Author(s) ID,Title,Year,DOI,Link,Abstract
"6701562113;8631239200;6602572031;7005751636;55665687100;55536747200;7006030430;7003495982;","Introducing subgrid-scale cloud feedbacks to radiation for regional meteorological and climate modeling",2012,"10.1029/2012GL054031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871574295&doi=10.1029%2f2012GL054031&partnerID=40&md5=2ee3719f45dd089e5bddafaa275b4a51","Convective systems and associated cloudiness directly influence regional and local atmospheric radiation budgets, as well as dynamics and thermodynamics, through feedbacks. However, most subgrid-scale convective parameterizations in regional weather and climate models do not consider cumulus cloud feedbacks to radiation, resulting in biases in several meteorological parameters. We have incorporated this key feedback process into a convective parameterization and a radiation scheme in the Weather Research and Forecasting model, and evaluated the impacts of including this process in short-term weather and multiyear climate simulations. Introducing subgrid-scale convective cloud-radiation feedbacks leads to a more realistic simulation of attenuation of downward surface shortwave radiation. Reduced surface shortwave radiation moderates the surface forcing for convection and results in a notable reduction in precipitation biases. Our research reveals a need for more in-depth consideration of the effects of subgrid-scale clouds in regional meteorology/climate and air quality models on radiation, photolysis, cloud mixing, and aerosol indirect effects. © 2012. American Geophysical Union. All Rights Reserved."
"55710310300;7403931916;7102018821;7006783796;7006518279;","Parameterization of contrail radiative properties for climate studies",2012,"10.1029/2012GL054043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871536718&doi=10.1029%2f2012GL054043&partnerID=40&md5=c6423abfee66292469b3f0fffb0d4509","The study of contrails and their impact on global climate change requires a cloud model that statistically represents contrail radiative properties. In this study, the microphysical properties of global contrails are statistically analyzed using collocated Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observations. The MODIS contrail pixels are detected using an automated contrail detection algorithm and a manual technique using the brightness temperature differences between the MODIS 11 and 12 m channels. The scattering and absorption properties of typical contrail ice crystals are used to determine an appropriate contrail model to minimize the uncertainties arising from the assumptions in a particular cloud model. The depolarization ratio is simulated with a variety of ice crystal habit fractions and matched to the collocated MODIS and CALIOP observations. The contrail habit fractions are determined and used to compute the bulk-scattering properties of contrails. A parameterization of shortwave and longwave contrail optical properties is developed for the spectral bands of the Rapid Radiative Transfer Model (RRTM). The contrail forcing at the top of the atmosphere is investigated using the RRTM and compared with spherical and hexagonal ice cloud models. Contrail forcing is overestimated when spherical ice crystals are used to represent contrails, but if a hexagonal ice cloud model is used, the forcing is underestimated for small particles and overestimated for large particles in comparison to the contrail model developed in this study. © 2012. American Geophysical Union. All Rights Reserved."
"7201587909;7403577184;6701653010;6603431534;7202772927;","Two distinct modes in one-day rainfall event during MC3E field campaign: Analyses of disdrometer observations and WRF-SBM simulation",2012,"10.1029/2012GL053329","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871558076&doi=10.1029%2f2012GL053329&partnerID=40&md5=466702d9bd78639ec3420057522c4784","A unique microphysical structure of rainfall is observed by the surface laser optical Particle Size and Velocity (Parsivel) disdrometers on 25 April 2011 during Midlatitude Continental Convective Clouds Experiment (MC3E). According to the systematic differences in rainfall rate and bulk effective droplet radius, the sampling data can be divided into two groups; the rainfall mostly from the deep convective clouds has relatively high rainfall rate and large bulk effective droplet radius, whereas the reverse is true for the rainfall from the shallow warm clouds. The Weather Research and Forecasting model coupled with spectral bin microphysics (WRF-SBM) successfully reproduces the two distinct modes in the observed rainfall microphysical structure. The results show that the up-to-date model can demonstrate how the cloud physics and the weather condition on the day are involved in forming the unique rainfall characteristic. © 2012. American Geophysical Union. All Rights Reserved."
"48661551300;7403931916;7102018821;7006783796;7102604282;","Simulation of the global contrail radiative forcing: A sensitivity analysis",2012,"10.1029/2012GL054042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871578922&doi=10.1029%2f2012GL054042&partnerID=40&md5=a8cfaee86a335c8705e42f84c9512914","The contrail radiative forcing induced by human aviation activity is one of the most uncertain contributions to climate forcing. An accurate estimation of global contrail radiative forcing is imperative, and the modeling approach is an effective and prominent method to investigate the sensitivity of contrail forcing to various potential factors. We use a simple offline model framework that is particularly useful for sensitivity studies. The most-up-to-date Community Atmospheric Model version 5 (CAM5) is employed to simulate the atmosphere and cloud conditions during the year 2006. With updated natural cirrus and additional contrail optical property parameterizations, the RRTMG Model (RRTM-GCM application) is used to simulate the global contrail radiative forcing. Global contrail coverage and optical depth derived from the literature for the year 2002 is used. The 2006 global annual averaged contrail net (shortwave + longwave) radiative forcing is estimated to be 11.3 mW m -2. Regional contrail radiative forcing over dense air traffic areas can be more than ten times stronger than the global average. A series of sensitivity tests are implemented and show that contrail particle effective size, contrail layer height, the model cloud overlap assumption, and contrail optical properties are among the most important factors. The difference between the contrail forcing under all and clear skies is also shown. © 2012. American Geophysical Union. All Rights Reserved."
"7201656946;7102447698;56244473600;7103206141;7101823091;","Climate versus emission drivers of methane lifetime against loss by tropospheric OH from 1860-2100",2012,"10.5194/acp-12-12021-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871265119&doi=10.5194%2facp-12-12021-2012&partnerID=40&md5=81381b065fde9d60b0ef0786ba6dedc4","With a more-than-doubling in the atmospheric abundance of the potent greenhouse gas methane (CH4) since preindustrial times, and indications of renewed growth following a leveling off in recent years, questions arise as to future trends and resulting climate and public health impacts from continued growth without mitigation. Changes in atmospheric methane lifetime are determined by factors which regulate the abundance of OH, the primary methane removal mechanism, including changes in CH4 itself. We investigate the role of emissions of short-lived species and climate in determining the evolution of methane lifetime against loss by tropospheric OH, (τCH4OH), in a suite of historical (1860-2005) and future Representative Concentration Pathway (RCP) simulations (2006-2100), conducted with the Geophysical Fluid Dynamics Laboratory (GFDL) fully coupled chemistry-climate model (CM3). From preindustrial to present, CM3 simulates an overall 5% increase in τCH4OH due to a doubling of the methane burden which offsets coincident increases in nitrogen oxide (NO x emissions. Over the last two decades, however, the τCH4OH declines steadily, coinciding with the most rapid climate warming and observed slow-down in CH4 growth rates, reflecting a possible negative feedback through the CH4 sink. Sensitivity simulations with CM 3 suggest that the aerosol indirect effect (aerosol-cloud interactions) plays a significant role in cooling the CM3 climate. The projected decline in aerosols under all RCPs contributes to climate warming over the 21st century, which influences the future evolution of OH concentration and τCH4OH. Projected changes in τCH4OH from 2006 to 2100 range from-13% to +4%. The only projected increase occurs in the most extreme warming case (RCP8.5) due to the near-doubling of the CH4 abundance, reflecting a positive feedback on the climate system. The largest decrease occurs in the RCP4.5 scenario due to changes in short-lived climate forcing agents which reinforce climate warming and enhance OH. This decrease is more-than-halved in a sensitivity simulation in which only well-mixed greenhouse gas radiative forcing changes along the RCP4.5 scenario (5% vs. 13%). © 2012 Author(s)."
"55918817700;36871965000;55495492100;7402835457;7402859325;16633837500;23481520000;9249656500;7201925326;56823691200;10144443500;9248799600;7004286908;7201350647;","Development of the RAQM2 aerosol chemical transport model and predictions of the Northeast Asian aerosol mass, size, chemistry, and mixing type",2012,"10.5194/acp-12-11833-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871272951&doi=10.5194%2facp-12-11833-2012&partnerID=40&md5=f68e3398bf18ddd7a8059a1c2143a328","A new aerosol chemical transport model, the Regional Air Quality Model 2 (RAQM2), was developed to simulate the Asian air quality. We implemented a simple version of a triple-moment modal aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super-μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized in which the aerosols were distributed into four categories: particles in the Aitken mode (ATK), soot-free particles in the accumulation mode (ACM), soot aggregates (AGR), and particles in the coarse mode (COR). The aerosol size distribution in each category is characterized by a single mode. The condensation, evaporation, and Brownian coagulations for each mode were solved dynamically. A regional-scale simulation (Δx Combining double low line 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. The modeled PM1/bulk ratios of the chemical components were consistent with observations, indicating that the simulated aerosol mixing types were consistent with those in nature. The non-sea-salt SO42- mixed with ATK + ACM was the largest at Hedo in summer, whereas the SOSO 42- was substantially mixed with AGR in the cold seasons. Ninety-eight percent of the modeled NO3- was mixed with sea salt at Hedo, whereas 53.7% of the NO3- was mixed with sea salt at Gosan, which is located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean accounts for the difference in the NO3- mixing type at the two sites. Because the aerosol mixing type alters the optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies. © Author(s) 2012."
"38863214100;55656837900;7102011703;","Radiative effects of ozone on the climate of a Snowball Earth",2012,"10.5194/cp-8-2019-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870990593&doi=10.5194%2fcp-8-2019-2012&partnerID=40&md5=579b9be696de79b5dbddb5fec3a62497","Some geochemical and geological evidence has been interpreted to suggest that the concentration of atmospheric oxygen was only 1-10 % of the present level in the time interval from 750 to 580 million years ago when several nearly global glaciations or Snowball Earth events occurred. This low concentration of oxygen would have been accompanied by a lower ozone concentration than exists at present. Since ozone is a greenhouse gas, this change in ozone concentration would alter surface temperature, and thereby could have an important influence on the climate of the Snowball Earth. Previous works that have focused either on initiation or deglaciation of the proposed Snowball Earth has not taken the radiative effects of ozone changes into account. We address this issue herein by performing a series of simulations using an atmospheric general circulation model with various ozone concentrations. Our simulation results demonstrate that, as ozone concentration is uniformly reduced from 100 % to 50 %, surface temperature decreases by approximately 0.8 K at the Equator, with the largest decreases located in the middle latitudes reaching as high as 2.5 K. When ozone concentration is reduced and its vertical and horizontal distribution is simultaneously modulated, surface temperature decreases by 0.4-1.0 K at the Equator and by 4-7 K in polar regions. These results here have uncertainties, depending on model parameterizations of cloud, surface snow albedo, and relevant feedback processes, while they are qualitatively consistent with radiative-convective model results that do not involve such parameterizations and feedbacks. These results suggest that ozone variations could have had a moderate impact on the climate during the Neoproterozoic glaciations. © Author(s) 2012."
"55512941600;57203053317;7003931528;","Effects of stratospheric sulfate aerosol geo-engineering on cirrus clouds",2012,"10.1029/2012GL053797","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870700615&doi=10.1029%2f2012GL053797&partnerID=40&md5=cdcf4d9612e0f0563ae1dfe1650eea2e","Cooling the Earth through the injection of sulphate into the stratosphere is one of the most discussed geo-engineering (GE) schemes. Stratospheric aerosols can sediment into the troposphere, modify the aerosol composition and thus might impact cirrus clouds. We use a global climate model with a physically based parametrization for cirrus clouds in order to investigate possible microphysical and dynamical effects. We find that enhanced stratospheric aerosol loadings as proposed by several GE approaches will likely lead to a reduced ice crystal nucleation rate and thus optically thinner cirrus clouds. These optically thinner cirrus clouds exert a strong negative cloud forcing in the long-wave which contributes by 60% to the overall net GE forcing. This shows that indirect effects of stratospheric aerosols on cirrus clouds may be important and need to be considered in order to estimate the maximum cooling derived from stratospheric GE. © 2012. American Geophysical Union. All Rights Reserved."
"36701462300;55686667100;","On the robustness of tropospheric adjustment in CMIP5 models",2012,"10.1029/2012GL054275","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871273100&doi=10.1029%2f2012GL054275&partnerID=40&md5=62ebd110e46e011339754074acf99130","Effective radiative forcing associated with the tropospheric adjustment (TA) caused by atmospheric CO<inf>2</inf> quadrupling (4×CO<inf>2</inf>) is quantified using fixed sea surface temperature experiments in CMIP5 models. Several features of TA in the tropics, partly related to weakening of the hydrological cycle, are found robust among the models: warming and drying of the free troposphere, near-surface moistening, strengthened stability in the lower troposphere, reduction in total cloud amount and shortwave cloud radiative effect (SWcld) over oceans. A positive SWcld change prevailing in the tropical subsidence regime gives rise to large uncertainty in total effective radiative forcing, and is regulated quantitatively by changes in relative humidity (RH) that measure cloud decrease in the lower troposphere. A robust tropospheric warming primarily explains the RH decrease in the lower troposphere, but the change in specific humidity is largely model-dependent, which contributes to the inter-model spread of TA. © 2012. American Geophysical Union. All Rights Reserved."
"15125055800;7004885872;6701378450;7006359574;55347084100;7403063262;","Strong evidence of surface tension reduction in microscopic aqueous droplets",2012,"10.1029/2012GL053706","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870676434&doi=10.1029%2f2012GL053706&partnerID=40&md5=a37fbb509066775440fd7270ff3ed8b8","The ability of airborne particles to take up water may be enhanced by surface-active components, but the importance of this effect is controversial because direct measurement of the surface tension of microscopic droplets has not been possible. Here we infer droplet surface tension from water uptake measurements of mixed organic-inorganic particles at relative humidities just below saturation (99.3-99.9%). The surface tension of droplets formed on particles composed of NaCl and-pinene ozonolysis products was reduced by 50-75%, but only when enough organic material was present to form a film on the droplet surface at least 0.8nm thick. This study suggests that if atmospheric particles are predominantly (≳80%) composed of surface-active material, their influence on cloud properties and thus climate could be enhanced, and their atmospheric lifetimes could be reduced. © 2012. American Geophysical Union. All Rights Reserved."
"7003974635;9240820800;7404395984;6507949344;7006338905;26643408200;57199451263;","Angular anisotropy of satellite observations of land surface temperature",2012,"10.1029/2012GL054059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870696984&doi=10.1029%2f2012GL054059&partnerID=40&md5=960ac4e3a6383f36bd3d4b789e6d9880","Satellite-based time series of land surface temperature (LST) have the potential to be an important tool to diagnose climate changes of the past several decades. Production of such a time series requires addressing several issues with using asynchronous satellite observations, including the diurnal cycle, clouds, and angular anisotropy. Here we evaluate the angular anisotropy of LST using one full year of simultaneous observations by two Geostationary Operational Environment Satellites, GOES-EAST and GOES-WEST, at the locations of five surface radiation (SURFRAD) stations. We develop a technique to convert directionally observed LST into direction-independent equivalent physical temperature of the land surface. The anisotropy model consists of an isotropic kernel, an emissivity kernel (LST dependence on viewing angle), and a solar kernel (effect of directional inhomogeneity of observed temperature). Application of this model reduces differences of LST observed from two satellites and between the satellites and surface ground truth-SURFRAD station observed LST. The techniques of angular adjustment and temporal interpolation of satellite observed LST open a path for blending together historical, current, and future observations of many geostationary and polar orbiters into a homogeneous multi-decadal data set for climate change research. © 2012. American Geophysical Union. All Rights Reserved."
"57196752024;","On the determination of the global cloud feedback from satellite measurements",2012,"10.5194/esd-3-97-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870577111&doi=10.5194%2fesd-3-97-2012&partnerID=40&md5=988680b1d1abb722350d7ff87849b3f4","A detailed analysis is presented in order to determine the sensitivity of the estimated short-term cloud feedback to choices of temperature datasets, sources of top-ofatmosphere (TOA) clear-sky radiative flux data, and temporal averaging. It is shown that the results of a previous analysis, which suggested a likely positive value for the short-term cloud feedback, depended upon combining all-sky radiative fluxes from NASA's Clouds and Earth's Radiant Energy System (CERES) with reanalysis clear-sky forecast fluxes when determining the cloud radiative forcing (CRF). These results are contradicted when ACRF is derived using both all-sky and clear-sky measurements from CERES over the same period. The differences between the radiative flux data sources are thus explored, along with the potential problems in each. The largest discrepancy is found when including the first two years (2000-2002), and the diagnosed cloud feedback from each method is sensitive to the time period over which the regressions are run. Overall, there is little correlation between the changes in the ACRF and surface temperatures on these timescales, suggesting that the net effect of clouds varies during this time period quite apart from global temperature changes. Given the large uncertainties generated from this method, the limited data over this period are insufficient to rule out either the positive feedback present in most climate models or a strong negative cloud feedback. ©Author(s) 2012."
"13403754000;7006614696;7007021059;7004379124;","Analysis of cloud properties associated with tropical convection in climate models and satellite data",2012,"10.2151/jmsj.2012-504","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870478967&doi=10.2151%2fjmsj.2012-504&partnerID=40&md5=573b1ea6a3eb37fd97902247ae44d23d","Cloud properties associated with tropical convection are analyzed for 11 models participating in Cloud Feedback Model Intercomparison Project Phase 1 (CFMIP1) in comparison with International Satellite Cloud Climatology Project (ISCCP) and other satellite observations and reanalysis datasets. Cloud properties are analyzed for different regimes of large-scale circulation field sorted by monthly mean of pressure coordinated vertical velocity at 500 hPa as an index of large-scale circulation. The present analysis is focused on warm oceanic regions with sea surface temperatures above 27°C where convection is active. The warm oceanic regions cover the vertical motion regimes ranging from strong ascent to weak descent. The ISCCP simulator outputs are used to evaluate cloud properties in the models. Cloud amount of optically thick high-clouds with optical thicknesses (τ) ≧ 3.6 and cloud-top pressure (CTP) ≦ 440 hPa is overestimated in the strong ascent regime while that of optically thin high-clouds with τ < 3.6 is underestimated for all the regimes. Cloud amount of optically thick low-clouds with CTP ≧ 680 hPa is overestimated in the weak vertical motion regime as well in some models. The relevance of cloud amount bias to cloud radiative effect bias is discussed. Observations show that optically thick clouds in the strong ascent regime often have tops around 180-310 hPa. In many models, the cloud top often reaches higher altitude compared to the observations. The tendency can especially be seen in the models adopting the moisture accumulation type scheme presumably due to excessively deep convection. Comparison of upward motion strength among the models and reanalyses suggests that cumulus parameterization performs better when entrainment rate is varied with large-scale environmental fields to reduce the convection deepness where necessary. © 2012, Meteorological Society of Japan."
"22958728400;7004559579;55976582900;35291927000;7005219614;","Impact of mineral dust on cloud formation in a Saharan outflow region",2012,"10.5194/acp-12-11383-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870568312&doi=10.5194%2facp-12-11383-2012&partnerID=40&md5=54c22e03aba28b1db9fb3d748908b633","We present a numerical modelling study investigating the impact of mineral dust on cloud formation over the Eastern Mediterranean for two case studies: (i) 25 September 2008 and (ii) 28/29 January 2003. In both cases dust plumes crossed the Mediterranean and interacted with clouds forming along frontal systems. For our investigation we used the fully online coupled model WRF-chem. <br><br> The results show that increased aerosol concentrations due to the presence of mineral dust can enhance the formation of ice crystals. This leads to slight shifts of the spatial and temporal precipitation patterns compared to scenarios where dust was not considered to act as ice nuclei. However, the total amount of precipitation did not change significantly. The only exception occurred when dust entered into an area of orographic ascent, causing glaciation of the clouds, leading to a local enhancement of rainfall. The impact of dust particles acting as giant cloud condensation nuclei on precipitation formation was found to be small. Based on our simulations the contribution of dust to the CCN population is potentially significant only for warm phase clouds. Nevertheless, the dust-induced differences in the microphysical structure of the clouds can contribute to a significant radiative forcing, which is important from a climate perspective. © Author(s) 2012. CC Attribution 3.0 License."
"57207200537;9535707500;35494005000;8058662600;7003728829;","GEWEX Cloud System Study (GCSS) cirrus cloud working group: Development of an observation-based case study for model evaluation",2012,"10.5194/gmd-5-829-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870463028&doi=10.5194%2fgmd-5-829-2012&partnerID=40&md5=1c4ee434a0152879c53d3ff4c042a1d9","The GCSS working group on cirrus focuses on an inter-comparison of model simulations ranging from very detailed microphysical and dynamical models through to general circulation models (GCMs). The past GCSS cirrus cloud inter-comparison highlighted the wide range in modelling results that was a surprise to the modelling community. That inter-comparison was idealised and, therefore, a key issue was that it did not benefit from observations to help distinguish between model performances. In this work, we aim to address this key issue by developing an observationally based case study to be used for the GCSS cirrus modelling inter-comparison study. We focused on developing a case that had sufficient observations with which to evaluate models, to help identify which models in the inter-comparison are performing well and highlight areas for model development. Furthermore, it will provide a base case for future model comparisons or testing of new or updated models. This paper outlines the modelling case development and the inter-comparison results will be presented in a follow-on paper. The case was based on the 9 March 2000 Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) during an intensive observation period (IOP). The case was developed utilising various observations including ARM SGP remote sensing including the MilliMeter Cloud Radar (MMCR), radiometers, radiosondes, air-craft observations, satellite observations, objective analysis and complemented with results from the Rapid Update Cycle (RUC) model as well as bespoke gravity wave simulations used to provide the best estimate for large scale forcing. The retrievals of ice water content, ice number concentration and fall velocity provide several constraints to evaluate model performances. Initial testing of the case has been reported using the UK Met Office Large Eddy Simulation Model (LEM) which suggests the case is appropriate for the model inter-comparison study. To our knowledge, this case offers the most detailed case study for cirrus comparison available and we anticipate this will offer significant benefits over past comparisons which have mostly been loosely based on observations. © Author(s)2012."
"7003696273;55504372600;6602493816;31267510200;36052878000;7102963655;8088667200;8088667300;7004647945;56572656100;9535769800;7401945370;9233214000;16643314500;","A multi-instrument comparison of integrated water vapour measurements at a high latitude site",2012,"10.5194/acp-12-10925-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870173719&doi=10.5194%2facp-12-10925-2012&partnerID=40&md5=0d8701768fab6c93ba9655f348608d70","We compare measurements of integrated water vapour (IWV) over a subarctic site (Kiruna, Northern Sweden) from five different sensors and retrieval Methods: Radiosondes, Global Positioning System (GPS), ground-based Fourier-transform infrared (FTIR) spectrometer, ground-based microwave radiometer, and satellite-based microwave radiometer (AMSU-B). Additionally, we compare also to ERA-Interim model reanalysis data. GPS-based IWV data have the highest temporal coverage and resolution and are chosen as reference data set. All datasets agree reasonably well, but the ground-based microwave instrument only if the data are cloud-filtered. We also address two issues that are general for such intercomparison studies, the impact of different lower altitude limits for the IWV integration, and the impact of representativeness error. We develop Methods for correcting for the former, and estimating the random error contribution of the latter. A literature survey reveals that reported systematic differences between different techniques are study-dependent and show no overall consistent pattern. Further improving the absolute accuracy of IWV measurements and providing climate-quality time series therefore remain challenging problems. © 2012 Author(s)."
"55613774900;6701410329;7006206130;","Cloud cover diurnal cycles in satellite data and regional climate model simulations",2012,"10.1127/0941-2948/2012/0423","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874617840&doi=10.1127%2f0941-2948%2f2012%2f0423&partnerID=40&md5=07019113a28d81c7d715fe8d4dc289d3","The amount and diurnal cycle of cloud cover play an important role in the energy and water cycle of the earth-atmosphere system and influence the radiation budget of the earth. Due to its importance and the challenging nature of its quantification, cloud cover is considered the biggest uncertainty factor in climate modeling. There is a clear need for reliable cloud datasets suitable for climate model evaluation studies. This study analyzes two datasets of cloud cover and its diurnal cycle derived from satellite observations by the International Satellite Cloud Climatology Project (ISCCP) and by EUMETSAT's Satellite Application Facility on Climate Monitoring (CM SAF) in Africa and Europe. Two regions, Europe and the subtropical southern Atlantic Ocean, were identified as offering distinct cloud cover diurnal cycles reasonably observed by both satellite datasets. In these regions, simulations by the regional climate model COSMO-CLM (CCLM) were evaluated in terms of cloud cover and its diurnal cycle during the time period of 1990 to 2007. Results show that the satellite derived cloud diurnal cycles largely agree, while discrepancies occur under extreme conditions like in the Sahara region. The CCLM is able to simulate the diurnal cycle observed consistently in the two satellite datasets in the South-Atlantic ocean, but not in Europe. CCLM misses the afternoon maximum cloud cover in Summer in Europe, which implies deficiencies in the parameterization of convection and in the treatment of surface-atmosphere interactions. The simulation of the diurnal cycle of the more stratiform cloud cover over the subtropical Atlantic was satisfactory in CCLM. © 2012 by Gebrüder Borntraeger."
"7501855361;16637291100;55977336000;7203059095;7005311892;7003415852;","Arctic climate variability and trends from satellite observations",2012,"10.1155/2012/505613","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874903940&doi=10.1155%2f2012%2f505613&partnerID=40&md5=a3650397043fc7ee3dd3322b3aba1332","Arctic climate has been changing rapidly since the 1980s. This work shows distinctly different patterns of change in winter, spring, and summer for cloud fraction and surface temperature. Satellite observations over 1982-2004 have shown that the Arctic has warmed up and become cloudier in spring and summer, but cooled down and become less cloudy in winter. The annual mean surface temperature has increased at a rate of 0.34°C per decade. The decadal rates of cloud fraction trends are -3.4%, 2.3%, and 0.5% in winter, spring, and summer, respectively. Correspondingly, annually averaged surface albedo has decreased at a decadal rate of -3.2%. On the annual average, the trend of cloud forcing at the surface is -2.11 W/m2 per decade, indicating a damping effect on the surface warming by clouds. The decreasing sea ice albedo and surface warming tend to modulate cloud radiative cooling effect in spring and summer. Arctic sea ice has also declined substantially with decadal rates of -8%, -5%, and -15% in sea ice extent, thickness, and volume, respectively. Significant correlations between surface temperature anomalies and climate indices, especially the Arctic Oscillation (AO) index, exist over some areas, implying linkages between global climate change and Arctic climate change. © 2012 Xuanji Wang et al."
"15848674200;7004885872;7005310521;6602514643;39762774100;","Coupling a new turbulence parametrization to RegCM adds realistic stratocumulus clouds",2012,"10.5194/gmd-5-989-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878109233&doi=10.5194%2fgmd-5-989-2012&partnerID=40&md5=cd7e362aa32007b75fa4f24196b3fcc4","To model stratocumulus clouds in the regional climate model, RegCM4.1, the University of Washington (UW) turbulence parametrization has been coupled to RegCM. We describe improvements in RegCM's coastal and near-coastal climatology, including improvements in the representation of stratiform clouds. By comparing output from a 27-yr (1982-2009) simulation of the climate of western North America to a wide variety of observational data (station data, satellite data, and aircraft in situ data), we show the following: (1) RegCM-UW is appropriate for use in general regional climate studies, and (2) the UW model distinctly improves the representation of the marine boundary layer in RegCM. These model-data comparisons also show that RegCM-UW has a slight cold bias, a (wet) precipitation bias, a systematic low bias in the vertically-integrated liquid water content near the coast, and a high bias in the fractional cloud coverage. The model represents well the diurnal, monthly, and interannual variability in low clouds. These results show RegCM-UW as a nascent mesoscale stratocumulus model that is appropriate for stratocumulus investigations at scales ranging from hourly to decadal. The source code for RegCM-UW is publicly available, under the GNU license, through the International Centre for Theoretical Physics. © Author(s) 2012."
"55541379500;23970271800;15726335100;57207603330;","Evaluation of the shortwave cloud radiative effect over the ocean by use of ship and satellite observations",2012,"10.5194/acp-12-12243-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871725714&doi=10.5194%2facp-12-12243-2012&partnerID=40&md5=cac51e74f797030cc51a9886b03ce6cf","In this study the shortwave cloud radiative effect (SWCRE) over ocean calculated by the ECHAM 5 climate model is evaluated for the cloud property input derived from ship based measurements and satellite based estimates and compared to ship based radiation measurements. The ship observations yield cloud fraction, liquid water path from a microwave radiometer, cloud bottom height as well as temperature and humidity profiles from radiosonde ascents. Level-2 products of the Satellite Application Facility on Climate Monitoring (CM∼SAF) from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) have been used to characterize clouds. Within a closure study six different experiments have been defined to find the optimal set of measurements to calculate downward shortwave radiation (DSR) and the SWCRE from the model, and their results have been evaluated under seven different synoptic situations. Four of these experiments are defined to investigate the advantage of including the satellite-based cloud droplet effective radius as additional cloud property. The modeled SWCRE based on satellite retrieved cloud properties has a comparable accuracy to the modeled SWCRE based on ship data. For several cases, an improvement through introducing the satellite-based estimate of effective radius as additional information to the ship based data was found. Due to their different measuring characteristics, however, each dataset shows best results for different atmospheric conditions. © 2012 Author(s)."
"25637373000;15044268700;7801492228;7005814217;7102976560;","Interannual tropospheric aerosol variability in the late twentieth century and its impact on tropical atlantic and west african climate by direct and semidirect effects",2012,"10.1175/JCLI-D-12-00029.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871757059&doi=10.1175%2fJCLI-D-12-00029.1&partnerID=40&md5=0d844ce703f7a212d88652749c0e1196","A new high-resolution global tropospheric aerosol dataset with monthly resolution is generated using version 4 of the Community Atmosphere Model (CAM4) coupled to a bulk aerosol model and forced with recent estimates of surface emissions for the period 1961-2000 to identify tropospheric aerosol-induced interannual climate variations. The surface emissions dataset is constructed from phase 5 of the Coupled Model Intercomparison Project (CMIP5) decadal-resolution surface emissions dataset to include reanalysis of tropospheric chemical composition [40-yr Reanalysis of Tropospheric Chemical Composition (RETRO)] wildfire monthly emissions data. A four-member ensemble run is conducted using the spectral configuration of CAM4, forced with the new tropospheric aerosol dataset and prescribed with observed sea surface temperature, sea ice, and greenhouse gases. CAM4 only simulates the direct and semidirect effects of aerosols on the climate. The simulations reveal that variations in tropospheric aerosol levels can induce significant regional climate variability on the interannual time scales. Regression analyses over tropical Atlantic and Africa suggest that increasing dust aerosols can cool the North African landmass and shift convection southward fromWest Africa into the Gulf of Guinea in the spring season. Further, it is found that carbonaceous aerosols emanating from the southwestern African savannas can significantly cool the region and increase the marine stratocumulus cloud cover over the southeast tropical Atlantic Ocean by aerosol-induced diabatic heating of the free troposphere above the low clouds. Experiments conducted with CAM4 coupled to a slab ocean model suggest that present-day aerosols can cool the tropical North Atlantic and shift the intertropical convergence zone southward and can reduce the ocean mixed layer temperature beneath the increasedmarine stratocumulus clouds in the southeastern tropicalAtlantic. © 2012 American Meteorological Society."
"35227762400;7006246996;7202252296;6701333444;","Cloud properties over the North Slope of Alaska: Identifying the prevailing meteorological regimes",2012,"10.1175/JCLI-D-11-00636.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871779810&doi=10.1175%2fJCLI-D-11-00636.1&partnerID=40&md5=fc654612f16640ec211afa7d6239ff33","Long time series of Arctic atmospheric measurements are assembled into meteorological categories that can serve as test cases for climate model evaluation. The meteorological categories are established by applying an objective k-means clustering algorithm to 11 years of standard surface-meteorological observations collected from 1 January 2000 to 31 December 2010 at the North Slope of Alaska (NSA) site of the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM). Four meteorological categories emerge. These meteorological categories constitute the first classification by meteorological regime of a long time series of Arctic meteorological conditions. The synoptic-scale patterns associated with each category, which include well-known synoptic features such as the Aleutian low and Beaufort Sea high, are used to explain the conditions at the NSA site. Cloud properties, which are not used as inputs to the k-means clustering, are found to differ significantly between the regimes and are also well explained by the synopticscale influences in each regime. Since the data available at the ARM NSA site include a wealth of cloud observations, this classification is well suited for model-observation comparison studies. Each category comprises an ensemble of test cases covering a representative range in variables describing atmospheric structure, moisture content, and cloud properties. This classification is offered as a complement to standard case-study evaluation of climate model parameterizations, in which models are compared against limited realizations of the Earth-atmosphere system (e.g., from detailed aircraft measurements). © 2012 American Meteorological Society."
"6603453147;57206332144;","Analysis of co-located MODIS and CALIPSO observations near clouds",2012,"10.5194/amt-5-389-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866615047&doi=10.5194%2famt-5-389-2012&partnerID=40&md5=cdb22ccd8075cd00d6d38fd9d075248c","This paper aims at helping synergistic studies in combining data from different satellites for gaining new insights into two critical yet poorly understood aspects of anthropogenic climate change, aerosol-cloud interactions and aerosol radiative effects. In particular, the paper examines the way cloud information from the MODIS (MODerate resolution Imaging Spectroradiometer) imager can refine our perceptions based on CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar measurements about the systematic aerosol changes that occur near clouds. The statistical analysis of a yearlong dataset of co-located global maritime observations from the Aqua and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellites reveals that MODIS's multispectral imaging ability can greatly help the interpretation of CALIOP observations. The results show that imagers on Aqua and CALIPSO yield very similar pictures, and that the discrepancies-due mainly to wind drift and differences in view angle-do not significantly hinder aerosol measurements near clouds. By detecting clouds outside the CALIOP track, MODIS reveals that clouds are usually closer to clear areas than CALIOP data alone would suggest. The paper finds statistical relationships between the distances to clouds in MODIS and CALIOP data, and proposes a rescaling approach to statistically account for the impact of clouds outside the CALIOP track even when MODIS cannot reliably detect low clouds, for example at night or over sea ice. Finally, the results show that the typical distance to clouds depends on both cloud coverage and cloud type, and accordingly varies with location and season. In maritime areas perceived cloud free, the global median distance to clouds below 3 km altitude is in the 4-5 km range. © 2012 Author(s)."
"38762392200;9275665400;55717074000;7006270084;55607020000;7003666669;","Indirect radiative forcing by ion-mediated nucleation of aerosol",2012,"10.5194/acp-12-11451-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877334135&doi=10.5194%2facp-12-11451-2012&partnerID=40&md5=36b47727a1133ca9dc7447f3f85c3464","A clear understanding of particle formation mechanisms is critical for assessing aerosol indirect radiative forcing and associated climate feedback processes. Recent studies reveal the importance of ion-mediated nucleation (IMN) in generating new particles and cloud condensation nuclei (CCN) in the atmosphere. Here we implement the IMN scheme into the Community Atmosphere Model version 5 (CAM5). Our simulations show that, compared to globally averaged results based on H2SO4-H2O binary homogeneous nucleation (BHN), the presence of ionization (i.e., IMN) halves H2SO4 column burden, but increases the column integrated nucleation rate by around one order of magnitude, total particle number burden by a factor of ∼3, CCN burden by ∼10% (at 0.2% supersaturation) to 65% (at 1.0% supersaturation), and cloud droplet number burden by ∼18%. Compared to BHN, IMN increases cloud liquid water path by 7.5%, decreases precipitation by 1.1%, and increases total cloud cover by 1.9%. This leads to an increase of total shortwave cloud radiative forcing (SWCF) by 3.67 W m-2 (more negative) and longwave cloud forcing by 1.78 W m-2 (more positive), with large spatial variations. The effect of ionization on SWCF derived from this study (3.67 W m-2) is a factor of ∼3 higher that of a previous study (1.15 W m-2) based on a different ion nucleation scheme and climate model. Based on the present CAM5 simulation, the 5-yr mean impacts of solar cycle induced changes in ionization rates on CCN and cloud forcing are small (∼-0.02 W m-2) but have larger inter-annual (from -0.18 to 0.17 W m-2) and spatial variations. © Author(s) 2012. CC Attribution 3.0 License."
"16246205000;55738957800;9249239700;","Evaluation of microphysics parameterization for convective clouds in the NCAR community atmosphere model CAM5",2012,"10.1175/JCLI-D-11-00563.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865463788&doi=10.1175%2fJCLI-D-11-00563.1&partnerID=40&md5=be76f34957ef3f957ce31b36d0f5dc41","A physically based two-moment microphysics parameterization scheme for convective clouds is implemented in the NCAR Community Atmosphere Model version 5 (CAM5) to improve the representation of convective clouds and their interaction with large-scale clouds and aerosols. The explicit treatment of mass mixing ratio and number concentration of cloud and precipitation particles enables the scheme to account for the impact of aerosols on convection. The scheme is linked to aerosols through cloud droplet activation and ice nucleation processes and to stratiform cloud parameterization through convective detrainment of cloud liquid/ice water content (LWC/IWC) and droplet/crystal number concentration (DNC/CNC). A 5-yr simulation with the new convective microphysics scheme shows that both cloud LWC/IWC and DNC/CNC are in good agreement with observations, indicating the scheme describes microphysical processes in convection well. Moreover, the microphysics scheme is able to represent the aerosol effects on convective clouds such as the suppression of warm rain formation and enhancement of freezing when aerosol loading is increased. With more realistic simulations of convective cloud microphysical properties and their detrainment, the mid- and low-level cloud fraction is increased significantly over the ITCZ-southern Pacific convergence zone (SPCZ) and subtropical oceans, making it much closer to the observations. Correspondingly, the serious negative bias in cloud liquid water path over subtropical oceans observed in the standard CAM5 is reduced markedly. The large-scale precipitation is increased and precipitation distribution is improved as well. The long-standing precipitation bias in the western Pacific is significantly alleviated because of microphysics- thermodynamics feedbacks. © 2012 American Meteorological Society."
"35221791100;55887849100;35422119400;7007078966;","A cosmic ray-climate link and cloud observations",2012,"10.1051/swsc/2012018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885586118&doi=10.1051%2fswsc%2f2012018&partnerID=40&md5=5bfa598a99371831a969290c95612672","Despite over 35 years of constant satellite-based measurements of cloud, reliable evidence of a long-hypothesized link between changes in solar activity and Earth's cloud cover remains elusive. This work examines evidence of a cosmic ray cloud link from a range of sources, including satellite-based cloud measurements and long-term ground-based climatological measurements. The satellite-based studies can be divided into two categories: (1) monthly to decadal timescale analysis and (2) daily timescale epoch-superpositional (composite) analysis. The latter analyses frequently focus on sudden high-magnitude reductions in the cosmic ray flux known as Forbush decrease events. At present, two long-term independent global satellite cloud datasets are available (ISCCP and MODIS). Although the differences between them are considerable, neither shows evidence of a solar-cloud link at either long or short timescales. Furthermore, reports of observed correlations between solar activity and cloud over the 1983-1995 period are attributed to the chance agreement between solar changes and artificially induced cloud trends. It is possible that the satellite cloud datasets and analysis methods may simply be too insensitive to detect a small solar signal. Evidence from ground-based studies suggests that some weak but statistically significant cosmic ray-cloud relationships may exist at regional scales, involving mechanisms related to the global electric circuit. However, a poor understanding of these mechanisms and their effects on cloud makes the net impacts of such links uncertain. Regardless of this, it is clear that there is no robust evidence of a widespread link between the cosmic ray flux and clouds. © Owned by the authors, Published by EDP Sciences 2012."
"26428178700;57207603330;","Radiative budget and cloud radiative effect over the Atlantic from ship-based observations",2012,"10.5194/amt-5-2391-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871792895&doi=10.5194%2famt-5-2391-2012&partnerID=40&md5=62d84eb7086aa999ba4733b2d2738e76","The aim of this study is to determine cloud-type resolved cloud radiative budgets and cloud radiative effects from surface measurements of broadband radiative fluxes over the Atlantic Ocean. Furthermore, based on simultaneous observations of the state of the cloudy atmosphere, a radiative closure study has been performed by means of the ECHAM5 single column model in order to identify the model's ability to realistically reproduce the effects of clouds on the climate system. An extensive database of radiative and atmospheric measurements has been established along five meridional cruises of the German research icebreaker. Besides pyranometer and pyrgeometer for downward broadband solar and thermal radiative fluxes, a sky imager and a microwave radiometer have been utilized to determine cloud fraction and cloud type on the one hand and temperature and humidity profiles as well as liquid water path for warm non-precipitating clouds on the other hand. Averaged over all cruise tracks, we obtain a total net (solar + thermal) radiative flux of 144 W m-2 that is dominated by the solar component. In general, the solar contribution is large for cirrus clouds and small for stratus clouds. No significant meridional dependencies were found for the surface radiation budgets and cloud effects. The strongest surface longwave cloud effects were shown in the presence of low level clouds. Clouds with a high optical density induce strong negative solar radiative effects under high solar altitudes. The mean surface net cloud radiative effect is-33 W m-2. For the purpose of quickly estimating the mean surface longwave, shortwave and net cloud effects in moderate, subtropical and tropical climate regimes, a new parameterisation was created, considering the total cloud amount and the solar zenith angle. The ECHAM5 single column model provides a surface net cloud effect that is more cooling by 17 W m-2 compared to the radiation observations. This overestimation in solar cooling is mostly caused by the shortwave impact of convective clouds. The latter show a large overestimation in solar cooling of up to 114 W m -2. Mean cloud radiative effects of cirrus and stratus clouds were simulated close to the observations. © 2012 Author(s)."
"7003696273;6505856601;36828400800;36052878000;16643314500;24460392200;35778419900;23466744600;56260361400;6603868770;7102001105;55915206300;57210222001;","Observing ice clouds in the submillimeter spectral range: The CloudIce mission proposal for ESA's Earth Explorer 8",2012,"10.5194/amt-5-1529-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865781709&doi=10.5194%2famt-5-1529-2012&partnerID=40&md5=631ec0cca9df6163863079e825e8abec","Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized ""essential climate variable"" ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals. © 2012 Author(s)."
"25227357000;7102018821;7404829395;56537463000;55717074000;","Dust aerosol impact on North Africa climate: A GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data",2012,"10.5194/acp-12-1667-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880592785&doi=10.5194%2facp-12-1667-2012&partnerID=40&md5=cd93ba810dc85c9828e35ac2798652da","The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM) developed at the University of California, Los Angeles (UCLA). The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA) generally increase with increasing aerosol optical depth. When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced in the case for an ice water path (IWP) larger than 20 g m2. The magnitude of the reduction increases with IWP. AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at TOA over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. Adding the aerosol direct effect into the model simulation reduces the precipitation in the normal rainfall band over North Africa, where precipitation is shifted to the south and the northeast produced by the absorption of sunlight and the subsequent heating of the air column by dust particles. As a result, rainfall is drawn further inland to the northeast. This study represents the first attempt to quantify the climate impact of the aerosol indirect effect using a GCM in connection with A-Train satellite data. The parameterization for the aerosol first indirect effect developed in this study can be readily employed for application to other GCMs. © 2012 Author(s)."
"57196489468;7102976560;56520921400;","Global transport of passive tracers in conventional and superparameterized Climate models: Evaluation of multi-scale methods",2012,"10.1029/2012MS000206","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868372226&doi=10.1029%2f2012MS000206&partnerID=40&md5=ebed627b36e4f50cbba4572f29f1934d","[1] The global transport of the surface-emitted short-lived passive tracers radon and methyl iodide is simulated in a cloud-resolving Global Climate Model (GCM) for the first time and compared against simulations with a conventional GCM in which cloud processes are not resolved. Both models are operated in chemical transport mode in which the large scale flow is set to observationally derived dynamic and thermodynamic fields from a meteorological reanalysis. Simulated vertical profiles of tracers concentrations from both models are compared with profiles observed in situ. The comparisons suggest that the cloud-resolving GCM is, to a small degree, better than the conventional GCM in reproducing the vertical gradients and hence the convective entrainment and detrainment of passive tracers. Contrasting only simulated climatological maps of tracers concentrations from the two models, we find consistent and appreciable relative differences that create a quadrupole pattern in the vertical direction. Relative to the conventional GCM, the tracer concentrations from the cloud-resolving GCM results are depleted from the surface to 1 km and from 4 to 12 Km and enriched from 1 to 4 km and above 12 km. This might have important implications for climate and atmospheric chemistry simulations but require further investigations. © 2012. American Geophysical Union. All Rights Reserved."
"9246517900;7003875148;7801532509;24332905600;7102171439;6603126554;","Influence of the Arctic Oscillation on the vertical distribution of clouds as observed by the A-Train constellation of satellites",2012,"10.5194/acp-12-10535-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871887841&doi=10.5194%2facp-12-10535-2012&partnerID=40&md5=f768315729318054c3db06a749c8d9f7","The main purpose of this study is to investigate the influence of the Arctic Oscillation (AO), the dominant mode of natural variability over the northerly high latitudes, on the spatial (horizontal and vertical) distribution of clouds in the Arctic. To that end, we use a suite of sensors onboard NASA's A-Train satellites that provide accurate observations of the distribution of clouds along with information on atmospheric thermodynamics. Data from three independent sensors are used (AQUA-AIRS, CALIOP-CALIPSO and CPR-CloudSat) covering two time periods (winter half years, November through March, of 2002-2011 and 2006-2011, respectively) along with data from the ERA-Interim reanalysis. We show that the zonal vertical distribution of cloud fraction anomalies averaged over 67-82 N to a first approximation follows a dipole structure (referred to as ""Greenland cloud dipole anomaly"", GCDA), such that during the positive phase of the AO, positive and negative cloud anomalies are observed eastwards and westward of Greenland respectively, while the opposite is true for the negative phase of AO. By investigating the concurrent meteorological conditions (temperature, humidity and winds), we show that differences in the meridional energy and moisture transport during the positive and negative phases of the AO and the associated thermodynamics are responsible for the conditions that are conducive for the formation of this dipole structure. All three satellite sensors broadly observe this large-scale GCDA despite differences in their sensitivities, spatio-temporal and vertical resolutions, and the available lengths of data records, indicating the robustness of the results. The present study also provides a compelling case to carry out process-based evaluation of global and regional climate models. © Author(s) 2012. CC Attribution 3.0 License."
"57044397100;35069282600;14018610000;16308514000;7202899330;7201888941;57196499374;","Occurrence of lower cloud albedo in ship tracks",2012,"10.5194/acp-12-8223-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878709900&doi=10.5194%2facp-12-8223-2012&partnerID=40&md5=d78b4b1a51a3754946c64ad1cbaa94ec","The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. Ship tracks, quasi-linear cloud features prevalent in oceanic regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease) and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air), nearly 30% of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming. © Author(s) 2012."
"15841308100;6603944055;7201903057;7005123759;7401636555;57200082194;","Remote sensing of tropical ecosystems: Atmospheric correction and cloud masking matter",2012,"10.1016/j.rse.2012.08.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867906798&doi=10.1016%2fj.rse.2012.08.035&partnerID=40&md5=73e8d93e4ee576d876872b0b29dd9350","Tropical rainforests are significant contributors to the global cycles of energy, water and carbon. As a result, monitoring of the vegetation status over regions such as AmazÔnia has been a long standing interest of Earth scientists trying to determine the effect of climate change and anthropogenic disturbance on the tropical ecosystems and its feedback on the Earth's climate. Satellite-based remote sensing is the only practical approach for observing the vegetation dynamics of regions like the Amazon over useful spatial and temporal scales, but recent years have seen much controversy over satellite-derived vegetation states in AmazÔnia, with studies predicting opposite feedbacks depending on data processing technique and interpretation. Recent results suggest that some of this uncertainty could stem from a lack of quality in atmospheric correction and cloud screening. In this paper, we assess these uncertainties by comparing the current standard surface reflectance products (MYD09, MYD09GA) and derived composites (MYD09A1, MCD43A4 and MYD13A2 - Vegetation Index) from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite to results obtained from the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. MAIAC uses a new cloud screening technique, and novel aerosol retrieval and atmospheric correction procedures which are based on time-series and spatial analyses. Our results show considerable improvements of MAIAC processed surface reflectance compared to MYD09/MYD13 with noise levels reduced by a factor of up to 10. Uncertainties in the current MODIS surface reflectance product were mainly due to residual cloud and aerosol contamination which affected the Normalized Difference Vegetation Index (NDVI): During the wet season, with cloud cover ranging between 90% and 99%, conventionally processed NDVI was significantly depressed due to undetected clouds. A smaller reduction in NDVI due to increased aerosol levels was observed during the dry season, with an inverse dependence of NDVI on aerosol optical thickness (AOT). NDVI observations processed with MAIAC showed highly reproducible and stable inter-annual patterns with little or no dependence on cloud cover, and no significant dependence on AOT (p< 0.05). In addition to a better detection of cloudy pixels, MAIAC obtained about 20-80% more cloud free pixels, depending on season, a considerable amount for land analysis given the very high cloud cover (75-99%) observed at any given time in the area. We conclude that a new generation of atmospheric correction algorithms, such as MAIAC, can help to dramatically improve vegetation estimates over tropical rain forest, ultimately leading to reduced uncertainties in satellite-derived vegetation products globally. © 2012 Elsevier Inc."
"7203047936;57204041349;7401892219;","Impacts of ice clouds on gps radio occultation measurements",2012,"10.1175/JAS-D-11-0199.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871969675&doi=10.1175%2fJAS-D-11-0199.1&partnerID=40&md5=931cd4e1b35f1033ce2062cead67e33a","Mathematical solutions accounting for the effects of liquid and ice clouds on the propagation of the GPS radio signals are first derived. The percentage contribution of ice water content (IWC) to the total refractivity increases linearly with the amount of IWC at a rate of 0.6 (g m23)21.Measurements of coincident profiles of IWC from CloudSat in deep convection during 2007-10 are then used for estimating the ice-scattering effects on GPS radio occultation (RO) measurements from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC). The percentage contribution of IWC to the total refractivity from CloudSat measurements is consistent with the theoretical model, reaching about 0.6% at 1 g m23 IWC. The GPSROrefractivity observations in deep convective clouds are found to be systematically greater than the refractivity calculated from the ECMWF analysis. The fractional N bias (GPS minus ECMWF) can be as high as 1.8% within deep convective clouds. Compared with ECMWF analysis, the GPS RO retrievals have a negative temperature bias and a positive water vapor bias, which is consistent with a positive bias in refractivity. The relative humidity calculated from GPS retrievals is usually as high as 80%-90% right above the 08C temperature level in deep convection and is about 15%-30% higher than the ECMWF analysis. The majority of the data points in deep convection are located on the negative side of temperature differences and the positive side of relative humidity differences between GPS RO retrievals and ECMWF analysis.© 2012 American Meteorological Society."
"55448015500;6603273568;56104525000;12801073500;7201471897;55973596200;16679661100;13403535300;57202733911;","Reconstruction of southeast Tibetan Plateau summer climate using tree ring δ18O: Moisture variability over the past two centuries",2012,"10.5194/cp-8-205-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871880826&doi=10.5194%2fcp-8-205-2012&partnerID=40&md5=e34c1646d123575dae727663a94b8cf1","A tree-ring δ18O chronology of Linzhi spruce, spanning from AD 1781 to 2005, was developed in Bomi, Southeast Tibetan Plateau (TP). During the period with instrumental data (AD 1961-2005), this record is strongly correlated with regional CRU (Climate Research Unit) summer cloud data, which is supported by a precipitation δ18O simulation conducted with the isotope-enabled atmospheric general circulation model LMDZiso. A reconstruction of a regional summer cloud index, based upon the empirical relationship between cloud and diurnal temperature range, was therefore achieved. This index reflects regional moisture variability in the past 225 yr. The climate appears drier and more stable in the 20th century than previously. The drying trend in late 19th century of our reconstruction is consistent with a decrease in the TP glacier accumulation recorded in ice cores. An exceptional dry decade is documented in the 1810s, possibly related to the impact of repeated volcanic eruptions on monsoon flow.© Author(s) 2012."
"53163111700;6506914844;25228122900;35552588700;","Numerical study of the impact of the changes in the tropospheric temperature profile on the microphysics, dynamics and precipitation of mid-latitude summer continental convective clouds",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871638027&partnerID=40&md5=f39913824d5f9e7395bec3380ea1b8a6","This paper investigates the effect of the expected changes of tropospheric temperature profile on the dynamical and microphysical characteristics of individual summertime convective storms and on the processes of precipitation development in these storms. Two dynamically different clouds (a 'big' and a 'small' one) were simulated with the Regional Atmospheric Modeling System (RAMS v6.0). The differences between simulations of the clouds, developed in a present-day and in a modified environment are discussed. Macro- and microphysical evolution is examined in detail, and the changes in precipitation intensity and total rainfall volume are explained physically as a consequence of the temperature increase in the upper troposphere. Results show that the warming leads to a decrease of precipitation in the 'small' cloud case, while in the 'big' cloud case, warming leads to the increase of precipitation. The detailed analysis reveals that the main reason for the opposite direction of the impact of the projected tropospheric changes on different sized clouds lies in the ice phase evolution."
"7202162685;6701324864;","Assessment of some parameterizations of heterogeneous ice nucleation in cloud and climate models",2012,"10.5194/acp-12-1151-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867594480&doi=10.5194%2facp-12-1151-2012&partnerID=40&md5=bf23863ffe1efda90ec6ce4e5c87c6e6","Several different types of parameterization of heterogeneous ice nucleation for cloud and climate models have been developed over the past decades, ranging from empirically-derived expressions to parameterizations of ice crystal nucleation rates derived from theory, including the parameterization developed by the authors that includes simultaneous dependence on the temperature and saturation ratio, hereafter referred to as KC. Parameterizations schemes that address the deliquescence-heterogeneous-freezing (DHetF), which combines the modes of condensation freezing and immersion freezing, are assessed here in the context of thermodynamic constraints, laboratory measurements, and recent field measurements. It is shown that empirical schemes depending only on the ice saturation ratio or only on temperature can produce reasonable crystal concentrations, but ice crystal nucleation is thermodynamically prohibited in certain regions of the temperature-saturation ratio phase space. Some recent empirical parameterizations yield clouds that are almost entire liquid at temperatures as low as -35 C in contrast to cloud climatology. Reasonable performance of the KC ice nucleation scheme is demonstrated by comparison with numerous data from several recent field campaigns, laboratory data, climatology of cloud phase-state. Several mis-applications of the KC parameterization that appeared recently in the literature are described and corrected. It is emphasized here that a correct application of the KC scheme requires integration of the individual nucleation rates over the measured size spectrum of ice nuclei that represent a fraction or several fractions of the environmental aerosol with specific ice nucleation properties. The concentration in these fractions can be substantially smaller than that of the total aerosol, but greater than the crystal concentration measured by an experimental device. Simulations with temperature-dependent active site area or with several IN fractions having different properties show that ice nucleation in the KC scheme occurs in a wide temperature range of 10-20 C, which depends on IN properties. Simulation with a spectral bin model and correct application of KC scheme adequately describes ice nucleation via the DHetF mode and yields crystal concentrations and phase state close to those measured in the single-layer stratocumulus cloud observed in the Mixed Phase Arctic Cloud Experiment (MPACE). An assessment of some deficiencies in current parcel modeling methods and cloud chamber observations and their impact on parameterization development and evaluation is provided. © 2012 Author(s). CC Attribution 3.0 License."
"8247122100;35584010200;6506537159;22975069200;37099564300;7005035762;","Observations of stratocumulus clouds and their effect on the eastern pacific surface heat budget along 20°S",2012,"10.1175/JCLI-D-11-00618.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871886156&doi=10.1175%2fJCLI-D-11-00618.1&partnerID=40&md5=0dec502d7ab1574b610581a0acc89840","Widespread stratocumulus clouds were observed on nine transects from seven research cruises to the southeastern tropical Pacific Ocean along 20°S, 75°-85°W in October-November of 2001-08. The nine transects sample a unique combination of synoptic and interannual variability affecting the clouds; their ensemble diagnoses longitude-vertical sections of the atmosphere, diurnal cycles of cloud properties and drizzle statistics, and the effect of stratocumulus clouds on surface radiation.Mean cloud fraction was 0.88, and 67% of 10-min overhead cloud fraction observations were overcast. Clouds cleared in the afternoon [1500 local time (LT)] to a minimum of fraction of 0.7. Precipitation radar found strong drizzle with reflectivity above 40 dBZ. Cloud-base (CB) heights rise with longitude from 1.0 km at 75°W to 1.2 km at 85°W in the mean, but the slope varies from cruise to cruise. CB-lifting condensation level (LCL) displacement, a measure of decoupling, increases westward. At night CB-LCL is 0-200 m and increases 400 m from dawn to 1600 LT, before collapsing in the evening. Despite zonal gradients in boundary layer and cloud vertical structure, surface radiation and cloud radiative forcing are relatively uniform in longitude. When present, clouds reduce solar radiation by 160 W m-2 and radiate 70 W m-2 more downward longwave radiation than clear skies. Coupled Model Intercomparison Project phase 3 (CMIP3) simulations of the climate of the twentieth century show 40 ± 20 W m-2 too little net cloud radiative cooling at the surface. Simulated clouds have correct radiative forcing when present, but models have ;50% too few clouds. © 2012 American Meteorological Society."
"23101467700;6602600408;","Incorporating the subgrid-scale variability of clouds in the autoconversion parameterization using a PDF-scheme",2012,"10.1029/2012MS000156","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869475061&doi=10.1029%2f2012MS000156&partnerID=40&md5=e711fe21416ba2ac86f815d05a4ab1c5","An investigation of the impact of the subgrid-scale variability of cloud liquid water on the autoconversion process as parameterized in a general circulation model is presented in this paper. For this purpose, a prognostic statistical probability density distribution (PDF) of the subgrid scale variability of cloud water is incorporated in a continuous autoconversion parameterization. Thus, the revised autoconversion rate is calculated by an integral of the autoconversion equation over the PDF of total water mixing ratio from the saturation vapor mixing ratio to the maximum of total water mixing ratio. An evaluation of the new autoconversion parameterization is carried out by means of one year simulations with the ECHAM5 climate model. The results indicate that the new autoconversion scheme causes an increase of the frequency of occurrence of high autoconversion rates and a decrease of low ones compared to the original scheme. This expected result is due to the emphasis on areas of high cloud liquid water in the new approach, and the non-linearity of the autoconversion with respect to liquid water mixing ratio. A similar trend as in the autoconversion is observed in the accretion process resulting from the coupling of both processes. As a consequence of the altered autoconversion, large-scale surface precipitation also shows a shift of occurrence from lower to higher rates. The vertically integrated cloud liquid water estimated by the model shows slight improvements compared to satellite data. Most importantly, the artificial tuning factor for autoconversion in the continuous parameterization could be reduced by almost an order of magnitude using the revised parameterization. ©2012. American Geophysical Union. All Rights Reserved."
"7005882490;7005254328;7101846027;35340122000;","A simple relationship between cloud drop number concentration and precursor aerosol concentration for the regions of Earth's large marine stratocumulus decks",2012,"10.5194/acp-12-1229-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864370479&doi=10.5194%2facp-12-1229-2012&partnerID=40&md5=18d271a7fd418ba4825e179f30a618c2","Aircraft-based measurements of cloud condensation nuclei (CCN), accumulation mode and Aitken mode number concentrations, cloud drop number concentration (CDNC), and selected ancillary measurements are presented for the three large, semi-permanent marine stratocumulus decks of the earth (in the Pacific offshore of California and Chile and in the Atlantic offshore of Namibia). Based on these data, a simple linear relationship between CDNC and the accumulation mode number concentration (AMNC) is derived via regression. The slope of the regression is 0.72 ± 0.04 with an R2 of 0.90, higher than those found for CDNC-CCN linear regressions. Explanations of the relatively favorable CDNC-AMNC relationship and its utility for climate studies are discussed. © Author(s) 2012. CC Attribution 3.0 License."
"55619312723;7403364976;36816663400;26644242300;36183023000;36816528900;36816530700;6507082749;8222885800;6603542355;55812376800;","Development and testing of the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS) cm and mm wavelength occultation instrument",2012,"10.5194/amt-5-439-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881099079&doi=10.5194%2famt-5-439-2012&partnerID=40&md5=fe1f904522ed3d517eb30f8db918c2d8","We present initial results from testing a new remote sensing system called the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS). ATOMMS is designed as a satellite-to-satellite occultation system for monitoring climate. We are developing the prototype instrument for an aircraft to aircraft occultation demonstration. Here we focus on field testing of the ATOMMS instrument, in particular the remote sensing of water by measuring the attenuation caused by the 22 GHz and 183 GHz water absorption lines. <br><br> Our measurements of the 183 GHz line spectrum along an 820 m path revealed that the AM 6.2 spectroscopic model provdes a much better match to the observed spectrum than the MPM93 model. These comparisons also indicate that errors in the ATOMMS amplitude measurements are about 0.3%. Pressure sensitivity bodes well for ATOMMS as a climate instrument. Comparisons with a hygrometer revealed consistency at the 0.05 mb level, which is about 1% of the absolute humidity. <br><br> Initial measurements of absorption by the 22 GHz line made along a 5.4 km path between two mountaintops captured a large increase in water vapor similar to that measured by several nearby hygrometers. A storm passage between the two instruments yielded our first measurements of extinction by rain and cloud droplets. Comparisons of ATOMMS 1.5 mm opacity measurements with measured visible opacity and backscatter from a weather radar revealed features simultaneously evident in all three datasets confirming the ATOMMS measurements. The combined ATOMMS, radar and visible information revealed the evolution of rain and cloud amounts along the signal path during the passage of the storm. The derived average cloud water content reached typical continental cloud amounts. These results demonstrated a significant portion of the information content of ATOMMS and its ability to penetrate through clouds and rain which is critical to its all-weather, climate monitoring capability. © 2012 Author(s)."
"15840467900;57194628631;56920790500;18635289400;7103353990;8503380800;12804309300;23977795400;7102122493;","Cloud retrievals from satellite data using optimal estimation: Evaluation and application to ATSR",2012,"10.5194/amt-5-1889-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870493654&doi=10.5194%2famt-5-1889-2012&partnerID=40&md5=51dd4735b8c4faf5d1b15171a2bc37b5","Clouds play an important role in balancing the Earth's radiation budget. Hence, it is vital that cloud climatologies are produced that quantify cloud macro and micro physical parameters and the associated uncertainty. In this paper, we present an algorithm ORAC (Oxford-RAL retrieval of Aerosol and Cloud) which is based on fitting a physically consistent cloud model to satellite observations simultaneously from the visible to the mid-infrared, thereby ensuring that the resulting cloud properties provide both a good representation of the short-wave and long-wave radiative effects of the observed cloud. The advantages of the optimal estimation method are that it enables rigorous error propagation and the inclusion of all measurements and any a priori information and associated errors in a rigorous mathematical framework. The algorithm provides a measure of the consistency between retrieval representation of cloud and satellite radiances. The cloud parameters retrieved are the cloud top pressure, cloud optical depth, cloud effective radius, cloud fraction and cloud phase. The algorithm can be applied to most visible/infrared satellite instruments. In this paper, we demonstrate the applicability to the Along-Track Scanning Radiometers ATSR-2 and AATSR. Examples of applying the algorithm to ATSR-2 flight data are presented and the sensitivity of the retrievals assessed, in particular the algorithm is evaluated for a number of simulated single-layer and multi-layer conditions. The algorithm was found to perform well for single-layer cloud except when the cloud was very thin; i.e., less than 1 optical depths. For the multi-layer cloud, the algorithm was robust except when the upper ice cloud layer is less than five optical depths. In these cases the retrieved cloud top pressure and cloud effective radius become a weighted average of the 2 layers. The sum of optical depth of multi-layer cloud is retrieved well until the cloud becomes thick, greater than 50 optical depths, where the cloud begins to saturate. The cost proved a good indicator of multi-layer scenarios. Both the retrieval cost and the error need to be considered together in order to evaluate the quality of the retrieval. This algorithm in the configuration described here has been applied to both ATSR-2 and AATSR visible and infrared measurements in the context of the GRAPE (Global Retrieval and cloud Product Evaluation) project to produce a 14 yr consistent record for climate research. © 2012 Author(s)."
"6603371044;","Constraints on the profiles of total water PDF in AGCMs from AIRS and a high-resolution mode",2012,"10.1175/JCLI-D-11-00412.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871764024&doi=10.1175%2fJCLI-D-11-00412.1&partnerID=40&md5=f809fbd051f458a4dc3cadfc2b4cb042","Atmospheric general circulation model (AGCM) cloud parameterizations generally include an assumption about the subgrid-scale probability distribution function (PDF) of total water and its vertical profile. In the present study, the Atmospheric Infrared Sounder (AIRS) monthly-mean cloud amount and relative humidity fields are used to compute a proxy for the second moment of an AGCM total water PDF called the &RH01 diagnostic,&which is the AIRS mean relative humidity for cloud fractions of 0.1 or less. The dependence of the second moment on horizontal grid resolution is analyzed using results from a high-resolution global model simulation. The AIRS-derived RH01 diagnostic is generally larger near the surface than aloft, indicating a narrower PDF near the surface, and varies with the type of underlying surface. High-resolution model results show that the vertical structure of profiles of theAGCMPDFsecond moment is unchanged as the grid resolution changes from 200 to 100 to 50 km, and that the second-moment profiles shift toward higher valueswith decreasing grid spacing. Several Goddard Earth Observing System, version 5 (GEOS-5), AGCM simulations were performed with several choices for the profile of the PDF second moment. The resulting cloud and relative humidity fields were shown to be quite sensitive to the prescribed profile, and the use of a profile based onthe AIRS-derived proxy results in improvements relative to observational estimates. The AIRS-guided total water PDF profiles, including their dependence on underlying surface type and on horizontal resolution, have been implemented in the version of theGEOS-5 AGCM used for publicly released simulations. © 2012 American Meteorological Society."
"7005051510;6701472827;44161353800;","Climate Change Meets Urban Environment",2012,"10.1007/978-94-007-2430-3_11","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883417217&doi=10.1007%2f978-94-007-2430-3_11&partnerID=40&md5=93bd89f26899f8f5569eae3d2d5909a8","The effects of global warming permeate to local scales in numerous ways, and at times the adverse effects of global change are amplified by urban anthropogenic activities. These local climate influences, however, have not received due attention as current climate discourse mainly focuses on global scales. In this paper, a brief overview is presented on how urban areas bear the brunt of global climate change, in particular, how such climatic signals as sea level rise, desertification, adjustment of hydrological cycle and enhanced cloud cover can have significant repercussions on local climate, thus raising human health and national security concerns. The reduction of diurnal temperature range (DTR) with global warming and its further amplification with urbanization are used as examples to illustrate local impacts of climate change. The possible amplification of urban heat island may even lead to local meteorological regime shifts, which have an important bearing on sustainability of cities. Meteorological variables are related to air pollution, and the relationship between particulate matter and meteorological variables in Phoenix area is used to illustrate possible relationships between human health and climate change. © Springer Science+Business Media B.V. 2012."
"23134785100;16443985900;26768051400;55561830100;56472932500;","Cloud condensation nuclei activity of fresh primary and aged biomass burning aerosol",2012,"10.5194/acp-12-7285-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880518410&doi=10.5194%2facp-12-7285-2012&partnerID=40&md5=a9c6a8e0e4eb478f5da199669756b91f","We quantify the hygroscopic properties of particles freshly emitted from biomass burning and after several hours of photochemical aging in a smog chamber. Values of the hygroscopicity parameter, κ, were calculated from cloud condensation nuclei (CCN) measurements of emissions from combustion of 12 biomass fuels commonly burned in North American wildfires. Prior to photochemical aging, the κ of the fresh primary aerosol varied widely, between 0.06 (weakly hygroscopic) and 0.6 (highly hygroscopic). The hygroscopicity of the primary aerosol was positively correlated with the inorganic mass fraction of the particles. Photochemical processing reduced the range of κ values to between 0.08 and 0.3. The changes in κ were driven by the photochemical production of secondary organic aerosol (SOA). SOA also contributed to growth of particles formed during nucleation events. Analysis of the nucleation mode particles enabled the first direct quantification of the hygroscopicity parameter κ for biomass burning SOA, which was on average 0.11, similar to values observed for biogenic SOA. Although initial CCN activity of biomass burning aerosol emissions are highly variable, after a few hours of photochemical processing κ converges to a value of 0.2 ± 0.1. Therefore, photochemical aging reduces the variability of biomass burning CCN κ, which should simplify analysis of the potential effects of biomass burning aerosol on climate. © 2012 Author(s). CC Attribution 3.0 License."
"55802246600;7402480218;55688930000;7006303509;7005877775;7401936984;","Evaluation of cloud fraction and its radiative effect simulated by IPCC AR4 global models against ARM surface observations",2012,"10.5194/acp-12-1785-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875590526&doi=10.5194%2facp-12-1785-2012&partnerID=40&md5=e22971d26ee8afd837695c2d18046a15","Cloud Fraction (CF) is the dominant modulator of radiative fluxes. In this study, we evaluate CF simulated in the IPCC AR4 GCMs against ARM long-term ground-based measurements, with a focus on the vertical structure, total amount of cloud and its effect on cloud shortwave transmissivity. Comparisons are performed for three climate regimes as represented by the Department of Energy Atmospheric Radiation Measurement (ARM) sites: Southern Great Plains (SGP), Manus, Papua New Guinea and North Slope of Alaska (NSA). Our intercomparisons of three independent measurements of CF or sky-cover reveal that the relative differences are usually less than 10% (5%) for multi-year monthly (annual) mean values, while daily differences are quite significant. The total sky imager (TSI) produces smaller total cloud fraction (TCF) compared to a radar/lidar dataset for highly cloudy days (CF > 0.8), but produces a larger TCF value than the radar/lidar for less cloudy conditions (CF < 0.3). The compensating errors in lower and higher CF days result in small biases of TCF between the vertically pointing radar/lidar dataset and the hemispheric TSI measurements as multi-year data is averaged. The unique radar/lidar CF measurements enable us to evaluate seasonal variation of cloud vertical structures in the GCMs. Both inter-model deviation and model bias against observation are investigated in this study. Another unique aspect of this study is that we use simultaneous measurements of CF and surface radiative fluxes to diagnose potential discrepancies among the GCMs in representing other cloud optical properties than TCF. The results show that the model-observation and inter-model deviations have similar magnitudes for the TCF and the normalized cloud effect, and these deviations are larger than those in surface downward solar radiation and cloud transmissivity. This implies that other dimensions of cloud in addition to cloud amount, such as cloud optical thickness and/or cloud height, have a similar magnitude of disparity as TCF within the GCMs, and suggests that the better agreement among GCMs in solar radiative fluxes could be a result of compensating effects from errors in cloud vertical structure, overlap assumption, cloud optical depth and/or cloud fraction. The internal variability of CF simulated in ensemble runs with the same model is minimal. Similar deviation patterns between inter-model and model-measurement comparisons suggest that the climate models tend to generate larger biases against observations for those variables with larger inter-model deviation. The GCM performance in simulating the probability distribution, transmissivity and vertical profiles of cloud are comprehensively evaluated over the three ARM sites. The GCMs perform better at SGP than at the other two sites in simulating the seasonal variation and probability distribution of TCF. However, the models remarkably underpredict the TCF at SGP and cloud transmissivity is less susceptible to the change of TCF than observed. In the tropics, most of the GCMs tend to underpredict CF and fail to capture the seasonal variation of CF at middle and low levels. The high-level CF is much larger in the GCMs than the observations and the inter-model variability of CF also reaches a maximum at high levels in the tropics, indicating discrepancies in the representation of ice cloud associated with convection in the models. While the GCMs generally capture the maximum CF in the boundary layer and vertical variability, the inter-model deviation is largest near the surface over the Arctic. © 2012 Author(s)."
"7003406400;55622713800;","Using CloudSat cloud retrievals to differentiate satellite-derived rainfall products over West Africa",2012,"10.1175/JHM-D-12-039.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874972313&doi=10.1175%2fJHM-D-12-039.1&partnerID=40&md5=6c18dd4eb95386cebce9a055f2a0a7a6","Daily precipitation retrievals from three algorithms [the Tropical Rainfall Measuring Mission 3B42 rain product (TRMM-3B42), the Climate Prediction Center morphing technique (CMORPH), and the second version (RFEv2) of the Famine Early Warning System (FEWS)] and CloudSat retrievals of cloud liquid water, ice amount, and cloud fraction are used to document the cloud structures associated with rainfall location and intensity in the West African monsoon. The different rainfall retrieval approaches lead to contrasting cloud sensitivities between all three algorithms most apparent in the onset period of June and July. During the monsoon preonset phase, CMORPH produces a precipitation peak at around 12°N associated with upper-level cirrus clouds, while FEWS and TRMM both produce rainfall maxima collocated with the tropospheric!-deep convective cloud structures at 4°-6°N. In July similar relative displacements of the rainfall maxima are observed. Conditional sampling of several hundred convection systems proves that, while upperlevel cirrus is advected northward relative to the motion of the convective system cores, the reduced cover and water content of lower-tropospheric clouds in the northern zone could be due to signal attenuation as the systems there appear to be more intense, producing higher ice water contents. Thus, while CMORPH may overestimate rainfall in the northern zone due to its reliance on cloud ice, TRMM and FEWS are likely underestimating precipitation in this zone, potentially due to the use of infrared based products inTRMMand FEWS when microwave is not available. Mapping the CloudSat retrievals as a function of rain rate confirms the greater sensitivity ofCMORPHto ice cloud and indicates that high-intensity rainfall events are associated with systems that are deeper and of a greater spatial scale. © 2012 American Meteorological Society."
"55469523400;15124698700;","Upward shift of the atmospheric general circulation under global warming: Theory and simulations",2012,"10.1175/JCLI-D-11-00699.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871744327&doi=10.1175%2fJCLI-D-11-00699.1&partnerID=40&md5=939df7ad2f3b354a72730223fd328a51","Many features of the general circulation of the atmosphere shift upward in response to warming in simulations of climate change with both general circulation models (GCMs) and cloud-system-resolving models. The importance of the upward shift is well known, but its physical basis and the extent to which it occurs coherently across variables are not well understood. A transformation is derived here that shows how an upward shift of a solution to the moist primitive equations gives a new approximate solution with higher tropospheric temperatures. According to the transformation, all variables shift upward with warming but with an additional modification to the temperature and a general weakening of the pressure velocity. The applicabilityof the vertical-shift transformation is explored using a hierarchy of models from adiabatic parcel ascents to comprehensive GCMs. The transformation is found to capture many features of the response to climate change in simulationswith an idealized GCM, including the mid- and upper-tropospheric changes in lapse rate, relative humidity, and meridional wind. The transformation is less accurate when applied to simulations with more realistic GCMs, but it nonetheless captures some important features. Deviations fromthe simulated response are primarily due to the surface boundary conditions, which do not necessarily conform to the transformation, especially in thecase of the zonal winds. The results allow for a physical interpretation of the upward shift in terms of the governing equations and suggest that it may be thought of asa coherent response of the general circulation of the mid- and upper troposphere. © 2012 American Meteorological Society."
"36659302700;14037971500;22935251000;9238068800;7102674341;56270700700;8724549600;7102578937;","SCIAMACHY WFM-DOAS XCO2: Comparison with CarbonTracker XCO 2 focusing on aerosols and thin clouds",2012,"10.5194/amt-5-1935-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874889409&doi=10.5194%2famt-5-1935-2012&partnerID=40&md5=6f324f2180596749d9fe1a8d4ac7aa3a","Carbon dioxide (CO2) is the most important greenhouse gas whose atmospheric loading has been significantly increased by anthropogenic activity leading to global warming. Accurate measurements and models are needed in order to reliably predict our future climate. This, however, has challenging requirements. Errors in measurements and models need to be identified and minimised. In this context, we present a comparison between satellite-derived column-averaged dry air mole fractions of CO2, denoted XCO 2, retrieved from SCIAMACHY/ENVISAT using the WFM-DOAS (weighting function modified differential optical absorption spectroscopy) algorithm, and output from NOAA's global CO2 modelling and assimilation system CarbonTracker. We investigate to what extent differences between these two data sets are influenced by systematic retrieval errors due to aerosols and unaccounted clouds. We analyse seven years of SCIAMACHY WFM-DOAS version 2.1 retrievals (WFMDv2.1) using CarbonTracker version 2010. We investigate to what extent the difference between SCIAMACHY and CarbonTracker XCO2 are temporally and spatially correlated with global aerosol and cloud data sets. For this purpose, we use a global aerosol data set generated within the European GEMS project, which is based on assimilated MODIS satellite data. For clouds, we use a data set derived from CALIOP/CALIPSO. We find significant correlations of the SCIAMACHY minus CarbonTracker XCO2 difference with thin clouds over the Southern Hemisphere. The maximum temporal correlation we find for Darwin, Australia (2 Combining double low line 54%). Large temporal correlations with thin clouds are also observed over other regions of the Southern Hemisphere (e.g. 43% for South America and 31% for South Africa). Over the Northern Hemisphere the temporal correlations are typically much lower. An exception is India, where large temporal correlations with clouds and aerosols have also been found. For all other regions the temporal correlations with aerosol are typically low. For the spatial correlations the picture is less clear. They are typically low for both aerosols and clouds, but depending on region and season, they may exceed 30% (the maximum value of 46% has been found for Darwin during September to November). Overall we find that the presence of thin clouds can potentially explain a significant fraction of the difference between SCIAMACHY WFMDv2.1 XCO2 and CarbonTracker over the Southern Hemisphere. Aerosols appear to be less of a problem. Our study indicates that the quality of the satellite derived XCO2 will significantly benefit from a reduction of scattering related retrieval errors at least for the Southern Hemisphere. © 2012 Author(s)."
"6506328135;7202048112;","Large-scale environmental variables and transition to deep convection in cloud resolving model simulations: A vector representation",2012,"10.1029/2012MS000155","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868637175&doi=10.1029%2f2012MS000155&partnerID=40&md5=4431bee5581bc9143f64e345cf6a645b","Cloud resolving model simulations and vector analysis are used to develop a quantitative method of assessing regional variations in the relationships between various large-scale environmental variables and the transition to deep convection. Results of the CRM simulations from three tropical regions are used to cluster environmental conditions under which transition to deep convection does and does not take place. Projections of the large-scale environmental variables on the difference between these two clusters are used to quantify the roles of these variables in the transition to deep convection. While the transition to deep convection is most sensitive to moisture and vertical velocity perturbations, the details of the profiles of the anomalies vary from region to region. In comparison, the transition to deep convection is found to be much less sensitive to temperature anomalies over all three regions. The vector formulation presented in this study represents a simple general framework for quantifying various aspects of how the transition to deep convection is sensitive to environmental conditions."
"23012705100;6701650121;35429035100;7202097052;","Biomass burning in Siberia as a source of BrO to the Arctic free troposphere",2012,"10.1016/j.atmosenv.2012.08.070","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866511886&doi=10.1016%2fj.atmosenv.2012.08.070&partnerID=40&md5=49816fa2e163a2726b638a019edccff9","During the ARCPAC (Aerosol, Radiation, and Cloud Processes affecting Arctic Climate) campaign in April 2008, several flights of the WP-3D research aircraft over the Arctic Ocean and Alaska sampled relatively rich bromine monoxide (BrO &gt; 5 pptv) air masses in the free troposphere. In most cases air masses were identified as either stratospheric intrusions or as being recently in contact with sea-ice and thereby pointing to an established BrO source. However, in at least two instances there was a strong indication that the BrO originated, directly or as a secondary product from forest fires in Siberia. In all cases the origin of the air masses studied (polluted or stratospheric influenced) was confirmed by trajectories calculations and carbon monoxide (CO), ozone (O 3), water vapor (H 2O), bromine monochloride (BrCl), and acetonitrile (CH 3CN) measurements on-board the aircraft. In spite of this finding, the mechanisms of BrO release in the free troposphere, possibly involving heterogeneous reactions, remain unclear. © 2012."
"38762392200;9275665400;7102783229;7006634316;6601992794;","Decreasing particle number concentrations in a warming atmosphere and implications",2012,"10.5194/acp-12-2399-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863443823&doi=10.5194%2facp-12-2399-2012&partnerID=40&md5=c319ef15a67ee880712a4413e07233ae","New particle formation contributes significantly to the number concentration of condensation nuclei (CN) as well as cloud CN (CCN), a key factor determining aerosol indirect radiative forcing of the climate system. Using a physics-based nucleation mechanism that is consistent with a range of field observations of aerosol formation, it is shown that projected increases in global temperatures could significantly inhibit new particle, and CCN, formation rates worldwide. An analysis of CN concentrations observed at four NOAA ESRL/GMD baseline stations since the 1970s and two other sites since 1990s reveals long-term decreasing trends that are consistent in sign with, but are larger in magnitude than, the predicted temperature effects. The possible reasons for larger observed long-term CN reductions at remote sites are discussed. The combined effects of rising temperatures on aerosol nucleation rates and other chemical and microphysical processes may imply substantial decreases in future tropospheric particle abundances associated with global warming, delineating a potentially significant feedback mechanism that increases Earth's climate sensitivity to greenhouse gas emissions. Further research is needed to quantify the magnitude of such a feedback process. © 2012 Author(s)."
"7006191743;6603253640;7403076976;24080123400;35316923500;","Predicting cloud-to-ground and intracloud lightning in weather forecast models",2012,"10.1175/WAF-D-11-00144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874562874&doi=10.1175%2fWAF-D-11-00144.1&partnerID=40&md5=5b5652df4d0258c9176e3e247eac44d4","A new prognostic, spatially and temporally dependent variable is introduced to the Weather Research and Forecasting Model (WRF). This variable is called the potential electrical energy (Ep). It was used to predict the dynamic contribution of the grid-scale-resolved microphysical and vertical velocity fields to the production of cloud-to-ground and intracloud lightning in convection-allowing forecasts. The source of Ep is assumed to be the noninductive charge separation process involving collisions of graupel and ice particles in the presence of supercooled liquid water. The Ep dissipates when it exceeds preassigned threshold values and lightning is generated. An analysis of four case studies is presented and analyzed. On the 4-km simulation grid, a single cloud-to-ground lightning event was forecast with about equal values of probability of detection (POD) and false alarm ratio (FAR). However, when lighting was integrated onto 12-km and then 36-km grid overlays, there was a large improvement in the forecast skill, and as many as 10 cloud-to-ground lighting events were well forecast on the 36-km grid. The impact of initial conditions on forecast accuracy is briefly discussed, including an evaluation of the scheme in wintertime, when lightning activity is weaker. The dynamic algorithm forecasts are also contrasted with statistical lightning forecasts and differences are noted. The scheme is being used operationally with the Rapid Refresh (13 km) data; the skill scores in these operational runs were very good in clearly defined convective situations. © 2012 American Meteorological Society."
"54400559100;7102687667;56141234300;57212981487;","Robustness of the aerosol weekly cycle over Southeastern China",2012,"10.1016/j.atmosenv.2012.07.029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865072584&doi=10.1016%2fj.atmosenv.2012.07.029&partnerID=40&md5=31b4ef1fbb2c3be09606c35764643fb8","A 7-day cycle is a special time-scale that corresponds with the weekly working schedule. However, there is no consensus on the existence of the weekly cycle of aerosol loading, which is closely related to human activities. In the present study, we analyzed the surface concentration of PM10 (Particulate Matter with a diameter of less than 10 μm) and other physically linked variables over Southeastern China under calm weather conditions to detect signs of the aerosol loading weekly cycle. Results show that the weekly cycle of PM10 is distinct; the maximum occurs on Thursday and the minimum occurs on Saturday and Sunday. The range of this cycle is over 8 μg m -3, approximately 8% of the daily average. The existence of the PM10 weekly cycle was supported by the pronounced amplitude of the 7-day cycle compared with those of 6-day and 8-day cycles and by significant results from the Monte-Carlo test. There are also distinct weekly cycles in the directly linked variables of adjusted horizontal visibility, sulfur dioxide (SO 2) and nitrogen dioxide (NO 2); the patterns of these cycles are corresponding with that of PM10. The changes of total cloud cover and relative humidity on the weekly time-scale were analyzed, and the relationship with PM10 was discussed. It is likely that the cloud cover weekly cycle is conducted by the change of PM10 through the semi-direct aerosol effect. We also found that precipitation and wind might weaken the PM10 weekly cycle by scavenging the heavy aerosol loading. © 2012 Elsevier Ltd."
"55684491100;","A contrail cirrus prediction model",2012,"10.5194/gmd-5-543-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861712590&doi=10.5194%2fgmd-5-543-2012&partnerID=40&md5=fd719e832a931898f8042c2d1f1e509f","A new model to simulate and predict the properties of a large ensemble of contrails as a function of given air traffic and meteorology is described. The model is designed for approximate prediction of contrail cirrus cover and analysis of contrail climate impact, e.g. within aviation system optimization processes. The model simulates the full contrail life-cycle. Contrail segments form between waypoints of individual aircraft tracks in sufficiently cold and humid air masses. The initial contrail properties depend on the aircraft. The advection and evolution of the contrails is followed with a Lagrangian Gaussian plume model. Mixing and bulk cloud processes are treated quasi analytically or with an effective numerical scheme. Contrails disappear when the bulk ice content is sublimating or precipitating. The model has been implemented in a ""Contrail Cirrus Prediction Tool"" (CoCiP). This paper describes the model assumptions, the equations for individual contrails, and the analysis-method for contrail-cirrus cover derived from the optical depth of the ensemble of contrails and background cirrus. The model has been applied for a case study and compared to the results of other models and in-situ contrail measurements. The simple model reproduces a considerable part of observed contrail properties. Mid-aged contrails provide the largest contributions to the product of optical depth and contrail width, important for climate impact. © Author(s) 2012."
"56448637100;36098422200;23010736100;6603125868;23482558100;6506152198;6507994712;56324515500;6506718302;7004047498;7006708207;7005069415;7006434689;7004278344;7003720206;35461255500;7003931528;55637266800;7006712143;","The regional aerosol-climate model REMO-HAM",2012,"10.5194/gmd-5-1323-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880523503&doi=10.5194%2fgmd-5-1323-2012&partnerID=40&md5=867815e258722d1e644df0b79c44092b","REMO-HAM is a new regional aerosol-climate model. It is based on the REMO regional climate model and includes most of the major aerosol processes. The structure for aerosol is similar to the global aerosol-climate model ECHAM5-HAM, for example the aerosol module HAM is coupled with a two-moment stratiform cloud scheme. On the other hand, REMO-HAM does not include an online coupled aerosol-radiation nor a secondary organic aerosol module. In this work, we evaluate the model and compare the results against ECHAM5-HAM and measurements. Four different measurement sites were chosen for the comparison of total number concentrations, size distributions and gas phase sulfur dioxide concentrations: Hyytiälä in Finland, Melpitz in Germany, Mace Head in Ireland and Jungfraujoch in Switzerland. REMO-HAM is run with two different resolutions: 50 × 50 km2 and 10 × 10 km2. Based on our simulations, REMO-HAM is in reasonable agreement with the measured values. The differences in the total number concentrations between REMO-HAM and ECHAM5-HAM can be mainly explained by the difference in the nucleation mode. Since we did not use activation nor kinetic nucleation for the boundary layer, the total number concentrations are somewhat underestimated. From the meteorological point of view, REMO-HAM represents the precipitation fields and 2 m temperature profile very well compared to measurement. Overall, we show that REMO-HAM is a functional aerosol-climate model, which will be used in further studies. © 2012 Author(s). CC Attribution 3.0 License."
"23012388900;57202119596;7004357137;","Reduction of radiation biases by incorporating the missing cloud variability by means of downscaling techniques: A study using the 3-D MoCaRT model",2012,"10.5194/amt-5-2261-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880536034&doi=10.5194%2famt-5-2261-2012&partnerID=40&md5=1750f377386a1875b021f018cacc9412","Handling complexity to the smallest detail in atmospheric radiative transfer models is unfeasible in practice. On the one hand, the properties of the interacting medium, i.e., the atmosphere and the surface, are only available at a limited spatial resolution. On the other hand, the computational cost of accurate radiation models accounting for three-dimensional heterogeneous media are prohibitive for some applications, especially for climate modelling and operational remote-sensing algorithms. Hence, it is still common practice to use simplified models for atmospheric radiation applications. Three-dimensional radiation models can deal with complex scenarios providing an accurate solution to the radiative transfer. In contrast, one-dimensional models are computationally more efficient, but introduce biases to the radiation results. With the help of stochastic models that consider the multi-fractal nature of clouds, it is possible to scale cloud properties given at a coarse spatial resolution down to a higher resolution. Performing the radiative transfer within the cloud fields at higher spatial resolution noticeably helps to improve the radiation results. We present a new Monte Carlo model, MoCaRT, that computes the radiative transfer in three-dimensional inhomogeneous atmospheres. The MoCaRT model is validated by comparison with the consensus results of the Intercomparison of Three-Dimensional Radiation Codes (I3RC) project. In the framework of this paper, we aim at characterising cloud heterogeneity effects on radiances and broadband fluxes, namely: the errors due to unresolved variability (the so-called plane parallel homogeneous, PPH, bias) and the errors due to the neglect of transversal photon displacements (independent pixel approximation, IPA, bias). First, we study the effect of the missing cloud variability on reflectivities. We will show that the generation of subscale variability by means of stochastic methods greatly reduce or nearly eliminate the reflectivity biases. Secondly, three-dimensional broadband fluxes in the presence of realistic inhomogeneous cloud fields sampled at high spatial resolutions are calculated and compared to their one-dimensional counterparts at coarser resolutions. We found that one-dimensional calculations at coarsely resolved cloudy atmospheres systematically overestimate broadband reflected and absorbed fluxes and underestimate transmitted ones. © 2012 Author(s)."
"57194933853;23767612400;8642075000;7006430057;6506728257;7202040286;7006813492;57213554495;16069590400;55800756800;25958887600;","Vegetation height and cover fraction between 60° S and 60° N from ICESat GLAS data",2012,"10.5194/gmd-5-413-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872007801&doi=10.5194%2fgmd-5-413-2012&partnerID=40&md5=ff79fbc8ac5816b3d163fb6260d2be92","We present new coarse resolution (0.5 &times; 0.5 ) vegetation height and vegetation-cover fraction data sets between 60° S and 60° N for use in climate models and ecological models. The data sets are derived from 2003-2009 measurements collected by the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat), the only LiDAR instrument that provides close to global coverage. Initial vegetation height is calculated from GLAS data using a development of the model of Rosette et al. (2008) with with further calibration on desert sites. Filters are developed to identify and eliminate spurious observations in the GLAS data, e.g. data that are affected by clouds, atmosphere and terrain and as such result in erroneous estimates of vegetation height or vegetation cover. Filtered GLAS vegetation height estimates are aggregated in histograms from 0 to 70 m in 0.5 m intervals for each 0.5 &times; 0.5 . The GLAS vegetation height product is evaluated in four ways. Firstly, the Vegetation height data and data filters are evaluated using aircraft LiDAR measurements of the same for ten sites in the Americas, Europe, and Australia. Application of filters to the GLAS vegetation height estimates increases the correlation with aircraft data from <i>r</i> Combining double low line 0.33 to <i>r</i> Combining double low line 0.78, decreases the root-mean-square error by a factor 3 to about 6 m (RMSE) or 4.5 m (68% error distribution) and decreases the bias from 5.7 m to -1.3 m. Secondly, the global aggregated GLAS vegetation height product is tested for sensitivity towards the choice of data quality filters; areas with frequent cloud cover and areas with steep terrain are the most sensitive to the choice of thresholds for the filters. The changes in height estimates by applying different filters are, for the main part, smaller than the overall uncertainty of 4.5-6 m established from the site measurements. Thirdly, the GLAS global vegetation height product is compared with a global vegetation height product typically used in a climate model, a recent global tree height product, and a vegetation greenness product and is shown to produce realistic estimates of vegetation height. Finally, the GLAS bare soil cover fraction is compared globally with the MODIS bare soil fraction (<i>r</i> Combining double low line 0.65) and with bare soil cover fraction estimates derived from AVHRR NDVI data (<i>r</i> Combining double low line 0.67); the GLAS tree-cover fraction is compared with the MODIS tree-cover fraction (<i>r</i> Combining double low line 0.79). The evaluation indicates that filters applied to the GLAS data are conservative and eliminate a large proportion of spurious data, while only in a minority of cases at the cost of removing reliable data as well. <br><br> The new GLAS vegetation height product appears more realistic than previous data sets used in climate models and ecological models and hence should significantly improve simulations that involve the land surface. © Author(s) 2012."
"7202684687;12801073500;35561911800;55708686800;22986631300;8954866200;7102567936;7006224475;","A Tropospheric Emission Spectrometer HDO/H2O retrieval simulator for climate models",2012,"10.5194/acp-12-10485-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875439525&doi=10.5194%2facp-12-10485-2012&partnerID=40&md5=cb35831affc6a1e9c32c56587fe6e4e1","Retrievals of the isotopic composition of water vapor from the Aura Tropospheric Emission Spectrometer (TES) have unique value in constraining moist processes in climate models. Accurate comparison between simulated and retrieved values requires that model profiles that would be poorly retrieved are excluded, and that an instrument operator be applied to the remaining profiles. Typically, this is done by sampling model output at satellite measurement points and using the quality flags and averaging kernels from individual retrievals at specific places and times. This approach is not reliable when the model meteorological conditions influencing retrieval sensitivity are different from those observed by the instrument at short time scales, which will be the case for free-running climate simulations. In this study, we describe an alternative, ""categorical"" approach to applying the instrument operator, implemented within the NASA GISS ModelE general circulation model. Retrieval quality and averaging kernel structure are predicted empirically from model conditions, rather than obtained from collocated satellite observations. This approach can be used for arbitrary model configurations, and requires no agreement between satellite-retrieved and model meteorology at short time scales. To test this approach, nudged simulations were conducted using both the retrieval-based and categorical operators. Cloud cover, surface temperature and free-tropospheric moisture content were the most important predictors of retrieval quality and averaging kernel structure. There was good agreement between the δD fields after applying the retrieval-based and more detailed categorical operators, with increases of up to 30% over the ocean and decreases of up to 40% over land relative to the raw model fields. The categorical operator performed better over the ocean than over land, and requires further refinement for use outside of the tropics. After applying the TES operator, ModelE had δD biases of -8% over ocean and -34% over land compared to TES δD, which were less than the biases using raw model δD fields. © 2012 Author(s). CC Attribution 3.0 License."
"55319187200;55500855300;35485055800;","Comparison of isolation and quantification methods to measure humic-like substances (HULIS) in atmospheric particles",2012,"10.1016/j.atmosenv.2012.06.063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864136455&doi=10.1016%2fj.atmosenv.2012.06.063&partnerID=40&md5=b52cc4fc8d6418b3ae384eb8eb0a341c","Humic-like Substances (HULIS) comprise a significant fraction of the water-soluble organic aerosol mass and influence the cloud microphysical properties and climate effects of aerosols in the atmosphere. In this work, the most frequently used HULIS isolation and quantification methods including ENVI-18, HLB, XAD-8 and DEAE were comparatively characterized with two model standards, ten interfering compounds, and five ambient aerosol samples. Quantification of HULIS is performed with a TOC analyzer, complemented by an investigation of the chemical structure of the extracted fractions by UV-Vis spectroscopy. The results show that the four isolation methods were all characterized by high reliability, high reproducibility, and low limit of detection (LOD), indicating that each method can be used to efficiently recover Suwannee River Fulvic Acid (SRFA) and be applied to the quantification of the lower amount of HULIS in atmospheric particles. The analytical results of the UV-Vis spectra of HULIS fractions isolated also indicate that they are all favorable for extraction of compounds of high UV absorbance, high MW, and high aromaticity and that the DEAE protocol is the most significant one. Compared with the DEAE method that favors extraction of highly UV-absorbing and more aromatic compounds, SRFA isolated by the ENVI-18, HLB, and XAD-8 protocols were more representative of the global matrix. Each method has its own advantages and disadvantages and is suitable for a particular application. No single method is ideal for both isolation and quantification of HULIS in atmospheric samples. © 2012 Elsevier Ltd."
"38863214100;7102011703;55656837900;","The initiation of modern soft and hard Snowball Earth climates in CCSM4",2012,"10.5194/cp-8-907-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859977062&doi=10.5194%2fcp-8-907-2012&partnerID=40&md5=1aae83daba7f52765a0978f74c68509a","Geochemical and geological evidence has suggested that several global-scale glaciation events occurred during the Neoproterozoic Era in the interval from 750-580 million years ago. The initiation of these glaciations is thought to have been a consequence of the combined influence of a low level of atmospheric carbon dioxide concentration and an approximately 6% weakening of solar luminosity. The latest version of the Community Climate System Model (CCSM4) is employed herein to explore the detailed combination of forcings required to trigger such extreme glaciation conditions under present-day circumstances of geography and topography. It is found that runaway glaciation occurs in the model under the following conditions: (1) an 8-9% reduction in solar radiation with 286 ppmv CO2 or (2) a 6% reduction in solar radiation with 70-100 ppmv CO2. These thresholds are moderately different from those found to be characteristic of the previously employd CCSM3 model reported recently in Yang et al. (2012a,b), for which the respective critical points corresponded to a 10-10.5% reduction in solar radiation with 286 ppmv CO 2 or a 6% reduction in solar radiation with 17.5-20 ppmv CO 2. The most important reason for these differences is that the sea ice/snow albedo parameterization employed in CCSM4 is believed to be more realistic than that in CCSM3. Differences in cloud radiative forcings and ocean and atmosphere heat transports also influence the bifurcation points. These results are potentially very important, as they are to serve as control on further calculations which will be devoted to an investigation of the impact of continental configuration. &lt;br&gt;&lt;br&gt; We demonstrate that there exist ""soft Snowball"" Earth states, in which the fractional sea ice coverage reaches approximately 60-65%, land masses in low latitudes are covered by perennial snow, and runaway glaciation does not develop. This is consistent with our previous results based upon CCSM3. Although our results cannot exclude the possibility of a ""hard Snowball"" solution, it is suggested that a ""soft Snowball"" solution for the Neoproterozoic remains entirely plausible. © Author(s) 2012."
"57203049177;57213407584;7201613656;7006766881;15023208900;","Modelling large-scale ice-sheet-climate interactions following glacial inception",2012,"10.5194/cp-8-1565-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881102664&doi=10.5194%2fcp-8-1565-2012&partnerID=40&md5=d9c637a86f38246112a25f7bdb3476df","We have coupled the FAMOUS global AOGCM (atmosphere-ocean general circulation model) to the Glimmer thermomechanical ice-sheet model in order to study the development of ice-sheets in north-east America (Laurentia) and north-west Europe (Fennoscandia) following glacial inception. This first use of a coupled AOGCM-ice-sheet model for a study of change on long palæoclimate timescales is made possible by the low computational cost of FAMOUS, despite its inclusion of physical parameterisations similar in complexity to higher-resolution AOGCMs. With the orbital forcing of 115 ka BP, FAMOUS-Glimmer produces ice caps on the Canadian Arctic islands, on the north-west coast of Hudson Bay and in southern Scandinavia, which grow to occupy the Keewatin region of the Canadian mainland and all of Fennoscandia over 50 ka. Their growth is eventually halted by increasing coastal ice discharge. The expansion of the ice-sheets influences the regional climate, which becomes cooler, reducing the ablation, and ice accumulates in places that initially do not have positive surface mass balance. The results suggest the possibility that the glaciation of north-east America could have begun on the Canadian Arctic islands, producing a regional climate change that caused or enhanced the growth of ice on the mainland. The increase in albedo (due to snow and ice cover) is the dominant feedback on the area of the ice-sheets and acts rapidly, whereas the feedback of topography on SMB does not become significant for several centuries, but eventually has a large effect on the thickening of the ice-sheets. These two positive feedbacks are mutually reinforcing. In addition, the change in topography perturbs the tropospheric circulation, producing some reduction of cloud, and mitigating the local cooling along the margin of the Laurentide ice-sheet. Our experiments demonstrate the importance and complexity of the interactions between ice-sheets and local climate. © Author(s) 2012."
"55682811900;7402655282;7003470549;55169826800;7004364676;","Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen",2012,"10.5194/acp-12-2541-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862142556&doi=10.5194%2facp-12-2541-2012&partnerID=40&md5=f96076f77958b0528fe33115552a4e3b","The ice nucleation of bioaerosols (bacteria, pollen, spores, etc.) is a topic of growing interest, since their impact on ice cloud formation and thus on radiative forcing, an important parameter in global climate, is not yet fully understood. Here we show that pollen of different species strongly differ in their ice nucleation behaviour. The average freezing temperatures in laboratory experiments range from 240 to 255 K. As the most efficient nuclei (silver birch, Scots pine and common juniper pollen) have a distribution area up to the Northern timberline, their ice nucleation activity might be a cryoprotective mechanism. Far more intriguingly, it has turned out that water, which has been in contact with pollen and then been separated from the bodies, nucleates as good as the pollen grains themselves. The ice nuclei have to be easily-suspendable macromolecules located on the pollen. Once extracted, they can be distributed further through the atmosphere than the heavy pollen grains and so presumably augment the impact of pollen on ice cloud formation even in the upper troposphere. Our experiments lead to the conclusion that pollen ice nuclei, in contrast to bacterial and fungal ice nucleating proteins, are non-proteinaceous compounds. © Author(s) 2012."
"57160765800;55842413500;","Global Water Security: Engineering the Future",2012,"10.1007/978-94-007-2430-3_22","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883349753&doi=10.1007%2f978-94-007-2430-3_22&partnerID=40&md5=68f807fa051ed74ed1f15a0cbc58f509","The paper introduces some of the general challenges of global water security, particularly in poverty stricken regions such as Africa, and highlights the likely global impact of climate change, increasing pollution and population growth etc. on water resources, as outlined in recent studies. The nexus between water, food and energy is introduced, along with the concept of virtual water and the impact of the water footprint and the need for society, industry and governments to become more conscious of the water footprint, alongside the carbon footprint. Various practical solutions to enhancing security of supply are introduced and discussed, such as desalination and integrated water management in the form of 'Cloud to Coast', together with global actions needed. Finally, some water security challenges and opportunities for developed countries, such as the UK, are discussed, particularly with regard to the need to price water appropriately and the need to appreciate that the price of water should cover more than just the cost of delivery to the home. The paper concludes with the urgent need to raise the profile of global water security at all levels of society and through international bodies, for the benefit of humanity worldwide. © Springer Science+Business Media B.V. 2012."
"6508201898;11241983900;","Inter-annual variations of snow days over Switzerland from 2000-2010 derived from MODIS satellite data",2012,"10.5194/tc-6-331-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868108191&doi=10.5194%2ftc-6-331-2012&partnerID=40&md5=1aefcce1448d2f11dd859ec594c3be66","Snow cover plays a vital role in the Swiss Alps and therefore it is of major interest to determine and understand its variability on different spatiotemporal scales. Within the activities of the National Climate Observing System (GCOS Switzerland) inter-annual variations of snow days over Switzerland were derived from 2000 to 2010 based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra satellite. To minimize the impact of cloud cover on the MODIS snow product MOD10C1, we implemented a post-processing technique based on a forward and backward gap-filling approach. Using the proposed methodology it was possible to determine the total number of annual snow days over Switzerland from 2000 to 2010 (SCDMODIS). The accuracy of the calculated snow days per year were quantitatively evaluated against three in situ snow observation sites representing different climatological regimes (SCDin-situ). Various statistical indices were computed and analysed over the entire period. The overall accuracy between SCDMODIS and SCD in-situ on a daily basis over 10 yr is 88% to 94%, depending on the regional characteristics of each validation site. Differences between SCDMODIS and SCDin-situ vary during the snow accumulation period in autumn and smaller differences after spring, in particularly for the Central Alps. © 2013 Author(s)."
"55502388100;6602877961;25222135800;55951088700;","Anthropogenic control of late-Holocene landscapes in the Cuzco region, Peru",2012,"10.1177/0959683612449760","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869988336&doi=10.1177%2f0959683612449760&partnerID=40&md5=937de64c3e5e5120fc95b36c669bff11","The rise of complex Andean cultures is tied to increasingly sophisticated use of natural resources and infrastructural development. Considerable debate surrounds the extent to which these societies were forced to respond to changing climates or whether their modifications to the landscape minimized climate impacts. Here, we present a region-wide perspective of paleoecological changes around Cuzco, Peru using three lake sediment records. We investigate whether vegetation shifts in the three records occurred simultaneously, and explore whether such changes were due to climatic conditions or human activities, or both. A new paleoecological record from Lake Huaypo reveals a transition from Amaranthaceae (i.e. quinoa) cultivars to maize at c. 2800 cal. yr BP. This agricultural change is also documented at two other Andean lakes: Marcacocha (Chepstow-Lusty A (2011) Agro-pastoralism and social change in the Cuzco heartland of Peru: A brief history using environmental proxies. Antiquity 85: 570-582) and Pacucha (Valencia BG, Urrego DH, Silman MR et al.(2010) From ice age to modern: A record of landscape change in an Andean cloud forest. Journal of Biogeography 37: 1637-1647). Wetter climatic conditions are inferred to be a leading cause behind the change from Amaranthaceae to maize cultivation. At 1300 cal. yr BP, a rapid increase in Andean forest pollen types, especially Alnus, is observed at Huaypo, with similar changes occurring at Marcacocha at c. 1000 cal. yr BP and at Pacucha at c. 500 cal. yr BP. Drier paleoclimatic conditions at the time and the importance of Alnus, a species well-known for its ability to grow quickly and its widespread use for fuel and timber, suggest that the expansion was due partly to agroforestry. The Huaypo paleoecological record reveals that the practice of agroforestry first began during the Wari Period, and then continued through the Late Intermediate Period and period of Incan rule. © The Author(s) 2012."
"55391863600;15724418700;","Quantifying the deep convective temperature signal within the tropical tropopause layer (TTL)",2012,"10.5194/acp-12-12183-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871761446&doi=10.5194%2facp-12-12183-2012&partnerID=40&md5=04c7ec8c7fe8dbd3dabb7fbca075d389","Dynamics on a vast range of spatial and temporal scales, from individual convective plumes to planetary-scale circulations, play a role in driving the temperature variability in the tropical tropopause layer (TTL). Here, we aim to better quantify the deep convective temperature signal within the TTL using multiple datasets. First, we investigate the link between ozone and temperature in the TTL using the Southern Hemisphere Additional Ozonesondes (SHADOZ) dataset. Low ozone concentrations in the TTL are indicative of deep convective transport from the boundary layer. We confirm the usefulness of ozone as an indicator of deep convection by identifying a typical temperature signal associated with reduced ozone events: an anomalously warm mid to upper troposphere and an anomalously cold upper TTL. We quantify these temperature signals using two diagnostics: (1) the ""ozone minimum"" diagnostic, which has been used in previous studies and identifies the upper tropospheric minimum ozone concentration as a proxy for the level of main convective outflow; and (2) the ""ozone mixing height"", which we introduce in order to identify the maximum altitude in a vertical ozone profile up to which reduced ozone concentrations, typical of transport from the boundary layer are observed. Results indicate that the ozone mixing height diagnostic better separates profiles with convective influence than the ozone minimum diagnostic. Next, we collocate deep convective clouds identified by CloudSat 2B-CLDCLASS with temperature profiles based on Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Position System (GPS) radio occultations. We find a robust large-scale deep convective TTL temperature signal, that is persistent in time. However, it is only the convective events that penetrate into the upper half of the TTL that have a significant impact on TTL temperature. A distinct seasonal difference in the spatial scale and the persistence of the temperature signal is identified. Deep-convective cloud top heights are on average found to be well described by the level of neutral buoyancy. © 2012 Author(s)."
"55717074000;7006270084;7003666669;6603268269;7006705919;55542833500;7102976560;25031430500;7103158465;6507575165;15724543600;55189671700;7102696626;36876405100;7005304841;57213743966;6603711967;56520921400;7003311618;7004479957;8570871900;23065650200;","Toward a minimal representation of aerosols in climate models: Description and evaluation in the Community Atmosphere Model CAM5",2012,"10.5194/gmd-5-709-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861693185&doi=10.5194%2fgmd-5-709-2012&partnerID=40&md5=32806d2bfa09d2558d14dfe284d70a51","A modal aerosol module (MAM) has been developed for the Community Atmosphere Model version 5 (CAM5), the atmospheric component of the Community Earth System Model version 1 (CESM1). MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically-based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7), and a version with three lognormal modes (MAM3) for the purpose of long-term (decades to centuries) simulations. In this paper a description and evaluation of the aerosol module and its two representations are provided. Sensitivity of the aerosol lifecycle to simplifications in the representation of aerosol is discussed. <br><br> Simulated sulfate and secondary organic aerosol (SOA) mass concentrations are remarkably similar between MAM3 and MAM7. Differences in primary organic matter (POM) and black carbon (BC) concentrations between MAM3 and MAM7 are also small (mostly within 10%). The mineral dust global burden differs by 10% and sea salt burden by 30-40% between MAM3 and MAM7, mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the observed geographical and temporal variations of aerosol mass and number concentrations, size distributions, and aerosol optical properties. However, there are noticeable biases; e.g., simulated BC concentrations are significantly lower than measurements in the Arctic. There is a low bias in modeled aerosol optical depth on the global scale, especially in the developing countries. These biases in aerosol simulations clearly indicate the need for improvements of aerosol processes (e.g., emission fluxes of anthropogenic aerosols and precursor gases in developing countries, boundary layer nucleation) and properties (e.g., primary aerosol emission size, POM hygroscopicity). In addition, the critical role of cloud properties (e.g., liquid water content, cloud fraction) responsible for the wet scavenging of aerosol is highlighted. © Author(s) 2012."
"7004506673;","The Height of the Atmospheric Planetary Boundary layer: State of the Art and New Development",2012,"10.1007/978-94-007-2430-3_13","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883415505&doi=10.1007%2f978-94-007-2430-3_13&partnerID=40&md5=bad0e6bb49df7d6428f3839fe1efcb6c","The planetary boundary layer (PBL) is defined as the strongly turbulent atmospheric layer immediately affected by dynamic, thermal and other interactions with the Earth's surface. It essentially differs in nature from the weakly turbulent and persistently stably-stratified free atmosphere. To some extent the PBL upper boundary acts as a lid preventing dust, aerosols, gases and any other admixtures released from ground sources to efficiently penetrate upwards, thus blocking them within the PBL. It is conceivable that the air pollution is especially hazardous when associated with shallow PBLs. Likewise, positive or negative perturbations of the heat budget at the Earth's surface immediately impact on the PBL and are almost completely absorbed within the PBL through the very efficient mechanism of turbulent heat transfer. Determination of the PBL height is, therefore, an important aspect of modelling and prediction of air-pollution events and extreme colds or heats dangerous for human health. Because of high sensitivity of shallow PBLs to thermal impacts, variability of the PBL height is an important factor controlling fine features of climate change. Deep convective PBLs strongly impact on the climate system through turbulent entrainment (""ventilation"") at the PBL upper boundary, and thus essentially control development of convective clouds. This paper outlines modern knowledge about physical mechanisms and theoretical models of the PBL height and turbulent entrainment, and presents an advanced model of geophysical convective PBL. © Springer Science+Business Media B.V. 2012."
"55486290300;35593636200;7005304841;7003827051;7102862273;7006960661;35600074800;","Wintertime Arctic Ocean sea water properties and primary marine aerosol concentrations",2012,"10.5194/acp-12-10405-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877872524&doi=10.5194%2facp-12-10405-2012&partnerID=40&md5=bb91d819eb6a40266ab8d9737dab19e6","Sea spray aerosols are an important part of the climate system through their direct and indirect effects. Due to the diminishing sea ice, the Arctic Ocean is one of the most rapidly changing sea spray aerosol source areas. However, the influence of these changes on primary particle production is not known. In laboratory experiments we examined the influence of Arctic Ocean water temperature, salinity, and oxygen saturation on primary particle concentration characteristics. Sea water temperature was identified as the most important of these parameters. A strong decrease in sea spray aerosol production with increasing water temperature was observed for water temperatures between -1°C and 9°C. Aerosol number concentrations decreased from at least 1400 -3 to 350 cm-3. In general, the aerosol number size distribution exhibited a robust shape with one mode close to dry diameter Dp 0.2 μm with approximately 45% of particles at smaller sizes. Changes in sea water temperature did not result in pronounced change of the shape of the aerosol size distribution, only in the magnitude of the concentrations. Our experiments indicate that changes in aerosol emissions are most likely linked to changes of the physical properties of sea water at low temperatures. The observed strong dependence of sea spray aerosol concentrations on sea water temperature, with a large fraction of the emitted particles in the typical cloud condensation nuclei size range, provide strong arguments for a more careful consideration of this effect in climate models. © Author(s) 2012. CC Attribution 3.0 License."
"10044631200;22636199100;9272538400;55812424300;6603292679;7005231450;13408504900;6603344816;","HadISD: A quality-controlled global synoptic report database for selected variables at long-term stations from 1973-2011",2012,"10.5194/cp-8-1649-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878106966&doi=10.5194%2fcp-8-1649-2012&partnerID=40&md5=00cb7f55d763e997b0fc2d536a55a9ad","This paper describes the creation of HadISD: an automatically quality-controlled synoptic resolution dataset of temperature, dewpoint temperature, sea-level pressure, wind speed, wind direction and cloud cover from global weather stations for 1973-2011. The full dataset consists of over 6000 stations, with 3427 long-term stations deemed to have sufficient sampling and quality for climate applications requiring sub-daily resolution. As with other surface datasets, coverage is heavily skewed towards Northern Hemisphere mid-latitudes. The dataset is constructed from a large pre-existing ASCII flatfile data bank that represents over a decade of substantial effort at data retrieval, reformatting and provision. These raw data have had varying levels of quality control applied to them by individual data providers. The work proceeded in several steps: merging stations with multiple reporting identifiers; reformatting to netCDF; quality control; and then filtering to form a final dataset. Particular attention has been paid to maintaining true extreme values where possible within an automated, objective process. Detailed validation has been performed on a subset of global stations and also on UK data using known extreme events to help finalise the QC tests. Further validation was performed on a selection of extreme events world-wide (Hurricane Katrina in 2005, the cold snap in Alaska in 1989 and heat waves in SE Australia in 2009). Some very initial analyses are performed to illustrate some of the types of problems to which the final data could be applied. Although the filtering has removed the poorest station records, no attempt has been made to homogenise the data thus far, due to the complexity of retaining the true distribution of high-resolution data when applying adjustments. Hence non-climatic, time-varying errors may still exist in many of the individual station records and care is needed in inferring long-term trends from these data. This dataset will allow the study of high frequency variations of temperature, pressure and humidity on a global basis over the last four decades. Both individual extremes and the overall population of extreme events could be investigated in detail to allow for comparison with past and projected climate. A version-control system has been constructed for this dataset to allow for the clear documentation of any updates and corrections in the future. © Author(s) 2012."
"56080932300;42661306000;8609238900;12041200900;12040992000;56785080900;55352089200;7102780088;","An investigation of Glacial Isostatic Adjustment over the Amundsen Sea sector, West Antarctica",2012,"10.1016/j.gloplacha.2012.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865833391&doi=10.1016%2fj.gloplacha.2012.08.001&partnerID=40&md5=3355acb7ff19b1bd0308d0d323e3fc8e","The present study focuses on the Amundsen Sea sector which is the most dynamical region of the Antarctic Ice Sheet (AIS). Based on basin estimates of mass changes observed by the Gravity Recovery and Climate Experiment (GRACE) and volume changes observed by the Ice, Cloud and Land Elevation Satellite (ICESat), the mean mass change induced by Glacial Isostatic Adjustment (GIA) is derived. This mean GIA-induced mass change is found to be 34.1. ±. 11.9. Gt/yr, which is significantly larger than the predictions of current GIA models. We show that the corresponding mean elevation change of 23.3. ±. 7.7. mm/yr in the Amundsen Sea sector is in good agreement with the uplift rates obtained from observations at three GPS sites. Utilising ICESat observations, the observed uplift rates were corrected for elastic deformations due to present-day ice-mass changes. Based on the GRACE-derived mass change estimate and the inferred GIA correction, we inferred a present-day ice-mass loss of -. 98.9. ±. 13.7. Gt/yr for the Amundsen Sea sector. This is equivalent to a global eustatic sea-level rise of 0.27. ±. 0.04. mm/yr. Compared to the results relying on GIA model predictions, this corresponds to an increase of the ice-mass loss or sea-level rise, respectively, of about 40%. © 2012 Elsevier B.V."
"26533302300;56213274700;24467861000;6506555110;52664397200;56953593400;55382330300;55382486900;55235428500;7006802109;","Assessing the quality of a real-time Snow Cover Area product for hydrological applications",2012,"10.1016/j.rse.2012.09.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867206169&doi=10.1016%2fj.rse.2012.09.006&partnerID=40&md5=56687c03840ae0082f93c8c04f575242","Using reliable observed data is important for performing real-time flood forecasts or hydrological simulation in order to calibrate parameters or to update model variables. Satellite snow products can be one of these data, since snow is a water reservoir with a high impact on the quality of discharge simulation. The satellite Snow Cover Area products are known to be of good quality and are regularly used for studies in the meteorological and hydrological fields. However, these products are reprocessed and thus are not representative of the quality of a real-time product that would be needed for operational applications. The assessment of a real-time Snow Cover Area daily product at 250. m-resolution (the EURAC MODIS SCA product, which is based on the MODIS sensor) by comparing it directly or indirectly to the classical NASA MODIS SCA daily product and to the simulated Snow Cover Area of the distributed hydrological model, LISFLOOD, is realized in this article at the pan-European scale. This real-time product showed an overall good performance compared with the classical product, and a good agreement with the LISFLOOD simulated snow over Europe. The study showed the impact of forest cover on the scores of the compared products, whereas altitude did not have an impact. Using quality flags that are provided with the EURAC product improved its performance by reducing the misclassification of clouds as snow. © 2012 Elsevier Inc."
"8068419200;55660519500;35755764700;7202671706;8954866200;7801340314;54940625500;7003975505;55390548700;12759949700;56033135100;8559604100;","A model-data comparison for a multi-model ensemble of early Eocene atmosphere-ocean simulations: EoMIP",2012,"10.5194/cp-8-1717-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866086717&doi=10.5194%2fcp-8-1717-2012&partnerID=40&md5=f2e66b12860f8c618f80479eee7fb354","The early Eocene (~55 to 50 Ma) is a time period which has been explored in a large number of modelling and data studies. Here, using an ensemble of previously published model results, making up ""EoMIP"" - the Eocene Modelling Intercomparison Project - and syntheses of early Eocene terrestrial and sea surface temperature data, we present a self-consistent inter-model and model-data comparison. This shows that the previous modelling studies exhibit a very wide inter-model variability, but that at high CO2, there is good agreement between models and data for this period, particularly if possible seasonal biases in some of the proxies are considered. An energy balance analysis explores the reasons for the differences between the model results, and suggests that differences in surface albedo feedbacks, water vapour and lapse rate feedbacks, and prescribed aerosol loading are the dominant cause for the different results seen in the models, rather than inconsistencies in other prescribed boundary conditions or differences in cloud feedbacks. The CO 2 level which would give optimal early Eocene model-data agreement, based on those models which have carried out simulations with more than one CO2 level, is in the range of 2500 ppmv to 6500 ppmv. Given the spread of model results, tighter bounds on proxy estimates of atmospheric CO2 and temperature during this time period will allow a quantitative assessment of the skill of the models at simulating warm climates. If it is the case that a model which gives a good simulation of the Eocene will also give a good simulation of the future, then such an assessment could be used to produce metrics for weighting future climate predictions. © Author(s) 2012."
"56978385600;35072202600;7410041005;56218480200;","The three-dimensional structure of transatlantic african dust transport: A new perspective from CALIPSO LIDAR measurements",2012,"10.1155/2012/850704","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874895036&doi=10.1155%2f2012%2f850704&partnerID=40&md5=f84dca1a26ad65046ee1af2cb7dd805e","The lack of information on the vertical distribution of dust, in turn, results in large uncertainties when attempting to evaluate the impacts of dust on climate processes. We analyzed over two years of LIDAR measurements from NASA's CALIPSO and CloudSat satellites to document the vertical pathways of transatlantic transport of Saharan dust. Our analysis overcomes the limitations of quantitative dust detections with passive satellite measurements over land and low clouds and provides the fine vertical resolved structures. The results show the strong seasonal shift in dust source regions and transportation pathways due to the meteorological and thermodynamical conditions, which also control the dust vertical distribution as well as the depth of the dust layer. The dust layer top descending rates of 35 m/degree in summer, 25 m/degree in autumn and spring, and 10 m/degree in winter are found, respectively, while the dust is being transported across the Atlantic. Comparison with the model simulation highlights the potentials of dust observations using CALIPSO LIDAR. The observed seasonal dependence of these pathways gives new insights into the transport of the Saharan dust and provides important guidance for simulations of the production and transport of the global dust aerosol. © 2012 Dong Liu et al."
"7005801342;7004683817;7004272837;11139640100;","Possible effect of extreme solar energetic particle event of 20 January 2005 on polar stratospheric aerosols: Direct observational evidence",2012,"10.5194/acp-12-769-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874309994&doi=10.5194%2facp-12-769-2012&partnerID=40&md5=bf9c056a4cac67c1f7a030efcf4dcf5a","Energetic cosmic rays are the main source of ionization of the low-middle atmosphere, leading to associated changes in atmospheric properties. Via the hypothetical influence of ionization on aerosol growth and facilitated formation of clouds, this may be an important indirect link relating solar variability to climate. This effect is highly debated, however, since the proposed theoretical mechanisms still remain illusive and qualitative, and observational evidence is inconclusive and controversial. Therefore, important questions regarding the existence and magnitude of the effect, and particularly the fraction of aerosol particles that can form and grow, are still open. Here we present empirical evidence of the possible effect caused by cosmic rays upon polar stratospheric aerosols, based on a case study of an extreme solar energetic particle (SEP) event of 20 January 2005. Using aerosol data obtained over polar regions from different satellites with optical instruments that were operating during January 2005, such as the Stratospheric Aerosol and Gas Experiment III (SAGE III), and Optical Spectrograph and Infrared Imaging System (OSIRIS), we found a significant simultaneous change in aerosol properties in both the Southern and Northern Polar regions in temporal association with the SEP event. We speculate that ionization of the atmosphere, which was abnormally high in the lower stratosphere during the extreme SEP event, might have led to formation of new particles and/or growth of preexisting ultrafine particles in the polar stratospheric region. However, a detailed interpretation of the effect is left for subsequent studies. This is the first time high vertical resolution measurements have been used to discuss possible production of stratospheric aerosols under the influence of cosmic ray induced ionization. The observed effect is marginally detectable for the analyzed severe SEP event and can be undetectable for the majority of weak-moderate events. The present interpretation serves as a conservative upper limit of solar energetic particle effect upon polar stratospheric aerosols. © 2012 Author(s). CC Attribution 3.0 License."
"55544443300;57111001300;","Expansion of the Hadley cell under global warming: Winter versus summer",2012,"10.1175/JCLI-D-12-00323.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871865573&doi=10.1175%2fJCLI-D-12-00323.1&partnerID=40&md5=e76c6b199e011dc91b66c21c11329fce","A scaling relationship is introduced to explain the seasonality in the outer boundary of the Hadley cell in both climatology and trend in the simulations of phase 3 of the Coupled Model Intercomparison Project (CMIP3). In the climatological state, the summer cell reaches higher latitudes than the winter cell since the Hadley cell in summer deviates more from the angular momentum conserving state, resulting in weaker upper-level zonal winds, which enables the Hadley cell to extend farther poleward before becoming baroclinically unstable. The Hadley cell can also reach farther poleward as the ITCZ gets farther away from the equator; hence, the Hadley cell extends farther poleward in solstices than in equinoxes. In terms of trend, a robust poleward expansion of the Hadley cell is diagnosed in all seasons with global warming. The scaling analysis indicates this is mostly due to an increase in the subtropical static stability, which pushes poleward the baroclinically unstable zone and hence the poleward edge of the Hadley cell. The relation between the trends in the Hadley cell edge and the ITCZ is also discussed. © 2012 American Meteorological Society."
"57204252724;6602085893;24537168200;23481381300;7403354324;8208591500;9271096600;8669971400;57204699163;55755927000;57197639350;14034301300;7102501029;6604023055;7003550808;24331763700;16032925200;57214160655;7101793845;35998927000;23482738200;7003276832;24477694300;21646972800;26028984000;7005287667;7005713081;7003731407;7005844507;","Soot reference materials for instrument calibration and intercomparisons: A workshop summary with recommendations",2012,"10.5194/amt-5-1869-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866100901&doi=10.5194%2famt-5-1869-2012&partnerID=40&md5=358ddb25049f06188dd77bf4843c603e","Soot, which is produced from biomass burning and the incomplete combustion of fossil and biomass fuels, has been linked to regional and global climate change and to negative health problems. Scientists measure the properties of soot using a variety of methods in order to quantify source emissions and understand its atmospheric chemistry, reactivity under emission conditions, interaction with solar radiation, influence on clouds, and health impacts. A major obstacle currently limiting progress is the absence of established standards or reference materials for calibrating the many instruments used to measure the various properties of soot. The current state of availability and practicability of soot standard reference materials (SRMs) was reviewed by a group of 50 international experts during a workshop in June of 2011. The workshop was convened to summarize the current knowledge on soot measurement techniques, identify the measurement uncertainties and limitations related to the lack of soot SRMs, and identify attributes of SRMs that, if developed, would reduce measurement uncertainties. The workshop established that suitable SRMs are available for calibrating some, but not all, measurement methods. The community of users of the single-particle soot-photometer (SP2), an instrument using laser-induced incandescence, identified a suitable SRM, fullerene soot, but users of instruments that measure light absorption by soot collected on filters did not. Similarly, those who use thermal optical analysis (TOA) to analyze the organic and elemental carbon components of soot were not satisfied with current SRMs. The workshop, and subsequent, interactive discussions, produced a number of recommendations for the development of new SRMs, and their implementation, that would be suitable for the different soot measurement methods. © Author(s) 2012."
"17345303300;26643041500;35459245100;55800347700;23051160600;6701620591;23991203900;6507755223;35461255500;6506718302;","Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model",2012,"10.5194/gmd-5-845-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869050669&doi=10.5194%2fgmd-5-845-2012&partnerID=40&md5=df4361f277fde83d8775aac8be62edc1","We present the implementation and evaluation of a sectional aerosol microphysics module SALSA within the aerosol-climate model ECHAM5-HAM. This aerosol microphysics module has been designed to be flexible and computationally efficient so that it can be implemented in regional or global scale models. The computational efficiency has been achieved by minimising the number of variables needed to describe the size and composition distribution. The aerosol size distribution is described using 10 size classes with parallel sections which can have different chemical compositions. Thus in total, the module tracks 20 size sections which cover diameters ranging from 3 nm to 10 μm and are divided into three subranges, each with an optimised selection of processes and compounds. <br><br> The implementation of SALSA into ECHAM5-HAM includes the main aerosol processes in the atmosphere: emissions, removal, radiative effects, liquid and gas phase sulphate chemistry, and the aerosol microphysics. The aerosol compounds treated in the module are sulphate, organic carbon, sea salt, black carbon, and mineral dust. In its default configuration, ECHAM5-HAM treats aerosol size distribution using the modal method. In this implementation, the aerosol processes were converted to be used in a sectional model framework. <br><br> The ability of the module to describe the global aerosol properties was evaluated by comparing against (1) measured continental and marine size distributions, (2) observed variability of continental number concentrations, (3) measured sulphate, organic carbon, black carbon and sea-salt mass concentrations, (4) observations of aerosol optical depth (AOD) and other aerosol optical properties from satellites and AERONET network, (5) global aerosol budgets and concentrations from previous model studies, and (6) model results using M7, which is the default aerosol microphysics module in ECHAM5-HAM. <br><br> The evaluation shows that the global aerosol properties can be reproduced reasonably well using a coarse resolution of 10 sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sulphate and carbonaceous species have an annual mean within a factor of two of the observations. The simulated sea-salt concentrations reproduce the observations within a factor of two, apart from the Southern Ocean over which the concentrations are within a factor of five. Regionally, AOD is in a relatively good agreement with the observations (within a factor of two). At mid-latitudes the observed AOD is captured well, while at high-latitudes as well as in some polluted and dust regions the modelled AOD is significantly lower than observed. <br><br> Regarding most of the investigated aerosol properties, the SALSA and the modal aerosol module M7 perform comparably well against observations. However, SALSA reproduces the observed number concentrations and the size distribution of CCN sized particles much more accurately than M7, and is therefore a good choice for aerosol-cloud interaction studies in global models. Our study also shows that when activation type nucleation in the boundary layer is included, the observed concentration of particles under 50 nm in diameter are reproduced much better compared to when only binary nucleation in the free troposphere is assumed. © Author(s) 2012."
"7006211890;7101764967;7004944088;55684491100;35183991500;36105949100;35998927000;6602914876;56187256200;7003478309;8643810200;","The evolution of microphysical and optical properties of an A380 contrail in the vortex phase",2012,"10.5194/acp-12-6629-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869019099&doi=10.5194%2facp-12-6629-2012&partnerID=40&md5=eed3be109015ca29ad111eec9a9512f4","A contrail from a large-body A380 aircraft at cruise in the humid upper troposphere has been probed with in-situ instruments onboard the DLR research aircraft Falcon. The contrail was sampled during 700 s measurement time at contrail ages of about 1-4 min. The contrail was in the vortex regime during which the primary wake vortices were sinking 270 m below the A380 flight level while the secondary wake remained above. Contrail properties were sampled separately in the primary wake at 90 and 115 s contrail age and nearly continously in the secondary wake at contrail ages from 70 s to 220 s. The scattering phase functions of the contrail particles were measured with a polar nephelometer. The asymmetry parameter derived from these data is used to distinguish between quasi-spherical and aspherical ice particles. In the primary wake, quasi-spherical ice particles were found with concentrations up to 160 cm-3, mean effective diameter Deff of 3.7 μm, maximum extinction of 7.0 km-1, and ice water content (IWC) of 3 mg m-3 at slightly ice-subsaturated conditions. The secondary and primary wakes were separated by an almost particle-free wake vortex gap. The secondary wake contained clearly aspherical contrail ice particles with mean Deff of 4.8 μm, mean (maximum) concentration, extinction, and IWC of 80 (350) cm-3, 1.6 (5.0) km-1, and 2.5 (10) mg m-3, respectively, at conditions apparently above ice-saturation. The asymmetry parameter in the secondary wake decreased with contrail age from 0.87 to 0.80 on average indicating a preferential aspherical ice crystal growth. A retrieval of ice particle habit and size with an inversion code shows that the number fraction of aspherical ice crystals increased from 2% initially to 56% at 4 min contrail age. The observed crystal size and habit differences in the primary and secondary wakes of an up to 4 min old contrail are of interest for understanding ice crystal growth in contrails and their climate impact. Aspherical contrail ice particles cause less radiative forcing than spherical ones. © 2012 Author(s). CC Attribution 3.0 License."
"8599674800;23989756500;24479016500;55961507700;7004389152;","Analysis of agricultural drought using vegetation temperature condition index (VTCI) from Terra/MODIS satellite data",2012,"10.1007/s10661-011-2487-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871711985&doi=10.1007%2fs10661-011-2487-7&partnerID=40&md5=05ab058f0b37544d4e49bc3f912f528f","The most commonly used normalized difference vegetation index (NDVI) from remote sensing often fall short in real-time drought monitoring due to a lagged vegetation response to drought. Therefore, research recently emphasized on the use of combination of surface temperature and NDVI which provides vegetation and moisture conditions simultaneously. Since drought stress effects on agriculture are closely linked to actual evapotranspiration, we used a vegetation temperature condition index (VTCI) which is more closely related to crop water status and holds a key place in real-time drought monitoring and assessment. In this study, NDVI and land surface temperature (Ts) from MODIS 8-day composite data during cloud-free period (September-October) were adopted to construct an NDVI-Ts space, from which the VTCI was computed. The crop moisture index (based on estimates of potential evapotranspiration and soil moisture depletion) was calculated to represent soil moisture stress on weekly basis for 20 weather monitoring stations. Correlation and regression analysis were attempted to relate VTCI with crop moisture status and crop performance. VTCI was found to accurately access the degree and spatial extent of drought stress in all years (2000, 2002, and 2004). The temporal variation of VTCI also provides drought pattern changes over space and time. Results showed significant and positive relations between CMI (crop moisture index) and VTCI observed particularly during prominent drought periods which proved VTCI as an ideal index to monitor terminal drought at regional scale. VTCI had significant positive relationship with yield but weakly related to crop anomalies. Duration of terminal drought stress derived from VTCI has a significant negative relationship with yields of major grain and oilseeds crops, particularly, groundnut. © Springer Science+Business Media B.V. 2011."
"55350670000;6701385171;7005863292;6602806364;","Investigation of the surface and circulation impacts of cloud-brightening geoengineering",2012,"10.1175/JCLI-D-11-00282.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870013856&doi=10.1175%2fJCLI-D-11-00282.1&partnerID=40&md5=738cb4d4443a53f7563acd88529858cd","Projected increases in greenhouse gases have prompted serious discussion on geoengineering the climate system to counteract global climate change. Cloud albedo enhancement has been proposed as a feasible geoengineering approach, but previous research suggests undesirable consequences of globally uniform cloud brightening. The present study uses GFDL's Climate Model version 2G (CM2G) global coupled model to simulate cloud albedo enhancement via increases in cloud condensation nuclei (CCN) to 1000 cm-3 targeted at the marine stratus deck of the Pacific Ocean, where persistent lowclouds suggest a regional approach to cloud brightening. The impact ofthis regional geoengineering on global circulationand climate in the presence of a 1% annual increase of CO2 was investigated. Surface temperatures returned to nearpreindustrial levels over much of the globe with cloud modifications in place. In the first 40 years and over the 140-yr mean, significant cooling over the equatorial Pacific, continued Arctic warming, large precipitation changes over the western Pacific, and a westward compression and intensification of the Walker circulation were observed in response to cloud brightening. The cloud brightening caused a persistent La Nin~ a condition associated with an increase in hurricane maximumpotential intensity and genesis potential index, and decreased vertical wind shear between July and November in the tropical Atlantic, South China Sea, and to the east of Japan. Responses were similar with CCN=500 cm-3. © 2012 American Meteorological Society."
"23486332900;6701455548;","Model-specific radiative kernels for calculating cloud and noncloud climate feedbacks",2012,"10.1175/JCLI-D-11-00726.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870014753&doi=10.1175%2fJCLI-D-11-00726.1&partnerID=40&md5=685c0b5d99dabeae83d03c29138f5f45","Radiative kernels have become a common tool for evaluating and comparing radiative feedbacks to climate change in different general circulation models. However, kernel feedback calculations are inaccurate for simulations where the atmosphere is significantly perturbed from its base state, such as for very large forcing or perturbed physics simulations. In addition, past analyses have not produced kernels relating to prognostic cloud variables because of strong nonlinearities in their relationship to radiative forcing. A new methodology is presented that allows for fast statistical optimizing of existing kernels such that accuracy is increased for significantly altered climatologies. International Satellite Cloud Climatology Project (ISCCP) simulator output is used to relate changes in cloud-type histograms to radiative fluxes. With minimal additional computation, an individual set of kernels is created for each climate experiment such that climate feedbacks can be reliably estimated even in significantly perturbed climates. This methodology is applied to successive generations of the Community Atmosphere Model (CAM).Increased climate sensitivity in CAM5 is shown to be due to reduced negative stratus and stratocumulus feedbacks in the tropics and midlatitudes, strong positive stratus feedbacks in the southern oceans, and a strengthened positive longwave cirrus feedback. Results also suggest that CAM5 exhibits a stronger surface albedo feedback than its predecessors, a feature not apparent when using a single kernel. Optimized kernels for CAM5 suggest weaker global-mean shortwave cloud feedback than one would infer from using the original kernels and an adjusted cloud radiative forcing methodology. © 2012 American Meteorological Society."
"56636540000;15726335100;6603873829;","A fast SEVIRI simulator for quantifying retrieval uncertainties in the CM SAF cloud physical property algorithm",2012,"10.5194/acp-12-10957-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869986965&doi=10.5194%2facp-12-10957-2012&partnerID=40&md5=ffd8bf25297821c066fdc0d690adf7d3","The uncertainties in the cloud physical properties derived from satellite observations make it difficult to interpret model evaluation studies. In this paper, the uncertainties in the cloud water path (CWP) retrievals derived with the cloud physical properties retrieval algorithm (CPP) of the climate monitoring satellite application facility (CM SAF) are investigated. To this end, a numerical simulator of MSG-SEVIRI observations has been developed that calculates the reflectances at 0.64 and 1.63 &mu;m for a wide range of cloud parameter values, satellite viewing geometries and surface albedos using a plane-parallel radiative transfer model. The reflectances thus obtained are used as input to CPP, and the retrieved values of CWP are compared to the original input of the simulator. Cloud parameters considered in this paper refer to e.g. sub-pixel broken clouds and the simultaneous occurrence of ice and liquid water clouds within one pixel. These configurations are not represented in the CPP algorithm and as such the associated retrieval uncertainties are potentially substantial. <br><br> It is shown that the CWP retrievals are very sensitive to the assumptions made in the CPP code. The CWP retrieval errors are generally small for unbroken single-layer clouds with COT > 10, with retrieval errors of ∼3% for liquid water clouds to ∼10% for ice clouds. In a multi-layer cloud, when both liquid water and ice clouds are present in a pixel, the CWP retrieval errors increase dramatically; depending on the cloud, this can lead to uncertainties of 40-80%. CWP retrievals also become more uncertain when the cloud does not cover the entire pixel, leading to errors of ∼50% for cloud fractions of 0.75 and even larger errors for smaller cloud fractions. Thus, the satellite retrieval of cloud physical properties of broken clouds as well as multi-layer clouds is complicated by inherent difficulties, and the proper interpretation of such retrievals requires extra care. © Author(s) 2012. CC Attribution 3.0 License."
"41862644800;35490828000;56118407000;57203078745;35119297700;7003627515;6603873829;55663749500;","Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: A study with a regional climate model",2012,"10.5194/tc-6-1175-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865225965&doi=10.5194%2ftc-6-1175-2012&partnerID=40&md5=88ba5e9ba0f8eecc351ba6170eef8876","We present a sensitivity study of the surface mass balance (SMB) of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo scheme. The snow albedo scheme uses grain size as a prognostic variable and further depends on cloud cover, solar zenith angle and black carbon concentration. For the control experiment the overestimation of absorbed shortwave radiation (+6%) at the K-transect (west Greenland) for the period 2004-2009 is considerably reduced compared to the previous density-dependent albedo scheme (+22%). To simulate realistic snow albedo values, a small concentration of black carbon is needed, which has strongest impact on melt in the accumulation area. A background ice albedo field derived from MODIS imagery improves the agreement between the modeled and observed SMB gradient along the K-transect. The effect of enhanced meltwater retention and refreezing is a decrease of the albedo due to an increase in snow grain size. As a secondary effect of refreezing the snowpack is heated, enhancing melt and further lowering the albedo. Especially in a warmer climate this process is important, since it reduces the refreezing potential of the firn layer that covers the Greenland Ice Sheet. © Author(s) 2012."
"55502010400;24485834000;","Thermodynamic causes for future trends in heavy precipitation over Europe based on an ensemble of regional climate model simulations",2012,"10.1175/JCLI-D-11-00304.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870035445&doi=10.1175%2fJCLI-D-11-00304.1&partnerID=40&md5=a2aeb6194695ac2818935942597dcf9d","An extreme-value analysis of projected changes in heavy precipitation is carried out for an ensemble of eight high-resolution regional climate model simulations over the European domain. The consideration of several regional climate models that are forced by different global models allows for an assessment of the robustness of the results in terms of intersimulation agreement. The extreme-value statistical method is based on a model that includes time-dependent parameters. Summer and winter are examined separately. This allows for identifying and sharpening the understanding of physical processes inducing the changes in precipitation characteristics. Thermodynamic aspects of changes in heavy precipitation are discussed. Variables that are related to the process of precipitation formation, such as precipitable water and cloud liquid water, are examined. In this context, the scaling of changes in heavy precipitation and other thermodynamic quantities with changes in temperature is explored. The validity of a Clausius-Clapeyron scaling of heavy precipitation is assessed on regional scales. Significant regional and seasonal differences in trends of heavy precipitation and only a limited validity of the Clausius-Clapeyron scaling are found. In winter, enhanced moisture transport and storm-track intensity lead to an increase in heavy precipitation, especially over the northern parts of the European continent. In summer, the increase of precipitable water is less than that required to maintain the same probability for saturation over southern Europe, which results in negative trends of heavy precipitation in these regions. © 2012 American Meteorological Society."
"7401936984;22635190100;7401974644;7402064802;52464731300;","On the Correspondence between short- and long-time-scale systematic errors in CAM4/CAM5 for the year of tropical convection",2012,"10.1175/JCLI-D-12-00134.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869795715&doi=10.1175%2fJCLI-D-12-00134.1&partnerID=40&md5=e285205b064e81a1e7f4698b78806369","The correspondence between short- and long-time-scale systematic errors in the Community Atmospheric Model, version 4 (CAM4) and version 5 (CAM5), is systematically examined. The analysis is based on the annual-mean data constructed from long-term ""free running"" simulations and short-range hindcasts. The hindcasts are initialized every day with the ECMWF analysis for the Year(s) of Tropical Convection. It has been found that most systematic errors, particularly those associated with moist processes, are apparent in day 2 hindcasts. These errors steadily grow with the hindcast lead time and typically saturate after five days with amplitudes comparable to the climate errors. Examples include the excessive precipitation inmuch of the tropics and the overestimate of net shortwave absorbed radiation in the stratocumulus cloud decks over the eastern subtropical oceans and the Southern Ocean at about 608S. This suggests that these errors are likely the result of model parameterization errors as the large-scale flow remains close to observed in the first few days of the hindcasts. In contrast, other climate errors are present in the hindcasts, but with amplitudes that are significantly smaller than and do not approach their climate errors during the 6-day hindcasts. These include the cold biases in the lower stratosphere, the unrealistic double-intertropical convergence zone pattern in the simulated precipitation, and an annular mode bias in extratropical sea level pressure. This indicates that these biases could be related to slower processes such as radiative and chemical processes, which are important in the lower stratosphere, or the result of poor interactions of the parameterized physics with the large-scale flow. © 2012 American Meteorological Society."
"7006306835;56744278700;","Nonlocal component of radiative flux perturbation",2012,"10.1029/2012GL054050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870585733&doi=10.1029%2f2012GL054050&partnerID=40&md5=073643329686a5cc6da0fd386a424701","Radiative flux perturbation (RFP) is defined as the top-of-the-atmosphere (TOA) radiative imbalance after the atmosphere-land system adjusts fully to an external perturbation, and serves as a useful metric for quantifying climate forcing. This paper presents an effort to address the issue of whether a forcing imposed persistently over a specific region may alter the radiative balance elsewhere through atmospheric circulation, thus giving rise to a nonlocal component of RFP. We perturb the climate simulated with an atmospheric general circulation model (AGCM) solely by increasing the cloud droplet number concentration over the land, and observe widespread positive (warming) RFP over the ocean, along with the expected negative (cooling) RFP over the land. A detailed analysis suggests that the oceanic (or nonlocal) RFP is closely associated with a reduction in low cloud amount, which can be attributed primarily to the horizontal advection of drier land boundary layer air and to the oceanic boundary layer top entrainment of drier free troposphere air. By examining how the land surface and atmospheric energy balances are re-established, we are able to identify the physical mechanisms behind the strong hydrological impact of a tropical land shortwave (SW) forcing (the multiplier effect). In contrast, the hydrological cycle is relatively insensitive to an extratropical forcing."
"55512618700;57202301596;","Origins of tropical-wide SST biases in CMIP multi-model ensembles",2012,"10.1029/2012GL053777","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870602021&doi=10.1029%2f2012GL053777&partnerID=40&md5=a384dc7c9052fe8d3e04ab19cdb8d455","Long-standing simulation errors limit the utility of climate models. Overlooked are tropical-wide errors, with sea surface temperature (SST) biasing high or low across all the tropical ocean basins. Our analysis based on Coupled Model Intercomparison Project (CMIP) multi-model ensembles shows that such SST biases can be classified into two types: one with a broad meridional structure and of the same sign across all basins that is highly correlated with the tropical mean; and one with large inter-model variability in the cold tongues of the equatorial Pacific and Atlantic. The first type can be traced back to biases in atmospheric simulations of cloud cover, with cloudy models biasing low in tropical-wide SST. The second type originates from the diversity among models in representing the thermocline depth; models with a deep thermocline feature a warm cold tongue on the equator. Implications for inter-model variability in precipitation climatology and SST threshold for convection are discussed. © 2012. American Geophysical Union. All Rights Reserved."
"55489380000;55198893200;36165729500;55198893000;6602097797;7003512900;7005415993;","Correcting the radar rainfall forcing of a hydrological model with data assimilation: Application to flood forecasting in the Lez catchment in Southern France",2012,"10.5194/hess-16-4247-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869480418&doi=10.5194%2fhess-16-4247-2012&partnerID=40&md5=b94386703143e9018ce6a62f08202951","The present study explores the application of a data assimilation (DA) procedure to correct the radar rainfall inputs of an event-based, distributed, parsimonious hydrological model. An extended Kalman filter algorithm was built on top of a rainfall-runoff model in order to assimilate discharge observations at the catchment outlet. This work focuses primarily on the uncertainty in the rainfall data and considers this as the principal source of error in the simulated discharges, neglecting simplifications in the hydrological model structure and poor knowledge of catchment physics. The study site is the 114 km2 Lez catchment near Montpellier, France. This catchment is subject to heavy orographic rainfall and characterised by a karstic geology, leading to flash flooding events. The hydrological model uses a derived version of the SCS method, combined with a Lag and Route transfer function. Because the radar rainfall input to the model depends on geographical features and cloud structures, it is particularly uncertain and results in significant errors in the simulated discharges. This study seeks to demonstrate that a simple DA algorithm is capable of rendering radar rainfall suitable for hydrological forecasting. To test this hypothesis, the DA analysis was applied to estimate a constant hyetograph correction to each of 19 flood events. The analysis was carried in two different modes: by assimilating observations at all available time steps, referred to here as reanalysis mode, and by using only observations up to 3 h before the flood peak to mimic an operational environment, referred to as pseudo-forecast mode. In reanalysis mode, the resulting correction of the radar rainfall data was then compared to the mean field bias (MFB), a corrective coefficient determined using rain gauge measurements. It was shown that the radar rainfall corrected using DA leads to improved discharge simulations and Nash-Sutcliffe efficiency criteria compared to the MFB correction. In pseudo-forecast mode, the reduction of the uncertainty in the rainfall data leads to a reduction of the error in the simulated discharge, but uncertainty from the model parameterisation diminishes data assimilation efficiency. While the DA algorithm used is this study is effective in correcting uncertain radar rainfall, model uncertainty remains an important challenge for flood forecasting within the Lez catchment. © 2012 Author(s)."
"7407104838;7102805852;","Sea-spray geoengineering in the HadGEM2-ES earth-system model: Radiative impact and climate response",2012,"10.5194/acp-12-10887-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869179182&doi=10.5194%2facp-12-10887-2012&partnerID=40&md5=c1b77003b161646f58afb980064de25f","The radiative impact and climate effects of geoengineering using sea-spray aerosols have been investigated in the HadGEM2-ES Earth system model using a fully prognostic treatment of the sea-spray aerosols and also including their direct radiative effect. Two different emission patterns were considered, one to maximise the direct effect in clear skies, the other to maximise the indirect effects of the sea-spray on low clouds; in both cases the emissions were limited to 10% of the ocean area. While the direct effect was found to be significant, the indirect effects on clouds were much more effective in reducing global mean temperature as well as having less of an impact on global mean precipitation per unit temperature reduction. The impact on the distribution of precipitation was found to be similar in character, but less in degree, to that simulated by a previous study using a much simpler treatment of this geoengineering process. © 2012 Author(s)."
"8728433200;13405658600;7501381728;24398842400;57203053317;","Uncertainty associated with convective wet removal of entrained aerosols in a global climate model",2012,"10.5194/acp-12-10725-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869162422&doi=10.5194%2facp-12-10725-2012&partnerID=40&md5=e5a9d69cf15a081f5672a966bd5937d7","The uncertainties associated with the wet removal of aerosols entrained above convective cloud bases are investigated in a global aerosol-climate model (ECHAM5-HAM) under a set of limiting assumptions for the wet removal of the entrained aerosols. The limiting assumptions for the wet removal of entrained aerosols are negligible scavenging and vigorous scavenging (either through activation, with size-dependent impaction scavenging, or with the prescribed fractions of the standard model). To facilitate this process-based study, an explicit representation of cloud-droplet-borne and ice-crystal-borne aerosol mass and number, for the purpose of wet removal, is introduced into the ECHAM5-HAM model. This replaces and is compared with the prescribed cloud-droplet-borne and ice-crystal-borne aerosol fraction scavenging scheme of the standard model. A 20% to 35% uncertainty in simulated global, annual mean aerosol mass burdens and optical depth (AOD) is attributed to different assumptions for the wet removal of aerosols entrained above convective cloud bases. Assumptions about the removal of aerosols entrained above convective cloud bases control modeled upper tropospheric aerosol concentrations by as much as one order of magnitude. Simulated aerosols entrained above convective cloud bases contribute 20% to 50% of modeled global, annual mean aerosol mass convective wet deposition (about 5% to 10% of the total dry and wet deposition), depending on the aerosol species, when including wet scavenging of those entrained aerosols (either by activation, size-dependent impaction, or with the prescribed fraction scheme). Among the simulations, the prescribed fraction and size-dependent impaction schemes yield the largest global, annual mean aerosol mass convective wet deposition (by about two-fold). However, the prescribed fraction scheme has more vigorous convective mixed-phase wet removal (by two to five-fold relative to the size-dependent impaction scheme) since nearly all entrained accumulation and coarse mode aerosols are assumed to be cloud-droplet borne or ice-crystal borne, and evaporation due to the Bergeron-Findeisen process is neglected. The simulated convective wet scavenging of entrained accumulation and coarse mode aerosols has feedbacks on new particle formation and the number of Aitken mode aerosols, which control stratiform and convective cloud droplet number concentrations and yield precipitation changes in the ECHAM5-HAM model. However, the geographic distribution of aerosol annual mean convective wet deposition change in the model is driven by changes to the assumptions regarding the scavenging of aerosols entrained above cloud bases rather than by precipitation changes, except for sea salt deposition in the tropics. Uncertainty in the seasonal, regional cycles of AOD due to assumptions about entrained aerosol wet scavenging is similar in magnitude to the estimated error in the AOD retrievals. The uncertainty in aerosol concentrations, burdens, and AOD attributed to different assumptions for the wet scavenging of aerosols entrained above convective cloud bases in a global model motivates the ongoing need to better understand and model the activation and impaction processes that aerosols undergo after entrainment into convective updrafts. © 2012 Author(s)."
"36608374800;7006107059;6701573579;","Atmospheric removal times of the aerosol-bound radionuclides 137Cs and 131I measured after the Fukushima Dai-ichi nuclear accident &ndash; A constraint for air quality and climate models",2012,"10.5194/acp-12-10759-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869195165&doi=10.5194%2facp-12-10759-2012&partnerID=40&md5=7dd10b977f1fbe2a77f622c44e08223a","Caesium-137 (137Cs) and iodine-131 (131I) are radionuclides of particular concern during nuclear accidents, because they are emitted in large amounts and are of significant health impact. 137Cs and 131I attach to the ambient accumulation-mode (AM) aerosols and share their fate as the aerosols are removed from the atmosphere by scavenging within clouds, precipitation and dry deposition. Here, we estimate their removal times from the atmosphere using a unique high-precision global measurement data set collected over several months after the accident at the Fukushima Dai-ichi nuclear power plant in March 2011. The noble gas xenon-133 (133Xe), also released during the accident, served as a passive tracer of air mass transport for determining the removal times of 137Cs and 131I via the decrease in the measured ratios 137Cs/133Xe and 131I/133Xe over time. After correction for radioactive decay, the 137Cs/133Xe ratios reflect the removal of aerosols by wet and dry deposition, whereas the 131I/133Xe ratios are also influenced by aerosol production from gaseous 131I. We find removal times for 137Cs of 10.0-13.9 days and for 131I of 17.1-24.2 days during April and May 2011. The removal time of 131I is longer due to the aerosol production from gaseous 131I, thus the removal time for 137Cs serves as a better estimate for aerosol lifetime. The removal time of 131I is of interest for semi-volatile species. We discuss possible caveats (e.g. late emissions, resuspension) that can affect the results, and compare the 137Cs removal times with observation-based and modeled aerosol lifetimes. Our 137Cs removal time of 10.0 13.9 days should be representative of a ""background"" AM aerosol well mixed in the extratropical Northern Hemisphere troposphere. It is expected that the lifetime of this vertically mixed background aerosol is longer than the lifetime of fresh AM aerosols directly emitted from surface sources. However, the substantial difference to the mean lifetimes of AM aerosols obtained from aerosol models, typically in the range of 3-7 days, warrants further research on the cause of this discrepancy. Too short modeled AM aerosol lifetimes would have serious implications for air quality and climate model predictions. © 2012 Author(s)."
"26768076600;7004596535;17433905200;6506258154;7006708207;16833315000;56472932500;","Functionalization and fragmentation during ambient organic aerosol aging: Application of the 2-D volatility basis set to field studies",2012,"10.5194/acp-12-10797-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869194060&doi=10.5194%2facp-12-10797-2012&partnerID=40&md5=5cff950401fbbe940c39ed7cb7f11a38","Multigenerational oxidation chemistry of atmospheric organic compounds and its effects on aerosol loadings and chemical composition is investigated by implementing the Two-Dimensional Volatility Basis Set (2-D-VBS) in a Lagrangian host chemical transport model. Three model formulations were chosen to explore the complex interactions between functionalization and fragmentation processes during gas-phase oxidation of organic compounds by the hydroxyl radical. The base case model employs a conservative transformation by assuming a reduction of one order of magnitude in effective saturation concentration and an increase of oxygen content by one or two oxygen atoms per oxidation generation. A second scheme simulates functionalization in more detail using group contribution theory to estimate the effects of oxygen addition to the carbon backbone on the compound volatility. Finally, a fragmentation scheme is added to the detailed functionalization scheme to create a functionalization-fragmentation parameterization. Two condensed-phase chemistry pathways are also implemented as additional sensitivity tests to simulate (1) heterogeneous oxidation via OH uptake to the particle-phase and (2) aqueous-phase chemistry of glyoxal and methylglyoxal. The model is applied to summer and winter periods at three sites where observations of organic aerosol (OA) mass and O:C were obtained during the European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) campaigns. The base case model reproduces observed mass concentrations and O:C well, with fractional errors (FE) lower than 55% and 25%, respectively. The detailed functionalization scheme tends to overpredict OA concentrations, especially in the summertime, and also underpredicts O:C by approximately a factor of 2. The detailed functionalization model with fragmentation agrees well with the observations for OA concentration, but still underpredicts O:C. Both heterogeneous oxidation and aqueous-phase processing have small effects on OA levels but heterogeneous oxidation, as implemented here, does enhance O:C by about 0.1. The different schemes result in very different fractional attribution for OA between anthropogenic and biogenic sources. © 2012 Author(s)."
"23051160600;6507755223;6506718302;57208121852;6701511324;56154540200;7003931528;35461255500;7006712143;","Brightening of the global cloud field by nitric acid and the associated radiative forcing",2012,"10.5194/acp-12-7625-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869034863&doi=10.5194%2facp-12-7625-2012&partnerID=40&md5=31b9a9e9aeabd511a3bfad3053f5bdea","Clouds cool Earth's climate by reflecting 20% of the incoming solar energy, while also trapping part of the outgoing radiation. The effect of human activities on clouds is poorly understood, but the present-day anthropogenic cooling via changes of cloud albedo and lifetime could be of the same order as warming from anthropogenic addition in CO2. Soluble trace gases can increase water condensation to particles, possibly leading to activation of smaller aerosols and more numerous cloud droplets. We have studied the effect of nitric acid on the aerosol indirect effect with the global aerosol-climate model ECHAM5.5-HAM2. Including the nitric acid effect in the model increases cloud droplet number concentrations globally by 7%. The nitric acid contribution to the present-day cloud albedo effect was found to be-0.32 W m -2 and to the total indirect effect-0.46 W m -2. The contribution to the cloud albedo effect is shown to increase to-0.37 W m -2 by the year 2100, if considering only the reductions in available cloud condensation nuclei. Overall, the effect of nitric acid can play a large part in aerosol cooling during the following decades with decreasing SO2 emissions and increasing NOx and greenhouse gases. © 2012 Author(s)."
"34876658200;56410144300;8349977900;36538539800;6701378450;7003666669;55717074000;7006270084;6603268269;","Global distribution and climate forcing of marine organic aerosol-Part 2: Effects on cloud properties and radiative forcing",2012,"10.5194/acp-12-6555-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867497371&doi=10.5194%2facp-12-6555-2012&partnerID=40&md5=1e4a149f64e8ec69c23ff89b321d52bf","A series of simulations with the Community Atmosphere Model version 5 (CAM5) with a 7-mode Modal Aerosol Model were conducted to assess the changes in cloud microphysical properties and radiative forcing resulting from marine organic aerosols. Model simulations show that the anthropogenic aerosol indirect forcing (AIF) predicted by CAM5 is decreased in absolute magnitude by up to 0.09 W mg -2 (7%) when marine organic aerosols are included. Changes in the AIF from marine organic aerosols are associated with small global increases in low-level in-cloud droplet number concentration and liquid water path of 1.3 cmg -3 (1.5%) and 0.22 g mg -2 (0.5%), respectively. Areas especially sensitive to changes in cloud properties due to marine organic aerosol include the Southern Ocean, North Pacific Ocean, and North Atlantic Ocean, all of which are characterized by high marine organic emission rates. As climate models are particularly sensitive to the background aerosol concentration, this small but non-negligible change in the AIF due to marine organic aerosols provides a notable link for ocean-ecosystem marine low-level cloud interactions and may be a candidate for consideration in future earth system models. © 2012 Author(s)."
"35280798500;57203053317;13403622000;","Bacteria in the ECHAM5-HAM global climate model",2012,"10.5194/acp-12-8645-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869068009&doi=10.5194%2facp-12-8645-2012&partnerID=40&md5=c2ebc2d8970d9558f97d70a0884177d3","Some bacteria are among the most active ice nuclei found in nature due to the ice nucleation active proteins on their surface, which serve as active sites for ice nucleation. Their potential impact on clouds and precipitation is not well known and needs to be investigated. Bacteria as a new aerosol species were introduced into the global climate model (GCM) ECHAM5-HAM. The inclusion of bacteria 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 are simulated, specifically in the boreal regions where tundra and forests act as sources of bacteria. Although bacteria contribute to heterogeneous freezing, their impact is reduced by their low numbers compared to other heterogeneous IN. This result confirms the outcome of several previous studies. © 2012 Author(s)."
"49261186800;7004469744;35810775100;12753162000;8942524900;8942525300;8758893600;35547807400;","Importance of tropospheric volcanic aerosol for indirect radiative forcing of climate",2012,"10.5194/acp-12-7321-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869054432&doi=10.5194%2facp-12-7321-2012&partnerID=40&md5=f5440c7eb6a520c5019f42f981c90b5e","Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the radiative state of the atmosphere. We use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo radiative forcing under pre-industrial (PI) and present-day (PD) conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of g -1.06 W mg -2 in the PI era but only g-0.56 W m -2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud radiative forcing because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud radiative state. Assuming a-50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo forcing to lie between-1.16 W m -2 and g-0.86 W m -2. Therefore, the volcanically induced uncertainty in the PI baseline cloud radiative state substantially adds to the already large uncertainty in the magnitude of the indirect radiative forcing of climate. © 2012 Author(s)."
"7102591209;7006211890;7101764967;","On the interpretation of an unusual in-situ measured ice crystal scattering phase function",2012,"10.5194/acp-12-9355-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869073621&doi=10.5194%2facp-12-9355-2012&partnerID=40&md5=34abbe75928510c2a2946cf0202172b4","In-situ Polar Nephelometer (PN) measurements of unusual ice crystal scattering phase functions, obtained near the cloud-top of a mid-latitude anvil cloud, at a temperature of about-58 °C, were recently reported by Gayet et al. (2012). The ice crystal habits that produced the phase functions consisted of aggregates of ice crystals and aggregates of quasi-spherical ice particles. The diameters of the individual quasi-spherical ice particles were estimated to be between about 15 μm and 20 μm. The measured-averaged scattering phase functions were featureless, at scattering angles less than about 100°, but an ice bow-like feature was noted between the scattering angles of about 120° to 160°. The estimated asymmetry parameter was 0.78 ± 0.04. In this paper, the averaged scattering phase function is interpreted in terms of a weighted habit mixture model. The model that provides the best overall fit to the measured scattering phase function comprises of highly distorted ten-element hexagonal ice aggregates and quasi-spherical ice particles. The smaller quasi-spherical ice crystals are represented by Chebyshev ice particles of order 3, and were assumed to have equivalent spherical diameters of 24 μm. The asymmetry parameter of the best overall model was found to be 0.79. It is argued that the Chebyshev-like ice particles are responsible for the ice bow-like feature and mostly dominate the scattered intensity measured by the PN. The results from this paper have important implications for climate modelling (energy balance of anvils), cloud physics and the remote sensing of cirrus properties. © 2012 Author(s)."
"21742333400;24167564500;56403904000;6701378450;","Adjoint sensitivity of global cloud droplet number to aerosol and dynamical parameters",2012,"10.5194/acp-12-9041-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868676555&doi=10.5194%2facp-12-9041-2012&partnerID=40&md5=f78a1c1a27bd76e03362ee43a32e4b62","We present the development of the adjoint of a comprehensive cloud droplet formation parameterization for use in aerosol-cloud-climate interaction studies. The adjoint efficiently and accurately calculates the sensitivity of cloud droplet number concentration (CDNC) to all parameterization inputs (e.g., updraft velocity, water uptake coefficient, aerosol number and hygroscopicity) with a single execution. The adjoint is then integrated within three dimensional (3-D) aerosol modeling frameworks to quantify the sensitivity of CDNC formation globally to each parameter. Sensitivities are computed for year-long executions of the NASA Global Modeling Initiative (GMI) Chemical Transport Model (CTM), using wind fields computed with the Goddard Institute for Space Studies (GISS) Global Circulation Model (GCM) II', and the GEOS-Chem CTM, driven by meteorological input from the Goddard Earth Observing System (GEOS) of the NASA Global Modeling and Assimilation Office (GMAO). We find that over polluted (pristine) areas, CDNC is more sensitive to updraft velocity and uptake coefficient (aerosol number and hygroscopicity). Over the oceans of the Northern Hemisphere, addition of anthropogenic or biomass burning aerosol is predicted to increase CDNC in contrast to coarse-mode sea salt which tends to decrease CDNC. Over the Southern Oceans, CDNC is most sensitive to sea salt, which is the main aerosol component of the region. Globally, CDNC is predicted to be less sensitive to changes in the hygroscopicity of the aerosols than in their concentration with the exception of dust where CDNC is very sensitive to particle hydrophilicity over arid areas. Regionally, the sensitivities differ considerably between the two frameworks and quantitatively reveal why the models differ considerably in their indirect forcing estimates. © 2012 Author(s)."
"56384704800;36098422200;6506152198;57208121852;56270311300;57203053317;16444232500;8728433200;6602600408;57202299549;56154540200;7003931528;","The global aerosol-climate model ECHAM-HAM, version 2: Sensitivity to improvements in process representations",2012,"10.5194/acp-12-8911-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868686716&doi=10.5194%2facp-12-8911-2012&partnerID=40&md5=8d888fcff727bc4d5542164d8b33ecbb","This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation. Results indicate that from HAM1 to HAM 2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced κ-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker in-cloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7) between accumulation mode and coarse mode emission fluxes of aerosol number concentration. This leads to a general increase in the number concentration of smaller particles over the oceans in HAM2, as reflected by the higher Ångström parameters. Evaluation against observation reveals that in terms of model performance, main improvements in HAM2 include a marked decrease of the systematic negative bias in the absorption aerosol optical depth, as well as smaller biases over the oceans in Ångström parameter and in the accumulation mode number concentration. The simulated geographical distribution of aerosol optical depth (AOD) is better correlated with the MODIS data, while the surface aerosol mass concentrations are very similar to those in the old version. The total aerosol water content in HAM2 is considerably closer to the multi-model average from Phase I of the AeroCom intercomparison project. Model deficiencies that require further efforts in the future include (i) positive biases in AOD over the ocean, (ii) negative biases in AOD and aerosol mass concentration in high-latitude regions, and (iii) negative biases in particle number concentration, especially that of the Aitken mode, in the lower troposphere in heavily polluted regions. © 2012 Author(s)."
"55480654300;7004469744;56757625500;8942524900;57203200427;","The scavenging processes controlling the seasonal cycle in Arctic sulphate and black carbon aerosol",2012,"10.5194/acp-12-6775-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869070295&doi=10.5194%2facp-12-6775-2012&partnerID=40&md5=187e273e59e29b0b1b44bd5b67384b07","The seasonal cycle in Arctic aerosol is typified by high concentrations of large aged anthropogenic particles transported from lower latitudes in the late Arctic winter and early spring followed by a sharp transition to low concentrations of locally sourced smaller particles in the summer. However, multi-model assessments show that many models fail to simulate a realistic cycle. Here, we use a global aerosol microphysics model (GLOMAP) and surface-level aerosol observations to understand how wet scavenging processes control the seasonal variation in Arctic black carbon (BC) and sulphate aerosol. We show that the transition from high wintertime concentrations to low concentrations in the summer is controlled by the transition from ice-phase cloud scavenging to the much more efficient warm cloud scavenging in the late spring troposphere. This seasonal cycle is amplified further by the appearance of warm drizzling cloud in the late spring and summer boundary layer. Implementing these processes in GLOMAP greatly improves the agreement between the model and observations at the three Arctic ground-stations Alert, Barrow and Zeppelin Mountain on Svalbard. The SO4 model-observation correlation coefficient (R) increases from:-0.33 to 0.71 at Alert (82.5 N), from-0.16 to 0.70 at Point Barrow (71.0 N) and from-0.42 to 0.40 at Zeppelin Mountain (78 N). The BC model-observation correlation coefficient increases from-0.68 to 0.72 at Alert and from-0.42 to 0.44 at Barrow. Observations at three marginal Arctic sites (Janiskoski, Oulanka and Karasjok) indicate a far weaker aerosol seasonal cycle, which we show is consistent with the much smaller seasonal change in the frequency of ice clouds compared to higher latitude sites. Our results suggest that the seasonal cycle in Arctic aerosol is driven by temperature-dependent scavenging processes that may be susceptible to modification in a future climate. © 2012 Author(s)."
"7007168548;8378887500;35334472800;8256598200;8280398300;55480930900;6602579980;8256598400;56151622000;56273253000;","Diurnal variations of reactive chlorine and nitrogen oxides observed by MIPAS-B inside the January 2010 Arctic vortex",2012,"10.5194/acp-12-6581-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869007940&doi=10.5194%2facp-12-6581-2012&partnerID=40&md5=1b75aa51a8c8d44e2a22381ec221a57a","The winter 2009/2010 was characterized by a strong Arctic vortex with extremely cold mid-winter temperatures in the lower stratosphere associated with an intense activation of reactive chlorine compounds (ClO x) from reservoir species. Stratospheric limb emission spectra were recorded during a flight of the balloon version of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) from Kiruna (Sweden) on 24 January 2010 inside the Arctic vortex. Several fast limb sequences of spectra (in time steps of about 10 min) were measured from nighttime photochemical equilibrium to local noon allowing the retrieval of chlorine-and nitrogen-containing species which change rapidly their concentration around the terminator between night and day. Mixing ratios of species like ClO, NO 2, and N 2O 5 show significant changes around sunrise, which are temporally delayed due to polar stratospheric clouds reducing the direct radiative flux from the sun. ClO variations were derived for the first time from MIPAS-B spectra. Daytime ClO values of up to 1.6 ppbv are visible in a broad chlorine activated layer below 26 km correlated with low values (below 0.1 ppbv) of the chlorine reservoir species ClONO 2. Observations are compared and discussed with calculations performed with the 3-dimensional Chemistry Climate Model EMAC (ECHAM5/MESSy Atmospheric Chemistry). Mixing ratios of the species ClO, NO 2, and N 2O 5 are well reproduced by the model during night and noon. However, the onset of ClO production and NO 2 loss around the terminator in the model is not consistent with the measurements. The MIPAS-B observations along with Tropospheric Ultraviolet-Visible (TUV) radiation model calculations suggest that polar stratospheric clouds lead to a delayed start followed by a faster increase of the photodissoziation of ClOOCl and NO 2 near the morning terminator since stratospheric clouds alter the direct and the diffuse flux of solar radiation. These effects are not considered in the EMAC model simulations which assume a cloudless atmosphere. © 2012 Author(s)."
"23051160600;6602506226;26643041500;8758100000;6701820813;7102062952;35461255500;","BVOC-aerosol-climate interactions in the global aerosol-climate model ECHAM5.5-HAM2",2012,"10.5194/acp-12-10077-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868697420&doi=10.5194%2facp-12-10077-2012&partnerID=40&md5=e82ab5caa096db9e370773549ebcfeba","The biosphere emits volatile organic compounds (BVOCs) which, after oxidation in the atmosphere, can partition on the existing aerosol population or even form new particles. The large quantities emitted provide means for a large potential impact on both aerosol direct and indirect effects. Biogenic responses to atmospheric temperature change can establish feedbacks even in rather short timescales. However, due to the complexity of organic aerosol partitioning, even the sign of these feedbacks is of large uncertainty. We use the global aerosol-climate model ECHAM5.5-HAM2 to explore the effect of BVOC emissions on new particle formation, clouds and climate. Two BVOC emission models, MEGAN2 and LPJ-GUESS, are used. MEGAN2 shows a 25% increase while LPJ-GUESS shows a slight decrease in global BVOC emission between years 2000 and 2100. The change of shortwave cloud forcing from year 1750 to 2000 ranges from-1.4 to-1.8 W m -2 with 5 different nucleation mechanisms. We show that the change in shortwave cloud forcing from the year 2000 to 2100 ranges from 1.0 to 1.5 W m -2. Although increasing future BVOC emissions provide 3-5% additional CCN, the effect on the cloud albedo change is modest. Due to simulated decreases in future cloud cover, the increased CCN concentrations from BVOCs can not provide significant additional cooling in the future. © 2012 Author(s)."
"6603746516;6507351719;24397397400;57199894357;6603321554;7005954699;57118069200;7402234295;55232643400;36844147900;14830881300;","Future flows climate: An ensemble of 1-km climate change projections for hydrological application in Great Britain",2012,"10.5194/essd-4-143-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893002835&doi=10.5194%2fessd-4-143-2012&partnerID=40&md5=2c91c090497ac3569dcc7806ea0aeed1","The dataset Future Flows Climate was developed as part of the project ""Future Flows and Groundwater Levels"" to provide a consistent set of climate change projections for the whole of Great Britain at both space and time resolutions appropriate for hydrological applications, and to enable climate change uncertainty and climate variability to be accounted for in the assessment of their possible impacts on the environment. Future Flows Climate is derived from the Hadley Centre's ensemble projection HadRM3-PPE that is part of the basis of UKCP09 and includes projections in available precipitation (water available to hydrological processes after snow and ice storages have been accounted for) and potential evapotranspiration. It corresponds to an 11-member ensemble of transient projections from January 1950 to December 2098, each a single realisation from a different variant of HadRM3. Data are provided on a 1-km grid over the HadRM3 land areas at a daily (available precipitation) and monthly (PE) time step as netCDF files. Because systematic biases in temperature and precipitation were found between HadRM3-PPE and gridded temperature and precipitation observations for the 1962-1991 period, a monthly bias correction procedure was undertaken, based on a linear correction for temperature and a quantile-mapping correction (using the gamma distribution) for precipitation followed by a spatial downscaling. Available precipitation was derived from the bias-corrected precipitation and temperature time series using a simple elevation-dependant snow-melt model. Potential evapotranspiration time series were calculated for each month using the FAO-56 Penman-Monteith equations and bias-corrected temperature, cloud cover, relative humidity and wind speed from HadRM3-PPE along with latitude of the grid and the day of the year. Future Flows Climate is freely available for non-commercial use under certain licensing conditions. It is the dataset used to generate Future Flows Hydrology, an ensemble of transient projections of daily river flow and monthly groundwater time series for representative river basins and boreholes in Great Britain. © 2012 Author(s)."
"36244268000;6602205640;","Diurnal, seasonal, and altitudinal trends in microclimate across a tropical montane cloud forest",2012,"10.3354/cr01127","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869766611&doi=10.3354%2fcr01127&partnerID=40&md5=7d7ad96ab18cf29420ce6d35289b3a74","Altitudinal gradients are often used as natural laboratories to study ecosystem dynamics, biodiversity, and species' distribution response to climate gradients. However, the underlying climate gradients are rarely described in detail, especially in the tropics. In this study, we describe the diurnal and seasonal patterns in microclimate across a 3900 m altitudinal gradient in and adjacent to the Kosñipata Valley in Manu National Park, Peru, on the eastern slope of the tropical Andes. We focus on the understudied altitudinal range between 1500 and 3500 m using micrometeorological data associated with a permanent tree plot network designed to study cloud forest biodiversity and ecosystem dynamics. Data from this plot network were supplemented with data in the public domain across a 20 000 km2 area with time series at individual sites lasting from 2 to 17 yr. Observed diurnal and seasonal trends in microclimate variables were explained by diurnal and seasonal variation in solar radiation and atmospheric moisture flux. Altitudinal trends in microclimate varied seasonally, with solar radiation, vapor pressure deficit, and temperature reaching their annual maximum earlier at higher altitudes, likely because of seasonally shifting cloud dynamics. Cloud dynamics were important in determining diurnal, seasonal, and altitudinal trends in several microclimate variables, suggesting that changes to cloud frequency and altitudinal occurrence associated with global climate change could have important impacts on cloud forest ecosystem dynamics, in addition to those of rising temperatures. © Inter-Research 2012."
"13403622000;","Uncertainties in aerosol direct and indirect effects attributed to uncertainties in convective transport parameterizations",2012,"10.1016/j.atmosres.2012.06.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865324734&doi=10.1016%2fj.atmosres.2012.06.022&partnerID=40&md5=bc5a072bfe403cbc4a51792ff2097c37","Deep convection is an important transport mechanism for aerosol particles, allowing them to be lifted to levels where they are subject to long-range transport from source regions to remote regions. The sensitivity of regional aerosol effects to the rate of entrainment in deep moist convection has been explored in a global modeling framework, and found to be crucial for the radiative balance both at the surface and at the top of the atmosphere. The fact that regions where deep convection is frequent often coincide with regions of particularly high black carbon emissions is found to be an important factor in understanding this sensitivity to entrainment. More entrainment leads to shallower convective plumes and less aerosol transport from the boundary layer to the upper troposphere in source regions. As a result, boundary layer aerosol concentrations are increased in source regions, while upper tropospheric aerosol concentrations are reduced globally. This generally leads to stronger aerosol effects in polluted regions and weaker aerosol effects in remote regions. Because black carbon particles have the ability to absorb solar radiation, reducing their concentration leads to more solar radiation reflected back to space, especially over bright surfaces. Conversely, at the surface more entrainment means more downwelling shortwave radiation everywhere but in source regions. Regions that experience increased aerosol concentrations in the boundary layer in response to increased entrainment observed a stronger aerosol indirect effect, while the opposite was true everywhere else. This study highlights that the relative strengths of the aerosol direct and indirect effects in clean versus polluted regions depend crucially on the rate of entrainment in deep convective clouds, a process that is presently not well understood and quantified. © 2012 Elsevier B.V."
"36169854600;57200055610;7005543472;35448188800;7102807964;57210538699;7006086673;7404597424;7005891596;57218359395;7003479494;7004643405;7004482886;7006025236;35737484800;7006686129;35429035100;7202097052;7201483081;7102581856;6602298788;","Characteristics of tropospheric ozone depletion events in the Arctic spring: Analysis of the ARCTAS, ARCPAC, and ARCIONS measurements and satellite BrO observations",2012,"10.5194/acp-12-9909-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868613790&doi=10.5194%2facp-12-9909-2012&partnerID=40&md5=5e0d5bc09aa32e1c1068be9bcc29bc0a","Arctic ozone depletion events (ODEs) are caused by halogen catalyzed ozone loss. In situ chemistry, advection of ozone-poor air mass, and vertical mixing in the lower troposphere are important factors affecting ODEs. To better characterize the ODEs, we analyze the combined set of surface, ozonesonde, and aircraft in situ measurements of ozone and bromine compounds during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC), and the Arctic Intensive Ozonesonde Network Study (ARCIONS) experiments (April 2008). Tropospheric BrO columns retrieved from satellite measurements and back trajectory calculations are also used to investigate the characteristics of observed ODEs. In situ observations from these field experiments are inadequate to validate tropospheric BrO columns derived from satellite measurements. In view of this difficulty, we construct an ensemble of tropospheric column BrO estimates from two satellite (OMI and GOME-2) measurements and with three independent methods of calculating stratospheric BrO columns. Furthermore, we select analysis methods that do not depend on the absolute magnitude of column BrO, such as time-lagged correlation analysis of ozone and tropospheric column BrO, to understand characteristics of ODEs. Time-lagged correlation analysis between in situ (surface and ozonesonde) measurements of ozone and satellite derived tropospheric BrO columns indicates that the ODEs are due to either local halogen-driven ozone loss or short-range (&sim;1 day) transport from nearby regions with ozone depletion. The effect of in situ ozone loss is also evident in the diurnal variation difference between low (10th and 25th percentiles) and higher percentiles of surface ozone concentrations at Alert, Canada. Aircraft observations indicate low-ozone air mass transported from adjacent high-BrO regions. Correlation analyses of ozone with potential temperature and time-lagged tropospheric BrO column show that the vertical extent of local ozone loss is surprisingly deep (1-2 km) at Resolute and Churchill, Canada. The unstable boundary layer during ODEs at Churchill could potentially provide a source of free-tropospheric BrO through convective transport and explain the significant negative correlation between free-tropospheric ozone and tropospheric BrO column at this site. © 2012 Author(s). CC Attribution 3.0 License."
"55339081600;35509639400;7004714030;6603925960;","The too few, too bright tropical low-cloud problem in CMIP5 models",2012,"10.1029/2012GL053421","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868620896&doi=10.1029%2f2012GL053421&partnerID=40&md5=10ec9b4b3b42a49aeb0d3ef417ccbedb","Previous generations of climate models have been shown to under-estimate the occurrence of tropical low-level clouds and to over-estimate their radiative effects. This study analyzes outputs from multiple climate models participating in the Fifth phase of the Coupled Model Intercomparison Project (CMIP5) using the Cloud Feedback Model Intercomparison Project Observations Simulator Package (COSP), and compares them with different satellite data sets. Those include CALIPSO lidar observations, PARASOL mono-directional reflectances and CERES radiative fluxes at the top of the atmosphere. We show that current state-of-the-art climate models predict overly bright low-clouds, even for a correct low-cloud cover. The impact of these biases on the Earth' radiation budget, however, is reduced by compensating errors. Those include the tendency of models to under-estimate the low-cloud cover and to over-estimate the occurrence of mid-and high-clouds above low-clouds. Finally, we show that models poorly represent the dependence of the vertical structure of low-clouds on large-scale environmental conditions. The implications of this too few, too bright low-cloud problem for climate sensitivity and model development are discussed. © 2012. American Geophysical Union. All Rights Reserved."
"10241250100;55686667100;55537426400;10241462700;10243650000;7003420726;35580303100;55314995700;36701462300;26667030700;55315186800;8979277400;10240710000;6603196127;7102857642;","Perturbed physics ensemble using the MIROC5 coupled atmosphere-ocean GCM without flux corrections: Experimental design and results: Parametric uncertainty of climate sensitivity",2012,"10.1007/s00382-012-1441-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869509286&doi=10.1007%2fs00382-012-1441-x&partnerID=40&md5=8f677c6ae23c989f3fc4a6dcebb68cd3","In this study, we constructed a perturbed physics ensemble (PPE) for the MIROC5 coupled atmosphere-ocean general circulation model (CGCM) to investigate the parametric uncertainty of climate sensitivity (CS). Previous studies of PPEs have mainly used the atmosphere-slab ocean models. A few PPE studies using a CGCM applied flux corrections, because perturbations in parameters can lead to large radiation imbalances at the top of the atmosphere and climate drifts. We developed a method to prevent climate drifts in PPE experiments using the MIROC5 CGCM without flux corrections. We simultaneously swept 10 parameters in atmosphere and surface schemes. The range of CS (estimated from our 35 ensemble members) was not wide (2. 2-3. 2 °C). The shortwave cloud feedback related to changes in middle-level cloud albedo dominated the variations in the total feedback. We found three performance metrics for the present climate simulations of middle-level cloud albedo, precipitation, and ENSO amplitude that systematically relate to the variations in shortwave cloud feedback in this PPE. © 2012 The Author(s)."
"55366637500;6603925960;7004714030;","A process oriented characterization of tropical oceanic clouds for climate model evaluation, based on a statistical analysis of daytime A-train observations",2012,"10.1007/s00382-012-1533-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868147271&doi=10.1007%2fs00382-012-1533-7&partnerID=40&md5=5b2bbd5c559c02823975ec9f29d190d7","This paper aims at characterizing how different key cloud properties (cloud fraction, cloud vertical distribution, cloud reflectance, a surrogate of the cloud optical depth) vary as a function of the others over the tropical oceans. The correlations between the different cloud properties are built from 2 years of collocated A-train observations (CALIPSO-GOCCP and MODIS) at a scale close to cloud processes; it results in a characterization of the physical processes in tropical clouds, that can be used to better understand cloud behaviors, and constitute a powerful tool to develop and evaluate cloud parameterizations in climate models. First, we examine a case study of shallow cumulus cloud observed simultaneously by the two sensors (CALIPSO, MODIS), and develop a methodology that allows to build global scale statistics by keeping the separation between clear and cloudy areas at the pixel level (250, 330 m). Then we build statistical instantaneous relationships between the cloud cover, the cloud vertical distribution and the cloud reflectance. The vertical cloud distribution indicates that the optically thin clouds (optical thickness >1.5) dominate the boundary layer over the trade wind regions. Optically thick clouds (optical thickness <3.4) are composed of high and mid-level clouds associated with deep convection along the ITCZ and SPCZ and over the warm pool, and by stratocumulus low level clouds located along the East coast of tropical oceans. The cloud properties are analyzed as a function of the large scale circulation regime. Optically thick high clouds are dominant in convective regions (CF < 80 %), while low level clouds with low optical thickness (>3.5) are present in regimes of subsidence but in convective regimes as well, associated principally to low cloud fractions (CF > 50 %). A focus on low-level clouds allows us to quantify how the cloud optical depth increases with cloud top altitude and with cloud fraction. © 2012 Springer-Verlag Berlin Heidelberg."
"25032301700;6602825148;56001448100;","A 1D microphysical cloud model for Earth, and Earth-like exoplanets: Liquid water and water ice clouds in the convective troposphere",2012,"10.1016/j.icarus.2012.08.028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866725501&doi=10.1016%2fj.icarus.2012.08.028&partnerID=40&md5=59d3ffb66dcfd91afeb20c8364bf82ef","One significant difference between the atmospheres of stars and exoplanets is the presence of condensed particles (clouds or hazes) in the atmosphere of the latter. In current 1D models clouds and hazes are treated in an approximate way by raising the surface albedo, or adopting measured Earth cloud properties. The former method introduces errors to the modeled spectra of the exoplanet, as clouds shield the lower atmosphere and thus modify the spectral features. The latter method works only for an exact Earth-analog, but it is challenging to extend to other planets.The main goal of this paper is to develop a self-consistent microphysical cloud model for 1D atmospheric codes, which can reproduce some observed properties of Earth, such as the average albedo, surface temperature, and global energy budget. The cloud model is designed to be computationally efficient, simple to implement, and applicable for a wide range of atmospheric parameters for planets in the habitable zone.We use a 1D, cloud-free, radiative-convective, and photochemical equilibrium code originally developed by Kasting, Pavlov, Segura, and collaborators as basis for our cloudy atmosphere model. The cloud model is based on models used by the meteorology community for Earth's clouds. The free parameters of the model are the relative humidity and number density of condensation nuclei, and the precipitation efficiency. In a 1D model, the cloud coverage cannot be self-consistently determined, thus we treat it as a free parameter.We apply this model to Earth (aerosol number density 100cm -3, relative humidity 77%, liquid cloud fraction 40%, and ice cloud fraction 25%) and find that a precipitation efficiency of 0.8 is needed to reproduce the albedo, average surface temperature and global energy budget of Earth. We perform simulations to determine how the albedo and the climate of a planet is influenced by the free parameters of the cloud model. We find that the planetary climate is most sensitive to changes in the liquid water cloud fraction and precipitation efficiency.The advantage of our cloud model is that the cloud height and the droplet sizes are self-consistently calculated, both of which influence the climate and albedo of exoplanets. © 2012 Elsevier Inc."
"34772240500;55713076400;7004544454;22635190100;","A treatment for the stratocumulus-to-cumulus transition in GCMs",2012,"10.1007/s00382-012-1342-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869507394&doi=10.1007%2fs00382-012-1342-z&partnerID=40&md5=98e79de4abb15aac5eda24b51224801f","Numerical models of climate have great difficulties with the simulation of marine low clouds in the subtropical Pacific and Atlantic Oceans. It has been especially difficult to reproduce the observed geographical distributions of the different cloud regimes in those regions. The present study discusses mechanisms proposed in previous works for changing one regime into another. One criterion is based on the theory of stratocumulus destruction through cloud top entrainment instability due to buoyancy reversal-situations in which the mixture of two air parcels becomes denser than either of the original parcels due to evaporation of cloud water. Another criterion is based on the existence of decoupling in the boundary layer. When decoupled, the stratocumulus regime changes to another in which these clouds can still exist together with cumulus. In a LES study, the authors have suggested that a combination of those two criteria can be used to diagnose whether, at a location, the cloud regime corresponds to a well-mixed stratocumulus regime, a shallow cumulus regime, or to a transitional regime where the boundary layer is decoupled. The concept is tested in the framework of an atmospheric general circulation model (GCM). It is found that several outstanding features of disagreement between simulation and observation can be interpreted as misrepresentations of the cloud regimes by the GCM. A novel criterion for switching among regimes is proposed to alleviate the effects of these misrepresentations. © 2012 Springer-Verlag."
"7004399781;57208464149;7003658685;24484158900;36892703600;","Atmospheric pollution in the Hindu Kush-Himalaya region",2012,"10.1659/MRD-JOURNAL-D-12-00066.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871537274&doi=10.1659%2fMRD-JOURNAL-D-12-00066.1&partnerID=40&md5=be11916f5349b36092b62e207348ab9c","This paper presents a detailed review of atmospheric pollution observed in the Hindu Kush-Himalaya (HKH) region and its implications for regional climate. Data from in situ measurements made at high-altitude stations in the HKH region, observations from satellite-based instruments, and global climate modeling study results are discussed. Experimental observations discussed include both atmospheric measurements and data from snow and ice core sampling from different glaciers in the HKH region. The paper focuses on the atmospheric brown cloud loadings over the Himalayas, particularly black carbon (BC) and ozone, which have links to regional climate and air-pollution-related impacts. Studies show elevated levels of anthropogenic ozone and BC over the Himalayas during the pre-monsoon season with concentrations sometimes similar to those observed over an average urban environment. The elevated concentration observed over the Himalayas is thought to come from the lowlands, especially the highly populated areas of the Indo-Gangetic Plains. The implications of high BC loading in the Himalayan atmosphere as well as elevated BC deposition on snow and ice surfaces for regional climate, hydrological cycle, and glacial melt are discussed. © 2012 International Mountain Society."
"7102084129;57207137435;35461763400;23987289400;55942083800;6701540733;","The scientific basis for a satellite mission to retrieve CCN concentrations and their impacts on convective clouds",2012,"10.5194/amt-5-2039-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867944556&doi=10.5194%2famt-5-2039-2012&partnerID=40&md5=6c12b06c8c45ca41a473a72717475f4e","The cloud-mediated aerosol radiative forcing is widely recognized as the main source of uncertainty in our knowledge of the anthropogenic forcing on climate. The current challenges for improving our understanding are (1) global measurements of cloud condensation nuclei (CCN) in the cloudy boundary layer from space, and (2) disentangling the effects of aerosols from the thermodynamic and meteorological effects on the clouds. Here, we present a new conceptual framework to help us overcome these two challenges, using relatively simple passive satellite measurements in the visible and infared (IR). The idea is to use the clouds themselves as natural CCN chambers by retrieving simultaneously the number of activated aerosols at cloud base, N a, and the cloud base updraft speed. The N a is obtained by analyzing the distribution of cloud drop effective radius in convective elements as a function of distance above cloud base. The cloud base updraft velocities are estimated by double stereoscopic viewing and tracking of the evolution of cloud surface features just above cloud base. In order to resolve the vertical dimension of the clouds, the field of view will be 100 m for the microphysical retrievals, and 50 m for the stereoscopic measurements. The viewing geometry will be eastward and 30 degrees off nadir, with the Sun in the back at 30 degrees off zenith westward, requiring a Sun-synchronous orbit at 14 LST. Measuring simultaneously the thermodynamic environment, the vertical motions of the clouds, their microstructure and the CCN concentration will allow separating the dynamics from the CCN effects. This concept is being applied in the proposed satellite mission named Clouds, Hazards and Aerosols Survey for Earth Researchers (CHASER). © 2012 Author(s)."
"7402215419;56900025900;55437980300;7003283811;7501447027;35331137500;55663817800;7005729142;6506385754;","Ice hydrometeor profile retrieval algorithm for high-frequency microwave radiometers: Application to the CoSSIR instrument during TC4",2012,"10.5194/amt-5-2277-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867946504&doi=10.5194%2famt-5-2277-2012&partnerID=40&md5=10a57a60e3f331b86358609a4fb5c3f2","A Bayesian algorithm to retrieve profiles of cloud ice water content (IWC), ice particle size (D me), and relative humidity from millimeter-wave/submillimeter-wave radiometers is presented. The first part of the algorithm prepares an a priori file with cumulative distribution functions (CDFs) and empirical orthogonal functions (EOFs) of profiles of temperature, relative humidity, three ice particle parameters (IWC, D me, distribution width), and two liquid cloud parameters. The a priori CDFs and EOFs are derived from CloudSat radar reflectivity profiles and associated ECMWF temperature and relative humidity profiles combined with three cloud microphysical probability distributions obtained from in situ cloud probes. The second part of the algorithm uses the CDF/EOF file to perform a Bayesian retrieval with a hybrid technique that uses Monte Carlo integration (MCI) or, when too few MCI cases match the observations, uses optimization to maximize the posterior probability function. The very computationally intensive Markov chain Monte Carlo (MCMC) method also may be chosen as a solution method. The radiative transfer model assumes mixtures of several shapes of randomly oriented ice particles, and here random aggregates of spheres, dendrites, and hexagonal plates are used for tropical convection. A new physical model of stochastic dendritic snowflake aggregation is developed. The retrieval algorithm is applied to data from the Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) flown on the ER-2 aircraft during the Tropical Composition, Cloud and Climate Coupling (TC4) experiment in 2007. Example retrievals with error bars are shown for nadir profiles of IWC, D me, and relative humidity, and nadir and conical scan swath retrievals of ice water path and average D me. The ice cloud retrievals are evaluated by retrieving integrated 94 GHz backscattering from CoSSIR for comparison with the Cloud Radar System (CRS) flown on the same aircraft. The rms difference in integrated backscattering is around 3 dB over a 30 dB range. A comparison of CoSSIR retrieved and CRS measured reflectivity shows that CoSSIR has the ability to retrieve low-resolution ice cloud profiles in the upper troposphere. © 2012 Author(s)."
"9941600400;23968109800;7402105994;10144486700;","Global radiative forcing and megacities",2012,"10.1016/j.uclim.2012.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870277237&doi=10.1016%2fj.uclim.2012.08.001&partnerID=40&md5=41946b0c689b14a584abf068b3e22f22","Emissions of greenhouse gases and air pollutants from megacities impact the climate. The long-lived greenhouse gases CO 2, CH 4 and N 2O as well as climate-active pollutants such as NO x, VOC and particulate matter (PM) are all emitted from megacities. NO x and VOC contribute to tropospheric ozone formation and affect the lifetime of long-lived greenhouse gases. Anthropogenic aerosols include sulphate, black carbon (BC) and particulate organic matter (POM). Aerosols impact climate directly (absorption, backscattering) and also have indirect (cloud) effects. We assess the climate impact of megacity emissions with the Met Office Hadley Centre Earth System Model HadGEM2 applying an ""annihilation"" scenario in which the emissions at megacities are entirely removed. Generally, the contribution of megacities to global pollutant emissions is on the order of 2-5% of the total global annual anthropogenic base emission flux. The impact of megacity climate-active pollutants is assessed via an annual mean top-of-atmosphere direct radiative forcing (AMTOA-DRF) from long-lived GHG as well as ozone, methane and aerosols. In this simulations the long-lived component (CO 2, CH 4 and N 2O) contributes a positive TOA-DRF of +120.0, +28.4 and +3.3mWm -2, respectively, under present-day conditions. Climate-active pollutants (NO x, VOC) contribute an AMTOA-DRF of +5.7±0.02mWm -2 from an increase in the ozone burden -1.9±0.04mWm -2, -6.1±0.21mWm -2 from the aerosol AMTOA-DRF in the short-wave spectrum and +1.5±0.01mWm -2 from aerosol in the long-wave spectrum. The combined AMTOA-DRF from all climate-active pollutants is slightly negative at -0.8±0.24mWm -2 and the total AMTOA-DRF amounts to +150.9±0.24mWm -2. Under future conditions (2050s) the total AMTOA-DRF from long-lived GHG is found to profoundly increase to +322.6mWm -2 while the total AMTOA-DRF from climate-active pollutants turns positive and decreases slightly to +0.5±0.09mWm -2 yielding a combined AMTOA-DRF of +323.1±0.09mWm -2 in the future. It is apparent that under the given emission scenarios the radiative forcing from long-lived GHG, particularly CO 2, by far dominates the impact of megacities on climate. © 2012."
"16025402200;45961150900;55821966900;7403573190;56744297600;7401435616;","An investigation of tropical Atlantic bias in a high-resolution coupled regional climate model",2012,"10.1007/s00382-012-1320-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866004814&doi=10.1007%2fs00382-012-1320-5&partnerID=40&md5=98e1b8ea010ad78e46ec1acebdf3d2c0","Coupled atmosphere-ocean general circulation models (AOGCMs) commonly fail to simulate the eastern equatorial Atlantic boreal summer cold tongue and produce a westerly equatorial trade wind bias. This tropical Atlantic bias problem is investigated with a high-resolution (27-km atmosphere represented by the Weather Research and Forecasting Model, 9-km ocean represented by the Regional Ocean Modeling System) coupled regional climate model. Uncoupled atmospheric simulations test climate sensitivity to cumulus, land-surface, planetary boundary layer, microphysics, and radiation parameterizations and reveal that the radiation scheme has a pronounced impact in the tropical Atlantic. The CAM radiation simulates a dry precipitation (up to -90%) and cold land-surface temperature (up to -8 K) bias over the Amazon related to an over-representation of low-level clouds and almost basin-wide westerly trade wind bias. The Rapid Radiative Transfer Model and Goddard radiation simulates doubled Amazon and Congo Basin precipitation rates and a weak eastern Atlantic trade wind bias. Season-long high-resolution coupled regional model experiments indicate that the initiation of the warm eastern equatorial Atlantic sea surface temperature (SST) bias is more sensitive to the local rather than basin-wide trade wind bias and to a wet Congo Basin instead of dry Amazon-which differs from AOGCM simulations. Comparisons between coupled and uncoupled simulations suggest a regional Bjerknes feedback confined to the eastern equatorial Atlantic amplifies the initial SST, wind, and deepened thermocline bias, while barrier layer feedbacks are relatively unimportant. The SST bias in some CRCM simulations resembles the typical AOGCM bias indicating that increasing resolution is unlikely a simple solution to this problem. © 2012 Springer-Verlag."
"14622582000;23091448100;6506644040;7101838542;8782763500;26643193500;","Stable isotopes reveal linkages among ecohydrological processes in a seasonally dry tropical montane cloud forest",2012,"10.1002/eco.268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867023214&doi=10.1002%2feco.268&partnerID=40&md5=756e542bccd1ec61deccbfa1f48cf3d7","Despite their critical role as freshwater resources and their vulnerability to anthropogenic pressures, our knowledge of the ecohydrology of tropical montane cloud forests remains limited. Here, we use a dual stable isotope approach (δ2H and δ18O) to trace water inputs, fluxes, and pools through a seasonally dry tropical montane cloud forest in central Veracruz, Mexico. We found strong seasonal variation in the isotope composition of precipitation inputs (δ2H ~130‰ and δ18O ~18‰), with significantly more depleted wet-season values as compared with dry-season values. These seasonal differences are subject to inter-annual variation, as reflected by shifts in the local meteoric water line. Even at the peak of the dry season, stable isotope values of plant xylem water from six different deciduous and evergreen species occurring in the understory and canopy of mature and secondary forests were all consistent with the use of shallow soil water (20-60cm). Alternative limiting factors, such as nutrient distribution along the soil profile, may be strongly contributing to plant rooting patterns. Stable isotope values of soil water were evaporatively enriched compared with precipitation inputs, whereas stream values plotted with precipitation on the local meteoric water line. In contrast to current hydrologic models, this indicates the presence of two distinct soil water pools, one highly mobile pool of precipitation that contributes to streams and a second less mobile pool of soil water that contributes to plant fluxes. This comprehensive perspective can provide the basis for generating process-based models of ecohydrology in the future. © 2011 John Wiley &amp; Sons, Ltd."
"36010237000;7004169476;56575686800;25030776200;57203049177;7201485519;7003976079;7403119519;","A step-response approach for predicting and understanding non-linear precipitation changes",2012,"10.1007/s00382-012-1571-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869500561&doi=10.1007%2fs00382-012-1571-1&partnerID=40&md5=57e3847e5c463770ea7c1ded31309d80","Future changes in precipitation represent one of the most important and uncertain possible effects of future climate change. We demonstrate a new approach based on idealised CO2 step-change general circulation model (GCM) experiments, and test it using the HadCM3 GCM. The approach has two purposes: to help understand GCM projections, and to build and test a fast simple model for precipitation projections under a wide range of forcing scenarios. Overall, we find that the CO2 step experiments contain much information that is relevant to transient projections, but that is more easily extracted due to the idealised experimental design. We find that the temporary acceleration of global-mean precipitation in this GCM following CO2 ramp-down cannot be fully explained simply using linear responses to CO2 and temperature. A more complete explanation can be achieved with an additional term representing interaction between CO2 and temperature effects. Energy budget analysis of this term is dominated by clear-sky outgoing long-wave radiation (CSOLR) and sensible heating, but cloud and short-wave terms also contribute. The dominant CSOLR interaction is attributable to increased CO2 raising the mean emission level to colder altitudes, which reduces the rate of increase of OLR with warming. This behaviour can be reproduced by our simple model. On regional scales, we compare our approach with linear 'pattern-scaling' (scaling regional responses by global-mean temperature change). In regions where our model predicts linear change, pattern-scaling works equally well. In some regions, however, substantial deviations from linear scaling with global-mean temperature are found, and our simple model provides more accurate projections. The idealised experiments reveal a complex pattern of non-linear behaviour. There are likely to be a range of controlling physical mechanisms, different from those dominating the global-mean response, requiring focussed investigation for individual regions, and in other GCMs. © 2012 Crown Copyright."
"56013059600;57198180447;36146289200;6701317546;7006045303;","Warming induces shifts in microzooplankton phenology and reduces time-lags between phytoplankton and protozoan production",2012,"10.1007/s00227-012-1947-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868504317&doi=10.1007%2fs00227-012-1947-0&partnerID=40&md5=33d372792a82d338ebb0e7679cce357d","Indoor mesocosm experiments were conducted to test for potential climate change effects on the spring succession of Baltic Sea plankton. Two different temperature (Δ0 °C and Δ6 °C) and three light scenarios (62, 57 and 49 % of the natural surface light intensity on sunny days), mimicking increasing cloudiness as predicted for warmer winters in the Baltic Sea region, were simulated. By combining experimental and modeling approaches, we were able to test for a potential dietary mismatch between phytoplankton and zooplankton. Two general predator-prey models, one representing the community as a tri-trophic food chain and one as a 5-guild food web were applied to test for the consequences of different temperature sensitivities of heterotrophic components of the plankton. During the experiments, we observed reduced time-lags between the peaks of phytoplankton and protozoan biomass in response to warming. Microzooplankton peak biomass was reached by 2. 5 day °C -1 earlier and occurred almost synchronously with biomass peaks of phytoplankton in the warm mesocosms (Δ6 °C). The peak magnitudes of microzooplankton biomass remained unaffected by temperature, and growth rates of microzooplankton were higher at Δ6 °C (μ {increment}0 °C = 0. 12 day -1 and μ {increment}6 °C = 0. 25 day -1). Furthermore, warming induced a shift in microzooplankton phenology leading to a faster species turnover and a shorter window of microzooplankton occurrence. Moderate differences in the light levels had no significant effect on the time-lags between autotrophic and heterotrophic biomass and on the timing, biomass maxima and growth rate of microzooplankton biomass. Both models predicted reduced time-lags between the biomass peaks of phytoplankton and its predators (both microzooplankton and copepods) with warming. The reduction of time-lags increased with increasing Q 10 values of copepods and protozoans in the tritrophic food chain. Indirect trophic effects modified this pattern in the 5-guild food web. Our study shows that instead of a mismatch, warming might lead to a stronger match between protist grazers and their prey altering in turn the transfer of matter and energy toward higher trophic levels. © 2012 Springer-Verlag."
"54387556900;12142232800;","Evaluating the utility of the EUMETSAT HSAF snow recognition product over mountainous areas of eastern Turkey [Evaluation de l'utilité du produit EUMETSAT HSAF de reconnaissance de la neige sur les régions montagneuses de Turquie orientale]",2012,"10.1080/02626667.2012.729132","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871254804&doi=10.1080%2f02626667.2012.729132&partnerID=40&md5=4c46e4c3167bafe66b538a116a2071cb","Monitoring snow parameters (e.g. snow-cover area, snow water equivalent) is challenging work. Because of its natural physical properties, snow strongly affects the evolution of weather on a daily basis and climate on a longer time scale. In this paper, the snow recognition product generated from the MSG-SEVIRI images within the framework of the Hydrological Satellite Facility (HSAF) Project of EUMETSAT is presented. Validation of the snow recognition product H10 was done for the snow season (from 1 January to 31 March) of the water year 2009. The MOD10A1 and MOD10C2 snow products were also used in the validation studies. Ground truth of the products was obtained by using 1890 snow depth observations from 20 meteorological stations, which are mainly located in mountainous areas and are distributed across the eastern part of Turkey. The possibility of 37% cloud cover reduction was obtained by merging 15-min observations from MSG-SEVIRI as opposed to using only one daily observation from MODIS. The coarse spatial resolution of the H10 product gave higher commission errors compared to the MOD10A1 product. Snow depletion curves obtained from the HSAF snow recognition product were compared with those derived from the MODIS 8-day snow cover product. The preliminary results show that the HSAF snow recognition product, taking advantage of using high temporal frequency measurement with spectral information required for snow mapping, significantly improves the mapping of regional snow-cover extent over mountainous areas. © 2012 Copyright 2012 IAHS Press."
"7410069943;7404240633;24468389200;7410070663;7501757094;7404976222;","A study on sulfate optical properties and direct radiative forcing using LASG-IAP general circulation model",2012,"10.1007/s00376-012-1257-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867757594&doi=10.1007%2fs00376-012-1257-y&partnerID=40&md5=f1d63e7ac378d1b4f04b0cc67aadbeb5","The direct radiative forcing (DRF) of sulfate aerosols depends highly on the atmospheric sulfate loading and the meteorology, both of which undergo strong regional and seasonal variations. Because the optical properties of sulfate aerosols are also sensitive to atmospheric relative humidity, in this study we first examine the scheme for optical properties that considers hydroscopic growth. Next, we investigate the seasonal and regional distributions of sulfate DRF using the sulfate loading simulated from NCAR CAM-Chem together with the meteorology modeled from a spectral atmospheric general circulation model (AGCM) developed by LASG-IAP. The global annual-mean sulfate loading of 3. 44 mg m -2 is calculated to yield the DRF of -1. 03 and -0. 57 W m -2 for clear-sky and all-sky conditions, respectively. However, much larger values occur on regional bases. For example, the maximum all-sky sulfate DRF over Europe, East Asia, and North America can be up to -4. 0 W m -2. The strongest all-sky sulfate DRF occurs in the Northern Hemispheric July, with a hemispheric average of -1. 26 W m -2. The study results also indicate that the regional DRF are strongly affected by cloud and relative humidity, which vary considerably among the regions during different seasons. This certainly raises the issue that the biases in model-simulated regional meteorology can introduce biases into the sulfate DRF. Hence, the model processes associated with atmospheric humidity and cloud physics should be modified in great depth to improve the simulations of the LASG-IAP AGCM and to reduce the uncertainty of sulfate direct effects on global and regional climate in these simulations. © 2012 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"56996271000;7202155374;7102953444;7402146514;","Atmospheric impacts on climatic variability of surface incident solar radiation",2012,"10.5194/acp-12-9581-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867870195&doi=10.5194%2facp-12-9581-2012&partnerID=40&md5=7a1a08d6dd2ba79681536c494e53c887","The Earth's climate is driven by surface incident solar radiation (R s). Direct measurements have shown that R s has undergone significant decadal variations. However, a large fraction of the global land surface is not covered by these observations. Satellite-derived R s has a good global coverage but is of low accuracy in its depiction of decadal variability. This paper shows that daily to decadal variations of R s, from both aerosols and cloud properties, can be accurately estimated using globally available measurements of Sunshine Duration (SunDu). In particular, SunDu shows that since the late 1980's R s has brightened over Europe due to decreases in aerosols but dimmed over China due to their increases. We found that variation of cloud cover determines R s at a monthly scale but that aerosols determine the variability of R s at a decadal time scale, in particular, over Europe and China. Because of its global availability and long-term history, SunDu can provide an accurate and continuous proxy record of R s, filling in values for the blank areas that are not covered by direct measurements. Compared to its direct measurement, R s from SunDu appears to be less sensitive to instrument replacement and calibration, and shows that the widely reported sharp increase in R s during the early 1990s in China was a result of instrument replacement. By merging direct measurements collected by Global Energy Budget Archive with those derived from SunDu, we obtained a good coverage of R s over the Northern Hemisphere. From this data, the average increase of R s from 1982 to 2008 is estimated to be 0.87 W mg-2 per decade. © 2012 Author(s)."
"54893098900;35509639400;","How may low-cloud radiative properties simulated in the current climate influence low-cloud feedbacks under global warming?",2012,"10.1029/2012GL053265","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868004805&doi=10.1029%2f2012GL053265&partnerID=40&md5=1d51d57a438ff50238be8239091afb9d","The influence of cloud modelling uncertainties on the projection of the tropical low-cloud response to global warming is explored by perturbing model parameters of the IPSL-CM5A climate model in a range of configurations (realistic general circulation model, aqua-planet, single-column model). While the positive sign and the mechanism of the low-cloud response to climate warming predicted by the model are robust, the amplitude of the response can vary considerably depending on the model tuning parameters. Moreover, the strength of the low-cloud response to climate change exhibits a strong correlation with the strength of the low-cloud radiative effects simulated in the current climate. We show that this correlation primarily results from a local positive feedback (referred to as the ""beta feedback"") between boundary-layer cloud radiative cooling, relative humidity and low-cloud cover. Based on this correlation and observational constraints, it is suggested that the strength of the tropical low-cloud feedback predicted by the IPSL-CM5A model in climate projections might be overestimated by about fifty percent. © 2012. American Geophysical Union. All Rights Reserved."
"30667558200;57203030873;6603925960;37099944400;7006041988;","Ubiquitous low-level liquid-containing Arctic clouds: New observations and climate model constraints from CALIPSO-GOCCP",2012,"10.1029/2012GL053385","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868029387&doi=10.1029%2f2012GL053385&partnerID=40&md5=0141214bee00df4d16ecba0c14ea0076","Ground-based observations show that persistent liquid-containing Arctic clouds occur frequently and have a dominant influence on Arctic surface radiative fluxes. Yet, without a hemispheric multi-year perspective, the climate relevance of these intriguing Arctic cloud observations was previously unknown. In this study, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations are used to document cloud phase over the Arctic basin (60-82N) during a five-year period (2006-2011). Over Arctic ocean-covered areas, low-level liquid-containing clouds are prevalent in all seasons, especially in Fall. These new CALIPSO observations provide a unique and climate-relevant constraint on Arctic cloud processes. Evaluation of one climate model using a lidar simulator suggests a lack of liquid-containing Arctic clouds contributes to a lack of ""radiatively opaque"" states. The surface radiation biases found in this one model are found in multiple models, highlighting the need for improved modeling of Arctic cloud phase. © 2012. American Geophysical Union. All Rights Reserved."
"30667558200;6603925960;","How well do climate models simulate cloud vertical structure? A comparison between CALIPSO-GOCCP satellite observations and CMIP5 models",2012,"10.1029/2012GL053153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868020148&doi=10.1029%2f2012GL053153&partnerID=40&md5=bc73cb3ddc8fe79b6e3b467af473f2bd","The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite provides robust and global direct measurements of the cloud vertical structure. The GCM-Oriented CALIPSO Cloud Product is used to evaluate the simulated clouds in five climate models using a lidar simulator. The total cloud cover is underestimated in all models (51% to 62% vs. 64% in observations) except in the Arctic. Continental cloud covers (at low, mid, high altitudes) are highly variable depending on the model. In the tropics, the top of deep convective clouds varies between 14 and 18km in the models versus 16km in the observations, and all models underestimate the low cloud amount (16% to 25%) compared to observations (29%). In the Arctic, the modeled low cloud amounts (37% to 57%) are slightly biased compared to observations (44%), and the models do not reproduce the observed seasonal variation. © 2012. American Geophysical Union. All Rights Reserved."
"6507224579;28367935500;6701835010;7005137442;13806362800;55446789300;37861539400;","Clouds and Snowball Earth deglaciation",2012,"10.1029/2012GL052861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868313389&doi=10.1029%2f2012GL052861&partnerID=40&md5=8f96a001d7d7a32a6a0de75a4b0ae538","Neoproterozoic, and possibly Paleoproterozoic, glaciations represent the most extreme climate events in post- Hadean Earth, and may link closely with the evolution of the atmosphere and life. According to the Snowball Earth hypothesis, the entire ocean was covered with ice during these events for a few million years, during which time volcanic CO<inf>2</inf> increased enough to cause deglaciation. Geochemical proxy data and model calculations suggest that the maximum CO<inf>2</inf> was 0.01-0.1 by volume, but early climate modeling suggested that deglaciation was not possible at CO<inf>2</inf> = 0.2. We use results from six different general circulation models (GCMs) to show that clouds could warm a Snowball enough to reduce the CO<inf>2</inf> required for deglaciation by a factor of 10-100. Although more work is required to rigorously validate cloud schemes in Snowball-like conditions, our results suggest that Snowball deglaciation is consistent with observations. © 2012. American Geophysical Union. All Rights Reserved."
"6603195697;6602871885;7003663632;55944549200;7006146499;6603665346;16069590400;","Upscaling latent heat flux for thermal remote sensing studies: Comparison of alternative approaches and correction of bias",2012,"10.1016/j.jhydrol.2012.08.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867102048&doi=10.1016%2fj.jhydrol.2012.08.005&partnerID=40&md5=5ebcf51e4efc589b4cf38c97029e1856","For instantaneous latent heat flux (λE) estimates from thermal remote sensing data to be useful in the hydrologic sciences, they require integration over longer time frames (e.g., months to years). This is not trivial because thermal remote sensing data acquired under cloud-free daytime conditions require upscaling to a monthly energy amount that is both relevant over cloudy periods and considers daytime and nighttime. Previous work has compared upscaling approaches, but as yet there is no authoritative comparison that does so under conditions relevant for thermal remote sensing. In this paper we describe, under the conditions relevant for thermal remote sensing, a generic framework for comparing any upscaling approach that assumes self-preservation. Then we use eddy-flux data from two sites in contrasting climates to systematically evaluate the accuracy of different upscaling proposals within the framework. We assumed that the instantaneous estimate of the latent heat flux measured by the eddy-flux technique would have been measured by a satellite sensor. We then scaled this estimate to a monthly period using four approaches and compared the result with the observed monthly integral. This design enabled us to isolate the accuracy of each upscaling method. The four methods upscaled λE by: (i) observed solar irradiance (S); (ii) modelled solar irradiance from a sine function (S SIN); (iii) modelled top-of-atmosphere solar irradiance (S TOA); and (iv) observed available energy (A E). We showed that upscaling λE using observed data (S, A E) resulted in underestimation of monthly evaporative energy, while the use of modelled data (S SIN, S TOA) led to overestimation, primarily due to the relationship between error and both the season (day-of-year) and cloud fraction. Of the two observed fluxes, upscaling with S resulted in lower overall errors than when using A E (S bias: -1.11MJm -2d -1 or -16%; A E bias: -2.15MJm -2d -1 or -34%). Of the two modelled fluxes, upscaling with S TOA had lower errors than the widely used S SIN method (S SIN bias: 1.03MJm -2d -1 or 14%; S TOA bias: 0.91MJm -2d -1 or 13%). We subsequently developed a simple procedure to minimise bias from all four upscaling approaches, and concluded that modelled data (S TOA) can be used to upscale λE to longer timescales for thermal remote sensing applications. This study developed the theory to minimise upscaling bias at two sites with contrasting climates, further work is needed to extend the approach to all global terrestrial climates. © 2012 Elsevier B.V."
"6701324864;7202162685;","Parameterization of homogeneous ice nucleation for cloud and climate models based on classical nucleation theory",2012,"10.5194/acp-12-9275-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867616971&doi=10.5194%2facp-12-9275-2012&partnerID=40&md5=11ea1f6efe2739297fb629f7b4dc86f5",[No abstract available]
"13610836500;6701659989;37099000200;7005428977;","Mechanisms for European summer temperature response to solar forcing over the last millennium",2012,"10.5194/cp-8-1487-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867484230&doi=10.5194%2fcp-8-1487-2012&partnerID=40&md5=e773ebb2b137cba66239e6405d35a973","A simulation of the last millennium is compared to a recent spatio-temporal reconstruction of summer temperature over Europe. The focus is on the response to solar forcing over the pre-industrial era. Although the correlation between solar forcing and the reconstruction remains small, the spatial regression over solar forcing shows statistically significant regions. The meridional pattern of this regression is found to be similar in the model and in the reconstruction. This pattern exhibits a large warming over Northern and Mediterranean Europe and a lesser amplitude response over Central and Eastern Europe. The mechanisms explaining this pattern in the simulation are mainly related to evapotranspiration fluxes. It is shown that the evapotranspiration is larger in summer over Central and Eastern Europe when solar forcing increases, while it decreases over the Mediterranean area. The explanation for the evapotranspiration increase over Central and Eastern Europe is found in the increase of winter precipitation there, leading to a soil moisture increase in spring. As a consequence, the evapotranspiration is larger in summer, which leads to an increase in cloud cover over this region, reducing the surface shortwave flux there and leading to less warming. Over the Mediterranean area, the surface shortwave flux increases with solar forcing, the soil becomes dryer and the evapotranspiration is reduced in summer leading to a larger increase in temperature. This effect appears to be overestimated in the model as compared to the reconstruction. Finally, the warming of Northern Europe is related to the albedo feedback due to sea-ice cover retreat with increasing solar forcing. © 2012 Author(s)."
"16029674800;","Is cumulus convection the concertmaster of tropical cyclone activity in the Atlantic?",2012,"10.1029/2012GL053449","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867517519&doi=10.1029%2f2012GL053449&partnerID=40&md5=5efc6c26e5c73a58caac1a00b3e7a0b6","The influence of the cloud representation in global climate models on the accuracy of the North Atlantic tropical cyclone simulations is investigated. The North Atlantic tropical cyclone activity is simulated with a standard climate model, CCSM. The conventional parameterization of cloud processes in CCSM is replaced by the ""super-parameterization"" and the simulation is run again. The comparison of tropical cyclone statistics reveals that the model with explicit representation of cloud processes produces a larger number of events, with stronger intensity and longer life-cycle. The results show that clouds have a significant impact on the mechanisms associated with tropical cyclone activity such as surface temperature and ocean subsurface processes, vertical wind shear, and the transport of moisture in the lower troposphere. © 2012. American Geophysical Union. All Rights Reserved."
"56118539900;16402575500;55391863600;36574252000;57138743300;7403079681;","In situ water vapor and ozone measurements in Lhasa and Kunming during the Asian summer monsoon",2012,"10.1029/2012GL052996","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867520211&doi=10.1029%2f2012GL052996&partnerID=40&md5=a6f324306b3bcbbc3de261f1725607f4","The Asian summer monsoon (ASM) anticyclone circulation system is recognized to be a significant transport pathway for water vapor and pollutants to enter the stratosphere. The observational evidence, however, is largely based on satellite retrievals. We report the first coincident in situ measurements of water vapor and ozone within the ASM anticyclone. The combined water vapor and ozonesondes were launched from Kunming, China in August 2009 and Lhasa, China in August 2010. In total, 11 and 12 sondes were launched in Kunming and Lhasa, respectively. We present the key characteristics of these measurements, and provide a comparison to similar measurements from an equatorial tropical location, during the Tropical Composition, Cloud and Climate Coupling (TC4) campaign in July and August of 2007. Results show that the ASM anticyclone region has higher water vapor and lower ozone concentrations in the upper troposphere and lower stratosphere than the TC4 observations. The results also show that the cold point tropopause in the ASM region has a higher average height and potential temperature. The in situ observations therefore support the satellite-based conclusion that the ASM is an effective transport pathway for water vapor to enter stratosphere. © 2012. American Geophysical Union. All Rights Reserved."
"21743098300;7006069664;55441669800;55217798700;","Numerical simulation of severe local storms over east India using WRF-NMM mesoscale model",2012,"10.1016/j.atmosres.2012.04.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865110770&doi=10.1016%2fj.atmosres.2012.04.015&partnerID=40&md5=186b504ecac7093316486a17068c3fc8","A common feature of the weather during the pre-monsoon season (March-May) over the east and northeast India is the outburst of severe local storms which have significant socio-economic impact due to loss of lives and properties. Forecasting thunderstorms is one of the most difficult tasks in weather prediction, due to their rather small spatial and temporal scales and the inherent non-linearity of their dynamics and physics. In the present study, an attempt has been made to simulate severe local storms that occurred over east India during STORM field experiments 2007, 2009 and 2010, using Non-hydrostatic Mesoscale Model (NMM) and validate the model results with observation. This study shows that the NMM model holds better promise for prediction of thunderstorm with reasonable accuracy. The intensity of rainfall rates is in good agreement with the observation. The model has well captured the stability indices, which act as indicators of severe convective activity. The surface temperature and relative humidity over Kolkata are reasonably well simulated by the NMM model even though one hour time lag or lead exists. The model simulated well the updraft and downdraft over Kolkata, which is an important phenomenon related to thunderstorm life cycle. From the model simulated spatial plots of composite radar reflectivity and cloud top temperature, we can see that the model has also been able to capture the movement of thunder squall. The results of these analyses determined that the 3. km WRF-NMM model has good skill when it comes to the thunderstorm simulation. © 2012 Elsevier B.V."
"18838758100;16029936600;","Multiphase halogen chemistry in the tropical atlantic ocean",2012,"10.1021/es300209f","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867036451&doi=10.1021%2fes300209f&partnerID=40&md5=2cc598bd3074612416583901526cd9bd","We used a one-dimensional model to simulate the chemical evolution of air masses in the tropical Atlantic Ocean, with a focus on halogen chemistry. The model results were compared to the observations of inorganic halogen species made in this region. The model could largely reproduce the measurements of most chlorine species, especially under unpolluted conditions, but overestimated sea salt chloride, BrCl, and bromine species. Agreement with the measurements could be improved by taking into account the reactivity with aldehydes and the effects of dimethyl sulfide (DMS) and Saharan dust on aerosol pH; a hypothetical HOX → X- aqueous-phase reaction could also improve the agreement with measured Cl2 and HOCl, especially under semipolluted conditions. The results also showed that halogens speciation and concentrations are very sensitive to cloud processing. The model was used to calculate the impact of the observed levels of halogens: Cl atoms accounted for 5.4-11.6% of total methane sinks and halogens (mostly bromine and iodine) accounted for 35-40% of total ozone destruction. © 2012 American Chemical Society."
"7402612084;27968009900;","Changing the climate sensitivity of an atmospheric general circulation model through cloud radiative adjustment",2012,"10.1175/JCLI-D-11-00590.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867669805&doi=10.1175%2fJCLI-D-11-00590.1&partnerID=40&md5=7e036c83d1200b294500745a4103e6e9","Conducting probabilistic climate projections with a particular climate model requires the ability to vary the model's characteristics, such as its climate sensitivity. In this study, the authors implement and validate a method to change the climate sensitivity of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, version 3 (CAM3), through cloud radiative adjustment. Results show that the cloud radiative adjustment method does not lead to physically unrealistic changes in the model's response to an external forcing, such as doubling CO 2 concentrations or increasing sulfate aerosol concentrations. Furthermore, this method has some advantages compared to the traditional perturbed physics approach. In particular, the cloud radiative adjustment method can produce any value of climate sensitivity within the wide range of uncertainty based on the observed twentieth century climate change. As a consequence, this method allows Monte Carlo-type probabilistic climate forecasts to be conducted where values of uncertain parameters not only cover the whole uncertainty range, but cover it homogeneously. Unlike the perturbed physics approach that can produce several versions of a model with the same climate sensitivity but with very different regional patterns of change, the cloud radiative adjustment method can only produce one version of the model with a specific climate sensitivity. As such, a limitation of this method is that it cannot cover the full uncertainty in regional patterns of climate change. © 2012 American Meteorological Society."
"8718425100;55915206300;7103060756;7601492669;","Modeling the response of marine boundary layer clouds to global warming: The impact of subgrid-scale precipitation formation",2012,"10.1175/JCLI-D-11-00623.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867662357&doi=10.1175%2fJCLI-D-11-00623.1&partnerID=40&md5=8e9ab96b6a2d3f1c3fca32ced70069a3","An important parameter often adjusted to achieve agreement between simulated and observed radiative fluxes in climate models is the rain formation efficiency. This adjustment has been justified as accounting for the effects of subgrid-scale variability in cloud properties, but this tuning approach is rather arbitrary. This study examines results from a regional climate model with precipitation formation schemes that have been conventionally tuned, and it compares them with simulations employing a recently developed scheme that uses satellite observations to explicitly account for the subgrid-scale variability of clouds (""integral constraint method""). Simulations with the International Pacific Research Center's Regional Atmospheric Model (iRAM) show that the integral constraint method is capable of simulating cloud fields over the eastern Pacific that are in good agreement with observations, without requiring model tuning. A series of global warming simulations for late twenty-first-century conditions is performed to investigate the impact of the treatment of the precipitation formation efficiency on modeled cloud-climate feedbacks. The results with the integral constraint method show that the simulated cloud feedbacks have similar patterns at all the model resolutions considered (grid spacings of 50, 100, and 200 km), but there are some quantitative differences (with smaller feedbacks at finer resolution). The cloud responses to global warming in simulations with a conventionally tuned autoconversion scheme and with the integral constraint method were found to be quite consistent, although differences in individual regions of ~10%-30% are evident. No conclusions can be drawn from this study on the validity of model tuning for thick clouds and mixed phase or ice clouds, however. © 2012 American Meteorological Society."
"35552588700;55328699600;6602096831;7005858663;","Weakening of hurricanes via marine cloud brightening (MCB)",2012,"10.1002/asl.402","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867951764&doi=10.1002%2fasl.402&partnerID=40&md5=6ba8e1505c35b129b061d1de83df98f7","This paper examines the potential to cool ocean surface waters in regions of hurricane genesis and early development.This would be achieved by seeding, with copious quantities of seawater cloud condensation nuclei (CCN), low-level maritime stratocumulus clouds covering these regions or those at the source of incoming currents.Higher cloud droplet density would increase these clouds' reflectivity to incoming sunlight, and possibly their longevity.This approach is therefore a more localized application of the marine cloud brightening (MCB) geoengineering technique promoting global cooling.By utilizing a climate ocean/atmosphere coupled model, HadGEM1, we demonstrate that-subject to the satisfactory resolution of defined but unresolved issues-judicious seeding of maritime stratocumulus clouds might significantly reduce sea surface temperatures (SSTs) in regions where hurricanes develop.Thus artificial seeding may reduce hurricane intensity; but how well the magnitude of this effect could be controlled is yet to be determined.We also address the important question as to how MCB seeding may influence precipitation.GCM modelling indicates that the influence of seeding on undesirable rainfall reductions depends on its location and magnitude. Much more work on this topic is required. © 2012 Royal Meteorological Society."
"9246517900;24332905600;","Sensitivity of cloud liquid water content estimates to the temperature-dependent thermodynamic phase: A global study using cloudsat data",2012,"10.1175/JCLI-D-11-00521.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867671533&doi=10.1175%2fJCLI-D-11-00521.1&partnerID=40&md5=cdac69cde301231399cab89abaf9ceb8","The main purpose of this study is to underline the sensitivity of cloud liquid water content (LWC) estimates purely to 1) the shape of computationally simplified temperature-dependent thermodynamic phase and 2) the range of subzero temperatures covered to partition total cloud condensate into liquid and ice fractions. Linear, quadratic, or sigmoid-shaped functions for subfreezing temperatures (down to 2208 or 2408C) are often used in climate models and reanalysis datasets for partitioning total condensate. The global vertical profiles of clouds obtained from CloudSat for the 4-yr period June 2006-May 2010 are used for sensitivity analysis and the quantitative estimates of sensitivities based on these realistic cloud profiles are provided. It is found that three cloud regimes in particular-convective clouds in the tropics, low-level clouds in the northern high latitudes, and middle-level clouds over the midlatitudes and Southern Ocean-are most sensitive to assumptions on thermodynamic phase. In these clouds, the LWC estimates based purely on quadratic or sigmoid-shaped functions with a temperature range down to 2208C can differ by up to 20%-40% over the tropics (in seasonal means), 10%-30%over the midlatitudes, and up to 50% over high latitudes compared to a linear assumption. When the temperature range is extended down to 2408C, LWC estimates in the sigmoid case can be much higher than the above values over high-latitude regions compared to the commonly used case with quadratic dependency down to 2208C. This sensitivity study emphasizes the need to critically investigate radiative impacts of cloud thermodynamic phase assumptions in simplified climate models and reanalysis datasets. © 2012 American Meteorological Society."
"8686475900;25645385100;7005219614;","Modelled suppression of boundary-layer clouds by plants in a CO 2 -rich atmosphere",2012,"10.1038/ngeo1554","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866975647&doi=10.1038%2fngeo1554&partnerID=40&md5=e3a4f5bf36875ae6a0fc38cd57bb3855","Cumulus clouds in the atmospheric boundary layer play a key role in the hydrologic cycle, in the onset of severe weather by thunderstorms and in modulating Earth's reflectivity and climate. How these clouds respond to climate change, in particular over land, and how they interact with the carbon cycle are poorly understood. It is expected that as a consequence of rising atmospheric CO 2 concentrations the plant stomata will close, leading to lower latent heat fluxes and higher sensible heat fluxes. Here we show that this causes a decline in boundary-layer cloud formation in middle latitudes. This could be partly counteracted by the greater ability of a warmer atmosphere to take up water and by a growth in biomass due to CO 2 fertilization. Our results are based on a new soil-water-atmosphere-plant model supported by comprehensive observational evidence, from which we identify the dominant atmospheric responses to plant physiological processes. They emphasize the intricate connection between biological and physical aspects of the climate system and the relevance of short-term and small-scale processes in establishing this connection."
"55686667100;10241250100;55537426400;10243650000;10241462700;35454141800;8979277400;7102857642;","Fast and slow timescales in the tropical low-cloud response to increasing CO2 in two climate models",2012,"10.1007/s00382-011-1178-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867101759&doi=10.1007%2fs00382-011-1178-y&partnerID=40&md5=95dc235fef8ec0529836ebe29d99b729","To obtain physical insights into the response and feedback of low clouds (Cl) to global warming, ensemble 4 × CO2 experiments were carried out with two climate models, the Model for Interdisciplinary Research on Climate (MIROC) versions 3. 2 and 5. For quadrupling CO2, tropical-mean Cl decreases, and hence, acts as positive feedback in MIROC3, whereas it increases and serves as negative feedback in MIROC5. Three time scales of tropical-mean Cl change were identified-an initial adjustment without change in the global-mean surface air temperature, a slow response emerging after 10-20 years, and a fast response in between. The two models share common features for the former two changes in which Cl decreases. The slow response reflects the variability of Cl associated with the El Niño-Southern Oscillation in the control integration, and may therefore be constrained by observations. However, the fast response is opposite in the two models and dominates the total response of Cl. Its sign is determined by a subtle residual of the Cl increase and decrease over the ascending and subsidence regions, respectively. The regional Cl increase is consistent with a more frequent occurrence of a stable condition, and vice versa, as measured by lower-tropospheric stability (LTS). The above frequency change in LTS is similarly found in six other climate models despite a large difference in both the mean and the changes in the low-cloud fraction for a given LTS. This suggests that the response of the thermodynamic constraint for Cl to increasing CO2 concentrations is a robust part of the climate change. © 2011 The Author(s)."
"8724962900;23484340400;","An improved representation of the raindrop size distribution for single-moment microphysics schemes",2012,"10.1002/qj.1949","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871627799&doi=10.1002%2fqj.1949&partnerID=40&md5=4a671ec339791df2cbefe3c4a394fe53","We analyse observations of the size distribution of raindrops from a variety of cloud types and precipitation rates. The measurements show a transition from large raindrops observed in convective showers and frontal rainbands to higher concentrations of much smaller drizzle drops observed in stratocumulus clouds. The observations are used to develop an improved parametrization of the raindrop size distribution that better captures the observed transition for use in single-moment microphysics schemes. Sensitivity tests are performed in both climate and numerical weather prediction versions of the Met Office Unified Model to demonstrate that the new parametrization leads to improvements in various precipitation and cloud-related metrics. © 2012 British Crown copyright, the Met Office."
"8309699900;","Coincidence errors in a cloud droplet probe (CDP) and a cloud and aerosol spectrometer (CAS), and the improved performance of a modified CDP",2012,"10.1175/JTECH-D-11-00208.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868028005&doi=10.1175%2fJTECH-D-11-00208.1&partnerID=40&md5=af3fb5e142ebd550bc70785f47fbe8bc","Central to the aerosol indirect effect on climate is the relationship between cloud droplet concentrations Nd and cloud condensation nuclei (CCN) concentrations. There are valid reasons to expect a sublinear relationship between measured Nd and CCN, and such relationships have been observed for clouds in a variety of locations. However, a measurement artifact known as ""coincidence""can also produce a sublinear trend. The current paper shows that two commonly used instruments, the cloud droplet probe (CDP) and the cloud and aerosol spectrometer (CAS), can be subject to significantly greater coincidence errors than are typically recognized, with an undercounting bias of at least 27% and an oversizing bias of 20%-30% on average at Nd = 500 cm-3, and with an undercounting bias of as much as 44% at Nd = 1000 cm-3. This type of systematic error may have serious implications for interpretation of in situ cloud observations. It is shown that a simple optical modification of the CDP dramatically reduces oversizing and undercounting biases due to coincidence. Guidance is provided for diagnosing coincidence errors in CAS and CDP instruments. © 2012 American Meteorological Society."
"6506004306;35596591300;","U.S. Diurnal temperature range variability and regional causal mechanisms, 1901-2002",2012,"10.1175/JCLI-D-11-00429.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867678420&doi=10.1175%2fJCLI-D-11-00429.1&partnerID=40&md5=bc2ce81a9b9189b3501e770798880932","Long-term (1901-2002) diurnal temperature range (DTR) data are evaluated to examine their spatial and temporal variability across the United States; the early century origin of the DTR declines; and the relative regional contributions to DTR variability among cloud cover, precipitation, soil moisture, and atmosphere/ocean teleconnections. Rotated principal component analysis (RPCA) of the Climatic Research Unit (CRU) Time Series (TS) 2.1 dataset identifies five regions of unique spatial U.S. DTR variability. RPCA creates regional orthogonal indices of cloud cover, soil moisture, precipitation, and the teleconnections used subsequently in stepwise multiple linear regression to examine their regional impact on DTR, maximum temperature (Tmax), and minimum temperature (Tmin). The southwestern United States has the smallest DTR and cloud cover trends as both Tmax and Tmin increase over the century. The Tmin increases are the primary influence on DTR trend in other regions, except in the south-central United States, where downward Tmax trend largely affects its DTR decline. The Tmax and DTR tend to both exhibit simultaneous decadal variations during unusually wet and dry periods in response to cloud cover, soil moisture, and precipitation variability. The widely reported post-1950 DTR decline began regionally at various times ranging from around 1910 to the 1950s. Cloud cover alone accounts for up to 63.2% of regional annual DTR variability, with cloud cover trends driving DTR in northern states. Cloud cover, soil moisture, precipitation, and atmospheric/oceanic teleconnection indices account for up to 80.0% of regional variance over 1901-2002 (75.4% in detrended data), although the latter only account for small portions of this variability. © 2012 American Meteorological Society."
"15922497600;55365937700;55366081200;55365474100;55366046500;55366972700;","Development of 1961-1990 monthly surface climatology of India and patterns of differences of some meteorological parameters with respect to the 1951-1980 climatology",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866675543&partnerID=40&md5=cd9a018144b9cd5e72c29dedfbec720f","Climate normals are used to describe the average climatic conditions of a particular place and are computed by National Meteorological Services of all countries. The World Meteorological Organization (WMO) recommends that all countries prepare climate normals for the 30-year periods ending in 1930, 1960, 1990 and so on, for which the WMO World Climate Normals are published. Recently, Climatological Normals for the period 1961-1990 have been prepared by India Meteorological Department (IMD) which will change the baseline of comparison from 1951-1980. In this paper, preparation of the 30-year Climatological Normals of India for the period 1961 to 1990 and spatial patterns of differences of annual means of temperatures, relative humidity, clouds, rainfall and wind speed from the previous normals (1951-1980) are documented. The changes from earlier climatological normals indicate increase in annual means of maximum temperature, relative humidity and decrease in annual means of minimum temperature, cloud amount, rainfall, rainy days and wind speed over large parts of the country during 1961-1990. The spatial patterns of changes in dry bulb temperatures and relative humidity are complementary over most parts of the country. Compared with 1951-1980 climatology, there are large scale decreases in annual mean rainfall, rainy days and wind speed over most parts of the country during 1961-1990. The decrease in wind speed may be partly due to changes in exposure conditions of observatories due to urbanization. © 2012 Government of India."
"55418382000;35509639400;7006861646;","Observational evidence for relationships between the degree of aggregation of deep convection, water vapor, surface fluxes, and radiation",2012,"10.1175/JCLI-D-11-00258.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867686898&doi=10.1175%2fJCLI-D-11-00258.1&partnerID=40&md5=6d4fcce8b9f689521571cb4f5753524e","Tropical deep convection exhibits complex organization over a wide range of scales. This study investigates the relationships between the spatial organization of deep convection and the large-scale atmospheric state. By using several satellite datasets and reanalyses, and by defining a simple diagnostic of convective aggregation, relationships between the degree of convective aggregation and the amount of water vapor, turbulent surface fluxes, and radiation are highlighted above tropical oceans. When deep convection is more aggregated, the middle and upper troposphere are drier in the convection-free environment, turbulent surface fluxes are enhanced, and the low-level and midlevel cloudiness is reduced in the environment. Humidity and cloudiness changes lead to a large increase in outgoing longwave radiation. Cloud changes also result in reduced reflected shortwave radiation. Owing to these opposing effects, the sensitivity of the radiative budget at the top of the atmosphere to convective aggregation turns out to be weak, but the distribution of radiative heating throughout the troposphere is affected. These results suggest that feedbacks between convective aggregation and the large-scale atmospheric state might influence large-scale dynamics and the transports of water and energy and, thus, play a role in the climate variability and change. These observational findings are qualitatively consistent with previous cloud-resolvingmodel results, except for the effects on cloudiness and reflected shortwave radiation. The proposed methodology may be useful for assessing the representation of convective aggregation and its interaction with the large-scale atmospheric state in various numerical models. © 2012 American Meteorological Society."
"7006783796;12803465300;8280879000;24322892500;24759591600;7005729142;7003283811;6602407753;35468686100;55486763600;35547214900;6603083860;7404597424;35331137500;7403931916;","Simulations of Infrared Radiances over a Deep Convective Cloud System Observed during TC 4: Potential for Enhancing Nocturnal Ice Cloud Retrievals",2012,"10.3390/rs4103022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869228142&doi=10.3390%2frs4103022&partnerID=40&md5=1c2fe8d655929d2fa2ff5ff96ea60947","Retrievals of ice cloud properties using infrared measurements at 3.7, 6.7, 7.3, 8.5, 10.8, and 12.0 μm can provide consistent results regardless of solar illumination, but are limited to cloud optical thicknesses τ &lt; ~6. This paper investigates the variations in radiances at these wavelengths over a deep convective cloud system for their potential to extend retrievals of τ and ice particle size D e to optically thick clouds. Measurements from an imager, an interferometer, the Cloud Physics Lidar (CPL), and the Cloud Radar System (CRS) aboard the NASA ER-2 aircraft during the NASA TC 4 (Tropical Composition, Cloud and Climate Coupling) experiment flight during 5 August 2007, are used to examine the retrieval potential of infrared radiances over optically thick ice clouds. Simulations based on coincident in situ measurements and combined cloud τ from CRS and CPL measurements are comparable to the observations. They reveal that brightness temperatures at these bands and their differences (BTD) are sensitive to τ up to ~20 and that for ice clouds having τ &gt; 20, the 3.7-10.8 μm and 3.7-6.7 μm BTDs are the most sensitive to D e. Satellite imagery appears to be consistent with these results suggesting that τ and D e could be retrieved for greater optical thicknesses than previously assumed. But, because of sensitivity of the BTDs to uncertainties in the atmospheric profiles of temperature, humidity, and ice water content, and sensor noise, exploiting the small BTD signals in retrieval algorithms will be very challenging. © 2012 by the authors."
"34768718200;6601927317;57189498750;7402027161;24398842400;9043417100;57199683903;6603497648;7004715270;23487049000;6701834052;","A particle-surface-area-based parameterization of immersion freezing on desert dust particles",2012,"10.1175/JAS-D-11-0249.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861948064&doi=10.1175%2fJAS-D-11-0249.1&partnerID=40&md5=033b1e78a05b2b470bf2c0e55543365d","In climate and weather models, the quantitative description of aerosol and cloud processes relies on simplified assumptions. This contributes major uncertainties to the prediction of global and regional climate change. Therefore, models need good parameterizations for heterogeneous ice nucleation by atmospheric aerosols. Here the authors present a new parameterization of immersion freezing on desert dust particles derived from a large number of experiments carried out at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber facility. The parameterization is valid in the temperature range between -12° and-36°C at or above water saturation and can be used in atmospheric models that include information about the dust surface area. The new parameterization was applied to calculate distribution maps of ice nuclei during a Saharan dust event based on model results from the regional-scale model Consortium for Small-Scale Modelling-Aerosols and Reactive Trace Gases (COSMO-ART). The results were then compared to measurements at the Taunus Observatory on Mount Kleiner Feldberg, Germany, and to three other parameterizations applied to the dust outbreak. The aerosol number concentration and surface area from the COSMO-ART model simulation were taken as input to different parameterizations. Although the surface area from the model agreed well with aerosol measurements during the dust event at Kleiner Feldberg, the ice nuclei (IN) number concentration calculated from the new surface-area-based parameterization was about a factor of 13 less than IN measurements during the same event. Systematic differences of more than a factor of 10 in the IN number concentration were also found among the different parameterizations. Uncertainties in the modeled and measured parameters probably both contribute to this discrepancy and should be addressed in future studies. © 2012 American Meteorological Society."
"38062135700;7005565819;57203579757;","Impact from a volumetric radar-sampling operator for radial velocity observations within EnKF supercell assimilation",2012,"10.1175/JTECH-D-12-00088.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871904638&doi=10.1175%2fJTECH-D-12-00088.1&partnerID=40&md5=4aaa87b22e169ba5900d7ee03df9a0f9","Maximizing the accuracy of ensemble Kalman filtering (EnKF) radar data assimilation requires that the observation operator sample the model state in the same manner that the radar sampled the atmosphere. It may therefore be desirable to include volume averaging and power weighting in the observation operator. This study examines the impact of including radar-sampling effects in the Doppler velocity observation operator on EnKF analyses and forecasts. Locally substantial differences are found between a simple point operator and a realistic radar-sampling operator when they are applied to the model state at a single time. However, assimilation results indicate that the radar-sampling operator does not substantially improve the EnKF analyses or forecasts, and it greatly increases the computational cost of the data assimilation. © 2012 American Meteorological Society."
"24759016700;7003667635;15122248200;36945025900;7003465848;","Global response to solar radiation absorbed by phytoplankton in a coupled climate model",2012,"10.1007/s00382-012-1300-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867103822&doi=10.1007%2fs00382-012-1300-9&partnerID=40&md5=66d807c1d092b055aa254173d3762a13","The global climate response to solar radiation absorbed by phytoplankton is investigated by performing multi-century simulations with a coupled ocean-atmosphere-biogeochemistry model. The absorption of solar radiation by phytoplankton increases radiative heating in the near-surface ocean and raises sea surface temperature (SST) by overall ~0.5°C. The resulting increase in evaporation enhances specific atmospheric humidity by 2-5%, thereby increasing the Earth's greenhouse effect and the atmospheric temperatures. The Hadley Cell exhibits a weakening and poleward expansion, therefore reducing cloudiness at subtropical-middle latitudes and increasing it at tropical latitudes except near the Equator. Higher SST at polar latitudes reduces sea ice cover and albedo, thereby increasing the high-latitude ocean absorption of solar radiation. Changes in the atmospheric baroclinicity cause a poleward intensification of mid-latitude westerly winds in both hemispheres. As a result, the North Atlantic Ocean meridional overturning circulation extends more northward, and the equatorward Ekman transport is enhanced in the Southern Ocean. The combination of local and dynamical processes decreases upper-ocean heat content in the Tropics and in the subpolar Southern Ocean, and increases it at middle latitudes. This study highlights the relevance of coupled ocean-atmosphere processes in the global climate response to phytoplankton solar absorption. Given that simulated impacts of phytoplankton on physical climate are within the range of natural climate variability, this study suggests the importance of phytoplankton as an internal constituent of the Earth's climate and its potential role in participating in its long-term climate adjustments. © 2012 Springer-Verlag."
"7004932211;7004050581;26026749200;","On the surface temperature sensitivity of the reflected shortwave, outgoing longwave, and net incident radiation",2012,"10.1175/JCLI-D-11-00607.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867686896&doi=10.1175%2fJCLI-D-11-00607.1&partnerID=40&md5=3ebab4dddaaf9cca280e71616d08e77d","The global-mean top-of-atmosphere incident solar radiation (ISR) minus the outgoing longwave radiation (OLR) and the reflected shortwave radiation (RSW) is the net incident radiation (NET). This study analyzes the global-mean NET sensitivity to a change in the global-mean surface temperature by applying the interannual anomaly correlation technique to 9yr of Atmospheric Infrared Sounder (AIRS) global measurements of RSW and OLR under cloudy and clear conditions. The study finds the observed sensitivity of NET that includes the effects of clouds to be -1.5±0.25 (1σ)W m -2 K -1 and the clear NET sensitivity to be -2.0 ± 0.2 (1σ) W m -2 K -1, consistent with previous work using Earth Radiation Budget Experiment and Clouds and the Earth's Radiant Energy System data. The cloud effect, +0.5 ± 0.2 (1σ) W mm -2 K -1, is a positive component of the NET sensitivity. The similarity of the NET sensitivities derived from forced and unforced models invites a comparison between the observed sensitivities and the effective sensitivities calculated for the Fourth Assessment Report models, although this requires some caution: The effective model sensitivities with clouds range from -0.88 to -1.64 W m -2 K -1, the clear NET sensitivity in the models ranges from -2.32 to -1.73 W m -2 K -1, and the cloud forcing sensitivities range from +0.14 to +1.18 W m -2 K -1. The effective NET and clear NET sensitivities derived from the models are statistically consistent with those derived from the AIRS data, considering the observational and model derivation uncertainties. © 2012 American Meteorological Society."
"6506643480;56000281400;25629339800;8373634800;6506424404;","Spatial and temporal variability of aerosol particles in Arctic spring",2012,"10.1002/qj.1940","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871630946&doi=10.1002%2fqj.1940&partnerID=40&md5=dc0242594915937275852082e5aeb1d6","The objective of this work is to investigate the variability in the aerosol particle number concentration in Arctic spring. The Indirect and Semi-Direct Aerosol Campaign (ISDAC) was conducted during April 2008 in the vicinities of Fairbanks and Barrow, Alaska. Aircraft-based measurements of total aerosol particle number concentration (Na) in the size range of 0.12-3 μm diameter were obtained using a passive cavity aerosol spectrometer probe (PCASP-100X). The analysis considers Na during cloud-free periods in biomass burning (BB) and non-BB aerosol loading scenarios, the latter including background cases and cases with elevated concentration in layers. The BB cases had air masses originating mainly from Russian and Asian forest and crop fires, whereas the non-BB cases originated predominantly from Arctic or oceanic regions. The average Na for all non-BB cases was 127 cm-3, while that for all BB cases was Na = 720 cm-3. These estimates do not, however, capture the details of aerosol particle layers encountered during most flights. Variability in Na was considered for constant altitude (horizontal) flight legs ranging from 50 to 650 km in length, as well as for vertical flight profiles up to 7 km above sea level. When aerosol particle layers were encountered, Na rapidly increased from 20 to 550 cm-3, and reached up to 2200 cm-3 within air masses dominated by BB plumes. The observed variability in Na may have important implications for estimating cloud microphysical properties as well as estimates of particle properties used in global climate model simulations, because averaging over large space- or time-scales may not represent real atmospheric conditions. The analysis demonstrates the difficulty in interpreting average aerosol particle characteristics along longer flight legs, particularly during cases with higher particle loading that varies over shorter distance scales and time periods. © 2012 Royal Meteorological Society and Crown in the right of Canada."
"44761502700;44760925800;6603850393;","Climate change along the arid coast of northern Chile",2012,"10.1002/joc.2395","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867010274&doi=10.1002%2fjoc.2395&partnerID=40&md5=cfda50c9d2bfab360d6908d5a4198df5","Long-term precipitation records from the extremely arid northern coast of Chile (18°S-30°S) were analysed to assess changes occurring at different time scales. Results are presented here along with a discussion on changes in the temperature and cloudiness regimes in order to offer a more comprehensive overview of the climate evolution in this extremely arid region. Apart from a significant influence of ENSO on the rainfall regime, characterized by a tendency for more frequent rainfall events during El Niño episodes, changes at the decadal time scale were identified in association with the Interdecadal Pacific Oscillation (IPO). Thus, the warm IPO-phase is associated with increased precipitation, while the opposite occurs during the cold IPO-phase. Changes occurring at the interannual and decadal time scales are superimposed on a long-term precipitation decline during the 20th century. Apart from the intensified dryness, the temperature records show a positive long-term trend resulting mainly from an abrupt warming in the mid-1970s, principally associated with a marked upwards shift of the minimum daily temperature, coinciding with the change from the cold to the warm phase of the IPO. However, the period following this step-like warming has been characterized by a persistent cooling trend, most evident in the maximum daily temperature, which is coherent with a negative trend in the sea surface temperature over a large oceanic region off the coast of northern Chile. In the northernmost region, this behaviour in the temperature regime was accompanied by a strong decrease in cloudiness since the 1970s. The negative trend in rainfall and the decrease in the total cloud cover are certainly important factors that could explain the coastal vegetation decline over the past decades in the coastal region north of 24°S. © 2011 Royal Meteorological Society."
"7003666669;55717074000;7006270084;6603268269;7006705919;55317177900;7102645933;","Toward a minimal representation of aerosols in climate models: Comparative decomposition of aerosol direct, semidirect, and indirect radiative forcing",2012,"10.1175/JCLI-D-11-00650.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864050326&doi=10.1175%2fJCLI-D-11-00650.1&partnerID=40&md5=06c60591055dd19f50d2c2cae1986cc6","The authors have decomposed the anthropogenic aerosol radiative forcing into direct contributions from each aerosol species to the planetary energy balance through absorption and scattering of solar radiation, indirect effects of anthropogenic aerosol on solar and infrared radiation through droplet and crystal nucleation on aerosol, and semidirect effects through the influence of solar absorption on the distribution of clouds. A three-mode representation of the aerosol in version 5.1 of the Community Atmosphere Model (CAM5.1) yields global annual mean radiative forcing estimates for each of these forcing mechanisms that are within 0.1 W m -2 of estimates using a more complex seven-mode representation that distinguishes between fresh and aged black carbon and primary organic matter. Simulating fresh black carbon particles separately from internally mixed accumulation mode particles is found to be important only near fossil fuel sources. In addition to the usual large indirect effect on solar radiation, this study finds an unexpectedly large positive longwave indirect effect (because of enhanced cirrus produced by homogenous nucleation of ice crystals on anthropogenic sulfate), small shortwave and longwave semidirect effects, and a small direct effect (because of cancelation and interactions of direct effects of black carbon and sulfate). Differences between the threemode and seven-mode versions are significantly larger (up to 0.2 W m -2) when the hygroscopicity of primary organic matter is decreased from 0.1 to 0 and transfer of the primary carbonaceous aerosol to the accumulation mode in the seven-mode version requires more hygroscopic material coating the primary particles. Radiative forcing by cloudborne anthropogenic black carbon is only 20.07 W m -2. © 2012 American Meteorological Society."
"55418943100;7007020226;7405489798;","CALIPSO-Derived three-dimensional structure of aerosol over the atlantic basin and adjacent continents",2012,"10.1175/JCLI-D-11-00672.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867046857&doi=10.1175%2fJCLI-D-11-00672.1&partnerID=40&md5=362ae71f64b05a3e7a6de3b3fe1d62c2","Accurate modeling of the impact of aerosols on climate requires a detailed understanding of the vertical distribution of aerosols. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) provides continuous high-resolution vertical profiles of aerosol properties on a near-global scale. Here the CALIPSO Vertical Feature Mask is used to document the three-dimensional (3D) frequency-of-occurrence distribution of aerosols over a broad region of the Atlantic Ocean, Africa, Europe, and the Americas. The 3D distributions illustrate the seasonal cycle in the zonal and meridional variability of the vertical profiles of mineral dust, biomass-burning smoke, polluted dust (externalmixture of dust and smoke), and polluted continental aerosol, and also of their emissions sources and transport pathways. Four aerosol domains stand out in the product: dust over NorthAfrica and theMiddle East and smoke over southern Africa and South America. The transport pathways of African dust and smoke over theAtlantic are evident. The intertropical convergence zone (ITCZ) plays a clear role in limiting the southward transport ofNorthAfrican dust and northward transport of SouthAfrican smoke. Dust and smoke aremixed in the ITCZ and consequently the highest probability of polluted dust is found there, even though the probabilities of dust and smoke in this region are relatively low. The mixing of dust and pollution has significant implications for cloud microphysical processes over a broad region of the Atlantic. © 2012 American Meteorological Society."
"6603013702;6508308083;6603689532;57090352200;","Diesel Vehicle Cold Operability: Design of Fuel System Essential Besides Fuel Properties",2012,"10.4271/2012-01-1592","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871276735&doi=10.4271%2f2012-01-1592&partnerID=40&md5=e945e31f96001b50f0434959ff7a2a95","Cold operability is estimated by fuel's cold filter plugging point (CFPP). However, correlation of CFPP with diesel vehicle performance originates from a period when simple in-line or distributor fuel injection systems were applied and fuels did not contain biocomponents. Today, common rail fuel injection systems are used and there seem to be remarkable differences in their design between vehicle models. Seven cars were tested in a climate chamber. The best cars operated down to 8°C below fuel's CFPP but the worst get into problems 5°C above CFPP with the same fuel. It is challenging to define what CFPP is needed in order to guarantee trouble-free winter performance because there are big differences between car models. It is fundamental to get the fuel temperature of a vehicle's fuel filter above the fuel's cloud point during driving, and this depends on fuel system design factors, such as location and size of fuel filter and fuel heater if it is used. Oil companies prefer diesel fuels which do not have unnecessary good cold properties because better cold properties reduce the diesel fuel yield at refineries at a time when there is shortage of diesel fuels in Europe. Light middle distillate fractions suitable for winter grades are needed also for aviation kerosene production. Cold operability problems related to biocomponents can be avoided by using isomerized HVO. Trouble-free operation in cold conditions is important for all stakeholders: Oil companies, automotive companies and vehicle owners. Further exchange of information and co-operation between oil, automotive and fuel additive companies would be valuable as well as more vehicle testing. © 2012 SAE International."
"55373025000;57208346904;35495958000;","WRF ensemble downscaling seasonal forecasts of China winter precipitation during 1982-2008",2012,"10.1007/s00382-011-1241-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867008540&doi=10.1007%2fs00382-011-1241-8&partnerID=40&md5=896c5bd8a3ec7f4b9ac540db3d354b9d","The non-hydrostatic Weather Research and Forecasting model (WRF) was nested into NCEP's operational seasonal forecast model Climate Forecast System (CFS) to downscale seasonal prediction of winter precipitation over continental China. Using the same initial conditions, 16 ensemble downscaling forecasts configured with two alternative schemes of microphysics, cumulus, land surface and radiation in WRF were conducted at 30 km for 27-cold seasons (December-February) during 1982-2008. On average, WRF downscaling forecasts reduced wet bias of seasonal mean precipitation from CFS prediction by 25-71%, decreased errors by up to 33%, and increased equitable threat score by 0. 1 for low threshold. With appropriate physical configurations, WRF could improve interannual variations over the region where CFS has correct anomaly signal. The spatial distribution of daily precipitation characteristics such as rainy frequency and extremes highlighted the sensitivity of downscaling forecasts to physical configurations, and the dominant uncertainties were introduced by land surface and radiation schemes. The differences in convective and resolved rainfall between alternative land surface and radiation schemes were consistent with differences of surface downwelling shortwave and longwave radiation through cloud-radiation feedback. Such feedback was strengthened in the land surface sensitivity experiments due to different parameterizations of surface albedo. As compared with CFS ensemble predictions with different initial conditions, the WRF ensemble downscaling forecasts with various physical schemes had larger spread, and some schemes could complement each other in different regions that provided a promising opportunity to enhance the prediction through optimization. The optimized WRF reduced error from the optimized CFS by 30% and increased pattern correlation by 0. 12. Moreover, WRF physical configuration ensemble increased percentage of skillful probabilistic forecasts from CFS initial condition ensemble. © 2011 Springer-Verlag."
"8543279200;36068817000;","A comprehensive study of surface and upper-air characteristics over two stations on the west coast of India during the occurrence of a cyclonic storm",2012,"10.1007/s11069-012-0282-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867229656&doi=10.1007%2fs11069-012-0282-6&partnerID=40&md5=6d82f01632d76f61b389d4c2bae5d87b","While qualitative information from meteorological satellites has long been recognized as critical for monitoring weather events such as tropical cyclone activity, quantitative data are required to improve the numerical prediction of these events. In this paper, the sea surface winds from QuikSCAT, cloud motion vectors and water vapor winds from KALPANA-1 are assimilated using three-dimensional variational assimilation technique within Weather Research Forecasting (WRF) modeling system. Further, the sensitivity experiments are also carried out using the available cumulus convective parameterizations in WRF modeling system. The model performance is evaluated using available observations, and both qualitative and quantitative analyses are carried out while analyzing the surface and upper-air characteristics over Mumbai (previously Bombay) and Goa during the occurrence of the tropical cyclone PHYAN at the west coast of Indian subcontinent. The model-predicted surface and upper-air characteristics show improvements in most of the situations with the use of the satellite-derived winds from QuikSCAT and KALPANA-1. Some of the model results are also found to be better in sensitivity experiments using cumulus convection schemes as compared to the CONTROL simulation. © 2012 Springer Science+Business Media B.V."
"7201375498;6602551610;55228417000;55228747300;","An integrated platform for observing the radiation budget of sea ice at different spatial scales",2012,"10.1016/j.coldregions.2012.05.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862896537&doi=10.1016%2fj.coldregions.2012.05.002&partnerID=40&md5=c9c2443a24a5da386404bfd52afdfda6","An integrated instrument package for measuring and understanding the surface radiation budget of sea ice is presented, along with results from its first deployment. The setup simultaneously measures broadband fluxes of upwelling and downwelling terrestrial and solar radiation (four components separately), spectral fluxes of incident and reflected solar radiation, and supporting data such as air temperature and humidity, surface temperature, and location (GPS), in addition to photographing the sky and observed surface during each measurement. The instruments are mounted on a small sled, allowing measurements of the radiation budget to be made at many locations in the study area to see the effect of small-scale surface processes on the large-scale radiation budget. Such observations have many applications, from calibration and validation of remote sensing products to improving our understanding of surface processes that affect atmosphere-snow-ice interactions and drive feedbacks, ultimately leading to the potential to improve climate modeling of ice-covered regions of the ocean. The photographs, spectral data, and other observations allow for improved analysis of the broadband data. An example of this is shown by using the observations made during a partly cloudy day, which show erratic variations due to passing clouds, and creating a careful estimate of what the radiation budget along the observed line would have been under uniform sky conditions, clear or overcast. Other data from the setup's first deployment, in June 2011 on fast ice near Point Barrow, Alaska, are also shown; these illustrate the rapid changes of the radiation budget during a cold period that led to refreezing and new snow well into the melt season. © 2012 Elsevier B.V.."
"56188404300;36995605400;7202019251;7401672948;55736987700;55544043300;12806183700;","A new approach of dynamic monitoring of 5-day snow cover extent and snow depth based on MODIS and AMSR-E data from Northern Xinjiang region",2012,"10.1002/hyp.8253","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866184894&doi=10.1002%2fhyp.8253&partnerID=40&md5=931a9d2190ea2e9ccaf5b71f6d3a5046","Taking the Northern Xinjiang region as an example, we develop a snow depth model by using the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) horizontal and vertical polarization brightness temperature difference data of 18 and 36GHz bands and in situ snow depth measurements from 20 climatic stations during the snow seasons November-March) of 2002-2005. This article proposes a method to produce new 5-day snow cover and snow depth images, using Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow cover products and AMSR-E snow water equivalent and daily brightness temperature products. The results indicate that (1) the brightness temperature difference (Tb 18h-Tb 36h) provides the most accurate and precise prediction of snow depth; (2) the snow, land and overall classification accuracies of the new images are separately 89.2%, 77.7% and 87.2% and are much better than those of AMSR-E or MODIS products (in all weather conditions) alone; (3) the snow classification accuracy increases as snow depth increases; and (4) snow accuracies for different land cover types vary as 88%, 92.3%, 79.7% and 80.1% for cropland, grassland, shrub, and urban and built-up, respectively. We conclude that the new 5-day snow cover-snow depth images can provide both accurate cloud-free snow cover extent and the snow depth dynamics, which would lay a scientific basis for water management and prevention of snow-related disasters in this dry and cold pastoral area. After validations of the algorithms over other regions with different snow and climate conditions, this method would also be used for monitoring snow cover and snow depth elsewhere in the world. © 2011 John Wiley &amp; Sons, Ltd."
"55363331800;7201871987;","Effects of ice-snow damage on forests",2012,"10.5846/stxb201201120072","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866513782&doi=10.5846%2fstxb201201120072&partnerID=40&md5=6a2f266e4c435e41664866a88dcba033","Ice-snow damage is a common natural disaster, and it often caused huge damage to forests. The frequency of ice storms may increase in response to climate change. Typically, warm, moist air overruns a shallow body of cold air, rain from warm air may become supercooled when it falls from the warmer clouds, causing it to freeze immediately upon contact. Ice-snow damage occurs when the ice loaded on crown exceeds the maximum bending moment for a tree of given size and species. Ice-snow damage of forests dependents on ice accumulation. Accumulation ice can cause tree damage ranged from the loss of tissues to structural failure. Ice-snow damage to trees can range from mere breakage of a few twigs, to bending stems to the ground, to moderate crown loss, to outright breakage of the trunk. There is a close relationship between ice- snow damage and forest characteristics, such as stand density and species composition as well as tree characteristics, such as diameter at breast height, tree height, stem taper, leaf area, crowns symmetry, root system and stand age, etc. The stands with the highest density are the most vulnerable to ice-snow damage, especially for a few years after thinning. Softwoods suffer less damage from the same degree of ice loading than do hardwoods. Trees with branches that droop or have pliable stems and limbs are better withstand ice-snow damage. Dominant canopy trees incur more ice-snow damage than sub-canopy trees. Moreover, ice-snow damage is affected by some external factors, such as topography and soil conditions, including elevation, slope grade, slope aspect, slope position, soil type, soil thickness and soil water content. Higher elevations are more prone to freezing rain. Elevation and aspects increasing exposure to stronger winds result in higher damage. Ice-snow damage also exerts an impact on forest understory light, soil, litter, disease fungi and wildlife. The understory light condition that followed ice-snow damages has great significance to species regeneration, forest dynamic and recovery. A transient increase in understory light following an ice-snow damage may accelerate the conversion of early successional stands to more shade-tolerant species. The rapid decrease in understory light following an ice-snow damage is likely a result of the recovery of both the overstory and understory vegetation. An ice-snow damage indirectly impacts natural plant regeneration by its impact on fruit and seed production. Wildlife first must endure the perils of the ice-snow storm-low temperatures, ice buildup, falling debris, and reduced mobility. Birds are especially vulnerable. Wounds caused by ice-snow damages permit infection by a wide array of disease fungi and become breeding grounds for bark beetles or other pests, especially when the injuries are large and do not heal rapidly. Ice damages also increase potential fire risk by elevating fuel loads. Future research in the field of ice-snow damage to forests should focus on effects of ice-snow damage on natural forests and the long-term research of nutrient cycling and soil, especially microorganism, wildlife, forest dynamics and forest understory light, and reducing the risk of ice-snow damage through forest management."
"7401856520;21742081100;","A new precipitation weighted method for determining the meteoric water line for hydrological applications demonstrated using Australian and global GNIP data",2012,"10.1016/j.jhydrol.2012.07.029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866175387&doi=10.1016%2fj.jhydrol.2012.07.029&partnerID=40&md5=f825974fe52b7c8902a8928211b0a20d","The relationship between δ 2H and δ 18O in precipitation at a site, known as the local meteoric water line (LMWL), is normally defined using an ordinary least squares regression (OLSR) which gives equal weighting to all data points regardless of the precipitation amount they represent. However, smaller precipitation amounts are more likely to have a lower D-excess due to re-evaporation of raindrops below the cloud-base or biases in the sampling method. In this paper we present an equation for a precipitation amount weighted least squares regression (PWLSR) that will correct these biases for use in groundwater and surface hydrology applications. New LMWL equations are presented for Australian sites in the Global Network of Isotopes in Precipitation (GNIP), where the PWLSR consistently produces a LMWL with a larger gradient than the OLSR. Perth and Alice Springs exhibit the largest change in slope. This is consistent with the higher frequency of small monthly precipitation amounts with low D-excess values occurring at these sites in summer for Perth and throughout the year for Alice Springs. The PWLSR method was also applied to 288 stations in the GNIP data base (N&gt;36) and the difference between the slopes of the LMWLs (Δa=slope PWLSR-slope OLSR) calculated for these stations. The mean change in slope, Δa was 0.12 with 56% of sites showing an increase in slope or positive Δa value and 44% having a decrease in slope or negative Δa. Sites with Mediterranean climates showed the greatest increase in slope. The magnitude of the change in slope followed some general trends showing a positive correlation with average δ 2H and δ 18O composition and rainfall variability, and negative correlation with period of record (N). © 2012."
"17434337000;7102111067;13606163100;7006592184;","Potential for a biogenic influence on cloud microphysics over the ocean: A correlation study with satellite-derived data",2012,"10.5194/acp-12-7977-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866109011&doi=10.5194%2facp-12-7977-2012&partnerID=40&md5=98755b4395ccf8949ef7a7e04dcad8fc","Aerosols have a large potential to influence climate through their effects on the microphysics and optical properties of clouds and, hence, on the Earth's radiation budget. Aerosol-cloud interactions have been intensively studied in polluted air, but the possibility that the marine biosphere plays an important role in regulating cloud brightness in the pristine oceanic atmosphere remains largely unexplored. We used 9 yr of global satellite data and ocean climatologies to derive parameterizations of the temporal variability of (a) production fluxes of sulfur aerosols formed by the oxidation of the biogenic gas dimethylsulfide emitted from the sea surface; (b) production fluxes of secondary organic aerosols from biogenic organic volatiles; (c) emission fluxes of biogenic primary organic aerosols ejected by wind action on sea surface; and (d) emission fluxes of sea salt also lifted by the wind upon bubble bursting. Series of global monthly estimates of these fluxes were correlated to series of potential cloud condensation nuclei (CCN) numbers derived from satellite (MODIS). More detailed comparisons among weekly series of estimated fluxes and satellite-derived cloud droplet effective radius (r e) data were conducted at locations spread among polluted and clean regions of the oceanic atmosphere. The outcome of the statistical analysis was that positive correlation to CCN numbers and negative correlation to r e were common at mid and high latitude for sulfur and organic secondary aerosols, indicating both might be important in seeding cloud droplet activation. Conversely, primary aerosols (organic and sea salt) showed widespread positive correlations to CCN only at low latitudes. Correlations to r e were more variable, non-significant or positive, suggesting that, despite contributing to large shares of the marine aerosol mass, primary aerosols are not widespread major drivers of the variability of cloud microphysics. Validation against ground measurements pointed out that the parameterizations used captured fairly well the variability of aerosol production fluxes in most cases, yet some caution is warranted because there is room for further improvement, particularly for primary organic aerosol. Uncertainties and synergies are discussed, and recommendations of research needs are given. © 2012 Author(s)."
"36465124400;7102805852;6602087140;55338801300;36106191000;7101838894;57195257572;7402838215;7006377579;57197233116;12753162000;25523100000;35547807400;7006837187;","A methodology for in-situ and remote sensing of microphysical and radiative properties of contrails as they evolve into cirrus",2012,"10.5194/acp-12-8157-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866107067&doi=10.5194%2facp-12-8157-2012&partnerID=40&md5=c1fc3889cc7d370573ea1d4481ab62a5","Contrails and especially their evolution into cirrus-like clouds are thought to have very important effects on local and global radiation budgets, though are generally not well represented in global climate models. Lack of contrail parameterisations is due to the limited availability of in situ contrail measurements which are difficult to obtain. Here we present a methodology for successful sampling and interpretation of contrail microphysical and radiative data using both in situ and remote sensing instrumentation on board the FAAM BAe146 UK research aircraft as part of the COntrails Spreading Into Cirrus (COSIC) study. <br><br> Forecast models were utilised to determine flight regions suitable for contrail formation and sampling; regions that were both free of cloud but showed a high probability of occurrence of air mass being supersaturated with respect to ice. The FAAM research aircraft, fitted with cloud microphysics probes and remote sensing instruments, formed a distinctive spiral-shaped contrail in the predicted area by flying in an orbit over the same ground position as the wind advected the contrails to the east. Parts of these contrails were sampled during the completion of four orbits, with sampled contrail regions being between 7 and 30 min old. Lidar measurements were useful for in-flight determination of the location and spatial extent of the contrails, and also to report extinction values that agreed well with those calculated from the microphysical data. A shortwave spectrometer was also able to detect the contrails, though the signal was weak due to the dispersion and evaporation of the contrails. Post-flight the UK Met Office NAME III dispersion model was successfully used as a tool for modelling the dispersion of the persistent contrail; determining its location and age, and determining when there was interference from other measured aircraft contrails or when cirrus encroached on the area later in the flight. The persistent contrails were found to consist of small (∼10 &mu;m) plate-like crystals where growth of ice crystals to larger sizes (∼100 &mu;m) was typically detected when higher water vapour levels were present. Using the cloud microphysics data, extinction co-efficient values were calculated and found to be 0.01-1 kmĝ̂'1. The contrails formed during the flight (referred to as B587) were found to have a visible lifetime of ∼40 min, and limited water vapour supply was thought to have suppressed ice crystal growth. © 2012 Author(s)."
"16028133700;57203073322;","Cloud pattern and water relations in Picea rubens and Abies fraseri, southern Appalachian Mountains, USA",2012,"10.1016/j.agrformet.2012.04.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860637473&doi=10.1016%2fj.agrformet.2012.04.005&partnerID=40&md5=24e83b584c6244626f268081677ad39f","The spruce-fir [Picea rubens Sarg.-Abies fraseri (Pursh) Poir.] forests of the southern Appalachian Mountains are considered refugial, endangered communities that exist on only seven mountaintop areas in Virginia and North Carolina, USA. These relict forests continue to be threatened by stress factors such as logging, acid rain deposition, attacks from invasive insects, and climate change. It has been suggested that these communities have persisted because of frequent cloudiness and periods of cloud immersion (fog), although few studies have examined corresponding effects on microclimate and tree ecophysiology. Incident sunlight (PPFD), air temperature, vapor pressure deficit (VPD), and xylem water potentials were measured throughout the summer growing season in Mount Mitchell State Park, NC (35°45'53'N, 82°15'54'W), along with continuous camera recordings of the forest canopy and accompanying cloud conditions. Approximately 60% of all summer days had at least 2h of cloud immersion with the large majority (80.3%) of immersion events occurring during morning hours. Cloud-immersed days had the greatest reduction in cumulative daily PPFD compared to clear days (11.09molm -2day -1 vs. 38.03molm -2day -1, respectively), as well as substantially reduced mean VPD (0.98kPa vs. 1.81kPa) but only slightly lower mean air temperatures (14.5°C vs. 14.9°C, respectively). Moreover, xylem water potential (Ψ) increased significantly (∼0.2MPa; values) from morning to afternoon on cloud-immersed days. In contrast, clear days showed no afternoon recovery in Ψ, but a continued decrease during the afternoon. Juvenile Ψ was more responsive to daily cloud regime compared to adult Ψ and had a strong negative correlation with vapor pressure deficit. When all measurement days were sorted by the cloud pattern of the previous day, there was a strong response in juveniles trees, i.e. Ψ increased following previous afternoon cloud-immersion. Juveniles of both species also had greater seasonal decreases in Ψ than adults (P. rubens, adult: 0.05MPa, juvenile: 0.13MPa; A. fraseri, adult: 0.06MPa, juvenile: 0.20Mpa). For climate change models that predict a higher cloud base (resulting in less immersion) and dryer conditions, the water relations of Abies fraseri and Picea rubens could be substantially and negatively influenced. © 2012 Elsevier B.V."
"6603447328;12767357300;6506942565;6603852912;6507639257;","Influence of regional climate forcing on surface water pCO 2,ΔO 2/Ar and dimethylsulfide (DMS) along the southern British Columbia coast",2012,"10.1016/j.csr.2012.07.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867142487&doi=10.1016%2fj.csr.2012.07.007&partnerID=40&md5=d3dd8c800a2b34eb156d211b86bb072c","Oceanographic surveys of surface water hydrography, pCO 2, biological O 2 saturation (ΔO 2/Ar) and dimethylsulfide (DMS) were conducted around Vancouver Island, B.C. during late spring of 2007 and 2010. Winter El Niño conditions during early 2010 resulted in strong downwelling and decreased sub-surface nutrient inventories relative to 2007, while reduced Fraser River input, high wind speeds and greater cloud cover led to relatively weak vertical stratification and decreased sea surface irradiance during the 2010 survey. Phytoplankton biomass (Chla) was significantly higher along the west coast of Vancouver Island (WCVI) during late May 2007, and we observed a strong biological imprint on surface gas distributions during this survey, with biologically induced O 2 saturation in excess of 40%. Minimum pCO 2 along the WCVI was 100ppm during the 2007 survey, and this region served as a moderate CO 2 sink at the time of our sampling (mean sea-air flux of -3.2mmolCO 2m -2d -1). By comparison, both pCO 2 and ΔO 2/Ar were much closer to atmospheric equilibrium during our 2010 survey. Despite these lower sea-air gradients, high wind speeds led to a significantly larger CO 2 sink (13.4mmolm -2d -1) during the 2010 survey, and a greater uncoupling of ΔO 2/Ar and pCO 2 through differential gas exchange. Relative to the WCVI, pCO 2 and ΔO 2/Ar distributions showed smaller differences among cruises along the east coast of Vancouver Island (ECVI), where surface water properties were largely driven by physical circulation. Nonetheless, we did observe lower pCO 2 and higher ΔO 2/Ar in the Strait of Georgia during the 2010 survey, possibly due to a wind-driven mixing event which may have stimulated local primary productivity. DMS concentrations exhibited large ranges and significant small-scale spatial variability for both cruises, but mean DMS concentrations were more than three-fold higher along the WCVI during late May 2007. Higher wind speeds in late May 2010 led to greater DMS fluxes during our 2010 survey (10 vs. 5γmolm -2d -1 for 2010 and 2007, respectively) despite lower sea-air concentration gradients. For both cruises, about 40% of the variability in surface water DMS concentrations was explained by Chla/mixed layer depth ratios when data were binned to a spatial resolution of 0.25°. Based on our results, we discuss the potential linkages between regional climate variability and surface gases in coastal B.C. waters. © 2012 Elsevier Ltd."
"36088530800;24460392200;36052878000;8670472000;7102425008;57199847019;","The representation of tropical upper tropospheric water in EC Earth V2",2012,"10.1007/s00382-012-1511-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868686771&doi=10.1007%2fs00382-012-1511-0&partnerID=40&md5=24c261fab9c76e3c4c63c5ba8a69bb2c","Tropical upper tropospheric humidity, clouds, and ice water content, as well as outgoing longwave radiation (OLR), are evaluated in the climate model EC Earth with the aid of satellite retrievals. The Atmospheric Infrared Sounder and Microwave Limb Sounder together provide good coverage of relative humidity. EC Earth's relative humidity is in fair agreement with these observations. CloudSat and CALIPSO data are combined to provide cloud fractions estimates throughout the altitude region considered (500-100 hPa). EC Earth is found to overestimate the degree of cloud cover above 200 hPa and underestimate it below. Precipitating and non-precipitating EC Earth ice definitions are combined to form a complete ice water content. EC Earth's ice water content is below the uncertainty range of CloudSat above 250 hPa, but can be twice as high as CloudSat's estimate in the melting layer. CERES data show that the model underestimates the impact of clouds on OLR, on average with about 9 W m-2. Regionally, EC Earth's outgoing longwave radiation can be ~20 W m-2 higher than the observation. A comparison to ERA-Interim provides further perspectives on the model's performance. Limitations of the satellite observations are emphasised and their uncertainties are, throughout, considered in the analysis. Evaluating multiple model variables in parallel is a more ambitious approach than is customary. © 2012 Springer-Verlag."
"55260519600;","Titan's transport-driven methane cycle",2012,"10.1088/2041-8205/756/2/L26","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866097528&doi=10.1088%2f2041-8205%2f756%2f2%2fL26&partnerID=40&md5=ba4438d0eb04e51963478d68de108f0e","The mechanisms behind the occurrence of large cloud outbursts and precipitation on Titan have been disputed. A global- and annual-mean estimate of surface fluxes indicated only 1% of the insolation, or 0.04Wm-2, is exchanged as sensible and/or latent fluxes. Since these fluxes are responsible for driving atmospheric convection, it has been argued that moist convection should be quite rare and precipitation even rarer, even if evaporation globally dominates the surface-atmosphere energy exchange. In contrast, climate simulations indicate substantial cloud formation and/or precipitation. We argue that the top-of-atmosphere (TOA) radiative imbalance is diagnostic of horizontal heat transport by Titan's atmosphere, and thus constrains the strength of the methane cycle. Simple calculations show the TOA radiative imbalance is ∼0.5-1Wm-2 in Titan's equatorial region, which implies 2-3MW of latitudinal heat transport by the atmosphere. Our simulation of Titan's climate suggests this transport may occur primarily as latent heat, with net evaporation at the equator and net accumulation at higher latitudes. Thus, the methane cycle could be 10-20times previous estimates. Opposing seasonal transport at solstices, compensation by sensible heat transport, and focusing of precipitation by large-scale dynamics could further enhance the local, instantaneous strength of Titan's methane cycle by a factor of several. A limited supply of surface liquids in regions of large surface radiative imbalance may throttle the methane cycle, and if so, we predict more frequent large storms over the lakes district during Titan's northern summer. © 2012 The American Astronomical Society. All rights reserved."
"26436423000;","Transpiration in a sub-tropical ridge-top cloud forest",2012,"10.1016/j.jhydrol.2011.08.069","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865573990&doi=10.1016%2fj.jhydrol.2011.08.069&partnerID=40&md5=e9b302204b53aff9b4d2f880753400fc","Laurel forests in the Canary Islands (Spain) survive where humid conditions are guaranteed throughout the year. On peaks and ridges, laurel forest gives way to mixed evergreen tree-heath/beech forest of low stature ("" fayal-brezal"" ) that has to cope with rapidly changing light, temperature and humidity conditions due to the occurrence of intermittent sunny and foggy periods during the mostly rainless summer. These conditions are poorly understood and there is a lack of information on the interrelations between tree physiological behavior and ambient climatic and soil water conditions in fayal-brezal. In this study sap velocities were measured for 2years in two dominant tree species (Myrica faya and Erica arborea) in a ridge-top forest in the National Park of Garajonay on the island of La Gomera. The resulted average daily stand transpiration was 1.2±0.12mm (416mmyear -1). However, the narrow-leaved E. arborea exhibited higher sap velocities than the broad-leaved M. faya. Also, sap velocity increased with stem diameter in E. arborea but not in M. faya. Nocturnal flow activity was observed throughout the year and reflected ambient conditions on some occasions, and stem water storage recovery on others. Strong stomatal control in response to increases in vapor pressure deficit was seen in both species. Fog reduced sap velocity from 10% up to 90% but no consistent pattern was found. Soil water uptake during the dry summer (246mm) was much larger than atmospheric water inputs (41mm, rain and fog). The low moisture levels in the top 0.3m of the soil had limited influence on transpiration rates indicating that vegetation must have had access to moisture in deeper layers. © 2011 Elsevier B.V."
"7103158465;","On the robustness of aerosol effects on an idealized supercell storm simulated with a cloud system-resolving model",2012,"10.5194/acp-12-7689-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865598452&doi=10.5194%2facp-12-7689-2012&partnerID=40&md5=ef6393b0c4b0c123cb4cdf523ecd3a4a","A cloud system-resolving model (the Weather Research and Forecasting model) with 1 km horizontal grid spacing is used to investigate the response of an idealized supercell storm to increased cloud droplet concentrations associated with polluted conditions. The primary focus is on exploring robustness of simulated aerosol effects in the face of complex process interactions and feedbacks between the cloud microphysics and dynamics. Simulations are run using sixteen different model configurations with various microphysical or thermodynamic processes modified or turned off. Robustness of the storm response to polluted conditions is also explored for each configuration by performing additional simulations with small perturbations to the initial conditions. Differences in the domain-mean accumulated surface precipitation and convective mass flux between polluted and pristine conditions are small for almost all model configurations, with relative differences in each quantity generally less than 15%. Configurations that produce a decrease (increase) in cold pool strength in polluted conditions also tend to simulate a decrease (increase) in surface precipitation and convective mass flux. Combined with an analysis of the dynamical and thermodynamic fields, these results indicate the importance of interactions between microphysics, cold pool evolution, and dynamics along outflow boundaries in explaining the system response. Several model configurations, including the baseline, produce an overall similar storm response (weakening) in polluted conditions despite having different microphysical or thermodynamic processes turned off. With hail initiation turned off or the hail fallspeed-size relation set to that of snow, the model produces an invigoration instead of weakening of the storm in polluted conditions. These results highlight the difficulty of foreseeing impacts of changes to model parameterizations and isolating process interactions that drive the system response to aerosols. Overall, these findings are robust, in a qualitative sense, to small perturbations in the initial conditions. However, there is sensitivity in the magnitude, and in some cases sign, of the storm response to polluted conditions with small perturbations in the temperature of the thermal used to initiate convection (less than ±0.5 K) or the vertical shear of the environmental wind (±5%). It is concluded that reducing uncertainty in simulations of aerosol effects on individual deep convective storms will likely require ensemble methods in addition to continued improvement of model parameterizations. © 2012 Author(s)."
"50662249600;26535775700;56134914900;7801628758;","Analysis of snow precipitation during the period 2000-09 and evaluation of a MSG/SEVIRI snow cover algorithm in SW Italian Alps",2012,"10.4461/GFDQ.2012.35.9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865472730&doi=10.4461%2fGFDQ.2012.35.9&partnerID=40&md5=51a04649e00ab251b1a477e738ab7070","The automatic meteorological station network of Piedmont (North-West Italy), whose realization started in 1988, together with the pre-existing manned stations are now providing snow depth and fresh snow depth measurements in more than 100 sites spread out over Western Alps, also outside the geographical borders of the Region. The high spatial resolution network in combination with satellite devices can be used for an integrated monitoring of snow cover that combines information on snow depth, amount of snow precipitation and snow cover extension. In particular satellites can provide complementary knowledge on snow cover over large scale with spatial continuity, supplying the lack of data where surface measurements are not available. This study focus the attention on the decade 2000-2009, for which both surface and satellite data are accessible. The high density of meteorological stations in Western Italian Alps makes this area appropriate for testing a novel snow cover algorithm using Meteosat Second Generation (MSG) satellite data. In the first part the analysis of the mean condition of snow precipitation over South Western Italian Alps is presented. Ground-based automatic daily total and fresh snow depth measurements provided by the Regional Agency for the Environmental Protection (ARPA Piemonte) have been used to determinate snow indices and the snow precipitation variability over the 10 years period. In the second part a novel method to estimate the snow cover extension using satellite data from the SMG Spinning Enhanced Visible and Infrared Imager (SEVIRI) is described and discussed. The snow cover algorithm minimizes the number of unclassified pixel due to cloud obscuration taking advantage of the MSG high frequency of acquisition, which provides daylight images over the investigated area every 15 minutes. The algorithm has been tested for 19 case-studies referring to the period 2007-2009 using surface stations data and then it has been applied to assess and compare the snow cover extension during the 2006-07 and 2007-08 snow seasons."
"7801581051;7004095131;6603738903;","Forecasting cloud forest in eastern and southern Mexico: Conservation insights under future climate change scenarios",2012,"10.1007/s10531-012-0327-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865436755&doi=10.1007%2fs10531-012-0327-x&partnerID=40&md5=e808422826418964f67296aecda8cd9e","Assuming that co-distributed species are exposed to similar environmental conditions, ecological niche models (ENMs) of cloud forest species were developed to study how climate change could affect the distribution of cloud forest in eastern and southern Mexico for the year 2050. Using ENM-based predictions and climatic data for IPCC climate change A2 and B2 scenarios, we observed 54-76% reduction of the cloud forest, mainly in the northern region of its current range (Sierra Madre Oriental) and the Pacific slope of Chiapas. With predicted 2050 climate change, cloud forest in the Los Tuxtlas region and El Cielo Biosphere Reserve may face a serious threat of extinction due to the observed upward migration to higher elevations. Our results add to recent studies detecting negative impacts of climate change in montane forests, but the negative impacts of climate change might be exacerbated by current environmental changes in the region. The integration of ecological-niche characteristics of cloud forest in conjunction with projections of extreme climate scenarios constitute a suitable tool to define appropriate areas in which proactive conservation and management strategies should be focused. © 2012 Springer Science+Business Media B.V."
"55998327100;6507224579;7006184606;7004247643;","Correlation between present-day model simulation of Arctic cloud radiative forcing and sea ice consistent with positive winter convective cloud feedback",2012,"10.1029/2012MS000153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867737015&doi=10.1029%2f2012MS000153&partnerID=40&md5=69b0a3cd2cd47eb9e9884bb96bf19055","A positive feedback on winter sea-ice loss, based on warming due to radiative forcing caused by the onset of convective clouds in response to sea-ice loss, has recently been proposed. This feedback has thus far been investigated using a hierarchy of climate models in high CO<inf>2</inf> scenarios. This paper examines the possibility that such feedback may be active within present-day like Arctic variability, using model output from two reanalysis models. It is emphasized that Arctic surface fluxes, radiative fluxes and clouds are effectively unconstrained by observations in reanalysis products. Consequently, the results here should be viewed only as a model study of the feedback in present-day model climate variability. Model winter sea ice and cloud radiative forcing are found to co-vary strongly and locally, consistent with a strong convective cloud feedback, which may contribute to sea ice variability. Furthermore, the anticorrelation between the two variables is found to be as strong in the model output analyzed here as in the IPCC global climate models that simulate the convective cloud feedback most strongly at high CO<inf>2</inf>. In those IPCC models the convective cloud feedback contributes to a total loss of winter sea ice in a CO<inf>2</inf> quadrupling scenario. These results do not necessarily prove that this feedback exists in the present-day Arctic and demonstrating this will require further study using actual Arctic observations. © 2012. American Geophysical Union."
"8866821900;7402435469;36876405100;57212416832;","Southeast Pacific stratocumulus in the community atmosphere model",2012,"10.1175/JCLI-D-11-00503.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865075822&doi=10.1175%2fJCLI-D-11-00503.1&partnerID=40&md5=e8d5c83337c60634fdc5131fd6b125a6","Forecasts of October 2006 are used to investigate southeast Pacific stratocumulus in the Community Atmosphere Model, versions 4 and 5 (CAM4 and CAM5). Both models quickly develop biases similar to their climatic biases, suggesting that parameterized physics are the root of the climate errors. An extensive cloud deck is produced in CAM4, but the cloud structure is unrealistic because the boundary layer is too shallow and moist. The boundary layer structure is improved inCAM5, but during the daytime the boundary layer decouples from the cloud layer, causing the cloud layer to break up and transition toward a more trade wind cumulus structure in the afternoon. The cloud liquid water budget shows how different parameterizations contribute to maintaining these different expressions of stratocumulus. Sensitivity experiments help elucidate the origins of the errors. The importance of the diurnal cycle of these clouds for climate simulations is emphasized. © 2012 American Meteorological Society."
"7201496259;55462312300;7401974644;7401936984;","Sensitivity of aerosol indirect effects to cloud nucleation and autoconversion parameterizations in short-range weather forecasts during the May 2003 aerosol IOP",2012,"10.1029/2012MS000161","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867723843&doi=10.1029%2f2012MS000161&partnerID=40&md5=ecfeb091b71c5708aa1656f036bca8d3","Aerosol-cloud interactions begin with the direct involvement of aerosols in cloud nucleation followed by its indirect contribution to the formation of precipitation through autoconversion. Since the treatments of cloud microphysics in climate models are highly parameterized, a thorough study is needed to examine the range of simulations associated with different parameterizations of aerosol-cloud interactions. Unlike previous studies focused on climate-mode simulations, our interest is in shortrange model response before the development of model bias and the compensation of multiple feedback mechanisms. In this study, we modified CAM4 to explore model sensitivity to treatments of cloud nucleation and autoconversion over the Atmospheric Radiation Measurement Southern Great Plains (SGP) facility during the May 2003 Aerosol Intensive Operations Period (IOP) under the Cloud-Associated Parameterizations Testbed framework. Simulated liquid water path and low cloud fraction were sensitive to the choice of parameterization; however, change of modeled precipitation was insignificant with varying parameterization in short-range (̃3 day) simulation. In general, simulated cloud properties were more sensitive to the treatment of autoconversion than nucleation. Calculations of sulfate indirect effects indicate that the change of shortwave fluxes from cloud lifetime effect is much more sensitive to cloud parameterizations than cloud albedo effect. Microphysical feedbacks complicate the local response of the climate system and can yield a positive 2nd indirect sulfate forcing that counters the expectation that increases in aerosol concentration decrease the shortwave fluxes. As a result, the calculated total sulfate indirect forcing over SGP varies widely ranging from 20.1 to 22.1 W m22 during the IOP. © 2012 by the American Geophysical Union."
"55325353200;57202121637;23570956400;6701742258;","Evaluation and bias correction of regional climate model results using model evaluation measures",2012,"10.1175/JAMC-D-11-0161.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868133257&doi=10.1175%2fJAMC-D-11-0161.1&partnerID=40&md5=c50d9d42b8d18515f57c6b7cedaae1e3","For the assessment of regional climate change the reliability of the regional climate models needs to be known. The main goal of this paper is to evaluate the quality of climate model data that are used for impact research. Temperature, precipitation, total cloud cover, relative humidity, and wind speed simulated by the regional climate models Climate Local Model (CLM) and Regional Model (REMO) are evaluated for the metropolitan region of Hamburg in northern Germany for the period 1961-2000. The same evaluation is performed for the global climate model ECHAM5 that is used to force the regional climate models. The evaluation is based on comparison of the simulated and observed climatological annual cycles and probability density functions of daily averages. Several model evaluation measures are calculated to assure an objective model evaluation. As a very selective model evaluation measure, the hit rate of the percentiles is introduced for the evaluation of daily averages. The influence of interannual climate variability is considered by determining confidence intervals for the model evaluation measures by bootstrap resampling. Evaluation shows that, with some exceptions, temperature and wind speed are well simulated by the climate models; whereas considerable biases are found for relative humidity, total cloud cover, and precipitation, although not for all models in all seasons. It is shown that model evaluation measures can be used to decide for which meteorological parameters a bias correction is reasonable. © 2012 American Meteorological Society."
"57189352415;55649026100;7202467963;","Spatial statistical analyses of global trends of ultraviolet B fluxes in the Continental United States",2012,"10.2747/1548-1603.49.5.735","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866880604&doi=10.2747%2f1548-1603.49.5.735&partnerID=40&md5=c4b9c15b810cf6da2b4afa2af9b1e7de","Many environmental factors, such as stratospheric ozone, aerosols, and clouds, may affect ultraviolet (UV) irradiance. The aim of this study is to investigate the possible association between ultraviolet B (UVB) radiation and total cloud amount, ozone, and aerosols simultaneously, leading to the assessment of possible impacts of climate change on UVB flux variations in the continental United States (U.S.). Spatiotemporal correlation analyses were conducted, based on data collected from the Total Ozone Mapping Spectrometer (TOMS) and the International Satellite Cloud Climatology Project (ISCCP), with a geographic information system (GIS). Findings indicate that in the past 22 years, while ozone decreased and aerosols increased across the U.S., the UVB decrease in the northern states was consistent with an increase in aerosols and total cloud amount. Therefore, to some extent, the trend characteristics of UVB over the U.S. between 1980 and 2002 were simultaneously affected by such dominant factors as total ozone and by such auxiliary factors as aerosol and total cloud amount. Climate change impact resulting in higher total cloud amount in the northern states might result in lower UVB in the future."
"55740664200;14019399400;55418458200;","The radiation budget of the West African Sahel and its controls: A perspective from observations and global climate models",2012,"10.1175/JCLI-D-11-00072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867670718&doi=10.1175%2fJCLI-D-11-00072.1&partnerID=40&md5=8353739dd1ca0e27186f77a04f9a8824","Continuous measurements of the shortwave (SW), longwave (LW), and net cross-atmosphere radiation flux divergence over the West African Sahel were made during the year 2006 using the Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) and the Geostationary Earth Radiation Budget (GERB) satellite. Accompanying AMF measurements enabled calculations of the LW, SW, and net top of the atmosphere (TOA) and surface cloud radiative forcing (CRF), which quantifies the radiative effects of cloud cover on the column boundaries. Calculations of the LW, SW, and net cloud radiative effect (CRE), which is the difference between the TOA and surface radiative flux divergences in all-sky and clear-sky conditions, quantify the radiative effects on the column itself. These measurements were compared to predictions in four global climate models (GCMs) used in the Intergovernmental Panel for Climate Change Fourth Assessment Report (IPCC AR4). All fourGCMs produced wet and dry seasons, but reproducing theSWcolumn radiative flux divergence was problematic in the GCMs and SW discrepancies translated into discrepancies in the net radiative flux divergence. Computing cloud-related quantities from the measurements produced yearly averages of the SW TOA CRF, surface CRF, and CRE of ~-19,-83, and 47 W m -2, respectively, and yearly averages of the LW TOA CRF, surface CRF, and CRE of ~39, 37, and 2 W m -2. These quantities were analyzed in two GCMs and compensating errors in the SW andLWclear-sky, cross-atmosphere radiative flux divergence were found to conspire to produce somewhat reasonable predictions of the net clear-sky divergence. Both GCMs underestimated the surface LW and SW CRF and predicted near-zero SW CRE when the measured values were substantially larger (~70 W m -2 maximum). © 2012 American Meteorological Society."
"6602142837;26534885500;","Biases in the diurnal temperature range in Central Europe in an ensemble of regional climate models and their possible causes",2012,"10.1007/s00382-011-1200-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866359714&doi=10.1007%2fs00382-011-1200-4&partnerID=40&md5=ab14d1ad30d3849698f8b65b641d5a2a","The study examines how regional climate models (RCMs) reproduce the diurnal temperature range (DTR) in their control simulations over Central Europe. We evaluate 30-year runs driven by perfect boundary conditions (the ERA40 reanalysis, 1961-1990) and a global climate model (ECHAM5) of an ensemble of RCMs with 25-km resolution from the ENSEMBLES project. The RCMs' performance is compared against the dataset gridded from a high-density stations network. We find that all RCMs underestimate DTR in all seasons, notwithstanding whether driven by ERA40 or ECHAM5. Underestimation is largest in summer and smallest in winter in most RCMs. The relationship of the models' errors to indices of atmospheric circulation and cloud cover is discussed to reveal possible causes of the biases. In all seasons and all simulations driven by ERA40 and ECHAM5, underestimation of DTR is larger under anticyclonic circulation and becomes smaller or negligible for cyclonic circulation. In summer and transition seasons, underestimation tends to be largest for the southeast to south flow associated with warm advection, while in winter it does not depend on flow direction. We show that the biases in DTR, which seem common to all examined RCMs, are also related to cloud cover simulation. However, there is no general tendency to overestimate total cloud amount under anticyclonic conditions in the RCMs, which suggests the large negative bias in DTR for anticyclonic circulation cannot be explained by a bias in cloudiness. Errors in simulating heat and moisture fluxes between land surface and atmosphere probably contribute to the biases in DTR as well. © 2011 Springer-Verlag."
"6602364115;6603566335;24173130300;","Continuous single-column model evaluation at a permanent meteorological supersite",2012,"10.1175/BAMS-D-11-00162.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864858063&doi=10.1175%2fBAMS-D-11-00162.1&partnerID=40&md5=2a34443bc245a719cba64b2b7393f0e7","A facility in the Netherlands has brought together simulations and observations, helping scientists improve efficiency and statistical significance of process-level evaluations of numerical weather and climate prediction models. The project, the Royal Netherlands Meteorological Institute (KNMI) Parametrization Testbed (KPT), is part of a general move toward more statistically significant process-level evaluation. A key goal of the KPT is to apply LES on a continuous basis and simulate multiyear periods, enabled for the first time by the use of GPUs. The cloud structure and time development evaluated at Cabauw on 8 April 2008 show the passage of individual cumuli that is distinguished in the high-frequency ceilometer observations. Relatively small deviations in the vertical thermodynamic structure can be associated with large deviations in cloud state."
"35789369900;23468652500;55233658000;6603776134;8853393600;7003880283;8594309800;7005628166;","Long-term features of cloud microbiology at the puy de Dôme (France)",2012,"10.1016/j.atmosenv.2012.03.072","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861608354&doi=10.1016%2fj.atmosenv.2012.03.072&partnerID=40&md5=d7378fa227e0aaaedb476c3553c58300","Despite the enormous volume they represent and the importance they have for Earth's climate, clouds remain environments where the microbiological features are still poorly understood. Studies of the microbial content existing in the atmosphere have demonstrated extreme quantitative and qualitative variability, of which the drivers yet need to be determined. Between 2007 and 2010, we collected cloud water from the puy de Dôme summit in France (1465m a.s.l.) for chemical and microbiological analysis. These data were combined with cloud data collected between 2004 and 2005 following similar protocols. Overall, the cultivable community of chemotrophic aerobic microorganisms was dominated by pigmented colonies and accounted for &lt;1% of the 3.3×10 3 to 2.5×10 5 total bacteria mL -1, but up to 41% of the 8.9×10 2 to 3.2×10 4 fungal cells mL -1. None of the concentrations of the chemical compounds measured was linked to the variations observed for the microbiological content, suggesting distinct sources and/or distinct modes of incorporation into cloud water. However, the overall dataset indicated that microorganisms in clouds were mostly originating from continental areas, especially from vegetation. We isolated and identified 185 heterotrophic bacteria and 150 yeasts from our samples (including -Alpha, -Beta and Gamma-Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria, and Basidiomycetous and Ascomycetous yeasts), the corresponding 16S and 26S rRNA gene sequences of which have been deposited in GenBank. A few genera largely dominated the pool of cultivable microorganisms in clouds, such as Pseudomonas and Sphingomonas for bacteria, which were detected in more than 40% of the clouds sampled, and Dioszegia and Udeniomyces for yeasts, detected in more than 60% of the samples. The recurring presence of some groups of microorganisms suggests that they have elaborated strategies of increased survival in the atmosphere and clouds. © 2012 Elsevier Ltd."
"8696069500;7201504886;7003979342;35605362100;6701689939;6603247427;56262883000;6603183022;36339753800;55111818600;7003625897;9248887100;57205867148;7404732357;24485834000;","Tuning the climate of a global model",2012,"10.1029/2012MS000154","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867617354&doi=10.1029%2f2012MS000154&partnerID=40&md5=ce445f3a0f8a760af8bb4891aaa53e9a","During a development stage global climate models have their properties adjusted or tuned in various ways to best match the known state of the Earth's climate system. These desired properties are observables, such as the radiation balance at the top of the atmosphere, the global mean temperature, sea ice, clouds and wind fields. The tuning is typically performed by adjusting uncertain, or even non-observable, parameters related to processes not explicitly represented at the model grid resolution. The practice of climate model tuning has seen an increasing level of attention because key model properties, such as climate sensitivity, have been shown to depend on frequently used tuning parameters. Here we provide insights into how climate model tuning is practically done in the case of closing the radiation balance and adjusting the global mean temperature for the Max Planck Institute Earth System Model (MPIESM). We demonstrate that considerable ambiguity exists in the choice of parameters, and present and compare three alternatively tuned, yet plausible configurations of the climate model. The impacts of parameter tuning on climate sensitivity was less than anticipated. © 2012. American Geophysical Union."
"26533570600;35794721100;55716700200;","Ocean-atmosphere characteristics of tropical instability waves simulated in the NCEP climate forecast system reanalysis",2012,"10.1175/JCLI-D-11-00477.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867686882&doi=10.1175%2fJCLI-D-11-00477.1&partnerID=40&md5=d7cf044e4279626f5f0cec7ea09fe003","The NCEP Climate Forecast System Reanalysis (CFSR) represents a new effort with the first guess from a high-resolution coupled system and offers prospects for improved simulation of mesoscale air-sea coupled variability. This study aims to describe the characteristics of ocean-atmosphere covariability associated with tropical instability waves (TIWs) in the Pacific for the CFSR, and to assess how well they agree with in situ and satellite observations. Multiyear daily high-resolution CFSR data are used to describe variability associated with TIWs. Results show that TIW-induced SST variations exhibit pronounced seasonal and interannual variability that are tightly connected with cold tongue variations. The analysis illustrates coherent patterns associated with TIWs, both in the ocean and the atmosphere. Moisture and air temperature maximums are located west of SST maximums, leading to downstream displacement of surface pressure minimums relative to SST maximums. Surface winds accelerate (decelerate) over warm (cold) water, and a thermally direct circulation is created. Significant signals are observed in low-level cloud cover, which are closely in phase with surface wind convergences. The magnitudes of TIW-induced surface wind, surface pressure, and cloud cover perturbations agree well with in situ and satellite observations. Further analysis shows that surface net heat flux perturbations are dominated by latent heat fluxes and have a large negative feedback on TIW SST variability (~40 W m -2 °C -1). Water vapor perturbation is the primary factor contributing to changes in latent heat fluxes, while SST-induced wind perturbation plays a secondary role. The analysis presented here highlights that the CFSR provides an unprecedented opportunity to study the physical mechanisms for the TIWs, as well as their influences on climate variability. © 2012 American Meteorological Society."
"57214786060;7006705919;55688930000;55317177900;","Fast and slow responses of the South Asian monsoon system to anthropogenic aerosols",2012,"10.1029/2012GL053043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867063319&doi=10.1029%2f2012GL053043&partnerID=40&md5=3c972463548d108a486124d5d8135a5c","Using a global climate model with fully predictive aerosol life cycle, we investigate the fast and slow responses of the South Asian monsoon system to anthropogenic aerosol forcing. Our results show that the feedbacks associated with sea surface temperature (SST) change caused by aerosols play a more important role than the aerosol's direct impact on radiation, clouds and land surface (rapid adjustments) in shaping the total equilibrium climate response of the monsoon system to aerosol forcing. Inhomogeneous SST cooling caused by anthropogenic aerosols eventually reduces the meridional tropospheric temperature gradient and the easterly shear of zonal winds over the region, slowing down the local Hadley cell circulation, decreasing the northward moisture transport, and causing a reduction in precipitation over South Asia. Although total responses in precipitation are closer to the slow responses in general, the fast component dominates over land areas north of 25°N. Our results also show an east-west asymmetry in the fast responses to anthropogenic aerosols causing increases in precipitation west of 80°E but decreases east of it. © 2012. American Geophysical Union."
"55555084100;7003459101;7403018615;7201352328;7003852865;","The microbial diversity of a storm cloud as assessed by hailstones",2012,"10.1111/j.1574-6941.2012.01402.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864633922&doi=10.1111%2fj.1574-6941.2012.01402.x&partnerID=40&md5=e516a70479cd0b189a46126cc9468d83","Being an extreme environment, the atmosphere may act as a selective barrier for bacterial dispersal, where only most robust organisms survive. By remaining viable during atmospheric transport, these cells affect the patterns of microbial distribution and modify the chemical composition of the atmosphere. The species evenness and richness, and the community composition of a storm cloud were studied applying cultivation-dependent and cultivation-independent techniques to a collection of hailstones. In toto 231 OTUs were identified, and the total species richness was estimated to be about 1800 OTUs. The diversity indices - species richness and evenness - suggest a functionally stable community, capable of resisting environmental stress. A broad substrate spectrum of the isolates with epiphytic origin (genus Methylobacterium) implied opportunistic ecologic strategy with high growth rates and fast growth responses. These may grow in situ despite their short residence times in cloud droplets. In addition, epiphytic isolates utilized many atmospheric organic compounds, including a variety of carboxylic acids. In summary, the highly diverse bacterial community, within which the opportunistic bacteria may be particularly important in terms of atmospheric chemistry, is likely to remain functional under stressful conditions. Overall our study adds important details to the growing evidence of active microbial life in clouds. © 2012 Federation of European Microbiological Societies."
"55440589800;6602929454;6508066111;","Testing and diagnosing the ability of the bureau of meteorology's numerical weather prediction systems to support prediction of solar energy production",2012,"10.1175/JAMC-D-10-05027.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868092042&doi=10.1175%2fJAMC-D-10-05027.1&partnerID=40&md5=d236cf33b8d76770a484436509dd0047","The ability of the Australian Bureau of Meteorology's numerical weather prediction (NWP) systems to predict solar exposure (or insolation) was tested, with the aim of predicting large-scale solar energy several days in advance. The bureau's Limited Area Prediction System (LAPS) and Mesoscale Assimilation model (MALAPS) were examined for the 2008 calendar year. Comparisons were made with estimates of solar exposure obtained from satellites for the whole Australian continent, as well as site-based exposure observations taken at eight locations across Australia. Monthly-averaged forecast solar exposure over Australia showed good agreement with satellite estimates; the day-to-day exposure values showed some consistent biases, however. Differences in forecast solar exposure were attributed to incorrect representation of convective cloud in the tropics during summer as well as clouds formed by orographic lifting over mountainous areas in southeastern Australia. Comparison with site-based exposure observations was conducted on a daily and hourly basis. The site-based exposure measurements were consistent with the findings from the analysis against satellite data. Hourly analysis at selected sites confirmed that models predicted the solar exposure accurately through low-level clouds (e.g., cumulus), provided that the forecast cloud coverage was accurate. The NWP models struggle to predict solar exposure through middle and high clouds formed by ice crystals (e.g., altocumulus). Sites located in central Australia showed that the monthly-averaged errors in daily solar exposure forecast by the NWP systems were within 5%-10%, up to two days in advance. These errors increased to 20%-30% in the tropics and coastal areas. © 2012 American Meteorological Society."
"10042470700;57217398916;","Albedo enhancement over land to counteract global warming: Impacts on hydrological cycle",2012,"10.1007/s00382-011-1256-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866356860&doi=10.1007%2fs00382-011-1256-1&partnerID=40&md5=a3ba91d64395436328921418f5966e46","A recent modelling study has shown that precipitation and runoff over land would increase when the reflectivity of marine clouds is increased to counter global warming. This implies that large scale albedo enhancement over land could lead to a decrease in runoff over land. In this study, we perform simulations using NCAR CAM3. 1 that have implications for Solar Radiation Management geoengineering schemes that increase the albedo over land. We find that an increase in reflectivity over land that mitigates the global mean warming from a doubling of CO2 leads to a large residual warming in the southern hemisphere and cooling in the northern hemisphere since most of the land is located in northern hemisphere. Precipitation and runoff over land decrease by 13. 4 and 22. 3%, respectively, because of a large residual sinking motion over land triggered by albedo enhancement over land. Soil water content also declines when albedo over land is enhanced. The simulated magnitude of hydrological changes over land are much larger when compared to changes over oceans in the recent marine cloud albedo enhancement study since the radiative forcing over land needed (-8. 2 W m-2) to counter global mean radiative forcing from a doubling of CO2 (3. 3 W m-2) is approximately twice the forcing needed over the oceans (-4. 2 W m-2). Our results imply that albedo enhancement over oceans produce climates closer to the unperturbed climate state than do albedo changes on land when the consequences on land hydrology are considered. Our study also has important implications for any intentional or unintentional large scale changes in land surface albedo such as deforestation/afforestation/reforestation, air pollution, and desert and urban albedo modification. © 2011 Springer-Verlag."
"7006331431;55419044600;","Intraseasonal variability in MERRA energy fluxes over the tropical oceans",2012,"10.1175/JCLI-D-11-00428.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867664999&doi=10.1175%2fJCLI-D-11-00428.1&partnerID=40&md5=e0517d4151727605523aec5a9cff35f6","This paper investigates intraseasonal variability as represented by the recent NASA Global Modeling and Assimilation Office (GMAO) reanalysis, the Modern-Era Retrospective analysis for Research and Applications (MERRA). The authors examine the behavior of heat, moisture, and radiative fluxes emphasizing their contribution to intraseasonal variations in heat and moisture balance integrated over the tropical oceans. MERRA successfully captures intraseasonal signals in both state variables and fluxes, though it depends heavily on the analysis increment update terms that constrain the reanalysis to be near the observations. Precipitation anomaly patterns evolve in close agreement with those from the Tropical Rainfall Measuring Mission (TRMM) though locally MERRA may occasionally be smaller by up to 20%. As in the TRMM observations, tropical convection increases lead tropospheric warming by approximately 7 days. Radiative flux anomalies are dominated by cloud forcing and are found to replicate the top-of-the-atmosphere (TOA) energy loss associated with increased convection found by other observationally based studies. However, MERRA's convectively produced clouds appear to deepen too soon as precipitation increases. Total fractional cloud cover variations appear somewhat weak compared to observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). Evolution of the surface fluxes, convection, and TOA radiation is consistent with the ""discharge-recharge""paradigm that posits the importance of lower-tropospheric moisture accumulation prior to the expansion of organized deep convection. The authors conclude that MERRA constitutes a very useful representation of intraseasonal variability that will support a variety of studies concerning radiative-convective-dynamical processes and will help identify pathways for improved moist physical parameterization in global models. © 2012 American Meteorological Society."
"6602682911;57218978870;8670860600;6602197389;57203030873;13406399300;57205867148;","DART/CAM: An ensemble data assimilation system for CESM atmospheric models",2012,"10.1175/JCLI-D-11-00395.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867673444&doi=10.1175%2fJCLI-D-11-00395.1&partnerID=40&md5=a1ed9da86b1df2ef7695b93536c8070a","The Community Atmosphere Model (CAM) has been interfaced to the Data Assimilation Research Testbed (DART), a community facility for ensemble data assimilation. This provides a large set of data assimilation tools for climate model research and development. Aspects of the interface to the Community Earth System Model (CESM) software are discussed and a variety of applications are illustrated, ranging from model development to the production of long series of analyses. CAM output is compared directly to real observations from platforms ranging from radiosondes to global positioning system satellites. Such comparisons use the temporally and spatially heterogeneous analysis error estimates available from the ensemble to provide very specific forecast quality evaluations. The ability to start forecasts from analyses, which were generated by CAM on its native grid and have no foreign model bias, contributed to the detection of a code error involving Arctic sea ice and cloud cover. The potential of parameter estimation is discussed. A CAM ensemble reanalysis has been generated for more than 15 yr. Atmospheric forcings from the reanalysis were required as input to generate an ocean ensemble reanalysis that provided initial conditions for decadal prediction experiments. The software enables rapid experimentation with differing sets of observations and state variables, and the comparison of different models against identical real observations, as illustrated by a comparison of forecasts initialized by interpolated ECMWF analyses and by DART/CAM analyses. © 2012 American Meteorological Society."
"25824496000;7202711754;57197137741;6603527577;","World War II contrails: A case study of aviation-induced cloudiness",2012,"10.1002/joc.2392","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865784276&doi=10.1002%2fjoc.2392&partnerID=40&md5=ffe50b95eb56855d17064965e9443416","Dense and persistent condensation trails or contrails were produced by daytime US Army Air Force (USAAF) bombing raids, flown from England to Europe during World War II (WW2). These raids occurred in years when civilian air travel was rare, giving a predominantly contrail-free background sky, in a period when there were more meteorological observations taken across England than at any time before or since. The aircraft involved in the raids entered formation at contrail-forming altitudes (generally over 16 000 ft, approximately 5 km) over a relatively small part of southeast England before flying on to their target. This formation strategy provides us a unique opportunity to carry out multiple observation-based comparisons of adjacent, same day, well-defined overflown and non-over-flown regions. We compile evidence from archived meteorological data, such as Met Office daily weather reports and individual station meteorological registers, together with historical aviation information from USAAF and Royal Air Force (RAF) tactical mission reports. We highlight a number of potential dates for study and demonstrate, for one of these days, a marked difference in the amount of high cloud cover, and a statistically significant (0.8 °C) difference in the 07:00-13:00 UTC temperature range when comparing data from highly overflown stations to those upwind of the flight path on the same day. Although one event cannot provide firm conclusions regarding the effect of contrails on climate, this study demonstrates that the wealth of observational data associated with WW2 bombing missions allows detailed investigation of meteorological perturbations because of aviation-induced cloudiness. © 2011 Royal Meteorological Society."
"7103325318;7404136779;7404147955;7403974748;7404815507;55348846700;36093551900;","Recent progress in studies of climate change in China",2012,"10.1007/s00376-012-1200-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865659823&doi=10.1007%2fs00376-012-1200-2&partnerID=40&md5=e6cc035596facfc8d63c591f8f309ac0","An overview of basic research on climate change in recent years in China is presented. In the past 100 years in China, average annual mean surface air temperature (SAT) has increased at a rate ranging from 0. 03°C (10 yr) -1 to 0. 12°C (10 yr) -1. This warming is more evident in northern China and is more significant in winter and spring. In the past 50 years in China, at least 27% of the average annual warming has been caused by urbanization. Overall, no significant trends have been detected in annual and/or summer precipitation in China on a whole for the past 100 years or 50 years. Both increases and decreases in frequencies of major extreme climate events have been observed for the past 50 years. The frequencies of extreme temperature events have generally displayed a consistent pattern of change across the country, while the frequencies of extreme precipitation events have shown only regionally and seasonally significant trends. The frequency of tropical cyclone landfall decreased slightly, but the frequency of sand/dust storms decreased significantly. Proxy records indicate that the annual mean SAT in the past a few decades is the highest in the past 400-500 years in China, but it may not have exceeded the highest level of the Medieval Warm Period (1000-1300 AD). Proxy records also indicate that droughts and floods in eastern China have been characterized by continuously abnormal rainfall periods, with the frequencies of extreme droughts and floods in the 20th century most likely being near the average levels of the past 2000 years. The attribution studies suggest that increasing greenhouse gas (GHG) concentrations in the atmosphere are likely to be a main factor for the observed surface warming nationwide. The Yangtze River and Huaihe River basins underwent a cooling trend in summer over the past 50 years, which might have been caused by increased aerosol concentrations and cloud cover. However, natural climate variability might have been a main driver for the mean and extreme precipitation variations observed over the past century. Climate models generally perform well in simulating the variations of annual mean SAT in China. They have also been used to project future changes in SAT under varied GHG emission scenarios. Large uncertainties have remained in these model-based projections, however, especially for the projected trends of regional precipitation and extreme climate events. © 2012 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"6701335949;7004676489;26323138400;7005212820;55189671700;6602858513;","A multiscale nonhydrostatic atmospheric model using centroidal Voronoi tesselations and C-grid staggering",2012,"10.1175/MWR-D-11-00215.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861385507&doi=10.1175%2fMWR-D-11-00215.1&partnerID=40&md5=753e5b901a3c9df22ad2b79a68e03908","The formulation of a fully compressible nonhydrostatic atmospheric model called the Model for Prediction Across Scales-Atmosphere (MPAS-A) is described. The solver is discretized using centroidal Voronoi meshes and a C-grid staggering of the prognostic variables, and it incorporates a split-explicit time-integration technique used in many existing nonhydrostatic meso- and cloud-scale models. MPAS can be applied to the globe, over limitedareas of the globe, and on Cartesian planes. The Voronoi meshes are unstructured grids that permit variable horizontal resolution. These meshes allow for applications beyond uniform-resolution NWP and climate prediction, in particular allowing embedded high-resolution regions to be used for regional NWP and regional climate applications. The rationales for aspects of this formulation are discussed, and results fromtests for nonhydrostatic flows on Cartesian planes and for large-scale flow on the sphere are presented. The resultsindicate that the solver is as accurate as existing nonhydrostatic solvers for nonhydrostatic-scale flows, and has accuracy comparable to existing global models using icosahedral(hexagonal) meshes for large-scale flows in idealized tests. Preliminary full-physics forecast results indicate that the solver formulation is robust and that the variable-resolution-mesh solutions are well resolved and exhibit no obvious problems in the mesh-transition zones. © 2012 American Meteorological Society."
"57190402490;8631019200;7402727711;","Evaluation of atmospheric aerosol optical depth products at ultraviolet bands derived from MODIS products",2012,"10.1080/02786826.2012.687475","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862567118&doi=10.1080%2f02786826.2012.687475&partnerID=40&md5=5772f0d63e24ce7759a3a77806b45b4a","Solar ultraviolet (UV) radiation plays a significant role in climate, atmospheric chemical processes, and ecosystem balance. Aerosol optical depth (AOD) at UV wavelengths, the UV-AOD, is an important quantity for studying the extinction of UV radiation in the atmosphere.Ground-based UV-AOD observations, such as those from the AErosol RObotic NETwork (AERONET), are limited in spatial coverage. Current space derived UV-AOD from the Total Ozone Mapping Spectrometer (TOMS) or the Ozone Monitoring Instrument (OMI), on the other hand, are subject to large errors associated with low resolution, cloud contamination, assumed height of aerosol layer, and low sensitivity to aerosols in the lower troposphere. In this study, a new UV-AOD product is derived for the year 2009 by extrapolating the Moderate Resolution Imaging Spectra-radiometer (MODIS) visible bands AOD product (VIS-AOD) to 380 and 340 nm. Results are evaluated against UV-AOD measurements taken at AERONET sites. Over the oceans, four extrapolating methods are investigated by using two to five wavelengths. The best result, which has a correlation coefficient (R) of 0.90 at both wavelengths and root mean square errors (RMSE) of 0.062 and 0.068 at 380 and 340 nm, respectively, is achieved by combining a linear-extrapolation and a second-order polynomial fitting that takes into account the wavelength dependence of the Ångström exponent.Moreover, more than 80% of the data fall within the uncertainty range of ±0.05 ± 0.20τ . Over land,UV-AOD is extrapolated using the Ångström exponent derived from VIS-AODs at 470 and 660 nm, the only two wavelengths available from the MODIS AOD product. Compared with AERONET observations, the correlation coefficient is about 0.90 at both 380 and 340 nm, while the RMSE increases to 0.152 at 380 nm and 0.174 at 340 nm, due to the larger uncertainty of MODIS AOD over land. With the relatively low biases, this UV-AOD product will be valuable for climate and atmospheric chemistry research. Copyright © American Association for Aerosol Research."
"57214672257;35779049500;","Synergistic analyses of optical and microphysical properties of agricultural crop residue burning aerosols over the Indo-Gangetic Basin (IGB)",2012,"10.1016/j.atmosenv.2012.04.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861675342&doi=10.1016%2fj.atmosenv.2012.04.025&partnerID=40&md5=b65f8689301145d7f8dac120066761ea","Agriculture crop residue burning is one of the important sources of trace gas emissions and aerosol loading over the Indo-Gangetic Basin (IGB). The present study deals with the spatial variability including the vertical structure of optical and microphysical properties of aerosols, during the crop residue burning season (October and November) of 2009 over the IGB. Increased number of fire counts observed by MODIS (MODerate resolution Imaging Spectroradiometer) that is associated with high aerosol optical depth (MODIS-AOD &gt; 0.7) and enhanced tropospheric columnar NO 2 concentrations observed by OMI (Ozone Monitoring Instrument), suggests agriculture crop residue burning as a main source of aerosol loading over the IGB during October and November. PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar) observations show an increase in fine mode AOD (at 865 nm) from October (0.1-0.2) to November (0.2-0.3) over the IGB, which is well corroborated with MODIS observations. CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) data shows the elevated aerosol plume (4.0-4.5 km) over the north-west IGB (associated with burning activities) that could have been caused by positive buoyancy through pyro-convection. However, large concentrations of aerosol were found below 1.0 km altitude. The averaged vertical structure of crop residue burning aerosols shows an exponential decrease with altitude (mean scale height ∼1.44 ± 0.20 km). Aerosol optical and microphysical properties coupled with backward air trajectories analyses at Kanpur indicated regional transport of biomass burning aerosols in a downwind direction from north-west IGB to south-east IGB. Aerosol classification, using AERONET (AErosol RObotic NETwork)-derived absorption properties coupled with size parameter (2006-2010) showed clear seasonal dependency of aerosol types which revealed the presence of biomass burning aerosols only during the crop residue burning season. The findings of this study will be further used for quantification of the properties of atmospheric brown clouds and their effects on global climate change. © 2012 Elsevier Ltd."
"55683526900;6701670597;","Interpretations of systematic errors in the NCEP Climate Forecast System at lead times of 2, 4, 8, 256 days",2012,"10.1029/2011MS000094","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867670486&doi=10.1029%2f2011MS000094&partnerID=40&md5=901c71613aca3df7e7cad0485f09e784","The climatology of mean bias errors (relative to 1-day forecasts) was examined in a 20-year hindcast set from version 1 of the Climate Forecast System (CFS), for forecast lead times of 2, 4, 8, 16 256 days, verifying in different seasons. Results mostly confirm the simple expectation that atmospheric model biases should be evident at short lead (2-4 days), while soil moisture errors develop over days-weeks and ocean errors emerge over months. A further simplification is also evident: surface temperature bias patterns have nearly fixed geographical structure, growing with different time scales over land and ocean. The geographical pattern has mostly warm and dry biases over land and cool bias over the oceans, with two main exceptions: (1) deficient stratocumulus clouds cause warm biases in eastern subtropical oceans, and (2) high latitude land is too cold in boreal winter. Further study of the east Pacific cold tongue-Intertropical Convergence Zone (ITCZ) complex shows a possible interaction between a rapidly-expressed atmospheric model bias (poleward shift of deep convection beginning at day 2) and slow ocean dynamics (erroneously cold upwelling along the equator in leads > 1 month). Further study of the high latitude land cold bias shows that it is a thermal wind balance aspect of the deep polar vortex, not just a near-surface temperature error under the wintertime inversion, suggesting that its development time scale of weeks to months may involve long timescale processes in the atmosphere, not necessarily in the land model. Winter zonal wind errors are small in magnitude, but a refractive index map shows that this can cause modest errors in Rossby wave ducting. Finally, as a counterpoint to our initial expectations about error growth, a case of non-monotonic error growth is shown: velocity potential bias grows with lead on a time scale of weeks, then decays over months. It is hypothesized that compensations between land and ocean errors may cause this behavior. © 2012. American Geophysical Union."
"35744479900;57203230296;7006982557;","Compilation of a glacier inventory for the western Himalayas from satellite data: Methods, challenges, and results",2012,"10.1016/j.rse.2012.06.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864102237&doi=10.1016%2fj.rse.2012.06.020&partnerID=40&md5=7809343b96693af7a17b75f39860c94d","Due to their sensitive reaction to changes in climatic conditions, glaciers have been selected as an essential climate variable (ECV). Although a large amount of ice is located in the Himalayas, this region is yet only sparsely represented in global glacier databases. Accordingly, a sound and comprehensive change assessment or determination of water resources was not yet possible. In this study, we present a new glacier inventory for the western Himalayas, compiled from Landsat ETM+ scenes acquired between 2000 and 2002, coherence images from ALOS PALSAR image pairs, the SRTM digital elevation model (DEM) and the ASTER Global DEM (GDEM). Several specific challenges for glacier mapping were found in this region and addressed. They are related to debris cover, orographic clouds, locally variable snow conditions, and creeping permafrost features in cold-dry regions. Additional to seven topographic parameters that are obtained from the ASTER GDEM for each glacier, we also determined the relative amount of debris cover on the glacier surface. The inventory contains 11,400 glaciers larger than 0.02km2, which cover a total area of 9,310km2. Analysis of the inventory data revealed characteristic patterns of mean glacier elevation and relative debris cover amounts that might be related to the governing climatic conditions. The full dataset will be freely available in the GLIMS glacier database to foster further analyses and modeling of the glaciers in this region. © 2012 Elsevier Inc."
"57213414254;7005453346;7003704096;","The influence of boundary layer processes on the diurnal variation of the climatological near-surface wind speed probability distribution over land",2012,"10.1175/JCLI-D-11-00321.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867686888&doi=10.1175%2fJCLI-D-11-00321.1&partnerID=40&md5=c1a67f425e2d4a815c2b39f331b14df5","Knowledge of the diurnally varying land surface wind speed probability distribution is essential for surface flux estimation and wind power management. Global observations indicate that the surface wind speed probability density function (PDF) is characterized by a Weibull-like PDF during the day and a nighttime PDF with considerably greater skewness. Consideration of long-term tower observations at Cabauw, the Netherlands, indicates that this nighttime skewness is a shallow feature connected to the formation of a stably stratified nocturnal boundary layer. The observed diurnally varying vertical structure of the leading three climatological moments of near-surface wind speed (mean, standard deviation, and skewness) and the wind power density at the Cabauw site can be successfully simulated using the single-column version of the Canadian Centre for Climate Modelling and Analysis (CCCma) fourth-generation atmospheric general circulation model (CanAM4) with a new semiempirical diagnostic turbulent kinetic energy (TKE) scheme representing downgradient turbulent transfer processes for cloud-free conditions. This model also includes a simple stochastic representation of intermittent turbulence at the boundary layer inversion. It is found that the mean and the standard deviation of wind speed are most influenced by large-scale ""weather""variability, while the shape of the PDF is influenced by the intermittent mixing process. This effect is quantitatively dependent on the asymptotic flux Richardson number, which determines the Prandtl number in stable flows. High vertical resolution near the land surface is also necessary for realistic simulation of the observed fine vertical structure of wind speed distribution. © 2012 American Meteorological Society."
"7402825289;55736958700;7201456037;","Isotopic effect of runoff in the Yarlung Zangbo River",2012,"10.1007/s11631-012-0580-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864229843&doi=10.1007%2fs11631-012-0580-4&partnerID=40&md5=2b99e8ee282ddc15b9db2e380b29fd89","This paper mainly analyzed the isotopic effect of precipitation in the Yarlung Zangbo River. On the whole, the isotopic compositions of most water samples fall on the upper right of the global meteoric water line. According to δD and δ 18O data of the samples, the precipitation equation is figured out as δD=8 δ 18O+10, showing that they are derived from precipitation but have experienced intensive evaporation. With obvious region-continental effect (a continuous depletion in heavy isotopes in water bodies occurs with increasing distance from the coast), the water presents a reducing trend of δD and δ 18O westwards and southwards. Altitudinal effect is evident here, occurring in both trunk stream and main branches of the Yarlung Zangbo River. The distribution of water isotopic compositions is concerned with the movement of precipitation clouds from the Bay of Bengal and the Nujiang River and is affected by the topographic and climatic conditions of the Tibetan Plateau. © 2012 Science Press, Institute of Geochemistry, CAS and Springer-Verlag Berlin Heidelberg."
"57206204252;8349977900;36623750900;","A global comparison of GEOS-Chem-predicted and remotely-sensed mineral dust aerosol optical depth and extinction profiles",2012,"10.1029/2011MS000109","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867725187&doi=10.1029%2f2011MS000109&partnerID=40&md5=8b7c85edcd89ff0e9e4d63af60a7b358","Dust aerosol optical depth (AOD) and vertical distribution of aerosol extinction predicted by a global chemical transport model (GEOS-Chem) are compared to spaceborne data from the Moderate-resolution Imaging Spectroradiometer (MODIS), Multi- Angle Imaging SpectroRadiometer (MISR), and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) for March 2009 to February 2010. Modelpredicted and remotely-sensed AOD/aerosol extinction profiles are compared over six regions where aerosol abundances are dominated by mineral dust. Calculations indicate that over the regions examined in this study (with the exception of Middle Eastern dust sources) GEOS-Chem predicts higher AOD values compared to MODIS and MISR. The positive bias is particularly pronounced over the Saharan dust source regions, where model-predicted AOD values are a factor of 2 to 3 higher. The comparison with CALIPSO-derived dust aerosol extinction profiles revealed that the model overestimations of dust abundances over the study regions primarily occur below,4 km, suggesting excessive emissions of mineral dust and/or uncertainties in dust optical properties. The implementation of a new dust size distribution scheme into GEOS-Chem reduced the yearly-mean positive bias in model-predicted AOD values over the study regions. The results were most noticeable over the Saharan dust source regions where the differences between model-predicted and MODIS/MISR retrieved AOD values were reduced from 0.22 and 0.17 to 0.02 and 20.04, respectively. Our results suggest that positive/negative biases between satellite and model-predicted aerosol extinction values at different altitudes can sometimes even out, giving a false impression for the agreement between remotely-sensed and model-predicted column-integrated AOD data. © 2012. American Geophysical Union."
"16444324800;7004854393;21740519000;","Observations of Diurnal Cycles Over a West African Meridional Transect: Pre-Monsoon and Full-Monsoon Seasons",2012,"10.1007/s10546-012-9723-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865405404&doi=10.1007%2fs10546-012-9723-8&partnerID=40&md5=aa781ea4a687a38628b6b5778e8eaa35","We document and characterize the climatology of the diurnal cycles encountered along a West African transect during the pre-monsoon and full-monsoon periods. The meridional gradient in low-level properties is fundamental for the monsoon dynamics and here, for the first time, it is studied based on a large set of observations from the African Monsoon Multidisciplinary Analysis (AMMA) campaign. A detailed analysis of surface energy budget, boundary-layer structures and cloud occurrence is carried out to investigate the diurnal cycles of the low levels. A relatively weak meridional gradient of net radiation is observed during the pre-monsoon period, and a large gradient in sensible heat flux is found over the transect with values increasing from south to north. This, as well as the boundary-layer structures, partly explains the large contrasts in the diurnal amplitude of potential temperature and specific humidity along the transect. During the monsoon period, the atmospheric regimes drastically change involving strong interactions between the surface, atmosphere and clouds. The maximum in net radiation is shifted northwards, towards the Sahel, which potentially has a significant impact on the monsoon circulation. The sensible heat flux is considerably reduced and the diurnal amplitude is strongly damped, while the daytime boundary-layer growth decreases significantly in the Sahel related to changes in the balance of boundary-layer processes. These results highlight the contrasted diurnal cycle regimes encountered over West Africa under dry, moist and wet conditions. They provide observationally-based diagnostics to investigate the ability of models to handle the representation of the diurnal cycle over land. © 2012 Springer Science+Business Media B.V."
"42661306000;56080932300;7102780088;","Volume and mass changes of the Greenland ice sheet inferred from ICESat and GRACE",2012,"10.1016/j.jog.2011.06.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863831673&doi=10.1016%2fj.jog.2011.06.003&partnerID=40&md5=c6649453c0586af2dada063528377ca4","This study examines the recent evolution of the Greenland ice sheet and its six major drainage basins. Based on laser altimetry data acquired by the Ice, Cloud and Land Elevation Satellite (ICESat), covering the period September-November 2003 to February-March 2008, ice surface height changes and their temporal variations were inferred. Our refined repeat track analysis is solely based on ICESat data and is independent of external elevation models, since it accounts for both ice height changes and the local topography. From the high resolution ice height change pattern we infer an overall mean surface height trend of -0.12±0.006myr -1. Furthermore, the largest changes could be identified at coastal margins of the ice sheet, exhibiting rates of more than -2myr -1. The total ice volume change of the entire ice sheet amounts to -205.4±10.6km 3yr -1. In addition, we assessed mass changes from 78 monthly Gravity Recovery and Climate Experiment (GRACE) solutions. The Release-04 gravity field solutions of GeoForschungsZentrum Potsdam cover the period between August 2002 and June 2009. We applied an adjusted regional integration approach in order to minimize the leakage effects. Attention was paid to an optimized filtering which reduces error effects from different sources. The overall error assessment accounts for GRACE errors as well as for errors due to imperfect model reductions. In particular, errors caused by uncertainties in the glacial isostatic adjustment models could be identified as the largest source of errors. Finally, we determined both seasonal and long-term mass change rates. The latter amounts to an overall ice mass change of -191.2±20.9Gtyr -1 corresponding to 0.53±0.06mmyr -1 equivalent eustatic sea level rise. From the combination of the volume and mass change estimates we determined a mean density of the lost mass to be 930±11kgm -3. This value supports our applied density assumption 900±30kgm -3 which was used to perform the volume-mass-conversion of our ICESat results. Hence, mass change estimates from two independent observation techniques were inferred and are generally in good agreement. © 2011 Elsevier Ltd."
"18433496200;7005924908;26643087200;35227954100;57203428273;35409312800;24556796800;","Decreased marine dimethyl sulfide production under elevated CO 2 levels in mesocosm and in vitro studies",2012,"10.1071/EN11125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865369108&doi=10.1071%2fEN11125&partnerID=40&md5=de1214e82954f4ccbde9bc8e69a6a15e","The oceans have absorbed approximately half of the CO 2 produced by human activities and it is inevitable that surface seawaters will become increasingly acidified. The effect of lower pH on marine organisms and oceanatmosphere exchanges is largely unknown but organisms with CaCO 3 structural components are likely to be particularly affected. Because calcifying phytoplankton are significant producers of dimethyl sulfide (DMS), it is vital to understand how lower seawater pH may affect DMS production and emission to the atmosphere. Here we show, by mesocosm (Raunefjorden, Norway, April-May 2003) and in vitro studies, that the net production of DMS and its cellular precursor dimethylsulfoniopropionate (DMSP) is approximately halved in microbial communities subjected to doubled CO 2 levels. Our findings provide evidence that the amount of DMS entering the atmosphere could decrease in the future. Because atmospheric oxidation of DMS can lead to climate cooling by increasing cloud albedo, a consequence of reduced DMS emissions from a lower pH ocean would be an enhancement in global warming. © 2012 CSIRO."
"7005485117;14070768100;14047829400;57195881858;","Impacts of cloud flare-ups on hurricane intensity resulting from departures from balance laws",2012,"10.3402/tellusa.v64i0.18399","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865119921&doi=10.3402%2ftellusa.v64i0.18399&partnerID=40&md5=0d2269b06fb3e24e9750df5c497cd764","Cloud flare-ups along the inner eye wall of a hurricane lead to enhancement of cloud scale divergence, which in turn leads to a large local enhancement of the departure from balance laws and can lead to local supergradient winds. This scenario is tested using the results from a mesoscale microphysical model at horizontal resolution of 1.33 km for the simulation of hurricane Katrina. Rainwater mixing ratio tags growing cloud elements. The departure from balance laws includes terms such as the local, horizontal and vertical advections of divergence, divergence square and a term invoking the gradient of vertical velocity. It is noted that these terms collectively contribute to a substantial local enhancement of the departure from balance laws. Departures from balance laws are related to the radial gradient wind imbalances in a storm-centred coordinate. In this study, several examples, from the hurricane Katrina simulations, that display this scenario of rapid intensification are illustrated. Organisation of convection in the azimuthal direction seems important for the hurricane scale; cloud flare-ups away from such regions of azimuthal organisation fail to contribute to this scenario for the overall intensification of the hurricane. © 2012 T.N. Krishnamurti et al."
"35213726000;57203049177;6603236154;57203479688;9239400200;","Vertical and horizontal processes in the global atmosphere and the maximum entropy production conjecture",2012,"10.5194/esd-3-19-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865115504&doi=10.5194%2fesd-3-19-2012&partnerID=40&md5=5cfb6eb38be50f257d13275cc5d1c02a","The objective of this paper is to reconsider the Maximum Entropy Production conjecture (MEP) in the context of a very simple two-dimensional zonal-vertical climate model able to represent the total material entropy production due at the same time to both horizontal and vertical heat fluxes. MEP is applied first to a simple four-box model of climate which accounts for both horizontal and vertical material heat fluxes. It is shown that, under condition of fixed insolation, a MEP solution is found with reasonably realistic temperature and heat fluxes, thus generalising results from independent two-box horizontal or vertical models. It is also shown that the meridional and the vertical entropy production terms are independently involved in the maximisation and thus MEP can be applied to each subsystem with fixed boundary conditions. We then extend the four-box model by increasing its resolution, and compare it with GCM output. A MEP solution is found which is fairly realistic as far as the horizontal large scale organisation of the climate is concerned whereas the vertical structure looks to be unrealistic and presents seriously unstable features. This study suggest that the thermal meridional structure of the atmosphere is predicted fairly well by MEP once the insolation is given but the vertical structure of the atmosphere cannot be predicted satisfactorily by MEP unless constraints are imposed to represent the determination of longwave absorption by water vapour and clouds as a function of the state of the climate. Furthermore an order-of-magnitude estimate of contributions to the material entropy production due to horizontal and vertical processes within the climate system is provided by using two different methods. In both cases we found that approximately 40mWm-2 K-1 of material entropy production is due to vertical heat transport and 5-7mWm-2 K-1 to horizontal heat transport. © Author(s) 2012."
"56162305900;7003666669;55717074000;6701606453;56384704800;7103158465;55405340400;7006270084;7101959253;7006643234;55802246600;7102604282;","Constraining cloud lifetime effects of aerosols using A-Train satellite observations",2012,"10.1029/2012GL052204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865473923&doi=10.1029%2f2012GL052204&partnerID=40&md5=a4e2ed1ebf77ff3762a698c2b41acc71","Aerosol indirect effects have remained the largest uncertainty in estimates of the radiative forcing of past and future climate change. Observational constraints on cloud lifetime effects are particularly challenging since it is difficult to separate aerosol effects from meteorological influences. Here we use three global climate models, including a multi-scale aerosol-climate model PNNL-MMF, to show that the dependence of the probability of precipitation on aerosol loading, termed the precipitation frequency susceptibility (S <inf>pop</inf>), is a good measure of the liquid water path response to aerosol perturbation (&), as both S<inf>pop</inf> and & strongly depend on the magnitude of autoconversion, a model representation of precipitation formation via collisions among cloud droplets. This provides a method to use satellite observations to constrain cloud lifetime effects in global climate models. S<inf>pop</inf> in marine clouds estimated from CloudSat, MODIS and AMSR-E observations is substantially lower than that from global climate models and suggests a liquid water path increase of less than 5% from doubled cloud condensation nuclei concentrations. This implies a substantially smaller impact on shortwave cloud radiative forcing over ocean due to aerosol indirect effects than simulated by current global climate models (a reduction by one-third for one of the conventional aerosol-climate models). Further work is needed to quantify the uncertainties in satellite-derived estimates of S<inf>pop</inf> and to examine S<inf>pop</inf> in high-resolution models. © 2012. American Geophysical Union. All Rights Reserved."
"55703847000;7601492669;8718425100;7103060756;15822963700;","Cloud base and top heights in the Hawaiian region determined with satellite and ground-based measurements",2012,"10.1029/2012GL052355","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865526806&doi=10.1029%2f2012GL052355&partnerID=40&md5=9435291271c3f849ead8b9fc9312d0da","We present a multi-year climatology of cloud-base-height (CBH), cloud-top-height (CTH), and trade wind inversion base height (TWIBH) for the Hawaiian region (18N-22.5N, 153.7W-160.7W). The new climatology is based on data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO), the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), ceilometer observations and radiosondes. The climatology reported here is well suited to evaluate climate model simulations and can serve as a reference state for studies of the impact of climate change on Hawaiian ecosystems. The averaged CBH from CALIPSO in the Hawaiian Region is 890m. The mean CTH from CALIPSO is 2110m, which is close to the mean TWIBH from COSMIC. For non-precipitating cases, the mean TWIBH at both Lihue and Hilo is close to 2000m. For precipitating cases, the mean TWIBH is 2450m and 2280m at Hilo and Lihue, respectively. The potential cloud thickness (PCT) is defined as the difference between TWIBH and CBH and the mean PCT is several hundred meters thicker for precipitating than for the non-precipitating cases at both stations. We find that the PCT is more strongly correlated to the TWIBH than the CBH and that precipitation is unlikely to occur if the TWIBH is below 1500m. The observed rainfall intensity is correlated to the PCT, i.e., thicker clouds are more likely to produce heavy rain. © 2012. American Geophysical Union. All Rights Reserved."
"55344397300;7006306835;","Nonlinear climate response to regional brightening of tropical marine stratocumulus",2012,"10.1029/2012GL052064","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865404654&doi=10.1029%2f2012GL052064&partnerID=40&md5=178d9196511727789c44136402aa3400","To counteract global warming, there have been suggestions to increase the albedo of low-level marine clouds through the aerosol indirect effects by injecting them with sea salt. However, the full climate response to this geoengineering scheme is currently poorly understood. We simulate cloud seeding in a coupled mixed-layer ocean-atmosphere general circulation model in order to identify the specific physical mechanisms through which seeding could perturb the climate system's radiative balance, and cause temperature and precipitation changes. Seeding stratocumulus decks over three tropical maritime regions in the North Pacific, South Pacific and South Atlantic produces strong local reductions in solar absorption. Over half of the radiative cooling is due to direct scattering of solar radiation by the added sea salt aerosols, while the rest comes from enhancement of the local cloud albedo. The oceanic cooling due to the seeding over the southeastern equatorial Pacific induces a La Nia-like response, with tropical precipitation changes resembling La Nia anomalies and teleconnections occurring in the mid-latitude North Pacific and North America. Additionally, model runs in which only one of the three regions is seeded indicate nonlinearity in the climate response. We identify dynamical and thermodynamical constraints respectively on the temperature and hydrological cycle responses to cloud seeding, but the full response to such geoengineering remains poorly constrained. © 2012. American Geophysical Union. All Rights Reserved."
"6506056264;55728284400;7005132811;7006689582;24167396300;","Tropical circulation and hydrological cycle response to orbital forcing",2012,"10.1029/2012GL052482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865414377&doi=10.1029%2f2012GL052482&partnerID=40&md5=444488d0120f4ec1cfa179893cc41fd5","The intensity of the two major atmospheric tropical circulations, the Hadley and Walker circulation, has been analyzed in simulations with the Kiel Climate Model (KCM) of the early Eemian and the early Holocene, both warmer climate epochs compared to the late Holocene, or pre-industrial era. The KCM was forced by changes in orbital parameters corresponding to the early and late Holocene (9.5kyr BP and pre-industrial) and the early Eemian (126kyr BP). An intensification of the Southern Hemisphere (SH) winter Hadley cell and a northward extension of its rising branch, the Intertropical Convergence Zone, relative to pre-industrial are simulated for both warm periods. The Walker circulation's rising branch is shifted westward towards the Indian Ocean due to an increased zonal tropical sea surface temperature (SST) gradient across the Indo-Pacific Ocean, which drives enhanced easterlies over this region. The simulated vertically-integrated water vapor transport across the Equator shows the strongest response for the SH winter (boreal summer) Hadley cell over the Pacific Ocean due to an enhanced cross-equatorial SST gradient in the tropical Pacific during the early Holocene and the early Eemian. The orbitally-induced increase of the cross-equatorial insolation gradient in the tropical Pacific leads to a strengthening (weakening) of the wind speed and enhanced (reduced) evaporative cooling over the southern (northern) tropical Pacific, which reinforces the initial radiatively-forced meridional SST gradient change. The increased cross-equatorial insolation gradient in combination with the strong wind-evaporation-SST feedback and changing humidity are important mechanisms to enhance the SH winter Hadley circulation response to orbital forcing. © 2012. American Geophysical Union. All Rights Reserved."
"7003875148;34976155900;7005753600;7003663305;9038337500;24472110700;8696069500;7003740015;7003900383;7801558983;55327762400;","Meteorological conditions in the central Arctic summer during the Arctic Summer Cloud Ocean Study (ASCOS)",2012,"10.5194/acp-12-6863-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864590873&doi=10.5194%2facp-12-6863-2012&partnerID=40&md5=c2ff726b874dd48a06d06a0c0653f93a","Understanding the rapidly changing climate in the Arctic is limited by a lack of understanding of underlying strong feedback mechanisms that are specific to the Arctic. Progress in this field can only be obtained by process-level observations; this is the motivation for intensive ice-breaker-based campaigns such as the Arctic Summer Cloud-Ocean Study (ASCOS), described here. However, detailed field observations also have to be put in the context of the larger-scale meteorology, and short field campaigns have to be analysed within the context of the underlying climate state and temporal anomalies from this. <br><br> To aid in the analysis of other parameters or processes observed during this campaign, this paper provides an overview of the synoptic-scale meteorology and its climatic anomaly during the ASCOS field deployment. It also provides a statistical analysis of key features during the campaign, such as key meteorological variables, the vertical structure of the lower troposphere and clouds, and energy fluxes at the surface. In order to assess the representativity of the ASCOS results, we also compare these features to similar observations obtained during three earlier summer experiments in the Arctic Ocean: the AOE-96, SHEBA and AOE-2001 expeditions. <br><br> We find that these expeditions share many key features of the summertime lower troposphere. Taking ASCOS and the previous expeditions together, a common picture emerges with a large amount of low-level cloud in a well-mixed shallow boundary layer, capped by a weak to moderately strong inversion where moisture, and sometimes also cloud top, penetrate into the lower parts of the inversion. Much of the boundary-layer mixing is due to cloud-top cooling and subsequent buoyant overturning of the cloud. The cloud layer may, or may not, be connected with surface processes depending on the depths of the cloud and surface-based boundary layers and on the relative strengths of surface-shear and cloud-generated turbulence. The latter also implies a connection between the cloud layer and the free troposphere through entrainment at cloud top. © 2012 Author(s)."
"55328209200;8696069500;6602600408;6507961483;","Arctic clouds and surface radiation-a critical comparison of satellite retrievals and the ERA-interim reanalysis",2012,"10.5194/acp-12-6667-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864621488&doi=10.5194%2facp-12-6667-2012&partnerID=40&md5=b4ee8a1c56641ff7c75665b30390518f","Clouds regulate the Earth's radiation budget, both by reflecting part of the incoming sunlight leading to cooling and by absorbing and emitting infrared radiation which tends to have a warming effect. Globally averaged, at the top of the atmosphere the cloud radiative effect is to cool the climate, while at the Arctic surface, clouds are thought to be warming. Here we compare a passive instrument, the AVHRR-based retrieval from CM-SAF, with recently launched active instruments onboard CloudSat and CALIPSO and the widely used ERA-Interim reanalysis. We find that in particular in winter months the three data sets differ significantly. While passive satellite instruments have serious difficulties, detecting only half the cloudiness of the modeled clouds in the reanalysis, the active instruments are in between. In summer, the two satellite products agree having monthly means of 70-80 percent, but the reanalysis are approximately ten percent higher. The monthly mean long-and shortwave components of the surface cloud radiative effect obtained from the ERA-Interim reanalysis are about twice that calculated on the basis of CloudSat's radar-only retrievals, while ground based measurements from SHEBA are in between. We discuss these differences in terms of instrument-, retrieval-and reanalysis characteristics, which differ substantially between the analyzed datasets. © 2012 Author(s)."
"14825561100;6506939784;6507475576;7004862771;","MODIS snow cover mapping accuracy in a small mountain catchment - Comparison between open and forest sites",2012,"10.5194/hess-16-2365-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864625029&doi=10.5194%2fhess-16-2365-2012&partnerID=40&md5=1b98ea6bf96cf766edbdbd18b4cd0b2e","Numerous global and regional validation studies have examined MODIS snow mapping accuracy by using measurements at climate stations, which are mainly at open sites. MODIS accuracy in alpine and forested regions is, however, still not well understood. The main objective of this study is to evaluate MODIS (MOD10A1 and MYD10A1) snow cover products in a small experimental catchment by using extensive snow course measurements at open and forest sites. The MODIS accuracy is tested in the Jalovecky creek catchment (northern Slovakia) in the period 2000-2011. The results show that the combined Terra and Aqua images enable snow mapping at an overall accuracy of 91.5%. The accuracies at forested, open and mixed land uses at the Aervenec sites are 92.7%, 98.3% and 81.8%, respectively. The use of a 2-day temporal filter enables a significant reduction in the number of days with cloud coverage and an increase in overall snow mapping accuracy. In total, the 2-day temporal filter decreases the number of cloudy days from 61% to 26% and increases the snow mapping accuracy to 94%. The results indicate three possible factors leading to misclassification of snow as land: patchy snow cover, limited MODIS geolocation accuracy and mapping algorithm errors. Out of a total of 27 misclassification cases, patchy snow cover, geolocation issues and mapping errors occur in 12, 12 and 3 cases, respectively. © 2012 Author(s). CC Attribution 3.0 License."
"57194759599;6602600408;","Convection-climate feedbacks in the ECHAM5 general circulation model: Evaluation of cirrus cloud life cycles with ISCCP satellite data from a lagrangian trajectory perspective",2012,"10.1175/JCLI-D-11-00345.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864274751&doi=10.1175%2fJCLI-D-11-00345.1&partnerID=40&md5=f27f2f76a9c61d25ae9228312bbc4976","A process-oriented climate model evaluation is presented, applying the International Satellite Cloud Climatology Project (ISCCP) simulator to pinpoint deficiencies related to the cloud processes in the ECHAM5general circulation model.ALagrangian trajectory analysis is performed to track the transitions of anvil cirrus originating from deep convective detrainment to cirrostratus and thin cirrus, comparing ISCCP observations and the ECHAM5 model. Trajectories of cloudy air parcels originating from deep convection are computed for both, the ISCCP observations and the model, over which the ISCCP joint histograms are used for analyzing the cirrus life cycle over 5 days. The cirrostratus and cirrus clouds originate from detrainment from deep convection decay and gradually thin out after the convective event over 3-4 days. The effect of the convection-cirrus transitions in a warmer climate is analyzed in order to understand the climate feedbacks due to deep convective cloud transitions. An idealized climate change simulation is performed using a+2-K sea surface temperature (SST) perturbation. The Lagrangian trajectory analysis over perturbed climate suggests that more and thicker cirrostratus and cirrus clouds occur in the warmer climate compared to the present-day climate. Stronger convection is noticed in the perturbed climate, which leads to an increased precipitation, especially on day-2 and-3 after the individual convective events. The shortwave and the longwave cloud forcings both increase in the warmer climate, with an increase of net cloud radiative forcing (NCRF), leading to an overall positive feedback of the increased cirrostratus and cirrus clouds from a Lagrangian transition perspective. © 2012 American Meteorological Society."
"57203030873;55338676800;7402064802;52464731300;8866821900;57205867148;25031430500;7102645933;7401974644;7101959253;7005626683;","Exposing global cloud biases in the Community Atmosphere Model (CAM) using satellite observations and their corresponding instrument simulators",2012,"10.1175/JCLI-D-11-00469.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859950845&doi=10.1175%2fJCLI-D-11-00469.1&partnerID=40&md5=4006f69b6d5d824f9b350e99368defb0","Satellite observations and their corresponding instrument simulators are used to document global cloud biases in the Community Atmosphere Model (CAM) versions 4 and 5. The model-observation comparisons show that, despite having nearly identical cloud radiative forcing, CAM5 has a much more realistic representation of cloud properties than CAM4. In particular, CAM5 exhibits substantial improvement in three long-standing climate model cloud biases: 1) the underestimation of total cloud, 2) the overestimation of optically thick cloud, and 3) the underestimation of midlevel cloud. While the increased total cloud and decreased optically thick cloud in CAM5 result from improved physical process representation, the increased midlevel cloud in CAM5 results from the addition of radiatively active snow. Despite these improvements, both CAM versions have cloud deficiencies. Of particular concern, both models exhibit large but differing biases in the subtropical marine boundary layer cloud regimes that are known to explain intermodel differences in cloud feedbacks and climate sensitivity. More generally, this study demonstrates that simulatorfacilitated evaluation of cloud properties, such as amount by vertical level and optical depth, can robustly expose large and at times radiatively compensating climate model cloud biases. © 2012 American Meteorological Society."
"55686667100;10241250100;10241462700;36701462300;55537426400;10243650000;7003420726;35580303100;8979277400;7102857642;","Using a multiphysics ensemble for exploring diversity in cloud-shortwave feedback in GCMs",2012,"10.1175/JCLI-D-11-00564.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865091777&doi=10.1175%2fJCLI-D-11-00564.1&partnerID=40&md5=20ba26eede1f7482db11d517d0091f30","This study proposes a systematic approach to investigate cloud-radiative feedbacks to climate change induced by an increase of CO2 concentrations in global climatemodels (GCMs). Based on two versions of theModel for Interdisciplinary Research on Climate (MIROC), which have opposite signs for cloud-shortwave feedback (DSWcld) and hence different equilibrium climate sensitivities (ECSs), hybrid models are constructed by replacing one or more parameterization schemes for cumulus convection, cloud, and turbulence between them. An ensemble of climate change simulations using a suite of eightmodels, called amultiphysics ensemble(MPE), is generated. TheMPE provides a range of ECS as wide as the CoupledModel Intercomparison Project phase 3 (CMIP3) multimodel ensemble and reveals a different magnitude and sign of DSWcld over the tropics, which is crucial for determining ECS. It is found that no single process controls DSWcld, but that the coupling of two processes does. Namely, changing the cloud and turbulence schemes greatly alters the mean and the response of low clouds, whereas replacing the convection and cloud schemes affects low and middle clouds over the convective region. For each of the circulation regimes, DSWcld and cloud changes in theMPE have a nonlinear, but systematic, relationship with the mean cloud amount, which can be constrained from satellite estimates. The analysis suggests a positive feedback over the subsidence regime and a near-neutral or weak negative DSWcld over the convective regime in these model configurations, which, however, may not be carried into other models. © 2012 American Meteorological Society."
"57203030873;57202754759;6602558284;36871512800;25031430500;15724543600;57210350827;","The influence of local feedbacks and northward heat transport on the equilibrium arctic climate response to increased greenhouse gas forcing",2012,"10.1175/JCLI-D-11-00622.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859966114&doi=10.1175%2fJCLI-D-11-00622.1&partnerID=40&md5=793dc5e14b3f33e4173b6fb8392018e0","This study uses coupled climate model experiments to identify the influence of atmospheric physics [Community Atmosphere Model, versions 4 and 5 (CAM4; CAM5)] and ocean model complexity (slab ocean, full-depth ocean) on the equilibrium Arctic climate response to an instantaneous CO2 doubling. In slab ocean model (SOM) experiments using CAM4 and CAM5, local radiative feedbacks, not atmospheric heat flux convergence, are the dominant control on the Arctic surface response to increased greenhouse gas forcing. Equilibrium Arctic surface air temperature warming and amplification are greater in the CAM5 SOM experiment than in the equivalent CAM4 SOM experiment. Larger 2 3 CO2 radiative forcing, more positive Arctic surface albedo feedbacks, and less negative Arctic shortwave cloud feedbacks all contribute to greater Arctic surface warming and sea ice loss in CAM5 as compared to CAM4. When CAM4 is coupled to an active full-depth ocean model, Arctic Ocean horizontal heat flux convergence increases in response to the instantaneous CO2 doubling. Though this increased ocean northward heat transport slightly enhances Arctic sea ice extent loss, the representation of atmospheric processes (CAM4 versus CAM5) has a larger influence on the equilibrium Arctic surface climate response than the degree of ocean coupling (slab ocean versus fulldepth ocean). These findings underscore that local feedbacks can be more important than northward heat transport for explaining the equilibrium Arctic surface climate response and response differences in coupled climate models. That said, the processes explaining the equilibrium climate response differences here may be different than the processes explaining intermodel spread in transient climate projections. © 2012 American Meteorological Society."
"7003848718;55615375000;26425029500;","Atmospheric boundary layer measurements at the 280 m high Hamburg weather mast 1995-2011: Mean annual and diurnal cycles",2012,"10.1127/0941-2948/2012/0338","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874596445&doi=10.1127%2f0941-2948%2f2012%2f0338&partnerID=40&md5=dbd44560dc36819e5dba3fc7f593307a","In this paper, the 280 m high Hamburg weather mast and its instrumentation are introduced. Digital data recorded since 1995 are used to calculate the mean annual and diurnal cycles of the primary climate variables (pressure, temperature, humidity, wind, short- and long-wave radiation, cloud coverage, cloud base, precipitation). The annual average of 2 m temperature is 9.8 °C indicating an increase compared to the period 1971-2000 at the Hamburg airport climate station. Absolute humidity follows the temperature cycle with a maximum in July/August. Relative humidity is highest in winter and lowest in April/May. The fraction of received to clear-sky short-wave radiation is between 61 % in May and 34 % in December. Cloud coverage classes of 0-1 octas and 7-8 octas occur most frequently, but have opposite annual cycles. Cloud base distribution is narrow in winter and peaks around 300 m and is distributed over a wide height range in summer. Average annual precipitation amounts to 716 mm and falls in 9.3 % of the time. Monthly mean wind speed is highest (lowest) in January (August). Winds from west are most frequent followed by winds from southeast. A channelling by the Elbe river valley is indicated. The diurnal temperature cycle is weak in winter but strong in summer showing the evening generation and morning rise of the inversion. While relative humidity has a single diurnal cycle, absolute humidity has a double cycle in summer, but not in winter. Shortwave radiation in summer shows a weak asymmetry between forenoon and afternoon. The diurnal cycles of cloud cover and base are small in winter. In summer, cloud bases show a continuous increase from morning to afternoon and a break afterwards simultaneously with the diurnal rain maximum. Wind speed has opposite diurnal cycles at lower and upper levels. The upper-level cycle shows a temporal asymmetry in summer, i.e. The upper-level wind minimum does not occur simultaneously with the lower-level wind maximum. The reversal height between the opposite cycles is around 130 m in summer and 80 m in winter. The wind direction difference (250 m-10 m) shows a strong diurnal variation between 15° (day) and 45° (night) in summer and a small one between 23° and 35° in winter. The annual and diurnal cycles of all primary climate variables together present an excellent basis for the validation of process, weather or climate models. © 2012 Gebrüder Borntraeger, Stuttgart."
"7202957110;7402480218;6701754792;","The diurnal cycle of the boundary layer, convection, clouds, and surface radiation in a coastal monsoon environment (Darwin, Australia)",2012,"10.1175/JCLI-D-11-00538.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865094963&doi=10.1175%2fJCLI-D-11-00538.1&partnerID=40&md5=21b55d4e68a736a5cf87435f22cff64b","The diurnal variation of convection and associated cloud and radiative properties remains a significant issue in global NWP and climate models. This study analyzes observed diurnal variability of convection in a coastal monsoonal environment examining the interaction of convective rain clouds, their associated cloud prop- erties, and the impact on the surface radiation and corresponding boundary layer structure during periods where convection is suppressed or active on the large scale. The analysis uses data from the Tropical Warm Pool International Cloud Experiment (TWP-ICE) as well as routine measurements from the Australian Bureau of Meteorology and the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program. Both active monsoonal and large-scale suppressed (buildup and break) conditions are examined and demonstrate that the diurnal variation of rainfall is much larger during the break periods and the spatial distribution of rainfall is very different between the monsoon and break regimes. During the active monsoon the total net radiative input to the surface is decreased by more than 3 times the amount than during the break regime-this total radiative cloud forcing is found to be dominated by the shortwave (SW) cloud effects because of the much larger optical thicknesses and persistence of long-lasting anvils and cirrus cloud decks associated with the monsoon regime. These differences in monsoon versus break surface radiative energy contribute to low-level air temperature differences in the boundary layer over the land surfaces. © 2012 American Meteorological Society."
"36020977200;54885320200;55927784300;","European snow cover characteristics between 2000 and 2011 derived from improved modis daily snow cover products",2012,"10.3390/rs4082432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868131706&doi=10.3390%2frs4082432&partnerID=40&md5=595d0e4f2f73f5ce1b44e133615b5024","Mean snow cover duration was derived for the entire continent of Europe based on the MODIS daily snow cover products MOD10A1 and MYD10A1 for the period from 2000 to 2011. Dates of snow cover start and snow cover melt were also estimated. Polar darkness north of ~62°N and extensive cloud coverage affected the daily snow cover, preventing a direct derivation of the desired parameters. Combining sensor data from both MODIS platforms and applying a temporal cloud filter, cloud coverage and polar darkness were removed from the input data and accuracy remained above 90% for 87% of the area. The typical snow cover characteristics of the whole continent are illustrated and constitute a unique dataset with respect to spatial and temporal resolution. Abnormal events, glacier inventories or studies on possible impacts of climate change on snow cover characteristics are only some examples for applications where the presented results may be utilized.© 2012 by the authors."
"56272964700;7005808242;","Detailed investigation of the self-aggregation of convection in cloud-resolving simulations",2012,"10.1175/JAS-D-11-0257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867920582&doi=10.1175%2fJAS-D-11-0257.1&partnerID=40&md5=ff2201a7c8bebb1c457db29980f6c8f7","In models of radiative-convective equilibrium it is known that convection can spontaneously aggregate into one single localized moist region if the domain is large enough. The large changes in the mean climate state and radiative fluxes accompanying this self-aggregation raise questions as to what simulations at lower resolutions with parameterized convection, in similar homogeneous geometries, should be expected to produce to be considered successful in mimicking a cloud-resolving model. The authors investigate this self-aggregation in a nonrotating, three-dimensional cloud-resolving model on a square domain without large-scale forcing. It is found that self-aggregation is sensitive not only to the domain size, but also to the horizontal resolution. With horizontally homogeneous initial conditions, convective aggregation only occurs on domains larger than about 200 km and with resolutions coarser than about 2 km in the model examined. The system exhibits hysteresis, so that with aggregated initial conditions, convection remains aggregated even at our finest resolution, 500 m, as long as the domain is greater than 200-300 km. The sensitivity of self-aggregation to resolution and domain size in this model is due to the sensitivity of the distribution of low clouds to these two parameters. Indeed, the mechanism responsible for the aggregation of convection is the dynamical response to the longwave radiative cooling from low clouds. Strong longwave cooling near cloud top in dry regions forces downward motion, which by continuity generates inflow near cloud top and near-surface outflow from dry regions. This circulation results in the net export of moist static energy from regions with low moist static energy, yielding a positive feedback. © 2012 American Meteorological Society."
"55437010000;23492864500;7201504886;","Marine boundary layer cloud feedbacks in a constant relative humidity atmosphere",2012,"10.1175/JAS-D-11-0203.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867966133&doi=10.1175%2fJAS-D-11-0203.1&partnerID=40&md5=ea60d5413e08b311d9bf3968f2e3b7ab","The mechanisms that govern the response of shallow cumulus, such as found in the trade wind regions, to a warming of the atmosphere in which large-scale atmospheric processes act to keep relative humidity constant are explored. Two robust effects are identified. First, and as is well known, the liquid water lapse rate increases with temperature and tends to increase the amount of water in clouds, making clouds more reflective of solar radiation. Second, and less well appreciated, the surface fluxes increase with the saturation specific humidity, which itself is a strong function of temperature. Using large-eddy simulations it is shown that the liquid water lapse rate acts as a negative feedback: a positive temperature increase driven by radiative forcing is reduced by the increase in cloud water and hence cloud albedo. However, this effect is more than compensated by a reduction of cloudiness associated with the deepening and relative drying of the boundary layer, driven by larger surface moisture fluxes. Because they are so robust, these effects are thought to underlie changes in the structure of the marine boundary layer as a result of global warming. © 2012 American Meteorological Society."
"25634105600;57203540849;27168081700;7004029924;","Atlantic warm-pool variability in the IPCC AR4 CGCM simulations",2012,"10.1175/JCLI-D-11-00376.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865731532&doi=10.1175%2fJCLI-D-11-00376.1&partnerID=40&md5=db1b374158d9cd89dc85d23ed664074f","This study investigates Atlantic warm pool (AWP) variability in the twentieth century and preindustrial simulations of coupled GCMs submitted to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). In the twentieth-century simulations, most coupled models show very weak AWP variability, represented by an AWP area index, because of the cold SST bias in the AWP. Among the IPCC models, a higher AWP SST index corresponds to increased net downward short wave radiation and decreased low-level cloud fraction during the AWP peak season. This suggests that the cold SST bias in the AWP region is at least partly caused by an excessive amount of simulated low-level cloud, which blocks short wave radiation from reaching the sea surface. AWP natural variability is examined in pre industrial simulations. Spectral analysis reveals that only multi decadal band variability of the AWP is significant in observations. All models successfully capture the multi decadal band, but they show that interannual and/or decadal variability is also significant. On the multi decadal time scale, the global SST difference pattern between large AW Pyears and small AWP years resembles the geographic pattern of the AM Ofor most coupled models. Observational analysis indicates that both positive ENSO phase and negative NAO phase in winter correspond to reduced trade winds in theAW Pregion. The westerly anomalies induced by positive ENSO and negative NAOlead to local heating and warm SST from March to May and February to April, respectively. This behavior as a known feature of anomalous AWP growth is well captured by only five models. © 2012 American Meteorological Society."
"6603606681;6603566335;7003656857;55436859200;","Parameterization of the vertical velocity equation for shallow cumulus clouds",2012,"10.1175/MWR-D-11-00277.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867966115&doi=10.1175%2fMWR-D-11-00277.1&partnerID=40&md5=5bd81337022c1d1c02aa38ea77083190","The application of a steady-state vertical velocity equation for parameterized moist convective updrafts in climate and weather prediction models is currently common practice. This equation usually contains an advection, a buoyancy, and a lateral entrainment term, whereas the effects of pressure gradient and subplume contributions are typically incorporated as proportionality constants a and b for the buoyancy and the entrainment terms, respectively. A summary of proposed values of these proportionality constants a and b in the literature demonstrates that there is a large uncertainty in their most appropriate values. To shed new light on this situation an analysis is presented of the full vertical budget equation for shallow cumulus clouds obtained from large eddy simulations of three different Global Energy and Water Cycle Experiment (GEWEX) Cloud System Study (GCSS) intercomparison cases. It is found that the pressure gradient term is the dominant sink term in the vertical velocity budget, whereas the entrainment term only gives a small contribution. This result is at odds with the parameterized vertical velocity equation in the literature as it employs the entrainment term as the major sink term. As a practical solution the damping effect of the pressure term may be parameterized in terms of the lateral entrainment rates as used for thermodynamic quantities like the total specific humidity. By using a least squares method, case-dependent optimal values are obtained for the proportionality constants a and b, which are linearly related with each other. This relation can be explained from a linear relationship between the lateral entrainment rate and the buoyancy. © 2012 American Meteorological Society."
"36117562200;35092719600;7407524806;57206835760;57216872142;7405374205;","The global temperature anomaly and solar north-south asymmetry",2012,"10.1007/s13143-012-0025-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871103201&doi=10.1007%2fs13143-012-0025-3&partnerID=40&md5=efa7cdb144e4940e2e6b09c4f1561967","We investigate whether the global temperature anomaly is associated with the solar North-South asymmetry using data archived approximately for five solar cycles. We are motivated by both the accumulating evidence for the connection of Galactic cosmic-rays (GCRs) to the cloud coverage and recent finding of the association of GCR influx and the solar North-South asymmetry. We have analyzed the data of the observed sunspot, the GCR influx observed at the Moscow station, and the global temperature anomaly. We have found that the mean global temperature anomaly is systematically smaller (~0.56 in the unit of its standard deviation) during the period when the solar northern hemisphere is more active than the solar southern hemisphere. The difference in the mean value of the global temperature anomaly for the two data sets sub-sampled according to the solar North-South asymmetry is large and statistically significant. We suggest the solar North-South asymmetry is related to the global temperature anomaly through modulating the amount of GCR influx. Finally, we conclude by discussing its implications on a climate model and a direction of future work. © The Korean Meteorological Society and Springer 2012."
"55522498000;14920052300;55802246600;","Simulation of Urban climate with high-resolution WRF model: A case study in Nanjing, China",2012,"10.1007/s13143-012-0023-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871061413&doi=10.1007%2fs13143-012-0023-5&partnerID=40&md5=a29629aed0aacd25f0b81377b381455e","In this study, urban climate in Nanjing of eastern China is simulated using 1-km resolution Weather Research and Forecasting (WRF) model coupled with a single-layer Urban Canopy Model. Based on the 10-summer simulation results from 2000 to 2009 we find that the WRF model is capable of capturing the high-resolution features of urban climate over Nanjing area. Although WRF underestimates the total precipitation amount, the model performs well in simulating the surface air temperature, relative humidity, and precipitation frequency and inter-annual variability. We find that extremely hot events occur most frequently in urban area, with daily maximum (minimum) temperature exceeding 36°C (28°C) in around 40% (32%) of days. Urban Heat Island (UHI) effect at surface is more evident during nighttime than daytime, with 20% of cases the UHI intensity above 2.5oC at night. However, The UHI affects the vertical structure of Planet Boundary Layer (PBL) more deeply during daytime than nighttime. Net gain for latent heat and net radiation is larger over urban than rural surface during daytime. Correspondingly, net loss of sensible heat and ground heat are larger over urban surface resulting from warmer urban skin. Because of different diurnal characteristics of urban-rural differences in the latent heat, ground heat and other energy fluxes, the near surface UHI intensity exhibits a very complex diurnal feature. UHI effect is stronger in days with less cloud or lower wind speed. Model results reveal a larger precipitation frequency over urban area, mainly contributed by the light rain events (&lt; 10 mm d-1). Consistent with satellite dataset, around 10-20% more precipitation occurs in urban than rural area at afternoon induced by more unstable urban PBL, which induces a strong vertical atmospheric mixing and upward moisture transport. A significant enhancement of precipitation is found in the downwind region of urban in our simulations in the afternoon. © The Korean Meteorological Society and Springer 2012."
"36011653700;7006933675;55216588300;6701676992;","Automated analysis of the temporal behavior of the double Intertropical Convergence Zone over the east Pacific",2012,"10.1016/j.rse.2012.03.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860998634&doi=10.1016%2fj.rse.2012.03.022&partnerID=40&md5=11db558adad867e55fcfae7ed9625c95","This paper presents new methods for an automated analysis of the double InterTropical Convergence Zone (dITCZ) phenomena on a daily time scale over the east Pacific. Long-term Geostationary Operational Environmental Satellite (GOES) visible and infrared data are used to spatially identify and segment the convection zones over the east Pacific basin on both sides of the equator and to track the temporal variability of the ITCZ, specifically to identify cases of dITCZs, northern or southern ITCZ, or non-presence events. For the segmentation approach, image processing techniques are developed to extract information about the spatial features of the ITCZ in both hemispheres for each satellite image. These features serve as input to a temporal classification algorithm that is based on a combination of hidden semi Markov model (HsMM) and support vector machine (SVM) methods. The performance of the proposed method is competitive with human experts and the methodology can thus be used to conduct an in-depth analysis of the dITCZ. Such an analysis could provide precise information for refining existing weather and climate models over the sparsely observed east Pacific where the dITCZ is greatly over-represented in most models. © 2012 Elsevier Inc."
"30267891500;30267501800;35178259500;7403872687;7401526171;7005052907;","Assessing the impacts of different WRF precipitation physics in hurricane simulations",2012,"10.1175/WAF-D-10-05000.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868315987&doi=10.1175%2fWAF-D-10-05000.1&partnerID=40&md5=621246d541538de12efb23bf9fb59b15","Numerical weather prediction models play a major role in weather forecasting, especially in cases of extreme events. The Weather Research and Forecasting Model (WRF), among others, is extensively used for both research and practical applications. Previous studies have highlighted the sensitivity of this model to microphysics and cumulus schemes. This study investigated the performance of the WRF in forecasting precipitation, hurricane track, and landfall time using various microphysics and cumulus schemes. A total of 20 combinations of microphysics and cumulus schemes were used, and the model outputs were validated against ground-based observations. While the choice of microphysics and cumulus schemes can significantly impact model output, it is not the case that any single combination can be considered ""ideal""for modeling all characteristics of a hurricane, including precipitation amount, areal extent, hurricane track, and the time of landfall. For example, the model's ability to simulate precipitation (with the least total bias) is best achieved using Betts-Miller-Janjić (BMJ) cumulus parameterization in combination with the WRF single-moment five-class microphysics scheme (WSM5). It was determined that the WSM5-BMJ, WSM3 (the three-class version of theWSMscheme)-BMJ, and Ferrier microphysics in combination with the Grell-Devenyi cumulus scheme were the best combinations for simulation of the landfall time. However, the hurricane track was best estimated using the Lin et al. and Kessler microphysics options withBMJ cumulus parameterization. Contrary to previous studies, these results indicated that the use of cumulus schemes improves model outputs when the grid size is smaller than 10 km. However, it was found that many of the differences between parameterization schemes may be well within the uncertainty of the measurements. © 2012 American Meteorological Society."
"56332041000;57189939159;57212230854;57208455536;","Satellite passive microwave detection of North America start of season",2012,"10.1016/j.rse.2012.03.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860312600&doi=10.1016%2fj.rse.2012.03.025&partnerID=40&md5=f13fae659fde291144aa1b066d5a5a03","The start of season (SOS) phenological metric indicates the seasonal onset of vegetation activity, including canopy growth, photosynthesis and associated increases in land-atmosphere water, energy and carbon (CO 2) exchanges influencing weather and climate variability. Satellite optical-infrared (IR) remote sensing is responsive to vegetation greenness and SOS, but measurement accuracy and global monitoring are constrained by atmosphere cloud/aerosol contamination and seasonal decreases in solar illumination for many areas. The vegetation optical depth (VOD) parameter from satellite passive microwave remote sensing provides an alternative means for global phenology monitoring that is sensitive to vegetation canopy biomass and water content, and insensitive to atmosphere and solar illumination constraints. A global VOD record from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) was used to estimate North America SOS patterns and annual variability at the ecoregion scale. The SOS metrics were derived for a four year (2004-2007) record using TIMESAT and AMSR-E 10.7GHz frequency VOD retrievals composited to 4-day median time series. The VOD SOS corresponded favorably with MODIS-for-NACP NDVI (0.73&lt;R&lt;0.81; p&lt;0.01) and LAI (0.66&lt;R&lt;0.89; p&lt;0.01) greenup dates, and stand level SOS estimates derived from flux tower gross primary production (r 2=0.61, p&lt;0.01) and ecosystem respiration (r 2=0.44, p&lt;0.01) estimates. The VOD SOS was temporally offset from MODIS greenup and tower SOS metrics by up to 4-7weeks (RMSE) and the offset patterns coincided with the primary climate constraints (temperature and water) to vegetation growth. The VOD SOS generally preceded greenup in cold temperature constrained ecoregions and followed greenup in warmer, water limited ecoregions, with delays increasing for areas with greater woody vegetation cover. The AMSR-E VOD record captures canopy biomass changes independent of NDVI greenness or LAI measures, providing new and complementary phenological information for regional carbon, water and energy cycle studies. © 2012 Elsevier Inc."
"36637539100;9244992800;","Tropical cold-point tropopause: Climatology, seasonal cycle, and intraseasonal variability derived from COSMIC GPS radio occultation measurements",2012,"10.1175/JCLI-D-11-00554.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865105776&doi=10.1175%2fJCLI-D-11-00554.1&partnerID=40&md5=9e23bead1de1f98644609eb7dfc36648","The finescale structure of the tropical cold-point tropopause (CPT) is examined using high-resolution temperature profiles derived from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) global positioning system (GPS) radio occultation measurements for 4 yr from September 2006 to August 2010. The climatology, seasonal cycle, and intraseasonal variability are analyzed for three CPT properties: temperature (T-CPT), pressure (P-CPT), and sharpness (S-CPT). Their relationships with tropospheric and stratospheric processes are also discussed. The climatological P-CPT is largely homogeneous in the deep tropics, whereas T-CPT and S-CPT exhibit local minima and maxima, respectively, at the equator in the vicinity of deep convection regions. All three CPT properties, however, show coherent seasonal cycle in the tropics; the CPT is colder, higher (lower in pressure), and sharper during boreal winter than during boreal summer. This seasonality is consistent with the seasonal cycle of tropical upwelling, which is largely driven by stratospheric and near-tropopause processes, although the amplitude of the seasonal cycle of T-CPT and S-CPT is modulated by tropospheric circulations. On intraseasonal time scales, P-CPT and T-CPT exhibit homogeneous variability in the deep tropics, whereas S-CPT shows pronounced local variability and seasonality. The wavenumber-frequency spectra reveal that intraseasonal variability of CPT properties is primarily controlled by Kelvin waves, with a nonnegligible contribution by Madden-Julian oscillation convection. The Kelvin waves, which are excited by deep convection but often propagate along the equator freely, explain the homogeneous P-CPT and T-CPT variabilities. On the other hand, the vertically tilted dipole of temperature anomalies, which is associated with convectively coupled equatorial waves, determines the local structure and seasonality of S-CPT variability. © 2012 American Meteorological Society."
