the production of cryosphere radiation budget products, which are used in the derivation of long-term data series for climate research. In this paper, a new method of clear-sky snow/ice identification for Moderate Resolution Imaging Spectroradiometer (MODIS) is presented. The algorithm's goal is to enhance the identification of snow and ice within the Clouds and the Earth's Radiant Energy System (CERES) data after application of the standard CERES scene identification scheme. The input of the algorithm uses spectral radiances from five MODIS bands and surface skin temperature available in the CERES Single Scanner Footprint (SSF) product. The algorithm produces a cryosphere rating from an aggregated test: a higher rating corresponds to a more certain identification of the clear-sky snow/ice-covered scene. Empirical analysis of regions of interest representing distinctive targets such as snow, ice, ice and water clouds, open waters, and snow-free land selected from a number of MODIS images shows that the cryosphere rating of snow/ice targets falls into 95% confidence intervals lying above the same confidence intervals of all other targets. This enables recognition of clear-sky cryosphere by using a single threshold applied to the rating, which makes this technique different from traditional branching techniques based on multiple thresholds. Limited tests show that the established threshold clearly separates the cryosphere rating values computed for the cryosphere from those computed for noncryosphere scenes, whereas individual tests applied consequently cannot reliably identify the cryosphere for complex scenes."
"43961759100;7004433410;55667075800;36721587000;55832723000;57200790631;6603369413;35448188800;","Estimating the influence of lightning on upper tropospheric ozone using NLDN lightning data and CMAQ model",2013,"10.1016/j.atmosenv.2012.11.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872386736&doi=10.1016%2fj.atmosenv.2012.11.001&partnerID=40&md5=2aa75cc5ee3f33a592602106dc0d7229","Lightning is a particularly significant NOx source in the middle and upper troposphere where it affects tropospheric chemistry and ozone. Because the version-4 Community Multiscale Air Quality Modeling System (CMAQ) does not account for NOx emission from lightning, it underpredicts NOx above the mixed layer. In this study, the National Lightning Detection Network™ (NLDN) lightning data are applied to the CMAQ model to simulate the influence of lightning-produced NOx (LNOx) on upper tropospheric NOx and subsequent ozone concentration. Using reasonable values for salient parameters (detection efficiency ~95%, cloud flash to ground flash ratio ~3, LNOx production rate ~500 mol N per flash), the NLDN ground flashes are converted into total lightning NOx amount and then vertically distributed on 39 CMAQ model layers according to a vertical-distribution profile of lightning N mass. This LNOx contributes 27% of the total NOx emission during 15 July ~7 September 2006. This additional NOx reduces the low-bias of simulated tropospheric O3 columns with respect to OMI tropospheric O3 columns from 10 to 5%. Although the model prediction of ozone in upper troposphere improves by ~20 ppbv due to lightning-produced NOx above the southeastern and eastern U.S.A., the improved ozone prediction is still ~20-25 ppbv lower than ozonesonde measurements. © 2012 Elsevier Ltd."
"24467994800;35107735600;55927784300;6701611146;","Intercomparison of leaf area index products for a gradient of sub-humid to arid environments in west africa",2013,"10.3390/rs5031235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877650271&doi=10.3390%2frs5031235&partnerID=40&md5=0b12d779f42857053279996955e8013a","The Leaf Area Index (LAI) is a key variable in many land surface and climate modeling studies. To date, a number of LAI datasets have been developed based on time series of medium resolution optical remote sensing observations. Global validation exercises show the high value of these datasets, but at the same time they point out shortcomings, particularly in the presence of persistent cloud coverage and dense vegetation. For regional modeling studies, the choice of an ideal LAI input dataset is not straightforward as global validation, and intercomparison studies do not necessarily allow conclusions on data quality at regional scale. This paper provides a comprehensive relative intercomparison of four freely available LAI products for a wide gradient of ecosystems in Africa. The region of investigation, West Africa, comprises typical African sub-humid to arid landscapes. The selected LAI time series are the Satellite Pour l'Observation de la Terre-VEGETATION (SPOT-VGT)-based Carbon Cycle and Change in Land Observational Products from an Ensemble of Satellites (CYCLOPES) LAI, the SPOTVGT- based Bio-geophysical Parameters (BioPar) LAI product GEOV1, the Moderate Resolution Imaging Spectroradiometer (MODIS) product MOD15A2, and the Meteosat- SEVIRI-based Satellite Application Facility on Land Surface Analysis (LSA-SAF) LAI. The comparative analyses focus on data gap occurrence, on the consistency of temporal LAI profiles, on their ability to adequately reproduce the phenological cycle and on the plausibility of LAI magnitudes for major land cover types in West Africa. A detailed quantitative validation of the LAI datasets, however, was not possible due to insufficient ground LAI measurements in the study region. © 2013 by the authors; licensee MDPI, Basel, Switzerland."
"6701746055;8301778200;36679794700;55025838700;","Least Bittern occupancy dynamics and detectability in Manitoba, Ontario, and Québec",2013,"10.1676/12-046.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874088113&doi=10.1676%2f12-046.1&partnerID=40&md5=6565dc4a003af1c202a79609dde58ed6","We conducted 3,050 point counts from 2005-2009 (May-Jul) in 82 wetlands in three Canadian provinces (Ontario, Québec, and Manitoba) to quantify colonization and extinction dynamics of Least Bittern (Ixobrychus exilis) populations to detect geographic variations across provinces and to analyze effects of weather conditions, date, and survey methodology that may affect detection probability of Least Bitterns. Least Bitterns were detected at 773 (25%) of the 3,050 point counts with birds detected in 25, 26, and 28% of all point counts in Ontario, Québec, and Manitoba, respectively. Occupancy probability in the first year of the study was lower in Québec sites (0.26) compared to Manitoba sites (0.53). However, Québec sites had higher probabilities of colonization (0.67) than Ontario (0.32) and Manitoba (0.27). Probabilities of extinction did not differ across provinces but varied across years. Detection probability did not vary with weather variables (cloud cover, wind speed, air temperature-linear or quadratic effect) but decreased from mid-May (0.19) to mid-July (0.09). Detection probability was lower (0.13) for the first passive listening period than the call-broadcast period (0.28) and the second passive listening period (0.33). Observed differences in extinction and colonization probability between provinces and years show that occupancy dynamics vary both temporally and geographically, stressing the need to continue long-term monitoring of Least Bittern populations across the breeding range to detect geographic variation and changes in occupancy. We recommend Least Bittern surveys begin in mid-May at higher latitudes and use a second passive listening period following the call-broadcast period to increase detection of the species. © 2013 by the Wilson Ornithological Society."
"7404970050;55637574100;47761806800;","E3DVar: Coupling an ensemble kalman filter with three-dimensional variational data assimilation in a limited-area weather prediction model and comparison to E4DVar",2013,"10.1175/MWR-D-12-00075.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875661845&doi=10.1175%2fMWR-D-12-00075.1&partnerID=40&md5=f170e06fcbdb4a9cee4fd13710454d71","This study examines the performance of a hybrid ensemble-variational data assimilation system (E3DVar) that couples an ensemble Kalman filter (EnKF) with the three-dimensional variational data assimilation (3DVar) system for the Weather Research and Forecasting (WRF) Model. The performance of E3DVar and the component EnKF and 3DVar systems are compared over the eastern United States for June 2003. Conventional sounding and surface observations as well as data from wind profilers, aircraft and ships, and cloud-tracked winds from satellites, are assimilated every 6 h during the experiments, and forecasts are verified using standard sounding observations. Forecasts with 12- to 72-h lead times are found to have noticeably smaller root-mean-square errors when initialized with the E3DVar system, as opposed to the EnKF, especially for the 12-h wind and moisture fields. The E3DVar system demonstrates similar performance as an EnKF, while using less than half the number of ensemble members, and is less sensitive to the use of a multiphysics ensemble to account for model errors. The E3DVar system is also compared with a similar hybrid method that replaces the 3DVar component with the WRF four-dimensional variational data assimilation (4DVar) method (denoted E4DVar). The E4DVar method demonstrated considerable improvements over E3DVar for nearly all model levels and variables at the shorter forecast lead times (12-48 h), but the forecast accuracies of all three ensemble-based methods (EnKF, E3DVar, and E4DVar) converge to similar results at longer lead times (60-72 h). Nevertheless, all methods that used ensemble information produced considerably better forecasts than the two methods that relied solely on static background error covariance (i.e., 3DVar and 4DVar). © 2013 American Meteorological Society."
"7102018821;7401622015;7005528388;7403931916;","On the radiative forcing of contrail cirrus contaminated by black carbon",2013,"10.1002/grl.50110","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878177962&doi=10.1002%2fgrl.50110&partnerID=40&md5=b2b0bd88b8d081c0ce3fe706845a197f","The effects of internal and external mixings of black carbon (BC) (soot) in ice particles on the radiative properties of contrail cirrus are investigated using a simple ice plate model. The internal mixing state absorbs substantially more radiation as compared with its external mixing counterpart due to light absorption enhancement from all directions. The soot absorption effect is largely confined to wavelengths shorter than about 1.4 μm, beyond which ice absorption predominates. For an ice crystal size of 5 μm internally mixed with a soot particle of 0.1 μm radius in contrail cirrus with an optical depth of 0.5, the instantaneous radiative forcings at the top of and within the atmosphere are approximately 0.2 and 0.8 W/m2, respectively. In view of the likelihood of multiple inclusions of soot particles in contrail cirrus, these values are lower limits. Thus, a realistic assessment of the global and regional radiative forcings of contrail cirrus for climate studies must account for the radiative effect induced by soot mixing states associated with the microscopic formation of ice particles. Key Points Black carbon can substantially impact the radiative forcing of contrail cirrus Internal mixing of BC in ice can alter its absorption of solar radiation Radiative forcing analysis for contrail must account for BC contamination ©2013. American Geophysical Union. All Rights Reserved."
"8570871900;","Arctic climate sensitivity to local black carbon",2013,"10.1002/jgrd.50176","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875744968&doi=10.1002%2fjgrd.50176&partnerID=40&md5=34bd35670a041613c684652a3663e971","Recent attention has focused on the impact of black carbon (BC) on Arctic climate. Here, idealized equilibrium climate experiments are conducted to explore the dependence of Arctic temperature change on the altitude and season of local BC forcing. BC residing in the lowest atmospheric layer produces very strong Arctic warming per unit mass and forcing [ 2.8 ± 0.5 K (Wm -2)-1] because of low cloud and sea-ice feedbacks that amplify both summer and winter warming. BC operating only within Arctic snow and sea-ice also effectively warms the surface, but forcings at 400-750mbar and 210-250mbar cause weak surface warming and cooling, respectively, despite increasing atmospheric moist static energy. This is a consequence of stable atmospheric conditions in the Arctic limiting vertical mixing, and of higher-altitude BC reducing surface insolation, increasing stability and summer low-cloud cover, and decreasing poleward energy transport. The current simulated distribution of Arctic atmospheric BC slightly cools the surface, supporting an earlier study, while local atmospheric and cryosphere-deposited BC warms the Arctic with a sensitivity of + 0.5 ± 0.4 K (Wm-2) -1. By season, April-May tropospheric BC induces the greatest mass-normalized Arctic warming [0.18 K (Gg yr) -1] because high insolation and surface albedo facilitate large specific forcing during this season. Forcing efficacy, however, increases with summer progression because of decreasing atmospheric stability, leading to a narrow range of mass-normalized response with season. Although limited by exclusion of aerosol indirect effects, changes in ocean heat transport and forcing by co-emitted species, these experiments show that Arctic climate response is sensitive to the vertical distribution and deposition efficiency of BC reaching the Arctic. Key PointsSurface climate change from Arctic black carbon depends strongly on its altitudeNear-surface BC causes strong warming because of cloud and sea-ice feedbacksCurrent Arctic atmosphere + snow BC warms the surface while atmospheric BC may not © 2013. American Geophysical Union. All Rights Reserved."
"55330960300;7202208382;8067118800;","Comparison of observed and simulated tropical cumuliform clouds by CloudSat and NICAM",2013,"10.1002/jgrd.50121","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880894311&doi=10.1002%2fjgrd.50121&partnerID=40&md5=582ae89c36ac2b9f0d7c79c229826872","We use CloudSat observations of boreal summer tropical ocean cumuliform clouds to evaluate the behavior of the non-parameterized cumuliform clouds in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), with a particular emphasis on deep convective clouds (DCCs). The CloudSat cloud mask and radar reflectivity profiles for cumuliform clouds are sorted by large-scale environmental variables taken from the Aqua satellite and NCEP/NCAR reanalysis. The variables are total precipitable water (TPW), sea surface temperature (SST), and 500 hPa vertical velocity (W500), representing the dynamical and thermodynamical environment in which the clouds form. The sorted CloudSat profiles are then compared with NICAM profiles simulated with the Quickbeam CloudSat simulator. We first use the cloud mask to examine the transition between shallow clouds and deep clouds rooted in the planetary boundary layer. We find that NICAM simulates this transition fairly realistically. However, the transition occurs at slightly higher TPW and W500 values than the observations show. This may be indication of NICAM's inability to represent the formation of isolated narrow DCCs in marginally favorable environments. We then use simple metrics of the DCC-only radar reflectivity profiles (cloud top height, cloud top reflectivity gradient, maximum reflectivity) to quantitatively compare the observations with NICAM. The results show that while the observed and simulated results agree generally, there are some disagreements in key respects. There is disagreement on the sensitivity of cloud top height to environmental conditions and on the transition between shallow and deep clouds in environments marginally suitable for deep convection. CloudSat observations are used to evaluate tropical convective clouds in NICAMCloud variables are evaluated relative to changes in environmental variablesNICAM shows mostly realistic cloud behavior, with a few minor disagreements © 2013. American Geophysical Union. All Rights Reserved."
"37099944400;7006329853;7201488063;","Microphysical simulations of large volcanic eruptions: Pinatubo and Toba",2013,"10.1002/jgrd.50196","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876801009&doi=10.1002%2fjgrd.50196&partnerID=40&md5=966e8fee56e89d417a21edc447627b0f","Simulations of stratospheric clouds from eruptions ranging in size from the 1991 eruption of Mount Pinatubo to that of Toba 74,000 years ago have been completed using a 3D microphysical sectional aerosol model advectively coupled to a general circulation model with prognostic chemistry (Whole Atmosphere Community Climate Model/Community Aerosol and Radiation Model for Atmospheres). For Pinatubo, properties of the aerosol cloud peak within the ranges derived from observations in the Northern Hemisphere, but reduce faster than observed, and a general low bias is found in the Southern Hemisphere. These biases could be reduced by adding aerosol radiative coupling, a quasi-biennial oscillation, and the Cerro Hudson eruption to the model. Simulations of eruptions 10 times and 100 times larger than Pinatubo suggest burdens and Aerosol Optical Depth increase less than linearly (a 100-fold injection increase produces a 20-fold AOD increase) due to particle growth and sedimentation, consistent with previous work that also found the radiative forcings from large eruptions to be self-limiting. Global-averaged AOD remains elevated for 1, 2, and 4 years, respectively, for the three simulated eruptions. The inclusion of van der Waals forces in our coagulation scheme increases peak effective radius and reduces peak AOD by about 10-20%, with bigger effects for larger eruptions. Our simulations find peak mode size to vary by up to an order of magnitude and mode width to vary by up to 50%, suggesting that two-moment modal models may not accurately capture the evolving size distribution. These simulations suggest the value of including van der Waals forces in the coagulation scheme and sectional size distributions in climate models. Key PointsOur model predicts Pinatubo peak but declines too quicklyLarger eruptions increase effective radius and mode widths varyvan der Waals forces increases coagulation and particle size © 2013. American Geophysical Union. All Rights Reserved."
"55807354200;21735369200;7006788343;55807701500;55670695200;57199246242;55807562800;","Characteristics of stratosphere-troposphere exchange during the Meiyu season",2013,"10.1029/2012JD018124","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880889496&doi=10.1029%2f2012JD018124&partnerID=40&md5=445b35258a61649b3c64aaf35d376e0f","Characteristics of stratosphere-troposphere exchange (STE) during the Meiyu season in the Yangtze-Huaihe valley, China, is investigated using the European Centre for Medium-Range Weather Forecasts interim reanalysis data, National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data, Meiyu records from the National Climate Center of China, the data from a trajectory model, and a general circulation model (GCM). Results show increases in potential vorticity and decreases in specific humidity in the upper troposphere and lower stratosphere (UTLS) before Meiyu onset, suggesting a strong downward transport of air masses around the tropopause that can be attributed to frequent tropopause folds over the Meiyu area. The minimum tropopause height occurs 3 days before Meiyu onset and then rises until about 6 days afterward. The downward cross-tropopause mass transport (CTMF) is evidenced before Meiyu onset, which is mainly caused by the sharp meridional gradients in the tropopause pressure over the Meiyu area. After Meiyu onset, the upward cross-tropopause transport intensifies due to enhanced convections. The analysis also suggests the strongest upward transport in the UTLS occurs northeast of the Meiyu region, within the core of the upper tropospheric westerly jet. Results from a trajectory model indicate that the lower stratospheric air intrudes into the troposphere before Meiyu onset. The significant upward movements of the middle tropospheric air are notable after Meiyu onset. As convections are weak and the upper level westerly jet is located far to the Meiyu area in poor Meiyu years, the upward CTMF over the Meiyu region is weaker during the Meiyu season compared with that in rich Meiyu years. Key PointsThe net transport is from the stratosphere to the troposphere before Meiyu onsetSTE caused by the sharp meridional gradients in the tropopause pressureThe air intrudes into the troposphere from levels above 18 km © 2012. American Geophysical Union. All Rights Reserved."
"24331295800;6701895637;7003627515;14045570100;36928248800;6602598448;","Meteorological regimes and accumulation patterns at Utsteinen, Dronning Maud Land, East Antarctica: Analysis of two contrasting years",2013,"10.1002/jgrd.50177","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879981534&doi=10.1002%2fjgrd.50177&partnerID=40&md5=125761b1b205a697a98dc532fba1a4c0","Since February 2009, an automatic weather station (AWS) has been operating near Utsteinen Nunatak, north of the Sør Rondane Mountains, in Dronning Maud Land at the ascent to the East Antarctic Plateau. This paper gives an assessment of the meteorological conditions, radiative fluxes, and snow accumulation for the first 2 years of operation, 2009 to 2010, analyzed in terms of meteorological regimes. Three major meteorological regimes - cold katabatic, warm synoptic, and transitional synoptic - are identified using cluster analysis based on five parameters derived from the AWS measurements (wind speed, specific humidity, near-surface temperature inversion, surface pressure, and incoming longwave flux indicative of cloud forcing). For its location, the relatively mild climate at Utsteinen can be explained by the high frequency of synoptic events (observed 41%-48% of the time), and a lack of drainage of cold air from the plateau due to mountain sheltering. During the cold katabatic regime, a strong surface cooling leads to a strong near-surface temperature inversion buildup. A large difference in accumulation is recorded by the AWS for the first 2 years: 235 mm water equivalent in 2009 and 27 mm water equivalent in 2010. Several large accumulation events during the warm synoptic regime occurring mainly in winter were responsible for the majority of the accumulation in 2009. Mostly, small accumulation events occurred during 2010, frequently followed by snow removal. This interannual variability in snow accumulation at the site is related to the intensity of the local synoptic events as recorded by meteorological regime characteristics. Key Points New meteorological data are available in Dronning Maud Land, East AntarcticaA few large accumulation events lead to significant annual accumulationMountain sheltering causes specific katabatic regime conditions © 2013. American Geophysical Union. All Rights Reserved."
"35578212100;14627622500;","How might Australian rainforest cloud interception respond to climate change?",2013,"10.1016/j.jhydrol.2012.12.028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873081010&doi=10.1016%2fj.jhydrol.2012.12.028&partnerID=40&md5=c262bb2d34569355f6a4066341b58217","The lower and upper montane rainforests in northern Queensland receive significant amounts of cloud interception that affect both in situ canopy wetness and downstream runoff. Cloud interception contributes 5-30% of the annual water input to the canopy and this increases to 40-70% of the monthly water input during the dry season. This occult water is therefore an important input to the canopy, sustaining the epiphytes, mosses and other species that depend on wet canopy conditions. The potential effect of climate change on cloud interception was examined using the relationship between cloud interception and cloud frequency derived from measurements made at four different rainforest locations. Any given change in cloud frequency produces a greater change in cloud interception and this 'amplification' increases from 1.1 to 1.7 as cloud frequency increases from 5% to 70%. This means that any changes in cloud frequency will have the greatest relative effects at the higher altitude sites where cloud interception is greatest. As cloud frequency is also a major factor affecting canopy wetness, any given change in cloud frequency will therefore have a greater impact on canopy wetness at the higher altitude sites. These changes in wetness duration will augment those due to changes in rainfall and may have important implications for the fauna and flora that depend on wet canopy conditions. We also found that the Australian rainforests may be more efficient (by ∼50% on average) in intercepting cloud water than American coniferous forests, which may be due to differences in canopy structure and exposure at the different sites. © 2013."
"55601032300;7003566416;55600326000;7004276549;37096246200;7102188656;56490302800;7004732931;","Composition and evolution of volcanic aerosol from eruptions of Kasatochi, Sarychev and Eyjafjallajökull in 2008-2010 based on CARIBIC observations",2013,"10.5194/acp-13-1781-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874027223&doi=10.5194%2facp-13-1781-2013&partnerID=40&md5=61921cc34a3ba1fa05a17397b5193358","Large volcanic eruptions impact significantly on climate and lead to ozone depletion due to injection of particles and gases into the stratosphere where their residence times are long. In this the composition of volcanic aerosol is an important but inadequately studied factor. Samples of volcanically influenced aerosol were collected following the Kasatochi (Alaska), Sarychev (Russia) and also during the Eyjafjallajökull (Iceland) eruptions in the period 2008-2010. Sampling was conducted by the CARIBIC platform during regular flights at an altitude of 10-12 km as well as during dedicated flights through the volcanic clouds from the eruption of Eyjafjallajökull in spring 2010. Elemental concentrations of the collected aerosol were obtained by accelerator-based analysis. Aerosol from the Eyjafjallajökull volcanic clouds was identified by high concentrations of sulphur and elements pointing to crustal origin, and confirmed by trajectory analysis. Signatures of volcanic influence were also used to detect volcanic aerosol in stratospheric samples collected following the Sarychev and Kasatochi eruptions. In total it was possible to identify 17 relevant samples collected between 1 and more than 100 days following the eruptions studied. The volcanically influenced aerosol mainly consisted of ash, sulphate and included a carbonaceous component. Samples collected in the volcanic cloud from Eyjafjallajökull were dominated by the ash and sulphate component (&sim;45% each) while samples collected in the tropopause region and LMS mainly consisted of sulphate (50-77%) and carbon (21-43%). These fractions were increasing/decreasing with the age of the aerosol. Because of the long observation period, it was possible to analyze the evolution of the relationship between the ash and sulphate components of the volcanic aerosol. From this analysis the residence time (1/e) of sulphur dioxide in the studied volcanic cloud was estimated to be 45 ± 22 days. © 2013 Author(s)."
"35119188100;12544502800;","An advanced scheme for wet scavenging and liquid-phase chemistry in a regional online-coupled chemistry transport model",2013,"10.5194/acp-13-1177-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873926937&doi=10.5194%2facp-13-1177-2013&partnerID=40&md5=87702ea2bcb7852bd84232be18c3da41","Clouds are reaction chambers for atmospheric trace gases and aerosols, and the associated precipitation is a major sink for atmospheric constituents. The regional chemistry-climate model COSMO-ART has been lacking a description of wet scavenging of gases and aqueous-phase chemistry. In this work we present a coupling of COSMO-ART with a wet scavenging and aqueous-phase chemistry scheme. The coupling is made consistent with the cloud microphysics scheme of the underlying meteorological model COSMO. While the choice of the aqueous-chemistry mechanism is flexible, the effects of a simple sulfur oxidation scheme are shown in the application of the coupled system in this work. We give details explaining the coupling and extensions made, then present results from idealized flow-over-hill experiments in a 2-D model setup and finally results from a full 3-D simulation. Comparison against measurement data shows that the scheme efficiently reduces SO2 trace gas concentrations by 0.3 ppbv (-30%) on average, while leaving O3 and NOx unchanged. PM10 aerosol mass was increased by 10% on average. While total PM2.5 changes only little, chemical composition is improved notably. Overestimations of nitrate aerosols are reduced by typically 0.5-1 μg m-3 (up to-2 μg m -3 in the Po Valley) while sulfate mass is increased by 1-1.5 μg m-3 on average (up to 2.5 μg m-3 in Eastern Europe). The effect of cloud processing of aerosols on its size distribution, i.e. a shift towards larger diameters, is observed. Compared against wet deposition measurements the system tends to underestimate the total wet deposited mass for the simulated case study. © 2013 Author(s)."
"55261195800;6602080205;6506298579;56724696200;","The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon",2013,"10.5194/acp-13-1521-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873924899&doi=10.5194%2facp-13-1521-2013&partnerID=40&md5=1883b80bb40802dfe06aee661fc47740","The response of East Asian Summer Monsoon (EASM) precipitation to long term changes in regional anthropogenic aerosols (sulphate and black carbon) is explored in an atmospheric general circulation model, the atmospheric component of the UK High-Resolution Global Environment Model v1.2 (HiGAM). Separately, sulphur dioxide (SO2) and black carbon (BC) emissions in 1950 and 2000 over East Asia are used to drive model simulations, while emissions are kept constant at year 2000 level outside this region. The response of the EASM is examined by comparing simulations driven by aerosol emissions representative of 1950 and 2000. The aerosol radiative effects are also determined using an off-line radiative transfer model. During June, July and August, the EASM was not significantly changed as either SO2 or BC emissions increased from 1950 to 2000 levels. However, in September, precipitation is significantly decreased by 26.4% for sulphate aerosol and 14.6% for black carbon when emissions are at the 2000 level. Over 80% of the decrease is attributed to changes in convective precipitation. The cooler land surface temperature over China in September (0.8 °C for sulphate and 0.5 °C for black carbon) due to increased aerosols reduces the surface thermal contrast that supports the EASM circulation. However, mechanisms causing the surface temperature decrease in September are different between sulphate and BC experiments. In the sulphate experiment, the sulphate direct and the 1st indirect radiative effects contribute to the surface cooling. In the BC experiment, the BC direct effect is the main driver of the surface cooling, however, a decrease in low cloud cover due to the increased heating by BC absorption partially counteracts the direct effect. This results in a weaker land surface temperature response to BC changes than to sulphate changes. The resulting precipitation response is also weaker, and the responses of the monsoon circulation are different for sulphate and black carbon experiments. This study demonstrates a mechanism that links regional aerosol emission changes to the precipitation changes of the EASM, and it could be applied to help understand the future changes in EASM precipitation in CMIP5 simulations. © 2013 Author(s)."
"35746048500;57203078745;6506022279;","Future projections of the Greenland ice sheet energy balance driving the surface melt",2013,"10.5194/tc-7-1-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873634308&doi=10.5194%2ftc-7-1-2013&partnerID=40&md5=6d71e5aba3ccce35300b5e9b1950364b","In this study, simulations at 25 km resolution are performed over the Greenland ice sheet (GrIS) throughout the 20th and 21st centuries, using the regional climate model MAR forced by four RCP scenarios from three CMIP5 global circulation models (GCMs), in order to investigate the projected changes of the surface energy balance (SEB) components driving the surface melt. Analysis of 2000-2100 melt anomalies compared to melt results over 1980-1999 reveals an exponential relationship of the GrIS surface melt rate simulated by MAR to the near-surface air temperature (TAS) anomalies, mainly due to the surface albedo positive feedback associated with the extension of bare ice areas in summer. On the GrIS margins, the future melt anomalies are preferentially driven by stronger sensible heat fluxes, induced by enhanced warm air advection over the ice sheet. Over the central dry snow zone, the surface albedo positive feedback induced by the increase in summer melt exceeds the negative feedback of heavier snowfall for TAS anomalies higher than 4 C. In addition to the incoming longwave flux increase associated with the atmosphere warming, GCM-forced MAR simulations project an increase of the cloud cover decreasing the ratio of the incoming shortwave versus longwave radiation and dampening the albedo feedback. However, it should be noted that this trend in the cloud cover is contrary to that simulated by ERA-Interim-forced MAR for recent climate conditions, where the observed melt increase since the 1990s seems mainly to be a consequence of more anticyclonic atmospheric conditions. Finally, no significant change is projected in the length of the melt season, which highlights the importance of solar radiation absorbed by the ice sheet surface in the melt SEB. © Author(s) 2013. CC Attribution 3.0 License."
"7102976560;7004214645;14007691200;25927718600;35338710200;13402933200;7004352797;9434771700;7402105994;24765842200;8354057400;12240390300;9941600400;7003666669;7103206141;55588510300;23485990000;55242994500;56244473600;7005723936;37089417300;23968109800;57205638870;11940188700;7402383878;16403452000;55183670500;15726660300;22986631300;7202802701;","The atmospheric chemistry and climate model intercomparison Project (ACCMIP): Overview and description of models, simulations and climate diagnostics",2013,"10.5194/gmd-6-179-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873679101&doi=10.5194%2fgmd-6-179-2013&partnerID=40&md5=a1d1039478eb005b60fafb619b8a1972","The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) consists of a series of time slice experiments targeting the long-term changes in atmospheric composition between 1850 and 2100, with the goal of documenting composition changes and the associated radiative forcing. In this overview paper, we introduce the ACCMIP activity, the various simulations performed (with a requested set of 14) and the associated model output. The 16 ACCMIP models have a wide range of horizontal and vertical resolutions, vertical extent, chemistry schemes and interaction with radiation and clouds. While anthropogenic and biomass burning emissions were specified for all time slices in the ACCMIP protocol, it is found that the natural emissions are responsible for a significant range across models, mostly in the case of ozone precursors. The analysis of selected present-day climate diagnostics (precipitation, temperature, specific humidity and zonal wind) reveals biases consistent with state-of-the-art climate models. The model-to-model comparison of changes in temperature, specific humidity and zonal wind between 1850 and 2000 and between 2000 and 2100 indicates mostly consistent results. However, models that are clear outliers are different enough from the other models to significantly affect their simulation of atmospheric chemistry. © Author(s) 2013. CC Attribution 3.0 License."
"7402064802;52464731300;26645289600;57205867148;7401974644;6507460574;","Are climate model simulations of clouds improving? An evaluation using the ISCCP simulator",2013,"10.1002/jgrd.50141","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880268669&doi=10.1002%2fjgrd.50141&partnerID=40&md5=be18a6c3655f8b2659c8bee2b5d6b360","The annual cycle climatology of cloud amount, cloud-top pressure, and optical thickness in two generations of climate models is compared to satellite observations to identify changes over time in the fidelity of simulated clouds. In more recent models, there is widespread reduction of a bias associated with too many highly reflective clouds, with the best models having eliminated this bias. With increased amounts of clouds with lesser reflectivity, the compensating errors that permit models to simulate the time-mean radiation balance have been reduced. Errors in cloud amount as a function of height or climate regime on average show little or no improvement, although greater improvement can be found in individual models. © 2013. American Geophysical Union. All Rights Reserved."
"35547807400;24329376600;36010237000;57203049177;24528108000;26645289600;","Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models",2013,"10.1002/jgrd.50174","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880273895&doi=10.1002%2fjgrd.50174&partnerID=40&md5=b58739d9cdfcbe6f26d9b7495b352b06","We utilize energy budget diagnostics from the Coupled Model Intercomparison Project phase 5 (CMIP5) to evaluate the models' climate forcing since preindustrial times employing an established regression technique. The climate forcing evaluated this way, termed the adjusted forcing (AF), includes a rapid adjustment term associated with cloud changes and other tropospheric and land-surface changes. We estimate a 2010 total anthropogenic and natural AF from CMIP5 models of 1.9 ± 0.9 W m-2 (5-95% range). The projected AF of the Representative Concentration Pathway simulations are lower than their expected radiative forcing (RF) in 2095 but agree well with efficacy weighted forcings from integrated assessment models. The smaller AF, compared to RF, is likely due to cloud adjustment. Multimodel time series of temperature change and AF from 1850 to 2100 have large intermodel spreads throughout the period. The intermodel spread of temperature change is principally driven by forcing differences in the present day and climate feedback differences in 2095, although forcing differences are still important for model spread at 2095. We find no significant relationship between the equilibrium climate sensitivity (ECS) of a model and its 2003 AF, in contrast to that found in older models where higher ECS models generally had less forcing. Given the large present-day model spread, there is no indication of any tendency by modelling groups to adjust their aerosol forcing in order to produce observed trends. Instead, some CMIP5 models have a relatively large positive forcing and overestimate the observed temperature change. Key PointsRadiative forcing of RCP scenarios in 2095 is underestimatedCMIP5 models have a large spread in temperature changes and radiative forcingClimate sensitivity was not adjusted to reproduce observed temperature trends ©2013. American Geophysical Union. All Rights Reserved."