"13403535300;57201565440;57207275546;22940608900;57217355793;35201640900;57199987338;","Anomalous temperature-growth response of Abies faxoniana to sustained freezing stress along elevational gradients in China's Western Sichuan Province",2012,"10.1007/s00468-012-0712-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864366915&doi=10.1007%2fs00468-012-0712-9&partnerID=40&md5=e3bfebae33d2d8008591cc446a3efb4b","A network of ten Faxon fir tree-ring width chronologies was constructed from sites ranging in elevation from 3,000 to 3,450 m in the Wolong Natural Reserve in Western Sichuan Province, China. The site chronologies display significant inter-site correlations (mean R = 0. 647, p < 0. 001) and the first principal component (PC1) accounts for 68. 32 % of the total variation of the chronologies, implying a high degree of similarity in growth variation among the elevation gradients. Correlation analysis using monthly climate data indicates that the radial growth response of Faxon fir along the elevation gradients is markedly similar to common climatic signals, such as sunshine duration (positive) and cloud cover (negative), from January to March. Thus, it appears that winter freezing stress, which is caused by low solar radiation and high cloudiness, is the major environmental factor regulating the growth of trees across the elevational gradients. In addition, the site chronologies have no elevation-dependent growth responses to temperature or precipitation. Irrespective of the elevational differences of the sample sites, an anomalous reduction in radial growth occurred consistently since the 1960s, diverging from the instrumental temperature records since the 1990s. The cause of this divergence may be ascribed to the recent accelerated winter freezing stress and its role in controlling radial growth. © 2012 Springer-Verlag."
"23065650200;6603133549;","Satellite retrieval of the liquid water fraction in tropical clouds between -20 and -38 °c",2012,"10.5194/amt-5-1683-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864240193&doi=10.5194%2famt-5-1683-2012&partnerID=40&md5=58ae9be14151868ca793ea7a3baaa0d3","This study describes a satellite remote sensing method for directly retrieving the liquid water fraction in mixed phase clouds, and appears unique in this respect. The method uses MODIS split-window channels for retrieving the liquid fraction from cold clouds where the liquid water fraction is less than 50% of the total condensate. This makes use of the observation that clouds only containing ice exhibit effective 12-to-11 μm absorption optical thickness ratios (β eff) that are quasi-constant with retrieved cloud temperature T. This observation was made possible by using two CO2 channels to retrieve T and then using the 12 and 11 μm channels to retrieve emissivities and β eff. Thus for T -40 °C, β eff is constant, but for T -40 °C, β eff slowly increases due to the presence of liquid water, revealing mean liquid fractions of ∼ 10% around -22 °C from tropical clouds identified as cirrus by the cloud mask. However, the uncertainties for these retrievals are large, and extensive in situ measurements are needed to refine and validate these retrievals. Such liquid levels are shown to reduce the cloud effective diameter De such that cloud optical thickness will increase by more than 50% for a given water path, relative to De corresponding to pure ice clouds. Such retrieval information is needed for validation of the cloud microphysics in climate models. Since low levels of liquid water can dominate cloud optical properties, tropical clouds between -25 and -20 °C may be susceptible to the first aerosol indirect effect. © Author(s) 2012."
"55319858000;7103101744;","Potential CO 2 mitigation in digital ecosystems",2012,"10.1109/DEST.2012.6227916","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864232566&doi=10.1109%2fDEST.2012.6227916&partnerID=40&md5=c46cc789d3aa796d0645a71c9faafb9a","Carbon dioxide is one of the main greenhouse gases (GHS) that is widely blamed for climate change. Reducing greenhouse gas emissions is becoming one of the most challenging global issues. Increase in the concentration of carbon dioxide (CO 2) in the atmosphere is primarily attributed to fossil fuel burning. There is a need for better planning of the electricity generation capacity expansion to meet the power demand, which powers the Internet's routers and data centres, as well as to achieve an overall reduction in CO 2 emissions. The data centres, networking, cloud computing resources should reduce their carbon footprint in order to have a positive impact for the cloud computing service providers and the customers. We try to develop a linear programming model to evaluate the effectiveness of possible CO 2 mitigation for the brown energy (non-renewable energy) in the Internet. © 2012 IEEE."
"6603412788;8653276300;35997064100;37016832400;7402345338;22134634600;10739772300;53871956100;7004250217;9249656500;13404531500;55320961800;7006642995;7404450233;8918407000;7004507076;57211224269;","A new global climate model of the Meteorological Research Institute: MRI-CGCM3: -Model description and basic performance-",2012,"10.2151/jmsj.2012-A02","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864247969&doi=10.2151%2fjmsj.2012-A02&partnerID=40&md5=c96b449c54c07029979a5824b9d46ccb","A new global climate model, MRI-CGCM3, has been developed at the Meteorological Research Institute (MRI). This model is an overall upgrade of MRI's former climate model MRI-CGCM2 series. MRI-CGCM3 is composed of atmosphere-land, aerosol, and ocean-ice models, and is a subset of the MRI's earth system model MRI-ESM1. Atmospheric component MRI-AGCM3 is interactively coupled with aerosol model to represent direct and indirect e{currency sign}ects of aerosols with a new cloud microphysics scheme. Basic experiments for pre-industrial control, historical and climate sensitivity are performed with MRI-CGCM3. In the pre-industrial control experiment, the model exhibits very stable behavior without climatic drifts, at least in the radiation budget, the temperature near the surface and the major indices of ocean circulations. The sea surface temperature (SST) drift is sufficiently small, while there is a 1 W m -2 heating imbalance at the surface. The model's climate sensitivity is estimated to be 2.11 K with Gregory's method. The transient climate response (TCR) to 1 % yr -1 increase of carbon dioxide (CO 2) concentration is 1.6 K with doubling of CO 2 concentration and 4.1 K with quadrupling of CO 2 concentration. The simulated present-day mean climate in the historical experiment is evaluated by comparison with observations, including reanalysis. The model reproduces the overall mean climate, including seasonal variation in various aspects in the atmosphere and the oceans. Variability in the simulated climate is also evaluated and is found to be realistic, including El Nin ̃o and Southern Oscillation and the Arctic and Antarctic oscillations. However, some important issues are identified. The simulated SST indicates generally cold bias in the Northern Hemisphere (NH) and warm bias in the Southern Hemisphere (SH), and the simulated sea ice expands excessively in the North Atlantic in winter. A double ITCZ also appears in the tropical Pacific, particularly in the austral summer. © 2012, Meteorological Society of Japan."
"6603370049;8507223000;57202396417;12647654300;36149741000;8612652300;36017183900;6505890285;55686667100;6504055943;55619302054;36842329100;7102857642;","The initialization of the MIROC climate models with hydrographic data assimilation for decadal prediction",2012,"10.2151/jmsj.2012-A14","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864259213&doi=10.2151%2fjmsj.2012-A14&partnerID=40&md5=a52caad6be8ef9c10f57ecf0ab68e019","This paper documents the procedure of ocean data assimilation that initializes the climate models MIROC3m, MIROC4h, and MIROC5 for decadal climate predictions following the CMIP5 protocol, and summarizes the performance of the climate models using this data assimilation. Only anomalies of observed ocean hydrographic data are assimilated using the incremental analysis update method in order to prevent model climate drifts during predictions. In the case of MIROC4h, which has an eddy-permitting ocean model, a spatial smoother is used in calculating analysis increments so that oceanic mesoscale eddies cannot be damped by observational constraints and that they are generated and decay physically in response to the assimilated background state. Globally, the decadal-scale variations of ocean temperatures in the assimilation runs are highly correlated with the observations. Variations of surface air temperature over oceans are also consistent with the observations, but this is not the case in some regions over continents. Atmospheric responses to the SST variations corresponding to the Pacific Decadal Oscillations and the Atlantic Multi-decadal Oscillation are better represented in MIROC4h and MIROC5 than in MIROC3m. The high resolution of MIROC4h and new cloud parameterizations in MIROC5 may contribute to this improvement. Root-mean-squared amplitudes of sea surface height variations associated with oceanic eddies (hereafter, eddy activity) are not suppressed undesirably in the MIROC4h assimilation run and these are comparable with those in the uninitialized runs. In the Kuroshio-Oyashio confluence zone, eddy activity is modulated on a decadal timescale. This modulation is reasonably represented in the assimilation run compared with the observations. In the hindcast experiments, significant decadal prediction skills are found for the North Atlantic, the subtropical North Pacific, and the Indian Ocean. The decadal climate predictions are expected to contribute to the IPCC AR5 and political decision-making for the coming decades. © 2012, Meteorological Society of Japan."
"9249605700;55320314000;7102490770;7404013996;","A regional-scale evaluation of changes in environmental stability for summertime afternoon precipitation under global warming from super-high-resolution GCM simulations: A study for the case in the kanto plain",2012,"10.2151/jmsj.2012-A10","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864216462&doi=10.2151%2fjmsj.2012-A10&partnerID=40&md5=17167d96799f53b8ef67031cab2c8af4","Understanding and forecasting of summertime afternoon precipitation due to rapidly developing cumulonimbus clouds without any significant synoptic-scale influences are important to prevent and mitigate the induced disasters. Future changes in the behavior of such precipitation events have recently gained scientific and societal interests. This study investigates the environmental stability for afternoon precipitation that develops under synoptically undisturbed conditions in summer by using the outputs of 20-km-mesh, super-high-resolution atmospheric general circulation model (GCM) simulations for a present, a near-future, and a future climate under global warming with the Intergovernmental Panel on Climate Change A1B emission scenario. The Kanto Plain was chosen as the analysis area. After verifying the usefulness of the GCM present-climate outputs with observations and gridded mesoscale analyses, we examine the future changes in the environmental stability for the afternoon precipitation by conducting statistical analyses. In the future climates, temperature lapse rate decreased in the lower troposphere, while water vapor mixing ratio increased throughout the deep troposphere. The changes in the temperature and moisture profiles resulted in the increase in both precipitable water vapor and convective available potential energy. These projected changes will be enhanced with the future period. Furthermore, the statistical analyses for the di{currency sign}erences of the stability parameters between no-rain and rain days under the synoptically undisturbed condition in each simulated climate period indicated that the representations of the stability parameters that distinguish no-rain and rain events are basically unchanged between the present and the future climates. This result suggests that the environmental characteristics favorable for afternoon precipitation in the synoptically undisturbed environments will not change under global warming. © 2012, Meteorological Society of Japan."
"36149741000;8612652300;36842329100;8507223000;6603370049;10241250100;57201565982;7201724034;36017183900;55619302054;26531444800;10240710000;14628012000;57202396417;6504055943;8979277400;7003967390;7102857642;","MIROC4h-A new high-resolution atmosphere-ocean coupled general circulation model",2012,"10.2151/jmsj.2012-301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864256365&doi=10.2151%2fjmsj.2012-301&partnerID=40&md5=0abce921fcca3dbf4a07675ed5889bd7","A new high-resolution atmosphere-ocean coupled general circulation model named MIROC4h has been developed, and its performance in a 120-year control experiment (including a 50-year spin-up) under the present conditions (the year 1950) is examined. The results of the control experiment by MIROC4h are compared with simulations of preindustrial conditions carried out for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) using the previous high- and medium-resolution versions of the model, called MIROC3h and MIROC3m, respectively. A major change in MIROC4h is a doubling of the resolution of the atmospheric component to 0.5625°, compared to 1.125° for MIROC3h. The oceanic components of MIROC4h and MIROC3h are eddy-permitting, with a horizontal resolution of 0.28125° (zonal) × 0.1875° (meridional). In MIROC3m, the horizontal resolution is 2.8125° for the atmospheric component and 1.40625° (zonal) × 0.56°-1.4° (meridional) for the ocean component. Compared with MIROC3h and MIROC3m, many improvements have been achieved; for example, errors in the surface air temperature and sea surface temperature are smaller, there is less drift of the ocean water temperature in the subsurface-deep ocean, and the frequency of heavy rain is comparable to observations. The fine horizontal resolution in the atmosphere makes orographic wind and its effects on the ocean more realistic than those of the former models, and the treatment of coastal upwelling motion in the ocean has been improved. Phenomena in the atmosphere and ocean related to the El Niño and southern oscillation are now closer to observations than was obtained by MIROC3h and MIROC3m. The effective climate sensitivity for CO 2 doubling is calculated to be about 5.7 K, which is much larger than the value obtained using the IPCC AR4 models, and is mainly due to a decrease in the low-level clouds at low latitudes. © 2012, Meteorological Society of Japan."
"7402786837;57208121852;6602600408;7006689276;","Aerosol indirect effects from shipping emissions: Sensitivity studies with the global aerosol-climate model ECHAM-HAM",2012,"10.5194/acp-12-5985-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864227470&doi=10.5194%2facp-12-5985-2012&partnerID=40&md5=6d1879e0761718c794f6eeefc891981f","In this study, we employ the global aerosol-climate model ECHAM-HAM to globally assess aerosol indirect effects (AIEs) resulting from shipping emissions of aerosols and aerosol precursor gases. We implement shipping emissions of sulphur dioxide (SO2), black carbon (BC) and particulate organic matter (POM) for the year 2000 into the model and quantify the model's sensitivity towards uncertainties associated with the emission parameterisation as well as with the shipping emissions themselves. Sensitivity experiments are designed to investigate (i) the uncertainty in the size distribution of emitted particles, (ii) the uncertainty associated with the total amount of emissions, and (iii) the impact of reducing carbonaceous emissions from ships. <br><br> We use the results from one sensitivity experiment for a detailed discussion of shipping-induced changes in the global aerosol system as well as the resulting impact on cloud properties. From all sensitivity experiments, we find AIEs from shipping emissions to range from ĝ̂'0.32 0.01 W mĝ'2 to ĝ'0.07 ± 0.01 W mĝ̂'2 (global mean value and inter-annual variability as a standard deviation). The magnitude of the AIEs depends much more on the assumed emission size distribution and subsequent aerosol microphysical interactions than on the magnitude of the emissions themselves. It is important to note that although the strongest estimate of AIEs from shipping emissions in this study is relatively large, still much larger estimates have been reported in the literature before on the basis of modelling studies. We find that omitting just carbonaceous particle emissions from ships favours new particle formation in the boundary layer. These newly formed particles contribute just about as much to the CCN budget as the carbonaceous particles would, leaving the globally averaged AIEs nearly unaltered compared to a simulation including carbonaceous particle emissions from ships."
"52464731300;7401936984;57206546845;57197705845;6507460574;7402064802;6508300972;6602963031;35388721500;","Regional assessment of the parameter-dependent performance of CAM4 in simulating tropical clouds",2012,"10.1029/2012GL052184","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864479965&doi=10.1029%2f2012GL052184&partnerID=40&md5=3bff9d8951ca12f08eb6be169d92ef70","Representation of clouds remains among the largest uncertainties in climate models and thus climate projections. Clouds vary significantly over different climate regimes and are controlled by different dynamics and physics. Using the cloud simulator output from perturbed-parameter ensemble climate runs with prescribed monthly sea surface temperature, this study examines the performance of the Community Atmosphere Model version 4 (CAM4) in simulating clouds over different tropical regions. Perturbing 28 selected parameters shows that model performance is quite sensitive to parameter values in different cloud regimes. Carefully adjusting these parameters could lead to a better simulation of clouds over many regions compared with the default model. Latin hypercube runs that pseudo-randomly sample the 28 parameters simultaneously have much wider spread and more spatial variations than the runs with parameters varied One-At-a-Time (OAT), suggesting the importance of non-linearities and interactions among parameters associated with different physical processes. The perturbed parameters have a relatively large impact on the mean bias compared to the pattern error. © 2012. American Geophysical Union."
"55463815300;36169932000;7403361959;","Effect of internal mixture on black carbon radiative forcing",2012,"10.3402/tellusb.v64i0.10925","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862755328&doi=10.3402%2ftellusb.v64i0.10925&partnerID=40&md5=e4b84d40fdf3c058873b6245da7c6b6d","The effects of coating on black carbon (BC) optical properties and global climate forcing are revisited with more realistic approaches. We use the Generalized Multiparticle Mie method along with a realistic size range of monomers and clusters to compute the optical properties of uncoated BC clusters. Mie scattering is used to compute the optical properties of BC coated by scattering material. When integrated over the size distribution, we find the coating to increase BC absorption by up to a factor of 1.9 (1.8-2.1). We also find the coating can significantly increase or decrease BC backscattering depending on shell size and how shell material would be distributed if BC is uncoated. The effect of coating on BC forcing is computed by the Monte-Carlo Aerosol Cloud Radiation model with observed clouds and realistic BC spatial distributions. If we assume all the BC particles to be coated, the coating increases global BC forcing by a factor of 1.4 from the 1.9×absorption increase alone. Conversely, the coating can decrease the forcing by up to 60% or increase it by up to 40% by only the BC backscattering changes. Thus, the combined effects generally, but not necessarily, amplify BC forcing. © 2012 C. E. Chung et al."
"36344435200;7005539346;","Stained glass and climate change: How are they connected?",2012,"10.1080/07055900.2012.667387","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863823359&doi=10.1080%2f07055900.2012.667387&partnerID=40&md5=d78e39c63d4a75a2bd81fe21ca596a2e","As expressions of regional architecture, sacred (Christian)Gothic structures often possess several adaptations to their prevailing climate regime. The latemedieval (Gothic) period in northernEurope is also, according to the evidence presented here, marked by a transition fromwarmand sunny to cooler and cloudier conditions. It iswithin the context of this climate change that we consider one of the most important features in Gothic churches - interior daylighting - during the transitional period (the thirteenth to the end of the fifteenth centuries) between the Medieval WarmPeriod(MWP) and the Little Ice Age (LIA). This paper seeks to determine whether increasingly cloudy conditions over northern continental Europe, in part due to a shift inNorth Atlantic Oscillation (NAO) phase,may have influenced the use of more white glass in the fourteenth century. To the best of our knowledge, this is the first time an extensive daylighting dataset has been collected in medieval sacred interiors. From an analysis of these illuminance and luminance data collected in European churches and cathedrals, we find that high-translucency glazing is associated with limited lighting gains compared to full-colour programs under sunny conditions but substantial lighting improvements (up to an order of magnitude) for cloudy conditions. Additionally, we find that backlighting from direct sunlight produces significant obscuration of some of the iconographical glass when interiors are dominated by high-translucency glazing, further suggesting that these interiors are not ideal for sunny conditions."
"35585284200;57203766520;","Development of a climate record of tropospheric and stratospheric column ozone from satellite remote sensing: Evidence of an early recovery of global stratospheric ozone",2012,"10.5194/acp-12-5737-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863462982&doi=10.5194%2facp-12-5737-2012&partnerID=40&md5=4954fcfbad076de47affafc614e1bba8","Ozone data beginning October 2004 from the Aura Ozone Monitoring Instrument (OMI) and Aura Microwave Limb Sounder (MLS) are used to evaluate the accuracy of the Cloud Slicing technique in effort to develop long data records of tropospheric and stratospheric ozone and for studying their long-term changes. Using this technique, we have produced a 32-yr (1979-2010) long record of tropospheric and stratospheric column ozone from the combined Total Ozone Mapping Spectrometer (TOMS) and OMI. Analyses of these time series suggest that the quasi-biennial oscillation (QBO) is the dominant source of inter-annual variability of stratospheric ozone and is clearest in the Southern Hemisphere during the Aura time record with related inter-annual changes of 30-40 Dobson Units. Tropospheric ozone for the long record also indicates a QBO signal in the tropics with peak-to-peak changes varying from 2 to 7 DU. The most important result from our study is that global stratospheric ozone indicates signature of a recovery occurring with ozone abundance now approaching the levels of year 1980 and earlier. The negative trends in stratospheric ozone in both hemispheres during the first 15 yr of the record are now positive over the last 15 yr and with nearly equal magnitudes. This turnaround in stratospheric ozone loss is occurring about 20 yr earlier than predicted by many chemistry climate models. This suggests that the Montreal Protocol which was first signed in 1987 as an international agreement to reduce ozone destroying substances is working well and perhaps better than anticipated. © 2012 Author(s)."
"56965949500;7202516876;35232818000;55258950300;56384666800;","A closure study of cloud condensation nuclei in the North China Plain using droplet kinetic condensational growth model",2012,"10.5194/acp-12-5399-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863210480&doi=10.5194%2facp-12-5399-2012&partnerID=40&md5=3fa38f6bd37430c7aa00c1a37777c1e8","Aerosol size distribution and cloud condensation nucleus (CCN) number concentration were measured in the North China Plain from 31 December 2009 to 20 January 2010. The CCN closure study was performed using these data and droplet kinetic condensational growth model. The calculated CCN concentration with the assumption of pure ammonium sulfate aerosol is 40-140% higher than that observed for the supersaturations in this study. A sensitivity test on aerosol solubility and mixing state indicates that 0.2-0.5 mass fraction of ammonium sulfate for internal mixture can lead to a ratio of 0.82-1.30 for the calculated to observed CCN concentrations, and that 0.4-0.7 mass fraction of ammonium sulfate for external mixture results in a ratio of 0.74-1.25 in the North China Plain during the time period of the field observations, suggesting that a relatively simple scheme may be used for CCN prediction in climate models for this region. Finally, we compare the calculated CCN concentrations from the kinetic condensational growth model and the equilibrium model. The kinetic condensational growth model can simulate droplet growth in a time period under a certain supersaturation, while the equilibrium model only predicts whether a certain aerosol can be activated as CCN under that supersaturation. The CCN concentration calculated with the kinetic model is higher than that with the equilibrium model at supersaturations of 0.056% and 0.083%, because some particles that are not activated from the equilibrium point-of-view can grow large enough to be considered as CCN in the kinetic model. While at a supersaturation of 0.17%, CCN concentration calculated with the kinetic model is lower than that with the equilibrium model, due to the limitation of droplet kinetic growth. The calculated CCN concentrations using the kinetic model and the equilibrium model are the same at supersaturations of 0.35% and 0.70%. © 2012 Author(s)."
"55274133500;6701597468;7004714030;24766067800;","Radiative forcing estimates of sulfate aerosol in coupled climate-chemistry models with emphasis on the role of the temporal variability",2012,"10.5194/acp-12-5583-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863195593&doi=10.5194%2facp-12-5583-2012&partnerID=40&md5=73162bafa39bc8c7a5c19bd8448f36ff","This paper describes the impact on the sulfate aerosol radiative effects of coupling the radiative code of a global circulation model with a chemistry-aerosol module. With this coupling, temporal variations of sulfate aerosol concentrations influence the estimate of aerosol radiative impacts. Effects of this coupling have been assessed on net fluxes, radiative forcing and temperature for the direct and first indirect effects of sulfate. The direct effect respond almost linearly to rapid changes in concentrations whereas the first indirect effect shows a strong non-linearity. In particular, sulfate temporal variability causes a modification of the short wave net fluxes at the top of the atmosphere of +0.24 and +0.22 W m -2 for the present and preindustrial periods, respectively. This change is small compared to the value of the net flux at the top of the atmosphere (about 240 W m -2). The effect is more important in regions with low-level clouds and intermediate sulfate aerosol concentrations (from 0.1 to 0.8μg (SO 4) m -3 in our model). The computation of the aerosol direct radiative forcing is quite straightforward and the temporal variability has little effect on its mean value. In contrast, quantifying the first indirect radiative forcing requires tackling technical issues first. We show that the preindustrial sulfate concentrations have to be calculated with the same meteorological trajectory used for computing the present ones. If this condition is not satisfied, it introduces an error on the estimation of the first indirect radiative forcing. Solutions are proposed to assess radiative forcing properly. In the reference method, the coupling between chemistry and climate results in a global average increase of 8% in the first indirect radiative forcing. This change reaches 50% in the most sensitive regions. However, the reference method is not suited to run long climate simulations. We present other methods that are simpler to implement in a coupled chemistry/climate model and that offer the possibility to assess radiative forcing. © 2012 Author(s)."
"11339401400;55965624000;55732558900;7102604282;7005219614;","New representation of water activity based on a single solute specific constant to parameterize the hygroscopic growth of aerosols in atmospheric models",2012,"10.5194/acp-12-5429-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863203844&doi=10.5194%2facp-12-5429-2012&partnerID=40&md5=e72d9cc88b7fca44be4ebb798dd29dfb","Water activity is a key factor in aerosol thermodynamics and hygroscopic growth. We introduce a new representation of water activity (a w), which is empirically related to the solute molality (μs) through a single solute specific constant, ν i. Our approach is widely applicable, considers the Kelvin effect and covers ideal solutions at high relative humidity (RH), including cloud condensation nuclei (CCN) activation. It also encompasses concentrated solutions with high ionic strength at low RH such as the relative humidity of deliquescence (RHD). The constant νi can thus be used to parameterize the aerosol hygroscopic growth over a wide range of particle sizes, from nanometer nucleation mode to micrometer coarse mode particles. In contrast to other a w-representations, our ν i factor corrects the solute molality both linearly and in exponent form x • a x. We present four representations of our basic a w-parameterization at different levels of complexity for different a w-ranges, e.g. up to 0.95, 0.98 or 1. ν i is constant over the selected a w-range, and in its most comprehensive form, the parameterization describes the entire a w range (0-1). In this work we focus on single solute solutions. ν i can be pre-determined with a root-finding method from our water activity representation using an a wμs data pair, e.g. at solute saturation using RHD and solubility measurements. Our a w and supersaturation (Köhler-theory) results compare well with the thermodynamic reference model E-AIM for the key compounds NaCl and (NH 4) 2SO 4 relevant for CCN modeling and calibration studies. Envisaged applications include regional and global atmospheric chemistry and climate modeling. © 2012 Author(s)."
"7004400879;16480716500;8684670500;6507001590;7003819791;57205863270;57192094610;","Tree-ring responses in Araucaria araucana to two major eruptions of Lonquimay Volcano (Chile)",2012,"10.1007/s00468-012-0749-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869195200&doi=10.1007%2fs00468-012-0749-9&partnerID=40&md5=a6ed72920125d411e5aa841152320306","Palaeoclimate proxies have demonstrated links between climate changes and volcanic activity. However, not much is known about the impact of volcanic eruptions on forest productivity. Here we used tree-ring width and annually resolved carbon and oxygen isotopic records from tree rings of Araucaria araucana (Molina) K. Koch, providing a centennial-scale reconstruction of tree ecophysiological processes in forest stands nearby the Lonquimay Volcano (Chile). We observed a mean decrease in tree-ring width following the major eruption of 1988-1990 (with aerosol emission), most probably caused by the modified ecological conditions due to acid rain and ash deposition, while a generally negative relationship between δ13C and δ18O would point to a decline in humidity and precipitation. More negative δ13C and lower δ18O values (positive correlation) following the major eruption of 1887-1890 (without aerosol emission) would suggest high stomatal conductance and moisture availability, though tree-ring width (and probably photosynthetic rate) was unaltered. At least for this sample of trees, in the case of eruption with large tephra emission, the beneficial effect of aerosol light scattering on tree productivity appears to be outweighed by the detrimental effect of eruption-induced toxic deposition. Signals of the two major eruptions of the past 200 years at Lonquimay were present in tree rings of nearby A. araucana. No unique response of tree functions to volcanic eruptions can be expected, but rather (1) the variable volcanic properties and (2) the complex interplay of diffuse light increase (aerosol scattering), air temperature decrease (cloud shading), and toxic deposition impact (volcanic ash), makes any prediction of tree growth and ecophysiological response very challenging. © 2012 Springer-Verlag."
"57193132723;","Representing the Sensitivity of Convective Cloud Systems to Tropospheric Humidity in General Circulation Models",2012,"10.1007/s10712-011-9148-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862694881&doi=10.1007%2fs10712-011-9148-9&partnerID=40&md5=ce7fb793d067a81392e75e433f231100","Convective cloud variability on many times scales can be viewed as having three major components: a suppressed phase of shallow and congestus clouds, a disturbed phase of deep convective clouds, and a mature phase of transition to stratiform upper-level clouds. Cumulus parameterization development has focused primarily on the second phase until recently. Consequently, many parameterizations are not sufficiently sensitive to variations in tropospheric humidity. This shortcoming may affect global climate model simulations of climate sensitivity to external forcings, the continental diurnal cycle of clouds and precipitation, and intraseasonal precipitation variability. The lack of sensitivity can be traced in part to underestimated entrainment of environmental air into rising convective clouds and insufficient evaporation of rain into the environment. As a result, the parameterizations produce deep convection too easily while stabilizing the environment too quickly to allow the effects of convective mesoscale organization to occur. Recent versions of some models have increased their sensitivity to tropospheric humidity and improved some aspects of their variability, but a parameterization of mesoscale organization is still absent from most models. Evidence about the effect of these uncertainties on climate change projections suggests that climate modelers should make improved simulation of high and convective clouds as high a priority as better representations of low clouds. © 2011 The Author(s)."
"12769875100;","The Role of Clouds: An Introduction and Rapporteur Report",2012,"10.1007/s10712-012-9182-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862668973&doi=10.1007%2fs10712-012-9182-2&partnerID=40&md5=124ff0d440120d2c7c758b9e3beed101","This paper presents an overview of discussions during the Cloud's Role session at the Observing and Modelling Earth's Energy FlowsWorkshop. N. Loeb and B. Soden convened this session including 10 presentations by B. Stevens, B. Wielicki, G. Stephens, A. Clement, K. Sassen, D. Hartmann, T. Andrews, A. Del Genio, H. Barker, and M. Sugi addressing critical aspects of the role of clouds in modulating Earth energy flows. Presentation topics covered a diverse range of areas from cloud microphysics and dynamics, cloud radiative transfer, and the role of clouds in large-scale atmospheric circulations patterns in both observations and atmospheric models. The presentations and discussions, summarized below, are organized around several key questions raised during the session. (1) What is the best way to evaluate clouds in climate models? (2) How well do models need to represent clouds to be acceptable for making climate predictions? (3) What are the largest uncertainties in clouds? (4) How can these uncertainties be reduced? (5) What new observations are needed to address these problems? Answers to these critical questions are the topics of ongoing research and will guide the future direction of this area of research. © 2012 The Author(s)."
"12801836100;6603631763;","Implementation of the daytime cloud optical and microphysical properties algorithm (DCOMP) in PATMOS-x",2012,"10.1175/JAMC-D-11-0108.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864860675&doi=10.1175%2fJAMC-D-11-0108.1&partnerID=40&md5=10883b035badf9e9f25209217fffa650","This paper describes the daytime cloud optical and microphysical properties (DCOMP) retrieval for the Pathfinder Atmosphere's Extended (PATMOS-x) climate dataset. Within PATMOS-x, DCOMP is applied to observations from the Advanced Very High Resolution Radiometer and employs the standard bispectral approach to estimate cloud optical depth and particle size. The retrievals are performed within the optimal estimation framework. Atmospheric-correction and forward-model parameters, such as surface albedo and gaseous absorber amounts, are obtained from numerical weather prediction reanalysis data and other climate datasets. DCOMP is set up to run on sensors with similar channel settings and has been successfully exercised on most current meteorological imagers. This quality makes DCOMP particularly valuable for climate research. Comparisons with the Moderate Resolution Imaging Spectroradiometer (MODIS) collection-5 dataset are used to estimate the performance of DCOMP. © 2012 American Meteorological Society."
"7403318365;55339475000;","Cloud simulations in response to turbulence parameterizations in the GISS model E GCM",2012,"10.1175/JCLI-D-11-00399.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865109405&doi=10.1175%2fJCLI-D-11-00399.1&partnerID=40&md5=be55d95964e9c6ba633cd12892a7fdc2","The response of cloud simulations to turbulence parameterizations is studied systematically using the GISS general circulation model (GCM) E2 employed in the Intergovernmental Panel on Climate Change's (IPCC) FifthAssessment Report (AR5).Without the turbulence parameterization, the relative humidity (RH) and the low cloud cover peak unrealistically close to the surface; with the dry convection or with only the local turbulence parameterization, these two quantities improve their vertical structures, but the vertical transport of water vapor is still weak in the planetary boundary layers (PBLs); with both local and nonlocal turbulence parameterizations, the RH and low cloud cover have better vertical structures in all latitudes due to more significant vertical transport of water vapor in the PBL. The study also compares the cloud and radiation climatologies obtained from an experiment using a newer version of turbulence parameterization being developed at GISS with those obtained from the AR5 version. This newer scheme differs from the AR5 version in computing nonlocal transports, turbulent length scale, and PBL height and shows significant improvements in cloud and radiation simulations, especially over the subtropical eastern oceans and the southern oceans. The diagnosed PBL heights appear to correlate well with the low cloud distribution over oceans. This suggests that a cloudproducing scheme needs to be constructed in a framework that also takes the turbulence into consideration."
"55340272500;15757708600;55340333300;55339773100;","Exploring perturbed physics ensembles in a regional climate model",2012,"10.1175/JCLI-D-11-00275.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865170933&doi=10.1175%2fJCLI-D-11-00275.1&partnerID=40&md5=98c5438608594cb7d92728b6b494383f","Perturbed physics ensembles (PPEs) have been widely used to assess climate model uncertainties and have provided new estimates of climate sensitivity and parametric uncertainty in state-of-the-art climate models. So far, mainly global climate models were used to generate PPEs, and little work has been conducted with regional climate models. This paper discusses the parameter uncertainty in two PPEs of a regional climate model driven by reanalysis data for the present climate over Europe. The uncertainty is evaluated for the variables of 2-m temperature, precipitation, and total cloud cover, with a focus on the annual cycle, interannual variability, and selected extremes. The authors show that the simulated spread of the PPEs encompasses the observations at a regional scale in terms of the annual cycle and the interannual variability, provided observational uncertainty is taken into account. To rank the PPEs a new skill metric is proposed, which takes into account observational uncertainty and natural variability. The metric is a generalization of the climate prediction index (CPI) and is compared to metrics used in other studies. The consideration of observational uncertainty is particularly important for total cloud cover and reveals that current observations do not allow for a systematic evaluation of high precipitation intensities over the entire European domain. The skill framework is additionally used to identify important model parameters, which are of interest for an objective model calibration. © 2012 American Meteorological Society."
"12801992200;","Aerosol Forcing: Rapporteur's Report and Summary",2012,"10.1007/s10712-011-9160-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862682317&doi=10.1007%2fs10712-011-9160-0&partnerID=40&md5=9d6fece99f718687a931f90897023ded","This paper summarizes the discussions held during the session dedicated to Aerosol forcing at the Workshop Observing and Modelling Earth's Energy Flows. The session Aerosol forcing was convened by P. Ingmann and J. Heintzenberg and included 10 presentations given by R. Kahn, D. Winker, U. Baltensperger, J. Haywood, S. Schwartz, J. Heintzenberg, H. Le Treut, U. Lohmann, R. Wood, and E. Philipona. The presentations given ranged from overviews of current observational capabilities to analyses of aerosol-cloud interactions in observations and models of varying complexity. This paper is organized around a few key points, summarizing the major points of agreement, disagreement, and discussion that the presentations gave rise to. The focus is largely on the uncertainties that remain with regard to aerosol forcing, particularly related to aerosol-cloud interactions and indirect aerosol effects on climate. © 2011 Springer Science+Business Media B.V."
"35221791100;55887849100;7202158002;","A decade of the moderate resolution imaging spectroradiometer: Is a solar-cloud link detectable?",2012,"10.1175/JCLI-D-11-00306.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865167626&doi=10.1175%2fJCLI-D-11-00306.1&partnerID=40&md5=2db127d32d4e0009045682eaed3d6c52","Based on the results of decadal correlation studies between the International Satellite Cloud Climatology Project-detected cloud anomalies and the galactic cosmic ray (GCR) flux, it has been suggested that a re- lationship exists between solar activity and cloud cover. If valid, such a relationship could have important implications for scientists' understanding of recent climate change. In this work, an analysis of the first decade of Moderate Resolution Imaging Spectroradiometer (MODIS)-detected cloud anomalies are presented, and the data at global and local geographical resolutions to total solar irradiance (TSI), GCR variations, and the multivariate El Niño-Southern Oscillation index are compared. The study identifies no statistically significant correlations between cloud anomalies and TSI/GCR variations, and concludes that solar-related variability is not a primary driver of monthly to annual MODIS cloud variability. The authors observe a net increase in cloud detected by MODIS over the past decade of ;0.58%, arising from a combination of a reduction in high- to midlevel cloud (20.31%) and an increase in low-level cloud (0.89%); these long-term changes may be largely attributed to ENSO-induced cloud variability. © 2012 American Meteorological Society."
"7202733689;7003543851;23082420800;","Diagnosing Climate Feedbacks in Coupled Ocean-Atmosphere Models",2012,"10.1007/s10712-012-9187-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862662745&doi=10.1007%2fs10712-012-9187-x&partnerID=40&md5=8367081ce2f300aacad0edfe2ee645af","We review the methodologies used to quantify climate feedbacks in coupled models. The method of radiative kernels is outlined and used to illustrate the dependence of lapse rate, water vapor, surface albedo, and cloud feedbacks on (1) the length of the time average used to define two projected climate states and (2) the time separation between the two climate states. Except for the shortwave component of water vapor feedback, all feedback processes exhibit significant high-frequency variations and intermodel variability of feedback strengths for sub-decadal time averages. It is also found that the uncertainty of lapse rate, water vapor, and cloud feedback decreases with the increase in the time separation. The results suggest that one can substantially reduce the uncertainty of cloud and other feedbacks with the accumulation of accurate, long-term records of satellite observations; however, several decades may be required. © 2012 Springer Science+Business Media B.V."
"14045744500;","Prognostic-cloud-scheme increment diagnostics: A novel addition to the case-study tool kit",2012,"10.1002/asl.380","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864069032&doi=10.1002%2fasl.380&partnerID=40&md5=21f1f14ef5ccae850318cc34a399fb37","Cloud increment diagnostics, from a simulation of present-day climate using a prognostic cloud scheme and from a case-study of a mid-latitude system, are used to highlight the variation in parametrized processes contributing to the creation and removal of cloud in the model. The diagnostics show that the initialization of the cloud fields away from cloud fractions of zero and one is a significant contribution to their evolution, drawing attention to the importance of the assumptions made when calculating those increments and highlighting a part of the cloud scheme where future development should be focused. © 2012 British Crown the Met Office. Published by John Wiley & Sons Ltd."
"9235235300;24529241300;13405658600;8871497700;7006593624;35461255500;7004596535;","The contribution of organics to atmospheric nanoparticle growth",2012,"10.1038/ngeo1499","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863326035&doi=10.1038%2fngeo1499&partnerID=40&md5=96f89f084bb4304c673ae24abda35f10","Aerosols have a strong, yet poorly quantified, effect on climate. The growth of the smallest atmospheric particles from diameters in the nanometre range to sizes at which they may act as seeds for cloud droplets is a key step linking aerosols to clouds and climate. In many environments, atmospheric nanoparticles grow by taking up organic compounds that are derived from biogenic hydrocarbon emissions. Several mechanisms may control this uptake. Condensation of low-volatility vapours and formation of organic salts probably dominate the very first steps of growth in particles close to 1 nm in diameter. As the particles grow further, formation of organic polymers and effects related to the phase of the particle probably become increasingly important. We suggest that dependence of particle growth mechanisms on particle size needs to be investigated more systematically. © 2012 Macmillan Publishers Limited. All rights reserved."
"7004893330;6701718281;6505932008;","Observational analysis of cloud and precipitation in midlatitude cyclones: Northern versus Southern hemisphere warm fronts",2012,"10.1175/JCLI-D-11-00569.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865145301&doi=10.1175%2fJCLI-D-11-00569.1&partnerID=40&md5=138643dd28c01fa1b3b7a66e13a7719a","Extratropical cyclones are responsible for most of the precipitation and wind damage in the midlatitudes during the cold season, but there are still uncertainties on how they will change in a warming climate. A ubiquitous problem among general circulation models (GCMs) is a lack of cloudiness over the southern oceans that may be in part caused by a lack of clouds in cyclones. This study analyzes CloudSat, Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) observations for three austral and boreal cold seasons, and composites cloud frequency of occurrence and precipitation at the warm fronts for Northern and Southern Hemisphere oceanic cyclones. The authors find that cloud frequency of occurrence and precipitation rate are similar in the early stage of the cyclone life cycle in both the Northern and Southern Hemispheres. As cyclones evolve and reach their mature stage, cloudiness and precipitation at the warm front increase in the Northern Hemisphere but decrease in the Southern Hemisphere. This is partly caused by lower amounts of precipitable water being available to Southern Hemisphere cyclones, and smaller increases in wind speed as the cyclones evolve. Southern Hemisphere cloud occurrence at the warm front is found to be more sensitive to the amount of moisture in the warm sector than to wind speeds. This suggests that cloudiness in Southern Hemisphere storms may be more susceptible to changes in atmospheric water vapor content, and thus to changes in surface temperature than their Northern Hemisphere counterparts. These differences between Northern and Southern Hemisphere cyclones are statistically robust, indicating A-Train-based analyses as useful tools for the evaluation of GCMs in the next Intergovernmental Panel on Climate Change (IPCC) report. © 2012 American Meteorological Society."
"57205867148;57208765879;7101677832;6701618837;35220400000;","Reconciling simulated and observed views of clouds: MODIS, ISCCP, and the limits of instrument simulators",2012,"10.1175/JCLI-D-11-00267.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862727533&doi=10.1175%2fJCLI-D-11-00267.1&partnerID=40&md5=8ea62308d47239883ed980f88aebbb5f","The properties of clouds that may be observed by satellite instruments, such as optical thickness and cloud-top pressure, are only loosely related to the way clouds are represented in models of the atmosphere. One way to bridge this gap is through ""instrument simulators,"" diagnostic tools that map the model representation to synthetic observations so that differences can be interpreted as model error. But simulators may themselves be restricted by limited information or by internal assumptions. This paper considers the extent to which instrument simulators are able to capture essential differences between the Moderate Resolution Imaging Spectroradiometer (MODIS) and the International Satellite Cloud Climatology Project (ISCCP), two similar but independent estimates of cloud properties. The authors review the measurements and algorithms underlying these two cloud climatologies, introduce a MODIS simulator, and detail datasets developed for comparison with global models using ISCCP and MODIS simulators. In nature MODIS observes less midlevel cloudiness than ISCCP, consistent with the different methods used to determine cloud-top pressure; aspects of this difference are reproduced by the simulators. Differences in observed distributions of optical thickness, however, are not captured. The largest differences can be traced to different approaches to partly cloudy pixels, which MODIS excludes and ISCCP treats as homogeneous. These cover roughly 15% of the planet and account for most of the optically thinnest clouds. Instrument simulators cannot reproduce these differences because there is no way to synthesize partly cloudy pixels. Nonetheless, MODIS and ISCCP observations are consistent for all but the optically thinnest clouds, and models can be robustly evaluated using instrument simulators by integrating over the robust subset of observations. © 2012 American Meteorological Society."
"35546736600;57202245193;7801566289;7006406683;16637291100;7005027331;","A satellite-derived climate-quality data record of the clear-sky surface temperature of the greenland ice sheet",2012,"10.1175/JCLI-D-11-00365.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865127867&doi=10.1175%2fJCLI-D-11-00365.1&partnerID=40&md5=4bae7fcf1832effc4c8c8063a87c436b","The authors have developed a climate-quality data record of the clear-sky surface temperature of the Greenland Ice Sheet using the Moderate-Resolution Imaging Spectroradiometer (MODIS) ice-surface temperature (IST) algorithm. Daily and monthly quality-controlled MODIS ISTs of the Greenland Ice Sheet beginning on 1 March 2000 and continuing through 31 December 2010 are presented at 6.25-km spatial resolution on a polar stereographic grid along with metadata to permit detailed accuracy assessment. The ultimate goal is to develop a climate data record (CDR) that starts in 1981 with the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder (APP) dataset and continues with MODIS data from 2000 to the present, and into the Visible Infrared Imager Radiometer Suite (VIIRS) era (the first VIIRS instrument was launched in October 2011). Differences in the APP and MODIS cloud masks have thus far precluded merging the APP and MODIS IST records, though this will be revisited after the APP dataset has been reprocessed with an improved cloud mask. IST of Greenland may be used to study temperature and melt trends and may also be used in data assimilation modeling and to calculate ice sheet mass balance. The MODIS IST climate-quality dataset provides a highly consistent and well-characterized record suitable for merging with earlier and future IST data records for climate studies. The complete MODIS IST daily and monthly data record is available online."
"55339081600;6602600408;","Evaluation of clouds and precipitation in the ECHAM5 general circulation model using CALIPSO and cloudsat satellite data",2012,"10.1175/JCLI-D-11-00347.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864242359&doi=10.1175%2fJCLI-D-11-00347.1&partnerID=40&md5=b20004d4197177ed5327d0610d69d582","Observations from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and CloudSat satellites are used to evaluate clouds and precipitation in the ECHAM5 general circulation model. Active lidar and radar instruments on board CALIPSO and CloudSat allow the vertical distribution of clouds and their optical properties to be studied on a global scale. To evaluate the clouds modeled by ECHAM5with CALIPSO and CloudSat, the lidar and radar satellite simulators of the Cloud Feedback Model Intercomparison Project's Observation Simulator Package are used. Comparison of ECHAM5 with CALIPSO and CloudSat found large-scale features resolved by the model, such as the Hadley circulation, are captured well. The lidar simulator demonstrated ECHAM5 overestimates the amount of high-level clouds, particularly optically thin clouds. High-altitude clouds in ECHAM5 consistently produced greater lidar scattering ratios compared with CALIPSO. Consequently, the lidar signal in ECHAM5 frequently attenuated high in the atmosphere. The large scattering ratios were due to an underestimation of effective ice crystal radii in ECHAM5. Doubling the effective ice crystal radii improved the scattering ratios and frequency of attenuation. Additionally, doubling the effective ice crystal radii improved the detection of ECHAM5's highest-level clouds by the radar simulator, in better agreement with CloudSat. ECHAM5 was also shown to significantly underestimate midlevel clouds and (sub)tropical low-level clouds. The low-level clouds produced were consistently perceived by the lidar simulator as too optically thick. The radar simulator demonstrated ECHAM5 overestimates the frequency of precipitation, yet underestimates its intensity compared with CloudSat observations. These findings imply compensating mechanisms inECHAM5 balance out the radiative imbalance caused by incorrect optical properties of clouds and consistently large hydrometeors in the atmosphere. © 2012 American Meteorological Society."
"16426140700;55915206300;8380252900;7404369915;","The Impact of Subscale Inhomogeneity on Oxygen A Band Cloud-Top Pressure Estimates: Using ESA's MERIS as a Proxy for DSCOVR-EPIC",2012,"10.3390/rs4071963","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864971715&doi=10.3390%2frs4071963&partnerID=40&md5=c5ce4e0296b3e8787fa88b178acea973","Medium Spectral Resolution Imaging Spectrometer (MERIS) oxygen A band measurements were used as a proxy for the Earth Polychromatic Imaging Camera (EPIC), to be launched on NASA's Deep Space Climate Observatory (DSCOVR). The high spatial resolution of MERIS (1 × 1 km 2) is exploited to study the effects of subscale spatial heterogeneity of clouds on the cloud-top pressure retrieved at the coarser spatial resolution of EPIC (10 × 10 km 2). In general, for a sub-scale cloud fraction less than 1, a shift of cloud-top pressure toward the middle atmosphere is found, with a low-bias for high clouds and a high-bias for low clouds. In addition, the deviation is found to be a function of surface reflectance. The subscale variability of fully clouded EPIC pixels causes a weak underestimation of cloud-top pressure, when compared to averaged high-resolution retrievals. © 2012 by the authors."
"7003663939;7004201700;6601970557;36342537900;7004210200;7401945370;16029674800;7202954964;41262568500;8255473900;35361704100;57192221583;36457546600;7403681584;36836680100;6602934046;","Simulating the diurnal cycle of rainfall in global climate models: Resolution versus parameterization",2012,"10.1007/s00382-011-1127-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863008896&doi=10.1007%2fs00382-011-1127-9&partnerID=40&md5=a722f013c21d17a4d0b968dd26943f9b","The effects of horizontal resolution and the treatment of convection on simulation of the diurnal cycle of precipitation during boreal summer are analyzed in several innovative weather and climate model integrations. The simulations include: season-long integrations of the Non-hydrostatic Icosahedral Atmospheric Model (NICAM) with explicit clouds and convection; year-long integrations of the operational Integrated Forecast System (IFS) from the European Centre for Medium-range Weather Forecasts at three resolutions (125, 39 and 16 km); seasonal simulations of the same model at 10 km resolution; and seasonal simulations of the National Center for Atmospheric Research (NCAR) low-resolution climate model with and without an embedded two-dimensional cloud-resolving model in each grid box. NICAM with explicit convection simulates best the phase of the diurnal cycle, as well as many regional features such as rainfall triggered by advancing sea breezes or high topography. However, NICAM greatly overestimates mean rainfall and the magnitude of the diurnal cycle. Introduction of an embedded cloud model within the NCAR model significantly improves global statistics of the seasonal mean and diurnal cycle of rainfall, as well as many regional features. However, errors often remain larger than for the other higher-resolution models. Increasing resolution alone has little impact on the timing of daily rainfall in IFS with parameterized convection, yet the amplitude of the diurnal cycle does improve along with the representation of mean rainfall. Variations during the day in atmospheric prognostic fields appear quite similar among models, suggesting that the distinctive treatments of model physics account for the differences in representing the diurnal cycle of precipitation. © 2011 The Author(s)."
"8846887600;6602729528;","The vertical distribution of climate forcings and feedbacks from the surface to top of atmosphere",2012,"10.1007/s00382-011-1233-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864394230&doi=10.1007%2fs00382-011-1233-8&partnerID=40&md5=f07ad469b712dd8e0d34bf62be03cacb","The radiative forcings and feedbacks that determine Earth's climate sensitivity are typically defined at the top-of-atmosphere (TOA) or tropopause, yet climate sensitivity itself refers to a change in temperature at the surface. In this paper, we describe how TOA radiative perturbations translate into surface temperature changes. It is shown using first principles that radiation changes at the TOA can be equated with the change in energy stored by the oceans and land surface. This ocean and land heat uptake in turn involves an adjustment of the surface radiative and non-radiative energy fluxes, with the latter being comprised of the turbulent exchange of latent and sensible heat between the surface and atmosphere. We employ the radiative kernel technique to decompose TOA radiative feedbacks in the IPCC Fourth Assessment Report climate models into components associated with changes in radiative heating of the atmosphere and of the surface. (We consider the equilibrium response of atmosphere-mixed layer ocean models subjected to an instantaneous doubling of atmospheric CO2). It is shown that most feedbacks, i. e., the temperature, water vapor and cloud feedbacks, (as well as CO2 forcing) affect primarily the turbulent energy exchange at the surface rather than the radiative energy exchange. Specifically, the temperature feedback increases the surface turbulent (radiative) energy loss by 2.87 W m-2 K-1 (0.60 W m-2 K-1) in the multimodel mean; the water vapor feedback decreases the surface turbulent energy loss by 1.07 W m-2 K-1 and increases the surface radiative heating by 0.89 W m-2 K-1; and the cloud feedback decreases both the turbulent energy loss and the radiative heating at the surface by 0.43 and 0.24 W m-2 K-1, respectively. Since changes to the surface turbulent energy exchange are dominated in the global mean sense by changes in surface evaporation, these results serve to highlight the fundamental importance of the global water cycle to Earth's climate sensitivity. © 2011 Springer-Verlag."
"7201504886;55207447000;","Observing and Modeling Earth's Energy Flows",2012,"10.1007/s10712-012-9184-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862654768&doi=10.1007%2fs10712-012-9184-0&partnerID=40&md5=7a22acd8a807e6c7be669ff7ea6b0501","This article reviews, from the authors' perspective, progress in observing and modeling energy flows in Earth's climate system. Emphasis is placed on the state of understanding of Earth's energy flows and their susceptibility to perturbations, with particular emphasis on the roles of clouds and aerosols. More accurate measurements of the total solar irradiance and the rate of change of ocean enthalpy help constrain individual components of the energy budget at the top of the atmosphere to within ±2 W m -2. The measurements demonstrate that Earth reflects substantially less solar radiation and emits more terrestrial radiation than was believed even a decade ago. Active remote sensing is helping to constrain the surface energy budget, but new estimates of downwelling surface irradiance that benefit from such methods are proving difficult to reconcile with existing precipitation climatologies. Overall, the energy budget at the surface is much more uncertain than at the top of the atmosphere. A decade of high-precision measurements of the energy budget at the top of the atmosphere is providing new opportunities to track Earth's energy flows on timescales ranging from days to years, and at very high spatial resolution. The measurements show that the principal limitation in the estimate of secular trends now lies in the natural variability of the Earth system itself. The forcing-feedback-response framework, which has developed to understand how changes in Earth's energy flows affect surface temperature, is reviewed in light of recent work that shows fast responses (adjustments) of the system are central to the definition of the effective forcing that results from a change in atmospheric composition. In many cases, the adjustment, rather than the characterization of the compositional perturbation (associated, for instance, with changing greenhouse gas concentrations, or aerosol burdens), limits accurate determination of the radiative forcing. Changes in clouds contribute importantly to this adjustment and thus contribute both to uncertainty in estimates of radiative forcing and to uncertainty in the response. Models are indispensable to calculation of the adjustment of the system to a compositional change but are known to be flawed in their representation of clouds. Advances in tracking Earth's energy flows and compositional changes on daily through decadal timescales are shown to provide both a critical and constructive framework for advancing model development and evaluation. © 2012 The Author(s)."
"7102731541;","Changes in Earth's Energy Flows and Clouds in 228-Year Simulation with a High-Resolution AGCM",2012,"10.1007/s10712-012-9183-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862694612&doi=10.1007%2fs10712-012-9183-1&partnerID=40&md5=ca1ac52bb8c0412ec6f3bd9935b1103d","We have examined long-term changes in Earth's energy flows at top of the atmosphere (TOA) and at Earth's surface (land and ocean) by using 228-year simulation of a high-resolution global atmosphere model, MRI-AGCM3. 2. It is found that the net downward short wave (SW) radiation (absorbed solar radiation, ASR) at TOA significantly increases during twenty-first century in agreement with a previous study. However, in the present study, the reason for the change is an increase in clear sky SW absorption by increased water vapor in the atmosphere, while it is a decrease in cloud amount in the previous study. It is also found that the long wave (LW) cloud radiative forcing for atmosphere is positive and increasing during twenty-first century in agreement with a previous study. The reason for the change in the present study is an increase in absorption by water vapor of the downward LW radiation emitted from clouds, while it is reductions of cloud amount in the middle troposphere in the previous study. © 2012 The Author(s)."
"7006263720;7005167347;","Improving the diurnal cycle of convection in GCMs",2012,"10.1002/qj.991","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864282107&doi=10.1002%2fqj.991&partnerID=40&md5=d9f857e0a7285f23d1fc3b27984cef36","The Met Office single-column model is used to examine the development phase of the diurnal cycle of tropical convection over land by comparing against previous results from an idealized cloud-resolving model study. Changing the deep convective parametrization over land to make the entrainment vary with the height of the lifting condensation level reduces the depth of the convection early in the day. The changes made to improve the early phase of diurnal cycle over land are tested in an atmosphere-only version of the Met Office Hadley Centre climate model and result in an improvement in the amplitude and timing of the diurnal peak in precipitation over land. © 2011."
"7101631674;","Solar Influence on Global and Regional Climates",2012,"10.1007/s10712-012-9181-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862658694&doi=10.1007%2fs10712-012-9181-3&partnerID=40&md5=c2d6a16b84d580cc71bcdd9fd47e9817","The literature relevant to how solar variability influences climate is vast-but much has been based on inadequate statistics and non-robust procedures. The common pitfalls are outlined in this review. The best estimates of the solar influence on the global mean air surface temperature show relatively small effects, compared with the response to anthropogenic changes (and broadly in line with their respective radiative forcings). However, the situation is more interesting when one looks at regional and season variations around the global means. In particular, recent research indicates that winters in Eurasia may have some dependence on the Sun, with more cold winters occurring when the solar activity is low. Advances in modelling ""top-down"" mechanisms, whereby stratospheric changes influence the underlying troposphere, offer promising explanations of the observed phenomena. In contrast, the suggested modulation of low-altitude clouds by galactic cosmic rays provides an increasingly inadequate explanation of observations. © 2012 The Author(s)."
"7006237834;7101857920;7005793077;","Geobiological constraints on Earth system sensitivity to CO 2 during the Cretaceous and Cenozoic",2012,"10.1111/j.1472-4669.2012.00320.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862211649&doi=10.1111%2fj.1472-4669.2012.00320.x&partnerID=40&md5=2ecc589e97c92101d0061140831720c5","Earth system climate sensitivity (ESS) is the long-term (&gt;10 3year) response of global surface temperature to doubled CO 2 that integrates fast and slow climate feedbacks. ESS has energy policy implications because global temperatures are not expected to decline appreciably for at least 10 3year, even if anthropogenic greenhouse gas emissions drop to zero. We report provisional ESS estimates of 3°C or higher for some of the Cretaceous and Cenozoic based on paleo-reconstructions of CO 2 and temperature. These estimates are generally higher than climate sensitivities simulated from global climate models for the same ancient periods (approximately 3°C). Climate models probably do not capture the full suite of positive climate feedbacks that amplify global temperatures during some globally warm periods, as well as other characteristic features of warm climates such as low meridional temperature gradients. These absent feedbacks may be related to clouds, trace greenhouse gases (GHGs), seasonal snow cover, and/or vegetation, especially in polar regions. Better characterization and quantification of these feedbacks is a priority given the current accumulation of atmospheric GHGs. © 2012 Blackwell Publishing Ltd."
"56703527900;7403931916;35468030800;7003266014;","Test of the fixed anvil temperature hypothesis",2012,"10.1175/JAS-D-11-0158.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864838504&doi=10.1175%2fJAS-D-11-0158.1&partnerID=40&md5=f989d7423a9ed7f3ee24feb56fc1fcc9","The fixed anvil temperature (FAT) hypothesis is examined based on the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS)-based cloud-top temperature (CTT) in conjunction with the tropical atmospheric profiles and sea surface temperature (SST) fromthe European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis. Consistent with the physical governing mechanism of the FAT hypothesis, the peak clear-sky diabatic subsidence and convergence profiles are located at roughly the same level (200 hPa) as the peak in the cloud profile, which is fundamentally determined by the rapid decrease of water vapor concentration above this level. The geographical maxima of cloud fraction agree well with those of water vapor, clear-sky cooling rates, and diabatic convergence at 200 hPa. The use of direct CTT measurements suggests the CTT in specific Pacific basins exhibit different characteristics as the frequency distribution of the tropical SST varies from boreal winter to summer. When averaging over the tropics as a whole, the CTT distributions are approximately unchanged primarily because of cancellation by the variations associated with individual regions. An analysis of the response of the tropical mean CTT anomaly time series to the SST indicates that a possible negative relationship is present, whereas the relationship tends to be positive over the tropical western Pacific and Indian Oceans. In addition, it is suggested to interpret the FAT hypothesis, and the more recent proportionately higher anvil temperature (PHAT) hypothesis, by using the temperature at the maximum cloud detrainment level instead of the CTT."
"7005516084;","Understanding and Measuring Earth's Energy Budget: From Fourier, Humboldt, and Tyndall to CERES and Beyond",2012,"10.1007/s10712-011-9162-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862690795&doi=10.1007%2fs10712-011-9162-y&partnerID=40&md5=6b07fde4d4899d5653154819971ecaf2","This historical perspective on the determination of Earth's energy fluxes, beginning with the classical description of climate, outlines the establishment of the basic physics of the Earth climate system in the nineteenth century. After recalling the early twentieth century ground-based attempts to determine the Earth's energy budget, I review the growing contributions of observations from space to quantifying these exchanges. In particular, space observations have shown that variations of solar luminosity have been extremely small (of order 0.1%) over past decades and probably past centuries and that they play practically no role in present-day climate variations or variations that may be expected in coming decades. Overall geographical structure, diurnal and seasonal cycles, and some of the interannual and interdecadal variations of Earth's energy exchanges with the Sun and space are now quite well determined, but much remains to be done regarding, on the one hand, fluxes at the surface and, on the other hand, variations of clouds. Improvements are essential if scientific assessment of anthropogenic climate change risk is to keep up with the changes themselves. © 2012 Springer Science+Business Media B.V."
"7402859325;36904222100;57215729754;7404864296;","Investigation of direct radiative effects of aerosols in dust storm season over East Asia with an online coupled regional climate-chemistry-aerosol model",2012,"10.1016/j.atmosenv.2012.01.041","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862827323&doi=10.1016%2fj.atmosenv.2012.01.041&partnerID=40&md5=a09dd5bd3edafb6a9c8fea9927f78594","A new online coupled regional climate-chemistry-aerosol model (RIEMS-Chemaero) has been developed and applied to investigate direct radiative effects of dust aerosol and mixed aerosols over East Asia in March 2010, when an extremely intense dust storm on 19-22 March swept across almost the entire east China including the Pearl River Delta of south China, where little dust storm was observed before. The model results are evaluated against ground observation of PM 10 concentration, aerosol optical depth (AOD) from both AERONET measurement and satellite retrieval (MODIS). The comparison demonstrates a good ability of RIEMS-Chemaero in reproducing major features of aerosol spatial distribution and temporal variation, as well as dust evolution during the dust storm period. However, the model tends to generally underpredict AOD at AERONET sites, with larger biases at urban sites than that at rural sites. Dust aerosols exerted a significant impact on radiation energy budget during the dust storm period, with the 4-day mean values of shortwave and longwave radiative forcings at the surface up to -90 W m -2 and +40 W m -2, respectively, over the Gobi desert. The monthly mean net dust radiative forcings at the surface ranged from -9 to -24 W m -2 over the dust source regions, and from -6 to -21 W m -2 over wide downwind areas including the middle and lower reaches of the Yellow River and the Yangtze River and the Yellow Sea. The net dust radiative forcing at TOA varied from near zero to +6.0 W m -2 in large areas of the continent. The monthly mean values of the net direct radiative forcings due to dust, non-dust aerosols and all aerosols (dust + sea salt + anthropogenic aerosols) averaged over the whole domain are estimated to be -3.9 W m -2, -5.6 W m -2 and -9.3 W m -2, respectively, at the surface, and to be +0.9 W m -2, -3.0 W m -2 and -2.0 W m -2, respectively, at TOA, indicating a light dust warming effect and an overall aerosol cooling effect in the springtime over East Asia. In east China, the net radiative forcings due to dust, non-dust aerosols and all aerosols at the surface are enhanced to -8.4 W m -2, -10.2 W m -2 and -18.0 W m -2, respectively, due to both the frequent dust influence and the intensive anthropogenic emissions in this region. The dust forcing accounts for about 42% of the total aerosol forcing at the surface in the domain, implying a potentially important role of mineral dust in radiation budget and regional climate. The semi-direct effect of dust aerosol tends to reduce cloud cover throughout the domain and it is partly responsible for the direct radiative forcings because of the feedbacks among aerosol, radiation, cloud and dynamics. © 2012 Elsevier Ltd."
"56013882400;6507027722;56013607400;23052226200;","Ecological niche modeling on the effect of climatic change and conservation of Ternstroemia lineata DC. (Ternstroemiaceae) in Mesoamerica",2012,"10.1139/B2012-019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863209295&doi=10.1139%2fB2012-019&partnerID=40&md5=2ec9f71a623dc22d99cfc6332e6102ba","A bioclimatic modeling of the tree Ternstroemia lineata DC. (Ternstroemiaceae) was undertaken. The genus itself is considered as diagnostic or characteristic of the Mexican cloud forest. Ternstroemia lineata has the broadest distribution of all species in this family in Mexico and northern Central America. This species consists of two subspecies, T. lineata subsp. lineata and T. lineata subsp. chalicophila (Loes.) B.M. Barthol. Ecological niche models for both subspecies were generated using the genetic algorithm for rule-set production method. The ecological models for the years 2020, 2050, and 2080 were obtained under the effects of global climatic change considering two emission scenarios (A2a and B2a). When climatic change values were introduced, the ecological niche representation for both subspecies contracted in such a way that they became almost lost throughout their entire geographical range. In both cases, predictions for all years in both scenarios contracted more than 90%. This species may not be able to adapt to modifications caused by climatic change to future conditions, so it is at risk of extinction in the immediate future."
"7004364155;56493740900;8891521600;7403531523;7102651635;6603546080;7401776640;8953038700;","Advances in Understanding Top-of-Atmosphere Radiation Variability from Satellite Observations",2012,"10.1007/s10712-012-9175-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862650504&doi=10.1007%2fs10712-012-9175-1&partnerID=40&md5=6400d0bf3114df3a0ade378a97dea74c","This paper highlights how the emerging record of satellite observations from the Earth Observation System (EOS) and A-Train constellation are advancing our ability to more completely document and understand the underlying processes associated with variations in the Earth's top-of-atmosphere (TOA) radiation budget. Large-scale TOA radiation changes during the past decade are observed to be within 0. 5 Wm -2 per decade based upon comparisons between Clouds and the Earth's Radiant Energy System (CERES) instruments aboard Terra and Aqua and other instruments. Tropical variations in emitted outgoing longwave (LW) radiation are found to closely track changes in the El Niño-Southern Oscillation (ENSO). During positive ENSO phase (El Niño), outgoing LW radiation increases, and decreases during the negative ENSO phase (La Niña). The coldest year during the last decade occurred in 2008, during which strong La Nina conditions persisted throughout most of the year. Atmospheric Infrared Sounder (AIRS) observations show that the lower temperatures extended throughout much of the troposphere for several months, resulting in a reduction in outgoing LW radiation and an increase in net incoming radiation. At the global scale, outgoing LW flux anomalies are partially compensated for by decreases in midlatitude cloud fraction and cloud height, as observed by Moderate Resolution Imaging Spectrometer and Multi-angle Imaging SpectroRadiometer, respectively. CERES data show that clouds have a net radiative warming influence during La Niña conditions and a net cooling influence during El Niño, but the magnitude of the anomalies varies greatly from one ENSO event to another. Regional cloud-radiation variations among several Terra and A-Train instruments show consistent patterns and exhibit marked fluctuations at monthly timescales in response to tropical atmosphere-ocean dynamical processes associated with ENSO and Madden-Julian Oscillation. © 2012 The Author(s)."
"26323963700;56276813400;6603335688;6603555567;8323981800;39961297800;","Changes in atmospheric circulation and the Arctic Oscillation preserved within a millennial length reconstruction of summer cloud cover from northern Fennoscandia",2012,"10.1007/s00382-011-1246-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862984857&doi=10.1007%2fs00382-011-1246-3&partnerID=40&md5=53744716aa5fab96d176e0864ba91c15","Cloud cover currently represents the single greatest source of uncertainty in General Circulation Models. Stable carbon isotope ratios (δ13C) from tree-rings, in areas of low moisture stress, are likely to be primarily controlled by photosynthetically active radiation (PAR), and therefore should provide a proxy record for cloud cover or sunshine; indeed this association has previously been demonstrated experimentally for Scots pine in Fennoscandia, with sunlight explaining ca 90% of the variance in photosynthesis and temperature only ca 4%. We present a statistically verifiable 1011-year reconstruction of cloud cover from a well replicated, annually-resolved δ13C record from Forfjord in coastal northwestern Norway. This reconstruction exhibits considerable variability in cloud cover over the past millennium, including extended sunny periods during the cool seventeenth and eighteenth centuries and warm cloudy periods during the eleventh, early fifteenth and twentieth centuries. We find that while a generally positive relationship persists between sunshine and temperature at high-frequency, at lower (multi-decadal) frequencies the relationship is more often a negative one, with cool periods being sunny (most notably the Little Ice Age period from 1600 to 1750 CE) and warm periods more cloudy (e. g. the mediaeval and the twentieth century). We conclude that these long-term changes may be caused by changes in the dominant circulation mode, likely to be associated with the Arctic Oscillation. There is also strong circumstantial evidence that prolonged periods of high summer cloud cover, with low PAR and probably high precipitation, may be in part responsible for major European famines caused by crop failures. © 2011 Springer-Verlag."
"55286185400;7005808242;57208455668;","Some counterintuitive dependencies of tropical cyclone frequency on parameters in a GCM",2012,"10.1175/JAS-D-11-0238.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864839450&doi=10.1175%2fJAS-D-11-0238.1&partnerID=40&md5=7ed36ecafff4fcdb3fc79afca7daab58","High-resolution global climate models (GCMs) have been increasingly utilized for simulations of the global number and distribution of tropical cyclones (TCs), and how they might change with changing climate. In contrast, there is a lack of published studies on the sensitivity of TC genesis to parameterized processes in these GCMs. The uncertainties in these formulations might be an important source of uncertainty in the future projections of TC statistics. This study investigates the sensitivity of the global number of TCs in present-day simulations using the Geophysical Fluid Dynamics Laboratory High Resolution Atmospheric Model (GFDL HIRAM) to alterations in physical parameterizations. Two parameters are identified to be important in TC genesis frequency in this model: the horizontal cumulus mixing rate, which controls the entrainment into convective cores within the convection parameterization, and the strength of the damping of the divergent component of the horizontal flow. The simulated global number of TCs exhibits nonintuitive response to incremental changes of both parameters. As the cumulus mixing rate increases, the model produces nonmonotonic response in global TC frequency with an initial sharp increase and then a decrease. However, storm mean intensity rises monotonically with the mixing rate. As the strength of the divergence damping increases, the model produces a continuous increase of global number of TCs and hurricanes with little change in storm mean intensity. Mechanisms for explaining these nonintuitive responses are discussed."
"55332029100;7101958466;7406368269;56991455900;6603796935;","Comparison of objective supercell identification techniques using an idealized cloud model",2012,"10.1175/MWR-D-11-00209.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864832693&doi=10.1175%2fMWR-D-11-00209.1&partnerID=40&md5=c2e2c815447620e0d3552107d33f64bd","The accuracy, reliability, and skill of several objective supercell identification methods are evaluated using 113 simulations from an idealized cloud model with 1-km horizontal grid spacing. Horizontal cross sections of vorticity and radar reflectivity at both mid- and low levels were analyzed for the presence of a supercell, every 5min of simulation time, to develop a ""truth"" database. Supercells were identified using well-known characteristics such as hook echoes, inflow notches, bounded weak-echo regions (BWERs), and the presence of significant vertical vorticity. The three objective supercell identification techniques compared were the Pearson correlation (PC) using an analysis window centered on the midlevel storm updraft; a modified Pearson correlation (MPC), which calculates the PC at every point in the horizontal using a small 3km 3 3km analysis window; and updraft helicity (UH). Results show that the UHmethod integrated from 2 to 5km AGL, and using a threshold value of 180 m2 s22, was equally as accurate as the MPC technique-averaged from 2 to 5km AGL and using a minimum updraft threshold of 7 m s21 with a detection threshold of 0.3-in discriminating between supercells and nonsupercells for 1-km horizontal grid spacing simulations. At courser resolutions, the UH technique performed best, while the MPC technique produced the largest threat scores for higher-resolution simulations. In addition, requiring that the supercell detection thresholds last at least 20min reduced the number of false alarms. © 2012 American Meteorological Society."
"25941200000;56493740900;7004768785;","Computation of Solar Radiative Fluxes by 1D and 3D Methods Using Cloudy Atmospheres Inferred from A-train Satellite Data",2012,"10.1007/s10712-011-9164-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862684516&doi=10.1007%2fs10712-011-9164-9&partnerID=40&md5=8fd98e610beb860ca3862e16f70524eb","This study used realistic representations of cloudy atmospheres to assess errors in solar flux estimates associated with 1D radiative transfer models. A scene construction algorithm, developed for the EarthCARE mission, was applied to CloudSat, CALIPSO and MODIS satellite data thus producing 3D cloudy atmospheres measuring 61 km wide by 14,000 km long at 1 km grid-spacing. Broadband solar fluxes and radiances were then computed by a Monte Carlo photon transfer model run in both full 3D and 1D independent column approximation modes. Results were averaged into 1,303 (50 km) 2 domains. For domains with total cloud fractions A c &lt; 0.7 top-of-atmosphere (TOA) albedos tend to be largest for 3D transfer with differences increasing with solar zenith angle. Differences are largest for A c &gt; 0. 7 and characterized by small bias yet large random errors. Regardless of A c, differences between 3D and 1D transfer rarely exceed ±30 W m -2 for net TOA and surface fluxes and ±10 W m -2 for atmospheric absorption. Horizontal fluxes through domain sides depend on A c with ~20% of cases exceeding ±30 W m -2; the largest values occur for A c &gt; 0.7. Conversely, heating rate differences rarely exceed ±20%. As a cursory test of TOA radiative closure, fluxes produced by the 3D model were averaged up to (20 km) 2 and compared to values measured by CERES. While relatively little attention was paid to optical properties of ice crystals and surfaces, and aerosols were neglected entirely, ~30% of the differences between 3D model estimates and measurements fall within ±10 W m -2; this is the target agreement set for EarthCARE. This, coupled with the aforementioned comparison between 3D and 1D transfer, leads to the recommendation that EarthCARE employ a 3D transport model when attempting TOA radiative closure. © 2011 The Author(s)."
"26643054400;24597874300;8986277400;9435289000;7005956491;23035720900;9248799600;","Reduction of black carbon aerosols in Tokyo: Comparison of real-time observations with emission estimates",2012,"10.1016/j.atmosenv.2012.02.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860635080&doi=10.1016%2fj.atmosenv.2012.02.003&partnerID=40&md5=0d79fb8249afd26c29b9f44331c449a2","Black carbon (BC) aerosols alter the radiation budget both directly (by absorbing solar visible radiation) and indirectly (by acting as cloud condensation nuclei) and cause adverse health effects. The absorbing efficiency and direct radiative effect of BC strongly depend on its mass concentration (M BC) and type of emission source. In the present study, we report measurements of M BC at the Research Center for Advanced Science and Technology (RCAST), located at the center of the urban boundary of Tokyo, using an EC-OC analyzer from 2003 to 2005 and a filter-based Continuous Soot Monitoring System (COSMOS) during 2007-2010. The results indicate that M BC have decreased significantly from 2.6 μg m -3 to 0.5 μg m -3 (∼80% reduction) between 2003 and 2010. Vehicular emissions are the dominant source of BC in Tokyo, and the observed reduction in M BC is mainly attributed to the stringent regulations of particulate matter exhaust from vehicles imposed by the Japanese government. In addition, this observation is also supported from emission estimates using diurnal-weekly variations of M BC in Tokyo and explains the observed reduction to within about 20%. This is the first clear evidence of a significant reduction in BC emissions in Tokyo and shows that measures taken to reduce BC emissions from traffic sources have a strong effect on air quality in a mega-city and also reduce the climate impact of traffic emissions. We highlight the importance of long-term and reliable measurements in detecting BC trends and for the validation and regulation of emission control measures in mega-cities. © 2012 Elsevier Ltd."
"55905970100;55317862000;55410418300;","Solar and thermal radiation profiles and radiative forcing measured through the atmosphere",2012,"10.1029/2012GL052087","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864026402&doi=10.1029%2f2012GL052087&partnerID=40&md5=575cb8a2dcd63d86f10a8af36cb61285","Solar shortwave and thermal longwave radiation at the Earth's surface and at the top of the atmosphere is commonly measured at surface stations, from airplanes and from satellites. Here we show radiative flux profiles measured with radiosondes ascending from the Earth's surface to 35km into the stratosphere. During two-hour flights solar shortwave and thermal longwave radiation are measured both downward and upward with four individual sensors. Daytime solar and thermal radiation is compared to nighttime measurements and 24-hour average radiation budget profiles are shown through the atmosphere. However, of even greater importance with regard to climate change are measured upward and downward longwave greenhouse radiation profiles. Their changes with temperature and water vapor enable direct measurement of radiative forcing through the atmosphere. Measurements during two cloud-free nights with different temperature and different water vapor amount, show an almost equal but opposite net longwave radiation change, or water vapor greenhouse forcing, downwards to the surface and upward into space. Radiative flux profiles clearly illustrate the Earth's atmospheric greenhouse effect, and allow important investigations of clouds and other atmospheric constituents and their effects on shortwave reflection, as well as longwave emission towards the surface and into space. © 2012. American Geophysical Union. All Rights Reserved."
"35435487400;7005446873;","Large-scale length and time-scales for use with stochastic convective parametrization",2012,"10.1002/qj.992","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864282046&doi=10.1002%2fqj.992&partnerID=40&md5=b23a6710d1dbdcbc9515e5ba77ecde06","Many numerical models for weather prediction and climate studies are run at resolutions that are too coarse to resolve convection explicitly, but too fine to justify the local equilibrium assumed by conventional convective parametrizations. The Plant-Craig (PC) stochastic convective parametrization scheme, developed in this paper, solves this problem by removing the assumption that a given grid-scale situation must always produce the same sub-grid-scale convective response. Instead, for each time step and grid point, one of the many possible convective responses consistent with the large-scale situation is randomly selected. The scheme requires as input the large-scale state as opposed to the instantaneous grid-scale state, but must nonetheless be able to account for genuine variations in the large-scale situation. Here we investigate the behaviour of the PC scheme in three-dimensional simulations of radiative-convective equilibrium, demonstrating in particular that the necessary space-time averaging required to produce a good representation of the input large-scale state is not in conflict with the requirement to capture large-scale variations. The resulting equilibrium profiles agree well with those obtained from established deterministic schemes, and with corresponding cloud-resolving model simulations. Unlike the conventional schemes, the statistics for mass flux and rainfall variability from the PC scheme also agree well with relevant theory and vary appropriately with spatial scale. The scheme is further shown to adapt automatically to changes in grid length and in forcing strength. © 2011 Royal Meteorological Society."
"57190658202;8285351400;7801685612;15725352400;","Heat balance and eddies in the Peru-Chile current system",2012,"10.1007/s00382-011-1170-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859886207&doi=10.1007%2fs00382-011-1170-6&partnerID=40&md5=b3cfef1692f038ce1efa6d96c578b8d3","The Peru-Chile current System (PCS) is a region of persistent biases in global climate models. It has strong coastal upwelling, alongshore boundary currents, and mesoscale eddies. These oceanic phenomena provide essential heat transport to maintain a cool oceanic surface underneath the prevalent atmospheric stratus cloud deck, through a combination of mean circulation and eddy flux. We demonstrate these behaviors in a regional, quasi-equilibrium oceanic model that adequately resolves the mesoscale eddies with climatological forcing. The key result is that the atmospheric heating is large (&gt;50 W m-2) over a substantial strip &gt;500 km wide off the coast of Peru, and the balancing lateral oceanic flux is much larger than provided by the offshore Ekman flux alone. The atmospheric heating is weaker and the coastally influenced strip is narrower off Chile, but again the Ekman flux is not sufficient for heat balance. The eddy contribution to the oceanic flux is substantial. Analysis of eddy properties shows strong surface temperature fronts and associated large vorticity, especially off Peru. Cyclonic eddies moderately dominate the surface layer, and anticyclonic eddies, originating from the nearshore poleward Peru-Chile Undercurrent (PCUC), dominate the subsurface, especially off Chile. The sensitivity of the PCS heat balance to equatorial intra-seasonal oscillations is found to be small. We demonstrate that forcing the regional model with a representative, coarse-resolution global reanalysis wind product has dramatic and deleterious consequences for the oceanic circulation and climate heat balance, the eddy heat flux in particular. © 2011 Springer-Verlag."
"57212988186;13404664500;7401945370;7202954964;","Quantitative assessment of diurnal variation of tropical convection simulated by a global nonhydrostatic model without cumulus parameterization",2012,"10.1175/JCLI-D-11-00295.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863493062&doi=10.1175%2fJCLI-D-11-00295.1&partnerID=40&md5=bc83cebad9423e16a9bda331f8011939","This study investigated the resolution dependence of diurnal variation in tropical convective systems represented by a global nonhydrostatic model without cumulus parameterization. This paper describes the detailed characteristics of diurnal variation in surface precipitation based on three-dimensional data, with the aim of explicitly clarifying the mechanism that underlies the variation. The study particularly focused on the evolution in the size of the precipitation area for deep convective systems with an analysis of the vertical structure of thermodynamic fields. This analysis compares the results of simulations with horizontal grid sizes of 14 and 7 km (R14 and R7, respectively). Over land, the phase delay of diurnal variations in R7 is about 3 h less than that in R14. R7 produces a pronounced diurnal variation in the size distributions of precipitating area(s), especially for areas with a radius of 0-100 km; this characteristic is not found for R14. Such areas actively evolve between noon and evening, leading to the smooth development of larger-scale precipitating areas having a radius of 100-150 km. Themaximumsurface precipitation in R7 over land occurs at around 2000 local time throughout the tropics, approximately 2 h prior to the development of nighttime deep convection. Deep convective regimes are important as agents of vertical heat transport in the tropics. The present results suggest that precipitating areas with a radius,100 km make a strong contribution to the total amount of precipitation and to mass transport. © 2012 American Meteorological Society."
"55315701500;6701643061;","Simulation of leader speeds at gigantic jet altitudes",2012,"10.1029/2012GL052251","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863894886&doi=10.1029%2f2012GL052251&partnerID=40&md5=f9fe669a1a7cbcdee0e102647a0fc7f1","Lightning leaders advance in space by creating a heating conversion zone in their tips (i.e., streamer-to-leader transition) in which Joule heating produced by currents of many non-thermal corona streamers transforms into a hot and conducting leader channel. It is believed that the initial stages of transient luminous events termed gigantic jets (GJs) propagating toward the lower ionosphere are directly related to leaders initiated by conventional intra-cloud lightning discharges and escaping upward from thundercloud tops. In the present work we provide quantitative description of speeds of these leaders as a function of leader current and ambient air density (altitude). The direct comparisons with available experimental data indicate that the initial speeds of GJs of ̃50 km/s are consistent with leaders possessing currents 2-8 A. The observed acceleration of GJs can be explained by growth of the leader current, and at high altitudes (low air densities) may be significantly affected by predominance of non-thermal (i.e., streamer) discharge forms. © 2012. American Geophysical Union."
"24485218400;7003278104;57204886915;55286185400;7006127310;7103366892;7103116704;55738957800;7501760109;6701346974;7102696626;56224155200;","Simulation of the intraseasonal variability over the Eastern Pacific ITCZ in climate models",2012,"10.1007/s00382-011-1098-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864383545&doi=10.1007%2fs00382-011-1098-x&partnerID=40&md5=ff227dc2f4da0444237ff17cee224ff8","During boreal summer, convective activity over the eastern Pacific (EPAC) inter-tropical convergence zone (ITCZ) exhibits vigorous intraseasonal variability (ISV). Previous observational studies identified two dominant ISV modes over the EPAC, i. e., a 40-day mode and a quasi-biweekly mode (QBM). The 40-day ISV mode is generally considered a local expression of the Madden-Julian Oscillation. However, in addition to the eastward propagation, northward propagation of the 40-day mode is also evident. The QBM mode bears a smaller spatial scale than the 40-day mode, and is largely characterized by northward propagation. While the ISV over the EPAC exerts significant influences on regional climate/weather systems, investigation of contemporary model capabilities in representing these ISV modes over the EPAC is limited. In this study, the model fidelity in representing these two dominant ISV modes over the EPAC is assessed by analyzing six atmospheric and three coupled general circulation models (GCMs), including one super-parameterized GCM (SPCAM) and one recently developed high-resolution GCM (GFDL HIRAM) with horizontal resolution of about 50 km. While it remains challenging for GCMs to faithfully represent these two ISV modes including their amplitude, evolution patterns, and periodicities, encouraging simulations are also noted. In general, SPCAM and HIRAM exhibit relatively superior skill in representing the two ISV modes over the EPAC. While the advantage of SPCAM is achieved through explicit representation of the cumulus process by the embedded 2-D cloud resolving models, the improved representation in HIRAM could be ascribed to the employment of a strongly entraining plume cumulus scheme, which inhibits the deep convection, and thus effectively enhances the stratiform rainfall. The sensitivity tests based on HIRAM also suggest that fine horizontal resolution could also be conducive to realistically capture the ISV over the EPAC, particularly for the QBM mode. Further analysis illustrates that the observed 40-day ISV mode over the EPAC is closely linked to the eastward propagating ISV signals from the Indian Ocean/Western Pacific, which is in agreement with the general impression that the 40-day ISV mode over the EPAC could be a local expression of the global Madden-Julian Oscillation (MJO). In contrast, the convective signals associated with the 40-day mode over the EPAC in most of the GCM simulations tend to originate between 150°E and 150°W, suggesting the 40-day ISV mode over the EPAC might be sustained without the forcing by the eastward propagating MJO. Further investigation is warranted towards improved understanding of the origin of the ISV over the EPAC. © 2011 Springer-Verlag."
"55214687200;57203078013;7101963685;55713316500;14623343800;23492820000;36193233200;6701578630;","Satellite-based evidence for shrub and graminoid tundra expansion in northern Quebec from 1986 to 2010",2012,"10.1111/j.1365-2486.2012.02708.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861858604&doi=10.1111%2fj.1365-2486.2012.02708.x&partnerID=40&md5=83b8777e3aca8791d915dadef84c328f","Global vegetation models predict rapid poleward migration of tundra and boreal forest vegetation in response to climate warming. Local plot and air-photo studies have documented recent changes in high-latitude vegetation composition and structure, consistent with warming trends. To bridge these two scales of inference, we analyzed a 24-year (1986-2010) Landsat time series in a latitudinal transect across the boreal forest-tundra biome boundary in northern Quebec province, Canada. This region has experienced rapid warming during both winter and summer months during the last 40 years. Using a per-pixel (30 m) trend analysis, 30% of the observable (cloud-free) land area experienced a significant (P &lt; 0.05) positive trend in the Normalized Difference Vegetation Index (NDVI). However, greening trends were not evenly split among cover types. Low shrub and graminoid tundra contributed preferentially to the greening trend, while forested areas were less likely to show significant trends in NDVI. These trends reflect increasing leaf area, rather than an increase in growing season length, because Landsat data were restricted to peak-summer conditions. The average NDVI trend (0.007 yr -1) corresponds to a leaf-area index (LAI) increase of ~0.6 based on the regional relationship between LAI and NDVI from the Moderate Resolution Spectroradiometer. Across the entire transect, the area-averaged LAI increase was ~0.2 during 1986-2010. A higher area-averaged LAI change (~0.3) within the shrub-tundra portion of the transect represents a 20-60% relative increase in LAI during the last two decades. Our Landsat-based analysis subdivides the overall high-latitude greening trend into changes in peak-summer greenness by cover type. Different responses within and among shrub, graminoid, and tree-dominated cover types in this study indicate important fine-scale heterogeneity in vegetation growth. Although our findings are consistent with community shifts in low-biomass vegetation types over multi-decadal time scales, the response in tundra and forest ecosystems to recent warming was not uniform. © 2012 Blackwell Publishing Ltd."
"25521967600;7005955015;12801746800;22950237000;6603400151;8061325100;","A 'hurricane-like' polar low fuelled by sensible heat flux: High-resolution numerical simulations",2012,"10.1002/qj.1876","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864279885&doi=10.1002%2fqj.1876&partnerID=40&md5=3b982b80d6380e28f68efa98caf6ff36","An unusually deep (961 hPa) hurricane-like polar low over the Barents Sea during 18-21 December 2002 is studied by a series of fine-mesh (3 km) experiments using the Weather Research and Forecasting (WRF) model. The simulated polar low was similar to hurricanes and similar previous case-studies in that it had a clear, calm and warm eye structure surrounded by moist convection organized in spiral cloud bands, and the highest surface wind speeds were found in the eye wall. The proximity to the sea ice and the high surface wind speeds (about 25 m s -1) during the deepening stage triggered extremely high surface sensible and latent heat fluxes at the eye wall of about 1200 and 400 W m -2, respectively. As the polar low moved eastward and weakened, maximum surface sensible and latent heat fluxes dropped to about 600 and 300 W m -2, respectively. Two types of sensitivity experiments were designed to analyse the physical properties of the polar low. Firstly, physical processes such as condensational heating and sensible and/or latent heat fluxes were switched off-on throughout the simulation. In the second type, these processes were turned off-on after the polar low had reached its peak intensity, which minimized the deformation of the polar-low environment, making it suitable to study the direct effect of physical processes on the mature vortex. The experiments suggest that the deepening stage of the polar low was dominated by baroclinic growth and that upper-level potential vorticity forcing contributed throughout its life cycle. After the deepening stage, the baroclinicity vanished and the polar low was fuelled by surface sensible heat fluxes while latent heat fluxes played a minor role. Condensational heating was not essential for the energetics of the polar low. Surprisingly, in experiments where condensational heating was turned off throughout the simulation, the polar low intensified. © 2012 Royal Meteorological Society."
"57202121637;6701559724;6701742258;","A statistical model for the urban heat island and its application to a climate change scenario",2012,"10.1002/joc.2348","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862649959&doi=10.1002%2fjoc.2348&partnerID=40&md5=c418c96e63b007464de56a12ea30d53e","A linear statistical model relating the nocturnal urban heat island (UHI) intensity of Hamburg with meteorological conditions is constructed from observations taken by the German Meteorological Service (DWD). To find the appropriate predictors the relationship between different meteorological variables and the UHI of Hamburg is analyzed. Results and physical plausibility suggest that cloud cover, wind speed and relative humidity are the relevant variables and can be used to construct a statistical model. The parameters for the statistical model are determined with the generalized least square method. With the help of the statistical model up to 42% of the UHI variance can be explained. The statistical model is then used to statistically downscale results from climate runs of the regional climate models (RCM) REMO and CLM. Both RCMs were driven with the A1B SRES emission scenario runs of the global climate model ECHAM5/MPI-OM. The resulting values for the future UHI are analyzed with respect to monthly averages and the frequency distribution. Results show that changes in the UHI are different for the different months. Significant change (decrease of UHI) in the results of both RCMs and for both realizations of the A1B scenario can be found for April in at the middle and the end of the century and in December at the end of the century. For the summer months which are most relevant to the development of adaption strategies the results differ between the RCMs. REMO results show no significant changes for the summer, while analyses of CLM suggest significant increase in July and August. The frequency distribution of the summer UHI shows no significant changes for REMO and only in one realization of CLM a significant increase in moderate and strong UHI days can be found for the end of the century. © 2011 Royal Meteorological Society."
"29867471100;6603383696;","Interfacing a one-dimensional lake model with a single-column atmospheric model: 2. Thermal response of the deep Lake Geneva, Switzerland under a 2 × CO2 global climate change",2012,"10.1029/2011WR011222","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862556863&doi=10.1029%2f2011WR011222&partnerID=40&md5=8151f473f70144faae42aa4d13f19201","In the companion to the present paper, the one-dimensional k-ε lake model SIMSTRAT is coupled to a single-column atmospheric model, nicknamed FIZC, and an application of the coupled model to the deep Lake Geneva, Switzerland, is described. In this paper, the response of Lake Geneva to global warming caused by an increase in atmospheric carbon dioxide concentration (i.e., 2 × CO2) is investigated. Coupling the models allowed for feedbacks between the lake surface and the atmosphere and produced changes in atmospheric moisture and cloud cover that further modified the downward radiation fluxes. The time evolution of atmospheric variables as well as those of the lake's thermal profile could be reproduced realistically by devising a set of adjustable parameters. In a ""control"" 1 × CO2 climate experiment, the coupled FIZC-SIMSTRAT model demonstrated genuine skills in reproducing epilimnetic and hypolimnetic temperatures, with annual mean errors and standard deviations of 0.25°C ± 0.25°C and 0.3°C ± 0.15°C, respectively. Doubling the CO2 concentration induced an atmospheric warming that impacted the lake's thermal structure, increasing the stability of the water column and extending the stratified period by 3 weeks. Epilimnetic temperatures were seen to increase by 2.6°C to 4.2°C, while hypolimnion temperatures increased by 2.2°C. Climate change modified components of the surface energy budget through changes mainly in air temperature, moisture, and cloud cover. During summer, reduced cloud cover resulted in an increase in the annual net solar radiation budget. A larger water vapor deficit at the air-water interface induced a cooling effect in the lake. © 2012 American Geophysical Union. All Rights Reserved."
"36816021800;7101800802;7005111709;","Uncertainties of parameterized surface downward clear-sky shortwave and all-sky longwave radiation",2012,"10.5194/acp-12-5077-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862141966&doi=10.5194%2facp-12-5077-2012&partnerID=40&md5=6e0497df484e489651d67e4764ea03a5","As many environmental models rely on simulating the energy balance at the Earth's surface based on parameterized radiative fluxes, knowledge of the inherent model uncertainties is important. In this study we evaluate one parameterization of clear-sky direct, diffuse and global shortwave downward radiation (SDR) and diverse parameterizations of clear-sky and all-sky longwave downward radiation (LDR). In a first step, SDR is estimated based on measured input variables and estimated atmospheric parameters for hourly time steps during the years 1996 to 2008. Model behaviour is validated using the high quality measurements of six Alpine Surface Radiation Budget (ASRB) stations in Switzerland covering different elevations, and measurements of the Swiss Alpine Climate Radiation Monitoring network (SACRaM) in Payerne. In a next step, twelve clear-sky LDR parameterizations are calibrated using the ASRB measurements. One of the best performing parameterizations is elected to estimate all-sky LDR, where cloud transmissivity is estimated using measured and modeled global SDR during daytime. In a last step, the performance of several interpolation methods is evaluated to determine the cloud transmissivity in the night. We show that clear-sky direct, diffuse and global SDR is adequately represented by the model when using measurements of the atmospheric parameters precipitable water and aerosol content at Payerne. If the atmospheric parameters are estimated and used as a fix value, the relative mean bias deviance (MBD) and the relative root mean squared deviance (RMSD) of the clear-sky global SDR scatter between between-2 and 5%, and 7 and 13% within the six locations. The small errors in clear-sky global SDR can be attributed to compensating effects of modeled direct and diffuse SDR since an overestimation of aerosol content in the atmosphere results in underestimating the direct, but overestimating the diffuse SDR. Calibration of LDR parameterizations to local conditions reduces MBD and RMSD strongly compared to using the published values of the parameters, resulting in relative MBD and RMSD of less than 5% respectively 10% for the best parameterizations. The best results to estimate cloud transmissivity during nighttime were obtained by linearly interpolating the average of the cloud transmissivity of the four hours of the preceeding afternoon and the following morning. Model uncertainty can be caused by different errors such as code implementation, errors in input data and in estimated parameters, etc. The influence of the latter (errors in input data and model parameter uncertainty) on model outputs is determined using Monte Carlo. Model uncertainty is provided as the relative standard deviation &sigma;rel of the simulated frequency distributions of the model outputs. An optimistic estimate of the relative uncertainty &sigma;rel resulted in 10% for the clear-sky direct, 30% for diffuse, 3% for global SDR, and 3% for the fitted all-sky LDR. © 2012 Author(s)."
"22834248200;7006377579;7006235542;35740180800;21933618400;7102354961;26027431900;7006837187;9043417100;7103197731;57195257572;37089603000;41361927700;13403627400;7006728825;","Ice formation and development in aged, wintertime cumulus over the UK: Observations and modelling",2012,"10.5194/acp-12-4963-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861941973&doi=10.5194%2facp-12-4963-2012&partnerID=40&md5=c301abb77296065c60e72f7f7f37fdee","In situ high resolution aircraft measurements of cloud microphysical properties were made in coordination with ground based remote sensing observations of a line of small cumulus clouds, using Radar and Lidar, as part of the Aerosol Properties, PRocesses And InfluenceS on the Earth's climate (APPRAISE) project. A narrow but extensive line (∼100 km long) of shallow convective clouds over the southern UK was studied. Cloud top temperatures were observed to be higher than-8°C, but the clouds were seen to consist of supercooled droplets and varying concentrations of ice particles. No ice particles were observed to be falling into the cloud tops from above. Current parameterisations of ice nuclei (IN) numbers predict too few particles will be active as ice nuclei to account for ice particle concentrations at the observed, near cloud top, temperatures (-7.5°C). The role of mineral dust particles, consistent with concentrations observed near the surface, acting as high temperature IN is considered important in this case. It was found that very high concentrations of ice particles (up to 100 L -1) could be produced by secondary ice particle production providing the observed small amount of primary ice (about 0.01 L -1) was present to initiate it. This emphasises the need to understand primary ice formation in slightly supercooled clouds. It is shown using simple calculations that the Hallett-Mossop process (HM) is the likely source of the secondary ice. Model simulations of the case study were performed with the Aerosol Cloud and Precipitation Interactions Model (ACPIM). These parcel model investigations confirmed the HM process to be a very important mechanism for producing the observed high ice concentrations. A key step in generating the high concentrations was the process of collision and coalescence of rain drops, which once formed fell rapidly through the cloud, collecting ice particles which caused them to freeze and form instant large riming particles. The broadening of the droplet size-distribution by collision-coalescence was, therefore, a vital step in this process as this was required to generate the large number of ice crystals observed in the time available. Simulations were also performed with the WRF (Weather, Research and Forecasting) model. The results showed that while HM does act to increase the mass and number concentration of ice particles in these model simulations it was not found to be critical for the formation of precipitation. However, the WRF simulations produced a cloud top that was too cold and this, combined with the assumption of continual replenishing of ice nuclei removed by ice crystal formation, resulted in too many ice crystals forming by primary nucleation compared to the observations and parcel modelling. © 2012 Author(s)."
"57188802223;14066802700;7101864035;55584815600;7005941217;15729001800;","Sulfur isotope fractionation during heterogeneous oxidation of SO2 on mineral dust",2012,"10.5194/acp-12-4867-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861829006&doi=10.5194%2facp-12-4867-2012&partnerID=40&md5=c737b520a416a96aef67b713e97fd6fb","Mineral dust is a major fraction of global atmospheric aerosol, and the oxidation of SO 2 on mineral dust has implications for cloud formation, climate and the sulfur cycle. Stable sulfur isotopes can be used to understand the different oxidation processes occurring on mineral dust. This study presents measurements of the 34S/ 32S fractionation factor &amp;alpha;34 for oxidation of SO 2 on mineral dust surfaces and in the aqueous phase in mineral dust leachate. Sahara dust, which accounts for ∼60% of global dust emissions and loading, was used for the experiments. The fractionation factor for aqueous oxidation in dust leachate is α leachate = 0.9917±0.0046, which is in agreement with previous measurements of aqueous SO 2 oxidation by iron solutions. This fractionation factor is representative of a radical chain reaction oxidation pathway initiated by transition metal ions. Oxidation on the dust surface at subsaturated relative humidity (RH) had an overall fractionation factor of α het = 1.0096±0.0036 and was found to be almost an order of magnitude faster when the dust was simultaneously exposed to ozone, light and RH of ∼40%. However, the presence of ozone, light and humidity did not influence isotope fractionation during oxidation on dust surfaces at subsaturated relative humidity. All the investigated reactions showed mass-dependent fractionation of 33S relative to 34S. A positive matrix factorization model was used to investigate surface oxidation on the different components of dust. Ilmenite, rutile and iron oxide were found to be the most reactive components, accounting for 85% of sulfate production with a fractionation factor of α 34 = 1.012±0.010. This overlaps within the analytical uncertainty with the fractionation of other major atmospheric oxidation pathways such as the oxidation of SO 2 by H 2O 2 and O 3 in the aqueous phase and OH in the gas phase. Clay minerals accounted for roughly 12% of the sulfate production, and oxidation on clay minerals resulted in a very distinct fractionation factor of α 34 = 1.085±0.013. The fractionation factors measured in this study will be particularly useful in combination with field and modelling studies to understand the role of surface oxidation on clay minerals and aqueous oxidation by mineral dust and its leachate in global and regional sulfur cycles. © 2012 Author(s)."
"55961513200;7403681878;37025370400;7404395984;","GPU acceleration of the updated goddard shortwave radiation scheme in the weather research and forecasting (WRF) model",2012,"10.1109/JSTARS.2012.2186119","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861742474&doi=10.1109%2fJSTARS.2012.2186119&partnerID=40&md5=1c930949df69c802069ee3da5304589d","Next-generation mesoscale numerical weather prediction system, the Weather Research and Forecasting (WRF) model, is a designed for dual use for forecasting and research. WRF offers multiple physics options that can be combined in any way. One of the physics options is radiance computation. The major source for energy for the earth's climate is solar radiation. Thus, it is imperative to accurately model horizontal and vertical distribution of the heating. Goddard solar radiative transfer model includes the absorption duo to water vapor, O 3, O 2, CO 2, clouds and aerosols. The model computes the interactions among the absorption and scattering by clouds, aerosols, molecules and surface. Finally, fluxes are integrated over the entire shortwave spectrum from 0.175 μm to 10 μm . In this paper, we develop an efficient graphics processing unit (GPU) based Goddard shortwave radiative scheme. The GPU-based Goddard shortwave scheme was compared to a CPU-based single-threaded counterpart on a computational domain of 422×297 horizontal grid points with 34 vertical levels. Both the original FORTRAN code on CPU and CUDA C code on GPU use double precision floating point values for computation. Processing time for Goddard shortwave radiance on CPU is 22106 ms. GPU accelerated Goddard shortwave radiance on 4 GPUs can be computed in 208.8 ms and 157.1 ms with and without I/O, respectively. Thus, the speedups are 116× with data I/O and 141× without I/O on two NVIDIA GTX 590 s. Using single precision arithmetic and less accurate arithmetic modes the speedups are increased to 536× and 259× ,with and without I/O, respectively. © 2012 IEEE."
"8570871900;55717074000;55245030000;7102604282;55235148400;","Enhanced solar energy absorption by internally-mixed black carbon in snow grains",2012,"10.5194/acp-12-4699-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861664187&doi=10.5194%2facp-12-4699-2012&partnerID=40&md5=9ef3c27e2796217a1197fafb9620646a","Here we explore light absorption by snowpack containing black carbon (BC) particles residing within ice grains. Basic considerations of particle volumes and BC/snow mass concentrations show that there are generally 0.05-109 BC particles for each ice grain. This suggests that internal BC is likely distributed as multiple inclusions within ice grains, and thus the dynamic effective medium approximation (DEMA) (ChÃ1/2lek and Srivastava, 1983) is a more appropriate optical representation for BC/ice composites than coated-sphere or standard mixing approximations. DEMA calculations show that the 460 nm absorption cross-section of BC/ice composites, normalized to the mass of BC, is typically enhanced by factors of 1.8-2.1 relative to interstitial BC. BC effective radius is the dominant cause of variation in this enhancement, compared with ice grain size and BC volume fraction. We apply two atmospheric aerosol models that simulate interstitial and within-hydrometeor BC lifecycles. Although only ∼2% of the atmospheric BC burden is cloud-borne, 71-83% of the BC deposited to global snow and sea-ice surfaces occurs within hydrometeors. Key processes responsible for within-snow BC deposition are development of hydrophilic coatings on BC, activation of liquid droplets, and subsequent snow formation through riming or ice nucleation by other species and aggregation/accretion of ice particles. Applying deposition fields from these aerosol models in offline snow and sea-ice simulations, we calculate that 32-73% of BC in global surface snow resides within ice grains. This fraction is smaller than the within-hydrometeor deposition fraction because meltwater flux preferentially removes internal BC, while sublimation and freezing within snowpack expose internal BC. Incorporating the DEMA into a global climate model, we simulate increases in BC/snow radiative forcing of 43-86%, relative to scenarios that apply external optical properties to all BC. We show that snow metamorphism driven by diffusive vapor transfer likely proceeds too slowly to alter the mass of internal BC while it is radiatively active, but neglected processes like wind pumping and convection may play much larger roles. These results suggest that a large portion of BC in surface snowpack may reside within ice grains and increase BC/snow radiative forcing, although measurements to evaluate this are lacking. Finally, previous studies of BC/snow forcing that neglected this absorption enhancement are not necessarily biased low, because of application of absorption-enhancing sulfate coatings to hydrophilic BC, neglect of coincident absorption by dust in snow, and implicit treatment of cloud-borne BC resulting in longer-range transport. © 2012 Author(s)."
"55233751500;56757585000;55213700400;24588327400;16401209100;7006823219;7006846637;","Vulnerability of cloud forest reserves in Mexico to climate change",2012,"10.1038/nclimate1453","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861622940&doi=10.1038%2fnclimate1453&partnerID=40&md5=2df478b4f6dd1c53668316e36a6ef374","Tropical montane cloud forests are among the most vulnerable terrestrial ecosystems to climate change owing to their restricted climatic requirements and their narrow and fragmented distribution. Although 12% of Mexican cloud forest is protected, it is not known whether reserves will ensure the persistence of the ecosystem and its endemic species under climate change. Here, we show that 68% of Mexico's cloud forest could vanish by 2080 because of climate change and more than 90% of cloud forest that is protected at present will not be climatically suitable for that ecosystem in 2080. Moreover, if we assume unprotected forests are cleared, 99% of the entire ecosystem could be lost through a combination of climate change and habitat loss, resulting in the extinction of about 70% of endemic cloud forest vertebrate species. Immediate action is required to minimize this loss-expansion of the protected-area estate in areas of low climate vulnerability is an urgent priority. Our analysis indicates that one key area for immediate protection is the Sierra de Jua rez in Oaxaca. This area supports many endemic species and is expected to retain relatively large fragments of cloud forest despite rapid climate change. © 2012 Macmillan Publishers Limited. All rights reserved."
"26645289600;7402064802;7202145115;","Computing and partitioning cloud feedbacks using cloud property histograms. Part I: Cloud radiative kernels",2012,"10.1175/JCLI-D-11-00248.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862735793&doi=10.1175%2fJCLI-D-11-00248.1&partnerID=40&md5=6a84290c37bf5624452b4335a41e92ca","This study proposes a novel technique for computing cloud feedbacks using histograms of cloud fraction as a joint function of cloud-top pressure (CTP) and optical depth (τ). These histograms were generated by the International Satellite Cloud Climatology Project (ISCCP) simulator that was incorporated into doubled-CO 2 simulations from 11 global climate models in the Cloud Feedback Model Intercomparison Project. The authors use a radiative transfer model to compute top of atmosphere flux sensitivities to cloud fraction perturbations in each bin of the histogram for each month and latitude. Multiplying these cloud radiative kernels with histograms of modeled cloud fraction changes at each grid point per unit of global warming produces an estimate of cloud feedback. Spatial structures and globally integrated cloud feedbacks computed in this manner agree remarkably well with the adjusted change in cloud radiative forcing. The global and annual mean model-simulated cloud feedback is dominated by contributions from medium thickness (3.6 &lt; τ ≤ 23) cloud changes, but thick (τ &gt; 23) cloud changes cause the rapid transition of cloud feedback values from positive in midlatitudes to negative poleward of 50°S and 70°N. High (CTP ≤ 440 hPa) cloud changes are the dominant contributor to longwave (LW) cloud feedback, but because their LW and shortwave (SW) impacts are in opposition, they contribute less to the net cloud feedback than do the positive contributions from low (CTP &gt; 680 hPa) cloud changes. Midlevel (440 &lt; CTP ≤ 680 hPa) cloud changes cause positive SW cloud feedbacks that are 80% as large as those due to low clouds. Finally, high cloud changes induce wider ranges of LW and SW cloud feedbacks across models than do low clouds. © 2012 American Meteorological Society."
"7202772927;55667257200;7409080503;7501627905;7405489798;","Impact of aerosols on convective clouds and precipitation",2012,"10.1029/2011RG000369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859813952&doi=10.1029%2f2011RG000369&partnerID=40&md5=57a4a353e4cc6ffc50f10a6021090862","Aerosols are a critical factor in the atmospheric hydrological cycle and radiation budget. As a major agent for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosol effects on clouds could further extend to precipitation, both through the formation of cloud particles and by exerting persistent radiative forcing on the climate system that disturbs dynamics. However, the various mechanisms behind these effects, in particular, the ones connected to precipitation, are not yet well understood. The atmospheric and climate communities have long been working to gain a better grasp of these critical effects and hence to reduce the significant uncertainties in climate prediction resulting from such a lack of adequate knowledge. Here we review past efforts and summarize our current understanding of the effect of aerosols on convective precipitation processes from theoretical analysis of microphysics, observational evidence, and a range of numerical model simulations. In addition, the discrepancies between results simulated by models, as well as those between simulations and observations, are presented. Specifically, this paper addresses the following topics: (1) fundamental theories of aerosol effects on microphysics and precipitation processes, (2) observational evidence of the effect of aerosols on precipitation processes, (3) signatures of the aerosol impact on precipitation from large-scale analyses, (4) results from cloud-resolving model simulations, and (5) results from large-scale numerical model simulations. Finally, several future research directions for gaining a better understanding of aerosol-cloud-precipitation interactions are suggested. Copyright 2012 by the American Geophysical Union."
"24492361700;7102128820;26659116700;","Impact of improved representation of horizontal and vertical cloud structure in a climate model",2012,"10.1007/s00382-011-1174-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861829512&doi=10.1007%2fs00382-011-1174-2&partnerID=40&md5=f143efa9c11eb5da0b0658306b71e3bb","Many studies have investigated the effects that misrepresentation of sub-grid cloud structure can have on the radiation budget. In this study, we perform 20-year simulations of the current climate using an atmosphere-only version of the Met Office Unified Model to investigate the effects of cloud approximation on model climate. We apply the ""Tripleclouds"" scheme for representing horizontal cloud inhomogeneity and ""exponential-random"" overlap, both separately and in combination, in place of a traditional plane-parallel representation with maximum-random overlap, to the clouds within the radiation scheme. The resulting changes to both the radiation budget and other meteorological variables, averaged over the 20 years, are compared. The combined global effect of the parameterizations on top-of-atmosphere short-wave and long-wave radiation budget is less than 1 W m-2, but changes of up to 10 W m-2 are identified in marine stratocumulus regions. A cooling near the surface over the winter polar regions of up to 3°C is also identified when horizontal cloud inhomogeneity is represented, and a warming of similar magnitude is found when exponential-random overlap is implemented. Corresponding changes of the same sign are also found in zonally averaged temperature, with maximum changes in the upper tropical troposphere of up to 0.5°C. Changes in zonally averaged cloud fraction in this location were of opposite sign and up to 0.02. The individual effects on tropospheric temperature of improving the two components of cloud structure are of similar magnitudes to about 2% of the warming created by a quadrupling of carbon dioxide. © 2011 Crown Copyright."
"26645289600;7402064802;7202145115;","Computing and partitioning cloud feedbacks using cloud property histograms. Part II: Attribution to changes in cloud amount, altitude, and optical depth",2012,"10.1175/JCLI-D-11-00249.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856973124&doi=10.1175%2fJCLI-D-11-00249.1&partnerID=40&md5=73b01742d011979dc04456ac6662e21c","Cloud radiative kernels and histograms of cloud fraction, both as functions of cloud-top pressure and optical depth, are used to quantify cloud amount, altitude, and optical depth feedbacks. The analysis is applied to doubled-CO 2 simulations from11 global climatemodels in the Cloud FeedbackModel Intercomparison Project. Global, annual, and ensemble mean longwave (LW) and shortwave (SW) cloud feedbacks are positive, with the latter nearly twice as large as the former. The robust increase in cloud-top altitude in both the tropics and extratropics is the dominant contributor to the positive LW cloud feedback. The negative impact of reductions in cloud amount offsets more than half of the positive impact of rising clouds onLWcloud feedback, but the magnitude of compensation varies considerably across the models. In contrast, robust reductions in cloud amount make a large and virtually unopposed positive contribution to SWcloud feedback, though the intermodel spread is greater than for any other individual feedback component. Overall reductions in cloud amount have twice as large an impact on SW fluxes as on LWfluxes, such that the net cloud amount feedback is moderately positive, with no models exhibiting a negative value. As a consequence of large but partially offsetting effects of cloud amount reductions onLWandSWfeedbacks, both the mean and intermodel spread in net cloud amount feedback are smaller than those of the net cloud altitude feedback. Finally, the study finds that the large negative cloud feedback at high latitudes results from robust increases in cloud optical depth, not from increases in total cloud amount as is commonly assumed. © 2012 American Meteorological Society."
"57203386948;55147025100;7102517130;7406683894;56239378700;7004174939;12645612500;24081888700;57203378050;","An integrated analysis of aerosol above clouds from A-Train multi-sensor measurements",2012,"10.1016/j.rse.2012.01.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862814715&doi=10.1016%2fj.rse.2012.01.011&partnerID=40&md5=f89b8bd3f0720963fbc4c2b78e3cafc6","Quantifying above-cloud aerosol can help improve the assessment of aerosol intercontinental transport and climate impacts. In this study we conduct an integrated analysis of aerosols above clouds by using multi-sensor A-Train measurements, including above-cloud aerosol optical depth at 532nm (AOD 532) from CALIPSO lidar, the UV aerosol index (AI) from OMI, and cloud fraction and cloud optical depth (COD) from MODIS. The analysis of Saharan dust outflow and Southwest African smoke outflow regions shows that the above-cloud AOD correlates positively with AI in an approximately linear manner, and that the AOD 532/AI ratio decreases with increasing COD. The dependence of AOD 532/AI ratio on COD doesn't depend on aerosol type when potential biases in the CALIOP AOD measurements are empirically accounted for. Our results may suggest the potential of combining OMI AI and MODIS cloud measurements to empirically derive above-cloud AOD with a spatial coverage much more extensive than CALIPSO measurements, which needs to be further explored in the future. © 2012 Elsevier Inc."
"6602878057;7004479957;8882641700;6701346974;","Fast cloud adjustment to increasing CO2 in a superparameterized climate model",2012,"10.1029/2011MS000092","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867736112&doi=10.1029%2f2011MS000092&partnerID=40&md5=7cb82500902641d38b77723ba8eb04c5","Two-year simulation experiments with a superparameterized climate model, SPCAM, are performed to understand the fast tropical (30S-30N) cloud response to an instantaneous quadrupling of CO2 concentration with SST held fixed at present-day values. The greenhouse effect of the CO2 perturbation quickly warms the tropical land surfaces by an average of 0.5 K. This shifts rising motion, surface precipitation, and cloud cover at all levels from the ocean to the land, with only small net tropical-mean cloud changes. There is a widespread average reduction of about 80 m in the depth of the trade inversion capping the marine boundary layer (MBL) over the cooler subtropical oceans. One apparent contributing factor is CO2-enhanced downwelling longwave radiation, which reduces boundary-layer radiative cooling, a primary driver of turbulent entrainment through the trade inversion. A second contributor is a slight CO2-induced heating of the free troposphere above the MBL, which strengthens the trade inversion and also inhibits entrainment. There is a corresponding downward displacement of MBL clouds with a very slight decrease in mean cloud cover and albedo. Two-dimensional cloud-resolving model (CRM) simulations of this MBL response are run to steady state using composite SP-CAM simulated thermodynamic and wind profiles from a representative cool subtropical ocean regime, for the control and 4xCO 2 cases. Simulations with a CRM grid resolution equal to that of SP-CAM are compared with much finer resolution simulations. The coarse-resolution simulations maintain a cloud fraction and albedo comparable to SP-CAM, but the fine-resolution simulations have a much smaller cloud fraction. Nevertheless, both CRM configurations simulate a reduction in inversion height comparable to SPCAM. The changes in low cloud cover and albedo in the CRM simulations are small, but both simulations predict a slight reduction in low cloud albedo as in SP-CAM. Copyright © 2012 by the American Geophysical Union."
"6701508198;7006245928;7202364010;35339707100;","Tropical Atlantic Biases in CCSM4",2012,"10.1175/JCLI-D-11-00315.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858263700&doi=10.1175%2fJCLI-D-11-00315.1&partnerID=40&md5=0cb4f87123add006e85b97ac0550b6df","This paper focuses on diagnosing biases in the seasonal climate of the tropical Atlantic in the twentiethcentury simulation of the Community Climate System Model, version 4 (CCSM4). The biases appear in both atmospheric and oceanic components. Mean sea level pressure is erroneously high by a few millibars in the subtropical highs and erroneously low in the polar lows (similar to CCSM3). As a result, surface winds in the tropics are ~1 m s -1 too strong. Excess winds cause excess cooling and depressed SSTs north of the equator. However, south of the equator SST is erroneously high due to the presence of additional warming effects. The region of highest SST bias is close to southern Africa near the mean latitude of the Angola-Benguela Front (ABF). Comparison of CCSM4 to ocean simulations of various resolutions suggests that insufficient horizontal resolution leads to the insufficient northward transport of cool water along this coast and an erroneous southward stretching of the ABF. A similar problem arises in the coupled model if the atmospheric component produces alongshore winds that are too weak. Erroneously warm coastal SSTs spread westward through a combination of advection and positive air-sea feedback involving marine stratocumulus clouds. This study thus highlights three aspects to improve to reduce bias in coupled simulations of the tropical Atlantic: 1) large-scale atmospheric pressure fields; 2) the parameterization of stratocumulus clouds; and 3) the processes, including winds and ocean model resolution, that lead to errors in seasonal SST along southwestern Africa. Improvements of the latter require horizontal resolution much finer than the 18 currently used in many climate models. © 2012 American Meteorological Society."
"11439669500;7004214080;","Remnant sugar maple (Acer saccharum subsp. skutchii) populations at their range edge: Characteristics, environmental constraints and conservation implications in tropical America",2012,"10.1016/j.biocon.2012.03.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860318186&doi=10.1016%2fj.biocon.2012.03.006&partnerID=40&md5=66074352589ac4c06a501d013caaff96","Relationships between environmental conditions and persistence of populations at edges of ranges should be useful for predicting consequences of climate change. We characterized environmental conditions of six disjunct sites in Mexico and Guatemala that contain all known relict populations of the most southern subspecies of sugar maple, cloud forest sugar maple (Acer saccharum subsp. skutchii). We also sampled abundance and basal area of all tree species, recording 164 species, 92 genera (61% tropical), and 54 families at these sites. Temperate genera decreased in number from north to south, but mixtures of temperate and tropical species were co-dominant with cloud forest sugar maple at all sites. For all species, basal area was 24-52m 2ha -1 and density was 990-2986 trees/ha at the six sites. Cloud forest sugar maple comprised 7-43% of total basal area and 1-16% of total densities at each site. Populations of cloud forest sugar maple currently are vulnerable to environmental change. Anthropogenic disturbance is negatively affecting four populations, and regeneration is successfully occurring in only two sites. As a result, densities and basal area are much reduced compared to more northern temperate populations. NMS-ordination indicated that elevation and hurricane frequency are major environmental constraints related to abundance. Maple recruitment is associated with short hurricane return intervals that maintain higher elevation cloud forests in states conducive for regeneration. We establish the conservation status of cloud forest sugar maple at the southern end of its range relative to expected climate change and propose this subspecies be included in the IUCN-Red List. © 2012 Elsevier Ltd."
"6603631763;8542741400;7202970886;12801836100;","A naive Bayesian cloud-detection scheme derived from Calipso and applied within PATMOS-x",2012,"10.1175/JAMC-D-11-02.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861402814&doi=10.1175%2fJAMC-D-11-02.1&partnerID=40&md5=7ce4946dc6ed7d6971a64942cbc3dfb8","The naive Bayesian methodology has been applied to the challenging problem of cloud detection with NOAA's Advanced Very High Resolution Radiometer (AVHRR). An analysis of collocated NOAA-18/ AVHRR and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)/Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations was used to automatically and globally derive the Bayesian classifiers. The resulting algorithm used six Bayesian classifiers computed separately for seven surface types. Relative to CALIPSO, the final results show a probability of correct detection of roughly 90% over water, deserts, and snow-free land; 82% over the Arctic; and below 80% over the Antarctic. This technique is applied within theNOAAPathfinder Atmosphere's Extended (PATMOS-x) climate dataset and the Clouds from AVHRR Extended (CLAVR-x) real-time product generation system. Comparisons of the PATMOS-x results with those from International Satellite Cloud Climatology Project (ISCCP) and Moderate Resolution Imaging Spectroradiometer (MODIS) indicate close agreement with zonal mean differences in cloud amount being less than 5% over most zones. Most areas of difference coincided with regions where the Bayesian cloud mask reported elevated uncertainties. The ability to report uncertainties is a critical component of this approach. © 2012 American Meteorological Society."
"35728460100;7003971889;","What determines meridional heat transport in climate models?",2012,"10.1175/JCLI-D-11-00257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856952160&doi=10.1175%2fJCLI-D-11-00257.1&partnerID=40&md5=409f8b59fb07c81838f2bfab86ef562c","The annual mean maximum meridional heat transport (MHT MAX) differs by approximately 20% among coupled climate models. The value of MHT MAX can be expressed as the difference between the equator-topole contrast in absorbed solar radiation (ASR*) and outgoing longwave radiation (OLR*). As an example, in the Northern Hemisphere observations, the extratropics (defined as the region with a net radiative deficit) receive an 8.2-PW deficit of net solar radiation (ASR*) relative to the global average that is balanced by a 2.4-PW deficit of outgoing longwave radiation (OLR*) and 5.8 PW of energy import via the atmospheric and oceanic circulation (MHT MAX). The intermodel spread of MHT MAX in the Coupled Model Intercomparison Project Phase 3 (CMIP3) simulations of the preindustrial climate is primarily (R 2 5 0.72) due to differences in ASR* while model differences in OLR* are uncorrelated with theMHT MAX spread. The net solar radiation (ASR*) is partitioned into contributions from (i) the equator-to-pole contrast in incident radiation acting on the global average albedo and (ii) the equator-to-pole contrast of planetary albedo, which is further subdivided into components due to atmospheric and surface reflection. In the observations, 62% of ASR* is due to the meridional distribution of incident radiation, 33% is due to atmospheric reflection, and 5% is due to surface reflection. The intermodel spread in ASR* is due to model differences in the equator-to-pole gradient in planetary albedo, which are primarily a consequence of atmospheric reflection differences (92% of the spread), and is uncorrelated with differences in surface reflection. As a consequence, the spread in MHT MAX in climate models is primarily due to the spread in cloud reflection properties. © 2012 American Meteorological Society."
"24492014600;57196489468;56520921400;55388694300;","Super-parameterization: A better way to simulate regional extreme precipitation",2012,"10.1029/2011MS000106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867720787&doi=10.1029%2f2011MS000106&partnerID=40&md5=282731383e4e640f95ea6285e081e02d","Extreme precipitation is generally underestimated by current climate models relative to observations of present-day rainfall distributions. Possible causes of this systematic error include the convective parameterization in these models that have been designed to reproduce measurements of climatological mean precipitation. One possible approach to improve the interaction of subgrid-scale physical processes and large-scale climate is to replace the conventional convective parameterizations with a high-resolution cloud-system resolving model. A ""super-parameterized"" Community Atmosphere Model (SP-CAM) utilizing this approach is used in this study to investigate the distribution of extreme precipitation in the United States. Results show that SP-CAM better simulates the distributions of both light and intense precipitation compared to the standard version of CAM based upon conventional parameterizations. The improvements are mostly seen in regions dominated by convective precipitation, suggesting that super-parameterization provides a better representation of subgrid convective processes. Copyright © 2012 by the American Geophysical Union."
"6602574676;6603453147;36098286300;7003397919;35468686100;","Taking the pulse of pyrocumulus clouds",2012,"10.1016/j.atmosenv.2012.01.045","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858781257&doi=10.1016%2fj.atmosenv.2012.01.045&partnerID=40&md5=384bf37261d60cc19dff4f87085d0eee","Large forest fires are a known natural and dominant disturbance factor in high northern latitudes, and form pyrocumulus (pyroCu), and occasionally pyrocumulonimbus (pyroCb) clouds. These clouds can transport emissions into the upper troposphere/lower stratosphere (UT/LS) and produce significant regional and even global climate effects, as is the case with some volcanoes. However, the lack of observational data within pyroCu or pyroCb complicates our ability to investigate pyro-convection and to understand the vertical and cross-isentropic transport mechanisms responsible for UT/LS injection. Here, we report detailed airborne radiation measurements within strong pyroCu taken over boreal forest fires in Saskatchewan, Canada during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) summer field campaign in 2008. We find a prominent smoke core within the pyroCu, which is defined by strong extinction in the UV, VIS and NIR, and high gas-particle concentrations. We also find that the angular distribution of radiance within the pyroCu is closely related to the diffusion domain in water clouds, which is dominated by multiple scattering processes. The radiation field of pyroCu can be described by diffusion approximations that are comprised of simple cosine functions, which can be used to calculate the spatial and temporal characteristics of the radiance field, and applied in cloud resolving models. We demonstrate with Monte Carlo simulations that radiation transport in pyroCu is inherently a 3D problem and must account for particle absorption. © 2012 Elsevier Ltd."
"57193132723;36851768400;57204886915;7403318365;","The MJO Transition from shallow to deep convection in cloudsat/CALIPSO data and GISS GCM simulations",2012,"10.1175/JCLI-D-11-00384.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862732224&doi=10.1175%2fJCLI-D-11-00384.1&partnerID=40&md5=90f15c894eb5bd57e82f2cec5051f093","The relationship between convective penetration depth and tropospheric humidity is central to recent theories of the Madden-Julian oscillation (MJO). It has been suggested that general circulation models (GCMs) poorly simulate the MJO because they fail to gradually moisten the troposphere by shallow convection and simulate a slow transition to deep convection. CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are analyzed to document the variability of convection depth and its relation to water vapor during the MJO transition from shallow to deep convection and to constrain GCM cumulus parameterizations. Composites of cloud occurrence for 10 MJO events show the following anticipated MJO cloud structure: shallow and congestus clouds in advance of the peak, deep clouds near the peak, and upper-level anvils after the peak. Cirrus clouds are also frequent in advance of the peak. The Advanced Microwave Scanning Radiometer for Earth Observing System (EOS) (AMSR-E) columnwater vapor (CWV) increases by~5 mmduring the shallow- deep transition phase, consistent with the idea of moisture preconditioning. Echo-top height of clouds rooted in the boundary layer increases sharply with CWV, with large variability in depth when CWV is between;46 and 68 mm. International Satellite Cloud Climatology Project cloud classifications reproduce these climatological relationships but correctly identify congestus-dominated scenes only about half the time. A version of the Goddard Institute for Space Studies Model E2 (GISS-E2) GCM with strengthened entrainment and rain evaporation that produces MJO-like variability also reproduces the shallow-deep convection transition, including the large variability of cloud-top height at intermediate CWV values. The variability is due to small grid-scale relative humidity and lapse rate anomalies for similar values of CWV."
"6603385031;7004715270;7202865036;56691914800;7005968859;7402049334;","Biomass burning as a potential source for atmospheric ice nuclei: Western wildfires and prescribed burns",2012,"10.1029/2012GL051915","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862542180&doi=10.1029%2f2012GL051915&partnerID=40&md5=42b1dc0e0cfbf7f95db4689062dcf81c","The sources, abundance and nature of atmospheric particles that serve as ice nuclei (IN) for cold cloud formation remain some of the most important, yet poorly-characterized, features of aerosol-cloud interactions that indirectly affect climate. Although a great deal of effort has focused on characterizing the ice nucleating ability of mineral dusts, less is known about carbonaceous particles. A primary source for carbonaceous IN is from biomass combustion. Here we report new measurements of IN activity at-30°C and above water saturation from biomass burning generated particles from prescribed burns and wildfires in the western US. These measurements suggest a range of IN activity, with variability largely dependent on the intensity of the fire. Although the fraction of particles generated during burns which serve as IN is quite small, the large numbers of particles generated in fires make biomass burning a potentially important source of IN to the atmosphere. © 2012. American Geophysical Union. All Rights Reserved."
"55588510300;57211106013;","A fast and efficient version of the TwO-Moment Aerosol Sectional (TOMAS) global aerosol microphysics model",2012,"10.1080/02786826.2011.643259","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859727424&doi=10.1080%2f02786826.2011.643259&partnerID=40&md5=96da28269c48613bdafcbacb19d1059c","This study develops more computationally efficient versions of the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithms, collectively called ""Fast TOMAS."" Several methods for speeding up the algorithm were attempted, but only reducing the number of size sections was adopted. Fast TOMAS models, coupled to the GISS GCM II-prime, require a new coagulation algorithm with less restrictive size resolution assumptions but only minor changes in other processes. Fast TOMAS models have been evaluated in a box model against analytical solutions of coagulation and condensation and in a 3-D model against the original TOMAS (TOMAS-30) model. Condensation and coagulation in the Fast TOMAS models agree well with the analytical solution but show slightly more bias than the TOMAS-30 box model. In the 3-D model, errors resulting from decreased size resolution in each process (i.e., emissions, cloud processing/wet deposition, microphysics) are quantified in a series of model sensitivity simulations. Errors resulting from lower size resolution in condensation and coagulation, defined as the microphysics error, affect number and mass concentrations by only a few percent. The microphysics error in CN70/CN100 (number concentrations of particles larger than 70/100 nm diameter), proxies for cloud condensation nuclei, range from -5% to 5% in most regions. The largest errors are associated with decreasing the size resolution in the cloud processing/wet deposition calculations, defined as cloud-processing error, and range from -20% to 15% in most regions for CN70/CN100 concentrations. Overall, the Fast TOMASmodels increase the computational speed by 2 to 3 times with only small numerical errors stemming from condensation and coagulation calculations when compared to TOMAS-30. The faster versions of the TOMAS model allow for the longer, multi-year simulations required to assess aerosol effects on cloud lifetime and precipitation. Copyright © American Association for Aerosol Research."
"55308082400;55308082300;55308082800;56143890000;55309001900;","Agriculture development-induced surface albedo changes and climatic implications across northeastern china",2012,"10.1007/s11769-012-0535-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863689316&doi=10.1007%2fs11769-012-0535-z&partnerID=40&md5=bcceadf2c89c157e2627e52d9d78ce54","To improve the understandings on regional climatic effects of past human-induced land cover changes, the surface albedo changes caused by conversions from natural vegetation to cropland were estimated across northeastern China over the last 300 years, and its climatic effects were simulated by using the Weather Research and Forecasting (WRF) model. Essential natural vegetation records compiled from historical documents and regional optimal surface albedo dataset were used. The results show that the surface albedo decreased by 0.01-0.03 due to conversions from grassland to cropland in the Northeast China Plain and it increased by 0.005-0.015 due to conversions from forests to cropland in the surrounding mountains. As a consequence, in the Northeast China Plain, the surface net radiation increased by 4-8 W/m2, 2-5 W/m2, and 1-3 W/m2, and the climate was therefore warmed by 0.1°C-0.2°C 0.1°C-0.2°C. 0.1°C-0.3°C in the spring., autumn and winter, respectively. In the surrounding mountain area, the net radiation decreased by less than 1.5 W/m 2, and the climate was therefore cooled too slight to be detected. In summer, effects of surface albedo changes on climate were closely associated with moisture dynamics, such as evapotranspiration and cloud, instead of being merely determined by surface radiation budget. The simulated summer climatic effects have large uncertainties. These findings demonstrate that surface albedo changes resulted in warming climate effects in the non-rainy seasons in Northeast China Plain through surface radiation processes while the climatic effects in summer could hardly be concluded so far. © Science Press, Northeast Institute of Geography and Agroecology, CAS and Springer-Verlag Berlin Heidelberg 2012."
"8971211200;7203062717;57204886915;6506276837;","El-Nino Southern Oscillation simulated and predicted in SNU coupled GCMs",2012,"10.1007/s00382-011-1171-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861800955&doi=10.1007%2fs00382-011-1171-5&partnerID=40&md5=78e16a910d9c677d307b2f6a9e04e970","The characteristics of the El-Nino Southern Oscillation (ENSO) simulated in free integrations using two versions of the Seoul National University (SNU) ocean-atmosphere coupled global climate model (CGCM) are examined. A revised version of the SNU CGCM is developed by incorporating a reduced air-sea coupling interval (from 1 day to 2 h), a parameterization for cumulus momentum transport, a minimum entrainment rate threshold for convective plumes, and a shortened auto-conversion time scale of cloud water to raindrops. With the revised physical processes, lower tropospheric zonal wind anomalies associated with the ENSO-related sea surface temperature anomalies (SSTA) are represented with more realism than those in the original version. From too weak, the standard deviation of SST over the eastern Pacific becomes too strong in the revised version due to the enhanced air-sea coupling strength and intraseasonal variability associated with ENSO. From the oceanic side, the stronger stratification and the shallower-than-observed thermocline over the eastern Pacific also contribute to the excessive ENSO. The impacts of the revised physical processes on the seasonal predictability are investigated in two sets of the hindcast experiment performed using the two versions of CGCMs. The prediction skill measured by anomaly correlation coefficients of monthly-mean SSTA shows that the new version has a higher skill over the tropical Pacific regions compared to the old version. The better atmospheric responses to the ENSO-related SSTA in the revised version lead to the basin-wide SSTA maintained and developed in a manner that is closer to observations. The symptom of an excessively strong ENSO of the new version in the free integration is not prominent in the hindcast experiment because the thermocline depth over the eastern Pacific is maintained as initialized over the arc of time of the hindcast (7 months). © 2011 Springer-Verlag."
"7004097357;","NovaSAR : Space-based radar for all : With its ability to acquire data at a fraction of the cost of conventional synthetic aperture RADAR sensors, NovaSAR looks set to support a wide variety of civil applications",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862576485&partnerID=40&md5=480d3a6a4ca8670debdf1ccbfaf20f49","Surrey Satellite Technology's (SSTL) low cost commercial RADAR system, NovaSAR, is capable of providing RADAR remote sensing capabilities for around 20 per cent of the cost of conventional large satellite missions, making SAR accessible to civil users around the world. Like optical remote sensing satellites, Synthetic Aperture RADAR (SAR) can be used for a wide variety of applications, including disaster relief, environmental monitoring and maritime surveillance. The big advantage of SAR over optical remote sensing is its ability to see through cloud and during the night providing 365-day capability unimpeded by the weather or light conditions. Climate change scientists can make great use of SAR data too, for instance analyzing woodland and vegetation to determine an area's potential for absorbing carbon dioxide, and keeping a healthy balance of land use. Another climate change application of interest to scientists is monitoring of the cryosphere."
"6603204960;7403340784;","Thermodynamic and magnetic properties of surface Fe 3+ species on quartz: Effects of gamma-ray irradiation and implications for aerosol-radiation interactions",2012,"10.1007/s00269-012-0507-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860367119&doi=10.1007%2fs00269-012-0507-y&partnerID=40&md5=f5f1962b48bd8172f5ec2c392d8ac1be","Samples of a natural amethyst, pulverized in air, and irradiated for gamma-ray doses from 0.14 to 70 kGy, have been investigated by powder electron paramagnetic resonance (EPR) spectroscopy from 90 to 294 K. The powder EPR spectra show that the surface Fe 3+ species on the gamma-ray-irradiated quartz differ from its counterpart without irradiation in both the effective g value and the observed line shape, suggesting marked radiation effects. This suggestion is supported by quantitatively determined thermodynamic properties, magnetic susceptibility, relaxation times, and geometrical radius. In particular, the surface Fe 3+ species on gamma-ray-irradiated quartz has larger Gibbs and activation energies than its non-irradiated counterpart, suggesting radiation-induced chemical reactions. The shorter phase-memory time (T m) but longer spin-lattice relaxation time (T 1) of the surface Fe 3+ species on the gamma-ray-irradiated quartz than that without irradiation indicate stronger dipolar interactions in the former. Moreover, the calculated geometrical radius of the surface Fe 3+ species on the gamma-ray-irradiated quartz is three orders of magnitude larger than that of its counterpart on the as-is sample. These results provide new insights into radiation-induced aerosol nucleation, with relevance to atmospheric cloud formation and global climate changes. © 2012 Springer-Verlag."
"55879681300;6505947323;53984268900;7004008609;7003765323;7004713805;7003907127;","Effect of aerosol-radiation feedback on regional air quality - A case study with WRF/Chem",2012,"10.1016/j.atmosenv.2011.10.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860590704&doi=10.1016%2fj.atmosenv.2011.10.009&partnerID=40&md5=50036be6c1640f1a559741a115cc29e6","Numerical simulations were performed in order to investigate the impact of the direct effect of aerosol particles on radiation and the indirect aerosol effect on meteorological variables and subsequent distributions of near surface ozone and PM10 over Europe. The fully coupled meteorology-chemistry community model WRF/Chem has been applied for June and July 2006 for a baseline case without any aerosol feedback on meteorology, a simulation with the direct effect included, and a simulation including the direct as well as the indirect aerosol effect. The impact of the subsequent changes in temperature, boundary layer height, and clouds that were triggered by the direct effect of aerosol on radiation ("" semi-direct effect"" ) was found to dominate the direct effect of aerosol particles on solar radiation. Over Central Europe the mean reduction of global radiation alone was mostly 3-7 W m -2, but changes in cloud cover due to semi-direct effects resulted in monthly mean changes between ±50 W m -2. The inclusion of the indirect aerosol effect resulted in a pronounced decrease of cloud water content by up to 70% and a significantly higher mean rain water content over the North Atlantic. Although generally plausible, the effect appears to be too strong due to too low simulated aerosol particle numbers in this area. Regional changes in precipitation between -100% and 100% were simulated over the European continent. For the simulation including only the direct aerosol effect these changes are almost entirely due to semi-direct effects. Mean ozone mixing ratios over Europe in July were modified by up to 4 ppb or 10% over continental Europe, mostly related to changes in cloud cover. For PM10 the inclusion of the direct effect resulted for the considered episode in a mean decrease by 20-50% due to an increased atmospheric boundary layer height except for the regions with high PM10 concentrations. When the indirect aerosol effect was additionally taken into account an increase of the monthly PM10 concentration by 1-3 μg m -3 was found for July 2006 over large parts of continental Europe. © 2011 Elsevier Ltd."
"35741200300;57203142176;24492504500;","The role of atmosphere feedbacks during ENSO in the CMIP3 models. Part III: The shortwave flux feedback",2012,"10.1175/JCLI-D-11-00178.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865189118&doi=10.1175%2fJCLI-D-11-00178.1&partnerID=40&md5=c89e534a99e785b4bbd4532cd7146741","Previous studies using coupled general circulation models (GCMs) suggest that the atmosphere model plays a dominant role in the modeled El Niño-Southern Oscillation (ENSO), and that intermodel differences in the thermodynamical damping of sea surface temperatures (SSTs) are a dominant contributor to the ENSO amplitude diversity. This study presents a detailed analysis of the shortwave flux feedback (α SW)in12 Coupled Model Intercomparison Project phase 3 (CMIP3) simulations, motivated by findings that α SW is the primary contributor to model thermodynamical damping errors. A ""feedback decomposition method,"" developed to elucidate the α SW biases, shows that all models un-derestimate the dynamical atmospheric response to SSTs in the eastern equatorial Pacific, leading to un-derestimated α SW values. Biases in the cloud response to dynamics and the shortwave interception by clouds also contribute to errors in α SW. Changes in the α SW feedback between the coupled and corresponding atmosphere-only simulations are related to changes in the mean dynamics. A large nonlinearity is found in the observed and modeled SW flux feedback, hidden when linearly cal-culating α SW. In the observations, two physical mechanisms are proposed to explain this nonlinearity: 1) a weaker subsidence response to cold SST anomalies than the ascent response to warm SST anomalies and 2) a nonlinear high-level cloud cover response to SST. The shortwave flux feedback nonlinearity tends to be underestimated by the models, linked to an underestimated nonlinearity in the dynamical response to SST. The process-based methodology presented in this study may help to correct model ENSO atmospheric biases, ultimately leading to an improved simulation of ENSO in GCMs. © 2012 American Meteorological Society."
"57191497381;7004189176;6603560040;","Trends, stability and stress in the Colombian Central Andes",2012,"10.1007/s10584-011-0228-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860915552&doi=10.1007%2fs10584-011-0228-0&partnerID=40&md5=6f7916ba8c45d02252dcb1d2195b047e","Mountain ecosystems have been projected to experience faster rates of warming than surrounding lowlands. These changes in climatic conditions could have significant impacts on high-altitude Andean environments, affecting the quality and magnitude of their economic and environmental services. Even though long-term data in these regions are limited, it is important to identify any discernible long-term trends in local climatic conditions. Time series of several variables were analyzed to detect statistically significant long-term linear trends that occurred over recent years in a páramo ecosystem of the Colombian Central Andes. Records included cloud characteristics, sunshine, rainfall, minimum and maximum temperatures, diurnal temperature range, and relative humidity. Conditions of atmospheric stability were also explored. Total sunshine exhibited decreasing trends ranging from -3. 7 to -8. 5% per decade at altitudes around the pluviometric optimum. The strongest changes in sunshine occurred during the December-January-February season. Mean relative humidity observed at altitudes around and below this threshold showed increasing trends of +0. 6 to +0. 7% per decade. Annual rainfall and mean relative humidity above the optimum showed decreasing trends ranging from -7 to -11% per decade and from -1. 5 to -3. 6% per decade, respectively. Minimum temperatures on the coldest days and maximum temperatures on the warmest days exhibited increasing trends at all altitudes ranging from +0. 1 to +0. 6, and from +0. 2 to +1. 1°C per decade, respectively. Increases in minimum and maximum temperatures at higher altitudes were significantly greater than those observed in average at lower altitudes. The strongest changes in minimum temperatures, particularly, occurred during the December-January-February and June-July-August dry seasons. All these changes suggest that atmospheric conditions in the area are shifting from statically unstable conditions to conditionally unstable or statically stable conditions. Observed historical trends indicate that climate impacts and other human activities have stressed these unique and fragile environments. © 2011 Springer Science+Business Media B.V."
"55908305800;7003627515;7005776035;7005939834;36574232400;22836772900;7003376659;6507206337;23569888300;","Timing and origin of recent regional ice-mass loss in Greenland",2012,"10.1016/j.epsl.2012.03.033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861331605&doi=10.1016%2fj.epsl.2012.03.033&partnerID=40&md5=3cdd73195796fa4ff0308ea26e34c993","Within the last decade, the Greenland ice sheet (GrIS) and its surroundings have experienced record high surface temperatures (Mote, 2007; Box et al., 2010), ice sheet melt extent (Fettweis et al., 2011) and record-low summer sea-ice extent (Nghiem et al., 2007). Using three independent data sets, we derive, for the first time, consistent ice-mass trends and temporal variations within seven major drainage basins from gravity fields from the Gravity Recovery and Climate Experiment (GRACE; Tapley et al., 2004), surface-ice velocities from Inteferometric Synthetic Aperture Radar (InSAR; Rignot and Kanagaratnam, 2006) together with output of the regional atmospheric climate modelling (RACMO2/GR; Ettema et al., 2009), and surface-elevation changes from the Ice, cloud and land elevation satellite (ICESat; Sørensen et al., 2011). We show that changing ice discharge (D), surface melting and subsequent run-off (M/R) and precipitation (P) all contribute, in a complex and regionally variable interplay, to the increasingly negative mass balance of the GrIS observed within the last decade. Interannual variability in P along the northwest and west coasts of the GrIS largely explains the apparent regional mass loss increase during 2002-2010, and obscures increasing M/R and D since the 1990s. In winter 2002/2003 and 2008/2009, accumulation anomalies in the east and southeast temporarily outweighed the losses by M/R and D that prevailed during 2003-2008, and after summer 2010. Overall, for all basins of the GrIS, the decadal variability of anomalies in P, M/R and D between 1958 and 2010 (w.r.t. 1961-1990) was significantly exceeded by the regional trends observed during the GRACE period (2002-2011). © 2012 Elsevier B.V."
"56253852700;7403143315;16835423100;6603262263;57203423392;6701342931;8670222900;7403252327;14043428200;53984268900;55880111500;16480889100;12546105000;14009037000;6505947323;7004020627;7404179087;7003658498;","Evaluation of the meteorological forcing used for the Air Quality Model Evaluation International Initiative (AQMEII) air quality simulations",2012,"10.1016/j.atmosenv.2011.10.065","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860593601&doi=10.1016%2fj.atmosenv.2011.10.065&partnerID=40&md5=9ea0c6bc374ef0b02f281049437dc7a6","Accurate regional air pollution simulation relies strongly on the accuracy of the mesoscale meteorological simulation used to drive the air quality model. The framework of the Air Quality Model Evaluation International Initiative (AQMEII), which involved a large international community of modeling groups in Europe and North America, offered a unique opportunity to evaluate the skill of mesoscale meteorological models for two continents for the same period. More than 20 groups worldwide participated in AQMEII, using several meteorological and chemical transport models with different configurations. The evaluation has been performed over a full year (2006) for both continents. The focus for this particular evaluation was meteorological parameters relevant to air quality processes such as transport and mixing, chemistry, and surface fluxes. The unprecedented scale of the exercise (one year, two continents) allowed us to examine the general characteristics of meteorological models' skill and uncertainty. In particular, we found that there was a large variability between models or even model versions in predicting key parameters such as surface shortwave radiation. We also found several systematic model biases such as wind speed overestimations, particularly during stable conditions. We conclude that major challenges still remain in the simulation of meteorology, such as nighttime meteorology and cloud/radiation processes, for air quality simulation. © 2011 Elsevier Ltd."
"23134745300;7003597653;6701707884;55967620900;7402545909;7202746102;","Infrared continental surface emissivity spectra and skin temperature retrieved from IASI observations over the tropics",2012,"10.1175/JAMC-D-11-0145.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859406439&doi=10.1175%2fJAMC-D-11-0145.1&partnerID=40&md5=50ea05f93ec917a1728e275f961277b3","Land surface temperature and emissivity spectra are essential variables for improving models of the earth surface-atmosphere interaction or retrievals of atmospheric variables such as thermodynamic profiles, chemical composition, cloud and aerosol characteristics, and so on. In most cases, emissivity spectral variations are not correctly taken into account in climate models, leading to potentially significant errors in the estimation of surface energy fluxes and temperature. Satellite infrared observations offer the dual opportunity of accurately estimating these properties of land surfaces as well as allowing a global coverage in space and time. Here, high-spectral-resolution observations from the Infrared Atmospheric Sounder Interferometer (IASI) over the tropics (308N-308S), covering the period July 2007-March 2011, are interpreted in terms of 18 3 18 monthly mean surface skin temperature and emissivity spectra from 3.7 to 14 mm at a resolution of 0.05 mm. The standard deviation estimated for the surface temperature is about 1.3 K. For the surface emissivity, it varies fromabout 1%-1.5%for the 10.5-14- and 5.5-8-mmwindows to about 4% around 4 mm. Results from comparisons with products such as Moderate Resolution Imaging Spectroradiometer (MODIS) low-resolution emissivity and surface temperature or ECMWF forecast data (temperature only) are presented and discussed. Comparisons with emissivity derived from the Airborne Research Interferometer Evaluation System (ARIES) radiances collected during an aircraft campaign over Oman and made at the scale of the IASI field of view offer valuable data for the validation of the IASI retrievals. © 2012 American Meteorological Society."
"35810775100;7004469744;7102795549;8942525300;8942524900;7004584381;35459245100;24477694300;43661479500;16242119400;24463029300;49261186800;35519380200;9333422400;36134816800;7004402705;56372694300;","Intercomparison of modal and sectional aerosol microphysics representations within the same 3-D global chemical transport model",2012,"10.5194/acp-12-4449-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861491079&doi=10.5194%2facp-12-4449-2012&partnerID=40&md5=c4d41b58040bf8c0943e52a5db004ca1","In the most advanced aerosol-climate models it is common to represent the aerosol particle size distribution in terms of several log-normal modes. This approach, motivated by computational efficiency, makes assumptions about the shape of the particle distribution that may not always capture the properties of global aerosol. Here, a global modal aerosol microphysics module (GLOMAP-mode) is evaluated and improved by comparing against a sectional version (GLOMAP-bin) and observations in the same 3-D global offline chemistry transport model. With both schemes, the model captures the main features of the global particle size distribution, with sub-micron aerosol approximately unimodal in continental regions and bi-modal in marine regions. Initial bin-mode comparisons showed that the current values for two size distribution parameter settings in the modal scheme (mode widths and inter-modal separation sizes) resulted in clear biases compared to the sectional scheme. By adjusting these parameters in the modal scheme, much better agreement is achieved against the bin scheme and observations. Annual mean surface-level mass of sulphate, sea-salt, black carbon (BC) and organic carbon (OC) are within 25% in the two schemes in nearly all regions. Surface level concentrations of condensation nuclei (CN), cloud condensation nuclei (CCN), surface area density and condensation sink also compare within 25% in most regions. However, marine CCN concentrations between 30° N and 30° S are systematically 25-60% higher in the modal model, which we attribute to differences in size-resolved particle growth or cloud-processing. Larger differences also exist in regions or seasons dominated by biomass burning and in free-troposphere and high-latitude regions. Indeed, in the free-troposphere, GLOMAP-mode BC is a factor 2-4 higher than GLOMAP-bin, likely due to differences in size-resolved scavenging. Nevertheless, in most parts of the atmosphere, we conclude that bin-mode differences are much less than model-observation differences, although some processes are missing in these runs which may pose a bigger challenge to modal schemes (e.g., boundary layer nucleation and ultra-fine sea-spray). The findings here underline the need for a spectrum of complexity in global models, with size-resolved aerosol properties predicted by modal schemes needing to be continually benchmarked and improved against freely evolving sectional schemes and observations. © 2012 Author(s)."
"15724233200;24172248700;13407563600;16549600900;35221167400;7005696579;24070152900;8645916500;8986277400;26643054400;6701753599;25633689000;7102597422;55545335600;36021733300;57205085102;7102294773;7006595513;35461763400;55942083800;","Size-resolved measurement of the mixing state of soot in the megacity Beijing, China: Diurnal cycle, aging and parameterization",2012,"10.5194/acp-12-4477-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861489037&doi=10.5194%2facp-12-4477-2012&partnerID=40&md5=726b1d428a3e9c9dfb53f67c5fc6dacc","Soot particles are the most efficient light absorbing aerosol species in the atmosphere, playing an important role as a driver of global warming. Their climate effects strongly depend on their mixing state, which significantly changes their light absorbing capability and cloud condensation nuclei (CCN) activity. Therefore, knowledge about the mixing state of soot and its aging mechanism becomes an important topic in the atmospheric sciences. The size-resolved (30-320 nm diameter) mixing state of soot particles in polluted megacity air was measured at a suburban site (Yufa) during the CAREBeijing 2006 campaign in Beijing, using a volatility tandem differential mobility analyzer (VTDMA). Particles in this size range with non-volatile residuals at 300 °C were considered to be soot particles. On average, the number fraction of internally mixed soot in total soot particles (F in), decreased from 0.80 to 0.57 when initial D p increased from 30 to 320 nm. Further analysis reveals that: (1) F in was well correlated with the aerosol hygroscopic mixing state measured by a CCN counter. More externally mixed soot particles were observed when particles showed more heterogeneous features with regard to hygroscopicity. (2) F in had pronounced diurnal cycles. For particles in the accumulation mode (D p at 100-320 nm), largest F in were observed at noon time, with apparent turnover rates (k ex→ in) up to 7.8% hg -1. (3)F in was subject to competing effects of both aging and emissions. While aging increases F in by converting externally mixed soot particles into internally mixed ones, emissions tend to reduce F in by emitting more fresh and externally mixed soot particles. Similar competing effects were also found with air mass age indicators. (4) Under the estimated emission intensities, actual turnover rates of soot (k ex→ in) up to 20% hg -1 were derived, which showed a pronounced diurnal cycle peaking around noon time. This result confirms that (soot) particles are undergoing fast aging/coating with the existing high levels of condensable vapors in the megacity Beijing. (5) Diurnal cycles of F in were different between Aitken and accumulation mode particles, which could be explained by the faster growth of smaller Aitken mode particles into larger size bins. To improve the F in prediction in regional/global models, we suggest parameterizing F in by an air mass aging indicator, i.e., F in Combining double low line, where and are empirical coefficients determined from observations, and x is the value of an air mass age indicator. At the Yufa site in the North China Plain, fitted coefficients (a) were determined as (0.57, 0.21), (0.47, 0.21), and (0.52, 0.0088) for x i (indicators) as [NOz]/[NOy], [E]/[X] ([ethylbenzene]/[m,p-xylene]) and ([IM] + [OM])/[EC] ([inorganic + organic matter]/[elemental carbon]), respectively. Such a parameterization consumes little additional computing time, but yields a more realistic description of F in compared with the simple treatment of soot mixing state in regional/global models. © 2012 Author(s)."
"56634334500;55120842000;6603336666;","A comprehensive study of aerosols around Visakhapatnam, a coastal region, India",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861380123&partnerID=40&md5=5a08470149f1dace9dbee362374a5d03","Aerosols play an important role in cloud formation and subsequent precipitation. In the long run from climatological point of view, the gradual increase in aerosol content leads to a change in earth atmosphere, heat balance and radiation balance leading to global warming and subsequent climate change. In the present article the aerosol concentrations in the urban atmosphere is measured and reported. The rain water analy-sis was also made to find out the chemical nature of aerosols that are washed down due to precipitation in the monsoon season. It is interesting to note that the aerosols play crucial role not only in the formation of cloud clusters but also the subsequent precipitation, the precipitation washes down the pollutant aerosols and the aerosol concentration goes down, in that way it is a cyclic process: the aerosols help in cloud formation and precipitation, where as precipitation washes down the aerosols in the atmosphere, there is an optimum concentration of aerosols which will promote precipitation either less aerosols or excess of aerosols hamper the growth of clouds and the subsequent precipitation will be less or nil, thus the aerosols are important component in cloud physics and precipitation chemistry, the aerosols also absorb effectively the insulation or net radiation, many of the urban aerosols have strong absorption bands in the infrared region, so they will allow insulation to reach the earth surface but will strongly absorb the outgoing long wave radiation from the earth surface, so part of the radiation is trapped and re-radiated back leading to global warming. Such aerosols are known as green house aerosols. Copyright © EM International."
"8687046600;12809562200;6602078681;6602458644;57191950113;57192693180;57198558737;7004866567;47861260200;57201726470;7103333823;7006730524;55234943200;","On the effect of dust aerosols on AIRS and IASI operational level 2 products",2012,"10.1029/2012GL052070","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861657199&doi=10.1029%2f2012GL052070&partnerID=40&md5=7f9686b265ff40e8fe52c4abf4b8de49","Satellite retrievals of environmental parameters can enable a global scale understanding of various atmospheric phenomena. Validation of these retrievals using in situ and other correlative measurements is critical to the success of our accurate interpretation of such phenomena. In this paper, we analyze the effect of dust on AIRS and IASI operational level 2 profiles using data obtained from the 2009-2011 AEROSE campaigns. We find that the presence of dust in the AIRS and IASI measurements biases the cloud-cleared radiances by as much as 4K. In addition, we find that the temperature and surface temperature retrievals resultant from these cloud-cleared radiances show 2 to 3K spurious oscillations throughout the troposphere. Copyright © 2012 by the American Geophysical Union."
"57202803751;6603562731;56289323700;7005473082;55968054200;6505778090;7103156669;57217904352;7003386805;","Fast simulators for satellite cloud optical centroid pressure retrievals; evaluation of OMI cloud retrievals",2012,"10.5194/amt-5-529-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860480855&doi=10.5194%2famt-5-529-2012&partnerID=40&md5=b80f9b6dd9752d1ae5792f84569ec742","The cloud Optical Centroid Pressure (OCP) is a satellite-derived parameter that is commonly used in trace-gas retrievals to account for the effects of clouds on near-infrared through ultraviolet radiance measurements. Fast simulators are desirable to further expand the use of cloud OCP retrievals into the operational and climate communities for applications such as data assimilation and evaluation of cloud vertical structure in general circulation models. In this paper, we develop and validate fast simulators that provide estimates of the cloud OCP given a vertical profile of optical extinction. We use a pressure-weighting scheme where the weights depend upon optical parameters of clouds and/or aerosols. A cloud weighting function is easily extracted using this formulation. We then use fast simulators to compare two different satellite cloud OCP retrievals, from the Ozone Monitoring Instrument (OMI), with estimates based on collocated cloud extinction profiles from a combination of CloudSat radar and MODIS visible radiance data. These comparisons are made over a wide range of conditions to provide a comprehensive validation of the OMI cloud OCP retrievals. We find generally good agreement between OMI cloud OCPs and those predicted by CloudSat. However, the OMI cloud OCPs from the two independent algorithms agree better with each other than either does with the estimates from CloudSat/MODIS. Differences between OMI cloud OCPs and those based on CloudSat/MODIS may result from undetected snow/ice at the surface, cloud 3-D effects, cases of low clouds obscurred by ground-clutter in CloudSat observations and by opaque high clouds in CALIPSO lidar observations, and the fact that CloudSat/CALIPSO only observes a relatively small fraction of an OMI field-of-view. © 2012 Author(s)."
"36803253000;6603591733;35887706900;","Determination of optical and microphysical properties of thin warm clouds using ground based hyper-spectral analysis",2012,"10.5194/amt-5-851-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860431083&doi=10.5194%2famt-5-851-2012&partnerID=40&md5=dbb28aa459f40d7b74be242d7c9eb301","Clouds play a critical role in the Earth's radiative budget as they modulate the atmosphere by reflecting shortwave solar radiation and absorbing long wave IR radiation emitted by the Earth's surface. Although extensively studied for decades, cloud modelling in global circulation models is far from adequate, mostly due to insufficient spatial resolution of the circulation models. In addition, measurements of cloud properties still need improvement, since the vast majority of remote sensing techniques are focused in relatively large, thick clouds. In this study, we utilize ground based hyperspectral measurements and analysis to explore very thin water clouds. These clouds are characterized by liquid water path (LWP) that spans from as high as ∼50g m -2 and down to 65 mg m -2 with a minimum of about 0.01 visible optical depth. The retrieval methodology relies on three elements: a detailed radiative transfer calculations in the longwave IR regime, signal enhancement by subtraction of a clear sky reference, and spectral matching method which exploits fine spectral differences between water droplets of different radii. A detailed description of the theoretical basis for the retrieval technique is provided along with a comprehensive discussion regarding its limitations. The proposed methodology was validated in a controlled experiment where artificial clouds were sprayed and their effective radii were both measured and retrieved simultaneously. This methodology can be used in several ways: (1) the frequency and optical properties of very thin water clouds can be studied more precisely in order to evaluate their total radiative forcing on the Earth's radiation budget. (2) The unique optical properties of the inter-region between clouds (clouds' ""twilight zone"") can be studied in order to more rigorously understanding of the governing physical processes which dominate this region. (3) Since the optical thickness of a developed cloud gradually decreases towards its edges, the proposed methodology can be used to study the spatial microphysical behaviour of these edges. (4) A spatial-temporal analysis can be used to study mixing processes in clouds' entrainment zone. © 2012 Author(s)."
"35499111100;6603432104;56382045300;36930275100;7006474330;22950300200;16426141700;23967631600;53864319300;55915890400;6701544201;","Dissolved organic matter in sea spray: A transfer study from marine surface water to aerosols",2012,"10.5194/bg-9-1571-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860485282&doi=10.5194%2fbg-9-1571-2012&partnerID=40&md5=4e932afea18475c493cbf41a88f41335","Atmospheric aerosols impose direct and indirect effects on the climate system, for example, by absorption of radiation in relation to cloud droplets size, on chemical and organic composition and cloud dynamics. The first step in the formation of Organic primary aerosols, i.e. the transfer of dissolved organic matter from the marine surface into the atmosphere, was studied. We present a molecular level description of this phenomenon using the high resolution analytical tools of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and nuclear magnetic resonance spectroscopy (NMR). Our experiments confirm the chemoselective transfer of natural organic molecules, especially of aliphatic compounds from the surface water into the atmosphere via bubble bursting processes. Transfer from marine surface water to the atmosphere involves a chemical gradient governed by the physicochemical properties of the involved molecules when comparing elemental compositions and differentiating CHO, CHNO, CHOS and CHNOS bearing compounds. Typical chemical fingerprints of compounds enriched in the aerosol phase were CHO and CHOS molecular series, smaller molecules of higher aliphaticity and lower oxygen content, and typical surfactants. A non-targeted metabolomics analysis demonstrated that many of these molecules corresponded to homologous series of oxo-, hydroxy-, methoxy-, branched fatty acids and mono-, di- and tricarboxylic acids as well as monoterpenes and sugars. These surface active biomolecules were preferentially transferred from surface water into the atmosphere via bubble bursting processes to form a significant fraction of primary organic aerosols. This way of sea spray production leaves a selective biological signature of the surface water in the corresponding aerosol that may be transported into higher altitudes up to the lower atmosphere, thus contributing to the formation of secondary organic aerosol on a global scale or transported laterally with possible deposition in the context of global biogeocycling. © 2012 Author(s)."
"8511991900;7102084129;54788887200;7202048112;7409080503;","Potential aerosol indirect effects on atmospheric circulation and radiative forcing through deep convection",2012,"10.1029/2012GL051851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861140684&doi=10.1029%2f2012GL051851&partnerID=40&md5=6bf6489d17c66ef7d79304f07014bff8","Aerosol indirect effects, i.e., the interactions of aerosols with clouds by serving as cloud condensation nuclei or ice nuclei constitute the largest uncertainty in climate forcing and projection. Previous IPCC reported negative aerosol indirect forcing, which does not account for aerosol-convective cloud interactions because the complex processes involved are poorly understood and represented in climate models. Here we elucidated how aerosols change convective intensity, diabatic heating, and regional circulation under different environmental conditions. We found that aerosol indirect effect on deep convective cloud systems could lead to enhanced regional convergence and a strong top-of-atmosphere warming. Aerosol invigoration effect occurs mainly in warmed-based convection with weak shear. This could result in a strong radiative warming in the atmosphere (up to +5.6 W m-2), a lofted latent heating, and a reduced diurnal temperature difference, all of which could potentially impact regional circulation and modify weather systems. The positive aerosol radiative forcing on deep clouds could offset the negative aerosol radiative forcing on low clouds to an unknown extent. © 2012 by the American Geophysical Union."
"14523673200;55073323400;7004442182;","European hot summers associated with a reduction of cloudiness",2012,"10.1175/JCLI-D-12-00040.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861374661&doi=10.1175%2fJCLI-D-12-00040.1&partnerID=40&md5=7ab5b78d23a5f450c036cff36ff8f7c7","A pronounced summer warming is observed in Europe since the 1980s that has been accompanied by an increase in the occurrence of heat waves. Water deficit that strongly reduces surface latent cooling is a widely accepted explanation for the causes of hot summers. The authors show that the variance of European summer temperature is partly explained by changes in summer cloudiness. Using observation-based products of climate variables, satellite-derived cloud cover, and radiation products, the authors show that, during the 1984-2007 period, Europe has become less cloudy (except northeastern Europe) and the regions east of Europe have become cloudier in summer daytime. In response, the summer temperatures increased in the areas of total cloud cover decrease and stalled or declined in the areas of cloud cover increase. Trends in the surface shortwave radiation are generally positive (negative) in the regions with summer warming (cooling or stalled warming), whereas the signs of trends in top-of-atmosphere (TOA) reflected shortwave radiation are reversed. The authors' results suggest that total cloud cover is either the important local factor influencing the summer temperature changes in Europe or a major indicator of these changes. © 2012 American Meteorological Society."
"24329376600;57203049177;7201485519;57210518852;","Forcing, feedbacks and climate sensitivity in CMIP5 coupled atmosphere-ocean climate models",2012,"10.1029/2012GL051607","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861180918&doi=10.1029%2f2012GL051607&partnerID=40&md5=49138d88aafa80b7517b3716f957836f","We quantify forcing and feedbacks across available CMIP5 coupled atmosphere-ocean general circulation models (AOGCMs) by analysing simulations forced by an abrupt quadrupling of atmospheric carbon dioxide concentration. This is the first application of the linear forcing-feedback regression analysis of Gregory et al. (2004) to an ensemble of AOGCMs. The range of equilibrium climate sensitivity is 2.1-4.7K. Differences in cloud feedbacks continue to be important contributors to this range. Some models show small deviations from a linear dependence of top-of-atmosphere radiative fluxes on global surface temperature change. We show that this phenomenon largely arises from shortwave cloud radiative effects over the ocean and is consistent with independent estimates of forcing using fixed sea-surface temperature methods. We suggest that future research should focus more on understanding transient climate change, including any time-scale dependence of the forcing and/or feedback, rather than on the equilibrium response to large instantaneous forcing."
"55705628000;57203174863;7202418453;55262499900;55417816200;","Comparative study of aerosol and cloud detected by CALIPSO and OMI",2012,"10.1016/j.atmosenv.2012.01.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862830530&doi=10.1016%2fj.atmosenv.2012.01.024&partnerID=40&md5=d31c34c582b2b0280b4f017790a5adec","Aerosol and cloud play important roles in the atmosphere and climate system. Accurately detecting their presence, altitude, and properties using satellite radiance measurements is a very important task. This paper presents a comparative analysis of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Level 2 Vertical Feature Mask (VFM) product with the Ozone Monitoring Instrument (OMI) UV Aerosol Index (UVAI) and reflectivity datasets for a full year of 2007 from regional to global scales. Based on CALIPSO and OMI observations, the vertical and horizontal extent of clouds and aerosols are determined and effects of aerosol type, load and cloud fraction on aerosol identification are discussed. It was found that the spatial-temporal correlation found between CALIPSO and OMI observations, is strongly dependent on aerosol types and cloud contamination. CALIPSO is more sensitivity to cloud and often misidentifies aerosol as cloud, while some small scale aerosol layers as well as some pollution aerosols are unidentified by OMI UVAI. Large differences in aerosol distribution patterns between CALIPSO and OMI are observed, especially for the smoke and pollution aerosol dominated areas. In addition, the results found a significant correlation between CALIPSO lidar 1064 nm backscatter and the OMI UVAI over the study regions. © 2012 Elsevier Ltd."
"12801992200;13406672500;6603422104;","Changes in extratropical storm track cloudiness 1983-2008: Observational support for a poleward shift",2012,"10.1007/s00382-011-1065-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860351521&doi=10.1007%2fs00382-011-1065-6&partnerID=40&md5=b21c63272abe9e30f787df6ca717f3aa","Climate model simulations suggest that the extratropical storm tracks will shift poleward as a consequence of global warming. In this study the northern and southern hemisphere storm tracks over the Pacific and Atlantic ocean basins are studied using observational data, primarily from the International Satellite Cloud Climatology Project, ISCCP. Potential shifts in the storm tracks are examined using the observed cloud structures as proxies for cyclone activity. Different data analysis methods are employed, with the objective to address difficulties and uncertainties in using ISCCP data for regional trend analysis. In particular, three data filtering techniques are explored; excluding specific problematic regions from the analysis, regressing out a spurious viewing geometry effect, and excluding specific cloud types from the analysis. These adjustments all, to varying degree, moderate the cloud trends in the original data but leave the qualitative aspects of those trends largely unaffected. Therefore, our analysis suggests that ISCCP data can be used to interpret regional trends in cloudiness, provided that data and instrumental artefacts are recognized and accounted for. The variation in magnitude between trends emerging from application of different data correction methods, allows us to estimate possible ranges for the observational changes. It is found that the storm tracks, here represented by the extent of the midlatitude-centered band of maximum cloud cover over the studied ocean basins, experience a poleward shift as well as a narrowing over the 25 year period covered by ISCCP. The observed magnitudes of these effects are larger than in current generation climate models (CMIP3). The magnitude of the shift is particularly large in the northern hemisphere Atlantic. This is also the one of the four regions in which imperfect data primarily prevents us from drawing firm conclusions. The shifted path and reduced extent of the storm track cloudiness is accompanied by a regional reduction in total cloud cover. This decrease in cloudiness can primarily be ascribed to low level clouds, whereas the upper level cloud fraction actually increases, according to ISCCP. Independent satellite observations of radiative fluxes at the top of the atmosphere are consistent with the changes in total cloud cover. The shift in cloudiness is also supported by a shift in central position of the mid-troposphere meridional temperature gradient. We do not find support for aerosols playing a significant role in the satellite observed changes in cloudiness. The observed changes in storm track cloudiness can be related to local cloud-induced changes in radiative forcing, using ERBE and CERES radiative fluxes. The shortwave and the longwave components are found to act together, leading to a positive (warming) net radiative effect in response to the cloud changes in the storm track regions, indicative of positive cloud feedback. Among the CMIP3 models that simulate poleward shifts in all four storm track areas, all but one show decreasing cloud amount on a global mean scale in response to increased CO2 forcing, further consistent with positive cloud feedback. Models with low equilibrium climate sensitivity to a lesser extent than higher-sensitivity models simulate a poleward shift of the storm tracks. © 2011 Springer-Verlag."
"57213493573;55896920900;18134195800;","A subgrid parameterization scheme for precipitation",2012,"10.5194/gmd-5-499-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860244342&doi=10.5194%2fgmd-5-499-2012&partnerID=40&md5=2c64d0eb9e6fb1facb33943bd7d1885a","With increasing computing power, the horizontal resolution of numerical weather prediction (NWP) models is improving and today reaches 1 to 5 km. Nevertheless, clouds and precipitation formation are still subgrid scale processes for most cloud types, such as cumulus and stratocumulus. Subgrid scale parameterizations for water vapor condensation have been in use for many years and are based on a prescribed probability density function (PDF) of relative humidity spatial variability within the model grid box, thus providing a diagnosis of the cloud fraction. A similar scheme is developed and tested here. It is based on a prescribed PDF of cloud water variability and a threshold value of liquid water content for droplet collection to derive a rain fraction within the model grid. Precipitation of rainwater raises additional concerns relative to the overlap of cloud and rain fractions, however. The scheme is developed following an analysis of data collected during field campaigns in stratocumulus (DYCOMS-II) and fair weather cumulus (RICO) and tested in a 1-D framework against large eddy simulations of these observed cases. The new parameterization is then implemented in a 3-D NWP model with a horizontal resolution of 2.5 km to simulate real cases of precipitating cloud systems over France. © 2012 Author(s)."
"6602558284;6701455548;7004890337;57210350827;6602688130;36809017200;57202754759;7005513582;","Climate sensitivity of the community climate system model, version 4",2012,"10.1175/JCLI-D-11-00290.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859369064&doi=10.1175%2fJCLI-D-11-00290.1&partnerID=40&md5=972859d1f498a524cefeee2cef4e68e3","Equilibrium climate sensitivity of the Community Climate System Model, version 4 (CCSM4) is 3.20°C for 1° horizontal resolution in each component. This is about a half degree Celsius higher than in the previous version (CCSM3). The transient climate sensitivity of CCSM4 at 1° resolution is 1.72°C, which is about 0.2°C higher than in CCSM3. These higher climate sensitivities in CCSM4 cannot be explained by the change to a preindustrial baseline climate. This study uses the radiative kernel technique to show that, from CCSM3 to CCSM4, the global mean lapse-rate feedback declines in magnitude and the shortwave cloud feedback increases. These two warming effects are partially canceled by cooling because of slight decreases in the global mean water vapor feedback and longwave cloud feedback from CCSM3 to CCSM4. A new formulation of the mixed layer, slab-ocean model in CCSM4 attempts to reproduce the SST and sea ice climatology from an integration with a full-depth ocean, and it is integrated with a dynamic sea ice model. These new features allow an isolation of the influence of ocean dynamical changes on the climate response when comparing integrations with the slab ocean and full-depth ocean. The transient climate response of the full-depth ocean version is 0.54 of the equilibrium climate sensitivity when estimated with the new slab-ocean model version for both CCSM3 and CCSM4. The authors argue the ratio is the same in both versions because they have about the same zonal mean pattern of change in ocean surface heat flux, which broadly resembles the zonal mean pattern of net feedback strength. © 2012 American Meteorological Society."
"15757708600;24329242600;6701847229;19638881500;7003748648;","Elevation gradients of European climate change in the regional climate model COSMO-CLM",2012,"10.1007/s10584-011-0195-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859213975&doi=10.1007%2fs10584-011-0195-5&partnerID=40&md5=b2a381c95e21395f9458a5a4842fb6a6","A transient climate scenario experiment of the regional climate model COSMO-CLM is analyzed to assess the elevation dependency of 21st century European climate change. A focus is put on near-surface conditions. Model evaluation reveals that COSMO-CLM is able to approximately reproduce the observed altitudinal variation of 2 m temperature and precipitation in most regions and most seasons. The analysis of climate change signals suggests that 21st century climate change might considerably depend on elevation. Over most parts of Europe and in most seasons, near-surface warming significantly increases with elevation. This is consistent with the simulated changes of the free-tropospheric air temperature, but can only be fully explained by taking into account regional-scale processes involving the land surface. In winter and spring, the anomalous high-elevation warming is typically connected to a decrease in the number of snow days and the snow-albedo feedback. Further factors are changes in cloud cover and soil moisture and the proximity of low-elevation regions to the sea. The amplified warming at high elevations becomes apparent during the first half of the 21st century and results in a general decrease of near-surface lapse rates. It does not imply an early detection potential of large-scale temperature changes. For precipitation, only few consistent signals arise. In many regions precipitation changes show a pronounced elevation dependency but the details strongly depend on the season and the region under consideration. There is a tendency towards a larger relative decrease of summer precipitation at low elevations, but there are exceptions to this as well. © 2011 Springer Science+Business Media B.V."
"16443985900;36969949500;9235235300;23134785100;8740849900;7101799663;56472932500;57211106013;55561830100;","New particle formation and growth in biomass burning plumes: An important source of cloud condensation nuclei",2012,"10.1029/2012GL050930","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861123804&doi=10.1029%2f2012GL050930&partnerID=40&md5=f99c90dd931ae819ff169e24d2b12a7c","Experiments were performed in an environmental chamber to characterize the effects of photo-chemical aging on biomass burning emissions. Photo-oxidation of dilute exhaust from combustion of 12 different North American fuels induced significant new particle formation that increased the particle number concentration by a factor of four (median value). The production of secondary organic aerosol caused these new particles to grow rapidly, significantly enhancing cloud condensation nuclei (CCN) concentrations. Using inputs derived from these new data, global model simulations predict that nucleation in photo-chemically aging fire plumes produces dramatically higher CCN concentrations over widespread areas of the southern hemisphere during the dry, burning season (Sept.-Oct.), improving model predictions of surface CCN concentrations. The annual indirect forcing from CCN resulting from nucleation and growth in biomass burning plumes is predicted to be -0.2Wm-2, demonstrating that this effect has a significant impact on climate that has not been previously considered. © 2012 by the American Geophysical Union."
"35239293700;8271783000;34975525200;","Evaluation on penetration rate of cloud for incoming solar radiation using geostationary satellite data",2012,"10.1007/s13143-012-0011-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864055207&doi=10.1007%2fs13143-012-0011-9&partnerID=40&md5=50286832c17c19ec8de0ab4692fe107b","Solar surface insolation (SSI) represents how much solar radiance reaches the Earth's surface in a specified area and is an important parameter in various fields such as surface energy research, meteorology, and climate change. This study calculates insolation using Multi-functional Transport Satellite (MTSAT-1R) data with a simplified cloud factor over Northeast Asia. For SSI retrieval from the geostationary satellite data, the physical model of Kawamura is modified to improve insolation estimation by considering various atmospheric constituents, such as Rayleigh scattering, water vapor, ozone, aerosols, and clouds. For more accurate atmospheric parameterization, satellite-based atmospheric constituents are used instead of constant values when estimating insolation. Cloud effects are a key problem in insolation estimation because of their complicated optical characteristics and high temporal and spatial variation. The accuracy of insolation data from satellites depends on how well cloud attenuation as a function of geostationary channels and angle can be inferred. This study uses a simplified cloud factor that depends on the reflectance and solar zenith angle. Empirical criteria to select reference data for fitting to the ground station data are applied to suggest simplified cloud factor methods. Insolation estimated using the cloud factor is compared with results of the unmodified physical model and with observations by ground-based pyranometers located in the Korean peninsula. The modified model results show far better agreement with ground truth data compared to estimates using the conventional method under overcast conditions. © The Korean Meteorological Society and Springer 2012."
"7201839229;55722479500;55487921900;","Factors for the simulation of convectively coupled Kelvin waves",2012,"10.1175/JCLI-D-11-00060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861355946&doi=10.1175%2fJCLI-D-11-00060.1&partnerID=40&md5=58bedc9eba6ed1a38e043ada4281640f","This study investigates the major factors for the realistic simulation of convectively coupled Kelvin waves (CCKWs) using the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) models. CFS simulations employing relaxed Arakawa-Schubert (RAS; hereafter CTRL) and simplified Arakawa-Schubert (SAS) cumulus parameterization schemes show that the former generates the observed Kelvin wave signature more realistically than the latter does. For example, the space-time spectral signal, eastward propagation, and tilted (and second baroclinic mode) vertical structures in convection, temperature, moisture, and circulation anomalies associated with CCKWs in CTRL are more comparable to observations than in the SAS simulation. CTRL and observations demonstrate the characteristic evolution and vertical heating profile associated with CCKWs similar to those seen in mesoscale convective systems in the tropics: shallow convection, followed by deep convection and then stratiform cloudiness, and resulting in a top-heavy diabatic heating profile. Five additional experiments demonstrate that the effects of convective downdrafts, subgrid-scale convective rain evaporation, and large-scale rain evaporation on CCKWs are assessed to be insignificant in CTRL, possibly due to a more humid environment than observation. However, the Kelvin wave signals are reduced by;40% when shallow convection is disabled. More importantly, the removal of convective detrainment at the cloud top results in the greatest reduction in Kelvin wave activity (by more than 70%). Therefore, the preconditioning of the atmosphere by shallow convection and detrainment of water vapor and condensate from convective updrafts to the environment and subsequent stratiform heating (gridscale condensational heating)/precipitation processes are the two most crucial factors for the successful simulation of CCKWs. © 2012 American Meteorological Society."
"6602506226;","Weakness of the weekend effect in aerosol number concentrations",2012,"10.1016/j.atmosenv.2012.01.060","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857789692&doi=10.1016%2fj.atmosenv.2012.01.060&partnerID=40&md5=7310a9e708a9eccaf7d139ca932d25e2","Weekday related anthropogenic aerosol emissions have been suggested to affect regional climate via indirect aerosol effects. I studied the variability of potential cloud condensation nuclei using measurements of number size distributions of Cloud Condensation Nuclei (CCN)-sized aerosol particles and CCNs measured at several European regional background stations, located at a wide variety of environments. With notably rare exceptions, there were no statistically significant difference between concentrations on different weekdays. I further analysed the concentration time-series of four long-period datasets in Germany and Finland with wavelet analysis. Outside of urban areas, very little weekday-connected variability was found. The lack of 7-day variability outside of cities is in contrast of earlier studies in this field, which used mostly particle mass as the representative measure of aerosol concentration. A time-scale and variability analysis showed that PM 10 and PM 2.5 are more sensitive for the weekly variation than CCN-sized particles. Using mass-based variations as a proxy for short-term variations of CCN particle numbers can thus overestimate the weekend effect for these particles. The results of this study do not support aerosol indirect effects from 50 to 500 nm diameter particles as a major contributor on potential weekday connected variations in European meteorology. © 2012 Elsevier Ltd."
"21739865400;7405524900;55716700200;7501732664;","Examination of the two types of ENSO in the NCEP CFS model and its extratropical associations",2012,"10.1175/MWR-D-11-00300.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862170599&doi=10.1175%2fMWR-D-11-00300.1&partnerID=40&md5=ca83604b5556888352ed814354513be9","Two types of El Nin{ogonek} o-Southern Oscillation (ENSO) simulated by the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) model are examined. The model is found to produce both the eastern Pacific (EP) and central Pacific (CP) types of ENSO with spatial patterns and temporal evolutions similar to the observed. The simulated ENSO intensity is comparable to the observed for the EP type, but weaker than the observed for the CP type. Further analyses reveal that the generation of the simulated CP ENSO is linked to extratropical forcing associated with the North Pacific Oscillation (NPO) and that the model is capable of simulating the coupled air-sea processes in the subtropical Pacific that slowly spreads the NPO-induced SST variability into the tropics, as shown in the observations. The simulated NPO, however, does not extend as far into the deep tropics as it does in the observations and the coupling in the model is not sustained as long as it is in the observations. As a result, the extratropical forcing of tropical central Pacific SST variability in the CFS model is weaker than in the observations. An additional analysis with the Bjerknes stability index indicates that the weaker CP ENSO in the CFS model is also partially due to unrealistically weak zonal advective feedback in the equatorial Pacific. These model deficiencies appear to be related to an underestimation in the amount of the marine stratus clouds off the North American coasts inducing an ocean surface warm bias in the eastern Pacific. This study suggests that a realistic simulation of these marine stratus clouds can be important for the CP ENSO simulation. © 2012 American Meteorological Society."
"36105812700;6603711967;6602741207;56250938500;7004038301;","Comparing modeled and observed changes in mineral dust transport and deposition to Antarctica between the Last Glacial Maximum and current climates",2012,"10.1007/s00382-011-1139-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860327009&doi=10.1007%2fs00382-011-1139-5&partnerID=40&md5=0e16cfdb349c2fe8b340c9de9e3dbf9c","Mineral dust aerosols represent an active component of the Earth's climate system, by interacting with radiation directly, and by modifying clouds and biogeochemistry. Mineral dust from polar ice cores over the last million years can be used as paleoclimate proxy, and provide unique information about climate variability, as changes in dust deposition at the core sites can be due to changes in sources, transport and/or deposition locally. Here we present results from a study based on climate model simulations using the Community Climate System Model. The focus of this work is to analyze simulated differences in the dust concentration, size distribution and sources in current climate conditions and during the Last Glacial Maximum at specific ice core locations in Antarctica, and compare with available paleodata. Model results suggest that South America is the most important source for dust deposited in Antarctica in current climate, but Australia is also a major contributor and there is spatial variability in the relative importance of the major dust sources. During the Last Glacial Maximum the dominant source in the model was South America, because of the increased activity of glaciogenic dust sources in Southern Patagonia-Tierra del Fuego and the Southernmost Pampas regions, as well as an increase in transport efficiency southward. Dust emitted from the Southern Hemisphere dust source areas usually follow zonal patterns, but southward flow towards Antarctica is located in specific areas characterized by southward displacement of air masses. Observations and model results consistently suggest a spatially variable shift in dust particle sizes. This is due to a combination of relatively reduced en route wet removal favouring a generalized shift towards smaller particles, and on the other hand to an enhanced relative contribution of dry coarse particle deposition in the Last Glacial Maximum. © 2011 Springer-Verlag."
"6603684021;13609954600;7005706662;55220305700;","Strong radiative heating due to wintertime black carbon aerosols in the Brahmaputra River Valley",2012,"10.1029/2012GL051148","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861164221&doi=10.1029%2f2012GL051148&partnerID=40&md5=0a8840bad322e14ebeade30015c5dea2","The Brahmaputra River Valley (BRV) of Southeast Asia recently has been experiencing extreme regional climate change. A week-long study using a micro-Aethalometer was conducted during January-February 2011 to measure black carbon (BC) aerosol mass concentrations in Guwahati (India), the largest city in the BRV region. Daily median values of BC mass concentration were 9-41 gm -3, with maxima over 50 gm-3 during evenings and early mornings. Median BC concentrations were higher than in mega cities of India and China, and significantly higher than in urban locations of Europe and USA. The corresponding mean cloud-free aerosol radiative forcing is -63.4 Wm-2 at the surface and +11.1 Wm-2 at the top of the atmosphere with the difference giving the net atmospheric BC solar absorption, which translates to a lower atmospheric heating rate of ∼2K/d. Potential regional climatic impacts associated with large surface cooling and high lower-atmospheric heating are discussed. © 2012 by the American Geophysical Union."
"35208307200;37027159300;36006313400;37025489400;","Differences in soil moisture, nutrients and the microbial community between forests on the upper Pacific and Caribbean slopes at Monteverde, Cordillera de Tilaran: Implications for responses to climate change",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855890592&partnerID=40&md5=44ffb69d74c276063df5835178b31b11","A study was conducted to identify soil ecosystem metrics for use in monitoring soil ecosystem health in tropical montane cloud forest habitats, and to establish a baseline of soil community characteristics. This work was performed in six unique forested habitats on the Caribbean and Pacific slopes of the Monteverde Reserve in Costa Rica. Comparisons were made of the soil moisture, nitrogen fixation activity, microbial biomass, fungal and bacterial abundance and diversity, and the abundance of key functional genes laccase (for lignin degradation by basidiomycete fungi) and nifH (for bacterial N- fixation). Differences were found in these metrics between habitats, which were correlated with soil moisture. The results of this work show that these metrics can be used as part of a program to monitor the soil ecosystems for early indicators of shifts in conditions in response to environmental change within this part of a fragile ecosystem. © International Society for Tropical Ecology."
"7004197652;15520555600;","Rainfall measurement revisited",2012,"10.1002/wea.875","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860692191&doi=10.1002%2fwea.875&partnerID=40&md5=f3d9685306088bfa470d192fe1767eb4","Although it seems so simple to measure rainfall with a gauge, the determination of the true rainfall at a point remains an elusive variable. A gauge sited with its rim level with the ground, in a pit covered with a non-splash surface, appears to give the best estimate of rainfall reaching the ground surface. However, very few of the world's 200 000 or so gauges used operationally for observing precipitation are sited in this manner. Hence there are inbuilt errors in their data which can cloud the results drawn from them. In times past, when water resources were not as stressed as they are at present, these errors were of little concern. But, now and for the future, they are becoming increasingly important, particularly in the context of climate change. Strangeways (2010) considers that despite the use of remote sensing from satellites, the most important and precise measurements of climate will continue to be made in situ at the surface with instruments in contact with what they are measuring. This applies especially to the measurement of rainfall. Gauge measurement of snow is an even more intractable problem. © 2012 Royal Meteorological Society."
"35209683700;55716995500;26324818700;","Process-based decomposition of the global surface temperature response to El Niño in boreal winter",2012,"10.1175/JAS-D-12-023.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864861322&doi=10.1175%2fJAS-D-12-023.1&partnerID=40&md5=b3dcb3e757b7b510398525f2ec0da26b","This paper reports an attribution analysis that quantifies addible contributions to the observed temperature anomalies from radiative and nonradiative processes in terms of both amplitude and spatial pattern for the two most prominent surface temperature patterns in an El Niño winter. One is the El Niño SST pattern consisting of warming SST anomalies over the eastern equatorial Pacific basin surrounded by cooling SST anomalies in the western and subtropical Pacific, and the other is a tripole surface temperature anomaly characteristic of a positive Pacific-North American (PNA) teleconnection pattern. The decomposition of the observed temperature anomalies is achieved with the coupled atmosphere-surface climate feedback-responses analysis method (CFRAM), which is formulated utilizing energy balance in the atmosphere-surface columns and linearization of radiative energy perturbation. Out of the mean amplitude of 0.78 K of the El Niño SST pattern, the oceanic dynamics and heat storage term alone contributes to 2.34 K. Water vapor feedback adds another 1.6 K whereas both cloud and atmospheric dynamical feedbacks are negative, reducing the mean amplitude by 2.02 and 1.07 K, respectively. Atmospheric dynamical feedback contributes more than 50% (0.73 K) of the mean amplitude (1.32 K) of the PNA surface temperature pattern. Water vapor and surface albedo feedbacks contribute 0.34 and 0.13 K, respectively. The surface processes, including oceanic dynamics in the North Pacific, heat storage anomalies, and surface sensible/latent heat flux anomalies of ocean and land also contribute positively to the PNA surface temperature pattern (about 0.14 K). Cloud and ozone feedback, although very weak, act to oppose the PNA surface temperature anomaly. © 2012 American Meteorological Society."
"35208307200;36006313400;","Characterization of soil ecosystems in Costa Rica using microbial community metrics",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855882005&partnerID=40&md5=5fa4ee83b26e9dd27c3210c87f4456e1","The goals of the research presented in this issue of Tropical Ecology were to demonstrate that differences in soil DNA-based microbial community characteristics, biomass, microbial activity, and C and N nutrient dynamics can be used as indicators of environmental change, specifically to show how land management, restoration strategies and climate change may be impacting the soil ecosystems of lowland forests and montane cloud forests of Costa Rica. In the studies conducted in lowland secondary forests, the bacterium Frankia was found to be critical for nitrogen-fixation in the soils associated with nitrogen-fixing tree Pentaclethra macroloba, but Frankia, Rhizobium, Archaea, and Type II methanotrophs were also collectively important in recuperation of the soil N and in enhancing microbial biomass C via more efficient use of organic C. These same secondary forest soils had greater levels of inorganic P and N, organic carbon, and microbial activity, and were more fungal-dominant soil ecosystem than grasslands of the same age. In an adjacent primary forest, the bromeliad Bromelia pinguin was found to demonstrate significant antifungal effects on the forest soil, resulting in decreases in fungal abundance, microbial biomass, and efficiency of organic C use. Lastly, in the Monteverde cloud forests, microbial metrics were used to show that habitats with the greatest soil moisture had more fungal-dominated soils, and unique fungal and bacterial population compositions. Given the importance of tropical soils in global C storage, their degradation, and current restoration efforts in these forests, as well as the very clear threat of decreases in precipitation due to climate change, belowground metrics should be considered as early indicators of the effects of forest restoration and/or further environmental disturbances. We hope that these articles will stimulate future studies in these important areas of Costa Rica. © International Society for Tropical Ecology."
"36060938100;7402989545;","Development and evaluation of a regional ocean-atmosphere coupled model with focus on the western North Pacific summer monsoon simulation: Impacts of different atmospheric components",2012,"10.1007/s11430-011-4281-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860654822&doi=10.1007%2fs11430-011-4281-3&partnerID=40&md5=10f4091ffd3f6fe4984559017863c89e","A regional ocean atmosphere coupled model (ROAM) is developed through coupler OASIS3, and is composed of regional climate model RegCM3 and CREM (Climate version of Regional Eta Model) as its atmospheric component and of a revised Princeton ocean model (POM2000) as its oceanic component. The performance of the ROAM over the western North Pacific summer monsoon region is assessed by the case simulation of warm season in 1998. Impacts of different atmospheric model components on the performance of ROAM are investigated. Compared with stand-alone simulation, CREM (RegCM3) produces more (or less) rainfall over ocean area with inclusion of the air-sea coupling. Different biases of rainfall are caused by the different biases of SST derived from the coupled simulation. Warm (or cold) SST bias simulated by CREM_CPL (RegCM3_CPL) increases (or decreases) the evaporation at sea surface, then increases (or decreases) the rainfall over ocean. The analyses suggest that the biases of vertical profile of temperature and specific humidity in stand-alone simulations may be responsible for the SST biases in regional coupled simulations. Compared with reanalysis data, the warmer (or colder) and moister (or dryer) lower troposphere simulated in CREM (RegCM3) produces less (or more) sea surface latent heat flux. Meanwhile, the more unstable (or stable) lower troposphere produces less (or more) cloudiness at low-level, which increases (or decreases) the solar radiation reaching on the sea surface. CREM (RegCM3) forced by observed SST overestimates (or underestimates) the sea surface net heat flux, implying a potential warm (or cold) heat source. After coupling with POM2000, the warm (or cold) heat source would further increase (or decrease) the SST. The biases of vertical profile of temperature and specific humidity may be ascribed to the different representation of cumulus convection in atmospheric models. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg."
"57196406039;36104362300;36816071900;36815705700;","Sensitivity of satellite-derived wind retrieval over cloudy scenes to target selection in tracking and pixel selection in height assignment",2012,"10.1109/TGRS.2011.2167754","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860319638&doi=10.1109%2fTGRS.2011.2167754&partnerID=40&md5=d143866fcf1e67d2fbfe93fafa445443","Satellite-derived atmospheric motion vectors (AMVs) are useful in weather analyses such as for identifying tropical lows, wind shears, and jet locations. AMVs are assimilated into numerical weather prediction models, particularly for ocean areas where wind observations are sparse. An AMV's accuracy is closely related to the processes of target tracking and height assignment (HA). The objective of this paper is to investigate the sensitivity of satellite-derived wind retrieval in cloudy scenes to the main components in these processes. AMVs are retrieved by identifying and tracking targets using advanced pattern-matching techniques based on cross-correlation statistics. In tracking targets, the main components of the AMV algorithm are the target selection methods such as the target box size, the grid size, the time interval between satellite images, and the method for determining the locations of targets. This study reveals that the optimal sizes of the target and grid could be determined differently according to the channel used for wind observation. The time interval between satellite images has a significant impact on the number of vectors with high quality and high accuracy. The HA method is also an important factor in determining the AMVs' accuracy. The heights of most vectors are assigned to cloud-top pressures using the representative radiances, and the current algorithm uses the coldest pixels to set these representative radiances. The template image used for feature tracking may contain various clouds with different movements and different heights. Therefore, without any information on feature tracking, the current approach may lead to HA errors. To mitigate these HA errors, a new approach using the individual-pixel contribution rate is tested. It tends to correct the heights of the AMVs using the water vapor channel and reduces the wind speed bias and root-mean-square vector difference. © 2012 IEEE."
"25926762100;6701333444;7103158465;9239331500;","Sensitivity of idealized squall-line simulations to the level of complexity used in two-moment bulk microphysics schemes",2012,"10.1175/MWR-D-11-00120.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864832165&doi=10.1175%2fMWR-D-11-00120.1&partnerID=40&md5=5fb6f2129dd04fc363c781a08fd0922a","This paper investigates the level of complexity that is needed within bulk microphysics schemes to represent the essential features associated with deep convection. To do so, the sensitivity of surface precipitation is evaluated in two-dimensional idealized squall-line simulations with respect to the level of complexity in the bulk microphysics schemes of H. Morrison et al. and of J. A. Milbrandt and M. K. Yau. Factors examined include the number of predicted moments for each of the precipitating hydrometeors, the number and nature of ice categories, and the conversion term formulations. First, it is shown that simulations of surface precipitation and cold pools are not only a two-moment representation of rain, as suggested by previous research, but also by two-moment representations for all precipitating hydrometeors. Cold pools weakened when both rain and graupel number concentrations were predicted, because size sorting led to larger graupel particles that melted into larger raindrops and caused less evaporative cooling. Second, surface precipitation was found to be less sensitive to the nature of the rimed ice species (hail or graupel). Production of hail in experiments including both graupel and hail strongly depends on an unphysical threshold that converts small hail back to graupel, indicating the need for a more physical treatment of the graupel-to-hail conversion. Third, it was shown that the differences in precipitation extremes between the two-moment microphysics schemes are mainly related to the treatment of drop breakup. It was also shown that, although the H. Morrison et al. scheme is dominated by deposition growth and low precipitation efficiency, the J. A. Milbrandt and M. K. Yau scheme is dominated by riming processes and high precipitation efficiency. © 2012 American Meteorological Society."
"55317870400;57206241721;55317510800;","An evaluation of ice nuclei characteristics from the long-term measurement data over North China",2012,"10.1007/s13143-012-0020-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864036463&doi=10.1007%2fs13143-012-0020-8&partnerID=40&md5=e01f45e87c11668497c38475a1a79e1b","An attempt was made to delineate the characteristics of ice nuclei (IN) over North China using the ground-based measurement data from 1963-2003. The results show that: (1) the IN concentrations increased during the period from 1963-1996, but decreased after 2000; (2) the average IN concentrations range from 1.0 to 26.3, 3.6 to 78.9, 19.2 to 627.3, and 92.9 to 5285.0 L -1 at temperature -15, -20, -25, and -30oC, with the overall average of 7.8, 20.6, 167.7, and 890.6 L -1, respectively; and (3) the number concentration of active IN increased nearly exponentially with decreasing temperature, with the slope (ranging from 0.11 to 0.42°C -1) being of a narrow range in a log-linear coordinate; the regression equations for the western central China and the eastern central China can be expressed as N(T) = 0.0396 exp (-0.317ΔT) and N(T) = 0.1496 exp (-0.299ΔT), respectively. The present study may be useful toward applications in models for predicting IN effects on the cloud, precipitation and climate over North China. © The Korean Meteorological Society and Springer 2012."
"55950830700;","Titan's methane weather",2012,"10.1146/annurev-earth-040809-152548","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860511262&doi=10.1146%2fannurev-earth-040809-152548&partnerID=40&md5=6a5d44585b71155445616eeba07f02bc","Conditions in Titan's troposphere are near the triple point of methane, the second most abundant component of its atmosphere. Our understanding of Titan's lower atmosphere has shifted considerably in the past decade. Ground-based observations, Hubble Space Telescope images, and data returned from the Cassini and Huygens spacecraft show that Titan's troposphere hosts a methane-based meteorology in direct analogy to the water-based meteorology of Earth. What once was thought to be a quiescent place, lacking in clouds or localized weather and changing only subtly on long seasonal timescales, is now understood to be a dynamic system with significant weather events regularly occurring against the backdrop of dramatic seasonal changes. Although the observational record of Titan's weather covers only a third of its 30-year seasonal cycle, Titan's atmospheric processes appear to be more closely analogous to those of Earth than to those of any other object in our solar system. © 2012 by Annual Reviews. All rights reserved."
"7102567936;7006198994;","An idealized semi-empirical framework for modeling the Madden-Julian oscillation",2012,"10.1175/JAS-D-11-0118.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864860562&doi=10.1175%2fJAS-D-11-0118.1&partnerID=40&md5=63e0de06b45c07e04aca5bde79ba6695","The authors present a simple semi-empirical model to explore the hypothesis that the Madden-Julian oscillation can be represented as a moisture mode destabilized by surface flux and cloud-radiative feedbacks. The model is one-dimensional in longitude; the vertical and meridional structure is entirely implicit. The only prognostic variable is column water vaporW. The zonal wind field is an instantaneous diagnostic function of the precipitation field. The linearized version of the model has only westward-propagating (relative to the mean flow) unstable modes because wind-induced surface latent heat flux anomalies occur to the west of precipitation anomalies. The maximum growth rate occurs at the wavelength at which the correlation between precipitation and surface latent heat flux is maximized. This wavelength lies in the synoptic- to planetary-scale range and is proportional to the horizontal scale associated with the assumed diagnostic wind response to precipitation anomalies. The nonlinear version of the model has behavior that can be qualitatively different from the linear modes and is strongly influenced by horizontal advection of moisture. The nonlinear solutions are very sensitive to small shifts in the phasing of wind and precipitation. Under some circumstances nonlinear eastwardpropagating disturbances emerge on a state of mean background westerlies. These disturbances have a shocklike discontinuous jump in humidity and rainfall at the leading edge; humidity decreases linearly and precipitation decreases exponentially to the west. © 2012 American Meteorological Society."
"25637684100;35510702700;7004557898;","A branch scale analytical model for predicting the vegetation collection efficiency of ultrafine particles",2012,"10.1016/j.atmosenv.2012.01.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857792771&doi=10.1016%2fj.atmosenv.2012.01.004&partnerID=40&md5=9d8acf34aae3188c87c31cef373ce431","The removal of ultrafine particles (UFP) by vegetation is now receiving significant attention given their role in cloud physics, human health and respiratory related diseases. Vegetation is known to be a sink for UFP, prompting interest in their collection efficiency. A number of models have tackled the UFP collection efficiency of an isolated leaf or a flat surface; however, up-scaling these theories to the ecosystem level has resisted complete theoretical treatment. To progress on a narrower scope of this problem, simultaneous experimental and theoretical investigations are carried out at the "" intermediate"" branch scale. Such a scale retains the large number of leaves and their interaction with the flow without the heterogeneities and added geometric complexities encountered within ecosystems. The experiments focused on the collection efficiencies of UFP in the size range 12.6-102 nm for pine and juniper branches in a wind tunnel facility. Scanning mobility particle sizers were used to measure the concentration of each diameter class of UFP upstream and downstream of the vegetation branches thereby allowing the determination of the UFP vegetation collection efficiencies. The UFP vegetation collection efficiency was measured at different wind speeds (0.3-1.5 m s -1), packing density (i.e. volume fraction of leaf or needle fibers; 0.017 and 0.040 for pine and 0.037, 0.055 for juniper), and branch orientations. These measurements were then used to investigate the performance of a proposed analytical model that predicts the branch-scale collection efficiency using conventional canopy properties such as the drag coefficient and leaf area density. Despite the numerous simplifications employed, the proposed analytical model agreed with the wind tunnel measurements mostly to within 20%. This analytical tractability can benefit future air quality and climate models incorporating UFP. © 2012 Elsevier Ltd."
"30767832000;7103292147;35270436100;15766514800;56601913500;","Studies on the relationships between land surface temperature and environmental factors in an inland river catchment based on geographically weighted regression and MODIS data",2012,"10.1109/JSTARS.2012.2190978","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863518047&doi=10.1109%2fJSTARS.2012.2190978&partnerID=40&md5=e2d72ff0327219b1bc4dfe36b08d8ec8","Despite growing concerns in Land Surface Temperature (LST) and its related environmental factors (geographical, climate, and atmospheric conditions), little attention was about the spatial variation that consider above conditions together. Our purpose is to analyze and quantify LST and related environmental factors, using Geographically Weighted Regression (GWR), and Moderate Resolution Imaging Spectroradiometer (MODIS) data in a typical inland river catchment, named Heihe River catchment, China. Considering thirteen environmental factors (altitude, latitude, Topographic Wetness Index, Cos(aspect), temperature, precipitation, humidity, wind speed, radiation, albedo, the normalized difference vegetation index (NDVI), water vapor, COT), 18 GWR models were set up. Results showed that yearly averaged LST changed from 264 K to 309 K, with the highest value recorded in the downstream desert region. LST has the same variable trend and seasonality with NDVI, precipitable water vapor, and cloud optical thickness (COT), but has an inverse relationship with albedo. All GWR models indicated better simulation with smaller Akaike Information Criterion (AICc), and higher coefficient of determination (R 2), compared with Ordinary Least Squares method (OLS). Furthermore, performance of multi-factor analysis was better than single-factor analysis, with model 18 showing the best performance achieving higher R 2 (0.94) and lower AICc (7760). For all GWR model, 86.4% of R 2 was higher than 0.60, most values distributed in the range of 0.80-0.99, and 86.59% of residual values were within the range of ±2 K. Different parameters resulted in different slope distribution, which indicated that altitude is the major driving factor, followed by NDVI, and albedo. © 2012 IEEE."
"35461255500;9235235300;26643041500;","Aerosols and climate change",2012,"10.1007/978-3-642-25550-2_15","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859755010&doi=10.1007%2f978-3-642-25550-2_15&partnerID=40&md5=cc0edad8f2c1a950751af9a31bb10f05","Climate change is probably the most crucial human-driven environmental problem: the humankind has changed the global radiative balance by changing the atmospheric composition. However, we do not know exactly how rapidly and in which way the global climate is changing. We know even less about what will happen to regional climate in the future. Aerosol particles and clouds can cool the climate, and therefore they counter the warming effect of greenhouse gases. Unfortunately, the effect of aerosols and clouds on radiative balance is currently uncertain, although - in recent years - scientific efforts have been able to improve our understanding. © 2012 Springer-Verlag Berlin Heidelberg."
"55961513200;7403681878;37025370400;7404395984;","GPU implementation of stony brook university 5-class cloud microphysics scheme in the WRF",2012,"10.1109/JSTARS.2011.2175707","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861739420&doi=10.1109%2fJSTARS.2011.2175707&partnerID=40&md5=ccfd28a00c8059e1bd74657eae058c05","The Weather Research and Forecasting (WRF) model is a next-generation mesoscale numerical weather prediction system. It is designed to serve the needs of both operational forecasting and atmospheric research for a broad spectrum of applications across scales ranging from meters to thousands of kilometers. Microphysics plays an important role in weather and climate prediction. Microphysics includes explicitly resolved water vapor, cloud, and precipitation processes. Several bulk water microphysics schemes are available within the WRF, with different numbers of simulated hydrometeor classes and methods for estimating their size, fall speeds, distributions and densities. Stony Brook University scheme is a 5-class scheme with riming intensity predicted to account for the mixed-phase processes. In this paper, we develop an efficient Graphics Processing Unit (GPU) based Stony Brook University scheme. The GPU-based Stony Brook University scheme was compared to a CPU-based single-threaded counterpart on a computational domain of 422 ×297 horizontal grid points with 34 vertical levels. The original Fortran code was first rewritten into a standard C code. After that, C code was verified against Fortran code and CUDA C extensions were added for data parallel execution on GPUs. On a single GPU, we achieved a speed-up of 213× with data I/O and 896× without I/O on NVIDIA GTX 590. Using multiple GPUs, a speed-up of 352× is achieved with I/O for 4 GPUs. We will also discuss how data I/O will be less cumbersome if we ran the complete WRF model on GPUs. © 2012 IEEE."
"57207584882;55183522200;57022054400;7004144610;","On the effect of non-raining parameters in retrieval of surface rain rate using TRMM PR and TMI measurements",2012,"10.1109/JSTARS.2012.2189557","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863508922&doi=10.1109%2fJSTARS.2012.2189557&partnerID=40&md5=393805aaa68ab333dbce560be95b0c27","Microwave radiation with the inherent advantage of its ability to partially penetrate clouds is ideally suited for remote measurements of precipitation, especially over the oceanic regions. The retrieval problem is of great practical interest, as precipitation over the oceans has to be necessarily remotely sensed. More importantly, precipitation is also a crucial input in many weather and climate models. A downward looking space borne radiometer such as the TRMM's Microwave Imager (TMI), however, does not sense the surface rain fall directly. Rather, it measures the upwelling radiation coming from the top-of-atmosphere which depends on the total quantities of the parameters that can affect the radiation in the chosen frequency range. In addition to precipitation, the attenuation and augmentation of total cloud content and integrated precipitable water content by absorption and emission, respectively, affect the microwave brightness temperatures in various frequencies. In the present work, a systematic study has been conducted to investigate the effect of total cloud and precipitable water contents on surface rainrate retrievals from the TMI measured brightness temperatures (BT). While a Bayesian framework is used to assimilate radar reflectivities into hydrometeor structures, a neural network is used to correlate rain and cloud parameters with brightness temperatures. The correlation between the TMI brightness temperatures and the TRMM's Precipitation Radar (TRMM-PR) is used as the benchmark for comparison. A community developed software meso-scale Weather Research and Forecast (WRF) is used to simulate the cloud and precipitable water content, along with the surface rainfall rate for several rain events in the past. Four cases are considered: (a) TRMM PR's near surface rain rate is correlated with TMI brightness temperatures directly; (b) the total cloud and precipitable water contents along with surface rainfall simulated using WRF are correlated with TMI BTs; (c) similar to case (b) with near surface rainfall taken from TRMM PR measurements; (d) total cloud and precipitable water contents and the surface rain rate are corrected with PR vertical reflectivity profile in a Bayesian framework. The freely available QuickBeam software has been used for simulation of reflectivities at the TRMM PR frequency. The corrected data are then correlated with TMI BTs. Results show that surface rain fall retrievals can be radically improved by using TRMM PR vertical rain corrected total cloud and precipitable water content. © 2012 IEEE."
"35205101700;7402146514;55713316500;55703649700;9240820800;7701313284;","Estimation of surface albedo and directional reflectance from Moderate Resolution Imaging Spectroradiometer (MODIS) observations",2012,"10.1016/j.rse.2012.01.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862800736&doi=10.1016%2fj.rse.2012.01.004&partnerID=40&md5=7bc59bd9b1759d92a3a577f344761716","Land surface albedo is one of the key geophysical variables controlling the surface radiation budget. In recent years, land surface albedo products have been generated using data from various satellites. However, some problems exist in those products due to either the failure of the current retrieving procedures resulting from persistent clouds and/or abrupt surface changes, or the reduced temporal or spatial coverage, which may limit their applications. Rapidly generated albedo products that help reduce the impacts of cloud contamination and improve the capture of events such as ephemeral snow and vegetation growth are in demand. In this study, we propose a method for estimating the land surface albedo from Moderate Resolution Imaging Spectroradiometer (MODIS) data using a short temporal window. Instead of executing the atmospheric correction first and then fitting the surface reflectance in the current MODIS albedo procedure, the atmospheric properties (e.g., aerosol optical depth) and surface properties (e.g., surface bidirectional reflectance) were estimated simultaneously. Validations were carried out using various data sources including ground measurements (e.g., from the Surface Radiation (SURFRAD) Network and Greenland Climate Network (GC-Net)) and MODIS AERONET-based Surface Reflectance Validation Network (MODASRVN) data. The results showed comparable albedo estimates with both MODIS data and ground measurements, and the MODASRVN instantaneous surface reflectance was in good agreement with the reflectance estimation from our method. Aerosol optical depth (AOD) retrievals over SURFRAD and MODASRVN sites were also compared with ground measurements. Validation results showed estimation accuracies similar to those of MODIS aerosol products. © 2012 Elsevier Inc."
"57203475350;22946279200;55863085500;55030209200;","A daily merged MODIS Aqua-Terra land surface temperature data set for the conterminous United States",2012,"10.1016/j.rse.2011.12.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857478518&doi=10.1016%2fj.rse.2011.12.019&partnerID=40&md5=9da444dc3ab7a0032f226810442b872f","A major shortcoming of any remotely-sensed land surface temperature (LST) dataset is the lack of observations for cloud-covered areas. A method is presented that uses the Moderate Resolution Imaging Spectroradiometer (MODIS) flying on the Terra platform to fill in spatial gaps in the Aqua MODIS LST dataset over the conterminous United States (CONUS) and limited adjacent areas. Over this domain, data are available for only about 50% of all times and pixels for each of the two MODIS sensors. Coverage is highest in summer and lowest in winter, with major regional variations. The relative close temporal proximity (~3. h) of the Aqua and Terra overpasses provides an opportunity to combine information from the two data sources, which can reduce the data loss, most of which we assume is cloud-related. We applied the approach to create a 'merged' data set that supplements existing Aqua and Terra daytime and nighttime LST products. We used Terra LST data to fill gaps in Aqua data, resulting in a data set tied to the ~1:30. AM/PM overpass times, so that the resulting data closely approximate daily minimum and maximum LST values. In order to use Terra LST observations to supplement Aqua data, an adjustment was applied to account for the different overpass times of the two platforms. Terra's 10:30. AM overpass usually senses a cooler surface than does Aqua with its 1:30. PM overpass. Conversely, for nighttime overpasses, Terra typically measures a warmer surface at 10:30. PM than does Aqua at 1:30. AM. Our approach was to determine, by season, mean Aqua and Terra LST values on the CONUS grid, based on data from a multi-year (2003-2008) period. Adding the mean Aqua-Terra LST differences for the respective season and time of day to a daily gridded Terra LST field removes the mean offset related to overpass time, resulting in LST values that can then be used to fill Aqua LST data gaps. Using independent offsets for each grid cell and season provides a first-order accounting for factors such as land cover, elevation, terrain slope and aspect, latitude, season and snow cover, which control the diurnal cycle of LST. For the six-year period, the merged data set increases data coverage by 24% and 30% for daytime and nighttime overpasses, respectively, relative to the Aqua LST product alone. The CONUS data set is a potentially valuable tool for weather and climate studies in which high spatial and temporal coverage are desired. © 2012."
"6603008554;57219343225;6603368261;","On the characterization of nanoparticles emitted from combustion sources related to understanding their effects on health and climate",2012,"10.1016/j.jhazmat.2011.10.097","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858299021&doi=10.1016%2fj.jhazmat.2011.10.097&partnerID=40&md5=ad93715465ef7305efe6065eb8e12cd3","This work describes the use of well-controlled laboratory flames to produce aerosols of organic carbon (OC) as model particles representative of the OC fraction of combustion-generated particulate matter emissions in fresh exhausts. Water-particle interactions are explored in two specific cases. In the first case, particles are exposed to saturated environments and come into direct contact with liquid water by bubbling flame samples through a column of water. This case is representative of particle-liquid interactions relevant to wet removal routes by particle interception by rain or fog droplets or in biological systems covered with biological fluids composed mostly of water. In the second case, the particles are exposed to sub-saturated vapors with H 2O concentrations representative of cloud-forming atmospheres. The particles' capacity to serve as atmospheric cloud condensation nuclei (CCN) by rapid growth to droplets was measured and compared to NaCl particles, which are highly soluble particles with well known activation diameters. The results show measureable interactions with water in highly saturated conditions. However, in sub-saturated environments, no growth by water condensation was observed, and fresh emissions of OC nanoparticles are not likely to act as CCN in atmospherically relevant humidity. © 2011 Elsevier B.V.."
"18437230800;6603779272;57203052274;55716092000;57196499374;6701378450;57211106013;7006461606;55605765360;7006550762;","Climatic effects of 1950-2050 changes in US anthropogenic aerosols-Part 2: Climate response",2012,"10.5194/acp-12-3349-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859540296&doi=10.5194%2facp-12-3349-2012&partnerID=40&md5=919da84ba1b7c9f96222ac30fec6a61e","We investigate the climate response to changing US anthropogenic aerosol sources over the 1950-2050 period by using the NASA GISS general circulation model (GCM) and comparing to observed US temperature trends. Time-dependent aerosol distributions are generated from the GEOS-Chem chemical transport model applied to historical emission inventories and future projections. Radiative forcing from US anthropogenic aerosols peaked in 1970-1990 and has strongly declined since due to air quality regulations. We find that the regional radiative forcing from US anthropogenic aerosols elicits a strong regional climate response, cooling the central and eastern US by 0.5-1.0 °C on average during 1970-1990, with the strongest effects on maximum daytime temperatures in summer and autumn. Aerosol cooling reflects comparable contributions from direct and indirect (cloud-mediated) radiative effects. Absorbing aerosol (mainly black carbon) has negligible warming effect. Aerosol cooling reduces surface evaporation and thus decreases precipitation along the US east coast, but also increases the southerly flow of moisture from the Gulf of Mexico resulting in increased cloud cover and precipitation in the central US. Observations over the eastern US show a lack of warming in 1960-1980 followed by very rapid warming since, which we reproduce in the GCM and attribute to trends in US anthropogenic aerosol sources. Present US aerosol concentrations are sufficiently low that future air quality improvements are projected to cause little further warming in the US (0.1 °C over 2010-2050). We find that most of the warming from aerosol source controls in the US has already been realized over the 1980-2010 period. © 2012 Author(s)."
"18437230800;6603779272;57203052274;55716092000;57196499374;6701378450;57211106013;7006461606;55605765360;7006550762;","Climatic effects of 1950-2050 changes in US anthropogenic aerosols-Part 1: Aerosol trends and radiative forcing",2012,"10.5194/acp-12-3333-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859557746&doi=10.5194%2facp-12-3333-2012&partnerID=40&md5=fe34d6ab523f648d0b07dc321153cc81","We calculate decadal aerosol direct and indirect (warm cloud) radiative forcings from US anthropogenic sources over the 1950-2050 period. Past and future aerosol distributions are constructed using GEOS-Chem and historical emission inventories and future projections from the IPCC A1B scenario. Aerosol simulations are evaluated with observed spatial distributions and 1980-2010 trends of aerosol concentrations and wet deposition in the contiguous US. Direct and indirect radiative forcing is calculated using the GISS general circulation model and monthly mean aerosol distributions from GEOS-Chem. The radiative forcing from US anthropogenic aerosols is strongly localized over the eastern US. We find that its magnitude peaked in 1970-1990, with values over the eastern US (east of 100° W) of-2.0 W m -2 for direct forcing including contributions from sulfate (-2.0 W m -2), nitrate (-0.2 W m -2), organic carbon (-0.2 W m -2), and black carbon (+0.4 W m -2). The uncertainties in radiative forcing due to aerosol radiative properties are estimated to be about 50%. The aerosol indirect effect is estimated to be of comparable magnitude to the direct forcing. We find that the magnitude of the forcing declined sharply from 1990 to 2010 (by 0.8 W m -2 direct and 1.0 W m -2 indirect), mainly reflecting decreases in SO 2 emissions, and project that it will continue declining post-2010 but at a much slower rate since US SO 2 emissions have already declined by almost 60% from their peak. This suggests that much of the warming effect of reducing US anthropogenic aerosol sources has already been realized. The small positive radiative forcing from US BC emissions (+0.3 W m -2 over the eastern US in 2010; 5% of the global forcing from anthropogenic BC emissions worldwide) suggests that a US emission control strategy focused on BC would have only limited climate benefit. © 2012 Author(s)."
"6506286471;12243565900;57191712049;","The impact of Arctic sea ice on the Arctic energy budget and on the climate of the Northern mid-latitudes",2012,"10.1007/s00382-012-1353-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868706498&doi=10.1007%2fs00382-012-1353-9&partnerID=40&md5=d7aee5ae3fb016a3add058658ef91fd1","The atmospheric general circulation model EC-EARTH-IFS has been applied to investigate the influence of both a reduced and a removed Arctic sea ice cover on the Arctic energy budget and on the climate of the Northern mid-latitudes. Three 40-year simulations driven by original and modified ERA-40 sea surface temperatures and sea ice concentrations have been performed at T255L62 resolution, corresponding to 79 km horizontal resolution. Simulated changes between sensitivity and reference experiments are most pronounced over the Arctic itself where the reduced or removed sea ice leads to strongly increased upward heat and longwave radiation fluxes and precipitation in winter. In summer, the most pronounced change is the stronger absorption of shortwave radiation which is enhanced by optically thinner clouds. Averaged over the year and over the area north of 70° N, the negative energy imbalance at the top of the atmosphere decreases by about 10 W/m2 in both sensitivity experiments. The energy transport across 70° N is reduced. Changes are not restricted to the Arctic. Less extreme cold events and less precipitation are simulated in sub-Arctic and Northern mid-latitude regions in winter. © 2012 The Author(s)."
"7004375028;","Cosmic rays and space weather: Effects on global climate change",2012,"10.5194/angeo-30-9-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859323971&doi=10.5194%2fangeo-30-9-2012&partnerID=40&md5=c2b487a4876100285b1dcbee9f49377a","We consider possible effects of cosmic rays and some other space factors on the Earth's climate change. It is well known that the system of internal and external factors formatting the climate is very unstable; decreasing planetary temperature leads to an increase of snow surface, and decrease of the total solar energy input into the system decreases the planetary temperature even more, etc. From this it follows that even energetically small factors may have a big influence on climate change. In our opinion, the most important of these factors are cosmic rays and cosmic dust through their influence on clouds, and thus, on climate. © 2012 Author(s)."
"28568055900;16550482700;7102294773;18437850800;57188966058;57213358341;57210590791;7004838931;7006901405;7101799663;55156148900;8247122100;35208232500;8684037700;22834248200;21933618400;6701562043;","Evaluating WRF-chem aerosol indirect effects in southeast pacific marine stratocumulus during VOCALS-REx",2012,"10.5194/acp-12-3045-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859153497&doi=10.5194%2facp-12-3045-2012&partnerID=40&md5=f0d7ee8e599735734b6a18c7eeb5a1f0","We evaluate a regional-scale simulation with the WRF-Chem model for the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), which sampled the Southeast Pacific's persistent stratocumulus deck. Evaluation of VOCALS-REx ship-based and three aircraft observations focuses on analyzing how aerosol loading affects marine boundary layer (MBL) dynamics and cloud microphysics. We compare local time series and campaign-averaged longitudinal gradients, and highlight differences in model simulations with (W) and without (NW) wet deposition processes. The higher aerosol loadings in the NW case produce considerable changes in MBL dynamics and cloud microphysics, in accordance with the established conceptual model of aerosol indirect effects. These include increase in cloud albedo, increase in MBL and cloud heights, drizzle suppression, increase in liquid water content, and increase in cloud lifetime. Moreover, better statistical representation of aerosol mass and number concentration improves model fidelity in reproducing observed spatial and temporal variability in cloud properties, including top and base height, droplet concentration, water content, rain rate, optical depth (COD) and liquid water path (LWP). Together, these help to quantify confidence in WRF-Chem's modeled aerosol-cloud interactions, especially in the activation parameterization, while identifying structural and parametric uncertainties including: irreversibility in rain wet removal; overestimation of marine DMS and sea salt emissions, and accelerated aqueous sulfate conversion. Our findings suggest that WRF-Chem simulates marine cloud-aerosol interactions at a level sufficient for applications in forecasting weather and air quality and studying aerosol climate forcing, and may do so with the reliability required for policy analysis. © 2012 Author(s)."
"24068728200;22953153500;7402267338;55942789700;7201453095;7201440389;6602765265;7004864963;6701648204;54790610300;35461763400;16443862200;55942083800;","Biogeography in the air: Fungal diversity over land and oceans",2012,"10.5194/bg-9-1125-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859124326&doi=10.5194%2fbg-9-1125-2012&partnerID=40&md5=b3915518e5c7dbdefbe0d4735582a133","Biogenic aerosols are relevant for the Earth system, climate, and public health on local, regional, and global scales. Up to now, however, little is known about the diversity and biogeography of airborne microorganisms. We present the first DNA-based analysis of airborne fungi on global scales, showing pronounced geographic patterns and boundaries. In particular we find that the ratio of species richness between Basidiomycota and Ascomycota is much higher in continental air than in marine air. This may be an important difference between the ""blue ocean"" and ""green ocean"" regimes in the formation of clouds and precipitation, for which fungal spores can act as nuclei. Our findings also suggest that air flow patterns and the global atmospheric circulation are important for the understanding of global changes in biodiversity. © Author(s) 2012."
"7005808242;6701455548;","Using relative humidity as a state variable in climate feedback analysis",2012,"10.1175/JCLI-D-11-00721.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859974350&doi=10.1175%2fJCLI-D-11-00721.1&partnerID=40&md5=b02dca05f21bee15dbc1c468efafc53f","An approach to climate change feedback analysis is described in which tropospheric relative humidity replaces specific humidity as the state variable that, along with the temperature structure, surface albedos, and clouds, controls the magnitude of the response of global mean surface temperature to a radiative forcing. Despite being simply a regrouping of terms in the feedback analysis, this alternative perspective has the benefit of removing most of the pervasive cancellation between water and lapse-rate feedbacks seen in models. As a consequence, the individual feedbacks have less scatter than in the traditional formulation. The role of cloud feedbacks in controlling climate sensitivity is also reflected more clearly in the new formulation. © 2012 American Meteorological Society."
"36244335600;7006306835;56744278700;","Tropical tropospheric-only responses to absorbing aerosols",2012,"10.1175/JCLI-D-11-00122.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859345608&doi=10.1175%2fJCLI-D-11-00122.1&partnerID=40&md5=540737a13305d3ff3f704f927228f56d","Absorbing aerosols affect the earth's climate through direct radiative heating of the troposphere. This study analyzes the tropical tropospheric-only response to a globally uniform increase in black carbon, simulated with an atmospheric general circulation model, to gain insight into the interactions that determine the radiative flux perturbation. Over the convective regions, heating in the free troposphere hinders the vertical development of deep cumulus clouds, resulting in the detrainment of more cloudy air into the large-scale environment and stronger cloud reflection. A different mechanism operates over the subsidence regions, where heating near the boundary layer top causes a substantial reduction in low cloud amount thermodynamically by decreasing relative humidity and dynamically by lowering cloud top. These findings, which align well with previous general circulation model and large-eddy simulation calculations for black carbon, provide physically based explanations for the main characteristics of the tropical tropospheric adjustment. The implications for quantifying the climate perturbation posed by absorbing aerosols are discussed. © 2012 American Meteorological Society."
"7202899330;7102953444;6602844274;6701606453;56493740900;55170496500;","The global character of the flux of downward longwave radiation",2012,"10.1175/JCLI-D-11-00262.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859368731&doi=10.1175%2fJCLI-D-11-00262.1&partnerID=40&md5=4a9612ff361a244fd74a3e5e06d07e26","Four different types of estimates of the surface downwelling longwave radiative flux (DLR) are reviewed. One group of estimates synthesizes global cloud, aerosol, and other information in a radiation model that is used to calculate fluxes. Because these synthesis fluxes have been assessed against observations, the globalmean values of these fluxes are deemed to be the most credible of the four different categories reviewed. The global, annual mean DLR lies between approximately 344 and 350 W m -2 with an error of approximately 610 W m -2 that arises mostly from the uncertainty in atmospheric state that governs the estimation of the clear-sky emission. The authors conclude that the DLR derived from global climate models are biased low by approximately 10 W m -2 and even larger differences are found with respect to reanalysis climate data. The DLR inferred from a surface energy balance closure is also substantially smaller that the range found from synthesis products suggesting that current depictions of surface energy balance also require revision. The effect of clouds on the DLR, largely facilitated by the new cloud base information from the CloudSat radar, is estimated to lie in the range from 24 to 34 W m -2 for the global cloud radiative effect (all-sky minus clear-sky DLR). This effect is strongly modulated by the underlying water vapor that gives rise to a maximum sensitivity of the DLR to cloud occurring in the colder drier regions of the planet. The bottom of atmosphere (BOA) cloud effect directly contrast the effect of clouds on the top of atmosphere (TOA) fluxes that is maximum in regions of deepest and coldest clouds in the moist tropics. © 2012 American Meteorological Society."
"14045744500;7006146719;7003582587;","Evaluation of two cloud parametrization schemes using ARM and Cloud-Net observations",2012,"10.1002/qj.969","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862228881&doi=10.1002%2fqj.969&partnerID=40&md5=481291ca7c1b341a4a65783d4bccc815","Ground-based remote-sensing observations from Atmospheric Radiation Measurement (ARM) and Cloud-Net sites are used to evaluate the clouds predicted by a weather forecasting and climate model. By evaluating the cloud predictions using separate measures for the errors in frequency of occurrence, amount when present, and timing, we provide a detailed assessment of the model performance, which is relevant to weather and climate time-scales. Importantly, this methodology will be of great use when attempting to develop a cloud parametrization scheme, as it provides a clearer picture of the current deficiencies in the predicted clouds. Using the Met Office Unified Model, it is shown that when cloud fractions produced by a diagnostic and a prognostic cloud scheme are compared, the prognostic cloud scheme shows improvements to the biases in frequency of occurrence of low, medium and high cloud and to the frequency distributions of cloud amount when cloud is present. The mean cloud profiles are generally improved, although it is shown that in some cases the diagnostic scheme produced misleadingly good mean profiles as a result of compensating errors in frequency of occurrence and amount when present. Some biases remain when using the prognostic scheme, notably the underprediction of mean ice cloud fraction due to the amount when present being too low, and the overprediction of mean liquid cloud fraction due to the frequency of occurrence being too high. © 2011 Royal Meteorological Society and British Crown Copyright, the Met Office."
"14045744500;","Improvements to a prognostic cloud scheme through changes to its cloud erosion parametrization",2012,"10.1002/asl.374","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859740870&doi=10.1002%2fasl.374&partnerID=40&md5=e67ea2992cfcb4015bb782c62212dd86","A cloud erosion parametrization is developed for use in a prognostic cloud scheme in a general circulation model. Using geometrical considerations, the rate of evaporation of cloud due to unresolved mixing of clear and cloudy air is related to the cloud fraction, in a way that maximizes evaporation when the sky is half covered in cloud and reduces it to zero when the sky is overcast or clear. When used to simulate present-day climate with the Met Office Unified Model, this parametrization leads to several improvements in the cloud and radiation fields. © 2012 British Crown copyright, the Met Office."
"24472110700;7003663305;7003875148;","On the relationship between thermodynamic structure and cloud top, and its climate significance in the Arctic",2012,"10.1175/JCLI-D-11-00186.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859343362&doi=10.1175%2fJCLI-D-11-00186.1&partnerID=40&md5=a0ccd91c2bf901277017a7312a512a11","Cloud and thermodynamic characteristics from three Arctic observation sites are investigated to understand the collocation between low-level clouds and temperature inversions.Aregime where cloud topwas 100-200 mabove the inversion base [cloud inside inversion (CII)] was frequently observed at central Arctic Ocean sites, while observations from Barrow, Alaska, indicate that cloud tops were more frequently constrained to inversion base height [cloud capped by inversion (CCI)]. Cloud base and top heights were lower, and temperature inversions were also stronger and deeper, during CII cases.Both cloud regimeswere often decoupled from the surface except for CCI over Barrow. In-cloud lapse rates differ and suggest increased cloud-mixing potential for CII cases. Specific humidity inversions were collocated with temperature inversions for more than 60% of the CCI and more than 85% of the CII regimes. Horizontal advection of heat and moisture is hypothesized as an important process controlling thermodynamic structure and efficiency of cloud-generated motions. The portion of CII clouds above the inversion contains cloud radar signatures consistent with cloud droplets. The authors test the longwave radiative impact of cloud liquid above the inversion through hypothetical liquid water distributions. Optically thin CII clouds alter the effective cloud emission temperature and can lead to an increase in surface flux on the order of 1.5 W m -2 relative to the same cloud but whose top does not extend above the inversion base. The top of atmosphere impact is even larger, increasing outgoing longwave radiation up to 10 W m -2. These results suggest a potentially significant longwave radiative forcing via simple liquid redistributions for a distinctly dominant cloud regime over sea ice. © 2012 American Meteorological Society."
"38863214100;7102011703;55656837900;","The initiation of modern ""soft snowball"" and ""hard snowball"" climates in CCSM3. Part II: Climate dynamic feedbacks",2012,"10.1175/JCLI-D-11-00190.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859950786&doi=10.1175%2fJCLI-D-11-00190.1&partnerID=40&md5=546b84d89afbbd7be560025cfb0656b0","This study investigates the climate dynamic feedbacks during a transition from the present climate to the extremely cold climate of a ""Snowball Earth"" using the Community Climate System Model, version 3 (CCSM3). With the land-sea distribution fixed to modern, it is found that by reducing solar luminosity and/or carbon dioxide concentration: 1) the amount of atmospheric water vapor and its attendant greenhouse effect decrease with the logarithm of sea ice cover, thereby promoting the expansion of sea ice; 2) over the sea ice, the cloud radiative feedback is positive, thus enhancing sea ice advance; over the ocean, the cloud radiative feedback is first negative and then becomes positive as sea ice enters the tropics; and 3) the strength of the atmospheric Hadley cell and the wind-driven ocean circulation increases significantly in the Southern Hemisphere, inhibiting the expansion of sea ice into the tropics. Meanwhile, the North Atlantic Deep Water cell disappears and the Antarctic Bottom Water cell strengthens and expands to occupy almost the entire Atlantic basin. In the experiment with 6% less solar radiation and 70 ppmv CO 2 compared to the control experiment with 100% solar radiation and 355 ppmv CO 2 near the ice edge (28°S latitude), the changes of solar radiation, CO 2 forcing, water vapor greenhouse effect, longwave cloud forcing at the top of the model, and atmospheric and oceanic energy transport are -22.4, -6.2, -54.4, +6.2, and +16.3 W m -2, respectively. Therefore, the major controlling factors in producing global ice cover are ice albedo feedback (Yang et al., Part I) and water vapor feedback. © 2012 American Meteorological Society."
"8877858700;7006698304;7006577693;6701754792;6603195572;","Assessing the performance of a prognostic and a diagnostic cloud scheme using single column model simulations of TWP-ICE",2012,"10.1002/qj.954","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858406890&doi=10.1002%2fqj.954&partnerID=40&md5=388c6cba75d4dc4695742a82d0568cdb","Single column model simulations using the UK Met Office Unified Model, as used in the Australian Community Climate Earth System Simulator, are presented for the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) field study. Two formulations for the representation of clouds are compared with the extensive observations taken during the campaign, giving insight into the ability of the model to simulate tropical cloud systems. During the active monsoon phase the modelled cloud cover has a stronger dependence on relative humidity than the observations. Observed ice cloud properties during the suppressed monsoon period show that the ice water content is significantly underestimated in the simulations. The profiles of modelled ice fall speeds are faster than those observed in the levels above 12 km, implying that the observations have smaller sized particles in larger concentrations than the models. Both simulations show similar errors in the diurnal cycle of relative humidity during the active monsoon phase, suggesting that the error is less sensitive to the choice of cloud scheme and rather is driven by the convection scheme. However, during the times of suppressed convection the relative humidity error is different between the simulations, with congestus convection drying the environment too much, particularly in the prognostic cloud-scheme simulation. This result shows that the choice of cloud scheme and the way that the cloud and convection schemes interact plays a role in the temperature and moisture errors during the suppressed monsoon phase, which will impact the three-dimensional model simulations of tropical variability. © 2011 Royal Meteorological Society."
"57200530823;25227357000;7102018821;7401895830;23028717700;","Direct and semi-direct radiative effects of anthropogenic aerosols in the Western United States: Seasonal and geographical variations according to regional climate characteristics",2012,"10.1007/s10584-011-0169-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857924587&doi=10.1007%2fs10584-011-0169-7&partnerID=40&md5=7bca4ac1fe2b261fdd178f8eaf8b16f9","The direct and semi-direct radiative effects of anthropogenic aerosols on the radiative transfer and cloud fields in the Western United States (WUS) according to seasonal aerosol optical depth (AOD) and regional climate are examined using a regional climate model (RCM) in conjunction with the aerosol fields from a GEOS-Chem chemical-transport model (CTM) simulation. The two radiative effects cannot be separated within the experimental design in this study, thus the combined direct- and semi-direct effects are called radiative effects hereafter. The CTM shows that the AOD associated with the anthropogenic aerosols is chiefly due to sulfates with minor contributions from black carbon (BC) and that the AOD of the anthropogenic aerosol varies according to local emissions and the seasonal low-level winds. The RCM-simulated anthropogenic aerosol radiative effects vary according to the characteristics of regional climate, in addition to the AOD. The effects on the top of the atmosphere (TOA) outgoing shortwave radiation (OSRT) range from -0.2 Wm -2 to -1 Wm -2. In Northwestern US (NWUS), the maximum and minimum impact of anthropogenic aerosols on OSRT occurs in summer and winter, respectively, following the seasonal AOD. In Arizona-New Mexico (AZNM), the effect of anthropogenic sulfates on OSRT shows a bimodal distribution with winter/summer minima and spring/fall maxima, while the effect of anthropogenic BC shows a single peak in summer. The anthropogenic aerosols affect surface insolation range from -0.6 Wm -2 to -2.4 Wm -2, with similar variations found for the effects on OSRT except that the radiative effects of anthropogenic BC over AZNM show a bimodal distribution with spring/fall maxima and summer/winter minima. The radiative effects of anthropogenic sulfates on TOA outgoing longwave radiation (OLR) and the surface downward longwave radiation (DLRS) are notable only in summer and are characterized by strong geographical contrasts; the summer OLR in NWUS (AZNM) is reduced (enhanced) by 0.52 Wm -2 (1.14 Wm -2). The anthropogenic sulfates enhance (reduce) summer DLRS by 0.2 Wm -2 (0.65 Wm -2) in NWUS (AZNM). The anthropogenic BC affect DLRS noticeably only in AZNM during summer. The anthropogenic aerosols affect the cloud water path (CWP) and the radiative transfer noticeably only in summer when convective clouds are dominant. Primarily shortwave-reflecting anthropogenic sulfates decrease and increase CWP in AZNM and NWUS, respectively, however, the shortwave-absorbing anthropogenic BC reduces CWP in both regions. Due to strong feedback via convective clouds, the radiative effects of anthropogenic aerosols on the summer radiation field are more closely correlated with the changes in CWP than the AOD. The radiative effect of the total anthropogenic aerosols is dominated by the anthropogenic sulfates that contribute more than 80% of the total AOD associated with the anthropogenic aerosols. © 2011 Springer Science+Business Media B.V."
"8321475300;57203259838;","A new view of the dynamics, stability and longevity of volcanic clouds",2012,"10.1016/j.epsl.2012.01.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857230375&doi=10.1016%2fj.epsl.2012.01.025&partnerID=40&md5=edf196494c2e8dd2f437bbef65be9407","Powerful explosive volcanic eruptions inject ash high into the atmosphere, which spreads to form umbrella clouds. Identifying key physical processes governing the dynamics, stability and longevity of umbrella clouds is central to assessing volcanic hazards as well as the nature of volcanic forcings on climate. Here we present a series of laboratory experiments producing turbulent particle-laden jets and subsequent axisymmetric intrusive gravity currents into a stratified environment. Our experiments reproduce many of the main dynamical regimes observed during the formation of an explosive volcanic column, and highlight new dynamics for the umbrella cloud. Theoretical predictions of column collapse from a simple model of a turbulent jet are in good agreement with experimental observations as well as previous studies. Depending on the flow intensity, the strength of the initial environmental density stratification and the particle concentration at the source, resulting umbrella clouds can, however, evolve through a series of new regimes as a result of the dynamics of particle sedimentation within these flows as well as from their bases. Using scaling theory we show that during cloud spreading, internal sedimentation drives the growth and intermittent overturn of thin, gravitationally unstable ""particle boundary layers"" (PBLs) as particle-rich plumes. This PBL-driven convection can have remarkable effects ranging from progressive dilution of clouds to their catastrophic overturn and collapse. In natural eruptions, whether the dynamics of PBLs play a major role in particle sedimentation depends on the grain size distribution inside the cloud and on eruption column height. In general, particles larger than ~. 60μm-1. mm are expected to settle individually, whereas finer particles will accumulate PBLs resulting in the formation of armless mammatus clouds or dangerous gravity currents at much larger distances from the volcanic vent than ever considered before. Such dynamics is apparent in observations of numerous modern eruptions and is inferred from the deposits of historic and prehistoric eruptions for where there exist appropriate data. Consideration of the consequences of these phenomena for problems such as volcanic hazards to humans and climate change may, thus, be very important in the assessment of future eruptions. © 2012 Elsevier B.V.."
"8315173500;6506738607;8696069500;","Separation of contributions from radiative feedbacks to polar amplification on an aquaplanet",2012,"10.1175/JCLI-D-11-00246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859950145&doi=10.1175%2fJCLI-D-11-00246.1&partnerID=40&md5=306f2dd1fdd32699a3ba07aded0c35fc","When climate is forced by a doubling of CO 2, a number of feedback processes are induced, such as changes of water vapor, clouds, and surface albedo. Here the CO 2 forcing and concomitant feedbacks are studied individually using a general circulation model coupled to an aquaplanet mixed layer ocean. A technique for fixing the radiative effects of moisture and clouds by reusing these variables from 1 × CO 2 and 2 × CO 2 equilibriumclimates in the model's radiation code allows for a detailed decomposition of forcings, feedbacks, and responses. The cloud feedback in this model is found to have a weak global average effect and surface albedo feedbacks have been eliminated. As in previous studies, the water vapor feedback is found to approximately double climate sensitivity, but while its radiative effect is strongly amplified at low latitudes, the resulting response displays about the same degree of polar amplification as the full all-feedbacks experiment. In fact, atmospheric energy transports are found to change in a way that yields the same meridional pattern of response as when the water vapor feedback is turned off. The authors conclude that while the water vapor feedback does not in itself lead to polar amplification by increasing the ratio of high- to low-latitude warming, it does double climate sensitivity both at low and high latitudes. A polar amplification induced by other feedbacks in the system, such as the Planck and lapse rate feedbacks here, is thus strengthened in the sense of increasing the difference in high- and low-latitude warming. © 2012 American Meteorological Society."
"57198064763;7102708039;7004032501;9239400200;57206924573;","Total cloud cover from satellite observations and climate models",2012,"10.1016/j.atmosres.2012.01.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857036934&doi=10.1016%2fj.atmosres.2012.01.005&partnerID=40&md5=ebea6468056fb4b50931f073c42e1125","Global and zonal monthly means of cloud cover fraction for total cloudiness (CF) from the ISCCP D2 dataset are compared to same quantities produced by the 20th century simulations of 21 climate models from the World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project phase 3 (CMIP3). The comparison spans the time frame from January 1984 to December 1999 and the global and zonal averages of CF are studied. It is shown that the global mean of CF for the PCMDI-CMIP3 models, averaged over the whole period, exhibits a considerable variance and generally underestimates the ISCCP value. Large differences among models, and between models and observations, are found in the polar areas, where both models and satellite observations are less reliable, and especially near Antarctica. For this reason the zonal analysis is focused over the 60° S-60° N latitudinal belt, which includes the tropical area and mid-latitudes. The two hemispheres are analysed separately to show the variation of the amplitude of the seasonal cycle. Most models underestimate the yearly averaged values of CF over all the analysed areas, whilst they capture, in a qualitatively correct way, the magnitude and the sign of the seasonal cycle over the whole geographical domain, but overestimate the amplitude of the seasonal cycle in the tropical areas and at mid-latitudes, when taken separately. The interannual variability of the yearly averages is underestimated by all models in each area analysed, and also the interannual variability of the amplitude of the seasonal cycle is underestimated, but to a lesser extent. This work shows that the climate models have a heterogeneous behaviour in simulating the CF over different areas of the Globe, with a very wide span both with observed CF and among themselves. Some models agree quite well with the observations in one or more of the metrics employed in this analysis, but not a single model has a statistically significant agreement with the observational datasets on yearly averaged values of CF and on the amplitude of the seasonal cycle over all analysed areas. © 2012 Elsevier B.V."
"7006041988;7203062127;57203030873;8866821900;7003663305;57202891769;7404416268;","A characterization of the present-day arctic atmosphere in CCSM4",2012,"10.1175/JCLI-D-11-00228.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858257292&doi=10.1175%2fJCLI-D-11-00228.1&partnerID=40&md5=5b9bfdbb5449d70c81d4dce13391e2de","Simulation of key features of the Arctic atmosphere in the Community Climate System Model, version 4 (CCSM4) is evaluated against observational and reanalysis datasets for the present-day (1981-2005). Surface air temperature, sea level pressure, cloud cover and phase, precipitation and evaporation, the atmospheric energy budget, and lower-tropospheric stability are evaluated. Simulated surface air temperatures are found to be slightly too cold when compared with the 40-yr ECMWF Re-Analysis (ERA-40). Spatial patterns and temporal variability are well simulated. Evaluation of the sea level pressure demonstrates some large biases, most noticeably an under simulation of the Beaufort High during spring and autumn. Monthly Arctic-wide biases of up to 13 mb are reported. Cloud cover is underpredicted for all but summer months, and cloud phase is demonstrated to be different from observations. Despite low cloud cover, simulated all-sky liquid water paths are too high, while ice water path was generally too low. Precipitation is found to be excessive over much of the Arctic compared to ERA-40 and the Global Precipitation Climatology Project (GPCP) estimates. With some exceptions, evaporation is well captured by CCSM4, resulting in P - E estimates that are too high. CCSM4 energy budget terms show promising agreement with estimates from several sources. The most noticeable exception to this is the top of the atmosphere (TOA) fluxes that are found to be too low while surface fluxes are found to be too high during summer months. Finally, the lower troposphere is found to be too stable when compared to ERA-40 during all times of year but particularly during spring and summer months. © 2012 American Meteorological Society."
"7005930509;26431001200;7006230094;57210350827;6602098362;57203030873;7004126618;55173848800;","True to milankovitch: Glacial inception in the new community climate system model",2012,"10.1175/JCLI-D-11-00044.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858257287&doi=10.1175%2fJCLI-D-11-00044.1&partnerID=40&md5=d9f9ddb737dbb191e6e08fc108dcb8c9","The equilibrium solution of a fully coupled general circulation model with present-day orbital forcing is compared to the solution of the same model with the orbital forcing from 115 000 years ago. The difference in snow accumulation between these two simulations has a pattern and a magnitude comparable to the ones inferred from reconstructions for the last glacial inception. This is a major improvement over previous similar studies, and the increased realism is attributed to the higher spatial resolution in the atmospheric model, which allows for a more accurate representation of the orography of northern Canada and Siberia. The analysis of the atmospheric heat budget reveals that, as postulated by Milankovitch's hypothesis, the only necessary positive feedback is the snow-albedo feedback, which is initiated by reduced melting of snow and sea ice in the summer. However, this positive feedback is almost fully compensated by an increased meridional heat transport in the atmosphere and a reduced concentration of low Arctic clouds. In contrast to similar previous studies, the ocean heat transport remains largely unchanged. This stability of the northern North Atlantic circulation is explained by the regulating effect of the freshwater import through the Nares Strait and Northwest Passage and the spiciness import by the North Atlantic Current. © 2012 American Meteorological Society."
"57200319057;7006705919;","Climate simulations with an isentropic finite-volume dynamical core",2012,"10.1175/2011JCLI4184.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859947788&doi=10.1175%2f2011JCLI4184.1&partnerID=40&md5=ea314bafaf1253fd027bdea5506a66cf","This paper discusses the impact of changing the vertical coordinate from a hybrid pressure to a hybridisentropic coordinate within the finite-volume (FV) dynamical core of the Community Atmosphere Model (CAM). Results from a 20-yr climate simulation using the new model coordinate configuration are compared to control simulations produced by the Eulerian spectral and FV dynamical cores of CAM, which both use a pressure-based (δ - P) coordinate. The same physical parameterization package is employed in all three dynamical cores. The isentropic modeling framework significantly alters the simulated climatology and has several desirable features. The revised model produces a better representation of heat transport processes in the atmosphere leading to much improved atmospheric temperatures. The authors show that the isentropic model is very effective in reducing the long-standing cold temperature bias in the upper troposphere and lower stratosphere, a deficiency shared among most climate models. The warmer upper troposphere and stratosphere seen in the isentropic model reduces the global coverage of high clouds, which is in better agreement with observations. The isentropic model also shows improvements in the simulated wintertime mean sea level pressure field in the Northern Hemisphere. © 2012 American Meteorological Society."
"24468968100;7006417494;7004093412;7102696626;","Temperature-moisture dependence of the deep convective transition as a constraint on entrainment in climate models",2012,"10.1175/JAS-D-11-0164.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861476064&doi=10.1175%2fJAS-D-11-0164.1&partnerID=40&md5=9956d6e9b4e25344dea4340e1f251a45","Properties of the transition to strong deep convection, as previously observed in satellite precipitation statistics, are analyzed using parcel stability computations and a convective plume velocity equation. A set of alternative entrainment assumptions yields very different characteristics of the deep convection onset boundary (here measured by conditional instability and plume vertical velocity) in a bulk temperature-water vapor thermodynamic plane. In observations the threshold value of column water vapor above which there is a rapid increase in precipitation, referred to as the critical value, increases with temperature, but not as quickly as column saturation, and this can be matched only for cases with sufficiently strong entrainment. This corroborates the earlier hypothesis that entraining plumes can explain this feature seen in observations, and it places bounds on the lower-tropospheric entrainment. Examination of a simple interactive entrainment scheme in which a minimum turbulent entrainment is enhanced by a dynamic entrainment (associated with buoyancy-induced vertical acceleration) shows that the deep convection onset curve is governed by the prescribed minimum entrainment. Results from a 0.5° resolution version of the Community Climate System Model, whose convective parameterization includes substantial entrainment, yield a reasonable match to satellite observations in several respects. Temperature-water vapor dependence is seen to agree well with the plume calculations and with offline simulations performed using the convection scheme of the model. These findings suggest that the convective transition characteristics, including the onset curve in the temperature- water vapor plane, can provide a substantial constraint for entrainment assumptions used in climate model deep convective parameterizations. © 2012 American Meteorological Society."
"55172258800;7401796996;8629713500;36570526700;","Evaluation and intercomparison of cloud fraction and radiative fluxes in recent reanalyses over the arctic using BSRN surface observations",2012,"10.1175/JCLI-D-11-00147.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859339102&doi=10.1175%2fJCLI-D-11-00147.1&partnerID=40&md5=c6a08c0cefc9bf6a8a4644509f256156","With continual advancements in data assimilation systems, new observing systems, and improvements in model parameterizations, several new atmospheric reanalysis datasets have recently become available. Before using these new reanalyses it is important to assess the strengths and underlying biases contained in each dataset. A study has been performed to evaluate and compare cloud fractions (CFs) and surface radiative fluxes in several of these latest reanalyses over the Arctic using 15 years (1994-2008) of high-quality Baseline Surface Radiation Network (BSRN) observations from Barrow (BAR) and Ny-Alesund (NYA) surface stations. The five reanalyses being evaluated in this study are (i) NASA's Modern-Era Retrospective analysis for Research and Applications (MERRA), (ii) NCEP's Climate Forecast System Reanalysis (CFSR), (iii) NOAA's Twentieth Century Reanalysis Project (20CR), (iv) ECMWF's Interim Reanalysis (ERA-I), and (v) NCEP-Department of Energy (DOE)'s Reanalysis II (R2). All of the reanalyses show considerable bias in reanalyzed CF during the year, especially in winter. The large CF biases have been reflected in the surface radiation fields, as monthly biases in shortwave (SW) and longwave (LW) fluxes are more than 90 (June) and 60 W m -2 (March), respectively, in some reanalyses. ERA-I and CFSR performed the best in reanalyzing surface downwelling fluxes with annual mean biases less than 4.7 (SW) and 3.4 W m -2 (LW) over both Arctic sites. Even when producing the observed CF, radiation flux errors were found to exist in the reanalyses suggesting that they may not always be dependent on CF errors but rather on variations of more complex cloud properties, water vapor content, or aerosol loading within the reanalyses. © 2012 American Meteorological Society."
"57202891769;57202754759;26431001200;57210350827;55193777900;","Twenty-first-century arctic climate change in CCSM4",2012,"10.1175/JCLI-D-11-00220.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859949670&doi=10.1175%2fJCLI-D-11-00220.1&partnerID=40&md5=624ab622ebb40457ab2e73b00a91bfbe","The authors summarize the twenty-first-century Arctic climate simulated by NCAR's Community Climate System Model, version 4 (CCSM4). Under a strong radiative forcing scenario, the model simulates a much warmer, wetter, cloudier, and stormier Arctic climate with considerably less sea ice and a fresher Arctic Ocean. The high correlation among the variables composing these changes-temperature, precipitation, cloudiness, sea level pressure (SLP), and ice concentration-suggests that their close coupling collectively represents a fingerprint of Arctic climate change. Although the projected changes in CCSM4 are generally consistent with those in other GCMs, several noteworthy features are identified. Despite more global warming in CCSM4, Arctic changes are generally less than under comparable greenhouse forcing in CCSM3, as represented by Arctic amplification (16% weaker) and the date of a seasonally ice-free Arctic Ocean (20 years later). Autumn is the season of the most pronounced Arctic climate change among all the primary variables. The changes are very similar across the five ensemble members, although SLP displays the largest internal variability. The SLP response exhibits a significant trend toward stronger extreme Arctic cyclones, implying greater wave activity that would promote coastal erosion. Based on a commonly used definition of the Arctic (the area encompassing the 10°C July air temperature isotherm), the region shrinks by about 40% during the twenty-first century, in conjunction with a nearly 10-K warming trend poleward of 70°N. Despite this pronounced long-term warming, CCSM4 simulates a hiatus in the secular Arctic climate trends during a decade-long stretch in the 2040s and to a lesser extent in the 2090s. These pauses occur despite averaging over five ensemble members and are remarkable because they happen under the most extreme greenhouseforcing scenario and in the most climatically sensitive region of the world. © 2012 American Meteorological Society."
"7005678429;7003521825;","Valuing the non-CO 2 climate impacts of aviation",2012,"10.1007/s10584-011-0168-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857916186&doi=10.1007%2fs10584-011-0168-8&partnerID=40&md5=759d5dfe662b42e596129acaa357c5b1","The non-CO 2 climate impact of aviation (NO x and contrails) is assessed and emissions weighting factors (EWFs) i. e., the factor by which aviation CO 2 emissions should be multiplied to get the CO 2-equivalent emissions for annual fleet average conditions are estimated. The EWFs are estimated using two economic metrics. One is based on the relative damage cost between non-CO 2 forcers and CO 2. The other is based on the cost-effective valuation between the non-CO 2 forcers and CO 2 given an upper ceiling on the global annual average surface temperature (set at 2 K above pre-industrial levels). We also estimate EWFs using three physical metrics, Global Warming Potential (GWP), Global Temperature change Potential (GTP) and Sustained GTP (SGTP) and compare our results with the economics based metrics. Given best estimates on the forcing contributions from CO 2, contrails and NO x from aviation and by using a discount rate of 3%/year, the RDC based metric gives an EWF equal to 1.4 (slightly higher than EWFs based on GWP and SGTP using a 100 year time horizon). EWF using the cost-effective approach depends on the time that remains before stabilization occurs. It is roughly equal to unity until a few years before the temperature reaches its ceiling, and approximately 2 when stabilization has taken place. EWFs based on GTP resemble those based on CETO when the time left to when stabilization occurs is sufficiently large. Once stabilization has occurred CETO values resemble RDC based values. If aviation-induced cirrus clouds are included, uncertainties increase and the EWFs for GWP, SGTP and RDC based metrics end up in the range 1.3-2.9, while EWFs for GTP and CETO remain close to unity in the near term. © 2011 The Author(s)."
"6503862357;7006146499;7006430057;6603665346;","Control of atmospheric particles on diffuse radiation and terrestrial plant productivity: A review",2012,"10.1177/0309133311434244","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858211704&doi=10.1177%2f0309133311434244&partnerID=40&md5=4fcd921568e997d4b67bc86144412c15","Terrestrial plant productivity tends to increase under increasing but non-saturating photosynthetically active solar radiation when water, temperature and nutrients are not limiting. However, studies have shown that photosynthesis can also be higher under enhanced diffuse light despite a decrease in total irradiance. Clouds and atmospheric aerosols are two important variables that determine the total and proportion of diffuse light reaching the surface and thereby the rate of photosynthesis and carbon accumulation in plants. In addition to these factors, the response of plants to diffuse radiation is also dependant on plant characteristics such as functional types, leaf physiology, leaf area, leaf inclination, canopy structure and shape (i.e. clumping). Local environmental conditions (i.e. temperature, soil moisture, vapour pressure deficit, etc.) then modulate these plant responses. Changes in solar radiation as a consequence of clouds and aerosols thus can modify the carbon balance of terrestrial ecosystems. Therefore, understanding the role of solar radiation in terrestrial carbon processes has become one of the goals in terrestrial carbon cycle studies. It can help to identify the control and mechanisms of carbon processes and determines the geographical and temporal distribution of the major pools and fluxes in the global carbon cycle. Here we review the role of clouds and aerosols in partitioning solar radiation and their interactions with carbon processes of terrestrial plants. We also focus our review on vegetation characteristics that control the impact of radiation partitioning on vegetation carbon processes and the role of modelling approach to study this impact. We identify gaps in this field of research and further propose recommendations to bridge the gap. © SAGE Publications 2012."
"7404894686;6602118945;16319355000;7006504263;8926905500;6701564513;6701836704;6604059069;56213950600;57200304476;8750834400;26643472200;55244987000;6602888227;56650257600;7006712738;7005352058;7006817766;6506763166;6602208685;6504825361;57205845766;6604017334;53165083100;","The 2010 European Venus Explorer (EVE) mission proposal",2012,"10.1007/s10686-011-9259-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860224520&doi=10.1007%2fs10686-011-9259-9&partnerID=40&md5=5bbb532ccfabbd07ee5351e93ce34ba2","The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an 'M-class' mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55 km, where temperatures and pressures are benign (~25°C and ~0. 5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond. © 2011 Springer Science+Business Media B.V."
"55924208000;","Towards the probabilistic Earth-system simulator: A vision for the future of climate and weather prediction",2012,"10.1002/qj.1923","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862160611&doi=10.1002%2fqj.1923&partnerID=40&md5=4ddc88682af65d393e6a91d4c3983da4","There is no more challenging problem in computational science than that of estimating, as accurately as science and technology allows, the future evolution of Earth's climate; nor indeed is there a problem whose solution has such importance and urgency. Historically, the simulation tools needed to predict climate have been developed, somewhat independently, at a number of weather and climate institutes around the world. While these simulators are individually deterministic, it is often assumed that the resulting diversity provides a useful quantification of uncertainty in global or regional predictions. However, this notion is not well founded theoretically and corresponding 'multi-simulator' estimates of uncertainty can be prone to systemic failure. Separate to this, individual institutes are now facing considerable challenges in finding the human and computational resources needed to develop more accurate weather and climate simulators with higher resolution and full Earth-system complexity. A new approach, originally designed to improve reliability in ensemble-based numerical weather prediction, is introduced to help solve these two rather different problems. Using stochastic mathematics, this approach recognizes uncertainty explicitly in the parametrized representation of unresolved climatic processes. Stochastic parametrization is shown to be more consistent with the underlying equations of motion and, moreover, provides more skilful estimates of uncertainty when compared with estimates from traditional multi-simulator ensembles, on time-scales where verification data exist. Stochastic parametrization can also help reduce long-term biases which have bedevilled numerical simulations of climate from the earliest days to the present. As a result, it is suggested that the need to maintain a large 'gene pool' of quasi-independent deterministic simulators may be obviated by the development of probabilistic Earth-system simulators. Consistent with the conclusions of the World Summit on Climate Modelling, this in turn implies that individual institutes will be able to pool human and computational resources in developing future-generation simulators, thus benefitting from economies of scale; the establishment of the Airbus consortium provides a useful analogy here. As a further stimulus for such evolution, discussion is given to a potential new synergy between the development of dynamical cores, and stochastic processing hardware. However, it is concluded that the traditional challenge in numerical weather prediction, of reducing deterministic measures of forecast error, may increasingly become an obstacle to the seamless development of probabilistic weather and climate simulators, paradoxical as that may appear at first sight. Indeed, going further, it is argued that it may be time to consider focusing operational weather forecast development entirely on high-resolution ensemble prediction systems. Finally, by considering the exceptionally challenging problem of quantifying cloud feedback in climate change, it is argued that the development of the probabilistic Earth-system simulator may actually provide a route to reducing uncertainty in climate prediction. © 2012 Royal Meteorological Society."
"7006506461;6508260037;15725317300;35577097300;6701689811;16052866300;56219238700;56495928700;7102953444;","Multi-decadal variation of the net downward shortwave radiation over south Asia: The solar dimming effect",2012,"10.1016/j.atmosenv.2011.11.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863421260&doi=10.1016%2fj.atmosenv.2011.11.008&partnerID=40&md5=21085a7e7eb19f39c4abc2d349b22654","The solar radiation flux at the earth's surface has gone through decadal changes of decreasing and increasing trends over the globe. These phenomena known as dimming and brightening, respectively, have attracted the scientific interest in relation to the changes in radiative balance and climate. Despite the interest in the solar dimming/brightening phenomenon in various parts of the world, south Asia has not attracted great scientific attention so far. The present work uses the net downward shortwave radiation (NDSWR) values derived from satellites (Modern Era Retrospective-analysis for Research and Applications, MERRA 2D) in order to examine the multi-decadal variations in the incoming solar radiation over south Asia for the period of 1979-2004. From the analysis it is seen that solar dimming continues over south Asia with a trend of-0.54Wm -2yr -1. Assuming clear skies an average decrease of-0.05Wm -2yr -1 in NDSWR was observed, which is attributed to increased aerosol emissions over the region. There is evidence that the increase in cloud optical depth plays the major role for the solar dimming over the area. The cloud optical depth (MERRA retrievals) has increased by 10.7% during the study period, with the largest increase to be detected for the high-level (atmospheric pressure P&lt;400hPa) clouds (31.2%). Nevertheless, the decrease in solar radiation and the role of aerosols and clouds exhibit large monthly and seasonal variations directly affected by the local monsoon system, the anthropogenic and natural aerosol emissions. All these aspects are examined in detail aiming at shedding light into the solar dimming phenomenon over a densely populated area. © 2011 Elsevier Ltd."
"23971426100;7004114883;25924878400;","Relationships between the raindrop size distribution and properties of the environment and clouds inferred from TRMM",2012,"10.1175/JCLI-D-11-00274.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859974388&doi=10.1175%2fJCLI-D-11-00274.1&partnerID=40&md5=231c10098e4df0ebb4d02654dc30bbb0","Raindrop size distribution (DSD) retrievals from two years of data gathered by the Tropical Rainfall Measuring Mission (TRMM) satellite and processed with a combined radar-radiometer algorithm over the oceans equatorward of 358 are examined for relationships with variables describing properties of the vertical precipitation profile, mesoscale organization, and background environment. In general, higher freezing levels and relative humidities (tropical environments) are associated with smaller reflectivity-normalized median drop size (ΕDSD) than in the extratropics. Within the tropics, the smallest ΕDSD values are found in large, shallow convective systems where warm rain formation processes are thought to be predominant, whereas larger sizes are found in the stratiform regions of organized deep convection. In the extratropics, the largest ΕDSD values are found in the scattered convection that occurs when cold, dry continental air moves over the much warmer ocean after the passage of a cold front. These relationships are formally attributed to variables describing the large-scale environment, mesoscale organization, and profile characteristics via principal component (PC) analysis. The leading three PCs account for 23% of the variance in ΕDSD at the individual profile level and 45% of the variance in 1°-gridded mean values. The geographical distribution of ΕDSD is consistent with many of the observed regional reflectivity-rainfall (Z-R) relationships found in the literature as well as discrepancies between the TRMM radar-only and radiometer-only precipitation products. In particular, midlatitude and tropical regions near land tend to have larger drops for a given reflectivity, whereas the smallest drops are found in the eastern Pacific Ocean intertropical convergence zone. © 2012 American Meteorological Society."
"55727417500;57203049177;","The last glacial cycle: Transient simulations with an AOGCM",2012,"10.1007/s00382-011-1283-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862829827&doi=10.1007%2fs00382-011-1283-y&partnerID=40&md5=a7d3f42053e13cfe16317985d26fd977","A number of transient climate runs simulating the last 120 kyr have been carried out using FAMOUS, a fast atmosphere-ocean general circulation model (AOGCM). This is the first time such experiments have been done with a full AOGCM, providing a three-dimensional simulation of both atmosphere and ocean over this period. Our simulation thus includes internally generated temporal variability over periods from days to millennia, and physical, detailed representations of important processes such as clouds and precipitation. Although the model is fast, computational restrictions mean that the rate of change of the forcings has been increased by a factor of 10, making each experiment 12 kyr long. Atmospheric greenhouse gases (GHGs), northern hemisphere ice sheets and variations in solar radiation arising from changes in the Earth's orbit are treated as forcing factors, and are applied either separately or combined in different experiments. The long-term temperature changes on Antarctica match well with reconstructions derived from ice-core data, as does variability on timescales longer than 10 kyr. Last Glacial Maximum (LGM) cooling on Greenland is reasonably well simulated, although our simulations, which lack ice-sheet meltwater forcing, do not reproduce the abrupt, millennial scale climate shifts seen in northern hemisphere climate proxies or their slower southern hemisphere counterparts. The spatial pattern of sea surface cooling at the LGM matches proxy reconstructions reasonably well. There is significant anti-correlated variability in the strengths of the Atlantic meridional overturning circulation (AMOC) and the Antarctic Circumpolar Current (ACC) on timescales greater than 10 kyr in our experiments. We find that GHG forcing weakens the AMOC and strengthens the ACC, whilst the presence of northern hemisphere ice-sheets strengthens the AMOC and weakens the ACC. The structure of the AMOC at the LGM is found to be sensitive to the details of the ice-sheet reconstruction used. The precessional component of the orbital forcing induces ~20 kyr oscillations in the AMOC and ACC, whose amplitude is mediated by changes in the eccentricity of the Earth's orbit. These forcing influences combine, to first order, in a linear fashion to produce the mean climate and ocean variability seen in the run with all forcings. © 2012 The Author(s)."
"53880473700;7101630970;7004942632;","A global blended tropopause based on ERA data. Part I: Climatology",2012,"10.1002/qj.951","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859768925&doi=10.1002%2fqj.951&partnerID=40&md5=bf04f7237eba220e09f9f94fca9eaa48","A new tropopause definition, based on a flow-dependent blending of the traditional thermal tropopause with one based on potential vorticity, has been developed. The benefits of such a blending algorithm are most apparent in regions with synoptic-scale fluctuations between tropical and extratropical air masses. The properties of the local air mass determine the relative contributions to the location of the blended tropopause, rather than this being determined by a specified function of latitude. Global climatologies of tropopause height, temperature, potential temperature and zonal wind, based on European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA) ERA-Interim data, are presented for the period 1989-2007. Features of the seasonal-mean tropopause are discussed on a global scale, alongside a focus on selected monthly climatologies for the two high-latitude regions and the tropical belt. The height differences between climatologies based on ERA-Interim and ERA-40 data are also presented. Key spatial and temporal features seen in earlier climatologies, based mainly on the World Meteorological Organization thermal tropopause definition, are reproduced with the new definition. Tropopause temperatures are consistent with those from earlier climatologies, despite some differences in height in the extratropics. © 2011 Royal Meteorological Society."
"54384916300;7003460432;54415316600;54415398600;37014914300;16445063600;","Extreme climate, not extreme weather: The summer of 1816 in Geneva, Switzerland",2012,"10.5194/cp-8-325-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858852694&doi=10.5194%2fcp-8-325-2012&partnerID=40&md5=07576ef6d8b90bf59a9398f3f9eacab5","We analyze weather and climate during the ""Year without Summer"" 1816 using sub-daily data from Geneva, Switzerland, representing one of the climatically most severely affected regions. The record includes twice daily measurements and observations of air temperature, pressure, cloud cover, wind speed, and wind direction as well as daily measurements of precipitation. Comparing 1816 to a contemporary reference period (1799-1821) reveals that the coldness of the summer of 1816 was most prominent in the afternoon, with a shift of the entire distribution function of temperature anomalies by 3-4 °C. Early morning temperature anomalies show a smaller change for the mean, a significant decrease in the variability, and no changes in negative extremes. Analyzing cloudy and cloud-free conditions separately suggests that an increase in the number of cloudy days was to a significant extent responsible for these features. A daily weather type classification based on pressure, pressure tendency, and wind direction shows extremely anomalous frequencies in summer 1816, with only one day (compared to 20 in an average summer) classified as high-pressure situation but a tripling of low-pressure situations. The afternoon temperature anomalies expected from only a change in weather types was much stronger negative in summer 1816 than in any other year. For precipitation, our analysis shows that the 80% increase in summer precipitation compared to the reference period can be explained by 80% increase in the frequency of precipitation, while no change could be found neither in the average intensity of precipitation nor in the frequency distribution of extreme precipitation. In all, the analysis shows that the regional circulation and local cloud cover played a dominant role. It also shows that the summer of 1816 was an example of extreme climate, not extreme weather. © Author(s) 2012."
"56084948700;57203528969;12646535800;7403513732;","Climatically-controlled siliceous productivity in the eastern Gulf of Guinea during the last 40 000 yr",2012,"10.5194/cp-8-415-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858837927&doi=10.5194%2fcp-8-415-2012&partnerID=40&md5=a3e288fa683e08c39ff73231766013c8","Opal content and diatom assemblages were analysed in core GeoB4905-4 to reconstruct siliceous productivity changes in the eastern Gulf of Guinea during the last 40 000 yr. Opal and total diatom accumulation rates presented low values over the considered period, except during the Last Glacial Maximum and between 15 000 calendar years Before Present (15 cal. ka BP) and 5.5 cal. ka BP, the so-called African Humid Period, when accumulation rates of brackish and freshwater diatoms at the core site were highest. Conversely, accumulation rates of windblown diatoms exhibited an opposite pattern with higher values before and after the African Humid Period and greatest values during Heinrich Events, the Younger Dryas and since 5.5 cal. ka BP. Our results demonstrate that siliceous productivity in the eastern Gulf of Guinea was directly driven by the nutrient load from local rivers, whose discharges were forced by precipitation changes over western Equatorial Africa and/or modification of the fluvio-deltaic systems forced by sea level changes. Precipitation in this region is controlled by the West African monsoon which is, in turn, partly dependent on the presence and intensity of the Atlantic Cold Tongue (ACT). Our results therefore suggest that the ACT was weakened, warmer trade winds were less vigorous, and cloud convection and precipitation were greater during the AHP though centennial-to-millennial timescale dry events were observed at ∼10 cal. ka BP, ∼8.5 cal. ka BP and ∼6 cal. ka BP. Conversely, the ACT was more intense, trade winds were more vigorous and African climate was more arid during H1, the Younger Dryas and after 5.5 cal. ka BP into the present. © 2012 Author(s)."
"6507111233;","Nonstationarities of regional climate model biases in European seasonal mean temperature and precipitation sums",2012,"10.1029/2012GL051210","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859317391&doi=10.1029%2f2012GL051210&partnerID=40&md5=67025faa3bb3253b5e18c73129dc90ae","Bias correcting climate models implicitly assumes stationarity of the correction function. This assumption is assessed for regional climate models in a pseudo reality for seasonal mean temperature and precipitation sums. An ensemble of regional climate models for Europe is used, all driven with the same transient boundary conditions. Although this model-dependent approach does not assess all possible bias non-stationarities, conclusions can be drawn for the real world. Generally, biases are relatively stable, and bias correction on average improves climate scenarios. For winter temperature, bias changes occur in the Alps and ice covered oceans caused by a biased forcing sensitivity of surface albedo; for summer temperature, bias changes occur due to a biased sensitivity of cloud cover and soil moisture. Precipitation correction is generally successful, but affected by internal variability in arid climates. As model sensitivities vary considerably in some regions, multi model ensembles are needed even after bias correction. Copyright 2012 by the American Geophysical Union."
"7004829302;7006592026;7003614389;","Large-scale origins of rainfall and temperature bias in high-resolution simulations over southern Africa",2012,"10.3354/cr01044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861591151&doi=10.3354%2fcr01044&partnerID=40&md5=141053c288349dfaf2d38bdf0590948f","We use the Abdus Salam International Centre for Theoretical Physics (ICTP) regional climate model, RegCM3, nested in NCEP and ERA-Interim reanalyses (NC-RegCM and ERARegCM, respectively) to explore the effect of large-scale forcings on the model biases over a southern Africa domain at 25 km grid spacing. RegCM3 shows a generally good performance in simulating the location of the main rainfall features, temperature and synoptic scale circulation patterns, along with cloud cover and surface radiation fluxes. However, it shows a wet bias which varies substantially when fields from the 2 reanalysis products are used to drive the model, being greater in NC-RegCM than in ERA-RegCM. The wetter bias in NC-RegCM originates from larger moisture inflow, amplified cloud cover and upward motion caused by stronger low-level convergence. Similarly, negative temperature biases are present over most of the land areas, and the wetter NC-RegCM exhibits larger magnitudes of temperature bias. Surface flux analysis reveals that these lower temperature values in the NCEP-driven experiment are due primarily to the surface latent heat flux rather than cloud radiative forcing. As a result, the hydrologic cycle is more intense in the NC-RegCM than in the ERA-RegCM. Our results are relevant for a better understanding of the propagation of errors from the large-scale forcings to the regional model over the region of interest. © 2012 Inter-Research."
"16639418500;57203232956;57206531303;15069732800;","Remote sensing of solar surface radiation for climate monitoring - the CM-SAF retrieval in international comparison",2012,"10.1016/j.rse.2011.11.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055214036&doi=10.1016%2fj.rse.2011.11.016&partnerID=40&md5=994832d96219c4938494063838f8a258","Solar surface irradiance (SIS) and direct (SID) irradiance as well as effective cloud albedo (CAL) climate data records (CDR) derived from the Meteosat first generation satellites (Meteosats 2 to 7, 1983-2005) are presented. The CDRs are available free of charge for all purposes from wui.cmsaf.eu at monthly, daily and hourly means at a spatial resolution of 0.03 <sup/>.The processing employed a climate version of the Heliosat algorithm combined with a clear sky model using an eigenvector look-up table method. Modifications to the Heliosat method include a self-calibration algorithm as well as a running mean based clear sky retrieval algorithm.The datasets are validated using ground based observations from the Baseline Surface Radiation Network (BSRN) as a reference. The validation threshold for the mean absolute bias between satellite-derived and surface-measured radiation is given by the target accuracy for solar irradiance fields defined by the Global Climate Observing system (GCOS) and a measurement uncertainty for the surface data. The results demonstrate that the target accuracy is achieved for monthly and daily means. Furthermore, an intercomparison with similar datasets reveal a better performance and climate monitoring potential of the CM SAF SIS CDR at most BSRN sites compared to established data sets like e.g. ERA-reanalysis, GEWEX (Global Energy and Water Cycle Experiment) and ISCCP (International Satellite Cloud Climatology Project). Lastly, the realistic representation of both seasonal and inter-annual variability guarantees the applicability of the satellite-based climate data sets for climate monitoring and analysis of extremes.No trends in the normalized bias between the CM SAF and the BSRN datasets are detectable, which demonstrates the stability and homogeneity of the global and direct irradiance for the period covered by BSRN measurements. However, inconsistencies are detectable at few satellite transition dates for certain regions in earlier years. © 2011 Elsevier Inc."
"35365381300;35782988600;6602826769;","Systematic bias of average winter-time land surface temperatures inferred from MODIS at a site on Svalbard, Norway",2012,"10.1016/j.rse.2011.10.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83455181670&doi=10.1016%2fj.rse.2011.10.025&partnerID=40&md5=576c087cd3b3d98aa11a2a7e12bb7bdc","Thermal remote sensing can quantify climate change in the Arctic, where ground-based measurements continue to be rare. The land surface temperature (LST) is accessible on the pan-arctic scale through a number of remote sensing platforms, such as the ""Moderate Resolution Imaging Spectrometer"" (MODIS). This study compares remotely sensed LST from MODIS to ground-based point measurements of the snow surface temperature on Svalbard for seven consecutive winters, thus covering more than half of the winter seasons in the operation period of MODIS Terra and Aqua. We find a systematic negative bias of the average winter surface temperature computed from single LST measurements between 1.5 and 6. K, with a mean bias of 3. K. The bias consistently occurs both for the MODIS L2 and for the daily and eight-day MODIS L3 products, which is explained by two reasons: i) During winter on Svalbard, cold surface temperatures are associated with clear-sky conditions, while warm surface temperatures typically occur during overcast periods. This leads to an overrepresentation of cold temperature in averages computed from remotely sensed LST measurements. ii) The MODIS cloud detection scheme fails to recognize some cloud-covered or partially cloud-covered situations, thus leading to admixing of colder cloud top temperatures. Both effects contribute equally to the total average bias accumulated over the winter season, with effect (i) dominating in some winters, while the observed bias can be fully explained by (ii) in other winters. © 2011 Elsevier Inc."
"54893959900;7003645727;","Evaluation of existing image matching methods for deriving glacier surface displacements globally from optical satellite imagery",2012,"10.1016/j.rse.2011.11.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855813621&doi=10.1016%2fj.rse.2011.11.024&partnerID=40&md5=f56bdf97928f606d99d370edad3399ae","Automatic matching of images from two different times is a method that is often used to derive glacier surface velocity. Nearly global repeat coverage of the Earth's surface by optical satellite sensors now opens the possibility for global-scale mapping and monitoring of glacier flow with a number of applications in, for example, glacier physics, glacier-related climate change and impact assessment, and glacier hazard management. The purpose of this study is to compare and evaluate different existing image matching methods for glacier flow determination over large scales. The study compares six different matching methods: normalized cross-correlation (NCC), the phase correlation algorithm used in the COSI-Corr software, and four other Fourier methods with different normalizations. We compare the methods over five regions of the world with different representative glacier characteristics: Karakoram, the European Alps, Alaska, Pine Island (Antarctica) and southwest Greenland. Landsat images are chosen for matching because they expand back to 1972, they cover large areas, and at the same time their spatial resolution is as good as 15. m for images after 1999 (ETM. +. pan). Cross-correlation on orientation images (CCF-O) outperforms the three similar Fourier methods, both in areas with high and low visual contrast. NCC experiences problems in areas with low visual contrast, areas with thin clouds or changing snow conditions between the images. CCF-O has problems on narrow outlet glaciers where small window sizes (about 16. pixels by 16. pixels or smaller) are needed, and it also obtains fewer correct matches than COSI-Corr in areas with low visual contrast. COSI-Corr has problems on narrow outlet glaciers and it obtains fewer correct matches compared to CCF-O when thin clouds cover the surface, or if one of the images contains snow dunes. In total, we consider CCF-O and COSI-Corr to be the two most robust matching methods for global-scale mapping and monitoring of glacier velocities. If combining CCF-O with locally adaptive template sizes and by filtering the matching results automatically by comparing the displacement matrix to its low pass filtered version, the matching process can be automated to a large degree. This allows the derivation of glacier velocities with minimal (but not without!) user interaction and hence also opens up the possibility of global-scale mapping and monitoring of glacier flow. © 2011 Elsevier Inc."
"55268770300;55720058600;7003386805;57200790631;7004433410;","Sensitivity study of ozone retrieval from UV measurements on geostationary platforms",2012,"10.1016/j.rse.2011.11.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863022751&doi=10.1016%2fj.rse.2011.11.010&partnerID=40&md5=36fe2c6aafdf1344b8f5334128f30500","This paper addresses several aspects related to ultraviolet (UV) measurements from an upcoming geostationary orbit (GEO) satellite mission. First, using simulated cloud coverage based on the MTSAT (Multi-functional Transport Satellite 1R) 650. nm channel as a proxy, we find that GEO observations can increase clear-sky coverage by ~. 4 times. Secondly, we examine the feasibility of improved ozone detection with GEO observations, using synthetic GEMS spectra with GEO geometries along with the TOMS total ozone algorithm and an ozone profile algorithm based on the optimal estimation method. The sensitivity of ozone retrievals to the lower troposphere is limited at large solar and satellite zenith angles, especially above 70° under clear-sky conditions. Third, we evaluate two new ideas for improving ozone retrieval sensitivity in the troposphere at large angle geometries; (1) a geosynchronous orbit with an inclination-angle of 30°, with smaller values of viewing zenith angles than those from a geostationary orbit; (2) a combination of UV measurements at multiple solar zenith angles to improve the accuracy of ozone profile retrievals. © 2011 Elsevier Inc."
"7202650266;55061863000;56284545500;","Tropospheric mid-level detrainment flow obtained from high-resolution non-hydrostatic atmospheric model experiments",2012,"10.2151/jmsj.2012-102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857865303&doi=10.2151%2fjmsj.2012-102&partnerID=40&md5=f7d9a09096bb80b22d1a1749f8da0caf","Time integration using the Regional Atmospheric Modeling System (RAMS), a non-hydrostatic cloud-resolving model, was performed for 12 days over a low-latitude band (45°S-45°N) circling an aqua planet with 5-km horizontal grid-point intervals. Tropical and subtropical regions with active precipitation and clear sky, respectively, were clearly divided at 10° latitudes. The numerical experiments derived obvious tropospheric mid-level detrainment (TMD) flows near the 0°C level (z ~ 5 km) out of the tropics into the subtropics. The TMD flows became largest near the border (10° latitude). In this paper, the time-longitudinal mean field was spotlighted and the atmospheric structure accompanying the TMD flow was investigated. When averaged over time and longitude, the subtropical mid-level troposphere, into which the TMD flows move, is approximately in a state of local thermodynamic equilibrium sustained mainly by the balance between the net radiative cooling and adiabatic heating due to mean subsidence flow. Considering the heat balance, a thermodynamic diagnosis of the mean subsidence flow field suggests the following mechanisms for the mean TMD flow: (1) The mean atmosphere near the melting level has stronger radiative cooling and a larger temperature lapse rate than the atmosphere above it. (2) Free subsidence in the mean subtropical mid-level troposphere, which is consistent with the vertical variation of thermal structure and suffers from no direct dynamic forcings, such as buoyancy, involves a vertically mass-divergent layer just above the melting level. (3) The steady poleward mean TMD flow out of the convective tropic atmosphere exists so as to compensate for the vertical mass divergence in the subtropical atmosphere. Because net meridional transports of sensible heat and water vapor in the middle troposphere are influenced by the mean TMD flow, the existence and the maintaining mechanisms of the mean TMD flow could be important elements of the climate system. © 2012, Meteorological Society of Japan."
"22952858000;55715899800;","Atmospheric dimethysulphide production from corals in the Great Barrier Reef and links to solar radiation, climate and coral bleaching",2012,"10.1007/s10533-012-9719-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867138708&doi=10.1007%2fs10533-012-9719-y&partnerID=40&md5=fdeb601eb8482c2a197ade705f42a6b5","Coral zooxanthellae contain high concentrations of dimethylsulphoniopropionate (DMSP), the precursor of dimethylsulphide (DMS), an aerosol substance that could affect cloud cover, solar radiation and ocean temperatures. Acropora intermedia a dominant staghorn coral in the Indo-Pacific region, contain some of the highest concentrations of DMSP reported in the literature but no studies have shown that corals produce atmospheric DMS in situ and thus could potentially participate in sea surface temperature (SST) regulation over reefs; or how production varies during coral bleaching. We show that A. intermedia from the Great Barrier Reef (GBR) produces significant amounts of atmospheric DMS, in chamber experiments, indicating that coral reefs in this region could contribute to an ""ocean thermostat"" similar to that described for the western Pacific warm pool, where significantly fewer coral reefs have bleached during the last 25 years because of a cloud-SST feedback. However, when Acropora intermedia was stressed with higher light levels and seawater temperatures DMSP production, an indicator of zooxanthellae expulsion, increased markedly in the chamber, whilst atmospheric DMS emissions almost completely shut down. These results suggest that during increased light levels and seawater temperatures in the GBR coral shut-down atmospheric DMS aerosol production, potentially increasing solar radiation levels over reefs and exacerbating coral bleaching. © 2012 Springer Science+Business Media B.V."
"24385863600;6602506226;8715232900;23052016900;6507755223;57207261095;35461255500;7006712143;7007039218;6603172418;6506718302;","Surfactant effects in global simulations of cloud droplet activation",2012,"10.1029/2011GL050467","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857946043&doi=10.1029%2f2011GL050467&partnerID=40&md5=25f44ef0eed8b2c84f97798bbeae8c8d","Atmospheric aerosols often contain surface active organics. We study the influence of these surfactants on predictions of particle cloud activation potential and aerosol indirect climate effects, by implementing different parametrizations of surfactant effects in the global circulation model ECHAM5.5-HAM2. A parametrization based only on droplet surface tension reduction produces significantly larger effects on predicted cloud droplet numbers than novel parametrizations based on detailed considerations of organic surface activity. It seems better to disregard surfactant effects altogether than employing parametrizations accounting only for effects on surface tension. We strongly recommend not using only the surface tension reduction to represent the surfactant effects in climate models. Copyright 2012 by the American Geophysical Union."
"25031430500;57203030873;6701455548;","The evolution of climate sensitivity and climate feedbacks in the community atmosphere model",2012,"10.1175/JCLI-D-11-00197.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858256367&doi=10.1175%2fJCLI-D-11-00197.1&partnerID=40&md5=88fe9b919c95f0a1906f7cab941b85f4","The major evolution of the National Center for Atmospheric Research Community Atmosphere Model (CAM) is used to diagnose climate feedbacks, understand how climate feedbacks change with different physical parameterizations, and identify the processes and regions that determine climate sensitivity. In the evolution of CAM from version 4 to version 5, the water vapor, temperature, surface albedo, and lapse rate feedbacks are remarkably stable across changes to the physical parameterization suite. However, the climate sensitivity increases from 3.2 K in CAM4 to 4.0 K in CAM5. The difference is mostly due to (i) more positive cloud feedbacks and (ii) higher CO 2 radiative forcing in CAM5. The intermodel differences in cloud feedbacks are largest in the tropical trade cumulus regime and in the midlatitude storm tracks. The subtropical stratocumulus regions do not contribute strongly to climate feedbacks owing to their small area coverage. A ""modified Cess"" configuration for atmosphere-only model experiments is shown to reproduce slab ocean model results. Several parameterizations contribute to changes in tropical cloud feedbacks between CAM4 and CAM5, but the new shallow convection scheme causes the largest midlatitude feedback differences and the largest change in climate sensitivity. Simulations with greater cloud forcing in the mean state have lower climate sensitivity. This work provides a methodology for further analysis of climate sensitivity across models and a framework for targeted comparisons with observations that can help constrain climate sensitivity to radiative forcing. © 2012 American Meteorological Society."
"55977336000;16637291100;7406671641;7501855361;57202891769;","A cloudier Arctic expected with diminishing sea ice",2012,"10.1029/2012GL051251","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863275739&doi=10.1029%2f2012GL051251&partnerID=40&md5=b1ae5649a94d7da37ffc945412d004e2","Arctic sea ice cover has decreased dramatically over the last three decades. Global climate models under-predicted this decline, most likely a result of the misrepresentation of one or more processes that influence sea ice. The cloud feedback is the primary source of uncertainty in model simulations, especially in the polar regions. A better understanding of the interaction between sea ice and clouds, and specifically the impact of decreased sea ice on cloud cover, will provide valuable insight into the Arctic climate system and may ultimately help in improving climate model parameterizations. In this study, an equilibrium feedback assessment is employed to quantify the relationship between changes in sea ice and clouds, using satellite-derived sea ice concentration and cloud cover over the period 2000-2010. Results show that a 1% decrease in sea ice concentration leads to a 0.36-0.47% increase in cloud cover, suggesting that a further decline in sea ice cover will result in an even cloudier Arctic. Copyright © 2012 by the American Geophysical Union."
"7401945370;8962699100;7202954964;7007021059;57212988186;","Response of upper clouds in global warming experiments obtained using a global nonhydrostatic model with explicit cloud processes",2012,"10.1175/JCLI-D-11-00152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858606867&doi=10.1175%2fJCLI-D-11-00152.1&partnerID=40&md5=7941fe443bcd4f7736dac28f15f51741","Using a global nonhydrostatic model with explicit cloud processes, upper-cloud changes are investigated by comparing the present climate condition under the perpetual July setting and the global warming condition, in which the sea surface temperature (SST) is raised by 2°. The sensitivity of the upper-cloud cover and the ice water path (IWP) are investigated through a set of experiments. The responses of convective mass flux and convective areas are also examined, together with those of the large-scale subsidence and relative humidity in the subtropics. The responses of the IWP and the upper-cloud cover are found to be opposite; that is, as the SST increases, the IWP averaged over the tropics decreases, whereas the upper-cloud cover in the tropics increases. To clarify the IWP response, a simple conceptual model is constructed. The model consists of three columns of deep convective core, anvil, and environmental subsidence regions. The vertical profiles of hydrometers are predicted with cloud microphysics processes and kinematically prescribed circulation. The reduction in convective mass flux is found to be a primary factor in the decrease of the IWP under the global warming condition. Even when a different and more comprehensive cloud microphysics scheme is used, the reduction in the IWP due to the mass flux change is also confirmed. © 2012 American Meteorological Society."
"7005634455;36495301700;7004993886;57203030873;26032130600;6602073516;7006246996;7004242319;24331295800;16444006500;6701802669;6701895637;","Tropospheric clouds in Antarctica",2012,"10.1029/2011RG000363","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855874545&doi=10.1029%2f2011RG000363&partnerID=40&md5=9501bcbe262d72338e5b681e006ab000","Compared to other regions, little is known about clouds in Antarctica. This arises in part from the challenging deployment of instrumentation in this remote and harsh environment and from the limitations of traditional satellite passive remote sensing over the polar regions. Yet clouds have a critical influence on the ice sheet's radiation budget and its surface mass balance. The extremely low temperatures, absolute humidity levels, and aerosol concentrations found in Antarctica create unique conditions for cloud formation that greatly differ from those encountered in other regions, including the Arctic. During the first decade of the 21st century, new results from field studies, the advent of cloud observations from spaceborne active sensors, and improvements in cloud parameterizations in numerical models have contributed to significant advances in our understanding of Antarctic clouds. This review covers four main topics: (1) observational methods and instruments, (2) the seasonal and interannual variability of cloud amounts, (3) the microphysical properties of clouds and aerosols, and (4) cloud representation in global and regional numerical models. Aside from a synthesis of the existing literature, novel insights are also presented. A new climatology of clouds over Antarctica and the Southern Ocean is derived from combined measurements of the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. This climatology is used to assess the forecast cloud amounts in 20th century global climate model simulations. While cloud monitoring over Antarctica from space has proved essential to the recent advances, the review concludes by emphasizing the need for additional in situ measurements. © Copyright 2012 by the American Geophysical Union."
"35512561700;54927347800;","Total ozone column measurements for an urban, tropical site in the Southern Hemisphere with a Microtops II",2012,"10.1016/j.jastp.2011.12.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857645329&doi=10.1016%2fj.jastp.2011.12.014&partnerID=40&md5=8b1618bced23ffbc0c9a9820c35b75a5","Atmospheric ozone remains an important topic especially because of global climate change. In this study, total ozone column (TOC) measurements by a Microtops II (MII) ozone monitor at an urban, tropical site in Brazil are considered with local cloud cover (LCC). The standard deviation (SD) for MII measurements was within 4% averaging 1.14±0.58%. Clouds' presence impacts SD and cloudless sky measurements had SD≤1. The average TOC for the period was 258.0±11.5 Dobson Units. MII TOC data comparison with the Ozone Monitoring Instrument (OMI) showed average differences≤2%. © 2012 Elsevier Ltd."
"7006708207;23991813700;55476534400;10042992100;54898277600;10739566100;8657171200;8561777300;36466105700;36562313200;57202559586;36609311400;49361284200;54899176600;35449990500;6602873453;6506286471;12243565900;","The Eyjafjallajökull ash plume - Part 2: Simulating ash cloud dispersion with REMOTE",2012,"10.1016/j.atmosenv.2011.10.037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855979677&doi=10.1016%2fj.atmosenv.2011.10.037&partnerID=40&md5=cae3448720d7f59f4a573513da3a2e9d","The recent eruption of Iceland's Eyjafjallajökull volcano caused extensive disruption across Europe. In this paper, we describe the volcanic ash parameterisation incorporated in the regional climate model (REMOTE) for forecasting volcanic ash dispersion. We investigate model sensitivity to emission parameters including eruption column height and vertical release distribution. Model results over a number of key ash incursion events are assessed in terms of agreement with both ground based measurements and retrieved LIDAR data at a number of European sites. © 2011 Elsevier Ltd."
"26028515700;7003865921;7005729142;7202016984;7404514776;55545601500;7004678728;","Cloud ice water content retrieved from the CALIOP space-based lidar",2012,"10.1029/2011GL050545","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863231968&doi=10.1029%2f2011GL050545&partnerID=40&md5=25bd8cd4b64bdb6589063e93fe26906d","Ice water content (IWC) profiles are derived from retrievals of optical extinction from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite lidar, using a parameterization derived from particle probe measurements acquired during several aircraft field campaigns. With more than five years of data now available, CALIOP IWC is well suited for characterization of the climate-sensitive upper troposphere/lower stratosphere where reliable global IWC measurements are needed to reduce climate model uncertainty. We describe CALIOP IWC and compare it with global satellite-based and regional airborne IWC measurements made during August 2007. IWC distributions in a convective cloud sampled during the Tropical Clouds, Chemistry, Composition and Climate experiment show temperature-dependent differences between in situ measured IWC, IWC retrieved from CloudSat and CALIOP, and IWC parameterized from the airborne Cloud Physics Lidar (CPL) 532 nm volume extinction coefficients. At temperatures above-50°C the CALIOP IWC retrieval indicates less cloud ice than the other instruments, due to signal attenuation and screening for horizontally-oriented ice crystals. Above 12 km where temperatures drop below-50°C CALIOP compares well with in situ IWC measurements. In situ measurements are limited above 12 km, and more cold-temperature comparisons are needed. Global zonal in-cloud IWC averages at altitudes above 9 km show that CloudSat IWC is roughly an order of magnitude higher than CALIOP IWC, consistent with a higher detection threshold. When averaged to the vertical resolution characteristic of Microwave Limb Sounder (MLS), global zonal averages of CALIOP and MLS IWC were found to agree to about 50%."
"36523706800;55067706600;7005600755;55069017600;","A new algorithm for the satellite-based retrieval of solar surface irradiance in spectral bands",2012,"10.3390/rs4030622","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857966480&doi=10.3390%2frs4030622&partnerID=40&md5=171dea8e55d5e5dde53a3965e692a820","Accurate solar surface irradiance data is a prerequisite for an efficient planning and operation of solar energy systems. Further, it is essential for climate monitoring and analysis. Recently, the demand on information about spectrally resolved solar surface irradiance has grown. As surface measurements are rare, satellite derived information with high accuracy might fill this gap. This paper describes a new approach for the retrieval of spectrally resolved solar surface irradiance from satellite data. The method combines a eigenvector-hybrid look-up table approach for the clear sky case with satellite derived cloud transmission (Heliosat method). The eigenvector LUT approach is already used to retrieve the broadband solar surface irradiance of data sets provided by the Climate Monitoring Satellite Application Facility (CM-SAF). This paper describes the extension of this approach to wavelength bands and the combination with spectrally resolved cloud transmission values derived with radiative transfer corrections of the broadband cloud transmission. Thus, the new approach is based on radiative transfer modeling and enables the use of extended information about the atmospheric state, among others, to resolve the effect of water vapor and ozone absorption bands. The method is validated with spectrally resolved measurements from two sites in Europe and by comparison with radiative transfer calculations. The validation results demonstrate the ability of the method to retrieve accurate spectrally resolved irradiance from satellites. The accuracy is in the range of the uncertainty of surface measurements, with exception of the UV and NIR (= 1200 nm) part of the spectrum, where higher deviations occur. © 2012 by the authors."
"6603901951;","Contrasts between Urban and rural climate in CCSM4 CMIP5 climate change scenarios",2012,"10.1175/JCLI-D-11-00098.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856829196&doi=10.1175%2fJCLI-D-11-00098.1&partnerID=40&md5=314df65e3d2e671b1bde1bf8db567be0","A new parameterization of urban areas in the Community Climate System Model version 4 (CCSM4) allows for simulation of temperature in cities where most of the global population lives. CCSM4 Coupled Model Intercomparison Project phase 5 (CMIP5) simulations [Representative Concentration Pathway (RCP) 2.6, 4.5, and 8.5] are analyzed to examine how urban and rural areas might respond differently to changes in climate. The urban heat island (UHI), defined as the urban minus rural air temperature, is used as a metric. The average UHI at the end of the twenty-first century is similar to present day in RCP2.6 and RCP4.5, but decreases in RCP8.5. Both the daytime and nocturnal UHIs decrease in RCP8.5, but the decrease in the daytime UHI is larger and more uniform across regions and seasons than in the nocturnal UHI. This is caused by changes in evaporation that warm the rural surface more than the urban. There is significant spatial and seasonal variability in the response of the nocturnal UHI caused mainly by changes in the rural surface. In Europe, the response to climate change of rural leaf-stem area in summer and clouds and rural soil moisture in winter explains the majority of this variability. Climate change increases the number of warm nights in urban areas substantially more than in rural areas. These results provide evidence that urban and rural areas respond differently to climate change. Thus, the unique aspects of the urban environment should be considered when making climate change projections, particularly since the global population is becoming increasingly urbanized. © 2012 American Meteorological Society."
"57188641259;7004950022;","Decadal climate variability in the Mediterranean region: Roles of large-scale forcings and regional processes",2012,"10.1007/s00382-011-1056-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857439651&doi=10.1007%2fs00382-011-1056-7&partnerID=40&md5=42540c741fe9ec706488cbe3c710a094","We analyze decadal climate variability in the Mediterranean region using observational datasets over the period 1850-2009 and a regional climate model simulation for the period 1960-2000, focusing in particular on the winter (DJF) and summer (JJA) seasons. Our results show that decadal variability associated with the winter and summer manifestations of the North Atlantic Oscillation (NAO and SNAO respectively) and the Atlantic Multidecadal Oscillation (AMO) significantly contribute to decadal climate anomalies over the Mediterranean region during these seasons. Over 30% of decadal variance in DJF and JJA precipitation in parts of the Mediterranean region can be explained by NAO and SNAO variability respectively. During JJA, the AMO explains over 30% of regional surface air temperature anomalies and Mediterranean Sea surface temperature anomalies, with significant influence also in the transition seasons. In DJF, only Mediterranean SST still significantly correlates with the AMO while regional surface air temperature does not. Also, there is no significant NAO influence on decadal Mediterranean surface air temperature anomalies during this season. A simulation with the PROTHEUS regional ocean-atmosphere coupled model is utilized to investigate processes determining regional decadal changes during the 1960-2000 period, specifically the wetter and cooler 1971-1985 conditions versus the drier and warmer 1986-2000 conditions. The simulation successfully captures the essence of observed decadal changes. Model set-up suggests that AMO variability is transmitted to the Mediterranean/European region and the Mediterranean Sea via atmospheric processes. Regional feedbacks involving cloud cover and soil moisture changes also appear to contribute to observed changes. If confirmed, the linkage between Mediterranean temperatures and the AMO may imply a certain degree of regional decadal climate predictability. The AMO and other decadal influences outlined here should be considered along with those from long-term increases in greenhouse gas forcings when making regional climate out-looks for the Mediterranean 10-20 years out. © 2011 Springer-Verlag."
"56033330500;57196170962;7402764213;","Numerical experiments of an advanced radiative transfer model in the U.S. Navy operational global atmospheric prediction system",2012,"10.1175/JAMC-D-11-018.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861692961&doi=10.1175%2fJAMC-D-11-018.1&partnerID=40&md5=494d37144f99a1c18c51b1379f272989","Ahigh-order accurate radiative transfer (RT) model developed by Fu and Liou has been implemented into the Navy Operational Global Atmospheric Prediction System (NOGAPS) to improve the energy budget and forecast skill. The Fu-LiouRT model is a four-stream algorithm (with a two-stream option) integrating over 6 shortwave bands and 12 longwave bands. The experimental 10-day forecasts and analyses from data assimilation cycles are compared with the operational output, which uses a two-stream RT model of three shortwave and five longwave bands, for both winter and summer periods. The verifications against observations of radiosonde and surface data show that the new RT model increases temperature accuracy in both forecasts and analyses by reducing mean bias and root-mean-square errors globally. In addition, the forecast errors also grow more slowly in time than those of the operational NOGAPS because of accumulated effects of more accurate cloud-radiation interactions. The impact of parameterized cloud effective radius in estimating liquid and ice water optical properties is also investigated through a sensitivity test by comparing with the cases using constant cloud effective radius to examine the temperature changes in response to cloud scattering and absorption. The parameterization approach is demonstrated to outperform that of constant radius by showing smaller errors and better matches to observations. This suggests the superiority of the new RT model relative to its operational counterpart, which does not use cloud effective radius. An effort has also been made to improve the computational efficiency of the new RT model for operational applications. © 2012 American Meteorological Society."
"6506392172;57202301596;57203199846;8266754800;24802472000;8986820700;35339707100;","Regional patterns of tropical indo-pacific climate change: Evidence of the walker circulation weakening",2012,"10.1175/JCLI-D-11-00263.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858165565&doi=10.1175%2fJCLI-D-11-00263.1&partnerID=40&md5=f4d1795e46a0044164458ab0e6976ce2","Regional patterns of tropical Indo-Pacific climate change are investigated over the last six decades based on a synthesis of in situ observations and ocean model simulations, with a focus on physical consistency among sea surface temperature (SST), cloud, sea level pressure (SLP), surface wind, and subsurface ocean temperature. A newly developed bias-corrected surface wind dataset displays westerly trends over the western tropical Pacific and easterly trends over the tropical Indian Ocean, indicative of a slowdown of the Walker circulation. This pattern of wind change is consistent with that of observed SLP change showing positive trends over the Maritime Continent and negative trends over the central equatorial Pacific. Suppressed moisture convergence over the Maritime Continent is largely due to surface wind changes, contributing to observed decreases in marine cloudiness and land precipitation there. Furthermore, observed ocean mixed layer temperatures indicate a reduction in zonal contrast in the tropical Indo-Pacific characterized by larger warming in the tropical eastern Pacific and western Indian Ocean than in the tropical western Pacific and eastern Indian Ocean. Similar changes are successfully simulated by an ocean general circulation model forced with the bias-corrected wind stress. Whereas results from major SST reconstructions show no significant change in zonal gradient in the tropical Indo-Pacific, both bucket-sampled SSTs and nighttime marine air temperatures (NMAT) show a weakening of the zonal gradient consistent with the subsurface temperature changes. All these findings fromindependent observations provide robust evidence for ocean-atmosphere coupling associatedwith the reduction in theWalker circulation over the last six decades. © 2012 American Meteorological Society."
"8068419200;7004500706;35561911800;6602208186;56033135100;6603535726;54940625500;","On the causes of mid-Pliocene warmth and polar amplification",2012,"10.1016/j.epsl.2011.12.042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856446764&doi=10.1016%2fj.epsl.2011.12.042&partnerID=40&md5=b0bd81e38b4c8e0370ac399e891e988c","The mid-Pliocene (~3 to 3.3Ma ago), is a period of sustained global warmth in comparison to the late Quaternary (0 to ~1Ma ago), and has potential to inform predictions of long-term future climate change. However, given that several processes potentially contributed, relatively little is understood about the reasons for the observed warmth, or the associated polar amplification. Here, using a modelling approach and a novel factorisation method, we assess the relative contributions to mid-Pliocene warmth from: elevated CO 2, lowered orography, and vegetation and ice sheet changes. The results show that on a global scale, the largest contributor to mid-Pliocene warmth is elevated CO 2. However, in terms of polar amplification, changes to ice sheets contribute significantly in the Southern Hemisphere, and orographic changes contribute significantly in the Northern Hemisphere. We also carry out an energy balance analysis which indicates that that on a global scale, surface albedo and atmospheric emmissivity changes dominate over cloud changes. We investigate the sensitivity of our results to uncertainties in the prescribed CO 2 and orographic changes, to derive uncertainty ranges for the various contributing processes. © 2012 Elsevier B.V."
"6603801892;41262339700;7003945505;41262443000;","Intra-Seasonal Oscillations Associated with Indian Ocean Warm Pool and Summer Monsoon Rainfall and Their Inter-Annual Variability",2012,"10.1007/s12524-011-0135-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856685170&doi=10.1007%2fs12524-011-0135-x&partnerID=40&md5=4cf274f56aabd09fbca4ee17741d407b","Sea surface temperature (SST) and wind speed (WS) derived from Multichannel Scanning Microwave Radiometer (MSMR), onboard IRS-P4 (Oceansat-1) satellite were used to generate spatially averaged (80° to 100° E & 0° to 10° S) daily data during June to September from 1999 to 2001 along with collocated outgoing long wave radiation (OLR) data from NCEP/NCAR reanalysis product. Daily rainfall data over the peninsular India during the above period was taken from the weekly weather report published by the Indian Meteorological Department. The data were then subjected to power spectral analysis. Dominant 30 to 60 days oscillations were observed over both ocean and land during all the 3 years investigated. It is quite interesting to note that the intra-seasonal oscillation with 60 days periodicity dominates in both ocean and land during 1999 and then transforms to 30 and 40 days periodicities in 2000 and 2001 respectively with a phase lag of about 25 to 30 days. It was also observed that the time-latitude section of zonally averaged OLR and TMI derived cloud liquid water data clearly depict the propagation of convection and cloud from the equator to the north at the rate of 0. 75° to 1° latitude per day which corroborates well with the rate of propagation derived from the phase lag obtained between the processes occurring at the equatorial Indian Ocean and rainfall recorded at the designated land segments. The results are in good agreement with the observations made by earlier investigators. © 2011 Indian Society of Remote Sensing."
"37098098600;6505921698;","Extratropical forcing of tropical atlantic variability during boreal summer and fall",2012,"10.1175/JCLI-D-11-00104.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857000944&doi=10.1175%2fJCLI-D-11-00104.1&partnerID=40&md5=1a91d5ccce122874e92ce999f75deaf1","The connection between midlatitude Atlantic sea surface temperature (SST) anomalies and tropical SST variations during boreal summer and fall are investigated using a coupled general circulation model (GCM). This research follows on an observational study that finds that, using linear inverse modeling (LIM), predictions of boreal summer tropical Atlantic Meridional Mode (AMM) variations can be made with skill exceeding persistence with lead times of about one year. The LIM framework identified extratropical Atlantic SST anomalies as important precursors to the AMM variations. The authors have corroborated this finding using a general circulation model coupled to a slab ocean, which represents a completely different physical basis from the LIM. Initializing the GCM with the LIM-derived ""optimal"" SST anomaly in November results in a steady equatorward propagation of SST anomalies into the subtropics during the following boreal spring. Thereafter, the GCM suggests that two possible feedbacks propagate the SST anomalies farther equatorward and westward with minimal loss of amplitude: the dominant wind-evaporation-SST (WES) thermodynamic feedback and a secondary low-cloud-SST radiative feedback. This study shows that this result has strong seasonal dependence and consists of nonlinear interactions when considering warm and cold ""optimal"" conditions separately. One main finding is that oceanic dynamics are not essential to understanding extratropical-tropical interaction in the Atlantic basin. The authors also discuss the results of the study in context with previous studies investigating the extratropical forcing of tropical air-sea variability. © 2012 American Meteorological Society."
"24481185800;7101879730;7801510158;6602315637;6701820813;50461498900;7007019891;54685053300;7004864963;8941151400;56962755600;7403063262;7005565383;6701703163;","Within-plant isoprene oxidation confirmed by direct emissions of oxidation products methyl vinyl ketone and methacrolein",2012,"10.1111/j.1365-2486.2011.02610.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857142363&doi=10.1111%2fj.1365-2486.2011.02610.x&partnerID=40&md5=c313b7330fe84155604634ae9da109dc","Isoprene is emitted from many terrestrial plants at high rates, accounting for an estimated 1/3 of annual global volatile organic compound emissions from all anthropogenic and biogenic sources combined. Through rapid photooxidation reactions in the atmosphere, isoprene is converted to a variety of oxidized hydrocarbons, providing higher order reactants for the production of organic nitrates and tropospheric ozone, reducing the availability of oxidants for the breakdown of radiatively active trace gases such as methane, and potentially producing hygroscopic particles that act as effective cloud condensation nuclei. However, the functional basis for plant production of isoprene remains elusive. It has been hypothesized that in the cell isoprene mitigates oxidative damage during the stress-induced accumulation of reactive oxygen species (ROS), but the products of isoprene-ROS reactions in plants have not been detected. Using pyruvate-2- 13C leaf and branch feeding and individual branch and whole mesocosm flux studies, we present evidence that isoprene (i) is oxidized to methyl vinyl ketone and methacrolein (i ox) in leaves and that i ox/i emission ratios increase with temperature, possibly due to an increase in ROS production under high temperature and light stress. In a primary rainforest in Amazonia, we inferred significant in plant isoprene oxidation (despite the strong masking effect of simultaneous atmospheric oxidation), from its influence on the vertical distribution of i ox uptake fluxes, which were shifted to low isoprene emitting regions of the canopy. These observations suggest that carbon investment in isoprene production is larger than that inferred from emissions alone and that models of tropospheric chemistry and biota-chemistry-climate interactions should incorporate isoprene oxidation within both the biosphere and the atmosphere with potential implications for better understanding both the oxidizing power of the troposphere and forest response to climate change. © 2012 Blackwell Publishing Ltd."
"35213726000;57203049177;6603236154;57203479688;","A parametric sensitivity study of entropy production and kinetic energy dissipation using the FAMOUS AOGCM",2012,"10.1007/s00382-011-0996-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857440377&doi=10.1007%2fs00382-011-0996-2&partnerID=40&md5=6db734e0b925e21b4e0ea8445346b3d8","The possibility of applying either the maximum entropy production conjecture of Paltridge (Q J R Meteorol Soc 101:475-484, 1975) or the conjecture of Lorenz (Generation of available potential energy and the intensity of the general circulation. Pergamon, Tarrytown, 1960) of maximum generation of available potential energy (APE) in FAMOUS, a complex but low-resolution AOGCM, is explored by varying some model parameters to which the simulated climate is highly sensitive, particularly the convective entrainment rate, ε, and cloud droplet-to-rain-conversion rate, cT. The climate response is analysed in terms of its entropy production and the strength of the Lorenz energy cycle. If either conjecture is true, the parameter values which yield the most realistic climate will also maximise the relevant quantity. No maximum is found in the total material entropy production, which is dominated by the hydrological cycle and tends to increase monotonically with global-mean temperature, which is not constant because the parameter variations affect the net input of solar radiation at the top of the atmosphere (TOA). In contrast, there is a non-monotonic, peaked behaviour in the generation of APE and entropy production associated with kinetic energy dissipation, with the standard FAMOUS values for ε and cT occurring nearly at the maximising ones. The maximum states are shown to be states of vigorous baroclinic activity. The peak in the generation of APE appears to be related to a trade-off between the mean vertical stability and horizontal stratification. Experiments are repeated for a simplified setup in which the net solar input at TOA is fixed. Again a peak in the generation of APE is found in association with the maximum baroclinic activity, but no trade-off of the kind shown by simple climate models is found between meridional heat transport and the meridional temperature gradient. We conclude that the maximum entropy production conjecture does not hold within the climate system when the effects of the hydrological cycle and radiative feedbacks are taken into account, but our experiments provide some evidence in support of the conjecture of maximum APE production (or equivalently maximum dissipation of kinetic energy). © 2011 Springer-Verlag."
"35389429300;7402891845;","A reconstruction of Madden-Julian oscillation variability from 1905 to 2008",2012,"10.1175/JCLI-D-11-00154.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858600996&doi=10.1175%2fJCLI-D-11-00154.1&partnerID=40&md5=b8be89bb958c15f066eb3162f6d7eb4a","The most widely accepted characterization of the Madden-Julian oscillation (MJO) is the bivariate index developed by Wheeler and Hendon. This index relies in part on satellite-based observations of outgoing longwave radiation and thus is not defined for the presatellite era. TheMJOis known to have a strong signature in surface pressure, and daily measurements of this variable are available as far back as the late nineteenth century. This study undertakes a statistical reconstruction of the Wheeler andHendonMJOindex from 1905 to 2008 based on tropical surface pressures estimated recently by the twentieth-century reanalysis project. The temporal and spectral properties of the reconstructed index are first shown to be consistent with the Wheeler and Hendon index over the common period (1979-2008). The reconstructed index is then validated over the earlier period (1905-1978) by examining its relationship with cloud cover, surface wind, precipitation, and sea level. These relationships are shown to be consistent with corresponding results obtained from theWheeler and Hendon index over the shared period and stable over the earlier period. Finally, a simple damped harmonic oscillator model is used to gain new insights into the predictability of the MJO index and also demonstrate consistency between the reconstructed index and theWheeler andHendon index. These results give confidence in the validity of the historical reconstruction of the MJO index over the last century. © 2012 American Meteorological Society."
"57201236064;7201897780;7402689885;","Relationship between stable isotope ratios and drop size distribution in tropical rainfall",2012,"10.1007/s10874-012-9227-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863194737&doi=10.1007%2fs10874-012-9227-4&partnerID=40&md5=f7271b560d6c82a6924c42d7b51694eb","We carried out simultaneous measurements of drop size distribution (DSD) and stable oxygen and hydrogen isotopic compositions (δ 18O and δD) of rain at the National Atmospheric Research Laboratory (NARL), Gadanki (13.5°N, 79.2°E), southern India, during September-October 2006, with the aim of understanding microphysical processes leading to rain formation. The MST radar at NARL was operated continuously during rain events, while rain samples were collected at very short time intervals (&lt;1 h), to capture small changes (&gt;0.2% and &gt;2%) in their δ 18O and δD. The slope of the local meteoric water line (δD- δ 18O line),was 8.07±0.47, similar to that of global meteoric water line, confirming that the precipitation occurred under isotopic equilibrium, and was unaffected by some anomalous process; further, the evaporation of rain drops at the cloud base was insignificant. Whenever the isotopic variations were larger during a rain event (&gt;2%) there was a significant negative correlation between the δ 18O and DSD. The possible explanation is that larger drops are mostly associated with convective rather than stratiform rain, and 18O (and D) depletion in convective rain is relatively more. Bin-resolved microphysical models incorporating water isotopologues could benefit by considering drop size spectra, which could improve the match with stable isotope observations of precipitation. © Springer Science+Business Media B.V. 2012."
"24069602600;7101688905;36025273600;","The potential of the satellite derived green chlorophyll index for estimating midday light use efficiency in maize, coniferous forest and grassland",2012,"10.1016/j.ecolind.2011.08.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054711372&doi=10.1016%2fj.ecolind.2011.08.018&partnerID=40&md5=301c808f1e369cf7716525080890dd12","Light use efficiency (LUE) is an important variable in carbon cycle and climate change research. We present an investigation of remotely estimating midday LUE using the green chlorophyll index (CI green) derived from the cloud-free Moderate Resolution Imaging Spectroradiometer (MODIS) images in maize, coniferous forest and grassland. Similar temporal patterns are observed in both canopy chlorophyll content and midday LUE which indicates that the chlorophyll content in the maize canopy servers as a proxy of midday LUE (R 2 = 0.736, p &lt; 0.001). Therefore, the CI green, tested as a good indicator of canopy chlorophyll content (R 2 = 0.840, p &lt; 0.001), has been demonstrated to be a reliable candidate in providing reasonable estimates of midday LUE with determination coefficient R 2 equals to 0.820 and a root mean square error (RMSE) of 0.002 mol CO 2 per mol incident photosynthetic photon flux density (PPFD). Further validation of the prediction model derived from the maize site demonstrates that the CI green has potential to be applied in the coniferous forest and grassland ecosystems with RMSE of 0.005 and 0.004 mol CO 2 mol -1 PPFD, respectively. A comparison analysis between different vegetation types is included and these results could be helpful in the development of future LUE and terrestrial models. © 2011 Elsevier Ltd."
"57205303892;7004462778;","Assimilation of reflectivity data in a convective-scale, cycled 3DVAR framework with hydrometeor classification",2012,"10.1175/JAS-D-11-0162.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858253081&doi=10.1175%2fJAS-D-11-0162.1&partnerID=40&md5=3dc375eac54947edfda3f4ed63b986eb","The impact of assimilating radar reflectivity and radial velocity data with an intermittent, cycled threedimensional variational assimilation (3DVAR) system is explored using an idealized thunderstorm case and a real data case on 8 May 2003. A new forward operator for radar reflectivity is developed that uses a background temperature field provided by a numerical weather prediction model for automatic hydrometeor classification. Three types of experiments are performed on both the idealized and real data cases. The first experiment uses radial velocity data only, the second experiment uses both radial velocity and reflectivity data without hydrometeor classification, and the final experiment uses both radial velocity and reflectivity data with hydrometeor classification. All experiments advance the analysis state to the next observation time using a numerical model prediction, which is then used as the background for the next analysis. Results from both the idealized and real data cases show that, assimilating only radial velocity data, the model can reconstruct the supercell thunderstorm after several cycles, but the development of precipitation is delayed because of the well-known spinup problem. The spinup problem is reduced dramatically when assimilating reflectivity without hydrometeor classification. The analyses are further improved using the new reflectivity formulation with hydrometeor classification. This study represents a successful first effort in variational convective-scale data assimilation to partition hydrometeors using a background temperature field from a numerical weather prediction model. © 2012 American Meteorological Society."
"20434739100;7003667635;7601533052;","Process studies on the ecological coupling between sea ice algae and phytoplankton",2012,"10.1016/j.ecolmodel.2011.11.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855280772&doi=10.1016%2fj.ecolmodel.2011.11.011&partnerID=40&md5=b7eded5825b6840245cedd39acb7b441","The seasonal dynamics of pelagic and sea ice communities are closely related in ice-covered waters, however, modelling works that analyse such interactions are scarce. We use the Biogeochemical Flux Model in Sea Ice (BFM-SI) coupled to the pelagic Biogeochemical Flux Model (BFM) in a study area in Greenland to quantitatively investigate: (1) the significance of photoacclimation/photoadaptation strategies of autotrophs, (2) the fate of the sea ice biomass in case of algae seeding, algae aggregation and at different mixed layer depths and (3) the changes in community production under a climate change scenario. The results show that sea ice algae need to be both photoacclimated and photoadapted to the sea ice environment in order to grow, while phytoplankton may adopt different strategies for optimising their growth. The seeding of the phytoplankton bloom shows to be driven, both in timing and magnitude, by the viability of sea ice algae and by the degree of aggregation of algae released from the ice, which also affects the sinking rate to the sea floor. Under a mild climate change scenario (SRES B2, 2071-2090) the sea ice community is projected to be generally more productive, whereas phytoplankton growth will be reduced because the melt of sea ice will occur earlier in the season when light is less favourable to sustain the growth. While it is generally anticipated that the melting of multi-year ice in the Arctic Ocean will cause an increase in marine production, this study shows that seasonal ice-covered seas in the Northern hemisphere may actually be less productive and may shift to more oligotrophic conditions within the next 100 years. © 2011 Elsevier B.V."
"7006508160;7202542476;6603768446;7005890897;","Assessment of the performance of a dual-frequency surface reference technique over ocean",2012,"10.1109/TGRS.2011.2180727","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864289635&doi=10.1109%2fTGRS.2011.2180727&partnerID=40&md5=ec32ef7a69543d2487dc9963b2305c4e","The high correlation of the rain-free surface cross sections at two frequencies suggests that the estimate of differential path-integrated attenuation caused by precipitation along the radar beam can be obtained to a higher degree of accuracy than the path attenuation at either frequency. We explore this potential first analytically and then by examining data from the JPL dual-frequency airborne radar using measurements from the Tropical Composition, Cloud, and Climate Coupling experiment obtained during July-August 2007. Despite an improvement in the accuracy of the differential path attenuation, solving for parameters of the particle size distribution often requires not only this quantity but the single-wavelength path attenuation as well. We investigate a simple method of estimating the single-frequency path attenuation from the differential attenuation and compare this estimate with that derived directly from the surface return. © 2012 IEEE."
"11940789000;15838700400;","Trends in daily solar radiation and precipitation coefficients of variation since 1984",2012,"10.1175/2011JCLI4115.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856998289&doi=10.1175%2f2011JCLI4115.1&partnerID=40&md5=a9b941285994516c4e8b94d6d793d329","This study investigates the possibility of changes in daily scale solar radiation and precipitation variability. Coefficients of variation (CVs) were computed for the daily downward surface solar radiation product from the International Satellite Cloud Climatology Project and the daily precipitation product from the Global Precipitation Climatology Project. Regression analysis was used to identify trends in CVs. Statistically significant changes in solar radiation variability were found for 35% of the globe, and particularly large increases were found for tropical Africa and the Maritime Continent. These increases in solar radiation variability were correlated with increases in precipitation variability and increases in deep convective cloud amount. The changes in high-frequency climate variability identified here have consequences for any process depending nonlinearly on climate, including solar energy production and terrestrial ecosystem photosynthesis. To assess these consequences, additional work is needed to understand how high-frequency climate variability will change in the coming decades. © 2012 American Meteorological Society."
"13403754000;7006614696;7007021059;7004379124;","Reproducibility by climate models of cloud radiative forcing associated with tropical convection",2012,"10.1175/JCLI-D-11-00114.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857027494&doi=10.1175%2fJCLI-D-11-00114.1&partnerID=40&md5=d5c69133b7cfd997c0c98723748df758","In this study, cloud radiative forcing (CRF) associated with convective activity over tropical oceans is analyzed for monthly mean data from twentieth-century simulations of 18 climate models participating in phase 3 of the Coupled Model Intercomparison Project (CMIP3) in comparison with observational and reanalysis data. The analysis is focused on the warm oceanic regions with sea surface temperatures (SSTs) above 27°C to exclude the regions with cold SSTs typically covered by low stratus clouds. CRF is evaluated for different regimes sorted by pressure-coordinated vertical motion at 500 hPa (ω 500) as an index of large-scale circulation. The warm oceanic regions cover the regime of vertical motion ranging from strong ascent to weak descent. The most notable feature found in this study is a systematic underestimation by most models of the ratio of longwave cloud radiative forcing (LWCRF) to shortwave cloud radiative forcing (SWCRF) over the weak vertical motion regime defined as -10, ω500, 20 hPa day -1. The underestimation of the ratio corresponds to the underestimation of LWCRF and the overestimation of SWCRF. Clouds in models seem to be lower in the amount of high clouds but more reflective than those in the observations in this regime. In the weak vertical motion regime, the lower free troposphere is dry. In the large-scale environment condition, the reproducibility of LWCRF is high in models adopting the scheme where the relative humidity- based suppression for deep convection occurrence is implemented. Models adopting the Zhang andMcFarlane scheme show good performance without such a suppression mechanism. © 2012 American Meteorological Society."
"39361982900;16162149600;57211064468;14020534200;35460698500;8750834400;","Automated cloud tracking system for the Akatsuki Venus Climate Orbiter data",2012,"10.1016/j.icarus.2011.05.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855358950&doi=10.1016%2fj.icarus.2011.05.017&partnerID=40&md5=30ac39dfb0f226b457624a44491c0918","Japanese Venus Climate Orbiter, Akatsuki, is cruising to approach to Venus again although its first Venus orbital insertion (VOI) has been failed. At present, we focus on the next opportunity of VOI and the following scientific observations.We have constructed an automated cloud tracking system for processing data obtained by Akatsuki in the present study. In this system, correction of the pointing of the satellite is essentially important for improving accuracy of the cloud motion vectors derived using the cloud tracking. Attitude errors of the satellite are reduced by fitting an ellipse to limb of an imaged Venus disk. Next, longitude-latitude distributions of brightness (cloud patterns) are calculated to make it easy to derive the cloud motion vectors. The grid points are distributed at regular intervals in the longitude-latitude coordinate. After applying the solar zenith correction and a highpass filter to the derived longitude-latitude distributions of brightness, the cloud features are tracked using pairs of images. As a result, we obtain cloud motion vectors on longitude-latitude grid points equally spaced. These entire processes are pipelined and automated, and are applied to all data obtained by combinations of cameras and filters onboard Akatsuki. It is shown by several tests that the cloud motion vectors are determined with a sufficient accuracy. We expect that longitude-latitude data sets created by the automated cloud tracking system will contribute to the Venus meteorology. © 2011 Elsevier Inc."
"6701374255;52363729200;36705771700;","Relationship of lower-troposphere cloud cover and cosmic rays: An updated perspective",2012,"10.1175/JCLI-D-11-00169.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856948216&doi=10.1175%2fJCLI-D-11-00169.1&partnerID=40&md5=c88b6098c559547c33209d4fc5d420e6","An updated assessment has been made of the proposed hypothesis that galactic cosmic rays (GCRs) are positively correlated with lower-troposphere global cloudiness. A brief review of the many conflicting studies that attempt to prove or disprove this hypothesis is also presented. It has been determined in this assessment that the recent extended quiet period between solar cycles 23 and 24 has led to a record-high level of GCRs, which in turn has been accompanied by a record-low level of lower-troposphere global cloudiness. This represents a possible observational disconnect, and the update presented here continues to support the need for further research on the GCR-cloud hypothesis and its possible role in the science of climate change. © 2012 American Meteorological Society."
"6507781926;57203056321;6507589406;","Late-Holocene successional dynamics in a transitional forest of west-central Mexico",2012,"10.1177/0959683611414929","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855379294&doi=10.1177%2f0959683611414929&partnerID=40&md5=03402277bfe6377f9d346866ae6029ab","The determination of past successional stages, as well as the factors triggering succession, is crucial for the understanding of forest dynamics and the design of current and future management and conservation strategies. Shifts between successional stages can take decades or even centuries to occur because of tree longevity; therefore palaeoecological studies are important tools for their study. The present research involved the palaeoreconstruction of a transitional forest dominated by Pinus-Carpinus-Quercus in west-central Mexico over the last ~1230 years. The proxies employed include fossil pollen, microscopic fossil charcoal, magnetic susceptibility and organic matter content evaluated by multivariate techniques. The findings reveal that an initial cloud forest stage developed from 1230 to 1050 cal. yr BP. This stage was then interrupted for ~400 years (1050-690 cal. yr BP) when a regional climate change event decreased the number of cloud forest taxa and increased herbaceous taxa including Asteraceae, Poaceae, Plantago and Zea. The cloud forest stage recovered at 690 cal. yr BP and the community has persisted to the present time, yet this stage is dominated by human-induced taxa such as Pinus and Acacia. Whilst the dynamics of individual taxa were related to forest fires and soil erosion, changes between community types were related to an interval of regional climate change (greater aridity) that occurred between 1050 and 690 cal. yr BP. Results from this study indicate that, in order to preserve the cloud forest stage, human disturbances such as logging and agriculture should be excluded; a conservation strategy established in the transitional forest in recent years. © SAGE Publications 2011."
"57192555519;8727832400;8557387300;7102615193;34873296500;","A statistical adjustment of regional climate model outputs to local scales: Application to Platja de Palma, Spain",2012,"10.1175/JCLI-D-10-05024.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856971561&doi=10.1175%2fJCLI-D-10-05024.1&partnerID=40&md5=bccbac3c82b71a7ba909fbf9e3e8f4b6","Projections of climate change effects for the System of Platja de Palma (SPdP) are derived using a novel statistical technique. Socioeconomic activities developed in this settlement are very closely linked to its climate. Any planning for socioeconomic opportunities in the mid- and long term must take into account the possible effects of climate change. To this aim, daily observed series of minimum and maximum temperatures, precipitation, relative humidity, cloud cover, and wind speed have been analyzed. For the climate projections, daily data generated by an ensemble of regional climate models (RCMs) have been used. To properly use RCM data at local scale, a quantile-quantile adjustment has been applied to the simulated regional projections. The method is based on detecting changes in the cumulative distribution functions between the recent past and successive time slices of the simulated climate and applying these, after calibration, to the recent past (observed) series. Results show an overall improvement in reproducing the present climate baseline when using calibrated series instead of raw RCM outputs, although the correction does not result in such clear improvement when dealing with very extreme rainfalls. Next, the corrected series are analyzed to quantify the climate change signal. Anincrease of the annual means for temperatures together with a decrease for the remaining variables is projected throughout the twenty-first century. Increases in weak and intense daily rainfalls and in high extremes for daily maximum temperature can also be expected. With this information at hand, the experts planning the future of SPdP can respond more effectively to the problem of local adaptation to climate change. © 2012 American Meteorological Society."
"14020238200;7402333910;7403077486;6603201254;55477039800;","Changes in hail and flood risk in high-resolution simulations over Colorado's mountains",2012,"10.1038/nclimate1344","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857478522&doi=10.1038%2fnclimate1344&partnerID=40&md5=25c518b446ebdc36f20f979dbd9beb37","The effect of a warming climate on hailstorm frequency and intensity is largely unknown. Global climate models have too coarse resolution to simulate hailstorms explicitly; thus it is unclear if a warmer climate will change hailstorm frequency and intensity, and if so, whether such events will become more likely through intensified thunderstorms or less likely owing to overall warmer conditions. Here we investigate hail generation and maintenance for warm-season extreme precipitation events in Colorado, USA, for both present-day and projected future climates using high-resolution model simulations capable of resolving hailstorms. Most simulations indicate a near-elimination of hail at the surface in future simulations for this region, despite more intense future storms and significantly larger amounts of hail generated in-cloud. An increase in the height of the environmental melting level due to climate warming is found to be the primary reason for the disappearance of surface hail, as the warmer atmosphere increases the melting of frozen precipitation. A decrease in future surface hail at high-elevation locations may imply potential changes in both hail damage and flood risk. © 2012 Macmillan Publishers Limited. All rights reserved."
"6603749411;7005634455;8204540500;","Atmospheric circulation anomalies due to 115 kyr BP climate forcing dominated by changes in the North Pacific Ocean",2012,"10.1007/s00382-011-1138-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856295977&doi=10.1007%2fs00382-011-1138-6&partnerID=40&md5=cbb42fd54a12d6a7fafc2dc8bb9a0fe6","Climate at the time of inception of the Laurentide Ice Sheet (LIS) at ~115 kyr BP is simulated with the fully coupled NCAR Community Climate System Model (CCSM3) and compared to a simulated preindustrial climate (circa 1870) in order to better understand land surface and atmospheric responses to orbital and greenhouse cooling at inception. The interaction between obliquity and eccentricity produces maximum decrease in TOA insolation in JJA over the Arctic but increases occur over the tropics in DJF. The land surface response is dominated by widespread summer cooling in the Northern Hemisphere (NH), increases in snowfall, and decreases in melt rates and total precipitation. CCSM3 responds to the climate forcing at 115 kyr BP by producing incipient glaciation in the areas of LIS nucleation. We find that the inception of the LIS could have occurred with atmospheric circulation patterns that differ little from the present. The location of the troughs/ridges, mean flow over the Canadian Arctic and dominant modes of the atmospheric circulation are all very similar to the present. Larger changes in mean sea level pressure occur upstream of the inception region in the North Pacific Ocean and downstream in Western Europe. In the North Pacific region, the 115 kyr BP anomalies weaken both the Pacific high and Aleutian low making NH summers look more like the PREIND winters and vice versa. The occurrence of cold JJA anomalies at 115 kyr BP favors outbreaks of cold air not in the winter as in contemporary climates but during the summer instead and reinforces the cooling from orbital and GHG reductions. Increased poleward eddy transport of heat and moisture characterizes the atmospheric response in addition to reduced total cloud cover in the Arctic. © 2011 Springer-Verlag."
"6701431208;13406399300;7005231450;7801492228;","Assessing possible dynamical effects of condensate in high resolution climate simulations",2012,"10.1029/2011GL050533","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857589289&doi=10.1029%2f2011GL050533&partnerID=40&md5=fbbd500082cfe37dd4287e4e5394ec9d","In areas of heavy precipitation, condensed water species can add significant mass to an atmospheric column. This mass can create positive pressure anomalies of up to several hPa at the surface. This pressure is expected to force a divergent component in the low-level flow that may have an impact on the evolution of the precipitating system. In this study we examine results from a cloud resolving model simulation of tropical convection to estimate the pressure induced by condensates. A simple parameterization of this condensate loading as a function of surface rain rate is derived and implemented in the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5). Our results suggest that at horizontal resolutions of 25km condensate loading is an important factor in controlling the frequency of intense rain rates in the model. Copyright 2012 by the American Geophysical Union."
"24480690400;23502556500;35171424700;6603384123;55007493900;15830196600;53865535800;6602948193;6701691417;35577097300;25926681100;","Spatio-temporal variations in aerosol optical and cloud parameters over Southern India retrieved from MODIS satellite data",2012,"10.1016/j.atmosenv.2011.10.032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84155163091&doi=10.1016%2fj.atmosenv.2011.10.032&partnerID=40&md5=bcd006cd0c84739a1fbd43a1ed2c4f19","Remote sensing of global aerosols has generated a great scientific interest in a variety of applications related to global warming and climate change. The spatial and temporal variations in aerosol particles over Southern India were described in the present study and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data retrieved from the Terra satellite. High mean Aerosol Optical Depth (AOD) values were observed in almost all regions during the summer season, whereas in Pune, Visakhapatnam and Hyderabad, high AOD values were noticed during the monsoon season. The ångström exponent that increases with AOD is opposite to what would be the case if swelling of particles due to hygroscopic growth near cloudy areas played a major role in the MODIS data. We then analyzed the relationships between AOD and four other cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP). Regional correlation maps and time series plots for aerosol (AOD) and cloud parameters were produced to provide a better understanding of aerosol-cloud interaction. The correlation between AOD and CF was greater than 0.51 in Visakhapatnam, 0.45 in Thiruvanantapuram, 0.42 in Pune and whereas in Bangalore, Hyderabad and Anantapur, it is 0.17, 0.39 and 0.12, respectively. The analyses showed strong positive correlations between AOD and WV for all cities investigated. The correlation between AOD and CF was positive for all selected cities. AOD showed a negative correlation with CTP and CTT in Southern Indian regions. © 2011 Elsevier Ltd."
"35608815200;24329133800;6603576275;7005659017;7404829395;","Evidence of atmospheric brown clouds over India during the 2009 drought year",2012,"10.1109/JSTARS.2011.2170554","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857716079&doi=10.1109%2fJSTARS.2011.2170554&partnerID=40&md5=24eb617dce6e21ce23eeb6dbeb927114","Using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite derived vertical profiles (Total Attenuated Backscatter at 532 nm, Depolarization Ratios at 532 nm, Vertical Feature Mask, monthly mean vertical aerosol and extinction variability), monthly precipitation anomalies from National Centers for Environmental Prediction-Climate Prediction Center (NCEP-CPC) and NCEP wind anomalies; we report the presence of Atmospheric Brown Clouds (ABCs) over India (65°E-95°E;8° N-35°N) during the summer monsoon of 2009. CALIPSO data revealed the persistent presence of a massive aerosol plume till 4 Km above sea level; this plume persisted for over 7 months (March through September 2009) over India and was loaded with anthropogenic aerosols like sulphates, black carbon products from biomass burning and fossil fuel combustion. The CALIPSO vertical profiles, NCEP-CPC monthly precipitation anomalies and NCEP monthly wind anomalies corroborate the presence of aerosol plume. © 2011 IEEE."
"23476370700;54959568500;","Global cloud height fluctuations measured by MISR on Terra from 2000 to 2010",2012,"10.1029/2011GL050506","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856734757&doi=10.1029%2f2011GL050506&partnerID=40&md5=b0375a4ae1fdb38fedd1a0a1851f617b","Self-consistent stereo measurements by the Multiangle Imaging SpectroRadiometer (MISR) on the Terra satellite yield a decrease in global effective cloud height over the decade from March 2000 to February 2010. The linear trend is-44 ± 22 m/decade and the interannual annual difference is-31 ± 11 m between the first and last years of the decade. The annual mean height is measured with a sampling error of 8m, which is less than the observed interannual fluctuation in global cloud height for most years. A maximum departure from the 10-year mean, of-80 ± 8 m, is observed towards the end of 2007. These height anomalies correlate well with the changes in the Southern Oscillation Index, with the effective height increasing over Indonesia and decreasing over the Central Pacific during the La Nia phase of the oscillation. After examining the net influence of Central Pacific/Indonesia heights on the global mean anomaly, we conclude that the integrated effects from outside these regions dominate the global mean height anomalies, confirming the existence of significant teleconnections. Copyright 2012 by the American Geophysical Union."
"35887706900;20435752700;7004174939;7003591311;7201798916;42361233000;","Aerosol-induced intensification of rain from the tropics to the mid-latitudes",2012,"10.1038/ngeo1364","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856702941&doi=10.1038%2fngeo1364&partnerID=40&md5=7c4d43129cd2149c5c3a483c8338ad2e","Atmospheric aerosols affect cloud properties, and thereby the radiation balance of the planet and the water cycle. However, the influence of aerosols on clouds, and in particular on precipitation, is far from understood 1, and seems to depend on factors such as location, season 2 and the spatiotemporal scale of the analysis. Here, we examine the relationship between aerosol abundance and rain rate-a key factor in climate and hydrological processes-using rain data from a satellite-based instrument sensitive to stronger rain rates (Tropical Rainfall Measuring Mission 3, TRMM), aerosol and cloud property data from the Moderate Resolution Imaging Spectroradiometer onboard the Aqua satellite 4,5 and meteorological information from the Global Data Assimilation System 6. We show that for a range of conditions, increases in aerosol abundance are associated with the local intensification of rain rates detected by the TRMM. The relationship is apparent over both the ocean and land, and in the tropics, subtropics and mid-latitudes. Further work is needed to determine how aerosols influence weaker rain rates, not picked up in the analysis. We also find that increases in aerosol levels are associated with a rise in cloud-top height. We suggest that the invigoration of clouds and the intensification of rain rates is a preferred response to an increase in aerosol concentration. © 2012 Macmillan Publishers Limited. All rights reserved."
"8900751100;35577008300;","Simulated impact of vegetation on climate across the North American monsoon region in CCSM3.5",2012,"10.1007/s00382-010-0990-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856255880&doi=10.1007%2fs00382-010-0990-0&partnerID=40&md5=33fa9aea8492b5f431986f992bb3758f","The influence of prescribed changes in vegetation on the climate of the North American monsoon region is examined using the National Center for Atmospheric Research Community Climate System Model Version 3. 5 (NCAR CCSM3. 5). Initial value ensemble experiments are performed in which the vegetation cover fraction over the North American monsoon region is reduced by 0. 2 and the intra-annual climatic response is assessed probabilistically in each one-year ensemble experiment. Changes in the surface radiation budget include decreases in sensible and latent heat fluxes and increases in upward longwave and downward shortwave radiation fluxes, with small net changes in surface albedo. The climatic responses to reduced vegetation cover fraction include year-round increases in ground and surface air temperature, a dampened hydrologic cycle with decreased springtime evaporation, springtime and autumnal precipitation, and autumnal cloud cover, and enhanced atmospheric subsidence in late autumn. Decreased vegetation shifts the monsoon season over the Southwest United States earlier in the year. Within the North American monsoon region, the most robust vegetation feedbacks to climate are found over woody landscapes. © 2011 Springer-Verlag."
"7004942632;6602080205;57197233116;8326850700;6701597468;","Climate model calculations of the impact of aerosols from road transport and shipping",2012,"10.1134/S1024856012010125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950291901&doi=10.1134%2fS1024856012010125&partnerID=40&md5=c32119b5a121b82062c39fd9bb03d090","Road transport and shipping are copious sources of aerosols, which exert a significant radiative forcing, compared to, for example, the CO2 emitted by these sectors. An advanced atmospheric general circulation model, coupled to a mixed-layer ocean, is used to calculate the climate response to the direct radiative forcing from such aerosols. The cases considered include imposed distributions of black carbon and sulphate aerosols from road transport, and sulphate aerosols from shipping; these are compared to the climate response due to CO2 increases. The difficulties in calculating the climate response due to small forcings are discussed, as the actual forcings have to be scaled by large amounts to enable a climate response to be easily detected. Despite the much greater geographical inhomogeneity in the sulphate forcing, the patterns of zonal and annual-mean surface temperature response (although opposite in sign) closely resembles that resulting from homogeneous changes in CO2. The surface temperature response to black carbon aerosols from road transport is shown to be notably non-linear in scaling applied, probably due to the semi-direct response of clouds to these aerosols. For the aerosol forcings considered here, the most widespread method of calculating radiative forcing significantly overestimates their effect, relative to CO2, compared to surface temperature changes calculated using the climate model. © 2012, Pleiades Publishing, Ltd."
"34979885900;6602888227;","Two boundary layers in Titan's lower troposphere inferred from a climate model",2012,"10.1038/ngeo1374","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856715358&doi=10.1038%2fngeo1374&partnerID=40&md5=4351cda955c7e030f4d26d2e6a0f0299","Saturn's moon Titan has a dense atmosphere, but its thermal structure is poorly known. Conflicting information has been gathered on the nature, extent and evolution of Titan's planetary boundary layer-the layer of the atmosphere that is influenced by the surface-from radio-occultation observations by the Voyager 1 spacecraft 1 and the Cassini orbiter 2, measurements by the Huygens probe 3-5 and by dune-spacing analyses 6. Specifically, initial analyses of the Huygens data suggested a boundary layer of 300m depth with no diurnal evolution 4, incompatible with alternative estimates of 2-3km (refs 1,2,6). Here we use a three-dimensional general circulation model 7, albeit not explicitly simulating the methane cycle, to analyse the dynamics leading to the thermal profile of Titan's lowermost atmosphere. In our simulations, a convective boundary layer develops in the course of the day, rising to an altitude of 800m. In addition, a seasonal boundary of 2km depth is produced by the reversal of the Hadley cell at the equinox, with a dramatic impact on atmospheric circulation. We interpret fog that had been discovered at Titan's south pole earlier 8 as boundary layer clouds. We conclude that Titan's troposphere is well structured, featuring two boundary layers that control wind patterns, dune spacing and cloud formation at low altitudes. © 2012 Macmillan Publishers Limited. All rights reserved."
"6603742681;57212075803;","Observing polar regions from space: Advantages of a satellite system on a highly elliptical orbit versus a constellation of low Earth polar orbiters",2012,"10.5589/m12-009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865755123&doi=10.5589%2fm12-009&partnerID=40&md5=308b20361439998c43c5bd83ab0718c2","Recent reports on Arctic climate change sparked an interest in the development of a new observing system for this region, specifically a satellite system making use of a highly elliptical orbit (HEO), an idea supported by the World Meteorological Organization. This paper attempts to quantify the advantages of such a system relative to a traditional constellation of Lower Earth Orbit (LEO) polar satellites. A realistic two-satellite HEO system is compared with currently operating two-, four-, and seven-satellite LEO constellations in terms of spatio-temporal coverage and capability to provide sequences of single, dual, and triplet images at a required temporal resolution. This is important to properly monitor dynamic events, such as volcanic ash transport, frontal systems, smoke from wild fires, and cloud motion from which wind vectors are derived. A two-satellite HEO system is 5-10 times more efficient for monitoring dynamic events from image pairs above 70°N than a standard four-satellite morning-afternoon sun synchronous LEO constellation. An analytical model was developed to quantify the spatio-temporal coverage from a LEO constellation. Results demonstrate that a LEO constellation with orbital characteristics similar to the upcoming Joint Polar Satellite System should include as many as 23 (34) spacecrafts to achieve coverage with 15 (10) min refresh rate at 60°N, i.e., the capability of a two-satellite HEO system. In addition, data reception issues and the need for complex image compositing affect the product latency of an LEO system, and further reduce its efficiency in comparison with an HEO system. © 2012 Government of Canada."
"37023394900;6506068111;6602186522;7004047676;","Understory spider diversity in two remnants of tropical montane cloud forest in Chiapas, Mexico",2012,"10.1007/s10841-011-9391-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855523518&doi=10.1007%2fs10841-011-9391-x&partnerID=40&md5=c8972249668ca142041ab49d45671850","We evaluated the spider diversity of a tropical montane cloud forest understory in two nearby sites with different degree of human disturbance at the Biosphere Reserve Volcán Tacaná, Chiapas, Mexico. The study was conducted over a 24 days period distributed in 6 months in 2009, covering dry and rainy seasons. A total of 8,370 spiders (1,208 adults and 7,162 juveniles) were collected. Determined specimens (7,747) represented 112 species and morphospecies, 71 genera and 22 families. The results showed that human disturbance has an influence on spider communities: species richness was significantly higher in the preserved site as regards to the disturbed site. Despite their proximity, the composition of spider communities showed only a moderate similarity between the two sites. No differences in abundance were found among sites when considering the whole sample, but sites differed clearly when seasons were analyzed separately. The rainy season had a negative effect on the abundance of spiders in the preserved site. Although the spider community structure was very similar between sites, there was a trend towards a greater species evenness in the preserved site for the whole sampling period and for the dry season. © 2011 Springer Science+Business Media B.V."
"55454551000;36836439900;","Bacterial abundance and viability in long-range transported dust",2012,"10.1016/j.atmosenv.2011.11.050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84155162793&doi=10.1016%2fj.atmosenv.2011.11.050&partnerID=40&md5=a5fe313cc933754761f4ba8e197b0b77","Transports of bacteria in the atmosphere relate to climate and global hydrological cycles by acting as nuclei of ice-cloud formation, and affect the ecosystems and public health in the downwind ecosystems. Here we present quantitative investigations of airborne bacterial cells coupled with LIVE/DEAD BacLight assay in southwestern Japan to show that airborne bacteria were widespread with Asian dust. Total bacterial cell-concentrations in dust varied between 1.0-×-10 6 and 1.6-×-10 7 cells m -3, which were one to two orders higher than those in non-dusty air and were correlated with the concentrations of aerosol particles larger than 1-μm. The ratio of viable bacterial cells to total bacterial cells (viability) of bacteria in dust ranged from 16 to 40%, which was quite smaller than the viability in non-dusty air. However viable bacterial cell concentrations in dust, 2.5-×-10 5---3.8-×-10 6 cells m -3, were similar to or higher than those in non-dusty air. Dust is thus a substantial source of airborne bacterial cells as well as mineral particles. These quantitative results suggest Asian dust is one of the processes for dispersal of airborne bacteria in the global atmosphere. © 2011 Elsevier Ltd."
"14023953700;57205479513;","A multidiagnostic intercomparison of tropical-width time series using reanalyses and satellite observations",2012,"10.1175/JCLI-D-11-00127.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857027430&doi=10.1175%2fJCLI-D-11-00127.1&partnerID=40&md5=ed4eaad7437ae97e80d93a69ee09bb9c","Poleward migration of the latitudinal edge of the tropics of 0.25°-3.0° decade -1 has been reported in several recent studies based on satellite and radiosonde data and reanalysis output covering the past ~30yr. The goal of this paper is to identify the extent to which this large range of trends can be explained by the use of different data sources, time periods, and edge definitions, as well as how the widening varies as a function of hemisphere and season. Toward this end, a suite of tropical edge latitude diagnostics based on tropopause height, winds, precipitation-evaporation, and outgoing longwave radiation (OLR) are analyzed using several reanalyses and satellite datasets. These diagnostics include both previously used definitions and new definitions designed for more robust detection. The wide range of widening trends is shown to be primarily due to the use of different datasets and edge definitions and only secondarily due to varying start-end dates. This study also shows that the large trends (&gt;~1° decade -1) previously reported in tropopause and OLR diagnostics are due to the use of subjective definitions based on absolute thresholds. Statistically significant Hadley cell expansion based on the mean meridional streamfunction of 1.0°-1.5° decade -1 is found in three of four reanalyses that cover the full time period (1979-2009), whereas other diagnostics yield trends of -0.5°-0.8° decade -1 that are mostly insignificant. There are indications of hemispheric and seasonal differences in the trends, but the differences are not statistically significant. © 2012 American Meteorological Society."
"35867172500;7004384155;7102591209;55869652000;","Bulk microphysical properties of semi-transparent cirrus from AIRS: A six year global climatology and statistical analysis in synergy with geometrical profiling data from CloudSat-CALIPSO",2012,"10.5194/acp-12-503-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855665251&doi=10.5194%2facp-12-503-2012&partnerID=40&md5=1f95ac4aeabcc8f3fb91887df90bd754","This article presents a retrieval method and a statistical analysis of the bulk microphysical properties of semi-transparent ice clouds using the Atmospheric Infrared Sounder (AIRS). The method relies on spectral differences of cirrus emissivities in the 8-12 μm range and is sensitive to the effective ice crystal diameter (D e) and ice water path (IWP) of up to 85 μm and 120 g mg -2, respectively. An indication of the most frequent ice crystal habit in the cirrus has been obtained by using separately single scattering properties of column-like and aggregate-like ice crystals in the simulations. Uncertainties due to hypotheses on atmospheric parameters and ice crystal single scattering properties are discussed and the cirrus emissivity and temperature range for the applicability of the method are determined. To be sure that the cirrus only includes ice crystals, one has to restrict the cloud temperature range to T cld &lt; 230 K. On a global scale, these semi-transparent ice clouds (cirrus) represent about 25% of all high clouds and are mainly encountered in the midlatitudes during winter and in the tropics, with an average D e and IWP of 52 μm and 27 g mg -2, respectively. A comparison with bulk microphysical properties from the TIROS-N Operational Vertical Sounder (TOVS) shows an agreement on global mean values. The addition of spectral information revealed improvements at the limits of the cirrus emissivity range. Collocated Radar-Lidar Geometrical Profiling (GEOPROF) data have been used to study the vertical structure of these clouds and to infer average ice water content (IWC) for cirrus with a small vertical extent. This allowed us to compare and contrast parameterizations of D e as functions of IWC and IWP, respectively. © 2012 Author(s)."
"56898331700;56576516000;7406200372;55612831900;15019752400;7501797728;","A high-resolution emission inventory of primary pollutants for the Huabei region, China",2012,"10.5194/acp-12-481-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862907732&doi=10.5194%2facp-12-481-2012&partnerID=40&md5=34141eac93839d42326ea69d6005656d","Huabei, located between 32° N and 42° N, is part of eastern China and includes administratively the Beijing and Tianjin Municipalities, Hebei and Shanxi Provinces, and Inner-Mongolia Autonomous Region. Over the past decades, the region has experienced dramatic changes in air quality and climate, and has become a major focus of environmental research in China. Here we present a new inventory of air pollutant emissions in Huabei for the year 2003 developed as part of the project Influence of Pollution on Aerosols and Cloud Microphysics in North China (IPAC-NC). &lt;br&gt;&lt;br&gt; Our estimates are based on data from the statistical yearbooks of the state, provinces and local districts, including major sectors and activities of power generation, industrial energy consumption, industrial processing, civil energy consumption, crop straw burning, oil and solvent evaporation, manure, and motor vehicles. The emission factors are selected from a variety of literature and those from local measurements in China are used whenever available. The estimated total emissions in the Huabei administrative region in 2003 are 4.73 Tg SO 2, 2.72 Tg NO x (in equivalent NO 2), 1.77 Tg VOC, 24.14 Tg CO, 2.03 Tg NH3, 4.57 Tg PM10, 2.42 Tg PM2.5, 0.21 Tg EC, and 0.46 Tg OC. &lt;br&gt;&lt;br&gt; For model convenience, we consider a larger Huabei region with Shandong, Henan and Liaoning Provinces included in our inventory. The estimated total emissions in the larger Huabei region in 2003 are: 9.55 Tg SO 2, 5.27 Tg NO x (in equivalent NO 2), 3.82 Tg VOC, 46.59 Tg CO, 5.36 Tg NH 3, 10.74 Tg PM 10, 5.62 Tg PM 2.5, 0.41 Tg EC, and 0.99 Tg OC. The estimated emission rates are projected into grid cells at a horizontal resolution of 0.1° latitude by 0.1° longitude. Our gridded emission inventory consists of area sources, which are classified into industrial, civil, traffic, and straw burning sectors, and large industrial point sources, which include 345 sets of power plants, iron and steel plants, cement plants, and chemical plants. br The estimated regional NO 2 emissions are about 2-3% (administrative Huabei region) or 5% (larger Huabei region) of the global anthropogenic NO 2 emissions. We compare our inventory (IPAC-NC) with the global emission inventory EDGAR-CIRCE and the Asian emission inventory INTEX-B. Except for a factor of 3 lower EC emission rate in comparison with INTEX-B, the biases of the total emissions of most primary air pollutants in Huabei estimated in our inventory, with respect to EDGAR-CIRCE and INTEX-B, generally range from 30% to +40%. Large differences up to a factor of 2-3 for local emissions in some areas (e.g. Beijing and Tianjin) are found. It is recommended that the inventories based on the activity rates and emission factors for each specific year should be applied in future modeling work related to the changes in air quality and atmospheric chemistry over this region. © 2012 Author(s)."
"35769047000;55944537900;55918993800;55704707000;7005742190;","Near surface air humidity in a megadiverse Andean mountain ecosystem of southern Ecuador and its regionalization",2012,"10.1016/j.agrformet.2011.08.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052703054&doi=10.1016%2fj.agrformet.2011.08.004&partnerID=40&md5=dd1a70e51faf5b82bd6f3ba6e08f2189","The near surface humidity in a megadiverse mountain ecosystem in southern Ecuador is examined on the basis of Relative Humidity (RH) measurements inside the natural mountain forest and at open sites along an altitudinal gradient from 1700 to 3200m. The main methodological aim of the current study is to generate a humidity regionalization tool to provide spatial datasets on average monthly mean, minimum and maximum RH, Specific Humidity (q) and Specific Saturation Deficit (DS) by using observation data of RH. The maps based on data of the period 1999-2009 are needed by ecological projects working on various plots where no climate station data are available. The humidity maps are generated by combining a straightforward detrending technique with a Digital Elevation Model and a satellite-based land cover classification which also provides the relative forest cover per pixel. The topical aim of the study is to investigate the humidity distribution and structure of both manifestations of our ecosystem (pastures and natural vegetation) with special considerations to the ecosystem regulation service by converting natural forest into pasture. The results reveal a clear differentiation over the year, partly triggered by the change of synoptic weather situation but also by land cover effects. Humidity amplitudes are particularly low during the main rainy season when cloudiness and rainfall are high, but markedly pronounced in the relative dry season when daily irradiance and outgoing nocturnal radiation causes distinct differences between the land cover units. Particularly the upper pasture areas gained by slash and burn of the natural forest exhibit the lowest humidity values while the humidity inside the mountain forest is significantly higher due to the regulating effects of the dense vegetation. Thus, clearing the forest clearly reduces the regulation function (regulating ecosystem services) of the ecosystem which might become problematic for reforestation under future global warming. © 2011 Elsevier B.V."
"16445227700;7004347243;7404087896;7005804345;6701594586;23029086100;6603425325;6603848988;23090057700;23567751700;25227472100;23866122100;7003479494;7202097052;7004643405;8261329600;7006497590;","Analysis of ozone and nitric acid in spring and summer Arctic pollution using aircraft, ground-based, satellite observations and MOZART-4 model: Source attribution and partitioning",2012,"10.5194/acp-12-237-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855512617&doi=10.5194%2facp-12-237-2012&partnerID=40&md5=b72b8edf6b594eee45d275439fd71c32","In this paper, we analyze tropospheric O3 together with HNO 3 during the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) program, combining observations and model results. Aircraft observations from the NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) and NOAA ARCPAC (Aerosol, Radiation and Cloud Processes affecting Arctic Climate) campaigns during spring and summer of 2008 are used together with the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) to assist in the interpretation of the observations in terms of the source attribution and transport of O 3 and HNO 3 into the Arctic (north of 60°N). The MOZART-4 simulations reproduce the aircraft observations generally well (within 15%), but some discrepancies in the model are identified and discussed. The observed correlation of O3 with HNO 3 is exploited to evaluate the MOZART-4 model performance for different air mass types (fresh plumes, free troposphere and stratospheric-contaminated air masses). Based on model simulations of O 3 and HNO 3 tagged by source type and region, we find that the anthropogenic pollution from the Northern Hemisphere is the dominant source of O 3 and HNO 3 in the Arctic at pressures greater than 400 hPa, and that the stratospheric influence is the principal contribution at pressures less 400 hPa. During the summer, intense Russian fire emissions contribute some amount to the tropospheric columns of both gases over the American sector of the Arctic. North American fire emissions (California and Canada) also show an important impact on tropospheric ozone in the Arctic boundary layer. Additional analysis of tropospheric O 3 measurements from ground-based FTIR and from the IASI satellite sounder made at the Eureka (Canada) and Thule (Greenland) polar sites during POLARCAT has been performed using the tagged contributions. It demonstrates the capability of these instruments for observing pollution at northern high latitudes. Differences between contributions from the sources to the tropospheric columns as measured by FTIR and IASI are discussed in terms of vertical sensitivity associated with these instruments. The first analysis of O 3 tropospheric columns observed by the IASI satellite instrument over the Arctic is also provided. Despite its limited vertical sensitivity in the lowermost atmospheric layers, we demonstrate that IASI is capable of detecting low-altitude pollution transported into the Arctic with some limitations. © 2012 Author(s)."
"55717075800;35093720000;13403810300;7202920576;7004960339;7201471897;15749870400;55783129300;55664298600;","Tree-ring δ 18O in southwestern China linked to variations in regional cloud cover and tropical sea surface temperature",2012,"10.1016/j.chemgeo.2011.10.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855429928&doi=10.1016%2fj.chemgeo.2011.10.001&partnerID=40&md5=261505262aa4af668d9e21b4b5a40e4e","In this paper, we present the first annual oxygen isotope (δ 18O) record (1902 to 2004) from the latewood cellulose of trees growing in a temperate-moist forest in southwestern China. Tree-ring δ 18O ranges from 12.8 to 18.6‰ and averages 15.2‰ δ 18O in the latewood negatively correlates with total cloud cover, relative humidity, and precipitation during the moist months (August to October) from 1951 to 2004 and, to a lesser extent, positively correlates with the temperature in June. Spatial correlation analysis revealed that tree-ring latewood δ 18O is more strongly related to variability in regional cloud cover and precipitation in autumn. Tree-ring δ 18O negatively correlates with the indices of the Indian summer monsoon (1948 to 2004), the western North Pacific monsoon (1948 to 2004), and with the East Asian summer monsoon (1902 to 2000), suggesting that these monsoons strongly influence the regional climate. Under global warming of last century, we found a strong inverse correlation between tree-ring δ 18O and the Southern Oscillation index in different periods, indicating a complex association between the El Niño-Southern Oscillation and the regional climate, which in turn affects tree-ring δ 18O. Correlation with the global sea surface temperature (SST) indicates that climatic conditions in the Indian Ocean might play a dominant role in modulating cloud cover and precipitation over the study region during the monsoon seasons. We also found a significant correlation between tree-ring δ 18O and SST over the western-north Pacific Ocean. Our results suggest strong links between tropical oceans and an ENSO-like climate with the oxygen-isotope sources and discrimination for trees in the study region. © 2011 Elsevier B.V."
"7005228425;","The aerosol-cloud-climate conundrum",2012,"10.1504/IJGW.2012.049438","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872713718&doi=10.1504%2fIJGW.2012.049438&partnerID=40&md5=f9026e5ad159a5806bd37b2885b059ce","The complexity of the atmospheric aerosol and its connection with clouds and climate are illustrated with a host of examples against the background of our present limited state of understanding. A discussion of related feedbacks demonstrates the difficulties of resolving all respective research issues. The key role of aerosols and clouds in anthropogenic climate change make the high uncertainties related to them ever more painful. Nevertheless, there are suggestions to manipulate aerosols and clouds by climate engineering to counteract global warming. Before considering such remedies the aerosol-cloud-climate conundrum needs to be reduced to a level of uncertainty that is comparable to those related to anthropogenic greenhouse gases. Considering the complexity of the aerosol/ cloud system the challenge will be to identify the necessary essential knowledge and differentiate that from marginal details and focus research efforts on these essentials in order to simplify the complex aerosol-cloud system without loosing indispensable features. Copyright © 2012 Inderscience Enterprises Ltd."
"7005321613;7004683817;","Persistent solar signatures in cloud cover: Spatial and temporal analysis",2012,"10.1088/1748-9326/7/4/044004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867757361&doi=10.1088%2f1748-9326%2f7%2f4%2f044004&partnerID=40&md5=b9f1c325d17fae478d9484c4fd4571e6","A consensus regarding the impact of solar variability on cloud cover is far from being reached. Moreover, the impact of cloud cover on climate is among the least understood of all climate components. This motivated us to analyze the persistence of solar signals in cloud cover for the time interval 1984-2009, covering two full solar cycles. A spatial and temporal investigation of the response of low, middle and high cloud data to cosmic ray induced ionization (CRII) and UV irradiance (UVI) is performed in terms of coherence analysis of the two signals. For some key geographical regions the response of clouds to UVI and CRII is persistent over the entire time interval indicating a real link. In other regions, however, the relation is not consistent, being intermittent or out of phase, suggesting that some correlations are spurious. The constant in phase or anti-phase relationship between clouds and solar proxies over some regions, especially for low clouds with UVI and CRII, middle clouds with UVI and high clouds with CRII, definitely requires more study. Our results show that solar signatures in cloud cover persist in some key climate-defining regions for the entire time period and supports the idea that, if existing, solar effects are not visible at the global level and any analysis of solar effects on cloud cover (and, consequently, on climate) should be done at the regional level. © 2012 IOP Publishing Ltd."
"55613105600;56298802300;6701915334;6701832491;36647779500;","Evaluation of two cloud parameterizations and their possible adaptation to arctic climate conditions",2012,"10.3390/atmos3030419","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874529910&doi=10.3390%2fatmos3030419&partnerID=40&md5=94cef0472a1a4e295a03da3a06a5a4d3","Based on the atmospheric regional climate model HIRHAM5, the single-column model version HIRHAM5-SCM was developed and applied to investigate the performance of a relative humidity based (RH-Scheme) and a prognostic statistical cloud scheme (PS-Scheme) in the central Arctic. The surface pressure as well as dynamical tendencies of temperature, specific humidity, and horizontal wind were prescribed from the ERA-Interim data set to enable the simulation of a realistic annual cycle. Both modeled temperature and relative humidity profiles were validated against radio soundings carried out on the 35th North Pole drifting station (NP-35). Simulated total cloud cover was evaluated with NP-35 and satellite-based ISCCP-D2 and MODIS observations. The more sophisticated PS-Scheme was found to perform more realistically and matched the observations better. Nevertheless, the model systematically overestimated the monthly averaged total cloud cover. Sensitivity studies were conducted to assess the effect of modified ""tuning"" parameters on cloud-related model variables. Two tunable parameters of the PS-Scheme and six tuning parameters contained in the cloud microphysics were analyzed. Lower values of the PS-Scheme adjustment parameter ~q0, which defines the shape of the symmetric beta distribution (acting as probability density function), as well as higher values of the cloud water threshold CWmin or autoconversion rate γ1 are able to reduce the overestimation of Arctic clouds. Furthermore, a lower cloud ice threshold γthr, which controls the Bergeron-Findeisen process, improves model cloudiness and the ratio of liquid to solid water content. © 2012 by the authors."
"13405561000;","Examples of mechanisms for negative cloud feedback of stratocumulus and stratus in cloud parameterizations",2012,"10.2151/sola.2012-037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920933805&doi=10.2151%2fsola.2012-037&partnerID=40&md5=a5ef485d2893cc77afd50048130d6104","Mechanisms of cloud feedback for marine boundary layer clouds in GCMs (General Circulation Models) to the sea surface temperature increase, which can depend on parameterization, were investigated using single column model version of a GCM with two different low cloud schemes. Both schemes showed negative cloud feedbacks and they were attributed to the increase of the liquid water path (LWP) with the future climate forcing for stratocumulus and stratus. The mechanisms of the LWP increase in the two schemes were investigated respectively through simple numerical experiments. The experimental results imply that in the first scheme, the increase of saturation specific humidity due to the temperature increase in the future climate forcing contributes to the negative cloud feedback through the parameterization determining in-cloud cloud water content (CWC). The results also imply that the increase of latent heat flux in the future climate contributes to increased LWP and hence negative cloud feedback in the other scheme. © 2012, the Meteorological Society of Japan."
"8511991900;7202048112;7409080503;7103158465;57138743300;35114405700;55802246600;57200702127;","Aerosol impacts on clouds and precipitation in eastern China: Results from bin and bulk microphysics",2012,"10.1029/2011JD016537","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863012201&doi=10.1029%2f2011JD016537&partnerID=40&md5=b9a38f1a075d2a0096793d34f934df7f","Using the Weather Research and Forecasting model coupled with a spectral-bin microphysics (""SBM"") and measurements from the Atmospheric Radiation Measurement Mobile Facility field campaign in China (AMF-China), the authors examine aerosol indirect effects (AIE) in the typical cloud regimes of the warm and cold seasons in Southeast China: deep convective clouds (DCC) and stratus clouds (SC), respectively. Comparisons with a two-moment bulk microphysics (""Bulk"") are performed to gain insights for improving bulk schemes in estimating AIE in weather and climate simulations. For the first time, measurements of aerosol and cloud properties acquired in China are used to evaluate model simulations to better understand aerosol impact on clouds in the southeast of China. It is found that changes in cloud condensation nuclei (CCN) concentration significantly change the timing of storms, the spatial and temporal distributions of precipitation, the frequency distribution of precipitation rate, as well as cloud base and top heights for the DCC, but not for the SC. Increasing CCN increases cloud droplet number (N<inf>c</inf>) and mass concentrations, decreases raindrop number concentration, and delays the onset of precipitation. Compared with SBM, Bulk predicts much higher N<inf>c</inf> and the opposite CCN effects on convection and heavy rain, stemming from the fixed CCN prescribed in Bulk. CCN have a significant effect on ice microphysical properties with SBM but not Bulk and different condensation/deposition freezing parameterizations employed could be the main reason. This study provided insights to further improve the bulk scheme to better account for aerosol-cloud interactions in regional and global climate simulations, which will be the focus for a follow-on paper. Copyright 2012 by the American Geophysical Union."
"11839134300;36884248500;","Probing the climatological impact of a cosmic ray-cloud connection through low-frequency radio observations",2012,"10.1016/j.jastp.2011.10.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83855164032&doi=10.1016%2fj.jastp.2011.10.003&partnerID=40&md5=e526ad01ff4302d8dd3e0eb0aadfaad9","It has been proposed that cosmic ray events could have a causal relationship with cloud formation rates. Given the weak constraints on the role that cloud formation plays in climate forcing it is essential to understand the role such a relationship could have in shaping the Earth's climate. This issue has been previously investigated in the context of the long-term effect of cosmic ray events on climate. However, in order to establish whether or not such a relationship exists, measurements of short-timescale solar events, individual cosmic ray events, and spatially correlated cloud parameters could be of great significance. Here we propose such a comparison using observations from a pair of radio telescopes arrays, the Long Wavelength Array (LWA) and the Eight-meter-wavelength Transient Array (ETA). These low-frequency radio arrays have a unique ability to simultaneously conduct solar, ionospheric and cosmic rays observations and are thus ideal for such a comparison. We will outline plans for a comparison using data from these instruments, satellite images of cloud formation as well as expected cloud formation rates from numerical models. We present some preliminary results illustrating the efficacy of this type of comparison and discuss future plans to carryout this program. © 2011 Elsevier Ltd."
"55705948900;7103206141;7402677913;7004091561;7201665727;","Global in-cloud production of secondary organic aerosols: Implementation of a detailed chemical mechanism in the GFDL atmospheric model AM3",2012,"10.1029/2012JD017838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864863361&doi=10.1029%2f2012JD017838&partnerID=40&md5=a741fab2ce6fae62ecb35c036d62b667","Secondary organic aerosols (SOA) constitute a significant fraction of ambient aerosols, but their global source is only beginning to be understood. Substantial evidence has shown that oxidation of water-soluble organic species in the liquid cloud leads to the formation of SOA. To evaluate this global source and explore its sensitivity to various assumptions concerning cloud properties, we simulate in-cloud SOA (IC-SOA) formation based on detailed multiphase chemistry incorporated into the newly developed Geophysical Fluid Dynamics Laboratory (GFDL) coupled chemistry-climate model AM3. We find global IC-SOA production is around 20-30 Tgyr-1 between 1999 and 2001. Depending on season and location, oxalic acid accounts for 40-90% of the total IC-SOA source (particularly between 800hPa-400hPa), and glyoxylic acid and oligomers (formed by glyoxal and methylglyoxal in evaporating clouds) each contribute an additional 10-20%. Besides glyoxal and methylglyoxal (extensively studied by previous research), glycolaldehyde and acetic acid are among the most important precursors leading to the formation of IC-SOA, particularly oxalic acid. Different implementations of cloud fraction or cloud lifetime in global climate models could potentially modify estimates of IC-SOA mass production by 20-30%. Dense IC-SOA production occurs in the tropical and midlatitude regions of the lower troposphere (surface to 500hPa). In DJF, IC-SOA production is concentrated over the western Amazon and southern Africa. In JJA, substantial IC-SOA production occurs over southern China and boreal forest regions. This study confirms a significant in-cloud source of SOA, which will directly and indirectly influence global radiation balance and regional climate. © 2012. American Geophysical Union. All Rights Reserved."
"35086136600;6602111828;7403296946;","Reducing the resolution bias in cloud fraction from satellite derived clear-conservative cloud masks",2012,"10.1029/2011JD017195","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862539710&doi=10.1029%2f2011JD017195&partnerID=40&md5=692227b904830d3b276c1ddadde9ddd9","Clear-conservative satellite cloud detection algorithms overestimate cloud fraction (CF), the degree to which depends on instrument resolution and the spatial distribution of cloud area, with boundary layer cumulus carrying the largest overestimation. This is because in the standard method of computing CF, partially cloudy pixels contribute in the amount of the pixel's area rather than the true cloud area. Development of analytical and pattern recognition techniques to reduce overestimation has been limited by the lack of coincident long-term, large scale, and high-resolution satellite data sets. Such data sets are now available from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Multiangle Imaging SpectroRadiometer (MISR) instruments onboard the satellite, Terra. These data sets are used to determine the resolution required to reduce the CF overestimation to ≤0.01 absolute CF using the standard, analytical, and pattern recognition techniques on perfect, clear-conservative cloud masks with future instrument design in mind; investigate the challenges of implementing these techniques on MISR's operational clear-conservative cloud mask; and demonstrate the impact of these techniques on a MISR-derived CF climatology similar to those used to evaluate climate models. Reducing the median CF bias to ≤0.01 requires resolutions of <45 m and ≤80 m for the standard and analytical techniques, respectively, while the pattern recognition technique has no resolution requirement up to a resolution of 1.2 km. When the pattern recognition technique is applied to 10-year, December, low cloud climatologies over the tropical Western Atlantic (10°N-20°N and 50°W-60°W) derived from MISR, the average CF reduces from 0.50 to 0.20. This is a large reduction in cloud fraction, particularly when considering the climate sensitivity to low clouds and the use of satellite derived CF climatologies for evaluation of climate model CF and radiative budgets. © 2012. American Geophysical Union. All Rights Reserved."
"8977001000;7403282069;7407116104;56493740900;","Impact of a cloud thermodynamic phase parameterization based on CALIPSO observations on climate simulation",2012,"10.1029/2011JD017263","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860635380&doi=10.1029%2f2011JD017263&partnerID=40&md5=6e69dd682f82b3cac9aadd73434325b9","This study examines the impact of a new cloud thermodynamic phase parameterization on climate simulation. The new parameterization is based on CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations and replaces the default parameterization in the Community Atmosphere Model version 4. It is shown that the application of the new cloud phase parameterization results in a small increase in global-mean liquid water path (LWP) and a small decrease in global-mean ice water path (IWP). Large regional increases in LWP mainly occur in tropical regions such as the western Pacific warm pool and northeastern Indian Ocean and middle latitudes, while large decreases in IWP occur in the midlatitude storm track regions. The increase in zonal-mean cloud water content occurs at temperatures between -15°C and -30°C and cloud fraction increases occur at higher altitudes near the -30°C isotherm. Two other sensitivity experiments that favor more ice-phase clouds also increase cloud fractions at the same altitudes, but decrease cloud water content at slightly lower altitudes. It is found that relative humidity increases at the same altitudes where the cloud fraction increases, caused by radiative cooling that is induced by cloud fraction increases but not changes in cloud water content. This result points to a deficiency in cloud fraction parameterizations that rely solely on ambient humidity without taking cloud water/ice content into account. Zonal-mean cloud albedo forcing is sensitive to LWP in mixed-phase clouds and the comparison with observations suggests that the CALIPSO and default parameterizations perform well in the extratropical regions. Copyright 2012 by the American Geophysical Union."
"24764834600;7004035832;7102739935;","Cloud frequency climatology at the Andes/Amazon transition: 1. Seasonal and diurnal cycles",2012,"10.1029/2012JD017770","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870612636&doi=10.1029%2f2012JD017770&partnerID=40&md5=19204e86ba3ff60b2e27f54095fd10f4","Tropical montane regions present a complex local climate but one that may be very sensitive to local and global change. Therefore, it is important to assess their current climatological state, and to understand how the large-scale circulation may affect local-scale cloud patterns. We examine the cloud climatology of a tropical Andean montane region in the context of tropical South American climate in terms of seasonal/diurnal cycles using a corrected ISCCP (International Satellite Cloud Climatology Project) DX cloud product (1983-2008), MODIS (Moderate Resolution Imaging Spectroradiometer) MOD35 visible cloud flags (2000-2008) and ground-based cloud observations. Cloud climatologies were compared for three elevation zones: highlands (puna grassland), eastern slope (the montane forest) and lowlands. We found that in the dry season (JJA) the study area is part of a localized region of higher cloud frequency relative to other parts the eastern slope, and also relative to the adjacent highlands and lowlands. The highlands exhibited the greatest amplitude mean annual cycle of cloud frequency, with a minimum in June for all times of day. There were contrasts between the three zones with regard to the month in which the minimum cloud frequency occurs between different times of day. Higher lowland and eastern slope cloud frequencies compared with those on the puna in the early hours in the wet season suggest low-level convergence at lower elevations. Comparisons between satellite products show that ISCCP and MODIS produce very similar annual cycles although the absolute cloud frequencies are higher in ISCCP data. © 2012. American Geophysical Union. All Rights Reserved."
"54403961000;24468389200;15830929400;22137065500;","Climate sensitivity and cloud feedback processes imposed by two different external forcings in an aquaplanet GCM",2012,"10.1007/s00704-012-0607-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857404705&doi=10.1007%2fs00704-012-0607-0&partnerID=40&md5=22d2eb82b19e574d56cda7e3c4c4f58f","The sensitivity of climate to an increase in sea surface temperature (SST) and CO2, as well as cloud feedback processes, is analyzed through a series of aquaplanet experiments listed in the Coupled Model Intercomparison Project. Rainfall is strengthened in a +4K anomaly SST experiment due to the enhanced surface evaporation; while in a quadruple CO2 experiment, precipitation and total cloud cover are appreciably weakened. In both the +4K and quadruple CO2 (4xCO2) experiments, the Hadley cell is impaired, with an increase in moderate subsidence and a decrease in the frequency of strong convective activity. Regarding cloud radiation forcing (CRF), the analysis technique of Bony et al. (Climate Dynamics, 22:71-86, 2004) is used to sort cloud variables by dynamic regimes using the 500-hPa vertical velocity in tropical areas (30°S-30°N). Results show that the tropically averaged CRF change is negative and is dominated mainly by the thermodynamic component. Within convective regimes, the behavior of longwave CRF is different in the +4K and 4xCO2 experiments, with positive and negative changes, respectively. The globally averaged CRF also reveals a negative change in both aquaplanet and Earthlike experiments, implying that clouds may play a role in decelerating global warming. The calculated climate sensitivity demonstrates that our results are close to those obtained from other models, with 0. 384 and 0. 584 Km2 W-1 for aquaplanet and Earthlike experiments, respectively. © 2012 Springer-Verlag."
"24467873200;55741696000;7003335370;7601492669;","Modeling low-level clouds over the Okhotsk Sea in summer: Cloud formation and its effects on the Okhotsk high",2012,"10.1029/2011JD016462","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863386332&doi=10.1029%2f2011JD016462&partnerID=40&md5=6dfe6560eb19298e272c05b3df4b0c87","In summer the Okhotsk Sea is often covered by low-level clouds, which occasionally co-occur with the Okhotsk high. We investigate the formation of low-level clouds and their effects on the Okhotsk high in July using reanalysis, satellite data, and a regional climate model. Statistical analysis suggests that the amount of low-level clouds over the Okhotsk Sea has a positive relationship with the strength of the Okhotsk high; however, the formation processes of the Okhotsk high and low-level clouds are not dependent on each other. A simulation focusing on July 2003, when the Okhotsk high was the strongest in the past decade, showed low-level cloud formation and resulting strong cooling over most of the Okhotsk Sea, which can be attributed to longwave radiation. Sensitivity experiments with reduced cloud amounts reveal that this radiative flux results in the cooling of the cloud top boundary layer (CBL), thereby reinforcing the Okhotsk high within the CBL. Trajectory analyses show that unsaturated air reaches saturation mainly because of the downward sensible heat flux. After cloud formation, radiative cooling causes an upward sensible heat flux below the clouds. Such cooling and heating roughly balance with the cooling due to evaporation of drizzle and cloud water and the heating due to condensation. Eventually, the CBL achieves a low-temperature steady state over the Okhotsk Sea. Although the latent heat flux is positive over the Okhotsk Sea irrespective of the presence or absence of low-level clouds, associated moisture flux is insignificant for achieving saturation. This positive latent heat flux is enhanced under cloudy conditions and compensates for the loss of water vapor due to condensation. Copyright 2012 by the American Geophysical Union."
"7006643234;24722339600;7003666669;56162305900;55405340400;7006705919;55476786400;6602379332;35115244100;","Aerosol optical depth increase in partly cloudy conditions",2012,"10.1029/2012JD017894","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866665497&doi=10.1029%2f2012JD017894&partnerID=40&md5=b21b5a5f5d3db1f37dca683f0af39c21","Remote sensing observations of aerosol from surface and satellite instruments are extensively used for atmospheric and climate research. From passive sensors, the apparent cloud-free atmosphere in the vicinity of clouds often appears to be brighter than further away from the clouds, leading to an increase in the retrieved aerosol optical depth (τ). Mechanisms contributing to this enhancement or increase, including contamination by undetected clouds, hygroscopic growth of aerosol particles, and meteorological conditions, have been debated in recent literature, but the extent to which each of these factors influence the observed enhancement (δ τ) is poorly known. Here we used 11 years of daily global observations at 10 × 10 km <inf>2</inf>resolution from the MODIS on the NASA Terra satellite to quantify τ as a function of cloud fraction (CF). Our analysis reveals that, averaged over the globe, the clear sky τ is enhanced by δ τ = 0.05 in cloudy conditions (CF = 0.8-0.9). This enhancement in δ τ corresponds to relative enhancement of 25% in cloudy conditions (CF = 0.8-0.9) compared with relatively clear conditions (CF = 0.1-0.2). Unlike the absolute enhancement δ τ the relative increase in τ is rather consistent in all seasons and is 25-35% in the subtropics and 15-25% at mid and higher latitudes. Using a simple Gaussian probability density function model to connect cloud cover and the distribution of relative humidity, we argue that much of the enhancement is consistent with aerosol hygroscopic growth in the humid environment surrounding clouds. Consideration of these cloud-dependent τ effects will facilitate understanding aerosol-cloud interactions and reduce the uncertainty in estimates of aerosol radiative forcing by global climate models. © 2012. American Geophysical Union. All Rights Reserved."