"6602078681;6602458644;7004866567;8687046600;57198558737;47861260200;57201726470;7103333823;","On the angular effect of residual clouds and aerosols in clear-sky infrared window radiance observations 2. Satellite experimental analyses",2013,"10.1029/2012JD018260","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880261946&doi=10.1029%2f2012JD018260&partnerID=40&md5=8a19be80ebe792803c729c067c17c4f2","This paper continues an investigation into the zenith angular effect of cloud-contamination within ""clear-sky"" infrared (IR) radiance observations commonly used in the retrieval of environmental data records (EDRs), which include ""cloud-cleared radiances"" (as is typical from hyper/ultra spectral IR sounders), as well as ""cloud-masked"" data (as is typical from imagers). The simple probability of clear line of sight (PCLoS) models and sensitivity studies of Part 1 (Nalli et al., 2012a) are corroborated with experimental analyses of environmental satellite data products as functions of sensor zenith angle, including sounder cloud-cleared radiances (CCRs) and retrieved effective cloud fraction, as well as narrowband imager cloud masking. Analyses of hyperspectral microwindow calc - obs are performed using MetOp-A Infrared Atmospheric Sounding Interferometer (IASI) CCR observations matched to dedicated radiosonde observations (RAOBs) during intensive validation field campaigns. The IASI calc - obs are found to exhibit a systematic positive bias with a strong concave-up variation with satellite zenith angle (i.e., an increasing positive bias symmetric over the scanning range) on the order of 1-3 K in magnitude, a signal associated with both residual clouds and dust aerosols. This is corroborated by analysis of the IASI retrieved effective cloud fraction product compared to the expected angular variations predicted by the PCLoS models, which show that the observed concave-up calc - obs variation may be the result of contamination by mid-to-upper tropospheric clouds. Finally, a corollary global analysis of the MetOp-A Advanced Very High Resolution Radiometer (AVHRR) cloud-mask shows concave-up variation that may be underestimating the angular variation for global ensembles containing clouds with vertical development (i.e., aspect ratios >0.5). The results presented in this work thus support the sensitivity studies of Part 1, indicating that contamination by residual clouds and/or aerosols within clear-sky observations can have a measurable concave-up impact on the angular agreement of observations with calculations. ©2012. American Geophysical Union. All Rights Reserved."
"35503830800;56253793500;7004060399;7102167757;","Air-mass origin as a diagnostic of tropospheric transport",2013,"10.1002/jgrd.50133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880273012&doi=10.1002%2fjgrd.50133&partnerID=40&md5=932a50359ba7b8ec563807242c97cbcd","We introduce rigorously defined air masses as a diagnostic of tropospheric transport. The fractional contribution from each air mass partitions air at any given point according to either where it was last in the planetary boundary layer or where it was last in contact with the stratosphere. The utility of these air-mass fractions is demonstrated for the climate of a dynamical core circulation model and its response to specified heating. For an idealized warming typical of end-of-century projections, changes in air-mass fractions are in the order of 10% and reveal the model's climate change in tropospheric transport: poleward-shifted jets and surface-intensified eddy kinetic energy lead to more efficient stirring of air out of the midlatitude boundary layer, suggesting that, in the future, there may be increased transport of black carbon and industrial pollutants to the Arctic upper troposphere. Correspondingly, air is less efficiently mixed away from the subtropical boundary layer. The air-mass fraction that had last stratosphere contact at midlatitudes increases all the way to the surface, in part due to increased isentropic eddy transport across the tropopause. Correspondingly, the air-mass fraction that had last stratosphere contact at high latitudes is reduced through decreased downwelling across the tropopause. A weakened Hadley circulation leads to decreased interhemispheric transport in the model's future climate. ©2013. American Geophysical Union. All Rights Reserved."
"7003475277;7006783796;12141789600;6506234624;7006518279;7102651635;","Contrail radiative forcing over the Northern Hemisphere from 2006 Aqua MODIS data",2013,"10.1002/grl.50168","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878168685&doi=10.1002%2fgrl.50168&partnerID=40&md5=96456159019987087e5d7f0489c0fca8","Radiative forcing due to linear-shaped jet contrails is calculated over the Northern Hemisphere for four seasonal months using 2006 Aqua Moderate-resolution Imaging Spectroradiometer cloud and contrail property retrieval data in a radiative transfer model. The 4 month mean shortwave, longwave, and net radiative forcings normalized to 100% contrail cover are -5.7, 14.2, and 8.5 Wm-2. Mean total net forcing over the northern half of the globe varies from 9.1 mW m-2 during October to 12.1 mW m -2 in January and is only representative at 01:30 and 13:30 LT in nonpolar regions. In some dense flight traffic corridors, the mean net forcing approaches 80 mW m-2. Scaling the 4 month average of 10.6 mW m -2 to the Southern Hemisphere air traffic yields global mean net forcing of 5.7 mW m-2, which is smaller than most model estimates. Nighttime net forcing is 3.6 times greater than during daytime, when net forcing is greatest over low clouds. Effects from contrail cirrus clouds that evolve from linear contrails are not considered in these results. Key Points Contrail radiative forcing over NH is smaller than most model estimates Contrail radiative forcing depends on background and is defined accurately here Maximum control radiative forcing occurs over the North Atlantic ©2013. American Geophysical Union. All Rights Reserved."
"7006518279;7006783796;36842724800;55747131500;55747560500;","Estimation of 2006 Northern Hemisphere contrail coverage using MODIS data",2013,"10.1002/grl.50097","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878195681&doi=10.1002%2fgrl.50097&partnerID=40&md5=908a3c46e914f617e9e32a3af513202a","A modified automated contrail detection algorithm (CDA) using five infrared channels available from the Moderate Resolution Imaging Spectrometer onboard the Aqua satellite is used to determine linear contrail coverage over the Northern Hemisphere during 2006. Commercial aircraft flight data are employed to filter false contrail detections by the CDA. The Northern Hemisphere annual mean linear contrail coverage ranges from 0.07% to 0.40% for three different CDA sensitivities. Based on visual analyses, the medium sensitivity CDA provides the best estimate of linear contrail coverage, which averages 0.13%. If scaled to the Southern Hemisphere, the global mean coverage would be 0.07%. Coverage is greatest during winter and least during the summer with maximum coverage over the North Atlantic. Less coverage is observed over heavy European and American traffic areas, likely as a result of difficulties in detecting linear contrails that overlap with each other and with older contrail cirrus. These results are valuable for evaluating the representation of contrails and contrail cirrus within global climate models and for retrieving contrail optical properties and radiative forcing. Key Points The first global estimate of contrail coverage with a single satellite imager First use of flight track data to reduce false detections in coverage estimate Less coverage observed over heavy air traffic areas with overlapping contrails ©2013. American Geophysical Union. All Rights Reserved."
"6701368631;","The melting level stability anomaly in the tropics",2013,"10.5194/acp-13-1167-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873558618&doi=10.5194%2facp-13-1167-2013&partnerID=40&md5=3d5c6e0739e642d24feed47e2453ba9a","On short timescales, the effect of deep convection on the tropical atmosphere is to heat the upper troposphere and cool the lower troposphere. This stratiform temperature response to deep convection gives rise to a local maximum in stability near the melting level. We use temperature measurements from five radiosonde stations in the Western Tropical Pacific, from the Stratospheric Processes and their Role in Climate (SPARC) archive, to examine the response of this mid-tropospheric stability maximum to changes in surface temperature. We find that the height of the stability maximum increases when the surface temperature increases, by an amount roughly equal to the upward displacement of the 0 °C melting level. Although this response was determined using monthly mean temperature anomalies from an 10 yr record (1999-2008), we use model results to show that a similar response should also be expected on longer timescales. © Author(s) 2013."
"37087270000;7401651197;","A new method for measuring optical scattering properties of atmospherically relevant dusts using the Cloud and Aerosol Spectrometer with Polarization (CASPOL)",2013,"10.5194/acp-13-1345-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873554278&doi=10.5194%2facp-13-1345-2013&partnerID=40&md5=80c12b04095bfe86403df93cf4cdbab7","Atmospheric aerosols have major impacts on regional and global climate through scattering and absorption of solar radiation. A new instrument, the Cloud and Aerosol Spectrometer with Polarization (CASPOL) from Droplet Measurement Technologies measures light scattered by aerosols in the forward (4° to 12°) and backward (168° to 176°) directions, with an additional polarized detector in the backward direction. Scattering by a single particle can be measured by all three detectors for aerosols in a broad range of sizes, 0.6 μm &lt; diameter &lt; 50 μm. The CASPOL is a unique measurement tool, since unlike most in-situ probes, it can measure optical properties on a particle-by-particle basis. In this study, single particle CASPOL measurements for thirteen atmospherically relevant dusts were obtained and their optical scattering signatures were evaluated. In addition, Scanning Electron Microscopy (SEM) was used to characterize the shape and morphology of each type of dust. The total and polarized backscatter intensities varied with particle size for all dust types. Using a new optical signature technique all but one dust type could be categorized into one of three optical scattering groups. Additionally, a composite method was used to derive the optical signature of Arizona Test Dust (ATD) by combining the signatures of its major components. The derived signature was consistent with the measured signature of ATD. Finally, calculated backscattering cross sections for representative dust from each of the three main groups were found to vary by as much as a factor of 7, the difference between the backscattering cross sections of white quartz (5.3 × 10-10 cm-2) and hematite (4.1 × 10 -9 cm-2). © Author(s) 2013."
"52264873100;55576500100;8331328200;7410041005;","Observational characteristics of cloud vertical profiles over the continent of east asia from the cloudsat data",2013,"10.1007/s13351-013-0104-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873438071&doi=10.1007%2fs13351-013-0104-0&partnerID=40&md5=653851f6e44ce9f5385f4f96055933a3","The CloudSat satellite data from June 2006 to April 2011 are used to investigate the characteristics of cloud vertical profiles over East Asia (20 ° -50 ° N, 80 ° -120 ° E), with particular emphasis on the profiles of precipitative clouds in comparison with those of nonprecipitative clouds, as well as the seasonal variations of these profiles. There are some obvious differences between the precipitative and nonprecipitative cloud profiles. Generally, precipitative clouds mainly locate below 8 km with radar reflectivity in the range of -20 to 15 dBZ and maximum values appearing within 2-4-km height, and the clouds usually reach the ground; while nonprecipitative clouds locate in the layers of 4-12 km with radar reflectivity between -28 and 0 dBZ and maximum values within 8-10-km height. There are also some differences among the liquid precipitative, solid precipitative, and possible drizzle precipitative cloud profiles. In precipitative clouds, radar reflectivity increases rapidly from 11 to 7 km in vertical, implying that condensation and collision-coalescence processes play a crucial role in the formation of large-size drops. The frequency distribution of temperature at -15°C is consistent with the highest frequency of radar reflectivity in solid precipitative clouds, which suggests that the temperatures near -15°C are conductive to deposition and accretion processes. The vertical profiles of liquid precipitative clouds show almost the same distributions in spring, summer, and autumn but with differences in winter at mainly lower levels. In contrast, the vertical profiles of solid precipitative clouds change from spring to winter with an alternate double and single high-frequency core, which is consistent with variations of the frequency distribution of temperature at -15°C. The vertical profiles of nonprecipitative clouds show a little change with season. The observations also show that the precipitation events over East Asia are mostly related to deep convective clouds and nimbostratus clouds. These results are expected to be useful for evaluation of weather and climate models and for improvement of microphysical parameterizations in numerical models. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2013."
"56188627800;55948466000;14625770800;56068624000;54402367600;","Tensor ensemble of ground-based cloud sequences: Its modeling, classification, and synthesis",2013,"10.1109/LGRS.2012.2236073","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879907728&doi=10.1109%2fLGRS.2012.2236073&partnerID=40&md5=8883344c6996d716ec39526161653f71","Since clouds are one of the most important meteorological phenomena related to the hydrological cycle and affect Earth radiation balance and climate changes, cloud analysis is a crucial issue in meteorological research. Most researchers only consider the classification task of cloud images while less attention has been paid to the synthesis one. In addition, all the existing research on cloud identification from sky images is based on single cloud images. However, the cloud-measuring devices on the ground actually take one image of the clouds every few minutes and collect a series of cloud images. Thus, the existing methods neglect the temporal information exhibited by contiguous cloud images. To overcome this drawback, in this letter we treat ground-based cloud sequences (GCSs) as dynamic texture. We then propose the Tensor Ensemble of Ground-based Cloud Sequences (eTGCS) model which represents the ensemble of GCSs in a tensor manner. In the eTGCS model, all GCSs form a single tensor, and each GCS is a subtensor of the single tensor. There are two main characteristics of the eTGCS model: 1) All GCSs share an identical mode subspace, which makes the classification convenient, and 2) a new GCS can be synthesized as long as the parameters of the eTGCS model are used. Therefore, less storage space is required. Comprehensive experiments are conducted to prove the superiority of our eTGCS model. The classification accuracy achieves 92.31%, and the synthesized GCSs are similar to the original ones in visual appearance. © 2012 IEEE."
"6603335688;26323963700;6602241511;56276813400;","Stable carbon isotopes from Torneträsk, northern Sweden provide a millennial length reconstruction of summer sunshine and its relationship to Arctic circulation",2013,"10.1016/j.quascirev.2012.11.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871894705&doi=10.1016%2fj.quascirev.2012.11.014&partnerID=40&md5=62c6deb9b371499512733a1b5825eb3f","This paper presents results from the first 1100 years of a long stable carbon isotope chronology currently in development from Scots Pine (Pinus sylvestris L.) trees growing in the Torneträsk region of northern Sweden. The isotope record currently comprises a total of 74 trees with a mean annual replication of &gt;12, thereby enabling it to be compared directly with other tree-ring based palæoclimate reconstructions from this region. In developing the reconstruction, several key topics in isotope dendroclimatology (chronology construction, replication, CO2 adjustment and age trends) were addressed. The resulting carbon isotope series is calibrated against instrumental data from the closest meteorological station at Abisko (AD1913-2008) to provide a record of June-August sunshine for northern Fennoscandia. This parameter is closely linked to the direct control of assimilation rate; Photosynthetically Active Radiation (PAR) and the indirect measures; mean July-August temperature and percent cloud cover. The coupled response of summer sunshine and temperature in this region permits a multi-parameter comparison with a local reconstruction of past temperature variability based upon tree growth proxies to explore the stability of this coupling through time. Several periods are identified where the temperature (X-ray density) and sunshine (stable carbon isotope ratio) records diverge. The most significant and sustained of these occur between c AD1200-1380 and c AD1550-1780, providing evidence for a cool, sunny, two-phase ""Little Ice Age"". Whilst summer sunshine reconstructed for the 20th century is significantly different from the mean of the last 1100 years (P &lt; 0.01), conditions during the early mediæval period are similar to those experienced in northern Fennoscandia during the 20th century (P &gt; 0.01), so it is the 17th-18th, and to a lesser extent, the 13th centuries rather than the early mediæval period that appear anomalous when viewed within the context of the last 1100 years. The observed departures between temperature and sunshine are interpreted as indicating a change in large-scale circulation associated with a southward migration of the Polar Front. Such a change, affecting the Northern Annular Mode (Arctic Oscillation) would result in more stable anticyclonic conditions (cool, bright, summers) over northern Fennoscandia, thus providing a testable mechanism for the development of a multi-phase, time-transgressive ""Little Ice Age"" across Europe. © 2012 Elsevier Ltd."
"36458535100;7202671706;7006328089;","Does Antarctic glaciation cool the world?",2013,"10.5194/cp-9-173-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873862548&doi=10.5194%2fcp-9-173-2013&partnerID=40&md5=317829901f6ad87c55beafeca1276f87","In this study, we compare the simulated climatic impact of adding an Antarctic ice sheet (AIS) to the ""greenhouse world"" of the Eocene and removing the AIS from the modern world. The modern global mean surface temperature anomaly (&Delta;T) induced by Antarctic Glaciation depends on the background CO2 levels and ranges from -1.22 to -0.18 K. The Eocene &Delta;T is nearly constant at ∼-0.25 K. We calculate an climate sensitivity parameter S[Antarctica] which we define as &Delta;T divided by the change in effective radiative forcing (&Delta;QAntarctica) which includes some fast feedbacks imposed by prescribing the glacial properties of Antarctica. <br><br> The main difference between the modern and Eocene responses is that a negative cloud feedback warms much of the Earth's surface as a large AIS is introduced in the Eocene, whereas this cloud feedback is weakly positive and acts in combination with positive sea-ice feedbacks to enhance cooling introduced by adding an ice sheet in the modern. Because of the importance of cloud feedbacks in determining the final temperature sensitivity of the AIS, our results are likely to be model dependent. Nevertheless, these model results suggest that the effective radiative forcing and feedbacks induced by the AIS did not significantly decrease global mean surface temperature across the Eocene-Oligocene transition (EOT -34.1 to 33.6 Ma) and that other factors like declining atmospheric CO2 are more important for cooling across the EOT. The results illustrate that the efficacy of AIS forcing in the Eocene is not necessarily close to one and is likely to be model and state dependent. This implies that using EOT paleoclimate proxy data by itself to estimate climate sensitivity for future climate prediction requires climate models and consequently these estimates will have large uncertainty, largely due to uncertainties in modelling low clouds. © Author(s) 2013."
"7201485519;56575686800;57203049177;","Origins of differences in climate sensitivity, forcing and feedback in climate models",2013,"10.1007/s00382-012-1336-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874816272&doi=10.1007%2fs00382-012-1336-x&partnerID=40&md5=778fe51acc32ac686c04fefbe2c42f82","We diagnose climate feedback parameters and CO2 forcing including rapid adjustment in twelve atmosphere/mixed-layer-ocean (""slab"") climate models from the CMIP3/CFMIP-1 project (the AR4 ensemble) and fifteen parameter-perturbed versions of the HadSM3 slab model (the PPE). In both ensembles, differences in climate feedbacks can account for approximately twice as much of the range in climate sensitivity as differences in CO2 forcing. In the AR4 ensemble, cloud effects can explain the full range of climate sensitivities, and cloud feedback components contribute four times as much as cloud components of CO2 forcing to the range. Non-cloud feedbacks are required to fully account for the high sensitivities of some models however. The largest contribution to the high sensitivity of HadGEM1 is from a high latitude clear-sky shortwave feedback, and clear-sky longwave feedbacks contribute substantially to the highest sensitivity members of the PPE. Differences in low latitude ocean regions (30°N/S) contribute more to the range than those in mid-latitude oceans (30-55°N/S), low/mid latitude land (55°N/S) or high latitude ocean/land (55-90°N/S), but contributions from these other regions are required to account fully for the higher model sensitivities, for example from land areas in IPSL CM4. Net cloud feedback components over the low latitude oceans sorted into percentile ranges of lower tropospheric stability (LTS) show largest differences among models in stable regions, mainly due to their shortwave components, most of which are positive in spite of increasing LTS. Differences in the mid-stability range are smaller, but cover a larger area, contributing a comparable amount to the range in climate sensitivity. These are strongly anti-correlated with changes in subsidence. Cloud components of CO2 forcing also show the largest differences in stable regions, and are strongly anticorrelated with changes in estimated inversion strength (EIS). This is qualitatively consistent with what would be expected from observed relationships between EIS and low-level cloud fraction. We identify a number of cases where individual models show unusually strong forcings and feedbacks compared to other members of the ensemble. We encourage modelling groups to investigate unusual model behaviours further with sensitivity experiments. Most of the models fail to correctly reproduce the observed relationships between stability and cloud radiative effect in the subtropics, indicating that there remains considerable room for model improvements in the future. © 2012 Crown Copyright."
"7004202450;55212769500;56532987400;7102021223;37065304600;","A study of vertical cloud structure of the Indian summer monsoon using CloudSat data",2013,"10.1007/s00382-012-1374-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874950401&doi=10.1007%2fs00382-012-1374-4&partnerID=40&md5=28f53e902ae1ff52b283e565fbe452af","Precise specification of the vertical distribution of cloud optical properties is important to reduce the uncertainty in quantifying the radiative impacts of clouds. The new global observations of vertical profiles of clouds from the CloudSat mission provide opportunities to describe cloud structures and to improve parameterization of clouds in the weather and climate prediction models. In this study, four years (2007-2010) of observations of vertical structure of clouds from the CloudSat cloud profiling radar have been used to document the mean vertical structure of clouds associated with the Indian summer monsoon (ISM) and its intra-seasonal variability. Active and break monsoon spells associated with the intra-seasonal variability of ISM have been identified by an objective criterion. For the present analysis, we considered CloudSat derived column integrated cloud liquid and ice water, and vertically profiles of cloud liquid and ice water content. Over the South Asian monsoon region, deep convective clouds with large vertical extent (up to 14 km) and large values of cloud water and ice content are observed over the north Bay of Bengal. Deep clouds with large ice water content are also observed over north Arabian Sea and adjoining northwest India, along the west coast of India and the south equatorial Indian Ocean. The active monsoon spells are characterized by enhanced deep convection over the Bay of Bengal, west coast of India and northeast Arabian Sea and suppressed convection over the equatorial Indian Ocean. Over the Bay of Bengal, cloud liquid water content and ice water content is enhanced by ~90 and ~200 % respectively during the active spells. An interesting feature associated with the active spell is the vertical tilting structure of positive CLWC and CIWC anomalies over the Arabian Sea and the Bay of Bengal, which suggests a pre-conditioning process for the northward propagation of the boreal summer intra-seasonal variability. It is also observed that during the break spells, clouds are not completely suppressed over central India. Instead, clouds with smaller vertical extent (3-5 km) are observed due to the presence of a heat low type of circulation. The present results will be useful for validating the vertical structure of clouds in weather and climate prediction models. © 2012 Springer-Verlag."
"35792367500;56225147400;","Use of hydroisomerization to reduce the cloud point of saturated fatty acids and methyl esters used in biodiesel production",2013,"10.1016/j.biombioe.2012.12.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872647331&doi=10.1016%2fj.biombioe.2012.12.008&partnerID=40&md5=dbc26ddca14e5258e3a778147a014efc","Biodiesel, an alternative diesel additive made from renewable sources, has problems associated with their cloud points when used in colder climate. One method of improving the cloud point of biodiesel is hydroisomerization which branches the saturated portion of the biodiesel and lowers the cloud point of the compound. Palmitic acid methyl ester, which is the major saturated fatty acid in vegetable oils, is hydroisomerized with a 5 g kg-1 Pt impregnated beta zeolite catalyst at reaction conditions 200-285 °C and 1.0-4.0 MPa H2 pressure. FTIR and GC/MS analyses confirmed the branching and the identity of the reaction products. The cloud point of the material was lowered from 30 °C to 20 °C under reaction conditions of 285 °C and 4.0 MPa H2 pressure at the yield of 42% after 16 h. This study reports the hydroisomerization reaction being successful in branching the starting material in order to lower the cloud points of methyl esters. © 2012 Elsevier Ltd."
"7102128820;24492361700;","Incorporating the effects of 3D radiative transfer in the presence of clouds intol two-stream multilayer radiation schemes",2013,"10.1175/JAS-D-12-041.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875041837&doi=10.1175%2fJAS-D-12-041.1&partnerID=40&md5=720db1fd1977531e363f1b4f78988967","This paper presents a new method for representing the important effects of horizontal radiation transport through cloud sides in two-stream radiation schemes. Ordinarily, the radiative transfer equations are discretized separately for the clear and cloudy regions within each model level, but here terms are introduced that represent the exchange of radiation laterally between regions and the resulting coupled equations are solved for each layer. This approach may be taken with both the direct incoming shortwave radiation, which is governed by Beer's law, and the diffuse shortwave and longwave radiation, governed by the two-stream equations. The rate of lateral exchange is determined by the area of cloud ''edge.'' The validity of the method is demonstrated by comparing with rigorous 3D radiative transfer calculations in the literature for two cloud types in which the 3D effect is strong, specifically cumulus and aircraft contrails. The 3D effect on shortwave cloud radiative forcing varies between around 225% and around 1100%, depending on solar zenith angle. Even with an otherwise very simplistic representation of the cloud, the new scheme exhibits good agreement with the rigorous calculations in the shortwave, opening the way for efficient yet accurate representation of this important effect in climate models. © 2013 American Meteorological Society."
"8900751100;54974783300;35338541500;55619258500;57202891769;26653341100;","Influence of the laurentian great lakes on regional climate",2013,"10.1175/JCLI-D-12-00140.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873103894&doi=10.1175%2fJCLI-D-12-00140.1&partnerID=40&md5=f9d053e7c1ee6fd209ac64669a485ba3","The influence of the Laurentian Great Lakes on climate is assessed by comparing two decade-long simulations, with the lakes either included or excluded, using the Abdus Salam International Centre for Theoretical Physics Regional Climate Model, version 4. The Great Lakes dampen the variability in near-surface air temperature across the surrounding region while reducing the amplitude of the diurnal cycle and annual cycle of air temperature. The impacts of the Great Lakes on the regional surface energy budget include an increase (decrease) in turbulent fluxes during the cold (warm) season and an increase in surface downward shortwave radiation flux during summer due to diminished atmospheric moisture and convective cloud amount. Changes in the hydrologic budget due to the presence of the Great Lakes include increases in evaporation and precipitation during October-March and decreases during May-August, along with springtime reductions in snowmelt-related runoff. Circulation responses consist of a regionwide decrease in sea level pressure in autumn- winter and an increase in summer, with enhanced ascent and descent in the two seasons, respectively. The most pronounced simulated impact of the Great Lakes on synoptic systems traversing the basin is a weakening of cold-season anticyclones. © 2013 American Meteorological Society."
"7004169476;","A new way of quantifying GCM water vapour feedback",2013,"10.1007/s00382-012-1294-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874947126&doi=10.1007%2fs00382-012-1294-3&partnerID=40&md5=a69dfa64fbff5b16d77ef826333a5fe8","The water vapour feedback probably makes the largest contribution to climate sensitivity, and the second-largest contribution to its uncertainty, in the sense of disagreement between General Circulation Models (GCMs, the most physically detailed models of climate we have). Yet there has been no quantification of it which allows these differences to be attributed physically with the aim of constraining the true value. This paper develops a new breakdown of the non-cloud LW (longwave) response to climate change, which avoids the problems of the conventional breakdown, and applies it to a set of 4 GCMs. The basic physical differences are that temperature is used as the vertical coordinate, and relative humidity as the humidity variable. In this framework the different GCMs' feedbacks look more alike, consistent with our understanding that their water vapour responses are physically very similar. Also, in the global mean all the feedback components have the same sign, allowing us to conveniently attribute the overall response fractionally (e. g. about 60% from the ""partly-Simpsonian"" component). The systematic cancellation between different feedback components in the conventional breakdown is lost, so now a difference in a feedback component actually contributes to a difference in climate sensitivity, and the differences between these GCMs in the non-cloud LW part of this can be traced to differences in formulation, mean climate and climate change response. Physical effects such as those due to variations in the formulation of LW radiative transfer become visible. Differences in the distribution of warming no longer dominate comparison of GCMs. The largest component depends locally only on the GCM's mean climate, so it can in principle be calculated for the real world and validated. However, components dependent on the climate change response probably account for most of the variation between GCMs. The effect of simply changing the humidity variable in the conventional breakdown is also examined. It gives some of this improvement-the loss of the cancellations that leave the conventional breakdown of no use to understand differences between GCMs' climate sensitivities-but not the link to mean climate. © 2012 Crown Copyright."
"8404481100;23981552800;16306632000;48861226600;35368268700;26643193500;7005625309;7005126171;35277762300;","Cloud shading and fog drip influence the metabolism of a coastal pine ecosystem",2013,"10.1111/gcb.12054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871931827&doi=10.1111%2fgcb.12054&partnerID=40&md5=6cb155e0f7b2ccd60ed150243dd60ce8","Assessing the ecological importance of clouds has substantial implications for our basic understanding of ecosystems and for predicting how they will respond to a changing climate. This study was conducted in a coastal Bishop pine forest ecosystem that experiences regular cycles of stratus cloud cover and inundation in summer. Our objective was to understand how these clouds impact ecosystem metabolism by contrasting two sites along a gradient of summer stratus cover. The site that was under cloud cover ~15% more of the summer daytime hours had lower air temperatures and evaporation rates, higher soil moisture content, and received more frequent fog drip inputs than the site with less cloud cover. These cloud-driven differences in environmental conditions translated into large differences in plant and microbial activity. Pine trees at the site with greater cloud cover exhibited less water stress in summer, larger basal area growth, and greater rates of sap velocity. The difference in basal area growth between the two sites was largely due to summer growth. Microbial metabolism was highly responsive to fog drip, illustrated by an observed ~3-fold increase in microbial biomass C with increasing summer fog drip. In addition, the site with more cloud cover had greater total soil respiration and a larger fractional contribution from heterotrophic sources. We conclude that clouds are important to the ecological functioning of these coastal forests, providing summer shading and cooling that relieve pine and microbial drought stress as well as regular moisture inputs that elevate plant and microbial metabolism. These findings are important for understanding how these and other seasonally dry coastal ecosystems will respond to predicted changes in stratus cover, rainfall, and temperature.© 2012 Blackwell Publishing Ltd."
"16025327700;55806927500;26641239800;57217371644;57210785732;","Lightning, convective rain and solar activity - Over the South/Southeast Asia",2013,"10.1016/j.atmosres.2012.07.026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876302034&doi=10.1016%2fj.atmosres.2012.07.026&partnerID=40&md5=a9dd2dc207df998bdd39349fea8832eb","The effect of solar variability parameters and meteorological parameters on total lightning flashes and convective rain in two selected regions is studied. The selected regions lie in the same latitude range but differ in longitude and have widely different topological, vegetation and habitat features. It is shown that the sunspot numbers, Ap index, cosmic ray flux and solar radio flux (F10.7cm) have almost very little effect on the total lightning flashes and convective rain in both the selected regions. The correlation coefficient is less than 0.01 and negative for lightning flashes. For the convective rain it is less than 0.09. For the meteorological parameters such as the temperature variation, convective available potential energy (CAPE), convective cloud layer: total cloud cover and columnar total ozone, the lightning flashes and convective rain are positively well correlated. The correlation coefficient varies between 0.5 and 0.95. However, both are negatively correlated with the mean outgoing long wave radiation (OLR). Lightning flashes are found to be well positively correlated with convective rain in both the regions, with correlation coefficient of ~0.7 and 0.8 respectively. Our study suggests that lightning flashes could be used as a measure of convective precipitation in isolated regions. © 2012 Elsevier B.V."
"6506393061;54795000600;6602744425;6602675795;","Acute coronary syndromes related to bio-climate in a Mediterranean area. The case of Ierapetra, Crete Island, Greece",2013,"10.1080/09603123.2012.699031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870582771&doi=10.1080%2f09603123.2012.699031&partnerID=40&md5=f051932eb8b91d85f68cc08d8f6b2fa6","The occurrence of non-fatal acute coronary syndromes (ACS) is examined in relation with the local bioclimatic conditions in the Ierapetra area, in the southernmost part of Crete Island, Greece, during the period 2004-2007. Daily ACS counts and corresponding meteorological parameters, such as maximum and minimum air temperature, relative humidity, wind speed and cloudiness, were analyzed. Besides, the daily values of the human thermal index, physiologically equivalent temperature (PET) was evaluated. Pearson's 2 test and generalized linear models (GLM) with Poisson distribution were applied. The ACS syndromes present a multiple variation within the year, with the primary maximum in August and the secondary in May, while relative high ACS frequencies exist in early winter time. The impact of the weather variability on the ACS incidence is not statistically significant (C.L. 95%). © 2013 Copyright Taylor and Francis Group, LLC."