"55359948400;16308514000;6602974799;7004885872;7003591311;55438848700;7004176333;7003710822;7101846027;","Aerosol and gas re-distribution by shallow cumulus clouds: An investigation using airborne measurements",2012,"10.1029/2012JD018089","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866309628&doi=10.1029%2f2012JD018089&partnerID=40&md5=905d537eda30755acf8b9397f0a35c79","Aircraft measurements during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) are used to examine the influence of shallow cumulus clouds on vertical profiles of aerosol chemical composition, size distributions, and secondary aerosol precursor gases. The data show signatures of convective transport of particles, gases and moisture from near the surface to higher altitudes, and of aqueous-phase production of aerosol mass (sulfate and organics) in cloud droplets and aerosol water. In cloudy conditions, the average aerosol volume concentration at an altitude of 2850 m, above typical cloud top levels, was found to be 34% of that at 450 m; for clear conditions, the same ratio was 13%. Both organic and sulfate mass fractions were on average constant with altitude (around 50%); however, the ratio of oxalate to organic mass increased with altitude (from 1% at 450 m to almost 9% at 3450 m), indicative of the influence of in-cloud production on the vertical abundance and characteristics of secondary organic aerosol (SOA) mass. A new metric termed ""residual cloud fraction"" is introduced as a way of quantifying the ""cloud processing history"" of an air parcel. Results of a parcel model simulating aqueous phase production of sulfate and organics reproduce observed trends and point at a potentially important role of SOA production, especially oligomers, in deliquesced aerosols. The observations emphasize the importance of shallow cumulus clouds in altering the vertical distribution of aerosol properties that influence both their direct and indirect effect on climate. © 2012. American Geophysical Union. All Rights Reserved."
"6701832491;55510446800;7004333708;36648197400;6701915334;9038337500;6508213402;7202240406;","Evaluation of atmospheric boundary layer-surface process relationships in a regional climate model along an East Antarctic traverse",2012,"10.1029/2011JD016441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861179775&doi=10.1029%2f2011JD016441&partnerID=40&md5=3483077bdee0ea7fb740ab7a9adfc12d","Some primary physical relationships related to the surface climate and atmospheric boundary layer were examined over East Antarctica and evaluated in the regional climate model HIRHAM for 2005-2008. For stable conditions, the observation-derived relationship between wind-scaled sensible heat flux and air-surface temperature difference distinctively differs between different surface flux parameterizations. Some of them decrease the heat transfer coefficient C<inf>H</inf> for strongly stable conditions, while others, such as the Louis scheme, do not. However, HIRHAM's application of the Louis parameterization produces small C<inf>H</inf> for strongly stable conditions similar to observations and other schemes, likely because a surface roughness much larger than observed is used and the bulk Richardson number differs. For Zhongshan, the observed radiation-cloud, temperature-cloud, and temperature-wind relationships are reproduced in the model, though quantitative differences are evident. An observed longwave warming effect of clouds is larger in the model, while the reduction of downwelling shortwave radiation by clouds is twice as large in the model. The model partially reproduces an observed weak wind regime associated with atmospheric decoupling, but fails to reproduce increasing temperatures with increasing winds. The quantitative differences in the radiation-cloud relationship suggest that errors in cloud characteristics produce a significant deficiency in downwelling net radiation for clear and cloudy conditions. This deficiency is the likely cause of HIRHAM's strong cold bias in the surface temperature and positive bias in near-surface stability. The sensible heat flux analyses and a sensitivity test suggest that errors in the sensible heat flux relationship are not the primary cause. Copyright 2012 by the American Geophysical Union."
"36538539800;7004046707;55462884000;7006461606;7004713805;6701378450;38762392200;55915206300;","Development and initial application of the global-through-urban weather research and forecasting model with chemistry (GU-WRF/Chem)",2012,"10.1029/2012JD017966","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868651483&doi=10.1029%2f2012JD017966&partnerID=40&md5=52f000948e0430a36b4ec03d042712fd","A unified model framework with online-coupled meteorology and chemistry and consistent model treatments across spatial scales is required to realistically simulate chemistry-aerosol-cloud-radiation-precipitation-climate interactions. In this work, a global-through-urban WRF/Chem model (i.e., GU-WRF/Chem) has been developed to provide such a unified model framework to simulate these important interactions across a wide range of spatial scales while reducing uncertainties from the use of offline-coupled model systems with inconsistent model treatments. Evaluation against available observations shows that GU-WRF/Chem is capable of reproducing observations with comparable or superior fidelity than existing mesoscale models. The net effect of atmospheric aerosols is to decrease shortwave and longwave radiation, NO<inf>2</inf> photolysis rate, near-surface temperature, wind speed at 10-m, planetary boundary layer height, and precipitation as well as to increase relative humidity at 2-m, aerosol optical depths, column cloud condensation nuclei, cloud optical thickness, and cloud droplet number concentrations at all scales. As expected, such feedbacks also change the abundance and lifetimes of chemical species through changing radiation, atmospheric stability, and the rates of many meteorologically- dependent chemical and microphysical processes. The use of higher resolutions in progressively nested domains from the global to local scale notably improves the model performance of some model predictions (especially for chemical predictions) and also captures spatial variability of aerosol feedbacks that cannot be simulated at a coarser grid resolution. Simulated aerosol, radiation, and cloud properties exhibit small-to-high sensitivity to various nucleation and aerosol activation parameterizations. Representing one of the few unified global-through-urban models, GU-WRF/Chem can be applied to simulate air quality and its interactions with meteorology and climate and to quantify the impact of global change on urban/regional air quality across various spatial scales. © 2012. American Geophysical Union. All Rights Reserved."
"55184057600;7102604282;","Global model comparison of heterogeneous ice nucleation parameterizations in mixed phase clouds",2012,"10.1029/2011JD016506","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859707920&doi=10.1029%2f2011JD016506&partnerID=40&md5=8aa43b44c915dea31ead1dbd660e925a","A new aerosol-dependent mixed phase cloud parameterization for deposition/condensation/immersion (DCI) ice nucleation and one for contact freezing are compared to the original formulations in a coupled general circulation model and aerosol transport model. The present-day cloud liquid and ice water fields and cloud radiative forcing are analyzed and compared to observations. The new DCI freezing parameterization changes the spatial distribution of the cloud water field. Significant changes are found in the cloud ice water fraction and in the middle cloud fractions. The new DCI freezing parameterization predicts less ice water path (IWP) than the original formulation, especially in the Southern Hemisphere. The smaller IWP leads to a less efficient Bergeron-Findeisen process resulting in a larger liquid water path, shortwave cloud forcing, and longwave cloud forcing. It is found that contact freezing parameterizations have a greater impact on the cloud water field and radiative forcing than the two DCI freezing parameterizations that we compared. The net solar flux at top of atmosphere and net longwave flux at the top of the atmosphere change by up to 8.73 and 3.52 W m-2, respectively, due to the use of different DCI and contact freezing parameterizations in mixed phase clouds. The total climate forcing from anthropogenic black carbon/organic matter in mixed phase clouds is estimated to be 0.16-0.93 W m-2 using the aerosol-dependent parameterizations. A sensitivity test with contact ice nuclei concentration in the original parameterization fit to that recommended by Young (1974) gives results that are closer to the new contact freezing parameterization."
"7402677913;24477694300;55705948900;7006212411;57208462871;7103206141;7201665727;7006306835;8147766700;","Inferring ice formation processes from global-scale black carbon profiles observed in the remote atmosphere and model simulations",2012,"10.1029/2012JD018126","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871390106&doi=10.1029%2f2012JD018126&partnerID=40&md5=c0f380b323abc1e263584158f9f3e196","Black carbon (BC) aerosol absorbs solar radiation and can act as cloud condensation nucleus and ice formation nucleus. The current generation of climate models have difficulty in accurately predicting global-scale BC concentrations. Previously, an ensemble of such models was compared to measurements, revealing model biases in the tropical troposphere and in the polar troposphere. Here global aerosol distributions are simulated using different parameterizations of wet removal, and model results are compared to BC profiles observed in the remote atmosphere to explore the possible sources of these biases. The model-data comparison suggests a slow removal of BC aerosol during transport to the Arctic in winter and spring, because ice crystal growth causes evaporation of liquid cloud via the Bergeron process and, hence, release of BC aerosol back to ambient air. By contrast, more efficient model wet removal is needed in the cold upper troposphere over the tropical Pacific. Parcel model simulations with detailed droplet and ice nucleation and growth processes suggest that ice formation in this region may be suppressed due to a lack of ice nuclei (mainly insoluble dust particles) in the remote atmosphere, allowing liquid and mixed-phase clouds to persist under freezing temperatures, and forming liquid precipitation capable of removing aerosol incorporated in cloud water. Falling ice crystals can scavenge droplets in lower clouds, which also results in efficient removal of cloud condensation nuclei. The combination of models with global-scale BC measurements in this study has provided new, latitude-dependent information on ice formation processes in the atmosphere, and highlights the importance of a consistent treatment of aerosol and moist physics in climate models. © 2012. American Geophysical Union. All Rights Reserved."
"7403564495;7401936984;7402064802;6701754792;7003663305;7005877775;7006303509;55235544700;26643615000;15065375800;7102128820;17135286400;57198616562;35494005000;18936046300;7006146719;7402934750;7410041005;","Toward understanding of differences in current cloud retrievals of ARM ground-based measurements",2012,"10.1029/2011JD016792","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861169645&doi=10.1029%2f2011JD016792&partnerID=40&md5=7389bd57c8f4b4d594b28fa27fad15ff","Accurate observations of cloud microphysical properties are needed for evaluating and improving the representation of cloud processes in climate models and better estimate of the Earth radiative budget. However, large differences are found in current cloud products retrieved from ground-based remote sensing measurements using various retrieval algorithms. Understanding the differences is an important step to address uncertainties in the cloud retrievals. In this study, an in-depth analysis of nine existing ground-based cloud retrievals using ARM remote sensing measurements is carried out. We place emphasis on boundary layer overcast clouds and high level ice clouds, which are the focus of many current retrieval development efforts due to their radiative importance and relatively simple structure. Large systematic discrepancies in cloud microphysical properties are found in these two types of clouds among the nine cloud retrieval products, particularly for the cloud liquid and ice particle effective radius. Note that the differences among some retrieval products are even larger than the prescribed uncertainties reported by the retrieval algorithm developers. It is shown that most of these large differences have their roots in the retrieval theoretical bases, assumptions, as well as input and constraint parameters. This study suggests the need to further validate current retrieval theories and assumptions and even the development of new retrieval algorithms with more observations under different cloud regimes. © Copyright 2012 by the American Geophysical Union."
"55235032500;56284543100;","Sensitivity of contrail cirrus radiative forcing to air traffic scheduling",2012,"10.1029/2011JD016736","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861665787&doi=10.1029%2f2011JD016736&partnerID=40&md5=b84bef334ef05f79df79fd2bcd22ca4f","Air traffic effects high cloudiness and therefore the Earth's radiation budget by producing contrail cirrus. Contrail cirrus comprise of line-shaped contrails and irregularly shaped ice clouds that originate from them. The warming effect of contrail cirrus is disproportionally large at night, since at daytime the cooling due to the short wave cloud albedo effect acts toward compensating the long wave warming effect. Therefore it has been suggested to restrict air traffic to daytime in order to reduce its climate impact. The potential for reducing the contrail cirrus radiative forcing by shifting air traffic to daytime depends on the diurnal cycle of contrail cirrus coverage which is in turn determined by the diurnal cycle of air traffic and the contrail cirrus lifetimes. Simulations with a global atmospheric general circulation model indicate that the annual mean contrail cirrus coverage may be almost constant over the day even in areas where air traffic is close to zero at night. A conceptual model describing the temporal evolution of contrail cirrus coverage reveals that this is due to the large variability in contrail cirrus lifetimes in combination with the spreading of contrail cirrus. This large variability of lifetimes is consistent with observational evidence but more observations are needed to constrain the contrail lifetime distribution. An idealized mitigation experiment, shifting nighttime flights to daytime, indicates that contrail cirrus radiative forcing is not significantly changed. © Copyright 2012 by the American Geophysical Union."
"55445972400;56744278700;57208462871;7006306835;7103206141;","Sensitivity of scattering and absorbing aerosol direct radiative forcing to physical climate factors",2012,"10.1029/2012JD018019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868307689&doi=10.1029%2f2012JD018019&partnerID=40&md5=666bc3c1b5d51e37851a719fc166aeb4","The direct radiative forcing of the climate system includes effects due to scattering and absorbing aerosols. This study explores how important physical climate characteristics contribute to the magnitudes of the direct radiative forcings (DRF) from anthropogenic sulfate, black carbon, and organic carbon. For this purpose, we employ the GFDL CM2.1 global climate model, which has reasonable aerosol concentrations and reconstruction of twentieth-century climate change. Sulfate and carbonaceous aerosols constitute the most important anthropogenic aerosol perturbations to the climate system and provide striking contrasts between primarily scattering (sulfate and organic carbon) and primarily absorbing (black carbon) species. The quantitative roles of cloud coverage, surface albedo, and relative humidity in governing the sign and magnitude of all-sky top-of-atmosphere (TOA) forcings are examined. Clouds reduce the global mean sulfate TOA DRF by almost 50%, reduce the global mean organic carbon TOA DRF by more than 30%, and increase the global mean black carbon TOA DRF by almost 80%. Sulfate forcing is increased by over 50% as a result of hygroscopic growth, while high-albedo surfaces are found to have only a minor (less than 10%) impact on all global mean forcings. Although the radiative forcing magnitudes are subject to uncertainties in the state of mixing of the aerosol species, it is clear that fundamental physical climate characteristics play a large role in governing aerosol direct radiative forcing magnitudes. © 2012. American Geophysical Union. All Rights Reserved."
"6602600408;","Evaluating the ""critical relative humidity"" as a measure of subgrid-scale variability of humidity in general circulation model cloud cover parameterizations using satellite data",2012,"10.1029/2012JD017495","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861168119&doi=10.1029%2f2012JD017495&partnerID=40&md5=02bce8e7c7922fe697e9be65e18d5682","A simple way to diagnose fractional cloud cover in general circulation models is to relate it to the simulated relative humidity, and allowing for fractional cloud cover above a ""critical relative humidity"" of less than 100%. In the formulation chosen here, this is equivalent to assuming a uniform ""top-hat"" distribution of subgrid-scale total water content with a variance related to saturation. Critical relative humidity has frequently been treated as a ""tunable"" constant, yet it is an observable. Here, this parameter, and its spatial distribution, is examined from Atmospheric Infrared Sounder (AIRS) satellite retrievals, and from a combination of relative humidity from the ECMWF Re-Analyses (ERA-Interim) and cloud fraction obtained from CALIPSO lidar satellite data. These observational data are used to evaluate results from different simulations with the ECHAM general circulation model (GCM). In sensitivity studies, a cloud feedback parameter is analyzed from simulations applying the original parameter choice, and applying parameter choices guided by the satellite data. Model sensitivity studies applying parameters adjusted to match the observations show larger positive cloud-climate feedbacks, increasing by up to 30% compared to the standard simulation. Copyright 2012 by the American Geophysical Union."
"55214879200;7101959253;7005626683;55843404000;","Identification and analysis of atmospheric states and associated cloud properties for Darwin, Australia",2012,"10.1029/2011JD017010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859141763&doi=10.1029%2f2011JD017010&partnerID=40&md5=a3b940b229655c32024344a464344d32","An iterative automated classification technique that combines European Centre for Medium-Range Weather Forecasts analysis data and vertically pointing millimeter wavelength cloud radar observations is used to identify commonly occurring atmospheric patterns or states around Darwin, Australia. The technique defines the atmospheric states by large-scale, synoptic variables such that, once defined, these states will be suitable to composite climate model output. Radar observations of clouds are used to test the statistical significance of each state and prompt the automated refinement of the states until each state produces a statistically stable and unique hydrometeor occurrence profile. The technique identifies eight atmospheric states: two monsoon states, two transition season states, and four dry season states. The two monsoon states can be identified as the active monsoon and the break monsoon. Among the dry season states, periods of isolated and suppressed convection can be identified. We use these states as the basis for compositing hydrometeor occurrence, precipitation rate, outgoing longwave radiation, and Madden-Julian Oscillation phase to further understand the meteorology of each state. © 2012 by the American Geophysical Union."
"7404829395;56537463000;22959252400;8781752600;57193132723;56203249800;7103271625;7103206141;6603171355;8397494800;25031430500;7003976079;6603809220;15736075100;7404815507;54893098900;7004714030;13405561000;8918407000;55686667100;36161790500;7003532926;56250250300;57192804561;24080737200;35550043200;7202796519;8525144100;36097134700;7202899330;","Evaluation of cloud and water vapor simulations in CMIP5 climate models Using NASA ""A-Train"" satellite observations",2012,"10.1029/2011JD017237","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864607759&doi=10.1029%2f2011JD017237&partnerID=40&md5=4a42882894525a286e75e042b608fa80","[1] Using NASA's A-Train satellite measurements, we evaluate the accuracy of cloud water content (CWC) and water vapor mixing ratio (H<inf>2</inf>O) outputs from 19 climate models submitted to the Phase 5 of Coupled Model Intercomparison Project (CMIP5), and assess improvements relative to their counterparts for the earlier CMIP3. We find more than half of the models show improvements from CMIP3 to CMIP5 in simulating column-integrated cloud amount, while changes in water vapor simulation are insignificant. For the 19 CMIP5 models, the model spreads and their differences from the observations are larger in the upper troposphere (UT) than in the lower or middle troposphere (L/MT). The modeled mean CWCs over tropical oceans range from ∼3% to ∼15× of the observations in the UT and 40% to 2× of the observations in the L/MT. For modeled H<inf>2</inf>Os, the mean values over tropical oceans range from ∼1% to 2× of the observations in the UT and within 10% of the observations in the L/MT. The spatial distributions of clouds at 215 hPa are relatively well-correlated with observations, noticeably better than those for the L/MT clouds. Although both water vapor and clouds are better simulated in the L/MT than in the UT, there is no apparent correlation between the model biases in clouds and water vapor. Numerical scores are used to compare different model performances in regards to spatial mean, variance and distribution of CWC and H<inf>2</inf>O over tropical oceans. Model performances at each pressure level are ranked according to the average of all the relevant scores for that level. © 2012. American Geophysical Union."
"54883743900;6701510679;","Cleaner air brings better views, more sunshine and warmer summer days in the Netherlands",2012,"10.1002/wea.854","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855397442&doi=10.1002%2fwea.854&partnerID=40&md5=abff5ac99570c0b7ee2ce776bb2dacf3","A major clearing of the air has occurred in the Netherlands in the past few decades. These changes are so large that they have become very obvious when looking at the data of individual stations. Strong indications can be found linking human emissions of aerosols to the visibility changes. Coincident with the visibility changes, large trends in cloud cover, sunshine duration and temperature are found, in particular during daytime in summer, showing that these tiny particles might have a significant influence on regional climate. Copyright © 2012 Royal Meteorological Society."
"35206143300;57197432263;","Deformations of frozen droplets formed at-40C",2012,"10.1029/2011GL050185","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855592288&doi=10.1029%2f2011GL050185&partnerID=40&md5=52c43136e628002fc6f59dd4d255fb3e","The optical properties of cirrus clouds are frequently computed with respect to various ice-crystal size distributions and shapes; small ice crystals are generally considered to be quasi-spherical. This approximation can lead to significant errors in the analysis of the in-situ microphysical data and also in the theoretical study of the radiative properties of cirrus clouds. Effective size and aspect ratio of the particles are the key parameters required to determine the optical parameters that are included in modeling and prediction of climate; their parameterizations need to be as accurate as possible. In this work, laboratory experiments were conducted to study the ice crystal shape formed from the freezing of water droplets at-40°C. Liquid and ice clouds were separately formed and sampled in a cloud chamber at-30 and-40°C, respectively. The effective water droplet diameter ranged from 8 to 20 μm, while the effective ice particle diameter ranged from 8 to 30 m. The average effective diameters were 11 μm for water drops and 14 μm for frozen droplets. The deformation of the frozen droplets was evident during inspection under microscope; bulges and spikes protuberances were found in many of the observed ice particles. The results show that the aspect ratio of the frozen droplets is 1.2. Copyright 2012 by the American Geophysical Union."
"23052016900;6506718302;6507755223;26643041500;7007039218;17345303300;6701620591;35459245100;","Direct and indirect effects of sea spray geoengineering and the role of injected particle size",2012,"10.1029/2011JD016428","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856603398&doi=10.1029%2f2011JD016428&partnerID=40&md5=3b20328a824af5e031e15ce31b2c7d91","Climate-aerosol model ECHAM5.5-HAM2 was used to investigate how geoengineering with artificial sea salt emissions would affect marine clouds and the Earth's radiative balance. Prognostic cloud droplet number concentration and interaction of aerosol particles with clouds and radiation were calculated explicitly, thus making this the first time that aerosol direct effects of sea spray geoengineering are considered. When a wind speed dependent baseline geoengineering flux was applied over all oceans (total annual emissions 443.9 Tg), we predicted a radiative flux perturbation (RFP) of -5.1 W m-2, which is enough to counteract warming from doubled CO<inf>2</inf> concentration. When the baseline flux was limited to three persistent stratocumulus regions (3.3% of Earth's surface, total annual emissions 20.6 Tg), the RFP was -0.8 Wm-2 resulting mainly from a 74-80% increase in cloud droplet number concentration and a 2.5-4.4 percentage point increase in cloud cover. Multiplying the baseline mass flux by 5 or reducing the injected particle size from 250 to 100 nm had comparable effects on the geoengineering efficiency with RFPs -2.2 and -2.1 Wm-2, respectively. Within regions characterized with persistent stratocumulus decks, practically all of the radiative effect originated from aerosol indirect effects. However, when all oceanic regions were seeded, the direct effect with the baseline flux was globally about 29% of the total radiative effect. Together with previous studies, our results indicate that there are still large uncertainties associated with the sea spray geoengineering efficiency due to variations in e.g., background aerosol concentration, updraft velocity, cloud altitude and onset of precipitation. Copyright 2012 by the American Geophysical Union."
"22978151200;7201837768;","Aerosol direct, indirect, semidirect, and surface albedo effects from sector contributions based on the IPCC AR5 emissions for preindustrial and present-day conditions",2012,"10.1029/2011JD016816","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856043564&doi=10.1029%2f2011JD016816&partnerID=40&md5=2bbf80686f0742c18d794e0fb79ec67e","The anthropogenic increase in aerosol concentrations since preindustrial times and its net cooling effect on the atmosphere is thought to mask some of the greenhouse gas-induced warming. Although the overall effect of aerosols on solar radiation and clouds is most certainly negative, some individual forcing agents and feedbacks have positive forcing effects. Recent studies have tried to identify some of those positive forcing agents and their individual emission sectors, with the hope that mitigation policies could be developed to target those emitters. Understanding the net effect of multisource emitting sectors and the involved cloud feedbacks is very challenging, and this paper will clarify forcing and feedback effects by separating direct, indirect, semidirect and surface albedo effects due to aerosols. To this end, we apply the Goddard Institute for Space Studies climate model including detailed aerosol microphysics to examine aerosol impacts on climate by isolating single emission sector contributions as given by the Coupled Model Intercomparison Project Phase 5 (CMIP5) emission data sets developed for Intergovernmental Panel on Climate Change (IPCC) AR5. For the modeled past 150 years, using the climate model and emissions from preindustrial times to present-day, the total global annual mean aerosol radiative forcing is -0.6 W/m2, with the largest contribution from the direct effect (-0.5 W/m2). Aerosol-induced changes on cloud cover often depends on cloud type and geographical region. The indirect (includes only the cloud albedo effect with -0.17 W/m2) and semidirect effects (-0.10 W/m2) can be isolated on a regional scale, and they often have opposing forcing effects, leading to overall small forcing effects on a global scale. Although the surface albedo effects from aerosols are small (0.016 W/m2), triggered feedbacks on top of the atmosphere (TOA) radiative forcing can be 10 times larger. Our results point out that each emission sector has varying impacts by geographical region. For example, the single sector most responsible for a net positive radiative forcing is the transportation sector in the United States, agricultural burning and transportation in Europe, and the domestic emission sector in Asia. These sectors are attractive mitigation targets. Copyright 2012 by the American Geophysical Union."
"7403180902;7005070958;6603546080;","Interpretation of cloud structure anomalies over the tropical Pacific during the 1997/98 El Niño",2012,"10.1029/2011JD015861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865846965&doi=10.1029%2f2011JD015861&partnerID=40&md5=5954090b6c609babb75ea14261019599","Cloud structure changes and their associated radiative property changes over the tropical Pacific Ocean during the strong 1997/98 El Niño are studied using a merged satellite data set from the Clouds and the Earth's Radiant Energy System (CERES) project. This one-degree by one-degree gridded data set provides monthly mean values of radiative fluxes at the top of the atmosphere in addition to cloud fraction, cloud top altitude and cloud optical depth for the first eight months of 1998. This time period includes much of the 1997/98 El Niño, which reached peak intensity in March 1998 and essentially subsided by August 1998. The west-to-east shift of the center of convection that occurred during the El Niño resulted in cloud fraction, cloud top altitude and cloud optical depth increasing in the eastern equatorial Pacific while decreasing in the western tropical Pacific. For both regions all three cloud parameters are strongly correlated with each other and contribute to the strong linear relationship between longwave (LW) and shortwave (SW) cloud-radiative forcings (CRFs). This strong El Niño serves as a suitable test case for climate models. Results using the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM) 4.0 show many of the observed changes in 500 hPa vertical velocity, cloud-radiative forcing, cloud top altitude and cloud fraction within the tropical Pacific during the El Niño event, but fail to capture the observed relationship between radiation anomalies and cloud optical depth anomalies. © 2012. American Geophysical Union. All Rights Reserved."
"57204041349;7203047936;","Assessments of cloud liquid water contributions to GPS radio occultation refractivity using measurements from COSMIC and CloudSat",2012,"10.1029/2011JD016452","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859454664&doi=10.1029%2f2011JD016452&partnerID=40&md5=3155ecfb4f1c200d0d4ac411e838f6ed","Global cloud parameters including cloud liquid water, cloud base height, cloud top height, and cloud type are observed from the cloud profiling radar onboard CloudSat. Global Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) data during a 3 year period from 2007 to 2009 are collocated in space and time with CloudSat data. The collocated data set is then classified into seven groups: one clear-sky condition and six different cloud types with liquid water content (LWC) measurements. For each group, atmospheric refractivity, temperature, and water vapor derived from COSMIC GPS ROs are compared with those of the European Centre for Medium-Range Weather Forecasts (ECMWF) analyses. It is found that the COSMIC GPS RO refractivity observations are systematically greater than the refractivity calculated from ECMWF analyses, which is to be referred as a positive N bias in clouds. The fractional N bias is as high as 1.2% depending on cloud types. Using CloudSat LWC, it is demonstrated that LWC can contribute 0.8% of the total refractivity by individual clouds and 0.16% of the positive N bias. The 0.16% positive N bias is comparable in magnitude to the retrieval uncertainty quantified by the mean difference (ΔN<inf>O-R</inf>) between the observed refractivity with LWC contribution subtracted and the refractivity calculated using GPS retrieved profiles of temperature, pressure, and humidity. The values of ΔN<inf>O-R</inf> increase linearly with LWC as anticipated theoretically. Positive N biases are spatially correlated with positive water vapor biases, negative temperature biases, and large liquid water contents. © 2012 by the American Geophysical Union."
"7403625607;55102805100;7006495234;35779178900;","Correlation between SCIAMACHY, MODIS, and CERES reflectance measurements: Implications for CLARREO",2012,"10.1029/2011JD017051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858427896&doi=10.1029%2f2011JD017051&partnerID=40&md5=709f2b0f4c8110f4838e15fd572f3621","We have analyzed the correlation between measurements by three different satellite sensors (SCIAMACHY, MODIS, and CERES) on two independent space platforms (Envisat and Terra). Though the instantaneous measurements from the two satellites are not collocated due to orbit offset, the monthly mean broadband and narrowband reflectances and their anomalies from the three instruments are highly correlated when averaged over large latitude regions. The mean reflectance from MODIS in each of those large domains is nearly the same as that derived from SCIAMACHY spectrum convolved with the filter function of the corresponding MODIS channel, with all correlation coefficients higher than 0.93. The interannual variability of monthly mean reflectance is also correlated with the variations of mean cloud and surface properties in large climate zones. The reflectance variation is correlated with the cloud fraction in low and middle latitude regions with correlation coefficients higher than 0.76 and with the snow and sea ice changes in the polar regions with correlation coefficients higher than 0.6. These correlations indicate that the nadir sampling strategy as proposed for CLARREO is sufficient for climate benchmarking of the reflected solar spectrum and provide the physical foundation for climate fingerprinting. However, the results also show the relatively large differences in trends in reflectance due to different instrument degradations and inconsistent calibrations which will affect the attribution of radiative signals of long-term climate change. Copyright 2012 by the American Geophysical Union."
"6603779272;18437230800;57203052274;7006550762;","Regional warming from aerosol removal over the United States: Results from a transient 2010-2050 climate simulation",2012,"10.1016/j.atmosenv.2011.07.030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82955233087&doi=10.1016%2fj.atmosenv.2011.07.030&partnerID=40&md5=4ee4b3009aa7e5b7024199f14b89cbd0","We use a general circulation model (NASA Goddard Institute for Space Studies GCM 3) to investigate the regional climate response to removal of aerosols over the United States. We perform a pair of transient 2010-2050 climate simulations following a scenario of increasing greenhouse gas concentrations, with and without aerosols over the United States and with present-day aerosols elsewhere. We find that removing U.S. aerosol significantly enhances the warming from greenhouse gases in a spatial pattern that strongly correlates with that of the aerosol. Warming is nearly negligible outside the United States, but annual mean surface temperatures increase by 0.4-0.6 K in the eastern United States. Temperatures during summer heat waves in the Northeast rise by as much as 1-2 K due to aerosol removal, driven in part by positive feedbacks involving soil moisture and low cloud cover. Reducing U.S. aerosol sources to achieve air quality objectives could thus have significant unintended regional warming consequences. © 2011 Elsevier Ltd."
"55519994900;23991212200;7003666669;56162305900;55411439700;7202252296;","Constraining the influence of natural variability to improve estimates of global aerosol indirect effects in a nudged version of the Community Atmosphere Model 5",2012,"10.1029/2012JD018588","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870917592&doi=10.1029%2f2012JD018588&partnerID=40&md5=aca35edc6a9188042f750b53d13c5f17","Natural modes of variability on many timescales influence aerosol particle distributions and cloud properties such that isolating statistically significant differences in cloud radiative forcing due to anthropogenic aerosol perturbations (indirect effects) typically requires integrating over long simulations. For state-of-the-art global climate models (GCM), especially those in which embedded cloud-resolving models replace conventional statistical parameterizations (i.e., multiscale modeling framework, MMF), the required long integrations can be prohibitively expensive. Here an alternative approach is explored, which implements Newtonian relaxation (nudging) to constrain simulations with both pre-industrial and present-day aerosol emissions toward identical meteorological conditions, thus reducing differences in natural variability and dampening feedback responses in order to isolate radiative forcing. Ten-year GCM simulations with nudging provide a more stable estimate of the global-annual mean net aerosol indirect radiative forcing than do conventional free-running simulations. The estimates have mean values and 95% confidence intervals of -1.19 0.02 W/m2 and -1.37 0.13 W/m 2 for nudged and free-running simulations, respectively. Nudging also substantially increases the fraction of the world's area in which a statistically significant aerosol indirect effect can be detected (66% and 28% of the Earth's surface for nudged and free-running simulations, respectively). One-year MMF simulations with and without nudging provide global-annual mean net aerosol indirect radiative forcing estimates of -0.81 W/m2 and -0.82 W/m2, respectively. These results compare well with previous estimates from three-year free-running MMF simulations (-0.83 W/m2), which showed the aerosol-cloud relationship to be in better agreement with observations and high-resolution models than in the results obtained with conventional cloud parameterizations. © 2012. American Geophysical Union. All Rights Reserved."
"57203200427;24074350700;57202411660;6602692238;56726831200;25030776200;7003976079;7202391479;7403119519;","Reversibility in an Earth System model in response to CO2 concentration changes",2012,"10.1088/1748-9326/7/2/024013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860871234&doi=10.1088%2f1748-9326%2f7%2f2%2f024013&partnerID=40&md5=2b5e1c7b2f54ba6fdccd5f699ce39137","We use the HadGEM2-ES Earth System model to examine the degree of reversibility of a wide range of components of the Earth System under idealized climate change scenarios where the atmospheric CO2 concentration is gradually increased to four times the pre-industrial level and then reduced at a similar rate from several points along this trajectory. While some modelled quantities respond almost immediately to the atmospheric CO2 concentrations, others exhibit a time lag relative to the change in CO 2. Most quantities also exhibit a lag relative to the global-mean surface temperature change, which can be described as a hysteresis behaviour. The most surprising responses are from low-level clouds and ocean stratification in the Southern Ocean, which both exhibit hysteresis on timescales longer than expected. We see no evidence of critical thresholds in these simulations, although some of the hysteresis phenomena become more apparent above 2×CO2 or 3×CO2. Our findings have implications for the parametrization of climate impacts in integrated assessment and simple climate models and for future climate studies of geoengineering scenarios. © 2012 IOP Publishing Ltd."
"57204886915;7203062717;","A bulk mass flux convection scheme for climate model: Description and moisture sensitivity",2012,"10.1007/s00382-010-0972-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855254358&doi=10.1007%2fs00382-010-0972-2&partnerID=40&md5=1bbd244272574e069effef4d4baac0ad","A convection scheme for climate model is developed based on Tiedtke's (Mon Weather Rev 117:1779-1800, 1989) bulk mass flux framework and is evaluated with observational data and cloud resolving model simulation data. The main differences between the present parameterization and Tiedtke's parameterization are the convection trigger, fractional entrainment and detrainment rate formulations, and closure method. Convection is triggered if the vertical velocity of a rising parcel is positive at the level at which the parcel is saturated. The fractional entrainment rate depends on the vertical velocity and buoyancy of the parcel as well as the environmental relative humidity. For the fractional detrainment rate, a linear decrease in the updraft mass flux above maximum buoyancy level is assumed. In the closure method, the cloud base mass flux is determined by considering both cloud layer instability and subcloud layer turbulent kinetic energy as controlling factors in the strength of the convection. The convection scheme is examined in a single column framework as well as using a general circulation model. The present bulk mass flux (BMF) scheme is compared with a simplified Relaxed Arakawa-Schubert (RAS) scheme. In contrast to the RAS, which specifies the cloud top, cloud top height in BMF depends on environmental properties, by considering the conditions of both the parcel and its environment in a fractional entrainment and detrainment rate formulations. As a result, BMF shows improved sensitivity in depth and strength of convection on environmental humidity compared to RAS, by strengthening coupling between cloud and environment. When the mid to lower troposphere is dry, the cloud resolving model and BMF produce cloud top around the dry layer and moisten the layer. In the framework of general circulation model, enhanced coupling between convection and environmental humidity in BMF results in improved representation of eastward propagating intraseasonal variability in the tropics-the Madden-Julian oscillation. © 2011 Springer-Verlag."
"55078244200;6701490531;7004154626;55077297800;35361704100;36006968000;","Aerosol and cloud feedbacks on surface energy balance over selected regions of the Indian subcontinent",2012,"10.1029/2011JD016363","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858057927&doi=10.1029%2f2011JD016363&partnerID=40&md5=728239fe4cda2022620ced7d57bda538","We investigate aerosol and cloud forcing on the surface energy balance over selected regions in India. Four regions were selected with different surface characteristics and have considerable differences in the long-term trends and seasonal distribution of clouds and aerosols. These regions are described as (1) northern semiarid, (2) humid subtropical, (3) populated central peninsula, and (4) northeast monsoon impacted. Modern Era Retrospective-analysis for Research and Applications (MERRA) data and Climate Forecast System Reanalysis version 2 (CFSR) data are used in this study. An intercomparison of cloud fractions from both data sets shows that CFSR systematically underestimates high-cloud fraction during premonsoon and monsoon seasons. However, there are fewer low-cloud fraction biases. The positive temporal trend over 31years (1979-2009) from MERRA in high clouds is greater than that of low clouds. This is due to positive anomalies in the cloud ice and supercooled liquid water content in MERRA. Biases in the radiative fluxes and surface fluxes show a strong relationship (correlations exceeding 0.8) with cloud fraction biases, more so for the high clouds. During the premonsoon season, aerosol forcing causes a change in surface shortwave radiation of -24.5, -25, -19, and -16Wm-2 over regions 1 -4, respectively. The corresponding longwave radiation decrease is -9.8, -6.8, -4.5, and -1.9Wm-2 over these same regions, respectively. The maximum surface shortwave reduction due to clouds, which is observed during the monsoon season, is -86, -113, -101, and -97Wm-2 for these same regions, respectively. A decreasing trend in the boundary layer height is noticed both in MERRA and CFSR. The variation in the Bowen ratio and its relation to aerosol and cloud effect anomalies are also discussed. Copyright 2012 by the American Geophysical Union."
"21740424900;57191966165;57203683180;21740203800;35184308500;7003673491;55035613600;26655776500;55992194500;55005053100;55260975200;","Decreasing trend of sunshine hours and related driving forces in Southwestern China",2012,"10.1007/s00704-012-0583-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862806933&doi=10.1007%2fs00704-012-0583-4&partnerID=40&md5=641864921762f9448c03fa869bf883d5","Total hours of sunshine are one of the most important factors affecting climate and environment, and its long-term variation is of much concern in climate studies. Trends of temporal and spatial patterns in sunshine hours and related climatic factors over southwestern China are evaluated for the period 1961-2009 based on data from 111 standard meteorological stations. The results showed that southwestern China is experiencing a statistical decrease of sunshine hours, at the rate of 31.9 h/10a during 1961-2009. The decline was particularly strong in summer, whereas it is nonsignificant in winter. Spatially, statistically significant decreases of sunshine hours mainly occurred in lower altitude regions, especially in the Sichuan basin and Guizhou plateau. Sunshine hours have a high correlation with wind speed, relative humidity, precipitation, cloud cover, surface downwards solar radiation flux, and cloud water content, with wind speed showing the strongest relationship to sunshine hours, implicit in the close correlation (temporally and spatially) between the two variables. Changing water vapor and cloud cover influence sunshine hours in southwestern China. In addition, the increased surface downwards solar radiation flux also made some contribution to a rise of sunshine hours during 1991-2009. The larger decreasing trends of sunshine hours at urban stations than rural stations may reflect the effect of urbanization on sunshine hours. Variations are dominated by the comprehensive functions of multiple factors owing to the complex nature of effects on sunshine hours. © 2012 Springer-Verlag."
"55456370300;9246517900;7402346120;7102223565;6701323933;7006689276;","A multi-sensor climatological view of double ITCZs over the Indian Ocean",2012,"10.1080/01431161.2011.625056","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857946790&doi=10.1080%2f01431161.2011.625056&partnerID=40&md5=88545897af1c6e5f014b83ed64cab99a","We characterize the climatological features of the double inter-tropical convergence zones (DITCZs) over the western Indian Ocean during November-December by a synergistic analysis of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite (HOAPS III) data (1988-2005) and the National Aeronautics and Space Administration's (NASA's) A-Train data (2002-2009). We investigate rainfall, freshwater flux and cloud liquid water, cloud fraction and relative humidity over the DITCZs. In addition, the daily rainfall data from the Global Precipitation Climatology Project (GPCP) are used to document the DITCZs during the El Niño southern oscillation (ENSO) events. An analysis of the GPCP data shows that the DITCZs are clearly discernible during strong ENSO events (1997, 2002 and 2006), in sharp contrast to the DITCZs in the eastern Pacific Ocean, where they are absent during ENSOs. Further, these convergence zones on either side of the equator are of short duration, approximately 3-6 pentads during November and December. All satellite sensor data sets consistently capture the major features of DITCZs. As an accurate simulation of DITCZs in coupled global climate models remains a challenge, the results from the present study would provide a platform for evaluating these models. © 2012 Taylor and Francis Group, LLC."
"24401083300;7103213900;7005899086;7005742394;","Turbulent effects on the microphysics and initiation of warm rain in deep convective clouds: 2-D simulations by a spectral mixed-phase microphysics cloud model",2012,"10.1029/2011JD016603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859448574&doi=10.1029%2f2011JD016603&partnerID=40&md5=a928aa77a50b9749ee3d960c9d67bb1d","The spectral bin microphysics Hebrew University cloud model with the spatial resolution of 50 × 50 m is used to simulate the evolution of isolated deep mixed phase convective clouds under different meteorological conditions and at different aerosol concentrations. The model takes into account the effects of turbulence on droplet collision rate. Turbulent collision kernels are calculated at each time step and at each grid point. The turbulence-induced collision rate enhancement is determined by means of lookup tables calculated in the recent studies for different values of turbulent dissipation rate and the Taylor microscale Reynolds numbers. Deep convective clouds observed during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Smoke, Aerosols, Clouds, Rainfall and Climate campaign in the Amazon region are simulated at different aerosol concentrations. Turbulence intensity in the simulated clouds is spatially inhomogeneous and reaches its maximum at the tops of multiple bubbles forming the clouds. It is shown that polluted clouds are more turbulent than those developing in the clean atmosphere. An agreement of the calculated droplet size distributions with those measured in situ is demonstrated. It is shown that turbulence accelerates formation of raindrops, especially in polluted clouds. At the same time, turbulence-induced collision enhancement lessens the amount of ice and leads to a decrease in the net accumulated rain from mixed-phase clouds. To a certain degree the effects of turbulence on precipitation counteract the aerosol effects. Since no turbulence effects on collisions of drops larger than 22 m in radius as well as on drop ice and ice collisions are considered in this study, and taking into account that a 2-D model geometry is used, the results of the study should be considered as preliminary. Additional numerical and theoretical investigations are required to quantify the turbulent effects. © 2012 by the American Geophysical Union."
"12801073500;6603581315;55708686800;9233141100;7004168515;56102017200;9250463400;7202489497;35372923700;57214536094;35509639400;57196135849;56813351300;7003339749;","Process-evaluation of tropospheric humidity simulated by general circulation models using water vapor isotopic observations: 2. Using isotopic diagnostics to understand the mid and upper tropospheric moist bias in the tropics and subtropics",2012,"10.1029/2011JD016623","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863246372&doi=10.1029%2f2011JD016623&partnerID=40&md5=3c588eb1387b3c9c481f767f2a274e2b","Evaluating the representation of processes controlling tropical and subtropical tropospheric relative humidity (RH) in atmospheric general circulation models (GCMs) is crucial to assess the credibility of predicted climate changes. GCMs have long exhibited a moist bias in the tropical and subtropical mid and upper troposphere, which could be due to the mis-representation of cloud processes or of the large-scale circulation, or to excessive diffusion during water vapor transport. The goal of this study is to use observations of the water vapor isotopic ratio to understand the cause of this bias. We compare the three-dimensional distribution of the water vapor isotopic ratio measured from space and ground to that simulated by several versions of the isotopic GCM LMDZ. We show that the combined evaluation of RH and of the water vapor isotopic composition makes it possible to discriminate the most likely cause of RH biases. Models characterized either by an excessive vertical diffusion, an excessive convective detrainment or an underestimated in situ cloud condensation will all produce a moist bias in the free troposphere. However, only an excessive vertical diffusion can lead to a reversed seasonality of the free tropospheric isotopic composition in the subtropics compared to observations. Comparing seven isotopic GCMs suggests that the moist bias found in many GCMs in the mid and upper troposphere most frequently results from an excessive diffusion during vertical water vapor transport. This study demonstrates the added value of water vapor isotopic measurements for interpreting shortcomings in the simulation of RH by climate models. Copyright 2012 by the American Geophysical Union."
"35221791100;35422119400;7003959903;55887849100;","Examining a solar-climate link in diurnal temperature ranges",2012,"10.1029/2012JD017683","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867021892&doi=10.1029%2f2012JD017683&partnerID=40&md5=2ab5ebbe46c7e7c28c4772a31c070834","A recent study has suggested a link between the surface level diurnal temperature range (DTR) and variations in the cosmic ray (CR) flux. As the DTR is an effective proxy for cloud cover, this result supports the notion that widespread cloud changes may be induced by the CR flux. If confirmed, this would have significant implications for our understanding of natural climate forcings. Here, we perform a detailed investigation of the relationships between DTR and solar activity (total solar irradiance and the CR flux) from more than 60 years of NCEP/NCAR reanalysis data and observations from meteorological station data. We find no statistically significant evidence to suggest that the DTR is connected to either long-term solar periodicities (11 or 1.68-year) or short-term (daily timescale) fluctuations in solar activity, and we attribute previous reports on the contrary to an incorrect estimation of the statistical significance of the data. If a CR-DTR relationship exists, based on the estimated noise in DTR composites during Forbush decrease (FD) events, the DTR response would need to be larger than 0.03°C per 1% increase in the CR flux to be reliably detected. Compared with a much smaller rough estimate of - 0.005°C per 1% increase in the CR flux expected if previous claims that FD events cause reductions in the cloud cover are valid, we conclude it is not possible to detect a solar related responses in station-based or reanalysis-based DTR data sets related to a hypothesized CR-cloud link, as potential signals would be drowned in noise. © 2012. American Geophysical Union."
"49261186800;35612904200;16029719200;7004299063;7101832608;","Climatic impact of the long-lasting 1783 Laki eruption: Inapplicability of mass-independent sulfur isotopic composition measurements",2012,"10.1029/2012JD018414","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871370802&doi=10.1029%2f2012JD018414&partnerID=40&md5=66385c585812daf4f2de33ec7007a7a3","The long-lasting 1783-1784 CE Laki flood lava eruption in Iceland released around 120 Tg of sulfur dioxide into the upper troposphere/lower stratosphere. Northern Hemisphere temperature proxy records of the 1780s indicate below-average temperatures for up to three years following the eruption. The very warm summer of 1783 in Europe, which was followed by a very cold winter, may have been caused by the eruption, but the mechanisms are not yet well understood. Some studies attributed the cold winter 1783-1784 to natural variability of climate. However, our climate model simulations show that the Laki radiative effects lasted long enough to contribute to the winter cooling. We suggest that sulfur isotopic composition measurements obtained using samples from Greenland ice cores do not provide evidence of either a short-lived volcanic aerosol cloud or a short-lived climatic impact of the Laki eruption. In fact, the applicability of mass-independent sulfur isotopic composition measurements for interpreting the climatic impact of any high-latitude eruption remains yet to be demonstrated. © 2012. American Geophysical Union. All Rights Reserved."
"7005920812;23393856300;56162305900;55405340400;7003666669;","PDF parameterization of boundary layer clouds in models with horizontal grid spacings from 2 to 16 km",2012,"10.1175/MWR-D-10-05059.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862947106&doi=10.1175%2fMWR-D-10-05059.1&partnerID=40&md5=5e676784eb38a9e506da151491f9fd3a","Many present-day numerical weather prediction (NWP) models are run at resolutions that permit deep convection. In these models, however, the boundary layer turbulence and boundary layer cloud features are still grossly underresolved. Underresolution is also present in climate models that use a multiscale modeling framework (MMF), in which a convection-permitting model is run in each grid column of a global general circulation model. To better represent boundary layer clouds and turbulence in convection-permitting models, a parameterization was developed that models the joint probability density function (PDF) of vertical velocity, heat, and moisture. Although PDF-based parameterizations are more complex and computationally expensive than many other parameterizations, in principle PDF parameterizations have several advantages. For instance, they ensure consistency of liquid (cloud) water and cloud fraction; they avoid using separate parameterizations for different cloud types such as cumulus and stratocumulus; and they have an appropriate formulation in the ""terra incognita"" in which updrafts are marginally resolved. In this paper, an implementation of a PDF parameterization is tested to see whether it improves the simulations of a state-of-the-art convection-permitting model. The PDF parameterization used is the Cloud Layers Unified By Binormals (CLUBB) parameterization. The host cloud-resolving model used is the System for Atmospheric Modeling (SAM).SAMis run both with and withoutCLUBBimplemented in it. Simulations of two shallow cumulus (Cu) cases and two shallow stratocumulus (Sc) cases are run in a 3Dconfiguration at 2-, 4-, and 16-km horizontal grid spacings. Including CLUBB in the simulations improves some of the simulated fields-such as vertical velocity variance, horizontal wind fields, cloud water content, and drizzle water content-especially in the two Cu cases. Implementing CLUBB in SAM improves the simulations slightly at 2-km horizontal grid spacing, significantly at 4-km grid spacing, and greatly at 16-km grid spacing. Furthermore, the simulations that include CLUBB exhibit a reduced sensitivity to horizontal grid spacing. © 2012 American Meteorological Society."
"7404297096;12041152300;","Arctic low cloud changes as observed by MISR and CALIOP: Implication for the enhanced autumnal warming and sea ice loss",2012,"10.1029/2011JD017050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859887095&doi=10.1029%2f2011JD017050&partnerID=40&md5=524d6674ebd7e86cbd347a8e890b0641","Retreat of Arctic sea ice extent has led to more evaporation over open water in summer and subsequent cloud changes in autumn. Studying recent satellite cloud data over the Arctic Ocean, we find that low (0.5-2 km) cloud cover in October has been increasing significantly during 2000-2010 over the Beaufort and East Siberian Sea (BESS). This change is consistent with the expected boundary layer cloud response to the increasing Arctic evaporation accumulated during summer. Because low clouds have a net warming effect at the surface, October cloud increases may be responsible for the enhanced autumnal warming in surface air temperature, which effectively prolong the melt season and lead to a positive feedback to Arctic sea ice loss. Thus, the new satellite observations provide a critical support for the hypothesized positive feedback involving interactions between boundary layer cloud, water vapor, temperature, and sea ice in the Arctic Ocean. Copyright 2012 by the American Geophysical Union."
"24173873500;55113736500;7004174939;","Comparing results from a physical model with satellite and in situ observations to determine whether biomass burning aerosols over the Amazon brighten or burn off clouds",2012,"10.1029/2011JD016856","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861402641&doi=10.1029%2f2011JD016856&partnerID=40&md5=513908759f02e8ec3ef5260b6e5cc7f9","Biomass burning (BB) aerosol particles affect clouds through competing microphysical and radiative (semi-direct and cloud absorption) effects, each of which dominates at different degrees of aerosol loading. Here, we analyze the influence of competing aerosol effects on mixed-phase clouds, precipitation, and radiative fields over the Amazon with a climate-air pollution-weather forecast model that treats aerosol-cloud-radiative interactions physically. Extensive comparisons with remotely sensed observations and in situ measurements are performed. Both observations and model results suggest an increase in cloud optical depth (COD) with increasing aerosol optical depth (AOD) at low AODs, and a decrease in COD with increasing AOD at higher AODs in accord with previous observational and modeling studies. The increase is attributed to a combination of microphysical and dynamical effects, whereas the decrease is attributed to a dominance of radiative effects that thin and darken clouds. An analogous relationship is shown for other modeled cloud variables as well. The similarity between the remotely sensed observations and model results suggests that these correlations are physically based and are not dominated by satellite retrieval artifacts. Cloud brightening due to BB is found to dominate in the early morning, whereas cloud inhibition is found to dominate in the afternoon and at night. BB decreased the net top of the atmosphere solar+IR irradiance modestly, but with large diurnal variation. We conclude that models that exclude treatment of aerosol radiative effects are likely to over-predict the microphysical effects of aerosols and underestimate the warming due to aerosols containing black and brown carbon. Copyright 2012 by the American Geophysical Union."
"8734784200;7202226478;7004617224;","How well do we know recent climate trends at the tropical tropopause?",2012,"10.1029/2012JD017444","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861149844&doi=10.1029%2f2012JD017444&partnerID=40&md5=e9650c2243a4356dea04ac12c7e09a0e","The tropical tropopause is a transition layer between the troposphere and stratosphere that influences global climate and atmospheric chemistry. Several studies have reported multidecadal tropical tropopause cooling and have suggested a correlation between observed tropopause temperature and stratospheric water vapor. Our more rigorous examination of the observations shows tropopause trends have greater uncertainty than previously suggested and the cooling may not be statistically significant. We used two approaches to remove time-varying bias effects from cold-point tropopause trends estimated from radiosonde observations. Our results are consistent with expectations from a conceptual model of tropopause changes and could resolve discrepancies between complex climate models and observations. Copyright 2012 by the American Geophysical Union."
"6603250042;36165094300;","The impact of a non-uniform land surface on the radiation environment over an Arctic fjord - A study with a 3D radiative transfer model for stratus clouds over the Hornsund fjord, Spitsbergen",2012,"10.5697/oc.54-4.509","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869803785&doi=10.5697%2foc.54-4.509&partnerID=40&md5=bc563e0c41a7be3b897848adf26722bf","This paper estimates the influence of land topography and cover on 3D radiative effects under overcast skies in the Arctic coastal environment, in particular in the Hornsund fjord region, Spitsbergen. The authors focus on the impact of a non- uniform surface on: (1) the spatial distribution of solar fluxes reaching the fjord surface, (2) spectral shortwave cloud radiative forcing at the fjord surface, (3) the solar flux anomaly at the domain surface resulting from the assumption of a uniform surface, i.e. the error due to plane parallel assumptions in climate models, and (4) remote sensing of cloud optical thickness over the fjord. Their dependence on spectral channel, cloud optical thickness, cloud type, cloud base height, surface albedo and solar zenith angle is discussed. The analysis is based on Monte Carlo simulations of solar radiation transfer over a heterogeneous surface for selected channels of the MODIS radiometer. The simulations showed a considerable impact of the land surrounding the fjord on the solar radiation over the fjord. The biggest differences between atmospheric transmittances over the fjord surface and over the ocean were found for a cloud optical thickness τ=12, low solar zenith angle ν, high cloud base and snow-covered land. For τ =12, ν=53°, cloud base height 1.8 km and wavelength λ =469 nm, the enhancement in irradiance transmittance over the fjord was 0.19 for the inner fjords and 0.10 for the whole fjord (λ =469 nm). The land surrounding the Hornsund fjord also had a considerable impact on the spectral cloud radiative forcing on the fjord surface and the solar flux anomaly at the domain surface due to the uniform surface assumption. For the mouth and central part of the fjord the error due to the use of channel 2 of the MODIS radiometer (λ =858 nm) for cloud optical thickness retrieval was <1 in the case of low-level clouds (cloud base height 1 km, nadir radiance, ν=53°, cloud optical thickness retrieved solely from MODIS channel 2). However, near the shoreline (up to 2 km from it), especially over the inner fjords, the cloud optical thickness was then overestimated by >3 for τ =5 and by >5 for τ =20. © Polish Academy of Sciences, Institute of Oceanology, 2012."
"25649028800;6603800142;6603767711;","The Shannon information content of hyperspectral shortwave cloud albedo measurements: Quantification and practical applications",2012,"10.1029/2011JD016771","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857498774&doi=10.1029%2f2011JD016771&partnerID=40&md5=6813aba1978d7675bc023fd4ccceceec","The Shannon information content provides an objective measure of the information in a data set. In this paper, we quantify the information content of hyperspectral liquid water cloud measurements over a spectral range (300-2500nm) representing approximately 95% of the total energy in the solar spectrum. We also use the Shannon information content to analyze the cloud retrieval wavelengths and weightings used by the Solar Spectral Flux Radiometer (SSFR) and to determine the cumulative information in the SSFR retrieval. These applications illustrate the utility of the Shannon information content in guiding the effective processing of hyperspectral data. Such efficiency is of growing importance considering the push toward spectrally resolved satellite measurements of reflected solar irradiance used to study climate. Copyright 2012 by the American Geophysical Union."
"57212020453;57212027049;57212023802;57212020923;","Evaluating the Performances of GAMIL1.0 and GAMIL2.0 during TWPICE with CAPT",2012,"10.1080/16742834.2012.11446963","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876444871&doi=10.1080%2f16742834.2012.11446963&partnerID=40&md5=d8762113acfbd9893cdfe5bfbf4f784a","CAPT (Climate Change Prediction Program and Atmospheric Radiation Measurement Program (CCPP-ARM) Parameterization Testbed) has been a valuable tool to assess climate models in recent years, and the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) has collected comprehensive measurements to verify its physical parameterizations. The present study evaluates the performances of the two GAMIL (grid-point atmospheric model of IAP LASG) versions during TWP-ICE using CAPT. The results indicate that GAMIL2.0 reproduced better shifts of clouds and rainfall during three distinct monsoon phases than GAMIL1.0, although both of them simulated the large-scale dynamical states well, which are mainly attributable to the different convective parameterizations. © 2012, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"25031430500;55717074000;22933265100;57203053317;57200319057;","Climate impacts of ice nucleation",2012,"10.1029/2012JD017950","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868019284&doi=10.1029%2f2012JD017950&partnerID=40&md5=760e0c7ffad4207d37247e4d286217c6","Several different ice nucleation parameterizations in two different General Circulation Models (GCMs) are used to understand the effects of ice nucleation on the mean climate state, and the Aerosol Indirect Effects (AIE) of cirrus clouds on climate. Simulations have a range of ice microphysical states that are consistent with the spread of observations, but many simulations have higher present-day ice crystal number concentrations than in-situ observations. These different states result from different parameterizations of ice cloud nucleation processes, and feature different balances of homogeneous and heterogeneous nucleation. Black carbon aerosols have a small (-0.06 Wm-2) and not statistically significant AIE when included as ice nuclei, for nucleation efficiencies within the range of laboratory measurements. Indirect effects of anthropogenic aerosols on cirrus clouds occur as a consequence of increasing anthropogenic sulfur emissions with different mechanisms important in different models. In one model this is due to increases in homogeneous nucleation fraction, and in the other due to increases in heterogeneous nucleation with coated dust. The magnitude of the effect is the same however. The resulting ice AIE does not seem strongly dependent on the balance between homogeneous and heterogeneous ice nucleation. Regional effects can reach several Wm -2. Indirect effects are slightly larger for those states with less homogeneous nucleation and lower ice number concentration in the base state. The total ice AIE is estimated at 0.27 ± 0.10 Wm-2 (1σ uncertainty). This represents a 20% offset of the simulated total shortwave AIE for ice and liquid clouds of -1.6 Wm-2. © 2012. American Geophysical Union. All Rights Reserved."
"26645289600;7202145115;","Climate feedbacks and their implications for poleward energy flux changes in a warming climate",2012,"10.1175/JCLI-D-11-00096.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856952465&doi=10.1175%2fJCLI-D-11-00096.1&partnerID=40&md5=015c73c7751d2e17a2df1fd8558e9c5b","Feedbacks determine the efficiency with which the climate system comes back into equilibrium in response to a radiative perturbation. Although feedbacks are integrated quantities, the processes from which they arise have rich spatial structures that alter the distribution of top of atmosphere (TOA) net radiation. Here, the authors investigate the implications of the structure of climate feedbacks for the change in poleward energy transport as the planet warms over the twenty-first century in a suite of GCMs. Using radiative kernels that describe the TOA radiative response to small perturbations in temperature, water vapor, and surface albedo, the change in poleward energy flux is partitioned into the individual feedbacks that cause it. This study finds that latitudinal gradients in the sum of climate feedbacks reinforce the preexisting latitudinal gradient in TOA net radiation, requiring that the climate system transport more energy to the poles on a warming planet. This is primarily due to structure of the water vapor and cloud feedbacks, which are strongly positive at low latitudes and decrease dramatically with increasing latitude. Using the change in surface fluxes, the authors partition the anomalous poleward energy flux between the atmosphere and ocean and find that reduced heat flux from the high-latitude ocean further amplifies the equator-to-pole gradient in atmospheric energy loss. This implied reduction in oceanic poleward energy flux requires the atmosphere to increase its share of the total poleward energy transport. As is the case for climate sensitivity, the largest source of intermodel spread in the change in poleward energy transport can be attributed to the shortwave cloud feedback. © 2012 American Meteorological Society."
"22934904700;57212988186;7401945370;","An assessment of the cloud signals simulated by NICAM using ISCCP, CALIPSO, and CloudSat satellite simulators",2012,"10.1029/2011JD017317","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863434957&doi=10.1029%2f2011JD017317&partnerID=40&md5=2801789914a7daebd41da45de9e8091b","This study presents an assessment of three-dimensional structures of hydrometeors simulated by the NICAM, global nonhydrostatic atmospheric model without cumulus parameterization, using multiple satellite data sets. A satellite simulator package (COSP: the CFMIP Observation Simulator Package) is employed to consistently compare model output with ISCCP, CALIPSO, and CloudSat satellite observations. Special focus is placed on high thin clouds, which are not observable in the conventional ISCCP data set, but can be detected by the CALIPSO observations. For the control run, the NICAM simulation qualitatively captures the geographical distributions of the high, middle, and low clouds, even though the horizontal mesh spacing is as coarse as 14 km. The simulated low cloud is very close to that of the CALIPSO low cloud. Both the CloudSat observations and NICAM simulation show a boomerang-type pattern in the radar reflectivity-height histogram, suggesting that NICAM realistically simulates the deep cloud development process. A striking difference was found in the comparisons of high thin cirrus, showing overestimated cloud and higher cloud top in the model simulation. Several model sensitivity experiments are conducted with different cloud microphysical parameters to reduce the model-observation discrepancies in high thin cirrus. In addition, relationships among clouds, Hadley circulation, outgoing longwave radiation and precipitation are discussed through the sensitivity experiments. © 2012 American Geophysical Union. All Rights Reserved."
"8273707700;6603859477;53865930800;55619308012;7202381052;7404280955;56269731600;36342344200;7004938676;14035386400;14019285600;6506981001;35364149600;15318942300;7402264430;7202957110;57190341192;7003899504;8536879700;57217658754;6602725432;7003811754;7402456565;37059457600;7403253796;57154391900;7003653764;36160629300;35756224600;","The Queensland cloud seeding Research Program",2012,"10.1175/Bams-d-11-00060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862924255&doi=10.1175%2fBams-d-11-00060.1&partnerID=40&md5=d4f2c1aab08d67f534a1c2f0dcecb7c4","As a response to extreme water shortages in southeast Queensland, Australia, brought about by reduced rainfall and increasing population, the Queensland government decided to explore the potential for cloud seeding to enhance rainfall. The Queensland Cloud Seeding Research Program (QCSRP) was conducted in the southeast Queensland region near Brisbane during the 2008/09 wet seasons. In addition to conducting an initial exploratory, randomized (statistical) cloud seeding study, multiparameter radar measurements and in situ aircraft microphysical data were collected. This comprehensive set of observational platforms was designed to improve the physical understanding of the effects of both ambient aerosols and seeding material on precipitation formation in southeast Queensland clouds. This focus on gaining physical understanding, along with the unique combination of modern observational platforms utilized in the program, set it apart from previous cloud seeding research programs. The overarching goals of the QCSRP were to 1) determine the characteristics of local cloud systems (i.e., weather and climate), 2) document the properties of atmospheric aerosol and their microphysical effects on precipitation formation, and 3) assess the impact of cloud seeding on cloud microphysical and dynamical processes to enhance rainfall. During the course of the program, it became clear that there is great variability in the natural cloud systems in the southeast Queensland region, and understanding that variability would be necessary before any conclusions could be made regarding the impact of cloud seeding. This article presents research highlights and progress toward achieving the goals of the program, along with the challenges associated with conducting cloud seeding research experiments. © 2012 american meteorological society."
"36952888700;23478660100;9239400400;16416791800;7003332823;54784434600;35744616200;6603538344;55637266800;6503855019;24511929800;23019803800;57205984002;24537837200;23478519800;","Future projections of the surface heat and water budgets of the Mediterranean Sea in an ensemble of coupled atmosphere-ocean regional climate models",2012,"10.1007/s00382-011-1261-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867101936&doi=10.1007%2fs00382-011-1261-4&partnerID=40&md5=f1d464203dbb068f19e3b967cda75568","Within the CIRCE project ""Climate change and Impact Research: the Mediterranean Environment"", an ensemble of high resolution coupled atmosphere-ocean regional climate models (AORCMs) are used to simulate the Mediterranean climate for the period 1950-2050. For the first time, realistic net surface air-sea fluxes are obtained. The sea surface temperature (SST) variability is consistent with the atmospheric forcing above it and oceanic constraints. The surface fluxes respond to external forcing under a warming climate and show an equivalent trend in all models. This study focuses on the present day and on the evolution of the heat and water budget over the Mediterranean Sea under the SRES-A1B scenario. On the contrary to previous studies, the net total heat budget is negative over the present period in all AORCMs and satisfies the heat closure budget controlled by a net positive heat gain at the strait of Gibraltar in the present climate. Under climate change scenario, some models predict a warming of the Mediterranean Sea from the ocean surface (positive net heat flux) in addition to the positive flux at the strait of Gibraltar for the 2021-2050 period. The shortwave and latent flux are increasing and the longwave and sensible fluxes are decreasing compared to the 1961-1990 period due to a reduction of the cloud cover and an increase in greenhouse gases (GHGs) and SSTs over the 2021-2050 period. The AORCMs provide a good estimates of the water budget with a drying of the region during the twenty-first century. For the ensemble mean, he decrease in precipitation and runoff is about 10 and 15% respectively and the increase in evaporation is much weaker, about 2% compared to the 1961-1990 period which confirm results obtained in recent studies. Despite a clear consistency in the trends and results between the models, this study also underlines important differences in the model set-ups, methodology and choices of some physical parameters inducing some difference in the various air-sea fluxes. An evaluation of the uncertainty sources and possible improvement for future generation of AORCMs highlights the importance of the parameterisation of the ocean albedo, rivers and cloud cover. © 2011 Springer-Verlag."
"36538539800;37014308100;20434404100;6701756440;","Impact of gas-phase mechanisms on Weather Research Forecasting Model with Chemistry (WRF/Chem) predictions: Mechanism implementation and comparative evaluation",2012,"10.1029/2011JD015775","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862932190&doi=10.1029%2f2011JD015775&partnerID=40&md5=644b1f070c01d67420f078b60c114cd2","Gas-phase mechanisms provide important oxidant and gaseous precursors for secondary aerosol formation. Different gas-phase mechanisms may lead to different predictions of gases, aerosols, and aerosol direct and indirect effects. In this study, WRF/Chem-MADRID simulations are conducted over the continental United States for July 2001, with three different gas-phase mechanisms, a default one (i.e., CBM-Z) and two newly implemented ones (i.e., CB05 and SAPRC-99). Simulation results are evaluated against available surface observations, satellite data, and reanalysis data. The model with these three gas-phase mechanisms gives similar predictions of most meteorological variables in terms of spatial distribution and statistics, but large differences exist in shortwave radiation and temperature and relative humidity at 2 m at individual sites under cloudy conditions, indicating the importance of aerosol semi-direct and indirect effects on these variables. Large biases exist in the simulated wind speed at 10 m, cloud water path, cloud optical thickness, and precipitation, due to uncertainties in current cloud microphysics and surface layer parameterizations. Simulations with all three gas-phase mechanisms well reproduce surface concentrations of O<inf>3</inf>, CO, NO<inf>2</inf>, and PM<inf>2.5</inf>, and column NO<inf>2</inf>. Larger biases exist in the surface concentrations of nitrate and organic matter (OM) and in the spatial distribution of column CO, tropospheric ozone residual, and aerosol optical depth, due to uncertainties in primary OM emissions, limitations in model representations of chemical transport, and radiative processes. Different gas-phase mechanisms lead to different predictions of mass concentrations of O<inf>3</inf> (up to 5 ppb), PM<inf>2.5</inf> (up to 0.5 μg m-3), secondary inorganic PM<inf>2.5</inf> species (up to 1.1 μg m-3), organic PM (up to 1.8 μg m-3), and number concentration of PM <inf>2.5</inf> (up to 2 × 104 cm-3). Differences in aerosol mass and number concentrations further lead to sizeable differences in simulated cloud condensation nuclei (CCN) and cloud droplet number concentration (CDNC) due to the feedback mechanisms among H<inf>2</inf>SO<inf>4</inf> vapor, PM<inf>2.5</inf> number, CCN, and CDNC through gas-phase chemistry, new particle formation via homogeneous nucleation, aerosol growth, and aerosol activation by cloud droplets. This study illustrates the important impact of gas-phase mechanisms on chemical and aerosol predictions, their subsequent effects on meteorological predictions, and a need for an accurate representation of such feedbacks through various atmospheric processes in the model. The online-coupled models that simulate feedbacks between meteorological variables and chemical species may provide more accurate representations of the real atmosphere for regulatory applications and can be applied to simulate chemistry-climate feedbacks over a longer period of time. Copyright 2012 by the American Geophysical Union."
"6603081424;6602513845;6701562494;6505818202;8397494800;7006131953;7003311618;7403625607;7410070663;26659116700;6701511324;7102651635;7601318782;57202530147;7004540083;","The Continual Intercomparison of Radiation Codes: Results from Phase i",2012,"10.1029/2011JD016821","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859471494&doi=10.1029%2f2011JD016821&partnerID=40&md5=1c194f1c0fbc4216ad1f2ea9c36154df","We present results from Phase I of the Continual Intercomparison of Radiation Codes (CIRC), intended as an evolving and regularly updated reference source for evaluation of radiative transfer (RT) codes used in global climate models and other atmospheric applications. CIRC differs from previous intercomparisons in that it relies on an observationally validated catalog of cases. The seven CIRC Phase I baseline cases, five cloud free and two with overcast liquid clouds, are built around observations by the Atmospheric Radiation Measurements program that satisfy the goals of Phase I, namely, to examine RT model performance in realistic, yet not overly complex, atmospheric conditions. Besides the seven baseline cases, additional idealized ""subcases"" are also employed to facilitate interpretation of model errors. In addition to quantifying individual model performance with respect to reference line-by-line calculations, we also highlight RT code behavior for conditions of doubled CO<inf>2</inf>, issues arising from spectral specification of surface albedo, and the impact of cloud scattering in the thermal infrared. Our analysis suggests that improvements in the calculation of diffuse shortwave flux, shortwave absorption, and shortwave CO<inf>2</inf> forcing as well as in the treatment of spectral surface albedo should be considered for many RT codes. On the other hand, longwave calculations are generally in agreement with the reference results. By expanding the range of conditions under which participating codes are tested, future CIRC phases will hopefully allow even more rigorous examination of RT codes. © 2012 by the American Geophysical Union."
"55458732800;7005634455;7004993886;","Evaluation of polar WRF forecasts on the arctic system reanalysis domain: 2. Atmospheric hydrologic cycle",2012,"10.1029/2011JD016765","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857755690&doi=10.1029%2f2011JD016765&partnerID=40&md5=3167e1036f8d4c34fc6ad83fe0ff42b3","The forecast atmospheric hydrologic cycle of the Polar version 3.1.1 of the Weather Research and Forecasting model (WRF) is examined for December 2006 - November 2007. The domain is similar to the Arctic System Reanalysis (ASR), an assimilation of model fields and Arctic observations being conducted partly by the Byrd Polar Research Center. Simulations are performed in 48h increments initialized daily at 0000 UTC, with the first 24h discarded for model spin-up of the hydrologic cycle and boundary layer processes. Precipitation analysis reveals a negative annual mean bias (-9.4%) in the polar region, with particularly dry station biases reflected in the Canadian Archipelago. Annual mean bias for the midlatitudes is small and positive (4.6%), attributed to excessive precipitation during spring and summer when convective precipitation is dominant. An examination of precipitation within four major Arctic river basins shows large positive biases due to excessive convective precipitation in summer as well, but highlights the Arctic climate's strong dependence on midlatitude precipitation. Nudging the model's boundary layer moisture toward drier conditions decreases convective precipitation improving the prediction. Cloud fraction analysis shows too little cloud cover, supported by an excess in incident shortwave radiation and a deficit in downwelling longwave radiation throughout the domain. The longwave bias is present regardless of the amount of cloud water or cloud ice, demonstrating a need to improve cloud effects on radiation in Polar WRF. This examination provides a benchmark of the forecast atmospheric hydrological cycle of Polar WRF and its use as ASR's primary model. Copyright © 2012 by the American Geophysical Union."
"24073317100;6601950693;7006963419;56151984200;6602724321;6603469383;56351042300;","Note on the quality of the (A)ATSR land surface temperature record from 1991 to 2009",2012,"10.1080/01431161.2011.645085","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855419778&doi=10.1080%2f01431161.2011.645085&partnerID=40&md5=9faa56b775421cf8e93bdad7a3c0184c","Land-surface temperature (LST) is a key parameter in the physical study of atmosphere-land interactions as well as for global warming and climate change monitoring on a longer timescale. Remote sensing provides an excellent way to measure LST at a global scale with appropriate spatial and temporal resolution. To retrieve LSTs, measured radiances at the sensor have to be corrected for surface emissivity, atmospheric effects and contaminating clouds. This study is based on the LST data provided by the Along-Track Scanning Radiometers (ATSR-1 and ATSR-2) and the Advanced ATSR (AATSR) on board the three European Space Agency (ESA) satellites, European Remote-Sensing Satellite 1 (ERS-1), ERS-2 and Enviromental Satellite (ENVISAT). The analysis covers data from August 1991 up to December 2009 and contains detailed investigations on global as well as on regional scales with a temporal resolution of 1 month, outlining problems and restrictions within the time series mainly due to cloud contamination and effects of calibration drifts on the cloud detection tests. It is demonstrated that the trends observed, for cooling as well as for warming, are likely to be related to the trends in cloud contamination rather than the trends in the actual LST. © 2012 Copyright Taylor and Francis Group, LLC."
"35917252100;7003495982;7103016965;15766838300;6506545080;42062523800;7003926380;7003582587;57199451114;56163602900;","A limited area model (LAM) intercomparison study of a TWP-ICE active monsoon mesoscale convective event",2012,"10.1029/2011JD016447","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862296140&doi=10.1029%2f2011JD016447&partnerID=40&md5=c72464393b45d63544bb63b295420528","A limited area model (LAM) intercomparison study is conducted based on a tropical monsoonal deep convection case observed during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE). The LAM simulations are compared with the variational analyses (VA) based on the Atmospheric Radiation Measurement (ARM) observations and the cloud resolving model (CRM) simulations forced by the VA. Driven by the ECMWF analyses or global model forecasts, LAMs are able to produce the large-scale thermodynamic field reasonably well compared with the VA. However, the LAM simulated dynamic fields, such as the large-scale horizontal divergence, vertical velocity, and cyclogenesis in the monsoonal trough, have a large inter-model spread and deviate substantially from observations. Despite the differences in large-scale forcing, there is certain consistency between the CRM and LAM simulations: stratiform (w ≤ 1 m s -1) ice clouds dominate the cloud fraction and convective (w > 3 m s-1) clouds occupy less than 3 percent of the total cloudy area. But the hydrometeor content of stratiform ice clouds is only one tenth of that of convective and transitional (1m s-1 < w ≤ 3m s-1) ice clouds. However, there is a large inter-LAM spread in the simulated cloud fraction and hydrometeor mixing ratios. The inter-LAM difference in solid phase hydrometeors (cloud ice, snow, and graupel) can be up to nearly a factor of 10. Among all the hydrometeor types, the stratiform ice clouds are simulated least consistently by the LAMs. The large inter-LAM spread suggests that obtaining consistent and reliable dynamic and cloud fields remains a challenge for the LAM approach. © 2012 American Geophysical Union. All Rights Reserved."
"15026371500;36720934300;","Extratropical influence on ITCZ shifts in slab ocean simulations of global warming",2012,"10.1175/JCLI-D-11-00116.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856971010&doi=10.1175%2fJCLI-D-11-00116.1&partnerID=40&md5=285f75a5f2bafd3baa2a5615c3eee0ce","Recent studies with climate models have demonstrated the power of extratropical forcing in causing the intertropical convergence zone (ITCZ) to shift northward or southward, and paleoclimate data support the notion that there have been large shifts in the ITCZ over time. It is shown that similar notions apply to slab ocean simulations of global warming. Nine slab ocean model simulations from different modeling centers show a wide range of ITCZ shifts in response to doubling carbon dioxide concentrations, which are experienced in a rather zonally symmetric way in the tropics. Using an attribution strategy based on fundamental energetic constraints, it is shown that responses of clouds and ice in the extratropics explain much of the range of ITCZ responses. There are also some positive feedbacks within the tropics due to increasing water vapor content and high clouds in the new ITCZ location, which amplify the changes driven from the extratropics. This study shows the clear importance of simulating extratropical climate responses with fidelity, because in addition to their local importance, the impacts of these climate responses have a large nonlocal impact on rainfall in the tropics. © 2012 American Meteorological Society."
"7004322783;7103404891;56219624100;","125 years of high-mountain research at Sonnblick Observatory (Austrian Alps)-from ""the house above the clouds"" to a unique research platform",2012,"10.1007/s00704-012-0689-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870393159&doi=10.1007%2fs00704-012-0689-8&partnerID=40&md5=a171258ecff5de87f8d6f4b959f74783","Mountain observatories around the world are unique sites for monitoring and investigating variations, trends, forcings and feedbacks in the climate system, which are of utmost interest for understanding global climate change. From the small number of these research platforms, Sonnblick Observatory (Austrian Alps) stands out because of its long time series dating back to 1886 at an elevation of 3,100 m a. s. l. The paper describes the contribution of mountain observatories to climatology by the example of Sonnblick Observatory. The observatory's scientific evolution is summarised, starting from the original idea of upper air atmospheric measurements to its recent role as an atmospheric background station and interdisciplinary research site. © 2012 Springer-Verlag."
"55340272500;15757708600;55533870100;53872031000;","Objective calibration of regional climate models",2012,"10.1029/2012JD018262","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871392778&doi=10.1029%2f2012JD018262&partnerID=40&md5=4a580adfbf927c67dfa8305e35dccba6","Climate models are subject to high parametric uncertainty induced by poorly confined model parameters of parameterized physical processes. Uncertain model parameters are typically calibrated in order to increase the agreement of the model with available observations. The common practice is to adjust uncertain model parameters manually, often referred to as expert tuning, which lacks objectivity and transparency in the use of observations. These shortcomings often haze model inter-comparisons and hinder the implementation of new model parameterizations. Methods which would allow to systematically calibrate model parameters are unfortunately often not applicable to state-of-the-art climate models, due to computational constraints facing the high dimensionality and non-linearity of the problem. Here we present an approach to objectively calibrate a regional climate model, using reanalysis driven simulations and building upon a quadratic metamodel presented by Neelin et al. (2010) that serves as a computationally cheap surrogate of the model. Five model parameters originating from different parameterizations are selected for the optimization according to their influence on the model performance. The metamodel accurately estimates spatial averages of 2 m temperature, precipitation and total cloud cover, with an uncertainty of similar magnitude as the internal variability of the regional climate model. The non-linearities of the parameter perturbations are well captured, such that only a limited number of 20-50 simulations are needed to estimate optimal parameter settings. Parameter interactions are small, which allows to further reduce the number of simulations. In comparison to an ensemble of the same model which has undergone expert tuning, the calibration yields similar optimal model configurations, but leading to an additional reduction of the model error. The performance range captured is much wider than sampled with the expert-tuned ensemble and the presented methodology is effective and objective. It is argued that objective calibration is an attractive tool and could become standard procedure after introducing new model implementations, or after a spatial transfer of a regional climate model. Objective calibration of parameterizations with regional models could also serve as a strategy toward improving parameterization packages of global climate models. © 2012. American Geophysical Union. All Rights Reserved."
"11539061800;55613308500;23493942300;7202434960;6603837066;55262544600;","Development of a ground based remote sensing approach for direct evaluation of Aerosol-Cloud interaction",2012,"10.3390/atmos3040468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874563180&doi=10.3390%2fatmos3040468&partnerID=40&md5=5c241cc8a601d5dfbad6e22251c8f1bc","The possible interaction and modification of cloud properties due to aerosols is one of the most poorly understood mechanisms within climate studies, resulting in the most significant uncertainty as regards radiation budgeting. In this study, we explore direct ground based remote sensing methods to assess the Aerosol-Cloud Indirect Effect directly, as space-borne retrievals are not directly suitable for simultaneous aerosol/cloud retrievals. To illustrate some of these difficulties, a statistical assessment of existing multispectral imagers on geostationary (e.g., GOES)/Moderate Resolution Imaging Spectroradiometer (MODIS) satellite retrievals of the Cloud Droplet Effective Radius (Reff) showed significant biases especially at larger solar zenith angles, further motivating the use of ground based remote sensing approaches. In particular, we discuss the potential of using a combined Microwave Radiometer (MWR)-Multi-Filter Rotating Shadowband Radiometer (MFRSR) system for real-time monitoring of Cloud Optical Depth (COD) and Cloud Droplet Effective Radius (Reff), which are combined with aerosol vertical properties from an aerosol lidar. An iterative approach combining the simultaneous observations from MFRSR and MWR are used to retrieve the COD and Reff for thick cloud cases and are extensively validated using the DoE Southern Great Plains (SGP) retrievals as well as regression based parameterized model retrievals. In addition, we account for uncertainties in background aerosol, surface albedo and the combined measurement uncertainties from the MWR and MFRSR in order to provide realistic uncertainty estimates, which is found to be ~10% for the parameter range of interest in Aerosol-Cloud Interactions. Finally, we analyze a particular case of possible aerosol-cloud interaction described in the literature at the SGP site and demonstrate that aerosol properties obtained at the surface can lead to inconclusive results in comparison to lidar-derived aerosol properties near the cloud base. © 2012 by the authors."
"56135632400;7103294028;7101899854;7005399437;35463545000;55725404100;26661481400;7003928082;7004672267;7406683894;7501460689;55470017900;7102903255;7402287860;","Evaluations of cirrus contamination and screening in ground aerosol observations using collocated lidar systems",2012,"10.1029/2012JD017757","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865332009&doi=10.1029%2f2012JD017757&partnerID=40&md5=5970856bd14fbc30b86d7ab5723e4d18","Cirrus clouds, particularly subvisual high thin cirrus with low optical thickness, are difficult to screen in operational aerosol retrieval algorithms. Collocated aerosol and cirrus observations from ground measurements, such as the Aerosol Robotic Network (AERONET) and the Micro-Pulse Lidar Network (MPLNET), provide us with an unprecedented opportunity to systematically examine the susceptibility of operational aerosol products to cirrus contamination. Quality assured aerosol optical thickness (AOT) measurements were also tested against the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) vertical feature mask (VFM) and the Moderate Resolution Imaging Spectroradiometer (MODIS) thin cirrus screening parameters for the purpose of evaluating cirrus contamination. Key results of this study include: (1) quantitative evaluations of data uncertainties in AERONET AOT retrievals are conducted; although AERONET cirrus screening schemes are successful in removing most cirrus contamination, strong residuals displaying strong spatial and seasonal variability still exist, particularly over thin cirrus prevalent regions during cirrus peak seasons; (2) challenges in matching up different data for analysis are highlighted and corresponding solutions proposed; and (3) estimates of the relative contributions from cirrus contamination to aerosol retrievals are discussed. The results are valuable for better understanding and further improving ground aerosol measurements that are critical for aerosol-related climate research. © 2012. American Geophysical Union. All Rights Reserved."
"55359866000;7404726484;55342744700;52464123400;","Simulation of in-cloud icing events on Mount Washington with the GEM-LAM",2012,"10.1029/2012JD017520","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866315778&doi=10.1029%2f2012JD017520&partnerID=40&md5=d64f3449d54e19aec4af932e20aa2700","In-cloud icing on structures such as transmission lines and wind turbines is an important consideration both for design and operations. It often occurs in coastal areas and over high terrain, where there are virtually no systematic observations. The regional mesoscale model GEM-LAM of the Canadian Meteorological Center (CMC) was used to model three historical icing events on Mount Washington, where observational data were available. These three events are representative of the most frequent low level wind directions for seven available observation periods. A newly developed sophisticated two-moment microphysics scheme (Milbrandt-Yau) is used in GEM-LAM. The simulated cloud properties and other meteorological data are compared with near surface observational data. Simulation results from the 1-km resolution run agree best with the observations, with an average RMSE (root mean square error) of 1.6°C for near surface temperature, 4.6 m s-1 for wind speed, 0.23 g -3 for liquid water content, and 5.8 μm for the median volume droplet diameter. These simulated meteorological fields and cloud properties were used as inputs to a cylindrical sleeve icing model. The modeled icing rate from the GEM-LAM simulated fields follows the temporal evolution of the observed one with average RMSE of 1.53 g m-1 min-1 compared to an average measured icing rate of 1.98 g m-1 min -1 for all the three cases. ©2012. American Geophysical Union. All Rights Reserved."
"36816703000;8437626600;35313639700;55452292200;","Satellite observation of regional haze pollution over the North China Plain",2012,"10.1029/2012JD017915","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863002981&doi=10.1029%2f2012JD017915&partnerID=40&md5=34fac2268ec7165bb03f43ec1c846523","Haze clouds often form over the North China Plain (NCP) of eastern China, where large amounts of aerosol particles and their precursors are emitted. To obtain general insights into regional pollution, a large-scale, long-term study was conducted using A-Train satellite observations, ground measurements, and meteorological data. Contrary to previous analyses, most of the haze clouds appeared to form abruptly (within 2-3h). Case studies show that natural sources contribute significantly to the formation of regional haze. Dust plumes can mix with local pollutants, causing smog clouds to form abruptly, while moist airflows can cause widespread haze-fog pollution. The combined observations revealed highly inhomogeneous haze clouds, in terms of both vertical and horizontal distribution, leading to clear discrepancies between site measurements near the surface and satellite observations at the top of the atmosphere. Surprisingly, prevailing dust plumes, which are closely connected with the haze clouds, were observed in winter. Airborne dust and water vapor transported from outside the region are the main drivers of regional haze over the NCP. Accumulation of local pollutants also leads to common occurrences of urban smog; however, the occurrence of most haze clouds shows no obvious correlation with local pollution. Local- and regional-scale haze pollution are common over the NCP, but they have differing formation mechanisms, and contrasting chemical and physical properties. The present findings improve our understanding of heavy pollution over eastern China and its links to climate. © 2012 American Geophysical Union. All Rights Reserved."
"24802663500;57203405965;6603800142;12801836100;6603631763;7201507866;22975069200;8309699900;","CalNex cloud properties retrieved from a ship-based spectrometer and comparisons with satellite and aircraft retrieved cloud properties",2012,"10.1029/2012JD017624","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868021582&doi=10.1029%2f2012JD017624&partnerID=40&md5=0351fb47162024e2884d6fb2f10e749c","An algorithm to retrieve cloud optical thickness and effective radius (r<inf>eff</inf>) from spectral transmittance was applied to radiance and irradiance observations of the Solar Spectral Flux Radiometer (SSFR) during the Research at the Nexus of Air Quality and Climate Change Campaign (CalNex). Data from an overcast day, 16 May 2010, was used to validate the algorithm. Retrievals from the SSFR, deployed on the Woods Hole Oceanic Institute R/V Atlantis, were compared to retrievals made from an airborne SSFR, the Geostationary Operations Environmental Satellite (GOES), an Atlantis-based microwave radiometer, and the Moderate Resolution Imaging Spectroradiometer. In situ observations of r<inf>eff</inf> during a flight over the Atlantis were compared to the Atlantis SSFR and GOES retrievals. The cloud statistics for the CalNex campaign were compared to previous studies. The agreement between the different retrievals, quantified by determining the number of coincident observations when retrieval uncertainty overlapped, improved as the difference between the field-of-views (FOV) of the instruments decreased. It is shown that averaging the 1Hz SSFR observations to the 15minute GOES interval cannot fully account for the impact of the different FOVs. The average in situ r <inf>eff</inf> (7.7 μm) fell between the average r<inf>eff</inf> retrieved using the Atlantis-based SSFR radiance (5.7 μm) and irradiance (9.5 μm). The CalNex clouds showed a diurnal pattern observed in previous studies of marine boundary layer clouds in the region. The distribution of cloud optical thickness and liquid water path during CalNex was shown to be a gamma distribution, consistent with previous studies of high cloud fraction marine boundary layer clouds. © 2012. American Geophysical Union. All Rights Reserved."
"24722339600;57210590791;12645767500;7004838931;7403682442;","Precipitation driving of droplet concentration variability in marine low clouds",2012,"10.1029/2012JD018305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867637517&doi=10.1029%2f2012JD018305&partnerID=40&md5=d94951e9e57ff98437329773954cafc4","The concentration N<inf>d</inf> of cloud droplets in marine low clouds is a primary determinant of their ability to reflect sunlight and modulates their ability to precipitate. Previous studies have focused upon aerosol source variability as the key driver of variability in N<inf>d</inf>. Here, we use a highly simplified aerosol budget model to examine the impact of precipitation on N<inf>d</inf>. This model considers: precipitation (coalescence) scavenging, constrained using new satellite measurements of light precipitation; entrainment of aerosol from above cloud combined with constant aerosol concentration based on recent field observations of aerosol particles in the free troposphere; and sea-surface aerosol production estimated using a wind speed dependent source function. Despite the highly simplified nature of this model, it skillfully predicts the geographical variability of N<inf>d</inf> in regions of extensive marine low clouds. Inclusion of precipitation results in reduction in N <inf>d</inf> by factors of 2-3 over the remote oceans. Within 500km of coastlines the reduction in N<inf>d</inf> due to precipitation is weak but in these regions the model is not able to accurately predict N<inf>d</inf> because of strong pollution sources. In general, neither free-tropospheric nor surface CCN sources alone are sufficient to maintain N<inf>d</inf> against precipitation losses. The results demonstrate that even the light precipitation rates typical of marine stratocumulus profoundly impact the radiative properties of marine low clouds. © 2012. American Geophysical Union. All Rights Reserved."
"6603888947;","A shared frequency set between the historical mid-latitude aurora records and the global surface temperature",2012,"10.1016/j.jastp.2011.10.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83855162766&doi=10.1016%2fj.jastp.2011.10.013&partnerID=40&md5=dc011a33e8cbe5fa8fa5511f594e4120","Herein we show that the historical records of mid-latitude auroras from 1700 to 1966 present oscillations with periods of about 9, 10-11, 20-21, 30 and 60 years. The same frequencies are found in proxy and instrumental global surface temperature records since 1650 and 1850, respectively, and in several planetary and solar records. We argue that the aurora records reveal a physical link between climate change and astronomical oscillations. Likely in addition to a Soli-Lunar tidal effect, there exists a planetary modulation of the heliosphere, of the cosmic ray flux reaching the Earth and/or of the electric properties of the ionosphere. The latter, in turn, has the potentiality of modulating the global cloud cover that ultimately drives the climate oscillations through albedo oscillations. In particular, a quasi-60-year large cycle is quite evident since 1650 in all climate and astronomical records herein studied, which also include a historical record of meteorite fall in China from 619 to 1943. These findings support the thesis that climate oscillations have an astronomical origin. We show that a harmonic constituent model based on the major astronomical frequencies revealed in the aurora records and deduced from the natural gravitational oscillations of the solar system is able to forecast with a reasonable accuracy the decadal and multidecadal temperature oscillations from 1950 to 2010 using the temperature data before 1950, and vice versa. The existence of a natural 60-year cyclical modulation of the global surface temperature induced by astronomical mechanisms, by alone, would imply that at least 60-70% of the warming observed since 1970 has been naturally induced. Moreover, the climate may stay approximately stable during the next decades because the 60-year cycle has entered in its cooling phase. © 2011 Elsevier Ltd."
"24764834600;7004035832;7102739935;","Cloud frequency climatology at the Andes/Amazon transition: 2. Trends and variability",2012,"10.1029/2012JD017789","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870614647&doi=10.1029%2f2012JD017789&partnerID=40&md5=5c9c60bddebbac9c4931cbd2e989478b","The climate and ecology of tropical montane systems is intimately connected with the complex spatial dynamics of cloud occurrence, but there have been few studies of the patterns and trends of cloud occurrence in tropical montane regions. We examine trends and variability in the cloud climatology of the Andes/Amazon transition in SW Amazonia using satellite data and ground-based observations. Results were compared for three zones within the study area: highlands (puna grassland), eastern slope (Tropical Montane Cloud Forest or TMCF) and lowlands. Time series of cloud frequency from ISCCP (International Satellite Cloud Climatology Project) were correlated with sea surface temperature (SST) anomalies from the HadISST data set for 5 regions including the tropical North Atlantic and the tropical Pacific. Detrended lowland cloud frequencies were significantly correlated with detrended tropical North Atlantic SSTs in the late dry season (August/September), whereas the eastern slope and the highlands were not significantly correlated with tropical North Atlantic SSTs. Pacific SST correlations were highest for eastern slope and highlands from March to May. Indian Ocean SST anomalies were significantly correlated with dry season cloud frequency for the lowlands and highlands. There are significant decreasing trends in cloud frequency on the lowlands in January, March and September and in March on the eastern slope. Trends in sunshine duration, 850 hPa zonal winds over the central Amazon, increases in diurnal temperature range, and comparisons with MODIS (Moderate Resolution Imaging Spectroradiometer) and observational data support the existence of these trends, and a link with the increasing trend in tropical North Atlantic SSTs. We suggest that continued increases in tropical North Atlantic SSTs will further reduce cloud frequency in the lowlands adjacent to the TMCF in the late dry season at least. In addition, a future increase in the occurrence of El Nio events would lead to decreased cloud frequency on the eastern slope and highlands. © 2012. American Geophysical Union. All Rights Reserved."
"6506152198;56384704800;57208121852;7003931528;57203053317;7202076777;","The present-day decadal solar cycle modulation of Earth's radiative forcing via charged H2SO4/H2O aerosol nucleation",2012,"10.1029/2011GL050058","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856196326&doi=10.1029%2f2011GL050058&partnerID=40&md5=89181933f57d2cca7850fb64e1ffd1a6","The decadal solar cycle modulation of Earth's radiative forcing via ionization of the atmosphere by galactic cosmic rays, aerosol formation from the gas phase, and the response of clouds to aerosol is quantified for the first time with a climate model that represents and couples the relevant processes. Simulations are conducted for solar maximum and minimum conditions, with present-day anthropogenic aerosol and aerosol precursor gas emissions, and contemporary large-scale meteorology. The solar cycle signal appears in atmospheric ionization, aerosol formation from the gas phase, aerosol concentrations, aerosol optical depth, and in cloud properties, and is most pronounced at mid-and high latitudes. The resulting solar cycle modulation of Earth's radiative forcing exhibits a distinct hemispheric asymmetry, with peak values of-0.14 W m-2 in the southern and-0.06 W m-2 in the northern mid-latitudes. Globally and annually averaged, the solar cycle modulation of Earth's radiative forcing, arising from the increase in atmospheric ionization by galactic cosmic rays from solar maximum to minimum, via charged nucleation of aerosol, the direct aerosol effect, and the cloud albedo effect, amounts to-0.05 W m-2. A limited relevance of this variation for the Earth's atmosphere and climate can be inferred, given that Earth's radiative forcing changes by-0.24 W m-2 from solar maximum to minimum because of a decrease in total solar irradiance. © 2012 by the American Geophysical Union."
"26039315200;","The future of environmental sustainability in the Taita Hills, Kenya: Assessing potential impacts of agricultural expansion and climate change",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867447980&partnerID=40&md5=6fd6e7b7651f645667a42028874081d4","The indigenous cloud forests in the Taita Hills have suffered substantial degradation for several centuries due to agricultural expansion. Currently, only 1% of the original forested area remains preserved. Furthermore, climate change imposes an imminent threat for local economy and environmental sustainability. In such circumstances, elaborating tools to conciliate socioeconomic growth and natural resources conservation is an enormous challenge. This article tackles essential aspects for understanding the ongoing agricultural activities in the Taita Hills and their potential environmental consequences in the future. Initially, an alternative method is proposed to reduce uncertainties and costs for estimating agricultural water demand. The main characteristic of the approach proposed in this study is the use of satellite data to overcome data availability limitations. Furthermore, a modelling framework was designed to delineate agricultural expansion projections and evaluate the future impacts of agriculture on soil erosion and irrigation water demand. The results indicate that if current trends persist, agricultural areas will occupy roughly 60% of the study area by 2030. Rainfall erosivity is likely to increase during April and November due to climate change and slight decrease during March and May. Although the simulations indicate that climate change will likely increase total annual rainfall volumes during the following decades, irrigation requirements will continue to increase due to agricultural expansion. By 2030, new cropland areas may cause an increase of approximately 40% in the annual volume of water necessary for irrigation."
"55085483100;28767872500;30867447000;6602725432;7003811754;","Case studies of orographic precipitation in the brindabella ranges: Model evaluation and prospects for cloud seeding",2012,"10.22499/2.6204.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879101463&doi=10.22499%2f2.6204.009&partnerID=40&md5=a82774d11301f9f3c86d9215fcaeeb52","Recent confirmatory results in cloud seeding trials in the Australian Snowy Mountains have generated interest in performing similar experiments elsewhere. The Brindabella Ranges, which form the western border and catchment watershed of the Australian Capital Territory, share similarities in both climate and topography to the Snowy Mountains, so there is some prospect of conducting cloud seeding operations there. This paper presents an analysis of observations and high-resolution weather research and forecasting (WRF) model simulations of two wintertime storms from 2008 with the purpose of (1) evaluating the performance of the WRF model in simulating wintertime storms in the Australian alpine environment, and (2) investigating the nature of these storms from the perspective of cloud seeding research. The WRF model results compare favourably with much of the meteorological data used. There was a tendency to simulate too much moisture in the lower levels, and as a result the simulated low-level cloud coverage was somewhat more extensive than observed. Precipitation amounts were generally well represented, but the paucity of the observational network in the Brindabella Ranges made a comprehensive evaluation impossible. Cloud liquid water path (LWP), observed with a mountain top dual-channel microwave radiometer, was surprisingly well represented by the WRF model, especially in the post-frontal conditions. Radar reflectivity in the analysis region showed significant differences upwind and downwind of the Brindabella Ranges, suggesting that the mountains played an important role in the modulation of precipitation structures. Both of the case study storms were characterised by extended periods with appreciable quantities of supercooled liquid water, which is central to the glaciogenic cloud seeding hypothesis. However, further research would need to be conducted to determine whether such conditions occur frequently enough to permit cloud seeding operations, and whether it would be feasible to target the catchment regions with seeding material."
"36537145700;6701753718;6603580448;7102925250;","Using horizontal transport characteristics to infer an emission height time series of volcanic SO2",2012,"10.1029/2012JD017957","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867210017&doi=10.1029%2f2012JD017957&partnerID=40&md5=06985b08262b4e8e12e9a23fbf611bc8","Characterizing the emission height of sulfur dioxide (SO2) from volcanic eruptions yields information about the strength of volcanic activity, and is crucial for the assessment of possible climate impacts and validation of satellite retrievals of SO2. Sensors such as the Ozone Monitoring Instrument (OMI) on the polar-orbiting Aura satellite provide accurate maps of the spatial distribution of volcanic SO2, but provide limited information on its vertical distribution. The goal of this work is to explore the possible use of a trajectory model in reconstructing both the temporal activity and injection altitude of volcanic SO2 from OMI column measurements observed far from the volcano. Using observations from the November 2006 eruption of Nyamuragira, back trajectories are run and statistical analyses are computed based on the distance of closest approach to the volcano. These statistical analyses provide information about the emission height time series of SO2 injection from that eruption. It is found that the eruption begins first injecting SO2 into the upper troposphere, between 13 km and 17 km, on November 28th 2006. This is then followed by a slow decay in injection altitude, down to 6 km, over subsequent days. The emission height profile is used to generate an optimal reconstruction based on forward trajectories and compared to OMI SO2 observations. The inferred altitude of the Nyamuragira SO2 cloud is also compared to the altitude of sulfate aerosols detected in aerosol backscatter vertical profiles from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). © 2012. American Geophysical Union. All Rights Reserved."
"6603406338;7103232081;","On the relationship between QBO and distribution of tropical deep convection",2012,"10.1029/2011JD016317","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856972074&doi=10.1029%2f2011JD016317&partnerID=40&md5=3d24716ccd66e1372c2880e2bef621bd","There have been several observational and modeling analyses that have indicated that the stratospheric quasi-biennial oscillation (QBO) significantly affects the tropical troposphere. This article aims to identify the QBO signal in tropical deep convection. Some difficulties in previous studies were ambiguities in the identification of tropical deep convection in observations, and also in separating the El Nio/Southern Oscillation (ENSO) and other tropospheric signals from QBO influences. We use a recent cluster analysis of 21.5 years of International Satellite Cloud Climatology Project tropical weather states to identify tropical deep convection and cirrus clouds, as well as 32.25 years of precipitation data as proxies for deep convection. Correlations between the QBO, ENSO, and other tropospheric patterns such as the tropospheric biennial oscillation and Pacific decadal oscillation are taken into account to isolate the influence of the QBO. Whereas tropical deep convection is mostly related to ENSO and the annual cycle, the QBO westerly phase, independent of the annual cycle as well as linear and nonlinear impacts of ENSO, leads to an eastward shift in the strength of meridional overturning contributions to the Hadley circulation over the Pacific and thus also affects the subtropical circulation. For deep convective clouds, relative differences in convective cloud cover between the QBO easterly and QBO westerly phases can be as large as 51% 7% of the annual average over isolated regions in the tropical west Pacific and 103% 35% over the east Pacific, where the absolute values are lower and where notable deviations occur during the QBO westerly phase. Copyright 2012 by the American Geophysical Union."
"55332291100;56219012200;57202531041;24344988500;","Effects of three-dimensional photon transport on the radiative forcing of realistic contrails",2012,"10.1175/JAS-D-11-0206.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864858331&doi=10.1175%2fJAS-D-11-0206.1&partnerID=40&md5=33d72ad59b2a95f7ffdd33b92b0d719f","Estimates of the global radiative forcing (RF) of line-shaped contrails and contrail cirrus exhibit a high level of uncertainty. In most cases, 1D radiative models have been used to determine the RF on a global scale. In this paper the effect of neglecting the 3D radiative effects of realistic contrails is quantified. Calculating the 3D effects of an idealized elliptical contrail as in the work of Gounou and Hogan with the 3D radiative transfer model MYSTIC (for ""Monte Carlo code for the physically correct tracing of photons in cloudy atmospheres"") produced comparable results: as in Gounou and Hogan's work the 3D effect (i.e., the difference in RF between a 3Dcalculation and a 1Dapproximation) on contrail RF was on the order of 10% in the longwave and shortwave. The net 3D effect, however, can be much larger, since the shortwave and longwave RF largely cancel during the day. For the investigation of the 3D effects of more realistic contrails, the microphysical input was provided by simulations of a 2D contrail-to-cirrus large-eddy simulation (LES) model. To capture some of the real variability in contrail properties, this paper examines two contrail evolutions from 20 min up to 6 h in an environment with either high or no vertical wind shear. This study reveals that the 3D effects show a high variability under realistic conditions since they depend strongly on the optical properties and the evolutionary state of the contrails. The differences are especially large for low elevations of the sun and contrails spreading in a sheared environment. Thus, a parameterization of the 3D effects in climate models would need to consider both geometry and microphysics of the contrail. © 2012 American Meteorological Society."
"55559635000;6701497788;","Diversity and distribution of forest canopy Coleoptera on eastern Viti Levu, Fiji Islands",2012,"10.1071/PC130177","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872457008&doi=10.1071%2fPC130177&partnerID=40&md5=c67886ab2883609e03e2537c97f8d747","In Fiji, few systematic studies have been conducted that describe insect distributions, especially with respect to ecological gradients (e.g., habitat type, climate, altitude, and seasonality) that are known to influence their diversity and distribution. In this study, canopy coleopteran assemblages within undisturbed forest in eastern Viti Levu, Fiji, were intensively surveyed over a range of geographical locations and altitudes, namely lowland Nakobalevu (200-400 m), upland Waisoi (400-600 m) and cloud montane forest Monasavu (600-1000 m). Dominant beetle families sampled from the canopy included Curculionidae, Chrysomelidae and Staphylinidae. Multidimensional scaling revealed a division in the canopy beetle assemblages between lowland forest (<400 m), upland forest (400-600 m) and cloud montane forests (600-1 000 m). We tentatively conclude that diversity was highest at mid-to-high altitudes represented at Monasavu. Direct Gradient Analysis (RDA) indicated that 49% of data variability was explained by two axes that represented altitude and seasonality respectively."
"35188850500;6602675795;","Evaluation of thermal comfort conditions in Ourmieh Lake, Iran",2012,"10.1007/s00704-011-0492-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856558130&doi=10.1007%2fs00704-011-0492-y&partnerID=40&md5=16b16349afabcefc9958b63bc0f062b9","Research in developing countries concerning the relationship of weather and climate conditions with tourism shows a high importance not only because of financial aspects but also an important part of the region's tourism resource base. Monthly mean air temperature, relative humidity, precipitation, vapor pressure, wind velocity, and cloud cover for the period 1985-2005 data collected from four meteorological stations Tabriz, Maragheh, Orumieh, and Khoy were selected. The purpose of this study is to determine the most suitable months for human thermal comfort in Ourmieh Lake, a salt sea in the northwest of Iran. To achieve this, the cooling power and physiologically equivalent temperature (PET) calculated by the RayMan model and the Climate Tourism/Transfer Information Scheme (CTIS) were used. The results based on cooling power indicate that the most favorable period for tourism, sporting, and recreational activities in Ourmieh Lake is between June and October and based on PET between June to September. In addition, the CTIS shows a detailed quantification of the relevant climate-tourism factors. © 2011 The Author(s)."
"8670213100;24778445700;6507681572;6603395511;15841350300;7102953444;6701796418;","Recent regional surface solar radiation dimming and brightening patterns: Inter-hemispherical asymmetry and a dimming in the Southern Hemisphere",2012,"10.1002/asl.361","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856005291&doi=10.1002%2fasl.361&partnerID=40&md5=df72152165739b7dfdcd785f091ab030","Recent variations in surface solar radiation (SSR) at the beginning of the 21st century (2000-2007) were determined at scales ranging from local/regional to hemispherical/global, on the basis of radiative transfer computations and information from satellites, reanalyses and surface measurements. Under all-sky conditions, in the Northern Hemisphere (NH) there is no clear dimming/brightening signal after 2000, whereas in the SH there is a more clear dimming arising from both increasing clouds and aerosols. Dimming is observed over land and ocean in the Southern Hemisphere (SH), and over oceans in the NH, whereas a slight brightening occurred over NH land. However, opposite tendencies are found even within the same continent, indicating the need to assess SSR changes at regional/local scales apart from hemispherical/global ones. © 2011 Royal Meteorological Society."
"15848446900;7005344194;","Species adaptation to both fire and climate change in tropical montane heath: Can Melaleuca uxorum (Myrtaceae) survive?",2012,"10.1071/PC120319","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937732591&doi=10.1071%2fPC120319&partnerID=40&md5=7fb7e5d41eb56e1bcb0a2817fcab17f9","Resprouting following fire is an effective and well utilized strategy for tropical montane heath species which have had a long evolutionary history of intermittent fire disturbance. Research conducted in both burnt and unburnt heath suggests that species richness is related to fire, however actual species presence is dependent upon local burning regimes. Taxa that persist in fire-adapted environments may survive through mechanisms including seed storage in the soil seed bank, resprouting from basal, axillary or epicormic buds, roots/rhizomes or terminal aerial buds and/or through migration of seed. We investigated the montane endemic Melaleuca uxorum's response to fire to understand local adaptation and persistence to fire in fire prone heath and to understand potential impacts of climate change on montane heath ecosystems. We found that the species resprouts at the stem base, along stems from epicormic buds and from axillary buds. The species forms small colonies which appear to be a mixture of sexual and asexual (clonal) reproduction. We predict that the effects of climate change will conspire against tropical montane heath below 1000 m, and those communities away from maritime influences will be under threat of increasingly reduced population numbers and extent as the dry season cloud base is expected to rise in elevation with anticipated rising temperatures. Furthermore, as evaporation rates increase, such communities are anticipated to lose their local specialized flora and to be replaced by more common unspecialized, widespread species."
"57214672257;35779049500;","Climatological aspects of seasonal variation of aerosol vertical distribution over central Indo-Gangetic belt (IGB) inferred by the space-borne lidar CALIOP",2012,"10.1016/j.atmosenv.2011.09.052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82955163134&doi=10.1016%2fj.atmosenv.2011.09.052&partnerID=40&md5=6baa586cdc768d6dc0c79c32db16c9a6","Climatological information on the vertical distribution of aerosol in the lower atmosphere is needed to assess the effects of aerosols on climate. Altitude profiles of the backscatter coefficient (at 532 nm), color ratio (CR) and particle depolarization ratio (PDR) derived from space-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate the climatological aspects of seasonal variation of aerosol vertical distribution over central Indo-Gangetic belt (IGB). Strong convective activity coupled with capping inversion lead to vertical extension (4-5 km) of aerosol distribution during the pre-monsoon (PrM) season. Trapping of pollution at low altitudes (below 1.5 km) by subsidence have been found during the late post-monsoon (PoM) and winter seasons. Combined results of CR and PDR suggest presence of elevated mineral dust particles during the PrM season, whereas fine mode and spherical (biomass burning/industrial pollution) particles are dominant during the PoM and winter seasons. The observations indicate a seasonal dependency of the aerosol vertical distribution over central IGB. © 2011 Elsevier Ltd."
"42262119100;23568523100;55484672400;","Factors affecting the yield of high yielding variety Boro rice: An evidence from Rajshahi district of Bangladesh",2012,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869142100&partnerID=40&md5=9e9b12aca5a8f4508deb36c114708297","Rice is the most important agricultural crop in Bangladesh. The high yielding variety (HYV) Boro rice has the largest share among all the varieties of rice in the country. The yield of HYV Boro rice is strongly interrelated with the climatic and non-climatic factors like rainfall, temperature, humidity, cloud coverage, carbon dioxide emission, wind speed and fertilizer use. Our particular interest is to extract the factors that are potential for the yield of HYV Boro rice in the study area. As a data reduction technique, factor analysis was employed in the selected data sets. Our analysis extracted five factors that explained about 82.33% variation of the total variance."
"55938693300;57209908958;55278022900;55695334600;26433470700;","Nested high-resolution modeling of the impact of urbanization on regional climate in three vast urban agglomerations in China",2012,"10.1029/2012JD018226","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868636190&doi=10.1029%2f2012JD018226&partnerID=40&md5=125c2e482a98772aa665941a9acb9d64","In this paper, the Weather Research and Forecasting Model, coupled to the Urban Canopy Model, is employed to simulate the impact of urbanization on the regional climate over three vast city agglomerations in China. Based on high-resolution land use and land cover data, two scenarios are designed to represent the nonurban and current urban land use distributions. By comparing the results of two nested, high-resolution numerical experiments, the spatial and temporal changes on surface air temperature, heat stress index, surface energy budget, and precipitation due to urbanization are analyzed and quantified. Urban expansion increases the surface air temperature in urban areas by about 1C, and this climatic forcing of urbanization on temperature is more pronounced in summer and nighttime than other seasons and daytime. The heat stress intensity, which reflects the combined effects of temperature and humidity, is enhanced by about 0.5 units in urban areas. The regional incoming solar radiation increases after urban expansion, which may be caused by the reduction of cloud fraction. The increased temperature and roughness of the urban surface lead to enhanced convergence. Meanwhile, the planetary boundary layer is deepened, and water vapor is mixed more evenly in the lower atmosphere. The deficit of water vapor leads to less convective available potential energy and more convective inhibition energy. Finally, these combined effects may reduce the rainfall amount over urban areas, mainly in summer, and change the regional precipitation pattern to a certain extent. © 2012. American Geophysical Union. All Rights Reserved."
"55506762000;7801518469;","Surface energy partitioning over four dominant vegetation types across the United States in a coupled regional climate model (Weather Research and Forecasting Model 3-Community Land Model 3.5)",2012,"10.1029/2011JD016991","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859478187&doi=10.1029%2f2011JD016991&partnerID=40&md5=d59774881412c51c08461a10aa1158eb","Accurate representation of surface energy partitioning is crucial for studying land surface processes and the climatic influence of land cover and land use change using coupled climate-land surface models. A critical question for these models, especially for newly coupled ones, is whether they can adequately distinguish differences in surface energy partitioning among different vegetation types. We evaluated 3years (2004-2006) of surface energy partitioning and surface climate over four dominant vegetation types (cropland, grassland, needleleaf evergreen forest, and broadleaf deciduous forest) across the United States in a recently coupled regional climate model, Weather Research and Forecasting Model 3-Community Land Model 3.5 (WRF3-CLM3.5), by comparing model output to observations (AmeriFlux, Clouds and the Earth's Radiant Energy System (CERES), and Parameter-elevation Regressions on Independent Slopes Model (PRISM) data) and to standard WRF model output. We found that WRF3-CLM3.5 can capture the seasonal pattern in energy partitioning for needleleaf evergreen forest but needs improvements in cropland, grassland, and broadleaf deciduous forest. Correcting the leaf area index representation for cropland and grassland could immediately improve the simulation of latent heat flux and hence the energy partitioning. Adding an irrigation scheme is especially important for cropland in the Midwest, where the strongly coupled soil moisture and precipitation can form a positive feedback that reduces latent heat flux and increases the warm bias. For deciduous forest, the simulated excess latent heat flux before leaf emergence is mainly from soil evaporation, requiring further improvement in the soil evaporation scheme. Finally, the domain-wide overestimated net radiation contributes to positive biases in sensible, latent, and ground heat flux, as well as surface temperature. The standard WRF simulation has a similar warm bias, implicating errors in modules other than the land surface code. A sensitivity test suggests that improved simulation of downward solar radiation could reduce the energy flux and temperature biases. After adding irrigation process and correcting the leaf area index, WRF3-CLM3.5 appears reliable for studying conversions between natural grassland and irrigated cropland and between needleleaf evergreen forest and grassland. © 2012 by the American Geophysical Union."
"57202413846;","Enhanced temperature variability in high-altitude climate change",2012,"10.1007/s00704-012-0687-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870390932&doi=10.1007%2fs00704-012-0687-x&partnerID=40&md5=6ad8a2c773f481444854e543435a30e9","In the present article, monthly mean temperature at 56 stations assembled in 18 regional groups in 10 major mountain ranges of the world were investigated. The periods of the analysis covered the last 50 to 110 years. The author found that the variability of temperature in climatic time scale tends to increase with altitude in about 65 % of the regional groups. A smaller number of groups, 20 %, showed the fastest change at an intermediate altitude between the peaks (or ridges) and their foot, while the remaining small number of sites, 15 %, showed the largest trends at the foot of mountains. This tendency provides a useful base for considering and planning the climate impact evaluations. The reason for the amplification of temperature variation at high altitudes is traced back to the increasing diabatic processes in the mid- and high troposphere as a result of the cloud condensation. This situation results from the fact that the radiation balance at the earth's surface is transformed more efficiently into latent heat of evaporation rather than sensible heat, the ratio between them being 4 to 1. Variation in the surface evaporation is converted into heat upon condensation into cloud particles and ice crystals in the mid- and high troposphere. Therefore, this is the altitude where the result of the surface radiation change is effectively transferred. Further, the low temperature of the environment amplifies the effect of the energy balance variation on the surface temperature, as a result of the functional shape of Stefan-Boltzmann law. These processes altogether contribute to enhancing temperature variability at high altitudes. The altitude plays an important role in determining the temperature variability, besides other important factors such as topography, surface characteristics, cryosphere/temperature feedback and the frequency and intensity of an inversion. These processes have a profound effect not only on the ecosystem but also on glaciers and permafrost. © 2012 Springer-Verlag."
"53663829700;8517509300;55476664600;36020828900;12762440500;","Observation of compact intracloud discharges using VHF broadband interferometers",2012,"10.1029/2011JD016185","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862973185&doi=10.1029%2f2011JD016185&partnerID=40&md5=e522eb25458780b433c4dc379ed46219","Compact intracloud discharge (CID) is a distinct intracloud lightning discharge characterized by strong VHF emissions, and it is one of the most mysterious lightning events. In this paper the CID channel evolution images obtained by using VHF broadband interferometers are presented for the first time. Analysis of 11 CIDs shows that the channels of CIDs develop mainly in a vertical direction. The vertical scale of CIDs is in the range of 0.40-1.9km. The average duration of VHF broadband emissions is 15 μs. The average apparent speed of CIDs is in a range of 0.44-1.0 × 108m/s with a mean value of 0.61 × 108m/s. The temporal-spatial evolution of the radiation sources of the CID shows an oscillation pattern, confirming the previous prediction that there is an oscillating current being reflected at the two ends of the CID channel. The estimated speed of the current wave in the CID channel is in a range of 0.56-2.6 × 108m/s with a mean value of 1.4 × 108m/s. Copyright 2012 by the American Geophysical Union."
"25031297200;7005978899;56110085900;55342796500;","Dominant modes of Diurnal Temperature Range variability over Europe and their relationships with large-scale atmospheric circulation and sea surface temperature anomaly patterns",2012,"10.1029/2011JD016669","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865325125&doi=10.1029%2f2011JD016669&partnerID=40&md5=a57580f6e1b8306474defe36290dcb89","The relationships between the dominant modes of interannual variability of Diurnal Temperature Range (DTR) over Europe and large-scale atmospheric circulation and sea surface temperature anomaly fields are investigated through statistical analysis of observed and reanalysis data. It is shown that the dominant DTR modes as well as their relationship with large-scale atmospheric circulation and sea surface temperature anomaly fields are specific for each season. During winter the first and second modes of interannual DTR variability are strongly related with the North Atlantic Oscillation and the Scandinavian pattern, while the third mode is related with the Atlantic Multidecadal Oscillation. Strong influence of the Atlantic Multidecadal Oscillation and the Arctic Oscillation on spring DTR modes of variability was also detected. During summer the DTR variability is influenced mostly by a blocking-like pattern over Europe, while the autumn DTR variability is associated with a wave train like pattern, which develops over the Atlantic Ocean and extends up to Siberia. It is also found that the response of DTR to global sea surface temperature is much weaker in spring and summer comparing to winter and autumn. A correlation analysis reveals a strong relationship between DTR modes of variability and the Cloud Cover anomalies during all seasons. The influence of the potential evapotranspiration and precipitation anomalies on DTR modes of variability is strongest during summer, but it is significant also in spring and autumn. It is suggested that a large part of interannual to decadal DTR variability over Europe is induced by the large-scale climate anomaly patterns via modulation of cloud cover, precipitation and potential evapotranspiration anomaly fields. © 2012. American Geophysical Union. All Rights Reserved."
"56693865600;37053783400;56659542700;","Variations in diurnal temperature range over India: Under global warming scenario",2012,"10.1029/2011JD016697","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856599532&doi=10.1029%2f2011JD016697&partnerID=40&md5=e255ac38710f1056ec58100dd34496ee","Annual, seasonal, and monthly trends in surface air temperature were examined over India during the period 1901-2003. Besides this, annual and seasonal trends were also scrutinized in view of global warming concerns during the 2 non-global (1901-1909 and 1946-1975) and global (1910-1945 and 1976-2003) warming periods as defined by Intergovernmental Panel on Climate Change. A significant increasing trend of 0.743, 0.224, 0.484, and 0.52C (100yr) -1 has been observed in maximum (T<inf>max</inf>), minimum (T <inf>min</inf>), mean (T<inf>mean</inf>) temperatures, and diurnal temperature range (DTR; T<inf>max</inf> - T<inf>min</inf>), respectively during the period 1901-2003. The annual temperatures (T<inf>mean</inf>, T<inf>min</inf>, and T<inf>max</inf>) show a cooling (warming) tendency during the non-global (global) warming periods, apart from the second non-global warming period of T<inf>max</inf>. The seasonal trends in T<inf>min</inf> and T<inf>mean</inf> also show similar behavior; whereas, T<inf>max</inf> shows warming in all sub-periods, excluding the first non-global warming period of the pre-monsoon and monsoon. Seasonal analysis depicts that, both post-monsoon and winter seasons are getting warmer with regard to T<inf>max</inf> and T<inf>min</inf>. During the analysis as well as in non-global and global warming periods, annual DTR has increased. DTR increases in all seasons, with the largest increase in winter and the smallest in post-monsoon; whereas monthly analysis reveals that all the months, except March, October, and November are contributing significantly to the annual increase of DTR. The partial correlation analysis reveals that the total cloud cover along with the secondary factors like precipitation and soil-moisture are responsible for increase in DTR over India during the period 1948-2003. Copyright 2012 by the American Geophysical Union."
"22936054800;25649651700;7004480520;6701751765;","Gravity waves, cold pockets and CO2 clouds in the Martian mesosphere",2012,"10.1029/2011GL050343","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856138054&doi=10.1029%2f2011GL050343&partnerID=40&md5=a19f69a58f287af3551681fb0f78d926","Many independent measurements have shown that extremely cold temperatures are found in the Martian mesosphere. These mesospheric ""cold pockets"" may result from the propagation of atmospheric waves. Recent observational achievements also hint at such cold pockets by revealing mesospheric clouds formed through the condensation of CO2, the major component of the Martian atmosphere. Thus far, modeling studies addressing the presence of cold pockets in the Martian mesosphere have explored the influence of large-scale circulations. Mesoscale phenomena, such as gravity waves, have received less attention. Here we show through multiscale meteorological modeling that mesoscale gravity waves could play a key role in the formation of mesospheric cold pockets propitious to CO2 condensation. © 2012 by the American Geophysical Union."
"54894018200;23981063100;6506545080;7203034123;57193132723;6603263640;42062523800;8511991900;","Analysis of cloud-resolving simulations of a tropical mesoscale convective system observed during TWP-ICE: Vertical fluxes and draft properties in convective and stratiform regions",2012,"10.1029/2012JD017759","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867226652&doi=10.1029%2f2012JD017759&partnerID=40&md5=faa40feb90577793cdc19d17b653ccb7","We analyze three cloud-resolving model simulations of a strong convective event observed during the TWP-ICE campaign, differing in dynamical core, microphysical scheme or both. Based on simulated and observed radar reflectivity, simulations roughly reproduce observed convective and stratiform precipitating areas. To identify the characteristics of convective and stratiform drafts that are difficult to observe but relevant to climate model parameterization, independent vertical wind speed thresholds are calculated to capture 90% of total convective and stratiform updraft and downdraft mass fluxes. Convective updrafts are fairly consistent across simulations (likely owing to fixed large-scale forcings and surface conditions), except that hydrometeor loadings differ substantially. Convective downdraft and stratiform updraft and downdraft mass fluxes vary notably below the melting level, but share similar vertically uniform draft velocities despite differing hydrometeor loadings. All identified convective and stratiform downdrafts contain precipitation below ∼10 km and nearly all updrafts are cloudy above the melting level. Cold pool properties diverge substantially in a manner that is consistent with convective downdraft mass flux differences below the melting level. Despite differences in hydrometeor loadings and cold pool properties, convective updraft and downdraft mass fluxes are linearly correlated with convective area, the ratio of ice in downdrafts to that in updrafts is ∼0.5 independent of species, and the ratio of downdraft to updraft mass flux is ∼0.5-0.6, which may represent a minimum evaporation efficiency under moist conditions. Hydrometeor loading in stratiform regions is found to be a fraction of hydrometeor loading in convective regions that ranges from ∼10% (graupel) to ∼90% (cloud ice). These findings may lead to improved convection parameterizations. © 2012. American Geophysical Union. All Rights Reserved."
"55729666100;16230926400;14024872700;6603174102;7003638602;7006593624;7004862277;","The deposition ice nucleation and immersion freezing potential of amorphous secondary organic aerosol: Pathways for ice and mixed-phase cloud formation",2012,"10.1029/2012JD018063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865746763&doi=10.1029%2f2012JD018063&partnerID=40&md5=24994bfa4803badd568cecc3a050d0be","Secondary organic aerosol (SOA) generated from the oxidation of organic gases are ubiquitous in the atmosphere, but their interaction with water vapor and their ice cloud formation potential at low temperatures remains highly uncertain. We report on onset conditions of water uptake and ice nucleation by amorphous SOA particles generated from the oxidation of naphthalene with OH radicals. Water uptake above 230K was governed by the oxidation level of the SOA particles expressed as oxygen-to-carbon (O/C) ratio, followed by moisture-induced phase transitions and immersion freezing. For temperatures from 200 to 230K, SOA particles nucleated ice via deposition mode from supersaturated water vapor independent of O/C ratio at relative humidity with respect to ice (RH<inf>ice</inf>) ∼10-15% below homogeneous ice nucleation limits. The glass transition temperature (T<inf>g</inf>) for the amorphous SOA particles was derived as a function of two parameters: (1) relative humidity (RH) with respect to water and (2) oxidation level of the SOA. The data show that particle phase and viscosity govern the particles' response to temperature and RH and provide a straightforward interpretation for the observed different heterogeneous ice nucleation pathways and water uptake by the laboratory-generated SOA and field-collected particles. Since SOA particles undergo glass transitions, these observations suggest that atmospheric SOA are potentially important for ice cloud formation and climate. © 2012. American Geophysical Union. All Rights Reserved."
"7103291287;35569458500;7404747615;54952648300;39262689400;6602087140;36608374800;7103197731;6602914876;15926468600;55684491100;7202344707;7003275916;57200275591;23485892500;9744189300;35566542600;57204987677;7102805852;7102569944;","Operational prediction of ash concentrations in the distal volcanic cloud from the 2010 Eyjafjallajkull eruption",2012,"10.1029/2011JD016790","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855654871&doi=10.1029%2f2011JD016790&partnerID=40&md5=c67156be9b4d981a2b9480973a00da51","During the 2010 eruption of Eyjafjallajkull, improvements were made to the modeling procedure at the Met Office, UK, enabling peak ash concentrations within the volcanic cloud to be estimated. In this paper we describe the ash concentration forecasting method, its rationale and how it evolved over time in response to new information and user requirements. The change from solely forecasting regions of ash to also estimating peak ash concentrations required consideration of volcanic ash emission rates, the fraction of ash surviving near-source fall-out, and the relationship between predicted mean and local peak ash concentrations unresolved by the model. To validate the modeling procedure, predicted peak ash concentrations are compared against observations obtained by ground-based and research aircraft instrumentation. This comparison between modeled and observed peak concentrations highlights the many sources of error and the uncertainties involved. Despite the challenges of predicting ash concentrations, the ash forecasting method employed here is found to give useful guidance on likely ash concentrations. Predicted peak ash concentrations lie within about one and a half orders of magnitude of the observed peak concentrations. A significant improvement in the agreement between modeled and observed values is seen if a buffer zone, accounting for positional errors in the predicted ash cloud, is used. Sensitivity of the predicted ash concentrations to the source properties (e.g., the plume height and the vertical distribution of ash at the source) is assessed and in some cases, seemingly minor uncertainties in the source specification have a large effect on predicted ash concentrations. Copyright 2012 by the American Geophysical Union."
"7003928082;7101899854;7103294028;35203432500;57189346402;7005399437;35463545000;7004248170;23053320400;56158622800;7409080503;57138743300;","An assessment of the surface longwave direct radiative effect of airborne dust in Zhangye, China, during the Asian Monsoon Years field experiment (2008)",2012,"10.1029/2011JD017370","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864046000&doi=10.1029%2f2011JD017370&partnerID=40&md5=6bd1b3ec8ec42cbd411501007f0d37b3","In April-June 2008, NASA Goddard's ground-based mobile laboratories (SMART-COMMIT) were deployed to Zhangye China (39.0°N; 101°W) to support the Asian Monsoon Years field experiment and the East Asian Study of Tropospheric Aerosols and Impact on Regional Climate. One of the primary objectives at Zhangye, a semi-arid region located between the Taklimakan and Gobi Deserts, was to capture and characterize dust aerosols near the source and to quantify their direct radiative effects (DRE). A regional dust optical model was constructed by combining previously measured soil mineralogy data at Zhangye with COMMIT's particle microphysical measurements. During a 2-week period of heightened dust activity, retrieved longwave (LW) aerosol optical thickness (τ) from SMART's Atmospheric Emitted Radiance Interferometer was used in the Fu-Liou radiative transfer model to derive LW instantaneous DRE (DRELW) at the surface, top of atmosphere, and heating rate profiles for cloud-free conditions. Conservatively, surface instantaneous DRELW and LW forcing efficiency range from about 2-20 Wm-2 and 31-35 Wm-2τ-1 (0 ≤ τ ≤ 0.83), respectively. The significance of DRELW relative to its shortwave counterpart was estimated to be between 51 and 58%, but of opposite sign, partly compensating shortwave surface cooling. Compared to Saharan dust observed during the NAMMA-2006 field experiment at Cape Verde, dust LW forcing efficiency for this study was found to be a factor of two larger stemming from differences in environmental and surface conditions, aerosol absorption, and Zhangye's close proximity to major desert sources. Relative to observed and modeled ranges in surface DRELW for clouds (-30-80 Wm-2) and greenhouse gases (-2 Wm-2), this study's upper range in DRELW represents a significant perturbation to the climate system with important implications for better understanding regional changes in surface temperatures and moisture budgets. © 2012. American Geophysical Union."
"7003291328;23668415500;6701380032;7403906746;","Recent advances in global electric circuit coupling between the space environment and the troposphere",2012,"10.1016/j.jastp.2012.03.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876170685&doi=10.1016%2fj.jastp.2012.03.015&partnerID=40&md5=49852f4a0c6d0ffeaa52880719e24939","The global atmospheric electric circuit is driven by thunderstorms and electrified rain/shower clouds and is also influenced by energetic charged particles from space. The global circuit maintains the ionosphere as an equipotential at~+250 kV with respect to the good conducting Earth (both land and oceans). Its ""load""is the fair weather atmosphere and semi-fair weather atmosphere at large distances from the disturbed weather ""generator""regions. The main solar-terrestrial (or space weather) influence on the global circuit arises from spatially and temporally varying fluxes of galactic cosmic rays (GCRs) and energetic electrons precipitating from the magnetosphere. All components of the circuit exhibit much variability in both space and time. Global circuit variations between solar maximum and solar minimum are considered together with Forbush decrease and solar flare effects. The variability in ion concentration and vertical current flow are considered in terms of radiative effects in the troposphere, through infra-red absorption, and cloud effects, in particular possible cloud microphysical effects from charging at layer cloud edges. The paper identifies future research areas in relation to Task Group 4 of the Climate and Weather of the Sun-Earth System (CAWSES-II) programme. © 2012 Elsevier Ltd."
"36008940000;6602926744;7003455444;","Local and large-scale atmospheric responses to reduced Arctic sea ice and ocean warming in the WRF model",2012,"10.1029/2011JD016969","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862299151&doi=10.1029%2f2011JD016969&partnerID=40&md5=1a0c0d21cd79aae0cb88c6c8a7d17349","The Weather Research and Forecasting (WRF) model is used to explore the sensitivity of the large-scale atmospheric energy and moisture budgets to prescribed changes in Arctic sea ice and sea surface temperatures (SSTs). Observed sea ice fractions and SSTs from 1996 and 2007, representing years of high and low sea ice extent, are used as lower boundary conditions. A pan-Arctic domain extending into the North Pacific and Atlantic Oceans is used. ERA-Interim reanalysis data from 1994 to 2008 are employed as initial and lateral forcing data for each high and low sea ice simulation. The addition of a third ensemble, with a mixed SST field between years 1996 and 2007 (using 2007 SSTs above 66N and 1996 values below), results in a total of three 15-member ensembles. Results of the simulations show both local and remote responses to reduced sea ice. The local polar cap averaged response is largest in October and November, dominated by increased turbulent heat fluxes resulting in vertically deep heating and moistening of the Arctic atmosphere. This warmer and moister atmosphere is associated with an increase in cloud cover, affecting the surface and atmospheric energy budgets. There is an enhancement of the hydrologic cycle, with increased evaporation in areas of sea ice loss paired with increased precipitation. Most of the Arctic climate response results from within-Arctic changes, although some changes in the hydrologic cycle reflect circulation responses to midlatitude SST forcing, highlighting the general sensitivity of the Arctic climate. © 2012 American Geophysical Union. All Rights Reserved."
"7003931528;57208121852;","Assessment of black carbon radiative effects in climate models",2012,"10.1002/wcc.180","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863843829&doi=10.1002%2fwcc.180&partnerID=40&md5=0479e81cd214d6564f9b18e0712cf9b3","Black carbon (BC) from the burning of fossil fuel and biomass absorbs solar radiation and might intensify the greenhouse gas warming. Therefore, ideas to combat climate warming by reducing black carbon emissions emerged. However, black carbon emissions are generally accompanied by co-emission of other aerosols that predominantly scatter and have a cooling effect, so that the net forcing is substantially smaller, reducing mitigation potentials. Moreover, indirect effects on clouds are likely to exert additional cooling. As in situ measurements do not sufficiently sample the global atmosphere and satellite data does not provide the necessary detail on aerosol absorption, our only tools to estimate the effect of mitigation are numerical climate models. A review of current model estimates of black carbon radiative effects gives an average estimate of the direct radiative forcing as +0.33 W/m2, indirect effects of -0.11 W/m2 and through BC deposition on snow/ice surfaces of about +0.05 W/m2. A key limitation of these estimates is that the numerical models required for their global quantification are insufficiently constrained by observations. In addition, the comparison of instantaneous forcings generally overestimates the relative importance of black carbon and policy makers should consider alternative metrics, incorporating time-horizons. © 2012 John Wiley &amp; Sons, Inc.."
"12144198300;37087012900;6701729202;","A comparison of the atmospheric conditions at Eureka, Canada, and Barrow, Alaska (2006-2008)",2012,"10.1029/2011JD017164","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863005552&doi=10.1029%2f2011JD017164&partnerID=40&md5=97218a3803f2ad3507fd504b03399abe","It is now well understood that the Arctic is particularly sensitive to climate change. Arctic sea ice is already undergoing significant changes. Some of the recent decrease in sea ice extent is due to changes in the surface energy budget, including the effect of clouds. Accurate ground-based measurements of atmospheric and cloud properties are valuable for estimating components of the surface energy budget. In this paper, measurements made between 2006 and 2008 at the Canadian Network for the Detection of Arctic Change (CANDAC) site at Eureka, Nunavut, Canada (80°N, 86°W) and the Atmospheric Radiation Measurement (ARM) program site at Barrow, Alaska (71°N, 156°W) are used to examine differences in the atmospheres over the two sites, including the temperature, humidity, winds, and the downwelling longwave radiation flux. A method is developed to convert infrared radiances to downwelling longwave fluxes since broadband measurements of flux were not available at Eureka during the study period; the method is validated by comparing the fluxes at Barrow to independent measurements made by a pyrgeometer. Comparisons of the derived fluxes show significant differences between the two sites. Eureka is consistently colder and drier than Barrow, and the infrared effect of clouds on the surface energy budget is less. To examine the meteorological conditions that cause such differences, the ERA-Interim reanalysis model is used; it is chosen over other models because it provides the best reproduction of longwave radiation at the surface. We find that the location of Eureka predisposes it to cold and dry air masses from the central Arctic Ocean and the Greenland Ice Sheet. In contrast, the air masses at Barrow come from a variety of directions, some of which are relatively warm and moist. © 2012 American Geophysical Union. All Rights Reserved."
"20433821100;6602859094;7402331557;7402590762;7102389501;7003468747;","Inclusion of sea-surface temperature variation in the U.S. Navy ensemble-transform global ensemble prediction system",2012,"10.1029/2011JD016937","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867636719&doi=10.1029%2f2011JD016937&partnerID=40&md5=c434cbb5339abdaf5c3bc74e1c61575b","The local ensemble transform (ET) analysis perturbation scheme is adapted to generate perturbations to both atmospheric variables and sea-surface temperature (SST). The adapted local ET scheme is used in conjunction with a prognostic model of SST diurnal variation and the Navy Operational Global Atmospheric Prediction System (NOGAPS) global spectral model to generate a medium-range forecast ensemble. When compared to a control ensemble, the new forecast ensemble with SST variation exhibits notable differences in various physical properties including the spatial patterns of surface fluxes, outgoing longwave radiation (OLR), cloud radiative forcing, near-surface air temperature and wind speed, and 24-h accumulated precipitation. The structure of the daily cycle of precipitation also is substantially changed, generally exhibiting a more realistic midday peak of precipitation. Diagnostics of ensemble performance indicate that the inclusion of SST variation is very favorable to forecasts in the Tropics. The forecast ensemble with SST variation outscores the control ensemble in the Tropics across a broad set of metrics and variables. The SST variation has much less impact in the Midlatitudes. Further comparison shows that SST diurnal variation and the SST analysis perturbations are each individually beneficial to the forecast from an overall standpoint. The SST analysis perturbations have broader benefit in the Tropics than the SST diurnal variation, and inclusion of the SST analysis perturbations together with the SST diurnal variation is essential to realize the greatest gains in forecast performance. © 2012. American Geophysical Union. All Rights Reserved."
"54384916300;7003460432;","A physics-based correction model for homogenizing sub-daily temperature series",2012,"10.1029/2012JD018067","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866713762&doi=10.1029%2f2012JD018067&partnerID=40&md5=12bdc5b98e832dd5674d6ed4e2cd9e52","A new physics-based technique for correcting inhomogeneities present in sub-daily temperature records is proposed. The approach accounts for changes in the sensor-shield characteristics that affect the energy balance dependent on ambient weather conditions (radiation, wind). An empirical model is formulated that reflects the main atmospheric processes and can be used in the correction step of a homogenization procedure. The model accounts for short- and long-wave radiation fluxes (including a snow cover component for albedo calculation) of a measurement system, such as a radiation shield. One part of the flux is further modulated by ventilation. The model requires only cloud cover and wind speed for each day, but detailed site-specific information is necessary. The final model has three free parameters, one of which is a constant offset. The three parameters can be determined, e.g., using the mean offsets for three observation times. The model is developed using the example of the change from the Wild screen to the Stevenson screen in the temperature record of Basel, Switzerland, in 1966. It is evaluated based on parallel measurements of both systems during a sub-period at this location, which were discovered during the writing of this paper. The model can be used in the correction step of homogenization to distribute a known mean step-size to every single measurement, thus providing a reasonable alternative correction procedure for high-resolution historical climate series. It also constitutes an error model, which may be applied, e.g., in data assimilation approaches. © 2012. American Geophysical Union. All Rights Reserved."
"12808494200;56234518300;6701507764;35273334200;7006630889;","Diagnostic tools for evaluating quasi-horizontal transport in global-scale chemistry models",2012,"10.1029/2012JD017644","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867212724&doi=10.1029%2f2012JD017644&partnerID=40&md5=008fab681ebfcb0f65a85688021281ab","The upper troposphere and lower stratosphere (UTLS) plays an important role in climate and atmospheric chemistry. Despite its importance on the point of causing deep intrusions of tropics originated air into the midlatitudes, the quasi-horizontal transport process in the UTLS, represented by global chemistry-transport models (CTMs) or chemistry-climate models (CCMs), cannot easily be diagnosed with conventional analyses on isobaric surfaces. We use improved diagnostic tools to better evaluate CTMs and CCMs relative to satellite observations in the region of UTLS. Using the Hellinger distance, vertical profiles of probability density functions (PDFs) of chemical tracers simulated by the Model for OZone And Related chemical Tracers 3.1 (MOZART-3.1) are quantitatively compared with satellite data from the Microwave Limb Sounder (MLS) instrument in the tropopause relative altitude coordinate to characterize features of tracer distributions near the tropopause. Overall, the comparison of PDFs between MLS and MOZART-3.1 did not satisfy the same population assumption. Conditional PDFs are used to understand the meteorological differences between global climate models and the real atmosphere and the conditional PDFs between MOZART-3.1 and MLS showed better agreement compared to the original PDFs. The low static stability during high tropopause heights at midlatitudes suggests that the variation of tropopause height is related to transport processes from the tropics to midlatitudes. MOZART-3.1 with the GEOS4 GCM winds reproduces episodes of the tropical air intrusions. However, our diagnostic analyses show that the GEOS4 GCM did not properly reproduce the high tropopause cases at midlatitudes especially in spring. © 2012. American Geophysical Union. All Rights Reserved."
"7403364008;55916925700;6603711967;39262305900;7005110573;57213743966;","The changing radiative forcing of fires: Global model estimates for past, present and future",2012,"10.5194/acp-12-10857-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869008836&doi=10.5194%2facp-12-10857-2012&partnerID=40&md5=5af2444e6cb802229b8be7edbeb65555","Fires are a global phenomenon that impact climate and biogeochemical cycles, and interact with the biosphere, atmosphere and cryosphere. These impacts occur on a range of temporal and spatial scales and are difficult to quantify globally based solely on observations. Here we assess the role of fires in the climate system using model estimates of radiative forcing (RF) from global fires in pre-industrial, present day, and future time periods. Fire emissions of trace gases and aerosols are derived from Community Land Model simulations and then used in a series of Community Atmosphere Model simulations with representative emissions from the years 1850, 2000, and 2100. Additional simulations are carried out with fire emissions from the Global Fire Emission Database for a present-day comparison. These results are compared against the results of simulations with no fire emissions to compute the contribution from fires. We consider the impacts of fire on greenhouse gas concentrations, aerosol effects (including aerosol effects on biogeochemical cycles), and land and snow surface albedo. Overall, we estimate that pre-industrial fires were responsible for a RF of g-1 W mg-2 with respect to a pre-industrial climate without fires. The largest magnitude pre-industrial forcing from fires was the indirect aerosol effect on clouds (g-1.6 W mg-2). This was balanced in part by an increase in carbon dioxide concentrations due to fires (+0.83 W mg-2). The RF of fires increases by 0.5 W mg-2 from 1850 to 2000 and 0.2 W mg-2 from 1850 to 2100 in the model representation from a combination of changes in fire activity and changes in the background environment in which fires occur, especially increases and decreases in the anthropogenic aerosol burden. Thus, fires play an important role in both the natural equilibrium climate and the climate perturbed by anthropogenic activity and need to be considered in future climate projections. © 2012 Author(s)."
"7404240633;8213069900;57189084438;55742840200;","Parameterization of instantaneous global horizontal irradiance: Cloudy-sky component",2012,"10.1029/2012JD017557","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864624805&doi=10.1029%2f2012JD017557&partnerID=40&md5=f47ec9bc6a22587af6a40f2703680939","[1] Radiation calculations in global numerical weather prediction (NWP) and climate models are usually conducted in 3-hourly time interval in order to reduce the computational cost. This treatment can lead to an incorrect solar radiation at the Earth's surface which could be one of the error sources in modeled convection and precipitation. In order to improve the simulation of the diurnal cycle of solar radiation a fast scheme has been developed based on detailed radiative transfer calculations for a wide range of atmospheric conditions and can be used to determine the surface solar radiation at each model integration time step with affordable costs. This scheme is divided into components for clear-sky and cloudy-sky conditions. The clear-sky component has been described in a companion paper. The cloudy-sky component is introduced in this paper. The input variables required by this scheme are all available in NWP and climate models or can be obtained from satellite observations. Therefore, the scheme can be used in a global model to determine the surface GHI. It can also be used as an offline scheme to calculate the surface GHI using data from satellite measurements. SUNFLUX scheme has been tested using observations obtained from three Atmospheric Radiation Measurements (ARM) stations established by the U. S. Department of Energy. The results show that a half hourly mean relative error of GHI under all-sky conditions is less than 7%. An important application of the scheme is in global climate models. The radiation sampling error due to infrequent radiation calculations is investigated using the SUNFLUX and ARM observations. It is found that errors in the surface net solar irradiance are very large, exceeding 800 W m-2 at many non-radiation time steps due to ignoring the effects of clouds. Use of the SUNFLUX scheme can reduce these errors to less than 50 W m-2. © 2012. American Geophysical Union."
"7004046707;36538539800;13405425900;55831981100;","Development of an extended chemical mechanism for global- through-urban applications",2012,"10.5094/APR.2011.047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870863225&doi=10.5094%2fAPR.2011.047&partnerID=40&md5=e3e35f2f2611b34d4ad89cbb4b45ea03","The interactions between climate and air quality are receiving increasing attention due to their high relevancy to climate change. Coupled climate and air quality models are being developed to study these interactions. These models need to address the transport and chemistry of atmospheric species over a large range of scales and atmospheric conditions. In particular, the chemistry mechanism is a key component of such models because it needs to include the relevant reactions to simulate the chemistry of the lower troposphere, the upper troposphere, and the lower stratosphere, as well as the chemistry of polluted, rural, clean, and marine environments. This paper describes the extension of an existing chemistry mechanism for urban/regional applications, the 2005 version of the Carbon Bond Mechanism (CB05), to include the relevant atmospheric chemistry for global and global-through-urban applications. Updates to the mechanism include the most important gas-phase reactions needed for the lower stratosphere as well as reactions involving mercury species, and a number of heterogeneous reactions on aerosol particles, cloud droplets, and Polar Stratospheric Clouds (PSCs). The extended mechanism, referred to as CB05 for Global Extension (CB05_GE), is tested for a range of atmospheric conditions using a zero-dimensional box-model. A comparison of results from the extended mechanism with those from the original starting mechanism for both clean and polluted conditions in the lower troposphere shows that the extended mechanism preserves the fidelity of the original mechanism under those conditions. Simulations of marine Arctic conditions, upper tropospheric conditions, and lower stratospheric conditions with the box model illustrate the importance of halogen chemistry and heterogeneous reactions (on aerosol surfaces as well as PSCs for stratospheric conditions) for predicting ozone and elemental mercury depletion events that are often observed during these conditions. Depletions that are comparable to observed depletions are predicted by the box model for very clean conditions (extremely low or zero concentrations of aldehydes and other VOCs) because, in the absence of continuous sources of active halogens, these conditions result in less conversion of active chlorine and bromine to more stable products, such as HCl and HBr. © Author(s) 2012."
"7005304841;7102188656;57217900818;7005228425;55742914900;7501627905;","Sub-micrometer aerosol particles in the upper troposphere/lowermost stratosphere as measured by CARIBIC and modeled using the MIT-CAM3 global climate model",2012,"10.1029/2011JD016777","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861946945&doi=10.1029%2f2011JD016777&partnerID=40&md5=fd8614efefcec794fd5dd3438df8dae1","In this study, we compare modeled (MIT-CAM3) and observed (CARIBIC) sub-micrometer nucleation (N<inf>4-12</inf>, 4 d 12 nm) and Aitken mode (N <inf>12</inf>, d > 12 nm) particle number concentrations in the upper troposphere and lowermost stratosphere (UT/LMS). Modeled and observed global median N<inf>4-12</inf> and N<inf>12</inf> agree fairly well (within a factor of two) indicating that the relatively simplified binary H<inf>2</inf>SO <inf>4</inf>-H<inf>2</inf>O nucleation parameterization applied in the model produces reasonable results in the UT/LMS. However, a comparison of the spatiotemporal distribution of sub-micrometer particles displays a number of discrepancies between MIT-CAM3 and CARIBIC data: N<inf>4-12</inf> is underestimated by the model in the tropics and overestimated in the extra-topics. N<inf>12</inf> is in general overestimated by the model, in particular in the tropics and during summer months. The modeled seasonal variability of N<inf>4-12</inf> is in poor agreement with CARIBIC data whereas it agrees rather well for N<inf>12</inf>. Modeled particle frequency distributions are in general narrower than the observed ones. The model biases indicate an insufficient diffusive mixing in MIT-CAM3 and a too large vertical transport of carbonaceous aerosols. The overestimated transport is most likely caused by the constant supersaturation threshold applied in the model for the activation of particles into cloud droplets. The annually constant SO <inf>2</inf> emissions in the model may also partly explain the poor representation of the N<inf>4-12</inf> seasonal cycle. Comparing the MIT-CAM3 with CARIBIC data, it is also clear that care has to be taken regarding the representativeness of the measurement data and the time frequency of the model output. Copyright 2012 by the American Geophysical Union."
"6603816167;26023140500;22133985200;35171227800;6602215448;55879681300;","Characterization of the Eyjafjallajökull ash-plume: Potential of lidar remote sensing",2012,"10.1016/j.pce.2011.01.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863781576&doi=10.1016%2fj.pce.2011.01.006&partnerID=40&md5=c0a67f91230f8113f9262d0eaeeb999a","Observations of the dispersion of volcanic ash clouds and their optical and microphysical characterization are essential for climate research and air traffic. This became obvious during the Eyjafjallajökull-eruption in April 2010. In this paper we report on continuous measurements with two EARLINET Raman- and depolarization lidars conducted at Maisach close to Munich, Germany. By means of range corrected signals the temporal development of the ash-plume could be documented in near real-time. They confirmed results from a chemistry transport model (MCCM). The optical characterization includes the backscatter coefficient at three wavelengths, and the extinction coefficient and particle linear depolarization ratio at two. The maximum extinction coefficient of the ash layer over Maisach was 0.75km -1 and wavelength independent, the particle linear depolarization ratio was about 37%. This is a strong indication of large non-spherical particles. An inversion of the optical data derived from the lidar measurements led to a maximum mass concentration of approximately 1.1mgm -3 over Maisach. As a consequence of the ambiguity of the inversion process and measurement-errors, relative uncertainties are between 30% and 50%. © 2011 Elsevier Ltd."
"7402934750;6506666311;6505921698;6602513845;","Impact of modifying the longwave water vapor continuum absorption model on community Earth system model simulations",2012,"10.1029/2011JD016440","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857710455&doi=10.1029%2f2011JD016440&partnerID=40&md5=dd65afeec664cfc604c37e83d1d6b8aa","The far-infrared (wavelengths longer than 17 μm) has been shown to be extremely important for radiative processes in the earth's atmosphere. The strength of the water vapor continuum absorption in this spectral region has largely been predicted using observations at other wavelengths that have been extrapolated using semiempirical approaches such as the Clough-Kneizys-Davies (CKD) family of models. Recent field experiments using new far-infrared instrumentation have supported a factor of 2 decrease in the modeled strength of the foreign continuum at 50 μm and a factor of 1.5 increase in the self-continuum at 24 μm in the Clough-Kneizys-Davies continuum model (CKD v2.4); these changes are incorporated in the Mlawer-Tobin-CKD continuum model (MT-CKD v2.4). The water vapor continuum in the Community Earth System Model (CESM v1.0) was modified to use the newer model, and the impacts of this change were investigated by comparing output from the original and modified CESM for 20 year integrations with prescribed sea surface temperatures. The change results in an increase in the net upward longwave flux of order 0.5 W m-2 between 300 and 400 mb, and a decrease in this flux of about the same magnitude for altitudes below 600 mb. The radiative impact results in a small but statistically significant change in the mean temperature and humidity fields, and also a slight decrease (order 0.5%) of high-cloud amount. The change in the cloud amount modified the longwave cloud radiative forcing, which partially offset the radiative heating caused by the change in the water vapor continuum absorption model. Copyright © 2012 by the American Geophysical Union."
"55628525997;48361871200;55712637800;7404147955;7201737956;","Debates on the causes of global warming",2012,"10.3724/sp.j.1248.2012.00038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900013904&doi=10.3724%2fsp.j.1248.2012.00038&partnerID=40&md5=03724edb14daa486c30aaa770b723445","The controversy between the IPCC and Non-governmental IPCC (NIPCC) on the attribution of global warming are reviewed. IPCC holds that today's global warming is mainly due to anthropogenic activities rather than natural variability, which is emphasized by NIPCC. The surface temperature observations since the mid-20th century support the hypothesis of anthropogenic impact, but for the last one hundred years or so, natural forcings such as solar activity, volcanic eruptions and thermohaline circulation variations also have had great influences on the Earth's climate, especially on inter-decadal timescales. In addition, evidence suggests that the Medieval Warm Period (MWP) and Little Ice Age (LIA) are closely associated with the solar activity over the past 1 thousand years. Over the past 10 thousand years, the North Atlantic cold events and solar activity are closely correlated. Nevertheless, the physical mechanisms of the solar-climate variability and interrelation are not well understood, yet. Notably, a prevailing view recently indicates that galactic cosmic rays may result in climatic cooling through modulating global low cloud cover. However, its process and mechanism need to be further investigated."
"7006425629;7003942283;8859027300;55963215000;36150087800;26537798400;24080775500;6603577900;7202252296;55133620400;6603379483;7006954827;","Changing polar environments: Interdisciplinary challenges",2012,"10.1029/2012EO110001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858847363&doi=10.1029%2f2012EO110001&partnerID=40&md5=8b5dbc2c6d74c24c99c7f17a3f022b6d","In the past few decades, there has been enormous growth in scientific studies of physical, chemical, and biological interactions among reservoirs in polar regions. This has come, in part, as a result of a few significant discoveries: There is dramatic halogen chemistry that occurs on and above the sea ice in the springtime that destroys lower tropospheric ozone and mercury [Simpson et al., 2007; Steffen et al., 2008], the sunlit snowpack is very photochemically active [Grannas et al., 2007], biology as a source of organic compounds plays a pivotal role in these processes, and these processes are occurring in the context of rapidly changing polar regions under climate feedbacks that are as of yet not fully understood [Serreze and Barry, 2011]. Stimulated by the opportunities of the International Polar Year (IPY, 2007-2009), a number of large-scale field studies in both polar environments have been undertaken, aimed at the study of the complex biotic and abiotic processes occurring in all phases (see Figure 1). Sea ice plays a critical role in polar environments: It is a highly reflective surface that interacts with radiation; it provides a habitat for mammals and micro-organisms alike, thus playing a key role in polar trophic processes and elemental cycles; and it creates a saline environment for chemical processes that facilitate release of halogenated gases that contribute to the atmosphere's ability to photochemically cleanse itself in an otherwise low-radiation environment. Ocean-air and sea ice-air interfaces also produce aerosol particles that provide cloud condensation nuclei."
"22941176100;57209589566;6602187911;","An observational analysis of Southern Hemisphere tropical expansion",2012,"10.1029/2011JD017033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866334605&doi=10.1029%2f2011JD017033&partnerID=40&md5=fb23b7ae33b3f2255e925d29b28a6aa2","Historical radiosonde data are analyzed using the tropopause height frequency method to investigate the variation of the Southern Hemisphere tropical edge from 1979/80-2010/11, independently of reanalysis-derived data. Averaged across the hemisphere we identify a tropical expansion trend of 0.41 ± 0.37 deg dec-1, significant at the 90% level. A comparison with four reanalyses shows generally consistent results between radiosondes and reanalyses. Estimated rates of tropical expansion in the SH are broadly similar, as is the interannual variability. However, notable differences remain. Some of these differences are related to the methodology used to identify the height of the tropopause in the reanalyses, which produces inconsistent results in the subtropics. Differences between radiosondes and reanalyses are also more manifest in data-poor regions. In these regions, the reanalyses are not fully constrained, allowing the internal model dynamics to drive the variability. The performance of the reanalyses varies temporally compared to the radiosonde data. These differences are particularly apparent from 1979 to 1985 and from 2001 to 2010. In the latter period, we hypothesize that the increased availability and quality of satellite-based data improves the results from the ERA Interim reanalysis, creating an inconsistency with earlier data. This apparent inhomogeneity results in a tropical expansion trend in that product that is inconsistent with the radiosonde-based observations. These results confirm the need for careful evaluation of reanalysis-based data for use in studies of long-term climate variability. ©2012. American Geophysical Union. All Rights Reserved."
"7004169476;","Water vapor feedback in a small ensemble of GCMs: Two approaches",2012,"10.1029/2011JD017221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863492176&doi=10.1029%2f2011JD017221&partnerID=40&md5=f1acf286ff908da782d9a898e1621cc9","The clear-sky longwave component of the climate sensitivity parameter λCSLW is estimated for 5 diverse state-of-the-art general circulation models (GCMs). A common radiation code is used to calculate 2 alternative breakdowns. The conventional breakdown, into ""surface temperature feedback"", ""lapse rate feedback"" and ""water vapor feedback"" shows only the well-known result of large but mostly compensating variations in the latter two components, due to variations in the distribution of warming. In one GCM, λCSLW is rather stronger than the rest, tending to reduce the sensitivity of climate. The ""partly Simpsonian"" breakdown shows that this is because of a combination of having less water vapor to start with and less increase in water vapor around the tropopause on warming. Two GCMs show λCSLW rather weaker than the rest, because of weaker amplification of the warming aloft, in one case combined with stronger-than-average relative humidity increases. The net effect of greater lapse rate changes (proportionally more warming aloft) can be seen to tend consistently to reduce climate sensitivity slightly. Also, though the impact of relative humidity changes is dominated by reductions through most of the depth of the troposphere, its variation across GCMs is dominated by increases around the tropopause. While the results from so small a sample will not be quantitatively general, they suggest that applying the new breakdown to a much wider range of GCMs would give useful quantitative and physical information on the variation of λCSLW across current GCMs."
"24081888700;7004174939;8045690700;35585284200;13408938100;7005054220;6603081424;7402115506;57203386948;7404327420;","Aerosol indirect effect on tropospheric ozone via lightning",2012,"10.1029/2012JD017723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867201595&doi=10.1029%2f2012JD017723&partnerID=40&md5=bdf44b39f320a91e12c73d32fcf3018d","[1] Tropospheric ozone (O<inf>3</inf>) is a pollutant and major greenhouse gas and its radiative forcing is still uncertain. Inadequate understanding of processes related to O<inf>3</inf> production, in particular those natural ones such as lightning, contributes to this uncertainty. Here we demonstrate a new effect of aerosol particles on O<inf>3</inf> production by affecting lightning activity and lightning-generated NOx (LNOx). We find that lightning flash rate increases at a remarkable rate of 30 times or more per unit of aerosol optical depth. We provide observational evidence that indicates the observed increase in lightning activity is caused by the influx of aerosols from a volcano. Satellite data analyses show O<inf>3</inf> is increased as a result of aerosol-induced increase in lightning and LNOx, which is supported by modle simulations with prescribed lightning change. O<inf>3</inf> production increase from this aerosollightning- ozone link is concentrated in the upper troposphere, where O<inf>3</inf> is most efficient as a greenhouse gas. In the face of anthropogenic aerosol increase our findings suggest that lightning activity, LNOx and O<inf>3</inf>, especially in the upper troposphere, have all increased substantially since preindustrial time due to the proposed aerosol-lightning- ozone link, which implies a stronger O<inf>3</inf> historical radiative forcing. Aerosol forcing therefore has a warming component via its effect on O <inf>3</inf> production and this component has mostly been ignored in previous studies of climate forcing related to O<inf>3</inf> and aerosols. Sensitivity simulations suggest that 4-8% increase of column tropospheric ozone, mainly in the tropics, is expected if aerosol-lighting-ozone link is parameterized, depending on the background emission scenario. We note, however, substantial uncertainties remain on the exact magnitude of aerosol effect on tropospheric O<inf>3</inf> via lightning. The challenges for obtaining a quantitative global estimate of this effect are also discussed. Our results have significant implications for understanding past and projecting future tropospheric O <inf>3</inf> forcing as well as wildfire changes and call for integrated investigations of the coupled aerosol-cloud-chemistry system. © 2012. American Geophysical Union. All Rights Reserved."
"25647939800;56479782300;7102857642;","A comparison of the Madden-Julian Oscillation simulated by different versions of the MIROC climate model",2012,"10.2151/sola.2012-040","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919694568&doi=10.2151%2fsola.2012-040&partnerID=40&md5=2b4f3c3ee7b6d8b3c1dea3b69b08140c","A pair of 20-year simulations by two different versions of MIROC (Model for Interdisciplinary Research on Climate) was examined by using a standardized set of Madden-Julian Oscillation (MJO) diagnostics. One of the major differences between version 4 (MIROC4) and version 5 (MIROC5) of MIROC is the cumulus parameterization scheme. MIROC4 uses a prognostic Arakawa-Schubert scheme, whereas MIROC5 uses the Chikira scheme. MIROC5 reproduced the MJO better than MIROC4: a stronger signal in the wavenumber-frequency diagram, a slower and more noticeable eastward movement in the lag-correlation plot, and a better phase relationship between outgoing longwave radiation and zonal winds. To investigate the impact of mid-tropospheric humidity on cumulus development in MIROC5, the atmosphere-only version of MIROC5 was used for a series of sensitivity runs, each with different entrainment parameter values. The entrainment parameter settings significantly influenced the simulated MJO. Largescale cloud systems tended to move westward with smaller entrainment parameter values, accompanied by a pair of rotations with quasi-symmetry about the equator in the lower troposphere, whereas eastward movements were faster, with larger entrainment parameter values. © 2012, the Meteorological Society of Japan."
"8958009400;7102389805;35264351500;","Variability of aerosols in the tropical Atlantic Ocean relative to African Easterly Waves and their relationship with atmospheric and oceanic environments",2012,"10.1029/2011JD017181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865803281&doi=10.1029%2f2011JD017181&partnerID=40&md5=01fa46e88cea6b636d93b2506abe9f44","It is well known that aerosols impact climate directly through modifying the radiation budget and indirectly through the modification of cloud processes. Yet, in spite of an improved understanding of the various roles that aerosols play in climate, there still exists uncertainty in their spatial and temporal distributions and their relationship to atmospheric dynamic. Here, we use the Aerosol Index from the Total Ozone Mapping Spectrometer and Aerosol Optical Depth from the Moderate Resolution Imaging Spectroradiometer, in conjunction with atmospheric and oceanic satellite observations and reanalysis data sets to investigate aerosol-environment relationships and interactions over the tropical Atlantic Ocean. Spectral and composite analyses of surface temperature, atmospheric wind, geopotential height, outgoing longwave radiation and precipitation, together with the climatology of aerosols, provide insight on how the variables interact. Different modes of variability, especially on intraseasonal time scales, appear as strong modulators of the aerosol distribution. In particular, we investigate how two modes of variability related to westward propagating African Easterly Waves affect the horizontal and vertical structure of the environment and thus the aerosol distribution. The pattern of propagation of aerosol load shows a strong correspondence with the progression of the atmospheric and oceanic synoptic conditions that have mobilized dust over the African continent and advect it over the Atlantic Ocean. We extend previous studies related with dust variability over the Atlantic region by evaluating the performance of the long period satellite aerosol retrievals in determining modes of aerosol variability. Results of this work are described as useful in allowing a more precise understanding of the response of the energy budget, precipitation and atmospheric circulation to changes in aerosol loading. © 2012. American Geophysical Union. All Rights Reserved."
"55615716800;55878640000;","Changes of the connection between the summer North Atlantic Oscillation and the East Asian summer rainfall",2012,"10.1029/2012JD017482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860648431&doi=10.1029%2f2012JD017482&partnerID=40&md5=43d03834a8119d326a7537edf83ae5b8","In this study, the relationship between the summer North Atlantic Oscillation (SNAO) and the East Asian summer rainfall was statistically diagnosed based on the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-year and interim reanalysis data (ERA-40 and ERA-Interim) as well as precipitation data from the Global Precipitation Climatology Centre (GPCC). The results show that the decadal change of the SNAO pattern around the late 1970s significantly enhanced its connection with summer rainfall over central and northern East Asia. Over the period before the late 1970s, the SNAO-related circulations were dominant over the North Atlantic region. Consequently, there was a weak connection between the SNAO and the East Asian summer rainfall. However, over the period after the late 1970s, the SNAO pattern experienced a decadal change, with the southern center shifting eastward. Such changes in the SNAO pattern can alter the stationary wave activity over the Eurasian Continent, producing an anomalous meridional dipole pattern over East Asia. This dipole pattern can then change the divergence circulation, vertical motion, water vapor, and total cloud cover, which would consequently provide beneficial conditions for more (less) summer rainfall over central (northern) East Asia in a positive (negative)-phase SNAO year. Copyright 2012 by the American Geophysical Union."
"55716995500;35209683700;26324818700;","Feedback attribution of the El Nio-Southern Oscillation-related atmospheric and surface temperature anomalies",2012,"10.1029/2012JD018468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870612607&doi=10.1029%2f2012JD018468&partnerID=40&md5=7665f92c1416ec1792fa8fdf6282525a","A feedback attribution analysis is conducted for the ENSO-related atmospheric and surface temperature anomalies in boreal winter. Local temperature anomalies are decomposed into partial temperature changes due to changes in oceanic dynamics/heat storage, water vapor, clouds, atmospheric dynamics, ozone, and surface albedo. It is shown that atmospheric dynamics plays distinctly different roles in establishing the tropical and extratropical temperature response to El Nio. The atmospheric dynamics serves as a primary negative feedback to the tropical (tropospheric) warming by transporting out of the tropics excessive energy production associated with oceanic dynamical forcing. In the northern extratropics, it is the main forcing of atmospheric temperature changes and also modulates surface temperatures via longwave radiative heating and cooling. This provides an alternative view of the ""atmospheric bridge"" mechanism from the perspective of local energetics and temperature feedback attribution. Substantial tropospheric cooling over the eastern North Pacific is found to be collectively contributed by water vapor, cloud, and atmospheric dynamical feedbacks, driven at least partly by the equatorward shift of the Pacific storm track during El Nio. Polar stratospheric warming (cooling), largely due to atmospheric dynamics, is seen over the Eurasian-Pacific (Atlantic) sector, with ozone feedback contributing significantly to the midstratospheric cooling over the Atlantic sector. Water vapor (atmospheric dynamical) feedback has an overall warming (cooling) effect throughout the tropical troposphere, and cloud feedback cools (warms) the tropical lower to middle (upper) troposphere. Atmospheric dynamics induces stratospheric warming over the entire northern extratropics and drives over northern midlatitudes (high latitudes) a tropospheric cooling (warming) that generally intensifies with altitude. © 2012. American Geophysical Union. All Rights Reserved."
"56095295800;55889906400;","The surface heat fluxes along the eastern Pacific coast from 10°N to 40°S",2012,"10.22499/2.6202.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866856107&doi=10.22499%2f2.6202.002&partnerID=40&md5=086075b58c38bf4933b7c4daf09c5cc5","An adequate understanding of the ocean-atmosphere interface is important for understanding climate variability on different time scales. Thus, this research focuses on surface heat fuxes over seasonal scales and their changes during el Niño and La Niña along the eastern Pacific coast (10°N-40°S), consistent with oceanographic and meteorological felds. We used a wide range of up-to-date databases, new mean monthly heat air-sea fuxes (NOCS Flux Dataset v2.0) and complementary global databases (SODA reanalysis, SeaWiFS). The results reported here show that of all the fuxes contributing to net heat fux (Qnet), net shortwave radiation (Qsw) is the term that warms and is most dominant, and latent heat flux (Qlat) is the term that most contributes to cooling. Considering seasonal variability, Qsw reduction due to cloud cover in the latter half of the year was associated with the presence of the Intertropical Convergence Zone and the stratus cloud deck at 10°N-Eq and Eq-30°S, respectively. The smaller seasonal amplitude south of 30°S was associated with the southern coastal jet that develops along the eastern flank of the low-level circulation over the southeast anticyclonic Pacific. During el Niño and La Niña, the most significant change was observed for Qlat in the first half of the year, between the equator and the Peruvian coast. Qlat tended to cool (warm) during el Niño (La Niña), acting as a negative feedback. Specifically for Qlat, we found that the air-sea specific humidity difference (rather than the wind) played a prominent role in both el Niño - Southern Oscillation phases. The sum of Qnet and the shortwave radiation that penetrates through the base of the mixed layer was compared with the sea surface temperature tendency and was discussed."
"7402469637;55262957100;25031430500;6506883710;7005134081;7403544649;","Wave activity in the tropical tropopause layer in seven reanalysis and four chemistry climate model data sets",2012,"10.1029/2011JD016808","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862877128&doi=10.1029%2f2011JD016808&partnerID=40&md5=1e4474b315fc5e6a0f1f73a4d9612cd1","Sub-seasonal variability including equatorial waves significantly influence the dehydration and transport processes in the tropical tropopause layer (TTL). This study investigates the wave activity in the TTL in 7 reanalysis data sets (RAs; NCEP1, NCEP2, ERA40, ERA-Interim, JRA25, MERRA, and CFSR) and 4 chemistry climate models (CCMs; CCSRNIES, CMAM, MRI, and WACCM) using the zonal wave number-frequency spectral analysis method with equatorially symmetric- antisymmetric decomposition. Analyses are made for temperature and horizontal winds at 100 hPa in the RAs and CCMs and for outgoing longwave radiation (OLR), which is a proxy for convective activity that generates tropopause-level disturbances, in satellite data and the CCMs. Particular focus is placed on equatorial Kelvin waves, mixed Rossby-gravity (MRG) waves, and the Madden-Julian Oscillation (MJO). The wave activity is defined as the variance, i.e., the power spectral density integrated in a particular zonal wave number-frequency region. It is found that the TTL wave activities show significant difference among the RAs, ranging from ∼0.7 (for NCEP1 and NCEP2) to∼1.4 (for ERA-Interim, MERRA, and CFSR) with respect to the averages from the RAs. The TTL activities in the CCMs lie generally within the range of those in the RAs, with a few exceptions. However, the spectral features in OLR for all the CCMs are very different from those in the observations, and the OLR wave activities are too low for CCSRNIES, CMAM, and MRI. It is concluded that the broad range of wave activity found in the different RAs decreases our confidence in their validity and in particular their value for validation of CCM performance in the TTL, thereby limiting our quantitative understanding of the dehydration and transport processes in the TTL. © 2012 American Geophysical Union. All Rights Reserved."
"7004014731;57207543362;26321457000;","Changes of the Antarctic ozone hole: Controlling mechanisms, seasonal predictability, and evolution",2012,"10.1029/2011JD016285","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861658050&doi=10.1029%2f2011JD016285&partnerID=40&md5=c43f1d4aca4262dd7a2a3de3e6056d46","The ozone hole changes considerably from one year to the next. It varies between conditions in which springtime ozone is strongly depleted to others in which ozone is only weakly depleted. Those changes are shown to closely track anomalous planetary wave forcing of the residual circulation. The strong coherence with planetary wave forcing is consistent with similar coherence of springtime temperature, which modulates Polar Stratospheric Cloud (PSC). By controlling the lifetime of PSC, anomalous wave forcing determines the net activation of chlorine and bromine and, hence, springtime depletion of ozone during individual years. The strong coherence with planetary wave forcing affords long-range predictability. It supports a seasonal forecast of springtime depletion, which, through the ozone mass deficit, perturbs ozone across much of the Southern Hemisphere during subsequent months of summer. Conditioned upon wintertime wave structure, a hindcast of springtime depletion faithfully predicts the anomalous ozone observed. A reliable forecast of tropospheric planetary waves would thus enable springtime depletion to be predicted. The current evolution of Antarctic ozone is dominated by dynamically-induced changes. Representing its climate variability, those large changes obscure the more gradual evolution of springtime depletion, like that associated with the decline of chlorine. The strong dependence on planetary wave forcing, however, enables dynamically-induced changes of ozone to be identified accurately. Removing them unmasks the secular variation of Antarctic ozone, the part coherent over a decade and longer. Independent of dynamically-induced changes, that component discriminates to changes associated with stratospheric composition. It reveals a gradual but systematic rebound over the last decade. The upward trend is shown to be robust, significant at the 99.5% level. Uncertainty in this trend is thus small enough to make the probability of it arising through chance alignment of error less than 0.5%. The discriminated component mirrors the decline of effective stratospheric chlorine, representing a gradual return of springtime ozone toward its level in 1980 of 10-15%. It enables Antarctic ozone to be tracked relative to changes of chlorine, CO <inf>2</inf>, and other features of climate more reliably than is otherwise possible. © Copyright 2012 by the American Geophysical Union."
"6507400558;57199689992;6603169474;","Convective momentum transport in a simple multicloud model for organized convection",2012,"10.1175/JAS-D-11-042.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863393334&doi=10.1175%2fJAS-D-11-042.1&partnerID=40&md5=b6a5e3fa9934e6472800f7c692d6b01e","Convective momentum transport (CMT) is the process of vertical transport of horizontal momentum by convection onto the environmental flow. The significance of CMT from mesoscale to synoptic- and planetaryscale organized cumulus convection has been established by various theoretical and observational studies. A new strategy mimicking the effect of unresolved mesoscale circulation based on the weak temperature gradient (WTG) approximation with a Gaussian profile to redistribute the heating due to parameterized cumulus convection at the subgrid scale is adopted here to construct a CMT parameterization for general circulation models (GCMs). Two main regimes of CMT are considered: an upscale squall-line regime and a downscale non-squall-line regime. An exponential probability distribution is used to select which of these two effects is active, conditional on the state of the large-scale shear. The shear itself is used as a measure of the persistence of mesoscale organized circulation due to the presence or not of tilted deep convective heating with lagged stratiform anvils. TheCMTmodel is tested in the simple case of the multicloud model of Khouider and Majda, used here as a toy GCM. Numerical simulations are performed here for the simple case without rotation, in a parameter regime where the multicloud model exhibits packets of convectively coupled gravity waves moving in one direction, at 17 m s -1, and planetary-scale wave envelopes moving in the opposite direction, at 4-6 m s -1, reminiscent of the Madden-Julian oscillation (MJO) and the associated embedded synopticscale superclusters. The results herein show that the inclusion of CMT intensifies both the synoptic-scale convectively coupled waves and the manifestation of planetary-scale waves in the multicloud model. This provides evidence that the present CMT model captures the essence of the physical mechanism through which kinetic energy is transferred from the subgrid-scale mesoscale circulation to the large-scale/resolved motion. Sensitivity simulations showed that two key parameters for the CMT parameterization are the relative strength of the parameterized stratiform anvils and the dimensional threshold used in the exponential distribution for the cumulus friction and the upscale CMT forcing resulting from organized subgrid mesoscale circulation. © 2012 American Meteorological Society."
"16480895800;","Modification of the IR sky temperature under different atmospheric conditions in an arid region in central Saudi Arabia: Experimental and theoretical justification",2012,"10.1029/2012JD017881","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867500131&doi=10.1029%2f2012JD017881&partnerID=40&md5=7f582b69b79eda0a1e1055fdfd3785cb","Sky temperatures that were estimated from a single-channel IR detector over Riyadh, Saudi Arabia, were analyzed from June 2008 to May 2011. The data were divided into three main categories: clear sky, cloudy sky, and dusty conditions. The observation and the research results were as follows. During periods of clear-sky conditions, it was found that the sky temperatures depend mainly on the atmospheric water content, the screen level temperature, and the suspended aerosol particles in the atmosphere. Under cloudy conditions, the sky temperature ranges between -37C and 5C. The mean sky temperatures in this case are higher than those of the clear-sky conditions by approximately 11C to 18C. The radiative properties of cloudy skies depend on the cloud characteristics and the intervening atmosphere between the ground and the cloud base. The sky temperature during dusty conditions ranged between -20C and 8.5C. The study showed that dusty conditions increase the atmospheric temperatures by approximately 17C to 31C. The sky temperatures during dusty periods are affected by several factors, such as the air mass properties, which bring the dust, and the dust particle characteristics, such as size, shape, and chemical composition, which are initially determined by the sources from which the dust originated. Theoretical simulations using MODTRAN software were used to investigate the atmospheric thermal radiation spectral distributions in the three categories. The results show that the major changes occurred within the atmospheric window (8-14 m). © 2012 American Geophysical Union. All Rights Reserved."
"7004893330;55547129338;7005280212;","Using satellites to investigate the sensitivity of longwave downward radiation to water vapor at high elevations",2012,"10.1029/2011JD016917","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863254533&doi=10.1029%2f2011JD016917&partnerID=40&md5=76a4443c859200c8745905ad7ed6d940","Many studies suggest that high-elevation regions may be among the most sensitive to future climate change. However, in situ observations in these often remote locations are too sparse to determine the feedbacks responsible for enhanced warming rates. One of these feedbacks is associated with the sensitivity of longwave downward radiation (LDR) to changes in water vapor, with the sensitivity being particularly large in many high-elevation regions where the average water vapor is often low. We show that satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earths Radiant Energy System (CERES) can be used to expand the current ground-based observational database and that the monthly averaged clear-sky satellite estimates of humidity and LDR are in good agreement with the well-instrumented Center for Snow and Avalanche Studies ground-based site in the southwestern Colorado Rocky Mountains. The relationship between MODIS-retrieved precipitable water vapor and surface specific humidity across the contiguous United States was found to be similar to that previously found for the Alps. More important, we show that satellites capture the nonlinear relationship between LDR and water vapor and confirm that LDR is especially sensitive to changes in water vapor at high elevations in several midlatitude mountain ranges. Because the global population depends on adequate fresh water, much of which has its source in high mountains, it is critically important to understand how climate will change there. We demonstrate that satellites can be used to investigate these feedbacks in high-elevation regions where the coverage of surface-based observations is insufficient to do so. Copyright 2012 by the American Geophysical Union."
"6507198695;36559769700;7202967741;24281680700;7801595201;26653350000;6604005739;7404661626;7006978226;","Year-round radiocarbon-based source apportionment of carbonaceous aerosols at two background sites in South Asia",2012,"10.1029/2011JD017161","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861709851&doi=10.1029%2f2011JD017161&partnerID=40&md5=9b2c855e40d4d8868f8858d6f331e028","Atmospheric Brown Clouds (ABC), regional-scale haze events, are a significant concern for both human cardiopulmonary health and regional climate impacts. In order to effectively mitigate this pollution-based phenomenon, it is imperative to understand the magnitude, scope and source of ABC in regions such as South Asia. Two sites in S. Asia were chosen for a 15-month field campaign focused on isotope-based source apportionment of carbonaceous aerosols in 2008-2009. Both the Maldives Climate Observatory in Hanimaadhoo (MCOH) and a mountaintop site in Sinhagad, India (SINH) act as regionally mixed receptor sites. Annual radiocarbon-based source apportionment for soot elemental carbon (SEC) at MCOH and SINH revealed 73 6% and 59 5% contribution from biomass combustion, respectively (remainder from fossil fuel). The contributions from biogenic/biomass combustion to total organic carbon were similar between MCOH and SINH (69 5% and 64 5, respectively). The biomass combustion contribution for SEC in the current study, especially the results from MCOH, shows good agreement with published black carbon emissions inventories for India. Geographic source assessment, including clustered back trajectory analysis and carbon contribution by source region, indicated that the highest SEC/TOC loads originated from the W. Indian coastal margin, including the coastal city of Mumbai, India. The winter dry season 14C-based source apportionment of the BC-tracing SEC fraction for 2006, 2008, 2009 were not statistically different (p = 0.7) and point to a near-constant two-thirds contribution from biomass combustion practices, including wood and other biofuels as well as burning of agricultural crop residues. © Copyright 2012 by the American Geophysical Union."
"6701718281;6505932008;7202899330;54983414800;","Changes in the interaction between tropical convection, radiation, and the large-scale circulation in a warming environment",2012,"10.1175/2011JCLI4167.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856948197&doi=10.1175%2f2011JCLI4167.1&partnerID=40&md5=392cf36094b5b7cdebc95a3f221625a6","This paper explores the response of the tropical hydrologic cycle to surface warming through the lens of large-domain cloud-system-resolving model experiments run in a radiative-convective equilibrium framework. Simulations are run for 55 days and are driven with fixed insolation and constant sea surface temparatures (SSTs) of 298 K, 300 K, and 302 K. In each experiment, convection organizes into coherent regions of large-scale ascent separated by areas with relatively clear air and troposphere-deep descent. Aspects of the simulations correspond to observed features of the tropical climate system, including the transition to large precipitation rates above a critical value of total column water vapor, and an increase in convective intensity with SST amidst weakening of the large-scale overturning circulation. However, the authors also find notable changes to the interaction between convection and the environment as the surface warms. In particular, organized convection in simulations with SSTs of 298 and 300 K is inhibited by the presence of a strong midtropospheric stable layer and dry upper troposphere. As a result, there is a decrease in the vigor of deep convection and an increase in stratiform precipitation fraction with an increase in SST from 298 to 300 K. With an increase in SST to 302 K, moistening of the middletroposphere and increase in lower-tropospheric buoyancy serve to overcome these limitations, leading to an overall increase in convective intensity and larger increase in upper-tropospheric relative humidity. The authors conclude that, while convective intensity increases with SST, the aggregate nature of deep convection is strongly affected by the details of the thermodynamic environment in which it develops. In particular, the positive feedback between increasing SST and a moistening upper troposphere found in the simulations, operates as a nonmonotonic function of SST and is modulated by a complex interaction between deep convection and the environmental relative humidity and static stability profile. The results suggest that projected changes in convection that assume a monotonic dependence on SST may constitute an oversimplification. © 2012 American Meteorological Society."
"35104877900;57211224269;7004507076;13404531500;7102193013;","Future changes and uncertainties in Asian precipitation simulated by multiphysics and multi-sea surface temperature ensemble experiments with high-resolution Meteorological Research Institute atmospheric general circulation models (MRI-AGCMs)",2012,"10.1029/2012JD017874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865844915&doi=10.1029%2f2012JD017874&partnerID=40&md5=9976c81c20488e6769fa8a77ea2b113f","This study focuses on projecting future changes in mean and extreme precipitation in Asia, and discusses their uncertainties. Time-slice experiments using a 20-km-mesh atmospheric general circulation (AGCM) were performed both in the present-day (1979-2003) and the future (2075-2099). To assess the uncertainty of the projections, 12 ensemble projections (i.e., combination of 3 different cumulus schemes and 4 different sea surface temperature (SST) change patterns) were conducted using 60-km-mesh AGCMs. For the present-day simulations, the models successfully reproduced the pattern and amount of mean and extreme precipitation, although the model with the Arakawa-Schubert (AS) cumulus scheme underestimated the amount of extreme precipitation. For the future climate simulations, in South Asia and Southeast Asia, mean and extreme precipitation generally increase, but their changes show marked differences among the projections, suggesting some uncertainty in their changes over these regions. In East Asia, northwestern China and Bangladesh, in contrast, mean and extreme precipitation show consistent increases among the projections, suggesting their increases are reliable for this model framework. Further investigation by analysis of variance (ANOVA) revealed that the uncertainty in the precipitation changes in South Asia and Southeast Asia are derived mainly from differences in the cumulus schemes, with an exception in the Maritime Continent where the uncertainty originates mainly from the differences in the SST pattern. © 2012. American Geophysical Union. All Rights Reserved."
"55178499100;","The lightning climatology of South Africa",2012,"10.4102/sajs.v108i3/4.740","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859516502&doi=10.4102%2fsajs.v108i3%2f4.740&partnerID=40&md5=d7b12a08195e784831ff3e24f5027110","In 2005, the South African Weather Service installed a state-of-the-art cloud-to-ground lightning detection network across the country. The data recorded by this network in 2006 was utilised in the development of an initial lightning climatology of South Africa. Until 2010, this climatology was based on data from a single year. This paper updates this climatology with the lightning data for the 2006-2010 period, which is the first actual lightning climatology by the South African Weather Service based on data covering 5 years. A number of different maps were created from these lightning data. These were lightning ground flash density, median peak kiloampere, percentage positive and average flash multiplicity maps. These four maps were in turn used to develop lightning intensity risk, positive lightning risk and total lightning risk maps. Analysis of the maps showed that the highest concentrations of lightning are found over the central to northern interior of the country, with areas along the northern parts of the eastern escarpment experiencing the highest flash densities and falling within the extreme risk category. Both the positive and total lightning risks are severe for almost the entire country. Only towards the west of the country does the lightning risk decrease. This lightning climatology can now be used throughout South Africa for various disciplines. It will be especially useful for setting lightning safety standards and identifying priority areas for installing lightning conductors and conducting public awareness campaigns. © 2012. The Authors."
"36017879100;36077992900;56339079100;55731174900;55993981800;","Heat wave frequency variability over North America: Two distinct leading modes",2012,"10.1029/2011JD016908","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862965925&doi=10.1029%2f2011JD016908&partnerID=40&md5=c9544c78535ed40a32f86bf5086f331f","Seasonal prediction of heat wave variability is a scientific challenge and of practical importance. This study investigates the heat wave frequency (HWF) variability over North America (NA) during the past 53 summers (1958-2010). It is found that the NA HWF is dominated by two distinct modes: the interdecadal (ID) mode and the interannual (IA) mode. The ID mode primarily depicts a HWF increasing pattern over most of the NA continent except some western coastal areas. The IA mode resembles a tripole HWF anomaly pattern with three centers over the northwestern, central, and southern NA. The two leading modes have different dynamic structures and predictability sources. The ID mode is closely associated with the prior spring sea surface temperature anomaly (SSTA) in the tropical Atlantic and tropical western Pacific that can persist throughout the summer, whereas the IA mode is linked to the development of El Niño-Southern Oscillation. A simplified general circulation model is utilized to examine the possible physical mechanism. For the ID mode the tropical Atlantic SSTA can induce a Gill-type response which extends to NA, while the northwestern Pacific SSTA excites a Rossby wave train propagating eastward toward NA. These two flow patterns jointly contribute to the formation of the large-scale circulation anomalies associated with the ID mode. For the IA mode the corresponding circulation anomalies are basically similar to a Pacific-North America pattern. The subsidence associated with high-pressure anomalies warms and dries the boundary layer, inhibiting cloud formation. The resulting surface radiative heating further warms the surface. For the low-pressure anomalies the situation is just opposite. Through such processes these SSTAs can exert profound influences on the HWF variability over NA. Copyright 2012 by the American Geophysical Union."
"55403837300;14324150200;6507931440;6602570616;","Trends and variability in pan evaporation and other climatic variables at Ibadan, Nigeria, 1973-2008",2012,"10.1002/met.281","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870695025&doi=10.1002%2fmet.281&partnerID=40&md5=ecc8d171438ca4b2f85c05ca6f01f88d","Understanding changes in evaporation rates is expected to be of great importance for water resource planning and management. This paper examines pan evaporation data as an example of the detection and attribution of trends in climate variables. Records of pan evaporation (Epan), rainfall (R), radiation (SR), wind speed (WS), temperature (Ta) and humidity (RH) for the period 1973-2008 were collected from the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria. Mann-Kendall trend and Sen's slope tests were performed on the respective meteorological variables and a variability index (VI) was also computed for these. The results showed that annually Epan, SR and WS significantly decrease (P &lt; 0.001) while R, Ta, and RH showed insignificant increasing trends in the last four decades. Epan and SR decrease at the rate of 8.3 mm year-2 and 37.8 MJ m-2 year-1, respectively. Similar to Epan, SR decreased significantly in all the months (P &lt; 0.01) and the reduction ranged from 5.1% per decade in March to 9.3% per decade in August. The result of VI showed that the decrease in Epan and other explanatory variables is rather recent. Regression between Epan and other variables indicates that about 30, 15 and 6% of its variance can be explained by SR, WS and VPD (vapour pressure deficit), respectively. The possible roles of dust-haze known as 'harmattan' winds and monsoon clouds in attenuating SR and hence reducing Epan are discussed. © 2011 Royal Meteorological Society."
"7004202450;37065304600;57190581716;56532987400;49664167700;","Northeast monsoon over India: Variability and prediction",2012,"10.1002/met.1322","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861793650&doi=10.1002%2fmet.1322&partnerID=40&md5=cac27e87973d58521b938917741d0d32","South peninsular India experiences a large portion of the annual rainfall during the northeast monsoon season (October to December). In this study, the facets of diurnal, intra-seasonal and inter-annual variability of the northeast monsoon rainfall (the NEMR) over India have been examined. The analysis of satellite derived hourly rainfall reveals that there are distinct features of diurnal variation over the land and oceans during the season. Over the land, rainfall peaks during the late afternoon/evening, while over the oceans an early morning peak is observed. The harmonic analysis of hourly data reveals that the amplitude and variance are the largest over south peninsular India. The NEMR also exhibits significant intra-seasonal variability on a 20-40 day time scale. Analysis also shows significant northward propagation of the maximum cloud zone from south of equator to the south peninsula during the season. The NEMR exhibits large inter-annual variability with the co-efficient of variation (CV) of 25%. The positive phases of ENSO and the Indian Ocean Dipole (IOD) are conducive for normal to above normal rainfall activity during the northeast monsoon. There are multi-decadal variations in the statistical relationship between ENSO and the NEMR. During the period 2001-2010 the statistical relationship between ENSO and the NEMR has significantly weakened. The analysis of seasonal rainfall hindcasts for the period 1960-2005 produced by the state-of-the-art coupled climate models, ENSEMBLES, reveals that the coupled models have very poor skill in predicting the inter-annual variability of the NEMR. This is mainly due to the inability of the ENSEMBLES models to simulate the positive relationship between ENSO and the NEMR correctly. © 2012 Royal Meteorological Society."
"56615268500;7004357137;16444240700;7004167838;","Application of an adaptive radiative transfer scheme in a mesoscale numerical weather prediction model",2012,"10.1002/qj.890","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856225448&doi=10.1002%2fqj.890&partnerID=40&md5=296eb856e376d97469a5669e85129d3e","The computational burden of radiative transfer parametrization is considerable, and hence operational atmospheric models use various sampling, coarsening and interpolation techniques to reduce this load; this, however, introduces new errors. An adaptive radiative transfer scheme takes advantage of the spatial and temporal correlations in the optical characteristics of the atmosphere to make the parametrization computationally more efficient. The adaptive scheme employed here generalizes the accurate radiation computations made in a fraction of the spatial and temporal space to the rest of the field. In this study, a previously developed scheme has been extended to atmospheric heating rates and implemented in the numerical weather prediction model COSMO. The performance of the adaptive scheme is compared with the performance of the currently operational COSMO-DE radiation configuration, in which radiation computations are performed quarter-hourly on 2 × 2 averaged atmospheric columns. The reference for both schemes is a set of frequent radiation computations for the full grid. We show that the adaptive scheme is able to reduce the sampling errors in the radiation surface fluxes by 15-25% and to conserve the spatial variability, in contrast to the operational scheme. Deviations in the heating-rate profiles are reduced for larger averaging scales. Physical relationships between the radiative quantities and cloud water or rain rates are better captured. We demonstrate that these improvements also lead to improvements with respect to the dynamical development of the model simulation, showing a smaller divergence from the reference model run. © 2011 Royal Meteorological Society."
"40462246800;7003330218;","Calculating the water and heat balances of the Eastern Mediterranean Basin using ocean modelling and available meteorological, hydrological and ocean data",2012,"10.5697/oc.54-2.199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862488873&doi=10.5697%2foc.54-2.199&partnerID=40&md5=7c50b8727d28c1bef0c357c74c2b474a","Eastern Mediterranean water and heat balances were analysed over 52 years. The modelling uses a process-oriented approach resolving the one-dimensional equations of momentum, heat and salt conservation; turbulence is modelled using a twoequation model. The results indicate that calculated temperature and salinity follow the reanalysed data well. The water balance in the Eastern Mediterranean basin was controlled by the difference between inflows and outflows through the Sicily Channel and by net precipitation. The freshwater component displayed a negative trend over the study period, indicating increasing salinity in the basin. The heat balance was controlled by heat loss from the water surface, solar radiation into the sea and heat flow through the Sicily Channel. Both solar radiation and net heat loss displayed increasing trends, probably due to decreased total cloud cover. In addition, the heat balance indicated a net import of approximately 9 W m-2 of heat to the Eastern Mediterranean Basin from the Western Basin. © Polish Academy of Sciences, Institute of Oceanology, 2012."
"8525144100;7003780337;7003278104;6603126554;7003263504;36097134700;","Intraseasonal temperature variability in the upper troposphere and lower stratosphere from the GPS radio occultation measurements",2012,"10.1029/2012JD017715","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865325471&doi=10.1029%2f2012JD017715&partnerID=40&md5=5302298c20c4849dd71a4e0ae9a13d9f","In this study, we examine the detailed spatiotemporal patterns and vertical structure of the intraseasonal temperature variability in the upper troposphere and lower stratosphere (UTLS) associated with the Madden-Julian Oscillation (MJO) using the temperature profiles from the recent Global Positioning System radio occultation (GPS RO) measurements including the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission. The MJO-related temperature anomalies in the UTLS are smaller near the equator (<0.6K) than over the subtropics and extratropics (>1.2K). Near the equator, the temperature anomalies exhibit an eastward tilt with height from the upper troposphere (UT) to the lower stratosphere (LS) and their magnitudes and signs are determined by the strength of convective anomalies and vertical pressure level. The subtropical temperature anomalies have similar magnitudes and patterns at a given location between the UT (250hPa to 150hPa) and the LS (150hPa to 50hPa) except for opposite signs that change around 150hPa. The subtropical warm (cold) anomalies in the UT and cold (warm) anomalies in the LS are typically collocated with the subtropical positive (negative) tropopause height anomalies/cyclones (anticyclones) and flank or lie to the west of equatorial enhanced (suppressed) convection. We also compare the intraseasonal temperature variability in the UTLS related to the MJO between the GPS RO and Atmospheric Infrared Sounder (AIRS) measurements to highlight the new features of the GPS RO temperature anomalies and to evaluate the quality of the AIRS temperature in the UTLS considering the GPS RO temperature in the UTLS as the benchmark. Both AIRS and GPS RO have a very consistent vertical structure in the subtropical UTLS with a high correlation coefficient 0.92 and similar magnitudes. Both AIRS and GPS RO also show a generally consistent vertical structure of the intraseasonal temperature anomalies in the equatorial UTLS. However, GPS RO reveals many detailed fine-scale vertical structures of the equatorial temperature anomalies between 150 and 50hPa that are not well captured by AIRS. Furthermore, the equatorial temperature anomalies are about 40% underestimated in AIRS in comparison to GPS RO, over the equatorial Indian and western Pacific Oceans for 250hPa and over all longitudes for 100hPa. The low sampling within the optically thick clouds and low vertical resolution near the tropopause may both contribute to these deficiencies of AIRS. © 2012. American Geophysical Union. All Rights Reserved."
"7003861754;7202155374;","Examining vegetation feedbacks on global warming in the Community Earth System Model",2012,"10.1029/2012JD017623","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868331272&doi=10.1029%2f2012JD017623&partnerID=40&md5=2234d07fb32fe71d2c405a8e946f5629","Leaves close their stomates in response to increases of CO<inf>2</inf>. Such a rapid physiological response is included in the land component of comprehensive climate models. However, observational studies have shown that they can further close their stomates as a consequence of ""down-regulation, "" further reducing canopy conductance. However, they may also increase the area of their leaves, hence increasing their canopy conductance. Changes of canopy conductance change surface ET, a reduction leading to surface warming. A simulation considering these mechanisms of modifying canopy conductance is carried out for the assumption of a doubled atmospheric CO<inf>2</inf> concentration, using the Community Earth System model. It finds that down-regulation as formulated in previous studies could have as large a warming impact on land temperatures as the standard leaf physiological response. Increases in LAI, if they were to occur, appear to have but a small cooling effect. The reduction of latent cooling in the model is amplified by a reduction of low-level cloud cover, hence enhanced net absorption of solar radiation. Reduction of low level cloudiness appears to be necessary to maintain global radiation balance as reported in a previous study. Over mid to high latitudes, decreases in surface albedo associated with reduced snow cover also contribute to amplifying the warming. The physiological feedbacks of leaf stomates in the simulation increase warming by 0.6 ± 0.2°C over land and 0.3 ± 0.1°C globally, not inconsistent with previous studies. Enhanced interhemispheric temperature differences weaken the southward shift of the ITCZ associated with CO<inf>2</inf> radiative warming. Regions with relatively high LAI tend to have greater vegetation feedback; but increases in large-scale precipitation may weaken this local warming effect. © 2012. American Geophysical Union. All Rights Reserved."
"6602636344;37161303900;","Classifying convective and stratiform rain using multispectral infrared Meteosat Second Generation satellite data",2012,"10.1007/s00704-011-0557-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860444114&doi=10.1007%2fs00704-011-0557-y&partnerID=40&md5=617e38f3bde5bb5c67204108e3d0c73e","This paper investigates the potential for developing schemes that classify convective and stratiform precipitation areas using the high infrared spectral resolution of the Meteosat Second Generation-Spinning Enhanced Visible and Infrared Imager (MSG-SEVIRI). Two different classification schemes were proposed that use the brightness temperature (BT) Τ10. 8 along with the brightness temperature differences (BTDs) Τ10. 8-Τ12. 1, Τ8. 7-Τ10. 8, and Τ6. 2-Τ10. 8 as spectral parameters, which provide information about cloud parameters. The first is a common multispectral thresholding scheme used to partition the space of the spectral cloud parameters and the second is an algorithm based on the probability of convective rain (PCR) for each pixel of the satellite data. Both schemes were calibrated using as a reference convective\stratiform rain classification fields derived from 87 stations in Greece for six rainy days with high convective activity. As a result, one single infrared technique (TB10) and two multidimensional techniques (BTDall and PCR) were constructed and evaluated against an independent sample of rain gauge data for four daily convective precipitation events. It was found that the introduction of BTDs as additional information to a technique works in improving the discrimination of convective from stratiform rainy pixels compared to the single infrared technique BT10. During the training phase, BTDall performed slightly better than BT10 while PCR technique outperformed both threshold techniques. All techniques clearly overestimate the convective rain occurrences detected by the rain gauge network. When evaluating against the independent dataset, both threshold techniques exhibited the same performance with that of the dependent dataset whereas the PCR technique showed a notable skill degradation. As a result, BTDall performed best followed at a short distance by PCR and BT10. These findings showed that it is possible to apply a convective/stratiform rain classification algorithm based on the enhanced infrared spectral resolution of MSG-SEVIRI, for nowcasting or climate purposes, despite the highly variable nature of convective precipitation. © 2011 Springer-Verlag."
"7402647384;7403717185;6603910424;7403232646;","Structural evolution of the Madden-Julian Oscillation from COSMIC radio occultation data",2012,"10.1029/2012JD017685","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870599905&doi=10.1029%2f2012JD017685&partnerID=40&md5=3412635c76d9e1c4ab94ca6488abd25e","The atmospheric temperature and specific humidity profiles derived from 4 years of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) measurements during the boreal winter (November thru April in 2006-2010) were employed to study the large-scale vertical structure of the Madden-Julian Oscillation (MJO). In a composited MJO cycle, both RO temperature and moisture anomalies propagate eastward along with the enhanced MJO convection over the Indo-Pacific region. In the same region, the RO temperature anomaly is positively correlated with the convection (Tropical Rainfall Measuring Mission (TRMM) rainfall) anomaly in the middle and upper troposphere (800 hPa-200 hPa) and negatively correlated in the lower troposphere and at the tropopause. A positive RO moisture anomaly has a westward tilt below 300 hPa and is well associated with the convection anomaly. RO bending angle and refractivity anomalies show vertical structure similar to that of temperature MJO anomaly above ∼300 hPa and to that of the moisture anomaly below that. These salient MJO features agree well with those revealed by global reanalysis data and meteorological satellite observations, such as the Atmospheric Infrared Sounder (AIRS), even though RO anomalies exhibit sharper structure at the tropopause region due to the higher vertical resolution of the RO. Investigation of the cold-point tropopause anomaly indicates that the enhanced convection is preceded by cooling of the tropopause and followed by lowering of the tropopause height. The MJO moisture structures during two boreal winters, November 2007-April 2008 (La Nia) and November 2009-April 2010 (El Nio), are individually presented to demonstrate the El Nio-Southern Oscillation (ENSO) effect on the MJO structure."
"35201784100;55745955800;8859530100;","An investigation of the initial development of the double-ITCZ warm SST biases in the CCSM",2012,"10.1175/2011JCLI4001.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863011542&doi=10.1175%2f2011JCLI4001.1&partnerID=40&md5=cf1c5c5fa7fd5472d7b64a380a7caddf","This paper investigates the initial development of the double ITCZ in the Community Climate SystemModel version 3 (CCSM3) in the central Pacific. Starting from a resting initial condition of the ocean in January, the model developed a warmbias of sea surface temperature (SST) in the central Pacific from 5°S to 10°S in the first threemonths. This initial bias is caused by excessive surface shortwave radiation that is also present in the standalone atmospheric model. The initial bias is further amplified by biases in both surface latent heat flux and horizontal heat transport in the upper ocean. These biases are caused by the responses of surface winds to SST bias and the thermocline structure to surface wind curls. This study also showed that the warming biases in surface solar radiation and latent heat fluxes are seasonally offset by cooling biases from reduced solar radiation after the austral summer due to cloud responses and in the austral fall due to enhanced evaporation when the maximum SST is closest to the equator. The warming biases from the dynamic heat transport by ocean currents however stay throughout all seasons once they are developed, which are eventually balanced by enhanced energy exchange and penetration of solar radiation below the mixed layer. It was also shown that the equatorial cold tongue develops after the warm biases in the south-central Pacific, and the overestimation of surface shortwave radiation recurs in the austral summer in each year. The results provide a case study on the physical processes leading to the development of the double ITCZ. Applicability of the results in other models is discussed. © 2012 American Meteorological Society."
"57211637736;24366038500;6701697023;7003414581;8927405700;55716266100;","One-year aerosol profiling with EUCAARI Raman lidar at Shangdianzi GAW station: Beijing plume and seasonal variations",2012,"10.1029/2012JD017577","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863442487&doi=10.1029%2f2012JD017577&partnerID=40&md5=9fbf40ac5fac5120885640623acdc92d","The study examines seasonal and air-flow-dependent variations of the vertical distribution of aerosols at the Global Atmospheric Watch (GAW) station of Shangdianzi in the North China Plain 100km northeast of Beijing. One-year Raman lidar observations of profiles of aerosol extinction and backscatter coefficients at 532nm were performed from April 2009 to March 2010 in the framework of the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project. In the nighttime statistics a two-layer structure with the main haze layer reaching to 1-1.5km height asl and an elevated aerosol layer on top with a top height of 2.5-5km height asl was generally observed. A case study of a Beijing haze plume is presented to document the drastic changes in the environmental conditions over the background monitoring station during the passage of a strong haze front. Aerosol optical depth (AOD) and extinction coefficients increased from 0.2 to 1.2 and from 200 Mm-1 to 1000 Mm-1, respectively, within less than two hours. The statistical analysis revealed layer mean extinction coefficients of the haze layer most frequently from 200-600 Mm-1 and typically from 50-100 Mm -1 in the elevated layer. The AOD ranged from about 0.3 for northerly air flows to, on average, 0.95 during southerly air flows. The lidar ratio shows a narrow distribution peaking at 60sr in the haze layer caused by anthropogenic fine-mode aerosol and a broad distribution from 40-90sr in the elevated layer caused by the complex mixture of aged desert dust, biomass burning smoke, and industrial pollution over eastern Asia. © 2012. American Geophysical Union. All Rights Reserved."
"57034458200;57192534657;","Importance of the upper-level warm core in the rapid intensification of a tropical cyclone",2012,"10.1029/2011GL050578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863031013&doi=10.1029%2f2011GL050578&partnerID=40&md5=fc933efff9d94b612b556c4ad8184d2e","In this study, the rapid intensification (RI) of tropical cyclone is examined using a 72-h cloud-permitting prediction of Hurricane Wilma (2005) with a record-breaking intensity of 882 hPa. Results show the formation of an upper-level warm core from the descending air of stratospheric origin in the eye, which coincides with the onset of RI; it reaches the peak amplitude of more than 18°C from its initial conditions at the time of peak intensity. The descending air is associated with the detrainment of convective bursts in the eyewall, and it appears as (perturbation) cyclonic radial inflows above the upper outflow layer and causes the subsidence warming below. We hypothesize that the upper divergent outflow layer favors the generation of a warm core by protecting it from ventilation by environmental flows. Use of the hydrostatic equation shows that the warm core of stratospheric origin contributes more than twice as much as the lower-level warm column to the pressure change at the peak intensity of Wilma. Results suggest that more attention be paid to the magnitude of storm-relative flows and vertical wind shear in the upper troposphere, rather than just vertical shear in the typical 850-200 hPa layer, in order to reasonably predict the RI of tropical cyclones. Copyright 2012 by the American Geophysical Union."
"23007626000;7006235116;","Mesoscale convective complexes over Southern Africa",2012,"10.1175/JCLI-D-10-05013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856950342&doi=10.1175%2fJCLI-D-10-05013.1&partnerID=40&md5=ee7eabaf8c04646954cdcd13a09ed210","The maximum spatial correlation technique (MASCOTTE) is an objective and automated method developed to simultaneously determine both the structural properties and evolution (tracking) of cloud shields of convective systems. Originally designed to monitor systems over the Amazon region, this method has now been adapted for subtropical southern Africa. In this paper, a detailed climatology of 70 mesoscale convective complexes (MCCs) that occurred during the austral summer months over southern Africa during the 1998-2006 period are presented. Most MCCs are clustered along the eastern regions of southern Africa, adjacent to the warm waters of the Mozambique Channel and Agulhas Current. A few infrequent systems are found to be developing in Namibia and Botswana. The systems are found to predominantly occur during the months of November-February, with maximum activity occurring in November and December. The transition from a more midlatitude-dominated circulation to a tropical circulation over the region during the late summer leads to an uncharacteristic equatorward migration of the MCC distribution then. The analysis also suggests that there is variability in MCC frequency on monthly and seasonal time scales. Although fewer in number (about nine per season) compared to MCC populations in other regions, the systems do tend to follow the nocturnal life cycle as documented elsewhere. © 2012 American Meteorological Society."
"57196050484;35577097300;8539422800;6602829165;","Monsoon sensitivity to aerosol direct radiative forcing in the community atmosphere model",2012,"10.1007/s12040-012-0198-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867666529&doi=10.1007%2fs12040-012-0198-2&partnerID=40&md5=8e1ebfb88e15663324fead301cfb7e86","Aerosol forcing remains a dominant uncertainty in climate studies. The impact of aerosol direct radiative forcing on Indian monsoon is extremely complex and is strongly dependent on the model, aerosol distribution and characteristics specified in the model, modelling strategy employed as well as on spatial and temporal scales. The present study investigates (i) the aerosol direct radiative forcing impact on mean Indian summer monsoon when a combination of quasi-realistic mean annual cycles of scattering and absorbing aerosols derived from an aerosol transport model constrained with satellite observed Aerosol Optical Depth (AOD) is prescribed, (ii) the dominant feedback mechanism behind the simulated impact of all-aerosol direct radiative forcing on monsoon and (iii) the relative impacts of absorbing and scattering aerosols on mean Indian summer monsoon. We have used CAM3, an atmospheric GCM (AGCM) that has a comprehensive treatment of the aerosol-radiation interaction. This AGCM has been used to perform climate simulations with three different representations of aerosol direct radiative forcing due to the total, scattering aerosols and black carbon aerosols. We have also conducted experiments without any aerosol forcing. Aerosol direct impact due to scattering aerosols causes significant reduction in summer monsoon precipitation over India with a tendency for southward shift of Tropical Convergence Zones (TCZs) over the Indian region. Aerosol forcing reduces surface solar absorption over the primary rainbelt region of India and reduces the surface and lower tropospheric temperatures. Concurrent warming of the lower atmosphere over the warm oceanic region in the south reduces the land-ocean temperature contrast and weakens the monsoon overturning circulation and the advection of moisture into the landmass. This increases atmospheric convective stability, and decreases convection, clouds, precipitation and associated latent heat release. Our analysis reveals a defining negative moisture-advection feedback that acts as an internal damping mechanism spinning down the regional hydrological cycle and leading to significant circulation changes in response to external radiative forcing perturbations. When total aerosol loading (both absorbing and scattering aerosols) is prescribed, dust and black carbon aerosols are found to cause significant atmospheric heating over the monsoon region but the aerosol-induced weakening of meridional lower tropospheric temperature gradient (leading to weaker summer monsoon rainfall) more than offsets the increase in summer-time rainfall resulting from the atmospheric heating effect of absorbing aerosols, leading to a net decrease of summer monsoon rainfall. Further, we have carried out climate simulations with globally constant AODs and also with the constant AODs over the extended Indian region replaced by realistic AODs. Regional aerosol radiative forcing perturbations over the Indian region is found to have impact not only over the region of loading but over remote tropical regions as well. This warrants the need to prescribe realistic aerosol properties in strategic regions such as India in order to accurately assess the aerosol impact. © Indian Academy of Sciences."
"36810780500;7402944490;","In-phase transition from the winter monsoon to the summer monsoon over East Asia: Role of the Indian Ocean",2012,"10.1029/2012JD017509","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862278251&doi=10.1029%2f2012JD017509&partnerID=40&md5=3bc8bad175c753702a6f9bd1f844c66f","Analysis of observations shows that the weak East Asian winter monsoon (EAWM) to weak East Asian summer monsoon (EASM) transitions mainly occur in El Nio decaying years whereas strong EAWM (denoting stronger northerly winds along East Asian coast) to strong EASM (denoting less precipitation along the Meiyu-Baiu rainband) transitions all occur in non-El Nio-Southern Oscillation (ENSO) years during the period 1979-2009. This new finding implies that ENSO is not indispensable to the in-phase EAWM to the EASM transitions. The present study reveals an important role of the Indian Ocean in the strong EAWM to strong EASM transitions and proposes a possible mechanism for these transitions. A strong EAWM induces more precipitation over the Maritime Continent, and the associated anomalous heating excites a Gill-Matsuno type pattern in the tropics. The resultant wind and cloud changes enhance latent heat flux and reduce downward shortwave radiation over the northwestern Indian Ocean in winter, which leads to SST cooling. The cold SST anomalies persist to summer and excite an anomalous cyclone over the subtropical western North Pacific, leading to a strong EASM. The above processes also operate in the weak EAWM to weak EASM transitions during which El Nio impacts dominate but with additional contributions from the EAWM. The results of observational analysis are confirmed by numerical experiments with a coupled model. © 2012 American Geophysical Union. All Rights Reserved."
"55915206300;57213789733;","Convective activity over Africa and the tropical Atlantic inferred from 20 Years of geostationary Meteosat infrared observations",2012,"10.1175/2011JCLI3984.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856955909&doi=10.1175%2f2011JCLI3984.1&partnerID=40&md5=2a71086af9ee4e599ecebc1f7eb3366a","A 20-yr (1986-2005) time series of Meteosat Visible and Infrared Imager (MVIRI) geostationary infrared observations was used to study deep convection over Africa and the tropical Atlantic. The 20-yr time period is covered by six consecutive satellites (Meteosat-2-7). To correct for possible systematic differences between instruments on the different satellite platforms, a time series of Meteosat infrared observations over cloud-free ocean surfaces was compared to reanalysis-based radiative transfer results. Based on the comparison of simulations with observations, a homogenization was performed for the MVIRI infrared channel. The homogenized 20-yr dataset was then subjected to a tracking analysis for deep convection over Africa and the tropical Atlantic for the boreal summer months of July-September. The mean state of convection as well as anomalies for high- and low-Sahel rainfall years were studied. Comparisons with the Global Precipitation Climatology Center's (GPCC) rainfall estimates were performed for the Sahel region and interannual variability was evaluated comparing convection for the five driest and five wettest Sahel years. Results support earlier findings that precipitation in the Sahel region is strongly linked to the latitudinal position of the African Easterly Jet with deep convection being triggered more strongly if the jet is displaced northward. A relationship between the jet position and long-lived convective systems over the tropical Atlantic was found as well. © 2012 American Meteorological Society."
"56568116700;55915046600;6602176524;7403401100;7103337730;57218412809;","Long-range transport of Saharan dust over northwestern Europe during EUCAARI 2008 campaign: Evolution of dust optical properties by scavenging",2012,"10.1029/2012JD017611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865974848&doi=10.1029%2f2012JD017611&partnerID=40&md5=ee7beb295e764929c6f7b7b18ef6331f","The evolution of dust optical properties is illustrated in this paper through a case of long-range transport of Saharan dust over northwestern Europe during the European Integrated Project on Aerosol-Cloud-Climate and Air Quality Interactions (EUCAARI) experimental campaign in 2008. This spread of dust over northwestern Europe is investigated by combining satellite, airborne, ground-based observations and the non-hydrostatic meso-scale model Meso-NH. The total dust amount emitted during the study period is estimated to 185 Tg. The analysis of the removal processes reveals that only 12.5 Tg is lost by dry deposition, and that wet deposition is the main process of dust removal (73 Tg). The observed aerosol optical thickness ranged from 0.1 to 0.5 at the wavelength of 440 nm, with a maximum value close to 1 is found over the Netherlands (51.97N, 4.93E). Over that site, the main dust layer is located between 2.5 and 5.2 km above sea level (asl), moreover dust was also present at 0.9 km asl. The nephelometer measurements on board the ATR-42 aircraft revealed a strong wavelength dependence of the scattering coefficient over the Netherlands. The Angstrm exponent is greater than 0.5, whereas usually it approaches zero in presence of Saharan dust. This is due to high precipitation scavenging efficiency for the coarse mode, particularly below 4 km. Our results confirm that atmospheric conditions govern the life cycle of dust microphysical phenomena, providing conditions for transformation processes during transport, and removal of particles from the atmosphere. © 2012. American Geophysical Union. All Rights Reserved."
"56029500900;6603849280;7003820847;6603459366;","Spatio-temporal prediction of daily temperatures using time-series of MODIS LST images",2012,"10.1007/s00704-011-0464-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855532082&doi=10.1007%2fs00704-011-0464-2&partnerID=40&md5=d98ac2d9b32d342f82bb5a3061a4c38d","A computational framework to generate daily temperature maps using time-series of publicly available MODIS MOD11A2 product Land Surface Temperature (LST) images (1 km resolution; 8-day composites) is illustrated using temperature measurements from the national network of meteorological stations (159) in Croatia. The input data set contains 57,282 ground measurements of daily temperature for the year 2008. Temperature was modeled as a function of latitude, longitude, distance from the sea, elevation, time, insolation, and the MODIS LST images. The original rasters were first converted to principal components to reduce noise and filter missing pixels in the LST images. The residual were next analyzed for spatio-temporal auto-correlation; sum-metric separable variograms were fitted to account for zonal and geometric space-time anisotropy. The final predictions were generated for time-slices of a 3D space-time cube, constructed in the R environment for statistical computing. The results show that the space-time regression model can explain a significant part of the variation in station-data (84%). MODIS LST 8-day (cloud-free) images are unbiased estimator of the daily temperature, but with relatively low precision (±4. 1°C); however their added value is that they systematically improve detection of local changes in land surface temperature due to local meteorological conditions and/or active heat sources (urban areas, land cover classes). The results of 10-fold cross-validation show that use of spatio-temporal regression-kriging and incorporation of time-series of remote sensing images leads to significantly more accurate maps of temperature than if plain spatial techniques were used. The average (global) accuracy of mapping temperature was ±2. 4°C. The regression-kriging explained 91% of variability in daily temperatures, compared to 44% for ordinary kriging. Further software advancement-interactive space-time variogram exploration and automated retrieval, resampling and filtering of MODIS images-are anticipated. © 2011 The Author(s)."
"6603400519;57215353127;35868180800;7005110573;","Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001-2009 MISR imagery of Borneo",2012,"10.5194/acp-12-3437-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880594727&doi=10.5194%2facp-12-3437-2012&partnerID=40&md5=1ca4727e3c8b9389e1d46f85f93dea44","Land clearing for crops, plantations and grazing results in anthropogenic burning of tropical forests and peatlands in Indonesia, where images of fire-generated aerosol plumes have been captured by the Multi-angle Imaging SpectroRadiometer (MISR) since 2001. Here we analyze the size, shape, optical properties, and age of distinct fire-generated plumes in Borneo from 2001-2009. The local MISR overpass at 10:30 a.m. misses the afternoon peak of Borneo fire emissions, and may preferentially sample longer plumes from persistent fires burning overnight. Typically the smoke flows with the prevailing southeasterly surface winds at 3-4 m s-1, and forms ovoid plumes whose mean length, height, and cross-plume width are 41 km, 708 m, and 27% of the plume length, respectively. 50% of these plumes have length between 24 and 50 km, height between 523 and 993 m and width between 18% and 30% of plume length. Length and cross-plume width are lognormally distributed, while height follows a normal distribution. Borneo smoke plume heights are similar to previously reported plume heights, yet Borneo plumes are on average nearly three times longer than previously studied plumes. This could be due to sampling or to more persistent fires and greater fuel loads in peatlands than in other tropical forests. Plume area (median 169 km2, with 25th and 75th percentiles at 99 km 2 and 304 km2, respectively) varies exponentially with length, though for most plumes a linear relation provides a good approximation. The MISR-estimated plume optical properties involve greater uncertainties than the geometric properties, and show patterns consistent with smoke aging. Optical depth increases by 15-25% in the down-plume direction, consistent with hygroscopic growth and nucleation overwhelming the effects of particle dispersion. Both particle single-scattering albedo and top-of-atmosphere reflectance peak about halfway down-plume, at values about 3% and 10% greater than at the origin, respectively. The initially oblong plumes become brighter and more circular with time, increasingly resembling smoke clouds. Wind speed does not explain a significant fraction of the variation in plume geometry. We provide a parameterization of plume shape that can help atmospheric models estimate the effects of plumes on weather, climate, and air quality. Plume age, the age of smoke furthest down-plume, is lognormally distributed with a median of 2.8 h (25th and 75th percentiles at 1.3 h and 4.0 h), different from the median ages reported in other studies. Intercomparison of our results with previous studies shows that the shape, height, optical depth, and lifetime characteristics reported for tropical biomass burning plumes on three continents are dissimilar and distinct from the same characteristics of non-tropical wildfire plumes. © Author(s) 2012."
"12646313600;25958833500;7102636633;35495958000;","Multi-model, multi-sensor estimates of global evapotranspiration: climatology, uncertainties and trends",2011,"10.1002/hyp.8393","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84155166951&doi=10.1002%2fhyp.8393&partnerID=40&md5=f94a84d9d683c81e1ac90d0284d8822e","Estimating evapotranspiration (ET) at continental to global scales is central to understanding the partitioning of energy and water at the earth's surface and the feedbacks with the atmosphere and biosphere, especially in the context of climate change. Recent evaluations of global estimates from remote sensing, upscaled observations, land surface models and atmospheric reanalyses indicate large uncertainty across the datasets of the order of 50% of the global annual mean value. In this paper, we explore the uncertainties in global land ET estimates using three process-based ET models and a set of remote sensing and observational based radiation and meteorological forcing datasets. Input forcings were obtained from International Satellite Cloud Climatology Project (ISCCP) and Surface Radiation Budget (SRB). The three process-based ET models are: a surface energy balance method (SEBS), a revised Penman-Monteith (PM) model, and a modified Priestley-Taylor model. Evaluations of the radiation products from ISCCP and SRB show large differences in the components of surface radiation, and temporal inconsistencies that relate to changes in satellite sensors and retrieval algorithms. In particular, step changes in the ISCCP surface temperature and humidity data lead to spurious increases in downward and upward longwave radiation that contributes to a step change in net radiation, and the ISCCP data are not used further. An ensemble of global estimates of land surface ET are generated at daily time scale and 0.5 degree spatial resolution for 1984-2007 using two SRB radiation products (SRB and SRBqc) and the three models. Uncertainty in ET from the models is much larger than the uncertainty from the radiation data. The largest uncertainties relative to the mean annual ET are in transition zones between dry and humid regions and monsoon regions. Comparisons with previous studies and an inferred estimate of ET from long-term inferred ET indicate that the ensemble mean value is reasonable, but generally biased high globally. Long-term changes over 1984-2007 indicate a slight increase over 1984-1998 and decline thereafter, although uncertainties in the forcing radiation data and lack of direct linkage with soil moisture limitations in the models prevents attribution of these changes. Copyright © 2011 John Wiley & Sons, Ltd."
"35221791100;35422119400;","Solar irradiance, cosmic rays and cloudiness over daily timescales",2011,"10.1029/2011GL049764","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855386925&doi=10.1029%2f2011GL049764&partnerID=40&md5=012b644e336b535b249b969ac412fac4","Although over centennial and greater timescales solar variability may be one of the most influential climate forcing agents, the extent to which solar activity influences climate over shorter time periods is poorly understood. If a link exists between solar activity and climate, it is likely via a mechanism connected to one (or a combination) of the following parameters: total solar irradiance (TSI), ultraviolet (UV) spectral irradiance, or the galactic cosmic ray (GCR) flux. We present an analysis based around a superposed epoch (composite) approach focusing on the largest TSI increases and decreases (the latter occurring in both the presence and absence of appreciable GCR reductions) over daily timescales. Using these composites we test for the presence of a robust link between solar activity and cloud cover over large areas of the globe using rigorous statistical techniques. We find no evidence that widespread variations in cloud cover at any tropospheric level are significantly associated with changes in the TSI, GCR or UV flux, and further conclude that TSI or UV changes occurring during reductions in the GCR flux are not masking a solar-cloud response. However, we note the detectability of any potential links is strongly constrained by cloud variability. Copyright 2011 by the American Geophysical Union."
"9249239700;7003278104;7404829395;","Correction to ""comparisons of satellites liquid water estimates to ECMWF and GMAO analyses, 20th century IPCC AR4 climate simulations, and GCM simulations""",2011,"10.1029/2011GL049956","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855326066&doi=10.1029%2f2011GL049956&partnerID=40&md5=e9d5eec3b73fd0060cfdf7082f2958f1","In the paper ""Comparisons of satellites liquid water estimates to ECMWF and GMAO analyses, 20th century IPCC AR4 climate simulations, and GCM simulations"" by Li et al. (Geophysical Research Letters, 35, L19710, doi:10.1029/2008GL035427, 2008, hereinafter LET), LET provided an assessment of the representation of the cloud liquid water path (LWP) by general circulation models (GCMs), namely the GCMs that contributed to the Coupled Model Intercomparison Project 3 (CMIP3) and that were utilized in the IPCC 4th Assessment. Since the publication of LET, discrepancies have been revealed in the interpretation of the request for model output and model documentation. Here we report a revision to the analysis results of LET based on correcting for these discrepancies. The corrected results illustrate smaller root mean square errors than that presented in LET and significantly improve the results of two GISS models and the IPSL model. While the results presented for a few specific models change, the main conclusions of LET remain valid, namely that significant disagreements of LWP are found among the models including both widely varying magnitudes and considerable differences in spatial patterns. Copyright © 2011 by the American Geophysical Union."
"54788308700;7003908632;12764954600;","An evaluation of arctic cloud and radiation processes simulated by the limited-area version of the Global Multiscale Environmental Model (GEM-LAM)",2011,"10.1080/07055900.2011.604266","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055211873&doi=10.1080%2f07055900.2011.604266&partnerID=40&md5=95fb035616e7e45d950c4a1ad887834d","Cloud and radiation processes simulated by the limited area version of the Global Environmental Multiscale Model (GEM-LAM) are evaluated for the period September 1997 to October 1998 over the western Arctic Ocean. This period coincides with the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment. Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path, precipitation, cloud cover and cloud radiative forcing simulated by GEM-LAM are evaluated against the SHEBA observation dataset. GEM-LAM simulates the annual cycle of the downwelling shortwave (SWD) and longwave (LWD) radiation at the surface reasonably well, as well as precipitable water at monthly and daily time scales. Cloud fraction at daily and monthly time scales is not captured well by the model. During winter, GEM-LAM produces a large negative bias for the vertically integrated liquid water path and a positive bias for cloud fraction. As a result, cloud radiative forcing at the surface and LWD radiation are well reproduced but for the wrong reasons because these two biases have an opposing effect on their magnitudes. During summer, the model underestimates the surface albedo, thus resulting in a substantial overestimation of the cloud radiative forcing at the surface. Precipitation is underestimated during winter and overestimated during summer and spring. The sensitivity of the results to the effective radius of ice crystals and the parameterization of cloud phase is also discussed."
"35461255500;6602506226;56127300900;7005069415;55896920900;7005601996;7102496779;7005254485;7006708207;55942083800;7006595513;57206330745;57203200427;7006960661;57204496157;7003931528;35593636200;7004015298;23995325300;57203053317;6603172418;6602354484;7004377728;9235235300;57205638870;7006107059;7005287667;56370934200;7102052227;34568413600;7005794259;33067634600;7004864963;24366038500;6602571316;7201966094;6602136905;57214957727;15833742800;53876886100;7101683010;7006837187;24343173500;6603186492;55984424900;6602523027;7402919163;15834652700;17433905200;7203052598;7103337730;24074350700;26024789300;36041280100;7402177459;41561458500;24398842400;55545335600;7007182077;6602607937;16689399100;56250250300;35221661700;7003489918;16833315000;12139043600;7101830914;42662973900;55826210400;8705440100;7005955015;7006182491;7006712143;6602350870;16233350800;7007039218;7102830450;23051160600;56370907100;9332706900;7004584381;6602914876;8663601100;35272531300;7003545995;36098422200;6602978326;6701596624;35998927000;35884266700;7005222105;6506773349;7006387246;7006219023;36134816800;7403401100;7102084129;7402433964;12139310900;8084443000;55366522200;6701753599;7103357902;6602085876;57203277084;55716266100;8715232900;6506180220;56037741700;36623061000;6603957672;6602493466;24435885300;54788679500;7005696579;20735974900;23101727900;7006593624;6701530981;14049331400;56384704800;15047358600;26643041500;7004469744;56472932500;","General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI)-integrating aerosol research from nano to global scales",2011,"10.5194/acp-11-13061-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054065257&doi=10.5194%2facp-11-13061-2011&partnerID=40&md5=8e4ec1736369649fad926be99a16a6eb","In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies. © 2011 Author(s)."
"24480463300;24385307600;26643041500;8705440100;7007182077;6602753217;7003984086;23995325300;","Secondary new particle formation in Northern Finland Pallas site between the years 2000 and 2010",2011,"10.5194/acp-11-12959-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055176678&doi=10.5194%2facp-11-12959-2011&partnerID=40&md5=644f073f276c7e883eb631133f577d75","Secondary new particle formation affects atmospheric aerosol and cloud droplet numbers and thereby, the aerosol effects on climate. In this paper, the frequency of nucleation events and the associated particle formation and growth rates, along with their seasonal variation, was analysed based on over ten years of aerosol measurements conducted at the Pallas GAW station in northern Finland. The long-term measurements also allowed a detailed examination of factors possibly favouring or suppressing particle formation. Effects of meteorological parameters and air mass properties as well as vapour sources and sinks for particle formation frequency and event parameters were inspected. In addition, the potential of secondary particle formation to increase the concentration of cloud condensation nuclei (CCN) sized particles was examined. Findings from these long-term measurements confirmed previous observations: event frequency peaked in spring and the highest growth rates were observed in summer, affiliated with increased biogenic activity. Events were almost exclusively observed in marine air masses on sunny cloud-free days. A low vapour sink by the background particle population as well as an elevated sulphuric acid concentration were found to favour particle formation. These were also conditions taking place most likely in marine air masses. Inter-annual trend showed a minimum in event frequency in 2003, when also the smallest annual median of growth rate was observed. This gives further evidence of the importance and sensitivity of particle formation for the condensing vapour concentrations at Pallas site. The particle formation was observed to increase CCN80 (>80 nm particle number) concentrations especially in summer and autumn seasons when the growth rates were the highest. When the growing mode exceeded the selected 80 nm limit, on average in those cases, 211 ± 114% increase of CCN80 concentrations was observed. © 2011 Author(s)."
"6508261814;16300532100;8538557300;7004054275;14625228300;25928520400;57215477525;","The December 2008 Crammont rock avalanche, Mont Blanc massif area, Italy",2011,"10.5194/nhess-11-3307-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83755186695&doi=10.5194%2fnhess-11-3307-2011&partnerID=40&md5=1db1ab4525e06f24f11ff87c0d137648","We describe a 0.5 Mm3 rock avalanche that occurred in 2008 in the western Alps and discuss possible roles of controlling factors in the context of current climate change. The source is located between 2410 m and 2653 m a.s.l. on Mont Crammont and is controlled by a densely fractured rock structure. The main part of the collapsed rock mass deposited at the foot of the rock wall. A smaller part travelled much farther, reaching horizontal and vertical travel distances of 3050 m and 1560 m, respectively. The mobility of the rock mass was enhanced by channelization and snow. The rock-avalanche volume was calculated by comparison of pre- and post-event DTMs, and geomechanical characterization of the detachment zone was extracted from LiDAR point cloud processing. Back analysis of the rock-avalanche runout suggests a two stage event. There was no previous rock avalanche activity from the Mont Crammont ridge during the Holocene. The 2008 rock avalanche may have resulted from permafrost degradation in the steep rock wall, as suggested by seepage water in the scar after the collapse in spite of negative air temperatures, and modelling of rock temperatures that indicate warm permafrost (T > -2 °C). © 2011 Author(s)."
"18438817800;21735084500;6506373162;55957189000;","The influence of eruption season on the global aerosol evolution and radiative impact of tropical volcanic eruptions",2011,"10.5194/acp-11-12351-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83755186684&doi=10.5194%2facp-11-12351-2011&partnerID=40&md5=c01f2b0a56014ebf3b671265b420448c","Simulations of tropical volcanic eruptions using a general circulation model with coupled aerosol microphysics are used to assess the influence of season of eruption on the aerosol evolution and radiative impacts at the Earth's surface. This analysis is presented for eruptions with SO 2 injection magnitudes of 17 and 700 Tg, the former consistent with estimates of the 1991 Mt. Pinatubo eruption, the later a near-""super eruption"". For each eruption magnitude, simulations are performed with eruptions at 15° N, at four equally spaced times of year. Sensitivity to eruption season of aerosol optical depth (AOD), clear-sky and all-sky shortwave (SW) radiative flux is quantified by first integrating each field for four years after the eruption, then calculating for each cumulative field the absolute or percent difference between the maximum and minimum response from the four eruption seasons. Eruption season has a significant influence on AOD and clear-sky SW radiative flux anomalies for both eruption magnitudes. The sensitivity to eruption season for both fields is generally weak in the tropics, but increases in the mid-and high latitudes, reaching maximum values of ∼75 %. Global mean AOD and clear-sky SW anomalies show sensitivity to eruption season on the order of 15-20 %, which results from differences in aerosol effective radius for the different eruption seasons. Smallest aerosol size and largest cumulative impact result from a January eruption for Pinatubo-magnitude eruption, and from a July eruption for the near-super eruption. In contrast to AOD and clear-sky SW anomalies, all-sky SW anomalies are found to be insensitive to season of eruption for the Pinatubo-magnitude eruption experiment, due to the reflection of solar radiation by clouds in the mid-to high latitudes. However, differences in all-sky SW anomalies between eruptions in different seasons are significant for the larger eruption magnitude, and the ∼15 % sensitivity to eruption season of the global mean all-sky SW anomalies is comparable to the sensitivity of global mean AOD and clear-sky SW anomalies. Our estimates of sensitivity to eruption season are larger than previously reported estimates: implications regarding volcanic AOD timeseries reconstructions and their use in climate models are discussed. © 2011 Author(s)."
"55193477400;7102466376;55193257300;6504384283;6602298992;","Macrolepidopteran assemblages along an altitudinal gradient in subtropical rainforest - exploring indicators of climate change",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859945552&partnerID=40&md5=1005817891b3a994f9d534f055cd1cd5","Moth assemblages have been widely used to estimate patterns of beta-diversity in forest ecosystems. As part of the IBISCA-Queensland project we examined patterns of diversity in a large subset of night-flying moths along an altitudinal gradient in subtropical rainforest. The permanent IBISCA-Queensland transect located in Lamington National Park, south-east Queensland, Australia, spans altitudes from 300 metres (m) to 1100 m above sea level (a.s.l.) within continuous, undisturbed rainforest. We sampled four replicate plots at each of five altitudes (300, 500, 700, 900, 1100 m a.s.l.). A total of 11 379 individual moths were sampled, belonging to approximately 865 morphospecies. Moth assemblages displayed a strong altitudinal signal at each of two sampling periods (October 2006 and March 2007). The results show that cloud forest above 900 m a.s.l. where Nothofagus moorei becomes dominant, contains a number of moth species that are restricted to the high elevation forest and these species may be most threatened by climatic change. The analyses presented here suggest a set of 18 moth species which may be useful as part of a multi-taxon predictor set for future monitoring of the impact of global warming on forest biodiversity. © The State of Queensland (Queensland Museum) 2011."
"36134816800;7004469744;8942525300;16401192300;57198068710;7004584381;6602914876;26024789300;7006837187;35461255500;7004296083;6603603545;55941661200;7004047498;7006595513;7005696579;6603948265;25631390600;7006708207;35449990500;24465126800;7005069415;7006434689;7102496779;6506180220;7004015298;8084443000;35770358000;7003276832;57209599724;7005287667;26029605900;6506810759;7006510157;7006058570;8093260300;6603563152;37078682300;7003658685;7004399781;31267503200;","Primary versus secondary contributions to particle number concentrations in the European boundary layer",2011,"10.5194/acp-11-12007-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83455231344&doi=10.5194%2facp-11-12007-2011&partnerID=40&md5=f5b24d28926f50adda1e5959c2fd7e8f","It is important to understand the relative contribution of primary and secondary particles to regional and global aerosol so that models can attribute aerosol radiative forcing to different sources. In large-scale models, there is considerable uncertainty associated with treatments of particle formation (nucleation) in the boundary layer (BL) and in the size distribution of emitted primary particles, leading to uncertainties in predicted cloud condensation nuclei (CCN) concentrations. Here we quantify how primary particle emissions and secondary particle formation influence size-resolved particle number concentrations in the BL using a global aerosol microphysics model and aircraft and ground site observations made during the May 2008 campaign of the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). We tested four different parameterisations for BL nucleation and two assumptions for the emission size distribution of anthropogenic and wildfire carbonaceous particles. When we emit carbonaceous particles at small sizes (as recommended by the Aerosol Intercomparison project, AEROCOM), the spatial distributions of campaign-mean number concentrations of particles with diameter &gt;50 nm (N 50) and &gt;100 nm (N100) were well captured by the model (R2≥0.8) and the normalised mean bias (NMB) was also small (-18% for N50 and-1% for N100). Emission of carbonaceous particles at larger sizes, which we consider to be more realistic for low spatial resolution global models, results in equally good correlation but larger bias (R2≥0.8, NMB =-52% and-29%), which could be partly but not entirely compensated by BL nucleation. Within the uncertainty of the observations and accounting for the uncertainty in the size of emitted primary particles, BL nucleation makes a statistically significant contribution to CCN-sized particles at less than a quarter of the ground sites. Our results show that a major source of uncertainty in CCN-sized particles in polluted European air is the emitted size of primary carbonaceous particles. New information is required not just from direct observations, but also to determine the ""effective emission size"" and composition of primary particles appropriate for different resolution models. © 2011 Author(s)."
"8942525300;57203776263;7004469744;7006593624;57217801354;35810775100;56384666800;6701643480;24537168200;7006837187;6603172418;12753162000;35547807400;","Aerosol mass spectrometer constraint on the global secondary organic aerosol budget",2011,"10.5194/acp-11-12109-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83455231309&doi=10.5194%2facp-11-12109-2011&partnerID=40&md5=3bdb63cf033dc473fc5fae0c80829858","The budget of atmospheric secondary organic aerosol (SOA) is very uncertain, with recent estimates suggesting a global source of between 12 and 1820 Tg (SOA) a -1. We used a dataset of aerosol mass spectrometer (AMS) observations from 34 different surface locations to evaluate the GLOMAP global chemical transport model. The standard model simulation (which included SOA from monoterpenes only) underpredicted organic aerosol (OA) observed by the AMS and had little skill reproducing the variability in the dataset. We simulated SOA formation from biogenic (monoterpenes and isoprene), lumped anthropogenic and lumped biomass burning volatile organic compounds (VOCs) and varied the SOA yield from each precursor source to produce the best overall match between model and observations. We assumed that SOA is essentially non-volatile and condenses irreversibly onto existing aerosol. Our best estimate of the SOA source is 140 Tg (SOA) a -1 but with a large uncertainty range which we estimate to be 50-380 Tg (SOA) a -1. We found the minimum in normalised mean error (NME) between model and the AMS dataset when we assumed a large SOA source (100 Tg (SOA) a -1) from sources that spatially matched anthropogenic pollution (which we term antropogenically controlled SOA). We used organic carbon observations compiled by Bahadur et al. (2009) to evaluate our estimated SOA sources. We found that the model with a large anthropogenic SOA source was the most consistent with these observations, however improvement over the model with a large biogenic SOA source (250 Tg (SOA) a -1) was small. We used a dataset of 14C observations from rural locations to evaluate our estimated SOA sources. We estimated a maximum of 10 Tg (SOA) a -1 (10 %) of the anthropogenically controlled SOA source could be from fossil (urban/industrial) sources. We suggest that an additional anthropogenic source is most likely due to an anthropogenic pollution enhancement of SOA formation from biogenic VOCs. Such an anthropogenically controlled SOA source would result in substantial climate forcing. We estimated a global mean aerosol direct effect of-0.26 plusmn; 0.15 Wm -2 and indirect (cloud albedo) effect of-0.6 +0.24 -0.14 Wm-2 from anthropogenically controlled SOA. The biogenic and biomass SOA sources are not well constrained with this analysis due to the limited number of OA observations in regions and periods strongly impacted by these sources. To further improve the constraints by this method, additional OA observations are needed in the tropics and the Southern Hemisphere. © 2011 Author(s)."
"7005135473;","Satellite remote sensing methods for estimating clear Sky shortwave Top of atmosphere fluxes used for aerosol studies over the global oceans",2011,"10.1016/j.rse.2011.06.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81355138678&doi=10.1016%2fj.rse.2011.06.003&partnerID=40&md5=3c14fd7d4dce19a7de593920b217ff29","The difference between the top of atmosphere shortwave clear sky (cloud and aerosol free, SWCLR) and aerosol sky radiative fluxes is known as direct radiative effect (DRE) for all aerosols or Direct Climate Forcing (DCF) for anthropogenic aerosols. There are several methods for calculating SWCLR including satellite-based methods and radiative transfer approaches. Since uncertainties in SWCLR can propagate into errors in DRE or DCF, we assess the SWCLR estimates over the global oceans using three approaches and quantify the differences among these methods both as a function of space and season. Our results indicate that the more commonly used intercept (73.4±3.6) and radiative transfer methods (74.7±4.0 Wm-2) are in close agreement to within±1.3 Wm-2. Values of SWCLR are provided as a function of space and season that can be used by other studies that require such values or as a source of validation. We further recommend that research studies report the methods and assumptions used to estimate SWCLR to facilitate easier intercomparisons among methods. © 2011 Elsevier Inc."
"37760934500;23978405300;8309699900;36093461100;6603135449;8871497700;17433787100;35461255500;7006593624;7006712143;7410177774;6701378450;","Aerosol hygroscopicity and CCN activation kinetics in a boreal forest environment during the 2007 EUCAARI campaign",2011,"10.5194/acp-11-12369-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955379896&doi=10.5194%2facp-11-12369-2011&partnerID=40&md5=c686824549ae8ae3208d60a4e405d7ea","Measurements of size-resolved cloud condensation nuclei (CCN) concentrations, subsaturated hygroscopic growth, size distribution, and chemical composition were collected from March through May, 2007, in the remote Boreal forests of Hyytiälä, Finland, as part of the European Integrated project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) campaign. Hygroscopicity parameter, κ, distributions were derived independently from Continuous Flow-Streamwise Thermal Gradient CCN Chamber (CFSTGC) and Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) measurements. CFSTGC-derived κ values for 40, 60, and 80 nm particles range mostly between 0.10 and 0.40 with an average characteristic of highly oxidized organics of 0.20 ± 0.10, indicating that organics play a dominant role for this environment. HTDMA-derived κ were generally 30% lower. Diurnal trends of κ show a minimum at sunrise and a maximum in the late afternoon; this trend covaries with inorganic mass fraction and the m/z 44 organic mass fraction given by a quadrupole aerosol mass spectrometer, further illustrating the importance of organics in aerosol hygroscopicity. The chemical dispersion inferred from the observed κ distributions indicates that while 60 and 80 nm dispersion increases around midday, 40 nm dispersion remains constant. Additionally, 80 nm particles show a markedly higher level of chemical dispersion than both 40 and 60 nm particles. An analysis of droplet activation kinetics for the sizes considered indicates that most of the CCN activate as rapidly as (NH 4) 2SO 4 calibration aerosol. © 2011 Author(s)."
"6701717474;7004863773;7003568043;","Intrapopulation variation in flowering phenology and fecundity of silver birch, implications for adaptability to changing climate",2011,"10.1016/j.foreco.2011.08.038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055022183&doi=10.1016%2fj.foreco.2011.08.038&partnerID=40&md5=b73cc988f0c7f48e8e657aaf6de9c233","Earlier modeling has suggested that long distance gene flow is of importance in increasing the adaptability of tree populations in a changing climate. In times of warming temperatures, early flowering phenotypes may be favored, because early flowering may be connected to early onset of growth. Long term direct measurements of flowering, pollen cloud and intrapopulation fecundity variations are needed to test this hypothesis. Having one of the furthest transported types of pollen grains, birch may have good potential for long distance gene flow. Our daily observations over eight years, of 30 silver birches (Betula pendula Roth), showed that the onset and duration of flowering phenology was determined by the accumulation of spring temperature sums, but the window for potential long distance gene flow was narrow. The interannual phenology variations were large, the order of timing of female and male catkins in various trees of this monoecious species tended to differ, and the timing of generative and vegetative spring phenologies were not correlated at tree level. Early flowering trees tended to have a higher variation in germinability than later flowering trees. No other connection between timing of phenology of flowering and seed quantity or quality was found. Although stochastic climatic conditions produce interannually variable phenological windows, probability for long distance gene flow from areas differing in timing of spring temperature accumulations may be low in silver birch. Intertree variations in fecundity were high, and the majority of seeds and pollen were produced by only a few trees. Moreover, the amount of seeds produced was positively related to seed germinability, thus large phenotypic fecundity variations may decrease interannual genetic variations in seed sets. © 2011 Elsevier B.V."
"14124224600;8368714300;37029909300;37029899800;55959710400;","A topographic geostatistical approach for mapping monthly mean values of daily global solar radiation: A case study in southern Spain",2011,"10.1016/j.agrformet.2011.07.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054909054&doi=10.1016%2fj.agrformet.2011.07.021&partnerID=40&md5=2253993335e2c6d76870d3b310853135","Local topography influences total incoming solar radiation at ground surface in mountainous areas, and so it becomes a key factor for the spatial distribution of plants. However, radiometric stations are often clustered only around farmland or populated areas, usually throughout valleys and flat regions. In this work, we use residual kriging methods to account for cloud- and terrain-related effects, especially when availability of measurements in mountains is scarce. Terrain-related effects have been considered through the terrain elevation and a topographic clear-sky solar radiation model that, additionally, also allow us to consider local clouds effects. Mesoscale-level phenomena were considered through the distance to the coast and the geographical longitude, that partially explain the atmospheric circulation in the studied region. The study has been conducted in the region of Andalusia, in southern Spain, using a target grid support of 1. km of grid-spacing and based on a 10-year length experimental dataset of 63 stations. Two different residual kriging approaches were evaluated and compared against ordinary kriging estimates. Overall, all kriging methods showed good skills in predicting the spatial regionalization of the monthly averages of daily solar radiation. The use of the distance to the coast and the geographical longitude enhanced the performance of residual kriging methods. Elevation proved to be important during summer months, while clear-sky solar radiation estimates were helpful especially during winter months. Overall, the RMSE value for ordinary kriging at the validation sites was about 3%. The residual kriging methods were able to outperform ordinary kriging around a 5% in winter and up to a 18% in summer, in relative terms. © 2011 Elsevier B.V."
"9941667900;9939319500;7003372967;7004543272;16052876100;6602219372;6602459393;7005640512;","Search for indications of stellar mass ejections using FUV spectra",2011,"10.1051/0004-6361/201015985","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83055165919&doi=10.1051%2f0004-6361%2f201015985&partnerID=40&md5=0a8c5dad5f0d2193d5040aa849ab3ea5","Aims. We search for highly energetic activity phenomena in a small sample of late-type main-sequence stars in the far ultraviolet (FUV) using data from the Far Ultraviolet Spectroscopic Explorer (FUSE). Methods. Because FUSE allows a simultaneous photometric and spectroscopic analysis, we are able to analyze variations in the light curves (flares) and possible, activity-related signatures (line asymmetries, enhancements, and shifts) in the spectra. Furthermore, the computation of the well-known density-sensitive line ratio C III (λ1176 Å)/C III(λ977 Å) is also possible, and allows the investigation of its dependence on stellar activity. Results. Three late-type main-sequence stars found in the FUSE archive (HD 36705, HD 197481, and Gl 388) show flares in their light curves. We find no obvious Doppler shifts in the brightest lines of these stars, but the O vI(λ1032 Å) transition region line of AD Leo shows a blue wing enhancement one spectrum after a flare event. This emission feature is shifted by ∼-84 km s -1 from the line core. We can exclude that the spectral feature was caused by a gas cloud co-rotating with the star and favor an interpretation of a mass ejection. In addition we find an increase of the C III(λ1176 Å)/C III(λ977 Å) line ratio during all detected flares. We compare this finding to the Sun using solar full-disk spectra from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) and SOlar Radiation and Climate Experiment (SORCE) missions, and find that powerful flare events also show an increased C III(λ1176 Å)/C III(λ977 Å) line ratio but this result is of low statistical significance. Owing to a lack of perfectly temporally coinciding TIMED/SORCE spectra and a low temporal resolution (∼15 spectra per day) it is not possible to distinguish clearly if this increase is caused by the flares or by the related mass ejections. © 2011 ESO."
"11940188700;6603749963;7003777747;55636322183;10243536500;17434636400;","Anthropogenic radiative forcing time series from pre-industrial times until 2010",2011,"10.5194/acp-11-11827-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82355184402&doi=10.5194%2facp-11-11827-2011&partnerID=40&md5=d16d2a29249f6f05b6d2631bdb03abec","In order to use knowledge of past climate change to improve our understanding of the sensitivity of the climate system, detailed knowledge about the time development of radiative forcing (RF) of the earth atmosphere system is crucial. In this study, time series of anthropogenic forcing of climate from pre-industrial times until 2010, for all well established forcing agents, are estimated. This includes presentation of RF histories of well mixed greenhouse gases, tropospheric ozone, direct-and indirect aerosol effects, surface albedo changes, stratospheric ozone and stratospheric water vapour. For long lived greenhouse gases, standard methods are used for calculating RF, based on global mean concentration changes. For short lived climate forcers, detailed chemical transport modelling and radiative transfer modelling using historical emission inventories is performed. For the direct aerosol effect, sulphate, black carbon, organic carbon, nitrate and secondary organic aerosols are considered. For aerosol indirect effects, time series of both the cloud lifetime effect and the cloud albedo effect are presented. Radiative forcing time series due to surface albedo changes are calculated based on prescribed changes in land use and radiative transfer modelling. For the stratospheric components, simple scaling methods are used. Long lived greenhouse gases (LLGHGs) are the most important radiative forcing agent with a RF of 2.83±0.28 W m-2 in year 2010 relative to 1750. The two main aerosol components contributing to the direct aerosol effect are black carbon and sulphate, but their contributions are of opposite sign. The total direct aerosol effect was-0.48±0.32 W m -22 in year 2010. Since pre-industrial times the positive RF (LLGHGs and tropospheric O3) has been offset mainly by the direct and indirect aerosol effects, especially in the second half of the 20th century, which possibly lead to a decrease in the total anthropogenic RF in the middle of the century. We find a total anthropogenic RF in year 2010 of 1.4 W m -22. However, the uncertainties in the negative RF from aerosols are large, especially for the cloud lifetime effect. © 2011 Author(s)."
"57209647985;6602715033;7005284577;6602890253;9271096600;7202050065;6603735912;7404062492;6701378450;","Hygroscopicity and composition of Alaskan Arctic CCN during April 2008",2011,"10.5194/acp-11-11807-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82355184378&doi=10.5194%2facp-11-11807-2011&partnerID=40&md5=baa5c0355652084b717c218ec53b87d1","We present a comprehensive characterization of cloud condensation nuclei (CCN) sampled in the Alaskan Arctic during the 2008 Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project, a component of the POLARCAT and International Polar Year (IPY) initiatives. Four distinct air mass types were sampled including a cleaner Arctic background and a relatively pristine sea ice boundary layer as well as biomass burning and anthropogenic pollution plumes. Despite differences in chemical composition, inferred aerosol hygroscopicities were fairly invariant and ranged from k = 0.1-0.3 over the atmospherically-relevant range of water vapor supersaturations studied. Organic aerosols sampled were found to be well-oxygenated, consistent with long-range transport and aerosol aging processes. However, inferred hygroscopicities are less than would be predicted based on previous parameterizations of biogenic oxygenated organic aerosol, suggesting an upper limit on organic aerosol hygroscopicity above which k is less sensitive to the O:C ratio. Most Arctic aerosols act as CCN above 0.1 % supersaturation, although the data suggest the presence of an externally-mixed, non-CCN-active mode comprising approximately 0-20% of the aerosol number. CCN closure was assessed using measured size distributions, bulk chemical composition, and assumed aerosol mixing states; CCN predictions tended toward overprediction, with the best agreement (±0-20 %) obtained by assuming the aerosol to be externally-mixed with soluble organics. Closure also varied with CCN concentration, and the best agreement was found for CCN concentrations above 100 cm-3 with a 1.5-to 3-fold overprediction at lower concentrations. © 2011 Author(s)."
"6701652286;","The role of low clouds in determining climate sensitivity in response to a doubling of CO2 as obtained from 16 mixed-layer models",2011,"10.1007/s10584-011-0047-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555203531&doi=10.1007%2fs10584-011-0047-3&partnerID=40&md5=9005caf8e8e2228781c3e54879c9d8fb","The effects that low clouds in sub-tropical to tropical latitudes have in determining a given model's climate sensitivity is investigated by analyzing the cloud data produced by 16 ""slab"" or mixed-layer models submitted to the PCMDI and CFMIP archives and their respective response to a doubling of CO2. It is found that, within the context of the 16 models analyzed, changes of these low clouds appear to play a major role in determining model sensitivity but with changes of middle cloud also contributing especially from middle to higher latitudes. It is noted that the models with the smallest overall cloud change produce the smallest climate sensitivities and vice versa although the overall signs of the respective cloud feedbacks are positive. It is also found that the amounts of low cloud as simulated by the respective control runs have very little correlation with their respective climate sensitivities. In general, the overall latitude-height patterns of cloud change as derived from these more recent experiments agree quite well with those obtained from much earlier studies which include increases of the highest cloud, decreases of cloud lower down in the middle and lower tropospheric and small increases of low clouds. Finally, other mitigating factors are mentioned which could also affect the spread of the resulting climate sensitivities. © 2011 U.S. Government."
"36339753800;57205867148;6602600408;","On constraining estimates of climate sensitivity with present-day observations through model weighting",2011,"10.1175/2011JCLI4193.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960351865&doi=10.1175%2f2011JCLI4193.1&partnerID=40&md5=91ecf954d348e0215e47a0ebb089b122","The distribution of model-based estimates of equilibrium climate sensitivity has not changed substantially in more than 30 years. Efforts to narrow this distribution by weighting projections according to measures of model fidelity have so far failed, largely because climate sensitivity is independent of current measures of skill in current ensembles of models. This work presents a cautionary example showing that measures of model fidelity that are effective at narrowing the distribution of future projections (because they are systematically related to climate sensitivity in an ensemble of models) may be poor measures of the likelihood that a model will provide an accurate estimate of climate sensitivity (and thus degrade distributions of projections if they are used as weights). Furthermore, it appears unlikely that statistical tests alone can identify robust measures of likelihood. The conclusions are drawn from two ensembles: one obtained by perturbing parameters in a single climate model and a second containing the majority of the world's climate models. The simple ensemble reproduces many aspects of the multimodel ensemble, including the distributions of skill in reproducing the present-day climatology of clouds and radiation, the distribution of climate sensitivity, and the dependence of climate sensitivity on certain cloud regimes. Weighting by error measures targeted on those regimes permits the development of tighter relationships between climate sensitivity and model error and, hence, narrower distributions of climate sensitivity in the simple ensemble. These relationships, however, do not carry into the multimodel ensemble. This suggests that model weighting based on statistical relationships alone is unfounded and perhaps that climate model errors are still large enough that model weighting is not sensible. © 2011 American Meteorological Society."
"56493740900;7004325649;7102651635;55717441600;12769875100;6603685334;7003854810;7404150761;6508194789;6506827279;7406061582;57211010680;","Detection of atmospheric changes in spatially and temporally averaged infrared spectra observed from space",2011,"10.1175/JCLI-D-10-05005.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84155179093&doi=10.1175%2fJCLI-D-10-05005.1&partnerID=40&md5=5c71a1bd083c77d8a4289626e3af48d6","Variability present at a satellite instrument sampling scale (small-scale variability) has been neglected in earlier simulations of atmospheric and cloud property change retrievals using spatially and temporally averaged spectral radiances. The effects of small-scale variability in the atmospheric change detection process are evaluated in this study. To simulate realistic atmospheric variability, top-of-the-atmosphere nadir-view longwave spectral radiances are computed at a high temporal (instantaneous) resolution with a 20-km fieldof- view using cloud properties retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements, along with temperature humidity profiles obtained from reanalysis. Specifically, the effects of the variability on the necessary conditions for retrieving atmospheric changes by a linear regression are tested. The percentage error in the annual 10° zonal mean spectral radiance difference obtained by assuming linear combinations of individual perturbations expressed as a root-mean-square (RMS) difference computed over wavenumbers between 200 and 2000 cm -1 is 10%-15% for most of the 10° zones. However, if cloud fraction perturbation is excluded, the RMS difference decreases to less than 2%. Monthly and annual 10° zonal mean spectral radiances change linearly with atmospheric property perturbations, which occur when atmospheric properties are perturbed by an amount approximately equal to the variability of the 10° zonal monthly deseasonalized anomalies or by a climate-model-predicted decadal change. Nonlinear changes in the spectral radiances of magnitudes similar to those obtained through linear estimation can arise when cloud heights and droplet radii in water cloud change. The spectral shapes computed by perturbing different atmospheric and cloud properties are different so that linear regression can separate individual spectral radiance changes from the sum of the spectral radiance change. When the effects of small-scale variability are treated as noise, however, the error in retrieved cloud properties is large. The results suggest the importance of considering small-scale variability in inferring atmospheric and cloud property changes from the satellite-observed zonally and annually averaged spectral radiance difference. © 2011 American Meteorological Society."
"7004022660;57189498750;7202968142;","The climate penalty for clean fossil fuel combustion",2011,"10.5194/acp-11-12917-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871317734&doi=10.5194%2facp-11-12917-2011&partnerID=40&md5=9af39c09cccda6db36c5684939510da9","To cope with the world's growing demand for energy, a large number of coal-fired power plants are currently in operation or under construction. To prevent environmental damage from acidic sulphur and particulate emissions, many such installations are equipped with flue gas cleaning technology that reduces the emitted amounts of sulphur dioxide (SO2) and nitrogen dioxide (NO2). However, the consequences of this technology for aerosol emissions, and in particular the regional scale impact on cloud microphysics, have not been studied until now. We performed airborne investigations to measure aerosol size distributions in the air masses downwind of coal-fired power installations. We show how the current generation of clean technology reduces the emission of sulphur and fine particulate matter, but leads to an unanticipated increase in the direct emission of ultrafine particles (1-10 nm median diameter) which are highly effective precursors of cloud condensation nuclei (CCN). Our analysis shows how these additional ultrafine particles probably modify cloud microphysics, as well as precipitation intensity and distribution on a regional scale downwind of emission sources. Effectively, the number of small water droplets might be increased, thus reducing the water available for large droplets and rain formation. The possible corresponding changes in the precipitation budget with a shift from more frequent steady rain to occasionally more vigorous rain events, or even a significant regional reduction of annual precipitation, introduce an unanticipated risk for regional climate and agricultural production, especially in semi-arid climate zones. © Author(s)2011."
"8608733900;55405340400;7102266120;13403957300;","Aerosol retrievals under partly cloudy conditions: challenges and perspectives",2011,"10.1007/978-94-007-1636-0_8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883360879&doi=10.1007%2f978-94-007-1636-0_8&partnerID=40&md5=e35da86ec9529cc49ceab657c9b919f8","There are many interesting and intriguing features of aerosols near clouds - many of which can be quite engaging, as well as being useful and climate- related. Exploring aerosols by means of remote sensing, in situ observations, and numerical modeling has piqued our curiosity and led to improved insights into the nature of aerosol and clouds and their complex relationship. This chapter conveys the outstanding issues of cloudy-sky aerosol retrievals and outlines fruitful connections between the remote sensing of important climate-related aerosol properties and other research areas such as in situ measurements and model simulations. The chapter focuses mostly on treating inverse problems in the context of passive satellite remote sensing and how they can improve our understanding of the cloud-aerosol interactions. The presentation covers basics of the inverse-problem theory, reviews available approaches, and discusses their applications to partly cloudy situations. © Springer Science+Business Media B.V. 2011."
"55537426400;35580303100;7003420726;10241462700;6603196127;","Dependency of feedbacks on forcing and climate state in physics parameter ensembles",2011,"10.1175/2011JCLI3954.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952170856&doi=10.1175%2f2011JCLI3954.1&partnerID=40&md5=ad6495ee801711a15eb2f4dc5d5575a1","Climate sensitivity is one of the most important metrics for future climate projections. In previous studies the climate of the last glacial maximum has been used to constrain the range of climate sensitivity, and similarities and differences of temperature response to the forcing of the last glacial maximum and to idealized future forcing have been investigated. The feedback processes behind the response have not, however, been fully explored in a large model parameter space. In this study, the authors first examine the performance of various feedback analysis methods that identify important feedbacks for a physics parameter ensemble in experiments simulating both past and future climates. The selected methods are then used to reveal the relationship between the different ensemble experiments in terms of individual feedback processes. For the first time, all of the major feedback processes for an ensemble of paleoclimate simulations are evaluated. It is shown that the feedback and climate sensitivity parameters depend on the nature of the forcing and background climate state. The forcing dependency arises through the shortwave cloud feedback while the state dependency arises through the combined water vapor and lapse-rate feedback. The forcing dependency is, however, weakened when the feedback is estimated from the forcing that includes tropospheric adjustments. Despite these dependencies, past climate can still be used to provide a useful constraint on climate sensitivity as long as the limitation is properly taken into account because the strength of each feedback correlates reasonably well between the ensembles. It is, however, shown that the physics parameter ensemble does not cover the range of results simulated by structurally different models, which suggests the need for further study exploring both structural and parameter uncertainties. © 2011 American Meteorological Society."
"7003995144;7102998392;56271066200;7006840372;7102006474;41762326300;6701501555;7202386372;6603734019;35414069200;","Thermodynamic atmospheric profiling during the 2010 winter olympics using ground-based microwave radiometry",2011,"10.1109/TGRS.2011.2154337","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82155185323&doi=10.1109%2fTGRS.2011.2154337&partnerID=40&md5=537cf1df4c12ae41f323806b6de7be46","Ground-based microwave radiometer profilers in the 20-60-GHz range operate continuously at numerous sites in different climate regions. Recent work suggests that a 1-D variational (1-DVAR) technique, coupling radiometric observations with outputs from a numerical weather prediction model, may outperform traditional retrieval methods for temperature and humidity profiling. The 1-DVAR technique is applied here to observations from a commercially available microwave radiometer deployed at Whistler, British Columbia, which was operated by Environment Canada to support nowcasting and short-term weather forecasting during the Vancouver 2010 Winter Olympic and Paralympic Winter Games. The analysis period included rain, sleet, and snow events ( ∼235-mm total accumulation and rates up to 18 mm/h). The 1-DVAR method is applied quasi-operationally, i.e., as it could have been applied in real time, as no data were culled. The 1-DVAR-achieved accuracy has been evaluated by using simultaneous radiosonde and ceilometer observations as reference. For atmospheric profiling from the surface to 10 km, we obtain retrieval errors within 1.5 K for temperature and 0.5 g/m3 for water vapor density. The retrieval accuracy for column-integrated water vapor is 0.8 kg/m 2, with small bias (-0.1kgm2) and excellent correlation (0.96). The retrieval of cloud properties shows a high probability of detection of cloud/no cloud (0.8/0.9, respectively), low false-alarm ratio (0.1), and cloud-base height estimate error within ∼0.60 km. © 2011 IEEE."
"55016523500;55016746600;24605848200;7003461830;","Net radiation estimation under pasture and forest in rondônia, Brazil, with TM landsat 5 images",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857352903&partnerID=40&md5=cf52dd41a4f94c2987fca58fba78f860","The main objective of this study is to obtain the spatial distribution of net radiation (RN) in two contrasting vegetation covers (forest and pasture) through the SEBAL algorithm, and to analyze its performance when applied to tropical humid atmospheric conditions. This study was conducted in the state of Rondônia in northwestern Brazil, using four Landsat TM images, as well as, digital elevation model data. The correlation coefficients between estimated (SEBAL) and measured values of RN, and surface albedo are of 0.97 and 0.88, respectively. These results present SEBAL as an important tool to be used in hydrological and environmental studies, and to obtain coherent temporal and spatial variations of surface characteristics, helping in the improvement and validation of model parameterizations. However, the applications of remote sensing techniques in tropical humid climates are difficult, because of the existence of a constant presence of convective clouds."
"7404334532;7405727977;16304578900;25822837600;","Earth's energy imbalance and implications",2011,"10.5194/acp-11-13421-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84555194782&doi=10.5194%2facp-11-13421-2011&partnerID=40&md5=a7ab7adbafffdf7fb83c31bb562f1909","Improving observations of ocean heat content show that Earth is absorbing more energy from the Sun than it is radiating to space as heat, even during the recent solar minimum. The inferred planetary energy imbalance, 0.58 ± 0.15 W mg -2 during the 6-yr period 2005-2010, confirms the dominant role of the human-made greenhouse effect in driving global climate change. Observed surface temperature change and ocean heat gain together constrain the net climate forcing and ocean mixing rates. We conclude that most climate models mix heat too efficiently into the deep ocean and as a result underestimate the negative forcing by human-made aerosols. Aerosol climate forcing today is inferred to be g -1.6 ± 0.3 W mg -2, implying substantial aerosol indirect climate forcing via cloud changes. Continued failure to quantify the specific origins of this large forcing is untenable, as knowledge of changing aerosol effects is needed to understand future climate change. We conclude that recent slowdown of ocean heat uptake was caused by a delayed rebound effect from Mount Pinatubo aerosols and a deep prolonged solar minimum. Observed sea level rise during the Argo float era is readily accounted for by ice melt and ocean thermal expansion, but the ascendency of ice melt leads us to anticipate acceleration of the rate of sea level rise this decade. © Author(s) 2011. CC Attribution 3.0 License."
"7006568483;7201549312;","Kalman filter-based CMORPH",2011,"10.1175/JHM-D-11-022.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755154526&doi=10.1175%2fJHM-D-11-022.1&partnerID=40&md5=563e58c60dc42df09c27ee26198afc60","A Kalman filter (KF)-based Climate Prediction Center (CPC) morphing technique (CMORPH) algorithm is developed to integrate the passive microwave (PMW) precipitation estimates from low-Earth-orbit (LEO) satellites and infrared (IR) observations from geostationary (GEO) platforms. With the new algorithm, the precipitation analysis at a grid box of 8 × 8 km 2 is defined in three steps. First, PMW estimates of instantaneous rain rates closest to the target analysis time in both the forward and backward directions are propagated from their observation times to the analysis time using the cloud system advection vectors (CSAVs) computed from the GEO-IR images. The ""prediction"" of the precipitation analysis is then defined by averaging the forward- and backward-propagated PMW estimates with weights inversely proportional to their error variance. The IR-based precipitation estimates are incorporated if the gap between the two PMW observations is longer than 90 min. Validation tests showed substantial improvements of the KF-based CMORPH against the original version in both the pattern correlation and fidelity of probability density function (PDF) of the precipitation intensity. In general, performance of the original CMORPH degrades sharply with poor pattern correlation and substantially elevated (damped) frequency for light (heavy) precipitation events when PMW precipitation estimates are available from fewer LEO satellites. The KF-based CMORPHis capable of producing high-resolution precipitation analysis with much more stable performance with various levels of availability for the PMW observations. © 2011 American Meteorological Society."
"14066601400;7003469326;7005899926;6506389946;55238619300;35487016600;25923454000;55951906300;7102113229;","CIAO: The CNR-IMAA advanced observatory for atmospheric research",2011,"10.5194/amt-4-1191-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81055147763&doi=10.5194%2famt-4-1191-2011&partnerID=40&md5=295ec413e7d66c0df0ba9e28d5671945","Long-term observations of aerosol and clouds are of crucial importance to understand the weather climate system. At the Istituto di Metodologie per l'Analisi Ambientale of the Italian National Research Council (CNR-IMAA) an advanced atmospheric observatory, named CIAO, is operative. CIAO (CNR-IMAA Atmospheric Observatory) main scientific objective is the long term measurement for the climatology of aerosol and cloud properties. Its equipment addresses the state-of-the-art for the ground-based remote sensing of aerosol, water vapour and clouds including active and passive sensors, like lidars, ceilometers, radiometers, and a radar. This paper describes the CIAO infrastructure, its scientific activities as well as the observation strategy. The observation strategy is mainly organized in order to provide quality assured measurements for satellite validation and model evaluation and to fully exploit the synergy and integration of the active and passive sensors for the improvement of atmospheric profiling. Data quality is ensured both by the application of protocols and dedicated quality assurance programs mainly related to the projects and networks in which the infrastructure is involved. The paper also introduces examples of observations performed at CIAO and of the synergies and integration algorithms (using Raman lidar and microwave profiler data) developed and implemented at the observatory for the optimization and improvement of water vapour profiling. CIAO database represents an optimal basis to study the synergy between different sensors and to investigate aerosol-clouds interactions, and can give a significant contribution to the validation programs of the incoming new generation satellite missions. © 2012 Author(s)."
"57214576588;8701353900;15919465200;6603679007;6507439946;56228193100;","Operational convective-scale numerical weather prediction with the COSMO model: Description and sensitivities",2011,"10.1175/MWR-D-10-05013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960533068&doi=10.1175%2fMWR-D-10-05013.1&partnerID=40&md5=81d9f8400edeb870532121ad93fcaa5e","Since April 2007, the numerical weather prediction model, COSMO (Consortium for Small Scale Modelling), has been used operationally in a convection-permitting configuration, named COSMO-DE, at the Deutscher Wetterdienst (DWD; German weather service). Here the authors discuss the model changes that were necessary for the convective scale, and report on the experience from the first years of operational application of the model. For COSMO-DE the ability of the numerical solver to treat small-scale structures has been improved by using a Runge-Kutta method, which allows for the use of higher-order upwind advection schemes. The one-moment cloud microphysics parameterization has been extended by a graupel class, and adaptations for describing evaporation of rain and stratiform precipitation processes were made. Comparisons with a much more sophisticated two-moment scheme showed only minor differences in most cases with the exception of strong squall-line situations. Whereas the deep convection parameterization was switched off completely, small-scale shallow convection was still parameterized by the appropriate part of the Tiedtke scheme. During the first year of operational use, convective events in synoptically driven situations were satisfactorily simulated. Also the daily cycles of summertime 10-m wind and 1-h precipitation sums were well captured. However, it became evident that the boundary layer description had to be adapted to enhance convection initiation in airmass convection situations. Here the asymptotic Blackadar length scale l∞ had proven to be a sensitive parameter. © 2011 American Meteorological Society."
"57196499374;","Insights on global warming",2011,"10.1002/aic.12780","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80355133224&doi=10.1002%2faic.12780&partnerID=40&md5=cdfe2e5bbc736b71d7b4ecfea47dbbd7","The global temperature increase over the last century and a half (~ 0.8°C), and the last three decades in particular, is well outside of that which can be attributed to natural climate fluctuations. The increase of atmospheric CO2 over this period has been conclusively demonstrated to be a result largely of fossil fuel burning. The global mean temperature change that results in response to a sustained perturbation of the Earth's energy balance after a time sufficiently long for both the atmosphere and oceans to come to thermal equilibrium is termed the Earth's climate sensitivity. The purely radiative (blackbody) warming from a doubling of CO2 from its preindustrial level of 280 parts-per-million (ppm) to 560 ppm is ~ 1.2°C; the actual warming that would result is considerably larger owing to amplification by climate feedbacks, including that owing to water vapor. Increases in greenhouse gas (GHG) levels are estimated to have contributed about +3.0 W m-2 perturbation (radiative forcing) to the Earth's energy balance. Particles (aerosols), on the whole, exert a cooling effect on climate, with a total forcing estimated by the Intergovernmental Panel on Climate Change (2007)1 as -1.2 W m-2, a value that is subject to considerable uncertainty. If the actual magnitude of aerosol forcing is close to the low end of its estimated uncertainty range, then it offsets a considerably smaller fraction of the GHG forcing and the total net forcing is at the high end of its range, ~ 2.4 W m-2; at the other extreme, if the actual aerosol cooling is at the high end of its range, then aerosol forcing is currently offsetting a major fraction of GHG forcing, and the total net forcing is only ~ 0.6 W m-2. To explain the actual global increase in temperature of ~ 0.8°C, these two extremes have major implications in terms of the Earth's climate sensitivity. Climate sensitivity is determined by the strength of feedbacks, of which cloud feedback is the most uncertain. That the Earth has warmed and that GHGs are responsible is unequivocal; the Earth's climate sensitivity and the effect of aerosols complicate answers to the question: how much warming and how soon? © 2011 American Institute of Chemical Engineers (AIChE)."
"8669714200;7406741310;6603546080;","The annual cycle of earth radiation budget from clouds and the Earth's Radiant Energy System (CERES) data",2011,"10.1175/JAMC-D-11-050.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862907857&doi=10.1175%2fJAMC-D-11-050.1&partnerID=40&md5=cd5adee2fc9a5dfa486de98e787e7424","The seasonal cycle of theEarth radiation budget is investigated by use of data fromtheClouds and theEarth's Radiant Energy System (CERES). Monthly mean maps of reflected solar flux and Earth-emitted flux on a 1° equal-angle grid are used for the study. The seasonal cycles of absorbed solar radiation (ASR), outgoing longwave radiation (OLR), and net radiation are described by use of principal components for the time variations, for which the corresponding geographic variations are the empirical orthogonal functions. Earth's surface is partitioned into land and ocean for the analysis. The first principal component describes more than 95% of the variance in the seasonal cycle ofASRand the net radiation fluxes and nearly 90%of the variance ofOLR over land. Because one term can express so much of the variance, principal component analysis is very useful to describe these seasonal cycles. The annual cycles of ASR are about 100 W m -2 over land and ocean, but the amplitudes of OLR are about 27W m -2 over land and 15W m -2 over ocean. The magnitude of OLR and its time lag relative to that of ASR are important descriptors of the climate system and are computed for the first principal components. OLR lags ASR by about 26 days over land and 42 days over ocean. The principal components are useful for comparing the observed radiation budget with that computed by a model. © 2011 American Meteorological Society."
"55003524100;7003510377;","How much can a priori hydrologic model predictability help in optimal merging of satellite precipitation products?",2011,"10.1175/JHM-D-10-05023.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858243878&doi=10.1175%2fJHM-D-10-05023.1&partnerID=40&md5=38790e5cc418eafe0993bea462315f62","In this study, the authors ask the question: Can a more superior precipitation product be developed by merging individual products according to their a priori hydrologic predictability? The performance of three widely used high-resolution satellite precipitation products [Tropical Rainfall Measuring Mission (TRMM) real-time precipitation product 3B42 (3B42-RT), the NOAA/Climate Prediction Center morphing technique (CMORPH), and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS)] was evaluated in terms streamflow predictability for the entire Mississippi River basin using the Variable Infiltration Capacity (VIC) macroscale hydrologic model. A merging concept that was not based on a single universal merging formula for the whole basin but rather used a ""localized"" (grid box by grid box) approach for merging precipitation products was then explored. In this merging technique, the a priori (historical) hydrologic predictive skill of each product for each grid box was first identified. Prior to streamflow routing, the corresponding accuracy of the spatially distributed simulations of soil moisture and runoff were used as proxy for weights in merging the precipitation products. It was found that the merged product derived on the basis of runoff predictability outperformed its counterpart merged product derived on the basis of soil moisture simulation. Results indicate that such a grid box by grid box merging concept that leverages a priori information on predictability of individual products has the potential to yield a more superior product for streamflow prediction than what the individual products can deliver for hydrologic prediction. © 2011 American Meteorological Society."
"57206332144;7003907406;25624545600;7003289221;","Spectrally invariant approximation within atmospheric radiative transfer",2011,"10.1175/JAS-D-11-060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855822402&doi=10.1175%2fJAS-D-11-060.1&partnerID=40&md5=ad83d952a33cf2e7b0e8c8236c1c8c12","Certain algebraic combinations of single scattering albedo and solar radiation reflected from, or transmitted through, vegetation canopies do not vary with wavelength. These ""spectrally invariant relationships"" are the consequence of wavelength independence of the extinction coefficient and scattering phase function in vegetation. In general, this wavelength independence does not hold in the atmosphere, but in cloud-dominated atmospheres the total extinction and total scattering phase function vary only weakly with wavelength. This paper identifies the atmospheric conditions under which the spectrally invariant approximation can accurately describe the extinction and scattering properties of cloudy atmospheres. The validity of the assumptions and the accuracy of the approximation are tested with 1D radiative transfer calculations using publicly available radiative transfer models: Discrete Ordinate Radiative Transfer (DISORT) and Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART). It is shown for cloudy atmospheres with cloud optical depth above 3, and for spectral intervals that exclude strong water vapor absorption, that the spectrally invariant relationships found in vegetation canopy radiative transfer are valid to better than 5%. The physics behind this phenomenon, its mathematical basis, and possible applications to remote sensing and climate are discussed. © 2011 American Meteorological Society."
"7404416268;7006961728;7004442182;7003467167;","Ongoing climate change in the arctic",2011,"10.1007/s13280-011-0211-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866339550&doi=10.1007%2fs13280-011-0211-z&partnerID=40&md5=8abfc0fc97f91cadf60d481f3c1e59f2","During the past decade, the Arctic has experienced its highest temperatures of the instrumental record, even exceeding the warmth of the 1930s and 1940s. Recent paleo-reconstructions also show that recent Arctic summer temperatures are higher than at any time in the past 2000 years. The geographical distribution of the recent warming points strongly to an influence of sea ice reduction. The spatial pattern of the near-surface warming also shows the signature of the Pacific Decadal Oscillation in the Pacific sector as well as the influence of a dipole-like circulation pattern in the Atlantic sector. Areally averaged Arctic precipitation over the land areas north of 55°N shows large year-to-year variability, superimposed on an increase of about 5% since 1950. The years since 2000 have been wetter than average according to both precipitation and river discharge data. There are indications of increased cloudiness over the Arctic, especially low clouds during the warm season, consistent with a longer summer and a reduction of summer sea ice. Storm events and extreme high temperature show signs of increases. The Arctic Ocean has experienced enhanced oceanic heat inflows from both the North Atlantic and the North Pacific. The Pacific inflows evidently played a role in the retreat of sea ice in the Pacific sector of the Arctic Ocean, while the Atlantic water heat influx has been characterized by increasingly warm pulses. Recent shipboard observations show increased ocean heat storage in newly sea-ice-free ocean areas, with increased influence on autumn atmospheric temperature and wind fields. © Royal Swedish Academy of Sciences 2012."
"35196437900;24495045400;7403401100;8899985400;7007160874;7003486240;7005773698;","Effect of organic compounds on cloud condensation nuclei (CCN) activity of sea spray aerosol produced by bubble bursting",2011,"10.1016/j.atmosenv.2011.04.034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053606932&doi=10.1016%2fj.atmosenv.2011.04.034&partnerID=40&md5=9078861fb3fb20688cf4513cad7967de","The ocean comprises over 70% of the surface of the earth and thus sea spray aerosols generated by wave processes represent a critical component of our climate system. The manner in which different complex oceanic mixtures of organic species and inorganic salts are distributed between individual particles in sea spray directly determines which particles will effectively form cloud nuclei. Controlled laboratory experiments were undertaken to better understand the full range of particle properties produced by bubbling solutions composed of simplistic model organic species, oleic acid and sodium dodecyl sulfate (SDS), mixed with NaCl to more complex artificial seawater mixed with complex organic mixtures produced by common oceanic microorganisms. Simple mixtures of NaCl and oleic acid or SDS had a significant effect on CCN activity, even in relatively small amounts. However, an artificial seawater (ASW) solution containing microorganisms, the common cyanobacteria (Synechococcus) and DMS-producing green algae (Ostreococcus), produced particles containing ~34 times more carbon than the particles produced from pure ASW, yet no significant change was observed in the overall CCN activity. We hypothesize that these microorganisms produce diverse mixtures of organic species with a wide range of properties that produced offsetting effects, leading to no net change in the overall average measured hygroscopicity of the collection of sea spray particles. Based on these observations, changes in CCN activity due to "" bloom"" conditions would be predicted to lead to small changes in the average CCN activity, and thus have a negligible impact on cloud formation. However, each sea spray particle will contain a broad spectrum of different species, and thus further studies are needed of the CCN activity of individual sea spray particles and biological processes under a wide range of controllable conditions. © 2011."
"22933641400;26427744500;7102294773;6603201426;36892703600;35760600800;7006461606;55624488227;7201483081;6602298788;6506458269;7006497590;","Meteorological and air quality forecasting using the WRF-STEM model during the 2008 ARCTAS field campaign",2011,"10.1016/j.atmosenv.2011.02.073","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755175804&doi=10.1016%2fj.atmosenv.2011.02.073&partnerID=40&md5=620814db273ea8c3f9210a36af50431c","In this study, the University of Iowa's Chemical Weather Forecasting System comprising meteorological predictions using the WRF model, and off-line chemical weather predictions using tracer and full chemistry versions of the STEM model, designed to support the flight planning during the ARCTAS 2008 mission is described and evaluated. The system includes tracers representing biomass burning and anthropogenic emissions from different geographical emissions source regions, as well as air mass age indicators. We demonstrate how this forecasting system was used in flight planning and in the interpretation of the experimental data obtained through the case study of the summer mission ARCTAS DC-8 flight executed on July 9 2008 that sampled near the North Pole. The comparison of predicted meteorological variables including temperature, pressure, wind speed and wind direction against the flight observations shows that the WRF model is able to correctly describe the synoptic circulation and cloud coverage in the Arctic region The absolute values of predicted CO match the measured CO closely suggesting that the STEM model is able to capture the variability in observations within the Arctic region. The time-altitude cross sections of source region tagged CO tracers along the flight track helped in identifying biomass burning (from North Asia) and anthropogenic (largely China) as major sources contributing to the observed CO along this flight. The difference between forecast and post analysis biomass burning emissions can lead to significant changes (~10-50%) in primary CO predictions reflecting the large uncertainty associated with biomass burning estimates and the need to reduce this uncertainty for effective flight planning. © 2011 Elsevier ltd."
"6506310749;36520305500;","Evaluation of diabatic initialization improvements in the numerical weather prediction model Hirlam, focusing on the effect this may have on precipitation and dispersion forecasts",2011,"10.1016/j.atmosenv.2010.12.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755153325&doi=10.1016%2fj.atmosenv.2010.12.013&partnerID=40&md5=cb4527ef1f4d92afab4d4403c434bfc1","Amongst the key issues concerning mesoscale modeling capability for air pollution and dispersion applications are precipitation and cloud cover forecasts. The long-standing problem of the spin-up of clouds and precipitation in numerical weather prediction models limits the accuracy of the prediction of short-range dispersion and deposition from local sources. Customary the spin-up problem is avoided by only using NWP forecasts with a lead time greater than the spin-up time of the model. Due to the increase of uncertainty with forecast range this reduces the quality of the associated forecasts of the atmospheric flow.Improvements through diabatic initialization in the spin-up of large-scale precipitation in the Hirlam NWP model are discussed. In a synthetic example the effects of these improvements on a dispersion forecast are explored specifically for wet deposition. Using a case study of several weeks the optimal lead time for precipitation is discussed.The analysis presented in this paper leads to the conclusion that, at least for situations where large-scale precipitation dominates, proper diabatic initialization of a weather model may limit spin-up so that its full forecast range can be used. The implication for dispersion modeling is that such an improved model is particularly useful for short-range forecasts and the calculation of local deposition. The sensitivity of the hydrological process to proper initialization implies that the spin-up problem may reoccur with changes in the model and increased model resolution. This is demonstrated using a recent version of Hirlam. Spin-up should therefore not only be an ongoing concern for atmospheric modelers, but a reason for close cooperation with dispersion modelers. © 2011 Elsevier Ltd."
"35794721100;55490014700;7404211378;55716700200;26533570600;7004223630;14421346500;","An assessment of oceanic variability in the NCEP climate forecast system reanalysis",2011,"10.1007/s00382-010-0954-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052764278&doi=10.1007%2fs00382-010-0954-4&partnerID=40&md5=30c8d79be1f93507b8d4f0b8934e121f","At the National Centers for Environmental Prediction (NCEP), a reanalysis of the atmosphere, ocean, sea ice and land over the period 1979-2009, referred to as the climate forecast system reanalysis (CFSR), was recently completed. The oceanic component of CFSR includes many advances: (a) the MOM4 ocean model with an interactive sea-ice, (b) the 6 h coupled model forecast as the first guess, (c) inclusion of the mean climatological river runoff, and (d) high spatial (0. 5° × 0. 5°) and temporal (hourly) model outputs. Since the CFSR will be used by many in initializing/validating ocean models and climate research, the primary motivation of the paper is to inform the user community about the saline features in the CFSR ocean component, and how the ocean reanalysis compares with in situ observations and previous reanalysis. The net ocean surface heat flux of the CFSR has smaller biases compared to the sum of the latent and sensible heat fluxes from the objectively analyzed air-sea fluxes (OAFlux) and the shortwave and longwave radiation fluxes from the International Satellite Cloud Climatology Project (ISCCP-FD) than the NCEP/NCAR reanalysis (R1) and NCEP/DOE reanalysis (R2) in both the tropics and extratropics. The ocean surface wind stress of the CFSR has smaller biases and higher correlation with the ERA40 produced by the European Centre for Medium-Range Weather Forecasts than the R1 and R2, particularly in the tropical Indian and Pacific Ocean. The CFSR also has smaller errors compared to the QuickSCAT climatology for September 1999 to October 2009 than the R1 and R2. However, the trade winds of the CFSR in the central equatorial Pacific are too strong prior to 1999, and become close to observations once the ATOVS radiance data are assimilated in late 1998. A sudden reduction of easterly wind bias is related to the sudden onset of a warm bias in the eastern equatorial Pacific temperature around 1998/1999. The sea surface height and top 300 m heat content (HC300) of the CFSR compare with observations better than the GODAS in the tropical Indian Ocean and extratropics, but much worse in the tropical Atlantic, probably due to discontinuity in the deep ocean temperature and salinity caused by the six data streams of the CFSR. In terms of climate variability, the CFSR provides a good simulation of tropical instability waves and oceanic Kelvin waves in the tropical Pacific, and the dominant modes of HC300 that are associated with El Nino and Southern Oscillation, Indian Ocean Dipole, Pacific Decadal Oscillation and Atlantic Meridional Overturning Circulation. © 2010 Springer-Verlag (outside the USA)."
"7004713805;7006770362;","Integrated modeling for forecasting weather and air quality: A call for fully coupled approaches",2011,"10.1016/j.atmosenv.2011.01.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958153895&doi=10.1016%2fj.atmosenv.2011.01.017&partnerID=40&md5=629491e232252c8b7df3ad42d9c3dc18","This paper discusses some of the differences between online and offline approaches for both air quality forecasting and numerical weather prediction, and argues in favor of an eventual migration to integrated modeling systems that allow two-way interactions of physical and chemical processes. Recent studies are used that directly compared online and offline simulations to discuss possible shortcomings for both air quality and weather forecasting. The disadvantages of offline approaches are easy to show for air quality forecasting. On the other hand, a positive impact on short to medium range weather forecasts that is significant enough to justify an implementation at operational weather forecasting centers is more difficult to prove, and may initially only come through an improvement of the meteorological data assimilation. Eventually though, a migration to an integrated modeling system will provide new opportunities for weather prediction modelers as well. The simulation of chemical species will allow identification of shortcomings in currently used forecast models as well as lead to better use of meteorological data assimilation. © 2011 Elsevier Ltd."
"40561779900;6603964947;6602838905;8068566100;","Oceanic and atmospheric patterns during spawning periods prior to extreme catches of the Brazilian sardine (sardinella brasiliensis) in the southwest Atlantic [Patrones oceánicos y atmosféricos durante períodos de puesta previos a capturas extremas de la sardina brasilera (sardinella brasiliensis) en el océano atlántico sudoeste]",2011,"10.3989/scimar.2011.75n4665","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80855164665&doi=10.3989%2fscimar.2011.75n4665&partnerID=40&md5=2ae865416295f9eb509f9419f2a87e7b","Relative maxima and minima of landings of Brazilian sardine captured in the Southeast Brazil Bight (SBB) were compared with oceanic and atmospheric composites relative to the spawning period in December and January, prior to these landings. Atmospheric and oceanic variables such as wind stress, Ekman transport, mixing index, sea surface temperature (SST), precipitation, outgoing long wave radiation and geopotential height were analyzed, revealing distinct climatological patterns in the SBB for these extreme catches that have not been described before. The system could be characterized by cooler SST composite anomaly (SSTA) along the SBB as a response to increased cloud cover and reduced incidence of short-wave radiation, predominating one year before the Brazilian sardine catch maxima. This system can take on a different configuration in which positive SSTA condition in the SBB is associated with a less intense South Atlantic Convergence Zone displaced southwards one year before the period of minimum catch. Our results indicate that the spatial structure of the spawning habitat is influenced by specific ocean-atmosphere interactions rather than simply resulting from the choice of a stable environment. This climatic constraint strongly affects the interannual variability of the Brazilian sardine production."
"56082867500;7004057920;7404433688;","1997/98 El Niño-induced changes in rainfall vertical structure in the east Pacific",2011,"10.1175/JCLI-D-11-00002.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84155179096&doi=10.1175%2fJCLI-D-11-00002.1&partnerID=40&md5=2a1f94aadf6860162ef4f15cf438b12c","The 1997/98 El Niño-induced changes in rainfall vertical structure in the east Pacific (EP) are investigated by using collocated Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and associated daily SST and 6-hourly reanalysis data during January, February, March, and April of 1998, 1999, and 2000. This study shows that there are five key parameters, that is, surface rain rate, precipitation-top height (or temperature), and precipitation growth rates at upper, middle, and low layers to define a rainfall profile, and those five key parameters are strongly influenced by both SST and large-scale dynamics. Under the influence of 1997/98 El Niño, the precipitation-top heights in the EP were systematically higher by about 1 km than those under non-El Niño conditions, while the freezing level was about 0.5 km higher. Under the constraints of rain type, surface rain rate, and the precipitation top, the shape of rainfall profile still showed significant differences: the rain growth was relatively faster in the mid-layer (-5° to +12°C isotherm) but slower in the lower layer (below +2°C isotherm) under the influence of El Niño. It is also evident that the dependence of precipitation top height on SST was stronger under large-scale decent (non-El Niño) circulations but much weaker under large-scale ascent (El Niño) circulations. The combined effect of larger vertical extent and greater growth rate in the middle layer further shifted latent heating upward as compared with the impact of horizontal changes in the rain type fractions (convective versus stratiform). Such additional latent heating shift would certainly further elevate circulation centers and strengthen the upper-layer circulation. © 2011 American Meteorological Society."
"57206533133;57210427921;7005216212;6507612473;8680433600;7401657374;","Description and validation of an AOT product over land at the 0.6 μm channel of the SEVIRI sensor onboard MSG",2011,"10.5194/amt-4-2543-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869040965&doi=10.5194%2famt-4-2543-2011&partnerID=40&md5=130d2b676ab6892cd6e7abbdf0d6f0a1","The Spinning Enhanced Visible and InfraRed Imager (SEVIRI) aboard Meteosat Second Generation (MSG) launched in 2003 by EUMETSAT is dedicated to the Nowcasting applications and Numerical Weather Prediction and to the provision of observations for climate monitoring and research. We use the data in visible and near infrared (NIR) channels to derive the aerosol optical thickness (AOT) over land. The algorithm is based on the assumption that the top of the atmosphere (TOA) reflectance increases with the aerosol load. This is a reasonable assumption except in case of absorbing aerosols above bright surfaces. We assume that the minimum in a 14-days time series of the TOA reflectance is, once corrected from gaseous scattering and absorption, representative of the surface reflectance. The AOT and the aerosol model (a set of 5 models is used), are retrieved by matching the simulated TOA reflectance with the TOA reflectances measured by SEVIRI in its visible and NIR spectral bands. The high temporal resolution of the data acquisition by SEVIRI allows to retrieve the AOT every 15 min with a spatial resolution of 3 km at sub-satellite point, over the entire SEVIRI disk covering Europe, Africa and part of South America. The resulting AOT, a level 2 product at the native temporal and spatial SEVIRI resolutions, is presented and evaluated in this paper. The AOT has been validated using ground based measurements from AErosol RObotic NETwork (AERONET), a sun-photometer network, focusing over Europe for 3 months in 2006. The SEVIRI estimates correlate well with the AERONET measurements, r = 0.64, with a slight overestimate, bias = -0.017. The sources of errors are mainly the cloud contamination and the bad estimation of the surface reflectance. The temporal evolutions exhibited by both datasets show very good agreement which allows to conclude that the AOT Level 2 product from SEVIRI can be used to quantify the aerosol content and to monitor its daily evolution with a high temporal frequency. The comparison with daily maps of Moderate Resolution Imaging Spectroradiometer (MODIS) AOT level 3 product shows qualitative good agreement in the retrieved geographic patterns of AOT. Given the high spatial and temporal resolutions obtained with this approach, our results have clear potential for applications ranging from air quality monitoring to climate studies. This paper presents a first evaluation and validation of the derived AOT over Europe in order to document the overall quality of a product that will be made publicly available to the users of the aforementioned research communities. © Author(s) 2011."
"35248473800;","Continental recycling and true continental growth",2011,"10.1016/j.rgg.2011.11.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82955186179&doi=10.1016%2fj.rgg.2011.11.001&partnerID=40&md5=9453b477a235e881432192fea6310fce","Continental crust is very important for evolution of life because most bioessential elements are supplied from continent to ocean. In addition, the distribution of continent affects climate because continents have much higher albedo than ocean, equivalent to cloud. Conventional views suggest that continental crust is gradually growing through the geologic time and that most continental crust was formed in the Phanerozoic and late Proterozoic. However, the thermal evolution of the Earth implies that much amounts of continental crust should be formed in the early Earth. This is ""Continental crust paradox"". Continental crust comprises granitoid, accretionary complex, and sedimentary and metamorphic rocks. The latter three components originate from erosion of continental crust because the accretionary and metamorphic complexes mainly consist of clastic materials. Granitoid has two components: a juvenile component through slab-melting and a recycling component by remelting of continental materials. Namely, only the juvenile component contributes to net continental growth. The remains originate from recycling of continental crust. Continental recycling has three components: intracrustal recycling, crustal reworking, and crust-mantle recycling, respectively. The estimate of continental growth is highly varied. Thermal history implied the rapid growth in the early Earth, whereas the present distribution of continental crust suggests the slow growth. The former regards continental recycling as important whereas the latter regarded as insignificant, suggesting that the variation of estimate for the continental growth is due to involvement of continental recycling.We estimated erosion rate of continental crust and calculated secular changes of continental formation and destruction to fit four conditions: present distribution of continental crust (no continental recycling), geochronology of zircons (intracontinental recycling), Hf isotope ratios of zircons (crustal reworking) and secular change of mantle temperature. The calculation suggests some important insights. (1) The distribution of continental crust around at 2.7 Ga is equivalent to the modern amounts. (2) Especially, the distribution of continental crust from 2.7 to 1.6 Ga was much larger than at present, and the sizes of the total continental crust around 2.4, 1.7, and 0.8 Ga became maximum. The distribution of continental crust has been decreasing since then. More amounts of continental crust were formed at higher mantle temperatures at 2.7, 1.9, and 0.9 Ga, and more amounts were destructed after then. As a result, the mantle overturns led to both the abrupt continental formation and destruction, and extinguished older continental crust. The timing of large distribution of continental crust apparently corresponds to the timing of icehouse periods in Precambrian. © 2011."
"56378881300;57217378594;7403203783;56412340900;57198101568;","Comparison of aerosol optical properties from Beijing and Kanpur",2011,"10.1016/j.atmosenv.2011.06.055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755133328&doi=10.1016%2fj.atmosenv.2011.06.055&partnerID=40&md5=802e15e5040b2c4fda565daf8e6e0bb7","Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) and almucantar retrievals (single scattering albedo (SSA) and aerosol size distribution) from 2005-2009 in Beijing and Kanpur are used to analyze differences and similarities in aerosol optical properties over these two regions. The examination of monthly mean AOD (440 nm) shows that maximum and minimum values occurred in summer and winter, respectively, for Beijing, while the range in AOD in Kanpur was lower. Precipitation in both Beijing and Kanpur peaked in summer; however, the columnar water vapor (CWV) exhibited a high correlation with AOD in Beijing (R2 = 0.79) but had a weak relationship with AOD in Kanpur (R2 = 0.13). The Angstrom exponent (α, 440-870 nm) generally increased linearly as the fine mode fraction (FMF) of AOD (500 nm) increased for FMF &lt; 90% in both regions, with a high correlation of R2 &gt; 0.96. However a clear decrease in α for FMF &gt; 90% found in Beijing is not shown distinctly in Kanpur, and is mainly due to the higher aerosol loading in this FMF bin at Beijing (AOD at 440 nm &gt; 2.2) which results in a stronger coagulation of fine mode particles. Bimodal seasonally-averaged size distributions reveals similar aerosol mixtures composed of fine pollution particles and coarse dust particles in both regions. The analysis of spectral SSA as a function of α is emphasized in this paper. The average SSA at 440 nm in both regions shows a similar low dynamic range of ~0.03 for α &lt; 1.4. The obvious increase in SSA at 440 nm for α &gt; 1.4 in both regions can be attributed to a higher FMF leading to fine mode coagulation. However, the distinctly smaller increase in Kanpur suggests that fine mode aerosols at Beijing are less absorbing than those at Kanpur. The visibly lower SSA at 675 nm at Kanpur compared to that at Beijing for α &gt; 0.4 is due to a larger find-coarse mode separation radius of ~0.76 μm in Beijing versus a value lower than ~0.58 μm in Kanpur. Another reason lies in the weaker absorption by fine mode aerosols in Beijing. The distinctly lower near-infrared SSA in Kanpur when α &lt; 1.4, compared to Beijing, may be attributed to lower aerosol concentrations in all α bins, resulting in less aggregation of absorbing black carbon particles on coarse particles in Kanpur. The classification of aerosol properties shows that the AOD accumulation mode in all seasons, even including spring, in Beijing and in post-monsoon and winter seasons in Kanpur can be attributed to fine particle coagulation or hygroscopic growth; during pre-monsoon and monsoon seasons in Kanpur, it is due to coarse mode particle accumulation or cloud contamination. © 2011 Elsevier Ltd."
"6506151257;6602300916;","Weather types accompanying very high pressure in Krakow in the period 1901-2000",2011,"10.1002/joc.2230","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054986204&doi=10.1002%2fjoc.2230&partnerID=40&md5=83fe539869472daaa8fb543682272031","The paper presents a classification of weather types observed in Krakow during the 20th century on days with particularly strong highs. The classification was based on daily values of a number of weather elements recorded at Krakow's Historic Weather Station during the period 1901-2000. Days with very high pressure were defined as those with an air pressure at 12 UTC equal to or greater than the 99th percentile of all the cases analysed (≥1037.5 hPa). A slightly modified version of a classification developed by Woś (1999) was used to determine weather types on each of the days identified. Very high pressure was found to have occurred solely during the cold half of the year (October-March). It was mostly accompanied by fairly frosty (9---) or moderately frosty (8---) weather types; subtype: sunny or with little cloud amount and very sunny (-02-) and very cloudy, without sunshine or with little sunshine (-20-); and weather class: without fog (---0). No significant annual or seasonal trends were found in the occurrence of days with very high pressure or in the various weather types. © 2010 Royal Meteorological Society."
"44761502700;6603850393;7402642949;","Phytogeographic divisions, climate change and plant dieback along the coastal desert of Northern Chile",2011,"10.3112/erdkunde.2011.02.05","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81855173738&doi=10.3112%2ferdkunde.2011.02.05&partnerID=40&md5=3824b5c1c96775e81f387d7b0103c453","Along the hyper-arid Chilean coastal desert between 30°S and 18°S the Loma vegetation undergoes a gradual transition from open shrubland to small isolated areas of a scarce plant cover. Floristic and physiognomic features allow a differentiation of five Loma formations, each of them characterized by a distinctive spectrum of plant communities. However, particularly in the northern section of the investigation area, numerous indications point to a strong vegetation decline including a deterioration of plant cover, reduction of the vitality of various taxa, probably also a local loss of some perennial species, and even a dieback of specific populations. These signs of a retrogression, which coincide with a regional disappearance of Guanaco herds in the coastal area between 20°S and 23°30'S, became apparent in the second half of the past century and were most likely provoked by recent climate change in the arid coastal region. Especially the decrease of rainfall frequency might have negative implications for the regeneration and preservation of plants. In addition, a strong reduction of cloudiness in the northernmost section affects plant growth due to further limitations in the water disposability. A projected sustained decline of rainfall is expected to continue endangering the surprisingly high floristic diversity of the sensitive ecosystem complexes in the coastal desert."
"8349977900;56410144300;34876658200;36538539800;6701378450;7003666669;55717074000;7006270084;6603268269;","Global distribution and climate forcing of marine organic aerosol: 1. Model improvements and evaluation",2011,"10.5194/acp-11-11689-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81855172322&doi=10.5194%2facp-11-11689-2011&partnerID=40&md5=dd6d242bfaecfab867138db02cf1c709","Marine organic aerosol emissions have been implemented and evaluated within the National Center of Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM5) with the Pacific Northwest National Laboratory's 7-mode Modal Aerosol Module (MAM-7). Emissions of marine primary organic aerosols (POA), phytoplankton-produced isoprene-and monoterpenes-derived secondary organic aerosols (SOA) and methane sulfonate (MS-) are shown to affect surface concentrations of organic aerosols in remote marine regions. Global emissions of submicron marine POA is estimated to be 7.9 and 9.4 Tg yr-1, for the Gantt et al. (2011) and Vignati et al. (2010) emission parameterizations, respectively. Marine sources of SOA and particulate MS-(containing both sulfur and carbon atoms) contribute an additional 0.2 and 5.1 Tg y-1, respectively. Widespread areas over productive waters of the Northern Atlantic, Northern Pacific, and the Southern Ocean show marine-source submicron organic aerosol surface concentrations of 100 ng m-3, with values up to 400 ng mg-3 over biologically productive areas. Comparison of long-term surface observations of water insoluble organic matter (WIOM) with POA concentrations from the two emission parameterizations shows that despite revealed discrepancies (often more than a factor of 2), both Gantt et al. (2011) and Vignati et al. (2010) formulations are able to capture the magnitude of marine organic aerosol concentrations, with the Gantt et al. (2011) parameterization attaining better seasonality. Model simulations show that the mixing state of the marine POA can impact the surface number concentration of cloud condensation nuclei (CCN). The largest increases (up to 20%) in CCN (at a supersaturation (S) of 0.2%) number concentration are obtained over biologically productive ocean waters when marine organic aerosol is assumed to be externally mixed with sea-salt. Assuming marine organics are internally-mixed with sea-salt provides diverse results with increases and decreases in the concentration of CCN over different parts of the ocean. The sign of the CCN change due to the addition of marine organics to sea-salt aerosol is determined by the relative significance of the increase in mean modal diameter due to addition of mass, and the decrease in particle hygroscopicity due to compositional changes in marine aerosol. Based on emerging evidence for increased CCN concentration over biologically active surface ocean areas/periods, our study suggests that treatment of sea spray in global climate models (GCMs) as an internal mixture of marine organic aerosols and sea-salt will likely lead to an underestimation in CCN number concentration. © Author(s) 2011."
"27468141900;25223599200;23994595000;54779879500;36183177600;22833630700;54403719700;7006434689;7005069415;6603825422;14033616600;9242126200;6602287115;7005794259;","Aging induced changes on NEXAFS fingerprints in individual combustion particles",2011,"10.5194/acp-11-11777-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81855167457&doi=10.5194%2facp-11-11777-2011&partnerID=40&md5=1f4abb51b1835a254bf40096ce571b69","Soot particles can significantly influence the Earth's climate by absorbing and scattering solar radiation as well as by acting as cloud condensation nuclei. However, despite their environmental (as well as economic and political) importance, the way these properties are affected by atmospheric processing of the combustion exhaust gases is still a subject of discussion. In this work, individual soot particles emitted from two different vehicles, a EURO 2 transporter, a EURO 3 passenger car, and a wood stove were investigated on a single-particle basis. The emitted exhaust, including the particulate and the gas phase, was processed in a smog chamber with artificial solar radiation. Single particle specimens of both unprocessed and aged soot were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and scanning electron microscopy. Comparison of NEXAFS spectra from the unprocessed particles and those resulting from exhaust photooxidation in the chamber revealed changes in the carbon functional group content. For the wood stove emissions, these changes were minor, related to the relatively mild oxidation conditions. For the EURO 2 transporter emissions, the most apparent change was that of carboxylic carbon from oxidized organic compounds condensing on the primary soot particles. For the EURO 3 car emissions oxidation of primary soot particles upon photochemical aging has likely contributed as well. Overall, the changes in the NEXAFS fingerprints were in qualitative agreement with data from an aerosol mass spectrometer. Furthermore, by taking full advantage of our in situ microreactor concept, we show that the soot particles from all three combustion sources changed their ability to take up water under humid conditions upon photochemical aging of the exhaust. Due to the selectivity and sensitivity of the NEXAFS technique for the water mass, also small amounts of water taken up into the internal voids of agglomerated particles could be detected. Because such small amounts of water uptake do not lead to measurable changes in particle diameter, it may remain beyond the limits of volume growth measurements, especially for larger agglomerated particles. © Author(s) 2011."
"7202824028;19638867200;54420455700;43461659100;6506081394;6701820543;","GPS radio occultation for climate monitoring and change detection",2011,"10.1029/2010RS004614","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81755176140&doi=10.1029%2f2010RS004614&partnerID=40&md5=be9518ba2b0f4473654cd6469822a6c9","Observation of the atmospheric climate and detection of changes require high quality data. Radio Occultation (RO) using Global Positioning System (GPS) signals is based on time measurements with precise atomic clocks. It provides a long-term stable and consistent data record with global coverage and favorable error characteristics. Highest quality and vertical resolution is given in the upper troposphere and lower stratosphere (UTLS). RO data exist from the GPS/Met mission within 1995-1997, and continuous observations are available since 2001. We give a review on studies using RO data for climate monitoring and change detection in the UTLS and discuss RO characteristics and error estimates, climate change indicators, trend detection, and comparison to conventional upper-air data. These studies showed that RO parameters cover the whole UTLS with useful indicators of climate change, being most robust in the tropics. Refractivity is most sensitive in the lower stratosphere (LS) and tropopause region, pressure/geopotential height and temperature over the UTLS region. An emerging climate change signal in the RO record can be detected for geopotential height of pressure levels and for temperature, reflecting warming of the troposphere and cooling of the LS. The results are in agreement with trends in radiosonde and ERA-Interim records. Climate model trends basically agree as well but they show less warming/cooling contrast across the tropical tropopause. (Advanced) Microwave Sounding Unit LS bulk temperature anomalies show significant differences to RO. Overall, the quality of RO climate records is suitable to fulfill the requirements of a global climate change monitoring system. Copyright 2011 by the American Geophysical Union."
"35338710200;13402933200;7102976560;7006399667;7402383878;56900249400;23479549200;7103294731;7004214645;7102167757;","Ozone database in support of CMIP5 simulations: Results and corresponding radiative forcing",2011,"10.5194/acp-11-11267-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81155127439&doi=10.5194%2facp-11-11267-2011&partnerID=40&md5=8a3863ededb32c0417b2505e813c5100","A continuous tropospheric and stratospheric vertically resolved ozone time series, from 1850 to 2099, has been generated to be used as forcing in global climate models that do not include interactive chemistry. A multiple linear regression analysis of SAGE I+II satellite observations and polar ozonesonde measurements is used for the stratospheric zonal mean dataset during the well-observed period from 1979 to 2009. In addition to terms describing the mean annual cycle, the regression includes terms representing equivalent effective stratospheric chlorine (EESC) and the 11-yr solar cycle variability. The EESC regression fit coefficients, together with pre-1979 EESC values, are used to extrapolate the stratospheric ozone time series backward to 1850. While a similar procedure could be used to extrapolate into the future, coupled chemistry climate model (CCM) simulations indicate that future stratospheric ozone abundances are likely to be significantly affected by climate change, and capturing such effects through a regression model approach is not feasible. Therefore, the stratospheric ozone dataset is extended into the future (merged in 2009) with multi-model mean projections from 13 CCMs that performed a simulation until 2099 under the SRES (Special Report on Emission Scenarios) A1B greenhouse gas scenario and the A1 adjusted halogen scenario in the second round of the Chemistry-Climate Model Validation (CCMVal-2) Activity. The stratospheric zonal mean ozone time series is merged with a three-dimensional tropospheric data set extracted from simulations of the past by two CCMs (CAM3.5 and GISS-PUCCINI) and of the future by one CCM (CAM3.5). The future tropospheric ozone time series continues the historical CAM3.5 simulation until 2099 following the four different Representative Concentration Pathways (RCPs). Generally good agreement is found between the historical segment of the ozone database and satellite observations, although it should be noted that total column ozone is overestimated in the southern polar latitudes during spring and tropospheric column ozone is slightly underestimated. Vertical profiles of tropospheric ozone are broadly consistent with ozonesondes and in-situ measurements, with some deviations in regions of biomass burning. The tropospheric ozone radiative forcing (RF) from the 1850s to the 2000s is 0.23 W m-2, lower than previous results. The lower value is mainly due to (i) a smaller increase in biomass burning emissions; (ii) a larger influence of stratospheric ozone depletion on upper tropospheric ozone at high southern latitudes; and possibly (iii) a larger influence of clouds (which act to reduce the net forcing) compared to previous radiative forcing calculations. Over the same period, decreases in stratospheric ozone, mainly at high latitudes, produce a RF of g-0.08 W m-2, which is more negative than the central Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) value of-0.05 W m-2, but which is within the stated range of-0.15 to +0.05 W m-2. The more negative value is explained by the fact that the regression model simulates significant ozone depletion prior to 1979, in line with the increase in EESC and as confirmed by CCMs, while the AR4 assumed no change in stratospheric RF prior to 1979. A negative RF of similar magnitude persists into the future, although its location shifts from high latitudes to the tropics. This shift is due to increases in polar stratospheric ozone, but decreases in tropical lower stratospheric ozone, related to a strengthening of the Brewer-Dobson circulation, particularly through the latter half of the 21st century. Differences in trends in tropospheric ozone among the four RCPs are mainly driven by different methane concentrations, resulting in a range of tropospheric ozone RFs between 0.4 and 0.1 W m-2 by 2100. The ozone dataset described here has been released for the Coupled Model Intercomparison Project (CMIP5) model simulations in netCDF Climate and Forecast (CF) Metadata Convention at the PCMDI website (http://cmip-pcmdi.llnl.gov/). © 2011 Author(s)."
"24332905600;6603001923;7003705113;9246517900;55916925700;56154540200;7003931528;7004637798;","Rate of non-linearity in DMS aerosol-cloud-climate interactions",2011,"10.5194/acp-11-11175-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80855140424&doi=10.5194%2facp-11-11175-2011&partnerID=40&md5=d12f7f70427413dd420eeb7136200542","The degree of non-linearity in DMS-cloud-climate interactions is assessed using the ECHAM5-HAMMOZ model by taking into account end-to-end aerosol chemistry-cloud microphysics link. The evaluation is made over the Southern oceans in austral summer, a region of minimal anthropogenic influence. In this study, we compare the DMS-derived changes in the aerosol and cloud microphysical properties between a baseline simulation with the ocean DMS emissions from a prescribed climatology, and a scenario where the DMS emissions are doubled. Our results show that doubling the DMS emissions in the current climate results in a non-linear response in atmospheric DMS burden and subsequently, in SO 2 and H2SO4 burdens due to inadequate OH oxidation. The aerosol optical depth increases by only ∼20 % in the 30° S-75° S belt in the SH summer months. This increases the vertically integrated cloud droplet number concentrations (CDNC) by 25 %. Since the vertically integrated liquid water vapor is constant in our model simulations, an increase in CDNC leads to a reduction in cloud droplet radius of 3.4 % over the Southern oceans in summer. The equivalent increase in cloud liquid water path is 10.7 %. The above changes in cloud microphysical properties result in a change in global annual mean radiative forcing at the TOA of-1.4 W m -2. The results suggest that the DMS-cloud microphysics link is highly non-linear. This has implications for future studies investigating the DMS-cloud climate feedbacks in a warming world and for studies evaluating geoengineering options to counteract warming by modulating low level marine clouds. © 2011 Author(s)."
"15836957100;16456768000;55569817500;8716123300;7004693622;","Volcanic and solar activity, and atmospheric circulation influences on cosmogenic 10Be fallout at Vostok and Concordia (Antarctica) over the last 60years",2011,"10.1016/j.gca.2011.09.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054691400&doi=10.1016%2fj.gca.2011.09.002&partnerID=40&md5=6379e7a0023f97b8bd3783d335b550ed","The cosmogenic nuclide beryllium-10 (10Be), recovered from ice cores, is often used to study solar activity on long timescales. However, the 10Be signal is also influenced by factors other than the Sun. To identify and quantify various contributions to the 10Be signal, two Antarctic snow records from the Vostok and Concordia sites spanning the last 60years were studied at a sub-annual resolution. Three factors that contribute to the 10Be signal were identified. First, a significant period of approximately 11yr that can be associated with the modulation of 10Be production by solar activity was detected in both records. The solar imprint constitutes 20-35% of the variance within the total signal. The 11-yr 10Be snow component was attenuated by a factor of ∼0.5 and was delayed by ∼1.4yr compared to the 10Be production expected within the polar atmosphere. The result could be interpreted as the composite response of a stratospheric 10Be reservoir with an 11-yr modulation that was attenuated and delayed (with respect to 10Be polar production) and to a tropospheric 10Be reservoir with an 11-yr modulation that was not attenuated or delayed. Then, peaks in 10Be concentrations that were ∼66% and ∼35% higher than the average concentration were observed during the stratospheric volcanic eruptions of Agung (in 1963) and Pinatubo (in 1991), respectively. In light of these new results, published 10Be ice core records could be reinterpreted because spikes in 10Be concentration appear at the time of several stratospheric events. The data indicate that stratospheric volcanic eruptions can impact 10Be transport and deposition as a result of the roles played by the sedimentation of sulfate aerosols and the formation and rapid settling of polar stratospheric clouds (PSC). Also, an interannual variability of ∼4yr was determined in both 10Be records, corresponding to ∼26% of the variance within the signal at Vostok. As with species of marine origin (sodium), this 4-yr variability is interpreted as a tropospheric modulation. The 4-yr variability could be associated with atmospheric circulation associated with the coupled Southern Ocean ocean-atmosphere system. The results presented here, from sites within the high Antarctic plateau, open new possibilities for ice core dating over the last few centuries and for the reconstruction of past solar activity in relation to climate. © 2011 Elsevier Ltd."
"16549600900;13407563600;24172248700;7006034630;24070152900;8645916500;7006595513;24503280300;8986277400;26643054400;55545335600;7102597422;36021733300;35461763400;55942083800;","Cloud condensation nuclei (CCN) from fresh and aged air pollution in the megacity region of Beijing",2011,"10.5194/acp-11-11023-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755180895&doi=10.5194%2facp-11-11023-2011&partnerID=40&md5=7db424aadb8a6b1a3e121d72b3bb29de","Atmospheric aerosol particles serving as cloud condensation nuclei (CCN) are key elements of the hydrological cycle and climate. CCN properties were measured and characterized during the CAREBeijing-2006 campaign at a regional site south of the megacity of Beijing, China. Size-resolved CCN efficiency spectra recorded for a supersaturation range of S Combining double low line0.07% to 0.86% yielded average activation diameters in the range of 190 nm to 45 nm. The corresponding effective hygroscopicity parameters (κ) exhibited a strong size dependence ranging from ∼0.25 in the Aitken size range to ∼0.45 in the accumulation size range. The campaign average value (κ = 0.3 ± 0.1) was similar to the values observed and modeled for other populated continental regions. The hygroscopicity parameters derived from the CCN measurements were consistent with chemical composition data recorded by an aerosol mass spectrometer (AMS) and thermo-optical measurements of apparent elemental and organic carbon (EC and OC). The CCN hygroscopicity and its size dependence could be parameterized as a function of only AMS based organic and inorganic mass fractions (forg, finorg) using the simple mixing rule κp ≈ 0.1 • forg + 0.7 • inorg. When the measured air masses originated from the north and passed rapidly over the center of Beijing (fresh city pollution), the average particle hygroscopicity was reduced (κ = 0.2 ± 0.1), which is consistent with enhanced mass fractions of organic compounds (∼50%) and EC (∼30%) in the fine particulate matter (PM1). Moreover, substantial fractions of externally mixed weakly CCN-active particles were observed at low supersaturation (S = 0.07%), which can be explained by the presence of freshly emitted soot particles with very low hygroscopicity (κ &lt; 0.1). Particles in stagnant air from the industrialized region south of Beijing (aged regional pollution) were on average larger and more hygroscopic, which is consistent with enhanced mass fractions (∼60%) of soluble inorganic ions (mostly sulfate, ammonium, and nitrate). Accordingly, the number concentration of CCN in aged air from the megacity region was higher than in fresh city outflow ((2.5-9.9) × 103 cm-3 vs. (0.4-8.3) × 103 cm-3for S = 0.07-0.86%) although the total aerosol particle number concentration was lower (1.2 × 104 cm -3 vs. 2.3 104 -3). A comparison with related studies suggests that the fresh outflow from Chinese urban centers generally may contain more, but smaller and less hygroscopic aerosol particles and thus fewer CCN than the aged outflow from megacity regions. © 2011 Author(s)."
"54406796600;54406827000;35109924900;7005804011;6603065779;54406540400;","Surface classification based on multi-temporal airborne lidar intensity data in high mountain environments a case study from hintereisferner, Austria",2011,"10.1127/0372-8854/2011/0055S2-0048","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755126006&doi=10.1127%2f0372-8854%2f2011%2f0055S2-0048&partnerID=40&md5=914161b5c9f76aff072395ac3ab74525","The use of airborne LiDAR (Light detection and ranging), also called airborne laser scanning(ALS), has evolved into a standard technique for acquiring topographic information in regional scale. Besidethe geometric attributes (x,y,z), the backscattered signal, often termed intensity or amplitude, is containedin the resulting ALS point cloud. Several studies showed the great potential of using ALS intensity data asinput for calculating surface or object parameters, for example in forestry, glaciology, geomorphology andhydrological applications. Due to impacts of climate change in high mountain environments and becauseof economic and ecological dependencies (e.g. water supply, hydro power and winter tourism), the interestin monitoring processes in these regions has strongly gained in importance during the last years. However,high-resolution, continuous data coverage and surface information acquisition in high mountain environmentis very difficult to achieve. As previous studies indicated the use of laser scanning devices can be aneffective monitoring instrument. In this study a threshold based classification method based on multi-temporalintensity raster data was developed to determine the main surface types (ice and water, snow, rock andvegetation) of a high mountain region. Before working with intensity data, it has to be corrected for knowninfluences, such as spherical loss, topographic effects and others. Hence an intensity correction model anda normalization are applied to the data. The classification is done for 7 data sets of the period between theyears 2001 and 2008. Furthermore, the suitability of ALS intensity for surface classification in high mountainenvironments is investigated. The study area is located at the Hintereisferner in the upper Otztal/Tyrolin Austria. The classification results show that particularly ice and water bodies can be classified in an accuratemanner from intensity raster data, while other surface classes are less accurately detected due to variousfactors, such as surface reflectance variability influencing the backscattered energy. © 2011 J. Cramer in Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany."
"55739389200;7402720392;7403295212;","Interpretation of GIA and ice-sheet mass trends over Antarctica using GRACE and ICESat data as a constraint to GIA models",2011,"10.1016/j.tecto.2010.11.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82655181360&doi=10.1016%2fj.tecto.2010.11.010&partnerID=40&md5=5ac1f3803ebd65c729909a853458982a","The Gravity Recovery and Climate Experiment (GRACE) and Ice, Cloud, and land Elevation Satellite (ICESat) have provided data sets covering observations over a period of more than 6. years since their respective launches. In this study, we used the GRACE mass change trend obtained by version 2 of CNES/GRGS solutions and the ICEsat elevation change trend from October 4, 2003, to March 21, 2008, to assess whether currently used glacial isostatic adjustment (GIA) models agree with the data sets. For six selected areas over West Antarctica, the mass trends for the surface ice sheet, which were obtained by subtracting the four GIA model trends (ICE-5G, IJ05, ANT5 and ANT6) from the estimated GRACE mass trend, were compared with the ICESat trends in order to assess whether these two trends are consistent within the uncertainty of the ice column density. The results show that the mass trend predicted by IJ05 GIA model is the most preferable to explain surface mass trends over some of these areas. The result is consistent with Riva et al. (2009); their estimated GIA trend from GRACE and ICESat data is very similar with IJ05 model. © 2010 Elsevier B.V."
"35619223100;16638618700;6603841282;57198283515;","The George Melendez Wright climate change fellowship program: Promoting innovative park science for resource management",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-82855162695&partnerID=40&md5=20ea02e74ddf4a368ff4b60c5a092731","In 2010 the National Park Service Climate Change Response Program created the George Melendez Wright Climate Change Fellowship to foster new and innovative research on climate change impacts in protected areas, and to promote national parks as laboratories for research on climate change. The program aims to increase the use of scientific knowledge to further resource management in parks and deepen the utility of place-based science for society in national parks. In its first year the program funded 22 proposals by graduate students from across the country. Research in progress covers an extensive variety of topics, from examination of how genetic factors mediate climate change effects in vulnerable tree species to ethnographic studies of the effects of environmental change on the practices of subsistence fisheries in coastal preserves and monuments. The geographic and ecosystem extent of projects ranges from Hawaiian cloud forests and Alaskan alpine environments, to forests in the Intermountain West, to coastal wetlands in Louisiana. Most program fellows have made field collections and are in the process of analyzing data. Preliminary results document the sensitivity of vegetation in the cloud forests of Haleakala National Park to drought, California seashore vulnerabilities, and a variety of climate and ecological impacts on subsistence fisheries in Alaska."
"35461255500;6701620591;8336962200;57217911076;6504793116;7006960661;7007039218;","The first estimates of global nucleation mode aerosol concentrations based on satellite measurements",2011,"10.5194/acp-11-10791-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80155177663&doi=10.5194%2facp-11-10791-2011&partnerID=40&md5=71df8247aef8d5dc3304736761dccc3c","Atmospheric aerosols play a key role in the Earth's climate system by scattering and absorbing solar radiation and by acting as cloud condensation nuclei. Satellites are increasingly used to obtain information on properties of aerosol particles with a diameter larger than about 100 nm. However, new aerosol particles formed by nucleation are initially much smaller and grow into the optically active size range on time scales of many hours. In this paper we derive proxies, based on process understanding and ground-based observations, to determine the concentrations of these new particles and their spatial distribution using satellite data. The results are applied to provide seasonal variation of nucleation mode concentration. The proxies describe the concentration of nucleation mode particles over continents. The source rates are related to both regional nucleation and nucleation associated with more restricted sources. The global pattern of nucleation mode particle number concentration predicted by satellite data using our proxies is compared qualitatively against both observations and global model simulations. © Author(s) 2011."
"36523706800;15069732800;41961756000;16639418500;57206531303;","The role of the effective cloud Albedo for climate monitoring and analysis",2011,"10.3390/rs3112305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856763572&doi=10.3390%2frs3112305&partnerID=40&md5=f0e1120f5c2cb01e9ec430ec2fdfdb43","Cloud properties and the Earth's radiation budget are defined as essential climate variables by the Global Climate Observing System (GCOS). The cloud albedo is a measure for the portion of solar radiation reflected back to space by clouds. This information is essential for the analysis and interpretation of the Earth's radiation budget and the solar surface irradiance. We present and discuss a method for the production of the effective cloud albedo and the solar surface irradiance based on the visible channel (0.45-1 μm) on-board of the Meteosat satellites. This method includes a newly developed self-calibration approach and has been used to generate a 23-year long (1983-2005) continuous and validated climate data record of the effective cloud albedo and the solar surface irradiance. Using this climate data record we demonstrate the ability of the method to generate the two essential climate variables in high accuracy and homogeneity. Further on, we discuss the role of the cloud albedo within climate monitoring and analysis. We found trends with opposite sign in the observed effective cloud albedo resulting in positive trends in the solar surface irradiance over ocean and partly negative trends over land. Ground measurements are scarce over the ocean and thus satellite-derived effective cloud albedo and solar surface irradiance constitutes a unique observational data source. Within this scope it has to be considered that the ocean is the main energy reservoir of the Earth, which emphasises the role of satellite-observed effective cloud albedo and derived solar surface irradiance as essential climate variables for climate monitoring and analysis. © 2011 by the authors."
"16025327700;57217371644;57210785732;26641239800;53979697300;36068180200;","Solar Activity, Lightning and Climate",2011,"10.1007/s10712-011-9127-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054003488&doi=10.1007%2fs10712-011-9127-1&partnerID=40&md5=f421f5923dea1473c4a692b73698b1d2","The physics of solar forcing of the climate and long term climate change is summarized, and the role of energetic charged particles (including cosmic rays) on cloud formation and their effect on climate is examined. It is considered that the cosmic ray-cloud cover hypothesis is not supported by presently available data and further investigations (during Forbush decreases and at other times) should be analyzed to further examine the hypothesis. Another player in climate is lightning through the production of NOx; this greenhouse gas, water vapour in the troposphere (and stratosphere) and carbon dioxide influence the global temperature through different processes. The enhancement of aerosol concentrations and their distribution in the troposphere also affect the climate and may result in enhanced lightning activity. Finally, the roles of atmospheric conductivity on the electrical activity of thunderstorms and lightning discharges in relation to climate are discussed. © 2011 Springer Science+Business Media B.V."
"6602999057;56522444900;54421076700;15069732800;7004585025;56990429400;","Ultra-low clouds over the southern West African monsoon region",2011,"10.1029/2011GL049278","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81155151420&doi=10.1029%2f2011GL049278&partnerID=40&md5=c9559390b31f259e2081077deed9606c","New ground-and space-based observations show that summertime southern West Africa is frequently affected by an extended cover of shallow, non-precipitating clouds only few hundred meters above the ground. These clouds are associated with nocturnal low-level wind speed maxima and frequently persist into the day, considerably reducing surface solar radiation. While the involved phenomena are well represented in re-analysis data, climate models show large errors in low-level wind, cloudiness, and solar radiation of up to 90 W m-2. Errors of such a magnitude could strongly affect the regional energy and moisture budgets, which might help to explain the notorious difficulties of many models to simulate the West African climate. More effort is needed in the future to improve the monitoring, modeling, and physical understanding of these ultra-low clouds and their importance for the West African monsoon system. © 2011 by the American Geophysical Union."
"7409792174;35364149600;7403077486;7201888941;7003495982;","High-resolution simulations of wintertime precipitation in the Colorado headwaters region: Sensitivity to physics parameterizations",2011,"10.1175/MWR-D-11-00009.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862907703&doi=10.1175%2fMWR-D-11-00009.1&partnerID=40&md5=d9e36132429dd3967c6216b2f479ddc7","An investigation was conducted on the effects of various physics parameterizations on wintertime precipitation predictions using a high-resolution regional climate model. The objective was to evaluate the sensitivity of cold-season mountainous snowfall to cloud microphysics schemes, planetary boundary layer (PBL) schemes, land surface schemes, and radiative transfer schemes at a 4-km grid spacing applicable to the next generation of regional climate models. The results indicated that orographically enhanced precipitation was highly sensitive to cloud microphysics parameterizations. Of the tested 7 parameterizations, 2 schemes clearly outperformed the others that overpredicted the snowfall amount by asmuch as;30%-60% on the basis of snowtelemetry observations. Significant differences among these schemes were apparent in domain averages, spatial distributions of hydrometeors, latent heating profiles, and cloud fields. In comparison, model results showed relatively weak dependency on the land surface, PBL, and radiation schemes, roughly in the order of decreasing level of sensitivity. © 2011 American Meteorological Society."
"56032511300;7102604282;","Dependence of aerosol-cloud interactions in stratocumulus clouds on liquid-water path",2011,"10.1016/j.atmosenv.2011.08.050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052971227&doi=10.1016%2fj.atmosenv.2011.08.050&partnerID=40&md5=4219870626ad0aefe43f940494c540f3","A recent study showed that aerosol-induced feedbacks between microphysics and dynamics predominantly determined the cloud-mass response to aerosols in thin clouds with liquid-water path (LWP) of ∼50 g m-2 or less; in this paper, cloud mass represents the time- and area-averaged LWP and LWP is the column-integrated cloud liquid content (LWC); LWC is the mass of cloud liquid per unit volume of air. This is contrary to studies which have shown that aerosol-induced inefficient conversion and sedimentation play an important role in the determination of the effect of aerosols on cloud mass. These studies are generally based on clouds with LWP &gt;50 g m-2. Hence, it is important to understand whether the role of aerosol-induced feedbacks in the effect of aerosols on cloud mass depends on the level of LWP. Pairs of numerical experiments for high and low-aerosol cases are run for four cases of stratiform clouds with different LWPs. All of these cases show that the role of condensation or evaporation of cloud liquid in the cloud-mass response to aerosol is more important than that of conversion of cloud liquid to rain and sedimentation (or precipitation). This indicates that focusing only on parameterization of autoconversion and sedimentation to represent aerosol effects on cloud mass in climate models can be misleading. Also, this study finds that the effect of aerosol-induced sedimentation suppression on the cloud-mass response to aerosol becomes less important as LWP lowers. Instead, the effect of aerosol-induced changes in condensation or evaporation on the cloud-mass response becomes more important with the decreasing LWP. These changes in condensation (and associated changes in evaporation) are caused by interactions (or feedbacks) among aerosol, droplet surface area, supersaturation, and instability around cloud base. © 2011 Elsevier Ltd."
"54381716300;7006698304;7007099717;16679271700;","The three-dimensional distribution of clouds around Southern Hemisphere extratropical cyclones",2011,"10.1029/2011GL049091","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80655128184&doi=10.1029%2f2011GL049091&partnerID=40&md5=ce7f3c167950d6f6212658e75927f34e","The organization and, for the first time, the three-dimensional structure of clouds associated with the Southern Hemisphere cyclones are studied using active observations from the CloudSat and CALIPSO satellites. First, a composite cyclone is constructed from more than 800 individual cases in the years 2007 and 2008 using the cyclone centre as the composite reference point. It is shown that the three-dimensional cloud distribution around the composite cyclone agrees well with conceptual models of extratropical cyclones. Composite mean fields of sea level pressure, vertical motion, potential temperature and relative humidity are superposed on the three-dimensional cloud structure to better define the relationship between the clouds and dynamical properties of extratropical cyclones. The methodology used here reveals the relationship between dynamical and cloud processes in three dimensions around cyclones and provides the foundation for in-depth evaluations of the ability of climate models to simulate the cloud and dynamical structures of Southern Hemisphere extratropical cyclones. Copyright 2011 by the American Geophysical Union."
"8529447300;7004307308;7003467276;","A dampened land use change climate response towards the tropics",2011,"10.1007/s00382-011-1018-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80355144721&doi=10.1007%2fs00382-011-1018-0&partnerID=40&md5=5ca8c63f821c364a15be1879108dea66","In climate simulations we find a pronounced meridional (equator to pole) gradient of climate response to land cover change. Climate response approaches zero in the tropics, and increases towards the poles. The meridional gradient in climate response to land cover change results from damping feedbacks in the tropics, rather than from polar amplification. The main cause for the damping in the tropics is the decrease in cloud cover after deforestation, resulting in increased incoming radiation at the surface and a lower planetary albedo, both counteracting the increase in surface albedo with deforestation. In our simulations, deforestation was also associated with a decrease in sensible heat flux but not a clear signal in evaporation. Meridional differences in climate response have implications for attribution of observed climate change, as well as for climate change mitigation strategies. © 2011 Springer-Verlag."
"42263280300;55796506900;7402721790;","Radiative forcing and climate response due to black carbon in snow and ice",2011,"10.1007/s00376-011-0117-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054094483&doi=10.1007%2fs00376-011-0117-5&partnerID=40&md5=31c27727c7ec36d142c842ef9f27bd7b","The radiative forcing and climate response due to black carbon (BC) in snow and/or ice were investigated by integrating observed effects of BC on snow/ice albedo into an atmospheric general circulation model (BCC_AGCM2. 0. 1) developed by the National Climate Center (NCC) of the China Meteorological Administration (CMA). The results show that the global annual mean surface radiative forcing due to BC in snow/ice is +0. 042 W m-2, with maximum forcing found over the Tibetan Plateau and regional mean forcing exceeding +2. 8 W m-2. The global annual mean surface temperature increased 0. 071°C due to BC in snow/ice. Positive surface radiative forcing was clearly shown in winter and spring and increased the surface temperature of snow/ice in the Northern Hemisphere. The surface temperatures of snow-covered areas of Eurasia and North America in winter (spring) increased by 0. 83°C (0. 6°C) and 0. 83°C (0. 46°C), respectively. Snowmelt rates also increased greatly, leading to earlier snowmelt and peak runoff times. With the rise of surface temperatures in the Arctic, more water vapor could be released into the atmosphere, allowing easier cloud formation, which could lead to higher thermal emittance in the Arctic. However, the total cloud forcing could decrease due to increasing cloud cover, which will offset some of the positive feedback mechanism of the clouds. © 2011 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"7006783796;6506827279;7404150761;6603809758;36973693100;57211010680;7003475277;6701539962;6507019560;24322892500;8280879000;8668585900;7406061582;12803465300;54880290400;7401622015;7102018821;55710310300;7403931916;","CERES edition-2 cloud property retrievals using TRMM VIRS and Terra and Aqua MODIS data-Part I: Algorithms",2011,"10.1109/TGRS.2011.2144601","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80455164717&doi=10.1109%2fTGRS.2011.2144601&partnerID=40&md5=668c9b4a314c1a9b82a056806d61cfc4","The National Aeronautics and Space Administration's Clouds and the Earth's Radiant Energy System (CERES) Project was designed to improve our understanding of the relationship between clouds and solar and longwave radiation. This is achieved using satellite broad-band instruments to map the top-of-atmosphere radiation fields with coincident data from satellite narrow-band imagers employed to retrieve the properties of clouds associated with those fields. This paper documents the CERES Edition-2 cloud property retrieval system used to analyze data from the Tropical Rainfall Measuring Mission Visible and Infrared Scanner and by the MODerate-resolution Imaging Spectrometer instruments on board the Terra and Aqua satellites covering the period 1998 through 2007. Two daytime retrieval methods are explained: the Visible Infrared Shortwave-infrared Split-window Technique for snow-free surfaces and the Shortwave-infrared Infrared Near-infrared Technique for snow or ice-covered surfaces. The Shortwave-infrared Infrared Split-window Technique is used for all surfaces at night. These methods, along with the ancillary data and empirical parameterizations of cloud thickness, are used to derive cloud boundaries, phase, optical depth, effective particle size, and condensed/frozen water path at both pixel and CERES footprint levels. Additional information is presented, detailing the potential effects of satellite calibration differences, highlighting methods to compensate for spectral differences and correct for atmospheric absorption and emissivity, and discussing known errors in the code. Because a consistent set of algorithms, auxiliary input, and calibrations across platforms are used, instrument and algorithm-induced changes in the data record are minimized. This facilitates the use of the CERES data products for studying climate-scale trends. © 2011 IEEE."
"21738966900;57206531303;23094223900;7004126618;7003499456;","COSMO-CLM2: A new version of the COSMO-CLM model coupled to the Community Land Model",2011,"10.1007/s00382-011-1019-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80355133518&doi=10.1007%2fs00382-011-1019-z&partnerID=40&md5=b830f7730e85e6c4ebd767bae4eba272","This study presents an evaluation of a new biosphere-atmosphere Regional Climate Model. COSMO-CLM2 results from the coupling between the non-hydrostatic atmospheric model COSMO-CLM version 4. 0 and the Community Land Model version 3. 5 (CLM3. 5). In this coupling, CLM3. 5 replaces a simpler land surface parameterization (TERRA_ML) used in the standard COSMO-CLM. Compared to TERRA_ML, CLM3. 5 comprises a more complete representation of land surface processes including hydrology, biogeophysics, biogeochemistry and vegetation dynamics. Historical climate simulations over Europe with COSMO-CLM and with the new COSMO-CLM2 are evaluated against various data products. The simulated climate is found to be substantially affected by the coupling with CLM3. 5, particularly in summer. Radiation fluxes as well as turbulent fluxes at the surface are found to be more realistically represented in COSMO-CLM2. This subsequently leads to improvements of several aspects of the simulated climate (cloud cover, surface temperature and precipitation). We show that a better partitioning of turbulent fluxes is the central factor allowing for the better performances of COSMO-CLM2 over COSMO-CLM. Despite these improvements, some model deficiencies still remain, most notably a substantial underestimation of surface net shortwave radiation. Overall, these results highlight the importance of land surface processes in shaping the European climate and the benefit of using an advanced land surface model for regional climate simulations. © 2011 Springer-Verlag."
"7004091067;7005773698;7005265210;","Exploring geophysical processes influencing U.S. West Coast precipitation and water supply",2011,"10.1029/2011EO410010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055021872&doi=10.1029%2f2011EO410010&partnerID=40&md5=c0e370eb7b012edc6a5688fcea65d6dd","CalWater Science Workshop; La Jolla, California, 8-10 June 2011 CalWater is a multiyear, multiagency research project with two primary research themes: the effects of changing climate on atmospheric rivers (ARs) and associated extreme events, and the potential role of aerosols in modulating cloud properties and precipitation, especially regarding orographic precipitation and water supply. Advances made in CalWater have implications for both water supply and flood control in California and other West Coast areas, both in the near term and in a changing climate."
"7006783796;6506827279;57211010680;6506582181;8833356300;8280879000;22233760100;7401796996;8668585900;6603809758;7403508241;8723505700;35567153700;6506234624;24322892500;7003475277;6507019560;8629713500;","CERES edition-2 cloud property retrievals using TRMM VIRS and Terra and Aqua MODIS data-Part II: Examples of average results and comparisons with other data",2011,"10.1109/TGRS.2011.2144602","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80455174757&doi=10.1109%2fTGRS.2011.2144602&partnerID=40&md5=48cc6d401061988c0bcc828a4becde09","Cloud properties were retrieved by applying the Clouds and Earth's Radiant Energy System (CERES) project Edition-2 algorithms to 3.5 years of Tropical Rainfall Measuring Mission Visible and Infrared Scanner data and 5.5 and 8 years of MODerate Resolution Imaging Spectroradiometer (MODIS) data from Aqua and Terra, respectively. The cloud products are consistent quantitatively from all three imagers; the greatest discrepancies occur over ice-covered surfaces. The retrieved cloud cover (∼59%) is divided equally between liquid and ice clouds. Global mean cloud effective heights, optical depth, effective particle sizes, and water paths are 2.5 km, 9.9, 12.9 μm , and 80 g · m -2, respectively, for liquid clouds and 8.3 km, 12.7, 52.2 μm, and 230 g· m-2 for ice clouds. Cloud droplet effective radius is greater over ocean than land and has a pronounced seasonal cycle over southern oceans. Comparisons with independent measurements from surface sites, the Ice Cloud and Land Elevation Satellite, and the Aqua Advanced Microwave Scanning Radiometer-Earth Observing System are used to evaluate the results. The mean CERES and MODIS Atmosphere Science Team cloud properties have many similarities but exhibit large discrepancies in certain parameters due to differences in the algorithms and the number of unretrieved cloud pixels. Problem areas in the CERES algorithms are identified and discussed. © 2011 IEEE."
"7004999694;26321163500;7004242319;17347195800;","Small irregular ice crystals in tropical cirrus",2011,"10.1175/2011JAS3733.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555200708&doi=10.1175%2f2011JAS3733.1&partnerID=40&md5=5530bea9dafc0bb5e471d2f9200ceff1","Images acquired by a Cloud Particle Imager (CPI) are analyzed to compile a statistical covariance function of radius for an ensemble of small, irregular, quasi-spherical ice crystals in tropical cirrus measured during the Department of Energy Atmospheric Radiation Measurement Program's Tropical Warm Pool International Cloud Experiment. The infrequent occurrence of multiple particles in single CPI frames suggests that most crystals sampled were natural ice crystals rather than artifacts from large particles shattering on probe tips. The covariance function is used in conjunction with the Gaussian random sphere geometry to generate threedimensional model ice particles for ray-optics simulations at 550-nm wavelength. The crystal shapes and single-scattering properties are compared with those obtained by the same methodology for midlatitude cirrus sampled over Oklahoma. The small tropical ice crystals are closer to spherical than their midlatitude counterparts and, consequently, their asymmetry parameters are larger, but the differences are not significant from the standpoint of climate studies. Because some quasi-spherical ice crystals seempartially faceted, a convex hull transformation is introduced that increases the asymmetry parameter from 0.785 to 0.808. Furthermodifying the covariance function to promote sixfold symmetry in the model crystals increases the asymmetry parameter to 0.818. The introduction of internal scatterers, such as air bubbles, has a larger impact, decreasing the asymmetry parameter by up to tens of percent, depending on their amount and characteristics. Unfortunately, no data are available to determine realistic values for the internal scatterers to assess their likely actual impact. © 2011 American Meteorological Society."
"55710405700;57196288797;57208263371;55613964600;","Satellite remote sensing of volcanic ash cloud in complicated meteorological conditions",2011,"10.1007/s11430-011-4265-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80255126303&doi=10.1007%2fs11430-011-4265-3&partnerID=40&md5=18f0da85952f16eeb896007c23a7c872","Volcanic ash cloud has serious impacts on aviation. With volcanic ash dispersion, it also has a profound and long-term impact on climate and the environment. A new volcanic ash cloud detecting method (SWIR-TIR Volcanic Ash method, STVA) is presented that uses satellite images of Medium Resolution Spectral Imager (MERSI) and Visible and Infrared Radiometer (VIRR) on board the second generation Polar-Orbiting meteorological satellite of China (FY-3A). STVA is applied in detecting Iceland's Eyjafjallajokull volcano eruption. Compared with the traditional Split Window Temperature Difference method (SWTD), the results show that STVA is more sensitive to volcanic ash cloud than SWTD and can fairly extract volcanic ash information from the background of meteorological cloud and the ocean. Ash Radiance Index (ARI) and Absorbing Aerosol Index (AAI) derived from Metop-A satellite images are used to validate the performance of STVA. It is shown that STVA provides similar results with ARI and AAI. FY-3A/MERSI, VIRR and Terra /MODIS data are used to test STVA and SWTD. It is demonstrated that STVA derived from FY-3A satellite data is more effective in complicated meteorological conditions. This study shows great potential of using China's own new generation satellite data in future global volcanic ash cloud monitoring operation. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg."
"54382826700;50461565700;6507258380;6602387361;7003495982;6602806615;","Evaluation of WRF parameterizations for climate studies over southern Spain using a multistep regionalization",2011,"10.1175/JCLI-D-11-00073.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755130493&doi=10.1175%2fJCLI-D-11-00073.1&partnerID=40&md5=fc86afc344e06a0155976d13878d6cc1","This paper evaluates the Weather Research and Forecasting model (WRF) sensitivity to eight different combinations of cumulus, microphysics, and planetary boundary layer (PBL) parameterization schemes over a topographically complex region in southern Spain (Andalusia) for the period 1990-99. The WRF configuration consisted of a 10-km-resolution domain nested in a coarser domain driven by 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) data, with spectral nudging above the PBL employed over the latter domain. The model outputs have been compared at different time scales with an observational dataset that comprises 438 rain gauges and 152 temperature stations with records of both daily maximum and minimum temperatures. To reduce the ""representation error,"" the validation with observations has been performed using a multistep regionalization that distinguishes five precipitation regions and four temperature regions. The analysis proves that both cumulus and PBL schemes have a crucial impact on the description of precipitation in Andalusia, whereas no noticeable differences between microphysics options were appreciated. Temperature is described similarly by all the configurations, except for the PBL choice affecting minimum values. WRF provides a definite improvement over ERA-40 in the climate description in terms of frequency, spatial distribution, and intensity of extreme events. It also captures more accurately the annual cycle and reduces the biases and the RMSE for monthly precipitation, whereas only a minor enhancement of these features was obtained for monthly-mean maximum and minimum temperatures. The results indicate that WRF is able to correctly reproduce Andalusian climate and produces useful added-value information for climate studies. © 2011 American Meteorological Society."
"6701552501;7006331431;7501894557;","Global energy and water budgets in MERRA",2011,"10.1175/2011JCLI4175.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959366257&doi=10.1175%2f2011JCLI4175.1&partnerID=40&md5=ef588a0f1d0e6d4f5e32c30116696226","Reanalyses, retrospectively analyzing observations over climatological time scales, represent a merger between satellite observations and models to provide globally continuous data and have improved over several generations. Balancing the earth's global water and energy budgets has been a focus of research for more than two decades. Models tend to their own climate while remotely sensed observations have had varying degrees of uncertainty. This study evaluates the latestNASAreanalysis, theModernEra Retrospective-Analysis for Research and Applications (MERRA), from a global water and energy cycles perspective, to place it in context of previous work and demonstrate the strengths and weaknesses. MERRA was configured to provide complete budgets in its output diagnostics, including the incremental analysis update (IAU), the term that represents the observations influence on the analyzed states, alongside the physical flux terms. Precipitation in reanalyses is typically sensitive to the observational analysis. For MERRA, the global mean precipitation bias and spatial variability are more comparable to merged satellite observations [the Global Precipitation and Climatology Project (GPCP) and Climate Prediction Center Merged Analysis of Precipitation (CMAP)] than previous generations of reanalyses. MERRA ocean evaporation also has a much lower value, which is comparable to independently derived estimate datasets. The global energy budget shows that MERRA cloud effects may be generally weak, leading to excess shortwave radiation reaching the ocean surface. Evaluating the MERRA time series of budget terms, a significant change occurs that does not appear to be represented in observations. In 1999, the global analysis increments of water vapor changes sign from negative to positive and primarily lead to more oceanic precipitation. This change is coincident with the beginning of Advanced Microwave Sounding Unit (AMSU) radiance assimilation. Previous and current reanalyses all exhibit some sensitivity to perturbations in the observation record, and this remains a significant research topic for reanalysis development. The effect of the changing observing system is evaluated for MERRA water and energy budget terms. © 2011 American Meteorological Society."
"56962915800;55717347500;","A model for scale interaction in the Madden-Julian oscillation",2011,"10.1175/2011JAS3660.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555213059&doi=10.1175%2f2011JAS3660.1&partnerID=40&md5=a7a32d1375eeb5117639023058498a6d","The Madden-Julian oscillation (MJO) is an equatorial planetary-scale circulation system coupled with a multiscale convective complex, and it moves eastward slowly (about 5 m s-1) with a horizontal quadrupole vortex and vertical rearward-tilted structure. The nature and role of scale interaction (SI) is one of the elusive aspects of the MJO dynamics. Here a prototype theoretical model is formulated to advance the current understanding of the nature of SI in MJO dynamics. The model integrates three essential physical elements: (a) large-scale equatorial wave dynamics driven by boundary layer frictional convergence instability (FCI), (b) effects of the upscale eddy momentum transfer (EMT) by vertically tilted synoptic systems resulting from boundary layer convergence and multicloud heating, and (c) interaction between planetary-scale wave motion and synoptic-scale systems (the eastward-propagating super cloud clusters and westward-propagating 2-day waves). It is shown that the EMT mechanism tends to yield a stationary mode with a quadrupole vortex structure (enhanced Rossby wave component), whereas the FCI yields a relatively fast eastward-moving and rearward-tilted Gill-like pattern (enhanced Kelvin wave response). The SI instability stems from corporative FCI orEMTmechanisms, and its property is a mixture of FCI andEMTmodes. The properties of the unstable modes depend on the proportion of deep convective versus stratiform/congestus heating or the ratio of deep convective versus total amount of heating. With increasing stratiform/congestus heating, the FCI weakens while the EMT becomes more effective. A growing SI mode has a horizontal quadrupole vortex and rearwardtilted structure and prefers slow eastward propagation, which resembles the observed MJO. The FCI sets the rearward tilt and eastward propagation, while the EMT slows down the propagation speed. The theoretical results presented here point to the need to observe multicloud structure and vertical heating profiles within the MJO convective complex and to improve general circulation models' capability to reproduce correct partitioning of cloud amounts between deep convective and stratiform/congestus clouds. Limitations and future work are also discussed. © 2010 American Meteorological Society."
"6701518904;8416469500;56275057700;23466498600;57202518424;7201423091;","Sensitivity studies for a space-based methane lidar mission",2011,"10.5194/amt-4-2195-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857733294&doi=10.5194%2famt-4-2195-2011&partnerID=40&md5=d0a0609cb1a11ee508928a5e78adec5b","Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1% over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised. © 2011 Author(s)."
"57210204746;7005920767;","Role of black carbon in aerosol properties and radiative forcing over western India during premonsoon period",2011,"10.1016/j.atmosres.2011.08.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054776226&doi=10.1016%2fj.atmosres.2011.08.003&partnerID=40&md5=9daff6ca52a7c408ccfd4d6c4519f756","The present study addresses the role of black carbon (BC) in aerosol radiative forcing (ARF) over western India, where the Thar Desert produces large amount of dust aerosols during premonsoon season (Mar-May) and its mixing with BC makes the investigation a real challenge. Measurements of aerosol physical and optical parameters were carried out at three stations, Ahmedabad (urban area), Udaipur (semi-arid region) and Mt. Abu (a hill-top representing background conditions), to investigate the regional variation of ARF during April 2007. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements show presence of dust layer in the altitude region from 1 to 5km over western India throughout the month leading to uniform distribution of dust. Ahmedabad has slightly higher AOD500(0.31) due to production of anthropogenic aerosols with BC concentration of 1.8μg.m-3 at surface, followed by Udaipur (AOD500=0.30 and BC=0.9μg.m-3) and Mt. Abu (0.28 and 0.7μg.m-3, respectively). The longwave ARF is found to be similar over all three stations whereas the shortwave ARF depends on type of location. The shortwave ARF at the top of atmosphere (TOA), surface, and within the atmosphere are found to be 1.7, μ46 and 47.7Wm-2, respectively, at Ahmedabad, μ1.5, μ35 and 33.5Wm-2 at Udaipur and μ1.5, μ31 and 29.5Wm-2 at Mt. Abu. On the other hand, the heating rates in the lower atmosphere (up to 5km) are 1.3, 1.0 and 0.4K/day over Ahmedabad, Udaipur and Mt. Abu, respectively. Sensitivity analysis shows that a 40% enhancement of BC could increase the heating rate by up to 50% over western India. Higher aerosol-induced heating in the atmosphere during premonsoon may have a large impact on the regional climate dynamics and hydrological processes. © 2011 Elsevier B.V."
"7501828310;7203001286;6603392379;7202258620;6701463335;7403143315;7005361537;55879827400;","Effects of black carbon aging on air quality predictions direct radiative forcing estimation",2011,"10.1111/j.1600-0889.2011.00558.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054868241&doi=10.1111%2fj.1600-0889.2011.00558.x&partnerID=40&md5=e9cf5b0b532940ebaa7bb5845854f7d9","An aging scheme for black carbon (BC) aerosol was implemented into a regional air-quality forecast model to study the impact of BC aging on air quality predictions. Three different assumptions for the mixing state of BC-external mixture, internal mixture gradual aging-were used to simulate the distribution of BC particles over North America in April 2002. Cloud -condensation nuclei number BC wet deposition rate increased significantly BC mass column loading decreased as a result of BC aging. With the gradual aging process incorporated into the model, the comparison of ground level BC concentration predictions with surface observations was slightly improved. Estimation of the average direct radiative forcing of BC over the spatial domain of this study showed that the factor of direct forcing enhancement by BC aging was much smaller than the mixing state effect factor. The effect of increased wet deposition due to aging compensated partially for the effect of increased absorbance suggesting that the change in the hygroscopic properties of BC due to aging must be taken into account to quantify accurately the effect of BC aging on climate. © 2011 The Authors Tellus B © 2011 John Wiley & Sons A/S."
"35423118500;54412909900;56975641800;7801624777;34868103400;34868961300;7005087624;8624810200;","Geostatistical exploration of spatial variation of summertime temperatures in the Detroit metropolitan region",2011,"10.1016/j.envres.2011.08.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755175702&doi=10.1016%2fj.envres.2011.08.012&partnerID=40&md5=3cafa8fe855a9b13f9354d2a19cfbe67","Background: Because of the warming climate urban temperature patterns have been receiving increased attention. Temperature within urban areas can vary depending on land cover, meteorological and other factors. High resolution satellite data can be used to understand this intra-urban variability, although they have been primarily studied to characterize urban heat islands at a larger spatial scale. Objective: This study examined whether satellite-derived impervious surface and meteorological conditions from multiple sites can improve characterization of spatial variability of temperature within an urban area. Methods: Temperature was measured at 17 outdoor sites throughout the Detroit metropolitan area during the summer of 2008. Kriging and linear regression were applied to daily temperatures and secondary information, including impervious surface and distance-to-water. Performance of models in predicting measured temperatures was evaluated by cross-validation. Variograms derived from several scenarios were compared to determine whether high-resolution impervious surface information could capture fine-scale spatial structure of temperature in the study area. Results: Temperatures measured at the sites were significantly different from each other, and all kriging techniques generally performed better than the two linear regression models. Impervious surface values and distance-to-water generally improved predictions slightly. Restricting models to days with lake breezes and with less cloud cover also somewhat improved the predictions. In addition, incorporating high-resolution impervious surface information into cokriging or universal kriging enhanced the ability to characterize fine-scale spatial structure of temperature. Conclusions: Meteorological and satellite-derived data can better characterize spatial variability in temperature across a metropolitan region. The data sources and methods we used can be applied in epidemiological studies and public health interventions to protect vulnerable populations from extreme heat events. © 2011 Elsevier Inc."
"54398596200;55754495900;7404976222;","Sensitivity of simulated tropical intraseasonal oscillations to cumulus schemes",2011,"10.1007/s11430-011-4215-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80255129691&doi=10.1007%2fs11430-011-4215-0&partnerID=40&md5=8c6788209e393cfc75e8162cd0eb5e2f","The sensitivity of simulated tropical intraseasonal oscillations (ISO) to different cumulus parameterization schemes was analyzed using an atmospheric general circulation model (latest version-SAMIL2. 2. 3) developed at the Laboratory for Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences. Results show that the basic features of tropical climatological intraseasonal oscillations (CISO) can be captured using all three cumulus schemes. The CISO simulated by the Tiedtke scheme was found to be more realistic than that of the Manabe and Zhang-McFarlane schemes. The results of simulated transient intraseasonal oscillations (TISO) indicate that although the Tiedtke and the Zhang-McFarlane schemes in the new version SAMIL2. 2. 3 have been adjusted according to different problems, only the latter can simulate the eastward propagation of the 27-50-day TISO mode. It may be associated with the more realistic diabatic heating profile simulated by the Zhang-McFarlane scheme. In addition, the Manabe scheme in SAMIL2. 2. 3 is the same as that in the prior version SAMIL2. 08. However, some aspects of the physical process, such as the radiation scheme and aerosol condition, have been changed. Conversely the eastward propagation from 100°E to the west of the tropical 27-50-day TISO mode only can be simulated using the Manabe scheme of SAMIL 2. 08. Consequently, not all the improvements of physical parameterization schemes work well in every respect. The coordinated developments between dynamic frame and physical processes, and among different physical processes, are important methods that may be used to improve the model. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg."
"11939918300;7004479957;","Simulating deep convection with a shallow convection scheme",2011,"10.5194/acp-11-10389-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054934526&doi=10.5194%2facp-11-10389-2011&partnerID=40&md5=21edbf13b59f3153031114547dafb9f4","Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES) as a benchmark to test and refine a unified convection scheme implemented in the Single-column Community Atmosphere Model (SCAM). Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle. Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and mid-latitude continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas. © 2011 Author(s)."
"35203929500;6701820543;21735380100;","Atmospheric influences on infrared-laser signals used for occultation measurements between Low Earth Orbit satellites",2011,"10.5194/amt-4-2273-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960492366&doi=10.5194%2famt-4-2273-2011&partnerID=40&md5=3de626ba46fc5449b72614010e86b1d7","LEO-LEO infrared-laser occultation (LIO) is a new occultation technique between Low Earth Orbit (LEO) satellites, which applies signals in the short wave infrared spectral range (SWIR) within 2 μm to 2.5 μm. It is part of the LEO-LEO microwave and infrared-laser occultation (LMIO) method that enables to retrieve thermodynamic profiles (pressure, temperature, humidity) and altitude levels from microwave signals and profiles of greenhouse gases and further variables such as line-of-sight wind speed from simultaneously measured LIO signals. Due to the novelty of the LMIO method, detailed knowledge of atmospheric influences on LIO signals and of their suitability for accurate trace species retrieval did not yet exist. Here we discuss these influences, assessing effects from refraction, trace species absorption, aerosol extinction and Rayleigh scattering in detail, and addressing clouds, turbulence, wind, scattered solar radiation and terrestrial thermal radiation as well. We show that the influence of refractive defocusing, foreign species absorption, aerosols and turbulence is observable, but can be rendered small to negligible by use of the differential transmission principle with a close frequency spacing of LIO absorption and reference signals within 0.5%. The influences of Rayleigh scattering and terrestrial thermal radiation are found negligible. Cloud-scattered solar radiation can be observable under bright-day conditions, but this influence can be made negligible by a close time spacing (within 5 ms) of interleaved laser-pulse and background signals. Cloud extinction loss generally blocks SWIR signals, except very thin or sub-visible cirrus clouds, which can be addressed by retrieving a cloud layering profile and exploiting it in the trace species retrieval. Wind can have a small influence on the trace species absorption, which can be made negligible by using a simultaneously retrieved or a moderately accurate background wind speed profile. We conclude that the set of SWIR channels proposed for implementing the LMIO method (Kirchengast and Schweitzer, 2011) provides adequate sensitivity to accurately retrieve eight trace species of key importance to climate and atmospheric chemistry (H 2O, CO 2, 13CO 2, C 18OO, CH 4, N 2O, O 3, CO) in the upper troposphere/lower stratosphere region outside clouds under all atmospheric conditions. Two further species (HDO, H 2 18O) can be retrieved in the upper troposphere. © Author(s) 2011."
"37041243400;55628589750;55817344400;55637266800;","Will the southern african west coast fog be affected by future climate change?: Results of an initial fog projection using a regional climate model",2011,"10.3112/erdkunde.2011.03.04","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053978184&doi=10.3112%2ferdkunde.2011.03.04&partnerID=40&md5=867e2b1cbeeca8aaf9b77b9d61df3104","We present an initial study to project the long-term development of fog occurrence along the southern African west coast. For this purpose, we implemented a basic fog diagnostic scheme based on liquid water content into the regional climate model REMO. The validation of the fog diagnostic scheme is conducted using satellite-derived low cloud information as well as local station observations. The validation reveals that REMO is able to adequately represent the major fog characteristics in the region. The observed strong fog gradient from the coast to the regions further inland is correctly simulated by the model. Also, the seasonal as well as diurnal fog distribution characteristics are captured by REMO. However, some deficits still remain in the absolute amount of simulated fog days. These deficits can mainly be attributed to the coarse vertical resolution of the model as well as to the simple fog diagnostics approach chosen. Regarding the long-term development of fog, two 20-year time slice simulations for a control (1981 to 2000) and a future (2081 to 2100) period following the A1B emission scenario were conducted. The model generally projects a slight increase in the number of fog days for the coastal areas and a slight decrease for the regions located further inland. Especially the latter has the potential to exacerbate the existing water scarcity in the region."
"16032925200;7006359574;7006151934;6602715033;53663237700;7005284577;37760934500;7006399419;7003298573;7202050065;7006195421;14024872700;57205351494;7006642884;6603735912;57209647985;6701378450;53664152600;6603174102;16480965400;18438062100;7202429440;7004643405;55469564700;36191376400;7006103811;7006593624;53664728400;7403996091;","Impact of fuel quality regulation and speed reductions on shipping emissions: Implications for climate and air quality",2011,"10.1021/es2013424","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054714724&doi=10.1021%2fes2013424&partnerID=40&md5=fee51df9fe9101cfb4440bc924639061","Atmospheric emissions of gas and particulate matter from a large ocean-going container vessel were sampled as it slowed and switched from high-sulfur to low-sulfur fuel as it transited into regulated coastal waters of California. Reduction in emission factors (EFs) of sulfur dioxide (SO 2), particulate matter, particulate sulfate and cloud condensation nuclei were substantial (≥90%). EFs for particulate organic matter decreased by 70%. Black carbon (BC) EFs were reduced by 41%. When the measured emission reductions, brought about by compliance with the California fuel quality regulation and participation in the vessel speed reduction (VSR) program, are placed in a broader context, warming from reductions in the indirect effect of SO 4 would dominate any radiative changes due to the emissions changes. Within regulated waters absolute emission reductions exceed 88% for almost all measured gas and particle phase species. The analysis presented provides direct estimations of the emissions reductions that can be realized by California fuel quality regulation and VSR program, in addition to providing new information relevant to potential health and climate impact of reduced fuel sulfur content, fuel quality and vessel speed reductions. © 2011 American Chemical Society."
"57199221342;7006399667;7202081585;","Cirrus cloud-temperature interactions in the tropical tropopause layer: A case study",2011,"10.5194/acp-11-10085-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053926078&doi=10.5194%2facp-11-10085-2011&partnerID=40&md5=01bca56f7c167e01fe5cfadbfafccb13","Thin cirrus clouds in the Tropical Tropopause Layer (TTL) have important ramifications for radiative transfer, stratospheric humidity, and vertical transport. A horizontally extensive and vertically thin cirrus cloud in the TTL was detected by the Cloud Aerosol LIDAR and Infrared Pathfinder Satellite Observations (CALIPSO) on 27-29 January 2009 in the Tropical Eastern Pacific region, distant from any regions of deep convection. These observations indicate that the cloud is close to 3000 km in length along the CALIPSO orbit track. Measurements over this three day period indicate that the cloud event extended over a region from approximately 15° S to 10° N and 90° W to 150° W and may be one of the most extensive cirrus events ever observed. Coincident temperature observations from the Constellation of Observing Satellites for Meteorology, Ionosphere, and Climate (COSMIC) suggest that the cloud formed in-situ as a result of a cold anomaly arising from a midlatitude intrusion. The event appears to last for up to 2 days and the temperature observations do not show any indication of the expected infrared heating. It is hypothesized that the cloud could be maintained by either nucleation of numerous small ice crystals that don't sediment or by multiple localized ice nucleation events driven by temperature variability at scales smaller than the overall cloud field, producing small ice-crystal sizes which have sufficiently long residence times (ĝ‰̂53 h) to maintain the cloud. It is possible that the residence times are augmented by vertical motion which could also act to offset the expected infrared heating. Further observations of similar events will be required in order to conclusively explain this curious cloud. © 2011 Author(s)."
"53881592700;6603256951;","A climate-induced threshold in hydrologic response in a semiarid ponderosa pine hillslope",2011,"10.1029/2011WR010384","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053602763&doi=10.1029%2f2011WR010384&partnerID=40&md5=a9fc4454cc6f18e734236e3de8bcf954","The temporal evolution of spatial hydrologic patterns in systems with strong seasonality in water availability is poorly understood. In this study, we use a distributed hydrologic model to explore the switching between local (vegetative) and nonlocal (topographic) factors in a semiarid ponderosa pine hillslope. Our modeling effort is focused on identifying threshold behavior in the hillslope response due to wetting during the North American monsoon (NAM). We calibrate the model to distributed surface soil moisture data for one summer and then test the model against a broader range of observations over multiple seasons. Model simulations are then used to identify vegetation and topographic controls on spatial patterns in soil moisture and runoff generation. Vegetation patterns primarily influence the hydrologic response during dry summer periods leading to patchiness related to the ponderosa pine stands. The spatial response switches to fine-scale terrain curvature controls during persistently wet NAM periods. Thus, a climatic threshold involving rainfall and weather conditions during the NAM is identified in the hillslope response when sufficient lateral soil moisture fluxes are activated by high rainfall amounts and the lower evapotranspiration induced by cloud cover. The spatial variability of hillslope soil moisture and runoff generation also increases due to the crossing of this threshold in the seasonal rainfall distribution. Our findings point to the influence of topography and lateral fluxes during summer periods of high wetness in forested hillslopes of the southwestern United States. © 2011 by the American Geophysical Union."
"21735380100;6701820543;35203929500;","Greenhouse gas profiling by infrared-laser and microwave occultation: Retrieval algorithm and demonstration results from end-to-end simulations",2011,"10.5194/amt-4-2035-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857771494&doi=10.5194%2famt-4-2035-2011&partnerID=40&md5=6678f795549cf05001b4cb6fdaa2b67f","Measuring greenhouse gas (GHG) profiles with global coverage and high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS) is key for improved monitoring of GHG concentrations in the free atmosphere. In this respect a new satellite mission concept adding an infrared-laser part to the already well studied microwave occultation technique exploits the joint propagation of infrared-laser and microwave signals between Low Earth Orbit (LEO) satellites. This synergetic combination, referred to as LEO-LEO microwave and infrared-laser occultation (LMIO) method, enables to retrieve thermodynamic profiles (pressure, temperature, humidity) and accurate altitude levels from the microwave signals and GHG profiles from the simultaneously measured infrared-laser signals. However, due to the novelty of the LMIO method, a retrieval algorithm for GHG profiling is not yet available. Here we introduce such an algorithm for retrieving GHGs from LEO-LEO infrared-laser occultation (LIO) data, applied as a second step after retrieving thermodynamic profiles from LEO-LEO microwave occultation (LMO) data. We thoroughly describe the LIO retrieval algorithm and unveil the synergy with the LMO-retrieved pressure, temperature, and altitude information. We furthermore demonstrate the effective independence of the GHG retrieval results from background (a priori) information in discussing demonstration results from LMIO end-to-end simulations for a representative set of GHG profiles, including carbon dioxide (CO2), water vapor (H2O), methane (CH4), and ozone (O3). The GHGs except for ozone are well retrieved throughout the UTLS, while ozone is well retrieved from about 10 km to 15 km upwards, since the ozone layer resides in the lower stratosphere. The GHG retrieval errors are generally smaller than 1% to 3% r.m.s., at a vertical resolution of about 1 km. The retrieved profiles also appear unbiased, which points to the climate benchmarking capability of the LMIO method. This performance, found here for clear-air atmospheric conditions, is unprecedented for vertical profiling of GHGs in the free atmosphere and encouraging for future LMIO implementation. Subsequent work will examine GHG retrievals in cloudy air, addressing retrieval performance when scanning through intermittent upper tropospheric cloudiness. © 2011 Author(s)."
"57210457351;23470656000;6603902085;7003644704;","Monitoring spatial and temporal variations of surface albedo on Saint Sorlin Glacier (French Alps) using terrestrial photography",2011,"10.5194/tc-5-759-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053308582&doi=10.5194%2ftc-5-759-2011&partnerID=40&md5=31afe8f95a4683d696a867411c61596f","Accurate knowledge of temperate glacier mass balance is essential to understand the relationship between glacier and climate. Defined as the reflected fraction of incident radiation over the whole solar spectrum, the surface broadband albedo is one of the most important variable in a glacier's mass balance. This study presents a new method to retrieve the albedo of frozen surfaces from terrestrial photography at visible and near infrared wavelengths. This method accounts for the anisotropic reflectance of snow and ice surfaces and uses a radiative transfer model for narrow-to-broadband conversion. The accuracy of the method was assessed using concomitant measurements of albedo during the summers 2008 and 2009 on Saint Sorlin Glacier (Grandes Rousses, France). These albedo measurements are performed at two locations on the glacier, one in the ablation area and the other in the accumulation zone, with a net radiometer Kipp and Zonen CNR1. The main sources of uncertainty are associated with the presence of high clouds and the georeferencing of the photographs. © Author(s) 2011."
"7003266014;","Cloud variations and the Earth's energy budget",2011,"10.1029/2011GL049236","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053550957&doi=10.1029%2f2011GL049236&partnerID=40&md5=38db85a7a6390cf15d4f7a147158bada","The question of whether clouds are the cause of surface temperature changes, rather than acting as a feedback in response to those temperature changes, is explored using data obtained between 2000 and 2010. An energy budget calculation shows that the radiative impact of clouds accounts for little of the observed climate variations. It is also shown that observations of the lagged response of top-of-atmosphere (TOA) energy fluxes to surface temperature variations are not evidence that clouds are causing climate change. Copyright 2011 by the American Geophysical Union."
"12242422700;15135280400;15122248200;","Climate sensitivity to changes in ocean heat transport",2011,"10.1175/JCLI-D-10-05029.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055033612&doi=10.1175%2fJCLI-D-10-05029.1&partnerID=40&md5=9b71963ac7bf4368f131ee8813361d4e","Using an atmospheric general circulation model coupled to a slab ocean, the effects of ocean heat transport (OHT) on climate are studied by prescribingOHTfrom 0 to 2 times the present-day values. In agreement with previous studies, an increase inOHTfrom zero to present-day conditions warms the climate by decreasing the albedo due to reduced sea ice extent and marine stratus cloud cover and by increasing the greenhouse effect through a moistening of the atmosphere. However, when the OHT is further increased, the solution becomes highly dependent on a positive radiative feedback between tropical low clouds and sea surface temperature. The strength of the low cloud-SST feedback combined with the model design may produce solutions that are globally colder than in the control run, mainly due to an unrealistically strong equatorial cooling. Excluding those cases, results indicate that the climate warms only if the OHT increase does not exceed more than 10% of the present-day value in the case of a strong cloud-SST feedback and more than 25% when this feedback is weak. Larger OHT increases lead to a cold state where low clouds cover most of the deep tropics, increasing the tropical albedo and drying the atmosphere. This suggests that the present-day climate is close to a state where the OHT maximizes its warming effects on climate and raises doubts about the possibility that greater OHT in the past may have induced significantly warmer climates than that of today. © 2011 American Meteorological Society."
"12801992200;7006307463;7005304841;56913197300;","Quantification of monthly mean regional-scale albedo of marine stratiform clouds in satellite observations and GCMs",2011,"10.1175/JAMC-D-11-049.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960684672&doi=10.1175%2fJAMC-D-11-049.1&partnerID=40&md5=cf5d3bc8406f12837c371efee0a721cf","Planetary albedo-the reflectivity for solar radiation-is of singular importance in determining the amount of solar energy taken in by the Earth-atmosphere system. Modeling albedo, and specifically cloud albedo, correctly is crucial for realistic climate simulations. A method is presented herein by which regional cloud albedo can be quantified fromthe relation between total albedo and cloud fraction,which in observations is found to be approximately linear on a monthly mean scale. This analysis is based primarily on the combination of cloud fraction data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and albedo data from the Clouds and the Earth's Radiant Energy System (CERES), but the results presented are also supported by the combination of cloud fraction and proxy albedo data from satelliteborne lidar [Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)]. These data are measured and derived completely independently from the CERES-MODIS data. Applied to low-level marine stratiform clouds in three regions (off the coasts of South America, Africa, and North America), the analysis reveals regionally uniform monthly mean cloud albedos, indicating that the variation in cloud shortwave radiative properties is small on this scale. A coherent picture of low ""effective"" cloud albedo emerges, in the range from 0.35 to 0.42, on the basis of data from CERES and MODIS. In its simplicity, the method presented appears to be useful as a diagnostic tool and as a constraint on climate models. To demonstrate this, the same method is applied to cloud fraction and albedo output from several current-generation climate models [from the Coupled Model Intercomparison Project, phase 3 (CMIP3), archive]. Although the multimodel mean cloud albedo estimates agree to within 20% with the satellite-based estimates for the three focus regions, model-based estimates of cloud albedo are found to display much larger variability than do the observations, within individual models as well as between models. © 2011 American Meteorological Society."
"16679271700;7006698304;7004540083;6603422104;36717393600;","Major characteristics of Southern Ocean cloud regimes and their effects on the energy budget",2011,"10.1175/2011JCLI4052.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959635038&doi=10.1175%2f2011JCLI4052.1&partnerID=40&md5=f2f17afe2161a55ae0009269a2e92d0e","Clouds over the Southern Ocean are often poorly represented by climate models, but they make a significant contribution to the top-of-atmosphere (TOA) radiation balance, particularly in the shortwave portion of the energy spectrum. This study seeks to better quantify the organization and structure of Southern Hemisphere midlatitude clouds by combining measurements from active and passive satellite-based datasets. Geostationary and polarorbiter satellite data from the International SatelliteCloud Climatology Project (ISCCP) are used to quantify largescale, recurringmodes of cloudiness, and active observations fromCloudSat and Cloud-AerosolLidar and Infrared Pathfinder Satellite Observation (CALIPSO) are used to examine vertical structure, radiative heating rates, and precipitation associated with these clouds. It is found that cloud systems are organized into eight distinct regimes and that ISCCP overestimates the midlevel cloudiness of these regimes. All regimes contain a relatively high occurrence of low cloud, with 79%of all cloud layers observed having tops below 3 km, but multiple-layered clouds systems are present in approximately 34% of observed cloud profiles. The spatial distribution of regimes varies according to season, with cloud systems being geometrically thicker, on average, during the austral winter. Those regimes found to be most closely associated with midlatitude cyclones produce precipitation the most frequently, although drizzle is extremely common in low-cloud regimes. The regimes associated with cyclones have the highest in-regime shortwave cloud radiative effect at the TOA, but the low-cloud regimes, by virtue of their high frequency of occurrence over the oceans, dominate both TOA and surface shortwave effects in this region as a whole. © 2011 American Meteorological Society."
"8872018100;35887706900;20435752700;20436169300;","Effect of coarse marine aerosols on stratocumulus clouds",2011,"10.1029/2011GL048504","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055063783&doi=10.1029%2f2011GL048504&partnerID=40&md5=3fc61bbc26274883f6343572dbac9e66","In contrast to fine anthropogenic aerosols (radii ∼<0.5 m), large aerosol particles are thought to enhance cloud droplet growth, promote precipitation formation and reduce cloud albedo. While shown in cloud simulation models, the impact of coarse aerosols on marine stratocumulus clouds lacks observational evidence. Here, by combining data from AMSR-E and MODIS, both aboard NASA's satellite Aqua, we link the amount of coarse marine aerosols emitted to the atmosphere through wind-driven processes with the size of cloud droplets, at the world's largest deck of marine stratocumulus clouds over the southeastern Pacific. For constrained meteorological conditions, approximately 1/2 of the change in droplet effective radius (r<inf>eff</inf>) is attributed to increase in coarse marine aerosol optical depth (T<inf>cm</inf>), as surface winds intensify. Accordingly, a twofold increase in T<inf>cm</inf> is associated with a 1.4 m 0.11 increase in r<inf>eff</inf>. Our results suggest that climatic changes in surface winds may play an important role not only over land for wind-power estimation but also over the oceans by changing clouds reflectance and lifetime. Copyright 2011 by the American Geophysical Union."
"40461229800;26639062900;24173873500;55113736500;7403401100;7005773698;","Measurements of aerosol chemistry during new particle formation events at a remote rural mountain site",2011,"10.1021/es103692f","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053424489&doi=10.1021%2fes103692f&partnerID=40&md5=23c5b3994390298599cc2b44663a7a78","Determining the major sources of particles that act as cloud condensation nuclei (CCN) represents a critical step in the development of a more fundamental understanding of aerosol impacts on cloud formation and climate. Reported herein are direct measurements of the CCN activity of newly formed ambient particles, measured at a remote rural site in the Sierra Nevada Mountains of Northern California. Nucleation events in the winter of 2009 occurred during two pristine periods following precipitation, with higher gas-phase SO 2 concentrations during the second period, when faster particle growth occurred (7-8 nm/h). Amines, as opposed to ammonia, and sulfate were detected in the particle phase throughout new particle formation (NPF) events, increasing in number as the particles grew to larger sizes. Interestingly, long-range transport of SO 2 from Asia appeared to potentially play a role in NPF during faster particle growth. Understanding the propensity of newly formed particles to act as CCN is critical for predicting the effects of NPF on orographic cloud formation during winter storms along the Sierra Nevada Mountain range. The potential impact of newly formed particles in remote regions needs to be compared with that of transported urban aerosols when evaluating the impact of aerosols on clouds and climate. © 2011 American Chemical Society."
"8934032500;36170230500;6603886699;","Testing WRF capability in simulating the atmospheric water cycle over Equatorial East Africa",2011,"10.1007/s00382-011-1024-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053320493&doi=10.1007%2fs00382-011-1024-2&partnerID=40&md5=ea3b1068cd88a9823e87c27b550eb518","Uncertainties in simulating the seasonal mean atmospheric water cycle in Equatorial East Africa are quantified using 58 one-year-long experiments performed with the Weather Research and Forecasting model (WRF). Tested parameters include physical parameterizations of atmospheric convection, cloud microphysics, planetary boundary layer, land-surface model and radiation schemes, as well as land-use categories (USGS vs. MODIS), lateral forcings (ERA-Interim and ERA40 reanalyses), and domain geometry (size and vertical resolution). Results show that (1) uncertainties, defined as the differences between the experiments, are larger than the biases; (2) the parameters exerting the largest influence on simulated rainfall are, in order of decreasing importance, the shortwave radiation scheme, the land-surface model, the domain size, followed by convective schemes and land-use categories; (3) cloud microphysics, lateral forcing reanalysis, the number of vertical levels and planetary boundary layer schemes appear to be of lesser importance at the seasonal scale. Though persisting biases (consisting of conditions that are too wet over the Indian Ocean and the Congo Basin and too dry over eastern Kenya) prevail in most experiments, several configurations simulate the regional climate with reasonable accuracy. © 2011 Springer-Verlag."
"7102953444;36618213200;","Assessment of global dimming and brightening in IPCC-AR4/CMIP3 models and ERA40",2011,"10.1007/s00382-010-0939-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053299511&doi=10.1007%2fs00382-010-0939-3&partnerID=40&md5=c91a2bcc58726db77f0a0951f2c3e4a2","Observations indicate that solar radiation incident at the Earth surface underwent substantial decadal variations in the second half of the twentieth century, with a tendency towards reduction from the 1950s to the 1980s (""global dimming"") and a partial recovery thereafter (""brightening"") at widespread locations. The most reliable observational records from the Global Energy Balance Archive (GEBA) are used to evaluate the ability of the climate models participating in CMIP3/IPCC-AR4 as well as the ERA40 reanalysis to reproduce these decadal variations. The results from 23 models and reanalysis are analyzed in five different climatic regions where strong decadal variations in surface solar radiation (SSR) have been observed. Only about half of the models are capable of reproducing the observed decadal variations in a qualitative way, and all models show much smaller amplitudes in these variations than seen in the observations. Largely differing tendencies between the models are not only found under all-sky conditions, but also in cloud-free conditions and in the representation of cloud effects. The ERA40 reanalysis neither reproduces the major decadal variations in SSR, despite strong observational constraints on the temporal evolution of the state of the atmosphere, since time varying aerosol loadings are missing. Climate models and reanalyses are therefore not yet at a stage to provide regionally consistent estimates of decadal changes in SSR. Reproduction of these changes would be essential for an adequate representation of regional scale climate variations and impacts, and short-term (decadal) climate projections. © 2010 Springer-Verlag."
"56927849100;7403254320;6602550399;36950167100;57208638573;","A high-quality monthly total cloud amount dataset for Australia",2011,"10.1007/s10584-010-9992-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052947561&doi=10.1007%2fs10584-010-9992-5&partnerID=40&md5=0b49d8dde5457832fe6514cdafa7b59d","A high-quality monthly total cloud amount dataset for 165 stations has been developed for monitoring and assessing long-term trends in cloud cover over Australia. The dataset is based on visual 9 a. m. and 3 p. m. observations of total cloud amount, with most records starting around 1957. The quality control process involved examination of historical station metadata, together with an objective statistical test comparing candidate and reference cloud series. Individual cloud series were also compared against rainfall and diurnal temperature range series from the same site, and individual cloud series from neighboring sites. Adjustments for inhomogeneities caused by relocations and changes in observers were applied, as well as adjustments for biases caused by the shift to daylight saving time in the summer months. Analysis of these data reveals that the Australian mean annual total cloud amount is characterised by high year-to-year variability and shows a weak, statistically non-significant increase over the 1957-2007 period. A more pronounced, but also non-significant, decrease from 1977 to 2007 is evident. A strong positive correlation is found between all-Australian averages of cloud amount and rainfall, while a strong negative correlation is found between mean cloud amount and diurnal temperature range. Patterns of annual and seasonal trends in cloud amount are in general agreement with rainfall changes across Australia, however the high-quality cloud network is too coarse to fully capture topographic influences. Nevertheless, the broadscale consistency between patterns of cloud and rainfall variations indicates that the new total cloud amount dataset is able to adequately describe the broadscale patterns of change over Australia. Favourable simple comparisons between surface and satellite measures of cloudiness suggest that satellites may ultimately provide the means for monitoring long-term changes in cloud over Australia. However, due to the relative shortness and homogeneity problems of the satellite record, a robust network of surface cloud observations will be required for many years to come. © 2010 The Author(s)."
"7004890337;6602688130;7103271625;57202754759;6602817609;6701871514;7402207328;7102696626;7006705919;6507312147;7004403539;7405429767;55745955800;","The community climate system model version 4",2011,"10.1175/2011JCLI4083.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958294849&doi=10.1175%2f2011JCLI4083.1&partnerID=40&md5=6eeb06b7e425de614633bd31f57358ce","The fourth version of the Community Climate System Model (CCSM4) was recently completed and released to the climate community. This paper describes developments to all CCSM components, and documents fully coupled preindustrial control runs compared to the previous version, CCSM3. Using the standard atmosphere and land resolution of 18 results in the sea surface temperature biases in the major upwelling regions being comparable to the 1.48-resolution CCSM3. Two changes to the deep convection scheme in the atmosphere component result in CCSM4 producing El Niño-Southern Oscillation variability with a much more realistic frequency distribution than in CCSM3, although the amplitude is too large compared to observations. These changes also improve the Madden-Julian oscillation and the frequency distribution of tropical precipitation. A new overflow parameterization in the ocean component leads to an improved simulation of the Gulf Stream path and the North Atlantic Ocean meridional overturning circulation. Changes to the CCSM4 land component lead to a much improved annual cycle of water storage, especially in the tropics. The CCSM4 sea ice component uses much more realistic albedos than CCSM3, and for several reasons the Arctic sea ice concentration is improved in CCSM4. An ensemble of twentieth-century simulations produces a good match to the observed September Arctic sea ice extent from 1979 to 2005. The CCSM4 ensemble mean increase in globally averaged surface temperature between 1850 and 2005 is larger than the observed increase by about 0.48C. This is consistent with the fact that CCSM4 does not include a representation of the indirect effects of aerosols, although other factors may come into play. The CCSM4 still has significant biases, such as the mean precipitation distribution in the tropical Pacific Ocean, too much low cloud in the Arctic, and the latitudinal distributions of shortwave and longwave cloud forcings. © 2011 American Meteorological Society."
"55264269400;36545079300;55494171200;40660999000;","Seasonal variability in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon",2011,"10.1007/s11430-011-4225-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053572731&doi=10.1007%2fs11430-011-4225-y&partnerID=40&md5=21bd695cd024e6a23e2f238025a3d722","Seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) rain products (2A25). Datasets from the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) 24 general circulation models (GCMs) are evaluated using TRMM PR rain products in terms of their ability to simulate convective and stratiform precipitation and their deficiencies. The results show that Asian monsoon convective and stratiform precipitation increases significantly after onset of the summer monsoon, but the percentage of convective precipitation clearly decreases over tropical areas while it increases in subtropical regions. The GCMs simulate well the seasonal variation in the contribution of Asian monsoon subtropical convective precipitation to the total rainfall; however, the simulated convective precipitation amount is high while the simulated stratiform precipitation amount is low relative to TRMM measurements, especially over the Asian monsoon tropical region. There is simultaneous TRMM-observed convective and stratiform precipitation in space and time, but GCMs cannot simulate this relationship between convective and stratiform precipitation, resulting in the deficiency of stratiform precipitation simulations. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg."
"23975368700;55461837700;15724418700;","Isentropic slopes, downgradient eddy fluxes, and the extratropical atmospheric circulation response to tropical tropospheric heating",2011,"10.1175/JAS-D-10-05025.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555213075&doi=10.1175%2fJAS-D-10-05025.1&partnerID=40&md5=868978be337dddbda576e78f8737320b","Climate change experiments run on Intergovernmental Panel on Climate Change (IPCC)-class numerical models consistently suggest that increasing concentrations of greenhouse gases will lead to a poleward shift of the midlatitude jets and their associated eddy fluxes of heat and potential vorticity (PV). Experiments run on idealized models suggest that the poleward contraction of the jets can be traced to the effects of increased latent heating and thus locally enhanced warming in the tropical troposphere. Here the authors provide new insights into the dynamics of the circulation response to tropical tropospheric heating using transient experiments in an idealized general circulation model. It is argued that the response of the midlatitude jets to tropical heating is driven fundamentally by 1) the projection of the heating onto the meridional slope of the lower tropospheric isentropic surfaces, and 2) a diffusive model of the eddy fluxes of heat and PV. In the lower and middle troposphere, regions where the meridional slope of the isentropes (i.e., the baroclinicity) is increased are marked by anomalously poleward eddy fluxes of heat, and vice versa. Near the tropopause, regions where the meridional gradients in PV are increased are characterized by anomalously equatorward eddy fluxes of PV, and vice versa. The barotropic component of the response is shown to be closely approximated by the changes in the lower-level heat fluxes. As such, the changes in the eddy fluxes of momentum near the tropopause appear to be driven primarily by the changes in wave generation in the lower troposphere. © 2011 American Meteorological Society."
"7501760109;7201549312;7401970381;35794721100;55716700200;7407059267;","An assessment of the surface climate in the NCEP climate forecast system reanalysis",2011,"10.1007/s00382-010-0935-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052756110&doi=10.1007%2fs00382-010-0935-7&partnerID=40&md5=6826fc3037d64d11424568d7429ff308","This paper analyzes surface climate variability in the climate forecast system reanalysis (CFSR) recently completed at the National Centers for Environmental Prediction (NCEP). The CFSR represents a new generation of reanalysis effort with first guess from a coupled atmosphere-ocean-sea ice-land forecast system. This study focuses on the analysis of climate variability for a set of surface variables including precipitation, surface air 2-m temperature (T2m), and surface heat fluxes. None of these quantities are assimilated directly and thus an assessment of their variability provides an independent measure of the accuracy. The CFSR is compared with observational estimates and three previous reanalyses (the NCEP/NCAR reanalysis or R1, the NCEP/DOE reanalysis or R2, and the ERA40 produced by the European Centre for Medium-Range Weather Forecasts). The CFSR has improved time-mean precipitation distribution over various regions compared to the three previous reanalyses, leading to a better representation of freshwater flux (evaporation minus precipitation). For interannual variability, the CFSR shows improved precipitation correlation with observations over the Indian Ocean, Maritime Continent, and western Pacific. The T2m of the CFSR is superior to R1 and R2 with more realistic interannual variability and long-term trend. On the other hand, the CFSR overestimates downward solar radiation flux over the tropical Western Hemisphere warm pool, consistent with a negative cloudiness bias and a positive sea surface temperature bias. Meanwhile, the evaporative latent heat flux in CFSR appears to be larger than other observational estimates over most of the globe. A few deficiencies in the long-term variations are identified in the CFSR. Firstly, dramatic changes are found around 1998-2001 in the global average of a number of variables, possibly related to the changes in the assimilated satellite observations. Secondly, the use of multiple streams for the CFSR induces spurious jumps in soil moisture between adjacent streams. Thirdly, there is an inconsistency in long-term sea ice extent variations over the Arctic regions between the CFSR and other observations with the CFSR showing smaller sea ice extent before 1997 and larger extent starting in 1997. These deficiencies may have impacts on the application of the CFSR for climate diagnoses and predictions. Relationships between surface heat fluxes and SST tendency and between SST and precipitation are analyzed and compared with observational estimates and other reanalyses. Global mean fields of surface heat and water fluxes together with radiation fluxes at the top of the atmosphere are documented and presented over the entire globe, and for the ocean and land separately. © 2010 Springer-Verlag (outside the USA)."
"23013520400;7402781278;7402966758;36668835800;7004452985;7403204511;","Daily and intraseasonal relationships between lightning and NO2 over the Maritime Continent",2011,"10.1029/2011GL048578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053950202&doi=10.1029%2f2011GL048578&partnerID=40&md5=2d27f9af7162b44d77011ad15d91b1b4","The relationship between lightning and NO2 over Indonesia is examined on daily and intraseasonal time scales based on lightning observations from the World Wide Lightning Location Network (WWLLN) and tropospheric NO 2 column densities from the Global Ozone Monitoring Experiment (GOME-2) satellite mission. Composites of the daily NO2 observations regressed onto lightning frequency reveal a plume of enhanced NO2 following a day of enhanced lightning. Lightning and NO2 also vary coherently with the intraseasonal Madden-Julian Oscillation (MJO) in a manner distinct from the cloudiness signature, with variations of up to ∼50% of the annual mean. Copyright 2011 by the American Geophysical Union."
"10639674700;6602205640;56013704800;55951088700;","Pollen-vegetation relationships along steep climatic gradients in western Amazonia",2011,"10.1111/j.1654-1103.2011.01289.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052275292&doi=10.1111%2fj.1654-1103.2011.01289.x&partnerID=40&md5=0da647c92ca94fd4af68d02c19f6af4a","Question: How accurately do Amazonian montane forest pollen spectra reflect the vegetation? Can compositional changes observed in the vegetation along environmental gradients be identified in the pollen spectra? How well do herbarium collection data and bioclimatic envelopes represent abundance changes along elevation gradients? Location: Amazonian montane forests, Peru. Methods: Moss polsters collected along five altitudinal transects spanning over 3000m a.s.l. were used to characterize pollen spectra. Vegetation plot data from a network of 15 1-ha permanent plots were used to correlate pollen spectra with present-day vegetation. Probability density functions (PDFs) fitted to pollen and plot data allowed comparisons using Spearman correlation coefficients. Ordination analyses were used to summarize changes in pollen spectra. Correlations between pollen-based PDFs and previously-published herbarium collection PDFs were also evaluated. Results: Pollen spectra closely reflected changes in species composition along elevation gradients. A mid-elevation shift in pollen spectra was identified using ordination analyses. Pollen spectra from the driest forest in our data set were statistically different from those of wet forests. Pollen abundance PDFs along the altitudinal gradient were significantly correlated (P<0.01) with PDFs fitted to plot abundance, basal area and herbarium collection data for ten out of 11 taxa analysed. Conclusions: Pollen spectra closely reflected the vegetation composition of Amazonian montane forests. The differentiation of pollen spectra from dry localities showed the potential of genus-level pollen data to reflect precipitation gradients. Pollen spectra also reflected mid-elevation compositional changes well along the lower elevation limit of ground cloud formation. Despite collection biases, herbarium-based bioclimatic envelope PDFs also represented well forest compositional changes along elevation gradients. © 2011 International Association for Vegetation Science."
"26643130200;","Arid sedimentation in the oceans and atmospheric particulate matter",2011,"10.1016/j.rgg.2011.09.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80355148700&doi=10.1016%2fj.rgg.2011.09.006&partnerID=40&md5=b31c99d4a7d2a263972f9185e37fea85","Recent studies on the continental sources of aerosol production, transport and deposition to the ocean (natural sink) allowed us to recognize the possibility of long-range high-altitude (transoceanic) transport of aerosol dust of specific composition and properties. The dust consists of fine (micro- and nanosized) particles (94%, less than 2 μm) originated in the arid (undrained) tropical and subtropical regions extending into the oceans and are similar in composition to deep-sea (pelagic) red clays. Satellite and aircraft observation data were used to track trajectories of long-range (and transoceanic) transport of dust clouds. These data were coupled with direct shipboard measurements on ice core records and data on nuclear explosions and volcanic eruptions. Several zones of arid sedimentation were identified based on climatic conditions (shortage of water), conditions of dust production, wind-blown transport at different altitudes and deposition onto the ocean surface. The main transport occurs at two altitude scales (from land to the cloud top and above) (5-7 km) where wind speed of 300 km/h will be critical for a long-range transport.Three types of transport are identified based on the particle dynamics, composition and properties: 1-local (0-10 km from the source); 2-regional (100-1000 km); 3-global (over 1000 km). The finer particles are a product of local-scale transport with a total flux of 1.6 billion t/yr, which is almost equal to the net influx of the riverine terrigenous material to the pelagic zones of the oceans (outside the marginal filters). There are four main sources of aerosol dust, which is transported and deposited over arid oceanic regions. The arid oceanic regions account for about 1/3 of the modern ocean surface. During glacial periods, the sea-level drop of 100-120 m caused a significant increase in the size of arid regions due to the exposure of the shelf areas, which is equal to the area of the African continent. This caused 3-5 times higher dust emission, a decrease in the heat flux and in the transparency of the atmosphere. Comparison of ice core records and deep drilling data provide basis for studies on the ancient arid sedimentation. © 2011, V.S. Sobolev IGM, Siberian Branch of the RAS."
"7201498373;8414341100;6506316395;","Irrigation induced surface cooling in the context of modern and increased greenhouse gas forcing",2011,"10.1007/s00382-010-0932-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053308316&doi=10.1007%2fs00382-010-0932-x&partnerID=40&md5=9c0f6ce71a87f6b186ccf40abdc6d454","There is evidence that expected warming trends from increased greenhouse gas (GHG) forcing have been locally 'masked' by irrigation induced cooling, and it is uncertain how the magnitude of this irrigation masking effect will change in the future. Using an irrigation dataset integrated into a global general circulation model, we investigate the equilibrium magnitude of irrigation induced cooling under modern (Year 2000) and increased (A1B Scenario, Year 2050) GHG forcing, using modern irrigation rates in both scenarios. For the modern scenario, the cooling is largest over North America, India, the Middle East, and East Asia. Under increased GHG forcing, this cooling effect largely disappears over North America, remains relatively unchanged over India, and intensifies over parts of China and the Middle East. For North America, irrigation significantly increases precipitation under modern GHG forcing; this precipitation enhancement largely disappears under A1B forcing, reducing total latent heat fluxes and the overall irrigation cooling effect. Over India, irrigation rates are high enough to keep pace with increased evaporative demand from the increased GHG forcing and the magnitude of the cooling is maintained. Over China, GHG forcing reduces precipitation and shifts the region to a drier evaporative regime, leading to a relatively increased impact of additional water from irrigation on the surface energy balance. Irrigation enhances precipitation in the Middle East under increased GHG forcing, increasing total latent heat fluxes and enhancing the irrigation cooling effect. Ultimately, the extent to which irrigation will continue to compensate for the warming from increased GHG forcing will primarily depend on changes in the background evaporative regime, secondary irrigation effects (e. g. clouds, precipitation), and the ability of societies to maintain (or increase) current irrigation rates. © 2010 Springer-Verlag (outside the USA)."
"57206454204;7404837587;26032538900;53664709200;36179190000;","Study of distinctive regional features of surface solar radiation in north and east China",2011,"10.1007/s13351-011-0408-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053099626&doi=10.1007%2fs13351-011-0408-x&partnerID=40&md5=85dcd3f7e01121d2de038c8201c2fe1b","Solar radiation is an important energy source for plants on the earth and also a major component of the global energy balance. Variations in solar radiation incident at the earth's surface profoundly affect the human and terrestrial environment, including the climate change. To provide useful information for predicting the future climate change in China, distinctive regional features in spatial and temporal variations of the surface solar radiation (SSR) and corresponding attributions (such as cloud and aerosol) are analyzed based on SSR observations and other meteorological measurements in North and East China from 1961 to 2007. Multiple models, such as the plane-parallel radiative transfer model, empirical and statistical models, and correlation and regression analysis methods are used in the study. The results are given as follows. (1) During 1961-2007, the total SSR in North China went through a process from quickly ""dimming to slowly ""dimming, while in East China, a significant transition from ""dimming to ""brightening occurred. Although there are some differences between the two regional variation trends, long-term variations in SSR in the two regions are basically consistent with the observation worldwide. (2) Between the 1960s and 1980s, in both North and East China, aerosols played a critical role in the radiation dimming. However, after 1989, different variation trends of SSR occurred in North and East China, indicating that aerosols were not the dominant factor. (3) Cloud cover contributed less to the variation of SSR in North China, but was the major attribution in East China and played a promoting role in the reversal of SSR from dimming to brightening, especially in the ""remarkable brightening"" period, with its contribution as high as 70%. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2011."
"7201798916;57206332144;7004174939;7102084129;35464731600;6506257601;35887706900;7103011104;7005880268;7004864963;","Remote sensing the vertical profile of cloud droplet effective radius, thermodynamic phase, and temperature",2011,"10.5194/acp-11-9485-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052872030&doi=10.5194%2facp-11-9485-2011&partnerID=40&md5=9b21379a82fc9d2da7a471bf6b38968e","Cloud-aerosol interaction is a key issue in the climate system, affecting the water cycle, the weather, and the total energy balance including the spatial and temporal distribution of latent heat release. Information on the vertical distribution of cloud droplet microphysics and thermodynamic phase as a function of temperature or height, can be correlated with details of the aerosol field to provide insight on how these particles are affecting cloud properties and their consequences to cloud lifetime, precipitation, water cycle, and general energy balance. Unfortunately, today's experimental methods still lack the observational tools that can characterize the true evolution of the cloud microphysical, spatial and temporal structure in the cloud droplet scale, and then link these characteristics to environmental factors and properties of the cloud condensation nuclei. Here we propose and demonstrate a new experimental approach (the cloud scanner instrument) that provides the microphysical information missed in current experiments and remote sensing options. Cloud scanner measurements can be performed from aircraft, ground, or satellite by scanning the side of the clouds from the base to the top, providing us with the unique opportunity of obtaining snapshots of the cloud droplet microphysical and thermodynamic states as a function of height and brightness temperature in clouds at several development stages. The brightness temperature profile of the cloud side can be directly associated with the thermodynamic phase of the droplets to provide information on the glaciation temperature as a function of different ambient conditions, aerosol concentration, and type. An aircraft prototype of the cloud scanner was built and flew in a field campaign in Brazil. The CLAIM-3D (3-Dimensional Cloud Aerosol Interaction Mission) satellite concept proposed here combines several techniques to simultaneously measure the vertical profile of cloud microphysics, thermodynamic phase, brightness temperature, and aerosol amount and type in the neighborhood of the clouds. The wide wavelength range, and the use of multi-angle polarization measurements proposed for this mission allow us to estimate the availability and characteristics of aerosol particles acting as cloud condensation nuclei, and their effects on the cloud microphysical structure. These results can provide unprecedented details on the response of cloud droplet microphysics to natural and anthropogenic aerosols in the size scale where the interaction really happens. © 2011 Author(s)."
"37088140000;55349963700;","Floristic mapping data as a proxy for the mean Urban heat Island",2011,"10.3354/cr01009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053244738&doi=10.3354%2fcr01009&partnerID=40&md5=01c4cc77926c38f108cffff66e866fec","Assessment of spatial variability in the long-term urban heat island (UHI) is severely restricted by coverage and availability of measurements. This also limits the opportunities to analyse its relation to surface characteristics. In this study we therefore introduce a new proxy dataset derived from floristic mapping. The basic assumption is that the species composition in an area reflects climatologic conditions of a certain time period. Ellenberg indicator values for temperature (EITs) were processed to summarise the overall temperature preferences of the occurring plant species. The EITs showed a clear heat island pattern, were highly correlated with existing measurements, and showed increased values in densely built urban classes. Hence, they are considered suitable as UHI proxies. Further, they were related to a large number of typical UHI predictors. The normalised difference vegetation index (NDVI) showed the strongest correlation with the derived pattern and was comparatively robust towards cloud contamination. Urban morphology also explained a noticeable proportion of the overall variance. All predictors explained more than 2/3 of the overall spatial variability, while the redundancy was high. Therefore, the predictors at least allow qualitative statements about the differential exposure to heat-related risks in cities. © Inter-Research 2011."
"15060156600;7401472342;55943946300;6507045503;57206454235;","Biological residues define the ice nucleation properties of soil dust",2011,"10.5194/acp-11-9643-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052897852&doi=10.5194%2facp-11-9643-2011&partnerID=40&md5=3789968f7e8f5ece4175f4f0808de45a","Soil dust is a major driver of ice nucleation in clouds leading to precipitation. It consists largely of mineral particles with a small fraction of organic matter constituted mainly of remains of micro-organisms that participated in degrading plant debris before their own decay. Some micro-organisms have been shown to be much better ice nuclei than the most efficient soil mineral. Yet, current aerosol schemes in global climate models do not consider a difference between soil dust and mineral dust in terms of ice nucleation activity. Here, we show that particles from the clay and silt size fraction of four different soils naturally associated with 0.7 to 11.8 % organic carbon (w/w) can have up to four orders of magnitude more ice nucleation sites per unit mass active in the immersion freezing mode at ĝ̂'12 °C than montmorillonite, the nucleation properties of which are often used to represent those of mineral dusts in modelling studies. Most of this activity was lost after heat treatment. Removal of biological residues reduced ice nucleation activity to, or below that of montmorillonite. Desert soils, inherently low in organic content, are a large natural source of dust in the atmosphere. In contrast, agricultural land use is concentrated on fertile soils with much larger organic matter contents than found in deserts. It is currently estimated that the contribution of agricultural soils to the global dust burden is less than 20 %. Yet, these disturbed soils can contribute ice nuclei to the atmosphere of a very different and much more potent kind than mineral dusts. © 2011 Author(s)."
"9746433100;6602574676;7004208584;36098286300;14032501300;35468686100;","Variability in surface BRDF at different spatial scales (30m-500m) over a mixed agricultural landscape as retrieved from airborne and satellite spectral measurements",2011,"10.1016/j.rse.2011.04.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958747827&doi=10.1016%2fj.rse.2011.04.012&partnerID=40&md5=b83215ade99725289bd631e16d95d384","Over the past decade, the role of multiangle remote sensing has been central to the development of algorithms for the retrieval of global land surface properties including models of the bidirectional reflectance distribution function (BRDF), albedo, land cover/dynamics, burned area extent, as well as other key surface biophysical quantities impacted by the anisotropic reflectance characteristics of vegetation. In this study, a new retrieval strategy for fine-to-moderate resolution multiangle observations was developed, based on the operational sequence used to retrieve the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5 reflectance and BRDF/albedo products. The algorithm makes use of a semiempirical kernel-driven bidirectional reflectance model to provide estimates of intrinsic albedo (i.e., directional-hemispherical reflectance and bihemispherical reflectance), model parameters describing the BRDF, and extensive quality assurance information. The new retrieval strategy was applied to NASA's Cloud Absorption Radiometer (CAR) data acquired during the 2007 Cloud and Land Surface Interaction Campaign (CLASIC) over the well-instrumented Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site in Oklahoma, USA. For the case analyzed, we obtained ~. 1.6. million individual surface bidirectional reflectance factor (BRF) retrievals, from nadir to 75° off-nadir, and at spatial resolutions ranging from 3. m to 500. m. This unique dataset was used to examine the interaction of the spatial and angular characteristics of a mixed agricultural landscape; and provided the basis for detailed assessments of: (1) the use of a land cover type-specific a priori knowledge in kernel-driven BRDF model inversions; (2) the interaction between surface reflectance anisotropy and instrument spatial resolution; and (3) the uncertainties that arise when sub-pixel differences in the BRDF are aggregated to a moderate resolution satellite pixel. Results offer empirical evidence concerning the influence of scale and spatial heterogeneity in kernel-driven BRDF models; providing potential new insights into the behavior and characteristics of different surface radiative properties related to land/use cover change and vegetation structure. © 2011."
"13406647100;7403288995;7202660824;","On the relationship between low cloud variability and lower tropospheric stability in the Southeast Pacific",2011,"10.5194/acp-11-9053-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052512541&doi=10.5194%2facp-11-9053-2011&partnerID=40&md5=8d10896e61b9f670f867e7e3c8ef0fa7","In this study, we examine marine low cloud cover variability in the Southeast Pacific and its association with lower-tropospheric stability (LTS) across a spectrum of timescales. On both daily and interannual timescales, LTS and low cloud amount are very well correlated in austral summer (DJF). Meanwhile in winter (JJA), when ambient LTS increases, the LTS-low cloud relationship substantially weakens. The DJF LTS-low cloud relationship also weakens in years with unusually large ambient LTS values. These are generally strong El Niño years, in which DJF LTS values are comparable to those typically found in JJA. Thus the LTS-low cloud relationship is strongly modulated by the seasonal cycle and the ENSO phenomenon. We also investigate the origin of LTS anomalies closely associated with low cloud variability during austral summer. We find that the ocean and atmosphere are independently involved in generating anomalies in LTS and hence variability in the Southeast Pacific low cloud deck. This highlights the importance of the physical (as opposed to chemical) component of the climate system in generating internal variability in low cloud cover. It also illustrates the coupled nature of the climate system in this region, and raises the possibility of cloud feedbacks related to LTS. We conclude by addressing the implications of the LTS-low cloud relationship in the Southeast Pacific for low cloud feedbacks in anthropogenic climate change. © 2011 Author(s)."
"16230926400;6603174102;14024872700;38460896200;38461735700;36508521900;7404477860;7006593624;7006372688;7003638602;","Laboratory studies of the chemical composition and cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) and oxidized primary organic aerosol (OPOA)",2011,"10.5194/acp-11-8913-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052281578&doi=10.5194%2facp-11-8913-2011&partnerID=40&md5=0845b3923cb989e1b960183d5b24c9a6","Secondary organic aerosol (SOA) and oxidized primary organic aerosol (OPOA) were produced in laboratory experiments from the oxidation of fourteen precursors representing atmospherically relevant biogenic and anthropogenic sources. The SOA and OPOA particles were generated via controlled exposure of precursors to OH radicals and/or O3 in a Potential Aerosol Mass (PAM) flow reactor over timescales equivalent to 1-20 days of atmospheric aging. Aerosol mass spectra of SOA and OPOA were measured with an Aerodyne aerosol mass spectrometer (AMS). The fraction of AMS signal at m/z Combining double low line 43 and m/z Combining double low line 44 (f43, f44), the hydrogen-to-carbon (H/C) ratio, and the oxygen-to-carbon (O/C) ratio of the SOA and OPOA were obtained, which are commonly used to characterize the level of oxidation of oxygenated organic aerosol (OOA). The results show that PAM-generated SOA and OPOA can reproduce and extend the observed f 44f43 composition beyond that of ambient OOA as measured by an AMS. Van Krevelen diagrams showing H/C ratio as a function of O/C ratio suggest an oxidation mechanism involving formation of carboxylic acids concurrent with fragmentation of carbon-carbon bonds. Cloud condensation nuclei (CCN) activity of PAM-generated SOA and OPOA was measured as a function of OH exposure and characterized as a function of O/C ratio. CCN activity of the SOA and OPOA, which was characterized in the form of the hygroscopicity parameter &amp;kappa;org, ranged from 8.4×10-4 to 0.28 over measured O/C ratios ranging from 0.05 to 1.42. This range of κorg and O/C ratio is significantly wider than has been previously obtained. To first order, the &amp;kappa;org-to-O/C relationship is well represented by a linear function of the form κorg Combining double low line (0.18±0.04) ×O/C + 0.03, suggesting that a simple, semi-empirical parameterization of OOA hygroscopicity and oxidation level can be defined for use in chemistry and climate models. © 2011 Author(s)."
"6603348111;15822624200;7006425629;7004811061;","Atmospheric cloud water contains a diverse bacterial community",2011,"10.1016/j.atmosenv.2011.06.041","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960934132&doi=10.1016%2fj.atmosenv.2011.06.041&partnerID=40&md5=7c3ba8edc6623e433ab2f9f7a8f786f0","Atmospheric cloud water contains an active microbial community which can impact climate, human health and ecosystem processes in terrestrial and aquatic systems. Most studies on the composition of microbial communities in clouds have been performed with orographic clouds that are typically in direct contact with the ground. We collected water samples from cumulus clouds above the upper U.S. Midwest. The cloud water was analyzed for the diversity of bacterial phylotypes by denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene amplicons. DGGE analyses of bacterial communities detected 17-21 bands per sample. Sequencing confirmed the presence of a diverse bacterial community; sequences from seven bacterial phyla were retrieved. Cloud water bacterial communities appeared to be dominated by members of the cyanobacteria, proteobacteria, actinobacteria and firmicutes. © 2011 Elsevier Ltd."
"12764954600;7003908632;7006204597;7003663305;","Modeling of the cloud and radiation processes observed during SHEBA",2011,"10.1016/j.atmosres.2011.05.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960902135&doi=10.1016%2fj.atmosres.2011.05.018&partnerID=40&md5=540cf0f42335a0f134e8f1bfaa8980e1","Six microphysics schemes implemented in the climate version of the Environment Canada's Global Multiscale Environmental (GEM) model are used to simulate the cloud and radiation processes observed during Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment. The simplest microphysics scheme (SUN) has one prognostic variable: the total cloud water content. The second microphysics scheme (MLO) has 12 prognostic variables. The four other microphysics schemes are modified versions of MLO. A new parameterization for heterogeneous ice nucleation based on laboratory experiments is included in these versions of MLO. One is for uncoated ice nuclei (ML-NAC) and another is for sulfuric acid coated ice nuclei (ML-AC). ML-AC and ML-NAC have been developed to distinguish non-polluted and polluted air masses, the latter being common over the Arctic during winter and spring. A sensitivity study, in which the dust concentration is reduced by a factor 5, is also performed to assess the sensitivity of the results to the dust concentration in ML-AC-test and ML-NAC-test.Results show that SUN, ML-AC and ML-AC-test reproduce quite well the downward longwave radiation and cloud radiative forcing during the cold season. The good results obtained with SUN are due to compensating errors. It overestimates cloud fraction and underestimates cloud liquid water path during winter. ML-AC and ML-AC-test reproduces quite well all these variables and their relationships. MLO, ML-NAC and ML-NAC-test underestimate the cloud liquid water path and cloud fraction during the cold season, which leads to an underestimation of the downward longwave radiation at surface. During summer, all versions of the model underestimate the downward shortwave radiation at surface. ML-AC and ML-NAC overestimate the total cloud water during the warm season, however, they reproduce relatively well the relationships between cloud radiative forcing and cloud microstructure, which is not the case for the most simple scheme SUN. © 2011 Elsevier B.V."
"50261552200;6701752471;7103271625;","Aerosol effects on stratocumulus water paths in a PDF-based parameterization",2011,"10.1029/2011GL048611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052725662&doi=10.1029%2f2011GL048611&partnerID=40&md5=bb5322ae5f27ef0beba90dbe33d79c55","Successful simulation of aerosol indirect effects in climate models requires parameterizations that capture the full range of cloud-aerosol interactions, including positive and negative liquid water path (LWP) responses to increasing aerosol concentrations, as suggested by large eddy simulations (LESs). A parameterization based on multi-variate probability density functions with dynamics (MVD PDFs) has been incorporated into the single-column version of GFDL AM3, extended to treat aerosol activation, and coupled with a two-moment microphysics scheme. We use it to explore cloud-aerosol interactions. In agreement with LESs, our single-column simulations produce both positive and negative LWP responses to increasing aerosol concentrations, depending on precipitation and free atmosphere relative humidity. We have conducted sensitivity tests to vertical resolution and droplet sedimentation parameterization. The dependence of sedimentation on cloud droplet size is essential to capture the full LWP responses to aerosols. Further analyses reveal that the MVD PDFs are able to represent changes in buoyancy profiles induced by sedimentation as well as enhanced entrainment efficiency with aerosols comparable to LESs. Copyright 2011 by the American Geophysical Union."
"57202891769;57204297539;7005537814;","Factors influencing simulated changes in future arctic cloudiness",2011,"10.1175/2011JCLI4029.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053161747&doi=10.1175%2f2011JCLI4029.1&partnerID=40&md5=1d3177e8547859d3d26dd19598749806","This study diagnoses the changes in Arctic clouds simulated by the Community Climate System Model version 3 (CCSM3) in a transient 2 × CO2 simulation. Four experiments-one fully coupled and three with prescribed SSTs and/or sea ice cover-are used to identify the mechanisms responsible for the projected cloud changes. The target simulation uses a T42 version of the CCSM3, in which the atmosphere is coupled to a dynamical ocean with mobile sea ice. This simulation is approximated by a T42 atmosphere-only integration using CCSM3's atmospheric component [the Community Atmosphere Model version 3 (CAM3)] forced at its lower boundary with the changes in both SSTs and sea ice concentration from CCSM3's 2 × CO2 run. The authors decompose the combined effect of the higher SSTs and reduced sea ice concentration on the Arctic cloud response in this experiment by running two additionalCAM3simulations: one forced with modern SSTs and the projected sea ice cover changes in CCSM3 and the other forced with modern sea ice coverage and the projected changes in SSTs in CCSM3. The results suggest that future increases in Arctic cloudiness simulated by CCSM3 are mostly attributable to two separate processes. Low cloud gains are primarily initiated locally by enhanced evaporation within the Arctic due to reduced sea ice, whereas cloud increases at middle and high levels are mostly driven remotely via greater meridional moisture transport from lower latitudes in a more humid global atmosphere. The enhanced low cloudiness attributable to sea ice loss causes large increases in cloud radiative forcing during the coldest months and therefore promotes even greater surface warming. Because CCSM3's Arctic cloud response to greenhouse forcing is similar to otherGCMs, the drivingmechanisms identified heremay be applicable to other models and could help to advance our understanding of likely changes in the vertical structure of polar clouds. © 2011 American Meteorological Society."
"36003052700;6603377670;","Altitudinal distribution patterns of bryophytes in the Canary Islands and vulnerability to climate change",2011,"10.1016/j.flora.2011.04.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052417267&doi=10.1016%2fj.flora.2011.04.007&partnerID=40&md5=b8fe2f742c8454754098d79dde040496","We report the pattern of bryophyte distribution through the elevation gradient of three Canary Islands (Fuerteventura, Tenerife and Gomera) assessing their vulnerability risk to climate change. We considered a conservative scenario of upslope climatic shift of 200-400. m and a drop in the upper limit of the cloud belt from 1500 to 1000. m. Climate change vulnerability was analyzed from the overlap between the predicted shift in isotherms or cloud-belt edges and the current species range, following the Colwell and colleagues's model.Liverworts show narrower ranges and tend to live at lower elevations than mosses. Perennials and long-lived shuttle species establish in the upper localities. Many perennials and most of the long-lived shuttle species grow in cloud forests. Many annual shuttle species and colonists establish in the lowest localities. Colonists also occupy the harsh summit in the highest islands.In accordance with the Colwell model, most elements of this bryoflora appears vulnerable to rapid climatic change. Upland extinction and contraction challenges the bryoflora on the driest, lowest island Fuerteventura; range-shift gaps do this on the highest island Tenerife. Liverworts tend to be more vulnerable to range-shift gaps; mosses are more vulnerable to upland extinction. On the lowest island, perennials and long-lived shuttle species are more vulnerable to upland extinction; perennials are also vulnerable to range-shift gaps. Colonists are most vulnerable to upland contraction or extinction on the high islands Gomera and Tenerife. Annual shuttle species tend to be more vulnerable to lowland attrition on these high, most humid islands. Many elements of the bryoflora of the upper limit of the cloud forests appear to be vulnerable, while most of the flora of other cloud forest areas presumably will not be so affected, with the exception of the most restricted species.A simple model illustrates the feasibility of preliminary assessments of climate change on organisms which show a lack of published detailed information on their distribution and biology. This assessment gains by incorporating estimates of biological attributes. © 2011 Elsevier GmbH."
"55461309100;23487258800;10641795600;6602080269;55463271000;","Snow cover depletion under changed climate with the help of remote sensing and temperature data",2011,"10.1007/s11069-010-9696-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961028732&doi=10.1007%2fs11069-010-9696-1&partnerID=40&md5=f79e0b05335ac5d227a134a4e434eb37","Snow cover depletion curve (SDC) is one of the important variables in snow hydrological applications, and these curves are very much required for snowmelt runoff modeling in a snowfed catchment. Remote sensing is an important source of snow cover area which is used for preparation of SDC. Snow cover maps produced by Moderate Resolution Imaging Spectroradiometer (MODIS) satellites are one of the best source of satellite-based snow cover area at a regular interval. Therefore, in this study, snow cover maps have been prepared for the years 2000-2005 using MODIS data. The study area chosen viz. Beas basin up to Pandoh dam falls in western Himalayan region. For snowmelt runoff modeling, catchment is divided into number of elevation zones and SDC is required for each zone. When sufficient satellite data are not available due to cloud cover or due to some other reasons, then SDC can to be generated using temperature data. Under changed climate conditions also, modified SDC is required. Therefore, to have SDC under such situations, a relationship between snow cover area and cumulative mean temperature has been developed for each zone of the catchment. This procedure of having snow cover maps has two main purposes. First, it could potentially be used to generate snow cover maps when cloud-free satellite data are not available. Second, it can be used to generate snow-covered area in a new climate to see the impact of climate change on snowmelt runoff studies. © 2010 Springer Science+Business Media B.V."
"7102171439;36097134700;6603126554;25031430500;6506948406;8953038700;57207588886;56865378100;7103119050;24722339600;55286185400;","Temperature and water vapor variance scaling in global models: Comparisons to satellite and aircraft data",2011,"10.1175/2011JAS3737.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053142362&doi=10.1175%2f2011JAS3737.1&partnerID=40&md5=88137e36a12a856f2c24619355915803","Observations of the scale dependence of height-resolved temperature T and water vapor q variability are valuable for improved subgrid-scale climate model parameterizations and model evaluation. Variance spectral benchmarks for T and q obtained from the Atmospheric Infrared Sounder (AIRS) are compared to those generated by state-of-the-art numerical weather prediction ""analyses"" and ""free-running"" climate model simulations with spatial resolution comparable to AIRS. The T and q spectra from both types of models are generally too steep, with small-scale variance up to several factors smaller than AIRS. However, the two model analyses more closely resemble AIRS than the two free-running model simulations. Scaling exponents obtained for AIRS column water vapor (CWV) and height-resolved layers of q are also compared to the superparameterized Community Atmospheric Model (SP-CAM), highlighting large differences in the magnitude of CWV variance and the relative flatness of height-resolved q scaling in SP-CAM. Height-resolved q spectra obtained from aircraft observations during the Variability of the American Monsoon Systems Ocean- Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) demonstrate changes in scaling exponents that depend on the observations' proximity to the base of the subsidence inversion with scale breaks that occur at approximately the dominant cloud scale (~10-30 km). This suggests that finer spatial resolution requirements must be considered for future satellite observations of T and q than those currently planned for infrared and microwave satellite sounders. © 2011 American Meteorological Society."
"11440653000;6506191803;6701530776;6603137309;","Cloud streets and land-water interactions in the Amazon",2011,"10.1007/s10533-011-9580-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052271970&doi=10.1007%2fs10533-011-9580-4&partnerID=40&md5=1fe55fca89455f2f26937a18b157fedc","Cloud streets are common feature in the Amazon Basin. They form from the combination of the vertical trade wind stress and moist convection. Here, satellite imagery, data collected during the COBRA-PARÁ (Caxiuanã Observations in the Biosphere, River and Atmosphere of Pará) field campaign, and high resolution modeling are used to understand the streets′ formation and behavior. The observations show that the streets have an aspect ratio of about 3. 5 and they reach their maximum activity around 15:00 UTC when the wind shear is weaker, and the convective boundary layer reaches its maximum height. The simulations reveal that the cloud streets onset is caused by the local circulations and convection produced at the interfaces between forest and rivers of the Amazon. The satellite data and modeling show that the large rivers anchor the cloud streets producing a quasi-stationary horizontal pattern. The streets are associated with horizontal roll vortices parallel to the mean flow that organizes the turbulence causing advection of latent heat flux towards the upward branches. The streets have multiple warm plumes that promote a connection between the rolls. These spatial patterns allow fundamental insights on the interpretation of the Amazon exchanges between surface and atmosphere with important consequences for the climate change understanding. © 2011 Springer Science+Business Media B.V."
"36720934300;15026371500;57203030873;","Coupling between Arctic feedbacks and changes in poleward energy transport",2011,"10.1029/2011GL048546","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052768870&doi=10.1029%2f2011GL048546&partnerID=40&md5=85067b5ef298b6907d3e4a160cc6ffa5","The relationship between poleward energy transport and Arctic amplification is examined using climate models and an energy balance model. In 21st century projections, models with large Arctic amplification have strong surface albedo and longwave cloud feedbacks, but only weak increases (or even decreases) in total energy transport into the Arctic. Enhanced Arctic warming weakens the equator-to-pole temperature gradient and decreases atmospheric dry static energy transport, a decrease that often outweighs increases from atmospheric moisture transport and ocean heat transport. Model spread in atmospheric energy transport cannot explain model spread in polar amplification; models with greater polar amplification must instead have stronger local feedbacks. Because local feedbacks affect temperature gradients, coupling between energy transports and Arctic feedbacks cannot be neglected when studying Arctic amplification. Copyright 2011 by the American Geophysical Union."
"10042470700;7004807312;35509463200;35301550500;14019100300;36837572400;","Albedo enhancement of marine clouds to counteract global warming: Impacts on the hydrological cycle",2011,"10.1007/s00382-010-0868-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052262179&doi=10.1007%2fs00382-010-0868-1&partnerID=40&md5=55f8537faf7ab925c5466cde2f31d181","Recent studies have shown that changes in solar radiation affect the hydrological cycle more strongly than equivalent CO2 changes for the same change in global mean surface temperature. Thus, solar radiation management ""geoengineering"" proposals to completely offset global mean temperature increases by reducing the amount of absorbed sunlight might be expected to slow the global water cycle and reduce runoff over land. However, proposed countering of global warming by increasing the albedo of marine clouds would reduce surface solar radiation only over the oceans. Here, for an idealized scenario, we analyze the response of temperature and the hydrological cycle to increased reflection by clouds over the ocean using an atmospheric general circulation model coupled to a mixed layer ocean model. When cloud droplets are reduced in size over all oceans uniformly to offset the temperature increase from a doubling of atmospheric CO2, the global-mean precipitation and evaporation decreases by about 1.3% but runoff over land increases by 7.5% primarily due to increases over tropical land. In the model, more reflective marine clouds cool the atmospheric column over ocean. The result is a sinking motion over oceans and upward motion over land. We attribute the increased runoff over land to this increased upward motion over land when marine clouds are made more reflective. Our results suggest that, in contrast to other proposals to increase planetary albedo, offsetting mean global warming by reducing marine cloud droplet size does not necessarily lead to a drying, on average, of the continents. However, we note that the changes in precipitation, evaporation and P-E are dominated by small but significant areas, and given the highly idealized nature of this study, a more thorough and broader assessment would be required for proposals of altering marine cloud properties on a large scale. © 2010 Springer-Verlag."
"56132618000;7201844203;36950518200;","Influence of Marcus convergence zone on western North Pacific summer monsoon",2011,"10.1016/j.atmosres.2011.05.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960912968&doi=10.1016%2fj.atmosres.2011.05.013&partnerID=40&md5=0edb3b653abc8b347d3ce5d19d177e02","This study investigates the atmospheric conditions in the mid-North Pacific Ocean prior to the western North Pacific summer monsoon (WNPSM) onset by focusing on 3. years (2007, 2009, and 2010) with the CloudSat Cloud Profiling Radar (CPR) observation. Two pentads prior to the onset, the mid-latitude upper-tropospheric high potential vorticity (PV) expanded southwestward and intruded into the mid-troposphere of the region around Marcus Island (Marcus region, 20-30°N, 150-170°E). Due to the intrusion of PV, the convection developed over the Marcus region, and the Marcus convergence zone (MCZ) formed. One pentad later, the WNPSM onset occurred when the mid-tropospheric high-PV center and the convection arrived at the subtropical western North Pacific (SWNP, 15-25°N, 130-150°E). It is found that the high-PV expansion is in association with the deepening of the mid-oceanic trough, which signifies the upper-level forcing on the monsoon. It is also found that the cloud water content increased significantly since two pentads prior to the monsoon onset over the mid-North Pacific Ocean. The MCZ-induced moisture advection might provide favorable large-scale atmospheric conditions for changing monsoon-phase. © 2011 Elsevier B.V."
"35262153300;7402934750;","Long-term trends in downwelling spectral infrared radiance over the U.S. Southern Great Plains",2011,"10.1175/2011JCLI4210.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053147557&doi=10.1175%2f2011JCLI4210.1&partnerID=40&md5=bb70d31cb7ed12d553ef49fae5f67c32","A trend analysis was applied to a 14-yr time series of downwelling spectral infrared radiance observations from the Atmospheric Emitted Radiance Interferometer (AERI) located at the Atmospheric Radiation Measurement Program (ARM) site in the U.S. Southern Great Plains. The highly accurate calibration of the AERI instrument, performed every 10 min, ensures that any statistically significant trend in the observed data over this time can be attributed to changes in the atmospheric properties and composition, and not to changes in the sensitivity or responsivity of the instrument. The measured infrared spectra, numbering more than 800 000, were classified as clear-sky, thin cloud, and thick cloud scenes using a neural network method. The AERI data record demonstrates that the downwelling infrared radiance is decreasing over this 14-yr period in the winter, summer, and autumn seasons but it is increasing in the spring; these trends are statistically significant and are primarily due to long-term change in the cloudiness above the site. The AERI data also show many statistically significant trends on annual, seasonal, and diurnal time scales, with different trend signatures identified in the separate scene classifications. Given the decadal time span of the dataset, effects from natural variability should be considered in drawing broader conclusions. Nevertheless, this dataset has high value owing to the ability to infer possible mechanisms for any trends from the observations themselves and to test the performance of climate models. © 2011 American Meteorological Society."
"8286496300;7203054240;35264351500;36627352900;55710583000;","Changes in cloudiness over the Amazon rainforests during the last two decades: Diagnostic and potential causes",2011,"10.1007/s00382-010-0903-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052272707&doi=10.1007%2fs00382-010-0903-2&partnerID=40&md5=b7bdd82f07b202c4cbdb5a316f7d6979","This study shows a decrease of seasonal mean convection, cloudiness and an increase of surface shortwave down-welling radiation during 1984-2007 over the Amazon rainforests based on the analysis of satellite-retrieved clouds and surface radiative flux data. These changes are consistent with an increase in surface temperature, increased atmospheric stability, and reduction of moisture transport to the Amazon based on in situ surface and upper air meteorological data and reanalysis data. These changes appear to link to the expansion of the western Pacific warm pool during the December-February season, to the positive phase of the Atlantic Multidecadal Oscillation and increase of SST over the eastern Pacific SST during the March-May season, and to an increase of the tropical Atlantic meridional SST gradient and an expansion of the western Pacific warm pool during September-November season. The resultant increase of surface solar radiation during all but the dry season in the Amazon could contribute to the observed increases in rainforest growth during recent decades. © 2010 The Author(s)."
"25031430500;8058018000;16402575500;7006399667;6506883710;15724418700;","The extratropical upper troposphere and lower stratosphere",2011,"10.1029/2011RG000355","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960518508&doi=10.1029%2f2011RG000355&partnerID=40&md5=058646e11facfba7878b60a68c3e0ac2","The extratropical upper troposphere and lower stratosphere (Ex-UTLS) is a transition region between the stratosphere and the troposphere. The Ex-UTLS includes the tropopause, a strong static stability gradient and dynamic barrier to transport. The barrier is reflected in tracer profiles. This region exhibits complex dynamical, radiative, and chemical characteristics that place stringent spatial and temporal requirements on observing and modeling systems. The Ex-UTLS couples the stratosphere to the troposphere through chemical constituent transport (of, e.g., ozone), by dynamically linking the stratospheric circulation with tropospheric wave patterns, and via radiative processes tied to optically thick clouds and clear-sky gradients of radiatively active gases. A comprehensive picture of the Ex-UTLS is presented that brings together different definitions of the tropopause, focusing on observed dynamical and chemical structure and their coupling. This integral view recognizes that thermal gradients and dynamic barriers are necessarily linked, that these barriers inhibit mixing and give rise to specific trace gas distributions, and that there are radiative feedbacks that help maintain this structure. The impacts of 21st century anthropogenic changes to the atmosphere due to ozone recovery and climate change will be felt in the Ex-UTLS, and recent simulations of these effects are summarized and placed in context. Copyright 2011 by the American Geophysical Union."
"34772240500;55713076400;7004544454;","Buoyancy reversal, decoupling and the transition from stratocumulus to shallow cumulus topped marine boundary layers",2011,"10.1007/s00382-010-0882-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052268128&doi=10.1007%2fs00382-010-0882-3&partnerID=40&md5=b5a62d1cd8ba77f7b41baadd08ad7072","The transition in a marine boundary layer (MBL) from stratocumulus topped to shallow cumulus topped is investigated by using a large eddy simulation (LES) model. The experiments performed aim to examine the influence on the transition of (1) the probability of buoyancy reversal at the MBL top (i.e. situations in which the mixture of two air parcels becomes denser than either of the original parcels due to phase change or other nonlinear processes involved in the mixing), and (2) the degree of decoupling in the MBL (i.e. the strength of a shallow stably stratified layer near cloud base). Our results suggest that a stratocumulus-topped MBL is most likely to transit to a cumulus-topped one when (1) there exists high probability of buoyancy reversal at the MBL top, and (2) the MBL is decoupled due to large surface evaporation. We argue that a parameterization that includes representation of those two effects combined has the potential to provide a simple way of predicting the MBL transition in climate models. © 2010 The Author(s)."
"51664124500;57062286700;8525144100;7202299505;6601946605;7005973015;55622719300;","El Niño-Southern oscillation in tropical and midlatitude column ozone",2011,"10.1175/JAS-D-11-045.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053210287&doi=10.1175%2fJAS-D-11-045.1&partnerID=40&md5=4e6263a8e5ec971ad20213dcacf5ff38","The impacts of El Niño-Southern Oscillation (ENSO) on the tropical total column ozone, the tropical tropopause pressure, and the 3.5-yr ozone signal in the midlatitude total column ozone were examined using the Goddard Earth Observing System Chemistry-Climate Model (GEOS CCM). Observed monthly mean sea surface temperature and sea ice between 1951 and 2004 were used as boundary conditions for the model. Since the model includes no solar cycle, quasi-biennial oscillation, or volcanic forcing, the ENSO signal was found to dominate the tropical total column ozone variability. Principal component analysis was applied to the detrended, deseasonalized, and low-pass filtered model outputs. The first mode of model total column ozone captured 63.8% of the total variance. The spatial pattern of this mode was similar to that in Total Ozone Mapping Spectrometer (TOMS) observations. There was also a clear ENSO signal in the tropical tropopause pressure in the GEOS CCM, which is related to the ENSO signal in the total column ozone. The regression coefficient between the model total column ozone and the model tropopause pressure was 0.71 Dobson units (DU) hPa-1. The GEOS CCM was also used to investigate a possible mechanism for the 3.5-yr signal observed in the midlatitude total column ozone. The 3.5-yr signal in the GEOS CCM column ozone is similar to that in the observations, which suggests that a model with realistic ENSO can reproduce the 3.5-yr signal. Hence, it is likely that the 3.5-yr signal was caused by ENSO. © 2011 American Meteorological Society."
"55715614000;36657972500;7406372329;","Dynamic and thermodynamic air-sea coupling associated with the indian ocean dipole diagnosed from 23 WCRP CMIP3 models",2011,"10.1175/2011JCLI4041.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053146418&doi=10.1175%2f2011JCLI4041.1&partnerID=40&md5=9225c7a5e21013a8b5e527a9f97b07b9","The performance of 23 World Climate Research Programme (WCRP) Coupled Model Intercomparison Project, phase 3 (CMIP3) models in the simulation of the Indian Ocean dipole (IOD) is evaluated, and the results show large diversity in the simulated IOD intensity. A detailed diagnosis is carried out to understand the role of the Bjerknes dynamic air-sea feedback and the thermodynamic air-sea coupling in shaping the different model behaviors. The Bjerknes feedback processes include the equatorial zonal wind response to SST, the thermocline response to the equatorial zonal wind, and the ocean subsurface temperature response to the thermocline variation. The thermodynamic feedback examined includes the wind-evaporation-SST and cloud-radiation-SST feedbacks. A combined Bjerknes and thermodynamic feedback intensity index is introduced. This index well reflects the simulated IOD strength contrast among the strong, moderate, and weak model groups. It gives a quantitative measure of the relative contribution of the dynamic and thermodynamic feedback processes. The distinctive features in the dynamic and thermodynamic coupling strength are closely related to the mean state difference in the coupled models. A shallower (deeper) equatorial mean thermocline, a stronger (weaker) background vertical temperature gradient, and a greater (smaller) mean vertical upwelling velocity are found in the strong (weak) IOD simulation group. Thus, the mean state biases greatly affect the air-sea coupling strength on the interannual time scale. A number of models failed to simulate the observed positive wind-evaporation-SST feedback during the IOD developing phase. Analysis indicates that the bias arises from a greater contribution to the surface latent heat flux anomaly by the sea-air specific humidity difference than by the wind speed anomaly. © 2011 American Meteorological Society."
"36574296000;7003382968;","The development of arctic air masses in northwest Canada and their behavior in a warming climate",2011,"10.1175/2011JCLI3855.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053152068&doi=10.1175%2f2011JCLI3855.1&partnerID=40&md5=d6f25e9b28de4cc826301c90c5ebb3a5","Surface observations, soundings, and a thermodynamic budget are used to investigate the formation process of 93 arctic airmass events. The events involve very cold surface temperatures-an average of -42.8°C at Norman Wells, a centrally located station in the formation region-and cooling in the 1000-500-h Pa layer. A multistage process for their formation in northwestern Canada is proposed. This process is contrary to the classical conceptualization of extremely shallow, surface formations. In the first stage of formation, snow falls into a layer of unsaturated air in the lee of the Rocky Mountains, causing sublimational cooling and moistening the subcloud layer. Simultaneously, the midtroposphere is cooled by cloud-top radiation emissions. In the second stage, snowfall abates, the air column dries, and clearsky surface radiational cooling predominates, augmented by the high emissivity of fresh snow cover. The surface temperature falls very rapidly, up to a maximum of 18°C day-1 in one event. In the final stage, after near-surface temperatures fall below the frost point, ice crystals and, nearer the surface, ice fog form. At the end of formation, there is cold-air damming, with a cold pool and anticyclone in the lee of the Rockies, lower pressure in the Gulf of Alaska, and an intense baroclinic zone oriented northwest to southeast along the mountains. There have been secular changes in the characteristics of the arctic air masses over the period 1948-2008. The surface temperature during the events has become warmer, and the air masses are deeper and moister. The 1000-hPa diabatic cooling during events, which includes latent heat and radiative processes, has decreased by 2.2°C day-1. © 2011 American Meteorological Society."
"55341341000;37107532000;6701587988;6701619700;","Albedo-rainfall Feedback Over Indian Monsoon Region Using Long Term Observations Between 1981 to 2000",2011,"10.1007/s12524-011-0136-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80355133383&doi=10.1007%2fs12524-011-0136-9&partnerID=40&md5=7d7b1a2cf2bb70a2cfd29bc420da332a","Albedo determines radiation balance of land (soil-canopy complex) surface and influence boundary layer structure of the atmosphere. Accurate surface albedo determination is important for weather forecasting, climate projection and ecosystem modelling. Albedo-rainfall feedback relationship has not been studied so far using observations on spatial scale over Indian monsoon region due to lack of consistent, systematic and simultaneous long-term measurements of both. The present study used dekadal (ten-day) composite of satellite (e. g. NOAA) based Pathfinder AVHRR Land (PAL) datasets between 1981 and 2000 over India (68-100°E, 5-40°N) at 8 km spatial resolution. Land surface albedo was computed using linear transformation of red and near infrared (NIR) surface reflectances. The cloud effects were removed using a smoothening filter with harmonic analysis applied to time series data in each year. The monthly, annual and long term means were computed from dekadal reconstructed albedo. The mean per year and coefficient of variation (CV) of surface albedo over seventeen years, averaged over Indian land region, were found to show a significantly decreasing (0.15 to 0.14 and 60 to 40%, respectively) trend between 1981 and 2000. Among all the land use patterns, the inter-annual variation of albedo of Himalayan snow cover showed a significant and the steepest reducing trend (0.42 - 0.35) followed by open shurbland, grassland and cropland. No significant change was noticed over different forest types.. This could be due to increase in snow melting period and snow melt area. A strong inverse exponential relation (correlation coefficient r = 0.95, n = 100) was found between annual rainfall and annual albedo over seven rainfall zones. The decreasing trend in snow-albedo of accumulation period (September to March) follows the declining trend in measured south-west monsoon rainfall between 1988 (980 mm) to 1998 (880 mm) over India. This finding perhaps suggests the possible reversal of reported coupling of increased snowfall followed by lower monsoon rainfall. © 2011 Indian Society of Remote Sensing."
"7501827637;","Integration of satellite-measured LST data into cokriging for temperature estimation on tropical and temperate islands",2011,"10.1002/joc.2185","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051894432&doi=10.1002%2fjoc.2185&partnerID=40&md5=acc719bdaf178cc93663047292b67d16","Cokriging, a multivariate geostatistical interpolation method, uses elevation information as a secondary variable to improve the prediction accuracy of air temperature in mountainous areas. Although the secondary variable plays an important role in cokriging, the performance of interpolation largely depends on the amount of input data. The purpose of this study was to improve air temperature estimation by merging hypertemporal Moderate Resolution Imaging Spectroradiometer land surface temperature (LST) data and ground observations as interpolation data. Two significantly different island environments, tropical Hawaii Island (USA) and temperate Jeju Island (Korea), were selected for interpolation experiments. Spatiotemporal characteristics of air temperature prediction were compared between three cokriging methods and the conventional inverse-distance weighted interpolation. Due to the year-round trade winds, there was significant difference in prediction errors between windward and leeward slopes of Hawaii Island. LST-derived temperature was not regularly sampled from cloud-prone, windward slopes. As a result, prediction reliability was lower on windward slopes than leeward slopes, and overall prediction accuracy decreased in the wet season. Jeju Island is a mid-latitude volcanic island heavily influenced by the Asian monsoons. This climatic setting creates the seasonal variations of air temperature that is far greater than its spatial variations. The environmental lapse rate (ELR) of Jeju Island became much steeper in winter, and prediction accuracy and reliability were reduced due to an increase in the spatial variations of air temperature. With the addition of satellite-derived air temperature data, the root mean square errors of cokriging decreased by 27.3-52.9% for Hawaii Island and 34.6-37.6% for Jeju Island depending on cokriging models. © 2010 Royal Meteorological Society."
"7403326970;13609115600;7402523567;6507506899;55724460500;55895104800;51663392900;57201410408;9245000500;6603230487;7202386372;7005131869;11940132500;6603871013;7202152636;","An intercomparison of T-REX mountain-wave simulations and implications for mesoscale predictability",2011,"10.1175/MWR-D-10-05042.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958706155&doi=10.1175%2fMWR-D-10-05042.1&partnerID=40&md5=e735288e64fe73e74b02ac07b4f5a255","Numerical simulations of flow over steep terrain using 11 different nonhydrostatic numerical models are compared and analyzed. A basic benchmark and five other test cases are simulated in a two-dimensional framework using the same initial state, which is based on conditions during Intensive Observation Period (IOP) 6 of the Terrain-Induced Rotor Experiment (T-REX), in which intense mountain-wave activity was observed. All of the models use an identical horizontal resolution of 1 km and the same vertical resolution. The six simulated test cases use various terrain heights: a 100-m bell-shaped hill, a 1000-m idealized ridge that is steeper on the lee slope, a 2500-m ridge with the same terrain shape, and a cross-Sierra terrain profile. The models are tested with both free-slip and no-slip lower boundary conditions. The results indicate a surprisingly diverse spectrum of simulated mountain-wave characteristics including lee waves, hydraulic-like jump features, and gravity wave breaking. The vertical velocity standard deviation is twice as large in the free-slip experiments relative to the no-slip simulations. Nevertheless, the no-slip simulations also exhibit considerable variations in the wave characteristics. The results imply relatively low predictability of key characteristics of topographically forced flows such as the strength of downslope winds and stratospheric wave breaking. The vertical flux of horizontal momentum, which is a domain-integrated quantity, exhibits considerable spread among the models, particularly for the experiments with the 2500-m ridge and Sierra terrain. The differences among the various model simulations, all initialized with identical initial states, suggest that model dynamical cores may be an important component of diversity for the design of mesoscale ensemble systems for topographically forced flows. The intermodel differences are significantly larger than sensitivity experiments within a single modeling system. © 2011 American Meteorological Society."
"55973699300;24305829500;","A time series for monitoring vegetation activity and phenology at 10-daily time steps covering large parts of South America",2011,"10.1080/17538947.2010.505664","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051901658&doi=10.1080%2f17538947.2010.505664&partnerID=40&md5=7375dd42768bed1d6c968277066e293b","It is widely accepted that natural resources should only be sustainably exploited and utilized to effectively preserve our planet for future generations. To better manage the natural resources, and to better understand the closely linked Earth systems, the concept of Digital Earth has been strongly promoted since US Vice President Al Gore's speech in 1998. One core element of Digital Earth is the use and integration of remote sensing data. Only satellite imagery can cover the entire globe repeatedly at a sufficient high-spatial resolution to map changes in land cover and land use, but also to detect more subtle changes related for instance to climate change. To uncover global change effects on vegetation activity and phenology, it is important to establish high quality time series characterizing the past situation against which the current state can be compared. With the present study we describe a time series of vegetation activity at 10-daily time steps between 1998 and 2008 covering large parts of South America at 1 km spatial resolution. Particular emphasis was put on noise removal. Only carefully filtered time series of vegetation indices can be used as a benchmark and for studying vegetation dynamics at a continental scale. Without temporal smoothing, subtle spatio-temporal patterns in vegetation composition, density and phenology would be hidden by atmospheric noise and undetected clouds. Such noise is immanent in data that have undergone solely a maximum value compositing. Within the present study, the Whittaker smoother (WS) was applied to a SPOT VGT time series. The WS balances the fidelity to the observations with the roughness of the smoothed curve. The algorithm is extremely fast, gives continuous control over smoothness with only one parameter, and interpolates automatically. The filtering efficiently removed the negatively biased noise present in the original data, while preserving the overall shape of the curves showing vegetation growth and development. Geostatistical variogram analysis revealed a significantly increased signal-to-noise ratio compared to the raw data. Analysis of the data also revealed spatially consistent key phenological markers. Extracted seasonality parameters followed a clear meridional trend. Compared to the unfiltered data, the filtered time series increased the separability of various land cover classes. It is thus expected that the data set holds great potential for environmental and vegetation related studies within the frame of Digital Earth. © 2011 European Union."
"35491260500;6506730508;7402942478;6602407753;35547214900;","The fate of saharan dust across the atlantic and implications for a central american dust barrier",2011,"10.5194/acp-11-8415-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051931544&doi=10.5194%2facp-11-8415-2011&partnerID=40&md5=d2fff55a9a083ab02a47a97625d09273","Saharan dust was observed over the Caribbean basin during the summer 2007 NASA Tropical Composition, Cloud, and Climate Coupling (TC4) field experiment. Airborne Cloud Physics Lidar (CPL) and satellite observations from MODIS suggest a barrier to dust transport across Central America into the eastern Pacific. We use the NASA GEOS-5 atmospheric transport model with online aerosol tracers to perform simulations of the TC4 time period in order to understand the nature of this barrier. Our simulations are driven by the Modern Era Retrospective-Analysis for Research and Applications (MERRA) meteorological analyses. Compared to observations from MODIS and CALIOP, GEOS-5 reproduces the observed location and magnitude of observed dust events, but our baseline simulation does not develop as strong a barrier to dust transport across Central America as observations suggest. Analysis of the dust transport dynamics and loss processes suggest that while both mechanisms play a role in defining the dust transport barrier, loss processes by wet removal of dust are about twice as important as transport. Sensitivity analyses with our model showed that the dust barrier would not exist without convective scavenging over the Caribbean. The best agreement between our model and the observations was obtained when dust wet removal was parameterized to be more aggressive, treating the dust as we do hydrophilic aerosols. © 2011 Author(s)."
"57214424016;12039464900;","Comparison of burn severities of consecutive large-scale fires in Florida sand pine scrubusing satellite imagery analysis",2011,"10.4996/fireecology.0702099","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051877463&doi=10.4996%2ffireecology.0702099&partnerID=40&md5=7cebbf1af645c794ef095d47ca42f41c","Remotely sensed imagery has been used extensively in the western US to evaluate patterns of burn severity and vegetation recovery following wildland fires. Its application in southern US ecosystems, however, has been limited. Challenges in southern areas include very high rates of vegetation recovery following fire, frequent cloud cover, and the presence of standing water. Use of remote sensing in southern forests should therefore be coupled with concurrent ground-based assessments, at least until the methods are tested for different ecosystems. Here, we assessed burn severity using remote sensing in a sand pine scrub ecosystem, which occurs on the central ridge of the Florida peninsula and is characterized by infrequent (>40 years on average) high severity fire. Two overlapping fires that burned in 2006 and 2009 provided a unique opportunity to explore compounded fire severity patterns. Landsat-based imagery analysis matched ground-based severity measures roughly half of the time. In general, higher severity fire led to lower severity or unburned conditions, while low severity fire had a less pronounced impact on either preventing or reducing fire severity in the subsequent fire. The unusually frequent fires both occurred during drought conditions. As the region's climate is predicted to be drier and hotter in the future, this work has implications for potential climate change effects on sand pine scrub fire regimes and, hence, ecosystem perpetuity."
"8309699900;7003663305;7003591311;7005284577;9271096600;7202050065;57209647985;6701378450;24477694300;8147766700;6602890253;7404062492;16480175700;6603872903;7006107059;15833742800;","Cloud condensation nuclei as a modulator of ice processes in Arctic mixed-phase clouds",2011,"10.5194/acp-11-8003-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051631900&doi=10.5194%2facp-11-8003-2011&partnerID=40&md5=241412a8dad0646e585de27c768e3bb0","We propose that cloud condensation nuclei (CCN) concentrations are important for modulating ice formation of Arctic mixed-phase clouds, through modification of the droplet size distribution. Aircraft observations from the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) study in northern Alaska in April 2008 allow for identification and characterization of both aerosol and trace gas pollutants, which are then compared with cloud microphysical properties. Consistent with previous studies, we find that the concentration of precipitating ice particles (>400 μ) is correlated with the concentration of large droplets (>30 μ). We are further able to link the observed microphysical conditions to aerosol pollution, originating mainly from long range transport of biomass burning emissions. The case studies demonstrate that polluted mixed-phase clouds have narrower droplet size distributions and contain 1-2 orders of magnitude fewer precipitating ice particles than clean clouds at the same temperature. This suggests an aerosol indirect effect leading to greater cloud lifetime, greater cloud emissivity, and reduced precipitation. This result is opposite to the glaciation indirect effect, whereby polluted clouds are expected to precipitate more readily due to an increase in the concentration of particles acting as ice nuclei. © 2011 Author(s)."
"24081888700;","Cloud macroscopic organization: Order emerging from randomness",2011,"10.5194/acp-11-7483-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960993154&doi=10.5194%2facp-11-7483-2011&partnerID=40&md5=443bc11dd41b4bb46bc838b44f47124e","Clouds play a central role in many aspects of the climate system and their forms and shapes are remarkably diverse. Appropriate representation of clouds in climate models is a major challenge because cloud processes span at least eight orders of magnitude in spatial scales. Here we show that there exists order in cloud size distribution of low-level clouds, and that it follows a power-law distribution with exponent γ close to 2. γ is insensitive to yearly variations in environmental conditions, but has regional variations and land-ocean contrasts. More importantly, we demonstrate this self-organizing behavior of clouds emerges naturally from a complex network model with simple, physical organizing principles: random clumping and merging. We also demonstrate symmetry between clear and cloudy skies in terms of macroscopic organization because of similar fundamental underlying organizing principles. The order in the apparently complex cloud-clear field thus has its root in random local interactions. Studying cloud organization with complex network models is an attractive new approach that has wide applications in climate science. We also propose a concept of cloud statistic mechanics approach. This approach is fully complementary to deterministic models, and the two approaches provide a powerful framework to meet the challenge of representing clouds in our climate models when working in tandem. © 2011 Author(s)."
"7005793536;6602889253;8918197800;7005134081;56259852000;6603480361;7004402705;55919935700;13402933200;16479703400;16443840500;15127430500;36088544000;55883034700;8263760800;6506553245;7004587644;55812487100;7202400272;7003800456;7005723936;7003683808;7103294731;7403544649;21735369200;55730744700;","Projections of UV radiation changes in the 21st century: Impact of ozone recovery and cloud effects",2011,"10.5194/acp-11-7533-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961009675&doi=10.5194%2facp-11-7533-2011&partnerID=40&md5=5b05ceb2cb02f6a6133ea51d80ea2129","Monthly averaged surface erythemal solar irradiance (UV-Ery) for local noon from 1960 to 2100 has been derived using radiative transfer calculations and projections of ozone, temperature and cloud change from 14 chemistry climate models (CCM), as part of the CCMVal-2 activity of SPARC. Our calculations show the influence of ozone depletion and recovery on erythemal irradiance. In addition, we investigate UV-Ery changes caused by climate change due to increasing greenhouse gas concentrations. The latter include effects of both stratospheric ozone and cloud changes. The derived estimates provide a global picture of the likely changes in erythemal irradiance during the 21st century. Uncertainties arise from the assumed scenarios, different parameterizations particularly of cloud effects on UV-Ery and the spread in the CCM projections. The calculations suggest that relative to 1980, annually mean UV-Ery in the 2090s will be on average ∼12 % lower at high latitudes in both hemispheres, ∼3 % lower at mid latitudes, and marginally higher (∼1 %) in the tropics. The largest reduction (∼16 %) is projected for Antarctica in October. Cloud effects are responsible for 2-3 % of the reduction in UV-Ery at high latitudes, but they slightly moderate it at mid-latitudes (∼1 %). The year of return of erythemal irradiance to values of certain milestones (1965 and 1980) depends largely on the return of column ozone to the corresponding levels and is associated with large uncertainties mainly due to the spread of the model projections. The inclusion of cloud effects in the calculations has only a small effect of the return years. At mid and high latitudes, changes in clouds and stratospheric ozone transport by global circulation changes due to greenhouse gases will sustain the erythemal irradiance at levels below those in 1965, despite the removal of ozone depleting substances. At northern high latitudes (60° 90°), the projected decreases in cloud transmittance towards the end of the 21st century will reduce the yearly average surface erythemal irradiance by ∼5 % with respect to the 1960s. © 2011 Author(s)."
"7005601387;7005063377;","Cosmic ray effects on cloud cover and their relevance to climate change",2011,"10.1016/j.jastp.2011.03.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961022131&doi=10.1016%2fj.jastp.2011.03.001&partnerID=40&md5=b594979517998e731906fb2d64ea42cf","A survey is made of the evidence for and against the hypothesis that cosmic rays influence cloud cover. The analysis is made principally for the troposphere. It is concluded that for the troposphere there is only a very small overall value for the fraction of cloud attributable to cosmic rays (CR); if there is linearity between CR change and cloud change, the value is probably ~1% for clouds below ~6.5km, but less overall. The apparently higher value for low cloud is an artifact. The contribution of CR to 'climate change' is quite negligible. © 2011 Elsevier Ltd."
"56676874900;6602230939;","On the misdiagnosis of surface temperature feedbacks from variations in Earth's radiant energy balance",2011,"10.3390/rs3081603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052645530&doi=10.3390%2frs3081603&partnerID=40&md5=b6144c98709c75e9c34345c6744f25e1","The sensitivity of the climate system to an imposed radiative imbalance remains the largest source of uncertainty in projections of future anthropogenic climate change. Here we present further evidence that this uncertainty from an observational perspective is largely due to the masking of the radiative feedback signal by internal radiative forcing, probably due to natural cloud variations. That these internal radiative forcings exist and likely corrupt feedback diagnosis is demonstrated with lag regression analysis of satellite and coupled climate model data, interpreted with a simple forcing-feedback model. While the satellite-based metrics for the period 2000-2010 depart substantially in the direction of lower climate sensitivity from those similarly computed from coupled climate models, we find that, with traditional methods, it is not possible to accurately quantify this discrepancy in terms of the feedbacks which determine climate sensitivity. It is concluded that atmospheric feedback diagnosis of the climate system remains an unsolved problem, due primarily to the inability to distinguish between radiative forcing and radiative feedback in satellite radiative budget observations. © 2011 by the authors."
"37104941200;21740519000;6506756436;18134195800;7005432249;24802319700;","Evaluation of statistical distributions for the Parametrization of subgrid boundary-layer clouds",2011,"10.1007/s10546-011-9607-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960052802&doi=10.1007%2fs10546-011-9607-3&partnerID=40&md5=f30d8e6c965b2313971eadc3e2ccc0cd","In numerical weather prediction and climate models, planetary boundary-layer (PBL) clouds are linked to subgrid-scale processes such as shallow convection. A comprehensive statistical analysis of large-eddy simulations (LES), obtained for warm PBL cloud cases, is carried out in order to characterize the distributions of the horizontal subgrid cloud variability. The production of subgrid clouds is mainly associated with the variability of the total water content. Nevertheless, in the case of PBL clouds, the temperature variability cannot be completely discarded and the saturation deficit, which summarizes both temperature and total water fluctuations, provides a better representation of the cloud variability than the total water content. The probability density functions (PDFs) of LES saturation deficit generally have the shape of a main asymmetric bell-shaped curve with a more or less distinct secondary maximum specific to each type of PBL clouds. Unimodal theoretical PDFs, even those with a flexible skewness, are not sufficient to correctly fit the LES distributions, especially the long tail that appears for cumulus clouds. They do not provide a unified approach for all cloud types. The cloud fraction and the mean cloud water content, diagnosed from these unimodal PDFs, are largely underestimated. The use of a double Gaussian distribution allows correction of these errors on cloud fields and provides a better estimation of the cloud-base and cloud-top heights. Eventually, insights for the design of a subgrid statistical cloud scheme are provided, in particular a new formulation for the weight of the two Gaussian distributions and for the standard deviation of the convective distribution. © 2011 Springer Science+Business Media B.V."
"6603383859;6603873829;6602239759;9233045100;","Evaluation of model-predicted top-of-atmosphere radiation and cloud parameters over Africa with observations from GERB and SEVIRI",2011,"10.1175/2011JCLI3856.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052790918&doi=10.1175%2f2011JCLI3856.1&partnerID=40&md5=eb7792b3ee1e24319eb10f7d7de79db4","This study compared the Regional Atmospheric Climate Model version 2 (RACMO) with satellite data by simultaneously looking at cloud properties and top-of-atmosphere (TOA) fluxes. This study used cloud properties retrieved from Spinning Enhanced Visible and Infrared Imager (SEVIRI) data and TOA shortwave and longwave outgoing radiative fluxes measured by one of the Geostationary Earth Radiation Budget (GERB) sensors. Both SEVIRI and GERB resolve the diurnal cycle extremely well with 96 images per day. To test the physical parameterizations of the model, RACMO was run for a domain-enclosing Africa and part of the surrounding oceans. Simulations for July 2006, forced at the lateral boundaries by ERA-Interim reanalyses, show generally accurate positioning of the various cloud regimes but also some important model-observation differences, which the authors tried to reduce by altering model parameterizations. These differences are as follows: 1) TOA albedo differences in clear-sky regions like the Sahara and southern Africa. These differences were considerably reduced by prescribing the surface albedo from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. 2) A considerable overestimation of outgoing longwave radiation within the continental ITCZ caused by the fact that modeled cirrus clouds are far too thin. 3) Underestimation by the model of cloud cover, condensed water path and albedo of the stratocumulus fields off the coast of Angola. The authors reduced these underestimations by suppressing the amount of turbulent mixing above the boundary layer, by prescribing droplet radii derived from SEVIRI data, and by assuming incloud horizontal homogeneity for the radiation calculations. 4) Overestimation by the model of the albedo of the trade wind cumulus fields over the Atlantic Ocean. This study argues that this overestimation is likely caused by a model overestimation of condensed water path. In general, the analyses demonstrate the power of the simultaneous evaluation of the TOA fluxes and cloud properties. © 2011 American Meteorological Society."
"7006444483;7102063144;33667732300;","A novel approach for selective reconstruction of cloud-contaminated satellite images",2011,"10.1175/2011JTECHA1529.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052356535&doi=10.1175%2f2011JTECHA1529.1&partnerID=40&md5=d588199d992293f83715a010782d62dc","The paper presents a robust technique for cloud clearing of satellite imagery. The proposed algorithm combines mathematical morphological techniques with a conventional cloud clearing scheme to restore clear sky values. The derived equivalent clear sky brightness temperature plays a very important role in numerical weather prediction, climate research, and monitoring. The developed methodology uses distinct approaches for reconstruction of partially clouded domains and overcast regions. It is found that the algorithm is especially suitable for pre- or postmonsoon months, where there is a high percentage of partially cloudy and small overcast cloudy regions. The algorithm is tested for the Kalpana Very High Resolution Radiometer (VHRR) thermal infrared (TIR) band data acquired over the oceanic region adjoining India throughout the month of May 2009. It is found that the algorithm is able to clear 25% of cloudy pixels with an RMSE of 1.2 K for brightness temperature. © 2011 American Meteorological Society."
"23991212200;7006095466;55411439700;","Orogenic propagating precipitation systems over the united states in a global climate model with embedded explicit convection",2011,"10.1175/2011JAS3699.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051811479&doi=10.1175%2f2011JAS3699.1&partnerID=40&md5=d476466a7c2c56b089c12e79f0502b93","In the lee of major mountain chains worldwide, diurnal physics of organized propagating convection project onto seasonal and climate time scales of the hydrologic cycle, but this phenomenon is not represented in conventional global climate models (GCMs). Analysis of an experimental version of the superparameterized (SP) Community Atmosphere Model (CAM) demonstrates that propagating orogenic nocturnal convection in the central U.S. warm season is, however, representable in GCMs that use the embedded explicit convection model approach [i.e., multiscale modeling frameworks (MMFs)]. SP-CAM admits propagating organized convective systems in the lee of the Rockies during synoptic conditions similar to those that generate mesoscale convective systems in nature. The simulated convective systems exhibit spatial scales, phase speeds, and propagation speeds comparable to radar observations, and the genesis mechanism in the model agrees qualitatively with established conceptual models. Convective heating and condensate structures are examined on both resolved scales in SP-CAM, and coherently propagating cloud ""metastructures"" are shown to transcend individual cloud-resolving model arrays. In reconciling how this new mode of diurnal convective variability is admitted in SP-CAM despite the severe idealizations in the cloud-resolving model configuration, an updated discussion is presented of what physics may transcend the re-engineered scale interface in MMFs. The authors suggest that the improved diurnal propagation physics in SP-CAM are mediated by large-scale first-baroclinic gravity wave interactions with a prognostic organization life cycle, emphasizing the physical importance of preserving ""memory"" at the inner resolved scale. © 2011 American Meteorological Society."
"13402835300;7201485519;35509639400;6603925960;7004714030;7402064802;52464731300;7101959253;16679271700;57205867148;7102963655;","COSP: Satellite simulation software for model assessment",2011,"10.1175/2011BAMS2856.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953115248&doi=10.1175%2f2011BAMS2856.1&partnerID=40&md5=b8beadabfa524b6ae8a0f63aab9ae94e","The Cloud Feedback Model Intercomparison Project (CFMIP) community has developed an integrated satellite simulator, the CFMIP Observation Simulator Package (COSP). COSP is a flexible software tool that enables the simulation from model variables of data from several satellite-borne active and passive sensors. COSP facilitates the evaluation of models against observations and comparisons between them in a more consistent manner. Two of the models used in this study are GCMs used in the latest IPCC assessment reports, and the others are two versions of the multiscale modeling framework (MMF) with different horizontal and vertical resolutions of the embedded cloud-resolving model. It is found that the MMF simulations perform better than the other climate models in all the diagnostics, showing a distribution of hydrometeors in the vertical and also in optical depth closer to the observations."
"35489706000;55220976100;7501720647;7003408439;","Sea surface temperature biases under the stratus cloud deck in the southeast Pacific ocean in 19 IPCC AR4 coupled general circulation models",2011,"10.1175/2011JCLI4172.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052789083&doi=10.1175%2f2011JCLI4172.1&partnerID=40&md5=ef80bf8151490d456cf10d188dd03b0e","This study examines systematic biases in sea surface temperature (SST) under the stratus cloud deck in the southeast Pacific Ocean and upper-ocean processes relevant to the SST biases in 19 coupled general circulation models (CGCMs) participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The 20 years of simulations from each model are analyzed. Pronounced warm SST biases in a large portion of the southeast Pacific stratus region are found in all models. Processes that could contribute to the SST biases are examined in detail based on the computation of major terms in the upper-ocean heat budget. Negative biases in net surface heat fluxes are evident in most of the models, suggesting that the cause of the warm SST biases in models is not explained by errors in net surface heat fluxes. Biases in heat transport by Ekman currents largely contribute to the warm SST biases both near the coast and the open ocean. In the coastal area, southwestward Ekman currents and upwelling in most models are much weaker than observed owing to weaker alongshore winds, resulting in insufficient advection of cold water from the coast. In the open ocean, warm advection due to Ekman currents is overestimated in models because of the larger meridional temperature gradient, the smaller zonal temperature gradient, and overly weaker Ekman currents. © 2011 American Meteorological Society."
"56272964700;15124698700;","An energetic perspective on the regional response of precipitation to climate change",2011,"10.1038/nclimate1169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856948972&doi=10.1038%2fnclimate1169&partnerID=40&md5=a58f98f395664be6b48092c3ffdf835d","Understanding and predicting the response of the hydrological cycle to climate change is a major challenge with important societal implications. Much progress has been made in understanding the response of global average precipitation by considering the energy balances of the atmosphere and the surface. This energetic perspective reveals that changes in temperature, greenhouse gases, aerosols, solar forcing and cloud feedbacks can all affect the global average rate of precipitation. Local precipitation changes have conventionally been analysed using the water vapour budget, but here we show that the energetic approach can be extended to local changes in precipitation by including changes in horizontal energy transport. In simulations of twenty-first century climate change, this energy transport accounts for much of the spatial variability in precipitation change. We show that changes in radiative and surface sensible heat fluxes are a guide to the local precipitation response over land and at large scales, but not at small scales over the ocean, where cloud and water vapour radiative feedbacks dampen the response. The energetic approach described here helps bridge the gap between our understanding of global and regional precipitation changes. It could be applied to better understand the response of regional precipitation to different radiative forcings, including geo-engineering schemes, as well as to understand the differences between the fast and slow responses of regional precipitation to such forcings. © 2011 Macmillan Publishers Limited. All rights reserved."
"22734679600;7006329853;6602229351;","Sulfuric acid aerosols in the atmospheres of the terrestrial planets",2011,"10.1016/j.pss.2010.05.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961167009&doi=10.1016%2fj.pss.2010.05.020&partnerID=40&md5=746d862fa6bad45fa86282c976423323","Clouds and hazes composed of sulfuric acid are observed to exist or postulated to have once existed on each of the terrestrial planets with atmospheres in our solar system. Venus today maintains a global cover of clouds composed of a sulfuric acid/water solution that extends in altitude from roughly 50 km to roughly 80 km. Terrestrial polar stratospheric clouds (PSCs) form on stratospheric sulfuric acid aerosols, and both PSCs and stratospheric aerosols play a critical role in the formation of the ozone hole. Stratospheric aerosols can modify the climate when they are enhanced following volcanic eruptions, and are a current focus for geoengineering studies. Rain is made more acidic by sulfuric acid originating from sulfur dioxide generated by industry on Earth. Analysis of the sulfur content of Martian rocks has led to the hypothesis that an early Martian atmosphere, rich in SO2 and H2O, could support a sulfur-infused hydrological cycle. Here we consider the plausibility of frozen sulfuric acid in the upper clouds of Venus, which could lead to lightning generation, with implications for observations by the European Space Agency's Venus Express and the Japan Aerospace Exploration Agency's Venus Climate Orbiter (also known as Akatsuki). We also present simulations of a sulfur-rich early Martian atmosphere. We find that about 40 cm/yr of precipitation having a pH of about 2.0 could fall in an early Martian atmosphere, assuming a surface temperature of 273 K, and SO2 generation rates consistent with the formation of Tharsis. This modeled acid rain is a powerful sink for SO2, quickly removing it and preventing it from having a significant greenhouse effect. © 2010 Elsevier Ltd."
"55942083800;","Gas-particle interactions of tropospheric aerosols: Kinetic and thermodynamic perspectives of multiphase chemical reactions, amorphous organic substances, and the activation of cloud condensation nuclei",2011,"10.1016/j.atmosres.2010.12.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953155796&doi=10.1016%2fj.atmosres.2010.12.018&partnerID=40&md5=afdef04231e0c8bc08519ee8f63871b5","Aerosols are of central importance in the Earth system, influencing the atmosphere, biosphere, climate, and public health. This article outlines recent advances and perspectives in the investigation and effects of gas-particle interactions in tropospheric aerosols, including physical, chemical and biological aspects. In particular, it addresses how multiphase processes and heterogeneous chemical reactions can be efficiently described by kinetic models, how amorphous organic substances can influence the kinetics of water uptake and phase transitions, and how the abundance and activation of cloud condensation nuclei (CCN) depend on thermodynamic and kinetic parameters. © 2010 Elsevier B.V."
"36141355100;57203053317;6701847229;7003748648;","Intercomparison of aerosol climatologies for use in a regional climate model over Europe",2011,"10.1029/2011GL048081","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051733007&doi=10.1029%2f2011GL048081&partnerID=40&md5=cde9810da25b9a4e8a4200e910105c4b","Many regional climate models (RCM) and numerical weather prediction (NWP) models use old aerosol data sets to calculate the direct aerosol effect. In this study, three multi-year simulations with COSMO-CLM using different aerosol climatologies and a simulation with monthly mean aerosol optical properties, stemming from a COSMO-CLM simulation with coupled aerosol microphysics and transport, are evaluated. The climatologies of Tegen et al. (1997), the AEROCOM-climatology for present-day conditions, and the monthly mean optical properties from Zubler et al. (2011), with realistic patterns of aerosol optical depth (AOD), lead to an increase of downward surface shortwave radiation (SSR) of 35 W m-2 (20%) in the Mediterranean region in comparison with the climatology of Tanré et al. (1984). The former is known to strongly overestimate AOD over Europe. The associated bias in SSR exceeds the observed variations of the recent decades by up to a factor 5. Despite an annual mean temperature increase of 0.5 K above Southern European land surfaces owing to enhanced SSR, the newer climatologies yield colder temperatures in the mid-troposphere because of a reduction of the shortwave absorption by desert dust. This reduced heating destabilizes the atmosphere relative to the simulation with the climatology of Tanré et al. (1984), enhancing cloud formation and precipitation in these simulations. It is recommended that the RCM community uses updated aerosol information for radiative transfer calculations. Copyright 2011 by the American Geophysical Union."
"6603742681;57212075803;","Spatial and temporal sampling of polar regions from two-satellite system on Molniya orbit",2011,"10.1175/JTECH-D-10-05013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052359236&doi=10.1175%2fJTECH-D-10-05013.1&partnerID=40&md5=8914b4f6ae12f2f541a7e080cb653fc0","There has been a significant increase of interest in the building of a comprehensive Arctic observing system in recent years to properly and timely track the environmental and climate processes in this vast region. In this regard, a satellite observing system on highly elliptical orbit (HEO) with 12-h period (Molniya type) is of particular interest, because it enables continuous coverage of the entire Arctic region (58°-90°N) from a constellation of two satellites. Canada is currently proposing to operate such a constellation by 2017. Extending the pioneering study of S. Q. Kidder and T. H. Vonder Haar, this paper presents in-depth analysis of spatiotemporal sampling properties of the imagery from this system. This paper also discusses challenges and advantages of this orbit for various applications that require high temporal resolution and angular sampling. © 2011 American Meteorological Society."
"6603968694;6701689811;","Ganges valley aerosol experiment",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053510167&partnerID=40&md5=c9dd004b3736aaaaa130a678a7a2d729","The US Department of Energy (DOE), in collaboration with the Indian Space Research Organization and the Indian Institute of Science, is conducting a large-scale field study, the Ganges Valley Aerosol Experiment, to study the effects of aerosols and associated pollution on solar input to the surface and on monsoon rainfall. During the experiment field studies, aerosols from the Ganges Valley were shown to affect cloud formation and monsoon activity over the Indian Ocean. The primary anchor facility for the project is the mobile climate monitoring facility AMF-1, offering an opportunity to study the prevailing patterns of cloud, convective mixing, and aerosol loads that are representative of the Indian subcontinent. The diurnal variability in aerosol, amounting to 50% and more, provides a unique opportunity to estimate the direct radiative forcing impact of aerosols on radiative transfer."
"7005548544;12040335900;","On the observational determination of climate sensitivity and its implications",2011,"10.1007/s13143-011-0023-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052608549&doi=10.1007%2fs13143-011-0023-x&partnerID=40&md5=3bb2d896b9cbfaabbff810f025120033","We estimate climate sensitivity from observations, using the deseasonalized fluctuations in sea surface temperatures (SSTs) and the concurrent fluctuations in the top-of-atmosphere (TOA) outgoing radiation from the ERBE (1985-1999) and CERES (2000- 2008) satellite instruments. Distinct periods of warming and cooling in the SSTs were used to evaluate feedbacks. An earlier study (Lindzen and Choi, 2009) was subject to significant criticisms. The present paper is an expansion of the earlier paper where the various criticisms are taken into account. The present analysis accounts for the 72 day precession period for the ERBE satellite in a more appropriate manner than in the earlier paper. We develop a method to distinguish noise in the outgoing radiation as well as radiation changes that are forcing SST changes from those radiation changes that constitute feedbacks to changes in SST. We demonstrate that our new method does moderately well in distinguishing positive from negative feedbacks and in quantifying negative feedbacks. In contrast, we show that simple regression methods used by several existing papers generally exaggerate positive feedbacks and even show positive feedbacks when actual feedbacks are negative. We argue that feedbacks are largely concentrated in the tropics, and the tropical feedbacks can be adjusted to account for their impact on the globe as a whole. Indeed, we show that including all CERES data (not just from the tropics) leads to results similar to what are obtained for the tropics alone - though with more noise. We again find that the outgoing radiation resulting from SST fluctuations exceeds the zerofeedback response thus implying negative feedback. In contrast to this, the calculated TOA outgoing radiation fluxes from 11 atmospheric models forced by the observed SST are less than the zerofeedback response, consistent with the positive feedbacks that characterize these models. The results imply that the models are exaggerating climate sensitivity. © The Korean Meteorological Society and Springer 2011."
"36613505400;7202401987;7006332352;6603772130;8613967400;","Modest diatom responses to regional warming on the southeast Tibetan Plateau during the last two centuries",2011,"10.1007/s10933-011-9533-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80955178877&doi=10.1007%2fs10933-011-9533-x&partnerID=40&md5=6476a9ba6436cab29eef4e1242802d42","A general mean annual temperature increase accompanied with substantial glacial retreat has been noted on the Tibetan Plateau during the last two centuries but most significantly since the mid 1950s. These climate trends are particularly apparent on the southeastern Tibetan Plateau. However, the Tibetan Plateau (due to its heterogeneous mountain landscape) has very complex and spatially differing temperature and precipitations patterns. As a result, intensive palaeolimnological investigations are necessary to decipher these climatic patterns and to understand ecological responses to recent environmental change. Here we present palaeolimnological results from a 210Pb/137Cs-dated sediment core spanning approximately the last 200 years from a remote high-mountain lake (LC6 Lake, working name) on the southeastern Tibetan Plateau. Sediment profiles of diatoms, organic variables (TOC, C:N) and grain size were investigated. The 210Pb record suggests a period of rapid sedimentation, which might be linked to major tectonic events in the region ca. 1950. Furthermore, unusually high 210Pb supply rates over the last 50 years suggest that the lake has possibly been subjected to increasing precipitation rates, sediment focussing and/or increased spring thaw. The majority of diatom taxa encountered in the core are typical of slightly acidic to circumneutral, oligotrophic, electrolyte-poor lakes. Diatom species assemblages were rich, and dominated by Cyclotella sp., Achnanthes sp., Aulacoseira sp. and fragilarioid taxa. Diatom compositional change was minimal over the 200-year period (DCCA = 0.85 SD, p = 0.59); only a slightly more diverse but unstable diatom assemblage was recorded during the past 50 years. The results indicate that large-scale environmental changes recorded in the twentieth century (i. e. increased precipitation and temperatures) are likely having an affect on the LC6 Lake, but so far these impacts are more apparent on the lake geochemistry than on the diatom flora. Local and/or regional peculiarities, such as increasing precipitation and cloud cover, or localized climatic phenomena, such as negative climate feedbacks, might have offset the effects of increasing mean surface temperatures. © 2011 Springer Science+Business Media B.V."
"23082420800;26767712900;7003843648;","Rethinking the ocean's role in the Southern Oscillation",2011,"10.1175/2011JCLI3973.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052837027&doi=10.1175%2f2011JCLI3973.1&partnerID=40&md5=c2ad11b592345cd55aa56386066f891e","The Southern Oscillation (SO) is usually described as the atmospheric component of the dynamically coupled El Niño-Southern Oscillation phenomenon. The contention in this work, however, is that dynamical coupling is not required to produce the SO. Simulations with atmospheric general circulation models that have varying degrees of coupling to the ocean are used to show that the SO emerges as a dominant mode of variability if the atmosphere and ocean are coupled only through heat and moisture fluxes. Herein this mode of variability is called the thermally coupled Walker (TCW) mode. It is a robust feature of simulations with atmospheric general circulation models (GCMs) coupled to simple ocean mixed layers. Despite the absence of interactive ocean dynamics in these simulations, the spatial patterns of sea level pressure, surface temperature, and precipitation variability associated with the TCW are remarkably realistic. This mode has a red spectrum indicating persistence on interannual to decadal time scales that appears to arise through an off-equatorial trade wind-evaporation-surface temperature feedback and cloud shortwave radiative effects in the central Pacific. When dynamically coupled to the ocean (in fully coupled ocean-atmosphere GCMs), the main change to this mode is increased interannual variability in the eastern equatorial Pacific sea surface temperature and teleconnections in the North Pacific and equatorial Atlantic, though not all coupled GCMs simulate this effect. Despite the oversimplification due to the lack of interactive ocean dynamics, the physical mechanisms leading to the TCW should be active in the actual climate system. Moreover, the robustness and realism of the spatial patterns of this mode suggest that the physics of the TCW can explain some of the primary features of observed interannual and decadal variability in the Pacific and the associated global teleconnections. © 2011 American Meteorological Society."
"6602996168;16551519100;","Simulations of contrail optical properties and radiative forcing for various crystal shapes",2011,"10.1175/2011JAMC2618.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052356536&doi=10.1175%2f2011JAMC2618.1&partnerID=40&md5=2b603cb1ab127aacaf707e9fd9a40992","The aim of this study is to investigate the sensitivity of radiative-forcing computations to various contrail crystal shape models. Contrail optical properties in the shortwave and longwave ranges are derived using a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods present good correspondence of the single-scattering albedo and the asymmetry parameter in a transition range (3-8 μm). There are substantial differences in single-scattering properties among 10 crystal models investigated here (e.g., hexagonal columns and plates with different aspect ratios, and spherical particles). The single-scattering albedo and the asymmetry parameter both vary by up to 0.1 among various crystal shapes. The computed single-scattering properties are incorporated in the moderate-resolution atmospheric radiance and transmittance model(MODTRAN) radiative transfer code to simulate solar and infrared fluxes at the top of the atmosphere. Particle shapes have a strong impact on the contrail radiative forcing in both the shortwave and longwave ranges. The differences in the net radiative forcing among optical models reach 50% with respect to the mean model value. The hexagonal-column and hexagonal-plate particles show the smallest net radiative forcing, and the largest forcing is obtained for the spheres. The balance between the shortwave forcing and longwave forcing is highly sensitive with respect to the assumed crystal shape and may even change the sign of the net forcing. The optical depth at which the mean diurnal radiative forcing changes sign from positive to negative varies from 4.5 to 10 for a surface albedo of 0.2 and from 2 to 6.5 for a surface albedo of 0.05. Contrails are probably never that optically thick (except for some aged contrail cirrus), however, and so will not have a cooling effect on climate. © 2011 American Meteorological Society."
"55969140000;48662342700;57198841083;7404433688;","Climatologic comparison of HadISST1 and TMI sea surface temperature datasets",2011,"10.1007/s11430-011-4214-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961208539&doi=10.1007%2fs11430-011-4214-1&partnerID=40&md5=2db85d367838c6a3060cfc0e8ace509f","Two monthly datasets of sea surface temperature (SST), TMI SST retrieved from satellite observations by Remote Sensing System and HadISST1 (Hadley Centre Sea-ice and Sea-surface Temperature Data Set Version 1) derived from in situ measurements by Hadley Centre, were compared on climatologic multiple time scales over tropical and subtropical areas from 1998 to 2006. Results indicate that there is a good consistency in the horizontal global distribution, with 1.0° resolution on multi-year and multi-season mean scales between the two datasets, and also in the time series of global mean SST anomalies. However, there are still some significant differences between the datasets. Generally, TMI SST is relatively higher than Had-ISST1. In addition, the differences between the two datasets show not only remarkable regionality, but also distinct seasonal variations. Moreover, the maximum departure occurs in summer, while the minimum takes place in autumn. For all seasons, over 30% of the regions in the Tropical and Subtropical areas have a difference of more than 0.3°C. EOF analysis of the SST anomaly field also shows that there are differences between the two datasets, where HadISST1 has more significant statistical characteristics than TMI SST. On the other hand, results show that the difference between the two datasets is related to the vertical structure of ocean temperatures, as well as other simultaneously retrieved parameters in TMI products, such as wind speed, water vapor, liquid cloud water and rain rates. In addition, large biases between HadISST1 and TMI SST are found in coastal regions, where TMI SST cannot be accurately retrieved because of polluted microwave signals. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg."
"7402845686;57195549023;7103122105;","Meteorological influences of eddy-resolving ocean assimilation around the cold tongue to the north of the Japanese islands during winter 2004/2005",2011,"10.1007/s13143-011-0019-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055099515&doi=10.1007%2fs13143-011-0019-6&partnerID=40&md5=159ac47eef345c4b9c003c7436a333ea","Use of ocean data assimilation in meteorological applications is expected to reveal the influence of cloud-covered oceanic mesoscale processes on wintertime weather and climate in coastal areas. In particular, eddy-resolving Ocean Circulation Model (OCM) data assimilation that reproduces seasonally persistent oceanic mesoscale eddies is useful when simulating coastal precipitation. In the present study, the OCM-assimilation sea surface temperature (SST) is applied to a long-term atmospheric simulation over the Japan/East Sea area in the 2004/2005 winter season (December-February, DJF), to investigate seasonal and daily influences of oceanic mesoscale eddies on precipitation. The simulated winter precipitation is improved by the OCM assimilation via the DJF evaporation around a cold tongue. The strong intrusion of the southeast-directed cold tongue reduces the degree of overestimation by coastal precipitation simulations in December and January. In contrast, the ocean assimilation barely improves the simulation results in February because of weak intrusion of the cold tongue. In December and January, an abruptly large anomaly of northwesterly surface wind (&gt; 1 m s?1) resulting from the OCM assimilation often influences 3-hour precipitation in the downstream area of the cold tongue. In contrast, the slowly-varying anomaly of evaporation does not necessarily lead to daily precipitation anomalies, although the DJF evaporation anomaly is important in the DJF precipitation. © The Korean Meteorological Society and Springer 2011."
"7102495313;7006904374;14035928700;8696069500;8879755400;7003390361;6508155070;7004461962;15739506300;8977001000;6504396585;6603292201;7005744770;7101733669;6603628078;24537575000;7005920812;7005056279;56270361500;7005432249;55717244800;6701497749;35462130800;7102625546;8683331200;","Evaluation of the diurnal cycle in the Atmospheric Boundary Layer over land as Represented by a Variety of Single-Column models: The second GABLS EXperiment",2011,"10.1007/s10546-011-9611-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960043791&doi=10.1007%2fs10546-011-9611-7&partnerID=40&md5=c0dd62ffa586e58bc4988bf783118ca5","We present the main results from the second model intercomparison within the GEWEX (Global Energy and Water cycle EXperiment) Atmospheric Boundary Layer Study (GABLS). The target is to examine the diurnal cycle over land in today's numerical weather prediction and climate models for operational and research purposes. The set-up of the case is based on observations taken during the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99), which was held in Kansas, USA in the early autumn with a strong diurnal cycle with no clouds present. The models are forced with a constant geostrophic wind, prescribed surface temperature and large-scale divergence. Results from 30 different model simulations and one large-eddy simulation (LES) are analyzed and compared with observations. Even though the surface temperature is prescribed, the models give variable near-surface air temperatures. This, in turn, gives rise to differences in low-level stability affecting the turbulence and the turbulent heat fluxes. The increase in modelled upward sensible heat flux during the morning transition is typically too weak and the growth of the convective boundary layer before noon is too slow. This is related to weak modelled near-surface winds during the morning hours. The agreement between the models, the LES and observations is the best during the late afternoon. From this intercomparison study, we find that modelling the diurnal cycle is still a big challenge. For the convective part of the diurnal cycle, some of the first-order schemes perform somewhat better while the turbulent kinetic energy (TKE) schemes tend to be slightly better during nighttime conditions. Finer vertical resolution tends to improve results to some extent, but is certainly not the solution to all the deficiencies identified. © 2011 Springer Science+Business Media B.V."
"7401745468;7402205043;","Incorporating additional sounding observations in weather analysis and rainfall prediction during the intensive observing period of 2006 TWP-ICE",2011,"10.3319/TAO.2011.04.11.01(A)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053246016&doi=10.3319%2fTAO.2011.04.11.01%28A%29&partnerID=40&md5=0190306952d5c514b78aad9b19783d08","Using additional sounding observations during the Intensive Observing Period (IOP) of the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) in 2006, the characteristics of weather systems and associated environmental conditions are further analyzed during four temporal regimes (active wet monsoon, suppressed dry monsoon, clear day, and monsoon break). Monsoon low-pressure systems are predominant during the active wet monsoon and monsoon break periods. During the active monsoon period, heavy rainfall (&gt; 100 mm day-1) is produced over the nearby tropical ocean of north Australia and the maritime continent centered on the Tiwi Islands, where the apparent southerly-to-southwesterly winds dominate at low levels over the ocean under the influence of the monsoon low in contrast to the westerly winds during a typical active north Australia summer monsoon regime. In the monsoon break, limited scattered rainfall is distributed over coastal regions of northern Australia and inland. During the suppressed monsoon period and clear days, the environment is very dry under the influence of a monsoon ridge. This is not favorable for the development of convection and the production of the rainfall. In a suppressed monsoon regime, the dry air intrusion in the mid-troposphere with the driest center around the 600-hPa level is related to dry air advection from the subtropical regions and the subsidence associated with the approaching of a monsoon ridge. Typical westerly winds prevail between 850 and 700 hPa in Darwin. During clear days, the subsidence related to the monsoon ridge is the major reason for the driest environmental condition during 2006 TWP-ICE. With the help of additional sounding data, dominant weather systems during four periods are clearly identified when compared with NCEP/FNL global analysis. Also the daily rainfall predictions are improved during the IOP, especially in the active monsoon period."
"57215596081;7402950566;","Climatology and interannual variability of convectively coupled equatorial waves activity",2011,"10.1175/2011JCLI4021.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052627027&doi=10.1175%2f2011JCLI4021.1&partnerID=40&md5=bfa311dbf85ed0204fe849658b91c9e4","Climatology and interannual variability of convectively coupled equatorial wave (CCEW) activity, including the mixed Rossby-gravity (MRG), tropical-depression-type (TD-type), equatorial Rossby (ER), and Kelvin waves, are investigated using the satellite-observed brightness temperature data from the Cloud Archive User Service. The monthly activity of CCEWs is represented by the root mean square of the daily filtered convections in each month based on the Wheeler-Kiladis filtering method. More precise seasonal cycles of CCEW activity are obtained from the meridional and zonal mean climatology. Interannual variance of CCEW activity is further investigated. Kelvin wave activity has maximum interannual variance over the eastern Pacific, while the other three waves are most variable in the intertropical convergence zone. The four active CCEWs all have significant correlation with the background convection and local sea surface temperature (SST) over the central and eastern Pacific, but they are not significantly correlated over other regions. The El Niño events may induce more trapped and active CCEWs over the central and eastern Pacific but weakerMRGand TD-type waves over the warm pool. In contrast, the El Niño Modoki has much weaker correlation with CCEW activity. CCEW activity over the southeastern Indian Ocean is negatively correlated with the Indian Ocean dipole, while that over the western and northern Indian Ocean may be determined by atmospheric internal disturbances. The tropical southern Atlantic mode is the strongest Atlantic SST anomaly mode correlated with the Atlantic CCEW activity. © 2011 American Meteorological Society."
"11939796800;23566342500;11939617300;","Dynamical downscaling of wind speed in complex terrain prone to bora-type flows",2011,"10.1175/2011JAMC2638.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052359493&doi=10.1175%2f2011JAMC2638.1&partnerID=40&md5=565b0392371c41b8ad9c83a3c2958f78","The results of numerically modeled wind speed climate, a primary component of wind energy resource assessment in the complex terrain of Croatia, are given. For that purpose, dynamical downscaling of 10 yr (1992-2001) of the 40-yr ECMWF Re-Analysis (ERA-40) was performed to 8-km horizontal grid spacing with the use of a spectral, prognostic full-physics model Aire Limitée Adaptation Dynamique Développement International (ALADIN; the ""ALHR"" version). Then modeled data with a 60-min frequency were refined to 2-km horizontal grid spacing with a simplified and cost-effective model version, the so-called dynamical adaptation (DADA). The statistical verification of ERA-40-, ALHR-, and DADA-modeled wind speed on the basis of data from measurement stations representing different regions of Croatia suggests that downscaling was successful and that model accuracy generally improves as horizontal resolution is increased. The areas of the highest mean wind speeds correspond well to locations of frequent and strong bora flow as well as to the prominent mountain peaks. The best results are achieved with DADA and contain bias of 1% of the mean wind speed for eastern Croatia while reaching 10% for complex coastal terrain, mainly because of underestimation of the strongest winds. Root-mean-square errors for DADA are significantly smaller for flat terrain than for complex terrain, with relative values close to 12% of the mean wind speed regardless of the station location. Spectral analyses suggest that the shape of the kinetic energy spectra generally relaxes from k-3 at the upper troposphere to the shape of orographic spectra near the surface and shows no seasonal variability. Apart from the buildup of energy on smaller scales of motions, it is shown that mesoscale simulations contain a considerable amount of energy related to near-surface and mostly divergent meso-β-scale (20-200 km) motions. Spectral decomposition of measured and modeled data in temporal space indicates a reasonable performance of all model datasets in simulating the primary maximum of spectral power related to synoptic and larger-than-diurnal mesoscale motions, with somewhat increased accuracy of mesoscale model data. The primary improvement of dynamical adaptation was achieved for cross-mountain winds, whereas mixed results were found for along-mountain wind directions. Secondary diurnal and tertiary semidiurnal maxima are significantly better simulated with the mesoscale model for coastal stations but are somewhat more erroneous for the continental station. The mesoscale model data underestimate the spectral power of motions with less-than-semidiurnal periods. © 2011 American Meteorological Society."
"24081888700;7004174939;57203386948;","Microphysical, macrophysical and radiative signatures of volcanic aerosols in trade wind cumulus observed by the A-Train",2011,"10.5194/acp-11-7119-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960682774&doi=10.5194%2facp-11-7119-2011&partnerID=40&md5=ac828a7f1f193fe1f4bc09c0dfbba796","Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-term degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The ""total shortwave aerosol forcin"", resulting from direct and indirect forcings including both cloud albedo and cloud amount, is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research. © 2011 Author(s)."
"56611366900;55707488500;57198616562;37018824600;","Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo",2011,"10.5194/acp-11-7155-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960664245&doi=10.5194%2facp-11-7155-2011&partnerID=40&md5=db1f7eb48628753dbf2f1c0339ed889e","This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surface-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fraction, and cloud albedo. The analytical expression is then used to deduce a new approach for inferring cloud albedo from concurrent surface-based measurements of downwelling surface shortwave radiation and cloud fraction. High-resolution decade-long data on cloud albedos are obtained by use of this surface-based approach over the US Department of Energy's Atmospheric Radiaton Measurement (ARM) Program at the Great Southern Plains (SGP) site. The surface-based cloud albedos are further compared against those derived from the coincident GOES satellite measurements. The three long-term (1997-2009) sets of hourly data on shortwave cloud radiative forcing, cloud fraction and cloud albedo collected over the SGP site are analyzed to explore the multiscale (diurnal, annual and inter-annual) variations and covariations. The analytical formulation is useful for diagnosing deficiencies of cloud-radiation parameterizations in climate models. © 2011 Author(s)."
"8608733900;26665326700;7102266120;13403957300;7402480218;","Sky cover from MFRSR observations",2011,"10.5194/amt-4-1463-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857768916&doi=10.5194%2famt-4-1463-2011&partnerID=40&md5=437cd38877d3c9bd764d1bd90183c8c9","The diffuse all-sky surface irradiances measured at two nearby wavelengths in the visible spectral range and their modeled clear-sky counterparts are the main components of a new method for estimating the fractional sky cover of different cloud types, including cumuli. The performance of this method is illustrated using 1-min resolution data from a ground-based Multi-Filter Rotating Shadowband Radiometer (MFRSR). The MFRSR data are collected at the US Department of Energy Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) Southern Great Plains (SGP) site during the summer of 2007 and represent 13 days with cumuli. Good agreement is obtained between estimated values of the fractional sky cover and those provided by a well-established independent method based on broadband observations. © 2011 Author(s)."
"6603640779;6507238286;22951422500;","Evaluating the impact of daily net radiation models on grass and alfalfa-reference evapotranspiration using the penman-monteith equation in a subhumid and semiarid climate",2011,"10.1061/(ASCE)IR.1943-4774.0000278","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651511791&doi=10.1061%2f%28ASCE%29IR.1943-4774.0000278&partnerID=40&md5=5ecfbf889465d6eedef2e8535a4017c7","Net radiation (Rn) is the main driving force of evapotranspiration (ET) and is a key input variable to the Penman-type combination and energy balance equations. However, Rn is not commonly measured. This paper analyzes the impact of 19 net radiation models that differ in model structure and intricacy on estimated grass and alfalfa-reference ET (ETo and ETr, respectively) and investigates how climate, season and cloud cover influence the impact of the Rn models on ETo and ETr. Datasets from two locations (Clay Center, Nebraska, subhumid; and Davis, California, a Mediterranean-type semiarid climate) were used. Rn values computed from the 19 models were used in the standardized ASCE-EWRI Penman-Monteith equation to estimate ETo and ETr on a daily time step. The influence of seasons on the estimation of Rn and on estimated ETo and ETr was investigated in winter (November-March) and summer (May-September) months. To analyze the influence of clouds on the impact of Rn models, relative shortwave radiation (Rrs) was used as a means to express the cloudiness of the days as: 0≤Rrs≤0.35 for completely cloudy days; 0.35&lt;Rrs≤0.70 for partially cloudy days; and 0.70&lt;Rrs≤1.0 for clear sky days. The performances of Rn models showed variations at the same location and between the locations for the same model based on methods used to calculate various model parameters. The most significant impact of Rn on estimated ETo and ETr was related to the methods used to calculate atmospheric emissivity (ε) rather than methods used to calculate clear sky solar radiation (Rso) or cloud adjustment factor (f). Rn models that used average air temperature to compute ε and an estimated f resulted in good performances at both locations. Empirical models that assumed f=1.0 showed poor to average performances at both locations. While model performances varied based on methods used to calculate Rso, f, and ε, there were significant seasonal variations in performances of models that calculated ε as a function of actual vapor pressure of the air (ea). The seasonal variations in performances of these models were greater under subhumid climate at Clay Center than in semiarid climate at Davis, Calif. The models that calculated ε as a function of ea performed better under completely cloudy days than on other days, more so at Clay Center. Methods used to calculate ε have a significant impact on the Rn model performance, especially in unstable climatic conditions such as at Clay Center where there are frequent and rapid changes in climatic variables in a given day and throughout the year. The results of this study can be used as a reference tool to provide practical information on which method to select based on the data availability for reliable estimates of daily Rn relative to the ASCE-EWRI Rn method in subhumid and semiarid climates similar to Clay Center, Neb. and Davis, Calif. © 2011 ASCE."
"56162305900;7003666669;55405340400;55717074000;7006270084;8608733900;55802246600;7103158465;","Aerosol indirect effects in a multi-scale aerosol-climate model PNNL-MMF",2011,"10.5194/acp-11-5431-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960187362&doi=10.5194%2facp-11-5431-2011&partnerID=40&md5=c7ac6b672679b092e40fdecdfaae907e","Much of the large uncertainty in estimates of anthropogenic aerosol effects on climate arises from the multi-scale nature of the interactions between aerosols, clouds and dynamics, which are difficult to represent in conventional general circulation models (GCMs). In this study, we use a multi-scale aerosol-climate model that treats aerosols and clouds across multiple scales to study aerosol indirect effects. This multi-scale aerosol-climate model is an extension of a multi-scale modeling framework (MMF) model that embeds a cloud-resolving model (CRM) within each vertical column of a GCM grid. The extension allows a more physically-based treatment of aerosol-cloud interactions in both stratiform and convective clouds on the global scale in a computationally feasible way. Simulated model fields, including liquid water path (LWP), ice water path, cloud fraction, shortwave and longwave cloud forcing, precipitation, water vapor, and cloud droplet number concentration are in reasonable agreement with observations. The new model performs quantitatively similar to the previous version of the MMF model in terms of simulated cloud fraction and precipitation. The simulated change in shortwave cloud forcing from anthropogenic aerosols is 0.77 W mg-2, which is less than half of that (1.79 W mg-2) calculated by the host GCM (NCAR CAM5) with traditional cloud parameterizations and is also at the low end of the estimates of other conventional global aerosol-climate models. The smaller forcing in the MMF model is attributed to a smaller (3.9 %) increase in LWP from preindustrial conditions (PI) to present day (PD) compared with 15.6 % increase in LWP in stratiform clouds in CAM5. The difference is caused by a much smaller response in LWP to a given perturbation in cloud condensation nuclei (CCN) concentrations from PI to PD in the MMF (about one-third of that in CAM5), and, to a lesser extent, by a smaller relative increase in CCN concentrations from PI to PD in the MMF (about 26 % smaller than that in CAM5). The smaller relative increase in CCN concentrations in the MMF is caused in part by a smaller increase in aerosol lifetime from PI to PD in the MMF, a positive feedback in aerosol indirect effects induced by cloud lifetime effects from aerosols. The smaller response in LWP to anthropogenic aerosols in the MMF model is consistent with observations and with high resolution model studies, which may indicate that aerosol indirect effects simulated in conventional global climate models are overestimated and point to the need to use global high resolution models, such as MMF models or global CRMs, to study aerosol indirect effects. The simulated total anthropogenic aerosol effect in the MMF is 1.05 W mg-2, which is close to the Murphy et al. (2009) inverse estimate of 1.1±0.4 W mg-2 (1&amp;sigma;) based on the examination of the Earth's energy balance. Further improvements in the representation of ice nucleation and low clouds in MMF are needed to refine the aerosol indirect effect estimate. © 2011 Author(s)."
"55911904900;57126848900;6602137800;7201966094;7006107059;","Simultaneous retrieval of aerosol and cloud properties during the MILAGRO field campaign",2011,"10.5194/acp-11-6245-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960159467&doi=10.5194%2facp-11-6245-2011&partnerID=40&md5=19b9ad6eea3db2a46404cfb98ae1426b","Estimation of Direct Climate Forcing (DCF) due to aerosols in cloudy areas has historically been a difficult task, mainly because of a lack of appropriate measurements. Recently, passive remote sensing instruments have been developed that have the potential to retrieve both cloud and aerosol properties using polarimetric, multiple view angle, and multi spectral observations, and therefore determine DCF from aerosols above clouds. One such instrument is the Research Scanning Polarimeter (RSP), an airborne prototype of a sensor on the NASA Glory satellite, which unfortunately failed to reach orbit during its launch in March of 2011. In the spring of 2006, the RSP was deployed on an aircraft based in Veracruz, Mexico, as part of the Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign. On 13 March, the RSP over flew an aerosol layer lofted above a low altitude marine stratocumulus cloud close to shore in the Gulf of Mexico. We investigate the feasibility of retrieving aerosol properties over clouds using these data. Our approach is to first determine cloud droplet size distribution using the angular location of the cloud bow and other features in the polarized reflectance. The selected cloud was then used in a multiple scattering radiative transfer model optimization to determine the aerosol optical properties and fine tune the cloud size distribution. In this scene, we were able to retrieve aerosol optical depth, the fine mode aerosol size distribution parameters and the cloud droplet size distribution parameters to a degree of accuracy required for climate modeling. This required assumptions about the aerosol vertical distribution and the optical properties of the coarse aerosol size mode. A sensitivity study was also performed to place this study in the context of future systematic scanning polarimeter observations, which found that the aerosol complex refractive index can also be observed accurately if the aerosol optical depth is larger than roughly 0.8 at a wavelength of (0.555 μm). © 2011 Author(s)."
"12782225200;6701646252;7102062952;16834291500;8522396600;21935606200;56158229700;","Isoprene suppression of new particle formation in a mixed deciduous forest",2011,"10.5194/acp-11-6013-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960176190&doi=10.5194%2facp-11-6013-2011&partnerID=40&md5=4b40464529af055765c995225d59df53","Production of new particles over forests is an important source of cloud condensation nuclei that can affect climate. While such particle formation events have been widely observed, their formation mechanisms over forests are poorly understood. Our observations made in a mixed deciduous forest with large isoprene emissions during the summer displayed a surprisingly rare occurrence of new particle formation (NPF). Typically, NPF events occur around noon but no NPF events were observed during the 5 weeks of measurements. The exceptions were two evening ultrafine particle events. During the day, sulfuric acid concentrations were in the 106 cm-3 range with very low preexisting aerosol particles, a favorable condition for NPF to occur even during the summer. The ratio of emitted isoprene carbon to monoterpene carbon at this site was similar to that in Amazon rainforests (ratio &gt;10), where NPF events are also very rare, compared with a ratio &lt;0.5 in Finland boreal forests, where NPF events are frequent. Our results suggest that large isoprene emissions can suppress NPF formation in forests although the underlying mechanism for the suppression is unclear. The two evening ultrafine particle events were associated with the transported anthropogenic sulfur plumes and ultrafine particles were likely formed via ion-induced nucleation. Changes in landcover and environmental conditions could modify the isoprene suppression of NPF in some forest regions resulting in a radiative forcing that could have influence on the climate. © 2011 Author(s)."
"16027961900;7103098751;7004214645;12240390300;","The impact of orbital sampling, monthly averaging and vertical resolution on climate chemistry model evaluation with satellite observations",2011,"10.5194/acp-11-6493-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960192280&doi=10.5194%2facp-11-6493-2011&partnerID=40&md5=ba95e05a68650b9c4fbdf65103d12397","Ensemble climate model simulations used for the Intergovernmental Panel on Climate Change (IPCC) assessments have become important tools for exploring the response of the Earth System to changes in anthropogenic and natural forcings. The systematic evaluation of these models through global satellite observations is a critical step in assessing the uncertainty of climate change projections. This paper presents the technical steps required for using nadir sun-synchronous infrared satellite observations for multi-model evaluation and the uncertainties associated with each step. This is motivated by need to use satellite observations to evaluate climate models. We quantified the implications of the effect of satellite orbit and spatial coverage, the effect of variations in vertical sensitivity as quantified by the observation operator and the impact of averaging the operators for use with monthly-mean model output. We calculated these biases in ozone, carbon monoxide, atmospheric temperature and water vapour by using the output from two global chemistry climate models (ECHAM5-MOZ and GISS-PUCCINI) and the observations from the Tropospheric Emission Spectrometer (TES) instrument on board the NASA-Aura satellite from January 2005 to December 2008. The results show that sampling and monthly averaging of the observation operators produce zonal-mean biases of less than ±3 % for ozone and carbon monoxide throughout the entire troposphere in both models. Water vapour sampling zonal-mean biases were also within the insignificant range of ±3 % (that is ±0.14 g kg -1) in both models. Sampling led to a temperature zonal-mean bias of ±0.3 K over the tropical and mid-latitudes in both models, and up to -1.4 K over the boundary layer in the higher latitudes. Using the monthly average of temperature and water vapour operators lead to large biases over the boundary layer in the southern-hemispheric higher latitudes and in the upper troposphere, respectively. Up to 8 % bias was calculated in the upper troposphere water vapour due to monthly-mean operators, which may impact the detection of water vapour feedback in response to global warming. Our results reveal the importance of using the averaging kernel and the a priori profiles to account for the limited vertical resolution and clouds of a nadir observation during model application. Neglecting the observation operators resulted in large biases, which are more than 60 % for ozone, ±30 % for carbon monoxide, and range between -1.5 K and 5 K for atmospheric temperature, and between -60 % and 100 % for water vapour. © 2011 Author(s)."
"55200758900;55807480400;7102040150;7005933635;55520820800;57214289652;55077923500;15729641400;56990480300;7405944157;55521311100;55875654600;57204845855;57196224798;","Effects of cloudiness change on net ecosystem exchange, light use efficiency, and water use efficiency in typical ecosystems of China",2011,"10.1016/j.agrformet.2011.01.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955582699&doi=10.1016%2fj.agrformet.2011.01.011&partnerID=40&md5=8db2456baf07795ea32dc0b8a82dc620","As a weather element, clouds can affect CO2 exchange between terrestrial ecosystems and the atmosphere by altering environmental conditions, such as solar radiation received on the ground surface, temperature, and moisture. Based on the flux data measured at five typical ecosystems of China during mid-growing season (June-August) from 2003 to 2006, we analyzed the responses of net ecosystem exchange of carbon dioxide (NEE), light use efficiency (LUE, defined as Gross ecosystem photosynthesis (GEP)/Photosynthetically active radiation (PAR)), and water use efficiency (WUE, defined as GEP/Evapotranspiration (ET)) to the changes in cloudiness. The five ecological sites included Changbaishan temperate mixed forest (CBS), Dinghushan subtropical evergreen broad-leaved forest (DHS), Xishuangbanna tropical rainforest (XSBN), Inner Mongolia semi-arid Leymus chinensis steppe (NMG), and Haibei alpine frigid Potentilla fruticosa shrub (HB). Our analyses show that cloudy sky conditions with cloud index (kt) values between 0.4 and 0.6 increased NEE, LUE, and WUE of the ecosystems at CBS, DHS, NMG and HB from June to August. The LUE of tropical rainforest at XSBN was higher under cloudy than under clear sky conditions, but NEE and WUE did not decrease significantly under clear sky conditions from June to August. The increase in GEP with increasing diffuse radiation received by ecosystems under cloudy skies was the main reason that caused the increases in LUE and net carbon uptake in forest ecosystem at CBS, DHS, and alpine shrub ecosystem at HB, compared with clear skies. Moreover, for the ecosystem at CBS, DHS, and HB, when sky condition became from clear to cloudy, GEP increased and ET decreased with decreasing VPD, leading to the increase in WUE and NEE under cloudy sky conditions. The decrease in Re with decreasing temperature and increase in GEP with decreasing VPD under cloudy skies led to the increase in LUE, WUE, and net carbon uptake of semi-arid steppe at NMG, compared to clear skies. These different responses among the five ecosystems are attributable to the differences in canopy characteristics and water conditions. From June to August, the peaks of the kt frequency distribution in temperate ecosystems (e.g., CBS, NMG, and HB) were larger than 0.5, but they were smaller than 0.4 in subtropical/tropical forest ecosystems (e.g., DHS and XSBN). These results suggest that the pattern of cloudiness during the years from 2003 to 2006 in the five ecosystems was not the best condition for their net carbon uptake. This study highlights the importance of cloudiness factor in the prediction of net carbon absorption in the Asia monsoon region under climate change. © 2011 Elsevier B.V."
"55686667100;10241250100;10241462700;10243650000;55537426400;8979277400;7102857642;","Constraints to the tropical low-cloud trends in historical climate simulations",2011,"10.1002/asl.337","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960507461&doi=10.1002%2fasl.337&partnerID=40&md5=0162d0414c9d9f7a21f75f154a20f9a9","Given the importance and difficulty in evaluating long-term trends in the tropical low-cloud amount (Cl), we examined mechanisms that determine the Cl trend in 20th century experiments using two different versions of the climate model called the Model for Interdisciplinary Research on Climate (MIROC). The Cl trend patterns are coherent with trends in vertical velocity (ω) and lower-tropospheric stability (LTS). While the mean LTS trend varies and gives a stronger constraint to the Cl trends, the ω trend cannot do so due to mass conservation. Two of three reanalysis products support the positive LTS trend, but it is inconclusive because of the diversity in pattern and sign. © 2011 Royal Meteorological Society © 2011 Royal Meteorological Society."
"12769875100;7006738324;26324818700;","Seasonal variations of climate feedbacks in the NCAR CCSM3",2011,"10.1175/2011JCLI3862.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960333163&doi=10.1175%2f2011JCLI3862.1&partnerID=40&md5=341b1fbf54ef07b166280e031081118f","This study investigates the annual cycle of radiative contributions to global climate feedbacks. A partial radiative perturbation (PRP) technique is used to diagnose monthly radiative perturbations at the top of atmosphere (TOA) due to CO2 forcing; surface temperature response; and water vapor, cloud, lapse rate, and surface albedo feedbacks using NCAR Community Climate System Model, version 3 (CCSM3) output from a Special Report on Emissions Scenarios (SRES) A1B emissions-scenario-forced climate simulation. The seasonal global mean longwave TOA radiative feedback was found to be minimal. However, the global mean shortwave (SW) TOA cloud and surface albedo radiative perturbations exhibit large seasonality. The largest contributions to the negative SW cloud feedback occur during summer in each hemisphere, marking the largest differences with previous results. Results suggest that intermodel spread in climate sensitivity may occur, partially from cloud and surface albedo feedback seasonality differences. Further, links between the climate feedback and surface temperature response seasonality are investigated, showing a strong relationship between the seasonal climate feedback distribution and the seasonal surface temperature response. © 2011 American Meteorological Society."
"57210785732;16025327700;57217371644;","Impact of galactic cosmic rays on Earth's atmosphere and human health",2011,"10.1016/j.atmosenv.2011.04.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957699879&doi=10.1016%2fj.atmosenv.2011.04.027&partnerID=40&md5=306932c5c62b3d4de67f817d5647d687","The galactic cosmic rays (GCRs) originating from astrophysical sources and traversing through the interstellar/interplanetary medium reach the terrestrial atmosphere and produce complex dynamic changes in it. The flow rate of GCRs incident on the Earth's upper atmosphere is varied by the solar wind and the geomagnetic field. Striking correlations between the cloud cover and GCR fluxes on long time scale are observed whereas on short time scale no significant correlation is found. These observations are directly related to climate variations on short term as well as long term. In the present paper, we have reviewed and attempted to provide an overview of cosmic ray effects on terrestrial processes such as electrical phenomena, lightning discharges cloud formation and cloud coverage, temperature variation, space weather phenomena, Earth's climate and the effects of GCRs on human health. It is shown that CRs control long term variations of some of the above mentioned physical processes, which in turn control short term and long term variations in climate. It is also pointed out that there are many basic phenomena which need further study and require new and long term data set. © 2011 Elsevier Ltd."
"36094524600;","Reducing warm bias over the north-eastern europe in a regional climate model",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051648449&partnerID=40&md5=ca139dbb8298ae76e8d5788be5f9405a","Large warm bias in near-surface temperature during winter was detected over northeastern Europe in simulations with RegCM4 regional climate model when compared to observational dataset. Modifications to alleviate warm bias included reductions of the low-level cloud cover fraction and the minimum turbulent mixing in stable planetary boundary layer. When implemented, these modifications reduced warm bias up to 50% and did not degrade, or substantially impact, the variables analyzed outside the region and season considered. Validations of the planetary boundary layer and cloud features were limited due to unavailability of appropriate observational data at climatological timescales."
"57070564300;7601492669;8718425100;45261669200;","Simulation of seasonal variation of marine boundary layer clouds over the Eastern Pacific with a regional climate model",2011,"10.1175/2010JCLI3935.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960304405&doi=10.1175%2f2010JCLI3935.1&partnerID=40&md5=dfb386433291df9ed1ac8b218f655887","The seasonal cycle of marine boundary layer (MBL) clouds over the eastern Pacific Ocean is studied with the International Pacific Research Center (IPRC) Regional Atmospheric Model (iRAM). The results show that the model is capable of simulating not only the overall seasonal cycle but also the spatial distribution, cloud regime transition, and vertical structure of MBL clouds over the eastern Pacific. Although the modeled MBL cloud layer is generally too high in altitude over the open ocean when compared with available satellite observations, the model simulated well the westward deepening and decoupling of the MBL, the rise in cloud base and cloud top of the low cloud decks off the Peru and California coasts, and the cloud regime transition from stratocumulus near the coast to trade cumulus farther to the west in both the southeast and northeast Pacific. In particular, the model reproduced major features of the seasonal variations in stratocumulus decks off the Peru and California coasts, including cloud amount, surface latent heat flux, subcloud-layer mixing, and the degree of MBL decoupling. In both observations and the model simulation, in the season with small low-level cloudiness, surface latent heat flux is large and the cloud base is high. This coincides with weak subcloud-layer mixing and strong entrainment at cloud top, characterized by a high degree of MBL decoupling, while the opposite is true for the season with large low-level cloudiness. This seasonal cycle in low-cloud properties resembles the downstream stratocumulus-to-cumulus transition of marine low clouds and can be explained by the ""deepening-decoupling"" mechanism proposed in previous studies. It is found that the seasonal variations of low-level clouds off the Peru coast are mainly caused by a large seasonal variability in sea surface temperature, whereas those off the California coast are largely attributed to the seasonal cycle in lower-tropospheric temperature. © 2011 American Meteorological Society."
"44061090200;35547807400;8326850700;","Spatial patterns of modeled climate feedback and contributions to temperature response and polar amplification",2011,"10.1175/2011JCLI3863.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960675006&doi=10.1175%2f2011JCLI3863.1&partnerID=40&md5=9de4abe7030e90b13f3df5add6194bb4","Spatial patterns of local climate feedback and equilibriumpartial temperature responses are produced from eight general circulation models with slab oceans forced by doubling carbon dioxide (CO2). The analysis is extended to other forcing mechanisms with the Met Office Hadley Centre slab ocean climate model version 3 (HadSM3). In agreement with previous studies, the greatest intermodel differences are in the tropical cloud feedbacks. However, the greatest intermodel spread in the equilibrium temperature response comes from the water vapor plus lapse rate feedback, not clouds, disagreeing with a previous study. Although the surface albedo feedback contributes most in the annual mean to the greater warming of high latitudes, compared to the tropics (polar amplification), its effect is significantly ameliorated by shortwave cloud feedback. In different seasons the relative importance of the contributions varies considerably, with longwave cloudy-sky feedback and horizontal heat transport plus ocean heat release playing a major role during winter and autumn when polar amplification is greatest. The greatest intermodel spread in annual mean polar amplification is due to variations in horizontal heat transport and shortwave cloud feedback. Spatial patterns of local climate feedback for HadSM3 forced with 2 × CO2, 12% solar, low-level scattering aerosol and high-level absorbing aerosol are more similar than those for different models forced with 2 × CO2. However, the equilibrium temperature response to high-level absorbing aerosol shows considerably enhanced polar amplification compared to the other forcing mechanisms, largely due to differences in horizontal heat transport and water vapor plus lapse rate feedback, with the forcing itself acting to reduce amplification. Such variations in highlatitude response between models and forcing mechanisms make it difficult to infer specific causes of recent Arctic temperature change. © 2011 American Meteorological Society."
"12761291000;24512349100;26635870100;56283400100;","Analysis of the tropical climate variability in a two-column framework",2011,"10.1007/s00382-010-0864-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959794650&doi=10.1007%2fs00382-010-0864-5&partnerID=40&md5=3caa684c0ce5ba539900606b4ad7fa21","This work examines the relevance of a classical two-column modeling framework of the tropical climate in terms of observed natural variability. A method is developed to analyze the observed tropical climate in a simple framework that features a moist, ascending column and a dry, subsiding one. This method is used to analyze the natural variability of the tropical climate in the ERA40 reanalysis and in ISCCP satellite data. It appears that the seasonal cycle of the tropic-wide sea surface temperature (SST) is almost linearly linked to the seasonal cycle of the relative area of the moist regions, as predicted by the sensitivity of the two-column models. A more detailed analysis shows that this link is the product of a complex interaction and adjustments between the moist and dry regions. The seasonal cycle of low-cloud cover in the dry regions also appears to interact with the SST seasonal cycle: the low-cloud cover influences the tropic-wide SST via its direct radiative forcing on the local SST and it appears to be controlled by the SST difference between moist and dry regions. By contrast, the SST interannual variability appears to be driven by the El Niño Southern Oscillation (ENSO), with no significant impact from the changes in the relative area of the moist regions or in the low-cloud cover in the dry regions independently of the ENSO. ENSO-related changes in the area of moist regions and low-cloud cover constitute negative feedbacks on the ENSO-related SST variability. © 2010 Springer-Verlag."
"7407075213;6603034631;7006158951;55636317853;8648373900;","Bubble cloud depth under a hurricane",2011,"10.1029/2011GL047966","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960511737&doi=10.1029%2f2011GL047966&partnerID=40&md5=42072b38541d2d27ee160b3c5bfb2a1a","The bubble cloud depth and its correlation with extreme winds are key elements of bubble-mediated gas injection, which are critical to the determination of the global gas budgets. The characteristics of bubble cloud depth were examined from measurements collected during the passage of a category-4 hurricane with winds up to 50 m s-1. The bubble cloud depth increases linearly with wind speed for winds less than 35 m s -1. Our findings are consistent with previous observations at low to moderate wind speeds. However, the rate of increase is reduced significantly at winds higher than 35 m s-1. Copyright 2011 by the American Geophysical Union."
"6701752471;35611334800;7103271625;7103206141;7006306835;55286185400;","Sensitivity of the aerosol indirect effect to subgrid variability in the cloud parameterization of the GFDL atmosphere general circulation model AM3",2011,"10.1175/2010JCLI3945.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960302456&doi=10.1175%2f2010JCLI3945.1&partnerID=40&md5=7ca791880346d6d1d05bb79fde42f6db","The recently developed GFDL Atmospheric Model version 3 (AM3), an atmospheric general circulation model (GCM), incorporates a prognostic treatment of cloud drop number to simulate the aerosol indirect effect. Since cloud drop activation depends on cloud-scale vertical velocities, which are not reproduced in present-day GCMs, additional assumptions on the subgrid variability are required to implement a local activation parameterization into a GCM. This paper describes the subgrid activation assumptions in AM3 and explores sensitivities by constructing alternate configurations. These alternate model configurations exhibit only small differences in their present-day climatology. However, the total anthropogenic radiative flux perturbation (RFP) between present-day and preindustrial conditions varies by ±50% from the reference, because of a large difference in the magnitude of the aerosol indirect effect. The spread in RFP does not originate directly from the subgrid assumptions but indirectly through the cloud retuning necessary to maintain a realistic radiation balance. In particular, the paper shows a linear correlation between the choice of autoconversion threshold radius and the RFP. Climate sensitivity changes only minimally between the reference and alternate configurations. If implemented in a fully coupled model, these alternate configurations would therefore likely produce substantially different warming from preindustrial to present day. © 2011 American Meteorological Society."
"7103271625;8733579800;6701618837;7103206141;7006306835;55286185400;6701752471;57208462871;57208455668;35514163500;7402093416;42961002600;7102665209;6701379896;6603396333;7401477391;6603715895;7005808242;6508244744;7402064802;7003554208;57081464900;57054407300;25823927100;6603779823;7005884486;7006003831;56244473600;7103033590;57205867148;6603173671;56744278700;6603171355;8733579000;6508004743;7103366892;7101632204;57199296506;7003802133;6602864692;54382704000;","The dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component AM3 of the GFDL global coupled model CM3",2011,"10.1175/2011JCLI3955.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955044421&doi=10.1175%2f2011JCLI3955.1&partnerID=40&md5=67c12e311444a23337eabd4464ea18ec","The Geophysical Fluid Dynamics Laboratory (GFDL) has developed a coupled general circulation model (CM3) for the atmosphere, oceans, land, and sea ice. The goal of CM3 is to address emerging issues in climate change, including aerosol-cloud interactions, chemistry-climate interactions, and coupling between the troposphere and stratosphere. The model is also designed to serve as the physical system component of earth system models and models for decadal prediction in the near-term future-for example, through improved simulations in tropical land precipitation relative to earlier-generation GFDL models. This paper describes the dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component (AM3) of this model. Relative to GFDL AM2, AM3 includes new treatments of deep and shallow cumulus convection, cloud droplet activation by aerosols, subgrid variability of stratiform vertical velocities for droplet activation, and atmospheric chemistry driven by emissions with advective, convective, and turbulent transport. AM3 employs a cubed-sphere implementation of a finite-volume dynamical core and is coupled to LM3, a new land model with ecosystem dynamics and hydrology. Its horizontal resolution is approximately 200 km, and its vertical resolution ranges approximately from 70 m near the earth's surface to 1 to 1.5 km near the tropopause and 3 to 4 km in much of the stratosphere. Most basic circulation features in AM3 are simulated as realistically, or more so, as in AM2. In particular, dry biases have been reduced over South America. In coupled mode, the simulation of Arctic sea ice concentration has improved. AM3 aerosol optical depths, scattering properties, and surface clear-sky downward shortwave radiation are more realistic than in AM2. The simulation of marine stratocumulus decks remains problematic, as in AM2. The most intense 0.2% of precipitation rates occur less frequently in AM3 than observed. The last two decades of the twentieth century warm in CM3 by 0.328C relative to 1881-1920. The Climate Research Unit (CRU) and Goddard Institute for Space Studies analyses of observations show warming of 0.568 and 0.528C, respectively, over this period. CM3 includes anthropogenic cooling by aerosol-cloud interactions, and its warming by the late twentieth century is somewhat less realistic than in CM2.1, which warmed 0.668C but did not include aerosol-cloud interactions. The improved simulation of the direct aerosol effect (apparent in surface clear-sky downward radiation) in CM3 evidently acts in concert with its simulation of cloud-aerosol interactions to limit greenhouse gas warming. © 2011 American Meteorological Society."
"7403364008;25953950400;","A method for forecasting cloud condensation nuclei using predictions of aerosol physical and chemical properties from WRF/Chem",2011,"10.1175/2011JAMC2644.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960388815&doi=10.1175%2f2011JAMC2644.1&partnerID=40&md5=85dc032e888f8ee1b1923069762b2ff4","Model investigations of aerosol-cloud interactions across spatial scales are necessary to advance basic understanding of aerosol impacts on climate and the hydrological cycle. Yet these interactions are complex, involving numerous physical and chemical processes. Models capable of combining aerosol dynamics and chemistry with detailed cloud microphysics are recent developments. In this study, predictions of aerosol characteristics from the Weather Research and Forecasting Model with Chemistry (WRF/Chem) are integrated into the Regional Atmospheric Modeling System microphysics package to form the basis of a coupled model that is capable of predicting the evolution of atmospheric aerosols from gas-phase emissions to droplet activation. The new integrated system is evaluated against measurements of cloud condensation nuclei (CCN) from a land-based field campaign and an aircraft-based field campaign in Colorado. The model results show the ability to capture vertical variations in CCN number concentration within an anthropogenic pollution plume. In a remote continental location the model-forecast CCN number concentration exhibits a positive bias that is attributable in part to an overprediction of the aerosol hygroscopicity that results from an underprediction in the organic aerosol mass fraction. In general, the new system for predicting CCN from forecast aerosol fields improves on the existing scheme in which aerosol quantities were user prescribed. © 2011 American Meteorological Society."
"57217271893;16444324800;7004854393;7403635969;57212940867;21740519000;23011239800;","Frequency of sahelian storm initiation enhanced over mesoscale soil-moisture patterns",2011,"10.1038/ngeo1173","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959924790&doi=10.1038%2fngeo1173&partnerID=40&md5=282a883b139c80ead18a69139d7ef5d2","Evapotranspiration of soil moisture can affect temperature and humidity in the lower atmosphere, and thereby the development of convective rain storms. Climate models have illustrated the importance of soil-moisture-precipitation feedbacks for weekly rainfall totals in semi-arid regions, such as the Sahel. However, large variations exist between model feedbacks, and the mechanisms governing the strength and sign of the feedback are uncertain. Here, we use satellite observations of land surface temperatures and convective cloud cover over West Africa-collected during the wet seasons between 2006 and 2010-to determine the impact of soil moisture on rainfall in the Sahel. We show that variations in soil moisture on length scales of approximately 10-40 km exert a strong control on storm initiation-as evidenced by the appearance of convective cloud. The probability of convective initiation is doubled over strong soil-moisture gradients compared with that over uniform soil-moisture conditions. We find that 37% of all storm initiations analysed occurred over the steepest 25% of soil-moisture gradients. We conclude that heterogeneities in soil moisture on scales of tens of kilometres have a pronounced impact on rainfall in the Sahel, and suggest that similar processes may be important throughout the semi-arid tropics. © 2011 Macmillan Publishers Limited. All rights reserved."
"7103158465;7005035762;7004242319;6506385754;7005729142;","Snow microphysical observations in shallow mixed-phase and deep frontal Arctic cloud systems",2011,"10.1002/qj.840","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052536734&doi=10.1002%2fqj.840&partnerID=40&md5=728485164249742da8dff5d537565e19","Snow particle size distributions (particle size &gt;400 μm) in the western Arctic measured with in situ aircraft instrumentation during the Surface Heat Budget of the Arctic/First ISCCP Regional Experiment - Arctic Clouds Experiment and Mixed-Phase Arctic Cloud Experiment are analysed. Three cases of shallow, precipitating mixed-phase boundary-layer clouds and two cases of deep, precipitating frontal clouds are examined. Overall, the shallow cases had much lower values of particle concentration and ice water content than the deep cases, indicating large differences in ice initiation and growth between these regimes. Within a given case for both the shallow and deep frontal systems, and for the dataset as a whole, crystal concentration had little correlation with temperature (height), despite an active aggregation process that was indicated by large aggregates (&gt;5 mm) observed in four out of the five cases. Exponential size distributions are fitted to the observations, allowing a direct comparison with the snow particle size distributions that are represented with exponential functions in many bulk microphysics schemes used in weather and climate models. Values of the fitted intercept parameter N0 are generally 2-10 times smaller for the shallow compared to the deep frontal cases as a result of differences in crystal concentration between these regimes. Values of N0 ∼ 107 m-4 specified for snow in many bulk microphysics schemes are broadly consistent with fitted N0 for the deep cases but larger than values for the shallow cases. The deep frontal cases also exhibit a relationship between N0 and temperature consistent with previous observations of midlatitude frontal systems. However, there are no consistent differences in N0 between the shallow and deep cases when partitioned by ice water content. Fitted values of slope parameter λ for the shallow and deep cases are generally consistent with previous studies of lower-latitude cloud systems. © 2011 Royal Meteorological Society."
"7201443624;6506416205;8982748700;8946494600;7102805852;","Examination of long-wave radiative bias in general circulation models over North Africa during may-july",2011,"10.1002/qj.717","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960717020&doi=10.1002%2fqj.717&partnerID=40&md5=d496d74b9f694fac5bc919f61964bee9","Satellite data are used to quantify and examine the bias in the outgoing long-wave (LW) radiation over North Africa during May-July simulated by a range of climate models and the Met Office global numerical weather prediction (NWP) model. Simulations from an ensemble-mean of multiple climate models overestimate outgoing clear-sky long-wave radiation (LWc) by more than 20 W m-2 relative to observations from Clouds and the Earth's Radiant Energy System (CERES) for May-July 2000 over parts of the west Sahara, and by 9 W m-2 for the North Africa region (20°W-30°E, 10-40°N). Experiments with the atmosphere-only version of the High-resolution Hadley Centre Global Environment Model (HiGEM), suggest that including mineral dust radiative effects removes this bias. Furthermore, only by reducing surface temperature and emissivity by unrealistic amounts is it possible to explain the magnitude of the bias. Comparing simulations from the Met Office NWP model with satellite observations from Geostationary Earth Radiation Budget (GERB) instruments suggests that the model overestimates the LW by 20-40 W m-2 during North African summer. The bias declines over the period 2003-2008, although this is likely to relate to improvements in the model and inhomogeneity in the satellite time series. The bias in LWc coincides with high aerosol dust loading estimated from the Ozone Monitoring Instrument (OMI), including during the GERBILS field campaign (18-28 June 2007) where model overestimates in LWc greater than 20 W m-2 and OMI-estimated aerosol optical depth (AOD) greater than 0.8 are concurrent around 20°N, 0-20°W. A model-minus-GERB LW bias of around 30 W m-2 coincides with high AOD during the period 18-21 June 2007, although differences in cloud cover also impact the model-GERB differences. © Royal Meteorological Society and Crown, 2010."
"36069754700;57205303892;57205299261;56258514000;7102080550;6505772340;","Assimilation of Indian radar data with ADAS and 3DVAR techniques for simulation of a small-scale tropical cyclone using ARPS model",2011,"10.1007/s11069-010-9640-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958807439&doi=10.1007%2fs11069-010-9640-4&partnerID=40&md5=f11c441595c929da665648ae9b931905","The center for Analysis and Prediction of Storms (CAPS) has developed a radar data assimilation system. The system consists of several principal components: (1) a program that quality-controls and remaps (or super-ob) radar data to the analysis grid, (2) a Bratseth analysis method (ADAS), or a 3DVAR method for analyzing all the data except for clouds and precipitation, (3) a cloud and hydrometer analysis package that applies diabetic adjustments to the temperature field, and (4) a non-hydrostatic forecast model named ARPS. In this study, the system is applied to a small cyclone named OGNI, which formed over Bay of Bengal, India during the last week of October 2006. Three experiments are carried out to test the impact of the radar data from Chennai, India. These experiments include (1) using NCEP GFS data to initialize the ARPS model (2) using initial and boundary condition produced from the ADAS and the cloud analysis, (3) using initial and boundary condition produced from the 3DVAR and cloud analysis. The inter-comparison of results reveals that the experiment with the 3DVAR assimilation technique produces more realistic forecast to capture the genesis, structure, and northward movement of the cyclone in the short-range time scale. © 2010 Springer Science+Business Media B.V."
"56575686800;7201485519;35570389600;","The relationship between land-ocean surface temperature contrast and radiative forcing",2011,"10.1175/2011JCLI3893.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960337918&doi=10.1175%2f2011JCLI3893.1&partnerID=40&md5=528388dd38d958c7529e79e47b69daef","Previous work has demonstrated that observed and modeled climates show a near-time-invariant ratio of mean land to mean ocean surface temperature change under transient and equilibrium global warming. This study confirms this in a range of atmospheric models coupled to perturbed sea surface temperatures (SSTs), slab (thermodynamics only) oceans, and a fully coupled ocean. Away from equilibrium, it is found that the atmospheric processes that maintain the ratio cause a land-to-ocean heat transport anomaly that can be approximated using a two-box energy balance model. When climate is forced by increasing atmospheric CO2 concentration, the heat transport anomaly moves heat from land to ocean, constraining the land to warm in step with the ocean surface, despite the small heat capacity of the land. The heat transport anomaly is strongly related to the top-of-atmosphere radiative flux imbalance, and hence it tends to a small value as equilibrium is approached. In contrast, when climate is forced by prescribing changes in SSTs, the heat transport anomaly replaces ""missing"" radiative forcing over land by moving heat from ocean to land, warming the land surface. The heat transport anomaly remains substantial in steady state. These results are consistent with earlier studies that found that both land and ocean surface temperature changes may be approximated as local responses to global mean radiative forcing. The modeled heat transport anomaly has large impacts on surface heat fluxes but small impacts on precipitation, circulation, and cloud radiative forcing compared with the impacts of surface temperature change. No substantial nonlinearities are found in these atmospheric variables when the effects of forcing and surface temperature change are added. © 2011 American Meteorological Society."
"6701669739;35331137500;57211301037;6603768446;","A robust dual-frequency radar profiling algorithm",2011,"10.1175/2011JAMC2655.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960349753&doi=10.1175%2f2011JAMC2655.1&partnerID=40&md5=eb5a3cc992c24876eb48875cbf8d303f","In this study, an algorithm to retrieve precipitation from spaceborne dual-frequency (13.8 and 35.6 GHz, or Ku/Ka band) radar observations is formulated and investigated. Such algorithms will be of paramount importance in deriving radar-based and combined radar-radiometer precipitation estimates from observations provided by the forthcoming NASA Global Precipitation Measurement (GPM) mission. In GPM, dualfrequency Ku-/Ka-band radar observations will be available only within a narrow swath (approximately one-half of the width of the Ku-band radar swath) over the earth's surface. Therefore, a particular challenge is to develop a flexible radar retrieval algorithm that can be used to derive physically consistent precipitation profile estimates across the radar swath irrespective of the availability of Ka-band radar observations at any specific location inside that swath, in other words, an algorithm capable of exploiting the information provided by dual-frequency measurements but robust in the absence of Ka-band channel. In the present study, a unified, robust precipitation retrieval algorithm able to interpret either Ku-only or dual-frequency Ku-/Ka-band radar observations in a manner consistent with the information content of the observations is formulated. The formulation is based on 1) a generalized Hitschfeld-Bordan attenuation correction method that yields generic Ku-only precipitation profile estimates and 2) an optimization procedure that adjusts the Ku-band estimates to be physically consistent with coincident Ka-band reflectivity observations and surface reference technique-based path-integrated attenuation estimates at both Ku and Ka bands. The algorithm is investigated using synthetic and actual airborne radar observations collected in the NASA Tropical Composition, Cloud, and Climate Coupling (TC4) campaign. In the synthetic data investigation, the dual-frequency algorithm performed significantly better than a single-frequency algorithm; dual-frequency estimates, however, are still sensitive to various assumptions such as the particle size distribution shape, vertical and cloud water distributions, and scattering properties of the ice-phase precipitation. © 2011 American Meteorological Society."
"56055143800;55703589700;35744799500;","Where have all the showers gone? Regional declines in light precipitation events in China, 1960-2000",2011,"10.1002/joc.2144","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251487601&doi=10.1002%2fjoc.2144&partnerID=40&md5=33ce4ee28f26cf7648ca916178c62f89","China has seen a decline in recorded precipitation events over 1960-2000. We find that this decline is mainly accounted for by the decrease of light precipitation events, those with intensities of 0.1-0.3 mm/day. The annual number of light precipitation events drops off remarkably around 1978 and decreases rapidly until 1985. Trace precipitation events (precipitation noted but measuring < 0.1 mm/day) decrease abruptly from 1982 through the end of the period. Meanwhile, the annual frequency of precipitation events with intensities above 0.3 mm/day shows almost no change for the same period. The analysis uses daily data from 272 stations distributed across China. We note regional and seasonal differences in the rates of change of different intensities of precipitation events. With almost no change in the frequency of precipitation events of 0.4-0.6 and 0.7-0.9 mm/day during the same period, it is difficult to attribute the abrupt decreases to inhomogeneities of the precipitation data. The temporal pattern of light precipitation events is similar to those observed for solar irradiance and total cloud cover, suggesting that there may be some connections between these climatic variables. Declines in solar irradiance and total cloud cover along with increased aerosol loading may have contributed to the abrupt decrease of these light precipitation events. However, light and trace precipitation events display different spatial and temporal patterns of change, complicating this explanation. © 2010 Royal Meteorological Society."
"36627288300;6603618077;16032479400;36598281300;24921885300;","Clouds in the atmospheres of extrasolar planets: II. Thermal emission spectra of Earth-like planets influenced by low and high-level clouds",2011,"10.1051/0004-6361/201014343","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958776643&doi=10.1051%2f0004-6361%2f201014343&partnerID=40&md5=ca220499a12cc20a6e91b673b433fb8b","Aims. We study the impact of multi-layered clouds (low-level water and high-level ice clouds) on the thermal emission spectra of Earth-like planets orbiting different types of stars. Clouds have an important influence on such planetary emission spectra due to their wavelength dependent absorption and scattering properties. We also investigate the influence of clouds on the ability to derive information about planetary surface temperatures from low-resolution spectra. Methods. We use a previously developed parametric cloud model based on observations in the Earth's atmosphere, coupled to a one-dimensional radiative-convective steady state climate model. This model is applied here to study the effect of clouds on the thermal emission spectra of Earth-like extrasolar planets in dependence of the type of central star. Results. The presence of clouds lead in general to a decrease of the planetary IR spectrum associated with the dampening of spectral absorption features such as the 9.6 μm absorption band of O3 for example. This dampening is not limited to absorption features originating below the cloud layers but was also found for features forming above the clouds. When only single cloud layers are considered, both cloud types exhibit basically the same effects on the spectrum but the underlying physical processes are clearly different. For model scenarios where multi-layered clouds have been considered with coverages which yield mean Earth surface temperatures, the low-level clouds have only a small influence on the thermal emission spectra. In these cases the major differences are caused by high-level ice clouds. The largest effect was found for a planet orbiting the F-type star, where no absorption features can be distinguished in the low-resolution emission spectrum for high cloud coverages. However, for most central stars, planetary atmospheric absorption bands are present even at high cloud coverages. Clouds also affect the derivation of surface temperatures from low-resolution spectra when fitting black-body radiation curves to the spectral shape of the IR emission spectra. With increasing amount of high-level clouds the derived temperatures increasingly under-estimate the real planetary surface temperatures. Consequently, clouds can alter significantly the measured apparent temperature of a planet as well as the detectability of the characteristic spectral signatures in the infrared. Therefore, planets with observationally derived somewhat lower surface temperatures should not be discarded too quickly from the list of potential habitable planets before further investigations on the presence of clouds have been made. © 2011 ESO."
"57213947466;56158622800;7006783796;57199033967;24337553400;","Comparison of CERES surface radiation fluxes with surface observations over Loess Plateau",2011,"10.1016/j.rse.2011.02.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953186422&doi=10.1016%2fj.rse.2011.02.008&partnerID=40&md5=32cab5f53b2acd73cc22dcccab6a0a46","Surface energy budget is an important factor in weather and climate processes. To estimate the errors in satellite-retrieved surface radiation budget over the interior of China, instantaneous-footprint surface radiation fluxes from the Terra/Aqua FLASHFlux SSF product are compared with the measurements taken at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) from July 2008 to March 2010. Validation is performed separately for different conditions: clear-sky and cloudy-sky, daytime and nighttime for four seasons. Differences between the FLASHFlux CERES shortwave radiation flux and surface measurements have larger standard deviations in cloudy-sky conditions than in clear-sky conditions, indicating that cloud contamination increases uncertainty in the retrieval algorithm. Upward shortwave radiation flux (USW) is overestimated in cloudy conditions suggesting that the cloud parameters and surface scene type in the retrieval process are not optimal for northwestern China. The CERES downward longwave radiation fluxes (DLW) accurately follow the variation of surface measurements during daytime, but are slightly underestimated during nighttime due to the coarse sounding profile and undetected low clouds at nighttime. The CERES upwelling longwave radiation fluxes (ULW) are strongly underestimated during daytime but are slightly underestimated during nighttime regardless of cloud coverage. This large bias could be caused by an underestimate of surface skin temperature and/or surface emissivity, or spatial inhomogeneity around the site. Generally, except for diurnal ULW, other components of the surface radiative fluxes obtained from CERES SSF datasets are close to meeting the accuracy requirements for climate research. © 2011 Elsevier Inc."
"35615548300;","The influence of atmospheric water clusters and halogen ions on ozone depletion",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958101857&partnerID=40&md5=5181a2ca4577b13aac479aea7a0a4ae5","Today, many signs point at the beginning of a global climate change which will have a severe impact on our earth. The global increase of tropospheric ozone also contributes to this phenomenon. At the same time depletion of stratospheric ozone layer is observed. Absorption of O3 and O 2 molecules by (H2O)50 cluster is investigated at its interaction with Cl- and Br- ions. More massive Br- ions are kept in water clusters much longer, than Cl- ions, allowing addition of ozone molecules to cluster. At the same time absorption of oxygen molecules, as a rule, leads to evaporation of part of Br- ions from the cluster and to a loss of some oxygen molecules from its environment. With absorbed ozone the intensity of infra-red (IR) absorption spectra of clusters decreases and with absorbed oxygen it increases as the number of Cl- ions grows. When Br- ions are present in the system, the opposite behaviour is observed. © 2011 Nova Science Publishers, Inc."
"9332706900;56333104300;8586682800;6603172418;7006837187;","Influences on the fraction of hydrophobic and hydrophilic black carbon in the atmosphere",2011,"10.5194/acp-11-5099-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957966427&doi=10.5194%2facp-11-5099-2011&partnerID=40&md5=11e1c5e908d911ed08ebadcb44b0aa9e","Black carbon (BC) is a short term climate forcer that directly warms the atmosphere, slows convection, and hinders quantification of the effect of greenhouse gases on climate change. The atmospheric lifetime of BC particles with respect to nucleation scavenging in clouds is controlled by their ability to serve as cloud condensation nuclei (CCN). To serve as CCN under typical conditions, hydrophobic BC particles must acquire hygroscopic coatings. However, the quantitative relationship between coatings and hygroscopic properties for ambient BC particles is not known nor is the time scale for hydrophobic-to- hydrophilic conversion. Here we introduce a method for measuring the hygroscopicity of externally and internally mixed BC particles by coupling a single particle soot photometer with a humidified tandem differential mobility analyzer. We test this technique using uncoated and coated laboratory generated model BC compounds and apply it to characterize the hygroscopicity distribution of ambient BC particles. From these data we derive that the observed number fraction of BC that is CCN active at 0.2 % supersaturation is generally low in an urban area near sources and that it varies with the trajectory of the airmass. We anticipate that our method can be combined with measures of air parcel physical and photochemical age to provide the first quantitative estimates for characterizing hydrophobic-to-hydrophilic conversion rates in the atmosphere. © 2011 Author(s)."
"7003543851;7006354215;","The vertical distribution of cloud feedback in coupled ocean-atmosphere models",2011,"10.1029/2011GL047632","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959689422&doi=10.1029%2f2011GL047632&partnerID=40&md5=acbd8cb5878431508b52c741b6893918","We assess the vertical distribution of cloud feedbacks in coupled climate models, taking care to distinguish between cloud feedbacks and a change in cloud forcing. We show that the effect of cloud changes on the longwave fluxes provides a strong positive feedback that is broadly consistent across models. In contrast, the effect of cloud changes on the shortwave fluxes ranges from a modest negative to a strong positive feedback, and is responsible for most of the intermodel spread in net cloud feedback. The feedback from high clouds is positive in all models, and is consistent with that anticipated by the Proportionately Higher Anvil Temperature hypothesis over the tropics. In contrast, low cloud cover is responsible for roughly three-quarters of the difference in global mean net cloud feedback among models, with the largest contributions from regions associated with low-level subtropical marine cloud systems. Copyright 2011 by the American Geophysical Union."
"8397494800;25941200000;7004364155;6603613067;","Assessing simulated clouds and radiative fluxes using properties of clouds whose tops are exposed to space",2011,"10.1175/2011JCLI3652.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959337703&doi=10.1175%2f2011JCLI3652.1&partnerID=40&md5=aa69e1f116786407cabdd9085cf07fa8","Coincident top-of-atmosphere (TOA) radiative fluxes and cloud optical properties for portions of clouds whose tops are exposed to space within several pressure ranges are used to evaluate how a GCM realizes its all-sky radiative fluxes and vertical structure. In particular, observations of cloud properties and radiative fluxes from the Clouds and the Earth's Radiant Energy System (CERES) Science Team are used to assess the Canadian Centre for Climate Modeling and Analysis atmospheric global climate model (CanAM4). Through comparison of CanAM4 with CERES observations it was found that, while the July-mean all-sky TOA shortwave and longwave fluxes simulated by CanAM4 agree well with those observed, this agreement rests on compensating biases in simulated cloud properties and radiative fluxes for low, middle, and high clouds. Namely, low and middle cloud albedos simulated by CanAM4 are larger than those observed by CERES attributable to CanAM4 simulating cloud optical depths via large liquid water paths that are too large but are partly compensated by too small cloud fractions. It was also found that CanAM4 produces 2D histograms of cloud fraction and cloud albedo for low, middle, and high clouds that are significantly different than generated using the CERES observations. © 2011 American Meteorological Society."
"12769875100;7006738324;26324818700;","Geographical distribution of climate feedbacks in the NCAR CCSM3.0",2011,"10.1175/2010JCLI3788.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959340766&doi=10.1175%2f2010JCLI3788.1&partnerID=40&md5=62b85407261e599955f80662374b408e","This study performs offline, partial radiative perturbation calculations to determine the geographical distributions of climate feedbacks contributing to the top-of-atmosphere (TOA) radiative energy budget. These radiative perturbations are diagnosed using monthly mean model output from the NCAR Community Climate System Model version 3 (CCSM3.0) forced with the Special Report Emissions Scenario (SRES) A1B emission scenario. The Monte Carlo Independent Column Approximation (MCICA) technique with a maximum-random overlap rule is used to sample monthly mean cloud frequency profiles to perform the radiative transfer calculations. It is shown that the MCICAtechnique provides a good estimate of all feedback sensitivity parameters. The radiative perturbation results are used to investigate the spatial variability of model feedbacks showing that the shortwave cloud and lapse rate feedbacks exhibit the most and second most spatial variability, respectively. It has been shown that the model surface temperature response is highly correlated with the change in the TOA net flux, and that the latter is largely determined by the total feedback spatial pattern rather than the external forcing. It is shown by representing the change in the TOA net flux as a linear combination of individual feedback radiative perturbations that the lapse rate explains the most spatial variance of the surface temperature response. Feedback spatial patterns are correlated with the model response and other feedback spatial patterns to investigate these relationships. The results indicate that the model convective response is strongly correlated with cloud and water vapor feedbacks, but the lapse rate feedback geographic distribution is strongly correlated with the climatological distribution of convection. The implication for the water vapor-lapse rate anticorrelation is discussed. © 2011 American Meteorological Society."
"56272964700;15124698700;8043701900;","Intensification of precipitation extremes with warming in a cloud-resolving model",2011,"10.1175/2011JCLI3876.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251510318&doi=10.1175%2f2011JCLI3876.1&partnerID=40&md5=497199fd78d46323e062da380c1c9d13","A cloud-resolving model is used to investigate the effect of warming on high percentiles of precipitation (precipitation extremes) in the idealized setting of radiative-convective equilibrium.While this idealized setting does not allow for several factors that influence precipitation in the tropics, it does allow for an evaluation of the response of precipitation extremes to warming in simulations with resolved rather than parameterized convection. The methodology developed should also be applicable to less idealized simulations. Modeled precipitation extremes are found to increase in magnitude in response to an increase in sea surface temperature. A dry static energy budget is used to relate the changes in precipitation extremes to changes in atmospheric temperature, vertical velocity, and precipitation efficiency. To first order, the changes in precipitation extremes are captured by changes in the mean temperature structure of the atmosphere. Changes in vertical velocities play a secondary role and tend to weaken the strength of precipitation extremes, despite an intensification of updraft velocities in the upper troposphere. The influence of changes in condensate transports on precipitation extremes is quantified in terms of a precipitation efficiency; it does not change greatly with warming. Tropical precipitation extremes have previously been found to increase at a greater fractional rate than the amount of atmospheric water vapor in observations of present-day variability and in some climate model simulations with parameterized convection. But the fractional increases in precipitation extremes in the cloud-resolving simulations are comparable in magnitude to those in surface water vapor concentrations (owing to a partial cancellation between dynamical and thermodynamical changes), and are substantially less than the fractional increases in column water vapor. © 2011 American Meteorological Society."
"26665643500;23082420800;7003922138;42661269900;","Climate feedbacks in response to changes in obliquity",2011,"10.1175/2010JCLI3986.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959330860&doi=10.1175%2f2010JCLI3986.1&partnerID=40&md5=2d95be62d1fb10b777bf52504e4cee3b","The feedbacks involved in the response of climate to a reduction of Earth's obliquity are investigated in the GFDL Climate Model version 2.1 (CM2.1). A reduction in obliquity increases the meridional gradient of the annual mean insolation, causing a strengthening of the atmospheric and ocean circulation that transports more heat poleward. The heat transport does not balance the direct obliquity forcing completely, and additional local radiative fluxes are required to explain the change in the equilibriumenergy budget. The surface temperature generally increases at low latitudes and decreases at high latitudes following the change in the insolation. However, in some areas, the sign of the temperature change is opposite of the forcing, indicating the strong influence of feedbacks. These feedbacks are also responsible for a decrease in the global mean temperature despite that the change in the global mean insolation is close to zero. The processes responsible for these changes are increases in the ice fraction at high latitudes and the global cloud fraction-both of which reduce the absorbed solar radiation. A reduction in the global greenhouse trapping, due to changes in the distribution of the water vapor content of the atmosphere as well as a change in the lapse rate, has an additional cooling effect. Among these feedbacks, clouds and the lapse rate have the larger contribution, with water vapor and surface albedo having a smaller effect. The implications of the findings presented here for interpretation of obliquity cycles in the paleoclimate record are discussed. © 2011 American Meteorological Society."
"7004944088;55684491100;36105949100;36106033000;35998927000;7006211890;42361292700;55878983900;7006212411;","Extinction and optical depth of contrails",2011,"10.1029/2011GL047189","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958816400&doi=10.1029%2f2011GL047189&partnerID=40&md5=9f0a08ffb1ca28f63126a717cac5d9f5","One factor limiting the understanding of the climate impact from contrails and aircraft induced cloud modifications is the accurate determination of their optical depth. To this end, 14 contrails were sampled for 2756 s with instruments onboard the research aircraft Falcon during the CONCERT (CONtrail and Cirrus ExpeRimenT) campaign in November 2008. The young (<10 min old) contrails were produced by 9 commercial aircraft with weights of 47 to 508 t, among them the largest operating passenger aircraft, the Airbus A380. The contrails were observed at temperatures between 214 and 224 K and altitudes between 8.8 and 11.1 km. The measured mean in-contrail relative humidity with respect to ice was 89 12%. Six contrails were observed in cloud free air, the others were embedded in thin cirrus clouds. The observed contrails exhibited a mean ice water content of 2 mg m-3 and had a mean number concentration of 117 cm-3 and effective radius of 2.9 m assuming asphericle particles with an aspect ratio of 0.5. Probability density functions of the extinction, with a mean (median) of 1.2 (0.7) km-1, and of the optical depth, with a mean (median) of 0.27 (0.13), are derived from the in situ measurements and are likely representative for young contrails from the present-day commercial aircraft fleet at observation conditions. Radiative transfer estimates using the in-situ measured contrail optical depth lead to a year-2005 estimate of line-shaped contrail radiative forcing of 15.9 mWm -2 with an uncertainty range of 11.1-47.7 mWm-2. Copyright © 2011 by the American Geophysical Union."
"6602890419;14627943600;13407014000;6701822254;6507937564;36089471100;57197060370;37050693200;20435050000;","225 years of Bering Sea climate and ecosystem dynamics revealed by coralline algal growth-increment widths",2011,"10.1130/G31996.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959236480&doi=10.1130%2fG31996.1&partnerID=40&md5=c8d966a6d58c32a8863df54b13b4cbbb","Bering Sea climate and ecosystem dynamics have recently undergone major changes that have affected seasonal sea ice distribution and marine life, including commercially important salmon fi sheries. Unfortunately, long-term Bering Sea dynamics are poorly understood, largely because of an absence of high-resolution marine proxy archives. Here we present the fi rst record compiled from annual growth-increment widths of long-lived coralline algae collected in shallow-water habitats spanning the entire Aleutian Islands. While algal growth in the Aleutians exhibits a variable relationship with regional temperatures, it is strongly driven by changes in solar radiation reaching the seafl oor. Therefore, it provides an exceptional archive of long-term light dynamics, which in the Bering Sea is attributed to changes in strength of the Aleutian Low (AL), the dominant climate pattern of the subarctic North Pacifi c. The AL is positively related to Bering Sea cloudiness and wind strength, which in turn fosters upper-ocean mixing. Mixing raises surfacewater nutrient concentrations and stimulates plankton production, which is positively linked to Alaskan salmon abundance. Enhanced clouds and plankton production increase shading on the shallow seafl oor and reduce algal growth. Light-driven algal growth rates track proxy-derived salmon abundance from 1782 onward, but are poorly related to temperature-dominated Pacifi c Decadal Oscillation (PDO) variability prior to the twentieth century. The algal record suggests that the present-day relationship of AL and PDO varied historically and that salmon stocks have been more closely related to AL strength via its effect on plankton abundance rather than PDO-related temperatures. © 2011 Geological Society of America."
"56249704400;22978151200;57193132723;12240390300;7203040996;7201837768;36705143500;7006550762;6604021707;35561911800;7004214645;","Coupled aerosol-chemistry-climate twentieth-century transient model investigation: Trends in short-lived species and climate responses",2011,"10.1175/2011JCLI3582.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959360924&doi=10.1175%2f2011JCLI3582.1&partnerID=40&md5=3884103db7d1e7307258655962c628a9","The authors simulate transient twentieth-century climate in the Goddard Institute for Space Studies (GISS) GCM, with aerosol and ozone chemistry fully coupled to one another and to climate including a full dynamic ocean. Aerosols include sulfate, black carbon (BC), organic carbon, nitrate, sea salt, and dust. Direct and BCsnow-albedo radiative effects are included. Model BC and sulfur trends agree fairly well with records from Greenland and European ice cores and with sulfur deposition in North America; however, the model underestimates the sulfur decline at the end of the century in Greenland. Global BC effects peak early in the century (1940s); afterward the BC effects decrease at high latitudes of the Northern Hemisphere but continue to increase at lower latitudes. The largest increase in aerosol optical depth occurs in the middle of the century (1940s-80s) when sulfate forcing peaks and causes global dimming. After this, aerosols decrease in eastern North America and northern Eurasia leading to regional positive forcing changes and brightening. These surface forcing changes have the correct trend but are too weak. Over the century, the net aerosol direct effect is 20.41 W m-2, the BC-albedo effect is 20.02 W m-2, and the net ozone forcing is 10.24 W m-2. Themodel polar stratospheric ozone depletion develops, beginning in the 1970s. Concurrently, the sea salt load and negative radiative flux increase over the oceans around Antarctica. Net warming over the century is modeled fairlywell; however, the model fails to capture the dynamics of the observedmidcentury cooling followed by the late century warming.Over the century, 20%ofArcticwarming and snow-ice cover loss is attributed to the BCalbedo effect. However, the decrease in this effect at the end of the century contributes to Arctic cooling. To test the climate responses to sulfate and BC pollution, two experiments were branched from 1970 that removed all pollution sulfate or BC. Averaged over 1970-2000, the respective radiative forcings relative to the full experiment were 10.3 and 20.3 W m-2; the average surface air temperature changes were +0.2° and -0.03°C. The small impact of BC reduction on surface temperature resulted from reduced stability and loss of low-level clouds. © 2011 American Meteorological Society."
"8248685800;6602077162;","New geostationary satellite-based snow-cover algorithm",2011,"10.1175/2010JAMC2568.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960236978&doi=10.1175%2f2010JAMC2568.1&partnerID=40&md5=f8d94ad76b822289b489e4c2ccf23d9d","Snow cover plays an important role in the climate system by changing the energy and mass transfer between the atmosphere and the surface. Reliable observations of the snow cover are difficult to obtain without satellites. This paper introduces a new algorithm for satellite-based snow-cover detection that is in operational use for Meteosat in the European Organisation for the Exploitation of Meteorological Satellites Satellite Application Facility on Land Surface Analysis (LSA SAF). The new version of the product is compared with the old version and the NOAA/National Environmental Satellite, Data, and Information Service Interactive Multisensor Snow and Ice Mapping System (IMS) snow-cover product. The new version of the LSA SAF snow-cover product improves the accuracy of snow detection and is comparable to the IMS product in cloud-free conditions. © 2011 American Meteorological Society."
"8625649800;36185521100;6701341272;55478675400;","A cloud-resolving 4DVAR assimilation experiment for a local heavy rainfall event in the Tokyo metropolitan area",2011,"10.1175/2011MWR3428.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959589979&doi=10.1175%2f2011MWR3428.1&partnerID=40&md5=2def9675cbf9b6a937aa21bd4577377f","A cloud-resolving nonhydrostatic four-dimensional variational data assimilation system (NHM-4DVAR) was modified to directly assimilate radar reflectivity and applied to a data assimilation experiment using actual observations of a heavy rainfall event. Modifications included development of an adjoint model of the warm rain process, extension of control variables, and development of an observation operator for radar reflectivity. The responses of the modified NHM-4DVAR were confirmed by single-observation assimilation experiments for an isolated deep convection, using pseudo-observations of rainwater at the initial and end times of the data assimilation window. The results showed that the intensity of convection could be adjusted by assimilating appropriate observations of rainwater near the convection and that undesirable convection could be suppressed by assimilating small or no reflectivity. An assimilation experiment using actual observations of a local heavy rainfall in the Tokyo, Japan, metropolitan area was conducted with a horizontal resolution of 2 km. Precipitable water vapor derived from global positioning system data was assimilated at 5-min intervals within 30-min assimilation windows, and surface and wind profiler data were assimilated at 10-min intervals. Doppler radial wind and radar-reflectivity data below the elevation angle of 5.4° were assimilated at 1-min intervals. The 4DVAR assimilation reproduced a line-shaped rainband with a shape and intensity consistent with the observation. Assimilation of radar-reflectivity data intensified the rainband and suppressed false convection. The simulated rainband lasted for 1 h in the extended forecast and then gradually decayed. Sustaining the low-level convergence produced by northerly winds in the western part of the rainband was key to prolonging the predictability of the convective system. © 2011 American Meteorological Society."
"6506956530;6504536362;7003739558;6602805181;6603262933;6602135743;","Atmospheric aerosol characterization in 2010 anomalous summer season in the Moscow region",2011,"10.3103/S106837391106001X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960467522&doi=10.3103%2fS106837391106001X&partnerID=40&md5=a2412579696e952307541db42ca41818","Daily measurements of atmospheric aerosol characteristics were carried out in Dolgoprudny (Moscow region) in June-August 2010. The particle concentrations at 11 size gradations within the range of 0.01-10 μm and the concentrations of cloud condensation nuclei active at water vapor supersaturation of 0.2-1% were determined. It is shown that the long anticyclonic conditions and the burning of forests and peat bogs resulted in the increase in total aerosol concentration in surface air by more than 1.5 times and in concentrations of particles with the diameter of 0.1-1 μm and > 1 μm by 5 and 10 times, respectively. The fire smoke mainly consisted of the particles with the size of 0.1-3 μm. The particles with the size of more than 5 μm were not observed. The recurrent visibility decrease up to hundreds of meters was caused by the increase in the concentration of particles with the diameter of more than 0.32μm in the air. During the smoke blanketing, the concentration of active condensation nuclei in aerosol increased almost by 20 times that created an opportunity for watering of aerosol particles and formation of the acid smog. © 2011 Allerton Press, Inc."
"49961189200;6603089483;","Strategies for incorporating high-resolution google earth databases to guide and validate classifications: Understanding deforestation in Borneo",2011,"10.3390/rs3061157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052543763&doi=10.3390%2frs3061157&partnerID=40&md5=b68111846f0acae05fc7ab1a56aa1d3c","International climate change mitigation initiatives such as REDD-plus have fuelled the need for forest monitoring efforts that focus especially on the carbon rich natural ecosystems that are found in the humid tropics. Such monitoring efforts must tackle challenges intrinsic to these regions, such as high atmospheric contamination from particulates and persistent cloud cover. The emergence of new high-resolution platforms like Google Earth offers new potential scientific uses that can help meet these challenges. Using data from MODIS and detailed observation of Google Earth images, we have produced a yearly time series of deforestation hotspots for the island of Borneo for the 2000 to 2009 period. Our workflow and results demonstrate how multiple free data sources can be combined to greatly enhance the individual capacities of each. The methodology employed to produce this time series demonstrates simple, low-expense techniques that can be used to circumvent the obstacles that typically hinder systematic remote sensing in Borneo and other heavily clouded areas. © 2011 by the authors."
"7202202734;","Dynamics of the tropopause for the cases of sharp changes in total ozone at the midlatitudes of the northern hemisphere",2011,"10.3103/S1068373911060021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960468563&doi=10.3103%2fS1068373911060021&partnerID=40&md5=5af426052a695d30cf0cc2bfdd6c0919","Analysis is presented of height changes of the tropopause as approximated by the level of 3.5 pvu of vertical component of Ertel potential vorticity, for the cases of sharp (exceeding 100 DU per day) changes in total ozone (TO) on the basis of a special series of synchronous values of the tropopause characteristics and TO at the 1 × 1° grid within 30°-70°N latitude belt in 2009. Occurrence frequency of the cases is estimated depending on latitude and longitude. It is shown that sharp increase (decrease) in TO is unambiguously associated with decreasing (increasing) tropopause height, regardless of its oscillations during the day. Separate cases of sharp TO changes are studied, and changes in the tropopause characteristics are quantitatively specified. © 2011 Allerton Press, Inc."
"8512338600;56746732000;7202652532;24178270500;35146408200;55660726400;","Monitoring canopy phenology in a deciduous broadleaf forest using the Phenological Eyes Network (PEN)",2011,"10.5141/JEFB.2011.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960298860&doi=10.5141%2fJEFB.2011.017&partnerID=40&md5=863218a9d3b0fdb9b386f14054723dc8","Phenological variables derived from remote sensing are useful in determining the seasonal cycles of ecosystems in a changing climate. Satellite remote sensing imagery is useful for the spatial continuous monitoring of vegetation phenology across broad regions; however, its applications are substantially constrained by atmospheric disturbances such as clouds, dusts, and aerosols. By way of contrast, a tower-based ground remote sensing approach at the canopy level can provide continuous information on canopy phenology at finer spatial and temporal scales, regardless of atmospheric conditions. In this study, a tower-based ground remote sensing system, called the ""Phenological Eyes Network (PEN)"", which was installed at the Gwangneung Deciduous KoFlux (GDK) flux tower site in Korea was introduced, and daily phenological progressions at the canopy level were assessed using ratios of red, green, and blue (RGB) spectral reflectances obtained by the PEN system. The PEN system at the GDK site consists of an automatic-capturing digital fisheye camera and a hemi-spherical spectroradiometer, and monitors stand canopy phenology on an hourly basis. RGB data analyses conducted between late March and early December in 2009 revealed that the 2G_RB (i.e., 2G - R - B) index was lower than the G/R (i.e., G divided by R) index during the off-growing season, owing to the effects of surface reflectance, including soil and snow effects. The results of comparisons between the daily PEN-obtained RGB ratios and daily moderate-resolution imaging spectroradiometer (MODIS)-driven vegetation indices demonstrate that ground remote sensing data, including the PEN data, can help to improve cloud-contaminated satellite remote sensing imagery. © The Ecological Society of Korea."
"6602675795;6506393061;","Analysis of tourism potential for Crete Island, Greece",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856550911&partnerID=40&md5=44c3ea35314d6ac1adebce336173449a","To describe the tourism potential of an area, not only single meteorological parameters have to be taken into account, but also thermal sensation and people's thermal comfort. The latter can be estimated by the use of human energy balance models and the derived thermal indices, which comprise all relevant meteorological parameters like air temperature, air humidity, wind speed, and short and long wave radiation fluxes. This paper makes an attempt to assess and analyze climatological parameters and the thermal comfort of Crete, its variations and trends for the period of time 1955-2001. In addition, a definition and quantification of the island's tourism potential is carried out. Long term data from several stations are used from the existing climatic and synoptic network of Crete, including daily mean, maximum and minimum temperature, relative humidity, wind speed, and cloud cover over the whole island, in order to derive the daily Physiologically Equivalent Temperature (PET) and precipitation. In addition, possible trends of thermal comfort and precipitation on an annual and seasonal basis are analyzed. Additionally, data of the 10-minutes climatology of the Climate Research Unit of the University of Norwich have been processed in order to create high resolution (1 km) mean monthly maps for climatological parameters such as air temperature, precipitation and Physiologically Equivalent Temperature. © 2011 Global NEST Printed in Greece. All rights reserved."
"8642592500;7005052420;","Estimation of net radiation from the moderate resolution imaging spectroradiometer over the continental united states",2011,"10.1109/TGRS.2010.2096227","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957660456&doi=10.1109%2fTGRS.2010.2096227&partnerID=40&md5=66761826aacb5f6df76e5e99a7a955a8","Net radiation, at the Earth's surface, is a key variable of interest in fields such as hydrology, climate research, and agriculture. Retrieval algorithms for estimation of the surface radiation budget (SRB) from remote sensing data generally suffer from two major shortcomings: difficulty in dealing with cloudy-sky conditions and reliance on study-site specific ancillary ground data. In this paper, we use the methodology of Bisht and Bras (BB10) to estimate SRB and its components, using only remote sensing data under all sky conditions. The BB10 framework is applied over seven sites of the Surface Radiation Budget network in the CONtinental United States (CONUS), along with 21 sites of the Atmospheric Radiation Measurement program in the Southern Great Plains. The data from both the Aqua and Terra satellites are used for entire 2006. The study examines instantaneous upwelling and downwelling shortwave, longwave, net shortwave, and net radiations, as well as daily average net shortwave and net radiations. The root-mean-square errors of estimated daily average net radiation and daily average net shortwave radiation when compared to ground observations are 52.42 and 52.21 Ẇ-2, respectively. An example of the retrieved instantaneous and daily average net radiation is also presented, which highlights the limitation of using only polar-orbiting satellite data in estimating the diurnal cycle of net radiation. Two adaptations to the algorithm are presented that make the production of SRB estimates over the CONUS feasible. Finally, the methodology is applied to produce daily SRB maps for the CONUS, and monthly SRB maps are presented. © 2011 IEEE."
"7401992736;6506879217;56730491100;38461694000;38461787400;38461607300;15049168200;8663124300;","High-resolution carbon and oxygen isotope records from a scleractinian (Porites) coral of Lakshadweep Archipelago",2011,"10.1016/j.quaint.2009.11.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955708741&doi=10.1016%2fj.quaint.2009.11.020&partnerID=40&md5=55207830c69fc832b9d0accd783c6578","A 17-year-long δ13C and δ18O record from a scleractinian coral (Porites spp.) of Bangaram island (Lakshadweep Archipelago) is based on a nearly-monthly sample interval. This live coral head of Porites spp. was recovered from the lagoon of Bangaram (Lakshadweep) island at ∼20m water-depth. The skeletal δ13C and δ18O values varied approximately in phase and exhibit a positive relationship with each other. High-density (monsoon) bands are characterized by enriched δ18O values and low-density (non-monsoon) bands by depleted δ18O values. Coral δ13C and δ18O primarily reflects local oceanographic and climatic variability. The high-density bands were formed during the southwest monsoon (June-September) because of increased turbidity and cloud cover, whereas low-density bands were deposited during the non-monsoon months (October-May). Temporal changes in coral-derived sea surface temperature (SST) show a good agreement with instrumental SST record. The δ18O values in monsoon and non-monsoon bands are mainly due to the sea surface temperature (SST) changes, controlled by monsoon-induced upwelling and insolation changes. Coral-derived SST values clearly show warming events during summer 1993 and 1998. Spectral analysis of δ18O data reveals a teleconnection between the local SST and tropical Pacific climate variability. Enriched δ18O values for the monsoon months of 1984, 1985, 1993 and 1997 are probably indicative of cooler surface water due to the stronger upwelling at the studied location.Generally higher δ13C values correlate with enriched δ18O values of the monsoon bands. This increase in δ13C during the southwest monsoon months is attributed to a decrease in endosymbiotic photosynthesis. Alternatively, an increase in biological production, due to monsoon-induced upwelling, may have resulted in the δ13C enrichment of dissolved inorganic carbon (DIC) in surface waters. However, other possibilities, such as higher δ13C values due to coral mass-spawning events during monsoon times cannot be ruled out. A progressive decrease of ∼0.5‰ in δ13C from 1985 to 2001 may be due to the changes in photosynthesis and/or changing food habits from autotrophy to heterotrophy as the coral grew in size. © 2009 Elsevier Ltd and INQUA."
"36098762900;6603196127;7005093524;7003928455;","Habitable zone limits for dry planets",2011,"10.1089/ast.2010.0545","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959990783&doi=10.1089%2fast.2010.0545&partnerID=40&md5=90ce70765c309c39d20d748ddb5f335a","Most discussion of habitable planets has focused on Earth-like planets with globally abundant liquid water. For an aqua planet like Earth, the surface freezes if far from its sun, and the water vapor greenhouse effect runs away if too close. Here we show that land planets (desert worlds with limited surface water) have wider habitable zones than aqua planets. For planets at the inner edge of the habitable zone, a land planet has two advantages over an aqua planet: (i) the tropics can emit longwave radiation at rates above the traditional runaway limit because the air is unsaturated and (ii) the dry air creates a dry stratosphere that limits hydrogen escape. At the outer limits of the habitable zone, the land planet better resists global freezing because there is less water for clouds, snow, and ice. Here we describe a series of numerical experiments using a simple three-dimensional global climate model for Earth-sized planets. Other things (CO2, rotation rate, surface pressure) unchanged, we found that liquid water remains stable at the poles of a low-obliquity land planet until net insolation exceeds 415 W/m 2 (170% that of modern Earth), compared to 330 W/m 2 (135%) for the aqua planet. At the outer limits, we found that a low-obliquity land planet freezes at 77%, while the aqua planet freezes at 90%. High-obliquity land and aqua planets freeze at 58% and 72%, respectively, with the poles offering the last refuge. We show that it is possible that, as the Sun brightens, an aqua planet like Earth can lose most of its hydrogen and become a land planet without first passing through a sterilizing runaway greenhouse. It is possible that Venus was a habitable land planet as recently as 1 billion years ago. © Copyright 2011, Mary Ann Liebert, Inc."
"7005137442;6507224579;28367935500;37861539400;","Climate of the neoproterozoic",2011,"10.1146/annurev-earth-040809-152447","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955489728&doi=10.1146%2fannurev-earth-040809-152447&partnerID=40&md5=6b899d2dcbacdbc02227f665e521e8f3","The Neoproterozoic is a time of transition between the ancient microbial world and the Phanerozoic, marked by a resumption of extreme carbon isotope fluctuations and glaciation after a billion-year absence. The carbon cycle disruptions are probably accompanied by changes in the stock of oxidants and connect to glaciations via changes in the atmospheric greenhouse gas content. Two of the glaciations reach low latitudes and may have been Snowball events with near-global ice cover. This review deals primarily with the Cryogenian portion of the Neoproterozoic, during which these glaciations occurred. The initiation and deglaciation of Snowball states are discussed in light of a suite of general circulation model simulations designed to facilitate intercomparison between different models. Snow cover and the nature of the frozen surface emerge as key factors governing initiation and deglaciation. The most comprehensive model discussed confirms the possibility of initiating a Snowball event with a plausible reduction of CO2. Deglaciation requires a combination of elevated CO2 and tropical dust accumulation, aided by some cloud warming. The cause of Neoproterozoic biogeochemical turbulence, and its precise connection with Snowball glaciations, remains obscure. Copyright © 2011 by Annual Reviews. All rights reserved."
"57211636621;7006329853;","Modeling sea-salt aerosol in a coupled climate and sectional microphysical model: Mass, optical depth and number concentration",2011,"10.5194/acp-11-4587-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956145603&doi=10.5194%2facp-11-4587-2011&partnerID=40&md5=694637b3e17e59641e253037fb7566ff","Sea-salt aerosol mass, optical depth, and number concentration over the global oceans have significant implications for aerosol direct and indirect climate effects. We model sea-salt aerosol in a coupled climate and sectional microphysical model, CAM/CARMA, with aerosol dynamics including sea-salt emission, gravitational sedimentation, dry deposition, wet scavenging, and hygroscopic growth. We aim to find an integrated sea-salt source function parameterization in the global climate model to simultaneously represent mass, optical depth, and number concentration. Each of these quantities is sensitive to a different part of the aerosol size distribution, which requires a size resolved microphysical model to treat properly. The CMS source function introduced in this research, based upon several earlier source functions, reproduces measurements of mass, optical depth and number concentration as well as the size distribution better than other source function choices we tried. However, as we note, it is also important to properly set the removal rate of the particles. The source function and removal rate are coupled in producing observed abundances. We find that sea salt mass and optical depth peak in the winter, when winds are highest. However, surprisingly, particle numbers and CCN concentrations peak in summer when rainfall is lowest. The quadratic dependence of sea-salt optical depth on wind speed, observed by some, is well represented in the model. We also find good agreement with the wind speed dependency of the number concentration at the measurement location and the regional scale. The work is the basis for further investigation of the effects of sea-salt aerosol on climate and atmospheric chemistry. © 2011 Author(s)."
"57194786669;35461763400;7003529604;7004864963;7004510293;6604023055;7006167299;7401728833;6602765265;","Evaluation of the carbon content of aerosols from the burning of biomass in the Brazilian Amazon using thermal, optical and thermal-optical analysis methods",2011,"10.5194/acp-11-4425-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956045810&doi=10.5194%2facp-11-4425-2011&partnerID=40&md5=9f8d207501782ed3fbf51b6f27b3e939","Aerosol samples were collected at a pasture site in the Amazon Basin as part of the project LBASMOCC- 2002 (Large-Scale Biosphere-Atmosphere Experiment in Amazonia . Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate). Sampling was conducted during the late dry season, when the aerosol composition was dominated by biomass burning emissions, especially in the submicron fraction. A 13-stage Dekati low-pressure impactor (DLPI) was used to collect particles with nominal aerodynamic diameters (Dp) ranging from 0.03 to 0.10 Êm. Gravimetric analyses of the DLPI substrates and filters were performed to obtain aerosol mass concentrations. The concentrations of total, apparent elemental, and organic carbon (TC, ECa, and OC) were determined using thermal and thermal-optical analysis (TOA) methods. A light transmission method (LTM) was used to determine the concentration of equivalent black carbon (BCe) or the absorbing fraction at 880 nm for the size-resolved samples. During the dry period, due to the pervasive presence of fires in the region upwind of the sampling site, concentrations of fine aerosols (Dp < 2.5 average 59.8 Êgm.3) were higher than coarse aerosols (Dp >2.5: 4.1 Êgm.3). Carbonaceous matter, estimated as the sum of the particulate organic matter (i.e., OC×1.8) plus BCe, comprised more than 90% to the total aerosol mass. Concentrations of ECa (estimated by thermal analysis with a correction for charring) and BCe (estimated by LTM) averaged 5.2±1.3 and 3.1±0.8 ìgm.3, respectively. The determination of EC was improved by extracting water-soluble organic material from the samples, which reduced the average light absorption A° ngström exponent of particles in the size range of 0.1 to 1.0 ìm from >2.0 to approximately 1.2. The size-resolved BCe measured by the LTM showed a clear maximum between 0.4 and 0.6 ìm in diameter. The concentrations of OC and BCe varied diurnally during the dry period, and this variation is related to diurnal changes in boundary layer thickness and in fire frequency. © 2011 Author(s)."
"35232705600;7003696133;57189498750;7402027161;","Regional scale effects of the aerosol cloud interaction simulated with an online coupled comprehensive chemistry model",2011,"10.5194/acp-11-4411-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955880319&doi=10.5194%2facp-11-4411-2011&partnerID=40&md5=9cd76ff728fa0ce237ffdf807b7ef903","We have extended the coupled mesoscale atmosphere and chemistry model COSMO-ART to account for the transformation of aerosol particles into cloud condensation nuclei and to quantify their interaction with warm cloud microphysics on the regional scale. The new model system aims to fill the gap between cloud resolving models and global scale models. It represents the very complex microscale aerosol and cloud physics as detailed as possible, whereas the continental domain size and efficient codes will allow for both studying weather and regional climate. The model system is applied in a first extended case study for Europe for a cloudy five day period in August 2005. The model results show that the mean cloud droplet number concentration of clouds is correlated with the structure of the terrain, and we present a terrain slope parameter TS to classify this dependency. We propose to use this relationship to parameterize the probability density function, PDF, of subgrid-scale cloud updraft velocity in the activation parameterizations of climate models. The simulations show that the presence of cloud condensation nuclei (CCN) and clouds are closely related spatially. We find high aerosol and CCN number concentrations in the vicinity of clouds at high altitudes. The nucleation of secondary particles is enhanced above the clouds. This is caused by an efficient formation of gaseous aerosol precursors above the cloud due to more available radiation, transport of gases in clean air above the cloud, and humid conditions. Therefore the treatment of complex photochemistry is crucial in atmospheric models to simulate the distribution of CCN. The mean cloud droplet number concentration and droplet diameter showed a close link to the change in the aerosol. To quantify the net impact of an aerosol change on the precipitation we calculated the precipitation susceptibility β for the whole model domain over a period of two days with an hourly resolution. The distribution function of β is slightly skewed to positive values and has a mean of 0.23. Clouds with a liquid water path LWP of approximately 0.85 kg m-2 are on average most susceptible to aerosol changes in our simulations with an absolute value of β of 1. The average β for LWP between 0.5 kg m-2 and 1 kg m-2 is approximately 0.4. © 2011 Author(s)."
"8404544300;55885831600;36560691800;38760907700;35723418200;","Heterogeneous freezing of water droplets containing kaolinite particles",2011,"10.5194/acp-11-4191-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955920251&doi=10.5194%2facp-11-4191-2011&partnerID=40&md5=f4c8f4818238044eeb4c6d78a997e7f8","Clouds composed of both ice particles and supercooled liquid water droplets exist at temperatures above ∼236 K. These mixed phase clouds, which strongly impact climate, are very sensitive to the presence of solid particles that can catalyse freezing. In this paper we describe experiments to determine the conditions at which the clay mineral kaolinite nucleates ice when immersed within water droplets. These are the first immersion mode experiments in which the ice nucleating ability of kaolinite has been determined as a function of clay surface area, cooling rate and also at constant temperatures. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and cooled at rates of between 0.8 and 10 K min-1 or held at constant sub-zero temperatures. The time and temperature at which individual 10-50 μm diameter droplets froze were determined by optical microscopy. For a cooling rate of 10 K min-1, the median nucleation temperature of 10-40 μm diameter droplets increased from close to the homogeneous nucleation limit (236 K) to 240.8 ± 0.6 K as the concentration of kaolinite in the droplets was increased from 0.005 wt% to 1 wt%. This data shows that the probability of freezing scales with surface area of the kaolinite inclusions. We also show that at a constant temperature the number of liquid droplets decreases exponentially as they freeze over time. The constant cooling rate experiments are consistent with the stochastic, singular and modified singular descriptions of heterogeneous nucleation; however, freezing during cooling and at constant temperature can be reconciled best with the stochastic approach. We report temperature dependent nucleation rate coefficients (nucleation events per unit time per unit area) for kaolinite and present a general parameterisation for immersion nucleation which may be suitable for cloud modelling once nucleation by other important ice nucleating species is quantified in the future. © 2011 Author(s)."
"26423040200;6701709684;7004024063;","Flux and polarisation spectra of water clouds on exoplanets",2011,"10.1051/0004-6361/201116449","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955828923&doi=10.1051%2f0004-6361%2f201116449&partnerID=40&md5=41aef3b1443a189181c2688cf87cd8a3","Context. A crucial factor for a planet's habitability is its climate. Clouds play an important role in planetary climates. Detecting and characterising clouds on an exoplanet is therefore crucial when addressing this planet's habitability. Aims. We present calculated flux and polarisation spectra of starlight that is reflected by planets covered by liquid water clouds with different optical thicknesses, altitudes, and particle sizes, as functions of the phase angle α. We discuss the retrieval of these cloud properties from observed flux and polarisation spectra. Methods. Our model planets have black surfaces and atmospheres with Earth-like temperature and pressure profiles. We calculate the spectra from 0.3 to 1.0 μm, using an adding-doubling radiative transfer code with integration over the planetary disk. The cloud particles' scattering properties are calculated using a Mie-algorithm. Results. Both flux and polarisation spectra are sensitive to the cloud optical thickness, altitude and particle sizes, depending on the wavelength and phase angle α. Conclusions. Reflected fluxes are sensitive to cloud optical thicknesses up to ∼40, and the polarisation to thicknesses up to ∼20. The shapes of polarisation features as functions of α are relatively independent of the cloud optical thickness. Instead, they depend strongly on the cloud particles' size and shape, and can thus be used for particle characterisation. In particular, a rainbow strongly indicates the presence of liquid water droplets. Single scattering features such as rainbows, which can be observed in polarisation, are virtually unobservable in reflected fluxes, and fluxes are thus less useful for cloud particle characterisation. Fluxes are sensitive to cloud top altitudes mostly for α < 60° and wavelengths <0.4 μm, and the polarisation for α around 90° and wavelengths between 0.4 and 0.6 μm. © 2011 ESO."
"35790739000;23110620300;","Monitoring snow cover variability in an agropastoral area in the Trans Himalayan region of Nepal using MODIS data with improved cloud removal methodology",2011,"10.1016/j.rse.2011.01.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952069549&doi=10.1016%2fj.rse.2011.01.006&partnerID=40&md5=9fe79d201068c919c1465acd4a9f7ce8","Monitoring the extent and pattern of snow cover in the dry, high altitude, Trans Himalayan region (THR) is significant to understand the local and regional impact of ongoing climate change and variability. The freely available Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover images, with 500. m spatial and daily temporal resolution, can provide a basis for regional snow cover mapping, monitoring and hydrological modelling. However, high cloud obscuration remains the main limitation. In this study, we propose a five successive step approach - combining data from the Terra and Aqua satellites; adjacent temporal deduction; spatial filtering based on orthogonal neighbouring pixels; spatial filtering based on a zonal snowline approach; and temporal filtering based on zonal snow cycle - to remove cloud obscuration from MODIS daily snow products. This study also examines the spatial and temporal variability of snow cover in the THR of Nepal in the last decade. Since no ground stations measuring snow data are available in the region, the performance of the proposed methodology is evaluated by comparing the original MODIS snow cover data with least cloud cover against cloud-generated MODIS snow cover data, filled by clouds of another densely cloud-covered product. The analysis indicates that the proposed five-step method is efficient in cloud reduction (with average accuracy of > 91%). The results show very high interannual and intra-seasonal variability of average snow cover, maximum snow extent and snow cover duration over the last decade. The peak snow period has been delayed by about 6.7. days per year and the main agropastoral production areas of the region were found to experience a significant decline in snow cover duration during the last decade. © 2011 Elsevier Inc."
"56138750800;7003946703;7404345600;56909323100;","Investigation of the impacts of vegetation distribution and evaporative cooling on synthetic urban daytime climate using a coupled LES-LSM model",2011,"10.1002/hyp.7919","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955538272&doi=10.1002%2fhyp.7919&partnerID=40&md5=c025ac2a4dd5d106ad5a5a448dda9b27","Local flow properties and regional weather or climate are strongly affected by land-atmosphere interactions of momentum and scalars within the daytime convective boundary layer (CBL). In this study, we investigate the impact of green space scale on the daytime atmospheric boundary layer (ABL) over a synthetic urban domain using a recently developed large-eddy simulation-land surface model (LES-LSM) framework. With the use of realistic soundings as initial conditions, a series of numerical experiments over synthetic urban surfaces with varied scale of vegetated area is performed. Simulated micrometeorological properties, surface fluxes, basic CBL characteristics, and cloud distribution are analysed. The results show reference-level air potential temperature and specific humidity as well as surface fluxes over green space are significantly affected by the scale of green space in the urban domain. The surface organization due to vegetated area scale also has impacts on horizontally averaged scalar and momentum profiles; however, the magnitude in this study is smaller than the results of a previous study using a set of offline surface fluxes as the lower boundary condition for LES. In addition, even though this study only performs a daytime diurnal cycle, the impact of green space scale on cloud distribution in simulations is significant. The cases with more organized green space yield lower-elevated cumulus cloud and larger-cloud cover fraction, which impacts the energy budget at the top of boundary layer and, in turn, could lead to additional surface cooling with respect to longer-term weather and climate. © 2010 John Wiley & Sons, Ltd."
"36971299500;7401513851;55577486600;37037519900;55499697100;","Reprocessing the MODIS Leaf Area Index products for land surface and climate modelling",2011,"10.1016/j.rse.2011.01.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952069750&doi=10.1016%2fj.rse.2011.01.001&partnerID=40&md5=ac71e3b6ac33a65b906c7ebe3e8ba36d","Land surface and climate modelling requires continuous and consistent Leaf Area Index (LAI). High spatiotemporal resolution and long-time record data are more in demand nowadays and will continue to be in the future. MODIS LAI products meet these requirements to some degree. However, due to the presence of cloud and seasonal snow cover, the instrument problems and the uncertainties of retrieval algorithm, the current MODIS LAI products are spatially and temporally discontinuous and inconsistent, which limits their application in land surface and climate modelling. To improve the MODIS LAI products on a global scale, we considered the characteristics of the MODIS LAI data and made the best use of quality control (QC) information, and developed an integrated two-step method to derive the improved MODIS LAI products effectively and efficiently on a global scale. First, we used the modified temporal spatial filter (mTSF) method taking advantage of background values and QC information at each pixel to do a simple data assimilation for relatively low quality data. Then we applied the post processing-TIMESAT (A software package to analyze time-series of satellite sensor data) Savitzky-Golay (SG) filter to get the final result. We implemented the method to 10. years of the MODIS Collection 5 LAI data. In comparison with the LAI reference maps and the MODIS LAI data, our results showed that the improved MODIS LAI data are closer to the LAI reference maps in magnitude and also more continuous and consistent in both time-series and spatial domains. In addition, simple statistics were used to evaluate the differences between the MODIS LAI and the improved MODIS LAI. © 2011 Elsevier Inc."
"37114958000;7202516876;15724722300;8700927900;","A study of shallow cumulus cloud droplet dispersion by large eddy simulations",2011,"10.1007/s13351-011-0024-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955550738&doi=10.1007%2fs13351-011-0024-9&partnerID=40&md5=ff2f38ae2514549b0d71f5a681fb263c","Cloud droplet dispersion is an important parameter in estimating aerosol indirect effect on climate in general circulation models (GCMs). This study investigates droplet dispersion in shallow cumulus clouds under different aerosol conditions using three-dimensional large eddy simulations (LES). It is found that cloud droplet mean radius, standard deviation, and relative dispersion generally decrease as aerosol mixing ratio increases from 25 mg-1 (clean case) to 100 mg-1 (moderate case), and to 2000 mg-1 (polluted case). Under all the three simulated aerosol conditions, cloud droplet mean radius and standard deviation increase with height. However, droplet relative dispersion increases with height only in the polluted case, and does not vary with height in the clean and moderate cases. The mechanisms for cloud droplet dispersion are also investigated. An additional simulation without considering droplet collision-coalescence and sedimentation under the aerosol mixing ratio of 25 mg-1 shows smaller values of droplet mean radius, standard deviation, and relative dispersion as compared to the base clean case. This indicates that droplet collision-coalescence plays an important role in broadening droplet spectra. Results also suggest that the impact of homogeneous mixing on cumulus cloud droplet spectra is significant under all the three simulated aerosol conditions. In weak mixing (strong updraft) regions where clouds are closer to be adiabatic, cloud droplets tend to have larger mean radius, smaller standard deviation, and hence smaller relative dispersion than those in stronger mixing (downdraft or weak updraft) regions. The parameterized cloud optical depth in terms of cloud liquid water content, droplet number concentration, and relative dispersion is only slightly smaller than the result calculated from detailed droplet spectra, indicating that current parameterization of cloud optical depth as used in many GCMs is plausible for low clouds. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2011."
"15827441200;37114229500;6602089703;","A simple correlation to estimate global solar irradiation on a horizontal surface using METEOSAT satellite images",2011,"10.3906/muh-1006-50","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955553063&doi=10.3906%2fmuh-1006-50&partnerID=40&md5=3e0072e48a843f5f0ea9436f8b378e74","A simple quadratic correlation, which is obtained from a universal Angström-type quadratic relation, between daily horizontal global solar irradiation and satellite images is presented. The performance of this correlation is seen to be in the acceptable accuracy limits for daily estimates. In addition, by using data from 5 locations in Turkey, a linear correlation between the bright sunshine hours and satellite based cloud index is derived. Utilizing these 2 correlations, one can easily obtain spatial daily solar irradiation and sunshine duration maps for the regions with similar latitudes and climates of locations of interest. © TÜBİTAK."
"9235235300;13405658600;24529241300;8336962200;36070429000;17433787100;11339750700;23967608200;8871497700;7003999574;8950640300;6506643480;7004027519;7003430284;26643041500;7006593624;56472932500;7004596535;35461255500;","Organic condensation: A vital link connecting aerosol formation to cloud condensation nuclei (CCN) concentrations",2011,"10.5194/acp-11-3865-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955537636&doi=10.5194%2facp-11-3865-2011&partnerID=40&md5=3763ec9ee065187bf6d55a9fa12670cb","Atmospheric aerosol particles influence global climate as well as impair air quality through their effects on atmospheric visibility and human health. Ultrafine (<100 nm) particles often dominate aerosol numbers, and nucleation of atmospheric vapors is an important source of these particles. To have climatic relevance, however, the freshly nucleated particles need to grow in size. We combine observations from two continental sites (Egbert, Canada and Hyytiälä, Finland) to show that condensation of organic vapors is a crucial factor governing the lifetimes and climatic importance of the smallest atmospheric particles. We model the observed ultrafine aerosol growth with a simplified scheme approximating the condensing species as a mixture of effectively non-volatile and semi-volatile species, demonstrate that state-of-the-art organic gas-particle partitioning models fail to reproduce the observations, and propose a modeling approach that is consistent with the measurements. We find that roughly half of the mass of the condensing mass needs to be distributed proportional to the aerosol surface area (thus implying that the condensation is governed by gas-phase concentration rather than the equilibrium vapour pressure) to explain the observed aerosol growth. We demonstrate the large sensitivity of predicted number concentrations of cloud condensation nuclei (CCN) to these interactions between organic vapors and the smallest atmospheric nanoparticles highlighting the need for representing this process in global climate models. © 2011 Author(s)."
"22933265100;6701378450;","Dynamical states of low temperature cirrus",2011,"10.5194/acp-11-3757-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955395027&doi=10.5194%2facp-11-3757-2011&partnerID=40&md5=7eb398a0fb402ee542c4e98fc53cc6fb","Low ice crystal concentration and sustained in-cloud supersaturation, commonly found in cloud observations at low temperature, challenge our understanding of cirrus formation. Heterogeneous freezing from effloresced ammonium sulfate, glassy aerosol, dust and black carbon are proposed to cause these phenomena; this requires low updrafts for cirrus characteristics to agree with observations and is at odds with the gravity wave spectrum in the upper troposphere. Background temperature fluctuations however can establish a ""dynamical equilibrium"" between ice production and sedimentation loss (as opposed to ice crystal formation during the first stages of cloud evolution and subsequent slow cloud decay) that explains low temperature cirrus properties. This newly-discovered state is favored at low temperatures and does not require heterogeneous nucleation to occur (the presence of ice nuclei can however facilitate its onset). Our understanding of cirrus clouds and their role in anthropogenic climate change is reshaped, as the type of dynamical forcing will set these clouds in one of two ""preferred"" microphysical regimes with very different susceptibility to aerosol. © 2011 Author(s)."
"57202068603;","Evaluation of the thermal convection influence in atmosphere on the evolution of the climate changes",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955375926&partnerID=40&md5=c3ef9dcb3624a067354e0501fd542912","The studies of the long-term trends in radiation and convection fluxes, cloudiness and temperature have great importance for the investigations of the climate changes. The main problems of the thermal radiation and convection can be also linked to the influence of the gases on the evolution of global warming. The main element of the system, permitting the evaluation of the thermal and dynamic aspects and its dynamic, is the intensity of the heat exchange. In order to analyse this problem, a model needs to consider: the convection, the radiation and the heat exchange in the atmosphere. The objective is to establish a correlation between the components, the thermal source and the equilibrium of the system. Based on a proposed model, the paper considers some aspects regarding the problems of the thermal convection in the troposphere. The present work tries to analyse some particularities of the convection in the troposphere establishing the variation of the temperature, the turbulence and the speed of the air streams influenced by general and local physical properties of the air. The solutions have to take into account more complex situations in the atmosphere. Finally, the goal of the model is to bring a contribution to the questions on the climate changes."
"57214668779;56038849000;7003740015;7801595201;7004920873;","Chemical composition of rainwater at Maldives Climate Observatory at Hanimaadhoo (MCOH)",2011,"10.5194/acp-11-3743-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955435261&doi=10.5194%2facp-11-3743-2011&partnerID=40&md5=5762ca5b2e1f2270a09798330b9fb59a","Water-soluble inorganic components in rain deposited at the Maldives Climate Observatory Hanimaadhoo (MCOH) were examined to determine seasonality and possible source regions. The study, which is part of the Atmospheric Brown Cloud (ABC) project, covers the period June 2005 to December 2007. Air mass trajectories were used to separate the data into situations with transport of air from India and adjacent parts of the Asian continent during the months December and January (Indian group) and those with southerly flow from the Indian Ocean during the summer monsoon season June to September (Marine group). A third trajectory group was identified with transport from the northern parts of the Arabian Sea and adjacent land areas during the months March, April and October (Arabian Sea group). The concentrations of nss-SO42&minus;, NH4+ and NO3&minus; were more than a factor of 4 higher in the Indian group than in the Marine group. The average rainwater pH was significantly lower in the Indian group (4.7) than in the Marine group (6.0). This shows a pronounced influence of continental pollutants during December and January. The origin of the very high concentration of nss-Ca2+ found in the Marine group ĝ€"" a factor of 7 higher than in the Indian group ĝ€"" is unclear. We discuss various possibilities including long-range transport from the African or Australian continents, local dust from nearby islands and calcareous plankton debris and exopolymer gels emitted from the ocean surface. The occurrence of NO3&minus; and NH4+ in the Marine group suggests emissions from the ocean surface. Part of the NO3&minus; could also be associated with lightning over the ocean. Despite the fact that the concentrations of nss-SO42&minus;, NO3&minus;, and NH4+ were highest in the Indian group the wet deposition was at least as big in the Marine group reflecting the larger amount of rainfall during the monsoon season. The annual wet deposition of NO3&minus;, NH4+ and nss-SO42&minus; at MCOH is about a factor of three lower than observed at rural sites in India. © 2011 Author(s)."
"7404211378;7403681584;8636990400;7501760109;57214194241;16029674800;7402363038;","Sensitivity of tropical climate to low-level clouds in the NCEP climate forecast system",2011,"10.1007/s00382-010-0797-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954620905&doi=10.1007%2fs00382-010-0797-z&partnerID=40&md5=51c8f1eddfa9101b28e59645cba54129","In this work, we examine the sensitivity of tropical mean climate and seasonal cycle to low clouds and cloud liquid water path (CLWP) by prescribing them in the NCEP climate forecast system (CFS). It is found that the change of low cloud cover alone has a minor influence on the amount of net shortwave radiation reaching the surface and on the warm biases in the southeastern Atlantic. In experiments where CLWP is prescribed using observations, the mean climate in the tropics is improved significantly, implying that shortwave radiation absorption by CLWP is mainly responsible for reducing the excessive surface net shortwave radiation over the southern oceans in the CFS. Corresponding to large CLWP values in the southeastern oceans, the model generates large low cloud amounts. That results in a reduction of net shortwave radiation at the ocean surface and the warm biases in the sea surface temperature in the southeastern oceans. Meanwhile, the cold tongue and associated surface wind stress in the eastern oceans become stronger and more realistic. As a consequence of the overall improvement of the tropical mean climate, the seasonal cycle in the tropical Atlantic is also improved. Based on the results from these sensitivity experiments, we propose a model bias correction approach, in which CLWP is prescribed only in the southeastern Atlantic by using observed annual mean climatology of CLWP. It is shown that the warm biases in the southeastern Atlantic are largely eliminated, and the seasonal cycle in the tropical Atlantic Ocean is significantly improved. Prescribing CLWP in the CFS is then an effective interim technique to reduce model biases and to improve the simulation of seasonal cycle in the tropics. © 2010 Springer-Verlag."
"7005601387;35221791100;7005063377;","Fluctuations in some climate parameters",2011,"10.1016/j.jastp.2011.01.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953313004&doi=10.1016%2fj.jastp.2011.01.021&partnerID=40&md5=49c447030502e0d5fb313e42ab3de2c6","There is argument as to the extent to which there has been an increase over the past few decades in the frequency of the extremes of climatic parameters, such as temperature, storminess, precipitation, etc, an obvious point being that Global Warming might be responsible. Here we report results on those parameters of which we have had experience during the last few years: Global surface temperature, Cloud Cover and the MODIS Liquid Cloud Fraction. In no case we have found indications that fluctuations of these parameters have increased with time. © 2011 Elsevier Ltd."
"7101959253;7005626683;","A cloud-resolving model with an adaptive vertical grid for boundary layer clouds",2011,"10.1175/2010JAS3638.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958695275&doi=10.1175%2f2010JAS3638.1&partnerID=40&md5=21a68e135f98e482baaa518690aa3730","Accurate cloud-resolving model simulations of cloud cover and cloud water content for boundary layer clouds are difficult to achieve without vertical grid spacing well below 100 m, especially for inversion-topped stratocumulus. The need for fine vertical grid spacing presents a significant impediment to global or large regional simulations using cloud-resolving models, including the Multiscale Modeling Framework (MMF), in which a two-dimensional or small three-dimensional cloud-resolving model is embedded into each grid cell of a global climate model in place of more traditional cloud parameterizations. One potential solution to this problem is to use a model with an adaptive vertical grid (i.e., a model that is able to add vertical layers where and when needed) rather than trying to use a fixed grid with fine vertical spacing throughout the boundary layer. This article examines simulations with an adaptive vertical grid for three well-studied stratocumulus cases based on observations from the second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) experiment, the Atlantic Stratocumulus Transition Experiment (ASTEX), and the Atlantic Trade Cumulus Experiment (ATEX). For each case, three criteria are examined for determining where to add or remove vertical layers. One criterion is based on the domain-averaged potential temperature profile; the other two are based on the ratio of the estimated subgrid-scale to total water flux and turbulent kinetic energy. The results of the adaptive vertical grid simulations are encouraging in that these simulations are able to produce results similar to simulations using fine vertical grid spacing throughout the boundary layer, while using many fewer vertical layers. © 2011 American Meteorological Society."
"28767872500;6602725432;7003811754;","A three-year climatology of cloud-top phase over the Southern Ocean and North Pacific",2011,"10.1175/2010JCLI3842.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958167183&doi=10.1175%2f2010JCLI3842.1&partnerID=40&md5=f347c2761a2a2a102746fb45157a01cf","Moderate Resolution Imaging Spectroradiometer (MODIS) Level 2 observations from the Terra satellite are used to create a 3-yr climatology of cloud-top phase over a section of the Southern Ocean (south of Australia) and the North Pacific Ocean. The intent is to highlight the extensive presence of supercooled liquid water over the Southern Ocean region, particularly during summer. The phase of such clouds directly affects the absorbed shortwave radiation, which has recently been found to be ""poorly simulated in both state-of-theart reanalysis and coupled global climate models"" (Trenberth and Fasullo). The climatology finds that supercooled liquid water is present year-round in the low-altitude clouds across this section of the Southern Ocean. Further, the MODIS cloud phase algorithm identifies very few glaciated cloud tops at temperatures above 220°C, rather inferring a large portion of ""uncertain"" cloud tops. Between 50° and 60°S during the summer, the albedo effect is compounded by a seasonal reduction in high-level cirrus. This is in direct contrast to the Bering Sea and Gulf of Alaska. Here MODIS finds a higher likelihood of observing warm liquid water clouds during summer and a reduction in the relative frequency of cloud tops within the 08 to 220°C temperature range. As the MODIS cloud phase product has limited ability to confidently identify cloud-top phase between25° and 225°C, future research should include observations from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and other space-based sensors to help with the classification within this temperature range. Further, multiregion in situ verification of any remotely sensed observations is vital to further understanding the cloud phase processes. © 2011 American Meteorological Society."
"37057488900;56068827500;21735369200;","Factors affecting the surface radiation trends over China between 1960 and 2000",2011,"10.1016/j.atmosenv.2011.02.028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953293022&doi=10.1016%2fj.atmosenv.2011.02.028&partnerID=40&md5=d26cbac7dbc9d66695422fd6df5aa42a","In this paper, the surface solar radiation data from 1960 to 2000 gathered from 40 weather stations over China were reexamined, and the relationship of long-term trends of the solar radiation and climate factors were analyzed. The results indicate that the surface solar radiation in most regions of China begins to increase after 1990. Decreases in cirrus and cirrostratus clouds, which account for a larger percentage of the total cloud amount over China, have an important contribution to the increasing trend of the surface solar radiation. Further examination of the surface water vapor changes reveals that the surface solar radiation negatively correlates with the near surface water vapor in most region of China, and this negative correlation is more pronounced in higher latitudes of China where the atmosphere is compared to regions in southern China. © 2011 Elsevier Ltd."
"55718911800;56349223500;37105039700;37105327100;56888287100;35975306400;","Cloud residues and interstitial aerosols from non-precipitating clouds over an industrial and urban area in northern China",2011,"10.1016/j.atmosenv.2011.02.044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953296132&doi=10.1016%2fj.atmosenv.2011.02.044&partnerID=40&md5=af134da629cfafcb39fe4b489ef959a5","Most studies of aerosol-cloud interactions have been conducted in remote locations; few have investigated the characterization of cloud condensation nuclei (CCN) over highly polluted urban and industrial areas. The present work, based on samples collected at Mt. Tai, a site in northern China affected by nearby urban and industrial air pollutant emissions, illuminates CCN properties in a polluted atmosphere. High-resolution transmission electron microscopy (TEM) was used to obtain the size, composition, and mixing state of individual cloud residues and interstitial aerosols. Most of the cloud residues displayed distinct rims which were found to consist of soluble organic matter (OM). Nearly all (91.7%) cloud residues were attributed to sulfate-related salts (the remainder was mostly coarse crustal dust particles with nitrate coatings). Half the salt particles were internally mixed with two or more refractory particles (e.g., soot, fly ash, crustal dust, CaSO4, and OM). A comparison between cloud residues and interstitial particles shows that the former contained more salts and were of larger particle size than the latter. In addition, a somewhat high number scavenging ratio of 0.54 was observed during cloud formation. Therefore, the mixtures of salts with OMs account for most of the cloud-nucleating ability of the entire aerosol population in the polluted air of northern China. We advocate that both size and composition - the two influential, controlling factors for aerosol activation - should be built into all regional climate models of China. © 2011."
"55663817800;7006393267;7005862984;6504027639;41761861400;15059362600;7003604530;42961300300;14031035200;","Deployment of a tethered-balloon system for microphysics and radiative measurements in mixed-phase clouds at Ny-Ålesund and South Pole",2011,"10.1175/2010JTECHA1439.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651292443&doi=10.1175%2f2010JTECHA1439.1&partnerID=40&md5=36144624c53a7133033177beb7af3355","A tethered-balloon system capable of making microphysical and radiative measurements in clouds is described and examples of measurements in boundary layer stratus clouds in the Arctic and at the South Pole are presented. A 43-m3 helium-filled balloon lofts an instrument package that is powered by two copper conductors in the tether. The instrument package can support several instruments, including, but not limited to, a cloud particle imager; a forward-scattering spectrometer probe; temperature, pressure, humidity, and wind sensors; ice nuclei filters; and a 4-π radiometer that measures actinic flux at 500 and 800 nm. The balloon can stay aloft for an extended period of time (in excess of 24 h) and conduct vertical profiles up to about 1-2 km, contingent upon payload weight, wind speed, and surface elevation. Examples of measurements in mixedphase clouds at Ny-Ålesund, Svalbard (79°N), and at the South Pole are discussed. The stratus clouds at Ny-Ålesund ranged in temperature from 0° to -10°C and were mostly mixed phase with heavily rimed ice particles, even when cloud-top temperatures were warmer than 25°C. Conversely, mixed-phase clouds at the South Pole contained regions with only water drops at temperatures as cold as 232°C and were often composed of pristine ice crystals. The radiative properties of mixed-phase clouds are a critical component of radiative transfer in polar regions, which, in turn, is a lynch pin for climate change on a global scale. © 2011 American Meteorological Society."
"57206424059;22236001900;55470017900;23020556600;55462598500;","Cirrus cloud macrophysical and optical properties over North China from CALIOP measurements",2011,"10.1007/s00376-010-0049-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955759874&doi=10.1007%2fs00376-010-0049-5&partnerID=40&md5=fa45a0490bca729ab013c270fb121a1e","Two years of mid-latitude cirrus cloud macrophysical and optical properties over North China are described from Earth-orbiting Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite measurements. Global cloud climatological studies based on active remote sensing data sets benefit from more accurate resolution of vertical structure and more reliable detection of optically thin layers. The mean values for cirrus cases over North China are 0. 19±0. 18 for infrared emittance, 0. 41±0. 68 for visible optical depth, 0. 26±0. 12 for integrated depolarization ratio, and 0. 72±0. 22 for integrated color ratio. When studied using reasonable assumptions for the relationship between extinction and ice crystal backscatter coefficients, our results show that most of the cirrus clouds profiled using the 0. 532 μm channel data stream correspond with an optical depth of less than 1. 0. The dependence of cirrus cloud properties on cirrus cloud mid-cloud temperature and geometry thickness are generally similar to the results derived from the ground-based lidar, which are mainly impacted by the adiabatic process on the ice cloud content. However, the differences in macrophysical parameter variability indicate the limits of spaceborne-lidar and dissimilarities in regional climate variability and the nature and source of cloud nuclei in different geographical regions. © 2011 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"16639418500;36523706800;57206531303;15069732800;","Spatial and temporal homogeneity of solar surface irradiance across satellite generations",2011,"10.3390/rs3051029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052501683&doi=10.3390%2frs3051029&partnerID=40&md5=b5a6fc5932a3eaec01e9d23725f35b06","Solar surface irradiance (SIS) is an essential variable in the radiation budget of the Earth. Climate data records (CDR's) of SIS are required for climate monitoring, for climate model evaluation and for solar energy applications. A 23 year long (1983-2005) continuous and validated SIS CDR based on the visible channel (0.45-1 μm) of the MVIRI instruments onboard the first generation of Meteosat satellites has recently been generated using a climate version of the well established Heliosat method. This version of the Heliosat method includes a newly developed self-calibration algorithm and an improved algorithm to determine the clear sky reflection. The climate Heliosat version is also applied to the visible narrow-band channels of SEVIRI onboard the Meteosat Second Generation Satellites (2004-present). The respective channels are observing the Earth in the wavelength region at about 0.6 μm and 0.8 μm. SIS values of the overlapping time period are used to analyse whether a homogeneous extension of the MVIRI CDR is possible with the SEVIRI narrowband channels. It is demonstrated that the spectral differences between the used visible channels leads to significant differences in the solar surface irradiance in specific regions. Especially, over vegetated areas the reflectance exhibits a high spectral dependency resulting in large differences in the retrieved SIS. The applied self-calibration method alone is not able to compensate the spectral differences of the channels. Furthermore, the extended range of the input values (satellite counts) enhances the cloud detection of the SEVIRI instruments resulting in lower values for SIS, on average. Our findings have implications for the application of the Heliosat method to data from other geostationary satellites (e.g., GOES, GMS). They demonstrate the need for a careful analysis of the effect of spectral and technological differences in visible channels on the retrieved solar irradiance. © 2011 by the authors."
"6602252422;42861180300;7102171439;6603126554;7006713033;56219284300;7201607592;","Comparing MODIS and AIRS infrared-based cloud retrievals",2011,"10.1175/2010JAMC2603.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959574483&doi=10.1175%2f2010JAMC2603.1&partnerID=40&md5=d875b75ec4f0140870a87a36f6213ddf","Comparisons are described for infrared-derived cloud products retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Atmospheric Infrared Sounder (AIRS) using measured spatial response functions obtained from prelaunch AIRS calibration. One full day (1 January 2005) of global collection-5 MODIS and version-5 AIRS retrievals of cloud-top temperature Tc, effective cloud fraction f, and derived effective brightness temperature Tb,e is investigated. Comparisons of Tb,e demonstrate thatMODIS and AIRS are essentially radiatively consistent and that MODIS Tb,e is 0.62 K higher than AIRS Tb,e for all scenes, increasing to 1.43 K for cloud described by AIRS as single layer and decreasing to 0.50 K for two-layer clouds. Somewhat larger differences in Tc and f are observed between the two instruments. The magnitudes of differences depend partly on whether MODIS uses a CO2-slicing or 11-mm brightness temperature window retrieval method. Some cloud- and regime-type differences and similarities between AIRS and MODIS cloud products are traceable to the assumptions made about the number of cloud layers in AIRS and also to the MODIS retrieval method. This (partially) holistic comparison approach should be useful for ongoing algorithm refinements, rigorous assessments of climate applicability, and establishment of the capability of synergistic MODIS and AIRS retrievals for improved cloud quantities and also should be useful for future observations to be made by the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP). © 2011 American Meteorological Society."
"42062002500;7004003763;22953316500;6602111828;","Trade wind cloud evolution observed by polarization radar: Relationship to giant condensation nuclei concentrations and cloud organization",2011,"10.1175/2010JAS3675.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958761701&doi=10.1175%2f2010JAS3675.1&partnerID=40&md5=4410abcdc775918c13fca36cd40026d4","Shallow marine trade wind cumuli are one of the most prevalent cloud types in the tropical atmosphere. Understanding how precipitation forms within these clouds is necessary to advance our knowledge concerning their role in climate. This paper presents a statistical analysis of the characteristic heights and times at which precipitation in trade wind clouds passes through distinct stages in its evolution as defined by the equivalent radar reflectivity factor at horizontal polarization ZH, the differential reflectivity ZDR, and the spatial correlation between and averages of these variables. The data were obtained during the Rain in Cumulus over the Ocean (RICO) field campaign by the National Center for Atmospheric Research (NCAR) S-band dual-polarization (S-Pol) Doppler radar, the National Science Foundation (NSF)-NCAR C130 aircraft, and soundings launched near the radar. The data consisted of 76 trade cumuli that were tracked from early echo development through rainout on six days during RICO. Trade wind clouds used in the statistical analyses were segregated based on giant condensation nuclei (GCN) measurements made during low-level aircraft flight legs on the six days. This study found that the rate of precipitation formation in shallow marine cumulus was unrelated to the GCN concentration in the ambient environment. Instead, the rate at which precipitation developed in the clouds appeared to be related to the mesoscale forcing as suggested by the cloud organization. Although GCN had no influence on the rate of precipitation development, the data suggest that they do contribute to a modification of the rain drop size distribution within the clouds. With very few exceptions, high threshold values ofZDR were found well above cloud base on days with high GCN concentrations. On the days that were exceptions, these threshold values were almost always achieved near cloud base. © 2011 American Meteorological Society."
"7003455444;7202840464;","Processes and impacts of Arctic amplification: A research synthesis",2011,"10.1016/j.gloplacha.2011.03.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956265876&doi=10.1016%2fj.gloplacha.2011.03.004&partnerID=40&md5=29ea783098aa76cfdfa189d1aafd9385","The past decade has seen substantial advances in understanding Arctic amplification - that trends and variability in surface air temperature tend to be larger in the Arctic region than for the Northern Hemisphere or globe as a whole. We provide a synthesis of research on Arctic amplification, starting with a historical context and then addressing recent insights into processes and key impacts, based on analysis of the instrumental record, modeling studies, and paleoclimate reconstructions. Arctic amplification is now recognized as an inherent characteristic of the global climate system, with multiple intertwined causes operating on a spectrum of spatial and temporal scales. These include, but are not limited to, changes in sea ice extent that impact heat fluxes between the ocean and the atmosphere, atmospheric and oceanic heat transports, cloud cover and water vapor that alter the longwave radiation flux to the surface, soot on snow and heightened black carbon aerosol concentrations. Strong warming over the Arctic Ocean during the past decade in autumn and winter, clearly associated with reduced sea ice extent, is but the most recent manifestation of the phenomenon. Indeed, periods of Arctic amplification are evident from analysis of both warm and cool periods over at least the past three million years. Arctic amplification being observed today is expected to become stronger in coming decades, invoking changes in atmospheric circulation, vegetation and the carbon cycle, with impacts both within and beyond the Arctic. © 2011."
"57212781009;6701715507;","On tropospheric adjustment to forcing and climate feedbacks",2011,"10.1007/s00382-011-1067-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954620930&doi=10.1007%2fs00382-011-1067-4&partnerID=40&md5=4a18c877f4a414413d68ac8101e46e0d","Motivated by findings that major components of so-called cloud 'feedbacks' are best understood as rapid responses to CO2 forcing (Gregory and Webb in J Clim 21:58-71, 2008), the top of atmosphere (TOA) radiative effects from forcing, and the subsequent responses to global surface temperature changes from all 'atmospheric feedbacks' (water vapour, lapse rate, surface albedo, 'surface temperature' and cloud) are examined in detail in a General Circulation Model. Two approaches are used: applying regressions to experiments as they approach equilibrium, and equilibrium experiments forced separately by CO2 and patterned sea surface temperature perturbations alone. Results are analysed using the partial radiative perturbation ('PRP') technique. In common with Gregory and Webb (J Clim 21:58-71, 2008) a strong positive addition to 'forcing' is found in the short wave (SW) from clouds. There is little evidence, however, of significant global scale rapid responses from long wave (LW) cloud, nor from surface albedo, SW water vapour or 'surface temperature'. These responses may be well understood to first order as classical 'feedbacks'-i. e. as a function of global mean temperature alone and linearly related to it. Linear regression provides some evidence of a small rapid negative response in the LW from water vapour, related largely to decreased relative humidity (RH), but the response here, too, is dwarfed by subsequent response to warming. The large rapid SW cloud response is related to cloud fraction changes-and not optical properties-resulting from small cloud decreases ranging from the tropical mid troposphere to the mid latitude lower troposphere, in turn associated with decreased lower tropospheric RH. These regions correspond with levels of enhanced heating rates and increased temperatures from the CO2 increase. The pattern of SW cloud fraction response to SST changes differs quite markedly to this, with large positive radiation responses originating in the upper troposphere, positive contributions in the lowest levels and patterns of positive/negative contributions in mid latitude low levels. Overall SW cloud feedback was diagnosed as negative, due to the substantial negative SW feedback in cloud optical properties more than offsetting these. This study therefore suggests the rapid response to CO2 forcing is (apart from a possible small negative response from LW water vapour) essentially confined to cloud fraction changes affecting SW radiation, and further that significant feedbacks with temperature occur in all cloud components (including this one), and indeed in all other classically understood 'feedbacks'. © 2011 Springer-Verlag."
"36459497700;36867646100;7003672811;","Estimating the climate and air quality benefits of aviation fuel and emissions reductions",2011,"10.1016/j.atmosenv.2011.02.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954594383&doi=10.1016%2fj.atmosenv.2011.02.025&partnerID=40&md5=332c0a86bdf91bd3699bbd49cab8cfe0","In this study we consider the implications of our current understanding of aviation climate impacts as it relates to the ratio of non-CO2 to CO2 effects from aviation. We take as inputs recent estimates from the literature of the magnitude of the component aviation impacts and associated uncertainties. We then employ a simplified probabilistic impulse response function model for the climate and a range of damage functions to estimate the ratio of non-CO2 to CO2 impacts of aviation for a range of different metrics, scientific assumptions, future background emissions scenarios, economic growth scenarios, and discount rates. We take cost-benefit analysis as our primary context and thus focus on integral metrics that can be related to damages: the global warming potential, the time-integrated change in surface temperature, and the net present value of damages. We also present results based on an endpoint metric, the global temperature change potential. These latter results would be more appropriate for use in a cost-effectiveness framework (e.g., with a well-defined policy target for the anthropogenic change in surface temperature at a specified time in the future).We find that the parameter that most influences the ratio of non-CO2 to CO2 impacts of aviation is the discount rate, or analogously the time window used for physical metrics; both are expressions of the relative importance of long-lived versus short-lived impacts. Second to this is the influence of the radiative forcing values that are assumed for aviation-induced cloudiness effects. Given the large uncertainties in short-lived effects from aviation, and the dominating influence of discounting or time-windowing, we find that the choice of metric is relatively less influential. We express the ratios of non-CO2 to CO2 impacts on a per unit fuel burn basis so that they can be multiplied by a social cost of carbon to estimate the additional benefits of fuel burn reductions from aviation beyond those associated with CO2 alone (all else being equal). For a non-CO2 to CO2 ratio based on economic damage costs, we find a central value of 1.8 at a 3% discount rate, with a range from 0.6 to 2.5 for the upper and lower bounds of scientific and scenario-based uncertainty. Since estimating the co-benefits in this way is an important requirement for cost-benefit analyses, we also provide estimates of the air quality benefits of aviation fuel burn reduction in a similar format. We find the marginal damage costs of aircraft emissions below 3000 feet to be of similar magnitude to the climate costs on a per unit fuel burn basis, or an order of magnitude smaller on a per flight basis since we take no account of the air quality impacts of emissions above 3000 feet where the majority of fuel is consumed for the fleet. © 2011 Elsevier Ltd."
"36675355500;7006513495;6602187075;","Picea rubens growth at high versus low elevations in the Great Smoky Mountains National Park: Evaluation by systems modeling",2011,"10.1139/x10-243","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955715963&doi=10.1139%2fx10-243&partnerID=40&md5=d451eca5d4fc205c366eb262ecf80596","For half a century, red spruce (Picea rubens Sarg.), a commercially and ecologically important boreal tree species, has experienced growth decline and high mortality in eastern North America. A tree growth systems model, ARIM (annual radial increment model), was developed to evaluate responsible factors for red spruce growth in the Great Smoky Mountains National Park. The dominant cause at higher elevations (1800-2000 m) was found to be air pollution involving high-frequency acidic rain and cloud immersion. The identified causes at lower elevations (1450-1700 m) were insufficient solar absorption due to photoinhibition, drought stress resulting from reduced precipitation and high evapotranspiration due to warmer temperatures, and minor effects of air pollution. The ARIM exemplifies a complex systems concept and methodology for evaluating multivariable factors in tree growth systems. ARIM provides a general model structure that incorporates complex direct and indirect interactions for tree system studies and quantitatively integrates knowledge and data from different disciplines by developing a new set of indices, the relative basis index values. The ARIM results implicate comprehensive habitat-dependent directions for long-term conservation policies and management of red spruce with environmental changes, climate change, and air pollution in the Great Smoky Mountains National Park."
"41661225600;6603536554;6603297777;","Analysis of the urban thermal fingerprint of the city of trento in the Alps",2011,"10.1175/2010JAMC2613.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959617575&doi=10.1175%2f2010JAMC2613.1&partnerID=40&md5=54e209310c50bfba76555a89bc168c21","The temperature contrasts typically marking urban heat island (UHI) effects in the city of Trento, Italy, located in an Alpine valley and inhabited in its inner urban area by a population of about 56 000, are investigated. Time series of air temperature data, collected at an urban weather station, in the city center, and at five extraurban stations are compared. The latter are representative of rural and suburban areas, both on the valley floor and on the valley sidewalls. It is found that the extraurban weather stations, being affected by different local-scale climatic conditions, display different temperature contrasts with the urban site. However, the diurnal cycle of the UHI is characterized by similar patterns of behavior at all of the extraurban weather stations: the UHI intensity is stronger at night, whereas during the central hours of the day an ""urban cool island"" is likely to occur. The diurnal maximum UHI intensity turns out to be typically of order 3°C, but under particularly favorable conditions it may be higher than 6°C. An urban cool island effect is also detected, which is probably caused by the compactness of the inner urban area, and displays typical diurnal maximum intensities of order 1.5°C. As to the seasonal dependence, at the extraurban weather stations on the valley floor the UHI intensity tends to be slightly stronger during dry months, whereas on the valley sidewalls it is mainly influenced by the seasonal lapse-rate changes. Further weather factors, such as wind speed and cloud cover, also affect urbanization effects, making them weaker with stronger winds and cloudier skies. © 2011 American Meteorological Society."
"55897485300;49561717600;6603425325;6701594586;6603848988;","Thermal infrared nadir observations of 24 atmospheric gases",2011,"10.1029/2011GL047271","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054720716&doi=10.1029%2f2011GL047271&partnerID=40&md5=feb3663c3f4c1ecd92b6d25258eb1acb","[1] Thermal infrared nadir sounders are ideal for observing total columns or vertical profiles of atmospheric gases such as water, carbon dioxide and ozone. High resolution sounders with a spectral resolution below 5 cm -1 can distinguish fine spectral features of trace gases. Forty years after the launch of the first hyperspectral sounder IRIS, we have now several state of the art instruments in orbit, with improved instrumental specifications. In this letter we give an overview of the trace gases which have been observed by infrared nadir sounders, focusing on new observations of the Infrared Atmospheric Sounding Interferometer (IASI). We present typical observations of 14 rare reactive trace gas species. Several species are reported here for the first time in nadir view, including nitrous acid, furan, acetylene, propylene, acetic acid, formaldehyde and hydrogen cyanide, observations which were made in a pyrocumulus cloud from the Australian bush fires of February 2009. Being able to observe this large number of reactive trace gases will likely improve our knowledge of source emissions and their impact on the environment and climate."
"7202233375;23019451200;7003626419;12645353200;7003283897;","Incorporation of aerosol effects in a clear-sky semi-empirical model of UVER radiation for Valencia, Spain",2011,"10.1002/joc.2133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954604489&doi=10.1002%2fjoc.2133&partnerID=40&md5=62e24089615dc21c1cf2407bebf29c7b","The study develops a simple but physically based model for estimating erythemal irradiance [(UV erythemal radiation (UVER)] for cloudless urban regions with substantial aerosol load, such as that of the Valencia environment in Spain. The model estimates direct and diffuse UVER for cloudless aerosol-free conditions using the LibRadtran model with a DISORT algorithm. Aerosol optical thickness for UVER (τaER) is obtained as a residual term by comparing measured direct UVER against modelled direct UVER in the absence of aerosol load. On average, τaER is 18% higher than τ data extrapolated to 305 nm using the CIMEL CE-318. Comparison of measured direct and diffuse UVER with model estimates provide the single scattering albedo (ωER), which on average is 0.88 for Burjassot, Valencia. When tested against independent data, hourly root mean square (RMS) errors are 6.2% if both aerosol properties are known independently. The error is 7.6% when monthly averages of these aerosol properties are used to estimate hourly erythemal irradiance in other years. However, errors are larger, at 18.0%, when monthly estimates of these aerosol properties are used at other experimental sites in the region with no aerosol data. © 2010 Royal Meteorological Society."
"24481425100;7005779291;7102166730;7102438103;7102385665;6603090418;56134743100;","Timing of seasonal migration in mule deer: Effects of climate, plant phenology, and life-history characteristics",2011,"10.1890/ES10-00096.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051974583&doi=10.1890%2fES10-00096.1&partnerID=40&md5=5384bc1840299432d6834ee0a7217476","Phenological events of plants and animals are sensitive to climatic processes. Migration is a life-history event exhibited by most large herbivores living in seasonal environments, and is thought to occur in response to dynamics of forage and weather. Decisions regarding when to migrate, however, may be affected by differences in life-history characteristics of individuals. Long-term and intensive study of a population of mule deer (Odocoileus hemionus) in the Sierra Nevada, California, USA, allowed us to document patterns of migration during 11 years that encompassed a wide array of environmental conditions. We used two new techniques to properly account for interval-censored data and disentangle effects of broad-scale climate, local weather patterns, and plant phenology on seasonal patterns of migration, while incorporating effects of individual life-history characteristics. Timing of autumn migration varied substantially among individual deer, but was associated with the severity of winter weather, and in particular, snow depth and cold temperatures. Migratory responses to winter weather, however, were affected by age, nutritional condition, and summer residency of individual females. Old females and those in good nutritional condition risked encountering severe weather by delaying autumn migration, and were thus risk-prone with respect to the potential loss of foraging opportunities in deep snow compared with young females and those in poor nutritional condition. Females that summered on the west side of the crest of the Sierra Nevada delayed autumn migration relative to east-side females, which supports the influence of the local environment on timing of migration. In contrast, timing of spring migration was unrelated to individual life-history characteristics, was nearly twice as synchronous as autumn migration, differed among years, was related to the southern oscillation index, and was influenced by absolute snow depth and advancing phenology of plants. Plasticity in timing of migration in response to climatic conditions and plant phenology may be an adaptive behavioral strategy, which should reduce the detrimental effects of trophic mismatches between resources and other life-history events of large herbivores. Failure to consider effects of nutrition and other life-history traits may cloud interpretation of phenological patterns of mammals and conceal relationships associated with climate change. © 2011 Monteith et al."
"8726272900;7005304841;7005712238;56250250300;12139043600;7003827051;12139310900;35600074800;","The effect of sea ice loss on sea salt aerosol concentrations and the radiative balance in the Arctic",2011,"10.5194/acp-11-3459-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954447911&doi=10.5194%2facp-11-3459-2011&partnerID=40&md5=1754f3c5fe6aa7c6327a5e0939aec725","Understanding Arctic climate change requires knowledge of both the external and the local drivers of Arctic climate as well as local feedbacks within the system. An Arctic feedback mechanism relating changes in sea ice extent to an alteration of the emission of sea salt aerosol and the consequent change in radiative balance is examined. A set of idealized climate model simulations were performed to quantify the radiative effects of changes in sea salt aerosol emissions induced by prescribed changes in sea ice extent. The model was forced using sea ice concentrations consistent with present day conditions and projections of sea ice extent for 2100. Sea salt aerosol emissions increase in response to a decrease in sea ice, the model results showing an annual average increase in number emission over the polar cap (70-90° N) of 86 × 106 m-2 s-1 (mass emission increase of 23 μgm-2 s-1). This in turn leads to an increase in the natural aerosol optical depth of approximately 23%. In response to changes in aerosol optical depth, the natural component of the aerosol direct forcing over the Arctic polar cap is estimated to be between -0.2 and -0.4 W m-2 for the summer months, which results in a negative feedback on the system. The model predicts that the change in first indirect aerosol effect (cloud albedo effect) is approximately a factor of ten greater than the change in direct aerosol forcing although this result is highly uncertain due to the crude representation of Arctic clouds and aerosol-cloud interactions in the model. This study shows that both the natural aerosol direct and first indirect effects are strongly dependent on the surface albedo, highlighting the strong coupling between sea ice, aerosols, Arctic clouds and their radiative effects. © 2011 Author(s)."
"23065650200;55663817800;9535817700;","Understanding effective diameter and its application to terrestrial radiation in ice clouds",2011,"10.5194/acp-11-3417-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953836201&doi=10.5194%2facp-11-3417-2011&partnerID=40&md5=8d59760a26d88ac41213c40ade162d86","The cloud property known as ""effective diameter"" or ""effective radius"", which in essence is the cloud particle size distribution (PSD) volume at bulk density divided by its projected area, is used extensively in atmospheric radiation transfer, climate modeling and remote sensing. This derives from the assumption that PSD optical properties can be uniquely described in terms of their effective diameter, De, and their cloud water content (CWC), henceforth referred to as the De-CWC assumption. This study challenges this assumption, showing that while the De-CWC assumption appears generally valid for liquid water clouds, it appears less valid for ice clouds in regions where (1) absorption is not primarily a function of either the PSD ice water content (IWC) or the PSD projected area, and (2) where wave resonance (i.e. photon tunneling) contributes significantly to absorption. These two regions often strongly coincide at terrestrial wavelengths when De&lt;∼60 μm, which is where this De-CWC assumption appears poorest. Treating optical properties solely in terms of De and IWC may lead to errors up to 24%, 26% and 20% for terrestrial radiation in the window region regarding the absorption and extinction coefficients and the single scattering albedo, respectively. Outside the window region, errors may reach 33% and 42% regarding absorption and extinction. The magnitude and sign of these errors can change rapidly with wavelength, which may produce significant errors in climate modeling, remote sensing and other applications concerned with the wavelength dependence of radiation. Where the De-CWC assumption breaks down, ice cloud optical properties appear to depend on De, IWC and the PSD shape. Optical property parameterizations in climate models and remote sensing algorithms based on historical PSD measurements may exhibit errors due to previously unknown PSD errors (i.e. the presence of ice artifacts due to the shattering of larger ice particles on the probe inlet tube during sampling). More recently developed cloud probes are designed to mitigate this shattering problem. Using realistic PSD shapes for a given temperature (and/or IWC) and cloud type may minimize errors associated with PSD shape in ice optics parameterizations and remote sensing algorithms. While this topic was investigated using two ice optics schemes (the Yang et al., 2005 database and the modified anomalous diffraction approximation, or MADA), a physical understanding of the limitations of the De-IWC assumption was made possible by using MADA. MADA allows one to approximate the contribution of photon tunneling to absorption relative to other optical processes, which reveals that part of the error regarding the De-IWC assumption can be associated with tunneling. By relating the remaining error to the radiation penetration depth in bulk ice (ΔL) due to absorption, the domain where the De-IWC assumption is weakest was described in terms of De and ΔL. © 2011 Author(s)."
"8336962200;10739072200;56370907100;8084443000;26643041500;35461255500;","Parameterization of ion-induced nucleation rates based on ambient observations",2011,"10.5194/acp-11-3393-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953837814&doi=10.5194%2facp-11-3393-2011&partnerID=40&md5=0aa93e30e3db732e7e517ba13a166741","Atmospheric ions participate in the formation of new atmospheric aerosol particles, yet their exact role in this process has remained unclear. Here we derive a new simple parameterization for ion-induced nucleation or, more precisely, for the formation rate of charged 2-nm particles. The parameterization is semi-empirical in the sense that it is based on comprehensive results of one-year-long atmospheric cluster and particle measurements in the size range ∼1-42 nm within the EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions) project. Data from 12 field sites across Europe measured with different types of air ion and cluster mobility spectrometers were used in our analysis, with more in-depth analysis made using data from four stations with concomitant sulphuric acid measurements. The parameterization is given in two slightly different forms: a more accurate one that requires information on sulfuric acid and nucleating organic vapor concentrations, and a simpler one in which this information is replaced with the global radiation intensity. These new parameterizations are applicable to all large-scale atmospheric models containing size-resolved aerosol microphysics, and a scheme to calculate concentrations of sulphuric acid, condensing organic vapours and cluster ions. © 2011 Author(s)."
"37089417300;56151703900;13402933200;7102988363;8718425100;35998927000;","Climate impact of biofuels in shipping: Global model studies of the aerosol indirect effect",2011,"10.1021/es1036157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954474909&doi=10.1021%2fes1036157&partnerID=40&md5=18da1f7dbac404ae6a7f03654cdb6dcd","Aerosol emissions from international shipping are recognized to have a large impact on the Earth's radiation budget, directly by scattering and absorbing solar radiation and indirectly by altering cloud properties. New regulations have recently been approved by the International Maritime Organization (IMO) aiming at progressive reductions of the maximum sulfur content allowed in marine fuels from current 4.5% by mass down to 0.5% in 2020, with more restrictive limits already applied in some coastal regions. In this context, we use a global bottom-up algorithm to calculate geographically resolved emission inventories of gaseous (NOx, CO, SO2) and aerosol (black carbon, organic matter, sulfate) species for different kinds of low-sulfur fuels in shipping. We apply these inventories to study the resulting changes in radiative forcing, attributed to particles from shipping, with the global aerosol-climate model EMAC-MADE. The emission factors for the different fuels are based on measurements at a test bed of a large diesel engine. We consider both fossil fuel (marine gas oil) and biofuels (palm and soy bean oil) as a substitute for heavy fuel oil in the current (2006) fleet and compare their climate impact to that resulting from heavy fuel oil use. Our simulations suggest that ship-induced surface level concentrations of sulfate aerosol are strongly reduced, up to about 40-60% in the high-traffic regions. This clearly has positive consequences for pollution reduction in the vicinity of major harbors. Additionally, such reductions in the aerosol loading lead to a decrease of a factor of 3-4 in the indirect global aerosol effect induced by emissions from international shipping. © 2011 American Chemical Society."
"24173873500;7004174939;55113736500;","Microphysical and radiative effects of aerosols on warm clouds during the Amazon biomass burning season as observed by MODIS: Impacts of water vapor and land cover",2011,"10.5194/acp-11-3021-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953693609&doi=10.5194%2facp-11-3021-2011&partnerID=40&md5=96434bdb0fbe01fc5344128e87f0b8b1","Aerosol, cloud, water vapor, and temperature profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are utilized to examine the impact of aerosols on clouds during the Amazonian biomass burning season in Rondnia, Brazil. It is found that increasing background column water vapor (CWV) throughout this transition season between the Amazon dry and wet seasons likely exerts a strong effect on cloud properties. As a result, proper analysis of aerosol-cloud relationships requires that data be stratified by CWV to account better for the influence of background meteorological variation. Many previous studies of aerosol-cloud interactions over Amazonia have ignored the systematic changes to meteorological factors during the transition season, leading to possible misinterpretation of their results. Cloud fraction (CF) is shown to increase or remain constant with aerosol optical depth (AOD), depending on the value of CWV, whereas the relationship between cloud optical depth (COD) and AOD is quite different. COD increases with AOD until AOD ∼ 0.3, which is assumed to be due to the first indirect (microphysical) effect. At higher values of AOD, COD is found to decrease with increasing AOD, which may be due to: (1) the inhibition of cloud development by absorbing aerosols (radiative effect/semi-direct effect) and/or (2) a possible retrieval artifact in which the measured reflectance in the visible is less than expected from a cloud top either from the darkening of clouds through the addition of carbonaceous biomass burning aerosols within or above clouds or subpixel dark surface contamination in the measured cloud reflectance. If (1) is a contributing mechanism, as we suspect, then an empirically-derived increasing function between cloud drop number and aerosol concentration, assumed in a majority of global climate models, is inaccurate since these models do not include treatment of aerosol absorption in and around clouds. The relationship between aerosols and both CWV and clouds over varying land surface types is also analyzed. The study finds that the difference in CWV between forested and deforested land is not correlated with aerosol loading, supporting the assumption that temporal variation of CWV is primarily a function of the larger-scale meteorology. However, a difference in the response of CF to increasing AOD is observed between forested and deforested land. This suggests that dissimilarities between other meteorological factors, such as atmospheric stability, may have an impact on aerosol-cloud correlations between different land cover types. © 2011 Author(s)."
"6602380901;55499821700;6603126554;","Scale-by-scale analysis of probability distributions for global MODIS-AQUA cloud properties: How the large scale signature of turbulence may impact statistical analyses of clouds",2011,"10.5194/acp-11-2893-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953203558&doi=10.5194%2facp-11-2893-2011&partnerID=40&md5=6d82979ba288b587ccdc24ab98d61a31","Means, standard deviations, homogeneity parameters used in models based on their ratio, and the probability distribution functions (PDFs) of cloud properties from the MODerate resolution Infrared Spectrometer (MODIS) are estimated globally as function of averaging scale varying from 5 to 500 km. The properties ĝ€"" cloud fraction, droplet effective radius, and liquid water path ĝ€"" all matter for cloud-climate uncertainty quantification and reduction efforts. Global means and standard deviations are confirmed to change with scale. For the range of scales considered, global means vary only within 3% for cloud fraction, 7% for liquid water path, and 0.2% for cloud particle effective radius. These scale dependences contribute to the uncertainties in their global budgets. Scale dependence for standard deviations and generalized flatness are compared to predictions for turbulent systems. Analytical expressions are identified that fit best to each observed PDF. While the best analytical PDF fit to each variable differs, <i>all</i> PDFs are well described by log-normal PDFs when the mean is normalized by the standard deviation inside each averaging domain. Importantly, log-normal distributions yield significantly better fits to the observations than gaussians at all scales. This suggests a possible approach for both sub-grid and unified stochastic modeling of these variables at all scales. The results also highlight the need to establish an adequate spatial resolution for two-stream radiative studies of cloud-climate interactions. © Author(s) 2011."
"15834571900;49662169400;55460969900;7006145109;","Phenological response of vegetation to upstream river flow in the Heihe Rive basin by time series analysis of MODIS data",2011,"10.5194/hess-15-1047-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953214601&doi=10.5194%2fhess-15-1047-2011&partnerID=40&md5=cc349d3ccd1711e6d02ee7db93b86f64","Liquid and solid precipitation is abundant in the high elevation, upper reach of the Heihe River basin in northwestern China. The development of modern irrigation schemes in the middle reach of the basin is taking up an increasing share of fresh water resources, endangering the oasis and traditional irrigation systems in the lower reach. In this study, the response of vegetation in the Ejina Oasis in the lower reach of the Heihe River to the water yield of the upper catchment was analyzed by time series analysis of monthly observations of precipitation in the upper and lower catchment, river streamflow downstream of the modern irrigation schemes and satellite observations of vegetation index. Firstly, remotely sensed NDVI data acquired by Terra-MODIS are used to monitor the vegetation dynamic for a seven years period between 2000 and 2006. Due to cloud-contamination, atmospheric influence and different solar and viewing angles, however, the quality and consistence of time series of remotely sensed NDVI data are degraded. A Fourier Transform method - the Harmonic Analysis of Time Series (HANTS) algorithm - is used to reconstruct cloud- and noise-free NDVI time series data from the Terra-MODIS NDVI dataset. Modification is made on HANTS by adding additional parameters to deal with large data gaps in yearly time series in combination with a Temporal-Similarity-Statistics (TSS) method developed in this study to seek for initial values for the large gap periods. Secondly, the same Fourier Transform method is used to model time series of the vegetation phenology. The reconstructed cloud-free NDVI time series data are used to study the relationship between the water availability (i.e. the local precipitation and upstream water yield) and the evolution of vegetation conditions in Ejina Oasis from 2000 to 2006. Anomalies in precipitation, streamflow, and vegetation index are detected by comparing each year with the average year. The results showed that: the previous year total runoff had a significant relationship with the vegetation growth in Ejina Oasis and that anomalies in the spring monthly runoff of the Heihe River influenced the phenology of vegetation in the entire oasis. Warmer climate expressed by the degree-days showed positive influence on the vegetation phenology in particular during drier years. The time of maximum green-up is uniform throughout the oasis during wetter years, but showed a clear S-N gradient (downstream) during drier years. © Author(s) 2011."
"7407104838;7102805852;57203200427;","A comparison of the climate impacts of geoengineering by stratospheric SO2 injection and by brightening of marine stratocumulus cloud",2011,"10.1002/asl.291","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954577299&doi=10.1002%2fasl.291&partnerID=40&md5=b5b4d7c2e7190905e8f800bce45dc7a0","We examine the climate impact of geoengineering via two different methods, namely, stratospheric SO2 injection and increasing reflectivity of marine stratocumulus clouds. Although both methods appear capable, in principle, of counteracting the global mean warming due to increases in greenhouse gas concentrations, significant changes in regional climate still result. The extent of this regional climate change appears linked to the location and degree of inhomogeneity of the radiative flux perturbations produced by each geoengineering method. © 2010."
"57202891769;57202754759;57210350827;","Changes in Arctic clouds during intervals of rapid sea ice loss",2011,"10.1007/s00382-010-0816-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953668349&doi=10.1007%2fs00382-010-0816-0&partnerID=40&md5=3af20458d677190c6f2e305f0b287ea6","We investigate the behavior of clouds during rapid sea ice loss events (RILEs) in the Arctic, as simulated by multiple ensemble projections of the 21st century in the Community Climate System Model (CCSM3). Trends in cloud properties and sea ice coverage during RILEs are compared with their secular trends between 2000 and 2049 during summer, autumn, and winter. The results suggest that clouds promote abrupt Arctic climate change during RILEs through increased (decreased) cloudiness in autumn (summer) relative to the changes over the first half of the 21st century. The trends in cloud characteristics (cloud amount, water content, and radiative forcing) during RILEs are most strongly and consistently an amplifying effect during autumn, the season in which RILEs account for the majority of the secular trends. The total cloud trends in every season are primarily due to low clouds, which show a more robust response than middle and high clouds across RILEs. Lead-lag correlations of monthly sea ice concentration and cloud cover during autumn reveal that the relationship between less ice and more clouds is enhanced during RILEs, but there is no evidence that either variable is leading the other. Given that Arctic cloud projections in CCSM3 are similar to those from other state-of-the-art GCMs and that observations show increased autumn cloudiness associated with the extreme 2007 and 2008 sea ice minima, this study suggests that the rapidly declining Arctic sea ice will be accentuated by changes in polar clouds. © 2010 Springer-Verlag."
"7004299063;","Bubble, bubble, toil and trouble: An editorial comment",2011,"10.1007/s10584-010-0017-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952746760&doi=10.1007%2fs10584-010-0017-1&partnerID=40&md5=e0d3083ad553a4307182c2b10bf9c840",[No abstract available]
"9434771700;7401666571;6602075440;7203015939;6602897033;","Changes in dimethyl sulfide oceanic distribution due to climate change",2011,"10.1029/2011GL047069","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955008165&doi=10.1029%2f2011GL047069&partnerID=40&md5=a69338e55b89ed3d8510b6d716b1ac0f","Dimethyl sulfide (DMS) is one of the major precursors for aerosols and cloud condensation nuclei in the marine boundary layer over much of the remote ocean. Here we report on coupled climate simulations with a state-of-the-art global ocean biogeochemical model for DMS distribution and fluxes using present-day and future atmospheric CO<inf>2</inf> concentrations. We find changes in zonal averaged DMS flux to the atmosphere of over 150% in the Southern Ocean. This is due to concurrent sea ice changes and ocean ecosystem composition shifts caused by changes in temperature, mixing, nutrient, and light regimes. The largest changes occur in a region already sensitive to climate change, so any resultant local CLAW/Gaia feedback of DMS on clouds, and thus radiative forcing, will be particularly important. A comparison of these results to prior studies shows that increasing model complexity is associated with reduced DMS emissions at the equator and increased emissions at high latitudes. Copyright 2011 by the American Geophysical Union."
"11241983900;6508201898;57198384395;57203230296;","The role of satellite data within GCOS Switzerland",2011,"10.3390/rs3040767","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052004013&doi=10.3390%2frs3040767&partnerID=40&md5=483c5e564223f61d306af59667177d24","The Global Climate Observing System (GCOS) was established in 1992 to ensure that the observations necessary to address climate-related issues are defined, obtained and made available, to all potential users. The Swiss GCOS Office at the Federal Office of Meteorology and Climatology MeteoSwiss has the task of coordinating all climate relevant measurements in Switzerland (GCOS Switzerland). As such, the Swiss GCOS Office also fosters the exploration of new measurement techniques and methods, in particular through the use of satellite-based data, to complement the long-term in situ observations in Switzerland. In this paper, the role of satellites is presented for climatological studies of atmospheric and terrestrial Essential Climate Variables in Switzerland. For the atmospheric domain, the 10-year climatology March 2000-February 2010 of cloud cover from MODIS is shown for Switzerland, in low (1° × 1°) and high (0.05° × 0.05°) resolution, and compared to ground-based synop observations. For the terrestrial domain, the satellite-derived Swiss glacier inventory from 1998/99 and the new Alpine-wide inventory from 2003 is presented along with area changes derived from a comparison with previous inventories. © 2011 by the authors."
"56284543100;26643250500;","Global radiative forcing from contrail cirrus",2011,"10.1038/nclimate1068","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960447494&doi=10.1038%2fnclimate1068&partnerID=40&md5=94bed63009b181a84822560e53fcf284","Aviation makes a significant contribution to anthropogenic climate forcing. The impacts arise from emissions of greenhouse gases, aerosols and nitrogen oxides, and from changes in cloudiness in the upper troposphere. An important but poorly understood component of this forcing is caused by 'contrail cirrus' - a type of cloud that consist of young line-shaped contrails and the older irregularly shaped contrails that arise from them. Here we use a global climate model that captures the whole life cycle of these man-made clouds to simulate their global coverage, as well as the changes in natural cloudiness that they induce. We show that the radiative forcing associated with contrail cirrus as a whole is about nine times larger than that from line-shaped contrails alone. We also find that contrail cirrus cause a significant decrease in natural cloudiness, which partly offsets their warming effect. Nevertheless, net radiative forcing due to contrail cirrus remains the largest single radiative-forcing component associated with aviation. Our findings regarding global radiative forcing by contrail cirrus will allow their effects to be included in studies assessing the impacts of aviation on climate and appropriate mitigation options. © 2011 Macmillan Publishers Limited."
"55702592400;6603550074;55717441600;55262499900;6701545503;7403931916;55967620900;9238037100;","Global land surface emissivity retrieved from satellite ultraspectral IR measurements",2011,"10.1109/TGRS.2010.2051036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953210715&doi=10.1109%2fTGRS.2010.2051036&partnerID=40&md5=2444579715ead0a82a513aa4ae8f05a9","Ultraspectral resolution infrared (IR) radiances obtained from nadir observations provide information about the atmosphere, surface, aerosols, and clouds. Surface spectral emissivity (SSE) and surface skin temperature from current and future operational satellites can and will reveal critical information about the Earth's ecosystem and land-surface-type properties, which might be utilized as a means of long-term monitoring of the Earth's environment and global climate change. In this study, fast radiative transfer models applied to the atmosphere under all weather conditions are used for atmospheric profile and surface or cloud parameter retrieval from ultraspectral and/or hyperspectral spaceborne IR soundings. An inversion scheme, dealing with cloudy as well as cloud-free radiances observed with ultraspectral IR sounders, has been developed to simultaneously retrieve atmospheric thermodynamic and surface or cloud microphysical parameters. This inversion scheme has been applied to the Infrared Atmospheric Sounding Interferometer (IASI). Rapidly produced SSE is initially evaluated through quality control checks on the retrievals of other impacted surface and atmospheric parameters. Initial validation of retrieved emissivity spectra is conducted with Namib and Kalahari desert laboratory measurements. Seasonal products of global land SSE and surface skin temperature retrieved with IASI are presented to demonstrate seasonal variation of SSE. © 2006 IEEE."
"55940162000;36617027200;","How air pollution affects climate: Short-lived climate forcers",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955694607&partnerID=40&md5=3aea2799be28c8d33613005080c74bfe","Black carbon and ozone, the so-called 'short-lived climate forcers' impact on air quality is discussed. A short-lived climate forcer (SLCF) is simply a pollutant that influences radiative forcing, but has a significantly shorter life span than long-lived GHGs (greenhouse gases). The indirect effects of particles on climate include impacts on cloud formation and lifetime, and precipitation patterns. Both black carbon and ozone are involved in complex atmospheric chemistry affecting formation, processing, transport, and environmental fate. One important feature of SLCFs is their ability to influence climate through mechanisms besides just temperature. Reducing black carbon or ozone precursors for climate purposes will have strong co-benefits for public health and the environment. EPA and other U.S. federal agencies have been involved in efforts to try to assign monetary values to reductions in climate pollutants such as CO2."
"6506545080;7203034123;","Estimating the sensitivity of radiative impacts of shallow, broken marine clouds to boundary layer aerosol size distribution parameter uncertainties for evaluation of satellite retrieval requirements",2011,"10.1175/2010JTECHA1520.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958750274&doi=10.1175%2f2010JTECHA1520.1&partnerID=40&md5=fb093cda1219b2df808e83207e7dddfc","A proposed objective of the planned Aerosol-Cloud-Ecosystem (ACE) satellite mission is to provide constraints on climate model representation of aerosol effects on clouds by retrieving profiles of aerosol number concentration, effective variance, and effective radius over the 0.1-1-μm radius range under humidified ambient conditions with 500-m vertical resolution and uncertainties of 100%, 50%, and 10%, respectively. Shallow, broken marine clouds provide an example of conditions where boundary layer aerosol properties would be retrieved in clear-sky gaps. To quantify the degree of constraint that proposed retrievals might provide on cloud radiative forcing (CRF) simulated by climate models under such conditions, dry aerosol size distribution parameters are independently varied here in large-eddy simulations of three wellestablished modeling case studies. Using the rudimentary available aerosol specifications, it is found that relative changes of total dry aerosol properties in simulations can be used as a proxy for relative changes of ambient aerosol properties targeted by ACE retrievals. The sensitivity of simulated daytime shortwave CRF to the proposed uncertainty in retrieved aerosol number concentration is 215 W m-2 in the overcast limit, roughly a factor of 2 smaller than a simple analytic estimate owing primarily to aerosol-induced reductions in simulated liquid water path across this particular set of case studies. The CRF sensitivity to proposed uncertainties in retrieved aerosol effective variance and effective radius is typically far smaller, with no corresponding analytic estimate. Generalization of the results obtained here using only three case studies would require statistical analysis of relevant meteorological and aerosol observations and quantification of observational and model uncertainties and biases. © 2011 American Meteorological Society."
"36449278400;6603599576;17434636400;6508262693;8670222900;7004402705;22633628500;8383395800;36449157300;56232242500;6701636816;57219139553;7006532784;","Representation of tropical deep convection in atmospheric models-Part 1: Meteorology and comparison with satellite observations",2011,"10.5194/acp-11-2765-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953139012&doi=10.5194%2facp-11-2765-2011&partnerID=40&md5=73f7bb05d6f6da3d4804fe2bb0c2edd9","Fast convective transport in the tropics can efficiently redistribute water vapour and pollutants up to the upper troposphere. In this study we compare tropical convection characteristics for the year 2005 in a range of atmospheric models, including numerical weather prediction (NWP) models, chemistry transport models (CTMs), and chemistry-climate models (CCMs). The model runs have been performed within the framework of the SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere) project. The characteristics of tropical convection, such as seasonal cycle, land/sea contrast and vertical extent, are analysed using satellite observations as a benchmark for model simulations. The observational datasets used in this work comprise precipitation rates, outgoing longwave radiation, cloud-top pressure, and water vapour from a number of independent sources, including ERA-Interim analyses. Most models are generally able to reproduce the seasonal cycle and strength of precipitation for continental regions but show larger discrepancies with observations for the Maritime Continent region. The frequency distribution of high clouds from models and observations is calculated using highly temporally-resolved (up to 3-hourly) cloud top data. The percentage of clouds above 15 km varies significantly between the models. Vertical profiles of water vapour in the upper troposphere-lower stratosphere (UTLS) show large differences between the models which can only be partly attributed to temperature differences. If a convective plume reaches above the level of zero net radiative heating, which is estimated to be ∼15 km in the tropics, the air detrained from it can be transported upwards by radiative heating into the lower stratosphere. In this context, we discuss the role of tropical convection as a precursor for the transport of short-lived species into the lower stratosphere. © 2011 Author(s)."
"6601958210;6701723617;","Possible impact of interplanetary and interstellar dust fluxes on the Earth's climate",2011,"10.1134/S0016793211020137","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953710052&doi=10.1134%2fS0016793211020137&partnerID=40&md5=71972cc9acc8acfa172de600e3fc5c8e","This article considers the process of entry of cosmic substance into the Earth's atmosphere and the further evolution of the formed extraterrestrial aerosol. It is shown that meteorite-derived aerosol generated in the atmosphere may affect the Earth's climate in two ways: (a) particles of meteoric haze may serve as condensation nuclei in the troposphere and stratosphere; (b) charged meteor particles residing in the mesosphere may markedly change (by a few percent) the total atmospheric resistance and, thereby, affect the global current circuit. Changes in the global electric circuit, in turn, may influence cloud formation processes. The obtained results argue for the fact that the meteoric dust in the Earth's atmosphere is potentially one of the important climate-forming agents. It is shown that the amount of interstellar dust in the Earth's atmosphere is too small to have a considerable affect on atmospheric processes. © 2011 Pleiades Publishing, Ltd."
"6602300399;37098567800;","Postprocessing of simulated precipitation for impact research in West Africa. Part II: A weather generator for daily data",2011,"10.1007/s00382-010-0840-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953652603&doi=10.1007%2fs00382-010-0840-0&partnerID=40&md5=ae28ec3d0555f802d407a6c447b70916","Data from global and regional climate models refer to grid cells and, hence, are basically different from station data. This particularly holds for variables with enhanced spatio-temporal variability like precipitation. On the other hand, many applications like for instance hydrological models require atmospheric data with the statistical characteristics of station data. Here, we present a dynamical-statistical tool to construct virtual station data based on regional climate model output for tropical West Africa. This weather generator (WEGE) incorporates daily gridded rainfall from the model, an orographic term and a stochastic term, accounting for the chaotic spatial distribution of local rain events within a model grid box. In addition, the simulated probability density function of daily precipitation is adjusted to available station data in Benin. It is also assured that the generated data are still consistent with other model parameters like cloudiness and atmospheric circulation. The resulting virtual station data are in excellent agreement with various observed characteristics which are not explicitly addressed by the WEGE algorithm. This holds for the mean daily rainfall intensity and variability, the relative number of rainless days and the scaling of precipitation in time. The data set has already been used successfully for various climate impact studies in Benin. © 2010 Springer-Verlag."
"6603369413;","A mixed exponential distribution model for retrieving ground flash fraction from satellite lightning imager data",2011,"10.1175/2010JTECHA1438.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958727925&doi=10.1175%2f2010JTECHA1438.1&partnerID=40&md5=df1df10acea448d5a58efc202eb76e83","A Bayesian inversion method is introduced for retrieving the fraction of ground flashes in a set of flashes observed from a (low earth orbiting or geostationary) satellite lightning imager. The method employs a constrained mixed exponential distribution model to describe the lightning optical measurements. Because the method also retrieves certain population statistics of ground and cloud flash optical properties, the method can be applied to an arbitrary geographical region, including those regions where the lightning optical statistics either are not known or are difficult to obtain. The approach is tested by performing simulated retrievals, and retrieval error statistics are provided. A first-attempt retrieval of the global geographical distribution of ground flash fraction is obtained using the 5-yr Optical Transient Detector (OTD) dataset; the spatially averaged ground flash fraction over the global-scale domain studied was 0.151 with a standard deviation of 0.081. The ability to retrieve ground flash fraction has important benefits to the atmospheric chemistry community. For example, using the method to partition the existing OTD/Lightning Imaging Sensor (LIS) satellite global lightning climatology into separate ground and cloud flash climatologies would improve estimates of regional and global lightning nitrogen oxides (NOx) production; this, in turn, would improve both regional air quality and global chemistry/climate model predictions. © 2011 American Meteorological Society."
"35768617200;7006717176;6701339904;","CALIPSO detection of an Asian tropopause aerosol layer",2011,"10.1029/2010GL046614","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955026963&doi=10.1029%2f2010GL046614&partnerID=40&md5=43f3f4363d00164d3862fc3a2e3a372d","The first four years of the CALIPSO lidar measurements have revealed the existence of an aerosol layer at the tropopause level associated with the Asian monsoon season in June, July and August. This Asian Tropopause Aerosol Layer (ATAL) extends geographically from Eastern Mediterranean (down to North Africa) to Western China (down to Thailand), and vertically from 13 to 18 km. The Scattering Ratio inferred from CALIPSO shows values between 1.10-1.15 on average with associated depolarization ratio of less than 5%. The Gaussian distribution of the points indicates that the mean value is statistically driven by an enhancement of the background aerosol level and not by episodic events such as a volcanic eruption or cloud contamination. Further satellite observations of aerosols and gases as well as field campaigns are urgently needed to characterize this layer, which is likely to be a significant source of non-volcanic aerosols for the global upper troposphere with a potential impact on its radiative and chemical balance. Copyright 2011 by the American Geophysical Union."
"12445513700;","Bright water: Hydrosols, water conservation and climate change",2011,"10.1007/s10584-010-9965-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952752663&doi=10.1007%2fs10584-010-9965-8&partnerID=40&md5=da59da81e7a6f11a6b8909385cfaec44","Because air-water and water-air interfaces are equally refractive, cloud droplets and microbubbles dispersed in bodies of water reflect sunlight in much the same way. The lifetime of sunlight-reflecting microbubbles, and hence the scale on which they may be applied, depends on Stokes Law and the influence of ambient or added surfactants. Small bubbles backscatter light more efficiently than large ones, opening the possibility of using highly dilute micron-radius hydrosols to substantially brighten surface waters. Such microbubbles can noticeably increase water surface reflectivity, even at volume fractions of parts per million and such loadings can be created at an energy cost as low as J m-2 to initiate and mW m-2 to sustain. Increasing water albedo in this way can reduce solar energy absorption by as much as 100 W m-2, potentially reducing equilibrium temperatures of standing water bodies by several Kelvins. While aerosols injected into the stratosphere tend to alter climate globally, hydrosols can be used to modulate surface albedo, locally and reversibly, without risk of degrading the ozone layer or altering the color of the sky. The low energy cost of microbubbles suggests a new approach to solar radiation management in water conservation and geoengineering: Don't dim the Sun; Brighten the water. © 2010 Springer Science+Business Media B.V."
"7103229409;57219759726;","A new mechanism for ocean-atmosphere coupling in midlatitudes",2011,"10.1002/qj.814","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957885934&doi=10.1002%2fqj.814&partnerID=40&md5=506032a5ffea3716c079f8df663ea1ac","The role of moist convection in 'transferring' upward surface ocean conditions throughout the troposphere is studied using reanalysis data for the extratropical Northern and Southern Hemispheres in winter. It is found that conditions for the development of a convective air column from the sea surface to the tropopause are met frequently over all major western boundary currents and their extension in the oceanic interior (sometimes for as much as 50% of the time). These frequent occurrences are shown to be jointly controlled by oceanic advection of warm waters and, on the atmospheric side, the downward displacement of the tropopause associated with synoptic weather systems. Based on these results, it is proposed that the oceans can influence the atmosphere directly through convection in midlatitudes, as is commonly thought to occur in the Tropics. Analysis of the Richardson number Ri found at low levels suggests that moist symmetric instability (0 &lt; Ri ≤ 1) is a key process involved in linking surface ocean temperatures to atmospheric lapse rates, in addition to standard upright convection. These low Ri processes are not currently parametrized in climate models, which raises the possibility that the extratropical oceanic influence on climate might be underestimated in the current generation of models. Copyright © 2011 Royal Meteorological Society."
"6602300399;","Postprocessing of simulated precipitation for impact research in West Africa. Part I: Model output statistics for monthly data",2011,"10.1007/s00382-010-0760-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953670210&doi=10.1007%2fs00382-010-0760-z&partnerID=40&md5=5f9fdd3b1a3757045350ce306e2e4274","Rainfall represents an important factor in agriculture and food security, particularly, in the low latitudes. Climatological and hydrological studies which attempt to diagnose the hydrological cycle, require high-quality precipitation data. In West Africa, like in many parts of the world, the density of observational data is low and climate models are needed in order to perform homogeneous and complete data sets. However, climate models tend to produce systematic errors, especially, in terms of rainfall and cloud processes, which are usually approximated by physical parameterizations. In this study, a 25-year climatology of monthly precipitation in West Africa is presented, derived from a regional climate model simulation, and evaluated with respect to observational data. It is found that the model systematically underestimates the rainfall amount and variability and does not capture some details of the seasonal cycle in sub-Saharan West Africa. Thus, in its present form the precipitation climatology is not appropriate to draw a realistic picture of the hydrological cycle in West Africa nor to serve as input data for impact research. Therefore, a statistical model is developed in order to adjust the simulated rainfall data to the characteristics of observed precipitation. Assuming that the regional climate model is much more reliable in terms of atmospheric circulation and thermodynamics, model output statistics is used to correct simulated rainfall by means of other simulated parameters of the near-surface climate like temperature, sea level pressure and wind components. Monthly data is adjusted by a cross-validated multiple regression model. The resulting adjusted rainfall climatology reveals a substantial improvement in terms of the model deficiencies mentioned above. In part II of this publication, the characteristics of simulated daily precipitation is adapted to station data by applying a weather generator. Once the postprocessing approach is trained, it can be extrapolated to simulation periods, for which observational data do not exist like for instance future climate. © 2010 Springer-Verlag."
"6701846706;6602205640;55951088700;55857096100;47961004800;7004035832;6602529747;36626171700;37028915500;7003557623;","Upslope migration of Andean trees",2011,"10.1111/j.1365-2699.2010.02444.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952684476&doi=10.1111%2fj.1365-2699.2010.02444.x&partnerID=40&md5=2c92b1330bacaea4e60fa8764394bd37","Aim Climate change causes shifts in species distributions, or 'migrations'. Despite the centrality of species distributions to biodiversity conservation, the demonstrated large migration of tropical plant species in response to climate change in the past, and the expected sensitivity of species distributions to modern climate change, no study has tested for modern species migrations in tropical plants. Here we conduct a first test of the hypothesis that increasing temperatures are causing tropical trees to migrate to cooler areas. Location Tropical Andes biodiversity hotspot, south-eastern Peru, South America. Methods We use data from repeated (2003/04-2007/08) censuses of 14 1-ha forest inventory plots spanning an elevational gradient from 950 to 3400m in Manu National Park in south-eastern Peru, to characterize changes in the elevational distributions of 38 Andean tree genera. We also analyse changes in the genus-level composition of the inventory plots through time. Results We show that most tropical Andean tree genera shifted their mean distributions upslope over the study period and that the mean rate of migration is approximately 2.5-3.5 vertical metres upslope per year. Consistent with upward migrations we also find increasing abundances of tree genera previously distributed at lower elevations in the majority of study plots. Main conclusions These findings are in accord with the a priori hypothesis of upward shifts in species ranges due to elevated temperatures, and are potentially the first documented evidence of present-day climate-driven migrations in a tropical plant community. The observed mean rate of change is less than predicted from the temperature increases for the region, possibly due to the influence of changes in moisture or non-climatic factors such as substrate, species interactions, lags in tree community response and/or dispersal limitations. Whatever the cause(s), continued slower-than-expected migration of tropical Andean trees would indicate a limited ability to respond to increased temperatures, which may lead to increased extinction risks with further climate change. © 2010 Blackwell Publishing Ltd."
"8266754800;57203199846;","The effect of explosive tropical volcanism on ENSO",2011,"10.1175/2010JCLI3990.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958163143&doi=10.1175%2f2010JCLI3990.1&partnerID=40&md5=68cd6eaf43097fbdb381156a648e72eb","This study examines the response of El Niñ o-Southern Oscillation (ENSO) to massive volcanic eruptions in a suite of coupled general circulation model (CGCM) simulations utilizing the Community Climate System Model, version 3 (CCSM3). The authors find that the radiative forcing due to volcanic aerosols injected into the stratosphere induces a model climatic response that projects onto the ENSO mode and initially creates a La Niñ a event that peaks around the time the volcanic forcing peaks. The curl of the wind stress changes accompanying this volcanically forced equatorial region cooling acts to recharge the equatorial region heat. For weaker volcanic eruptions, this recharging results in an El Niño event about two seasons after the peak of the volcanic forcing. The results of the CCSM3 volcanic forcing experiments lead the authors to propose that the initial tropical Pacific Ocean response to volcanic forcing is determined by four different mechanisms- one process is the dynamical thermostat mechanism (the mean upwelling of anomalous temperature) and the other processes are related to the zonal equatorial gradients of the mean cloud albedo, Newtonian cooling, andmixed layer depth. The zonal gradient in CCSM3 set by bothmixed layer depth and Newtonian cooling terms oppose the zonal sea surface temperature anomaly (SSTA) gradient produced by the dynamical thermostat and initially dominate the mixed layer zonal equatorial heat budget response. Applying this knowledge to a simple volcanically forced mixed layer equation using observed estimates of the spatially varying variables, the authors again find that the mixed layer depth and Newtonian cooling terms oppose and dominate the zonal SSTA gradient produced by the dynamical thermostat. This implies that the observed initial response to volcanic forcing should be La Niñ a-like not El Niñ o, as suggested by paleoclimate records. © 2011 American Meteorological Society."
"57213298157;7201439545;","Adaptive mesh method in the Met Office variational data assimilation system",2011,"10.1002/qj.801","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955468468&doi=10.1002%2fqj.801&partnerID=40&md5=1be19c706ecc455f288c44f7b8bcb061","A frequent problem in forecasting fog or icy roads in a numerical weather prediction (NWP) system is attributed to the misinterpretation of the boundary-layer structure in the assimilation procedure. Case-studies showed that the misinterpretation of temperature inversions and stratocumulus layers in the assimilation is due to inappropriate background-error covariances. This paper looks at the application of static adaptive mesh methods in the Met Office variational assimilation system to modify the background-error correlations in the boundary layer when temperature inversions or stratocumulus layers are present in the background state. Results show improvements in the analysis root mean square errors with respect to radiosonde observations and surface observations and improvements in forecast errors in 2 m temperature in the presence of low clouds. This enhancement in 2 m temperature forecast is attributed to reduced background vertical correlations and increased temperature background-error variances in the assimilation due to the movement of the grid near the surface. © 2011 British Crown copyright, the Met Office. Published by JohnWiley & Sons, Ltd."
"37079244300;6603092635;7004427005;7402839597;55441652200;12042577100;7103390273;","GNSS remote sensing of the Australian tropopause",2011,"10.1007/s10584-010-9894-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952754446&doi=10.1007%2fs10584-010-9894-6&partnerID=40&md5=27166f107839b145a95f77b491a9a9ca","Radio occultation (RO) techniques that use signals transmitted by Global Navigation Satellite Systems (GNSS) have emerged over the past decade as an important tool for measuring global changes in tropopause temperature and height, a valuable capacity given the tropopause's sensitivity to temperature variations. This study uses 45,091 RO data from the CHAMP (CHAllenging Minisatellite Payload, 80 months), GRACE (Gravity Recovery And Climate Experiment, 23 months) and COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate, 20 months) satellites to analyse the variability of the tropopause's height and temperature over Australia. GNSS RO temperature profiles from CHAMP, GRACE, and COSMIC are first validated using radiosonde observations provided by the Bureau of Meteorology (Australia). These are compared to RO soundings from between 2001 and 2007 that occurred within 3 h and 100 km of a radiosonde. The results indicate that RO soundings provide data of a comparable quality to radiosonde observations in the tropopause region, with temperature deviations of less than 0.5 ± 1.5 K. An analysis of tropopause height and temperature anomalies indicates a height increase over Australia as a whole of ca. 4.8 ± 1.3 m between September 2001 and April 2008, with a corresponding temperature decrease of -0.019 ± 0.007 K. A similar pattern of increasing height/decreasing temperature was generally observed when determining the spatial distribution of the tropopause height and temperature rate of change over Australia. Although only a short period has been considered in this study, a function of the operating time of these satellites, the results nonetheless show an increase in the height of the tropopause over Australia during this period and thus may indicate regional warming. Several mechanisms could be responsible for these changes, such as an increase in the concentration of greenhouse gases in the atmosphere, and lower stratospheric cooling due to ozone loss, both of which have been observed during the last decades. © 2010 Springer Science+Business Media B.V."
"13407563600;16549600900;24172248700;7006034630;56967163800;35221167400;15724233200;7005696579;24070152900;8645916500;7006595513;8986277400;26643054400;55545335600;57205085102;35461763400;55942083800;","Cloud condensation nuclei in polluted air and biomass burning smoke near the mega-city Guangzhou, China - Part 2: Size-resolved aerosol chemical composition, diurnal cycles, and externally mixed weakly CCN-active soot particles",2011,"10.5194/acp-11-2817-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953138142&doi=10.5194%2facp-11-2817-2011&partnerID=40&md5=6fca270c23f1792c5f949e7024c4806b","Size-resolved chemical composition, mixing state, and cloud condensation nucleus (CCN) activity of aerosol particles in polluted mega-city air and biomass burning smoke were measured during the PRIDE-PRD2006 campaign near Guangzhou, China, using an aerosol mass spectrometer (AMS), a volatility tandem differential mobility analyzer (VTDMA), and a continuous-flow CCN counter (DMT-CCNC). The size-dependence and temporal variations of the effective average hygroscopicity parameter for CCN-active particles (κa) could be parameterized as a function of organic and inorganic mass fractions (f org, finorg) determined by the AMS: κa, pCombining double low lineκorg·forg + κinorg·finorg. The characteristic values of organic and inorganic components were similar to those observed in other continental regions of the world: κorg0.1 and κinorg0.6. The campaign average κa values increased with particle size from ∼0.25 at ∼50 nm to ∼0.4 at ∼200 nm, while forg decreased with particle size. At ∼50 nm, forg was on average 60% and increased to almost 100% during a biomass burning event. The VTDMA results and complementary aerosol optical data suggest that the large fractions of CCN-inactive particles observed at low supersaturations (up to 60% at S Currency sign0.27%) were externally mixed weakly CCN-active soot particles with low volatility (diameter reduction &lt;5% at 300 °C) and effective hygroscopicity parameters around κLV0.01. A proxy for the effective average hygroscopicity of the total ensemble of CCN-active particles including weakly CCN-active particles (κt) could be parameterized as a function of κa,p and the number fraction of low volatility particles determined by VTDMA (φLV): κt,pCombining double low lineκa,LV·(κa,p- κLV). Based on ° values derived from AMS and VTDMA data, the observed CCN number concentrations (NCCN,S-102-104 cmg-3 at Combining double low line 0.068-0.47%) could be efficiently predicted from the measured particle number size distribution. The mean relative deviations between observed and predicted CCN concentrations were ∼10% when using κt,p, and they increased to ∼20% when using only &amp;kappa;a,p. The mean relative deviations were not higher (∼20%) when using an approximate continental average value of κ-0.3, although the constant ° value cannot account for the observed temporal variations in particle composition and mixing state (diurnal cycles and biomass burning events). Overall, the results confirm that on a global and climate modeling scale an average value of κ 0.3 can be used for approximate predictions of CCN number concentrations in continental boundary layer air when aerosol size distribution data are available without information about chemical composition. Bulk or size-resolved data on aerosol chemical composition enable improved CCN predictions resolving regional and temporal variations, but the composition data need to be highly accurate and complemented by information about particle mixing state to achieve high precision (relative deviations &lt;20%). © 2011 Author(s) ."
"21234634500;7403375920;16195546300;7006896637;7403549847;","Ash storms: Impacts of wind-remobilised volcanic ash on rural communities and agriculture following the 1991 Hudson eruption, southern Patagonia, Chile",2011,"10.1007/s00445-010-0396-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955685820&doi=10.1007%2fs00445-010-0396-1&partnerID=40&md5=58b15e4d3f97283743172bd226cd7462","Tephra fall from the August 1991 eruption of Volcán Hudson affected some 100,000 km2 of Patagonia and was almost immediately reworked by strong winds, creating billowing clouds of remobilised ash, or 'ash storms'. The immediate impacts on agriculture and rural communities were severe, but were then greatly exacerbated by continuing ash storms. This paper describes the findings of a 3-week study tour of the diverse environments of southern Patagonia affected by ash storms, with an emphasis on determining the impacts of repeated ash storms on agriculture and local practices that were developed in an attempt to mitigate these impacts. Ash storms produce similar effects to initial tephra eruptions, prolonged for considerable periods. These have included the burial of farmland under dune deposits, abrasion of vegetation and contamination of feed supplies with fine ash. These impacts can then cause problems for grazing animals such as starvation, severe tooth abrasion, gastrointestinal problems, corneal abrasion and blindness, and exhaustion if sheep fleeces become laden with ash. In addition, ash storms have led to exacerbated soil erosion, human health impacts, increased cleanup requirements, sedimentation in irrigation canals, and disruption of aviation and land transport. Ash deposits were naturally stabilised most rapidly in areas with high rainfall (&gt;1,500 mm/year) through compaction and enhanced vegetation growth. Stabilisation was slowest in windy, semi-arid regions. Destruction of vegetation and suppression of regrowth by heavy tephra fall (&gt;100 mm) hindered the stabilisation of deposits for years, and reduced the surface friction which increased wind erosivity. Stabilisation of tephra deposits was improved by intensive tillage, use of windbreaks and where there was dense and taller vegetative cover. Long-term drought and the impracticality of mixing ash deposits with soil by tillage on large farms was a barrier to stabilising deposits and, in turn, agricultural recovery. The continuing ash storms motivated the partial evacuation of small rural towns such as Chile Chico (Chile) and Los Antiguos (Argentina) in September-December 1991, after the primary tephra fall in August 1991. Greatly increased municipal cleanup efforts had to be sustained beyond the initial tephra fall to cope with the ongoing impacts of ash storms. Throughout the 1990s, ash storms contributed to continued population migration out of the affected area, leaving hundreds of farms abandoned on the Argentine steppe. The major lesson from our study is the importance of stabilisation of ash deposits as soon as possible after the initial eruption, particularly in windy, arid climates. Suggested mitigation measures include deep cultivation of the ash into the soil and erecting windbreaks. © 2010 Springer-Verlag."
"21735071800;7004467879;22950237000;56262897700;7006720957;37051915300;16022771900;","Harmonic analysis of climatological temperature over Antarctica: Present day and greenhouse warming perspectives",2011,"10.1002/joc.2090","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952301129&doi=10.1002%2fjoc.2090&partnerID=40&md5=09b6546f1c00d9deb7ced05e4175f58b","On the basis of ERA40 and NCEP/NCAR Reanalysis (NNR) and simulations from CCCma, CCSM, CSIRO, HadCM3, MIROC-MEDRES and GFDL, which support the Intergovernmental Panel on Climate Change (IPCC) 4th Assessment Report (AR4), we demonstrated that the amplitude of the annual and the semi-annual harmonics delivered by the ERA40 and NNR is dominated by distinct seasonal variability. The maximum first harmonic amplitude of near surface temperature 2-metre air temperature (t2m) according the NNR is located over the Plateau of East Antarctica, whereas analyses for ERA40 show maximum amplitude over the west Antarctic ice sheet. The spatial pattern of the first harmonic of t2m in NNR more closely corresponds to station observations, suggesting that the seasonal cycle of t2m over Antarctica may be biased in ERA-40. A comparison between the global climate models (GCMs) and NNR demonstrates that the models satisfactorily simulate the amplitude of the first and second harmonics; however, the modelling results differ among themselves in terms of the amplitude values. Larger seasonal variability is identified for CCCma, HadCM3 and MIROC-MEDRES with values as high as 20 °C over the Antarctic plateau. We have further identified that the CSIRO GCM does not reproduce the seasonal amplitude of t2m as compared to other models, which is primarily due to its overestimation of the cloud cover and weak seasonal changes of precipitation. Calculations of the harmonic analysis based upon greenhouse warming (GW) conditions reveal that there is no substantial seasonal difference between the amplitude of the first harmonic as projected by GW and present day (PD) simulations over the Antarctic continent. Over the polar ocean, however, the amplitude of the first harmonic is reduced in all climate models under future conditions. In order to narrow down the uncertainties on future climate projections, analyses of the cloud forcing which include the short- and long-wave radiation and the surface mass balance (SMB) may provide substantial information on the cause of the discrepancies as simulated by climate models over the Antarctic region. © 2010 Royal Meteorological Society."
"6602523027;56370934200;56050447600;8208591500;6603308622;6602264539;55107948800;7004864963;","Sources of carbonaceous aerosol in the Amazon basin",2011,"10.5194/acp-11-2747-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953044845&doi=10.5194%2facp-11-2747-2011&partnerID=40&md5=b3dd8582147b0b6fbeb227f89eab4c8e","The quantification of sources of carbonaceous aerosol is important to understand their atmospheric concentrations and regulating processes and to study possible effects on climate and air quality, in addition to develop mitigation strategies. <br><br> In the framework of the European Integrated Project on Aerosol Cloud Climate Interactions (EUCAARI) fine (<i>D</i>p < 2.5 &mu;m) and coarse (2.5 &mu;m < <i>D</i>p <10 &mu;m) aerosol particles were sampled from February to June (wet season) and from August to September (dry season) 2008 in the central Amazon basin. The mass of fine particles averaged 2.4 &mu;g m&minus;3 during the wet season and 4.2 &mu;g m&minus;3 during the dry season. The average coarse aerosol mass concentration during wet and dry periods was 7.9 and 7.6 &mu;g m&minus;3, respectively. The overall chemical composition of fine and coarse mass did not show any seasonality with the largest fraction of fine and coarse aerosol mass explained by organic carbon (OC); the average OC to mass ratio was 0.4 and 0.6 in fine and coarse aerosol modes, respectively. The mass absorbing cross section of soot was determined by comparison of elemental carbon and light absorption coefficient measurements and it was equal to 4.7 m2 g&minus;1 at 637 nm. Carbon aerosol sources were identified by Positive Matrix Factorization (PMF) analysis of thermograms: 44% of fine total carbon mass was assigned to biomass burning, 43% to secondary organic aerosol (SOA), and 13% to volatile species that are difficult to apportion. In the coarse mode, primary biogenic aerosol particles (PBAP) dominated the carbonaceous aerosol mass. The results confirmed the importance of PBAP in forested areas. <br><br> The source apportionment results were employed to evaluate the ability of global chemistry transport models to simulate carbonaceous aerosol sources in a regional tropical background site. The comparison showed an overestimation of elemental carbon (EC) by the TM5 model during the dry season and OC both during the dry and wet periods. The overestimation was likely due to the overestimation of biomass burning emission inventories and SOA production over tropical areas. © 2011 Author(s)."
"7005284577;9271096600;6602715033;6602890253;6603735912;14035836100;16480175700;6603872903;7006107059;6603054830;7004176333;7006212411;7003729315;34769585100;7003452377;7202050065;7006128445;57200679067;16032925200;8309699900;57209647985;7404062492;6701378450;7003496673;7202097052;7006634316;16480965400;7201483081;6603800142;7202429440;7004643405;57203405965;24477694300;8633162900;8147766700;7202245296;7202586843;35965825900;17436376200;7007172001;7003710822;11139835100;","Characteristics, sources, and transport of aerosols measured in spring 2008 during the aerosol, radiation, and cloud processes affecting Arctic Climate (ARCPAC) Project",2011,"10.5194/acp-11-2423-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952714175&doi=10.5194%2facp-11-2423-2011&partnerID=40&md5=46957030ae580a5a409d907b94afb004","We present an overview of the background, scientific goals, and execution of the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project of April 2008. We then summarize airborne measurements, made in the troposphere of the Alaskan Arctic, of aerosol particle size distributions, composition, and optical properties and discuss the sources and transport of the aerosols. The aerosol data were grouped into four categories based on gas-phase composition. First, the background troposphere contained a relatively diffuse, sulfate-rich aerosol extending from the top of the sea-ice inversion layer to 7.4 km altitude. Second, a region of depleted (relative to the background) aerosol was present within the surface inversion layer over sea-ice. Third, layers of dense, organic-rich smoke from open biomass fires in southern Russia and southeastern Siberia were frequently encountered at all altitudes from the top of the inversion layer to 7.1 km. Finally, some aerosol layers were dominated by components originating from fossil fuel combustion. <br></br> Of these four categories measured during ARCPAC, the diffuse background aerosol was most similar to the average springtime aerosol properties observed at a long-term monitoring site at Barrow, Alaska. The biomass burning (BB) and fossil fuel layers were present above the sea-ice inversion layer and did not reach the sea-ice surface during the course of the ARCPAC measurements. The BB aerosol layers were highly scattering and were moderately hygroscopic. On average, the layers produced a noontime net heating of ∼0.1 K day&minus;1 between 3 and 7 km and a slight cooling at the surface. The ratios of particle mass to carbon monoxide (CO) in the BB plumes, which had been transported over distances >5000 km, were comparable to the high end of literature values derived from previous measurements in wildfire smoke. These ratios suggest minimal precipitation scavenging and removal of the BB particles between the time they were emitted and the time they were observed in dense layers above the sea-ice inversion layer. © 2011 Author(s)."
"28367935500;6507224579;7005137442;7003975505;","Initiation of a Marinoan snowball earth in a state-of-the-art atmosphere-ocean general circulation model",2011,"10.5194/cp-7-249-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952610700&doi=10.5194%2fcp-7-249-2011&partnerID=40&md5=c50e810927d154ed8f64bc05aa0cddb0","We study the initiation of a Marinoan Snowball Earth (∼635 million years before present) with the state-of-the-art atmosphere-ocean general circulation model ECHAM5/MPI-OM. This is the most sophisticated model ever applied to Snowball initiation. A comparison with a pre-industrial control climate shows that the change of surface boundary conditions from present-day to Marinoan, including a shift of continents to low latitudes, induces a global-mean cooling of 4.6 K. Two thirds of this cooling can be attributed to increased planetary albedo, the remaining one third to a weaker greenhouse effect. The Marinoan Snowball Earth bifurcation point for pre-industrial atmospheric carbon dioxide is between 95.5 and 96% of the present-day total solar irradiance (TSI), whereas a previous study with the same model found that it was between 91 and 94% for present-day surface boundary conditions. A Snowball Earth for TSI set to its Marinoan value (94% of the present-day TSI) is prevented by doubling carbon dioxide with respect to its pre-industrial level. A zero-dimensional energy balance model is used to predict the Snowball Earth bifurcation point from only the equilibrium global-mean ocean potential temperature for present-day TSI. We do not find stable states with sea-ice cover above 55%, and land conditions are such that glaciers could not grow with sea-ice cover of 55%. Therefore, none of our simulations qualifies as a ""slushball"" solution. While uncertainties in important processes and parameters such as clouds and sea-ice albedo suggest that the Snowball Earth bifurcation point differs between climate models, our results contradict previous findings that Snowball Earth initiation would require much stronger forcings. © Author(s) 2011."
"6603555567;6701344406;56276813400;26323963700;6602241511;6701792123;6603335688;8915901800;8323981800;","Cloud response to summer temperatures in Fennoscandia over the last thousand years",2011,"10.1029/2010GL046216","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952128868&doi=10.1029%2f2010GL046216&partnerID=40&md5=99445bb64fe6e02e9f1fefb0d1a05ce6","Cloud cover is one of the most important factors controlling the radiation balance of the Earth. The response of cloud cover to increasing global temperatures represents the largest uncertainty in model estimates of future climate because the cloud response to temperature is not well-constrained. Here we present the first regional reconstruction of summer sunshine over the past millennium, based on the stable carbon isotope ratios of pine treerings from Fennoscandia. Comparison with the regional temperature evolution reveals the Little Ice Age (LIA) to have been sunny, with cloudy conditions in the warmest periods of the Medieval at this site. A negative shortwave cloud feedback is indicated at high latitude. A millennial climate simulation suggests that regionally low temperatures during the LIA were mostly maintained by a weaker greenhouse effect due to lower humidity. Simulations of future climate that display a negative shortwave cloud feedback for high-latitudes are consistent with our proxy interpretation. Copyright © 2011 by the American Geophysical Union."
"57203209031;26632348900;26632290800;","Drizzle correlations with giant nuclei",2011,"10.1029/2010GL046207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952678780&doi=10.1029%2f2010GL046207&partnerID=40&md5=4fbf97eaca59c7d5bab052ed72ea28c4","Giant nuclei (GN) concentrations (N<inf>GN</inf>) below RICO small cumulus clouds were substantially correlated with drizzle drop concentrations (N <inf>d</inf>), especially at higher cloud altitudes. The N<inf>GN</inf>-N <inf>d</inf> correlation coefficients (R) progressively increased with altitude whereas R for CCN concentrations with N<inf>d</inf> were negative with mostly decreasing magnitudes at increasing altitudes. These results indicate that the positive influence of GN [or CCN with low critical supersaturations (S <inf>c</inf>)] on N<inf>d</inf> is greater than the negative influence of high S<inf>c</inf> CCN on N<inf>d</inf> at high cloud altitudes where there are more drizzle drops. This work has implications not only for fundamental cloud physics but also for climate change; i.e., global warming and the indirect aerosol effect as well as geoengineering and hygroscopic cloud seeding. Copyright 2011 by the American Geophysical Union."
"6508240165;","An analysis of precipitation data from the Antarctic base Faraday/Vernadsky",2011,"10.1002/joc.2083","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951826922&doi=10.1002%2fjoc.2083&partnerID=40&md5=0ef1190a7dc049c3dcc85c498e32b58a","A recent study on cloud observations reports an increase in total cloud cover at Faraday/Vernadsky since 1960 in the annual and wintertime data. The aim of this present study is to investigate whether this increase in total cloud cover has influenced the precipitation in this region. For this purpose, precipitation observations at the Antarctic base Faraday/Vernadsky between 1960 and 1999 were analysed. A positive trend, significant at the 5% level, was found in the number of precipitation events recorded during winter, showing an increase of 13 events per decade. The annual number of precipitation days has increased by 5.7 per decade during the period of investigation, with highest increase rates being observed in winter and autumn. The characteristics of these findings confirm that results previously published though trends presented here are ~50% smaller due to a more thorough data quality control of the observational data. These results indicate that an increase in total cloud cover at Faraday/Vernadsky observed since 1960 in the annual and wintertime data is reflected in higher numbers of precipitation events and days. Analyses of the precipitation type found an increase in the proportion of events of non-frozen precipitation, which is significant (1% level) on an annual basis as well as in spring and autumn (both significant at 5% level). This is a clear manifestation of the year round temperature increase observed over the Antarctic Peninsula. The increase in non-frozen precipitation will have reduced the albedo in the region and will thus have contributed to the temperature-albedo feedback. To refreeze rain that is draining through glaciers energy is extracted from the surrounding ice, thereby physically corroding the ice. This will have contributed to the observed retreat of glaciers around the Antarctic Peninsula. As non-frozen precipitation falling on frozen ground cannot be stored but instead runs off, less water will be available for the ecosystem. Copyright © 2010 Royal Meteorological Society."
"27067942000;35795122700;7004573666;55944537900;7005742190;","Canopy level fog occurrence in a tropical lowland forest of French Guiana as a prerequisite for high epiphyte diversity",2011,"10.1016/j.agrformet.2010.11.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651440095&doi=10.1016%2fj.agrformet.2010.11.003&partnerID=40&md5=be5962e871f3bdc90c76d69d81f95546","Fog frequency and the meteorological processes leading to fog formation have never been studied in depth in tropical lowland forest areas. This study provides detailed evidence of frequent fog occurrence in lowland valleys of central French Guiana. Fog frequency showed a clear diurnal course, with a maximum before sunrise; average fog duration was 4.6. h. The diurnal course of visibility was positively correlated with the diurnal course of humidity in the above-canopy air. Fog persistence correlated significantly with atmospheric parameters during the dry season, but not during the rainy season. The main trigger of fog development in the lowland forest seemed to be precipitation, leading to higher soil moisture, greater evapotranspiration and, thus, higher water content of air. An increasing temperature difference between valley and hill sites after sunset, together with more frequent down-slope winds during nights with long fog periods, points at some influence of katabatic flows. The frequent occurrence of fog in the valleys correlated with significantly higher epiphyte diversities in valley forests as compared to hill forests, and supported the occurrence of the hitherto undescribed, epiphyte-rich "" tropical lowland cloud forest"" (LCF) in the valleys. The higher epiphyte diversity in LCF coincided with significantly higher relative air humidity in LCF than in hill forest. The ecological benefits of fog for the epiphytes in LCF are surplus of moisture and delayed onset of the stress period, particularly in the dry season. © 2010 Elsevier B.V."
"56001448100;7003928455;","Clouds and the Faint Young Sun Paradox",2011,"10.5194/cp-7-203-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952382904&doi=10.5194%2fcp-7-203-2011&partnerID=40&md5=7285d96449711041b51d6e51e942f87f","We investigate the role which clouds could play in resolving the Faint Young Sun Paradox (FYSP). Lower solar luminosity in the past means that less energy was absorbed on Earth (a forcing of -50 W m-2 during the late Archean), but geological evidence points to the Earth having been at least as warm as it is today, with only very occasional glaciations. We perform radiative calculations on a single global mean atmospheric column. We select a nominal set of three layered, randomly overlapping clouds, which are both consistent with observed cloud climatologies and reproduced the observed global mean energy budget of Earth. By varying the fraction, thickness, height and particle size of these clouds we conduct a wide exploration of how changed clouds could affect climate, thus constraining how clouds could contribute to resolving the FYSP. Low clouds reflect sunlight but have little greenhouse effect. Removing them entirely gives a forcing of +25 W m-2 whilst more modest reduction in their efficacy gives a forcing of +10 to +15 W m-2. For high clouds, the greenhouse effect dominates. It is possible to generate +50 W m-2 forcing from enhancing these, but this requires making them 3.5 times thicker and 14 K colder than the standard high cloud in our nominal set and expanding their coverage to 100% of the sky. Such changes are not credible. More plausible changes would generate no more than +15 W m-2 forcing. Thus neither fewer low clouds nor more high clouds can provide enough forcing to resolve the FYSP. Decreased surface albedo can contribute no more than +5 W m-2 forcing. Some models which have been applied to the FYSP do not include clouds at all. These overestimate the forcing due to increased CO2 by 20 to 25% when pCO2 is 0.01 to 0.1 bar. © 2011 Author(s)."
"7005453641;35472747700;37057068400;7006717176;","The 2009-2010 Arctic polar stratospheric cloud season: A CALIPSO perspective",2011,"10.5194/acp-11-2161-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952422106&doi=10.5194%2facp-11-2161-2011&partnerID=40&md5=c03362159f81cdf8c1992f8695761cf5","Spaceborne lidar measurements from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) are used to provide a vortex-wide perspective of the 2009-2010 Arctic PSC (polar stratospheric cloud) season to complement more focused measurements from the European Union RECONCILE (reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) field campaign. The 2009-2010 Arctic winter was unusually cold at stratospheric levels from mid-December 2009 until the end of January 2010, and was one of only a few winters from the past fifty-two years with synoptic-scale regions of temperatures below the frost point. More PSCs were observed by CALIPSO during the 2009-2010 Arctic winter than in the previous three Arctic seasons combined. In particular, there were significantly more observations of high number density NAT (nitric acid trihydrate) mixtures (referred to as Mix 2-enh) and ice PSCs. We found that the 2009-2010 season could roughly be divided into four periods with distinctly different PSC optical characteristics. The early season (15-30 December 2009) was characterized by patchy, tenuous PSCs, primarily low number density liquid/NAT mixtures. No ice clouds were observed by CALIPSO during this early phase, suggesting that these early season NAT clouds were formed through a non-ice nucleation mechanism. The second phase of the season (31 December 2009-14 January 2010) was characterized by frequent mountain wave ice clouds that nucleated widespread NAT particles throughout the vortex, including Mix 2-enh. The third phase of the season (15-21 January 2010) was characterized by synoptic-scale temperatures below the frost point which led to a rare outbreak of widespread ice clouds. The fourth phase of the season (22-28 January) was characterized by a major stratospheric warming that distorted the vortex, displacing the cold pool from the vortex center. This final phase was dominated by STS (supercooled ternary solution) PSCs, although NAT particles may have been present in low number densities, but were masked by the more abundant STS droplets at colder temperatures. We also found distinct variations in the relative proportion of PSCs in each composition class with altitude over the course of the 2009-2010 Arctic season. Lower number density liquid/NAT mixtures were most frequently observed in the lower altitude regions of the clouds (below ∼18-20 km), which is consistent with CALIPSO observations in the Antarctic. Higher number density liquid/NAT mixtures, especially Mix 2-enh, were most frequently observed at altitudes above 18-20 km, primarily downstream of wave ice clouds. This pattern is consistent with the conceptual model whereby low number density, large NAT particles are precipitated from higher number density NAT clouds (i.e. mother clouds) that are nucleated downstream of mountain wave ice clouds. © 2011 Author(s)."
"6701404949;7003372165;7202035883;35305673400;8217208200;7005382046;","VOCALS-CUpEx: The Chilean Upwelling Experiment",2011,"10.5194/acp-11-2015-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952326434&doi=10.5194%2facp-11-2015-2011&partnerID=40&md5=c6880b3b71f556a739f2cb4dd32334e9","The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was a major field experiment conducted in spring of 2008 off southern Peru and northern Chile, aimed at better understanding the coupled climate systems of the southeast Pacific. Because of logistical constrains, the coastal area around 30° S was not sampled during VOCALS-REx. This area not only marks the poleward edge of the subtropical stratocumulus cloud regime (thus acting as a source of transient disturbances) but is also one of the most active upwelling centers and source of surface ocean kinetic energy along the Chilean coast. To fill such an observational gap, a small, brief, but highly focused field experiment was conducted in late spring 2009 in the near-shore region around 30° S. The Chilean Upwelling Experiment (CUpEx) was endorsed by VOCALS as a regional component. CUpEx included long-term monitoring, an intensive twoweek field campaign and off-shore research flights. Our goal was to obtain an atmospheric/oceanic dataset with enough temporal and spatial coverage to be able to document (a) the mean diurnal cycles of the lower-troposphere and upper-ocean in a region of complex topography and coastline geometry, and (b) the ocean-atmosphere response to the rapid changes in coastal winds from strong, upwelling-favorable equatorward flow (southerly winds) to downwelling-favorable poleward flow (northerly winds). In this paper we describe the measurement platforms and sampling strategy, and provide an observational overview, highlighting some key mean-state and transient features. © 2011 Author(s)."
"43461874800;26643251000;7003613864;15032439200;6602087787;7102578937;","Synergetic cloud fraction determination for SCIAMACHY using MERIS",2011,"10.5194/amt-4-319-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857692644&doi=10.5194%2famt-4-319-2011&partnerID=40&md5=ad79bf4d964244f9c7ddeadc3e762e16","Since clouds play an essential role in the Earth's climate system, it is important to understand the cloud characteristics as well as their distribution on a global scale using satellite observations. The main scientific objective of SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) onboard the ENVISAT satellite is the retrieval of vertical columns of trace gases. On the one hand, SCIAMACHY has to be sensitive to low variations in trace gas concentrations which means the ground pixel size has to be large enough. On the other hand, such a large pixel size leads to the problem that SCIAMACHY spectra are often contaminated by clouds. SCIAMACHY spectral measurements are not well suitable to derive a reliable sub-pixel cloud fraction that can be used as input parameter for subsequent retrievals of cloud properties or vertical trace gas columns. Therefore, we use MERIS/ENVISAT spectral measurements with its high spatial resolution as sub-pixel information for the determination of MerIs Cloud fRation fOr Sciamachy (MICROS). Since MERIS covers an even broader swath width than SCIAMACHY, no problems in spatial and temporal collocation of measurements occur. This enables the derivation of a SCIAMACHY cloud fraction with an accuracy much higher as compared with other current cloud fractions that are based on SCIAMACHY's PMD (Polarization Measurement Device) data. We present our new developed MICROS algorithm, based on the threshold approach, as well as a qualitative validation of our results with MERIS satellite images for different locations, especially with respect to bright surfaces such as snow/ice and sands. In addition, the SCIAMACHY cloud fractions derived from MICROS are intercompared with other current SCIAMACHY cloud fractions based on different approaches demonstrating a considerable improvement regarding geometric cloud fraction determination using the MICROS algorithm. © 2011 Author(s) CC Attribution 3.0 License."
"35494005000;37261286100;7202652226;7402064802;7004057920;","Critical evaluation of the ISCCP simulator using ground-based remote sensing data",2011,"10.1175/2010JCLI3517.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955148232&doi=10.1175%2f2010JCLI3517.1&partnerID=40&md5=1e738030cbeaf7ae5de13ddc46d87c9d","Given the known shortcomings in representing clouds in global climate models (GCMs), comparisons with observations are critical. The International Satellite Cloud Climatology Project (ISCCP) diagnostic products provide global descriptions of cloud-top pressure and column optical depth that extend over multiple decades. Given the characteristics of the ISCCP product, the model output must be converted into what the ISCCP algorithm would diagnose from an atmospheric column with similar physical characteristics. This study evaluates one component of this so-called ISCCP simulator by comparing ISCCP results with simulated ISCCP diagnostics that are derived from data collected at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Climate Research Facility. It is shown that if a model were to simulate the cloud radiative profile with the same accuracy as can be derived from theARMdata, the likelihood of that occurrence being classified with similar cloud-top pressure and optical depth as ISCCP would range from 30% to 70% depending on optical depth. The ISCCP simulator improved the agreement of cloud-top pressure between ground-based remote sensors and satellite observations, and we find only minor discrepancies because of the parameterization of cloud-top pressure in the ISCCP simulator. The differences seem to be primarily due to discrepancies between satellite and ground-based sensors in the visible optical depth. The source of the optical depth bias appears to be due to subpixel cloud field variability in the retrieval of optical depths from satellite sensors. These comparisons suggest that caution should be applied to comparisons between models and ISCCP observations until the differences in visible optical depths are fully understood. The simultaneous use of ground-based and satellite retrievals in the evaluation of model clouds is encouraged. © 2011 American Meteorological Society."
"57205867148;57197996988;57210837523;6602682911;8670860600;7202748672;","Can fully accounting for clouds in data assimilation improve short-term forecasts by global models?",2011,"10.1175/2010MWR3412.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955045632&doi=10.1175%2f2010MWR3412.1&partnerID=40&md5=9b9925e30634835cbd7c911c40977a7d","This paper explores the degree to which short-term forecasts with global models might be improved if clouds were fully included in a data assimilation system, so that observations of clouds affected all parts of the model state and cloud variables were adjusted during assimilation. The question is examined using a single ensemble data assimilation system coupled to two present-generation climate models with different treatments of clouds. ""Perfect-model"" experiments using synthetic observations, taken from a free run of the model used in subsequent assimilations, are used to circumvent complications associated with systematic model errors and observational challenges; these provide a rough upper bound on the utility of cloud observations with these models. Aseries of experiments is performed in which direct observations of the model's cloud variables are added to the suite of observations being assimilated. In both models, observations of clouds reduce the 6-h forecast error, with much greater reductions in one model than in the other. Improvements are largest in regions where other observations are sparse. The two cloud schemes differ in their complexity and number of degrees of freedom; the model using the simpler scheme makes better use of the cloud observations because of the stronger correlations between cloud-related and dynamical variables (particularly temperature). This implies that the impact of real cloud observations will depend on both the strength of the instantaneous, linear relationships between clouds and other fields in the natural world, and how well each assimilating model's cloud scheme represents those relationships. © 2011 American Meteorological Society."
"55879900300;7406200372;57217720842;55487543500;36119737000;56948583000;","Influence of multi-chemical-component aerosols on the microphysics of warm clouds in North China",2011,"10.1007/s11430-010-4075-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952360502&doi=10.1007%2fs11430-010-4075-z&partnerID=40&md5=d1764102d2b3893b94e7848b98cb120b","An adiabatic bin-sized cloud parcel model is developed by incorporating the multi-chemical-component (MCC) aerosol effects into the UWyo single-chemical-component (SCC) parcel model. The effects of MCC aerosols on the warm cloud microphysics in North China are investigated with the model. The simulations are initialized using the data on chemical components and number size distribution of aerosols measured during the IPAC (Influence of Pollution on Aerosols and Cloud Microphysics in North China) campaign in spring 2006. It is found that the MCC aerosols in North China increase the cloud droplet number concentration (CDNC) and decrease the effective radius more efficiently than pure ammonium-sulfate aerosols. It is also shown that the MCC aerosols in North China can narrow the cloud droplet spectra (CDS) by increasing CDNC in small size and decreasing CDNC in large size. Our results indicate that aerosol chemical components and their size distributions can influence the microphysics of warm clouds, and thus affect atmospheric radiation and precipitation. This should attract more attentions in weather and climate change research in the future. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg."
"35090272500;25928176700;11940135900;7006206130;","The radiation budget in a regional climate model",2011,"10.1007/s00382-009-0733-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952252493&doi=10.1007%2fs00382-009-0733-2&partnerID=40&md5=88960042c710ea3f934552f86a7f8839","The long- and short-wave components of the radiation budget are among the most important quantities in climate modelling. In this study, we evaluated the radiation budget at the earth's surface and at the top of atmosphere over Europe as simulated by the regional climate model CLM. This was done by comparisons with radiation budgets as computed by the GEWEX/SRB satellite-based product and as realised in the ECMWF re-analysis ERA40. Our comparisons show that CLM has a tendency to underestimate solar radiation at the surface and the energy loss by thermal emission. We found a clear statistical dependence of radiation budget imprecision on cloud cover and surface albedo uncertainties in the solar spectrum. In contrast to cloud fraction errors, surface temperature errors have a minor impact on radiation budget uncertainties in the long-wave spectrum. We also evaluated the impact of the number of atmospheric layers used in CLM simulations. CLM simulations with 32 layers perform better than do those with 20 layers in terms of the surface radiation budget components but not in terms of the outgoing long-wave radiation and of radiation divergence. Application of the evaluation approach to similar simulations with two additional regional climate models confirmed the results and showed the usefulness of the approach. © 2010 Springer-Verlag."
"7003663305;","Clouds at arctic atmospheric observatories. Part II: Thermodynamic phase characteristics",2011,"10.1175/2010JAMC2468.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955009770&doi=10.1175%2f2010JAMC2468.1&partnerID=40&md5=f680b267845549aa3784cf3b9d03d123","Cloud phase defines many cloud properties and determines the ways in which clouds interact with other aspects of the climate system. The occurrence fraction and characteristics of clouds distinguished by their phase are examined at three Arctic atmospheric observatories. Each observatory has the basic suite of instruments that are necessary to identify cloud phase, namely, cloud radar, depolarization lidar, microwave radiometer, and twice-daily radiosondes. At these observatories, ice clouds are more prevalent than mixed-phase clouds, which are more prevalent than liquid-only clouds. Cloud ice occurs 60%-70% of the time over a typical year, at heights up to 11 km. Liquid water occurs at temperatures above -40°C and is increasingly more likely as temperatures increase. Within the temperature range from -40° to -30°C, liquid water occurs in 3%-5% of the observed cloudiness. Liquid water is found higher in the atmosphere when accompanied by ice; there are few liquid-only clouds above 3 km, although liquid in mixed-phase clouds occurs at heights up to about 7-8 km. Regardless of temperature or height, liquid water occurs 56% of the time at Barrow, Alaska, and at a western Arctic Ocean site, but only 32% of the time at Eureka, Nunavut, Canada. This significant difference in liquid occurrence is due to a relatively dry lower troposphere during summer at Eureka in addition to warmer cloud temperatures with more persistent liquid water layers at the far western locations. The most persistent liquid clouds at these locations occur continuously for more than 70 h in the autumnand more than 30 h in the winter. Ice clouds persist for much longer than do liquid clouds at Eureka and occur more frequently in the winter season, leading to a total cloud occurrence annual cycle that is distinct from the other observatories. © 2011 American Meteorological Society."
"25927181300;6603315547;57203053317;6603613067;","Improvement and implementation of a parameterization for shallow cumulus in the global climate model ECHAM5-HAM",2011,"10.1175/2010JAS3447.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78951474858&doi=10.1175%2f2010JAS3447.1&partnerID=40&md5=63de81213d31205715ecd78e5ec4c7df","A transient shallow-convection scheme is implemented into the general circulation model ECHAM5 and the coupled aerosol model HAM, developed at the Max Planck Institute for Meteorology in Hamburg. The shallow-convection scheme is extended to take the ice phase into account. In addition, a detailed doublemoment microphysics approach has been added. In this approach, the freezing processes and precipitation formation are dependent on aerosols. Furthermore, in the scheme, tracers are transported and scavenged consistently as in the rest of the model. Results of a single-column model simulation for the Barbados Oceanography and Meteorology Experiment (BOMEX) campaign are compared with previously published large-eddy simulation (LES) results. Compared to the standard version, the global ECHAM5-HAM simulations with the newly implemented scheme show a decreased frequency of shallow convection in better agreement with LES. Less shallow convection is compensated by more stratus and stratocumulus. Deep and especially midlevel convection are markedly affected by those changes, which in turn influence high-level clouds. Generally, a better agreement with the observations can be obtained. For a better understanding of the scheme's impact and to test different setting parameters, sensitivity analyses are performed. The mixing properties, cloud-base vertical velocity, and launching layer of the test parcel, respectively, are varied. In this context, results from simulations without shallow convection are also presented. © 2011 American Meteorological Society."
"23975649000;7003663731;","Modelling climate change effects on the spatial distribution of mountain permafrost at three sites in northwest Canada",2011,"10.1007/s10584-010-9818-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951812223&doi=10.1007%2fs10584-010-9818-5&partnerID=40&md5=331e6d775935ec65893fb4b14d8be603","Spatial models of present-day mountain permafrost probability were perturbed to examine potential climate change impacts. Mean annual air temperature (MAAT) changes were simulated by adjusting elevation in the models, and cloud cover changes were examined by altering the partitioning of direct beam and diffuse radiation within the calculation for potential incoming solar radiation (PISR). The effects of changes in MAAT on equilibrium permafrost distribution proved to be more important than those due to cloud cover. Under a -2 K scenario (approximating Little Ice Age conditions), permafrost expanded into an additional 22-43% of the study areas as zonal boundaries descended by 155-290 m K-1. Under warming scenarios, permafrost probabilities progressively declined and zonal boundaries rose in elevation. A MAAT change of +5 K, caused two of the areas to become essentially permafrost-free. The absolute values of these predictions were affected up to ±10% when lapse rates were altered by ±1.5 K km-1 but patterns and trends were maintained. A higher proportion of diffuse radiation (greater cloud cover) produced increases in permafrost extent of only 2-4% while decreases in the diffuse radiation fraction had an equal but opposite effect. Notwithstanding the small change in overall extent, permafrost probabilities on steep south-facing slopes were significantly impacted by the altered partitioning. Combined temperature and PISR partitioning scenarios produced essentially additive results, but the impact of changes in the latter declined as MAAT increased. The modelling illustrated that mountain permafrost in the discontinuous zone is sensitive spatially to long-term climate change and identified those areas where changes may already be underway following recent atmospheric warming. © 2010 Springer Science+Business Media B.V."
"23486332900;","A multimodel study of parametric uncertainty in predictions of climate response to rising greenhouse gas concentrations",2011,"10.1175/2010JCLI3498.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954998482&doi=10.1175%2f2010JCLI3498.1&partnerID=40&md5=62877a32eae589ab1b5df5cb569149ca","One tool for studying uncertainties in simulations of future climate is to consider ensembles of general circulation models where parameterizations have been sampled within their physical range of plausibility. This study is about simulations from two such ensembles: a subset of the climateprediction.net ensemble using the Met Office Hadley Centre Atmosphere Model, version 3.0 and the new ""CAMcube"" ensemble using the Community Atmosphere Model, version 3.5. The study determines that the distribution of climate sensitivity in the two ensembles is very different: the climateprediction.net ensemble subset range is 1.7-9.9 K, while the CAMcube ensemble range is 2.2-3.2 K. On a regional level, however, both ensembles show a similarly diverse range in their mean climatology. Model radiative flux changes suggest that the major difference between the ranges of climate sensitivity in the two ensembles lies in their clear-sky longwave responses. Large clear-sky feedbacks present only in the climateprediction.net ensemble are found to be proportional to significant biases in upper-tropospheric water vapor concentrations, which are not observed in the CAMcube ensemble. Both ensembles have a similar range of shortwave cloud feedback, making it unlikely that they are causing the larger climate sensitivities in climateprediction.net. In both cases, increased negative shortwave cloud feedbacks at high latitudes are generally compensated by increased positive feedbacks at lower latitudes. © 2011 American Meteorological Society."
"25823927100;7103271625;7003997130;","Parameterization of riming intensity and its impact on ice fall speed using ARM data",2011,"10.1175/2010MWR3299.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955034077&doi=10.1175%2f2010MWR3299.1&partnerID=40&md5=0af9603f8fedbefcf9ac3b5bdc0ac78e","Riming within mixed-phase clouds can have a large impact on the prediction of clouds and precipitation within weather and climate models. The increase of ice particle fall speed due to riming has not been considered in most general circulation models (GCMs), and many weather models only consider ice particles that are either unrimed or heavily rimed (not a continuum of riming amount). Using the Atmospheric Radiation Measurement (ARM) Program dataset at the Southern Great Plains (SGP) site of the United States, a new parameterization for riming is derived, which includes a diagnosed rimed mass fraction and its impact on the ice particle fall speed. When evaluated against a vertical-pointing Doppler radar for stratiform mixed-phase clouds, the new parameterization produces better ice fall speeds than a conventional parameterization. The new parameterization is tested in the recently developed Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric model (AM3) using prescribed sea surface temperature (SST) simulations. Compared with the standard (CTL) simulation, the new parameterization increases ice amount aloft by ~20%~30% globally, which reduces the global mean outgoing longwave radiation (OLR) by 2.8 W m-2 and the top-of-atmosphere (TOA) shortwave absorption by ~1.5 W m-2. Global mean precipitation is also slightly reduced, especially over the tropics. Overall, the new parameterization produces a comparable climatology with the CTL simulation and it improves the physical basis for using a fall velocity larger than a conventional parameterization in the current AM3. © 2011 American Meteorological Society."
"7003278104;9249239700;6701606453;55716092000;","The impact of precipitating ice and snow on the radiation balance in global climate models",2011,"10.1029/2010GL046478","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953212567&doi=10.1029%2f2010GL046478&partnerID=40&md5=f5b1a1fe170728a159c64d38e69d39cb","Climate models often ignore the radiative impact of precipitating hydrometeors. CloudSat retrievals provide the first means to distinguish between cloud versus precipitating ice mass and characterize its vertical structure. With this information, radiative transfer calculations are performed to examine the impact of excluding precipitating ice on atmospheric radiative fluxes and heating rates. The preliminary results show that such exclusion can result in underestimates of the reflective shortwave flux at the top of the atmosphere (TOA) and overestimates of the downwelling surface shortwave and emitted TOA longwave flux, with the differences being about 5-10 Wm-2 in the most convective and rainfall intensive areas and greatest for the TOA longwave flux. There are also considerable differences (∼10-25%) in the vertical profiles of shortwave and longwave heating, resulting in an overestimation (∼up to 10%) of the integrated column cooling. The implications of these results are that models that exclude these ice components are achieving TOA radiation balance through compensating errors as well as possibly introducing biases in atmospheric circulations. Copyright © 2011 by the American Geophysical Union."
"6507944872;7203068499;8728117200;7006329853;7006173230;","Potential climatic impact of organic haze on early earth",2011,"10.1089/ast.2010.0541","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952980027&doi=10.1089%2fast.2010.0541&partnerID=40&md5=c08deee2510b0163b2e6e5a4c97761b7","We have explored the direct and indirect radiative effects on climate of organic particles likely to have been present on early Earth by measuring their hygroscopicity and cloud nucleating ability. The early Earth analog aerosol particles were generated via ultraviolet photolysis of an early Earth analog gas mixture, which was designed to mimic possible atmospheric conditions before the rise of oxygen. An analog aerosol for the present-day atmosphere of Saturn's moon Titan was tested for comparison. We exposed the early Earth aerosol to a range of relative humidities (RHs). Water uptake onto the aerosol was observed to occur over the entire RH range tested (RH=80-87%). To translate our measurements of hygroscopicity over a specific range of RHs into their water uptake ability at any RH < 100% and into their ability to act as cloud condensation nuclei (CCN) at RH > 100%, we relied on the hygroscopicity parameter κ, developed by Petters and Kreidenweis. We retrieved κ=0.22±0.12 for the early Earth aerosol, which indicates that the humidified aerosol (RH < 100 %) could have contributed to a larger antigreenhouse effect on the early Earth atmosphere than previously modeled with dry aerosol. Such effects would have been of significance in regions where the humidity was larger than 50%, because such high humidities are needed for significant amounts of water to be on the aerosol. Additionally, Earth organic aerosol particles could have activated into CCN at reasonable-and even low-water-vapor supersaturations (RH > 100%). In regions where the haze was dominant, it is expected that low particle concentrations, once activated into cloud droplets, would have created short-lived, optically thin clouds. Such clouds, if predominant on early Earth, would have had a lower albedo than clouds today, thereby warming the planet relative to current-day clouds. © Mary Ann Liebert, Inc."
"7101690206;7005132811;55728284400;6506122183;","On the Tropical Atlantic SST warm bias in the Kiel Climate Model",2011,"10.1007/s00382-009-0690-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952245828&doi=10.1007%2fs00382-009-0690-9&partnerID=40&md5=8c09dd2cf1ffeaa5521efe34767166ed","Most of the current coupled general circulation models show a strong warm bias in the eastern Tropical Atlantic. In this paper, various sensitivity experiments with the Kiel Climate Model (KCM) are described. A largely reduced warm bias and an improved seasonal cycle in the eastern Tropical Atlantic are simulated in one particular version of KCM. By comparing the stable and well-tested standard version with the sensitivity experiments and the modified version, mechanisms contributing to the reduction of the eastern Atlantic warm bias are identified and compared to what has been proposed in literature. The error in the spring and early summer zonal winds associated with erroneous zonal precipitation seems to be the key mechanism, and large-scale coupled ocean-atmosphere feedbacks play an important role in reducing the warm bias. Improved winds in boreal spring cause the summer cooling in the eastern Tropical Atlantic (ETA) via shoaling of the thermocline and increased upwelling, and hence reduced sea surface temperature (SST). Reduced SSTs in the summer suppress convection and favor the development of low-level cloud cover in the ETA region. Subsurface ocean structure is shown to be improved, and potentially influences the development of the bias. The strong warm bias along the southeastern coastline is related to underestimation of low-level cloud cover and the associated overestimation of surface shortwave radiation in the same region. Therefore, in addition to the primarily wind forced response at the equator both changes in surface shortwave radiation and outgoing longwave radiation contribute significantly to reduction of the warm bias from summer to fall. © 2009 Springer-Verlag."
"56387672900;6506756436;34770938700;57207510696;6603202619;18134195800;7005432249;","The AROME-France convective-scale operational model",2011,"10.1175/2010MWR3425.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955011377&doi=10.1175%2f2010MWR3425.1&partnerID=40&md5=088dfb7caa1666e92a7da069cea7a44d","After six years of scientific, technical developments and meteorological validation, the Application of Research to Operations at Mesoscale (AROME-France) convective-scale model became operational at Mé téo-France at the end of 2008. This paper presents the main characteristics of this new numerical weather prediction system: the nonhydrostatic dynamical model core, detailed moist physics, and the associated three-dimensional variational data assimilation (3D-Var) scheme. Dynamics options settings and variables are explained. The physical parameterizations are depicted as well as their mutual interactions. The scale-specific features of the 3D-Var scheme are shown. The performance of the forecast model is evaluated using objective scores and case studies that highlight its benefits and weaknesses. © 2011 American Meteorological Society."
"57203209031;26632290800;26632348900;","On the relative role of sea salt cloud condensation nuclei (CCN)",2011,"10.1007/s10874-011-9210-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858294599&doi=10.1007%2fs10874-011-9210-5&partnerID=40&md5=7d104434608c6b23b922265bd88ca453","Contrasts between cloud condensation nuclei (CCN) spectral volatility (thermal fractionation) measurements in two aircraft field projects provide insight into the relative contribution of sea salt. During the much more cloudy Rain in Cumulus over the Ocean (RICO) project there was a high correlation coefficient (R) between refractory (non-volatile) CCN concentrations (N CCN) and horizontal wind speed (U), especially for low supersaturation (S) N CCN, whereas this R was significantly lower in the nearly cloud free Pacific Aerosol Sulfur Experiment (PASE) project. Volatile N CCN at all S were uncorrelated with U. Ambient particle concentrations over a broad range of large sizes displayed consistently high R with U in both projects that was similar to the R of refractory N CCN with U in RICO. The size range of this high R extended down to 0.2 μm in RICO but only down to 9 μm in PASE. In both projects particle concentrations smaller than these respective sizes were highly correlated with N CCN, at all S in PASE, but mainly with N CCN at high S in RICO. In each project N CCN at all S was uncorrelated with all ambient particle concentrations larger than these same respective sizes. N CCN at all S was also uncorrelated with U in both projects. The contrast in cloudiness between the two projects was responsible for many of the differences noted between the two projects. The results indicate that the effects of clouds on N CCN play a major role in the relative influence of sea salt on N CCN and ultimately on climate. Sea salt is a minor component of maritime CCN except at high wind speeds especially at low S. © 2011 The Author(s)."
"36183094200;","A New Single-Filter Method for Analyzing Coastal Aerosol Production and Links to Meteorology",2011,"10.1007/s12237-010-9322-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79751524164&doi=10.1007%2fs12237-010-9322-1&partnerID=40&md5=ba5516d5501d2ee7176f8ebee4a25b23","Aerosols are known to influence the climate system in a range of ways; they affect radiation budgets, cloud formation and circulation patterns, and contribute to local biogeochemical cycling and ecology. Despite this recognized role for marine aerosol, however, recent research has emphasized the impact of global climate change on coastal environments rather than the other way around. This occurs in part because most methods for sampling marine aerosol are expensive and studies tend to occur only on specialized marine stations and ocean-crossing research vessels. This project tests a new method for aerosol sampling, specifically designed for use in local studies of coastal environments and costing little to set up. It also reports the results of a pilot study in Alderney (Channel Islands) where changes in both aerosol abundance and aerosol composition, including fractionation effects, were observed using the new method and linked to local meteorological conditions. © 2010 Coastal and Estuarine Research Federation."
"37105152800;57193132723;7004540083;","Synoptically driven Arctic winter states",2011,"10.1175/2010JCLI3817.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955157021&doi=10.1175%2f2010JCLI3817.1&partnerID=40&md5=343c45f0cefed22b3c3c12eeb3d7bdb3","The dense network of the Surface Heat Budget of the Arctic (SHEBA) observations is used to assess relationships between winter surface and atmospheric variables as the SHEBA site came under the influence of cyclonic and anticyclonic atmospheric circulation systems. Two distinct and preferred states of subsurface, surface, atmosphere, and clouds occur during the SHEBA winter, extending from the oceanic mixed layer through the troposphere and preceded by same-sign variations in the stratosphere. These states are apparent in distributions of surface temperature, sensible heat and longwave radiation fluxes, ocean heat conduction, cloudbase height and temperature, and in the atmospheric humidity and temperature structure. Surface and atmosphere are in radiative-turbulent-conductive near-equilibrium during a warm opaquely cloudy-sky state, which persists up to 10 days and usually occurs during the low surface pressure phase of a baroclinic wave, although occasionally occurs during the high surface pressure phase because of low, scattered clouds. Clouds occurring in this state have near-unity emissivity and the lowest bases in the vicinity of, or below, the temperature inversion peak. Acold radiatively clear-sky state persists up to two weeks, and occurs only in the high surface pressure phase of a baroclinic wave. The radiatively clear state has clouds that are too tenuous when surface based or, irrespective of opacity, located too far aloft to contribute significantly to the surface energy budget. There is a 13-K surface temperature difference between the two states, and atmospheric inversion peak temperatures are linearly related to the surface temperature in both states. The snow-sea ice interface temperature oscillates over the course of thewinter season, as it cools during the radiatively clear state and iswarmed from atmospheric emission above and ocean heat conduction from below during the opaquely cloudy state. Analysis of satellite data over theArctic from 708-908Nindicates that the radiatively clear and opaquely cloudy states observed at SHEBA may be representative of the entire Arctic basin. The results suggest that model formulation inadequacies should be easier to diagnose if modeled energy transfers are compared with observations using process-based metrics that acknowledge the bimodal nature of the Arctic ocean-ice-snow-atmosphere column, rather thanmonthly and regionally averaged quantities. Climate change projections of thinnerArctic sea ice and larger advective water vapor influxes into the Arctic could yield different frequencies of occupation of the radiatively clear and opaquely cloudy states and higher wintertime temperatures of SHEBA ocean, ice, snow, atmosphere, and clouds-in particular, a wintertime warming of the snow-sea ice interface temperature. © 2011 American Meteorological Society."
"36470000800;37012768000;36463717300;37012712200;6701705132;55665336100;6603260088;","Effect of local weather on butterfly flight behaviour, movement, and colonization: Significance for dispersal under climate change",2011,"10.1007/s10531-010-9960-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951768343&doi=10.1007%2fs10531-010-9960-4&partnerID=40&md5=83fbccaf18ba3a59c0dd3f38768222bf","Recent climate change is recognized as a main cause of shifts in geographical distributions of species. The impacts of climate change may be aggravated by habitat fragmentation, causing regional or large scale extinctions. However, we propose that climate change also may diminish the effects of fragmentation by enhancing flight behaviour and dispersal of ectothermic species like butterflies. We show that under weather conditions associated with anticipated climate change, behavioural components of dispersal of butterflies are enhanced, and colonization frequencies increase. In a field study, we recorded flight behaviour and mobility of four butterfly species: two habitat generalists (Coenonympha pamphilus; Maniola jurtina) and two specialists (Melitaea athalia; Plebejus argus), under different weather conditions. Flying bout duration generally increased with temperature and decreased with cloudiness. Proportion of time spent flying decreased with cloudiness. Net displacement generally increased with temperature. When butterflies fly longer, start flying more readily and fly over longer distances, we expect dispersal propensity to increase. Monitoring data showed that colonization frequencies moreover increased with temperature and radiation and decreased with cloudiness. Increased dispersal propensity at local scale might therefore lower the impact of habitat fragmentation on the distribution at a regional scale. Synergetic effects of climate change and habitat fragmentation on population dynamics and species distributions might therefore appear to be more complex than previously assumed. © 2010 The Author(s)."
"36998390000;55951088700;","An analysis of modern pollen representation and climatic conditions on the galápagos islands",2011,"10.1177/0959683610378874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952085245&doi=10.1177%2f0959683610378874&partnerID=40&md5=1e3c60692600515a54f6df60815cf2f8","In the first modern pollen trapping study conducted in the Galápagos Islands, 58 clusters of pollen traps were established on four islands: Genovesa, Rocas Bainbridge, Santa Cruz, and San Cristobal. HOBO data loggers collected temperature, humidity, and dew point every 30 min for 1 year at eight locations. The trapping locations were selected to provide a wide diversity of Galápagos habitat types and to support active or future analyses from bog and lake core records recovered from the islands. Pollen influx to the traps was generally low (>100 grains/cm 2 per yr), but broad habitat types were clearly identifiable based on the pollen collected. More precise identification of trapping sites and vegetation zones within the islands were identified using ordinations of the pollen and climate data. Long-distance dispersal from the mainland and neighboring islands were found to be significant elements of pollen records, particularly those where local pollen production was low (>150 grains/cm 2 per yr). Over-representation and under-representation of ecological dominants was documented, as was the significant representation of invasive exotic species in some settings. Temperature and relative humidity data were used to reconstruct the presence of ground-level cloud (garúa). Garúa caused substantial cooling, beyond what would be expected from adiabatic lapse rate, in the highlands. The cloud formation associated with garúa caused low-elevation temperatures to be cooler than maximum sea-surface temperatures. The data emphasize the importance of garúa to the endemic flora of the islands and their long-term conservation. © The Author(s) 2010."
"15065565300;7201568549;24513528600;7004070482;57213561342;6602888227;","Decadal variations in a Venus general circulation model",2011,"10.1016/j.icarus.2010.11.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951968514&doi=10.1016%2fj.icarus.2010.11.015&partnerID=40&md5=973f003a1fb2bc2c95e91d830f0b670f","The Community Atmosphere Model (CAM), a 3-dimensional Earth-based climate model, has been modified to simulate the dynamics of the Venus atmosphere. The most current finite volume version of CAM is used with Earth-related processes removed, parameters appropriate for Venus introduced, and some basic physics approximations adopted. A simplified Newtonian cooling approximation has been used for the radiation scheme. We use a high resolution (1° by 1° in latitude and longitude) to take account of small-scale dynamical processes that might be important on Venus. A Rayleigh friction approach is used at the lower boundary to represent surface drag, and a similar approach is implemented in the uppermost few model levels providing a 'sponge layer' to prevent wave reflection from the upper boundary. The simulations generate superrotation with wind velocities comparable to those measured in the Venus atmosphere by probes and around 50-60% of those measured by cloud tracking. At cloud heights and above the atmosphere is always superrotating with mid-latitude zonal jets that wax and wane on an approximate 10 year cycle. However, below the clouds, the zonal winds vary periodically on a decadal timescale between superrotation and subrotation. Both subrotating and superrotating mid-latitude jets are found in the approximate 40-60. km altitude range. The growth and decay of the sub-cloud level jets also occur on the decadal timescale. Though subrotating zonal winds are found below the clouds, the total angular momentum of the atmosphere is always in the sense of superrotation. The global relative angular momentum of the atmosphere oscillates with an amplitude of about 5% on the approximate 10 year timescale. Symmetric instability in the near surface equatorial atmosphere might be the source of the decadal oscillation in the atmospheric state. Analyses of angular momentum transport show that all the jets are built up by poleward transport by a meridional circulation while angular momentum is redistributed to lower latitudes primarily by transient eddies. Possible changes in the structure of Venus' cloud level mid-latitude jets measured by Mariner 10, Pioneer Venus, and Venus Express suggest that a cyclic variation similar to that found in the model might occur in the real Venus atmosphere, although no subrotating winds below the cloud level have been observed to date. Venus' atmosphere must be observed over multi-year timescales and below the clouds if we are to understand its dynamics. © 2010 Elsevier Inc."
"6504512777;24178522800;7403288995;6603126554;","Atmospheric inversion strength over polar oceans in winter regulated by sea ice",2011,"10.1007/s00382-010-0756-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952245890&doi=10.1007%2fs00382-010-0756-8&partnerID=40&md5=ab52248309cbe64266592a5f6f7d14d5","Low-level temperature inversions are a common feature of the wintertime troposphere in the Arctic and Antarctic. Inversion strength plays an important role in regulating atmospheric processes including air pollution, ozone destruction, cloud formation, and negative longwave feedback mechanisms that shape polar climate response to anthropogenic forcing. The Atmospheric Infrared Sounder (AIRS) instrument provides reliable measures of spatial patterns in mean wintertime inversion strength when compared with available radiosonde observations and reanalysis products. Here, we examine the influence of sea ice concentration on inversion strength in the Arctic and Antarctic. Correlation of inversion strength with mean annual sea ice concentration, likely a surrogate for the effective thermal conductivity of the wintertime ice pack, yields strong, linear relationships in the Arctic (r = 0.88) and Antarctic (r = 0.86). We find a substantially greater (stronger) linear relationship between sea ice concentration and surface air temperature than with temperature at 850 hPa, lending credence to the idea that sea ice controls inversion strength through modulation of surface heat fluxes. As such, declines in sea ice in either hemisphere may imply weaker mean inversions in the future. Comparison of mean inversion strength in AIRS and global climate models (GCMs) suggests that many GCMs poorly characterize mean inversion strength at high latitudes. © 2010 Springer-Verlag."
"56981805100;36933950200;7402989545;","Multi-model projection of July-August climate extreme changes over China under CO2 doubling. Part II: Temperature",2011,"10.1007/s00376-010-0052-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551675676&doi=10.1007%2fs00376-010-0052-x&partnerID=40&md5=949efb359249716564db62ad031ec758","This is the second part of the authors' analysis on the output of 24 coupled climate models from the Twentieth-Century Climate in Coupled Models (20C3M) experiment and 1% per year CO2 increase experiment (to doubling) (1pctto2x) of phase 3 of the Coupled Model Inter-comparison Project (CMIP3). The study focuses on the potential changes of July-August temperature extremes over China. The pattern correlation coefficients of the simulated temperature with the observations are 0.6-0.9, which are higher than the results for precipitation. However, most models have cold bias compared to observation, with a larger cold bias over western China (&gt;5°C) than over eastern China (&lt;2°C). The multi-model ensemble (MME) exhibits a significant increase of temperature under the 1pctto2x scenario. The amplitude of the MME warming shows a northwest-southeast decreasing gradient. The warming spread among the models (~1°C-2°C) is less than MME warming (~2°C-4°C), indicating a relatively robust temperature change under CO2 doubling. Further analysis of Geophysical Fluid Dynamics Laboratory coupled climate model version 2.1 (GFDL-CM2. 1) simulations suggests that the warming pattern may be related to heat transport by summer monsoons. The contrast of cloud effects also has contributions. The different vertical structures of warming over northwestern China and southeastern China may be attributed to the different natures of vertical circulations. The deep, moist convection over southeastern China is an effective mechanism for ""transporting"" the warming upward, leading to more upper-level warming. In northwestern China, the warming is more surface-orientated, possibly due to the shallow, dry convection. © 2011 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"56000854300;6602394131;6602860889;6602789161;","Tropical montane cloud forests: Current threats and opportunities for their conservation and sustainable management in Mexico",2011,"10.1016/j.jenvman.2010.11.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650521773&doi=10.1016%2fj.jenvman.2010.11.007&partnerID=40&md5=1302ba3affbfc45f933df29cb9aa48f1","Tropical montane cloud forests (TMCF) are among the most threatened ecosystems globally in spite of their high strategic value for sustainable development due to the key role played by these forests in hydrological cycle maintenance and as reservoirs of endemic biodiversity. Resources for effective conservation and management programs are rarely sufficient, and criteria must be applied to prioritise TMCF for conservation action. This paper reports a priority analysis of the 13 main regions of TMCF distribution in Mexico, based on four criteria: (1) forest quality, (2) threats to forest permanence, (3) threats to forest integrity, and (4) opportunities for conservation. Due to the diverse socio-environmental conditions of the local communities living in Mexican TMCF regions, their associated social characteristics were also evaluated to provide a background for the planning of conservation actions. A set of indicators was defined for the measurement of each criterion. To assign priority values for subregions within each main region, an international team of 40 participants evaluated all the indicators using multicriteria decision-making analysis. This procedure enabled the identification of 15 subregions of critical priority, 17 of high priority, and 10 of medium priority; three more were not analysed due to lack of information. The evaluation revealed a number of subjects that had hitherto been undetected and that may prove useful for prioritisation efforts in other regions where TMCF is similarly documented and faces equally severe threats. Based on this analysis, key recommendations are outlined to advance conservation objectives in those TMCF areas that are subjected to high pressure on forest resources. © 2010 Elsevier Ltd."
"7007026669;14050275600;6507949344;9240820800;","Evaluation of the relationship between air and land surface temperature under clear- and cloudy-sky conditions",2011,"10.1175/2010JAMC2460.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955003744&doi=10.1175%2f2010JAMC2460.1&partnerID=40&md5=e35648e1848d68a73fbe9a042f2d0e85","Clear and cloudy daytime comparisons of land surface temperature (LST) and air temperature (Tair) were made for 14 stations included in the U.S. Climate Reference Network (USCRN) of stations from observations made from 2003 through 2008. Generally, LST was greater than Tair for both the clear and cloudy conditions; however, the differences between LST and Tair were significantly less for the cloudy-sky conditions. In addition, the relationships between LST and Tair displayed less variability under the cloudy-sky conditions than under clear-sky conditions. Wind speed, time of the observation of Tair and LST, season, the occurrence of precipitation at the time of observation, and normalized difference vegetation index values were all considered in the evaluation of the relationship between Tair and LST. Mean differences between LST and Tair of less than 2°C were observed under cloudy conditions for the stations, as compared with a minimum difference of greater than 2°C (and as great as 7+°C) for the clear-sky conditions. Under cloudy conditions, Tair alone explained over 94%-and as great as 98%-of the variance observed in LST for the stations included in this analysis, as compared with a range of 81%-93% for clear-sky conditions. Because of the relatively homogeneous land surface characteristics encouraged in the immediate vicinity of USCRN stations, and potential regional differences in surface features that might influence the observed relationships, additional analyses of the relationships between LST and Tair for additional regions and land surface conditions are recommended. © 2011 American Meteorological Society."
"24512349100;24511929800;56283400100;","Some atmospheric processes governing the large-scale tropical circulation in idealized aquaplanet simulations",2011,"10.1175/2010JAS3439.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955014678&doi=10.1175%2f2010JAS3439.1&partnerID=40&md5=cc87c6f348311ff2d922382140b81e23","The large-scale tropical atmospheric circulation is analyzed in idealized aquaplanet simulations using an atmospheric general circulation model. Idealized sea surface temperatures (SSTs) are used as lowerboundary conditions to provoke modifications of the atmospheric general circulation. Results show that 1) an increase in the meridional SST gradients of the tropical region drastically strengthens the Hadley circulation intensity, 2) the presence of equatorial zonal SST anomalies weakens the Hadley cells and reinforces the Walker circulation, and 3) a uniform SST warming causes small and nonsystematic changes of the Hadley and Walker circulations. In all simulations, the jet streams strengthen and move equatorward as the Hadley cells strengthen and become narrower. Some relevant mechanisms are then proposed to interpret the large range of behaviors obtained from the simulations. First, the zonal momentum transport by transient and stationary eddies is shown to modulate the eddy-driven jets, which causes the poleward displacements of the jet streams. Second, it is found that theHadley circulation adjusts to the changes of the poleward moist static energy flux and gross moist static stability, associated with the geographical distribution of convection and midlatitude eddies. The Walker circulation intensity corresponds to the zonal moist static energy transport induced by the zonal anomalies of the turbulent fluxes and radiative cooling. These experiments provide some hints to understand a few robust changes of the atmospheric circulation simulated by ocean-atmosphere coupled models for future and past climates. © 2011 American Meteorological Society."
"6701450462;7103294731;6603561402;7005723936;6602256427;8941127900;7003287025;","Separating the dynamical effects of climate change and ozone depletion. Part II: Southern Hemisphere troposphere",2011,"10.1175/2010JCLI3958.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952145734&doi=10.1175%2f2010JCLI3958.1&partnerID=40&md5=d6991d79ab0eb419a5f327fa4cd40753","The separate effects of ozone depleting substances (ODSs) and greenhouse gases (GHGs) on forcing circulation changes in the Southern Hemisphere extratropical troposphere are investigated using a version of the Canadian Middle Atmosphere Model (CMAM) that is coupled to an ocean. Circulation-related diagnostics include zonalwind, tropopause pressure, Hadley cellwidth, jet location, annularmode index, precipitation,wave drag, and eddy fluxes ofmomentumand heat.As expected, the tropospheric response to theODS forcing occurs primarily in austral summer, with past (1960-99) and future (2000-99) trends of opposite sign, while the GHG forcing produces more seasonally uniform trends with the same sign in the past and future. In summer the ODS forcing dominates past trends in all diagnostics,while the two forcings contribute nearly equally but oppositely to future trends. TheODS forcing produces a past surface temperature response consisting of cooling over eastern Antarctica, and is the dominant driver of past summertime surface temperature changes when the model is constrained by observed sea surface temperatures. For all diagnostics, the response to the ODS and GHG forcings is additive; that is, the linear trend computed from the simulations using the combined forcings equals (within statistical uncertainty) the sum of the linear trends fromthe simulations using the two separate forcings. Space-time spectra of eddy fluxes and the spatial distribution of transient wave drag are examined to assess the viability of several recently proposed mechanisms for the observed poleward shift in the tropospheric jet. © 2011 American Meteorological Society."
"24070817300;7005639482;14826390200;","Temporal Dynamics in Soil Oxygen and Greenhouse Gases in Two Humid Tropical Forests",2011,"10.1007/s10021-010-9402-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952443166&doi=10.1007%2fs10021-010-9402-x&partnerID=40&md5=ce3431921d14c0fd5fae9949b0647745","Soil redox plays a key role in regulating biogeochemical transformations in terrestrial ecosystems, but the temporal and spatial patterns in redox and associated controls within and across ecosystems are poorly understood. Upland humid tropical forest soils may be particularly prone to fluctuating redox as abundant rainfall limits oxygen (O2) diffusion through finely textured soils and high biological activity enhances O2 consumption. We used soil equilibration chambers equipped with automated sensors to determine the temporal variability in soil oxygen concentrations in two humid tropical forests with different climate regimes. We also measured soil trace gases (CO2, N2O, and CH4) as indices of redox-sensitive biogeochemistry. On average, the upper elevation cloud forest had significantly lower O2 concentrations (3.0 ± 0.8%) compared to the lower elevation wet tropical forest (7.9 ± 1.1%). Soil O2 was dynamic, especially in the wet tropical forest, where concentrations changed as much as 10% in a single day. The periodicity in the O2 time series at this site was strongest at 16 day intervals and was associated with the hourly precipitation. Greenhouse gas concentrations differed significantly between sites, but the relationships with soil O2 were consistent: O2 was negatively related to both CO2 and CH4 and positively related to N2O. These results are among the first to quantify the temporal and spatial scale of variability in soil redox in humid tropical forests, and show that the timing of precipitation plays a strong role in biogeochemical cycling on the scale of hours to weeks. © 2010 The Author(s)."
"56266071600;7005753600;7006960661;6602211117;7003740015;7201572145;34976155900;7003875148;","Measurements of bubble size spectra within leads in the Arctic summer pack ice",2011,"10.5194/os-7-129-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951783277&doi=10.5194%2fos-7-129-2011&partnerID=40&md5=1733d593cbe3b14a25896efce796a5c5","The first measurements of bubble size spectra within the near-surface waters of open leads in the central Arctic pack ice were obtained during the Arctic Summer Cloud-Ocean Study (ASCOS) in August 2008 at 87-87.6° N, 1-11° W. A significant number of small bubbles (30-100 μm diameter) were present, with concentration decreasing rapidly with size from 100-560 μm; no bubbles larger than 560 μm were observed. The bubbles were present both during periods of low wind speed (U&lt;6 m s-1) and when ice covered the surface of the lead. The low wind and short open-water fetch precludes production of bubbles by wave breaking suggesting that the bubbles are generated by processes below the surface. When the surface water was open to the atmosphere bubble concentrations increased with increasing heat loss to the atmosphere. The presence of substantial numbers of bubbles is significant because the bursting of bubbles at the surface provides a mechanism for the generation of aerosol and the ejection of biological material from the ocean into the atmosphere. Such a transfer has previously been proposed as a potential climate feedback linking marine biology and Arctic cloud properties. © Author(s) 2011."
"7004932211;12809562200;26026749200;","Deep convective clouds at the tropopause",2011,"10.5194/acp-11-1167-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951638874&doi=10.5194%2facp-11-1167-2011&partnerID=40&md5=29a2fa271ba5e7bc92b22190b1576df6","Data from the Atmospheric Infrared Sounder (AIRS) on the EOS Aqua spacecraft each day show tens of thousands of Cold Clouds (CC) in the tropical oceans with 10 μm window channel brightness temperatures colder than 225 K. These clouds represent a mix of cold anvil clouds and Deep Convective Clouds (DCC). This mix can be separated by computing the difference between two channels, a window channel and a channel with strong CO2 absorption: for some cold clouds this difference is negative, i.e. the spectra for some cold clouds are inverted. We refer to cold clouds with spectra which are more than 2 K inverted as DCCi2. Associated with DCCi2 is a very high rain rate and a local upward displacement of the tropopause, a cold ""bulge"", which can be seen directly in the brightness temperatures of AIRS and Advanced Microwave Sounding Unit (AMSU) temperature sounding channels in the lower stratosphere. The very high rain rate and the local distortion of the tropopause indicate that DCCi2 objects are associated with severe storms. Significant long-term trends in the statistical properties of DCCi2 could be interesting indicators of climate change. While the analysis of the nature and physical conditions related to DCCi2 requires hyperspectral infrared and microwave data, the identification of DCCi2 requires only one good window channel and one strong CO2 sounding channel. This suggests that improved identification of severe storms with future advanced geostationary satellites could be accomplished with the addition of one or two narrow band channels. © 2011 Author(s)."
"55597088322;55199339300;57212997273;","Remote sensing of water cloud properties from MSG/SEVIRI nighttime imagery",2011,"10.1016/j.rse.2010.10.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650893525&doi=10.1016%2fj.rse.2010.10.015&partnerID=40&md5=8f4c2dc97f2f181f3e81a806601b0542","The Spinning Enhanced Visible and Infrared Imager (SEVIRI) measurements from the Meteosat Second Generation (MSG) satellites enable global monitoring of the distribution of clouds during day and night, with a spatial, temporal and spectral resolution that allows for better understanding of the role of clouds in global radiation budget and in climate in general. A method to retrieve cloud properties from nighttime SEVIRI measurements is described in this paper. The method is applicable to single-layer water clouds over sea surfaces and it is based on the inversion of a forward theoretical radiative transfer model, that simulates the radiances reaching the SEVIRI infrared detectors from a specified configuration of the earth-cloud-atmosphere system. This model accounts for scattering and absorption processes in the assumed horizontally homogeneous adiabatic cloud layer. For the inversion of this model, artificial neural networks techniques have been used in this work. The main advantage that these techniques provide is their low computational cost, which makes them suitable for the implementation of operational retrieval procedures. Results obtained by the proposed method are compared with the values provided by the CloudSat derived 2B-TAU product, and those derived from NOAA-AVHRR nighttime imagery, obtaining good agreements. © 2010 Elsevier Inc."
"6602836349;57196503168;25825840000;55920272000;6602243908;8853844100;7005692975;","Monitoring elevation variations in leaf phenology of deciduous broadleaf forests from SPOT/VEGETATION time-series",2011,"10.1016/j.rse.2010.10.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650922806&doi=10.1016%2fj.rse.2010.10.006&partnerID=40&md5=142487db6d2078a5ddfe1685f8b1ac44","In mountain forest ecosystems where elevation gradients are prominent, temperature gradient-based phenological variability can be high. However, there are few studies that assess the capability of remote sensing observations to monitor ecosystem phenology along elevation gradients, despite their relevance under climate change. We investigated the potential of medium resolution remotely sensed data to monitor the elevation variations in the seasonal dynamics of a temperate deciduous broadleaf forested ecosystem. Further, we explored the impact of elevation on the onset of spring leafing. This study was based on the analysis of multi-annual time-series of VEGETATION data acquired over the French Pyrenees Mountain Region (FPMR), in conjunction with simultaneous ground-based observations of leaf phenology made for two dominant tree species in the region (oak and beech). The seasonal variations in the perpendicular vegetation index (PVI) were analyzed during a five-year period (2002 to 2006). The five years of data were averaged into a one sole year in order to fill the numerous large spatio-temporal gaps due to cloud and snow presence - frequent in mountains - without altering the temporal resolution. Since a VEGETATION pixel (1. km2) includes several types of land cover, the broadleaf forest-specific seasonal dynamics of PVI was reconstructed pixel-by-pixel using a temporal unmixing method based on a non-parametric statistical approach. The spatial pattern of the seasonal response of PVI was clearly consistent with the relief. Nevertheless the elevational or geographic range of tree species, which differ in their phenology sensitivity to temperature, also has a significant impact on this pattern. The reduction in the growing season length with elevation was clearly observable from the delay in the increase of PVI in spring and from the advance of its decrease in the fall. The elevation variations in leaf flushing timing were estimated from the temporal change in PVI in spring over the study area. They were found to be consistent with those measured in situ (R2 &gt; 0.95). It was deduced that, over FPMR, the mean delay of leaf flushing timing for every 100. m increase in elevation was estimated be approximately 2.3. days. The expected estimation error of satellite-based leaf unfolding date for a given elevation was approximately 2. days. This accuracy can be considered as satisfactory since it would allow us to detect changes in leafing timing of deciduous broadleaf forests with a magnitude equivalent to that due to an elevation variation of 100. m (2.3. days on average), or in other words, to that caused by a variation in the mean annual air temperature of 0.5 °C. Although averaging the VEGETATION data over five years led to a loss of interannual information, it was found to be a robust approach to characterise the elevation variations in spring leafing and its long-term trends. © 2010 Elsevier Inc."
"56249704400;6701597468;22978151200;7006270084;16444232500;7003666669;24398842400;56250250300;12139043600;7005955015;55717074000;57203053317;7201837768;6602600408;57205638870;12139310900;7202079615;25634713100;","Soot microphysical effects on liquid clouds, a multi-model investigation",2011,"10.5194/acp-11-1051-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79751496458&doi=10.5194%2facp-11-1051-2011&partnerID=40&md5=0e1609251e0e576033b3951c9ac2a03e","We use global models to explore the microphysical effects of carbonaceous aerosols on liquid clouds. Although absorption of solar radiation by soot warms the atmosphere, soot may cause climate cooling due to its contribution to cloud condensation nuclei (CCN) and therefore cloud brightness. Six global models conducted three soot experiments; four of the models had detailed aerosol microphysical schemes. The average cloud radiative response to biofuel soot (black and organic carbon), including both indirect and semi-direct effects, is -0.11 Wm-2, comparable in size but opposite in sign to the respective direct effect. In a more idealized fossil fuel black carbon experiment, some models calculated a positive cloud response because soot provides a deposition sink for sulfuric and nitric acids and secondary organics, decreasing nucleation and evolution of viable CCN. Biofuel soot particles were also typically assumed to be larger and more hygroscopic than for fossil fuel soot and therefore caused more negative forcing, as also found in previous studies. Diesel soot (black and organic carbon) experiments had relatively smaller cloud impacts with five of the models &lt;±0.06 Wm-2 from clouds. The results are subject to the caveats that variability among models, and regional and interrannual variability for each model, are large. This comparison together with previously published results stresses the need to further constrain aerosol microphysical schemes. The non-linearities resulting from the competition of opposing effects on the CCN population make it difficult to extrapolate from idealized experiments to likely impacts of realistic potential emission changes. © 2011 Author(s)."
"24340241400;7004307308;15726335100;","Evaluation of rainfall retrievals from SEVIRI reflectances over West Africa using TRMM-PR and CMORPH",2011,"10.5194/hess-15-437-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551695707&doi=10.5194%2fhess-15-437-2011&partnerID=40&md5=eda1b47c794639054dbaa34e6758e24b","This paper describes the evaluation of the KNMI Cloud Physical Properties - Precipitation Properties (CPP-PP) algorithm over West Africa. The algorithm combines condensed water path (CWP), cloud phase (CPH), cloud particle effective radius (re), and cloud-top temperature (CTT) retrievals from visible, near-infrared and thermal infrared observations of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) satellites to estimate rain occurrence frequency and rain rate. For the 2005 and 2006 monsoon seasons, it is investigated whether the CPP-PP algorithm is capable of retrieving rain occurrence frequency and rain rate over West Africa with sufficient accuracy, using Tropical Monsoon Measurement Mission Precipitation Radar (TRMM-PR) as reference. As a second goal, it is assessed whether SEVIRI is capable of monitoring the seasonal and daytime evolution of rainfall during the West African monsoon (WAM), using Climate Prediction Center Morphing Technique (CMORPH) rainfall observations. The SEVIRI-detected rainfall area agrees well with TRMM-PR, with the areal extent of rainfall by SEVIRI being ∼10% larger than from TRMM-PR. The mean retrieved rain rate from CPP-PP is about 8% higher than from TRMM-PR. Examination of the TRMM-PR and CPP-PP cumulative frequency distributions revealed that differences between CPP-PP and TRMM-PR are generally within +/-10%. Relative to the AMMA rain gauge observations, CPP-PP shows very good agreement up to 5 mm h-1. However, at higher rain rates (5-16 mm h-1) CPP-PP overestimates compared to the rain gauges. With respect to the second goal of this paper, it was shown that both the accumulated precipitation and the seasonal progression of rainfall throughout the WAM is in good agreement with CMORPH, although CPP-PP retrieves higher amounts in the coastal region of West Africa. Using latitudinal Hovmüller diagrams, a fair correspondence between CPP-PP and CMORPH was found, which is reflected by high correlation coefficients (∼0.7) for both rain rate and rain occurrence frequency. The daytime cycle of rainfall from CPP-PP shows distinctly different patterns for three different regions in West Africa throughout the WAM, with a decrease in dynamical range of rainfall near the Inter Tropical Convergence Zone (ITCZ). The dynamical range as retrieved from CPP-PP is larger than that from CMORPH. It is suggested that this results from both the better spatio-temporal resolution of SEVIRI, as well as from thermal infrared radiances being partly used by CMORPH, which likely smoothes the daytime precipitation signal, especially in case of cold anvils from convective systems. The promising results show that the CPP-PP algorithm, taking advantage of the high spatio-temporal resolution of SEVIRI, is of added value for monitoring daytime precipitation patterns in tropical areas. © Author(s) 2011."
"24437444900;7003836546;36621776000;8372868700;6602365657;6701378450;7003886299;","An integrated modeling study on the effects of mineral dust and sea salt particles on clouds and precipitation",2011,"10.5194/acp-11-873-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551529799&doi=10.5194%2facp-11-873-2011&partnerID=40&md5=67f872561be1d7b8f106ef399f2d2173","This report addresses the effects of pollution on the development of precipitation in clean (""pristine"") and polluted (""hazy"") environments in the Eastern Mediterranean by using the Integrated Community Limited Area Modeling System (ICLAMS) (an extended version of the Regional Atmospheric Modeling System, RAMS). The use of this model allows one to investigate the interactions of the aerosols with cloud development. The simulations show that the onset of precipitation in hazy clouds is delayed compared to pristine conditions. Adding small concentrations of GCCN to polluted clouds promotes early-stage rain. The addition of GCCN to pristine clouds has no effect on precipitation amounts. Topography was found to be more important for the distribution of precipitation than aerosol properties. Increasing by 15% the concentration of hygroscopic dust particles for a case study over the Eastern Mediterranean resulted in more vigorous convection and more intense updrafts. The clouds that were formed extended about three kilometers higher, delaying the initiation of precipitation by one hour. Prognostic treatment of the aerosol concentrations in the explicit cloud droplet nucleation scheme of the model, improved the model performance for the twenty-four hour accumulated precipitation. The spatial distribution and the amounts of precipitation were found to vary greatly between the different aerosol scenarios. These results indicate the large uncertainty that remains and the need for more accurate description of aerosol feedbacks in atmospheric models and climate change predictions. © 2011 Author(s)."
"35565372000;36621710200;36622005700;15769385500;57203531598;7003754050;40660976700;7006296776;","Soil surface moisture estimation over a semi-arid region using ENVISAT ASAR radar data for soil evaporation evaluation",2011,"10.5194/hess-15-345-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551478562&doi=10.5194%2fhess-15-345-2011&partnerID=40&md5=33c48c19f9eb1c09e40ef1026ceff982","The present paper proposes a method for the evaluation of soil evaporation, using soil moisture estimations based on radar satellite measurements. We present firstly an approach for the estimation and monitoring of soil moisture in a semi-arid region in North Africa, using ENVISAT ASAR images, over two types of vegetation covers. The first mapping process is dedicated solely to the monitoring of moisture variability related to rainfall events, over areas in the ""non-irrigated olive tree"" class of land use. The developed approach is based on a simple linear relationship between soil moisture and the backscattered radar signal normalised at a reference incidence angle. The second process is proposed over wheat fields, using an analysis of moisture variability due to both rainfall and irrigation. A semi-empirical model, based on the water-cloud model for vegetation correction, is used to retrieve soil moisture from the radar signal. Moisture mapping is carried out over wheat fields, showing high variability between irrigated and non-irrigated wheat covers. This analysis is based on a large database, including both ENVISAT ASAR and simultaneously acquired ground-truth measurements (moisture, vegetation, roughness), during the 2008-2009 vegetation cycle. Finally, a semi-empirical approach is proposed in order to relate surface moisture to the difference between soil evaporation and the climate demand, as defined by the potential evaporation. Mapping of the soil evaporation is proposed. © Author(s) 2011."
"57219951382;7102495313;","The simulation of Arctic clouds and their influence on the winter surface temperature in present-day climate in the CMIP3 multi-model dataset",2011,"10.1007/s00382-010-0758-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551576449&doi=10.1007%2fs00382-010-0758-6&partnerID=40&md5=c2d380f3e184fe6128534b598592f9d7","We investigate the influence of clouds on the surface energy budget and surface temperature in the sea-ice covered parts of the ocean north of the Arctic circle in present-day climate in nine global climate models participating in the Coupled Model Intercomparison Project phase 3, CMIP3. Monthly mean simulated surface skin temperature, radiative fluxes and cloud parameters are evaluated using retrievals from the extended AVHHR Polar Pathfinder (APP-x) product. We analyzed the annual cycle but the main focus is on the winter, in which large parts of the region experience polar night. We find a smaller across-model spread as well as better agreement with observations during summer than during winter in the simulated climatological annual cycles of total cloudiness and surface skin temperature. The across-model spread in liquid and ice water paths is substantial during the whole year. These results qualitatively agree with earlier studies on the present-day Arctic climate in GCMs. The climatological ensemble model mean annual cycle of surface cloud forcing shows good agreement with observations in summer. However, during winter the insulating effect of clouds tends to be underestimated in models. During winter, most of the models as well as the observations show higher monthly mean total cloud fractions, associated with larger positive surface cloud forcing. Most models also show good correlation between the surface cloud forcing and the vertically integrated ice and liquid cloud condensate. The wintertime ensemble model mean total cloud fraction (69%) shows excellent agreement with observations. The across-model spread in the winter mean cloudiness is substantial (36-94%) however and several models significantly underestimate the cloud liquid water content. If the two models not showing any relationship between cloudiness and surface cloud forcing are disregarded, a tentative across-model relation exists, in such a way that models that simulate large winter mean cloudiness also show larger surface cloud forcing. Even though the across-model spread in wintertime surface cloud forcing is large, no clear relation to the surface temperature is found. This indicates that other processes, not explicitly cloud related, are important for the simulated across-model spread in surface temperature. © 2010 Springer-Verlag."
"7004242319;7003666669;6701873414;35572096100;7003535385;7102654014;35276210200;6602681732;7401651197;6701762451;7004346367;8511991900;13403957300;56000281400;6603569074;7007160874;7004462227;8363388700;7003430284;25629339800;55717074000;7006246996;6701845055;35556482500;8899985400;7103158465;55405340400;7003663305;7402934750;7401936984;6506424404;37086973100;21739304600;37087270000;","Indirect and semi-direct aerosol campaign: The impact of arctic aerosols on clouds",2011,"10.1175/2010BAMS2935.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953222223&doi=10.1175%2f2010BAMS2935.1&partnerID=40&md5=cf1b6f5e420115f51e51326479a42a96","An overview of Indirect and Semi-Direct Aerosol Campaign (ISDAC), aimed to study the impact of Arctic aerosol on clouds, is provided. The general theme of the campaign was to provide detailed observations of aerosols and clouds and gather high-quality data needed to improve the treatment of clouds and aerosols in climate models. The NRC Convair-580 was used for the in situ measurements of clouds, aerosols, and state parameters, and for active and passive remote sensing observations. The results show that ice nuclei (IN) concentrations in the Arctic are generally low, making accurate IN measurements a challenge. Many aerosol layers had horizontal and vertical filamentous structures, in which aerosol number concentration, their size distributions, and compositions varied rapidly along the flight paths."
"57203694321;33867681300;7102953444;6602098362;15071907100;","Constraints on climate sensitivity from radiation patterns in climate models",2011,"10.1175/2010JCLI3403.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955074437&doi=10.1175%2f2010JCLI3403.1&partnerID=40&md5=9558f836f882bb8227aec54ba3a24784","The estimated range of climate sensitivity, the equilibrium warming resulting from a doubling of the atmospheric carbon dioxide concentration, has not decreased substantially in past decades. New statistical methods for estimating the climate sensitivity have been proposed and provide a better quantification of relative probabilities of climate sensitivity within the almost canonical range of 2- 4.5 K; however, large uncertainties remain, in particular for the upper bound. Simple indices of spatial radiation patterns are used here to establish a relationship between an observable radiative quantity and the equilibrium climate sensitivity. The indices are computed for the Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel dataset and offer a possibility to constrain climate sensitivity by considering radiation patterns in the climate system. High correlations between the indices and climate sensitivity are found, for example, in the cloud radiative forcing of the incoming longwave surface radiation and in the clear-sky component of the incoming surface shortwave flux, the net shortwave surface budget, and the atmospheric shortwave attenuation variable b. The climate sensitivity was estimated from the mean of the indices during the years 1990-99 for the CMIP3 models. The surface radiative flux dataset from the Clouds and the Earth's Radiant Energy System (CERES) together with its top-of-atmosphere Energy Balanced and Filled equivalent (CERES EBAF) are used as a reference observational dataset, resulting in a best estimate for climate sensitivity of 3.3 K with a likely range of 2.7-4.0 K. A comparison with other satellite and reanalysis datasets show similar likely ranges and best estimates of 1.7-3.8 (3.3 K) [Earth Radiation Budget Experiment (ERBE)], 2.9-3.7 (3.3 K) [International Satellite Cloud Climatology Project radiative surface flux data (ISCCP-FD)], 2.8-4.1 (3.5 K) [NASA's Modern Era Retrospective-Analysis for Research and Application (MERRA)], 3.0-4.2 (3.6 K) [Japanese 25-yr Reanalysis (JRA-25)], 2.7-3.9 (3.4 K) [European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-Interim)], 3.0-4.0 (3.5 K) [ERA-40], and 3.1-4.7 (3.6 K) for the NCEP reanalysis. For each individual reference dataset, the results suggest that values for the sensitivity below 1.7 K are not likely to be consistent with observed radiation patterns given the structure of current climate models. For the aggregation of the reference datasets, the climate sensitivity is not likely to be below 2.9 K within the framework of this study, whereas values exceeding 4.5 K cannot be excluded from this analysis. While these ranges cannot be interpreted properly in terms of probability, they are consistent with other estimates of climate sensitivity and reaffirm that the current climatology provides a strong constraint on the lower bound of climate sensitivity even in a set of structurally different models. © 2011 American Meteorological Society."