"7007088807;23988450000;","The CMSAF hourly solar irradiance database (product CM54): Accuracy and bias corrections with illustrations for Romania (south-eastern Europe)",2013,"10.1016/j.jastp.2012.12.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872040753&doi=10.1016%2fj.jastp.2012.12.001&partnerID=40&md5=0bb54963f4c636de8a3fe22b2e49383d","Product CM54 of CMSAF (Climate Monitoring Satellite Application Facility) consists of Surface Incoming Shortwave Radiation (SIS). This product is obtained by using the MAGICSOL algorithm, which needs only the broadband visible channel as Meteosat satellites input. Hourly, daily and monthly averaged data sets are available, covering on a regular 0.03×0.03° grid the Meteosat scene up to a scanning angle of 70°. The CM54 product has been tested by using global hourly averaged solar irradiance data measured in 2010 in five Romanian meteorological stations. The available satellite database is structured into three sub-databases. Two databases (Z85 and Z75) consist of recordings associated with solar zenith angle Z<85° and Z<75°, respectively. A third database (Z85SIS+) was obtained by removing from the database Z85 the null irradiance values. The databases Z85 and Z75 underestimate the measured values and their RMSE is relatively similar, around 35%. The database Z85SIS+ has MBE and RMSE values around 0.1% and 25%, respectively. Independent of the database, MBE increases while RMSE decreases by increasing the fractional cloudiness class. The database Z85SIS+ has an MBE between -1% and 1%, independent of the cloudiness class. The RMSE of Z85SIS+ database is about 9%, 20% and 37% for clear skies, vaguely and partly cloudy skies and overcast skies, respectively. The CM54 product overestimates the ground-based measurements at small zenith angles and underestimates at very large zenith angles. Regression relationships have been prepared to remove the bias errors from the database Z85SIS+. These relationships are function of location, total cloud cover amount and class of zenith angle. © 2012 Elsevier Ltd."
"7004540083;6701680080;8633248700;55075228200;","Tropical precipitation extremes",2013,"10.1175/JCLI-D-11-00725.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874791049&doi=10.1175%2fJCLI-D-11-00725.1&partnerID=40&md5=c734a90ec3a681755d54f40f99cfaf7d","Classifying tropical deep convective systems by the mesoscale distribution of their cloud properties and sorting matching precipitation measurements over an 11-yr period reveals that the whole distribution of instantaneous precipitation intensity and daily average accumulation rate is composed of (at least) two separate distributions representing distinctly different types of deep convection associated with different meteorological conditions (the distributions of non-deep-convective situations are also shown for completeness). The two types of deep convection produce very different precipitation intensities and occur with very different frequencies of occurrence. Several previous studies have shown that the interaction of the largescale tropical circulation with deep convection causes switching between these two types, leading to a substantial increase of precipitation. In particular, the extreme portion of the tropical precipitation intensity distribution, above 2 mm h-1, is produced by 40% of the larger, longer-lived mesoscale-organized type of convection with only about 10% of the ordinary convection occurrences producing such intensities. When average precipitation accumulation rates are considered, essentially all of the values above 2 mm h-1 are produced by the mesoscale systems. Yet today's atmospheric models do not represent mesoscale-organized deep convective systems that are generally larger than current-day circulation model grid cell sizes but smaller than the resolved dynamical scales and last longer than the typical physics time steps. Thus, model-based arguments for how the extreme part of the tropical precipitation distribution might change in a warming climate are suspect. © 2013 American Meteorological Society."
"43661005000;35240599900;","Tropospheric column O3 and NO2 over the Indian region observed by Ozone Monitoring Instrument (OMI): Seasonal changes and long-term trends",2013,"10.1016/j.atmosenv.2012.09.033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868555700&doi=10.1016%2fj.atmosenv.2012.09.033&partnerID=40&md5=98bfd8c1b68256c315410b3aec5e8523","Monthly mean tropospheric column O3 and NO2 retrieved from Ozone Monitoring Instrument on board Aura for the period December 2007 to November 2008 have been analysed to study the spatial and seasonal variations at selected locations over the Indian landmass and surrounding oceanic region. The annual change in tropospheric O3 and NO2 over the study region was ∼15-20 DU and ∼0.03-0.1 DU, respectively. Latitudinal gradient of -0.84 DU/° and 0.005 DU/°, respectively has been estimated for O3 and NO2 over this region. High levels of O3 were measured over parts of Arabian Sea and Bay of Bengal owing to transport from adjacent landmass. The dependence of O3 on NO2, solar radiation, cloud cover, rainfall, fire count, outgoing longwave radiation and boundary layer height (BLH) were investigated in detail along with the airflow pattern and airmass back trajectory analysis. There were regional variations in O3 seasonal patterns associated with differences in NO2, availability of solar radiation and prevailing airmass. BLH plays a role in the seasonal variation of tropospheric O3. The long-term trend in tropospheric O3 over a period of ten years has been examined for the different regions and both positive and negative trends were observed. © 2012 Elsevier Ltd."
"23089590700;54790529900;15745984700;","Length of growing period over africa: Variability and trends from 30 years of NDVI time series",2013,"10.3390/rs5020982","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874782058&doi=10.3390%2frs5020982&partnerID=40&md5=838a74aac69f78a3d539c40f12aa9ede","The spatial distribution of crops and farming systems in Africa is determined by the duration of the period during which crop and livestock water requirements are met. The length of growing period (LGP) is normally assessed from weather station data-scarce in large parts of Africa-or coarse-resolution rainfall estimates derived from weather satellites. In this study, we analyzed LGP and its variability based on the 1981-2011 GIMMS NDVI3g dataset. We applied a variable threshold method in combination with a searching algorithm to determine start- and end-of-season. We obtained reliable LGP estimates for arid, semi-arid and sub-humid climates that are consistent in space and time. This approach effectively mapped bimodality for clearly separated wet seasons in the Horn of Africa. Due to cloud contamination, the identified bimodality along the Guinea coast was judged to be less certain. High LGP variability is dominant in arid and semi-arid areas, and is indicative of crop failure risk. Significant negative trends in LGP were found for the northern part of the Sahel, for parts of Tanzania and northern Mozambique, and for the short rains of eastern Kenya. Positive trends occurred across western Africa, in southern Africa, and in eastern Kenya for the long rains. Our LGP analysis provides useful information for the mapping of farming systems, and to study the effects of climate variability and other drivers of change on vegetation and crop suitability. © 2013 by the authors."
"55939316400;24467868900;","Trend analysis of global MODIS-terra vegetation indices and land surface temperature between 2000 and 2011",2013,"10.1109/JSTARS.2013.2239607","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884813267&doi=10.1109%2fJSTARS.2013.2239607&partnerID=40&md5=a42c8795e2a9fa82554338492ed7aff5","Previous works have shown that the combination of vegetation indices with land surface temperature (LST) improves the analysis of vegetation changes. Here, global MODIS-Terra monthly data from 2000 to 2011 were downloaded and organized into LST, NDVI (Normalized Difference Vegetation Index) and EVI (Enhanced Vegetation Index) time series. These time series were then corrected from cloud and atmospheric residual contamination through the IDR (iterative Interpolation for Data Reconstruction) method. Then, statistics were retrieved from both corrected time series, and the YLCD (Yearly Land Cover Dynamics) approach has been applied to data sources (NDVI-LST and EVI-LST) to analyze changes in the vegetation. Finally, trends were retrieved and their statistical significance was assessed through the Mann-Kendall statistical framework. Global statistics show that both data sets lead to similar trends, as is the case for the spatial distribution of observed trends. These trends confirm previous results as well as prediction of climate warming consequences, such as a marked increase in boreal temperatures. © 2008-2012 IEEE."
"35114688200;26028982800;42061208800;","An assessment of cumulus parameterization schemes in the short range prediction of rainfall during the onset phase of the Indian Southwest Monsoon using MM5 Model",2013,"10.1016/j.atmosres.2012.09.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880699160&doi=10.1016%2fj.atmosres.2012.09.002&partnerID=40&md5=d108cebcaac6082b0d44c7c9e4c7936f","The performance of cumulus parameterization schemes in the short range prediction of rainfall during onset phase of the Indian Southwest Monsoon (ISM) was evaluated using Fifth-Generation Pennsylvania State University / National Center for Atmospheric Research Mesoscale Model (MM5). MM5 model was used to predict rainfall at 30. km resolution up to 72. h over the Indian subcontinent for each day during the period 1-30 June 2002, which corresponds to the onset phase of the ISM. Experiments were performed with 5 different cumulus parameterization schemes of Anthes-Kuo (AK), Grell (GR), Betts-Miller (BM), Kain-Fritsch (KF) and Kain-Fritsch2 (KF2). Rainfall prediction assessment was made over five zones through comparison with corresponding APHRODITE gridded precipitation data and for selected location with station observations by analyzing the statistical parameters of correlation coefficient, mean absolute error and Hanssen-Kuipers score. Monthly mean zone-wise rainfall was well predicted by GR and AK schemes up to 48. hours and slight overestimation beyond. GR scheme predicted higher rainfall over west coast, central parts of India and low rainfall over southeast peninsula. BM and KF schemes showed overestimation with prediction of rainfall over dry southeast peninsula. All the schemes underestimated the coefficient of variability (CV) over all the five zones. AK and GR schemes had the mean and CV nearer to the APHRODITE observations, with AK scheme slightly better than GR scheme over Zones 1, 2 and 3 while GR scheme had the best agreement over Zones 4 and 5. GR scheme had also shown higher CC values and lower MAE over most of the zones up to 72. h, while BM had the least predictability with lower CC and HK scores and higher MAE over most of the zones. Over Western Ghats, the uncertainty limits could be higher than shown due to dominant heavy rains. Of the ten stations selected for verification, GR scheme had shown better prediction with significant positive CC values at nine of the ten stations and consistently lower MAE values and higher HK scores. Further analysis has shown that GR scheme predicted higher grid-scale and nighttime rainfall agreeing with earlier studies concerning monsoon rainfall. All other schemes predicted the features contrarily with higher convective and daytime rainfall. GR scheme alone was found to have provided the best prediction considering the mean monthly, daily zone-wise and station rainfall predictions. The present study concludes that GR cumulus parameterization scheme is the most suitable at 30. km resolution. © 2012 Elsevier B.V."
"7004160106;22635081500;6603081424;22933265100;6701378450;35497573900;","Performance of McRAS-AC in the GEOS-5 AGCM: Aerosol-cloud-microphysics, precipitation, cloud radiative effects, and circulation",2013,"10.5194/gmd-6-57-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872699847&doi=10.5194%2fgmd-6-57-2013&partnerID=40&md5=ea72d0b4a783afb624b0c28fea753123","A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud interaction scheme (McRAS-AC) including, among others, a new ice nucleation parameterization, is implemented in the GEOS-5 AGCM. Various fields from a 10-yr-long integration of the AGCM with McRAS-AC are compared with their counterparts from an integration of the baseline GEOS-5 AGCM, as well as satellite observations. Generally McRAS-AC simulations have smaller biases in cloud fields and cloud radiative effects over most of the regions of the Earth than the baseline GEOS-5 AGCM. Two systematic biases are identified in the McRAS-AC runs: one is underestimation of cloud particle numbers around 40 S-60 S, and one is overestimate of cloud water path during the Northern Hemisphere summer over the Gulf Stream and North Pacific. Sensitivity tests show that these biases potentially originate from biases in the aerosol input. The first bias is largely eliminated in a test run using 50% smaller radius of sea-salt aerosol particles, while the second bias is substantially reduced when interactive aerosol chemistry is turned on. The main weakness of McRAS-AC is the dearth of low-level marine stratus clouds, a probable outcome of lack of explicit dry-convection in the cloud scheme. Nevertheless, McRAS-AC largely simulates realistic clouds and their optical properties that can be improved further with better aerosol input. An assessment using the COSP simulator in a 1-yr integration provides additional perspectives for understanding cloud optical property differences between the baseline and McRAS-AC simulations and biases against satellite data. Overall, McRAS-AC physically couples aerosols, the microphysics and macrophysics of clouds, and their radiative effects and thereby has better potential to be a valuable tool for climate modeling research. © 2013 Author(s)."
"7403625607;52264136000;8968548000;7006495234;","An efficient and effective method to simulate the earth spectral reflectance over large temporal and spatial scales",2013,"10.1002/grl.50116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874885845&doi=10.1002%2fgrl.50116&partnerID=40&md5=2217ccea665f6ea1673705d337628b4c","Atmospheric and surface properties have been measured from space with various spatial resolutions for decades. It is very challenging to derive the mean solar spectral radiance or reflectance over large temporal and spatial scales by explicit radiative transfer computations from the large volume of instantaneous data, especially at high spectral resolution. We propose a procedurally simple but effective method to compute the solar spectral reflectance in large climate domains, in which the probability distribution function (PDF) of cloud optical depth is used to account for the wide variation of cloud properties in different sensor footprints, and to avoid the repeated computations for footprints with similar conditions. This approach is tested with MODIS/CERES data and evaluated with SCIAMACHY measured spectral reflectance. The mean difference between model and observation is about 3% for the monthly global mean reflectance. This PDF-based approach provides a simple, fast, and effective way to simulate the mean spectral reflectance over large time and space scales with a large volume of high-resolution satellite data. © 2013. American Geophysical Union. All Rights Reserved."
"36955999600;6701370412;13407563600;55942083800;","Mass-based hygroscopicity parameter interaction model and measurement of atmospheric aerosol water uptake",2013,"10.5194/acp-13-717-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872691442&doi=10.5194%2facp-13-717-2013&partnerID=40&md5=808313a2da0d49ca3ec3dcbbc26cce9e","In this study we derive and apply a mass-based hygroscopicity parameter interaction model for efficient description of concentration-dependent water uptake by atmospheric aerosol particles with complex chemical composition. The model approach builds on the single hygroscopicity parameter model of Petters and Kreidenweis (2007). We introduce an observable mass-based hygroscopicity parameter &amp;kappa;m which can be deconvoluted into a dilute hygroscopicity parameter (kappa;m0) and additional self-and cross-interaction parameters describing non-ideal solution behavior and concentration dependencies of single-and multi-component systems. For reference aerosol samples of sodium chloride and ammonium sulfate, the &amp;kappa;m-interaction model (KIM) captures the experimentally observed concentration and humidity dependence of the hygroscopicity parameter and is in good agreement with an accurate reference model based on the Pitzer ion-interaction approach (Aerosol Inorganic Model, AIM). Experimental results for pure organic particles (malonic acid, levoglucosan) and for mixed organic-inorganic particles (malonic acid-ammonium sulfate) are also well reproduced by KIM, taking into account apparent or equilibrium solubilities for stepwise or gradual deliquescence and efflorescence transitions. The mixed organic-inorganic particles as well as atmospheric aerosol samples exhibit three distinctly different regimes of hygroscopicity: (I) a quasi-eutonic deliquescence &amp; efflorescence regime at low-humidity where substances are just partly dissolved and exist also in a non-dissolved phase, (II) a gradual deliquescence &amp; efflorescence regime at intermediate humidity where different solutes undergo gradual dissolution or solidification in the aqueous phase; and (III) a dilute regime at high humidity where the solutes are fully dissolved approaching their dilute hygroscopicity. For atmospheric aerosol samples collected from boreal rural air and from pristine tropical rainforest air (secondary organic aerosol) we present first mass-based measurements of water uptake over a wide range of relative humidity (1-99.4%) obtained with a new filter-based differential hygroscopicity analyzer (FDHA) technique. For these samples the concentration dependence of κm can be described by a simple KIM model equation based on observable mass growth factors and a total of only six fit parameters summarizing the combined effects of the dilute hygroscopicity parameters, self-and cross-interaction parameters, and solubilities of all involved chemical components. One of the fit parameters represents κm0 and can be used to predict critical dry diameters for the activation of cloud condensation nuclei (CCN) as a function of water vapor supersaturation according to Köhler theory. For sodium chloride and ammonium sulfate reference particles as well as for pristine rainforest aerosols consisting mostly of secondary organic matter, we obtained good agreement between the KIM predictions and measurement data of CCN activation. The application of KIM and mass-based measurement techniques shall help to bridge gaps in the current understanding of water uptake by atmospheric aerosols: (1) the gap between hygroscopicity parameters determined by hygroscopic growth measurements under sub-saturated conditions and by CCN activation measurements at water vapor supersaturation, and (2) the gap between the results of simplified single parameter models widely used in atmospheric or climate science and the results of complex multi-parameter ion-and molecule-interaction models frequently used in physical chemistry and solution thermodynamics (e.g., AIM, E-AIM, ADDEM, UNIFAC, AIOMFAC). © 2013 Author(s)."
"55574205800;7402112599;","(A)ATSR solar channel on-orbit radiometric calibration",2013,"10.1109/TGRS.2012.2230333","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874665450&doi=10.1109%2fTGRS.2012.2230333&partnerID=40&md5=9682a746a59fc3b2e451c17f29279a33","Data from the solar reflectance channels of the Along Track Scanning Radiometer (ATSR) series of instruments are being used in applications for monitoring trends in many climate variables, for example, clouds and aerosols. In order to provide quantitative information, the radiometric calibrations of the sensors must be consistent, stable, and ideally traced to international standards with uncertainties quantified. In this paper, the authors describe the current methodology used to monitor the long-term drifts and determine the relative biases of the ATSR solar channel radiometric calibrations. Top-of-atmosphere bidirectional reflectance factors (BRFs) over quasi-stable desert and ice sites are extracted from level-1 images and compared against a reference BRF model derived from averages of measurements over the site from a reference sensor. This enables comparisons to be performed where there is limited or no temporal overlap between sensors. The results of the drift monitoring and intercomparisons are used to provide lookup tables to be applied by users for existing products and in subsequent reprocessing of ATSR data. The method is extended to perform comparisons against the Medium Resolution Imaging Spectrometer and the Moderate Resolution Imaging Spectrometer. Results of the comparisons are presented and show that the sensors are stable throughout the mission lifetime and biases relative to the Advanced ATSR are presented. Improvements to the methodology are discussed to account for spectral mismatches of the sensors under comparison and to increase the range of view angles that the BRF model presently covers. © 2012 IEEE."
"35273334200;7006630889;55754604900;","Comparison of global 3-D aviation emissions datasets",2013,"10.5194/acp-13-429-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872340199&doi=10.5194%2facp-13-429-2013&partnerID=40&md5=f2986aee90d81d8ef3f7b1ac9725fb74","Aviation emissions are unique from other transportation emissions, e.g., from road transportation and shipping, in that they occur at higher altitudes as well as at the surface. Aviation emissions of carbon dioxide, soot, and water vapor have direct radiative impacts on the Earth's climate system while emissions of nitrogen oxides (NOx), sulfur oxides, carbon monoxide (CO), and hydrocarbons (HC) impact air quality and climate through their effects on ozone, methane, and clouds. The most accurate estimates of the impact of aviation on air quality and climate utilize three-dimensional chemistry-climate models and gridded four dimensional (space and time) aviation emissions datasets. We compare five available aviation emissions datasets currently and historically used to evaluate the impact of aviation on climate and air quality: NASA-Boeing 1992, NASA-Boeing 1999, QUANTIFY 2000, Aero2k 2002, and AEDT 2006 and aviation fuel usage estimates from the International Energy Agency. Roughly 90% of all aviation emissions are in the Northern Hemisphere and nearly 60% of all fuelburn and NOx emissions occur at cruise altitudes in the Northern Hemisphere. While these datasets were created by independent methods and are thus not strictly suitable for analyzing trends they suggest that commercial aviation fuelburn and NOx emissions increased over the last two decades while HC emissions likely decreased and CO emissions did not change significantly. The bottom-up estimates compared here are consistently lower than International Energy Agency fuelburn statistics although the gap is significantly smaller in the more recent datasets. Overall the emissions distributions are quite similar for fuelburn and NOx with regional peaks over the populated land masses of North America, Europe, and East Asia. For CO and HC there are relatively larger differences. There are however some distinct differences in the altitude distribution of emissions in certain regions for the Aero2k dataset. © 2013 Author(s)."
"22953153500;24398842400;55942083800;24458137900;","Ice nuclei in marine air: Biogenic particles or dust?",2013,"10.5194/acp-13-245-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872258850&doi=10.5194%2facp-13-245-2013&partnerID=40&md5=7a913ff578d5c0dc4e22fd437469108a","Ice nuclei impact clouds, but their sources and distribution in the atmosphere are still not well known. Particularly little attention has been paid to IN sources in marine environments, although evidence from field studies suggests that IN populations in remote marine regions may be dominated by primary biogenic particles associated with sea spray. In this exploratory model study, we aim to bring attention to this long-neglected topic and identify promising target regions for future field campaigns. We assess the likely global distribution of marine biogenic ice nuclei using a combination of historical observations, satellite data and model output. By comparing simulated marine biogenic immersion IN distributions and dust immersion IN distributions, we predict strong regional differences in the importance of marine biogenic IN relative to dust IN. Our analysis suggests that marine biogenic IN are most likely to play a dominant role in determining IN concentrations in near-surface-air over the Southern Ocean, so future field campaigns aimed at investigating marine biogenic IN should target that region. Climate-related changes in the abundance and emission of biogenic marine IN could affect marine cloud properties, thereby introducing previously unconsidered feedbacks that influence the hydrological cycle and the Earth's energy balance. Furthermore, marine biogenic IN may be an important aspect to consider in proposals for marine cloud brightening by artificial sea spray production. © 2013 Author(s)."
"13403622000;7005955015;53878006900;12779071400;22933265100;6701378450;","Cirrus cloud seeding has potential to cool climate",2013,"10.1029/2012GL054201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874920293&doi=10.1029%2f2012GL054201&partnerID=40&md5=ab1c3c3722ccadc3dcf87a5d10ac3d85","Cirrus clouds, thin ice clouds in the upper troposphere, have a net warming effect on Earth's climate. Consequently, a reduction in cirrus cloud amount or optical thickness would cool the climate. Recent research indicates that by seeding cirrus clouds with particles that promote ice nucleation, their lifetimes and coverage could be reduced. We have tested this hypothesis in a global climate model with a state-of-the-art representation of cirrus clouds and find that cirrus cloud seeding has the potential to cancel the entire warming caused by human activity from pre-industrial times to present day. However, the desired effect is only obtained for seeding particle concentrations that lie within an optimal range. With lower than optimal particle concentrations, a seeding exercise would have no effect. Moreover, a higher than optimal concentration results in an over-seeding that could have the deleterious effect of prolonging cirrus lifetime and contributing to global warming. © 2013. American Geophysical Union. All Rights Reserved."
"6507308842;56249704400;7201837768;","Uncertainties and importance of sea spray composition on aerosol direct and indirect effects",2013,"10.1029/2012JD018165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874373986&doi=10.1029%2f2012JD018165&partnerID=40&md5=f2fa178c88188c6b46b45d7a7b8d9f26","Although ocean-derived aerosols play a critical role in modifying the radiative balance over much of the Earth, their sources are still subject to large uncertainties, concerning not only their total mass flux but also their size distribution and chemical composition. These uncertainties are linked primarily to their source drivers, which is mainly wind speed, but are also linked to other factors, such as the presence of organic compounds in sea spray in addition to sea salt. In order to quantify these uncertainties and identify the larger knowledge gaps, we performed several model runs with online calculation of aerosol sources, removal, and underlying climate. In these simulations, both the direct and indirect aerosol effects on climate are included. The oceanic source of organic aerosols was found to be heavily dependent on the sea-salt parameterization selected. For only a factor of 2 change in assumed fine-mode sea-salt size, a factor of 10 difference in mass emissions was calculated for both sea salt and primary oceanic organics. The annual emissions of oceanic organics were calculated to range from 7.5 to 76 Tg yr-1. The model's performance against remote oceanic measurements was greatly improved when including the high estimates of organics. However, the uncertainty could not be further reduced by bulk sea-salt measurements alone since most parameterizations tested agree reasonably well with measurements of both the (coarse-mode-dominated) sea salt and aerosol optical depth due to large changes in lifetime and optical properties of aerosols when different aerosol sizes are used. Key Points Understand sea-salt emissions uncertainties and impacts on marine aerosol Quantify marine organic aerosol production sources and uncertainties Study the marine aerosol composition and impact on AOD, CDNC and climate. © 2012 American Geophysical Union. All Rights Reserved."
"6603385031;16200336000;55372151500;7004715270;9843579700;55620143100;7005968859;6507417147;35774441900;55942083800;","The impact of rain on ice nuclei populations at a forested site in Colorado",2013,"10.1029/2012GL053953","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874851820&doi=10.1029%2f2012GL053953&partnerID=40&md5=e344e32607679566ae3c01379ea815a0","It has long been known that precipitation can impact atmospheric aerosol, altering number concentrations and size-dependent composition. Such effects result from competing mechanisms: precipitation can remove particles through wet deposition, or precipitation can lead to the emission of particles through mechanical ejection, biological processes, or re-suspension from associated wind gusts. These particles can feed back into the hydrologic cycle by serving as cloud nuclei. In this study, we investigated how precipitation at a forested site impacted the concentration and composition of ice nuclei (IN). We show that ground level IN concentrations were enhanced during rain events, with concentrations increasing by up to a factor of 40 during rain. We also show that a fraction of these IN were biological, with some of the IN identified using DNA sequencing. As these particles get entrained into the outflow of the storm, they may ultimately reach cloud levels, impacting precipitation of subsequent storms. © 2013. American Geophysical Union. All Rights Reserved."
"7006218108;13310165300;","Variability of the surface radiation budget over the United States from 1996 through 2011 from high-quality measurements",2013,"10.1029/2012JD018551","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874652925&doi=10.1029%2f2012JD018551&partnerID=40&md5=e23ce7a86cd6f8fa259bd32951feda35","Sixteen years of high-quality surface radiation budget (SRB) measurements over seven U.S. stations are summarized. The network average total surface net radiation increases by +8.2 Wm-2 per decade from 1996 to 2011. A significant upward trend in downwelling shortwave (SW-down) of +6.6 Wm -2 per decade dominates the total surface net radiation signal. This SW brightening is attributed to a decrease in cloud coverage, and aerosols have only a minor effect. Increasing downwelling longwave (LW-down) of +1.5 Wm -2 per decade and decreasing upwelling LW (LW-up) of -0.9 Wm -2 per decade produce a +2.3 Wm-2 per decade increase in surface net-LW, which dwarfs the expected contribution to LW-down from the 30 ppm increase of CO<inf>2</inf> during the analysis period. The dramatic surface net radiation excess should have stimulated surface energy fluxes, but, oddly, the temperature trend is flat, and specific humidity decreases. The enigmatic nature of LW-down, temperature, and moisture may be a chaotic result of their large interannual variations. Interannual variation of the El Niño/Southern Oscillation (ENSO) ONI index is shown to be moderately correlated with temperature, moisture, and LW-down. Thus, circulations associated with ENSO events may be responsible for manipulating (e.g., by advection or convection) the excess surface energy available from the SRB increase. It is clear that continued monitoring is necessary to separate the SRB's response to long-term climate processes from natural variability and that collocated surface energy flux measurements at the SRB stations would be beneficial. Key Points The SRB over the U.S. increased by 8.2 Wm-2 per decade from 1996 to 2011 The increase in U.S. SRB from 1996 to 2011 was dominated by solar brightening Interannual variability of SRB components masks long-term climate signals. © 2012 American Geophysical Union. All Rights Reserved."
"36600036800;7005955015;","The sign of the radiative forcing from marine cloud brightening depends on both particle size and injection amount",2013,"10.1029/2012GL054286","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874928124&doi=10.1029%2f2012GL054286&partnerID=40&md5=9cf208e2916ca986d905c405a79f80ac","Marine cloud brightening (MCB) is a proposed technique to limit global warming through injections of sea spray into the marine boundary layer. Using the Norwegian Earth System Model, the sensitivity of MCB to sea salt amount and particle size was studied by running a set of simulations in which Aitken (re = 0.04 μm), accumulation (re = 0.22 μm), or coarse (re = 2.46 μm) mode sea salt emissions were increased uniformly by 10-11 to 10-8 kg m-2 s -1. As desired, accumulation mode particles had a negative radiative effect of down to -3.3W m-2. Conversely, for Aitken mode particles, injections of 10-10 kg m-2 s-1 or greater led to a positive forcing of up to 8.4W m-2, caused by a strong competition effect combined with the high critical supersaturation of Aitken mode sea salt. The coarse mode particles gave a positive forcing of up to 1.2W m-2 because of a decrease in activation of background aerosols. Sensitivity experiments show that the competition effect dominated our results. MCB may have a cooling effect, but if the wrong size or injection amount is used, our simulations show a warming effect on the climate system. © 2013. American Geophysical Union. All Rights Reserved."
"55504422400;6602360450;15077026300;10140927300;8976327600;","Climatic drivers of hourly to yearly tree radius variations along a 6°C natural warming gradient",2013,"10.1016/j.agrformet.2012.08.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870214751&doi=10.1016%2fj.agrformet.2012.08.002&partnerID=40&md5=1d1fe6457a8cd763834a04ea497f7cee","Climate affects the timing, rate and dynamics of tree growth, over time scales ranging from seconds to centuries. Monitoring how a tree's stem radius varies over these time scales can provide insight into intra-annual stem dynamics and improve our understanding of climate impacts on tree physiology and growth processes. Here, we quantify the response of radial conifer stem size to environmental fluctuations via a novel assessment of tree circadian cycles. We analyze four years of sub-hourly data collected from 56 larch and spruce trees growing along a natural temperature gradient of ∼6. °C in the central Swiss Alps. During the growing season, tree stem diameters were greatest at mid-morning and smallest in the late evening, reflecting the daily cycle of water uptake and loss. Along the gradient, amplitudes calculated from the stem radius cycle were ∼50% smaller at the upper site (∼2200. m a.s.l.) relative to the lower site (∼800. m a.s.l.). We show changes in precipitation, temperature and cloud cover have a substantial effect on typical growing season diurnal cycles; amplitudes were nine times smaller on rainy days (>10. mm), and daily amplitudes are approximately 40% larger when the mean daily temperature is 15-20. °C than when it is 5-10. °C. We find that over the growing season in the sub-alpine forests, spruce show greater daily stem water movement than larch. However, under projected future warming, larch could experience up to 50% greater stem water use, which may severely affect future growth on already dry sites. Our data further indicate that because of the confounding influences of radial growth and short-term water dynamics on stem size, conventional methodology probably overstates the effect of water-linked meteorological variables (i.e. precipitation and relative humidity) on intra-annual tree growth. We suggest future studies use intra-seasonal measurements of cell development and consider whether climatic factors produce reversible changes in stem diameter. These study design elements may help researchers more accurately quantify and attribute changes in forest productivity in response to future warming. © 2012 Elsevier B.V."
"9241987300;7004978125;","Test models for filtering and prediction of moisture-coupled tropical waves",2013,"10.1002/qj.1956","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873313708&doi=10.1002%2fqj.1956&partnerID=40&md5=24303dfc6423fadf20724cc4e1936e79","The filtering/data assimilation and prediction of moisture-coupled tropical waves is a contemporary topic with significant implications for extended-range forecasting. The development of efficient algorithms to capture such waves is limited by the unstable multiscale features of tropical convection which can organize large-scale circulations and the sparse observations of the moisture-coupled wave in both the horizontal and vertical. The approach proposed here is to address these difficult issues of data assimilation and prediction through a suite of analogue models which, despite their simplicity, capture key features of the observational record and physical processes in moisture-coupled tropical waves. The analogue models emphasized here involve the multicloud convective parametrization based on three cloud types (congestus, deep, and stratiform) above the boundary layer. Two test examples involving an MJO-like turbulent travelling wave and the initiation of a convectively coupled wave train are introduced to illustrate the approach. A suite of reduced filters with judicious model errors for data assimilation of sparse observations of tropical waves, based on linear stochastic models in a moisture-coupled eigenmode basis is developed here and applied to the two test problems. Both the reduced filter and 3D-Var with a full moist background covariance matrix can recover the unobserved troposphere humidity and precipitation rate; on the other hand, 3D-Var with a dry background covariance matrix fails to recover these unobserved variables. The skill of the reduced filtering methods in recovering the unobserved precipitation, congestus, and stratiform heating rates as well as the front-to-rear tilt of the convectively coupled waves exhibits a subtle dependence on the sparse observation network and the observation time. © 2012 Royal Meteorological Society."