"7801693068;7403282069;7403531523;","An estimate of low-cloud feedbacks from variations of cloud radiative and physical properties with sea surface temperature on interannual time scales",2011,"10.1175/2010JCLI3670.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955037981&doi=10.1175%2f2010JCLI3670.1&partnerID=40&md5=def656fdf744c4e29fd3c0e0d52b68ae","Simulations of climate change have yet to reach a consensus on the sign and magnitude of the changes in physical properties of marine boundary layer clouds. In this study, the authors analyze how cloud and radiative properties vary with SST anomaly in low-cloud regions, based on five years (March 2000-February 2005) of Clouds and the Earth's Radiant Energy System (CERES)-Terra monthly gridded data and matched European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological reanalaysis data. In particular, this study focuses on the changes in cloud radiative effect, cloud fraction, and cloud optical depth with SST anomaly. The major findings are as follows. First, the low-cloud amount (-1.9% to 3.4% K-1) and the logarithm of low-cloud optical depth (-0.085 to 0.100 K-1) tend to decrease while the net cloud radiative effect (3.86 W m-2 K-1) becomes less negative as SST anomalies increase. These results are broadly consistent with previous observational studies. Second, after the changes in cloud and radiative properties with SST anomaly are separated into dynamic, thermodynamic, and residual components, changes in the dynamic component (taken as the vertical velocity at 700 hPa) have relatively little effect on cloud and radiative properties. However, the estimated inversion strength decreases with increasing SST, accounting for a large portion of the measured decreases in cloud fraction and cloud optical depth. The residual positive change in net cloud radiative effect (1.48 W m-2 K-1) and small changes in low-cloud amount (-0.81% to 0.22% K-1) and decrease in the logarithm of optical depth (-0.035 to -0.046 K-1) with SST are interpreted as a positive cloud feedback, with cloud optical depth feedback being the dominant contributor. Last, the magnitudes of the residual changes differ greatly among the six low-cloud regions examined in this study, with the largest positive feedbacks (~4 W m-2 K-1) in the southeast and northeast Atlantic regions and a slightly negative feedback (-0.2 W m-2 K-1) in the south-central Pacific region. Because the retrievals of cloud optical depth and/or cloud fraction are difficult in the presence of aerosols, the transport of heavy African continental aerosols may contribute to the large magnitudes of estimated cloud feedback in the two Atlantic regions. © 2011 American Meteorological Society."
"35572026100;7101752236;","Ice-Ice collisions: An Ice multiplication process in atmospheric clouds",2011,"10.1175/2010JAS3607.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953188395&doi=10.1175%2f2010JAS3607.1&partnerID=40&md5=cb47178c1165d6287da0d3c24de2275e","Ice in atmospheric clouds undergoes complex physical processes, interacting especially with radiation, which leads to serious impacts on global climate. After their primary production, atmospheric ice crystals multiply extensively by secondary processes. Here, it is shown that a mostly overlooked process of mechanical breakup of ice particles by ice-ice collisions contributes to such observed multiplication. A regime for explosive multiplication is identified in its phase space of ice multiplication efficiency and number concentration of ice particles. Many natural mixed-phase clouds, if they have copious millimeter-sized graupel, fall into this explosive regime. The usual Hallett-Mossop (H-M) process of ice multiplication is shown to dominate the overall ice multiplication when active, as it starts sooner, compared to the breakup ice multiplication process. However, for deep clouds with a cold base temperature where the usual H-M process is inactive, the ice breakup mechanism should play a critical role. Supercooled rain, which may freeze to form graupel directly in only a few minutes, is shown to hasten such ice multiplication by mechanical breakup, with an ice enhancement ratio exceeding 104 approximately 20 min after small graupel first appear. The ascent-dependent onset of subsaturation with respect to liquid water during explosive ice multiplication is predicted to determine the eventual ice concentrations. © 2011 American Meteorological Society."
"9246517900;7003875148;7201472576;24332905600;8670472000;24472110700;56239378700;","The vertical distribution of thin features over the Arctic analysed from CALIPSO observations: Part I: Optically thin clouds",2011,"10.1111/j.1600-0889.2010.00516.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650936246&doi=10.1111%2fj.1600-0889.2010.00516.x&partnerID=40&md5=75c4ea04714d1aa5dec90d4035542717","Clouds play a crucial role in the Arctic climate system. Therefore, it is essential to accurately and reliably quantify and understand cloud properties over the Arctic. It is also important to monitor and attribute changes in Arctic clouds. Here, we exploit the capability of the CALIPSO-CALIOP instrument and provide comprehensive statistics of tropospheric thin clouds, otherwise extremely difficult to monitor from passive satellite sensors. We use 4 yr of data (June 2006-May 2010) over the circumpolar Arctic, here defined as 67-82°N, and characterize probability density functions of cloud base and top heights, geometrical thickness and zonal distribution of such cloud layers, separately for water and ice phases, and discuss seasonal variability of these properties. When computed for the entire study area, probability density functions of cloud base and top heights and geometrical thickness peak at 200-400, 1000-2000 and 400-800 m, respectively, for thin water clouds, while for ice clouds they peak at 6-8, 7-9 and 400-1000 m, respectively. In general, liquid clouds were often identified below 2 km during all seasons, whereas ice clouds were sensed throughout the majority of the upper troposphere and also, but to a smaller extent, below 2 km for all seasons. © 2010 The Authors Tellus B © 2010 International Meteorological Institute in Stockholm."
"6602421589;57198235788;57212830102;6506879405;6507553065;6701774395;","Some results of activities on the improvement of weather conditions over metropolises",2011,"10.3103/S1068373911020063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952994891&doi=10.3103%2fS1068373911020063&partnerID=40&md5=cfae0d3a793b0e2cba0e0327cfe33196","Some results of activities on cloud seeding operations to modify the weather conditions over metropolises are given. The main objective of these activities was to dissipate the clouds and to decrease or to stop the precipitation on the territory under protection during the political, cultural, or sporting events. Up to 12 aircraft specially equipped with the measuring equipment needed to carry out the cloud seeding, with the Land-Aircraft-Land radio data transmission system, and with the cloud seeding means were used to fulfill the works on the weather modification. The liquid nitrogen, ""dry ice"", silver iodide, and coarse-dispersion powder were used as the reagents for the cloud seeding. To control the aviation works and the results of the cloud seeding, the ground-based automated meteorological radar systems were used. The results of more than 40 large-scale operations on the improvement of weather conditions carried out since 1995 in different regions of Russia and near abroad indicate the efficiency of the methods and technical means of cloud seeding developed by the specialists of Roshydromet to modify the atmospheric precipitation. © 2011 Allerton Press, Inc."
"6603422104;7004540083;","Time scales of variability of the tropical atmosphere derived from cloud-defined weather states",2011,"10.1175/2010JCLI3574.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953769530&doi=10.1175%2f2010JCLI3574.1&partnerID=40&md5=2761cbdd54359077f711890d77934119","The recent analysis of Rossow et al. used a clustering technique to derive six tropical weather states (WS) based on mesoscale cloud-type patterns and documented the spatial distribution of those WS and the modes of variability of the convective WS in the tropical western Pacific. In this study, the global tropics are separated into 30° × 30° regions, and a clustering algorithm is applied to the regional WS frequency distributions to derive the dominant modes of weather state variability (or the climate state variability) in each region. The results show that the whole tropical atmosphere oscillates between a convectively active and a convectively suppressed regime with the exception of the eastern parts of the two ocean basins, where the oscillation is between a stratocumulus and a trade cumulus regime. The dominant mode of both those oscillations is the seasonal cycle with the exception of the eastern Indian and western-central Pacific region, where El Nin{ogonek}o frequencies dominate. The transitions between the convectively active and suppressed regimes produce longwave (LW) and shortwave (SW) top-of-atmosphere (TOA) radiative differences that are of opposite sign and of similar magnitude, being of order 20-30 W m-2 over ocean and 10-20 W m-2 over land and thus producing an overall balance in the TOA radiative budget. The precipitation differences between the convectively active and suppressed regimes are found to be of order 2.5-3 mm day-1 over ocean and 1-2.4 mm day-1 over land. Finally, the transitions between the stratocumulus and shallow cumulus regimes produce noticeable TOA SW differences of order 10-20 W m-2 and very small TOA LW and precipitation differences. The potential climate feedback implications of the regime radiation and precipitation differences are discussed. © 2011 American Meteorological Society."
"55113736500;","Numerical solution to drop coalescence/breakup with a volume-conserving, positive-definite, and unconditionally stable scheme",2011,"10.1175/2010JAS3605.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953167208&doi=10.1175%2f2010JAS3605.1&partnerID=40&md5=d25b8c0c36fdec9cbf00be5b818563ff","This paper discusses a new volume- and volume concentration-conserving, positive-definite, unconditionally stable iterative numerical scheme for solving temporary cloud/raindrop coalescence followed by breakup and the coupling of the scheme with an existing noniterative, volume- and volume concentration- conserving collision/coalescence (coagulation) scheme. The breakup scheme alone compares nearly exactly with a constant-kernel analytical solution at a 300-s time step. The combined coagulation/breakup schemes are stable and conservative, regardless of the time step and number of size bins, and convergent with higher temporal and size resolution. The schemes were designed with these characteristics in mind for use in longterm global or regional simulations. The use of 30 geometrically spaced size bins and a time step of 60 s provides a good compromise between obtaining sufficient accuracy (relative to a much higher-resolution result) and speed, although solutions with a 600-s time step and 30 bins are stable and conservative and take one-eighth the computer time. The combined coagulation/breakup schemes were implemented into the nested Gas, Aerosol, Transport, Radiation, General Circulation, Mesoscale, and Ocean Model (GATORGCMOM), a global-urban climate-weather-air pollution model. Coagulation was solved over liquid, ice, and graupel distributions and breakup simultaneously over the liquid distribution. Each distribution included 30 size bins and 16 chemical components per bin. Timing tests demonstrate the feasibility of the scheme in long-term global simulations. © 2011 American Meteorological Society."
"24329376600;6602692238;57203200427;35547807400;","A regional and global analysis of carbon dioxide physiological forcing and its impact on climate",2011,"10.1007/s00382-010-0742-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551598300&doi=10.1007%2fs00382-010-0742-1&partnerID=40&md5=a55461b5486fc8df7ffeca33204ef92f","An increase in atmospheric carbon dioxide concentration has both a radiative (greenhouse) effect and a physiological effect on climate. The physiological effect forces climate as plant stomata do not open as wide under enhanced CO2 levels and this alters the surface energy balance by reducing the evapotranspiration flux to the atmosphere, a process referred to as 'carbon dioxide physiological forcing'. Here the climate impact of the carbon dioxide physiological forcing is isolated using an ensemble of twelve 5-year experiments with the Met Office Hadley Centre HadCM3LC fully coupled atmosphere-ocean model where atmospheric carbon dioxide levels are instantaneously quadrupled and thereafter held constant. Fast responses (within a few months) to carbon dioxide physiological forcing are analyzed at a global and regional scale. Results show a strong influence of the physiological forcing on the land surface energy budget, hydrological cycle and near surface climate. For example, global precipitation rate reduces by ~3% with significant decreases over most land-regions, mainly from reductions to convective rainfall. This fast hydrological response is still evident after 5 years of model integration. Decreased evapotranspiration over land also leads to land surface warming and a drying of near surface air, both of which lead to significant reductions in near surface relative humidity (~6%) and cloud fraction (~3%). Patterns of fast responses consistently show that results are largest in the Amazon and central African forest, and to a lesser extent in the boreal and temperate forest. Carbon dioxide physiological forcing could be a source of uncertainty in many model predicted quantities, such as climate sensitivity, transient climate response and the hydrological sensitivity. These results highlight the importance of including biological components of the Earth system in climate change studies. © 2010 Springer-Verlag."
"7006422317;37093232500;7005485117;","Influence of rain-rate initialization, cloud microphysics, and cloud torques on hurricane intensity",2011,"10.1175/2010MWR3382.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953172961&doi=10.1175%2f2010MWR3382.1&partnerID=40&md5=6c089e393c88291932b5ef935c53963a","This study examines the impact of rain-rate initialization (RINIT), microphysical modifications, and cloud torques (in the context of angular momentum) on hurricane intensity forecasts using a mesoscale model [the Advanced Research Weather Research and Forecasting model (ARW-WRF)] at a cloud-resolving resolution of 2.7 km. The numerical simulations are performed in a triple-nested manner (25, 8.3, and 2.7 km) for Hurricane Dennis of 2005. Unless mentioned otherwise, all the results discussed are from the innermost grid with finest resolution (2.7 km). It is found that the model results obtained from the RINIT technique demonstrated robust improvement in hurricane structure, track, and intensity forecasts compared to the control experiment (CTRL; i.e., without RINIT). Thereafter, using RINIT initial conditions datasets three sensitive experiments are designed by modifying specific ice microphysical parameters (i.e., temperature-independent snow intercept parameter, doubling number of concentrations of ice, and ice crystal diameter) within the explicit parameterization scheme [i.e., the WRF Single-Moment 6-class (WSM6)]. It is shown that the experiment with enhanced ice mass concentration and temperature-independent snow intercept parameter produces the strongest and weakest storms, respectively. The results suggest that the distributions of hydrometeors are also impacted by the limited changes introduced in the microphysical scheme (e.g., the quantitative amount of snow drastically reduced to 0.1-0.2 g kg-1 when the intercept parameter of snow is made independent of temperature). It is noted that the model holds ice at a warmer temperature for a longer time with a temperature-independent intercept parameter. These variations in hydrometeor distribution in the eyewall region of the storm affect diabatic heating and vertical velocity structure and modulated the storm intensity. However, irrespective of the microphysical changes the quantitative amount of graupel hydrometeors remained nearly unaffected. Finally, the indirect effect of microphysical modifications on storm intensity through angular momentum and cloud torques is examined. A formulation to predict the short-term changes in the storm intensity using a parcel segment angular momentum budget method is developed. These results serve to elucidate the indirect impact of microphysical modifications on tropical cyclone intensity changes through modulation in cloud torque magnitude. © 2011 American Meteorological Society."
"57193017893;7402480218;7103373860;56228672600;","Convective signals from surface measurements at ARM Tropical Western Pacific site: Manus",2011,"10.1007/s00382-009-0736-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551603566&doi=10.1007%2fs00382-009-0736-z&partnerID=40&md5=108fe36271be3e4fee3a6b55b45686c1","Madden-Julian Oscillation (MJO) signals have been detected using highly sampled observations from the U. S. DOE ARM Climate Research Facility located at the Tropical Western Pacific Manus site. Using downwelling shortwave radiative fluxes and derived shortwave fractional sky cover, and the statistical tools of wavelet, cross wavelet, and Fourier spectrum power, we report finding major convective signals and their phase change from surface observations spanning from 1996 to 2006. Our findings are confirmed with the satellite-gauge combined values of precipitation from the NASA Global Precipitation Climatology Project and the NOAA interpolated outgoing longwave radiation for the same location. We find that the Manus MJO signal is weakest during the strongest 1997-1998 El Niño Southern Oscillation (ENSO) year. A significant 3-5-month lead in boreal winter is identified further between Manus MJO and NOAA NINO3. 4 sea surface temperature (former leads latter). A striking inverse relationship is found also between the instantaneous synoptic and intraseasonal phenomena over Manus. To further study the interaction between intraseasonal and diurnal scale variability, we composite the diurnal cycle of cloudiness for 21-MJO events that have passed over Manus. Our diurnal composite analysis of shortwave and longwave fractional sky covers indicates that during the MJO peak (strong convection), the diurnal amplitude of cloudiness is reduced substantially, while the diurnal mean cloudiness reaches the highest value and there are no significant phase changes. We argue that the increasing diurnal mean and decreasing diurnal amplitude are caused by the systematic convective cloud formation that is associated with the wet phase of the MJO, while the diurnal phase is still regulated by the well-defined solar forcing. This confirms our previous finding of the anti-phase relationship between the synoptic and intraseasonal phenomena. The detection of the MJO over the Manus site provides further opportunities in using other ground-based remote sensing instruments to investigate the vertical distributions of clouds and radiative heatings of the MJO that currently is impossible from satellite observations. © 2010 US Government."
"7004060399;7102167757;55126391900;9244992800;","Stratospheric ozone depletion: The main driver of twentieth-century atmospheric circulation changes in the Southern Hemisphere",2011,"10.1175/2010JCLI3772.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79851507098&doi=10.1175%2f2010JCLI3772.1&partnerID=40&md5=caf0f073bf2570fcc592591a34dc72a4","The importance of stratospheric ozone depletion on the atmospheric circulation of the troposphere is studied with an atmospheric general circulation model, the Community Atmospheric Model, version 3 (CAM3), for the second half of the twentieth century. In particular, the relative importance of ozone depletion is contrasted with that of increased greenhouse gases and accompanying sea surface temperature changes. By specifying ozone and greenhouse gas forcings independently, and performing long, time-slice integrations, it is shown that the impacts of ozone depletion are roughly 2-3 times larger than those associated with increased greenhouse gases, for the Southern Hemisphere tropospheric summer circulation. The formation of the ozone hole is shown to affect not only the polar tropopause and the latitudinal position of the midlatitude jet; it extends to the entire hemisphere, resulting in a broadening of the Hadley cell and a poleward extension of the subtropical dry zones. The CAM3 results are compared to and found to be in excellent agreement with those of the multimodel means of the recent Coupled Model Intercomparison Project (CMIP3) and Chemistry-Climate Model Validation (CCMVal2) simulations. This study, therefore, strongly suggests that most Southern Hemisphere tropospheric circulation changes, in austral summer over the second half of the twentieth century, have been caused by polar stratospheric ozone depletion. © 2011 American Meteorological Society."
"7004869183;16642939100;8279855000;12645090400;","From Observations to Forecasts - Part 8: The use of satellite observations in numerical weather prediction",2011,"10.1002/wea.736","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251643416&doi=10.1002%2fwea.736&partnerID=40&md5=af7103e648284471fae9bc9825c05931","Satellite observations combine to form the most important source of observations in NWP, and provide information on atmospheric and surface temperature, water vapour and wind fields. This article has described the main types of satellite observations used in numerical weather prediction, but it is not an exhaustive account. The growing importance of air quality forecasting, and links to climate studies, means that information on aerosol and chemical species is also of increasing interest. Satellite observations, with their global coverage, are ideally suited to providing this type of information. The MACC project (http://www.gmes-atmosphere.eu/) is one example of active research in this area. Innovative improvements in the use of existing data are constantly sought, and many centres are beginning to make use of information on cloud properties and precipitation from satellite observations to improve weather forecasts in meteorologically active areas. Every year new instruments provide more data, improving the coverage and filling gaps in the global observing system. The hugely important role of satellite data in NWP is therefore set to continue to grow over the coming decades."
"14064156500;7004144610;","Radiative transfer simulations for the MADRAS imager of Megha-Tropiques",2011,"10.1007/s12040-011-0012-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052669247&doi=10.1007%2fs12040-011-0012-6&partnerID=40&md5=d7df2000f6376bfbd9a1d707fd10ddf2","This paper reports the radiative transfer simulations for the passive microwave radiometer onboard the proposed Indian climate research satellite Megha-Tropiques due to be launched in 2011. These simulations have been performed by employing an in-house polarized radiative transfer code for raining systems ranging from depression and tropical cyclones to the Indian monsoon. For the sake of validation and completeness, simulations have also been done for the Tropical Rainfall Measuring Mission (TRMM)'s Microwave Imager (TMI) of the highly successful TRMM mission of NASA and JAXA. The paper is essentially divided into two parts: (a) Radiometer response with specific focus on high frequency channels in both the radiometers is discussed in detail with a parametric study of the effect of four hydrometeors (cloud liquid water, cloud ice, precipitating water and precipitating ice) on the brightness temperatures. The results are compared with TMI measurements wherever possible. (b) Development of a neural network-based fast radiative transfer model is elucidated here. The goal is to speed up the computational time involved in the simulation of brightness temperatures, necessitated by the need for quick and online retrieval strategies. The neural network model uses hydrometeor profiles as inputs and simulates spectral microwave brightness temperature at multiple frequencies as output. A huge database is generated by executing the in-house radiative transfer code for seven different cyclones occurred in North Indian Ocean region during the period 2001-2006. A part of the dataset is used to train the network while the remainder is used for testing purposes. For the purpose of testing, a typical scene from the southwest monsoon rain is also considered. The results obtained are very encouraging and show that the neural network is able to mimic the underlying physics of the radiative transfer simulations with a correlation coefficient of over 99%. © Indian Academy of Sciences."
"57192546908;56201438000;6604010263;57213985830;23016429600;7404557035;8636336800;","Numerical simulations of effects of soil moisture and modification by mountains over New Zealand in summer",2011,"10.1175/2010MWR3324.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953185792&doi=10.1175%2f2010MWR3324.1&partnerID=40&md5=d3476bbb4e940b04681fecb49958895f","Historically most soil moisture-land surface impact studies have focused on continents because of the important forecasting and climate implications involved. For a relatively small isolated mountainous landmass in the ocean such as New Zealand, these impacts have received less attention. This paper addresses some of these issues for New Zealand through numerical experiments with a regional configuration of the Met Office Unified Model atmospheric model. Two pairs of idealized simulations with only contrasting dry or wet initial soil moisture over a 6-day period in January 2004 were conducted, with one pair using realistic terrain and the other pair flat terrain. For the mean of the 6 days, the differences in the simulated surface air temperature between the dry and moist cases were 3-5 Kon the leeside slopes and 1-2 K on the windward slopes and the central leeside coastal region of the South Island in the afternoon. This quite nonuniform response in surface air temperature to a uniformly distributed soil moisture content and soil type is mainly attributed to modification of the effects of soil moisture by mountains through two different processes: 1) spatial variation in cloud coverage across the mountains ranges leading to more shortwave radiation at ground surface on the leeside slope than the windward slope, and 2) the presence of a dynamically and thermally induced onshore flow on the leeside coast bringing in air with a lower sensitivity to soil moisture. The response of local winds to soil moisture content is through direct or indirect effects. The direct effect is due to the thermal contrast between land and sea/land shown for the leeside solenoidal circulations, and the indirect effect is through the weakening of the upstream blocking of the South Island for dryer soils shown by the weakening and onshore shift of the upstream deceleration and forced ascent of incoming airflow. © 2011 American Meteorological Society."
"25943390200;57208275038;","The climate of cloud forests",2011,"10.1002/hyp.7847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751513623&doi=10.1002%2fhyp.7847&partnerID=40&md5=d7a279165b1d8676780842bbce0da4c5","This chapter analyses the climatic conditions prevailing at sites where tropical montane cloud forests (TMCF) have been reported. Spatial data-sets of climate were used to describe the climate at 477 cloud forest sites identified by United Nations Environment Program (UNEP)-WCMC. Some 85% of the sites are found at altitudes between 400 and 2800 m a.s.l., with an average altitude of 1700 m. The range of altitudes at which cloud forests are found is extensive (220-5005 m). The climate of cloud forests is highly variable from site to site, with an average rainfall of ∼2000 mm year-1 and an average temperature of 17·7 °C. In addition, cloud forests are found in seasonal and aseasonal environments alike, both in terms of rainfall and temperature. There are some clear differences in the climates of cloud forests found in Africa, Latin America and the Caribbean, and those in Asia. Cloud forests are found to be wetter (with incident rainfall being 184 mm year-1 higher on average), cooler (by 4·2 °C on average), and less seasonally variable than other montane forests not affected significantly by fog and low cloud. Cloud forests are also almost completely confined to a zone within 350 km from the nearest coast. Finally, the climatic representativity of 14 intensively studied cloud forest sites (ISS) was analysed, as a group, the sites provided a fair representation of the climates found in cloud forests, evenly covering the ranges in temperature and rainfall. The majority of cloud forest sites occur in regions with 2000-2600 mm of rainfall and annual mean temperatures (Tmean) of 14-18 °C. Relatively dry cloud forest sites (&lt;1000 mm of rain year-1) are under-represented in the UNEP-WCMC data-base. Copyright © 2010 John Wiley &amp; Sons, Ltd."
"56702490400;57208275038;35614096800;","Hydrometeorology of tropical montane cloud forests: Emerging patterns",2011,"10.1002/hyp.7974","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751521670&doi=10.1002%2fhyp.7974&partnerID=40&md5=f15e4a5c15f52755b64d5a07c9a676cb","Tropical montane cloud forests (TMCF) typically experience conditions of frequent to persistent fog. On the basis of the altitudinal limits between which TMCF generally occur (800-3500 m.a.s.l. depending on mountain size and distance to coast) their current areal extent is estimated at ∼215 000 km2 or 6·6% of all montane tropical forests. Alternatively, on the basis of remotely sensed frequencies of cloud occurrence, fog-affected forest may occupy as much as 2·21 Mkm2. Four hydrologically distinct montane forest types may be distinguished, viz. lower montane rain forest below the cloud belt (LMRF), tall lower montane cloud forest (LMCF), upper montane cloud forest (UMCF) of intermediate stature and a group that combines stunted sub-alpine cloud forest (SACF) and 'elfin' cloud forest (ECF). Average throughfall to precipitation ratios increase from 0·72 ± 0·07 in LMRF (n = 15) to 0·81 ± 0·11 in LMCF (n = 23), to 1·0 ± 0·27 (n = 18) and 1·04 ± 0·25 (n = 8) in UMCF and SACF-ECF, respectively. Average stemflow fractions increase from LMRF to UMCF and ECF, whereas leaf area index (LAI) and annual evapotranspiration (ET) decrease along the same sequence. Although the data sets for UMCF (n = 3) and ECF (n = 2) are very limited, the ET from UMCF (783 ± 112 mm) and ECF (547 ± 25 mm) is distinctly lower than that from LMCF (1188 ± 239 mm, n = 9) and LMRF (1280 ± 72 mm; n = 7). Field-measured annual 'cloud-water' interception (CWI) totals determined with the wet-canopy water budget method (WCWB) vary widely between locations and range between 22 and 1990 mm (n = 15). Field measured values also tend to be much larger than modelled amounts of fog interception, particularly at exposed sites. This is thought to reflect a combination of potential model limitations, a mismatch between the scale at which the model was applied (1 × 1 km) and the scale of the measurements (small plots), as well as the inclusion of near-horizontal wind-driven precipitation in the WCWB-based estimate of CWI. Regional maps of modelled amounts of fog interception across the tropics are presented, showing major spatial variability. Modelled contributions by CWI make up less than 5% of total precipitation in wet areas to more than 75% in low-rainfall areas. Catchment water yields typically increase from LMRF to UMCF and SACF-ECF reflecting concurrent increases in incident precipitation and decreases in evaporative losses. The conversion of LMCF (or LMRF) to pasture likely results in substantial increases in water yield. Changes in water yield after UMCF conversion are probably modest due to trade-offs between concurrent changes in ET and CWI. General circulation model (GCM)-projected rates of climatic drying under SRES greenhouse gas scenarios to the year 2050 are considered to have a profound effect on TMCF hydrological functioning and ecology, although different GCMs produce different and sometimes opposing results. Whilst there have been substantial increases in our understanding of the hydrological processes operating in TMCF, additional research is needed to improve the quantification of occult precipitation inputs (CWI and wind-driven precipitation), and to better understand the hydrological impacts of climate- and land-use change. Copyright © 2010 John Wiley &amp; Sons, Ltd."
"36704614100;6505777444;","Hydrometeorology and structure of tropical montane cloud forests under contrasting biophysical conditions in north-western Costa Rica",2011,"10.1002/hyp.7726","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751483927&doi=10.1002%2fhyp.7726&partnerID=40&md5=5619ca143e518a588eb82784d40f4d50","Tropical cloud forests have received increasing attention because of their significance for freshwater supply. This study aimed to understand hydro-meteorological gradients in relation to spatial changes in forest structure in north-western Costa Rica. Seven climate stations (measuring rainfall, horizontal precipitation, throughfall, temperature and soil moisture) were installed along a 2·5 km transect between 1200 and 1500 m.a.s.l. on the Atlantic (windward) slope and the Pacific (leeward) slope of the Tilarán mountains. Forest structure was investigated on seven 10 × 50 m plots. Epiphytic vegetation was assessed on six trees at 1450 m and at 1200 m on the Pacific slope. Annual rainfall ranged from 3690 mm on the leeward slope to 6390 mm on the windward side. Horizontal precipitation was 3560 mm at the ridge, where it exceeded rainfall during the dry season, compared to 330 mm and 28 mm at the lowest windward and leeward plots, respectively. Throughfall remained below rainfall on the lower slopes but exceeded rainfall on the ridge. Soil water content ranged between 70% and 80% on the ridge top, where waterlogging occurred frequently. The studied forests were classified as lower montane rain forest, lower montane cloud forest and elfin cloud forest. The greatest canopy heights and basal areas occurred on the leeward slope between 1200 and 1450 m and at the lowest windward plot. Tree heights remained below 15 m on the ridge, where stilt roots occurred frequently. Near the ridge, epiphyte abundance and species richness were greater, compared to the lower leeward slope. These findings prove the importance of horizontal precipitation in the study area, confirm the important role of epiphytes as indicators for moisture gradients and elucidate the variability of forest structure under the given biophysical conditions. Copyright © 2010 John Wiley & Sons, Ltd."
"24722339600;7004544454;7004479957;57201235812;7004775578;6602229667;35473805400;7006837187;8684037700;7102132806;7005862399;22975069200;7006643234;7801515303;6701404949;18935008000;7005254328;7201432984;35593636200;7202252296;8247122100;7005680021;35584010200;6701562043;55963363300;6507501796;7006783796;6506234624;8724962900;7404195755;35419560700;23570437900;16480175700;7006377579;","The VAMOS ocean-cloud-atmosphere-land study regional experiment (VOCALS-REx): Goals, platforms, and field operations",2011,"10.5194/acp-11-627-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78951474997&doi=10.5194%2facp-11-627-2011&partnerID=40&md5=dd7a355e2e6a93eea6a2f272bdb20986","The VAMOS1 Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was an international field program designed to make observations of poorly understood but critical components of the coupled climate system of the southeast Pacific. This region is characterized by strong coastal upwelling, the coolest SSTs in the tropical belt, and is home to the largest subtropical stratocumulus deck on Earth. The field intensive phase of VOCALS-REx took place during October and November 2008 and constitutes a critical part of a broader CLIVAR program (VOCALS) designed to develop and promote scientific activities leading to improved understanding, model simulations, and predictions of the southeastern Pacific (SEP) coupled ocean-atmosphere-land system, on diurnal to interannual timescales. The other major components of VOCALS are a modeling program with a model hierarchy ranging from the local to global scales, and a suite of extended observations from regular research cruises, instrumented moorings, and satellites. The two central themes of VOCALS-REx focus upon (a) links between aerosols, clouds and precipitation and their impacts on marine stratocumulus radiative properties, and (b) physical and chemical couplings between the upper ocean and the lower atmosphere, including the role that mesoscale ocean eddies play. A set of hypotheses designed to be tested with the combined field, monitoring and modeling work in VOCALS is presented here. A further goal of VOCALS-REx is to provide datasets for the evaluation and improvement of large-scale numerical models. VOCALS-REx involved five research aircraft, two ships and two surface sites in northern Chile. We describe the instrument payloads and key mission strategies for these platforms and give a summary of the missions conducted. 1 Variability of the American Monsoon Systems, an international CLIVAR program. © 2011 Author(s)."
"7404829395;56537463000;22959252400;7003398293;7006278987;6506730508;57208765879;25227357000;7102018821;","Influence of convection and aerosol pollution on ice cloud particle effective radius",2011,"10.5194/acp-11-457-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751495570&doi=10.5194%2facp-11-457-2011&partnerID=40&md5=01a340ee8cbc72de944fa7b7e6472602","Satellite observations show that ice cloud effective radius (re) increases with ice water content (IWC) but decreases with aerosol optical thickness (AOT). Using least-squares fitting to the observed data, we obtain an analytical formula to describe the variations of re with IWC and AOT for several regions with distinct characteristics of re-IWC-AOT relationships. As IWC directly relates to convective strength and AOT represents aerosol loading, our empirical formula provides a means to quantify the relative roles of dynamics and aerosols in controlling re in different geographical regions, and to establish a framework for parameterization of aerosol effects on re in climate models. © 2011 Author(s)."
"55836997000;35770703500;7201525750;7003740015;56109615300;","Glycine in aerosol water droplets: A critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations",2011,"10.5194/acp-11-519-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751504505&doi=10.5194%2facp-11-519-2011&partnerID=40&md5=11f0364b7ef8076ce807e89573df1bd7","Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Köhler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems, the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Köhler equation could be improved by incorporating surface tension corrections. © 2011 Author(s)."
"36052878000;7003696273;9233214000;24460392200;7102963655;","Assessing observed and modelled spatial distributions of ice water path using satellite data",2011,"10.5194/acp-11-375-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651497386&doi=10.5194%2facp-11-375-2011&partnerID=40&md5=29a7540a1e7788988701870dd8d43986","The climate models used in the IPCC AR4 show large differences in monthly mean ice water path (IWP). The most valuable source of information that can be used to potentially constrain the models is global satellite data. The satellite datasets also have large differences. The retrieved IWP depends on the technique used, as retrievals based on different techniques are sensitive to different parts of the cloud column. Building on the foundation of Waliser et al. (2009), this article provides a more comprehensive comparison between satellite datasets. IWP data from the CloudSat cloud profiling radar provide the most advanced dataset on clouds. For all its unmistakable value, CloudSat data are too short and too sparse to assess climatic distributions of IWP, hence the need to also use longer datasets. We evaluate satellite datasets from CloudSat, PATMOS-x, ISCCP, MODIS and MSPPS in terms of monthly mean IWP, in order to determine the differences and relate them to the sensitivity of the instrument used in the retrievals. This information is also used to evaluate the climate models, to the extent that is possible. ISCCP and MSPPS were shown to have comparatively low IWP values. ISCCP shows particularly low values in the tropics, while MSPPS has particularly low values outside the tropics. MODIS and PATMOS-x were in closest agreement with CloudSat in terms of magnitude and spatial distribution, with MODIS being the better of the two. Additionally PATMOS-x and ISCCP, which have a temporal range long enough to capture the inter-annual variability of IWP, are used in conjunction with CloudSat IWP (after removing profiles that contain precipitation) to assess the IWP variability and mean of the climate models. In general there are large discrepancies between the individual climate models, and all of the models show problems in reproducing the observed spatial distribution of cloud-ice. Comparisons consistently showed that ECHAM-5 is probably the GCM from IPCC AR4 closest to satellite observations. © 2011 Author(s)."
"35192263300;55235064100;35722808700;16202021900;57196548688;","Solar radiation trend across China in recent decades: A revisit with quality-controlled data",2011,"10.5194/acp-11-393-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651497087&doi=10.5194%2facp-11-393-2011&partnerID=40&md5=9375f1a6d9b788d5c1d5ad773bb09baa","Solar radiation is one of the most important factors affecting climate and environment, and its long-term variation is of much concern in climate change studies. In the light of the limited number of radiation stations with reliable long-term time series observations, this paper presents a new evaluation of the long-term variation of surface solar radiation over China by combining quality-controlled observed data and two radiation models. One is the ANN-based (Artificial Neutral Network) model and the other is a physical model. The two models produce radiation trends comparable to the observed ones at a few validation stations possessing reliable and continuous data. Then, the trend estimate is extended by the ANN-based model to all 96 radiation stations and furthermore extended by the physical model to all 716 China Meteorological Administration (CMA) routine stations. The new trend estimate is different from previous ones in two aspects. First, the magnitude of solar radiation over China decreased by about -0.23 W m-2 yr--1 between 1961 and 2000, which is greatly less in magnitude than trend slopes estimated in previous studies (ranging over -0.41 ∼ -0.52 W m-2 yr--1). Second, the ""From Dimming to Brightening"" transition in China during the late 1980s ∼ the early 1990s was addressed in previous studies, but this study indicates the solar radiation reached a stable level since the 1990s and the transition is not noticeable. These differences indicate the importance of data-quality control and analysis approaches. Finally, an obvious transition from brightening to dimming around 1978 is found over the Tibetan Plateau, where aerosol loads are very low, indicating that the importance of cloud changes in altering solar radiation may be comparable to that of the aerosol changes. © 2011 Author(s)."
"7401472342;7101686436;6701784984;7102141244;57189498750;56162114200;7003942283;57201527657;","Microbiology and atmospheric processes: Research challenges concerning the impact of airborne micro-organisms on the atmosphere and climate",2011,"10.5194/bg-8-17-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650918685&doi=10.5194%2fbg-8-17-2011&partnerID=40&md5=d63652a47bdcfa02a3359494f40baa98","For the past 200 years, the field of aerobiology has explored the abundance, diversity, survival and transport of micro-organisms in the atmosphere. Micro-organisms have been explored as passive and severely stressed riders of atmospheric transport systems. Recently, an interest in the active roles of these micro-organisms has emerged along with proposals that the atmosphere is a global biome for microbial metabolic activity and perhaps even multiplication. As part of a series of papers on the sources, distribution and roles in atmospheric processes of biological particles in the atmosphere, here we describe the pertinence of questions relating to the potential roles that air-borne micro-organisms might play in meteorological phenomena. For the upcoming era of research on the role of air-borne micro-organisms in meteorological phenomena, one important challenge is to go beyond descriptions of abundance of micro-organisms in the atmosphere toward an understanding of their dynamics in terms of both biological and physico-chemical properties and of the relevant transport processes at different scales. Another challenge is to develop this understanding under contexts pertinent to their potential role in processes related to atmospheric chemistry, the formation of clouds, precipitation and radiative forcing. This will require truly interdisciplinary approaches involving collaborators from the biological and physical sciences, from disciplines as disparate as agronomy, microbial genetics and atmosphere physics, for example. © Author(s) 2011."
"55448015500;57202733911;12801073500;23990100700;55973596200;16679661100;37029222100;56637331500;7004479395;56104525000;6603273568;","Sampling strategy and climatic implications of tree-ring stable isotopes on the southeast Tibetan Plateau",2011,"10.1016/j.epsl.2010.11.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650302948&doi=10.1016%2fj.epsl.2010.11.014&partnerID=40&md5=aa13eaf2af78bd818c7e6fb13b76a4db","We explore the potential of tree-ring cellulose δ18O and δ13C records for reconstructing climate variability in the southeast Tibetan Plateau. Our sampling strategy was designed to investigate intra and inter-tree variability, and the effects of the age of tree on δ18O variation. We show that intra-tree δ13C and δ18O variability is negligible, and inter-tree coherence is sufficient to build robust tree-ring δ18O or δ13C chronologies based on only four trees. There is no evidence of an age effect regarding δ18O, in contrast with tree-ring width. In our warm and moist sampling site, young tree δ13C is not clearly correlated with monthly mean meteorological data. Tree-ring δ18O appears significantly anti-correlated with summer precipitation amount, regional cloud cover, and relative humidity. Simulations conducted with the ORCHIDEE land surface model confirm the observed contribution of relative humidity to tree cellulose δ18O, and explain the weak correlation of δ13C with climate by the non-linear integration linked with photosynthesis. Altogether, the tree-ring cellulose δ18O is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period. © 2010 Elsevier B.V."
"55915206300;8718425100;55896920900;","Scale-aware integral constraints on autoconversion and accretion in regional and global climate models",2011,"10.1029/2011gl047618","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957969676&doi=10.1029%2f2011gl047618&partnerID=40&md5=b8fa9ada85444d98aa42f25f2be9ad40","We describe a novel method to constrain autoconversion and accretion rates in climate models. The method offers two desirable features that might ultimately help to effectively eliminate autoconversion efficiency as a free tuning parameter in climate models. Firstly, it can be constrained based on concurrent observations of column integrated cloud properties, namely cloud droplet number concentration, liquid water path, and precipitation rate. Secondly, the scale-dependency of autoconversion can be incorporated and resolved explicitly. The new method was implemented into the University of Hawaii's regional climate model iRAM. A series of test integrations were performed at horizontal resolutions ranging from 0.25° × 0.25° to 2° × 2°. The constrained approach was compared with a conventional approach commonly found in current climate models. Comparisons with an observational climatology of cloud liquid water path reveal significant improvements, in particular a better consistency between different model resolutions. Copyright 2011 by the American Geophysical Union."
"7201443624;","Combining satellite data and models to estimate cloud radiative effect at the surface and in the atmosphere",2011,"10.1002/met.285","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051879400&doi=10.1002%2fmet.285&partnerID=40&md5=a7feeda7833aa2321a3129e7bf577eba","Satellite measurements and numerical forecast model reanalysis data are used to compute an updated estimate of the cloud radiative effect on the global multi-annual mean radiative energy budget of the atmosphere and surface. The cloud radiative cooling effect through reflection of short wave radiation dominates over the long wave heating effect, resulting in a net cooling of the climate system of - 21 Wm-2. The short wave radiative effect of cloud is primarily manifest as a reduction in the solar radiation absorbed at the surface of - 53 Wm-2. Clouds impact long wave radiation by heating the moist tropical atmosphere (up to around 40 Wm-2 for global annual means) while enhancing the radiative cooling of the atmosphere over other regions, in particular higher latitudes and sub-tropical marine stratocumulus regimes. While clouds act to cool the climate system during the daytime, the cloud greenhouse effect heats the climate system at night. The influence of cloud radiative effect on determining cloud feedbacks and changes in the water cycle are discussed. © 2011 Royal Meteorological Society."
"6508287655;57209692325;35330367300;42361599300;6603631763;7102797196;","The recent state of the climate: Driving components of cloud-type variability",2011,"10.1029/2010JD014559","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958784184&doi=10.1029%2f2010JD014559&partnerID=40&md5=ee57573cc3066cf5fb2fdabd4a8f7540","To reduce the Earth's radiation budget uncertainty related to cloud types' changes, and better understand the climate constraints resulting from long-term clouds' variability, frequent and finer (than actually existing) observations are necessary. This is one of the aims of future satellite programs such as the Global Change Observation Mission-Climate (GCOM-C) satellite, to be launched by the Japan Aerospace Exploration Agency (JAXA). To facilitate the transition from past to future observations, the actual state of climate variables (e.g., cloud types) needs to be evaluated. This evaluation is attempted in the present work with the analysis of long-term cloud types' distribution and amounts. The data set used for this study is 25 years (1982-2006) of global daytime cloud properties observed by the National Oceanic and Atmospheric Administration- Advanced Very-High-Resolution Radiometer (NOAA-AVHRR) satellites sensors. Though various calibrations have been applied on NOAA-AVHRR data, the effects of the orbit drift experienced by these satellites need to be corrected. A signal processing decomposition method allowing the filtering of the cloud types' amount trend affected by the orbit drift is used to perform the necessary corrections. The results obtained show a quantifiable improvement of the cloud amount estimation and trends of the individual NOAA satellites initial observations, at the global and regional scales. The corrected global cloud amount shows a slight decrease in its linear trend. The driving factors of this trend are the decrease in mid and low clouds overwhelming the increase in high clouds (+0.04% cloud amount/yr). A comparison with other cloud climatology studies such as the International Cloud Satellite Climatology Project (ISCCP) data set shows that the global cloud decrease noticed in NOAA-AVHRR's data is smaller. And, contrary to the NOAA-AVHRR's data, the driving force of the ISCCP linear trend is a sharp decrease in low clouds (-0.20% cloud amount/yr). Copyright 2011 by the American Geophysical Union."
"12801992200;","Planetary albedo in strongly forced climate, as simulated by the CMIP3 models",2011,"10.1007/s00704-011-0411-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052707202&doi=10.1007%2fs00704-011-0411-2&partnerID=40&md5=490309ca70604d4d40f8773f2155a9a8","In an ensemble of general circulation models, the global mean albedo significantly decreases in response to strong CO2 forcing. In some of the models, the magnitude of this positive feedback is as large as the CO2 forcing itself. The models agree well on the surface contribution to the trend, due to retreating snow and ice cover, but display large differences when it comes to the contribution from shortwave radiative effects of clouds. The ""cloud contribution"" defined as the difference between clear-sky and all-sky albedo anomalies and denoted as ΔCC is correlated with equilibrium climate sensitivity in the models (correlation coefficient 0. 76), indicating that in high sensitivity models the clouds to a greater extent act to enhance the negative clear-sky albedo trend, whereas in low sensitivity models the clouds rather counteract this trend. As a consequence, the total albedo trend is more negative in more sensitive models (correlation coefficient 0. 73). This illustrates in a new way the importance of cloud response to global warming in determining climate sensitivity in models. The cloud contribution to the albedo trend can primarily be ascribed to changes in total cloud fraction, but changes in cloud albedo may also be of importance. © 2011 The Author(s)."
"35974951200;6603390592;6602244257;","The aerosol-Bénard cell effect on marine stratocumulus clouds and its contribution to glacial-interglacial cycles",2011,"10.1029/2010JD014470","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958066490&doi=10.1029%2f2010JD014470&partnerID=40&md5=85fe36887135fbe3535e1ed9d30e022e","Aerosol-cloud interactions, such as aerosol loading in convective clouds resulting in either precipitation suppression or cloud invigoration, in higher cloud tops, and in longer-lived clouds, are well known. Here we investigate a new aerosol-cloud interaction, the effect of aerosol loading on Bénard cells, on the stratocumulus cloud fraction, and ultimately on the climate over glacial-interglacial cycles, using a two-dimensional model running a million year continuous simulation. This radiative effect is observed only in marine boundary layer stratocumulus clouds that have a convective cellular structure. Recent research suggests that aerosols can switch the direction of convection in Bénard cells (from open cells to closed cells) by suppressing precipitation and therefore dramatically change the cloud fraction. The effect investigated in this work differs from previously known aerosol effects on convective clouds by its intensity and magnitude and has never been taken into account in past climate simulations. The results show that accounting for the aerosol-Bénard cell effect alone contributes a negative radiative forcing, affecting both the Northern Hemisphere mean annual surface temperature and ice volume. Adding the aerosol-Bénard cell effect to the direct radiative effect of dust and to the effect of dust on snow and ice albedo shows that the aerosol-Bénard cell effect plays a significant role in glacial-interglacial climate change, strengthening the earlier glacial cycles and creating a larger glacial-interglacial surface temperature amplitude while preserving the continental ice volume amplitude. Because of the model limitations, there are a number of uncertainties involved. However, the results serve to give a preliminary evaluation of the aerosol-Bénard cell effect at least qualitatively if not quantitatively. Copyright 2011 by the American Geophysical Union."
"36097134700;57210717926;6507506306;8397494800;57193132723;6507017020;8877858700;36876405100;7006698304;7102211934;57219951382;24537575000;56865378100;23975989200;54408955600;7410070663;7005056279;16441664100;7102630621;7201798956;7004544454;55666843400;56529731700;7103332540;7004909320;6602364115;7403295159;7202208382;7006705919;6701571700;7004540083;7005496842;6603566335;7006091410;8408994300;7003557662;6603409060;55286185400;","Tropical and subtropical cloud transitions in weather and climate prediction models: The GCSS/WGNE pacific cross-section intercomparison (GPCI)",2011,"10.1175/2011JCLI3672.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955578692&doi=10.1175%2f2011JCLI3672.1&partnerID=40&md5=91757f22b93df0502bbd19a71187d4a3","A model evaluation approach is proposed in which weather and climate prediction models are analyzed along a Pacific Ocean cross section, from the stratocumulus regions off the coast of California, across the shallow convection dominated trade winds, to the deep convection regions of the ITCZ-the Global Energy and Water Cycle Experiment Cloud System Study/Working Group on Numerical Experimentation (GCSS/WGNE) Pacific Cross-Section Intercomparison (GPCI). The main goal of GPCI is to evaluate and help understand and improve the representation of tropical and subtropical cloud processes in weather and climate prediction models. In this paper, a detailed analysis of cloud regime transitions along the cross section from the subtropics to the tropics for the season June-July-August of 1998 is presented. This GPCI study confirms many of the typical weather and climate prediction model problems in the representation of clouds: underestimation of clouds in the stratocumulus regime by most models with the corresponding consequences in terms of shortwave radiation biases; overestimation of clouds by the 40-yrECMWFRe-Analysis (ERA-40) in the deep tropics (in particular) with the corresponding impact in the outgoing longwave radiation; large spread between the different models in terms of cloud cover, liquid water path and shortwave radiation; significant differences between the models in terms of vertical cross sections of cloud properties (in particular), vertical velocity, and relative humidity. An alternative analysis of cloud cover mean statistics is proposed where sharp gradients in cloud cover along the GPCI transect are taken into account. This analysis shows that the negative cloud bias of some models and ERA-40 in the stratocumulus regions [as compared to the first International Satellite Cloud Climatology Project (ISCCP)] is associated not only with lower values of cloud cover in these regimes, but also with a stratocumulus-to-cumulus transition that occurs too early along the trade wind Lagrangian trajectory. Histograms of cloud cover along the cross section differ significantly between models. Some models exhibit a quasi-bimodal structure with cloud cover being either very large (close to 100%) or very small, while other models show a more continuous transition. The ISCCP observations suggest that reality is in-between these two extreme examples. These different patterns reflect the diverse nature of the cloud, boundary layer, and convection parameterizations in the participating weather and climate prediction models. © 2011 American Meteorological Society."
"16246205000;55738957800;","Microphysics parameterization for convective clouds in a global climate model: Description and single-column model tests",2011,"10.1029/2010JD014833","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251603439&doi=10.1029%2f2010JD014833&partnerID=40&md5=abadfc0569434b178f66e1e2485c58ca","An efficient two-moment microphysics parameterization scheme for convective clouds is developed to improve the representation of convective clouds and its interactions with stratiform clouds and aerosol in global climate models (GCMs). The scheme explicitly treats mass mixing ratio and number concentration of four hydrometeor species (cloud water, cloud ice, rain, and snow) and describes several microphysical processes, including autoconversion, self-collection, collection between hydrometeor species, freezing, cloud ice nucleation, droplet activation, and sedimentation. Thus this physically based scheme is suitable for investigating the interaction between convection and aerosol and the indirect aerosol effect on climate. An evaluation of the scheme in the single-column version of NCAR Community Atmospheric Model version 3.5 (CAM3.5) with the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) data shows that the simulation of cloud microphysical properties in convective core is significantly improved, indicating that the new parameterization describes the microphysical processes in convection reasonably well. The contribution from convective detrainment to large-scale cloud ice and liquid water budgets is enhanced greatly. With more realistic convective cloud microphysical properties and their detrainment, the surface stratiform precipitation, which is seriously underestimated in the model, is increased by a factor of roughly 2.5, and therefore is much closer to the observations. In addition, the simulations of net surface shortwave radiation flux, OLR, specific humidity, and temperature are also improved to some extent. Sensitivity experiments show that the microphysics scheme is moderately sensitive to model vertical resolution, updraft vertical velocity, and numerics, but less so to the lower boundary conditions of hydrometeor budget equations. The experiments with climatological aerosol distribution show that convective precipitation is suppressed with increasing aerosol amount, consistent with some available observations. Copyright 2011 by the American Geophysical Union."
[No author id available],"Part III: Clouds, Storms and Global Climate",2011,"10.1016/S0074-6142(10)09906-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023114100&doi=10.1016%2fS0074-6142%2810%2909906-7&partnerID=40&md5=d4b7b1f8da591644a3a57d55f3983a28",[No abstract available]
"6603081424;7004540083;","The cloud radiative effects of International Satellite Cloud Climatology Project weather states",2011,"10.1029/2010JD015472","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959638009&doi=10.1029%2f2010JD015472&partnerID=40&md5=60e25d096b996e39322a6f4c07443bed","The salient features of the daytime cloud radiative effect (CRE, also known as cloud radiative forcing) corresponding to various cloud regimes or weather states are examined. The analysis is based on a 24 year long data set from the International Satellite Cloud Climatology Project (ISCCP) for three distinct geographical zones covering most of the Earth's surface area. Conditional sampling and averaging of the ISCCP cloud fraction and CRE in 2.5 grid cells is performed for each weather state, and the state's radiative importance expressed as the relative contribution to the total CRE of its geographical zone is explained in terms of dominant cloud type, cloud fraction, and frequency of occurrence. Similarities and differences within and between geographical zones in the cloud fraction and CRE characteristics of the various weather states are identified and highlighted. By providing an exposition of the radiative energy characteristics of different cloud type mixtures, we facilitate the meteorological situation-dependent evaluation of radiation budget effects due to clouds in climate models. Copyright 2011 by the American Geophysical Union."
"55543656200;55545601500;7202418453;37094283000;","Global cloud-layer distribution statistics from 1 year CALIPSO lidar observations",2011,"10.1080/01431160903530821","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953218735&doi=10.1080%2f01431160903530821&partnerID=40&md5=fdbd6f113dd2edb2ccf18a53ec052d5c","In this paper, the cloud statistics and global cloud distributions are derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) level 2, 5 km lidar cloud-layer products between 13 June 2006 and 24 June 2007. The global cloud-layer occurrence frequency, the horizontal and the vertical distributions of cloud-occurrence frequency, the global cloud-top height statistics and their seasonal changes are given for 1 year CALIPSO observations. Opaque cloudlayer statistics are analysed for better understanding the statistics of the clouds observed using CALIPSO. Parts of the results are compared with some results from the High Resolution Infrared Radiation Sounder (HIRS) observations, the Geoscience Laser Altimeter System (GLAS) observations and the global rawinsonde observations, the Aqua MODerate Resolution Imaging Spectroradiometer (MODIS) monthly cloud-fraction data. The comparisons show that results are in agreement with other observations. Due to the primary advance from the active optical sensing, CALIPSOlidar can offermeasurements of accurate, highly resolved vertical profiles of atmospheric scattering layers. It has advantages in determining the location of optically thin clouds and detecting occurrences of multiple layers. Long-term observations by CALIPSO lidar can provide valuable information for the better understanding of the climate system and global climate change. © 2011 Taylor & Francis."
"23065650200;55463274000;55663817800;","Representing the ice fall speed in climate models: Results from Tropical Composition, Cloud and Climate Coupling (TC4) and the Indirect and Semi-Direct Aerosol Campaign (ISDAC)",2011,"10.1029/2010JD015433","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053067481&doi=10.1029%2f2010JD015433&partnerID=40&md5=2bc3e3ff854933d5384afcca0859b985","Ice fall velocity has a strong impact on climate feedback, influencing cirrus cloud coverage and radiative forcing as well as upper troposphere relative humidity. This study aims to provide the atmospheric modeling community with better parameterizations of the ice fall speed in cirrus clouds on the basis of aircraft measurements from recent field campaigns, especially the Tropical Composition, Cloud and Climate Coupling (TC4) campaign in 2007 and the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in 2008. These campaigns provide improved measurements of the ice particle size distribution (PSD) where the concentrations of artifact small ice particles (due to shattering of ice particles on the probe inlet tube) are greatly reduced. In addition to the PSD, the mass-weighted fall velocity (V<inf>m</inf>) depends on the ice particle projected area and mass. The calculation of V<inf>m</inf> was based on improved direct measurements of the PSD number and area concentration and improved estimates of ice particle mass. The effective diameter (D<inf>e</inf>) was calculated in a similar way. The TC4 analysis has provided a diagnostic relationship that relates V<inf>m</inf> to both cloud temperature (T) and ice water content (IWC) with an r2 of 0.78. A similar relationship for D<inf>e</inf> was also obtained with an r2 of 0.82. The V<inf>m</inf> relationship and associated V<inf>m</inf>-IWC-T measurements were found to agree well with a V<inf>m</inf> scheme based on T and cloud radar retrievals of V<inf>m</inf> and IWC in tropical cirrus clouds. However, a critical climate-influencing parameter like the ice fall speed needs to be coupled with the cloud microphysics and radiation in climate models. This is made possible through strong correlations between D<inf>e</inf> and V<inf>m</inf> regarding TC4 and ISDAC cirrus. Finally, TC4 satellite retrievals of D<inf>e</inf> and V<inf>m</inf> are found to be consistent with corresponding observations. Copyright 2011 by the American Geophysical Union."
"7403625607;7004325649;57209967483;6701859365;7404150761;7004419968;","Spectral kernel approach to study radiative response of climate variables and interannual variability of reflected solar spectrum",2011,"10.1029/2010JD015228","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958024913&doi=10.1029%2f2010JD015228&partnerID=40&md5=5679e607a2ab2b40cebcc91c99103c4c","The radiative kernel approach provides a simple way to separate the radiative response to different climate parameters and to decompose the feedback into radiative and climate response components. Using CERES/MODIS/Geostationary data, we calculated and analyzed the solar spectral reflectance kernels for various climate parameters on zonal, regional, and global spatial scales. The kernel linearity is tested. Errors in the kernel due to nonlinearity can vary strongly depending on climate parameter, wavelength, surface, and solar elevation; they are large in some absorption bands for some parameters but are negligible in most conditions. The spectral kernels are used to calculate the radiative responses to different climate parameter changes in different latitudes. The results show that the radiative response in high latitudes is sensitive to the coverage of snow and sea ice. The radiative response in low latitudes is contributed mainly by cloud property changes, especially cloud fraction and optical depth. The large cloud height effect is confined to absorption bands, while the cloud particle size effect is found mainly in the near infrared. The kernel approach, which is based on calculations using CERES retrievals, is then tested by direct comparison with spectral measurements from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) (a different instrument on a different spacecraft). The monthly mean interannual variability of spectral reflectance based on the kernel technique is consistent with satellite observations over the ocean, but not over land, where both model and data have large uncertainty. RMS errors in kernel-derived monthly global mean reflectance over the ocean compared to observations are about 0.001, and the sampling error is likely a major component. Copyright 2011 by the American Geophysical Union."
"7410070663;6602513845;7007067997;","Parameterization of cloud optical properties for semidirect radiative forcing",2011,"10.1029/2011JD016611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055211813&doi=10.1029%2f2011JD016611&partnerID=40&md5=d91171a55569444b53b11e008ce0cfeb","A parameterization of liquid cloud optical properties with a mixture of black carbon is proposed. It is found that the changes in cloud optical properties due to mixture of black carbon can be treated as a perturbation to existing cloud optical property parameterizations in climate models. The advantage of the proposed scheme is that current cloud optical property parameterizations used in climate models can be kept. It is shown that the dominant factor with respect to radiative forcing due to the inclusion of black carbon in cloud droplets is the resulting change in single-scattering albedo values. Therefore, a simple scheme to modify only the single-scattering albedo is considered. The additional consideration of the modification of asymmetry factor only applies to the case of very large black carbon volume fraction. The results in a one-dimensional radiation model show that internal mixtures of black carbon can have a significant impact on solar flux and heating rates. For a black carbon volume fraction of 10-7, the reduction in solar flux at the top of the atmosphere can be over 0.5 Wm-2 and the heating rate can increase by about 0.08 Kd-1 for a solar zenith angle of 53. Copyright 2011 by the American Geophysical Union."
"26639062900;7406215388;7404187535;7006029393;40461229800;35731251200;7004091067;7005773698;","Detection of Asian dust in California orographic precipitation",2011,"10.1029/2010JD015351","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052327641&doi=10.1029%2f2010JD015351&partnerID=40&md5=30c182df413f81539db1f131fa388c05","Aerosols impact the microphysical properties of clouds by serving as cloud condensation nuclei (CCN) and ice nuclei (IN). By modifying cloud properties, aerosols have the potential to alter the location and intensity of precipitation, but determining the magnitude and reproducibility of aerosol-induced changes to precipitation remains a significant challenge to experimentalists and modelers. During the CalWater Early Start campaign (22 February to 11 March 2009), a uniquely comprehensive set of atmospheric chemistry, precipitation, and meteorological measurements were made during two extratropical cyclones. These two storms showed enhanced integrated water vapor concentrations and horizontal water vapor transports due to atmospheric river conditions and, together, produced 23% of the annual precipitation and 38% of the maximum snowpack at California's Central Sierra Snow Lab (CSSL). Precipitation measurements of insoluble residues showed very different chemistry occurring during the two storms with the first one showing mostly organic species from biomass burning, whereas the second storm showed a transition from biomass burning organics to the dominance of Asian dust. As shown herein, the dust was transported across the Pacific during the second storm and became incorporated into the colder high-altitude precipitating orographic clouds over the Sierra Nevada. The second storm produced 1.4 times as much precipitation and increased the snowpack by 1.6 times at CSSL relative to the first storm. As described in previous measurement and modeling studies, dust can effectively serve as ice nuclei, leading to increased riming rates and enhanced precipitation efficiency, which ultimately can contribute to differences in precipitation. Future modeling studies will help deconvolute the meteorological, microphysical, and aerosol factors leading to these differences and will use CalWater's meteorological and aerosol observations to constrain the model-based interpretations. The ultimate goal of such combined efforts is to use the results to improve aerosol-cloud impacts on precipitation in regional climate models. Copyright © 2011 by the American Geophysical Union. Copyright © 2011 by the American Geophysical Union."
"7102171439;6602252422;56219284300;7201826462;","Impacts of subpixel cloud heterogeneity on infrared thermodynamic phase assessment",2011,"10.1029/2011JD015774","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054820866&doi=10.1029%2f2011JD015774&partnerID=40&md5=0537b9f5eb5de2fdb4a96d02e2c3e57b","A combination of spatially collocated Atmospheric Infrared Sounder (AIRS) radiances and Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products are used to quantify the impact of cloud heterogeneity on AIRS-based assessments of cloud thermodynamic phase. While radiative transfer simulations have demonstrated that selected AIRS channels have greater sensitivity to cloud thermodynamic phase in comparison to the relevant MODIS bands, the relative trade-offs of spectral and spatial resolution differences that are inherent between AIRS and MODIS have not been quantified. Global distributions of AIRS field-of-view scale frequencies of clear sky (13-14%), heterogeneous cloud (26-28%), and homogeneous cloud (59-60%) are quantified for a four week time period using cloud fraction, and further categorization of cloud uniformity is assessed with the variance of cloud top temperature. Homogeneous clouds with window brightness temperatures (T<inf>b</inf>) between 250 and 265 K are shown to have larger cloud thermodynamic phase signatures than heterogeneous clouds. Clouds in this limited T<inf>b</inf> range occur 30-50% of the time in the mid-and high latitude storm track regions, are generally difficult to identify as being water or ice phase, and show strong responses in forced CO<inf>2</inf> climate change modeling experiments. Two-dimensional histograms of T<inf>b</inf> differences sensitive to cloud phase (1231-960 cm-1) and column water vapor (1231-1227 cm-1) show distinct differences between many homogeneous and heterogeneous cloud scenes. The results suggest the potential for a quantitative approach using a combination of hyperspectral sounders with high-spatial-resolution imagers, and their derived geophysical products, to assess cloud thermodynamic phase estimates within increasingly complex subpixel-scale cloud variability. Copyright 2011 by the American Geophysical Union."
"8511991900;7003666669;55405340400;55717074000;7006705919;35572096100;","Representation of Arctic mixed-phase clouds and the Wegener-Bergeron- Findeisen process in climate models: Perspectives from a cloud-resolving study",2011,"10.1029/2010JD015375","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051846056&doi=10.1029%2f2010JD015375&partnerID=40&md5=96cb596cd44b1b034c7a71e6b1836aa2","Two types of Arctic mixed-phase clouds observed during the ISDAC and M-PACE field campaigns are simulated using a 3-dimensional cloud-resolving model (CRM) with size-resolved cloud microphysics. The modeled cloud properties agree reasonably well with aircraft measurements and surface-based retrievals. Cloud properties such as the probability density function (PDF) of vertical velocity (w), cloud liquid and ice, regimes of cloud particle growth, including the Wegener-Bergeron-Findeisen (WBF) process, and the relationships among properties/processes in mixed-phase clouds are examined to gain insights for improving their representation in General Circulation Models (GCMs). The PDF of the simulated w is well represented by a Gaussian function, validating, at least for arctic clouds, the subgrid treatment used in GCMs. The PDFs of liquid and ice water contents can be approximated by Gamma functions, and a Gaussian function can describe the total water distribution, but a fixed variance assumption should be avoided in both cases. The CRM results support the assumption frequently used in GCMs that mixed phase clouds maintain water vapor near liquid saturation. Thus, ice continues to grow throughout the stratiform cloud but the WBF process occurs in about 50% of cloud volume where liquid and ice co-exist, predominantly in downdrafts. In updrafts, liquid and ice particles grow simultaneously. The relationship between the ice depositional growth rate and cloud ice strongly depends on the capacitance of ice particles. The simplified size-independent capacitance of ice particles used in GCMs could lead to large deviations in ice depositional growth. Copyright 2011 by the American Geophysical Union."
"36060938100;7402989545;","Sensitivity of a regional ocean-atmosphere coupled model to convection parameterization over western North Pacific",2011,"10.1029/2011JD015844","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053376169&doi=10.1029%2f2011JD015844&partnerID=40&md5=1b4851e09baf70686f15a588c25e72ee","With the motivation to improve the simulation of western North Pacific (WNP) summer monsoon, the regional climate model RegCM3 is coupled with the Princeton ocean model (POM2000) through the coupler OASIS3.0 (Ocean Atmosphere Sea Ice Soil 3.0). The performance of the regional ocean-atmosphere coupled model (hereafter ROAM) is assessed by doing case simulation of the 1998 summer monsoon. The cold bias of simulated sea surface temperature (SST) is evident as previous ROAM simulations over the Asian-Australian summer monsoon region. Five sets of sensitivity experiments with convection suppression criterion based on the averaged relative humidity from cloud base to cloud top are designed to improve the performance of ROAM. The results show that the column-averaged cloud fraction is reduced in convection suppression experiments. A reduction of column-averaged cloud cover, which is dominated by the decrease of convective cloud cover, increases the solar shortwave radiation reaching in sea surface, then warms the SST. A reduction of convective rainfall is followed by an increase of large-scale rainfall which results from increasing cloud water. When the critical value is set to 0.70, the rainfall is partly improved in terms of the spatial distribution and root-mean-square error. The percentage of convective rainfall over WNP is also improved. The authors show evidence that the SST cold biases, which are evident in many regional ocean-atmosphere coupled models in the Asian-Australian summer monsoon region, may partly stem from the overestimation of convection frequency by the atmospheric model. Copyright 2011 by the American Geophysical Union."
"35776608800;16403070500;","Snow/ice and cloud responses to future climate change around Hokkaido",2011,"10.2151/sola.2011-052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891481925&doi=10.2151%2fsola.2011-052&partnerID=40&md5=e2883e2ce50a68d6016485dd4e531a41","Wintertime climate around Hokkaido is highly sensitive to fluctuations in snow and sea-ice. We examined future climate change in heavy snowfall region around Hokkaido, using the Pseudo-Global-Warming method (PGW) by a regional climate model. The boundary conditions of the PGW run were obtained by adding the difference between the future (2090s) and past (1990s) climates simulated by coupled general circulation models, into the 6-hourly reanalysis and daily sea surface temperature data. The PGW experiments show that snow depth decreases significantly over mountainous areas. However, snow cover decreases mainly over plain areas, which accelerates surface warming due to the decreased snow albedo. Despite the snow reductions, precipitation increases over the mountainous areas because of enhanced water vapor content. However, precipitation decreases over the Japan Sea and neighboring the coastal areas, suggesting a weakening of the convergent cloud band which is formed by convergence between cold northwesterly from the Eurasian continent and anticyclonic circulation over the Okhotsk Sea. Our results indicate the contrasting cloud responses to future climate change over the Japan and Okhotsk Seas in terms of meso-scale climate system. © 2011, the Meteorological Society of Japan."
"8866821900;7201504886;","Revealing differences in GCM representations of low clouds",2011,"10.1007/s00382-009-0694-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957577169&doi=10.1007%2fs00382-009-0694-5&partnerID=40&md5=204772404443d260eb82ed8d35875ee7","Aquaplanet configurations of four atmospheric general circulation models (GCMs) are compared with standard, Earth-like configurations and observations. The focus here is on tropical, low-level clouds, which have been identified as important for estimates of climate sensitivity. Investigating the distribution of the monthly mean vertical velocity and lower-tropospheric stability, the aquaplanets are seen to capture the core of the distribution of the more Earth-like configurations, whose distributions are, in turn, similar to that of reanalysis data. By conditionally sampling over these distributions, low-cloud regimes are defined, separating shallow cumulus convection from stratocumulus. Within each regime, the GCMs produce similar large-scale environments, yet disparate depictions of the clouds. Aquaplanets lack stratocumulus because of their zonally symmetric boundary conditions, but produce extensive trade-wind regions populated by shallow cumulus clouds just like those in the Earth-like setting. The analysis shows that aquaplanets can be compared with observations, just as well as the Earth-like configuration, with the added ability to focus on particular regimes without complications from geographical or temporal biases. © 2009 The Author(s)."
"49962867200;6603135083;36193844800;","Using coralline algae to understand historic marine cloud cover",2011,"10.1016/j.palaeo.2010.07.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951809982&doi=10.1016%2fj.palaeo.2010.07.027&partnerID=40&md5=f2bec5bf5f707f1014a3c394c6ce1e55","Free-living coralline algae lay down growth bands formed by areas of more and less calcified cells which, in certain species, are associated with winter and summer growth respectively. Band width and cell calcification of Lithothamnion glaciale from Scotland were compared to annual and seasonal cloud cover and sea surface temperature (SST). There was a negative relationship between summer calcification (the degree of cellular carbonate infilling) and winter cloud cover. Annual and summer SST were also negatively related to summer calcification. This indicates that summer calcification may be affected by the previous winter's cloud cover and that summer's/year's SST. No relationships between band width and cloud cover were observed. A cloud cover hindcast using summer calcification and SST indicated a modest rise in cloud cover trends from 1910 to 2006 and a 12 (mean) year cyclicity in cloud cover, however, the latter may be associated with other site-specific factors. This study demonstrates the utility of densitometric algochronology in understanding marine temperature and cloud cover histories. © 2010 Elsevier B.V."
"7102805852;10139397300;7407104838;57203200427;7102953444;7004942632;","The roles of aerosol, water vapor and cloud in future global dimming/brightening",2011,"10.1029/2011JD016000","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055055695&doi=10.1029%2f2011JD016000&partnerID=40&md5=715be3349a82b9842ef7d644ac0eced6","Observational evidence indicates significant regional trends in solar radiation at the surface in both all-sky and cloud-free conditions. Negative trends in the downwelling solar surface irradiance (SSI) have become known as dimming while positive trends have become known as brightening. We use the Met Office Hadley Centre HadGEM2 climate model to model trends in cloud-free and total SSI from the pre-industrial to the present-day and compare these against observations. Simulations driven by CMIP5 emissions are used to model the future trends in dimming/brightening up to the year 2100. The modeled trends are reasonably consistent with observed regional trends in dimming and brightening which are due to changes in concentrations in anthropogenic aerosols and, potentially, changes in cloud cover owing to the aerosol indirect effects and/or cloud feedback mechanisms. The future dimming/brightening in cloud-free SSI is not only caused by changes in anthropogenic aerosols: aerosol impacts are overwhelmed by a large dimming caused by increases in water vapor. There is little trend in the total SSI as cloud cover decreases in the climate model used here, and compensates the effect of the change in water vapor. In terms of the surface energy balance, these trends in SSI are obviously more than compensated by the increase in the downwelling terrestrial irradiance from increased water vapor concentrations. However, the study shows that while water vapor is widely appreciated as a greenhouse gas, water vapor impacts on the atmospheric transmission of solar radiation and the future of global dimming/brightening should not be overlooked. Copyright © 2011 by the American Geophysical Union."
"45661986200;57203492395;23017945100;8629257200;7102128820;6602999057;54401423900;9536598800;","The vertical cloud structure of the West African monsoon: A 4 year climatology using CloudSat and CALIPSO",2011,"10.1029/2011JD016029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81755168285&doi=10.1029%2f2011JD016029&partnerID=40&md5=e45e3c27660cd0548f7ec766ee3d5a5e","The West African summer monsoon (WAM) is an important driver of the global climate and locally provides most of the annual rainfall. A solid climatological knowledge of the complex vertical cloud structure is invaluable to forecasters and modelers to improve the understanding of the WAM. In this paper, 4 years of data from the CloudSat profiling radar and CALIPSO are used to create a composite zonal mean vertical cloud and precipitation structure for the WAM. For the first time, the near-coincident vertical radar and lidar profiles allow for the identification of individual cloud types from optically thin cirrus and shallow cumulus to congestus and deep convection. A clear diurnal signal in zonal mean cloud structure is observed for the WAM, with deep convective activity enhanced at night producing extensive anvil and cirrus, while daytime observations show more shallow cloud and congestus. A layer of altocumulus is frequently observed over the Sahara at night and day, extending southward to the coastline, and the majority of this cloud is shown to contain supercooled liquid in the top. The occurrence of deep convective systems and congestus in relation to the position of the African easterly jet is studied, but only the daytime cumulonimbus distribution indicates some influence of the jet position. Copyright 2011 by the American Geophysical Union."
"55628589750;7005742190;","Detecting ground fog from space - a microphysics-based approach",2011,"10.1080/01431161003747505","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960055865&doi=10.1080%2f01431161003747505&partnerID=40&md5=ef15aca2f6b0168427279353f62d7bc8","The detection of ground fog from satellite data is of interest in operational now-casting applications, as well as in studies of the climate system. A discrimination between fog at the ground and other low-stratus situations from satellite data requires information on cloud vertical geometry to establish whether the cloud touches the ground. This article introduces a technique that allows for the discrimination between low stratus and (ground) fog on the basis of geostationary satellite imagery. The cloud-base height is derived using a subadiabatic model of cloud microphysics. In this model, the cloud base is varied until model liquid-water path matches that retrieved from satellite data. The performance of this technique is shown to be good in a comparison with METeorological Aerodrome Report data comprising 1030 satellite scenes. With a hit rate of 81% and a threat score of 0.62, the skill is satisfactory. © 2011 Taylor & Francis."
"6602650107;36788535600;45761444600;6603022543;","Cloud effective transmittance at two sites of the Atacama Desert, Chile",2011,"10.1029/2011JD015905","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055063274&doi=10.1029%2f2011JD015905&partnerID=40&md5=84d12f5212f46b2f6a9020805f52854a","Broadband overcast cloud effective transmittance was determined at Arica (18.47S, 70.31°W, 20 m above sea level (asl)) and Poconchile (18.45°S, 70.07°W, 560 m asl), Atacama Desert, northern Chile, from 10 min averaged pyranometer measurements of total solar irradiance (ToSI) and ultraviolet solar irradiance (UVSI) during the period 2002-2005. The predominant cloud type is marine stratocumulus, characteristic of the southeastern Pacific tropical environment. The region's very regular climate conditions, characterized by overcast mornings and cloudless afternoons, allow the application of an empirical method to determine the expected clear-sky irradiance during cloudy mornings. The cloud effective transmittance (CET) is determined as the ratio of the measured cloudy-sky irradiance over the expected clear-sky irradiance. CET<inf>To</inf> = 0.26 (0.31) for ToSI and CET<inf>UV</inf> = 0.37 (0.43) for UVSI characterize overcast cloudiness at Arica (Poconchile). One-dimensional radiative transfer model calculations in both ToSI and UVSI ranges are also used. The measured and modeled relationships between CET<inf>To</inf> and CET<inf>UV</inf> closely agree. New insights are given to explain the sparsely populated data around CET = 0.8 observed also by other similar studies. Copyright © 2011 by the American Geophysical Union."
"57203030873;6602682911;25031430500;57202521210;","The boundary layer response to recent arctic sea ice loss and implications for high-latitude climate feedbacks",2011,"10.1175/2010JCLI3651.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79851477259&doi=10.1175%2f2010JCLI3651.1&partnerID=40&md5=186408a01fec387980fa493b0ea09d21","This study documents and evaluates the boundary layer and energy budget response to record low 2007 sea ice extents in the Community Atmosphere Model version 4 (CAM4) using 1-day observationally constrained forecasts and 10-yr runs with a freely evolving atmosphere.While near-surface temperature and humidity are minimally affected by sea ice loss in July 2007 forecasts, near-surface stability decreases and atmospheric humidity increases aloft over newly open water in September 2007 forecasts. Ubiquitous low cloud increases over the newly ice-free Arctic Ocean are found in both the July 2007 and the September 2007 forecasts. In response to the 2007 sea ice loss, net surface [top of the atmosphere (TOA)] energy budgets change by +19.4 W m-2 (+21.0 W m-2) and -17.9 W m-2 (+1.4 W m-2) in the July 2007 and September 2007 forecasts, respectively. While many aspects of the forecasted response to sea ice loss are consistent with physical expectations and available observations, CAM4's ubiquitous July 2007 cloud increases over newly open water are not. The unrealistic cloud response results from the global application of parameterization designed to diagnose stratus clouds based on lower-tropospheric stability (CLDST). In theArctic, the well-mixed boundary layer assumption implicit in CLDST is violated. Requiring a well-mixed boundary layer to diagnose stratus clouds improves the CAM4 cloud response to sea ice loss and increases July 2007 surface (TOA) energy budgets over newly open water by +11 W m-2 (+14.9 W m-2). Of importance to high-latitude climate feedbacks, unrealistic stratus cloud compensation for sea ice loss occurs only when stable and dry atmospheric conditions exist. Therefore, coupled climate projections that use CAM4 will underpredict Arctic sea ice loss only when dry and stable summer conditions occur. © 2011 American Meteorological Society."
"26536569500;","Response of tropical precipitation to global warming",2011,"10.1175/2010JAS3542.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251491692&doi=10.1175%2f2010JAS3542.1&partnerID=40&md5=5fbecd0f3f781ebf7e266d6b429da86b","Using high-resolution cloud-resolving simulations with different CO2 concentrations, local precipitation fluxes are found to obey Clausius-Clapeyron (CC) scaling. Previous studies of the effect of CO2 concentration on precipitation extremes have used general circulation models, which are poor platforms for studying tropical convection because convection is parameterized. In idealized cloud-resolving simulations, it is possible to identify not only the changes in local precipitation fluxes, but also the factors responsible for those changes. There are many properties of convection that can change as the atmosphere warms, each of which could produce deviations from CC scaling. These properties include the effective watervapor gradient, cloud pressure depth, and cloud velocity. A simple theory is developed that predicts the changes in these properties consistent with CC scaling. Convection in the cloudresolving simulations is found to change as predicted by this theory, leading to an ~20% increase in local precipitation fluxes when the CO2 concentration is doubled. Overall, an increase in CO2 leads to more vigorous convection, composed of clouds that are wider, taller, and faster. © 2011 American Meteorological Society."
"26645289600;7202145115;","The observed sensitivity of high clouds to mean surface temperature anomalies in the tropics",2011,"10.1029/2011JD016459","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82955164959&doi=10.1029%2f2011JD016459&partnerID=40&md5=a6b3183040bd48163c2cc17ee1993e67","Cloud feedback represents the source of largest diversity in projections of future warming. Observational constraints on both the sign and magnitude of the feedback are limited, since it is unclear how the natural variability that can be observed is related to secular climate change, and analyses have rarely been focused on testable physical theories for how clouds should respond to climate change. In this study we use observations from a suite of satellite instruments to assess the sensitivity of tropical high clouds to interannual tropical mean surface temperature anomalies. We relate cloud changes to a physical governing mechanism that is sensitive to the vertical structure of warming. Specifically, we demonstrate that the mean and interannual variability in both the altitude and fractional coverage of tropical high clouds as measured by CloudSat, the Moderate Resolution Imaging Spectroradiometer, the Atmospheric Infrared Sounder, and the International Satellite Cloud Climatology Project are well diagnosed by upper tropospheric convergence computed from the mass and energy budget of the clear-sky atmosphere. Observed high clouds rise approximately isothermally in accordance with theory and exhibit an overall reduction in coverage when the tropics warms, similar to their behavior in global warming simulations. Such cloud changes cause absorbed solar radiation to increase more than does outgoing longwave radiation, resulting in a positive but statistically insignificant net high cloud feedback in response to El Nio-Southern Oscillation. The results suggest that the convergence metric based on simple mass and energy budget constraints may be a powerful tool for understanding observed and modeled high cloud behavior and for evaluating the realism of modeled high cloud changes in response to a variety of forcings. Copyright 2011 by the American Geophysical Union."
"57188557549;7402434077;7005072865;","Influence of tropical easterly jet on upper tropical cirrus: An observational study from CALIPSO, Aura-MLS, and NCEP/NCAR data",2011,"10.1029/2011JD015923","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959622243&doi=10.1029%2f2011JD015923&partnerID=40&md5=e41b969ffe3c8c3b94398f291641ec86","The role of the redistribution of tropical upper tropospheric humidity in the formation of tropical cirrus is studied using three years (June 2006 to December 2008) of observations with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) as well as the Microwave Limb Sounder (MLS) onboard the Aura satellite. The National Centers for Environmental Prediction and Atmospheric Research reanalysis data are also used. Results show that the redistribution of upper tropospheric humidity from a highly convective zone to the Indian peninsular region leads to the formation of the tropical cirrus. Advection of upper layer humidity is caused by the tropical easterly jet (TEJ) associated with the Asian summer monsoon (ASM). Thus the present analysis brings out, for the first time, the role of the TEJ in the redistribution of upper tropospheric humidity and consequently in the formation of tropical cirrus. As little observational evidence exists in support of the generative mechanisms of the cirrus, the present results can be useful in quantifying the formation process of these clouds, which have implications for Earth's radiation budget and improving global climate models. Copyright 2011 by the American Geophysical Union."
"7006508549;7406892723;26654147000;7101688723;35453054300;7102653983;","The role of land use change on the development and evolution of the west coast trough, convective clouds, and precipitation in southwest Australia",2011,"10.1029/2010JD014950","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954555921&doi=10.1029%2f2010JD014950&partnerID=40&md5=1a5e5d48fa4a6e5f1ffc380091418e33","Land clearing for agricultural purposes in southwest Australia has created a landscape where a 750 km rabbit-proof fence separates 13 million hectares of croplands from the remnant native vegetation to the east. The Bunny Fence Experiment (BuFex) was conducted in the vicinity of the intended vermin-proof boundary in December 2005 and August 2007. The experiment examined the role of land cover change (LCC) on the preferential formation of clouds over the native vegetation that often terminates along the vermin-proof fence as well as the regional rainfall reduction observed in this region. Observations and numerical model analysis show that the formation and development of the west coast trough (WCT), which is a synoptic-scale feature that initiates spring and summertime convection, is impacted by land cover change and that the cloud fields induced by the WCT would extend farther west in the absence of the LCC. The surface convergence patterns associated with the wintertime WCT circulation are substantially altered by LCC, due to changes in both WCT dynamics and surface aerodynamic roughness, leading to a rainfall decrease to the west of the rabbit fence. Although this study focuses on only two events, it further illustrates that LCC has significant regional impacts in southwest Western Australia regardless of large-scale shifts in the climate system. Copyright 2011 by the American Geophysical Union."
"57195574170;41560941500;56520921400;54788302000;6603800142;","Simulation studies for the detection of changes in broadband albedo and shortwave nadir reflectance spectra under a climate change scenario",2011,"10.1029/2011JD016407","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055221761&doi=10.1029%2f2011JD016407&partnerID=40&md5=404235bfd4976fde7eb9e596d9daf7d7","Climate forcing by greenhouse gases and aerosols and climate feedbacks from snow, sea-ice, and clouds all significantly impact the future evolution of the climate system's shortwave energy budget. We examine prospects for tracking changes in these forcings and feedbacks using top-of-atmosphere measurements of shortwave reflected radiation. We quantify the extent to which spectral measurements may reduce the time required to detect changes in the climate the climate system with high statistical confidence relative to conventional broadband measurements. We have developed an Observing System Simulation Experiment (OSSE) based on the Community Climate System Model 3.0 for the NASA CLARREO mission and have analyzed forced and unforced simulations of the 21st Century from the Intergovernmental Panel on Climate Change assessments. We find that changes in the simulated nadir spectral reflectance measurements in the visible window and between near-infrared water-vapor overtone channels under clear-sky conditions are detectible faster than the corresponding changes in broadband albedo, with many trends detectible within a five-year satellite mission lifetime. Under all-sky conditions, the superposition of unforced cloud variability on the secular climate trends lengthens the times required for climate-change detection in both the spectral and broadband data. However, migration of the ITCZ and stratus regions can be detected after 16-18 years of observation while broadband albedo measurements require 33-61 years of observation. We find that measurement uncertainty and instrument drift significantly lengthen detection times for broadband albedo and spectral reflectances in window channels but do not have the same effect for spectral measurements in water vapor bands. Copyright 2011 by the American Geophysical Union."
"36141355100;6602809597;57203053317;53871434100;53872031000;7102953444;","Simulation of dimming and brightening in Europe from 1958 to 2001 using a regional climate model",2011,"10.1029/2010JD015396","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053342037&doi=10.1029%2f2010JD015396&partnerID=40&md5=8b169ce22402f93000f8ea06981739c6","The present study applies a regional climate model with coupled aerosol microphysics and transport in order to simulate dimming and brightening in Europe from 1958 to 2001. Two simulations are performed, one with transient emissions and another with climatological mean emissions over the same period. Both simulations are driven at the lateral boundaries by the ERA-40 reanalysis and by large-scale aerosol concentrations stemming from a global simulation. We find distinct patterns of dimming and brightening in the aerosol optical depth and thus clear-sky downward surface shortwave radiation (SSR) in all analyzed subregions. The strongest brightening between 1973 and 1998 under clear-sky conditions is found in mid-Europe (+3.4 W m-2 per decade, in line with observations). However, the simulated all-sky SSR is dominated by the surface shortwave cloud radiative forcing (CRF). The correlation coefficient R between 5 year moving averages of the CRF and all-sky SSR equals 0.87 for all of Europe. Both model simulations show a similar evolution of cloud fraction and thus all-sky SSR due to the constrained circulation induced by the reanalysis at the lateral boundaries. For most subregions, the modeled differences in all-sky SSR due to transient versus climatological emissions are insignificant in comparison with estimates of the model's internal variability. Copyright 2011 by the American Geophysical Union."
"7006246996;6701333444;","The influence of mixed-phase clouds on surface shortwave irradiance during the Arctic spring",2011,"10.1029/2011JD015761","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054825374&doi=10.1029%2f2011JD015761&partnerID=40&md5=f502c1e35a369f746b1eeb75657ba1e5","The influence of mixed-phase stratiform clouds on the surface shortwave irradiance is examined using unique spectral shortwave irradiance measurements made during the Indirect and Semi-Direct Aerosol Campaign (ISDAC), supported by the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program. An Analytical Spectral Devices (ASD, Inc.) spectroradiometer measured downwelling spectral irradiance from 350 to 2200 nm in one-minute averages throughout April-May 2008 from the ARM Climate Research Facility's North Slope of Alaska (NSA) site at Barrow. This study examines spectral irradiance measurements made under single-layer, overcast cloud decks having geometric thickness < 3000 m. Cloud optical depth is retrieved from irradiance in the interval 1022-1033 nm. The contrasting surface radiative influences of mixed-phase clouds and liquid-water clouds are discerned using irradiances in the 1.6-m window. Compared with liquid-water clouds, mixed-phase clouds during the Arctic spring cause a greater reduction of shortwave irradiance at the surface. At fixed conservative-scattering optical depth (constant optical depth for wavelengths < 1100 nm), the presence of ice water in cloud reduces the near-IR surface irradiance by an additional several watts-per-meter-squared. This additional reduction, or supplemental ice absorption, is typically ∼5 W m-2 near solar noon over Barrow, and decreases with increasing solar zenith angle. However, for some cloud decks this additional absorption can be as large as 8-10 W m-2. Copyright 2011 by the American Geophysical Union."
"54783781000;7004057920;7006675203;35478813200;6701333444;7402934750;","Retrievals of cloud optical depth and effective radius from Thin-Cloud Rotating Shadowband Radiometer measurements",2011,"10.1029/2011JD016192","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83655190982&doi=10.1029%2f2011JD016192&partnerID=40&md5=2b7d9522695d2f95a75bc2a07f53d52d","A Thin-Cloud Rotating Shadowband Radiometer (TCRSR) was developed and deployed in a field test at the Atmospheric Radiation Measurement Climate Research Facility's Southern Great Plains site. The TCRSR measures the forward-scattering lobe of the direct solar beam (i.e., the solar aureole) through an optically thin cloud (optical depth < 8). We applied the retrieval algorithm of Min and Duan (2005) to the TCRSR measurements of the solar aureole to derive simultaneously the cloud optical depth (COD) and cloud drop effective radius (DER), subsequently inferring the cloud liquid-water path (LWP). After careful calibration and preprocessing, our results indicate that the TCRSR is able to retrieve simultaneously these three properties for optically thin water clouds. Colocated instruments, such as the MultiFilter Rotating Shadowband Radiometer (MFRSR), atmospheric emitted radiance interferometer (AERI), and Microwave Radiometer (MWR), are used to evaluate our retrieval results. The relative difference between retrieved CODs from the TCRSR and those from the MFRSR is less than 5%. The distribution of retrieved LWPs from the TCRSR is similar to those from the MWR and AERI. The differences between the TCRSR-based retrieved DERs and those from the AERI are apparent in some time periods, and the uncertainties of the DER retrievals are discussed in detail in this article. Copyright 2011 by the American Geophysical Union."
"7202079615;56489410500;","Global climate modeling of regional changes in cloud, precipitation, and radiation budget due to the aerosol semi-direct effect of black carbon",2011,"10.2151/sola.2011-046","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867661349&doi=10.2151%2fsola.2011-046&partnerID=40&md5=148e3a0c36e3aec2d4694a260a6e2d2c","The aerosol semi-direct effect is generally explained as follows: aerosols, such as black carbon (BC) and mineral dust, absorb solar radiation, which warms and stabilizes the atmosphere, resulting in reduced cloudiness and cloud formation. However, the present study suggests that BC can intensify atmospheric instability and thus increase cloud water and precipitation if the BC is concentrated near the surface. Simulations using a global aerosol climate model, based on a general circulation model, show decreased cloud water over biomass-burning regions where BC is emitted to the free troposphere through the boundary layer. In contrast, increased cloud water is indicated over East and South Asia where BC from urban and industrial activities is concentrated near the surface. While the global mean change in the radiation budget at the top of the atmosphere due to the semi-direct effect of BC is estimated to be as small as +0.06 W m-2, regional changes in cloud water, precipitation, and shortwave radiation are suggested to be large enough to modify meteorological conditions in urban and biomass-burning regions. © 2011, the Meteorological Society of Japan."
"37055982600;14324150200;8951681900;6602999938;7005922032;","The coupling of cloud base height and surface fluxes: A transferability intercomparison",2011,"10.1007/s00704-011-0421-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054687434&doi=10.1007%2fs00704-011-0421-0&partnerID=40&md5=8cfe4c634090a64d7008263e903c0c0b","This paper presents an evaluation of the simulated coupling between cloud base height (CBH) and surface fluxes over selected Coordinated Enhanced Observing Period (CEOP) reference stations by five regional climate models as part of a transferability intercomparison experiment. The model results are compared with station data obtained during the first phase of the CEOP measuring campaigns. The models gave a credible simulation of both diurnal and seasonal cycles of cloud base height and surface variables over the stations. However, the models exhibited some difficulty in reproducing the diurnal and seasonal temperatures over the tropical stations. The study used principal component analysis to show that three factors account for most of the variability in the observed and simulated data and to investigate the coupling between cloud base height and surface fluxes in the data. In the observations, CBH is well coupled with the surface fluxes over Cabauw, Bondville, Lamont, and Berms, but coupled only with temperature over Lindenberg and Tongyu. All models but GEMLAM simulate substantial coupling between CBH and surface fluxes at all stations; GEMLAM does not couple CBH with surface fluxes, but with surface temperature and specific humidity. © 2011 Springer-Verlag."
"35309913700;6602675795;","Analysis of high-resolution simulations for the Black Forest region from a point of view of tourism climatology - a comparison between two regional climate models (REMO and CLM)",2011,"10.1007/s00704-010-0311-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951810686&doi=10.1007%2fs00704-010-0311-x&partnerID=40&md5=a1129a9ef3d1c421270189d049e77332","An analysis of climate simulations from a point of view of tourism climatology based on two regional climate models, namely REMO and CLM, was performed for a regional domain in the southwest of Germany, the Black Forest region, for two time frames, 1971-2000 that represents the twentieth century climate and 2021-2050 that represents the future climate. In that context, the Intergovernmental Panel on Climate Change (IPCC) scenarios A1B and B1 are used. The analysis focuses on human-biometeorological and applied climatologic issues, especially for tourism purposes - that means parameters belonging to thermal (physiologically equivalent temperature, PET), physical (precipitation, snow, wind), and aesthetic (fog, cloud cover) facets of climate in tourism. In general, both models reveal similar trends, but differ in their extent. The trend of thermal comfort is contradicting: it tends to decrease in REMO, while it shows a slight increase in CLM. Moreover, REMO reveals a wider range of future climate trends than CLM, especially for sunshine, dry days, and heat stress. Both models are driven by the same global coupled atmosphere-ocean model ECHAM5/MPI-OM. Because both models are not able to resolve meso- and micro-scale processes such as cloud microphysics, differences between model results and discrepancies in the development of even those parameters (e. g., cloud formation and cover) are due to different model parameterization and formulation. Climatic changes expected by 2050 are small compared to 2100, but may have major impacts on tourism as for example, snow cover and its duration are highly vulnerable to a warmer climate directly affecting tourism in winter. Beyond indirect impacts are of high relevance as they influence tourism as well. Thus, changes in climate, natural environment, demography, tourists' demands, among other things affect economy in general. The analysis of the CLM results and its comparison with the REMO results complete the analysis performed within the project Climate Trends and Sustainable Development of Tourism in Coastal and Low Mountain Range Regions (CAST) funded by the German Federal Ministry of Education and Research (BMBF). © 2010 Springer-Verlag."
"57212892864;7006508549;7005135473;7801654745;","Land use change impacts on regional climate over Kilimanjaro",2011,"10.1029/2010JD014712","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951920407&doi=10.1029%2f2010JD014712&partnerID=40&md5=5307429b24e9875e8fd1899b469af67b","Glacier recession on Kilimanjaro has been linked to reduction in precipitation and cloudiness largely because of large-scale changes in tropical climate. Prior studies show that local changes in land cover can also impact orographic cloudiness, precipitation, and terrain-generated circulation patterns. This study uses the Regional Atmospheric Modeling System to simulate dry season orographic cloudiness, rainfall, and orographic flow patterns over Kilimanjaro for current deforested and reforested land cover scenarios. The simulations for current land cover show satisfactory performance compared to surface meteorology and satellite-observed cloudiness. Clouds occur less frequently in response to deforestation, with the magnitude of decrease increasing with deforestation. On the windward side, cloud liquid water path (LWP) and precipitation both show decreases at lower elevations (∼1000-2000 m) and increases at higher elevations (2000-4000 m) in response to deforestation. This pattern is caused by decreased aerodynamic resistance, leading to enhanced wind speeds and convergence at higher elevations. On the lee regions, LWP deficits found in deforested simulations coincide with regions of reduced moisture while precipitation increased slightly at lower elevations (1000-1800 m) and decreased at higher elevations (1800-4000 m). Kilimanjaro offers less obstruction to background airflow, and reduced moisture transport to the lee side is found for deforested conditions, causing reduced LWP and rainfall. However, land use change has little effect on cloudiness and rainfall at elevations in excess of 4000 m and is not expected to impact glaciers in the summit zone of Kilimanjaro during the dry season. The effect in other seasons requires further investigation. Copyright 2011 by the American Geophysical Union."
"57195574170;41560941500;41562003200;56520921400;","CLARREO shortwave observing system simulation experiments of the twenty-first century: Simulator design and implementation",2011,"10.1029/2010JD015350","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958060443&doi=10.1029%2f2010JD015350&partnerID=40&md5=b156ecb052500aa050030af213c24ebf","Projected changes in the Earth system will likely be manifested in changes in reflected solar radiation. This paper introduces an operational Observational System Simulation Experiment (OSSE) to calculate the signals of future climate forcings and feedbacks in top-of-atmosphere reflectance spectra. The OSSE combines simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report for the NCAR Community Climate System Model (CCSM) with the MODTRAN radiative transfer code to calculate reflectance spectra for simulations of current and future climatic conditions over the 21st century. The OSSE produces narrowband reflectances and broadband fluxes, the latter of which have been extensively validated against archived CCSM results. The shortwave reflectance spectra contain atmospheric features including signals from water vapor, liquid and ice clouds, and aerosols. The spectra are also strongly influenced by the surface bidirectional reflectance properties of predicted snow and sea ice and the climatological seasonal cycles of vegetation. By comparing and contrasting simulated reflectance spectra based on emissions scenarios with increasing projected and fixed present-day greenhouse gas and aerosol concentrations, we find that prescribed forcings from increases in anthropogenic sulfate and carbonaceous aerosols are detectable and are spatially confined to lower latitudes. Also, changes in the intertropical convergence zone and poleward shifts in the subsidence zones and the storm tracks are all detectable along with large changes in snow cover and sea ice fraction. These findings suggest that the proposed NASA Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission to measure shortwave reflectance spectra may help elucidate climate forcings, responses, and feedbacks. Copyright 2011 by the American Geophysical Union."
"6506606807;14020751800;7003525439;57202531041;6701410329;22935251000;7402305181;","Validation of cloud property retrievals with simulated satellite radiances: A case study for SEVIRI",2011,"10.5194/acp-11-5603-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960194516&doi=10.5194%2facp-11-5603-2011&partnerID=40&md5=b4844a6b043496d3e78f62617c33d934","Validation of cloud properties retrieved from passive spaceborne imagers is essential for cloud and climate applications but complicated due to the large differences in scale and observation geometry between the satellite footprint and the independent ground based or airborne observations. Here we illustrate and demonstrate an alternative approach: starting from the output of the COSMO-EU weather model of the German Weather Service realistic three-dimensional cloud structures at a spatial scale of 2.33 km are produced by statistical downscaling and microphysical properties are associated to them. The resulting data sets are used as input to the one-dimensional radiative transfer model libRadtran to simulate radiance observations for all eleven low resolution channels of MET-8/SEVIRI. At this point, both cloud properties and satellite radiances are known such that cloud property retrieval results can be tested and tuned against the objective input ""truth"". As an example, we validate a cloud property retrieval of the Institute of Atmospheric Physics of DLR and that of EUMETSAT's Climate Monitoring Science Application Facility CMSAF. Cloud detection and cloud phase assignment perform well. By both retrievals 88% of the pixels are correctly classified as clear or cloudy. The DLR algorithm assigns the correct thermodynamic phase to 95% of the cloudy pixels and the CMSAF retrieval to 84%. Cloud top temperature is slightly overestimated by the DLR code (+3.1 K mean difference with a standard deviation of 10.6 K) and to a very low extent by the CMSAF code (0.12 K with a standard deviation of 7.6 K). Both retrievals account reasonably well for the distribution of optical thickness for both water and ice clouds, with a tendency to underestimation. Cloud effective radii are most difficult to evaluate but the APICS algorithm shows that realistic histograms of occurrences can be derived (CMSAF was not evaluated in this context). Cloud water path, which is a combination of the last two quantities, is slightly underestimated by APICS, while CMSAF shows a larger scattering. © 2011 Author(s)."
"36495301700;7005634455;","Climate of West Antarctica and influence of marine air intrusions",2011,"10.1175/2010JCLI3522.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251547982&doi=10.1175%2f2010JCLI3522.1&partnerID=40&md5=52793d182c72554a1ca1b6c7590a8ece","High-resolution numerical weather forecasts from the Antarctic Mesoscale Prediction System (AMPS) archive are used to investigate the climate of West Antarctica (WA) during 2006-07. A comparison with observations from West Antarctic automatic weather stations confirms the skill of the model at simulating near-surface variables. AMPS cloud cover is also compared with estimates of monthly cloud fractions over Antarctica derived from spaceborne lidar measurements, revealing close agreement between both datasets. Comparison with 20-yr averages from the Interim ECMWF Re-Analysis (ERA-Interim) dataset demonstrates that the 2006-07 time period as a whole is reflective of the West Antarctic climate from the last two decades. On the 2006-07 annual means computed from AMPS forecasts, the most salient feature is a tongue-shaped pattern of higher cloudiness, accumulation, and 2-m potential temperature stretching over central WA. This feature is caused by repeated intrusions of marine air inland linked to the sustained cyclonic activity in the Ross and western Amundsen Seas. It is further enhanced by the ice sheet's topography and by the mid-low-tropospheric wind flow on either side of the central ice divide. Low pressures centered over the Ross Sea (as opposed to the Bellingshausen Sea) are found to be most effective in conveying heat and moisture into WA. This study offers a perspective on how recent and projected changes in cyclonic activity in the South Pacific sector of the Southern Ocean may affect the climate and surface mass balance of WA. © 2011 American Meteorological Society."
"6504033814;7006246996;40361595000;","Transect method for antarctic cloud property retrieval using AVHRR data",2011,"10.1080/01431161003745624","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957592403&doi=10.1080%2f01431161003745624&partnerID=40&md5=dc64751d22d709796996e0d78e733373","For studies of Antarctic climate change, the Advanced Very High Resolution Radiometer (AVHRR) offers a time series spanning more than two decades, with numerous overpasses per day from converging polar orbits, and with radiometrically calibrated thermal infrared channels. However, over the Antarctic Plateau, standard multispectral application of AVHRR data for cloud optical property retrieval with individual pixels is problematic due to poor scene contrasts and measurement uncertainties. We present a method that takes advantage of rapid changes in radiances at well-defined cloud boundaries. We examine a transect of AVHRR-measured radiances in the three thermal infrared channels across a boundary between cloudy and cloud-free parts of the image. Using scatter diagrams, made from the data along this transect, of the brightness temperature differences between channels 3 and 4, and channels 4 and 5, it is possible to fit families of radiative transfer solutions to the data to estimate cloud effective temperature, thermodynamic phase, and effective particle radius. The major approximation with this method is that along such a transect, cloud water path has considerable spatial variability, while effective radius, phase, and cloud temperature have much less variability. To illustrate this method, two AVHRR images centred about the South Pole are analysed. The two images are chosen based on their differing contrasts in brightness temperature between clear and cloud-filled pixels, to demonstrate that our method can work with varying cloud top heights. In one image the data are consistent with radiative transfer simulations using ice cloud. In the other, the data are inconsistent with ice cloud and are well simulated with supercooled liquid water cloud at 241.5 K. This method therefore has potential for climatological investigation of the radiatively important phase transition in the extremely cold and pristine Antarctic environment. © 2011 Taylor & Francis."
"7405367162;7403282069;7004160106;7103246957;","Recent trends of the tropical hydrological cycle inferred,fromglobal precipitation climatology project and international satellite cloud climatology project data",2011,"10.1029/2010JD015197","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053529787&doi=10.1029%2f2010JD015197&partnerID=40&md5=8f2d2febd2db64bde472ffe5871801e6","Scores of modeling studies have shown that increasing greenhouse gases in the atmosphere impact the global hydrologic cycle; however, disagreements on regional scales are large, and thus the simulated trends of such impacts, even for regions as large as the tropics, remain uncertain. The present investigation attempts to examine such trends in the observations using satellite data products comprising Global Precipitation Climatology Project precipitation and International Satellite Cloud Climatology Project cloud and radiation. Specifically, evolving trends of the tropical hydrological cycle over the last 20-30 years were identified and analyzed. The results show (1) intensification of tropical precipitation in the rising regions of the Walker and Hadley circulations and weakening over the sinking regions of the associated overturning circulation; (2) poleward shift of the subtropical dry zones (up to 2° decade-1 in June-July-August (JJA) in the Northern Hemisphere and 0.3-0.7° decade-1 in June-July-August and September-October-November in the Southern Hemisphere) consistent with an overall broadening of the Hadley circulation; and (3) significant poleward migration (0.9-1.7° decade-1) of cloud boundaries of Hadley cell and plausible narrowing of the high cloudiness in the Intertropical Convergence Zone region in some seasons. These results support findings of some of the previous studies that showed strengthening of the tropical hydrological cycle and expansion of the Hadley cell that are potentially related to the recent global warming trends. Copyright 2011 by the American Geophysical Union."
"35119297700;7003627515;35490828000;8570871900;22937577900;12767251100;","A new albedo parameterization for use in climate models over the Antarctic ice sheet",2011,"10.1029/2010JD015113","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952765855&doi=10.1029%2f2010JD015113&partnerID=40&md5=cec3c3dcdafabf18e1de212a41a36ca4","A parameterization for broadband snow surface albedo, based on snow grain size evolution, cloud optical thickness, and solar zenith angle, is implemented into a regional climate model for Antarctica and validated against field observations of albedo for the period 1995-2004. Over the Antarctic continent, modeled snow grain size exhibits expected behavior. The agreement between modeled and observed albedo at Neumayer, Dronning Maud Land, is very good, and subtle variability in albedo is well captured by the model. December-February mean differences in modeled and observed net shortwave radiation range from -8.7 to +3.8 W m-2 between 1995 and 2004, with a mean value of -2.7 W m-2. This is a considerable improvement compared to the previous albedo parameterization in the model, which led to overestimates of the net shortwave fluxes by +15.0 to +22.7 W m-2, or 40-55% of the observed net shortwave flux, in the same period. Copyright 2011 by the American Geophysical Union."
"55686667100;16645036600;26531444800;7102857642;","Convective control of ENSO simulated in MIROC",2011,"10.1175/2010JCLI3878.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650546335&doi=10.1175%2f2010JCLI3878.1&partnerID=40&md5=0e9d7cef8aa6dd5c6dfa31118da9c2f8","The high sensitivity of the El Niño-Southern Oscillation (ENSO) to cumulus convection is examined by means of a series of climate simulations using an updated version of the Model for Interdisciplinary Research on Climate (MIROC), called MIROC5. Given that the preindustrial control run using MIROC5 shows a realistic ENSO, the integration is repeated with four different values of the parameter, l, which affects the efficiency of the entrainment rate in cumuli. The ENSO amplitude is found to be proportional to l21 and to vary from 0.6 to 1.6 K. A comparison of four experiments reveals the mechanisms for which the cumulus convections control behavior of ENSO in MIROC as follows. Efficient entrainment due to a large l increases congestus clouds over the intertropical convergence zone (ITCZ) and reduces the vertical temperature gradient over the eastern Pacific, resulting in a wetter ITCZ and drier cold tongue via accelerated meridional circulation. The dry cold tongue then shifts the atmospheric responses to El Niño/La Niña westward, thereby reducing the effective Bjerknes feedback. The first half of these processes is identifiable in a companion set of atmosphere model experiments, but the difference in mean precipitation contrast is quite small. On one hand, the mean meridional precipitation contrast over the eastern Pacific is a relevant indicator of the ENSO amplitude in MIROC. On the other hand, the nonlinear feedback from ENSO affects the mean state, the latter therefore not regarded as a fundamental cause for different ENSO amplitudes. © 2011 American Meteorological Society."
"10139397300;18134523600;7407104838;7405666962;7102805852;57203200427;","Aerosol forcing in the Climate Model Intercomparison Project (CMIP5) simulations by HadGEM2-ES and the role of ammonium nitrate",2011,"10.1029/2011JD016074","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80455150395&doi=10.1029%2f2011JD016074&partnerID=40&md5=04260d7410aff283c9f74572d66382d9","The latest Hadley Centre climate model, HadGEM2-ES, includes Earth system components such as interactive chemistry and eight species of tropospheric aerosols. It has been run for the period 1860-2100 in support of the fifth phase of the Climate Model Intercomparison Project (CMIP5). Anthropogenic aerosol emissions peak between 1980 and 2020, resulting in a present-day all-sky top of the atmosphere aerosol forcing of -1.6 and -1.4 W m-2 with and without ammonium nitrate aerosols, respectively, for the sum of direct and first indirect aerosol forcings. Aerosol forcing becomes significantly weaker in the 21st century, being weaker than -0.5 W m-2 in 2100 without nitrate. However, nitrate aerosols become the dominant species in Europe and Asia and decelerate the decrease in global mean aerosol forcing. Considering nitrate aerosols makes aerosol radiative forcing 2-4 times stronger by 2100 depending on the representative concentration pathway, although this impact is lessened when changes in the oxidation properties of the atmosphere are accounted for. Anthropogenic aerosol residence times increase in the future in spite of increased precipitation, as cloud cover and aerosol-cloud interactions decrease in tropical and midlatitude regions. Deposition of fossil fuel black carbon onto snow and ice surfaces peaks during the 20th century in the Arctic and Europe but keeps increasing in the Himalayas until the middle of the 21st century. Results presented here confirm the importance of aerosols in influencing the Earth's climate, albeit with a reduced impact in the future, and suggest that nitrate aerosols will partially replace sulphate aerosols to become an important anthropogenic species in the remainder of the 21st century. Copyright 2011 by the American Geophysical Union."
"36851768400;55547129338;7201706787;7401548835;","Projected regime shift in Arctic cloud and water vapor feedbacks",2011,"10.1088/1748-9326/6/4/044007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81355164176&doi=10.1088%2f1748-9326%2f6%2f4%2f044007&partnerID=40&md5=dd8670e6569cc09cd05036f5c79b33e4","The Arctic climate is changing faster than any other large-scale region on Earth. A variety of positive feedback mechanisms are responsible for the amplification, most of which are linked with changes in snow and ice cover, surface temperature (Ts), atmospheric water vapor (WV), and cloud properties. As greenhouse gases continue to accumulate in the atmosphere, air temperature and water vapor content also increase, leading to a warmer surface and ice loss, which further enhance evaporation and WV. Many details of these interrelated feedbacks are poorly understood, yet are essential for understanding the pace and regional variations in future Arctic change. We use a global climate model (Goddard Institute for Space Studies, Atmosphere-Ocean Model) to examine several components of these feedbacks, how they vary by season, and how they are projected to change through the 21st century. One positive feedback begins with an increase in Ts that produces an increase in WV, which in turn increases the downward longwave flux (DLF) and Ts, leading to further evaporation. Another associates the expected increases in cloud cover and optical thickness with increasing DLF and T s. We examine the sensitivities between DLF and other climate variables in these feedbacks and find that they are strongest in the non-summer seasons, leading to the largest amplification in Ts during these months. Later in the 21st century, however, DLF becomes less sensitive to changes in WV and cloud optical thickness, as they cause the atmosphere to emit longwave radiation more nearly as a black body. This regime shift in sensitivity implies that the amplified pace of Arctic change relative to the northern hemisphere could relax in the future. © 2011 IOP Publishing Ltd."
"6602835531;7005619103;56668843600;57191504846;14017835500;55981836400;","Exceptional cloud-to-ground lightning during an unusually warm summer in Yukon, Canada",2011,"10.1029/2011JD016080","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81255210984&doi=10.1029%2f2011JD016080&partnerID=40&md5=b3c17716a6772108efc364f82a5a64b6","The 2004 lightning season and related wildfire activity in Yukon, Canada, was exceptional in many aspects. The synoptic environment during the summer was dominated by a persistent upper level ridge over Alaska and Yukon, bringing above-normal temperatures and below-normal precipitation to Yukon. The number of cloud-to-ground (CG) flashes, lightning-initiated forest fires, and extent of the area burned exceeded historic records. Forest fire smoke affected most of Yukon during the summer. Thunderstorms forming in this northern environment in July exhibited unusual lightning characteristics as detected by Canadian Lightning Detection Network. Changes in the frequency of extreme lightning days and in the fraction of nocturnal lightning occurrence were observed. Lightning properties in July differed from climatology in several ways. The central regions of Yukon experienced enhanced positive CG lightning activity. First-stroke positive peak currents were found to be stronger, while negative peak currents were weaker than climatology. Our observations are consistent with the previous findings reported in southerly climates. Although thunderstorms related to the diurnal heating and cooling cycle influenced positive lightning occurrences in Yukon, other possible sources, including pyrocumulonimbus clouds and inverted-polarity thunderstorms, cannot be overlooked. Evidence is presented suggesting that both atmospheric conditions and smoke from the fires may have influenced the electrification process of thunderstorms to enhance +CG production. The extreme summer of 2004 experienced in Yukon may provide a hint of future impacts due to climate change. Copyright 2011 by the American Geophysical Union."
"35335123900;56013882400;6506340699;","Species richness, endemism, and conservation of American tree ferns (Cyatheales)",2011,"10.1007/s10531-010-9946-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650414934&doi=10.1007%2fs10531-010-9946-2&partnerID=40&md5=464286ffc5f404e038a77b8f1d6cf734","Analyses of richness and endemism of Cyatheales (tree ferns) in tropical America were performed and evidence of a diversity gradient is presented. For this, the occurrence ranges of 239 species were plotted into a 5° × 5° grid-cell map and then analyzed using species richness and endemism indices. Here we show that species richness and endemism are not distributed randomly over the landscape, but do aggregate into defined regions of high diversity in tropical America: the northern Andes, lower Central America, upper Central America and Mexico, the Guyana Highlands, southeastern Brazil, and the Antilles. These distributional patterns are congruent with the geographical distribution of cloud forest, which in turn is determined by topography, high humidity, and persistent cloud immersion. The mountain regions of tropical America, especially the cloud forests, harbour most of the species of American Cyatheales and have high levels of habitat loss and climatic fragility. Conservation policies for Cyatheales are centred on the local use and trade of many tree fern species, but none such policies focus on cloud forest habitat loss. This makes tree ferns a critically endangered group of plants. In the face of the current environmental crisis and global climate change, the presence of Cyatheales in these regions sounds the alarm on their conservation priorities. © 2010 Springer Science+Business Media B.V."
"35974951200;20435752700;35887706900;","Global analysis of cloud field coverage and radiative properties, using morphological methods and MODIS observations",2011,"10.5194/acp-11-191-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651336323&doi=10.5194%2facp-11-191-2011&partnerID=40&md5=8485e9eb42299697ae5099e87ca867d0","The recently recognized continuous transition zone between detectable clouds and cloud-free atmosphere (""the twilight zone"") is affected by undetectable clouds and humidified aerosol. In this study, we suggest to distinguish cloud fields (including the detectable clouds and the surrounding twilight zone) from cloud-free areas, which are not affected by clouds. For this classification, a robust and simple-to-implement cloud field masking algorithm which uses only the spatial distribution of clouds, is presented in detail. A global analysis, estimating Earth's cloud field coverage (50° Sĝ€""50° N) for 28 July 2008, using the Moderate Resolution Imaging Spectroradiometer (MODIS) data, finds that while the declared cloud fraction is 51%, the global cloud field coverage reaches 88%. The results reveal the low likelihood for finding a cloud-free pixel and suggest that this likelihood may decrease as the pixel size becomes larger. A global latitudinal analysis of cloud fields finds that unlike oceans, which are more uniformly covered by cloud fields, land areas located under the subsidence zones of the Hadley cell (the desert belts), contain proper areas for investigating cloud-free atmosphere as there is 40ĝ€""80% probability to detect clear sky over them. Usually these golden-pixels, with higher likelihood to be free of clouds, are over deserts. Independent global statistical analysis, using MODIS aerosol and cloud products, reveals a sharp exponential decay of the global mean aerosol optical depth (AOD) as a function of the distance from the nearest detectable cloud, both above ocean and land. Similar statistical analysis finds an exponential growth of mean aerosol fine-mode fraction (FMF) over oceans when the distance from the nearest cloud increases. A 30 km scale break clearly appears in several analyses here, suggesting this is a typical natural scale of cloud fields. This work shows different microphysical and optical properties of cloud fields, urging to separately investigate cloud fields and cloud-free atmosphere in future climate research. © 2011 Author(s)."
"55716092000;9244954000;9249239700;7003278104;7101801476;7202772927;7404829395;7003406400;","Partitioning CloudSat ice water content for comparison with upper tropospheric ice in global atmospheric models",2011,"10.1029/2010JD015179","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054827157&doi=10.1029%2f2010JD015179&partnerID=40&md5=1d1abe0cd95b8acf2a4148985895bfeb","The ice cloud estimates in current global models exhibit significant inconsistency, resulting in a significant amount of uncertainties in climate forecasting. Vertically resolved ice water content (IWC) is recently available from new satellite products, such as CloudSat, providing important observational constraints for evaluating the global models. To account for the varied nature of the model parameterization schemes, it is valuable to develop methods to distinguish the cloud versus precipitating ice components from the remotely sensed estimates in order to carry out meaningful model-data comparisons. The present study develops a new technique that partitions CloudSat total IWC into small and large ice hydrometeors, using the ice particle size distribution (PSD) parameters provided by the retrieval algorithm. The global statistics of CloudSat-retrieved PSD are analyzed for the filtered subsets on the basis of convection and precipitation flags to identify appropriate particle size separation. Results are compared with previous partitioning estimates and suggest that the small particles contribute to ∼25-45% of the global mean total IWC in the upper to middle troposphere. Sensitivity measures with respect to the PSD parameters and the retrieval algorithm are presented. The current estimates are applied to evaluate the IWC estimates from the European Centre for Medium-Range Weather Forecasts model and the finite-volume multiscale modeling framework model, pointing to specific areas of potential model improvements. These results are discussed in terms of applications to model diagnostics, providing implications for reducing the uncertainty in the model representation of cloud feedback and precipitation. Copyright 2011 by the American Geophysical Union."
"13408945500;","A daytime cloud detection algorithm for FY-3A/VIRR data",2011,"10.1080/01431161.2010.523730","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82055173105&doi=10.1080%2f01431161.2010.523730&partnerID=40&md5=7027c135b76a35baff14e12d3514bf6e","Cloud detection is essential for the retrieval of atmospheric and surface parameters and it directly impacts the quality of many satellite geophysical products used in weather, climate and environmental research. In this article, a daytime cloud detection algorithm based on multi-spectral thresholds is proposed to discriminate clouds from clear skies for the visible and infrared radiometer (VIRR), which is a key instrument on board the Chinese FengYun-3A (FY-3A) polar-orbiting meteorological satellite, launched 27 May 2008. The VIRR has ten bands in the wavelengths 0.43-12.5 μm and provides global observations of atmosphere, ocean and land in the visible and infrared regions of the spectrum. In this algorithm, the underlying surface is divided into five ecological types: snow/ice, desert, coastal, land and water, and seven spectral bands of the VIRR are used to indicate a level of confidence that the VIRR is observing clear skies. This algorithm also utilizes the 1.6 μm band and the difference between the 1.38 and 1.6 μm bands to respectively detect water cloud and high cloud. An example of cloud detection and a comparison with an official cloud masking product are given; the results show that this algorithm performs well and is better than the official algorithm in cloud detection. © 2011 Taylor & Francis."
"8527821500;7003875148;35462130800;7102495313;","An ensemble of arctic simulations of the AOE-2001 field experiment",2011,"10.3390/atmos2020146","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874542911&doi=10.3390%2fatmos2020146&partnerID=40&md5=b1fc50340ac8650d0f97a1608ff55046","An ensemble of model runs with the COAMPS© regional model is compared to observations in the central Arctic for August 2001 from the Arctic Ocean Experiment 2001 (AOE-2001). The results are from a 6-km horizontal resolution 2nd, inner, nest of the model while the outermost model domain covers the pan-Arctic region, including the marginal ice zone and some of the land areas around the Arctic Ocean. Sea surface temperature and ice cover were prescribed from satellite data while sea-ice surface properties were modeled with an energy balance model, assuming a constant ice thickness. Five ensemble members were generated by altering the initialization time for the innermost nest, the surface roughness and the turbulent mixing scheme for clouds. The large size of the outer domain means that the model simulations have substantial deviations from the observations at synoptic-scale time scales. Therefore the evaluation focuses on statistical measures, rather than in details of individual ensemble member performance as compared directly to observations. In this context, the ensemble members are surprisingly similar even though details differ significantly. The ensemble average results features two main systematic problems: a consistent temperature bias, with too low temperatures below 2-3 km and slightly high temperatures through the rest of the troposphere, and a significant underestimation of the lowest clouds. In terms of total cloud cover, however, the model produces a realistic result; it is the very lowest clouds that are essentially missing. The temperature bias initially appears to be related to an interaction between clouds and radiation; the shape of the mean radiative heating-rate profile is very similar to that of the temperature bias. The lack of the lowest clouds could be due to the too low temperatures in conjunction with a cloud scheme that overestimates the transfer of cloud droplets to ice particles that precipitate. The different terms in the surface energy balance as well as the surface stress has only small systematic errors and are surprisingly consistent between the members. © 2011 by the authors; licensee MDPI, Basel, Switzerland."
"55723061900;35849722200;","Modeling the impact of aerosols on tropical overshooting thunderstorms and stratospheric water vapor",2011,"10.1029/2011JD015591","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054014374&doi=10.1029%2f2011JD015591&partnerID=40&md5=060b89aac47e0df4d31d7d6314311c7c","Overshooting deep convection plays an important role in regulating the water vapor content of the tropical tropopause layer and is also an important mechanism for transporting water vapor into the lower stratosphere (LS). The aim of this study is to examine the effect of aerosols as cloud condensation nuclei (CCN) on the water vapor content of the LS via single isolated overshooting thunderstorms. The development of a severe Hector thunderstorm in northern Australia observed during the Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere/Aerosol and Chemical Transport in Tropical Convection (SCOUT-O3/ACTIVE) campaign is simulated using a three-dimensional nonhydrostatic convective cloud model with a double-moment bulk microphysics scheme. The results show that the ice hydrometeors account for over 50% of the total condensate mass, indicating that ice processes play an important role in regulating the structure of thunderstorms in the tropics. A large number of ice particles occurring in the LS are not formed in situ but are transported upward by convective overshooting with subsequent mixing. Sensitivity tests show that the increase in cloud droplet numbers induced by increasing CCN concentrations would increase the number concentrations of the ice crystals transported to the LS, which had the effect of reducing the sizes and fall speeds of the ice crystal, thereby causing a moistening of the LS by sublimation of the injected ice particles. This result suggests that aerosols in the boundary layer can affect stratospheric water vapor via overshooting deep convection. Copyright © 2011 by the American Geophysical Union."
"56865378100;13006055400;7004461962;","Unified treatment of dry convective and stratocumulus-topped boundary layers in the ECMWF model",2011,"10.1002/qj.713","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251482201&doi=10.1002%2fqj.713&partnerID=40&md5=598d045b6662893c44e546de3a9da227","The unified parametrization of the dry boundary layer and stratocumulus in the ECMWF model is described using the eddy diffusivity mass-flux framework. Model simulations are compared to observations at a few selected research field experiments, to ISCCP cloud cover, to LIDAR from space cloud observations, to SYNOP observations over Europe and to the climatology. It is shown that the new stratocumulus formulation improved the quality of the stratocumulus simulations rather dramatically. The key ingredients are: (i) mixing in moist conserved variables, (ii) diffusion related to cloud-top cooling, (iii) an additional mass-flux term, (iv) an entrainment parametrization and (v) a switching between shallow cumulus and stratocumulus based on lower tropospheric stability. To illustrate the relevance of various aspects, the sensitivity to different parameters is also presented. © 2011 Royal Meteorological Society."
"7005528388;7102171439;6603126554;36097134700;","Relationship between marine boundary layer clouds and lower tropospheric stability observed by AIRS, CloudSat, and CALIOP",2011,"10.1029/2011JD016136","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053579766&doi=10.1029%2f2011JD016136&partnerID=40&md5=3c4ba1680d6c5ec4e179c1a95e6082d3","Thirteen months of matched temperature and water vapor profiles from the Atmospheric Infrared Sounder (AIRS), collocated European Centre for Medium-Range Weather Forecasts (ECMWF) model analyses, National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis, and cloud profiles from the CloudSat and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instruments are investigated to quantify aspects of maritime boundary layer (MBL) clouds and their thermodynamic environment. This study highlights the strengths and limitations of this multisensor A-Train approach. The AIRS retrieval yield (percentage of high-quality temperature and water vapor profiles to the surface) over the oceans between 40°S and 40°N within MBL clouds is between 61% and 71% globally and is greater than 80%-90% throughout most of the subtropics. The lower tropospheric stability (LTS) and estimated inversion strength (EIS) are derived from AIRS temperature and water vapor profiles over the global oceans as well as from collocated ECMWF model analysis data. Positive values of EIS derived from AIRS well represent MBL conditions, demonstrating that AIRS contains quantitatively useful information with regard to relative changes in dynamic range of temperature and water vapor in the MBL. The relative magnitude and seasonality of LTS and EIS from the collocated satellite data set in stratocumulus regions are very similar to spatially and temporally collocated ECMWF model analyses, but differences are found between different subsampling criteria of reanalysis data. For coincident vertical profiles, the MBL in AIRS data shows a more smoothed structure than that of ECMWF. This multisensor investigation establishes a basis for using A-train observations to quantify elements of low cloud-climate feedback. © 2011 by the American Geophysical Union."
"55705948900;7402677913;7103206141;7201665727;","Evaluation of factors controlling long-range transport of black carbon to the Arctic",2011,"10.1029/2010JD015145","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952294338&doi=10.1029%2f2010JD015145&partnerID=40&md5=8d003ae2809374a81e58425445c4729a","This study evaluates the sensitivity of long-range transport of black carbon (BC) from midlatitude and high-latitude source regions to the Arctic to aging, dry deposition, and wet removal processes using the Geophysical Fluid Dynamics Laboratory (GFDL) coupled chemistry and climate model (AM3). We derive a simple parameterization for BC aging (i.e., coating with soluble materials) which allows the rate of aging to vary diurnally and seasonally. Slow aging during winter permits BC to remain largely hydrophobic throughout transport from midlatitude source regions to the Arctic. In addition, we apply surface-dependent dry deposition velocities and reduce the wet removal efficiency of BC in ice clouds. The inclusion of the above parameterizations significantly improves simulated magnitude, seasonal cycle, and vertical profile of BC over the Arctic compared with those in the base model configuration. In particular, wintertime concentrations of BC in the Arctic are increased by a factor of 100 throughout the tropospheric column. On the basis of sensitivity tests involving each process, we find that the transport of BC to the Arctic is a synergistic process. A comprehensive understanding of microphysics and chemistry related to aging, dry and wet removal processes is thus essential to the simulation of BC concentrations over the Arctic. Copyright 2011 by the American Geophysical Union."
"24074386100;57204297539;6602357073;7006127690;57203326554;15319527800;","Large-scale climate controls of interior Alaska river ice breakup",2011,"10.1175/2010JCLI3809.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251494500&doi=10.1175%2f2010JCLI3809.1&partnerID=40&md5=b9b1fccd29829f74cb1fa859548b8e1f","Frozen rivers in the Arctic serve as critical highways because of the lack of roads; therefore, it is important to understand the key mechanisms that control the timing of river ice breakup. The relationships between springtime Interior Alaska river ice breakup date and the large-scale climate are investigated for the Yukon, Tanana, Kuskokwim, and Chena Rivers for the 1949-2008 period. The most important climate factor that determines breakup is April-May surface air temperatures (SATs). Breakup tends to occur earlier when Alaska April-May SATs and river flow are above normal. Spring SATs are influenced bystorms approaching the state from the Gulf of Alaska, which are part of large-scale climate anomalies that compare favorably with ENSO. During the warm phase of ENSO fewer storms travel into the Gulf of Alaska during the spring, resulting in a decrease of cloud cover over Alaska, which increases surface solar insolation. This results in warmer-than-average springtime SATs and an earlier breakup date. The opposite holds true for the cold phase of ENSO. Increased wintertime precipitation over Alaska has a secondary impact on earlier breakup by increasing spring river discharge. Improved springtime Alaska temperature predictions would enhance the ability to forecast the timing of river ice breakup. © 2011 American Meteorological Society."
"7003532404;6602621536;24784233900;","Agroclimatic application of a simple methodology based on surface radiation measurements",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-80155160047&partnerID=40&md5=dd97db04801b113d70a6bd5f574eda0c","The present work concerns the development and the application of a methodology to compute the surface radiative balance components and the cloud fraction index. The obtained results, regarding the cloud effects on surface available energy, give an idea of the great importance of this kind of studies. As a matter of fact, through this analysis, it is feasible to correlate possible climatic changes with the warming or cooling caused by clouds. The methodology was verified and applied considering a site in the Po river valley (SPC) in Emilia Romagna region. Through a specifically modified web cam, it was possible to automatically compute the cloud fraction by means of the inversion of the Kasten and Czeplack formula (1980) and to retrieve the parameterization coefficients that are strongly dependent on the site. The image analysis software for cloud fraction detection developed by the authors gave good results in all sky conditions. This study shows that it is possible to monitor, with a simple methodology, the climate modifications caused by the radiative forcing induced by a change in land use and, more generally, by anthropic influences. The application to four Italian sites is here reported to describe the usefulness for climatic classification."
"16425609300;55777759900;7005453641;56250119900;37094740100;","The effect of orographic gravity waves on Antarctic polar stratospheric cloud occurrence and composition",2011,"10.1029/2010JD015184","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953240642&doi=10.1029%2f2010JD015184&partnerID=40&md5=272cf9e3ddd39957cedc088211a99b7a","A seasonal analysis of the relationship between mesoscale orographic gravity wave activity and polar stratospheric cloud (PSC) composition occurrence around the whole of Antarctica is presented. Gravity wave variances are derived from temperature measurements made with the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Global Positioning System Radio Occultation (GPS-RO) satellites. Data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite are used to determine the PSC composition class distribution and spatial volume. The results show intermittent large wave activity above the Antarctic Peninsula which is coincident with large volumes of H<inf>2</inf>O ice PSCs. These ice PSC volumes advect downstream, where increases in nitric acid trihydrate (NAT) PSC volumes occur, supporting the mountain wave seeding hypothesis. During winter 2007 in the latitude range 60°S-70°S, near the edge of the vortex and where temperatures are close to PSC formation thresholds, 30% of all PSCs are attributable to orographic gravity waves. In the separate composition classes, around 50% of both H<inf>2</inf>O ice PSCs and a high NAT number density liquid-NAT mixture class of PSCs are due to these waves. While we show that planetary waves are the major determinant of PSC presence at temperatures close to the NAT formation threshold, we also demonstrate the important role of mesoscale, intermittent orographic gravity wave activity in accounting for the composition and distribution of PSCs around Antarctica. Copyright 2011 by the American Geophysical Union."
"7102988363;53871530800;57203053317;","Effects of ice nuclei on cirrus clouds in a global climate model",2011,"10.1029/2010JD015302","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053366568&doi=10.1029%2f2010JD015302&partnerID=40&md5=99426e3592df41ba72ee19d565b0c230","A multiple-mode ice microphysical scheme is applied in the European Centre/Hamburg (ECHAM) general circulation model to simulate effects of aerosol-ice interactions on global cirrus properties. The different ice modes represent cirrus ice formed by homogeneous freezing of liquid aerosols and heterogeneous nucleation on mineral dust or black carbon particles. A fourth ice mode represents ice from other sources. The competition of these modes for available water is realized in a physical parameterization scheme considering also the effect of preexisting ice on the ice nucleation process. The model is applied to analyze the global characteristics of ice formed by the different aerosol types and to study potential global effects of mineral dust and black carbon particles on cirrus microphysical parameters. The simulations reveal that, on average, ice from heterogeneous nucleation shows fewer but larger crystals and has a smaller contribution to the mean cirrus ice water content than ice from homogeneous freezing. However, heterogeneous ice nuclei may have important effects on the overall cirrus properties. Reductions in zonal mean annual average cirrus ice particle number concentrations induced by heterogeneous nucleation of up to 20% in the tropics and 1%-10% in the midlatitudes are simulated. The effect is further amplified by ice formation on aircraft-generated soot. Significant reductions in the mean ice water content are modeled, which likely result from efficient sedimentation and precipitation of large ice particles generated by heterogeneous nucleation. This leads to reductions in the zonal mean annual average water vapor mixing ratio of up to 5% at cirrus levels. Copyright 2011 by the American Geophysical Union."
"13403627400;7004469744;7006728825;","The Coupled Effect of Mid-Tropospheric Moisture and Aerosol Abundance on Deep Convective Cloud Dynamics and Microphysics",2011,"10.3390/atmos2030222","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874571063&doi=10.3390%2fatmos2030222&partnerID=40&md5=43ba136bf015a24cde1db65b933272fb","The humidity of the mid troposphere has a significant effect on the development of deep convection. Dry layers (dry intrusions) can inhibit deep convection through the effect of a thermal inversion resulting from radiation and due to the reduction in buoyancy resulting from entrainment. Recent observations have shown that the sensitivity of cloud top height to changes in mid-tropospheric humidity can be larger than straightforward ""parcel dilution"" would lead us to expect. Here, we investigate how aerosol effects on cloud development and microphysics are coupled to the effects of mid-tropospheric dry air. The two effects are coupled because the buoyancy loss through entrainment depends on droplet evaporation, so is controlled both by the environmental humidity and by droplet sizes, which are, in turn, controlled in part by the aerosol size distribution. Previous studies have not taken these microphysical effects into account. Cloud development and microphysics are examined using a 2-D non-hydrostatic cloud model with a detailed treatment of aerosol, drop, and ice-phase hydrometeor size spectra. A moderately deep mixed-phase convective cloud that developed over the High Plains of the United States is simulated. We find that a dry layer in the mid troposphere leads to a reduction in cloud updraft strength, droplet number, liquid water content and ice mass above the layer. The effect of the dry layer on these cloud properties is greatly enhanced under elevated aerosol conditions. In an environment with doubled aerosol number (but still realistic for continental conditions) the dry layer has about a three-times larger effect on cloud drop number and 50% greater effect on ice mass compared to an environment with lower aerosol. In the case with high aerosol loading, the dry layer stops convective development for over 10 min, and the maximum cloud top height reached is lower. However, the effect of the dry layer on cloud vertical development is significantly reduced when aerosol concentrations are lower. The coupled effect of mid-tropospheric dry air and aerosol on convective development is an additional way in which long term changes in aerosol may impact planetary cloud processes and climate. © 2011 by the authors."
"14024070000;7404493635;","Regional long-term climate change (1950-2000) in the midtropical Atlantic and its impacts on the hydrological cycle of Puerto Rico",2011,"10.1029/2010JD015414","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959589806&doi=10.1029%2f2010JD015414&partnerID=40&md5=bea94a33b3354b7b666bb47980fe1c3a","Large-scale climate data for the north tropical Atlantic (NTA) region show that air temperatures have increased during the past 50 years (1955-1959 to 2000-2004) with moderate warming near the Caribbean islands to considerable heating in the northern region. This pattern may be driven by sea surface temperature anomalies in the same region of study that follow relatively small changes in the Caribbean basin to stronger anomalies in the northeast. These changes might be associated with changes in the long-term pattern of the NTA high-pressure system that drives climate in the region. A series of mesoscale numerical experiments were designed to study the regional impacts these large-scale changes have on the hydrological cycle of the island of Puerto Rico. Results indicate that increased easterly surface winds for the 1950-2000 time frame disrupts a pattern of inland moisture advection and convergence zone, increasing cloud base heights and reducing the total column liquid water content over high elevations. This combination of factors produces a reduction in precipitation over the central and eastern mountains of Puerto Rico. Copyright 2011 by the American Geophysical Union."
"23974441400;7202019251;36995605400;24752305800;","Validation of MODIS snow cover products using landsat and ground measurements during the 2001-2005 snow seasons over northern Xinjiang, China",2011,"10.1080/01431160903439924","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551678231&doi=10.1080%2f01431160903439924&partnerID=40&md5=26de819957e0f61f122bbddc8a42a214","The Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra daily snow cover product MOD10A1 was compared with in situ climate station measurements and a snow map generated from Landsat Enhanced Thematic Mapper Plus (ETM+) data. Snow-covered area (SCA) dynamics were assessed using the MODIS 8-day snow cover composite product MOD10A2 for the 2001-2005 snow seasons in northern Xinjiang, China. The results indicate that the snowmapping agreement between MODIS daily snow maps and surface observations is high at 94.6% over the four snow seasons under clear-sky conditions. The snow classification accuracy in a mountainous area was lower than that in a plain area and caused higher omission errors, probably resulting in an underestimation of the SCA. The omission errors were mainly determined by snow depth, land cover types, the terrain and mixed pixels. The cloud agreement was 95.9%, and approximately 4.1% of cloud was misclassified as snow when the sky view at the climate stations was covered by clouds. An improvement was found in suppressing clouds using the 8-day products, with MOD10A2 reducing about 88.4% of the average cloud cover compared with MOD10A1. SCA in northern Xinjiang retrieved using MOD10A2 shows a clear seasonal trend. The air temperature plays an important role in the fractional SCA, and the spatial distribution of the snow cover differs considerably in the various areas in the northern Xinjiang region. © 2011 Taylor & Francis."
"6602705884;","Bias correction and post-processing under climate change",2011,"10.5194/npg-18-911-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984410003&doi=10.5194%2fnpg-18-911-2011&partnerID=40&md5=75e77a7f132805601e75a7c6fec5a2be","The statistical and dynamical properties of bias correction and linear post-processing are investigated when the system under interest is affected by model errors and is experiencing parameter modifications, mimicking the potential impact of climate change. The analysis is first performed for simple typical scalar systems, an Ornstein-Uhlenbeck process (O-U) and a limit point bifurcation. It reveals system's specific (linear or non-linear) dependences of biases and post-processing corrections as a function of parameter modifications. A more realistic system is then investigated, a low-order model of moist general circulation, incorporating several processes of high relevance in the climate dynamics (radiative effects, cloud feedbacks…), but still sufficiently simple to allow for an extensive exploration of its dynamics. In this context, bias or post-processing corrections also display complicate variations when the system experiences temperature climate changes up to a few degrees. This precludes a straightforward application of these corrections from one system's state to another (as usually adopted for climate projections), and increases further the uncertainty in evaluating the amplitudes of climate changes. © Author(s) 2011."
"6603821988;25647168900;35338710200;23485410200;7006629146;21735084500;7006735547;7202400272;24921742700;6701348935;6602256427;57070575500;7005134081;7402093416;56259852000;9738329300;6603480361;36636692600;7004402705;55919935700;6504688501;13402933200;7403263977;16479703400;15127430500;7102976560;7102059695;6506553245;7004587644;55812487100;57062286700;7005723936;7006532784;7003683808;6603561402;7103294731;7403544649;57206421971;16445242100;21735369200;7102167757;55730744700;","Multimodel climate and variability of the stratosphere",2011,"10.1029/2010JD014995","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952483337&doi=10.1029%2f2010JD014995&partnerID=40&md5=9f7ab0a2a45e67991c31846303c1195b","The stratospheric climate and variability from simulations of sixteen chemistry-climate models is evaluated. On average the polar night jet is well reproduced though its variability is less well reproduced with a large spread between models. Polar temperature biases are less than 5 K except in the Southern Hemisphere (SH) lower stratosphere in spring. The accumulated area of low temperatures responsible for polar stratospheric cloud formation is accurately reproduced for the Antarctic but underestimated for the Arctic. The shape and position of the polar vortex is well simulated, as is the tropical upwelling in the lower stratosphere. There is a wide model spread in the frequency of major sudden stratospheric warnings (SSWs), late biases in the breakup of the SH vortex, and a weak annual cycle in the zonal wind in the tropical upper stratosphere. Quantitatively, ""metrics"" indicate a wide spread in model performance for most diagnostics with systematic biases in many, and poorer performance in the SH than in the Northern Hemisphere (NH). Correlations were found in the SH between errors in the final warming, polar temperatures, the leading mode of variability, and jet strength, and in the NH between errors in polar temperatures, frequency of major SSWs, and jet strength. Models with a stronger QBO have stronger tropical upwelling and a colder NH vortex. Both the qualitative and quantitative analysis indicate a number of common and long-standing model problems, particularly related to the simulation of the SH and stratospheric variability. Copyright 2011 by the American Geophysical Union."
"6507224579;7004547152;7005137442;","Bifurcations leading to summer Arctic sea ice loss",2011,"10.1029/2011JD015653","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054984920&doi=10.1029%2f2011JD015653&partnerID=40&md5=df5e774e098573abd217c44857948b8a","There is significant interest in whether there could be a bifurcation, sometimes referred to as a ""tipping point,"" associated with Arctic sea ice loss. A low-order model of Arctic sea ice has recently been proposed and used to argue that a bifurcation associated with summer sea ice loss (the transition from perennial to seasonal ice) is unlikely. Here bifurcations are investigated in a variation of this model that incorporates additional effects, including parameterizations of changes in clouds and heat transport as sea ice is lost. It is shown that bifurcations can separate perennially and seasonally ice-covered states in this model in a robust parameter regime, although smooth loss of summer sea ice is also possible. Hysteresis and jumps associated with bifurcations involving winter sea ice loss are larger than those associated with summer sea ice loss. Finally, in analogy with simulations in global climate models, the low-order model is integrated with time-varying greenhouse gas forcing in both the regime in which summer sea ice is lost via bifurcations and the regime in which it is not. The resulting time series are compared as a preliminary way of investigating ways in which these regimes could be distinguished from each other. Copyright 2011 by the American Geophysical Union."
"7201375498;","Estimating the global radiative impact of the sea ice-albedo feedback in the Arctic",2011,"10.1029/2011JD015804","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860404001&doi=10.1029%2f2011JD015804&partnerID=40&md5=bfcfdc4faa0176198bb159b98094b475","A simple method for estimating the global radiative forcing caused by the sea ice-albedo feedback in the Arctic is presented. It is based on observations of cloud cover, sea ice concentration, and top-of-atmosphere broadband albedo. The method does not rely on any sort of climate model, making the assumptions and approximations clearly visible and understandable and allowing them to be easily changed. Results show that the globally and annually averaged radiative forcing caused by the observed loss of sea ice in the Arctic between 1979 and 2007 is approximately 0.1 W m-2; a complete removal of Arctic sea ice results in a forcing of about 0.7 W m-2, while a more realistic ice-free summer scenario (no ice for 1 month and decreased ice at all other times of the year) results in a forcing of about 0.3 W m-2, similar to present-day anthropogenic forcing caused by halocarbons. The potential for changes in cloud cover as a result of the changes in sea ice makes the evaluation of the actual forcing that may be realized quite uncertain since such changes could overwhelm the forcing caused by the sea ice loss itself, if the cloudiness increases in the summertime. Copyright 2011 by the American Geophysical Union."
"36141355100;6602809597;57203053317;6701847229;26632168400;36931129200;7003748648;7102953444;","Implementation and evaluation of aerosol and cloud microphysics in a regional climate model",2011,"10.1029/2010JD014572","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551638388&doi=10.1029%2f2010JD014572&partnerID=40&md5=ceaea2080fbb67c159850459ebeadd73","A new aerosol modeling framework is presented within the regional climate model COSMO-CLM. The model accounts for the microphysical interactions of internally and externally mixed aerosol particles. Sulfate, black carbon, particulate organic matter, sea salt, and mineral dust are considered. The model is applied over Europe at a horizontal resolution of 50 km. The lateral boundary conditions are given by the ERA-Interim reanalysis for the meteorological fields and by a global ECHAM5-HAM simulation for the aerosols. Present-day AeroCom emissions are used for the evaluation period from 1997 to 2003. The model largely reproduces the annual mean pattern of the aerosol optical depth derived from satellite data over Europe (model and observed domain mean is 0.17, but it is 0.37 with standard model version). The annual cycle is overestimated in COSMO-CLM in some regions due to strong dust transport across the Mediterranean in late spring. Day-to-day variability in aerosol optical depth and the Angstrom exponent is also captured by the model. The corresponding correlations of the daily mean time series between measurements from AERONET stations and the model range from 0.17 to 0.74. In comparison with the standard model version, which does not account for aerosol transport and indirect aerosol effects and uses an outdated aerosol climatology, the mid-European summer cold bias disappears with the new framework. The new framework allows studies of mesoscale interactions between aerosols, clouds, precipitation, and radiation on climatological time scales due to the advanced physical representation of the underlying processes. Copyright 2011 by the American Geophysical Union."
"57195992785;","Earth system models: An overview",2011,"10.1002/wcc.148","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80855131004&doi=10.1002%2fwcc.148&partnerID=40&md5=5ca4f273ae129edaf8205adc16be428d","Earth System models (ESMs) are global climate models with the added capability to explicitly represent biogeochemical processes that interact with the physical climate and so alter its response to forcing such as that associated with human-caused emissions of greenhouse gases. Representing the global carbon cycle allows for feedbacks between the physical climate and the biological and chemical processes in the ocean and on land that take up some of the emitted carbon dioxide and so act to reduce warming. The sulfur cycle is also important in that both natural and human emissions of sulfur contribute to the production of sulfate aerosols which reflect incoming solar radiation (a direct cooling effect) and alter cloud properties (an indirect cooling effect). Other components such as ozone are also being incorporated into some ESMs. Evaluating the physical component of an ESM is becoming increasingly comprehensive and sophisticated, but the evaluation of the biogeochemical components suffer somewhat from a lack of comprehensive global-scale observational data. Nevertheless, such models provide valuable insight into climate variability and change, and the role of human activities and possible mitigation actions on future climate change. Internationally coordinated experiments are increasingly important in providing a multimodel ensemble of climate simulations, thereby taking advantage of some 'cancellation of errors' and allowing better quantification of uncertainty. © 2011 John Wiley & Sons, Ltd."
"35096299800;7004299063;9248919400;7005126327;55488312400;6701490421;55707289500;26435213200;35734944400;57189255986;6701796926;7402287860;","Simulation and observations of stratospheric aerosols from the 2009 Sarychev volcanic eruption",2011,"10.1029/2010JD015501","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053579987&doi=10.1029%2f2010JD015501&partnerID=40&md5=8d35ff89b15ae5d6f28293da18315fd6","We used a general circulation model of Earth's climate to conduct simulations of the 12-16 June 2009 eruption of Sarychev volcano (48.1°N, 153.2°E). The model simulates the formation and transport of the stratospheric sulfate aerosol cloud from the eruption and the resulting climate response. We compared optical depth results from these simulations with limb scatter measurements from the Optical Spectrograph and Infrared Imaging System (OSIRIS), in situ measurements from balloon-borne instruments lofted from Laramie, Wyoming (41.3°N, 105.7°W), and five lidar stations located throughout the Northern Hemisphere. The aerosol cloud covered most of the Northern Hemisphere, extending slightly into the tropics, with peak backscatter measured between 12 and 16 km in altitude. Aerosol concentrations returned to near-background levels by spring 2010. After accounting for expected sources of discrepancy between each of the data sources, the magnitudes and spatial distributions of aerosol optical depth due to the eruption largely agree. In conducting the simulations, we likely overestimated both particle size and the amount of SO<inf>2</inf> injected into the stratosphere, resulting in modeled optical depth values that were a factor of 2-4 too high. Modeled optical depth due to the eruption shows a peak too late in high latitudes and too early in low latitudes, suggesting a problem with stratospheric circulation in the model. The model also shows a higher decay rate in optical depth than is observed, showing an inaccuracy in stratospheric removal rates in some seasons. The modeled removal rate of sulfate aerosols from the Sarychev eruption is higher than the rate calculated for aerosols from the 1991 eruption of Mt. Pinatubo. © 2011 by the American Geophysical Union."
"57205192907;36646313800;8855923200;7003799326;7102687667;55719408100;56448294200;8284622100;","Interannual teleconnections between the summer North Atlantic Oscillation and the East Asian summer monsoon",2011,"10.1029/2010JD015235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960533770&doi=10.1029%2f2010JD015235&partnerID=40&md5=0da2c7238c3bf9f856143ac1c4fa6500","Here we present a study of the relationship between July-August (JA) mean climate over China, which is strongly linked to the East Asian summer monsoon (EASM), and the summer (JA) North Atlantic Oscillation (SNAO). The variations of temperature, precipitation, and cloud cover related to the SNAO were analyzed for the period 1951-2002 using gridded data sets as well as instrumental data from 160 stations in China. It was shown that the major patterns of summer climate over China are highly connected with the interannual variation of the SNAO, supporting a teleconnection between the North Atlantic region and East Asia. Based on the analyses of the daily and monthly reanalysis data sets, we propose possible mechanisms of this teleconnection. Changes in the position of the North Atlantic storm tracks and transient eddy activity associated with the positive (negative) SNAO phase contribute downstream to negative (positive) sea level pressure anomalies in northeastern East Asia. In negative SNAO years, a stationary wave pattern is excited from the southern SNAO center over northwestern Europe to northeastern East Asia. However, during positive SNAO years, a stationary wave pattern is excited extending from the SNAO center across the central Eurasian continent at around 40N and downstream to the southeast. This may explain a connection between the positive SNAO and atmospheric circulation in middle and southeastern China. Copyright 2011 by the American Geophysical Union."
"9249627300;55183670500;24470422300;7202079615;8832995400;10240710000;","Future projections of surface UV-B in a changing climate",2011,"10.1029/2011JD015749","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052340018&doi=10.1029%2f2011JD015749&partnerID=40&md5=3eee30ccf801d3219eb7426a9a243a63","Results of comprehensive long-term simulations of surface all-sky and clear-sky ultraviolet (UV) radiation through 1960-2100 are presented. A new earth system model, MIROC-ESM-CHEM, is used for the simulation, which considers key processes that change the surface UV radiation: atmospheric dynamics and chemistry affecting ozone in the stratosphere and troposphere, aerosols and clouds in the troposphere, and changes in surface albedo with sea ice and snow cover. In contrast to previous assessments considering only the effect of long-term change in stratospheric ozone, the simulated long-term behavior of UV radiation in this study is strongly affected by other processes. In one of two simulations, all-sky UV radiation in the northern midlatitudes is projected to increase in the 21st century despite the expected recovery of the stratospheric ozone layer. Reductions in aerosols and clouds are expected to overcompensate for the effect of ozone recovery. The results are sensitive to the future socioeconomic scenario, describing GHG concentrations and emissions of aerosol and ozone precursors in the troposphere. The interannual variability of UV radiation associated with the 11 year solar cycle and local processes is also discussed. Copyright © 2011 by the American Geophysical Union."
"26659013400;26659116700;7003582587;","Reducing noise associated with the Monte Carlo Independent Column Approximation for weather forecasting models",2011,"10.1002/qj.732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251494497&doi=10.1002%2fqj.732&partnerID=40&md5=87623d7030f60fd59f0c0300163e115b","The Monte Carlo Independent Column Approximation (McICA) is a flexible method for representing subgrid-scale cloud inhomogeneity in radiative transfer schemes. It does, however, introduce conditional random errors but these have been shown to have little effect on climate simulations, where spatial and temporal scales of interest are large enough for effects of noise to be averaged out. This article considers the effect of McICA noise on a numerical weather prediction (NWP) model, where the time and spatial scales of interest are much closer to those at which the errors manifest themselves; this, as we show, means that noise is more significant. We suggest methods for efficiently reducing the magnitude of McICA noise and test these methods in a global NWP version of the UK Met Office Unified Model (MetUM). The resultant errors are put into context by comparison with errors due to the widely used assumption of maximum-random-overlap of plane-parallel homogeneous cloud. For a simple implementation of the McICA scheme, forecasts of near-surface temperature are found to be worse than those obtained using the plane-parallel, maximum-random-overlap representation of clouds. However, by applying the methods suggested in this article, we can reduce noise enough to give forecasts of near-surface temperature that are an improvement on the plane-parallel maximum-random-overlap forecasts. We conclude that the McICA scheme can be used to improve the representation of clouds in NWP models, with the provision that the associated noise is sufficiently small. © Crown Copyright 2011. Published by John Wiley & Sons, Ltd."
"7202559581;36969998000;22433535300;","Satellite-observed urbanization characters in Shanghai, China: Aerosols, urban heat Island effect, and land-atmosphere interactions",2011,"10.3390/rs3010083","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051862674&doi=10.3390%2frs3010083&partnerID=40&md5=e1798650a583fcb50f2f5251ad349a91","Urbanization reflects how human-activities affect natural climate system. Accurately assessing the urban system by comparing it with the nearby rural regions helps to identify the impacts of urbanization. This work uses the recent satellite observed aerosol, skin temperature, land cover, albedo, cloud fraction and water vapor measurements to reveal how the city of Shanghai, one of the biggest, dense urban areas in East Asia, affects land surface and atmosphere conditions. In addition, the National Aeronautics and Space Administration (NASA) ground observations from AErosol RObotic NETwork (AERONET) is also used to reveal diurnal, seasonal, and interannual variations of the heavy aerosol load over Shanghai region. Furthermore, Shanghai reduces surface albedo, total column water vapor, cloud fraction and increases land skin temperature than rural region. These observations prove that Shanghai significantly modifies local and regional land surface physical properties as well as physical processes, which lead to the urban heat island effect (UHI). © 2011 by the authors."
"41662112800;24722339600;7006705919;","Direct and semidirect aerosol effects of southern African biomass burning aerosol",2011,"10.1029/2010JD015540","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959588402&doi=10.1029%2f2010JD015540&partnerID=40&md5=3e9e524ea332c1762f95952d778626d1","Direct and semidirect radiative effects of biomass burning aerosols from southern African fires during July-October are investigated using 20 year runs of the Community Atmospheric Model (CAM) coupled to a slab ocean model. Aerosol optical depth is constrained using observations in clear skies from Moderate Resolution Imaging Spectroradiometer (MODIS) and for aerosol layers above clouds from Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). Over the ocean, where the aerosol layers are primarily located above cloud, negative top of atmosphere (TOA) semidirect radiative effects associated with increased low cloud cover dominate over a weaker positive all-sky direct radiative effect (DRE). In contrast, over the land where the aerosols are often below or within cloud layers, reductions in cloud liquid water path (LWP) lead to a positive semidirect radiative effect that dominates over a near-zero DRE. Over the ocean, the cloud response can be understood as a response to increased lower tropospheric stability (LTS) which is caused both by radiative heating in overlying layers and surface cooling in response to direct aerosol forcing. The marine cloud changes are robust to changes in the cloud parameterization (removal of the hard-wired dependence of clouds on LTS), suggesting that they are physically realistic. Over land, decreased LWP is consistent with weaker convection driven by increased static stability. Over the entire region the overall TOA radiative effect from the biomass burning aerosols is almost zero due to opposing effects over the land and ocean. However, the surface forcing is strongly negative, which leads to a reduction in precipitation and also a reduction in sensible heat flux. The former is primarily realized through reductions in convective precipitation on both the southern and northern flanks of the convective precipitation region spanning the equatorial rain forest and the Intertropical Convergence Zone (ITCZ) in the southern Sahel. The changes are consistent with the low-level aerosol-forced cooling pattern. The results highlight the importance of semidirect radiative effects and precipitation responses for determining the climatic effects of aerosols in the African region. Copyright 2011 by the American Geophysical Union."
"7004993886;7005634455;7201957405;57201215091;7102987843;","Development and testing of polar WRF. Part III: Arctic land",2011,"10.1175/2010JCLI3460.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251580355&doi=10.1175%2f2010JCLI3460.1&partnerID=40&md5=91a7d839197c859d362fe8e7efb47c31","A version of the state-of-the-art Weather Research and Forecasting model (WRF) has been developed for use in polar climates. The model known as ""Polar WRF"" is tested for land areas with a western Arctic grid that has 25-km resolution. This work serves as preparation for the high-resolution Arctic System Reanalysis of the years 2000-10. The model is based upon WRF version 3.0.1.1, with improvements to the Noah land surface model and snow/ice treatment. Simulations consist of a series of 48-h integrations initialized daily at 0000 UTC, with the initial 24 h taken as spinup for atmospheric hydrology and boundary layer processes. Soil temperature and moisture that have a much slower spinup than the atmosphere are cycled from 48-h output of earlier runs. Arctic conditions are simulated for a winter-to-summer seasonal cycle from 15 November 2006 to 1 August 2007. Simulation results are compared with a variety of observations from several Alaskan sites, with emphasis on the North Slope. Polar WRF simulation results show good agreement with most near-surface observations. Warm temperature biases are found for winter and summer. A sensitivity experiment with reduced soil heat conductivity, however, improves simulation of near-surface temperature, ground heat flux, and soil temperature during winter. There is a marked deficit in summer cloud cover over land with excessive incident shortwave radiation. The cloud deficit may result from anomalous vertical mixing of moisture by the turbulence parameterization. The new snow albedo parameterization for WRF 3.1.1 is successfully tested for snowmelt over the North Slope of Alaska. © 2011 American Meteorological Society."
"7102832130;7202768538;6701589832;","Air temperature and anthropogenic forcing: Insights from the solid earth",2011,"10.1175/2010JCLI3500.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79851478452&doi=10.1175%2f2010JCLI3500.1&partnerID=40&md5=116c7cc33b2710459e089730f2e93cc8","Earth's rotation rate [i.e., length of day (LOD)], the angular momentumof the core (CAM), and surface air temperature (SAT) all have decadal variability. Previous investigators have found that the LOD fluctuations are largely attributed to core-mantle interactions and that the SAT is strongly anticorrelated with the decadal LOD. It is shown here that 1) the correlation among these three quantities exists until 1930, at which time anthropogenic forcing becomes highly significant; 2) correcting for anthropogenic effects, the correlation is present for the full span with a broadband variability centered at 78 yr; and 3) this result underscores the reality of anthropogenic temperature change, its size, and its temporal growth. The cause of this common variability needs to be further investigated and studied. Since temperature cannot affect the CAMor LOD to a sufficient extent, the results favor either a direct effect of Earth's core-generated magnetic field (e.g., through the modulation of charged-particle fluxes, which may impact cloud formation) or a more indirect effect of some other core process on the climate-or yet another process that affects both. In all three cases, their signals would be much smaller than the anthropogenic greenhouse gas effect on Earth's radiation budget during the coming century. © 2011 American Meteorological Society."
"7006860780;6507965363;6701724418;23968308900;","A complex relationship between calving glaciers and climate",2011,"10.1029/2011EO370001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052992358&doi=10.1029%2f2011EO370001&partnerID=40&md5=213bd5c13e6d5b797010fbd376738ed1","Many terrestrial glaciers are sensitive indicators of past and present climate change as atmospheric temperature and snowfall modulate glacier volume. However, climate interpretations based on glacier behavior require careful selection of representative glaciers, as was recently pointed out for surging and debris-covered glaciers, whose behavior often defies regional glacier response to climate [Yde and Paasche, 2010]. Tidewater calving glaciers (TWGs)mountain glaciers whose termini reach the sea and are generally grounded on the seaflooralso fall into the category of non-representative glaciers because the regional-scale asynchronous behavior of these glaciers clouds their complex relationship with climate. TWGs span the globe; they can be found both fringing ice sheets and in high-latitude regions of each hemisphere. TWGs are known to exhibit cyclic behavior, characterized by slow advance and rapid, unstable retreat, largely independent of short-term climate forcing. This so-called TWG cycle, first described by Post [1975], provides a solid foundation upon which modern investigations of TWG stability are built. Scientific understanding has developed rapidly as a result of the initial recognition of their asynchronous cyclicity, rendering greater insight into the hierarchy of processes controlling regional behavior. This has improved the descriptions of the strong dynamic feedbacks present during retreat, the role of the ocean in TWG dynamics, and the similarities and differences between TWG and ice sheet outlet glaciers that can often support floating tongues."
"16402575500;36611965700;","Relationship of cloud top to the tropopause and jet structure from CALIPSO data",2011,"10.1029/2010JD015462","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959644678&doi=10.1029%2f2010JD015462&partnerID=40&md5=eaacf62cba40d79208573ec8a2e6837b","Cloud top and tropopause relationships are examined using cloud top observations from the Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) cloud data and National Centers for Environmental Prediction Global Forecast System (GFS) tropopause data. Statistical analyses of cloud top occurrence in tropopause and jet referenced relative altitude coordinates are performed on a global scale using 4 years (2006-2010) of CALIPSO 5 km resolution cloud layer data. The results show that the thermal tropopause appears to be a significant constraint for the cloud top. The zonal vertical distribution of cloud tops in tropopause-relative coordinates shows a maximum at the tropopause level for both the tropics (20S-20N) and midlatitudes (40-60S, 40-60N) for all four seasons. Occurrence of cloud tops above the tropopause is examined and quantified. The results show that with the consideration of tropopause height uncertainty, the data do not provide sufficient evidence of significant presence of cloud tops above the tropopause in the midlatitudes. In the tropics, the significant occurrences of cloud top above the thermal tropopause are found in regions known for seasonal deep convection. In most cases, the occurrence is up to 24% in 2 × 3 latitude-longitude bins with isolated higher frequencies in the western Pacific during the northern hemispheric winter season. The vertical distributions show that these events are mostly up to 2.5 km above the lapse rate tropopause, which is comparable to the differences between the lapse rate and the cold point tropopause in regions of active convection. We speculate that this separation may be responsible for a significant fraction of the cloud tops that do occur above the lapse rate tropopause in our analyses. It is also important to note that our results are limited by the CALIPSO twice-daily sampling with local equator crossing times of 0130 and 1330. The data therefore do not provide a good representation of convection over land, which is known to have maxima in afternoon local times. The tropopause determination is a significant component of this type of studies, and errors in the tropopause height may lead to significantly different conclusions. Our analyses show that the tropopause product from the GFS model is in better agreement with radiosonde measurements. The Goddard Earth Observing System Model Version 5 tropopause product, given as the ancillary data in the CALIPSO data file, shows a much larger uncertainty, primarily because the tropopause is identified at the model grid levels. Copyright 2011 by the American Geophysical Union."
"26031933700;54792020400;26032408000;7202050052;6507649982;6602250939;7005189402;7404413845;","Asymmetric boundary shifts of tropical montane Lepidoptera over four decades of climate warming",2011,"10.1111/j.1466-8238.2010.00594.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650039241&doi=10.1111%2fj.1466-8238.2010.00594.x&partnerID=40&md5=1091737b64158e110fab39242cce28e9","Aim To estimate whether species have shifted at equal rates at their leading edges (cool boundaries) and trailing edges (warm boundaries) in response to climate change. We provide the first such evidence for tropical insects, here examining elevation shifts for the upper and lower boundaries shifts of montane moths. Threats to species on tropical mountains are considered.Location Mount Kinabalu, Sabah, Malaysia.Methods We surveyed Lepidoptera (Geometridae) on Mount Kinabalu in 2007, 42 years after the previous surveys in 1965. Changes in species upper and lower boundaries, elevational extents and range areas were assessed. We randomly subsampled the data to ensure comparable datasets between years. Estimated shifts were compared for endemic versus more widespread species, and for species that reached their range limits at different elevations.Results Species that reached their upper limits at 2500-2700 m (n= 28 species, 20% of those considered) retreated at both their lower and upper boundaries, and hence showed substantial average range contractions (-300 m in elevational extent and -45 km2 in estimated range area). These declines may be associated with changes in cloud cover and the presence of ecological barriers (geological and vegetation transitions) which impede uphill movement. Other than this group, most species (n= 109, 80% of the species considered) expanded their upper boundaries upwards (by an average of 152 m) more than they retreated at their lower boundaries (77 m).Main conclusions Without constraints, leading margins shifted uphill faster than trailing margins retreated, such that many species increased their elevational extents. However, this did not result in increases in range area because the area of land available declines with increasing elevation. Species close to a major ecological/geological transition zone on the mountain flank declined in their range areas. Extinction risk may increase long before species reach the summit, even when undisturbed habitats are available. © 2010 Blackwell Publishing Ltd."
"36150977900;7102018821;7403288995;","Parameterization of solar fluxes over mountain surfaces for application to climate models",2011,"10.1029/2010JD014722","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651310360&doi=10.1029%2f2010JD014722&partnerID=40&md5=e27b09b1157f2f1cf35c8292706526c0","On the basis of 3-D Monte Carlo photon tracing simulations, we have developed a parameterization of solar fluxes over mountain surfaces by means of the multiple linear regression analysis associated with topographic information, including elevation, solar incident angle, sky view factor, and terrain configuration factor. For clear skies without aerosols and clouds, the regression equation for the direct flux can explain more than 98% of the variation in which the solar incident angle is the dominant factor, except when the Sun is very low or at zenith. About 60% of the variation in the diffuse flux is predicted by the regression equation in which the mean elevation, sky view factor, and solar incident angle are key factors. The terrain-reflected fluxes, proportional to the surface albedo, are well correlated with the terrain configuration factor with more than 80% of the variation that can be explained. The coupled fluxes involve intricate interactions, and the regression analysis is less satisfactory in cases of low albedo values. However, over high-albedo surfaces, the terrain configuration factor becomes most dominant, leading to a significant improvement in regression performance. In these analyses, a surface albedo invariant with wavelength has been used. Using a region over the Sierra Nevada as a testbed, the preceding regression parameterizations have been specifically developed so that the fluxes evaluated from the 3-D Monte Carlo model over intense topography can be used as a perturbation term to correct those computed from the plane-parallel counterpart, commonly used in regional climate models and GCMs. © 2011 by the American Geophysical Union."
"35794588800;6603698240;57205842560;55915387400;7404747615;7202141884;6701679993;","Simulation of aerosol radiative effects over West Africa during DABEX and AMMA SOP-0",2011,"10.1029/2010JD014829","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955068350&doi=10.1029%2f2010JD014829&partnerID=40&md5=315cb35fda3b94d191d15e24c29fde7f","The regional climate model RegCM3 has been used to assess optical properties and clear-sky direct radiative forcing (DRF) of mineral dust and carbonaceous aerosols over West Africa for the period October 2005 to April 2006. Our results display a significant seasonal variation of the aerosol single scattering albedo (SSA) due to varying contributions from biomass burning (BB) and dust. During December-January, simulated SSA values dropped to around 0.81-0.83 at 440 nm and to 0.80-0.85 at 675 nm when absorbing aerosols from biomass burning dominate the mixture. During March and April, when mineral dust dominates, simulated SSA values increased reaching around 0.90-0.92 at 440 nm and 0.94-0.96 at 675 nm. The simulated aerosol optical thickness (AOT) was maximum over central Africa where it far exceeded estimates of AOT from satellite which showed the greatest AOT in the gulf of Guinea. This discrepancy was linked to an overestimation of BB emissions in central Africa and a possible underestimation of AOT over central Africa due a high occurrence of cloud and associated difficulties in cloud screening. The DRF calculations were extremely sensitive to aerosol optical properties and underlying surface albedo. Over dark surfaces, the sum of shortwave (SW) and longwave (LW) top of the atmosphere (TOA) direct radiative forcing averaged from December to February was negative (-5.25 to -4.0 W/m2) while over bright surfaces it was close to zero (-0.15 W/m2). Large differences between SW surface and SW TOA direct radiative forcing indicated that SW absorption had an important influence on the radiative budget. The SW radiative heating rate associated with the aerosol reached 1.2 K/d at local noon (diurnal mean of 0.40 K/d) over Niamey (∼13.5°N, 2°E) and peaked at altitudes of 2-4 km, corresponding to the BB aerosol layer. Copyright 2011 by the American Geophysical Union."
"34976900400;8105442200;57210240500;36544937700;6506121213;35318562800;6506534909;7401511851;57202637284;","Investigations on the physical and optical properties of cirrus clouds and their relationship with ice nuclei concentration using LIDAR at Gadanki, India (13.5°N, 79.2°E)",2011,"10.1117/1.3662877","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855233896&doi=10.1117%2f1.3662877&partnerID=40&md5=fe3513c5fb474a7b2e01c20bca3ca987","Cirrus cloud measurements over the tropics are receiving much attention recently due to their role in the Earth's radiation budget. The interaction of water vapor and aerosols plays a major role in phase formation of cirrus clouds. Many factors control the ice supersaturation and microphysical properties in cirrus clouds and, as such, investigations on these properties of cirrus clouds are critical for proper understanding and simulating the climate. In this paper we report on the evolution, microphysical, and optical properties of cirrus clouds using the Mie LIDAR operation at the National Atmospheric Research Laboratory, Gadanki, India (13.5°N, 79.2°E), an inland tropical station. The occurrence statistics, height, optical depth, depolarization ratio of the cirrus clouds, and their relationship with ice nuclei concentration were investigated over 29 days of observation during the year 2002. Cirrus clouds with a base altitude as low as 8.4 km are observed during the month of January and clouds with a maximum top height of 17.1 km are observed during the month of May. The cirrus has a mean thickness of 2 km during the period of study. The LIDAR ratio varies from 30 to 36 sr during the summer days of observation and 25 to 31 sr during the winter days of observation. Depolarization values range from 0.1 to 0.58 during the period of observation. The ice nuclei concentration has been calculated using the De Motts equation. It is observed that during the monsoon months of June, July, and August, there appears to be an increase in the ice nuclei number concentration. From the depolarization data an attempt is made to derive the ice crystal orientation and their structure of the cirrus. Crystal structures such as thin plates, thick plates, regular hexagons, and hexagonal columns are observed in the study. From the observed crystal structure and ice nuclei concentration, the possible nucleation mechanism is suggested. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE)."
"16444028600;57209647985;6701378450;6602715033;7202050065;7005284577;6603735912;7004643405;57203776263;6602496366;23027558200;7403384594;6701455725;7202558218;7006025236;","Airborne cloud condensation nuclei measurements during the 2006 Texas Air Quality Study",2011,"10.1029/2010JD014874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955383528&doi=10.1029%2f2010JD014874&partnerID=40&md5=e797b1cb52139ffcd0672c302593c555","Airborne measurements of aerosol and cloud condensation nuclei (CCN) were conducted aboard the National Oceanic and Atmospheric Administration WP-3D platform during the 2006 Texas Air Quality Study/Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS/GoMACCS). The measurements were conducted in regions influenced by industrial and urban sources. Observations show significant local variability of CCN activity (CCN/CN from 0.1 to 0.5 at s = 0.43%), while variability is less significant across regional scales (∼100 km × 100 km; CCN/CN is ∼0.1 at s = 0.43%). CCN activity can increase with increasing plume age and oxygenated organic fraction. CCN measurements are compared to predictions for a number of mixing state and composition assumptions. Mixing state assumptions that assumed internally mixed aerosol predict CCN concentrations well. Assuming organics are as hygroscopic as ammonium sulfate consistently overpredicted CCN concentrations. On average, the water-soluble organic carbon (WSOC) fraction is 60 ± 14% of the organic aerosol. We show that CCN closure can be significantly improved by incorporating knowledge of the WSOC fraction with a prescribed organic hygroscopicity parameter (κ = 0.16 or effective κ ∼ 0.3). This implies that the hygroscopicity of organic mass is primarily a function of the WSOC fraction. The overall aerosol hygroscopicity parameter varies between 0.08 and 0.88. Furthermore, droplet activation kinetics are variable and 60% of particles are smaller than the size characteristic of rapid droplet growth. Copyright 2011 by the American Geophysical Union."
"7004057920;55714098700;","Factors controlling CO2 exchange in a middle latitude forest",2011,"10.1029/2010JD015428","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755126977&doi=10.1029%2f2010JD015428&partnerID=40&md5=2279aede794785673ff81ddc1b1132e4","The forest carbon uptake experiences a relatively steady state, in which both radiation use efficiency and Bowen ratio exhibit relatively small change in tendency during the middle growing season at a deciduous forest in New England. The net ecosystem exchange (NEE) during the steady state varies from 2.1 to 5.1 Mg C Ha-1 y-1, accounting for 58-83% of the annual amount over 1992-2004. The cloudiness, combined with the effect of antecedent accumulated precipitation from late January, plays a key role in controlling interannual fluctuations of the steady state GEE and NEE among other environmental factors, and determines the long-term trend of the site GEE and NEE. These two factors account for 74% of the interannual variability of forest carbon uptake for the steady state, and 58% for the entire growing season, respectively. This suggests that winter precipitation and summer clouds probably play a key role in regulating the carbon uptake, an important mechanism of the carbon cycle/climate interaction. Copyright 2011 by the American Geophysical Union."
"23035769400;36182839400;36182891800;35190053100;23487729100;56812479700;","Strategy for the meteorological and environmental airborne observations over the Korean Peninsula",2011,"10.1007/s13143-011-1005-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951804596&doi=10.1007%2fs13143-011-1005-8&partnerID=40&md5=8e80ef3881b28f394a133e44e203a8e0","Aircraft campaigns for the meteorological and environmental research have been conducted in regional and global scales. The aircraft is increasingly considered as one of the best platforms to get the atmospheric three-dimensional information, especially over sea. We discuss the airborne observation plan and payloads designed for the aircraft campaigns over the Korean Peninsula. The main goals of the campaigns are to (i) conduct precipitation (snow) enhancement experiments with observations of the microphysical properties of clouds, dominantly in winter, (ii) monitor the severe weather generally in summer, (iii) characterize the climate change composition and the outflow of pollution from the Asian continent of the troposphere over the Korean Peninsula generally in spring or fall, and (iv) validate satellite and ground-based remote measurements of tropospheric composition generally in spring or fall. © 2011 Korean Meteorological Society and Springer."
"56127418900;56537463000;7404829395;","Regional simulations of deep convection and biomass burning over South America: 2. Biomass burning aerosol effects on clouds and precipitation",2011,"10.1029/2011JD016106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053082153&doi=10.1029%2f2011JD016106&partnerID=40&md5=a3cdc09d41c3b95ee517aece2221ac6e","A fully coupled meteorology-chemistry-aerosol mesoscale model (WRF-Chem) is used to simulate a multiday biomass burning event in the dry season of South America. The effects of biomass burning aerosols on clouds and precipitation are described at both 36 km and 4 km horizontal resolutions. The dominant effect of the aerosols is to reduce the diurnal amplitude of convection by decreasing clouds and precipitation in the afternoon but increasing them at night, with the afternoon decrease greater than the nighttime increase on the daily mean. On average, the decrease of surface precipitation is about 5% (3%) and the amplitude of diurnal cycle is reduced by about 11% (5%) in the 36 km (4 km) simulations. Such a modulation of clouds and precipitation is primarily contributed by the aerosol radiative effect, i.e., their ability to scatter and absorb solar radiation. The aerosol microphysical effect as cloud condensation nuclei tends to act oppositely to the aerosol radiative effect but with a smaller magnitude, especially in the simulations at 36 km horizontal resolution. The 4 km resolution runs exhibit similar behaviors to the 36 km simulations, with a slightly stronger role of the aerosol microphysical effect relative to the aerosol radiative effect. We find another important effect of biomass burning aerosols. When uplifted into the upper troposphere by deep convection, they can significantly warm the upper troposphere through their local radiative heating effect and result in significant moistening in the upper troposphere, potentially affecting the water vapor transport from the troposphere to the stratosphere. Copyright 2011 by the American Geophysical Union."
"36443431900;7006450978;55684491100;","Modeling the flash rate of thunderstorms. Part II: Implementation",2011,"10.1175/MWR-D-10-05032.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81355139179&doi=10.1175%2fMWR-D-10-05032.1&partnerID=40&md5=da3f3a33725f60bd360aad1eee58947c","In Part I of this two-part paper a new method of predicting the total lightning flash rate in thunderstorms was introduced. In this paper, the implementation of this method into the convection-permitting Consortium for Small Scale Modeling (COSMO) model is presented. The new approach is based on a simple theoretical model that consists of a dipole charge structure, which is maintained by a generator current and discharged by lightning and, to a small extent, by a leakage current. This approach yields a set of four predictor variables, which are not amenable to direct observations and consequently need to be parameterized (Part I). Using an algorithm that identifies thunderstorm cells and their properties, this approach is applied to determine the flash frequency of every thunderstorm cell in the model domain. With this information, the number of flashes that are accumulated by each cell and during the interval between the activation of the lightning scheme can be calculated. These flashes are then randomly distributed in time and beneath each cell. The output contains the longitude, the latitude, and the time of occurrence of each simulated discharge. Simulations of real-world scenarios are presented, which are compared to measurements with the lightning detection network, LINET. These comparisons are done on the cloud scale as well as in a mesoscale region composing southern Germany (two cases each). The flash rates of individual cumulonimbus clouds at the extreme ends of the intensity spectrum are realistically simulated. The simulated overall lightning activity over southern Germany is dominated by spatiotemporal displacements of the modeled convective clouds, although the scheme generally reproduces realistic patterns such as coherent lightning swaths. © 2011 American Meteorological Society."
"6508260037;15725317300;6701615913;6506393061;56495928700;7004089395;7006506461;","Satellite monitoring of the biomass-burning aerosols during the wildfires of August 2007 in Greece: Climate implications",2011,"10.1016/j.atmosenv.2010.09.043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751581957&doi=10.1016%2fj.atmosenv.2010.09.043&partnerID=40&md5=22d541b1544429c0b1889d454f4247a8","Biomass burning and associated emissions of aerosols into the atmosphere play a vital role in atmospheric composition and climate change. During summer of 2007, Greece faced the worst natural disaster recorded in recent decades in terms of human losses, number of fire outbreaks and extent of the estimated burned area (more than 12% of the total forested areas in Greece). The present study aims at analyzing the impact of these fire events in western Peloponnese on atmospheric aerosol concentrations using satellite data. MODIS-derived Aerosol Optical Depth (AOD), effective radius, Ångström exponent, mass concentration, cloud-condensation nuclei (CCN) and OMI Aerosol Index (AI), single scattering albedo, absorption and extinction optical depths were analyzed. MODIS data showed smoke plumes traversing thousands of kilometers southwards influencing the central Mediterranean as well as the north African coastal regions. These thick smoke plumes dramatically affected AOD and aerosol-mass concentrations over the region and altered the microphysical aerosol properties, such as the effective radius and absorption coefficient. Model calculations suggested that the shortwave radiation at the ground was reduced by ∼50 Wm2, while that at the top of the atmosphere was reduced by ∼20 Wm2 resulting in atmospheric heating of ∼30 Wm2 over the areas affected by the smoke plumes. © 2010 Elsevier Ltd."
"36141391900;7202226478;6701752471;7003843648;7003674085;","Climatological characteristics of Arctic and Antarctic surface-based inversions",2011,"10.1175/2011JCLI4004.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052759640&doi=10.1175%2f2011JCLI4004.1&partnerID=40&md5=95c39a32be778308a5c79e0e46ed053c","Surface-based inversions (SBIs) are frequent features of the Arctic and Antarctic atmospheric boundary layer. They influence vertical mixing of energy, moisture and pollutants, cloud formation, and surface ozone destruction. Their climatic variability is related to that of sea ice and planetary albedo, important factors in climate feedback mechanisms. However, climatological polar SBI properties have not been fully characterized nor have climate model simulations of SBIs been compared comprehensively to observations. Using 20 years of twice-daily observations from 39 Arctic and 6 Antarctic radiosonde stations, this study examines the spatial and temporal variability of three SBI characteristic-frequency of occurrence, depth (from the surface to the inversion top), and intensity (temperature difference over the SBI depth)-and relationships among them. In both polar regions, SBIs are more frequent, deeper, and stronger in winter and autumn than in summer and spring. In the Arctic, these tendencies increase from the Norwegian Sea eastward toward the East Siberian Sea, associated both with (seasonal and diurnal) variations in solar elevation angle at the standard radiosonde observation times and with differences between continental and maritime climates. Two state-of-the-art climate models and one reanalysis dataset show similar seasonal patterns and spatial distributions of SBI properties as the radiosonde observations, but with biases in their magnitudes that differ among the models and that are smaller in winter and autumn than in spring and summer. SBI frequency, depth, and intensity are positively correlated, both spatially and temporally, and all three are anticorrelated with surface temperature. © 2011 American Meteorological Society."
"7006075455;7406741310;7404655255;10144959100;7408202424;6506702878;7202302369;7005616409;55740124200;","Radiometric performance of the CERES earth radiation budget climate record sensors on the EOS Aqua and Terra spacecraft through April 2007",2011,"10.1175/2010JTECHA1521.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952288213&doi=10.1175%2f2010JTECHA1521.1&partnerID=40&md5=e1ae8099fbfc12a213cd0fa429462712","The Clouds and the Earth's Radiant Energy System (CERES) flight models 1 through 4 instruments were launched aboard NASA's Earth Observing System (EOS) Terra and Aqua spacecraft into 705-km sunsynchronous orbits with 10:30 p.m. and 1:30 a.m. local time equatorial crossing times. With these instruments CERES provides state-of-the-art observations and products related to the earth's radiation budget at the top of the atmosphere (TOA). The archived CERES science data products consist of geolocated and calibrated instantaneous filtered and unfiltered radiances through temporally and spatially averaged TOA, surface, and atmospheric fluxes.CERES-filtered radiance measurements cover three spectral bands: shortwave (0.3-5 μm), total (0.3.100 μm), and an atmospheric window channel (8-12 μm). CERES climate data products realize a factor of 2-4 improvement in calibration accuracy and stability over the previotus Earth Radiation Budget Experiment (ERBE) products. To achieve this improvement there are three editions of data products. Edition 1 generates data products using gain coefficients derived from ground calibrations. After a minimum of four months, the calibration data are examined to remove drifts in the calibration. The data are then reprocessed to produce the edition 2 data products. These products are available for science investigations for which an accuracy of 2% is sufficient. Also, a validation protocol is applied to these products to find problems and develop solutions, after which edition 3 data products will be computed, for which the objectives are calibration stability of better than 0.2% and calibration traceability from ground to flight of 0.25%. This paper reports the status of the radiometric accuracy and stability of the CERES edition 2 instrument data products through April 2007. © 2011 American Meteorological Society."
"12786571000;6701527006;6603724288;","Stable carbon isotopes in tree rings indicate improved water use efficiency and drought responses of a tropical dry forest tree species",2011,"10.1007/s00468-010-0474-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651413104&doi=10.1007%2fs00468-010-0474-1&partnerID=40&md5=ae5ebaf977860aa066e9d9d05aae5ae0","Understanding the responses of tropical trees to increasing [CO2] and climate change is important as tropical forests play an important role in carbon and hydrological cycles. We used stable carbon isotopes (δ13C) in tree rings to study the physiological responses of a tropical dry forest tree species in southern Mexico, Mimosa acantholoba to changes in atmospheric [CO2] and variation in climate. Based on annual records of tree ring δ13C, we calculated intrinsic water use efficiency (Wi) and intercellular [CO2] (ci). Our results showed that trees responded strongly to the increase in atmospheric [CO2] over the last four decades; Wi increased dramatically by 40%, while ci remained largely constant. The maintenance of a constant ci indicates that photosynthetic rates are unlikely to have increased in response to higher [CO2], and that improvements in Wi are probably due to a reduction in stomatal conductance. This may have large consequences for the hydrological cycle. Inter-annual variation in ci was strongly correlated with total annual rainfall (r = 0.70), and not influenced by temperature, solar radiation or cloud cover. Our results show that δ13C in tree rings of tropical dry forest trees may be a powerful tool to evaluate long-term responses of trees to increasing [CO2] and to variation in climate. © 2010 Springer-Verlag."
"36183369000;6603955973;7102063144;","Use of Atmospheric Infrared Sounder clear-sky and cloud-cleared radiances in the Weather Research and Forecasting 3DVAR assimilation system for mesoscale weather predictions over the Indian region",2011,"10.1029/2011JD016379","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82355181436&doi=10.1029%2f2011JD016379&partnerID=40&md5=734a0006ee1b77f9f199a097cdcf98b3","A set of assimilation experiments is conducted with the Three-Dimensional Variational (3DVAR) data assimilation system associated with the Weather Research and Forecasting (WRF) model. The purpose of the investigation is to assess the impact on forecast skill in response to assimilation of the Atmospheric Infrared Sounder (AIRS) clear-sky and cloud-cleared radiances over the Indian region. This is the first study that makes use of cloud-cleared radiances in the WRF system. Two sets of thirty-one 72 h forecasts are performed, all initialized at 00:00 UTC each day throughout the month of July 2010, to compare the model performance consequent to assimilation of clear-sky versus cloud-cleared radiances. A rigorous validation is produced against National Centers for Environmental Prediction analyzed wind, temperature, and moisture. In addition, the precipitation forecast skill is assessed against Tropical Rainfall Measuring Mission observations. The results show improvement in forecast skill consequent to the assimilation of cloud-cleared radiances (CCR). The implications of using CCR for operational weather forecasting appear to be significant. Since only a small fraction of AIRS channels are cloud-free, information obtained in cloudy regions, which is meteorologically very significant, is lost when assimilating only clear-sky radiances (CSR). On the contrary, assimilation of CCR allows a larger yield, which leads to improved model performance. The assimilation of CCR resulted in significantly improved rainfall prediction compared to that obtained from the use of CSR. The finding of this study clearly shows the advantage of CCR available from clear-sky as well as from partly cloudy regions as compared to CSR, which are available only in clear-sky regions. Copyright 2011 by the American Geophysical Union."
"7401559815;7405584618;","Climatology and changes in tropical oceanic rainfall characteristics inferred from Tropical Rainfall Measuring Mission (TRMM) data (1998-2009)",2011,"10.1029/2011JD015827","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053077595&doi=10.1029%2f2011JD015827&partnerID=40&md5=464598967aa2e51eaffd043969e77470","This study investigates the climatological and changing characteristics of tropical rain and cloud systems in relation to sea surface temperature (SST) changes using Tropical Rainfall Measuring Mission (TRMM) data (1998-2009). Rainfall and cloud characteristics are determined from probability distribution functions (pdf), derived from daily TRMM Microwave Imager (TMI) and Precipitation Radar (PR) surface rain, Visible and Infrared Scanner (VIRS) brightness temperature (T<inf>b</inf>), and PR echo top height (H<inf>ET</inf>). Results show that the top 10% heavy rain is associated with cold cloud tops (T<inf>b</inf> < 220 K) and elevated echo top heights (H<inf>ET</inf> > 6 km), associated with ice phase rain in the Intertropical Convergence Zone and monsoon regions. The bottom 5% light rain occurs most frequently in the subtropics and also in the warm pool regions with low cloud top (T<inf>b</inf> > 273 K) and H<inf>ET</inf> ∼ 1-4 km. Intermediate rain (25th to 75th percentile) is contributed by a wide range of middle clouds and mixed-phase rain centered at T<inf>b</inf> ∼ 230-260 K and H<inf>ET</inf> ∼ 4-6 km within the warm pool. The relationships between rainfall and SST depend strongly on rain types. We find that a warmer tropical ocean favors a large increase in annual heavy rain accumulation, a mild reduction in light to moderate rain, and a slight increase in extremely light rain. The annual accumulation of extreme heavy rain increases approximately 80%-90% for every degree rise in SST, much higher than that expected from the Clausius-Clapeyron equation for global water balance. This is possibly because heavy rain is only a component of the tropical water cycle and is strongly associated with ice phase processes and convective dynamics feedback. Copyright 2011 by the American Geophysical Union."
"7201410870;","Meteorological data from numerical weather prediction or observations for dispersion modelling",2011,"10.1504/IJEP.2011.038405","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79751519602&doi=10.1504%2fIJEP.2011.038405&partnerID=40&md5=b8b2c6301e6d98071470266f6532f9c1","Synoptic observations of wind speed, direction, cloud cover, precipitation and temperature are inputs to regulatory dispersion modelling. Numerical Weather Prediction (NWP) data generated by national meteorological services are easily formatted for dispersion models. Changing from observations to NWP data raises concerns amongst regulators and model users - how might impact assessments differ if the source of meteorological data is changed. It is important to identify factors influencing the acceptability of NWP data. This paper compares numerical and surface synoptic meteorological data at locations across the UK. Further work is needed to harmonise the regulatory use of meteorological data. Copyright © 2011 Inderscience Enterprises Ltd."
"23480385400;7201837768;","Regional climate consequences of large-scale cool roof and photovoltaic array deployment",2011,"10.1088/1748-9326/6/3/034001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053503598&doi=10.1088%2f1748-9326%2f6%2f3%2f034001&partnerID=40&md5=42487fe51aff5ea34c42527a33b7b0f5","Modifications to the surface albedo through the deployment of cool roofs and pavements (reflective materials) and photovoltaic arrays (low reflection) have the potential to change radiative forcing, surface temperatures, and regional weather patterns. In this work we investigate the regional climate and radiative effects of modifying surface albedo to mimic massive deployment of cool surfaces (roofs and pavements) and, separately, photovoltaic arrays across the United States. We use a fully coupled regional climate model, the Weather Research and Forecasting (WRF) model, to investigate feedbacks between surface albedo changes, surface temperature, precipitation and average cloud cover. With the adoption of cool roofs and pavements, domain-wide annual average outgoing radiation increased by 0.16 0.03Wm-2 (mean 95% C.I.) and afternoon summertime temperature in urban locations was reduced by 0.11-0.53 °C, although some urban areas showed no statistically significant temperature changes. In response to increased urban albedo, some rural locations showed summer afternoon temperature increases of up to + 0.27 °C and these regions were correlated with less cloud cover and lower precipitation. The emissions offset obtained by this increase in outgoing radiation is calculated to be 3.3 0.5Gt CO2 (mean 95% C.I.). The hypothetical solar arrays were designed to be able to produce one terawatt of peak energy and were located in the Mojave Desert of California. To simulate the arrays, the desert surface albedo was darkened, causing local afternoon temperature increases of up to + 0.4 °C. Due to the solar arrays, local and regional wind patterns within a 300km radius were affected. Statistically significant but lower magnitude changes to temperature and radiation could be seen across the domain due to the introduction of the solar arrays. The addition of photovoltaic arrays caused no significant change to summertime outgoing radiation when averaged over the full domain, as interannual variation across the continent obscured more consistent local forcing. © 2011 IOP Publishing Ltd."
"6505906590;8303142200;7102767303;","Challenges of satellite rainfall estimation over mountainous and arid parts of east africa",2011,"10.1080/01431161.2010.499381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82055185083&doi=10.1080%2f01431161.2010.499381&partnerID=40&md5=c99b9b94079a57876d9d6366ea17283c","Different satellite rainfall products are used in different applications over different parts of the world. These products are particularly important over many parts of Africa, where they are used to augment the very sparse rain-gauge network. However, the quality of the different satellite products varies from one product to another and from one climatic region to another. The climate over eastern Africa varies from wet coastal and mountainous regions to dry arid regions. Significant variations could be observed within short distances. The different climates will pose different challenges to satellite rainfall retrieval over this region. This study explores the effect of mountainous and arid climates on four different satellite rainfall-estimation (RFE) algorithms. The mountainous climate is located over the Ethiopian highlands, while the arid region covers parts of Ethiopia, Djibouti and Somalia. One infrared-only product, African rainfall climatology (ARC), one passive-microwave-only product (the Climate Prediction Center morphing technique, CMORPH) and two products (the RFE algorithm and the tropical rainfall measuring mission (TRMM-3B42)), which combine both infrared and passive-microwave estimates, are used for this investigation. All the products exhibit moderate underestimation of rainfall over the highlands of Ethiopia, while the overestimation over the dry region is found to be very high. The underestimation over the mountainous region is ascribed to the warm orographic rain process, while the overestimation over the dry region may be because of sub-cloud evaporation. Local calibration of satellite algorithms and merging of satellite estimates with all locally available rain-gauge observations are some of the approaches that could be employed to alleviate these problems. © 2011 Taylor & Francis."
"23978587100;55188785600;6602931316;36453305000;56315880100;22633932300;34571084000;","Local-scale Urban Meteorological Parameterization Scheme (LUMPS): Longwave radiation parameterization and seasonality-related developments",2011,"10.1175/2010JAMC2474.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751686901&doi=10.1175%2f2010JAMC2474.1&partnerID=40&md5=c000b9a34dcf5f08d78e3d4fc01248e1","Recent developments to the Local-scale Urban Meteorological Parameterization Scheme (LUMPS), a simple model able to simulate the urban energy balance, are presented. The major development is the coupling of LUMPS to the Net All-Wave Radiation Parameterization (NARP). Other enhancements include that the model now accounts for the changing availability of water at the surface, seasonal variations of active vegetation, and the anthropogenic heat flux, while maintaining the need for only commonly available meteorological observations and basic surface characteristics. The incoming component of the longwave radiation (L↓) inNARP is improved through a simple relation derived using cloud cover observations froma ceilometer collected in central London, England. The new L↓ formulation is evaluated with two independent multiyear datasets (Łódź, Poland, and Baltimore, Maryland) and compared with alternatives that include the original NARP and a simpler one using the National Climatic Data Center cloud observation database as input. The performance for the surface energy balance fluxes is assessed using a 2-yr dataset (Łódź). Results have an overallRMSE,34 W m-2 for all surface energy balance fluxes over the 2-yr period when usingLY as forcing, and RMSE , 43 W m-2 for all seasons in 2002 with all other options implemented to model L↓. © 2011 American Meteorological Society."
"55544443300;7004060399;","The interannual relationship between the latitude of the eddy-driven jet and the edge of the Hadley cell",2011,"10.1175/2010JCLI4077.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79851495476&doi=10.1175%2f2010JCLI4077.1&partnerID=40&md5=2f00b710e18bc36c1049c8eebe50ee84","Astrong correlation between the latitudes of the eddy-driven jet and of the Hadley cell edge, on interannual time scales, is found to exist during austral summer, in both the NCEP-NCAR reanalysis and the models participating in the Coupled Model Intercomparison Project, phase 3 (CMIP3). In addition, a universal ratio close to 1:2 characterizes the robust connection between these two latitudes on a year-to-year basis: for a 2° shift of the eddy-driven jet, the edge of the Hadley cell shifts by 1°. This 1:2 interannual ratio remains the same in response to climate change, even though the values of the two latitudes increase. The corresponding trends are also highly correlated; in the CMIP3 scenario integrations, however, no universal ratio appears to exist connecting these long-term trends. In austral winter and in the Northern Hemisphere, no strong interannual correlations are found. © 2011 American Meteorological Society."
"57197599584;7006392180;7006435011;10144282600;36619476000;6603785227;","Monitoring the transport of biomass burning emission in South America",2011,"10.5094/APR.2011.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882801731&doi=10.5094%2fAPR.2011.031&partnerID=40&md5=3fdc27142d65c410a807fbf0de32d2d9","The main objective of this work is to use Fire Radiative Power (FRP) to estimate particulate matter with diameter less than 2.5 μm (PM2.5) and carbon monoxide (CO) emissions for the South America 2002 burning season. Sixteen small-scale combustion experiments were performed near the Laboratory of Radiometry (LARAD) at the National Institute for Space Research (DSR/INPE) to obtain the coefficient that relates the biomass consumption with the FRP released. The fire products MOD14/MYD14 from the MODIS Terra/Aqua platforms and the Wildfire Automated Biomass Burning Algorithm (WFABBA) on the Geostationary Operational Environmental Satellite (GOES) were utilized to calculate the total amount of biomass burned. This inventory is modeled in the Coupled Chemistry- Aerosol-Tracer Transport model coupled to the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS) and compared with data collected in the Large Scale Biosphere-Atmosphere (LBA) Smoke, Aerosols, Clouds, rainfall, and Climate (SMOCC) and Radiation, Cloud, and Climate Interactions (RaCCI) Experiments. The relationship between the modeled PM2.5 and CO shows a good agreement with SMOCC/RaCCI data in the general pattern of temporal evolution. The results showed high correlations, with values between 0.80 and 0.95 (significant at 0.05 level by student t-test), for the CCATT-BRAMS simulations with PM2.5 and CO. Furthermore, the slope analysis reveals an underestimation of emission values with CCATT-BRAMS modeled values, 20-30% lower than observed data with discrepancies mainly on days with large fires. However, the underestimation is similar to the uncertainties in traditional emissions methods. © Author(s) 2011."
"7202048112;8042408300;55802246600;56438411600;","Climate-soil-vegetation control on groundwater table dynamics and its feedbacks in a climate model",2011,"10.1007/s00382-010-0746-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651104999&doi=10.1007%2fs00382-010-0746-x&partnerID=40&md5=342e393f315ed43a19640ded67a023f8","Among the three dynamically linked branches of the water cycle, including atmospheric, surface, and subsurface water, groundwater is the largest reservoir and an active component of the hydrologic system. Because of the inherent slow response time, groundwater may be particularly relevant for long time-scale processes such as multi-years or decadal droughts. This study uses regional climate simulations with and without surface water-groundwater interactions for the conterminous US to assess the influence of climate, soil, and vegetation on groundwater table dynamics, and its potential feedbacks to regional climate. Analyses show that precipitation has a dominant influence on the spatial and temporal variations of groundwater table depth (GWT). The simulated GWT is found to decrease sharply with increasing precipitation. Our simulation also shows some distinct spatial variations that are related to soil porosity and hydraulic conductivity. Vegetation properties such as minimum stomatal resistance, and root depth and fraction are also found to play an important role in controlling the groundwater table. Comparing two simulations with and without groundwater table dynamics, we find that groundwater table dynamics mainly influences the partitioning of soil water between the surface (0-0.5 m) and subsurface (0.5-5 m) rather than total soil moisture. In most areas, groundwater table dynamics increases surface soil moisture at the expense of the subsurface, except in regions with very shallow groundwater table. The change in soil water partitioning between the surface and subsurface is found to strongly correlate with the partitioning of surface sensible and latent heat fluxes. The evaporative fraction (EF) is generally higher during summer when groundwater table dynamics is included. This is accompanied by increased cloudiness, reduced diurnal temperature range, cooler surface temperature, and increased cloud top height. Although both convective and non-convective precipitation are enhanced, the higher EF changes the partitioning to favor more non-convective precipitation, but this result could be sensitive to the convective parameterization used. Compared to simulations without groundwater table dynamics, the dry bias in the summer precipitation is slightly reduced over the central and eastern US Groundwater table dynamics can provide important feedbacks to atmospheric processes, and these feedbacks are stronger in regions with deeper groundwater table, because the interactions between surface and subsurface are weak when the groundwater table is deep. This increases the sensitivity of surface soil moisture to precipitation anomalies, and therefore enhances land surface feedbacks to the atmosphere through changes in soil moisture and evaporative fraction. By altering the groundwater table depth, land use change and groundwater withdrawal can alter land surface response and feedback to the climate system. © 2010 The Author(s)."
"36976449700;7102080550;35351704600;57205299261;57205303892;","The analysis and prediction of the 8-9 May 2007 Oklahoma tornadic mesoscale convective system by assimilating WSR-88D and CASA radar data using 3DVAR",2011,"10.1175/2010MWR3336.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951649710&doi=10.1175%2f2010MWR3336.1&partnerID=40&md5=a16bb51aa288e7050561c496c3f11490","The Advanced Regional Prediction System (ARPS) model is employed to perform high-resolution numerical simulations of a mesoscale convective system and associated cyclonic line-end vortex (LEV) that spawned several tornadoes in central Oklahoma on 8-9 May 2007. The simulation uses a 1000 km × 1000 km domain with 2-km horizontal grid spacing. The ARPS three-dimensional variational data assimilation (3DVAR) is used to assimilate a variety of data types. All experiments assimilate routine surface and upperair observations as well as wind profiler and Oklahoma Mesonet data over a 1-h assimilation window. Asubset of experiments assimilates radar data. Cloud and hydrometeor fields as well as in-cloud temperature are adjusted based on radar reflectivity data through the ARPS complex cloud analysis procedure. Radar data are assimilated from the Weather Surveillance Radar-1988 Doppler (WSR-88D) network as well as from the Engineering Research Center for Collaborative and Adaptive Sensing of the Atmosphere (CASA) network of four X-band Doppler radars. Three-hour forecasts are launched at the end of the assimilation window. The structure and evolution of the forecast MCS and LEV are markedly better throughout the forecast period in experiments in which radar data are assimilated. The assimilation of CASA radar data in addition to WSR-88D data increases the structural detail of the modeled squall line and MCS at the end of the assimilation window, which appears to yield a slightly better forecast track of the LEV. © 2011 American Meteorological Society."
"18538088400;35331037200;7401492246;6602657653;7005890921;8950640300;10939473600;7004027519;22940851800;6603458409;56140087300;6603882582;57203231853;","Dimethyl sulfide air-sea fluxes and biogenic sulfur as a source of new aerosols in the Arctic fall",2011,"10.1029/2011JD016336","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055211781&doi=10.1029%2f2011JD016336&partnerID=40&md5=579ddc87fe6159c38bc65dbc7590e3de","Dimethyl sulfide (DMS) and its oxidation products, which have been proposed to provide a climate feedback mechanism by affecting aerosol and cloud radiative properties, were measured on board the Canadian Coast Guard ship Amundsen in sampling campaigns in the Arctic in the fall of 2007 and 2008. DMS flux was calculated based on the surface water measurements and yielded 0.1-2.6 mol m-2 d-1 along the Northwest Passage in 2007 and 0.2-1.3 mol m-2 d-1 along Baffin Bay in 2008. DMS oxidation products, sulfur dioxide (SO<inf>2</inf>), methane sulfonic acid (MSA), and sulfate in aerosols were also measured. The amounts of biogenic SO<inf>2</inf> and sulfate were approximated using stable isotope apportionment techniques. Calculating the threshold amount of SO<inf>2</inf> needed for significant new particle formation from the formulation by Pirjola et al. (1999), the study suggests that instances of elevated biogenic SO<inf>2</inf> concentrations (between 8 and 9 September 2008) derived using conservative assumptions may have been sufficient to form new aerosols in clean air conditions in the Arctic region. Copyright 2011 by the American Geophysical Union."
"6602809597;7102953444;","Aerosol emissions and dimming/brightening in Europe: Sensitivity studies with ECHAM5-HAM",2011,"10.1029/2011JD016227","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755180941&doi=10.1029%2f2011JD016227&partnerID=40&md5=190541c33af041b99458282282e8a77e","Observational data indicate a decrease of surface solar radiation (SSR) in Europe from about 1950 to the mid-1980s, followed by a renewed increase. Changing aerosol emissions have been suggested as a likely cause for this observed dimming and brightening. To quantify this hypothesis, we performed ensembles of transient sensitivity experiments with the global climate model ECHAM5-HAM, which includes interactive treatment of aerosols. The simulations cover the period 1950-2005 and use transient aerosol emissions (National Institute of Environmental Science, Japan) and prescribed sea surface temperatures (SSTs) from the Hadley Centre. The simulated clear-sky dimming and brightening can be attributed to changing aerosol emissions from fossil fuel combustion. Ensemble means of modeled SSR trends are in agreement with observed values. Dimming ceases too early in the model, around 1970. Potential causes are discussed. Brightening sets in at about the right time. Regional differences of modeled SSR are substantial, with clear-sky dimming trends ranging from-6.1 (eastern Europe) to-0.4 W m-2 decade-1 (British Isles) and brightening trends ranging from +1.3 to +6.3 W m-2 decade -1 (Scandinavia and eastern Europe). All-sky conditions show similar trends in the ensemble mean, but the spread among ensemble members is considerable, emphasizing the importance of clouds. Surface temperatures are found to depend mostly on the prescribed SSTs, with an additional aerosol component in some regions like eastern Europe. For precipitation, internal variability is too large to allow for any firm conclusions. Copyright 2011 by the American Geophysical Union."
"7004006601;8670472000;6603341831;6602547442;6507002117;7006665163;14325221500;57202917221;6602185880;6602178158;","The Rossby Centre Regional Climate model RCA3: Model description and performance",2011,"10.1111/j.1600-0870.2010.00478.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650111164&doi=10.1111%2fj.1600-0870.2010.00478.x&partnerID=40&md5=bc0b893a8c82ccff7af4d093c02bdb54","This paper describes the third full release of the Rossby Centre Regional Climate model (RCA3), with an emphasis on changes compared to earlier versions, in particular the introduction of a new tiled land-surface scheme. The model performance over Europe when driven at the boundaries by ERA40 reanalysis is discussed and systematic biases identified. This discussion is performed for key near-surface variables, such as temperature, precipitation, wind speed and snow amounts at both seasonal and daily timescales. An analysis of simulated clouds and surface turbulent and radiation fluxes is also made, to understand the causes of the identified biases. RCA3 shows equally good, or better, correspondence to observations than previous model versions at both analysed timescales. The primary model bias relates to an underestimate of the diurnal surface temperature range over Northern Europe, which maximizes in summer. This error is mainly linked to an overestimate of soil heat flux. It is shown that the introduction of an organic soil component reduces the error significantly. During the summer season, precipitation and surface evaporation are both overestimated over Northern Europe, whereas for most other regions and seasons precipitation and surface turbulent fluxes are well simulated. ©2010 The Authors Tellus A©2010 International Meteorological Institute in Stockholm."
"6507926049;55777759900;8700803100;7801433517;55578807504;","Troposphere and stratosphere influence on tropopause in the polar regions during winter and spring",2011,"10.1080/01431161.2010.541515","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960073247&doi=10.1080%2f01431161.2010.541515&partnerID=40&md5=556b2d62ed3909477dc15933de6c4cab","Arctic and Antarctic tropopause is formed under unique climate conditions, both in the troposphere and stratosphere. Individual patterns of polar tropopause anomalies are formed under dominance or competition of the tropospheric and stratospheric sources. We analyse the thermal tropopause climatology in the polar regions using National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) Reanalysis-1 data between 1979 and 2008. The role of the troposphere and stratosphere in tropopause anomaly distribution is examined using corresponding temperature and geopotential height fields. By location, the tropopause anomalies in the Arctic and Antarctic are closer to patterns of cold anomalies in the troposphere and stratosphere respectively. Results indicate that the 30-year climatological tropopause anomalies in polar winter and spring could have different relationships to troposphere and stratosphere influences, even in neighbouring parts of the polar atmosphere. © 2011 Taylor & Francis."
"7402483824;36646423500;23569301000;8430345000;36614328400;37012597400;","Performance of observation-based prediction algorithms for very short-range, probabilistic clear-sky condition forecasting",2011,"10.1175/2010JAMC2529.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951603054&doi=10.1175%2f2010JAMC2529.1&partnerID=40&md5=2ecdf02af5c0835136b46b8aeeb7103e","Very short-range sky condition forecasts are produced to support a variety of military, civil, and commercial activities. In this investigation, six advanced, observation (obs)-based prediction algorithms were developed and tested that generated probabilistic sky condition forecasts for 1-, 2-, 3-, 4-, and 5-h forecast intervals, for local and regional target types, in six geographic regions within the continental United States. Three of the methods were based on predictive learning algorithms including neural network, random forest, and regression tree. The other three methods were statistical techniques including a k-nearest neighbor algorithm, a classifier based on the Bayes decision rule, and a multialgorithm ensemble. The performances of these six algorithms were compared with forecasts from three benchmark methods: basic persistence, the climatological-expectancy-of-persistence, and satellite cloud climatology. The obs database for each forecast target was composed of a multiyear, half-hourly time series of atmospheric parameters that included cloud features extracted from weather satellite imagery and meteorological variables extracted or derived from data assimilation-based model analyses generated by NCEP's Eta Data Assimilation System. The performances of the advanced prediction algorithms exceeded those of the benchmarks at all five forecast intervals for both target types in all regions, on the basis of a group ofmetrics that included receiver operating characteristic score, sharpness, accuracy, expected best cost, and reliability. © 2011 American Meteorological Society."
"7201724034;7003499257;19337904400;7402331145;19337201300;37061989400;55858477800;44561045800;57202396417;36149741000;6603370049;8612652300;55619302054;36842329100;36017183900;12647654300;6505890285;26531444800;8604965200;55686667100;10241250100;10240710000;57201565982;8507223000;7102857642;","Impact of the assimilation of sea ice concentration data on an atmosphere-ocean-sea ice coupled simulation of the Arctic Ocean climate",2011,"10.2151/sola.2011-010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878308564&doi=10.2151%2fsola.2011-010&partnerID=40&md5=7f397e41a16b72687ad363b40320489c","We have investigated the effects of assimilating sea ice concentration (SIC) data on a simulation of Arctic Ocean climate using an atmosphere-ocean-sea ice coupled model. Our results show that the normal overestimation of summertime SIC in the East Siberian Sea and the Beaufort Sea in simulations without sea-ice data input can be greatly reduced by assimilating seaice data and that this improvement is also evident in a following hindcast experiment for 3-4 years after the initialization of the assimilation. In the hindcast experiment, enhanced heat storage in both sea ice and in the ocean surface layer plays a central role in improving the accuracy of the sea ice distribution, particularly in summer. Our detailed investigation suggests that the ice-albedo feedback and the feedback associated with the atmospheric pressure pattern generated by the improved estimation of SIC work more effectively to retain the heat signal after initialization for a coupled atmosphere-ocean-sea ice system prediction. In addition, comparison with field observations confirms that the model fails to produce a realistic feedback loop, which is (presumably) due to inadequacies in both the ice-cloud feedback model and the feedback via the Beaufort Gyre circulation. Further development of coupled models is thus required to better define Arctic Ocean climate processes and to improve the accuracy of their predictions. © 2011, the Meteorological Society of Japan."
"56135632400;7103294028;7101899854;26661481400;7005399437;7004672267;35463545000;","Susceptibility of aerosol optical thickness retrievals to thin cirrus contamination during the BASE-ASIA campaign",2011,"10.1029/2010JD014910","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955616296&doi=10.1029%2f2010JD014910&partnerID=40&md5=f44b7e2596d28cc7c90609dc489c3700","We used a combination of ground measurements (Aerosol Robotic Network, AERONET; Micro-Pulse Lidar Network, MPLNET) and satellite data (Moderate Resolution Imaging Spectroradiometer, MODIS; Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, CALIPSO) to examine the susceptibility of ground and satellite aerosol retrievals to thin cirrus contamination at Phimai, Thailand (102.56°E, 15.18°N, also known as Pimai), during the Biomass-burning Aerosols in South East-Asia: Smoke Impact Assessment (BASE-ASIA) campaign (February-May 2006). Using the strengths of spaceborne or ground lidars to detect cirrus clouds, we conducted statistical analyses for four different scenarios: MPLNET versus AERONET, MPLNET versus MODIS, CALIPSO versus AERONET, and CALIPSO versus MODIS. Cirrus identifications from MPLNET or CALIPSO were paired up with concurrent aerosol optical thickness (AOT) measurements from AERONET or MODIS. Results from the BASE-ASIA campaign suggest that current operational AERONET and MODIS AOT products are influenced by thin cirrus contamination featuring strong seasonality. Concurrent AERONET and MPLNET observations indicate that additional thin cirrus screening changes AOT monthly means by 5%, with 20% of the AERONET aerosol data at Phimai being cirrus contaminated in boreal spring. From noncirrus cases to cirrus-contaminated cases, AERONET AOT increases along with larger particle sizes. We further evaluated the performance of eight MODIS-derived cirrus screening parameters for their effectiveness on thin cirrus screening: apparent reflectance at 1.38 μm (R1.38), cirrus reflectance at 0.66 μm (CR0.66), CR0.66 cirrus flag, reflectance ratio between 1.38 μm and 0.66 μm (RR1.38/0.66), reflectance ratio between 1.38 μm and 1.24 μm (RR1.38/1.24), brightness temperature difference between 8.6 μm and 11 μm (BTD8.6-11), brightness temperature difference between 11 μm and 12 μm (BTD11-12), and cloud phase infrared approach. Correlation analysis with the MPLNET cirrus flag indicates that RR1.38/0.66 is slightly preferable for high thin cirrus screening for the AERONET AOT measurements. The quantitative findings from this study suggest particular caution and careful evaluation of thin cirrus contamination in the satellite and ground AOT measurements before they are used for aerosol-related climatic forcing studies. Copyright 2011 by the American Geophysical Union."
"7102591209;9043417100;7005729142;6506385754;","Using in situ estimates of ice water content, volume extinction coefficient, and the total solar optical depth obtained during the tropical ACTIVE campaign to test an ensemble model of cirrus ice crystals",2011,"10.1002/qj.731","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251517441&doi=10.1002%2fqj.731&partnerID=40&md5=6958de6f6162d1ddce2fdd9d00ab4fff","An ensemble model of cirrus ice crystals combined with a parametrized particle size distribution function (PSD) is used to predict the ice water content (IWC), column-integrated IWC (ice water path, IWP), volume extinction coeffi{ligature}cient, and the total solar optical depth, for fi{ligature}ve tropical cirrus cases. The PSD is estimated from the IWC and in-cloud temperature, and comparisons are presented between the ensemble model predictions and in situ estimates of these microphysical and macrophysical quantities. The in situ estimates were obtained during the Aerosol and Chemical Transport In tropical conVection (ACTIVE) campaign between November-December 2005 and January-February 2006, based at Darwin, Australia. The microphysical instrumentation deployed on the Airborne Australia Egrett research aircraft were the SPEC Cloud Particle Imaging (CPI) probe, Cloud and Aerosol Spectrometer (CAS) and Cloud Imaging Probe (CIP). The CPI was used to measure ice crystal size from about 5 to 1800 μm, ice crystal number concentration, and to estimate ice crystal shape, IWC, IWP, volume extinction coeffi{ligature}cient and the total solar optical depth. The CIP instrument was also used to measure ice crystal size from about 25 to 1550 μm, ice crystal number concentration and to estimate IWC. For all fl{ligature}ights the limited CPI shape recognition algorithm recorded that about 80% or greater of the ice crystal populations were composed of small irregular or 'quasi-spherical' ice crystals. The CPI- and CIP-estimated IWC distributions are compared against each other and it is shown that the distributions are not signifi{ligature}cantly diff{ligature}erent at the 95% level of confi{ligature}dence. The CPI-estimated averaged IWC ranged between approximately 5.3 and 98.2 mg m-3. The CPI-estimated IWP and total solar optical depth ranged between ∼1.0 ± 0.5 and 35.0 ± 17 g m-2 and between 0.1 ± 0.05 and 1.46 ± 0.73, respectively. To predict the IWC and IWP, an ensemble model eff{ligature}ective density-size relationship is derived, and it is shown that the uncertainty in the model predictions are generally within the uncertainty of the CPI estimates for all cases considered. It is also demonstrated that, when the CPI-estimated total solar optical depth is greater than unity, the ensemble model combined with the PSD scheme predicts an uncertainty in the volume extinction coeffi{ligature}cient and total solar optical depth that is within the CPI experimental range of uncertainty. However, for total solar optical depths much less than unity, the ensemble model combined with the PSD scheme does not generally predict an uncertainty in the volume extinction coeffi{ligature}cient and total solar optical depth that is within the lower range of the CPI uncertainty; the physical reason for this is further explored. The paper demonstrates that there is predictive value in combining an ensemble model of ice crystals with a universal PSD scheme to predict the microphysical and macrophysical properties of importance to radiative transfer through tropical cirrus. Moreover, in the case of very low IWC tropical cirrus, further characterization of the PSD is required using a number of in situ instruments. © Royal Meteorological Society and Crown Copyright, 2011."
"6603580448;6602890253;35396858200;7006497590;8261329600;35230757600;7006686129;35551376300;7006510465;7005891596;6506458269;57136469800;35390825100;","In situ measurements of tropospheric volcanic plumes in Ecuador and Colombia during TC4",2011,"10.1029/2010JD014718","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955895909&doi=10.1029%2f2010JD014718&partnerID=40&md5=797a9280bff327802a6d9d2b68f9f528","A NASA DC-8 research aircraft penetrated tropospheric gas and aerosol plumes sourced from active volcanoes in Ecuador and Colombia during the Tropical Composition, Cloud and Climate Coupling (TC4) mission in July-August 2007. The likely source volcanoes were Tungurahua (Ecuador) and Nevado del Huila (Colombia). The TC4 data provide rare insight into the chemistry of volcanic plumes in the tropical troposphere and permit a comparison of SO2 column amounts measured by the Ozone Monitoring Instrument (OMI) on the Aura satellite with in situ SO2 measurements. Elevated concentrations of SO2, sulfate aerosol, and particles were measured by DC-8 instrumentation in volcanic outflow at altitudes of 3-6 km. Estimated plume ages range from ∼2 h at Huila to ∼22-48 h downwind of Ecuador. The plumes contained sulfate-rich accumulation mode particles that were variably neutralized and often highly acidic. A significant fraction of supermicron volcanic ash was evident in one plume. In-plume O3 concentrations were ∼70%-80% of ambient levels downwind of Ecuador, but data are insufficient to ascribe this to O3 depletion via reactive halogen chemistry. The TC4 data record rapid cloud processing of the Huila volcanic plume involving aqueous-phase oxidation of SO2 by H 2O2, but overall the data suggest average in-plume SO 2 to sulfate conversion rates of ∼1%-2% h-1. SO 2 column amounts measured in the Tungurahua plume (∼0.1-0.2 Dobson units) are commensurate with average SO2 columns retrieved from OMI measurements in the volcanic outflow region in July 2007. The TC 4 data set provides further evidence of the impact of volcanic emissions on tropospheric acidity and oxidizing capacity. Copyright 2011 by the American Geophysical Union."
"54788302000;6603800142;6602584093;","Evaluating the observed variability in hyperspectral Earth-reflected solar radiance",2011,"10.1029/2011JD016448","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055216862&doi=10.1029%2f2011JD016448&partnerID=40&md5=93d0789d211519a508f31b8163b7701d","We explore the potential for directly measured hyperspectral Earth-reflected solar radiances to provide sufficient information to study changes in Earth's climate based on the quantified variability of the data using principal component analysis (PCA) and singular spectrum analysis. To do this we used these two multivariate analysis techniques on Earth-reflected radiances between 300 and 1750 nm measured from space by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instrument. The spatial and temporal variability of hyperspectral reflected radiances over global, hemispherical, and regional scales was quantified. As few as six components were needed to explain over 99.5% of the variance in all cases studied, with the exception of an Arctic Ocean case in which only four components were needed. Both of these values represent large reductions in dimensionality of the input radiances from 291 spectral bands. PCA facilitated attribution of the dominant spectral patterns extracted to atmospheric and surface variables, including water vapor, clouds, surface albedo, and sea ice. The second most dominant spectral variable, that is, the second principal component, in the Arctic closely resembled sea ice reflectance and followed the temporal behavior of sea ice extent determined from AMSR-E observations. The extraction of the spectral, spatial, and temporal variability in reflected shortwave hyperspectral radiance using multivariate analysis provides an alternate and complementary approach to inverse methods for applying space-based observations to climate studies. Copyright 2011 by the American Geophysical Union."
"36551761100;7401672948;53981326400;35788393500;7101808591;","Water level variation of Lake Qinghai from satellite and in situ measurements under climate change",2011,"10.1117/1.3601363","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054087261&doi=10.1117%2f1.3601363&partnerID=40&md5=827b558ab232ad1b4731f142891848bf","Lake level elevation and variation are important indicators of regional and global climate and environmental change. Lake Qinghai, the largest saline lake in China, located in the joint area of the East Asian monsoon, Indian summer monsoon, and Westerly jet stream, is particularly sensitive to climate change. This study examines the lake's water level and temporal change using the ice, cloud, and land elevation satellite (ICESat) altimetry data and gauge measurements. Results show that the mean water level from ICESat rose 0.67 m from 2003 to 2009 with an increase rate of 0.11 m/yr and that the ICESat data correlates well (r2 = 0.90, root mean square difference 0.08 m) with gauge measurements. Envisat altimetry data show a similar change rate of 0.10 m/yr, but with ∼0.52 m higher, primarily due to different referencing systems. Detailed examination of three sets of crossover ICESat tracks reveals that the lake level increase from 2004 to 2006 was 3 times that from 2006 to 2008, with the largest water level increase of 0.58 m from Feb. 2005 to Feb. 2006. Combined analyses with in situ precipitation, evaporation, and runoff measurements from 1956 to 2009 show that an overall decreasing trend of lake level (-0.07 m/yr) correlated with an overall increasing trend (+0.03°C/yr) of temperature, with three major interannual peaks of lake level increases. The longest period of lake level increase from 2004 to 2009 could partly be due to accelerated glacier/perennial snow cover melt in the region during recent decades. Future missions of ICESat type, with possible increased repeatability, would be an invaluable asset for continuously monitoring lake level and change worldwide, besides its primary applications to polar regions. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE)."
"55351012600;22635029200;7004919328;","Spectral mapping of the Paraíba do sul River plume (Brazil) using multitemporal Landsat images",2011,"10.1117/1.3630220","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054116457&doi=10.1117%2f1.3630220&partnerID=40&md5=310b411205b28b76b97d6f7e33e01d31","Coastal zones are influenced by oceanic, atmospheric, and continental forces, which make them highly vulnerable to climate and anthropogenic changes. The Paraíba do Sul River (PSR) Estuary (Brazil), is especially affected by intensive industrial, urban, and rural activities, along its catchment area. Few works, though, have been done concerning the impacts of these changes. Remote sensing is, thus, an important and unique tool to assess the past scenes for a temporal analysis. The present work aimed to analyze spatial-temporal trends of the PSR plume from 1985 to 2009, using Landsat 5 TM images. Two spectral classification methods were used to map the river plume: maximum likelihood and spectral linear mixture analysis (SLMA). The images corresponded to the months of greatest river discharge, totalizing 11 cloud-free images. Geographical, radiometric, and atmospheric corrections were applied to the five spectral bands used for the classification. Both methods showed good results, however the SLMA provided more information of the water constituent's distribution. The sediment river plume and inner shelf phytoplankton dominated waters showed a negative trend associated with a diminishing of the river discharge. Further works concern in situ validation of the classifications, bio-optical modeling, and more investigations of climate and anthropogenic changes on the PSR. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE)."
"26029605900;7005287667;15072064200;6603256829;57214957723;6603898548;57214957565;9739389400;","Aerosol ageing in an urban plume-implication for climate",2011,"10.5194/acp-11-5897-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959956309&doi=10.5194%2facp-11-5897-2011&partnerID=40&md5=86b6741a84817f70fcc0f8e8dfcc1c94","The climate effects downwind of an urban area resulting from gaseous and particulate emissions within the city are as yet inadequately quantified. The aim of this work was to estimate these effects for Malmö city in southern Sweden (population 280 000). The chemical and physical particle properties were simulated with a model for Aerosol Dynamics, gas phase CHEMistry and radiative transfer calculations (ADCHEM) following the trajectory movement from upwind of Malmö, through the urban background environment and finally tens and hundreds of kilometers downwind of Malmö. The model results were evaluated using measurements of the particle number size distribution and chemical composition. The total particle number concentration 50 km (∼ 3 h) downwind, in the center of the Malmö plume, is about 3700 cmg-3 of which the Malmö contribution is roughly 30%. Condensation of nitric acid, ammonium and to a smaller extent oxidized organic compounds formed from the emissions in Malmö increases the secondary aerosol formation with a maximum of 0.7-0.8 mg-3 6 to 18 h downwind of Malmö. The secondary mass contribution dominates over the primary soot contribution from Malmö already 3 to 4 h downwind of the emission sources and contributes to an enhanced total surface direct or indirect aerosol shortwave radiative forcing in the center of the urban plume ranging from 0.3 to -3.3 W mg-2 depending on the distance from Malmö, and the specific cloud properties. © 2011 Author(s)."
"36899513900;7003597952;","Precipitation response to land subsurface hydrologic processes in atmospheric general circulation model simulations",2011,"10.1029/2010JD015134","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952470257&doi=10.1029%2f2010JD015134&partnerID=40&md5=652db3a4aae42b906d064d78a7972da6","Several studies have established that soil moisture increases after adding a groundwater component in land surface models, owing to the additional supply of subsurface water. However, the impact of groundwater on the spatial-temporal variability of precipitation has received little attention. This study explores how a groundwater representation in land surface models alters precipitation distributions through coupled groundwater-land-atmosphere simulations. Results indicate that the addition of groundwater yields a global increase in soil water content and evapotranspiration, a decrease in surface air temperature, and an increase in cloud cover fraction. These result in globally inhomogeneous changes in precipitation. In the boreal summer, tropical land regions show a positive anomaly in the Northern Hemisphere and a negative anomaly in the Southern Hemisphere. As a result, an asymmetric dipole is found over tropical land regions along the equator. Furthermore, in the transition climatic zone where the land and atmosphere are strongly coupled, precipitation also increases. Two main mechanisms are suggested for the two different regions with increased precipitation. The ""rich-get-richer"" mechanism is responsible for the positive precipitation anomalies over the tropical land regions, while a positive feedback of land-atmosphere interaction is the major contributor to increased precipitation over central North America. This study highlights the importance of land subsurface hydrologic processes in the climate system and has further implications for global water cycle dynamics. Copyright 2011 by the American Geophysical Union."
"57205984068;6701618694;57193552574;7004289682;","A complete long-term series of integrated water vapour from ground-based microwave radiometers",2011,"10.1080/01431161.2010.517792","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952400280&doi=10.1080%2f01431161.2010.517792&partnerID=40&md5=c87e067eba743ff5010a8b0105a2520c","Integrated water vapour (IWV) is the vertical column density of atmospheric water vapour. IWV can be determined from microwave radiances measured by multi-channel radiometers on the ground or in space. Both quality and quantity of IWV measurements have rapidly increased during the past 10 to 20 years. Global maps and time series of IWV give evidence for a strong spatio-temporal variability of atmospheric water vapour, playing a key role in weather prediction and climate-change research. We analyse the relationships between microwave radiances and IWV using long-term observations of two radiometers at Bern, Switzerland. The first radiometer (Tropospheric Water Vapour Radiometer; TROWARA) measures 21 and 31 GHz radiances and permits the accurate retrieval of IWV. The long-term series of the TROWARA have some data gaps that possibly influence the trend analysis. On the other hand, the series of 142 GHz radiance of the second radiometer (Ground-based Millimeter-wave Ozone Spectrometer; GROMOS) are almost complete. The 142 GHz radiance is more affected by integrated cloud liquid water (ILW) than the 21 and 31 GHz radiances. The coincident radiometer data of GROMOS and TROWARA are utilized for exploration of the relationship between 142 GHz radiance, IWV and ILW. The IWV is calculated from the 142 GHz radiance of GROMOS when TROWARA data are not available. Thus, we can derive a complete series of IWV above Bern from 1994 to 2009. The combination of both series and the trend analysis are performed by means of multiple linear regression and bootstrapping. The observations indicate a positive trend up to +10% decade-1 of IWV in summer and a negative trend of about -15% decade-1 in winter. © 2011 Taylor &amp; Francis."
"23995787700;6701419565;","Multiplicity of solutions of the inverse problem for determining optical atmospheric parameters from remote observations",2011,"10.1080/01431161.2010.517806","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952375969&doi=10.1080%2f01431161.2010.517806&partnerID=40&md5=687391617f32ce022bfad72f03cdfd05","Global climate change observed during the last two decades of the 20th century has attracted the attention of the world's scientific community. The non-uniqueness of atmospheric aerosols and the impact of clouds on warming (or cooling) of the atmosphere-underlying surface system need more detailed modelling to elucidate the optical properties of the atmosphere and surface. In multi-angle remote sensing, inverse problem retrieval using radiances over only one pixel presents a fundamental difficulty involving the multiplicity of solutions. In particular, it was found that different analytical approaches for the retrieval of optical parameters give a multiplicity of solutions, even in the simplest case of the slab homogeneous model and the standard scheme of illumination of the clear atmosphere. The phase function was approximated with one parameter functions. Only four parameters of the homogeneous atmosphere are retrieved in our simple variant. The found effect does not link with the low information content of observational data in respect to the desired parameters. It is not a result of the ill-posed inverse problem, insofar as it concerns properties of integral functionals in customary comprehension and calls for strong variations of vertical profiles of parameters. It seems that the effect of solution multiplicity is a direct consequence of radiation field non-linear dependence on atmospheric and surface parameters that leads to closely coinciding radiation fields forming with essentially different combinations of optical parameters. © 2011 Taylor & Francis."
"19933330400;7006329926;6504316823;35319691100;","An evaluation and improvement of microphysical parameterization from a two-moment cloud microphysics scheme and the Southwest Monsoon Experiment (SoWMEX)/Terrain-influenced Monsoon Rainfall Experiment (TiMREX) observations",2011,"10.1029/2011JD015718","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053605224&doi=10.1029%2f2011JD015718&partnerID=40&md5=e4091d6d10097a48ef30320dfcfb7c17","This study evaluates the simulated cloud properties, especially the simulated raindrop size distribution, by the Chinese Academy of Meteorological Sciences bulk microphysics scheme (CAMS BMS) and two other two-moment microphysics schemes (Morrison and WDM6) in the Weather Research and Forecasting model (WRF v3.1). Measurements from a mesoscale convective system that occurred on 14 June 2008 during the Southwest Monsoon Experiment (SoWMEX) and Terrain-influenced Monsoon Rainfall Experiment (TiMREX) are used. The model reflectivity (Z<inf>H</inf>), differential reflectivity (Z<inf>DR</inf>), and microwave brightness temperature (T<inf>B</inf>) are compared with the corresponding observations by the S band dual-polarization Doppler radar (S-Pol) and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). Results show that the simulated Z<inf>DR</inf>, which is sensitive to the drop size distribution (DSD) of raindrops, from the original CAMS BMS and Morrison schemes are larger than those from the S-Pol observations. On the other hand, the simulated Z<inf>DR</inf> values from the WDM6 scheme are smaller than the radar observations. To improve the model results, modifications are made by controlling the intercept parameter of raindrop DSD and by increasing the raindrop breakup rates in the original CAMS BMS scheme. The modifications reduce the raindrop size and consequently increase the rain evaporation rate. The improved simulations of Z<inf>H</inf> and Z<inf>DR</inf> indicate that the modified CAMS BMS scheme adequately simulates the amount and size of liquid hydrometeors. Moreover, the simulated brightness temperatures at liquid water absorption frequency and the simulated surface precipitation rates are also significantly improved by using the modified CAMS BMS scheme. © 2011 by the American Geophysical Union."
"9244992800;55399935700;7004060399;","The fine-scale structure of the global tropopause derived from COSMIC GPS radio occultation measurements",2011,"10.1029/2011JD016030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055042665&doi=10.1029%2f2011JD016030&partnerID=40&md5=3b9de9b11a1cefe58fab0f9321f91894","The spatiotemporal structure of the lapse-rate tropopause is examined by using state-of-the-art Global Positioning System radio occultation measurements from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Formosa Satellite Mission 3 mission. The high temporal and spatial resolutions of the data reveal the detailed structure of tropopause properties such as pressure (p<inf>t</inf>), temperature (T<inf>t</inf>), and sharpness (N<inf>t</inf>2) and their relationships to upper tropospheric and lower stratospheric processes. The overall results are generally in good agreement with previous studies. The climatology of all three tropopause properties shows largely homogeneous structure in the zonal direction: noticeable asymmetries are found only in the tropics and the Northern Hemisphere extratropics during boreal winter owing to localized tropospheric processes. This contrasts with the seasonal cycles of tropopause properties which are significantly influenced by stratospheric processes such as the Brewer-Dobson circulation, the polar vortex, and the radiative processes near the tropopause. On intraseasonal time scales, p<inf>t</inf> and T<inf>t</inf> exhibit significant variability over the Asian summer monsoon and the subtropics where double tropopauses frequently occur. In contrast, N<inf>t</inf>2 shows maximum variability in the tropics where p<inf>t</inf> and T<inf>t</inf> have minimum variability, possibly a consequence of vertically propagating waves. The tropopause properties derived from COSMIC observations are further applied to evaluate tropopause data directly available from the NCEP-NCAR Reanalysis (NNR). Although the NNR tropopause data have been widely used in climate studies, they are found to have significant and systematic biases, especially in the subtropics. This suggests that the NNR tropopause data should be treated with great caution in any quantitative studies. Copyright © 2011 by the American Geophysical Union."
"7406752778;7402711645;","Investigating RADARSAT-2 as a tool for monitoring grassland in western Canada",2011,"10.5589/m11-027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80955153371&doi=10.5589%2fm11-027&partnerID=40&md5=0de5c99d1072bff9fe0a188080e35c73","Native grasslands play an important role in ecosystem function, biodiversity, climate change, and economics, yet quantifiable estimates of the rate and location of native grassland change in western Canada are not readily available. To date, optical remote sensing has been explored for grassland mapping, but cloud cover limits the availability of timely data for the discrimination of improved, as opposed to native, grassland. In this study we investigated the utility of RADARSAT-2 polarimetric imagery to map native grassland, improved grassland, and agricultural crops. Fine quad-polarisation mode RADARSAT-2 data were acquired at two incidence angles over a test site in southern Alberta every 24 days from 1 April to 31 October 2009 and were processed using the Freeman–Durden decomposition. Double-bounce, volumetric, and surface scattering properties suggest that native grasslands can be distinguished from cultivated cropping, especially using a mid- to late-season image. However, discriminating native grasslands from improved grasslands was more difficult. Land cover classification of a single RADARSAT-2 image from July 2009 provided reasonable but slightly less accurate results compared with a single Landsat-5 Thematic Mapper image (Kappa value of 0.65 compared with 0.81). © 2011 CASI."
"7501627905;7005942405;","Potential climatic impacts and reliability of large-scale offshore wind farms",2011,"10.1088/1748-9326/6/2/025101","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960296390&doi=10.1088%2f1748-9326%2f6%2f2%2f025101&partnerID=40&md5=e767e145881d3ba8b65bd8676c64d627","The vast availability of wind power has fueled substantial interest in this renewable energy source as a potential near-zero greenhouse gas emission technology for meeting future world energy needs while addressing the climate change issue. However, in order to provide even a fraction of the estimated future energy needs, a large-scale deployment of wind turbines (several million) is required. The consequent environmental impacts, and the inherent reliability of such a large-scale usage of intermittent wind power would have to be carefully assessed, in addition to the need to lower the high current unit wind power costs. Our previous study (Wang and Prinn 2010 Atmos. Chem. Phys. 10 2053) using a three-dimensional climate model suggested that a large deployment of wind turbines over land to meet about 10% of predicted world energy needs in 2100 could lead to a significant temperature increase in the lower atmosphere over the installed regions. A global-scale perturbation to the general circulation patterns as well as to the cloud and precipitation distribution was also predicted. In the later study reported here, we conducted a set of six additional model simulations using an improved climate model to further address the potential environmental and intermittency issues of large-scale deployment of offshore wind turbines for differing installation areas and spatial densities. In contrast to the previous land installation results, the offshore wind turbine installations are found to cause a surface cooling over the installed offshore regions. This cooling is due principally to the enhanced latent heat flux from the sea surface to lower atmosphere, driven by an increase in turbulent mixing caused by the wind turbines which was not entirely offset by the concurrent reduction of mean wind kinetic energy. We found that the perturbation of the large-scale deployment of offshore wind turbines to the global climate is relatively small compared to the case of land-based installations. However, the intermittency caused by the significant seasonal wind variations over several major offshore sites is substantial, and demands further options to ensure the reliability of large-scale offshore wind power. The method that we used to simulate the offshore wind turbine effect on the lower atmosphere involved simply increasing the ocean surface drag coefficient. While this method is consistent with several detailed fine-scale simulations of wind turbines, it still needs further study to ensure its validity. New field observations of actual wind turbine arrays are definitely required to provide ultimate validation of the model predictions presented here. © 2011 IOP Publishing Ltd."
"57212020392;57212001919;","Modeling of the Second Indirect Effect of Anthropogenic Aerosols in East Asia",2011,"10.1080/16742834.2011.11446948","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981233717&doi=10.1080%2f16742834.2011.11446948&partnerID=40&md5=42cba7a17f1552973f37de86eaca8f1d","This study investigated the second indirect climatic effect of anthropogenic aerosols, including sulfate, organic carbon (OC), and black carbon (BC), over East Asia. The seasonal variation of the climatic response to the second indirect effect was also characterized. The simulation period for this study was 2006. Due to a decrease in autoconversion rate from cloud water to rain as a result of aerosols, the cloud liquid water path (LWP), and radiative flux (RF) at the top of the atmosphere (TOA) changed dramatically, increasing by 14.3 g m-2 and decreasing by −4.1 W m-2 in terms of domain and annual average. Both LWP and RF changed most in autumn. There were strong decreases in ground temperature in Southwest China, the middle reaches of the Yangtze River in spring and autumn, while maximum cooling of up to −1.5 K occurred in the Chongqing district. The regional and annual mean change in ground temperature reached −0.2 K over eastern China. In all seasons except summer, precipitation generally decreased in most areas north of the Yangtze River, whereas precipitation changed little in South China. Precipitation changed most in summer, with alternating bands of increasing (˜40 mm) and decreasing (˜40 mm) precipitation appearing in eastern China. Precipitation decreased by 1.5–40 mm over large areas of Northeast China and the Huabei Plain. The domain and annual mean change in precipitation was approximately −0.3 mm over eastern China. The maximum reduction in precipitation occurred in summer, with mean absolute and relative changes of −1.2 mm and −3.8% over eastern China. This study revealed considerable climate responses to the second indirect effect of aerosols over specific regions of China. © 2011, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"53864564400;57204345432;7103161516;8567332800;","Effects of implementing satellite observed aerosols into a mesoscale atmosphere model",2011,"10.1080/01431161.2010.502157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053094626&doi=10.1080%2f01431161.2010.502157&partnerID=40&md5=5c3bd22db4c2dd1bfbe5aef4a886ea03","This study investigated the performance of the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) in calculating the aerosol forcing on cloud cover, incoming surface solar radiation, and near-surface air temperature via the implementation of aerosol optical depth in the shortwave radiation parameterization. MM5 simulations with and without aerosol data are performed in the periods of 6-7 August 2003 and 19-21 September 2003 during which strong aerosol forcing was observed with Moderate Resolution Imaging Spectroradiometer (MODIS) data in the mid-Atlantic region. Both periods clearly showed that aerosols had a direct negative effect on surface solar radiation through aerosol scattering. For example, every 0.1 change in MODIS aerosol optical thickness (AOT) results in 44 and 59Wm-2 decreases in surface solar radiation for the first and second periods, respectively. A magnitude of 0.1 increment in MODIS AOT reduces air temperature 0.36 and 0.56K for the first and second periods, respectively. Comparisons with satellite-derived surface solar radiation retrievals showed that aerosol implementation in MM5 consistently showed better incoming surface solar radiation than that of the non-aerosol case. This helps to reduce uncertainties related to the radiation-cloud-aerosol interaction in numerical weather modelling systems. © 2011 Taylor &amp; Francis."
"26431137300;7006033615;35272055900;","Dramatic interannual changes of perennial Arctic sea ice linked to abnormal summer storm activity",2011,"10.1029/2011JD015847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051687805&doi=10.1029%2f2011JD015847&partnerID=40&md5=49717f25b56d365033df730adafe528f","The perennial (September) Arctic sea ice cover exhibits large interannual variability, with changes of over a million square kilometers from one year to the next. Here we explore the role of changes in Arctic cyclone activity, and related factors, in driving these pronounced year-to-year changes in perennial sea ice cover. Strong relationships are revealed between the September sea ice changes and the number of cyclones in the preceding late spring and early summer. In particular, fewer cyclones over the central Arctic Ocean during the months of May, June, and July appear to favor a low sea ice area at the end of the melt season. Years with large losses of sea ice are characterized by abnormal cyclone distributions and tracks: they lack the normal maximum in cyclone activity over the central Arctic Ocean, and cyclones that track from Eurasia into the central Arctic are largely absent. Fewer storms are associated with above-average mean sea level pressure, strengthened anticyclonic winds, an intensification of the transpolar drift stream, and reduced cloud cover, all of which favor ice melt. It is also shown that a strengthening of the central Arctic cyclone maximum helps preserve the ice cover, although the association is weaker than that between low cyclone activity and reduced sea ice. The results suggest that changes in cyclone occurrence during late spring and early summer have preconditioning effects on the sea ice cover and exert a strong influence on the amount of sea ice that survives the melt season. Copyright 2011 by the American Geophysical Union."
"37116849700;7404433688;7102049897;","Is the tropopause higher over the Tibetan Plateau? Observational evidence from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) data",2011,"10.1029/2011JD016140","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81255210998&doi=10.1029%2f2011JD016140&partnerID=40&md5=ab0c379142efa03009f8619b9f7f3084","Using Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation data from June 2006 to December 2009, the temperature structure and the tropopause height over the Tibetan Plateau (TP) is studied in this paper. The temperature over the TP is warmer and experiences a lager magnitude of change than that over the same latitudinal plain area (hereinafter referred to as the Plain) at the same level of lower troposphere. The lapse rate tropopause (LRT) shows a strong correlation with thermal properties of the atmosphere. Its height variation is anticorrelated with its temperature, highest at ∼19 km and coldest at approximately -72C in boreal summer, but lowest at ∼13 km and approximately -56C in boreal winter. Those of the cold point tropopause (CPT) exhibit a positive correlation but barely seasonal variation all year long. As an outstanding heat source in boreal summer, the TP thermally pushes the LRT upward by ∼2 km compared with the Plain, while the LRT drops below that over the Plain in boreal winter. The LRT height is also strongly dependent on the subtropical jet that is associated with the tropopause fold and/or multiple tropopauses, leading to fairly bimodal distribution of the LRT probability density function. As the ""roof of the world,"" the elevated topography of the TP dynamically lifts the CPT to a higher altitude without significantly seasonal variations. Along the latitude of 32.5N the CPT is located at ∼18 km over the main body of the TP and drops to ∼15 km over the Plain. Given the area in the TP (30-35N, 87-95E) as well as in the Plain (30-35N, 112-120E), the CPT primarily resides at 17-18 km, 72.52% over the TP and 69.22% over the Plain. Their monthly mean difference can reach 1.4 km for the complete analysis period. Copyright 2011 by the American Geophysical Union."
"7401892295;7405489798;7006095466;7003495982;35984036000;7202048112;36843654900;","Role of the atmospheric mean state on the initiation of the Madden-Julian oscillation in a tropical channel model",2011,"10.1007/s00382-010-0859-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650984254&doi=10.1007%2fs00382-010-0859-2&partnerID=40&md5=22ff01fcdb27a4f84d16ae812129a1ab","Tropical channel models, defined as models that are global in the zonal direction but bounded in the meridional direction, are particularly useful for simulating the Madden-Julian oscillation (MJO) and understanding its physical and dynamical basis. Influences from the extratropics through the lateral boundaries have been found to be essential to the reproduction of the initiation of certain MJO events. This led to a hypothesis that multi-year simulations using a tropical channel model would reproduce reasonable MJO statistics under the influence of prescribed lateral boundary conditions derived from global reanalyses. Interestingly, the MJO statistics in such a multi-year simulation by a high-resolution tropical channel model are not better than those from global climate models. The error in the atmospheric mean state is found to be a possible reason for the poor MJO statistics in the simulation. Nevertheless, even with a large error in the mean state, the multi-year simulation captures two MJO events previously found to be initiated by extratropical influences. However, the model does not reproduce a third event, whose initiation is not directly influenced by the extratropics. This implies that in the absence of dynamical interactions between the MJO and the lateral boundary conditions, the error in the mean state could be sufficient to prevent the MJO initiation. To explore this third MJO event further, a series of sensitivity tests are conducted. These tests show that the simulation of this event is neither critically influenced by the cumulus parameterization employed, nor the initial conditions when the model is integrated 2 weeks prior to the MJO initiation. The model captures this event when the MJO signal is already present in the initial conditions. The use of high-resolution sea surface temperature does not improve the simulation of the third MJO event. A higher-resolution nested domain covering the Indo-Pacific warm pool region and including a cloud-system resolving domain over the Indonesian Maritime Continent has little effect on the MJO initiation over the Indian Ocean. In <2 weeks the error in the simulation is comparable to the climate error. The role of the simulated MJO on the mean state is also explored. Implications and limitations of these results are discussed. © 2010 Springer-Verlag."
"56127418900;56537463000;7404829395;","Regional simulations of deep convection and biomass burning over South America: 1. Model evaluations using multiple satellite data sets",2011,"10.1029/2011JD016105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053062794&doi=10.1029%2f2011JD016105&partnerID=40&md5=e916fe783d3f60e82b7a8af8dfbfff84","Multiple data sets, mostly from satellite observations, are used to evaluate the performance of the Weather Research and Forecasting model with Chemistry (WRF-Chem) in simulating the distribution and evolution of aerosol, clouds, precipitation and chemistry during the dry season in South America. A 9-day WRF-Chem simulation with 36 km horizontal resolution is performed from 15 to 24 September 2006, during which frequent biomass burnings were observed. It is shown that the model reproduces the spatial distribution of aerosols produced by biomass burning and approximately captures convective transport of trace gases (e.g., CO and O<inf>3</inf>) into the upper troposphere. Surface precipitation is also in reasonable agreement with observation. The model simulations overestimate the magnitude of water vapor in the upper troposphere while the magnitude of cloud water content is lower than measurements from satellites, which may indicate problems in the cumulus and microphysical parameterizations. The model simulations capture temporal variations of outgoing longwave radiation at the top of atmosphere and downward shortwave radiation at the surface shown in the NASA GEWEX SRB data set. A sensitivity run at 4 km horizontal resolution shows similar results to the 36 km simulation, with a high bias of precipitation. The uncertainty and weakness in both satellite observations and model simulations are identified. This study demonstrates that satellite data are valuable to the evaluation of regional model simulations for climatologically important processes such as deep convection and biomass burning, especially in regions with little in situ observation. Copyright 2011 by the American Geophysical Union."
"16029830700;","Investigation of the oceanic cloudiness according to the data of satellite observations in the spectral range 10.3-11.3 μm",2011,"10.1007/s11110-011-9098-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958839929&doi=10.1007%2fs11110-011-9098-2&partnerID=40&md5=0f5138bd473ae6cd05d692d380b41576","The temperature of waters in the upper layer of the ocean and effective cloudiness (cloudiness with simultaneous indication of its amount and optical density) are important characteristics of the natural environments. They determine the greenhouse effects and the energy of the ocean and atmosphere, and regulate climate. The satellite data on these characteristics enable one to reconstruct all components of the radiation, heat, and water budgets in the ocean-atmosphere system and study their intra- and interannual variations. We describe the procedures of evaluation of the effective cloudiness according to the sea-surface temperature and the radiation temperature in the spectral range 10.3-11.3 μm. The development of these investigations is connected with the advances in satellite hydrophysics: the satellite data become more and more accurate, regular, and global. © 2011 Springer Science+Business Media, Inc."
"33167514000;7401874732;24462074700;23476419700;24167002800;7006807562;","Time-series analysis of multi-resolution optical imagery for quantifying forest cover loss in Sumatra and Kalimantan, Indonesia",2011,"10.1016/j.jag.2010.11.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952904839&doi=10.1016%2fj.jag.2010.11.004&partnerID=40&md5=68deb96becbc29b8a4efab67a935ed0b","Monitoring loss of humid tropical forests via remotely sensed imagery is critical for a number of environmental monitoring objectives, including carbon accounting, biodiversity, and climate modeling science applications. Landsat imagery, provided free of charge by the U.S. Geological Survey Center for Earth Resources Observation and Science (USGS/EROS), enables consistent and timely forest cover loss updates from regional to biome scales. The Indonesian islands of Sumatra and Kalimantan are a center of significant forest cover change within the humid tropics with implications for carbon dynamics, biodiversity maintenance and local livelihoods. Sumatra and Kalimantan feature poor observational coverage compared to other centers of humid tropical forest change, such as Mato Grosso, Brazil, due to the lack of ongoing acquisitions from nearby ground stations and the persistence of cloud cover obscuring the land surface. At the same time, forest change in Indonesia is transient and does not always result in deforestation, as cleared forests are rapidly replaced by timber plantations and oil palm estates. Epochal composites, where single best observations are selected over a given time interval and used to quantify change, are one option for monitoring forest change in cloudy regions. However, the frequency of forest cover change in Indonesia confounds the ability of image composite pairs to quantify all change. Transient change occurring between composite periods is often missed and the length of time required for creating a cloud-free composite often obscures change occurring within the composite period itself. In this paper, we analyzed all Landsat 7 imagery with <50% cloud cover and data and products from the Moderate Resolution Imaging Spectroradiometer (MODIS) to quantify forest cover loss for Sumatra and Kalimantan from 2000 to 2005. We demonstrated that time-series approaches examining all good land observations are more accurate in mapping forest cover change in Indonesia than change maps based on image composites. Unlike other time-series analyses employing observations with a consistent periodicity, our study area was characterized by highly unequal observation counts and frequencies due to persistent cloud cover, scan line corrector off (SLC-off) gaps, and the absence of a complete archive. Our method accounts for this variation by generating a generic variable space. We evaluated our results against an independent probability sample-based estimate of gross forest cover loss and expert mapped gross forest cover loss at 64 sample sites. The mapped gross forest cover loss for Sumatra and Kalimantan was 2.86% of the land area, or 2.86Mha from 2000 to 2005, with the highest concentration having occurred in Riau and Kalimantan Tengah provinces. © 2010 Elsevier B.V."
"55957596200;8072265400;","Areal changes of land ecosystems in the Alaskan Yukon River Basin from 1984 to 2008",2011,"10.1088/1748-9326/6/3/034012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053491878&doi=10.1088%2f1748-9326%2f6%2f3%2f034012&partnerID=40&md5=16ffd33c8bb1859ed450e09a4334cd50","Multivariate alteration detection (MAD) and Bayesian inference (BI) methods are used to analyze land cover changes with Landsat images for the Alaskan Yukon River Basin from 1984 to 2008. The US Geological Survey National Land Cover Database 2001 (NLCD 2001) is treated as reference information to detect the changes. It is found that the regional land cover change has three general trends with various potential causes during the study period: (1)forests decreased mainly due to wildfire, (2)the closed water bodies were shrinking possibly due to permafrost degradation if water drains well in discontinuous permafrost regions, (3)shrubs had expanded and a large portion of grassland was converted into shrubland likely due to forest fire and warming. The uncertainty of this analysis may mainly arise from image acquisition date differences and illumination angles and remaining cloud contamination to the images. This study provides a method to analyze land cover changes with Landsat data for other regions. The developed land cover data should help future understanding of permafrost dynamics, biogeochemistry, hydrology and regional climate in the region. © 2011 IOP Publishing Ltd."
"15058680900;6602342255;53664192000;15058828800;","South Pole ice core record of explosive volcanic eruptions in the first and second millennia A.D. and evidence of a large eruption in the tropics around 535 A.D.",2011,"10.1029/2011JD015916","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053058349&doi=10.1029%2f2011JD015916&partnerID=40&md5=fea90b970f5eb155d0dd4d5c89faed53","A record of explosive eruptions over the last 1830 years reconstructed from a South Pole, Antarctica, ice core extends the coverage of volcanic history to the start of the first millennium A.D. The ice core dating by annual layer counting carries an uncertainty of 2% of the number of years from time markers, with the largest dating error of 20 years at the bottom of the 182 m core. Several aspects of the methodology of detecting and quantifying volcanic sulfate signals in ice cores are examined in developing this record. The new record is remarkably consistent with previous South Pole records. A comparison with records from several Antarctica locations suggests that the South Pole location is among the best for ice core reconstruction of volcanic records, owing to the excellent preservation of volcanic signals at the South Pole, the relatively low and uniform sulfate background, and the moderately high snow accumulation rates which allow for dating by annual layer counting. A prominent volcanic event dated at 531(15) A.D., along with evidence from other records, indicates that an unusually large eruption took place in the tropics and was probably responsible for the ""mystery cloud"" climate episode of 536-537 A.D. The date of 536 is suggested for a prominent volcanic signal that appears in the first half of the sixth century A.D. in ice cores, which can in turn be used as a time stratigraphic marker in dating ice cores by annual layer counting or by computing average accumulation rates or layer thicknesses with such markers. Copyright 2011 by the American Geophysical Union."
"23994595000;36448336300;57217726421;22833630700;14034301300;36183177600;6602496366;6602085876;42762174700;7006434689;7005069415;","Changes of hygroscopicity and morphology during ageing of diesel soot",2011,"10.1088/1748-9326/6/3/034026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053479402&doi=10.1088%2f1748-9326%2f6%2f3%2f034026&partnerID=40&md5=650799c4f3cb50f07d8189a5fc41c619","Soot particles are an important component of atmospheric aerosol and their interaction with water is important for their climate effects. The hygroscopicity of fresh and photochemically aged soot and secondary organic aerosol (SOA) from diesel passenger car emissions was studied under atmospherically relevant conditions in a smog chamber at sub-and supersaturation of water vapor. Fresh soot particles show no significant hygroscopic growth nor cloud condensation nucleus (CCN) activity. Ageing by condensation of SOA formed by photooxidation of the volatile organic carbon (VOC) emission leads to increased water uptake and CCN activity as well as to a compaction of the initially non-spherical soot particles when exposed to high relative humidity (RH). It is important to consider the latter effect for the interpretation of mobility based measurements. The vehicle with oxidation catalyst (EURO3) emits much fewer VOCs than the vehicle without after-treatment (EURO2). Consequently, more SOA is formed for the latter, resulting in more pronounced effects on particle hygroscopicity and CCN activity. Nevertheless, the aged soot particles did not reach the hygroscopicity of pure SOA particles formed from diesel VOC emissions, which are similarly hygroscopic (0.06 &lt; κH - TDMA &lt; 0.12 and 0.09 &lt; κCCN &lt; 0.14) as SOA from other precursor gases investigated in previous studies. © 2011 IOP Publishing Ltd."
"24177361900;53980117600;","Daily covariations in near-surface relative humidity and temperature over the ocean",2011,"10.1029/2011JD015792","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053617513&doi=10.1029%2f2011JD015792&partnerID=40&md5=32a55d0f936796042f1c3a24ba6be643","Changes in atmospheric relative humidity in concert with temperature changes in a future climate may have large consequences for the water vapor feedback, the hydrological cycle, and its interaction with weather systems. This study contributes to the basic understanding of the relationship between temperature and humidity by investigating the processes leading to synoptic-scale covariations of the two variables close to the ocean surface. Daily data from in situ observations between 10°S and 50°N and global ERA-Interim reanalyses are used. Correlations between temperature and both specific and relative humidity are calculated. The results from the two data sets appear to be greatly consistent. They show strong anticorrelation between temperature and relative humidity (RH) in the inner tropics with minimum correlation coefficients below -0.8. In midlatitudes, there are large areas where the correlation coefficient of temperature and RH is positive and greater than 0.6. The anticorrelation in the tropics is found to be related to convective precipitation, which, on the one hand, leads to local temperature decrease due to vertical mixing and reduction of solar radiation by clouds. On the other hand, rainfall is associated with an increase in boundary layer RH. Over the midlatitude ocean, daily temperature variations are mainly controlled by meridional transport, as shown with the help of backward trajectories. Moreover, advection of cold air typically goes along with vertical moisture transport, either due to large-scale subsidence or turbulent mixing, causing a reduction of near-surface RH. All together, this dynamical effect induces the positive temperature-RH correlation. © 2011 by the American Geophysical Union."
"13606720900;35115909000;55434335500;21833327900;37561650900;","The ice sheet height changes and mass variations in Antarctica by using ICESat and GRACE data",2011,"10.1080/19479832.2010.491803","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860420841&doi=10.1080%2f19479832.2010.491803&partnerID=40&md5=69a8629d21e9a986278a389cd9fa27ba","The Gravity Recovery and Climate Experiment (GRACE) satellite mission has provided the monthly earth's gravity field models since August 2002, from which the mass variations in Antarctica can be estimated. Because of the very lowdegree spherical harmonic coefficients, especially the degree-2 zonal term J2 are not well determined by GRACE, more attention should be paid on the effects of J2 when the earth's mass variations are derived from spherical harmonic coefficients. To see the differences more clearly, wavelet transformation is applied to the J2 time series derived from GRACE measurements by different agencies, such as Centre National d'Études Spatiales/Groupe de Recher de Deodesie Spatiale, GeoForschungsZentrum Potsdam, University of Texas Center for Space Research and that from satellite laser ranging observations. Periodic signals can be seen from the wavelet spectra. A Gaussian smoothing with a radius of 300km is used in the gravity model-based mass rate estimation. Meanwhile, NASA's Ice, Cloud, and land Elevation Satellite (ICESat) has provided repeated laser altimeter data, and the ice sheet height changes are estimated by using crossover analysis. The mass rates estimated from GRACE are compared to the ice sheet height changes from ICESat. The mass rate in Amundsen Sea Embayment is estimated up to -8 cm/yr from GRACE, while the ice sheet height changes observed from ICESat is up to -32 cm over more than 3 years, this shows the comparable results in this region. © 2011 Taylor &amp; Francis."
"55502822200;6602626321;6603669676;","Estimating surface-soil moisture for retrieving maize leaf-area index from SAR data",2011,"10.5589/m11-021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870021200&doi=10.5589%2fm11-021&partnerID=40&md5=1a96c243d1e0234a9a308046faebc5a1","The leaf-area index (LAI) is a key parameter for coupling earth-observation data with crop-growth models from the perspective of crop-yield forecasting. Remote sensing is of particular interest in estimating LAI over large areas. SAR data, thanks to their systematic acquisition, offer an ideal temporal resolution throughout the crop-growing season. Nevertheless, surface soil dielectric permittivity, which is strongly correlated with soil moisture, also affects the SAR signal. Thus, surface-soil permittivity or moisture has to be taken into account. This study tackles the issues related to soil influence on the SAR signal in monitoring maize crop growth. Different methods of assessing surface-soil moisture or permittivity are explored in order to retrieve LAI values from SAR data. The first method is based on a hydrological model — the soil, water, atmosphere, and plant (SWAP) model — with which the surface-soil moisture level can be estimated as a function of time. This method is tested with two kinds of meteorological data as inputs for the hydrological model: ground meteorological data and estimated meteorological data. The second method resorts to ground-penetrating radar, an alternative means of estimating surface-soil permittivity. This study demonstrates that both soil-moisture levels estimated by the SWAP model and soil permittivity measured by ground-penetrating radar can be successfully used for retrieving maize LAI values from SAR data using the water cloud model. © 2011 CASI."
"7005631653;7003592683;17135505200;","Sulfur degassing from volcanoes: Source conditions, surveillance, plume chemistry and earth system impacts",2011,"10.2138/rmg.2011.73.13","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053319875&doi=10.2138%2frmg.2011.73.13&partnerID=40&md5=b065e7826aaab3d7ec7e7590efe83a55","Although this review has focused on sulfur, its behavior and impacts should always be regarded as part of a larger picture of chemical and physical interactions, notably in magmas where interactions with other volatile species are important. Nevertheless, sulfur is a truly remarkable element in its own right. Its behavior in magmatic, hydrothermal, volcanic, atmospheric, terrestrial and aquatic environments is complex owing to a range of factors including its important role in redox chemistry (and biogeochemistry). In the atmosphere, the oxidation of sulfur gases to sulfuric acid, either in the aqueous aerosol phase in the troposphere or via homogenous reactions in the stratosphere (with sulfuric acid condensing under the prevailing conditions), is of particular significance. The short-term (months-to-years) impacts of volcanism on the atmosphere, climate and environment are strongly controlled by location, timing, flux, magnitude and emission height of sulfur gases (principally S02 or H2S depending strongly on the physical conditions of the magmatic source). Episodic explosive eruptions represent the principal perturbation to stratospheric aerosol (though the atmospheric effects of sulfur degassing associated with continental flood basalts might well be more profound). In the troposphere, the picture is less clear but a significant part of the global tropospheric sulfate burden may be volcanogenic. Sulfate aerosol influences the Earth's radiation budget by scattering and absorption of shortwave and long-wave radiation, and by acting as cloud condensation nuclei. When they are brought to the boundary layer and Earth's surface, clouds containing volcanic sulfur in both gaseous and aerosol phases can result in profound environmental and health impacts. The global impacts of only one large eruption (magnitude &gt; 1013 kg) have been studied with any instrumental detail-the 1991 eruption of Mt. Pinatubo. As the twentieth anniversary of that event looms (at the time of writing), it is remarkable to note that new findings concerning its climatic, environmental and ecological consequences are still emerging. Despite the tremendous insights afforded by this event, it represents a very small sample of the range of volcanic eruption styles, geographic locations and atmospheric states that could combine to produce significant perturbations to atmospheric radiation and dynamics. An important issue is the readiness of the scientific community to record the next major climate-forcing eruption as effectively as possible. More generally, substantial further work is required to constrain the temporal and spatial distribution of gas and particle emissions (including sulfur, halogens and trace metal species) to the atmosphere from all erupting and dormant volcanoes. In addition to improved observational data on the spatial and temporal distributions of volcanic volatiles to the atmosphere, further studies are required to characterize the physical and chemical interactions of gases and particles in the atmosphere. This will be essential for the realistic application of numerical models describing the transport and chemical evolution of plumes, and will contribute to a better understanding of volcanogenic pollution and improved mitigation of its effects. Surveillance of gas composition and flux are essential for interpretation of volcanic activity, since degassing is intimately linked with the physical and chemical environments of magma storage and the dynamics of magma transport. A revolution in spectroscopic and electrochemical techniques has taken place over the past decade providing greatly improved means for volcanic gas surveillance at all scales. In the near future, we can anticipate further revolutions in the ability to measure volcanic volatile emissions in the field thanks to current developments of laser spectroscopy and ldar systems (enabling in situ determination of isotopic compositions of C, O, H, S, Cl, etc., and remote measurement of 02 fluxes). Satellite remote sensing methods and the use of unmanned aerial vehicles will also lead to improved measurements of volcanic plumes and better inventories of the temporal and spatial distribution of sulfur (and carbon and halogen) fluxes. Unfortunately, the modeling frameworks for interpretation of geochemical data remain underdeveloped, impeding the application of such data in hazard assessment. Advances in this area will benefit from development and validation of comprehensive physico-chemical models for volcanic degassing and associated magma storage and transport based on the integration of results from experiments on the controls on distribution of volatiles in synthetic and natural melts (with an emphasis on understanding redox controls), analysis of dissolved volatiles preserved in melt inclusions, and observed volcanic gas geochemistry. Ultimately, such models can be applied to integrated inversions of geophysical, geodetic and geochemical monitoring data to support hazard assessment. © Mineralogical Society of America."
"6602495271;7203036010;56422076900;7102939688;18635831500;56260361400;6602610108;","Land surface microwave emissivities derived from AMSR-E and MODIS measurements with advanced quality control",2011,"10.1029/2010JD015429","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052548282&doi=10.1029%2f2010JD015429&partnerID=40&md5=311ca8e476e9e3573c90e7eb7bce00a1","A microwave emissivity database has been developed with data from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and with ancillary land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the same Aqua spacecraft. The primary intended application of the database is to provide surface emissivity constraints in atmospheric and surface property retrieval or assimilation. An additional application is to serve as a dynamic indicator of land surface properties relevant to climate change monitoring. The precision of the emissivity data is estimated to be significantly better than in prior databases from other sensors due to the precise collocation with high-quality MODIS LST data and due to the quality control features of our data analysis system. The accuracy of the emissivities in deserts and semiarid regions is enhanced by applying, in those regions, a version of the emissivity retrieval algorithm that accounts for the penetration of microwave radiation through dry soil with diurnally varying vertical temperature gradients. These results suggest that this penetration effect is more widespread and more significant to interpretation of passive microwave measurements than had been previously established. Emissivity coverage in areas where persistent cloudiness interferes with the availability of MODIS LST data is achieved using a classification-based method to spread emissivity data from less-cloudy areas that have similar microwave surface properties. Evaluations and analyses of the emissivity products over homogeneous snow-free areas are presented, including application to retrieval of soil temperature profiles. Spatial inhomogeneities are the largest in the vicinity of large water bodies due to the large water/land emissivity contrast and give rise to large apparent temporal variability in the retrieved emissivities when satellite footprint locations vary over time. This issue will be dealt with in the future by including a water fraction correction. Also note that current reliance on the MODIS day-night algorithm as a source of LST limits the coverage of the database in the Polar Regions. We will consider relaxing the current restrictions as part of future development. Copyright 2011 by the American Geophysical Union."
"14049863300;57206038917;","Pollution transport efficiency toward the Arctic: Sensitivity to aerosol scavenging and source regions",2011,"10.1029/2010JD015096","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955612392&doi=10.1029%2f2010JD015096&partnerID=40&md5=1a778b37066c2e6116d96261e22a82e8","The processes driving current changes in Arctic atmospheric composition and climate are still uncertain. In particular the relative contributions of major source regions from the midlatitudes remain a matter of debate in the literature. The objectives of this study are to better quantify the relative contributions of different processes governing the transport of pollution from the midlatitudes to the Arctic and the relative contributions of different geopolitical source regions. We use a suite of observational data sets (including the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaigns and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite instrument) to constrain a global aerosol simulation from the ECHAM5-HAMMOZ model. Preliminary comparison of model results with vertical profiles of sulfate and black carbon (BC) collected during the ARCTAS campaigns and with aerosol extinction time series retrieved from CALIOP indicates that the model underestimates export of aerosols from the planetary boundary layer to the free troposphere in the midlatitudes and long-range transport of aerosols from the midlatitudes toward the Arctic. In contrast, observed CO profiles are relatively well simulated, which points to a possible problem with wet scavenging. Decreasing the prescribed aerosol scavenging coefficients within the range of experimental data available in the literature significantly improves the agreement with observations. Sulfate and BC burdens in the Arctic increase by a factor 5-6. Annual global lifetimes of sulfate and BC increase from 3.1 to 4.6 days and from 4.4 to 5.9 days, respectively. Using the improved simulation, we find that 59% of sulfate in the Arctic troposphere comes from the oxidation of SO<inf>2</inf> emitted in Siberia (19%), Europe (18%), Asia (13%), and North America (9%). Anthropogenic and biomass burning BC emitted in Siberia, Asia, Europe, and North America contributes 29, 27, 25, and 17%, respectively, to the Arctic BC burden. Emissions of aerosols (or precursors) from Siberia and Europe are more susceptible to be transported and subsequently deposited on the Arctic (about 7-12%) compared to those from North America and Asia (1-4%). Overall, the study shows that aerosol scavenging removal processes play a crucial role on the aerosol transport from the midlatitudes toward the Arctic and should be carefully characterized in aerosol models. Copyright 2011 by the American Geophysical Union."
"56981683600;56066760100;55697757300;","Effects of convective parameterization schemes on estimation of the annual wet deposition over Northeast Asia",2011,"10.1016/j.atmosenv.2010.09.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751581903&doi=10.1016%2fj.atmosenv.2010.09.031&partnerID=40&md5=964c957752a00d05f5c42324947e350c","This paper presents technique used to estimate annual total wet depositions of NO3- and SO42-, and describes their sensitivities arising from various convective parameterization schemes over Northeast Asia. The representative synoptic meteorological conditions for the precipitation were identified by employing a cluster analysis technique, and four cumulus convective parameterization schemes, the Anthes-Kuo (AK), Betts-Miller (BM), Grell (GR), and Kain-Fritsch 2 (KF2) schemes, were applied to estimate annual wet deposition simulations. The four convective parameterization schemes were found to reproduce the overall observed precipitation band for each of the classified synoptic patterns. When cluster analysis was used with these four schemes, the estimated annual total wet depositions of SO42- and NO3- over South Korea were found to reach 184-197 and 277-337 kton year-1, respectively, with the highest estimation found with the KF2 scheme. These estimates were higher than the results of the continuous full year-long simulations by three dimensional comprehensive acid deposition model, which found values of 130 kton year-1 for SO42- and 270 kton year-1 for NO3-. There was a 15.2% variability in the annual total precipitation from the use of the different convective parameterizations of the four schemes, but the annual total wet depositions of the four cloud parameterization schemes were in good agreement, with estimated variabilities of approximately 9.1 and 8.8% for SO42- and NO3-, respectively. At less than ∼10%, these variations were small and negligible in an estimation of the long-term depositions over the region of Korean Peninsula. © 2010 Elsevier Ltd."
"35731251200;24495045400;6602311240;6603980201;7201432984;7202429440;6507224602;35467405200;7005773698;","Unique ocean-derived particles serve as a proxy for changes in ocean chemistry",2011,"10.1029/2010JD015289","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053601471&doi=10.1029%2f2010JD015289&partnerID=40&md5=991748c6e0e0af574ad9ef97b65c6be2","Oceans represent a significant natural source of gases and particles to the atmosphere. Relative to gas phase compounds, less is known regarding the influence of changes in biological activity in the ocean on the chemistry of sea spray aerosols produced in marine environments. To gain insight into the influence of ocean biology and chemistry on atmospheric aerosol chemistry, simultaneous real-time measurements were made of atmospheric aerosol size and chemical mixing-state, gas phase dimethyl sulfide (DMS), as well as seawater DMS and chlorophyll a. In three different marine environments with elevated chlorophyll a and DMS, unique Mg particles were detected containing Mg 2+, Ca2+, K+, and organic carbon. These particles were segregated from sea salt particles highlighting that two subpopulations within the sea spray were being ejected from the ocean. Strong temporal correlations were observed between these unique ocean-derived particles and freshly emitted sea salt particles (R2 = 0.86), particularly as wind speed increased to at least 10 m/s, and atmospheric DMS (R2 = 0.76). Time series correlations between ocean measurements and atmospheric aerosol chemistry suggest that chlorophyll a and DMS serve as indicators of changes in the chemistry of the ocean, most likely an increase in organic material, which is directly reflected in the single particle mixing-state. This is the first time such real-time correlations are shown between ocean chemistry and atmospheric aerosol mixing-state. The reasons behind these observed changes in aerosol chemistry are critical for understanding the heterogeneous reactivity, water uptake, and cloud forming potential of sea spray aerosols. © 2011 by the American Geophysical Union."
"7403326970;7402523567;57203348817;57201410408;","Three-dimensional characteristics of stratospheric mountain waves during T-REX",2011,"10.1175/2010MWR3466.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951649279&doi=10.1175%2f2010MWR3466.1&partnerID=40&md5=f715dd500a4a462362f357e770d8e221","Measurements from the National Science Foundation/National Center for Atmospheric Research (NSF/NCAR) Gulfstream V (G-V) obtained during the recent Terrain-Induced Rotor Experiment (T-REX) indicate marked differences in the character of the wave response between repeated flight tracks across the Sierra Nevada, which were separated by a distance of approximately 50 km. Observations from several of the G-V research flights indicate that the vertical velocities in the primary wave exhibited variations up to a factor of 2 between the southern and northern portions of the racetrack flight segments in the lower stratosphere, with the largest amplitude waves most often occurring over the southern flight leg, which has a terrain maximum that is 800 m lower than the northern leg. Multiple racetracks at 11.7- and 13.1-km altitudes indicate that these differences were repeatable, which is suggestive that the deviations were likely due to vertically propagating mountain waves that varied systematically in amplitude rather than associated with transients. The cross-mountain horizontal velocity perturbations are also a maximum above the southern portion of the Sierra Nevada ridge. Real data and idealized nonhydrostatic numerical model simulations are used to test the hypothesis that the observed variability in the wave amplitude and characteristics in the along-barrier direction is a consequence of blocking by the three-dimensional Sierra Nevada and the Coriolis effect. The numerical simulation results suggest that wave launching is sensitive to the overall three-dimensional characteristics of the Sierra Nevada barrier, which has an important impact on the wave amplitude and characteristics in the lower stratosphere. Real-time high-resolution Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) forecasts successfully capture the along-barrier variations in the wave amplitude (using vertical velocity as a proxy) as well as skillfully distinguishing between large- and small-amplitude stratospheric wave events during T-REX. © 2011 American Meteorological Society."
"8229909100;7404587604;","Regional variability of convection over northern India during the pre-monsoon season",2011,"10.1007/s00704-010-0289-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951556277&doi=10.1007%2fs00704-010-0289-4&partnerID=40&md5=1cc9dff29732af7fc90d6733742b17d0","In general, the overall differences in activity and timing of convection are a result of the influence of large-scale regional and synoptic flow patterns on the local mesoscale environment. The linkage between the space-time variability of observed clouds and rainfall, with large-scale circulation patterns and mesoscale variables over north India during the pre-monsoon season (March to May) is the focus of this paper. We use harmonic analysis to identify the first hour of rainfall for 42 stations spread over the north Indian region during the pre-monsoon summer season (March to May), from 1980 to 2000. The variability is observed to be systematic, with large regions having similar timing for occurrence of rainfall. The stations located in the foothills of the Himalayas have a late night to early morning maximum of first hour rainfall. In the northwestern plains, the first hour of rainfall mostly starts in the early afternoon to evening hours. Further eastward, the rainfall occurs in the late evening hours. Overall, there is a gradient in the occurrence of first rainfall events from late afternoon hours in the southern sections of the north Indian region to nocturnal maxima in the higher altitude regions. Five of these stations, located in different regions of homogenous timing of rainfall occurrence, were selected to analyze in detail the variable trigger for convection. Our results indicate that convective episodes occur mostly in association with the passage of westerly troughs over this region. These upper atmosphere troughs enable moisture to flow from the surrounding oceanic regions to the dry inland regions and also provide some dynamic support to the episodes of convection. However, the actual occurrence of convection is triggered by local factors, giving rise to the mesoscale structure of the weather systems during this season. Specifically, over the plains of northwest India, convection is triggered in a moistened environment by diurnal solar heating. The late night to early morning convection over the foothills is triggered by the orography, when the moistened airflow is normally incident on the mountain slopes. Further eastward, the primary trigger for localized moist convection is downdrafts from south-eastward propagating convective systems that originate at a north-south dry line over north India. These systems propagate with a speed of about 15 m s-1. The above results are supported by geostationary satellite brightness temperature data for March to May 2008. © 2010 Springer-Verlag."
"16177084000;57205638870;6701597468;14051743300;7007020226;56270311300;22978151200;57203200427;7102517130;7003851845;14059827200;7006270084;8661887700;7003666669;57208462871;6507533363;7103206141;56249704400;55598938800;7004936821;55717074000;6603711967;36705143500;24322005900;7003777747;7102604282;55403720400;57208121852;7202079615;6603400519;","Global dust model intercomparison in AeroCom phase i",2011,"10.5194/acp-11-7781-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961118323&doi=10.5194%2facp-11-7781-2011&partnerID=40&md5=9796bb68194cd63443abb083de5aa505","This study presents the results of a broad intercomparison of a total of 15 global aerosol models within the AeroCom project. Each model is compared to observations related to desert dust aerosols, their direct radiative effect, and their impact on the biogeochemical cycle, i.e., aerosol optical depth (AOD) and dust deposition. Additional comparisons to Angström exponent (AE), coarse mode AOD and dust surface concentrations are included to extend the assessment of model performance and to identify common biases present in models. These data comprise a benchmark dataset that is proposed for model inspection and future dust model development. There are large differences among the global models that simulate the dust cycle and its impact on climate. In general, models simulate the climatology of vertically integrated parameters (AOD and AE) within a factor of two whereas the total deposition and surface concentration are reproduced within a factor of 10. In addition, smaller mean normalized bias and root mean square errors are obtained for the climatology of AOD and AE than for total deposition and surface concentration. Characteristics of the datasets used and their uncertainties may influence these differences. Large uncertainties still exist with respect to the deposition fluxes in the southern oceans. Further measurements and model studies are necessary to assess the general model performance to reproduce dust deposition in ocean regions sensible to iron contributions. Models overestimate the wet deposition in regions dominated by dry deposition. They generally simulate more realistic surface concentration at stations downwind of the main sources than at remote ones. Most models simulate the gradient in AOD and AE between the different dusty regions. However the seasonality and magnitude of both variables is better simulated at African stations than Middle East ones. The models simulate the offshore transport of West Africa throughout the year but they overestimate the AOD and they transport too fine particles. The models also reproduce the dust transport across the Atlantic in the summer in terms of both AOD and AE but not so well in winter-spring nor the southward displacement of the dust cloud that is responsible of the dust transport into South America. Based on the dependency of AOD on aerosol burden and size distribution we use model bias with respect to AOD and AE to infer the bias of the dust emissions in Africa and the Middle East. According to this analysis we suggest that a range of possible emissions for North Africa is 400 to 2200 Tg yr-1 and in the Middle East 26 to 526 Tg yr-1. © 2011 Author(s)."
"36071197200;7402989545;","El Niño-Southern Oscillation-related principal interannual variability modes of early and late summer rainfall over East Asia in sea surface temperature-driven atmospheric general circulation model simulations",2011,"10.1029/2011JD015691","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961245334&doi=10.1029%2f2011JD015691&partnerID=40&md5=ad5e9451b1ad0fec9b83e049075c6334","A large portion of interannual variability during early summer (May-June mean; hereinafter referred to as MJ) and late summer (July-August mean; hereinafter referred to as JA) rainfall over East Asia is dominated by El Nio-Southern Oscillation (ENSO) events. Four ENSO-related modes have been identified by using empirical orthogonal function (EOF) decomposition analysis on East Asian rainfall for the period 1980-1999, with EOF2 for MJ rainfall (hereinafter referred to as MJ-2; similar notations are used for other modes) corresponding to the developing phase of La Nia events, while MJ-3, JA-1, and JA-2 correspond to the decaying phase of El Nio events. The authors investigate the predictability of ENSO-related MJ and JA rainfall modes by analyzing the outputs of 12 atmospheric general circulation models (AGCMs) of the Atmospheric Model Intercomparison Project Phase II (AMIP II), which were run in an AGCM stand-alone mode and were forced by the monthly historical sea surface temperature (SST) from 1980 to 1999. The results show that although the climatological differences between MJ and JA rainfall are reasonably reproduced by most AGCMs, the four ENSO-related interannual variability modes of MJ and JA rainfall show different predictabilities. While both atmospheric circulation and precipitation anomalies associated with MJ-3 (the slow El Nio decaying mode) are reasonably reproduced by nearly all the models, the JA-1 (MJ-2) mode is only partly reproduced by about two thirds (half) of the AMIP II models. All models fail to reproduce the JA-2 mode. The relatively low skills in predicting both JA-1 and JA-2 modes are primarily due to the bias of the AMIP models in simulating both the intensity and the position of the western North Pacific anticyclone. The predictability of the JA-1 mode is slightly higher than that of JA-2, and the difference results from the stronger and longer persistence of SST anomaly (SSTA) forcing associated with the decaying ENSO events. The low skill of the MJ-2 prediction is due to the weak SSTA forcing associated with the developing phase of La Nia. The skills of the AMIP II models in predicting the leading interannual variability modes of East Asian summer rainfall do not depend on the horizontal resolutions of the models. Copyright 2011 by the American Geophysical Union."
"57202025812;6603124065;7003798485;7005876722;7003396358;8598244800;35910740000;6602151929;","Physical and chemical consequences of artificially deepened thermocline in a small humic lake - A paired whole-lake climate change experiment",2010,"10.5194/hess-14-2629-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650558580&doi=10.5194%2fhess-14-2629-2010&partnerID=40&md5=09a60aa76484dacd6a2b915dd0d1b792","Climate change with higher air temperatures and changes in cloud cover, radiation and wind speed alters the heat balance and stratification patterns of lakes. A paired whole-lake thermocline manipulation experiment of a small (0.047 km2) shallow dystrophic lake (Halsjärvi) was carried out in southern Finland. A thermodynamic model (MyLake) was used for both predicting the impacts of climate change scenarios and for determining the manipulation target of the experiment. The model simulations assuming several climate change scenarios indicated large increases in the whole-lake monthly mean temperature (+1.4-4.4 °C in April-October for the A2 scenario), and shortening of the length of the ice covered period by 56-89 days. The thermocline manipulation resulted in large changes in the thermodynamic properties of the lake, and those were rather well consistent with the simulated future increases in the heat content during the summer-autumn season. The manipulation also resulted in changes in the oxygen stratification, and the expansion of the oxic water layer increased the spatial extent of the sediment surface oxic-anoxic interfaces. In addition, the experiment affected several other chemical constituents; concentrations of organic carbon, TotN, and NH4 showed a statistically significant decrease, likely due to both changes in hydrological conditions during the experiment period and increased decomposition and sedimentation. In comparison with the results of a similar whole-lake manipulation experiment in a deep, oligotrophic, clear-watered lake in Norway, it is evident that shallow dystrophic lakes, common in the boreal region, are more sensitive to physical perturbations. This means that projected climate change may modify their physical and chemical conditions in the future. © 2010 Author(s)."
"8422280800;7005968859;7004715270;8586682800;6603385031;6601927317;","Laboratory investigations of the impact of mineral dust aerosol on cold cloud formation",2010,"10.5194/acp-10-11955-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955782953&doi=10.5194%2facp-10-11955-2010&partnerID=40&md5=31604aa1d41320dc682e9e27fc42e3da","Dust particles represent a dominant source of particulate matter (by mass) to the atmosphere, and their emission from some source regions has been shown to be transported on regional and hemispherical scales. Dust particles' potential to interact with water vapor in the atmosphere can lead to important radiative impacts on the climate system, both direct and indirect. We have investigated this interaction for several types of dust aerosol, collected from the Southwestern United States and the Saharan region. A continuous flow diffusion chamber was operated to measure the ice nucleation ability of the dust particles in the temperature range of relevance to cirrus and mixed-phase clouds (-65>T>-20 °C). In most experiments, particles were size selected using a differential mobility analyzer prior to sampling to give information on heterogeneity of the sample with size, generally in the range of diameters 100-400 nm. All dust nucleated ice heterogeneously in the deposition mode colder than about -40 °C, but required droplet activation in the exclusively heterogeneous ice nucleation regime warmer than -36 °C. Ice nucleated on 1% of dry generated dust particles of a given type at a similar relative humidity with respect to ice irrespective of temperature between -60 and -40 °C, however differences in relative humidity for ice nucleation was observed between the different dust types. The Saharan dust types exhibited a dependency on particle size below 500 nm. Additional data were collected during the International Workshop on Comparing Ice Nucleation Measurement Systems (ICIS, 2007) which indicated that ice nucleation on larger, polydisperse dust particles occurs at warmer temperatures than found for the smaller particles. When particles were coated with secondary organic aerosol (SOA) species, higher relative humidity was required for ice nucleation below -40 °C, similar to that required for homogeneous nucleation of sulfates. However, ice nucleation was still observed on SOA-coated dust at warmer temperatures than are required for homogeneous nucleation of sulfates, indicating that condensation freezing occurs without any apparent deactivation for temperatures between -25 and -35 °C. © 2010 Author(s)."
"8309699900;7005284577;7402049334;16031217900;","Water droplet calibration of the Cloud Droplet Probe (CDP) and in-flight performance in liquid, ice and mixed-phase clouds during ARCPAC",2010,"10.5194/amt-3-1683-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952168646&doi=10.5194%2famt-3-1683-2010&partnerID=40&md5=421b6b40392129c64048f5f19342f053","Laboratory calibrations of the Cloud Droplet Probe (CDP) sample area and droplet sizing are performed using water droplets of known size, generated at a known rate. Although calibrations with PSL and glass beads were consistent with theoretical instrument response, liquid water droplet calibrations were not, and necessitated a 2 1/4m shift in the manufacturer's calibration. We show that much of this response shift may be attributable to a misalignment of the optics relative to the axis of the laser beam. Comparison with an independent measure of liquid water content (LWC) during in-flight operation suggests much greater biases in the droplet size and/or droplet concentration measured by the CDP than would be expected based on the laboratory calibrations. Since the bias in CDP-LWC is strongly concentration dependent, we hypothesize that this discrepancy is a result of coincidence, when two or more droplets pass through the CDP laser beam within a very short time. The coincidence error, most frequently resulting from the passage of one droplet outside and one inside the instrument sample area at the same time, is evaluated in terms of an ""extended sample area"" (SAE), the area in which individual droplets can affect the sizing detector without necessarily registering on the qualifier. SAE is calibrated with standardized water droplets, and used in a Monte-Carlo simulation to estimate the effect of coincidence on the measured droplet size distributions. The simulations show that extended coincidence errors are important for the CDP at droplet concentrations even as low as 200 cm 3, and these errors are necessary to explain the trend between calculated and measured LWC observed in liquid and mixed-phase clouds during the Aerosol, Radiation and Cloud Processes Affecting Arctic Climate (ARCPAC) study. We estimate from the simulations that 60% oversizing error and 50% undercounting error can occur at droplet concentrations exceeding 400 cm -3. Modification of the optical design of the CDP is currently being explored in an effort to reduce this coincidence bias. © 2010 Author(s)."
"7004299063;","New START, eyjafjallajkull, and nuclear winter",2010,"10.1029/2010EO470004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650293992&doi=10.1029%2f2010EO470004&partnerID=40&md5=2321bf27f3d9b5ef36838b794314a9bc","On 8 April 2010, U.S. president Barack Obama and Russian president Dmitry Medvedev signed the Treaty Between the United States of America and the Russian Federation on Measures for the Further Reduction and Limitation of Strategic Offensive Arms, committing the United States and Russia to reducing their nuclear arsenals to levels less than 5% of the maximum during the height of the cold war in the 1980s. This treaty is called ""New START,"" as it is a follow-on to the 1991 Strategic Arms Reductions Treaty (START). On 14 April 2010 the Eyjafjallajkull volcano in Iceland began an explosive eruption phase that shut down air traffic in Europe for 6 days and continued to disrupt it for another month. What do these two events have in common? Nuclear weapons, when targeted at cities and industrial areas, would start fires, producing clouds of sooty smoke. Volcanic eruptions emit ash particles and sulfur dioxide (SO 2), which forms sulfate aerosols in the atmosphere. Thus, both the use of nuclear weapons and volcanic eruptions produce particles that can be transported large distances from the source and can affect weather and climate."
"7005706662;","Stratocumulus cloud thickening beneath layers of absorbing smoke aerosol",2010,"10.5194/acp-10-11769-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650096813&doi=10.5194%2facp-10-11769-2010&partnerID=40&md5=863da403e71b064f78633a44b4269990","Marine stratocumulus cloud properties, and the free-tropospheric environment above them, are examined in NASA A-Train satellite data for cases where smoke from seasonal burning of the West African savannah overlay the persistent southeast Atlantic stratocumulus cloud deck. CALIPSO space-borne lidar observations show that features identified as layers of aerosol occur predominantly between 2 km and 4 km. Layers identified as cloud features occur predominantly below 1.5 km altitude and beneath the layer of elevated smoke aerosol. The diurnal mean shortwave heating rates attributable to the absorption of solar energy in the aerosol layer is nearly 1.5 K d-1 for an aerosol optical thickness value of 1, and increases to 1.8 K d-1 when the smoke resides above clouds owing to the additional component of upward solar radiation reflected by the cloud. As a consequence of this heating, the 700 hPa air temperature above the cloud deck is warmer by approximately 1 K on average for cases where smoke is present above the cloud compared to cases without smoke above cloud. The warmer conditions in the free-troposphere above the cloud during smoke events coincide with cloud liquid water path values that are greater by 20 g m-2 and cloud tops that are lower for overcast conditions compared to periods with low amounts of smoke. The observed thickening and subsidence of the cloud layer are consistent with published results of large-eddy simulations showing that solar absorption by smoke above stratocumulus clouds increases the buoyancy of free-tropospheric air above the temperature inversion capping the boundary layer. Increased buoyancy inhibits the entrainment of dry air through the cloud-top, thereby helping to preserve humidity and cloud cover in the boundary layer. The direct radiative effect of absorbing aerosols residing over a bright cloud deck is a positive radiative forcing (warming) at the top of the atmosphere. However, the greater liquid water path for cases of smoke overlaying cloud contributes an additional negative semi-direct radiative forcing (cooling) of climate in locations such as the southeast Atlantic Ocean owing to the enhanced albedo of the thicker cloud. © 2010 Author(s)."
"18434033000;6701363731;26432415000;7003286544;6602712032;36675127200;35272412300;6602884114;6603413642;","Decadal regional air quality simulations over Europe in present climate: Near surface ozone sensitivity to external meteorological forcing",2010,"10.5194/acp-10-11805-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650156291&doi=10.5194%2facp-10-11805-2010&partnerID=40&md5=a8df14c0155a111b474bc3a6b367f9fb","Regional climate-air quality decadal simulations over Europe were carried out with the RegCM3/CAMx modeling system for the time slice 1991-2000, in order to study the impact of different meteorological forcing on surface ozone. The RegCM3 regional climate model was firstly constrained by the ERA40 reanalysis dataset which is considered as an experiment with perfect meteorological boundary conditions and then it was constrained by the global circulation model ECHAM5. A number of meteorological parameters were examined including the 500 mb geopotential height, solar radiation, temperature, cloud liquid water path, planetary boundary layer height and surface wind. The different RegCM meteorological forcing resulted in changes of near surface ozone over Europe ranging between &amp;plusmn; 4 ppb for winter and summer. The area showing the greatest sensitivity in O3 during winter is central and southern Europe while in summer central north continental Europe. The different meteorological forcing impacts on the atmospheric circulation, which in turn affects cloudiness and solar radiation, temperature, wind patterns and the meteorology depended biogenic emissions. For comparison reasons, the impact of chemical boundary conditions on surface ozone was additionally examined with a series of sensitivity studies, indicating that surface ozone changes are comparable to those caused by the different meteorological forcing. These findings suggest that, when it comes to regional climate-air quality simulations, the selection of external meteorological forcing can be as important as the selection of adequate chemical lateral boundary conditions. © 2010 Author(s)."
"35857960400;7004940109;7003375121;6701427386;","Simulation of the surface temperature anomalies in the Northern Hemisphere during the last 300 years of the Little Ice Age using a thermodynamic model",2010,"10.3354/cr00938","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649876330&doi=10.3354%2fcr00938&partnerID=40&md5=d9ca4cf9c0cce9c2a27c8472ea6eafbb","The last 300 yr of the Little Ice Age are characterized by 3 minima in solar activity, known as the Maunder Minimum (∼1645-1710), the Dalton Minimum (∼1795-1823) and a minimum between ∼1880 and 1930. In particular, during the Maunder and Dalton minima, surface temperature reconstructions present anomalies larger than -0.7°C. Experiments using an energy balance model, known as the thermodynamic climate model (TCM), show that the changes in CO2 and solar irradiance, relative to the period 1961-1990, produced a temperature decrease of approximately -0.27°C during the Maunder Minimum in the Northern Hemisphere. The incorporation of changes in low cloud cover, which we assumed as induced by the galactic cosmic rays, caused an even larger decrease in the surface temperature, which reached approximately -0.46°C in the Maunder Minimum. The results of the model are compared with reconstructions of surface temperature anomalies developed by several authors, showing good agreement. We conclude that including an empirical relationship between low cloud cover and cosmic rays in the TCM produces a noticeable cooling in model results. © Inter-Research 2010."
"57189372185;35461763400;6701697023;7004864963;24366038500;7005941217;56477623800;13403849600;7102062952;16549600900;57203776263;8941151400;6603785227;7003461830;57214160655;13408773700;8586682800;6603385031;55942083800;7102830450;55730602600;7410177774;7005287667;26434039800;57192695511;7006595513;26024519600;","An overview of the Amazonian Aerosol Characterization Experiment 2008 (AMAZE-08)",2010,"10.5194/acp-10-11415-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649896351&doi=10.5194%2facp-10-11415-2010&partnerID=40&md5=c9cbfd7347c60ea73a4dd8f0942cd97a","The Amazon Basin provides an excellent environment for studying the sources, transformations, and properties of natural aerosol particles and the resulting links between biological processes and climate. With this framework in mind, the Amazonian Aerosol Characterization Experiment (AMAZE-08), carried out from 7 February to 14 March 2008 during the wet season in the central Amazon Basin, sought to understand the formation, transformations, and cloud-forming properties of fine- and coarse-mode biogenic aerosol particles, especially as related to their effects on cloud activation and regional climate. Special foci included (1) the production mechanisms of secondary organic components at a pristine continental site, including the factors regulating their temporal variability, and (2) predicting and understanding the cloud-forming properties of biogenic particles at such a site. In this overview paper, the field site and the instrumentation employed during the campaign are introduced. Observations and findings are reported, including the large-scale context for the campaign, especially as provided by satellite observations. New findings presented include: (i) a particle number-diameter distribution from 10 nm to 10 Î1/4m that is representative of the pristine tropical rain forest and recommended for model use; (ii) the absence of substantial quantities of primary biological particles in the submicron mode as evidenced by mass spectral characterization; (iii) the large-scale production of secondary organic material; (iv) insights into the chemical and physical properties of the particles as revealed by thermodenuder-induced changes in the particle number-diameter distributions and mass spectra; and (v) comparisons of ground-based predictions and satellite-based observations of hydrometeor phase in clouds. A main finding of AMAZE-08 is the dominance of secondary organic material as particle components. The results presented here provide mechanistic insight and quantitative parameters that can serve to increase the accuracy of models of the formation, transformations, and cloud-forming properties of biogenic natural aerosol particles, especially as related to their effects on cloud activation and regional climate. © 2010 Author(s)."
"25031484700;7003627515;6603873829;12767251100;","Climate of the Greenland ice sheet using a high-resolution climate model - Part 2: Near-surface climate and energy balance",2010,"10.5194/tc-4-529-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649861157&doi=10.5194%2ftc-4-529-2010&partnerID=40&md5=4fdd2c17116c042a41a5b096c538fb33","The spatial variability of near-surface variables and surface energy balance components over the Greenland ice sheet are presented, using the output of a regional atmospheric climate model for the period 1958-2008. The model was evaluated in Part 1 of this paper. The near-surface temperature over the ice sheet is affected by surface elevation, latitude, longitude, large-scale and small-scale advection, occurrence of summer melt and mesoscale topographical features. The atmospheric boundary layer is characterised by a strong temperature inversion, due to continuous longwave cooling of the surface. In combination with a gently sloping surface the radiative loss maintains a persistent katabatic wind. This radiative heat loss is mainly balanced by turbulent sensible heat transport towards the surface. In summer, the surface is near radiative balance, resulting in lower wind speeds. Absorption of shortwave radiation and a positive subsurface heat flux due to refreezing melt water are heat sources for surface sublimation and melt. The strongest temperature deficits (&gt;13 °C) are found on the northeastern slopes, where the strongest katabatic winds (&gt;9 m s-1) and lowest relative humidity (&lt;65%) occur. Due to strong large scale winds, clear sky (cloud cover &lt;0.5) and a concave surface, a continuous supply of cold dry air is generated, which enhances the katabatic forcing and suppresses subsidence of potentially warmer free atmosphere air. © Author(s) 2010."
"57203053317;16444232500;","Impact of parametric uncertainties on the present-day climate and on the anthropogenic aerosol effect",2010,"10.5194/acp-10-11373-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649703815&doi=10.5194%2facp-10-11373-2010&partnerID=40&md5=e20089fcf4ef2553b77c80fcc4c6e6df","Clouds constitute a large uncertainty in global climate modeling and climate change projections as many clouds are smaller than the size of a model grid box. Some processes, such as the rates of rain and snow formation that have a large impact on climate, cannot be observed. The uncertain parameters in the representation of these processes are therefore adjusted in order to achieve radiation balance. Here we systematically investigate the impact of key tunable parameters within the convective and stratiform cloud schemes and of the ice cloud optical properties on the present-day climate in terms of clouds, radiation and precipitation. The total anthropogenic aerosol effect between pre-industrial and present-day times amounts to -1.00 W m-2 obtained as an average over all simulations as compared to -1.02 W m-2 from those simulations where the global annual mean top-of-the atmosphere radiation balance is within &amp;plusmn;1 W m-2. Thus tuning of the present-day climate does not seem to have an influence on the total anthropogenic aerosol effect. The parametric uncertainty regarding the above mentioned cloud parameters has an uncertainty range of 25% between the minimum and maximum value when taking all simulations into account. It is reduced to 11% when only the simulations with a balanced top-of-the atmosphere radiation are considered. © 2010 Author(s)."
"7006813055;56878283500;7004399781;6506129917;7003658685;6602631793;","Sunphotometry of the 2006-2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079ma.s.l.)",2010,"10.5194/acp-10-11209-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77749263931&doi=10.5194%2facp-10-11209-2010&partnerID=40&md5=51c12d6644ffb96d85b16db438efdcf7","n spite of being located at the heart of the highest mountain range in the world, the Himalayan Nepal Climate Observatory (5079ma.s.l.) at the Ev-K2-CNR Pyramid is shown to be affected by the advection of pollution aerosols from the populated regions of southern Nepal and the Indo-Gangetic plains. Such an impact is observed along most of the period April 2006-March 2007 addressed here, with a minimum in the monsoon season. Backtrajectoryanalysis indicates long-range transport episodes occurring in this year to originate mainly in the west Asian deserts. At this high altitude site, the measured aerosol optical depth is observed to be about one order of magnitude lower than the one measured at Ghandi College (60ma.s.l.), in the Indo- Gangetic basin. As for Ghandi College, and in agreement with the in situ ground observations at the Pyramid, the fine mode aerosol optical depth maximizes during winter and minimizes in the monsoon season. Conversely, total optical depth maximizes during the monsoon due to the occurrence of elevated, coarse particle layers. Possible origins of these particles are wind erosion from the surrounding peaks and hydrated/cloud- processed aerosols. Assessment of the aerosol radiative forcing is then expected to be hampered by the presence of these high altitude particle layers, which impede an effective, continuous measurement of anthropogenic aerosol radiative properties from sky radiance inversions and/or ground measurements alone. Even though the retrieved absorption coefficients of pollution aerosols were rather large (single scattering albedo of the order of 0.6-0.9 were observed in the month of April 2006), the corresponding low optical depths (∼0.03 at 500 nm) are expected to limit the relevant radiative forcing. Still, the high specific forcing of this aerosol and its capability of altering snow surface albedo provide good reasons for continuous monitoring. © 2010 Author(s)."
"7401776563;7404597424;7005054220;36455634700;6505876262;57203859138;","Observations of ozone production in a dissipating tropical convective cell during TC4",2010,"10.5194/acp-10-11189-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649571368&doi=10.5194%2facp-10-11189-2010&partnerID=40&md5=580868411519454a237094d8106ae781","From 13 July-9 August 2007, 25 ozonesondes were launched from Las Tablas, Panama as part of the Tropical Composition, Cloud, and Climate Coupling (TC4) mission. On 5 August, a strong convective cell formed in the Gulf of Panama. World Wide Lightning Location Network (WWLLN) data indicated 563 flashes (09:00-17:00 UTC) in the Gulf. NO2 data from the Ozone Monitoring Instrument (OMI) show enhancements, suggesting lightning production of NO x. At 15:05 UTC, an ozonesonde ascended into the southern edge of the now dissipating convective cell as it moved west across the Azuero Peninsula. The balloon oscillated from 2.5-5.1 km five times (15:12-17:00 UTC), providing a unique examination of ozone (O3) photochemistry on the edge of a convective cell. Ozone increased at a rate of ∼1.6-4.6 ppbv/hr between the first and last ascent, resulting cell wide in an increase of ∼(2.1-2.5) × 106 moles of O3. This estimate agrees to within a factor of two of our estimates of photochemical lightning O3 production from the WWLLN flashes, from the radar-inferred lightning flash data, and from the OMI NO2 data (∼1.2, ∼1.0, and ∼1.7 × 106 moles, respectively), though all estimates have large uncertainties. Examination of DC-8 in situ and lidar O3 data gathered around the Gulf that day suggests 70-97% of the O3 change occurred in 2.5-5.1 km layer. A photochemical box model initialized with nearby TC4 aircraft trace gas data suggests these O3 production rates are possible with our present understanding of photochemistry. © Author(s) 2010."
"23020321400;35592560600;","An ensemble cumulus convection parameterization with explicit cloud treatment",2010,"10.1175/2010JAS3485.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651062867&doi=10.1175%2f2010JAS3485.1&partnerID=40&md5=3197d3fc65528adb8e39633374070642","The paper describes a convection parameterization employing a new formulation of the quasi-equilibrium closure hypothesis of Arakawa and Schubert. The scheme models a full spectrum of different cumulus clouds and its evolution within one time step of the host global climate model. Each cloud is simulated using a one-dimensional Lagrangian entraining parcel model, which includes mixed phase microphysics and vertical velocity. Hence, the model delivers explicit information on distribution of vertical velocities, precipitation intensities, cloud heights, and cloud coverage. The parameterization is evaluated in the ECHAM single-column model for midlatitude summer and tropical convection. Results show an improved temporal distribution, including the diurnal cycle, of convective heating and moistening in comparison to the Tiedtke-Nordeng scheme, which is the standard convection parameterization within ECHAM. The amount and temporal distribution of precipitation are clearly improved compared with the original parameterization. The convective cloud field model (CCFM) does not produce spurious convection events occurring with the standard parameterization. © 2010 American Meteorological Society."
"36720934300;15026371500;","Increasing atmospheric poleward energy transport with global warming",2010,"10.1029/2010GL045440","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650875283&doi=10.1029%2f2010GL045440&partnerID=40&md5=681388b8059996979948f1ea6c032df4","Most state-of-the-art global climate models (GCMs) project an increase in atmospheric poleward energy transport with global warming; however, the amount of increase varies significantly from model to model. Using an energy balance model that diffuses moist static energy, it is shown that: (1) the increase in atmospheric moisture content causes most of the increase in transport, and (2) changes in the radiation budget due to clouds explain most of the spread among GCMs. This work also shows that biases in clouds, surface albedo, ocean heat uptake, and aerosols will not only affect climate locally but will also influence other latitudes through energy transport. © 2010 by the American Geophysical Union."
"6603431534;35473805400;","Vertical velocity statistics in fair-weather cumuli at the ARM TWP nauru climate research facility",2010,"10.1175/2010JCLI3449.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251580378&doi=10.1175%2f2010JCLI3449.1&partnerID=40&md5=10071e87a731dbc636c1f109b271ff2b","Fair-weather cumuli are fundamental in regulating the vertical structure of water vapor and entropy in the lowest 2-3 km of the earth's atmosphere over vast areas of the oceans. In this study, a long record of profiling cloud radar observations at the Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) at Nauru Island is used to investigate cloud vertical air motion statistics over an 8-yr observing period. Appropriate processing of the observed low radar reflectivities provides radar volume samples that contain only small cloud droplets; thus, the Doppler velocities are used as air motion tracers. The technique is applied to shallow boundary layer clouds (less than 1000 m thick) during the 1999-2007 period when radar data are available. Using the boundary layer winds from the soundings obtained at the Nauru ACRF, the fair-weather cumuli fields are classified in easterly and westerly boundary layer wind regimes. This distinction is necessary to separate marine-forced (westerlies) from land-forced (easterlies) shallow clouds because of a well-studied island effect at the Nauru ACRF. The two regimes exhibit large diurnal differences in cloud fraction and cloud dynamics as manifested by the analysis of the hourly averaged vertical air motion statistics. The fair-weather cumuli fields associated with easterlies exhibit a strong diurnal cycle in cloud fraction and updraft strength and fraction, indicating a strong influence of land-forced clouds. In contrast over the fair-weather cumuli with oceanic origin, land-forced clouds are characterized by uniform diurnal cloudiness and persistent updrafts at the cloud-base level. This study provides a unique observational dataset appropriate for testing fair-weather cumulus mass flux and turbulence parameterizations in numerical models. © 2010 American Meteorological Society."
"36705293400;7409390483;56170414300;56171203400;","Climatic trend of cloud amount related to the aerosol characteristics in Beijing during",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952762870&partnerID=40&md5=b49ea64831715a4b4e3b11fbc6a2d9b7","This paper analyzes the correlation between variations of total and low cloud amounts and the varying features of aerosols related to urban development of Beijing by using the cubic spline fi{ligature}tting method based on the monthly meteorological data of temperature, humidity, precipitation, clouds, and aerosol optical depth (AOD) during 1950-2005. The statistics on the development of the city of Beijing in this period, including the total industrial output, population, residential housing development, highway construction, charcoal production, etc., is revealed. Accompanying the rapid urban development of Beijing over the past 55 years or so, the urban aerosol concentration and composition have changed. The results indicate that: 1) there is a general trend of climate warming and drying in Beijing; 2) the total cloud amount in all seasons declines drastically, but lower cloud amount climbs up slightly; 3) the high correlations between cloud amount and the indices of Beijing urban development such as the housing area, charcoal production, and road construction show that the variation of cloud amount is closely related to the urban development; 4) the changing trend of AOD coincides more closely with the variation of low cloud amount. The evident drop of total cloud amount is in agreement with the trend of climate warming and drying, while the slight growth of low cloud amount is likely caused by more haze and fog occurrences in the lower troposphere in association with the pollution responsible for the ""darkening"" of Beijing and the surrounding areas."
"7202885713;7201990763;7103232081;35512883100;7101631674;7006039508;7004109472;6507411998;7403906746;7201602110;6701818964;7006518289;7004214645;7006241374;7402245653;","Solar influences on climate",2010,"10.1029/2009RG000282","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953746643&doi=10.1029%2f2009RG000282&partnerID=40&md5=42965cd442a5b63b19b05ef976fa4e79","Understanding the influence of solar variability on the Earth's climate requires knowledge of solar variability, solar-terrestrial interactions, and the mechanisms determining the response of the Earth's climate system. We provide a summary of our current understanding in each of these three areas. Observations and mechanisms for the Sun's variability are described, including solar irradiance variations on both decadal and centennial time scales and their relation to galactic cosmic rays. Corresponding observations of variations of the Earth's climate on associated time scales are described, including variations in ozone, temperatures, winds, clouds, precipitation, and regional modes of variability such as the monsoons and the North Atlantic Oscillation. A discussion of the available solar and climate proxies is provided. Mechanisms proposed to explain these climate observations are described, including the effects of variations in solar irradiance and of charged particles. Finally, the contributions of solar variations to recent observations of global climate change are discussed. © 2010 by the American Geophysical Union."
"23486332900;6701455548;7004169476;","Climate feedbacks determined using radiative kernels in a multi-thousand member ensemble of AOGCMs",2010,"10.1007/s00382-009-0661-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649327281&doi=10.1007%2fs00382-009-0661-1&partnerID=40&md5=12a36881d76f4ddd9e6c5e1a52a7d79c","The use of radiative kernels to diagnose climate feedbacks is a recent development that may be applied to existing climate change simulations. We apply the radiative kernel technique to transient simulations from a multi-thousand member perturbed physics ensemble of coupled atmosphere-ocean general circulation models, comparing distributions of model feedbacks with those taken from the CMIP-3 multi GCM ensemble. Although the range of clear sky longwave feedbacks in the perturbed physics ensemble is similar to that seen in the multi-GCM ensemble, the kernel technique underestimates the net clear-sky feedbacks (or the radiative forcing) in some perturbed models with significantly altered humidity distributions. In addition, the compensating relationship between global mean atmospheric lapse rate feedback and water vapor feedback is found to hold in the perturbed physics ensemble, but large differences in relative humidity distributions in the ensemble prevent the compensation from holding at a regional scale. Both ensembles show a similar range of response of global mean net cloud feedback, but the mean of the perturbed physics ensemble is shifted towards more positive values such that none of the perturbed models exhibit a net negative cloud feedback. The perturbed physics ensemble contains fewer models with strong negative shortwave cloud feedbacks and has stronger compensating positive longwave feedbacks. A principal component analysis used to identify dominant modes of feedback variation reveals that the perturbed physics ensemble produces very different modes of climate response to the multi-model ensemble, suggesting that one may not be used as an analog for the other in estimates of uncertainty in future response. Whereas in the multi-model ensemble, the first order variation in cloud feedbacks shows compensation between longwave and shortwave components, in the perturbed physics ensemble the shortwave feedbacks are uncompensated, possibly explaining the larger range of climate sensitivities observed in the perturbed simulations. Regression analysis suggests that the parameters governing cloud formation, convection strength and ice fall speed are the most significant in altering climate feedbacks. Perturbations of oceanic and sulfur cycle parameters have relatively little effect on the atmospheric feedbacks diagnosed by the kernel technique. © 2009 Springer-Verlag."
"35221791100;6701656335;6701798229;","Cosmic rays linked to rapid mid-latitude cloud changes",2010,"10.5194/acp-10-10941-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649427070&doi=10.5194%2facp-10-10941-2010&partnerID=40&md5=bb1cd3c2763f60d65912bc4fb5e831d4","The effect of the Galactic Cosmic Ray (GCR) flux on Earth's climate is highly uncertain. Using a novel sampling approach based around observing periods of significant cloud changes, a statistically robust relationship is identified between short-term GCR flux changes and the most rapid mid-latitude (60-30 N/S) cloud decreases operating over daily timescales; this signal is verified in surface level air temperature (SLAT) reanalysis data. A General Circulation Model (GCM) experiment is used to test the causal relationship of the observed cloud changes to the detected SLAT anomalies. Results indicate that the anomalous cloud changes were responsible for producing the observed SLAT changes, implying that if there is a causal relationship between significant decreases in the rate of GCR flux (∼0.79 GU, where GU denotes a change of 1% of the 11- year solar cycle amplitude in four days) and decreases in cloud cover (∼1.9 CU, where CU denotes a change of 1% cloud cover in four days), an increase in SLAT (∼0.05 KU, where KU denotes a temperature change of 1K in four days) can be expected. The influence of GCRs is clearly distinguishable from changes in solar irradiance and the interplanetary magnetic field. However, the results of the GCM experiment are found to be somewhat limited by the ability of the model to successfully reproduce observed cloud cover. These results provide perhaps the most compelling evidence presented thus far of a GCR-climate relationship. From this analysis we conclude that a GCR-climate relationship is governed by both short-term GCR changes and internal atmospheric precursor conditions. © 2010 Author(s)."
"55686667100;55619302054;26667030700;8612652300;9249627300;8979277400;7202079615;16645036600;10243650000;36722732500;14628012000;35231763100;10241462700;10240710000;7003967390;6603370049;7102857642;","Improved climate simulation by MIROC5: Mean states, variability, and climate sensitivity",2010,"10.1175/2010JCLI3679.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650547976&doi=10.1175%2f2010JCLI3679.1&partnerID=40&md5=6e09229388fd769c17e067a409754f06","A new version of the atmosphere-ocean general circulation model cooperatively produced by the Japanese research community, known as the Model for Interdisciplinary Research on Climate (MIROC), has recently been developed. A century-long control experiment was performed using the new version (MIROC5) with the standard resolution of the T85 atmosphere and 18 ocean models. The climatological mean state and variability are then compared with observations and those in a previous version (MIROC3.2) with two different resolutions (medres, hires), coarser and finer than the resolution of MIROC5.A few aspects of the mean fields in MIROC5 are similar to or slightly worse than MIROC3.2, but otherwise the climatological features are considerably better. In particular, improvements are found in precipitation, zonal mean atmospheric fields, equatorial ocean subsurface fields, and the simulation of El Niño-Southern Oscillation. The difference between MIROC5 and the previous model is larger than that between the two MIROC3.2 versions, indicating a greater effect of updating parameterization schemes on the model climate than increasing the model resolution. The mean cloud property obtained from the sophisticated prognostic schemes in MIROC5 shows good agreement with satellite measurements. MIROC5 reveals an equilibrium climate sensitivity of 2.6 K, which is lower than that in MIROC3.2 by 1 K. This is probably due to the negative feedback of low clouds to the increasing concentration of CO2, which is opposite to that in MIROC3.2. © 2010 American Meteorological Society."
"57192560178;7501797728;55695193600;35271129900;","Simulations of hydrological cycle changes between the LGM and the present day over China",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952437501&partnerID=40&md5=3dcd259e14bd6914e23ca7510135fe61","Based on the International Satellite Cloud Climatology Project (ISCCP) data in 1983-2006, it is found that there is a high value center of high cloud amount over the Tibetan Plateau (TP), while there is a high value center of middle cloud amount over the Sichuan Basin extending to the coastal area of southeastern China along the same latitude, and a low one over the TP. The present day (PD) and Last Glacial Maximum (LGM) climates are simulated by using the NCAR Community Climate Model (CCM3) nested with a regional mesoscale model (MM5). Comparing the clouds simulated by MM5 with the ISCCP data, it is found that the main patterns of high and middle clouds over China can be reproduced by MM5, which implies that the climate characteristics of clouds might be dominated by relative humidity. Meanwhile, the vertical distributions of water vapor and temperature are also well simulated by MM5. Furthermore, the hydrological cycle changes between the LGM and PD simulations are examined. The results show that during the LGM, the tropospheric temperature decreases in summer with a high value reduction center in the upper and middle troposphere; in winter, a high value reduction center of temperature appears in the middle troposphere over southern China, while the temperature in the upper and middle troposphere increases over northern China. There obviously exists a positive correlation between the water vapor content and temperature change. The water vapor content mostly decreases with the maximum drop in the near-ground surface layer, but it increases in the upper and middle troposphere over northern China in winter. Changes of water vapor content gradually weaken with the altitude increasing, reaching the minimum in the upper troposphere. The relative humidity can either increase or decrease with the maximum change greater than 15%. It is not conservative on the regional scale, and its change is consistent with the changes of middle and low clouds. During the LGM, the high cloud reduces nationwide except over Southwest China,and the middle and low clouds also decrease with the greatest reduction seen in the low cloud. Precipitation changes correspond to the changes of middle and low clouds. Based on the changes of the relative humidity and effective precipitation, it is found that during the LGM, Southwest China is wetter in summer, so is Northwest China."
"6506537159;7102743829;7202619752;","Large-Eddy simulation of post-cold-frontal continental stratocumulus",2010,"10.1175/2010JAS3467.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651090259&doi=10.1175%2f2010JAS3467.1&partnerID=40&md5=2b965d6285987c1caef5facd37457704","Previous large-eddy simulations (LES) of stratocumulus-topped boundary layers have been exclusively set in marine environments. Boundary layer stratocumulus clouds are also prevalent over the continent but have not been simulated previously. A suite of LES runs was performed for a case of continental post-cold-frontal stratocumulus observed by the Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF), located in northern Oklahoma. Comparison with fixed, ground-based sensors necessitated an Eulerian approach in which it was necessary to supply to the model estimates of synoptic-scale advection and vertical motion, particularly given the quickly evolving, baroclinic nature of the synoptic environment. Initial analyses from the Rapid Update Cycle model supplied estimates for these forcing terms. Turbulent statistics calculated from the LES results are consistent with large-eddy observations obtained from millimeter-wave cloud radar. The magnitude of turbulence is weaker than in typical marine stratocumulus, a result attributed to highly decoupled cloud and subcloud circulations associated with a deep layer of negative buoyancy flux arising from the entrainment of warm, free-tropospheric air. Model results are highly sensitive to variations in advection of temperature and moisture and much less sensitive to changes in synoptic-scale vertical velocity and surface fluxes. For this case, moisture and temperature advection, rather than entrainment, tend to be the governing factors in the analyzed cloud system maintenance and decay. Typical boundary layer entrainment scalings applied to this case do not perform very well, a result attributed to the highly decoupled nature of the circulation. Shear production is an important part of the turbulent kinetic energy budget. The dominance of advection provides an optimistic outlook for mesoscale, numerical weather prediction, and climate models because these classes of models represent these grid-scale processes better than they do subgrid-scale processes such as entrainment. © 2010 American Meteorological Society."
"50261552200;6701752471;7103271625;7005920812;23393856300;23392868000;","Multi-variate probability density functions with dynamics for cloud droplet activation in large-scale models: Single column tests",2010,"10.5194/gmd-3-475-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960322463&doi=10.5194%2fgmd-3-475-2010&partnerID=40&md5=977f6d2977eed05c1b2081ec200815df","Successful simulation of cloud-aerosol interactions (indirect aerosol effects) in climate models requires relating grid-scale aerosol, dynamic, and thermodynamic fields to small-scale processes like aerosol activation. A turbulence and cloud parameterization, based on multi-variate probability density functions of sub-grid vertical velocity, temperature, and moisture, has been extended to treat aerosol activation. Multi-variate probability density functions with dynamics (MVD PDFs) offer a solution to the problem of the gap between the resolution of climate models and the scales relevant for aerosol activation and a means to overcome the limitations of diagnostic estimates of cloud droplet number concentration based only on aerosol concentration. Incorporated into the single-column version of GFDL AM3, the MVD PDFs successfully simulate cloud properties including precipitation for cumulus, stratocumulus, and cumulus-under-stratocumulus. The extension to treat aerosol activation predicts droplet number concentrations in good agreement with large eddy simulations (LES). The droplet number concentrations from the MVD PDFs match LES results more closely than diagnostic relationships between aerosol concentration and droplet concentration. <br><br> In the single-column model simulations, as aerosol concentration increases, droplet concentration increases, precipitation decreases, but liquid water path can increase or decrease. © 2012 Author(s)."
"36627288300;6603618077;16032479400;36598281300;16403388800;8691336700;55667384900;24921885300;","Clouds in the atmospheres of extrasolar planets: I. Climatic effects of multi-layered clouds for Earth-like planets and implications for habitable zones",2010,"10.1051/0004-6361/200913491","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650938046&doi=10.1051%2f0004-6361%2f200913491&partnerID=40&md5=2662532eeb227163b8d7044cfd74f1d2","Aims: The effects of multi-layered clouds in the atmospheres of Earth-like planets orbiting different types of stars are studied. The radiative effects of cloud particles are directly correlated with their wavelength-dependent optical properties. Therefore the incident stellar spectra may play an important role for the climatic effect of clouds. We discuss the influence of clouds with mean properties measured in the Earth's atmosphere on the surface temperatures and Bond albedos of Earth-like planets orbiting different types of main sequence dwarf stars. The influence of clouds on the position of the habitable zone around these central star types is discussed. Methods: A parametric cloud model has been developed based on observations in the Earth's atmosphere. The corresponding optical properties of the cloud particles are calculated with the Mie theory accounting for shape effects of ice particles by the equivalent sphere method. The parametric cloud model is linked with a one-dimensional radiative-convective climate model to study the effect of clouds on the surface temperature and the Bond albedo of Earth-like planets in dependence of the type of central star. Results: The albedo effect of the low-level clouds depends only weakly on the incident stellar spectra because the optical properties remain almost constant in the wavelength range of the maximum of the incident stellar radiation. The greenhouse effect of the high-level clouds on the other hand depends on the temperature of the lower atmosphere, which is itself an indirect consequence of the different types of central stars. In general the planetary Bond albedo increases with the cloud cover of either cloud type. An anomaly was found for the K and M-type stars however, resulting in a decreasing Bond albedo with increasing cloud cover for certain atmospheric conditions. Depending on the cloud properties, the position of the habitable zone can be located either farther from or closer to the central star. As a rule, low-level water clouds lead to a decrease of distance because of their albedo effect, while the high-level ice clouds lead to an increase in distance. The maximum variations are about 15% decrease and 35% increase in distance compared to the clear sky case for the same mean Earth surface conditions in each case. © 2010 ESO."
"8140555300;7003800456;7004416203;7003535176;7102604282;35998927000;7005275092;55684491100;7005793536;6603749963;16443840500;8314917200;7004194999;","Transport impacts on atmosphere and climate: Aviation",2010,"10.1016/j.atmosenv.2009.06.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957878815&doi=10.1016%2fj.atmosenv.2009.06.005&partnerID=40&md5=c2e819556434741ca725ba2af560d817","Aviation alters the composition of the atmosphere globally and can thus drive climate change and ozone depletion. The last major international assessment of these impacts was made by the Intergovernmental Panel on Climate Change (IPCC) in 1999. Here, a comprehensive updated assessment of aviation is provided. Scientific advances since the 1999 assessment have reduced key uncertainties, sharpening the quantitative evaluation, yet the basic conclusions remain the same. The climate impact of aviation is driven by long-term impacts from CO2 emissions and shorter-term impacts from non-CO2 emissions and effects, which include the emissions of water vapour, particles and nitrogen oxides (NOx). The present-day radiative forcing from aviation (2005) is estimated to be 55 mW m-2 (excluding cirrus cloud enhancement), which represents some 3.5% (range 1.3-10%, 90% likelihood range) of current anthropogenic forcing, or 78 mW m-2 including cirrus cloud enhancement, representing 4.9% of current forcing (range 2-14%, 90% likelihood range). According to two SRES-compatible scenarios, future forcings may increase by factors of 3-4 over 2000 levels, in 2050. The effects of aviation emissions of CO2 on global mean surface temperature last for many hundreds of years (in common with other sources), whilst its non-CO2 effects on temperature last for decades. Much progress has been made in the last ten years on characterizing emissions, although major uncertainties remain over the nature of particles. Emissions of NOx result in production of ozone, a climate warming gas, and the reduction of ambient methane (a cooling effect) although the overall balance is warming, based upon current understanding. These NOx emissions from current subsonic aviation do not appear to deplete stratospheric ozone. Despite the progress made on modelling aviation's impacts on tropospheric chemistry, there remains a significant spread in model results. The knowledge of aviation's impacts on cloudiness has also improved: a limited number of studies have demonstrated an increase in cirrus cloud attributable to aviation although the magnitude varies: however, these trend analyses may be impacted by satellite artefacts. The effect of aviation particles on clouds (with and without contrails) may give rise to either a positive forcing or a negative forcing: the modelling and the underlying processes are highly uncertain, although the overall effect of contrails and enhanced cloudiness is considered to be a positive forcing and could be substantial, compared with other effects. The debate over quantification of aviation impacts has also progressed towards studying potential mitigation and the technological and atmospheric tradeoffs. Current studies are still relatively immature and more work is required to determine optimal technological development paths, which is an aspect that atmospheric science has much to contribute. In terms of alternative fuels, liquid hydrogen represents a possibility and may reduce some of aviation's impacts on climate if the fuel is produced in a carbon-neutral way: such fuel is unlikely to be utilized until a 'hydrogen economy' develops. The introduction of biofuels as a means of reducing CO2 impacts represents a future possibility. However, even over and above land-use concerns and greenhouse gas budget issues, aviation fuels require strict adherence to safety standards and thus require extra processing compared with biofuels destined for other sectors, where the uptake of such fuel may be more beneficial in the first instance. © 2009 Elsevier Ltd."
"57191295772;22953639000;7006589419;6603760659;","Chemical characteristics and source reconciliation of organic aerosols in Algiers city area",2010,"10.1007/978-1-4419-1017-2_42","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877942611&doi=10.1007%2f978-1-4419-1017-2_42&partnerID=40&md5=be88d2ed1be703e57904f7d64229b8a4","Aerosols affect environment at the local, regional, and global levels. At the local level, aerosols are now becoming recognized as a significant health problem, especially in regard to respiratory illnesses, including asthma (Dockery et al., 1993). At global scale, atmospheric aerosols influence climate in two main ways, referred to as direct forcing and indirect forcing (Charlson et al., 1992). In the direct forcing mechanism, aerosols reflect sunlight back to space, thus cooling the planet. The indirect effect involves aerosol particles acting as (additional) cloud condensation nuclei, spreading the cloud's liquid water over smaller droplets. This makes clouds more reflective and longer lasting."
"7403906746;6603236154;","Observing Forbush decreases in cloud atShetland",2010,"10.1016/j.jastp.2010.09.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78449303503&doi=10.1016%2fj.jastp.2010.09.025&partnerID=40&md5=406841e590e1be777dca9a7b37b2455e","Meteorological measurements from Lerwick Observatory, Shetland (60°09'N, 1°08'W), are compared with short-term changes in Climax neutron counter cosmic ray measurements. For transient neutron count reductions of 10-12%, broken cloud becomes at least 10% more frequent on the neutron minimum day, above expectations from sampling. This suggests a rapid timescale (̃1. day) cloud response to cosmic ray changes. However, larger or smaller neutron count reductions do not coincide with cloud responses exceeding sampling effects. Larger events are too rare to provide a robust signal above the sampling noise. Smaller events are too weak to be observed above the natural variability. © 2010 Elsevier Ltd."
"55737207400;36560265300;23488286900;55786864200;36560270000;23490969200;","The impact of climate, soil and their interactions on reducing-sugar, nicotine and total nitrogen contents of flue-cured tobacco in Hunan high-quality tobacco region",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952766018&partnerID=40&md5=7b3a64ca5ed3d58f1e64bdb133bf743f","The impact of climate, soil and their interactions on reducing-sugar, nicotine and total nitrogen contents of flue-cured tobacco leaf were investigated through pot experiments in Hunan high-quality tobacco regions of Yongzhou, Liuyang and Sangzhi from 2006 to 2007. The experiments disclose the following results; First, the variation coefficients of reducing-sugar, nicotine and total nitrogen of tobacco leaves are of medium intensity and the intensity decreases in the order of reducing-sugar, nicotine and total nitrogen. Furthermore, climate, soil and their interactions impact reducing-sugar, nicotine and total nitrogen contents of tobacco leaves in different ways, i. e. climate has strong impact on all of the three while soil's impact is insignificant; the impact of the interactions between climate and soil vary from year to year with climate, soil and their interactions each contributing 51. 42%,19. 78% and 28. 79% respectively to the total impact. Above all, climate is the main ecological factor that affects the abovementioned chemical components contents of tobacco leaves. Thirdly, sunshine hours, diurnal temperature variance and quantity of evaporation in tobacco rooting stage, relative humidity, average air temperature and cloud coverage in tobacco vigorous growth stage, average air temperature, diurnal temperature variance and sunshine hours in tobacco mature stage were the top three climate factors that relate closely to the contents of reducing-sugar, nicotine and total nitrogen of tobacco leaves during their growth periods. Overall, average air temperature, relative humidity and diurnal temperature variance are the main factors that relate closely to the contents of abovementioned tobacco chemical components during the whole tobacco growth periods."
"7005524881;7003674085;7202979963;7004590414;7004364155;7004687638;","Frontal scale air-sea interaction in high-resolution coupled climate models",2010,"10.1175/2010JCLI3665.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649686734&doi=10.1175%2f2010JCLI3665.1&partnerID=40&md5=c3d5830d04d3c84261f21cf816326f43","The emerging picture of frontal scale air-sea interaction derived from high-resolution satellite observations of surface winds and sea surface temperature (SST) provides a unique opportunity to test the fidelity of high-resolution coupled climate simulations. Initial analysis of the output of a suite of Community Climate System Model (CCSM) experiments indicates that characteristics of frontal scale ocean-atmosphere interaction, such as the positive correlation between SST and surface wind stress, are realistically captured only when the ocean component is eddy resolving. The strength of the coupling between SST and surface stress is weaker than observed, however, as has been found previously for numerical weather prediction models and other coupled climate models. The results are similar when the atmospheric component model grid resolution is doubled from 0.58 to 0.258, an indication that shortcomings in the representation of subgrid scale atmospheric planetary boundary layer processes, rather than resolved scale processes, are responsible for the weakness of the coupling. In the coupled model solutions the response to mesoscale SST features is strongest in the atmospheric boundary layer, but there is a deeper reaching response of the atmospheric circulation apparent in free tropospheric clouds. This simulated response is shown to be consistent with satellite estimates of the relationship between mesoscale SST and all-sky albedo. © 2010 American Meteorological Society."
"55796506900;37057694400;7404837587;","Modeling study of the global distribution of radiative forcing by dust aerosol",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952401362&partnerID=40&md5=724a6cfe924cd369a50fff8a0b1270be","To quantitatively understand the dust aerosol effects on climate change, we calculated the global dis- tribution of direct radiative forcing due to dust aerosol under clear and cloudy skies in both winter and summer, by using an improved radiative transfer model and the global distribution of dust mass concentra- tion given by GADS (Global Aerosol Data Set). The results show that the global means of the solar forcing due to dust aerosol at the tropopause for winter and summer are -0.48 and -0.50 W m-2, respectively; the corresponding values for the longwave forcing due to dust are 0.11 and 0.09 W m-2, respectively. At the surface, the global means of the solar forcing due to dust are -1.36 W m-2 for winter and -1.56 W m-2 for summer, whereas the corresponding values for the longwave forcing are 0.27 and 0.23 W m-2, respectively. This work points out that the absolute values of the solar forcing due to dust aerosol at both the tropopause and surface increase linearly with the cosine of solar zenith angle and surface albedo. The solar zenith angle influences both the strength and distribution of the solar forcing greatly. Clouds exert great effects on the direct radiative forcing of dust, depending on many factors including cloud cover, cloud height, cloud water path, surface albedo, solar zenith angle, etc. The effects of low clouds and middle clouds are larger than those of high clouds. The existence of clouds reduces the longwave radiative forcing at the tropopause, where the influences of low clouds are the most obvious. Therefore, the impacts of clouds should not be ignored when estimating the direct radiative forcing due to dust aerosol."
"6603714196;7005174120;","Climate proxies for recent fjord sediments in the inner Sognefjord region, western Norway",2010,"10.1144/SP344.19","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053344323&doi=10.1144%2fSP344.19&partnerID=40&md5=708339878a5bb2a98d485776af2afa37","Three high-resolution sediment cores from the periodically anoxic Inner Barsnesfjord and the oxic Outer Barsnesfjord and Sogndalsfjord, Western Norway, are analysed for signals of climate variation. Sedimentation rates are 0.85, 0.75 and 0.45 cm a -1, respectively. Sediment slices are taken of 0.3-0.5 cm thickness revealing annual resolution. Corresponding peaks of mineral clay particles, total organic matter and freshwater diatoms correlate well with maxima in regional precipitation, temperature and cloud cover over the last 20 years. This regional climate record is also correlated to the wider NAO (North Atlantic Oscillation) winter index, northern hemisphere temperature and solar activity (cosmic rays and open solar flux) based on 60 years of continuous observation. There is a strong indication that the fjord sediment record contains a climate archive spanning the last 20-100 a; it is suggested that these proxies might also work on longer timescales. A simple box model is presented describing the use of the sediment record for the interpretation of climate variability on a regional scale and at a longer timescale on a millennium scale. It is predicted that this model can be transferred to sediment settings of similar regional climate influence. © The Geological Society of London 2010."
"7004399781;7004015298;7003658685;7005274759;56878283500;7801467546;6603094181;57215223917;56275058000;55984424900;26641045500;6603943978;7004452267;31267503200;7005601996;7006354036;7006813055;7005182425;23098283400;23025467900;8084443000;17435961300;6506129917;57050508600;24484158900;57208464149;","Atmospheric Brown Clouds in the Himalayas: First two years of continuous observations at the Nepal Climate Observatory-Pyramid (5079 m)",2010,"10.5194/acp-10-7515-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956506238&doi=10.5194%2facp-10-7515-2010&partnerID=40&md5=2a7094ca2168fd2a12425e9f7d79ceb2","This paper provides a detailed description of the atmospheric conditions characterizing the high Himalayas, thanks to continuous observations begun in March 2006 at the Nepal Climate Observatory-Pyramid (NCO-P) located at 5079 m a.s.l. on the southern foothills of Mt. Everest, in the framework of ABC-UNEP and SHARE-Ev-K2-CNR projects. The work presents a characterization of meteorological conditions and air-mass circulation at NCO-P during the first two years of activity. The mean values of atmospheric pressure, temperature and wind speed recorded at the site were: 551 hPa,-3.0 °C, 4.7 m s-1, respectively. The highest seasonal values of temperature (1.7 °C) and relative humidity (94%) were registered during the monsoon season, which was also characterized by thick clouds, present in about 80% of the afternoon hours, and by a frequency of cloud-free sky of less than 10%. The lowest temperature and relative humidity seasonal values were registered during winter,-6.3 °C and 22%, respectively, the season being characterised by mainly cloud-free sky conditions and rare thick clouds. The summer monsoon influenced rain precipitation (seasonal mean: 237 mm), while wind was dominated by flows from the bottom of the valley (S-SW) and upper mountain (N-NE). The atmospheric composition at NCO-P has been studied thanks to measurements of black carbon (BC), aerosol scattering coefficient, PM1, coarse particles and ozone. The annual behaviour of the measured parameters shows the highest seasonal values during the pre-monsoon (BC: 316.9 ng m-3, PM 1: 3.9 μgm-3, scattering coefficient: 11.9 Mm -1, coarse particles: 0.37 cm-3 and O3: 60.9 ppbv), while the lowest concentrations occurred during the monsoon (BC: 49.6 ng m-3, PM1: 0.6 μg m-3, scattering coefficient: 2.2 Mm-1, and O3: 38.9 ppbv) and, for coarse particles, during the post-monsoon (0.07 cm-3. At NCO-P, the synoptic-scale circulation regimes present three principal contributions: Westerly, South-Westerly and Regional, as shown by the analysis of in-situ meteorological parameters and 5-day LAGRANTO back-trajectories. The influence of the brown cloud (AOD&gt;0.4) extending over Indo-Gangetic Plains up to the Himalayan foothills has been evaluated by analysing the in-situ concentrations of the ABC constituents. This analysis revealed that brown cloud hot spots mainly influence the South Himalayas during the pre-monsoon, in the presence of very high levels of atmospheric compounds (BC: 1974.1 ng m-3, PM 1: 23.5 μg m-3, scattering coefficient: 57.7 Mm -1, coarse particles: 0.64 cm-3, O3: 69.2 ppbv, respectively). During this season 20% of the days were characterised by a strong brown cloud influence during the afternoon, leading to a 5-fold increased in the BC and PM1 values, in comparison with seasonal means. Our investigations provide clear evidence that, especially during the pre-monsoon, the southern side of the high Himalayan valleys represent a ""direct channel"" able to transport brown cloud pollutants up to 5000 m a.s.l., where the pristine atmospheric composition can be strongly influenced. © 2010 Author(s)."
"7005822617;57194244669;","Air pollution and climate change progress toward integrated strategies and Co-benefits",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952691168&partnerID=40&md5=f584ab36c354f780ea5ebec76eef6a56","The scientific and policy drivers that is critical in developing plans to improve air quality while simultaneously reducing greenhouse gas (GHG) emissions are discussed. A key area of debate is the magnitude of the net warming effect of black carbon once factors such as aerosol-cloud interactions are taken into account. Methane is the second most significant driver of climate warming after CO2, but lasts only for a decade. So, to achieve quick cooling in sensitive regions like the Arctic, methane reductions may be a more powerful tool, even though CO2 reductions are needed over the long run. Existing regional air pollution networks can play an important role in linking the climate and air pollution communities at different scales and in sharing expertise. The GAP Forum partners are considering how to encourage outreach to help developing nations implement best practices for regulation of methane sources with an initial focus on improving regional air quality, but with the clear co-benefit of climate protection."
"24741225300;7003561239;","Diurnal and Seasonal Trends in Convective Mixed-Layer Heights Estimated from Two Years of Continuous Ceilometer Observations in Vancouver, BC",2010,"10.1007/s10546-010-9535-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78549282383&doi=10.1007%2fs10546-010-9535-7&partnerID=40&md5=4378ebb5cab93fe841a7be8b9c411eb9","Twenty-six months of continuous ceilometer data are used to estimate the convective mixed-layer height for 710 days by identifying backscatter gradients associated with the entrainment zone. To accomplish this, a semi-automatic procedure is developed that removes all non-applicable data before applying a mixed-layer height algorithm to the backscatter profiles. Two different algorithms for estimating the mixed-layer height are assessed: the minimum-gradient method and the ideal-profile method. The latter of these two algorithms is found to be more robust. Comparisons of mixed-layer height values estimated from the ceilometer agree with previous observations with slightly higher estimates in the mornings and evenings. For clear days with no cumulus cloud formation, the seasonal cycle in mixed-layer heights peaks in late June to early July. Daily maximum values are suppressed by the site's coastal location, remaining below 800 m for all but a few days. The mean daily maximum mixed-layer height increases by 384 m for days with boundary-layer clouds. The mean summer diurnal trend is found not to differ greatly from that in spring on clear days, while days with boundary-layer clouds have higher spring values than in summer. Net surface heat flux and synoptic stability likely have the largest influence on the mixed-layer heights. Additionally, large intra-monthly variability suggests a strong influence from regional dynamics. © 2010 Springer Science+Business Media B.V."
"24460392200;15835468800;36088530800;57199847019;8726272900;16444232500;57203053317;","Diurnal variations of humidity and ice water content in the tropical upper troposphere",2010,"10.5194/acp-10-11519-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651484655&doi=10.5194%2facp-10-11519-2010&partnerID=40&md5=99d2181a5c65848b1b9f027ce29d7251","Observational results of diurnal variations of humidity from Odin-SMR and AURA-MLS, and cloud ice mass from Odin-SMR and CloudSat are presented for the first time. Comparisons show that the retrievals of humidity and cloud ice from these two satellite combinations are in good agreement. The retrieved data are combined from four almost evenly distributed times of the day allowing mean values, amplitudes and phases of the diurnal variations around 200 hpa to be estimated. This analysis is applied to six climatologically distinct regions, five located in the tropics and one over the subtropical northern Pacific Ocean. The strongest diurnal cycles are found over tropical land regions, where the amplitude is ∼7 RHi for humidity and ∼50% for ice mass. The greatest ice mass for these regions is found during the afternoon, and the humidity maximum is observed to lag this peak by ∼6 h. Over tropical ocean regions the variations are smaller and the maxima in both ice mass and humidity are found during the early morning. Observed results are compared with output from three climate models (ECHAM, EC-EARTH and CAM3). Direct measurement-model comparisons were not possible because the measured and modelled cloud ice masses represent different quantities. To make a meaningful comparison, the amount of snow had to be estimated from diagnostic parameters of the models. There is a high probability that the models underestimate the average ice mass (outside the 1-σ uncertainty). The models also show clear deficiencies when it comes to amplitude and phase of the regional variations, but to varying degrees. © 2010 Author(s)."
"37013249500;37057586400;56232770200;","Past and future changes in the climate of Hong Kong",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650674291&partnerID=40&md5=b589fc0eade5d4c505db798007a2171f","Over the years, the Hong Kong Observatory has carried out scientific studies to evaluate the observed climate trends and project the future climate in Hong Kong. Analysis of the meteorological observations at the observatory's headquarters in Tsim Sha Tsui since 1885 reveals that the temperature rise in Hong Kong during the past 124 years is in accord with the global rising trend. The accelerated rising trend in the mean temperature in last few decades may be attributed to the anthropogenic influences, especially urbanization. A similar increasing trend is also observed for rainfall. Other observations such as increasing cloud amount and decreasing total global solar radiation are all consistent with the global trend. Studies of past occurrences of extreme temperature and rainfall have also been carried out. The results indicate that cold episodes have become rarer while very hot days and heavy rain events are becoming more frequent. The observatory also makes use of the data from the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) and employs statistical downscaling techniques to carry out projections of temperature and precipitation in the 21st century. It is found that the rise in temperature in Hong Kong will be slightly higher than the global mean in the 21st century. The annual rainfall in Hong Kong is also expected to rise by the end of the 21st century, so is its year-to-year variability."
"6603292201;36796969000;","Observed trends in frost and hours of cold in Majorca",2010,"10.1002/joc.2051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649583448&doi=10.1002%2fjoc.2051&partnerID=40&md5=799454d56254739b4834d77e2d087a40","The observed trends in some cold indices in the island of Majorca are analysed using the available series of the daily minimum temperatures of the Majorca Airport (1972-2008), supplemented with the inspection of eight more climatological stations of the island covering at least 30 simultaneous years. The analysis yields a statistically significant trend to a rise of about 0.6 °C per decade for the ensemble of the stations. There is also a clear shortening of the season with days with T below 0 °C or 7 °C, but the yearly minima or the dates of the first and last occurrence of these values do not show so well-defined tendencies. A rise in night-time cloud cover could be related to such behaviour. © 2009 Royal Meteorological Society."
"26656757300;56065668600;57192185295;","Impacts of environmental factors on urban heating",2010,"10.1016/S1001-0742(09)60337-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649935287&doi=10.1016%2fS1001-0742%2809%2960337-5&partnerID=40&md5=19231ad9ce46f4f15ca67657d993be6d","This study investigated the impact of important environmental variables (i.e., wind speed, solar radiation and cloud cover) on urban heating. Meteorological parameters for fifteen years (from 1990 to 2005), collected at a well developed and densely populated commercial area (Tsim Sha Tsui, Hong Kong), were analyzed in details. Urban heat island intensity (UHII), a well known indicator of urban heating, has been determined as the spatially averaged air-temperature difference between Tsim Sha Tsui and Ta Kwu Ling (a thinly populated rural area with lush vegetation). Results showed that the UHII and cloud cover have increased by around 9.3% and 4%, respectively, whereas the wind speed and solar radiation have decreased by around 24% and 8.5%, respectively. The month of December experienced the highest UHII (10.2°C) but the lowest wind speed (2.6 m/sec) and cloud cover (3.8 oktas). Conversely, the month of April observed the highest increases in the UHII (over 100%) and the highest decreases in wind speed (over 40 %) over fifteen years. Notably, the increases in the UHII and reductions in the wind speed were the highest during the night-time and early morning. Conversely, the intensity of solar radiation reduced while the intensity of urban cool island (UCII) increased during solar noon-time. Results demonstrated strong negative correlation between the UHII and wind speed (coefficient of determination, R2= 0.8) but no negative correlation between UCII and solar radiation attenuation. A possible negative correlation between UHII and cloud cover was investigated but could not be substantiated. © 2010 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences."
"24778445700;15841350300;8670213100;6701796418;6701821355;","Regional co-variability and teleconnection patterns in surface solar radiation on a planetary scale",2010,"10.1002/joc.2031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649579098&doi=10.1002%2fjoc.2031&partnerID=40&md5=5f32fe0e6ae5cd6be16870cdfd751aed","The spatial and temporal distribution of the downward solar radiation (DSR) at the Earth's surface, which is a key parameter for the Earth-atmosphere climate system, is studied on a global scale by applying the multivariate statistical method of factor analysis (FA) on mean monthly DSR values for the period 1984-2000 for winter and summer. DSR fluxes have been computed with a physical deterministic radiation transfer model, which uses satellite and reanalysis climatological input data. FA objectively groups grid points with common temporal variability of solar radiation, identifying areas with characteristic solar radiation variability and revealing teleconnection patterns. The globally distributed DSR exhibits strong variability and can be represented by about 30 factors (sub-areas) explaining approximately 85% of the total variance. The main factors are located in the tropical Pacific (El Niño Southern Oscillation), the northern Pacific (Aleutian low), desert areas (Africa, Middle East, and Australia), and oceanic areas (storm track zone around 60°S). Furthermore, some of these areas are teleconnected indicating common DSR variability in remote places of the Earth. The primary physical parameter for the co-variability of surface solar radiation is found to be cloud cover. The time series of the factor scores (solar radiation) exhibit features associated with natural climatic phenomena (e.g. NAO, ENSO), thus revealing that DSR might be considered as an indirect indicator for these phenomena. On the other hand, DSR determines these phenomena through its effects on major climate parameters such as surface temperature or evaporation, thus playing a key role in their formation and explanation. Finally, our analysis revealed some statistically significant trends of solar radiation, for example, a reduction in the northern Pacific and an increase in tropical and subtropical regions, which are important for global dimming/brightening and associated surface warming of the Earth. © 2009 Royal Meteorological Society."
"55710583000;7202155374;7005231450;7003663939;","Detection and attribution of anthropogenic forcing to diurnal temperature range changes from 1950 to 1999: Comparing multi-model simulations with observations",2010,"10.1007/s00382-009-0644-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649323429&doi=10.1007%2fs00382-009-0644-2&partnerID=40&md5=10466f376a4b4ecf2ebc206e06c515fe","Observations show that the surface diurnal temperature range (DTR) has decreased since 1950s over most global land areas due to a smaller warming in maximum temperatures (Tmax) than in minimum temperatures (Tmin). This paper analyzes the trends and variability in Tmax, Tmin, and DTR over land in observations and 48 simulations from 12 global coupled atmosphere-ocean general circulation models for the later half of the 20th century. It uses the modeled changes in surface downward solar and longwave radiation to interpret the modeled temperature changes. When anthropogenic and natural forcings are included, the models generally reproduce observed major features of the warming of Tmax and Tmin and the reduction of DTR. As expected the greenhouse gases enhanced surface downward longwave radiation (DLW) explains most of the warming of Tmax and Tmin while decreased surface downward shortwave radiation (DSW) due to increasing aerosols and water vapor contributes most to the decreases in DTR in the models. When only natural forcings are used, none of the observed trends are simulated. The simulated DTR decreases are much smaller than the observed (mainly due to the small simulated Tmin trend) but still outside the range of natural internal variability estimated from the models. The much larger observed decrease in DTR suggests the possibility of additional regional effects of anthropogenic forcing that the models can not realistically simulate, likely connected to changes in cloud cover, precipitation, and soil moisture. The small magnitude of the simulated DTR trends may be attributed to the lack of an increasing trend in cloud cover and deficiencies in charactering aerosols and important surface and boundary-layer processes in the models. © 2009 Springer-Verlag."
"36663291700;7202299505;6507745014;26643531100;7102253065;7005973015;","Photolysis of sulphuric acid as the source of sulphur oxides in the mesosphere of Venus",2010,"10.1038/ngeo989","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649856905&doi=10.1038%2fngeo989&partnerID=40&md5=b3d4b88bb5c981ef930b9f01fb1e2c5e","The sulphur cycle plays fundamental roles in the chemistry and climate 4,5 of Venus. Thermodynamic equilibrium chemistry at the surface of Venus favours the production of carbonyl sulphide6 and to a lesser extent sulphur dioxide. These gases are transported to the middle atmosphere by the Hadley circulation cell7,8. Above the cloud top, a sulphur oxidation cycle involves conversion of carbonyl sulphide into sulphur dioxide, which is then transported further upwards. A significant fraction of this sulphur dioxide is subsequently oxidized to sulphur trioxide and eventually reacts with water to form sulphuric acid3. Because the vapour pressure of sulphuric acid is low, it readily condenses and forms an upper cloud layer at altitudes of 60-70 km, and an upper haze layer above 70 km (ref.? 9), which effectively sequesters sulphur oxides from photochemical reactions. Here we present simulations of the fate of sulphuric acid in the Venusian mesosphere based on the Caltech/JPL kinetics model3,10, but including the photolysis of sulphuric acid. Our model suggests that the mixing ratios of sulphur oxides are at least five times higher above 90 km when the photolysis of sulphuric acid is included. Our results are inconsistent with the previous model results but in agreement with the recent observations using ground-based microwave spectroscopyN and by Venus Express12. © 2010 Macmillan Publishers Limited. All rights reserved."
"13402933200;7003927831;6603749963;7402105994;35228780900;55907029900;7103353990;6508166573;56187256200;7402383878;","Transport impacts on atmosphere and climate: Shipping",2010,"10.1016/j.atmosenv.2009.04.059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957862455&doi=10.1016%2fj.atmosenv.2009.04.059&partnerID=40&md5=2f4d8d0da810d63c497d26253babc665","Emissions of exhaust gases and particles from oceangoing ships are a significant and growing contributor to the total emissions from the transportation sector. We present an assessment of the contribution of gaseous and particulate emissions from oceangoing shipping to anthropogenic emissions and air quality. We also assess the degradation in human health and climate change created by these emissions. Regulating ship emissions requires comprehensive knowledge of current fuel consumption and emissions, understanding of their impact on atmospheric composition and climate, and projections of potential future evolutions and mitigation options. Nearly 70% of ship emissions occur within 400 km of coastlines, causing air quality problems through the formation of ground-level ozone, sulphur emissions and particulate matter in coastal areas and harbours with heavy traffic. Furthermore, ozone and aerosol precursor emissions as well as their derivative species from ships may be transported in the atmosphere over several hundreds of kilometres, and thus contribute to air quality problems further inland, even though they are emitted at sea. In addition, ship emissions impact climate. Recent studies indicate that the cooling due to altered clouds far outweighs the warming effects from greenhouse gases such as carbon dioxide (CO2) or ozone from shipping, overall causing a negative present-day radiative forcing (RF). Current efforts to reduce sulphur and other pollutants from shipping may modify this. However, given the short residence time of sulphate compared to CO2, the climate response from sulphate is of the order decades while that of CO2 is centuries. The climatic trade-off between positive and negative radiative forcing is still a topic of scientific research, but from what is currently known, a simple cancellation of global mean forcing components is potentially inappropriate and a more comprehensive assessment metric is required. The CO2 equivalent emissions using the global temperature change potential (GTP) metric indicate that after 50 years the net global mean effect of current emissions is close to zero through cancellation of warming by CO2 and cooling by sulphate and nitrogen oxides. © 2009 Elsevier Ltd."
"36628729000;7003487440;","Air-sea energy exchanges measured by eddy covariance during a localised coral bleaching event, Heron Reef, Great Barrier Reef, Australia",2010,"10.1029/2010GL045291","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650493484&doi=10.1029%2f2010GL045291&partnerID=40&md5=15471060cadf10a3e8c5f632e07a4efb","Despite the widely claimed association between climate change and coral bleaching, a paucity of data exists relating to exchanges of heat, moisture and momentum between the atmosphere and the reef-water surface. We present in situ measurements of reef-water-air energy exchanges made using the eddy covariance method during a summer coral bleaching event at Heron Reef, Australia. Under settled, cloud-free conditions and light winds, daily net radiation exceeded 800 W m-2, with up to 95% of the net radiation during the morning partitioned into heating the water column, substrate and benthic cover including corals. Heating was exacerbated by a mid-afternoon low tide when shallow reef flat water reached 34C and near-bottom temperatures 33C, exceeding the thermal tolerance of corals, causing bleaching. Results suggest that local to synoptic scale meteorology, particularly clear skies, solar heating, light winds and the timing of low tide were the primary controls on coral bleaching. © 2010 by the American Geophysical Union."
"16245391700;6602321641;14020796800;23992921200;16550520400;7004115624;24376225300;7003972559;23491714700;15835124500;6701762952;","Precipitation measurement at CESAR, the Netherlands",2010,"10.1175/2010JHM1245.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651448965&doi=10.1175%2f2010JHM1245.1&partnerID=40&md5=6e289071addaf4971d70821c0ffef5ac","The Cabauw Experimental Site for Atmospheric Research (CESAR) observatory hosts a unique collection of instruments related to precipitation measurement. The data collected by these instruments are stored in a database that is freely accessible through a Web interface. The instruments present at the CESAR site include three disdrometers (two on the ground and one at 200 mabove ground level), a dense network of rain gauges, three profiling radars (1.3, 3.3, and 35 GHz), and an X-band Doppler polarimetric scanning radar. In addition to these instruments, operational weather radar data from the nearby (~25 km) De Bilt C-band Doppler radar are also available. The richness of the datasets available is illustrated for a rainfall event, where the synergy of the different instruments provides insight into precipitation at multiple spatial and temporal scales. These datasets, which are freely available to the scientific community, can contribute greatly to our understanding of precipitation-related atmospheric and hydrologic processes. © 2010 American Meteorological Society."
"41961756000;36523706800;15069732800;7005742190;","Evaluation of ERA-40 and ERA-interim re-analysis incoming surface shortwave radiation datasets with mesoscale remote sensing data",2010,"10.1127/0941-2948/2010/0466","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959791552&doi=10.1127%2f0941-2948%2f2010%2f0466&partnerID=40&md5=b6184359fe8422c8c87c88f4ed675722","In this paper an evaluation of the European Center for Medium Range Forecasting 40-year re-analysis (ERA-40) and interim re-analysis (ERA-Interim) solar irradiation datasets is presented. The goal of the study is to evaluate the accuracy of the downward solar surface radiation fluxes of ERA-40 and ERA-Interim. A positive result of these examinations would justify the use of ERA-40 and ERA-Interim, respectively, to investigate long-term changes of anomaly patterns. Unlike other recent studies that operate on a global scale, this study concentrates on regional aspects of climate research. As reference, high-resolution remote sensing data derived from METEOSAT using the Heliosat method are used. The study area covers Germany and adjacent countries. Structures were found which indicate that ERA-40 does not properly represent cloud and fog occurrence. Especially during the solar season May, June, July (MJJ) large deviations of up to 40 and 60 W/m2, respectively, compared to the reference dataset were found. During the solar seasons of August, September, October (ASO) and November, December, January (NDJ) the deviations are negligible for both re-analysis datasets as well as for ERA-40 during the season of February, March, April (FMA). The results lead to the conclusion that in and around Germany, the accuracy of the parameter surface solar irradiation downward (ssrd) of ERA-40 and ERA-Interim re-analysis is limited, especially during the season of MJJ and in ERA-Interim also during the season of FMA. © Gebruder Borntraeger, Stuttgart 2010."
"6603342397;6701448397;","Summer 2009 thermal and bioclimatic conditions in Ebba Valley, central Spitsbergen",2010,"10.2478/v10183-010-0009-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751531637&doi=10.2478%2fv10183-010-0009-x&partnerID=40&md5=bda3f994511392f3492bd79a226f068e","The thermal, anemometric and bioclimatic conditions on the topoclimatic scale were investigated in the summer season in the EbbaValley region in central Spitsbergen. Eight measurement sites, representing different ecosystems and different types of active surfaces typical of Spitsbergen, were chosen and automatic, hourly recorded, measurements were per-formed at the sites between 11 and 25 of July 2009. The analysis of the spatial distribution of the air temperature and thewind-chill temperature, both for the dayswith radiation and non-ra-diation weather, indicates that the most favorable regions in the interior of Spitsbergen are those situated in the shielded central parts of the valleys and in the lower parts of the slopes with southern exposure. The thermal and wind conditions are definitely less favorable at the tops of elevations and on the glacier. Large differences between the air temperature and the wind-chill temperature were noted, particularly during the unfavorable non-radiation weather, on the glacier and on open peaks due to a large horizontal and vertical wind-chill temperature gradient. The thermal inversions observed in the Ebba Valley in July 2009 were not of the typi-cal, glacier katabatic wind origin. They appeared during the western air circulation, which brings advection of cooled air from above the cold waters of Petunia Bay. The cold air pene-trates into the valley and pushes upwards themass of warmer air in the valley, creating a rather thin inversion layer, whose upper edge is marked with thin Stratus clouds."
"7007182077;23995325300;8705440100;6602978326;55463048400;36011801900;7003984086;","Aerosol measurements at the Gual Pahari EUCAARI station: Preliminary results from in-situ measurements",2010,"10.5194/acp-10-7241-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650547223&doi=10.5194%2facp-10-7241-2010&partnerID=40&md5=5c0eba1dfc419e799e1d9caff439b6d6","The Finnish Meteorological Institute (FMI), together with The Energy and Resources Institute of India (TERI), contributed to the European Integrated project on Aerosol Cloud Climate and Air Quality Interactions, EUCAARI, by conducting aerosol measurements in Gual Pahari, India, from December 2007 to January 2010. This paper describes the station setup in detail for the first time and provides results from the aerosol in-situ measurements, which include PM and BCe masses, aerosol size distribution from 4 nm to 10 Î1/4m, and the scattering and absorption coefficients. The seasonal variation of the aerosol characteristics was very distinct in Gual Pahari. The highest concentrations were observed during the winter and the lowest during the rainy season. The average PM10 concentration (at STP conditions) was 216 Î1/4gmĝ̂'3 and the average PM2.5 concentration was 126 Î1/4gmĝ̂'3. A high percentage (4ĝ€""9%) of the PM10 mass consisted of BCe which indicates anthropogenic influence. The percentage of BCe was higher during the winter; and according to the diurnal pattern of the BCe fraction, the peak occurred during active traffic hours. Another important source of aerosol particles in the area was new particle formation. The nucleated particles grew rapidly reaching the Aitken and accumulation mode size, thus contributing considerably to the aerosol load. The rainy season decreased the average fraction of particle mass in the PM2.5 size range, i.e. of secondary origin. The other mechanism decreasing the surface concentrations was based on convective mixing and boundary layer evolution. This diluted the aerosol when sun radiation and the temperature was high, i.e. especially during the pre-monsoon day time. The lighter and smaller particles were more effectively diluted. © 2010 Author(s)."
"6506152198;57208121852;56384704800;6602600408;56270311300;36098422200;56154540200;6701689939;16444232500;57203053317;7003931528;","Aerosol nucleation and its role for clouds and Earth's radiative forcing in the aerosol-climate model ECHAM5-HAM",2010,"10.5194/acp-10-10733-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649243446&doi=10.5194%2facp-10-10733-2010&partnerID=40&md5=69d4ea041705aa1e1fb18e847c60b663","Nucleation from the gas phase is an important source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosol-climate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth's radiative forcing. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are -1.15 W/m2 for charged H2SO4/H 2O nucleation, -0.235 W/m2 for cluster activation, and -0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is -2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with -2.18 W/m 2 to total absorbed solar short-wave radiation, compared to -0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth's radiative forcing over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local measurements: over southern Finland, where cluster activation proceeds efficiently, we find that charged nucleation of sulfuric acid and water contributes on average less than 10% to ultrafine aerosol concentrations, in good agreement with observations. © 2010 Author(s)."
"26643041500;8871497700;56370907100;10739072200;8336962200;6701853225;11339750700;17433787100;16028301700;7006182491;9235235300;6701574983;6508032361;7003505923;57207261095;8568391400;7007182077;23995325300;24437458400;7007039218;7004172687;8663601100;6602607937;23108400400;7006415284;7004047498;7006595513;34971726900;6603825422;7005069415;16833315000;6602354484;20735974900;10640192200;57193157754;35998927000;6602914876;55941661200;55942083800;7006712143;35461255500;","Atmospheric nucleation: Highlights of the EUCAARI project and future directions",2010,"10.5194/acp-10-10829-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649269915&doi=10.5194%2facp-10-10829-2010&partnerID=40&md5=acdd90a7c3044d86888b8acad0463443","Within the project EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions), atmospheric nucleation was studied by (i) developing and testing new air ion and cluster spectrometers, (ii) conducting homogeneous nucleation experiments for sulphate and organic systems in the laboratory, (iii) investigating atmospheric nucleation mechanism under field conditions, and (iv) applying new theoretical and modelling tools for data interpretation and development of parameterisations. The current paper provides a synthesis of the obtained results and identifies the remaining major knowledge gaps related to atmospheric nucleation. The most important technical achievement of the project was the development of new instruments for measuring sub-3 nm particle populations, along with the extensive application of these instruments in both the laboratory and the field. All the results obtained during EUCAARI indicate that sulphuric acid plays a central role in atmospheric nucleation. However, also vapours other than sulphuric acid are needed to explain the nucleation and the subsequent growth processes, at least in continental boundary layers. Candidate vapours in this respect are some organic compounds, ammonia, and especially amines. Both our field and laboratory data demonstrate that the nucleation rate scales to the first or second power of the nucleating vapour concentration(s). This agrees with the few earlier field observations, but is in stark contrast with classical thermodynamic nucleation theories. The average formation rates of 2-nm particles were found to vary by almost two orders of magnitude between the different EUCAARI sites, whereas the formation rates of charged 2-nm particles varied very little between the sites. Overall, our observations are indicative of frequent, yet moderate, ion-induced nucleation usually outweighed by much stronger neutral nucleation events in the continental lower troposphere. The most concrete outcome of the EUCAARI nucleation studies are the new semi-empirical nucleation rate parameterizations based on field observations, along with updated aerosol formation parameterizations. © 2010 Author(s)."
"7004056721;7004346367;6701845055;35291021400;7006383649;55718857500;23161713000;","Optical-chemical-microphysical relationships and closure studies for mixed carbonaceous aerosols observed at Jeju Island; 3-laser photoacoustic spectrometer, particle sizing, and filter analysis",2010,"10.5194/acp-10-10387-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149344620&doi=10.5194%2facp-10-10387-2010&partnerID=40&md5=2c89613071af9455ee83e2971a18da34","Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX) field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer (PASS-3), chemical filter analysis, and size distributions. The PASS-3 directly measures the effects of morphology (e.g. coatings) on light absorption that traditional filter-based instruments are unable to address. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 74% of the deployment days, showing large variations in their measured chemical and optical properties. Analysis of eight distinct episodes, spanning wide ranges of chemical composition, optical properties, and source regions, reveals that episodes with higher organic carbon (OC)/sulfate (SO 2-4 ) and nitrate (NO-3 )/SO2- 4 composition ratios exhibit lower single scatter albedo at shorter wavelengths (!405). We infer complex refractive indices (n-ik) as a function of wavelength for the high, intermediate, and low OC/SO2-4 pollution episodes by using the observed particle size distributions and the measured optical properties. The smallest mean particle diameter corresponds to the high OC/SO2-4 aerosol episode. The imaginary part of the refractive index (k) is greater for the high OC/SO2- 4 episode at all wavelengths. A distinct, sharp increase in k at short wavelength implies enhanced light absorption by OC, which accounts for 50% of the light absorption at 405 nm, in the high OC/SO2-4 episode. Idealized analysis indicates increased absorption at 781 nm by factors greater than 3 relative to denuded black carbon in the laboratory. We hypothesize that coatings of black carbon cores are the mechanism of this enhancement. This implies that climate warming and atmospheric heating rates from black carbon particles can be significantly larger than have been estimated previously. The results of this study demonstrate ways in which atmospheric processing and mixing can amplify particle light absorption for carbonaceous aerosol, significantly at short wavelength, underscoring the need to understand and predict chemical composition effects on optical properties to accurately estimate the climate radiative forcing by mixed carbonaceous aerosols. © 2010 Author(s)."
"35112806400;24802319700;55915046600;57205842560;7103337730;6506810759;","Development of an online radiative module for the computation of aerosol optical properties in 3-D atmospheric models: Validation during the EUCAARI campaign",2010,"10.5194/gmd-3-553-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80755182698&doi=10.5194%2fgmd-3-553-2010&partnerID=40&md5=d68016280f1f2f2d2e633b3390b89ffa","Obtaining a good description of aerosol optical properties for a physically and chemically complex evolving aerosol is computationally very expensive at present. The goal of this work is to propose a new numerical module computing the optical properties for complex aerosol particles at low numerical cost so that it can be implemented in atmospheric models. This method aims to compute the optical properties online as a function of a given complex refractive index deduced from the aerosol chemical composition and the size parameters corresponding to the particles. The construction of look-up tables from the imaginary and the real part of the complex refractive index and size parameters will also be explained. This approach is validated for observations acquired during the EUCAARI (European integrated project on aerosol cloud climate air quality interactions) campaign on the Cabauw tower during May 2008 and its computing cost is also estimated. These comparisons show that the module manages to reproduce the scattering and absorbing behaviour of the aerosol during most of the fifteen-day period of observation with a very cheap computationally cost. © Author(s) 2010."
"8718425100;7103060756;7601492669;7101752236;55915206300;","The impact of global warming on marine boundary layer clouds over the eastern Pacific-A regional model study",2010,"10.1175/2010JCLI3666.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649247484&doi=10.1175%2f2010JCLI3666.1&partnerID=40&md5=c439445c47b8e052e4a28163d24bbe24","Cloud simulations and cloud-climate feedbacks in the tropical and subtropical eastern Pacific region in 16 state-of-the-art coupled global climate models (GCMs) and in the International Pacific Research Center (IPRC) Regional Atmospheric Model (iRAM) are examined. The authors find that the simulation of the present-day mean cloud climatology for this region in the GCMs is very poor and that the cloud-climate feedbacks vary widely among the GCMs. By contrast, iRAM simulates mean clouds and interannual cloud variations that are quite similar to those observed in this region. The model also simulates well the observed relationship between lower-tropospheric stability (LTS) and low-level cloud amount. To investigate cloud-climate feedbacks in iRAM, several global warming scenarios were run with boundary conditions appropriate for late twenty-first-century conditions. All the global warming cases simulated with iRAM show a distinct reduction in low-level cloud amount, particularly in the stratocumulus regime, resulting in positive local feedback parameters in these regions in the range of 4-7 W m-2 K-1. Domain-averaged (30°S-30°N, 150°-60°W) feedback parameters from iRAM range between +1.8 and +1.9 W m-2 K-1. At most locations both the LTS and cloud amount are altered in the global warming cases, but the changes in these variables do not follow the empirical relationship found in the present-day experiments. The cloud-climate feedback averaged over the same east Pacific region was also calculated from the Special Report on Emissions Scenarios (SRES) A1B simulations for each of the 16 GCMs with results that varied from -1.0 to +1.3 W m-2 K-1, all less than the values obtained in the comparable iRAM simulations. The iRAM results by themselves cannot be connected definitively to global climate feedbacks; however, among the global GCMs the cloud feedback in the full tropical-subtropical zone is correlated strongly with the east Pacific cloud feedback, and the cloud feedback largely determines the global climate sensitivity. The present iRAM results for cloud feedbacks in the east Pacific provide some support for the high end of current estimates of global climate sensitivity. © 2010 American Meteorological Society."
"6701511324;35392584500;","Impact of cloud and radiation scheme modifications on climate simulated by the ECHAM5 atmospheric GCM",2010,"10.1002/qj.674","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958569438&doi=10.1002%2fqj.674&partnerID=40&md5=801ff7185c64b3fef7c2d869d3b264c0","The impact of modifying two physical parametrizations in the ECHAM5 atmospheric general circulation model (GCM) is reported. First, a diagnostic (relative humidity-based) cloud fraction scheme is replaced by one based on a prognostic description of the subgrid-scale distribution of total water content (the Tompkins scheme). Second, the subgrid-scale information provided by the Tompkins scheme is introduced into radiation calculations using the Monte Carlo Independent Column Approximation (McICA). Experiments are carried out in three model configurations: (1) ECHAM5 with prescribed distributions of sea-surface temperature and sea ice; (2) ECHAM5 coupled to a mixed-layer ocean model; and (3) ECHAM5 coupled to the MPIOM ocean GCM.The primary direct impact of replacing the RH-based cloud fraction scheme by the Tompkins scheme is an increase in very low cloudiness, mainly at mid and high latitudes, along with a reduction in mid-level cloudiness. The most notable effect of using McICA is a strengthening of the negative short-wave cloud radiative effect, without substantial effects on cloudiness. However, when compared to observational data, all model versions perform in essence equally well. For all of them, cloud field statistical properties show substantial differences from the International Satellite Cloud Climatology Project data; in particular, there is a general lack of low- and mid-level clouds with low optical depth. The differences in temperature, precipitation and sea-level pressure between the model versions are rather small. However, in spite of similar performance for present climate, the different model versions show marked differences in their response to increased atmospheric CO2. © 2010 Royal Meteorological Society."
"12040335900;7404653593;55718857500;7005548544;","Observational diagnosis of cloud phase in the winter Antarctic atmosphere for parameterizations in climate models",2010,"10.1007/s00376-010-9175-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649475690&doi=10.1007%2fs00376-010-9175-3&partnerID=40&md5=8a22ebdbb29df14ebc9519a6808cdb60","The cloud phase composition of cold clouds in the Antarctic atmosphere is explored using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instruments for the period 2000-2006. We used the averaged fraction of liquid-phase clouds out of the total cloud amount at the cloud tops since the value is comparable in the two measurements. MODIS data for the winter months (June, July, and August) reveal liquid cloud fraction out of the total cloud amount significantly decreases with decreasing cloud-top temperature below 0°C. In addition, the CALIOP vertical profiles show that below the ice clouds, low-lying liquid clouds are distributed over ∼20% of the area. With increasing latitude, the liquid cloud fraction decreases as a function of the local temperature. The MODIS-observed relation between the cloud-top liquid fraction and cloud-top temperature is then applied to evaluate the cloud phase parameterization in climate models, in which condensed cloud water is repartitioned between liquid water and ice on the basis of the grid point temperature. It is found that models assuming overly high cut-offs (≫ -40°C) for the separation of ice clouds from mixed-phase clouds may significantly underestimate the liquid cloud fraction in the winter Antarctic atmosphere. Correction of the bias in the liquid cloud fraction would serve to reduce the large uncertainty in cloud radiative effects. © 2010 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"16025531300;56550089500;56219282100;6603718837;6507815511;6602972127;6507791659;36601773500;36623022500;","Assessing 20th century climate-vegetation feedbacks of land-use change and natural vegetation dynamics in a fully coupled vegetation-climate model",2010,"10.1002/joc.2132","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958545011&doi=10.1002%2fjoc.2132&partnerID=40&md5=0df9c5b84c08d718214d391c5692d6d0","This study describes the coupling of the dynamic global vegetation model (DGVM), Lund-Potsdam-Jena Model for managed land (LPJmL), with the general circulation model (GCM), Simplified Parameterizations primitivE Equation DYnamics model (SPEEDY), to study the feedbacks between land-use change and natural vegetation dynamics and climate during the 20th century. We show that anthropogenic land-use change had a stronger effect on climate than the natural vegetation's response to climate change (e.g. boreal greening). Changes in surface albedo are an important driver of the climate's response; but, especially in the (sub)tropics, changes in evapotranspiration and the corresponding changes in latent heat flux and cloud formation can be of equal importance in the opposite direction. Our study emphasizes that implementing dynamic vegetation into climate models is essential, especially at regional scales: the dynamic response of natural vegetation significantly alters the climate change that is driven by increased atmospheric greenhouse gas concentrations and anthropogenic land-use change. Copyright © 2010 Royal Meteorological Society."
"35392584500;6701511324;7102422542;6701498473;6701756058;7005964053;23036934200;7003475150;","Estimation of ECHAM5 climate model closure parameters with adaptive MCMC",2010,"10.5194/acp-10-9993-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958533201&doi=10.5194%2facp-10-9993-2010&partnerID=40&md5=886e1bf79f17a400778fc488534eadaf","Climate models contain closure parameters to which the model climate is sensitive. These parameters appear in physical parameterization schemes where some unresolved variables are expressed by predefined parameters rather than being explicitly modeled. Currently, best expert knowledge is used to define the optimal closure parameter values, based on observations, process studies, large eddy simulations, etc. Here, parameter estimation, based on the adaptive Markov chain Monte Carlo (MCMC) method, is applied for estimation of joint posterior probability density of a small number (n=4) of closure parameters appearing in the ECHAM5 climate model. The parameters considered are related to clouds and precipitation and they are sampled by an adaptive random walk process of the MCMC. The parameter probability densities are estimated simultaneously for all parameters, subject to an objective function. Five alternative formulations of the objective function are tested, all related to the net radiative flux at the top of the atmosphere. Conclusions of the closure parameter estimation tests with a low-resolution ECHAM5 climate model indicate that (i) adaptive MCMC is a viable option for parameter estimation in large-scale computational models, and (ii) choice of the objective function is crucial for the identifiability of the parameter distributions. © 2010 Author(s)."
"7003277623;6507693998;","The climate of Socotra Island (Yemen): A first-time assessment of the timing of the monsoon wind reversal and its influence on precipitation and vegetation patterns",2010,"10.1016/j.jaridenv.2010.05.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956228957&doi=10.1016%2fj.jaridenv.2010.05.017&partnerID=40&md5=96ac455c1f5996347f83cad941ee929d","The climate of Socotra, influenced by the Indian Ocean Monsoon, is poorly known, hampering understanding of its paleoclimate and (endemic) biodiversity. Mean annual rainfall and temperature, measured in a network of meteorological stations from 2002 to 06, were 216 mm and 28.9 °C. Combined with cloud cover information from satellite images, this data provides clear ideas on inter- and intra-annual variability. Precipitation derived from the northeast (NE) winter monsoon influences especially the NE plateaus and windward side of the Haggeher Mountains because of orographic effects. The southwest (SW) summer monsoon concentrates at the southern half of the island and generally produces less rainfall. During the SW summer monsoon, clouds cover the highlands and plateaus south of the Haggeher Mountains, creating fog. Preliminary measurements suggest that at higher altitudes, fog-derived moisture may constitute up to two-thirds of total moisture, amounting up to 800 mm. The predominant SW aspect of the enigmatic dragonblood tree underlines the importance of fog. Long-term weather observations by Socotri put these short-term meteorological observations into a longer perspective. Socotri informants also described the drought years when livestock populations crashed, after which windows of opportunities for the regeneration of dragonblood and other grazing-sensitive trees may have occurred. © 2010 Elsevier Ltd."
"36634069800;6603431534;8658386900;7402064802;","Long-term observations of the convective boundary layer using insect radar returns at the SGP ARM climate research facility",2010,"10.1175/2010JCLI3395.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649264248&doi=10.1175%2f2010JCLI3395.1&partnerID=40&md5=3bed9bb65075fd93893628d1a57d9140","A long-term study of the turbulent structure of the convective boundary layer (CBL) at the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Climate Research Facility is presented. Doppler velocity measurements from insects occupying the lowest 2 km of the boundary layer during summer months are used to map the vertical velocity component in the CBL. The observations cover four summer periods (2004-08) and are classified into cloudy and clear boundary layer conditions. Profiles of vertical velocity variance, skewness, and mass flux are estimated to study the daytime evolution of the convective boundary layer during these conditions. Aconditional sampling method is applied to the original Doppler velocity dataset to extract coherent vertical velocity structures and to examine plume dimension and contribution to the turbulent transport. Overall, the derived turbulent statistics are consistent with previous aircraft and lidar observations. The observations provide unique insight into the daytime evolution of the convective boundary layer and the role of increased cloudiness in the turbulent budget of the subcloud layer. Coherent structures (plumes-thermals) are found to be responsible for more than 80% of the total turbulent transport resolved by the cloud radar system. The extended dataset is suitable for evaluating boundary layer parameterizations and testing large-eddy simulations (LESs) for a variety of surface and cloud conditions. © 2010 American Meteorological Society."
"7405763496;16507181000;36059595100;36782365500;","Future climate change scenarios over Korea using a multi-nested downscaling system: A pilot study",2010,"10.1007/s13143-010-0024-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651459441&doi=10.1007%2fs13143-010-0024-1&partnerID=40&md5=93e0f52fa3d28ac6ac3e4798c0749a21","This study examines a scenario of future summer climate change for the Korean peninsula using a multi-nested regional climate system. The global-scale scenario from the ECHAM5, which has a 200 km grid, was downscaled to a 50 km grid over Asia using the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM). This allowed us to obtain large-scale forcing information for a one-way, double-nested Weather and Research Forecasting (WRF) model that consists of a 12 km grid over Korea and a 3 km grid near Seoul. As a pilot study prior to the multi-year simulation work the years 1995 and 2055 were selected for the present and future summers. This RSM-WRF multi-nested downscaling system was evaluated by examining a downscaled climatology in 1995 with the largescale forcing from the NCEP/Department of Energy (DOE) reanalysis. The changes in monsoonal flows over East Asia and the associated precipitation change scenario over Korea are highlighted. It is found that the RSM-WRF system is capable of reproducing large-scale features associated with the East-Asian summer monsoon (EASM) and its associated hydro-climate when it is nested by the NCEP/DOE reanalysis. The ECHAM5-based downscaled climate for the present (1995) summer is found to suffer from a weakening of the low-level jet and sub-tropical high when compared the reanalysis-based climate. Predicted changes in summer monsoon circulations between 1995 and 2055 include a strengthened subtropical high and an intensified mid-level trough. The resulting projected summer precipitation is doubled over much of South Korea, accompanied by a pronounced surface warming with a maximum of about 2 K. It is suggested that downscaling strategy of this study, with its cloud-resolving scale, makes it suitable for providing high-resolution meteorological data with which to derive hydrology or air pollution models. © 2010 Korean Meteorological Society and Springer Netherlands."
"7004288767;7006515850;","Measurements of atmospheric nanoparticles (1875-1980)",2010,"10.1175/2010BAMS2929.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650456076&doi=10.1175%2f2010BAMS2929.1&partnerID=40&md5=2987dc634c8097173b828c633d943533","Nanoparticles are a contemporary name for a dominant portion of condensation nuclei (CN) found in the atmosphere. Although the observational science of atmospheric nanoparticles is over a century old, much could be done to continue accumulating knowledge of this particle size range combined with larger particles. There are a knowledge gaps to quantify the formation processes of nanoparticles and how they grow to sizes that can serve as cloudcondensation nuclei, potentially affecting cloud albedo and indirect climate forcing. There is also a lack of knowledge of the fraction of these particles that is formed by direct source emissions, nucleation of warm vapor emissions with cooling in ambient air. Many of the measurements now needed require advanced instrumentation currently underdevelopment with focus on elucidating the chemical composition of nanoparticles, including the contemporary aerosol mass spectrometers. Although renewed interest has stimulated the generation of a substantial body of new information about atmospheric aerosols, investigators should keep in mind that a body of historical knowledge about nanoparticles also is accessible dating back to the nineteenth century. Indeed, some of the earliest truly scientificinterest in atmospheric aerosols derives from then-innovative observations of the total number of particles in the air dominated by nanoparticles. © 2010 American Meteorological Society."
"36059844000;7102643810;7006575272;7004484970;","Evaluating the snow crystal size distribution and density assumptions within a single-moment microphysics scheme",2010,"10.1175/2010MWR3485.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650189514&doi=10.1175%2f2010MWR3485.1&partnerID=40&md5=286a8fa5eb8f0f3d0a225c5079f13de0","The Canadian CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Validation Project (C3VP) was a field campaign designed to obtain aircraft, surface, and radar observations of clouds and precipitation in support of improving the simulation of snowfall and cold season precipitation, their microphysical processes represented within forecast models, and radiative properties relevant to remotely sensed retrievals. During the campaign, a midlatitude cyclone tracked along the U.S.-Canadian border on 22 January 2007, producing an extensive area of snowfall. Observations of ice crystals from this event are used to evaluate the assumptions and physical relationships for the snow category within the Goddard six-class, single-moment microphysics scheme, as implemented within the Weather Research and Forecasting (WRF) model. The WRF model forecast generally reproduced the precipitation and cloud structures sampled by radars and aircraft, permitting a comparison between C3VP observations and model snowfall characteristics. Key snowfall assumptions in the Goddard scheme are an exponential size distribution with fixed intercept and effective bulk density, and the relationship between crystal diameter and terminal velocity. Fixed values for the size distribution intercept and density did not represent the vertical variability of naturally occurring populations of aggregates, and the current diameter and fall speed relationship underestimated terminal velocities for all sizes of crystals. © 2010 American Meteorological Society."