"25031430500;57203030873;6602098362;","Spatial decomposition of climate feedbacks in the community earth system model",2013,"10.1175/JCLI-D-12-00497.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878961535&doi=10.1175%2fJCLI-D-12-00497.1&partnerID=40&md5=3dc456d71d754e763a294d53c5c9cb56","An ensemble of simulations from different versions of the Community Atmosphere Model in the Community Earth System Model (CESM) is used to investigate the processes responsible for the intermodel spread in climate sensitivity. In the CESM simulations, the climate sensitivity spread is primarily explained by shortwave cloud feedbacks on the equatorward flank of the midlatitude storm tracks. Shortwave cloud feedbacks have been found to explain climate sensitivity spread inprevious studies, but the location of feedback differences was in the subtropics rather than in the storm tracks as identified in CESM. The cloudfeedback relationships are slightly stronger in the winter hemisphere. The spread in climate sensitivity in this study is related both to the cloud-base state and to the cloud feedbacks. Simulated climate sensitivity is correlated with cloud-fraction changes on the equatorward side of the storm tracks, cloud condensate in the storm tracks, and cloud microphysical state on the poleward side of the storm tracks. Changes in the extent and water content of stratiform clouds (that make up cloud feedback) are regulated by the base-state vertical velocity, humidity, and deep convective mass fluxes. Within the storm tracks, the cloud-base state affects the cloud response to CO2-induced temperature changes and alters the cloud feedbacks, contributing to climate sensitivity spread within the CESM ensemble. © 2013 American Meteorological Society."
"54893098900;35509639400;","Interpretation of the positive low-cloud feedback predicted by a climate model under global warming",2013,"10.1007/s00382-011-1279-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876877680&doi=10.1007%2fs00382-011-1279-7&partnerID=40&md5=cbee3a5224b918bff0b5b74400717070","The response of low-level clouds to climate change has been identified as a major contributor to the uncertainty in climate sensitivity estimates among climate models. By analyzing the behaviour of low-level clouds in a hierarchy of models (coupled ocean-atmosphere model, atmospheric general circulation model, aqua-planet model, single-column model) using the same physical parameterizations, this study proposes an interpretation of the strong positive low-cloud feedback predicted by the IPSL-CM5A climate model under climate change. In a warmer climate, the model predicts an enhanced clear-sky radiative cooling, stronger surface turbulent fluxes, a deepening and a drying of the planetary boundary layer, and a decrease of tropical low-clouds in regimes of weak subsidence. We show that the decrease of low-level clouds critically depends on the change in the vertical advection of moist static energy from the free troposphere to the boundary-layer. This change is dominated by variations in the vertical gradient of moist static energy between the surface and the free troposphere just above the boundary-layer. In a warmer climate, the thermodynamical relationship of Clausius-Clapeyron increases this vertical gradient, and then the import by large-scale subsidence of low moist static energy and dry air into the boundary layer. This results in a decrease of the low-level cloudiness and in a weakening of the radiative cooling of the boundary layer by low-level clouds. The energetic framework proposed in this study might help to interpret inter-model differences in low-cloud feedbacks under climate change. © 2012 The Author(s)."
"55796506900;55669799600;55355176000;7410070663;","The features of cloud overlapping in Eastern Asia and their effect on cloud radiative forcing",2013,"10.1007/s11430-012-4489-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876946629&doi=10.1007%2fs11430-012-4489-x&partnerID=40&md5=10d2d19d14874e867ba88a0c51d07bbc","Characteristics of cloud overlap over Eastern Asia are analyzed using a three-year dataset (2007-2009) from the cloud observing satellite CloudSat. Decorrelation depth L*cf is retrieved, which represents cloud overlap characteristics in the simulation of cloud-radiation processes in global climate models. Results show that values of L*cf in six study regions are generally within the range 0-3 km. By categorizing L*cf according to cloud amount in subregions, peak L*cf appears near subregions with cloud amount between 0. 6 and 0. 8. Average L*cf is 2. 5 km. L*cf at higher altitudes is generally larger than at lower latitudes. Seasonal variations of L*cf are also clearly demonstrated. The sensitivity of cloud radiative forcing (CRF) to L*cf in Community Atmosphere Model 3. 0 of the National Center for Atmospheric Research (CAM3/NCAR) is analyzed. The result shows that L*cf can have a big impact on simulation of CRF, especially in major monsoon regions and the Mid-Eastern Pacific, where the difference in CRF can reach 40-50 W m-2. Therefore, accurate parameterization of cloud vertical overlap structure is important to CRF simulation and its feedback to climate. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg."
"35280798500;57203053317;13403622000;","Modelling the impact of fungal spore ice nuclei on clouds and precipitation",2013,"10.1088/1748-9326/8/1/014029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876189955&doi=10.1088%2f1748-9326%2f8%2f1%2f014029&partnerID=40&md5=33164e5744bdabd528112b338998faa4","Some fungal spore species have been found in laboratory studies to be very efficient ice nuclei. However, their potential impact on clouds and precipitation is not well known and needs to be investigated. Fungal spores as a new aerosol species were introduced into the global climate model (GCM) ECHAM5-HAM. The inclusion of fungal spores acting as ice nuclei in a GCM leads to only minor changes in cloud formation and precipitation on a global level; however, changes in the liquid water path and ice water path as well as stratiform precipitation can be observed in the boreal regions where tundra and forests act as sources of fungal spores. Although fungal spores contribute to heterogeneous freezing, their impact is reduced by their low numbers as compared to other heterogeneous ice nuclei. © 2013 IOP Publishing Ltd."
"38762392200;55607020000;9275665400;","Anthropogenic contribution to cloud condensation nuclei and the first aerosol indirect climate effect",2013,"10.1088/1748-9326/8/2/024029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880902662&doi=10.1088%2f1748-9326%2f8%2f2%2f024029&partnerID=40&md5=0dc83813bf02dd03886d362b308064bb","Atmospheric particles influence the climate indirectly by acting as cloud condensation nuclei (CCN). The first aerosol indirect radiative forcing (FAIRF) constitutes the largest uncertainty among the radiative forcings quantified by the latest IPCC report (IPCC2007) and is a major source of uncertainty in predicting climate change. Here, we investigate the anthropogenic contribution to CCN and associated FAIRF using a state-of-the-art global chemical transport and aerosol model (GEOS-Chem/APM) that contains a number of advanced features (including sectional particle microphysics, online comprehensive chemistry, consideration of all major aerosol species, online aerosol-cloud-radiation calculation, and usage of more accurate assimilated meteorology). The model captures the absolute values and spatial distributions of CCN concentrations measured in situ around the globe. We show that anthropogenic emissions increase the global mean CCN in the lower troposphere by ∼60-80% and cloud droplet number concentration by ∼40%. The global mean FAIRF based on GEOS-Chem/APM is -0.75 W m-2, close to the median values of both IPCC2007 and post-IPCC2007 studies. To the best of our knowledge, this is the first time that a global sectional aerosol model with full online chemistry and considering all major aerosol species (including nitrate, ammonium, and second organic aerosols) has been used used to calculate FAIRF. © 2013 IOP Publishing Ltd."
"35552588700;35546841500;55789925900;55328699600;6602096831;","Can marine cloud brightening reduce coral bleaching?",2013,"10.1002/asl2.442","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886314640&doi=10.1002%2fasl2.442&partnerID=40&md5=445976b585d99e26afd50f5da5315fe0","Increases in coral bleaching events over the last few decades have been largely caused by rising sea surface temperatures (SST), and continued warming is expected to cause even greater increases through this century. We use a Global Climate Model to examine the potential of marine cloud brightening (MCB) to cool oceanic surface waters in three coral reef provinces. Our simulations indicate that under doubled CO2 conditions, the substantial increases in coral bleaching conditions from current values in three reef regions (Caribbean, French Polynesia, and the Great Barrier Reef) were eliminated when MCB was applied, which reduced the SSTs at these sites roughly to their original values. © 2013 Royal Meteorological Society."
"8877858700;7404240633;7006744538;7006577693;55806795100;13402835300;","Evaluation of clouds in access using the satellite simulator package cosp: Global, seasonal, and regional cloud properties",2013,"10.1029/2012JD018469","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880915814&doi=10.1029%2f2012JD018469&partnerID=40&md5=0e2cb59849a148154d7a7b3162e60491","Cloud properties from the Australian Community Climate and Earth System Simulator (ACCESS1.3) are evaluated using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP). CloudSat, CALIPSO, and International Satellite Cloud Climatology Project (ISCCP) observations are used to evaluate the modeled cloud cover, condensate properties, and cloud optical depths for two seasons. The global distribution of cloud in the model is generally well represented with maximum high cloud in the tropics and low cloud over the eastern edges of the ocean basins. The model captures the observed position of the midlatitude storm track clouds and the modeled cloud top heights compare well with the observations in the upper troposphere. However, there is a lack of modeled midlevel cloud in the tropics and midlatitudes. The average high cloud cover in the Tropical Warm Pool region shows good agreement with CALIPSO. However, the modeled radar reflectivities and lidar scattering ratios are biased toward lower values, suggesting that the ice water contents and particles sizes of these clouds in the model are too small. Over the Southern Ocean the modeled cloud cover is underestimated due to a lack of mid- And low-level cloud. The low clouds over the Southern Ocean and the California stratocumulus clouds in the model have too little condensate and optical thickness and too much rain and drizzle. A sensitivity experiment showed that reducing the ice fall speeds improves aspects of the modeled cloud properties by increasing the frequency of occurrence of high clouds with large scattering ratios and optically thick low clouds. ACCESS1.3 has a reasonable representation of cloud. However, the underestimate of ice water content and particles sizes in high clouds and the too frequent occurrence of drizzle may impact the modeled cloud feedbacks and regional precipitation associated with current and perturbed climates. © 2012. American Geophysical Union."
"7404240633;8877858700;55743213400;55683917900;16316578300;7006744538;7006577693;7007107813;24492361700;7005705115;","Modifications to atmospheric physical parameterisations aimed at improving SST simulations in the ACCESS coupled model",2013,"10.22499/2.6301.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882385784&doi=10.22499%2f2.6301.015&partnerID=40&md5=0e058d5377d59e186f91fec8cc13f188","The Australian Community Climate and Earth System Simulator (ACCESS) has been developed at the Centre for Australian Weather and Climate Research. It is a coupled modeling system consisting of ocean, atmosphere and land surface. The ACCESS atmospheric component is the UK Met Office Unified Model (UM). The initial results from the ACCESS coupled model had significant errors in the sea surface temperature (SST). It has been identified that the SST bias is largely due to errors in the representation of clouds. We have found that the use of the homogenous cloud distribution within model grid-boxes produced an underestimation of solar radiation reaching the surface, causing a cooling effect. The model cloud scheme PC2 does not produce enough high cloud cover, which also led to a cooling effect. These two deficiencies have been largely remedied by the implementation of the triple-cloud scheme and a modification to the ice cloud fraction parameterisation in the PC2 cloud scheme. We have also modified the air-sea flux exchange scheme to improve the simulation of ocean currents. These modifications have led to significant improvements in the simulation of SST in ACCESS. Copyright © 2013, Common wealth of Australia."
"13204619900;8891521600;","Evaluating and understanding top of the atmosphere cloud radiative effects in intergovernmental panel on climate change (ipcc) fifth assessment report (ar5) coupled model intercomparison project phase 5 (cmip5) models using satellite observations",2013,"10.1029/2012JD018619","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884892785&doi=10.1029%2f2012JD018619&partnerID=40&md5=dd92fe16d985fa67cae3816bae8aa299","In this study, the annual mean climatology of top of the atmosphere (TOA) shortwave and longwave cloud radiative effects in 12 Atmospheric Model Intercomparison Project (AMIP)-type simulations participating in the CoupledModel Intercomparison Project Phase 5 (CMIP5) is evaluated and investigated using satellite-based observations, with a focus on the tropics. Results show that the CMIP5 AMIPs simulate large-scale regional mean TOA radiative fluxes and cloud radiative forcings (CRFs) well but produce considerably less cloud amount, particularly in the middle and lower troposphere. The good model simulations in tropical means, with multimodel mean biases of -3.6W/m2 for shortwave CRF and -1.0 W/m2 for longwave CRF, are, however, a result of compensating errors over different dynamical regimes. Over the Maritime Continent, most of the models simulate moderately less highcloud fraction, leading to weaker shortwave cooling and longwave warming and a larger net cooling. Over subtropical strong subsidence regimes, most of the CMIP5 models strongly underestimate stratocumulus cloud amount and show considerably weaker local shortwave CRF. Over the transitional trade cumulus regimes, a notable feature is that while at varying amplitudes, most of the CMIP5 models consistently simulate a deeper and drier boundary layer, more moist free troposphere, and more high clouds and, consequently, overestimate shortwave cooling and longwave warming effects there. While most of the CMIP5 models show the same sign as the multimodel mean, there are substantial model spreads, particularly over the tropical deep convective and subtropical strong subsidence regimes. Representing clouds and their TOA radiative effects remains a challenge in the CMIP5 models. © 2012. American Geophysical Union."
"23099339900;8670472000;7003557662;23571234400;","On the relationship between cloud-radiation interaction, atmospheric stability and Atlantic tropical cyclones in a variable-resolution climate model",2013,"10.1007/s00382-012-1311-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874330414&doi=10.1007%2fs00382-012-1311-6&partnerID=40&md5=846fa739e46deefc995582cb6c932b85","We compare two 28-year simulations performed with two versions of the Global Environmental Multiscale model run in variable-resolution mode. The two versions differ only by small differences in their radiation scheme. The most significant modification introduced is a reduction in the ice effective radius, which is observed to increase absorption of upwelling infrared radiation and increase temperature in the upper troposphere. The resulting change in vertical lapse rate is then observed to drive a resolution-dependent response of convection, which in turn modifies the zonal circulation and induces significant changes in simulated Atlantic tropical cyclone activity. The resulting change in vertical lapse rate and its implication in the context of anthropogenic climate change are discussed. © 2012 The Author(s)."
"6602334551;","Some aspects of the urban climates of Greater Cairo Region, Egypt",2013,"10.1002/joc.3661","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897100275&doi=10.1002%2fjoc.3661&partnerID=40&md5=2c71b20786e9c2d0eaeb8d021e644973","Rapid urbanization and industrialization over Greater Cairo Region (GCR), Egypt, have resulted in sharp land cover changes. Urban change not only impacts on land cover but also on urban climate. Detailed studies on the effect of urbanization and industrialization processes on climatic elements in GCR have been performed in this study. Five different districts were selected to represent rural, suburban, urban and industrial areas in GCR. The data of monthly mean values of minimum, maximum and mean temperatures, wind speed, relative humidity, cloud amount and rainfall amounts for the period (1990-2010) were used. The results revealed that, for each district, whenever urbanization and/or industrialization increase, the values of minimum, maximum and mean temperatures increase while the values of wind speed, relative humidity, cloud amount and rainfall amounts decrease. The effects of industrialization processes on the climatic elements were found stronger than the effects of urbanization processes. The greatest urban-rural climatic differences were found to be 5.9, 3.1, 3.9°C, 3.6kt, 13.9%, 1.1octas and 7.0mm for the minimum, maximum and mean temperatures, wind speed, relative humidity, cloud amount and rainfall amounts, respectively, while the greatest industrial-rural climatic differences were found to be 6.7, 4.3, 4.4°C, 4.4kt, 17.6%, 1.7octas and 8.0mm for the minimum, maximum and mean temperatures, wind speed, relative humidity, cloud amount and rainfall amounts, respectively. © 2013 Royal Meteorological Society."
"6701735773;6602080773;23981063100;35509639400;36096767000;6602504047;54881950900;6602886421;6505465237;8937991200;7004714030;6507014409;54883121500;36187387300;","LMDZ5B: The atmospheric component of the IPSL climate model with revisited parameterizations for clouds and convection",2013,"10.1007/s00382-012-1343-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876843065&doi=10.1007%2fs00382-012-1343-y&partnerID=40&md5=a3baed238841373fe7ca16c299d5bcf5","Based on a decade of research on cloud processes, a new version of the LMDZ atmospheric general circulation model has been developed that corresponds to a complete recasting of the parameterization of turbulence, convection and clouds. This LMDZ5B version includes a mass-flux representation of the thermal plumes or rolls of the convective boundary layer, coupled to a bi-Gaussian statistical cloud scheme, as well as a parameterization of the cold pools generated below cumulonimbus by re-evaporation of convective precipitation. The triggering and closure of deep convection are now controlled by lifting processes in the sub-cloud layer. An available lifting energy and lifting power are provided both by the thermal plumes and by the spread of cold pools. The individual parameterizations were carefully validated against the results of explicit high resolution simulations. Here we present the work done to go from those new concepts and developments to a full 3D atmospheric model, used in particular for climate change projections with the IPSL-CM5B coupled model. Based on a series of sensitivity experiments, we document the differences with the previous LMDZ5A version distinguishing the role of parameterization changes from that of model tuning. Improvements found previously in single-column simulations of case studies are confirmed in the 3D model: (1) the convective boundary layer and cumulus clouds are better represented and (2) the diurnal cycle of convective rainfall over continents is delayed by several hours, solving a longstanding problem in climate modeling. The variability of tropical rainfall is also larger in LMDZ5B at intraseasonal time-scales. Significant biases of the LMDZ5A model however remain, or are even sometimes amplified. The paper emphasizes the importance of parameterization improvements and model tuning in the frame of climate change studies as well as the new paradigm that represents the improvement of 3D climate models under the control of single-column case studies simulations. © 2012 The Author(s)."
"35194444600;56002700700;35293855400;","Cloud forest and climate change scenarios: An assessment in Hidalgo, México [Bosque mesófilo de montaña y escenarios de cambio climático: una evaluación en Hidalgo, México]",2013,"10.5154/r.rchscfa.2012.03.029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879218481&doi=10.5154%2fr.rchscfa.2012.03.029&partnerID=40&md5=81395acea488bd10e406531a13e55900","The habitat of eight forest species (Liquidambar macrophylla, Alnus arguta, Carpinus caroliniana, Clethra mexicana, Pinus patula, Nectandra sanguínea, Podocarpus reichei and Quercus spp.) representative of cloud forest in the state of Hidalgo was assessed under current and projected climate conditions. We used the ecological niche conceptual framework and considered twelve variables: one related to topography, five to landscape and six to climate. An ecological niche factorial analysis was carried out with Biomapper software. Habitat suitability maps were obtained for each forest species by changing six climatic variables for each climate change model applied, generating the same number of maps for future conditions. We analyzed the differences in suitable habitat for current conditions and those projected by climate change, finding that the optimal growth area for six species may be reduced. The species identified as threatened by climate change are L. macrophylla, A. arguta, C. caroliniana, C. mexicana, P. patula, and N. sanguinea, which comprise mainly the high tree layer of the cloud forest. We therefore conclude that the ecosystem can be seriously affected by climate change."
"6508287655;35330367300;7102797196;","Performance of the GCOM-C/SGLI satellite prelaunch phase cloud properties' algorithm",2013,"10.1117/1.JRS.7.073693","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887433875&doi=10.1117%2f1.JRS.7.073693&partnerID=40&md5=e7f3563267e9aaae0460adaaa80b14c3","The performance of the cloud properties algorithm of the future Global Change Observation Mission-Climate/Second-Generation Global Imager (GCOM-C/SGLI) satellite is compared with that of a spectrally compatible sensor, the moderate resolution image spectroradiometer (MODIS). The results obtained are evaluated against the target accuracy of the GCOM-C/SGLI satellite mission. Three direct cloud parameters: the cloud optical thickness (COT), the cloud particle effective radius (CLER), and the cloud top temperature (CTT), and an indirect parameter: the cloud liquid water path (CLWP), are the cloud properties that are evaluated. The satellite-satellite comparison shows a good alignment between the retrievals of the GCOM-C/SGLI algorithm and those of MODIS in most of the areas and agreement with the accuracy targets of the new satellite mission. However, the COT comparison shows an increasing dispersion with the increase of the cloud thickness along the GCOM-C/SGLIMODIS 1:1 line. The CTT is systematically overestimated by the GCOM-C/SGLI (against MODIS), particularly in mid-thermal clouds. This is found to be due to an insufficient cloud emissivity correction of the thermal radiances by the GCOM-C/SGLI algorithm. The lowest COT, CLER, and CLWP accuracies, noticed in forest areas, are found to be related to the cloud detection uncertainty and the nonabsorption channel sensitivity differences. © The Authors 2013."
"23017945100;6701754792;6506887943;7006577245;36573991900;24465126800;7006211890;55533258800;","Comparison of airborne in situ, airborne radar-lidar, and spaceborne radar-lidar retrievals of polar ice cloud properties sampled during the POLARCAT campaign",2013,"10.1175/JTECH-D-11-00200.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871378006&doi=10.1175%2fJTECH-D-11-00200.1&partnerID=40&md5=146271fd89439ac995b7084614a43441","This study illustrates the high potential of RALI, the French airborne radar-lidar instrument, for studying cloud processes and evaluating satellite products when satellite overpasses are available. For an Arctic nimbostratus ice cloud collected on 1 April 2008 during the Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport (POLARCAT) campaign, the capability of this synergistic instrument to retrieve cloud properties and to characterize the cloud phase at scales smaller than a kilometer, which is crucial for cloud process analysis, is demonstrated. A variational approach, which combines radar and lidar, is used to retrieve the ice-water content (IWC), extinction, and effective radius. The combination of radar and lidar is shown to provide better retrievals than do stand-alone methods and, in general, the radar overestimates and the lidar underestimates IWC. As the sampled ice cloud was simultaneously observed by CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellites, a new way to assess satellite cloud products by combining in situ and active remote sensing measurements is identified. It was then possible to compare RALI to three satellite ice cloud products: CloudSat, CALIPSO, and the Cloud-Aerosol-Water-Radiation Interactions (ICARE) center's radar-lidar project (DARDAR). © 2013 American Meteorological Society."
"35191486300;57192192815;8720083500;57214056158;36494729400;55710051100;13403147100;7201796620;","Investigation on semi-direct and indirect climate effects of fossil fuel black carbon aerosol over China",2013,"10.1007/s00704-013-0862-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887316962&doi=10.1007%2fs00704-013-0862-8&partnerID=40&md5=38b7ae3afa6c9a5525be1aa386744a68","A Regional Climate Chemistry Modeling System that employed empirical parameterizations of aerosol-cloud microphysics was applied to investigate the spatial distribution, radiative forcing (RF), and climate effects of black carbon (BC) over China. Results showed high levels of BC in Southwest, Central, and East China, with maximum surface concentrations, column burden, and optical depth (AOD) up to 14 μg m-3, 8 mg m-2, and 0.11, respectively. Black carbon was found to result in a positive RF at the top of the atmosphere (TOA) due to its direct effect while a negative RF due to its indirect effect. The regional-averaged direct and indirect RF of BC in China was about +0.81 and -0.95 W m-2, respectively, leading to a net RF of -0.15 W m-2 at the TOA. The BC indirect RF was larger than its direct RF in South China. Due to BC absorption of solar radiation, cloudiness was decreased by 1.33 %, further resulting in an increase of solar radiation and subsequently a surface warming over most parts of China, which was opposite to BC's indirect effect. Further, the net effect of BC might cause a decrease of precipitation of -7.39 % over China. Investigations also suggested large uncertainties and non-linearity in BC's indirect effect on regional climate. Results suggested that: (a) changes in cloud cover might be more affected by BC's direct effect, while changes in surface air temperature and precipitation might be influenced by BC's indirect effect; and (b) BC second indirect effect might have more influence on cloud cover and water content compared to first indirect effect. This study highlighted a substantial role of BC on regional climate changes. © 2013 Springer-Verlag Wien."
"57203043665;7003278104;9249239700;7402942478;","Evaluating the impact of orbital sampling on satellite-climate model comparisons",2013,"10.1029/2012JD018590","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881650794&doi=10.1029%2f2012JD018590&partnerID=40&md5=e4d430dcb73aefd8a0783518ce737a37","The effect of orbital sampling is one of the chief uncertainties in satellite-climate model comparisons. In the context of an ongoing activity to make satellite data more accessible for model evaluation (i.e., obs4MIPs), six variables (temperature, specific humidity, ozone, cloud water, cloud cover, and ocean surface wind) associated with six satellite instruments are evaluated for the orbital sampling effect. Comparisons are made between reanalysis and simulated satellite-sampled data in terms of bias and pattern similarity. It is found that the bias introduced by orbital sampling for long-term annual means, monthly climatologies, and monthly means is largely negligible, which is within ∼3% of the standard deviation of the three quantities for most fields. The bias for 2-hPa temperature and specific humidity, while relatively large (9-10%), is within the estimated observational uncertainty. In terms of pattern similarity, cloud water and upper level specific humidity are the most sensitive to orbital sampling among the variables considered, with the magnitude of the sampling effect dependent on the spatial resolution-insignificant at 1.25° ×1.25° resolution for both. For all variables considered, orbital sampling effects are not an important consideration for model evaluation at 1.25° ×1.25° resolution. At 0.5° ×0.5° , orbital sampling is potentially important for cloud water and upper level specific humidity when evaluating model long-term annual means and monthly climatologies, and for cloud water when evaluating monthly means, all in terms of pattern similarities. Orbital sampling is not an important factor for evaluating zonal means in call cases considered. © 2012. American Geophysical Union."
"36706881700;7409080503;57138743300;8839875600;","Validation of a radiosonde-based cloud layer detection method against a ground-based remote sensing method at multiple arm sites",2013,"10.1029/2012JD018515","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884842262&doi=10.1029%2f2012JD018515&partnerID=40&md5=c44790b7e011e4fbe1509e914bec42bc","Cloud vertical structure is a key quantity in meteorological and climate studies, but it is also among the most difficult quantities to observe. In this study, we develop a long-term (10 years) radiosonde-based cloud profile product for the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP), Tropical Western Pacific (TWP), and North Slope of Alaska (NSA) sites and a shorter-term product for the ARM Mobile Facility (AMF) deployed in Shouxian, Anhui Province, China (AMF-China). The AMF-China site was in operation from 14 May to 28 December 2008; the ARM sites have been collecting data for over 15 years. The Active Remote Sensing of Cloud (ARSCL) value-added product (VAP), which combines data from the 95-GHz W-band ARM Cloud Radar (WACR) and/or the 35-GHz Millimeter Microwave Cloud Radar (MMCR), is used in this study to validate the radiosonde-based cloud layer retrieval method. The performance of the radiosonde-based cloud layer retrieval method applied to data from different climate regimes is evaluated. Overall, cloud layers derived from the ARSCL VAP and radiosonde data agree very well at the SGP and AMF-China sites. At the TWP and NSA sites, the radiosonde tends to detect more cloud layers in the upper troposphere. © 2012. American Geophysical Union."
"57212007232;57212007242;57212017862;","Variability and Long-Term Trend of Total Cloud Cover in China Derived from ISCCP, ERA-40, CRU3, and Ground Station Datasets",2013,"10.3878/j.issn.1674-2834.12.0100","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898014352&doi=10.3878%2fj.issn.1674-2834.12.0100&partnerID=40&md5=0d6f4123927c99b34208c51f1ee4a2da","Total Cloud Cover (TCC) over China determined from four climate datasets including the International Satellite Cloud Climatology Project (ISCCP), the 40-year ReAnalysis Project of the European Centre for Medium-Range Weather Forecasts (ERA-40), Climate Research Unit Time Series 3.0 (CRU3), and ground station datasets are used to show spatial and temporal variation of TCC and their differences. It is demonstrated that the four datasets show similar spatial pattern and seasonal variation. The maximum value is derived from ISCCP. TCC value in North China derived from ERA-40 is 50% larger than that from the station dataset; however, the value is 50% less than that in South China. The annual TCC of ISCCP, ERA-40, and ground station datasets shows a decreasing trend during 1984–2002; however, an increasing trend is derived from CRU3. The results of this study imply remarkable differences of TCC derived from surface and satellite observations as well as model simulations. The potential effects of these differences on cloud climatology and associated climatic issues should be carefully considered. © 2013, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"55556288600;7403079681;","A new method for retrieving equivalent cloud base height and equivalent emissivity by using the ground-based Atmospheric Emitted Radiance Interferometer (AERI)",2013,"10.1007/s11430-012-4398-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872283026&doi=10.1007%2fs11430-012-4398-z&partnerID=40&md5=41d58138641010c19b2452117f9e0ef8","In the paper, we propose a new method of identifying the clear sky based on the Atmospheric Emitted Radiance Interferometer (AERI). Using the Atmospheric Radiation Measurement (ARM) Mobile Facility (AFM) dataset in Shouxian in 2008, we simulate the downwelling radiances on the surface in the 8-12 μm window region using Line-By-Line Radiative Transfer Model (LBLRTM), and compare the results with the AERI radiances. The differences larger (smaller) than 3 mW (cm2 sr cm-1)-1 suggest a cloudy (clear) sky. Meanwhile, we develop the new algorithms for retrieving the zenith equivalent cloud base height (CBHe) and the equivalent emissivity (e{open}e), respectively. The retrieval methods are described as follows. (1) An infinitely thin and isothermal blackbody cloud is simulated by the LBLRTM. The cloud base height (H) is adjusted iteratively to satisfy the situation that the contribution of the blackbody to the downwelling radiance is equal to that of realistic cloud. The final H is considered as CBHe. The retrieval results indicate that the differences between the CBHe and observational cloud base height (CBH) are much smaller for thick low cloud, and increase with the increasing CBH. (2) An infinitely thin and isothermal gray body cloud is simulated by the LBLRTM, with the CBH specified as the observed value. The cloud base emissivity (e{open}c) is adjusted iteratively until the contribution of the gray body to the downwelling radiance is the same as that of realistic cloud. The corresponding e{open}c is e{open}e. The average e{open}e for the low, middle, and high cloud is 0. 967, 0. 781, and 0. 616 for the 50 cases, respectively. It decreases with the increasing CBH. The retrieval results will be useful for studying the role of cloud in the radiation budget in the window region and cloud parameterizations in the climate model. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg."
"8953038700;8397494800;56900391700;7102268722;6603081424;22635081500;35497573900;7004364155;","Longwave band-by-band cloud radiative effect and its application in GCM evaluation",2013,"10.1175/JCLI-D-12-00112.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872981954&doi=10.1175%2fJCLI-D-12-00112.1&partnerID=40&md5=ba543e2d30f28c4a9ca30f23c8523001","The cloud radiative effect (CRE) of each longwave (LW) absorption band of a GCM's radiation code is uniquely valuable for GCM evaluation because 1) comparing band-by-band CRE avoids the compensating biases in the broadband CRE comparison and 2) the fractional contribution of each band to the LW broadband CRE (fCRE) is sensitive to cloud-top height but largely insensitive to cloud fraction, thereby presenting a diagnostic metric to separate the two macroscopic properties of clouds. Recent studies led by the first author haveestablished methods to derive such band-by-band quantities from collocated Atmospheric Infrared Sounder (AIRS) and Clouds and the Earth's Radiant Energy System (CERES)observations. A study is presented here that compares the observed band-by-band CRE over the tropical oceans with those simulated by three different atmospheric GCMs-the GFDL Atmospheric Model version 2 (GFDL AM2), NASA Goddard Earth Observing System version 5 (GEOS-5), and the fourth-generation AGCM of the Canadian Centre for Climate Modelling and Analysis (CCCmaCanAM4)-forced by observed SST. The models agree with observation on the annual-mean LW broadband CRE over the tropical oceans within ±1 W m-2. However, the differences among these three GCMs in some bands can be as large as or even largerthan ±1 W m-2. Observed seasonal cycles of fCRE in major bands are shown to be consistent with the seasonal cycle ofcloud-top pressure for both the amplitude and the phase. However, while the three simulated seasonal cycles of fCRE agree with observations on the phase, the amplitudes are underestimated. Simulated interannual anomalies from GFDL AM2 and CCCma CanAM4 are in phase with observed anomalies. The spatial distribution of fCRE highlights the discrepancies between models and observation over the low-cloud regions and the compensating biases from different bands. © 2013 American Meteorological Society."
"57207473157;7401436524;55899884100;35207733900;55745955800;","Dynamic and thermodynamic relations of distinctive stratus clouds on the lee side of the tibetan plateau in the cold season",2013,"10.1175/JCLI-D-13-00009.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886257664&doi=10.1175%2fJCLI-D-13-00009.1&partnerID=40&md5=9efda06ca2d176248679c70eba99b343","Given the large discrepancies that exist in climate models for shortwave cloud forcing over eastern China (EC), the dynamic (vertical motion and horizontal circulation) and thermodynamic (stability) relations of stratus clouds and the associated cloud radiative forcing in the cold season are examined. Unlike the stratus clouds over the southeastern Pacific Ocean (as a representative of marine boundary stratus), where thermodynamic forcing plays a primary role, the stratus clouds over EC are affected by both dynamic and thermodynamic factors. The Tibetan Plateau (TP)-forced low-level large-scale lifting and high stability overEC favor the accumulation of abundant saturated moist air, which contributes to the formation of stratus clouds. The TP slows down thewesterly overflow through a frictional effect, resulting inmidlevel divergence, and forces the low-level surrounding flows, resulting in convergence. Both midlevel divergence and low-level convergence sustain a rising motion and vertical water vapor transport over EC. The surface cold air is advected from the Siberian high by the surrounding northerly flow, causing low-level cooling. The cooling effect is enhanced by the blocking of theYunGui Plateau. The southwesterlywind carryingwarm, moist air fromthe eastBay ofBengal is uplifted by the HengDuan Mountains via topographical forcing; the midtropospheric westerly flow further advects thewarmair downstream of the TP, moistening andwarming themiddle troposphere on the lee side of the TP. The low-level cooling and midlevel warming together increase the stability. The favorable dynamic and thermodynamic large-scale environment allows for the formation of stratus clouds overECduring the cold season. © 2013 American Meteorological Society."
"35221791100;35422119400;","Does the diurnal temperature range respond to changes in the cosmic ray flux?",2013,"10.1088/1748-9326/8/4/045018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891940277&doi=10.1088%2f1748-9326%2f8%2f4%2f045018&partnerID=40&md5=58f7b6a13af2ff071f34b40b485b8887","Recent studies have suggested that measurements of the diurnal temperature range (DTR) over Europe may provide evidence of a long-hypothesized link between the cosmic ray (CR) flux and cloud cover. Such propositions are interesting, as previous investigations of CR-cloud links are limited by data issues including long-term reliability and view-angle artifacts in satellite-based cloud measurements. Consequently, the DTR presents a further independent opportunity for assessment. Claims have been made that during infrequent high-magnitude increases (ground level enhancements, GLE) and decreases (Forbush decreases, Fd) in the CR flux significant anti-correlated DTR changes may be observed, and the magnitude of the DTR deviations increases with the size of the CR disturbance. If confirmed this may have important consequences for the estimation of natural climate forcing. We analyze these claims, and conclude that no statistically significant fluctuations in DTR (p < 0.05) are observed. Using detailed Monte Carlo significance testing we show that past claims to the contrary result from a methodological error in estimating significance connected to the effects of sub-sampling. © 2013 IOP Publishing Ltd."
"15070481300;36951202700;55957072000;55957567300;55957853400;55279905600;","Comparison of ground techniques used to estimate cloud cover in Florianópolis, southern Brazil",2013,"10.22564/rbgf.v31i1.248","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889865038&doi=10.22564%2frbgf.v31i1.248&partnerID=40&md5=14cfbbd07aef27f4ae13bf80abebab64","Cloud cover is a key feature in Earth images acquired from space. Cloud cover data play a significant role in the weather forecast and climate knowledge, as well as in several human activities. Several studies have been conducted to establish a methodology and experimental setup in order to acquire reliable cloud cover data from remote sense observations performed on the surface. This research aimed at comparing ground data acquired by different systems for the same atmospheric scenario regarding cloud cover. Solar radiation data and sky images acquired at SONDA station located in Florianópolis, in 2002, were used to evaluate cloud cover. Also, cloud cover data collected at the international airport meteorological station distant 7,700 m from the SONDA station were used. This work compares these two sets of data acquired for sky scenarios with only one type of cloud. The results show good agreement in clear and completely overcast sky conditions. Future studies using longer time series will be developed in order to evaluate the influence of seasonal variability and atmospheric scenarios with several cloud types (low, medium and high clouds)."
"24343173500;57189215242;8084443000;7403401100;7103337730;7006107059;7004015298;55871322800;55871415400;55871394300;7004393835;24069972000;7004611350;55908042400;57050508600;7006808794;8657166100;","Airborne investigation of the aerosols-cloud interactions in the vicinity and within a marine stratocumulus over the North Sea during EUCAARI (2008)",2013,"10.1016/j.atmosenv.2013.08.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884919209&doi=10.1016%2fj.atmosenv.2013.08.035&partnerID=40&md5=fbaabc5d073b190c71f7d2670f8765e3","Within the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Meteo France research aircraft ATR-42 was operated from Rotterdam (Netherlands) airport during May 2008, to perform scientific flights dedicated to the investigation of aerosol-cloud interactions. The objective of this study is to illustrate the impact of cloud processing on the aerosol particle physical and chemical properties. The presented results are retrieved from measurements during flight operation with two consecutive flights, first from Rotterdam to Newcastle (United Kingdom) and subsequently reverse along the same waypoints back to Rotterdam using data measured with compact Time of Flight Aerosol Mass Spectrometer (cToF-AMS) and Scanning Mobility Particle Sizer (SMPS). Cloud-related measurements during these flights were performed over the North Sea within as well as in close vicinity of a marine stratocumulus cloud layer. Particle physical and chemical properties observed in the close vicinity, below and above the stratocumulus cloud, show strong differences: (1) the averaged aerosol size distributions, observed above and below the cloud layer, are of bimodal character with pronounced minima between Aitken and accumulation mode, very likely due to cloud processing. (2) the chemical composition of aerosol particles is strongly dependent on the position relative to the cloud layer (vicinity or below/above cloud). In general, the nitrate and organic relative mass fractions decrease with decreasing distance to the cloud, in the transit from cloud-free conditions towards the cloud boundaries. This relative mass fraction decrease ranges from a factor of three to ten, thus leading to an increase of the sulfate and ammonium relative mass concentrations while approaching the cloud layer. (3), the chemical composition of cloud droplet residuals, analyzed downstream of a Counterflow virtual Impactor (CVI) inlet indicates increased fractions of mainly soluble chemical compounds such as nitrate and organics, compared to non cloud processed particles. Finally, a net overbalance of nitrate aerosol has been revealed by comparing cloud droplet residual and non cloud processed aerosol chemical compositions. Conclusively, this study highlights gaps concerning the sampling strategy that need to be addressed for the future missions. © 2013 Elsevier Ltd."
"8726272900;7005304841;7005712238;56250250300;12139043600;12139310900;7003827051;7005088845;35600074800;","Climate-induced changes in sea salt aerosol number emissions: 1870 to 2100",2013,"10.1002/jgrd.50129","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884840473&doi=10.1002%2fjgrd.50129&partnerID=40&md5=14ad1c34b55b3729bb4337f8acdcf4cb","Global climate model output is combined with an emission parameterization to estimate the change in the global and regional sea salt aerosol number emission from 1870 to 2100. Global average results suggest a general increase in sea salt aerosol number emission due to increasing surface wind speed. However, the emission changes are not uniform over the aerosol size spectrum due to an increase in sea surface temperature. From 1870 to 2100 the emission of coarse mode particles (dry diameter DP>655 nm) increase by approximately 10 % (global average), whereas no significant change in the emission of ultrafine mode aerosols (dry diameter Dp<76 nm) was found over the same period. Significant regional differences in the number emission trends were also found. Based on CAM-Oslo global climate model output, no straight-forward relationship was found between the change in the number emissions and changes in the sea salt aerosol burden or optical thickness. This is attributed to a change in the simulated residence time of the sea salt aerosol. For the 21st century, a decrease in the residence time leads to a weaker sea salt aerosol-climate feedback that what would be inferred based on changes in number emissions alone. Finally, quantifying any potential impact on marine stratocumulus cloud microphysical and radiative properties due to changes in sea salt aerosol number emissions is likely to be complicated by commensurate changes in anthropogenic aerosol emissions and changes in meteorology. © 2012. American Geophysical Union."
"55552038100;7006765934;","Late Pleistocene tropical Pacific temperature sensitivity to radiative greenhouse gas forcing",2013,"10.1130/G33425.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872134017&doi=10.1130%2fG33425.1&partnerID=40&md5=a422a6dae8ba92a6b1d8bc6550d5fe88","Understanding how global temperature changes with increasing atmospheric greenhouse gas concentrations, or climate sensitivity, is of central importance to climate change research. Climate models provide sensitivity estimates that may not fully incorporate slow, long-term feedbacks such as those involving ice sheets and vegetation. Geological studies, on the other hand, can provide estimates that integrate long- and short-term climate feedbacks to radiative forcing. Because high latitudes are thought to be most sensitive to greenhouse gas forcing owing to, for example, ice-albedo feedbacks, we focus on the tropical Pacifi c Ocean to derive a minimum value for long-term climate sensitivity. Using Mg/Ca paleothermometry from the planktonic foraminifera Globigerinoides ruber from the past 500 k.y. at Ocean Drilling Program (ODP) Site 871 in the western Pacifi c warm pool, we estimate the tropical Pacifi c climate sensitivity parameter (?) to be 0.94-1.06 °C (W m-2)-1, higher than that predicted by model simulations of the Last Glacial Maximum or by models of doubled greenhouse gas concentration forcing. This result suggests that models may not yet adequately represent the longterm feedbacks related to ocean circulation, vegetation and associated dust, or the cryosphere, and/or may underestimate the effects of tropical clouds or other short-term feedback processes."
"7003266014;","Observations of climate feedbacks over 2000-10 and comparisons to climate models",2013,"10.1175/JCLI-D-11-00640.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872946004&doi=10.1175%2fJCLI-D-11-00640.1&partnerID=40&md5=d65ee2550f654c92f9ea1a00a8f63be8","Feedbacks in response to climate variations during the period 2000-10 have been calculated using reanalysis meteorological fields and top-of-atmosphere flux measurements. Over this period, the climate was stabilized by a strongly negative temperature feedback (̃-3 W m2 K1); climate variations were also amplified by a strong positive water vapor feedback (̃+1.2 W m2 K1) and smaller positive albedo and cloud feedbacks (̃+0.3 and 10.5 W m2 K1, respectively). These observations are compared to two climate model ensembles, one dominated by internal variability (the control ensemble) and the other dominated by long-term global warming (the A1B ensemble). The control ensemble produces global average feedbacks that agree within uncertainties with the observations, as well as producing similar spatial patterns. The most significant discrepancy was in the spatial pattern for the total (shortwave + longwave) cloud feedback. Feedbacks calculated from the A1B ensemble show a stronger negative temperature feedback (due to a stronger lapse-rate feedback), but that is cancelled by a stronger positive water vapor feedback. The feedbacks in the A1B ensemble tend to be more smoothly distributed in space, which is consistent with the differences between El Niñ o-Southern Oscillation (ENSO) climate variations and long-term global warming. The sum of all of the feedbacks, sometimes referred to as the thermal damping rate, is-1.15±0.88 W m2 K1 in the observations and-0.60±0.37 W m2 K1 in the control ensemble.Within the control ensemble, models that more accurately simulate ENSO tend to produce thermal damping rates closer to the observations. The A1B ensemble average thermal damping rate is -1.26 ± 0.45 W m2 K1. © 2013 American Meteorological Society."
"53880473700;6602080205;12787547600;","The influence of anthropogenic aerosol on multi-decadal variations of historical global climate",2013,"10.1088/1748-9326/8/2/024033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880874790&doi=10.1088%2f1748-9326%2f8%2f2%2f024033&partnerID=40&md5=edc0b207f942f3424842a8e5cd8bcc4c","Analysis of single forcing runs from CMIP5 (the fifth Coupled Model Intercomparison Project) simulations shows that the mid-twentieth century temperature hiatus, and the coincident decrease in precipitation, is likely to have been influenced strongly by anthropogenic aerosol forcing. Models that include a representation of the indirect effect of aerosol better reproduce inter-decadal variability in historical global-mean near-surface temperatures, particularly the cooling in the 1950s and 1960s, compared to models with representation of the aerosol direct effect only. Models with the indirect effect also show a more pronounced decrease in precipitation during this period, which is in better agreement with observations, and greater inter-decadal variability in the inter-hemispheric temperature difference. This study demonstrates the importance of representing aerosols, and their indirect effects, in general circulation models, and suggests that inter-model diversity in aerosol burden and representation of aerosol-cloud interaction can produce substantial variation in simulations of climate variability on multi-decadal timescales. © 2013 IOP Publishing Ltd."
"35596591300;","The 20th century cooling trend over the southeastern United States",2013,"10.1007/s00382-012-1437-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871922541&doi=10.1007%2fs00382-012-1437-6&partnerID=40&md5=058cbf3168d99a208f89c7e6093394db","Portions of the southern and southeastern United States, primarily Mississippi, Alabama, and Georgia, have experienced century-long (1895-2007) downward air temperature trends that occur in all seasons. Superimposed on them are shifts in mean temperatures on decadal scales characterized by alternating warm (1930s-1940s, 1990s) and cold (1900s; 1960s-1970s) regimes. Regional atmospheric circulation and SST teleconnection indices, station-based cloud cover and soil moisture (Palmer drought severity index) data are used in stepwise multiple linear regression models. These models identify predictors linked to observed winter, summer, and annual Southeastern air temperature variability, the observed variance (r2) they explain, and the resulting prediction and residual time series. Long-term variations and trends in tropical Pacific sea temperatures, cloud cover, soil moisture and the North Atlantic and Arctic oscillations account for much of the air temperature downtrends. Soil moisture and cloud cover are the primary predictors of 59. 6 % of the observed summer temperature variance. While the teleconnections, cloud cover and moisture data account for some of the annual and summer Southeastern cooling trend, large significant downward trending residuals remain in winter and summer. Comparison is made to the northeastern United States where large twentieth century upward air temperature trends are driven by cloud cover increases and Atlantic Multidecadal Oscillation (AMO) variability. Differences between the Northeastern warming and the Southeastern cooling trends in summer are attributable in part to the differing roles of cloud cover, soil moisture, the Arctic Oscillation and the AMO on air temperatures of the 2 regions. © 2012 Springer-Verlag."
"6601973842;7006497331;7004515812;6701858892;7003488425;7101746767;55503533600;55503576200;26428663900;23008850700;6701461133;","Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records",2013,"10.1016/j.quascirev.2012.10.030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881370103&doi=10.1016%2fj.quascirev.2012.10.030&partnerID=40&md5=988fde52bdc61e51ba07d6c140047745","Here we present δ;18Odiatom data from two high-latitude lakes; one has short residence time and a water isotopic composition (δ18Olake) that fluctuate due to seasonal variations in precipitation and temperature, and the other has δ18Olake that is influenced by longer lake water residence times and evaporation. The δ18Odiatom records reveal common responses to precipitation forcing over the past millennium. Relatively wet summers are inferred from δ18Odiatom between 1000 and 1080 AD, 1300 and 1440 AD, and during the early 19th century, coincided with periods of high cloud cover inferred from tree-ring carbon isotopes, and other data for high Arctic Oscillation index. While relatively dry summers with increasing influence of winter snow are indicated between 1600 and 1750 AD. The co-response between carbon isotopes in trees and oxygen isotopes in diatoms strengthens the relationship between cloud cover and precipitation and the hypothesis that these changes were the result of significant regional shifts in atmospheric circulation. © 2012 Elsevier Ltd."
"9635764200;12645767500;6701606453;","Low cloud precipitation climatology in the southeastern Pacific marine stratocumulus region using CloudSat",2013,"10.1088/1748-9326/8/1/014027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876196047&doi=10.1088%2f1748-9326%2f8%2f1%2f014027&partnerID=40&md5=6a499a8b49e79b2e9c791be5dd285012","A climatology of low cloud surface precipitation occurrence and intensity from the new CloudSat 2C-RAIN-PROFILE algorithm is presented from June 2006 through December 2010 for the southeastern Pacific region of marine stratocumulus. Results show that over 70% of low cloud precipitation falls as drizzle. Application of an empirical evaporation model suggests that 50-80% of the precipitation evaporates before it reaches the surface. Segregation of the CloudSat ascending and descending overpasses shows that the majority of precipitation occurs at night. Examination of the seasonal cycle shows that the precipitation is most frequent during the austral winter and spring; however there is considerable regional variability. Conditional rain rates increase from east to west with a maximum occurring in the region influenced by the South Pacific Convergence Zone. Area average rain rates are highest in the region where precipitation rates are moderate, but most frequent. The area average surface rain rate for low cloud precipitation for this region is ∼0.22 mm d-1, in good agreement with in situ estimates, and is greatly improved over earlier CloudSat precipitation products. These results provide a much-needed quantification of surface precipitation in a region that is currently underestimated in existing satellite-based precipitation climatologies. © 2013 IOP Publishing Ltd."
"57194336826;","Climate Change and carbon dioxide: Geological perspective",2013,"10.5169/seals-391145","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019757367&doi=10.5169%2fseals-391145&partnerID=40&md5=15d8d73addc258ba838a138fa6172d45","The climate history of the Earth is a history of con tinuous change. Through geological time the aver age global temperature remained always within the constraints set by the presence of abundant liquid water, while the atmospheric CO2concentration varied strongly. Its 30% rise since the beginning of the 20th century can, at least partly, be attributed to human activities. According to the ""general circulation models"" (GCMsl used by the IPCC the ongoing rise in atmospheric CO2concentration will lead to significant global warming. However, in these GCMs the (small! net CO2forcing is amplified by strong positive feedbacks, particularly from water vapour and clouds. Real world observations and data of the geologic past do not support the role of c02 as the principal climate regulator."
"16245393100;7202315562;36945731200;35221560200;7103248807;7202754530;7003979342;7003465848;7004714030;6602864991;16403404400;15828193000;6603247427;10243911900;36945025900;","Regional hydrological cycle changes in response to an ambitious mitigation scenario",2013,"10.1007/s10584-013-0829-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881615839&doi=10.1007%2fs10584-013-0829-x&partnerID=40&md5=6745234c0d483cf31d61f3292b5296d2","Climate change impacts on the regional hydrological cycle are compared for model projections following an ambitious emissions-reduction scenario (E1) and a medium-high emissions scenario with no mitigation policy (A1B). The E1 scenario is designed to limit global annual mean warming to 2 °C or less above pre-industrial levels. A multi-model ensemble consisting of ten coupled atmosphere-ocean general circulation models is analyzed, which includes five Earth System Models containing interactive carbon cycles. The aim of the study is to assess the changes that could be mitigated under the E1 scenario and to identify regions where even small climate change may lead to strong changes in precipitation, cloud cover and evapotranspiration. In these regions the hydrological cycle is considered particularly vulnerable to climate change, highlighting the need for adaptation measures even if strong mitigation of climate change would be achieved. In the A1B projections, there are significant drying trends in sub-tropical regions, precipitation increases in high latitudes and some monsoon regions, as well as changes in cloudiness and evapotranspiration. These signals are reduced in E1 scenario projections. However, even under the E1 scenario, significant precipitation decrease in the subtropics and increase in high latitudes are projected. Particularly the Amazon region shows strong drying tendencies in some models, most probably related to vegetation interaction. Where climate change is relatively small, the E1 scenario tends to keep the average magnitude of potential changes at a level comparable to current intra-seasonal to inter-annual variability at that location. Such regions are mainly located in the mid-latitudes. © 2013 Springer Science+Business Media Dordrecht."
"7004215973;7102546082;","Atmospheric aerosol particles: A mineralogical introduction",2013,"10.1180/EMU-notes.13.6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900341599&doi=10.1180%2fEMU-notes.13.6&partnerID=40&md5=cb344f1044a0bfc6aca7b150af53baa8","Aerosol particles in the atmosphere interact with sunlight and initiate cloud formation, thereby affecting radiation transfer and modifying our climate. Aerosol particles also influence air quality and play important roles in various environmental processes. As the tropospheric aerosol is a heterogeneous mixture of various particle types, its climate and environmental effects can only be fully understood through detailed knowledge of the physical and chemical properties of the particles. Here, we review the formation and removal mechanisms of aerosol particles, the major approaches to study their physical and chemical properties, and discuss the most important categories of particle types. The focus of this review is on the 'mineralogical' identification and characterization of individual particles. We review the sources, transport and transformation mechanisms of the various particle types, their interactions with radiation and clouds, focusing on the results of the last 15 years.© 2013 the European Mineralogical Union and the Mineralogical Society of Great Britain and Ireland."
"7801375648;6602386601;","Recent (1980-2009) evidence of climate change in the upper Karakoram, Pakistan",2013,"10.1007/s00704-012-0803-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880829456&doi=10.1007%2fs00704-012-0803-y&partnerID=40&md5=d64b99d7f5210d19d06429be8ad700ac","We investigate here recent (1980-2009) climate variability in the upper Karakoram, Northern Pakistan, of particular interest given the peculiar glacier behavior during the last two decades. Differently from other glacierized regions in the Hindu Kush-Karakoram-Himalaya region, glaciers in the Karakoram display limited ice thinning, and in some cases advancing has been detected. Climate analysis is required to describe recent (i.e., last three decades) variability, to aid highlighting of the factors driving glacier evolution. Starting from monthly data, we analyze seasonal values of total precipitation, number of wet days, maximum (max) and minimum (min) air temperature, max precipitation in 24 h, and cloud cover for 17 weather stations in the upper Karakoram, clustered within three climatic regions as per use of principal components analysis. We detect possible nonstationarity in each of these regions by way of (1) linear regression, (2) moving window average, and (3) Mann-Kendall test, also in progressive form, to detect the onset date of possible trends. We then evaluate linear correlation coefficients between Northern Atlantic Oscillation (NAO) index and climate variables to assess effectiveness of teleconnections, claimed recently to affect climate in this area. Also, we compare temperature within the investigated zone against global temperature anomalies, to evidence enhanced warming within this area. We found mostly nonsignificant changes of total precipitation, unless for few stations displaying increase in Chitral-Hindu Kush region and Northwest Karakoram, or Gilgit area, and decrease in Western Himalaya, Kotli region. Max precipitation is mostly unchanged, unless for slight increase in Chitral and Gilgit areas, and slight decrease in Kotli region. Number of wet days is mostly increasing in Gilgit area, and decreasing in Chitral area, with no clear signal in Kotli region. Min temperatures increase always but during Summer, when decreasing values are detected, especially for Gilgit and Chitral regions. Max temperatures are found to increase everywhere. Cloud cover is significantly increasing in Gilgit area, but decreasing otherwise, especially in Kotli region. Max temperature regime is significantly positively correlated against global thermal anomaly, while min temperature regime is nonsignificantly negatively correlated. Max and min temperatures seem mostly negatively correlated to NAO. Some dependence of trend intensity for the considered variables against altitude is found, different for each region, suggesting that investigation of weather variables at the highest altitudes is warranted to discriminate further climate variability in the area. © 2012 Springer-Verlag Wien."
"7004690545;55827003100;7201502185;7006577693;7601491332;15841319100;55597313700;8598454000;7003401981;23098909000;","The land surface model component of ACCESS: Description and impact on the simulated surface climatology",2013,"10.22499/2.6301.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882402863&doi=10.22499%2f2.6301.005&partnerID=40&md5=2345e87dab351e74e0cf0536c1ceeec1","The land surface component of the Australian Community Climate and Earth System Simulator (ACCESS) is one difference between the two versions of ACCESS used to run simulations for the Coupled Model Intercomparison Project (CMIP5). The Met Office Surface Exchange Scheme (MOSES) and the Community Atmosphere Biosphere Land Exchange (CABLE) model are described and compared. The impact on the simulated present day land surface climatology is assessed, in both atmosphere only and coupled model cases. Analysis is focused on seasonal mean precipitation and screen-level temperature, both globally and for Australia. Many of the biases from observations are common across both ACCESS versions and both atmosphere only and coupled cases. Where the simulations from the two versions differ, the choice of land surface model is often only a small contributor with changes to the cloud simulation also important. Differences that can be traced to the land surface model include warm biases with CABLE due to underestimation of surface albedo, better timing of northern hemisphere snowmelt and smaller seasonal and diurnal temperature ranges with CABLE than MOSES. Copyright © 2013, Common wealth of Australia."
"7102718675;7202772927;7101801476;56122626400;6701845806;","The NASA-Goddard Multi-scale Modeling Framework-Land Information System: Global land/atmosphere interaction with resolved convection",2013,"10.1016/j.envsoft.2012.02.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870301611&doi=10.1016%2fj.envsoft.2012.02.023&partnerID=40&md5=f4476ff6bbffc2090d6c821398fdce33","The present generation of general circulation models (GCM) use parameterized cumulus schemes and run at hydrostatic grid resolutions. To improve the representation of cloud-scale moist processes and land-atmosphere interactions, a global, Multi-scale Modeling Framework (MMF) coupled to the Land Information System (LIS) has been developed at NASA-Goddard Space Flight Center. The MMF-LIS has three components, a finite-volume (fv) GCM (Goddard Earth Observing System Ver. 4, GEOS-4), a 2D cloud-resolving model (Goddard Cumulus Ensemble, GCE), and the LIS, representing the large-scale atmospheric circulation, cloud processes, and land surface processes, respectively. The non-hydrostatic GCE model replaces the single-column cumulus parameterization of fvGCM. The model grid is composed of an array of fvGCM gridcells each with a series of embedded GCE models. A horizontal coupling strategy, GCE ↔ fvGCM ↔ Coupler ↔ LIS, offered significant computational efficiency, with the scalability and I/O capabilities of LIS permitting land-atmosphere interactions at cloud-scale. Global simulations of 2007-2008 and comparisons to observations and reanalysis products were conducted. Using two different versions of the same land surface model but the same initial conditions, divergence in regional, synoptic-scale surface pressure patterns emerged within two weeks. The sensitivity of large-scale circulations to land surface model physics revealed significant functional value to using a scalable, multi-model land surface modeling system in global weather and climate prediction. © 2012."
"25648525300;24537421700;","Aerosol, clouds and rainfall: Inter-annual and regional variations over India",2013,"10.1007/s00382-012-1594-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875759747&doi=10.1007%2fs00382-012-1594-7&partnerID=40&md5=513070340e8e3b6800c576f3c3d39de2","Inter-annual and regional variations in aerosol and cloud characteristics, water vapor and rainfall over six homogeneous rainfall zones in India during the core monsoon month of July from 2000 to 2010, and their correlations are analyzed. Aerosol optical depth (AOD) and aerosol absorbing index (AAI) in July 2002, a drought year are higher over India when compared to normal monsoon years. The drier conditions that existed due to deficient rainfall in July 2002 could be responsible for raising more dust and smoke resulting in higher AODs over India. In addition, over India precipitation is not uniform and large-scale interruptions occur during the monsoon season. During these interruptions aerosols can build up over a region and contribute to an increase in AODs. This finding is supported by the occurrence of higher anomalies in AOD, AAI and rainfall over India in July 2002. Aerosol characteristics and rainfall exhibit large regional variations. Cloud effective radius (CER), cloud optical thickness and columnar water vapor over India are the lowest in July 2002. CER decreases as AOD and AAI increase, providing an observational evidence for the indirect effect of aerosols. Eighty percent of CER in northwest India, and 30% of CER over All India in July 2002 are <14 μm, the precipitation threshold critical cloud effective radius. Northeast India shows contrasting features of correlation among aerosols, clouds and rainfall when compared to other regions. These results will be important while examining the inter-annual variation in aerosols, cloud characteristics, rainfall and their trends. © 2012 Springer-Verlag Berlin Heidelberg."
"16639472200;7201368610;7003480967;57204252724;","Aerosol particles in the Mexican East Pacific. Part II: Numerical simulations of the impact of enhanced CCN on precipitation development",2013,"10.1016/S0187-6236(13)71073-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875547242&doi=10.1016%2fS0187-6236%2813%2971073-7&partnerID=40&md5=dfdc86c7dfa8f5ad3bcd583692c38920","A number of studies have explored the effect of anthropogenic emissions on the development and evolution of precipitation in different types of clouds; however, the magnitude of the effect is still not clear, particularly for the case of deep, mixed-phase clouds. In this study, changes in the parameterization of the autoconversion process were introduced in the Advanced Regional Prediction System (ARPS) model to further evaluate this question. The simulations were initialized with cloud droplet distributions measured from an instrumented C-130 aircraft flying 600-800 km offshore in the intertropical convergence zone during the East Pacific Investigations of Climate (EPIC) project. Two contrasting cases were selected, one with and the other without the influence of anthropogenic aerosols. The simulations indicate that the increased cloud condensation nuclei (CCN) concentrations lead to a delay in the formation of rain and to a decrease in precipitation that reaches the surface as a result of the inhibition of the autoconversion of cloud water to rain water and the subsequent delay in the formation of hail. In addition, hail forms at higher levels in the cloud for the case of anthropogenic CCN. The most important process in the production of rain water in both cases is the melting of hail. A decrease in the mass of hail that falls below the freezing level in the polluted case, leads to a decrease in the resulting precipitation at the surface. Changes in the initial concentration of CCN do not appear to influence the storm strength in terms of updrafts and cloud top height, suggesting little sensitivity of the cloud dynamics. A control case simulation using the old microphysics scheme produces much more precipitation than either of the clean and polluted cases. In addition, the clean case with the modified parameterization shows a better agreement to observations than the control case. It is suggested to use the new scheme to simulate deep convective development over tropical maritime regions."
"7003440089;53871913200;38361063500;57210222492;6603925178;16313387500;","Transport of Snow by the Wind: A Comparison Between Observations in Adélie Land, Antarctica, and Simulations Made with the Regional Climate Model MAR",2013,"10.1007/s10546-012-9764-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870812407&doi=10.1007%2fs10546-012-9764-z&partnerID=40&md5=1e4e674e4ee29483bd2a4063d28fd30b","For the first time a simulation of blowing snow events was validated in detail using one-month long observations (January 2010) made in Adélie Land, Antarctica. A regional climate model featuring a coupled atmosphere/blowing snow/snowpack model is forced laterally by meteorological re-analyses. The vertical grid spacing was 2 m from 2 to 20 m above the surface and the horizontal grid spacing was 5 km. The simulation was validated by comparing the occurrence of blowing snow events and other meteorological parameters at two automatic weather stations. The Nash test allowed us to compute efficiencies of the simulation. The regional climate model simulated the observed wind speed with a positive efficiency (0. 69). Wind speeds higher than 12 m s-1 were underestimated. Positive efficiency of the simulated wind speed was a prerequisite for validating the blowing snow model. Temperatures were simulated with a slightly negative efficiency (-0.16) due to overestimation of the amplitude of the diurnal cycle during one week, probably because the cloud cover was underestimated at that location during the period concerned. Snowfall events were correctly simulated by our model, as confirmed by field reports. Because observations suggested that our instrument (an acoustic sounder) tends to overestimate the blowing snow flux, data were not sufficiently accurate to allow the complete validation of snow drift values. However, the simulation of blowing snow occurrence was in good agreement with the observations made during the first 20 days of January 2010, despite the fact that the blowing snow flux may be underestimated by the regional climate model during pure blowing snow events. We found that blowing snow occurs in Adélie Land only when the 30-min wind speed value at 2 m a.g.l. is &gt;10 m s-1. The validation for the last 10 days of January 2010 was less satisfactory because of complications introduced by surface melting and refreezing. © 2012 Springer Science+Business Media B.V."
"37104438900;57204253860;7005877775;","Radiative heating of the ISCCP upper level cloud regimes and its impact on the large-scale tropical circulation",2013,"10.1002/jgrd.50114","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884237543&doi=10.1002%2fjgrd.50114&partnerID=40&md5=e8a21dd2ce175104475b7a2035a05a31","Radiative heating profiles of the International Satellite Cloud Climatology Project (ISCCP) cloud regimes (or weather states) were estimated by matching ISCCP observations with radiative properties derived from cloud radar and lidar measurements from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) sites at Manus, Papua New Guinea, and Darwin, Australia. Focus was placed on the ISCCP cloud regimes containing the majority of upper level clouds in the tropics, i.e., mesoscale convective systems (MCSs), deep cumulonimbus with cirrus, mixed shallow and deep convection, and thin cirrus. At upper levels, these regimes have average maximum cloud occurrences ranging from 30% to 55% near 12 km with variations depending on the location and cloud regime. The resulting radiative heating profiles have maxima of approximately 1 K/day near 12 km, with equal heating contributions from the longwave and shortwave components. Upper level minima occur near 15 km, with the MCS regime showing the strongest cooling of 0.2 K/day and the thin cirrus showing no cooling. The gradient of upper level heating ranges from 0.2 to 0.4 K/(daykm), with the most convectively active regimes (i.e., MCSs and deep cumulonimbus with cirrus) having the largest gradient. When the above heating profiles were applied to the 25-year ISCCP data set, the tropics-wide average profile has a radiative heating maximum of 0.45Kday-1 near 250 hPa. Column-integrated radiative heating of upper level cloud accounts for about 20% of the latent heating estimated by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The ISCCP radiative heating of tropical upper level cloud only slightly modifies the response of an idealized primitive equation model forced with the tropics-wide TRMM PR latent heating, which suggests that the impact of upper level cloud is more important to large-scale tropical circulation variations because of convective feedbacks rather than direct forcing by the cloud radiative heating profiles. However, the height of the radiative heating maxima and gradient of the heating profiles are important to determine the sign and patterns of the horizontal circulation anomaly driven by radiative heating at upper levels. © 2012. American Geophysical Union."