"36988140900;7202772927;7403577184;7006874359;7006957668;7401701196;6701653010;7404340979;6701845806;6701684534;7005461477;7102643810;","WRF simulations of the 20-22 January 2007 snow events over eastern Canada: Comparison with in situ and satellite observations",2010,"10.1175/2010JAMC2282.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149376149&doi=10.1175%2f2010JAMC2282.1&partnerID=40&md5=4e0d5677fccebca8779a4e7b89f01776","One of the grand challenges of the Global Precipitation Measurement (GPM) mission is to improve coldseason precipitation measurements in mid- and high latitudes through the use of high-frequency passive microwave radiometry. For this purpose, the Weather Research and Forecasting model (WRF) with the Goddard microphysics scheme is coupled with a Satellite Data Simulation Unit (WRF-SDSU) to facilitate snowfall retrieval algorithms over land by providing a virtual cloud library and corresponding microwave brightness temperature measurements consistent with the GPM Microwave Imager (GMI). When this study was initiated, there were no prior published results using WRF at cloud-resolving resolution (1 km or finer) for high-latitude snow events. This study tested the Goddard cloud microphysics scheme in WRF for two different snowstorm events (a lake-effect event and a synoptic event between 20 and 22 January 2007) that took place over the Canadian CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Validation Project (C3VP) site in Ontario, Canada. The 24-h-accumulated snowfall predicted by WRF with the Goddard microphysics was comparable to that observed by the ground-based radar for both events. The model correctly predicted the onset and termination of both snow events at the Centre for Atmospheric Research Experiments site. The WRF simulations captured the basic cloud patterns as seen by the ground-based radar and satellite [i.e., CloudSat and Advanced Microwave Sounding Unit B (AMSU-B)] observations, including the snowband featured in the lake event. The results reveal that WRF was able to capture the cloud macrostructure reasonably well. Sensitivity tests utilizing both the ""2ICE"" (ice and snow) and ""3ICE"" (ice, snow, and graupel) options in the Goddard microphysical scheme were also conducted. The domain- and time-averaged cloud species profiles from the WRFsimulations with both microphysical options show identical results (due to weak vertical velocities and therefore the absence of large precipitating liquid or high-density ice particles like graupel). Both microphysics options produced an appreciable amount of liquid water, and the model cloud liquid water profiles compared well to the in situ C3VP aircraft measurements when only grid points in the vicinity of the flight paths were considered. However, statistical comparisons between observed and simulated radar echoes show that the model tended to have a high bias of several reflectivity decibels (dBZ), which shows that additional research is needed to improve the current cloud microphysics scheme for the extremely cold environment in high latitudes, despite the fact that the simulated ice/liquid water contents may have been reasonable for both events. Future aircraft observations are also needed to verify the existence of graupel in high-latitude continental snow events. © 2010 American Meteorological Society."
"11739169500;6602228395;7003811919;","Implications of high altitude desert dust transport from Western Sahara to Nile Delta during biomass burning season",2010,"10.1016/j.envpol.2010.07.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956611362&doi=10.1016%2fj.envpol.2010.07.035&partnerID=40&md5=32bd709d85b96c2bb18359981007afbb","The air over major cities and rural regions of the Nile Delta is highly polluted during autumn which is the biomass burning season, locally known as black cloud. Previous studies have attributed the increased pollution levels during the black cloud season to the biomass or open burning of agricultural waste, vehicular, industrial emissions, and secondary aerosols. However, new multi-sensor observations (column and vertical profiles) from satellites, dust transport models and associated meteorology present a different picture of the autumn pollution. Here we show, for the first time, the evidence of long range transport of dust at high altitude (2.5-6 km) from Western Sahara and its deposition over the Nile Delta region unlike current Models. The desert dust is found to be a major contributor to the local air quality which was previously considered to be due to pollution from biomass burning enhanced by the dominant northerly winds coming from Europe. © 2010 Elsevier Ltd. All rights reserved."
"16475714800;7005702722;","Mechanisms of poleward propagating, intraseasonal convective anomalies in cloud system-resolving models",2010,"10.1175/2010JAS3515.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649455480&doi=10.1175%2f2010JAS3515.1&partnerID=40&md5=ade8bbf121f3175b429cc795f09e0763","An envelope of convection that propagates both poleward and eastward accounts for the largest fraction of intraseasonal variance of the tropical atmosphere during boreal summer. Here the mechanisms of poleward propagating convective anomalies are examined in a nonhydrostatic model with zonally symmetric boundary conditions, integrated on a beta plane at resolutions high enough to explicitly represent moist convection. When the domain has a narrow zonal dimension of 100 km or less, the model produces a quasisteady intertropical convergence zone (ITCZ). Meridionally propagating transients are produced for some prescribed sea surface temperature distributions, but these transients are shallow, vanish at finer resolutions, and have a structure that bears little resemblance to that of observed poleward propagating anomalies. This is in sharp contrast to previous studies that obtained robust poleward propagating anomalies in axisymmetric models using parameterized moist convection, and it suggests that the anomalies seen in those models may be caused by deficient representations of dynamics or subgrid-scale physics. Robust poleward propagating anomalies are obtained when the high-resolution, nonhydrostatic model is integrated in a wider domain with a zonal dimension near 1000 km. Diagnostics suggest that poleward propagation in this wide domain results from the convectively coupled beta drift of low-level vorticity anomalies. Deep near-equatorial ascent produces low-level cyclones that migrate poleward through the process of beta drift; Ekman pumping in these drifting cyclones then humidifies the free troposphere ahead of the initial deep ascent, shifting the convection poleward. The moist static energy budget and model sensitivity tests suggest that these anomalies can be viewed as moisture modes destabilized through a moisture-radiation feedback. Wind-evaporation feedback also seems to contribute to the instability of these anomalies, but because it enhances surface fluxes on the equatorward side of the anomalies, it also reduces their propagation speed. These results suggest a novel mechanism for the poleward propagation of intraseasonal convective anomalies and illustrate the need to evaluate theoretical models that use parameterized convection against cloud system-resolving models. © 2010 American Meteorological Society."
"7004978335;36611380200;6603724288;36611651000;","Growth of epiphytic bromeliads in a changing world: The effects of CO2, water and nutrient supply",2010,"10.1016/j.actao.2010.10.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649774164&doi=10.1016%2fj.actao.2010.10.003&partnerID=40&md5=3d323137b38f676f05a1e2c3d29b2130","Vascular epiphytes, which respond to varying water supply more than any other life form, are thought to be particularly vulnerable to climate change because they are de-coupled from the soil and are thus more directly affected by atmospheric conditions. The few available studies addressing the effect of climate change on epiphytes have either studied plant responses to changes in water supply or to elevated CO2, but none has looked at possible interactions of these abiotic factors. Here, we present a growth chamber study on the response of individuals of 11 species of epiphytic bromeliads from both tropical lowlands and montane areas to varying CO2, water and nutrient levels. Water availability had by far the strongest and most consistent impact on plant growth, while the effects of elevated CO2 and increased nutrient supply were much less consistent across species or habitats. A significant mitigation of reduced water availability by increased CO2 levels could not be detected. While some species from montane areas were very susceptible to low water availability, lowland species were mostly quite drought-tolerant. These results suggest that global change can pose a real threat to vascular epiphytes through changes in the altitude of cloud formation and altered precipitation patterns, acknowledging substantial differences between species and habitats. Other aspects of global change like the increase of atmospheric CO2 levels as such seem of limited relevance for the functioning of epiphytic plants. © 2010 Elsevier Masson SAS."
"8278450900;7006508549;57203047484;57209089997;7005135473;57203793097;","Comparison of satellite-derived TOA shortwave clear-sky fluxes to estimates from GCM simulations constrained by satellite observations of land surface characteristics",2010,"10.1002/joc.2107","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958566927&doi=10.1002%2fjoc.2107&partnerID=40&md5=fd4dc7bbe127707904b5d9bae90dbc55","Clear-sky, upwelling shortwave flux at the top of the atmosphere $\left(S_{\rm {TOA}}^{\uparrow}\right)$, simulated using the atmospheric and land model components of the Community Climate System Model 3 (CCSM3), is compared to corresponding observational estimates from the Clouds and Earth's Radiant Energy System (CERES) sensor. Improvements resulting from the use of land surface albedo derived from Moderate Resolution Imaging Spectroradiometer (MODIS) to constrain the simulations are also examined. Compared to CERES observations, CCSM3 overestimates global, annual averaged $S_{\rm {TOA}}^{\uparrow}$ over both land and oceans. However, regionally, CCSM3 overestimates $S_{\rm {TOA}}^{\uparrow}$ over some land and ocean areas while underestimating it over other sites. CCSM3 underestimates $S_{\rm {TOA}}^{\uparrow}$ over the Saharan and Arabian Deserts and substantial differences exist between CERES observations and CCSM3 over agricultural areas. Over selected sites, after using ground-based observations to remove systematic biases that exist in CCSM computation of $S_{\rm {TOA}}^{\uparrow}$, it is found that use of MODIS albedo improves the simulation of $S_{\rm {TOA}}^{\uparrow}$. Inability of coarse resolution CCSM3 simulation to resolve spatial heterogeneity of snowfall over high altitude sites such as the Tibetan Plateau causes overestimation of $S_{\rm {TOA}}^{\uparrow}$ in these areas. Discrepancies also exist in the simulation of $S_{\rm {TOA}}^{\uparrow}$ over ocean areas as CCSM3 does not account for the effect of wind speed on ocean surface albedo. This study shows that the radiative energy budget at the TOA is improved through the use of MODIS albedo in Global Climate Models. Copyright © 2010 Royal Meteorological Society."
"33567925300;57217271893;7202611735;","Coupled land-atmosphere intraseasonal variability of the West African monsoon in a GCM",2010,"10.1175/2010JCLI3419.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958101587&doi=10.1175%2f2010JCLI3419.1&partnerID=40&md5=7e31ac6fdb1f59c51370d1a47cc8bfcd","Recent observational studies have suggested a role for soil moisture and land-atmosphere coupling in the 15-day westward-propagating mode of intraseasonal variability in the West African monsoon. This hypothesis is investigated with a set of three atmospheric general circulation model experiments. 1) When soil moisture is fully coupled with the atmospheric model, the 15-day mode of land-atmosphere variability is clearly identified. Precipitation anomalies lead soil moisture anomalies by 1-2 days, similar to the results from satellite observations. 2) To assess whether soil moisture is merely a passive response to the precipitation, or an active participant in this mode, the atmospheric model is forced with a 15-day westward-propagating cycle of regional soil moisture anomalies based on the fully coupled mode. Through a reduced surface sensible heat flux, the imposed wet soil anomalies induce negative low-level temperature anomalies and increased pressure (a cool high). An anticyclonic circulation then develops around the region of wet soil, enhancing northward moisture advection and precipitation to the west. Hence, in a coupled framework, this soil moisture-forced precipitation response would provide a self-consistent positive feedback on the westward-propagating soil moisture anomaly and implies an active role for soil moisture. 3) In a final sensitivity experiment, soil moisture is again externally prescribed but with all intraseasonal fluctuations suppressed. In the absence of soil moisture variability there are still pronounced surface sensible heat flux variations, likely due to cloud changes, and the 15-day westward-propagating precipitation signal is still present. However, it is not as coherent as in the previous experiments when interaction with soil moisture was permitted. Further examination of the soil moisture forcing experiment in GCM experiment 2 shows that this precipitation mode becomes phase locked to the imposed soil moisture anomalies. Hence, the 15-day westward-propagating mode in the West African monsoon can exist independently of soil moisture; however, soil moisture and land-atmosphere coupling act to feed back on the atmosphere and further enhance and organize it. © 2010 American Meteorological Society."
"57197233116;7004942632;","Validating ECMWF forecasts for the occurrence of ice supersaturation using visual observations of persistent contrails and radiosonde measurements over England",2010,"10.1002/qj.670","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958596687&doi=10.1002%2fqj.670&partnerID=40&md5=087f28f63c5452feb27cc6dff84270bd","One of the largest uncertainties in quantifying the impact of aviation on climate concerns the formation and spreading of persistent contrails. The inclusion of a cloud scheme that allows for ice supersaturation into the integrated forecast system (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) can be a useful tool to help reduce these uncertainties. This study evaluates the quality of the ECMWF forecasts with respect to ice supersaturation in the upper troposphere by comparing them with visual observations of persistent contrails and radiosonde measurements of ice supersaturation over England. The performance of 1-3 day forecasts is compared, also including the vertical accuracy of the supersaturation forecasts. It is found that the operational forecasts from the ECMWF are able to predict cold ice-supersaturated regions very well. For the best cases Peirce skill scores of 0.7 are obtained, with hit rates at times exceeding 80% and false-alarm rates below 20%. Results are very similar for comparisons with visual observations and radiosonde measurements, the latter providing the better statistical significance. © 2010 Royal Meteorological Society."
"14024070000;7404493635;6602545330;7005837895;26536456500;","A land-atmospheric interaction study in the coastal tropical city of San Juan, Puerto Rico",2010,"10.1175/2010EI309.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650381766&doi=10.1175%2f2010EI309.1&partnerID=40&md5=ab6ed0daa8246864c1cde75c02d80d6d","This paper focuses on the surface-atmospheric interaction in a tropical coastal city including the validation of an atmospheric modeling and an impact study of land-cover and land-use (LCLU) changes. The Regional Atmospheric Modeling System (RAMS), driven with regional reanalysis data for a 10-day simulation, is used to perform the study in the San Juan metropolitan area (SJMA), one of the largest urban conglomerations in the Caribbean, which is located in the island of Puerto Rico and taken as the test case. The model's surface characteristics were updated using airborne high-resolution remote sensing information to obtain a more accurate and detailed configuration of the SJMA. Surface and rawinsonde data from the San Juan Airborne Thermal and Land Applications Sensor (ATLAS) Mission are used to validate the modeling system, yielding satisfactory results in surface/canopy temperature, near-surface air temperatures, and vertical profiles. The impact analysis, performed with the updated SJMA configuration and a potential natural vegetation (PNV) scenario, showed that the simulation with specified urban LCLU indexes in the bottom boundary produced higher air temperatures over the area occupied by the city, with positive values of up to 2.5°C. The same analysis showed changes in the surface radiative balance in the urban case attributed to modifications in the LCLU. This additional heat seems to motivate additional vertical convection that may be leading to possible urban-induced precipitation downwind of the SJMA. This was evident in a precipitation disturbance when the city is present (∼0.9 mm, 22.5% increase) captured by the model that was accompanied by increases in cloud formation and vertical motions mainly downwind of the city. Copyright © 2010, Paper 14-016; 7813."
"23667726100;55963073000;","Detection of the Kuroshio frontal instable processes (KFIP) in the East China Sea using the MODIS images",2010,"10.1007/s13131-010-0074-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866068447&doi=10.1007%2fs13131-010-0074-3&partnerID=40&md5=7ca13c3ce1956a37cd08f7f48ad4c619","The Kuroshio frontal instable processes (KFIP) in the East China Sea (ECS) not only have a great impact on the hydrologic characteristics, the pollutants drift, the distribution of seafloor sediment and the ships navigation of the ECS, but also are closely related to the climate changes of the coastal areas of the ECS. However the frequency and area of occurrence of the KFIP have not been studied fully and detailedly. Because of its high spatial and temporal resolution, MODIS data is a kind of very good data source for surveying and researching the KFIP in the ECS. The aim of this study is to detect the KFIP in the ECS by using MODIS data, and to study the frequency and region of occurrence of the KFIP in the ECS. The selection has coverage of level 2 data of MODIS SST and Kd490 ranging from July 1, 2002 to June 30, 2009 of the ECS when there was no cloud impact or little. By using of the data, the minimum standard of the Kuroshio temperature fronts and the diffuse attenuation coefficient (Kd490) fronts of the ECS are given. Based on these standards and the curvature distinguish methods, the standard of curvature distinguish for the KFIP in the ECS are put forward. By making use of this standard, we study a total of 2073 satellite-derived images, and discover that as long as there is no cloud impact from January to May and October to December, the KFIP in the ECS are surely found in MODIS satellite images. From June to September, the frequency of occurrence can also reach to 82.9% at least. Moreover, it is obtained that there are three source regions of these instability processes, namely, (26?N, 121.5?E) nearby, (27?N, 125?E) nearby and (30?N, 128?E) nearby. The differences of the characteristics of these instability processes which are generated in different regions are analyzed in the present study. © The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2010."
"23096635200;6701751765;6603035923;28568039300;26323026900;6507421222;","Is Gliese 581d habitable? Some constraints from radiative-convective climate modeling",2010,"10.1051/0004-6361/201015053","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78049336988&doi=10.1051%2f0004-6361%2f201015053&partnerID=40&md5=cc63757d82eaa0ba1dbdfe62a4e92ea2","The recently discovered exoplanet Gl 581d is extremely close to the outer edge of its system's habitable zone, which has led to much speculation on its possible climate. We have performed a range of simulations to assess whether, given simple combinations of chemically stable greenhouse gases, the planet could sustain liquid water on its surface. For best estimates of the surface gravity, surface albedo and cloud coverage, we find that less than 10 bars of CO2 is sufficient to maintain a global mean temperature above the melting point of water. Furthermore, even with the most conservative choices of these parameters, we calculate temperatures above the water melting point for CO2 partial pressures greater than about 40 bar. However, we note that as Gl 581d is probably in a tidally resonant orbit, further simulations in 3D are required to test whether such atmospheric conditions are stable against the collapse of CO2 on the surface. © 2010 ESO."
"55607020000;6603613067;8397494800;","Constraints on interactions between aerosols and clouds on a global scale from a combination of MODIS-CERES satellite data and climate simulations",2010,"10.5194/acp-10-9851-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958114114&doi=10.5194%2facp-10-9851-2010&partnerID=40&md5=b307bfdd63cc34004ccdccc7919c44ea","Satellite-based cloud top effective radius retrieved by the CERES Science Team were combined with simulated aerosol concentrations from CCCma CanAM4 to examine relationships between aerosol and cloud that underlie the first aerosol indirect (cloud albedo) effect. Evidence of a strong negative relationship between sulphate, and organic aerosols, with cloud top effective radius was found for low clouds, indicating both aerosol types are contributing to the first indirect effect on a global scale. Furthermore, effects of aerosol on the cloud droplet effective radius are more pronounced for larger cloud liquid water paths. While CanAM4 broadly reproduces the observed relationship between sulphate aerosols and cloud droplets, it does not reproduce the dependency of cloud top droplet size on organic aerosol concentrations nor the dependency on cloud liquid water path. Simulations with a modified version of the model yield a more realistic dependency of cloud droplets on organic carbon. The robustness of the methods used in the study are investigated by repeating the analysis using aerosol simulated by the GOCART model and cloud top effective radii derived from the MODIS Science Team. © 2010 Author(s)."
"24737203600;56744278700;","Direct and semi-direct impacts of absorbing biomass burning aerosol on the climate of southern Africa: A Geophysical Fluid Dynamics Laboratory GCM sensitivity study",2010,"10.5194/acp-10-9819-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958135578&doi=10.5194%2facp-10-9819-2010&partnerID=40&md5=e7493727ceefb4f47d7ca62ce8e5075e","Tropospheric aerosols emitted from biomass burning reduce solar radiation at the surface and locally heat the atmosphere. Equilibrium simulations using an atmospheric general circulation model (GFDL AGCM) indicate that strong atmospheric absorption from these particles can cool the surface and increase upward motion and low-level convergence over southern Africa during the dry season. These changes increase sea level pressure over land in the biomass burning region and spin-up the hydrologic cycle by increasing clouds, atmospheric water vapor, and, to a lesser extent, precipitation. Cloud increases serve to reinforce the surface radiative cooling tendency of the aerosol. Conversely, if the climate over southern Africa were hypothetically forced by high loadings of scattering aerosol, then the change in the low-level circulation and increased subsidence would serve to decrease clouds, precipitation, and atmospheric water vapor. Surface cooling associated with scattering-only aerosols is mitigated by warming from cloud decreases. The direct and semi-direct climate impacts of biomass burning aerosol over southern Africa are sensitive to the total amount of aerosol absorption and how clouds change in response to the aerosol-induced heating of the atmosphere. © 2010 Author(s)."
"35487814900;36911153100;8611587300;6602797994;55399842300;17340414700;6701504447;","Climatology-based regional modelling of potential vegetation and average annual long-term runoff for Mesoamerica",2010,"10.5194/hess-14-1801-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958005459&doi=10.5194%2fhess-14-1801-2010&partnerID=40&md5=91f356218033f46c7bc46639e2e6ea3d","Mean annual cycles of runoff, evapotranspiration, leaf area index (LAI) and potential vegetation were modelled for Mesoamerica using the SVAT model MAPSS with different climatology datasets. We calibrated and validated the model after building a comprehensive database of regional runoff, climate, soils and LAI. The performance of several gridded precipitation climatology datasets (CRU, FCLIM, WorldClim, TRMM, WindPPT and TCMF) was evaluated and FCLIM produced the most realistic runoff. Annual runoff was successfully predicted (R 2=0.84) for a set of 138 catchments, with a low runoff bias (12%) that might originate from an underestimation of the precipitation over cloud forests. The residuals were larger in small catchments but remained homogeneous across elevation, precipitation, and land-use gradients. Assuming a uniform distribution of parameters around literature values, and using a Monte Carlo-type approach, we estimated an average model uncertainty of 42% of the annual runoff. The MAPSS model was most sensitive to the parameterization of stomatal conductance. Monthly runoff seasonality was mimicked ""fairly"" in 78% of the catchments. Predicted LAI was consistent with MODIS collection 5 and GLOBCARBON remotely sensed global products. The simulated evapotranspiration:runoff ratio increased exponentially for low precipitation areas, highlighting the importance of accurately modelling evapotranspiration below 1500 mm of annual rainfall with the help of SVAT models such as MAPSS. We propose the first high-resolution (1 km2 pixel) maps combining average long-term runoff, evapotranspiration, leaf area index and potential vegetation types for Mesoamerica. © Author(s) 2010."
"8147766700;34769585100;7102253788;24477694300;7007172001;7006212411;7202050065;7004643405;16480965400;7005284577;","Aircraft observations of enhancement and depletion of black carbon mass in the springtime Arctic",2010,"10.5194/acp-10-9667-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957950116&doi=10.5194%2facp-10-9667-2010&partnerID=40&md5=4c82c6732f501a7ae8a70f221bc2a1d1","Understanding the processes controlling black carbon (BC) in the Arctic is crucial for evaluating the impact of anthropogenic and natural sources of BC on Arctic climate. Vertical profiles of BC mass loadings were observed from the surface to near 7-km altitude in April 2008 using a Single-Particle Soot Photometer (SP2) during flights on the NOAA WP-3D research aircraft from Fairbanks, Alaska. These measurements were conducted during the NOAA-sponsored Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project. In the free troposphere, the Arctic air mass was influenced by long-range transport from biomass-burning and anthropogenic source regions at lower latitudes especially during the latter part of the campaign. Average BC mass mixing ratios peaked at about 150 ng BC (kg dry air )&amp;minus;1 near 5.5 km altitude in the aged Arctic air mass and 250 ng kg&amp;minus;1 at 4.5 km in biomass-burning influenced air. BC mass loadings were enhanced by up to a factor of 5 in biomass-burning influenced air compared to the aged Arctic air mass. At the bottom of some of the profiles, positive vertical gradients in BC were observed over the sea-ice. The vertical profiles generally occurred in the vicinity of open leads in the sea-ice. In the aged Arctic air mass, BC mass loadings more than doubled with increasing altitude within the ABL and across the boundary layer transition while carbon monoxide (CO) remained constant. This is evidence for depletion of BC mass in the ABL. BC mass loadings were positively correlated with O3 in ozone depletion events (ODEs) for all the observations in the ABL. Since bromine catalytically destroys ozone in the ABL after being released as molecular bromine in regions of new sea-ice formation at the surface, the BC-O3 correlation suggests that BC particles were removed by a surface process such as dry deposition. We develop a box model to estimate the dry deposition flux of BC mass to the snow constrained by the vertical profiles of BC mass in the ABL. Open leads in the sea-ice may increase vertical mixing and entrainment of pollution from the free troposphere possibly enhancing the deposition of BC aerosol to the snow. © 2010 Author(s)."
"8930977600;36551575300;8577958100;36937494400;","New data on the mineralogy of the salt deposit from Sovata (Mureş county-Romania)",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957859973&partnerID=40&md5=4493cf362068fc640c1a6b7c5f00d8a2","The Badenian salt massif from Sovata is among the main salt diapirs from the Transylvanian Basin. It belongs to the eastern diapiric alignments (Şieu-Odorheiu Secuiesc-Sovata-Praid). The salt tectonics was mainly controlled by the uplift of Eastern Carpathians accompanied by high heat flow due to Neogene volcanism, generating the gravity spreading of the overburden salt. In Sovata area younger deposits are cropping out too: Pannonian sediments and Neogene volcanic breccias and agglomerates. The salt deposition was controlled by climate, tectonics, eustatism and palaeogeography. As indicated by the salt deposit mineralogy, the sedimentary conditions covered the range from the last stage of carbonates precipitation to halite. Simultaneously, an input of clastic material into the sedimentary basin from the surrounding area, took place. Such environment explains the presence of two geneticallydifferent sets of minerals in the salt deposit from Sovata: of authigenic (halite, anhydrite, gypsum, calcite, and dolomite), as well as allogenic (quartz, clay minerals, feldspars etc.) origins. Under the microscope, two different types of fluid inclusions in halite were identified: primary inclusions in undissolved ""core"" of halite crystals, and secondary fluids distributed either parallel to the new cleavage planes of the recrystallized halite, or as clouds next to the planes/cracks generated by deformational events."
"7102514911;8603356700;8293676000;6603928204;6507059522;8542639900;6701579717;7006495018;7004864963;35461763400;7004510293;","Polar organic marker compounds in atmospheric aerosols during the LBA-SMOCC 2002 biomass burning experiment in Rondônia, Brazil: Sources and source processes, time series, diel variations and size distributions",2010,"10.5194/acp-10-9319-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957705132&doi=10.5194%2facp-10-9319-2010&partnerID=40&md5=3c4fec6590dfcf0549a71182ef905c2f","Measurements of polar organic marker compounds were performed on aerosols that were collected at a pasture site in the Amazon basin (Rondônia, Brazil) using a high-volume dichotomous sampler (HVDS) and a Micro-Orifice Uniform Deposit Impactor (MOUDI) within the framework of the 2002 LBA-SMOCC (Large-Scale Biosphere Atmosphere Experiment in Amazônia-Smoke Aerosols, Clouds, Rainfall, and Climate: Aerosols From Biomass Burning Perturb Global and Regional Climate) campaign. The campaign spanned the late dry season (biomass burning), a transition period, and the onset of the wet season (clean conditions). In the present study a more detailed discussion is presented compared to previous reports on the behavior of selected polar marker compounds, including levoglucosan, malic acid, isoprene secondary organic aerosol (SOA) tracers and tracers for fungal spores. The tracer data are discussed taking into account new insights that recently became available into their stability and/or aerosol formation processes. During all three periods, levoglucosan was the most dominant identified organic species in the PM2.5 size fraction of the HVDS samples. In the dry period levoglucosan reached concentrations of up to 7.5 μg mg-3 and exhibited diel variations with a nighttime prevalence. It was closely associated with the PM mass in the size-segregated samples and was mainly present in the fine mode, except during the wet period where it peaked in the coarse mode. Isoprene SOA tracers showed an average concentration of 250 ng mg-3 during the dry period versus 157 ng mg-3 during the transition period and 52 ng mg-3 during the wet period. Malic acid and the 2-methyltetrols exhibited a different size distribution pattern, which is consistent with different aerosol formation processes (i.e., gas-to-particle partitioning in the case of malic acid and heterogeneous formation from gas-phase precursors in the case of the 2-methyltetrols). The 2-methyltetrols were mainly associated with the fine mode during all periods, while malic acid was prevalent in the fine mode only during the dry and transition periods, and dominant in the coarse mode during the wet period. The sum of the fungal spore tracers arabitol, mannitol, and erythritol in the PM2.5 fraction of the HVDS samples during the dry, transition, and wet periods was, on average, 54 ng mg-3, 34 ng mg-3, and 27 ng mg -3, respectively, and revealed minor day/night variation. The mass size distributions of arabitol and mannitol during all periods showed similar patterns and an association with the coarse mode, consistent with their primary origin. The results show that even under the heavy smoke conditions of the dry period a natural background with contributions from bioaerosols and isoprene SOA can be revealed. The enhancement in isoprene SOA in the dry season is mainly attributed to an increased acidity of the aerosols, increased NOx concentrations and a decreased wet deposition. © 2010 Author(s)."
"14045744500;7003582587;","Analysis of prognostic cloud scheme increments in a climate model",2010,"10.1002/qj.720","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650038871&doi=10.1002%2fqj.720&partnerID=40&md5=607777f30fc3528e38df81d14ffaac4f","An analysis of a cloud scheme is presented, which can aid the development of climate and weather forecasting models. Budget tendency terms, or cloud increment diagnostics, are analysed to show the relative importance of the various physical processes in creating the cloud fields simulated by a climate model. When looking at time-averaged diagnostics, the use of mean positive and mean negative increments separately, as well as mean net increments, is shown to be informative in understanding how the model is behaving. Maps of vertically integrated tendency terms illustrate how the dominant cloud production terms vary geographically. A cross-section through the Hadley Circulation shows how the tendency terms vary across a transition region as the clouds change from stratocumulus to shallow cumulus and then to cumulonimbus. Although there are no observations against which these increment diagnostics can be compared, identification of the key cloud formation and dissipation processes highlights the parts of the cloud scheme where further work should be focussed in order to improve the climatological cloud fields. Simulations with changes to a part of the cloud parametrization are analysed using the increment diagnostics and the change in the relative importance of the different processes highlights some of the feedbacks present in the model. While our detailed findings are model specific, the analysis technique could be used in the development of any weather forecasting or climate model. © Crown Copyright 2010."
"23484340400;14045744500;","Parametrization of area cloud fraction",2010,"10.1002/asl.293","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952793170&doi=10.1002%2fasl.293&partnerID=40&md5=d44d617bf54f2ff54a7fcab496dcee3b","Comparisons of radiosonde data to model profiles show that the relative coarseness of the vertical grid can lead to poorly resolved changes in thermodynamic properties. This can lead to the model underestimating cloud cover. A parametrization for area cloud fraction, compatible with a prognostic cloud scheme, is developed and tested. The parametrization is then implemented in a general circulation model and used to produce a weather forecast and a climate simulation. The simulated cloud cover is improved in both models, whilst feedbacks within the climate model lead to an improvement in the surface temperature, particularly in the Northern-Hemisphere winter. © Crown Copyright 2010. Published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"55825234900;","A materials scientist ponders global warming/cooling",2010,"10.1260/0958-305X.21.6.611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958565656&doi=10.1260%2f0958-305X.21.6.611&partnerID=40&md5=5899e49796c915b788b9c154cebcf948","Eminent climatologists support the opinion of the Intergovernmental Panel on Climate Change (IPCC) that rising global average temperature is due to anthropogenic CO2 emissions. A number dispute this. This paper is written by a physical scientist aiming to understand the controversy for himself. An elementary account is given of the physical theory of the Earth's average temperature so as to introduce the principal parameters: solar irradiance; earth's albedo; physics of the factors determining the emissivity of the earth. The rise in mean global temperature observed intermittently over the last one hundred years has markedly slowed over the last ten. This discrepancy with the prediction of accepted models of a secular change of climate, coupled with the known uncertainties concerning the effects of clouds and of water vapour cast doubt on the accuracy of the models. The lead position of CO2 in forcing a change of climate is hence questioned. The apparent neglect of man-made changes in the distribution of water is emphasised. The uncertainties regarding the behaviour of water vapour and cloudiness must be resolved if the cited causes of any climate change are to be fully reliable."
"6506537159;7102743829;7202619752;","Large-eddy observation of post-cold-frontal continental stratocumulus",2010,"10.1175/2010JAS3389.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958543484&doi=10.1175%2f2010JAS3389.1&partnerID=40&md5=716b52c088c10634dd14ea33ce9ee920","More studies on the dynamics of marine stratus and stratocumulus clouds have been performed than comparable studies on continental stratocumulus. Therefore, to increase the number of observations of continental stratocumulus and to compare marine and continental stratocumulus to each other, the approach of large-eddy observation (LEO) was applied to a case of nocturnal continental stratocumulus observed over the Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) in the central United States on 8 April 2006. The stratocumulus occurred in cold-air and dry-air advection behind a surface cold front. LEOs were obtained from millimeter-wavelength cloud radar and micropulse lidar, whereas traditional meteorological observations described the synoptic environment. This study focuses on a 9-h period of a predominantly nonprecipitating stratocumulus layer 250-400 m thick. A slight thinning of the cloud layer over time is consistent with dry-air advection. Adeep layer of descent overlaid a shallower layer of ascent from the surface up to 800 mb, providing a mechanism for strengthening the inversion at cloud top. Time series of Doppler velocity indicate vertically coherent structures identifiable throughout much of the cloud layer. The magnitude of turbulence, as indicated by the variance of the vertical velocity, was weak relative to typical marine stratocumulus and to the one other case of continental stratocumulus in the literature. Conditional sampling of the eddy structures indicate that strong downdrafts were more prevalent than strong updrafts, and negative skewness of vertical velocity in the cloud implies an in-cloud circulation driven by longwave cooling at cloud top, similar to that in marine stratocumulus. © 2010 American Meteorological Society."
"6602845217;","The slab ocean El Niño",2010,"10.1029/2010GL044888","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958451584&doi=10.1029%2f2010GL044888&partnerID=40&md5=24fde80d4ba9341e856699ee8154ae48","In a series of Atmospheric model simulations coupled to a simple slab ocean model it is illustrated that El Nio type of SST variability can exist in the absence of any ocean dynamics. Atmospheric feedbacks in cloud cover and changes in the wind field can produce positive and delayed negative feedbacks that together with the heat capacity of the upper ocean can produce a damped interannual oscillation in the equatorial Pacific that is comparable in strength and has characteristics to the observed phenomenon. The evolution of the SST pattern is similar to the SST-mode of El Nio, but is entirely controlled by atmospheric feedbacks. The results challenge and extend our current understanding of the feedback mechanisms of El Nio in climate models and may also highlight possible atmospheric mechanisms that could partly control some observed ENSO events. © 2010 by the American Geophysical Union."
"18635820300;7102128820;7007114756;","Using Doppler radar with a simple explicit microphysics model to diagnose problems with ice sublimation depth-scales in forecast models",2010,"10.1002/qj.698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650045146&doi=10.1002%2fqj.698&partnerID=40&md5=d91d2662bfefa0328f2b4ad0fb40cefc","Several previous studies have attempted to assess the sublimation depth-scales of ice particles from clouds into clear air. Upon examining the sublimation depth-scales in the Met Office Unified Model (MetUM), it was found that the MetUM has evaporation depth-scales 2-3 times larger than radar observations. Similar results can be seen in the European Centre for Medium-Range Weather Forecasts (ECMWF), Regional Atmospheric Climate Model (RACMO) and Météo-France models. In this study, we use radar simulation (converting model variables into radar observations) and one-dimensional explicit microphysics numerical modelling to test and diagnose the cause of the deep sublimation depth-scales in the forecast model. The MetUM data and parametrization scheme are used to predict terminal velocity, which can be compared with the observed Doppler velocity. This can then be used to test the hypothesis as to why the sublimation depth-scale is too large within the MetUM. Turbulence could lead to dry air entrainment and higher evaporation rates; particle density may be wrong, particle capacitance may be too high and lead to incorrect evaporation rates or the humidity within the sublimating layer may be incorrectly represented. We show that the most likely cause of deep sublimation zones is an incorrect representation of model humidity in the layer. This is tested further by using a one-dimensional explicit microphysics model, which tests the sensitivity of ice sublimation to key atmospheric variables and is capable of including sonde and radar measurements to simulate real cases. Results suggest that the MetUM grid resolution at ice cloud altitudes is not sufficient enough to maintain the sharp drop in humidity that is observed in the sublimation zone. © 2010 Royal Meteorological Society and Crown Copyright."
"6507149664;","A study of atmospheric processes based on neutron monitor data and Cherenkov counter measurements at high mountain altitude",2010,"10.1016/j.jastp.2010.07.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956616547&doi=10.1016%2fj.jastp.2010.07.021&partnerID=40&md5=946bbe7af8ebecb0e90fd266008c42e6","The cause of the correlation between cloud cover and cosmic ray intensity is still a subject of discussion. The atmospheric transparency is the primary signature of the atmospheric state. The ability to use neutron monitor and Cherenkov telescope data in order to study atmospheric processes is demonstrated. The recently designed lead free neutron monitor at the Basic Environmental Observatory Moussala (42.11N, 23.35E, 2925. m a.s.l.) is described. The possibility to use Cherenkov telescope measurements for estimation of atmospheric transparency is demonstrated on the basis of Monte Carlo simulations and experimental data. The Monte Carlo simulations are carried out with CORSIKA code assuming FLUKA and QGSJET II hadron interaction models. Experimental data from Cherenkov telescope are presented. Several physical mechanisms related to the influence of cosmic rays on the cloud cover, respectively, the atmospheric transparency are widely discussed. © Elsevier Ltd."
"55802246600;7102687667;7202048112;","Light rain events change over North America, Europe, and Asia for 1973-2009",2010,"10.1002/asl.298","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952777549&doi=10.1002%2fasl.298&partnerID=40&md5=e758be191e057138f793059891da992f","Analysis of daily precipitation data reveals diverse long-term trends of light rain events in North America (NA), Europe (EU), and Asia (AS), but overall a decreasing trend is found from 1973-2009, especially over East Asia, where a remarkable shift from light to heavy rain events has been observed. Although it has been argued that global warming may lead to a shift from light to heavy rain, regionally little correspondence is found between light rain trends and temperature/precipitable water (PW) trends. This argues for the need to include other factors such as atmospheric circulation and aerosol changes that affect regional rain rates and cloud processes. Copyright © 2010 Royal Meteorological Society."
"7004364155;8891521600;","Direct aerosol radiative forcing uncertainty based on a radiative perturbation analysis",2010,"10.1175/2010JCLI3543.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958090187&doi=10.1175%2f2010JCLI3543.1&partnerID=40&md5=6e3e17d05aa190a49f64c1ec93e7fd94","To provide a lower bound for the uncertainty inmeasurement-based clear-and all-sky direct aerosol radiative forcing (DARF), a radiative perturbation analysis is performed for the ideal case in which the perturbations in global mean aerosol properties are given by published values of systematic uncertainty in Aerosol Robotic Network (AERONET) aerosol measurements. DARF calculations for base-state climatological cloud and aerosol properties over ocean and land are performed, and then repeated after perturbing individual aerosol optical properties (aerosol optical depth, single-scattering albedo, asymmetry parameter, scale height, and anthropogenic fraction) from their base values, keeping all other parameters fixed. The total DARF uncertainty from all aerosol parameters combined is 0.5-1.0 W m-2, a factor of 2-4 greater than the value cited in the Intergovernmental Panel on Climate Change's (IPCC's) Fourth Assessment Report. Most of the total DARF uncertainty in this analysis is associatedwith single-scattering albedo uncertainty. Owing to the greater sensitivity to single-scattering albedo in cloudy columns, DARF uncertainty in all-sky conditions is greater than in clear-sky conditions, even though the global mean clear-sky DARF is more than twice as large as the all-sky DARF. © 2010 American Meteorological Society."
"35498628900;56122626400;6508150016;35495189300;55575192900;","Assimilation of satellite-derived skin temperature observations into land surface models",2010,"10.1175/2010JHM1262.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78049312763&doi=10.1175%2f2010JHM1262.1&partnerID=40&md5=75dc8f17ba8ab9851595def49425abd7","Land surface (or ""skin"") temperature (LST) lies at the heart of the surface energy balance and is a key variable in weather and climate models. In this research LST retrievals from the International Satellite Cloud Climatology Project (ISCCP) are assimilated into the Noah land surface model and Catchment land surface model (CLSM) using an ensemble-based, offline land data assimilation system. LST is described very differently in the two models. A priori scaling and dynamic bias estimation approaches are applied because satellite and model LSTs typically exhibit different mean values and variabilities. Performance is measured against 27 months of in situ measurements from the Coordinated Energy and Water Cycle Observations Project at 48 stations. LST estimates from Noah and CLSM without data assimilation (""open loop"") are comparable to each other and superior to ISCCP retrievals. For LST, the RMSE values are 4.9 K (CLSM), 5.5 K(Noah), and 7.6 K(ISCCP), and the anomaly correlation coefficients (R) are 0.61 (CLSM), 0.63 (Noah), and 0.52 (ISCCP). Assimilation of ISCCP retrievals provides modest yet statistically significant improvements (over an open loop, as indicated by nonoverlapping 95% confidence intervals) of up to 0.7 K in RMSE and 0.05 in the anomalyR. The skill of the latent and sensible heat flux estimates from the assimilation integrations is essentially identical to the corresponding open loop skill. Noah assimilation estimates of ground heat flux, however, can be significantly worse than open loop estimates. Provided the assimilation system is properly adapted to each land model, the benefits from the assimilation of LST retrievals are comparable for both models. © 2010 American Meteorological Society."
"16834247400;7102271172;56131406800;","Similarity Weighted Instance-based Learning for the Generation of Transition Potentials in Land Use Change Modeling",2010,"10.1111/j.1467-9671.2010.01226.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649514497&doi=10.1111%2fj.1467-9671.2010.01226.x&partnerID=40&md5=38cc9f34f5c658bab94664a39109aeb3","Land use change models are increasingly being used to evaluate the effect of land change on climate and biodiversity and to generate scenarios of deforestation. Although many methods are available to model land transition potentials, they are usually not user-friendly and require the specification of many parameters, making the task difficult for decision makers not familiar with the tools, as well as making the process difficult to interpret. In this article we propose a simple method for modeling transition potentials. SimWeight is an instance-based learning algorithm based on the logic of the K-Nearest Neighbor algorithm. The method identifies the relevance of each driver variable and predicts the transition potential of locations given known instances of change. A case study was used to demonstrate and validate the method. Comparison of results with the Multi-Layer Perceptron neural network (MLP) suggests that SimWeight performs similarly in its capacity to predict transition potentials, without the need for complex parameters. Another advantage of SimWeight is that it is amenable to parallelization for deployment on a cloud computing platform. © 2010 Blackwell Publishing Ltd."
"16203386300;7003465317;7006188966;","Tropical land-cover change alters biogeochemical inputs to ecosystems in a Mexican montane landscape",2010,"10.1890/09-1125.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957729914&doi=10.1890%2f09-1125.1&partnerID=40&md5=d2130b2775fd468583f11834973c3e1d","In tropical regions, the effects of land-cover change on nutrient and pollutant inputs to ecosystems remain poorly documented and may be pronounced, especially in montane areas exposed to elevated atmospheric deposition. We examined atmospheric deposition and canopy interactions of sulfate-sulfur (SO42--S), chloride (Cl-), and nitrate-nitrogen (NO3--N) in three extensive tropical montane land-cover types: clearings, forest, and coffee agroforest. Bulk and fog deposition to clearings was measured as well as throughfall (water that falls through plant canopies) ion fluxes in seven forest and five coffee sites. Sampling was conducted from 2005 to 2008 across two regions in the Sierra Madre Oriental, Veracruz, Mexico. Annual throughfall fluxes to forest and coffee sites ranged over 6-27 kg SO42--S/ha, 12-69 kg Cl-/ha, and 2-6 kg NO3--N/ha. Sulfate-S in forest and coffee throughfall was higher or similar to bulk S deposition measured in clearings. Throughfall Cl- inputs, however, were consistently higher than Cl- amounts deposited to cleared areas, with net Cl- fluxes enhanced in evergreen coffee relative to semi-deciduous forest plots. Compared to bulk nitrate-N deposition, forest and coffee canopies retained 1-4 kg NO3--N/ha annually, reducing NO3 --N inputs to soils. Overall, throughfall fluxes were similar to values reported for Neotropical sites influenced by anthropogenic emissions, while bulk S and N deposition were nine-and eightfold greater, respectively, than background wet deposition rates for remote tropical areas. Our results demonstrate that land-cover type significantly alters the magnitude and spatial distribution of atmospheric inputs to tropical ecosystems, primarily through canopy-induced changes in fog and dry deposition. However, we found that land cover interacts with topography and climate in significant ways to produce spatially heterogeneous patterns of anion fluxes, and that these factors can converge to create deposition hotspots. For land managers, this finding suggests that there is potential to identify species and ecosystems at risk of excess and increasing deposition in montane watersheds undergoing rapid transformation. Our data further indicate that montane ecosystems are vulnerable to air pollution impacts in this and similar tropical regions downwind of urban, industrial, and agricultural emission sources. © 2010 by the Ecological Society of America."
"57204257582;55463878800;35547795500;7101860955;7006906138;7402661940;35120595000;55455737600;7004123903;7003353475;","Hydrology and water quality of the headwaters of the River Severn: Stream acidity recovery and interactions with plantation forestry under an improving pollution climate",2010,"10.1016/j.scitotenv.2010.07.047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956058345&doi=10.1016%2fj.scitotenv.2010.07.047&partnerID=40&md5=f181345c699046e07cea44e028c64f0a","This paper presents new information on the hydrology and water quality of the eroding peatland headwaters of the River Severn in mid-Wales and links it to the impact of plantation conifer forestry further down the catchment.The Upper Hafren is dominated by low-growing peatland vegetation, with an average annual precipitation of around 2650. mm with around 250. mm evaporation. With low catchment permeability, stream response to rainfall is ""flashy"" with the rising limb to peak stormflow typically under an hour. The water quality is characteristically ""dilute""; stormflow is acidic and enriched in aluminium and iron from the acid organic soil inputs. Baseflow is circum-neutral and calcium and bicarbonate bearing due to the inputs of groundwater enriched from weathering of the underlying rocks. Annual cycling is observed for the nutrients reflecting uptake and decomposition processes linked to the vegetation and for arsenic implying seasonal water-logging within the peat soils and underlying glacial drift. Over the decadal scale, sulphate and nitrate concentrations have declined while Gran alkalinity, dissolved organic carbon and iron have increased, indicating a reduction in stream acidification.Within the forested areas the water quality is slightly more concentrated and acidic, transgressing the boundary for acid neutralisation capacity as a threshold for biological damage. Annual sulphate and aluminium concentrations are double those observed in the Upper Hafren, reflecting the influence of forestry and the greater ability of trees to scavenge pollutant inputs from gaseous and mist/cloud-water sources compared to short vegetation. Acidification is decreasing more rapidly in the forest compared to the eroding peatland possibly due to the progressive harvesting of the mature forest reducing the scavenging of acidifying inputs. For the Lower Hafren, long-term average annual precipitation is slightly lower, with lower average altitude, at around 2520. mm and evaporation is around double that of the Upper Hafren. © 2010 Elsevier B.V."
"6701713329;7201524440;55977051700;6603196961;6604066497;6602668989;","The earthshine telescope project",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957075229&partnerID=40&md5=dc70b05d07dd6b5d9577bcec996b63a0","The Earthshine telescope project is a collaborative effort between Lund Observatory (LO) in Sweden and the Danish Meteorological Institute (DMI) with the purpose of constructing one or more robotic telescopes to record the albedo of the Earth over a long time. The objective is to measure long-term development of the global cloud cover and reflectivity for climate modeling. A 1% change in the Earth's albedo results in an average temperature change of 0.5 K which calls for high precision in the albedo measurements. This poses strict demands on the telescope design, in particular with respect to suppression of straylight. The paper describes our proposed optical and mechanical design of the Earthshine telescope, and presents a preliminary straylight analysis of the design as well as first steps towards an 'error budget' for the system. Polarisation due to light-path folding could be an issue for the design being studied."
"14060093900;7501496581;7202021201;8850306700;7102906031;57205567497;36087509700;57212346416;36446122900;57204781628;55686307900;55739545700;11240493100;11241508000;","Enhanced production of oceanic dimethylsulfide resulting from co 2-induced grazing activity in a high CO2 world",2010,"10.1021/es102028k","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78549257161&doi=10.1021%2fes102028k&partnerID=40&md5=5617e1988609605e461d5e2af21f0a69","Oceanic dimethylsulfide (DMS) released to the atmosphere affects the Earth's radiation budget through the production and growth of cloud condensation nuclei over the oceans. However, it is not yet known whether this negative climate feedback mechanism will intensify or weaken in oceans characterized by high CO2 levels and warm temperatures. To investigate the effects of two emerging environmental threats (ocean acidification and warming) on marine DMS production, we performed a perturbation experiment in a coastal environment. Two sets of CO2 and temperature conditions (a pCO2 of ∼900 ppmv at ambient temperature conditions, and a pCO2 of ∼900 ppmv at a temperature ∼3 °C warmer than ambient) significantly stimulated the grazing rate and the growth rate of heterotrophic dinoflagellates (ubiquitous marine microzooplankton). The increased grazing rate resulted in considerable DMS production. Our results indicate that increased grazing-induced DMS production may occur in high CO2 oceans in the future. © 2010 American Chemical Society."
"7403490605;57193537889;6602354484;7403204849;7006221812;16833315000;6601974344;6602443410;6602127608;36021733300;6701410575;","Novel method of generation of Ca(HCO3)2 and CaCO 3 aerosols and first determination of hygroscopic and cloud condensation nuclei activation properties",2010,"10.5194/acp-10-8601-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956704511&doi=10.5194%2facp-10-8601-2010&partnerID=40&md5=d37d8eef285537e71bd8d60e163b9ddd","Atmospheric mineral aerosols contain CaCO3 as a reactive component. A novel method to produce CaCO3 aerosol was developed by spraying Ca(HCO3)2 solution, which was generated from a CaCO3 suspension and CO2. By aerosol mass spectrometry the freshly sprayed and dried aerosol was characterized to consist of pure Ca(HCO3)2 which under annealing in a tube furnace transformed into CaCO3. Transmission Electron Microscopy demonstrated that the particles produced were spherical. The method was able to generate aerosol of sufficient concentration and proper size for the study of physiochemical properties and investigations of heterogeneous reactions of mineral aerosol. The dried Ca(HCO3)2 particles were somewhat more hygroscopic than CaCO3 particles. However, during humidification a restructuring took place and ∼2/3 of the Ca(HCO 3)2 was transformed to CaCO3. The mixed Ca(HCO3)2/CaCO3(s) particles were insoluble with a growth factor of 1.03 at 95% (hygroscopicity parameter κ=0.011±0.007) relative humidity. This compares to a corresponding growth factor of 1.01 for CaCO3(s) (κ0.0016± 0.0004). Mass spectrometric composition analysis, restructuring, and insolubility of the mixed particles suggested that solid Ca(HCO3)2(s) was observed. This would be in contrast to the current belief that Ca(HCO 3)2(s) is thermodynamically instable. The CCN activity of Ca(HCO3)2(s) aerosol (κ ≈0.15) is remarkably higher than that of CaCO3 aerosol (κ=0.0019±0.0007) and less than that of Ca(NO3)2. The noticeable but limited solubility of Ca(HCO3)2 of ≈.01 mol/l explains limited hygroscopic growth and good CCN activity. Experiments in the Large Jülich Aerosol Chamber indicated that Ca(HCO3)2(s) could exist for several hours under dry atmospheric conditions. However, it was likely buried in a protective layer of CaCO3(s). We conclude that Ca(HCO3)2 may be formed in the atmosphere in cloud droplets of activated mineral dust by reaction of CaCO3 with CO 2 and H2O. The presence of Ca(HCO3)2 and as a consequence an enhanced CCN activity may alter the influence of mineral aerosol on global climate. © 2010 Author(s)."
"6603327182;6602336407;7005275497;35419152500;9272538400;6603955469;","Reference quality upper-air measurements: Guidance for developing GRUAN data products",2010,"10.5194/amt-3-1217-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960075431&doi=10.5194%2famt-3-1217-2010&partnerID=40&md5=0e33a29d12905b754d0d9e3f3b089e1b","The accurate monitoring of climate change imposes strict requirements upon observing systems, in particular regarding measurement accuracy and long-term stability. Currently available data records of the essential climate variables (temperature-T, geopotential-p, humidity-RH, wind, and cloud properties) in the upper-air generally fail to fulfil such requirements. This raises serious issues about the ability to detect, quantify and understand recent climate changes and their causes. GCOS is currently implementing a Reference Upper-Air Network (GRUAN) in order to fill this major void within the global observing system. As part of the GRUAN implementation plan we provide herein fundamental guidelines for establishing and maintaining reference quality atmospheric observations which are based on principal concepts of metrology, in particular traceability. It is argued that the detailed analysis of the uncertainty budget of a measurement technique is the critical step for achieving this goal. As we will demonstrate with an example, detailed knowledge of the calibration procedures and data processing algorithms are required for determining the uncertainty of each individual data point. Of particular importance is the careful assessment of the uncertainties introduced by correction schemes adjusting for systematic effects. © 2010 Author(s)."
"7003658685;57208464149;7004015298;31267503200;57215223917;55984424900;8084443000;24484158900;6506129917;57050508600;7004399781;","Aerosol mass and black carbon concentrations, a two year record at NCO-P (5079 m, Southern Himalayas)",2010,"10.5194/acp-10-8551-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956512233&doi=10.5194%2facp-10-8551-2010&partnerID=40&md5=31a815694afe4594d416983e896a1dad","Aerosol mass and the absorbing fraction are important variables, needed to constrain the role of atmospheric particles in the Earth radiation budget, both directly and indirectly through CCN activation. In particular, their monitoring in remote areas and mountain sites is essential for determining source regions, elucidating the mechanisms of long range transport of anthropogenic pollutants, and validating regional and global models. Since March 2006, aerosol mass and black carbon concentration have been monitored at the Nepal Climate Observatory-Pyramid, a permanent high-altitude research station located in the Khumbu valley at 5079 m a.s.l. below Mt. Everest. The first two-year averages of PM1 and PM1-10 mass were 1.94 μg mg-3 and 1.88 μg mg-3, with standard deviations of 3.90 μg mg -3 and 4.45 μg mg-3, respectively, while the black carbon concentration average is 160.5 ng m-3, with a standard deviation of 296.1 ng m-3. Both aerosol mass and black carbon show well defined annual cycles, with a maximum during the pre-monsoon season and a minimum during the monsoon. They also display a typical diurnal cycle during all the seasons, with the lowest particle concentration recorded during the night, and a considerable increase during the afternoon, revealing the major role played by thermal winds in influencing the behaviour of atmospheric compounds over the high Himalayas. The aerosol concentration is subject to high variability: in fact, as well as frequent ""background conditions"" (55% of the time) when BC concentrations are mainly below 100 ng m-3, concentrations up to 5 μg mg-3 are reached during some episodes (a few days every year) in the pre-monsoon seasons. The variability of PM and BC is the result of both short-term changes due to thermal wind development in the valley, and long-range transport/synoptic circulation. At NCO-P, higher concentrations of PM1 and BC are mostly associated with regional circulation and westerly air masses from the Middle East, while the strongest contributions of mineral dust arrive from the Middle East and regional circulation, with a special contribution from North Africa and South-West Arabian Peninsula in post-monsoon and winter season. © 2010 Author(s)."
"35758711800;7501627905;","Climate effects of seasonally varying Biomass Burning emitted Carbonaceous Aerosols (BBCA)",2010,"10.5194/acp-10-8373-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956435880&doi=10.5194%2facp-10-8373-2010&partnerID=40&md5=34826781f2c446eda073433112b99eff","The climate impact of the seasonality of Biomass Burning emitted Carbonaceous Aerosols (BBCA) is studied using an aerosol-climate model coupled with a slab ocean model in a set of 60-year long simulations, driven by BBCA emission data with and without seasonal variation, respectively. The model run with seasonally varying emission of BBCA leads to an increase in the external mixture of carbonaceous aerosols as well as in the internal mixture of organic carbon and sulfate but a decrease in the internal mixture of black carbon and sulfate relative to those in the run with constant annual BBCA emissions, as a result of different strengths of source/sink processes. The differences in atmospheric direct radiative forcing (DRF) caused by BBCA seasonality are in phase with the differences in column concentrations of the external mixture of carbonaceous aerosols in space and time. In contrast, the differences in all-sky radiative forcing at the top of the atmosphere and at the earth's surface extend beyond the BBCA source regions due to climate feedback through cloud distribution and precipitation. The seasonality of biomass burning emissions uniquely affects the global distributions of convective clouds and precipitation, indicating that these emissions have an impact on atmospheric circulation. In addition, the climate response to the periodic climate forcing of BBCA is not limited to biomass burning seasons but dynamically extends into non-biomass burning seasons as well. © 2010 Author(s)."
"7402548443;7202174228;56283402900;36829694300;","A closer look at Arctic ozone loss and polar stratospheric clouds",2010,"10.5194/acp-10-8499-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956405539&doi=10.5194%2facp-10-8499-2010&partnerID=40&md5=2ce723fd424d4e2358466ab7364dd172","The empirical relationship found between column-integrated Arctic ozone loss and the potential volume of polar stratospheric clouds inferred from meteorological analyses is recalculated in a self-consistent manner using the ERA Interim reanalyses. The relationship is found to hold at different altitudes as well as in the column. The use of a PSC formation threshold based on temperature dependent cold aerosol formation makes little difference to the original, empirical relationship. Analysis of the photochemistry leading to the ozone loss shows that activation is limited by the photolysis of nitric acid. This step produces nitrogen dioxide which is converted to chlorine nitrate which in turn reacts with hydrogen chloride on any polar stratospheric clouds to form active chlorine. The rate-limiting step is the photolysis of nitric acid: this occurs at the same rate every year and so the interannual variation in the ozone loss is caused by the extent and persistence of the polar stratospheric clouds. In early spring the ozone loss rate increases as the solar insolation increases the photolysis of the chlorine monoxide dimer in the near ultraviolet. However the length of the ozone loss period is determined by the photolysis of nitric acid which also occurs in the near ultraviolet. As a result of these compensating effects, the amount of the ozone loss is principally limited by the extent of original activation rather than its timing. In addition a number of factors, including the vertical changes in pressure and total inorganic chlorine as well as denitrification and renitrification, offset each other. As a result the extent of original activation is the most important factor influencing ozone loss. These results indicate that relatively simple parameterisations of Arctic ozone loss could be developed for use in coupled chemistry climate models. © 2010 Author(s)."
"57207189160;56158622800;35286080700;7402162859;24337553400;57213516894;24476647200;57199033967;","The effects of clouds and aerosols on net ecosystem CO2 exchange over semi-arid Loess Plateau of Northwest China",2010,"10.5194/acp-10-8205-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956312234&doi=10.5194%2facp-10-8205-2010&partnerID=40&md5=6f6cb107c33be98762e6b235cc05b83c","The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) site. Daytime (solar elevation angles of larger than 50°) net ecosystem exchange (NEE) of CO2 obtained during the midgrowing season (July-August) are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD). Results show a significant impact by clouds on the CO2 uptake by the grassland (with smaller LAI values) located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in the canopy are low, with a value of about 434.8 W mĝ̂'2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index (the ratio of global solar radiation received at the Earth surface to the extraterrestrial irradiance at a plane parallel to the Earth surface), and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions, CO2 uptake decreases with cloudiness but light use efficiency is enhanced, due to increased diffuse fraction of PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a slightly negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure. © 2010 Author(s)."
"35767679900;6602205640;7004035832;7404016992;6602529747;55896917400;35767339900;55857096100;35767749800;","Ecosystem Carbon Storage Across the Grassland-Forest Transition in the High Andes of Manu National Park, Peru",2010,"10.1007/s10021-010-9376-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957754746&doi=10.1007%2fs10021-010-9376-8&partnerID=40&md5=e2ad42c52d8edeef515ed67b8b953670","Improved management of carbon storage by terrestrial biomes has significant value for mitigating climate change. The carbon value of such management has the potential to provide additional income to rural communities and provide biodiversity and climate adaptation co-benefits. Here, we quantify the carbon stores in a 49,300-ha landscape centered on the cloud forest-grassland transition of the high Andes in Manu National Park, Peru. Aboveground carbon densities were measured across the landscape by field sampling of 70 sites above and below the treeline. The forest near the treeline contained 63.4 ± 5.2 Mg C ha-1 aboveground, with an additional 13.9 ± 2.8 Mg C ha-1 estimated to be stored in the coarse roots, using a root to shoot ratio of 0.26. Puna grasslands near the treeline were found to store 7.5 ± 0.7 Mg C ha-1 in aboveground biomass. Comparing our result to soil data gathered by Zimmermann and others (Ecosystems 13:62-74, 2010), we found the ratio of belowground:aboveground carbon decreased from 15.8 on the puna to 8.6 in the transition zone and 2.1 in the forest. No significant relationships were found between carbon densities and slope, altitude or fire disturbance history, though grazing (for puna) was found to reduce aboveground carbon densities significantly. We scaled our study sites to the study region with remote sensing observations from Landsat. The carbon sequestration potential of improved grazing management and assisted upslope treeline migration was also estimated. Afforestation of puna at the treeline could generate revenues of US $1,374 per ha over the project lifetime via commercialization of the carbon credits from gains in aboveground carbon stocks. Uncertainties in the fate of the large soil carbon stocks under an afforestation scenario exist. © 2010 Springer Science+Business Media, LLC."
"55718911800;7202842863;7004938676;","Haze types in Beijing and the influence of agricultural biomass burning",2010,"10.5194/acp-10-8119-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956248669&doi=10.5194%2facp-10-8119-2010&partnerID=40&md5=ebe77881cf62eeb0607a0de3f9822cc6","Emissions from agricultural biomass burning (ABB) in northern China have a significant impact on the regional and global climate. The monthly average aerosol optical depth (AOD) at 550 nm in northern China in 2007 had a maximum of 0.7 in June. The AOD measurements are consistent with regional brown hazes that occurred at that time, which was a period of severe aerosol pollution. Aerosol particles were collected in urban Beijing from 12 to 30 June 2007, during a period of high haze, and studied using transmission electron microscopy with energy-dispersive X-ray spectrometry. The dominant particle types collected in the fine fraction (diameter <1 μm) were ammonium sulfate, soot, K2SO4, KNO3, and organic matter, except that the K salts were minor between 21 and 30 June. K-rich particles as tracers of biomass burning, together with wildfire maps, show that intense regional ABB in northern China contributed significantly to the regional haze between 12 and 20 June. We therefore grouped the episodes into type-1 and -2 haze, with the former occurring between 12 and 20 June and the latter between 21 and 30 June. After long-range transport, ABB particles in the type-1 haze exhibited marked changes in morphology, composition, and mixing state. KCl particles were absent, presumably having been converted by heterogeneous reactions to K2SO4 and KNO3. Soot particles were mixed with the other particle types. Abundant organic matter and soluble salts emitted by ABB increased their sizes during transport and resulted in more hygroscopic aerosol particles in downwind areas, becoming additional cloud condensation nuclei. The high AOD (average value 2.2) in Beijing during 12 to 20 June is partly explained by the hygroscopic growth of fine aerosol particles and by the strong absorption of internally mixed soot particles, both coming from regional ABB emissions. Therefore, it is important to consider the origins of the haze, which in turn leads to the different particle types. © Author(s) 2010."
"35195849700;14034301300;7006434689;6602496366;25647910500;7005069415;","Measured and modelled cloud condensation nuclei number concentration at the high alpine site Jungfraujoch",2010,"10.5194/acp-10-7891-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956085777&doi=10.5194%2facp-10-7891-2010&partnerID=40&md5=afba7708b78f3e68bd8326474cd9dc0f","Atmospheric aerosol particles are able to act as cloud condensation nuclei (CCN) and are therefore important for the climate and the hydrological cycle, but their properties are not fully understood. Total CCN number concentrations at 10 different supersaturations in the range of SS Combining double low line0.12-1.18% were measured in May 2008 at the remote high alpine research station, Jungfraujoch, Switzerland (3580 m a.s.l.). In this paper, we present a closure study between measured and predicted CCN number concentrations. CCN predictions were done using dry number size distribution (scanning particle mobility sizer, SMPS) and bulk chemical composition data (aerosol mass spectrometer, AMS, and multi-angle absorption photometer, MAAP) in a simplified Köhler theory. The predicted and the measured CCN number concentrations agree very well and are highly correlated. A sensitivity study showed that the temporal variability of the chemical composition at the Jungfraujoch can be neglected for a reliable CCN prediction, whereas it is important to know the mean chemical composition. The exact bias introduced by using a too low or too high hygroscopicity parameter for CCN prediction was further quantified and shown to be substantial for the lowest supersaturation. Despite the high average organic mass fraction (∼45%) in the fine mode, there was no indication that the surface tension was substantially reduced at the point of CCN activation. A comparison between hygroscopicity tandem differential mobility analyzer (HTDMA), AMS/MAAP, and CCN derived κ values showed that HTDMA measurements can be used to determine particle hygroscopicity required for CCN predictions if no suitable chemical composition data are available. © Author(s) 2010."
"56370907100;8336962200;24480463300;16028301700;36070429000;23967608200;7004296083;7004056699;7004172687;8663601100;6602607937;55941661200;24345184500;7101830914;7102692123;25824487500;7006510157;57194237061;7006960661;36070497100;8093260300;16479877100;7006058570;7006708207;10739566100;6701820813;57214957433;7005287667;36070780200;55984424900;7005601996;7004047498;25631390600;7006595513;35770358000;8084443000;7004015298;14034301300;7801565183;7006434689;26029015900;7006712143;9276570300;6603729297;8871497700;26643041500;35461255500;","EUCAARI ion spectrometer measurements at 12 European sites-analysis of new particle formation events",2010,"10.5194/acp-10-7907-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956091619&doi=10.5194%2facp-10-7907-2010&partnerID=40&md5=0ea2679dcc06c240f9839e3f42012ebb","We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range ∼1-42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1-30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale. © Author(s) 2010."
"7003865921;7006577245;7102290666;7101677832;7006307463;6506730508;7005421048;55087038900;7101788438;55047039200;23094149200;56283400100;7202418453;7006247122;35472747700;7201862239;36627616400;7202016984;7004325649;","The Calipso Mission: A Global 3D View of Aerosols and Clouds",2010,"10.1175/2010BAMS3009.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78049321517&doi=10.1175%2f2010BAMS3009.1&partnerID=40&md5=9340aa56d1346bb6ecd0281e286f8454","The energy that drives Earth's climate system comes from the sunlight absorbed by the Earth. Aerosols may either suppress or enhance precipitation, thus affecting the water cycle and latent as well as radiative heating. The cloud environment may also alter aerosol properties through hygroscopic growth in the humid air between clouds or through in-cloud processing of the aerosol. Launched in April 2006, the CALIPSO mission was conceived and developed to provide new insights into aerosols and clouds, their various interactions, and their roles in the climate system. The largest uncertainties in climate forcings have been identified as the aerosol direct and indirect radiative forcings. Passive satellites measure column-averaged aerosol properties. They have limited capabilities to resolve the vertical distribution of aerosols within the atmosphere, yet the effects of aerosol on climate depend critically on this distribution, especially relative to that of clouds."
"36538539800;35273830500;25121514600;","Simulating chemistry-aerosol-cloud-radiation-climate feedbacks over the continental U.S. using the online-coupled Weather Research Forecasting Model with chemistry (WRF/Chem)",2010,"10.1016/j.atmosenv.2010.05.056","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955308388&doi=10.1016%2fj.atmosenv.2010.05.056&partnerID=40&md5=e92b185b62a332827ba13a3c3794a7f7","The chemistry-aerosol-cloud-radiation-climate feedbacks are simulated using WRF/Chem over the continental U.S. in January and July 2001. Aerosols can reduce incoming solar radiation by up to -9% in January and -16% in July and 2-m temperatures by up to 0.16 °C in January and 0.37 °C in July over most of the continental U.S. The NO2 photolysis rates decrease in July by up to -8% over the central and eastern U.S. where aerosol concentrations are high but increase by up to 7% over the western U.S. in July and up to 13% over the entire domain in January. Planetary boundary layer (PBL) height reduces by up to -23% in January and -24% in July. Temperatures and wind speeds in July in big cities such as Atlanta and New York City reduce at/near surface but increase at higher altitudes. The changes in PBL height, temperatures, and wind speed indicate a more stable atmospheric stability of the PBL and further exacerbate air pollution over areas where air pollution is already severe. Aerosols can increase cloud optical depths in big cities in July, and can lead to 500-5000 cm-3 cloud condensation nuclei (CCN) at a supersaturation of 1% over most land areas and 10-500 cm-3 CCN over ocean in both months with higher values over most areas in July than in January, particularly in the eastern U.S. The total column cloud droplet number concentrations are up to 4.9 × 106 cm-2 in January and up to 11.8 × 106 cm-2 in July, with higher values over regions with high CCN concentrations and sufficient cloud coverage. Aerosols can reduce daily precipitation by up to 1.1 mm day-1 in January and 19.4 mm day-1 in July thus the wet removal rates over most of the land areas due to the formation of small CCNs, but they can increase precipitation over regions with the formation of large/giant CCN. These results indicate potential importance of the aerosol feedbacks and an urgent need for their accurate representations in current atmospheric models to reduce uncertainties associated with climate change predictions. © 2010 Elsevier Ltd."
"6506416572;6701754792;23017945100;7006577245;6507679962;6506846397;7003406400;7410084319;8206969400;6602137606;7006146719;7102128820;7007114756;7102410621;6507128092;","Using continuous ground-based radar and lidar measurements for evaluating the representation of clouds in four operational models",2010,"10.1175/2010JAMC2333.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957739358&doi=10.1175%2f2010JAMC2333.1&partnerID=40&md5=85dc46f3e35d106e670a03e4cad1a5ed","The ability of four operational weather forecast models [ECMWF, Action de Recherche Petite Echelle Grande Echelle model (ARPEGE), Regional Atmospheric Climate Model (RACMO), and Met Office] to generate a cloud at the right location and time (the cloud frequency of occurrence) is assessed in the present paper using a two-year time series of observations collected by profiling ground-based active remote sensors (cloud radar and lidar) located at three different sites in western Europe (Cabauw, Netherlands; Chilbolton, United Kingdom; and Palaiseau, France). Particular attention is given to potential biases that may arise from instrumentation differences (especially sensitivity) from one site to another and intermittent sampling. In a second step the statistical properties of the cloud variables involved in most advanced cloud schemes of numerical weather forecast models (ice water content and cloud fraction) are characterized and compared with their counterparts in the models. The two years of observations are first considered as a whole in order to evaluate the accuracy of the statistical representation of the cloud variables in each model. It is shown that all models tend to produce too many high-level clouds, with too-high cloud fraction and ice water content. The midlevel and low-level cloud occurrence is also generally overestimated, with too-low cloud fraction but a correct ice water content. The dataset is then divided into seasons to evaluate the potential of the models to generate different cloud situations in response to different large-scale forcings. Strong variations in cloud occurrence are found in the observations from one season to the same season the following year as well as in the seasonal cycle. Overall, the model biases observed using the whole dataset are still found at seasonal scale, but the models generally manage to well reproduce the observed seasonal variations in cloud occurrence. Overall, models do not generate the same cloud fraction distributions and these distributions do not agree with the observations. Another general conclusion is that the use of continuous ground-based radar and lidar observations is definitely a powerful tool for evaluating model cloud schemes and for a responsive assessment of the benefit achieved by changing or tuning a model cloud parameterization. © 2010 American Meteorological Society."
"57197432263;6504005508;6602519468;57206309503;6602172528;8925505000;","Correlations between deep convection and lightning activity on a global scale",2010,"10.1016/j.jastp.2010.07.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955660598&doi=10.1016%2fj.jastp.2010.07.019&partnerID=40&md5=c6669b05264802c7fa74b356de0c0329","Satellite observations of cloud top temperature and lightning flash distribution are used to examine the relationship between deep convection and lightning activity over the tropical regions of the northern and southern hemispheres. In agreement with previous work, the analysis of the results shows that, in the summer of both hemispheres, the lightning activity in continental deep convective storms is more intense than that in marine deep convective storms by a factor of between 7 and 10. Furthermore, it was observed that on average the daily lightning rate per 1°×1° grid cell for the southern hemisphere (SH) is about 20% greater than that of the northern hemisphere (NH), which can be attributed to a larger fractional cover by deep convective clouds in the SH. By using a set of independent indicators, it is shown that deep convection and lightning activity over land are well correlated (with correlation coefficients of 0.8 and 0.6 for NH and SH, respectively). This suggests the capacity for observations to act as a possible method of monitoring continental deep convective clouds, which play a key role in regulating the Earth's climate. Since lightning can be monitored easily from ground networks and satellites, it could be a useful tool for validating the performance of model convective schemes and for monitoring changes in climate parameters. © 2010 Elsevier Ltd."
"7004057920;56082867500;","Longwave indirect effect of mineral dusts on ice clouds",2010,"10.5194/acp-10-7753-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956053144&doi=10.5194%2facp-10-7753-2010&partnerID=40&md5=e11e05be25e8e18d84a187ca0b573769","In addition to microphysical changes in clouds, changes in nucleation processes of ice cloud due to aerosols would result in substantial changes in cloud top temperature as mildly supercooled clouds are glaciated through heterogenous nucleation processes. Measurements from multiple sensors on multiple observing platforms over the Atlantic Ocean show that the cloud effective temperature increases with mineral dust loading with a slope of +3.06 °C per unit aerosol optical depth. The macrophysical changes in ice cloud top distributions as a consequence of mineral dust-cloud interaction exert a strong cooling effect (up to 16 Wmĝ̂'2) of thermal infrared radiation on cloud systems. Induced changes of ice particle size by mineral dusts influence cloud emissivity and play a minor role in modulating the outgoing longwave radiation for optically thin ice clouds. Such a strong cooling forcing of thermal infrared radiation would have significant impacts on cloud systems and subsequently on climate. © 2010 Author(s)."
"7402647384;6603910424;","Effect of sporadic e clouds on GPS radio occultation signals",2010,"10.1029/2010GL044561","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957694477&doi=10.1029%2f2010GL044561&partnerID=40&md5=edfd9f1a6b8008444e5d00a3f1136131","In this study the effects of sporadic E (Es) clouds on GPS radio occultation (RO) signals are investigated by modeling wave propagation and analyzing observational GPS RO data. It has been shown that when the Es clouds are aligned with the propagation direction, they cause defocusing of the GPS RO signal, accompanied by scintillation above and below the defocusing region (due to the interference of direct and refracted radio waves). These effects result in specific U-shape structures in the amplitude of the GPS RO signals. When Es clouds are tilted with respect to the propagation direction, the effects reduce and disappear with the increase of the tilt angle. The U-shape structures are clearly identified in the observed GPS RO signals mainly at tangent point (TP) heights 90-120 km, but also at much lower TP heights. The latter indicates that some Es clouds are tilted with respect to the local horizon (this has also been shown in other studies). The distributions of the observed U-shape structures in latitude, local time, tilt angle, and vertical thickness of the cloud are evaluated in this study based on one month of COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) RO data in July 2009. © 2010 by the American Geophysical Union."
"7406319763;55678879300;55365584100;","Do global warming targets limit heatwave risk?",2010,"10.1029/2010GL043898","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956436286&doi=10.1029%2f2010GL043898&partnerID=40&md5=6232c5086f4aa491c66970bffbc9e4d3","Climate change mitigation targets are often described in terms of annually averaged global mean temperature increases. However local interpretation of impacts resulting from these targets are required if the public is to have a sound appreciation of their consequences. Some of the largest impacts are likely to arise from changes in extreme events, for example heatwaves and floods. This article estimates future regional heat extreme changes consistent with specific global warming targets, using a new and presently unique ensemble of physically plausible climate simulations. We find that a subset of ensemble members giving globally averaged temperature increases of 2.0 0.5C shows a wide range of changes in regional temperature extremes. For example, changes in extreme single-day hot events range between 2 and 6 C for large parts of Europe, North America and Asia for this target. Plausible variations in the model representation of forest roughness length, vegetation root depth and boundary layer cloud make the largest individual contributions to the spread of changes found in different parts of the world. However, a wide range of processes contribute to the uncertainties in the regional changes, particularly through their direct or indirect influences on the simulation of soil moisture. © 2010 by the American Geophysical Union."
"55234835700;7102567936;6602748142;","Diagnosis of zonal mean relative humidity changes in a warmer climate",2010,"10.1175/2010JCLI3488.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958111211&doi=10.1175%2f2010JCLI3488.1&partnerID=40&md5=d22ef159e7eff6613dac73da9f27cc2d","The zonal mean relative humidity response to a doubling of CO2 in a climate model is examined using a global climate model and an offline tracer transport model. Offline tracer transport model simulations are driven by the output from two configurations of the climate model, one with 1979 concentrations of atmospheric greenhouse gases and one with doubled CO2. A set of last saturation tracers is applied within the tracer transport model to diagnose the dynamics responsible for features in the water vapor field. Two different methods are used to differentiate the effects of circulation and transport shifts from spatially inhomogeneous temperature changes. The first of these uses the tracer transport model and is achieved by decoupling the input temperature and circulation fields; the second uses the reconstruction of humidity from the last saturation tracers and is achieved by decoupling the tracer concentrations from their saturation specific humidities. The responses of the tropical and subtropical relative humidities are found to be largely dependent on circulation and transport changes, particularly a poleward expansion of the Hadley cell, a deepening of the height of convective detrainment, a poleward shift of the extratropical jets, and an increase in the height of the tropopause. The last saturation tracers are used to illustrate the influence of changes in transport pathways within the GCM on the zonal mean relative humidity, particularly in the tropical upper troposphere and subtropical dry zones. Relative humidity changes near the extratropical tropopause and in the lower troposphere are largely dependent on changes in the distribution and gradients of temperature. Increases in relative humidity near the extratropical tropopause in both hemispheres are coincident with increases in the occurrence of local saturation and high cloud cover. © 2010 American Meteorological Society."
"7005251120;36008399500;","A comparison of optical-band based snow extent products during spring over North America",2010,"10.1016/j.rse.2010.03.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954816889&doi=10.1016%2fj.rse.2010.03.015&partnerID=40&md5=fe60ffc1ca41a98f9841ead354113fb7","We compare the performances of two widely used hemispheric scale snow products during April, May, and June over North America. The Interactive Multisensor Snow and Ice Mapping System (IMS), based primarily on optical-band remotely sensed images, is the latest incarnation of a product that dates back to the 1960s and has been used as input to operational weather forecasting models as well as for establishing the historical climatology of snow extent over land surfaces. NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) has been used for numerous applications since it was launched aboard the Terra satellite platform in 1999. The MODIS snow product is based primarily on optical-band reflectances. We include in our analysis only observations that are largely unobstructed by clouds as determined using the MODIS cloud detection algorithm. Then, after removing the influences of terrain and projection errors, we identify regions and land surface types where discrepancies between these two products occur. We also compare IMS and MODIS to the snow reanalysis produced by the Canadian Meteorological Center (CMC).We find that on seasonal time scales, the most pronounced differences between the IMS and MODIS snow products occurs during the ablation season over North America. Our results corroborate earlier studies showing pronounced differences over the northern tundra in June, where MODIS appears to be in agreement with other observations; as well as differences in April and May in the boreal forest, where evidence suggests that both products may be biased (although MODIS biases may be smaller) in comparison with the CMC product (which is based on station observations). The influence of clouds may be a factor even though the analysis includes only clear days. Another possible explanation for these discrepancies involves the impact of numerous small lakes over the North American landscape on the interpretation of satellite retrievals in the visible band, although there are other potential sources of error in both products. For example, comparison to the CMC reanalysis suggests that MODIS may be overestimating snow during the ablation season in the boreal forest. The resolution of these discrepancies may affect our understanding of the seasonal snow cover cycle, the evaluation of and development of parameterization schemes for climate models, and the development of a climate data record for snow cover. © 2010 Elsevier Inc."
"6602098362;","Robust land-ocean contrasts in energy and water cycle feedbacks",2010,"10.1175/2010JCLI3451.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958099032&doi=10.1175%2f2010JCLI3451.1&partnerID=40&md5=028590ce55503f3848c39f54165a5dd5","Building on recent observational evidence showing disproportionate increases in temperature and aridity over land in a warming climate, this study examines simulated land-ocean contrasts in fully coupled projections from the Third Coupled Model Intercomparison Project (CMIP3) archive. In addition to the projection of disproportionate changes in temperature and moisture over land, the analysis reveals contrasts in clouds and radiative fluxes that play a key role in the eventual equilibration of the planetary energy budget in response to forcing. Despite differences in magnitude, the nature of the feedbacks governing the land-ocean contrast are largely robust across models, notwithstanding the large intermodel differences in cloud parameterizations, and suggest the involvement of fundamental constraints. The model responses are consistent with previously proposed ideas maintaining that relative humidity (RH) over land decreases with warming because precipitation and the hydrological cycle are governed primarily by transports of moisture from the oceans, where increases in lower-tropospheric temperature and saturated humidity fail to keep pace with those over land. Here, it is argued additionally that constraints on RH imply systematic changes in the cloud distribution and radiative feedbacks over land, as decreased RH raises the lifting condensation level, even as moist instability increases, and suppresses convective clouds. This effect is shown to be particularly strong at low latitudes where the dynamical influence of competing sources of maritime deep convection may further suppress convection. It is found that as a result of the coincidence between strong warming and a muted net greenhouse feedback associated with decreases in RH and clouds, the mean increase in outgoing longwave radiation (OLR) over land (1.0 W m-2 K-1) in transient simulations at 2200 is almost double that over the ocean (0.6 W m-2 K-1), and a strong negative net top-of-atmosphere (TOA) radiative perturbation emerges as the simulations approach and attain equilibrium. However, over the oceans a positive radiative imbalance persists and the increase in water vapor and other greenhouse gases does not allow a local TOA equilibration to occur. The contrast results in an increase in the transport of energy from ocean to land relative to the twentieth century that is accompanied by lasting increases in both OLR and absorbed shortwave radiation globally. A conceptual model to describe the simulated variability is proposed that involves the following: 1) the differing albedos and lower-tropospheric lapse rates over land and ocean, 2) the nonlinearity of the saturated lapse rate in a warming environment, and 3) the disproportionate response in temperature, moisture, clouds, and radiation over land versus ocean. It is noted that while the land-ocean contrast plays a key role in achieving global radiative equilibrium, it entails disproportionate increases in temperature and aridity over land and therefore is likely to be associated with substantial environmental impacts. © 2010 American Meteorological Society."
"7003880283;7003708056;","A review of our understanding of the aerosol-cloud interaction from the perspective of a bin resolved cloud scale modelling",2010,"10.1016/j.atmosres.2010.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955771077&doi=10.1016%2fj.atmosres.2010.05.008&partnerID=40&md5=a32e1d3b145989dd408518391f655638","This review compiles the main results obtained using a mesoscale cloud model with bin resolved cloud micophysics and aerosol particle scavenging, as developed by our group over the years and applied to the simulation of shallow and deep convective clouds. The main features of the model are reviewed in different dynamical frameworks covering parcel model dynamics, as well as 1.5D, 2D and 3D dynamics. The main findings are summarized to yield a digested presentation which completes the general understanding of cloud-aerosol interaction, as currently available from textbook knowledge. Furthermore, it should provide support for general cloud model development, as it will suggest potentially minor processes that might be neglected with respect to more important ones and can support development of parameterizations for air quality, chemical transport and climate models.Our work has shown that in order to analyse dedicated campaign results, the supersaturation field and the complex dynamics of the specific clouds needs to be reproduced. Only 3D dynamics represents the variation of the supersaturation over the entire cloud, the continuous nucleation and deactivation of hydrometeors, and the dependence upon initial particle size distribution and solubility.However, general statements on certain processes can be obtained also by simpler dynamics. In particular, we found:. Nucleation incorporates about 90% of the initial aerosol particle mass inside the cloud drops. Collision and coalescence redistributes the scavenged aerosol particle mass in such a way that the particle mass follows the main water mass. Small drops are more polluted than larger ones, as pollutant mass mixing ratio decreases with drops size. Collision and coalescence mixes the chemical composition of the generated drops. Their complete evaporation will release processed particles that are mostly larger and more hygroscopic than the initial particles. An interstitial aerosol is left unactivated between the cloud drops which is reduced in number and almost devoid of large particles. Consequently, impaction scavenging can probably be neglected inside clouds. Below clouds, impaction scavenging contributes around 30% to the particle mass reaching the ground by a rainfall event. The exact amount depends on the precise case studied. Nucleation and impaction scavenging directly by the ice phase in mixed phase clouds seems to play a minor role with respect to the particle mass that enters the ice particles via freezing of the liquid phase.The aerosol scavenging efficiency generally follows rather closely the precipitation scavenging value. The nucleation scavenging efficiency is around 90% for the liquid phase clouds and impaction scavenging generally contributed to about 30% of the particle mass in the rain. Clouds are very efficient in pumping up the boundary layer aerosol which essentially determines the cloud properties. For a marine case studied the net pumping depleted about 70% of the aerosol from the section of the boundary layer considered. The larger particles (and thus 70% of the mass vented up) got activated inside the cloud. A weak net import through cloud top and the upwind side was found, as well as a larger net export at the downwind side. The outside cloud subsidence can add to the replenishment of the boundary layer and eventually cause a recycling of the particles into the cloud.The results of the parcel model studies seem to indicate that increasing particulate pollution and decreasing solubility suppresses rain formation. In individual and short time cloud simulations this behaviour was even confirmed in our 3D model studies. However, taking into account entire cloud fields over longer periods of time yields the strong spatial and temporal variability of the results with isolated regions of inverse correlation of the effects. Even though in general initially the expected behaviour was found, after several hours of simulation, the overall precipitation amounts of the more polluted cases caught up. This suggests that a changing pollution will affect the spatial and temporal pattern of precipitation, but will probably not reduce the overall long term precipitation amount which might be entirely governed by the moisture state of the atmosphere. Our results regarding mixed phase precipitation with respect to ""all liquid"" cases seem to confirm this idea, as with increasing modelling time the precipitation mass of both cases also become similar. © 2010 Elsevier B.V."
"7201839229;7501760109;","The Madden-Julian oscillation simulated in the NCEP climate forecast system model: The importance of stratiform heating",2010,"10.1175/2010JCLI2983.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958095645&doi=10.1175%2f2010JCLI2983.1&partnerID=40&md5=c402cb7dabf47fda8430bf81ea757924","This study investigates the capability for simulating the Madden-Julian oscillation (MJO) in a series of atmosphere-ocean coupled and uncoupled simulations using NCEP operational general circulation models. The effect of air-sea coupling on the MJO is examined by comparing long-term simulations from the coupled Climate Forecast System (CFS T62) and the atmospheric Global Forecast System (GFS T62) models. Another coupled simulation with a higher horizontal resolution model (CFS T126) is performed to investigate the impact of model horizontal resolution. Furthermore, to examine the impact on a deep convection scheme, an additional coupled T126 run (CFS T126RAS) is conducted with the relaxed Arakawa-Schubert (RAS) scheme. The most important factors for the proper simulation of the MJO are investigated from these runs. The empirical orthogonal function, lagged regression, and spectral analyses indicated that the interactive air-sea coupling greatly improved the coherence between convection, circulation, and other surface fields on the intraseasonal time scale. A higher horizontal resolution run (CFS T126) did not show significant improvements in the intensity and structure. However, GFS T62, CFS T62, and CFS T126 all yielded the 30-60-day variances that were not statistically distinguishable from the background red noise spectrum. Their eastward propagation was stalled over the Maritime Continent and far western Pacific. In contrast to the model simulations using the simplified Arakawa-Schubert (SAS) cumulus scheme, CFS T126RAS produced statistically significant spectral peaks in the MJO frequency band, and greatly improved the strength of the MJO convection and circulation. Most importantly, the ability of MJO convection signal to penetrate into the Maritime Continent and western Pacific was demonstrated. In this simulation, an early-stage shallow heating and moistening preconditioned the atmosphere for subsequent intense MJO convection and a top-heavy vertical heating profile was formed by stratiform heating in the upper and middle troposphere, working to increase temperature anomalies and hence eddy available potential energy that sustains the MJO. The stratiform heating arose from convective detrainment of moisture to the environment and stratiform anvil clouds. Therefore, the following factors were analyzed to be most important for the proper simulation of the MJO rather than the correct simulations of basic-state precipitation, sea surface temperature, intertropical convergence zone, vertical zonal wind shear, and lower-level zonal winds: 1) an elevated vertical heating structure (by stratiform heating), 2) a moisture-stratiform instability process (a positive feedback process between moisture and convective-stratiform clouds), and 3) the low-level moisture convergence to the east of MJO convection (through the appropriate moisture and convective-stratiform cloud processes-circulation interactions). The improved MJO simulation did improve the global circulation response to the tropical heating and may extend the predictability of weather and climate over Asia and North America. © 2010 American Meteorological Society."
"55999772700;6507693923;6602667252;6506961196;8658853400;7006380976;","A 10-year climatology of warm-season cloud patterns over Europe and the Mediterranean from Meteosat IR observations",2010,"10.1016/j.atmosres.2010.05.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955772950&doi=10.1016%2fj.atmosres.2010.05.014&partnerID=40&md5=564d31e9a662288f8fff9c0ca475cd44","Thermal infrared (IR, 10.5-12.5μm) images from the Meteosat Visible and InfraRed Imager (MVIRI) of cold cloud episodes (cloud top brightness temperature &lt;241. K) are used as a proxy of precipitating clouds to derive a warm-season (May-August) climatology of their coherency, duration, span, and propagation speed over Europe and the Mediterranean. The analysis focuses over the 30°-54° N, 15°W-40°E domain in May-August 1996-2005. Harmonic analysis using discrete Fourier transforms is applied together with a statistical analysis and an investigation of the diurnal cycle. The objective of the study is to make available a set of results on the propagation dynamics of the cloud systems with the aim of assisting numerical modellers in improving summer convection parameterization.The zonal propagation of cold cloud systems is accompanied by a weak meridional component confined to narrow latitude belts. The persistence of cold clouds over the area evidences the role of orography, the Pyrenees, the Alps, the Balkans and Anatolia. A diurnal oscillation is found with a maximum marking the initiation of convection in the lee of the mountains and shifting from about 1400 UTC at 40°E to 1800 UTC at 0°. A moderate eastward propagation of the frequency maximum from all mountain chains across the domain exists and the diurnal maxima are completely suppressed west of 5°W. The mean power spectrum of the cold cloud frequency distribution evidences a period of one day all over Europe disappearing over the ocean (west of 10°W). Other maxima are found in correspondence of 3 to 7day synoptic activity. A median zonal phase speed of 16.1ms-1 is found for all events &gt;1000km and &gt;20h and a full set of results divided by year and recurrence categories is also presented. The maxima of the diurnal signal are in phase with the presence of elevated terrain and with land masses. © 2010 Elsevier B.V."
"7004940109;35857960400;7003375121;6701427386;","Modelling the Northern Hemisphere temperature for solar cycles 24 and 25",2010,"10.1016/j.jastp.2010.05.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955638275&doi=10.1016%2fj.jastp.2010.05.018&partnerID=40&md5=b8a1fa158b35afb2bcb0d5d88dfb4412","It is uncertain whether the solar cycle 24 will have a high or a low sunspot maximum number. In its last revision the Solar Cycle 24 Prediction Panel indicates that the low prediction is the most likely. Also, solar cycle 25 is considered to present an equal or lower activity than cycle 24. In order to assess the possible effect of the solar activity on temperature, in the present work we attempt to model the tendency of the Northern Hemisphere temperature for the years 2009-2029, corresponding to solar cycles 24 and 25, using a thermodynamic climate model. We include as forcings the atmospheric carbon dioxide (CO2) and the solar activity by means of the total solar irradiance, considering that the latter has not only a direct effect on climate, but also an indirect one through the modulation of the low cloud cover. We use two IPCC-2007 CO2 scenarios, one with a high fossil consumption and other with a low use of fossil sources. Also we consider higher and lower solar activity conditions. We found that in all the performed experiments the inclusion of the solar activity produces a noticeable reduction in warming respect to the IPCC-2007 CO2 scenarios. Such reduction goes between ~14% and ~44%. In order to evaluate the efficiency of the TCM, we use the root mean square (RMS) between the observed and model temperatures for the period 1980-2003. We find that the RMS for the experiment using the CO2 as the only forcing is 0.06°C,while for the experiment that includes also the solar activity it is higher, 0.13°C. © 2010 Elsevier Ltd."
"7005064275;7401586132;35267857500;8321510900;7403682675;","Negative feedback in the cold: Ice retreat produces new carbon sinks in Antarctica",2010,"10.1111/j.1365-2486.2009.02071.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955287012&doi=10.1111%2fj.1365-2486.2009.02071.x&partnerID=40&md5=b4148d3db16d6840e8f5daad6eb22af5","Feedbacks on climate change so far identified are predominantly positive, enhancing the rate of change. Loss of sea-ice, increase in desert areas, water vapour increase, loss of tropical rain forest and the restriction of significant areas of marine productivity to higher latitude (thus smaller geographical zones) all lead to an enhancement of the rate of change. The other major feedback identified, changes in cloud radiation, will produce either a positive feedback, if high level clouds are produced, or a negative feedback if low level clouds are produced. Few significant negative feedbacks have been identified, let alone quantified. Here, we show that the loss of ice shelves and retreat of coastal glaciers around the Antarctic Peninsula in the last 50 years has exposed at least 2.4 × 104 km2 of new open water. We estimate that these new areas of open water have allowed new phytoplankton blooms containing a total standing stock of ∼5.0 × 105 tonnes of carbon to be produced. New marine zooplankton and seabed communities have also been produced, which we estimate contain ∼4.1 × 105 tonnes of carbon. This previously unquantified carbon sink acts as a negative feedback to climate change. New annual productivity, as opposed to standing stock, amounts to 3.5 × 106 tonnes yr-1 of carbon, of which 6.9 × 105 tonnes yr-1 deposits to the seabed. By comparison the total aboveground biomasses of lowland American tropical rainforest is 160-435 tonnes ha-1. Around 50% of this is carbon. On this basis the carbon held in new biomass described here is roughly equivalent to 6000-17 000 ha of tropical rainforest. As ice loss increases in polar regions this feedback will become stronger, and eventually, over thousands to hundreds of thousands of years, over 50 Mtonnes of new carbon could be fixed annually in new coastal phytoplankton blooms and over 10 Mtonnes yr-1 locked in biological standing stock around Antarctica. © 2009 Blackwell Publishing Ltd."
"7006253952;35552423300;","The Late Cretaceous environment of the Arctic: A quantitative reassessment based on plant fossils",2010,"10.1016/j.palaeo.2010.02.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953979225&doi=10.1016%2fj.palaeo.2010.02.025&partnerID=40&md5=a8f8dc759b3cebe62605f580b26e4707","Late Cretaceous megafossil floras from the palaeo-Arctic of northeastern Russia and northern Alaska are reviewed in respect of their age, composition, structure and floral dynamics. Palaeofloral correlations and comparisons are made between the two regions. Nine angiosperm-rich, predominantly Cenomanian to Coniacian, floras from the palaeo-Arctic are re-evaluated using Climate Leaf Analysis Multivariate Program (CLAMP) calibrated using a global gridded (0.5°×0.5°) climate data set derived from that used in climate modelling. Additional floras from lower palaeolatitudes were used to derive latitudinal temperature gradients: seven from N. America, five from around 30°N palaeolatitude in Europe and one from Kazakhstan. The Arctic climatic determinations, similar to previous estimates, support the existence of a northern Pacific Ocean cold gyre and a warm Arctic Ocean. At palaeolatitudes greater than 80°N floras are insufficiently diverse in woody dicot taxa to use CLAMP, but using CLAMP-derived latitudinal temperature gradients Arctic Ocean coastal environments at 70Ma and 82°N, and which supported a diverse dinosaur magafauna, are predicted to have experienced a mean annual temperature of 6.3±2.2°C, a warm month mean of 14.5±3.1°C and a cold month mean no colder than -2.0±3.9°C. All uncertainties are 2σ. The new estimates are in good agreement with a wide range of non-palaeobotanical climate proxies and render as an outlier warmer temperature estimates for the Arctic Ocean derived from the TEX86 proxy. Modelling, however, shows that land to ocean temperature gradients could have been steep. The CLAMP estimates also suggest high values for humidity and precipitation consistent with sedimentological indicators and, coupled with warm temperatures, support the existence of a persistent polar cloud cap that helped maintain high terrestrial air temperatures throughout prolonged periods (up to 5months) of winter darkness. © 2010 Elsevier B.V."
"56975691100;7102669677;37030925300;55778084100;7202205546;6603539863;57161403000;7102866323;","A study on the relationship between Atlantic sea surface temperature and Amazonian greenness",2010,"10.1016/j.ecoinf.2010.05.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956819071&doi=10.1016%2fj.ecoinf.2010.05.005&partnerID=40&md5=ed28d40b0e422ecaacdaf7024b0808dd","The growth of tropical rainforest in Amazon is critically vulnerable to the change in rainfall and radiation than in temperature, and that amount of rainfall and cloudiness in the northeast region of South American is strongly affected by the Atlantic sea surface temperature (SST). Results from recent model experiments for future climate projection have indicated a reduction of Amazonian greenness by a weakening of tropical vapor circulation system related with the change in SST. Therefore, the observational investigation of the relations between the Amazon greenness and Atlantic SST is fundamental to understand the response of Amazonian tropical forest to climate change. In this study, the effect of Atlantic SST on the spatial and temporal change of the Normalized Difference Vegetation Index (NDVI) in the Amazonian region is examined by using satellite remote sensing data for the period of 1981-2001. A strong correlation between NDVI and SST is found for certain regions in Amazon during the periods of 1980s and 1990s, respectively. In addition, strong correlations with NDVI lagging behind SST for two months and one year, respectively, are also identified from the interannual December-to-February (rain season) variations during 1981-2001. Despite these findings, the mechanisms behind the identified correlation remain unclear. Further analyses using observed precipitation and radiation data are required to understand the potential changes of Amazonian rainforest in the context of global warming. © 2010 Elsevier B.V."
"27171906700;36538539800;25937584800;55624488227;55501554900;7006461606;25121514600;35975306400;7202839433;","Understanding of regional air pollution over China using CMAQ, part II. Process analysis and sensitivity of ozone and particulate matter to precursor emissions",2010,"10.1016/j.atmosenv.2010.03.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955512288&doi=10.1016%2fj.atmosenv.2010.03.036&partnerID=40&md5=c932b224dd718e057a4f8928b88849a0","Following model evaluation in part I, this part II paper focuses on the process analysis and chemical regime analysis for the formation of ozone (O3) and particulate matter with aerodynamic diameter less than or equal to 10 μm (PM10) in China. The process analysis results show that horizontal transport is the main contributor to the accumulation of O3 in Jan., Apr., and Oct., and gas-phase chemistry and vertical transport contribute to the production and accumulation of O3 in Jul. Removal pathways of O3 include vertical and horizontal transport, gas-phase chemistry, and cloud processes, depending on locations and seasons. PM10 is mainly produced by primary emissions and aerosol processes and removed by horizontal transport. Cloud processes could either decrease or increase PM10 concentrations, depending on locations and seasons. Among all indicators examined, the ratio of PHNO3/PH2O2 provides the most robust indicator for O3 chemistry, indicating a VOC-limited O3 chemistry over most of the eastern China in Jan., NOx-limited in Jul., and either VOC- or NOx-limited in Apr. and Oct. O3 chemistry is NOx-limited in most central and western China and VOC-limited in major cities throughout the year. The adjusted gas ratio, AdjGR, indicates that PM formation in the eastern China is most sensitive to the emissions of SO2 and may be more sensitive to emission reductions in NOx than in NH3. These results are fairly consistent with the responses of O3 and PM2.5 to the reductions of their precursor emissions predicted from sensitivity simulations. A 50% reduction of NOx or AVOC emissions leads to a reduction of O3 over the eastern China. Unlike the reduction of emissions of SO2, NOx, and NH3 that leads to a decrease in PM10, a 50% reduction of AVOC emissions increases PM10 levels. Such results indicate the complexity of O3 and PM chemistry and a need for an integrated, region-specific emission control strategy with seasonal variations to effectively control both O3 and PM2.5 pollution in China. © 2010 Elsevier Ltd."
"7101621283;36856321600;7102450474;","Preliminary study of California wintertime model wet bias",2010,"10.1175/2010MWR3409.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958495882&doi=10.1175%2f2010MWR3409.1&partnerID=40&md5=efae864af08c3be71533b4780addea88","The Weather Research and Forecasting (WRF) model version 3.0.1 is used in both short-range (days) and long-range (years) simulations to explore the California wintertime model wet bias. California is divided into four regions (the coast, central valley, mountains, and Southern California) for validation. Three sets of gridded surface observations are used to evaluate the impact of measurement uncertainty on the model wet bias. Short-range simulations are driven by the North American Regional Reanalysis (NARR) data and designed to test the sensitivity of model physics and grid resolution to the wet bias using eight winter storms chosen from four major types of large-scale conditions: the Pineapple Express, El Niño, La Niña, and synoptic cyclones. Control simulations are conducted with 12-km grid spacing (low resolution) but additional experiments are performed at 2-km (high) resolution to assess the robustness of microphysics and cumulus parameterizations to resolution changes. Additionally, long-range simulations driven by both NARR and general circulation model (GCM) data are performed at low resolution to gauge the impact of the GCM forcing on the model wet bias. These short- and long-range simulations show that low-resolution runs tend to underpredict precipitation in the coast region and overpredict it elsewhere in California. The sensitivity test of WRF physics in short-range simulations indicates that model precipitation depends most strongly on the microphysics scheme, though convective parameterization is also important, particularly near the coast. In contrast, high-resolution (2 km) simulation increases model precipitation in all regions. As a result, it improves the forecast bias in the coast region while it downgrades the model performance in the other regions. It is also found that the choice of validation dataset has a significant impact on the model wet bias of both short- and long-range simulations. However, this impact in long-range simulations appears to be a secondary contribution as compared to its counterpart from the GCM forcing. © 2010 American Meteorological Society."
"23995016900;6701590980;","A numerical study of the evolving convective boundary layer and orographic circulation around the santa catalina mountains in Arizona. Part II: Interaction with deep convection",2010,"10.1175/2010MWR3318.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958456210&doi=10.1175%2f2010MWR3318.1&partnerID=40&md5=512d9c4c4c4cfe05c27f00efcfbd8647","This is the second part of a study that examines the daytime evolution of the thermally forced boundary layer (BL) circulation over a relatively isolated mountain, about 30 km in diameter and 2 km high, and its interaction with locally initiated deep convection by means of numerical simulations validated with data collected in the 2006 Cumulus Photogrammetric, In Situ, and Doppler Observations (CuPIDO) field campaign in southeastern Arizona. Part I examined the BL circulation in cases with, at most, rather shallow orographic cumulus (Cu) convection; the present part addresses deep convection. The results are based on output from version 3 of the Weather Research and Forecasting model run at a horizontal resolution of 1 km. The model output verifies well against CuPIDO observations. In the absence of Cu convection, the thermally forced (solenoidal) circulation is largely contained within the BL over the mountain. Thunderstorm development deepens this BL circulation with inflow over the depth of the BL and outflow in the free troposphere aloft. Primary deep convection results from destabilization over elevated terrain and tends to be triggered along a convergence line, which arises from the solenoidal circulation but may drift downwind of the terrain crest. While the solenoidal anabatic flow converges moisture over the mountain, it also cools the air. Thus, a period of suppressed anabatic flow following a convective episode, at a time when surface heating is still intense, can trigger new and possibly deeper convection. The growth of deep convection may require enhanced convergent flow in the BL, but this is less apparent in the mountain-scale surface flow signal than the decay of orographic convection. A budget study over the mountain suggests that the precipitation efficiency of the afternoon convection is quite low, ~ 10% in this case. © 2010 American Meteorological Society."
"7004159166;7006930059;16833315000;7006960661;25522357400;6602914876;6601943623;","Evaluation of simulated aerosol properties with the aerosol-climate model ECHAM5-HAM using observations from the IMPACT field campaign",2010,"10.5194/acp-10-7709-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955928329&doi=10.5194%2facp-10-7709-2010&partnerID=40&md5=977ed9bed0ce2f533945e1a3bb5bbe05","In May 2008, the measurement campaign IMPACT for observation of atmospheric aerosol and cloud properties was conducted in Cabauw, The Netherlands. With a nudged version of the coupled aerosol-climate model ECHAM5-HAM we simulate the size distribution and chemical composition of the aerosol and the associated aerosol optical thickness (AOT) for the campaign period. Synoptic scale meteorology is represented realistically through nudging of the vorticity, the divergence, the temperature and the surface pressure. Simulated concentrations of aerosol sulfate and organics at the surface are generally within a factor of two from observed values. The monthly averaged AOT from the model is 0.33, about 20% larger than observed. For selected periods of the month with relatively dry and moist conditions discrepancies are approximately ĝ̂'30% and +15%, respectively. Discrepancies during the dry period are partly caused by inaccurate representation of boundary layer (BL) dynamics by the model affecting the simulated AOT. The model simulates too strong exchange between the BL and the free troposphere, resulting in weaker concentration gradients at the BL top than observed for aerosol and humidity, while upward mixing from the surface layers into the BL appears to be underestimated. The results indicate that beside aerosol sulfate and organics also aerosol ammonium and nitrate significantly contribute to aerosol water uptake. The simulated day-to-day variability of AOT follows synoptic scale advection of humidity rather than particle concentration. Even for relatively dry conditions AOT appears to be strongly influenced by the diurnal cycle of RH in the lower boundary layer, further enhanced by uptake and release of nitric acid and ammonia by aerosol water. © Author(s) 2010."
"56249704400;57193132723;","Black carbon semi-direct effects on cloud cover: Review and synthesis",2010,"10.5194/acp-10-7685-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955792628&doi=10.5194%2facp-10-7685-2010&partnerID=40&md5=fce28405abe0dab4439e9adc539119d5","Absorbing aerosols (AAs) such as black carbon (BC) or dust absorb incoming solar radiation, perturb the temperature structure of the atmosphere, and influence cloud cover. Previous studies have described conditions under which AAs either increase or decrease cloud cover. The effect depends on several factors, including the altitude of the AA relative to the cloud and the cloud type. We attempt to categorize the effects into several likely regimes. Cloud cover is decreased if the AAs are embedded in the cloud layer. AAs below cloud may enhance convection and cloud cover. AAs above cloud top stabilize the underlying layer and tend to enhance stratocumulus clouds but may reduce cumulus clouds. AAs can also promote cloud cover in convergent regions as they enhance deep convection and low level convergence as it draws in moisture from ocean to land regions. Most global model studies indicate a regional variation in the cloud response but generally increased cloud cover over oceans and some land regions, with net increased low-level and/or reduced upper level cloud cover. The result is a net negative semi-direct effect feedback from the cloud response to AAs. In some of these climate model studies, the cooling effect of BC due to cloud changes is strong enough to essentially cancel the warming direct effects. © 2010 Author(s)."
"42263280300;55796506900;7402721790;7203001286;56068376200;","Modeling study of aerosol indirect effects on global climate with an AGCM",2010,"10.1007/s00376-010-9120-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955821707&doi=10.1007%2fs00376-010-9120-5&partnerID=40&md5=97397a7a1a334bf3aea022c899437e25","Aerosol indirect effects (AIEs) on global climate were quantitatively investigated by introducing aerosol-cloud interaction parameterizations for water stratus clouds into an AGCM (BCC_AGCM2. 0.1), which was developed by the National Climate Center of the China Meteorological Administration. The study yielded a global annual mean of -1.14 W m-2 for the first indirect radiative forcing (IRF), with an obvious seasonal change. In summer, large forcing mainly occurred in mid to high latitudes of the Northern Hemisphere, whereas in winter, large values were found at 60°S. The second indirect effect led to global annual mean changes in net shortwave flux of -1.03 W m-2 at the top of the atmosphere (TOA), which was relatively significant in mid-latitude regions of both hemispheres. The total AIE reduced the global annual means of net shortwave flux at the TOA and of surface temperature by 1.93 W m-2 and 0. 12 K, respectively. Change in surface temperature induced by the total AIE was clearly larger in the Northern Hemisphere (-0. 23 K) than in the Southern Hemisphere, where changes were negligible. The interhemispheric asymmetry in surface cooling resulted in significant differences in changes of the interhemispheric annual mean precipitation rate, which could lead to a tendency for the ITCZ to broaden. The total AIE decreased the global annual mean precipitation rate by 0.055 mm d-1. © 2010 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"15830929400;7404976222;24468389200;54397987500;22137065500;7402989545;","An introduction to the coupled model FGOALS1.1-s and its performance in East Asia",2010,"10.1007/s00376-010-9177-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955782915&doi=10.1007%2fs00376-010-9177-1&partnerID=40&md5=be590af7803f3e45bcfb12778498f269","The spectral version 1.1 of the Flexible Global Ocean-atmosphere-land System (FGOALS1. 1-s) model was developed in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics at the Institute of Atmospheric Physics (LASG/IAP). This paper reports the major modifications to the physical parameterization package in its atmospheric component, including the radiation scheme, convection scheme, and cloud scheme. Furthermore, the simulation of the East Asian Summer Monsoon (EASM) by FGOALS1. 1-s is examined, both in terms of climatological mean state and interannual variability. The results indicate that FGOALS1. 1-s exhibits significant improvements in the simulation of the balance of energy at the top of the atmosphere: the net radiative energy flux at the top was 0.003 W m-2 in the 40 years fully coupled integration. The distribution of simulated sea surface temperature was also quite reasonable, without obvious climate drift. FGOALS1. 1-s is also capable of capturing the major features of the climatological mean state of the EASM: major rainfall maximum centers, the annual cycle of precipitation, and the lower-level monsoon circulation flow were highly consistent with observations in the EASM region. Regarding interannual variability, simulation of the EASM leading patterns and their relationship with sea surface temperature was examined. The results show that FGOALS1. 1-s can reproduce the first leading pattern of the EASM and its close relationship with the decaying phase of the ENSO. However, the model lacked the ability to capture either the second major mode of the EASMor its relationship with the developing phase of the ENSO. © 2010 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"24463029300;7004469744;35810775100;13606163100;22836898100;24074350700;57203200427;","Low sensitivity of cloud condensation nuclei to changes in the sea-air flux of dimethyl-sulphide",2010,"10.5194/acp-10-7545-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955764965&doi=10.5194%2facp-10-7545-2010&partnerID=40&md5=aa79cd0190f7d304af59a462e23eca11","The emission of dimethyl-sulphide (DMS) gas by phytoplankton and the subsequent formation of aerosol has long been suggested as an important climate regulation mechanism. The key aerosol quantity is the number concentration of cloud condensation nuclei (CCN), but until recently global models did not include the necessary aerosol physics to quantify CCN. Here we use a global aerosol microphysics model to calculate the sensitivity of CCN to changes in DMS emission using multiple present-day and future sea-surface DMS climatologies. Calculated annual fluxes of DMS to the atmosphere for the five model-derived and one observations based present day climatologies are in the range 15.1 to 32.3 Tg a-1 sulphur. The impact of DMS climatology on surface level CCN concentrations was calculated in terms of summer and winter hemispheric mean values of δCCN/δFluxDMS, which varied between g-43 and +166 cm -3/(mg mg-2 dayg-1 sulphur), with a mean of 63 cmg -3/(mg mg-2 day-1 sulphur). The range is due to CCN production in the atmosphere being strongly dependent on the spatial distribution of the emitted DMS. The relative sensitivity of CCN to DMS (i.e. fractional change in CCN divided by fractional change in DMS flux) depends on the abundance of non-DMS derived aerosol in each hemisphere. The relative sensitivity averaged over the five present day DMS climatologies is estimated to be 0.02 in the northern hemisphere (i.e. a 0.02% change in CCN for a 1% change in DMS) and 0.07 in the southern hemisphere where aerosol abundance is lower. In a globally warmed scenario in which the DMS flux increases by ∼1% relative to present day we estimate a ∼0.1% increase in global mean CCN at the surface. The largest CCN response occurs in the Southern Ocean, contributing to a Southern Hemisphere mean annual increase of less than 0.2%. We show that the changes in DMS flux and CCN concentration between the present day and global warming scenario are similar to interannual differences due to variability in windspeed. In summary, although DMS makes a significant contribution to global marine CCN concentrations, the sensitivity of CCN to potential future changes in DMS flux is very low. This finding, together with the predicted small changes in future seawater DMS concentrations, suggests that the role of DMS in climate regulation is very weak. © 2010 Author(s)."
"56032511300;7102604282;","Comparison of a global-climate model to a cloud-system resolving model for the long-term response of thin stratocumulus clouds to preindustrial and present-day aerosol conditions",2010,"10.5194/acp-10-6371-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954944762&doi=10.5194%2facp-10-6371-2010&partnerID=40&md5=f0330cf0fcc8a8a586a426ef7efedb8a","The response of a case of thin, warm marine-boundary-layer (MBL) clouds to preindustrial (PI) and present-day (PD) conditions is simulated by a cloud-system resolving model (CSRM). Here, both the aerosol conditions and environmental conditions match those of a general circulation model (GCM). The environmental conditions are characterized by the initial condition and the large-scale forcings of humidity and temperature, as well as the surface fluxes. The response of the CSRM is compared to that simulated by the GCM. The percentage increase of liquid-water path (LWP) due to a change from the PI to PD conditions is ∼3 times larger in the CSRM than that in the GCM due to the formation of cumulus clouds. The formation of cumulus clouds is controlled by a larger increase in the surface latent-heat (LH) flux in the PD environment than in the PI environment rather than by the change in aerosols. However, the aerosol increase from the PI to PD level determines the LWP response in the stratocumulus clouds, while the impacts of changes in environmental conditions are negligible for stratocumulus clouds. The conversion of cloud liquid to rain through autoconversion and accretion plays a negligible role in the CSRM in the response to aerosols, whereas it plays a role that is as important as condensation in the GCM. Also, it is notable that the explicit simulation of microphysics in the CSRM leads to a smaller LWP in the CSRM than that in the GCM using heavily parameterized microphysics for stratocumulus clouds. The smaller LWP in the CSRM is closer to an observed LWP than the LWP in the GCM for stratocumulus clouds. Supplementary simulations show that increasing aerosols increase the sensitivity of the cloud responses to the PI and PD environmental conditions. They also show that aerosol effects on clouds depend on the cloud type. The LWP of warm cumulus clouds is more sensitive to aerosols than that of stratocumulus clouds. © Author(s) 2010."
"7201606127;7401776640;","Cluster analysis of midlatitude oceanic cloud regimes: Mean properties and temperature sensitivity",2010,"10.5194/acp-10-6435-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955678558&doi=10.5194%2facp-10-6435-2010&partnerID=40&md5=6a60ea515bd0a99134c4137c77a8efd1","Clouds play an important role in the climate system by reducing the amount of shortwave radiation reaching the surface and the amount of longwave radiation escaping to space. Accurate simulation of clouds in computer models remains elusive, however, pointing to a lack of understanding of the connection between large-scale dynamics and cloud properties. This study uses a k-means clustering algorithm to group 21 years of satellite cloud data over midlatitude oceans into seven clusters, and demonstrates that the cloud clusters are associated with distinct large-scale dynamical conditions. Three clusters correspond to low-level cloud regimes with different cloud fraction and cumuliform or stratiform characteristics, but all occur under large-scale descent and a relatively dry free troposphere. Three clusters correspond to vertically extensive cloud regimes with tops in the middle or upper troposphere, and they differ according to the strength of large-scale ascent and enhancement of tropospheric temperature and humidity. The final cluster is associated with a lower troposphere that is dry and an upper troposphere that is moist and experiencing weak ascent and horizontal moist advection. Since the present balance of reflection of shortwave and absorption of longwave radiation by clouds could change as the atmosphere warms from increasing anthropogenic greenhouse gases, we must also better understand how increasing temperature modifies cloud and radiative properties. We therefore undertake an observational analysis of how midlatitude oceanic clouds change with temperature when dynamical processes are held constant (i.e., partial derivative with respect to temperature). For each of the seven cloud regimes, we examine the difference in cloud and radiative properties between warm and cold subsets. To avoid misinterpreting a cloud response to large-scale dynamical forcing as a cloud response to temperature, we require horizontal and vertical temperature advection in the warm and cold subsets to have near-median values in three layers of the troposphere. Across all of the seven clusters, we find that cloud fraction is smaller and cloud optical thickness is mostly larger for the warm subset. Cloud-top pressure is higher for the three low-level cloud regimes and lower for the cirrus regime. The net upwelling radiation flux at the top of the atmosphere is larger for the warm subset in every cluster except cirrus, and larger when averaged over all clusters. This implies that the direct response of midlatitude oceanic clouds to increasing temperature acts as a negative feedback on the climate system. Note that the cloud response to atmospheric dynamical changes produced by global warming, which we do not consider in this study, may differ, and the total cloud feedback may be positive. © Author(s) 2010."
"24332905600;6603001923;7003705113;56154540200;9246517900;55916925700;7003931528;7004637798;","Quantification of DMS aerosol-cloud-climate interactions using the ECHAM5-HAMMOZ model in a current climate scenario",2010,"10.5194/acp-10-7425-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955499377&doi=10.5194%2facp-10-7425-2010&partnerID=40&md5=d34c3170e768cea7a8099d6627c921b0","The contribution of ocean dimethyl sulfide (DMS) emissions to changes in cloud microphysical properties is quantified seasonally and globally for present day climate conditions using an aerosol-chemistry-climate general circulation model, ECHAM5-HAMMOZ, coupled to a cloud microphysics scheme. We evaluate DMS aerosol-cloud-climate linkages over the southern oceans where anthropogenic influence is minimal. The changes in the number of activated particles, cloud droplet number concentration (CDNC), cloud droplet effective radius, cloud cover and the radiative forcing are examined by analyzing two simulations: a baseline simulation with ocean DMS emissions derived from a prescribed climatology and one in which the ocean DMS emissions are switched off. Our simulations show that the model realistically simulates the seasonality in the number of activated particles and CDNC, peaking during Southern Hemisphere (SH) summer coincident with increased phytoplankton blooms and gradually declining with a minimum in SH winter. In comparison to a simulation with no DMS, the CDNC level over the southern oceans is 128% larger in the baseline simulation averaged over the austral summer months. Our results also show an increased number of smaller sized cloud droplets during this period. We estimate a maximum decrease of up to 15-18% in the droplet radius and a mean increase in cloud cover by around 2.5% over the southern oceans during SH summer in the simulation with ocean DMS compared to when the DMS emissions are switched off. The global annual mean top of the atmosphere DMS aerosol all sky radiative forcing is-2.03 W/m2, whereas, over the southern oceans during SH summer, the mean DMS aerosol radiative forcing reaches 9.32 W/m2. © 2010 Author(s)."
"22978151200;7201837768;56249704400;7005809959;6507308842;","A global modeling study on carbonaceous aerosol microphysical characteristics and radiative effects",2010,"10.5194/acp-10-7439-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955483991&doi=10.5194%2facp-10-7439-2010&partnerID=40&md5=b045b73c1e1f051bfb48a566e2542d09","Recently, attention has been drawn towards black carbon aerosols as a short-term climate warming mitigation candidate. However the global and regional impacts of the direct, indirect and semi-direct aerosol effects are highly uncertain, due to the complex nature of aerosol evolution and the way that mixed, aged aerosols interact with clouds and radiation. A detailed aerosol microphysical scheme, MATRIX, embedded within the GISS climate model is used in this study to present a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative effects. Our best estimate for net direct and indirect aerosol radiative flux change between 1750 and 2000 is 0.56 W/m2. However, the direct and indirect aerosol effects are quite sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative flux change can vary between-0.32 to-0.75 W/m2 depending on these carbonaceous particle properties at emission. Taking into account internally mixed black carbon particles let us simulate correct aerosol absorption. Absorption of black carbon aerosols is amplified by sulfate and nitrate coatings and, even more strongly, by organic coatings. Black carbon mitigation scenarios generally showed reduced radiative fluxeswhen sources with a large proportion of black carbon, such as diesel, are reduced; however reducing sources with a larger organic carbon component as well, such as bio-fuels, does not necessarily lead to a reduction in positive radiative flux. © 2010 Author(s)."
"24345630100;","Life cycle of contrails from a time series of geostationary satellite images",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955389033&partnerID=40&md5=a5239333d509da09a8db49e5f88f8561","This work describes the development of a contrail-tracking algorithm (ACTA). The algorithm follows the evolution of contrails from their linear stage until they are undistinguishable from natural cirrus clouds. Therefore, the study of the effect of aircraft-induced clouds In the atmosphere is no longer restricted to linear contrails and can include contrail-cirrus. The ACTA algorithm takes advantage of the high spatial resolution of polar orbiting satellites and the high temporal resolution of geostationary satellites. It allows for the first time to retrieve a very accurate dataset of contrails as they evolve into contrail-cirrus. The dataset generated is then combined with algorithms developed to study the Irradiance using the narrowband radiometer on board a geostationary satellite. The irradiance retrieval algorithms have then been used to develop a method of retrieving the radiative forcing of the contrails and contrailcirrus tracked. in addition to the radiative forcing, measurements of optical thickness, geographical distribution and mean lifetime have also been retrieved. Results are in good agreement with previous works on linear contrails and with case studies on contrail-cirrus. They also highlight the need for considering the effect of surrounding cloudiness when assessing the impact of contrail-cirrus in the climate system."
"35570389600;7201485519;35094424100;35204593500;","Stratospheric water vapour and high climate sensitivity in a version of the HadSM3 climate model",2010,"10.5194/acp-10-7161-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955316011&doi=10.5194%2facp-10-7161-2010&partnerID=40&md5=0e3df6e0bf687b30bd8d720bc94b9a89","It has been shown previously that one member of the Met Office Hadley Centre single-parameter perturbed physics ensemble-the so-called ""low entrainment parameter"" member-has a much higher climate sensitivity than other individual parameter perturbations. Here we show that the concentration of stratospheric water vapour in this member is over three times higher than observations, and, more importantly for climate sensitivity, increases significantly when climate warms. The large surface temperature response of this ensemble member is more consistent with stratospheric humidity change, rather than upper tropospheric clouds as has been previously suggested. The direct relationship between the bias in the control state (elevated stratospheric humidity) and the cause of the high climate sensitivity (a further increase in stratospheric humidity) lends further doubt as to the realism of this particular integration. This, together with other evidence, lowers the likelihood that the climate system's physical sensitivity is significantly higher than the likely upper range quoted in the Intergovernmental Panel on Climate Change's Fourth Assessment Report. © 2010 Author(s)."
"55802246600;8922308700;57193213111;","An investigation of the sub-grid variability of trace gases and aerosols for global climate modeling",2010,"10.5194/acp-10-6917-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955152884&doi=10.5194%2facp-10-6917-2010&partnerID=40&md5=9ffd8d8da8f7b003e2c9c567a86c08ec","One fundamental property and limitation of grid based models is their inability to identify spatial details smaller than the grid cell size. While decades of work have gone into developing sub-grid treatments for clouds and land surface processes in climate models, the quantitative understanding of sub-grid processes and variability for aerosols and their precursors is much poorer. In this study, WRF-Chem is used to simulate the trace gases and aerosols over central Mexico during the 2006 MILAGRO field campaign, with multiple spatial resolutions and emission/terrain scenarios. Our analysis focuses on quantifying the sub-grid variability (SGV) of trace gases and aerosols within a typical global climate model grid cell, i.e. 75&times;75 km2. <br><br> Our results suggest that a simulation with 3-km horizontal grid spacing adequately reproduces the overall transport and mixing of trace gases and aerosols downwind of Mexico City, while 75-km horizontal grid spacing is insufficient to represent local emission and terrain-induced flows along the mountain ridge, subsequently affecting the transport and mixing of plumes from nearby sources. Therefore, the coarse model grid cell average may not correctly represent aerosol properties measured over polluted areas. Probability density functions (PDFs) for trace gases and aerosols show that secondary trace gases and aerosols, such as O3, sulfate, ammonium, and nitrate, are more likely to have a relatively uniform probability distribution (i.e. smaller SGV) over a narrow range of concentration values. Mostly inert and long-lived trace gases and aerosols, such as CO and BC, are more likely to have broad and skewed distributions (i.e. larger SGV) over polluted regions. Over remote areas, all trace gases and aerosols are more uniformly distributed compared to polluted areas. Both CO and O3 SGV vertical profiles are nearly constant within the PBL during daytime, indicating that trace gases are very efficiently transported and mixed vertically by turbulence. But, simulated horizontal variability indicates that trace gases and aerosols are not well mixed horizontally in the PBL. During nighttime the SGV for trace gases is maximum at the surface, and quickly decreases with height. Unlike the trace gases, the SGV of BC and secondary aerosols reaches a maximum at the PBL top during the day. The SGV decreases with distance away from the polluted urban area, has a more rapid decrease for long-lived trace gases and aerosols than for secondary ones, and is greater during daytime than nighttime. <br><br> The SGV of trace gases and aerosols is generally larger than for meteorological quantities. Emissions can account for up to 50% of the SGV over urban areas such as Mexico City during daytime for less-reactive trace gases and aerosols, such as CO and BC. The impact of emission spatial variability on SGV decays with altitude in the PBL and is insignificant in the free troposphere. The emission variability affects SGV more significantly during daytime (rather than nighttime) and over urban (rather than rural or remote) areas. The terrain, through its impact on meteorological fields such as wind and the PBL structure, affects dispersion and transport of trace gases and aerosols and their SGV. © Author(s) 2010."
"23568239000;55917711400;","Relationships between mineral dust and cloud properties in the West African Sahel",2010,"10.5194/acp-10-6901-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955043396&doi=10.5194%2facp-10-6901-2010&partnerID=40&md5=495fdb018ef723368d70353f816db0ae","Aerosol cloud interactions are known to be of great importance to many parts of the climate system. Five years of observations from three different satellites (Aqua, ENVISAT and Meteosat Second Generation) are used to statistically analyse the relationship of mineral dust aerosol, separated from other aerosol species, with monsoon season cloud state in the West African Sahel domain. Additionally, observations of the Tropical Rainfall Measuring Mission are used for discrimination of dry and wet seasons. The aerosol-cloud- interactions are analysed separately by season and air mass in order to minimise spurious correlations with meteorological conditions. The detailed analysis uncovers different counteracting relationships of the mineral dust aerosol with the cloud state, which is also evident from an analysis of the spatial distribution patterns of cloud properties changes with dust activity. The aerosol-cloud relationships found from the analysis of this multiple year dataset are mainly consistent with the hypothesis of a suppression of convective activity, but also indications of lifetime enhancement and thus increased cloud cover and convective intensity are found in some subsets. © 2010 Author(s)."
"57203596463;7006347751;36705143500;","Interactions between mineral dust, climate, and ocean ecosystems",2010,"10.2113/gselements.6.4.247","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650141647&doi=10.2113%2fgselements.6.4.247&partnerID=40&md5=627121e1de92dcd048867806f82a01eb","New, sophisticated instrumentation and improvements in computer models have expanded enormously our understanding of how dust transport impacts climate and biological processes in the oceans. For example, the nutrients and harmful substances contained in dust can affect the development of microalgae in the ocean. The initial composition of dust and its chemical transformations during transport determine the way dust interacts with ocean ecosystems and, more generally, with clouds and the climate as a whole. These new developments open the door for future research initiatives that will require the collaboration of scientists from several disciplines to fully understand the effects of dust in the atmosphere and ocean ecosystems."
"55942789700;56501802200;","Atmospheric brown clouds: From local air pollution to climate change",2010,"10.2113/gselements.6.4.223","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650157385&doi=10.2113%2fgselements.6.4.223&partnerID=40&md5=d93a4c88a9f6c2a4e3f4f630188d40e5","Atmospheric brown clouds are atmospheric accumulations of carbonaceous aerosol particles spanning vast areas of the globe. They have recently gained much attention, from the scientific community and from the general population, as they severely impact several aspects of everyday life. Aside from affecting regional air quality and negatively impacting human health, these clouds affect biogeochemical cycles and profoundly influence the radiation budget of the Earth, resulting in severe climatic and economic consequences. Carbonaceous aerosol particles are generated primarily by combustion processes, including biomass and fossil fuel burning. Natural emissions and transformations of volatile organic species in the atmosphere also contribute to the development of atmospheric brown clouds."
"6701701497;","The stabilising effect of the oceans on climate",2010,"10.1260/0958-305X.21.4.237","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954413862&doi=10.1260%2f0958-305X.21.4.237&partnerID=40&md5=439ccfef32178bf5643d9e4e70fe9799","Based on some simple calculations and a few estimates, it is demonstrated that the oceans have a stabilising effect on the earth's climate. Any additional incoming infrared radiation will be compensated by evaporation of water followed by infrared irradiation from high clouds into space and by heat flow into the deep sea."
"55225734700;35885960400;","Tornadoes and other whirlwinds in the United Kingdom 2009",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650615833&partnerID=40&md5=d122fa7327c09e23b8ec05e49d36fa64","Tornadoes, waterspouts, funnel clouds, and other whirlwinds are summarised for the United Kingdom for 2009, and the data compared with those for the preceding five years. After the very low total in 2008, 2009's figures were not far from the long-term average (but still lower than in any of the four years preceding 2008). © THE INTERNATIONAL JOURNAL OF METEOROLOGY."
"24398842400;7005955015;55667257200;15050523700;","A classical-theory-based parameterization of heterogeneous ice nucleation by mineral dust, soot, and biological particles in a global climate model",2010,"10.1175/2010JAS3425.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957594879&doi=10.1175%2f2010JAS3425.1&partnerID=40&md5=afe1eeaf6a00d3b96acca6c67c153c99","An ice nucleation parameterization based on classical nucleation theory, with aerosol-specific parameters derived from experiments, has been implemented into a global climate model-the Community Atmosphere Model (CAM)-Oslo. The parameterization treats immersion, contact, and deposition nucleation by mineral dust, soot, bacteria, fungal spores, and pollen in mixed-phase clouds at temperatures between 0° and -38°C. Immersion freezing is considered for insoluble particles that are activated to cloud droplets, and deposition and contact nucleation are only allowed for uncoated, unactivated aerosols. Immersion freezing by mineral dust is found to be the dominant ice formation process, followed by immersion and contact freezing by soot. The simulated biological aerosol contribution to global atmospheric ice formation is marginal, even with high estimates of their ice nucleation activity, because the number concentration of ice nucleation active biological particles in the atmosphere is low compared to other ice nucleating aerosols. Because of the dominance of mineral dust, the simulated ice nuclei concentrations at temperatures below -20°C are found to correlate with coarse-mode aerosol particle concentrations. The ice nuclei (IN) concentrations in the model agree well overall with in situ continuous flow diffusion chamber measurements. At individual locations, the model exhibits a stronger temperature dependence on IN concentrations than what is observed. The simulated IN composition (77% mineral dust, 23% soot, and 10-5% biological particles) lies in the range of observed ice nuclei and ice crystal residue compositions. © 2010 American Meteorological Society."
"7402721800;10641308400;36179190000;57201725986;","Roles of large-scale forcing, thermodynamics, and cloud microphysics in tropical precipitation processes",2010,"10.1016/j.atmosres.2010.04.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954176137&doi=10.1016%2fj.atmosres.2010.04.014&partnerID=40&md5=89f3ae21eaab8e897c44976a1f9539d2","Roles of large-scale forcing, thermodynamics, and cloud microphysics in tropical precipitation processes are investigated by analyzing data from a two-dimensional cloud-resolving model simulation. The model is forced by large-scale vertical velocity, zonal wind, horizontal advection, and sea surface temperature observed and derived from TOGA COARE and is integrated from 22 December 1992 to 8 January 1993. The composite analyses of imposed large-scale vertical velocity and water vapor mass flux, and surface rainfall, heat, and cloud microphysical budgets are carried out in eight cases that are categorized by water vapor convergence associated with imposed large-scale vertical velocity and local changes of water vapor and hydrometeor concentration. The analysis of model domain mean surface rainfall budgets shows that the local changes in water vapor and cloud hydrometeor concentration could be as important as the water vapor convergence in producing precipitation. The accurate estimates of these precipitation processes are needed in the climate models to avoid climate biases.The regional analysis shows that the imposed large-scale tropospheric upward motions enhance water vapor convergence and heat divergence and convective rainfall whereas imposed lower-tropospheric downward motions enhance water vapor divergence over stratiform regions and suppress stratiform rainfall. The local atmospheric drying over raining regions is associated with the strengthening of surface rainfall in the cases with mean local atmospheric drying. The local atmospheric moistening is associated with the strengthening of the water vapor convergence over non-raining regions and the convective rainfall is reduced by the weakening of the water vapor convergence over convective regions in the cases with mean local atmospheric moistening. The decrease and increase of mean local hydrometeor concentration are mainly from raining stratiform and convective regions, respectively. The enhancement and reduction of stratiform and convective rainfall are associated with the decrease and increase of local hydrometeor concentration, respectively, in the cases with decrease and increase of mean local hydrometeor concentration. © 2010 Elsevier B.V."
"6508240165;","An analysis of cloud observations from Vernadsky, Antarctica",2010,"10.1002/joc.1998","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956461329&doi=10.1002%2fjoc.1998&partnerID=40&md5=a3f702b5d3f8ceb74cd404d8234a3e49","This paper presents results of a combined analysis of cloud observations made at the Antarctic base Faraday/Vernadsky between 1960 and 2005 and sea ice concentration from the HadISST1 data set. The annual total cloud cover has increased significantly during this period with the strongest and most significant positive trend found in winter, and positive tendencies observable in all seasons. This trend is associated with a decrease in sea ice concentration in the area of the Western Antarctic Peninsula. Though the observed sea ice reduction is actually larger and more significant in summer and autumn, there is actually a significant relation between total cloud cover and sea ice concentration only in winter. The increase in the total cloud cover is neither reflected in the low cloud amount nor in the number of records for low, medium or high level clouds. It is therefore thought that the increase in the total cloud cover is caused by an increase in the amount of medium and/or high level clouds. Instead, records for the low cloud amount show a redistribution from cases of extreme cloud cover (0, 1, 7 and 8 okta), which account for up to 90% of annual records, to cases of moderate cloud cover. In accordance with the decrease in sea ice, this may indicate a shift from low-level stratiform towards convective clouds. © 2009 Royal Meteorological Society."
"8247122100;22975069200;7201507866;18633507200;7005035762;","Surface flux observations on the southeastern tropical pacific ocean and attribution of sst errors in coupled ocean-atmosphere models",2010,"10.1175/2010JCLI3411.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954735779&doi=10.1175%2f2010JCLI3411.1&partnerID=40&md5=5058f458121aebe12fcbdd8e96d584b7","A new dataset synthesizes in situ and remote sensing observations from research ships deployed to the southeastern tropical Pacific stratocumulus region for 7 years in boreal fall. Surface meteorology, turbulent and radiative fluxes, aerosols, cloud properties, and rawinsonde profiles were measured on nine ship transects along 20°S from 75° to 85°W. Fluxes at the ocean surface are essential to the equilibrium SST. Solar radiation is the only warming net heat flux, with 180-200 W m-2 in boreal fall. The strongest cooling is evaporation (60-100 W m-2), followed by net thermal infrared radiation (30 W m22) and sensible heat flux (, 10 W m22). The 70 W m-2 imbalance of heating at the surface reflects the seasonal SST tendency and some 30 W m-2 cooling that is mostly due to ocean transport. Coupled models simulate significant SST errors in the eastern tropical Pacific Ocean. Three different observation-based gridded ocean surface flux products agree with ship and buoy observations, while fluxes simulated by 15 Coupled Model Intercomparison Project phase 3 [CMIP3; used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report] general circulation models have relatively large errors. This suggests the gridded observation-based flux datasets are sufficiently accurate for verifying coupled models. Longwave cooling and solar warming are correlated among model simulations, consistent with cloud radiative forcing and low cloud amount differences. In those simulations with excessive solar heating, elevated SST also results in larger evaporation and longwave cooling to compensate for the solar excess. Excessive turbulent heat fluxes (10-90 W m-2 cooling, mostly evaporation) are the largest errors in simulations once the compensation between solar and longwave radiation is taken into account. In addition to excessive solar warming and evaporation, models simulate too little oceanic residual cooling in the southeastern tropical Pacific Ocean. © 2010 American Meteorological Society."
"7004198777;7004715270;26434854300;26028984000;57188949475;55438848700;7801653576;7005729142;7410041005;7005773698;57196499374;","Relationships of biomass-burning aerosols to ice in orographic wave clouds",2010,"10.1175/2010JAS3310.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958538988&doi=10.1175%2f2010JAS3310.1&partnerID=40&md5=a28d733e94b52b4c6c2fb57a944f0572","Ice concentrations in orographic wave clouds at temperatures between -24 ° and -29 °C were shown to be related to aerosol characteristics in nearby clear air during five research flights over the Rocky Mountains. When clouds with influence from colder temperatures were excluded from the dataset, mean ice nuclei and cloud ice number concentrations were very low, on the order of 1-5 L-1. In this environment, ice number concentrations were found to be significantly correlated with the number concentration of larger particles, those larger than both 0.1- and 0.5-μm diameter. Avariety of complementary techniques was used to measure aerosol size distributions and chemical composition. Strong correlations were also observed between ice concentrations and the number concentrations of soot and biomass-burning aerosols. Ice nuclei concentrations directly measured in biomass-burning plumes were the highest detected during the project. Taken together, this evidence indicates a potential role for biomass-burning aerosols in ice formation, particularly in regions with relatively low concentrations of other ice nucleating aerosols. © 2010 American Meteorological Society."
"13806244300;","Climate sensitivity distributions dependence on the possibility that models share biases",2010,"10.1175/2010JCLI3503.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958109762&doi=10.1175%2f2010JCLI3503.1&partnerID=40&md5=a024aecfac17c2958ad804edca07f2ab","Uncertainty about biases common across models and about unknown and unmodeled feedbacks is important for the tails of temperature change distributions and thus for climate risk assessments. This paper develops a hierarchical Bayes framework that explicitly represents these and other sources of uncertainty. It then uses models' estimates of albedo, carbon cycle, cloud, and water vapor-lapse rate feedbacks to generate posterior probability distributions for feedback strength and equilibrium temperature change. The posterior distributions are especially sensitive to prior beliefs about models' shared structural biases: nonzero probability of shared bias moves some probability mass toward lower values for climate sensitivity even as it thickens the distribution's positive tail. Obtaining additional models of these feedbacks would not constrain the posterior distributions as much as narrowing prior beliefs about shared biases or, potentially, obtaining feedback estimates having biases uncorrelated with those impacting climate models. Carbon dioxide concentrations may need to fall below current levels to maintain only a 10% chance of exceeding official 28C limits on global average temperature change. © 2010 American Meteorological Society."
"7003574176;7004532767;","Solid particulate matter in the atmosphere",2010,"10.2113/gselements.6.4.215","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650078701&doi=10.2113%2fgselements.6.4.215&partnerID=40&md5=a97e45221a1177816c9b646f864c0784","Atmospheric particulates - tiny particles in the air - represent an exciting new research area for mineralogists and geochemists. Emitted directly into or formed within the atmosphere, these particles are generated by both natural processes and human activity. Although derived mostly from sources that are spatially and temporally confined, the particles are ubiquitous globally due to atmospheric circulation. Depending on their physical and chemical properties, these small particles have local- to planetary-scale environmental impacts, influencing the radiative properties of the atmosphere and the cryosphere, the nucleation of both warm and ice clouds, and the nutrient contents of oceans and soils. Because airborne particles can affect human health and transportation, mainly aviation, they have become a focus of government attention and regulation."
"57198285474;","The thermodynamic relationship between surface temperature and water vapour concentration in the troposphere",2010,"10.1260/0958-305X.21.4.263","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954407953&doi=10.1260%2f0958-305X.21.4.263&partnerID=40&md5=3cfdbd814446f3b2b08795106a3ee7c1","The theoretical and empirical thermodynamics discussed in this paper explain the physics behind the observed reduction in relative humidity in the upper troposphere as surface temperature and surface humidity increase. This contradicts the physics embedded in current GCM models commonly used by the climate science community. The key to the physics discussed in this paper is the understanding of the relationship between water vapor condensation and the resulting PV work energy distribution under the influence of a gravitational field. New analyses of empirical, observational radiosonde data are presented which show the relationship between thermal energy and PV work energy resulting from this water vapor condensation process."
"7003821079;","CloudSat studies of stratiform precipitation systems observed in the vicinity of the southern Great Plains atmospheric radiation measurement site",2010,"10.1175/2010JAMC2444.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957742932&doi=10.1175%2f2010JAMC2444.1&partnerID=40&md5=f78cbd4670cd2f58682a0ea2be9213c0","The spaceborne W-band (94 GHz) radar on board the CloudSat polar-orbiting satellite offers new opportunities for retrieving parameters of precipitating cloud systems. CloudSat measurements can resolve the vertical cross sections of such systems. The radar brightband features, which are commonly present when observing stratiform precipitating systems, allow the vertical separation of the ice, mixed, and liquid precipitating hydrometeor layers. In this study, the CloudSat data are used to simultaneously retrieve ice water path (IWP) values for ice layers of precipitating systems using absolute radar reflectivity measurements and mean rainfall rates Rm in the liquid hydrometeor layers using the attenuation-based reflectivity gradient method. The retrievals were performed for precipitating events observed in the vicinity of the Southern Great Plains (SGP) Atmospheric Radiation Measurement Program (ARM) Climate Research Facility. The retrieval results indicated that IWP values in stratiform precipitating systems vary from a few hundreds up to about 10 thousands of grams per meter squared, and the mean rain rates were in a general range between 0.5 and about 12 mmh-1. On average, mean rainfall increases with an increase in ice mass observed above the melting layer; the corresponding mean correlation coefficient is about 0.35, although events with higher correlation as well as those with no appreciable correlation were observed. Horizontal advection, wind shear, and vertical air motions might be some of the reasons for decorrelation between IWP and Rm retrieved for the same vertical atmospheric column. A mean statistical relation between IWP and Rm derived from CloudSat retrievals is in good agreement with the data obtained from multiwavelength ground-based cloud radar measurements at the SGP site. © 2010 American Meteorological Society."
"23027816700;6507615174;6602462824;","Atmospheric and environmental impacts of volcanic particulates",2010,"10.2113/gselements.6.4.235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650094355&doi=10.2113%2fgselements.6.4.235&partnerID=40&md5=d0fed7d4958fffad02d4025135bda440","Volcanic emissions consist of a mixture of gases, aerosol, and silicate particles, which collectively span seven orders of magnitude in size. Airborne ash and sulfate aerosol in the lower atmosphere has shortlived atmospheric and climatic effects. Volcanic aerosol injected high into the stratosphere impacts atmospheric chemical cycles and the solar and terrestrial radiation budgets, and may influence climate over longer timescales than aerosol particles in the lower atmosphere. Once at the surface, the impacts on local environments can be substantial through transport of halogens, trace metals, and metalloids, and subsequent leaching in aqueous solutions. Volcanic emissions may cause disruption to travel and aviation, and may damage surface infrastructure, potentially causing large economic losses."
"6507224579;23099730900;","Dust aerosol important for snowball earth deglaciation",2010,"10.1175/2010JCLI3378.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958113093&doi=10.1175%2f2010JCLI3378.1&partnerID=40&md5=3d39fd9158704d47fd23a0f100ccae72","Most previous global climate model simulations could only produce the termination of Snowball Earth episodes at CO2 partial pressures of several tenths of a bar, which is roughly an order of magnitude higher than recent estimates of CO2 levels during and shortly after Snowball events. These simulations have neglected the impact of dust aerosols on radiative transfer, which is an assumption of potentially grave importance. In this paper it is argued, using the Dust Entrainment and Deposition (DEAD) box model driven by GCM results, that atmospheric dust aerosol concentrations may have been one to two orders of magnitude higher during a Snowball Earth event than today. It is furthermore asserted on the basis of calculations using NCAR's Single Column Atmospheric Model (SCAM)-a radiative-convective model with sophisticated aerosol, cloud, and radiative parameterizations-that when the surface albedo is high, such increases in dust aerosol loading can produce several times more surface warming than an increase in the partial pressure of CO2 from 10-4 to 10-1 bar. Therefore the conclusion is reached that including dust aerosols in simulations may reconcile the CO2 levels required for Snowball termination in climate models with observations. © 2010 American Meteorological Society."
"15724418700;","Residual circulation and tropopause structure",2010,"10.1175/2010JAS3287.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953714837&doi=10.1175%2f2010JAS3287.1&partnerID=40&md5=58a3e86cc5af29854d274cabaa94875a","The effect of large-scale dynamics as represented by the residual mean meridional circulation in the transformed Eulerian sense, in particular its stratospheric part, on lower stratospheric static stability and tropopause structure is studied using a comprehensive chemistry-climate model (CCM), reanalysis data, and simple idealized modeling. Dynamical forcing of static stability as associated with the vertical structure of the residual circulation results in a dominant dipole forcing structure with negative static stability forcing just below the tropopause and positive static stability forcing just above the tropopause. This dipole forcing structure effectively sharpens the tropopause, especially during winter. Furthermore, the strong positive lowermost stratospheric static stability forcing causes a layer of strongly enhanced static stability just above the extratropical tropopause, a tropopause inversion layer (TIL), especially in the winter midlatitudes. The strong positive static stability forcing is shown to be mainly due to the strong vertical gradient of the vertical residual velocity found just above the tropopause in the winter midlatitudes. Stratospheric radiative equilibrium (SRE) solutions are obtained using offline radiative transfer calculations for a given tropospheric climate as simulated by the CCM. The resulting tropopause height in SRE is reduced by several kilometers in the tropics but is increased by 1-2 km in the extratropics, strongly reducing the equator-to-pole contrast in tropopause height. Moreover, the TIL in winter midlatitudes disappears in the SRE solution in contrast to the polar summer TIL, which stays intact. When the SRE solution is modified to include the effect of stratospheric dynamics as represented by the stratospheric residual circulation, the TIL in winter midlatitudes is recovered, suggesting that the static stability forcing associated with the stratospheric residual circulation represents the main cause for the TIL in the winter midlatitudes whereas radiation seems dominant in causing the polar summer TIL. © 2010 American Meteorological Society."
"7402530272;7402093790;7005350376;7202626176;35748657000;57208264711;","Growth and shrinkage of new particles in the atmosphere in Hong Kong",2010,"10.1080/02786826.2010.482576","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954726982&doi=10.1080%2f02786826.2010.482576&partnerID=40&md5=303d71024c75c5b776dc97d2ef6c92cd","Grown nucleated particles &gt;50 nm in diameter are an important source of cloud condensation nuclei (CCN) and when the size is &gt;100 nm, they can also have direct influence on the climate. In this study, the nucleation and growth of new particles in the atmosphere in Hong Kong were investigated during dry season (monthly averaged RH &lt;75%). The maximum size of grown nucleated particles was generally less than 40 nm during new particle burst and growth events. The exception, accounting for ∼20% of all burst and growth events, was those induced by strong photochemical reactions, in which subsequent particle shrinkage occurred. Temporal particle and gas concentration variability and meteorological conditions support the occurrence of particle shrinkage. The shrinkage rate calculated (∼8 nm h-1) was close to the growth rate. The observation of particle shrinkage sheds new light on particle transformation dynamics and it would add to the understanding of particle behavior in the atmosphere. Copyright © American Association for Aerosol Research."
"56012593900;7007018426;27868165400;57197840312;36446796300;","Land surface phenology from MODIS: Characterization of the Collection 5 global land cover dynamics product",2010,"10.1016/j.rse.2010.04.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955333361&doi=10.1016%2fj.rse.2010.04.005&partnerID=40&md5=4d790d5c1f96d3b9ceb4407d48040567","Information related to land surface phenology is important for a variety of applications. For example, phenology is widely used as a diagnostic of ecosystem response to global change. In addition, phenology influences seasonal scale fluxes of water, energy, and carbon between the land surface and atmosphere. Increasingly, the importance of phenology for studies of habitat and biodiversity is also being recognized. While many data sets related to plant phenology have been collected at specific sites or in networks focused on individual plants or plant species, remote sensing provides the only way to observe and monitor phenology over large scales and at regular intervals. The MODIS Global Land Cover Dynamics Product was developed to support investigations that require regional to global scale information related to spatio-temporal dynamics in land surface phenology. Here we describe the Collection 5 version of this product, which represents a substantial refinement relative to the Collection 4 product. This new version provides information related to land surface phenology at higher spatial resolution than Collection 4 (500-m vs. 1-km), and is based on 8-day instead of 16-day input data. The paper presents a brief overview of the algorithm, followed by an assessment of the product. To this end, we present (1) a comparison of results from Collection 5 versus Collection 4 for selected MODIS tiles that span a range of climate and ecological conditions, (2) a characterization of interannual variation in Collections 4 and 5 data for North America from 2001 to 2006, and (3) a comparison of Collection 5 results against ground observations for two forest sites in the northeastern United States. Results show that the Collection 5 product is qualitatively similar to Collection 4. However, Collection 5 has fewer missing values outside of regions with persistent cloud cover and atmospheric aerosols. Interannual variability in Collection 5 is consistent with expected ranges of variance suggesting that the algorithm is reliable and robust, except in the tropics where some systematic differences are observed. Finally, comparisons with ground data suggest that the algorithm is performing well, but that end of season metrics associated with vegetation senescence and dormancy have higher uncertainties than start of season metrics. © 2010 Elsevier Inc."
"7006267742;","Multiple remote sensing techniques as a tool for reconstructing late Quaternary drainage in the Amazon lowland",2010,"10.1002/esp.1996","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955757781&doi=10.1002%2fesp.1996&partnerID=40&md5=d6cb8fdc4cc6361ce47a2fbdaefa0c3e","Morphologies related to paleochannels are widespread through large areas of the Brazilian Amazonia. Despite the relevance for reconstructing the evolution of the largest fluvial system on Earth, detailed mapping of most of these features is still unavailable. The lack of works emphasizing Amazonian paleochannels represents an enormous bias toward the understanding of both migrating dynamics of Amazonian rivers through time and processes (e.g. tectonics, climate, sea-level fluctuation) that might have promoted channel abandonment. A few previous studies have demonstrated the successful application of digital elevation model (DEM) collected during the Shuttle Radar Topography Mission (SRTM) for mapping morphologies related to paleochannels still preserved under forested lowland Amazonian areas. The present study applies different remote sensing techniques, including JERS-1 90m, SAR/SIPAM-6m, Landsat, and ASTER, to successfully unravel a myriad of paleochannels in Marajo Island (Amazon mouth), which were previously undetected using solely SRTM data. The results presented in this work are promising for mapping paleodrainage in other forested areas of the Amazonas basin. Considering the several problems involved on data acquisition aiming to approach the evolution of Amazonian rivers in space and time (e.g. large dimension, lack of natural geological exposures, difficult access, dense forest cover, and high cloud volume), a proper mapping of Amazonas paleodrainage using different remote sensing techniques is crucial to visualize potential paleochannel morphologies and patterns that are of high relevance for reconstructing the Amazonian fluvial dynamics through time. © 2010 John Wiley & Sons, Ltd."
"36344209700;15845667400;","Climatic factors controlling chemical and isotopic characteristics of precipitation in Syria",2010,"10.1002/hyp.7646","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955626450&doi=10.1002%2fhyp.7646&partnerID=40&md5=25e33bf996da04303c8db0087e366a7e","The chemical and isotopic composition of monthly composite rain samples collected at 13 meteoric stations in Syria during two hydrological cycles from 1991 to 1993 have been measured. The chemical analysis of the samples revealed at a number of stations pollution due to industry and sand storms. The temporal and spatial variation of the isotopic composition has been found to be comparable with one of the neighbouring countries such as Jordan and others. The average weighted oxygen-18 and deuterium values are -7·5 and -39·11‰, respectively, and the deuterium excess is 21‰. The individual isotope values can be divided into two groups. One group is represented by winter precipitation and fits closely the Mediterranean Meteorological Water Line (MMWL). Thus, for winter precipitation, condensation of Mediterranean water vapour appears to be the dominating isotope fractionation process. The other group represents spring precipitation and is spread along an evaporation line below the MMWL, thus indicating the influence of sub-cloud evaporation. The d-excess has been found to be lower in the north of Syria (19.9‰ at Tartous, 18.1‰ at Jarablous) than in the south of the country (23.4‰ at Sweida, 24.1‰ at Izra) where Mediterranean air mass dominates. The d-excess of precipitation in neighbouring countries is also close to the average value of the eastern Mediterranean basin of 22‰, e.g. for Jordan the value is 23‰, which signifies that Mediterranean water vapour is, for all these countries, the dominant source of precipitation. The tritium content of precipitation was found to increase with distance from the coast (5.3 TU at coastal station Tartous, 8.8 TU at continental station Palmyra). Low tritium content and high d-excess at coastal stations clearly indicate a Mediterranean air moisture source. Copyright © 2010 John Wiley & Sons, Ltd."
"56032511300;7103271625;7102604282;","Thunderstorm and stratocumulus: How does their contrasting morphology affect their interactions with aerosols?",2010,"10.5194/acp-10-6819-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954894867&doi=10.5194%2facp-10-6819-2010&partnerID=40&md5=308c238669a8021726a2b656354bdf7e","It is well-known that aerosols affect clouds and that the effect of aerosols on clouds is critical for understanding human-induced climate change. Most climate model studies have focused on the effect of aerosols on warm stratiform clouds (e.g., stratocumulus clouds) for the prediction of climate change. However, systems like the Asian and Indian Monsoon, storm tracks, and the intertropical convergence zone, play important roles in the global hydrological cycle and in the circulation of energy and are driven by thunderstorm-type convective clouds. Here, we show that the different morphologies of these two cloud types lead to different aerosol-cloud interactions. Increasing aerosols are known to suppress the conversion of droplets to rain (i.e., so-called autoconversion). This increases droplets as a source of evaporative cooling, leading to an increased intensity of downdrafts. The acceleration of the intensity of downdrafts is larger in convective clouds due to their larger cloud depths (providing longer paths for downdrafts to follow to the surface) than in stratiform clouds. More accelerated downdrafts intensify the gust front, leading to significantly increased updrafts, condensation and thus the collection of cloud liquid by precipitation, which offsets the suppressed autoconversion. This leads to an enhancement of precipitation with increased aerosols in convective clouds. However, the downdrafts are less accelerated in stratiform clouds due to their smaller cloud depths, and they are not able to induce changes in updrafts as large as those in convective clouds. Thus, the offset is not as effective, and this allows the suppression of precipitation with increased aerosols. Thus aerosols affect these cloud systems differently. The dependence of the effect of aerosols on clouds on the morphology of clouds should be taken into account for a more complete assessment of climate change. © Author(s) 2010."
"56158622800;7006783796;57213947466;8833356300;55723070100;56123335600;8280879000;","Dust aerosol effect on semi-arid climate over Northwest China detected from A-Train satellite measurements",2010,"10.5194/acp-10-6863-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954940457&doi=10.5194%2facp-10-6863-2010&partnerID=40&md5=8dd9eefe3dec547bdf7b34948ec3f06f","The impact of dust aerosols on the semi-arid climate of Northwest China is analyzed by comparing aerosol and cloud properties derived over the China semi-arid region (hereafter, CSR) and the United States semi-arid region (hereafter, USR) using several years of surface and A-Train satellite observations during active dust event seasons. These regions have similar climatic conditions, but aerosol concentrations are greater over the CSR. Because the CSR is close to two major dust source regions (Taklamakan and Gobi deserts), the aerosols over the CSR not only contain local anthropogenic aerosols (agricultural dust, black carbon and other anthropogenic aerosols), but also include natural dust transported from the source regions. The aerosol optical depth, averaged over a 3-month period, derived from MODIS for the CSR is 0.27, which is 47% higher than that over the USR (0.19). Although transported natural dust only accounts for 53% of this difference, it is a major contributor to the average absorbing aerosol index, which is 27% higher in the CSR (1.07) than in the USR (0.84). During dust event periods, liquid water cloud particle size, optical depth and liquid water path are smaller by 9%, 30% and 33% compared to dust-free conditions, respectively. © Author(s) 2010."
"7801685271;57207415190;7401945370;","The genesis of tropical cyclone Nargis (2008): Environmental modulation and numerical predictability",2010,"10.2151/jmsj.2010-314","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954928410&doi=10.2151%2fjmsj.2010-314&partnerID=40&md5=3d7c5f71293d12cd7dc1fdab5051f301","Tropical cyclone Nargis, generated over the Bay of Bengal in late April 2008, caused catastrophic destruction after making landfall in Myanmar. Here, the large-scale environment of cyclogenesis was investigated using reanalysis datasets and a cloud-system resolving model. The reanalysis datasets showed that a westerly wind axis over the Bay of Bengal shifted northward from mid-April to early May. This shift is attributed to a seasonal transition of the Asian summer monsoon and a boreal summer intraseasonal oscillation. The timing of this environmental modulation was consistent with the climatologically early tropical cyclogenesis over the Bay of Bengal. This period was also characterized by high genesis potential, which is an empirical index of the environmental field favorable for tropical cyclogenesis. An analysis of genesis potential showed that the genesis of Nargis was associated with reduced vertical shear and increased lower-tropospheric vorticity. A cloud-system-resolving model successfully reproduced the high probability of tropical cyclogenesis during the observed period of cyclogenesis in late April. The model also simulated the large-scale environment including the northward shift of the westerly wind axis, although the precise location of tropical cyclogenesis was sensitive to initial conditions in the model. The anomaly of sea surface temperature in 2008 had little influence on the simulated probability of tropical cyclogenesis. Therefore, a cloud-system-resolving atmospheric model even without ocean feedback is a promising tool for predicting the probability of tropical cyclogenesis over the Bay of Bengal around the onset of the Asian summer monsoon, which is a favorable environment for tropical cyclogenesis. © 2010, Meteorological Society of Japan."
"24343173500;56370907100;8084443000;7403401100;7103337730;35461255500;57189215242;7004015298;8657166100;","New particle formation events measured on board the ATR-42 aircraft during the EUCAARI campaign",2010,"10.5194/acp-10-6721-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954926959&doi=10.5194%2facp-10-6721-2010&partnerID=40&md5=109ccbf9d33d0e12b93a1b062d1ded72","Aerosol properties were studied during an intensive airborne measurement campaign that took place at Rotterdam in Netherlands in May 2008 within the framework of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). The objective of this study is to illustrate seven events of new particle formation (NPF) observed with two Condensation Particle Counters (CPCs) operated on board the ATR-42 research aircraft in airsectors around Rotterdam, and to provide information on the spatial extent of the new particle formation phenomenon based on 1-s resolution measurements of ultra-fine particle (in the size range 3-10 nm diameter, denoted N3-10 hereafter) concentrations. The results show that particle production occurred under the influence of different air mass origins, at different day times and over the North Sea as well as over the continent. The number concentration of freshly nucleated particles (N3-10) varied between 5000 and 100 000 cm -3 within the boundary layer (BL). Furthermore the vertical extension for all nucleation events observed on the ATR-42 never exceeded the upper limit of the BL. The horizontal extent of N3-10 could not be delimited due to inflexible flight plans which could not be modified to accommodate real-time results. However, the NPF events were observed over geographically large areas; typically the horizontal extension was about 100 km and larger. © 2010 Author(s)."
"57085459500;16206263100;16833484300;7003301093;7102235157;35760401500;10142675100;35459699300;7101933764;35430463900;34769585100;7006103811;","Vertical transport rates and concentrations of OH and Cl radicals in the tropical tropopause layer from observations of CO2 and halocarbons: Implications for distributions of long-and short-lived chemical species",2010,"10.5194/acp-10-6669-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954880840&doi=10.5194%2facp-10-6669-2010&partnerID=40&md5=c7c1e75d394a4e886bb1093f58d0733e","Rates for large-scale vertical transport of air in the Tropical Tropopause Layer (TTL) were determined using high-resolution, in situ observations of CO2 concentrations in the tropical upper troposphere and lower stratosphere during the NASA Tropical Composition, Cloud and Climate Coupling (TC4) campaign in August 2007. Upward movement of trace gases in the deep tropics was notably slower in TC4 than during the Costa Rica AURA Validation Experiment (CR-AVE), in January 2006. Transport rates in the TTL were combined with in situ measurements of chlorinated and brominated organic compounds from whole air samples to determine chemical loss rates for reactive chemical species, providing empirical vertical profiles for 24-h mean concentrations of hydroxyl radicals (OH) and chlorine atoms in the TTL. The analysis shows that important short-lived species such as CHCl3, CH2Cl 2, and CH2Br2 have longer chemical lifetimes than the time for transit of the TTL, implying that these species, which are not included in most models, could readily reach the stratosphere and make significant contributions of chlorine and/or bromine to stratospheric loading. © 2010 Author(s)."
"23006459500;53980793000;","Mountain-valley precipitation differences in the northern Alps: An exemplary high-resolution modeling study",2010,"10.1007/s00703-010-0083-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955853853&doi=10.1007%2fs00703-010-0083-y&partnerID=40&md5=a72e8f0ff2a0e180ad5348b5a04be846","This paper investigates the dependence on environmental conditions of altitudinal precipitation differences in the northern Alps, based on high-resolution numerical simulations with the MM5 model for a selected region in the Bavarian Alps (Zugspitze mountain and surrounding valley stations). Three exemplary precipitation events representing climatological regimes with different orographic enhancement characteristics are selected. After validating the MM5 precipitation fields against the available surface observations, the model results are used to analyse the interactions of atmospheric dynamics and cloud microphysics with the local orography. The first two cases (19-22 March 1997, 05-09 February 1999) are characterized by a strong northwesterly or northerly flow, associated with large precipitation differences between the mountain and the surrounding valley stations. For these cases, the model results indicate a dominance of the classical seeder-feeder mechanism, with strong orographic lifting generating dense orographic clouds over each individual mountain ridge, which in turn intensify precipitation. The related surface precipitation maxima can be found near the mountain peaks or somewhat in the lee due to hydrometeor drifting. The third case (05-07 December 1992) represents conditions with relatively small (i.e. below climatological average) precipitation differences between the Zugspitze and the surrounding valley stations. For this event, the model results indicate that relatively weak ambient winds at and below Alpine crest level (700 hPa) were primarily responsible for the lack of substantial precipitation enhancement. Precipitation was nevertheless moderately intense because of strong frontal lifting at higher levels. In all three cases, the agreement between simulated and observed precipitation patterns is so high that there is good reason to expect that mountain-valley precipitation differences will be quantitatively predictable for nonconvective events once a sufficiently high model resolution is computationally affordable. © 2010 Springer-Verlag."
"7003361863;8247122100;7005035762;7403247998;","A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck",2010,"10.5194/acp-10-6527-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954751051&doi=10.5194%2facp-10-6527-2010&partnerID=40&md5=2c7d3aae823a9b513b24865e2f00242e","Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003-2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that Cloud-Sat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP∼h9) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP∼h2) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Zmax&gt;-15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h∼LWP1/2). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20° S, 85°W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20deg; S, 75deg; W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface. © 2010 Author(s)."
"35429035100;7202097052;7006025236;7006599572;7006686129;7202050065;35737484800;16480965400;7410324641;7004643405;56049333200;7202245296;6701455725;7202558218;7003479494;","Bromine measurements in ozone depleted air over the Arctic Ocean",2010,"10.5194/acp-10-6503-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954712945&doi=10.5194%2facp-10-6503-2010&partnerID=40&md5=43bcadabf75067db42616f0a6142b8b5","In situ measurements of ozone, photochemically active bromine compounds, and other trace gases over the Arctic Ocean in April 2008 are used to examine the chemistry and geographical extent of ozone depletion in the arctic marine boundary layer (MBL). Data were obtained from the NOAA WP-3D aircraft during the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) study and the NASA DC-8 aircraft during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) study. Fast (1 s) and sensitive (detection limits at the low pptv level) measurements of BrCl and BrO were obtained from three different chemical ionization mass spectrometer (CIMS) instruments, and soluble bromide was measured with a mist chamber. The CIMS instruments also detected Br2. Subsequent laboratory studies showed that HOBr rapidly converts to Br2 on the Teflon instrument inlets. This detected Br2 is identified as active bromine and represents a lower limit of the sum HOBr + Br2. The measured active bromine is shown to likely be HOBr during daytime flights in the arctic. In the MBL over the Arctic Ocean, soluble bromide and active bromine were consistently elevated and ozone was depleted. Ozone depletion and active bromine enhancement were confined to the MBL that was capped by a temperature inversion at 200-500 m altitude. In ozone-depleted air, BrO rarely exceeded 10 pptv and was always substantially lower than soluble bromide that was as high as 40 pptv. BrCl was rarely enhanced above the 2 pptv detection limit, either in the MBL, over Alaska, or in the arctic free troposphere. © 2010 Author(s)."
"6602600408;7201504886;57208121852;57203053317;","Interpreting the cloud cover-Aerosol optical depth relationship found in satellite data using a general circulation model",2010,"10.5194/acp-10-6129-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954498624&doi=10.5194%2facp-10-6129-2010&partnerID=40&md5=ea7c4546ea6f8af9ebeb4bc0744c9283","Statistical analysis of satellite data shows a positive correlation between aerosol optical depth (AOD) and total cloud cover (TCC). Reasons for this relationship have been disputed in recent literature. The aim of this study is to explore how different processes contribute to one model's analog of the positive correlation between aerosol optical depth and total cloud cover seen in the satellite retrievals. We compare the slope of the linear regression between the logarithm of TCC and the logarithm of AOD, or the strength of the relationship, as derived from three satellite data sets to the ones simulated by a global aerosol-climate model. We analyse model results from two different simulations with and without a parameterisation of aerosol indirect effects, and using dry compared to humidified AOD. Perhaps not surprisingly we find that no single one of the hypotheses discussed in the literature is able to uniquely explain the positive relationship. However the dominant contribution to the model's AOD-TCC relationship can be attributed to aerosol swelling in regions where humidity is high and clouds are coincidentally found. This finding leads us to hypothesise that much of the AOD-TCC relationship seen in the satellite data is also carried by such a process, rather than the direct effects of the aerosols on the cloud fields themselves. © Author(s) 2010."
"6603038761;","A comparison of multi-spectral, multi-angular, and multi-temporal remote sensing datasets for fractional shrub canopy mapping in Arctic Alaska",2010,"10.1016/j.rse.2010.01.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951113128&doi=10.1016%2fj.rse.2010.01.012&partnerID=40&md5=912062f1afd8347a0c0d44beb44c9291","Shrub cover appears to be increasing across many areas of the Arctic tundra biome, and increasing shrub cover in the Arctic has the potential to significantly impact global carbon budgets and the global climate system. For most of the Arctic, however, there is no existing baseline inventory of shrub canopy cover, as existing maps of Arctic vegetation provide little information about the density of shrub cover at a moderate spatial resolution across the region. Remotely-sensed fractional shrub canopy maps can provide this necessary baseline inventory of shrub cover. In this study, we compare the accuracy of fractional shrub canopy (&gt; 0.5 m tall) maps derived from multi-spectral, multi-angular, and multi-temporal datasets from Landsat imagery at 30 m spatial resolution, Moderate Resolution Imaging SpectroRadiometer (MODIS) imagery at 250 m and 500 m spatial resolution, and MultiAngle Imaging Spectroradiometer (MISR) imagery at 275 m spatial resolution for a 1067 km2 study area in Arctic Alaska. The study area is centered at 69 °N, ranges in elevation from 130 to 770 m, is composed primarily of rolling topography with gentle slopes less than 10°, and is free of glaciers and perennial snow cover. Shrubs &gt; 0.5 m in height cover 2.9% of the study area and are primarily confined to patches associated with specific landscape features. Reference fractional shrub canopy is determined from in situ shrub canopy measurements and a high spatial resolution IKONOS image swath. Regression tree models are constructed to estimate fractional canopy cover at 250 m using different combinations of input data from Landsat, MODIS, and MISR. Results indicate that multi-spectral data provide substantially more accurate estimates of fractional shrub canopy cover than multi-angular or multi-temporal data. Higher spatial resolution datasets also provide more accurate estimates of fractional shrub canopy cover (aggregated to moderate spatial resolutions) than lower spatial resolution datasets, an expected result for a study area where most shrub cover is concentrated in narrow patches associated with rivers, drainages, and slopes. Including the middle infrared bands available from Landsat and MODIS in the regression tree models (in addition to the four standard visible and near-infrared spectral bands) typically results in a slight boost in accuracy. Including the multi-angular red band data available from MISR in the regression tree models, however, typically boosts accuracy more substantially, resulting in moderate resolution fractional shrub canopy estimates approaching the accuracy of estimates derived from the much higher spatial resolution Landsat sensor. Given the poor availability of snow and cloud-free Landsat scenes in many areas of the Arctic and the promising results demonstrated here by the MISR sensor, MISR may be the best choice for large area fractional shrub canopy mapping in the Alaskan Arctic for the period 2000-2009."
"7201899383;7103010648;57201806565;","Remote sensing of the tropical rain forest boundary layer using pulsed Doppler lidar",2010,"10.5194/acp-10-5891-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74249102116&doi=10.5194%2facp-10-5891-2010&partnerID=40&md5=9ab807fa7104e218c46b9fe991ef564b","Within the framework of the Natural Environment Research Council (NERC) Oxidant and Particle Photochemical Processes (OP3) project, a pulsed Doppler lidar was deployed for a 3 month period in the tropical rain forest of Borneo to remotely monitor vertical and horizontal transport, aerosol distributions and clouds in the lower levels of the atmosphere. The Doppler velocity measurements reported here directly observe the mixing process and it is suggested that this is the most appropriate methodology to use in analysing the dispersion of canopy sourced species into the lower atmosphere. These data are presented with a view to elucidating the scales and structures of the transport processes, which effect the chemical and particulate concentrations in and above the forest canopy, for applications in the parameterisation of climate models. © 2010 Author(s)."
"49261186800;7004469744;35810775100;8758893600;35519380200;56372694300;35612904200;","The impact of the 1783-1784 AD Laki eruption on global aerosol formation processes and cloud condensation nuclei",2010,"10.5194/acp-10-6025-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954342028&doi=10.5194%2facp-10-6025-2010&partnerID=40&md5=c9d06f9c1a129f582f4fb6addd49da18","The 1783-1784 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles and their growth to cloud condensation nuclei (CCN) using a comprehensive Global Model of Aerosol Processes (GLOMAP). Total particle concentrations in the free troposphere increase by a factor ∼16 over large parts of the Northern Hemisphere in the 3 months following the onset of the eruption. Particle concentrations in the boundary layer increase by a factor 2 to 5 in regions as far away as North America, the Middle East and Asia due to long-range transport of nucleated particles. CCN concentrations (at 0.22% supersaturation) increase by a factor 65 in the upper troposphere with maximum changes in 3-month zonal mean concentrations of ∼1400 cm-3 at high northern latitudes. 3-month zonal mean CCN concentrations in the boundary layer at the latitude of the eruption increase by up to a factor 26, and averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The simulations show that the Laki eruption would have completely dominated as a source of CCN in the pre-industrial atmosphere. The model also suggests an impact of the eruption in the Southern Hemisphere, where CCN concentrations are increased by up to a factor 1.4 at 20&amp;deg; S. Our model simulations suggest that the impact of an equivalent wintertime eruption on upper tropospheric CCN concentrations is only about one-third of that of a summertime eruption. The simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different after an eruption when compared to the unperturbed atmosphere, underlining the importance of using a fully coupled microphysics model when studying long-lasting, high-latitude eruptions. © 2010 Author(s)."
"8372868700;7003836546;22635944500;57144697100;7005219614;57204496157;","Modelling the chemically aged and mixed aerosols over the eastern central Atlantic Ocean-potential impacts",2010,"10.5194/acp-10-5797-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954221420&doi=10.5194%2facp-10-5797-2010&partnerID=40&md5=125dac150786396a02d15d449324d79d","Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size distribution, using chemistry-transport models, satellite data and in situ measurements. We focus on August 2005, a period with intense hurricane and tropical storm activity over the Atlantic Ocean. A mixture of anthropogenic (sulphates, nitrates), natural (desert dust, sea salt) and chemically aged (sulphate and nitrate on dust) aerosols is found entering the hurricane genesis region, most likely interacting with clouds in the area. Results from our modelling study suggest rather small amounts of accumulation mode desert dust, sea salt and chemically aged dust aerosols in this Atlantic Ocean region. Aerosols of smaller size (Aitken mode) are more abundant in the area and in some occasions sulphates of anthropogenic origin and desert dust are of the same magnitude in terms of number concentrations. Typical aerosol number concentrations are derived for the vertical layers near shallow cloud formation regimes, indicating that the aerosol number concentration can reach several thousand particles per cubic centimetre. The vertical distribution of the aerosols shows that the desert dust particles are often transported near the top of the marine cloud layer as they enter into the region where deep convection is initiated. The anthropogenic sulphate aerosol can be transported within a thick layer and enter the cloud deck through multiple ways (from the top, the base of the cloud, and by entrainment). The sodium (sea salt related) aerosol is mostly found below the cloud base. The results of this work may provide insights relevant for studies that consider aerosol influences on cloud processes and storm development in the Central Atlantic region. © 2010 Author(s)."
"35271924400;57214957751;15072064200;57214957433;35461763400;6602128405;56251307100;7102692123;57214957727;7101830914;6507946266;7102680152;7005601996;55984424900;7005287667;","Hygroscopic properties of Amazonian biomass burning and European background HULIS and investigation of their effects on surface tension with two models linking H-TDMA to CCNC data",2010,"10.5194/acp-10-5625-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954096033&doi=10.5194%2facp-10-5625-2010&partnerID=40&md5=abf410a9e4e410ab2f2301886f21cf1a","HUmic-LIke Substances (HULIS) have been identified as major contributors to the organic carbon in atmospheric aerosol. The term &HULIS is used to describe the organic material found in aerosol particles that resembles the humic organic material in rivers and sea water and in soils. In this study, two sets of filter samples from atmospheric aerosols were collected at different sites. One set of samples was collected at the K-puszta rural site in Hungary, about 80 km SE of Budapest, and a second was collected at a site in Rond̂nia, Amazonia, Brazil, during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) biomass burning season experiment. HULIS were extracted from the samples and their hygroscopic properties were studied using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) at relative humidity (RH) <100%, and a cloud condensation nucleus counter (CCNC) at RH >100%. The H-TDMA measurements were carried out at a dry diameter of 100 nm and for RH ranging from 30 to 98%. At 90% RH the HULIS samples showed diameter growth factors between 1.04 and 1.07, reaching values of 1.4 at 98% RH. The cloud nucleating properties of the two sets of aerosol samples were analysed using two types of thermal static cloud condensation nucleus counters. Two different parameterization models were applied to investigate the potential effect of HULIS surface activity, both yielding similar results. For the K-puszta winter HULIS sample, the surface tension at the point of activation was estimated to be lowered by between 34% (47.7 mN/m) and 31% (50.3 mN/m) for dry sizes between 50 and 120 nm in comparison to pure water. A moderate lowering was also observed for the entire water soluble aerosol sample, including both organic and inorganic compounds, where the surface tension was decreased by between 2% (71.2 mN/m) and 13% (63.3 mN/m). © 2010 Author(s)."
"7005793728;55273571800;7007039835;7701316840;6603921515;7410249965;","NCEP-ECPC monthly to seasonal US fire danger forecasts",2010,"10.1071/WF07079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954093336&doi=10.1071%2fWF07079&partnerID=40&md5=18f0eb6ea5ff9970cc712e8dfb5eb15b","Five National Fire Danger Rating System indices (including the Ignition Component, Energy Release Component, Burning Index, Spread Component, and the KeetchByram Drought Index) and the Fosberg Fire Weather Index are used to characterise US fire danger. These fire danger indices and input meteorological variables, including temperature, relative humidity, precipitation, cloud cover and wind speed, can be skilfully predicted at weekly to seasonal time scales by a global to regional dynamical prediction system modified from the National Centers for Environmental Prediction's Coupled Forecast System. The System generates global and regional spectral model ensemble forecasts, which in turn provide required input meteorological variables for fire danger. Seven-month US regional forecasts were generated every month from 1982 to 2007. This study shows that coarse-scale global predictions were more skilful than persistence, and fine-scale regional model predictions were more skilful than global predictions. The fire indices were better related to fire counts and area burned than meteorological variables, although relative humidity and temperature were useful predictors of fire characteristics. © 2010 IAWF."
"7202970886;57190749913;","Employing cluster analysis to detect significant cloud 3D RT effect indicators",2010,"10.1175/2010JAS3414.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955565715&doi=10.1175%2f2010JAS3414.1&partnerID=40&md5=cdcfa1daf7bee054131c0f36b2992313","Three-dimensional cloud field morphology contributes to scene-averaged cloud reflectivity, but climate models do not currently incorporate methods of identifying situations where this contribution is substantial. This work represents an effort to identify atmospheric conditions conducive to the formation of cloud field configurations that significantly affect shortwave radiative fluxes. Once identified, these characteristics may form the basis of a parameterization that accounts for radiative impact of complex cloud fields. A k-means clustering algorithm is applied to observed cloud properties taken from the Atmospheric Radiation Measurement Program tropical western Pacific sites to identify specific cloud regimes. Results from a stand-alone stochastic model, which statistically represents shortwave radiative transfer through broken cloud fields, are compared with those of a plane-parallel model. The aggregate scenes in each regime are examined to measure the bias in shortwave flux calculations due to neglected cloud field morphology. The results from the model comparison and cluster analysis suggest that cloud fraction, vertical wind shear, and spacing between cloudy layers are all important indicators of complex cloud field geometry and that these criteria are most often met in cloud regimes characterized by moderate to strong convection. The cluster criteria are applied to output from the Community Climate System Model (version 3.0) and it is found that the presence of persistent high cirrus cloud in model simulations inhibits identification of specific cloud regimes. © 2010 American Meteorological Society."
"23975989200;16312087900;55910202200;","An improved PDF cloud scheme for climate simulations",2010,"10.1002/qj.660","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957130017&doi=10.1002%2fqj.660&partnerID=40&md5=2ba610db47a26904d47e686eca891eab","An efficient grid-scale cloud scheme for climate simulation is implemented in the atmospheric general circulation model for the Earth Simulator (AFES). The new cloud scheme uses statistical partial condensation using joint-Gaussian probability distribution functions (PDFs) of the liquid water potential temperature and total water content, with standard deviations estimated by the moist Mellor-Yamada level-2 turbulence scheme. It also adopts improved closure parameters based on large-eddy simulations and a revised mixing length that varies with the stability and turbulent kinetic energy. These changes not only enable better representation of low-level boundary layer clouds, but also improve the atmospheric boundary layer structure. Sensitivity experiments for vertical resolution suggest that O(100-200 m) intervals are adequate to representwell-mixed boundary layerswith the new scheme. Thenew scheme performs well at relatively low horizontal resolution (about 150 km), although inversion layers near the coast become more intense at a higher horizontal resolution (about 50 km). © 2010 Royal Meteorological Society."
"24081888700;7409080503;","General macro- and microphysical properties of deep convective clouds as observed by MODIS",2010,"10.1175/2009JCLI3136.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955478282&doi=10.1175%2f2009JCLI3136.1&partnerID=40&md5=049004fa72d206921c7b8305b64e051d","Deep convective clouds (DCCs) are an important player in the climate system. In this paper the authors use remote sensing data mainly from the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud product to investigate a few general cloud macro- and microphysical properties of DCCs. This investigation concentrates on the tallest convective clouds and associated thick anvils that are labeled ""deep convective clouds."" General geographical patterns of DCCs from MODIS data are consistent with previous studies. By examining statistics of optical properties of DCCs over different locations of the globe, it is found that cloud optical depth distribution for DCCs shows little interannual variability for individual regions. These distributions, however, change with geographical regions. DCC ice particle size varies with surface elevation and cloud brightness temperature. DCCs that develop over elevated areas tend to have smaller ice particles at cloud top. There is a positive correlation between ice particle size and brightness temperature. The slope of this correlation has significant regional variations, which can be explained either with a simple thermodynamic consideration or with homogeneous freezing of aerosols. The findings have important implications in studying radiation budget, ice cloud microphysics parameterization, and troposphere-stratosphere water vapor exchange. © 2010 American Meteorological Society."
"7003390361;55017656900;8696069500;","Performance of an eddy diffusivity-mass flux scheme for shallow cumulus boundary layers",2010,"10.1175/2010MWR3142.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958452930&doi=10.1175%2f2010MWR3142.1&partnerID=40&md5=3550e12dc1440276f330880306477e90","Comparisons between single-column (SCM) simulations with the total energy-mass flux boundary layer scheme (TEMF) and large-eddy simulations (LES) are shown for four cases from the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) 2006 field experiment in the vicinity of Houston, Texas. The SCM simulations were run with initial soundings and surface forcing identical to those in the LES, providing a clean comparison with the boundary layer scheme isolated from any other influences. Good agreement is found in the simulated vertical transport and resulting moisture profiles. Notable differences are seen in the cloud base and in the distribution of moisture between the lower and upper cloud layer. By the end of the simulations, TEMF has dried the subcloud layer and moistened the lower cloud layer more than LES. TEMF gives more realistic profiles for shallow cumulus conditions than traditional boundary layer schemes, which have no transport above the dry convective boundary layer. Changes to the formulation and its parameters from previous publications are discussed. © 2010 American Meteorological Society."
"57198719030;7006111328;57062286700;7202400272;7102167757;","Narrowing of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in chemistry-climate model simulations of the 21st century",2010,"10.1029/2010GL043718","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954667651&doi=10.1029%2f2010GL043718&partnerID=40&md5=39d353abb789f468401160d8c822fea7","Changes in the width of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in the 21st Century are investigated using simulations from a coupled chemistry-climate model. In these model simulations the tropical upwelling region narrows in the troposphere and lower stratosphere. The narrowing of the Brewer-Dobson circulation is caused by an equatorward shift of Rossby wave critical latitudes and Eliassen-Palm flux convergence in the subtropical lower stratosphere. In the troposphere, the model projects an expansion of the Hadley cell's poleward boundary, but a narrowing of the Hadley cell's rising branch. Model results suggest that eddy forcing may also play a part in the narrowing of the rising branch of the Hadley cell. © 2010 by the American Geophysical Union."
"24492361700;7102128820;","Effect of improving representation of horizontal and vertical cloud structure on the Earth's global radiation budget. Part II: The global effects",2010,"10.1002/qj.646","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956207859&doi=10.1002%2fqj.646&partnerID=40&md5=6c5ba9d008eedf091a92a4b48af3551c","Reliably representing both horizontal cloud inhomogeneity and vertical cloud overlap is fundamentally important for the radiation budget of a general circulation model. Here, we build on the work of Part I of this two-part paper by applying a pair of parametrizations that account for horizontal inhomogeneity and vertical overlap to global re-analysis data. These are applied both together and separately in an attempt to quantify the effects of poor representation of the two components on radiation budget. Horizontal inhomogeneity is accounted for using the 'Tripleclouds' scheme, which uses two regions of cloud in each layer of a gridbox as opposed to one; vertical overlap is accounted for using 'exponential-random' overlap, which aligns vertically continuous cloud according to a decorrelation height. These are applied to a sample of scenes from a year of ERA-40 data. The largest radiative effect of horizontal inhomogeneity is found to be in areas of marine stratocumulus; the effect of vertical overlap is found to be fairly uniform, but with larger individual short-wave and long-wave effects in areas of deep, tropical convection. The combined effect of the two parametrizations is found to reduce themagnitude of the net top-of-atmosphere (TOA) cloud radiative forcing by 2.25Wm-2, with shifts of up to 10Wm-2 in areas of marine stratocumulus. The effects on radiation budget of the uncertainty in our parametrizations is also investigated. It is found that the uncertainty in the impact of horizontal inhomogeneity is of order ±60%, while the uncertainty in the impact of vertical overlap is much smaller. This suggests an insensitivity of the radiation budget to the exact nature of the global decorrelation height distribution derived in Part I. © 2010 Royal Meteorological Society."
"24492361700;7102128820;57193920163;35494005000;","Effect of improving representation of horizontal and vertical cloud structure on the earth's global radiation budget. Part I: Review and parametrization",2010,"10.1002/qj.647","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956222214&doi=10.1002%2fqj.647&partnerID=40&md5=3cc4838b7333a4f9c707ce9202d12c14","A poor representation of cloud structure in a general circulation model (GCM) is widely recognised as a potential source of error in the radiation budget. Here, we develop a new way of representing both horizontal and vertical cloud structure in a radiation scheme. This combines the 'Tripleclouds' parametrization, which introduces inhomogeneity by using two cloudy regions in each layer as opposed to one, each with different water content values, with 'exponential-random' overlap, in which clouds in adjacent layers are not overlapped maximally, but according to a vertical decorrelation scale. This paper, Part I of two, aims to parametrize the two effects such that they can be used in a GCM. To achieve this, we first review a number of studies for a globally applicable value of fractional standard deviation of water content for use in Tripleclouds. We obtain a value of 0.75 ±0.18 from a variety of different types of observations, with no apparent dependence on cloud type or gridbox size. Then, through a second short review, we create a parametrization of decorrelation scale for use in exponential-random overlap, which varies the scale linearly with latitude from 2.9 km at the Equator to 0.4 km at the poles. When applied to radar data, both components are found to have radiative impacts capable of offsetting biases caused by cloud misrepresentation. Part II of this paper implements Tripleclouds and exponential-random overlap into a radiation code and examines both their individual and combined impacts on the global radiation budget using re-analysis data. © 2010 Royal Meteorological Society and Crown Copyright."
"7006246996;6701333444;","Observational quantification of a total aerosol indirect effect in the Arctic",2010,"10.1111/j.1600-0889.2010.00460.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649393451&doi=10.1111%2fj.1600-0889.2010.00460.x&partnerID=40&md5=5cef240d6d489eb32b92eaa11fe5093d","We use 6 yr of multisensor radiometric data (1998-2003) from the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program to provide an observational quantification of the short-wave aerosol first indirect effect in the Arctic. Combined with the previously determined long-wave indirect effect, the total (short-wave and long-wave) first indirect effect in the high Arctic is found to yield a transition from surface warming of +3 W m-2 during March to a cooling of -11 W m-2 during May, therefore altering the seasonal cycle of energy input to the Arctic Earth-atmosphere system. These data also reveal evidence of a first indirect effect that affects optically thinner clouds during summer, which may represent an additional negative climate feedback that responds to a warming Arctic Ocean with retreating sea ice. © 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard."
"36238722200;7403441483;7103167530;55729249200;","A polar low embedded in a blocking high over the Pacific Arctic",2010,"10.1029/2010GL043946","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955298546&doi=10.1029%2f2010GL043946&partnerID=40&md5=82dd474b9db3045d85754dd78fbbf422","A polar low (PL) is a short-lived phenomenon involving strong winds that occurs over polar oceans. In October 2009, the R/V Mirai encountered a PL with a 600-km-wide, comma-shaped cloud that developed over the Chukchi Sea. A shipboard Doppler radar and radiosondes were used to understand the fine structure of this PL. Analyses of low-level winds and the thermodynamic structure indicated that the development of the PL was decoupled from sea surface thermal forcing. The PL was likely triggered by an intrusion of a potential vorticity (PV) anomaly at the tropopause. A southerly warm advection associated with a blocking high over Alaska resulted in rapid development of the PL in front of the cold dome induced by the upper-level PV anomaly. The westerly winds after passage of the PL seemed to modify the upper-ocean structure dramatically. © 2010 by the American Geophysical Union."
"7401829771;7004590414;","Comparisons of daily Sea surface temperature analyses for 2007-08",2010,"10.1175/2010JCLI3294.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955481877&doi=10.1175%2f2010JCLI3294.1&partnerID=40&md5=00483f1b350e9a2fe0db65b95a23770a","Six different SST analyses are compared with each other and with buoy data for the period 2007-08. All analyses used different combinations of satellite data [for example, infrared Advanced Very High Resolution Radiometer (AVHRR) and microwave Advanced Microwave Scanning Radiometer (AMSR) instruments] with different algorithms, spatial resolution, etc. The analyses considered are the National Climatic Data Center (NCDC) AVHRR-only and AMSR1AVHRR, the Navy Coupled Ocean Data Assimilation (NCODA), the Remote Sensing Systems (RSS), the Real-Time Global High-Resolution (RTG-HR), and the Operational SST and Sea Ice Analysis (OSTIA); the spatial grid sizes were 1/4°, 1/4°, 1/9°, 1/11°, 1/12°, and 1/20°, respectively. In addition, all analyses except RSS used in situ data. Most analysis procedures and weighting functions differed. Thus, differences among analyses could be large in high-gradient and data-sparse regions. An example off the coast of South Carolina showed winter SST differences that exceeded 5°C. To help quantify SST analysis differences, wavenumber spectra were computed at several locations. These results suggested that the RSS is much noisier and that the RTG-HR analysis is much smoother than the other analyses. Further comparisons made using collocated buoys showed that RSS was especially noisy in the tropics and that RTG-HR had winter biases near the Aleutians region during January and February 2007. The correlation results show that NCODA and, to a somewhat lesser extent, OSTIA are strongly tuned locally to buoy data. The results also show that grid spacing does not always correlate with analysis resolution. The AVHRR-only analysis is useful for climate studies because it is the only daily SST analysis that extends back to September 1981. Furthermore, comparisons of the AVHRR-only analysis and the AMSR1AVHRR analysis show that AMSR data can degrade the combined AMSR and AVHRR resolution in cloud-free regions while AMSR otherwise improves the resolution. These results indicate that changes in satellite instruments over time can impact SST analysis resolution. © 2010 American Meteorological Society."
"7004941120;6602077574;55574223422;55829111000;55974229900;6508003871;55465376400;6701899848;9272538400;7101692211;7101936669;22636199100;","State of the climate in 2009",2010,"10.1175/BAMS-91-7-StateoftheClimate","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955590864&doi=10.1175%2fBAMS-91-7-StateoftheClimate&partnerID=40&md5=dd45ec13f0f80545cde20815a413db77","The year was characterized by a transition from a waning La Niña to a strengthening El Niño, which first developed in June. By December, SSTs were more than 2.0°C above average over large parts of the central and eastern equatorial Pacific. Eastward surface current anomalies, associated with the El Niño, were strong across the equatorial Pacific, reaching values similar to the 2002 El Niño during November and December 2009. The transition from La Niña to El Niño strongly influenced anomalies in many climate conditions, ranging from reduced Atlantic basin hurricane activity to large scale surface and tropospheric warmth. Global average surface and lower-troposphere temperatures during the last three decades have been progressively warmer than all earlier decades, and the 2000s (2000-09) was the warmest decade in the instrumental record. This warming has been particularly apparent in the mid- and high-latitude regions of the Northern Hemisphere and includes decadal records in New Zealand, Australia, Canada, Europe, and the Arctic. The stratosphere continued a long cooling trend, except in the Arctic. Atmospheric greenhouse gas concentrations continued to rise, with CO2 increasing at a rate above the 1978 to 2008 average. The global ocean CO 2 uptake flux for 2008, the most recent year for which analyzed data are available, is estimated to have been 1.23 Pg C yr-1, which is 0.25 Pg C yr-1 smaller than the long-term average and the lowest estimated ocean uptake in the last 27 years. At the same time, the total global ocean inventory of anthropogenic carbon stored in the ocean interior as of 2008 suggests an uptake and storage of anthropogenic CO2 at rates of 2.0 and 2.3 ±0.6 Pg C yr-1 for the decades of the 1990s and 2000s, respectively. Total-column ozone concentrations are still well below pre-1980 levels but have seen a recent reduction in the rate of decline while upper-stratospheric ozone showed continued signs of ongoing slow recovery in 2009. Ozone-depleting gas concentrations continued to decline although some halogens such as hydrochlorofluorocarbons are increasing globally. The 2009 Antarctic ozone hole was comparable in size to recent previous ozone holes, while still much larger than those observed before 1990. Due to large interannual variability, it is unclear yet whether the ozone hole has begun a slow recovery process. Global integrals of upper-ocean heat content for the last several years have reached values consistently higher than for all prior times in the record, demonstrating the dominant role of the oceans in the planet's energy budget. Aside from the El Niño development in the tropical Pacific and warming in the tropical Indian Ocean, the Pacific Decadal Oscillation (PDO) transitioned to a positive phase during the fall/winter 2009. Ocean heat fluxes contributed to SST anomalies in some regions (e.g., in the North Atlantic and tropical Indian Oceans) while dampening existing SST anomalies in other regions (e.g., the tropical and extratropical Pacific). The downward trend in global chlorophyll observed since 1999 continued through 2009, with current chlorophyll stocks in the central stratified oceans now approaching record lows since 1997. Extreme warmth was experienced across large areas of South America, southern Asia, Australia, and New Zealand. Australia had its second warmest year on record. India experienced its warmest year on record; Alaska had its second warmest July on record, behind 2004; and New Zealand had its warmest August since records began 155 years ago. Severe cold snaps were reported in the UK, China, and the Russian Federation. Drought affected large parts of southern North America, the Caribbean, South America, and Asia. China suffered its worst drought in five decades. India had a record dry June associated with the reduced monsoon. Heavy rainfall and floods impacted Canada, the United States, the Amazonia and southern South America, many countries along the east and west coasts of Africa, and the UK. The U.S. experienced its wettest October in 115 years and Turkey received its heaviest rainfall over a 48-hr period in 80 years. Sea level variations during 2009 were strongly affected by the transition from La Niña to El Niño conditions, especially in the tropical Indo-Pacific. Globally, variations about the long-term trend also appear to have been influenced by ENSO, with a slight reduction in global mean sea level during the 2007/08 La Niña event and a return to the long-term trend, and perhaps slightly higher values, during the latter part of 2009 and the current El Niño event. Unusually low Florida Current transports were observed in May and June and were linked to high sea level and coastal flooding along the east coast of the United States in the summer. Sea level significantly decreased along the Siberian coast through a combination of wind, ocean circulation, and steric effects. Cloud and moisture increased in the tropical Pacific. The surface of the western equatorial Pacific freshened considerably from 2008 to 2009, at least partially owing to anomalous eastward advection of fresh surface water along the equator during this latest El Niño. Outside the more variable tropics, the surface salinity anomalies associated with evaporation and precipitation areas persisted, consistent with an enhanced hydrological cycle. Global tropical cyclone (TC) activity was the lowest since 2005, with six of the seven main hurricane basins (the exception is the Eastern North Pacific) experiencing near-normal or somewhat below-normal TC activity. Despite the relatively mild year for overall hurricane activity, several storms were particularly noteworthy: Typhoon Morakot was the deadliest typhoon on record to hit Taiwan; Cyclone Hamish was the most intense cyclone off Queensland since 1918; and the state of Hawaii experienced its first TC since 1992. The summer minimum ice extent in the Arctic was the third-lowest recorded since 1979. The 2008/09 boreal snow cover season marked a continuation of relatively shorter snow seasons, due primarily to an early disappearance of snow cover in spring. Preliminary data indicate a high probability that 2009 will be the 19th consecutive year that glaciers have lost mass. Below normal precipitation led the 34 widest marine terminating glaciers in Greenland to lose 101 km 2 ice area in 2009, within an annual loss rate of 106 km2 over the past decade. Observations show a general increase in permafrost temperatures during the last several decades in Alaska, northwest Canada, Siberia, and Northern Europe. Changes in the timing of tundra green-up and senescence are also occurring, with earlier green-up in the High Arctic and a shift to a longer green season in fall in the Low Arctic. The Antarctic Peninsula continues to warm at a rate five times larger than the global mean warming. Associated with the regional warming, there was significant ice loss along the Antarctic Peninsula in the last decade. Antarctic sea ice extent was near normal to modestly above normal for the majority of 2009, with marked regional contrasts within the record. The 2008/09 Antarctic-wide austral summer snowmelt was the lowest in the 30-year history. This 20th annual State of the Climate report highlights the climate conditions that characterized 2009, including notable extreme events. In total, 37 Essential Climate Variables are reported to more completely characterize the State of the Climate in 2009."
"6701744586;","Global analysis of reptile elevational diversity",2010,"10.1111/j.1466-8238.2010.00528.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954795356&doi=10.1111%2fj.1466-8238.2010.00528.x&partnerID=40&md5=550bf8dcab95ecf49c9790ffc9d92d18","Aim: Latitudinal- and regional-scale studies of reptile diversity suggest a predominant temperature effect, unlike many other vertebrate richness patterns which tend to be highly correlated with both temperature and water variables. Here I examine montane gradients in reptile species richness with separate analyses of snakes and lizards from mountains around the world to assess a predominant temperature effect and three additional theories of diversity, including a temperature-water effect, the species-area effect and the mid-domain effect (MDE). Location: Twenty-five elevational gradients of reptile diversity from temperate, tropical and desert mountains in both hemispheres, spanning 10.3° N to 46.1° N. Methods: Elevational gradients in reptile diversity are based on data from the literature. Of the 63 data sets found or compiled, only those with a high, unbiased sampling effort were used in analyses. Twelve predictions and three interactions of diversity theory were tested using nonparametric statistics, linear regressions and multiple regression with the Akaike information criterion (AIC). Results: Reptile richness and, individually, snake and lizard richness on mountains followed four distinct patterns: decreasing, low-elevation plateaus, low-elevation plateaus with mid-elevation peaks, and mid-elevation peaks. Elevational reptile richness was most strongly correlated with temperature. The temperature effect was mediated by precipitation; reptile richness was more strongly tied to temperature on wet gradients than on arid gradients. Area was a secondary factor of importance, whereas the MDE was not strongly associated with reptile diversity on mountains. Main conclusions: Reptile diversity patterns on mountains did not follow the predicted temperature-water effect, as all diversity patterns were found on both wet and dry mountains. But the influence of precipitation on the temperature effect most likely reflects reptiles' use of radiant heat sources (sunning opportunities) that are more widespread on arid mountains than wet mountains due to lower humidity, sparser vegetation and less cloud cover across low and intermediate elevations. © 2010 Blackwell Publishing Ltd."
"6507285268;6602692048;7003629951;7202810546;","Long and short-time scale climatic variability in the last 5500years in Africa according to modern and fossil diatoms from Lake Ossa (Western Cameroon)",2010,"10.1016/j.gloplacha.2010.01.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957276042&doi=10.1016%2fj.gloplacha.2010.01.011&partnerID=40&md5=de333cc7d3f9c711bf2ecf567f18857f","The reconstruction of paleoenvironmental changes from diatoms in lake sediments is based on the usual assumption that, in each studied sample, the dominant species reflect the environment that prevailed during the time of deposition. If the environment changed significantly during the period of deposition (several years) one can expect a mixture of species having different or contradictory ecological affinities. In this paper we present analyses of diatoms in surface sediment samples collected in the Lake Ossa area (3°50'N, 9°36E) and fossil diatoms from a mid-late Holocene core retrieved in the deepest part of the lake. The Lake Ossa area alternates between a short dry season centered at around the northern winter and a long rainy season during the rest of the year entailing significant changes in water level and pH. Based on multivariate analyses, we will show here that mean annual water depth is the most significant variable explaining the distribution of diatoms in the entire Lake. However, seasonal changes of water level are poorly recorded by diatom assemblages, except in some flat areas on the borders of the lakes where a mixing between species with different affinities to water depth is likely due to seasonal changes in water level. Inferred water depth based on a quantitative transfer function reflected essentially secular to millennial changes in the studied core. The relationship between pH and diatoms is not statistically significant but seasonal to multi-annual pH variations mainly observed in the central parts of the lake are reflected by a mixing of acidophilous and alkaliphilous species. Hierarchical ascending cluster analysis (HAC) considered as the most efficient mean of describing diatom mixing shows that seasonal to multi-annual changes in pH are recorded both in the modern and fossil assemblages. According to the degree of mixing between diatoms with different pH affinities we conclude that short-term pH variability was weaker than today between 5200 and 2700. cal. yr. BP, stronger between 2700 and 2000. cal. yr. BP, weaker again between 2000 and 600. cal. yr. BP and similar to present from 400. cal. yr. BP onwards. Short-term changes were thus superimposed on secular to millennium trends recorded by modifications in the abundance of alkaliphilous diatoms. All these changes are interpreted as variations in precipitation according to a previous model showing that pH is strongly controlled by acidic meteoric water. Inferred water depth slightly changed over the last 5500. years showing weak variations of precipitation minus evaporation balance at secular to millennial time scales. These results will be used to refine previously published paleoclimatic interpretations, which explained changes in precipitation and P-E balance by modifications in the vertical structure of the atmosphere and subsequently by changes in cloud cover, convective or stratiform. © 2010 Elsevier B.V."
"56162305900;7102604282;","Cirrus clouds in a global climate model with a statistical cirrus cloud scheme",2010,"10.5194/acp-10-5449-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953816257&doi=10.5194%2facp-10-5449-2010&partnerID=40&md5=4211644d9c416d1c8937e3e36d22978b","A statistical cirrus cloud scheme that accounts for mesoscale temperature perturbations is implemented in a coupled aerosol and atmospheric circulation model to better represent both subgrid-scale supersaturation and cloud formation. This new scheme treats the effects of aerosol on cloud formation and ice freezing in an improved manner, and both homogeneous freezing and heterogeneous freezing are included. The scheme is able to better simulate the observed probability distribution of relative humidity compared to the scheme that was implemented in an older version of the model. Heterogeneous ice nuclei (IN) are shown to decrease the frequency of occurrence of supersaturation, and improve the comparison with observations at 192 hPa. Homogeneous freezing alone can not reproduce observed ice crystal number concentrations at low temperatures (<205 K), but the addition of heterogeneous IN improves the comparison somewhat. Increases in heterogeneous IN affect both high level cirrus clouds and low level liquid clouds. Increases in cirrus clouds lead to a more cloudy and moist lower troposphere with less precipitation, effects which we associate with the decreased convective activity. The change in the net cloud forcing is not very sensitive to the change in ice crystal concentrations, but the change in the net radiative flux at the top of the atmosphere is still large because of changes in water vapor. Changes in the magnitude of the assumed mesoscale temperature perturbations by 25% alter the ice crystal number concentrations and the net radiative fluxes by an amount that is comparable to that from a factor of 10 change in the heterogeneous IN number concentrations. Further improvements on the representation of mesoscale temperature perturbations, heterogeneous IN and the competition between homogeneous freezing and heterogeneous freezing are needed. © 2010 Author(s)."
"7004215973;7004938676;","Nature and climate effects of individual tropospheric aerosol particles",2010,"10.1146/annurev.earth.031208.100032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953667026&doi=10.1146%2fannurev.earth.031208.100032&partnerID=40&md5=178aa316c462a3ba696b8edca2a97906","Aerosol particles in the atmosphere exert a strong influence on climate by interacting with sunlight and by initiating cloud formation. Because the tropospheric aerosol is a heterogeneous mixture of various particle types, its climate effects can only be fully understood through detailed knowledge of the physical and chemical properties of individual particles. Here we review the results of individual-particle studies that use microscopy-based techniques, emphasizing transmission electron microscopy and focusing on achievements of the past ten years. We discuss the techniques that are best suited for studying distinct particle properties and provide a brief overview of major particle types, their identification, and their sources. The majority of this review is concerned with the optical properties and hygroscopic behavior of aerosol particles; we discuss recent results and highlight the potential of emerging microscopy techniques for analyzing the particle properties that contribute most to climate effects. Copyright © 2010 by Annual Reviews. All rights reserved."
"36757271900;","Changes of diurnal temperature range in taiwan and their large-scale associations: Univariate and multivariate trend analyses",2010,"10.2151/jmsj.2010-206","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953521275&doi=10.2151%2fjmsj.2010-206&partnerID=40&md5=3afda0db5b2891d74b724e1d98e529ff","By analyzing the long-term (1950-2007) variability of diurnal temperature range [DTR; daytime maximum (Tmax minus nighttime minimum (Tmin)] at 21 stations in Taiwan, this study applies univariate analysis, a trend-free prewhitening procedure combined with a modified Mann-Kendall test, and EOF-based multivariate trend analysis (TEOFA) to the ranked station DTR, Tmax, and Tmin. To reveal the large-scale associations with the local TEOFA results, this study also uses global gridded Tmax, Tmin, nighttime marine air temperature, and sea level pressure (SLP) datasets archived at the U.K. Meteorological Office Hadley Centre. On the basis of the signs and relative magnitudes between the annually-mean Tmax and Tmin trends, the stations can be classified into three types through univariate analysis. With a common increasing Tmin, type-A (type-B) stations have an increasing Tmin(Tmax faster than Tmax (Tmin whereas type-C stations have a decreasing Tmax. Both type-A and type-C (type-B) thus show(s) a decreasing (an increasing) DTR. For most stations, the increasing Tmin is the largest in December-February. In contrast, all type-B stations have an increasing Tmax peaking in June-August. Noticeably, six of nine type-B stations, either in the remote islands or in the seaports, are particularly influenced by the ocean. Three DTR trend modes stand out of TEOFA. The first mode, TEOF1, captures increasing DTR trends at four type-B stations and decreasing DTR trends elsewhere. The associated increasing Tmin(Tmax trend is consistent with the increasing (decreasing) clouds during nighttime (daytime) and is well-correlated with the largescale patterns, suggesting that it is part of the global warming scenario. Nevertheless, TEOF1 also captures a decreasing Tmax trend in Taiwan's highly developed western plains (i.e., type C) and eastern China where an increasing SLP pattern is observed, implying the anthropogenic forcings on DTR. TEOFM2 (TEOF3) depicts the decadal-to-interdecadal DTR variability in central (northern) Taiwan. Evolution of TEOF2 shows smaller (larger) amplitude before 1970s (after mid-1980s). The associated large-scale patterns suggest that TEOF2 (TEOF3) captures the relationship between an intensified (weakened) East Asian winter monsoon and La Nin ̃a (El Nin ̃o)-like condition in eastern (central) equatorial Pacific. Embedded in a Pacific-Japan-like teleconnection pattern, the southwestward intrusion of Pacific subtropical anticyclone in June-August that signifies the weakened southwesterly monsoon is also depicted by TEOF2. © 2010, Meteorological Society of Japan."
"56174306000;55499659200;57192671220;35424175300;","Trend in pan evaporation and its attribution over the past 50 years in China",2010,"10.1007/s11442-010-0557-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953343523&doi=10.1007%2fs11442-010-0557-3&partnerID=40&md5=ebfcbd5245f2a89f13f0fd99513c9b75","Trends in pan evaporation are widely relevant to the hydrological community as indicators of hydrological and climate change. Pan evaporation has been decreasing in the past few decades over many large areas with differing climates globally. This study analyzes pan evaporation data from 671 stations in China over the past 50 years in order to reveal the trends of it and the corresponding trend attribution. Mann-Kendall test shows a significant declining trend in pan evaporation for most stations, with an average decrease of 17. 2 mm/10a in China as a whole, the rate of decline was the steepest in the humid region (29. 7 mm/10a), and was 17. 6 mm/10a and 5. 5 mm/10a in the semi-humid/semi-arid region and arid region, respectively. Complete correlation coefficients of pan evaporation with 7 climate factors were computed, and decreases in diurnal temperature range (DTR), SD (sunshine duration) and wind speed were found to be the main attributing factors in the pan evaporation declines. Decrease in DTR and SD may relate to the increase of clouds and aerosol as well as the other pollutants, and decrease in wind speed to weakening of the Asian winter and summer monsoons under global climate warming. © 2010 Science in China Press and Springer-Verlag Berlin Heidelberg."
"35491126200;7005397699;","Daily MODIS products for analyzing early season vegetation dynamics across the North Slope of Alaska",2010,"10.1016/j.rse.2010.01.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949488879&doi=10.1016%2fj.rse.2010.01.017&partnerID=40&md5=bed9b7eec20e14daa7d66d72f36ce6b8","Monitoring the growth and distribution of Arctic tundra vegetation is important for understanding changes in early growing season conditions in Arctic ecosystems in response to a warming climate. The primary objective of this study is to examine the utility of computed Daily Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) products relative to 16-day maximum value composite (MVC) datasets for observing early season green-up dynamics of Arctic tundra vegetation across the North Slope of Alaska. Greening in the Arctic typically occurs shortly after snowmelt and can potentially be captured by using satellite observations that are available on a daily basis. Daily MODIS Snow Cover products were employed to retrieve dates of complete snowmelt (DOCS) for 2003-2005 for pixels that were cloud free at the time of complete snowmelt. Given the sparseness of cloud-free observations in both space and time, early season NDVI trajectories for cloud-free pixels were derived using daily MODIS data based on two approaches: a chronosequence (temporally continuous but aspatial) and a pixel trajectory (temporally discontinuous but spatial explicit) approach. On average during the three-year period, 12.5% of the North Slope region was cloud free at the time of complete snowmelt and a majority of these cloud-free pixels (65%) were associated with the Coastal Plain province. In contrast, the Foothills region was relatively less cloudy from the time following complete snowmelt until peak greenness (56%) than the Coastal Plain province (61%). As a result, vegetation communities that lie mostly in the Foothills province such as shrub tundra and moist acidic tundra classes had more cloud-free observations available to characterize NDVI trajectories using the pixel trajectory approach. Complete snowmelt in the North Slope generally occurred between day of year (DOY) 140 and 170 over the three years with areas covered by the shrub tundra vegetation community (Foothills province) experiencing snowmelt first in all three years with mean DOCS ranging from DOY 148 in 2004 to DOY 158 in 2003. For approximately two weeks following complete snowmelt (Phase I, a period of rapid NDVI increase), the Daily NDVI derived trajectories were substantially different from the MVC NDVI trajectories. Early season integrated NDVI (ESINDVI) values computed for Phase I were 7% higher using the Daily NDVI approaches relative to those derived from the MVC MODIS data for the North Slope region. Following this initial period, until peak greenness (Phase 2, a period of gradual NDVI increase), the Daily and MVC trajectories were similar in shape and magnitude. This study demonstrates the utility of the Daily MODIS Snow product for assessing cloud cover and snowmelt patterns and Daily MODIS NDVI data for observing and detecting sharp and rapid changes in early season vegetation phenology as seen during Phase I. © 2010 Elsevier Inc. All rights reserved."
"55719072500;7003893896;","Multiple factors causing Holocene lake-level change in monsoonal and arid central Asia as identified by model experiments",2010,"10.1007/s00382-010-0861-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958152996&doi=10.1007%2fs00382-010-0861-8&partnerID=40&md5=7625e447538fb144045220521846f6c9","Lake-level records provide a rich resource of information about past changes in effective moisture, but water-balance fluctuations can be driven by a number of different climate variables and it is often difficult to pinpoint their exact cause. This understanding is essential, however, for reconciling divergent paleo-records or for making predictions about future lake-level variations. This research uses a series of models, the NCAR CCSM3, a lake energy-balance and a lake water-balance model, to examine the reasons for lake-level changes in monsoonal Asia and arid central Asia between the early (8.5 ka), middle (6.0 ka) and late (ca. 1800 AD) Holocene. Our results indicate that the components of the lake water balance responsible for lake-level changes varied by region and through time. High lake levels at 8.5 and 6.0 ka in the monsoon region were caused by the combined effects of low lake evaporation and high precipitation. The low lake evaporation resulted from low winter solar radiation and high summer cloud cover. Precipitation associated with the mid-latitude westerlies increased from the early to middle Holocene and maintained high lake levels throughout most of arid central Asia ca. 6 ka. The modeled evolution of lake level in arid central Asia from the mid to late Holocene was spatially heterogeneous, due to different sensitivities of the northern and southern parts of the region to seasonally-changing insolation, particularly regarding the duration of lake ice cover. The model results do not suggest that precipitation and lake evaporation changes compete with one another in forcing lake-level change, as has been hypothesized. © 2010 Springer-Verlag."
"35887706900;7004174939;20435752700;7201798916;35195594800;","Aerosol-induced changes of convective cloud anvils produce strong climate warming",2010,"10.5194/acp-10-5001-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952985164&doi=10.5194%2facp-10-5001-2010&partnerID=40&md5=04be59aae131b4bb34afb890761a6d9d","The effect of aerosol on clouds poses one of the largest uncertainties in estimating the anthropogenic contribution to climate change. Small human-induced perturbations to cloud characteristics via aerosol pathways can create a change in the top-of-atmosphere radiative forcing of hundreds of Wm-2. Here we focus on links between aerosol and deep convective clouds of the Atlantic and Pacific Intertropical Convergence Zones, noting that the aerosol environment in each region is entirely different. The tops of these vertically developed clouds consisting of mostly ice can reach high levels of the atmosphere, overshooting the lower stratosphere and reaching altitudes greater than 16 km. We show a link between aerosol, clouds and the free atmosphere wind profile that can change the magnitude and sign of the overall climate radiative forcing. We find that increased aerosol loading is associated with taller cloud towers and anvils. The taller clouds reach levels of enhanced wind speeds that act to spread and thin the anvil clouds, increasing areal coverage and decreasing cloud optical depth. The radiative effect of this transition is to create a positive radiative forcing (warming) at top-of-atmosphere. Furthermore we introduce the cloud optical depth (τ), cloud height (Z) forcing space and show that underestimation of radiative forcing is likely to occur in cases of non homogenous clouds. Specifically, the mean radiative forcing of towers and anvils in the same scene can be several times greater than simply calculating the forcing from the mean cloud optical depth in the scene. © 2010 Author(s)."
"6602878057;24722339600;7004479957;7004544454;6701431208;6603752634;7101964663;6507671561;16312624300;57193213111;36876405100;57219113417;24537575000;7402064802;36134539200;6602934046;7403295159;13406647100;57203504470;7601492669;","The PreVOCA experiment: Modeling the lower troposphere in the Southeast Pacific",2010,"10.5194/acp-10-4757-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952959680&doi=10.5194%2facp-10-4757-2010&partnerID=40&md5=86dccc23e4517e7a6ef06f8c376f4e25","The Preliminary VOCALS Model Assessment (PreVOCA) aims to assess contemporary atmospheric modeling of the subtropical South East Pacific, with a particular focus on the clouds and the marine boundary layer (MBL). Models results from fourteen modeling centers were collected including operational forecast models, regional models, and global climate models for the month of October 2006. Forecast models and global climate models produced daily forecasts, while most regional models were run continuously during the study period, initialized and forced at the boundaries with global model analyses. Results are compared in the region from 40&deg; S to the equator and from 110° W to 70° W, corresponding to the Pacific coast of South America. Mean-monthly model surface winds agree well with QuikSCAT observed winds and models agree fairly well on mean weak large-scale subsidence in the region next to the coast. However they have greatly differing geographic patterns of mean cloud fraction with only a few models agreeing well with MODIS observations. Most models also underestimate the MBL depth by several hundred meters in the eastern part of the study region. The diurnal cycle of liquid water path is underestimated by most models at the 85° W 20° S stratus buoy site compared with satellite, consistent with previous modeling studies. The low cloud fraction is also underestimated during all parts of the diurnal cycle compared to surface-based climatologies. Most models qualitatively capture the MBL deepening around 15 October 2006 at the stratus buoy, associated with colder air at 700 hPa. © Author(s) 2010."
"35320263800;35263095800;7004934146;","Pollution in coastal fog at Alto Patache, Northern Chile",2010,"10.1007/s11356-010-0343-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957163791&doi=10.1007%2fs11356-010-0343-x&partnerID=40&md5=c94cdccbaeddf904c47a24a3eecc3cf6","Background: The Atacama Desert in Northern Chile is one of the most arid places on earth. However, fog occurs regularly at the coastal mountain range and can be collected at different sites in Chile to supply settlements at the coast with freshwater. This is also planned in the fog oasis Alto Patache (20°49′S, 70°09′W). For this pilot study, we collected fog water samples in July and August 2008 for chemical analysis to find indications for its suitability for domestic use. Methods: Fog water samples were taken with a cylindrical scientific fog collector and from the net and the storage tank of a Large Fog Collector (LFC). Results: The pHs of advective fog, originating from the stratus cloud deck over the Eastern Pacific, varied between 2.9 and 3.5. Orographic fog, which was formed locally, exhibited a pH of 2.5. About 50% of the total ionic concentration was due to sea salt. High percentages of sulfate and very high enrichment factors (versus sea salt) of heavy metals were found. Both backward trajectories and the enrichment factors indicate that the high concentrations of ions and heavy metals in fog were influenced by anthropogenic activities along the Chilean Pacific Coast such as power plants, mining, and steel industry. Conclusions: We found no direct indication for the importance of other sources such as the emission of dimethyl sulfide from the ocean and subsequent atmospheric oxidation for acidity and sulfate or soil erosion for heavy metal concentrations. When fog water was collected by the LFC, it apparently picked up large amounts of dry deposition which accumulated on the nets during fog-free periods. This material is rinsed off the collector shortly after the onset of a fog event with the water collected first. During the first flush, some concentrations of acidity, nitrate, As, and Se, largely exceeded the Chilean drinking water limits. Before any use of fog water for domestic purpose, its quality should be checked on a regular basis. Strategies to mitigate fog water pollution are given. © 2010 Springer-Verlag."
"6507781926;57203056321;6507589406;","Cloud forest dynamics in the mexican neotropics during the last 1300 years",2010,"10.1111/j.1365-2486.2009.02024.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953679270&doi=10.1111%2fj.1365-2486.2009.02024.x&partnerID=40&md5=e65d1473fe1cba68bcb92a7345851a58","Key questions for understanding the resilience and variability of Mexican Neotropical cloud forest assemblages in current and future climate change include: How have human disturbances and climate change affected the dynamics of the cloud forest assemblage? What are the predominant processes responsible for its present day composition and distribution? Are the current conservation strategies for the cloud forest in accordance with preserving its natural variability through time? In this study, the temporal dynamics of the cloud forest in west-central Mexico over the last ∼1300 years were reconstructed using palaeoecological techniques. These included analyses of fossil pollen, microfossil charcoal, and sediment geochemistry. Results indicated that a cloud forest assemblage has been the predominant vegetation type in this region over the last ∼1300 years. During this time, however, there have been changes in the vegetation with an apparent expansion of cloud forest from ∼832 to 620 cal years bp and a decline from 1200 to 832 cal years bp. Climate change (intervals of aridity) and human disturbances through anthropogenic burning appear to have been the main factors influencing the dynamics of this cloud forest. The spatial heterogeneity reported for high-altitude forests in this region, in concert with high beta diversity, appears to be a manifestation of the high temporal variability in species composition for these forests. Greater turnover in cloud forest taxa occurred during intervals of increased humidity and is probably representative of a higher temporal competition for resources among the cloud forest taxa. The present results support the current protection scheme for cloud forests in west-central Mexico where areas are kept in exclusion zones to avoid timber extraction, grazing, and agriculture; this will maintain diversity within these forests, even if there are only a few individuals per species, and enable the forests to retain some resilience to current and future climate change. © 2009 Blackwell Publishing Ltd."
"7004893330;57193132723;57191598636;6507993848;","Cloud vertical distribution across warm and cold fronts in cloudsat-CALIPSO data and a general circulation model",2010,"10.1175/2010JCLI3282.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955478870&doi=10.1175%2f2010JCLI3282.1&partnerID=40&md5=230b1d5ca83b4700273f46cb2d0f4bdf","Cloud vertical distributions across extratropical warm and cold fronts are obtained using two consecutive winters of CloudSat-Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations and National Centers for Environmental Prediction reanalysis atmospheric state parameters over the Northern and Southern Hemisphere oceans (30°-70°N/S) between November 2006 and September 2008. These distributions generally resemble those from the original model introduced by the Bergen School in the 1920s, with the following exceptions: 1) substantial low cloudiness, which is present behind and ahead of the warm and cold fronts; 2) ubiquitous high cloudiness, some of it very thin, throughout the warm-frontal region; and 3) upright convective cloudiness near and behind some warm fronts. One winter of GISS general circulation model simulations of Northern and Southern Hemisphere warm and cold fronts at 2° × 2.5° × 32 levels resolution gives similar cloud distributions but with much lower cloud fraction, a shallower depth of cloudiness, and a shorter extent of tilted warm-frontal cloud cover on the cold air side of the surface frontal position. A close examination of the relationship between the cloudiness and relative humidity fields indicates that water vapor is not lifted enough in modeled midlatitude cyclones and this is related to weak vertical velocities in the model. The model also produces too little cloudiness for a given value of vertical velocity or relative humidity. For global climate models run at scales coarser than tens of kilometers, the authors suggest that the current underestimate of modeled cloud cover in the storm track regions, and in particular the 50°-60°S band of the Southern Oceans, could be reduced with the implementation of a slantwise convection parameterization. © 2010 American Meteorological Society."
"12787718700;7003769239;","Strong relationships between vegetation and two perpendicular climate gradients high on a tropical mountain in Hawaii",2010,"10.1111/j.1365-2699.2010.02277.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954050153&doi=10.1111%2fj.1365-2699.2010.02277.x&partnerID=40&md5=282fbda029adf8bdf1bf8f337473b616","Aim: We compared vegetation patterns at high elevation on a tropical mountain with edaphic properties and position along climate gradients to examine this landscape's potential sensitivity to climate change. Location: Our study covers the cloud forest, the ecotone at the cloud forest's upper limit, and the alpine grassland, on the north-east corner of windward Haleakalā, Hawai'i. The study area brackets the mean trade wind inversion (TWI), encompasses a perpendicular, east-west precipitation gradient and includes multiple edaphic contexts. Methods: We collected vegetation structure and composition data in 134 plots from 1900 to 2400 m elevation, stratified east to west. We used classification trees to compare species assemblage groups with spatial (elevation, easting, aspect) and edaphic (substrate age, texture, degree slope) variables derived from a 10-m digital elevation model and a digital geological map. Results: The forest line was physiognomically sharp, and a Shipley-Keddy test showed that species distributional limits were aggregated there. Forest line elevation was not consistent, but dropped nearly 200 m from east to west. Indicator taxa for positions above or below the forest line varied from east to west. Hierarchical clustering identified species assemblage groups with significantly different composition that were distributed across the TWI and/or along east-west climate gradients. Classification trees showed that edaphic properties were not well associated with species assemblage groups, but position along two perpendicular climate gradients was. Compositional turnover was detected along both elevational and east-west gradients. Turnover of the cloud forest's epiphytic community was particularly pronounced across east-west gradients. Lichen abundance was significantly higher at the drier end of the east-west moisture gradient, and bryophyte abundance was higher at the wetter end. Main conclusions: Modern spatial patterns suggest that this landscape will respond to changes in moisture balance through changes in species assemblage and structure, especially at the ecotone. Furthermore, ecotone response to climate change may vary from east to west because of differences in species-specific constraints or climatic context. © 2010 Blackwell Publishing Ltd."
"8906055900;56142281300;7201404844;57203939102;36015299300;7405437902;36924657100;57196174591;","Climate response over Asia/Arctic to change in orbital parameters for the last interglacial maximum",2010,"10.1007/s12303-010-0017-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954568362&doi=10.1007%2fs12303-010-0017-1&partnerID=40&md5=5faf3e45a10962eee074612eb1a91621","The climate response over Asia/Arctic to the change in orbital parameters for the last interglacial maximum (LIGM) is investigated using the NCAR CCM3. After implementing LIGM orbital parameters, the insolation decreases in January and increases in July in the northern hemisphere in comparison to present values. The reduced net short-wave radiative heat fluxes in January lead to the surface cooling in low to mid latitudes of Asia, whereas a warming is obtained in northern Asia where the net short-wave radiative heat fluxes change little. The January warming in northern Asia/Arctic in the LIGM, consistent with proxy records, is mainly due to the marked increase in downward long wave heat fluxes associated with the increase in cloud and in part by the increase in the Arctic Oscillation polarity. In July, the increased insolation leads to the surface warming over most Asia, even though a slight cooling is obtained in low latitudes in spite of the increase in insolation, due to the decrease in the short-wave heat fluxes at the surface by the increase in the cloud amount. Precipitation overall increases at South and East Asia in July, due to the stronger southwest and southerly winds. The change in insolation due to the orbital parameters determines the climate change pattern in low- to mid-latitudes over Asia in the LIGM, even though the degree of climate change is much lower than suggested by proxy estimates. The results obtained in this study implies that, under the different climate background such as future global warming, the change in greenhouse effect associated with cloud feedback could play an important role in determining the climate change over Asia/Arctic. © 2010 The Association of Korean Geoscience Societies and Springer-Verlag Berlin Heidelberg."
"6507501796;","Climate variability in the south-eastern tropical Pacific and its relation with ENSO: A GCM study",2010,"10.1007/s00382-009-0602-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952876425&doi=10.1007%2fs00382-009-0602-z&partnerID=40&md5=e5ad9cb15627862c70173bebb434205e","About a third of the El-Niño/Southern Oscillation (ENSO) variability in the HadCM3 coupled general-circulation model is shown to be associated with variability in the south-east tropical Pacific (SETP) area. Sea-surface temperature (SST) anomalies along the east Pacific tend to precede ENSO anomalies. In HadCM3, SST tendencies in the SETP area are controlled mainly by surface latent heat fluxes and short-wave cloud forcing. Interannual SST anomalies in the SETP tend to propagate meridionally. In the winter season (JJA), this is consistent with a wind-evaporation-SST (WES) mode. Coupling with the strato-cumulus cloud (Sc) cover is critical in reducing the evaporative damping of the WES mode, and external forcing is provided by extratropical circulation anomalies. In spring, SETP variability and ENSO are coupled via the low-level circulation, resulting in a mutual reinforcement. Cloud-cover anomalies are not strongly controlled by local SSTs, and appear mainly dependent on atmospheric meridional advection. The apparent association between cold SSTs and Sc cover does not reflect a positive local feedback. These conclusions are not sensitive to the model's warm SST bias, associated with reduced stratocumulus clouds and weak southerly wind stress, which depends on erroneous near-field orographic forcing of the coastal circulation. Some of our results are supported by similar evidence from observational datasets and other CMIP3 models. © 2009 Springer-Verlag."
"36124786200;7004479395;","Analysis of aerosol-cloud interaction from multi-sensor satellite observations",2010,"10.1029/2009GL041828","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953568989&doi=10.1029%2f2009GL041828&partnerID=40&md5=02cf81c1c0ffcada652bb992ec7273d3","Aerosol interaction with clouds is the main uncertainty for the quantification of the anthropogenic forcing on climate. The first step of the so-called ""aerosol indirect effect"" is the change of cloud droplet size distribution when seeded by anthropogenic aerosols. Satellite data provide the density and diversity of observations needed for a statistical estimate of this effect. Numerous such studies have demonstrated the correlation between aerosol load and Cloud Droplet Radius (CDR) and a few have quantified the impact of aerosol on the microphysics. Here, we go one step further by using the profiles from the spaceborne CALIPSO lidar that indicates the respective position of aerosol and cloud layers. The results show that, when aerosol and cloud layers are clearly separated, there is no correlation between aerosol load and CDR. On the other hand, when the lidar profile indicates mixing, there is a strong correlation. We focus on the stratocumulus cloud fields off the coast of Namibia and Angola that are seeded by biomass burning aerosols from Africa. The log-log slope of CDR and a proxy of the condensation nuclei number are-0.24 in excellent agreement with theoretical estimate. When the vertical profile information is not used, the slope is significantly smaller. Copyright © 2010 by the American Geophysical Union."
"57197802873;","Compensation between model feedbacks and curtailment of climate sensitivity",2010,"10.1175/2010JCLI3380.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954367350&doi=10.1175%2f2010JCLI3380.1&partnerID=40&md5=3ae9269477a8bded77f546d0c460a9c3","The spread in climate sensitivity obtained from 12 general circulation model runs used in the Fourth Assessment of the Intergovernmental Panel on Climate Change indicates a 95% confidence interval of 2.1°-5.5°C, but this reflects compensation between model feedbacks. In particular, cloud feedback strength negatively covaries with the albedo feedback as well as with the combined water vapor plus lapse rate feedback. If the compensation between feedbacks is removed, the 95% confidence interval for climate sensitivity expands to 1.9°-8.0°C. Neither of the quoted 95% intervals adequately reflects the understanding of climate sensitivity, but their differences illustrate that model interdependencies must be understood before model spread can be correctly interpreted. The degree of negative covariance between feedbacks is unlikely to result from chance alone. It may, however, result from the method by which the feedbacks were estimated, physical relationships represented in the models, or from conditioning the models upon some combination of observations and expectations. This compensation between model feedbacks-when taken together with indications that variations in radiative forcing and the rate of ocean heat uptake play a similar compensatory role in models-suggests that conditioning of the models acts to curtail the intermodel spread in climate sensitivity. Observations used to condition the models ought to be explicitly stated, or there is the risk of doubly calling on data for purposes of both calibration and evaluation. Conditioning the models upon individual expectation (e.g., anchoring to the Charney range of 3° ± 1.5°C), to the extent that it exists, greatly complicates statistical interpretation of the intermodel spread. © 2010 American Meteorological Society."
"57208147276;7005920767;7402689885;7005143387;","In-cloud and below-cloud scavenging of aerosol ionic species over a tropical rural atmosphere in India",2010,"10.1007/s10874-011-9190-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052619656&doi=10.1007%2fs10874-011-9190-5&partnerID=40&md5=c7b622983893c2ea09da7ba933f2748b","The temporal variation in concentrations of major water soluble ionic species has been studied from several rain events occurred over Gadanki (13.5 °N, 79.2 °E), located in tropical semi arid region in southern India. The contribution from rain-out (in cloud) and wash-out (below cloud) processes to the total removal of ionic species by rain events is also estimated using the pattern of variations of ionic species within an individual event. A number of rain samples were collected from each rain event during June-November in 2006, 2007 and 2008. On average, nearly 20% of the total NH 4 + and non-sea SO 4 2- is removed by in-cloud scavenging, suggesting that their removal by ""below cloud"" washout is relatively dominant. In contrast Na +, Ca 2+, Mg 2+, NO 3 - and sea-SO 4 2- are mainly removed by below-cloud scavenging or wash-out process. A significant variation in the acidity was observed within rain events with successive precipitation showing higher acidity at the final stage of the precipitation due to partial neutralization of non-sea SO 4 2- . Overall, greater influence of both terrestrial and anthropogenic sources is recorded in the rain events compared to that from marine sources. © 2011 Springer Science+Business Media B.V."
"57212781009;7101785401;","Atmospheric radiative feedbacks associated with transient climate change and climate variability",2010,"10.1007/s00382-009-0541-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952876531&doi=10.1007%2fs00382-009-0541-8&partnerID=40&md5=106edc392bbad1a1b53845613d64d67f","This study examines in detail the 'atmospheric' radiative feedbacks operating in a coupled General Circulation Model (GCM). These feedbacks (defined as the change in top of atmosphere radiation per degree of global surface temperature change) are due to responses in water vapour, lapse rate, clouds and surface albedo. Two types of radiative feedback in particular are considered: those arising from century scale 'transient' warming (from a 1% per annum compounded CO2 increase), and those operating under the model's own unforced 'natural' variability. The time evolution of the transient (or 'secular') feedbacks is first examined. It is found that both the global strength and the latitudinal distributions of these feedbacks are established within the first two or three decades of warming, and thereafter change relatively little out to 100 years. They also closely approximate those found under equilibrium warming from a 'mixed layer' ocean version of the same model forced by a doubling of CO2. These secular feedbacks are then compared with those operating under unforced (interannual) variability. For water vapour, the interannual feedback is only around two-thirds the strength of the secular feedback. The pattern reveals widespread regions of negative feedback in the interannual case, in turn resulting from patterns of circulation change and regions of decreasing as well as increasing surface temperature. Considering the vertical structure of the two, it is found that although positive net mid to upper tropospheric contributions dominate both, they are weaker (and occur lower) under interannual variability than under secular change and are more narrowly confined to the tropics. Lapse rate feedback from variability shows weak negative feedback over low latitudes combined with strong positive feedback in mid-to-high latitudes resulting in no net global feedback-in contrast to the dominant negative low to mid-latitude response seen under secular climate change. Surface albedo feedback is, however, slightly stronger under interannual variability-partly due to regions of extremely weak, or even negative, feedback over Antarctic sea ice in the transient experiment. Both long and shortwave global cloud feedbacks are essentially zero on interannual timescales, with the shortwave term also being very weak under climate change, although cloud fraction and optical property components show correlation with global temperature both under interannual variability and transient climate change. The results of this modelling study, although for a single model only, suggest that the analogues provided by interannual variability may provide some useful pointers to some aspects of climate change feedback strength, particularly for water vapour and surface albedo, but that structural differences will need to be heeded in such an analysis. © 2009 Springer-Verlag."
"7004469744;8942525300;24463029300;","From the sea to the sky",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649790749&partnerID=40&md5=f3d3d68884ec5d98fff4aa80335c12cc","Ken Carslaw and colleagues from the Institute for Climate and Atmospheric Science in Leeds set out to test the 23-year old CLAW hypothesis, coming up with some surprising results. If one wanted to identify one theory that launched Earth system science as a major subject of the 21st century it would be CLAW. The hypothesis takes its name from Charlson, Lovelock (of Gaia fame), Andreae and Warren, whose 1987 paper suggested that phytoplankton could help regulate Earth's climate. Phytoplankton - single-celled algae - emit a gas called dimethylsulphide (DMS) and the authors suggested that DMS forms tiny new particles in the atmosphere which controls climate by affecting the amount of sunlight reflected by clouds. They used a new and advanced global model of aerosols. A bit like a weather forecast model, it uses rapidly changing weather patterns to transport aerosols around the world until they are removed by rain after sometime."
"22935251000;7402305181;23028121100;6701410329;","A method for estimating the sampling error applied to cm-saf monthly mean cloud fractional cover data retrieved from msg seviri",2010,"10.1109/TGRS.2010.2041240","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952585938&doi=10.1109%2fTGRS.2010.2041240&partnerID=40&md5=8d08d57b739633c10adb58fc1195ddaa","Averaging a set of individual measurements can reduce the stochastic error but can introduce a sampling error particularly for irregularly sampled data. We present a general method to estimate the total error of an averaged quantity as a combination of the measurement error and the sampling error without knowledge about the true average value of the distribution. Our approach requires covariance matrices connecting the retrieved measurement values to an independent reference data set. These covariance matrices can be obtained from a representative validation data set. We confirm the validity of the method by estimating the temporal sampling error of monthly mean cloud fractional cover (CFC) data derived from the Spinning-Enhanced Visible and Infrared Imager radiometer onboard the METEOSAT Second Generation (MSG) spacecraft, operated by the European Organization for the Exploitation of Meteorological Satellites. The estimated sampling errors are then compared with the true sampling errors calculated from an hourly sampled complete data set. For this purpose, we use ten sampling scenarios. Some of them address typical sampling problems like systematic over- and undersampling as well as hourly, daily, and random data gaps. Two additional sampling scenarios are directly related to the satellite application facility on climate monitoring monthly mean CFC data record. These are used to estimate the worst case sampling errors of this data record. The estimated total and sampling errors agree well with corresponding calculated values. We derive the needed covariance matrices by analyzing synoptic observations of the cloud fraction which are MSG diskwide available, the majority of them over European land surfaces. The method is not limited to temporal averaging cloud fraction data. Moreover, it is a general method that is also applicable to temporal and spatial averaging of other parameters as long as appropriate covariance matrices are available. © 2006 IEEE."
"24528108000;35547807400;","An empirical study of geographic and seasonal variations in diurnal temperature range",2010,"10.1175/2010JCLI3215.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955486567&doi=10.1175%2f2010JCLI3215.1&partnerID=40&md5=8e9e71823703a7489b562df33e7b7494","The diurnal temperature range (DTR) of surface air over land varies geographically and seasonally. The authors have investigated these variations using generalized additive models (GAMs), a nonlinear regression methodology. With DTR as the response variable, meteorological and land surface parameters were treated as explanatory variables. Regression curves related the deviation of DTR from its mean value to values of the meteorological and land surface variables. Cloud cover, soil moisture, distance inland, solar radiation, and elevation were combined as explanatory variables in an ensemble of 84 GAM models that used data grouped into seven vegetation types and 12 months. The ensemble explained 80% of the geographical and seasonal variation in DTR. Vegetation type and cloud cover exhibited the strongest relationships with DTR. Shortwave radiation, distance inland, and elevation were positively correlated with DTR, whereas cloud cover and soil moisture were negatively correlated. A separate analysis of the surface energy budget showed that changes in net longwave radiation represented the effects of solar and hydrological variation on DTR. It is found that vegetation and its associated climate is important for DTR variation in addition to the climatic influence of cloud cover, soil moisture, and solar radiation. It is also found that surface net longwave radiation is a powerful diagnostic of DTR variation, explaining over 95% of the seasonal variation of DTR in tropical regions. © 2010 American Meteorological Society."
"7004862277;55729666100;7004462227;8899985400;7007160874;","Heterogeneous nucleation of ice on anthropogenic organic particles collected in Mexico City",2010,"10.1029/2010GL043362","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953608075&doi=10.1029%2f2010GL043362&partnerID=40&md5=457527c7e5352404e9a53c5c2af33e69","This study reports on heterogeneous ice nucleation activity of predominantly organic (or coated with organic material) anthropogenic particles sampled within and around the polluted environment of Mexico City. The onset of heterogeneous ice nucleation was observed as a function of particle temperature (Tp), relative humidity (RH), nucleation mode, and particle chemical composition which is influenced by photochemical atmospheric aging. Particle analyses included computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). In contrast to most laboratory studies employing proxies of organic aerosol, we show that anthropogenic organic particles collected in Mexico City can potentially induce ice nucleation at experimental conditions relevant to cirrus formation. The results suggest a new precedent for the potential impact of organic particles on ice cloud formation and climate. Copyright © 2010 by the American Geophysical Union."
"6603680545;6603752490;36144476800;36144101000;","Modeling the variability of gas and aerosol components in the stratosphere of polar regions",2010,"10.1134/S0001433810030011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954041742&doi=10.1134%2fS0001433810030011&partnerID=40&md5=f6335aa3367bf1586ddb290d77f65ca3","A thermodynamics-microphysics model of the formation and evolution of stratospheric clouds is developed. This model was integrated into the global chemistry-climate model of the lower and middle atmosphere. Model experiments on the study of the evolution of the gas and aerosol compositions of the Arctic and Antarctic atmosphere were performed. The results of an investigation into the observed differences of changes in the contents of gaseous impurities and aerosol in polar regions showed that the presence of nitrification in the Antarctic and its absence in the Arctic are the main factors controlling distinctions between the formation of a full-value ozone hole in the Antarctic and only occasional ""mini-holes"" in the Arctic. © 2010 Pleiades Publishing, Ltd."
"8849029800;57192534657;57034458200;","An examination of the pressure-wind relationship for intense tropical cyclones",2010,"10.1175/2010WAF2222344.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955566185&doi=10.1175%2f2010WAF2222344.1&partnerID=40&md5=62bda42c068761f861ca73d93141e984","In this study, the dynamical constraints underlining the pressure-wind relationship (PWR) for intense tropical cyclones (TCs) are examined with the particular focus on the physical connections between the maximum surface wind (VMAX) and the minimum sea level pressure (PMIN). Use of the Rankine vortex demonstrates that the frictional forcing in the planetary boundary layer (PBL) could explain a sizeable portion of the linear contributions of VMAX to pressure drops. This contribution becomes increasingly important for intense TCs with small eye sizes, in which the radial inflows in the PBL could no longer be neglected. Furthermore, the inclusion of the tangential wind tendency can make an additional contribution to the pressure drops when coupled with the surface friction. An examination of the double-eyewall configuration reveals that the formation of an outer eyewall or well-organized spiral rainbands complicates the PWR. An analysis of a cloud-resolving simulation of Hurricane Wilma (2005) shows that the outer eyewall could result in the continuous deepening of PMIN even with a constant VMAX. The results presented here suggest that (i) the TC size should be coupled with VMAX rather than being treated as an independent predictor as in the current PWRs, (ii) the TC intensity change should be at least coupled linearly with the radius of VMAX, and (iii) the radial wind in the PBL is of equal importance to the linear contribution of VMAX and its impact should be included in the PWR. © 2010 American Meteorological Society."
"6603452105;6701796926;7201689616;","Climate trends at Eureka in the Canadian high arctic",2010,"10.3137/AO1103.2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953815877&doi=10.3137%2fAO1103.2010&partnerID=40&md5=a212d3b673c3cdcbd8f7320168c1be2e","Weather observations made at Eureka, on Ellesmere Island in the Canadian High Arctic, have been archived since 1953. The time series, averages, and seasonal cycles of surface temperature, pressure, dew point, relative humidity, cloud cover, wind speed, and direction are presented for the period from 1954 to 2007. Also shown are the time series and averages for the 500 mb temperature, 900 to 500 mb thickness, 500 mb wind speed, and various boundary-layer stability parameters. Some of the main trends found are 1) an annual average surface warming of 3.2°C since 1972, with summer exhibiting the least warming, 2) a reduction in the frequency of strong anticyclonic events in the winter, 3) a reduction in surface wind speeds except in the summer, 4) a 1.0°C warming in the 500 mb temperature since 1961, with the greatest warming occurring in the spring and summer, and 5) a 10% increase in precipitable water all year round since 1961 but dominated by the spring, summer, and autumn seasons. The importance of open water in the Arctic Ocean for summer temperatures and humidity, of the North Atlantic Oscillation for winter interannual pressure variability, and of precipitable water for winter temperatures are highlighted in this climatology.[Traduit par la rédaction] Les observations météorologiques faites à Eureka, sur l'île Ellesmere, dans l'Arctique canadien septentrional, ont été archivées depuis 1953. Nous présentons les séries chronologiques, les moyennes et les cycles saisonniers de la température de surface, de la pression, du point de rosée, de l'humidité relative, de la couverture nuageuse ainsi que de la vitesse et de la direction du vent pour la période allant de 1954 à 2007. Nous présentons également les séries chronologiques et les moyennes pour la température à 500 mb, l'épaisseur 900-500 mb, la vitesse moyenne du vent à 500 mb et divers paramètres de stabilité dans la couche limite. Certaines des principales tendances que nous trouvons sont 1) un réchauffement annuel moyen à la surface de 3,2°C depuis 1972, l'été étant le moment du plus faible réchauffement; 2) une réduction de la fréquence des forts événements anticycloniques en hiver; 3) une réduction de la vitesse moyenne des vents de surface, sauf en été; 4) une augmentation de 1,0°C de la température à 500 mb depuis 1961, le réchauffement le plus marqué se produisant au printemps et à l'été; et 5) une augmentation de 10 % de l'eau précipitable toute l'année depuis 1961 mais plus particulièrement au printemps, à l'été et à l'automne. Cette climatologie met en évidence le rôle important de l'eau libre dans l'océan Arctique relativement aux températures et à l'humidité en été, de l'oscillation Nord-Atlantique relativement à la variabilité interannuelle de la pression ainsi que de l'eau précipitable relativement aux températures en hiver."
"7402859325;","Direct radiative effect of aerosols over East Asia with a Regional coupled Climate/Chemistry model",2010,"10.1127/0941-2948/2010/0461","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955621865&doi=10.1127%2f0941-2948%2f2010%2f0461&partnerID=40&md5=fc787b0ae2907877be42e79a3bf9dfc2","Tropospheric chemistry and aerosol processes have recently been incorporated into a Regional Integrated Environmental Model System (RIEMS) to study direct radiative effect of aerosols (DRE) over East Asia where intense human activity and continuous economic growth occur. Five aerosol components (sulfate, black carbon, organic carbon, soil dust and sea salt) and their relevant processes affecting distribution (emission, transport, diffusion, deposition, chemistry etc.) are added into RIEMS, with gas phase chemistry represented by CB-IV mechanism. The study periods areMarch, July, October and December 2006, generally representing 4 typical seasons in East Asia. The modeled monthly average aerosol optical depth (AOD) is generally consistent with MISR retrievals, although the model tends to underpredict AOD in some regions. The AOD distribution was characterized by high values in eastern China and deserts of western China, and AOD in winter is apparently lower than that in other seasons. The DRE show apparent seasonal variation, with maximum surface cooling in March and minimum surface cooling in winter, but maximum Top Of the Atmosphere (TOA) cooling in July and minimum TOA cooling in winter. The light TOA heating in March under all-sky condition is due to both the abundant absorbing aerosol and the enhanced heating effect by cloud. The DRE averaged over the study domain and the four periods under all-sky condition are -6.2 W m-2 at the surface and -0.2 W m-2 at TOA, respectively, over East Asia. © Gebrüder Borntraeger, Stuttgart 2010."
"55984424900;7005601996;35228452800;35305158900;21834810800;16233296800;7006354036;7003658685;57208464149;31267503200;7004399781;24484158900;9271096600;7003603120;7004015298;","Chemical composition of PM10 and PM1 at the high-altitude Himalayan station Nepal Climate Observatory-Pyramid (NCO-P) (5079 m a.s.l.)",2010,"10.5194/acp-10-4583-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952504037&doi=10.5194%2facp-10-4583-2010&partnerID=40&md5=4617922fef2b3d5046f80eb560f1f4a7","We report chemical composition data for PM10 and PM1 from the Nepal Climate Observatory-Pyramid (NCO-P), the world's highest aerosol observatory, located at 5079 m a.s.l. at the foothills of Mt. Everest. Despite its high altitude, the average PM10 mass apportioned by the chemical analyses is of the order of 6 μgm-3 (i.e., 10 μg/scm), with almost a half of this mass accounted for by organic matter, elemental carbon (EC) and inorganic ions, the rest being mineral dust. Organic matter, in particular, accounted for by 2.0 μg m-3 (i.e., 3.6 μg/scm) on a yearly basis, and it is by far the major PM10 component beside mineral oxides. Non-negligible concentrations of EC were also observed (0.36 μg/scm), confirming that light-absorbing aerosol produced from combustion sources can be efficiently transported up the altitudes of Himalayan glaciers. The concentrations of carbonaceous and ionic aerosols follow a common time trend with a maximum in the premonsoon season, a minimum during the monsoon and a slow recovery during the postmonsoon and dry seasons, which is the same phenomenology observed for other Nepalese Himalayan sites in previous studies. Such seasonal cycle can be explained by the seasonal variations of dry and moist convection and of wet scavenging processes characterizing the climate of north Indian subcontinent. We document the effect of orographic transport of carbonaceous and sulphate particles upslope the Himalayas, showing that the valley breeze circulation, which is almost permanently active during the out-of-monsoon season, greatly impacts the chemical composition of PM10 and PM1 in the high Himalayas and provides an efficient mechanism for bringing anthropogenic aerosols into the Asian upper troposphere (&gt;5000 m a.s.l.). The concentrations of mineral dust are impacted to a smaller extent by valley breezes and follow a unique seasonal cycle which suggest multiple source areas in central and south-west Asia. Our findings, based on two years of observations of the aerosol chemical composition, provide clear evidence that the southern side of the high Himalayas is impacted by transport of anthropogenic aerosols which constitute the Asian brown cloud. © 2010 Author(s)."
"55723070100;56158622800;7006783796;7407116104;8833356300;7406683894;56707735900;35239166400;","Detection of dust aerosol by combining CALIPSO active lidar and passive IIR measurements",2010,"10.5194/acp-10-4241-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952193737&doi=10.5194%2facp-10-4241-2010&partnerID=40&md5=3d2c66de736989ada017c7dff727be15","The version 2 Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) dust layer detection method, which is based only on lidar measurements, misclassified about 43% dust layers (mainly dense dust layers) as cloud layers over the Taklamakan Desert. To address this problem, a new method was developed by combining the CALIPSO Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and passive Infrared Imaging Radiometer (IIR) measurements. This combined lidar and IR measurement (hereafter, CLIM) method uses the IIR tri-spectral IR brightness temperatures to discriminate between ice cloud and dense dust layers, and lidar measurements alone to detect thin dust and water cloud layers. The brightness temperature difference between 10.60 and 12.05 &mu;m (BTD11&minus;12) is typically negative for dense dust and generally positive for ice cloud, but it varies from negative to positive for thin dust layers, which the CALIPSO lidar correctly identifies. Results show that the CLIM method could significantly reduce misclassification rates to as low as ∼7% for the active dust season of spring 2008 over the Taklamakan Desert. The CLIM method also revealed 18% more dust layers having greatly intensified backscatter between 1.8 and 4 km altitude over the source region compared to the CALIPSO version 2 data. These results allow a more accurate assessment of the effect of dust on climate. © Author(s) 2010."
"7003806719;6602082604;7003629951;","Vegetation response to the ""african Humid Period"" termination in Central Cameroon (7° N)- new pollen insight from Lake Mbalang",2010,"10.5194/cp-6-281-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952031074&doi=10.5194%2fcp-6-281-2010&partnerID=40&md5=a2ae5b0035d1cf590c36c654004ca534","A new pollen sequence from the Lake Mbalang (7°19́ N, 13°44́ E, 1110 m a.s.l.) located on the eastern Adamawa plateau, in Central Cameroon, is presented in this paper to analyze the Holocene African Humid Period (AHP) termination and related vegetation changes at 7° N in tropical Africa, completing an important transect for exploring shifts in the northern margin of the African Monsoon. This sequence, spanning the last 7000 cal yr BP, shows that the vegetation response to this transitional climatic period was marked by significant successional changes within the broad context of long-term aridification. Semi-deciduous/sub-montane forest retreat in this area is initially registered as early as ca. 6100 cal yr BP and modern savannah was definitely established at ca. 3000 cal yr BP and stabilized at ca. 2400 cal yr BP; but a slight forest regeneration episode is observed between ca. 5200 and ca. 4200 cal yr BP. In this area with modern high rainfall, increasing in the length of the dry season during the AHP termination linked to a contraction of the northern margin of the Intertropical Convergence Zone (ITCZ) from ca. 6100 cal yr BP onward, probably associated with decreasing in cloud cover and/or fog frequency, has primarily controlled vegetation dynamics and above all the disappearance of the forested environment on the Adamawa plateau. Compared to previous studies undertaken in northern tropical and Central Africa, this work clearly shows that the response of vegetation to transitional periods between climatic extremes such as the AHP termination might be different in timing, mode and amplitude according to the regional climate of the study sites, but also according to the stability of vegetation before and during these climatic transitions. © Author(s) 2010."
"35254201000;7202048112;55802246600;57207969036;","Regional climate model projections for the State of Washington",2010,"10.1007/s10584-010-9849-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957189293&doi=10.1007%2fs10584-010-9849-y&partnerID=40&md5=da558b894722e16de41f17ab550f4777","Global climate models do not have sufficient spatial resolution to represent the atmospheric and land surface processes that determine the unique regional climate of the State of Washington. Regional climate models explicitly simulate the interactions between the large-scale weather patterns simulated by a global model and the local terrain. We have performed two 100-year regional climate simulations using the Weather Research and Forecasting (WRF) model developed at the National Center for Atmospheric Research (NCAR). One simulation is forced by the NCAR Community Climate System Model version 3 (CCSM3) and the second is forced by a simulation of the Max Plank Institute, Hamburg, global model (ECHAM5). The mesoscale simulations produce regional changes in snow cover, cloudiness, and circulation patterns associated with interactions between the large-scale climate change and the regional topography and land-water contrasts. These changes substantially alter the temperature and precipitation trends over the region relative to the global model result or statistical downscaling. To illustrate this effect, we analyze the changes from the current climate (1970-1999) to the mid twenty-first century (2030-2059). Changes in seasonal-mean temperature, precipitation, and snowpack are presented. Several climatological indices of extreme daily weather are also presented: precipitation intensity, fraction of precipitation occurring in extreme daily events, heat wave frequency, growing season length, and frequency of warm nights. Despite somewhat different changes in seasonal precipitation and temperature from the two regional simulations, consistent results for changes in snowpack and extreme precipitation are found in both simulations. © 2010 Springer Science+Business Media B.V."
"9249605700;","Dependence of the precipitation intensity in mesoscale convective systems to temperature lapse rate",2010,"10.1016/j.atmosres.2009.09.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952320973&doi=10.1016%2fj.atmosres.2009.09.002&partnerID=40&md5=c132c9ed19e5b692947020fd7e65f92e","The dependence of the structure and intensity of precipitation generated within squall lines to environmental temperature lapse rate is investigated by the use of a large set of numerical experiments under idealized model configurations. The lapse rate in a convectively unstable layer is used for the present analysis. The mean precipitation intensity during the simulated period generally increases with the increase in lapse rate, while the maximum precipitation intensity increases with the decrease in lapse rate. The precipitation mean is dependent on the intensity of cold pool resulting from organized convective clouds. In contrast, the precipitation maxima is regulated by relative humidity within the tropospheric lower layer. In an environment with higher lapse rate, a larger amount of CAPE is distributed in a deeper layer of the lower troposphere, which is beneficial for the development and intensification of convection and precipitation. Lapse rate in the troposphere is useful in comparing the characteristics of precipitation produced by mesoscale convective systems that occur in various climate regions of the world and also produced in a future climate under global warming. © 2009 Elsevier B.V."
"36059595100;7405763496;","Development of an effective double-moment cloud microphysics scheme with prognostic cloud condensation nuclei (CCN) for weather and climate models",2010,"10.1175/2009MWR2968.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955579497&doi=10.1175%2f2009MWR2968.1&partnerID=40&md5=7a14ec64387c02fb8f5d0986e1985342","A new double-moment bulk cloud microphysics scheme, the Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) Microphysics scheme, which is based on the WRF Single-Moment 6-class (WSM6) Microphysics scheme, has been developed. In addition to the prediction for the mixing ratios of six water species (water vapor, cloud droplets, cloud ice, snow, rain, and graupel) in the WSM6 scheme, the number concentrations for cloud and rainwater are also predicted in the WDM6 scheme, together with a prognostic variable of cloud condensation nuclei (CCN) number concentration. The new scheme was evaluated on an idealized 2D thunderstorm test bed. Compared to the simulations from the WSM6 scheme, there are greater differences in the droplet concentration between the convective core and stratiform region in WDM6. The reduction of light precipitation and the increase of moderate precipitation accompanying a marked radar bright band near the freezing level from the WDM6 simulation tend to alleviate existing systematic biases in the case of the WSM6 scheme. The strength of this new microphysics scheme is its ability to allow flexibility in variable raindrop size distribution by predicting the number concentrations of clouds and rain, coupled with the explicit CCN distribution, at a reasonable computational cost. © 2010 American Meteorological Society."
"6701448397;","Days with thunderstorms, tornadoes and funnel clouds in Poland in 2009",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955221068&partnerID=40&md5=b56301a8eaf88d75775d986f16d69a15","This report represents an analysis of the occurrence of days with thunderstorms and tornadoes in Poland in 2009. The number of days with thunderstorms was analysed with respect to their frequency in individual months, seasons of the year and the year as a whole and compared to the corresponding average values from the period between the years 1951-2009. Occurrences of tornadoes in 2009 were analysed taking into account their intensity and the resulting material damage, followed by a description of the accompanying weather conditions. © THE INTERNATIONAL JOURNAL OF METEOROLOGY."
"23106262500;","Ua 'afa le Aso Stormy weather today: Traditional ecological knowledge of weather and climate. The Samoa experience",2010,"10.1007/s10584-009-9722-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952673270&doi=10.1007%2fs10584-009-9722-z&partnerID=40&md5=e6b179b47076de2705df2ca2e6a694b5","This paper examines traditional ecological knowledge of weather and climate in Samoa, a Polynesian community in the South Pacific. The research found Samoans have their own unique seasonal calendar. The Samoan seasonal calendar is predominantly based on the observations of local environmental changes, which are in turn influenced by weather and climate. Monitoring changes in plants and animal behaviour, for example, are key indicators used by the Samoans to forecast changes in weather and climate. In addition, their communal and family social activities like hunting, fishing and feasting are driven by the seasonal calendar. The Samoans knowledge of cloud formation, conditions conducive to the formation and onset of severe weather systems and seasonal changes in climate, helped them anticipate, plan and adapt to extreme weather and climate events. The ability and knowledge of the Samoans to forecast the onset of extreme weather and climate events, relying predominantly on local environmental changes are vital tools that should be incorporated in the formulation of human induced climate change adaptation strategies. © 2009 The Author(s)."
"55716092000;55588510300;57211106013;6701378450;57196499374;","Will black carbon mitigation dampen aerosol indirect forcing?",2010,"10.1029/2010GL042886","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952187225&doi=10.1029%2f2010GL042886&partnerID=40&md5=58e32b104b0c4d8852f6315d73e921a6","If mitigation of black carbon (BC) particulate matter is accompanied by a decrease in particle number emissions, and thereby by a decrease in global cloud condensation nuclei (CCN) concentrations, a decrease in global cloud radiative forcing (a reverse-gcloud albedo effect-h) results. We consider two present-day mitigation scenarios: 50% reduction of primary black carbon/organic carbon (BC/OC) mass and number emissions from fossil fuel combustion (termed HF), and 50% reduction of primary BC/OC mass and number emissions from all primary carbonaceous sources (fossil fuel, domestic biofuel, and biomass burning) (termed HC). Radiative forcing effects of these scenarios are assessed through present-day equilibrium climate simulations. Global average top-of-the- atmosphere changes in radiative forcing for the two scenarios, relative to present day conditions, are +0.13-2 0.33 W m.2 (HF) and + 0.31 ±0.33 W m.-2 (HC). Copyright © 2010 by the American Geophysical Union."
"24329545900;7004154626;24757696000;","Aerosol indirect effect during successive contrasting monsoon seasons over Indian subcontinent using MODIS data",2010,"10.1016/j.atmosenv.2010.02.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951091554&doi=10.1016%2fj.atmosenv.2010.02.015&partnerID=40&md5=2ca20b1e93c5a1e799ee0a960f00bbba","Aerosol indirect effect (AIE) was estimated over six Indian regions, which have been identified as main source regions of absorbing aerosol emissions, for four successive contrasting monsoon years, 2001 (normal monsoon rainfall year), 2002 (drought year), 2003 (excess monsoon rainfall year) and 2004 (below normal rainfall year). The AIE has been estimated both for fixed cloud liquid water path (CLWP) and for fixed cloud ice path (CIP) bins, ranging from 1 to 350 gm-2 at 25 gm-2 intervals obtained from Moderate resolution imaging spectroradiometer (MODIS). In 2002 and 2004, AIE found to be of positive (Twomey effect) in majority of the fixed CLWP and CIP bins, while in 2001 and 2003 majority of the bins were found to be showing negative indirect effect (Anti-Twomey effect). Changes in circulation patterns during contrasting monsoon seasons, bringing up air mass containing aerosols of different source origins may be the main reason for this positive and negative AIE. The study suggests that AIE could be one of the factors in modulating Indian summer monsoon. However, further research on this topic is to be carried out to establish the relationship between AIE and Indian monsoon rainfall and also AIE values may be parameterized in climate models for better prediction of monsoon. © 2010 Elsevier Ltd."
"6506917847;57217497474;7005297975;7402105994;35755882100;26664554200;57200275591;7405666962;14034142600;55722586400;35569458500;35757000000;57204987677;","An assessment of the impact of climate change on air quality at two UK sites",2010,"10.1016/j.atmosenv.2010.02.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950933513&doi=10.1016%2fj.atmosenv.2010.02.024&partnerID=40&md5=41961541d6ac54de8b1d33124630ac83","Possible effects of climate change on air quality are studied for two urban sites in the UK, London and Glasgow. Hourly meteorological data were obtained from climate simulations for two periods representing the current climate and a plausible late 21st century climate. Of the meteorological quantities relevant to air quality, significant changes were found in temperature, specific humidity, wind speed, wind direction, cloud cover, solar radiation, surface sensible heat flux and precipitation. Using these data, dispersion estimates were made for a variety of single sources and some significant changes in environmental impact were found in the future climate. In addition, estimates for future background concentrations of NOx, NO2, ozone and PM10 upwind of London and Glasgow were made using the meteorological data in a statistical model. These showed falls in NOx and increases in ozone for London, while a fall in NO2 was the largest percentage change for Glasgow. Other changes were small. With these background estimates, annual-average concentrations of NOx, NO2, ozone and PM10 were estimated within the two urban areas. For London, results averaged over a number of sites showed a fall in NOx and a rise in ozone, but only small changes in NO2 and PM10. For Glasgow, the changes in all four chemical species were small. Large-scale background ozone values from a global chemical transport model are also presented. These show a decrease in background ozone due to climate change. To assess the net impact of both large scale and local processes will require models which treat all relevant scales. © 2010."
"11940789000;7004134577;7005830548;56853406500;","The ocean-land-atmosphere model: Optimization and evaluation of simulated radiative fluxes and precipitation",2010,"10.1175/2009MWR3131.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955582921&doi=10.1175%2f2009MWR3131.1&partnerID=40&md5=473c7878ed6ba1ab5d6631158dea11c3","This work continues the presentation and evaluation of the Ocean-Land-Atmosphere Model (OLAM), focusing on the model's ability to represent radiation and precipitation. OLAM is a new, state-of-the-art earth system model, capable of user-specified grid resolution and local mesh refinement. An objective optimization of the microphysics parameterization is carried out. Data products from the Clouds and the Earth's Radiant Energy System (CERES) and the Global Precipitation Climatology Project (GPCP) are used to construct a maximum likelihood function, and thousands of simulations using different values for key parameters are carried out. Shortwave fluxes are found to be highly sensitive to both the density of cloud droplets and the assumed shape of the cloud droplet diameter distribution function. Because there is considerable uncertainty in which values for these parameters to use in climate models, they are targeted as the tunable parameters of the objective optimization procedure, which identified high-likelihood volumes of parameter space as well as parameter uncertainties and covariances. Once optimized, the model closely matches observed large-scale radiative fluxes and precipitation. The impact of model resolution is also tested. At finer characteristic length scales (CLS), smaller-scale features such as the ITCZ are better resolved. It is also found that the Amazon was much better simulated at 100- than 200-km CLS. Furthermore, a simulation using OLAM's variable resolution functionality to cover South America with 100-km CLS and the rest of the world with 200-km CLS generates a precipitation pattern in the Amazon similar to the global 100-km CLS run. © 2010 American Meteorological Society."
"7801450226;6507121473;8701353900;6603340224;","Simulations of a hailstorm and the impact of CCN using an advanced two-moment cloud microphysical scheme",2010,"10.1016/j.atmosres.2009.09.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952321304&doi=10.1016%2fj.atmosres.2009.09.008&partnerID=40&md5=c32f860f79ad09b2903e09bc3c7dc95b","A hailstorm that caused significant damage in South-West Germany was simulated with the numerical weather prediction model COSMO. To cover hail evolution a sophisticated two-moment cloud microphysical scheme was extended by a particle class representing hail and implemented into COSMO. The horizontal resolution was 1. km. For initialization and boundary values COSMO forecasts with a coarser resolution and the standard one-moment microphysical scheme were used. Running this model system several convective cells develop including a severe hailstorm that resembles the observations qualitatively well and produces realistic amounts of precipitation and hail at the ground. Sensitivity studies were conducted varying the concentration of cloud condensation nuclei (CCN) and the shape of the cloud droplet size distribution (CDSD). Results show that both have a significant impact on hail accumulated at the ground and on the size of the hailstones. For two of the three CDSDs assumed the intensity of the severe storm decreases with increasing CCN concentration. However, this is not true for some of the weaker storms that form as well as for the third CDSD. Two model runs are analyzed and compared in more detail revealing the strong coupling between the numerous microphysical processes and between microphysics and dynamics. The sensitivity studies illustrate that the complexity of such storms makes it difficult to foresee, what will happen, when one microphysical parameter is changed. Thus, general conclusions whether an increase or decrease in CCN concentration invigorates a hailstorm cannot be drawn. © 2009 Elsevier B.V."
"55231686100;7005206687;7003429458;57203362490;","Investigation into clouds and precipitation over an urban area using micro rain radars, satellite remote sensing and fluorescence spectrophotometry",2010,"10.1016/j.atmosres.2009.08.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952323628&doi=10.1016%2fj.atmosres.2009.08.003&partnerID=40&md5=d56e021bbf3f3b940c674aca642c373a","The observation and modeling of the indirect effects of aerosols on clouds remain an enormous challenge. Aerosols have a significant yet complicated impact on the precipitation processes. They can either enhance or suppress precipitation depending upon type of aerosol, seasonality, climate regime, cloud type or orographic profile of a region, particularly over populated areas. In order to observe and examine both cloud and precipitation processes, a combination of both satellite and ground-based remote sensing techniques can be employed. This paper presents the results from three years of data collection in Birmingham, United Kingdom. It describes and explains the application of a range of complimentary techniques: fluorescence spectrophotometry to examine dissolved organic carbon compounds in rainwater samples; satellite analysis tools are used to assess cloud-top microphysics; and an array of vertically-pointing micro-rain radars (MRRs) are used to assess variations in drop size distribution (DSD) for categorized events. Events are classified as microphysically 'maritime' or 'continental', showing that full development of the ice phase was reached at relatively warm temperatures for microphysically 'maritime' events, but at colder temperatures for microphysically 'continental' events. The importance of updrafts in severe thunderstorms and tornadic events is highlighted. High rainwater content of tyrosine-like substances (TYLIS) and tryptophan-like substances (TRYLIS) is found to be associated mainly with microphysically 'maritime' events, providing evidence for these substances acting as ice nuclei at relatively warm temperatures. High rainwater content of humic-like substances (HULIS) is associated with both microphysically 'maritime' and 'continental' events due to the complexity of such substances. As might be expected, continentally-sourced events had a similar structure to microphysically 'continental' events, whereas maritime-sourced events differed in their microphysical structure, indicating the local impacts on their microstructure. The DSD appears to vary between different events - for example, continentally-sourced, microphysically 'continental', convective events with low rainwater TRYLIS have a DSD containing fewer smaller droplets, whereas maritime-sourced, microphysically 'maritime', stratiform events with high TRYLIS had a DSD containing a greater number of smaller droplets. Satellite observations and vertically-pointing radars were found to be useful for analyzing clouds and precipitation since they provide a wealth of information to allow microphysical parameters to be investigated in detail. © 2009 Elsevier B.V."
"26323963700;56276813400;6603335688;8323981800;","A 500-year record of summer near-ground solar radiation from tree-ring stable carbon isotopes",2010,"10.1177/0959683609351902","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951279814&doi=10.1177%2f0959683609351902&partnerID=40&md5=575a8b7903a82fabc7300ebb02762e32","Tree-ring stable carbon isotope ratios (d13C) in environments of low moisture stress are likely to be controlled primarily by photosynthetic rate. Therefore, sunshine, rather than temperature, represents the more direct controlling factor. Temperature reconstructions based on tree-ring d13C results thus rest on the assumption that temperature and sunshine are strongly coupled. This assumption is tested using a d13C series from pine trees in NW Norway, where there are long (&gt;100 yr) records of both summer temperature and cloud cover. It is demonstrated that when summer temperature and d13C diverge, summer temperature and cloud cover also diverge, and that cloud cover/sunshine may provide a stronger and more consistent parameter with which to calibrate tree-ring d13C series in this area. When a 500-year reconstruction of summer cloudiness is compared with a published reconstruction of summer temperatures in northern Sweden based on tree-ring maximum densities, the two time-series are largely parallel, with high levels of annual-decadal coherence. We identify, however, three distinct periods of lower frequency divergence: two (AD 1600-1650 and AD 1900-1927) when we propose summers were cool but sunny and one during the first half of the sixteenth century when summers were warm but cloudy. These episodes where temperature and sunshine decouple may represent large-scale changes in circulation as recorded in the Arctic Oscillation (AO) index. Strongly negative values of the summer AO index, as occurred during the early twentieth century, are associated with persistent high pressure over northern Norway and Fennoscandia, bringing cool summers with clear skies. Long reconstructions of cloudiness (near-ground radiation), based on tree-ring d13C series from suitable sites, would be extremely valuable for testing General Circulation Models (GCMs), because the generation of cloud is a strong control on temperature evolution, but remains a major source of uncertainty © The Author(s) 2010."
"25723426400;7005602760;","Geographical features of changes in surface shortwave irradiance in East Asia estimated using the potential radiative forcing index",2010,"10.1016/j.atmosres.2009.09.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952319655&doi=10.1016%2fj.atmosres.2009.09.016&partnerID=40&md5=c76181231e6f324f4c4d7acf9de013a2","Using a recently-proposed index of the potential radiative forcing (PRF), we quantified 2-dimentional relative contributions of atmospheric parameters (clouds, aerosols and precipitable water) on the change of surface shortwave irradiance (S) over East Asia in July from 2003 to 2004. Analyses at some points revealed that contributions of the cloud optical depth, cloud amount and aerosol optical depth took various values, including the sign, depending the combination of atmospheric parameters' values and differences. The contribution of precipitable water was rather small compared to other parameters'. For example, the S change of totally about -70 (W/m2) was estimated in the south China case because of all the negative factors. On the other hand, the S change of nearly 20 (W/m2) was calculated as a result of a small negative aerosol effect and a moderate positive effect by the cloud optical depth in the central China case. Like these cases, PRF is useful in determining which of the parameters has a dominant effect on the overall change in S. Comparison of the summation of each PRF-derived contribution and the difference in S from the ISCCP products were fairly favorable (the correlation coefficient of 0.84). Regardless of a few shortcomings, obtained results demonstrated the usefulness of PRF for various climate investigations. Nonetheless, rigid validation against estimated S changes using PRF should be done with independent observations such as ground-based pyranometer measurements. © 2009 Elsevier B.V."
"8971211200;6506276837;7203062717;7201785152;57203199846;","Impact of diurnal atmosphere-ocean coupling on tropical climate simulations using a coupled GCM",2010,"10.1007/s00382-009-0586-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951666303&doi=10.1007%2fs00382-009-0586-8&partnerID=40&md5=5f61ccd88cde7840d98c9c30359f6ace","The impacts of diurnal atmosphere-ocean (air-sea) coupling on tropical climate simulations are investigated using the SNU coupled GCM. To investigate the effect of the atmospheric and oceanic diurnal cycles on a climate simulation, a 1-day air-sea coupling interval experiment is compared to a 2-h coupling experiment. As previous studies have suggested, cold temperature biases over equatorial western Pacific regions are significantly reduced when diurnal air-sea coupling strategy is implemented. This warming is initiated by diurnal rectification and amplified further by the air-sea coupled feedbacks. In addition to its effect on the mean climatology, the diurnal coupling has also a distinctive impact on the amplitude of the El Nino-Southern Oscillation (ENSO). It is demonstrated that a weakening of the ENSO magnitude is caused by reduced (increased) surface net heat fluxes into the ocean during El Nino (La Nina) events. Primarily, decreased (increased) incoming shortwave radiation during El Nino (La Nina) due to cloud shading is responsible for the net heat fluxes associated with ENSO. © Springer-Verlag 2009."
"34873294000;6602208179;","Ensemble kalman filter data assimilation in a 1d numerical model used for fog forecasting",2010,"10.1175/2009MWR3110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955577803&doi=10.1175%2f2009MWR3110.1&partnerID=40&md5=41aeb278ec75516a10b5e4d7e6a14d12","Because poor visibility conditions have a considerable influence on airport traffic, a need exists for accurate and updated fog and low-cloud forecasts. Couche Brouillard Eau Liquide (COBEL)-Interactions between Soil, Biosphere, and Atmosphere (ISBA), a boundary layer 1D numerical model, has been developed for the very short-term forecast of fog and low clouds. This forecast system assimilates local observations to produce initial profiles of temperature and specific humidity. The initial conditions have a great impact on the skill of the forecast. In this work, the authors first estimated the background error statistics; they varied greatly with time, and cross correlations between temperature and humidity in the background were significant. This led to the implementation of an ensemble Kalman filter (EnKF) within COBEL-ISBA. The new assimilation system was evaluated with temperature and specific humidity scores, as well as in terms of its impact on the quality of fog forecasts. Simulated observations were used and focused on the modeling of the atmosphere before fog formation and also on the simulation of the life cycle of fog and low clouds. For both situations, the EnKF brought a significant improvement in the initial conditions and the forecasts. The forecast of the onset and burn-off times of fogs was also improved. The EnKF was also tested with real observations and gave good results. The size of the ensemble did not have much impact when simulated observations were used, thanks to an adaptive covariance inflation algorithm, but the impact was greater when real observations were used. © 2010 American Meteorological Society."
"7004468723;","Relative contribution of soil moisture and snow mass to seasonal climate predictability: A pilot study",2010,"10.1007/s00382-008-0508-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951878461&doi=10.1007%2fs00382-008-0508-1&partnerID=40&md5=f6455ff86ee1241694a0ee65701d0a29","Land surface hydrology (LSH) is a potential source of long-range atmospheric predictability that has received less attention than sea surface temperature (SST). In this study, we carry out ensemble atmospheric simulations driven by observed or climatological SST in which the LSH is either interactive or nudged towards a global monthly re-analysis. The main objective is to evaluate the impact of soil moisture or snow mass anomalies on seasonal climate variability and predictability over the 1986-1995 period. We first analyse the annual cycle of zonal mean potential (perfect model approach) and effective (simulated vs. observed climate) predictability in order to identify the seasons and latitudes where land surface initialization is potentially relevant. Results highlight the influence of soil moisture boundary conditions in the summer mid-latitudes and the role of snow boundary conditions in the northern high latitudes. Then, we focus on the Eurasian continent and we contrast seasons with opposite land surface anomalies. In addition to the nudged experiments, we conduct ensembles of seasonal hindcasts in which the relaxation is switched off at the end of spring or winter in order to evaluate the impact of soil moisture or snow mass initialization. LSH appears as an effective source of surface air temperature and precipitation predictability over Eurasia (as well as North America), at least as important as SST in spring and summer. Cloud feedbacks and large-scale dynamics contribute to amplify the regional temperature response, which is however, mainly found at the lowest model levels and only represents a small fraction of the observed variability in the upper troposphere. © Springer-Verlag 2009."
"7102976560;56604618200;","Impact of changes in climate and halocarbons on recent lower stratosphere ozone and temperature trends",2010,"10.1175/2010JCLI3179.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954360930&doi=10.1175%2f2010JCLI3179.1&partnerID=40&md5=2867a1630829f4cf1f4c8e1889263892","The primary focus of this paper is the analysis of the roles of long-term increases in carbon dioxide (CO2) and sea surface temperatures (used as indicators of climate change) and man-made halocarbons (indicators of chemical ozone depletion linked to halogens) in explaining the observed trend of ozone in the tropical lower stratosphere and implications for related variables including temperature and tropopause height. Published estimates indicate a decrease of approximately 10% in observed ozone concentrations in this region between 1979 and 2005. Using a coupled chemistry-climate atmosphere model forced by observed sea surface temperatures and surface concentrations of long-lived greenhouse gases and halocarbons, the authors show that the simulations display substantial decreases in tropical ozone that compare well in both latitudinal and vertical structure with those observed. Based on sensitivity simulations, the analysis indicates that the decreases in the lower stratospheric (85-50 hPa) tropical ozone distribution are mostly associated with increases in CO2 and sea surface temperatures, in contrast to those at higher latitudes, which are largely driven by halocarbon increases. Factors influencing temperature trends and tropopause heights in this region are also probed. It is shown that the modeled temperature trends in the lower tropical stratosphere are also associated with increases in CO2 and sea surface temperatures. Following the analysis of lower stratospheric tropical temperature trends, the secondary focus of this paper is on related changes in tropopause height. Much of the simulated tropopause rise in the tropical zone as measured by tropopause height is found to be linked to increases in sea surface temperatures and CO2, while increases in halocarbons dominate the tropopause height changes in the subtropics near 30°; both drivers thus affect different regions of the simulated changes in the position of the tropopause. Finally, it is shown that halocarbon increases dominate the changes in the width of the region where modeled total ozone displays tropical character (as indicated by low values of the column abundance). Hence the findings suggest that climate changes and halocarbon changes make different contributions to different metrics used to characterize tropical change. © 2010 American Meteorological Society."
"35239293700;8271783000;","Improved estimation of surface solar insolation using a neural network and MTSAT-1R data",2010,"10.1016/j.cageo.2009.08.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950835336&doi=10.1016%2fj.cageo.2009.08.012&partnerID=40&md5=3f78ae71b0fd62f5f51d6e562499c942","Solar surface insolation (SSI) provides information on how much solar radiance reaches the Earth's surface at a specified location during the daytime. The amount of insolation reaching the surface is a critical parameter for climate change estimation and numerical weather prediction (NWP). We calculated SSI from MTSAT-1R data using a neural network (NN) model to obtain more accurate results than obtained using empirical and physical methods. The use of retrieved SSI data depends on the accuracy of the output results. Thus, before adding the input parameters to the NN, principal component transformation was performed using the eigenvectors and normalized input data to eliminate data redundancy. An NN model with one hidden layer was then used to simulate SSI using early-stop and Levenberg-Marquardt back-propagation (LMBP) methods. We separated the NN architecture into two parts according to cloudy or clear-sky conditions, which have different processes because of complicated cloud physical characteristics. The SSI estimates from the NN model were compared with pyranometer measurements and showed better agreement with ground-truth values than did estimates obtained using conventional methods, especially under the clear-sky condition. © 2010 Elsevier Ltd."
"6602675795;6506612024;11939464600;7201389451;","Bioclimatic maps for tourism purposes",2010,"10.1016/j.pce.2010.03.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951246930&doi=10.1016%2fj.pce.2010.03.009&partnerID=40&md5=4917de0fcb7a4db79418a0260ad21db8","Several daily measurements of air temperature, relative humidity, wind velocity and mean cloud cover are required for the calculation of the Physiologically Equivalent Temperature (PET). Using data obtained from daily measurements at 7, 14 and 19 CET over the period from 1991 to 2000 of 201 Austrian climate stations, we analysed the thermal bioclimate in Austria. The calculated PET-values were compared with the results of another computation using synoptic data not only from Austria but also from neighbouring countries. The mean radiant temperature is rather complex, as it covers all relevant short and long-wave radiation fluxes and plays an important role in the energy balance of humans. Based on the individual current conditions, this parameter was calculated using the well-established 'RayMan' model, which was development based on guidelines of the German Engineering Society, i.e. VDI 3789 (VDI, 1994). The mean radiant temperature is determined based on the mean cloud cover and the maximum possible global radiation at a certain time and location. Statistical and GIS methods were used to convert the point-data consisting of PET-values for individual climate stations into a continuous surface. PET was spatially interpolated through a multiple linear regression analysis on a given grid. The results reveal fundamental information which is of particular relevance to the tourism and recreation authorities. The results are also important for spas and wellness resorts. © 2010 Elsevier Ltd. All rights reserved."
"56284543100;26643250500;55684491100;","Global modeling of the contrail and contrail cirrus climate impact",2010,"10.1175/2009BAMS2656.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952699906&doi=10.1175%2f2009BAMS2656.1&partnerID=40&md5=62408067343a66328e8cc5146186506c","The physical processes governing the life cycle of contrail cirrus clouds are modeled to substantially decrease the uncertainty associated with the aviation climate impact. These climate model simulations of contrail cirrus are based on the parameterization of physical processes that are represented in the model form and can be easily evaluated. The resulting cirrus and contrail cirrus fields depends on the performance of models simulating ice particle formation, growth, and sedimentation, the moisture budget, vertical wind, wind shear, and turbulence in the upper troposphere. Improvements in the representation of the moisture field, including ice supersaturation and suitable observational datasets for validation, are also required for realistic estimation of the climate effect of contrail cirrus. These models also require upper-tropospheric meteorological datasets such as absolute and relative humidity, vertical wind, and cloud microphysical variables."
"13405561000;36097134700;","Probability density functions of liquid water path and cloud amount of marine boundary layer clouds: Geographical and seasonal variations and controlling meteorological factors",2010,"10.1175/2009JCLI3070.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953690934&doi=10.1175%2f2009JCLI3070.1&partnerID=40&md5=5203221bc4c0ec5a7e54136046742db4","The subgrid-scale variability of the liquid water path (LWP) of marine boundary layer clouds in areas that correspond to the typical grid size of large-scale (global climate and weather prediction) atmospheric models (200 km × 200 km) is investigated using geostationary satellite visible data. Geographical and seasonal variations of homogeneity, skewness, and kurtosis of probability density functions (PDFs) of LWP are discussed, in addition to cloud amount. It is clear that not only cloud amount but also these subgrid-scale statistics have well-defined geographical patterns and seasonal variations. Furthermore, the meteorological factors that control subgrid-scale statistics of LWP that are related to boundary layer clouds are investigated using reanalysis data and PDFs of LWP data from satellites. Meteorological factors related to stability between 850 and 1000 hPa show high correlations with cloud amount and with the homogeneity, skewness, and kurtosis of PDFs of LWP of marine boundary layer clouds. The corrected gap of low-level moist static energy (CGLMSE) index, which is related to cloud-top entrainment instability, shows the highest correlation with the shape of LWP PDFs. © 2010 American Meteorological Society."
"20435752700;35887706900;6603253640;7403076976;","Lightning response to smoke from Amazonian fires",2010,"10.1029/2010GL042679","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950505936&doi=10.1029%2f2010GL042679&partnerID=40&md5=b4a1d05b0c8332eb837590e2399a7b92","The effect of anthropogenic aerosols on clouds has the potential to be a key component for climate change predictions, yet is one of the least understood. It is possible that high aerosol loading can change the convection intensity and hence the electrical activity of thunderstorm clouds. Focusing on the Amazon dry season, where thousands of man-made forest fires inject smoke into the atmosphere, we studied the aerosol effects on thunderclouds. We used the ground-based World-Wide Lightning Location Network (WWLLN) lightning measurements together with Aqua-MODIS aerosol and cloud data to show evidence for the transition between two opposing effects of aerosols on clouds. The first is the microphysical effect which is manifested in an increase in convective intensity (and electrical activity), followed by the radiative effect that becomes dominant with the increase in aerosol loading leading to a decrease in convective intensity. Copyright © 2010 by the American Geophysical Union."
"57151771800;56014511300;","Aerosol-cloud semi-direct effect and land-sea temperature contrast in a GCM",2010,"10.1029/2010GL042759","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949910664&doi=10.1029%2f2010GL042759&partnerID=40&md5=4a4d994a4177ff870861fab5293e1d4c","Simulations with the CAM3 climate model show that prescribed heating by anthropogenic aerosols significantly affects cloud cover. Globally the dominant effect is a decrease in mid-level clouds, which contributes to a semi-direct effect (SDE) that warms the surface by 0.5 W m-2. The SDE negates some of the impact of absorbing aerosol on surface fluxes, up to 50% over the Northern Hemisphere extratropical (NHE) land during JJA. The SDE-not direct effects-drives NHE JJA warming and a land-sea contrast in surface temperature that may help explain recent trends. This behavior is mainly due to 1. the trapping of near-surface moisture associated with aerosol induced enhanced lower tropospheric stability, which preferentially increases low cloud over the sea; and 2. a burn-off of cloud, especially over land, due to reduced relative humidity in the low and middle troposphere. These effects are due to vertical redistribution of energy rather than to the horizontal heterogeneity of aerosol forcing. Copyright © 2010 by the American Geophysical Union."
"26021924800;6701773156;7003467276;7004307308;","Response of the Western European climate to a collapse of the thermohaline circulation",2010,"10.1007/s00382-008-0513-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951665559&doi=10.1007%2fs00382-008-0513-4&partnerID=40&md5=b27f33fd93ed30392c9c7e68f7438428","Two ensemble simulations with the ECHAM5/MPI-OM climate model have been investigated for the atmospheric response to a thermohaline circulation (THC) collapse. The model forcing was specified from observations between 1950 and 2000 and it followed a rising greenhouse gases emission scenario from 2001 to 2100. In one ensemble, a THC collapse was induced by adding freshwater in the northern North Atlantic, from 2001 onwards. After about 20 years, an almost stationary response pattern develops, that is, after the THC collapse, global mean temperature rises equally fast in both ensembles with the hosing ensemble displaying a constant offset. The atmospheric response to the freshwater hosing features a strong zonal gradient in the anomalous 2-m air temperature over Western Europe, associated with a strong land-sea contrast. Since Western Europe climate features a strong marine impact due to the prevailing westerlies, the question arises how such a strong land-sea contrast can be maintained. We show that a strong secondary cloud response is set up with increased cloud cover over sea and decreased cloud cover over land. Also, the marine impact on Western European climate decreases, which results from a reduced transport of moist static energy from sea to land. As a result, the change in lapse rate over the cold sea surface temperature (SST) anomalies west of the continent is much larger than over land, dominated by changes in moisture content rather than temperature. © Springer-Verlag 2009."
"7403931916;12803465300;7003266014;35985515200;7102018821;7006783796;57203400519;","Contrails and induced cirrus",2010,"10.1175/2009BAMS2837.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952676574&doi=10.1175%2f2009BAMS2837.1&partnerID=40&md5=29b987a95c4d2bf1821406163822826e","An understanding of the optical properties of contrails and contrail cirrus and enhancing the global satellite detection and retrieval of clouds benefiting the evaluation of the radiative impact of aviation-induced cloudiness on climate change is presented. Results from surface observation and satellite data show an upward trend of cirrus cloud over the past 50 yrs near the US flight corridors, and this increase corresponds to the rising trend of jet fuel consumption. The optical depths of contrails measured from passive satellite imagers are found to be between 0.1 and 0.5, but they can be much smaller, and values larger than 1 are not uncommon. Improved satellite detection of all types of contrails and contrail cirrus over the globe and developing effective algorithms to infer contrail optical depth and particle sizes along with their radiative environment is required."
"12645767500;7004114883;7202899330;","An observed tropical oceanic radiative-convective cloud feedback",2010,"10.1175/2009JCLI3091.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953702221&doi=10.1175%2f2009JCLI3091.1&partnerID=40&md5=991af70dd979fea8d2c8c2efb315fb52","Anomalies of precipitation, cloud, thermodynamic, and radiation variables are analyzed on the large spatial scale defined by the tropical oceans. In particular, relationships between the mean tropical oceanic precipitation anomaly and radiative anomalies are examined. It is found that tropical mean precipitation is well correlated with cloud properties and radiative fields. In particular, the tropical mean precipitation anomaly is positively correlated with the top of the atmosphere reflected shortwave anomaly and negatively correlated with the emitted longwave anomaly. The tropical mean relationships are found to primarily result from a coherent oscillation of precipitation and the area of high-level cloudiness. The correlations manifest themselves radiatively as a modest decrease in net downwelling radiation at the top of the atmosphere, and a redistribution of energy from the surface to the atmosphere through reduced solar radiation to the surface and decreased longwave emission to space. Integrated over the tropical oceanic domain, the anomalous atmospheric column radiative heating is found to be about 10% of the magnitude of the anomalous latent heating. The temporal signature of the radiative heating is observed in the column mean temperature that indicates a coherent phase-lagged oscillation between atmospheric stability and convection. These relationships are identified as a radiative-convective cloud feedback that is observed on intraseasonal time scales in the tropical atmosphere. © 2010 American Meteorological Society."
"55977336000;7101677832;24802640400;16637291100;7201607592;","Errors in cloud detection over the arctic using a satellite imager and implications for observing feedback mechanisms",2010,"10.1175/2009JCLI3386.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953699014&doi=10.1175%2f2009JCLI3386.1&partnerID=40&md5=5c62602e75ffbd24324b77a267705b3f","Arctic sea ice extent has decreased dramatically over the last 30 years, and this trend is expected to continue through the twenty-first century. Changes in sea ice extent impact cloud cover, which in turn influences the surface energy budget. Understanding cloud feedback mechanisms requires an accurate determination of cloud cover over the polar regions, which must be obtained from satellite-based measurements. The accuracy of cloud detection using observations from space varies with surface type, complicating any assessment of climate trends aswell as the understanding of ice-albedo and cloud-radiative feedbackmechanisms. To explore the implications of this dependence on measurement capability, cloud amounts from the Moderate Resolution Imaging Spectroradiometer (MODIS) are compared with those from the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder (CALIPSO) satellites in both daytime and nighttime during the time period from July 2006 to December 2008. MODIS is an imager that makes observations in the solar and infrared spectrum. The active sensors of CloudSat and CALIPSO, a radar and lidar, respectively, provide vertical cloud structures along a narrow curtain. Results clearly indicate that MODIS cloud mask products perform better over open water than over ice. Regional changes in cloud amount from CloudSat/CALIPSO and MODIS are categorized as a function of independent measurements of sea ice concentration (SIC) from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). As SIC increases from 10% to 90%, the mean cloud amounts from MODIS and CloudSat-CALIPSO both decrease; water that is more open is associated with increased cloud amount. However, this dependency on SIC is much stronger for MODIS than for CloudSat-CALIPSO, and is likely due to a low bias in MODIS cloud amount. The implications of this on the surface radiative energy budget using historical satellite measurements are discussed. The quantified ice-water difference in MODIS cloud detection can be used to adjust estimated trends in cloud amount in the presence of changing sea ice cover from an independent dataset. It was found that cloud amount trends in the Arctic might be in error by up to 2.7% per decade. The impact of these errors on the surface net cloud radiative effect (""forcing"") of the Arctic can be significant, as high as 8.5%. © 2010 American Meteorological Society."
"6701783232;7202358048;","Generation of infrasound by evaporating hydrometeors in a cloud model",2010,"10.1175/2009JAMC2226.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955578251&doi=10.1175%2f2009JAMC2226.1&partnerID=40&md5=dc93dec2edb320286a2bd7d2a6b60875","The dynamical core of the Regional Atmospheric Modeling System has been tailored to simulate the infrasound of vortex motions and diabatic cloud processes in a convective storm. Earlier studies have shown that the customized model (c-RAMS) adequately simulates the infrasonic emissions of generic vortex oscillations. This paper provides evidence that c-RAMS accurately simulates the infrasound associated with parameterized phase transitions of cloud moisture. Specifically, analytical expressions are derived for the infrasonic emissions of evaporating water droplets in dry and humid environments. The dry analysis considers two single-moment parameterizations of the microphysics, which have distinguishable acoustic signatures. In general, the analytical results agree with the numerical output of the model. An appendix briefly demonstrates the ability of c-RAMS to accurately simulate the infrasound of the entropy and mass sources generated by an equilibrating cloud of icy hydrometeors. © 2010 American Meteorological Society."
"7003789044;35374698100;7003763119;7403442230;","Aviation and chemistry and transport processes in the upper troposphere and lower stratosphere",2010,"10.1175/2009BAMS2841.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952677610&doi=10.1175%2f2009BAMS2841.1&partnerID=40&md5=593ba6085757dd5b7c6af8a849f6dfcf","The potential climate impacts of transport of nitrogen oxides, measurements of water vapor, NOx-HOx reactions, and heterogeneous chemistry of halogens occurring due to aircraft emissions on upper troposphere and lower stratosphere (UTLS) are discussed. Studies have shown that the fraction of planetary boundary layer-NOx (PBL-NOx) that is transported to the UT by large-scale convection is not well characterized and likely depends on season and continent. Increases in tropospheric ozone resulting from aviation emissions would increase OH, thereby decreasing CH 4. NOx sources from the PBL by convective transport are found to be significantly larger than previously believed, suggesting that aircraft emissions could have a smaller net impact on ozone. The discrepancies in water vapor measurements and associated implications for ice supersaturation and cirrus cloud formation and evolution, may require more creative solutions."
"25923261200;6603077997;","Cirrus clouds physical and spatiotemporal features in the Wider Caribbean",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950670932&partnerID=40&md5=60476a8c9b7f82511668a07f8dad2af5","Studies on cirrus clouds, their occurrence frequency and the physical characteristics are an actual research topic for the scientific community. Cirrus clouds influence on the radiation budget of the surface-atmosphere system and thus the climate. Moreover, cirrus clouds play a determinant role in the regulation of the water vapor quantity in the upper troposphere and lower stratosphere. The lack of information and studies about cirrus clouds distribution in the Wider Caribbean region is the motivation of the present work. In the present article the atmospheric extinction profiles from the SAGE II sensor onboard the Earth Radiation Budget Satellite (ERBS) have been used to analize the occurrence frequency and the optical and geometrical depth of the optically thin cirrus clouds over the Wider Caribbean region. The extinction ratio between the two wavelengths at 0.525 and 1.02 μm was used to separate the profiles containing only aerosols from thus containing a cloud/aerosols mixture (Kent and McCormick, 1991). This ratio shows a different behavior in the interaction between solar radiation crystal ice and aerosols at both wavelengths. The SAGE II dataset version 6.2 was used, extending 21 years, from October 1984 to August 2005. The results show a seasonal behavior in the cirrus clouds occurrence frequency; with a maximum of 35.5 and 17.2% in the rainy and little rainy periods, respectively. These peaks of cirrus clouds frequencies are located at 14.5 and 12.0 km of altitude. An occurrence of 9% was obtained above the tropopause level. About 75% of the clouds never reached the tropopause height, and 16% are in the tropopause. The isolated cirrus clouds have lesser frequency and optical and geometrical depth than the optically thin clouds attached to a lower opaque clouds. The more frequent geometrical depths of isolated clouds were in the 0.5 and 2.5 km range for the altitudes between 10 to 20 km, with a mean value of 1.96 km, with a mean optical depth of 4.0 × 10-3 at 0.525 μm. The 99% of the clouds were classified as subvisual cirrus, below the threshold value of 3.0 × 10-2. A comparison of the present results with other studies for the whole tropical region was conducted, finding some particular features for the Wider Caribbean region."
"7005516084;6701633912;","Observation of the Earth's radiation budget from space",2010,"10.1016/j.crte.2010.01.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951621556&doi=10.1016%2fj.crte.2010.01.005&partnerID=40&md5=8002c46d1c345d59ae154734213b1c6f","The planet's radiation budget includes practically all energy exchange between the Sun, the Earth, and space, and so is a fundamental factor of climate. The terms of this budget, observable only from space, are determined from sampled direct measurements of the solar and terrestrial radiation fields. On the contrary, however, it should be remembered that energy exchange between the Earth's surface and its atmosphere involves not only radiative but also non-radiative energy fluxes. Nevertheless, only observations from space can provide satisfactory global coverage of the different energy fluxes that determine climate at the Earth's surface, by way of indirect retrievals of radiative fluxes at the surface and at different heights in the atmosphere. We describe the methods, applied to measurements made with a variety of instruments on board different artificial satellites, that have led to our present knowledge of the Earth's radiation budget (ERB) at the ""top of the atmosphere"": global annual mean values of the ERB terms, its annual cycle, its geographical structure, and its variations. We know that solar irradiance, averaged over the globe and the year, varies by only 0.1% with the solar activity cycle; we also know that planetary (Bond) albedo is close to 0.3, that the global annual mean emission of thermal infrared radiation to space is close to 240 Wm-2, and that these terms exhibit a weak but well determined annual cycle. We also know that cloud cover plays a major role in the radiation budget, both in the ""shortwave"" domain (global SW ""cloud radiative forcing"" -50 Wm-2) and in the ""longwave"" domain (+20 Wm-2), thus a net forcing of -30 Wm-2. Successive satellite missions give consistent results for the shape, the phase, and the amplitude of the annual cycle of the planetary radiation balance. However, the different estimates of its annual mean absolute value remain uncertain, not differing significantly from zero, although generally excessively positive. We also rapidly review the methods used to determine the surface radiation budget as well as that of the atmosphere. For the planetary (TOA) radiation budget, we examine to what extent interannual variations and interdecadal trends have been or could be detected. We conclude with a review of projects under way. We also discuss priorities for future efforts, considering in particular, on the one hand (Ringer, 1997), the need to better quantify the factors that govern climate sensitivity to modifications of the atmosphere's radiative properties, on the other hand, the importance of monitoring the evolution of the present disequilibrium situation. © 2010 Académie des sciences."
"55202885600;7203047936;7005281574;7403232646;","COSMIC GPS radio occultation temperature profiles in clouds",2010,"10.1175/2009MWR2986.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955538558&doi=10.1175%2f2009MWR2986.1&partnerID=40&md5=eb7b073a70ce85af2207f84d47231efa","Thermodynamic states in clouds are closely related to physical processes such as phase changes of water and longwave and shortwave radiation. Global Positioning System (GPS) radio occultation (RO) data are not affected by clouds and have high vertical resolution, making them ideally suited to cloud profiling on a global basis. By comparing the ConstellationObserving SystemforMeteorology, Ionosphere, and Climate (COSMIC) RO refractivity data with those of the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis andECMWFanalysis for soundings in clouds and clear air separately, a systematic bias of opposite sign was found between large-scale global analyses and the GPS RO observations under cloudy and clear-sky conditions. As a modification to the standard GPS RO wet temperature retrieval that does not distinguish between cloudy-and clear-sky conditions, a new cloudy retrieval algorithm is proposed to incorporate the knowledge that in-cloud specific humidity (which affects the GPS refractivities) should be close to saturation. To implement this new algorithm, a linear regression model for a sounding-dependent relative humidity parameter α is first developed based on a high correlation between relative humidity and ice water content. In the absence of ice water content information, α takes an empirical value of 85%. The in-cloud temperature profile is then retrieved from GPS RO data modeled by a weighted sum of refractivities with and without the assumption of saturation. Compared to the standard wet retrieval, the cloudy temperature retrieval is consistently warmer within clouds by ~2 K and slightly colder near the cloud top (~1 K) and cloud base (1.5 K), leading to a more rapid increase of the lapse rate with height in the upper half of the cloud, from a nearly constant moist lapse rate below and at the cloud middle (~6°C km-1) to a value of 7.7°C km-1, which must be closer to the dry lapse rate than the standard wet retrieval. © 2010 American Meteorological Society."
"7003928082;7101899854;35203432500;7103294028;26661481400;16551540700;7404548584;7102018821;35985515200;","An assessment of the surface longwave direct radiative effect of airborne Saharan dust during the NAMMA field campaign",2010,"10.1175/2009JAS3257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953327402&doi=10.1175%2f2009JAS3257.1&partnerID=40&md5=5147196b66bda4e88258e3c3e7823584","In September 2006, NASA Goddard's mobile ground-based laboratories were deployed to Sal Island in Cape Verde (16.73°N, 22.93°W) to support the NASA African Monsoon Multidisciplinary Analysis (NAMMA) field study. The Atmospheric Emitted Radiance Interferometer (AERI), a key instrument for spectrally characterizing the thermal IR, was used to retrieve the dust IR aerosol optical depths (AOTs) in order to examine the diurnal variability of airborne dust with emphasis on three separate dust events. AERI retrievals of dust AOT are compared with those from the coincident/collocated multifilter rotating shadowband radiometer (MFRSR), micropulse lidar (MPL), and NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) sensors. The retrieved AOTs are then inputted into the Fu-Liou 1D radiative transfer model to evaluate local instantaneous direct longwave radiative effects (DRELW) of dust at the surface in cloud-free atmospheres and its sensitivity to dust microphysical parameters. The top-of-atmosphere DRELW and longwave heating rate profiles are also evaluated. Instantaneous surface DRELW ranges from 2 to 10 W m-2 and exhibits a strong linear dependence with dust AOT yielding a DRELW of 16 W m-2 per unit dust AOT. The DRELW is estimated to be ~42% of the diurnally averaged direct shortwave radiative effect at the surface but of opposite sign, partly compensating for the shortwave losses. Certainly nonnegligible, the authors conclude that DRELW can significantly impact the atmospheric energetics, representing an important component in the study of regional climate variation. © 2010 American Meteorological Society."
"24765069600;56893048100;36127653100;55717224100;35113492400;56611366900;","Distributions of raindrop sizes and fall velocities in a semiarid plateau climate: Convective versus stratiform rains",2010,"10.1175/2009JAMC2208.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955576617&doi=10.1175%2f2009JAMC2208.1&partnerID=40&md5=93d98890fda40390e6d144ed49863984","Joint size and fall velocity distributions of raindrops were measured with a Particle Size and Velocity (PARSIVEL) precipitation particle disdrometer in a field experiment conducted during July and August 2007 at a semiarid continental site located in Guyuan, Ningxia Province, China (36°N, 106°16́E). Data from both stratiform and convective clouds are analyzed. Comparison of the observed raindrop size distributions shows that the increase of convective rain rates arises from the increases of both drop concentration and drop diameter while the increase of the rain rate in the stratiform clouds is mainly due to the increase of median and large drop concentration. Another striking contrast between the stratiform and convective rains is that the size distributions from the stratiform (convective) rains tend to narrow (broaden) with increasing rain rates. Statistical analysis of the distribution pattern shows that the observed size distributions from both rain types can be well described by the gamma distribution. Examination of the raindrop fall velocity reveals that the difference in air density leads to a systematic change in the drop fall velocity while organized air motions (updrafts and downdrafts), turbulence, drop breakup, and coalescence likely cause the large spread of drop fall velocity, along with additional systematic deviation from terminal velocity at certain raindrop diameters. Small (large) drops tend to have superterminal (subterminal) velocities statistically, with the positive deviation from the terminal velocity of small drops being much larger than the negative deviation of large drops. © 2010 American Meteorological Society."
"57207603330;26428178700;6701410329;","Validation of downward surface radiation derived from MSG data by in-situ observations over the Atlantic ocean",2010,"10.1127/0941-2948/2010/0433","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952598375&doi=10.1127%2f0941-2948%2f2010%2f0433&partnerID=40&md5=4bfaae6ece4e108c6af38e94e8effaef","The present work investigates the quality of the shortwave and and longwave downward radiation (DSR, DLR) at the sea surface over the Atlantic Ocean as retrieved from Meteosat Second Generation (MSG) measurements and EUMETSAT's Climate Monitoring - Satellite Application Facility (CM-SAF) algorithms. The observations taken at two transatlantic research cruises have been an ideal basis to be compared with the MSG products for DSR and DLR derived from Meteosat-8 and Meteosat-9. Onboard the research vessels ""Akademik Ioffe"" and ""Polarstern"" high quality in situ measurements of both radiation fluxes have been performed. Continuous full sky imagery and standard meteorological observations enable a comprehensive evaluation of the skills of MSG DSR- and DLR-retrievals in different climate zones and under various cloud and weather conditions. The DSR was retrieved by MSG with a positive bias of 2.77Wm-2 during theIoffe cruise, and 22.23Wm-2 during the Polarstern cruise. The bias for the DLR was -1.73Wm-2 and 2.76Wm -2, respectively. The differences between the two cruises mainly arise from the different weather conditions. No significant differences between the satellite products from Meteosat-8 and Meteosat-9 were found. In general DSR and DLR for clear sky conditions are captured with a high accuracy. Largest retrievalerrors occur for fast fluctuating broken cloud conditions, though on average the MSG algorithm match the in-situ observations well. Semitransparent cirrus was found to cause a negative bias for the retrieved DSR. In tropics and subtropics the errors for DLR are smaller compared to higher latitudes. Most importantly, no significant dependencies of the satellite retrieval errors for both the DSR and the DLR on the solar elevation, near-surface humidity, cloud cover, SST and the shift of day and night were found, indicating that the CMSAF radiation products are not subject to significant systematic errors. © Gebrüder Borntraeger, Stuttgart 2010."
"23065650200;6603133549;55663817800;","Inferring cirrus size distributions through satellite remote sensing and microphysical databases",2010,"10.1175/2009JAS3150.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953345831&doi=10.1175%2f2009JAS3150.1&partnerID=40&md5=2424530acf80d6fdf84beb182d9a4b71","Since cirrus clouds have a substantial influence on the global energy balance that depends on their microphysical properties, climate models should strive to realistically characterize the cirrus ice particle size distribution (PSD), at least in a climatological sense. To date, the airborne in situ measurements of the cirrus PSD have contained large uncertainties due to errors in measuring small ice crystals (D≲60 μm). This paper presents a method to remotely estimate the concentration of the small ice crystals relative to the larger ones using the 11- and 12-mm channels aboard several satellites. By understanding the underlying physics producing the emissivity difference between these channels, this emissivity difference can be used to infer the relative concentration of small ice crystals. This is facilitated by enlisting temperature-dependent characterizations of the PSD (i.e., PSD schemes) based on in situ measurements. An average cirrus emissivity relationship between 12 and 11 mm is developed here using the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument and is used to ""retrieve"" the PSD based on six different PSD schemes. The PSDs from the measurement-based PSD schemes are compared with corresponding retrieved PSDs to evaluate differences in small ice crystal concentrations. The retrieved PSDs generally had lower concentrations of small ice particles, with total number concentration independent of temperature. In addition, the temperature dependence of the PSD effective diameter De and fall speed Vf for these retrieved PSD schemes exhibited less variability relative to the unmodified PSD schemes. The reduced variability in the retrieved De and Vf was attributed to the lower concentrations of small ice crystals in the retrieved PSD. © 2010 American Meteorological Society."
"7006191743;7006111925;56402486000;7006550762;7003498065;57190531316;7006224475;7003495982;7202963086;35600785900;","Testing GISS-MM5 physics configurations for use in regional impacts studies",2010,"10.1007/s10584-009-9729-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950461808&doi=10.1007%2fs10584-009-9729-5&partnerID=40&md5=c4d9173fcda4c6a5fb41fc08735f8346","The Mesoscale Modeling System Version 5 (MM5) was one-way nested to the Goddard Institute for Space Studies global climate model (GISS GCM), which provided the boundary conditions for present (1990s) and future (IPCC SRES A2 scenario, 2050s) five-summer ""time-slice"" simulations over the continental and eastern United States. Five configurations for planetary boundary layer, cumulus parameterization, and radiation scheme were tested, and one set was selected for use in the New York City Climate and Health Project-a multi-disciplinary study investigating the effects of climate change and land-use change on human health in the New York metropolitan region. Although hourly and daily data were used in the health project, in this paper we focus on long-term current and projected mean climate change. The GISS-MM5 was very sensitive to the choice of cumulus parameterization and planetary boundary layer scheme, leading to significantly different temperature and precipitation outcomes for the 1990s. These differences can be linked to precipitation type (convective vs. non-convective), to their effect on solar radiation received at the ground, and ultimately to surface temperature. The projected changes in climate (2050s minus 1990s) were not as sensitive to choice of model physics combination. The range of the projected surface temperature changes at a given grid point among the model versions was much less than the mean change for all five model configurations, indicating relative consensus for simulating surface temperature changes among the different model projections. The MM5 versions, however, offer less consensus regarding 1990s to 2050s changes in precipitation amounts. All of the projected 2050s temperature changes were found to be significant at the 95th percent confidence interval, while the majority of the precipitation changes were not. © Springer Science+Business Media B.V. 2009."
"7402031560;","Cold flow properties of biodiesel by automatic and manual analysis methods",2010,"10.1520/JAI102618","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953489851&doi=10.1520%2fJAI102618&partnerID=40&md5=d9ee4c5e404a41e409fe9bb6cf257138","Biodiesel from most common feedstocks has inferior cold flow properties compared to conventional diesel fuel. Blends with as little as 10 vol % biodiesel content typically have significantly higher cloud point (CP), pour point (PP), and cold filter plugging point (CFPP) than No. 2 grade diesel fuel (DF2). Although PP and CFPP may be lowered by treating with cold flow improver additives, these additives do not reduce CP by more than 3-5°C. When stored in moderate temperature climates, biodiesel should be periodically monitored during cooler months. This work examines the use of automated ASTM test methods to reliably monitor CP, PP, and CFPP. Automated instruments have a number of advantages over manually operated apparatus, namely small sample volumes, consistency, speed of analysis, and accuracy of results. Some deviations in data from automated and manual techniques were observed across a diverse set of biodiesel samples. Biodiesel samples were analyzed by subambient differential scanning calorimetry performed at various heating and cooling scan rates for comparison with cold flow property results. Copyright © 2010 by ASTM International."
"7005729142;7007061674;7004715270;35547807400;7003535176;26643250500;","Contrail microphysics",2010,"10.1175/2009BAMS2839.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952686065&doi=10.1175%2f2009BAMS2839.1&partnerID=40&md5=59b9989625079918a4da49190917c5a2","Contrails are products of aircraft emissions in the upper troposphere at temperatures of about -40°C or below, which are among the most visible human influences on the Earth's climate. Initially, the microphysical properties of contrails differ from those of natural cirrus, but with age contrails may lose their shape and spread, becoming virtually indistinguishable from natural cirrus, both visually and perhaps also in their microphysical properties. Contrail microphysical properties include ice water content (IWC), the total ice particle number concentration (Nt) ice particle size distributions (PSD), ice particle effective radii and ice particle shapes. Observations of the ice crystal shapes during the early phase of contrail formation and beyond are sparse. Studies have revealed that measurements of small ice crystals can be artificially enhanced as a result of several hundred micron or larger particles either shattering on the inlets or arms of optical spectrometers or bouncing or shattering on upstream surfaces of the measurement aircraft."
"55737506400;35274011100;6701808415;","Generation of typical weather data using the ISO Test Reference Year (TRY) method for major cities of South Korea",2010,"10.1016/j.buildenv.2009.10.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949107747&doi=10.1016%2fj.buildenv.2009.10.002&partnerID=40&md5=64cfdb4347bc7cd13f401fde535e1388","Computer simulation of buildings and solar energy systems is being used increasingly in energy assessments and design. Simulation often requires hourly weather data. Such data sets are the Test Reference Years (TRYs), Typical Meteorological Year (TMY) and Weather Year for Energy Calculations (WYEC). Typical weather data consists of 8760 values of various selected meteorological parameters such as ambient temperature, solar radiation, relative humidity and wind velocity and are originally derived from long-term data. This paper discusses methods of selecting typical weather data, the possibility of using the cloud cover data instead of daily global radiation and describes the selection of ISO Test Reference Year (TRY) for major cities of South Korea. The ISO-15927 procedure and algorithms are explained in detail and the Finkelstein-Schafer statistic, the basic selector statistic explained. ISO TRYs for the major cities of South Korea are derived from 20 years of meteorological data recorded during the period 1986-2005. A comparison is made between the 7 sites demonstrating the link between dry-bulb temperature, solar radiation and latitude. © 2009 Elsevier Ltd."
"8502619400;7005446873;56284582200;7402579146;","Perturbation growth at the convective scale for CSIP IOP18",2010,"10.1002/qj.587","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953068634&doi=10.1002%2fqj.587&partnerID=40&md5=89fc41ecc3efd1beb8557e83c109f66c","The Met Office Unified Model is run for a case observed during Intensive Observation Period 18 (IOP18) of the Convective Storms Initiation Project (CSIP). The aims are to identify the physical processes that lead to perturbation growth at the convective scale in response to model-state perturbations and to determine their sensitivity to the character of the perturbations. The case is strongly upper-level forced but with detailed mesoscale/convective-scale evolution that is dependent on smallerscale processes. Potential temperature is perturbed within the boundary layer. The effects on perturbation growth of both the amplitude and typical scale length of the perturbations are investigated, and perturbations are applied either sequentially (every 30 minutes throughout the simulation) or at specific times. The direct effects (within one time step) of the perturbations are to generate propagating Lamb and acoustic waves and produce generally small changes in cloud parameters and convective instability. In exceptional cases a perturbation at a specific grid point leads to switching of the diagnosed boundary-layer type or discontinuous changes in convective instability, through the generation or removal of a lid. The indirect effects (during the entire simulation) are changes in the intensity and location of precipitation and in the cloud-size distribution. Qualitatively different behaviour is found for strong (1 K amplitude) and weak (0.01K amplitude) perturbations, with faster growth after sunrise found only for the weaker perturbations. However, the overall perturbation growth (as measured by the root-mean-square error of accumulated precipitation) reaches similar values at saturation, regardless of the perturbation characterization. © 2010 Royal Meteorological Society and Crown."
"8958009400;35264351500;7102389805;","Spatial and temporal distribution of latent heating in the South Asian monsoon region",2010,"10.1175/2009JCLI3026.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953692183&doi=10.1175%2f2009JCLI3026.1&partnerID=40&md5=26a26b7b3d5a1b3e15b6c07ba3e8bac0","Information from the Tropical Rainfall Measuring Mission (TRMM) level 3 monthly 0.5° × 0.5° Convective and Stratiform Heating (CSH) product and TRMM Microwave Imager (TMI) 2A12 datasets is used to examine the four-dimensional latent heating (LH) structure over the Asian monsoon region between 1998 and 2006. High sea surface temperatures, ocean-land contrasts, and complex terrain produce large precipitation and atmospheric heating rates whose spatial and temporal characteristics are relatively undocumented. Analyses show interannual and intraseasonal LH variations with a large fraction of the interannual variability induced by internal intraseasonal variability. Also, the analyses identify a spatial dipole of LH anomalies between the equatorial Indian Ocean and the Bay of Bengal regions occurring during the summer active and suppressed phases of the monsoon intraseasonal oscillation. Comparisons made between the TRMM CSH and TMI 2A12 datasets indicate differences in the shape of the vertical profile of LH. A comparison of TRMM LH retrievals with sounding budget observations made during the South China Sea Monsoon Experiment shows a high correspondence in the timing of positive LH episodes during the rainy periods. Negative values of atmospheric heating, associated with radiative cooling and with upper-tropospheric cooling from nonsurface-precipitating clouds, are not captured by either of the TRMM datasets. In summary, LH algorithms based on satellite information are capable of representing the spatial and temporal characteristics of the vertically integrated heating in the Asian monsoon region. However, the vertical distribution of atmospheric heating is not captured accurately throughout different convective phases. It is suggested that satellite-derived radiative heating/cooling products are needed to supplement the LH products in order to give a better overall depiction of atmospheric heating. © 2010 American Meteorological Society."
"36757271900;7405524900;","A CGCM study on the northward propagation of tropical intraseasonal oscillation over the asian summer monsoon regions",2010,"10.3319/TAO.2009.02.18.01(A)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953270926&doi=10.3319%2fTAO.2009.02.18.01%28A%29&partnerID=40&md5=3791743bd5f71dd153e521e5d5bea184","This study performs numerical experiments to (1) examine the influences of Pacific and Indian Ocean couplings on the propagation of tropical intraseasonal oscillation (ISO) in the extended boreal summer (May-through-October) and (2) determine the relative contributions of the ocean coupling and internal atmospheric dynamics to the ISO propagation over the Asian-Pacific monsoon regions. For (1), three basin-coupling experiments are performed with a coupled atmosphere-ocean general circulation model (CGCM), in which the air-sea coupling is limited respectively to the Indian Ocean, the Pacific Ocean, and both the Indian and Pacific oceans. For (2), three forced experiments are performed with the atmospheric GCM (AGCM) component of the CGCM, in which the sea surface temperature (SST) climatologies are prescribed from the CGCM experiments. Using extended Empirical Orthogonal Function and composite analyses, the leading ISO modes are identified and compared between the observation and the model experiments. The CGCM modeling results show that the Indian ocean coupling is more important than the Pacific Ocean coupling to promoting both zonal and meridional propagations of the summertime ISO. In this season, the Indo-Pacific warm pool retracts westward and shifts into the Northern Hemisphere allowing the Indian Ocean coupling to become more important. The Indian Ocean coupling is found to promote the northward propagation mainly through wind-evaporation feedback, whereas in observations the cloud-radiation feedback is found to be equally important. The AGCM modeling results indicate that monsoonal dynamics aid the meridional ISO propagation mainly in the low-level winds. Without the ocean coupling, the northward ISO convection feature is weaker and is limited by the northern boundary of climatic easterly vertical shear. The ocean coupling enables the simulated ISO-related convections to cross the northern boundary of the shear. This modeling study concludes that the Indian Ocean coupling plays a crucial rather than a secondary role for the observed northward propagation of summertime ISO."
"35316923500;7004250903;7102080550;57205302128;","Growth of spread in convection-allowing and convection-parameterizing ensembles",2010,"10.1175/2009WAF2222318.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955536003&doi=10.1175%2f2009WAF2222318.1&partnerID=40&md5=62a72298541e244e2b5d6eeed80112ef","During the 2007 NOAA Hazardous Weather Testbed Spring Experiment, a 10-member 4-km grid-spacing Storm-Scale Ensemble Forecast (SSEF) system was run in real time to provide experimental severe weather forecasting guidance. Five SSEF system members used perturbed initial and lateral boundary conditions (ICs and LBCs) and mixed physics (ENS4), and five members used only mixed physics (ENS4phys). This ensemble configuration facilitates a comparison of ensemble spread generated by a combination of perturbed ICs/LBCs and mixed physics to that generated by only mixed physics, which is examined herein. In addition, spread growth and spread-error metrics for the two SSEF system configurations are compared to similarly configured 20-km grid-spacing convection-parameterizing ensembles (ENS20 and ENS20phys). Twelve forecast fields are examined for 20 cases. For most fields, ENS4 mean spread growth rates are higher than ENS20 for ensemble configurations with both sets of perturbations, which is expected as smaller scales of motion are resolved at higher resolution. However, when ensembles with only mixed physics are compared, mass-related fields (i.e., geopotential height and mean sea level pressure) in ENS20phys have slightly higher spread growth rates than ENS4phys, likely resulting from the additional physics uncertainty in ENS20phys from varied cumulus parameterizations that were not used at 4-km grid spacing. For 4- and 20-km configurations, the proportion of spread generated by mixed physics in ENS4 and ENS20 increased with increasing forecast lead time. In addition, low-level fields (e.g., 2-m temperature) had a higher proportion of spread generated by mixed physics than mass-related fields. Spread-error analyses revealed that ensemble variance from the current uncalibrated ensemble systems was not a reliable indicator of forecast uncertainty. Furthermore, ENS4 had better statistical consistency than ENS20 for some mass-related fields, wind-related fields, precipitation, and most unstable convective available potential energy (MUCAPE) with no noticeable differences for low-level temperature and dewpoint fields. The variety of results obtained for the different types of fields examined suggests that future ensemble design should give careful consideration to the specific types of forecasts desired by the user. © 2010 American Meteorological Society."
"8439519800;26643308800;15129098800;35435195400;","The MJO in an AGCM with three different cumulus parameterization schemes",2010,"10.1016/j.dynatmoce.2009.02.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149151578&doi=10.1016%2fj.dynatmoce.2009.02.003&partnerID=40&md5=ae211820dd8966ea4007daf1ff294824","The Madden-Julian oscillation (MJO) is simulated using an AGCM with three different cumulus parameterization schemes: a moist convective adjustment (MCA) scheme, the Zhang-McFarlane (ZM) mass-flux scheme, and the Tiedtke scheme. Results show that the simulated MJO is highly dependent on the cumulus parameterization used. Among the three cumulus parameterizations, only the MCA scheme produces MJO features similar to observations, including the reasonable spatial distribution, intraseasonal time scales and eastward propagation. Meanwhile, the amplitude is too large and the eastward propagation speed too fast than observations and the relationship between precipitation and low-level wind anomaly is unrealistic with enhanced convection occurring within easterly anomalies instead of westerly anomalies as in observations. The over-dependence of precipitation on boundary convergence produced by the MCA scheme is presumably responsible for this unrealistic phase relation in the simulation. The other two schemes produce very poor simulations of the MJO: spectral power of westward propagation is larger than that of eastward propagation in zonal wind and precipitation, indicating a westward propagation of the intraseasonal variability. The mean state and vertical profile of diabatic heating are perhaps responsible for the differences in these simulations. The MCA scheme produces relatively realistic climate background. When either ZM or Tiedtke scheme is used, the observed extension of westerly winds from the western Pacific to the dateline is missing and precipitation over the equatorial region and SPCZ is dramatically underestimated. In addition, diabatic heating produced by both ZM and Tiedtke schemes are very weak and nearly uniform with height. The heating profile produced by the MCA scheme has a middle-heavy structure with much larger magnitude than those produced by the other two schemes. In addition, a very unrealistic boundary layer heating maximum produced by the MCA scheme induces too strong surface convergence, which perhaps contributes to the too strong intraseasonal variability in the simulation. © 2009 Elsevier B.V. All rights reserved."
"35546736600;7004305415;56528811300;56122626400;","Development and evaluation of a cloud-gap-filled MODIS daily snow-cover product",2010,"10.1016/j.rse.2009.10.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74149091611&doi=10.1016%2fj.rse.2009.10.007&partnerID=40&md5=10d4548846bc77ebf00f51fb0d91cf76","The utility of the Moderate Resolution Imaging Spectroradiometer (MODIS) snow-cover products is limited by cloud cover which causes gaps in the daily snow-cover map products. We describe a cloud-gap-filled (CGF) daily snow-cover map using a simple algorithm to track cloud persistence, to account for the uncertainty created by the age of the snow observation. Developed from the 0.05° resolution climate-modeling grid daily snow-cover product, MOD10C1, each grid cell of the CGF map provides a cloud-persistence count (CPC) that tells whether the current or a prior day was used to make the snow decision. Percentage of grid cells ""observable"" is shown to increase dramatically when prior days are considered. The effectiveness of the CGF product is evaluated by conducting a suite of data assimilation experiments using the community Noah land surface model in the NASA Land Information System (LIS) framework. The Noah model forecasts of snow conditions, such as snow-water equivalent (SWE), are updated based on the observations of snow cover which are obtained either from the MOD10C1 standard product or the new CGF product. The assimilation integrations using the CGF maps provide domain-averaged bias improvement of ~11%, whereas such improvement using the standard MOD10C1 maps is ~3%. These improvements suggest that the Noah model underestimates SWE and snow depth fields, and that the assimilation integrations contribute to correcting this systematic error. We conclude that the gap-filling strategy is an effective approach for increasing cloud-free observations of snow cover. © 2009 Elsevier Inc."
"6603754709;6603667298;","A climatology of warm-season mesoscale convective complexes in subtropical South America",2010,"10.1002/joc.1893","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76849085078&doi=10.1002%2fjoc.1893&partnerID=40&md5=9f8be54bf984d89b2cefb73d1412f71f","This study extends investigations of mesoscale convective complexes (MCCs) over subtropical South America (SSA) by describing the physical characteristics of MCCs during the austral warm season (October-May) for 1998-2007 in SSA. Within the nine warm seasons, 330 events were documented. An average of 37 MCCs occurred each warm season and reached a maximum cloud-shield size of 256500 km2, and lasted 14 h on average. Although 85% of the MCC population occurred over the South American continent, the remaining systems that occurred over the adjacent Atlantic Ocean were significantly larger by nearly 30%. These findings show MCCs in SSA are larger and longer-lived than shown in previous work. Compared to the United States, MCCs in SSA are significantly larger with longer durations. Unlike the US systems, these events do not exhibit much poleward migration throughout the warm season. The highest frequency and concentration of MCC cloud shields are centred east of the Andes Mountains between 20 °S and 30°S over Paraguay, northern Argentina, and southern Brazil throughout the warm season. As a result, relationships between latitude, and MCC maximum extent or duration are weak or non-existent, respectively. There is, however, a moderate positive relationship between duration and maximum extent. Ultimately, MCCs in SSA are large, long-lasting events that possess great potential for contributing significantly to precipitation totals across the region. © 2009 Royal Meteorological Society."
"36757271900;7405524900;","Impacts of pacific and indian ocean coupling on wintertime tropical intraseasonal oscillation: A basin-coupling CGCM study",2010,"10.1002/joc.1902","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76849099678&doi=10.1002%2fjoc.1902&partnerID=40&md5=239fb0e85299aaf20e266606186d36eb","This study examines the respective influences of Pacific and Indian Ocean couplings on tropical intraseasonal oscillation (ISO) in boreal winter (November-April). Three basin-coupling experiments are performed with a coupled atmosphere-ocean general circulation model (CGCM), in which air-sea coupling is limited respectively to the Indian Ocean, the Pacific Ocean, and both the oceans. The modelling results show that zonal ISO propagations can be found in the Indo-Pacific region with or without the ocean coupling; however, the propagation signals are enhanced by the coupling. In this particular model the Pacific Ocean coupling has a stronger influence on the ISO propagation than the Indian Ocean coupling. Without the Pacific coupling, the ISO propagation signal is weakened significantly when it enters the Pacific Ocean sector. Without the Indian Ocean coupling, the simulated ISO intensity is weakened less in the Indain Ocean, and significant zonal propagations of ISO can still be simulated in the sector. The relative importance of the ocean coupling is likely related to the smaller ISO-related sea surface temperature (SST) anomalies in the Indian Ocean than in the Pacific Ocean. In this particular CGCM, the ocean coupling affects the ISO propagation mainly through a wind-evaporation-SST feedback rather than a cloud-radiation-SST feedback, while in observations both processes are equally important. To further confirm the importance of the ocean coupling, forced atmospheric GCM experiments are performed with SSTs prescribed from the climatologies produced in the basin-coupling experiments. It is found that the eastward propagating feature seen in the CGCM experiments is weakened and dominated by the strong standing feature in the forced AGCM runs. The difference demonstrates the contribution of the ocean coupling to the ISO propagation, and also confirm that biases in the mean SST and low-level wind caused by the ocean coupling are responsible for the spurious standing ISO oscillation feature in the central Pacific and Indian Oceans. © 2009 Royal Meteorological Society."
"35726852100;7004617100;6603223309;22635123500;","A regional climate model simulation over West Africa: Parameterization tests and analysis of land-surface fields",2010,"10.1007/s00382-010-0769-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954142002&doi=10.1007%2fs00382-010-0769-3&partnerID=40&md5=1ef5d3e53e2d88c5afb85c6eee8e8653","The West African Monsoon has been simulated with the regional climate model PROMES, coupled to the land-surface model ORCHIDEE and nested in ECMWF analysis, within AMMA-EU project. Three different runs are presented to address the influence of changes in two parameterizations (moist convection and radiation) on the simulated West African Monsoon. Another aim of the study is to get an insight into the relationship of simulated precipitation and 2-m temperature with land-surface fluxes. To this effect, data from the AMMA land-surface model intercomparison project (ALMIP) have been used. In ALMIP, offline simulations have been made using the same land-surface model than in the coupled simulation presented here, which makes ALMIP data particularly relevant for the present study, as it enables us to analyse the simulated soil and land-surface fields. The simulation of the monsoon depends clearly on the two analysed parameterizations. The inclusion of shallow convection parametrization affects the intensity of the simulated monsoon precipitation and modifies some dynamical aspects of the monsoon. The use of a fractional cloud-cover parameterization and a more complex radiation scheme is important for better reproducing the amplitude of the latitudinal displacement of the precipitation band. This is associated to an improved simulation of the surface temperature field and the easterly jets. However, the parameterization changes do not affect the timing of the main rainy and break periods of the monsoon. A better representation of downward solar radiation is associated with a smaller bias in the surface heat fluxes. The comparison with ALMIP land-surface and soil fields shows that precipitation and temperature biases in the regional climate model simulation are associated to certain biases in land-surface fluxes. The biases in soil moisture seem to be driven by atmospheric biases as they are strongly affected by the parameterization changes in atmospheric processes. © 2010 Springer-Verlag."
"7102269357;15832187900;24461933800;","Light limitation of summer primary production in the coastal Gulf of Alaska: Physiological and environmental causes",2010,"10.3354/meps08456","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954110073&doi=10.3354%2fmeps08456&partnerID=40&md5=7e1ed6fb9614ac51c7268e3aacd33f7d","We examined photosynthesis-irradiance (P-E) relationships for coastal Gulf of Alaska phytoplankton communities during summer 2003. Phytoplankton were adapted to high light levels, with elevated light saturation parameters (average Ek 390 μmol photons m-2 s-1), low photosynthetic efficiencies (α), and an absence of photoinhibition. Maximum photosynthesis rates (Pmax) ranged from 0.9 to 12.9 μg C μg chl a-1 h-1 and were consistently higher in the nearshore Alaska Coastal Current than elsewhere in the region. Differences between photosynthetic responses of phytoplankton communities from near surface versus the subsurface chlorophyll maximum layer were minor. Small phytoplankton (&lt;20 μm) had consistently higher Pmax and α-values than did large phytoplankton (&gt;20 μm), a difference associated with the higher C:chlorophyll ratios of the small phytoplankton. Acclimation to high light probably arose because of the shallow pycnocline and the highly variable light environment, the latter generated by internal waves and variable cloud cover. Simulations showed that estimated water column productivity, which ranged from 359 to 909 mg C m-2 d-1, was sensitive to modeled changes in cloud cover and pycnocline depth, through both direct effects on light availability and indirect effects on phytoplankton physiology. Climate change could therefore affect summer primary production rates in the coastal Gulf of Alaska through changes in stratification, wind mixing energy, and cloud cover. However, summer phytoplankton growth in this region is also limited by nutrient availability and microzooplankton grazing, indicating a potentially complex relationship between phytoplankton production and environmental variability. © Inter-Research 2010. www.int-res.com."
"10241462700;7201485519;35204593500;7404142321;55537426400;35580303100;7003420726;","Structural similarities and differences in climate responses to CO2 increase between two perturbed physics ensembles",2010,"10.1175/2009JCLI2917.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953653197&doi=10.1175%2f2009JCLI2917.1&partnerID=40&md5=f9e08343da8c3b214bbb16ca307a1a39","The equilibrium climate sensitivity (ECS) of the two perturbed physics ensembles (PPE) generated using structurally different GCMs, Model for Interdisciplinary Research on Climate (MIROC3.2) and the Third Hadley Centre Atmospheric Model with slab ocean (HadSM3), is investigated. A method to quantify the shortwave (SW) cloud feedback by clouds with different cloud-top pressure is developed. It is found that the difference in the ensemble means of the ECS between the two ensembles is mainly caused by differences in the SW low-level cloud feedback. The ensemble mean SW cloud feedback and ECS of the MIROC3.2 ensemble is larger than that of the HadSM3 ensemble. This is likely related to the 1XCO2 low-level cloud albedo of the former being larger than that of the latter. It is also found that the largest contribution to the within-ensemble variation of ECS comes from the SW low-level cloud feedback in both ensembles. The mechanism that causes the within-ensemble variation is different between the two ensembles. In the HadSM3 ensemble, members with large 1XCO2 low-level cloud albedo have large SW cloud feedback and large ECS; ensemble members with large 1XCO2 cloud cover have large negative SW cloud feedback and relatively low ECS. In the MIROC3.2 ensemble, the 1XCO2 low-level cloud albedo is much more tightly constrained, and no relationship is found between it and the cloud feedback. These results indicate that both the parametric uncertainties sampled in PPEs and the structural uncertainties of GCMs are important and worth further investigation. © 2010 American Meteorological Society."
"12040335900;7404653593;57200530823;7005548544;","Satellite retrievals of (quasi-)spherical particles at cold temperatures",2010,"10.1029/2009GL041818","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949305780&doi=10.1029%2f2009GL041818&partnerID=40&md5=bf4c6b798e0933ce8ffe1fe388abd07e","Measurements from NASA's A-train satellites indicate that spherical or quasi-spherical particles may constitute up to 30% of the total cloud particles at temperatures below-30°C, and up to 10% even for temperatures below-40°C, the temperature range typically found in the upper troposphere and the lower stratosphere. Current climate models calculate cloud radiative forcing on the basis on an assumption that essentially no spherical or quasi-spherical particles exist below-40°C (even below-15°C). The findings in this study show that this widely used assumption in climate models may need re-examination. Further research is also needed to confirm and quantify these findings, especially improvements in the satellite retrievals of cloud particle shapes that, in the mean, currently contain about 10% uncertainties. Copyright © 2010 by the American Geophysical Union."
"55738957800;6701333444;57198616562;56520921400;19337612500;","Relating satellite-observed cloud properties from MODIS to meteorological conditions for marine boundary layer clouds",2010,"10.1175/2009JCLI2897.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953669025&doi=10.1175%2f2009JCLI2897.1&partnerID=40&md5=f2285c1ab3b4c21bd3a5d6ffb015ee6f","This study examines 6 yr of cloud properties observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the NASA Terra satellite in five prominent marine boundary layer (MBL) cloud regions (California, Peru, Canary, Angola, and Australia) and investigates their relationships with near-surface meteorological parameters obtained from NCEP reanalyses. About 62 000 independent scenes are used to examine the instantaneous relationships between cloud properties and meteorological parameters that may be used for global climate model (GCM) diagnostics and parameterization. Cloud liquid water path (LWP) generally increases with lower-tropospheric stability (LTS) and lifting condensation level (LCL), whereas cloud drizzle frequency is favored by weak LTS and negligible cold air advection. Cloud fraction (CF) depends strongly on variations in LTS, and to a lesser extent on surface air temperature advection and LCL, although the relationships vary from region to region. The authors propose capturing the effects of these three parameters on CF via their linear combination in terms of a single parameter, the effective lower-tropospheric stability (eLTS). Results indicate that eLTS offers a marked improvement over LTS alone in explaining the median CF variations within the different study regions. A parameterization of CF in terms of eLTS is provided, which produces results that are improved over those of Klein and Hartmann's LTS-only parameterization. However, the new parameterization may not predict the observed variability correctly, and the authors propose a method that might address this shortcoming via a statistical approach. © 2010 American Meteorological Society."
"22946263800;7007026915;","Mesoscale associations between midwest land surface properties and convective cloud development in the warm season",2010,"10.2747/0272-3646.31.2.107","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952960182&doi=10.2747%2f0272-3646.31.2.107&partnerID=40&md5=ff8122da8371abc9ae7319125cc0fae4","The study of land surface-atmosphere interactions is vital to understanding climatic variations in the Earth's planetary boundary layer, particularly given continual land cover modifications by humans on local to regional scales. An agriculturally important region ideal for the study of land surface-atmosphere interactions is the Midwest United States ""Corn Belt."" To evaluate the mesoscale relationships between Corn Belt land surface properties and a key indicator of the surface-atmosphere feedback in humid climates-warm-season convective cloud development-conventional meteorological data, digital maps of land surface properties, and satellite data were examined in a GIS framework for the May-September periods of 1991 through 1999. The results indicate associations between the surface and atmospheric moisture content and the formation of convective clouds: cumulus clouds initiate first and persist longer over a dry (moist) surface with an initially dry (moist) atmosphere. These relationships are evident when forcing from the free atmosphere is either extremely weak (i.e., when fronts and other disturbances are absent and 500 mb winds are <7 ms-1), weak (same as extremely weak, except 500 mb winds are 7-13 ms-1), or strong (same as extremely weak, except 500 mb winds >18 ms-1). However, the association between convective cloud development and other land surface properties (e.g., land use-land cover [LULC], soil order, elevation, and slope) is not consistent spatially. We find that a surface moisture-convective cloud relationship dominates Corn Belt land surface-atmosphere interactions across a range of barotropic synoptic conditions under different atmospheric moisture contents. The study results can help lead to improved prediction of convective cloud formation, and more realistic modeling of land surface-atmospheric interactions for weather and climate forecasting."
"10639674700;55951088700;6602205640;","A long history of cloud and forest migration from Lake Consuelo, Peru",2010,"10.1016/j.yqres.2009.10.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76949084255&doi=10.1016%2fj.yqres.2009.10.005&partnerID=40&md5=b090f5476efb451b23bc0a327af20606","The complete paleoecological history from Lake Consuelo forest yields a record of ground-level cloud formation and changes in its lower altitudinal limit over the last 46,300 cal yr BP. The timing of early lake level fluctuations prior to 37,000 cal yr BP appears sensitive to North Atlantic temperature oscillations, corresponding to Dansgaard-Oeschger interstadials 11, 10 and 8 recorded in GISP2. After the LGM, the first hint of warming is recorded in Lake Consuelo at 22,000 cal yr BP and agrees with other estimates for the region. The mid-Holocene (7400-5000 cal yr BP) was the period of highest rates of change and most significant reorganizations in the Consuelo forest. These community changes resulted from a regionally widespread dry period. Results from Lake Consuelo indicate that moisture availability, mediated through cloud cover, played the most significant role in ecological change in this system. Rates of past climate fluctuations never exceeded the forest capacity to accommodate change. Unfortunately, this might not be the case under predicted scenarios for the end of the current century. © 2009 University of Washington."
"7403282069;8977001000;55745955800;","Cloud-Resolving Simulation of Low-Cloud Feedback to an Increase in Sea Surface Temperature",2010,"10.1175/2009JAS3239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953347773&doi=10.1175%2f2009JAS3239.1&partnerID=40&md5=5e3a24729f0c7c4072326e89f5614f69","This study investigates the physical mechanisms of the low cloud feedback through cloud-resolving simulations of cloud-radiative equilibrium response to an increase in sea surface temperature (SST). Six pairs of perturbed and control simulations are performed to represent different regimes of low clouds in the subtropical region by specifying SST differences (ΔSST) in the range of 4 and 14 K between the warm tropical and cool subtropical regions. The SST is uniformly increased by 2 Kin the perturbed set of simulations.Equilibriumstates are characterized by cumulus and stratocumulus cloud regimes with variable thicknesses and vertical extents for the range of specied ΔSSTs, with the perturbed set of simulations having higher cloud bases and tops and larger geometric thicknesses. The cloud feedback effect is negative for this ΔSST range (-0.68 to -5.22 W m-2 K-1) while the clear-sky feedback effect is mostly negative (-1.45 to 0.35 W m-2 K-1). The clear-sky feedback effect contributes greatly to the climate sensitivity parameter for the cumulus cloud regime whereas the cloud feedback effect dominates for the stratocumulus regime. The increase of liquid water path (LWP) and cloud optical depth is related to the increase of cloud thickness and liquid water content with SST. The rates of change in surface latent heat flux are much higher than those of saturation water vapor pressure in the cumulus simulations. The increase in surface latent heat flux is the pri marymechanism for the large change of cloud physical properties with +2 K SST, which leads to the negative cloud feedback effects. The changes in cloud fraction also contribute to the negative cloud feedback effects in the cumulus regime. Comparison of these results with prior modeling studies is also discussed. © 2010 American Meteorological Society."
"23570843600;8670472000;7003557662;","Using ARM observations to evaluate cloud and clear-sky radiation processes as simulated by the Canadian regional climate model GEM",2010,"10.1175/2009MWR2745.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953194774&doi=10.1175%2f2009MWR2745.1&partnerID=40&md5=708878bb9a6e7d22a5c6173840eff5c6","The total downwelling shortwave (SWD) and longwave (LWD) radiation and its components are assessed for the limited-area version of the Global Environmental Multiscale Model (GEM-LAM) against Atmospheric Radiation Measurements (ARM) at two sites: the southern Great Plains (SGP) and the North Slope of Alaska (NSA) for the 1998-2005 period. The model and observed SWD and LWD are evaluated as a function of the cloud fraction (CF), that is, for overcast and clear-sky conditions separately, to isolate and analyze different interactions between radiation and 1) atmospheric aerosols and water vapor and 2) cloud liquid water. Through analysis of the mean diurnal cycle and normalized frequency distributions of surface radiation fluxes, the primary radiation error in GEM-LAM is seen to be an excess in SWD in the middle of the day. The SWD bias results from a combination of underestimated CF and clouds, when present, possessing a too-high solar transmissivity, which is particularly the case for optically thin clouds. Concurrent with the SWD bias, a near-surface warm bias develops in GEM-LAM, particularly at the SGP site in the summer. The ultimate cause of this warm bias is difficult to uniquely determine because of the range of complex interactions between the surface, atmospheric, and radiation processes that are involved. Possible feedback loops influencing this warm bias are discussed. The near-surface warm bias is the primary cause of an excess clear-sky LWD. This excess is partially balanced with respect to the all-sky LWD by an underestimated CF, which causes a negative bias in simulated all-sky emissivity. It is shown that there is a strong interaction between all the components influencing the simulated surface radiation fluxes with frequent error compensation, emphasizing the need to evaluate the individual radiation components at high time frequency. © 2010 American Meteorological Society."
"28767872500;6602725432;7003811754;57197141130;","A modeling case study of mixed-phase clouds over the Southern Ocean and Tasmania",2010,"10.1175/2009MWR3011.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953199450&doi=10.1175%2f2009MWR3011.1&partnerID=40&md5=b0e7e46ad892e7f9d37eed188952d580","The cloud structure associated with two frontal passages over the Southern Ocean and Tasmania is investigated. The first event, during August 2006, is characterized by large quantities of supercooled liquid water and little ice. The second case, during October 2007, is more mixed phase. The Weather Research and Forecasting model (WRFV2.2.1) is evaluated using remote sensed and in situ observations within the post frontal air mass. The Thompson microphysics module is used to describe in-cloud processes, where ice is initiated using the Cooper parameterization at temperatures lower than 288C or at ice supersaturations greater than 8%. The evaluated cases are then used to numerically investigate the prevalence of supercooled and mixed-phase clouds over Tasmania and the ocean to the west. The simulations produce marine stratocumulus-like clouds with maximum heights of between 3 and 5 km. These are capped by weak temperature and strong moisture inversions. When the inversion is at temperatures warmer than 2108C, WRF produces widespread supercooled cloud fields with little glaciation. This is consistent with the limited in situ observations.When the inversion is at higher altitudes, allowing cooler cloud tops, glaciated (and to a lesser extentmixed phase) clouds are more common. The simulations are further explored to evaluate any orographic signature within the cloud structure over Tasmania. No consistent signature is found between the two cases. © 2010 American Meteorological Society."
"24780687700;7403203783;8437626600;56412340900;7202950780;","Multiangular polarized characteristics of optically thin cirrus in the visible and near-infrared spectral region",2010,"10.1175/2009JAS2996.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953344203&doi=10.1175%2f2009JAS2996.1&partnerID=40&md5=9013e04848268dc0ccdf184ed9209215","Optically thin cirrus play a key role in the earth's radiation budget and global climate change. Their radiative effects depend critically on the thin cirrus optical and microphysical properties. In this paper, in-homogeneous hexagonal monocrystals (IHMs), which consist of a pure hexagon with spherical air bubble or aerosol inclusions, are applied to calculate the single-scattering properties of individual ice crystals. The multiangular polarized characteristics of optically thin cirrus for the 0.865-and 1.38-μm spectral bands are simulated on the basis of an adding-doubling radiative transfer program. The sensitivity of total and polarized reflectance at the top of the atmosphere (TOA) to different aerosol, cirrus, and surface parameters is studied. A new sensitivity index is introduced to further quantify the sensitivity study. The TOA polarized reflectance measured by the Polarization and Directionality of the Earth's Reflectance (POLDER) instruments is compared to simulated TOA total and polarized reflectance. The test results are reasonable, although small deviations caused by the change of aerosol properties and thin cirrus optical thickness do exist. Finally, on the basis of the sensitivity study, a conceptual approach is suggested to simultaneously retrieve thin cirrus clouds' optical thickness, ice particle shape, and the underlying aerosol optical thickness using the TOA total and polarized reflectance of the 0.865-and 1.38-μm spectral bands measured at multiple viewing angles. © 2010 American Meteorological Society."
"7103010852;14819069200;","On the variability of the global net radiative energy balance of the nonequilibrium earth",2010,"10.1175/2009JCLI2797.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953667708&doi=10.1175%2f2009JCLI2797.1&partnerID=40&md5=587b8d4d1af49e1dd4ec9f083a97832d","Recent observations and model studies of the earth's radiative energy balance have focused attention on the earth's top of atmosphere (TOA) energy balance. This is the balance between the shortwave energy absorbed by the earth, which is represented by a spatially and temporally averaged absorbed flux F{downwards arrow to bar}, and theemitted longwave energy, which is represented by the corresponding averaged emitted flux F{upwards arrow to bar}. The TOA average net flux FN is dened as the difference between the two over the averaged area and time, which may be a local, regional, or global average. A global nonzero net flux represents a measure of imbalance between the energy being absorbed and emitted by the earth for the time interval in question. It is of interest to ask what the natural variability of the net flux might be and whether, during times of climate change, signals of important climate change processes might be detected against this natural background variation; examples of these signals include evidence of ocean heat storage, the effects of El Niňo, and the radiative effects of volcanic eruptions. In this paper, the authors review the signicance of the net flux, survey the observational evidence from a range of satellite instruments over several decades, and analyze some of the most recent observations from the Clouds and the Earth's Radiant Energy System (CERES) program to determine what signals and what natural variability might be expected in the TOA net flux. Based on this analysis, the use of broadband radiation measurements for global climate change studies can be assessed. © 2010 American Meteorological Society."
"9537045600;10144312200;57196933120;7004167838;","Characterization of precipitating clouds by ground-based measurements with the triple-frequency polarized Microwave Radiometer ADMIRARI",2010,"10.1175/2009JAMC2340.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953511851&doi=10.1175%2f2009JAMC2340.1&partnerID=40&md5=e14696f98d0bc8b4b0bc88dd9123051f","A groundbreaking new-concept multiwavelength dual-polarized Advanced Microwave Radiometer for Rain Identification (ADMIRARI) has been built and continuously operated in two field campaigns: the Convective and Orographically Induced Precipitation Study (COPS) and the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). The radiometer has 6 channels working in horizontal and vertical polarization at 10.65, 21.0, and 36.5 GHz, and it is completely steerable both in azimuth and in elevation. The instrument is suited to be operated in rainy conditions and is intended for retrieving simultaneously water vapor, rain, and cloud liquid water paths. To this goal the authors implemented a Bayesian retrieval scheme based on many state realizations simulated by the Goddard Cumulus Ensemble model that build up a prior probability density function of rainfall profiles. Detailed three-dimensional radiative transfer calculations, which account for the presence of nonspherical particles in preferential orientation, simulate the downwelling brightness temperatures and establish the similarity of radiative signatures and thus the probability that a given profile is actually observed. Particular attention is devoted to the sensitivity of the ADMIRARI signal to 3D effects, raindrop size distribution, and axial ratio parameterizations. The polarization and multifrequency signals represent key information to separate the effects introduced by non-Rayleigh scatterers and to separate rainwater (r-LWP) from the cloud water component (c-LWP). Longterm observations demonstrate that observed brightness temperatures and polarization differences can be well interpreted and reproduced by the simulated ones for all three channels simultaneously. Rough estimates of r-LWP derived from collocated observations with a micro rain radar confirm the rain/no rain separation and the variability trend of r-LWP provided by the radiometer-based retrieval algorithm. With this work the authors demonstrate the potential of ADMIRARI to retrieve information about the rain/cloud partitioning for midlatitude precipitation systems; future studies with this instrument will provide crucial information on rain efficiency of clouds for cloud modelers that might lead toward a better characterization of rain processes. © 2010 American Meteorological Society."
"7402270607;6602628253;6603235520;7004544454;57203054708;7103002245;","Global and seasonal assessment of interactions between climate and vegetation biophysical processes: A GCM study with different land-vegetation representations",2010,"10.1175/2009JCLI3054.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950633125&doi=10.1175%2f2009JCLI3054.1&partnerID=40&md5=c8293e86069eb94e70520146bfebe7ad","A global and seasonal assessment of regions of the earth with strong climate-vegetation biophysical process (VBP) interactions is provided. The presence of VBP and degree of VBP effects on climate were assessed based on the skill of simulations of observed global precipitation by two general circulation models of the atmosphere coupled to three land models with varying degrees of complexity in VBP representation. The simulated VBP effects on precipitation were estimated to be about 10% of observed precipitation globally and 40% over land; the strongest impacts were in the monsoon regions. Among these, VBP impacts were highest on the West African, South Asian, East Asian, and South American monsoons. The specific characteristics of vegetation- precipitation interactions in northern high latitudes were identified. Different regions had different primary impact season(s) depending on regional climate characteristics and geographical features. The characteristics of VBP effects on surface energy and water balance as well as their interactions were also analyzed. The VBP- induced change in evaporation was the dominant factor in modulating the surface energy and water balance. The land-cloud interaction had substantial effects in the feedback. Meanwhile, the monsoon regions, midlatitudes lands, and high-latitude lands each exhibited quite different characteristics in circulation response to surface heating changes. This study is the first to compare simulations with observations to identify and assess global seasonal mean VBP feedback effects. It is concluded that VBPs are a major component of the global water cycle. © 2010 American Meteorological Society."
"8673949200;6603574267;","Evaluation of remote-sensing-based rainfall products through predictive capability in hydrological runoff modelling",2010,"10.1002/hyp.7529","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951659770&doi=10.1002%2fhyp.7529&partnerID=40&md5=aae8d4a078c56f78a045d2e6bf8ac9d2","The emergence of regional and global satellite-based rainfall products with high spatial and temporal resolution has opened up new large-scale hydrological applications in data-sparse or ungauged catchments. Particularly, distributed hydrological models can benefit from the good spatial coverage and distributed nature of satellite-based rainfall estimates (SRFE). In this study, five SRFEs with temporal resolution of 24 h and spatial resolution between 8 and 27 km have been evaluated through their predictive capability in a distributed hydrological model of the Senegal River basin in West Africa. The main advantage of this evaluation methodology is the integration of the rainfall model input in time and space when evaluated at the sub-catchment scale. An initial data analysis revealed significant biases in the SRFE products and large variations in rainfall amounts between SRFEs, although the spatial patterns were similar. The results showed that the Climate Prediction Center/Famine Early Warning System (CPC-FEWS) and cold cloud duration (CCD) products, which are partly based on rain gauge data and produced specifically for the African continent, performed better in the modelling context than the global SRFEs, Climate Prediction Center MORPHing technique (CMORPH), Tropical Rainfall Measuring Mission (TRMM) and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN). The best performing SRFE, CPC-FEWS, produced good results with values of R2NS between 0·84 and 0·87 after bias correction and model recalibration. This was comparable to model simulations based on traditional rain gauge data. The study highlights the need for input specific calibration of hydrological models, since major differences were observed in model performances even when all SRFEs were scaled to the same mean rainfall amounts. This is mainly attributed to differences in temporal dynamics between products. Copyright © 2009 John Wiley &amp; Sons, Ltd."
"25647575500;6701895637;","A new method to estimate air-quality levels using a synoptic-regression approach. Part II: Future O3 concentrations",2010,"10.1016/j.atmosenv.2009.06.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649183964&doi=10.1016%2fj.atmosenv.2009.06.019&partnerID=40&md5=06be433757367eb6d41ad797033b5042","Using the synoptic-regression based approach developed in Part I of this research, this study estimates future maximum 8 hourly mean O3 levels (m8hO3) using three future SRES (Special Report on Emission) scenarios for a rural background area situated in The Netherlands. The statistical downscaling tool was used to downscale the Atmospheric-Ocean Coupled General Circulation Model (AOGCM) ECHAM5-MPI/OM for the present-day 20 Century (20C) control run (1991-2000) and the future SRES scenarios A2, A1B and B1 for two periods (2051-2060 and 2091-2100). First, the statistical downscaling tool is evaluated in terms of downscaled m8hO3 levels for the present-day climate, using a long record of observed m8hO3 concentrations. It was found that a bias correction is needed and this bias correction is then further used to estimate future m8hO3 concentrations. Under the various SRES scenarios, the overall mean m8hO3 increases with 2.5-6.5 and 6.1-10.9 μg m-3, for the 2051-2060 and 2091-2100 period respectively, which is about 20% of the present-day 10-year average. This effect is enhanced when considering the summer season only, with a range of increase between the different future scenarios of 5.4-12.5 μg m-3 and 13.4-26 μg m-3 (for 2051-2060 and 2091-2100 respectively) against a present-day summer average of 73.5 μg m-3. An increase in maximum temperature and shortwave radiation, associated with a decrease in cloud cover under the various future scenarios are the main drivers of ozone increase. A comparison with August 2003 shows the physical plausibility of our results and reflects that the extreme summer of 2003 might show a close resemblance to future European summers in terms of m8hO3 and meteorological characteristics. © 2009 Elsevier Ltd. All rights reserved."
"8919299300;6602903407;6603701937;7003861526;","Satellite observations of the seasonal cycles of absorbing aerosols in Africa related to the monsoon rainfall, 1995-2008",2010,"10.1016/j.atmosenv.2009.12.038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77349115465&doi=10.1016%2fj.atmosenv.2009.12.038&partnerID=40&md5=477728d6555f4634e9178af930df901f","The link between the African Monsoon systems and aerosol loading in Africa is studied using multi-year satellite observations of UV-absorbing aerosols and rain gauge measurements. The main aerosol types occurring over Africa are desert dust and biomass burning aerosols, which are UV-absorbing. The abundance of these aerosols over Africa is characterised in this paper using residues and Absorbing Aerosol Index (AAI) data from Global Ozone Monitoring Experiment (GOME) on board ERS-2 and SCanning Imaging Absorption SpectroMeter for Atmospheric ChartograpHY (SCIAMACHY) on board Envisat. Time series of regionally averaged residues from 1995 to 2008 show the seasonal variations of aerosols in Africa. Zonally averaged daily residues over Africa are related to monthly mean precipitation data and show monsoon-controlled atmospheric aerosol loadings. A distinction is made between the West African Monsoon (WAM) and the East African Monsoon (EAM), which have different dynamics, mainly due to the asymmetric distribution of land masses around the equator in the west. The seasonal variation of the aerosol distribution is clearly linked to the seasonal cycle of the monsoonal wet and dry periods in both studied areas. The residue distribution over Africa shows two distinct modes, one associated with dry periods and one with wet periods. During dry periods the residue varies freely, due to aerosol emissions from deserts and biomass burning events. During wet periods the residue depends linearly on the amount of precipitation, due to scavenging of aerosols and the prevention of aerosol emissions from the wet surface. This is most clear over east Africa, where the sources and sinks of atmospheric aerosols are controlled directly by the local climate, i.e. monsoonal precipitation. Here, the wet mode has a mean residue of -1.4 and the dry mode has a mean residue of -0.3. During the wet modes a reduction of one residue unit for every 160 mm monthly averaged precipitation was found. Shielding effects due to cloud cover may also play a role in the reduction of the residue during wet periods. A possible influence of aerosols on the monsoon, via aerosol direct and indirect effects, is plausible, but cannot directly be deduced from these data. © 2010 Elsevier Ltd. All rights reserved."
"7006083502;57200540848;14020457700;7003495982;6701590980;8363135900;7006618175;26642959500;","Simulating the IHOP_2002 Fair-weather CBL with the WRF-ARW-Noah modeling system. Part II: Structures from a few kilometers to 100 km across",2010,"10.1175/2009MWR3004.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953220540&doi=10.1175%2f2009MWR3004.1&partnerID=40&md5=66ed656ec510eb4079c0cf8e106af6d8","Fair-weather data along the May-June 2002 International H2O Project (IHOP_2002) eastern track and the nearby Argonne Boundary Layer Experiments (ABLE) facility in southeast Kansas are compared to numerical simulations to gain insight into how the surface influences convective boundary layer (CBL) structure, and to evaluate the success of the modeling system in replicating the observed behavior. Simulations are conducted for 4 days, using the Advanced Research version of the Weather Research and Forecasting (WRF) model coupled to the Noah land surface model (LSM), initialized using the High-Resolution Land Data Assimilation System (HRLDAS). Because the observations focus on phenomena less than 60 km in scale, the model is run with 1-km grid spacing, offering a critical look at high-resolution model behavior in an environment uncomplicated by precipitation. The model replicates the type of CBL structure on scales from a few kilometers to;100 km, but some features at the kilometer scales depend on the grid spacing.Mesoscale (tens of kilometers) circulations were clearly evident on 2 of the 4 days (30 May and 20 June), clearly not evident on 1 day (22 June), with the situation for the fourth day (17 June) ambiguous. Both observed and modeled surface-heterogeneitygenerated mesoscale circulations are evident for 30 May. On the other hand, 20 June satellite images show north-northwest-south-southeast cloud streets (rolls) modulated longitudinally, presumably by tropospheric gravity waves oriented normal to the roll axis, creating northeast-southwest ridges and valleys spaced 50-100 km apart. Modeled cloud streets showed similar longitudinal modulation, with the associated two-dimensional structure having maximum amplitude above the CBL and no relationship to the CBL temperature distribution; although there were patches of mesoscale vertical velocity correlated with CBL temperature. On 22 June, convective rolls were the dominant structure in both model and observations. For the 3 days for which satellite images show cloud streets,WRF produces rolls with the right orientation and wavelength, which grows with CBL depth. Modeled roll structures appeared for the range of CBL depth to Obukhov length ratios (-zi/L) associated with rolls. However, sensitivity tests show that the roll wavelength is also related to the grid spacing, and the modeled convection becomes more cellular with smaller grid spacing. © 2010 American Meteorological Society."
"7005485117;25226620200;57104288000;","Improving multimodel forecasts of the vertical distribution of heating using the TRMM profiles",2010,"10.1175/2009JCLI2878.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953673915&doi=10.1175%2f2009JCLI2878.1&partnerID=40&md5=e22e7ac5e3a113fa21cbc66d9101b213","Recently the National Aeronautics and Space Administration (NASA) Tropical Rainfall Measuring Mission (TRMM) project office made available a new product called the convective-stratiform heating (CSH). These are the datasets for vertical profiles of diabatic heating rates (the apparent heat source). These observed estimates of heating are obtained from the TRMM satellite's microwave radiances and the precipitation radar. The importance of such datasets for defining the vertical distribution of heating was largely the initiative of Dr. W.-K. Tao from NASA's Goddard Laboratory. The need to examine how well some of the current cumulus parameterization schemes perform toward describing the amplitude and the threedimensional distributions of heating is addressed in this paper. Three versions of the Florida State University (FSU) global atmospheric model are run that utilize different versions of cumulus parameterization schemes; namely, modified Kuo parameterization, simple Arakawa-Schubert parameterization, and Zhang-McFarlane parameterization. The Kuo-type scheme used here relies on moisture convergence and tends to overestimate the rainfall generally compared to the TRMM estimates. The other schemes used here show only a slight overestimate of rain rates compared to TRMM; those invoke mass fluxes that are less stringent in this regard in defining cloud volumes. The mass flux schemes do carry out a total moisture budget for a vertical column model and include all components of the moisture budget and are not limited to the horizontal convergence of moisture. The authors carry out a numerical experimentation that includes over a hundred experiments from each of these models; these experiments differ only in their use of the cumulus parameterization. The rest of the model physics, resolution, and initial states are kept the same for each set of 117 forecasts. The strategy for this experimentation follows the authors' previous studies with the FSU multimodel superensemble. This includes a 100-day training and a 17-day forecast phase, both of which include a large number of forecast experiments. The training phase provides a useful statistical database for tagging the systematic errors of the respective models. The forecast phase is designed to minimize the collective bias errors of these member models. In these forecasts the authors also include the ensemble mean and the multimodel superensemble. In this paper the authors examine model errors in their representations of the heating (amplitude, vertical level of maximum, and the geographical distributions). The main message of this study is that some cumulus parameterization schemes overestimate the amplitude of heating, whereas others carry lower values. The models also exhibit large errors in the placement of the vertical level of maximum heating. Some significant errors were also found in the geographical distributions of heating. The ensemble mean largely mimics the model features and also carries some large errors. The superensemble is more selective in reducing the three-dimensional collective bias errors of the models and provides the best short range forecasts, through hour 60, for the heating. This study shows that it is possible to diagnose some of the modeling errors in the heating for individual member models and that information can be important for correcting such features. © 2010 American Meteorological Society."
"14825561100;35757949900;7003910184;35757993300;7004862771;","A regional snow-line method for estimating snow cover from MODIS during cloud cover",2010,"10.1016/j.jhydrol.2009.11.042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74549170985&doi=10.1016%2fj.jhydrol.2009.11.042&partnerID=40&md5=5f94a478b5aab268034389e5f3c30fe0","The objective of this study is to propose and evaluate a method for snow cover mapping during clouds using the daily MODIS/Terra snow cover product. The proposed SNOWL approach is based on reclassifying pixels assigned as clouds to snow or land according to their relative position to the regional snow-line elevation. The accuracy of the SNOWL approach is evaluated over Austria, using daily snow depth measurements at 754 climate stations and daily MODIS/Terra images in the period July 2002-December 2005. The results indicate that the SNOWL method provides a robust snow cover mapping over the entire region even if the MODIS/Terra cloud cover is as large as 90%. Cloudiness is decreased from 60% (MODIS/Terra) to 10% (SNOWL) without hardly any change in mapping accuracy. Sensitivity analyses indicate that the estimation of the regional snow-line elevation is particularly sensitive to the misclassification of cirrus clouds as snow in the period between May and October. © 2009 Elsevier B.V. All rights reserved."
"23494047900;8303142200;6505906590;7102767303;","Evaluation of MODIS land surface temperature data to estimate air temperature in different ecosystems over Africa",2010,"10.1016/j.rse.2009.10.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71549139406&doi=10.1016%2fj.rse.2009.10.002&partnerID=40&md5=20fdc5e5b942ada30654d0ca3ed4fd88","The estimation of near surface air temperature (Ta) is useful for a wide range of applications such as agriculture, climate related diseases and climate change studies. Air temperature is commonly obtained from synoptic measurements in weather stations. In Africa, the spatial distribution of weather stations is often limited and the dissemination of temperature data is variable, therefore limiting their use for real-time applications. Compensation for this paucity of information may be obtained by using satellite-based methods. However, the derivation of near surface air temperature (Ta), from the land surface temperature (Ts) derived from satellite is far from straight forward. Some studies have tried to derive maximum Ta from satellites through regression analysis but the accuracy obtained is quite variable according to the study. The main objective of this study was to explore the possibility of retrieving high-resolution Ta data from the Moderate Resolution Imaging Spectroradiometer (MODIS) Ts products over different ecosystems in Africa. First, comparisons between night MODIS Ts data with minimum Ta showed that MODIS nighttime products provide a good estimation of minimum Ta over different ecosystems (with (ΔTs - Ta) centered at 0 °C, a mean absolute error (MAE) = 1.73 °C and a standard deviation = 2.4 °C). Secondly, comparisons between day MODIS Ts data with maximum Ta showed that (ΔTs - Ta) strongly varies according to the seasonality, the ecosystems, the solar radiation, and cloud-cover. Two factors proposed in the literature to retrieve maximum Ta from Ts, i.e. the Normalized Difference Vegetation Index (NDVI) and the Solar Zenith Angle (SZA), were analyzed. No strong relationship between (ΔTs - Ta) and (i) NDVI and (ii) SZA was observed, therefore requiring further research on robust methods to retrieve maximum Ta. © 2009 Elsevier Inc. All rights reserved."
"35422119400;35422020900;7202488998;7201990763;6602940179;55667304400;","Sudden cosmic ray decreases: No change of global cloud cover",2010,"10.1029/2009GL041327","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76349094064&doi=10.1029%2f2009GL041327&partnerID=40&md5=06f9ce4018503e87d085e3a8b2d17eba","Currently a cosmic ray cloud connection (CRC) hypothesis is subject of an intense controversial debate. It postulates that galactic cosmic rays (GCR) intruding the Earth's atmosphere influence cloud cover. If correct it would have important consequences for our understanding of climate driving processes. Here we report on an alternative and stringent test of the CRC-hypothesis by searching for a possible influence of sudden GCR decreases (so-called Forbush decreases) on clouds. We find no response of global cloud cover to Forbush decreases at any altitude and latitude. Copyright © 2010 by the American Geophysical Union."
"35746258100;7003922583;57200684699;56917398600;","Parameterization of solar radiation from model and observations",2010,"10.1127/0941-2948/2010/0423","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949466142&doi=10.1127%2f0941-2948%2f2010%2f0423&partnerID=40&md5=fe64b59c842e76b99b3a266141d2ef38","The influence of the external and internal structure of clouds on the incoming solar radiation cannot yet be included in parameterizations used in numerical models. Based on numerical simulations, SCHEWSKI and MACKE (2003) (Schewski-parameterization) have shown that a robust link exists between the domain averaged cloud and the domain averaged solar broadband radiation fluxes, despite the 3d nature of the cloud fields involved. The present work revisits this approach with observed cloud (cloud cover and liquid water path) and radiation (downwelling shortwave radiative flux) properties obtained from the Richard Assmann Observatory (RAO) of the German Weather Service in Lindenberg. Applying the original (model based) cloud-radiation parameterization by SCHEWSKI and MACKE (2001) to observed domain averaged cloud fields yields an overall good correlation between observed and parameterized downwelling solar radiation fluxes. However, the parameterized fluxes strongly underestimate the observations. The Schewski parameterization has been modified by removing the bias and re-adjusting the parameterization coefficients to match the observed cloud and radiation correlation. Furthermore, the empirical parameterization by ZILLMAN (1972) has been implemented for describing the clear conditions. Applying the new parameterization to an independent data set provides significant improvements. However, the accuracy remains in the order of previously used one- or two-parameter empirical cloud-radiation parameterizations. We conclude that cloud cover and liquid water path, i.e. those data that are available from large scale climate models, cannot be regarded as sufficient to describe the cloud radiative effect at the surface. © 2010 Gebrüder Borntraeger, Berlin, Stuttgart."
"36100216200;7601443168;35298413500;","The diurnal cycle of winds, rain, and clouds over Taiwan during the Mei-Yu, summer, and autumn rainfall regimes",2010,"10.1175/2009MWR3031.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953212875&doi=10.1175%2f2009MWR3031.1&partnerID=40&md5=07c6e1021c54554d01f42c94a0b01000","The diurnal variations in surface winds, rain, and clouds over Taiwan are presented for three rainfall regimes: the mei-yu (16 May-15 June), summer (16 July-31 August), and autumn (16 September-15 October). Though the magnitude of diurnal island divergence and convergence is similar under each regime, the diurnal variations of rain and clouds vary considerably between the regimes. These differences are related to the seasonal changes in environment winds, stability, moisture, and weather systems. In addition to orographic lifting on the windward side, rainfall occurrences for all three rainfall regimes are strongly modulated by the diurnal heating cycle with an afternoon maximum. The largest day-night differences in rainfall occur in summer and the smallest differences occur in autumn. The upper-level high cloud (<235 K) frequencies have a pronounced afternoon maximum over the mountainous areas in the afternoon because of combined effects of orographic lifting and solar heating. These clouds are advected downstream by the upper-level winds in late afternoon and early evening. The highest afternoon high cloud frequencies occur in summer (>30%) with the lowest upper-level cloud cover in autumn (~10%). In autumn, most of the orographic showers on the eastern and northeastern windward side in the late afternoon and early evening are not from deep clouds. The weak early-morning rainfall maxima for all three seasons are related to the localized boundary layer convergence due to the orographic blocking of the prevailing winds and their interactions with the offshore/land breeze. During disturbed, prefrontal periods in the mei-yu, bands of high clouds and rain tend to develop in the early morning in the convergence zone off the northwest coast. These rainbands are responsible for the early-morning rainfall maximum on the northwest coast. They do not occur in summer or autumn. © 2010 American Meteorological Society."
"6701773156;","The atmospheric response to a thermohaline circulation collapse: Scaling relations for the hadley circulation and the response in a coupled climate model",2010,"10.1175/2009JCLI3159.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952267330&doi=10.1175%2f2009JCLI3159.1&partnerID=40&md5=c6079c429ed7c94d3fd5e2a154d33018","The response of the tropical atmosphere to a collapse of the thermohaline circulation (THC) is investigated by comparing two 5-member ensemble runs with a coupled climate model (CCM), the difference being that in one ensemble a hosing experiment was performed. An extension of the Held-Hou-Lindzen model for the Hadley circulation is developed to interpret the results. The forcing associated with a THC collapse is qualitatively similar to, but smaller in amplitude than, the solstitial shift from boreal summer to winter. This forcing results from reduced ocean heat transport creating an anomalous cross-equatorial SST gradient. The small amplitude of the forcing makes it possible to arrive at analytical expressions using standard perturbation theory. The theory predicts the latitudinal shift between the Northern Hemisphere (NH) and Southern Hemisphere (SH) Hadley cells, and the relative strength of the anomalous cross-equatorial Hadley cell compared to the solstitial cell. The poleward extent of the Hadley cells is controlled by other physics. In the NH the Hadley cell contracts, while zonal velocities increase and the subtropical jet shifts equatorward, whereas in the SH cell the opposite occurs. This behavior can be explained by assuming that the poleward extent of the Hadley cell is determined by baroclinic instability: it scales with the inverse of the isentropic slopes. Both theory and CCM results indicate that a THC collapse and changes in tropical circulation do not act in competition, as a possible explanation for abrupt climate change; they act in concert. © 2010 American Meteorological Society."
"55738957800;16246205000;","Convection parameterization, tropical pacific double ITCZ, and upper-ocean biases in the NCAR CCSM3. Part II: Coupled feedback and the role of ocean heat transport",2010,"10.1175/2009JCLI3109.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952258150&doi=10.1175%2f2009JCLI3109.1&partnerID=40&md5=1223134dfeb9d98cf7dd9458bdcbd335","This study investigates the coupled atmosphere-ocean feedback and the role of ocean dynamic heat transport in the formation of double ITCZ over the tropical Pacific in the NCAR Community Climate System Model, version 3 (CCSM3) and its alleviation when a revised Zhang-McFarlane (ZM) convection scheme is used. A hierarchy of coupling strategy is employed for this purpose. A slab ocean model is coupled with the atmospheric component of the Community Atmosphere Model, version 3 (CAM3) to investigate the local feedback between the atmosphere and the ocean. It is shown that the net surface energy flux differences in the southern ITCZ region between the revised and original ZM scheme seen in the stand-alone CAM3 simulations can cool the SST by up to 1.58C. However, the simulated SST distribution is very sensitive to the prescribed ocean heat transport required in the slab ocean model. To understand the role of ocean heat transport, the fully coupled CCSM3 model is used. The analysis of CCSM3 simulations shows that the altered ocean dynamic heat transport when the revised ZM scheme is used is largely responsible for the reduction of SST bias in the southern ITCZ region, although surface energy flux also helps to cool the SST in the first few months of the year in seasonal variation. The results, together with those from Part I, suggest that the unrealistic simulation of convection over the southern ITCZ region in the standard CCSM3 leads to the double-ITCZ bias through complex coupled interactions between atmospheric convection, surface winds, latent heat flux, cloud radiative forcing, SST, and upper-ocean circulations. The mitigation of the double-ITCZ bias using the revised ZM scheme is achieved by altering this chain of interactions. © 2010 American Meteorological Society."
"7102949705;56241347800;","Study of cloud-to-ground lightning and precipitation and their seasonal and geographical characteristics over Taiwan",2010,"10.1016/j.atmosres.2009.08.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73949090967&doi=10.1016%2fj.atmosres.2009.08.016&partnerID=40&md5=71ba8de3fd286822992b90199171aa92","A long term (1998-2006) study of annual precipitation and cloud-to-ground (CG) lightning has been made at 31 stations over Taiwan. The CG-lightning data were collected by the ground-based Lightning Location System (LLS) built by Tai-Power Company of Taiwan while the precipitation data were collected from the Central Weather Bureau (CWB) of Taiwan. For the present study, a spatial scale of 0.1° latitude × 0.1° longitude (≈ 102 km2) is selected to determine the flash density. CG-lightning and precipitation data are used to compute the values of ""rain yield"", defined as the mass of rain produced per CG-lightning flash in units of kg fl- 1 over a given surface area. The rain yield is found to vary considerably with seasonal and climatic conditions, and geographical location. A positive linear correlation is observed between precipitation and lightning flash density with a highest correlation coefficient of 0.70 over inland stations. Out of the 31 stations, 13 stations are inland stations and these stations show higher rain yields clustering close to a mean of 0.7 × 1010 kg fl- 1, compared to the coastal stations which show a mean value 1.4 × 1010 kg fl- 1. When the stations are classified according to seasonal climate zones, the winter and winter-dominant rainfall stations show comparatively higher value of rain yield with an average of 2.8 × 1010 kg fl- 1 than the summer and summer-dominant rainfall stations which exhibit a significantly lower value of rain yield of 2.1 × 1010 kg fl- 1. Inland stations exhibit a lower value of rain yield with a mean of 1.6 × 109 kg fl- 1 and 1.4 × 1010 kg fl- 1 respectively during warm and cold seasons compared to the coastal stations. For each station, the average cold season rain yields are significantly higher than that of warm season values. These differences in rain yield values are attributed to local surface heating which indirectly controls such parameters as cloud base height and convectively available potential energy (CAPE) in the atmosphere. The variation of rain yield with geographical, seasonal, and climatic conditions, found in our observations, are in good agreement with studies found in the literature from other parts of the world. © 2009 Elsevier B.V. All rights reserved."
"6701606453;35799889800;","A 10-year climatology of tropical radiative heating and its vertical structure from trmm observations",2010,"10.1175/2009JCLI3018.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952244782&doi=10.1175%2f2009JCLI3018.1&partnerID=40&md5=ec7e1a9f6a22216916ba03ae61b76649","This paper outlines recent advances in estimating atmospheric radiative heating rate profiles from the sensors aboard the Tropical Rainfall Measuring Mission (TRMM). The approach employs a deterministic framework in which four distinct retrievals of clouds, precipitation, and other atmospheric and surface properties are combined to form input to a broadband radiative transfer model that simulates profiles of upwelling and downwelling longwave and shortwave radiative fluxes in the atmosphere. Monthly, 5° top of the atmosphere outgoing longwave and shortwave flux estimates agree with corresponding observations from the Clouds and the Earth's Radiant Energy System (CERES) to within 7 W m-2 and 3%, respectively, suggesting that the resulting products can be thought of as extending the eight-month CERES dataset to cover the full lifetime of TRMM. The analysis of a decade of TRMM data provides a baseline climatology of the vertical structure of atmospheric radiative heating in today's climate and an estimate of the magnitude of its response to environmental forcings on weekly to interannual time scales. In addition to illustrating the scope and properties of the dataset, the results highlight the strong influence of clouds, water vapor, and large-scale dynamics on regional radiation budgets and the vertical structure of radiative heating in the tropical and subtropical atmospheres. The combination of the radiative heating rate product described here, with profiles of latent heating that are now also being generated from TRMM sensors, provides a unique opportunity to develop large-scale estimates of vertically resolved atmospheric diabatic heating using satellite observations. © 2010 American Meteorological Society."
"35756119400;6507954505;","Utilization of minimum temperature prediction",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949714922&partnerID=40&md5=c0661fe0e4ca29ecc6da84e83a65bcf8","Techniques for forecasting the minimum temperature are mostly empirically based, using collections of statistics over a long period of time for a range of weather situations. The very popular method is McKenzie's method, which uses the maximum temperature and the dew-point at the time of maximum temperature, together with a set of correction factors for cloud and wind. Main aim is to adjust the corrections to aerodromes currently used by Czech air force. Adjustment of McKenzie technique to the territory of Czech Republic could be very useful tool in particular forecast, especially in forecast of dangerous weather phenomena that are linked with minimal temperature prediction, e.g. forecasting of road surface conditions etc. ""The Road meteorology"" is a branch of an applied meteorology, which deals with the meteorological elements and phenomena in the light of their influence over running of communication, namely the major roads and motorways on a given territory inclusive of bridges and tunnels constructions. Road meteorology tries to solve the theoretic problems pair with the meteorological support of the road maintenance."
"26431137300;7006130951;6507847353;7401572191;","Mixed layer temperature response to the southern annular mode: Mechanisms and model representation",2010,"10.1175/2009JCLI2976.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952274776&doi=10.1175%2f2009JCLI2976.1&partnerID=40&md5=0b18c0d7ef6c91812806bb88d9ad2352","Previous studies have shown that simulated sea surface temperature (SST) responses to the southern annular mode (SAM) in phase 3 of the Coupled Model Intercomparison Project (CMIP3) climate models compare poorly to the observed response. The reasons behind these model inaccuracies are explored. The ocean mixed layer heat budget is examined in four of the CMIP3 models and by using observations- reanalyses. The SST response to the SAM is predominantly driven by sensible and latent heat flux and Ekman heat transport anomalies. The radiative heat fluxes play a lesser but nonnegligible role. Errors in the simulated SST responses are traced back to deficiencies in the atmospheric response to the SAM. The models exaggerate the surface wind response to the SAM leading to large unrealistic Ekman transport anomalies. During the positive phase of the SAM, this results in excessive simulated cooling in the 40°-65°S latitudes. Problems with the simulated wind stress responses, which relate partly to errors in the simulated winds themselves and partly to the transfer coefficients used in the models, are a key cause of the errors in the SST response. In the central Pacific sector (90°-150°W), errors arise because the simulated SAM is too zonally symmetric. Substantial errors in the net shortwave radiation are also found, resulting from a poor repre- sentation of the changes in cloud cover associated with the SAM. The problems in the simulated SST re- sponses shown by this study are comparable to deficiencies previously identified in the CMIP3 multimodel mean. Therefore, it is likely that the deficiencies identified here are common to other climate models. © 2010 American Meteorological Society."
"35223585400;7003895878;","Oxygen and hydrogen isotopes of rainfall and dripwater at DeSoto Caverns (Alabama, USA): Key to understanding past variability of moisture transport from the Gulf of Mexico",2010,"10.1016/j.gca.2009.10.043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149083358&doi=10.1016%2fj.gca.2009.10.043&partnerID=40&md5=086dfedbbf5822ca5e10c855479eb32b","The Southeast and the US Gulf Coast in particular are notably lacking isotope data in the water cycle despite the fact that moisture transport from the Gulf of Mexico (GOM) has a considerable influence on both regional and continental rainfall patterns. This study reports time-series of oxygen and hydrogen isotopes acquired over a 3-year period (2005-2008) from GOM-derived rainfall, cave dripwater and shallow groundwaters, and offers valuable insights on the links between factors controlling regional rainfall and the ubiquitous karst hydrology. Amount-weighted mean monthly rainwater δ18O and δD values in Tuscaloosa, Alabama range from -1.5 to -8.3‰ and -1.2 to -49.5‰, respectively, and show mean seasonal amplitudes of ∼4‰ (δ18O) and ∼25‰ (δD). In comparison d-excess values display large seasonal amplitudes of 10-20‰ resulting from differences in the degree of evaporation from falling raindrops between summer and winter months, and correlate well with the coeval air temperature (r2 = 0.59; p &lt; 0.05). Deviations of the Gulf Coast Meteoric Water Line (GCMWL) slope and d-excess from the global meteoric water line (GMWL) are attributed to different rates of evaporation after condensation, and to humidity contrast between the cloud boundary layer and the surrounding atmosphere in the vapor source region, respectively. Rainfall amounts declined during the study interval from an excessive ""wet"" year, ascribed to six tropical storms incursions during an unusually active hurricane season in 2005, to an onset of a regional drought during 2007-2008 with monthly rainfall amounts substantially below normal values (30-year monthly means). An interannual trend of 18O and 2H enrichments is discerned from 2005 to 2008 (1.4‰ and 11.6‰, respectively) coeval with the decline in rainfall amounts. Dripwater samples from nearby DeSoto Caverns show weak δ18O and δD seasonal variations and record only 20% and 51% of the 18O and 2H enrichments, respectively, discerned in the rainwater 3-year time-trends. The seasonal and interannual amplitude attenuations in the dripwaters are attributed to a relatively thick overlying bedrock (∼30-40 m) and a relatively large, well-mixed, epikarst-storage reservoir. Residence time of water in the cave's epikarst is estimated to be 1-3 months based on high-resolution flow-rate data. Our investigation suggests that global atmospheric circulation patterns (ENSO and Bermuda High) likely govern the interannual δ18O and δD isotope trends discerned in the water cycle compartments but much longer time-series are required to confirm our conjectures. The results of this study form a solid basis for future acquisition and interpretation of climate proxy records from regional speleothems. © 2009 Elsevier Ltd. All rights reserved."
"7003459317;22986783400;35847652200;35847652900;35847477200;35847830300;6601998115;10739974600;6602777705;","Galactic cosmic rays-clouds effect and bifurcation model of the Earth global climate. Part 2. Comparison of theory with experiment",2010,"10.1016/j.jastp.2009.12.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950516547&doi=10.1016%2fj.jastp.2009.12.006&partnerID=40&md5=b7383af263a144b3327c1e09bb1c2e1d","The solution of energy-balance model of the Earth global climate and the EPICA Dome C and Vostok experimental data of the Earth surface palaeotemperature evolution over past 420 and 740. kyr are compared.In the framework of proposed bifurcation model (i) the possible sharp warmings of the Dansgaard-Oeschger type during the last glacial period due to stochastic resonance is theoretically argued; (ii) the concept of climatic sensitivity of water in the atmosphere, whose temperature instability has the form of so-called hysteresis loop, is proposed, and based on this concept the time series of global ice volume over the past 1000kyr, which is in good agreement with the time series of δ18O concentration in the sea sediments, is obtained; (iii) the so-called ""CO2 doubling"" problem is discussed. © 2010 Elsevier Ltd."
"7003459317;16434502700;22986783400;35847652900;35847477200;35847830300;35847652200;10739974600;6602777705;","Galactic cosmic rays-clouds effect and bifurcation model of the Earth global climate. Part 1. Theory",2010,"10.1016/j.jastp.2009.12.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950518294&doi=10.1016%2fj.jastp.2009.12.007&partnerID=40&md5=9ead88f47ec749d7683ecb9781aca310","Based on theoretical and experimental consideration of the first (the Twomey effect) and second indirect aerosol effects the quasianalytic description of physical connection between the galactic cosmic rays intensity and the Earth's cloud cover is obtained.It is shown that the basic equation of the Earth's climate energy-balance model is described by the bifurcation equation (with respect to the temperature of the Earth's surface) in the form of assembly-type catastrophe with the two governing parameters defining the variations of insolation and Earth's magnetic field (or the galactic cosmic rays intensity in the atmosphere), respectively.The principle of hierarchical climatic models construction, which consists in the structural invariance of balance equations of these models evolving on different time scales, is described. © 2010 Elsevier Ltd."
"16678944000;6603144464;56134359300;7004828383;","Toward the snowball earth deglaciation...",2010,"10.1007/s00382-010-0748-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954955417&doi=10.1007%2fs00382-010-0748-8&partnerID=40&md5=06feb4a66e146708d9169e5f03fcc71e","The current state of knowledge suggests that the Neoproterozoic snowball Earth is far from deglaciation even at 0.2 bars of CO2. Since understanding the termination of the fully ice-covered state is essential to sustain, or not, the snowball Earth theory, we used an Atmospheric General Climate Model (AGCM) to explore some key factors which could induce deglaciation. After testing the models' sensitivity to their parameterizations of clouds, CO2 and snow, we investigated the warming effect caused by a dusty surface, associated with ash release during a mega-volcanic eruption. We found that the snow aging process, its dirtiness and the ash deposition on the snow-free ice are key factors for deglaciation. Our modelling study suggests that, under a CO2 enriched atmosphere, a dusty snowball Earth could reach the deglaciation threshold. © 2010 Springer-Verlag."
"26645289600;7202145115;","Why is longwave cloud feedback positive?",2010,"10.1029/2010JD013817","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956338119&doi=10.1029%2f2010JD013817&partnerID=40&md5=48d03c48c64370fe655ffc47e3d67116","Longwave cloud feedback is systematically positive and nearly the same magnitude across all global climate models used in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4). Here it is shown that this robust positive longwave cloud feedback is caused in large part by the tendency for tropical high clouds to rise in such a way as to remain at nearly the same temperature as the climate warms. Furthermore, it is shown that such a cloud response to a warming climate is consistent with well-known physics, specifically the requirement that, in equilibrium, tropospheric heating by convection can only be large in the altitude range where radiative cooling is efficient, following the fixed anvil temperature hypothesis of Hartmann and Larson (2002). Longwave cloud feedback computed assuming that high-cloud temperature follows upper tropospheric convergence-weighted temperature, which we refer to as proportionately higher anvil temperature, gives an excellent prediction of the longwave cloud feedback in the AR4 models. The ensemble-mean feedback of 0.5 W m-2 K-1 is much larger than that calculated assuming clouds remain at fixed pressure, highlighting the large contribution from rising cloud tops to the robustly positive feedback. An important result of this study is that the convergence profile computed from clear-sky energy and mass balance warms slightly as the climate warms, in proportion to the increase in stability, which results in a longwave cloud feedback that is slightly smaller than that calculated assuming clouds remain at fixed temperature. Copyright 2010 by the American Geophysical Union."
"35221494300;6603315547;57203053317;","Influence of a future climate on the microphysical and optical properties of orographic cirrus clouds in ECHAM5",2010,"10.1029/2010JD013824","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958524738&doi=10.1029%2f2010JD013824&partnerID=40&md5=25992b86ec683e8d4fc9910a6673173e","The European Centre/Hamburg 5 (ECHAM5) general circulation model is used in order to investigate the influence of a warmer climate on the microphysical and optical properties of orographic cirrus clouds. The main goal of this study is to highlight the variety of processes influencing the formation of orographic cirrus and to emphasize the importance of coupling dynamics and cloud microphysics in order to provide realistic predictions of the influence of a future climate on cloud microphysical and radiative properties. Therefore, a coupling of gravity wave dynamics and cloud microphysics is implemented in the model. The influence of additional moisture on the propagation of gravity waves is investigated by using the dry and moist Brunt-Väisäla frequency in the calculation of the gravity wave-induced vertical velocity in two different simulations. In both simulations, the vertical velocities increase in the warmer climate. The additional moisture decreases the Brunt-Väisäla frequencies leading to less flow blocking and thus higher effective mountain heights. As this effect dominates over the decrease of the gravity wave amplitude due to more moisture, higher vertical velocities occur in a future climate. The opposite effect of a decreased vertical velocity in a future climate can be seen over the dry regions. From the present to the future climate, the ice crystal number concentration decreases despite the increased vertical velocities. Higher temperatures lead to a faster growth of the ice crystals, and the supersaturation is depleted faster such that no new crystals can be formed. The ice water content increases as more water vapor is available in a warmer climate. The net effect of a decreased ice crystal number concentration and an increased ice water content is an increased optical depth in a future climate. This result is in good agreement with recent cloud resolving studies. The effect of orographic cirrus clouds on the radiation is given by an increased short- and long-wave cloud forcing, whereas the latter dominates. However, from the present to the future climate, no changes in orographic cloud cover and cloud forcing over mountains can be seen. Copyright 2010 by the American Geophysical Union."
"57218150582;55544443300;7005808242;","Sensitivity of climate change induced by the weakening of the Atlantic meridional overturning circulation to cloud feedback",2010,"10.1175/2009JCLI3118.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949337608&doi=10.1175%2f2009JCLI3118.1&partnerID=40&md5=378bf2bf8e09b88bc36890b7142dcc2b","A variety of observational and modeling studies show that changes in the Atlantic meridional overturning circulation (AMOC) can induce rapid global-scale climate change. In particular, a substantially weakened AMOC leads to a southward shift of the intertropical convergence zone (ITCZ) in both the Atlantic and the Pacific Oceans. However, the simulated amplitudes of the AMOC-induced tropical climate change differ substantially among different models. In this paper, the sensitivity to cloud feedback of the climate response to a change in the AMOC is studied using a coupled ocean-atmosphere model [the GFDL Coupled Model, version 2.1 (CM2.1)]. Without cloud feedback, the simulated AMOC-induced climate change in this model is weakened substantially. Low-cloud feedback has a strong amplifying impact on the tropical ITCZ shift in this model, whereas the effects of high-cloud feedback are weaker. It is concluded that cloud feedback is an important contributor to the uncertainty in the global response to AMOC changes. © 2010 American Meteorological Society."
"7005578774;6602098362;","Simulation of present-day and twenty-first-century energy budgets of the southern oceans",2010,"10.1175/2009JCLI3152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949340634&doi=10.1175%2f2009JCLI3152.1&partnerID=40&md5=0a1e79b0636938feee755ecded26dbc1","The energy budget of the modern-day Southern Hemisphere is poorly simulated in both state-of-the-art reanalyses and coupled global climate models. The ocean-dominated Southern Hemisphere has low surface reflectivity and therefore its albedo is particularly sensitive to cloud cover. In modern-day climates, mainly because of systematic deficiencies in cloud and albedo at mid- and high latitudes, too much solar radiation enters the ocean. Along with too little radiation absorbed at lower latitudes because of clouds that are too bright, unrealistically weak poleward transports of energy by both the ocean and atmosphere are generally simulated in the Southern Hemisphere. This implies too little baroclinic eddy development and deficient activity in storm tracks. However, projections into the future by coupled climate models indicate that the Southern Ocean features a robust and unique increase in albedo, related to clouds, in association with an intensification and poleward shift in storm tracks that is not observed at any other latitude. Such an increase in cloud may be untenable in nature, as it is likely precluded by the present-day ubiquitous cloud cover that models fail to capture. There is also a remarkably strong relationship between the projected changes in clouds and the simulated current-day cloud errors. The model equilibrium climate sensitivity is also significantly negatively correlated with the Southern Hemisphere energy errors, and only the more sensitive models are in the range of observations. As a result, questions loom large about how the Southern Hemisphere will actually change as global warming progresses, and a better simulation of the modern-day climate is an essential first step. © 2010 American Meteorological Society."
"16029674800;6701346974;6507017020;55431666500;7101851249;7202208382;6601970557;7102486629;","An ocean-atmosphere climate simulation with an embedded cloud resolving model",2010,"10.1029/2009GL040822","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75749145021&doi=10.1029%2f2009GL040822&partnerID=40&md5=569c704d727d46d9c9e7784986df726a","Mean climate and intraseasonal to interannual variability of two versions of the Community Climate System Model (CCSM) coupled atmosphere-ocean general circulation model (CGCM) are analyzed. The first version is the standard CCSM, in which cloud effects on the large-scale circulation are represented via parameterizations. The second version includes ""super- parameterization"" (SP) of convective processes by replacing parameterized cloud processes with a two-dimensional (2D) cloud-process resolving model (CRM) at each CGCM grid column. The SP-CCSM improves several shortcomings of the CCSM simulation, including mean precipitation patterns, equatorial SST cold tongue structure and associated double intertropical convergence zone (ITCZ), the Asian monsoon, periodicity of the El Nio-Southern Oscillation, and the intraseasonal Madden-Julian Oscillation. These improvements were obtained without the retuning of the coupled model, which is surprising in view of previous experience with other coupled models. Copyright 2010 by the American Geophysical Union."
"35104535800;7404416268;","Observed and reanalysis cloud fraction",2010,"10.1029/2009JD013235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650255856&doi=10.1029%2f2009JD013235&partnerID=40&md5=14bbec34e5c7f4b9cef34b3d708592a4","Because the Arctic climate is particularly sensitive to cloud-radiative interactions, climate models must represent Arctic clouds realistically in order to capture the variations and feedbacks in high-latitude climate. Observations of clouds and radiative fluxes for the North Slope of Alaska are available from the Department of Energy's Atmospheric Radiation Measurement (ARM) program. Reanalysis models also calculate cloud and radiative variables. In this study, ARM measurements and North American Regional Reanalysis output for four midseason months are used to show that boundary layer clouds are not only the most common type of cloud observed on the North Slope but they are also a major cause for error by the reanalysis. Near-surface clouds are associated with large overestimates of the cloud fraction during the cold season and large underestimates during the warm season. These results were synthesized with other data to produce a comprehensive picture of synoptic conditions that are commonly present when the reanalysis fails to simulate the cloud fraction. When errors in the simulated cloud fraction are largest during the cold season, anomalously high pressure is observed north of the Bering Strait, with the departure being largest in magnitude and most widespread spatially in January. Large undersimulations in the summer are associated with a +9 hPa deviation from climatology over the Arctic Ocean, a configuration that favors onshore flow from the northeast and east. More generally, large undersimulations in the summer clouds at Barrow are almost exclusively associated with onshore flow. Copyright 2010 by the American Geophysical Union."
"6701802669;","Antarctic clouds",2010,"10.1111/j.1751-8369.2010.00148.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955083758&doi=10.1111%2fj.1751-8369.2010.00148.x&partnerID=40&md5=4fe35edd40eaeebb130aad09d12d2d05","Sensitivity studies with global climate models show that, by their influence on the radiation balance, Antarctic clouds play a major role in the climate system, both directly at high southern latitudes and indirectly globally, as the local circulation changes lead to global teleconnections. Unfortunately, observations of cloud distribution in the Antarctic are limited and often of low quality because of the practical difficulty in observing clouds in the harsh Antarctic environment. The best surface observations suggest that the fractional cloud cover at the South Pole is around 50-60% in all seasons, whereas the cloud cover rises to around 80-90% close to the coast of the continent. Microphysical observations of cloud parameters are also very sparse in the Antarctic. However, the few measurements that do exist show predominantly ice-crystal clouds across the interior, with mixed-phase clouds close to the coasts. Crystal sizes vary from 5 to 30 μm (effective radius) in the interior to somewhat larger ice crystals and water drops near the coast. A wide range of crystal shapes is observed at all sites. This review considers the available cloud observations and highlights the importance of Antarctic clouds and the need for better observations in the future. © 2010 the author, journal compilation © 2010 Blackwell Publishing Ltd."
"7101959253;7005626683;7202702025;7004540083;","A review of cloud top height and optical depth histograms from MISR, ISCCP, and MODIS",2010,"10.1029/2009JD013422","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956204954&doi=10.1029%2f2009JD013422&partnerID=40&md5=30782036559325da5ed6e40e60e834f8","There are notable differences in the joint histograms of cloud top height and optical depth being produced from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging Spectro-Radiometer (MISR) and by the International Satellite Cloud Climatology Project (ISCCP). These differences have their roots in the different retrieval approaches used by the three projects and are driven largely by responses of the retrievals to (1) stratocumulus (or more broadly low-level clouds under temperature inversions), (2) small (subpixel) or broken low-level clouds, and (3) multilayer clouds. Because each data set has different strengths and weakness, the combination tells us more about the observed cloud fields than any of the three by itself. In particular, the MISR stereo height retrieval provides a calibration insensitive approach to determining cloud height that is especially valuable in combination with ISCCP or MODIS because the combination provides a means to estimate the amount of multilayer cloud, where the upper cloud is optically thin. In this article we present a review of the three data sets using case studies and comparisons of annually averaged joint histograms on global and regional scales. Recommendations for using these data in climate model evaluations are provided. Copyright 2010 by the American Geophysical Union."
"7101959253;7005626683;","An analysis of cloud cover in multiscale modeling framework global climate model simulations using 4 and 1 km horizontal grids",2010,"10.1029/2009JD013423","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956203733&doi=10.1029%2f2009JD013423&partnerID=40&md5=82a97b14b037f14e39631faf580b9c5f","Over the past few years, a new type of global climate model (GCM) has emerged in which a two-dimensional or small three-dimensional cloud resolving model is embedded into each grid cell of a GCM. This approach is frequently called the multiscale modeling framework (MMF) but is also known as a cloud-resolving convection parameterization or a superparameterization. In this article, we compare joint histograms of cloud top height and optical depth from the MMF with those being produced by the International Satellite Cloud Climatology Project (ISCCP) and from the Multiangle Imaging Spectroradiometer (MISR). While the form of the ISCCP and MISR data sets is conceptually similar, the satellite sensors and the algorithms differ, with the result that the joint histograms can differ quite significantly even when viewing exactly the same clouds. The analysis takes advantages of the strengths of each data set, as well as the differences in these data (which, for example, allow one to characterize the amount of some multilayer clouds). MMF simulation runs with three different resolutions are analyzed. One simulation is run using a 4 km horizontal grid with 26 vertical levels (on a stretched grid), a second simulation is run with a 1 km horizontal grid and the same 26 vertical levels, and a third simulation is run with a 1 km horizontal grid and 52 vertical levels. The analysis shows that the MMF reproduces the broad pattern of tropical convergence zones, subtropical belts, and midlatitude storm tracks as observed by ISCCP and MISR. However, the model has several significant shortcomings. Perhaps most seriously, it significantly underpredicts the amount of low-level cloud in most regions. The simulation with a 1 km horizontal grid and 52 vertical layers is found to improve modestly several aspect of the MMF low-level cloud cover. The model output is obtained using ISCCP and MISR instrument simulators and the role of horizontal resolution in the instrument simulators is examined. Copyright 2010 by the American Geophysical Union."
"35191486300;56672215300;35976805500;8720083500;55730024300;","Semidirect radiative forcing of internal mixed black carbon cloud droplet and its regional climatic effect over China",2010,"10.1029/2009JD013165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957585927&doi=10.1029%2f2009JD013165&partnerID=40&md5=1741fc654d70341706b9625516440bd1","Black carbon (BC) is one of the most important atmospheric aerosols. It can exert a positive radiative forcing by absorbing solar radiation and a negative radiative forcing by acting as cloud condensation nuclei (CCN) at the top of the atmosphere (TOA). Furthermore, cloud droplets with BC can absorb more solar radiation and reduce their single-scattering albedo (SSA), leading to a positive cloud radiative forcing (SSA forcing) at TOA. Here we include such a process into the coupled modeling system (RegCCMS) which consists of a regional climate model (RegCM3) and a tropospheric atmosphere chemistry model (TACM) to investigate BC loading, SSA forcing, and its climatic responses in different seasons over China. The year 2003 was selected as the base year for this study. Results show high BC loadings in Sichuan, Hebei, and Shandong provinces with weak seasonal variations. The national average SSA forcing due to the cloud droplets absorption is 0.04, 0.096, 0.085, and 0.056 W/m2 at TOA, while -0.05, -0.14, -0.12, and -0.077 W/m2 at the surface in January, April, July, and October, respectively. It can reach as much as 0.6 W/m 2 at TOA and -0.8 W/m2 at the surface in the regions with high BC concentration and cloud cover. Numerical experiments indicate that internal mixed BC and cloud droplet can absorb more solar radiation, then heat the air, hence reducing the cloud cover and increasing vertical velocity. On the other hand, more solar absorption due to mixture droplets can alter atmospheric and hydrologic cycle, which consequently changes the distribution of cloud cover and eventually affects surface air temperature, precipitation, and solar radiation. Given an above 90% confidence level of statistical significance of linear correlation between SSA forcing and climate changes, surface air temperature changes for 4 months vary from -0.0022 to +0.0103 K and precipitation changes range from -0.0047 in January to 0.029 mm/d in April. These changes show an extremely large seasonal variation; so do those of cloud amount (Max: -0.066%) and solar flux (Max: 0.21 W/m2). Owing to the small SSA forcing, its climatic responses are easily masked by internal model variability in summer season, especially for precipitation and cloud. Even so, small SSA forcing in colder seasons may lead to noticeable local surface drought or cooling. For example, precipitation decreases in Yangtze River Basin reaching 1.2 mm/d in October; surface air temperatures decrease by 0.2 to 0.4 K in east China in April. It is obvious that SSA forcing and its climate responses are weaker compared to BC direct, indirect, and semidirect effects. However, it does have nonnegligible influence on regional climate changes over China. Copyright 2010 by the American Geophysical Union."
"25624545600;36458493200;57206332144;7004299722;8625545200;7005399437;7003907406;7003289221;","Cloud optical depth retrievals from the aerosol robotic network (AERONET) cloud mode observations",2010,"10.1029/2009JD013121","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955590817&doi=10.1029%2f2009JD013121&partnerID=40&md5=9562340a0eb1752c20b2fc623265dd95","Cloud optical depth is one of the most poorly observed climate variables. The new ""cloud mode"" capability in the Aerosol Robotic Network (AERONET) will inexpensively yet dramatically increase cloud optical depth observations in both number and accuracy. Cloud mode optical depth retrievals from AERONET were evaluated at the Atmospheric Radiation Measurement program's Oklahoma site in sky conditions ranging from broken clouds to overcast. For overcast cases, the 1.5 min average AERONET cloud mode optical depths agreed to within 15% of those from a standard ground-based flux method. For broken cloud cases, AERONET retrievals also captured rapid variations detected by the microwave radiometer. For 3 year climatology derived from all nonprecipitating clouds, AERONET monthly mean cloud optical depths are generally larger than cloud radar retrievals because of the current cloud mode observation strategy that is biased toward measurements of optically thick clouds. This study has demonstrated a new way to enhance the existing AERONET infrastructure to observe cloud optical properties on a global scale. Copyright 2010 by the American Geophysical Union."
"7406200372;36119737000;56948583000;55487543500;55719328100;55879900300;57217720842;7005219614;","Strong air pollution causes widespread haze-clouds over China",2010,"10.1029/2009JD013065","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957591267&doi=10.1029%2f2009JD013065&partnerID=40&md5=1349af1e0553999cc9b6fe94537cc452","North China (Huabei in Chinese) is a geographical region located between 32N and 42°N latitude in eastern China, including several provinces and large municipalities (e.g., Beijing and Tianjin). In the past decades the region has experienced dramatic changes in air quality and climate. Among the multiple causes aerosol pollution is expected to play a particularly important role. To investigate this, a field measurement campaign was performed in April-May 2006 as part of the project Influence of Pollution on Aerosols and Cloud Microphysics in North China. Here we report the first aircraft measurements of atmospheric trace gases, aerosols, and clouds over this part of China, a region strongly affected by both natural desert dust and pollution smog. We observed very high concentrations of gaseous air pollutants and haze particles, partly together with nonprecipitating stratiform clouds. The clouds were characterized by numerous droplets, much smaller than in a less-polluted atmosphere. Our data reveal that the highly efficient coating of dust particles by pollution acids provides the predominant source of cloud condensation nuclei. The pollution-enhanced activation of dust particles into droplets is shown to be remarkably efficient so that clouds even form below 100% relative humidity. Contrary to previous analyses, we find that the haze particles influence the spectral shape of the cloud droplet size distribution such that the indirect climate cooling effect of aerosols on clouds is increased. The widespread haze, combined with low clouds, diminishes air quality and exerts an unusually strong cooling forcing on climate. © 2010 by the American Geophysical Union."
"16027966800;7006329853;7202081585;6701410484;7202607288;24778157400;7402332362;8453485500;","Numerical simulations of the three-dimensional distribution of polar mesospheric clouds and comparisons with Cloud Imaging and Particle Size (CIPS) experiment and the Solar Occultation For Ice Experiment (SOFIE) observations",2010,"10.1029/2009JD012451","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953168133&doi=10.1029%2f2009JD012451&partnerID=40&md5=9ca7ed97fb54ad391212e8f86c8aefb8","Polar mesospheric clouds (PMC) routinely form in the cold summer mesopause region when water vapor condenses to form ice. We use a three-dimensional chemistry-climate model based on the Whole-Atmosphere Community Climate Model (WACCM) with sectional microphysics from the Community Aerosol and Radiation Model for Atmospheres (CARMA) to study the distribution and characteristics of PMCs formed by heterogeneous nucleation of water vapor onto meteoric smoke particles. We find good agreement between these simulations and cloud properties for the Northern Hemisphere in 2007 retrieved from the Solar Occultation for Ice Experiment (SOFIE) and the Cloud Imaging and Particle Size (CIPS) experiment from the Aeronomy of Ice in the Mesosphere (AIM) mission. The main discrepancy is that simulated ice number densities are less than those retrieved by SOFIE. This discrepancy may indicate an underprediction of nucleation rates in the model, the lack of small-scale gravity waves in the model, or a bias in the SOFIE results. The WACCM/CARMA simulations are not very sensitive to large changes in the barrier to heterogeneous nucleation, which suggests that large supersaturations in the model nucleate smaller meteoric smoke particles than are traditionally assumed. Our simulations are very sensitive to the temperature structure of the summer mesopause, which in the model is largely dependent upon vertically propagating gravity waves that reach the mesopause region, break, and deposit momentum. We find that cloud radiative heating is important, with heating rates of up to 8 K/d. Copyright 2010 by the American Geophysical Union."
"55716092000;6701378450;55714712500;57211106013;9249239700;57196499374;","Global climate response to anthropogenic aerosol indirect effects: Present day and year 2100",2010,"10.1029/2008JD011619","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954530206&doi=10.1029%2f2008JD011619&partnerID=40&md5=3908226512830464c18cf3ae68f95c86","Aerosol indirect effects (AIE) are a principal source of uncertainty in future climate predictions. The present study investigates the equilibrium response of the climate system to present-day and future AIE using the general circulation model (GCM), Goddard Institute for Space Studies (GISS) III. A diagnostic formulation correlating cloud droplet number concentration (N <inf>c</inf>) with concentrations of aerosol soluble ions is developed as a basis for the calculation. Explicit dependence on N<inf>c</inf> is introduced in the treatments of liquid-phase stratiform clouds in GISS III. The model is able to reproduce the general patterns of present-day cloud frequency, droplet size, and radiative balance observed by CloudSat, Moderate Resolution Imaging Spectroradiometer, and Earth Radiation Budget Experiment. For perturbations of N<inf>c</inf> from preindustrial to present day, a net AIE forcing of-1.67 W m-2 is estimated, with a global mean surface cooling of 1.12 K, precipitation reduction of 3.36%, a southward shift of the Intertropical Convergence Zone, and a hydrological sensitivity of +3.00% K-1. For estimated perturbations of N<inf>c</inf> from present day to year 2100, a net AIE forcing of-0.58 W m-2, a surface cooling of 0.47 K, and a decrease in precipitation of 1.7% are predicted. Sensitivity calculations show that the assumption of a background minimum N<inf>c</inf> value has more significant effects on AIE forcing in the future than on that in present day. When AIE-related processes are included in the GCM, a decrease in stratiform precipitation is predicted over future greenhouse gas (GHG)-induced warming scenario, as opposed to the predicted increase when only GHG and aerosol direct effects are considered. Copyright 2010 by the American Geophysical Union."
"26434854300;7004198777;55438848700;8899985400;7005729142;35731251200;7004715270;7103016965;55919282000;7402049334;7007160874;57196499374;7005773698;","Observation of playa salts as nuclei in orographic wave clouds",2010,"10.1029/2009JD013606","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955542579&doi=10.1029%2f2009JD013606&partnerID=40&md5=396316940dc8dc8ee8133f1938ec0ca1","During the Ice in Clouds Experiment-Layer Clouds (ICE-L), dry lakebed, or playa, salts from the Great Basin region of the United States were observed as cloud nuclei in orographic wave clouds over Wyoming. Using a counterflow virtual impactor in series with a single-particle mass spectrometer, sodium-potassium-magnesium-calcium-chloride salts were identified as residues of cloud droplets. Importantly, these salts produced similar mass spectral signatures to playa salts with elevated cloud condensation nuclei (CCN) efficiencies close to sea salt. Using a suite of chemical characterization instrumentation, the playa salts were observed to be internally mixed with oxidized organics, presumably produced by cloud processing, as well as carbonate. These salt particles were enriched as residues of large droplets (>19 m) compared to smaller droplets (>7 m). In addition, a small fraction of silicate-containing playa salts were hypothesized to be important in the observed heterogeneous ice nucleation processes. While the high CCN activity of sea salt has been demonstrated to play an important role in cloud formation in marine environments, this study provides direct evidence of the importance of playa salts in cloud formation in continental North America has not been shown previously. Studies are needed to model and quantify the impact of playas on climate globally, particularly because of the abundance of playas and expected increases in the frequency and intensity of dust storms in the future due to climate and land use changes. Copyright 2010 by the American Geophysical Union."
"7102988363;43561316500;7004384155;56219012200;","A method for comparing properties of cirrus clouds in global climate models with those retrieved from IR sounder satellite observations",2010,"10.1127/0941-2948/2010/0484","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959782747&doi=10.1127%2f0941-2948%2f2010%2f0484&partnerID=40&md5=89c4e99d6830273081808b05d10798ad","A methodology to compare cloud properties simulated by global climate models with those retrieved from observations by satellite-based infrared (IR) sounders has been developed. The relatively high spectral resolution in the CO2 absorption band of these instruments leads to especially reliable cirrus properties, day and night. Additionally, bulk microphysical properties can be retrieved for semi-transparent cirrus, based on the observed spectral emissivity differences between 8 and 11 μm. The particular intention of this study is to compare macro-and microphysical properties of high cloudiness as represented by the model simulations and the satellite data. For this purpose, a method has been developed to process the model output to be comparable to the satellite measurements, as in other observational simulator packages (for example the ISCCP-simulator). This simulator method takes into account i) the differences in horizontal resolution of the model and the observations, ii) the specific observation time windows, iii) the determination of the pressure of a cloud system, identified with the pressure at the middle of the uppermost cloud, and iv) the selection of high clouds with specific cloud optical thickness ranges for the microphysical property retrieval using IR sounder data. Applying this method to simulations by the global climate model ECHAM and TOVS satellite observations has important effects. The frequency of high clouds selected from the model output by using the method is significantly smaller than the total frequency of high cloudiness in the model. Largest differences occur around the equator where the zonal mean frequency of high cloudiness is reduced by about 30 % (relative change). The selection method is essential for the comparison of modelled and observed microphysical properties of high clouds. The selection of high clouds from the ECHAM simulation according to the optical thickness range of the TOVS data results in a reduction of the mean water path of high clouds by factors of more than 3 compared to the case where also high clouds of other optical thicknesses are considered. Furthermore, the selection by optical thickness causes a significant increase in the mean effective cloud particle diameter. These changes significantly reduce the differences between the simulation and the observations. The method can also be applied for comparisons with other IR sounder climatologies such as from AIRS and IASI. © Gebruder Borntraeger, Stuttgart 2010."
"57217268037;7410041005;","Comparison of Arctic clouds between European Center for Medium-Range Weather Forecasts simulations and Atmospheric Radiation Measurement Climate Research Facility long-term observations at the North Slope of Alaska Barrow site",2010,"10.1029/2010JD014285","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650035288&doi=10.1029%2f2010JD014285&partnerID=40&md5=dd05fb89288ca623e0c806baacf0f73e","This study evaluated the European Center for Medium-Range Weather Forecasts (ECMWF) model-simulated clouds and boundary layer (BL) properties based upon Atmospheric Radiation Measurement Climate Research Facility observations at the North Slope of Alaska site during 1999-2007. The ECMWF model-simulated near-surface humidity had seasonal dependent biases as large as 20%, while also experiencing difficulty representing BL temperature inversion height and strength during the transition seasons. Although the ECMWF model captured the seasonal variation of surface heat fluxes, it had sensible heat flux biases over 20 W m-2 in most of the cold months. Furthermore, even though the model captured the general seasonal variations of low-level cloud fraction (LCF) and liquid water path (LWP), it still overestimated the LCF by 20% or more and underestimated the LWP over 50% in the cold season. On average, the ECMWF model underestimated LWP by ∼30 g m-2 but more accurately predicted ice water path for BL clouds. For BL mixed-phase clouds, the model predicted water-ice mass partition was significantly lower than the observations, largely due to the temperature dependence of water-ice mass partition used in the model. The ECMWF model captured the general response of cloud fraction and LWP on large-scale vertical motion changes but overpredicted the magnitude of the difference, especially for LWP. The new cloud and BL schemes of the ECMWF model that were implemented after 2003 only resulted in minor improvements in BL cloud simulations in summer. These results indicate that significant improvements in cold season BL and mixed-phase cloud processes in the model are needed. Copyright 2010 by the American Geophysical Union."
"55714647400;7101959253;7005626683;","A comparison of observations in the tropical western Pacific from ground-based and satellite millimeter-wavelength cloud radars",2010,"10.1029/2009JD013575","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650553518&doi=10.1029%2f2009JD013575&partnerID=40&md5=461a3495a8a9ce9666810a2059b36c79","Millimeter-wavelength cloud radar (MMCR) can provide information on the vertical structure of cloud fields and thereby improve our understanding of the spatial distribution of clouds and their role in the climate system. Here we consider the representativeness of ground-based vertically pointing MMCR observations, which have been used in numerous climate studies. MMCR cloud statistics collected at Darwin, Australia, are compared against CloudSat (spaceborne) observations gathered in the near vicinity of the ground site. Overall, the total cloud occurrence vertical profiles observed by CloudSat and the ground-based MMCR agree on a spatial scale of 4° × 4°, although CloudSat is found to observe more high reflectivity cloud than the ground-based MMCR. Computed radar reflectivity using idealized atmospheric profiles suggests that rain (especially below the melting level) influences the observed reflectivities, and this appears to account for much of the differences in the observed distributions of radar reflectivity. After removal of precipitation profiles, CloudSat and ground-based MMCR observations show reasonable agreement. Sampling uncertainty in the CloudSat observations makes comparison at smaller region spatial scales (e.g., 2.5°) difficult and unfeasible for analysis at the time scale of months. Comparison of CloudSat observations with the ground-based data on scales of 4 and 7.5 works well. Comparison of total cloud occurrence and reflectivity distribution of nonprecipitating cloud from the MMCR and CloudSat at spatial scales from 4 to 7.5 show good agreement. This suggests that the properties of the nonprecipitating cloud are relatively homogeneous at this large scale. Copyright 2010 by the American Geophysical Union."
"8891521600;13402835300;7403282069;6701859365;","Comparison of the tropical radiative flux and cloud radiative effect profiles in a climate model with Clouds and the Earth's Radiant Energy System (CERES) data",2010,"10.1029/2009JD012490","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76249107388&doi=10.1029%2f2009JD012490&partnerID=40&md5=da2e5197eab00bfe48e2636e62b4ccdb","An insightful link of model performance to the physical assumptions in general circulation models (GCMs) can be explored if assessment of radiative fluxes and cloud radiative effects go beyond those at the top of the atmosphere (TOA). In this study, we compare the radiative flux profiles (at surface, 500 hPa, 200 hPa, 70 hPa, and TOA) and cloud effect profiles (500 hPa, 200 hPa, and TOA) from HadGAM1, using Surface and Atmospheric Radiation Budget (SARB) data from Clouds and the Earth's Radiant Energy System (CERES) on the TRMM satellite over the tropics (30°S-30°N). Comparison at TOA reveals that HadGAM1 agrees well with CERES for mean cloud height but lacks in cloudiness. Comparing to its predecessor, HadAM3, HadGAM1 agrees better with observations in TOA LW cloud effects, net cloud effects, and the ratio of SW to LW cloud effects. Extending the comparison to multiple levels, we gain additional insight into the vertical differences in clouds: for clouds at heights below 500 hPa, HadGAM1 and CERES are in good agreement in terms of cloudiness, but HadGAM1 underestimates the average cloud height; for clouds between 500 and 200 hPa, HadGAM1 underestimates the cloudiness but overestimates the average cloud height; for clouds at heights above 200 hPa, HadGAM1 produces more clouds than in CERES. Stratifying the cloud effects by dynamic regimes, we find that HadGAM1 underestimates cloudiness and overestimates averaged cloud height in the convective regimes, but the opposite is true in the strong subsidence regimes. Copyright 2010 by the American Geophysical Union."
"35974951200;35887706900;20435752700;","Estimating cloud field coverage using morphological analysis",2010,"10.1088/1748-9326/5/1/014022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950680996&doi=10.1088%2f1748-9326%2f5%2f1%2f014022&partnerID=40&md5=005f5c486553bafa0f4c5a336c68f299","The apparent cloud-free atmosphere in the vicinity of clouds ('the twilight zone') is often affected by undetectable weak signature clouds and humidified aerosols. It is suggested here to classify the atmosphere into two classes: cloud fields, and cloud-free (away from a cloud field), while detectable clouds are included in the cloud field class as a subset. Since the definition of cloud fields is ambiguous, a robust cloud field masking algorithm is presented here, based on the cloud spatial distribution. The cloud field boundaries are calculated then on the basis of the Moderate Resolution Imaging Spectroradiometer(MODIS) cloud mask products and the total cloud field area is estimated for the Atlantic Ocean (50°S-50°N). The findings show that while the monthly averaged cloud fraction over the Atlantic Ocean during July is 53%, the cloud field fraction may reach 97%, suggesting that cloud field properties should be considered in climate studies. A comparison between aerosol optical depth values inside and outside cloud fields reveals differences in the retrieved radiative properties of aerosols depending on their location. The observed mean aerosol optical depth inside the cloud fields is more than 10% higher than outside it, indicating that such convenient cloud field masking may contribute to better estimations of aerosol direct and indirect forcing. © 2010 IOP Publishing Ltd."
"35459245100;7004469744;35547807400;15519671300;7201606127;6506718302;","Aerosol climate feedback due to decadal increases in southern hemisphere wind speeds",2010,"10.1029/2009GL041320","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76749090406&doi=10.1029%2f2009GL041320&partnerID=40&md5=20281273d637a24c97c5c73321da59e6","Observations indicate that the westerly jet in the Southern Hemisphere troposphere is accelerating. Using a global aerosol model we estimate that the increase in wind speed of 0.45 ± 0.2 m s-1decade-1 at 50-65°S since the early 1980s caused a higher sea spray flux, resulting in an increase of cloud condensation nucleus concentrations of more than 85% in some regions, and of 22% on average between 50 and 65°S. These fractional increases are similar in magnitude to the decreases over many northern hemisphere land areas due to changes in air pollution over the same period. The change in cloud drop concentrations causes an increase in cloud reflectivity and a summertime radiative forcing between at 50 and 65°S comparable in magnitude but acting against that from greenhouse gas forcing over the same time period, and thus represents a substantial negative climate feedback. However, recovery of Antarctic ozone depletion in the next two decades will likely cause a fall in wind speeds, a decrease in cloud drop concentration and a correspondingly weaker cloud feedback. © Copyright 2010 by the American Geophysical Union."
"55495496100;35454141800;7202079615;7202149369;55537009700;","Characterization of ice cloud properties obtained by shipborne radar/lidar over the tropical western Pacific Ocean for evaluation of an atmospheric general circulation model",2010,"10.1029/2009JD012944","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955533239&doi=10.1029%2f2009JD012944&partnerID=40&md5=6135ec2c20200aa24549f99a80b00bde","This study analyzed 95-GHz radar/lidar data collected from the R/V Mirai over the tropical western Pacific to characterize the vertical distribution of ice cloud effective radius r<inf>eff</inf>, ice water content IWC, and in-cloud vertical velocity of the region in conjunction with weather regimes classified by International Satellite Cloud Climatology Project (ISCCP) cluster analysis. Ice clouds observed from the Mirai were roughly consistent with the ISCCP weather regimes; more convectively active regimes had larger amounts of high cloud consisting of deeper cloud with larger ice water path (IWP) and precipitating ice fraction. Ice cloud microphysics of the Center for Climate System Research, National Institute for Environmental Studies, Frontier Research Center for Global Change atmospheric general circulation model (AGCM) was then evaluated using the radar-lidar simulator and ISCCP weather regimes for comparison of the statistics at different scales. The model tended to produce a high cloud fraction that was two times larger in the cirrus regimes but 50% lower in the deepest convective regime. The simulated IWP could only weakly reproduce the observed variety and generally underestimated the observed values despite the weather regimes. Cutoff in the simulated grid mean IWC around 0.1 g-3 was too small, especially above 11 km. The AGCM successfully predicted the observed frequency distribution for r<inf>eff</inf> above 11 km, but produced large overestimation in the peak value below 11 km due to the excessively large fraction of r<inf>eff</inf> ∼100 m. Establishing a cutoff for cloud ice at r<inf>eff</inf> > 120 m was found to be quite reasonable, although it would miss some of the larger particles that were observed. Copyright 2010 by the American Geophysical Union."
"7005941690;36669169800;7005981420;7004586688;","Influence of Arctic sea ice extent on polar cloud fraction and vertical structure and implications for regional climate",2010,"10.1029/2010JD013900","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649305408&doi=10.1029%2f2010JD013900&partnerID=40&md5=8f2c48bc2e66dc864e54ad81fd80ec6d","Recent satellite lidar measurements of cloud properties spanning a period of 5 years are used to examine a possible connection between Arctic sea ice amount and polar cloud fraction and vertical distribution. We find an anticorrelation between sea ice extent and cloud fraction with maximum cloudiness occurring over areas with little or no sea ice. We also find that over ice-free regions, there is greater low cloud frequency and average optical depth. Most of the optical depth increase is due to the presence of geometrically thicker clouds over water. In addition, our analysis indicates that over the last 5 years, October and March average polar cloud fraction has increased by about 7% and 10%, respectively, as year average sea ice extent has decreased by 5%-7%. The observed cloud changes are likely due to a number of effects including, but not limited to, the observed decrease in sea ice extent and thickness. Increasing cloud amount and changes in vertical distribution and optical properties have the potential to affect the radiative balance of the Arctic region by decreasing both the upwelling terrestrial longwave radiation and the downward shortwave solar radiation. Because longwave radiation dominates in the long polar winter, the overall effect of increasing low cloud cover is likely a warming of the Arctic and thus a positive climate feedback, possibly accelerating the melting of Arctic sea ice. Copyright 2010 by the American Geophysical Union."
"8560603600;7102171439;36097134700;","Characterization of cloud liquid water content distributions from CloudSat",2010,"10.1029/2009JD013272","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78049405124&doi=10.1029%2f2009JD013272&partnerID=40&md5=2c1c1f886d428c8751ee3195a3b76bed","The development of realistic cloud parameterizations requires accurate characterizations of subgrid distributions of thermodynamic variables. To this end, cloud liquid water content (CLWC) distributions are characterized with respect to cloud phase, cloud type, precipitation occurrence, and geolocation using CloudSat radar measurements. The probability density function (PDF) of CLWC is estimated using maximum likelihood estimation. The best-estimated PDF of CLWC is found to follow either a gamma or a lognormal distribution depending on temperature (cloud phase), cloud type, the occurrence of precipitation, and geolocation. The data sampling with respect to cloud phase and precipitation significantly affects the distributional characteristics of CLWC in some regions. In the lower to midtroposphere (altitudes of 1-6 km) in the tropics and subtropics, where nonprecipitating and pure liquid phase clouds are dominant, the PDFs of CLWC are best described by lognormal distributions. In contrast, at altitudes above 6 km and in regions poleward of the midlatitudes, the CLWC more closely resembles a gamma distribution that coincides with a high frequency of occurrence of supercooled liquid clouds containing low CLWC values. When the contributions of supercooled water and precipitation are removed, the CLWC PDFs transition from gamma to lognormal distributions in two areas: (1) the high altitude and middle-to-polar latitude regions where the contribution of supercooled cloud is significant and (2) in the lower troposphere where precipitation is frequently detected. Although the CloudSat radar does not sample all cloud hydrometeors, coherent regional and cloud type dependence of CLWC distributional characteristics are observed that may provide useful constraints for cloud parameterizations in climate models. Copyright © 2010 by the American Geophysical Union."
"8719703500;7006783796;","GOES 12 observations of convective storm variability and evolution during the Tropical Composition, Clouds and Climate Coupling Experiment field program",2010,"10.1029/2009JD013227","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956460568&doi=10.1029%2f2009JD013227&partnerID=40&md5=8f96864855c156b781802900e2d69bd8","This study characterizes convective clouds that occurred during the Tropical Composition, Clouds and Climate Coupling Experiment as observed within GOES imagery. Overshooting deep convective cloud tops (OT) that penetrate through the tropical tropopause layer and into the stratosphere are of particular interest in this study. The results show that there were clear differences in the areal coverage of anvil cloud, deep convection, and OT activity over land and water and also throughout the diurnal cycle. The offshore waters of Panama, northwest Colombia, and El Salvador were the most active regions for OT-producing convection. A cloud object tracking system is used to monitor the duration and areal coverage of convective cloud complexes as well as the time evolution of their cloud-top microphysical properties. The mean lifetime for these complexes is 5 hours, with some existing for longer than 16 hours. Deep convection is found within the anvil cloud during 60% of the storm lifetime and covered 24% of the anvil cloud. The cloud-top height and optical depth at the storm core followed a reasonable pattern, with maximum values occurring 20% into the storm lifetime. The values in the surrounding anvil cloud peaked at a relative age of 20%-50% before decreasing as the convective cloud complex decayed. Ice particle diameter decreased with distance from the core but generally increased with storm age. These results, which characterize the average convective system during the experiment, should be valuable for formulating and validating convective cloud process models. © Copyright 2010 by the American Geophysical Union."
"55545601500;8258673100;7403282069;35779178900;56158622800;7403508241;35263384600;25928347900;","Occurrence, liquid water content, and fraction of supercooled water clouds from combined CALIOP/IIR/MODIS measurements",2010,"10.1029/2009JD012384","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958185165&doi=10.1029%2f2009JD012384&partnerID=40&md5=b0e69c49c948acae1375a2e39ddb4473","The CALIOP depolarization measurements, combined with backscatter intensity measurements, are effective in discriminating between water clouds and ice clouds. The same depolarization measurements can also be used for estimating liquid water content information. Using cloud temperature information from the collocated infrared imaging radiometer measurements and cloud water paths from collocated MODIS measurements, this study compiles global statistics of the occurrence frequency, liquid water content, liquid water path, and their temperature dependence. For clouds with temperatures between -40°C and 0°C, the liquid phase fractions and liquid water paths are significantly higher than the ones from previous studies using passive remote sensing measurements. At midlatitudes, the occurrence of liquid phase clouds at temperatures between -40°C and 0°C depends jointly on both cloud height and cloud temperature. At high latitudes, more than 95% of low-level clouds with temperatures between -40°C and 0°C are water clouds. Supercooled water clouds are mostly observed over ocean near the storm-track regions and high-latitude regions. Supercooled water clouds over land are observed in the Northern Hemisphere over Europe, East Asia, and North America, and these are the supercooled water clouds with highest liquid water contents. The liquid water content of all supercooled water clouds is characterized by a Gamma (Γ) distribution. The mode values of liquid water content are around 0.06 g/m 3 and are independent of cloud temperature. For temperatures warmer than -15°C, mean value of the liquid water content is around 0.14 g/m 3. As the temperature decreases, the mean cloud liquid water content also decreases. These results will benefit cloud models and cloud parameterizations used in climate models in improving their ice-phase microphysics parameterizations and the aviation hazard forecast."
"36600036800;35183351400;24398842400;","Do anthropogenic aerosols enhance or suppress the surface cloud forcing in the Arctic?",2010,"10.1029/2010JD014015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78249253759&doi=10.1029%2f2010JD014015&partnerID=40&md5=c30068e27b5dc10825c9e4b3a4e46051","Earlier studies suggest that aerosol-cloud interactions may have contributed to the increase in surface air temperature recently observed in the Arctic. While those studies focused on longwave effects of strong pollution events around Barrow, Alaska, we use a global climate model (CAM-Oslo) to study the annual and seasonal net radiative effect of aerosol-cloud interactions over the entire Arctic region. The model is validated against and adjusted to match observations from the Surface Heat Budget of the Arctic Ocean campaign along with measuring stations within the Arctic region. Several sensitivity experiments were conducted which included changes in both cloud properties and aerosol concentrations. Results show that the longwave indirect effect at the surface lies between 0.10 and 0.85 W/m2 averaged annually north of 71°N, while the shortwave indirect effect lies between -1.29 W/m2 and -0.52 W/m2. Due to longwave dominance in winter, 6 of 11 simulations give a positive change in net cloud forcing between October and May (-0.16 to 0.29 W/m2), while the change in forcing averaged over the summer months is negative for all model simulations (from -2.63 to -0.23 W/m2). The annually averaged change in net cloud forcing at the surface is negative in 10 of 11 simulations, lying between -0.98 and 0.12 W/m2. In conclusion, our results point to a small decrease in the surface radiative flux due to the aerosol indirect effect in the Arctic, but these estimates are subject to uncertainties in the frequency of thin clouds and biases in the estimated cloud cover. © 2010 by the American Geophysical Union."
"7201472576;6504058972;","Evaluation of arctic cloud products from the EUMETSAT climate monitoring satellite application facility based on CALIPSO-CALIOP observations",2010,"10.5194/acp-10-1789-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77149179444&doi=10.5194%2facp-10-1789-2010&partnerID=40&md5=cd09b085d378f9cc37b6915d2e2f0dec","The performance of the three cloud products cloud fractional cover, cloud type and cloud top height, derived from NOAA AVHRR data and produced by the EUMETSAT Climate Monitoring Satellite Application Facility, has been evaluated in detail over the Arctic region for four months in 2007 using CALIPSO-CALIOP observations. The evaluation was based on 142 selected NOAA/Metop overpasses allowing almost 400 000 individual matchups between AVHRR pixels and CALIOP measurements distributed approximately equally over the studied months (June, July, August and December 2007). Results suggest that estimations of cloud amounts are very accurate during the polar summer season while a substantial loss of detected clouds occurs in the polar winter. Evaluation results for cloud type and cloud top products point at specific problems related to the existence of near isothermal conditions in the lower troposphere in the polar summer and the use of reference vertical temperature profiles from Numerical Weather Prediction model analyses. The latter are currently not detailed enough in describing true conditions relevant on the pixel scale. This concerns especially the description of near-surface temperature inversions which are often too weak leading to large errors in interpreted cloud top heights."
"7202181543;35453054300;7006508549;57203474131;","Roles of atmospheric and land surface data in dynamic regional downscaling",2010,"10.1029/2009JD012218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949534494&doi=10.1029%2f2009JD012218&partnerID=40&md5=e5b9d388666efea7aac65e44ce2d712a","In studies dealing with the impact of land use changes on atmospheric processes, a key methodological step is the validation of simulated current conditions. However, regions lacking detailed atmospheric and land use data provide limited information with which to accurately generate control simulations. In this situation, the difference between baseline control simulations and different land use change simulations can be quite different owing to the quality of the atmospheric and land use data sets. Using multiple simulations at the Monteverde cloud forest region of Costa Rica as an example, we show that when a regional climate model is used to study the effect of land use change, it can produce distinctly different results at regional scales, depending on the amount of data available to run the climate simulations. We show that for the specific case of land use change impact studies, the simulation results are very sensitive to the prescribed atmospheric information (e.g., lateral boundary conditions) compared to the land use(surface boundary) information. Copyright 2010 by the American Geophysical Union."
"35561911800;6604021707;36705143500;7006399110;","Attribution of the present-day total greenhouse effect",2010,"10.1029/2010JD014287","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958587213&doi=10.1029%2f2010JD014287&partnerID=40&md5=4a8c6d14388889f1b9a1da9c6fa7a78f","The relative contributions of atmospheric long-wave absorbers to the present-day global greenhouse effect are among the most misquoted statistics in public discussions of climate change. Much of the interest in these values is however due to an implicit assumption that these contributions are directly relevant for the question of climate sensitivity. Motivated by the need for a clear reference for this issue, we review the existing literature and use the Goddard Institute for Space Studies ModelE radiation module to provide an overview of the role of each absorber at the present-day and under doubled CO<inf>2</inf>. With a straightforward scheme for allocating overlaps, we find that water vapor is the dominant contributor (∼50% of the effect), followed by clouds (∼25%) and then CO<inf>2</inf> with ∼20%. All other absorbers play only minor roles. In a doubled CO<inf>2</inf> scenario, this allocation is essentially unchanged, even though the magnitude of the total greenhouse effect is significantly larger than the initial radiative forcing, underscoring the importance of feedbacks from water vapor and clouds to climate sensitivity."
"7103246957;25624545600;","Idealized model for changes in equilibrium temperature, mixed layer depth, and boundary layer cloud over land in a doubled CO2 climate",2010,"10.1029/2009JD012888","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958121043&doi=10.1029%2f2009JD012888&partnerID=40&md5=01dd5230982b6848c3342375c785b4c1","An idealized equilibrium model for the undisturbed partly cloudy boundary layer (BL) is used as a framework to explore the coupling of the energy, water, and carbon cycles over land in midlatitudes and show the sensitivity to the clear-sky shortwave flux, the midtropospheric temperature, moisture, CO 2, and subsidence. The changes in the surface fluxes, the BL equilibrium, and cloud cover are shown for a warmer, doubled CO2 climate. Reduced stomatal conductance in a simple vegetation model amplifies the background 2 K ocean temperature rise to an (unrealistically large) 6 K increase in near-surface temperature over land, with a corresponding drop of near-surface relative humidity of about 19%, and a rise of cloud base of about 70 hPa. Cloud changes depend strongly on changes of mean subsidence; but evaporative fraction (EF) decreases. EF is almost uniquely related to mixed layer (ML) depth, independent of background forcing climate. This suggests that it might be possible to infer EF for heterogeneous landscapes from ML depth. The asymmetry of increased evaporation over the oceans and reduced transpiration over land increases in a warmer doubled CO2 climate. Copyright 2010 by the American Geophysical Union."
"35725421500;57204986042;6506063574;6701759982;57214367679;35600074800;7004864963;","A possible role of ground-based microorganisms on cloud formation in the atmosphere",2010,"10.5194/bg-7-387-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76449112439&doi=10.5194%2fbg-7-387-2010&partnerID=40&md5=3c3f7579f1331fa0f4db405f494c524e","The formation of clouds is an important process for the atmosphere, the hydrological cycle, and climate, but some aspects of it are not completely understood. In this work, we show that microorganisms might affect cloud formation without leaving the Earth's surface by releasing biological surfactants (or biosurfactants) in the environment, that make their way into atmospheric aerosols and could significantly enhance their activation into cloud droplets. In the first part of this work, the cloud-nucleating efficiency of standard biosurfactants was characterized and found to be better than that of any aerosol material studied so far, including inorganic salts. These results identify molecular structures that give organic compounds exceptional cloud-nucleating properties. In the second part, atmospheric aerosols were sampled at different locations: a temperate coastal site, a marine site, a temperate forest, and a tropical forest. Their surface tension was measured and found to be below 30 mN/m, the lowest reported for aerosols, to our knowledge. This very low surface tension was attributed to the presence of biosurfactants, the only natural substances able to reach to such low values. The presence of strong microbial surfactants in aerosols would be consistent with the organic fractions of exceptional cloud-nucleating efficiency recently found in aerosols, and with the correlations between algae bloom and cloud cover reported in the Southern Ocean. The results of this work also suggest that biosurfactants might be common in aerosols and thus of global relevance. If this is confirmed, a new role for microorganisms on the atmosphere and climate could be identified."
"12753162000;35547807400;7407104838;57203200427;7102805852;10139397300;16233122400;","Parameterization of contrails in the UK Met Office climate model",2010,"10.1029/2009JD012443","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953146128&doi=10.1029%2f2009JD012443&partnerID=40&md5=6cec33903ca5f7dde38903b080f6c7b1","Persistent contrails are believed to currently have a relatively small but significant positive radiative forcing on climate. With air travel predicted to continue its rapid growth over the coming years, the contrail warming effect on climate is expected to increase. Nevertheless, there remains a high level of uncertainty in the current estimates of contrail radiative forcing. Contrail formation depends mostly on the aircraft flying in cold and moist enough air masses. Most studies to date have relied on simple parameterizations using averaged meteorological conditions. In this paper we take into account the short-term variability in background cloudiness by developing an on-line contrail parameterization for the UK Met Office climate model. With this parameterization, we estimate that for the air traffic of year 2002 the global mean annual linear contrail coverage was approximately 0.11%. Assuming a global mean contrail optical depth of 0.2 or smaller and assuming hexagonal ice crystals, the corresponding contrail radiative forcing was calculated to be less than 10 mW m-2 in all-sky conditions. We find that the natural cloud masking effect on contrails may be significantly higher than previously believed. This new result is explained by the fact that contrails seem to preferentially form in cloudy conditions, which ameliorates their overall climate impact by approximately 40%. Copyright 2010 by the American Geophysical Union."
"35090272500;7006206130;","On the radiation budget in regional climate simulations for West Africa",2010,"10.1029/2010JD014331","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650463911&doi=10.1029%2f2010JD014331&partnerID=40&md5=213249ebc06b03bc4058bd91dec3dc67","This paper discusses the simulated monthly radiation budget of West Africa by eight regional climate models and the impact of three uncertainty sources in the simulations: cloud fraction, surface albedo, and surface temperature. The models were driven by the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis data within the European Union project ENSEMBLES. The simulated budgets were compared to the satellite-based Global Energy and Water Cycle Experiment Surface Radiation Budget and ERA-Interim data sets. The simulations tended to underestimate the net solar radiation and the outgoing long-wave radiation, and they showed a regionally varying over- or underestimation in all budget components (up to 75%). The evaluation showed that uncertainty in the cloud fraction is the most important of the uncertainty sources over the ocean (with explained error variances between 25% and 60% depending on the budget component averaged over all models). Over land, the surface albedo and surface temperature were, on average, of similar importance as the cloud fraction. The latter result differed from that in a recent study for Europe, indicating that the importance of land surface on the radiation budget is regionally dependent. The relatively simple factor of surface albedo still explains a substantial part of the solar budget error variance in this study: more than 10% over ocean and more than 20% over land, peaking to more than 60% over the Sahelian and Saharan areas. It is worth improving on that in the models, in view of the complexity of other factors like cloud inhomogeneity and direct and indirect aerosol effects. Copyright 2010 by the American Geophysical Union."
"16555667700;","A westward propagating roll cloud and cool change on Tasmania's north coast",2010,"10.22499/2.6004.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953887383&doi=10.22499%2f2.6004.002&partnerID=40&md5=be917639f5efa706e57ff9c5ef458643","On 1 March 1997 a recreational pilot reported flying under and in front of a roll cloud on the northern Tasmanian coastline. This roll cloud, which was accompanied by a marked wind change at the surface, was propagating westward along the northern Tasmanian coastline, rather than in the easterly direction usual for cool change passage in the mid-latitudes. This paper describes the synoptic environment in which the roll cloud formed, and using mesoscale numerical weather prediction (NWP) simulations of the event shows that the roll cloud was associated with a gravity-current-like structure that developed after a cool change had surged northward along the Tasmanian east coast, and which has much of the character of the better-known Southerly Burster (or Southerly Buster) of the New South Wales coastline. It is argued that there is the potential for such events to occur on any day when a dry cool change surges northward along Tasmania's east coast, and several other events are documented."
"7102478067;56014511300;","Insights into Cloud-top height and Dynamics from the Seasonal cycle of cloud-top heights observed by MISR in the west Pacific region",2010,"10.1175/2009JAS3099.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953243076&doi=10.1175%2f2009JAS3099.1&partnerID=40&md5=038e44c29ab4bbcf63be1eb46e2fa334","The connection between environmental stability and the height of tropical deep convective clouds is analyzed using stereo cloud height data from the Multiangle Imaging Spectroradiometer (MISR), focusing on the seasonal cycle of clouds over the western Pacific Ocean. Three peaks in cloud-top height representing low, mid-topped, and deep convective clouds are found as in previous studies. The optically thickest cloud heights are roughly 2 km higher on the summer side of the equator, where CAPE is higher, than on the winter side. Overall cloud height, however, is about the same on both sides of the equator, but ~600 m higher in December-February (DJF) than in June-August (JJA). Because of variations in stratospheric upwelling, temperatures near the tropopause exhibit a significant seasonal cycle, mainly above 13 km. Using an ensemble of simulations by the Weather Research and Forecasting (WRF) cloud-resolving model and a simple overshooting parcel calculation, the authors show that the cloud height variation can be explained by that of near-tropopause stability changes, including influence from heights above 14 km, even though the cloud height peaks only near 12 km. This suggests that mixing above cloud top-not typically accounted for in simple models of convection-is important in setting the height of the laminar (anvil) high clouds that result. The MISR data indicate a seasonal variation in peak cloud-top temperature of ~5 K, despite the recent proposal that cloud-top heights should track a fixed isotherm. That proposal must therefore be applied with caution to any climate-change scenario that may involve significant changes in stratospheric upwelling. © 2010 American Meteorological Society."
"14035492400;7202400272;","21st century trends in Antarctic temperature and polar stratospheric cloud (PSC) area in the GEOS chemistry-climate model",2010,"10.1029/2009JD013397","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958129813&doi=10.1029%2f2009JD013397&partnerID=40&md5=943a5a2c1db4958a7e97e4da9bb24530","This study examines trends in Antarctic temperature and A<inf>PSC</inf>, a temperature proxy for the area of polar stratospheric clouds, in an ensemble of Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) simulations of the 21st century. A selection of greenhouse gas, ozone-depleting substance, and sea surface temperature scenarios is used to test the trend sensitivity to these parameters. One scenario is used to compare temperature trends in two versions of the GEOS CCM. An extended austral winter season is examined in detail. In May, June, and July, the expected future increase in CO <inf>2</inf>-related radiative cooling drives temperature trends in the Antarctic lower stratosphere. At 50 hPa, a 1-3 K cooling is expected between 2000 and 2100. Ozone levels increase, despite this robust cooling signal and the consequent increase in A<inf>PSC</inf>, suggesting the enhancement of stratospheric transport in future. In the lower stratosphere, the choice of climate change scenarios does not affect the magnitude of the early winter cooling. Midwinter temperature trends are generally small. In October, A <inf>PSC</inf> trends have the same sign as the prescribed halogen trends. That is, there are negative A<inf>PSC</inf> trends in ""realistic future"" simulations, where halogen loading decreases in accordance with the Montreal Protocol and CO<inf>2</inf> continues to increase. In these simulations, the speed of ozone recovery is not influenced by either the choice of sea surface temperature and greenhouse gas scenarios or by the model version. Copyright 2010 by the American Geophysical Union."
"57203053317;6603809220;13403622000;7407104838;7201837768;6602600408;7005304841;56249704400;6604021707;","Total aerosol effect: Radiative forcing or radiative flux perturbation?",2010,"10.5194/acp-10-3235-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950842193&doi=10.5194%2facp-10-3235-2010&partnerID=40&md5=92a7e1b2e5df8933f33e11217a73b9ff","Uncertainties in aerosol radiative forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of precipitation formation. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to define properly. Here we argue that fast feedbacks should be included because they act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models."
"24340241400;23970271800;7004307308;9233045100;15726335100;","Broken and inhomogeneous cloud impact on satellite cloud particle effective radius and cloud-phase retrievals",2010,"10.1029/2009JD012205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953149728&doi=10.1029%2f2009JD012205&partnerID=40&md5=0131b9f3ef8a8c0d65d46d56abc532da","The impact of sensor resolution on satellite-derived cloud particle effective radius (r<inf>e</inf>) and cloud phase (CPH) for broken and overcast inhomogeneous clouds is investigated for the Cloud Physical Properties (CPP) retrieval algorithm used by the Climate Monitoring Satellite Application Facility. First, synthetic data sets of high-resolution (1 × 1 km 2) and low-resolution (3 × 3 km2) radiances are used to illustrate the effect on the r<inf>e</inf> and cloud top temperature (CTT) retrieval, the cloud properties that are used for the CPH retrieval. It is shown that low-resolution r<inf>e</inf> can be overestimated by up to 12 μm and CTT by up to 20K for thick broken and inhomogeneous overcast water clouds over ocean and land surfaces. The overestimation of r<inf>e</inf> may cause erroneous assignments of ""ice"" to water clouds. Second, 2 months of CPP retrievals on Moderate Resolution Imaging Spectroradiometer (MODIS) radiances are used to quantify the effect on r<inf>e</inf> and CPH over the Atlantic Ocean and central Europe. Over both areas, the low-resolution r<inf>e</inf> is overestimated by up to +5 μm for broken and up to 2 μm for inhomogeneous overcast clouds. At low resolution, the fraction of water clouds is underestimated by 2.3% over the Atlantic Ocean and 0.6% over central Europe. The increase of CTT partly compensates for the increase in r<inf>e</inf> in the CPH retrievals at low resolution. If no CTT information were used, the underestimation of the water cloud fraction would be 3.5% and 2.2% for the Atlantic Ocean and central Europe, respectively. For inhomogeneous overcast clouds integrated over all inhomogeneity classes, the difference is -1.3% and -2.3% for central Europe and the Atlantic Ocean, respectively. Our results indicate that (1) the retrieval of r<inf>e</inf> in the CPP algorithm is sensitive to satellite sensor resolution in case of broken clouds and inhomogeneous overcast clouds and (2) despite this large r<inf>e</inf> sensitivity the CPH retrieval is much less sensitive to sensor resolution. Copyright 2010 by the American Geophysical Union."
"8728433200;57203053317;7501381728;57208121852;6701843835;7003931528;24398842400;35734113800;15926418500;16444232500;","Influences of in-cloud aerosol scavenging parameterizations on aerosol concentrations and wet deposition in ECHAM5-HAM",2010,"10.5194/acp-10-1511-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76749127970&doi=10.5194%2facp-10-1511-2010&partnerID=40&md5=8c2fb8c21e26d36ece3c8a39d9b593a8","A diagnostic cloud nucleation scavenging scheme, which determines stratiform cloud scavenging ratios for both aerosol mass and number distributions, based on cloud droplet, and ice crystal number concentrations, is introduced into the ECHAM5-HAM global climate model. This scheme is coupled with a size-dependent in-cloud impaction scavenging parameterization for both cloud droplet-aerosol, and ice crystal-aerosol collisions. The aerosol mass scavenged in stratiform clouds is found to be primarily (&gt;90%) scavenged by cloud nucleation processes for all aerosol species, except for dust (50%). The aerosol number scavenged is primarily (&gt;90%) attributed to impaction. 99% of this impaction scavenging occurs in clouds with temperatures less than 273 K. Sensitivity studies are presented, which compare aerosol concentrations, burdens, and deposition for a variety of in-cloud scavenging approaches: prescribed fractions, a more computationally expensive prognostic aerosol cloud processing treatment, and the new diagnostic scheme, also with modified assumptions about in-cloud impaction and nucleation scavenging. Our results show that while uncertainties in the representation of in-cloud scavenging processes can lead to differences in the range of 20-30% for the predicted annual, global mean aerosol mass burdens, and near to 50% for accumulation mode aerosol number burden, the differences in predicted aerosol mass concentrations can be up to one order of magnitude, particularly for regions of the middle troposphere with temperatures below 273 K where mixed and ice phase clouds exist. Different parameterizations for impaction scavenging changed the predicted global, annual mean number removal attributed to ice clouds by seven-fold, and the global, annual dust mass removal attributed to impaction by two orders of magnitude. Closer agreement with observations of black carbon profiles from aircraft (increases near to one order of magnitude for mixed phase clouds), mid-troposphere 210Pb vertical profiles, and the geographic distribution of aerosol optical depth is found for the new diagnostic scavenging scheme compared to the prescribed scavenging fraction scheme of the standard ECHAM5-HAM. The diagnostic and prognostic schemes represent the variability of scavenged fractions particularly for submicron size aerosols, and for mixed and ice phase clouds, and are recommended in preference to the prescribed scavenging fractions method."
"6507112497;8882641700;7403282069;7003554893;6602176524;35773341100;6603568514;8723504500;7003582587;12800106700;7401936984;","Modelling convective processes during the suppressed phase of a madden-julian oscillation: Comparing single-column models with cloud-resolving models",2010,"10.1002/qj.568","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949416699&doi=10.1002%2fqj.568&partnerID=40&md5=45359850544d5cafb549eb3cec501d39","The role of convective processes in moistening the atmosphere during suppressed periods of the suppressed phase of a Madden-Julian oscillation is investigated in cloud-resolving model (CRM) simulations, and the impact of moistening on the subsequent evolution of convection is assessed as part of a Global Energy and Water Cycle Experiment Cloud System Study (GCSS) inter comparison project. The ability of single-column model (SCM) versions of a number of state-of-the-art climate and numerical weather prediction models to capture these convective processes is also evaluated. During the suppressed periods, the CRMs are found to simulate a maximum moistening around 3 km, which is associated with a predominance of shallow convection. All SCMs produce adequate amounts of shallow convection during the suppressed periods, comparable to that seen in CRMs, but the relatively drier SCMs have higher precipitation rates than the relatively wetter SCMs and CRMs. The relatively drier SCMs dry, rather than moisten, the lower troposphere below the melting level. During the transition periods, convective processes act to moisten the atmosphere above the level at which mean advection changes from moistening to drying, despite an overall drying effect for the column. The SCMs capture some essence of this moistening at upper levels. A gradual transition from shallow to deep convection is simulated by the CRMs and the wetter SCMs during the transition periods, but the onset of deep convection is delayed in the drier SCMs. This results in lower precipitation rates for these SCMs during the active periods, although much better agreement exists between the models at this time. © 2010 Royal Meteorological Society."
"26643615000;35494005000;7410041005;35454141800;","Tropical composition, cloud and climate coupling experiment validation for cirrus cloud profiling retrieval using cloudsat radar and CALIPSO lidar",2010,"10.1029/2009JD013104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957582363&doi=10.1029%2f2009JD013104&partnerID=40&md5=1732e553c6aa253a815b3cefd27267a6","A profiling retrieval algorithm for ice cloud properties, such as effective radius (r<inf>e</inf>), ice water content (IWC), and an extinction coefficient, has been developed to use combined CloudSat radar reflectivity factor (Ze) and CALIPSO attenuated backscattering coefficient measurements based on an optimal estimation framework. Developed as an operational standard data product for the CloudSat project, the algorithm can treat a wide range of ice cloud situations from optically tenuous cirrus in the upper troposphere to geometrically and optically thick anvil clouds. It is designed to consider the attenuation of thick clouds in the radar and lidar forward model equations and multiple scattering in the lidar data. An optimal estimation approach allows for inversion of the forward model equations so that the uncertainty due to the assumptions can be evaluated. A sensitivity study shows that lidar multiple scattering has to be accounted for carefully. As for all ice cloud retrieval algorithms, assumptions regarding particle habits and size distribution shapes are critical to the accuracy of the results. The deviation in simulated Ze among different size distribution assumptions is smaller than among different habit assumptions, which indicates that the uncertainty due to particle habits is larger than the size distribution assumption. Those uncertainties are included in the forward model error covariance matrix to analyze the retrieval error. The algorithm is applied to CloudSat-CALIPSO data as well as lidar and radar data collected by the ER-2 during the Tropical Composition, Cloud and Climate Coupling Experiment mission on 22 July 2007. The retrieved r<inf>e</inf>, IWC, and extinction are shown to compare favorably with coincident in situ measurements collected by instruments on the NASA DC-8. This algorithm is expected to be complementary to the set of standard data products that is already being produced by the CloudSat project. © 2010 by the American Geophysical Union."
"55471474500;13404664500;7401945370;7202954964;7801685271;","Projection of changes in tropical cyclone activity and cloud height due to greenhouse warming: Global cloud‐system‐resolving approach",2010,"10.1029/2010GL042518","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992305563&doi=10.1029%2f2010GL042518&partnerID=40&md5=5949a5ecb7514cc0fb9df6450395a720","Tropical cyclone (TC) activity change due to global warming (GW) has been investigated using general circulation models. However, they involve uncertainty in treating the ensemble effects of deep convections. Here we sidestep such uncertainty by using a global cloud‐system-resolving model (GCRM) and assess TC changes with a time‐slice experiment for the present‐day and future GW experiments spanning 5 months each. The results support the Intergovernmental Panel on Climate Change Fourth Assessment Report; reduction in global frequency but increase in more intense TCs. Consistent with recent studies, frequency is reduced over the North Atlantic due to intensified vertical wind shear. Over the Pacific, frequency is almost unchanged and the genesis location shifts eastward under the prescribed El‐Niño like sea surface temperature change. With the GCRM’s advantage of representing mesoscale properties, we find that the cloud height becomes taller for more intense TCs and that this relationship is strengthened with GW. © 2010 by the American Geophysical Union."
"8668565900;24331185200;7102953444;6507634643;","Influence of climate shifts on decadal variations of surface solar radiation in Alaska",2010,"10.1029/2009JD012533","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949451761&doi=10.1029%2f2009JD012533&partnerID=40&md5=7fb66fabfbfd021d80340cda967375bc","From past studies it has been known that the Pacific Decadal Oscillation (PDO) shifted toward a positive mode in 1976 and a new climate regime occurred that produced a warming of the mean annual and seasonal temperatures and associated increases in cloud cover and precipitation in the North Pacific including Alaska. In this study, this climate shift is examined with regard to the variations in surface solar radiation before and after 1976 during the period 1961-2005. The results show greatest changes occurring in the southeast region in winter with a significant rise of 1.67% yr-1 during 1961-1975 before the shift and a nonsignificant decline of 1.07% yr-1 during 1977-1991 after the shift. In addition to the variations in solar radiation that occurred after 1976, the PDO and the solar radiation time series show common changes around 1989 and 1998. Thus, these two variables are compared to assess the strength of their relationship. The results show a good to moderate correlation with a maximum found in winter in Big Delta (interior region). The Pacific North American (PNA) circulation pattern is also strongly correlated with the solar radiation, with a maximum in winter in Anchorage (south-central region). In addition, a close relationship is found between cloud cover and solar radiation, particularly in the south-central and southwest regions. These results suggest that circulation patterns and associated cloud cover changes may play a large role, especially during wintertime, in the variations in the surface solar radiation in these regions of Alaska. © 2010 by the American Geophysical Union."
"6602584093;57203405965;6603800142;7201826462;7403931916;57208765879;","Observations and modeling of ice cloud shortwave spectral albedo during the tropical composition, cloud and climate coupling experiment (TC4)",2010,"10.1029/2009JD013127","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956053722&doi=10.1029%2f2009JD013127&partnerID=40&md5=fbeeb70d50763ce765b5795557fa92f0","Ice cloud optical thickness and effective radius have been retrieved from hyperspectral irradiance and discrete spectral radiance measurements for four ice cloud cases during the Tropical Composition, Cloud and Climate Coupling Experiment (TC4) over a range of solar zenith angle (23°-53°) and high (46-90) and low (5-15) optical thicknesses. The retrieved optical thickness and effective radius using measurements at only two wavelengths from the Solar Spectral Flux Radiometer (SSFR) irradiance and the Moderate Resolution Imaging Spectroradiometer Airborne Simulator (MAS) were input to a radiative transfer model using two libraries of ice crystal single-scattering optical properties to reproduce spectral albedo over the spectral range from 400 to 2130 nm. The two commonly used ice single-scattering models were evaluated by examining the residuals between observed spectral and predicted spectral albedo. The SSFR and MAS retrieved optical thickness and effective radius were found to be in close agreement for the low to moderately optically thick clouds with a mean difference of 3.42 in optical thickness (SSFR lower relative to MAS) and 3.79 μm in effective radius (MAS smaller relative to SSFR). The higher optical thickness case exhibited a larger difference in optical thickness (40.5) but nearly identical results for effective radius. The single-scattering libraries were capable of reproducing the spectral albedo in most cases examined to better than 0.05 for all wavelengths. Systematic differences between the model and measurements increased with increasing optical thickness and approached 0.10 between 400 and 600 nm and selected wavelengths between 1200 and 1300 nm. Differences between radiance and irradiance based retrievals of optical thickness and effective radius error sources in the modeling of ice single-scattering properties are examined. © 2010 by the American Geophysical Union."
"57196143493;7006016266;24921297200;6602336407;55605771904;","Separation of longwave climate feedbacks from spectral observations",2010,"10.1029/2009JD012766","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951045672&doi=10.1029%2f2009JD012766&partnerID=40&md5=0aac8c7f0db9deebbc47d5374c6ec2de","We conduct a theoretical investigation into whether changes in the outgoing longwave radiation (OLR) spectrum can be used to constrain longwave greenhousegas forcing and climate feedbacks, with a focus on isolating and quantifying their contributions to the total OLR change in all-sky conditions. First, we numerically compute the spectral signals of CO2 forcing and feedbacks of temperature, water vapor, and cloud. Then, we investigate whether we can separate these signals from the total change in the OLR spectrum through an optimal detection method. Uncertainty in optimal detection arises from the uncertainty in the shape of the spectral fingerprints, the natural variability of the OLR spectrum, and a nonlinearity effect due to the crosscorrelation of different climate responses. We find that the uncertainties in optimally detected greenhousegas forcing, water vapor, and temperature feedbacks are substantially less than their overall magnitudes in a double-CO2 experiment, and thus the detection results are robust. The accuracy in surface temperature and cloud feedbacks, however, is limited by the ambiguity in their fingerprints. Combining ambiguous feedback signals reduces the uncertainty in the combined signal. Auxiliary data are required to fully resolve the difficulty. Copyright 2010 by the American Geophysical Union."
"56014511300;7004169476;7007021059;7401945370;7404029779;6602887222;15124698700;","Relative humidity changes in a warmer climate",2010,"10.1029/2009JD012585","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893201500&doi=10.1029%2f2009JD012585&partnerID=40&md5=a6b539ebb275cf453e0477eeb499b213","Key climate feedback due to water vapor and clouds rest largely on how relative humidity R changes in a warmer climate, yet this has not been extensively analyzed in models. General circulation models (GCMs) from the CMIP3 archive and several higherresolution atmospheric GCMs examined here generally predict a characteristic pattern of R trend with global temperature that has been reported previously in individual models, including increase around the tropopause, decrease in the tropical upper troposphere, and decrease in midlatitudes. This pattern is very similar to that previously reported for cloud cover in the same GCMs, confirming the role of R in controlling changes in simulated cloud. Comparing different models, the trend in each part of the troposphere is approximately proportional to the upward and/or poleward gradient of R in the present climate. While this suggests that the changes simply reflect a shift of the R pattern upward with the tropopause and poleward with the zonal jets, the drying trend in the subtropics is roughly 3 times too large to be attributable to shifts of subtropical features, and the subtropical R minima deepen in most models. R trends are correlated with horizontal model resolution, especially outside the tropics, where they show signs of convergence and latitudinal gradients become close to available observations for GCM resolutions near T85 and higher. We argue that much of the systematic change in R can be explained by the local specific humidity having been set (by condensation) in remote regions with different temperature changes, hence the gradients and trends each depend on a model's ability to resolve moisture transport. Finally, subtropical drying trends predicted from the warming alone fall well short of those observed in recent decades. While this discrepancy supports previous reports of GCMs underestimating Hadley cell expansion, our results imply that shifts alone are not a sufficient interpretation of changes. Copyright © 2010 by the American Geophysical Union."
"25647910500;14034301300;7006434689;25648051300;6701762451;7006762521;57214957433;6701820813;7005069415;","Subarctic atmospheric aerosol composition: 3. Measured and modeled properties of cloud condensation nuclei",2010,"10.1029/2009JD012447","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649145861&doi=10.1029%2f2009JD012447&partnerID=40&md5=f6b0a79ee83c1af3c212fa5083fb274b","Aerosol particles can modify cloud properties by acting as cloud condensation nuclei (CCN). Predicting CCN properties is still a challenge and not properly incorporated in current climate models. Atmospheric particle number size distributions, hygroscopic growth factors, and polydisperse CCN number concentrations were measured at the remote subarctic Stordalen mire, 200 km north of the Arctic Circle in northern Sweden. The CCN number concentration was highly variable, largely driven by variations in the total number of sufficiently large particles, though the variability of chemical composition was increasingly important for decreasing supersaturation. The hygroscopicity of particles measured by a hygroscopicity tandem differential mobility analyzer (HTDMA) was in agreement with large critical diameters observed for CCN activation (κ ≈ 0.07-0.21 for D = 50-200 nm). Size distribution and time- and size-resolved HTDMA data were used to predict CCN number concentrations. Agreement of predictions with measured CCN within ± 11% was achieved using parameterized Khler theory and assuming a surface tension of pure water. The sensitivity of CCN predictions to various simplifying assumptions was further explored: We found that (1) ignoring particle mixing state did not affect CCN predictions, (2) averaging the HTDMA data in time with retaining the size dependence did not introduce a substantial bias, while individual predictions became more uncertain, and (3) predictions involving the hygroscopicity parameter recommended in literature for continental sites (κ ≈ 0.3 0.1) resulted in a significant prediction bias. Future modeling studies should therefore at least aim at using averaged, size-resolved, site-specific hygroscopicity or chemical composition data for predictions of CCN number concentrations. Copyright 2010 by the American Geophysical Union."
"23003667300;36021468400;56158622800;8439637100;57219274747;56142459700;","Seasonal and regional variability of cloud liquid water path in northwestern China derived from MODIS/CERES observations",2010,"10.1080/01431160903154309","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951120669&doi=10.1080%2f01431160903154309&partnerID=40&md5=22bef11586cd3b3557cbdff7ef03dcc3","This article describes the seasonal and regional variability of cloud liquid water path (LWP) in northwestern China. The regions of interest are: the area influenced by the Asian monsoon, the Tianshan Mountains, the Qilian Mountains and the Taklimakan Desert. The results presented here were derived from the instantaneous observations of cloud LWP from National Aeronautics and Space Administration (NASA) Clouds and the Earth's Radiant Energy System (CERES) Single Scanner Footprint (SSF) Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Edition 1B data from July 2002 to June 2004, and reflect more detailed subregional features than previous results from International Satellite Cloud Climatology Project (ISCCP) D2 monthly mean data. The seasonal and annual variation in cloud LWP is found to be significant in northwestern China, even within the same climate region. © 2010 Taylor & Francis."
"25031430500;55717074000;7003666669;7103158465;55717244800;15724543600;7402064802;7401974644;23065650200;9249239700;","Global simulations of ice nucleation and ice supersaturation with an improved cloud scheme in the Community Atmosphere Model",2010,"10.1029/2009JD013797","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957575116&doi=10.1029%2f2009JD013797&partnerID=40&md5=a6e21f9dcb4717934979fd330b8538b1","A process-based treatment of ice supersaturation and ice nucleation is implemented in the National Center for Atmospheric Research Community Atmosphere Model (CAM). The new scheme is designed to allow (1) supersaturation with respect to ice, (2) ice nucleation by aerosol particles, and (3) ice cloud cover consistent with ice microphysics. The scheme is implemented with a two-moment microphysics code and is used to evaluate ice cloud nucleation mechanisms and supersaturation in CAM. The new model is able to reproduce field observations of ice mass and mixed phase cloud occurrence better than previous versions. The model is able to reproduce observed patterns and frequency of ice supersaturation. Simulations indicate homogeneous freezing of sulfate and heterogeneous freezing on dust are both important ice nucleation mechanisms, in different regions. Simulated cloud forcing and climate is sensitive to different formulations of the ice microphysics. Arctic surface radiative fluxes are sensitive to the parameterization of ice clouds. These results indicate that ice clouds are potentially an important part of understanding cloud forcing and potential cloud feedbacks, particularly in the Arctic. Copyright 2010 by the American Geophysical Union."
"6603497730;6701705691;","Sensitivity of atmospheric motion vectors height assignment methods to semitransparent cloud properties using simulated Meteosat-8 radiances",2010,"10.1175/2010JAMC2352.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955528758&doi=10.1175%2f2010JAMC2352.1&partnerID=40&md5=a5c3768f763e59d5818c875ea7a652a7","This paper presents the sensitivity to various atmospheric parameters of two height assignment methods that aim to retrieve the cloud-top height of semitransparent clouds. The use of simulated Meteosat-8 radiances has the advantage that the pressure retrieved by a given method can be compared to the initial pressure set to the cloud in the model, which is exactly known. The methods retrieve the pressure of a perfectly opaque cloud to within a few hectopascals. However, considering more realistic ice clouds, methods are sensitive to all of the tested atmospheric parameters and, especially, to the cloud microphysics, which can bias the results of the CO2-slicing method by several tens of hectopascals. The cloud-top pressure retrieval is especially difficult for thinner clouds with optical thicknesses smaller than 2, for which the errors can reach several tens of hectopascals. The methods have also been tested after introducing realistic perturbations in the temperature and humidity profiles and on the clear-sky surface radiances. The corresponding averages of errors on the retrieved pressures are also very large, especially for thin clouds. In multilayer cloud situations the height assignment methods do not work properly, placing the cloud-top height somewhere between the two cloud layers for most cirrus cloud layers with optical thicknesses between 0.1 and 10. © 2010 American Meteorological Society."
"6603685334;55495155800;6603585313;36118350700;","Validation of the CERES edition 2B surface-only flux algorithms",2010,"10.1175/2009JAMC2246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953499345&doi=10.1175%2f2009JAMC2246.1&partnerID=40&md5=6883cdd23bc39996accae2b633f68c6e","The Clouds and the Earth's Radiant Energy System (CERES) project uses two shortwave (SW) and two longwave (LW) algorithms to derive surface radiative fluxes on an instantaneous footprint basis from a combination of top-of-atmosphere fluxes, ancillary meteorological data, and retrieved cloud properties. Since the CERES project examines the radiative forcings and feedbacks for Earth's entire climate system, validation of these models for a wide variety of surface conditions is paramount. The present validation effort focuses upon the ability of these surface-only flux algorithms to produce accurate CERES Edition 2B single scanner footprint data from the Terra and Aqua spacecraft measurements. To facilitate the validation process, high-quality radiometric surface observations have been acquired that were coincident with the CERESderived surface fluxes. For bothSWmodels, systematic errors range from-20 to-12 W m-2 (from-2.8% to -1.6%) for global clear-sky cases, while for the all-sky SW model, the systematic errors range from 14 to 21 W m-2 (3.2%-4.8%) for global cloudy-sky cases. Larger systematic errors were seen for the individual surface types, and significant random errors where observed, especially for cloudy-sky cases. While the SW models nearly achieved the 20 W m-2 accuracy requirements established for climate research, further improvements are warranted. For the clear-sky LW model, systematic errors were observed to fall within ±5.4 W m-2 (±1.9%) except for the polar case in which systematic errors on the order from -15 to -11 W m-2 (from-13% to -7.2%) occurred. For the all-sky LW model, systematic errors were less than ±9.2 W m-2 (±7.6%) for both the clear-sky and cloudy-sky cases. The random errors were less than 17 W m-2 (6.2%) for clear-sky cases and 28 W m-2 (13%) for cloudy-sky cases, except for the desert cases in which very high surface skin temperatures caused an overestimation in the model-calculated surface fluxes. Overall, however, the LW models met the accuracy requirements for climate research."
"35574655300;18936046300;7402064802;6701464294;7003289221;7006204393;6507865754;6701752471;35737212200;57198616562;55476479200;25823927100;7402480218;7103373860;35121796300;7005877775;57217692852;57155431600;7402934750;","ARM climate modeling best estimate data: A new data product for climate studies",2010,"10.1175/2009BAMS2891.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77249114707&doi=10.1175%2f2009BAMS2891.1&partnerID=40&md5=c88c76fa8b36ce1dcf135d08e6920d42","The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program has established a number of ARM Climate Research Facility (ACRF) and deployed an ARM Mobile Facility (AMF) in diverse climatic regimes around the world. The AMF has been deployed in diverse climatic regimes around the world to perform long-term continuous field measurements. The long-term continuous ACRF data provide significant information to improve understanding of the interaction between clouds and radiation, along with an observational basis for model validation, improvement, and climate studies. ARM has developed a data product specifically to be used by climate professionals to make ACRF data better serve the needs of climate studies and model development. The new data product is called, Climate Modeling Best Estimate (CMBE) dataset and assembles those quantities that are observed by ACRF and used in model evaluation into a single dataset."
"35221059800;55640225400;","A Dual-scheme approach of cumulus parameterization for simulating the Asian summer monsoon",2010,"10.1002/met.169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956816282&doi=10.1002%2fmet.169&partnerID=40&md5=0bf9f56ec10fe832e6753da98ecad158","The objective of this study is to introduce a novel approach of applying cumulus parameterization schemes (CPSs) in regional climate models. In this approach, two CPSs are running at alternate time steps during time integration. The two common CPSs of Emanuel and Anthes-Kuo have been examined. The results presented suggest that this dualscheme approach may enhance the performance of the model in simulating the Asian summer monsoon over East Asia, in comparison with the corresponding results by using any single CPS. This empirical study suggests that the dual-scheme approach can be considered as a potential alternative to the common ensemble approaches in short-term climate simulation or prediction. © 2009 Royal Meteorological Society."
"57202754759;7003455444;6602079010;","The sea ice mass budget of the Arctic and its future change as simulated by coupled climate models",2010,"10.1007/s00382-008-0493-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949265564&doi=10.1007%2fs00382-008-0493-4&partnerID=40&md5=c0d7b9d3cc232d86aea28e7523ec20b8","Arctic sea ice mass budgets for the twentieth century and projected changes through the twenty-first century are assessed from 14 coupled global climate models. Large inter-model scatter in contemporary mass budgets is strongly related to variations in absorbed solar radiation, due in large part to differences in the surface albedo simulation. Over the twenty-first century, all models simulate a decrease in ice volume resulting from increased annual net melt (melt minus growth), partially compensated by reduced transport to lower latitudes. Despite this general agreement, the models vary considerably regarding the magnitude of ice volume loss and the relative roles of changing melt and growth in driving it. Projected changes in sea ice mass budgets depend in part on the initial (mid twentieth century) ice conditions; models with thicker initial ice generally exhibit larger volume losses. Pointing to the importance of evolving surface albedo and cloud properties, inter-model scatter in changing net ice melt is significantly related to changes in downwelling longwave and absorbed shortwave radiation. These factors, along with the simulated mean and spatial distribution of ice thickness, contribute to a large inter-model scatter in the projected onset of seasonally ice-free conditions. © Springer-Verlag 2008."
"57191076887;7202556083;56042933000;7202158002;23570923700;37000099900;35733927300;","27-day variation in cloud amount in the Western Pacific warm pool region and relationship to the solar cycle",2010,"10.5194/acp-10-1577-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76749167036&doi=10.5194%2facp-10-1577-2010&partnerID=40&md5=212259789ff172e0a6cb8a2979d70a8f","Although linkages between solar activity and the earth's climate have been suggested and the 11-year cycle in solar activity evident in sunspot numbers is the most examined example of periodicity in previous studies, no quantitative evidence indicating a relationship for tropospheric phenomena has been found for a short period. Based on FFT analysis for OLR (Outgoing Longwave Radiation) compared with the F10.7 index, we clearly demonstrate a 27-day variation in the cloud amount in the region of the Western Pacific warm pool, which is only seen in the maximum years of 11-year solar activity. The average spectrum in such years also shows an enhancement in the range of the MJO (Madden-Julian Oscillation) period. Although there exist some explanations for possible mechanisms, the exact cause is unknown. Therefore, the proposed connection between 27-day cloud variation and solar cycle in the WPWP region is still a hypothesis and various kinds of varification based on other meteorological and solar parameters are strongly required."
"6506316395;7201498373;8414341100;","Contribution of soil moisture feedback to hydroclimatic variability",2010,"10.5194/hess-14-505-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949544533&doi=10.5194%2fhess-14-505-2010&partnerID=40&md5=2041b77ac10e4b77b5eebef826bf03ae","While a variety of model experiments and analyses of observations have explored the impact of soil moisture variation on climate, it is not yet clear how large or detectable soil moisture feedback is across spatial and temporal scales. Here, we study the impact of dynamic versus climatological soil moisture in the GISS GCM ModelE (with prescribed sea-surface temperatures) on the variance and on the spatial and temporal correlation scale of hydrologically relevant climate variables (evaporation, precipitation, temperature, cloud cover) over the land surface. We also confirm that synoptic variations in soil moisture have a substantial impact on the mean climate state, because of the nonlinearity of the dependence of evapotranspiration on soil moisture. We find that including dynamic soil moisture increases the interannual variability of seasonal (summer and fall) and annual temperature, precipitation, and cloudiness. Dynamic soil moisture tends to decrease the correlation length scale of seasonal (warm-season) to annual land temperature fluctuations and increase that of precipitation. Dynamic soil moisture increases the persistence of temperature anomalies from spring to summer and from summer to fall, and makes the correlation between land precipitation and temperature fluctuations substantially more negative. Global observation sets that allow determination of the spacetime correlation of variables such as temperature, precipitation, and cloud cover could provide empirical measures of the strength of soil moisture feedback, given that the feedback strength varies widely among models. © 2010 Author(s)."
"7004508767;55667257200;35223562800;7501757094;7003927831;","Sulfur cycle and sulfate radiative forcing simulated from a coupled global climate-chemistry model",2010,"10.5194/acp-10-3693-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951586615&doi=10.5194%2facp-10-3693-2010&partnerID=40&md5=aa82636985e58f41e24f21020c5c63d3","The sulfur cycle and radiative effects of sulfate aerosol on climate are studied with a Global tropospheric Climate-Chemistry Model in which chemistry, radiation and dynamics are fully coupled. Production and removal mechanisms of sulfate are analyzed for the conditions of natural and anthropogenic sulfur emissions. Results show that the 1985 anthropogenic emission tripled the global SO2 and sulfate loadings from its natural value of 0.16 and 0.10 Tg S, respectively. Under natural conditions, the fraction of sulfate produced in-cloud is 74%; whereas with anthropogenic emissions, the fraction of in-cloud sulfate production slightly increased to 76%. Lifetimes of SO2 and sulfate under polluted conditions are estimated to be 1.7 and 2.0 days, respectively. The tripling of sulfate results in a direct radiative forcing of -0.43 W - -2 (clear-sky) or -0.24 W mminus;-2 (all-sky), and a significant first indirect forcing of -1.85 W m-2, leading to a mean global cooling of about 0.1 K. Regional forcing and responses are significantly stronger than the global values. The first indirect forcing is sensitive to the relationship between aerosol concentration and cloud droplet number concentration which requires further investigation. Two aspects of chemistry-climate interaction are addressed. Firstly, the coupling effects lead to a slight decrease of 1% in global sulfate loading for both the cases of natural and anthropogenic added sulfur emissions. Secondly, only the indirect effect of sulfate aerosols yields significantly stronger signals in changes of near surface temperature and sulfate loading than changes due to intrinsic climate variability, while other responses to the indirect effect and all responses to the direct effect are below noise level. © 2010 Authors(s)."
"7003440089;24331295800;","Validation of a limited area model over Dome C, Antarctic Plateau, during winter",2010,"10.1007/s00382-008-0499-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049110244&doi=10.1007%2fs00382-008-0499-y&partnerID=40&md5=1fff570b4bfbbef0527a6820665fd45f","The limited area model MAR (Modèle Atmosphérique Régional) is validated over the Antarctic Plateau for the period 2004-2006, focussing on Dome C during the cold season. MAR simulations are made by initializing the model once and by forcing it through its lateral and top boundaries by the ECMWF operational analyses. Model outputs compare favourably with observations from automatic weather station (AWS), radiometers and atmospheric soundings. MAR is able to simulate the succession of cold and warm events which occur at Dome C during winter. Larger longwave downwelling fluxes (LWD) are responsible for higher surface air temperatures and weaker surface inversions during winter. Warm events are better simulated when the small Antarctic precipitating snow particles are taken into account in radiative transfer computations. MAR stratosphere cools during the cold season, with the coldest temperatures occurring in conjunction with warm events at the surface. The decrease of saturation specific humidity associated with these coldest temperatures is responsible for the formation of polar stratospheric clouds (PSCs) especially in August-September. PSCs then contribute to the surface warming by increasing the surface downwelling longwave flux. © 2008 Springer-Verlag."
"15766838300;7101661890;7202957110;7006698304;7003811754;6602725432;","Cloud-system-resolving model simulations of tropical cloud systems observed during the tropical warm pool-international cloud experiment",2010,"10.1175/2009MWR2993.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953187291&doi=10.1175%2f2009MWR2993.1&partnerID=40&md5=04cb05704fc07f1c9a2d6d165512872f","Nested cloud-system-resolving model simulations of tropical convective clouds observed during the recent Tropical Warm Pool-International Cloud Experiment (TWP-ICE) are conducted using the Weather Research and Forecasting (WRF) model. The WRF model is configured with a highest-resolving domain that uses 1.3-km grid spacing and is centered over Darwin, Australia. The performance of the model in simulating two different convective regimes observed during TWP-ICE is considered. The first regime is characteristic of the active monsoon, which features widespread cloud cover that is similar to maritime convection. The second regime is a monsoon break, which contains intense localized systems that are representative of diurnally forced continental convection. Many aspects of the model performance are considered, including their sensitivity to physical parameterizations and initialization time, and the spatial statistics of rainfall accumulations and the rain-rate distribution. While the simulations highlight many challenges and difficulties in correctly modeling the convection in the two regimes, they show that provided the mesoscale environment is adequately reproduced by the model, the statistics of the simulated rainfall agrees reasonably well with the observations. © 2010 American Meteorological Society."
"35271719200;7401776640;9534896800;","Do climate models reproduce observed solar dimming and brightening over China and Japan?",2010,"10.1029/2009JD012945","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905332817&doi=10.1029%2f2009JD012945&partnerID=40&md5=526275104d2f400494adf312b3eb3d3a","Previous research indicates that clear-sky downward solar radiation measured at the surface over China significantly decreased by about-8.6 W m -2 per decade during 1961-1989 and insignificantly increased during 1990-1999. Furthermore, solar radiation over Japan remained relatively constant during 1971-1989 and significantly increased by +5.3 W m-2 per decade during 1990-1999. The present study compares observed trends with those from twentieth century simulations by 14 global climate models in the CMIP3/IPCC-AR4. Since radiative forcing by aerosols is the primary contributor to long-term variations in surface solar radiation, the simulations are expected to resemble the observed trends if the input aerosol histories are realistic. To minimize the confounding impact of different cloud realizations in the observations and models, the radiative effects of cloud cover anomalies are removed from the surface solar radiation anomalies via linear regression. Although all of the models exhibit significant dimming trends over China before 1990, the largest model trend is-3.4 W m-2 per decade, less than half the magnitude and significantly different from the observed trend. Models including black carbon aerosol produce stronger decreasing trends than those that do not. The models also fail to reproduce the trend during 1990-1999 over Japan, and the largest model trend is +2.3 W m-2 per decade, only about half of the observed trend. These results suggest that global climate models uniformly underestimate the increase in aerosol radiative forcing over China prior to 1990 and uniformly underestimate the decrease in aerosol radiative forcing over Japan after 1990. Copyright © 2010 by the American Geophysical Union."
"7003398293;7102242175;7102239370;6602856988;55945122000;35550043200;7003865921;","HIRDLS and CALIPSO observations of tropical cirrus",2010,"10.1029/2009JD012100","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957560160&doi=10.1029%2f2009JD012100&partnerID=40&md5=933a34011bcbc82bbac7daf567863877","High Resolution Dynamics Limb Sounder (HIRDLS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements of cirrus frequency of occurrence in the upper tropical troposphere are quantified for September 2006 to August 2007. Monthly geospatial averages of cloud frequency of occurrence between 90 and 177 hPa are similar and correlate well with Microwave Limb Sounder (MLS) relative humidity with respect to ice (RHI) data, though clouds are present at individual RHI values less than 100%, due to the 5, 1, and sub-1 km vertical resolutions of the MLS, HIRDLS, and CALIPSO experiments. Seasonal variations in cloud frequency of occurrence are similar, with largest frequencies during winter (December-February). Though the CALIPSO and HIRDLS experiments employ nadir- and limb-viewing observational geometries, respectively, CALIPSO horizontal scales of cirrus are frequently larger than 100 km, and therefore similarities are present in the geospatial distributions of cloud occurrence. Isolated laminar cirrus is most prevalent away from the equator. The monthly patterns of HIRDLS and CALIPSO cloud occurrence are archived for useful comparisons to climate models. Copyright 2010 by the American Geophysical Union."
"8623972800;7405614202;36196693000;7101984634;7003962399;7003725697;6602480054;26031191700;14031984200;57216454359;","Analysis and characterization of the synergistic AIRS and MODIS cloud-cleared radiances",2010,"10.1007/s11707-010-0023-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955172154&doi=10.1007%2fs11707-010-0023-7&partnerID=40&md5=8328a99d05f7b2e3dd9438bd258e7da3","The Atmospheric Infrared Sounder (AIRS) and MODerate-Resolution Imaging Spectroradiometer (MODIS) on board NASA Earth Observing System (EOS) Aqua spacecraft measure the upwelling infrared radiance used for numerous remote-sensing- and climate-related applications. AIRS provides high spectral resolution infrared radiances, while MODIS provides collocated high spatial resolution radiances at 16 broad infrared bands. An optimal algorithm for cloud-clearing has been developed for AIRS cloudy soundings at the University of Wisconsin-Madison, where the spatially and spectrally collocated AIRS and MODIS data has been used to analyze the characteristic of this algorithm. An analysis and characterization of the global AIRS cloud-cleared radiances using the bias and the standard deviation between the cloud-cleared and the nearby clear measurements are studied. Scene inhomogeneity for both land- and water-surface types has been estimated to account for the assessed error. Both monthly and seasonal changes of global AIRS/MODIS cloud-clearing performance also have been analyzed. © 2010 Higher Education Press and Springer-Verlag Berlin Heidelberg."
"35331137500;7003283811;7005729142;6506385754;7501447027;7004198777;56332567800;","A study of cirrus ice particle size distribution using TC4 observations",2010,"10.1175/2009JAS3114.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953234205&doi=10.1175%2f2009JAS3114.1&partnerID=40&md5=a0df922caa6f584249c2776dc587eb08","An analysis of two days of in situ observations of ice particle size spectra, in convectively generated cirrus, obtained during NASA's Tropical Composition, Cloud, and Climate Coupling (TC4) mission is presented. The observed spectra are examined for their fit to the exponential, gamma, and lognormal function distributions. Characteristic particle size and concentration density scales are determined using two (for the exponential) or three (for the gamma and lognormal functions) moments of the spectra. It is shown that transformed exponential, gamma, and lognormal distributions should collapse onto standard curves. An examination of the transformed spectra, and of deviations of the transformed spectra from the standard curves, shows that the lognormal function provides a better fit to the observed spectra. © 2010 American Meteorological Society."
"7402093416;8726272900;6603561402;7005723936;7005134081;9738329300;56259852000;23479549200;6603480361;55393706100;6603821988;7004402705;36464907600;55919935700;6504688501;13609746100;16479703400;25031430500;23485410200;15127430500;6701511321;36088544000;7102976560;55883034700;8263760800;7102059695;6506553245;7004587644;55812487100;57203488770;7003800456;7006532784;7003683808;7103294731;7403544649;57206421971;16445242100;55730744700;","Chemistry-climate model simulations of spring Antarctic ozone",2010,"10.1029/2009JD013577","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955873925&doi=10.1029%2f2009JD013577&partnerID=40&md5=d8dc9235d4100078bb02ca84d5077b17","Coupled chemistry-climate model simulations covering the recent past and continuing throughout the 21st century have been completed with a range of different models. Common forcings are used for the halogen amounts and greenhouse gas concentrations, as expected under the Montreal Protocol (with amendments) and Intergovernmental Panel on Climate Change A1b Scenario. The simulations of the Antarctic ozone hole are compared using commonly used diagnostics: the minimum ozone, the maximum area of ozone below 220 DU, and the ozone mass deficit below 220 DU. Despite the fact that the processes responsible for ozone depletion are reasonably well understood, a wide range of results is obtained. Comparisons with observations indicate that one of the reasons for the model underprediction in ozone hole area is the tendency for models to underpredict, by up to 35%, the area of low temperatures responsible for polar stratospheric cloud formation. Models also typically have species gradients that are too weak at the edge of the polar vortex, suggesting that there is too much mixing of air across the vortex edge. Other models show a high bias in total column ozone which restricts the size of the ozone hole (defined by a 220 DU threshold). The results of those models which agree best with observations are examined in more detail. For several models the ozone hole does not disappear this century but a small ozone hole of up to three million square kilometers continues to occur in most springs even after 2070. Copyright © 2010 by the American Geophysical Union."
"23028121100;6504587461;7004419968;7201479825;","Comparison of monthly means of global total column water vapor retrieved from independent satellite observations",2010,"10.1029/2010JD013946","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650287563&doi=10.1029%2f2010JD013946&partnerID=40&md5=b8146517c65898faff49af21019a1ef3","Two independent data sets of monthly means of total column water vapor (TCWV) have been compared. The first data set is the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility on Climate Monitoring's (CM-SAF) Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS) product, which is based on passive microwave observations from the Special Sensor Microwave/Imager (SSM/I). It is available over oceans only and includes the TCWV also from cloudy scenes. The second one relies on Global Ozone Monitoring Experiment/Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (GOME/SCIAMACHY) measurements, which 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 comparison is performed for the period 1996 to 2005 for ice-free ocean areas. This comparison helps to analyze the potential of the two data sets to provide an independent merged TCWV data set for all surface types in the future. A systematic difference or bias is observed between both data sets, with lower TCWV for GOME/SCIAMACHY. The dominating cause (80-90%) for the difference in monthly averages is the cloud correction approach used within the GOME/SCIAMACHY retrieval scheme. We show that the bias contains a pronounced seasonal component and relies on cloud properties such as the cloud water path. Copyright 2010 by the American Geophysical Union."
"57202803751;6603562731;7005473082;24538154100;57208765879;7102063963;","Detection of multi-layer and vertically-extended clouds using A-train sensors",2010,"10.5194/amt-3-233-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956199396&doi=10.5194%2famt-3-233-2010&partnerID=40&md5=fff7ab52a0eca5db132ef30b2b832569","The detection of multiple cloud layers using satellite observations is important for retrieval algorithms as well as climate applications. In this paper, we describe a relatively simple algorithm to detect multiple cloud layers and distinguish them from vertically-extended clouds. The algorithm can be applied to coincident passive sensors that derive both cloud-top pressure from the thermal infrared observations and an estimate of solar photon pathlength from UV, visible, or near-IR measurements. Here, we use data from the A-train afternoon constellation of satellites: cloud-top pressure, cloud optical thickness, the multi-layer flag from the Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) and the optical centroid cloud pressure from the Aura Ozone Monitoring Instrument (OMI). For the first time, we use data from the CloudSat radar to evaluate the results of a multi-layer cloud detection scheme. The cloud classification algorithms applied with different passive sensor configurations compare well with each other as well as with data from CloudSat.<br> <br> We compute monthly mean fractions of pixels containing multi-layer and vertically-extended clouds for January and July 2007 at the OMI spatial resolution (12 km×24 km at nadir) and at the 5 km×5 km MODIS resolution used for infrared cloud retrievals. There are seasonal variations in the spatial distribution of the different cloud types. The fraction of cloudy pixels containing distinct multi-layer cloud is a strong function of the pixel size. Globally averaged, these fractions are approximately 20% and 10% for OMI and MODIS, respectively. These fractions may be significantly higher or lower depending upon location. There is a much smaller resolution dependence for fractions of pixels containing vertically-extended clouds (∼20% for OMI and slightly less for MODIS globally), suggesting larger spatial scales for these clouds. We also find higher fractions of vertically-extended clouds over land as compared with ocean, particularly in the tropics and summer hemisphere."
"7003821079;","Synergetic use of millimeter- and centimeter-wavelength radars for retrievals of cloud and rainfall parameters",2010,"10.5194/acp-10-3321-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950803592&doi=10.5194%2facp-10-3321-2010&partnerID=40&md5=5c72ba058f901428c8ea26914713ea5e","A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE) Climate Research Facility at the Tropical Western Pacific (TWP) Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP). C-band radar reflectivities are also used to estimate ice water path (IWP) in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500-800 g m2 (for CLWP) and a factor of 2 (for IWP). The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimation accuracies and provide retrievals for a wider range of stratiform precipitating cloud events."
"7202899330;6701606453;7102425008;36696314500;6701752471;13402835300;8067118800;7004899626;16679271700;","Dreary state of precipitation in global models",2010,"10.1029/2010JD014532","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650471505&doi=10.1029%2f2010JD014532&partnerID=40&md5=25f697f13cd1e4fa6eec249c72f109ef","New, definitive measures of precipitation frequency provided by CloudSat are used to assess the realism of global model precipitation. The character of liquid precipitation (defined as a combination of accumulation, frequency, and intensity) over the global oceans is significantly different from the character of liquid precipitation produced by global weather and climate models. Five different models are used in this comparison representing state-of-the-art weather prediction models, state-of-the-art climate models, and the emerging high-resolution global cloud ""resolving"" models. The differences between observed and modeled precipitation are larger than can be explained by observational retrieval errors or by the inherent sampling differences between observations and models. We show that the time integrated accumulations of precipitation produced by models closely match observations when globally composited. However, these models produce precipitation approximately twice as often as that observed and make rainfall far too lightly. This finding reinforces similar findings from other studies based on surface accumulated rainfall measurements. The implications of this dreary state of model depiction of the real world are discussed. Copyright 2010 by the American Geophysical Union."
"52063586400;57034458200;56424145700;","Impact of horizontal resolution on the regional climate simulations of the summer 1998 extreme rainfall along the Yangtze River Basin",2010,"10.1029/2009JD012746","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954461997&doi=10.1029%2f2009JD012746&partnerID=40&md5=4d988585b8a8922706f0f4a8e6cf7b26","In this study, the effects of varying horizontal grid resolutions on the regional climate model (RCM) simulation of the summer 1998 extreme rainfall events along the middle to lower reaches of the Yangtze-River Basin (YRB-ML) are examined using the Pennsylvania State University-National Center for Atmospheric Research mesoscale model (i.e., MM5). Results show that the MM5 simulation with the finest grid size of 4 km reproduces reasonably well the rainfall intensity and rainbelt distribution over the YRB-ML during all the Meiyu phases, whereas lower-resolution simulations tend to shift the east-west-oriented major rainbelt southwestward as a result of the generated local storms and excessive rainfall during the second Meiyu rainy phase in which vertical (horizontal) wind shears are weak (strong). The excessive rainfall occurs during the evening hours when the low-level jet is relatively strong and in the Meiyu frontal zone where convergence of warm and moist air is pronounced. Results reveal the importance of incorporating convective parameterizations in removing potential instability in heavy rain-producing storms even for RCMs with 3-5 km horizontal resolutions. It is highly desirable to use higher-resolution models with realistic parameterized and grid-scale cloud physics schemes to study the regional climate of heavy rainfall events. Copyright 2010 by the American Geophysical Union."
"35461255500;9235235300;8336962200;24385313900;6504793116;56370907100;10739072200;35741633800;57207261095;7004296083;7006444931;7004683817;7004090779;8663601100;7004172687;6602914876;35998927000;6602607937;35741534400;7004047498;26643041500;","Atmospheric data over a solar cycle: No connection between galactic cosmic rays and new particle formation",2010,"10.5194/acp-10-1885-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77249109507&doi=10.5194%2facp-10-1885-2010&partnerID=40&md5=94cfbf44970a8cd1f010e2a2f50bd47b","Aerosol particles affect the Earth's radiative balance by directly scattering and absorbing solar radiation and, indirectly, through their activation into cloud droplets. Both effects are known with considerable uncertainty only, and translate into even bigger uncertainties in future climate predictions. More than a decade ago, variations in galactic cosmic rays were suggested to closely correlate with variations in atmospheric cloud cover and therefore constitute a driving force behind aerosol-cloud-climate interactions. Later, the enhancement of atmospheric aerosol particle formation by ions generated from cosmic rays was proposed as a physical mechanism explaining this correlation. Here, we report unique observations on atmospheric aerosol formation based on measurements at the SMEAR II station, Finland, over a solar cycle (years 1996-2008) that shed new light on these presumed relationships. Our analysis shows that none of the quantities related to aerosol formation correlates with the cosmic ray-induced ionisation intensity (CRII). We also examined the contribution of ions to new particle formation on the basis of novel ground-based and airborne observations. A consistent result is that ion-induced formation contributes typically significantly less than 10% to the number of new particles, which would explain the missing correlation between CRII and aerosol formation. Our main conclusion is that galactic cosmic rays appear to play a minor role for atmospheric aerosol formation events, and so for the connected aerosol-climate effects as well."
"34871270600;56016741300;55751698900;35751387000;","Is cloud seeding in coastal Antarctica linked to bromine and nitrate variability in snow?",2010,"10.1088/1748-9326/5/1/014009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950672917&doi=10.1088%2f1748-9326%2f5%2f1%2f014009&partnerID=40&md5=937f171aab3f3dee64d0b07e0d648a17","Considering the significance of methanesulfonate (MSA) in the sulfur cycle and global climate, we analyzed MSA and other ionic species in snow from the coastal Larsemann Hills, East Antarctica. MSA concentrations recorded were high (0.58 0.7νM) with ice-cap regions showing significantly higher concentrations (df = 10, p &lt; 0.001) than ice-free regions. High nutrient concentration in ice-cap snow appears to have favored algal growth (7.6 × 10 2cellsl-1) with subsequent production of brominated compounds. The consequent elevated Br- (3.2 2.2νM) in the ice-cap region could result in the release of Br atoms through photoactivated reactions on aerosols and the snow surface. Activated Br atoms in the atmosphere could react with ozone leading to BrO enhancement with subsequent dimethylsulfide(DMS) oxidation and production of sulfur aerosols. Since BrO based DMS oxidation is much faster than the OH/NO3 pathway, elevated Br- in ice-cap snow could contribute more than ice-free sites towards formation of cloud condensation nuclei at the expense of ozone. © 2010 IOP Publishing Ltd."
"34574098100;","Identifying early morning fog and low cloud predictors for northern parts of the Northern Territory of Australia, utilising satellite-derived data",2010,"10.22499/2.6004.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953837363&doi=10.22499%2f2.6004.003&partnerID=40&md5=ba10e644b686190153ba9ba7f758a364","Strong fog and low cloud predictors are identified for northern parts of the Northern Territory during dry-season months. A large-scale morning fog and low-cloud climatology was derived from geostationary-satellite imagery. This was statistically compared with meteorological station data from the previous afternoon. This approach utilised point location data to forecast the probability of occurrence of fog and low cloud over a larger area. Therefore, forecast domains are regional and not site specific. The satellite data indicated that during the early months of the dry season the bulk of the fog and low cloud occurred over eastern parts, whereas during the later months it was more widespread over the total area. Mean sea level pressure at central Australian locations and gradients of mean sea level pressure across northern Australia are good fog and low cloud predictors for southern and western parts of the region. Low-level moisture at locations along and inland from the Gulf of Carpentaria are better predictors for eastern land areas. This is explained in terms of the direction and strength of the easterly trade winds and the modification when these pass over the Gulf of Carpentaria. The total data was filtered in order to identify Australia-wide mean sea level pressure patterns corresponding to particular fog and low cloud distributions over the target area. Finally, predictor testing on an independent data-set showed best results for the eastern land areas where fog and low cloud was observed most frequently."
"35810775100;7004469744;8942525300;7102795549;16242119400;7004402705;56372694300;7405666962;","Description and evaluation of GLOMAP-mode: A modal global aerosol microphysics model for the UKCA composition-climate model",2010,"10.5194/gmd-3-519-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77049128065&doi=10.5194%2fgmd-3-519-2010&partnerID=40&md5=5fe2716304886544d84d5495b2746547","A new version of the Global Model of Aerosol Processes (GLOMAP) is described, which uses a twomoment pseudo-modal aerosol dynamics approach rather than the original two-moment bin scheme. GLOMAP-mode simulates the multi-component global aerosol, resolving sulfate, sea-salt, dust, black carbon (BC) and particulate organic matter (POM), the latter including primary and biogenic secondary POM. Aerosol processes are simulated in a size-resolved manner including primary emissions, secondary particle formation by binary homogeneous nucleation of sulfuric acid and water, particle growth by coagulation, condensation and cloud-processing and removal by dry deposition, in-cloud and below-cloud scavenging. A series of benchmark observational datasets are assembled against which the skill of the model is assessed in terms of normalised mean bias (b) and correlation coefficient (R). Overall, the model performs well against the datasets in simulating concentrations of aerosol precursor gases, chemically speciated particle mass, condensation nuclei (CN) and cloud condensation nuclei (CCN). Surface sulfate, sea-salt and dust mass concentrations are all captured well, while BC and POM are biased low (but correlate well). Surface CN concentrations compare reasonably well in free troposphere and marine sites, but are underestimated at continental and coastal sites related to underestimation of either primary particle emissions or new particle formation. The model compares well against a compilation of CCN observations covering a range of environments and against vertical profiles of size-resolved particle concentrations over Europe. The simulated global burden, lifetime and wet removal of each of the simulated aerosol components is also examined and each lies close to multi-model medians from the AEROCOM model intercomparison exercise. © 2010 Author(s)."
"7004901018;55145417300;","Schumann resonances excitation due to positive and negative cloud-to-ground lightning",2010,"10.1029/2009JD012539","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649142005&doi=10.1029%2f2009JD012539&partnerID=40&md5=381f593db9f4389bbc7bfd807feb90a6","In this paper, we have applied a statistical approach to the problem of Schumann resonances excitation due to both negative and positive cloud-to-ground lightning (-CG and +CG, respectively). Correlation matrices and a power spectrum of natural electromagnetic variations resulted from the global lightning activity are estimated. On the basis of these estimates we have shown that the global +CG lightning activity can make a significant contribution to the low-frequency portion of power spectrum and to the Schumann resonances. Despite their infrequent occurrence compared to the negative flashes, the global +CG lightning can be of primary importance in generating the power spectrum since their charge moment and continuing current are, on average, larger than those of the -CG lightning. Copyright 2010 by the American Geophysical Union."
"57198588945;7405763496;7202216319;57203055233;","Test of a convectively forced gravity wave drag parameterization in a general circulation model",2010,"10.1007/s13143-010-0001-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953481683&doi=10.1007%2fs13143-010-0001-8&partnerID=40&md5=0bcbc74c4075b7824dc8f958e080dad5","The influence of gravity wave drag induced by cumulus convection (GWDC) on a simulated boreal summer climate was evaluated in a general circulation model. For this, the GWDC scheme developed by Chun and Baik was implemented into a version of the National Centers for Environmental Prediction (NCEP) global spectral model (GSM). Ensemble simulations with the two different convection schemes, the simplified Arakawa-Schubert (SAS) scheme and Community Climate Model (CCM) convection scheme, were conducted for the boreal summer of 1996. A cloud factor to modulate the stress intensity with respect to the cloud type was introduced in this study, in order to prevent unrealistic behaviors of the GWDC scheme in GSM. The effect of gravity wave drag on the zonal mean of wind and temperature fields was focused. On the whole, the effect of GWDC in this study is positive on the simulated seasonal climate. It is evident that biases in temperature in the polar region as well as in the zonal and meridional winds in the upper atmosphere are reduced. The percentage of reduction of the bias in zonal winds is about 10-20%. Such a response of the GWDC forcing widely appears not only in tropical regions but also in mid-latitude regions. These characteristics are prominent in the case of the SAS scheme, which is due to the various convective cloud types. The magnitude of GWDC forcing is generally small, but still positive, in the case of the CCM scheme, which is due to rather homogeneous cloud types. It is also found that the role of a particular GWDC forcing depends upon the inherent systematic biases of a particular model. It is concluded that incorporation of the GWDC parameterization in GCMs should be taken into account to improve the seasonal prediction. © The Korean Meteorological Society and Springer 2010."
"25031430500;6506883710;9244992800;36637539100;7402469637;15724418700;24381474400;56283402900;6507562207;7005134081;7402093416;56259852000;57209997787;36636692600;6603821988;7004402705;55919935700;6504688501;16479703400;23485410200;15127430500;6701511321;7102976560;8263760800;7102059695;6506553245;7004587644;57062286700;7003800456;7005723936;7006532784;7003683808;6603561402;7103294731;7403544649;57206421971;36465590400;21735369200;","Multimodel assessment of the upper troposphere and lower stratosphere: Tropics and global trends",2010,"10.1029/2009JD013638","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867806014&doi=10.1029%2f2009JD013638&partnerID=40&md5=a6b3311d3584f833aeeace30135e18e5","The performance of 18 coupled Chemistry Climate Models (CCMs) in the Tropical Tropopause Layer (TTL) is evaluated using qualitative and quantitative diagnostics. Trends in tropopause quantities in the tropics and the extratropical Upper Troposphere and Lower Stratosphere (UTLS) are analyzed. A quantitative grading methodology for evaluating CCMs is extended to include variability and used to develop four different grades for tropical tropopause temperature and pressure, water vapor and ozone. Four of the 18 models and the multi-model mean meet quantitative and qualitative standards for reproducing key processes in the TTL. Several diagnostics are performed on a subset of the models analyzing the Tropopause Inversion Layer (TIL), Lagrangian cold point and TTL transit time. Historical decreases in tropical tropopause pressure and decreases in water vapor are simulated, lending confidence to future projections. The models simulate continued decreases in tropopause pressure in the 21st century, along with ∼1K increases per century in cold point tropopause temperature and 0.5-1 ppmv per century increases in water vapor above the tropical tropopause. TTL water vapor increases below the cold point. In two models, these trends are associated with 35% increases in TTL cloud fraction. These changes indicate significant perturbations to TTL processes, specifically to deep convective heating and humidity transport. Ozone in the extratropical lowermost stratosphere has significant and hemispheric asymmetric trends. O <inf>3</inf> is projected to increase by nearly 30% due to ozone recovery in the Southern Hemisphere (SH) and due to enhancements in the stratospheric circulation. These UTLS ozone trends may have significant effects in the TTL and the troposphere. Copyright © 2010 by the American Geophysical Union."
"9244992800;8558370300;6701348935;7004060399;7006130951;7201839229;13402933200;7103294731;7102167757;7005134081;7402093416;9738329300;56259852000;6603480361;55393706100;6603821988;7004402705;36464907600;55919935700;6504688501;13609746100;16479703400;7403263977;23485410200;15127430500;7102976560;8263760800;7102059695;6506553245;55812487100;7004587644;7003800456;7005723936;7006532784;7003683808;6603561402;7403544649;57206421971;36465590400;21735369200;55730744700;","Impact of stratospheric ozone on Southern Hemisphere circulation change: A multimodel assessment",2010,"10.1029/2010JD014271","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955486759&doi=10.1029%2f2010JD014271&partnerID=40&md5=ce426ab9ae1d6b581d62e8be0cd6139a","The impact of stratospheric ozone on the tropospheric general circulation of the Southern Hemisphere (SH) is examined with a set of chemistry-climate models participating in the Stratospheric Processes and their Role in Climate (SPARC)/Chemistry-Climate Model Validation project phase 2 (CCMVal-2). Model integrations of both the past and future climates reveal the crucial role of stratospheric ozone in driving SH circulation change: stronger ozone depletion in late spring generally leads to greater poleward displacement and intensification of the tropospheric midlatitude jet, and greater expansion of the SH Hadley cell in the summer. These circulation changes are systematic as poleward displacement of the jet is typically accompanied by intensification of the jet and expansion of the Hadley cell. Overall results are compared with coupled models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), and possible mechanisms are discussed. While the tropospheric circulation response appears quasi-linearly related to stratospheric ozone changes, the quantitative response to a given forcing varies considerably from one model to another. This scatter partly results from differences in model climatology. It is shown that poleward intensification of the westerly jet is generally stronger in models whose climatological jet is biased toward lower latitudes. This result is discussed in the context of quasi-geostrophic zonal mean dynamics. Copyright 2010 by the American Geophysical Union."
"22956952000;57203012011;","Effects of convective processes on GCM simulations of the Madden-Julian oscillation",2010,"10.1175/2009JCLI3114.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949335248&doi=10.1175%2f2009JCLI3114.1&partnerID=40&md5=1b2ccaa6dc552d7beb37178739cdf795","Weak temporal variability in tropical climates such as the Madden-Julian oscillation (MJO) is one of major deficiencies in general circulation models (GCMs). The uncertainties in the representation of convection and cloud processes are responsible for these deficiencies. With the improvement made to the convection scheme, the Iowa State University (ISU) GCM, which is based on a version of the NCAR Community Climate Model, is able to simulate many features of MJO as revealed by observations. In this study, four 10-yr (1979-88) ISU GCM simulations with observed sea surface temperatures are analyzed and compared to examine the effects of the revised convection closure, convection trigger condition, and convective momentum transport (CMT) on the MJO simulations. The modifications made in the convection scheme improve the simulations of amplitude, spatial distribution, eastward propagation, and horizontal and vertical structures, especially for the coherent feature of eastward-propagating convection and the precursor sign of convective center. The revised convection closure plays a key role in the improvement of the eastward propagation of MJO. The convection trigger helps produce less frequent but more vigorous moist convection and enhance the amplitude of the MJO signal. The inclusion of CMT results in a more coherent structure for the MJO deep convective center and its corresponding atmospheric variances. © 2010 American Meteorological Society."
"24398842400;7005955015;22953153500;","How important is biological ice nucleation in clouds on a global scale?",2010,"10.1088/1748-9326/5/2/024009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958538314&doi=10.1088%2f1748-9326%2f5%2f2%2f024009&partnerID=40&md5=3b2e4533d1f7814aa891419c2fbefcbb","The high ice nucleating ability of some biological particles has led to speculations about living and dead organisms being involved in cloud ice and precipitation formation, exerting a possibly significant influence on weather and climate. In the present study, the role of primary biological aerosol particles (PBAPs) as heterogeneous ice nuclei is investigated with a global model. Emission parametrizations for bacteria, fungal spores and pollen based on recent literature are introduced, as well as an immersion freezing parametrization based on classical nucleation theory and laboratory measurements. The simulated contribution of PBAPs to the global average ice nucleation rate is only 10-5%, with an uppermost estimate of 0.6%. At the same time, observed PBAP concentrations in air and biological ice nucleus concentrations in snow are reasonably well captured by the model. This implies that 'bioprecipitation' processes (snow and rain initiated by PBAPs) are of minor importance on the global scale. © 2010 IOP Publishing Ltd."
"57203405965;6603800142;57202531041;7005174340;6602584093;57208765879;35468686100;24538154100;7202727242;35331137500;7003283811;36243762400;","Apparent absorption of solar spectral irradiance in heterogeneous ice clouds",2010,"10.1029/2009JD013124","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956015831&doi=10.1029%2f2009JD013124&partnerID=40&md5=9df721a7176e59ec2b869eb90c73eba0","Coordinated flight legs of two aircraft above and below extended ice clouds played an important role in the Tropical Composition, Cloud and Climate Coupling Experiment (Costa Rica, 2007). The Solar Spectral Flux Radiometer measured up- and downward irradiance on the high-altitude (ER-2) and the low-altitude (DC-8) aircraft, which allowed deriving apparent absorption on a point-by-point basis along the flight track. Apparent absorption is the vertical divergence of irradiance, calculated from the difference of net flux at the top and bottom of a cloud. While this is the only practical method of deriving absorption from aircraft radiation measurements, it differs from true absorption when horizontal flux divergence is nonzero. Differences between true and apparent absorption are inevitable in any inhomogeneous atmosphere, especially clouds. We show, for the first time, the spectral shape of measured apparent absorption and compare with results from a three-dimensional radiative transfer model. The model cloud field is created from optical thickness and effective radius retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator and from reflectivity profiles from the Cloud Radar System, both on board the ER-2. Although the spectral shape is reproduced by the model calculations, the measured apparent absorption in the visible spectral range is higher than the model results along extended parts of the flight leg. This is possibly due to a net loss of photons into neighboring cirrus-free areas that are not contained within the model domain. Copyright © 2010 by the American Geophysical Union."
"14023953700;6602407753;7202081585;57205479513;37025898200;36807959100;7005941217;35490380800;8363388700;6505759999;35430463900;","In situ and lidar observations of tropopause subvisible cirrus clouds during TC4",2010,"10.1029/2009JD013093","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957575464&doi=10.1029%2f2009JD013093&partnerID=40&md5=55e6286e62ac4ae21f732479c366e60b","During the Tropical Composition, Clouds, and Climate Coupling (TC4) experiment in July-August 2007, the NASA WB-57F and ER-2 aircraft made coordinated flights through a tropopause subvisible cirrus (SVC) layer off the Pacific Coast of Central America. The ER-2 aircraft was equipped with a remote sensing payload that included the cloud physics lidar (CPL). The WB-57F payload included cloud microphysical and trace gas measurements, and the aircraft made four vertical profiles through the SVC layer shortly after the ER-2 flew over. The in situ and remotely sensed data are used to quantify the meteorological and microphysical properties of the SVC layer, and these data are compared to the limited set of SVC measurements that have previously been made. It is found that the layer encountered was particularly tenuous, with optical depths (τ) between about 10-4 and 10-3. From the in situ and other meteorological data, radiative heating rate perturbations of ∼0.05-0.1 K day-1 are calculated. These heating rates are smaller than previous estimates for tropopause SVC, consistent with the smaller τ in the present study. Coverage statistics based on CPL data from other TC4 flights indicate that this cloud was not an outlier among the sampled population. SVC with properties similar to the one presented here are below the detection limit of space-based lidars such as CALIPSO, and a comparison with the TC4 statistics suggests that a majority (>50%) of tropopause SVC (with τ < 0.01) could be unaccounted for in studies using CALIPSO data. © 2010 by the American Geophysical Union."
"57209052991;14060058300;56304425300;49662622100;57192787704;7402146514;56996271000;","Analysis of Global Land Surface Shortwave Broadband Albedo From Multiple Data Sources",2010,"10.1109/JSTARS.2010.2049342","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956214891&doi=10.1109%2fJSTARS.2010.2049342&partnerID=40&md5=514159b0c06d04ba517df619645b1617","Land surface shortwave albedo plays a central role in global and regional climate modeling. In this study, we analyzed the land surface shortwave broadband albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000 to 2008. The statistical results are obtained using MODIS Collection 5 land surface albedo (MCD43C3), land cover (MOD12C1) datasets, and Global Energy and Water-cycle Experiment (GEWEX) surface radiation data. The results include all nine-year shortwave Black-Sky albedo (BSA) and White-Sky albedo (WSA) variability for global, Northern Hemisphere (NH), Southern Hemisphere (SH), and 15 International Geosphere-Biosphere Program (IGBP) ecosystem surface types; each has a discernible signature. We also compared spatial and temporal variations of MODIS albedos with other datasets: International Satellite Cloud Climatology Project (ISCCP), 21 Global Circulation Models (GCMs)—which were used in the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC-AR4)—and GEWEX albedos. The comparison results show that most GCM-simulated albedos are lower than the remotely sensed MODIS data. The MODIS-based global average land surface albedo is 0.24, and has its peak value in the winter and lowest in summer. Comparison of global albedo anomalies from MODIS shows a small decrease of ~0.01 during these years in the Northern Hemisphere (NH), and increases of ~0.01 in the Southern Hemisphere (SH). Moreover, the map of the nine-year global MODIS albedo, and normalized difference vegetation index (NDVI) variation trends, are correlated in this paper. We also summarize global and zonal albedos for different IGBP land surface classes, and present the global and zonal albedos under both snow-covered and snow-free conditions. © 2010, IEEE. All rights reserved."
"6603742400;6602675795;","Evaluation of atmospheric thermal radiation algorithms for daylight hours",2010,"10.1007/s00704-010-0325-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84755160869&doi=10.1007%2fs00704-010-0325-4&partnerID=40&md5=b8b64907ceedee5bcba81771e3943da3","Existing simple but theoretically based clear-sky models for longwave down-welling radiation (LDRc) and cloud impact algorithms transforming them to all-sky radiation (LDR) are checked against locally calibrated empirical algorithms. They are evaluated for daylight hours based on measurements in regionally differing climates of Germany. The Prata clear-sky scheme is additionally tested with adjusted coefficients so that LDRc converges against a realistic emissivity for a completely dry atmosphere. This version is characterised by an improved modelled variance. Compared with locally calibrated schemes, bias and root mean square error (RMSE) of the more theoretical clear-sky schemes do not differ significantly and yield even better results at a mountain site. In contrast, the locally calibrated algorithms yield biases up to 9% and an increase in RMSE between 6% and 67%, if applied for other sites. For daylight hours, the cloud impact on LDR can be calculated via the ratio of observed to clear-sky global irradiation (CMFsol). With CMFsol, the Crawford and Duchon scheme reveals the lowest bias and a decrease in RMSE by 22% against the next best performing algorithms. Compared with synoptic cloud observations as input, the bias is reduced by 9 to 28 W m-2 and the scattering of the residuals decreases by 20% to 30%. Based on published results for also non-European sites, it is inferred that the more theoretically based LDRc schemes and cloud impact evaluated via CMFsol are universally applicable and perform at least in the order of magnitude of locally calibrated empirical algorithms. © 2010 Springer-Verlag."
"24822250800;7003696273;7102963655;36052878000;","Comparing upper tropospheric humidity data from microwave satellite instruments and tropical radiosondes",2010,"10.1029/2010JD013962","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650946846&doi=10.1029%2f2010JD013962&partnerID=40&md5=64d145a06b2644b4c677ac657b863eb8","Atmospheric humidity plays an important role in the Earth's climate. Microwave satellite data provide valuable humidity observations in the upper troposphere with global coverage. In this study, we compare upper tropospheric humidity (UTH) retrieved from the Advanced Microwave Sounding Unit and the Microwave Humidity Sounder against radiosonde data measured at four of the central facilities of the Atmospheric Radiation Measurement program. The Atmospheric Radiative Transfer Simulator (ARTS) was used to simulate satellite brightness temperatures from the radiosonde profiles. Strong ice clouds were filtered out, as their influence on microwave measurements leads to incorrect UTH values. Day and night radiosonde profiles were analyzed separately to take into account the radiosonde radiation bias. The comparison between radiosonde and satellite is most meaningful for data in cloud-free, nighttime conditions and with a time difference of less than 2 hr. We found good agreement between the two data sets. The satellite data were slightly moister than the radiosonde data, with a mean difference of 1%-2.3% relative humidity (RH), depending on the radiosonde site. Monthly gridded data were also compared and showed a slightly larger mean difference of up to 3.3% RH, which can be explained by sampling issues. Copyright 2010 by the American Geophysical Union."
"25228570800;25228265200;36769514400;25228443100;25228219700;","Innovative solution for warning on high intensity rainfalls",2010,"10.30638/eemj.2010.095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956952665&doi=10.30638%2feemj.2010.095&partnerID=40&md5=3624f3c390d5b3ef90f9e199bf255a9e","Climate change is one of the major challenges of our century and becomes a major research topic. Obtaining rapid provision of information about dangerous hydro meteorological phenomena becomes a necessity. This paper presents a device able to provide information on rainfall characteristics and vertical development of clouds, which generates precipitations to effectively manage the hazardous phenomena they generate."
"6603821988;35338710200;13402933200;7103294731;7102167757;7005134081;7402093416;55393706100;7004402705;7003893639;55919935700;22933643300;6504688501;13609746100;7403263977;25031430500;6603247427;6701511321;57198719030;8263760800;6701450462;57062286700;7003800456;7005723936;7003683808;56228733900;6603561402;7403544649;55965624000;21735369200;","Chemistry-climate model simulations of twenty-first century stratospheric climate and circulation changes",2010,"10.1175/2010JCLI3404.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951100073&doi=10.1175%2f2010JCLI3404.1&partnerID=40&md5=9a4c6c89ec3a516cc9ddf0eab9021cc0","The response of stratospheric climate and circulation to increasing amounts of greenhouse gases (GHGs) and ozone recovery in the twenty-first century is analyzed in simulations of 11 chemistry-climate models using near-identical forcings and experimental setup. In addition to an overall global cooling of the stratosphere in the simulations (0.59 ± 0.07 K decade-1 at 10 hPa), ozone recovery causes a warming of the Southern Hemisphere polar lower stratosphere in summer with enhanced cooling above. The rate of warming correlates with the rate of ozone recovery projected by the models and, on average, changes from 0.8 to 0.48 Kdecade-1 at 100 hPa as the rate of recovery declines from the first to the second half of the century. In the winter northern polar lower stratosphere the increased radiative cooling from the growing abundance of GHGs is, in most models, balanced by adiabatic warming from stronger polar downwelling. In the Antarctic lower stratosphere the models simulate an increase in low temperature extremes required for polar stratospheric cloud (PSC) formation, but the positive trend is decreasing over the twenty-first century in all models. In the Arctic, none of the models simulates a statistically significant increase in Arctic PSCs throughout the twentyfirst century. The subtropical jets accelerate in response to climate change and the ozone recovery produces awestward acceleration of the lower-stratosphericwind over theAntarctic during summer, though this response is sensitive to the rate of recovery projected by the models. There is a strengthening of the Brewer-Dobson circulation throughout the depth of the stratosphere, which reduces the mean age of air nearly everywhere at a rate of about 0.05 yr decade-1 in those models with this diagnostic. On average, the annual mean tropical upwelling in the lower stratosphere (~70 hPa) increases by almost 2% decade-1, with 59% of this trend forced by the parameterized orographic gravity wave drag in the models. This is a consequence of the eastward acceleration of the subtropical jets, which increases the upward flux of (parameterized) momentum reaching the lower stratosphere in these latitudes. © 2010 American Meteorological Society."
"7006329853;7006423931;7202081585;7202400272;57208765879;7006278987;7006497590;7006103811;6701615891;56016057500;6603758021;36476093400;6602169391;35459699300;57205479513;6603083860;6506730508;35448324200;35494005000;7006783796;7005054220;","Planning, implementation, and first results of the Tropical Composition, Cloud and Climate Coupling Experiment (TC4)",2010,"10.1029/2009JD013073","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77749325715&doi=10.1029%2f2009JD013073&partnerID=40&md5=d7c6ebeb74a9febe2ac52a2462d61148","[1] The Tropical Composition, Cloud and Climate Coupling Experiment (TC4), was based in Costa Rica and Panama during July and August 2007. The NASA ER-2, DC-8, and WB-57F aircraft flew 26 science flights during TC4. The ER-2 employed 11 instruments as a remote sampling platform and satellite surrogate. The WB-57F used 25 instruments for in situ chemical and microphysical sampling in the tropical tropopause layer (TTL). The DC-8 used 25 instruments to sample boundary layer properties, as well as the radiation, chemistry, and microphysics of the TTL. TC4 also had numerous sonde launches, two ground-based radars, and a ground-based chemical and microphysical sampling site. The major goal of TC4 was to better understand the role that the TTL plays in the Earth's climate and atmospheric chemistry by combining in situ and remotely sensed data from the ground, balloons, and aircraft with data from NASA satellites. Significant progress was made in understanding the microphysical and radiative properties of anvils and thin cirrus. Numerous measurements were made of the humidity and chemistry of the tropical atmosphere from the boundary layer to the lower stratosphere. Insight was also gained into convective transport between the ground and the TTL, and into transport mechanisms across the TTL. New methods were refined and extended to all the NASA aircraft for real-time location relative to meteorological features. The ability to change flight patterns in response to aircraft observations relayed to the ground allowed the three aircraft to target phenomena of interest in an efficient, well-coordinated manner. © 2010 by the American Geophysical Union."
"9534896800;7401776640;55905970100;","Is there evidence for an aerosol indirect effect during the recent aerosol optical depth decline in Europe?",2010,"10.1029/2009JD012867","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952264501&doi=10.1029%2f2009JD012867&partnerID=40&md5=21b70c677a1611759656b84594a37634","Aerosol indirect effects are some of the largest uncertainties of anthropogenic climate change. To estimate the first aerosol indirect radiative effect (or cloud albedo effect), we analyzed global solar irradiance measurements under completely overcast skies during the recent period of aerosol optical depth decline in Europe. Although measurements from 15 Swiss and 8 northern German sites show clear evidence for an aerosol direct radiative effect under cloud-free skies, trends of transmitted solar irradiance (SW tran) under overcast skies are ambiguous. Time series from 1981 to 2005 of SWtran for all overcast conditions show slightly negative, but nonsignificant trends. SWtran under overcast conditions with ""thick"" clouds (SWtran smaller than the long-term mean) exhibit on average an increasing trend of +0.29 [+0.01 to +0.57] W m -2 / decade. The increase of SWtran under ""thick"" overcast skies, however, is about nine times smaller than the increase under cloud-free skies. Since cirrus clouds are generally excluded from and low-level stratiform clouds are more frequently represented by ""thick"" overcast skies, the slight increase in SWtran may possibly result from a weak aerosol indirect effect. Alternatively, the increase in SWtran may be due to a decreasing trend in low-level stratiform cloud amount under overcast conditions observed for these sites. We further find that solar irradiance changes caused by decreasing aerosol direct effect and increasing sunshine duration can account for most of the observed increasing all-sky solar radiation trend. This suggests that the first aerosol indirect effect makes little contribution to surface solar radiation changes over Europe. Copyright 2010 by the American Geophysical Union."
"7101857920;16177844800;26425102400;7006765934;","High Earth-system climate sensitivity determined from Pliocene carbon dioxide concentrations",2010,"10.1038/ngeo724","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73449133402&doi=10.1038%2fngeo724&partnerID=40&md5=87f514a64bd1e08430f9b20bc0c9023c","Climate sensitivitythe mean global temperature response to a doubling of atmospheric CO 2 concentrations through radiative forcing and associated feedbacksis estimated at 1.5-4.5 C (ref.1). However, this value incorporates only relatively rapid feedbacks such as changes in atmospheric water vapour concentrations, and the distributions of sea ice, clouds and aerosols. Earth-system climate sensitivity, by contrast, additionally includes the effects of long-term feedbacks such as changes in continental ice-sheet extent, terrestrial ecosystems and the production of greenhouse gases other than CO 2. Here we reconstruct atmospheric carbon dioxide concentrations for the early and middle Pliocene, when temperatures were about 3-4 C warmer than preindustrial values, to estimate Earth-system climate sensitivity from a fully equilibrated state of the planet. We demonstrate that only a relatively small rise in atmospheric CO 2 levels was associated with substantial global warming about 4.5 million years ago, and that CO 2 levels at peak temperatures were between about 365 and 415 ppm. We conclude that the Earth-system climate sensitivity has been significantly higher over the past five million years than estimated from fast feedbacks alone. © 2010 Macmillan Publishers Limited. All rights reserved."
"7003904922;","Electric charge modulation of aerosol scavenging in clouds: Rate coefficients with Monte Carlo simulation of diffusion",2010,"10.1029/2010JD014580","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650298278&doi=10.1029%2f2010JD014580&partnerID=40&md5=3a6bb3c56cc9d4eab673ede8dac7fba1","The effects of electric charge on the scavenging by droplets of aerosol particles, particularly cloud condensation nuclei, appear to have a significant effect on cloud properties and climate. The effects on scavenging are calculated here in a trajectory model relative to the falling droplets, with a Monte Carlo simulation of particle diffusion along the trajectory. The charges are in the range 5-100 elementary charges, consistent with the measured and modeled deposition of small amounts of charge by the flow everywhere of atmospheric electric current density (part of the global circuit) through clouds. Particles move through a corrected Stokes flow field, under the influence of gravitational, phoretic, electric, and drag forces while diffusing. For the general situation of like charges on droplets and aerosol particles, the model simulates the long-range electrical repulsive force that has a net effect of reducing the collision rates for small particles (radii less than about 0.1 μm) below the values for combined Brownian diffusion and phoretic forces. It also simulates the net effect for larger particles of the short-range attractive electric forces in increasing the rate coefficients above the Brownian and phoretic values. Initial validation is provided by treating the case of ventilation in pure Brownian diffusion, for which new and more accurate ventilation coefficients are obtained as a function of the Pclet number. These are applicable to combined diffusion and phoretic scavenging with pure inverse square scavenging forces. The rate constants obtained for the electrical effects, comparable to those for Brownian and phoretic scavenging process, lead to time scales for scavenging in clouds of a few hours, consistent with observations of significant electrical effects on clouds associated with modulation of the global circuit. Copyright 2010 by the American Geophysical Union."
"54783792600;7410041005;56978385600;","A global view of midlevel liquid-layer topped stratiform cloud distribution and phase partition from CALIPSO and CloudSat measurements",2010,"10.1029/2009JD012143","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899654730&doi=10.1029%2f2009JD012143&partnerID=40&md5=559c6fea23e0723120d584212a659fa9","The first 2 year measurements from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar and CloudSat radar were analyzed to study the distribution and phase partition of midlevel liquid-layer topped stratiform clouds (MLTSC, top higher than 2.5 km above the Earth's surface and top temperature warmer than -40°C) globally The global mean MLTSC occurrence was ∼7.8% and the global mean MLTSC percentage fraction related to all midlevel clouds was ∼33.6%. Strong seasonal and day-night variations of MLTSC occurrence were observed over different latitude regions. In the polar regions, the maximum occurrence was in summer, while the minimum occurred in winter, with small day-night differences. In the tropics, a high MLTSC occurrence band shifted southward from June-July-August to December-January-February with significantly more MLTSC during the nighttime. The global mean MLTSC top height and temperature were ∼4.5 km above the surface and - 13.6°C. Overall, 61.8% of MLTSCs were mixed phase and 12.4% were supercooled liquid (contains only liquid phase or with ice below the detection limit). The fraction of mixed-phase MLTSC increased as the cloud top temperature decreased, with a sharp increase between -10 and - 15°C and a noticeable latitude difference. This temperature dependence indicated that ice nucleation is active at - 10°C in these clouds. The global mean ice water path (IWP) of mixed-phase MLTSCs, estimated based on an empirical temperature-radar reflectivity-ice water content relationship, was ∼13.4 g/m, and the IWP increased as cloud top temperature decreased. To improve MLTSC parameterizations in global climate models, further studies are needed to better understand the latitude dependence of MLTSC distributions and microphysical properties and how aerosol and water phase cloud properties affecting ice generation in MLTSCs. Copyright 2010 by the American Geophysical Union."
"57205000966;7405489798;7007020226;","African dust outbreaks: A satellite perspective of temporal and spatial variability over the tropical Atlantic Ocean",2010,"10.1029/2009JD012516","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949434906&doi=10.1029%2f2009JD012516&partnerID=40&md5=038fd1a59499fcb144040ba2e72b8189","We describe the temporal evolution and spatial structure of extreme African dust outbreaks and their associated meteorological fields over West Africa and the tropical Atlantic using A-Train data and a global reanalysis product. We used Aqua.Moderate Resolution Imaging Spectroradiometer daily aerosol optical depth (AOD) to identify major dust outbreaks, defined as AOD events one standard deviation above the background along the African coast. Dry air outbreaks were defined using water vapor data of the Aqua Atmospheric Infrared Sounder. Dry air outbreaks do not always coincide with dust outbreaks. Most boreal summer outbreaks reached the West Indies between 10°N and 20°N, some traveling on to the southeastern United States; winter outbreaks moved to South America between 0° and 10°N. Outbreaks travel westward at an average speed of 1000 km d-1, reaching the Caribbean or South America in a week's time. The advance of a dust front is associated with decreases in water vapor (up to -1.0 g kg-1) and increases in temperature (up to 1.0 K) and, behind the fronts, an anticyclonic circulation. We used Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data to characterize dust altitude distributions. The vertical distribution of warm dry air is similar to that of dust observed in CALIPSO. The dust layer altitude decreases during transport across the Atlantic and is significantly lower in boreal winter than summer. The study highlights the temporal and spatial variability of African dust outbreaks, which are important to improving our understanding of climate impacts of African dust and Atlantic climate variability in general. Copyright 2010 by the American Geophysical Union."
"7003397735;7402093416;55883034700;8706262900;","Introduction to special section on Climate and Weather of the Sun Earth System",2010,"10.1029/2009JD013784","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956037470&doi=10.1029%2f2009JD013784&partnerID=40&md5=33beee5c49187004e98211bffd91a4fa","[1] In the special section on CAWSES (Climate and Weather of the Sun Earth System) a total of 19 papers are published covering several aspects of Sun-Earth coupling. Six papers concentrate on summer mesospheric ice clouds including detection by satellites, radar-based derivation of particle properties, and water vapor observations in the mesosphere. Solar radiation affects ice clouds on time scales of the 11 year solar cycle and 27 days. Stratospheric shrinking contributes significantly to long-term trends of ice clouds. The seasonal variability of smoke particles is confirmed to be impacted by global circulation. Six papers address the external forcing of the atmosphere caused by the Sun. The relevance of radionuclei and solar radiation spectral irradiance is presented. The impact of precipitating energetic solar particles on trace gas concentrations is studied. Ion chemistry and electron production can be important to destroy ozone in the mesosphere and upper stratosphere. Strong solar events can reduce ice clouds on short time scales owing to dynamical feed back mechanisms. The 27 day solar signal is identified in ozone concentration using satellite measurements. Model studies show that the dynamical response of the stratospheric polar vortex to solar cycle forcing depends on the phase of the quasi-biennial oscillation. The year 2009 was a remarkable exception from this rule reinforcing natural variability. Regarding centennial time scales it is shown that changes in the stratosphere can influence tropospheric circulation. Tides have extensively been studied within CAWSES. As is demonstrated, nonmigrating tides originating in the troposphere can propagate into the thermosphere. © 2010 by the American Geophysical Union."
"26434854300;7005773698;","Aircraft measurements of vertical profiles of aerosol mixing states",2010,"10.1029/2009JD013150","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953748370&doi=10.1029%2f2009JD013150&partnerID=40&md5=cf9177bc5d512cd8a151c0561ab59f4c","To examine the overall impact of aerosols on climate, direct measurements of the size-resolved mixing states of atmospheric particles are needed as a function of altitude. During the Ice in Clouds Experiment-Layer Clouds, the recently developed aircraft aerosol time-of-flight mass spectrometer directly measured the vertical profiles of size-resolved single-particle chemistry in cloud-free air over Wyoming and northern Colorado. These represent the first aircraft-based, dual polarity mass spectrometry measurements, allowing a detailed examination of in situ single-particle mixing state as a function of altitude. Measurement of both positive and negative ions for each individual particle provides the ability to identify the primary particle type/source, such as biomass burning, organic carbon, or soot, and examine the extent of mixing with secondary species, such as ammonium, nitrate, sulfate, and sulfuric acid. For the primary particle cores, biomass burning represented the largest source of submicron particles: ∼33-39% by number from 1 to 7 km. Organic carbon particles were the second most abundant type (maximum of ∼33% by number from 1.2 to 2.0 km) with elemental carbon (soot) particles comprising 14-22% by number from 1 to 7 km. In general, biomass burning, organic carbon, and soot particles were frequently internally mixed with ammonium, nitrate, and sulfate at lower altitudes, switching to sulfate and sulfuric acid mixtures at higher altitudes. Further, the number fraction of externally mixed sulfuric acid particles increased with altitude from 1 to 9%, likely because of cloud processing of SO<inf>2</inf>. The variance of particle mixing state with altitude significantly changes absorption and hygroscopic properties, and must be taken into account in models calculating aerosol direct and indirect radiative forcings. Copyright 2010 by the American Geophysical Union."
"6603764342;7103086283;7006033481;","Witnessing the impact of the 1783-1784 Laki eruption in the Southern Hemisphere",2010,"10.1007/s10584-009-9676-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950461031&doi=10.1007%2fs10584-009-9676-1&partnerID=40&md5=3a7a3337efbe4480393c30057716476c","The Icelandic Laki eruption in 1783/1784 produced a large volume of lava while the associated aerosols were directly responsible for severe environmental and health effects in Iceland and northern Europe. The intense plume of smoke and sulphurous dry fog has been reported to have affected a considerable fraction of Eurasia and Northeastern Canada but no impact descriptions have been reported for the Southern Hemisphere. Here we reproduce the description of an abnormally high incidence of unusual dry fog and haze days during the years 1784-1786 in Rio de Janeiro (20° S, Brazil) obtained by Bento Sanches Dorta, a Portuguese astronomer. Using monthly averages of fog days registered by Dorta between 1781 and 1788 it is shown that the outstanding peak observed between September and November of 1784 might be linked to the Laki eruption. The vast majority of observational and modeling studies appear to contradict such hypothesis; however recent modeling studies of the impact of large high latitude eruptions support the existence of large-scale climatic anomalies in the Southern Hemisphere tropical region, and in particular the appearance of above-normal cloud cover over central Brazil. © Springer Science+Business Media B.V. 2009."
"23398428900;55156242700;7003937407;7006185793;7003385765;16306589900;","A comparative study of negative cloud-to-ground lightning characteristics in São Paulo (Brazil) and Arizona (United States) based on high-speed video observations",2010,"10.1029/2009JD012604","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953767082&doi=10.1029%2f2009JD012604&partnerID=40&md5=31c81c642c587122275d4f8dc4daecbe","There are only a few prior reports that detail accurate measurements of the number of strokes in natural negative cloud-to-ground (CG) lightning flashes. These are known as ""accurate-stroke-count"" studies, and they have been performed using various instruments and techniques. Here, we will examine the lightning characteristics produced by warm-season thunderstorms in two different climate regimes (southern Arizona, United States, and So Paulo, Brazil) using the same instrumentation. The lightning parameters were obtained from high-speed video recordings and time-correlated data provided by lightning locating systems (LLS). The use of these instruments has allowed us to measure the number of strokes in each flash and their polarity, the interstroke intervals, the number of different ground contacts, and the durations of the continuing currents. Altogether 209 negative flashes were recorded on video in the United States and 223 in Brazil (containing a total of 1681 strokes), and the majority of these flashes had at least one stroke reported by a LLS. Statistical analyses of these data sets as a whole did not show any significant differences in the characteristics of negative CG flashes from warm-season thunderstorms in both locations. The mean values for all data are as follows: video multiplicity, 3.9; single-stroke flashes, 19.5%; flash duration, 226.5 ms; interstroke interval, 61.5 ms; long continuing current, 17.5%; multigrounded flashes, 49.5%. Those characteristics were very similar to the well-accepted values for negative flashes in other regions. However, there were large storm-to-storm variations. Copyright 2010 by the American Geophysical Union."
"56049333200;7006686129;7004198777;7402049334;7005729142;6506385754;","Evidence of nitric acid uptake in warm cirrus anvil clouds during the NASA TC4 campaign",2010,"10.1029/2009JD012716","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953779296&doi=10.1029%2f2009JD012716&partnerID=40&md5=12a528f5107eea11c8b4173d0de5dff6","Uptake of HNO<inf>3</inf> onto cirrus ice may play an important role in tropospheric NO<inf>x</inf> cycling. Discrepancies between modeled and in situ measurements of gas-phase HNO<inf>3</inf> in the troposphere suggest that redistribution and removal mechanisms by cirrus ice have been poorly constrained. Limited in situ measurements have provided somewhat differing results and are not fully compatible with theory developed from laboratory studies. We present new airborne measurements of HNO<inf>3</inf> in cirrus clouds from anvil outflow made during the Tropical Composition, Cloud, and Climate Coupling Experiment (TC4). Upper tropospheric (>9 km) measurements made during three flights while repeatedly traversing the same cloud region revealed depletions of gas-phase HNO<inf>3</inf> in regions characterized by higher ice water content and surface area. We hypothesize that adsorption of HNO<inf>3</inf> onto cirrus ice surfaces could explain this. Using measurements of cirrus ice surface area density and some assumptions about background mixing ratios of gas-phase HNO<inf>3</inf>, we estimate molecular coverages of HNO <inf>3</inf> on cirrus ice surface in the tropical upper troposphere during the TC4 racetracks to be about 1 × 1013 molecules cm-2. This likely reflects an upper limit because potential dilution by recently convected, scavenged air is ignored. Also presented is an observation of considerably enhanced gas-phase HNO<inf>3</inf> at the base of a cirrus anvil suggesting vertical redistribution of HNO<inf>3</inf> by sedimenting cirrus particles and subsequent particle sublimation and HNO<inf>3</inf> evaporation. The impact of released HNO<inf>3</inf>, however, appears to be restricted to a very thin layer just below the cloud. Copyright 2010 by the American Geophysical Union."
"6701754792;23017945100;7006146719;6701606453;","The evaluation of CloudSat and CALIPSO ice microphysical products using ground-based cloud radar and lidar observations",2010,"10.1175/2009JTECHA1397.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955528117&doi=10.1175%2f2009JTECHA1397.1&partnerID=40&md5=e9aba03f3dc24ec7025f0893c1dbdc39","In this paper, the statistical properties of tropical ice clouds (ice water content, visible extinction, effective radius, and total number concentration) derived from 3 yr of ground-based radar-lidar retrievals from the U.S. Department of Energy Atmospheric Radiation Measurement Climate Research Facility in Darwin, Australia, are compared with the same properties derived using the official CloudSat microphysical retrieval methods and from a simpler statistical method using radar reflectivity and air temperature. It is shown that the two official CloudSat microphysical products (2B-CWC-RO and 2B-CWC-RVOD) are statistically virtually identical. The comparison with the ground-based radar-lidar retrievals shows that all satellite methods produce ice water contents and extinctions in a much narrower range than the ground-based method and overestimate the mean vertical profiles of microphysical parameters below 10-km height by over a factor of 2. Better agreements are obtained above 10-km height. Ways to improve these estimates are suggested in this study. Effective radii retrievals from the standard CloudSat algorithms are characterized by a large positive bias of 8-12 μm.Asensitivity test shows that in response to such a bias the cloud longwave forcing is increased from 44.6 to 46.9 W m-2 (implying an error of about 5%), whereas the negative cloud shortwave forcing is increased from 281.6 to 282.8 W m-2. Further analysis reveals that these modest effects (although not insignificant) can be much larger for optically thick clouds. The statistical method using CloudSat reflectivities and air temperature was found to produce inaccurate mean vertical profiles and probability distribution functions of effective radius. This study also shows that the retrieval of the total number concentration needs to be improved in the official CloudSat microphysical methods prior to a quantitative use for the characterization of tropical ice clouds. Finally, the statistical relationship used to produce ice water content from extinction and air temperature obtained by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite is evaluated for tropical ice clouds. It is suggested that the CALIPSOice water content retrieval is robust for tropical ice clouds, but that the temperature dependence of the statistical relationship used should be slightly refined to better reproduce the radar-lidar retrievals. © 2010 American Meteorological Society."
"7201459977;7102636633;35495958000;7402971417;","Quantifying uncertainty in a remote sensing-based estimate of evapotranspiration over continental USA",2010,"10.1080/01431161.2010.483490","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953344402&doi=10.1080%2f01431161.2010.483490&partnerID=40&md5=2e50509392a91270a0eadcc6bd1fd754","We calculate evapotranspiration (E) from remote sensing (RS) data using the Penman-Monteith model over continental USA for four years (2003-2006) and explore, through an ensemble generation framework, the impact of input dataset (meteorological, radiation and vegetation) selection on performance (uncertainty) at the monthly time-scale. The impact of failed or missed RS retrievals and algorithmic assumptions are also quantified. To evaluate bias, we inter-compare RS-E with three independent sources of E: Variable Infiltration Capacity (VIC)model simulated, North American Regional Reanalysis (NARR) inferred, and Gravity Recovery and Climate Experiment (GRACE) inferred. Overall, we find that the choice of vegetation parameterization, followed by surface temperature, has the greatest impact on RS-E uncertainty. Additional uncertainty (4-18%) is linked to sources of net radiation-used to scale instantaneous RS-E under the assumption of constant daytime evaporative fraction-including the Surface Radiation Budget (SRB), International Satellite Cloud Climatology Project (ISCCP), and North American Land Data Assimilation System (NLDAS)-VIC. The ensemble median agrees to within 21% of VIC-modelled E, except for the Colorado and Great Basins for which the need for a soil moisture constraint on RS-E becomes evident. © 2010 Taylor & Francis."
"6506416572;23017945100;6602417968;6701754792;35305025100;26421356200;","Microphysical characterisation of West African MCS anvils",2010,"10.1002/qj.557","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949358975&doi=10.1002%2fqj.557&partnerID=40&md5=2db0c159be93872521dc227956ef67c7","Deep convection in the Tropics is the source of large tropospheric extended clouds usually called anvils. These anvils may produce precipitation (stratiform region of deep convective storms), and also cirrus shields persisting from several hours to several days. Anvils impact the radiation budget, they induce a storage term in the whole water budget which is still relatively poorly quantified, and dynamical feedbacks may be induced in the upper troposphere. The AMMA field campaign which was held over West Africa during the 2006 wet season provided a unique opportunity to document the microphysics of these anvils from unprecedented airborne observations. Airborne in situ measurements of ice crystals and observations from a 95 GHz Doppler radar are used to characterize the microphysical properties of tropical anvils. The dataset is binned into stratiform and cirriform regions. Some data in the stratiform regions were likely obtained close enough to convective cores that the particles may have grown primarily within those cores. The data obtained over the continent and over the ocean are also characterized separately. Particle habit and growth processes are inferred from an examination of the collected particle images, from quantitative comparisons of 95 GHz reflectivities calculated from the in situ microphysical observations with the measured radar reflectivities, and from a statistical analysis of the two-dimensional particle images. The predominant precipitation particles above the 0°C isotherm in the stratiform anvil region are rimed aggregates. These rimed aggregates seem to get less dense and of smaller diameter when moving rearward of the system towards the cirriform region. The retrieved density laws (assumed to be power laws) lie close to the relationship for rimed particles of Locatelli and Hobbs. Particle size distributions in tropical anvils are also studied. The exponential shape seems to be a good approximation for these particle size distributions overall. The decrease in concentration with diameter is also found to be faster for cirriform regions than for stratiform regions. Normalising these particle size distributions produces a relatively invariant shape (in agreement with earlier studies), with however an increased variability for the smallest and largest values of the normalised diameter. The characterisation of the bulk microphysical properties using these in situ microphysical observations shows that the ice water content, the effective radius and the reflectivity-weighted fall velocity generally increase with air temperature, in agreement with earlier studies. These parameters are found to be systematically smaller on average in cirriform regions than in stratiform regions, and this is true at all temperatures. These values are then compared with statistical relationships used in cloud-resolving models and general circulation models, since a realistic representation of microphysics in models is very important to understand not only the processes at work, but the dynamical feedbacks and effects on climate. Large differences are found, the current parametrizations being unable to reproduce the large values of the considered microphysical parameters. © 2010 Royal Meteorological Society."
"23065336100;36024547100;","Observations of volcanic emissions from space: Current and future perspectives",2010,"10.1007/s11069-009-9471-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955774888&doi=10.1007%2fs11069-009-9471-3&partnerID=40&md5=74c5fdbe7a4f232ba0403d1fa9c8cee6","Volcanoes worldwide pose a major threat to humans at both local and global scales. The effective monitoring of volcanoes is essential to manage and reduce risk associated with the threat that they pose. The measurement of volcanic cloud composition can provide important clues to the underlying volcanic processes and can be indicative of impending eruption. Hazards posed by plumes to humans and animals are significant, as well as the potential climatic impacts and the threat to aircraft by the ingestion of volcanic ash all justify careful monitoring. Recent advances in instrument technology have allowed for high resolution monitoring of volcanic clouds from satellite-based instruments. There exists a suite of instruments with varying spatial, spectral and temporal resolutions, which when used in conjunction can provide detailed information about cloud properties. Such instruments have the capability to quantify sulphur dioxide, ash and aerosol content as well as the spatial and vertical distribution of species. Here we present an overview of the range of instruments useful for such monitoring, outline their functionality and describe the potential of future missions. © 2009 Springer Science+Business Media B.V."
"12786571000;26221848900;9039487900;56013675200;","Climate-growth analysis for a Mexican dry forest tree shows strong impact of sea surface temperatures and predicts future growth declines",2010,"10.1111/j.1365-2486.2009.02059.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954165051&doi=10.1111%2fj.1365-2486.2009.02059.x&partnerID=40&md5=2ecfc6dfa483a8ff8b67436b5f8cde86","Tropical forests will experience relatively large changes in temperature and rainfall towards the end of this century. Little is known about how tropical trees will respond to these changes. We used tree rings to establish climate-growth relations of a pioneer tree, Mimosa acantholoba, occurring in tropical dry secondary forests in southern Mexico. The role of large-scale climatic drivers in determining interannual growth variation was studied by correlating growth to sea surface temperature anomalies (SSTA) of the Atlantic and Pacific Oceans, including the El Niño-Southern Oscillation (ENSO). Annual growth varied eightfold over 1970-2007, and was correlated with wet season rainfall (r=0.75). Temperature, cloud cover and solar variation did not affect growth, although these climate variables correlated with growth due to their relations with rainfall. Strong positive correlations between growth and SSTA occurred in the North tropical Atlantic during the first half of the year, and in the Pacific during the second half of the year. The Pacific influence corresponded closely to ENSO-like influences with negative effects of high SSTA in the eastern Pacific Niño3.4 region on growth due to decreases in rainfall. During El Niño years growth was reduced by 37%. We estimated how growth would be affected by the predicted trend of decreasing rainfall in Central America towards the end of this century. Using rainfall predictions of two sets of climate models, we estimated that growth at the end of this century will be reduced by 12% under a medium (A1B) and 21% under a high (A2) emission scenario. These results suggest that climate change may have repercussions for the carbon sequestration capacity of tropical dry forests in the region. © 2009 Blackwell Publishing Ltd."
"6701551871;6602301713;57197703326;","Dependence of accumulated precipitation on cloud drop size distribution",2010,"10.1007/s00704-010-0332-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78249272319&doi=10.1007%2fs00704-010-0332-5&partnerID=40&md5=d93085a8e872cfcb043f7dca0039c95c","Convective precipitation is the main cause of extreme rainfall events in small areas. Its primary characteristics are both large spatial and temporal variability. For this reason, the monitoring of accumulated precipitation fields (liquid and solid components) at the surface is difficult to carry out through the use of rain gauge networks or remote-sensing observations. Alternatively, numerical models seem to be the most powerful tool in simulating convective precipitation for various analyses and predictions. Due to a lack of comparisons between modelled and observed precipitation characteristics over a long period of time, we focus our research on comparisons between observations and three model samples of accumulated convective precipitation over a particular study area. We use a numerical cloud model with two model schemes involving the unified Khrgian-Mazin size distribution of cloud drops and a model scheme involving a monodisperse cloud droplet spectrum and the Marshall-Palmer size distribution for raindrops, respectively. For comparison, we have selected a study area with a sounding site. Our analysis shows that the model version with the Khrgian-Mazin size distribution exhibits a better agreement with the observed mean, median and range of extreme values of accumulated convective precipitation. Model simulations with the Khrgian-Mazin size distribution most closely match observations, with a correlation coefficient of 0.91. Use of the Marshall-Palmer size distribution, on the other hand, systemically underestimates the observed precipitation and has the lowest correlation coefficient among the methods, 0.83. Such an investigation is crucial to improve predictions of accumulated convective precipitation for various climatological and hydrological analyses and predictions. © 2010 Springer-Verlag."
"8605057200;6701606453;16679271700;55476786400;7201527458;","CloudSat precipitation profiling algorithm-model description",2010,"10.1175/2009JAMC2181.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955571109&doi=10.1175%2f2009JAMC2181.1&partnerID=40&md5=4583fb67b6729705bfdae81f1a7e158a","Identifying and quantifying the intensity of light precipitation at global scales is still a difficult problem for most of the remote sensing algorithms in use today. The variety of techniques and algorithms employed for such a task yields a rather wide spectrum of possible values for a given precipitation event, further hampering the understanding of cloud processes within the climate. The ability of CloudSat's millimeter-wavelength Cloud Profiling Radar (CPR) to profile not only cloud particles but also light precipitation brings some hope to the above problems. Introduced as version zero, the present work uses basic concepts of detection and retrieval of light precipitation using spaceborne radars. Based on physical principles of remote sensing, the radar model relies on the description of clouds and rain particles in terms of a drop size distribution function. Use of a numerical model temperature and humidity profile ensures the coexistence of mixed phases otherwise undetected by the CPR. It also provides grounds for evaluating atmospheric attenuation, important at this frequency. Related to the total attenuation, the surface response is used as an additional constraint in the retrieval algorithm. Practical application of the profiling algorithm includes a 1-yr preliminary analysis of global rainfall incidence and intensity. These results underscore once more the role of CloudSat rainfall products for improving and enhancing current estimates of global light rainfall, mostly at higher latitudes, with the goal of understanding its role in the global energy and water cycle. © 2010 American Meteorological Society."
"7006861646;23977377900;22956930200;6603651431;57208461039;7801577502;6507876616;35766145000;6508369265;35264733400;36054649900;35729333400;6507594716;7801336936;6701633912;","On the water and energy cycles in the Tropics",2010,"10.1016/j.crte.2010.01.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951620665&doi=10.1016%2fj.crte.2010.01.003&partnerID=40&md5=9e5884de19bc6fc48f2cee5a414ee310","The water and energy cycles are major elements of the Earth climate. These cycles are especially active in the intertropical belt where satellites provide the most suitable observational platform. The history of Earth observations of the water cycle and of the radiation budget viewed from space reveals that the fundamental questions from the early times are still relevant for today's research. The last 2 decades have seen a number of milestones regarding the documentation of rainfall, mesoscale convective systems (MCS), water vapour and radiation at the top of the atmosphere (TOA). Beyond dedicated missions that provided enhanced characterizations of some elements of the atmospheric water cycle and field campaigns that allowed the gathering of validation data, the advent of the long record of meteorological satellites lead to new questioning on the homogenisation of the data time series, etc. The use of this record to document the tropical climate brought new results of the distribution of humidity and reinforced the understanding of some robust features of the African monsoon. Challenges for the immediate future concerns the deepening of the understanding of the role of cloud systems in the monsoon circulation, the downscaling of the documentation of the water and energy cycle at the scale of these cloud systems, the research of better adequation between the users and the satellite estimate of rainfall and finally a much needed methodological effort to build exploitable time series for the estimation of climatic trends in the water and energy cycle in the Tropics. The required observations to address these challenges are rapidly presented with emphasis on the upcoming Megha-Tropiques (MT) mission. © 2010 Académie des sciences."
"6506643480;8950640300;7003999574;8437866600;7004027519;7003430284;","Slower CCN growth kinetics of anthropogenic aerosol compared to biogenic aerosol observed at a rural site",2010,"10.5194/acp-10-299-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74549213137&doi=10.5194%2facp-10-299-2010&partnerID=40&md5=c66b0b2e08ba6b0af6d60cba4a5a0186","Growth rates of water droplets were measured with a static diffusion cloud condensation chamber in Mayĝ€""June 2007 at a rural field site in Southern Ontario, Canada, 70 km north of Toronto. The observations include periods when the winds were from the south and the site was impacted by anthropogenic air from the U.S. and Southern Ontario as well as during a 5-day period of northerly wind flow when the aerosol was dominated by biogenic sources. The growth of droplets on anthropogenic size-selected particles centred at 0.1 μm diameter and composed of approximately 40% organic and 60% ammonium sulphate (AS) by mass, was delayed by on the order of 1 s compared to a pure AS aerosol. Simulations of the growth rate on monodisperse particles indicate that a lowering of the water mass accommodation coefficient from αcαcCombining double low line1 to an average of αcCombining double low line0.04 is needed (assuming an insoluble organic with hygroscopicity parameter, Korg, of zero). Simulations of the initial growth rate on polydisperse anthropogenic particles agree best with observations for αcCombining double low line0.07. In contrast, the growth rate of droplets on size-selected aerosol of biogenic character, consisting of &gt;80% organic, was similar to that of pure AS. Simulations of the predominantly biogenic polydisperse aerosol show agreement between the observations and simulations when KorgCombining double low line0.2 (with upper and lower limits of 0.5 and 0.07, respectively) and αcCombining double low line1. Inhibition of water uptake by the anthropogenic organic applied to an adiabatic cloud parcel model in the form of a constant low αc increases the number of droplets in a cloud compared to pure AS. If the αc is assumed to increase with increasing liquid water on the droplets, then the number of droplets decreases which could diminish the indirect climate forcing effect. The slightly lower Korg in the biogenic case decreases the number of droplets in a cloud compared to pure AS."
"7102284923;57206526682;55453681500;7004423053;15071907100;7005978899;57202733911;","What caused Earth's temperature variations during the last 800,000 years? Data-based evidence on radiative forcing and constraints on climate sensitivity",2010,"10.1016/j.quascirev.2009.09.026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549097426&doi=10.1016%2fj.quascirev.2009.09.026&partnerID=40&md5=68cb50e9f38f9ab990ec62a8f0b3b98b","The temperature on Earth varied largely in the Pleistocene from cold glacials to interglacials of different warmths. To contribute to an understanding of the underlying causes of these changes we compile various environmental records (and model-based interpretations of some of them) in order to calculate the direct effect of various processes on Earth's radiative budget and, thus, on global annual mean surface temperature over the last 800,000 years. The importance of orbital variations, of the greenhouse gases CO2, CH4 and N2O, of the albedo of land ice sheets, annual mean snow cover, sea ice area and vegetation, and of the radiative perturbation of mineral dust in the atmosphere are investigated. Altogether we can explain with these processes a global cooling of 3.9 ± 0.8 K in the equilibrium temperature for the Last Glacial Maximum (LGM) directly from the radiative budget using only the Planck feedback that parameterises the direct effect on the radiative balance, but neglecting other feedbacks such as water vapour, cloud cover, and lapse rate. The unaccounted feedbacks and related uncertainties would, if taken at present day feedback strengths, decrease the global temperature at the LGM by -8.0 ± 1.6 K. Increased Antarctic temperatures during the Marine Isotope Stages 5.5, 7.5, 9.3 and 11.3 are in our conceptual approach difficult to explain. If compared with other studies, such as PMIP2, this gives supporting evidence that the feedbacks themselves are not constant, but depend in their strength on the mean climate state. The best estimate and uncertainty for our reconstructed radiative forcing and LGM cooling support a present day equilibrium climate sensitivity (excluding the ice sheet and vegetation components) between 1.4 and 5.2 K, with a most likely value near 2.4 K, somewhat smaller than other methods but consistent with the consensus range of 2-4.5 K derived from other lines of evidence. Climate sensitivities above 6 K are difficult to reconcile with Last Glacial Maximum reconstructions. © 2009 Elsevier Ltd. All rights reserved."
"7004508111;55714712500;55716092000;57196499374;","Atmospheric chemistry-climate feedbacks",2010,"10.1029/2009JD013300","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954486082&doi=10.1029%2f2009JD013300&partnerID=40&md5=54a4706db1a2b3e0d0faf4c7ec6d7d6f","We extend the theory of climate feedbacks to include atmospheric chemistry. A change in temperature caused by a radiative forcing will include, in general, a contribution from the chemical change that is fed back into the climate system; likewise, the change in atmospheric burdens caused by a chemical forcing will include a contribution from the associated climate change that is fed back into the chemical system. The theory includes two feedback gains, G <inf>che</inf> and G<inf>cli</inf>. G<inf>che</inf> is defined as the ratio of the change in equilibrium global mean temperature owing to long-lived greenhouse gas radiative forcing, under full climate-chemistry coupling, to that in the absence of coupling. G<inf>cli</inf> is defined as the ratio of the change in equilibrium mean aerosol or gas-phase burdens owing to chemical forcing under full coupling, to that in the absence of coupling. We employ a climate-atmospheric chemistry model based on the Goddard Institute for Space Studies (GISS) GCM II', including tropospheric gas-phase chemistry, sulfate, nitrate, ammonium, black carbon, and organic carbon. While the model describes many essential couplings between climate and atmospheric chemistry, not all couplings are accounted for, such as indirect aerosol forcing and the role of natural dust and sea salt aerosols. Guided by the feedback theory, we perform perturbation experiments to quantify G<inf>che</inf> and G<inf>cli</inf>. We find that G<inf>che</inf> for surface air temperature is essentially equal to 1.00 on a planetary scale. Regionally, G<inf>che</inf> is estimated to be 0.80-1.30. The gains are small compared to those of the physical feedbacks in the climate system (e.g., water vapor, and cloud feedbacks). These values for G<inf>che</inf> are robust for the specific model used, but may change when using more comprehensive climate-atmospheric chemistry models. Our perturbation experiments do not allow one to obtain robust values for G<inf>cli</inf>. Globally averaged, the values range from 0.99 to 1.28, depending on the chemical species, while, in areas of high pollution, G<inf>cli</inf> can be up to 1.15 for ozone, and as large as 1.40 for total aerosol. These preliminary values indicate a significant role of climate feedbacks in the atmospheric chemistry system. Copyright 2010 by the American Geophysical Union."
"38762392200;9275665400;","Oceanic dimethyl sulfide emission and new particle formation around the coast of antarctica: A modeling study of seasonal variations and comparison with measurements",2010,"10.3390/atmos1010034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79751490991&doi=10.3390%2fatmos1010034&partnerID=40&md5=5abb1b3d5041d562cab2195e532df19f","A clear understanding of new particle formation processes in remote oceans is critical for properly assessing the role of oceanic dimethyl sulfide (DMS) emission on the Earth's climate and associated climate feedback processes. Almost free from anthropogenic pollutants and leafed plants, the Antarctic continent and surrounding oceans are unique regions for studying the lifecycle of natural sulfate aerosols. Here we investigate the well-recognized seasonal variations of new particle formation around Antarctic coastal areas with a recently developed global size-resolved aerosol model. Our simulations indicate that enhanced DMS emission and photochemistry during the austral summer season lead to significant new particle formation via ion-mediated nucleation (IMN) and much higher particle number concentrations over Antarctica and surrounding oceans. By comparing predicted condensation nuclei larger than 10 nm (CN10) during a three-year period (2005-2007) with the long-period continuous CN10 measurements at the German Antarctic station Neumayer, we show that the model captures the absolute values of monthly mean CN10 (within a factor 2-3) as well as their seasonal variations. Our simulations confirm that the observed Antarctic CN10 and cloud condensation nuclei (CCN) seasonal variations are due to the formation of secondary particles during the austral summer. From the austral winter to summer, the zonally averaged CN10 and CCN in the lower troposphere over Antarctica increase by a factor of ~4-6 and ~2-4, respectively. This study appears to show that the H2SO4-H2O IMN mechanism is able to account for the new particle formation frequently observed in the Antarctica region during the austral summer. © 2010 by the authors: 2010 by the authors; licensee MDPI, Basel, Switzerland."
"8846887600;","Radiative feedbacks on global precipitation",2010,"10.1088/1748-9326/5/2/025211","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951889146&doi=10.1088%2f1748-9326%2f5%2f2%2f025211&partnerID=40&md5=151afaf54fb68643c2b030803385a8eb","The radiative kernel technique is employed to quantify twenty-first century changes to the tropospheric energy budget in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) models in order to better understand changes in global-mean precipitation. The strongest feedbacks on the tropospheric radiative cooling are found to be associated with increases in temperature and water vapor, with the water vapor feedback offsetting a significant portion (∼39%) of the increase in radiative cooling due to higher temperatures. Cloud and surface sensible heat flux feedbacks, though not as large in magnitude as the temperature and water vapor feedbacks, are important contributors to the intermodel difference in the global precipitation response to warming, or hydrological sensitivity. The direct effects of radiative forcing agents on the tropospheric energy budget are also important. Rising CO2 levels reduce tropospheric radiative cooling and hence limit the increase in global rainfall. Additionally, in some of the models, further reductions in radiative cooling occur due to increases in absorbing aerosol, suggesting that differences in aerosol forcing can explain part of the difference in hydrological sensitivity between models. © 2010 IOP Publishing Ltd."
"35568218100;6603768446;","Influence of turbulence parameterizations on high-resolution numerical modeling of tropical convection observed during the TC4 field campaign",2010,"10.1029/2009JD013302","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956044593&doi=10.1029%2f2009JD013302&partnerID=40&md5=3b1b4fc61cb390832928a2ee33cb783a","In this work, deep moist convective processes, observed during the Tropical Composition, Cloud and Climate Coupling Experiment (TC4) over the East Pacific Intertropical Convergence Zone, were modeled by means of high-resolution numerical simulations with the Weather Research and Forecasting model. Three different turbulence parameterizations and two microphysical parameterizations are used. Their impact on the spatio-temporal structure of predicted convective fields is compared to TC4 observations from a geostationary imager, airborne precipitation radar, and dropsondes. It is found that the large-eddy simulation turbulence closure ""upscaled"" to the terra incognita range of grid spacings (i.e., 0.1-1 km) is best suited to model the deep convective processes under examination. © Copyright 2010 by the American Geophysical Union."
"26028515700;7004198777;56457837200;57202803751;9272304000;16206263100;8359591200;35430463900;8261329600;7006686129;6506458269;8363388700;35547214900;7402049334;57136469800;56049333200;7404597424;7004678728;7006497590;35585284200;","Convective distribution of tropospheric ozone and tracers in the Central American ITCZ region: Evidence from observations during TC4",2010,"10.1029/2009JD013450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956026954&doi=10.1029%2f2009JD013450&partnerID=40&md5=ee85ef9b4a133aab7b06fcee74cb1158","During the Tropical Composition, Clouds and Climate Coupling (TC4) experiment that occurred in July and August of 2007, extensive sampling of active convection in the ITCZ region near Central America was performed from multiple aircraft and satellite sensors. As part of a sampling strategy designed to study cloud processes, the NASA ER-2, WB-57 and DC-8 flew in stacked ""racetrack patterns"" in convective cells. On July 24, 2007, the ER-2 and DC-8 probed an actively developing storm and the DC-8 was hit by lightning. Case studies of this flight, and of convective outflow on August 5, 2007 reveal a significant anti-correlation between ozone and condensed cloud water content. With little variability in the boundary layer and a vertical gradient, low ozone in the upper troposphere indicates convective transport. Because of the large spatial and temporal variability in surface CO and other pollutants in this region, low ozone is a better convective indicator. Lower tropospheric tracers methyl hydrogen peroxide, total organic bromine and calcium substantiate the ozone results. OMI measurements of mean upper tropospheric ozone near convection show lower ozone in convective outflow. A mass balance estimation of the amount of convective turnover below the tropical tropopause transition layer (TTL) is 50%, with an altitude of maximum convective outflow located between 10 and 11 km, 4 km below the cirrus anvil tops. It appears that convective lofting in this region of the ITCZ is either a two-stage or a rapid mixing process, because undiluted boundary layer air is never sampled in the convective outflow. Copyright 2010 by the American Geophysical Union."
"36618250200;55887849100;24315205000;","Long-term changes in insolation and temperatures at different altitudes",2010,"10.1088/1748-9326/5/2/024006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149326101&doi=10.1088%2f1748-9326%2f5%2f2%2f024006&partnerID=40&md5=43e23c29a14fdf012c9f0f61c8755d98","Over the past few years, ground-and space-based atmospheric measurements have revealed a large inter-decadal variability in the amount of radiation reaching the Earth's surface, also known as global dimming and brightening. However, the underlying physical causes of these changes remain unexplained. Clouds and aerosols, or their interactions, could both be responsible for the insolation changes, which in turn may impact the radiative balance of the planet. Here, making use of the special topology and clean environment of the Canary Islands, we compare trends in sunshine duration and temperature series, as a function of altitude. The temperature dataset is constituted by a series of mean, minimum and maximum temperatures, and daily temperature ranges. We find that the insolation and temperature trends are identical at sea level and at more than 2 km height, but the changes in diurnal temperature range are not, suggesting a possible urban heat effect at the sea level location, as well as a possible different influence of clouds and/or aerosols at different altitudes. We also find that during the summer, especially at the high altitude site, there is a clear correspondence between daytime insolation and nighttime cloud-free atmospheric extinction measurements. This suggests that atmospheric aerosol concentrations are the major contributor to the variations in the flux of solar radiation reaching the ground at high altitude sites over the Canary Islands. © 2010 IOP Publishing Ltd."
"12143654900;7005548544;","Can thin cirrus clouds in the tropics provide a solution to the faint young Sun paradox?",2010,"10.1029/2009JD012050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887828673&doi=10.1029%2f2009JD012050&partnerID=40&md5=e19891d7e1797c6e1066d858c7eed024","In this paper we present radiative-convective simulations to test the idea that tropical cirrus clouds, acting as a negative feedback on climate, can provide a solution to the faint young Sun paradox. We find that global mean surface temperatures above freezing can indeed be found for luminosities larger than about 0.8 (corresponding to ∼2.9 Ga and nearly complete tropical cirrus coverage). For luminosities smaller than 0.8, even though global mean surface temperatures are below freezing, tropical mean temperatures are still above freezing, indicating the possibility of a partially ice-free Earth for the Early Archean. We discuss possible mechanisms for the functioning of this negative feedback. While it is feasible for tropical cirrus to completely eliminate the paradox, it is similarly possible for tropical cirrus to reduce the amounts of other greenhouse gases needed for solving the paradox and therefore easing the constraints on CO2 and CH<inf>4</inf> that appear to be in disagreement with geological evidence. Copyright 2010 by the American Geophysical Union."
"57196263428;56265106600;57213050732;24329724000;7003431244;7102059695;56259852000;","Radiosonde stratospheric temperatures at Dumont d'Urville (Antarctica): Trends and link with polar stratospheric clouds",2010,"10.5194/acp-10-3813-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951600863&doi=10.5194%2facp-10-3813-2010&partnerID=40&md5=7e04d685a58ad8c34afea21c4bccf162","Temperature profiles measurements are performed daily (00:00 UT) in Dumont d'Urville (66&deg;40' S, 140deg;01' E) by Météo-France, using standard radiosondes, since the International Geophysical Year in 1957. Yet, due to a 16 years data gap between 1963 and 1978, the entire dataset is only used for a qualitative overview. Only the most recent series, between 1979 and 2008, is used to investigate the inter-annual stratospheric temperatures variability. Over Dumont d'Urville, at the edge of the vortex, the annual mean temperature cooling of about 1 K/decade at 20 km is the result of the cooling trends between 0.5 and 1.4 K/decade, in summer and autumn and a warming of about 1.1 K/decade in spring. These values are consistent with values obtained using data from inner vortex stations, but with smaller amplitude. No statistically significant trend is detected in winter. We propose here the first attempt to link stratospheric temperature trends to Polar Stratospheric Cloud (PSC) trends in Antarctica based on the only continuous 20 years database of PSC lidar detection. Despite the absence of mean temperature trend during winter, the occurrence of temperatures below the NAT threshold between 1989 and 2008 reveals a significant trend of about +6%/decade. The PSCs occurrences frequency exhibits a concomitant trend of about +3%/decade, although not statistically significant. Yet, this is consistent with results obtained in the Northern Hemisphere. Such a possible positive trend in PSC occurrence has to be further explored to be confirmed or invalidated. If confirmed, this PSC trend is likely to have strong impacts, both on ozone recovery and climate evolution in Antarctica. The study also reveals the importance of trends on extreme temperatures, and not only on mean temperatures. © 2010 Author(s)."
"57219346724;7202219883;7407577047;55614411200;57077274600;7404438372;7201997905;13604745000;7404705296;57209149302;7404592444;","Radiation partitioning and its relation to environmental factors above a meadow ecosystem on the Qinghai-Tibetan Plateau",2010,"10.1029/2009JD012373","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953172473&doi=10.1029%2f2009JD012373&partnerID=40&md5=bb3cad124d2abc8d33bd13b74b7472b2","Understanding the energy balance on the Qinghai-Tibetan Plateau is essential for better prediction of global climate change. To characterize the energy balance on the plateau, we examined the radiation partitioning over a Kobresia meadow, the most widely distributed vegetation on the plateau, for the period from 2002 to 2005. The incident solar radiation (R<inf>s</inf>) and net radiation (R<inf>n</inf>) averaged 6298 and 2779 MJ m-2 yr -1, respectively. The albedo averaged 0.220 annually, with a slightly low value of 0.202 in the growing season from May to September. An increase in soil water or leaf area index was correlated with a decrease of albedo over the meadow. The annual solar radiation lost 34% as longwave radiation, which was higher than values reported for lowland grasslands. The annual radiation efficiency (R<inf>n</inf>/R<inf>s</inf>) over the meadow, at an average of 0.44, was, however, much lower than that for lowland grasslands. The net longwave radiation (L<inf>n</inf>) and the normalized effective radiation (L <inf>n</inf>/R<inf>s</inf>) over the meadow were much higher than that for the global surface or for lowland grasslands, indicating that the longwave exchange between alpine meadow and atmosphere is the most important component of energy losses. A path analysis suggests that the water vapor pressure, air temperature, and cloud cover are the major factors governing the variations of both the net radiation and the net longwave radiation in the alpine meadow ecosystem. Copyright 2010 by the American Geophysical Union."
"57191954932;7402689885;","Differences in cyclonic raindrop size distribution from southwest to northeast monsoon season and from that of noncyclonic rain",2010,"10.1029/2009JD013355","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956197319&doi=10.1029%2f2009JD013355&partnerID=40&md5=072a7d2c5766e6585d886a808497e47e","The raindrop size distributions (RSDs) measured with an impact-type disdrometer have been utilized to study the differences in cyclonic RSD (1) from southwest monsoon (SWM) to northeast monsoon (NEM), (2) from that of noncyclonic rain, and (3) from cyclonic rain elsewhere. The stratified (based on rainfall rate R) cyclonic RSD exhibits significant seasonal variation, with more large drops and fewer small drops in SWM than in NEM. The big drops are almost absent in cyclonic RSD, whereas the small and medium-sized drops are larger in number than they are in noncyclonic rain. The average cloud effective radius in cyclones is nearly equal in SWM and NEM, suggesting that the nature of the cyclonic cloud may be similar (oceanic) in both seasons. The cyclonic RSD in the Bay of Bengal is consistent qualitatively with that observed elsewhere, but there exist some differences in rainfall bulk parameters. Implications of the observed seasonal and cyclonic to noncyclonic differences in RSD on quantitative rainfall estimation and cloud-modeling studies are also discussed. Copyright 2010 by the American Geophysical Union."
"15831005100;55520916400;55647723000;","Weather condition characteristics at the H. Arctowski station (South Shetlands, Antarctica) for 2006, in comparison with multi-year research results",2010,"10.2478/mgrsd-2010-0008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876016082&doi=10.2478%2fmgrsd-2010-0008&partnerID=40&md5=4e57c98a84f63ac34f1333fe7ea61ba5","The maritime Antarctic is characterised by highly variable weather conditions throughout the year, as well as over multi-year periods. The annual variability of weather conditions constitutes an important basis for biological and geographical studies, allowing for the monitoring of the functioning and changes of the geographical environment of the west coast of Admiralty Bay (King George Island, South Shetlands, Antarctica). Year-round meteorological observations (1.2006-12.2006) measured: atmospheric pressure, wind speed and direction, cloud cover, air temperature, relative humidity, total precipitation, snow cover, and Admiralty Bay ice cover."
"55878983900;6602890253;7404062492;7202586843;35396858200;6603372665;6603548530;","Persistence of organic carbon in heated aerosol residuals measured during Tropical Composition Cloud and Climate Coupling (TC4)",2010,"10.1029/2009JD012721","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76849107890&doi=10.1029%2f2009JD012721&partnerID=40&md5=ed0a5c984caeac45bdcf002cdc65ce28","The Particle Analysis by Laser Mass Spectrometry (PALMS) single particle mass spectrometer was used to analyze the composition of the nonvolatile fraction of atmospheric aerosol in a number of different environments. The mass spectra of individual particles sampled through an inlet section heated to 300°C were compared to unheated particles during flights of the NASA DC-8 aircraft during the Tropical Composition Cloud and Climate Coupling (TC4) mission. Comparisons are presented of measurements made in the marine boundary layer, the free troposphere, and the continental boundary layer over the Colombian jungle. The heated section completely removed sulfate from the aerosols except for sodium sulfate and related compounds in sea salt particles. Organic material in sea salt particles was observed to be less volatile than chlorine. Biomass burning particles were more likely to survive heating than other mixed sulfate-organic particles. For all particle types, there was a significant contribution to the residues from carbonaceous material other than elemental carbon. These results demonstrate the remaining compositional complexity of aerosol residuals that survive heating in a thermal denuder. Copyright 2010 by the American Geophysical Union."
"56014511300;","Direct versus indirect effects of tropospheric humidity changes on the hydrologic cycle",2010,"10.1088/1748-9326/5/2/025206","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951883408&doi=10.1088%2f1748-9326%2f5%2f2%2f025206&partnerID=40&md5=7997a6c2a78cfd295d20cf351a92ea88","Abundant evidence indicates that tropospheric specific humidity increases in a warmer atmosphere, at rates roughly comparable to those at constant relative humidity. While the implications for the planetary energy budget and global warming are well recognized, it is the net atmospheric cooling (or surface heating) that controls the hydrologic cycle. Relative humidity influences this directly through gas-phase radiative transfer, and indirectly by affecting cloud cover (and its radiative effects) and convective heating. Simple calculations show that the two indirect impacts are larger than the direct impact by roughly one and two orders of magnitude respectively. Global or regional relative humidity changes could therefore have significant indirect impacts on energy and water cycles, especially by altering deep convection, even if they are too small to significantly affect global temperature. Studies of climate change should place greater emphasis on these indirect links, which may not be adequately represented in models. © 2010 IOP Publishing Ltd."
"6603375387;6603695169;","A drop in upper tropospheric humidity in autumn 2001, as derived from radiosonde measurements at Uccle, Belgium",2010,"10.1029/2009JD013587","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78049384215&doi=10.1029%2f2009JD013587&partnerID=40&md5=b428fecfd8b90d60725909b354826558","Simulations of climate models predict a doubling of the amount of upper tropospheric water vapor by the end of this century, caused by the increasing concentrations of greenhouse gases. Observations indicate that the tropopause height has increased by several hundred meters since 1979. In this paper, we verify and link these two results by carrying out a time series analysis on a uniform database of corrected radiosonde vertical profiles gathered at Uccle, Belgium, and covering the 1990-2007 time period. The most remarkable finding of this trend analysis is a significant drop in upper tropospheric humidity (UTH) around autumn 2001, which marks an end to the upper tropospheric moistening of the precedent decade. This UTH drop in autumn 2001 coexists with a sudden lifting and cooling of the tropopause and with a significant stretch-out of the free troposphere. Therefore, we conclude that these autumn 2001 trends are certainly associated with the dynamical behavior of the troposphere, triggered by the surface warming. Links with the solar variability and the lower stratosphere were investigated but could not be established definitely. Copyright © 2010 by the American Geophysical Union."
"23048575400;7005174340;6603382350;7103204204;57203405965;7202245296;6603800142;23990280900;7006813055;7003729315;57214160655;7403682442;","A new method to retrieve the aerosol layer absorption coefficient from airborne flux density and actinic radiation measurements",2010,"10.1029/2009JD013636","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955390982&doi=10.1029%2f2009JD013636&partnerID=40&md5=362bb4cf29a78e8a99656054ee96f10b","A new method is presented to derive the mean value of the spectral absorption coefficient of an aerosol layer from combined airborne measurements of spectral net irradiance and actinic flux density. While the method is based on a theoretical relationship of radiative transfer theory, it is applied to atmospheric radiation measurements for the first time. The data have been collected with the Spectral Modular Airborne Radiation Measurement System (SMART-Albedometer), the Solar Spectral Flux Radiometer (SSFR), and the Actinic Flux Spectroradiometer (AFSR) during four field campaigns between 2002 and 2008 (the Saharan Mineral Dust Experiment (SAMUM), the Influence of Clouds on the Spectral Actinic Flux in the Lower Troposphere (INSPECTRO) project, and the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites and Aerosol, Radiation, and Cloud Processes Affecting Arctic Climate (ARCTAS/ARCPAC) projects). The retrieval algorithm is tested in a series of radiative transfer model runs and then applied to measurement cases with different aerosol species and loading. The method is shown to be a feasible approach to obtain the mean aerosol absorption coefficient across a given accessible altitude range. The results indicate that the method is viable whenever the difference of the net irradiance at the top and bottom of a layer is equal to or higher than the measurement uncertainty for net irradiance. This can be achieved by a high optical depth or a low single-scattering albedo within the layer. Copyright 2010 by the American Geophysical Union."
"7401974644;7402064802;","Impact of horizontal resolution on climate model forecasts of tropical precipitation and diabatic heating for the TWP-ICE period",2010,"10.1029/2010JD014262","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649911898&doi=10.1029%2f2010JD014262&partnerID=40&md5=f495db68f9083b9737887f477b7358a8","In order to study the impact of horizontal resolution on climate model simulations of tropical moist processes, short-term forecasts using the Community Atmospheric Model (version 4) at several resolutions are performed for a time period encompassing the Tropical Warm Pool-International Cloud Experiment (TWP-ICE). TWP-ICE occurred in the environment of Darwin, Australia in January and February 2006. The experimental period encompasses a number of atmospheric phenomena, such as an MJO passage, mesoscale convective systems, monsoon trough, and active and dry conditions. The CAM is run with four horizontal resolutions: 2°, 1°, 0.5°, and 0.25° latitude-longitude. Simulated profiles of diabatic heating and moistening at the TWP-ICE site show that the model parameterizations respond reasonably well for all resolutions to the sequence of varying conditions imposed by the analyses used to initialize the model. The spatial patterns of global model biases in time mean precipitation are largely unchanged over resolutions, and in some regions the 0.25° model significantly overestimates the observed precipitation. However, there are substantive positive aspects of finer resolution. The diurnally forced circulations over the Maritime continent are more realistically captured by the 0.25° simulation, which is able to better resolve the land-sea breeze. The intensity distribution of rainfall events is also improved at higher resolution through an increased frequency of very intense events and an increased frequency of little or no precipitation. Finally, the ratio of stratiform to convective precipitation systematically increases toward better agreement with observational estimates with increases in resolution. Copyright 2010 by the American Geophysical Union."
"7102805852;7407104838;55897485300;9248919400;7402287860;35228087800;10139397300;57203200427;36668171300;6603848988;6603425325;6602478960;6603480361;","Observations of the eruption of the Sarychev volcano and simulations using the HadGEM2 climate model",2010,"10.1029/2010JD014447","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649260983&doi=10.1029%2f2010JD014447&partnerID=40&md5=8637d1a3d6237289ac8259ad718b85c2","In June 2009 the Sarychev volcano located in the Kuril Islands to the northeast of Japan erupted explosively, injecting ash and an estimated 1.2 0.2 Tg of sulfur dioxide into the upper troposphere and lower stratosphere, making it arguably one of the 10 largest stratospheric injections in the last 50 years. During the period immediately after the eruption, we show that the sulfur dioxide (SO<inf>2</inf>) cloud was clearly detected by retrievals developed for the Infrared Atmospheric Sounding Interferometer (IASI) satellite instrument and that the resultant stratospheric sulfate aerosol was detected by the Optical Spectrograph and Infrared Imaging System (OSIRIS) limb sounder and CALIPSO lidar. Additional surface-based instrumentation allows assessment of the impact of the eruption on the stratospheric aerosol optical depth. We use a nudged version of the HadGEM2 climate model to investigate how well this state-of-the-science climate model can replicate the distributions of SO <inf>2</inf> and sulfate aerosol. The model simulations and OSIRIS measurements suggest that in the Northern Hemisphere the stratospheric aerosol optical depth was enhanced by around a factor of 3 (0.01 at 550 nm), with resultant impacts upon the radiation budget. The simulations indicate that, in the Northern Hemisphere for July 2009, the magnitude of the mean radiative impact from the volcanic aerosols is more than 60% of the direct radiative forcing of all anthropogenic aerosols put together. While the cooling induced by the eruption will likely not be detectable in the observational record, the combination of modeling and measurements would provide an ideal framework for simulating future larger volcanic eruptions. Copyright 2010 by the American Geophysical Union."
"7501627905;7005942405;","Potential climatic impacts and reliability of very large-scale wind farms",2010,"10.5194/acp-10-2053-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77249112811&doi=10.5194%2facp-10-2053-2010&partnerID=40&md5=106de39ba40efdc3544926150394887c","Meeting future world energy needs while addressing climate change requires large-scale deployment of low or zero greenhouse gas (GHG) emission technologies such as wind energy. The widespread availability of wind power has fueled substantial interest in this renewable energy source as one of the needed technologies. For very large-scale utilization of this resource, there are however potential environmental impacts, and also problems arising from its inherent intermittency, in addition to the present need to lower unit costs. To explore some of these issues, we use a three-dimensional climate model to simulate the potential climate effects associated with installation of wind-powered generators over vast areas of land or coastal ocean. Using wind turbines to meet 10% or more of global energy demand in 2100, could cause surface warming exceeding 10deg;C over land installations. In contrast, surface cooling exceeding 10deg;C is computed over ocean installations, but the validity of simulating the impacts of wind turbines by simply increasing the ocean surface drag needs further study. Significant warming or cooling remote from both the land and ocean installations, and alterations of the global distributions of rainfall and clouds also occur. These results are influenced by the competing effects of increases in roughness and decreases in wind speed on near-surface turbulent heat fluxes, the differing nature of land and ocean surface friction, and the dimensions of the installations parallel and perpendicular to the prevailing winds. These results are also dependent on the accuracy of the model used, and the realism of the methods applied to simulate wind turbines. Additional theory and new field observations will be required for their ultimate validation. Intermittency of wind power on daily, monthly and longer time scales as computed in these simulations and inferred from meteorological observations, poses a demand for one or more options to ensure reliability, including backup generation capacity, very long distance power transmission lines, and onsite energy storage, each with specific economic and/or technological challenges."
"7402456930;6701313597;7006838702;24367405100;7005284903;24308208100;13310165300;25629339800;57205351494;6701915334;25647920200;35734944400;35974255700;6701862401;8909993500;","A three-dimensional characterization of Arctic aerosols from airborne Sun photometer observations: PAM-ARCMIP, April 2009",2010,"10.1029/2009JD013605","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953932978&doi=10.1029%2f2009JD013605&partnerID=40&md5=bd8ac3c9a2570923d5148944b4d9de3b","[1] The Arctic climate is modulated, in part, by atmospheric aerosols that affect the distribution of radiant energy passing through the atmosphere. Aerosols affect the surface-atmosphere radiation balance directly through interactions with solar and terrestrial radiation and indirectly through interactions with cloud particles. Better quantification of the radiative forcing by different types of aerosol is needed to improve predictions of future climate. During April 2009, the airborne campaign Pan-Arctic Measurements and Arctic Regional Climate Model Inter-comparison Project (PAM-ARCMIP) was conducted. The mission was organized by Alfred Wegener Institute for Polar and Marine Research of Germany and utilized their research aircraft, Polar-5. The goal was to obtain a snapshot of surface and atmospheric conditions over the central Arctic prior to the onset of the melt season. Characterizing aerosols was one objective of the campaign. Standard Sun photometric procedures were adopted to quantify aerosol optical depth AOD, providing a three-dimensional view of the aerosol, which was primarily haze from anthropogenic sources. Independent, in situ measurements of particle size distribution and light extinction, derived from airborne lidar, are used to corroborate inferences made using the AOD results. During April 2009, from the European to the Alaskan Arctic, from sub-Arctic latitudes to near the pole, the atmosphere was variably hazy with total column AOD at 500 nm ranging from ∼0.12 to >0.35, values that are anomalously high compared with previous years. The haze, transported primarily from Eurasian industrial regions, was concentrated within and just above the surface-based temperature inversion layer. Extinction, as measured using an onboard lidar system, was also greatest at low levels, where particles tended to be slightly larger than at upper levels. Black carbon (BC) (soot) was observed at all levels sampled, but at moderate to low concentrations compared with historical records. BC was highest near the North Pole, suggesting there had been an accumulation of soot within the Arctic vortex. Few, optically thick elevated aerosol layers were observed along the flight track, although independent lidar observations reveal evidence of the passage of volcanic plumes, which may have contributed to abnormally high values of AOD above 4 km. Enhanced opacity at higher altitudes during the campaign is attributed to an accumulation of industrial pollutants in the upper troposphere in combination with volcanic aerosol resulting from the March-April 2009 eruptions of Mount Redoubt in Alaska. The presence of Arctic haze during April 2009 is estimated to have reduced the net shortwave irradiance by ∼2-5 W m-2, resulting in a slight cooling of the surface. © 2010 by the American Geophysical Union."
"7102945169;6602389694;6505921698;","Evaporation change and global warming: The role of net radiation and relative humidity",2010,"10.1029/2010JD013949","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149309694&doi=10.1029%2f2010JD013949&partnerID=40&md5=1d11e79942be94b9d0a2d3b946fc24e7","The change in evaporation over the oceans in climate models is analyzed from the perspective of air-sea turbulent fluxes of water and energy. The results challenge the view that the change in evaporation is predominantly constrained by the change in the net radiation at the surface. For fixed net radiation change, it is found that (1) robust increases in near-surface relative humidity and (2) robust decreases in turbulent exchange coefficient lead to a substantial reduction in evaporation below the rate of increase implied by the net radiation alone. This reduction of evaporation is associated with corresponding changes in the sensible heat flux. In addition, a net imbalance in the surface energy budget under transient greenhouse gas forcing provides a further reduction in the evaporation change in climate models. Further results also suggest that it might be more physical to view the evaporation change as a function of relative humidity change rather than net radiation. In this view, the relative humidity controls the net surface shortwave radiation through changes in low-level cloudiness and the temperature controls the net surface radiation through the changes in longwave radiation. In addition, the results demonstrate the dominant role of both the air-sea temperature difference and relative humidity over, for example, wind speed in reducing the evaporation change in climate models below the Clausius-Clapeyron rate. Copyright 2010 by the American Geophysical Union."
"35868180800;7005110573;6603400519;8570871900;7006705919;","Do biomass burning aerosols intensify drought in equatorial Asia during El Niño?",2010,"10.5194/acp-10-3515-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951282870&doi=10.5194%2facp-10-3515-2010&partnerID=40&md5=0df9fda593b60ce1c696d437545b95f2","During El Niño years, fires in tropical forests and peatlands in equatorial Asia create large regional smoke clouds. We characterized the sensitivity of these clouds to regional drought, and we investigated their effects on climate by using an atmospheric general circulation model. Satellite observations during 2000ĝ€""2006 indicated that El Niño-induced regional drought led to increases in fire emissions and, consequently, increases in aerosol optical depths over Sumatra, Borneo and the surrounding ocean. Next, we used the Community Atmosphere Model (CAM) to investigate how climate responded to this forcing. We conducted two 30 year simulations in which monthly fire emissions were prescribed for either a high (El Niño, 1997) or low (La Niña, 2000) fire year using a satellite-derived time series of fire emissions. Our simulations included the direct and semi-direct effects of aerosols on the radiation budget within the model. We assessed the radiative and climate effects of anthropogenic fire by analyzing the differences between the high and low fire simulations. Fire aerosols reduced net shortwave radiation at the surface during Augustĝ€""October by 19.1&plusmn;12.9 W m&minus;2 (10%) in a region that encompassed most of Sumatra and Borneo (90&deg; Eĝ€""120&deg; E, 5&deg; Sĝ€""5&deg; N). The reductions in net shortwave radiation cooled sea surface temperatures (SSTs) and land surface temperatures by 0.5&plusmn;0.3 and 0.4&plusmn;0.2 &deg;C during these months. Tropospheric heating from black carbon (BC) absorption averaged 20.5&plusmn;9.3 W m&minus;2 and was balanced by a reduction in latent heating. The combination of decreased SSTs and increased atmospheric heating reduced regional precipitation by 0.9&plusmn;0.6 mm d&minus;1 (10%). The vulnerability of ecosystems to fire was enhanced because the decreases in precipitation exceeded those for evapotranspiration. Together, the satellite and modeling results imply a possible positive feedback loop in which anthropogenic burning in the region intensifies drought stress during El Niño. © 2010 Author(s)."
"24537445000;57203540849;7004029924;","The Intra-Americas springtime sea surface temperature anomaly dipole as fingerprint of remote influences",2010,"10.1175/2009JCLI3006.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949335329&doi=10.1175%2f2009JCLI3006.1&partnerID=40&md5=2fef4c8d7ddad9fa535c8ec20154e95a","The influence of teleconnections on the Intra-Americas Sea (IAS; Gulf of Mexico and Caribbean Sea) has been mostly analyzed from the perspective of El Niño-Southern Oscillation (ENSO) on the Caribbean Sea (the latter being an extension of the tropical North Atlantic). This emphasis has overlooked both 1) the influence of other teleconnections on the IAS and 2) which teleconnections affect the Gulf of Mexico climate variability. In this study the different fingerprints that major teleconnection patterns have on the IAS during boreal spring are analyzed. Indices of teleconnection patterns are regressed and correlated to observations of oceanic temperature and atmospheric data from reanalyses and observational datasets. It is found that the Pacific teleconnection patterns that influence the IAS SSTs do so by affecting the Gulf of Mexico in an opposite manner to the Caribbean Sea. These analyzed Pacific climate patterns are the Pacific-North American (PNA) teleconnection, the Pacific decadal oscillation (PDO), and ENSO. The North Atlantic Oscillation (NAO) is related to a lesser degree with the north-south SST anomaly dipole than are Pacific teleconnection patterns. It is also found that the IAS influence from the midlatitude Pacific mostly affects the Gulf of Mexico, whereas the influence from the tropical Pacific mostly affects the Caribbean Sea. Therefore, the combination of a warm ENSO event and a positive PNA event induces a strong IAS SST anomaly dipole between the Gulf of Mexico and the Caribbean Sea during spring. By calculating an index that represents the IAS SST anomaly dipole, it is found that the dipole forms mostly in response to changes in the air-sea heat fluxes. In the Gulf of Mexico the dominant mechanisms are the air-sea differences in humidity and temperature. The changes in shortwave radiation also contribute to the dipole of net air-sea heat flux. The changes in shortwave radiation arise, in part, by the cloudiness triggered by the air-sea differences in humidity, and also by the changes in the convection cell that connects the Amazon basin to the IAS. Weaker Amazon convection (e.g., in the event of a warm ENSO event) reduces the subsidence over the IAS, and henceforth the IAS cloudiness increases (and the shortwave radiation decreases). This study contributes to a greater understanding of how the IAS is influenced by different Pacific and Atlantic teleconnections. © 2010 American Meteorological Society."
"28367935500;7003975505;","The transition from the present-day climate to a modern Snowball Earth",2010,"10.1007/s00382-009-0633-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957020407&doi=10.1007%2fs00382-009-0633-5&partnerID=40&md5=fe0f245158441c06f2e0b250ae6fb41f","We use the coupled atmosphere-ocean general circulation model ECHAM5/MPI-OM to investigate the transition from the present-day climate to a modern Snowball Earth, defined as the Earth in modern geography with complete sea-ice cover. Starting from the present-day climate and applying an abrupt decrease of total solar irradiance (TSI) we find that the critical TSI marking the Snowball Earth bifurcation point is between 91 and 94% of the present-day TSI. The Snowball Earth bifurcation point as well as the transition times are well reproduced by a zero-dimensional energy balance model of the mean ocean potential temperature. During the transition, the asymmetric distribution of continents between the Northern and Southern Hemisphere causes heat transports toward the more water-covered Southern Hemisphere. This is accompanied by an intensification of the southern Hadley cell and the wind-driven subtropical ocean cells by a factor of 4. If we set back TSI to 100% shortly before the transition to a modern Snowball Earth is completed, a narrow band of open equatorial water is sufficient for rapid melting. This implies that for 100% TSI the point of unstoppable glaciation separating partial from complete sea-ice cover is much closer to complete sea-ice cover than in classical energy balance models. Stable states can have no greater than 56.6% sea-ice cover implying that ECHAM5/MPI-OM does not exhibit stable states with near-complete sea-ice cover but open equatorial waters. © 2009 The Author(s)."
"6603753015;25629654200;7202252296;","Coatings and clusters of carboxylic acids in carbon-containing atmospheric particles from spectromicroscopy and their implications for cloud-nucleating and optical properties",2010,"10.1029/2009JD012622","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76249087642&doi=10.1029%2f2009JD012622&partnerID=40&md5=9cdd9897637355d26ce8c90b37990aa5","Particle shape and distribution of chemical compounds within individual particles are implied in the parameterizations used in air quality and climate models for radiative transfer, volatility, and mass transfer. In this study we employ Scanning Transmission X-Ray Microscopy with Near-Edge X-Ray Absorption Fine Structure Spectroscopy with image analysis and pattern recognition techniques to characterize the chemical structure of 636 particles collected on six field campaigns in the western hemisphere between 2004 and 2008. Many of the particles were chemically heterogeneous. A few observed types include black carbon particles covered by aqueous-phase components (n = 90), dust particles with organic clumps (106), organic particles enriched in carboxylic acid at the surface (54), and inorganic cores encapsulated by organic shells (10). The 90 particles in the first category collectively contained 95 regions showing a strong black-carbon spectral signature associated with the aqueous-phase components, of which 78 were between 0.1 and 1 μm. Organic mass fraction of the organic dust particles varied significantly (mean and standard deviation of 0.3 ±0.2), and over half of these dust particles were found to be nearly spherical. Thickness of acid-enriched coatings and carbon on inorganic cores were less than 0.6 μm in most cases, but accounted for <0.01 to 0.98 of the particle volume fraction. More than half of the identified organic particles (359) were found to be chemically heterogeneous, and 32 particles were observed as agglomerations or inclusions but did not meet one or more of the criteria of the categories described here. The acidic coatings on black carbon are calculated to have a significant impact on the critical supersaturation of these particles. The measured distribution of aspect ratios of dust and other particles in our samples ranged nonuniformly between 1.0 and 4.6 with a mean of 1.4, which can affect assessment of extinction-to-backscatter ratios over the case where spherical geometry is assumed. Copyright 2010 by the American Geophysical Union."
"55717074000;36076994600;","How important is organic aerosol hygroscopicity to aerosol indirect forcing?",2010,"10.1088/1748-9326/5/4/044010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751487432&doi=10.1088%2f1748-9326%2f5%2f4%2f044010&partnerID=40&md5=e506c53a445438e24b7d7c8428b70d49","Organics are among the most abundant aerosol components in the atmosphere. However, there are still large uncertainties with emissions of primary organic aerosol (POA) and volatile organic compounds (VOCs) (precursor gases of secondary organic aerosol, SOA), formation of SOA, and chemical and physical properties (e.g., hygroscopicity) of POA and SOA. All these may have significant impacts on aerosol direct and indirect forcing estimated from global models. In this study a modal aerosol module (MAM) in the NCAR community atmospheric model (CAM) is used to examine sensitivities of aerosol indirect forcing to hygroscopicity (represented by a single parameter 'κ') of POA and SOA. Our model simulation indicates that in the present-day (PD) condition changing the 'κ' value of POA from 0 to 0.1 increases the number concentration of cloud condensational nuclei (CCN) at supersaturation S = 0.1% by 40-80% over the POA source regions, while changing the 'κ' value of SOA by ±50% (from 0.14 to 0.07 and 0.21) changes the CCN concentration within 40%. There are disproportionally larger changes in CCN concentration in the pre-industrial (PI) condition. Due to the stronger impact of organics hygroscopicity on CCN and cloud droplet number concentration at PI condition, global annual mean anthropogenic aerosol indirect forcing (AIF) between PD and PI conditions reduces with the increase of the hygroscopicity of organics. Global annual mean AIF varies by 0.4 W m-2 in the sensitivity runs with the control run of -1.3 W m-2, highlighting the need for improved understanding of organics hygroscopicity and its representation in global models. © 2010 IOP Publishing Ltd."
"7202559581;7202155374;","Land surface skin temperature climatology: Benefitting from the strengths of satellite observations",2010,"10.1088/1748-9326/5/4/044004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149310394&doi=10.1088%2f1748-9326%2f5%2f4%2f044004&partnerID=40&md5=2fe0f36c52c4df9e09b26059fbfa9106","Surface skin temperature observations (Tskin), as obtained by satellite remote sensing, provide useful climatological information of high spatial resolution and global coverage that enhances the traditional ground observations of surface air temperature (Tair) and so, reveal new information about land surface characteristics. This letter analyzes nine years of moderate-resolution imaging spectroradiometer (MODIS) skin temperature observations to present monthly skin temperature diurnal, seasonal, and inter-annual variations at a 0.05° latitude/longitude grid over the global land surface and combines these measurements with other MODIS-based variables in an effort to understand the physical mechanisms responsible for T skin variations. In particular, skin temperature variations are found to be closely related to vegetation cover, clouds, and water vapor, but to differ from 2 m surface Tair in terms of both physical meaning and magnitude. Therefore, the two temperatures (Tskin and T air) are complementary in their contribution of valuable information to the study of climate change. © 2010 IOP Publishing Ltd."
"7004319487;","For how long should what data be assimilated for the mesoscale forecasting of convection and why? Part II: On the observation signal from different sensors",2010,"10.1175/2009MWR2884.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953207987&doi=10.1175%2f2009MWR2884.1&partnerID=40&md5=4b73bb917dc47152798d954965ef77bf","The ability of data assimilation to correct for initial conditions depends on the presence of a usable signal in the variables observed as well as on the capability of instruments to detect that signal. In Part I, the nature, properties, and limits in the usability of signals in model variables were investigated. Here, the focus is on studying the skill of measurements to pull out a useful signal for data assimilation systems to use. Using model runs of the evolution of convective storms in the Great Plains over an active 6-day period, simulated measurements from a variety of instruments are evaluated in terms of their ability to detect various initial condition errors and to provide a signal above and beyond measurement errors. The usability of the signal for data assimilation is also investigated. Imaging remote sensing systems targeting cloud and precipitation properties such as radars and thermal IR imagers provided both the strongest signals and the hardest ones to assimilate to recover fields other than clouds and precipitation because of the nonlinear behavior of the sensors combined with the limited predictability of the signal observed. The performance of other sensors was also evaluated, leading to several unexpected results. If used with caution, these findings can help determine assimilation priorities for improving mesoscale forecasting. © 2010 American Meteorological Society."
"35265542800;7201483914;7102763209;","Diurnal variation of precipitation over the Carolina Sandhills region",2010,"10.1007/s12040-010-0045-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149455134&doi=10.1007%2fs12040-010-0045-2&partnerID=40&md5=5d64fd800093072b6fcb0f968d8fa104","The Carolina Sandhills are known to have an area of maximum precipitation on its western boundary during the summer mainly due to differences in soil types. Statistical analysis was performed on summer precipitation data from automated weather stations in the Carolinas, along the Sandhills for the years 2001 to 2006. Statistically significant difference was observed between the day and night precipitation amounts. A case study also revealed the diurnal pattern of convective precipitation. North American Mesoscale (NAM) model forecasts for the summers of 2004 to 2006 were evaluated using observations. The model underpredicted precipitation significantly during nights. A numerical simulation using Weather Research and Forecast (WRF) model was performed for August 9-11, 2001 and the forecasts were compared with observed precipitation data. The model precipitation forecasts were better for daytime as compared to the night. This feature is attributed to model physics not capturing cloud-radiation interaction processes dominant during nights. Although this study is for a specific region in the US, results are applicable for other regions for similar conditions. © Indian Academy of Sciences."
"24558717100;23569952600;7006027075;56477623800;36521979100;10341169500;7005838371;55942083800;57189372185;","Cloud droplet activation of mixed organic-sulfate particles produced by the photooxidation of isoprene",2010,"10.5194/acp-10-3953-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951874971&doi=10.5194%2facp-10-3953-2010&partnerID=40&md5=62be52a67afbd100612c4bc8682164e0","The cloud condensation nuclei (CCN) properties of ammonium sulfate particles mixed with organic material condensed during the hydroxyl-radical- initiated photooxidation of isoprene (C5H8) were investigated in the continuous-flow Harvard Environmental Chamber. CCN activation curves were measured for organic particle mass concentrations of 0.5 to 10.0 μ-3, NOx concentrations from under 0.4 ppbv up to 38 ppbv, particle mobility diameters from 70 to 150 nm, and thermodenuder temperatures from 25 to 100 °C. At 25 °C, the observed CCN activation curves were accurately described by a Köhler model having two internally mixed components, namely ammonium sulfate and secondary organic material. The modeled physicochemical parameters of the organic material were equivalent to an effective hygroscopicity parameter &amp;kappa;ORG of 0.10±0.03, regardless of the C5H8:NOx concentration ratio for the span of &gt;200:0.4 to 50:38 (ppbv:ppbv). The volatilization curves (i.e., plots of the residual organic volume fraction against temperature) were also similar for the span of investigated C5H8:NO x ratios, suggesting a broad similarity of particle chemical composition. This suggestion was supported by limited variance at 25 °C among the particle mass spectra. For example, the signal intensity at m/z 44 (which can result from the fragmentation of oxidized molecules believed to affect hygroscopicity and CCN properties) varied weakly from 6 to 9% across the range of investigated conditions. In contradistinction to the results for 25 &amp; C, conditioning up to 100 °C in the thermodenuder significantly reduced CCN activity. The altered CCN activity might be explained by chemical reactions (e.g., decomposition or oligomerization) of the secondary organic material at elevated temperatures. The study's results at 25 °C, in conjunction with the results of other chamber and field studies for a diverse range of conditions, suggest that a value of 0.10±0.05 for κORG is representative of both anthropogenic and biogenic secondary organic material. This finding supports the use of κORG as a simplified yet accurate general parameter to represent the CCN activation of secondary organic material in large-scale atmospheric and climate models. © 2010 Author(s)."
"55113736500;","Short-term effects of controlling fossil-fuel soot, biofuel soot and gases, and methane on climate, Arctic ice, and air pollution health",2010,"10.1029/2009JD013795","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955409713&doi=10.1029%2f2009JD013795&partnerID=40&md5=c238f5f3f9c57c753441a3fcc609ccc5","This study examines the short-term (∼15 year) effects of controlling fossil-fuel soot (FS) (black carbon (BC), primary organic matter (POM), and S(IV) (H<inf>2</inf>SO<inf>4</inf>(aq), HSO<inf>4</inf>-, and SO <inf>4</inf>2-)), solid-biofuel soot and gases (BSG) (BC, POM, S(IV), K+, Na+, Ca2+, Mg2+, NH <inf>4</inf>+, NO<inf>3</inf>-, Cl- and several dozen gases, including CO<inf>2</inf> and CH<inf>4</inf>), and methane on global and Arctic temperatures, cloudiness, precipitation, and atmospheric composition. Climate response simulations were run with GATOR-GCMOM, accounting for both microphysical (indirect) and radiative effects of aerosols on clouds and precipitation. The model treated discrete size-resolved aging and internal mixing of aerosol soot, discrete size-resolved evolution of clouds/precipitation from externally and internally mixed aerosol particles, and soot absorption in aerosols, clouds/precipitation, and snow/sea ice. Eliminating FS, FS+BSG (FSBSG), and CH<inf>4</inf> in isolation were found to reduce global surface air temperatures by a statistically significant 0.3-0.5 K, 0.4-0.7 K, and 0.2-0.4 K, respectively, averaged over 15 years. As net global warming (0.7-0.8 K) is due mostly to gross pollutant warming from fossil-fuel greenhouse gases (2-2.4 K), and FSBSG (0.4-0.7 K) offset by cooling due to non-FSBSG aerosol particles (-1.7 to -2.3 K), removing FS and FSBSG may reduce 13-16% and 17-23%, respectively, of gross warming to date. Reducing FS, FSBSG, and CH<inf>4</inf> in isolation may reduce warming above the Arctic Circle by up to ∼1.2 K, ∼1.7 K, and ∼0.9 K, respectively. Both FS and BSG contribute to warming, but FS is a stronger contributor per unit mass emission. However, BSG may cause 8 times more mortality than FS. The global e-folding lifetime of emitted BC (from all fossil sources) against internal mixing by coagulation was ∼3 h, similar to data, and that of all BC against dry plus wet removal was ∼4.7 days. About 90% of emitted FS BC mass was lost to internal mixing by coagulation, ∼7% to wet removal, ∼3% to dry removal, and a residual remaining airborne. Of all emitted plus internally mixed BC, ∼92% was wet removed and ∼8% dry removed, with a residual remaining airborne. The 20 and 100 year surface temperature response per unit continuous emissions (STRE) (similar to global warming potentials (GWPs)) of BC in FS were 4500-7200 and 2900-4600, respectively; those of BC in BSG were 2100-4000 and 1060-2020, respectively; and those of CH<inf>4</inf> were 52-92 and 29-63, respectively. Thus, FSBSG may be the second leading cause of warming after CO<inf>2</inf>. Controlling FS and BSG may be a faster method of reducing Arctic ice loss and global warming than other options, including controlling CH<inf>4</inf> or CO<inf>2</inf>, although all controls are needed. Copyright 2010 by the American Geophysical Union."
"56265041500;7103294028;7401559815;","Premonsoon aerosol characterization and radiative effects over the Indo-Gangetic plains: Implications for regional climate warming",2010,"10.1029/2010JD013819","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957554427&doi=10.1029%2f2010JD013819&partnerID=40&md5=8c29645613eb4c4602dc8d4300831339","The Himalayas have a profound effect on the South Asian climate and the regional hydrological cycle, as it forms a barrier for the strong monsoon winds and serves as an elevated heat source, thus controlling the onset and distribution of precipitation during the Indian summer monsoon. Recent studies have suggested that radiative heating by absorbing aerosols, such as dust and black carbon over the Indo-Gangetic Plains (IGP) and slopes of the Himalayas, may significantly accelerate the seasonal warming of the Hindu Kush-Himalayas-Tibetan Plateau (HKHT) and influence the subsequent evolution of the summer monsoon. This paper presents a detailed characterization of aerosols over the IGP and their radiative effects during the premonsoon season (April-May-June) when dust transport constitutes the bulk of the regional aerosol loading, using ground radiometric and spaceborne observations. During the dust-laden period, there is a strong response of surface shortwave flux to aerosol absorption indicated by the diurnally averaged forcing efficiency of -70 Wm-2 per unit optical depth. The simulated aerosol single-scattering albedo, constrained by surface flux and aerosol measurements, is estimated to be 0.89 ± 0.01 (at ∼550 nm) with diurnal mean surface and top-of-atmosphere forcing values ranging from -11 to -79.8 Wm-2 and +1.4 to +12 Wm-2, respectively, for the premonsoon period. The model-simulated solar heating rate profile peaks in the lower troposphere with enhanced heating penetrating into the middle troposphere (5-6 km), caused by vertically extended aerosols over the IGP with peak altitude of ∼5 km as indicated by spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization observations. On a long-term climate scale, our analysis, on the basis of microwave satellite measurements of tropospheric temperatures from 1979 to 2007, indicates accelerated annual mean warming rates found over the Himalayan-Hindu Kush region (0.21°C/decade ± 0.08°C/decade) and underscores the potential role of enhanced aerosol solar absorption in the maximum warming localized over the western Himalayas (0.26°C/decade ± 0.09°C/decade) that significantly exceed the entire HKHT and global warming rates. We believe the accelerated warming rates reported here are critical to both the South Asian summer monsoon and hydro-glaciological resource variability in the Himalayan-Hindu Kush snowpack and therefore to the densely populated downstream regions. © 2010 by the American Geophysical Union."
"7005202019;24168849300;35498501900;8437188000;","Radiative effects of aerosols in sub-Sahel Africa: Dust and biomass burning",2010,"10.1029/2009JD013335","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955894730&doi=10.1029%2f2009JD013335&partnerID=40&md5=70510f3439e8d165b968c9b0256a7495","Information on radiative fluxes that reach the ground is needed in numerous areas of climate research. On a global scale, such information is obtainable only from satellites. Top of the atmosphere satellite observations during clear and cloudy sky conditions have been found useful for inferring, among others, information on aerosol optical depth (AOD) and cloud optical depth (COD). These are important elements for estimating surface radiative fluxes. Satellite retrievals of AOD are based on the assumption that the aerosols are of a specific type. In certain climatic regions, dust aerosols and those from biomass burning are injected into the atmosphere simultaneously and are distributed distinctly in the vertical. In this study, it is demonstrated that in such scenarios inaccurate assumption on the vertical distribution of the aerosols can lead to errors in AOD estimates from satellites and, subsequently, in the inferred shortwave (SW) radiative fluxes that reach the surface. The magnitude of such errors can be as high as 80 W m-2. The frequency of these mixed situations has not as yet been documented, and it is possible that on global scale the impact is small. Using available records of observed SW radiative fluxes, their reduction (""dimming"") at numerous locations has been reported. Some relate this reduction to aerosol effects. The findings of this study have implications for the ability to assess such ""dimming"" from satellites in areas where the vertical structure of aerosol distribution needs to be accounted for. Copyright 2010 by the American Geophysical Union."
"27170375100;56006103500;","Observation and numerical prediction of torrential rainfall over Korea caused by Typhoon Rusa (2002)",2010,"10.1029/2009JD012581","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954461050&doi=10.1029%2f2009JD012581&partnerID=40&md5=c39617abfa980d195b7e74abde545bd9","On landfall in 2002, Typhoon Rusa caused record-breaking rainfall (870.5 mm/d) in Gangneung at the foot of the Taebaek Mountain range, Korea. In this study, the predictability of the torrential rainfall associated with the typhoon and the detailed mesoscale precipitation distribution were investigated through numerical simulation. The weather research and forecasting (WRF) model successfully simulates the mesoscale rainfall distibution and timing. With a 10 km (3.3 km) horizontal grid, the model predicted 830.8 mm (1307.9 mm) of rain with some uncertainty in the observed local maximum in coverage. This study shows that the complexity of forecasting is associated with the interactions between environmental flows, typhoon flow, and topography. In bogus and 1-day-earlier initial-time experiments, the typhoon track and intensity are substantially improved, although this has little impact on successful rainfall simulation. The interaction between the large-scale features and the proper vertical structure of the typhoon is key. The simulated rainfall at the cloud-resolving spacing of 3.3 km is greater than that at 10 km because of the increased terrain height and not the greater resolution. Analysis of observed and simulated data shows that the torrential rainfall had two different causes with two peaks in the hourly rainfall at Gangneung. The first peak links to a mesoscale frontal structure, characterized by strong moisture and thermal gradients formed by the intrusion of cold, dry northerly air from a midlatitude trough and moist southerly air from the typhoon. The second peak results from the direct effect of the typhoon and the lifting of the moisture-laden typhoon winds. Copyright 2010 by the American Geophysical Union."
"6603550074;55262499900;55702592400;55717441600;35413553600;14025125600;7402545909;55967620900;","IASI spectral radiance validation inter-comparisons: Case study assessment from the JAIVEx field campaign",2010,"10.5194/acp-10-411-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74549214297&doi=10.5194%2facp-10-411-2010&partnerID=40&md5=ecec7e8cb9085e567aa780efe9ec7dd0","Advanced satellite sensors are tasked with improving global-scale measurements of the Earth's atmosphere, clouds, and surface to enable enhancements in weather prediction, climate monitoring, and environmental change detection. Measurement system validation is crucial to achieving this goal and maximizing research and operational utility of resultant data. Field campaigns employing satellite under-flights with well-calibrated Fourier Transform Spectrometer (FTS) sensors aboard high-altitude aircraft are an essential part of this validation task. The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I) has been a fundamental contributor in this area by providing coincident high spectral and spatial resolution observations of infrared spectral radiances along with independently-retrieved geophysical products for comparison with like products from satellite sensors being validated. This manuscript focuses on validating infrared spectral radiance from the Infrared Atmospheric Sounding Interferometer (IASI) through a case study analysis using data obtained during the recent Joint Airborne IASI Validation Experiment (JAIVEx) field campaign. Emphasis is placed upon the benefits achievable from employing airborne interferometers such as the NAST-I since, in addition to IASI radiance calibration performance assessments, cross-validation with other advanced sounders such as the AQUA Atmospheric InfraRed Sounder (AIRS) is enabled."
"7501855361;16637291100;55977336000;","A thermodynamic model for estimating sea and lake ice thickness with optical satellite data",2010,"10.1029/2009JC005857","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650508764&doi=10.1029%2f2009JC005857&partnerID=40&md5=1e69337b6d78779b9aaf7f79d9c3e336","Sea ice is a very important indicator and an effective modulator of regional and global climate change. Current remote sensing techniques provide an unprecedented opportunity to monitor the cryosphere routinely with relatively high spatial and temporal resolutions. In this paper, we introduce a thermodynamic model to estimate sea and lake ice thickness with optical (visible, near-infrared, and infrared) satellite data. Comparisons of nighttime ice thickness retrievals to ice thickness measurements from upward looking submarine sonar show that this thermodynamic model is capable of retrieving ice thickness up to 2.8 m. The mean absolute error is 0.18 m for samples with a mean ice thickness of 1.62 m, i.e., an 11% mean absolute error. Comparisons with in situ Canadian stations and moored upward looking sonar measurements show similar results. Sensitivity studies indicate that the largest errors come from uncertainties in surface albedo and downward solar radiation flux estimates from satellite data, followed by uncertainties in snow depth and cloud fractional coverage. Due to the relatively large uncertainties in current satellite retrievals of surface albedo and surface downward shortwave radiation flux, the current model is not recommended for use with daytime data. For nighttime data, the model is capable of resolving regional and seasonal variations in ice thickness and is useful for climatological analysis. © 2010 by the American Geophysical Union."
"7003999574;7005361537;7006544721;7005560252;8950640300;8608660400;6701463335;7501381728;7403143315;6506643480;10939473600;15926418500;8437866600;7006705580;7005444075;55720332500;7003430284;7004027519;","Characterization of a large biogenic secondary organic aerosol event from eastern Canadian forests",2010,"10.5194/acp-10-2825-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952966524&doi=10.5194%2facp-10-2825-2010&partnerID=40&md5=fa0b8d30d5a914735308d5a147ca3b44","Measurements of aerosol composition, volatile organic compounds, and CO are used to determine biogenic secondary organic aerosol (SOA) concentrations at a rural site 70 km north of Toronto. These biogenic SOA levels are many times higher than past observations and occur during a period of increasing temperatures and outflow from Northern Ontario and Quebec forests in early summer. A regional chemical transport model approximately predicts the event timing and accurately predicts the aerosol loading, identifying the precursors as monoterpene emissions from the coniferous forest. The agreement between the measured and modeled biogenic aerosol concentrations contrasts with model underpredictions for polluted regions. Correlations of the oxygenated organic aerosol mass with tracers such as CO support a secondary aerosol source and distinguish biogenic, pollution, and biomass burning periods during the field campaign. Using the Master Chemical Mechanism, it is shown that the levels of CO observed during the biogenic event are consistent with a photochemical source arising from monoterpene oxidation. The biogenic aerosol mass correlates with satellite measurements of regional aerosol optical depth, indicating that the event extends across the eastern Canadian forest. This regional event correlates with increased temperatures, indicating that temperature-dependent forest emissions can significantly affect climate through enhanced direct optical scattering and higher cloud condensation nuclei numbers. © Author(s) 2010."
"35753336400;57198013681;13403526200;35739165200;6701688830;","The impact of urbanization on current and future coastal precipitation: A case study for houston",2010,"10.1068/b34102t","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949637185&doi=10.1068%2fb34102t&partnerID=40&md5=c9d2b2935597bd13d94db5dfbc93eeba","The approach of this study was to determine, theoretically, what impact current and future urban land use in the coastal city of Houston, Texas has on the space and time evolution of precipitation on a 'typical' summer day. Regional model simulations of a case study for 25 July 2001 were applied to investigate possible effects of urban land cover on precipitation development. Simulations in which Houston urban land cover was included resolved rain cells associated with the sea breeze front and a possible urban circulation on the northwest fringe of the city. Simulations without urban land cover did not capture the initiation and full intensity of the 'hypothesized' urban-induced rain cell. The response is given the terminology the 'urban rainfall effect' or URE. An urban growth model (UrbanSim) was used to project the urban land-cover growth of Houston, Texas from 1992 to 2025. A regional atmospheric-land surface model was then run with the 2025 urban land-cover scenario. Though we used a somewhat theoretical treatment, our results show the sensitivity of the atmosphere to urban land cover and illustrate how atmosphere-land interactions can affect cloud and precipitation processes. Two urban-induced features, convergence zones along the inner fringe of the city and an urban low-pressure perturbation, appear to be important factors that lead to enhanced rain clouds independently or in conjunction with the sea breeze. Simulations without the city (NOURBAN) produced less cumulative rainfall in the west-northwest Houston area than simulations with the city represented (URBAN). Future urban land-cover growth projected by UrbanSim (URBAN2025) led to a more expansive area of rainfall, owing to the extended urban boundary and increased secondary outflow activity. This suggests that the future urban land cover might lead to temporal and spatial precipitation variability in coastal urban microclimates. It was beyond the scope of the analysis to conduct an extensive sensitivity analysis of cause-effect relationships, though the experiments provide some clues as to why the rainfall evolution differs. This research demonstrates a novel application of urban planning and weather-climate models. It also raises viable questions concerning future planning strategies in urban environments in consideration of hydroclimate changes. © 2010 Pion Ltd and its Licensors."
"22133430700;56631340400;6701751100;7102632172;56387247900;6603496571;","Multi-scale analysis of the 25-27 july 2006 convective period over Niamey: Comparison between doppler radar observations and simulations",2010,"10.1002/qj.539","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949405448&doi=10.1002%2fqj.539&partnerID=40&md5=f68c3ca6c3f2fa89959012f7f5002ffa","The present study investigates the multi-scale processes associated with a sequence of convective events that occurred over Niamey during the period 25-26 July 2006. This period corresponds to the active stage of the first intense monsoon surge over Sahel for 2006. During this two-day period, two successive sequences of mesoscale convective systems (MCSs) were located ahead of and in phase with the trough of an African Easterly Wave (AEW). They were followed by suppressed or isolated convection behind the trough and in the vicinity of the ridge. The large AMMA-SOP dataset, in particular the UHF radar and the MIT Doppler radar in Niamey, are used in combination with a low-resolution (5 km) cloud-resolving model to understand the convection organization and its interaction with the environment. Several initial and boundary conditions have been tested, but only the simulation starting with the ECMWF AMMA reanalysis succeeds in reproducing the observed features; this emphasizes the importance of the initial state. From the simulated MCSs, the along-line component of the apparent source of momentum due to the convection is found to be up to 1ms-1h-1. It seems that MCSs globally reduce the monsoon flow and generate southerlies at mid levels which can reinforce the rotation of the wind at the passage of the trough. During the afternoon of 26 July, the local convection over Niamey resulted from some favourable factors (humidity, CAPE, CIN) that triggered convection, while inhibiting factors (mid-level dry layer, weaker low-level wind shear pointing to the north, anticyclonic curvature of the streamlines at 700hPa) prevented it organizing itself and propagating. In particular, the low-level wind shear seems of critical importance. © 2010 Royal Meteorological Society."
"26421356200;35305025100;6506416572;6701705691;6602417968;6701754792;6602108977;","Numerical simulation of the 7 to 9 september 2006 AMMA mesoscale convective system: Evaluation of the dynamics and cloud microphysics using synthetic observations",2010,"10.1002/qj.558","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77149152898&doi=10.1002%2fqj.558&partnerID=40&md5=388c211af08ff057b540da07d74b3844","This paper presents a numerical simulation of a Mesoscale Convective System (MCS) observed during the AMMA (African Monsoon Multidisciplinary Analysis) experiment with the BRAMS model (Brazilian Regional Atmospheric Modelling System). The aim is to document the life cycle of the MCS and to identify key cloud microphysical processes and their signatures by making use of synthetic observations calculated from the simulated fields. These observations: ARM (Atmospheric Radiation Measurement) 95 GHz equivalent radar reflectivity factor and Doppler velocity and infrared brightness temperatures in three SEVIRI (Spinning Enhanced Visible and InfraRed Imager) channels centred at 8.7, 10.6 and 12 μm are simulated using respectively Mie scattering theory and FASDOM (Fast Discrete Ordinate Method), a fast radiative transfer code. Synthetic observations and model variables are compared to various measurements from several platforms (W-band and Massachusetts Institute of Technology (MIT) ground-based Doppler radars, soundings, aircraft measurements, and Meteosat Second Generation) to evaluate the model at different scales and to identify the signatures of microphysical properties with a focus on the anvil part of the MCS. A method using both the ARM and the MIT radar data is used to identify the different regimes within the MCS. A relatively good agreement with direct comparisons is found, as well as discrepancies in the microphysical scheme parametrization that clearly need improvements (using in situ measurements). Microphysical signatures are also studied using joint radar reflectivity/Doppler-height histograms. Their analysis shows that the model tends to overplay the role of the riming processes, even in the anvil part of the MCS. Comparisons of the Particle Size Distributions (simulated and measured in situ) show the model's ability to reproduce complex PSDs (e.g. a multimodal behaviour). © 2010 Royal Meteorological Society."
"7404597424;57210006342;7401776563;8627503500;18437404000;8076740100;6602969645;6603955469;26028515700;7005891596;6506458269;7006510465;36657036600;6506667896;36623905100;6602407753;","Convective and wave signatures in ozone profiles over the equatorial Americas: Views from TC4 2007 and SHADOZ",2010,"10.1029/2009JD012909","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955563371&doi=10.1029%2f2009JD012909&partnerID=40&md5=ddedf716e9fba463794c6b145df0ef0a","During the TC4 (Tropical Composition, Clouds, and Climate Coupling) campaign in July-August 2007, daily ozonesondes were launched over coastal Las Tablas, Panamá (7.8°N, 80°W) and several times per week at Alajuela, Costa Rica (10°N, 84°W). Wave activity, detected most prominently in 100-300 m thick ozone laminae in the tropical tropopause layer, occurred in 50% (Las Tablas) and 40% (Alajuela) of the soundings. These layers, associated with vertical displacements and classified as gravity waves (GW, possibly Kelvin waves) by laminar identification, occur with similar structure and frequency over the Paramaribo (5.8°N, 55°W) and San Cristóbal (0.92°S, 90°W) Southern Hemisphere Additional Ozonesondes (SHADOZ) sites. GW-labeled laminae in individual soundings correspond to cloud outflow as indicated by DC-8 tracers and other aircraft data, confirming convective initiation of equatorial waves. Layers representing quasihorizontal displacements, referred to as Rossby waves by the laminar technique, are robust features in soundings from 23 July to 5 August. The features associated with Rossby waves correspond to extratropical influence, possibly stratospheric, and sometimes to pollution transport. Comparison of Las Tablas and Alajuela ozone budgets with 1999- 2007 Paramaribo and San Cristóbal soundings shows that TC4 is typical of climatology for the equatorial Americas. Overall during TC4, convection and associated waves appear to dominate ozone transport in the tropical tropopause layer; intrusions from the extratropics occur throughout the free troposphere. Copyright © 2010 by the American Geophysical Union."
"7402944490;6601970557;","Atmosphere-ocean relationship in the midlatitude North Pacific: Seasonal dependence and east-west contrast",2010,"10.1029/2009JD012579","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950174263&doi=10.1029%2f2009JD012579&partnerID=40&md5=1e525ce157e02bbf2468a53a84c4b5a6","The present study documents the relationship between the surface heat flux and sea surface temperature (SST) and estimates the contribution of different processes to SST changes in the midlatitude North Pacific. It is found that the atmosphere-ocean relationship displays pronounced differences between winter and summer and between the western and central basins of the North Pacific. In the western basin, the shortwave radiation change associated with a positive cloud-SST feedback is a dominant factor for the development of SST anomalies in boreal summer. In boreal winter, surface latent heat flux anomalies develop in response to SST and in turn damp the SST anomalies. The meridional advection induced by anomalous geostrophic currents near the coast and by anomalous Ekman currents away from the coast has important contributions to the SST changes. In the central basin, the latent heat flux change is a dominant factor for the development of SST anomalies, and the shortwave radiation mainly responds passively to SST anomalies in boreal summer. Both latent heat flux and meridional advection contribute to the SST changes in boreal winter. The wind changes over the North Pacific play an important role for the SST changes both in winter and summer through their impacts on cloud, surface wind speed, advection of atmospheric boundary layer moisture, and Ekman transport. Copyright 2010 by the American Geophysical Union."
"7102582535;55938215400;35752192700;7103197356;35622410000;7005456532;","Assessing surface solar irradiance and its long-term variations in the northern Africa desert climate using Meteosat images",2010,"10.1080/01431160902882645","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649169643&doi=10.1080%2f01431160902882645&partnerID=40&md5=8d38804e4c8d4469d2a929bb6b538305","Two databases of solar surface irradiance (SSI) derived from satellites were compared to ground measurements in Algeria, Egypt, Libya and Tunisia. We found that it was possible to accurately derive the SSI from geostationary meteorological satellites, even with a coarse spatial resolution. The two databases HelioClim-1 (HC1) and SSE exhibited similar and good performances. The bias was generally lower for SSE than for HC1; however, HC1 exhibited a smaller scattering of data compared to ground measurements (smaller standard deviation) than the SSE, allowing better performance when mapping the long-term variations in SSI. The long-term variations in SSI from 1985 to 2005 show that these four countries as a whole experienced dimming. Detailed analyses of the range of dimming at sites with long-term records and of its spatial distribution were performed. We found that the analysis of SSI from HC1 supports the findings for the individual sites. Dimming may be explained by: (1) transportation of sand dust northwards from the Sahel, (2) an increase in urbanization, and (3) an increase in cloud cover and aerosol loading. © 2010 Taylor & Francis."
"57200534631;49561837700;55506701100;","Snow cover monitoring using MODIS data in liaoning province, Northeastern China",2010,"10.3390/rs2030777","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051755256&doi=10.3390%2frs2030777&partnerID=40&md5=6fae9d101b3535f72625765e9ff0a37c","This paper presents the results of snow cover monitoring studies in Liaoning Province, northeastern China, using MODIS data. Snow cover plays an important role in both the regional water balance and soil moisture properties during the early spring in northeastern China. In addition, heavy snowfalls commonly trigger hazards such as flooding, caused by rapid snow melt, or crop failure, resulting from fluctuations in soil temperature associated with changes in the snow cover. The latter is a function of both regional, or global, climatic changes, as well as fluctuations in the albedo resulting from variations in the Snow Covered Area (SCA). These impacts are crucial to human activities, especially to those living in middle-latitude areas such as Liaoning Province. Thus, SCA monitoring is currently an important tool in studies of global climate change, particularly because satellite remote sensing data provide timely and efficient snow cover information for large areas. In this study, MODIS L1B data, MODIS Daily Snow Products (MOD10A1) and MODIS 8-day Snow Products (MOD10A2) were used to monitor the SCA of Liaoning Province over the winter months of November-April, 2006-2008. The effects of cloud masking and forest masking on the snow monitoring results were also assessed. The results show that the SCA percentage derived from MODIS L1B data is relatively consistent, but slightly higher than that obtained from MODIS Snow Products. In situ data from 25 snow stations were used to assess the accuracy of snow cover monitoring from the SCA compared to the results from MODIS Snow Products. The studies found that the SCA results were more reliable than MODIS Snow Products in the study area. © 2010 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland."
"6506862390;35755214900;55259753300;56238720500;56088026700;7005428977;7102577046;","Simulated effects of a seasonal precipitation change on the vegetation in tropical Africa",2010,"10.5194/cp-6-169-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950343952&doi=10.5194%2fcp-6-169-2010&partnerID=40&md5=7cdf71b24635117efc5a5e53c9b84cb2","Pollen data collected in Africa at high (Kuruyange, valley swamp, Burundi) and low altitude (Victoria, lake, Uganda; Ngamakala, pond, Congo) showed that after 6 ky before present (BP), pollen of deciduous trees increase their relative percentage, suggesting thus the reduction of the annual amount of precipitation and/or an increase of in the length of the dry season. Until now, pollen-climate transfer functions only investigated mean annual precipitation, due to the absence of modern pollen-assemblage analogs under diversified precipitation regimes. Hence these functions omit the potential effect of a change in precipitation seasonality modifying thus the length of the dry season. In the present study, we use an equilibrium biosphere model (i.e. BIOME3.5) to estimate the sensitivity of equatorial African vegetation, at specific sites, to such changes. Climatic scenarios, differing only in the monthly distribution of the current annual amount of precipitation, are examined at the above three locations in equatorial Africa. Soil characteristics, monthly temperatures and cloudiness are kept constant at their present-day values. Good agreement is shown between model simulations and current biomes assemblages, as inferred from pollen data. To date, the increase of the deciduous forest component in the palaeodata around 6 ky BP has been interpreted as the beginning of a drier climate period. However, our results demonstrate that a change in the seasonal distribution of precipitation could also induce the observed changes in vegetation types. This study confirms the importance of taking into account seasonal changes in the hydrological balance. Palaeoecologists can greatly benefit from the use of dynamic process based vegetation models to acccount for modification of the length of the dry season when they wish to reconstruct vegetation composition or to infer quantitative climate parameters, such as temperature and precipitation, from pollen or vegetation proxy."
"6506730508;7402942478;7102517130;14059827200;","Online simulations of global aerosol distributions in the NASA GEOS-4 model and comparisons to satellite and ground-based aerosol optical depth",2010,"10.1029/2009JD012820","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955392726&doi=10.1029%2f2009JD012820&partnerID=40&md5=fce4e9f339b4fbd1f9f71672a17fa2b1","We have implemented a module for tropospheric aerosols (GOCART) online in the NASA Goddard Earth Observing System version 4 model and simulated global aerosol distributions for the period 2000-2006. The new online system offers several advantages over the previous offline version, providing a platform for aerosol data assimilation, aerosol-chemistry-climate interaction studies, and short-range chemical weather forecasting and climate prediction. We introduce as well a methodology for sampling model output consistently with satellite aerosol optical thickness (AOT) retrievals to facilitate model-satellite comparison. Our results are similar to the offline GOCART model and to the models participating in the AeroCom intercomparison. The simulated AOT has similar seasonal and regional variability and magnitude to Aerosol Robotic Network (AERONET), Moderate Resolution Imaging Spectroradiometer, and Multiangle Imaging Spectroradiometer observations. The model AOT and Angstrom parameter are consistently low relative to AERONET in biomass-burning-dominated regions, where emissions appear to be underestimated, consistent with the results of the offline GOCART model. In contrast, the model AOT is biased high in sulfate-dominated regions of North America and Europe. Our model-satellite comparison methodology shows that diurnal variability in aerosol loading is unimportant compared to sampling the model where the satellite has cloud-free observations, particularly in sulfate-dominated regions. Simulated sea salt burden and optical thickness are high by a factor of 2-3 relative to other models, and agreement between model and satellite over-ocean AOT is improved by reducing the model sea salt burden by a factor of 2. The best agreement in both AOT magnitude and variability occurs immediately downwind of the Saharan dust plume. Copyright 2010 by the American Geophysical Union."
"24367914600;","Underground meteorology - ""what's the weather underground?"" [Podzemna meteorologija: ""kakšno je vreme v podzemlju?""]",2010,"10.3986/ac.v39i3.74","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650982385&doi=10.3986%2fac.v39i3.74&partnerID=40&md5=b0c15213ba0a784d6b6350b754a8a7dc","The aim of this work is to provide a synthetic outline of some of the processes of transient nature occurring in caves, focusing on poorly studied general aspects of underground physics and mainly making use of original experimental data. In the first part, the average climatic conditions of a caves, their connection to the external climate, and the general role played by rock, water, air and external morphology are discussed. The variation of the internal temperature with the altitude is a key parameter for the cave physics: The related energetic consequences are briefly discussed. In the second part, transient processes are considered, and a general overview of main meteorological phenomena occurring underground is given. The physics of thermal sedimentation, of underground temperature ranges, of infrasonic oscillations of cave atmospheres and, above all, of water vapour condensation in caves is synthetically described. The experimental study of these processes is extremely difficult, because they are time dependent and have very small amplitude; the first measurements show, however, that their variability from one cave to another, and from point to point inside a cave, is surprisingly high. To provide a more correct interpretation of underground climatic measurements, for their speleogenetic role and importance in cave environment protection, a better understanding of the processes described here is essential."
"8255698000;35459699300;6701859178;7006539346;35595682100;14048087800;56715028200;8395857700;7004194005;55605771904;","Influence of convection on the water isotopic composition of the tropical tropopause layer and tropical stratosphere",2010,"10.1029/2009JD013100","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957561553&doi=10.1029%2f2009JD013100&partnerID=40&md5=9698f9c8af29a73d3cdd4fd76aedc4a7","We present the first in situ measurements of HDO across the tropical tropopause, obtained by the integrated cavity output spectroscopy (ICOS) and Hoxotope water isotope instruments during the Costa Rica Aura Validation Experiment (CR-AVE) and Tropical Composition, Cloud and Climate Coupling (TC4) aircraft campaigns out of Costa Rica in winter and summer, respectively. We use these data to explore the role convection plays in delivering water to the tropical tropopause layer (TTL) and stratosphere. We find that isotopic ratios within the TTL are inconsistent with gradual ascent and dehydration by in-situ cirrus formation and suggest that convective ice lofting and evaporation play a strong role throughout the TTL. We use a convective influence model and a simple parameterized model of dehydration along back trajectories to demonstrate that the convective injection of isotopically heavy water can account for the predominant isotopic profile in the TTL. Air parcels with significantly enhanced water vapor and isotopic composition can be linked via trajectory analysis to specific convective events in the Western Tropical Pacific, Southern Pacific Ocean, and South America. Using a simple model of dehydration and hydration along trajectories we show that convection during the summertime TC4 campaign moistened the upper part of the TTL by as much as 2.0 ppmv water vapor. The results suggest that deep convection is significant for the moisture budget of the tropical near-tropopause region and must be included to fully model the dynamics and chemistry of the TTL and lower stratosphere. Copyright 2010 by the American Geophysical Union."
"55927861900;7006069664;57203474131;7201786471;35768178600;","Simulation of heavy rainfall events over Indian monsoon region using WRF-3DVAR data assimilation system",2010,"10.1007/s00703-009-0054-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949272722&doi=10.1007%2fs00703-009-0054-3&partnerID=40&md5=bca6f9f63a79d5975a8304001808dda6","We present the results of the impact of the 3D variational data assimilation (3DVAR) system within the Weather Research and Forecasting (WRF) model to simulate three heavy rainfall events (25-28 June 2005, 29-31 July 2004, and 7-9 August 2002) over the Indian monsoon region. For each event, two numerical experiments were performed. In the first experiment, namely the control simulation (CNTL), the low-resolution global analyses are used as the initial and boundary conditions of the model. In the second experiment (3DV-ANA), the model integration was carried out by inserting additional observations in the model's initial conditions using the 3DVAR scheme. The 3DVAR used surface weather stations, buoy, ship, radiosonde/rawinsonde, and satellite (oceanic surface wind, cloud motion wind, and cloud top temperature) observations obtained from the India Meteorological Department (IMD). After the successful inclusion of additional observational data using the 3DVAR data assimilation technique, the resulting reanalysis was able to successfully reproduce the structure of convective organization as well as prominent synoptic features associated with the mid-tropospheric cyclones (MTC). The location and intensity of the MTC were better simulated in the 3DV-ANA as compared to the CNTL. The results demonstrate that the improved initial conditions of the mesoscale model using 3DVAR enhanced the location and amount of rainfall over the Indian monsoon region. Model verification and statistical skill were assessed with the help of available upper-air sounding data. The objective verification further highlighted the efficiency of the data assimilation system. The improvements in the 3DVAR run are uniformly better as compared to the CNTL run for all the three cases. The mesoscale 3DVAR data assimilation system is not operational in the weather forecasting centers in India and a significant finding in this study is that the assimilation of Indian conventional and non-conventional observation datasets into numerical weather forecast models can help improve the simulation accuracy of meso-convective activities over the Indian monsoon region. Results from the control experiments also highlight that weather and regional climate model simulations with coarse analysis have high uncertainty in simulating heavy rain events over the Indian monsoon region and assimilation approaches, such as the 3DVAR can help reduce this uncertainty. © Springer-Verlag 2009."
"36604878800;6506539438;7006629146;","Advection-condensation paradigm for stratospheric water vapor",2010,"10.1029/2010JD014352","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650533211&doi=10.1029%2f2010JD014352&partnerID=40&md5=71ae03a3587da8d495585e0f10c85d30","The advection-condensation (A-C) paradigm is a starting point for a theoretical framework for analysis of atmospheric water vapor distributions and changes therein in a changing climate. It postulates that water vapor concentrations are governed to leading order by the transport through the full four-dimensional temperature (and hence saturation mixing ratio) field. Brewer's (1949) qualitative deduction of the stratospheric circulation based on water vapor measurements was a first and prominently successful application of this paradigm. Here we examine the quantitative validity of the A-C paradigm by predicting stratospheric water vapor based on the saturation mixing ratio at the Lagrangian dry point of trajectories calculated using data from the European Centre for Medium-range Weather Forecasts. Using different data sets for the calculation, we show that results are sensitive to seemingly small differences in temperatures and wind fields and that interpretation of results (in terms of identification of effects of processes deliberately neglected by the advection-condensation paradigm) requires a careful error calculation. We introduce a semiempirical approach to analyze errors in the Lagrangian predictions of water vapor. We show that persistent (in time and space) errors in the temperature fields lead to similar errors in the Lagrangian model predictions. Conversely, biases in the variance of the temperature fields introduces a systematic bias in the model prediction. Further, model predictions are affected by dispersion and the time scale of troposphere-to-stratosphere transport. Our conclusion is that water vapor predictions for the stratospheric overworld based on the A-C paradigm have a dry bias of -40% ± 10% and -50% ± 10% when small-space-scale and short-time-scale temperature fluctuations not resolved by the ECMWF reanalyses are taken into account. We suggest that the correction to the A-C paradigm most likely to remove this dry bias is the inclusion of cloud microphysical processes (such as incomplete sedimentation of particles allowing reevaporation), which relax the assumption of instantaneous dehydration to the saturation mixing ratio. Interestingly, the bias attributed to the A-C paradigm in terms of water vapor concentration is found to be proportional to the measured water concentration, and a constant offset in terms of frost point temperature can account for much of the bias and its variability in water vapor mixing ratios. Copyright 2010 by the American Geophysical Union."
"35585284200;57203766520;16029719200;7005473082;","A new ENSO index derived from satellite measurements of column ozone",2010,"10.5194/acp-10-3711-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951598058&doi=10.5194%2facp-10-3711-2010&partnerID=40&md5=b70bed0716fa3b7b6e83306f7c0b2f4c","Column Ozone measured in tropical latitudes from Nimbus 7 total ozone mapping spectrometer (TOMS), Earth Probe TOMS, solar backscatter ultraviolet (SBUV), and Aura ozone monitoring instrument (OMI) are used to derive an El Nino-Southern Oscillation (ENSO) index. This index, which covers a time period from 1979 to the present, is defined as the ""Ozone ENSO Index"" (OEI) and is the first developed from atmospheric trace gas measurements. The OEI is constructed by first averaging monthly mean column ozone over two broad regions in the western and eastern Pacific and then taking their difference. This differencing yields a self-calibrating ENSO index which is independent of individual instrument calibration offsets and drifts in measurements over the long record. The combined Aura OMI and MLS ozone data confirm that zonal variability in total column ozone in the tropics caused by ENSO events lies almost entirely in the troposphere. As a result, the OEI can be derived directly from total column ozone instead of tropospheric column ozone. For clear-sky ozone measurements a +1 K change in Nino 3.4 index corresponds to +2.9 Dobson Unit (DU) change in the OEI, while a +1 hPa change in SOI coincides with a &minus;1.7 DU change in the OEI. For ozone measurements under all cloud conditions these numbers are +2.4 DU and -1.4 DU, respectively. As an ENSO index based upon ozone, it is potentially useful in evaluating climate models predicting long term changes in ozone and other trace gases. © 2010 Author(s)."
"16242119400;7004469744;35810775100;8942525300;","The impact of dust on sulfate aerosol, CN and CCN during an East Asian dust storm",2010,"10.5194/acp-10-365-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860389343&doi=10.5194%2facp-10-365-2010&partnerID=40&md5=69bc9bd8ca733d663f8e1bf0229fc650","A global model of aerosol microphysics is used to simulate a large East Asian dust storm during the ACE-Asia experiment. We use the model together with size resolved measurements of aerosol number concentration and composition to examine how dust modified the production of sulfate aerosol and the particle size distribution in East Asian outflow. Simulated size distributions and mass concentrations of dust, sub- and super-micron sulfate agree well with observations from the C-130 aircraft. Modeled mass concentrations of fine sulfate (Dp&lt;1.3 μm) decrease by ≃10% due to uptake of sulfur species onto super-micron dust. We estimate that dust enhanced the mass concentration of coarse sulfate (Dp&gt;1.0 μm) by more than an order of magnitude, but total sulfate concentrations increase by less than 2% because decreases in fine sulfate have a compensating effect. Our analysis shows that the sulfate associated with dust can be explained largely by the uptake of H2SO4 rather than reaction of SO2 on the dust surface, which we assume is suppressed once the particles are coated in sulfate. We suggest that many previous model investigations significantly overestimated SO2 oxidation on East Asian dust, possibly due to the neglect of surface saturation effects. We extend previous model experiments by examining how dust modified existing particle concentrations in Asian outflow. Total particle concentrations (condensation nuclei, CN) modeled in the dust-pollution plume are reduced by up to 20%, but we predict that dust led to less than 10% depletion in particles large enough to act as cloud condensation nuclei (CCN). Our analysis suggests that E. Asian dust storms have only a minor impact on sulfate particles present at climate-relevant sizes. © 2010Author(s)."
"56265354200;44861287300;55466293500;","Impact of degradation on biodiversity status and management of an alpine meadow within Govind Wildlife Sanctuary and National Park, Uttarkashi, India",2010,"10.1080/21513732.2011.568972","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960126501&doi=10.1080%2f21513732.2011.568972&partnerID=40&md5=bf84dd849be9763d0e98f0d6208fbf4d","This study investigates the biodiversity status of degraded and intact sites at Har-ki-Dun alpine meadow in the Govind Wildlife Sanctuary and National Park, India, between altitudes of 3200 and 3900 m. This vast alpine meadow is extensively used for tourist campsites, illegal medicinal and aromatic plant extraction and grazing by local villagers. The increasing pressure of grazing, along with abrupt observed climatic changes and natural stress in the form of cloud bursts, has had a marked impact on biodiversity of the area. Meadow degradation was mapped using satellite data IRS P6 LISS-III and PAN merged data. We studied the biodiversity status and extent of degradation at various degraded and intact sites. The degraded sites were classified into 'naturally degraded' and 'anthropogenically degraded'. The Har-ki-Dun alpine meadow occupies about 55 km2, out of which 22 km2 are in different states of degradation. We recorded 93 species in intact sites against 73 in naturally degraded and 76 in anthropogenically degraded sites, with varying frequency and density of palatable and unpalatable species. A total of 25% of the plant species in the intact protected site were not recorded in the naturally degraded sites, and 23% did not occur in the anthropogenically degraded sites. We recommend the restoration of each degradation category, according to the area's suitability for grassland protection, fodder cultivation and farming of medicinal plants. © 2010 Taylor &amp; Francis."
"15125055800;7004885872;6701378450;","Aerosol hygroscopicity at high (99 to 100%) relative humidities",2010,"10.5194/acp-10-1329-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76349125075&doi=10.5194%2facp-10-1329-2010&partnerID=40&md5=dad0b9c9d3dab04b20c4f3d680f9c43a","The hygroscopicity of an aerosol strongly influences its effects on climate and, for smaller particles, atmospheric lifetime. While many aerosol hygroscopicity measurements have been made at lower relative humidities (RH) and under cloud formation conditions (RH>100%), relatively few have been made at high RH (99 to 100%), where the Kelvin (curvature) effect is comparable to the Raoult (solute) effect. We measured the size of droplets at high RH that had formed on particles composed of one of seven compounds with dry diameters between 0.1 and 0.5 μm. We report the hygroscopicity of these compounds using a parameterization of the Kelvin term, in addition to a standard parameterization (κ) of the Raoult term. For inorganic compounds, hygroscopicity could reliably be predicted using water activity data (measured in macroscopic solutions) and assuming a surface tension of pure water. In contrast, most organics exhibited a slight to mild increase in hygroscopicity with droplet diameter. This trend was strongest for sodium dodecyl sulfate (SDS), the most surface-active compound studied. The results suggest that, for single-component aerosols at high RH, partitioning of solute to the particle-air interface reduces particle hygroscopicity by reducing the bulk solute concentration. This partitioning effect is more important than the increase in hygroscopicity due to surface tension reduction. Furthermore, we found no evidence that micellization limits SDS activity in micron-sized solution droplets, as observed in macroscopic solutions. We conclude that while the high-RH hygroscopicity of inorganic compounds can be reliably predicted using readily available data, surface-activity parameters obtained from macroscopic solutions with organic solutes may be inappropriate for calculations involving micron-sized droplets."
"7103386012;37561150400;","Using genetic algorithms to calibrate a dimethylsulfide production model in the Arctic ocean",2010,"10.1007/s00343-010-9062-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955521921&doi=10.1007%2fs00343-010-9062-x&partnerID=40&md5=a317daeea9582f2c32f13940f70c6296","The global climate is intimately connected to changes in the polar oceans. The variability of sea ice coverage affects deep-water formations and large-scale thermohaline circulation patterns. The polar radiative budget is sensitive to sea-ice loss and consequent surface albedo changes. Aerosols and polar cloud microphysics are crucial players in the radioactive energy balance of the Arctic Ocean. The main biogenic source of sulfate aerosols to the atmosphere above remote seas is dimethylsulfide (DMS). Recent research suggests the flux of DMS to the Arctic atmosphere may change markedly under global warming. This paper describes climate data and DMS production (based on the five years from 1998 to 2002) in the region of the Barents Sea (30-35°E and 70-80°N). A DMS model is introduced together with an updated calibration method. A genetic algorithm is used to calibrate the chlorophyll-a (CHL) measurements (based on satellite SeaWiFS data) and DMS content (determined from cruise data collected in the Arctic). Significant interannual variation of the CHL amount leads to significant interannual variability in the observed and modeled production of DMS in the study region. Strong DMS production in 1998 could have been caused by a large amount of ice algae being released in the southern region. Forcings from a general circulation model (CSIRO Mk3) were applied to the calibrated DMS model to predict the zonal mean sea-to-air flux of DMS for contemporary and enhanced greenhouse conditions at 70-80°N. It was found that significantly decreasing ice coverage, increasing sea surface temperature and decreasing mixed-layer depth could lead to annual DMS flux increases of more than 100% by the time of equivalent CO2 tripling (the year 2080). This significant perturbation in the aerosol climate could have a large impact on the regional Arctic heat budget and consequences for global warming. © 2010 Chinese Society for Oceanology and Limnology, Science Press and Springer-Verlag Berlin Heidelberg."
"7006228584;","Simulations of wintertime precipitation in the vicinity of Japan: Sensitivity to fine-scale distributions of sea surface temperature",2010,"10.1029/2009JD012576","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953174071&doi=10.1029%2f2009JD012576&partnerID=40&md5=bca276f086ca3f5829c27b2c4b20fa8d","In the present study, the winter precipitation in the vicinity of Japan is simulated by the Weather Research Forecasting model by using two sets of sea surface temperature (SST) data with different spatial resolutions. On comparing the simulated mean precipitations, we found that SST resolution has a significant influence on the simulated precipitation along the northwestern coast of Japan; in this region, the coarse-resolution SST data have a systematic cold bias. In the simulation using high-resolution SST data, the moisture supply to the atmosphere increases over the relatively warm coastal SST. The increase in the moisture supply leads to an increase in the moisture convergence near the mountain ranges in Japan on the Japan Sea side, leading to an increase in precipitation amount. The result suggests that coastal SST must be carefully used for dynamic downscaling of the climate simulation, in particular, in Japan, which is surrounded by boundary currents. We also found that a small-scale SST anomaly in the Kuroshio-Oyashio Extension (KOE) region near Japan enhances the interannual variance of local precipitation in the regions downwind of the SST anomaly. The associated anomalous ascent extends to the midtroposphere and is accompanied by an increase in cloud ice, suggesting that the interannual SST variation over the KOE region may affect the free atmosphere. Moisture budget analysis indicates the influence of moisture advection by mean wind on the spatial phase difference between the SST and precipitation anomalies. Copyright 2010 by the American Geophysical Union."
"12141789600;35411782100;35413553600;7006453382;7402934750;","An assessment of the absolute accuracy of the atmospheric infrared sounder v5 precipitable water vapor product at tropical, midlatitude, and arctic ground-truth sites: September 2002 through August 2008",2010,"10.1029/2009JD013139","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957550155&doi=10.1029%2f2009JD013139&partnerID=40&md5=43b67074baf1a4585e1af6d97f688c45","The Atmospheric Infrared Sounder (AIRS) is the first of a series of satellite sensors that exploit high spectral resolution and broad spectral coverage of the midinfrared to improve the retrieval accuracy of passive infrared sounding. The AIRS atmospheric retrieval goals are to obtain 1 K accuracy for 1 km layers below 100 mb for temperature and 10% for 2 km layers for water vapor in clear and most cloud conditions. The AIRS total column precipitable water vapor (PWV) is obtained by integrating the vertical profile of water vapor mixing ratio derived from cloud-cleared radiances. The accuracy goal of the AIRS PWV product is 5%. This paper provides a validation of the AIRS PWV product at three distinct climate sites over the nearly full range of total water amounts observed on Earth (between 0.1 and 6.5 cm). Six years (September 2002 to August 2008) of AIRS v5 retrievals of PWV are evaluated against ground-based microwave radiometer (MWR) data at three Department of Energy Atmospheric Radiation Measurement program (ARM) sites. The accuracy of the MWR PWV retrieval is estimated to be between 1% and 3%. This study shows that the agreement between the MWR and AIRS retrievals of PWV is within 5% at all three ARM climate sites for most conditions. The notable exceptions are (1) very dry cases (PWV < 1 cm) over the Southern Great Plains (SGP) land site during both daytime and nighttime, where AIRS is too moist by 15%-30% and (2) nighttime observations over the SGP land site for PWV > 1 cm, where AIRS is too dry by about 10%. The moist bias for low water amounts (usually observed during the winter) over land could be a surface emissivity-related error since very little bias is seen at the ARM Arctic site for similar water amounts. The cause of the dry bias at nighttime over land for moderate water amounts is not determined by this study. However, a spatial map of the diurnal bias in monthly AIRS water amount suggests that this effect is related to meteorological conditions in the U. S. Great Plains, which in the summertime is characterized by a moist boundary layer. The diurnal error in AIRS PWV at the SGP site seen with respect to the MWR data are confirmed by PWV amounts derived from a coincident ground-based GPS receiver. © 2010 by the American Geophysical Union."
"56038849000;36454623700;36454868700;7004920873;","Light absorbing material (soot) in rainwater and in aerosol particles in the Maldives",2010,"10.1029/2009JD013768","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954826196&doi=10.1029%2f2009JD013768&partnerID=40&md5=8175ab8afedddbe8ccf6aef1418aaed9","Simultaneous measurements of soot (absorbing material at 528 nm) and inorganic ions in aerosol and precipitation at the Maldives Climate Observatory Hanimaadhoo during the period May 2005 to February 2007 have made it possible to calculate the washout ratio (WR) of these components as a measure of how efficiently they are scavenged by precipitation. On the basis of air trajectories the data have been separated into days with polluted air arriving from the Indian subcontinent in a northeasterly sector during winter and clean monsoon days with southerly flow from the Indian Ocean. The average soot concentration was a factor of 10 higher in the former situations. Despite considerable scatter for individual days, a systematic pattern emerged when the WR for the different components were compared with each other. During the monsoon season the WR for soot was similar to that of sulfate and other fine mode aerosol components, indicating that soot containing particles in these situations were efficient as cloud condensation nuclei. The origin of the light absorbing material during the monsoon season is unclear. During the polluted winter days, on the other hand, the WR for soot was three times smaller than that of sulfate. This indicates that, even after a travel time of several days, the soot containing particles from India have retained much of their hydrophobic property. The low WR and the infrequent rain during this season probably contribute to extending the atmospheric lifetime of soot well beyond several days. Surprisingly high concentrations of non-sea-salt calcium were measured during the monsoon season, substantially higher than during the winter season. The origin of these high values could be long-range transport from the Australian or African continents. Another possibility might be exopolymer gels derived from the ocean surface microlayer. Copyright 2010 by the American Geophysical Union."
"24344988500;7003535176;","Numerical simulations of contrail-to-cirrus transition-Part 2: Impact of initial ice crystal number, radiation, stratification, secondary nucleation and layer depth",2010,"10.5194/acp-10-2037-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77249124951&doi=10.5194%2facp-10-2037-2010&partnerID=40&md5=410a202c86d150196370955cd10bd411","Simulations of contrail-to-cirrus transition were performed with an LES model. In Part 1 the impact of relative humidity, temperature and vertical wind shear was explored in a detailed parametric study. Here, we study atmospheric parameters like stratification and depth of the supersaturated layer and processes which may affect the contrail evolution. We consider contrails in various radiation scenarios herein defined by the season, time of day and the presence of lower-level cloudiness which controls the radiance incident on the contrail layer. Under suitable conditions, controlled by the radiation scenario and stratification, radiative heating lifts the contrail-cirrus and prolongs its lifetime. The potential of contrail-driven secondary nucleation is investigated. We consider homogeneous nucleation and heterogeneous nucleation of preactivated soot cores released from sublimated contrail ice crystals. In our model the contrail dynamics triggered by radiative heating does not suffice to force homogeneous freezing of ambient liquid aerosol particles. Furthermore, our model results suggest that heterogeneous nucleation of preactivated soot cores is unimportant. Contrail evolution is not controlled by the depth of the supersaturated layer as long as it exceeds roughly 500 m. Deep fallstreaks however need thicker layers. A variation of the initial ice crystal number is effective during the whole evolution of a contrail. A cut of the soot particle emission by two orders of magnitude can reduce the contrail timescale by one hour and the optical thickness by a factor of 5. Hence future engines with lower soot particle emissions could potentially lead to a reduction of the climate impact of aviation."
"13407563600;8645916500;24070152900;7006595513;55545335600;7102597422;57205085102;35461763400;55942083800;","Cloud condensation nuclei in polluted air and biomass burning smoke near the mega-city Guangzhou, China - Part 1: Size-resolved measurements and implications for the modeling of aerosol particle hygroscopicity and CCN activity",2010,"10.5194/acp-10-3365-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860389563&doi=10.5194%2facp-10-3365-2010&partnerID=40&md5=623280d85e0ab5e91ce03f483b9ceb57","Atmospheric aerosol particles serving as Cloud Condensation Nuclei (CCN) are key elements of the hydrological cycle and climate. We measured and characterized CCN in polluted air and biomass burning smoke during the PRIDE-PRD2006 campaign from 1-30 July 2006 at a rural site ≃60 km northwest of the mega-city Guangzhou in southeastern China. CCN efficiency spectra (activated fraction vs. dry particle diameter; 20-290 nm) were recorded at water vapor supersaturations (S) in the range of 0.068% to 1.27%. The corresponding effective hygroscopicity parameters describing the influence of particle composition on CCN activity were in the range of k≈0.1-0.5. The campaign average value of k=0.3 equals the average value of k for other continental locations. During a strong local biomass burning event, the average value of k dropped to 0.2, which can be considered as characteristic for freshly emitted smoke from the burning of agricultural waste. At low S (≤0.27%), the maximum activated fraction remained generally well below one, indicating substantial portions of externally mixed CCN-inactive particles with much lower hygroscopicity - most likely soot particles (up to ≃60% at ≃250 nm). The mean CCN number concentrations (NCCN,S) ranged from 1000 cm?3 at S=0.068% to 16 000 cm?3 at S=1.27%, which is about two orders of magnitude higher than in pristine air. Nevertheless, the ratios between CCN concentration and total aerosol particle concentration (integral CCN efficiencies) were similar to the ratios observed in pristine continental air (≃6% to ≃85% at S=0.068% to 1.27%). Based on the measurement data, we have tested different model approaches for the approximation/prediction of NCCN,S. Depending on S and on the model approach, the relative deviations between observed and predicted NCCN,S ranged from a few percent to several hundred percent. The largest deviations occurred at low S with a simple power law. With a Köhler model using variable k values obtained from individual CCN efficiency spectra, the relative deviations were on average less than ≃10% and hardly exceeded 20%, confirming the applicability of the k-Köhler model approach for efficient description of the CCN activity of atmospheric aerosols. Note, however, that different types of k-parameters must be distinguished for external mixtures of CCN-active and -inactive aerosol particles (ka, kt, kcut). Using a constant average hygroscopicity parameter (k=0.3) and variable size distributions as measured, the deviations between observed and predicted CCN concentrations were on average less than 20%. In contrast, model calculations using variable hygroscopicity parameters as measured and constant size distributions led to much higher deviations: ≃70% for the campaign average size distribution, ≃80% for a generic rural size distribution, and ≃140% for a generic urban size distribution. These findings confirm earlier studies suggesting that aerosol particle number and size are the major predictors for the variability of the CCN concentration in continental boundary layer air, followed by particle composition and hygroscopicity as relatively minor modulators. Depending on the required and applicable level of detail, the information and parameterizations presented in this study should enable efficient description of the CCN activity of atmospheric aerosols in detailed process models as well as in large-scale atmospheric and climate models. © Author(s) 2010."
"7403253358;57201725986;","Effects of time-dependent large-scale forcing, solar zenith angle, and sea surface temperature on time-mean tropical rainfall processes",2010,"10.1007/s00703-009-0053-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949272744&doi=10.1007%2fs00703-009-0053-4&partnerID=40&md5=440c98e265447b818ea1cbd1ffdf2a7d","Effects of time-dependent large-scale forcing (LSF), solar zenith angle (SZA), and sea surface temperature (SST) on time-mean rainfall processes during Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) are examined by conducting a control experiment and a series of sensitivity experiments with a two-dimensional cloud-resolving model. The model is forced by time-dependent LSF, SZA, and SST in the control experiment. The sensitivity experiments are forced only by either time-dependent LSF, or SZA, or SST while others are replaced with their time averages. When the model is imposed by time-dependent LSF, time dependence of SZA and SST has no discernable effect on surface rainfall, but it affects rainfall processes. The rainfall is reduced by 15% when the time-dependent LSF is replaced by its time mean. The reduction of rainfall is associated with the suppression of water vapor convergence as a result of low correlation between upward motion and water vapor variation. © Springer-Verlag 2009."
"8663601100;7004172687;6602914876;35998927000;6602607937;26643041500;35461255500;","Atmospheric sub-3 nm particles at high altitudes",2010,"10.5194/acp-10-437-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74549174928&doi=10.5194%2facp-10-437-2010&partnerID=40&md5=00fc8250402ff6a433ef857927074114","Formation of new atmospheric aerosol particles is known to occur almost all over the world and the importance of these particles to climate and air quality has been recognized. Recently, it was found that atmospheric aerosol particle formation begins at the diameter of around 1.5ĝ€""2.0 nm and a pool of sub-3 nm atmospheric particles ĝ€"" consisting of both charged and uncharged ones ĝ€"" was observed at the ground level. Here, we report on the first airborne observations of the pool of sub-3 nm neutral atmospheric particles. Between 2 and 3 nm, their concentration is roughly two orders of magnitude larger than that of the ion clusters, depending slightly on the altitude. Our findings indicate that new particle formation takes place throughout the tropospheric column up to the tropopause. Particles were found to be formed via neutral pathways in the boundary layer, and there was no sign of an increasing role by ion-induced nucleation toward the upper troposphere. Clouds, while acting as a source of sub-10 nm ions, did not perturb the overall budget of atmospheric clusters or particles."
"36920234100;6701865015;","Parametric studies of contrail ice particle formation in jet regime using microphysical parcel modeling",2010,"10.5194/acp-10-3261-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950794003&doi=10.5194%2facp-10-3261-2010&partnerID=40&md5=54dad00c2823e59b885fa344a2fa7dd8","Condensation trails (contrails) formed from water vapor emissions behind aircraft engines are the most uncertain components of the aviation impacts on climate change. To gain improved knowledge of contrail and contrail-induced cirrus cloud formation, understanding of contrail ice particle formation immediately after aircraft engines is needed. Despite many efforts spent in modeling the microphysics of ice crystal formation in jet regime (with a plume age &lt;5 s), systematic understanding of parametric effects of variables affecting contrail ice particle formation is still limited. In this work, we apply a microphysical parcel modeling approach to study contrail ice particle formation in near-field aircraft plumes up to 1000 m downstream of an aircraft engine in the soot-rich regime (soot number emission index &gt;1×10 15 (kg-fuel)-1) at cruise. The effects of dilution history, ion-mediated nucleation, ambient relative humidity, fuel sulfur contents, and initial soot emissions were investigated. Our simulation results suggest that ice particles are mainly formed by water condensation on emitted soot particles. The growth of ice coated soot particles is driven by water vapor emissions in the first 1000 m and by ambient relative humidity afterwards. The presence of chemi-ions does not significantly contribute to the formation of ice particles in the soot-rich regime, and the effect of fuel sulfur contents is small over the range typical of standard jet fuels. The initial properties of soot emissions play the most critical role, and our calculations suggest that higher number concentration and smaller size of contrail particle nuclei may be able to effectively suppress the formation of contrail ice particles. Further modeling and experimental studies are needed to verify if our findings can provide a possible approach for contrail mitigation."
"7201837768;35355580500;6508150016;6603140753;7006631883;","Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets",2010,"10.1088/1748-9326/5/1/014005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950656112&doi=10.1088%2f1748-9326%2f5%2f1%2f014005&partnerID=40&md5=5f47dc5cf10321f64f81491e4838f855","The two main forcings that can counteract to some extent the positive forcings from greenhouse gases from pre-industrial times to present day are the aerosol and related aerosol-cloud forcings, and the radiative response to changes in surface albedo. Here, we quantify the change in radiative forcing and land surface temperature that may be obtained by increasing the albedos of roofs and pavements in urban areas in temperate and tropical regions of the globe by 0.1. Using the catchment land surface model (the land model coupled to the GEOS-5 Atmospheric General Circulation Model), we quantify the change in the total outgoing (outgoing shortwave+longwave) radiation and land surface temperature to a 0.1 increase in urban albedos for all global land areas. The global average increase in the total outgoing radiation was 0.5Wm-2, and temperature decreased by ∼0.008K for an average 0.003 increase in surface albedo. These averages represent all global land areas where data were available from the land surface model used and are for the boreal summer (June-July-August). For the continental US the total outgoing radiation increased by 2.3Wm-2, and land surface temperature decreased by ∼0.03K for an average 0.01 increase in surface albedo. Based on these forcings, the expected emitted CO2 offset for a plausible 0.25 and 0.15 increase in albedos of roofs and pavements, respectively, for all global urban areas, was found to be ∼57GtCO2. A more meaningful evaluation of the impacts of urban albedo increases on global climate and the expected CO2 offsets would require simulations which better characterize urban surfaces and represent the full annual cycle. © 2010 IOP Publishing Ltd."
"24831179300;8839231800;56962915800;55311589500;","Decadal cooling in the Indian summer monsoon after 1997/1998 El Niño and its impact on the East Asian summer monsoon",2010,"10.1029/2009GL041539","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75749155377&doi=10.1029%2f2009GL041539&partnerID=40&md5=4266366715138e482e3b33458b311ded","Observational evidences are presented to show a significant atmospheric diabatic cooling in the Indian summer monsoon (ISM) region after the 1997/1998 El Nio. This study investigates the cause of this decadal cooling and its impact on the East Asian summer monsoon (EASM). After 1997/1998, the abnormal sea surface temperature warming in the western Pacific, which is not fully demonstrated in this study, induces enhanced local convection. This enhanced convection strengthens the Walker-type circulation and leads to moisture divergence, subsidence, and decreased cloudiness over the ISM, which in turn causes the diabatic cooling. The decadal cooling of the ISM, on the other hand, may affect the EASM through development of an anomalous local meridional cell over the EASM region and through enhancement of the Eurasian wave train pattern. Consequently, rainfall over the ISM and northern EASM decreases concurrently, while the southern EASM rainfall increases after 1997/1998. Copyright 2010 by the American Geophysical Union."
"36538539800;36065603800;27171906700;55113736500;7005956394;7402822814;7405728922;6701756440;","A comparative study of nucleation parameterizations: 2. Three-dimensional model application and evaluation",2010,"10.1029/2010JD014151","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149289941&doi=10.1029%2f2010JD014151&partnerID=40&md5=82b44e6093e6d80289461f116283ed8b","Following the examination and evaluation of 12 nucleation parameterizations presented in part 1, 11 of them representing binary, ternary, kinetic, and cluster-activated nucleation theories are evaluated in the U.S. Environmental Protection Agency Community Multiscale Air Quality (CMAQ) modeling system version 4.4. The 12-28 June 1999 Southern Oxidants Study episode is selected as a testbed to evaluate simulated particulate matter (PM) number and size predictions of CMAQ with different nucleation parameterizations. The evaluation shows that simulated domain-wide maximum PM<inf>2.5</inf> number concentrations with different nucleation parameterizations can vary by 3 orders of magnitude. All parameterizations overpredict (by a factor of 1.4 to 1.7) the total number concentrations of accumulation-mode PM and significantly underpredict (by factors of 1.3 to 65.7) those of Aitken-mode PM, resulting in a net underprediction (by factors of 1.3 to 13.7) of the total number concentrations of PM<inf>2.5</inf> under a polluted urban environment at a downtown station in Atlanta. The predicted number concentrations for Aitken-mode PM at this site can vary by up to 3 orders of magnitude, and those for accumulation-mode PM can vary by up to a factor of 3.2, with the best predictions by the power law of Sihto et al. (2006) (NMB of -31.7%) and the worst predictions by the ternary nucleation parameterization of Merikanto et al. (2007) (NMB of -93.1%). The ternary nucleation parameterization of Napari et al. (2002) gives relatively good agreement with observations but for a wrong reason. The power law of Kuang et al. (2008) and the binary nucleation parameterization of Harrington and Kreidenweis (1998) give better agreement than the remaining parameterizations. All the parameterizations fail to reproduce the observed temporal variations of PM number, volume, and surface area concentrations. The significant variation in the performance of these parameterizations is caused by their different theoretical bases, formulations, and dependence on temperature, relative humidity, and the ambient levels of H<inf>2</inf>SO<inf>4</inf> and NH <inf>3</inf>. The controlling processes are different for PM number, mass, and surface areas. At urban/rural locations, some PM processes (e.g., homogeneous nucleation) and/or vertical transport may dominate the production of PM <inf>2.5</inf> number, and emissions, or PM processes, or vertical transport or their combinations may dominate the production of PM<inf>2.5</inf> mass and surface area. Dry deposition or some PM processes such as coagulation may dominate PM<inf>2.5</inf> number loss, and horizontal and vertical transport, and cloud processes (e.g., cloud scavenging and wet deposition) may dominate the loss of PM<inf>2.5</inf> mass and surface area concentrations. Sensitivity simulations show that the PM number and size distribution predictions are most sensitive to prescribed emission fractions of Aitken and accumulation-mode PM and the assumed initial PM size distribution, in addition to different nucleation parameterizations. Copyright 2010 by the American Geophysical Union."
"6603059928;7005392086;14023953700;57205479513;7006747377;7005913300;7402711358;25029309200;35459699300;7005891596;57218359395;26028515700;7404597424;","Low-ozone bubbles observed in the tropical tropopause layer during the TC4 campaign in 2007",2010,"10.1029/2009JD012804","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957585300&doi=10.1029%2f2009JD012804&partnerID=40&md5=d6a8855bc681f34006c48d3483d719dc","In the summer of 2007, the NASA DC-8 aircraft took part in the Tropical Composition, Cloud and Climate Coupling campaign based in San Jose, Costa Rica. During this campaign, multiple in situ and remote-sensing instruments aboard the aircraft measured the atmospheric composition of the tropical tropopause layer (TTL) in the equatorial region around Central and South America. During the 17 July flight off the Ecuadorian coast, well-defined ""bubbles"" of anomalously low-ozone concentration (less than 75 ppbv) were detected above the aircraft in the TTL at the altitude near 365 K (between 14 and 16 km) and at ∼3°S and ∼82°W. Backward trajectories from meteorological analyses and the aircraft in situ measurements suggest that the ozone-depleted air mass originated from deep convection in the equatorial eastern Pacific and/or Panama Bight regions at least 5 days before observation by the DC-8; this was not a feature produced by local convection. Given uncertainties known in regard to trajectories calculated from global reanalysis, it is not possible to identify the exact convective system that produced this particular low-ozone anomaly, but only the general origin from a region of high convective activity. However, the fact that the feature apparently maintained its coherency for at least 5 days suggests a significant contribution to the chemical composition of the tropical upper troposphere portion of the TTL from convective systems followed by quasi-horizontal transport. It also suggests that mixing time scales for these relatively small spatial features are greater than 5 days. © 2010 by the American Geophysical Union."
"6603083860;6603955469;8605657900;35459699300;7401604274;7004180583;56230679900;16744791500;25121572200;","Detailed structure of the tropical upper troposphere and lower stratosphere as revealed by balloon sonde observations of water vapor, ozone, temperature, and winds during the NASA TCSP and TC4 campaigns",2010,"10.1029/2009JD013209","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956037703&doi=10.1029%2f2009JD013209&partnerID=40&md5=1f86b5d9f3c23645bf14c4cf07400fd1","We report on balloon sonde measurements of water vapor and ozone using the cryogenic frost point hygrometer and electrochemical concentration cell ozonesondes made at Alajuela, Costa Rica (10.0°N, 84.2°W) during two NASA airborne campaigns: the Tropical Convective Systems and Processes (TCSP) mission in July 2005 and the Tropical Composition, Clouds, and Climate Coupling Experiment (TC4), July-August 2007. In both campaigns we found an upper troposphere that was frequently supersaturated but no evidence that deep convection had reached the tropopause. The balloon sondes were complemented by campaigns of 4 times daily high-resolution radiosondes from mid-June through mid-August in both years. The radiosonde data reveal vertically propagating equatorial waves that caused a large increase in the variability of temperature in the tropical tropopause layer (TTL). These waves episodically produced cold point tropopauses (CPTs) above 18 km, yet in neither campaign was saturation observed above ∼380 K or 17 km. The averages of the water vapor minima below this level were 5.2 ppmv in TCSP and 4.8 ppmv in TC4, and the individual profile minima all lay at or above ∼360 K. The average minima in this 360-380 K layer provide a better estimate of the effective stratospheric entry value than the average mixing ratio at the CPT. We refer to this upper portion of the TTL as the tropopause saturation layer and consider it to be the locus of the final dehydration of nascent stratospheric air. As such, it is the local equivalent to the tape head of the water vapor tape recorder. © 2010 by the American Geophysical Union."
"55200758900;55807480400;55077923500;57219035052;15729641400;7405944157;55521311100;","Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China",2010,"10.5194/bg-7-711-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649177178&doi=10.5194%2fbg-7-711-2010&partnerID=40&md5=ff4cd8dbdb36e9aaf2e22c20bfe3b04b","Clouds can significantly affect carbon exchange process between forest ecosystems and the atmosphere by influencing the quantity and quality of solar radiation received by ecosystem's surface and other environmental factors. In this study, we analyzed the effects of cloudiness on net ecosystem exchange of carbon dioxide (NEE) in a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS) and a subtropical evergreen broad-leaved forest at Dinghushan (DHS), based on the flux data obtained during Juneg-August from 2003 to 2006. The results showed that the response of NEE of forest ecosystems to photosynthetically active radiation (PAR) differed under clear skies and cloudy skies. Compared with clear skies, the light-saturated maximum photosynthetic rate (Pec,max) at CBS under cloudy skies during mid-growing season (from June to August) increased by 34%, 25%, 4% and 11% in 2003, 2004, 2005 and 2006, respectively. In contrast, Pec,max of the forest ecosystem at DHS was higher under clear skies than under cloudy skies from 2004 to 2006. When the clearness index (k)t ranged between 0.4 and 0.6, the NEE reached its maximum at both CBS and DHS. However, the NEE decreased more dramatically at CBS than at DHS when k)t exceeded 0.6. The results indicate that cloudy sky conditions are beneficial to net carbon uptake in the temperate forest ecosystem and the subtropical forest ecosystem. Under clear skies, vapor pressure deficit (VPD) and air temperature increased due to strong light. These environmental conditions led to greater decrease in gross ecosystem photosynthesis (GEP) and greater increase in ecosystem respiration (R )e) at CBS than at DHS. As a result, clear sky conditions caused more reduction of NEE in the temperate forest ecosystem than in the subtropical forest ecosystem. The response of NEE of different forest ecosystems to the changes in cloudiness is an important factor that should be included in evaluating regional carbon budgets under climate change conditions. © 2010 Author(s)."
"55727166700;55649026100;57204225175;9241886700;10243890700;","Moisture availability influences the effect of ultraviolet-B radiation on leaf litter decomposition",2010,"10.1111/j.1365-2486.2009.01973.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74049145386&doi=10.1111%2fj.1365-2486.2009.01973.x&partnerID=40&md5=820cdfc22e04729191cfa3f796b72cfb","Altered surface ultraviolet-B (UV-B) radiation resulting from a combination of factors that include changes in stratospheric ozone concentrations, cloud cover, and aerosol conditions may affect litter decomposition and, thus, terrestrial nutrient cycling on a global scale. Although litter decomposition rates vary across biomes, patterns of decomposition suggest that UV-B radiation accelerates litter decay in xeric environments where precipitation is infrequent. However, under more frequent precipitation regimes where litter decay rates are characteristically high, the effect of UV-B radiation on litter decomposition has not been fully elucidated. To evaluate this association between moisture regime and UV-B exposure, a litter decomposition experiment was designed for aspen (Populus tremuloides) leaf litter, where conditions that influence both abiotic (photodegradation) and biotic (microbial) processes could be manipulated quantitatively. We found that experimentally increasing UV-B exposure (0, 7.4, and 11.2 kJm-2 day-1, respectively) did not consistently increase litter decomposition rates across simulated precipitation frequencies of 4, 12, and 24 days. Instead, a UV-B exposure of 11.2 kJm-2 day-1 resulted in a 13% decrease in decomposition rates under the 4-day precipitation frequency, but an increase of 80% under the 24-day frequency. Furthermore, the same UV-B dose increased litter decomposition rates under the 24-day precipitation frequency by 78% even in conditions where microbial activity was suppressed. Therefore, under more xeric conditions, greater exposure to UV-B radiation increased decomposition rates, presumably through photodegradation. In contrast, when decomposition was not moisture-limited, greater UV-B exposure slowed decomposition rates, most likely from the resulting inhibition of microbial activity. Ultimately, these experimental results highlight UV-B radiation as a potential driver of decomposition, as well as indicate that both the direction and magnitude of the UV-B effect is dependent on moisture availability, a factor that may change according to future patterns in global precipitation. © 2009 Blackwell Publishing Ltd."
"7202226478;7003780337;55488049400;","Estimating climatological planetary boundary layer heights from radiosonde observations: Comparison of methods and uncertainty analysis",2010,"10.1029/2009JD013680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956325798&doi=10.1029%2f2009JD013680&partnerID=40&md5=d7a8936beae10afc638ad3b19e36e140","Planetary boundary layer (PBL) processes control energy, water, and pollutant exchanges between the surface and free atmosphere. However, there is no observation-based global PBL climatology for evaluation of climate, weather, and air quality models or for characterizing PBL variability on large space and time scales. As groundwork for such a climatology, we compute PBL height by seven methods, using temperature, potential temperature, virtual potential temperature, relative humidity, specific humidity, and refractivity profiles from a 10 year, 505-station radiosonde data set. Six methods are directly compared; they generally yield PBL height estimates that differ by several hundred meters. Relative humidity and potential temperature gradient methods consistently give higher PBL heights, whereas the parcel (or mixing height) method yields significantly lower heights that show larger and more consistent diurnal and seasonal variations (with lower nighttime and wintertime PBLs). Seasonal and diurnal patterns are sometimes associated with local climatological phenomena, such as nighttime radiation inversions, the trade inversion, and tropical convection and associated cloudiness. Surface-based temperature inversions are a distinct type of PBL that is more common at night and in the morning than during midday and afternoon, in polar regions than in the tropics, and in winter than other seasons. PBL height estimates are sensitive to the vertical resolution of radiosonde data; standard sounding data yield higher PBL heights than high-resolution data. Several sources of both parametric and structural uncertainty in climatological PBL height values are estimated statistically; each can introduce uncertainties of a few 100 m. Copyright 2010 by the American Geophysical Union."
"8734615600;6504452801;16199172000;7005054220;55708686800;7404597424;","Lightning NOx emissions over the USA constrained by TES ozone observations and the GEOS-Chem model",2010,"10.5194/acp-10-107-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74049104027&doi=10.5194%2facp-10-107-2010&partnerID=40&md5=176325136408a38af2071099efe41c6e","Improved estimates of NOx from lightning sources are required to understand tropospheric NOx and ozone distributions, the oxidising capacity of the troposphere and corresponding feedbacks between chemistry and climate change. In this paper, we report new satellite ozone observations from the Tropospheric Emission Spectrometer (TES) instrument that can be used to test and constrain the parameterization of the lightning source of NOx in global models. Using the National Lightning Detection (NLDN) and the Long Range Lightning Detection Network (LRLDN) data as well as the HYPSLIT transport and dispersion model, we show that TES provides direct observations of ozone enhanced layers downwind of convective events over the USA in July 2006. We find that the GEOS-Chem global chemistry-transport model with a parameterization based on cloud top height, scaled regionally and monthly to OTD/LIS (Optical Transient Detector/Lightning Imaging Sensor) climatology, captures the ozone enhancements seen by TES. We show that the model's ability to reproduce the location of the enhancements is due to the fact that this model reproduces the pattern of the convective events occurrence on a daily basis during the summer of 2006 over the USA, even though it does not well represent the relative distribution of lightning intensities. However, this model with a value of 6 Tg N/yr for the lightning source (i.e.: with a mean production of 260 moles NO/Flash over the USA in summer) underestimates the intensities of the ozone enhancements seen by TES. By imposing a production of 520 moles NO/Flash for lightning occurring in midlatitudes, which better agrees with the values proposed by the most recent studies, we decrease the bias between TES and GEOS-Chem ozone over the USA in July 2006 by 40%. However, our conclusion on the strength of the lightning source of NOx is limited by the fact that the contribution from the stratosphere is underestimated in the GEOS-Chem simulations."
"8723504200;7401742385;","Atlanta's urban heat island under extreme heat conditions and potential mitigation strategies",2010,"10.1007/s11069-009-9406-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649273259&doi=10.1007%2fs11069-009-9406-z&partnerID=40&md5=f44210d4a8f42edcf96edfbc34ab3ec0","The urban heat island (UHI), together with summertime heat waves, foster's biophysical hazards such as heat stress, air pollution, and associated public health problems. Mitigation strategies such as increased vegetative cover and higher albedo surface materials have been proposed. Atlanta, Georgia, is often affected by extreme heat, and has recently been investigated to better understand its heat island and related weather modifications. The objectives of this research were to (1) characterize temporal variations in the magnitude of UHI around Metro Atlanta area, (2) identify climatological attributes of the UHI under extremely high temperature conditions during Atlanta's summer (June, July, and August) period, and (3) conduct theoretical numerical simulations to quantify the first-order effects of proposed mitigation strategies. Over the period 1984-2007, the climatological mean UHI magnitude for Atlanta-Athens and Athens-Monticello was 1.31 and 1.71°C, respectively. There were statistically significant minimum temperature trends of 0.70°C per decade at Athens and -1.79°C per decade at Monticello while Atlanta's minimum temperature remained unchanged. The largest (smallest) UHI magnitudes were in spring (summer) and may be coupled to cloud-radiative cycles. Heat waves in Atlanta occurred during 50% of the years spanning 1984-2007 and were exclusively summertime phenomena. The mean number of heat wave events in Atlanta during a given heat wave year was 1.83. On average, Atlanta heat waves lasted 14.18 days, although there was quite a bit of variability (standard deviation of 9.89). The mean maximum temperature during Atlanta's heat waves was 35.85°C. The Atlanta-Athens UHI was not statistically larger during a heat wave although the Atlanta-Monticello UHI was. Model simulations captured daytime and nocturnal UHIs under heat wave conditions. Sensitivity results suggested that a 100% increase in Atlanta's surface vegetation or a tripling of its albedo effectively reduced UHI surface temperature. However, from a mitigation and technological standpoint, there is low feasibility of tripling albedo in the foreseeable future. Increased vegetation seems to be a more likely choice for mitigating surface temperature. © Springer Science+Business Media B.V. 2009."
"36668426500;36669047600;","Homeostasis and perpetual change",2010,"10.2495/ARC100031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78549267215&doi=10.2495%2fARC100031&partnerID=40&md5=09eb4049d6abcdd88333c2f7fa60302e","Historically, we have built to overpower nature with minimal concern for environmental impact. The Solar Energy Efficient Dwelling: SEEDpod prototype is intended to respond to and advantageously interact with the forces of nature and the unique characteristics of each project site. These include the sun-utilized to create electricity, heat water/air and provide day lighting; water-harvested for domestic needs and irrigation of edible plants and landscaping; and air-used for ventilation and maintaining a healthy environment. The SEEDpod provides a tool for engagement with specific microclimates and the natural environment of its location. The arid Sonoran Desert, with limited vegetation, water resources and cloud cover has a climate characterized by a year round average diurnal temperature swing of 26°F. This variable condition enables the SEEDpod to employ an environmental control strategy in which the building envelope and surrounding vegetation form a ""selective filter"" that dynamically interacts with the surroundings. Establishing a homeostatic relationship becomes the premise upon which we can begin to improve the design quality, efficiency and environmental responsiveness of residential construction. Balance is achieved in this energy efficient solar prototype by dynamically interacting with energy inputs and outputs in service of climatic stability. Air exchange, humidity and thermal control, interior and exterior lighting conditions and natural resource management are integral components that are continuously engaged in order to achieve a healthy, energy-efficient, and sustainably-built environment. © 2010 WIT Press."
"8839231600;56241347800;8839231800;57219323345;","Diurnal and spatial variabilities of monsoonal CG lightning and precipitation and their association with the synoptic weather conditions over South Korea",2010,"10.1007/s00704-009-0235-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84755161527&doi=10.1007%2fs00704-009-0235-5&partnerID=40&md5=1d516116d3bdc1d77b0d35c426f9bb20","The spatial and temporal variations in cloud-to-ground (CG) lightning and precipitation during the summer monsoon months in Korea have been analyzed in relation to the regional synoptic weather conditions. The lightning data used in this study were collected from a lightning detection network installed by the Korean Meteorological Administration, while the precipitation data were collected from 386 Automatic Weather Stations spread over the entire Korean Peninsula during 2000 to 2001. A distinctive morning peak of precipitation is observed over the midwest region of Korea. Along the east coast, little precipitation and CG flash counts are found. Despite the strong afternoon peaks of convective rainfall due to the high elevation over the southern inland region, the south coast shows nocturnal or early morning peaks, which represents a common oceanic pattern of flash counts. In 2000, the nighttime peak for lightning counts dominates over the southern area, while the afternoon peak was strong in the midland during the summer, mainly due to the northward transportation of moisture to the Korean Peninsula. Conversely, the strong afternoon peak for the southern region was confronted with early morning peaks in the midwestern region during 2001. The eastward transport of moisture has been analyzed and was considered to be dominant in 2001. The study of several warm and cold type fronts in 2000 and 2001 indicate that the warm type fronts in 2000 were associated with very little lightning, while the cold type fronts appeared to be responsible for the occurrence of abundant lightning in 2001, thereby, indicating that the warm and cold type fronts were representative of the local lightning distribution in the respective years. © 2009 The Author(s)."
"7004944088;55684491100;36106033000;35183991500;56187256200;35998927000;7006211890;57201124395;55730602600;7005941217;36106370400;36105949100;26024789300;16480316200;13408545500;36106049900;36106191000;36105911100;35490380800;36243762400;10144486700;24458137900;6602576218;7202488998;7005174340;7801315779;36106039100;7202556112;6506126751;22981551200;36106329000;55895104800;","In-situ observations of young contrails - Overview and selected results from the CONCERT campaign",2010,"10.5194/acp-10-9039-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957703519&doi=10.5194%2facp-10-9039-2010&partnerID=40&md5=4b4810ad5a92246fbd001525bd707b0f","Lineshaped contrails were detected with the research aircraft Falcon during the CONCERT -CONtrail and Cirrus ExpeRimenT -campaign in October/November 2008. The Falcon was equipped with a set of instruments to measure the particle size distribution, shape, extinction and chemical composition as well as trace gas mixing ratios of sulfur dioxide (SO2), reactive nitrogen and halogen species (NO, NOy, HNO3, HONO, HCl), ozone (O3) and carbon monoxide (CO). During 12 mission flights over Europe, numerous contrails, cirrus clouds and a volcanic aerosol layer were probed at altitudes between 8.5 and 11.6 km and at temperatures above 213 K. 22 contrails from 11 different aircraft were observed near and below ice saturation. The observed NO mixing ratios, ice crystal and soot number densities are compared to a process based contrail model. On 19 November 2008 the contrail from a CRJ-2 aircraft was penetrated in 10.1 km altitude at a temperature of 221 K. The contrail had mean ice crystal number densities of 125 cm-3 with effective radii reff of 2.6 μm. The presence of particles with r &gt; 50 μm in the less than 2 min old contrail suggests that natural cirrus crystals were entrained in the contrail. Mean HONO/NO (HONO/NOy) ratios of 0.037 (0.024) and the fuel sulfur conversion efficiency to H2SO4 (εs) of 2.9 % observed in the CRJ-2 contrail are in the range of previous measurements in the gaseous aircraft exhaust. On 31 October 2010 aviation NO emissions could have contributed by more than 40% to the regional scale NO levels in the mid-latitude lowest stratosphere. The CONCERT observations help to better quantify the climate impact from contrails and will be used to investigate the chemical processing of trace gases on contrails. © 2010 Author(s)."
"35519900900;57203176082;7003529604;7102692123;35461763400;","Molecular distributions of dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in biomass burning aerosols: Implications for photochemical production and degradation in smoke layers",2010,"10.5194/acp-10-2209-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860389983&doi=10.5194%2facp-10-2209-2010&partnerID=40&md5=739cc59a6e3bbc78eff89c1fde5376ac","Aerosols in the size class &lt;2.5 μm (6 daytime and 9 nighttime samples) were collected at a pasture site in Rondônia, Brazil, during the intensive biomass burning period of 16-26 September 2002 as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC). Homologous series of dicarboxylic acids (C2-C11) and related compounds (ketocarboxylic acids and α-dicarbonyls) were identified using gas chromatography (GC) and GC/mass spectrometry (GC/MS). Among the species detected, oxalic acid was found to be the most abundant, followed by succinic, malonic and glyoxylic acids. Average concentrations of total dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in the aerosol samples were 2180, 167 and 56 ngm ?3, respectively. These are 2-8, 3-11 and 2-16 times higher, respectively, than those reported in urban aerosols, such as in 14 Chinese megacities. Higher ratios of dicarboxylic acids and related compounds to biomass burning tracers (levoglucosan and K+) were found in the daytime than in the nighttime, suggesting the importance of photochemical production. On the other hand, higher ratios of oxalic acid to other dicarboxylic acids and related compounds normalized to biomass burning tracers (levoglucosan and K +) in the daytime provide evidence for the possible degradation of dicarboxylic acids (≥C3) in this smoke-polluted environment. Assuming that these and related compounds are photo-chemically oxidized to oxalic acid in the daytime, and given their linear relationship, they could account for, on av-erage, 77% of the formation of oxalic acid. The remaining portion of oxalic acid may have been directly emitted from biomass burning as suggested by a good correlation with the biomass burning tracers (K+, CO and ECa) and organic carbon (OC). However, photochemical production from other precursors could not be excluded. © 2010 Author(s)."
"8152536600;16206263100;6603689569;8359591200;6506458269;6603788056;","Effect of local and regional sources on the isotopic composition of nitrous oxide in the tropical free troposphere and tropopause layer",2010,"10.1029/2009JD013117","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956039278&doi=10.1029%2f2009JD013117&partnerID=40&md5=39a798145b0e7a2a77d7bc87321b40ad","Measurements and models of the spatiotemporal variability of surface N <inf>2</inf>O mixing ratios and isotopic compositions are increasingly used to constrain the global N<inf>2</inf>O budget. However, large variability observed on the small spatial scales of soil chambers and shipboard sampling, which appears to be very sensitive to local environmental conditions, has made extrapolation to the global scale difficult. In this study, we present measurements of the isotopic composition of N<inf>2</inf>O (δ 15Nbulk, δ15N, δ15N, and δ18O) from whole-air samples collected at altitudes of 0.5 to 19km by the NASA DC-8 and WB-57 aircraft during the Costa Rica-Aura Validation Experiment (CR-AVE) and the Tropical Composition, Cloud and Climate Coupling Experiment (TC4) campaigns in January-February 2006 and July-August 2007, respectively. The vertical profiles of isotopic composition showed predictable, repeating patterns consistent with the influence of a surface source at lower altitudes and the influence of stratospheric photochemistry in the lower stratosphere. Their correlations with marine tracers at lower altitudes are consistent with a predominantly oceanic source, although a soil source cannot be ruled out. Measurements in a combustion plume revealed a strong depletion in 15N at the central nitrogen atom (i.e., low δ15N values), providing new information on N<inf>2</inf>O isotopic compositions from combustion. This new data set demonstrates that a coherent picture of the isotopic composition of tropospheric N<inf>2</inf>O is possible at currently attainable precisions and that its variations from 0.5 km to the lower stratosphere are a useful tool in investigating the sources and distributions of this important greenhouse gas. Copyright 2010 by the American Geophysical Union."
"7003620878;35549146800;13403957300;7006477233;6603712566;7003889149;6602436848;55207447000;","Climatology of aerosol optical depth in North Central Oklahoma: 1992-2008",2010,"10.1029/2009JD012197","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951076389&doi=10.1029%2f2009JD012197&partnerID=40&md5=3b0a9b86594ad7761138f434d6871afc","Aerosol optical depth (AOD) has been measured at the Atmospheric Radiation Measurement Program central facility near Lamont, Oklahoma, since the fall of 1992. Most of the data presented are from the multifilter rotating shadowband radiometer, a narrow-band, interference-filter Sun radiometer with five aerosol bands in the visible and near infrared; however, AOD measurements have been made simultaneously and routinely at the site by as many as three different types of instruments, including two pointing Sun radiometers. Scatterplots indicate high correlations and small biases consistent with earlier comparisons. The early part of this 16 year record had a disturbed stratosphere with residual Mt. Pinatubo aerosols, followed by the cleanest stratosphere in decades. As such, the last 13 years of the record reflect changes that have occurred predominantly in the troposphere. The field calibration technique is briefly described and compared to Langley calibrations from Mauna Loa Observatory. A modified cloudscreening technique is introduced that increases the number of daily averaged AODs retrieved annually to about 250 days compared with 175 days when a more conservative method was employed in earlier studies. AODs are calculated when the air mass is less than six; that is, when the Suns elevation is greater than 9.25°. The more inclusive cloud screen and the use of most of the daylight hours yield a data set that can be used to more faithfully represent the true aerosol climate for this site. The diurnal aerosol cycle is examined month-by-month to assess the effects of an aerosol climatology on the basis of infrequent sampling such as that from satellites. Copyright 2010 by the American Geophysical Union."
"55613035800;7201844203;7403225300;","Parameterization of topographic effect on surface solar radiation",2010,"10.1029/2009JD012305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76249099448&doi=10.1029%2f2009JD012305&partnerID=40&md5=2648098f8cb5a02d1c7f7f3e9bf7a79d","Topographic impact on the surface solar (shortwave (SW)) radiation was investigated using a 40 m high-resolution digital topographic data model and a radiative transfer model. With applications to the complex terrain of Taiwan, we found that the spatial variation of the surface SW radiation has a strong diurnal cycle. The standard deviation of the SW radiation, σ<inf>f</inf>, over Taiwan is nearly constant for a given solar zenith angle (SZA). The maximum σ<inf>f</inf> occurs at SZA ∼55°, corresponding to midmorning (early morning) and midafternoon (late afternoon) in winter (summer). For a spatial resolution of 40 m, the σ<inf>f</inf> over Taiwan attains a maximum value of 300 W m-2, which is ∼50% of the domain mean SW radiation. The topographic impact on the spatial variation of SW radiation increases with decreasing grid box size, Δx. In mesoscale land and atmospheric models, Δx is small, and the topographic impact is strong. Over Taiwan, the standard deviation of the difference between the daily mean SW radiation computed with a spatial resolution of 40 m and that computed with degraded spatial resolution reaches 25 W m-2 for Δx = 1 km and 8 W m-2 for Δx = 10 km, indicating the importance of topographic impact on the surface SW radiation in mesoscale land and atmospheric models. We developed a parameterization of the topographic impact on the surface SW radiation that scales the SW radiation computed for a flat surface without shading by surrounding terrains. The scaling is separately applied to the direct and diffuse radiation. It is applicable to all clear, aerosol-laden, and cloudy conditions and to all spatial resolutions with Δx > 40 m. Copyright 2010 by the American Geophysical Union."
"12142232800;35546736600;7004305415;55940433600;","Evaluating the utility of the ANSA blended snow cover product in the mountains of eastern Turkey",2010,"10.1080/01431161.2010.483484","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955134968&doi=10.1080%2f01431161.2010.483484&partnerID=40&md5=fea7babf24eb44d2c7eef64da6aade7b","Snow-covered area depletion curves represent a key input for snow run-off melting models, e.g. the snowmelt run-off model (SRM). SRM is a degree-day-based model fordaily run-off simulations and forecasts in mountainous are asin which snow meltis the major run-off contributor. Satellite images and aerial photographs are valuable sources for retrieving snow-covered area. The accuracy of snow cover mapping studies in the optical wavebands is highly dependent upon the algorithm's ability to detect clouds. On very cloudy days it is not possible to map snow cover using only optical sensors; however, microwave sensors can be used to obtain snow information on cloudy days. The snow-water equivalent (SWE) of a dry snowpack can be estimated with passive-microwave sensors such as Special Sensor Microwave/ Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSRE). Development of snow cover products based on multi-sensor data sources is needed for continuous regional and global snow cover mapping for climate, hydro- logical and weather applications. A preliminary blended snow product has been developed jointly by the US Air Force Weather Agency (AFWA) and NASA/ Goddard Space Flight Center. The AFWA-NASA Snow Algorithm, or ANSA, blended snow product is an all-weather product that utilizes both visible and near- infrared (Moderate Resolution Imaging Spectroradiometer, MODIS) and micro- wave (Advanced Microwave Scanning Radiometer-Earth, AMSR-E) data. In this study the validation of the ANSA blended snow cover product, having 25 and 5 km resolution, respectively, was performed for the eastern part of Turkey for five months in the winter of 2007-2008. This is the first time that the ANSA snow cover product has been evaluated in a mountainous area, where the elevation ranges between 850 and 3000 m. Daily snow data collected at 36 meteorological stations were used in the analysis.Use of the ANSA snow products was found to improve the mapping of snow cover extent relative to using either MODIS or AMSR-E products alone, for the 2007-2008 winter in the eastern part of Turkey.91% agreement was obtained between the ANSA snow maps and in situ observations for February. The lowest agreement percentage of 68% was obtained for March due to shallow snow depth and wetnessof the snow. Change in the spatial resolution of the ANSA product from 25 km to 5 km increased the agreement percentages from 68% to 74% for March. ANSA prototype maps of 5 km resolution from February and March 2008 were used to derive snow cover depletion curves for the upper Euphrates basin located in the eastern part of Turkey. The results were compared with the curves obtained from MODIS daily snow products, and found to provide an improvement over using MODIS daily maps alone. This is because the ability of the microwave sensors to map snow through clouds provides snow cover information on cloudy days when the MODIS maps cannot, though at a coarser spatial resolution than can be obtained using MODIS. © 2010 Taylor & Francis."
"33167668500;8323441600;15922138800;","Species dynamics in a montane cloud forest: Identifying factors involved in changes in tree diversity and functional characteristics",2009,"10.1016/j.foreco.2009.07.055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71649116214&doi=10.1016%2fj.foreco.2009.07.055&partnerID=40&md5=f0ec38b784b8bdb4596d543ece0174f4","Tropical montane cloud forests constitute a rare and fragile ecosystem, which is threatened in many of the areas in which it is found due to the pressure of human-originated disturbances. Cloud forests have been identified as a forest type with high levels of species endemism and biodiversity. The aim of this study, which focuses on a patch of cloud forest located in the Piura region of the Peruvian Andes, is to assess the changes in species composition and to identify the factors involved in the loss of biodiversity using data from a single inventory. Random sampling plots were established throughout the forest area. An index of the difference in species richness between recruitment and older trees (Tree Diversity Change index, TDC index) was calculated for each plot. A Tree Diversity Change Index (TDC) and an index of species replacement based on the second order properties of the diameter distribution (RE) were defined to assess changes in species richness and to characterize the change in the functional groups of tree species within the plot. The factors involved in these processes were also identified by means of a Universal Kriging model. The negative correlation between the TDC and the distance to the nearest track indicates that species richness is decreasing close to these tracks and that it is only maintained in the inner areas. The negative correlation of the RE index with altitude and deeper zones indicates that dynamic replacement of humid-condition species by dry-condition species is occurring at lower elevations. A loss in diversity along with a change towards species adapted to dryer conditions was observed throughout the forest. Zones at lower altitudes, on spurs or at the edges of the forest are more prone to these processes. This suggests that a change in the functions of the ecosystem has been taking place and that a minimum extension of cloud forest is required to maintain the ecological processes necessary for the continued existence of the cloud forest. © 2009 Elsevier B.V. All rights reserved."
"7005706662;7004160106;7402390191;","Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions - Part 2: The Americas",2009,"10.5194/angeo-27-4009-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749095465&doi=10.5194%2fangeo-27-4009-2009&partnerID=40&md5=8e3e8fa9fc01f25c829a9252de93b00e","Aerosol perturbations over selected land regions are imposed in Version-4 of the Goddard Earth Observing System (GEOS-4) general circulation model (GCM) to assess the influence of increasing aerosol concentrations on regional circulation patterns and precipitation in four selected regions: India, Africa, and North and South America. Part 1 of this paper addresses the responses to aerosol perturbations in India and Africa. This paper presents the same for aerosol perturbations over the Americas. GEOS-4 is forced with prescribed aerosols based on climatological data, which interact with clouds using a prognostic scheme for cloud microphysics including aerosol nucleation of water and ice cloud hydrometeors. In clear-sky conditions the aerosols interact with radiation. Thus the model includes comprehensive physics describing the aerosol direct and indirect effects on climate (hereafter ADE and AIE respectively). Each simulation is started from analyzed initial conditions for 1 May and was integrated through June-July-August of each of the six years: 1982 - 1987 to provide a 6-ensemble set. Results are presented for the difference between simulations with double the climatological aerosol concentration and one-half the climatological aerosol concentration for three experiments: two where the ADE and AIE are applied separately and one in which both the ADE and AIE are applied. The ADE and AIE both yield reductions in net radiation at the top of the atmosphere and surface while the direct absorption of shortwave radiation contributes a net radiative heating in the atmosphere. A large net heating of the atmosphere is also apparent over the subtropical North Atlantic Ocean that is attributable to the large aerosol perturbation imposed over Africa. This atmospheric warming and the depression of the surface pressure over North America contribute to a northward shift of the inter-Tropical Convergence Zone over northern South America, an increase in precipitation over Central America and the Caribbean, and an enhancement of convergence in the North American monsoon region."
"6701689811;6508063123;25926681100;35577097300;24605747000;","Vertical distribution of aerosols over the east coast of India inferred from airborne LIDAR measurements",2009,"10.5194/angeo-27-4157-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749149051&doi=10.5194%2fangeo-27-4157-2009&partnerID=40&md5=a9324dca39955328f94689be7f74bce9","The information on altitude distribution of aerosols in the atmosphere is essential in assessing the impact of aerosol warming on thermal structure and stability of the atmosphere. In addition, aerosol altitude distribution is needed to address complex problems such as the radiative interaction of aerosols in the presence of clouds. With this objective, an extensive, multi-institutional and multi-platform field experiment (ICARB-Integrated Campaign for Aerosols, gases and Radiation Budget) was carried out under the Geosphere Biosphere Programme of the Indian Space Research Organization (ISRO-GBP) over continental India and adjoining oceans during March to May 2006. Here, we present airborne LIDAR measurements carried out over the east Coast of the India during the ICARB field campaign. An increase in aerosol extinction (scattering + absorption) was observed from the surface upwards with a maximum around 2 to 4 km. Aerosol extinction at higher atmospheric layers (gt;2 km) was two to three times larger compared to that of the surface. A large fraction (75-85%) of aerosol column optical depth was contributed by aerosols located above 1 km. The aerosol layer heights (defined in this paper as the height at which the gradient in extinction coefficient changes sign) showed a gradual decrease with an increase in the offshore distance. A large fraction (60-75%) of aerosol was found located above clouds indicating enhanced aerosol absorption above clouds. Our study implies that a detailed statistical evaluation of the temporal frequency and spatial extent of elevated aerosol layers is necessary to assess their significance to the climate. This is feasible using data from space-borne lidars such as CALIPSO, which fly in formation with other satellites like MODIS AQUA and MISR, as part of the A-Train constellation."
"7401559815;7409322518;7004160106;7402390191;","A GCM study of the response of the atmospheric water cycle of West Africa and the Atlantic to Saharan dust radiative forcing",2009,"10.5194/angeo-27-4023-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749123060&doi=10.5194%2fangeo-27-4023-2009&partnerID=40&md5=b7b2445df11204113437cb5860d0d54e","The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence of an ""elevated heat pump"" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feedback triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Eastern Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while longwave has the opposite response. The elevated dust layer warms the air over West Africa and the eastern Atlantic. As the warm air rises, it spawns a large-scale onshore flow carrying the moist air from the eastern Atlantic and the Gulf of Guinea. The onshore flow in turn enhances the deep convection over West Africa land, and the eastern Atlantic. The condensation heating associated with the ensuing deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in a northward shift of the West Africa precipitation over land, increased low-level westerly flow over West Africa at the southern edge of the dust layer, and a near surface westerly jet underneath the dust layer over the Sahara. The dust radiative forcing also leads to significant changes in surface energy fluxes, resulting in cooling of the West African land and the eastern Atlantic, and warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at 0.95 or higher."
"12803465300;7403931916;7201826462;7005729142;7403282069;","Parameterization of shortwave and longwave radiative properties of ice clouds for use in climate models",2009,"10.1175/2009JCLI2844.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649280122&doi=10.1175%2f2009JCLI2844.1&partnerID=40&md5=ee7787baa989edc24737d32c39d3a301","Climate modeling and prediction require that the parameterization of the radiative effects of ice clouds be as accurate as possible. The radiative properties of ice clouds are highly sensitive to the single-scattering properties of ice particles and ice cloud microphysical properties such as particle habits and size distributions. In this study, parameterizations for shortwave (SW) and longwave (LW) radiative properties of ice clouds are developed for three existing schemes using ice cloud microphysical properties obtained from five field campaigns and broadband-averaged single-scattering properties of nonspherical ice particles as functions of the effective particle size De (defined as 1.5 times the ratio of total volume to total projected area), which include hexagonal solid columns and hollow columns, hexagonal plates, six-branch bullet rosettes, aggregates, and droxtals. A combination of the discrete ordinates radiative transfer model and a line-by-line model is used to sim- ulate ice cloud radiative forcing (CRF) at both the surface and the top of the atmosphere (TOA) for the three redeveloped parameterization schemes. The differences in CRF for different parameterization schemes are in the range of -5 to 5 Wm-2. In general, the large differences in SW and total CRF occur for thick ice clouds, whereas the large differences in LW CRF occur for ice clouds with small ice particles (De less than 20 μm). The redeveloped parameterization schemes are then applied to the radiative transfer models used for climate models. The ice cloud optical and microphysical properties from the Moderate Resolution Imaging Spec- troradiometer (MODIS) cloud product over a granule and the collocated atmospheric profiles from the Atmospheric Infrared Sounder (AIRS) product are input into these radiative transfer models to compare the differences in CRF between the redeveloped and existing parameterization schemes. Although differences between these schemes are small in the LW CRF, the differences in the SW CRF are quite large. © 2009 American Meteorological Society."
"6602096831;7006728825;35552588700;7005858663;35337852200;","Whitening the clouds",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-73949110721&partnerID=40&md5=a816b614a7c101c9fb45ce9c3f4ddb15","Research scientists Alan Gadian at the National Center for Atmospheric Science INCAS), at the University of Leeds, suggests how geo-engineering the clouds to become whiter and reflect more sunlight back into space before it reaches the Earth can prevent global warming. This scheme will provide extra time to the scientists to implement carbon dioxide reduction methods. A large international field project, Arica, Chile, used over 200 scientists, five aircraft, and two ships in November 2008 to measure low-level stratocumulus clouds in situ using remote sensing. The water droplets in clouds reflect sunlight back into space. The numbers of these droplets in clouds depend largely on the number of Cloud Condensation Nuclei (CCN). Clouds with smaller droplets tend to be whiter and more reflective. Initial results from climate models show that a modest increase of CCN in marine stratocumulus clouds could produce the desired cooling."
"23571129400;8670472000;23571234400;6506579205;","The surface radiation budget over north america: Gridded data assessment and evaluation of regional climate models",2009,"10.1002/joc.1860","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71449122865&doi=10.1002%2fjoc.1860&partnerID=40&md5=31079a964dc7f65b2cfea8e180395643","While surface station observations of downwelling radiation offer accuracy at high temporal resolution, they do not easily allow an evaluation of model surface radiation budgets (SRB) over a wide geographical area. We evaluate three gridded SRB data sets against detailed observations from six surface radiation sites from the US surface radiation (SURFRAD) network. We subsequently use the most accurate surrogate observational data set for evaluation of model- simulated SRB. The data sets assessed are: ERA40 - reanalysis of European Centre for Medium-Range Weather Forecasts (ECMWF), North American Regional Reanalysis (NARR) - regional reanalysis of National Centres for Environmental Prediction (NCEP) and the surface radiative budget (SRB) from the International Satellite Cloud Climatology Project (ISCCP). Due to varying constraints with respect to temporal coverage of each data set, the evaluation period used in this study is 1996-2001, inclusive. The ERA40 downwelling longwave radiation (DLR) appears the most accurate surrogate observation, while both ERA40 and ISCCP show accurate results when the incoming shortwave radiation (ISR) is considered across the annual cycle. Winter DLR is less accurate in ISCCP with a positive bias and lack of very low (&lt;200 Wm&amp;#x2212;2) flux values. The NARR SRB shows a large positive bias in the ISR throughout the annual cycle, linked to a significant underestimate of cloud cover. The ERA40 data are subsequently used to evaluate the simulated SRB in three regional climate models across North America. With respect to solar radiation, cloud cover biases are seen to be crucial, while for longwave fluxes both cloud fraction and in-cloud water content are important to simulate correctly. Inclusion of trace gases beyond H2O, CO2 and O3 appears necessary for an accurate calculation of clear-sky longwave radiation. Error compensation frequently occurs between the various components contributing to a model total-sky SRB. This is important to consider when trying to identify the underlying causes of errors in the simulated total SRB. © 2009 Royal Meteorological Society."
"35461255500;6602506226;56127300900;7004469744;55942083800;7005069415;7005254485;55803534000;56472932500;7005601996;7102496779;7006595513;7006708207;","Introduction: European Integrated Project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI)-integrating aerosol research from nano to global scales",2009,"10.5194/acp-9-2825-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880742133&doi=10.5194%2facp-9-2825-2009&partnerID=40&md5=7e1ca95f0f188fe45b4c82bed94f8e34","The European Aerosol Cloud Climate and Air Quality Interactions project EUCAARI is an EU Research Framework 6 integrated project focusing on understanding the interactions of climate and air pollution. EUCAARI works in an integrative and multidisciplinary way from nano-to global scale. EUCAARI brings together several leading European research groups, state-of-the-art infrastructure and some key scientists from third countries to investigate the role of aerosol on climate and air quality. Altogether 48 partners from 25 countries are participating in EUCAARI. During the first 16 months EUCAARI has built operational systems, e.g. established pan-European measurement network for Lagrangian studies and four stations in developing countries. Also an improved understanding of nanoscale processes (like nucleation) has been implemented in global models. Here we present the research methods, organisation, operations and first results of EUCAARI. © 2011 Author(s)."
"8728433200;57203053317;7501381728;57208121852;6701843835;7003931528;16639418500;16444232500;","Aerosol size-dependent below-cloud scavenging by rain and snow in the ECHAM5-HAM",2009,"10.5194/acp-9-4653-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149121937&doi=10.5194%2facp-9-4653-2009&partnerID=40&md5=3b21ad4b916779d3d2c90949fe42fdc4","Wet deposition processes are highly efficient in the removal of aerosols from the atmosphere, and thus strongly influence global aerosol concentrations, and clouds, and their respective radiative forcings. In this study, physically detailed size-dependent below-cloud scavenging parameterizations for rain and snow are implemented in the ECHAM5-HAM global aerosol-climate model. Previously, below-cloud scavenging by rain in the ECHAM5-HAM was simply a function of the aerosol mode, and then scaled by the rainfall rate. The below-cloud scavenging by snow was a function of the snowfall rate alone. The global mean aerosol optical depth, and sea salt burden are sensitive to the below-cloud scavenging coefficients, with reductions near to 15% when the more vigorous size-dependent below-cloud scavenging by rain and snow is implemented. The inclusion of a prognostic rain scheme significantly reduces the fractional importance of below-cloud scavenging since there is higher evaporation in the lower troposphere, increasing the global mean sea salt burden by almost 15%. Thermophoretic effects are shown to produce increases in the global and annual mean number removal of Aitken size particles of near to 10%, but very small increases (near 1%) in the global mean below-cloud mass scavenging of carbonaceous and sulfate aerosols. Changes in the assumptions about the below-cloud scavenging by rain of particles with radius smaller than 10 nm do not cause any significant changes to the global and annual mean aerosol mass or number burdens, despite a change in the below-cloud number removal rate for nucleation mode particles by near to five-fold. Annual and zonal mean nucleation mode number concentrations are enhanced by up to 30% in the lower troposphere with the more vigourous size-dependent below-cloud scavenging. Closer agreement with different observations is found when the more physically detailed below-cloud scavenging parameterization is employed in the ECHAM5-HAM model. © 2009 Author(s)."
"7003900383;6507189548;6504311455;8892176600;8909177900;6603604042;7007182077;24480463300;7003875148;7003740015;","Finnish contribution to the Arctic summer cloud ocean study (ASCOS) expedition, Arctic ocean 2008",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955248683&partnerID=40&md5=69b2f38828738bb0fe64e2907007daac","The Arctic Summer Cloud Ocean Study, ASCOS, was a six-week expedition in August-September 2008 north of the 87th latitude onboard the Swedish icebreaker Oden. The expedition was a contribution to the International Polar Year 2007/2008. ASCOS studies some of the controlling factors of the low-level cloud system, especially the formation of cloud condensation and ice nuclei, over the Arctic pack ice. This will improve the accuracy of the climate models in the Arctic area where the climate is expected to change faster than in any other part of the world. A distinct feature of ASCOS is its necessarily interdisciplinary nature, which includes physical oceanography, marine and sea ice biogeochemistry, surface microlayer chemistry, aerosol, gas-phase and cloud chemistry and physics, and meteorology. The expedition sailed from Longyearbyen, Svalbard, in the beginning of August. After a week's cruise the icebreaker was moored to a several square kilometres wide ice floe north of the 87th latitude. The ship was drifting with the ice floe for a month before the return voyage to Svalbard in the early September. The Finnish contribution to the experimental part of ASCOS consisted of researchers and instruments from the Finnish Meteorological Institute (FMI) and the University of Kuopio (UKu). The FMI's measurement programme consisted of meteorology, ozone and radioactivity soundings, a UV radiation sensor, a visibility meter, a ceilometer, filter sampling for radionuclide, heavy metal and PAH analyses, canister sampling for VOC analyses, fog droplet and aerosol particle size distribution measurements, an ozone monitor, and a sea water bubble camera. The UKu measurement programme consisted of ultrafine particles organic fraction measurements."
"7101689290;7006661408;25927742100;7004114067;","The stable isotope amount effect: New insights from NEXRAD echo tops, Luquillo Mountains, Puerto Rico",2009,"10.1029/2008WR007515","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72249114288&doi=10.1029%2f2008WR007515&partnerID=40&md5=f8fe765958ead5f8440ebd3009c10455","The stable isotope amount effect has often been invoked to explain patterns of isotopic composition of rainfall in the tropics. This paper describes a new approach, correlating the isotopic composition of precipitation with cloud height and atmospheric temperature using NEXRAD radar echo tops, which are a measure of the maximum altitude of rainfall within the clouds. The seasonal differences in echo top altitudes and their corresponding temperatures are correlated with the isotopic composition of rainfall. These results offer another factor to consider in interpretation of the seasonal variation in isotopic composition of tropical rainfall, which has previously been linked to amount or rainout effects and not to temperature effects. Rain and cloud water isotope collectors in the Luquillo Mountains in northeastern Puerto Rico were sampled monthly for three years and precipitation was analyzed for δ18O and δ2H. Precipitation enriched in , 18O and 2H occurred during the winter dry season (approximately December-May) and was associated with a weather pattern of trade wind showers and frontal systems. During the summer rainy season (approximately June-November), precipitation was depleted in 18O and 2H and originated in low pressure systems and convection associated with waves embedded in the prevailing easterly airflow. Rain substantially depleted in 18O and 2H compared to the aforementioned weather patterns occurred during large low pressure systems. Weather analysis showed that 29% of rain input to the Luquillo Mountains was trade wind orographic rainfall, and 30% of rainfall could be attributed to easterly waves and low pressure systems. Isotopic signatures associated with these major climate patterns can be used to determine their influence on streamflow and groundwater recharge and to monitor possible effects of climate change on regional water resources."
"7005601387;26431868500;8686542400;7004912890;7005063377;","On the correlation between cosmic ray intensity and cloud cover",2009,"10.1016/j.jastp.2009.06.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71749103629&doi=10.1016%2fj.jastp.2009.06.012&partnerID=40&md5=5a53910dcbde6d2e13b76ce0b8b453c3","Various aspects of the connection between cloud cover (CC) and cosmic rays (CR) are analyzed. Most features of this connection viz. an altitude dependence of the absolute values of CC and CR intensity, no evidence for the correlation between the ionization of the atmosphere and cloudiness, the absence of correlations in short-term low cloud cover (LCC) and CR variations indicate that there is no direct causal connection between LCC and CR in spite of the evident long-term correlation between them. However, these arguments are indirect. If only some part of the LCC is connected and varies with CR, then its value, obtained from the joint analysis of their 11-year variations and averaged over the Globe, should be most likely less than 20%. The most significant argument against causal connection of CR and LCC is the anticorrelation between LCC and the medium cloud cover (MCC). The scenario of the parallel influence of the solar activity on the Global temperature and CC from one side and CR from the other side, which can lead to the observed correlations, is discussed and advocated. © 2009 Elsevier Ltd."
"35325348800;6507605950;13006903300;8955317200;6603628691;","Assimilation of AIRS radiances Affected by Mid- to Low-Level Clouds",2009,"10.1175/2009MWR3020.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949129901&doi=10.1175%2f2009MWR3020.1&partnerID=40&md5=cacf304c53e1454b7acae2a1dfe7db40","An approach to make use of Atmospheric Infrared Sounder (AIRS) cloud-affected infrared radiances has been developed at Météo-France in the context of the global numerical weather prediction model. The method is based on (i) the detection and the characterization of clouds by the CO2-slicing algorithm and (ii) the identification of clear-cloudy channels using the ECMWF cloud-detection scheme. Once a hypothetical cloud-affected pixel is detected by the CO2-slicing scheme, the cloud-top pressure and the effective cloud fraction are provided to the radiative transfer model simultaneously with other atmospheric variables to simulate cloud-affected radiances. Furthermore, the ECMWF scheme flags each channel of the pixel as clear or cloudy. In the current configuration of the assimilation scheme, channels affected by clouds whose cloudtop pressure ranges between 600 and 950 hPa are assimilated over sea in addition to clear channels. Results of assimilation experiments are presented. On average, 3.5% of additional pixels are assimilated over the globe but additional assimilated channels are much more numerous for midto high latitudes (10% of additional assimilated channels on average). Encouraging results are found in the quality of the analyses: background departures of AIRS observations are reduced, especially for surface channels, which are globally 4 times smaller, and the analysis better fits some conventional and satellite data. Global forecasts are slightly improved for the geopotential field. These improvements are significant up to the 72-h forecast range. Predictability improvements have been obtained for a case study: a low pressure system that affected the southeastern part of Italy in September 2006. The trajectory, intensity, and the whole development of the cyclogenesis are better predicted, whatever the forecast range, for this case study. © 2009 American Meteorological Society."
"6603140753;7201837768;7004242319;","Simulating mixed-phase Arctic stratus clouds: Sensitivity to ice initiation mechanisms",2009,"10.5194/acp-9-4747-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961199866&doi=10.5194%2facp-9-4747-2009&partnerID=40&md5=42e9c4491dc9302d5601bbf830c1260c","The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM) scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE) campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP) on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during 9-10 October, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-h simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors' concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity) against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process of ice phase initiation due to freezing of supercooled water in both saturated and subsaturated (w.r.t. water) environments is as important as primary ice crystal origination from water vapor. We also find that the BFP is a process mainly responsible for the rates of glaciation of simulated clouds. These glaciation rates cannot be adequately represented by a water-ice saturation adjustment scheme that only depends on temperature and liquid and solid hydrometeors' contents as is widely used in bulk microphysics schemes and are better represented by processes that also account for supersaturation changes as the hydrometeors grow. © 2009 Author(s)."
"35240023700;7405763496;34568038900;9233714800;","Effects of precipitation physics algorithms on a simulated climate in a general circulation model",2009,"10.1016/j.jastp.2009.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71749088929&doi=10.1016%2fj.jastp.2009.08.001&partnerID=40&md5=7636f76a47403914f5a7ccce17f29e88","The purpose of this study is to investigate the effects of precipitation physics in a general circulation model (GCM) on a simulated climate. Experiments are performed under the single column model (SCM) framework to examine basic features and under the general circulation model framework to investigate the impact on seasonal simulation. The SCM simulation shows that convection processes in the model have a considerable influence on the change in vertical thermodynamic structure, resulting in a change in precipitation, whereas in the GCM framework stratiform precipitation physics play a distinct role in changing the atmospheric structure. The GCM experiments also show that the overall reduction of precipitation in simulations with prognostic stratiform precipitation physics is highly related to changes in cloudiness and corresponding changes in radiative flux, which in turn leads to the reduction of convective activities. © 2009 Elsevier Ltd. All rights reserved."
"6701791841;54391679700;","On the inter-annual variation of rainfall in Israel since 1931: No change, much deviation, but with a useful signal",2009,"10.1560/IJES.58.2.113","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054933858&doi=10.1560%2fIJES.58.2.113&partnerID=40&md5=5fade7915e0117e5afb42bba269cb5ca","Analysis of measurements of the annual volume of rain falling in Israel and other areas west of the Jordan River between 1931 and 2008 shows no evidence of a significant change during the last 78 years. Significant time trends were also absent during the 1967-2002 period when a marked increase in the regional annual air temperature occurred and during the 1976-2007 period when a cloud seeding program was operational. The use of the documented inter-annual distribution to calculate probabilities of the occurrence of regional water deficits and surpluses is illustrated. © 2011 Science From Israel/ LPPLtd."
"7006630335;16835072800;7006056992;6603789210;56219624100;7103404891;7004322783;","Climate variability and change in the greater alpine region over the last two centuries based on multi-variable analysis",2009,"10.1002/joc.1857","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71449105681&doi=10.1002%2fjoc.1857&partnerID=40&md5=5f7a556ea3b66cfebb63ddfa20174ae1","An extensive analysis of the HISTALP database is presented with the aim of giving a comprehensive picture of secular climate variability and change in the Greater Alpine Region (GAR, 4-19 E, 43-49 N). The HISTALP database encompasses 242 sites and concerns temperature, pressure, precipitation, cloudiness, sunshine duration, vapour pressure and relative humidity. The analyses are based on four regional mean records representing different GAR low-level areas and on an additional mean record representing high-level locations. The first goal of the paper is to give an overview of the seasonal and annual records for the different variables, aiming to highlight both variability on decadal time scale and long-term evolution. Then it focuses on trend and correlation analysis. Trends are presented both for the period of common data availability for all regional average series and for moving windows that permit studying the trends over a wide range of timescales. Correlations among the different variables are presented both for the regional average series and for their high-pass-filtered versions. The analyses, beside highlighting a warming that is about twice as large as the global trend, also show that the different variables have responded in different ways to this warming and that the mutual interactions linking the different variables are often present only at specific temporal scales and only in parts of the GAR and in defined seasons. In spite of this complex behaviour, which may also be due to some residual inhomogeneities still affecting the data, the analyses give evidence that the HISTALP database has an excellent internal consistency and show that the availability of a multi-variable database turns out to be very useful in order to evaluate the reliability of the reconstruction of each variable and to better understand the behaviour and the mutual interactions of the different variables. © 2009 Royal Meteorological Society."
"57206614982;57131535300;55532103900;26666356300;35239166400;36521979100;7404476279;7407969381;35975306400;","Continuous observations of water-soluble ions in PM2.5 at Mount Tai (1534 ma.s.l.) in central-eastern China",2009,"10.1007/s10874-010-9172-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951672951&doi=10.1007%2fs10874-010-9172-z&partnerID=40&md5=9ed487db4b2a8beaf4b60c78cbcdfb89","Near real-time measurements of PM2.5 ionic compositions were performed at the summit of the highest mountain in the central-eastern plains in the spring and summer of 2007 in order to characterize aerosol composition and its interaction with clouds. The average concentrations of total water soluble ions were 27.5 and 36.7 μgm-3, accounting for 44% and 62% of the PM2.5 mass concentration in the spring and summer, respectively. A diurnal pattern of SO2-4, NH+4 and NO-3 was observed in both campaigns and attributed to the upslope/downslope transport of air mass and the development of the planetary boundary layer (PBL). The average SO2 oxidation ratio (SOR) in summer was 57% (±27%), more than twice that in spring 24% (±16%); the fine nitrate oxidation ratio (NOR) was comparable in the two seasons (9±6% and 11±10% in summer and spring, respectively). This result indicates strong summertime production of sulfate aerosol. A principal component analysis shows that short-range and long-range transport of pollution, cloud processing, and crustal source were the main factors affecting the variability of the measured ions (and other trace gases and aerosols) at Mt. Tai. Strong indications of biomass burning were observed in summer. Cloud scavenging rates showed larger variations for different ions and in different cloud events. The elevated concentrations of the water soluble ions at Mt. Tai indicate serious aerosol pollution over the North China plain of eastern China. © Springer Science+Business Media B.V. 2010."
"6701483524;6603744071;35313179900;","The effect of synoptic scale weather systems on sub-surface soil temperatures in a diurnal frost environment: Preliminary observations from sub-Antarctic Marion Island",2009,"10.1111/j.1468-0459.2009.00372.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72549084521&doi=10.1111%2fj.1468-0459.2009.00372.x&partnerID=40&md5=7dbcec2b51675508b36208952222ad35","Marion Island in the South Indian Ocean has a maritime climate dominated by diurnal frost processes in the landscape. We test the hypothesis that synoptic time-scale measurements are essential in understanding the drivers of diurnal frost processes. Preliminary results from automated microclimate measurements in a polar desert habitat show that diurnal soil surface temperatures on Marion Island are influenced by a complex interaction of radiation balance, air mass circulation, cloud cover and snow. The passage of synoptic scale weather systems influences soil thermal characteristics through changes in dominance of the radiation budget. Soil frost on Marion appears to be dependent on clear skies, while synoptic weather systems affect the duration and intensity of soil frost processes and non-radiative heat fluxes. Air circulation patterns at Marion Island influence diurnal scale temperature fluctuations and its direct and indirect interactions with ecosystem processes. The data suggest that in a maritime sub-Antarctic environment the climatic drivers of soil frost occur at a finertemporal resolution than for seasonal and permafrost environments and needs to be measured at a diurnal time-scale to be meaningful. © The authors 2009 Journal compilation © 2009 Swedish Society for Anthropology and Geography."
"15319750700;7006204393;7202784114;6701873414;","Statistical analysis of forecasting models across the north slope of Alaska during the mixed-phase Arctic clouds experiment",2009,"10.1175/2009WAF2222218.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74549142868&doi=10.1175%2f2009WAF2222218.1&partnerID=40&md5=16e2388c5a46c20e7bf71f0e034e1439","The National Centers for Environmental Prediction's (NCEP) Eta Model, the models of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Aeronautics and Space Administration's (NASA) Global Modeling and Assimilation Office (GMAO) models, and the Regional Atmospheric Modeling System (RAMS) model are all examined during the Mixed-Phase Arctic Clouds Experiment (MPACE) that took place from 27 September through 22 October 2004. During two intensive observation periods, soundings were launched every 6 h from four sites across the North Slope of Alaska (NSA): Barrow, Atqasuk, Oliktok Point, and Toolik Lake. Measurements of temperature, moisture, and winds, along with surface measurements of radiation and cloud cover, were compared to model outputs from the Eta, ECMWF, GMAO, and RAMS models using the bootstrap statistical technique to ascertain if differences in model performance were statistically significant. Ultimately, three synoptic regimes controlled NSA weather during the MPACE period for varying amounts of time. Each posed a unique challenge to the forecasting models during the study period. Temperature forecasts for all models were good at the MPACE sites with mean bias errors generally under 2 K, and the models had the fewest significant errors predicting temperature. Forecasting moisture and wind proved to be more difficult for the models, especially aloft in the 500-300-hPa layer. The largest errors occurred in the GMAO model, with significant moist biases of 40% and wind errors of 10 ms-1 or more. The RAMS, Eta, and ECMWF models had smaller moist biases in this layer. Both the Eta and RAMS models overestimated the surface incident shortwave radiation, underestimated longwave radiation, and underestimated cloud cover fraction. Overall, the bootstrapping results coincided with findings from conventional statistical comparisons as model outputs with the largest errors were most likely to be captured and declared statistically significant in the bootstrapping process. The significant model errors during MPACE were predominantly traced to the inability of the models to simulate disturbances in synoptic regime I, warm or cold biases over higher inland terrain, a warm bias along the NSA coastal waters in the Beaufort Sea, and difficulty in forecasting the intensity of the explosive cyclone in synoptic regime III. © 2009 American Meteorological Society."
"7004160106;7005706662;7402933297;7402390191;55717074000;6701378450;22635081500;7409322518;7405367162;35621564700;","Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions-Part 1: Africa and India",2009,"10.5194/angeo-27-3989-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749089251&doi=10.5194%2fangeo-27-3989-2009&partnerID=40&md5=d2df2b99440622ea3b42a1de43ec81e9","Version-4 of the Goddard Earth Observing System (GEOS-4) General Circulation Model (GCM) was employed to assess the influence of potential changes in aerosols on the regional circulation, ambient temperatures, and precipitation in four selected regions: India and Africa (current paper), as well as North and South America (companion paper). Ensemble-simulations were carried out with the GCM to assess the aerosol direct and indirect effects, hereafter ADE and AIE. Each simulation was started from the NCEP-analyzed initial conditions for 1 May and was integrated through May-June-July-August of each year: 1982-1987 to provide an ensemble set of six simulations. In the first set, called experiment (#1), climatological aerosols were prescribed. The next two experiments (#2 and #3) had two sets of simulations each: one with 2X and other with 1/2X the climatological aerosols over each of the four selected regions. In experiment #2, the anomaly regions were advectively restricted (AR), i.e., the large-scale prognostic fields outside the aerosol anomaly regions were prescribed while in experiment #3, the anomaly regions were advectively Interactive (AI) as is the case in a normal GCM integrations, but with the same aerosols anomalies as in experiment #2. Intercomparisons of circulation, diabatic heating, and precipitation difference fields showed large disparities among the AR and AI simulations, which raised serious questions about the proverbial AR assumption, commonly invoked in regional climate simulation studies. Consequently AI simulation mode was chosen for the subsequent studies. Two more experiments (#4 and #5) were performed in the AI mode in which ADE and AIE were activated one at a time. The results showed that ADE and AIE work in concert to make the joint influences larger than sum of each acting alone. Moreover, the ADE and AIE influences were vastly different for the Indian and Africa regions, which suggest an imperative need to include them rationally in climate models. We also found that the aerosol induced increase of tropical cirrus clouds would potentially offset any cirrus thinning that may occur due to warming in response to CO2 increase."
"6602506659;35332639100;7101668902;57190523096;","Analysis of results of numerical experiments with an atmospheric general circulation model with allowance for peculiarities of the underlying surface in megalopolises",2009,"10.3103/S1068373909100045","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949760879&doi=10.3103%2fS1068373909100045&partnerID=40&md5=e98792525ff1093a36897a9f4d9c15c3","A hypothesis is put forward that underlying surface peculiarities over large cities should be taken into account in the atmospheric circulation modeling, climate change studies, and in the numerical weather forecast. It is demonstrated based on the analysis of satellite images that the scales of changes in the underlying surface properties amount to hundreds of kilometers and that their influence can be studied with a large-scale atmospheric general circulation model. The influence of changes in the underlying surface characteristics in the cities on the surface temperature is analyzed. It is shown that the model atmosphere is sensitive to changes in surface properties in the cities. It is also shown that the surface air temperature approaches the observed climate over most land part of the urban territories, where peculiarities of the urban territories are taken into account. The model of the city should be changed in the areas, where such a result was not obtained. According to the experimental results, the model of the city in the mid- and high latitudes should differ from the model in the southern latitudes, but it should be taken into consideration for all urbanized areas of the world. © 2009 Allerton Press, Inc."
"6701363731;","A study on the direct effect of anthropogenic aerosols on near surface air temperature over Southeastern Europe during summer 2000 based on regional climate modeling",2009,"10.5194/angeo-27-3977-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949438435&doi=10.5194%2fangeo-27-3977-2009&partnerID=40&md5=773a89096a29cfa2e0a5b9699567d197","In the present work it is investigated the direct shortwave effect of anthropogenic aerosols on the near surface temperature over Southeastern Europe and the atmospheric circulation during summer 2000. In summer 2000, a severe heat-wave and droughts affected many countries in the Balkans. The study is based on two yearly simulations with and without the aerosol feedback of the regional climate model RegCM3 coupled with a simplified aerosol model. The surface radiative forcing associated with the anthropogenic aerosols is negative throughout the European domain with the more negative values in Central and Central-eastern Europe. A basic pattern of the aerosol induced changes in air temperature at the lower troposphere is a decrease over Southeastern Europe and the Balkan Peninsula (up to about 1.2°C) thus weakening the pattern of the climatic temperature anomalies of summer 2000. The aerosol induced changes in air temperature from the lower troposphere to upper troposphere are not correlated with the respective pattern of the surface radiative forcing implying the complexity of the mechanisms linking the aerosol radiative forcing with the induced atmospheric changes through dynamical feedbacks of aerosols on atmospheric circulation. Investigation of the aerosol induced changes in the circulation indicates a southward shift of the subtropical jet stream playing a dominant role for the decrease in near surface air temperature over Southeastern Europe and the Balkan Peninsula. The southward shift of the jet exit region over the Balkan Peninsula causes a relative increase of the upward motion at the northern flank of the jet exit region, a relative increase of clouds, less solar radiation absorbed at the surface and hence relative cooler air temperatures in the lower troposphere between 45° N and 50° N. The southward extension of the lower troposphere aerosol induced negative temper-ature changes in the latitudinal band 35° N-45° N over the Balkan Peninsula is justified from the prevailing northerly flow advecting the relatively cooler air from the latitudinal band 45° N-50° N towards the lower latitudes. The present regional climate modeling study indicates the important role of anthropogenic aerosols for the regional climate and their dynamical feedback on atmospheric circulation."
"55881697700;10642255900;55274286200;25222135800;55951088700;","Long-term drivers of change in Polylepis woodland distribution in the central Andes",2009,"10.1111/j.1654-1103.2009.01102.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78049484208&doi=10.1111%2fj.1654-1103.2009.01102.x&partnerID=40&md5=540142ba1f532771f72690998907e61e","Question: Is the modern patchy distribution of highly biodiverse Polylepis woodlands a consequence of human activity or natural fluctuations in environmental conditions? What are the consequences of changing climate for the tree genus Polylepis? Location: High central tropical Andes. Methods: We characterized the ecological baseline conditions for Polylepis woodlands over the last ca. 370 000 years through: (i) examination of fossil pollen records (Salar de Uyuni and Lake Titicaca) and (ii) a review of autecological information concerning Polylepis. Results: Fossil pollen data revealed fluctuations in the abundance (ca. 0-34%) of Polylepis pollen before the arrival of humans in South America (412 000 years ago), indicating that Polylepis did not form permanent continuous woodland before the arrival of humans and that climatic factors can drive rapid vegetation change. Autecological assessment of Polylepis revealed: (i) negative moisture balance, (ii) fire, (iii) waterlogging, and (iv) cloud cover to be critical in determining the niche space available for Polylepis. Conclusions: Polylepis niche space in the central Andes was at a maximum during warm and wet conditions in the past, but might be at a minimum during the warmer and drier than modern conditions predicted for later this century. The sensitivity to past global climate change emphasizes the need for conservation planners to consider model predictions of a warmer central Andes in the coming decades when developing planting schemes. Natural fluctuations in woodland abundance suggest the most effective way for conservation efforts to ""mimic"" the natural baseline would be to develop a reproductively connected patchwork of communities. © 2009 International Association for Vegetation Science."
"57204886915;7006127310;7103366892;7003278104;7203062717;7006198994;7501760109;6603975189;35767566800;6701346974;56224155200;7102696626;35497573900;35768521600;55738957800;","Application of MJO simulation diagnostics to climate models",2009,"10.1175/2009JCLI3063.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649307988&doi=10.1175%2f2009JCLI3063.1&partnerID=40&md5=c80f0f9671e3b08ed3ebadb8eacc89e9","The ability of eight climate models to simulate the Madden-Julian oscillation (MJO) is examined using diagnostics developed by the U.S. Climate Variability and Predictability (CLIVAR) MJO Working Group. Although the MJO signal has been extracted throughout the annual cycle, this study focuses on the boreal winter (November-April) behavior. Initially, maps of the mean state and variance and equatorial space-time spectra of 850-hPa zonal wind and precipitation are compared with observations. Models best represent the intraseasonal space-time spectral peak in the zonal wind compared to that of precipitation. Using the phase-space representation of the multivariate principal components (PCs), the life cycle properties of the simulated MJOs are extracted, including the ability to represent how the MJO evolves from a given subphase and the associated decay time scales. On average, the MJO decay (e-folding) time scale for all models is shorter (~20- 29 days) than observations (~31 days). All models are able to produce a leading pair of multivariate principal components that represents eastward propagation of intraseasonal wind and precipitation anomalies, although the fraction of the variance is smaller than observed for all models. In some cases, the dominant time scale of these PCs is outside of the 30-80-day band. Several key variables associated with the model's MJO are investigated, including the surface latent heat flux, boundary layer (925 hPa) moisture convergence, and the vertical structure of moisture. Low-level moisture convergence ahead (east) of convection is associated with eastward propagation in most of the models. A few models are also able to simulate the gradual moistening of the lower troposphere that precedes observed MJO convection, as well as the observed geographical difference in the vertical structure of moisture associated with the MJO. The dependence of rainfall on lower tropospheric relative humidity and the fraction of rainfall that is stratiform are also discussed, including implications these diagnostics have for MJO simulation. Based on having the most realistic intraseasonal multivariate empirical orthogonal functions, principal component power spectra, equatorial eastward propagating outgoing longwave radiation (OLR), latent heat flux, low-level moisture convergence signals, and vertical structure of moisture over the Eastern Hemisphere, the superparameterized Community Atmosphere Model (SPCAM) and the ECHAM4/Ocean Isopycnal Model (OPYC) show the best skill at representing the MJO. © 2009 American Meteorological Society."
"6507767420;7005541454;56249611100;7003698160;","Late quaternary mass movement events in lake el'gygytgyn, north-eastern Siberia",2009,"10.1111/j.1365-3091.2009.01074.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73249143083&doi=10.1111%2fj.1365-3091.2009.01074.x&partnerID=40&md5=1b5ef6542624aa9487178d4d60a93477","Lake El'gygytgyn is situated in a 3·6 Myr old impact crater in North-eastern Siberia. Its sedimentary record probably represents the most complete archive of Pliocene and Quaternary climate change in the terrestrial Arctic. In order to investigate the influence of gravitational sediment transport on the pelagic sediment record in the lake centre, two sediment cores were recovered from the lower western lake slope. The cores penetrate a sub-recent mass movement deposit that was identified by 3·5 kHz echo sounding. In the proximal part of this deposit, deformed sediments reflect an initial debris flow characterized by limited sediment mixture. Above and in front of the debrite, a wide massive densite indicates a second stage with a liquefied dense flow. The mass movement event led to basal erosion of ca 1 m thick unconsolidated sediments along parts of its flow path. The event produced a suspension cloud, whose deposition led to the formation of a turbidite. The occurrence of the turbidite throughout the lake and the limited erosion at its base mainly suggest deposition by 'pelagic rain' following Stokes' Law. Very similar radiocarbon dates obtained in the sediments directly beneath and above the turbidite in the central lake confirm this interpretation. When applying the depositional model for the Late Quaternary sediment record of Lake El'gygytgyn, the recovered turbidites allow reconstruction of the frequency and temporal distribution of large mass movement events at the lake slopes. In total, 28 turbidites and related deposits were identified in two, 12·9 and 16·6 m long, sediment cores from the central lake area covering approximately 300 kyr. © 2009 The Authors. Journal compilation © 2009 International Association of Sedimentologists."
"6603077997;6507562207;6603540682;57211811048;","Professor Zalman Makhover: A relevant contributor to early tropopause studies",2009,"10.1127/0941-2948/2009/0414","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949620853&doi=10.1127%2f0941-2948%2f2009%2f0414&partnerID=40&md5=db086a85fe202b52548fe94d091c60f0","We present an assessment of the work of Zalman Meerovich Makhover (1922-99), a leading expert on tropopause studies in the former USSR. Although a much-respected scientist among his peers, his work remains unknown, possibly as a result of much of never having been translated into English. His most important contributions were on the subject of the spatial and temporal structure of the altitude and temperature of the tropopause, as well as its variability over a range of different time scales from annual to daily. We describe the determination of the seasonal features of the tropopause and note his achievements in determining the roles of synoptic conditions and the annual cycle on tropopause characteristics. Recent tropopause research has confirmed much of his earlier work and provided important results for, among other things, stratospheretroposphere exchange processes, climate change indicator studies, and the climatology of aircraft exhaust traces. The legacy of Makhover includes his own research on tropopause phenomena, as well as a synthesis of the numerous studies conducted by former Soviet and other researchers. Here we provide a brief biography, citation data, as well as graphical material taken from his monographs and papers. © by Gebrüder Borntraeger 2009."
"7005428121;35517202300;7005285298;","On the NOx production by laboratory electrical discharges and lightning",2009,"10.1016/j.jastp.2009.07.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71749085985&doi=10.1016%2fj.jastp.2009.07.009&partnerID=40&md5=e0b0b3fd502350a692928ff67b06036a","Different approaches are used in estimating the global production of NOx by lightning flashes, including field measurements carried out during thunderstorm conditions, theoretical studies combining the physics and chemistry of the electrical discharges, and measurements of NOx yield in laboratory sparks with subsequent extrapolation to lightning. In the latter procedure, laboratory data are extrapolated to lightning using the energy as the scaling quantity. Further, in these studies only the return strokes are considered assuming that contributions from other processes such as leaders, continuing currents, M components, and K processes are negligible. In this paper, we argue that the use of energy as the scaling quantity and omission of all lightning processes other than return strokes are not justified. First, a theory which can be used to evaluate the NOx production by electrical discharges, if the current flowing in the discharge is known, is presented. The results obtained from theory are compared with the available experimental data and a reasonable agreement is found. Numerical experiments suggest that the NOx production efficiency of electrical discharges depends not only on the energy dissipated in the discharge, but also on the shape of current waveform. Thus, the current signature, can influence extrapolation of laboratory data to lightning flashes. Second, an estimation of the NOx yield per lightning flash is made by treating the lightning flash as a composite event consisting of several discharge processes. We show that the NOx production takes place mainly in slow discharge processes such as leaders, M components, and continuing currents, with return strokes contributing only a small fraction of the total NOx. The results also show that cloud flashes are as efficient as ground flashes in NOx generation. In estimating the global NOx production by lightning flashes the most influencing parameter is the length of the lightning discharge channel inside the cloud. For the total length of channels inside the cloud of a typical ground flash of about 45 km, we estimate that the global annual production of NOx is about 4 Tg(N). © 2009."
"7404976222;24468389200;57190494123;36627352900;7006493632;55754495900;22135291000;","Multi-scale forcing and the formation of subtropical desert and monsoon",2009,"10.5194/angeo-27-3631-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955799414&doi=10.5194%2fangeo-27-3631-2009&partnerID=40&md5=5994de25055de47ee2820b7f9a980574","This study investigates three types of atmospheric forcing across the summertime subtropics that are shown to contribute in various ways to the occurrence of dry and wet climates in the subtropics. To explain the formation of desert over the western parts of continents and monsoon over the eastern parts, we propose a new mechanism of positive feedback between diabatic heating and vorticity generation that occurs via meridional advection of planetary vorticity and temperature. Monsoon and desert are demonstrated to coexist as twin features of multi-scale forcing, as follows. First, continent-scale heating over land and cooling over ocean induce the ascent of air over the eastern parts of continents and western parts of oceans, and descent over eastern parts of oceans and western parts of continents. Second, local-scale sea-breeze forcing along coastal regions enhances air descent over eastern parts of oceans and ascent over eastern parts of continents. This leads to the formation of the well-defined summertime subtropical LOSECOD quadruplet-heating pattern across each continent and adjacent oceans, with long-wave radiative cooling (LO) over eastern parts of oceans, sensible heating (SE) over western parts of continents, condensation heating (CO) over eastern parts of continents, and double dominant heating (D: LO+CO) over western parts of oceans. Such a quadruplet heating pattern corresponds to a dry climate over the western parts of continents and a wet climate over eastern parts. Third, regional-scale orographic-uplift-heating generates poleward ascending flow to the east of orography and equatorward descending flow to the west. The Tibetan Plateau (TP) is located over the eastern Eurasian continent. The TP-forced circulation pattern is in phase with that produced by continental-scale forcing, and the strongest monsoon and largest deserts are formed over the Afro-Eurasian Continent. In contrast, the Rockies and the Andes are located over the western parts of their respective continents, and orography-induced ascent is separated from ascent due to continental-scale forcing. Accordingly, the deserts and monsoon climate over these continents are not as strongly developed as those over the Eurasian Continent. A new mechanism of positive feedback between diabatic heating and vorticity generation, which occurs via meridional transfer of heat and planetary vorticity, is proposed as a means of explaining the formation of subtropical desert and monsoon. Strong low-level longwave radiative cooling over eastern parts of oceans and strong surface sensible heating on western parts of continents generate negative vorticity that is balanced by positive planetary vorticity advection from high latitudes. The equatorward flow generated over eastern parts of oceans produces cold sea-surface temperature and stable stratification, leading in turn to the formation of low stratus clouds and the maintenance of strong in situ longwave radiative cooling. The equatorward flow over western parts of continents carries cold, dry air, thereby enhancing local sensible heating as well as moisture release from the underlying soil. These factors result in a dry desert climate. Over the eastern parts of continents, condensation heating generates positive vorticity in the lower troposphere, which is balanced by negative planetary vorticity advection of the meridional flow from low latitudes. The flow brings warm and moist air, thereby enhancing local convective instability and condensation heating associated with rainfall. These factors produce a wet monsoonal climate. Overall, our results demonstrate that subtropical desert and monsoon coexist as a consequence of multi-scale forcing along the subtropics."
"35182923700;40161409300;32667960800;32667627700;7006100982;6603199875;","Stuck in the clouds: Bringing the CBD's Ecosystem Approach for conservation management down to Earth in Canada and Germany",2009,"10.1016/j.jnc.2009.04.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450285187&doi=10.1016%2fj.jnc.2009.04.005&partnerID=40&md5=85de8335baadf4de774858c49dac3b8e","In order to successfully conduct integrated management of land, water and living resources the Convention on Biological Diversity (CBD) has developed a strategy called the Ecosystem Approach (EA). This paper analyses the obstacles preventing the implementation of the EA in two case study countries, Canada and Germany. We briefly describe the EA, followed by the results of literature research of protected area management and the EA, as well as structured telephone interviews conducted with managers of large protected areas in Germany and expert interviews in the Canadian Provinces of Manitoba and Ontario, in addition to the German Federal State of Brandenburg all conducted in 2005-2006. Results reveal that the EA is faced with a wide range of barriers and its implementation seems to be stuck in the political arena, not reaching the practical level. Most notable were issues concerning general knowledge of the EA, top-down information sharing, both administrative and cross-sectoral cooperation and stakeholder involvement. Major outcomes are the need for more cooperation and knowledge sharing, as well as for a correct combination of both top-down and bottom-up approaches to ecosystem management. The results partially reflect eight general obstacles considered in a Strategic Plan of the CBD, with the exception of socio-economic factors and natural phenomena and environmental change. We rather see these as issues demonstrating the urgent need for implementing the EA. In particular, climate change increases the need of the implementation of the EA and actually could lead to a broader acceptance of its principles. © 2009 Elsevier GmbH. All rights reserved."
"7102816537;","Atmospheric hydrogen peroxide: Evidence for aqueous-phase formation from a historic perspective and a one-year measurement campaign",2009,"10.1016/j.atmosenv.2009.08.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71749105265&doi=10.1016%2fj.atmosenv.2009.08.013&partnerID=40&md5=b6a3da53341cfb798d8d0d3e0fa1ef1a","H2O2 is produced in the atmospheric gas phase only through a single pathway, the HO2 radical recombination. Its main role has been identified in oxidizing SO2 dissolved in hydrometeors to sulphate. Thus aqueous-phase chemistry has been considered to be a main sink (apart from dry deposition and scavenging) but rarely a source of H2O2 despite early findings of its heterogeneous and aqueous-phase production. The aim of this paper is to discuss the atmospheric budget of H2O2 from the multiphase chemistry approach with special emphasis on new sources other than gas-phase HO2 recombination. After providing a brief historic view on H2O2 chemistry, often unknown to young atmospheric chemists but important for a complete understanding, the results of a one-year study of simultaneous measurements of H2O2 in rain and air are presented that show strong evidence for aqueous-phase H2O2 formation. Implications for future changes in atmospheric chemistry are discussed from the viewpoint of an ""interfacial chemistry"". © 2009 Elsevier Ltd. All rights reserved."
"6701580874;7005265210;6603568514;","The great 2006 heat wave over California and Nevada: Signal of an increasing trend",2009,"10.1175/2009JCLI2465.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649146460&doi=10.1175%2f2009JCLI2465.1&partnerID=40&md5=25ad42a803c85e4a9a1c8d82b4c1a5b7","Most of the great California-Nevada heat waves can be classified into primarily daytime or nighttime events depending on whether atmospheric conditions are dry or humid. A rash of nighttime-accentuated events in the last decade was punctuated by an unusually intense case in July 2006, which was the largest heat wave on record (1948-2006). Generally, there is a positive trend in heat wave activity over the entire region that is expressed most strongly and clearly in nighttime rather than daytime temperature extremes. This trend in nighttime heat wave activity has intensified markedly since the 1980s and especially since 2000. The two most recent nighttime heat waves were also strongly expressed in extreme daytime temperatures. Circulations associated with great regional heat waves advect hot air into the region. This air can be dry or moist, depending on whether a moisture source is available, causing heat waves to be expressed preferentially during day or night. A remote moisture source centered within a marine region west of Baja California has been increasing in prominence because of gradual sea surface warming and a related increase in atmospheric humidity. Adding to the very strong synoptic dynamics during the 2006 heat wave were a prolonged stream of moisture from this southwestern source and, despite the heightened humidity, an environment in which afternoon convection was suppressed, keeping cloudiness low and daytime temperatures high. The relative contributions of these factors and possible relations to global warming are discussed. © 2009 American Meteorological Society."
"35767527800;8970508600;7006033615;","Cold events over southern Australia: Synoptic climatology and hemispheric structure",2009,"10.1175/2009JCLI2997.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649277022&doi=10.1175%2f2009JCLI2997.1&partnerID=40&md5=aa4050d4571c97040fb065aea09508ec","Cold events (CEs) are an important feature of southern Australian weather. Unseasonably cold conditions can have a significant impact on Australia's agricultural industry and other aspects of society. In this study the bottom 0.4% of maximum temperatures in Melbourne and Perth from the 1958-2006 period are defined as CEs, representing the large-scale patterns affecting most of extratropical Australia. Compiling 6-hourly progressions of the tracks of the cyclones and anticyclones that are geostrophically associated with CEs gives for the first time a detailed synoptic climatology over the area. The anticyclone tracks display a ""cloud"" of high density across the Indian Ocean, which is linked, in the mean, to weak but significant negative SST anomalies in the region. The cyclone tracks display much variability, with system origins ranging from subpolar to tropical. Several CEs are found to involve tropical and extratropical interaction or extratropical transition of originally tropical cyclones (hurricanes). CE-associated systems travel farther and exhibit longer life spans than similar, non-CE systems. Upper-level analyses indicate the presence of a wave train originating more than 1208 west of the CE. This pattern greatly intensifies over the affected area in conjunction with a merging of the subpolar and subtropical jets. The upper-level wave train is present up to five days before the CE. The absence of large orographic features in Australia highlights the importance of wave amplification in CE occurrence. No consistent trend in CE intensity over the period is found, but a significant negative trend in event frequency is identified for both Melbourne and Perth. © 2009 American Meteorological Society."
"36140403600;7402872647;","The effects of terrain slope and orientation on different weather processes in China under different model resolutions",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954466950&partnerID=40&md5=6f6e78e4f0bd9f6ec22062babf5a9701","Currently, short wave radiation at the ground surface (GSW) is calculated under the assumption of a horizontal surface. This method of estimating the GSW may lead to considerable errors when the model resolution becomes higher and the model terrain becomes steeper. In this paper, to improve the short wave solar radiation simulations, a terrain slope and orientation parameterization has been implemented into the non-hydrostatic mesoscale model GRAPES (Global/Regional Assimilation and Prediction System). The effects of the terrain slope and orientation on different short range weather processes in China under different model resolutions are simulated and discussed. In the simulations, topography height is taken from NCEP (National Centers for Environmental Prediction) with a resolution of 1 km, and the slope and orientation of terrain are calculated using different staggering schemes and under different weather conditions. The results show that when the model resolution is low (30 and 60 km) and the slope of terrain is not large, the influence of the slope and orientation of terrain on the GSW is not evident; otherwise, however, it is not negligible. Under high model resolutions (3 and 6 km), the increase (decrease) of simulated precipitation corresponds to the decrease (increase) of the GSW induced by the slope effect, and the variations of precipitation are usually ranged between -5 and 5 mm. Under the high resolution, the surface temperature and heat fluxes are strongly correlated to each other and the high correlation exists mostly in the complex terrain regions. The changes of the GSW, precipitation, surface temperature, and heat fluxes induced by the effects of the terrain slope and orientation are more obvious in mountainous regions, due to the alternations in the atmospheric circulation. It is found as well that under the weather condition of less cloud and less precipitation, the effects of the terrain slope and orientation can be more realistically seen. Therefore, the terrain slope and orientation can usually be neglected in numerical models when the horizontal model resolution is low and the slopes are moderate, but should be taken into account when the model resolution becomes high and the terrain is steep and undulating."
"8043701900;7004479957;","A simple model of climatological rainfall and vertical motion patterns over the tropical oceans",2009,"10.1175/2009JCLI2393.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69249160114&doi=10.1175%2f2009JCLI2393.1&partnerID=40&md5=db8a8f943ac3cb730a61e0b41183b6b4","A simple model is developed that predicts climatological rainfall, vertical motion, and diabatic heating profiles over the tropical oceans given the sea surface temperature (SST), using statistical relationships deduced from the 40-yrECMWFRe-Analysis (ERA-40). The model allows for two modes of variability in the vertical motion profiles: a shallow mode responsible for all ""boundary layer"" convergence between 850 hPa and the surface, and a deep mode with no boundary layer convergence. The model is based on the argument expressed in the authors' companion paper that boundary layer convergence can be usefully viewed as a forcing on deep convection, not just a result thereof. The shallow mode is either specified from satellite observations or modeled using a simple mixed-layer model that has SST as well as 850-hPa geopotential height, winds, and temperature as boundary conditions. The deep-mode amplitude is empirically shown to be proportional to a simple measure of conditional instability in convecting regions, and is determined by the constraint that radiative cooling must balance adiabatic warming in subsidence regions. This two-mode model is tested against a reanalysis-derived dry static energy budget and in a reanalysisindependent framework based on satellite-derived surface convergence and using SST as a proxy for conditional instability. It can predict the observed annual mean and seasonal cycle of rainfall, vertical motion, and diabatic heating profiles across the tropical oceans with significantly more skill than optimized predictions using a thresholded linear relationship with SST. In most warm-ocean regions, significant rainfall only occurs in regions of monthly-mean boundary layer convergence. In such regions, deep-mode amplitude and rainfall increase linearly with SST, with an additional rainfall contribution from the shallow mode directly tied to boundary layer convergence. This second contribution is significant mainly in the east and central Pacific ITCZ, where it is responsible for that region's ""bottom-heavy"" vertical-velocity, diabatic heating, and cloud profiles. © 2009 American Meteorological Society."