"7003679645;7007107813;6603809220;","A skill score based evaluation of simulated Australian climate",2013,"10.22499/2.6301.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882423721&doi=10.22499%2f2.6301.011&partnerID=40&md5=91b8b11e42552fcef1f8322b13ecb755","The three Australian submissions to CMIP5, based on two versions of the ACCESS coupled climate model and the upgraded CSIRO model Mk3.6, are evaluated using skill scores for both global fields and for features of Australian climate. Global means of surface air temperature and precipitation are similar to those from observational datasets, except for a cool bias in Mk3.6. The agreement of the climatological seasonal mean fields for these and eleven other quantities, as measured by the M score, is comparable to the Australian CMIP3 models, in the case of Mk3.6, but mostly improved on by both ACCESS1.0 and ACCESS1.3. The ACCESS mean sea-level pressure and winds are notably better. An overall skill score, calculated for both global and Australian land, shows that the ACCESS models are among the best performing of 25 CMIP5 models. ACCESS1.0 improves slightly on the U.K. Met Office submissions. A suite of tests developed for the CAPTIVATE project is applied, and again ACCESS1.0 matches the U.K. Met Office reference model. ACCESS1.3 has improved cloud cover and a better link between equatorial sea surface temperatures (SSTs), using the Pacific-Indian Dipole index, and Australian rainfall. Mk3.6 has excessive variability in the SST index. In all, both versions of ACCESS are highly successful, while the ensembles of simulations of Mk3.6 make it also a very worthwhile submission to CMIP5. Copyright © 2013, Common wealth of Australia."
"7006399110;7404334532;7401548835;6506806004;16304488000;","The role of long-lived greenhouse gases as principal LW control knob that governs the global surface temperature for past and future climate change",2013,"10.3402/tellusb.v65i0.19734","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907421657&doi=10.3402%2ftellusb.v65i0.19734&partnerID=40&md5=b465aa4653be85d561037b05c3d9a008","The climate system of the Earth is endowed with a moderately strong greenhouse effect that is characterised by non-condensing greenhouse gases (GHGs) that provide the core radiative forcing. Of these, the most important is atmospheric CO2. There is a strong feedback contribution to the greenhouse effect by water vapour and clouds that is unique in the solar system, exceeding the core radiative forcing due to the non-condensing GHGs by a factor of three. The significance of the non-condensing GHGs is that once they have been injected into the atmosphere, they remain there virtually indefinitely because they do not condense and precipitate from the atmosphere, their chemical removal time ranging from decades to millennia. Water vapour and clouds have only a short lifespan, with their distribution determined by the locally prevailing meteorological conditions, subject to Clausius-Clapeyron constraint. Although solar irradiance is the ultimate energy source that powers the terrestrial greenhouse effect, there has been no discernable long-term trend in solar irradiance since precise monitoring began in the late 1970s. This leaves atmospheric CO2 as the effective control knob driving the current global warming trend. Over geological time scales, volcanoes are the principal source of atmospheric CO2, and the weathering of rocks is the principal sink, with the biosphere participating as both a source and a sink. The problem at hand is that human industrial activity is causing atmospheric CO2, to increase by 2ppm yr-1, whereas the interglacial rate has been 0.005ppm yr-1. This is a geologically unprecedented rate to turn the CO2 climate control knob. This is causing the global warming that threatens the global environment. © 2013 A. A. Lacis et al."
"55916122400;19934314300;7403745160;","Use of traditional weather/climate knowledge by farmers in the South-Western free State of South Africa: Agrometeorological learning by scientists",2013,"10.3390/atmos4040383","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891499222&doi=10.3390%2fatmos4040383&partnerID=40&md5=b29102e5367eae054fdf584967a9c0b6","The variety of natural indicators, associated with weather forecasting and climate prediction, as used by farmers in the South-Western Free State province of South Africa, is described. Most farmers in this area were not familiar with the application of weather forecasts/climate predictions for agricultural production, or with other science-based agrometeorological products. They relied almost fully on their experience and traditional knowledge for farming decision making. The indicators for traditional knowledge are demonstrated here in broad terms, relying on the stories and indications from observations and years of experience of their use by the farmers. These means of engagement with the natural environment, are skills not well understood by most scientists, but useful to the farmers. They range from the constellation of stars, animal behavior, cloud cover and type, blossoming of certain indigenous trees, appearance and disappearance of reptiles, to migration of bird species and many others. It is suggested that some short-term traditional forecasts/predictions may be successfully merged with science-based climate predictions. The traditional knowledge and its use, reported on in this paper, is what scientists learned from farmers. Berkes was right that scholars have wasted too much time and effort on a science versus traditional knowledge debate; we should reframe it instead as a science and traditional knowledge dialogue and partnership. The complications of a changing climate make this even more necessary. © 2013 by the authors; licensee MDPI, Basel, Switzerland."
"8590892500;7005961973;7005784518;","Weather research and forecasting model simulations of extended warm-season heavy precipitation episode over the US southern great plains: Data assimilation and microphysics sensitivity experiments",2013,"10.3402/tellusa.v65i0.19599","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882627297&doi=10.3402%2ftellusa.v65i0.19599&partnerID=40&md5=eeeb9454a8b89ee5ebdf043979b21c8b","This study examines eight microphysics schemes (Lin, WSM5, Eta, WSM6, Goddard, Thompson, WDM5, WDM6) in the Advanced Research Weather Research and Forecasting Model (WRF-ARW) for their reproduction of observed strong convection over the US Southern Great Plains (SGP) for three heavy precipitation events of 27-31 May 2001. It also assesses how observational analysis nudging (OBNUD), threedimensional (3DVAR) and four-dimensional variational (4DVAR) data assimilation (DA) affect simulated cloud properties relative to simulations with no DA (CNTRL). Primary evaluation data were cloud radar reflectivity measurements by the millimetre cloud radar (MMCR) at the Central Facility (CF) of the SGP site of the ARM Climate Research Facility (ACRF). All WRF-ARW microphysics simulations reproduce the intensity and vertical structure of the first two major MMCR-observed storms, although the first simulated storm initiates a few hours earlier than observed. Of three organised convective events, the model best identifies the timing and vertical structure of the second storm more than 50 hours into the simulation. For this wellsimulated cloud structure, simulated reflectivities are close to the observed counterparts in the mid- and upper troposphere, and only overestimate observed cloud radar reflectivity in the lower troposphere by less than 10 dBZ. Based on relative measures of skill, no single microphysics scheme excels in all aspects, although the WDM schemes show much-improved frequency bias scores (FBSs) in the lower troposphere for a range of reflectivity thresholds. The WDM6 scheme has improved FBSs and high simulated-observed reflectivity correlations in the lower troposphere, likely due to its large production of liquid water immediately below the melting level. Of all the DA experiments, 3DVAR has the lowest mean errors (MEs) and root mean-squared errors (RMSEs), although both the 3DVAR and 4DVAR simulations reduced noticeably the MEs for seven of eight microphysics schemes relative to CNTRL. Lower-tropospheric θ<inf>e</inf> and convective available potential energy (CAPE) also are closer to the observations for the 4DVAR than CNTRL simulations. © 2013 Z. T. Segele et al."
"6507861017;7006735547;7006797602;","Summertime climate response to mountain pine beetle disturbance in British Columbia",2013,"10.1038/ngeo1642","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871576962&doi=10.1038%2fngeo1642&partnerID=40&md5=991d2a9830104113aa86d9286d72e3ee","The present mountain pine beetle infestation in forests in British Columbia ranks among the largest ecological disturbances recorded in Canada so far. These recent outbreaks are thought to have been favoured by large-scale climatic shifts, and may foreshadow outbreaks of a similar magnitude in North American forests over the coming decades. The associated forest dieback could result in substantial shifts in evapotranspiration and albedo, thereby altering the local surface energy balance, and in turn regional temperature and climate. Here we quantify the impact of the Canadian pine beetle disturbance on the local summertime surface energy budget, using measurements of evapotranspiration, albedo and surface temperature, obtained primarily through remote sensing. We show that over the 170,000 km 2 of affected forest, the typical decrease in summertime evapotranspiration is 19%. Changes to the absorbed short-wave flux are negligible, in comparison. As a result, outgoing sensible and radiative heat fluxes increased by 8% and 1%, respectively, corresponding to a typical increase in surface temperature of 1C. These changes are comparable to those observed for other types of disturbance, such as wildfire, and may have secondary consequences for climate, including modifications to circulation, cloud cover and precipitation. © 2013 Macmillan Publishers Limited. All rights reserved."
"35746376000;7006754493;26643193500;","Oxygen and carbon stable isotopes in coast redwood tree rings respond to spring and summer climate signals",2013,"10.1002/jgrg.20111","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892908794&doi=10.1002%2fjgrg.20111&partnerID=40&md5=911a0ec82cbab2dea7bacd6927392eef","Interannual variability in the oxygen and carbon isotope composition of tree ring cellulose was investigated in coast redwood (Sequoia sempervirens) from three sites in coastal Northern California. Middle and late wood samples from annual tree rings were compared to regional climate indices and gridded ocean-atmosphere fields for the years 1952-2003. The strongest climate-isotope relationship (r = 0.72) was found with summer (June-September) daily maximum temperature and middle wood δ13, which also responds positively to coastal sea surface temperature and negatively to summer low cloud frequency. Late wood δ18O reflects a balance between 18O-enriched summer fog drip and depleted summer rainwater, while a combined analysis of late wood δ18O and δ13C revealed sensitivity to the sign of summer precipitation anomalies. Empirical orthogonal function analysis of regional summer climate indices and coast redwood stable isotopes identified multivariate isotopic responses to summer fog and drought that correspond to atmospheric circulation anomalies over the NE Pacific and NW U.S. The presence of regional climate signals in coast redwood stable isotope composition, consistent with known mechanistic processes and prior studies, offers the potential for high-resolution paleoclimate reconstructions of the California current system from this long-lived tree species. ©2013. American Geophysical Union. All Rights Reserved."
"7004215973;15318942300;55557622700;14035386400;6603859477;7004938676;","Interactions of mineral dust with pollution and clouds: An individual-particle TEM study of atmospheric aerosol from Saudi Arabia",2013,"10.1016/j.atmosres.2012.12.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872423198&doi=10.1016%2fj.atmosres.2012.12.001&partnerID=40&md5=71c052e5b52b9674633fa2d8a8d76b73","Aerosol particles from desert dust interact with clouds and influence climate on regional and global scales. The Riyadh (Saudi Arabia) aerosol campaign was initiated to study the effects of dust particles on cloud droplet nucleation and cloud properties. Here we report the results of individual-particle studies of samples that were collected from an aircraft in April 2007. We used analytical transmission electron microscopy, including energy-dispersive X-ray spectrometry, electron diffraction, and imaging techniques for the morphological, chemical, and structural characterization of the particles.Dust storms and regional background conditions were encountered during four days of sampling. Under dusty conditions, the coarse (supermicrometer) fraction resembles freshly crushed rock. The particles are almost exclusively mineral dust grains and include common rock-forming minerals, among which clay minerals, particularly smectites, are most abundant. Unaltered calcite grains also occur, indicating no significant atmospheric processing. The particles have no visible coatings but some contain traces of sulfur. The fine (submicrometer) fraction is dominated by particles of anthropogenic origin, primarily ammonium sulfate (with variable organic coating and some with soot inclusions) and combustion-derived particles (mostly soot). In addition, submicrometer, iron-bearing clay particles also occur, many of which are internally mixed with ammonium sulfate, soot, or both. We studied the relationships between the properties of the aerosol and the droplet microphysics of cumulus clouds that formed above the aerosol layer. Under dusty conditions, when a large concentration of coarse-fraction mineral particles was in the aerosol, cloud drop concentrations were lower and droplet diameters larger than under regional background conditions, when the aerosol was dominated by submicrometer sulfate particles. © 2012 Elsevier B.V."
"55871190900;56000906600;6602381281;","Relationship between solar radiation and dimethylsulfide concentrations using in situ data for the pristine region of the southern hemisphere",2013,"10.1016/S0016-7169(13)71481-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884966575&doi=10.1016%2fS0016-7169%2813%2971481-8&partnerID=40&md5=067409dde5e89b282c9b76e1143f93b4","The biological processes have been proposed as climate variability contributors. Dimethylsulfide (DMS) is the main biogenic sulfur compound in the atmosphere; it is mainly produced by the marine biosphere and plays an important role in the atmospheric sulfur cycle. Currently it is accepted that terrestrial biota not only adapts to environmental conditions but also influences them through regulations of the chemical composition of the atmosphere. In the present study we used a wavelet method to investigate the relationship between DMS, Low cloud cover (LCC), Ultraviolet Radiation A (UVA), Total Solar Irradiance (TSI) and Sea Surface Temperature (SST) in the so called pristine zone of the Southern Hemisphere. We found that the series analyzed have different periodicities which can be associated with large scale climatic phenomena such as El Niño (ENSO) or the Quasi-Biennial Oscillation (QBO), and/or to solar activity. Our results show an intermittent but sustained DMS-SST correlation and a DMS-UVA anti correlation; but DMS-TSI and DMS-LCC show nonlinear relationships. The time-span of the series allow us to study only periodicities shorter than 11 years, then we limit our analysis to the possibility that solar radiation influences the Earth climate in periods shorter than the 11-year solar cycle. Our results also suggest a positive feedback interaction between DMS and solar radiation."
"57217999869;7007014370;","Surface tension of solutions containing dicarboxylic acids with ammonium sulfate, d-glucose, or humic acid",2013,"10.1016/j.jaerosci.2013.06.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880390965&doi=10.1016%2fj.jaerosci.2013.06.004&partnerID=40&md5=f2277435ecd44bbd433e2aa62b39a56d","To examine the effect of organic/inorganic solutes on the properties of cloud condensation nuclei and other atmospheric aerosols, the surface tension of various mixtures including dicarboxylic acids, ammonium sulfate, d-glucose, and humic acid sodium salt (NaHA) was measured at 20. °C using the Wilhelmy plate method. An equimolar mixture of oxalic/malonic acids (0-0.5. mol/kg water) was added to ammonium sulfate (0.1-3. mol/kg water), d-glucose (0.01-2. mol/kg water), and NaHA (0.1-10. g/kg water) solutions. The surface tensions of ammonium sulfate, d-glucose, and NaHA solutions decreased as the concentration of the added oxalic/malonic acid mixture increased. The trend in surface tension for the ammonium sulfate solution is roughly similar with and without the addition of the oxalic/malonic acid mixture. However, the surface tension trend for the d-glucose and NaHA solutions with the oxalic/malonic acid mixtures does not follow that of pure d-glucose and NaHA solutions. With the presence of oxalic/malonic acids in the solution, the surface tension increase by d-glucose becomes larger and the surface tension reduction by NaHA becomes smaller. © 2013 Elsevier Ltd."
"37022019200;55159691800;20935741900;","Climate change vulnerability assessments as catalysts for social learning: Four case studies in south-eastern Australia",2013,"10.1007/s11027-012-9376-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876945675&doi=10.1007%2fs11027-012-9376-4&partnerID=40&md5=3335853d7374f659f72ff8f155d9ff56","Technical assessments of vulnerability and/or risk are increasingly being undertaken to assess the impacts of climate change. Underlying this is the belief that they will bring clarity to questions regarding the scale of institutional investments required, plausible adaptation policies and measures, and the timing of their implementation. Despite the perceived importance of technical assessments in 'evidence-based' decision environments, assessments cannot be undertaken independent of values and politics, nor are they capable of eliminating the uncertainty that clouds decision-making on climate adaptation As such, assessments can trigger as many questions as they answer, leaving practitioners and stakeholders to question their value. This paper explores the value of vulnerability/risk assessments in climate change adaptation planning processes as a catalyst for learning in four case studies in Southeastern Australia. Data were collected using qualitative interviews with stakeholders involved in the assessments and analysed using a social learning framework. This analysis revealed that detailed and tangible strategies or actions often do not emerge directly from technical assessments. However, it also revealed that the assessments became important platforms for social learning. In providing these platforms, assessments present opportunities to question initial assumptions, explore multiple framings of an issue, generate new information, and galvanise support for collective actions. This study highlights the need for more explicit recognition and understanding of the important role social learning plays in climate change vulnerability assessments and adaptation planning more broadly. © 2012 Springer Science+Business Media B.V."
"55716995500;35209683700;26324818700;8855923200;15756666000;","A dissection of the surface temperature biases in the Community Earth System Model",2013,"10.1007/s00382-013-2029-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890963157&doi=10.1007%2fs00382-013-2029-9&partnerID=40&md5=4a6516cec2af180ab0fdf2cdda249530","Based upon the climate feedback-responses analysis method, a quantitative attribution analysis is conducted for the annual-mean surface temperature biases in the Community Earth System Model version 1 (CESM1). Surface temperature biases are decomposed into partial temperature biases associated with model biases in albedo, water vapor, cloud, sensible/latent heat flux, surface dynamics, and atmospheric dynamics. A globally-averaged cold bias of −1.22 K in CESM1 is largely attributable to albedo bias that accounts for approximately −0.80 K. Over land, albedo bias contributes −1.20 K to the averaged cold bias of −1.45 K. The cold bias over ocean, on the other hand, results from multiple factors including albedo, cloud, oceanic dynamics, and atmospheric dynamics. Bias in the model representation of oceanic dynamics is the primary cause of cold (warm) biases in the Northern (Southern) Hemisphere oceans while surface latent heat flux over oceans always acts to compensate for the overall temperature biases. Albedo bias resulted from the model’s simulation of snow cover and sea ice is the main contributor to temperature biases over high-latitude lands and the Arctic and Antarctic region. Longwave effect of water vapor is responsible for an overall warm (cold) bias in the subtropics (tropics) due to an overestimate (underestimate) of specific humidity in the region. Cloud forcing of temperature biases exhibits large regional variations and the model bias in the simulated ocean mixed layer depth is a key contributor to the partial sea surface temperature biases associated with oceanic dynamics. On a global scale, biases in the model representation of radiative processes account more for surface temperature biases compared to non-radiative, dynamical processes. © 2013, Springer-Verlag Berlin Heidelberg."
"54408544700;","Climate impact mitigation potential given by flight profile and aircraft optimization",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904473559&partnerID=40&md5=14cbcbcceca591cb46a08ff9d94fc23f","Air traffic has an impact on the radiation balance and resulting temperature change of the Earth-atmosphere system through the emission of gases and particles that alter the concentration of atmospheric Greenhouse gases and trigger the formation of contrails and cirrus clouds. Studies estimate that aviation accounted until 2005 for approx. 5% of the total anthropogenic radiative forcing. Considering the projected air traffic growth for the next decades of 5% (RPK) per year, the climate impact from aviation will further increase. The atmospheric perturbations provoked from the emission of CO 2, NOx, H2O, soot and sulfate aerosols as well as through the formation of contrails and contrail-cirrus clouds act on very different temporal and spatial scales. The resulting climate impact differs per emitted compound as function of altitude, geographic position, daytime and season, local atmospheric sensitivities and other parameters of the Earth-atmosphere system. This increases the complexity of any mitigation effort but also offers chances for mitigation beyond the sole reduction of emissions, e.g. through climate optimized flight profiles. However, the cost-efficient optimization of air traffic towards reduced climate impact requires an interdisciplinary approach that includes models and expertise from atmospheric physics, aircraft design and performance, aircraft operations, air traffic management and airline economics. The present thesis therefore develops a comprehensive simulation workflow with detailed models that consider the driving effects in the involved disciplines. It enables the assessment of current and future aircraft with novel technologies that are operated on a global route network. It further allows the assessment of operational mitigation strategies with the variation of vertical and lateral flight profiles for each defined route and aircraft model. Each route in the network can be optimized individually for economic and environmental goals. The simulation workflow is applied in the present thesis to analyze the climate impact mitigation potential and related costs resulting from the combined optimization of flight profile and aircraft design changes. The assessment includes the world fleets of a current representative long-range aircraft and a novel climate-optimized aircraft configuration that are operated on a global route network. For each route, numerous combinations of cruise altitude and speed are computed for both aircraft. The resulting 4D flight trajectories are evaluated with respect to the resulting average temperature response (ATR) and cash operating costs (COC). Based on this, the Pareto optimal cruise conditions that maximize the cost-benefit ratio of climate impact reduction vs. cost penalty are derived for each route and aircraft type. The route-specific mitigation potentials and costs are summed for the entire route network and expressed relative to a realistic traffic scenario and flight profiles from Eurocontrol data. Based on the conducted assessment, the present study identifies a considerable potential to reduce the climate impact of aviation at small to moderate cost penalties. It is for example possible to reduce the fleet average temperature response with the reference aircraft by 41.8% for a 10% increase in cash operating cost through average 30% lower cruise alti-tudes and 8% lower speeds. The analysis of the reference aircraft further shows increasing performance losses and related fuel burn penalties due to off-design effects at lower cruise altitudes and speeds. To counter these inefficiencies, a novel aircraft configuration is developed based on the optimization of the reference aircraft for flight profiles with reduced climate impact. As result, the optimized aircraft exhibits a fuel burn improvement of 10-13% compared to the reference aircraft at identical operating conditions. The reduced fuel burn leads to lower operating costs and the reduced amount of emission to lower climate impact. The superposition of both effects considerably increases the mitigation potential and enables the redesigned aircraft to reduce the climate impact by 53.5% for 10% increase of cash operating costs relative to current air traffic. It is also possible to reduce the climate impact by 32.3% without increase of cash operating costs. On the other hand, the lower cruise altitudes and speeds analyzed in the present study are likely to provoke impacts on airline flight schedule, fleet size and economics, passenger acceptance as well as ATM and airport capacity constraints that might limit or decrease the identified climate impact mitigation potential. The present thesis thus concludes with a qualitative discussion of system effects and their impact on the analyzed mitigation concept from an ATS stakeholder perspective."
"55523241000;55851948174;55470270800;7401527632;","Spatial and temporal variability in maximum, minimum and mean air temperatures at Madhya Pradesh in central India",2013,"10.1016/j.crte.2012.10.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873992883&doi=10.1016%2fj.crte.2012.10.016&partnerID=40&md5=05e792a13c2e39e4ad67463902162d13","In the present study, an investigation has been made to study the spatial and temporal variability in the maximum, the minimum and the mean air temperatures at Madhya Pradesh (MP), in central India on monthly, annual and seasonal time scale from 1901 to 2002. Further, impact of urbanization and cloud cover on air temperature has been studied. The annual mean, maximum and minimum temperatures are increased by 0.60, 0.60 and 0.62. °C over the past 102 years, respectively. Seasonally, the warming is more pronounced during winter than summer. The temperature decreased during the less urbanized period (from 1901 to 1951) and increased during the more urbanized period (1961 to 2001). It is also found that the minimum temperature increased at higher rate (0.42. °C) followed by the mean (0.36. °C) and the maximum (0.32. °C) temperature during the more urbanized period. Furthermore, cloud cover is significantly negatively related with air temperature in monsoon season and as a whole of the year. © 2012 Académie des sciences."
"55823844500;7201906181;7003371185;57195452780;","Validation of the MODIS reflectance product under UK conditions",2013,"10.1080/01431161.2013.820363","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881636525&doi=10.1080%2f01431161.2013.820363&partnerID=40&md5=16b336b87396e8e377a0d3b6adb942e8","Surface reflectance obtained from remote-sensing data is the main input to almost all remote-sensing applications. The availability and special characteristics of Moderate Resolution Imaging Spectroradiometer (MODIS) products have led to their use worldwide. Validation of the MODIS reflectance product is then crucial to provid information on uncertainty in the reflectance data, and in other MODIS products and in the applied surface-atmosphere models. Compact Airborne Spectrographic Imager (CASI) and Système Pour l'Observation de la Terre (SPOT) data, collected during the Network for Calibration and Validation in Earth Observation (NCAVEO) 2006 Field Campaign, were applied to validate daily MODIS reflectance data over a site in the southern UK. The difference in the view geometry of at-nadir CASI and SPOT data and off-nadir MODIS data was dealt with using a semi-empirical bidirectional reflectance distribution function (BRDF) model. The validation results showed that for our particular study site, the absolute errors in the MODIS reflectance product were too large to allow the albedo data to be used directly in climate models. The errors were mainly related to the uncertainties in the MODIS atmospheric variables, the BRDF model, and undetected clouds and cloud shadows. More generally, the study highlights the extreme difficulty of achieving pixel-level validation of coarse spatial resolution satellite sensor data in an environment in which the atmosphere is constantly changing, and in which the landscape is characterized by high space-time heterogeneity. © 2013 Copyright 2013 Taylor & Francis."
"57190731566;7102700868;57213396721;7406294260;","An improved parametric model for simulating cloudy sky daily direct solar radiation on tilted surfaces",2013,"10.1109/JSTARS.2012.2211000","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897112923&doi=10.1109%2fJSTARS.2012.2211000&partnerID=40&md5=be19a9c352a670e251188c3e35f286b7","Incoming solar radiation absorbed by the Earth's surface is important for simulation models in addressing issues of ecosystem dynamics and climate change. The objective of this study was to simulate the daily direct solar radiation on tilted surfaces under cloudy sky conditions using an improved parametric model that integrates the atmospheric attenuation with the correction of three dimensional effects of cloud shadow and topographic factors. The model is validated by implementing four comparative case studies (Lhasa, Beijing, Kunming and Erjinaqi) based on the daily atmospheric products of MODIS TERRA/AQUA and SRTM DEM. The results show that the proposed parametric model is convincingly efficient, as the computed coefficients of determination (R ) are relatively high for all stations except Lhasa (0.62 for Lhasa, 0.70 for Kunming, 0.70 for Beijing and 0.78 for Erjinaqi), and the RMSE (root mean square error) are 4.89 MJ/m for Lhasa, 4.09 MJ/m for Kunming, 4.02 MJ/m for Beijing and 3.79 MJ/m for Erjinaqi. A possible explanation is that the complex terrain accounts for the greater attenuation of solar radiation at Lhasa, while in our study, the data are retrieved at a spatial resolution of 1 km and the detailed terrain can not be clearly represented. The proposed model also indicates that clouds are the primary contributors to the amount and spatiotemporal distribution of solar radiation. The accuracy of the developed model is largely dependent on the temporal resolution of the data sources, especially the cloud optical thickness data. Meanwhile, the model reveals that topography and the spatial resolution of the DEM are important factors that affect the model results on tilted surfaces. © 2012 IEEE."
"7006241374;7101754471;","IPCC underestimates the Sun's role in climate change",2013,"10.5169/seals-391146","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019761126&doi=10.5169%2fseals-391146&partnerID=40&md5=8f977742e77ee93e8e51f0f167789c1b","For the understanding of current and future chinate change it is a basic pre requisite to properly understand the mechanisms, which controlled climate change after the Last Ice Age. According to the IPCC 5lh assessment report the Sun has not been a major driver of climate change during the Post-Little Ice Age slow warming, and particularly n°t during the last 40 years. This statement requires critical review as the IPCC neglects strong Paleo-climatologic evidence for the high sensitivity of the climate system to changes in solar activity. This high climate sensitivity is not alone due to variations in total solar irradiance-related direct solar forcing, but also due to additional, so-called indirect solar forcings. These include solar-related chemical-based UV irradiance-related variations in stratospheric temperatures and galactic cosmic ray-related changes in cloud cover and surface temperatures, as well as ocean oscillations, such as the Pacific Decadal Oscillation and the North Atlantic Oscillation that significant affect the clizie. As it is still difficult to quantify the relative contribution of combined direct and indirect solar forcing and of increased atmospheric CO2concen trations to the slow warming of the last 40 years, Predictions about future global warming based delusively on anthropogenic CO2emission scenarios are premature. Nevertheless, the cyclical temperature increase of the 20th century coincided with 'he buildup and culmination of the Grand Solar Maximum that commenced in 1924 and ended in 2008. The anticipated phase of declining solar activity of the coming decades will be a welcome ""natural laboratory"" to clarify and quantify the Present and future role of solar variation in climate change."
"7003279098;7103386012;6603809220;6701751927;","Global simulations of the impact on contemporary climate of a perturbation to the sea-to-air flux of dimethylsulfide",2013,"10.22499/2.6303.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895558665&doi=10.22499%2f2.6303.002&partnerID=40&md5=933780d7958ab31d9c1f9a18b11e1d90","The sea-to-air flux of the biogenic sulfur (S) compound dimethylsulfide (DMS) is thought to constitute an important radiative impact on climate, especially in remote marine areas. Previous biogeochemical modelling analyses simulate medium to large changes in the sea-to-air flux of DMS in polar regions under warming scenarios. Here we assess the global radiative impact of such a prescribed change in DMS flux on contemporary climate using a low-resolution atmospheric general circulation model. This impact operates through the atmospheric oxidation of DMS to radiatively-active sulfate aerosols, which are known to both reflect incoming short-wave radiation and to affect the microphysical properties of clouds, for example, through an increase in cloud albedo. We use an atmospheric GCM with incorporated sulfur cycle, coupled to a mixed-layer ('q-flux') ocean, to estimate the climatic response to a prescribed meridionally-variable change in zonal DMS flux, as simulated in a previous modelling analysis. We compare baseline sulfur emissions (contemporary anthropogenic S and contemporary DMS sea-to-air flux), with contemporary anthropogenic S and a perturbed DMS flux. Our results indicate that the global mean DMS vertically integrated concentration increases by about 41 per cent. The relative increase in DMS annual emission is around 17 per cent in 70-80°N, although the most significant increase is in 50-70°S, up to 70 per cent. However, concentrations of atmospheric SO2 and SO4 2- increase by only about eight per cent. The oxidation of DMS by OH increases by about 20 per cent. Oxidation of SO2 to SO 42 by H2O2 increases seven per cent. The oxidation of SO2 by O3 increases around six per cent. Overall sulfur emissions increase globally by around 4.6 per cent. Global mean aerosol optical depth (AOD) increases by 3.5 per cent. Global mean surface temperature decreases by 0.6 K. There is a notable difference between the impacts in the southern and northern hemispheres. In general, most processes and chemical species related to the sulfur cycle show a larger increase in the southern hemisphere, except SO2 and the oxidation of DMS by NO 3. The global mean direct radiative forcing due to the DMS change is -0.05 Wm-2 with total forcing (direct + indirect effects) of -0.48 Wm-2. This perturbation on DMS flux leads to a mean surface temperature decrease in the southern hemisphere of around 0.8 K, compared with a decrease of 0.4 K in the northern hemisphere."
"7202970886;6603631763;","PATMOS-x: Results from a diurnally corrected 30-yr satellite cloud climatology",2013,"10.1175/JCLI-D-11-00666.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872976212&doi=10.1175%2fJCLI-D-11-00666.1&partnerID=40&md5=5511a01249012b4086e908796534643d","Satellite drift is a historical issue affecting the consistency of those few satellite records capable of being used for studies on climate time scales. Here, the authors address this issue for the Pathfinder Atmospheres Extended (PATMOS-x)/Advanced Very High Resolution Radiometer (AVHRR) cloudiness record, which spans three decades and 11 disparatesensors.Atwo-harmonic sinusoidal function is fit to a mean diurnal cycle of cloudiness derived over the course of the entire AVHRRrecord. The authors validate this function against measurements from Geostationary Operational Environmental Satellite (GOES) sensors, finding good agreement, and then test the stability of the diurnal cycle over the course ofthe AVHRR record. It is found that the diurnal cycle is subject to some interannual variability over land but that the differences are somewhat offset when averaged over an entire day. The fit function is used to generate daily averaged time series of ice, water, andtotal cloudiness over the tropics, where it is found that the diurnal correction affects the magnitude and even the sign of long-term cloudiness trends. A statistical method is applied to determine the minimum length of time required to detect significant trends, andthe authors find that only recently have they begun generating satellite records of sufficient length to detect trends in cloudiness. © 2013 American Meteorological Society."
"57201177267;34972803800;7101931045;36720575300;6603137309;","Changes in extreme daily rainfall for São Paulo, Brazil",2013,"10.1007/s10584-012-0504-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872654383&doi=10.1007%2fs10584-012-0504-7&partnerID=40&md5=aa7b62a5ecf9c79debc07b5b3a99e642","Significant positive trends are found in the evolution of daily rainfall extremes in the city of São Paulo (Brazil) from 1933 to 2010. Climatic indices including ENSO, PDO, NAO and the sea surface temperature at the coast near São Paulo explain 85 % of the increasing frequency of extremes during the dry season. During the wet season the climatic indices and the local sea surface temperature explain a smaller fraction of the total variance when compared to the dry season indicating that other factors such as the growth of the urban heat island and the role of air pollution in cloud microphysics need to be taken into account to explain the observed trends over the almost eight decades. © 2012 Springer Science+Business Media B.V."
"7404476158;7402270607;56063950500;","Potential impacts on regional climate due to land degradation in the Guizhou Karst Plateau of China",2013,"10.1088/1748-9326/8/4/044037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891947659&doi=10.1088%2f1748-9326%2f8%2f4%2f044037&partnerID=40&md5=7cc9b31386c7f1fa817f885675f258b5","The possible regional climatic effects of land condition change in the Guizhou Karst Plateau (GKP), which has experienced serious Karst Rocky Desertification (KRD) in the past decades, were investigated in this study using the Weather Research and Forecasting (WRF) regional climate model. It was shown that when compared with validation datasets, the WRF showed a high ability to downscale NCEP-DOE Reanalysis-2, which provided the initial and lateral boundary conditions for WRF, especially for the precipitation simulation. After land degradation over the GKP, the net radiation and evaporation were reduced mainly within the desertification area, consistent with the reduction in rainfall and the increase in surface temperature there. The southwest monsoon flow from the Bay of Bengal was weakened over the adjacent area to the northeast, influencing the East Asian summer monsoon. Meanwhile, the weaker low-layer anti-cyclone and the stronger horizontal convergence enhanced vertical motion in the southeastern coastal areas. Furthermore, owing to the decreased surface heating in the degradation experiment, the lifting over the GKP and neighboring regions to the east was limited, which resulted in a reduced rainfall within the GKP and strengthened the ascending motion downstream over 114°-122° E. Such circulation differences favored an increase in moisture flux and clouds, thereby causing more precipitation in coastal areas of southeast China. © 2013 IOP Publishing Ltd."
"28367935500;7201504886;7201627869;8696069500;","The observed hemispheric symmetry in reflected shortwave irradiance",2013,"10.1175/JCLI-D-12-00132.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872974209&doi=10.1175%2fJCLI-D-12-00132.1&partnerID=40&md5=5c7cdf5e7441958855cd2c7a43d62411","While the concentration of landmasses and atmospheric aerosols on the NorthernHemisphere suggests that the Northern Hemisphere is brighter than the Southern Hemisphere, satellite measurements of top-of-atmosphere irradiances found that both hemispheres reflect nearly the same amount of shortwave irradiance.Here, the authors document that the most precise and accurate observation, the energy balanced and filled dataset of the Clouds and the Earth'sRadiant Energy System covering the period 2000-10, measures an absolute hemispheric difference in reflected shortwave irradiance of 0.1 W m-2. In contrast, the longwaveirradiance of the two hemispheres differs by more than 1 W m-2. indicating that the observed climate system exhibits hemispheric symmetry in reflected shortwave irradiance but not in longwave irradiance. The authors devise a variety of methods to estimate the spatialdegrees of freedom of the time-mean reflected shortwave irradiance. These are used to show that the hemispheric symmetry in reflected shortwave irradiance isa nontrivial property of the Earth system in the sense that most partitionings of Earth into two random halves do not exhibit hemispheric symmetry in reflected shortwave irradiance. Climate models generally do not reproduce the observed hemispheric symmetry, which the authors interpret as further evidence that the symmetry is nontrivial. While the authors cannot rule out that the observed hemispheric symmetry in reflected shortwave irradiance is accidental, their results motivate a search for mechanisms that minimize hemisphericdifferences in reflected shortwave irradiance and planetary albedo. © 2013 American Meteorological Society."
"57200400501;8954866200;9242540400;35561911800;","Modeling insights into deuterium excess as an indicator of water vapor source conditions",2013,"10.1029/2012JD017804","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884880557&doi=10.1029%2f2012JD017804&partnerID=40&md5=47034c7638cd5a62d1f43dc8b36614e9","Deuterium excess (d) is interpreted in conventional paleoclimate reconstructions as a tracer of oceanic source region conditions, such as temperature, where precipitation originates. Previous studies have adopted coisotopic approaches (using both d18O and d) to estimate past changes in both site and oceanic source temperatures for ice core sites using empirical relationships derived from conceptual distillation models, particularly Mixed Cloud Isotopic Models (MCIMs). However, the relationship between d and oceanic surface conditions remains unclear in past contexts. We investigate this climate-isotope relationship for sites in Greenland and Antarctica using multiple simulations of the water isotope-enabled Goddard Institute for Space Studies ModelE-R general circulation model and apply a novel suite of model vapor source distribution (VSD) tracers to assess d as a proxy for source temperature variability under a range of climatic conditions. Simulated average source temperatures determined by the VSDs are compared to synthetic source temperature estimates calculated using MCIM equations linking d to source region conditions. We show that although deuterium excess is generally a faithful tracer of source temperatures as estimated by the MCIM approach, large discrepancies in the isotope-climate relationship occur around Greenland during the Last Glacial Maximum simulation, when precipitation seasonality and moisture source regions were notably different from the present. This identified sensitivity in d as a source temperature proxy suggests that quantitative climate reconstructions from deuterium excess should be treated with caution for some sites when boundary conditions are significantly different from the present day. Also, the exclusion of the influence of humidity and other evaporative source changes inMCIMregressions may be a limitation of quantifying source temperature fluctuations from deuterium excess in some instances. © 2012. American Geophysical Union."
"6602504047;55334544700;12645700600;6603433697;6701735773;6602137606;6507495053;6505465237;","Combined influence of atmospheric physics and soil hydrology on the simulated meteorology at the SIRTA atmospheric observatory",2013,"10.1007/s00382-012-1469-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876836103&doi=10.1007%2fs00382-012-1469-y&partnerID=40&md5=74a3af56c48c1cad496934df20d99c93","The identification of the land-atmosphere interactions as one of the key source of uncertainty in climate models calls for process-level assessment of the coupled atmosphere/land continental surface system in numerical climate models. To this end, we propose a novel approach and apply it to evaluate the standard and new parametrizations of boundary layer/convection/clouds in the Earth System Model (ESM) of Institut Pierre Simon Laplace (IPSL), which differentiate the IPSL-CM5A and IPSL-CM5B climate change simulations produced for the Coupled Model Inter-comparison Project phase 5 exercise. Two different land surface hydrology parametrizations are also considered to analyze different land-atmosphere interactions. Ten-year simulations of the coupled land surface/atmospheric ESM modules are confronted to observations collected at the SIRTA (Site Instrumental de Recherche par Télédection Atmosphérique), located near Paris (France). For sounder evaluation of the physical parametrizations, the grid of the model is stretched and refined in the vicinity of the SIRTA, and the large scale component of the modeled circulation is adjusted toward ERA-Interim reanalysis outside of the zoomed area. This allows us to detect situations where the parametrizations do not perform satisfactorily and can affect climate simulations at the regional/continental scale, including in full 3D coupled runs. In particular, we show how the biases in near surface state variables simulated by the ESM are explained by (1) the sensible/latent heat partitionning at the surface, (2) the low level cloudiness and its radiative impact at the surface, (3) the parametrization of turbulent transport in the surface layer, (4) the complex interplay between these processes. We also show how the new set of parametrizations can improve these biases. © 2012 Springer-Verlag."
"57197944382;57214957750;8917907300;","Characterization of Halyomorpha halys (brown marmorated stink bug) biogenic volatile organic compound emissions and their role in secondary organic aerosol formation",2013,"10.1080/10962247.2013.819047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885939511&doi=10.1080%2f10962247.2013.819047&partnerID=40&md5=712a433e9402f6131f4de9733c0ee0ea","The formation of aerosols is a key component in understanding cloud formation in the context of radiative forcings and global climate modeling. Biogenic volatile organic compounds (BVOCs) are a significant source of aerosols, yet there is still much to be learned about their structures, sources, and interactions. The aims of this project were to identify the BVOCs found in the defense chemicals of the brown marmorated stink bug Halymorpha halys and quantify them using gas chromatography-mass spectrometry (GC/MS) and test whether oxidation of these compounds by ozone-promoted aerosol and cloud seed formation. The bugs were tested under two conditions: agitation by asphyxiation and direct glandular exposure. Tridecane, 2(5H)-furanone 5-ethyl, and (E)-2-decenal were identified as the three most abundant compounds. H. halys were also tested in the agitated condition in a smog chamber. It was found that in the presence of 100-180 ppm ozone, secondary aerosols do form. A scanning mobility particle sizer (SMPS) and a cloud condensation nuclei counter (CCNC) were used to characterize the secondary aerosols that formed. This reaction resulted in 0.23 μg/bug of particulate mass. It was also found that these secondary organic aerosol particles could act as cloud condensation nuclei. At a supersaturation of 1%, we found a kappa value of 0.09. Once regional populations of these stink bugs stablilize and the populations estimates can be made, the additional impacts of their contribution to regional air quality can be calculated. Halymorpha halys (brown marmorated stink bugs) are a relatively new invasive species introduced in the United States near Allentown, Pennsylvania. The authors chemically speciated the bugs' defense pheromones and found that tridecane, 5-ethyl-2(5H)-furanone, and (E)-2-decenal dominated their emissions. Their defense emissions were reacted with atmospherically relevant concentrations of ozone and resulted in 0.23 μg of particulate matter per emission per bug. Due to the large population of these bugs in some regions, these emissions could contribute appreciably to a region's PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) levels. © 2013 Copyright 2013 A&amp;WMA."
"7003336749;12241043000;8259996100;6506321882;54795557700;55801346600;36091220000;","Is hail suppression useful in Serbia? - General review and new results",2013,"10.3986/AGS53302","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880587437&doi=10.3986%2fAGS53302&partnerID=40&md5=3d7f0ac061aa93cd8877f032ef110eca","Anthropogenic influence on weather has been increasingly published and discussed in the last decades. Climate changes caused by inadvertent anthropogenic influence are well underway. Hail suppression, which has been proven to have no influence on weather, will be considered in the article. Even though hail suppression as scientifically ungrounded activity seemed to promise certain success several decades ago, it has spread over the whole territory of the Republic of Serbia after abundant experience, when many developed countries have given up on this activity. Reasons will be presented for the senselessness of hail suppression based on the latest research. By processing all hail data from the territory of Serbia in the period from 1967 to 2010, it was found out that the hail trend is rising which is in contrary to expectations and previous claims that hail suppression decreases hail frequency."
"57210337677;15048845800;7005884117;35620654900;35756335100;","Validation of MODIS, MISR, OMI, and CALIPSO aerosol optical thickness using ground-based sunphotometers in Hong Kong",2013,"10.1080/01431161.2012.720739","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867240376&doi=10.1080%2f01431161.2012.720739&partnerID=40&md5=321ea4df1b9f17dc6687c199da28568c","Aerosol observations are essential for understanding the Earth's radiation budget and the complexities of climate change, as they are involved in the backscattering of solar radiation and the formation of cloud condensation nuclei. In Hong Kong, the most direct effect is on air quality. Atmospheric haze caused by the emission of aerosols from industrial and vehicular sources creates visibility lower than 8 km for approximately 20% of the time, having risen at 6% per decade since 1980, but regional emissions are at least as influential as local ones. The 179,000 km2 covered by Hong Kong and neighbouring Guangdong Province cannot be adequately covered by the 76 monitoring stations set up by the two governments, and satellite images offer the only potential source of regional air quality data. However, the current satellite-based aerosol optical thickness (AOT) products are intended for global air quality monitoring, and may contain errors over a humid coastal city such as Hong Kong and its surrounding industrialized regions. This research compares the AOT retrieved from several AOT operational products, namely the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD04 product, the MODIS 500 m product, the Multiangle Imaging Spectroradiometer (MISR) product, the Ozone Monitoring Instrument (OMI) multiwavelength aerosol product, and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) product, with ground-based AOT from sunphotometers in Hong Kong. These sunphotometers include two AERONET stations, and are deployed in Hong Kong over urban, suburban, and coastal areas. The rigorous correlations, root mean square errors, and mean absolute differences available from the multilocational field data within one city region provide a strong base for validating the AOT products from different sensors and at different spatial scales over different land surface types. The results suggest that the AOT products, especially those from MODIS 10 km, provide reliable and accurate observations for daily air quality monitoring over a variety of land-cover types, as well as for identifying emission sources for coordinated actions by the governments of Hong Kong and the Chinese mainland. © 2013 Copyright Taylor and Francis Group, LLC."
"57202891769;8900751100;35338541500;","The role of ice cover in heavy lake-effect snowstorms over the great lakes basin as simulated by RegCM4",2013,"10.1175/MWR-D-12-00107.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874795858&doi=10.1175%2fMWR-D-12-00107.1&partnerID=40&md5=6102ee22806892b0036fcd10a5bcec34","A 20-km regional climate model, the Abdus Salam International Centre for Theoretical Physics Regional Climate Model version 4 (ICTP RegCM4), is employed to investigate heavy lake-effect snowfall (HLES) over the Great Lakes Basin and the role of ice cover in regulating these events. When coupled to a lake model and driven with atmospheric reanalysis data between 1976 and 2002, RegCM4 reproduces the major characteristics of HLES. The influence of lake ice cover on HLES is investigated through 10 case studies (2 per Great Lake), in which a simulated heavy lake-effect event is compared with a companion simulation having 100% ice cover imposed on one or all of the Great Lakes. These experiments quantify the impact of ice cover on downstream snowfall and demonstrate that Lake Superior has the strongest, most widespread influence on heavy snowfall and Lake Ontario the least. Ice cover strongly affects a wide range of atmospheric variables above and downstream of lakes during HLES, including snowfall, surface energy fluxes, wind speed, temperature, moisture, clouds, and air pressure. Averaged among the 10 events, complete ice coverage causes major reductions in lake-effect snowfall (>80%) and turbulent heat fluxes over the lakes (>90%), less low cloudiness, lower temperatures, and higher air pressure. Another important consequence is a consistent weakening (30%-40%) of lower-tropospheric winds over the lakes when completely frozen. This momentum reduction further decreases over-lake evaporation and weakens downstream wind convergence, thus mitigating lake-effect snowfall. This finding suggests a secondary, dynamical mechanism by which ice cover affects downstream snowfall duringHLES events, in addition to themorewidely recognized thermodynamic influence. © 2013 American Meteorological Society."
"48662824200;7006783796;6506234624;35498628900;26666977800;24759591600;55574305800;55575192900;","Retrieving clear-sky surface skin temperature for numerical weather prediction applications from geostationary satellite data",2013,"10.3390/rs5010342","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873134781&doi=10.3390%2frs5010342&partnerID=40&md5=1907ce0c9b51671d1284bfb1bfd65eaa","Atmospheric models rely on high-accuracy, high-resolution initial radiometric and surface conditions for better short-term meteorological forecasts, as well as improved evaluation of global climate models. Remote sensing of the Earth's energy budget, particularly with instruments flown on geostationary satellites, allows for near-real-time evaluation of cloud and surface radiation properties. The persistence and coverage of geostationary remote sensing instruments grant the frequent retrieval of near-instantaneous quasi-global skin temperature. Among other cloud and clear-sky retrieval parameters, NASA Langley provides a non-polar, high-resolution land and ocean skin temperature dataset for atmospheric modelers by applying an inverted correlated k-distribution method to clear-pixel values of top-of-atmosphere infrared temperature. The present paper shows that this method yields clear-sky skin temperature values that are, for the most part, within 2 K of measurements from ground-site instruments, like the Southern Great Plains Atmospheric Radiation Measurement (ARM) Infrared Thermometer and the National Climatic Data Center Apogee Precision Infrared Thermocouple Sensor. The level of accuracy relative to the ARM site is comparable to that of the Moderate-resolution Imaging Spectroradiometer (MODIS) with the benefit of an increased number of daily measurements without added bias or increased error. Additionally, matched comparisons of the high-resolution skin temperature product with MODIS land surface temperature reveal a level of accuracy well within 1 K for both day and night. This confidence will help in characterizing the diurnal and seasonal biases and root-mean-square differences between the retrievals and modeled values from the NASA Goddard Earth Observing System Version 5 (GEOS-5) in preparation for assimilation of the retrievals into GEOS-5. Modelers should find the immediate availability and broad coverage of these skin temperature observations valuable, which can lead to improved forecasting and more advanced global climate models. © 2013 by the authors."
"55223809300;26643193200;57139379600;","Estimate of extended long-term LAI data set derived from AVHRR and MODIS based on the correlations between LAI and key variables of the climate system from 1982 to 2009",2013,"10.1080/01431161.2013.826840","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884486689&doi=10.1080%2f01431161.2013.826840&partnerID=40&md5=17edaae26891624115a4f993d24c54ef","The global long-term leaf area index (LAI) series is a critical variable to validate the terrestrial ecological processes of simulation by Earth system models (ESMs) and ESM input. However, the lack of long-term LAI data restricts studies on the interaction between atmosphere and biosphere. This study focuses on obtaining a robust long-term LAI data set through combining Advanced Very High Resolution Radiometer (AVHRR; available from August 1981 to May 2001) and Moderate Resolution Imaging Spectroradiometer (MODIS; available from January 2000 to December 2009) data sets, and on investigating the relationship between LAI data and the key variables of the climate system. Regional discrepancies in LAI exist between these two data sets. In high northern latitudes, there are significant differences (&gt;1.7 m2 m-2) between AVHRR- and MODIS-derived LAI during the overlapping period from January 2000 to May 2001 because of effects of vegetation structure, low saturation threshold of remote-sensing data and cloud contamination, and the effects of aerosols and atmospheric water vapour on the AVHRR sensor. Using the LAI data set derived from MODIS as the benchmark, AVHRR-derived LAI data from the same periods as those of MODIS were first calibrated through a region-based linear regression method. Then the regression relationship was employed to other periods of AVHRR-derived LAI, resulting in a complete long-term LAI data set. The results showed that the data set has a better convergence and continuity than the original data set, with the regional discrepancies in LAI significantly reduced. Further analyses of correlations between LAI and variables of the climate system demonstrate that the modified LAI is more suitable to describe the response of vegetation to variables in the climate system. This is probably attributed to temperature as the main driver affecting vegetation and to the persistent presence of frozen soil in this region. In comparison with results from previous studies, the response to temperature, precipitation, and soil moisture in the long-term modified LAI data is more reasonable than for unmodified LAI. © 2013 © 2013 The Author(s). Published by Taylor &amp; Francis."
"53463606500;7501414348;35203634700;53983376400;7401629637;","Quantitative relationships between precipitation and temperature over Northeast China, 1961-2010",2013,"10.1007/s00704-012-0815-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880840609&doi=10.1007%2fs00704-012-0815-7&partnerID=40&md5=3a584709ed415c0d9bd658eec349bcb5","This paper investigates monthly and seasonal precipitation-temperature relationships (PTRs) over Northeast China using a method proposed in this study. The PTRs are influenced by clouds, latent and sensible heat conversion, precipitation type, etc. In summer, the influences of these factors on temperature decrease are different for various altitudes, latitudes, longitudes, and climate types. Stronger negative PTRs ranging from -0.049 to -0.075 °C/mm mostly occur in the semi-arid region, where the cold frontal-type precipitation dominates. In contrast, weaker negative PTRs ranging from -0.004 to -0.014 °C/mm mainly distribute in Liaoning Province, where rain is mainly orographic rain controlled by the warm and humid air of East Asian summer monsoon. In winter, surface temperature increases owing to the release of latent heat and sensible heat when precipitation occurs. The stronger positive PTRs ranging from 0.963 to 3.786 °C/mm mostly occur at high altitudes and latitudes due to more release of sensible heat. The enhanced atmospheric counter radiation by clouds is the major factor affecting increases of surface temperature in winter and decreases of surface temperature in summer when precipitation occurs. © 2012 Springer-Verlag Wien."
"8973018300;57190301630;57206222796;","Post-glacial spatial dynamics in a rainforest biodiversity hot spot",2013,"10.3390/d5010124","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878345968&doi=10.3390%2fd5010124&partnerID=40&md5=31252759102bd6ddad1f72a54d21fc24","Here we investigate the interaction between ecology and climate concerning the distribution of rainforest species differentially distributed along altitudinal gradients of eastern Australia. The potential distributions of the two species closely associated with different rainforest types were modelled to infer the potential contribution of post-glacial warming on spatial distribution and altitudinal range shift. Nothofagus moorei is an integral element of cool temperate rainforest, including cloud forests at high elevation. This distinct climatic envelope is at increased risk with future global warming. Elaeocarpus grandis on the other hand is a lowland species and typical element of subtropical rainforest occupying a climatic envelope that may shift upwards into areas currently occupied by N. moorei. Climate envelope models wereused to infer range shift differences between the two species in the past (21 thousand years ago), current and future (2050) scenarios, and to provide a framework to explain observed genetic diversity/structure of both species. The models suggest continuing contraction of the highland cool temperate climatic envelope and expansion of the lowland warm subtropical envelope, with both showing a core average increase in elevation in response to post-glacial warming. Spatial and altitudinal overlap between the species climatic envelopes was at a maximum during the last glacial maximum and is predicted to be a minimum at 2050. © 2013 by the authors; licensee MDPI, Basel, Switzerland."
"24922812300;7006460542;6701408944;","High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa",2013,"10.1002/joc.3420","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871614932&doi=10.1002%2fjoc.3420&partnerID=40&md5=faf7af8ce6f5ba0e6dc0a9e641ffa748","Mid-tropospheric closed-lows (cold-core cut-off lows and warm-core tropical lows) are important rain producing weather systems for the southern Africa region. Over South Africa, most wide-spread flood events are caused by these systems. It is therefore important to explore the potential impact of anthropogenic forcing on the occurrence of closed-lows and extreme rainfall events over the region. Coupled global circulation models (CGCMs) can not be directly applied for this purpose because of their relatively low spatial resolution-some form of downscaling is required to adequately resolve these systems and the rainfall they cause. In this study, a variable-resolution atmospheric global circulation model is applied as a regional climate model to simulate closed-low characteristics over southern Africa under current and future forcings. The model is forced with greenhouse gas concentrations according to the A2 SRES scenario and with sea surface temperatures (SSTs) and sea-ice as specified by the CSIRO Mk3 CGCM. The model projects a general decrease in closed-low frequencies over the region, which occurs in association with a general strengthening of the subsiding branch of the Hadley cell. However, the climate-change signal shows variation in time and space and certain sub-regions are projected to experience an increase in closed-low frequencies during certain seasons. A general increase in extreme rainfall events is projected over southern Africa despite the projected decrease in closed-low frequencies. It is deduced that this increase in extreme rainfall events is driven by intense convective rainfall events occurring within more frequently forming tropical-temperate cloud bands. Over Mozambique, extreme rainfall events are projected to increase in association with more frequently occurring closed-lows. © 2012 Royal Meteorological Society."
"54797479000;35553737900;6603774028;","Achieving downscaling of Meteosat thermal infrared imagery using artificial neural networks",2013,"10.1080/01431161.2013.825384","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884490983&doi=10.1080%2f01431161.2013.825384&partnerID=40&md5=a0245c14f9847537f9a8b119129f8d3c","This study presents the successful application of artificial neural networks (ANNs) for downscaling Meteosat Second Generation thermal infrared satellite imagery. The scope is to examine, propose, and develop an integrated methodology to improve the spatial resolution of Meteosat satellite images. The proposed approach may contribute to the development of a general methodology for monitoring and downscaling Earth's surface characteristics and cloud systems, where there is a clear need for contiguous, accurate, and high-spatial resolution data sets (e.g. improvement of climate model input data sets, early warning systems about extreme weather phenomena, monitoring of parameters such as solar radiation fluxes, land-surface temperature, etc.). Moderate Resolution Imaging Spectroradiometer (MODIS) images are used to validate the downscaled Meteosat images. In terms of the ANNs, a multilayer perceptron (MLP) is used and the results are shown to compare favourably against a linear regression approach. © 2013 Copyright Taylor & Francis."
"55981818400;57204542986;16307875900;","Diurnal evolution of solar radiation in UV, PAR and NIR bands in high air masses",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878319479&partnerID=40&md5=1c610cf36da2b8cc639776d18497b9c2","Solar surface insolation appears constant from an everyday's point of view but this quantity has been found to be changing in small scale that may lead to climate change over an extended period of time. However, the factors impacting this variance are always a subject of much debate. In long term observations for low air masses, the variation is governed by cloud cover, aerosol loading, relative humidity as well as water vapor content. Parallel observations in high air masses for the variation of received solar radiation are rather lacking. To fill up the existing gap, this paper aims to investigate the diurnal evolution of solar radiation spectrum in UV, PAR and NIR bands in high air masses. In the current work, a total of 25 days of global and diffuse solar spectrum ranges from air mass 2 to 6 were collected using shadowband technique. It is found that the evolution pattern for all spectral components follows a high coefficient of determination with respect to global radiation. The result analysis also shows that variation of solar radiation is the least in UV fraction, followed by PAR and the most in NIR fraction. It is deduced that the broader amplitude of fraction in PAR and NIR because they incorporate variation of aerosol and water vapor. Decreasing trend in NIR fraction for constant UV fraction is likely associated to the increase of water vapor content. While reduction of PAR fraction for specific air mass interval is due to the increase in aerosol loading."
"55831966300;","Grants versus financing for domestic retrofits: A case study from efficiency maine",2013,"10.3390/su5062827","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882800933&doi=10.3390%2fsu5062827&partnerID=40&md5=ab4eafae2c22d2d2e620688bca42067f","Any attempts to limit the impacts of climate change must maximize the potential for energy efficiency in existing dwellings. Retrofitting the existing stock of aging and inefficient dwellings is a challenge on many fronts. A number of programs have been put in place to encourage domestic retrofits by reducing barriers such as the upfront costs and access to capital. While many such programs are delivering positive results, there is much uncertainty regarding what constitutes success, as well as the long term cost effectiveness of various approaches. Geographic, demographic, and programmatic differences frequently cloud the ability to make comparisons across programs. This work examines a case study from Efficiency Maine in the United States, in which a grant program transitioned to a financing program. The grant program was highly popular and delivered significant energy savings, but used considerable public funds. The financing program reaches fewer homeowners, but delivers larger retrofit projects per homeowner, and leverages private investment with smaller public expenditures. Which of the two programs can be considered more successful? This work explores the methods of assessing this question and offers the author's perspectives. © 2013 by the authors."
"55616624500;26321147900;6505699584;6602549190;7003991987;","Classifying tree and nontree echoes from airborne laser scanning in the forest–tundra ecotone",2013,"10.5589/m12-053","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874745801&doi=10.5589%2fm12-053&partnerID=40&md5=5640684c3ad08be46a5964662d4f1de7","Temperature-sensitive ecosystems such as the forest–tundra ecotone are expected to be particularly affected by the changing climate. A large proportion of the total land area in Norway is represented by the forest–tundra ecotone, and effective monitoring techniques for these areas are required. Airborne laser scanning (ALS) has been proposed for detection of small pioneer trees and its height and intensity data may hold potential for monitoring tasks. The main objective of the present study was to assess the capability of high-density ALS data (e.g., &gt;2 m−2) to classify tree and nontree echoes directly from the laser point cloud. For this purpose, the laser height and intensity, a geospatial variable represented by the area of Voronoi polygons, and the terrain variables of aspect and slope were used to distinguish between tree and nontree laser echoes along a 1000 km transect stretching from northern Norway (66°19′ N) to the southern part of the country (58°3′ N). Generalised linear models (GLM) and support vector machines (SVM) were employed for the classification using different combinations of the aforementioned variables. Total accuracy and the Cohen's kappa coefficient were used for performance assessment for the different models. A total accuracy of at least 93% was found irrespective of classification method or model, and Cohen's kappa coefficients indicated moderate fits for all models using both classification methods. Comparisons of Cohen's kappa coefficients revealed equivalent performances for the GLM and SVM classification methods for models consisting of different combinations of the laser height, intensity, geospatial variable, and aspect. However, SVM was superior when laser height and intensity were used together with slope. In summary, the capability of high-density ALS data for the classification of tree and nontree echoes directly from the laser point cloud could be verified irrespective of the classification method. © 2013 CASI."
"16645127300;8953038700;7004364155;7402516470;","Comparisons of clear-sky outgoing Far-IR flux inferred from satellite observations and computed from the three most recent reanalysis products",2013,"10.1175/JCLI-D-12-00212.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872919218&doi=10.1175%2fJCLI-D-12-00212.1&partnerID=40&md5=4faf9309c3b2f77f585447b957cf0a8e","The far-IR spectrum plays an important role in the earth's radiation budget and remote sensing. The authors compare the near-global (808S-808N) outgoing clear-sky far-IR flux inferred from the collocated Atmospheric Infrared Sounder (AIRS) and Clouds and the Earth's Radiant Energy System (CERES) observations in 2004 with the counterparts computed from reanalysis datasets subsampled along the same satellite trajectories. The threemost recent reanalyses are examined: theECMWF InterimRe-Analysis (ERA-Interim), NASAModern-Era Retrospective Analysis for Research and Application (MERRA), and NOAA/NCEP Climate Forecast System Reanalysis (CFSR). Following a previous study by X. Huang et al., clear-sky spectral angular distribution models (ADMs) are developed for five of the CERES land surface scene types as well as for the extratropical oceans. The outgoing longwave radiation (OLR) directly estimated from the AIRS radiances using the authors' algorithm agrees well with the OLR in the collocated CERES Single Satellite Footprint (SSF) dataset. The daytime difference is 0.96 ±2.02 W m-2, and the nighttime difference is 0.86 ±1.61 W m-2. To a large extent, the far-IR flux derived in this way agreeswith those directly computed from three reanalyses. The near-global averaged differences between reanalyses and observationstend to be slightly positive (0.66%-1.15%) over 0-400 cm-1 and slightly negative (20.89% to 20.44%) over 400-600 cm-1. For all threereanalyses, the spatial distributions of suchdifferences show the largest discrepancies over the high-elevation areas during the daytime but not during the nighttime, suggesting discrepancies in the diurnal variation of such areas among different datasets. The composite differences with respect to temperature or precipitable water suggest largediscrepancies for cold and humid scenes. © 2013 American Meteorological Society."
"7006515850;7004288767;7102751564;","Tropospheric aerosols: Size-differentiated chemistry and large-scale spatial distributions",2013,"10.1080/10962247.2012.760499","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875927789&doi=10.1080%2f10962247.2012.760499&partnerID=40&md5=939651384d4373b0a215ce67dba9131c","Worldwide interest in atmospheric aerosols has emerged since the late 20th century as a part of concerns for air pollution and radiative forcing of the earth's climate. The use of aircraft and balloons for sampling and the use of remote sensing have dramatically expanded knowledge about tropospheric aerosols. Our survey gives an overview of contemporary tropospheric aerosol chemistry based mainly on in situ measurements. It focuses on fine particles less than 1-2.5 μm in diameter. The physical properties of particles by region and altitude are exemplified by particle size distributions, total number and volume concentration, and optical parameters such as extinction coefficient and aerosol optical depth. Particle chemical characterization is size dependent, differentiated by ubiquitous sulfate, and carbon, partially from anthropogenic activity. Large-scale particle distributions extend to intra- and intercontinental proportions involving plumes from population centers to natural disturbances such as dust storms and vegetation fires. In the marine environment, sea salt adds an important component to aerosols. Generally, aerosol components, most of whose sources are at the earth's surface, tend to dilute and decrease in concentration with height, but often show different (layered) profiles depending on meteorological conditions. Key microscopic processes include new particle formation aloft and cloud interactions, both cloud initiation and cloud evaporation. Measurement campaigns aloft are short term, giving snapshots of inherently transient phenomena in the troposphere. Nevertheless, these data, combined with long-term data at the surface and optical depth and transmission observations, yield a unique picture of global tropospheric particle chemistry.Aerosols in the troposphere incorporate issues of air pollution exposing humans and ecosystems, and global forcing of the climate of the atmosphere. Fundamental physicochemical knowledge of suspended particles of different sizes is essential to addressing these as technical issues across the world. Current literature informs policymakers about the nature of tropospheric aerosols and their global scale spatial and temporal distributions. With this knowledge, cooperative programs for addressing environmental issues across national borders can be constructed with insight into sources and receptors of pollution and natural air chemistry. For the United States the policy-relevant background for particles is better defined from this work.Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for detailed data tables, color graphics, summary dynamics, and additional references. © 2013 Copyright 2013 A&WMA."