"24832504800;57204346059;","Planetary scale land-ocean contrast of near-surface air temperature and precipitation forced by present and future SSTs",2009,"10.2151/jmsj.87.877","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450164043&doi=10.2151%2fjmsj.87.877&partnerID=40&md5=e330bf0af03767a3cc8577ef73ebcd6d","The land-ocean contrasts of near-surface temperature and precipitation averaged over tropics (40 S-40 N) and extra tropics in the Northern Hemisphere (40 N-70 N) were studied using the global version of the Experimental Climate Prediction Center (ECPC) global to regional forecast system (G-RSM) under current and projected sea surface temperatures (SSTs) with four different stratiform cloud parameterizations. As common features of the simulations, we found that there is a large land-ocean contrast in surface downward longwave radiation flux (LWd), downward shortwave flux (SWd), upward shortwave flux (SWu), latent heat flux (LHF) and sensible heat flux (SHF). Since smaller LWd is compensated by larger SWd, and larger SWu is compensated by smaller LHF, there is a tendency toward the reduction of the land-ocean contrast of the total surface fluxes. There were significant differences in near-surface air temperature and precipitation among the four simulations. The main cause is due to clear-sky LWd. The second largest term is the SWd, which works in the opposite direction of the difference in LWd. The difference in the near-surface temperature among the schemes is mostly determined by the sum of the LWd and SWd. The variability of precipitation among the four cloud schemes is large everywhere except in tropical oceans. In general, the difference in evaporation explains the precipitation difference among the schemes everywhere except tropical oceans where moisture convergence is negative. When the simulations are performed with warmer SST, the differences among the cloud schemes are very similar to those in present-day simulations. However, the magnitude of the response to warm SST depends on the cloud scheme. Those sensitivities are connected to that of the effect of cloudiness on SWd and surface albedo. © 2009, Meteorological Society of Japan."
"7202318056;6602077574;55974229900;6508003871;55465376400;6701899848;9272538400;7101692211;7101936669;","State of the climate in 2008",2009,"10.1175/BAMS-90-8-StateoftheClimate","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450173109&doi=10.1175%2fBAMS-90-8-StateoftheClimate&partnerID=40&md5=3897c5869d2fb485e740615478760f1b","The global mean temperature in 2008 was slightly cooler than that in 2007; however, it still ranks within the 10 warmest years on record. Annual mean temperatures were generally well above average in South America, northern and southern Africa, Iceland, Europe, Russia, South Asia, and Australia. In contrast, an exceptional cold outbreak occurred during January across Eurasia and over southern European Russia and southern western Siberia. There has been a general increase in land-surface temperatures and in permafrost temperatures during the last several decades throughout the Arctic region, including increases of 1° to 2°C in the last 30 to 35 years in Russia. Record setting warm summer (JJA) air temperaty res were observed throughout Greenland. The year 2008 was also characterized by heavy precipitation in a number of regions of northern Sooth America, Africa, and South Asia. In contrast, a prolonged and intense drought occurred during most of 2008 in northern Argentina, Paraguay, Uruguay, and southern Brazil, causing severe impacts to agriculture and affecting many communities. The year began with a strong La Niña episode that ended in June. Eastward surface current anomalies in the tropical Pacific Ocean in early 2008 played a major role in adjusting the basin from strong La Niña conditions to ENSO-neutral conditions by July-August, followed by a return to La Nina conditions late in December. The La Niña conditions resulted in far-reaching anomalies such as a cooling in the central tropical Pacific, Arctic Ocean, and the regions extending from the Gulf of Alaska to die west coast of North America; changes in the sea surface salinity and heat content anomalies in the tropics; and total column water vapor, cloud cover, tropospheric temperature, and precipitation patterns typical of a La Niña. Anomalously salty ocean surface salinity values in climatologically drier locations and anomalously fresh values in rainier locations observed in recent years generally persisted in 2008, suggesting an increase in the hydrological cycle. The 2008 Atlantic hurricane season was the 14th busiest on record and the only season ever recorded with major hurricanes each month from July through November. Conversely, activity in the northwest Pacific was considerably below normal during 2008. While activity in the north Indian Ocean was only slightly above average, the season was punctuated by Cyclone Nargis, which killed over 145,000 people; in addition, it was the seventh-strongest cyclone ever in the basin and the most devastating to hit Asia since 1991. Greenhouse gas concentrations continued to rise, with CO2 increasing by more than expected based on the 1979 to 2007 trend. In the oceans, the global mean CO2 uptake for 2007 is estimated to be 1.67 Pg-C, about 0.07 Pg-C lower than the long-term average, making it the third-largest anomaly determined with this method since 1983, with the largest uptake of carbon over the past decade coming from the eastern Indian Ocean. Global phytoplankton chlorophyll concentrations were slightly elevated in 2008 relative to 2007, but regional changes were substantial (ranging to about 50%) and followed long-term patterns of net decreases in chlorophyll with increasing sea surface temperature. Ozone-depleting gas concentrations continued to fall globally to about 4% below the peak levels of the 2000-02 period. Total column ozone concentrations remain well below pre1980, levels and the 2008 ozone hole was unusually large (sixth worst on record) and persistent, with low ozone values extending into the late December period. In fact the polar vortex in 2008 persisted longer than for any previous year since 1979. Northern Hemisphere snow cover extent for the year was well below average due in large part to the recordlow ice extent in March and despite the record-maximum coverage in January and the shortest snow cover duration on record (which started in 1966) in the North American Arctic. Limited preliminary dataimply that in 2008 glaciers continued to lose mass, and full data for 2007 show it was the 17th consecutive year of loss. The northern region of Greenland and adjacent areas of Arctic Canada experienced a particularly intense melt season, even though there was an abnormally cold winter across Greenland's southern half. One of the most dramatic signals of the general warming trend was the continued significant reduction in the extent of the summer sea-ice cover and, importantly, the decrease in the amount of relatively older, thicker ice. The extent of the 2008 summer sea-ice cover was the second-lowest value of the satellite record (which started in 1979) and 36% below the 1979-2000 average. Significant losses in the mass of ice sheets and the area of ice shelves continued, with several fjords on the northern coast of Ellesmere Island being ice free for the first time in 3,000-5,500 years. In Antarctica, the positive phase of the SAM led to record-high total sea ice extent for much of early 2008 dirough enhanced equatorward Ekman transport. With colder continental temperatures at this time, the 2007-08 austral summer snowmelt season was dramatically weakened, making it the second shortest melt season since 1978 (when the record began). There was strong warming and increased precipitation along the Antarctic Peninsula and west Antarctica in 2008, and also pockets of warming along coastal east Antarctica, in concert with continued declines in sea-ice concentration in the Amundsen/Bellingshausen Seas. One significant event indicative of this warming was the disintegration and retreat of the Wilkins Ice Shelf in the southwest peninsula area of Antarctica."
"6602504047;6603934441;","Cluster analysis of cloud properties over the Southern European Mediterranean area in observations and a model",2009,"10.1175/2009MWR2882.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70449130237&doi=10.1175%2f2009MWR2882.1&partnerID=40&md5=70ee8fa827be0131acf75d3579fb3e83","This paper demonstrates how satellite observations of the cloudiness over a complex area such as the European Mediterranean area can be classified into distinct cloud regimes by application of a K-means clustering algorithm to pixel-level cloud properties. The study contrasts with previous approaches in the fact that the clustering is done on the cloud physical properties at the pixel level and not on statistics of these properties over a coarser grid. A method to choose the number of clusters is described. ""Shallow cumulus,"" ""stratocumulus,"" and ""frontal"" clusters are robustly identified, and associated environmental properties are described. The approach helps to refine the diagnosis of errors in model simulations. In addition to isolated classical errors of climate models (lack of midlevel clouds, overestimation of the cloud optical thickness, and underestimation of the stratocumulus) and a dramatic underestimation of the shallow cumulus clouds over land, an underestimation of the boundary layer depth is detected for some regimes as well as an incorrect stratification for the shallow cumulus. The clustering on the individual cloud properties classifies them in a much more homogeneous way than the clustering on the statistics of the cloud properties; the use of individual cloud properties at the pixel level produced by climate models activating simulators combined with subgrid-scale sampling procedures may be considered as an alternative to the use of the statistical products for the evaluation of models. The approach can also be applied to a high-resolution regional climate model. © 2009 American Meteorological Society."
"35185039700;7003667860;","The impact of positive-definite moisture advection and low-level moisture flux bias over orography",2009,"10.1175/2009MWR2873.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350784288&doi=10.1175%2f2009MWR2873.1&partnerID=40&md5=5cca997c2755cae86e8a46e673fa1cd6","Overprediction of precipitation has been a frequently noted problem near terrain. Higher model resolution helps simulate sharp microphysical gradients more realistically but can increase spuriously generated moisture in some numerical schemes. The positive-definite moisture advection (PDA) scheme in the Weather Research and Forecasting (WRF) model reduces a significant nonphysical moisture source in the model. This study examines the 13-14 December 2001 second Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) case, in which PDA reduces storm-total precipitation over Oregon by 3%-17%, varying with geographical region, model resolution, and the phase of the storm. The influence of PDA is then analyzed for each hydrometeor species in the Thompson microphysics scheme. Without PDA, the cloud liquid water field generates most of the spurious moisture because of the high frequency of sharp gradients near upwind cloud edges. It is shown that PDA substantially improves precipitation verification and that subtle, but significant, changes occur in the distribution of microphysical species aloft. Finally, another potential source of orographic precipitation error is examined: excessive low-level moisture flux upstream of regional orography. © 2009 American Meteorological Society."
"7202208148;7103158465;56835353400;7003663305;7201398636;","Investigation of microphysical parameterizations of snow and ice in arctic clouds during M-PACE through model observation comparisons",2009,"10.1175/2009MWR2688.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350787338&doi=10.1175%2f2009MWR2688.1&partnerID=40&md5=7c849f6b08c83e7d77beecaadb7ded6e","In this study the Weather Research Forecast model is used with 1-km horizontal grid spacing to investigate the microphysical properties of Arctic mixed-phase stratocumulus. Intensive measurements taken during the Department of Energy Atmospheric Radiation Measurement Program Mixed-Phase Arctic Cloud Experiment (M-PACE) on the North Slope of Alaska, during 9-12 October 2004, are used to verify the microphysical characteristics of the model's simulation of mixed-phase clouds (MPCs). A series of one- and two-moment bulk microphysical cloud schemes are tested to identify how the treatment of snow and ice affects the maintenance of cloud liquid water at low temperatures. The baseline two-moment simulation results in realistic liquid water paths and in size distributions of snow reasonably similar to observations. With a one-moment simulation for which the size distribution intercept parameter for snow is fixed at values taken from the two-moment simulation, reasonable snow size distributions are again obtained but the cloud liquid water is reduced because the one-moment scheme couples the number concentration to the mixing ratio. The one-moment scheme with the constant snow intercept parameter set to a value typical of midlatitude frontal clouds results in a substantial underprediction of the liquid water path. In the simulations, the number concentration of small ice crystals is found to be underestimated by an order of magnitude. A sensitivity test with the concentration of ice particles larger than 53 μm increased to the observed value results in underprediction of the liquid water path. If ice (not snow) is the primary driver for the depletion of cloud liquid water, then the results of this study suggest that the feedbacks among ice-snow-cloud liquid water may be misrepresented in the model. © 2009 American Meteorological Society."
"36941730100;7202129754;7402579146;14045744500;","The surprising role of orography in the initiation of an isolated thunderstorm in southern England",2009,"10.1175/2009MWR2743.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350772496&doi=10.1175%2f2009MWR2743.1&partnerID=40&md5=e3463f295a508f7ddf013cbd0a80cd1d","Many factors, both mesoscale and larger scale, often come together in order for a particular convective initiation to take place. The authors describe a modeling study of a case from the Convective Storms Initiation Project (CSIP) in which a single thunderstorm formed behind a front in the southern United Kingdom. The key features of the case were a tongue of low-level high θw air associated with a forward-sloping split front (overrunning lower θw air above), a convergence line, and a ""lid"" of high static stability air, which the shower was initially constrained below but later broke through. In this paper, the authors analyze the initiation of the storm, which can be traced back to a region of high ground (Dartmoor) at around 0700 UTC, in more detail using model sensitivity studies with the Met Office Unified Model (MetUM). It is established that the convergence line was initially caused by roughness effects but had a significant thermal component later. Dartmoor had a key role in the development of the thunderstorm. A period of asymmetric flow over the high ground, with stronger low-level descent in the lee, led to a hole in a layer of low-level clouds downstream. The surface solar heating through this hole, in combination with the tongue of low-level high θw air associated with the front, caused the shower to initiate with sufficient lifting to enable it later to break through the lid."
"6507224579;7402887257;7004247643;","Can a convective cloud feedback help to eliminate winter sea ice at high CO2 concentrations?",2009,"10.1175/2009JCLI2854.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649296808&doi=10.1175%2f2009JCLI2854.1&partnerID=40&md5=2e6fe3d69c71a35e53a890be986bb2f8","Winter sea ice dramatically cools the Arctic climate during the coldest months of the year and may have remote effects on global climate as well. Accurate forecasting of winter sea ice has significant social and economic benefits. Such forecasting requires the identification and understanding of all of the feedbacks that can affect sea ice. A convective cloud feedback has recently been proposed in the context of explaining equable climates, for example, the climate of the Eocene, which might be important for determining future winter sea ice. In this feedback, CO2-initiated warming leads to sea ice reduction, which allows increased heat and moisture fluxes from the ocean surface, which in turn destabilizes the atmosphere and leads to atmospheric convection. This atmospheric convection produces optically thick convective clouds and increases high-altitude moisture levels, both of which trap outgoing longwave radiation and therefore result in further warming and sea ice loss. Here it is shown that this convective cloud feedback is active at high CO2 during polar night in the coupled ocean-sea ice-land-atmosphere global climate models used for the 1% yr-1 CO2 increase to the quadrupling (1120 ppm) scenario of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. At quadrupledCO2, model forecasts of maximum seasonal (March) sea ice volume are found to be correlated with polar winter cloud radiative forcing, which the convective cloud feedback increases. In contrast, sea ice volume is entirely uncorrelated with model global climate sensitivity. It is then shown that the convective cloud feedback plays an essential role in the elimination of March sea ice at quadrupled CO2 in NCAR's Community Climate System Model (CCSM), one of the IPCC models that loses sea ice year-round at thisCO2 concentration. A new method is developed to disable the convective cloud feedback in the Community Atmosphere Model (CAM), the atmospheric component of CCSM, and to show that March sea ice cannot be eliminated in CCSM at CO2 = 1120 ppm without the aide of the convective cloud feedback. © 2009 American Meteorological Society."
"56253852700;57203260074;","Control of recent European surface climate change by atmospheric flow",2009,"10.1029/2009GL040480","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049087200&doi=10.1029%2f2009GL040480&partnerID=40&md5=a95a542e4a51f5073720eb175753736e","Many changes in European surface climate have occurred over the past decades, but most of the processes driving them are not identified. In particular, the role of atmospheric flow in driving surface trends needs to be evaluated to better predict future regional climate. We compare observed surface climate trends with those constructed from daily flow analogues. We find that during the last 60 years atmospheric circulation changes are the main drivers of surface weather trends in winter, but not in summer where temperature strongly interacts with the water cycle. For instance, increasing anticyclonic conditions control the decreasing summer rainfall frequency, but rainfall amount and cloud cover have not decreased accordingly, because individual rainfall events bring more rain now than decades ago. Over the past three decades the control by atmospheric flow changes has weakened, indicating evolutions in the processes steering European surface climate change. Copyright 2009 by the American Geophysical Union."
"7003865921;7202016984;56239378700;7407116104;7201862239;7406683894;7201736677;7404514776;","Overview of the CALIPSO mission and CALIOP data processing algorithms",2009,"10.1175/2009JTECHA1281.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049113742&doi=10.1175%2f2009JTECHA1281.1&partnerID=40&md5=dbd3bca964f04ce9fc19d34f6924105a","The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is a two-wavelength polarization lidar that performs global profiling of aerosols and clouds in the troposphere and lower stratosphere. CALIOP is the primary instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite, which has flown in formation with the NASA A-train constellation of satellites since May 2006. The global, multiyear dataset obtained from CALIOP provides a new view of the earth's atmosphere and will lead to an improved understanding of the role of aerosols and clouds in the climate system. A suite of algorithms has been developed to identify aerosol and cloud layers and to retrieve a variety of optical and microphysical properties. CALIOP represents a significant advance over previous space lidars, and the algorithms that have been developed have many innovative aspects to take advantage of its capabilities. This paper provides a brief overview of the CALIPSO mission, the CALIOP instrument and data products, and an overview of the algorithms used to produce these data products. © 2009 American Meteorological Society."
"57189755950;7005137442;7202671706;","Global warming, convective threshold and false thermostats",2009,"10.1029/2009GL039849","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049085776&doi=10.1029%2f2009GL039849&partnerID=40&md5=4de9c7e480f160fc7a7bc4e540a01483","We demonstrate a theoretically expected behavior of the tropical sea surface temperature probability density function (PDF) in future and past (Eocene) greenhouse climate simulations. To first order this consists of a shift to warmer temperatures as climate warms, without change of shape of the PDF. The behavior is tied to a shift of the temperature for deep convection onset. Consequently, the threshold for appearance of high clouds and associated radiative forcing shifts along with temperature. An excess entropy coordinate provides a reference to which the onset of deep convection is invariant, and gives a compact description of SST changes and cloud feedbacks suitable for diagnostics and as a basis for simplified climate models. The results underscore that the typically skewed appearance of tropical SST histograms, with a sharp drop-off above some threshold value, should not be taken as evidence for tropical thermostats. Copyright 2009 by the American Geophysical Union."
"9635764200;25924878400;7004114883;","A combined multisensor optimal estimation retrieval algorithm for oceanic warm rain clouds",2009,"10.1175/2009JAMC2156.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649149746&doi=10.1175%2f2009JAMC2156.1&partnerID=40&md5=79b57b2fdf966b77842c306e60e43823","The complicated interactions between cloud processes in the tropical hydrologic cycle and their responses to changes in environmental variables have been the focus of many recent investigations. Most studies that examine the response of the hydrologic cycle to temperature changes focus on deep convection and cirrus production, but recent results suggest that warm rain clouds may be more sensitive to temperature changes. These clouds are prevalent in the tropics and make considerable contributions to the radiation budget and to total tropical rainfall, as well as serving to moisten and precondition the atmosphere for deep convection. A change in the properties of these clouds in climate-change scenarios could have significant implications for the hydrologic cycle. Existing microwave and visible retrievals of warm rain cloud liquid water path (LWP) disagree over the range of sea surface temperatures (SST) observed in the tropical western Pacific Ocean. Although both retrieval methods show similar behavior for nonraining clouds, the two methods show very different warm-rain-cloud LWP responses to SST, both in magnitude and trend. This makes changes to the relationship between precipitation and cloud properties in changing temperature regimes difficult to interpret. A combined optimal estimation retrieval algorithm that takes advantage of the strengths of the different satellite measurements available on the Tropical Rainfall Measuring Mission (TRMM) satellite has been developed. Deconvolved TRMM Microwave Imager brightness temperatures are combined with cloud fraction from the Visible and Infrared Scanner and rainwater estimates from the TRMM precipitation radar to retrieve the cloud LWP in warm rain systems. This algorithm is novel in that it takes into account the water in the rain and estimates the LWP due to only the cloud water in a raining cloud, thus allowing investigation of the effects of precipitation on cloud properties. © 2009 American Meteorological Society."
"7501627905;55742914900;7005304841;7102913661;7006705919;","Impact of anthropogenic aerosols on Indian summer monsoon",2009,"10.1029/2009GL040114","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049093977&doi=10.1029%2f2009GL040114&partnerID=40&md5=a4c96fab5f83149419ea64d17f2a0075","Using an interactive aerosol-climate model we find that absorbing anthropogenic aerosols, whether coexisting with scattering aerosols or not, can significantly affect the Indian summer monsoon system.We also show that the influence is reflected in a perturbation to the moist static energy in the sub-cloud layer, initiated as a heating by absorbing aerosols to the planetary boundary layer. The perturbation appears mostly over land, extending from just north of the Arabian Sea to northern India along the southern slope of the Tibetan Plateau. As a result, during the summer monsoon season, modeled convective precipitation experiences a clear northward shift, coincidently in general agreement with observed monsoon precipitation changes in recent decades particularly during the onset season.We demonstrate that the sub-cloud layer moist static energy is a useful quantity for determining the impact of aerosols on the northward extent and to a certain degree the strength of monsoon convection. Copyright 2009 by the American Geophysical Union."
"7003278104;8525144100;7402761465;16197778800;10141883400;6603126554;","How well can satellite data characterize the water cycle of the Madden-Julian Oscillation?",2009,"10.1029/2009GL040005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049096083&doi=10.1029%2f2009GL040005&partnerID=40&md5=bdaece75d1da05943fd86822d50f7335","Most characterizations of the Madden-Julian Oscillation (MJO) have focused on its convection and circulation features, ocean interactions, and weather and climate impacts. The water cycle of the MJO has yet to be examined or quantified despite it offering an additional constraint on model representations of the MJO, which are still woefully poor. Recent satellite products now make it possible to characterize the MJO water cycle from observations. These include water vapor profiles, column water vapor, cloud ice profiles, total cloud liquid, rainfall, surface evaporation and column moisture convergence. From these, we quantify the water budget for disturbed and suppressed phases of the MJO. The column-integrated results indicate that precipitation is nearly balanced with moisture convergence, with variations in surface evaporation being an order of magnitude smaller. However, residuals in the column-integrated budget are relatively large, indicating the need for improved satellite retrievals and/or the necessity of using model-based assimilation products. Copyright 2009 by the American Geophysical Union."
"55688930000;7003591311;","Modeling mesoscale cellular structures and drizzle in marine stratocumulus. Part II: The microphysics and dynamics of the boundary region between open and closed cells",2009,"10.1175/2009JAS3120.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549093850&doi=10.1175%2f2009JAS3120.1&partnerID=40&md5=65fef2fb223c2d3f6d0b4236071b14d6","This is the second of two companion papers on modeling of mesoscale cellular structures and drizzle in marine stratocumulus. In the first, aerosol-cloud-precipitation interactions and dynamical feedbacks were investigated to study the formation and evolution of open and closed cellular structures separately. In this paper, coexisting open and closed cells and how they influence one another are examined in a model domain of 180 × 60 × 1.5 km3. Simulations show that gradients in aerosol at the open-closed-cell boundary cause gradients in precipitation that generate a mesoscale circulation. The circulation promotes precipitation in the polluted closed cells but suppresses it in open cells by transporting water vapor to the closed-cell regime and carrying drier air and aerosol back to the open cells. The strength of this circulation depends on the contrast in precipitation under clean and polluted conditions at the boundary. Ship plumes emitted into clean, precipitating regions, simulated as a special case of a clean-polluted boundary, develop a similar circulation. Drizzle in the ship track is first suppressed by the increase in aerosol particles but later recovers and becomes even stronger because the local circulation enhances liquid water path owing to the convergence of water vapor from the region adjacent to the track. This circulation modifies the transport and mixing of ship plumes and enhances their dispersal. Finally, results show that whereas ship emissions do increase cloud albedo in regions of open cells, even the addition of very large aerosol concentrations cannot transform an open cellular structure to a closed one, for the case considered. © 2009 American Meteorological Society."
"55688930000;7003591311;","Modeling mesoscale cellular structures and drizzle in marine stratocumulus. Part I: Impact of drizzle on the formation and evolution of open cells",2009,"10.1175/2009JAS3022.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549103137&doi=10.1175%2f2009JAS3022.1&partnerID=40&md5=2bf871e974ce0a323669e97599a78b9e","A new modeling framework is used to investigate aerosol-cloud-precipitation interactions and dynamical feedbacks at the mesoscale. The focus is on simulation of the formation and evolution of cellular structures that are commonly seen in satellite images of marine stratocumulus clouds. Simulations are performed at moderate resolution in a 60 × 60 km2 domain for 16 h to adequately represent the mesoscale organization associated with open cells and precipitation. Results support the emerging understanding that precipitation plays a critical role in the formation and evolution of open cells. Evaporation of raindrops generates a dynamic response that manifests itself in cellular organization of updrafts and downdrafts and promotes and sustains the formation of an open cellular structure in cloud fields. Vertical motion in open-cell centers with thin clouds is minimal. It is shown that a mean surface rain rate as low as 0.02 mm day-1 is, for the case considered, sufficient to promote the formation of open cells. The maximum dimension of individual open cells ranges between 5 and 30 km. Individual cells grow at a mean rate of between 5 and 10 km h-1. Irregularity in the shape of open cells is caused by formation of new precipitating regions at the cell walls and interference with neighboring cells, which erode, and eventually eliminate, the old cells. The typical lifetime of large individual open cells is about 2 h, close to that observed by radar, although a collection of open cells as a whole may last for tens of hours. © 2009 American Meteorological Society."
"16639635900;7004647146;7102883986;","Spatial patterns of Holocene glacier advance and retreat in Central Asia",2009,"10.1016/j.yqres.2009.03.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349973249&doi=10.1016%2fj.yqres.2009.03.007&partnerID=40&md5=afaa57e111ab467871c04dca4db43ac3","Glaciers in the southern Himalayas advanced in the early Holocene despite an increase in incoming summer solar insolation at the top of the atmosphere. These glacier advances are in contrast to the smaller alpine glaciers in the western and northern regions of Central Asia. Two different glacier mass-balance models are used to reconcile this Holocene glacier history with climate by quantifying the change in equilibrium-line altitudes (ELA) for simulated changes in Holocene climate. Both ELA models clearly show that the lowering of ELAs in the southern Himalayas is largely due to a decrease in summer temperatures, and that an increase in monsoonal precipitation accounts for less than 30% of the total ELA changes. The decrease in summer temperatures is a dynamic response to the changes in solar insolation, resulting in both a decrease in incoming shortwave radiation at the surface due to an increase in cloudiness and an increase in evaporative cooling. In the western and northern zones of Central Asia, both ELA models show a rise in ELAs in response to a general increase in summer temperatures. This increase in temperatures in the more northern regions is a direct radiative response to the increase in summer solar insolation. © 2009 Elsevier Inc. All rights reserved."
"7103259757;7404778968;7501855361;16637291100;7202660824;7403288995;","Controls on Northern Hemisphere snow albedo feedback quantified using satellite Earth observations",2009,"10.1029/2009GL040057","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049084238&doi=10.1029%2f2009GL040057&partnerID=40&md5=d321591bdd195c9c2fd5bbb83e34161b","Observation based estimates of controls on snow albedo feedback (SAF) are needed to constrain the snow and albedo parameterizations in general circulation model (GCM) projections of air temperature over the Northern Hemisphere (NH) landmass. The total April-May NH SAF, corresponding to the sum of the effect of temperature on surface albedo over snow covered surfaces ('metamorphism') and over surfaces transitioning from snow covered to snow free conditions ('snow cover'), is derived with daily NH snow cover and surface albedo products using Advanced Very High Resolution Radiometer Polar Pathfinder satellite data and surface air temperature from ERA40 reanalysis data between 1982-1999.Without using snow cover information, the estimated total SAF, for land surfaces north of 30°N, of -0.93 ± 0.06%K-1 was not significantly different (95% confidence) from estimates based on International Satellite Cloud Climatology Project surface albedo data. The SAF, constrained to only snow covered areas, grew to -1.06 ± 0.08%K-1 with similar magnitudes for the 'snow cover' and 'metamorphosis' components. The SAF pattern was significantly correlated with the 'snow cover' component pattern over both North America and Eurasia but only over Eurasia for the 'metamorphosis' component. However, in contrast to GCM model based diagnoses of SAF, the control on the 'snow cover' component related to the albedo contrast of snow covered and snow free surfaces was not strongly correlated to the total SAF. Copyright 2009 by the American Geophysical Union."
"7401899077;57200818577;56998026500;56411195600;56411079900;7404865816;35190462200;55778082300;","A multifunctional HTDMA system with a robust temperature control",2009,"10.1007/s00376-009-8134-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70849122121&doi=10.1007%2fs00376-009-8134-3&partnerID=40&md5=5bb1e99308cebb85d81587df2a1c3393","The hygroscopicity of atmospheric aerosols significantly influences their size distribution, cloud condensation nuclei ability, atmospheric residence time, and climate forcing. In order to investigate the hygroscopic behavior of aerosol particles and serious haze in China, a Hygroscopic Tandem Differential Mobility Analyzers (HTDMA) system was designed and constructed at Fudan University. It can function as a scanning mobility particle sizing system to measure particle size distribution in the range of 20-1000 nm in diameter, as well as a hygroscopicity analyzer for aerosol particles with diameters between 20-400 nm in the range of 20%-90% RH (relative humidity). It can also measure the effect of uptake of inorganic acids or semi-VOCs on the hygroscopic behavior of aerosols, such as typical inorganic salts in atmospheric dust or their mixtures. The performance tests show that the system measured particle size of the standard polystyrene latex spheres (PSLs) is 197 nm, which is in excellent agreement with the certified diameter D=199±6 nm, as well as a standard deviation of the repeated runs SD=8.9×10-4. In addition, the measured hygroscopic growth factors of the model compounds, (NH 4)2SO4 and NaNO3, agree with the Köhler theoretical curves. The results indicate that the HTDMA system is an excellent and powerful tool for studying the hygroscopic behavior of submicron aerosols and meets the demand required for laboratory research and fieldwork on atmospheric aerosols in China. © 2009 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer Berlin Heidelberg."
"7004697990;26643530600;7101677832;6601976847;","High-spectral-and high-temporal-resolution infrared measurements from geostationary orbit",2009,"10.1175/2009JTECHA1248.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73149090984&doi=10.1175%2f2009JTECHA1248.1&partnerID=40&md5=f3bdcb0b1d9a331cf44931d753bde6e9","The first of the next-generation series of the Geostationary Operational Environmental Satellite (GOES-R) is scheduled for launch in 2015. The new series of GOES will not have an infrared (IR) sounder dedicated to acquiring high-vertical-resolution atmospheric temperature and humidity profiles. High-spectral-resolution sensors have a much greater vertical-resolving power of temperature, moisture, and trace gases than low-spectral-resolution sensors. Because of coarse vertical resolution and limited accuracy in the legacy sounding products from the current GOES sounders, placing a high-spectral-resolution IR sounder with high temporal resolution in the geostationary orbit can provide nearly time-continuous three-dimensional moisture and wind profiles. This would allow substantial improvements in monitoring the mesoscale environment for severe weather forecasting and other applications. Application areas include nowcasting (and short-term forecasts) and numerical weather prediction, which require products such as atmospheric moisture and temperature profiles as well as derived parameters, clear-sky radiances, vertical profiles of atmospheric motion vectors, sea surface temperature, cloud-top properties, and surface properties. Other application areas include trace gases/air quality, dust detection and characterization, climate, and calibration. This paper provides new analysis that further documents the available information regarding the anticipated improvements and their benefits. © 2009 American Meteorological Society."
"55688930000;6701335949;7003591311;","Evaluation of scalar advection schemes in the advanced research WRF model using large-eddy simulations of aerosol-cloud interactions",2009,"10.1175/2009MWR2820.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350303196&doi=10.1175%2f2009MWR2820.1&partnerID=40&md5=b355487dd5b0fd1dc796c2eac5975af3","In the Advanced Research Weather Research and Forecasting Model (ARW), versions 3.0 and earlier, advection of scalars was performed using the Runge-Kutta time-integration scheme with an option of using a positive-definite (PD) flux limiter. Large-eddy simulations of aerosol-cloud interactions using the ARW model are performed to evaluate the advection schemes. The basic Runge-Kutta scheme alone produces spurious oscillations and negative values in scalar mixing ratios because of numerical dispersion errors. The PD flux limiter assures positive definiteness but retains the oscillations with an amplification of local maxima by up to 20% in the tests. These numerical dispersion errors contaminate active scalars directly through the advection process and indirectly through physical and dynamical feedbacks, leading to a misrepresentation of cloud physical and dynamical processes. A monotonic flux limiter is introduced to correct the generally accurate but dispersive solutions given by high-order Runge-Kutta scheme. The monotonic limiter effectively minimizes the dispersion errors with little significant enhancement of numerical diffusion errors. The improvement in scalar advection using the monotonic limiter is discussed in the context of how the different advection schemes impact the quantification of aerosol-cloud interactions. The PD limiter results in 20% (10%) fewer cloud droplets and 22% (5%) smaller cloud albedo than the monotonic limiter under clean (polluted) conditions. Underprediction of cloud droplet number concentration by the PD limiter tends to trigger the early formation of precipitation in the clean case, leading to a potentially large impact on cloud albedo change. © 2009 American Meteorological Society."
"56322590900;","Eastward-propagating undular bores over Cape York Peninsula",2009,"10.1175/2009MWR2833.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350335892&doi=10.1175%2f2009MWR2833.1&partnerID=40&md5=200b5e244a230849d4f238b35040617b","The existence of eastward-propagating bores over Cape York Peninsula is shown from data obtained during the Gulf Lines Experiment (GLEX) conducted during September and October 2002 and from numerical modeling experiments. The disturbances were detected regularly at two stations, observable on 24 days during the 40-day experiment. The passage of a typical disturbance exhibits a sudden increase in pressure of around 1 hPa, often accompanied by undulations, and a change in the wind speed and direction from an easterly to a westerly flow. Disturbances were not observed during days of strong easterly flow. A two-dimensional nonhydrostatic mesoscale model is used to examine the formation of these disturbances. It is shown that the west coast sea breeze is shallow and does not penetrate far inland because of the opposing low-level easterly flow. In contrast, the east coast sea breeze is deeper and is less stable because it is modified by daytime convective mixing as it crosses the peninsula. As the east coast sea breeze overrides the west coast sea breeze, the west coast sea breeze produces an eastward-propagating bore on the stable layer laid down by the east coast sea breeze. About 2 h after generation, the bore becomes undular. These eastward-propagating disturbances are shown to be associated with the westward-propagating north Australian cloud line and the northeasterly morning glory. In addition, it is shown here that an undular bore can be formed when cold-air downdrafts from afternoon deep convection enter the stable layer created by the east coast sea breeze. Four events from GLEX are believed to have been formed in this way. The eastward-propagating disturbances produced in this way are accompanied neither by the north Australian cloud line nor by the northeasterly morning glory. © 2009 American Meteorological Society."
"8670222900;36449278400;7006532784;8618282100;7006471143;","Quantifying the imprint of a severe hector thunderstorm during ACTIVE/SCOUT-O3 onto the water content in the upper troposphere/lower stratosphere",2009,"10.1175/2008MWR2666.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350302279&doi=10.1175%2f2008MWR2666.1&partnerID=40&md5=31d4c1cf7b68eb650b5b73f1e9dd296c","The development of a severe Hector thunderstorm that formed over the Tiwi Islands, north of Australia, during the Aerosol and Chemical Transport in Tropical Convection/Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere (ACTIVE/ SCOUT-O3) field campaign in late 2005, is simulated by the Advanced Research Weather Research and Forecasting (ARW) model and the Met Office Unified Model (UM). The general aim of this paper is to investigate the role of isolated deep convection over the tropics in regulating the water content in the upper troposphere/lower stratosphere (UT/LS). Using a horizontal resolution as fine as 1 km, the numerical simulations reproduce the timing, structure, and strength of Hector fairly well when compared with field campaign observations. The sensitivity of results from ARW to horizontal resolution is investigated by running the model in a large-eddy simulation mode with a horizontal resolution of 250 m. While refining the horizontal resolution to 250 m leads to a better representation of convection with respect to rainfall, the characteristics of the Hector thunderstorm are basically similar in space and time to those obtained in the 1-km-horizontal-resolution simulations. Several overshooting updrafts penetrating the tropopause are produced in the simulations during the mature stage of Hector. The penetration of rising towering cumulus clouds into the LS maintains the entrainment of air at the interface between the UT and the LS. Vertical exchanges resulting from this entrainment process have a significant impact on the redistribution of atmospheric constituents within the UT/ LS region at the scale of the islands. In particular, a large amount of water is injected in the LS. The fate of the ice particles as Hector develops drives the water vapor mixing ratio to saturation by sublimation of the injected ice particles, moistening the air in the LS. The moistening was found to be fairly significant above 380 K and averaged about 0.06 ppmv in the range 380-120 K for ARW. As for UM, the moistening was found to be much larger (about 2.24 ppmv in the range of 380-120 K) than for ARW. This result confirms that convective transport can play an important role in regulating the water vapor mixing ratio in the LS. © 2009 American Meteorological Society."
"7101959253;55843404000;7005626683;","Evaluation of hydrometeor occurrence profiles in the multiscale modeling framework climate model using atmospheric classification",2009,"10.1175/2009JCLI2638.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350023630&doi=10.1175%2f2009JCLI2638.1&partnerID=40&md5=e31b60ce5059b79a479a8cc4b3831134","Vertical profiles of hydrometeor occurrence from the multiscale modeling framework (MMF) climate model are compared with profiles observed by a vertically pointing millimeter wavelength cloud radar (located in the U.S. southern Great Plains) as a function of the large-scale atmospheric state. The atmospheric state is determined by classifying (or clustering) the large-scale (synoptic) fields produced by the MMF and a numerical weather prediction model using a neural network approach. The comparison shows that for coldfrontal and post-cold-frontal conditions theMMF produces profiles of hydrometeor occurrence that compare favorably with radar observations, while for warm-frontal conditions the model tends to produce hydrometeor fractions that are too large with too much cloud (nonprecipitating hydrometeors) above 7 km and too much precipitating hydrometeor coverage below 7 km. It is also found that the MMF has difficulty capturing the formation of low clouds and that, for all atmospheric states that occur during June, July, and August, the MMF produces too much high and thin cloud, especially above 10 km. © 2009 American Meteorological Society."
"26767712900;23082420800;7006354215;7003543851;7006256622;27168081700;","Climate response of the equatorial pacific to global warming",2009,"10.1175/2009JCLI2982.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350026709&doi=10.1175%2f2009JCLI2982.1&partnerID=40&md5=e274a3ef7ccb3d427da9890d36529ffa","The climate response of the equatorial Pacific to increased greenhouse gases is investigated using numerical experiments from 11 climate models participating in the Intergovernmental Panel on Climate Change's Fourth Assessment Report.Multimodelmean climate responses to CO2 doubling are identified and related to changes in the heat budget of the surface layer.Weaker ocean surface currents driven by a slowing down of the Walker circulation reduce ocean dynamical cooling throughout the equatorial Pacific. The combined anomalous ocean dynamical plus radiative heating from CO2 is balanced by different processes in the western and eastern basins: Cloud cover feedbacks and evaporation balance the heating over the warm pool, while increased cooling by ocean vertical heat transport balances the warming over the cold tongue. This increased cooling by vertical ocean heat transport arises from increased near-surface thermal stratification, despite a reduction in vertical velocity. The stratification response is found to be a permanent feature of the equilibrium climate potentially linked to both thermodynamical and dynamical changes within the equatorial Pacific. Briefly stated, ocean dynamical changes act to reduce (enhance) the net heating in the east (west). This explains why the models simulate enhanced equatorial warming, rather than El Niño-like warming, in response to a weaker Walker circulation. To conclude, the implications for detecting these signals in the modern observational record are discussed. © 2009 American Meteorological Society."
"57196143493;56744278700;","Evolution and trend of the outgoing longwave radiation spectrum",2009,"10.1175/2009JCLI2874.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350002161&doi=10.1175%2f2009JCLI2874.1&partnerID=40&md5=d32832673d35c3444465773f0ff13bf0","The variability and change occurring in the outgoing longwave radiation (OLR) spectrum are investigated by using simulations performed with a Geophysical Fluid Dynamics Laboratory coupled atmosphere-ocean-land general circulation model. First, the variability in unforced climate (natural variability) is simulated. Then, the change of OLR spectrum due to forced changes in climate is analyzed for a continuous 25-yr time series and for the difference between two time periods (1860s and 2000s). Spectrally resolved radiances have more pronounced and complex changes than broadband fluxes. In some spectral regions, the radiance change is dominated by just one controlling factor (e.g., the window region and CO2 band center radiances are controlled by surface and stratospheric temperatures, respectively) and well exceeds the natural variability. In some other spectral bands, the radiance change is influenced by multiple and often competing factors (e.g., the water vapor band radiance is influenced by both water vapor concentration and temperature) and, although still detectable against natural variability at certain frequencies, demands stringent requirements (drift less than 0.1 K decade-1 at spectral resolution no less than 1 cm-1) of observational platforms. The difference between clear-sky and all-sky radiances in the forced climate problem offers a measure of the change in the cloud radiative effect, but with a substantive dependence on the temperature lapse rate change. These results demonstrate that accurate and continuous observations of the OLR spectrum provide an advantageous means for monitoring the changes in the climate system and a stringent means for validating climate models. © 2009 American Meteorological Society."
"16403070500;25647939800;7401945370;6602908667;7601492669;","Diurnal cycle of precipitation in the tropics simulated in a global cloud-resolving model",2009,"10.1175/2009JCLI2890.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68949138948&doi=10.1175%2f2009JCLI2890.1&partnerID=40&md5=acd8504dc71545b92a0f71d2e3726931","This study analyzes the diurnal cycle of precipitation simulated in a global cloud-resolving model (GCRM) named the Nonhydrostatic Icosahedral Atmospheric Model (NICAM). A 30-day integration of NICAM successfully simulates the precipitation diurnal cycle associated with the land-sea breeze and the thermally induced topographic circulations as well as the horizontal propagation of diurnal cycle signals. The first harmonic of the diurnal cycle of precipitation in the 7-km run agrees well with that from satellite observations in its geographical distributions although its amplitude is slightly overestimated. The NICAM simulation revealed that the precipitation diurnal cycle over the Maritime Continent is strongly coupled with the land-sea breeze that controls the convergence/ divergence pattern in the lower troposphere around the islands. The analysis also suggests that the cold pool often forms over the open ocean where the precipitation intensity is high, and the propagation of the cold pool events is related to the precipitation diurnal cycle as well as the land-sea breeze. Sensitivity experiments suggest a prominent horizontal resolution dependence of the simulated precipitation diurnal cycle. Over continental areas the 14-km run induces the diurnal peak about three hours later than the 7-km run. The 3.5-km run produces the peak time and amplitude that are very similar to those in Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) observations. Meanwhile, the resolution dependence in phase and amplitude is negligibly small over the open oceans. This contrast sensitivity to the horizontal resolution is attributed to the differences in structure and life cycle of convective systems over land and ocean. Diurnal peaks of precipitable water vapor, precipitation, and outgoing longwave radiation (OLR) are compared over land areas using the NICAM 7-km run. The daily precipitable water vapor maximum appears around 1500 local time (LT), which is followed by the precipitation peak around 1630 LT. The diurnal cycle of high clouds tends to peak around 1930 LT, three hours later than the precipitation peak. These results from NICAM simulations can explain the cause of the phase differences among precipitation products based on several satellite observations. The authors demonstrate that the GCRM is a promising tool for realistically simulating the precipitation diurnal cycle and could be quite useful for studying the role of the diurnal cycle in the climate systems in a global context. © 2009 American Meteorological Society."
"8683331200;7005246023;56253852700;55399842300;6602922582;57203260074;","Hot European summers and the role of soil moisture in the propagation of mediterranean drought",2009,"10.1175/2009JCLI2568.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350025014&doi=10.1175%2f2009JCLI2568.1&partnerID=40&md5=0ec980947ad077f0cda1d50e994f3580","Drought in spring and early summer has been shown to precede anomalous hot summer temperature. In particular, drought in the Mediterranean region has been recently shown to precede and to contribute to the development of extreme heat in continental Europe. In this paper, this mechanism is investigated by performing integrations of a regional mesoscale model at the scale of the European continent in order to reproduce hot summer inception, starting with different initial values of soil moisture south of 46°N. The mesoscale model is driven by the large-scale atmospheric conditions corresponding to the 10 hottest summers on record from the European Climate Assessment dataset. A northward progression of heat and drought from late spring to summer is observed from the Mediterranean regions, which leads to a further increase of temperature during summer in temperate continental Europe. Dry air formed over dry soils in the Mediterranean region induces less convection and diminished cloudiness, which gets transported northward by occasional southerly wind, increasing northward temperature and vegetation evaporative demand. Later in the season, drier soils have been established in western and central Europe where they further amplify the warming through two main feedback mechanisms: 1) higher sensible heat emissions and 2) favored upper-air anticyclonic circulation. Drier soils in southern Europe accelerate the northward propagation of heat and drying, increasing the probability of strong heat wave episodes in the middle or the end of the summer. © 2009 American Meteorological Society."
"7005350396;7103033590;","A model investigation of the role of air-sea interaction in the climatological evolution and ENSO-related variability of the summer monsoon over the South China Sea and Western North Pacific",2009,"10.1175/2009JCLI2758.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350005243&doi=10.1175%2f2009JCLI2758.1&partnerID=40&md5=a0a6b5adaecf3f1b7e8314926a2b8546","The summertime northeastward march of the climatological maritime monsoon over the South China Sea (SCS) and subtropical western North Pacific (WNP) is examined using the output from a 200-yr integration of a coupled atmosphere-ocean general circulation model (GCM). Increased cloud cover and surface wind speed during monsoon onset over the SCS in May-June reduce the incoming shortwave flux and enhance the upward latent heat flux at the ocean surface, thereby cooling the local sea surface temperature (SST). The resulting east-west gradient in the SST pattern, with lower temperature in the SCS and higher temperature in the WNP, is conducive to eastward migration of the monsoon precipitation over this region. Upon arrival of the precipitation center in the WNP in July-August, the local circulation changes lead to weakening of the mei-yu-baiu rainband near 30°N. The subsequent increases in local shortwave flux and SST impart a northward tendency to the evolution of the WNP monsoon. Many of these model inferences are supported by a parallel analysis of various observational datasets. The modulation of the above climatological scenario by El Niño-Southern Oscillation (ENSO) events is investigated by diagnosing the output from the coupled GCM and from experiments based on the atmospheric component of this GCM with SST forcings being prescribed separately in the equatorial Pacific, Indian Ocean, and SCS/WNP domains. During the May period after the peak phase of ENSO, the simulated monsoon onset over the SCS occurs later (earlier) than normal in El Niño (La Niña) events. These changes are primarily remote responses to the anomalous SST forcing in the equatorial Pacific and Indian Ocean. The ENSO-related changes in the SCS/WNP are associated with above-normal (below normal) mei-yu-baiu activity during warm (cold) events. In the ensuing July period of the warm events, the simulated precipitation response over the SCS to the local warm SST anomaly tends to oppose the remote response to SST forcing in the northern Indian Ocean. In the July period of cold events, the equatorial Pacific SST anomaly retains its strength and moves still farther westward. This forcing cooperates with the cold SST anomaly in the SCS in influencing the precipitation pattern in the SCS/WNP sector."
"35095470500;7007181954;6603875926;23987220000;","Impact of greenhouse gas concentration changes on surface energetics in IPSL-CM4: Regional warming patterns, land-sea warming ratios, and glacial-interglacial differences",2009,"10.1175/2009JCLI2771.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350025597&doi=10.1175%2f2009JCLI2771.1&partnerID=40&md5=a47943a4e5f99cc7ad11f9009b60fd37","The temperature response to a greenhouse gas (GHG) concentration change is studied in an ocean-atmosphere coupled model - L'Institut Pierre-Simon Laplace Coupled Model, version 4 (IPSL-CM4) - for both a glacial and an interglacial context. The response to a GHG concentration changing from Last Glacial Maximum (LGM) to preindustrial values is similar for both climatic contexts in terms of temperature pattern, but the magnitude is greater under modern ones. The model simulates the classical amplification of the temperature response in the northern high latitudes compared to lower latitudes and over the land surfaces compared to the ocean. The physical reasons for the differential warming according to the latitude and to the surface type are studied through an analysis of the energy flux changes, which are decomposed to consider and quantify many different physical processes. The results highlight the role of many different factors in the thermal response to a GHG forcing for different regions, and stress, for instance, the large effect of increased water vapor concentration in the atmosphere. Concerning the land-sea warming ratio, several fluxes contribute to the final value of the ratio, with latent flux having the greatest influence. The different contributions are quantified. The comparison of the flux changes between the interglacial and glacial contexts shows that the differences are more than a simple effect of different surface emissions of the base state. It suggests that the climatic context is particularly important for the cloud and oceanic advection responses to the forcing, along with albedo effects. © 2009 American Meteorological Society."
"36787519500;8554472500;55939363100;6507355875;","Rainfall variability over mountainous and adjacent lake areas: The case of Lake Tana basin at the source of the Blue Nile River",2009,"10.1175/2009JAMC2092.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349661995&doi=10.1175%2f2009JAMC2092.1&partnerID=40&md5=f22dd61134503b4e3d4f5f25f00d4615","The water resource of the Blue Nile River is of key regional importance to the northeastern African countries. However, little is known about the characteristics of the rainfall in the basin. In this paper, the authors presented the space-time variability of the rainfall in the vicinity of Lake Tana, which is the source of the Blue Nile River. The analysis was based on hourly rainfall data from a network of newly installed rain gauges, and cloud temperature indices from the Meteosat Second Generation (MSG-2) Spinning Enhanced Visible and Infrared Imager (SEVIRI) satellite sensor. The spatial and temporal patterns of rainfall were examined using not only statistical techniques such as exceedance probabilities, spatial correlation structure, harmonic analysis, and fractal analysis but also marginal statistics such as mean and standard deviation. In addition, a convective index was calculated from remote sensing images to infer the spatial and temporal patterns of rainfall. Heavy rainfall is frequent at stations that are relatively close to the lake. The correlation distances for the hourly and the daily rainfall are found at about 8 and 18 km, respectively. The rainfall shows a strong spatially varying diurnal cycle. The nocturnal rainfall was found to be higher over the southern shore of Lake Tana than over the mountainous area farther to the south. The maximum convection occurs between 1600 and 1700 local standard time (LST) over the Gilgel Abbay, Ribb, and Gumara catchments, and between 2200 and 2300 LST over Lake Tana and the Megech catchments. In addition, the hourly rainfall of the station with the highest elevation is relatively closely clustered as compared to those stations at lower elevation. The study provides relevant information for understanding rainfall variation with elevation and distance from a lake. This understanding benefits climate and hydrological studies, water resources management, and energy development in the region. © 2009 American Meteorological Society."
"20433349200;24339189300;","Peculiarities of climatic changes in cloud cover over the Russian Federation",2009,"10.3103/S1068373909070012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349588344&doi=10.3103%2fS1068373909070012&partnerID=40&md5=3cdff6c6b33d3616ae6160eb44c02fc1","Modern climatic changes in cloud cover over Russia are analyzed from standard ground-based meteorological observations in 1951-2000 and information on cloudiness obtained from the actinometrical observations in 1976-2000. In addition to studies of changes in total cloud amount, a special attention is paid to the distribution of basic forms of cloudiness with respect to their frequency. A spatial generalization of the results for large-scale regions (the European and Asian parts of Russia) allowed revealing dominant tendencies in cloud cover changes that are slightly related to seasons of year and reflect large-scale changes in cloud characteristics in the second half of the 20th century. © Allerton Press, Inc. 2009."
"16313088100;7102797196;","An algorithm to screen cloud-affected data for sky radiometer data analysis",2009,"10.2151/jmsj.87.189","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349588070&doi=10.2151%2fjmsj.87.189&partnerID=40&md5=976d05ce8bfde21b0230c6361736af09","Aerosol optical parameters obtained from sky radiometer instrument are important not only for studying aerosol effects on climate change, but also for validating several results obtained from satellite retrievals and numerical simulations. However, the greatest challenge is to separate cloud-affected and cloud free data from data measured by sky radiometer. In this study, we present an algorithm to separate such cloud-affected and cloud free data. The proposed algorithm is comprehensively tested with observational data. The algorithm consists of three tests: (i) test with global irradiance data, (ii) spectral variability test, and (iii) statistical analyses test. Though the test with the global irradiance data is the most powerful test, our study shows that it has some limitations, which can sometimes cause some clear sky data to be detected as cloud-affected data. In order to cope with this problem, a modified version of spectral variability algorithm is proposed. As the second test, the modified spectral variability algorithm is applied to filter clear sky data from data detected as cloud-affected by the first test. Finally, statistical analyses tests are performed to remove any outlier, if exists, from clear sky data detected by the first and second tests. It is shown that our proposed algorithm can screen cloud-affected data more effectively in comparison to other cloud screening algorithms. An application of this algorithm to screen observation data of one year collected in Chiba, Japan produces the seasonal means of optical thickness at 500 nm (Angstrom exponent) as ~0.17(~1.42), ~0.38(~0.98), ~0.53(~1.21), and ~0.21(~1.28) for winter, spring, summer and autumn seasons, respectively. Depending on the season, the initial seasonal mean optical thicknesses at 500 nm decrease by ~0.07 to ~0.16 and mean Angstrom exponents increase by ~0.087 to ~0.162 due to cloud screening. An application of this algorithm to dust-loaded atmospheres is also discussed. The proposed algorithm can be applied to any sky radiometer observation site as long as global irradiance data are available. © 2009, Meteorological Society of Japan."
"6701802669;6603571570;7404250633;7003871110;7402287546;7003796684;8791306500;7004169476;","Antarctic winter tropospheric warming - the potential role of polar stratospheric clouds, a sensitivity study",2009,"10.1002/asl.237","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72449154393&doi=10.1002%2fasl.237&partnerID=40&md5=60be24512df8837c324fff7dc3ba353b","Over the last 30 years, Antarctic mid-tropospheric temperatures in winter have increased by 0.5 K per decade, the largest regional tropospheric warming observed. Over this period, amounts of polar stratospheric cloud(PSC) have also increased, as rising CO2 concentrations cooled the stratosphere. By imposing an idealisation of these increases in PSC within the radiation scheme of an atmosphere-only general circulation model, we find that they could have contributed to the observed warming. The present generation of global climate models do not properly represent PSCs, and so these results demonstrate the need to improve the representation of PSCs. © 2009 Royal Meteorological Society and Crown Copyright."
"55977336000;16637291100;7501855361;","Influence of changes in sea ice concentration and cloud cover on recent Arctic surface temperature trends",2009,"10.1029/2009GL040708","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149089005&doi=10.1029%2f2009GL040708&partnerID=40&md5=b2b82a6fef85a86b052d1591fcd0a0a5","The influence of trends in sea ice concentration (SIC) and cloud cover on trends in surface temperature over the Arctic Ocean from 1982 to 2004 is investigated analytically, and evaluated empirically with satellite products. The results demonstrate that changes in SIC and cloud cover played major roles in the magnitude of recent Arctic surface temperature trends. Significant surface warming associated with sea ice loss, over 0.9 K decade-1, is found over the Chukchi and Beaufort Seas in autumn, accounting for most of the observed 1.1 K decade-1 warming trend. If the mean SIC over the Arctic Ocean in each season is reduced by half, our analysis shows that the surface temperature will increase by approximately 10 K in winter and 6 K in spring and autumn. In winter, surface temperature trends associated with changes in cloud cover are negative over most of the Arctic Ocean, and with cloud cover trends explaining -0.91 out of -1.2 K decade-1 of the surface temperature cooling. In spring, 0.55 K decade-1 of the total 1.0 K decade-1 warming can be attributed to the trend associated with cloud cover changes. After eliminating the effects of changes in SIC and cloud cover on surface temperature trends, the residual surface temperature trends can be used in a more robust diagnosis of surface warming or cooling in the Arctic. The same procedure can be applied to study the impact of changes in sea ice thickness, ocean inflow, and other parameters on the temperature trends, and to completely different sets of climate variables, whether they are measured or modeled. Copyright 2009 by the American Geophysical Union."
"7003668116;","A 2 year comparison of AMSR-E and MODIS cloud liquid water path observations",2009,"10.1029/2009GL040394","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149118201&doi=10.1029%2f2009GL040394&partnerID=40&md5=317726ab49e22161ebe46e38e88b4407","An extensive comparison of cloud liquid water path (LWP) observations from solar reflectance and passive microwave satellite measurements over the global oceans is presented. Two years of MODerate resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer-EOS (AMSR-E) LWP observations were collocated at full resolution and compared under special conditions to minimize errors, i.e., overcast, low-level liquid clouds with no detectable precipitation. Best agreement occurred in stratus regions off the west coasts of North/South America, southern Africa, and Australia. Large differences found in the winter hemispheres at higher latitudes were caused by a strong dependence of MODIS optical depth retrievals on solar zenith angle. Other differences, notably in the tropics and parts of the subtropics, were due to a dependence of AMSR-E LWP observations on surface wind speed and total precipitable water. Results highlight the need to provide more accurate cloud LWP observations for climate studies and model verification. Copyright 2009 by the American Geophysical Union."
"26021924800;6701773156;7003467276;8943391800;","Global surface cooling: The atmospheric fast feedback response to a collapse of the thermohaline circulation",2009,"10.1029/2009GL040938","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149129762&doi=10.1029%2f2009GL040938&partnerID=40&md5=c7f7ea2d0feb956875e86bd61cf3b1f4","In the ECHAM5/MPI-OM model a collapse of the Atlantic thermohaline circulation results in a global surface cooling of 0.72 K. The mechanisms that are responsible for this cooling are investigated. Additional experiments were performed with a one-dimensional radiative convective model in which anomalies from the climate model were prescribed. Fast atmospheric feedbacks are essential to maintain and strengthen the global surface cooling caused by a THC collapse. Reduced downward long wave radiation exceeds the decreased upward long wave radiation. This decreased downward long wave radiation is caused by reduced water vapor content rather than by ice-albedo feedbacks. Also, the decrease in water vapor is much stronger than suggested by the water vapor feedback expected from the simulated albedo change. The large decrease in water vapor is the main feedback. On the regional scale, changes in cloud water and cloud radiative forcing further modify the surface cooling. Copyright 2009 by the American Geophysical Union."
"55628589750;16024614000;35321997000;7401491382;","European climatology of fog and low stratus based on geostationary satellite observations",2009,"10.1002/qj.503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74849084094&doi=10.1002%2fqj.503&partnerID=40&md5=82b021dd34d676b3be081860e771a25d","The distribution of fog and low stratus (FLS) is of importance in nowcasting, aviation forecasting and climate applications. This paper presents satellite-derived FLS maps as a basis for building a European FLS climatology with high spatial and temporal resolution. Averaged maps covering several winter seasons of Meteosat Second Generation (MSG) data are analysed and compared to a cloud climatology based on a 26-year record of ground-based visual cloud observations. The general patterns seen in both products are found to be in good agreement and plausible. © 2009 Royal Meteorological Society."
"55220976100;7501720647;","Interannual variability of the upper ocean in the Southeast Pacific stratus cloud region",2009,"10.1175/2009JCLI2696.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76649136941&doi=10.1175%2f2009JCLI2696.1&partnerID=40&md5=c08a2aaadbdee500d3db2cbfc95529a7","Persistent stratus/stratocumulus cloud decks in the southeast Pacific near the coasts of Peru and northern Chile play an important role in regional and global climate variability. Interannual variability of the upper ocean under stratus cloud decks in the southeast Pacific is investigated using ocean general circulation model (OGCM) experiments. The model was first forced with daily surface fluxes based on the NCEP-NCAR reanalysis and satellite-derived surface shortwave and longwave radiation for the period of 1979-2004. Gridded surface heat flux estimates used in the model integration agree well with those based on Woods Hole Oceanographic Institution (WHOI) Improved Meteorology (IMET) buoy measurements at 20°S, 85°W. Also, the OGCM is able to reproduce well the observed interannual SST and sea surface height variations in this region. The results suggest that the interannual variation of the upper ocean north of 20°S is mostly associated with ENSO variability. Additional model experiments were conducted to examine the relative importance of ocean dynamics and surface heat fluxes in determining the interannual variation in SST. The results of these experiments indicate that upper-ocean dynamics play a dominant role in controlling the interannual variation of SST north of 20°S in the stratus cloud region. The upper-ocean heat budget analysis shows that meridional heat advection associated with ENSO events primarily controls the interannual SST variation in the stratus cloud region north of 20°S. © 2009 American Meteorological Society."
"11939918300;57198857563;7004479957;7003748648;","The soil moisture-precipitation feedback in simulations with explicit and parameterized convection",2009,"10.1175/2009JCLI2604.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70849097380&doi=10.1175%2f2009JCLI2604.1&partnerID=40&md5=5914ff7290eef235d3f46d34e36ee1b0","Moist convection is a key aspect of the extratropical summer climate and strongly affects the delicate balance of processes that determines the surface climate in response to larger-scale forcings. Previous studies using parameterized convection have found that the feedback between soil moisture and precipitation is predominantly positive (more precipitation over wet soils) over Europe. Here this feedback is investigated for one full month (July 2006) over the Alpine region using two different model configurations. The first one employs regional climate simulations performed with the Consortium for Small-Scale Modeling Model in Climate Mode (CCLM) on a grid spacing of 25 km. The second one uses the same model but integrated on a cloud-resolving grid of 2.2 km, allowing an explicit treatment of convection. Each configuration comprises one control and two sensitivity experiments. The latter start from perturbed soil moisture initial conditions. Comparison of the simulated soil moisture-precipitation feedback reveals significant differences between the two systems. The 25-km simulations sustain a strong positive feedback, while those at 2.2-km resolution are associated with a predominantly negative feedback. Thus the two systems yield not only different strengths of this key feedback but also different signs. This has important implications, with the cloudresolving model exhibiting a shorter soil moisture memory and a smaller soil moisture-temperature feedback. Analysis shows that the different feedback signs relate to the sensitivity of the simulated convective development to the presence of a stable layer sitting on top of the planetary boundary layer. In the 2.2-km integrations, dry initial soil moisture conditions yield more vigorous thermals (owing to stronger daytime heating), which can more easily break through the stable air barrier, thereby leading to deep convection and ultimately to a negative soil moisture-precipitation feedback loop. In the 25-km integrations, deep convection is much less sensitive to the stable layer because of the design of the employed convective parameterization. The authors also show that there are considerable differences in the simulated soil moisture-precipitation feedback between low-resolution modeling frameworks using different cloud convection schemes. © 2009 American Meteorological Society."
"7004940109;6507462423;6506754178;6507187685;","Possible dependence between the total solar irradiance and dimethylsulphide",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350136269&partnerID=40&md5=b72660e0974da09158f0edf5d492af07","Solar variability is one of the main natural influences on the Earth's climate. Biological processes are profoundly affected by the solar irradiance. Some of these processes have been proposed to change the cloud albedo and therefore impact the climate. Here we investigate the relation between the total solar irradiance (TSI) and the global concentration of Dimethylsulphide (DMS), produced by plancktonic algae in seawater. DMS has been frequently mentioned as a forcing of climate through its effect on clouds and therefore on albedo. In the present work we attempt to find the relation between TSI and DMS. We found that the TSI and the DMS production data series display a correlation. A probabilistic scheme is introduced, the Mutual Information Function (MIF) which is a measure of the dependence between the parameters of interest. The MIF seems to present solar cycle dependence: larger values during lower solar activity times (lower TSI times) than during higher solar activity epochs (higher TSI epochs). Or in other words, the dependence between TSI and DMS is stronger during lower solar activity times than during higher solar activity epochs."
"7403409903;55887784200;35412263600;7402397262;56284443600;7101950057;","Coupled climate simulation by constraining ocean fields in a coupled model with ocean data",2009,"10.1175/2009JCLI2814.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76649083262&doi=10.1175%2f2009JCLI2814.1&partnerID=40&md5=da33471442cedd83f1990c5142612c22","The authors developed a system for simulating climate variation by constraining the ocean component of a coupled atmosphere-ocean general circulation model (CGCM) through ocean data assimilation and conducted a climate simulation [Multivariate Ocean Variational Estimation System-Coupled Version Reanalysis (MOVE-C RA)]. The monthly variation of sea surface temperature (SST) is reasonably recovered in MOVE-C RA. Furthermore, MOVE-C RA has improved precipitation fields over the Atmospheric Model Intercomparison Project (AMIP) run (a simulation of the atmosphere model forced by observed daily SST) and the CGCM free simulation run. In particular, precipitation in the Philippine Sea in summer is improved over the AMIP run. This improvement is assumed to stem from the reproduction of the interaction between SST and precipitation, indicated by the lag of the precipitation change behind SST. Enhanced (suppressed) convection tends to induce an SST drop (rise) because of cloud cover and ocean mixing in the real world. A lack of this interaction in the AMIP run leads to overestimating the precipitation in the Bay of Bengal in summer. Because it is recovered in MOVE-C RA, the overestimate is suppressed. This intensifies the zonal Walker circulation and the monsoon trough, resulting in enhanced convection in the Philippine Sea. The spurious positive correlation between SST and precipitation around the Philippines in the AMIP run in summer is also removed in MOVE-C RA. These improvements demonstrate the effectiveness of simulating ocean interior processes with the ocean model and data assimilation for reproducing the climate variability. © 2009 American Meteorological Society."
"57203049177;56726831200;9536987500;6602135031;","Quantifying carbon cycle feedbacks",2009,"10.1175/2009JCLI2949.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350006360&doi=10.1175%2f2009JCLI2949.1&partnerID=40&md5=d85e5c15118d2194e65c4c53db9bbcc4","Perturbations to the carbon cycle could constitute large feedbacks on future changes in atmospheric CO2 concentration and climate. This paper demonstrates how carbon cycle feedback can be expressed in formally similar ways to climate feedback, and thus compares their magnitudes. The carbon cycle gives rise to two climate feedback terms: the concentration-carbon feedback, resulting from the uptake of carbon by land and ocean as a biogeochemical response to the atmospheric CO2 concentration, and the climate-carbon feedback, resulting from the effect of climate change on carbon fluxes. In the earth system models of the Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP), climate-carbon feedback on warming is positive and of a similar size to the cloud feedback. The concentration-carbon feedback is negative; it has generally received less attention in the literature, but in magnitude it is 4 times larger than the climate-carbon feedback and more uncertain. The concentration-carbon feedback is the dominant uncertainty in the allowable CO2 emissions that are consistent with a given CO2 concentration scenario. In modeling the climate response to a scenario of CO2 emissions, the net carbon cycle feedback is of comparable size and uncertainty to the noncarbon-climate response. To quantify simulated carbon cycle feedbacks satisfactorily, a radiatively coupled experiment is needed, in addition to the fully coupled and biogeochemically coupled experiments, which are referred to as coupled and uncoupled in C4MIP. The concentration-carbon and climate-carbon feedbacks do not combine linearly, and the concentration-carbon feedback is dependent on scenario and time. © 2009 American Meteorological Society."
"26323066900;6602080205;8633784600;8633783900;","Changes in the global sulfate burden due to perturbations in global CO2 concentrations",2009,"10.1175/2009JCLI2536.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76649133772&doi=10.1175%2f2009JCLI2536.1&partnerID=40&md5=1d44d2d524061b640f33a1ee40eaf764","A large ensemble of general circulation model (GCM) integrations coupled to a fully interactive sulfur cycle scheme were run on the climateprediction.net platform to investigate the uncertainty in the climate response to sulfate aerosol and carbon dioxide (CO2) forcing. The sulfate burden within the model (and the atmosphere) depends on the balance between formation processes and deposition (wet and dry). The wet removal processes for sulfate aerosol are much faster than dry removal and so any changes in atmospheric circulation, cloud cover, and precipitation will feed back on the sulfate burden. When CO2 is doubled in the Hadley Centre Slab Ocean Model (HadSM3), global mean precipitation increased by 5%; however, the global mean sulfate burden increased by 10%. Despite the global mean increase in precipitation, there were large areas of the model showing decreases in precipitation (and cloud cover) in the Northern Hemisphere during June-August, which reduced wet deposition and allowed the sulfate burden to increase. Further experiments were also undertaken with and without doubling CO2 while including a future anthropogenic sulfur emissions scenario. Doubling CO2 further enhanced the increases in sulfate burden associated with increased anthropogenic sulfur emissions as observed in the doubled CO2-only experiment. The implications are that the climate response to doubling CO2 can influence the amount of sulfate within the atmosphere and, despite increases in global mean precipitation, may act to increase it. © 2009 American Meteorological Society."
"7201862239;7004166136;7406683894;7202016984;7005420497;7201736677;7501502356;7004678728;35746906700;7404514776;7003865921;","Calipso lidar calibration algorithms. Part I: Nighttime 532-nm parallel channel and 532-nm perpendicular channel",2009,"10.1175/2009JTECHA1242.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349136700&doi=10.1175%2f2009JTECHA1242.1&partnerID=40&md5=15343e5e9fa58014f2555405282b4839","The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission was launched in April 2006 and has continuously acquired collocated multisensor observations of the spatial and optical properties of clouds and aerosols in the earth's atmosphere. The primary payload aboard CALIPSO is the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), which makes range-resolved measurements of elastic backscatter at 532 and 1064 nm and linear depolarization ratios at 532 nm. CALIOP measurements are important in reducing uncertainties that currently limit understanding of the global climate system, and it is essential that these measurements be accurately calibrated. This work describes the procedures used to calibrate the 532-nm measurements acquired during the nighttime portions of the CALIPSO orbits. Accurate nighttime calibration of the 532-nm parallel-channel data is fundamental to the success of the CALIOP measurement scheme, because the nighttime calibration is used to infer calibration across the day side of the orbits and all other channels are calibrated relative to the 532-nm parallel channel. The theoretical basis of the molecular normalization technique as applied to space-based lidar measurements is reviewed, and a comprehensive overview of the calibration algorithm implementation is provided. Also included is a description of a data filtering procedure that detects and removes spurious high-energy events that would otherwise introduce large errors into the calibration. Error estimates are derived and comparisons are made to validation data acquired by the NASA airborne high-spectral resolution lidar. Similar analyses are also presented for the 532-nm perpendicular-channel calibration technique. © 2009 American Meteorological Society."
"55537426400;7003922138;","On the link between Hadley circulation changes and radiative feedback processes",2009,"10.1029/2009GL040488","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149087440&doi=10.1029%2f2009GL040488&partnerID=40&md5=69ed2141fddffba8ec06f7ada089404d","Previous studies have demonstrated that meridional displacements of precipitation in the tropics and changes in the Hadley circulation accompany interhemispherically asymmetric surface temperature changes. In this study, an attempt is made to provide a different perspective by linking this dynamical response to radiative feedback processes. An idealized experiment is conducted in which solar irradiance is reduced in the northern hemisphere extratropics. Radiative feedback analysis indicates that the interhemispheric asymmetry of water vapor and lapse rate feedbacks play a key role in maintaining the simulated cross-equatorial heat transport and Hadley circulation change. On the other hand, cloud feedback plays a relatively minor role because of a large cancellation between shortwave and longwave components. While the experiment is idealized, the implications of the results apply widely from paleoclimate to future climate changes. Copyright 2009 by the American Geophysical Union."
"7202016984;7201862239;7005420497;7404514776;7003865921;7004166136;7201736677;7406683894;35547214900;35319507500;","Fully automated detection of cloud and aerosol layers in the CALIPSO lidar measurements",2009,"10.1175/2009JTECHA1228.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349091460&doi=10.1175%2f2009JTECHA1228.1&partnerID=40&md5=97fdf396b0dece6e0b6f9bdb3dbb6fe5","Accurate knowledge of the vertical and horizontal extent of clouds and aerosols in the earth's atmosphere is critical in assessing the planet's radiation budget and for advancing human understanding of climate change issues. To retrieve this fundamental information from the elastic backscatter lidar data acquired during the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, a selective, iterated boundary location (SIBYL) algorithm has been developed and deployed. SIBYL accomplishes its goals by integrating an adaptive context-sensitive profile scanner into an iterated multiresolution spatial averaging scheme. This paper provides an in-depth overview of the architecture and performance of the SIBYL algorithm. It begins with a brief review of the theory of target detection in noise-contaminated signals, and an enumeration of the practical constraints levied on the retrieval scheme by the design of the lidar hardware, the geometry of a space-based remote sensing platform, and the spatial variability of the measurement targets. Detailed descriptions are then provided for both the adaptive threshold algorithmused to detect features of interest within individual lidar profiles and the fully automated multiresolution averaging engine within which this profile scanner functions. The resulting fusion of profile scanner and averaging engine is specifically designed to optimize the trade-offs between the widely varying signal-to-noise ratio of the measurements and the disparate spatial resolutions of the detection targets. Throughout the paper, specific algorithm performance details are illustrated using examples drawn from the existing CALIPSO dataset. Overall performance is established by comparisons to existing layer height distributions obtained by other airborne and space-based lidars. © 2009 American Meteorological Society."
"26436423000;56702490400;7006563002;","Modelling canopy conductance under wet and dry conditions in a subtropical cloud forest",2009,"10.1016/j.agrformet.2009.03.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67949097334&doi=10.1016%2fj.agrformet.2009.03.008&partnerID=40&md5=301837f605a242ec5a1b1f92e013922c","Canopy conductance (gc) in a ridge-top cloud forest in the Garajonay National Park on La Gomera (Canary Islands) was derived by using the Jarvis-Stewart multiplicative algorithm and validated by inverting the Penman-Monteith equation using measured sap-flow data for the two main species, Myrica faya (beech) and Erica arborea (tree-heath). Canopy conductance correlated well with global radiation and vapour pressure deficit, and the multiplicative algorithm reproduced the daytime and seasonal course of gc satisfactorily using only these two factors under moderate and high evaporative conditions. There was no significant relation between soil moisture content in the first 0.3 m and gc, even though topsoil moisture reached very low values in summer, suggesting the roots had access to water at deeper levels. © 2009 Elsevier B.V. All rights reserved."
"6602273584;36842807800;6701362371;7005196173;26654999200;7003553425;","Evolution of supra-glacial lakes across the Greenland Ice Sheet",2009,"10.1016/j.rse.2009.05.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67849124156&doi=10.1016%2fj.rse.2009.05.018&partnerID=40&md5=dd55d0526cf65fce3ffc744ec5b4292f","We used 268 cloud-free Moderate-resolution Imaging Spectroradiometer (MODIS) images from 2003 and 2005-2007 to study the seasonal evolution of supra-glacial lakes in three different regions of the Greenland Ice Sheet. Lake area estimates were obtained by developing an automated classification method for their identification based on 250 m resolution MODIS surface reflectance observations. Widespread supra-glacial lake formation and drainage is observed across the ice sheet, with a 2-3 week delay in the evolution of total supra-glacial lake area in the northern areas compared to the south-west. The onset of lake growth varies by up to one month inter-annually, and lakes form and drain at progressively higher altitudes during the melt season. A positive correlation was found between the annual peak in total lake area and modelled annual runoff. High runoff and lake extent years are generally characterised by low accumulation and high melt season temperatures, and vice versa. Our results indicate that, in a future warmer climate [Meehl, G. A., Stocker, T. F., Collins W. D., Friedlingstein, P., Gaye, A. T., Gregory, J. M., Kitoh, A., Knutti, R., Murphy, J. M., Noda, A., Raper, S. C. B., Watterson, I. G., Weaver, A. J. & Zhao, Z. C. (2007). Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor & H. L. Miller (eds.), Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.], Greenland supra-glacial lakes can be expected to form at higher altitudes and over a longer time period than is presently the case, expanding the area and time period over which connections between the ice sheet surface and base may be established [Das, S., Joughin, M., Behn, M., Howat, I., King, M., Lizarralde, D., & Bhatia, M. (2008). Fracture propagation to the base of the Greenland Ice Sheet during supra-glacial lake drainage. Science, 5877, 778-781] with potential consequences for ice sheet discharge [Zwally, H.J., Abdalati, W., Herring, T., Larson, K., Saba, J. & Steffen, K. (2002). Surface melt-induced acceleration of Greenland Ice Sheet flow. Science, 297, 218-221.]. © 2009 Elsevier Inc. All rights reserved."
"36105786800;7401526171;7005052907;24081550100;6507229952;57189710110;","Bias adjustment of satellite precipitation estimation using ground-based measurement: A case study evaluation over the southwestern United States",2009,"10.1175/2009JHM1099.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952589110&doi=10.1175%2f2009JHM1099.1&partnerID=40&md5=d8c748c7a519bf9d719a8991c46cf7b4","Reliable precipitation measurement is a crucial component in hydrologic studies. Although satellite-based observation is able to provide spatial and temporal distribution of precipitation, the measurements tend to show systematic bias. This paper introduces a grid-based precipitation merging procedure in which satellite estimates from the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS) are adjusted based on the Climate Prediction Center (CPC) daily rain gauge analysis. To remove the bias, the hourly CCS estimates were spatially and temporally accumulated to the daily 1°×1° scale, the resolution of CPC rain gauge analysis. The daily CCS bias was then downscaled to the hourly temporal scale to correct hourly CCS estimates. The bias corrected CCS estimates are called the adjusted CCS (CCSA) product. With the adjustment from the gauge measurement, CCSA data have been generated to provide more reliable high temporal/spatial-resolution precipitation estimates. In the case study, the CCSA precipitation estimates from the proposed approach are compared against ground-based measurements in high-density gauge networks located in the southwestern United States. © 2009 American Meteorological Society."
"35577097300;15846270900;8836278700;6701689811;","Spatial and vertical heterogeneities in aerosol properties over oceanic regions around india: Implications for radiative forcing",2009,"10.1002/qj.525","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74849139258&doi=10.1002%2fqj.525&partnerID=40&md5=ddd5ad0f946857184b78b27903566bd9","The influence of atmospheric aerosols on Earth's radiation budget and hence climate, though well recognized and extensively investigated in recent years, remains largely uncertain mainly because of the large spatio-temporal heterogeneity and the lack of data with adequate resolution. To characterize this diversity, a major multi-platform field campaign ICARB (Integrated Campaign for Aerosols, gases and Radiation Budget) was carried out during the pre-monsoon period of 2006 over the Indian landmass and surrounding oceans, which was the biggest such campaign ever conducted over this region. Based on the extensive and concurrent measurements of the optical and physical properties of atmospheric aerosols during ICARB, the spatial distribution of aerosol radiative forcing was estimated over the entire Bay of Bengal (BoB), northern Indian Ocean and Arabian Sea (AS) as well as large spatial variations within these regions. Besides being considerably lower than the mean values reported earlier for this region, our studies have revealed large differences in the forcing components between the BoB and the AS. While the regionally averaged aerosol-induced atmospheric forcing efficiency was 31 ± 6 W m-2 τ-1 for the BoB, it was only ∼18 ± 7 W m-2 τ-1 for the AS. Airborne measurements revealed the presence of strong, elevated aerosol layers even over the oceans, leading to vertical structures in the atmospheric forcing, resulting in significant warming in the lower troposphere. These observations suggest serious climate implications and raise issues ranging from the impact of aerosols on vertical thermal structure of the atmospheric and hence cloud formation processes to monsoon circulation. © 2009 Royal Meteorological Society."
"7006745049;6701557562;","Canopy seed banks as time capsules of biodiversity in pasture-remnant tree crowns",2009,"10.1111/j.1523-1739.2009.01235.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349208655&doi=10.1111%2fj.1523-1739.2009.01235.x&partnerID=40&md5=8ab595a18149aaef78aed787a1c06265","Tropical pastures present multiple barriers to tree regeneration and restoration. Relict trees serve as ""regeneration foci"" because they ameliorate the soil microclimate and serve as safe spots for dispersers. Here, we describe another mechanism by which remnant trees may facilitate pasture regeneration: the presence of seed banks in the canopy soil that accumulates from decomposing epiphytes within the crowns of mature remnant trees in tropical cloud forest pastures. We compared seed banks of canopy soils (histosols derived from fallen leaves, fruits, flower, and twigs of host trees and epiphytes, dead bryophytes, bark, detritus, dead animals, and microorganisms, and dust that accumulate on trunks and the upper surfaces of large branches) in pastures, canopy soils in primary forest trees, and soil on the forest floor in Monteverde, Costa Rica. There were 5211 epiphytic and terrestrial plant seeds in the three habitats. All habitats were dominated by seeds in a relatively small number of plant families, most of which were primarily woody, animal pollinated, and animal dispersed. The density of seeds on the forest floor was greater than seed density in either pasture-canopy or forest-canopy soils; the latter two did not differ. Eight species in 44 families and 61 genera from all of the habitats were tallied. There were 37 species in the pasture-canopy soil, 33 in the forest-canopy soil, and 57 on the forest floor. Eleven species were common to all habitats. The mean species richness in the pasture canopy was significantly higher than the forest canopy (F = 83.38; p < 0.02). Nonmetric multidimensional scaling ordination revealed that the communities were distinct. Greenhouse experiments verified that many of these seeds were viable, with 29 taxa germinating (23 taxa in pruned mats [mimic of exposed conditions] and 16 taxa in control mats [intact conditions]) within 2 months of observation. Nearly half the species that germinated were characteristic of primary forests (primary forest samples, 19%; pasture samples, 29%). This supports the idea that canopy seed banks of pasture trees can function as time capsules by providing propagules that are removed in both space and time from the primary forest. Their presence may enhance the ability of pastures to regenerate more quickly, reinforcing the importance of trees in agricultural settings. © 2009 Society for Conservation Biology."
"57197651332;57202725379;26655473700;7004593987;","Predicting Enhanced Vegetation Index (EVI) curves for ecosystem modeling applications",2009,"10.1016/j.rse.2009.05.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67849103568&doi=10.1016%2fj.rse.2009.05.015&partnerID=40&md5=698e7dc59d905f59cbfd13803ce04bc5","Vegetation indices derived from remote sensing data provide information about the variability in stature, growth and vigor of the vegetation across a region, and have been used to model plant processes. For example, the Enhanced Vegetation Index (EVI) provides a measure of greenness of the vegetation that can be used to predict net primary production. However, ecosystem models relying on remote sensing data for EVI or other vegetation indices are limited by the time series of the satellite data record. Our objective was to develop a statistical model to predict EVI in order to extend the time series for modeling applications. To explain the functional behavior of the seasonal EVI curves, a two-stage multiple regression fitting procedure within a semi-parametric mixed effect (SPME) model framework was used. First, a linear mixed effect (LME) model was fitted to the EVI with climate indexes, crop and irrigation information as predictor variables. Second, Penalized B-splines were used to explain the behavior of the smooth residuals, which result from a smooth model fit to the smooth EVI data curve, in order to describe the uncertainty of the EVI curve. Individual models were fit within individual Major Land Resources Areas (MLRAs). Predicted seasonal EVI, derived from our regression equations, showed a strong agreement with the observed EVI and was able to capture the site by site and year by year variation in the EVI curve. Out-of-sample prediction produced excellent results for a majority of the sites, except for sites without clear seasonal patterns, which may have resulted from cloud contamination and/or snow cover. Therefore, given the appropriate climate, crop, and irrigation information, the proposed approach can be used to predict seasonal EVI curves for extending the time series into the past and future. © 2009 Elsevier Inc. All rights reserved."
"57197599584;10144282600;7006435011;7006652365;7006392180;7402899368;6603785227;","Estimating trace gas and aerosol emissions over South America: Relationship between fire radiative energy released and aerosol optical depth observations",2009,"10.1016/j.atmosenv.2009.09.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70949103482&doi=10.1016%2fj.atmosenv.2009.09.013&partnerID=40&md5=61462568f925e3ec808bb8a1263b5661","Contemporary human activities such as tropical deforestation, land clearing for agriculture, pest control and grassland management lead to biomass burning, which in turn leads to land-cover changes. However, biomass burning emissions are not correctly measured and the methods to assess these emissions form a part of current research area. The traditional methods for estimating aerosols and trace gases released into the atmosphere generally use emission factors associated with fuel loading and moisture characteristics and other parameters that are hard to estimate in near real-time applications. In this paper, fire radiative power (FRP) products were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) and from the Geostationary Operational Environmental Satellites (GOES) fire products and new South America generic biomes FRE-based smoke aerosol emission coefficients were derived and applied in 2002 South America fire season. The inventory estimated by MODIS and GOES FRP measurements were included in Coupled Aerosol-Tracer Transport model coupled to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) and evaluated with ground truth collected in Large Scale Biosphere-Atmosphere Smoke, Aerosols, Clouds, rainfall, and Climate (SMOCC) and Radiation, Cloud, and Climate Interactions (RaCCI). Although the linear regression showed that GOES FRP overestimates MODIS FRP observations, the use of a common external parameter such as MODIS aerosol optical depth product could minimize the difference between sensors. The relationship between the PM2.5μm (Particulate Matter with diameter less than 2.5 μm) and CO (Carbon Monoxide) model shows a good agreement with SMOCC/RaCCI data in the general pattern of temporal evolution. The results showed high correlations, with values between 0.80 and 0.95 (significant at 0.5 level by student t test), for the CATT-BRAMS simulations with PM2.5μm and CO. © 2009 Elsevier Ltd. All rights reserved."
"7005884117;7102150330;56065666500;57210337677;","Urban heat island diagnosis using ASTER satellite images and 'in situ' air temperature",2009,"10.1016/j.atmosres.2009.06.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68949162024&doi=10.1016%2fj.atmosres.2009.06.011&partnerID=40&md5=bc7d57e8805ad14a6e4c0503b81392f3","This study demonstrates that thermal satellite images combined with 'in situ' ground data can be used to examine models of heat island genesis and thus identify the main causes of urban heat islands (UHIs). The models, although proposed over 30 years ago, have not been thoroughly evaluated due to a combination of inadequate ground data and the low resolution of thermal satellite data. Also there has been limited understanding of the relevance of satellite-derived surface temperatures to local and regional scale air temperatures. A cloud-free ASTER thermal image of urban and rural areas of Hong Kong was obtained on a winter night with a well-developed heat island, accompanied by a 148 km vehicle traverse of air temperatures. Over the whole traverse a high R2 of 0.80 was observed between surface and air temperatures, with the two datasets showing a similar amplitude and general trend, but with the surface exhibiting much higher local variability than air temperature. Gradients in both surface and air temperature could be related to differences in land cover, with little evidence of large scale advection, thus supporting the population/physical structure model of UHI causation, rather than the advection model. However, the much higher surface and air temperatures observed over the largest urban area, Kowloon, than over any smaller urban centre with similar physical structure in the New Territories, would seem more indicative of the advection model. The image and ground data suggest that Kowloon's urban canopy layer climate is mainly influenced by local city structure, but it is also modified by a strongly developed, regional scale urban boundary layer which has developed over the largest urban centre of Kowloon, and reinforces heating from both above and below. © 2009."
"23094223900;7005274759;","Vorticity, deformation and divergence signals associated with stratosphere-troposphere exchange",2009,"10.1002/qj.482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350633288&doi=10.1002%2fqj.482&partnerID=40&md5=3a6c980bcce4b7c3776cf5d5789da85b","The dynamical tropopause of the extratropics, defined as an isosurface of potential vorticity, acts as a barrier to stratosphere-troposphere exchange (STE). Therefore, any transport across this barrier is necessarily associated with diabatic or frictional processes such as turbulence, radiative forcing or condensational heating. Most of these processes are linked to distinct flow phenomena and hence with distinct signatures of the velocity field. The focus of this study is on the characteristics of the velocity field at the time and location of the tropopause crossing, as given by the flow-components divergence (DIV), deformation (DEF) and vorticity (VORT). Firstly, the prevalence of distinct signals is shown for three case studies. Then a Lagrangian climatology of STE is used to assess the climatological aspects of this link for the year 1990. Methodologically, the flow-field components are traced along the STE trajectories, both derived from ERA-40. Some key results of this study are as follows. (1) DEF, positive values of VORT and negative values of DIV are markedly correlated with stratosphere-to-troposphere transport (STT). Therefore, the typical flow field associated with STT is deformative, cyclonic and convergent. (2) For troposphere-to-stratosphere transport (TST), the link with the flow-field components is less pronounced. DEF, VORT and DIV all show small, but distinct local maxima just before the exchange. The flow field during TST is therefore rather divergent and less cyclonic. (3) Sensitivity studies reveal that these findings are robust with respect to temporal and spatial variability. Copyright © 2009 Royal Meteorological Society."
"7404570418;","A novel ocean color index to detect floating algae in the global oceans",2009,"10.1016/j.rse.2009.05.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67849132399&doi=10.1016%2fj.rse.2009.05.012&partnerID=40&md5=f197c3e196507985f8db09dfb1501ff1","Various types of floating algae have been reported in open oceans and coastal waters, yet accurate and timely detection of these relatively small surface features using traditional satellite data and algorithms has been difficult or even impossible due to lack of spatial resolution, coverage, revisit frequency, or due to inherent algorithm limitations. Here, a simple ocean color index, namely the Floating Algae Index (FAI), is developed and used to detect floating algae in open ocean environments using the medium-resolution (250- and 500-m) data from operational MODIS (Moderate Resolution Imaging Spectroradiometer) instruments. FAI is defined as the difference between reflectance at 859 nm (vegetation ""red edge"") and a linear baseline between the red band (645 nm) and short-wave infrared band (1240 or 1640 nm). Through data comparison and model simulations, FAI has shown advantages over the traditional NDVI (Normalized Difference Vegetation Index) or EVI (Enhanced Vegetation Index) because FAI is less sensitive to changes in environmental and observing conditions (aerosol type and thickness, solar/viewing geometry, and sun glint) and can ""see"" through thin clouds. The baseline subtraction method provides a simple yet effective means for atmospheric correction, through which floating algae can be easily recognized and delineated in various ocean waters, including the North Atlantic Ocean, Gulf of Mexico, Yellow Sea, and East China Sea. Because similar spectral bands are available on many existing and planned satellite sensors such as Landsat TM/ETM+ and VIIRS (Visible Infrared Imager/Radiometer Suite), the FAI concept is extendable to establish a long-term record of these ecologically important ocean plants. © 2009 Elsevier Inc. All rights reserved."
"6507719789;34979263600;","Detecting and following atmospheric disturbances with a potential to generate meteotsunamis in the Adriatic",2009,"10.1016/j.pce.2009.08.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70449522069&doi=10.1016%2fj.pce.2009.08.009&partnerID=40&md5=41ee7a073e7afc9febe17eb78f48ddd9","The paper deals with a possibility to detect the presence and to follow the movement of an atmospheric disturbance that could lead to a meteotsunami formation. The analysis of the four strongest meteotsunami cases in the past 30 years in the Adriatic shows that three of four cases happened in the south-westerly stream on the front side of a large upper-level trough, whereas in one of the cases large-scale streaming was westerly and north-westerly. It was also noted that all cases occurred during summer months and in each case a convective system was present in the area. That led to the assumption that a convective system is responsible for causing the disturbance leading to meteotsunami formation. Since the convective cells can be recognized and their movement can be followed using the nowcasting tools based on satellite data, a method for predicting the occurrence of meteotsunamis in the Adriatic is proposed. © 2009 Elsevier Ltd. All rights reserved."
"34881780600;7401796996;8629713500;","A method to merge WSR-88D data with ARM SGP millimeter cloud radar data by studying deep convective systems",2009,"10.1175/2008JTECHA1190.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349185696&doi=10.1175%2f2008JTECHA1190.1&partnerID=40&md5=c26576fa1eb9862fc852efa92e47c923","A decade of collocated Atmospheric Radiation Measurement Program (ARM) 35-GHz Millimeter Cloud Radar (MMCR) and Weather Surveillance Radar-1988 Doppler (WSR-88D) data over the ARM Southern Great Plains (SGP) site have been collected during the period of 1997-2006. A total of 28 winter and 45 summer deep convective system (DCS) cases over the ARM SGP site have been selected for this study during the 10-yr period. For the winter cases, the MMCR reflectivity, on average, is only 0.2 dB lower than that of the WSR-88D, with a correlation coefficient of 0.85. This result indicates that the MMCR signals have not been attenuated for ice-phase convective clouds, and the MMCR reflectivity measurements agree well with the WSR-88D, regardless of their vastly different characteristics. For the summer nonprecipitating convective clouds, however, the MMCR reflectivity, on average, is 10.6 dB lower than the WSR-88D measurement, and the average differences between the two radar reflectivities are nearly constant with height above cloud base. Three lookup tables with Mie calculations have been generated for correcting the MMCR signal attenuation. After applying attenuation correction for the MMCR reflectivity measurements, the averaged difference between the two radars has been reduced to 9.1 dB. Within the common sensitivity range (-10 to 20 dBZ), the mean differences for the uncorrected and corrected MMCR reflectivities have been reduced to 6.2 and 5.3 dB, respectively. The corrected MMCR reflectivities were then merged with the WSR-88D data to fill in the gaps during the heavy precipitation periods. This merged dataset provides a more complete radar reflectivity profile for studying convective systems associated with heavier precipitation than the original MMCR dataset. It also provides the intensity, duration, and frequency of the convective systems as they propagate over the ARM SGP for climate modelers. Eventually, it will be possible to improve understanding of the cloud-precipitation processes, and evaluate GCM predictions using the long-term merged dataset, which could not have been done with either the MMCR or the WSR-88D dataset alone. © 2009 American Meteorological Society."
"35550520500;7201596294;","Shallow groundwater temperature response to climate change and urbanization",2009,"10.1016/j.jhydrol.2009.07.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69349088808&doi=10.1016%2fj.jhydrol.2009.07.009&partnerID=40&md5=df0f1230c88b71bb053717e7c9a29e7b","Groundwater temperatures, especially in shallow (quaternary) aquifers respond to ground surface temperatures which in turn depend on climate and land use. Groundwater temperatures, therefore, are modified by climate change and urban development. In northern temperate climate regions seasonal temperature cycles penetrate the ground to depths on the order of 10-15 m. In this paper, we develop and apply analytic heat transfer relationships for 1-D unsteady effective diffusion of heat through an unsaturated zone into a flowing aquifer a short distance below the ground surface. We estimate how changes in land use (urban development) and climate change may affect shallow groundwater temperatures. We consider both long-term trends and seasonal cycles in surface temperature changes. Our analysis indicates that a fully urbanized downtown area at the latitude of Minneapolis/St. Paul is likely to have a groundwater temperature that is nearly 3 °C warmer than an undeveloped agricultural area at the same geographic location. Pavements are the main cause of this change. Data collected by the Minnesota Pollution Control Agency (MPCA) in the St. Cloud, MN area confirm that land use influences groundwater temperatures. Ground surface temperatures are also projected to rise in response to global warming. In the extreme case of a doubling of atmospheric carbon dioxide (2 × CO2 climate scenario), groundwater temperatures in the Minneapolis/St. Paul metropolitan area could therefore rise by up to 4 °C. Compounding a land use change from ""undeveloped"" to ""fully urbanized"" and a 2 × CO2 climate scenario, groundwater temperatures are projected to rise by about 5 °C at the latitude of Minneapolis/St. Paul. © 2009 Elsevier B.V. All rights reserved."
"6701324864;7202162685;","Parameterization of cloud drop activation based on analytical asymptotic solutions to the supersaturation equation",2009,"10.1175/2009JAS2811.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949183944&doi=10.1175%2f2009JAS2811.1&partnerID=40&md5=3501e1e8ea06e2f752bdbdc63832c6e3","Toward improving parameterization of cloud droplet activation in cloud and climate models, the integrodifferential equation for supersaturation is solved analytically for the algebraic size spectrum of the cloud condensation nuclei (CCN) that is equivalent to the lognormal spectrum. The analytical solutions are obtained for four limiting cases that are combinations of two different values of the updraft vertical velocity (small and large) and two different values of the condensation coefficient that correspond to pure and polluted cloud drops. The characteristics of the CCN can vary within each limit. Thus, these four limits and interpolation among them cover the vast majority of cloudy conditions. Analytical expressions are obtained for the time of CCN activation, maximum supersaturation, and the concentration of activated droplets. For small updraft vertical velocities, these quantities are the products of the power laws by six variables: CCN concentration, mean radius, soluble fraction, vertical velocities, surface tension, and condensation coefficient. At large updraft vertical velocities, the activation time and maximum supersaturation are the products of the power laws of only two variables - CCN concentration and vertical velocity-and are independent of the CCN physicochemical properties. The first limit is a generalization of the Twomey power laws, with Twomey's coefficient CT and index k expressed via CCN physicochemical properties; the other three limits are new. The accuracy and regions of validity of these limits are determined by comparison with the exact numerical solution to the supersaturation equation. These solutions can be used for parameterization of drop activation in cloud and climate models and for control of numerical solutions. An advantage of this method is that it does not require running parcel models, and the drop concentrations can be obtained from lookup tables or as simple interpolation among the limiting solutions for the instantaneous model parameters. © 2009 American Meteorological Society."
"6701622352;57204343259;","Large-eddy simulation of moist convection during a cold air outbreak over the Gulf Stream",2009,"10.1175/2008JAS2755.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69849107711&doi=10.1175%2f2008JAS2755.1&partnerID=40&md5=64798f6d6ce978a5f68de554f07b13f3","Cold air outflow over the Gulf Stream is modeled using a cloud-resolving large-eddy simulation model with three classes of precipitation. Simulations are conducted in a quasi-Lagrangian framework using an idealized sounding and uniform geostrophic winds based on observations taken on 20 February 2007 as part of the World Climate Research Program Climate Variability and Predictability (CLIVAR) Mode Water Dynamics Experiment (CLIMODE) project. Two cases are considered, one with an increasing sea surface temperature (SST) representing the crossing of the Gulf Stream front, and a second case with constant SST. Cloud systems develop in the model with strong convective plumes that spread into regions of stratus clouds at the top of the boundary layer. Simulated boundary layer growth is forced by a combination of evaporative cooling at the cloud top, upward radiative flux, and mechanical entrainment of the overlying warmer and drier air. Constant growth of the boundary layer acts to maintain a near-constant water vapor level in the boundary layer, promoting high latent and sensible heat fluxes. Frictional surface drag is distributed throughout the boundary layer by convection, causing increased shear at the cloud top, qualitatively agreeing with observed sounding profiles. Overall, the frontal case develops stronger precipitation and turbulence in comparison with the constant SST case. A near-uniform stratocumulus layer and stronger radiative cooling are produced in the constant SST case, whereas the frontal case generates open cumuliform clouds with reduced cloud coverage. Cloud evolution in the frontal case is similar to the transition from stratocumulus to shallow cumulus observed in the subtropics, as cumuliform clouds enhance cloud-top entrainment and evaporation of stratus clouds. © 2009 American Meteorological Society."
"56355030000;55386235300;","A critical examination of the observed first aerosol indirect effect",2009,"10.1175/2008JAS2812.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69849092294&doi=10.1175%2f2008JAS2812.1&partnerID=40&md5=2ccc3813917b6f0df9f0ac6398893769","The relative change in cloud droplet number concentration with respect to the relative change in aerosol number concentration, α, is an indicator of the strength of the aerosol indirect effect and is commonly used in models to parameterize this effect. Based on Twomey's analytical expression, the values of α derived from measurements of an individual cloud (i.e., αT) can be as large as 0.60-0.90. In contrast, the values of α derived from direct measurements of polluted and clean clouds (i.e., α Δ) typically range from 0.25 to 0.85, corresponding to a weaker but more uncertain cooling effect. Clearly, reconciling αΔ with αT is necessary to properly calculate the indirect aerosol forcing. In this study, the terms that are involved in determining αT and αΔ are first analytically examined. Then, by analyzing satellite data over subtropical oceans, the satellite-observed αΔ can be successfully related to Twomey's analytical solution. It is found that except for the dust-influenced region of the northeastern Atlantic Ocean, injecting continental aerosols into a marine background may significantly reduce the average aerosols' ability to act as cloud condensation nuclei. Taking this competing effect into account may reduce the cooling effect proposed by Twomey from 0.76 to 0.28. It is also found that the variability of the adiabaticity (i.e., the cloud dilution state with respect to adiabatic cloud) among different clouds accounts for ∼50% uncertainty in αΔ. Based on these results, the authors explain the claimed discrepancies in the first aerosol indirect effect (AIE) from different methods and on different scales and present an improved parameterization of the first AIE that can be used in global climate models. © 2009 American Meteorological Society."
"12797783300;6701358938;","Is there a link between Earth's magnetic field and low-latitude precipitation?",2009,"10.1130/G25238A.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69649097346&doi=10.1130%2fG25238A.1&partnerID=40&md5=912c7d31f2577c831cd3e10050648b6d","Some studies indicate that the solar modulation of galactic cosmic ray (GCR) particles has profound consequences for Earth's climate system. A corollary of the GCR-climate theory involves a link between Earth's magnetic field and climate, since the geomagnetic field also modulates the GCR flux reaching Earth's atmosphere. In this study, we explore this potential geomagnetic-climate link by comparing a new reconstruction of the Holocene geomagnetic dipole moment with high-resolution speleothem data from China and Oman. The speleothem 18O data represent proxy records for past precipitation in low-latitude regions, which is a climate parameter that is likely to have been sensitive to variations in the GCR flux modulated by the dipole moment. Intriguingly, we observe a relatively good correlation between the high-resolution speleothem δ18O records and the dipole moment, suggesting that Earth's magnetic field to some degree influenced low-latitude precipitation in the past. In addition to supporting the notion that variations in the geomagnetic field may have influenced Earth's climate in the past, our study also provides some degree of support for the controversial link between GCR particles, cloud formation, and climate. © 2009 The Geological Society of America."
"7202772927;7006095466;","Multiscale cloud system modeling",2009,"10.1029/2008RG000276","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957586906&doi=10.1029%2f2008RG000276&partnerID=40&md5=24db6f3f4ec91d7dab1fb0bf518cebb4","The central theme of this paper is to describe how cloud system resolving models (CRMs) of grid spacing ∼1 km have been applied to various important problems in atmospheric science across a wide range of spatial and temporal scales and how these applications relate to other modeling approaches. A long-standing problem concerns the representation of organized precipitating convective cloud systems in weather and climate models. Since CRMs resolve the mesoscale to large scales of motion (i.e., 10 km to global) they explicitly address the cloud system problem. By explicitly representing organized convection, CRMs bypass restrictive assumptions associated with convective parameterization such as the scale gap between cumulus and large-scale motion. Dynamical models provide insight into the physical mechanisms involved with scale interaction and convective organization. Multiscale CRMs simulate convective cloud systems in computational domains up to global and have been applied in place of contemporary convective parameterizations in global models. Multiscale CRMs pose a new challenge for model validation, which is met in an integrated approach involving CRMs, operational prediction systems, observational measurements, and dynamical models in a new international project: the Year of Tropical Convection, which has an emphasis on organized tropical convection and its global effects. © Copyright 2009 by the American Geophysical Union."
"10140984600;","In-flight spectral characterization and calibration stability estimates for the clouds and the earth's radiant energy system (CERES)",2009,"10.1175/2009JTECHA1243.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73149125334&doi=10.1175%2f2009JTECHA1243.1&partnerID=40&md5=46bdf9f3f28be10eab1a9a3384fd7e71","It is essential to maintain global measurements of the earth radiation budget (ERB) from space, the scattered solar and emitted thermal radiative fluxes leaving the planet. These are required for the purpose of validating current climate model predictions of the planet's future response to anthropogenic greenhouse gas forcing. The measurement accuracy and calibration stability required to resolve the magnitude of modelsuggested cloud-climate feedbacks on the ERB have recently been estimated. The suggestion is for ERB data to strive for a calibration stability of ±0.3% decade-1 for scattered solar, ±0.5% decade-1 for emitted thermal, and an overall absolute accuracy of 1 W m-2. The Clouds and the Earth's Radiant Energy System (CERES) is currently the only satellite program to make global ERB measurements, beginning in January 1998. However, the new climate calibration standards are beyond those originally specified by the NASA CERES program for its edition 2 data release. Furthermore, the CERES instrument optics have been discovered to undergo substantial in-flight degradation because of contaminant issues. This is not directly detectable by using established calibration methods. Hence, user-applied revisions for edition 2 shortwave (SW) data were derived to compensate for this effect, which is described as ""spectral darkening."" Also, an entirely new in-flight calibration protocol has been developed for CERES that uses deep convective cloud albedo as a primary solar wavelength stability metric. This is then combinedwith a sophisticated contaminationmobilization/ polymerization model. The intention is to assign spectral coloration to any optical degradation occurring to the different CERES Earth observing telescopes. This paper quantifies the stability of revised edition 2 data. It also calculates stability, which the new protocols could give CERES measurements if used. The conclusion is that the edition 2 revisions restore the originally specified stability of CERES SW data. It is also determined that the climate calibration stability goals are reachable by using the new in-flight methodologies presented in this paper. However, this will require datasets of longer than approximately 10 yr. It will also require obtaining regular raster scans of the Moon by all operational CERES instruments. © 2009 American Meteorological Society."
"57196084096;57203859138;6602550636;","A study of relationships between florida thunderstorm properties and corresponding anvil cloud characteristics",2009,"10.1175/2009JAMC1991.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649118965&doi=10.1175%2f2009JAMC1991.1&partnerID=40&md5=f2b231f797cd5ea9ff5c923d7a123c52","Tropical thunderstorms produce large amounts of cirrus anvil clouds, which have a large effect on the climate system. Modeling of the cirrus anvil is a very important factor in the driving processes in atmospheric, climate, and radiation budget models. The current research project is focused on determining the relationships between the thunderstorm intensity and cirrus anvil characteristics of storms during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE). During July 2002, 19 different storms were selected for analysis. A vertical profile of reflectivity was extracted for each cell in which the maximum reflectivity, and maximum 10- and 40-dBZ height were identified. A majority of the thunderstorms in this study were single cells or isolated multicell clusters initiated from outflow boundaries or sea-breeze interactions. The results show that a general thunderstorm life cycle characteristic time sequence was determined, finding that the maximum reflectivity occurred on average 10 min after the cell first appeared in the base scan reflectivity image. The anvil origin and maximum height were found to occur approximately 10 and 25 min after maximum reflectivity, respectively. The anvil's mean particle size was found to increase with time and decrease with altitude. The opposite relationship holds true for the particle concentration. Contour analysis has shown that the particle size increased with increased thunderstorm intensity and time after maximum reflectivity. An increase in convective core intensity corresponds to increased anvil particle concentrations early after maximum reflectivity, as was observed. © 2009 American Meteorological Society."
"55717881500;7003545639;7006698304;","Convection in a parameterized and superparameterized model and its role in the representation of the MJO",2009,"10.1175/2009JAS3097.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549121745&doi=10.1175%2f2009JAS3097.1&partnerID=40&md5=5d5eeba9a4b00ee65a965aa926e6bac4","The behavior of convection and the Madden-Julian oscillation (MJO) is compared in two simulations from the same global climate model but with two very different treatments of convection: one has a conventional parameterization of moist processes and the other replaces the parameterization with a two-dimensional cloud-resolving model, the so-called superparameterization. The different behavior of local convection and the MJO in the two model simulations reveals that the accurate representation of the following characteristics in the modes of convection might contribute to the improvement of the MJO simulations: (i) precipitation should be an exponentially increasing function of the column saturation fraction, (ii) heavy precipitation should be associated with a stratiform diabatic heating profile, and (iii) there should be a positive relationship between precipitation and surface latent heat flux. © 2009 American Meteorological Society."
"35219670500;7102128820;7006146719;","Evaluating forecasts of the evolution of the cloudy boundary layer using diurnal composites of radar and lidar observations",2009,"10.1029/2009GL038919","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949121703&doi=10.1029%2f2009GL038919&partnerID=40&md5=6e3f487fce626953b0dcc67f17449c75","Observations of boundary-layer cloud have been made using radar and lidar at Chilbolton, Hampshire, UK. These have been compared with output from 7 different global and regional models. Fifty-five cloudy days have been composited to reveal the mean diurnal variation of cloud top and base heights, cloud thickness and liquid water path of the clouds. To enable like-for-like comparison between model and observations, the observations have been averaged on to the grid of each model. The composites show a distinct diurnal cycle in observed cloud; the cloud height exhibits a sinusoidal variation throughout the day with a maximum at around 1600 and a minimum at around 0700 UTC. This diurnal cycle is captured by six of the seven models analysed, although the models generally under-predict both cloud top and cloud base heights throughout the day. The two worst performing models in terms of cloud boundaries also have biases of around a factor of two in liquid water path; these were the only two models that did not include an explicit formulation for cloud-top entrainment. Copyright 2009 by the American Geophysical Union."
"7006041988;57203233100;7003663305;","Arctic mixed-phase stratiform cloud properties from multiple years of surface-based measurements at two high-latitude locations",2009,"10.1175/2009JAS3029.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049125518&doi=10.1175%2f2009JAS3029.1&partnerID=40&md5=b3504389cb748bab55b1556b9e957c25","Macro-and microphysical properties of single-layer stratiform mixed-phase clouds are derived from multiple years of lidar, radar, and radiosonde observations. Measurements were made as part of the Mixed-Phase Arctic Clouds Experiment (MPACE) and the Study of Environmental Arctic Change (SEARCH) in Barrow, Alaska, and Eureka, Nunavut, Canada, respectively. Single-layer mixed-phase clouds occurred between 4% and 26% of the total time observed, varying with season and location. They had mean cloud-base heights between ~700 and 2100 m and thicknesses between ~200 and 700 m. Seasonal mean cloud optical depths ranged from 2.2 up. The clouds existed at temperatures of ~242-271 K and occurred under different wind conditions, depending on season. Utilizing retrievals from a combination of lidar, radar, and microwave radiometer, mean cloud microphysical properties were derived, with mean liquid effective diameters estimated from 16 to 49 μm, mean liquid number densities on the order of 104-105 L-1, and mean water contents estimated between 0.07 and 0.28 g m-3. Ice precipitation was shown to have mean ice effective diameters of 50-125 μm, mean ice number densities on the order of 10 L-1, and mean water contents estimated between 0.012 and 0.031 g m-3. Mean cloud liquid water paths ranged from 25 to 100 g m-2. All results are compared to previous studies, and potential retrieval errors are discussed. Additionally, seasonal variation in macro-and microphysical properties was highlighted. Finally, fraction of liquid water to ice mass was shown to decrease with decreasing temperature. © 2009 American Meteorological Society."
"7410069943;24468389200;7404976222;","Cloud radiative forcing in Asian monsoon region simulated by IPCC AR4 AMIP models",2009,"10.1007/s00376-009-8111-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70849121834&doi=10.1007%2fs00376-009-8111-x&partnerID=40&md5=258cb894ff336297270bba75816423eb","This study examines cloud radiative forcing (CRF) in the Asian monsoon region (0°-50°N-60°-150°E) simulated by Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) AMIP models. During boreal winter, no model realistically reproduces the larger long-wave cloud radiative forcing (LWCF) over the Tibet Plateau (TP) and only a couple of models reasonably capture the larger short-wave CRF (SWCF) to the east of the TP. During boreal summer, there are larger biases for central location and intensity of simulated CRF in active convective regions. The CRF biases are closely related to the rainfall biases in the models. Quantitative analysis further indicates that the correlation between simulated CRF and observations are not high, and that the biases and diversity in SWCF are larger than that in LWCF. The annual cycle of simulated CRF over East Asia (0°-50°N, 100°-145°E) is also examined. Though many models capture the basic annual cycle in tropics, strong LWCF and SWCF to the east of the TP beginning in early spring are underestimated by most models. As a whole, GFDL-CM2.1, MPI-ECHAM5, UKMO-HadGAM1, and MIROC3.2 (medres) perform well for CRF simulation in the Asian monsoon region, and the multi-model ensemble (MME) has improved results over the individual simulations. It is suggested that strengthening the physical parameterizations involved over the TP, and improving cumulus convection processes and model experiment design are crucial to CRF simulation in the Asian monsoon region. © 2009 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer Berlin Heidelberg."
"7004816254;6603608668;57190689375;","Comparative analysis of geo-engineering approaches to climate stabilization",2009,"10.3103/S1068373909060016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69249198071&doi=10.3103%2fS1068373909060016&partnerID=40&md5=8fefc231362f2031b729ca0cf2183925","Geo-engineering approaches to modern climate stabilization, irrelative to the Kyoto Protocol measures, are under consideration. Conditionally, these approaches are subdivided into two groups: Purposive changes in the Earth radiation balance to compensate the greenhouse gas effect and removal of the excessive amount of carbon dioxide from the atmosphere. The first group includes such methods as injection of sulfate and other reflecting aerosols into the stratosphere, creation of orbital reflectors or reflectors at the Lagrange point, an increase in cloudiness over the World Ocean, and a change in the Earth surface albedo. Increased carbon dioxide uptake by forests, ocean, and artificial absorbers are considered within the second group. The methods considered were subject to a comparative analysis using the following criteria: possible fast realization, the ability to counteract the doubling of greenhouse gases, availability of natural analogs, impact on geophysical systems within natural variations, the absence of unacceptable ecological implications, possibility, if necessary, to immediately halt the action. The comparison showed that the use of stratospheric sulfate aerosols can be the most effective. It is emphasized that all geo-engineering directions can be realized simultaneously with the measures stipulated by the Kyoto Protocol. © Allerton Press, Inc. 2009."
"7006328089;57212302930;","Impact of midlatitude stationary waves on regional Hadley cells and ENSO",2009,"10.1029/2009GL039668","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949131409&doi=10.1029%2f2009GL039668&partnerID=40&md5=6638266ff9477cb328df2724452543f0","Stationary planetary waves are excited in the midlatitudes, propagate equatorward and are absorbed in the subtropics. The impact these waves have on the tropical climate has yet to be fully unraveled. Previous work has shown that interannual variability of zonal-mean stationary eddy stress is well correlated with interannual variability in Hadley cell strength. A separate line of research has shown that changes in midlatitude planetary waves local to the Pacific strongly affect ENSO variability. Here, we show that the two phenomena are in fact closely connected. Interannual variability of wave activity flux impinging on the subtropical central Pacific affects the local Hadley cell. The associated changes in subtropical subsidence affect the surface pressure field and wind stresses, which in turn affect ENSO. As a result, a winter with an anomalously weak Hadley cell tends to be followed a year later by an El Niño event. Copyright 2009 by the American Geophysical Union."
"6603964947;7004108287;","An analysis of the seasonal precipitation forecasts in South America using wavelets",2009,"10.1002/joc.1813","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349203896&doi=10.1002%2fjoc.1813&partnerID=40&md5=bc446a8404f13d0965bc3a95b1ec1d3b","A post-processing technique was applied to statistically correct the seasonal rainfall forecasts over South America (SA). The aim of this work was to reduce errors in the seasonal climate simulations obtained from the Centro de Previsão de Tempo e Estudos Climáticos (CPTEC) atmospheric general circulation model (AGCM) which was run with different deep cumulus convection parameterizations. One of the main contributions of this study is the discussion of the super-ensemble approach to reduce errors in the seasonal rainfall prediction for SA. A novel aspect here is the use of the wavelet technique to compare forecast and observed time series by investigating their time-frequency structures. This methodology has not yet been applied to super-ensemble model validations. The statistical algorithm used in the super-ensemble technique was based on the linear multiple regression method. The time series of the super-ensemble forecast (FCT), arithmetic averaged forecast (MEM) and individual model forecasts and the observed (OBS) ones for selected areas of SA were compared by calculating the root mean square errors (RMSEs) and by applying the wavelet technique on these time series. In general, for the analysed areas we obtained a super-ensemble skill superior to that for the MEM. The wavelet analysis proved to be very useful to compare forecast and observed time series. In fact, differences and similarities among the time series such as the dominant scale of variability and the time location of the largest variances in the time series were detected with the wavelet analyses. © 2008 Royal Meteorological Society."
"6507926049;8700803100;55777759900;7801433517;","Total ozone and tropopause zonal asymmetry during the Antarctic spring",2009,"10.1029/2008JD009881","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649084484&doi=10.1029%2f2008JD009881&partnerID=40&md5=b22a727e5e039194cc654fac7bac4288","Analysis of zonal anomalies in total ozone and thermal tropopause height shows that ozone depletion during austral spring has a strong influence on the height and sharpness of the tropopause over West Antarctica. The seasonal change of tropopause peak height occurs between 9 km (summer and autumn) and 13-14 km (winter and spring) over the Weddell Sea region, and in the range of 9-10 km at opposite longitudes in the Australian sector. Elevation of the tropopause is explained by low stratospheric temperature due to the seasonal temperature minimum in winter and ozone losses in spring. Accordingly, tropopause zonal asymmetry is determined by strong east-west asymmetry of the surface temperatures in the winter and total ozone asymmetry in spring. Lowering of the elevated tropopause over the boundary of the Antarctic continent is explained by the influence of the cold continental troposphere both in winter and spring. Overall, this work reports some details of relative contribution of radiative (strong cooling of the lower stratosphere and continental troposphere) and dynamical (quasi-stationary planetary wave 1 in total ozone) processes to the Antarctic tropopause formation. The sloping meridional profile of the tropopause and widening of the transition layer between the troposphere and stratosphere over West Antarctica suggest the possibility of enhanced air mixing not only vertically but also horizontally. This may contribute to the east-west asymmetry in Antarctic climate change. Copyright 2008 by the American Geophysical Union."
"55544443300;15026371500;7005808242;","The tropical response to extratropical thermal forcing in an idealized GCM: The importance of radiative feedbacks and convective parameterization",2009,"10.1175/2009JAS2924.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549113106&doi=10.1175%2f2009JAS2924.1&partnerID=40&md5=efa56971492d0665a91d1262beb84fc3","The response of tropical precipitation to extratropical thermal forcing is reexamined using an idealized moist atmospheric GCM that has no water vapor or cloud feedbacks, simplifying the analysis while retaining the aquaplanet configuration coupled to a slab ocean from the authors' previous study. As in earlier studies, tropical precipitation in response to high-latitude forcing is skewed toward the warmed hemisphere. Comparisons with a comprehensive GCM in an identical aquaplanet, mixed-layer framework reveal that the tropical responses tend to be much larger in the comprehensive GCM as a result of positive cloud and water vapor feedbacks that amplify the imposed extratropical thermal forcing. The magnitude of the tropical precipitation response in the idealized model is sensitive to convection scheme parameters. This sensitivity as well as the tropical precipitation response can be understood from a simple theory with two ingredients: the changes in poleward energy fluxes are predicted using a onedimensional energy balance model and a measure of the ""total gross moist stability"" [δm, which is defined as the total (mean plus eddy) atmospheric energy transport per unit mass transport] of the model tropics converts the energy flux change into a mass flux and a moisture flux change. The idealized model produces a low level of compensation of about 25% between the imposed oceanic flux and the resulting response in the atmospheric energy transport in the tropics regardless of the convection scheme parameter. Because Geophysical Fluid Dynamics Laboratory Atmospheric Model 2 (AM2) with prescribed clouds and water vapor exhibits a similarly low level of compensation, it is argued that roughly 25% of the compensation is dynamically controlled through eddy energy fluxes. The sensitivity of the tropical response to the convection scheme in the idealized model results from different values of δm: smaller δm leads to larger tropical precipitation changes for the same response in the energy transport. © 2009 American Meteorological Society."
"7102909972;6603770566;55906046800;","Detecting the equilibrium-line altitudes of New Zealand glaciers using ASTER satellite images",2009,"10.1080/00288300909509887","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72449127162&doi=10.1080%2f00288300909509887&partnerID=40&md5=2cecadc33af1719eaace1c6193bd9312","The glaciers of the Southern Alps of New Zealand play an important role in understanding regional and global patterns of climate change. They constitute the third largest ice mass in the Southern Hemisphere after Antarctica and South America, and present unique glaciological features in the region: high sensitivity, high input-output systems that represent the temperate, maritime end of glacier process-behaviour continuum. Since 1977 equilibrium-line altitudes (ELA) of 48 New Zealand index glaciers have been surveyed using oblique aerial photographs as a low-cost proxy for monitoring glacier mass balance. Although this method yields good results, it is location-specific. The use of synoptic high resolution satellite imagery can potentially maximise opportunities to get a wider picture of glacier response to climate variability throughout the New Zealand Southern Alps. Hence, our objective was to investigate how well ELAs detected from 15 m ASTER satellite imagery compare with reference ELAs obtained from aerial photographs taken approximately at the same time, and thus determine whether this imagery could in the future provide a more comprehensive view of glacier wellbeing and trends throughout the Southern Alps. End-of-summer ASTER images were selected and orthorectified. Glaciers were extracted, and ice and snow patterns were classified, using supervised classification of principal components. ELAs were digitised and projected over a digital elevation model. The comparison of ELAs gave a mean height departure of 61 ± 55 m, or 14.4 ± 13.4% expressed relative to the glacier elevation range. We conclude that ASTER data could extend ELAs estimated by the current snowline program across the whole Southern Alps. However, small and steep glaciers with complex shapes generate large errors (dominant in the New Zealand context), and thus we suggest that only the largest glaciers can be monitored reliably. ASTER imagery cannot easily replace the annual aerial surveys, mainly because of the difficulty in obtaining the appropriate imagery. The short temporal window, high percentage of cloud cover within the area, and the potential for early unseasonable snowfall are significant limitations to the use of ASTER imagery, without mentioning the recent deterioration of the shortwave infrared ASTER instrument. © The Royal Society of New Zealand 2009."
"55260519600;7005137442;15026371500;7006328089;","The impact of methane thermodynamics on seasonal convection and circulation in a model Titan atmosphere",2009,"10.1016/j.icarus.2009.03.043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749094068&doi=10.1016%2fj.icarus.2009.03.043&partnerID=40&md5=b03ac9ee60ca7dabed93976bb126219c","We identify mechanisms controlling the distribution of methane convection and large-scale circulation in a simplified, axisymmetric model atmosphere of Titan forced by gray radiation and moist (methane) convection. The large-scale overturning circulation, or Hadley cell, is global in latitudinal extent and provides fundamental control of precipitation and tropospheric winds. The precipitating, large-scale updraft regularly oscillates in latitude with seasons. The distance of greatest poleward excursion of the Hadley cell updraft is set by the mass of the convective layer of the atmosphere; convection efficiently communicates seasonal warming of the surface through the cold and dense lower atmosphere, increasing the heat capacity of the system. The presence of deep, precipitating convection introduces three effects relative to the case with no methane latent heating: (1) convection is narrowed and enhanced in the large-scale updraft of the Hadley cell; (2) the latitudinal amplitude of Hadley cell updraft oscillations is decreased; and (3) a time lag is introduced. These effects are observable in the location and timing of convective methane clouds in Titan's atmosphere as a function of season. A comparison of simulations over a range of convective regimes with available observations suggest methane thermodynamic-dynamic feedback is important in the Titan climate. © 2009 Elsevier Inc. All rights reserved."
"6602352339;16400684800;7006567885;57200553302;7004176296;6507952920;24773641300;24554058600;","The contribution of biological particles to observed particulate organic carbon at a remote high altitude site",2009,"10.1016/j.atmosenv.2009.06.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651030020&doi=10.1016%2fj.atmosenv.2009.06.012&partnerID=40&md5=a9df2384a6b8f0378e60438d7831761e","Although a significant fraction of atmospheric particulate mass is organic carbon, the sources of particulate organic carbon (POC) are not always apparent. One potential source of atmospheric POC is biological particles, such as bacteria, pollen, and fungal spores. Measurements of POC and biological particles, including bacteria, fungal spores, and pollen, were made as part of the Storm Peak Aerosol and Cloud Characterization Study in Steamboat Springs, CO in March-April 2008. Biological particles were identified and characterized using several methods. The results suggest that biological particles could account for an average of 40% of the organic carbon mass in particles with aerodynamic diameters less than 10 μm. These estimates of POC mass from biological particles are highly uncertain; however, the results suggest that biological particles could be a significant source of organic aerosol in the background continental atmosphere and further observations are needed to better constrain these estimates. © 2009 Elsevier Ltd. All rights reserved."
"7402170368;23032969000;24334624000;36719970800;57203496094;","A simple algorithm for large-scale mapping of evergreen forests in tropical America, Africa and Asia",2009,"10.3390/rs1030355","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051705715&doi=10.3390%2frs1030355&partnerID=40&md5=516cbb5a196e72d0609c901130cce812","The areal extent and spatial distribution of evergreen forests in the tropical zones are important for the study of climate, carbon cycle and biodiversity. However, frequent cloud cover in the tropical regions makes mapping evergreen forests a challenging task. In this study we developed a simple and novel mapping algorithm that is based on the temporal profile analysis of Land Surface Water Index (LSWI), which is calculated as a normalized ratio between near infrared and shortwave infrared spectral bands. The 8-day composites of MODIS Land Surface Reflectance data (MOD09A1) in 2001 at 500-m spatial resolution were used to calculate LSWI. The LSWI-based mapping algorithm was applied to map evergreen forests in tropical Africa, America and Asia (30°N-30°S). The resultant maps of evergreen forests in the tropical zone in 2001, as estimated by the LSWI-based algorithm, are compared to the three global forest datasets [FAO FRA 2000, GLC2000 and the standard MODIS Land Cover Product (MOD12Q1) produced by the MODIS Land Science Team] that are developed through complex algorithms and processes. The inter-comparison of the four datasets shows that the area estimate of evergreen forest from the LSWI-based algorithm fall within the range of forest area estimates from the FAO FRA 2000, GLC2000 and MOD12Q1 at a country level. The area and spatial distribution of evergreen forests from the LSWI-based algorithm is to a large degree similar to those of the MOD12Q1 produced by complex mapping algorithms. The results from this study demonstrate the potential of the LSWI-based mapping algorithm for large-scale mapping of evergreen forests in the tropical zone at moderate spatial resolution. © 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland."
"6603944055;7005573482;57200082194;7404614089;7403441497;26643251000;","Retrieval of snow grain size over Greenland from MODIS",2009,"10.1016/j.rse.2009.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651166601&doi=10.1016%2fj.rse.2009.05.008&partnerID=40&md5=04e0ef56be97910ae55d41679758f6eb","This paper presents a new automatic algorithm to derive optical snow grain size at 1 km resolution using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. The retrieval is conceptually based on an analytical asymptotic radiative transfer model which predicts spectral bidirectional snow reflectance as a function of the grain size and ice absorption. The snow grains are modeled as fractal rather than spherical particles in order to account for their irregular shape. The analytical form of solution leads to an explicit and fast retrieval algorithm. The time series analysis of derived grain size shows a good sensitivity to snow melting and snow precipitation events. Pre-processing is performed by a Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm, which includes gridding MODIS data to 1 km resolution, water vapor retrieval, cloud masking and an atmospheric correction. MAIAC cloud mask is a new algorithm based on a time series of gridded MODIS measurements and an image-based rather than pixel-based processing. Extensive processing of MODIS TERRA data over Greenland shows a robust discrimination of clouds over bright snow and ice. Because in-situ grain size measurements over Greenland were not available at the time of this work, the validation was performed using data of Aoki et al. (Aoki, T., Hori, M., Motoyoshi, H., Tanikawa, T., Hachikubo, A., Sugiura, K., et al. (2007). ADEOS-II/GLI snow/ice products - Part II: Validation results using GLI and MODIS data. Remote Sensing of Environment, 111, 274-290) collected at Barrow (Alaska, USA), and Saroma, Abashiri and Nakashibetsu (Japan) in 2001-2005. The retrievals correlate well with measurements in the range of radii ~ 0.1-1 mm, although retrieved optical diameter may be about a factor of 1.5 lower than the physical measured diameter. As part of validation analysis for Greenland, the derived grain size from MODIS over selected sites in 2004 was compared to the microwave brightness temperature measurements of SSM/I radiometer which is sensitive to the amount of liquid water in the snowpack. The comparison showed a good qualitative agreement, with both datasets detecting two main periods of snowmelt. Additionally, MODIS grain size was compared with predictions of the snow model CROCUS driven by measurements of the automatic weather stations of the Greenland Climate Network. We found that the MODIS value is on average a factor of two smaller than CROCUS grain size. This result agrees with the direct validation analysis indicating that the snow reflectance model may need a ""calibration"" factor of ~ 1.5 for the retrieved grain size to match the physical snow grain size. Overall, the agreement between CROCUS and MODIS results was satisfactory, in particular before and during the first melting period in mid-June. Following detailed time series analysis of snow grain size for four permanent sites, the paper presents maps of this important parameter over the Greenland ice sheet for the March-September period of 2004. © 2009 Elsevier Inc."
"7004854393;6602743662;7003798418;6506539095;16678672300;7003516381;6602344979;","Surface thermodynamics and radiative budget in the Sahelian Gourma: Seasonal and diurnal cycles",2009,"10.1016/j.jhydrol.2008.09.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69549135788&doi=10.1016%2fj.jhydrol.2008.09.007&partnerID=40&md5=cce1344ad23c085e459f0a1340f28cf4","Our understanding of the role of surface-atmosphere interactions in the West African monsoon has been particularly limited by the scarcity of measurements. The present study provides a quantitative analysis of the very pronounced seasonal and diurnal cycles of surface thermodynamics and radiative fluxes in the Central Sahel. It makes use of data collected from 2002 to 2007 in the Malian Gourma, close to Agoufou, at 1.5°W-15.3°N and sounding data collected during the AMMA field campaign. The seasonal cycle is characterized by a broad maximum of temperature in May, following the first minimum of the solar zenith angle (SZA) by a few weeks, when Agoufou lies within the West African Heat Low, and a late summer maximum of equivalent potential temperature (θe) within the core of the monsoon season, around the second yearly maximum of SZA. Distinct temperature and moisture seasonal and diurnal dynamics lead to a sharpening of the early (late) monsoon increase (decrease), more steadiness of θe and larger changes of relative humidity in between. Rainfall starts after the establishment of the monsoon flow, once temperature already started to decrease slowly, typically during June. Specific humidity increases progressively from May until August, while the monsoon flow weakens during the same period. Surface net radiation (Rnet) increases from around 10-day mean values of 20 W m-2 in Winter to 120-160 W m-2 in late Summer, The increase is sharper during the monsoon than before, and the decrease fast. The seasonal cycle of Rnet arises from distinct shortwave and longwave fluctuations that are both strongly shaped by modifications of surface properties related to rainfall events and vegetation phenology (with a decrease of both surface longwave emission and albedo). During the monsoon, clouds and aerosols reduce the incoming solar radiation by 20-25% (about 70 W m-2). They also significantly enhance the day-to-day variability of Rnet. Nevertheless, the surface incoming longwave radiative flux (LWin) is observed to decrease from June to September. As higher cloud covers and larger precipitable water amounts are typically expected to enhance LWin, this feature points to the significance of changes in atmospheric temperature and aerosols during the monsoon season. The strong dynamics associated with the transition from a drier hot Spring to a brief cooler moist tropical Summer climate involves large transformations of the diurnal cycle, even within the monsoon season, which significantly affect both thermodynamical, dynamical and radiative fields (and low-level dynamics). In particular, for all moist Summer months except August, specific humidity decreases in such a way during daytime that it prevents an afternoon increase of θe. In agreement with some previous studies, strong links are found between moisture and LWnet all year long and a positive correlation is identified between Rnet and θe during the monsoon. The observational results presented in this study further provide valuable ground truth for assessing models over an area displaying a rich variety of surface-atmosphere regimes. © 2008 Elsevier B.V. All rights reserved."
"33267959500;7101801476;35425197200;6701346974;12040633300;7003278104;7006957668;55109904700;6701845806;7402933297;7404829395;35467186900;","A multi-scale modeling system: Developments, applications, and critical issues",2009,"10.1175/2008BAMS2542.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68949201812&doi=10.1175%2f2008BAMS2542.1&partnerID=40&md5=e8adaacd0eebecc945337c9ea0b5c368","A multiscale modeling framework (MMF), which replaces the conventional cloud parameterizations with a cloud-resolving model (CRM) in each grid column of a GCM, constitutes a new and promising approach for climate modeling. The MMF can provide for global coverage and two-way interactions between the CRMs and their parent GCM. The CRM allows for explicit simulation of cloud processes and their interactions with radiation and surface processes, and the GCM allows for global coverage. A new MMF has been developed that is based on the NASA Goddard Space Flight Center (GSFC) finite-volume GCM (fvGCM) and the Goddard Cumulus Ensemble (GCE) model. This Goddard MMF produces many features that are similar to another MMF that was developed at Colorado State University (CSU), such as an improved surface precipitation pattern, better cloudiness, improved diurnal variability over both oceans and continents, and a stronger propagating Madden-Julian oscillation (MJO) compared to their parent GCMs using traditional cloud parameterizations. Both MMFs also produce a large and positive precipitation bias in the Indian Ocean and western Pacific during the Northern Hemisphere summer. However, there are also notable differences between the two MMFs. For example, the CSU MMF simulates less rainfall over land than its parent GCM. This is why the CSU MMF simulated less overall global rainfall than its parent GCM. The Goddard MMF simulates more global rainfall than its parent GCM because of the high contribution from the oceanic component. A number of critical issues (i.e., the CRM's physical processes and its configuration) involving the Goddard MMF are discussed in this paper. © 2009 American Meteorological Society."
"15125055800;7004885872;6701378450;","Distinct CCN activation kinetics above the marine boundary layer along the California coast",2009,"10.1029/2009GL038839","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350004809&doi=10.1029%2f2009GL038839&partnerID=40&md5=ea7a3b842851f2bea4cd5c01478ccd6d","The influence of aerosols on cloud properties remains one of the largest sources of uncertainty in estimates of the anthropogenic component of climate change. Here we report the rate of cloud droplet formation on particles sampled at a site near the California coast that is typically above the marine boundary layer. We observed persistent bimodal diameter spectra which are better explained by kinetic limitations than by differences in equilibrium properties. The slowly-growing mode contained 10-25% of the total cloud condensation nuclei (CCN) and had apparent mass accommodation coefficients (a) 10-30 times smaller than mat measured for ammonium sulfate. Cloud parcel modeling suggests that most of these slowly-growing CCN will not form cloud droplets. The relatively small and narrow size distribution of the low-a droplets suggest that a condensed film is a more likely cause of these limitations than slow dissolution. Copyright 2009 by the American Geophysical Union."
"6602940714;6506694774;35095671300;","Cosmic ray decreases affect atmospheric aerosols and clouds",2009,"10.1029/2009GL038429","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350006802&doi=10.1029%2f2009GL038429&partnerID=40&md5=04eb331de6c460437de6bec5fdea959a","Close passages of coronal mass ejections from the sun are signaled at the Earth's surface by Forbush decreases in cosmic ray counts. We find mat low clouds contain less liquid water following Forbush decreases, and for the most influential events the liquid water in the oceanic atmosphere can diminish by as much as 7%. Cloud water content as gauged by the Special Sensor Microwave/Imager (SSM/I) reaches a minimum ≈7 days after the Forbush minimum in cosmic rays, and so does the fraction of low clouds seen by the Moderate Resolution Imaging Spectroradiometer (MODIS) and in the International Satellite Cloud Climate Project (ISCCP). Parallel observations by the aerosol robotic network AERONET reveal falls in the relative abundance of fine aerosol particles which, in normal circumstances, could have evolved into cloud condensation nuclei. Thus a link between me sun, cosmic rays, aerosols, and liquid-water clouds appears to exist on a global scale. Copyright 2009 by the American Geophysical Union."
"7404653593;12040335900;24597299800;","Long-term changes in summer weekend effect over northeastern China and the connection with regional warming",2009,"10.1029/2009GL039509","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350029223&doi=10.1029%2f2009GL039509&partnerID=40&md5=de4ca6c7420caf92a518e07990725ed4","The 7-day cycle of human activities may lead to the ""weekend effect"" in climate variables and air pollutants. The weekend effect is defined as the average value (e.g., the diurnal temperature range) for Saturday through Monday minus the average value for Wednesday through Friday. A composite of the ground observations over northeastern China presents that, during 26-year (1980-2005) summers, the weekend effect in the diurnal temperature range increased by 1.2°C. Conversely, the weekend effects in the relative humidity, cloud amount, and light rain (≤5 mm day-1) events decreased. These changes are due to a shifted phase of the weekly cycle of the meteorological variables. The long-term change in weekend effects have a high correlation coefficient (|r| 0.8) with the decrease in relative humidity over the region, which is likely induced by regional warming. The results suggest that regional warming is a possible factor in a transition of dominant aerosol effects in the weekend effect. Copyright 2009 by the American Geophysical Union."
"9244992800;55399935700;7004060399;7102167757;","Ozone hole and Southern Hemisphere climate change",2009,"10.1029/2009GL038671","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350017984&doi=10.1029%2f2009GL038671&partnerID=40&md5=93ac5d6de62887a25162ced470be6d7c","Climate change in the Southern Hemisphere (SH) has been robustly documented in the last several years. It has altered the atmospheric circulation in a surprising number of ways: a rising global tropopause, a poleward intensification of the westerly jet, a poleward shift in storm tracks, a poleward expansion of the Hadley cell, and many others. While these changes have been extensively related with anthropogenic warming resulting from the increase in greenhouse gases, their potential link to stratospheric cooling resulting from ozone depletion has only recently been examined and a comprehensive picture is still lacking. Examining model output from the coupled climate models participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment (AR4), and grouping them depending on the stratospheric ozone forcing used, we here show that stratospheric ozone affects the entire atmospheric circulation in the SH, from the polar regions to the subtropics, and from the stratosphere to the surface. Furthermore, model projections suggest that the anticipated ozone recovery, resulting from the implementation of the Montreal Protocol, will likely decelerate future climate change resulting from increased greenhouse gases, although it might accelerate surface warming over Antarctica. Copyright 2009 by the American Geophysical Union."
"26649925100;7003979342;24485834000;6701359648;","Parametric uncertainty effects on aerosol radiative forcing",2009,"10.1029/2009GL039050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350017983&doi=10.1029%2f2009GL039050&partnerID=40&md5=930b4faeb0a83cbe8a03fbd38b2278c1","Among the known radiative forcings, the fourth IPCC assessment report estimates the aerosol radiative forcing to harbor the widest range of uncertainty extending from -1.8 to -0.3 W/m2. The IPCC estimates focus mainly on structural uncertainties, including uncertainties in aerosol sources. Here, we study the uncertainty of the sulfate aerosol radiative forcing due to parametric uncertainty in a state-of-the-art general circulation model (GCM). Numerical experiments were carried out by perturbing seven cloud parameters in the model. We find that the uncertainty due to a single one of diese parameters can be as large as 0.5 W/m2, and the uncertainty due to combinations of diese parameters can reach more than 1 W/m2. These numbers should be compared with the sulfate aerosol forcing of -1.9 W/m2 for the year 2000, obtained using the default values of the parameters. The uncertainty results from a high sensitivity of cloud optical properties to aerosol concentrations, which can be amplified by changing cloud parameter setting. Copyright 2009 by the American Geophysical Union."
"57203378050;7404548584;","An analysis of clear sky and contextual biases using an operational over ocean MODIS aerosol product",2009,"10.1029/2009GL038723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350026279&doi=10.1029%2f2009GL038723&partnerID=40&md5=03bee37b8a12638c3c64018976a0e570","Clear sky and other cloud-related contextual biases are critical yet unsolved mysteries for aerosol related climatological studies using satellite observations. For the first time, we simulated contextual biases over ocean using 2-years of Navy Aerosol Analysis and Prediction System (NAAPS) products that include the Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) assimilation. We compared model-derived AOD in regions with and without observations, and found mat sampling results in negligible seasonal globally averaged AOD bias (<5%). Biases are more pronounced in regions with frequent overcast skies and high aerosol loadings, such as Southeast Asia, and mid-latitude South America. This suggests that contextual biases may develop from transport covariance and other observing biases. Lastly, we found that over remote oceans, under cloud decks, a slight increase aerosol optical depth values could exist, comparing with cloud free regions. But this is still small relative to cloud artifacts in the retrieval Copyright 2009 by the American Geophysical Union."
"24477694300;7202245296;8147766700;7004643405;16480965400;7004549950;34769585100;7007172001;7006212411;","Heating rates and surface dimming due to black carbon aerosol absorption associated with a major U.S. city",2009,"10.1029/2009GL039213","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350037700&doi=10.1029%2f2009GL039213&partnerID=40&md5=6cca073a089ffd4bd4a43e8cc0f1a320","In situ airborne measurements of actinic flux and the mass and mixing state of individual refractory black carbon (BC) particles were made in the lower troposphere around a major U.S. metropolitan area. These data were used to estimate atmospheric heating rates and surface dimming due to absorption of solar radiation by refractory BC. Direct absorption by ozone is also calculated and averages 10% of that of BC below 4 km but becomes dominant above this altitude. Variability in BC absorption is large due to source variability and clouds. Average BC heating rates are much smaller than those associated with BC and other absorbing aerosol components in global hotspot regions. These results, which are specific to refractory BC. absorption, will help determine the value of short-term climate-change mitigation strategies involving BC emission reductions. They may also be used to estimate refractory BC contributions to total aerosol absorption Copyright 2009 by the American Geophysical Union."
"22633257000;57213211484;","Key dynamical features of the 2005/06 European winter",2009,"10.1175/2008MWR2533.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249159680&doi=10.1175%2f2008MWR2533.1&partnerID=40&md5=995c507d1f8afc75b3477213000203a2","A three-part study of the anomalously cold European winter of 2005/06 is undertaken. Climatological analysis indicates that the dominant pattern of climate variability in the Euro-Atlantic sector during this winter was not a negative phase of the North Atlantic Oscillation (NAO), but a pattern with a ""blocklike"" center located immediately upstream of the continent. Synoptic-dynamical diagnosis of the winter indicates the frequent occurrence of long-lasting blocks in this region, and a Lagrangian trajectory analysis points to the significant role of cloud-diabatic effects in the dynamics of block inception. A series of heuristic numerical simulations lend credence to the hypothesis that the occurrence of the blocks was sensitive to, and significantly influenced by, the warm surface temperature anomalies upstream over the western Atlantic Ocean and North America. Brief comments are made on the significance of the foregoing results for seasonal numerical weather prediction and also their relevance to the consideration of interannual climate variability. © 2009 American Meteorological Society."
"9243777900;6701738681;57198260527;","Variability of updraft and downdraft characteristics in a large parameter space study of convective storms",2009,"10.1175/2008MWR2703.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249152250&doi=10.1175%2f2008MWR2703.1&partnerID=40&md5=40ad182400e5dd8c229a6dacad8c92d4","Over 200 convective storm simulations are analyzed to examine the variability in storm vertical velocity and updraft area characteristics as a function of basic environmental parameters. While it is known that bulk properties of the troposphere such as convective available potential energy (CAPE) and deep-layer wind shear exert significant influence over updraft intensity and area, additional parameters such as the temperature at the cloud base, the height of the level of free convection (LFC), and the vertical distribution of buoyancy also have an effect. For example, at low CAPE, updraft strength is strongly related to the vertical distribution of buoyancy, and also to the bulk environmental wind shear. More generally, updraft area and its temporal variability both tend to increase in environments where the LFC is raised. Additionally, in environments with persistent storms, downdraft strength is sensitive to the bulk shear, environmental temperature, and LFC height. Using multiple linear regression methods, the best combinations of environmental parameters explain up to 81% of the interexperiment variance in second-hour mean peak updraft velocity, 74% for midlevel updraft area, and 64% for downdraft velocity. Downdraft variability is explained even less well (49%) when only persistent storms are considered. These idealized simulation results show that it is easier to predict storm updraft characteristics than those of the downdraft. © 2009 American Meteorological Society."
"7005913397;6701410329;36523706800;","Surface radiation at sea - Validation of satellite-derived data with shipboard measurements",2009,"10.1127/0941-2948/2009/356","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249152260&doi=10.1127%2f0941-2948%2f2009%2f356&partnerID=40&md5=6460ef629a79dec50193abde9a996adb","Quality-controlled and validated radiation products are the basis for their ability to serve the climate and solar energy community. Satellite-derived radiation fluxes are well preferred for this task as they cover the whole research area in time and space. In order to monitor the accuracy of these data, validation with well maintained and calibrated ground based measurements is necessary. Over sea, however, long-term accurate reference data sets from calibrated instruments recording radiation are scarce. Therefore data from research vessels operating at sea are used to perform a reasonable validation. A prerequisite is that the instruments on board are maintained as well as land borne stations. This paper focuses on the comparison of radiation data recorded on board of the German Research Vessel ""Meteor"" during her 13 months cruise across the Mediterranean and the Black Sea with CM-SAF products using NOAA- and MSG-data (August 2006-August 2007): surface incoming short-wave radiation (SIS) and surface downward long-wave radiation (SDL). Measuring radiation fluxes at sea causes inevitable errors, e.g. shadowing of fields of view of the radiometers by parts of the ship. These ship-inherent difficulties are discussed at first. A comparison of pairs of ship-recorded and satellitederived mean fluxes for the complete measuring period delivers a good agreement: the mean bias deviation (MBD) for SIS daily means is -7.6 W/m2 with a median bias of -4 W/m2 and consistently the MBD for monthly means is -7.3 W/m2, for SDL daily means the MBD is 8.1 and 6 W/m2 median bias respectively. The MBD for monthly means is 8.2 W/m2. The variances of the daily means (ship and satellite) have the same annual courses for both fluxes. No significant dependence of the bias on the total cloud cover recorded according to WMO (1969) has been found. The results of the comparison between ship-based observations and satellite retrieved surface radiation reveal the good accuracy of the satellite-based CM-SAF products over sea. © by Gebrüdr Borntraeger 2009."
"23393651400;6701843355;7004307308;36772864900;16933919600;6507524182;","Projected changes in mean and extreme precipitation in Africa under global warming. Part I: Southern Africa",2009,"10.1175/2009JCLI2317.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67849086612&doi=10.1175%2f2009JCLI2317.1&partnerID=40&md5=716d7adc6c6a31de95bcd85153eb8e5c","This study investigates likely changes in mean and extreme precipitation over southern Africa in response to changes in radiative forcing using an ensemble of global climate models prepared for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Extreme seasonal precipitation is defined in terms of 10-yr return levels obtained by inverting a generalized Pareto distribution fitted to excesses above a predefined high threshold. Both present (control) and future climate precipitation extremes are estimated. The future-to-control climate ratio of 10-yr return levels is then used as an indicator for the likely changes in extreme seasonal precipitation. A Bayesian approach to multimodel ensembling is adopted. The relative weights assigned to each of the model simulations is determined from bias, convergence, and correlation. Using this method, the probable limits of the changes in mean and extreme precipitation are estimated from their posterior distribution. Over the western parts of southern Africa, an increase in the severity of dry extremes parallels a statistically significant decrease in mean precipitation during austral summer months. A notable delay in the onset of the rainy season is found in almost the entire region. An early cessation is found in many parts. This implies a statistically significant shortening of the rainy season. A substantial reduction in moisture influx from the southwestern Indian Ocean during austral spring is projected. This and the preaustral spring moisture deficits are possible mechanisms delaying the rainfall onset in southern Africa. A possible offshore (northeasterly) shift of the tropical-temperate cloud band is consistent with more severe droughts in the southwest of southern Africa and enhanced precipitation farther north in Zambia, Malawi, and northern Mozambique. This study shows that changes in the mean vary on relatively small spatial scales in southern Africa and differ between seasons. Changes in extremes often, but not always, parallel changes in the mean precipitation. © 2009 American Meteorological Society."
"36938871600;7103373205;55678879300;6602235428;","Analyzing the climate sensitivity of the HadSM3 climate model using ensembles from different but related experiments",2009,"10.1175/2008JCLI2533.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67749118304&doi=10.1175%2f2008JCLI2533.1&partnerID=40&md5=79331639e7fb8ea7c6bebf0682afc16a","Global climate models (GCMs) contain imprecisely defined parameters that account, approximately, for subgrid-scale physical processes. The response of a GCM to perturbations in its parameters, which is crucial for quantifying uncertainties in simulations of climate change, can - in principle - be assessed by simulating the GCM many times. In practice, however, such ""perturbed physics"" ensembles are small because GCMs are so expensive to simulate. Statistical tools can help in two ways. First, they can be used to combine ensembles from different but related experiments, increasing the effective number of simulations. Second, they can be used to describe the GCM's response in ways that cannot be extracted directly from the ensemble(s). The authors combine two experiments to learn about the response of the Hadley Centre Slab Climate Model version 3 (HadSM3) climate sensitivity to 31 model parameters. A Bayesian statistical framework is used in which expert judgments are required to quantify the relationship between the two experiments; these judgments are validated by detailed diagnostics. The authors identify the entrainment rate coefficient of the convection scheme as the most important single parameter and find that this interacts strongly with three of the large-scale-cloud parameters. © 2009 American Meteorological Society."
"36782028900;7005302245;35618283200;7402590526;26645133400;","Customization of RegCM3 Regional Climate Model for eastern Africa and a tropical Indian Ocean domain",2009,"10.1175/2009JCLI2388.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67749120143&doi=10.1175%2f2009JCLI2388.1&partnerID=40&md5=cb2d4cd50764ce95d4b02d0032684bea","Rainfall is a driving factor of climate in the tropics and needs to be properly represented within a climate model. This study customizes the precipitation processes over the tropical regions of eastern Africa and the Indian Ocean using the International Centre for Theoretical Physics (ICTP) Regional Climate Model (RegCM3). The convective schemes of Grell with closures Arakawa-Schubert (Grell-AS)/Fritch-Chappel (Grell-FC) and Massachusetts Institute of Technology-Emanuel (MIT-EMAN) were compared to determine the most realistic spatial distribution of rainfall and partitioning of convective/stratiform rainfall when compared to observations from the Tropical Rainfall Measuring Mission (TRMM). Both Grell-AS and Grell-FC underpredicted convective rainfall rates over land, while over the ocean Grell-FC (Grell-AS) over- (under-) estimates convective rainfall. MIT-EMAN provides the most realistic pardoning and spatial distribution of convective rainfall despite the tendency for overestimating total rainfall. MIT-EMAN was used to further customize the subgrid explicit moisture scheme (SUBEX). Sensitivity tests were performed on the gridbox relative humidity threshold for cloudiness (RHmin) and the autoconversion scale factor (Cacs). An RHmin value of 60% (RHmin-60) reduced the amount of total rainfall over five heterogeneous rainfall regions in eastern Africa, with most of the reduction coming from the convective rainfall. Then, Cacs sensitivity tests improved upon the total rainfall amounts and convective stratiform partitioning compared to RHmin-60. Based upon all sensitivity simulations performed, the combination of the MIT-EMAN convective scheme, RHmin-60, and halving the model default value (0.4) of Cacs provided the most realistic simulation in terms of spatial distribution, convective partition, rainfall totals, and temperature bias when compared to observations. © 2009 American Meteorological Society."
"7202474186;57202301596;7005170782;","Vertical mixing in the ocean and its impact on the coupled ocean-atmosphere system in the eastern tropical Pacific",2009,"10.1175/2009JCLI2702.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67749113626&doi=10.1175%2f2009JCLI2702.1&partnerID=40&md5=8c6ad4f886be2265ad8c97919a4e9f3e","The zonal and meridional asymmetries in the eastern tropical Pacific (the eastern equatorial cold tongue and the northern intertropical convergence zone) are key aspects of the region that are strongly influenced by ocean-atmosphere interactions. Here the authors investigate the impact of vertical mixing in the ocean on these asymmetries, employing a coupled ocean-atmosphere regional model. Results highlight the need to study the impact of processes such as vertical mixing in the context of the coupled system. Changes to the vertical mixing in the ocean are found to produce large changes in the state of the system, which include changes to the surface properties of the ocean, the ocean currents, the surface wind field, and clouds and precipitation in the atmosphere. Much of the strength of the impact is through interactions between the ocean and atmosphere. Increasing ocean mixing has an opposite effect on the zonal and meridional asymmetries. The zonal asymmetry is increased (i.e., a colder eastern equatorial cold tongue and increased easterly winds), whereas the meridional asymmetry is decreased (a reduced north-south temperature difference and reduced southerlies), with the impact being enhanced by the Bjerknes and wind-evaporation-sea surface temperature feedbacks. Water mass transformations are analyzed by consideration of the diapynic fluxes. Although the general character of the diapycnic transport remains relatively unchanged with a change in ocean mixing, there are changes to the magnitude and location of the transport in density space. Oceanic vertical mixing impacts the balance of terms contributing to the heating of the ocean surface mixed layer. With reduced mixing the advection of heat plays an increased role in areas such as the far eastern tropical Pacific and under the intertropical convergence zone. © 2009 American Meteorological Society."
"35264934000;7004885872;7003591311;55017656900;","Can aerosol decrease cloud lifetime?",2009,"10.1029/2009GL038888","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949119419&doi=10.1029%2f2009GL038888&partnerID=40&md5=576f6a97e8226ff6ec6d6e75fd0eef21","Cloud responses to changes in aerosol remain a dominant uncertainty in the radiative forcing of climate. Two main constructs related to aerosol effects on clouds have been postulated: (i) the ""albedo effect"" whereby anthropogenic aerosol results in increased droplet concentrations mat generate increases in cloud albedo, all else (particularly cloud water) being equal; (ii) the ""lifetime effect"" whereby anthropogenic aerosol suppresses precipitation and results in clouds witii more liquid water, higher fractional cloudiness, and longer lifetimes. Based on new observations presented here, and supported by previous fine-scale modeling studies, we suggest that the balance of evidence shows mat non-precipitating cumulus clouds can experience an evaporation-entrainment feedback, and respond to aerosol perturbations in a manner inconsistent with the traditional ""lifetime effect."" Because most cumulus clouds evaporate without producing significant precipitation, this is particularly relevant to estimates of aerosol indirect effects on climate. Copyright 2009 by the American Geophysical Union."
"57188557549;7402434077;7005072865;","Characteristics of cirrus clouds and its radiative properties based on lidar observation over Chung-Li, Taiwan",2009,"10.1016/j.atmosres.2009.02.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649203069&doi=10.1016%2fj.atmosres.2009.02.008&partnerID=40&md5=6ea729569876c4062d0dff5c7a0f3a89","In this paper, characterization of cirrus clouds are made by using data from ground based polarization lidar and radiosonde measurements over Chung-Li (24.58°N, 121.10°E), Taiwan for a period of 1999-2006. During this period, the occurrence of cirrus clouds is about 37% of the total measurement nights over the lidar site. Analysis of the measurement gives the statistical characteristics about the macrophysical properties such as occurrence height, ambient temperature, and its geometrical thickness while the microphysical properties are interpreted in terms of extinction coefficient, optical depth, effective lidar ratio and depolarization ratio. The effective lidar ratio has been retrieved by using the simulation technique of backscattered lidar signals. The effect of multiple scattering has been taken into the account by a model calculation. Summer (Jun-Aug) shows the maximum appearances of cirrus due to its formation mechanism. It is shown that tropopause cirrus clouds may occur with a probability of about 24%. These clouds are usually optically thin and having laminar in structure with some cases resembling the characteristics similar to that of polar stratospheric clouds (PSCs). The radiative properties of the cirrus clouds are also discussed in detail by the empirical equations with results show a positive feedback on any climate change. © 2009 Elsevier B.V. All rights reserved."
"8718425100;13402933200;35228780900;36876999900;7003777023;","Assessment of near-future policy instruments for oceangoing shipping: Impact on atmospheric aerosol burdens and the earth's radiation budget",2009,"10.1021/es900922h","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649972735&doi=10.1021%2fes900922h&partnerID=40&md5=f289e5874543d7cc6b94c9ed3f068e2f","We apply the global climate model ECHAM5/MESSy1-MADE with detailed aerosol and cloud microphysics to study the impact of shipping on tropospheric aerosol burdens, clouds, and the radiationbudgetfor four near-future ship emission policy scenarios for the year 2012. We compare a ""No Control"" scenario with global sulfur limits and regionally applied reductions. We show that, if no control measures are taken, near surface sulfate increases by about 10-20% over the main transoceanic shipping routes from 2002 to 2012. A reduction of the maximum fuel sulfur (S) content allowed within 200 nautical miles of coastal areas (""global emission control areas"") to 0.5% or 0.1% (5000 or 1000 ppm S, respectively) results in a distinctive reduction in near surface sulfate from shipping in coastal regions compared with the year 2002. The model results also show that if emissions of nitrogen oxides (NOx) remain unabated, a reduction of the fuel sulfur content favors a strong increase in aerosol nitrate (NO3) which could counteract up to 20% of the decrease in sulfate mass achieved by sulfur emission reductions. The most important impact of shipping on the radiation budget is related to the modification of low maritime stratus clouds resulting in an increased reflectivity and enhanced shortwave cloud forcing. The direct aerosol effect from shipping is small. Our study shows that one can expect a less negative (less cooling) radiative forcing due to reductions in the current fuel sulfur content of ocean-going ships. The global annual average net cloud forcings due to shipping (year 2012) are in the range of -0.27 to -0.58 W/m2 with regional cooling occurring most over the remote oceans. © 2009 American Chemical Society."
"7005648526;7402079126;8315270100;","A preliminary statistical study of correlations between inflow feeder clouds, supercell or multicell thunderstorms, and severe weather",2009,"10.1175/2009WAF2222149.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74549197596&doi=10.1175%2f2009WAF2222149.1&partnerID=40&md5=9c06eb511d9807ee4c537d741dd3b646","This study examines the relationship between severe weather and organized lines of cumulus towers, called feeder clouds, which form in the inflow region of supercell and multicell thunderstorms. Using Geostationary Operational Environmental Satellite (GOES) imagery, correlations between the occurrence of feeder clouds and severe weather reports are explored. Output from the Weather Surveillance Radar-1988 Doppler (WSR88D) mesocyclone detection algorithm (MDA) is also assessed for a subset of the satellite case days. Statistics from the satellite and radar datasets are assembled to estimate not only the effectiveness of feeder cloud signatures as sole predictors of severe weather, but also the potential utility of combining feeder cloud analysis with the radar's MDA output. Results from this study suggest that the formation of feeder clouds as seen in visible satellite imagery is often followed by the occurrence of severe weather in a storm. The study finds that feeder cloud signatures by themselves have low skill in predicting severe weather. However, if feeder clouds are observed in a storm, there is a 77% chance that severe weather will occur within 30 min of the observation. For the cases considered, the MDA turns out to be the more effective predictor of severe weather. However, results show that combined predictions (feeder clouds plus mesocyclones) outperform both feeder cloud signatures and the MDA as separate predictors by ~10%-20%. Thus, the presence of feeder clouds as observed in visible imagery is a useful adjunct to the MDA in diagnosing a storm's potential for producing severe weather. © 2009 American Meteorological Society."
"7801654745;7003782348;7202621525;24777742800;6603757377;","Quantifying climate change in the tropical midtroposphere over East Africa from glacier shrinkage on Kilimanjaro",2009,"10.1175/2009JCLI2954.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69249098228&doi=10.1175%2f2009JCLI2954.1&partnerID=40&md5=6ee450a502a647042843b052e93ad35c","Slope glaciers on Kilimanjaro (ca. 5000-6000 m MSL) reached their most recent maximum extent in the late nineteenth century (L19) and have receded since then. This study quantifies the climate signal behind the recession of Kersten Glacier, which generates information on climate change in the tropical midtroposphere between L19 and present. Multiyear meteorological measurements at 5873m MSL serve to force and verify a spatially distributed model of the glacier's mass balance (the most direct link between glacier behavior and atmospheric forcing). At present the glacier is losing mass (522 ± 105 kg m-2 yr-1), terminates at 5100 m, and the interannual variability of mass and energy budgets largely reflects variability in atmospheric moisture. Backward modeling of the L19 steady-state glacier extent (down to 4500 m) reveals higher precipitation (+160 to +240 mm yr-1), higher air humidity, and increased fractional cloud cover in L19 but no significant changes in local air temperature, air pressure, and wind speed. The atmosphere in the simulated L19 climate transfers more energy to the glacier surface through atmospheric longwave radiation and turbulent heat - but this is almost entirely balanced by the decrease in absorbed solar radiation (due to both increased cloudiness and higher surface albedo). Thus, the energy-driven mass loss per unit area (sublimation plus meltwater runoff) was not appreciably different from today. Higher L19 precipitation rates therefore dominated the mass budget and produced a larger glacier extent in the past. © 2009 American Meteorological Society."
"55701363700;26324818700;","Seasonality of polar surface warming amplification in climate simulations",2009,"10.1029/2009GL040133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949125607&doi=10.1029%2f2009GL040133&partnerID=40&md5=1a26dddabb9a947847b8a816a8a7a602","The IPCC AR4 global warming climate simulations reveal a pronounced seasonality of polar warming amplification with maximum warming amplification in winter and minimum in summer. In this paper, we study me relative importance of surface albedo feedback (SAF), changes in cloud radiative forcing (CRF), changes in surface sensible and latent heat fluxes, changes in heat storage, and changes in me clear-sky downward infrared radiation in causing the strong seasonality of polar warming amplification by calculating partial temperature changes due to each of these processes using me surface energy budget equation. The main thermodynamic factor for a small polar warming amplification in summer is mat me positive SAF is largely cancelled out by the negative surface CRF feedback in summer. The positive SAF is relatively much weaker in winter compared to its amplitude in summer, therefore does not contribute to the pronounced polar warming amplification in winter. The seasonal cycle, of polar surface warming amplification, in terms of both spatial patterns and temporal amplitude, closely follows the seasonal cycle of the warming due to changes in clear-sky downward longwave radiation alone,' indicating the importance of the atmospheric processes, such as water vapor feedback and dynamical feedbacks associated wim the enhancement of poleward moist static energy transport, in causing the pronounced seasonality of polar warming amplification. Copyright 2009 by the American Geophysical Union."
"23096193700;34969751200;7005437964;6701738768;33467894100;34968972200;7202036497;","Evidence of climate change declines with elevation based on temperature and snow records from 1930s to 2006 on Mount Washington, New Hampshire, U.S.A.",2009,"10.1657/1938-4246-41.3.362","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69149102041&doi=10.1657%2f1938-4246-41.3.362&partnerID=40&md5=8b717f2ed4c6158e345d6c72702fb1f8","Mount Washington, New Hampshire, has the longest northeastern U.S. mountain climatological record (1930s to present), both at the summit (1914 m) and at Pinkham Notch (612 m). Pinkham's homogenized daily temperature exhibits annual (mean = +0.07°C/decade, p = 0.07; min = +0.11°C/decade, p = 0.01), winter (min = +0.18°C/decade, p = 0.07), spring (max = +0.13°C/decade, p = 0.10), and summer (min = +0.11°C/decade, p = 0.01) warming trends. Though suggesting annual, winter, and spring warming (0.05 to 0.12°C/decade), mean summit temperature trends were not significant. Pinkham shows no significant change in date of first and last snow; however, the summit does but its period of record is shorter. Onset of continuous snow cover has not changed significantly at either site. Thawing degree days trended earlier at the summit (2.8 days/decade; p = 0.01) and Pinkham Notch (1.6 days/decade, p < 0.01), but end of continuous snow cover trended significantly earlier (1.6 days/decade; p = 0.02) only at Pinkham. Growing degree days showed no significant trends at either location. Pinkham exhibits more climatic change than the summit but less than regional lower elevations. Thermal inversions and high incidence of cloud fog commonly at or above the regional atmospheric boundary layer may explain the summit's resistance to climate warming. Caution is needed when extrapolating climate change trends from other mountains or proximate lower elevation climate data to upper elevations."
"56228672600;36774212000;55461158100;35346000200;","Elevation dependency of recent and future minimum surface air temperature trends in the Tibetan Plateau and its surroundings",2009,"10.1016/j.gloplacha.2009.03.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68049094196&doi=10.1016%2fj.gloplacha.2009.03.017&partnerID=40&md5=b586db7d2104bb175f298b2769409000","Elevation dependency of climate change signals has been found over major mountain ranges such as the European Alps and the Rockies, as well as over the Tibetan Plateau. In this study we examined the temporal trends in monthly mean minimum temperatures from 116 weather stations in the eastern Tibetan Plateau and its vicinity during 1961-2006. We also analyzed projected climate changes in the entire Tibetan Plateau and its surroundings from two sets of modeling experiments under future global warming conditions. These analyses included the output of the NCAR Community Climate System Model (CCSM3) with approximately 150 km horizontal resolution for the scenario of annual 1% increase in atmospheric CO2 for future 100 years and physically-based downscaling results from the NCAR CAM3/CLM3 model at 10' × 10' resolution during three 20-year mean periods (1980-1999, 2030-2049 and 2080-2099) for the IPCC mid-range emission (A1B) scenario. We divided the 116 weather stations and the regional model grids into elevation zones of 500 m interval to examine the relationship of climatic warming and elevation. With these corroborating datasets, we were able to confirm the elevation dependency in monthly mean minimum temperature in and around the Tibetan Plateau. The warming is more prominent at higher elevations than at lower elevations, especially during winter and spring seasons, and such a tendency may continue in future climate change scenarios. The elevation dependency is most likely caused by the combined effects of cloud-radiation and snow-albedo feedbacks among various influencing factors. © 2009 Elsevier B.V. All rights reserved."
"33567601200;8502619500;7006401221;7004137530;14520585800;","The relationship of transient upper-level troughs to variability of the North American monsoon system",2009,"10.1175/2009JCLI2487.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69249085689&doi=10.1175%2f2009JCLI2487.1&partnerID=40&md5=62e308f1324eab592be6c2d406389e2f","Relationships between transient upper-tropospheric troughs and warm season convective activity over the southwest United States and northern Mexico are explored. Analysis of geopotential height and vorticity fields from the North American Regional Reanalysis and cloud-to-ground lightning data indicates that the passage of mobile inverted troughs (IVs) significantly enhances convection when it coincides with the peak diurnal cycle (1800-0900 UTC) over the North American monsoon (NAM) region. The preferred tracks of IVs during early summer are related to the dominant modes of Pacific sea surface temperature (SST) variability. When La Niña-like (El Niño-like) conditions prevail in the tropical Pacific and the eastern North Pacific has a horseshoe-shaped negative (positive) SST anomaly, IVs preferentially track farther north (south) and are slightly (typically one IV) more (less) numerous. These results point to the important role that synoptic-scale disturbances play in modulating the diurnal cycle of precipitation over the NAM region and the significant impact that the statistically supported low-frequency Pacific SST anomalies exert on the occurrence and track of these synoptic transients. © 2009 American Meteorological Society."
"56604019400;7404548584;7201527458;6603652793;7004371379;","Impact of modeled versus satellite measured tropical precipitation on regional smoke optical thickness in an aerosol transport model",2009,"10.1029/2009GL038823","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949182127&doi=10.1029%2f2009GL038823&partnerID=40&md5=1f477a528c68c76266789afb8abcd4b9","Aerosol and climate models are dependent on die parameterizations of the underlying meteorological model. Precipitation schemes in global meteorological models are designed to close die regional water budget, without concern for representative wet removal. By substituting numerical model precipitation for a multi-satellite precipitation dataset, we demonstrate me impact of modeled versus satellitederived precipitation on aerosol optical depth (AOD) in the Navy Aerosol Analysis and Prediction System (NAAPS). The model and satellite-derived precipitation are shown to have similar precipitation amounts, but die precipitation area from me model is about twice mat in die satellite data. The resulting difference in scavenging results in an increase in mid-visible AOD of about 20-200% in parts of Southeast Asia and South America during the burning seasons (or 0.1-0.2 in AOD). This suggests that care must be taken when combining free-running model and remote sensing data to evaluate smoke-cloud interactions or to estimate source magnitudes. Copyright 2009 by the American Geophysical Union."
"56221423400;7003460432;24331185200;55912769000;16445063600;","The early twentieth century warm period in the European Arctic",2009,"10.1127/0941-2948/2009/0391","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949372288&doi=10.1127%2f0941-2948%2f2009%2f0391&partnerID=40&md5=fd6c256b84b8f6ad14f666341a9931d6","The European Arctic experienced a pronounced warming around 1920 and a sustained warm period in the 1920s and 1930s. The causes of this climatic event are not fully known. However, understanding this event is considered important for assessing current and future climate change in the Arctic. Here we investigate the role of atmospheric circulation variability based on newly available historical upper-air data and statistical reconstructions of atmospheric circulation. The strongest warming at the ground from the 1910s to the 1920s and 1930s was found in wintertime. Historical upper-air data in this region from the 1930s show warm temperatures also in the lower troposphere. Reconstructed geopotential height fields suggest stronger than normal meridional transport of warm air into the European Arctic during the warm period compared to the preceding cold period. We propose that the 1920-1940 warm period can be subdivided into two periods with distinct circulation regimes: During the 1920s, warm, relatively clean air masses from the North Atlantic lead to a warming, while during the 1930s warm, rather polluted air masses from Western Europe played an important role. This is reflected in a sudden increase in sulphate concentrations in an ice core from Svalbard around 1930. The aerosols might have amplified the warming via changing cloud long wave emissivity, but this mechanism remains to be further studied. The circulation anomalies in the North Atlantic region during the early 20th century warm period that are shown in this paper form an observation-based counterpart against which model studies can be compared. © by Gebrüder Borntraeger 2009."
"7003460432;16445063600;55912769000;56308032100;56221423400;24331185200;7402989545;8661012100;7003683808;7102011023;","Variability of large-scale atmospheric circulation indices for the northern hemisphere during the past 100 years",2009,"10.1127/0941-2948/2009/0389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949391434&doi=10.1127%2f0941-2948%2f2009%2f0389&partnerID=40&md5=794fc4f833ef00b36f5ec994dc8886c8","We present an analysis of the large-scale atmospheric circulation variability since 1900 based on various circulation indices. They represent the main features of the zonal mean circulation in the northern hemisphere in boreal winter (such as the Hadley circulation, the subtropical jet, and the polar vortex in the lower stratosphere) as well as aspects of the regional and large-scale circulation (the Pacific Walker Circulation, the Indian monsoon, the North Atlantic Oscillation, NAO, and the Pacific North American pattern, PNA). For the past decades we calculate the indices from different reanalyses (NCEP/NCAR, ERA-40, JRA-25, ERAInterim). For the first half of the 20 th century the indices are statistically reconstructed based on historical upper-air and surface data as well as calculated from the Twentieth Century Reanalysis. The indices from all these observation-based data sets are compared to indices calculated from a 9-member ensemble of ""all forcings"" simulations performed with the chemistry-climate model SOCOL. After discussing the agreement among different data products, we analyse the interannual-to-decadal variability of the indices in the context of possible driving factors, such as El Niño/Southern Oscillation (ENSO), volcanic eruptions, and solar activity. The interannual variability of the Hadley cell strength, the subtropical jet strength, or the PNA is well reproduced by the model ensemble mean, i.e., it is predictable in the context of the specified forcings. The source of this predictability is mainly related to ENSO (or more generally, tropical sea-surface temperatures). For other indices such as the strength of the stratospheric polar vortex, the NAO, or the poleward extent of the Hadley cell the correlations between observations and model ensemble mean are much lower, but so are the correlations within the model ensemble. Multidecadal variability and trends in the individual series are discussed in the context of the underlying anthropogenic and natural forcings. While consistent trends were found for some of the indices, results also indicate that care should be taken when analysing trends in reconstructions or reanalysis data. © by Gebrüder Borntraeger 2009."
"18936286500;55891942100;","Effects of patch size and type of coffee matrix on ithomiine butterfly diversity and dispersal in cloud-forest fragments",2009,"10.1111/j.1523-1739.2009.01213.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650462259&doi=10.1111%2fj.1523-1739.2009.01213.x&partnerID=40&md5=a6517e068338d5b82d81d817bed6fa0d","Determining the permeability of different types of landscape matrices to animal movement is essential for conserving populations in fragmented landscapes. We evaluated the effects of habitat patch size and matrix type on diversity, isolation, and dispersal of ithomiine butterflies in forest fragments surrounded by coffee agroecosystems in the Colombian Andes. Because ithomiines prefer a shaded understory, we expected the highest diversity and abundance in large fragments surrounded by shade coffee and the lowest in small fragments surrounded by sun coffee. We also thought shade coffee would favor butterfly dispersal and immigration into forest patches. We marked 9675 butterflies of 39 species in 12 forest patches over a year. Microclimate conditions were more similar to the forest interior in the shade-coffee matrix than in the sun-coffee matrix, but patch size and matrix type did not affect species richness and abundance in forest fragments. Furthermore, age structure and temporal recruitment patterns of the butterfly community were similar in all fragments, independent of patch size or matrix type. There were no differences in the numbers of butterflies flying in the matrices at two distances from the forest patch, but their behavior differed. Flight in the sun-coffee matrix was rapid and directional, whereas butterflies in shade-coffee matrix flew slowly. Seven out of 130 recaptured butterflies immigrated into patches in the shade-coffee matrix, and one immigrated into a patch surrounded by sun coffee. Although the shade-coffee matrix facilitated movement in the landscape, sun-coffee matrix was not impermeable to butterflies. Ithomiines exhibited behavioral plasticity in habitat use and high mobility. These traits favor their persistence in heterogeneous landscapes, opening opportunities for their conservation. Understanding the dynamics and resource requirements of different organisms in rural landscapes is critical for identifying management options that address both animals' and farmers' needs. © 2009 Society for Conservation Biology."
"55537426400;10241462700;6603196127;","A comparison of climate feedback strength between CO2 doubling and LGM experiments",2009,"10.1175/2009JCLI2801.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651219260&doi=10.1175%2f2009JCLI2801.1&partnerID=40&md5=6153913f6fded6699de184d0cf55756b","Studies of the climate in the past potentially provide a constraint on the uncertainty of climate sensitivity, but previous studies warn against a simple scaling to the future. Climate sensitivity is determined by a number of feedback processes, and they may vary according to climate states and forcings. In this study, the similarities and differences in feedbacks for CO2 doubling, a Last Glacial Maximum (LGM), and LGM greenhouse gas (GHG) forcing experiments are investigated using an atmospheric general circulation model coupled to a slab ocean model. After computing the radiative forcing, the individual feedback strengths of water vapor, lapse-rate, albedo, and cloud feedbacks are evaluated explicitly. For this particular model, the difference in the climate sensitivity between the experiments is attributed to the shortwave cloud feedback, in which there is a tendency for it to become weaker or even negative in cooling experiments. No significant difference is found in the water vapor feedback between warming and cooling experiments by GHGs. The weaker positive water vapor feedback in the LGM experiment resulting from a relatively weaker tropical forcing is compensated for by the stronger positive lapse-rate feedback resulting from a relatively stronger extratropical forcing. A hypothesis is proposed that explains the asymmetric cloud response between the warming and cooling experiments associated with a displacement of the region of mixed-phase clouds. The difference in the total feedback strength between the experiments is, however, relatively small compared to the current intermodel spread, and does not necessarily preclude the use of LGM climate as a future constraint. © 2009 American Meteorological Society."
"55717244800;7004479957;","The University of Washington shallow convection and moist turbulence schemes and their impact on climate simulations with the community atmosphere model",2009,"10.1175/2008JCLI2557.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650512617&doi=10.1175%2f2008JCLI2557.1&partnerID=40&md5=fef52b4484310f821c1d84632a63c579","This paper describes a new version of the University of Washington shallow cumulus parameterization. The new version includes improved treatments of lateral mixing rates into cumulus updrafts, the evaporation of precipitation and of the interaction of cumuli with the underlying subcloud layer, and a treatment of the convective inhibition-based mass-flux closure that is more numerically stable and is suitable for the long time steps of global climate models. The paper also documents its performance when combined with a new moist turbulence parameterization in simulations with version 3.5 of the Community Atmosphere Model (CAM3.5). A single-column simulation of nonprecipitating trade cumulus shows considerable improvements in vertical thermodynamic structure and less resolution sensitivity in the new schemes compared to CAM3.5. In global simulations, the new schemes, combined with an increase of vertical resolution from 26 to 30 levels, produce a significant (7%) reduction in overall climate bias, calculated from root-mean-squared error of the seasonal model climatology compared to a suite of global observations of various fields. Biases in almost all fields, particularly the shortwave cloud radiative forcing, are reduced. Geographical bias patterns in surface rainfall, liquid water path, and surface air temperature are only mildly affected by the model parameterization and vertical resolution changes. © 2009 American Meteorological Society."
"7004479957;55717244800;","A new moist turbulence parameterization in the community atmosphere model",2009,"10.1175/2008JCLI2556.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650512618&doi=10.1175%2f2008JCLI2556.1&partnerID=40&md5=cfbbc88b96dc5b4d7a10f7537b5a5c6e","A new moist turbulence parameterization is presented and implemented in the Community Atmosphere Model (CAM). It is derived from Grenier and Bretherton but has been heavily modified to improve its numerical stability and efficiency with the long time steps used in climate models. A goal was to provide a more physically realistic treatment of marine stratocumulus-topped boundary layers than in the current CAM. Key features of the scheme include use of moist-conserved variables, an explicit entrainment closure for convective layers, diagnosis of turbulent kinetic energy (TKE) for computation of turbulent diffusivities, an efficient new formulation of TKE transport as a relaxation to layer-mean TKE, and unified treatment of all turbulent layers in each atmospheric column. The scheme is compared with the default turbulence parameterizations in the CAM using three singlecolumn modeling cases, using both operational and high vertical and time resolution. Both schemes performed comparably well on the dry convective boundary layer case. For a stable boundary layer case, the default CAM overdeepens the boundary layer unless its free-tropospheric mixing length is greatly reduced, whereupon the new scheme and default CAM again both perform well at both tested resolutions. A nocturnal stratocumulus case was much better simulated by the new scheme than the default CAM, with much less resolution sensitivity. Global climate simulations with the new scheme in tandem with a new shallow cumulus parameterization are presented in a companion paper. © 2009 American Meteorological Society."
"6506718302;8669968400;6506152198;6506373162;23052016900;7003931528;55957189000;","Aerosol microphysics modules in the framework of the ECHAM5 climate model-intercomparison under stratospheric conditions",2009,"10.5194/gmd-2-97-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954607021&doi=10.5194%2fgmd-2-97-2009&partnerID=40&md5=a7b290794567383c3efc0bb68a2c1fa5","In this manuscript, we present an intercomparison of three different aerosol microphysics modules that are implemented in the climate model ECHAM5. The comparison was done between the modal aerosol microphysics module M7, which is currently the default aerosol microphysical core in ECHAM5, and two sectional aerosol microphysics modules SALSA, and SAM2. The detailed aerosol microphysical model MAIA was used as a reference to evaluate the results of the aerosol microphysics modules with respect to sulphate aerosol. The ability of the modules to describe the development of the aerosol size distribution was tested in a zero dimensional framework. We evaluated the strengths and weaknesses of different approaches under different types of stratospheric conditions. Also, we present an improved method for the time integration in M7 and study how the setup of the modal aerosol modules affects the evolution of the aerosol size distribution. Intercomparison simulations were carried out with varying SO2 concentrations from background conditions to extreme values arising from stratospheric injections by large volcanic eruptions. Under background conditions, all microphysics modules were in good agreement describing the shape of the aerosol size distribution, but the scatter between the model results increased with increasing SO2 concentrations. In particular in the volcanic case the setups of the aerosol modules have to be adapted in order to dependably capture the evolution of the aerosol size distribution, and to perform in global model simulations. In summary, this intercomparison serves as a review of the different aerosol microphysics modules which are currently available for the climate model ECHAM5. © 2009 Author(s)."
"8559490800;6603206037;57209057193;","Impact of swell on simulations using a regional atmospheric climate model",2009,"10.1111/j.1600-0870.2009.00403.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651052913&doi=10.1111%2fj.1600-0870.2009.00403.x&partnerID=40&md5=1f97c5b0bbf80b155460dd4f65e15e9d","When long, fast swell waves travel in approximately the same direction as the wind, the surface stress is reduced compared with under wind-sea conditions. Using measurements from the Östergarnsholm site in the Baltic Sea, new expressions of the roughness length were developed for wind sea and swell. These new expressions were implemented in the RCA3 regional climate model covering Europe. A 3-year simulation and two case studies using the wavefield from the ECMWF reanalysis (ERA-40) were analysed using the improved formulations. Wind-following swell led to a significant reduction of mean wind stress and heat fluxes. The mean surface layer wind speed was redistributed horizontally and the marine boundary layer cooled and dried slightly. This cooling was most pronounced over North Sea and the Norwegian Sea (almost 0.2°C annually on average) whereas the drying was most pronounced over the Mediterranean Sea (almost 0.4 g kg-1). Somewhat less convective precipitation and low-level cloudiness over the sea areas were also indicated, in particular over the Mediterranean Sea. The impact on the atmosphere, however, is significantly locally greater in time and space. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard."
"57192615132;55717074000;7401936984;7401974644;7005877775;","Testing ice microphysics parameterizations in the NCAR Community Atmospheric Model Version 3 using Tropical Warm Pool-International Cloud Experiment data",2009,"10.1029/2008JD011220","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350064177&doi=10.1029%2f2008JD011220&partnerID=40&md5=b1ba6dff07ee879910d349ea5d2e9163","Cloud properties have been simulated with a new double-moment microphysics scheme under the framework of the single-column version of NCAR Community Atmospheric Model version 3 (CAM3). For comparison, the same simulation was made with the standard single-moment microphysics scheme of CAM3. Results from both simulations compared favorably with observations during the Tropical Warm Pool-International Cloud Experiment by the U.S. Department of Energy Atmospheric Radiation Measurement Program in terms of the temporal variation and vertical distribution of cloud fraction and cloud condensate. Major differences between the two simulations are in the magnitude and distribution of ice water content within the mixed-phase cloud during the monsoon period, though the total frozen water (snow plus ice) contents are similar. The ice mass content in the mixed-phase cloud from the new scheme is larger than that from the standard scheme, and ice water content extends 2 km further downward, which is in better agreement with observations. The dependence of the frozen water mass fraction on temperature from the new scheme is also in better agreement with available observations. Outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from the simulation with the new scheme is, in general, larger than that with the standard scheme, while the surface downward longwave radiation is similar. Sensitivity tests suggest that different treatments of the ice crystal effective radius contribute significantly to the difference in the calculations of TOA OLR, in addition to cloud water path. Numerical experiments show that cloud properties in the new scheme can respond reasonably to changes in the concentration of aerosols and emphasize the importance of correctly simulating aerosol effects in climate models for aerosol-cloud interactions. Further evaluation, especially for ice cloud properties based on in situ data, is needed."
"34976155900;7005753600;7003875148;8982748700;16312624300;35462130800;9038337500;","The performance of a global and mesoscale model over the central Arctic Ocean during late summer",2009,"10.1029/2008JD010790","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349316889&doi=10.1029%2f2008JD010790&partnerID=40&md5=3e4160403a59b8fbabacf44079d16f37","Measurements of turbulent fluxes, clouds, radiation, and profiles of mean meteorological parameters, obtained over an ice floe in the central Arctic Ocean during the Arctic Ocean Experiment 2001, are used to evaluate the performance of U.K. Met Office Unified Model (MetUM) and Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) in the lower atmosphere during late summer. Both the latest version of the MetUM and the version operational in 2001 are used in the comparison to gain an insight as to whether updates to the model have improved its performance over the Arctic region. As with previous model evaluations over the Arctic, the pressure, humidity, and wind fields are satisfactorily represented in all three models. The older version of the MetUM underpredicts the occurrence of low-level Arctic clouds, and the liquid and ice cloud water partitioning is inaccurate compared to observations made during SHEBA. In the newer version, simulated ice and liquid water paths are improved, but the occurrence of low-level clouds are overpredicted. Both versions overestimate the amount of radiative heat absorbed at the surface, leading to a significant feedback of errors involving the surface albedo, which causes a large positive bias the surface temperature. Cloud forcing in COAMPS produces similar biases in the downwelling shortwave and longwave radiation fluxes to those produced by UM(G25). The surface albedo parameterization is, however, more realistic, and thus, the total heat flux and surface temperature are more accurate for the majority of the observation period. Copyright 2009 by the American Geophysical Union."
"7004034323;57199362778;57216980911;7402254888;","Overview of observations from the RADAGAST experiment in Niamey, Niger: 2. Radiative fluxes and divergences",2009,"10.1029/2008JD010497","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349311887&doi=10.1029%2f2008JD010497&partnerID=40&md5=b82ec504457d632b83630f53b0a5e2cf","Broadband shortwave and longwave radiative fluxes observed both at the surface and from space during the Radiative Atmospheric Divergence using ARM Mobile Facility, GERB data and AMMA Stations (RADAGAST) experiment in Niamey, Niger, in 2006 are presented. The surface fluxes were measured by the Atmospheric Radiation Measurement (ARM) Program Mobile Facility (AMF) at Niamey airport, while the fluxes at the top of the atmosphere (TOA) are from the Geostationary Earth Radiation Budget (GERB) instrument on the Meteosat-8 satellite. The data are analyzed as daily averages, in order to minimize sampling differences between the surface and top of atmosphere instruments, while retaining the synoptic and seasonal changes that are the main focus of this study. A cloud mask is used to identify days with cloud versus those with predominantly clear skies. The influence of temperature, water vapor, aerosols, and clouds is investigated. Aerosols are ubiquitous throughout the year and have a significant impact on both the shortwave and longwave fluxes. The large and systematic seasonal changes in temperature and column integrated water vapor (CWV) through the dry and wet seasons are found to exert strong influences on the longwave fluxes. These influences are often in opposition to each other, because the highest temperatures occur at the end of the dry season when the CWV is lowest, while in the wet season the lowest temperatures are associated with the highest values of CWV. Apart from aerosols, the shortwave fluxes are also affected by clouds and by the seasonal changes in CWV. The fluxes are combined to provide estimates of the divergence of radiation across the atmosphere throughout 2006. The longwave divergence shows a relatively small variation through the year, because of a partial compensation between the seasonal variations in the outgoing longwave radiation (OLR) and surface net longwave radiation. A simple model of the greenhouse effect is used to interpret this result in terms of the dependence of the normalized greenhouse effect at the TOA and of the effective emissivity of the atmosphere at the surface on the CWV. It is shown that, as the CWV increases, the atmosphere loses longwave energy to the surface with about the same increasing efficiency with which it traps the OLR. When combined with the changes in temperature, this maintains the atmospheric longwave divergence within the narrow range that is observed. The shortwave divergence is mainly determined by the CWV and aerosol loadings and the effect of clouds is much smaller than on the component fluxes. Copyright 2009 by the American Geophysical Union."
"26643250500;7004027519;7403420115;57197256645;7004944088;","Trapping of trace gases by growing ice surfaces including surface-saturated adsorption",2009,"10.1029/2009JD011857","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349311888&doi=10.1029%2f2009JD011857&partnerID=40&md5=1807b62729712739e586dc6c9e57cc16","Key steps leading to the uptake of trace gases into atmospheric cloud ice particles include gas phase diffusion of trace gas molecules toward growing ice crystals and the kinetics of molecular interactions at the ice surfaces. In the case of nitric acid, laboratory studies and airborne field observations indicate uptake in growing ice films and cirrus ice particles above the thermodynamic solubility limit. This implies that uptake of nitric acid molecules on growing ice surfaces (trapping) controls the nitric acid content in ice particles residing in supersaturated air. A previous trapping model is updated to include effects of surface-saturated adsorption. Exact analytical solutions to the problem are derived to enable the calculation of the amount of vapor trapped for a given ice growth rate, assuming Langmuir-type adsorption isotherms. Those solutions are provided in terms of trapping efficiencies and equivalent uptake coefficients, net vapor fluxes toward ice crystals or ice films, steady state molar ratios of trapped molecules in the ice phase, and gas-ice partitioning factors. The trapping model includes the underlying adsorption equilibrium model asymptotically for nongrowing ice particles. Comparisons to laboratory and field measurements of nitric acid uptake are carried out. Observed dependences of uptake as a function of nitric acid partial pressure, ice growth rate, and temperature are reproduced fairly well. Nitric acid molar ratios in cirrus ice are neither controlled purely by adsorption nor purely by gas phase diffusion, underscoring the importance of using the trapping concept to interpret these observations. These results also suggest further mechanisms that enhance the nitric acid content in cirrus ice at the tropical tropopause at very low temperatures. A discussion of potential model improvements outlines the physical conditions in which the updated model describes trapping well and leads to further insight into the physical nature of the trapping process. Copyright 2009 by the American Geophysical Union."
"25031430500;13406399300;55479189900;57203030873;","Processes regulating short-lived species in the tropical tropopause layer",2009,"10.1029/2009JD0011785","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349312969&doi=10.1029%2f2009JD0011785&partnerID=40&md5=ba9e4df54429edf8a3c40e1b245368ce","A one-dimensional model of vertical transport in the tropical tropopause layer (TTL) is developed. The model uses vertical advection, a convective source, and a chemical sink to simulate the profiles of very short lived substances in the TTL. The model simulates evanescent profiles of short-lived hydrocarbon species observed by satellite and is also used to simulate short-lived bromine species. Tracers with chemical lifetimes of 25 days or longer have significant concentrations in the stratosphere, and vertical advection is critical. Convection is important up to its peak altitude, nearly 19 km. Convection dominates the distribution of species with lifetimes less than 25 days. The annual cycle of species with lifetimes longer than 25 days is governed primarily by the variations of vertical velocity, not convection. This is particularly true for carbon monoxide, where a seasonal cycle in the lower stratosphere of the right phase is produced without variations in tropospheric emissions. An analysis of critical short-lived bromine species (CH <inf>2</inf>Br<inf>2</inf> and CHBr<inf>3</inf>) indicates that substantial amounts of these tracers may get advected into the lower stratosphere as source gases at 18 km, and are estimated to contribute 2.8 pptv (1.1-4.1) to stratospheric bromine. Copyright 2009 by the American Geophysical Union."
"26659116700;7004028051;7003582587;26659013400;57193920163;","Two fast radiative transfer methods to improve the temporal sampling of clouds in numerical weather prediction and climate models",2009,"10.1002/qj.385","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649419182&doi=10.1002%2fqj.385&partnerID=40&md5=860cb1e4d592914321da13612dd368b9","The high computational cost of calculating the radiative heating rates in numerical weather prediction (NWP) and climate models requires that calculations are made infrequently, leading to poor sampling of the fast-changing cloud field and a poor representation of the feedback that would occur. This paper presents two related schemes for improving the temporal sampling of the cloud field. Firstly, the 'split time-stepping' scheme takes advantage of the independent nature of the monochromatic calculations of the 'correlated-k' method to split the calculation into gaseous absorption terms that are highly dependent on changes in cloud (the optically thin terms) and those that are not (optically thick). The small number of optically thin terms can then be calculated more often to capture changes in the grey absorption and scattering associated with cloud droplets and ice crystals. Secondly, the 'incremental time-stepping' scheme uses a simple radiative transfer calculation using only one or two monochromatic calculations representing the optically thin part of the atmospheric spectrum. These are found to be sufficient to represent the heating rate increments caused by changes in the cloud field, which can then be added to the last full calculation of the radiation code. We test these schemes in an operational forecast model configuration and find a significant improvement is achieved, for a small computational cost, over the current scheme employed at the Met Office. The 'incremental time-stepping' scheme is recommended for operational use, along with a new scheme to correct the surface fluxes for the change in solar zenith angle between radiation calculations. Copyright © Crown Copyright 2009. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd."
"17347195800;7004242319;","Single-scattering properties of aggregates of plates",2009,"10.1002/qj.378","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649424386&doi=10.1002%2fqj.378&partnerID=40&md5=c96ae00a9b59e91683ae319e06a09c26","During the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) sponsored by the Atmospheric Radiation Measurement programme, the Scaled Composites Proteus aircraft executed spiral profiles and flew horizontal legs through aging anvils, fresh anvils, and cirrus of unknown origin in the vicinity of Darwin, Australia. Pristine ice crystals including both plates and bullet rosettes, their aggregates, and unclassifiable ice crystals were observed by a Cloud Particle Imager. The widths of observed plates ranged between 80 μm and 200 μm. When a fresh dissipating anvil was observed on 2 February, aggregates of plates contributed 46.2% of the total area of measured ice crystals with maximum dimensions greater than 200 μm, while it was only 7.2% and 1.0% for 27 and 29 January, respectively, when aged cirrus was sampled. Because aggregates of plates have been observed to make large contributions to projected ice crystal area near convection during TWP-ICE and other projects, their single-scattering properties that have not been previously examined are investigated here. The dependence of the scattering phase function P11, asymmetry parameter g, and single-scattering albedo ω0 on three parameters (the area ratio AR, normalized projected area An, and a newly defined aggregation index AI which varies between 0 and 1 with ice crystals with more compact shape having lower AI) defining the three-dimensional shapes of aggregates of plates were calculated using a geometric ray-tracing code at wavelengths λ of 0.55, 1.38 and 2.13 μm. The scattering properties depended on the crystal morphology with, for example, the g of an aggregate of plates with a high AI of 0.818 differing by +6.89% (+6.44%; +4.55%) from that with a lower AI of 0.378 at λ of 0.55 μm (1.38 μm; 2.13 μm), but by only +0.29% (+0.25%; -0.03%) from those of the component plates. The ω 0 at absorbing λ increased with AI, 1 - AR, and An. Adding ray distortion to the aggregates caused a decrease in forward scattering and an increase in lateral and backward scattering, decreasing g, an effect that weakened with λ due to absorption. The aggregates of plates with low AI were more influenced by ray distortion compared to those with high AI. The dependence of scattering properties on crystal morphology noted here should be considered when computing bulk scattering properties of ice clouds to determine its importance for climate and remote-sensing studies. Copyright © 2009 Royal Meteorological Society."
"7005354212;7005236944;7004587891;14014252200;55465604600;6602128668;22234180300;","A geometry-based approach to identifying cloud shadows in the VIIRS cloud mask algorithm for NPOESS",2009,"10.1175/2009JTECHA1198.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73049088947&doi=10.1175%2f2009JTECHA1198.1&partnerID=40&md5=1d550b2ff87707efc1579b6337b60043","A geometry-based approach is presented to identify cloud shadows using an automated cloud classification algorithm developed for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) program. These new procedures exploit both the cloud confidence and cloud phase intermediate products generated by the Visible/Infrared Imager/Radiometer Suite (VIIRS) cloud mask (VCM) algorithm. The procedures have been tested and found to accurately detect cloud shadows in global datasets collected by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) sensor and are applied over both land and ocean background conditions. These new procedures represent a marked departure from those used in the heritage MODIS cloud mask algorithm, which utilizes spectral signatures in an attempt to identify cloud shadows. However, they more closely follow those developed to identify cloud shadows in the MODIS Surface Reflectance (MOD09) data product. Significant differences were necessary in the implementation of the MOD09 procedures to meet NPOESS latency requirements in the VCM algorithm. In this paper, the geometry-based approach used to predict cloud shadows is presented, differences are highlighted between the heritage MOD09 algorithm and new VIIRS cloud shadow algorithm, and results are shown for both these algorithms plus cloud shadows generated by the spectral-based approach. The comparisons show that the geometry-based procedures produce cloud shadows far superior to those predicted with the spectral procedures. In addition, the new VCM procedures predict cloud shadows that agree well with those found in the MOD09 product while significantly reducing the execution time as required to meet the operational time constraints of the NPOESS system. © 2009 American Meteorological Society."
"11839267100;7202772927;55745955800;7006957668;7401936984;7401701196;55718206700;35072928400;57201725986;","A contribution by ice nuclei to global warming",2009,"10.1002/qj.449","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949170600&doi=10.1002%2fqj.449&partnerID=40&md5=9aebfdfe9a1197f3f25ac1c2543ff69a","Ice nuclei (IN) significantly affect clouds via supercooled droplets, that in turn modulate atmospheric radiation and thus climate change. Since the IN effect is relatively strong in stratiform clouds but weak in convective ones, the overall effect depends on the ratio of stratiform to convective cloud amount. In this paper, ten years of TRMM (Tropical Rainfall Measuring Mission) satellite data are analyzed to confirm that stratiform precipitation fraction increases with increasing latitude, which implies that the IN effect is stronger at higher latitudes. To quantitatively evaluate the IN effect versus latitude, large-scale forcing data from ten field campaigns are used to drive a cloud-resolving model to generate long-term cloud simulations. As revealed in the simulations, the increase in the net downward radiative flux at the top of the atmosphere from doubling the current IN concentrations is larger at higher latitude, which is attributed to the meridional tendency in the stratiform precipitation fraction. Surface warming from doubling the IN concentrations, based on the radiative balance of the globe, is compared with that from anthropogenic CO2. It is found that the former effect is stronger than the latter in middle and high latitudes but not in the Tropics. With regard to the impact of IN on global warming, there are two factors to consider: the radiative effect from increasing the IN concentration and the increase in IN concentration itself. The former relies on cloud ensembles and thus varies mainly with latitude. In contrast, the latter relies on IN sources (e.g. the land surface distribution) and thus varies not only with latitude but also longitude. Global desertification and industrialization provide clues on the geographic variation of the increase in IN concentration since pre-industrial times. Thus, their effect on global warming can be inferred and can then be compared with observations. A general match in geographic and seasonal variations between the inferred and observed warming suggests that IN may have contributed positively to global warming over the past decades, especially in middle and high latitudes. © 2009 Royal Meteorological Society."
"7102128820;7006146719;7007114756;","Verification of cloud-fraction forecasts",2009,"10.1002/qj.481","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349589800&doi=10.1002%2fqj.481&partnerID=40&md5=e79a805ddd23d8cc22b3e10ac4fc03b3","Cloud radar and lidar can be used to evaluate the skill of numerical weather prediction models in forecasting the timing and placement of clouds, but care must be taken in choosing the appropriate metric of skill to use due to the non- Gaussian nature of cloud-fraction distributions. We compare the properties of a number of different verification measures and conclude that of existing measures the Log of Odds Ratio is the most suitable for cloud fraction. We also propose a new measure, the Symmetric Extreme Dependency Score, which has very attractive properties, being equitable (for large samples), difficult to hedge and independent of the frequency of occurrence of the quantity being verified. We then use data from five European ground-based sites and seven forecast models, processed using the 'Cloudnet' analysis system, to investigate the dependence of forecast skill on cloud fraction threshold (for binary skill scores), height, horizontal scale and (for the Met Office and German Weather Service models) forecast lead time. The models are found to be least skillful at predicting the timing and placement of boundary-layer clouds and most skilful at predicting mid-level clouds, although in the latter case they tend to underestimate mean cloud fraction when cloud is present. It is found that skill decreases approximately inverse-exponentially with forecast lead time, enabling a forecast 'half-life' to be estimated. When considering the skill of instantaneous model snapshots, we find typical values ranging between 2.5 and 4.5 days. © 2009 Royal Meteorological Society."
"55796506900;42263280300;7101700943;22137065500;","A modeling study of the effects of direct radiative forcing due to carbonaceous aerosol on the climate in East Asia",2009,"10.1007/s00376-009-0057-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649361964&doi=10.1007%2fs00376-009-0057-5&partnerID=40&md5=37bb30aded791f9036e0b94bc72bd305","The study investigated the effects of global direct radiative forcing due to carbonaceous aerosol on the climate in East Asia, using the CAM3 developed by NCAR. The results showed that carbonaceous aerosols cause negative forcing at the top of the atmosphere (TOA) and surface under clear sky conditions, but positive forcing at the TOA and weak negative forcing at the surface under all sky conditions. Hence, clouds could change the sign of the direct radiative forcing at the TOA, and weaken the forcing at the surface. Carbonaceous aerosols have distinct effects on the summer climate in East Asia. In southern China and India, it caused the surface temperature to increase, but the total cloud cover and precipitation to decrease. However, the opposite effects are caused for most of northern China and Bangladesh. Given the changes in temperature, vertical velocity, and surface streamflow caused by carbonaceous aerosol in this simulation, carbonaceous aerosol could also induce summer precipitation to decrease in southern China but increase in northern China. © Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH 2009."
"25649157100;6506914844;25650618700;","Environmental conditions responsible for the type of precipitation in summer convective storms over Bulgaria",2009,"10.1016/j.atmosres.2008.10.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349231434&doi=10.1016%2fj.atmosres.2008.10.010&partnerID=40&md5=9531728840202a654ef29e595643691b","Environmental conditions of 155 days with precipitation over a part of the Upper Thracian lowland in Bulgaria from May to September of 2002-2006 are studied in order to determine meteorological variables that may be used to specify the type of precipitation (rain or hail) on the ground. The cases have been divided into two samples - days with frontal convective clouds (125) and days with free convection (30). Analyses reveal that the mean values and the thresholds of CAPE and LI during the days with hail are similar to their corresponding values determined for thunderstorm development in other regions in Europe. Results show that none of the analyzed instability indices or environmental parameters alone is able to determine the type of precipitation on the ground. The best classification function of the cases according to the type of precipitation (rain or hail) is derived when the in-cloud characteristics simulated by 1-D numerical cloud model are included together with the instability indices and the environmental parameters as variables in the stepwise discriminant analysis. The analysis reveals that the simulated characteristics of the vertical velocity are an important ingredient in the classification function of the type of precipitation on the ground, due to the incorporation of the non-linear impact of environmental conditions on the formation of precipitation. © 2008 Elsevier B.V. All rights reserved."
"56962915800;57199180379;57218273453;","A review on aspects of climate simulation assessment",2009,"10.1007/s00376-009-9038-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70849112159&doi=10.1007%2fs00376-009-9038-y&partnerID=40&md5=39fd606b47b0f48fde58d85513d10f16","This paper reviews some aspects of evaluation of climate simulation, including the ITCZ, the surface air temperature (SAT), and the monsoon. A brief introduction of some recently proposed approaches in weather forecast verification is followed by a discussion on their possible application to evaluation of climate simulation. The authors suggest five strategies to extend the forecast verification methods to climate simulation evaluation regardless significant differences between the forecasts and climate simulations. It is argued that resolution, convection scheme, stratocumulus cloud cover, among other processes in the atmospheric general circulation model (AGCM) and the ocean-atmosphere feedback are the potential causes for the double ITCZ problem in coupled models and AGCM simulations, based on the system- and component-level evaluations as well as the downscaling strategies in some recent research. Evaluations of simulated SAT and monsoons suggest that both coupled models and AGCMs show good performance in representing the SAT evolution and its variability over the past century in terms of correlation and wavelet analysis but poor at reproducing rainfall, and in addition, the AGCM alone is not suitable for monsoon regions due to the lack of air-sea interactions. © 2009 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH."
"8140555300;7006212411;35547807400;7103312958;26632388700;8314917200;55754604900;7004194999;","Aviation and global climate change in the 21st century",2009,"10.1016/j.atmosenv.2009.04.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649312432&doi=10.1016%2fj.atmosenv.2009.04.024&partnerID=40&md5=1b2df386db7efc51041e92c4af7e7b95","Aviation emissions contribute to the radiative forcing (RF) of climate. Of importance are emissions of carbon dioxide (CO2), nitrogen oxides (NOx), aerosols and their precursors (soot and sulphate), and increased cloudiness in the form of persistent linear contrails and induced-cirrus cloudiness. The recent Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) quantified aviation's RF contribution for 2005 based upon 2000 operations data. Aviation has grown strongly over the past years, despite world-changing events in the early 2000s; the average annual passenger traffic growth rate was 5.3% yr-1 between 2000 and 2007, resulting in an increase of passenger traffic of 38%. Presented here are updated values of aviation RF for 2005 based upon new operations data that show an increase in traffic of 22.5%, fuel use of 8.4% and total aviation RF of 14% (excluding induced-cirrus enhancement) over the period 2000-2005. The lack of physical process models and adequate observational data for aviation-induced cirrus effects limit confidence in quantifying their RF contribution. Total aviation RF (excluding induced cirrus) in 2005 was ∼55 mW m-2 (23-87 mW m-2, 90% likelihood range), which was 3.5% (range 1.3-10%, 90% likelihood range) of total anthropogenic forcing. Including estimates for aviation-induced cirrus RF increases the total aviation RF in 2005-78 mW m-2 (38-139 mW m-2, 90% likelihood range), which represents 4.9% of total anthropogenic forcing (2-14%, 90% likelihood range). Future scenarios of aviation emissions for 2050 that are consistent with IPCC SRES A1 and B2 scenario assumptions have been presented that show an increase of fuel usage by factors of 2.7-3.9 over 2000. Simplified calculations of total aviation RF in 2050 indicate increases by factors of 3.0-4.0 over the 2000 value, representing 4-4.7% of total RF (excluding induced cirrus). An examination of a range of future technological options shows that substantive reductions in aviation fuel usage are possible only with the introduction of radical technologies. Incorporation of aviation into an emissions trading system offers the potential for overall (i.e., beyond the aviation sector) CO2 emissions reductions. Proposals exist for introduction of such a system at a European level, but no agreement has been reached at a global level. © 2009 Elsevier Ltd."
"7801654745;7201425334;6506421999;7003782348;","Temporal precipitation variability versus altitude on a tropical high mountain: Observations and mesoscale atmospheric modelling",2009,"10.1002/qj.461","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69249103992&doi=10.1002%2fqj.461&partnerID=40&md5=33942cec6ff2683d64403e67ad9df2b1","The occurrence of maximum precipitation amounts (Pmax) on tropical high mountains at mid elevations is well documented (spatial variability), but little is known about the temporal variability of precipitation in different elevation zones. The present study targets this issue by combining various types of observations on and around Kilimanjaro (East Africa, 5895 m a.s.l.) with mesoscale atmospheric modelling. In observations, the vertical moisture profiles of air masses approaching the mountain clearly differ during 'normal' and 'significant' daily precipitation events on Kilimanjaro's summit, while model experiments illustrate that the elevation zone of Pmax is shifted upslope substantially during the latter events. Large (small) differences in precipitation therefore appear in the dry (moist) high-elevation (mid- and low-elevation) zones of the mountain. This space-time pattern is evident in observations of seasonal precipitation variability on Kilimanjaro and on nearby Mount Kenya for anomalous wet seasons, which are controlled by the frequency of 'significant' daily events. The upslope shift of Pmax in the model is favoured by dynamical factors (stronger air ascent and higher static instability of clouds), microphysical processes (greater efficiency in converting condensate to precipitation over high-elevation terrain), and related feedback mechanisms (stronger latent heating). Beyond the seasonal scale, tropical climate change also entails changed frequencies of dry- and moist-air advection, which is demonstrated for the Kilimanjaro region over 1979-2006. Thus, long-term changes of precipitation are probably most drastic in the dry summit zones of tropical high mountains. © 2009 Royal Meteorological Society."
"7404570418;7006003656;10143713900;57197127150;7405403772;8262135300;7004646998;57203259172;24775595900;34770246300;","Building an automated integrated observing system to detect sea surface temperature anomaly events in the Florida keys",2009,"10.1109/TGRS.2009.2024992","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651165163&doi=10.1109%2fTGRS.2009.2024992&partnerID=40&md5=8c35326d824d33d1d89ec2e87b173969","Satellite-derived sea surface temperature (SST) images have had limited applications in near-shore and coastal environments due to inadequate spatial resolution, incorrect geocorrection, or cloud contamination. We have developed a practical approach to remove these errors using Advanced Very High Resolution Radiometer (AVHRR) and MODerate-resolution Imaging Spectroradiometer (MODIS) 1-km resolution data. The objective was to improve the accuracy of SST anomaly estimates in the Florida Keys and to provide the best quality (in particular, high temporal and spatial resolutions) SST data products for this region. After manual navigation of over 47000 AVHRR images (19932005), we implemented a cloud-filtering technique that differs from previously published image processing methods. The filter used a 12-year climatology and ±3-day running SST statistics to flag cloud-contaminated pixels. Comparison with concurrent ( ±0.5 h) data from the SEAKEYS in situ stations in the Florida Keys showed near-zero bias errors (< 0.05°C) in the weekly anomaly for SST anomalies between -3° and 3 °, with standard deviations <0.5°C. The cloud filter was implemented using Interactive Data Language for near-real-time processing of AVHRR and MODIS data. The improved SST products were used to detect SST anomalies and to estimate degree-heating weeks (DHWs) to assess the potential for coral reef stress. The mean and anomaly products are updated weekly, with periodic updates of the DHW products, on a Web site. The SST data at specific geographical locations were also automatically ingested in near real time into National Oceanic and Atmospheric Administration's (NOAA) Integrated Coral Observing Network Web-based application to assist in management and decision making through a novel expert system tool (G2) implemented at NOAA. © 2006 IEEE."
"35107879000;7407456789;","Identifying the relationships between urban water consumption and weather variables in Seoul, Korea",2009,"10.2747/0272-3646.30.4.324","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450270679&doi=10.2747%2f0272-3646.30.4.324&partnerID=40&md5=7d7d237bcdfa2c61391a9f1e607ef6c4","As anthropogenic climate change threatens the reliability of urban water supplies, it is essential to build understanding of the relationships between weather and water consumption. We used daily and monthly data from 2002 to 2007 to conduct a statistical analysis of how seasonal water use in Seoul, South Korea is affected by weather variables. The Pearson, Kendall, and Spearman tests indicated that all weather variables were significantly correlated with per capita water use at most timescales, with mean, minimum, and maximum temperatures and daylight length positively correlated, and precipitation, wind speed, relative humidity, and cloud cover showing an inverse relation with water use. Once the influence of maximum temperature is controlled, water consumption is only significantly associated with wind speed and daylight length, as indicated by the partial correlation coefficient values. Ordinary least square (OLS) regression models explain between 39 and 61% of the variance in seasonal water use, indicating that approximately one-third to two-thirds of the variation is due to weather variables alone. Daily water consumption in July increases up to 4 liters per person with a one degree increase in maximum temperature. Significant improvement of the modeling of seasonal water use was achieved by developing autoregressive integrated moving average (ARIMA) models, which account for autocorrelation in the time series and explain up to 66% of the variance in water use. Our results indicate that weather plays a significant role in determining water consumption in Seoul, and that has important implications for management of urban water resources under potential future climate change."
"7402205043;56962915800;","Critical roles of the stratiform rainfall in sustaining the Madden-Julian oscillation: GCM experiments",2009,"10.1175/2009JCLI2610.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749095363&doi=10.1175%2f2009JCLI2610.1&partnerID=40&md5=b1d654d635d2a4845c6e79a5f017f3e6","This study assesses the impact of stratiform rainfall (i.e., large-scale rainfall) in the development and maintenance of theMadden-Julian oscillation (MJO) in a contemporary general circulation model: ECHAM4 AGCM and its coupled version. To examine how the model MJO would change as the stratiform proportion (the ratio of the stratiform versus total rainfall) varies, a suite of sensitivity experiments has been carried out under a weather forecast setting and with three 20-yr free integrations. In these experiments, the detrainment rates of deep/ shallow convections that function as a water supply to stratiform clouds were modified, which results in significant changes of stratiform rainfall. Both the forecast experiments and long-term free integrations indicate that only when the model produces a significant proportion (≥30%) of stratiform rainfall can a robust MJO be sustained. When the stratiform rainfall proportion becomes small, the tropical rainfall in the model is dominated by drizzle-like regimes with neither eastward-propagating nor northward-propagating MJO being sustained. It is found that the latent heat release of stratiform rainfall significantly warms up the upper troposphere. The covariability between the heating and positive temperature anomaly produces eddy available potential energy that sustains the MJO against dissipation and also allows the direct interaction between the precipitation heating and large-scale low-frequency circulations, which is critical to the development and maintenance of the MJO. This finding calls for better representations of stratiform rainfall and its connections with the convective component in GCMs in order to improve their simulations of the MJO. © 2009 American Meteorological Society."
"6603765232;","Forage evapotranspiration and photosynthetically active radiation interception in proximity to deciduous trees",2009,"10.1016/j.agwat.2009.02.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64949102287&doi=10.1016%2fj.agwat.2009.02.011&partnerID=40&md5=b7a12fd21c0c170cd504c248d4efe98e","Practically all of the extensive body of research on evapotranspiration (ET) in agricultural systems has been done for open fields. There is a lack of information on how the microclimate variability within silvopasture systems affects water requirements of forages. Small 26 cm diameter, 23 cm deep lysimeters planted with either orchardgrass (Dactylis glomerata L.) or tall fescue (Schedonorus phoenix (Scop.) Holub) were placed in the ground along the north and south edge of two 15 m wide × 50 m deep notches cleared into a mature second growth hardwood forest. One notch opened to pasture on the east receiving more early day solar radiation and one to pasture on the west receiving more wind and late day solar radiation. There was no significant difference in ET between orchardgrass and tall fescue. North edges, receiving more direct beam radiation, had significantly higher ET (39%) than south edges which received a higher percentage of diffuse radiation. The west notch had significantly higher ET (11%) than the east notch. At the sunniest sites, advection provided 20% of the energy used for ET while at the shadiest sites it provided more than half (56%) with the rest provided by incident solar radiation. Dates where photosynthetically active radiation (PAR) was restricted by clouds resulted in decreased ET relative to PAR compared to more sunny days. However, sites where PAR was restricted by tree shade had higher ET relative to PAR than more open sites. These results indicate tree modification of microclimate does not decrease forage ET to the extent that PAR is decreased."
"7006329266;18133256900;","A study of the triggering mechanisms for deep convection in the Tropics using a Mesoscale Model: Hector events during SCOUT-O3 and TWP-ICE campaigns. (3.10)",2009,"10.1016/j.atmosres.2008.11.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349287404&doi=10.1016%2fj.atmosres.2008.11.004&partnerID=40&md5=31bac004b54d0f35780425578f07274d","One of the purposes of SCOUT-O3 (Stratosphere-Climate Links with emphasis on the Upper Troposphere and Lower Stratosphere) campaign was to improve our understanding of the interaction between convection and the tropical tropopause layer. Within the framework of SCOUT-O3 project a study on Hector events has been carried out. Hector is a deep convective cell developing on Tiwi Islands during the pre-monsoon period and break monsoon period. In this study two Hector events are investigated: 30 November 2005 a multicells event occurred during SCOUT-O3 campaign, and a single cell developed on 6 February 2006 during the TWP-ICE (Tropical Warm Pool International Cloud Experiment) campaign. The first event was characterized by two cells: the first cell downdraft triggering the second cell. The second Hector event was characterized by a cell triggered by the interaction of a previous convective cell and the south breeze front. The dynamics and thermodynamics of both events have been analyzed using the mesoscale model MM5V3 (Fifth-Generation Mesoscale Model Version 3). A few preliminary experiments have been performed to the aim of tuning the MM5 for the tropics; to this purpose two parameters are considered as the mass flux in the convective scheme and the condensation nuclei in the microphysical parameterization. Satellite and Radar images are used together with MM5V3 results to investigate the triggering mechanisms of the two Hector events. The MM5 results for the Hector event of Nov 30, 2005 shows a slightly lower Hector first cell, whereas the second one is very well reproduced, suggesting a stronger triggering acting in this second case. Moreover, the structure and the precipitation produced are in good agreement with the observation. For Feb 6, 2006 MM5 shows a shortcoming in the timing of maximum development of Hector (1 h earlier), but the structure and the precipitation are in good agreement with the observations. Finally, numerical experiments are performed to the aim of investigating the triggering factor for the two Hector events, which allows for assessing type A for the first cell of November 30, 2005 and type B for the second cell of November 30, 2005 and February 6, 2006 event. © 2008 Elsevier B.V. All rights reserved."
"6701402691;6506543806;","Updated and extended European dataset of daily climate observations",2009,"10.1002/joc.1779","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649958143&doi=10.1002%2fjoc.1779&partnerID=40&md5=d01c458b2aafdac15c25f4226df69660","The European Climate Assessment (ECA) dataset of daily observations, which has been widely used for studies on climate extremes, has been updated and extended. It now contains observational series of 2191 stations located in Europe and the Mediterranean (average inter-station distance: ∼75 km). About 1200 precipitation series and 750 temperature series cover the period 1960-2000. For a small number of stations (&lt;15%) air pressure, cloud cover, sunshine duration, snow depth and relative humidity series have been collected. All series are quality controlled and the homogeneity of the precipitation and temperature series is assessed. About 50% of the daily series are publicly available for climate studies through the website http://eca.knmi.nl. The main potential of the ECA dataset follows from its daily resolution, enabling studies of impact relevant climate extremes and variability. To guide these studies, climate indices calculated from the ECA series are presented on the website too. Besides, gridded versions of the daily ECA data are available for easy comparison with climate model simulations. A trend analysis for the diurnal temperature range (DTR) demonstrates the utility of the dataset. Seasonal and annual DTR trends were calculated for 333 homogeneous temperature series in ECA and a Europe average trend was estimated. In spring and summer, the DTR increased from 1979 to 2005, whereas in autumn and winter the DTR generally decreased. The European average trend in annual DTR was 0.09 °C decade-1. Copyright © 2008 Royal Meteorological Society."
"16022341000;7101677292;16023380900;7402086159;6602479434;26647180400;23110266900;","A remote sensing solution for estimating runoff and recharge in arid environments",2009,"10.1016/j.jhydrol.2009.04.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67049117859&doi=10.1016%2fj.jhydrol.2009.04.002&partnerID=40&md5=edf89572eef834a86aaf97bb6a34e217","Efforts to understand and to quantify precipitation and its partitioning into runoff evapo-transpiration, and recharge are often hampered by the absence or paucity of appropriate monitoring systems. We applied methodologies for rainfall-runoff and groundwater recharge computations that heavily rely on observations extracted from a wide-range of global remote sensing data sets (TRMM, SSM/I, Landsat TM, AVHRR, AMSR-E, and ASTER) using the arid Sinai Peninsula (SP; area: 61,000 km2) and the Eastern Desert (ED; area: 220,000 km2) of Egypt as our test sites. A two-fold exercise was conducted. Spatiotemporal remote sensing data (TRMM, AVHRR and AMSR-E) were extracted from global data sets over the test sites using RESDEM, the Remote Sensing Data Extraction Model, and were then used to identify and to verify precipitation events throughout the past 10 years (1998-2007). This was accomplished by using an automated cloud detection technique to identify clouds and to monitor their propagation prior to and throughout the identified precipitation events, and by examining changes in soil moisture (extracted from AMSR-E data) following the identification of clouds. For the investigated period, 246 of 327 events were verified in the SP, and 179 of 304 in the ED. A catchment-based, continuous, semi-distributed hydrologic model (Soil Water and Assessment Tool model; SWAT) was calibrated against observed runoff values from Wadi Girafi Watershed (area: 3350 km2) and then used to provide a continuous simulation (1998-2007) of the overland flow, channel flow, transmission losses, evaporation on bare soils and evapo-transpiration, and groundwater recharge for the major (area: 2014-22,030 km2) watersheds in the SP (Watir, El-Arish, Dahab, and Awag) and the ED (Qena, Hammamat, Asyuti, Tarfa, El-Quffa, El-Batur, Kharit, Hodein, and Allaqi) covering 48% and 51% of the total areas of the SP and the ED, respectively. For the investigated watersheds in the SP, the average annual precipitation, average annual runoff, and average annual recharge through transmission losses were found to be: 2955 × 106m3, 508 × 106m3 (17.1% total precipitation (TP)), and 463 × 106m3 (15.7% TP), respectively, whereas in the ED these values are: 807 × 106m3, 77.8 × 106m3 (9.6% TP), and 171 × 106m3 (21.2% TP), respectively. Results demonstrate the enhanced opportunities for groundwater development in the SP (compared to the ED) and highlight the potential for similar applications in arid areas elsewhere. The adopted remote sensing-based, regionalization approach is not a substitute for traditional methodologies that rely on extensive field datasets from rain gauge and stream flow networks, yet could provide first-order estimates for rainfall, runoff, and recharge over large sectors of the arid world lacking adequate coverage with spatial and temporal precipitation and field data. © 2009 Elsevier B.V. All rights reserved."
"6603196991;7402934750;6603868770;","Ground-based temperature and humidity profiling using spectral infrared and microwave observations. Part I: Simulated retrieval performance in clear-sky conditions",2009,"10.1175/2008JAMC2060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949138279&doi=10.1175%2f2008JAMC2060.1&partnerID=40&md5=4c0aae96d1c69365164c88961c4828b2","Two independent ground-based passive remote sensing methods are used to retrieve lower-tropospheric temperature and humidity profiles in clear-sky cases. A simulation study for two distinctly different climatic zones is performed to evaluate the accuracies of a standard microwave profiler [humidity and temperature profiler (HATPRO)] and an infrared spectrometer [Atmospheric Emitted Radiance Interferometer (AERI)] by applying a unified optimal estimation scheme to each instrument. Different measurement modes for each instrument are also evaluated in which the retrieval uses different spectral channels and observational view angles. In addition, both instruments have been combined into the same physically consistent retrieval scheme to evaluate the differences between a combined retrieval relative to the single-instrument retrievals. In general, retrievals derived from only infrared measurements yield superior RMS error and bias to retrievals derived only from microwave measurements. The AERI retrievals show high potential, especially for retrieving humidity in the boundary layer, where accuracies are on the order of 0.25-0.5 g m-3 for a central European climate. In the lowest 500 m the retrieval accuracies for temperature from elevation scanning microwave measurements and spectral infrared measurements are very similar (0.2-0.6 K). Above this level the accuracies of the AERI retrieval are significantly more accurate (,1 K RMSE below 4 km). The inclusion of microwave measurements to the spectral infrared measurements within a unified physical retrieval scheme only results in improvements in the high-humidity tropical climate. However, relative to the HATPRO retrieval, the accuracy of the AERI retrieval is more sensitive to changes in the measurement uncertainty. The discussed results are drawn from a subset of ""pristine"" clear-sky cases: in the general case in which clouds and aerosols are present, the combined HATPRO-AERI retrieval algorithm is expected to yield much more beneficial results. © 2009 American Meteorological Society."
"7202067582;7102936448;","News from the lower Ionosphere: A review of recent developments",2009,"10.1007/s10712-009-9074-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350539402&doi=10.1007%2fs10712-009-9074-2&partnerID=40&md5=96e05caf477fc25469a773591215664a","Current knowledge concerning the lower ionosphere (D- and E-region) is reviewed with an emphasis on new aspects of empirical results. Starting with an overview of experimental techniques and corresponding data bases, both regarding charged as well as the most relevant neutral constituents of this altitude range, the ionospheric variability is discussed both concerning regular (e.g. diurnal and seasonal) as well as irregular variations (e.g. driven by the variability of nitric oxide). We then turn to 'new players' in the lower ionosphere, i.e. charged aerosol particles such as mesospheric ice particles in noctilucent clouds or polar mesospheric summer echoes and meteor smoke particles originating from ablated meteoric matter. These species have received considerable attention in recent years, in part because it is speculated that observations of their properties might be useful for the detection of climate change signals. The available experimental data base regarding these species is reviewed and we show that there is now compelling evidence for the ubiquitous presence of these very heavy charge carriers throughout the lower ionosphere. While many fundamental details regarding these charged species are not yet completely understood, this emphasizes that charged aerosol particles may not be neglected in a comprehensive treatment of the lower ionospheric charge balance and related phenomena. Finally, we close with suggestions for future research. © Springer Science+Business Media B.V. 2009."
"36065603800;8618000600;56962915800;57211224269;57211223914;7406372329;6602546234;7402205043;24492188100;13404531500;8539422800;7003278104;57204886915;","Tropical intraseasonal variability in the MRI-20km60L AGCM",2009,"10.1175/2008JCLI2406.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949121407&doi=10.1175%2f2008JCLI2406.1&partnerID=40&md5=df272ceb903ef3899f606ba4b6a903d6","This study documents the detailed characteristics of the tropical intraseasonal variability (TISV) in the MRI-20km60L AGCM that uses a variant of the Arakawa-Schubert cumulus parameterization. Mean states, power spectra, propagation features, leading EOF modes, horizontal and vertical structures, and seasonality associated with the TISV are analyzed. Results show that the model reproduces the mean states in winds realistically and in convection comparable to that of the observations. However, the simulated TISV is less realistic. It shows low amplitudes in convection and low-level winds in the 30-60-day band. Filtered anomalies have standing structures. Power spectra and lag correlation of the signals do not propagate dominantly either in the eastward direction during boreal winter or in the northward direction during boreal summer. A combined EOF (CEOF) analysis shows that winds and convection have a loose coupling that cannot sustain the simulated TISV as realistically as that observed. In the composited mature phase of the simulated MJO, the low-level convergence does not lead convection clearly so that the moisture anomalies do not tilt westward in the vertical, indicating that the low-level convergence does not favor the eastward propagation. The less realistic TISV suggests that the representation of cumulus convection needs to be improved in this model. © 2009 American Meteorological Society."
"56249704400;7201837768;57193132723;6604021707;26644743100;35561911800;","Distinguishing aerosol impacts on climate over the past century",2009,"10.1175/2008JCLI2573.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61349105575&doi=10.1175%2f2008JCLI2573.1&partnerID=40&md5=636a1a5b333f9ef7bea0a86831824e08","Aerosol direct (DE), indirect (IE), and black carbon-snow albedo (BAE) effects on climate between 1890 and 1995 are compared using equilibrium aerosol-climate simulations in the Goddard Institute for Space Studies General Circulation Model coupled to a mixed layer ocean. Pairs of control (1890)-perturbation (1995) with successive aerosol effects allow isolation of each effect. The experiments are conducted both with and without concurrent changes in greenhouse gases (GHG).Anew scheme allowing dependence of snow albedo on black carbon snow concentration is introduced. The fixed GHG experiments global surface air temperature (SAT) changed by -0.2°, -1.0°, and -0.2°C from the DE, IE, and BAE. Ice and snow cover increased 1% from the IE and decreased 0.3% from the BAE. These changes were a factor of 4 larger in the Arctic. Global cloud cover increased by 0.5% from the IE. Net aerosol cooling effects are about half as large as the GHG warming, and their combined climate effects are smaller than the sum of their individual effects. Increasing GHG did not affect the IE impact on cloud cover, however they decreased aerosol effects on SAT by 20%, and on snow/ice cover by 50%; they also obscure the BAE on snow/ice cover. Arctic snow, ice, cloud, and shortwave forcing changes occur mostly during summer-fall, but SAT, sea level pressure, and longwave forcing changes occur during winter. An explanation is that aerosols impact the cryosphere during the warm season but the associated SAT effect is delayed until winter. © 2009 American Meteorological Society."
"7401776640;7102953444;","Trends in aerosol radiative effects over China and Japan inferred from observed cloud cover, solar ""dimming,"" and solar "" brightening""",2009,"10.1029/2008JD011378","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951089907&doi=10.1029%2f2008JD011378&partnerID=40&md5=65ca33acf0515c1ac5de5c5db1a04006","This study examines multidecadal changes in surface downward shortwave (SW) radiation flux, total cloud cover, SW cloud effect, and related parameters over China and Japan during 1960-2004 using monthly gridded data from the Global Energy Balance Archive, synoptic cloud reports, and the International Satellite Cloud Climatology Project. We use the concept of cloud cover radiative effect, defined as the change in downward SW flux produced by a change in cloud cover, to quantify and remove the impact of cloud cover anomalies on surface solar flux. This will allow radiative effects of long-term changes in anthropogenic aerosol to be more clearly distinguished from natural weather and climate variability. As fit by a linear trend between. 1971 and 1989, surface solar flux decreased by a statistically significant 11 W m-2 per decade over China and decreased by a nonsignificant 1 W m-2 per decade over Japan. The small decline over Japan can be entirely explained by an increase in cloud cover, but changes in cloud cover made negligible contribution to the 1971-1989 solar flux trend over China. Between 1990 and 2002, surface solar flux increased by a statistically significant 8 W m-2 per decade over Japan and increased by a nonsignificant 4 W m-2 per decade over China. Half of the 1990-2002 solar flux trend over China and one third of the trend over Japan can be attributed to a reduction in cloud cover. The 1971-1989 decrease in surface solar flux over China and the 1990-2002 increase in surface solar flux over Japan are both spatially widespread and exhibit consistent sign across seasons. Copyright 2009 by the American Geophysical Union."
"8859530100;55745955800;7004364155;","Seasonal variation of the physical properties of marine boundary layer clouds off the California coast",2009,"10.1175/2008JCLI2478.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849111887&doi=10.1175%2f2008JCLI2478.1&partnerID=40&md5=33a104415f63b544e23ba135297968ce","Marine boundary layer (MBL) clouds can significantly regulate the sensitivity of climate models, yet they are currently poorly simulated. This study aims to characterize the seasonal variations of physical properties of these clouds and their associated processes by using multisatellite data. Measurements from several independent satellite datasets [International Satellite Cloud Climatology Project (ISCCP), Clouds and the Earth's Radiant Energy System-Moderate Resolution Imaging Spectroradiometer (CERES-MODIS), Geoscience Laser Altimeter System (GLAS), and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)], in conjunction with balloon soundings from the mobile facility of the Atmospheric Radiation Measurement (ARM) program at Point Reyes and reanalysis products, are used to characterize the seasonal variations of MBL cloud-top and cloud-base heights, cloud thickness, the degree of decoupling between clouds and MBL, and inversion strength off the California coast. The main results from this study are as follows: (i) MBL clouds over the northeast subtropical Pacific in the summer are more prevalent and associated with a larger in-cloud water path than in winter. The cloud-top and cloud-base heights are lower in the summer than in the winter. (ii) Although the lower-tropospheric stability of the atmosphere is higher in the summer, the MBL inversion strength is only weakly stronger in the summer because of a negative feedback from the cloud-top altitude. Summertime MBL clouds are more homogeneous and are associated with lower surface latent heat flux than those in the winter. (iii) Seasonal variations of low-cloud properties from summer to winter resemble the downstream stratocumulus-to-cumulus transition of MBL clouds in terms of MBL depth, cloud-top and cloud-base heights, inversion strength, and spatial homogeneity. The ""deepening-warming"" mechanism of Bretherton and Wyant for the strato-cumulus-to-trade-cumulus transition downstream of the cold eastern ocean can also explain the seasonal variation of low clouds from the summer to the winter, except that warming of the sea surface temperature needs to be taken as relative to the free-tropospheric air temperature, which occurs in the winter. The observed variation of low clouds from summer to winter is attributed to the much larger seasonal cooling of the free-tropospheric air temperature than that of the sea surface temperature. © 2009 American Meteorological Society."
"7404416268;7203062127;6602447903;","Arctic cloud fraction and radiative fluxes in atmospheric reanalyses",2009,"10.1175/2008JCLI2213.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849131559&doi=10.1175%2f2008JCLI2213.1&partnerID=40&md5=fc5c0352dfbe6450fc5795d12ef362d7","Arctic radiative fluxes, cloud fraction, and cloud radiative forcing are evaluated from four currently available reanalysis models using data from the North Slope of Alaska (NSA) Barrow site of the Atmospheric Radiation Measurement Program (ARM). A primary objective of the ARM-NSA program is to provide a high-resolution dataset of direct measurements of Arctic clouds and radiation so that global climate models can better parameterize high-latitude cloud radiative processes. The four reanalysis models used in this study are the 1) NCEP-NCAR global reanalysis, 2) 40-yr ECMWF Re-Analysis (ERA-40), 3) NCEP- NCAR North American Regional Reanalysis (NARR), and 4) Japan Meteorological Agency and Central Research Institute of Electric Power Industry 25-yr Reanalysis (JRA25). The reanalysis models simulate the radiative fluxes well if/when the cloud fraction is simulated correctly. However, the systematic errors of climatological reanalysis cloud fractions are substantial. Cloud fraction and radiation biases show considerable scatter, both in the annual mean and over a seasonal cycle, when compared to those observed at the ARM-NSA. Large seasonal cloud fraction biases have significant impacts on the surface energy budget. Detailed comparisons of ARM and reanalysis products reveal that the persistent low-level cloud fraction in summer is particularly difficult for the reanalysis models to capture creating biases in the shortwave radiation flux that can exceed 160 W m-2. ERA-40 is the best performer in both shortwave and longwave flux seasonal representations at Barrow, largely because its simulation of the cloud coverage is the most realistic of the four reanalyses. Only two reanalyses (ERA-40 and NARR) capture the observed transition from positive to negative surface net cloud radiative forcing during a 2-3-month period in summer, while the remaining reanalyses indicate a net warming impact of Arctic clouds on the surface energy budget throughout the entire year. The authors present a variable cloud radiative forcing metric to diagnose the erroneous impact of reanalysis cloud fraction on the surface energy balance. The misrepresentations of cloud radiative forcing in some of the reanalyses are attributable to errors in both simulated cloud amounts and the models' radiative response to partly cloudy conditions. © 2009 American Meteorological Society."
"7004364155;7004325649;7403531523;15751856900;","Impact of data gaps on satellite broadband radiation records",2009,"10.1029/2008JD011183","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749092695&doi=10.1029%2f2008JD011183&partnerID=40&md5=c5258268bee5d244eae098c802cc156c","A simulated 30-year climate data record of net cloud radiative effect (defined as the difference between clear- and all-sky net top-of-atmosphere radiative flux) based on the first 5 years of Clouds and the Earth's Radiant Energy System (CERES) Terra measurements is created in order to investigate how gaps in the record affect our ability to constrain cloud radiative feedback. To ensure a trend estimate with an uncertainty small enough to constrain cloud radiative feedback to 25% of anthropogenic forcing in the next few decades, the absolute calibration change across the gap must be <0.3% in the shortwave (SW) region and <0.1% in the longwave (LW) region for a 1-year gap occurring in the middle of the record. Given that current calibration accuracy of CERES is 2% in the SW and 1% in the LW (at the 95% significance level), a gap of any length anywhere in the record will significantly increase the time required in order to detect a trend above natural variability because data collected prior to and after the gap cannot be combined accurately enough to ensure trend detection at the required level. To avoid gaps, at least 6 months of global or 1 year of tropical overlapping measurements between successive instruments are needed, based on overlapping CERES Terra and Aqua data."
"6603095001;10042470700;6701537033;56985140700;7201687375;6603794982;","Regional differences in the influence of irrigation on climate",2009,"10.1175/2008JCLI2703.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849087646&doi=10.1175%2f2008JCLI2703.1&partnerID=40&md5=2d871da5f07103affe302e2e8299e4d0","A global climate model experiment is performed to evaluate the effect of irrigation on temperatures in several major irrigated regions of the world. The Community Atmosphere Model, version 3.3, was modified to represent irrigation for the fraction of each grid cell equipped for irrigation according to datasets from the Food and Agriculture Organization. Results indicate substantial regional differences in the magnitude of irrigation-induced cooling, which are attributed to three primary factors: differences in extent of the irrigated area, differences in the simulated soil moisture for the control simulation (without irrigation), and the nature of cloud response to irrigation. The last factor appeared especially important for the dry season in India, although further analysis with other models and observations are needed to verify this feedback. Comparison with observed temperatures revealed substantially lower biases in several regions for the simulation with irrigation than for the control, suggesting that the lack of irrigationmay be an important component of temperature bias in thismodel or that irrigation compensates for other biases. The results of this study should help to translate the results from past regional efforts, which have largely focused on the United States, to regions in the developing world that in many cases continue to experience significant expansion of irrigated land. © 2009 American Meteorological Society."
"6506298579;7004404984;7102625188;7404029779;6602887222;7102640697;6505595743;7401572191;6506416205;26644701600;6603563919;57201933049;7103308691;25638488400;14619883300;6603571570;26643588800;8218496600;7103248807;55636317328;7004307226;7003314664;7004034323;6507591092;7404678955;","U.K. HiGEM: The new U.K. high-resolution global environment model - Model description and basic evaluation",2009,"10.1175/2008JCLI2508.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849089737&doi=10.1175%2f2008JCLI2508.1&partnerID=40&md5=2422b9cb1c074d294737e14b16de455c","This article describes the development and evaluation of the U.K.'s new High-Resolution Global Environmental Model (HiGEM), which is based on the latest climate configuration of the Met Office Unified Model, known as the Hadley Centre Global Environmental Model, version 1 (HadGEM1). In HiGEM, the horizontal resolution has been increased to 0.83° latitude × 1.25° longitude for the atmosphere, and 1/3° × 1/ 3° globally for the ocean. Multidecadal integrations of HiGEM, and the lower-resolution HadGEM, are used to explore the impact of resolution on the fidelity of climate simulations. Generally, SST errors are reduced in HiGEM. Cold SST errors associated with the path of the North Atlantic drift improve, and warm SST errors are reduced in upwelling stratocumulus regions where the simulation of low-level cloud is better at higher resolution. The ocean model in HiGEM allows ocean eddies to be partially resolved, which dramatically improves the representation of sea surface height variability. In the Southern Ocean, most of the heat transports in HiGEM is achieved by resolved eddy motions, which replaces the parameterized eddy heat transport in the lower-resolution model. HiGEM is also able to more realistically simulate small-scale features in the wind stress curl around islands and oceanic SST fronts, which may have implications for oceanic upwelling and ocean biology. Higher resolution in both the atmosphere and the ocean allows coupling to occur on small spatial scales. In particular, the small-scale interaction recently seen in satellite imagery between the atmosphere and tropical instability waves in the tropical Pacific Ocean is realistically captured in HiGEM. Tropical instability waves play a role in improving the simulation of the mean state of the tropical Pacific, which has important implications for climate variability. In particular, all aspects of the simulation of ENSO (spatial patterns, the time scales at which ENSO occurs, and global teleconnections) are much improved in HiGEM. © 2009 American Meteorological Society."
"13404664500;57212988186;7401945370;56962915800;57202301596;55711668600;57211223914;","Asian summer monsoon simulated by a global cloud-system-resolving model: Diurnal to intra-seasonal variability",2009,"10.1029/2009GL038271","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68949119391&doi=10.1029%2f2009GL038271&partnerID=40&md5=2a13b103f7edc086759b4da010a6f594","Interaction of convection and circulation is key to the Asian summer monsoon, but difficult to represent in global models. Here we report results from simulations for the summer of 2004 by a global cloud-system-resolving model, NICAM. At both 14- and 7-km horizontal resolution, NICAM simulates the observed monsoon circulation patterns, and the northward propagation of precipitation. The 7-km run simulates summer-mean precipitation maxima in narrow bands along the western Ghats, Himalayan foothills, the Arakan Yoma highlands, and the Annamite range. Precipitation 1) is modulated by orography, 2) is affected by synoptic-scale systems, and 3) displays a pronounced diurnal cycle, especially over Indo-China, with its strong/weak signal propagating westward/eastward in the wet/dry phase of the intraseasonal oscillation. This set of simulations captures these intraseasonal changes of the Indian monsoon with high fidelity from June to early July. NICAM exhibits a positive bias in precipitation over the Indian Ocean, common to atmospheric models with prescribed sea surface temperature. This calls for the inclusion of ocean-atmosphere coupling process to improve monsoon simulation skills. Copyright 2009 by the American Geophysical Union."
"36017879100;57202721532;56962915800;36994870600;","Can the Southern Hemisphere annular mode affect China winter monsoon?",2009,"10.1029/2008JD011501","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749106954&doi=10.1029%2f2008JD011501&partnerID=40&md5=51912a8c5bfd50c7ba3c49dec3d55f2f","Many previous studies suggested that the anomalous Northern Hemisphere annular mode (NAM) and associated low boundary forcing (e.g., snow cover) greatly influence the China winter monsoon (CWM) variability on interannual to inter-decadal timescales. In this article, it is found that the Southern Hemisphere annular mode (SAM) also well correlates with the two observed CWM major modes, which has not been revealed before. Note that the two CWM major modes are obtained by performing Empirical Orthogonal Function (EOF) analysis on winter surface air temperature at 160 gauge stations across China for the 1951-2006 period. They explain around 70% of the total CWM variances. The first EOF mode exhibits a homogeneous spatial pattern with the corresponding principal component displaying a significant inter-decadal variation, which reflects the warming trend in China during the past 56 years. The second EOF mode shows a meridional seesaw pattern and is basically associated with significant interannual variations. Both of the leading modes are intimately associated with the simultaneous SAM-like hemispheric circulation anomalies. Moreover, the SAM-like anomalies signal precursory conditions for the first CWM mode in boreal autumn. The relevant physical mechanisms by which anomalous autumn SAM may affect the CWM are investigated with NCAR Community Atmospheric Model version 3 (CAM3). When SAM is in a strong phase during boreal autumn, the circum-Antarctic upper level jet stream displaces poleward and the corresponding surface wind speeds reduce in the region between 45°S and 30°S, inducing a hemispheric-scale warm sea surface temperature (SST) belt beneath. Such an anomalously warm SST belt persists through boreal winter and weakens the Hadley cell. The weakened Hadley cell in boreal winter corresponds to anomalous southerlies prevailing in the lower troposphere over China, which favor a weak CWM. The intimate linkage between the autumn SAM and CWM may be instrumental for understanding interactions between the Northern and Southern Hemisphere and can provide a way to predict the CWM variations. Copyright 2009 by the American Geophysical Union."
"55736987700;7401672948;","New methods for studying the spatiotemporal variation of snow cover based on combination products of MODIS Terra and Aqua",2009,"10.1016/j.jhydrol.2009.03.028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65449119879&doi=10.1016%2fj.jhydrol.2009.03.028&partnerID=40&md5=8d8b91fd6345fe9acada16467e0e301a","Based on multi-day combination of Terra and Aqua MODIS snow cover products (cloud cover less than 10%), this study developed new snow cover index (SCI), snow-covered duration/days (SCD) map, snow cover onset dates (SCOD) map and snow cover melting dates (SCMD) map, one each per hydrological year, to further examine the spatiotemporal variations of snow cover. Daily in situ snow depth observations in northern Xinjiang, China from 2001 to 2005 were used to validate the new maps. Our results indicate that the SCD maps had an overall agreement of 90% with in situ observations of snow cover days at 20 stations in the study area, and the SCOD and SCMD maps also had good agreements with the in situ measurements, with a mean value of 1 week forward shift and 1 week backward shift, respectively, due to transient snowfall events in early fall and in late spring. The snow cover index (SCI) (km2 day), first proposed here, contains both snow cover duration and extent for 1 hydrological year and indicates that the 2001-2002 hydrologic year had the most snow cover while the 2005-2006 had the least. While the SCD map provides the snow cover duration/days of each pixel in a hydrologic year, the SCOD and SCMD maps give specific dates when the snow cover begins and when it melts away at the pixel. Together, SCD, SCI, SCOD and SCMD can provide crucial information on spatiotemporal variation of snow cover conditions for any region of interest. This could potentially be critical information for local water agencies for planning water use and for mitigating snow-caused disaster. Long term availability of MODIS type of snow cover data for producing such datasets is key to study the connection between snow cover change and global climate change. © 2009 Elsevier B.V."
"22935251000;7402305181;7103056450;26635422600;57212639275;7201472576;7404369915;","The CM-SAF and FUB cloud detection schemes for SEVIRI: Validation with synoptic data and initial comparison with MODIS and CALIPSO",2009,"10.1175/2008JAMC1982.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66149102046&doi=10.1175%2f2008JAMC1982.1&partnerID=40&md5=257e45600f60be4e11376e99c2a94f74","The Satellite Application Facility on Climate Monitoring (CM-SAF) is aiming to retrieve satellite-derived geophysical parameters suitable for climate monitoring. CM-SAF started routine operations in early 2007 and provides a climatology of parameters describing the global energy and water cycle on a regional scale and partially on a global scale. Here, the authors focus on the performance of cloud detection methods applied to measurements of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on the first Meteosat Second Generation geostationary spacecraft. The retrieved cloud mask is the basis for calculating the cloud fractional coverage (CFC) but is also mandatory for retrieving other geophysical parameters. Therefore, the quality of the cloud detection directly influences climate monitoring of many other parameters derived from spaceborne sensors. CM-SAF products and results of an alternative cloud coverage retrieval provided by the Institut für Weltraumwissenschaften of the Freie Universität in Berlin, Germany (FUB), were validated against synoptic measurements. Furthermore, and on the basis of case studies, an initial comparison was performed of CM-SAF results with results derived from the Moderate Resolution Imaging Spectrometer (MODIS) and from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Results show that the CFC from CM-SAF and FUB agrees well with synoptic data and MODIS data over midlatitudes but is underestimated over the tropics and overestimated toward the edges of the visible Earth disk. © 2009 American Meteorological Society."
"24398842400;7005955015;56250250300;12139043600;12139310900;25031430500;","Constraining cloud droplet number concentration in GCMs suppresses the aerosol indirect effect",2009,"10.1029/2009GL038568","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749088350&doi=10.1029%2f2009GL038568&partnerID=40&md5=29655103f69ba5e1425613dc49ec992a","Global aerosol-climate models with prognostic treatment of cloud droplet number concentration (CDNC) often prescribe lower bounds for CDNC or aerosol concentrations. Here we demonstrate that this possibly unphysical constraint reduces the simulated aerosol indirect effect by up to 80%, caused by extensively uniform CDNCs. In present-day conditions, the impact of the prescribed lower bound for CDNC is mainly visible over oceans, while with preindustrial emissions, large parts of both land and ocean areas are influenced. We furthermore show that imposing the same constraints on aerosol instead of on CDNC reduces the aerosol indirect effect to a lesser extent. Copyright 2009 by the American Geophysical Union."
"7102354961;7007114756;","Testing the influence of small crystals on ice size spectra using Doppler lidar observations",2009,"10.1029/2009GL038186","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749099446&doi=10.1029%2f2009GL038186&partnerID=40&md5=f86966ec56a608b65ebf53f27e78af42","Analysis of the vertical velocity of ice crystals observed with a 1.5μm Doppler lidar from a continuous sample of stratiform ice clouds over 17 months show that the distribution of Doppler velocity varies strongly with temperature, with mean velocities of 0.2ms-1 at -40°C, increasing to 0.6ms-1 at -10°C due to particle growth and broadening of the size spectrum. We examine the likely influence of crystals smaller than 60μm by forward modelling their effect on the area-weighted fall speed, and comparing the results to the lidar observations. The comparison strongly suggests that the concentration of small crystals in most clouds is much lower than measured in-situ by some cloud droplet probes. We argue that the discrepancy is likely due to shattering of large crystals on the probe inlet, and that numerous small particles should not be included in numerical weather and climate model parameterizations. Copyright 2009 by the American Geophysical Union."
"26434854300;7004715270;7403331283;7410041005;7004371379;7005729142;7004198777;6603385031;7005773698;","In situ detection of biological particles in cloud ice-crystals",2009,"10.1038/ngeo521","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67449107632&doi=10.1038%2fngeo521&partnerID=40&md5=a7691fdae97ea49e0fe29cc9f01e84a3","The impact of aerosol particles on the formation and properties of clouds is one of the largest remaining sources of uncertainty in climate change projections. Certain aerosol particles, known as ice nuclei, initiate ice-crystal formation in clouds, thereby affecting precipitation and the global hydrological cycle. Laboratory studies suggest that some mineral dusts and primary biological particlessuch as bacteria, pollen and fungican act as ice nuclei. Here we use aircraft-aerosol time-of-flight spectrometry to directly measure the chemistry of individual cloud ice-crystal residues (obtained after evaporation of the ice), which were sampled at high altitude over Wyoming. We show that biological particles and mineral dust comprised most of the ice-crystal residues: mineral dust accounted for 50% of the residues and biological particles for 33%. Along with concurrent measurements of cloud ice-crystal and ice-nuclei concentrations, these observations suggest that certain biological and dust particles initiated ice formation in the sampled clouds. Finally, we use a global aerosol model to show long-range transport of desert dust, suggesting that biological particles can enhance the impact of desert dust storms on the formation of cloud ice. © 2009 Macmillan Publishers Limited. All rights reserved."
"35219491500;7102080550;","Assimilation of coastal Doppler radar data with the ARPS 3DVAR and cloud analysis for the prediction of Hurricane Ike (2008)",2009,"10.1029/2009GL038658","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749099447&doi=10.1029%2f2009GL038658&partnerID=40&md5=fb916d99b88e0618b3be8ea0e6541a9d","The impact of radar data on the analysis and prediction of the structure, intensity, and track of landfalling Hurricane Ike (2008), at a cloud-resolving resolution, is examined. Radial velocity (Vr) and reflectivity (Z) data from coastal radars are assimilated over a 6-h period before Ike landfall, using the ARPS 3DVAR and cloud analysis package through 30-min assimilation cycles. Eighteen-hour predictions were made. All 4 experiments that assimilate radar data produce better structure, intensity and precipitation forecasts than that from operational GFS analysis. The improvement to the track forecast lasts for the entire 18 hours while that to intensity prediction lasts about 12 hours. The Vr data help improve the track forecast more while reflectivity data help improve intensity forecast most. Best results are obtained when both Z and Vr data are assimilated Copyright 2009 by the American Geophysical Union."
"55618221000;57197071909;35185932000;35185982300;50261535000;","Evaluating the effects of UHI on climate parameters (A case study for Mashhad, Khorrasan)",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349646280&partnerID=40&md5=634e838dea390135bdbf25dd6bada44e","Urban expansion, pollution growth, and development of major industrial activities in metropolitan areas impacted local climates of major towns. Transforming big cities into heat islands is one of the most important results of micro-climate change. In this study, variation of some of the important climate factors (such as precipitation, temperature, relative humidity, and percentage of cloudiness) was reviewed in order to study microclimate changes. The city of Mashhad selected for this study, as metropolitan area. The study performed by comparing the climate parameters of this city with the neighboring regions, which placed at the same climate categories. According to the effective role of rainfall in the urban weather modification and decreasing of pollutions, rainfall variation will be more important and sensitive. The result of this research shows that rainfall variation follows the change of temperature trend. A significant correlation between temperature and precipitation changes showed the effect of heat island on urban climate parameters. The urban heat island phenomenon increases the hot season rainfalls when we have decreasing effects on cold season."
"7103180783;57203049177;7402401574;","Undestanding land-sea warming contrast in response to increasing greenhouse gases. Part I: Transient adjustment",2009,"10.1175/2009JCLI2652.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849102885&doi=10.1175%2f2009JCLI2652.1&partnerID=40&md5=b3acc02c04484d1f67c63ede0f7c4a7d","Climate model simulations consistently show that surface temperature over land increases more rapidly than over sea in response to greenhouse gas forcing. The enhanced warming over land is not simply a transient effect caused by the land-sea contrast in heat capacities, since it is also present in equilibrium conditions. This paper elucidates the transient adjustment processes over time scales of days to weeks of the surface and tropospheric climate in response to a doubling of CO2 and to changes in sea surface temperature (SST), imposed separately and together, using ensembles of experiments with an atmospheric general circulation model. These adjustment processes can be grouped into three stages: immediate response of the troposphere and surface processes (day 1), fast adjustment of surface processes (days 2-5), and adjustment of the whole troposphere (days 6-20). Some land surface warming in response to doubled CO2 (with unchanged SSTs) occurs immediately because of increased downward longwave radiation. Increased CO2 also leads to reduced plant stomatal resistance and hence restricted evaporation, which increases land surface warming in the first day. Rapid reductions in cloud amount lead in the next few days to increased downward shortwave radiation and further warming, which spreads upward from the surface, and by day 5 the surface and tropospheric response is statistically consistent with the equilibrium value. Land surface warming in response to imposed SST change (with unchanged CO2) is slower. Tropospheric warming is advected inland from the sea, and over land it occurs at all levels together rather than spreading upward from the surface. The atmospheric response to prescribed SST change in about 20 days is statistically consistent with the equilibrium value, and the warming is largest in the upper troposphere over both land and sea. The land surface warming involves reduction of cloud cover and increased downward shortwave radiation, as in the experiment with CO2 change, but in this case it is due to the restriction of moisture supply to the land (indicated by reduced soil moisture), whereas in the CO2 forcing experiment it is due to restricted evaporation despite increased moisture supply (indicated by increased soil moisture). The warming over land in response to SST change is greater than over the sea and is the dominant contribution to the land-sea warming contrast under enhanced CO2 forcing. © 2009 American Meteorological Society."
"55234835700;7102567936;35561911800;","Influence of condensate evaporation on water vapor and its stable isotopes in a GCM",2009,"10.1029/2009GL038091","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749092663&doi=10.1029%2f2009GL038091&partnerID=40&md5=cf6a1361287114bef7b732a253b885f1","The direct effect of condensate evaporation on atmospheric water vapor and its isotopic composition is assessed in a climate model. The model contains two parallel hydrologic cycles, an active one which influences the model physics and dynamics and a passive one which does not. Two model simulations are performed, one in which passive cloud and precipitation can evaporate and one in which they cannot. The active hydrologie cycles, and thus the simulated circulations and temperatures, are identical in both simulations. Eliminating passive condensate evaporation reduces the specific humidity in the passive cycle by around 5%; this reduction varies from a few percent to 25% of the control value, depending on location. Zonal mean water vapor in the lower and middle troposphere is enriched in HDO relative to the control case, and is depleted in the upper troposphere. Copyright 2009 by the American Geophysical Union."
"36876405100;7402435469;7005814217;7005513582;57212416832;7402064802;7004479957;56865378100;","Evaluation of forecasted southeast Pacific stratocumulus in the NCAR, GFDL, and ECMWF models",2009,"10.1175/2008JCLI2479.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650535975&doi=10.1175%2f2008JCLI2479.1&partnerID=40&md5=deb38e2e5a3b8dc62dd12d8db2728122","Forecasts of southeast Pacific stratocumulus at 20°S and 85°W during the East Pacific Investigation of Climate (EPIC) cruise of October 2001 are examined with the ECMWF model, the Atmospheric Model (AM) from GFDL, the Community Atmosphere Model (CAM) from NCAR, and the CAM with a revised atmospheric boundary layer formulation from the University of Washington (CAM-UW). The forecasts are initialized from ECMWF analyses and each model is run for 3-5 days to determine the differences with the EPIC field observations. Observations during the EPIC cruise show a well-mixed boundary layer under a sharp inversion. The inversion height and the cloud layer have a strong and regular diurnal cycle. A key problem common to the models is that the planetary boundary layer (PBL) depth is too shallow when compared to EPIC observations. However, it is suggested that improved PBL depths are achieved with more physically realistic PBL schemes: at one end, CAM uses a dry and surface-driven PBL scheme and produces a very shallow PBL, while the ECWMF model uses an eddy-diffusivity/ mass-flux approach and produces a deeper and bettermixed PBL. All the models produce a strong diurnal cycle in the liquid water path (LWP), but there are large differences in the amplitude and phase when compared to the EPIC observations. This, in turn, affects the radiative fluxes at the surface and the surface energy budget. This is particularly relevant for coupled simulations as this can lead to a large SST bias. © 2009 American Meteorological Society."
"26041039600;56244473600;7103206141;55705948900;7005034250;","Present and potential future contributions of sulfate, black and organic carbon aerosols from China to global air quality, premature mortality and radiative forcing",2009,"10.1016/j.atmosenv.2009.02.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549128789&doi=10.1016%2fj.atmosenv.2009.02.017&partnerID=40&md5=53c5f749374dc5d45c0d9c489e3b6b2b","Aerosols are harmful to human health and have both direct and indirect effects on climate. China is a major contributor to global emissions of sulfur dioxide (SO2), a sulfate (SO42-) precursor, organic carbon (OC), and black carbon (BC) aerosols. Although increasingly examined, the effect of present and potential future levels of these emissions on global premature mortality and climate change has not been well quantified. Through both direct radiative effects and indirect effects on clouds, SO42- and OC exert negative radiative forcing (cooling) while BC exerts positive forcing (warming). We analyze the effect of China's emissions of SO2, SO42-, OC and BC in 2000 and for three emission scenarios in 2030 on global surface aerosol concentrations, premature mortality, and radiative forcing (RF). Using global models of chemical transport (MOZART-2) and radiative transfer (GFDL RTM), and combining simulation results with gridded population data, mortality rates, and concentration-response relationships from the epidemiological literature, we estimate the contribution of Chinese aerosols to global annual premature mortality and to RF in 2000 and 2030. In 2000, we estimate these aerosols cause approximately 470 000 premature deaths in China and an additional 30 000 deaths globally. In 2030, aggressive emission controls lead to a 50% reduction in premature deaths from the 2000 level to 240 000 in China and 10 000 elsewhere, while under a high emissions scenario premature deaths increase 50% from the 2000 level to 720 000 in China and to 40 000 elsewhere. Because the negative RF from SO42- and OC is larger than the positive forcing from BC, Chinese aerosols lead to global net direct RF of -74 mW m-2 in 2000 and between -15 and -97 mW m-2 in 2030 depending on the emissions scenario. Our analysis indicates that increased effort to reduce greenhouse gases is essential to address climate change as China's anticipated reduction of aerosols will result in the loss of net negative radiative forcing. © 2009 Elsevier Ltd."
"24490739700;","A robust method for tropopause altitude identification using GPS radio occultation data",2009,"10.1029/2009GL039231","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749104403&doi=10.1029%2f2009GL039231&partnerID=40&md5=32949fb240c3f9188ab9480a8af4649e","A robust method to determine the tropopause altitude directly from GPS Radio Occultation (RO) measurements of bending angle is presented. An objective covariance transform method is applied to identify transitions in a bending angle profile. The tropopause is identified by the maximum in the convolution of the natural logarithm of an observed bending angle profile with a gradient window function. Identification of the tropopause from bending angles is of particular value since they are directly derived from climate benchmark observations. This method avoids additional RO data processing and assumptions to derive parameters such as dry temperature, and use of subjective tropopause identification criteria. The RO tropopause altitude is compared with lapse rate and cold point criteria using dry temperatures and radiosonde temperature profiles. A longer-term tropopause altitude analysis for May to November 2008 using the RO bending angle method shows good agreement with tropopause altitudes computed from dry temperature parameters."
"26533041700;6506433071;7101749421;26431225600;","Coral-associated bacteria and their role in the biogeochemical cycling of sulfur",2009,"10.1128/AEM.02567-08","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66249145391&doi=10.1128%2fAEM.02567-08&partnerID=40&md5=d3bd4a07df8dc4c4766b39874b84c9e9","Marine bacteria play a central role in the degradation of dimethylsulfoniopropionate (DMSP) to dimethyl sulfide (DMS) and acrylic acid, DMS being critical to cloud formation and thereby cooling effects on the climate. High concentrations of DMSP and DMS have been reported in scleractinian coral tissues although, to date, there have been no investigations into the influence of these organic sulfur compounds on coral-associated bacteria. Two coral species, Montipora aequituberculata and Acropora millepora, were sampled and their bacterial communities were characterized by both culture-dependent and molecular techniques. Four genera, Roseobacter, Spongiobacter, Vibrio, and Alteromonas, which were isolated on media with either DMSP or DMS as the sole carbon source, comprised the majority of clones retrieved from coral mucus and tissue 16S rRNA gene clone libraries. Clones affiliated with Roseobacter sp. constituted 28% of the M. aequituberculata tissue libraries, while 59% of the clones from the A. millepora libraries were affiliated with sequences related to the Spongiobacter genus. Vibrio spp. were commonly isolated from DMS and acrylic acid enrichments and were also present in 16S rRNA gene libraries from coral mucus, suggesting that under ""normal"" environmental conditions, they are a natural component of coral-associated communities. Genes homologous to dddD, and dddL, previously implicated in DMSP degradation, were also characterized from isolated strains, confirming that bacteria associated with corals have the potential to metabolize this sulfur compound when present in coral tissues. Our results demonstrate that DMSP, DMS, and acrylic acid potentially act as nutrient sources for coral-associated bacteria and that these sulfur compounds are likely to play a role in structuring bacterial communities in corals, with important consequences for the health of both corals and coral reef ecosystems. Copyright © 2009, American Society for Microbiology. All Rights Reserved."
"7006701742;","Illawarra Reversal: The fingerprint of a superplume that triggered Pangean breakup and the end-Guadalupian (Permian) mass extinction",2009,"10.1016/j.gr.2008.12.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62949116798&doi=10.1016%2fj.gr.2008.12.007&partnerID=40&md5=f0848c4bddc746bcf4b2d3b7ab8ef08a","The Permian magnetostratigraphic record demonstrates that a remarkable change in geomagnetism occurred in the Late Guadalupian (Middle Permian; ca. 265 Ma) from the long-term stable Kiaman Reverse Superchron (throughout the Late Carboniferous and Early-Middle Permian) to the Permian-Triassic Mixed Superchron with frequent polarity changes (in the Late Permian and Triassic). This unique episode called the Illawarra Reversal probably reflects a significant change in the geodynamo in the outer core of the planet after a 50 million years of stable geomagnetism. The Illawarra Reversal was likely led by the appearance of a thermal instability at the 2900 km-deep core-mantle boundary in connection with mantle superplume activity. The Illawarra Reversal and the Guadalupian-Lopingian boundary event record the significant transition processes from the Paleozoic to Mesozoic-Modern world. One of the major global environmental changes in the Phanerozoic occurred almost simultaneously in the latest Guadalupian, as recorded in 1) mass extinction, 2) ocean redox change, 3) sharp isotopic excursions (C and Sr), 4) sea-level drop, and 5) plume-related volcanism. In addition to the claimed possible links between the above-listed environmental changes and mantle superplume activity, I propose here an extra explanation that a change in the core's geodynamo may have played an important role in determining the course of the Earth's surface climate and biotic extinction/evolution. When a superplume is launched from the core-mantle boundary, the resultant thermal instability makes the geodynamo's dipole of the outer core unstable, and lowers the geomagnetic intensity. Being modulated by the geo- and heliomagnetism, the galactic cosmic ray flux into the Earth's atmosphere changes with time. The more cosmic rays penetrate through the atmosphere, the more clouds develop to increase the albedo, thus enhancing cooling of the Earth's surface. The Illawarra Reversal, the Kamura cooling event, and other unique geologic phenomena in the Late Guadalupian are all concordantly explained as consequences of the superplume activity that initially triggered the breakup of Pangea. The secular change in cosmic radiation may explain not only the extinction-related global climatic changes in the end-Guadalupian but also the long-term global warming/cooling trend in Earth's history in terms of cloud coverage over the planet. © 2009 Elsevier B.V. All rights reserved."
"7006729638;26632560000;","Composite meteorological forcing of Puerto Rican springtime flood events",2009,"10.1175/2008WAF2222151.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65849251571&doi=10.1175%2f2008WAF2222151.1&partnerID=40&md5=936b8388b48837f9e0335347c80cc4dd","The central Antilles Islands experience short periods of heavy rainfall during the spring season (April and May) when trade winds weaken across the Caribbean Sea. Composite analysis of the top 10 flood events in the period 1979-2005 is carried out to understand the meteorological forcing. Cases are selected when mean rainfall over Puerto Rico exceeds 50 mm day-1 and emergency management reports indicate the day is a ""declared weather disaster."" In the NCEP-NCAR composite analyses, pulses of moisture shift westward across the tropical Atlantic about 10 days before a flood event. Five days before the composite flood a westerly trough penetrates eastward from the Gulf of Mexico. Northward flow develops over the Caribbean Sea and a southwest-oriented cloud band extends from Colombia toward Puerto Rico. A key feature of the midtropospheric circulation field is the development of anomalous twin rotors east of Florida in the mid- to upper troposphere. The flood events coincide with a change in zonal wind shear from westerly to easterly that is brought about by slow tropical and fast subtropical wave systems. © 2009 American Meteorological Society."
"16310203200;6507881102;","The MSG global instability indices product and its use as a nowcasting tool",2009,"10.1175/2008WAF2222141.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65849383956&doi=10.1175%2f2008WAF2222141.1&partnerID=40&md5=71e71f58d1dc3b4d7bcab4e50788eb10","The European geostationary Meteosat Second Generation (MSG) satellite offers a variety of channels to use for various purposes, including nowcasting of convection. A number of applications have also been developed to make use of these new capabilities for nowcasting, especially for the detection and prediction of severe weather. The MSG infrared channel selection makes it possible to assess the air stability in preconvective, that is, still cloud-free, conditions. Instability indices are traditionally derived from radiosonde profiles. Such indices typically combine measures of the thermal and moisture properties and often only use a small quantity of vertical profile parameters. MSG-based temperature and moisture retrievals are used for the derivation of stability indices, which are a part of the MSG meteorological products derived centrally at the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). Such indices are of an empirical nature, are often only applicable to certain geographic regions, and their thresholds are dependent on seasonal variation, but they can assess the likelihood of convection within the next few hours, thus providing a warning lead of about 6-9 h. Numerous test cases and the more quantitative verification process that was initiated by the South African Weather Service show the generally good warning potential of the derived instability fields. The added capability of a nearly continuous monitoring of the instability fields that is guaranteed by MSG's 15-min repeat cycle is most valuable, since it provides nowcasters with new information much more regularly than the twice-a-day soundings at only a limited number of radiosonde stations. The current EUMETSAT instability product is aimed at helping forecasters to focus their attention on a certain region, which can then be monitored more closely with other means, like satellite imagery and radar data, over the next few hours. © 2009 American Meteorological Society."
"6603809220;56611366900;","Cloud droplet spectral dispersion and the indirect aerosol effect: Comparison of two treatments in a GCM",2009,"10.1029/2009GL038216","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651124657&doi=10.1029%2f2009GL038216&partnerID=40&md5=219e5adf38697cb922eaf56f40ee97aa","[1] Two parameterizations of cloud droplet spectral dispersion and their impact on the indirect aerosol effect are compared in a global climate model. The earlier scheme specifies β, the ratio of droplet effective radius to volume-mean radius, in terms of N, the cloud droplet number concentration. The new scheme specifies β in terms of mean droplet mass (LIN), where L is liquid water content, to account for the effect of variations in L. For low to moderate N, the new scheme gives a stronger increase of β with increasing N than the old scheme. In a present-climate simulation, the new scheme shows a stronger gradient between remote regions (small β) and polluted/continental regions (large β). The new scheme also offsets the first indirect aerosol forcing (ΔF) more strongly: ΔF = -0.65 W m-2 with constant β, -0.43 W m-2 with the old β, and -0.38 W m -2 with the new β. Copyright 2009 by the American Geophysical Union."
"7404291795;57200790631;35551376300;7102925250;6603580448;","Estimating the altitude of volcanic sulfur dioxide plumes from space borne hyper-spectral UV measurements",2009,"10.1029/2009GL038025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651098665&doi=10.1029%2f2009GL038025&partnerID=40&md5=1d4fa18bdf150078f04bbf7779d14839","[1] The altitude of volcanic sulfur dioxide (SO2) plumes determines the transport and atmospheric residence time 01 derived sulfate aerosol, and hence their impacts on the environment and climate. Knowledge of the altitude of fresh eruption clouds is also very important in aviation safety to avoid flying through ash clouds and for forecasting of plume drift. In this paper, we demonstrate the altitude dependence of the spectral response in the backscattered ultraviolet (BUV) radiance when a SO2 absorption layer is added to an ozone-laden atmosphere. The distinctive spectral response serves as the physical basis for simultaneous SO2 loading and altitude retrievals, which can improve the characterization of volcanic emissions. We accomplish this by extending the recently developed Iterative Spectral Fitting (ISF) algorithm to include effective plume altitude determination when performing simultaneous ozone and SO2 retrievals. The extended ISF algorithm is applied to hyper-spectral Ozone Monitoring Instrument (OMI) measurements of two volcanic eruptions: Sierra Negra in October 2005 and Jebel al Tair in September 2007. The results show for the first time that a wide range of SO2 plume altitudes can be estimated directly from hyper-spectral BUV radiance measurement Copyright 2009 by the American Geophysical Union."
"57212892824;56052932000;6603581921;","The origin of an unusual tuff ring of perlitic rhyolite pyroclasts: The last explosive phase of the Ramadas Volcanic Centre, Andean Puna, Salta, NW Argentina",2009,"10.1016/j.jvolgeores.2009.02.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953038730&doi=10.1016%2fj.jvolgeores.2009.02.014&partnerID=40&md5=a059ac732cae522942d23b68d920e854","A thick sequence of bedded pyroclastic deposits, comprised largely of crystal poor, partially flow-banded perlite fragments defines the remains of a tuff ring around the eastern margin of the Miocene Ramadas Volcanic Centre (RVC), Central Andes, NW Argentina. In numerous quarry exposures, planar bed-forms dominate, but low-angle cross-stratification, lensoidal truncations and lateral pinching and swelling of cm- dm scale bed-forms occur, consistent with pyroclastic surge as the dominant transport and depositional mechanism. Intercalated are mantling, very fine grained, well-sorted, mm-cm scale planar ash layers that represent deposition from pyroclastic fall out and are most likely the products of co-surge ash clouds. Also observed are thick m-scale, laterally continuous, poorly-sorted horizons that are interpreted as pyroclastic flow deposits. Grainsize variations within the N70 m thick succession range from fine ash to coarse lapilli, with occasional large blocks reaching 20 cm. Clast vesicularities are typically very low. The sequence constitutes a rhyolitic tuff ring around the proximal margins of the RVC. Stratigraphic relationships indicate that the tuff ring was developed following cessation of the major plinian eruption phase of the RVC. A series of pyroclastic density currents and associated ash clouds is inferred to have resulted in the construction of the rhyolitic tuff ring, with deposition focussed on the eastern and southern margins of the central vent. The fine-grained nature of the deposits and low clast vesicularity are consistent with some degree of magma: water interaction during fragmentation. Pervasive perlitic fracturing of clasts found within the tuff deposits also indicates hydration and an extended, post-depositional hydration of the pyroclastic sequence, due to the influence of meteoric water, is likely to have occurred, with deposit permeability, clast specific surface and climate influential in facilitating additional textural modification of pyroclasts. © 2009 Elsevier B.V."
"12753162000;57197784699;57212870163;","Shepard and Hardy multiquadric interpolation methods for multicomponent aerosol-cloud parameterization",2009,"10.1175/2008JAS2626.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549100647&doi=10.1175%2f2008JAS2626.1&partnerID=40&md5=dfed56f0d74e650fd156964801fa8ce4","This paper presents a novel method based on the application of interpolation techniques to the multi-component aerosol-cloud parameterization for global climate modeling. Quantifying the aerosol indirect effect still remains a difficult task, and thus developing parameterizations for general circulation models (GCMs) of the microphysics of clouds and their interactions with aerosols is a major challenge for climate modelers. Three aerosol species are considered in this paper - namely sulfate, sea salt, and biomass smoke - and a detailed microphysical chemical parcel model is used to obtain a dataset of points relating the cloud droplet number concentration (CDNC) to the three aerosol input masses. The resulting variation of CDNC with the aerosol mass has some nonlinear features that require a complex but efficient parameterization to be easily incorporated into GCMs. In bicomponent systems, simple interpolation techniques may be sufficient to relate the CDNC to the aerosol mass, but with increasing components, simple methods fail. The parameterization technique proposed in this study employs either the modified Shepard interpolation method or the Hardy multiquadrics interpolation method, and the numerical results obtained show that both methods provide realistic results for a wide range of aerosol mass loadings. This is the first application of these two interpolation techniques to aerosol-cloud interaction studies. © 2009 American Meteorological Society."
"6507224579;7004247643;","Controls on the activation and strength of a high-latitude convective cloud feedback",2009,"10.1175/2008JAS2840.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549114592&doi=10.1175%2f2008JAS2840.1&partnerID=40&md5=ab7770d549d55d421f03dec41e7bb1a6","Previous work has shown that a convective cloud feedback can greatly increase high-latitude surface temperature upon the removal of sea ice and can keep sea ice from forming throughout polar night. This feedback activates at increased greenhouse gas concentrations. It may help to explain the warm ""equable climates"" of the late Cretaceous and early Paleogene eras (∼100 to ∼35 million years ago) and may be relevant for future climate under global warming. Here, the factors that determine the critical threshold CO2 concentration at which this feedback is active and the magnitude of the warming caused by the feedback are analyzed using both a highly idealized model and NCAR's single-column atmospheric model (SCAM) run under Arctic-like conditions. The critical CO2 is particularly important because it helps to establish the relevance of the feedback for past and future climates. Both models agree that increased heat flux into the high latitudes at low altitudes generally decreases the critical CO2. Increases in oceanic heat transport and in solar radiation absorbed during the summer should cause a sharp decrease in the critical CO2, but the effect of increases in atmospheric heat transport depends on its vertical distribution. It is furthermore found (i) that if the onset of convection produces more clouds and moisture, the critical CO2 should decrease, and the maximum temperature increase caused by the convective cloud feedback should increase and (ii) that reducing the depth of convection reduces the critical CO2 but has little effect on the maximum temperature increase caused by the convective cloud feedback. These results should help with interpretation of the strength and onset of the convective cloud feedback as found, for example, in Intergovernmental Panel on Climate Change (IPCC) coupled ocean - atmosphere models with different cloud and convection schemes. © 2009 American Meteorological Society."
"36856321600;7004479957;","Large eddy simulation of the diurnal cycle in southeast pacific stratocumulus",2009,"10.1175/2008JAS2785.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549168351&doi=10.1175%2f2008JAS2785.1&partnerID=40&md5=df1b942c495b7e9d2e601416aca0b324","This paper describes a series of 6-day large eddy simulations of a deep, sometimes drizzling stratocumulus-topped boundary layer based on forcings from the East Pacific Investigation of Climate (EPIC) 2001 field campaign. The base simulation was found to reproduce the observed mean boundary layer properties quite well. The diurnal cycle of liquid water path was also well captured, although good agreement appears to result partially from compensating errors in the diurnal cycles of cloud base and cloud top due to overentrainment around midday. At all times of the day, entrainment is found to be proportional to the vertically integrated buoyancy flux. Model stratification matches observations well; turbulence profiles suggest that the boundary layer is always at least somewhat decoupled. Model drizzle appears to be too sensitive to liquid water path and subcloud evaporation appears to be too weak. Removing the diurnal cycle of subsidence had little effect on simulated liquid water path. Simulations with changed droplet concentration and drizzle susceptibility showed large liquid water path differences at night, but differences were quite small at midday. Droplet concentration also had a significant impact on entrainment, primarily through droplet sedimentation feedback rather than through drizzle processes. © 2009 American Meteorological Society."
"7005435915;6602494687;","Russian studies of atmospheric radiation in 2003-2006",2009,"10.1134/S0001433809020042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549085801&doi=10.1134%2fS0001433809020042&partnerID=40&md5=32c115080591e92d3fc9debbedcde481","The Russian Radiation Commission, in cooperation with interested departments and institutions, has held two international symposia on atmospheric radiation for the Commonwealth of Independent States in the recent past. The participants of the symposia discussed problems that are currently particularly relevant in atmospheric physics: radiative transfer, atmospheric optics, greenhouse gases, clouds, aerosols, climate changes, remote sensing, and new observational data. Five directions covering the complete spectrum of investigations on atmospheric radiation are presented in this report. © Pleiades Publishing, Ltd. 2009."
"13405658600;57211106013;","Can cosmic rays affect cloud condensation nuclei by altering new particle formation rates?",2009,"10.1029/2009GL037946","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249149177&doi=10.1029%2f2009GL037946&partnerID=40&md5=733f35366b079e05985d8313af08399f","Although controversial, many observations have suggested that low-level cloud cover correlates with the cosmic ray flux. Because galactic cosmic rays have likely decreased in intensity over the last century, this hypothesis, if true, could partly explain 20th century warming, thereby upsetting the consensus view that greenhouse-gas forcing has caused most of the warming. The ""ion-aerosol clearair"" hypothesis suggests that increased cosmic rays cause increases in new-particle formation, cloud condensation nuclei concentrations (CCN), and cloud cover. In this paper, we present the first calculations of the magnitude of the ionaerosol clear-air mechanism using a general circulation model with online aerosol microphysics. In our simulations, changes in CCN from changes in cosmic rays during a solar cycle are two orders of magnitude too small to account for the observed changes in cloud properties; consequently, we conclude that the hypothesized effect is too small to play a significant role in current climate change. Copyright 2009 by the American Geophysical Union."
"11940701600;7003926380;","Implications of the day versus night differences of water vapor, carbon monoxide, and thin cloud observations near the tropical tropopause",2009,"10.1029/2008JD011524","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249096968&doi=10.1029%2f2008JD011524&partnerID=40&md5=a3c557b313d8634bc8abd8f685f4413e","[1] There are some interesting day versus night differences in the water vapor and carbon monoxide concentrations near the tropopause over tropical land and ocean from 4 years of EOS Microwave Limb Sounder (MLS) observations. To interpret these differences, the diurnal cycle of deep convection reaching near tropical tropopause summarized from a decade of tropical rainfall measuring mission (TRMM) observations. We also present the diurnal cycle of the cold point tropopause temperature and height derived from 2 years of constellation observing system for meteorology ionosphere and climate (COSMIC) GPS temperature profiles, the day versus night differences of occurrence of thin clouds from 2 years of cloud-aerosol lidar and infrared pathfinder satellite observations (CALIPSO) and 16 years of stratospheric aerosol and gaseous experiment (SAGE) II. In the tropical upper troposphere, day versus night differences of water vapor and carbon monoxide are consistent with the diurnal cycle of the vertical transport of water vapor and carbon monoxide-rich air from the surface by deep convection. However, in the tropical tropopause layer (TTL) over land, day versus night differences of water vapor concentration are more consistent with the diurnal variations of temperature in a saturated TTL, which is related to the diurnal cycle of cooling in the TTL induced by deep convection. The day versus night differences of occurrences of thin clouds in the TTL are also consistent with the freeze drying, controlled by the diurnal cycles of temperature in the TTL. Copyright 2009 by the American Geophysical Union."
"6603156461;36867775200;6603268269;7006270084;","Simulating the evolution of soot mixing state with a particle-resolved aerosol model",2009,"10.1029/2008JD011073","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249099910&doi=10.1029%2f2008JD011073&partnerID=40&md5=c467cb6ac85d1f4ad2780f0064fefdef","[1] The mixing state of soot particles in the atmosphere is of crucial importance for assessing their climatic impact, since it governs their chemical reactivity, cloud condensation nuclei activity, and radiative properties. To improve the mixing state representation in models, we present a new approach, the stochastic particle-resolved model PartMC-MOSAIC, which explicitly resolves the composition of individual particles in a given population of different types of aerosol particles. This approach tracks the evolution of the mixing state of particles due to emission, dilution, condensation, and coagulation. To make this direct stochastic particle-based method practical, we implemented a new multiscale stochastic coagulation method. With this method we achieved high computational efficiency for situations when the coagulation kernel is highly nonuniform, as is the case for many realistic applications. PartMC-MOSAIC was applied to an idealized urban plume case representative of a large urban area to simulate the evolution of carbonaceous aerosols of different types due to coagulation and condensation. For this urban plume scenario we quantified the individual processes that contributed to the aging of the aerosol distribution, illustrating the capabilities of our modeling approach. The results showed for the first time the multidimensional structure of particle composition, which is usually lost in sectional or modal aerosol models. Copyright 2009 by the American Geophysical Union."
"7005784518;7005961973;23393924800;7102166640;","Multidecadal variability of eastern Australian dust and northern New Zealand sunshine: Associations with pacific climate system",2009,"10.1029/2008JD011184","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249102553&doi=10.1029%2f2008JD011184&partnerID=40&md5=91d2b1983e340f3390e5b3f671c5017c","[1] Central eastern Australia is a major global source region for atmospheric dust. Time series of surface dust observations show that a striking multidecadal oscillation of dust frequency has occurred in this large region since the late 1950s. From 1959 to 1973, there was a pronounced and consistent dust maximum, after which a sharp decline was followed by a much more dust-free 1977-2006. Time series of surface and 925 hPa (∼725 m) winds reveal that the dust oscillation was associated locally with strengthening and then weakening of the southerly component of the low level wind over the dust-prone region. Composite maps for 1959-1973 (dusty) and 1977-2006 (more dust-free) indicate that these local wind changes reflected the relative speed of the southerly-southeasterly airflow into southeastern Australia. Correlation analyses show that this multidecadal regional wind oscillation was associated with similar timescale changes in the behavior of the Pacific climate system, including the latitudinal displacement of the South Pacific Convergence Zone, and more remotely with the sea surface temperature changes of the Pacific Decadal Oscillation (tropical North Pacific and extratropical North-Northeast Pacific) and North Pacific Oscillation (central subtropical North Pacific). Further correlation analyses suggest these Pacific climate system oscillations modulated other key environmental conditions (cloud regime, sunshine duration, rainfall rate) across the Southwest Pacific, including northern New Zealand sunshine. Copyright 2009 by the American Geophysical Union."
"7004060135;36153573000;6506945155;","An integrated analysis of lidar observations in association with optical properties of aerosols from a high altitudelocation in central Himalayas",2009,"10.1002/asl.209","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549165902&doi=10.1002%2fasl.209&partnerID=40&md5=24c9f35bdaad34efeb152e7598bb7d25","In order to study the aerosol backscatter profiles, a portable micro pulse lidar (MPL) system was installed in the year 2006 at Manora Peak, (29°22′N, 79°27′E, ∼1960 m amsl) Nainital, a high altitude location in the central Himalayas. In the present study the results of observed lidar profiles, columnar aerosol optical depths (AOD) and prevailing meteorology during May 2006 to June 2007 are presented. Although the lidar was operated from a sparsely inhabited free tropospheric site, nevertheless the height distribution of aerosol layers are found to be extended up to the summit of ∼2 km above the ground level (AGL). The backscatter ratio (BSR) varies from ∼10 to ∼20 having lowest values during post-monsoon and highest during pre-monsoon period. The observed boundary layer height during the post monsoon was shallower to the pre-monsoon period. Occasionally the lidar profiles reveal the presence of cirrus clouds at an altitude of 8-10 km AGL. The extended lidar observations over Manora Peak not only provided the profiles of aerosol extinction coefficient but also significantly substantiate the elevated aerosol layers and clouds, which are important in the study of climate modelling. Copyright © 2009 Royal Meteorological Society."
"36523706800;6507681572;6507040878;7005913397;6701410329;","The CM-SAF operational scheme for the satellite based retrieval of solar surface irradiance - A LUT based eigenvector hybrid approach",2009,"10.1016/j.rse.2009.01.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-63649110320&doi=10.1016%2fj.rse.2009.01.012&partnerID=40&md5=2839a685386b6bd1427c6aec97478a99","The radiation budget at the earth surface is an essential climate variable for climate monitoring and analysis as well as for verification of climate model output and reanalysis data. Accurate solar surface irradiance data is a prerequisite for an accurate estimation of the radiation budget and for an efficient planning and operation of solar energy systems. This paper describes a new approach for the retrieval of the solar surface irradiance from satellite data. The method is based on radiative transfer modelling and enables the use of extended information about the atmospheric state. Accurate analysis of the interaction between the atmosphere, surface albedo, transmission and the top of atmosphere albedo has been the basis for the new method, characterised by a combination of parameterisations and ""eigenvector"" look-up tables. The method is characterised by a high computing performance combined with a high accuracy. The performed validation shows that the mean absolute deviation is of the same magnitude as the confidence level of the BSRN (Baseline Surface Radiation Measurement) ground based measurements and significant lower as the CM-SAF (Climate Monitoring Satellite Application Facility) target accuracy of 10 W/m2. The mean absolute difference between monthly means of ground measurements and satellite based solar surface irradiance is 5 W/m2 with a mean bias deviation of - 1 W/m2 and a RMSD (Root Mean Square Deviation) of 5.4 W/m2 for the investigated European sites. The results for the investigated African sites obtained by comparing instantaneous values are also encouraging. The mean absolute difference is with 2.8% even lower as for the European sites being 3.9%, but the mean bias deviation is with - 1.1% slightly higher as for the European sites, being 0.8%. Validation results over the ocean in the Mediterranean Sea using shipboard data complete the validation. The mean bias is - 3.6 W/m2 and 2.3% respectively. The slightly higher mean bias deviation over ocean is at least partly resulting from inherent differences due to the movement of the ship (shadowing, allocation of satellite pixel). The validation results demonstrate that the high accuracy of the surface solar irradiance is given in different climate regions. The discussed method has also the potential to improve the treatment of radiation processes in climate and Numerical Weather Prediction (NWP) models, because of the high accuracy combined with a high computing speed. © 2009 Elsevier Inc. All rights reserved."
"7402655099;6701806265;","Validation of components of the water cycle in the ECHAM4 general circulation model based on the Newtonian relaxation technique: A case study of an intense winter cyclone",2009,"10.1007/s00703-009-0018-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651119925&doi=10.1007%2fs00703-009-0018-7&partnerID=40&md5=0617fc6d9ce773666393fb134000bfc4","The representation of a simulated synoptic-scale weather system is compared with observations. To force the model to the observed state, the so-called Newtonian relaxation technique (nudging) is applied to relax vorticity, divergence, temperature, and the logarithm of surface pressure to the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis fields. The development of an extraordinary strong cyclone along the East Coast of the USA during 12-14 March 1993 was chosen as the case study. The synoptic-scale features were well represented in the model simulation. However, systematic differences to observations of the International Satellite Cloud Climatology Project (ISCCP) occurred. The model underestimated clouds in lower and middle levels of the troposphere. Low-level clouds were mainly underestimated behind the cold front of the developing cyclone, while the underestimation of mid-level clouds seems to be a more general feature. The reason for the latter is the fact that the relative humidity has to exceed a critical threshold before clouds can develop. In contrast, thin upper-level cirrus clouds in pre-frontal regions were systematically overestimated by the model. Therefore, we investigated the effects of changed physical parameterizations with two sensitivity studies. In the PCI experiment, the standard cloud scheme operated in ECHAM4 was replaced by a more sophisticated one which defines separate prognostic equations for cloud liquid water and cloud ice. The second experiment, RHCRIT, changed the profile of the critical relative humidity threshold for the development of clouds in the standard scheme. Both experiments showed positive changes in the representation of clouds during the development of the cyclone as compared to the ISCCP. PCI clearly reduced the upper-level cloud amounts by intensifying the precipitation flux in the middle troposphere. The changed condensation threshold in the RHCRIT experiment led to a sharper represented cold front and a better represented cloudiness on its rear side as compared to the PCI and the CONTROL simulations. © pringer-Verlag 2009."
"9737279300;7005038449;7201772478;26535471800;6603859477;57203859138;8658853400;7006095466;7003735935;57203663945;8982198500;","International relations: The Ucar Africa initiative",2009,"10.1175/2008BAMS2452.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549083135&doi=10.1175%2f2008BAMS2452.1&partnerID=40&md5=74015fe912751d6f0c793d6b15a419cc","The overarching goal of the UCAR AI is to enhance opportunities for African scientists to perform research on problems relevant to their continent. The initiative is motivated by the fact that Africa has been underrepresented in international efforts to improve research capabilities, observing facilities, operational forecasting, and meteorological education. This is in spite of the fact that sub-Saharan countries are especially vulnerable to weather and climate variations, and that Sahelian weather directly impacts the United States in the form of hurricanes and dust clouds. Thus far, we have focused on UCAR's own capacity for enhancing and providing access to African observations, especially radar data and high-resolution models. The radar data and the final analyses and forecasts from the operational WRF model, as well as the availability of other data through UNIDATA, are designed to provide much needed data and infrastructure for African researchers. We hope that this paper demonstrates UCAR's capacity to contribute to atmospheric science research in Africa, and we hope the outlined pilot efforts will provide a springboard for collaboration with universities and other organizations. In the future, we will focus on facilitating informal and formal collaborations between U.S. and African atmospheric scientists, including facilitating visitor exchanges and fostering productive mentoring and training for early and pre-career scientists in Africa. While UCAR would participate in these efforts, we see our primary role as enabling partnerships between universities and programs in Africa that seek to develop new research capacity and universities with relevant research programs. We offer this paper, in part, to initiate a dialogue about these possibilities."
"7202079615;55805639500;55806383700;55805512000;26667030700;6603196127;","A simulation of the global distribution and radiative forcing of soil dust aerosols at the Last Glacial Maximum",2009,"10.5194/acp-9-3061-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450266226&doi=10.5194%2facp-9-3061-2009&partnerID=40&md5=99a552287c5f7e4f46b2663a10fe331b","In this study an integrated simulation of the global distribution and the radiative forcing of soil dust aerosols at the Last Glacial Maximum (LGM) is performed with an aerosol climate model, SPRINTARS. It is compared with another simulation for the present climate condition. The global total emission flux of soil dust aerosols at the LGM is simulated to be about 2.4 times as large as that in the present climate, and the simulated deposition flux is in general agreement with estimations from ice core and marine sediment samplings though it appears to be underestimated over the Antarctic. The calculated direct radiative forcings of soil dust aerosols at the LGM is close to zero at the tropopause and &minus;0.4 W m&minus;2 at the surface. These radiative forcings are about twice as large as those in the present climate. SPRINTARS also includes the microphysical parameterizations of the cloud-aerosol interaction both for liquid water and ice crystals, which affect the radiation budget. The positive radiative forcing from the indirect effect of soil dust aerosols is mainly caused by their properties to act as ice nuclei. This effect is simulated to be smaller (&minus;0.9 W m&minus;2) at the LGM than in the present. It is suggested that atmospheric dust might contribute to the cold climate during the glacial periods both through the direct and indirect effects, relative to the interglacial periods. © 2012 Author(s)."
"15726335100;26535193500;","Evaluation of the daylight cycle of model-predicted cloud amount and condensed water path over Europe with observations from MSG SEVIRI",2009,"10.1175/2008JCLI2391.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65449141268&doi=10.1175%2f2008JCLI2391.1&partnerID=40&md5=f46f50546e501df4314b05c701b85c72","The evaluation of the diurnal cycle of cloud amount (CA) and cloud condensed water path (CWP) as predicted by climate models receives relatively little attention, mostly because of the lack of observational data capturing the diurnal cycle of such quantities. The Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the geostationary Meteosat-8 satellite is the first instrument able to provide accurate information on diurnal cycles during daylight hours of cloud properties over land and ocean surfaces. This paper evaluates the daylight cycle of CA and CWP as predicted by the Regional Atmospheric Climate Model version 2 (RACMO2), using corresponding SEVIRI retrievals. The study is done for Europe using hourly cloud properties retrievals from SEVIRI during the summer months from May to September 2004. The results of this study show that SEVIRI-retrieved daylight cycles of CA and CWP provide a powerful tool for identifying climate model deficiencies. Over Europe the SEVIRI retrievals of cloud condensed water paths comprise about 80% liquid water and about 20% ice water. The daylight cycles of CA and CWP from SEVIRI show large spatial variations in their mean values and time of daily maximum and daytime-normalized amplitude. In general, RACMO2 overestimates CWP by about 30% and underestimates CA by about 20% as compared to SEVIRI. The largest amplitudes are observed in the Mediterranean and northern Africa. For the greater part of the ocean and coastal areas the time of daily maximum CWP is found during morning, whereas over land this maximum is found after local solar noon. These features are reasonably well captured by RACMO2. In the Mediterranean and continental Europe RACMO2 tends to predict maximum CWP associated with convection to occur about two hours earlier than SEVIRI indicates. © 2009 American Meteorological Society."
"7006961728;","Meteorology of the beaufort sea",2009,"10.1029/2008JC004861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149133443&doi=10.1029%2f2008JC004861&partnerID=40&md5=b4064706d2daa1d03af5bb9f63653012","The unique meteorology of the Beaufort sea region is dominated by the presence of sea ice and a seasonal swing from a large heat loss in winter to a gain in summer. The primary determinant of this seasonal climate shift is the annual cycle of insolation from a maximum of 500 W/m2 near the summer solstice to darkness in winter, as the Beaufort sea lies north of Alaska and northwestern Canada beyond 72°N. Even though the Sun angle is low in summer, the length of daylight provides as much energy to the surface as anywhere on the planet. As summer progresses, relative absorption of insolation at the surface increases as the albedo decreases due to snow and ice melt and increased open water area. This annual cycle results in a change from a winter continental-like air mass similar to the adjacent land areas to a summertime marine air mass characterized by low cloud and fogs. In winter the region is also influenced by the polar atmospheric vortex with strong westerly winds centered in the stratosphere, whose presence is felt at the surface. Recent sea ice losses are changing the climatology of the region, with extended periods of increased temperatures through the autumn months."
"6701762451;8728866200;22982059600;55857180100;55984419100;6602915564;8708685100;7003323678;7005941217;6602890253;6701842515;6601927317;57203053317;","Inadvertent climate modification due to anthropogenic lead",2009,"10.1038/ngeo499","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649170821&doi=10.1038%2fngeo499&partnerID=40&md5=aadfe1a647522f3910e0917ab6da9bf2","Aerosol particles can interact with water vapour in the atmosphere, facilitating the condensation of water and the formation of clouds. At temperatures below 273 K, a fraction of atmospheric particles act as sites for ice-crystal formation. Atmospheric ice crystalswhich are incorporated into clouds that cover more than a third of the globeare thought to initiate most of the terrestrial precipitation. Before the switch to unleaded fuel last century, the atmosphere contained substantial quantities of particulate lead; whether this influenced ice-crystal formation is not clear. Here, we combine field observations of ice-crystal residues with laboratory measurements of artificial clouds, to show that anthropogenic lead-containing particles are among the most efficient ice-forming substances commonly found in the atmosphere. Using a global climate model, we estimate that up to 0.8 W m 2 more long-wave radiation is emitted when 100% of ice-forming particles contain lead, compared with when no particles contain lead. We suggest that post-industrial emissions of particulate lead may have offset a proportion of the warming attributed to greenhouse gases. © 2009 Macmillan Publishers Limited."
"6602964178;6701621757;7004995517;","Maximum vehicle cabin temperatures under different meteorological conditions",2009,"10.1007/s00484-009-0211-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65049090496&doi=10.1007%2fs00484-009-0211-x&partnerID=40&md5=48f55f560b6b7e7beca794b6321c6d0c","A variety of studies have documented the dangerously high temperatures that may occur within the passenger compartment (cabin) of cars under clear sky conditions, even at relatively low ambient air temperatures. Our study, however, is the first to examine cabin temperatures under variable weather conditions. It uses a unique maximum vehicle cabin temperature dataset in conjunction with directly comparable ambient air temperature, solar radiation, and cloud cover data collected from April through August 2007 in Athens, GA. Maximum cabin temperatures, ranging from 41-76°C, varied considerably depending on the weather conditions and the time of year. Clear days had the highest cabin temperatures, with average values of 68°C in the summer and 61°C in the spring. Cloudy days in both the spring and summer were on average approximately 10°C cooler. Our findings indicate that even on cloudy days with lower ambient air temperatures, vehicle cabin temperatures may reach deadly levels. Additionally, two predictive models of maximum daily vehicle cabin temperatures were developed using commonly available meteorological data. One model uses maximum ambient air temperature and average daily solar radiation while the other uses cloud cover percentage as a surrogate for solar radiation. From these models, two maximum vehicle cabin temperature indices were developed to assess the level of danger. The models and indices may be useful for forecasting hazardous conditions, promoting public awareness, and to estimate past cabin temperatures for use in forensic analyses. © 2009 ISB."
"55898333500;56122761300;","Assimilation of the radar-derived water vapour mixing ratio into the LM COSMO model with a high horizontal resolution",2009,"10.1016/j.atmosres.2009.01.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-63149122264&doi=10.1016%2fj.atmosres.2009.01.012&partnerID=40&md5=ae90aed15f2728da076bff5f5d193a22","We use a WVC (Water Vapour Correction) method to assimilate radar reflectivity into the NWP (Numerical Weather Prediction) Local Model COSMO (LM; version 3.18) with a horizontal resolution of 2.8 km. The WVC method takes into account differences between the model and radar-derived precipitation by modifying vertical profiles of the water vapour mixing ratio at each model time step using the nudging approach. We describe the application of the WVC method and apply it to five severe convective events. The LM contains an explicit formulation of cloud and rain processes, in which microphysics parameterization includes rain water, snow, ice, and graupels. We evaluate the WVC method performance and compare it with the latent heat nudging method (LHN), which is a part of the LM code. The evaluation is focused on a very short range forecast of precipitation caused by particular storms. Results show that in most studied cases, both methods can forecast precipitation development three hours ahead, which is approximately the life cycle length of studied storms, and that the assimilation significantly improves precipitation forecasts obtained by the NWP model. Three approaches are used to evaluate and compare the methods. The first evaluates the forecast ""by eye"", the second is based on similarity measure (SRMSE) between precipitation cores, which takes into account area distribution of precipitation, and the third compares values of forecasted maximum precipitation in given areas. The results show that WVC yields better results than LHN in some cases and could be a good alternative to LHN. The relatively good agreement between the verification ""by eye"" and SRMSE confirms that SRMSE can be employed in similar studies. © 2009 Elsevier B.V. All rights reserved."
"8859530100;55745955800;56093699900;","Simulation of low clouds from the CAM and the regional WRF with multiple nested resolutions",2009,"10.1029/2008GL037088","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67449142948&doi=10.1029%2f2008GL037088&partnerID=40&md5=c3c4fadbeffabee8a9f2ed9bc4e8646a","[1] Current climate models have shown systematic simulation biases of low clouds that have cast great uncertainties on the climate sensitivity of these models. Among them is the deficient amount of low clouds over the storm tracks. This study uses the NCAR Community Atmospheric Model (CAM) and the Weather Research and Forecasting model (WRF) to study the cause of the failure of the global model in simulating low clouds associated with a frontal passage over the North Atlantic. The global model is shown to simulate the large-scale circulation that can support the boundary layer instabilities responsible for the observed clouds, but because the global model does not resolve the unstable modes, the instability cannot be realized. The resolution requirement of cloud simulations is discussed. This study also demonstrates the feasibility of cloud parameterization by nesting high resolution models into coarse resolution models to tap into the dynamical properties of the large-scale flows. Copyright 2009 by the American Geophysical Union."
"7003278104;9249239700;9244954000;7202857052;6701431208;7101801476;57193132723;7404829395;7005702722;8412168800;7006783796;57208765879;7004540083;7202899330;6506827279;7202772927;7003406400;7004485096;7402887257;7404297096;","Cloud ice: A climate model challenge with signs and expectations of progress",2009,"10.1029/2008JD010015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949122507&doi=10.1029%2f2008JD010015&partnerID=40&md5=efdde613225c98eeb79e4b1f523bd973","Present-day shortcomings in the representation of upper tropospheric ice clouds in general circulation models (GCMs) lead to errors in weather and climate forecasts as well as account for a source of uncertainty in climate change projections. An ongoing challenge in rectifying these shortcomings has been the availability of adequate, high-quality, global observations targeting ice clouds and related precipitating hydrometeors. In addition, the inadequacy of the modeled physics and the often disjointed nature between model representation and the characteristics of the retrieved/observed values have hampered GCM development and validation efforts from making effective use of the measurements that have been available. Thus, even though parameterizations in GCMs accounting for cloud ice processes have, in some cases, become more sophisticated in recent years, this development has largely occurred independently of the global-scale measurements. With the relatively recent addition of satellite-derived products from Aura/Microwave Limb Sounder (MLS) and CloudSat, there are now considerably more resources with new and unique capabilities to evaluate GCMs. In this article, we illustrate the shortcomings evident in model representations of cloud ice through a comparison of the simulations assessed in the Intergovernmental Panel on Climate Change Fourth Assessment Report, briefly discuss the range of global observational resources that are available, and describe the essential components of the model parameterizations that characterize their ""cloud"" ice and related fields. Using this information as background, we (1) discuss some of the main considerations and cautions that must be taken into account in making model-data comparisons related to cloud ice, (2) illustrate present progress and uncertainties in applying satellite cloud ice (namely from MLS and CloudSat) to model diagnosis, (3) show some indications of model improvements, and finally (4) discuss a number of remaining questions and suggestions for pathways forward. Copyright 2009 by the American Geophysical Union."
"25941200000;","Overlap of fractional cloud for radiation calculations in GCMs: A global analysis using CloudSat and CALIPSO data",2009,"10.1029/2007JD009677","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949174443&doi=10.1029%2f2007JD009677&partnerID=40&md5=f71616285c99b08223744a643364d3d0","Assumptions made by global climate models (GCMs) regarding vertical overlap of fractional amounts of clouds have significant impacts on simulated radiation budgets. A global survey of fractional cloud overlap properties was performed using 2 months of cloud mask data derived from CloudSat-CALIPSO satellite measurements. Cloud overlap was diagnosed as a combination of maximum and random overlap and characterized by vertically constant decorrelation length ℒ<inf>cf</inf>*. Typically, clouds overlap between maximum and random with smallest ℒ<inf>cf</inf>* (medians →; 0 km) associated with small total cloud amounts Ĉ, while the largest ℒ<inf>cf</inf>* (medians∼3 km) tend to occur at Ĉ near 0.7. Global median ℒ<inf>cf</inf>* is ∼2 km with a slight tendency for largest values in the tropics and polar regions during winter. By crudely excising near-surface precipitation from cloud mask data, ℒ<inf>cf</inf>* were reduced by typically <1 km. Median values of ℒ<inf>cf</inf>* when Sun is down exceed those when Sun is up by almost 1 km when cloud masks are based on radar and lidar data; use of radar only shows minimal diurnal variation but significantly larger ℒ<inf>cf</inf>*. This suggests that sunup inferences of ℒ<inf>cf</inf>* might be biased low by solar noise in lidar data. Cloud mask cross-section lengths L of 50, 100, 200, 500, and 1000 km were considered. Distributions of ℒ<inf>cf</inf> * are mildly sensitive to L thus suggesting the convenient possibility that a GCM parametrization of ℒ<inf>cf</inf>* might be resolution-independent over a wide range of resolutions. Simple parametrization of ℒ<inf>cf</inf>* might be possible if excessive random noise in Ĉ, and hence radiative fluxes, can be tolerated. Using just cloud mask data and assuming a global mean shortwave cloud radiative effect of -45 W m-2, top of atmosphere shortwave radiative sensitivity to Cp was estimated at 2 to 3 W m-2 km-1."
"7202899330;7004485096;6603768446;7006718891;7005890897;6507169830;7005073894;6602209040;35494005000;7202857052;6701606453;16679271700;12645767500;8067118800;7003278104;7404297096;57203030873;25031430500;7410041005;7101959253;","CloudSat mission: Performance and early science after the first year of operation",2009,"10.1029/2008JD009982","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949135003&doi=10.1029%2f2008JD009982&partnerID=40&md5=299a645ee0cbef4e996c8c71df0c7e63","This paper reports on the early mission performance of the radar and other major aspects of the CloudSat mission. The Cloudsat cloud profiling radar (CPR) has been operating since 2 June 2006 and has proven to be remarkably stable since turn-on. A number of products have been developed using these space-borne radar data as principal inputs. Combined with other A-Train sensor data, these new observations offer unique, global views of the vertical structure of clouds and precipitation jointly. Approximately 11% of clouds detected over the global oceans produce precipitation that, in all likelihood, reaches the surface. Warm precipitating clouds are both wetter and composed of larger particles than nonprecipitating clouds. The frequency of precipitation increases significantly with increasing cloud depth, and the increased depth and water path of precipitating clouds leads to increased optical depths and substantially more sunlight reflected from precipitating clouds compared to than nonprecipitating warm clouds. The CloudSat observations also provide an authoritative estimate of global ice water paths. The observed ice water paths are larger than those predicted from most climate models. CloudSat observations also indicate that clouds radiatively heat the global mean atmospheric column (relative to clear skies) by about 10 Wm-2. Although this heating appears to be contributed almost equally by solar and infrared absorption, the latter contribution is shown to vary significantly with latitude being influenced by the predominant cloud structures of the different region in questions. Copyright 2008 by the American Geophysical Union."
"7101959253;16679271700;35494005000;7005626683;7202899330;","A comparison of simulated cloud radar output from the multiscale modeling framework global climate model with CloudSat cloud radar observations",2009,"10.1029/2008JD009790","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949117429&doi=10.1029%2f2008JD009790&partnerID=40&md5=01b8dfb24e40097435ea7a5e7e622121","Over the last few years a new type of global climate model (GCM) has emerged in which a cloud-resolving model is embedded into each grid cell of a GCM. This new approach is frequently called a multiscale modeling framework (MMF) or superparameterization. In this article we present a comparison of MMF output with radar observations from the NASA CloudSat mission, which uses a near-nadir-pointing millimeter-wavelength radar to probe the vertical structure of clouds and precipitation. We account for radar detection limits by simulating the 94 GHz radar reflectivity that CloudSat would observe from the high-resolution cloud-resolving model output produced by the MMF. Overall, the MMF does a good job of reproducing the broad pattern of tropical convergence zones, subtropical belts, and midlatitude storm tracks, as well as their changes in position with the annual solar cycle. Nonetheless, the comparison also reveals a number of model shortfalls including (1) excessive hydrometeor coverage at all altitudes over many convectively active regions, (2) a lack of low-level hydrometeors over all subtropical oceanic basins, (3) excessive low-level hydrometeor coverage (principally precipitating hydrometeors) in the midlatitude storm tracks of both hemispheres during the summer season (in each hemisphere), and (4) a thin band of low-level hydrometeors in the Southern Hemisphere of the central (and at times eastern and western) Pacific in the MMF, which is not observed by CloudSat. This band resembles a second much weaker ITCZ but is restricted to low levels. Copyright 2009 by the American Geophysical Union."
"23092821200;24722339600;7409080503;7005034568;26427916400;","Studying the vertical variation of cloud droplet effective radius using ship and space-borne remote sensing data",2009,"10.1029/2007JD009596","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949146159&doi=10.1029%2f2007JD009596&partnerID=40&md5=afae2dd2a071fcc076eece7b24613df9","The albedo of marine stratocumuli depends upon cloud liquid water content, droplet effective radius (r<inf>e</inf>), and how these parameters vary with height. Using satellite data and shipborne data from the East Pacific Investigation of Climate (EPIC) Stratocumulus Study, this study investigates the cloud r<inf>e</inf> vertical variation for drizzling and nondrizzling clouds. Visible/near-infrared retrievals from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate the vertical profile of r <inf>e</inf>. MODIS re observations and collocated shipborne scanning C-band precipitation radar data show that r<inf>e</inf> generally increases with height in nondrizzling clouds, consistent with aircraft observations. It is found that in clouds with precipitation rates greater than a few hundredths of a mm h -1 the vertical gradient of r<inf>e</inf> is significantly less than that in nondrizzling clouds and can become negative when the drizzle is heavier than approximately 0.1 mm h-1. High values of r<inf>e</inf> at drizzling cloud base are consistent with estimates of the ratio of liquid water in the drizzle drops to that in the cloud droplets. C-band derived cloud base precipitation rates are found to be better correlated with r<inf>e</inf> at cloud base than with r<inf>e</inf> at cloud top, suggesting that passive remote sensing may be useful for drizzle detection. Copyright 2008 by the American Geophysical Union."
"7202181543;35453054300;7006508549;7201914101;7103142686;","Importance of land use versus atmospheric information verified from cloud simulations from a frontier region in Costa Rica",2009,"10.1029/2007JD009565","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949112553&doi=10.1029%2f2007JD009565&partnerID=40&md5=f2d58ae4e7e0a8b19f9c986cc7e6a1c1","Land-use/land-cover (LULC) change has been recognized as a key component in global climate change, and numerous climate modeling studies at regional to global scales document this. The research strategies have invariably been to first conduct baseline simulations of current conditions to evaluate model performance. Then simulation of regional climate with land cover changes (LCC) implemented within the model allows differences with the baseline simulation to be used as evidence of global to regionalscale climate impacts of LCC. However, even state-of-the-art regional climate models require two data sets to conduct reasonable baseline simulations. These are representative current land cover and atmospheric information over the study region. In frontier and developing areas (where most of the rapid land-use conversion is taking place), these data sets are frequently unavailable and the errors in simulations are due to either inaccurate land cover, insufficient atmospheric information, nonrepresentative model physics, or a combination of one or more of the above. This study shows that in one frontier region, that surrounding the Cordillera de Tilarán of Costa Rica, the accuracy of simulating clouds decreases by 1% to 3% if default model land cover information is used. If the atmospheric data sets used are the ones usually available to researchers (with land cover information held constant), then the model accuracy is reduced by 21% to 25%. Model runs without updated land cover or atmospheric information reduce model accuracy slightly further. Precipitation comparisons also provide similar results. This study thus shows that the critically important data set for conducting accurate simulations is not land cover information but atmospheric information. Researchers may similarly get significant increase in the accuracy of their baseline simulations elsewhere by using radiosondes/rawinsondes over their study region. Finally, since atmospheric information is not available for different landscape scenarios, assessments of the relative role of LULC change will have to continue to rely on using the standard atmospheric data set and the acceptance that the use of more detailed atmospheric data to initialize and provide lateral boundary conditions would have reduced the uncertainties in such landscape sensitivity studies. Copyright 2009 by the American Geophysical Union."
"7005171879;7410041005;56978385600;","Global distribution of cirrus clouds from CloudSat/cloud-aerosol lidar and infrared pathfinder satellite observations (CALIPSO) measurements",2009,"10.1029/2008JD009972","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949124660&doi=10.1029%2f2008JD009972&partnerID=40&md5=8b3d6a55849fd3d3dbb7b1a72a68f19f","The cirrus clouds of the upper troposphere are globally widespread and are important regulators of the radiative balance, and hence climate, of the Earth-atmosphere system. Despite their wide distribution, however, cirrus are difficult to study from satellite radiance measurements or from scattered ground observing sites because they can occur as part of multilayered cloud systems and are characteristically optically thin. The need to better characterize the global distribution of cirrus clouds was therefore a major justification for the formation flying of the CloudSat and CALIPSO satellites, which support a cloud radar and polarization lidar, respectively. Measurements by these active remote sensors, when analyzed by appropriate algorithms, have the ability to identify and accurately measure the locations and heights of this category of clouds. The combined CloudSat/ Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data cirrus cloud algorithm used in this study is aimed at identifying those clouds that would likely be classified as cirrus by a surface weather observer: it is based on previous experience with multiple remote sensor approaches and knowledge gleaned from extensive surface lidar and radar observations of visually identified cirrus clouds with a minimum of a priori assumptions. We report on the global and seasonal frequencies of cirrus clouds, and on their heights and thicknesses obtained over the initial 1 year of data collected. We find a global average frequency of cirrus cloud occurrence of 16.7%. These new results are compared with other cirrus cloud climatologies and are interpreted in terms of local cirrus cloud formation mechanisms and the responsible global weather phenomena. Copyright 2008 by the American Geophysical Union."
"7006595513;15724233200;8645916500;7005696579;24070152900;35221167400;7004047498;56374442600;55545335600;36021733300;8986277400;7201529399;26643054400;55568131800;36160390900;7102247437;6701410575;16549600900;13407563600;24172248700;55942083800;","Rapid aerosol particle growth and increase of cloud condensation nucleus activity by secondary aerosol formation and condensation: A case study for regional air pollution in northeastern China",2009,"10.1029/2008JD010884","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954321838&doi=10.1029%2f2008JD010884&partnerID=40&md5=db1b173818161f40328c23ddcaf69218","This study was part of the international field measurement Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing-2006). We investigated a new particle formation event in a highly polluted air mass at a regional site south of the megacity Beijing and its impact on the abundance and properties of cloud condensation nuclei (CCN). During the 1-month observation, particle nucleation followed by significant particle growth on a regional scale was observed frequently (∼30%), and we chose 23 August 2006 as a representative case study. Secondary aerosol mass was produced continuously, with sulfate, ammonium, and organics as major components. The aerosol mass growth rate was on average 19 μg m-3 h-1 during the late hours of the day. This growth rate was observed several times during the 1-month intensive measurements. The nucleation mode grew very quickly into the size range of CCN, and the CCN size distribution was dominated by the growing nucleation mode (up to 80% of the total CCN number concentration) and not as usual by the accumulation mode. At water vapor supersaturations of 0.07-0.86%, the CCN number concentrations reached maximum values of 4000-19,000 cm -3 only 6-14 h after the nucleation event. During particle formation and growth, the effective hygroscopicity parameter κ increased from about 0.1-0.3 to 0.35-0.5 for particles with diameters of 40-90 nm, but it remained nearly constant at ∼ 0.45 for particles with diameters of ∼ 190 nm. This result is consistent with aerosol chemical composition data, showing a pronounced increase of sulfate. Copyright 2009 by the American Geophysical Union."
"25639577800;6506576301;6603482421;","Enhanced estimation of glacier mass balance in unsampled areas by means of topographic data",2009,"10.3189/172756409787769519","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64549115912&doi=10.3189%2f172756409787769519&partnerID=40&md5=4e9c25dd27b11d53e9f4f54c415521f2","A new method was developed to estimate the mass balance in unsampled areas from existing datasets. Three years of mass-balance data from two glaciers in the central Italian Alps were used to develop and test a multiple-regression method based exclusively on a 10 m resolution digital terrain model. The introduction of a relative elevation attribute, which expresses the degree of wind exposure of the gridcells, notably increased the amount of explainable variance in winter balance with respect to altitude itself. The summer balance is highly correlated with elevation, but, in order to obtain reliable extrapolations, the clear-sky shortwave radiation and the diurnal cloud-cover cycle had to be taken into account. The net annual mass balance on a glacier system comprising the two monitored glaciers was calculated by applying both a single regression of winter and summer balance with altitude and the new regression method. The consistency of results was assessed against measured net balances and snowcover maps drawn in the ablation season. The results of the new method were in close agreement with observations and proved to be less sensitive to the spatial representation of the sampled areas."
"7005578774;6602098362;","Global warming due to increasing absorbed solar radiation",2009,"10.1029/2009GL037527","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67449146612&doi=10.1029%2f2009GL037527&partnerID=40&md5=8a161e37b4de7f689634e14db24d908e","[1] Global climate models used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) are examined for the top-of-atmosphere radiation changes as carbon dioxide and other greenhouse gases build up from 1950 to 2100. There is an increase in net radiation absorbed, but not in ways commonly assumed. While there is a large increase in the greenhouse effect from increasing greenhouse gases and water vapor (as a feedback), this is offset to a large degree by a decreasing greenhouse effect from reducing cloud cover and increasing radiative emissions from higher temperatures. Instead the main warming from an energy budget standpoint comes from increases in absorbed solar radiation that stem directly from the decreasing cloud amounts. These findings underscore the need to ascertain the credibility of the model changes, especially insofar as changes in clouds are concerned. Copyright 2009 by the American Geophysical Union."
"57203405965;7003591311;6603800142;55017656900;25649028800;7005174340;","Irradiance in polluted cumulus fields: Measured and modeled cloud-aerosol effects",2009,"10.1029/2008GL036848","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67449131796&doi=10.1029%2f2008GL036848&partnerID=40&md5=36a8454e9248c5b0f3c924b3fc1485f0","[1] We present a new strategy to validate modeled spectral irradiance of shallow cumulus cloud fields in a polluted background with airborne measurements. The concept is based on a spectral distinction of effects associated with heterogeneous clouds, aerosol particles, and surface albedo. We use measurements from the Gulf of Mexico Atmospheric Composition and Climate Study, conducted in the urban-industrial Houston area. Modeled irradiance fields were obtained from extensive three-dimensional radiative transfer calculations applied to the output of large eddy simulations. We show that the measurements below clouds or cloud gaps can only be reproduced by the calculations when including the aerosol radiative effects. The technique enables the derivation of measurement-based spectral forcing and absorption of the cloud-aerosol system which will help substantiate model calculations. At 400 nm wavelength, the inclusion of aerosol increases forcing of the cloud-aerosol system by 8%, and absorption by 20%. Copyright 2009 by the American Geophysical Union."
"23981063100;6701735773;6602080773;6701751100;","Shifting the diurnal cycle of parameterized deep convection over land",2009,"10.1029/2008GL036779","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67449110399&doi=10.1029%2f2008GL036779&partnerID=40&md5=e2d3af75cba969292f30cabb7eb39c28","[1] In most atmospheric circulation models used for climate projections, cloud and convective processes are not explicitly resolved but parameterized. Such models are known to produce a diurnal cycle of continental thunderstorms in phase with insolation, while observed precipitation peaks in late afternoon. We propose a new approach which corrects this long standing bias of parameterized convection. In this approach, deep convection triggering and intensity are controlled by sub-cloud processes: here boundary layer thermals and gust fronts, and potentially orography or surface heterogeneities. The representation of the diurnal cycle of deep convection is greatly improved in 1D mode, with rainfall maximum delayed from midday to late afternoon, provided parameterizations account for the key role played by shallow cumulus in preconditioning deep convection and by gust fronts in the self-sustaining of thunderstorms in the afternoon. Copyright 2009 by the American Geophysical Union."
"26655075300;6506238357;","Use of radio occultation for long-term tropopause studies: Uncertainties, biases, and instabilities",2009,"10.1029/2008JD009886","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649115018&doi=10.1029%2f2008JD009886&partnerID=40&md5=35b0e488f25b456a738d3e4e3dd9f22b","Research suggests that changes in tropopause structure can both indicate and impact changes in the global climate system. The Global Positioning System radio occultation (RO) technique shows tremendous potential for monitoring the global tropopause because of its precision, temporal consistency, and global measurement density. This study examines the capability of RO to monitor the global tropopause by addressing three specific objectives: (1) quantify sources of uncertainty in individual RO tropopause measurements, (2) examine mean bias and long-term stability of RO tropopause parameters with respect to those obtained from radiosondes, and (3) distinguish between differences due to processing and RO instrument differences by comparing tropopause parameters from different RO products. In this study, we make use of data from four different RO missions, including the recent Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). RO tropopause uncertainty is shown to be largely due to the use of a highly nonlinear tropopause definition (1.6 K or 510 m), although uncertainties in the RO derived temperature profiles themselves (0.25 K or 75 m) are still significant. Global mean temperature and height biases between RO instruments and radiosondes are within 0.5 K and 75 m. One long-term RO data set examined in this study appeared to contain spurious temperature trends, but these have since been corrected. Tropopause measurements from different RO instruments are generally within 41 m and 0.1 K for the globe. Dissimilarly processed temperature data, however, can differ by as much as 2 K in the mean. These results confirm the precision of RO data, but also demonstrate the importance of consistent processing for long-term tropopause temperature studies. Tropopause height data do not appear to be significantly affected by the differences in processing examined in this study. Copyright 2008 by the American Geophysical Union."
"7402093416;6506238357;","Long-term evolution of the cold point tropical tropopause: Simulation results and attribution analysis",2009,"10.1029/2007JD009768","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649130999&doi=10.1029%2f2007JD009768&partnerID=40&md5=cf319f9bedec1bc21760675471fd9f05","The height, pressure, and temperature of the cold point tropical tropopause are examined in three 140 year simulations of a coupled chemistry climate model. Tropopause height increases approximately steadily in the simulations at a mean rate of 63 ± m/decade (2σ confidence interval). The pressure trend changes near the year 2000 from -1.03 ± 0.30 hPa/decade in the past to -0.55 ± 0.06 hPa/decade for the future. The trend in tropopause temperature changes even more markedly from -0.13 ± 0.07 K/decade in the past to +0.254 ±0.014 K/decade in the future. The tropopause data were fit using regression by terms representing total column ozone, tropical mean sea surface temperatures, and tropical mass upwelling. Tropopause height and pressure closely follow the upwelling term, whereas tropopause temperature is primarily related to sea surface temperature and ozone. The change in tropopause temperature trend near the year 2000 is related to the change in the sign of the ozone trend with the sea surface temperature having an increased role after 2040. A conceptual model is used to estimate tropopause changes. The results confirm the regression analysis in showing the importance of upper tropospheric warming (connected with sea surface temperature) and stratospheric cooling (connected with CO2 and O3). In the past, global warming and ozone depletion have opposite effects on the tropopause temperature, which decreases slightly. For the future simulation, global warming and ozone recovery reinforce which increases the tropopause temperature. In particular, future tropopause change is found not to be an indicator of climate change alone. Copyright 2008 by the American Geophysical Union."
"36805856400;21735369200;7004402705;","Radiative effect of ozone change on stratosphere-troposphere exchange",2009,"10.1029/2008JD009829","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649122837&doi=10.1029%2f2008JD009829&partnerID=40&md5=88e28da7d7abb2b751591840f742f585","The potential radiative impact of ozone changes on stratosphere-troposphere exchange (STE) is investigated by a series of climate model simulations. The impact of an arbitrary 15% O3 change on temperature, stratospheric water vapor, and cross-tropopause mass flux are compared to the corresponding effects from a doubling of atmospheric CO2. Our analysis shows that a 15% global O3 decrease can cause a maximum cooling of 2.4 K in the stratosphere and ~7.2% increase in the tropical upwelling. This cooling also results in a higher tropical tropopause and lower tropopause temperatures, and hence less stratospheric water vapor and smaller amplitude of the so-called tape recorder signal. A global 15% O3 increase gives rise to ~2.1 K stratospheric warming and ~4% decrease in the tropical upwelling. This O3 increase results in more water vapor entering the stratosphere owing to a lower tropopause and higher tropopause temperatures. The effect of a ±15% change in O3 below 100 hPa is relatively small. However, the effect of a 15% O3 increase between 200 and 70 hPa is similar to that of a 15% O3 increase through the whole domain, suggesting that ozone increases in the UTLS dominate the impacts on temperature and tropical upwelling. Sea surface temperature (SST) changes associated with increasing atmospheric greenhouse gases (GHG) have a profound impact on the STE. Without corresponding SST changes, the radiative effects of the CO2 doubling on the STE is less significant than a global 15% O3 increase. When the SST changes are considered in the doubled CO2 experiment, the tropical upwelling is significantly increased (by 20.4%) with a much higher, but warmer, tropopause. Copyright 2008 by the American Geophysical Union."
"7202252296;6603753015;25629654200;35208232500;7005254328;7202429440;7201432984;","Oxygenated fraction and mass of organic aerosol from direct emission and atmospheric processing measured on the R/V Ronald Brown during TEXAQS/GoMACCS 2006",2009,"10.1029/2008JD011275","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75249098804&doi=10.1029%2f2008JD011275&partnerID=40&md5=ceffad4b7a2569aaa428b77450d25dd8","Submicron particles collected on Teflon filters aboard the R/V Ronald Brown during the Texas Air Quality Study and Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS/GoMACCS) 2006 in and around the port of Houston, Texas, were measured by Fourier transform infrared (FTIR) and X-ray fluorescence for organic functional groups and elemental composition. Organic mass (OM) concentrations (1-25 μm-3) for ambient particle samples measured by FTIR showed good agreement with measurements made with an aerosol mass spectrometer. The fractions of organic mass identified as alkane and carboxylic acid groups were 47% and 32%, respectively. Three different types of air masses were identified on the basis of the air mass origin and the radon concentration, with significantly higher carboxylic acid group mass fractions in air masses from the north (35%) than the south (29%) or Gulf of Mexico (26%). Positive matrix factorization analysis attributed carboxylic acid fractions of 30-35% to factors with mild or strong correlations (r &gt; 0.5) to elemental signatures of oil combustion and 9-24% to wood smoke, indicating that part of the carboxylic acid fraction of OM was formed by the same sources that controlled the metal emissions, namely the oil and wood combustion activities. The implication is that a substantial part of the measured carboxylic acid contribution was formed independently of traditionally ""secondary"" processes, which would be affected by atmospheric (both photochemical and meteorological) conditions and other emission sources. The carboxylic acid group fractions in the Gulf of Mexico and south air masses (GAM and SAM, respectively) were largely oil combustion emissions from ships as well, as background marine sources, with only limited recent land influences (based on radon concentrations). Alcohol groups accounted for 14% of OM (mostly associated with oil combustion emissions and background sources), and amine groups accounted for 4% of OM in all air masses. Organosulfate groups were found in GAM and SAM, accounting for 1% and 3% of OM, respectively. Two thirds of the OM and oxygen-to-carbon (O/C) measured could be attributed to oil and wood combustion sources on the basis of mild or strong correlations to coemitted, nonvolatile trace metals, with the remaining one third being associated with atmospherically processed organic aerosol. The cloud condensation nuclei (CCN) fraction (normalized by total condensation nuclei) had weak correlations to the alcohol and amine group fractions and mild correlation with O/C, also varying inversely with alkane group fraction. The chemical components that influenced f(RH) were sulfate, organic, and nitrate fraction, but this contrast is consistent with the size-distribution dependence of CCN counters and nephelometers. Copyright 2009 by the American Geophysical Union."
"7402689885;6506387443;7006346740;","Climatology of tropopause folds over a European Arctic station (Esrange)",2009,"10.1029/2007JD009638","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649128736&doi=10.1029%2f2007JD009638&partnerID=40&md5=18ef892ae63a168b3e7aa3f7907b7b4c","Eleven years (September 1996 to August 2007) of continuous measurements of threedimensional wind and backscattered signal strength observed with Esrange Radar (ESRAD) have been utilized to study the annual and interannual variation of tropopause folds over an Arctic station. Two typical tropopause fold events (one is associated with a streamer type of system and the other with a cutoff low) are selected and are characterized with the help of synoptic charts and potential vorticity (PV) analysis. Typical characteristics of radar parameters during the passage of folds are identified, such as the sudden rise in the tropopause altitude, high-reflectivity layer sloping downward from the tropopause beneath the jet stream, and intensification of the jet stream. These characteristics are utilized to discern the tropopause fold in the radar data. The climatology of tropopause folds exhibits a pronounced annual cycle with a large number of folds in winter and fewer in summer. The annual cycle of folds is more or less similar in all the years; however, significant interannual variation is observed with winter periods exhibiting maximum interannual variability. The climatology of folds and its annual cycle are compared and contrasted with similar climatological studies available in the literature. The differences in the climatologies are discussed in light of differences in the algorithms and the spatial variability of fold frequency. Copyright 2008 by the American Geophysical Union."
"7006306835;56744278700;","Nonlinear climate and hydrological responses to aerosol effects",2009,"10.1175/2008JCLI2362.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049119404&doi=10.1175%2f2008JCLI2362.1&partnerID=40&md5=253f46f99f00aad49f3e1fb63501b679","The equilibrium temperature and hydrological responses to the total aerosol effects (i.e., direct, semidirect, and indirect effects) are studied using a modified version of the Geophysical Fluid Dynamics Laboratory atmosphere general circulation model (AM2.1) coupled to a mixed layer ocean model. The treatment of aerosol-liquid cloud interactions and associated indirect effects is based upon a prognostic scheme of cloud droplet number concentration, with an explicit representation of cloud condensation nuclei activation involving sulfate, organic carbon, and sea salt aerosols. Increasing aerosols from preindustrial (1860) to present-day (1990) levels leads to a decrease of 1.9 K in the global annual mean surface temperature. The cooling is relatively strong over the Northern Hemisphere midlatitude land owing to the high aerosol burden there, while being amplified at high latitudes. When being subject to aerosols and radiatively active gases (i.e., well-mixed greenhouse gases and ozone) simultaneously, the model climate behaves nonlinearly; the simulated increase in surface temperature (0.55 K) is considerably less than the arithmetic sum of separate aerosol and gas effects (0.86 K). The thermal responses are accompanied by the nonlinear changes in cloud fields, which are amplified owing to the surface albedo feedback at high latitudes. The two effects completely offset each other in the Northern Hemisphere, while gas effect is dominant in the Southern Hemisphere. Both factors are crucial in shaping the regional responses. Interhemispheric asymmetry in aerosol-induced cooling yields a southward shift of the intertropical convergence zone, thus giving rise to a significant reduction in precipitation north of the equator, and an increase to the south. The simulations show that the change of precipitation in response to the simultaneous increases in aerosols and gases not only largely follows the same pattern as that for aerosols alone, but that it is also substantially strengthened in terms of magnitude south of 10°N. This is quite different from the damping expected from adding up individual responses, and further indicates the nonlinearity in the model's hydrological response."
"16245459800;35514012200;","Mechanisms for the interannual variability of SST in the East Pacific warm pool",2009,"10.1175/2008JCLI2467.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049097972&doi=10.1175%2f2008JCLI2467.1&partnerID=40&md5=cb9f4a59fc007903c95d66f905383b3d","In comparison with the western and equatorial Pacific Ocean, relatively little is known about the east Pacific warm pool (EPWP). Observations indicate that the interannual variability of sea surface temperature (SST) in the EPWP is highly correlated (0.95) with the El Niño-Southern Oscillation (ENSO). In this paper, an ocean general circulation model (OGCM) of the tropical Pacific Ocean and various atmospheric and oceanic observations are used to diagnose the physical processes governing the interannual variability of SST in the EPWP. Atmospheric forcings for the OGCM are derived purely from satellite observations between 1988 and 2004. Shortwave heating is identified as playing a dominant role in the interannual SST tendency of the EPWP. The high correlation between SST in the EPWP and eastern equatorial Pacific is therefore explained not by ocean processes, but by an atmospheric link. ENSO-driven equatorial SST anomalies modify the distribution of the overlying atmospheric vertical motions and therefore cloud cover and ultimately shortwave heating. During an El Niño event, for example, the ITCZ is equatorward displaced from its normal position over the EPWP, resulting in anomalously large shortwave heating over the EPWP. Analysis of poleward ocean heat transport and coastal Kelvin waves confirms that oceanic processes are not sufficient to explain the interannual variability of the EPWP. © 2009 American Meteorological Society."
"13906443400;35551238800;7004044484;57203492395;6701751100;7003540690;7006577245;","Seasonal evolution of the West African heat low: A climatological perspective",2009,"10.1007/s00382-009-0553-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649224647&doi=10.1007%2fs00382-009-0553-4&partnerID=40&md5=4c7646a1b900c17c472785bbc4ecc747","The West African heat low (WAHL), a region of high surface temperatures and low surface pressures, is a key element of the West African monsoon system. In this study, we propose a method to detect the WAHL in order to monitor its climatological seasonal displacement over West Africa during the period 1979-2001, using the European Centre for Medium-range Weather Forecast (ECMWF) ERA-40 reanalyses. The low-level atmospheric thickness (LLAT), a variable defined as the difference of geopotential heights at 700 and 925 hPa, is used to detect the dilatation of these levels generated by an increase of the temperature. We define grid points with 10% highest values of the LLAT as the WAHL. We show that our method reliably positions the WAHL over areas of high surface temperatures and low surface pressures, and that it is effective at detecting heat lows. In the course of the year, the climatological WAHL is shown to migrate north-westward from a position south of the Darfur mountains in the winter (November-March) to a location over the Sahara, between the Hoggar and the Atlas mountains, during the summer (June-September). The temperature tendency equation is used to investigate the processes controlling the displacement of the WAHL, and more particularly the heating at low levels. The specific period of the onset of the WAHL in its summer location over the Sahara (referred to as the Saharan heat low -SHL- onset) is also analysed during the 1984-2001 period, using complementary brightness temperature data from the European Union-funded Cloud Archive User Service (CLAUS). The climatological onset of the SHL occurs around 20 June, i.e. just before the climatological monsoon onset date. The present study suggests that the onset of the WAHL occurs approximately 5 days before the monsoon onset for the 1984-2001 period. This is confirmed independently by comparing the SHL onset date and the monsoon onset date for the 1984-2001 period. The seasonal evolution of the WAHL for the year 2006 (the year of the African Monsoon Multidisciplinary Analysis project Special Observation Period) is analysed and compared with the climatological results. The operational ECMWF analyses were used for that purpose. Except in April, the spatial distribution of the WAHL remains relatively unchanged and agrees with the climatology. The onset of the SHL in 2006 occurs on 18 June, which is close to the climatological date, in spite of the delay in the onset of the rainy season in Sahel. © The Author(s) 2009."
"57190749913;7201646465;6602654938;7202970886;","Stochastic radiative transfer on modeled cloud fields",2009,"10.1109/LGRS.2008.2007814","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65049085635&doi=10.1109%2fLGRS.2008.2007814&partnerID=40&md5=f6abd782bb40e88dd4e966f55485330b","Several efforts are currently underway to improve cloud-radiation parameterizations in Global Climate Models (GCMs) by incorporating statistical properties of the cloud field. Although some radiation parameterizations, which are already computationally costly, now incorporate subgrid scale variability in cloud properties, they are not yet capable of using this information in their calculations of the 3-D radiation fields. Before drastic changes are made to such algorithms to incorporate cloudcloud radiation interactions, the impact of including realistic high-resolution cloud distributions on the shortwave fluxes should be assessed. This letter provides a framework for carrying out such assessments, including a new methodology that blends a stochastic radiative transfer model, high-resolution cloud fields from a mesoscale meteorological model, and a threshold and object identification technique applied to cloud water content fields. This process provides a link between the radiative fluxes calculated in GCMs, where clouds occur at a subgrid scale, and the highly resolved cloud fields in a regional climate model, which can provide cloud field statistics. Two case studies are described herein. © 2009 IEEE."
"7402955227;35277762300;23981552800;","Significance of summer fog and overcast for drought stress and ecological functioning of coastal California endemic plant species",2009,"10.1111/j.1365-2699.2008.02025.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62249103646&doi=10.1111%2fj.1365-2699.2008.02025.x&partnerID=40&md5=9297d68d657f81f0d444828c56b71e97","Aim Fog drip is a crucial water source for plants in many ecosystems, including a number of global biodiversity hotspots. In California, dozens of rare, drought-sensitive plant species are endemic to coastal areas where the dominant summer moisture source is fog. Low clouds that provide water to these semi-arid ecosystems through fog drip can also sharply reduce evaporative water losses by providing shade. We quantified the relative hydrological importance of cloud shading vs. fog drip. We then examined how both factors influence the range dynamics of an apparently fog-dependent plant species spanning a small-scale cloud gradient. Location The study area is on Santa Cruz Island off the coast of southern California. It is near the southern range limit of bishop pine (Pinus muricata D. Don), a tree endemic to the coasts of California and Baja, Mexico. Methods We measured climate across a pine stand along a 7 km, coastal-inland elevation transect. Short-term (1-5 years) monitoring and remote sensing data revealed strong climatic gradients driven primarily by cloud cover. Long-term (102 years) effects of these gradients were estimated using a water balance model. Results We found that shade from persistent low clouds near the coast reduced annual drought stress by 22-40% compared with clearer conditions further inland. Fog drip at higher elevations provided sufficient extra water to reduce annual drought stress by 20-36%. Sites located at both high elevation and nearer the coast were subject to both effects. Together, these effects reduced average annual drought stress by 56% and dramatically reduced the frequency of severe drought over the last century. At lower elevation (without appreciable fog drip) and also near the inland edge of the stand (with less cloud shading) severe droughts episodically kill most pine recruits, thereby limiting the local range of this species. Main conclusions Persistent cloud shading can influence hydrology as much as fog drip in cloud-affected ecosystems. Understanding the patterns of both cloud shading and fog drip and their respective impacts on ecosystem water budgets is necessary to fully understand past species range shifts and to anticipate future climate change-induced range shifts in fog-dependent ecosystems. © 2008 Blackwell Publishing Ltd."
"24070915600;56346289200;55707280000;7403349409;","A simulation study on the characteristics of cloud microphysics of heavy rainfall in the meiyu front",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651112021&partnerID=40&md5=8d1bda1f8722025889efc1a6ee2a05ab","A heavy rainfall in the Meiyu front during 4-5 July 2003 is simulated by use of the non-hydrostatic mesoscale model MM5 (V3-6) with different explicit cloud microphysical parameterization schemes. The characteristics of microphysical process of convective cloud are studied by the model outputs. The simulation study reveals that: (1) The mesoscale model MM5 with explicit cloud microphysical process is capable of simulating the instant heavy rainfall in the Meiyu front, the rainfall simulation could be improved significantly as the model resolution is increased, and the Goddard scheme is better than the Reisner or Schultz scheme. (2) The convective cloud in the Meiyu front has a comprehensive structure composed of solid, liquid and vapor phases of water, the mass density of water vapor is the largest one in the cloud; the next one is graupel, while those of ice, snow, rain water and the cloud water are almost same. The height at which mass density peaks for different hydrometeors is almost unchangeable during the heavy rainfall period. The mass density variation of rain water, ice, and graupel are consistent with that of ground precipitation, while that of water vapor in the low levels is 1-2 h earlier than the precipitation. (3) The main contribution to the water vapor budget in the atmosphere is the convergence of vapor flux through advection and convection, which provides the main vapor source of the rainfall. Besides the basic process of the auto-conversion of cloud water to rain water, there is an additional cloud microphysical process that is essential to the formation of instant heavy rainfall, the ice-phase crystals are transformed into graupels first and then the increased graupels mix with cloud water and accelerates the conversion of cloud water to rain water. The positive feedback mechanism between latent heat release and convection is the main cause to maintain and develop the heavy precipitation."
"7601345593;55418553100;27170375100;","Investigating the role of MODIS Leaf Area Index and vegetation-climate interaction in regional climate simulations over Asia",2009,"10.3319/TAO.2008.04.03.01(A)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68149160865&doi=10.3319%2fTAO.2008.04.03.01%28A%29&partnerID=40&md5=a920b3004611a74ac3b5e271b106e900","Four yearlong climate simulations using the Seoul National University, regional climate model have been performed to assess the role of the MODIS Leaf Area Index (LAI) and interactive LAI in influencing Asian climate. The control experiment employs the fixed monthly LAI according to the original land surface model. Another additional simulation replaces the LAI by 4-year mean MODIS climatology. The last two integrations both allow the LAI to interact with the atmosphere, but adopt two different simple parameterization schemes. Although the control experiment generally reproduces spatial distribution and the magnitude of Asian surface climate, it contains large biases in some specific areas, which are partly improved by the implementation of MODIS LAI and vegetation interaction schemes. In winter months (January-to-March), greener land surface introduced in the last three simulations reduces cold biases over Northeast China and adjacent areas, southern China, Korea, and Japan, and warm biases over South Asia, and precipitation discrepancies over South Asia, southern China and West Japan. In contrast, LAI changes only play a limited role in summer. There are significant differences between regions with respect to mechanisms explaining winter-month improvement in surface climate simulations. Over Northeast China and adjacent areas, increased LAI increases net solar radiation by about 12 W m-2 mainly through the effects on surface albedo, thereby warming the surface by about 1.8°C. A decrease in clouds makes a major contribution to surface warming and precipitation reduction over southern China. Increased evapotranspiration dominates changes in surface energy balance, and cause less net radiation to be partitioned into sensible heat over South Asia. As a result, the model simulates about 1.5°C colder surface air temperature and about 0.1 mm day-1more precipitation over this region. Finally, the implications and limitations of this study are also discussed."
"57208802674;7102193873;21734155600;36774907600;","The WRF 3DVar System Combined with Physical Initialization for Assimilation of Doppler Radar Data",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651092280&partnerID=40&md5=92ea07cf65ffc25aa1ea1b165a3ec67e","The three-dimensional variational data assimilation (3DVar) system of the Weather Research and Forecasting (WRF) model (WRF-Var) is further developed with a physical initialization (PI) procedure to assimilate Doppler radar radial velocity and reflectivity observations. In this updated 3DVar system, specific humidity, cloud water content, and vertical velocity are first derived from reflectivity with PI, then the model fields of specific humidity and cloud water content are replaced with the modified ones, and finally, the estimated vertical velocity is added to the cost-function of the existing WRF-Var (version 2.0) as a new observation type, and radial velocity observations are assimilated directly by the method afforded by WRF-Var. The new assimilation scheme is tested with a heavy convective precipitation event in the middle reaches of Yangtze River on 19 June 2002 and a Meiyu front torrential rain event in the Huaihe River Basin on 5 July 2003. Assimilation results show that the increments of analyzed variables correspond well with the horizontal distribution of the observed reflectivity. There are positive increments of cloud water content, specific humidity, and vertical velocity in echo region and negative increments of vertical velocity in echo-free region where the increments of horizontal winds present a clockwise transition. Results of forecast experiments show that the effects of adjusting cloud water content or vertical velocity directly with PI on forecast are not obvious. Adjusting specific humidity shows better performance in forecasting the precipitation than directly adjusting cloud water content or vertical velocity. Significant improvement in predicting precipitation as well as in reducing the model's spin-up time are achieved when radial velocity and reflectivity observations are assimilated with the new scheme."
"7003355879;34872178900;6602185880;","Variability of the Northern Hemisphere polar stratospheric cloud potential: The role of North Pacific disturbances",2009,"10.1002/qj.409","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70149124939&doi=10.1002%2fqj.409&partnerID=40&md5=ca773b95796056b6daeff547f417248e","The potential of the Arctic stratosphere to sustain the formation of Polar Stratospheric Clouds (PSCs) is a key factor in determining the amount of ozone destroyed each winter, and is often measured as a 'PSC volume'. The latter quantity has been shown to closely follow a near-linear compact relationship with winter-averaged column ozone loss, and displays a high variability from monthly to decadal time-scales. We examine the connection between meteorological conditions in the troposphere and the variability of lower polar stratospheric temperatures over the last four decades, and specifically, conditions leading to a high PSC volume. In addition to the well-established connection between the North Atlantic Oscillation (NAO) and the polar vortex, we demonstrate the large influence of precursory disturbances over the North Pacific and the Far East, the region of maximum climatological upward wave activity flux. Namely, very high monthly PSC volume (in the top 12%) predominantly follows the development of positive tropospheric height anomalies over the Far East, which lead to a weakening of the background planetary wave trough, and lessened upward wave activity flux into the stratosphere. Precursory anomalies over the Far East are reminiscent of East Asian monsoon amplification episodes. © 2009 Royal Meteorological Society."
"7004500706;7102886537;56033135100;6602208186;8068419200;6603535726;","Comparison of mid-Pliocene climate predictions produced by the HadAM3 and GCMAM3 General Circulation Models",2009,"10.1016/j.gloplacha.2008.12.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-63349089935&doi=10.1016%2fj.gloplacha.2008.12.014&partnerID=40&md5=b23252969657a39aa3cd581eb1cba149","The mid-Pliocene warm period (ca. 3 to 3.3 million years ago) has become an important interval of time for palaeoclimate modelling exercises, with a large number of studies published during the last decade. However, there has been no attempt to assess the degree of model dependency of the results obtained. Here we present an initial comparison of mid-Pliocene climatologies produced by the Goddard Institute for Space Studies and Hadley Centre for Climate Prediction and Research atmosphere-only General Circulation Models (GCMAM3 and HadAM3). Whilst both models are consistent in the simulation of broad-scale differences in mid-Pliocene surface air temperature and total precipitation rates, significant variation is noted on regional and local scales. There are also significant differences in the model predictions of total cloud cover. A terrestrial data/model comparison, facilitated by the BIOME 4 model and a new data set of Piacenzian Stage land cover [Salzmann, U., Haywood, A.M., Lunt, D.J., Valdes, P.J., Hill, D.J., (2008). A new global biome reconstruction and data model comparison for the Middle Pliocene. Global Ecology and Biogeography 17, 432-447, doi:10.1111/j.1466-8238.2007.00381.x] and combined with the use of Kappa statistics, indicates that HadAM3-based biome predictions provide a closer fit to proxy data in the mid to high-latitudes. However, GCMAM3-based biomes in the tropics provide the closest fit to proxy data. © 2008 Elsevier B.V."
"56135632400;7405489798;7007020226;","Large-scale effect of aerosols on precipitation in the West African Monsoon region",2009,"10.1002/qj.391","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650227165&doi=10.1002%2fqj.391&partnerID=40&md5=b6236013e6ebb09075efef9013867802","We used multi-year satellite observations to study aerosol effects on the large-scale variability in precipitation of the West African Monsoon (WAM) region, which is often impacted by high concentrations of desert dust and biomass-burning smoke. We find a statistically significant precipitation reduction associated with high aerosol concentration near the coast of the Gulf of Guinea from late boreal autumn to winter. The largest aerosol-related precipitation reduction (∼1.5 mm d-1) is about 50% of the climatological mean precipitation in the region and occurs mainly at rain rates in the range of 2-17 mm d-1 off the northern coast of the Gulf of Guinea. This reduction cannot be linearly attributed to known climate and weather factors such as El Niño-Southern Oscillation, North Atlantic Oscillation, Atlantic sea-surface temperature, or water vapour. The fractional precipitation variance related to aerosol is about 13%, a value comparable to those related to the known climate factors. Based on the spatial pattern and seasonality of the observed precipitation reduction and its dependence on the rain rate, the observed negative correlation cannot be readily attributed to precipitation effects on aerosol by wet deposition or to rain and cloud contamination of satellite aerosol retrievals. We therefore suggest that our results can be taken as observational evidence of aerosol effects on precipitation. The aerosol associated with the observed precipitation reduction can be traced back to various African sources where large quantities of desert dust and biomass-burning smoke are emitted during much of the year. Given that the emissions of dust and smoke have varied considerably over the past several decades, in part attributable to human activities, our observed rainfall reduction may reflect an anthropogenic impact to some degree. © 2009 Royal Meteorological Society."
"13402651100;55524267300;7005030035;6602176524;7004585020;56259764300;","Improving the numerical prediction of a cyclone in the Mediterranean by local potential vorticity modifications",2009,"10.1002/qj.422","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70149112097&doi=10.1002%2fqj.422&partnerID=40&md5=aab9e1a43339b09a969f364dbda183dc","This study explores the benefit that can be drawn from incorporating local potential vorticity (PV) modifications into a numerical forecast. The case under study is the severe cyclogenesis that occurred in the Western Mediterranean from 9 to 12 November 2001. This case was shown to be extremely sensitive to the upper-level flow, which governed to a great extent the deepening of the depression and the location and intensity of its associated precipitation. Corrections of PV were guided by METEOSAT-7 water vapour observations and restricted to the upper troposphere, mainly altering the topography of the dynamical tropopause. Using both the French operational global model ARPEGE and the non-hydrostatic mesoscale model Meso-NH, it is shown that carefully designed PV corrections lead to a substantial improvement in the simulation of the storm, both in terms of surface pressure, cloud cover and precipitation forecasts. Furthermore, the impact of the modifications is shown to be a maximum when they are introduced at the time corresponding to the incipient stage of cyclogenesis. © 2009 Royal Meteorological Society."
"7202014256;7004479395;8144850900;","The Earth as an extrasolar planet: The vegetation spectral signature today and during the last Quaternary climatic extrema",2009,"10.1017/S1473550409004406","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349591700&doi=10.1017%2fS1473550409004406&partnerID=40&md5=e877b6ae52126c2f9b476347d364d085","The so-called vegetation red-edge (VRE), a sharp increase in the reflectance around 700 nm, is a characteristic of vegetation spectra, and can therefore be used as a biomarker if it can be detected in an unresolved extrasolar Earth-like planet integrated reflectance spectrum. Here, we investigate the potential for the detection of vegetation spectra during the last Quaternary climatic extrema, the Last Glacial Maximum (LGM) and the Holocene optimum, for which past climatic simulations have been made. By testing the VRE detectability during these extrema, when Earth's climate and biomes maps were different from today, we are able to test the vegetation detectability on a terrestrial planet different from our modern Earth. Data from the Biome3.5 model have been associated to visible Global Ozone Monitoring Experiment (GOME) spectra for each biome and cloud cover to derive Earth's integrated spectra for given Earth phases and observer positions. The VRE is then measured. Results show that the vegetation remains detectable during the last climatic extrema. Compared to the current Earth, the Holocene optimum, with a greener Sahara, slightly increases the mean VRE on one hand, while on the other hand, the large ice cap over the northern hemisphere during the LGM decreases vegetation detectability. We finally discuss the detectability of the VRE in the context of recently proposed space missions. © 2009 Cambridge University Press."
"7004909806;6701561763;","A simple strategy for linearizing complex moist convective schemes",2009,"10.1002/qj.427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70149083901&doi=10.1002%2fqj.427&partnerID=40&md5=aa455f3d97dcb198ff88cdf936cc309f","Variational data assimilation methods and related applications depend on the validity of the tangent-linear approximation, which is truly challenging when applied to deep moist convection. A simple strategy for linearizing complex moist convective schemes in numerical weather prediction models is proposed. This strategy represents a trade-off between code development and maintenance on the one hand and expected benefit on the other hand. The generic linearized scheme described hereafter can be used in conjunction with any nonlinear moist convective scheme, thus eliminating the need to linearize complex codes. The universality of the scheme stems from the fact that conditional triggers and cloud vertical extent are supplied by the trajectory of the nonlinear scheme. In active columns, the convective tendencies cancel the largescale dynamical tendencies. Potential uses of the scheme include variational data assimilation and diagnostic studies such as tropical singular vectors and key analysis errors with precipitation. The relevance of the methodology is examined with the Global Environmental Multiscale model using the Kain-Fritsch mass-flux scheme that is operational at the Canadian Meteorological Centre. It is shown that the tangent-linear approximation is improved when compared to a linearized convection scheme having its own trigger functions. The improvement is particularly noticeable for the partition between stratiform and convective components of surface precipitation. Finally the examination of adjoint sensitivities of surface precipitation with the simplified linearized scheme triggered by the Kain-Fritsch scheme reveals a more pronounced sensitivity to midlatitude baroclinic instability and less predictability for tropical systems when compared to a Kuo-type scheme. Copyright © 2009 Royal Meteorological Society and Crown in the Right of Canada."
"8672586200;55600504900;","Improving the behavior of the cumulus parameterization for tropical cyclone prediction: Convection trigger",2009,"10.1016/j.atmosres.2008.09.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60549086765&doi=10.1016%2fj.atmosres.2008.09.022&partnerID=40&md5=4f914d12d4f8ae614175f7767a5ba7bd","Numerical studies have consistently shown the importance of moist convection in the evolution of tropical cyclones. However, a systematic evaluation of cumulus parameterization in the simulation of tropical cyclone is rare. The objective of this study is to 1) assess the performance of various subgrid-scale cumulus parameterization schemes in the simulation of tropical cyclones. Emphasis is placed on the intensity, distribution, and character of precipitation and on the forecast location and intensity of tropical cyclones; 2) improve the behavior of one of the cumulus parameterization schemes by modifying the parameterization, the weakness of which is identified in 1). The distribution and intensity of precipitation, its partitioning into grid-resolvable and subgrid-scale portions, the location and intensity of tropical cyclone were extremely sensitive to the choice of cumulus parameterization scheme. The scheme developed by Betts and Miller [Betts, A.K., Miller, M.J., 1993. The Betts-Miller scheme. In:Emanuel, K.A., Raymond, D.J. (Eds.), The Representation of Cumulus Convection in Numerical Models. Amer. Meteor. Soc., 246 pp] reproduced most of the features of rainfall distribution over the land, it tends to overestimate the rainfall coverage and make false alarm of intense rainfall. The mass flux scheme developed by Kain and Fritsch [Kain, J.S., Fritsch, J.M., 1993. Convective parameterization for mesoscale models: the Kain-Fritsch scheme. The Representation of Cumulus Convection in Numerical Models, Meteor. Monogr., No. 46, Amer. Meteor. Soc., 165-170] gave the best simulation of tropical cyclone on the 15 km grids, while the quasi-equilibrium scheme proposed by Grell [Grell, G., 1993. Prognostic evaluation of assumptions used by cumulus parameterization. Mon. Weather Rev., 121, 764-787] tended to underestimate sub-grid scale rainfall due to its deficiency in removing instability. Finally, it is also suggested that the Kain-Fritsch scheme can be improved for the case of weak synoptic forcing. In particular, the parameterization of the convective parcel's temperature perturbation by the environmental vertical velocity in the convective trigger function seems not quite robust. To improve this deficiency for our application, the effect of moisture advection is taken into account in determining the convective parcel's temperature perturbation. Preliminary results show that, the modified scheme can eliminate reasonably well the convective instability under weak synoptic forcing, change the response of the disturbance in the lower troposphere disturbance to environmental humidity and in favor of simulation of tropical cyclone. The results of this study should be of potential use for improving the performance of operational tropical cyclone prediction. © 2008 Elsevier B.V. All rights reserved."
"26665643500;23082420800;","Simulated variability in the mean atmospheric meridional circulation over the 20th century",2009,"10.1029/2008GL036741","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949171004&doi=10.1029%2f2008GL036741&partnerID=40&md5=2fe2b774ce096fc577c706b654de28ed","The variability in the zonally averaged atmospheric meridional circulation over the last 150 years is investigated using two atmospheric general circulation models (GCMs). A multi-decadal signal, with an approximately 70 year timescale, is identified in the cross-equatorial circulation. This signal is associated with a latitudinal shift in the ascending branch of the Hadley cell and precipitation in the tropics, as well as a change in the atmospheric meridional heat transport. These changes are well-correlated with the inter-hemispheric SST difference: When Northern Hemisphere sea surface temperatures (SSTs) are colder than the Southern Hemisphere, the ITCZ and precipitation shift to the south in a zonal mean sense, and the northward atmospheric energy transport increases. Previous studies with idealized climate forcings have shown similar results, but the findings presented here highlight the potential relevance of the inter-hemispheric SST contrast for understanding 20th century climate changes. Copyright 2009 by the American Geophysical Union."
"6602137800;35304081800;7401844779;7101886364;7004174939;","Case studies of aerosol remote sensing in the vicinity of clouds",2009,"10.1029/2008JD010774","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66449098749&doi=10.1029%2f2008JD010774&partnerID=40&md5=0812c0c0cc3c4135b51b181319bbd932","Studying the spatial variability of aerosol properties in the vicinity of clouds is essential to our ability to determine aerosol direct and indirect effects on climate. In this paper, we describe aerosol observations collected near cloud edges by an airborne Sun photometer over dark ocean waters. Focusing on case studies of aerosol measurements near eight cloud edges within a dissipating stratiform cloud deck, we compare the airborne Sun photometer observations to retrievals of aerosol properties using the standard Moderate Resolution Imaging Spectroradiometer- (MODIS) aerosol algorithm applied to 500-m-resolution MODIS spectral reflectances. We find a persistent, spectrally neutral increase in the Sun photometer-derived aerosol optical depth (AOD) of up to 10% (0.015) in the 2-km distances closest to the edges of several distinct clouds. At midvisible wavelengths, the MODIS AOD retrievals show similar increases toward cloud edges, although a larger increase in AOD is found in the MODIS along-scan direction. At shortwave infrared (SWIR) wavelengths (1240-2130 nm), the MODIS-derived AOD increases near cloud edges are of the order of 0.03 and as such three times as large as the Sun photometer-derived values. Hence, in contrast to recently discussed ""bluing"" of aerosols near cloud edges, i.e., a preferential apparent increase in the visible reflectances of clearsky pixels due to 3-D radiative transfer effects in the vicinity of clouds, we find a ""reddening"" of aerosols in the MODIS 500-m-resolution aerosol retrievals near clouds. This ""reddening"" in our study can be traced to larger absolute increases in SWIR reflectances when compared to visible reflectances near clouds, which in turn seem to stem from larger electronic cross talk in the MODIS SWIR bands (5-7). We note that the lack of ""bluing"" in our MODIS observations is likely due to the small geometric and optical thicknesses of the clouds considered. . Copyright 2009 by the American Geophysical Union."
"7402284525;7005275092;","Stratospheric variability and tropospheric ozone",2009,"10.1029/2008JD010942","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66449104099&doi=10.1029%2f2008JD010942&partnerID=40&md5=4e482ddba7c5cf309a5fb3c5aaf0b840","Changes in the stratosphere-troposphere exchange (STE) of ozone over the last few decades have altered the tropospheric ozone abundance and are likely to continue doing so in the coming century as climate changes. Combining an updated linearized stratospheric ozone chemistry (Linoz v2) with parameterized polar stratospheric clouds (PSCs) chemistry, a 5-year (2001-2005) sequence of the European Centre for Medium-Range Weather Forecasts (ECMWF) meteorology data, and the University of California, Irvine (UCI) chemistry transport model (CTM), we examined variations in STE O<inf>3</inf> flux and how it perturbs tropospheric O<inf>3</inf>. Our estimate for the current STE ozone flux is 290 Tg/a in the Northern Hemisphere (NH) and 225 Tg/a in the Southern Hemisphere (SH). The 2001-2005 interannual root-mean-square (RMS) variability is 25 Tg/a for the NH and 30 Tg/a for the SH. STE drives a seasonal peak-to-peak NH variability in tropospheric ozone of about 7-8 Dobson unit (DU). Of the interannual STE variance, 20% and 45% can be explained by the quasi-biennial oscillation (QBO) in the NH and SH, respectively. The CTM matches the observed QBO variations in total column ozone, and the STE O3 flux shows negative anomalies over the midlatitudes during the easterly phases of the QBO. When the observed column ozone depletion from 1979 to 2004 is modeled with Linoz v2, we predicted STE reductions of at most 10% in the NH, corresponding to a mean decrease of 1 ppb in tropospheric O<inf>3</inf>. Copyright 2009 by the American Geophysical Union."
"6603742681;55712621500;36842724800;55728284300;7410340979;","Arctic circumpolar mosaic at 250 m spatial resolution for IPY by fusion of MODIS/TERRA land bands B1-B7",2009,"10.1080/01431160802348119","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650224994&doi=10.1080%2f01431160802348119&partnerID=40&md5=30f924ee2f264ebddaedc3655d11d29d","The first spatially enhanced Moderate Resolution Imaging Spectroradiometer (MODIS) clear-sky mosaic for the Arctic circumpolar zone (9000 km × 9000 km) is presented, as a contribution to the Canadian component of the International Polar Year (IPY) Programme. The imagery was obtained by fusion of MODIS bands B1-B2 observed at 250 m spatial resolution with bands B3-B7 observed at 500 m spatial resolution to satisfy the Global Climate Observing System (GCOS) requirement for a spatial resolution of 250 m for satellite-based products for climate. The fusion method used adaptive regression and normalization to preserve the image radiometric properties. A new cloud and cloud shadow detection method and a clear-sky compositing scheme were used for the 250 m multispectral data. By the end of the IPY in 2009, a decade-long (2000-2009) time series of these data documenting the state and variability of the Arctic region at fine spatial (250 m) and temporal (10-day) resolution will be produced if MODIS continues to operate until the end of this period. The product is generated in the Lambert Azimuthal Equal-Area (LAEA) projection centred over the North Pole. The major intended application of the new data is mapping the surface albedo at 250 m spatial resolution. This product in turn can be used as an input for generating several other Essential Climate Variables (ECVs) as defined by the GCOS."
"6507224579;7202671706;55259419600;7402887257;","High-CO2 cloud radiative forcing feedback over both land and ocean in a global climate model",2009,"10.1029/2008GL036703","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65649093701&doi=10.1029%2f2008GL036703&partnerID=40&md5=ae3ad62f3fecc817fd69027d174408ed","A positive feedback on high-latitude winter marine climate change involving convective clouds has recently been proposed using simple models. This feedback could help explain data from equable climates, e.g., the Eocene, and might be relevant for future climate. Here this convective cloud feedback is shown to be active in an atmospheric GCM in modern configuration (CAM) at CO2 = 2240 ppm and in a coupled GCM in Eocene configuration (CCSM) at CO2 = 560 ppm. Changes in boundary conditions that increase surface temperature have a similar effect as increases in CO2 concentration. It is also found that the high-latitude winter cloud radiative forcing over land increases with increases in surface temperature due to either increased CO2 or changes in boundary conditions, which could represent an important part of the explanation for warm continental interior winter surface temperatures during equable climates. This is due to increased low-level layered clouds caused by increased relative humidity. Copyright 2009 by the American Geophysical Union."
"35917252100;7005035762;","On the use of PDF schemes to parameterize sub-grid clouds",2009,"10.1029/2008GL036817","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65649146447&doi=10.1029%2f2008GL036817&partnerID=40&md5=6d9dccdaffd2314c1d5dfd37f033f1a1","Using high resolution simulations of eight well-documented cloud cases in different climate regimes, this study investigated the statistical distributions of dynamic and thermodynamic variables in the cloud layer and examined various assumptions used by the current statistical cloud schemes. It is found that dynamic and thermodynamic variables skew differently in the cloud layer of shallow cumulus, stratocumulus, and deep convective clouds. Vertical velocity is positively skewed, but the skewed dynamic structure cannot account for the large skewness of positively skewed total mixing ratio qt and negatively skewed liquid water potential temperature θl. It is, thus, not physically sound to assume that the sub-grid variation of different variables follows the same skewed PDF. The simulations further show that the weighted standard deviations of qt and θl have the same order of magnitude in all types of clouds, indicating that the variations of temperature and moisture are the equally important factors for sub-grid clouds. Thus, neglecting either one of them in a statistical cloud scheme may introduce significant bias in the parameterized clouds. Copyright 2009 by the American Geophysical Union."
"56108439300;6602764979;","Role of a simplified hydrological cycle and clouds in regulating the climate - Biota system of Daisyworld",2009,"10.1111/j.1600-0889.2008.00411.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61849181541&doi=10.1111%2fj.1600-0889.2008.00411.x&partnerID=40&md5=225dd3a2c3895e672ae86744362bc915","The role of a simplified hydrological cycle and a physical representation of clouds is investigated in the Daisyworld model, subject to constant and variable solar forcing and varying cloud albedo and height. Under constant forcing, properties of the cloudy hydrologic cycle control the long-term system dynamics to non-oscillatory, oscillatory, abiotic or biotic states. In case of oscillatory solutions, their amplitude and periodicity are controlled by the net cooling or warming effects from clouds. Two conditions are considered under variable forcing-active or neutral-depending on the existence or not of biota-environment feedbacks. Temperature, cloudiness and hydrological variables are self-regulated in the active condition, whereas non-regulated in the neutral condition. Self-regulation is quantified through two measurements (luminosity range and total life), both of which can be larger in our model than in several other variants of Daisyworld, depending on cloud characteristics. The hydrological cycle and clouds can make the planet more habitable for life, independent of the capacity of the system for biological adaptation. Two hypotheses are put forward: (1) beneficial effects for life emerge from biota-clouds interactions, enhancing the global amount of life and extending the life span; and (ii) the existence of a maximum self-regulation capacity principle. © 2009 The Author Journal compilation © 2009 Blackwell Munksgaard."
"7404778968;7103259757;","Daily snow cover estimation from Advanced Very High Resolution Radiometer Polar Pathfinder data over Northern Hemisphere land surfaces during 1982-2004",2009,"10.1029/2008JD011272","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65849438758&doi=10.1029%2f2008JD011272&partnerID=40&md5=d1e8b0bb1fcef869b680f6c97c5f360a","The Global Climate Observing System has identified the need for systematic global daily snow cover data sets over land. Current in situ snow cover data sets have limited spatial coverage while satellite-based snow cover records have either limited historical extent or limited temporal and spatial resolution because of cloud cover or specific sensor availability. NOAA Advanced Very High Resolution Radiometer (AVHRR) data offers nearly complete daily global coverage of the Northern Hemisphere, extending back to the early 1980s with successors slated to continue into the next decade. In this paper, we apply a new algorithm, Snowcover, to estimate daily snow cover, including periods of cloudy conditions, from AVHRR Polar Pathfinder (APP) data over Northern Hemisphere land surfaces. This new snow cover product is compared to snow cover estimates derived from long-term in situ snow depth measurements over Canada and the northern Eurasia. The APP snow cover maps showed an 80% agreement rate or better at 95% of the in situ sites. This performance was comparable to the agreement of MODIS 0.05 degree snow cover products over the same sites; although the MODIS product was only retrieved ~20% of the time corresponding to clear sky conditions in contrast to over 95% of the time with the APP snow product. The almost continuously temporal and spatial coverage for the past 23 years from 1982 to 2004 over Northern Hemisphere makes the new daily snow cover product especially suitable for analysis of large-scale patterns of spring snowmelt in association with variability of circumpolar climate and ecological parameters. Copyright 2009 by the American Geophysical Union."
"7403968239;7406250414;7404373922;","Tropical water vapor and cloud feedbacks in climate models: A further assessment using coupled simulations",2009,"10.1175/2008JCLI2267.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049117621&doi=10.1175%2f2008JCLI2267.1&partnerID=40&md5=22bf19468287087f68e66e7304082faa","By comparing the response of clouds and water vapor to ENSO forcing in nature with that in Atmospheric Model Intercomparison Project (AMIP) simulations by some leading climate models, an earlier evaluation of tropical cloud and water vapor feedbacks has revealed the following two common biases in the models: 1) an underestimate of the strength of the negative cloud albedo feedback and 2) an overestimate of the positive feedback from the greenhouse effect of water vapor. Extending the same analysis to the fully coupled simulations of these models as well as other Intergovernmental Panel on Climate Change (IPCC) coupled models, it is found that these two biases persist. Relative to the earlier estimates from AMIP simulations, the overestimate of the positive feedback from water vapor is alleviated somewhat for most of the coupled simulations. Improvements in the simulation of the cloud albedo feedback are only found in the models whose AMIP runs suggest either a positive or nearly positive cloud albedo feedback. The strength of the negative cloud albedo feedback in all other models is found to be substantially weaker than that estimated from the corresponding AMIP simulations. Consequently, although additional models are found to have a cloud albedo feedback in their AMIP simulations that is as strong as in the observations, all coupled simulations analyzed in this study have a weaker negative feedback from the cloud albedo and therefore a weaker negative feedback from the net surface heating than that indicated in observations. The weakening in the cloud albedo feedback is apparently linked to a reduced response of deep convection over the equatorial Pacific, which is in turn linked to the excessive cold tongue in the mean climate of these models. The results highlight that the feedbacks of water vapor and clouds-the cloud albedo feedback in particular - may depend on the mean intensity of the hydrological cycle. Whether the intermodel variations in the feedback from cloud albedo (water vapor) in the ENSO variability are correlated with the intermodel variations of the feedback from cloud albedo (water vapor) in global warming has also been examined. While a weak positive correlation between the intermodel variations in the feedback of water vapor during ENSO and the intermodel variations in the water vapor feedback during global warming was found, there is no significant correlation found between the intermodel variations in the cloud albedo feedback during ENSO and the intermodel variations in the cloud albedo feedback during global warming. The results suggest that the two common biases revealed in the simulated ENSO variability may not necessarily be carried over to the simulated global warming. These biases, however, highlight the continuing difficulty that models have in simulating accurately the feedbacks of water vapor and clouds on a time scale of the observations available. © 2009 American Meteorological Society."
"7004242054;26533675100;7202505831;7101952886;35236029000;","Comparison of algorithms for incoming atmospheric long-wave radiation",2009,"10.1029/2008WR007394","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65349094020&doi=10.1029%2f2008WR007394&partnerID=40&md5=b14377eebf9af11f3794ee21f388f031","While numerous algorithms exist for predicting incident atmospheric long-wave radiation under clear (Lclr) and cloudy skies, few comparisons have been published to assess the accuracy of the different algorithms. Virtually no comparisons have been made for both clear and cloudy skies across multiple sites. This study evaluates the accuracy of 13 algorithms for predicting incident long-wave radiation under clear skies, ten cloud correction algorithms, and four algorithms for all-sky conditions using data from 21 sites across North America and China. Data from five research sites were combined with publicly available data from nine sites in the AmeriFlux network for initial evaluation and optimization of cloud cover estimates; seven additional AmeriFlux sites were used as an independent test of the algorithms. Clear-sky algorithms that excelled in predicting Lclr were the Dilley, Prata, and Angström algorithms. Root mean square deviation (RMSD) between predicted and measured 30-minute or hourly Lclr averaged approximately 23 W m-2 for these three algorithms across all sites, while RMSD of daily estimates was as low as 14 W m-2. Cloud-correction algorithms of Kimball, Unsworth, and Crawford described the data best when combined with the Dilley clear-sky algorithm. Average RMSD across all sites for these three cloud corrections was approximately 24 to 25 W m -2 for 30-minute or hourly estimates and approximately 15 to 16 W m-2 for daily estimates. The Kimball and Unsworth cloud corrections require an estimate of cloud cover, while the Crawford algorithm corrects for cloud cover directly from measured solar radiation. Optimum limits in the clearness index, defined as the ratio of observed solar radiation to theoretical terrestrial solar radiation, for complete cloud cover and clear skies were suggested for the Kimball and Unsworth algorithms. Application of the optimized algorithms to seven independent sites yielded similar results. On the basis of the results, the recommended algorithms can be applied with reasonable accuracy for a wide range of climates, elevations, and latitudes. © 2009 by American Geophysical Union."
"6602748142;","Rain shadow development during the growth of mountain ranges: An atmospheric dynamics perspective",2009,"10.1029/2008JF001085","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349480815&doi=10.1029%2f2008JF001085&partnerID=40&md5=f24812634f21e5769c001f6219b2126f","An idealized atmospheric model is used to explore the links between climate and topography in the development of orographic rain shadows during orogenesis. The atmospheric dynamics theory of density stratified fluid flow over topography is used to interpret the results. The controlling nondimensional parameter is Nh/U, where N is the Brunt-Vaisala frequency, a measure of atmospheric stability, h is the terrain relief, and U is the initial' horizontal wind speed. Rain shadow development is found to be a nonlinear and nonunique function of both topography and atmospheric state, indicating that geological records of orographic aridity cannot be interpreted in terms of relief alone. When upstream topography exceeds Nh/U ≈ 1 during surface uplift, downstream orographic precipitation vanishes, and downstream orographic cloud mass decreases by as much as 90%. Upstream blocking of air flow can generate a forward projecting rain shadow in which a relatively low ridge (Nh/U < 1) situated upstream of a relatively high ridge (Nh/U > 1) may be decoupled from the atmospheric flow by a zone of flow • stagnation extending upstream of the high terrain. Such an effect may occur if the valley separating the two ranges is narrower than the length scale of flow stagnation. In the model configuration used here, lateral widening of a relatively low (Nh/U < 1) range changes downstream orographic cloud mass by only a few percent, while lateral growth of a relatively high (Nh/U > 1) range increases downstream cloud mass by up to a factor of 3. These results help to refine interpretations of climate-tectonic interactions in shaping the geological record of the Sierra Nevada and Andes. Copyright 2009 by the American Geophysical Union."
"7003799326;7401751388;57205192907;6507877620;6602799064;55305207800;","The summer North Atlantic oscillation: Past, present, and future",2009,"10.1175/2008JCLI2459.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049109355&doi=10.1175%2f2008JCLI2459.1&partnerID=40&md5=8fb04943a6be163101ab74e16397c7f3","Summer climate in the North Atlantic-European sector possesses a principal pattern of year-to-year variability that is the parallel to the well-known North Atlantic Oscillation in winter. This summer North Atlantic Oscillation (SNAO) is defined here as the first empirical orthogonal function (EOF)-of observed summertime extratropical North Atlantic pressure at mean sea fevel. It is shown to be characterized by a more northerly location and smaller spatial scale than its winter counterpart. The SNAO is also detected by cluster analysis and has a near-equivalent barotropic structure on daily and monthly-time scales. Although of lesser amplitude than its wintertime counterpart, the-SNAO exerts a strong influence on northern European rainfall, temperature, and cloudiness through changes in the-position of the North Atlantic storm track, It is, therefore, of key importance in generating-summer climate extremes, including-flooding, drought,and heat stress in northwestern Europe. The El Niño-Southern Oscillation (ENSO) phenomenon is known to influence summertime European climate; however, interannual variations of the SNAO are only weakly influencea by ENSO. On interdecadal time icales, both modeling and observational results indicate that SNAO variations-are partly related to the Atlantic multidecadal oscillation. It is shown that SNAO variations extend far back in time, as evidenced by reconstructions of SNAO variations back to 1706 using tree-ring records. Very long instrumental records, such as central England temperature, are used to validate the reconstruction. Finally, two climate models are shown to simulate the present-day SNAO and predict a trend toward a more positive index phase in the future under increasing greenhouse gas concentrations. This implies the long-term likelihood of increased summer drought for northwestern Europe. © 2009 American Meteorological Society."
"6602692238;6701705691;","Detection of volcanic SO2 by spaceborne infrared radiometers",2009,"10.1016/j.atmosres.2008.08.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58549098025&doi=10.1016%2fj.atmosres.2008.08.009&partnerID=40&md5=2c28b3ae022097fd9d4e575fa0ba45f4","Current infrared narrowband instruments, such as Moderate Resolution Imaging Spectrometer (MODIS) or Spinning Enhanced Visible and InfraRed Imager (SEVIRI), can be used to locate volcanic SO2 plumes. A three-channel technique has been proposed by Prata et. al. [Prata, A.J., Rose, W.I., Self, S., O'Brien, D.M., 2003. Global, long-term sulphur dioxide measurements from TOVS data: a new tool for studying explosive volcanism and climate. AGU Geophysical Monograph 139: Volcanism and the Earth's Atmosphere (pp. 75-92). Ed. by A. Robock and C. Oppenhaimer.], which considers the difference in brightness temperature (BT) in the SO2 absorption band around 7-8 μm between an observed value and an estimated value interpolated from two other channels. The technique relies on the assumption that the interpolated BT value is a good approximation of the BT that would have been observed in the absence of SO2. In this study we use a sophisticated radiative transfer model in order to test this assumption and assess the sensitivity of this three-channel technique to the vertical profiles of temperature and water vapour, the surface temperature, the vertical distribution of the SO2, the viewing geometry, the presence of ash, and the presence of low- and high-level clouds. The capabilities and limitations of such a technique are discussed. An example is also shown as a proof of concept using data from the SEVIRI instrument onboard the MSG satellite. Crown Copyright © 2008."
"36856321600;7004479957;","Response of a subtropical stratocumulus-capped mixed layer to climate and aerosol changes",2009,"10.1175/2008JCLI1967.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749119482&doi=10.1175%2f2008JCLI1967.1&partnerID=40&md5=8b2bd37705ef28edea2b890cfe7f1904","In this paper, an idealized framework based on a cloud-topped mixed layer model is developed for investigating feedbacks between subtropical stratocumulus (Sc) and global warming. The two principal control parameters are Sc-region sea surface temperature (SST) and intertropical convergence zone (ITCZ) SST (which controls the temperature and mean subsidence profiles above the Sc). The direct effect of CO2 doubling (leaving all other parameters fixed) is tested and found to somewhat reduce liquid water path; discussion of this effect on the SST-change simulations is included. The presence of a cold boundary layer is found to significantly affect the temperature and subsidence rate just above cloud top by enhancing lower-tropospheric diabatic cooling in this region. A simple representation of this effect (easily generalizable to a more realistic boundary layer model) is developed. Steady-state solutions are analyzed as a function of local and ITCZ SST. Two climate change scenarios are considered. The first scenario is an equal increase of local and ITCZ SSTs. In this case, predicted boundary layer depth and cloud thickness increase. This is found in a simplified context to result from subsidence and entrainment decreases due to increased static stability in a warmer climate. In the second case, local SST change is diagnosed from a surface energy balance under the assumption that ocean heat transport remains unchanged. In this case, predicted boundary layer depth decreases. Cloud continues to thicken with rising ITCZ SST, but at a rate much reduced in comparison to the equal-warming scenario. This cloud shading feedback keeps SST in the Sc region nearly constant as the ITCZ SST increases. Model sensitivity to aerosol indirect effects is also considered by varying the assumed droplet concentration. The resulting change in liquid water path is small, suggesting a weaker dependence on second indirect effect than found in previous studies. © 2009 American Meteorological Society."
"16032925200;35228780900;6603174102;7006195421;14024872700;7202429440;7201432984;7005254328;7006399419;6602085876;35601748800;24537168200;11440963500;7003605315;7101959920;7403996091;","Particulate emissions from commercial shipping: Chemical, physical, and optical properties",2009,"10.1029/2008JD011300","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649991417&doi=10.1029%2f2008JD011300&partnerID=40&md5=402f0c64831204bc3cd393e430f370c5","We characterize particulate emissions on the basis of chemical, physical, and optical properties from commercial vessels. Observations during the Texas Air Quality Study/ Gulf of Mexico Atmospheric Composition and Climate Study 2006 field campaign provide chemical and physical characteristics including sulfate (SO2<inf>4</inf>-) mass, organic matter (OM) mass, black carbon (BC) mass, particulate matter (PM) mass, number concentrations (condensation nuclei (CN) > 5 nm), and cloud condensation nuclei (CCN). Optical characterization included multiple wavelength visible light absorption and extinction, extinction relative humidity dependence, and single scatter albedo (SSA). The global contribution of shipping PM was calculated to be 0.90 Tg a-1, in good agreement with previous inventories (0.91 and 1.13 Tg a-1 from Eyring et al. (2005a) and Wang et al. [2008]). Observed PM composition was 46% SO2<inf>4-</inf>, 39% OM, and 15% BC and differs from inventories that used 81%, 14%, and 5% and 31%, 63%, and 6% SO2<inf>4-</inf>, OM, and BC, respectively. SO2<inf>4</inf> and OM mass were found to be dependent on fuel sulfur content as were SSA, hygroscopicity, and CCN concentrations. BC mass was dependent on engine type and combustion efficiency. A plume evolution study conducted on one vessel showed conservation of particle light absorption, decrease in CN > 5 nm, increase in particle hygroscopicity, and an increase in average particle size with distance from emission. These results suggest emission of small nucleation mode particles that subsequently coagulate/condense onto larger BC and OM. This work contributes to an improved understanding of the impacts of ship emissions on climate and air quality and will also assist in determining potential effects of altering fuel standards. Copyright 2009 by the American Geophysical Union."
"6701324864;7202162685;","Critical humidities of homogeneous and heterogeneous ice nucleation: Inferences from extended classical nucleation theory",2009,"10.1029/2008J0011197","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66249130991&doi=10.1029%2f2008J0011197&partnerID=40&md5=761a42d310340c517cf1fcdb7294b0b4","A generalization of classical ice nucleation theory is used to derive analytical expressions for the critical (threshold) humidities of homogeneous and heterogeneous freezing. The critical radius and energy of an ice embryo and nucleation rates were derived previously by the authors as functions of temperature, pressure, water saturation ratio, and radii of freezing particles. Here we invert the analytical expressions for the nucleation rates and solve them relative to the critical water and ice saturation ratios (or critical relative humidities). The critical humidities are expressed as analytical functions of temperature, pressure, nucleation or cooling rates, radius of freezing particles and their physico-chemical properties, misfit strain, and activation energy. Calculations of critical ice relative humidities are made using these equations over an extended temperature range down to -75°C and are compared with previous empirical parameterizations and experimental data, and differences are interpreted in the context of variation of the