"9638398100;55245821500;7101787483;13605965600;7006147270;","Weekend-weekday aerosols and geographic variability in cloud-to-ground lightning for the urban region of Atlanta, Georgia, USA",2013,"10.1007/s10113-012-0327-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873526478&doi=10.1007%2fs10113-012-0327-0&partnerID=40&md5=5447599e40ba8afafc7f41b995fb2b60","We characterized the differences in warm-season weekday and weekend aerosol conditions and cloud-to-ground (CG) flashes (1995-2008) for an 80,000 square kilometer region around Atlanta, Georgia, a city of 5. 5 million in the humid subtropics of the southeastern United States. An integration of distance-based multivariate techniques (hierarchical agglomerative clustering, multiresponse permutation procedures, fuzzy kappa statistics, and Mantel tests) indicated a greater concentration of CG flash activity within a 100 km radius around Atlanta under weekday aerosol concentrations. On weekends, these effects contracted toward the city. This minimized any weekly anthropogenic cycle over the more densely populated urban center even though this location had a higher flash density, a higher percentage of days with flashes, and stronger peak currents over the course of a week compared to the surrounding region. The sharper contrasts in weekday and weekend lightning regime developed outside the perimeter of the city over nonurban land uses. Here, lightning on weekend and weekdays differed more in its density, frequency, polarity, and peak current. Across the full extent of the study region, weekday peak currents were stronger and flash days more frequent, suggesting that weekly CG lightning signals have a regional component not tied to a single city source. We integrate these findings in a conceptual model that illustrates the dependency of weekly anthropogenic weather signals on spatial and temporal extent. © 2012 Springer-Verlag."
"7202733689;7003543851;7102963655;","Intercalibrating microwave satellite observations for monitoring long-term variations in upper- and midtropospheric water vapor",2013,"10.1175/JTECH-D-13-00001.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886616969&doi=10.1175%2fJTECH-D-13-00001.1&partnerID=40&md5=b8bde9edc6f4b3b4824dcec3d2f92229","This paper analyzes the growing archive of 183-GHz water vapor absorption band measurements from the Advanced Microwave Sounding Unit B (AMSU-B) and Microwave Humidity Sounder (MHS) on board polar-orbiting satellites and document adjustmentsnecessary to use the data for long-term climate monitoring. The water vapor channels located at 183.31 6 1GHz and 183.31 6 3GHz are sensitive to upper- and midtropospheric relative humidity and less prone to the clear-sky sampling bias than infrared measurements, making them a valuable but underutilized source of information on free-tropospheric water vapor. A method for the limb correction of the satellite viewing angle based upon a simplified model of radiative transfer is introduced toremove the scan angle dependence of the radiances. Biases due to the difference inlocal observation time between satellites and spurious trends associated with satellite orbital drift are then diagnosed and adjusted for using synthetic radiative simulations based on the Interim European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-Interim). The adjusted, cloud-filtered, and limbcorrected brightness temperatures are then intercalibrated using zonal-mean brightness temperature differences. It is found that these correction procedures significantly improve consistency and quantitative agreement between microwave radiometric satellite observations that can be used to monitor upper- and midtropospheric water vapor. The resulting radiances are converted to estimates of the deep-layer-mean upper- and midtropospheric relative humidity, and can be used to evaluate trends in upper-tropospheric relative humidity from reanalysis datasets and coupled ocean-atmosphere models. © 2013 American Meteorological Society."
"36559769700;7202967741;6507198695;24281680700;7801595201;26653350000;6604005739;7404661626;7006978226;","13C- And 14C-based study of sources and atmospheric processing of water-soluble organic carbon (WSOC) in South Asian aerosols",2013,"10.1002/jgrd.50130","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879372057&doi=10.1002%2fjgrd.50130&partnerID=40&md5=aa7f2c71f49813d3882e21e02b3ae47c","Water-soluble organic carbon (WSOC) is typically a large component of carbonaceous aerosols with a high propensity for inducing cloud formation. The sources of WSOC, which may be both of primary and secondary origins, are in general poorly constrained. This study assesses the concentrations and dual-carbon isotope (14C and 13C) signatures of South Asian WSOC during a 15-month continuous campaign in 2008-2009. Total suspended particulate matter samples were collected at Sinhagad (SINH) India and at the Maldives Climate Observatory at Hanimaadhoo (MCOH). Monsoon-driven meteorology yields significant WSOC concentration differences between the dry winter season (0.94 ± 0.43 mg m-3MCOH and 3.6 ± 2.3 mg m-3 SINH) and the summer monsoon season (0.10 ± 0.04 mg m-3 MCOH and 0.35 ± 0.21 mg m-3 SINH). Radiocarbon-based source apportionment of WSOC not only shows the dominance of biogenic/biomass combustion sources but also a substantial anthropogenic fossil-fuel contribution (17 ± 4% MCOH and 23 ± 4% SINH). Aerosols reaching MCOH after long-range over-ocean transport were enriched by 3-4% in d13C-WSOC relative to SINH. This is consistent with particle-phase aging processes influencing the δ13 C-WSOC signal in the South Asian regional receptor atmosphere. © 2012. American Geophysical Union."
"12786571000;6603724288;6701527006;57204744052;","Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico",2013,"10.1002/2013JG002304","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892936813&doi=10.1002%2f2013JG002304&partnerID=40&md5=ca9bd40bd914020f24a23c40f3b724c8","Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes influencing precipitation δ18O. Key Points Variation in oxygen isotopes in Mimosa tree rings is mostly due to source water Oxygen isotope records show a regional amount effect © 2013 The Authors. Journal of Geophysical Research: Biogeosciences published by Wiley on behalf of the American Geophysical Union."
"55243411600;9234412200;57200241494;55871224200;6603647965;6507406094;","Application of terrestrial laser scanner techniques for monitoring dynamic geomorphological processes: Snow accumulation and ice masses in mountain areas [Utilización de técnicas de láser escáner terrestre en la monitorización de procesos geomorfológicos dinámicos: El manto de nieve y heleros en áreas de montaña]",2013,"10.18172/cig.1994","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884923775&doi=10.18172%2fcig.1994&partnerID=40&md5=444a753888a66dc48a25ddcc5d1e1cf7","This paper presents the application of a long range terrestrial laser scanner for monitoring snow accumulation and evolution of glaciers in the Pyrenees. With this study we are showing the great potential of the methodology presented for studies in mountain environments, particularly in research related to the cryosphere monitoring in relation to climate variability and the complex topography typical of mountain environments. We present a comprehensive protocol for the acquisition and processing of point clouds measured by a laser scanner (RIEGL LPM-321) for the generation of digital terrain models, in order to compare the models obtained at different times. Thus it is possible to obtain snow thickness and changes of ice thickness. As case studies, results from two small ice masses located in the massif of Monte Perdido and snow accumulation on a small basin located in the Tena Valley are presented. © Universidad de La Rioja."
"23974441400;7401672948;36551761100;7202019251;","A novel solution for outlier removal of ICESat altimetry data: A case study in the Yili watershed, China",2013,"10.1007/s11707-013-0362-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877027290&doi=10.1007%2fs11707-013-0362-2&partnerID=40&md5=72f04cfe202faeb2a32563aa91156054","Due to the influence of cloud and saturated waveforms, ICESat data contain many contaminated elevation data that cannot be directly used in examining surface elevation and change. This study provides a novel solution for removing bad data and getting clean ICESat data for land applications by using threshold values of reflectivity, saturation, and gain directly from ICESat's GLAS (Geoscience Laser Alteimeter System) 01, 05, and 06 products. It is found that each laser campaign needs different threshold compositions to assure qualified ICESat data and that bad data removal rates range from 9. 6% (laser 2A) to 62. 3% (laser 2B) for the test area in the Yili watershed, China. These thresholds would possibly be used in other regions to extract qualified ICESat footprints for land applications. However, it is recommended to use the steps proposed here to further examine the transferability of threshold values for other regions of different elevations and climate regimes. As an example, the resulting ICESat data are applied to examine lake level changes of two lakes in the study area. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg."
"23480736000;7004021966;","Evaluating the temperature sensitivity of radial growth patterns from whitebark pine in the western Canadian Cordillera",2013,"10.1016/j.dendro.2012.04.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875606629&doi=10.1016%2fj.dendro.2012.04.001&partnerID=40&md5=252b4bd5b45d8d0acbb5db9404a43090","We present a network of thirteen annual ring-width chronologies from high elevation whitebark pine (Pinus albicaulis Engelm.) sites in the western Canadian Cordillera in order to assess the dendroclimatic potential of this long-lived tree species. The temperature signal within the chronologies is complex and strongly influenced by diverging trends in the summer temperature and ring-width records from across the region. A first differences transformation of the tree-ring and temperature records illustrates a loss of frequency coherence in growth response to summer temperatures following reduced radial growth in the 1950s. Prior to reduced growth, we note a positive association with summer temperatures for both first differenced (rd=0.60) and traditional (r=0.50) records. Following reduced growth, the association at first differences is maintained (rd=0.49) whereas there is a change in the lower frequency component of tree growth response to summer temperatures (r=-0.34). We suggest the cause of this reduced temperature sensitivity is related to the interaction between diurnal temperature and cloud cover patterns, the hydrological regime of snowpack, and site conditions which have been amenable to the initiation of moisture stress during the latter half of the 20th century. Reduced radial growth is coincident with the arrival of white pine blister rust (Cronatium ribicola J.C. Fisch. ex Raben) into the study region which suggests this infestation may be related to the observed reduction in radial growth. Whitebark pine has considerable potential for the field of dendroclimatology. Unfortunately, the decline of the species due to the combined effects of climate change, white pine blister rust, mountain pine beetle (Dendroctonus ponderosae Hopk.), and forest fire exclusion practices indicate this potential may remain unfulfilled. © 2012 Elsevier GmbH."
"7006173341;16315767700;7005441447;7005327035;6603303751;","Validating ICESat over thick sea ice in the Northern Canada Basin",2013,"10.1109/TGRS.2012.2211603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875709815&doi=10.1109%2fTGRS.2012.2211603&partnerID=40&md5=73aeab185e33cc8e7e76b7e56af90f4d","Only in the past eight years has the feasibility of using satellite-borne altimeters to estimate sea ice freeboard and thickness been demonstrated, and these estimates still have uncertainties primarily associated with limited knowledge of snow loading on sea ice. Because accurate estimates of Arctic-wide sea ice thickness and volume are fundamental inputs to global climate models, validation of satellite-derived thickness estimates using independent data is required. A detailed assessment of freeboard retrieved by the Geoscience Laser Altimeter System (GLAS) aboard the Ice, Cloud, and land Elevation Satellite has been carried out using high-resolution laser altimetry from the National Aeronautics and Space Administration's Airborne Topographic Mapper (ATM), the Delay-Doppler radar altimeter, and digital photography collected along a 300-km segment of sea ice in the Canada Basin. Exploiting the repeat coverage of the aircraft flight line, a correction was applied to GLAS footprint geolocations to adjust for sea ice drift that occurred during the time between satellite and aircraft acquisitions. Comparisons of GLAS and ATM measurements over sea ice show excellent agreement (about a 0.00-m mean) with no apparent bias between data sets. Freeboard estimates were examined using data from GLAS and ATM independently, employing measurements over refrozen leads to estimate local sea surface heights (SSHs). The results demonstrate the sensitivity of freeboard and thickness calculations to an accurate estimation of local SSH. Snow depth derived by differencing laser and radar data was combined with the freeboard estimates to yield a mean sea ice thickness of ∼5.5 m over a 250-km subsection of the flight track. © 1980-2012 IEEE."
"55501093800;8412168800;7005034568;24822250800;22957143800;","Cross-scan asymmetry of AMSU-a window channels: Characterization, correction, and verification",2013,"10.1109/TGRS.2012.2211884","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874644712&doi=10.1109%2fTGRS.2012.2211884&partnerID=40&md5=175d7975e7dc42c5b8fa97b4f8e47a6a","More than one decade of observations from the Advanced Microwave Sounding Unit-A (AMSU-A) onboard the polar-orbiting satellites NOAA-15 to NOAA-19 and European Meteorological Operational satellite program-A (MetOp-A) provide global information on atmospheric temperature profile, water vapor, cloud, precipitation, etc. However, a pronounced asymmetric cross-scan bias of the AMSU-A window channels was discovered, and it severely impacted water cycle product generation. Several approaches, including vicarious cold and hot reference calibration techniques, are applied to characterize the cross-scan bias. The bias pattern appears to be stable through several years of data examined from the same satellite but is quite different among those onboard the different NOAA (NOAA-15, NOAA-16, NOAA-17, NOAA-18, and NOAA-19) and EUMETSAT (MetOp-A) satellites. The scan bias may be caused by sensor polarization misalignment or cross-polarization, even after the radiance/brightness temperature data have been geocorrected with regard to geolocation and view angles. Based upon the characterization information, two-point and three-point correction approaches are proposed; both approaches provide promising results for AMSU-A window channels at brightness temperature level and product level and outperform the current operational correction approach, which is essentially a one-point correction. This serves as the first step toward a more stable fundamental and thematic climate data record to be used in hydrological and meteorological applications. © 2012 IEEE."
"8612873400;6506068752;55620946400;","The Inclusion of IWV Estimates from AIRS/AMSU and SSM/I sensors into the CPTEC/INPE Global data assimilation system",2013,"10.1175/MWR-D-10-05061.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874909185&doi=10.1175%2fMWR-D-10-05061.1&partnerID=40&md5=26d071d4678b6e2e23df28e80a845e70","Water vapor plays a crucial role in atmospheric processes and its distribution is associated with cloud-cover fraction and rainfall. The inclusion of integrated water vapor (IWV) estimates in numerical weather prediction improves the vertical structure of the humidity analysis and consequently contributes to obtaining a more realistic atmospheric state. Currently, satellite remote sensing is the most important source of humidity measurements in the Southern Hemisphere, providing information with good horizontal resolution and global coverage. In this study, the inclusion of IWV retrieved from the Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit-A (AIRS/AMSU) and Special Sensor Microwave Imager (SSM/I) were investigated as additional information in the Physical-space Statistical Analysis System (PSAS), which is the operational data assimilation system at the Center for Weather Forecasting and Climate Studies of the Brazilian National Institute for Space Research (CPTEC/INPE). Experiments were carried out with and without the assimilation of IWV values from both sensors. Results show that, in general, the IWV assimilation reduces the error in short-range forecasts of humidity profile, particularly over tropical regions. In these experiments, an analysis of the impact of the inclusion of IWV values from SSM/I and AIRS/AMSU sensors was done. Results indicated that the impact of the SSM/I values is significant over high-latitude oceanic regions in the Southern Hemisphere, while the impact of AIRS/AMSU values is more significant over continental regions where surface measurements are scarce, such as the Amazonian region. In that area the assimilation of IWV values from the AIRS/AMSUsensor shows a tendency to reduce the overestimate of the precipitation in short-range forecasts. © 2013 American Meteorological Society."
"55571119000;7102495313;36876405100;","Evaluation of near-surface parameters in the two versions of the atmospheric model in CESM1 using flux station observations",2013,"10.1175/JCLI-D-12-00020.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872918638&doi=10.1175%2fJCLI-D-12-00020.1&partnerID=40&md5=d01436a33f27d41e86b34108f43d62a6","This paper describes the performance of the Community Atmosphere Model (CAM) versions 4 and 5 in simulating near-surface parameters. CAM is the atmospheric component of the Community Earth System Model (CESM). Most of the parameterizations in the two versions are substantially different, and that is also true for the boundary layer scheme: CAM4 employs a nonlocal K-profile scheme, whereas CAM5 uses a turbulent kinetic energy (TKE) scheme. The evaluation focuses on the diurnal cycle and global observational and reanalysis datasets are used together with multiyear observations from 35 flux tower sites, providing highfrequency measurements in a range of different climate zones. It is found that both model versions capture the timing of the diurnal cycle but considerably overestimate the diurnal amplitude of net radiation, temperature, wind, and turbulent heat fluxes. The seasonal temperature range at mid- and high latitudes is also overestimated with too warm summer temperatures and too cold winter temperatures. The diagnosed boundary layer is deeper in CAM5 over ocean in regions with low-level marine clouds as a result of the turbulence generated by cloud-top cooling. Elsewhere, the boundary layer is in general shallower in CAM5. The two model versions differ substantially in their representation of near-surface wind speeds over land. The lowlevel wind speed in CAM5 is about half as strong as in CAM4, and the difference is even larger in areas where the subgrid-scale terrain is significant. The reason is the turbulent mountain stress parameterization, only applied in CAM5, which acts to increase the surface stress and thereby reduce the wind speed. © 2013 American Meteorological Society."
"55181662600;8207896100;7003917433;","Landsat imagery reveals declining clarity of Maine's lakes during 1995-2010",2013,"10.1899/12-070.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884311669&doi=10.1899%2f12-070.1&partnerID=40&md5=8f67d3320f7772099ce4ed0e00d9b728","Water clarity is a strong indicator of regional water quality. Unlike other common water-quality metrics, such as chlorophyll a, total P, or trophic status, clarity can be accurately and efficiently estimated remotely on a regional scale. Satellite-based remote sensing is useful in regions with many lakes where traditional field-sampling techniques may be prohibitively expensive. Repeated sampling of easily accessed lakes can lead to spatially irregular, nonrandom samples of a region. Remote sensing remedies this problem. We applied a remote monitoring protocol we had previously developed for Maine lakes >8 ha based on Landsat satellite data recorded during 1995-2010 to identify spatial and temporal patterns in Maine lake clarity. We focused on the overlapping region of Landsat paths 11 and 12 to increase availability of cloud-free images in August and early September, a period of relative lake stability and seasonal poor-clarity conditions well suited for annual monitoring. We divided Maine into 3 regions (northeastern, south-central, western) based on morphometric and chemical lake features. We found a general decrease in average statewide lake clarity from 4.94 to 4.38 m during 1995-2010. Water clarity ranged from 4 to 6 m during 1995-2010, but it decreased consistently during 2005-2010. Clarity in both the northeastern and western lake regions has decreased from 5.22 m in 1995 to 4.36 and 4.21 m, respectively, in 2010, whereas lake clarity in the south-central lake region (4.50 m) has not changed since 1995. Climate change, timber harvesting, or watershed morphometry may be responsible for regional water-clarity decline. Remote sensing of regional water clarity provides a more complete spatial perspective of lake water quality than existing, interest-based sampling. However, field sampling done under existing monitoring programs can be used to calibrate accurate models designed to estimate water clarity remotely. © 2013 by The Society for Freshwater Science."
"57217726421;23994595000;35195849700;36183177600;6602085876;7006434689;22833630700;14034301300;7006387246;7005069415;57203053317;","Hygroscopic properties of fresh and aged wood burning particles",2013,"10.1016/j.jaerosci.2012.08.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871979897&doi=10.1016%2fj.jaerosci.2012.08.006&partnerID=40&md5=1d362c671b444d2fe34f635b50697c85","Biomass burning is one of the largest aerosol sources worldwide. In this study, the hygroscopic properties of fresh and aged wood burning particles were investigated under controlled laboratory conditions in several smog chamber experiments. Beech log wood was burnt in a residential log wood burner and the particles emitted during the different burning phases (starting, flaming, and smoldering) were analyzed. The particles were photochemically aged using the own volatile organic compound emissions from the burnt wood. The hygroscopic properties of the particles at relative humidities below and above 100% were determined and compared.The freshly emitted soot particles have a fractal-like structure. The structure collapsed in half of the experiments where soot was present for particles ≥100 nm under the presence of a high relative humidity, leading to a more compact structure. This restructuring induces an underestimation of the hygroscopicity measured with mobility diameter based methods.The hygroscopicity parameter ""apparent κ"" of fresh wood combustion particles varies between 0 and 0.39. With aging, the hygroscopicity of the particles generally increases. This is due to the uptake of organic matter and inorganic salts, and because the particles become more oxidized.One smoldering phase experiment was carried out, which, in contrast to the other experiments, showed very high apparent κ values between 0.2 and 0.4 at the beginning of the experiment, depending on the size of the particles. These values were decreasing with time. This suggests a different composition of the particles, with a higher fraction of inorganic components initially.The results indicate that it is not possible to use only one κ value for different burning phases and aging times of wood combustion particles in climate models. © 2012 Elsevier Ltd."
"14321349000;7004922068;8537012400;7401860380;7004182023;7004207364;7006152782;","A software engineering perspective on environmental modeling framework design: The Object Modeling System",2013,"10.1016/j.envsoft.2012.03.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870298278&doi=10.1016%2fj.envsoft.2012.03.006&partnerID=40&md5=e4cbd1188405ccb98a538062d55a2154","The environmental modeling community has historically been concerned with the proliferation of models and the effort associated with collective model development tasks (e.g., code generation, data transformation, etc.). Environmental modeling frameworks (EMFs) have been developed to address this problem, but much work remains before EMFs are adopted as mainstream modeling tools. Environmental model development requires both scientific understanding of environmental phenomena and software developer proficiency. EMFs support the modeling process through streamlining model code development, allowing seamless access to data, and supporting data analysis and visualization. EMFs also support aggregation of model components into functional units, component interaction and communication, temporal-spatial stepping, scaling of spatial data, multi-threading/multi-processor support, and cross-language interoperability. Some EMFs additionally focus on high-performance computing and are tailored for particular modeling domains such as ecosystem, socio-economic, or climate change research. The Object Modeling System Version 3 (OMS3) EMF employs new advances in software framework design to better support the environmental model development process. This paper discusses key EMF design goals/constraints and addresses software engineering aspects that have made OMS3 framework development efficacious and its application practical, as demonstrated by leveraging software engineering efforts outside of the modeling community and lessons learned from over a decade of EMF development. Software engineering approaches employed in OMS3 are highlighted including a non-invasive lightweight framework design supporting component-based model development, use of implicit parallelism in system design, use of domain specific language design patterns, and cloud-based support for computational scalability. The key advancements in EMF design presented herein may be applicable and beneficial for other EMF developers seeking to better support environmental model development through improved framework design. © 2012 Elsevier Ltd."
"56489062200;7005501098;","Latent heating and cooling rates in developing and nondeveloping tropical disturbances during TCS-08: TRMM PR versus ELDORA retrievals",2013,"10.1175/JAS-D-12-083.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874976179&doi=10.1175%2fJAS-D-12-083.1&partnerID=40&md5=ce36a7883f9f254d10895a3cffd4c16d","Unique sets of Electra Doppler Radar (ELDORA) observations in both developing and nondeveloping tropical disturbances in the western North Pacific are used to retrieve latent heating and cooling rates. During the reintensification of Sinlaku, maximum heating rates of about 80 K h-1 are diagnosed in the upper troposphere in the region of a strong updraft and maximum cooling rates of about 245 K h-1 are diagnosed in the lower troposphere in the region of a strong convective-scale downdraft. The southern convective burst in the pre-Nuri mission had a lower-tropospheric maximum in latent heating that was a more favorable condition for tropical cyclone formation than was the upper-tropospheric maximum in heating and the lowertropospheric maximum in cooling in the northern convective burst. Two nondeveloping tropical disturbances had deeper layers of more uniform heating and of cooling rates, and some evidence of more shallow cloud tops, that distinguished them from the developing cases. Although the Shige et al. Tropical RainfallMeasuring Mission (TRMM) precipitation radar (PR) algorithm was only intended to be applied over large areas on longer time scales, the PR-derived latent heating profiles were compared with the ELDORA-derived profiles to reveal importantmesoscale effects. Because all six cases indicated near-zero cooling rates, a new TRMM PR algorithm should be developed that would include the effects of saturated convective-scale downdrafts in tropical mesoscale convective systems (MCSs). Production of a legacy TRMMPRdatasetwith this improvement would be useful for diagnosing tropical cyclone formation dating back to 1998, and for specifying initial and validation conditions for numerical models in the tropics. © 2013 American Meteorological Society."
"57192534657;57034458200;","On the rapid intensification of hurricane wilma (2005). Part II: Convective bursts and the upper-level warm core",2013,"10.1175/JAS-D-12-062.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874951393&doi=10.1175%2fJAS-D-12-062.1&partnerID=40&md5=ec4c9fc9daf07a25a070bc678895d45a","Previous studies have focused mostly on the roles of environmental factors in the rapid intensification (RI) of tropical cyclones (TCs) because of the lack of high-resolution data in inner-core regions. In this study, the RI of TCs is examined by analyzing the relationship between an upper-level warm core, convective bursts (CBs), sea surface temperature (SST), and surface pressure falls from 72-h cloud-permitting predictions of Hurricane Wilma (2005) with the finest grid size of 1 km. Results show that both the upper-level inertial stability increases and static stability decreases sharply 2-3 h prior to RI, and that the formation of an upperlevel warm core, from the subsidence of stratospheric air associated with the detrainment of CBs, coincides with the onset of RI. It is found that the development of CBs precedes RI, but most subsidence warming radiates away by gravity waves and storm-relative flows. In contrast, many fewer CBs occur during RI, but more subsidence warming contributes to the balanced upper-level cyclonic circulation in the warm-core (as intense as 20°C) region. Furthermore, considerable CB activity can still take place in the outer eyewall as the storm weakens during its eyewall replacement. A sensitivity simulation, in which SSTs are reduced by 1°C, shows pronounced reductions in the upper-level warm-core intensity and CB activity. It is concluded that significant CB activity in the inner-core regions is an important ingredient in generating the upper-level warm core that is hydrostatically more efficient for the RI of TCs, given all of the other favorable environmental conditions. © 2013 American Meteorological Society."
"6602598233;7004208584;57197840312;7006708838;7402439028;6701726317;14032501300;14033392700;6507268436;7402534046;7202588306;7701313284;24755928100;8723496500;7404982967;","Daily MODIS 500 m reflectance anisotropy direct broadcast (DB) products for monitoring vegetation phenology dynamics",2013,"10.1080/01431161.2013.803169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879040139&doi=10.1080%2f01431161.2013.803169&partnerID=40&md5=d2fd891524d4a0aeab3a5d82a56fc698","Land surface vegetation phenology is an efficient bio-indicator for monitoring ecosystem variation in response to changes in climatic factors. The primary objective of the current article is to examine the utility of the daily MODIS 500 m reflectance anisotropy direct broadcast (DB) product for monitoring the evolution of vegetation phenological trends over selected crop, orchard, and forest regions. Although numerous model-fitted satellite data have been widely used to assess the spatio-temporal distribution of land surface phenological patterns to understand phenological process and phenomena, current efforts to investigate the details of phenological trends, especially for natural phenological variations that occur on short time scales, are less well served by remote sensing challenges and lack of anisotropy correction in satellite data sources. The daily MODIS 500 m reflectance anisotropy product is employed to retrieve daily vegetation indices (VI) of a 1 year period for an almond orchard in California and for a winter wheat field in northeast China, as well as a 2 year period for a deciduous forest region in New Hampshire, USA. Compared with the ground records from these regions, the VI trajectories derived from the cloud-free and atmospherically corrected MODIS Nadir BRDF (bidirectional reflectance distribution function) adjusted reflectance (NBAR) capture not only the detailed footprint and principal attributes of the phenological events (such as flowering and blooming) but also the substantial inter-annual variability. This study demonstrates the utility of the daily 500 m MODIS reflectance anisotropy DB product to provide daily VI for monitoring and detecting changes of the natural vegetation phenology as exemplified by study regions comprising winter wheat, almond trees, and deciduous forest. © 2013 Copyright Taylor and Francis Group, LLC."
"25648525300;55478977700;55574182494;35511789800;","Multiscale periodicities in aerosol optical depth over India",2013,"10.1088/1748-9326/8/1/014034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876173325&doi=10.1088%2f1748-9326%2f8%2f1%2f014034&partnerID=40&md5=824875e5a675c477e9227836120b7875","Aerosols exhibit periodic or cyclic variations depending on natural and anthropogenic sources over a region, which can become modulated by synoptic meteorological parameters such as winds, rainfall and relative humidity, and long-range transport. Information on periodicity and phase in aerosol properties assumes significance in prediction as well as examining the radiative and climate effects of aerosols including their association with changes in cloud properties and rainfall. Periodicity in aerosol optical depth, which is a columnar measure of aerosol distribution, is determined using continuous wavelet transform over 35 locations (capitals of states and union territories) in India. Continuous wavelet transform is used in the study because continuous wavelet transform is better suited to the extraction of the periodic and local modulations present in various frequency ranges when compared to Fourier transform. Monthly mean aerosol optical depths (AODs) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra satellite at 1° × 1° resolution from January 2001 to December 2012 are used. Annual and quasi-biennial oscillations (QBOs) in AOD are evident in addition to the weak semi-annual (5-6 months) and quasi-triennial oscillations (∼40 months). The semi-annual and annual oscillations are consistent with the seasonal and yearly cycle of variations in AODs. The QBO type periodicity in AOD is found to be non-stationary while the annual period is stationary. The 40 month periodicity indicates the presence of long term correlations in AOD. The observed periodicities in MODIS Terra AODs are also evident in the ground-based AOD measurements made over Kanpur in the Indo-Gangetic Plain. The phase of the periodicity in AOD is stable in the mid-frequency range, while local disturbances in the high-frequency range and long term changes in the atmospheric composition give rise to unstable phases in the low-frequency range. The presence of phase relations among different locations reveals that modulations in AOD over a location/region can influence aerosol characteristics over other locations/regions. © 2013 IOP Publishing Ltd."
"56663417400;7402989545;36784202000;","Observational analysis and numerical simulation of the interannual variability of the boreal winter Hadley circulation over the recent 30 years",2013,"10.1007/s11430-012-4497-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876030563&doi=10.1007%2fs11430-012-4497-x&partnerID=40&md5=6c03d3163f1b92e937c4228d7a7f0a88","The interannual variability of the boreal winter (DJF) Hadley Cell strength during 1979-2008 is investigated using NCEP/NCAR reanalysis data. The results of AMIP simulation of LASG/IAP AGCM GAMIL2. 0 are compared against the reanalysis data. Both the reanalysis data and the simulation show that the interannual variability of the Hadley Cell strength has a non-uniform spatial distribution, as evidenced by the 1st Empirical Orthogonal Function (EOF) mode. The change of Hadley cell strength in the tropics is opposite to that in the subtropical regions. Our analysis indicates that a positive phase of EOF1 is associated with an El Niño-like warmer equatorial central and eastern Pacific and a warmer southern Indian Ocean. Above features are also seen in the results of GAMIL2. 0 simulation, indicating that the interannual variability of the Hadley Cell strength is driven by the tropical ocean variability. Our analysis also demonstrates that the contribution of the warmer central-eastern Pacific to the 1st EOF mode is larger than that of the South Indian Ocean. The SST forcing enhances the local Hadley circulation strength in the central Pacific and Africa (30°S-30°N, 150°E-90°W), while it weakens the local Hadley circulation in other regions (30°S-30°N, 90°-10°W). The western Pacific anticyclone remotely driven by the El Niño forcing leads to a weakened local Hadley cell in the Northern Hemisphere, while the South Indian Ocean anticyclone driven by the remote El Niño forcing and the local warmer SST anomalies in the southern Indian Ocean results in a weakened local Hadley Cell in the Southern Hemisphere. The enhancement of the Pacific local Hadley Cell is stronger (weaker) than that of the Atlantic, the western Pacific, and the southern Indian Ocean in the tropical (subtropical) part, thus for the zonal mean condition the strength of the total Hadley Cell is stronger (weaker) in the tropical (subtropical) limb. The amplitude of the Hadley Cell change in the Northern Hemisphere is stronger than that in the Southern Hemisphere. Hence the leading interannual variability mode of boreal winter Hadley Cell exhibits a non-uniform spatial pattern. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg."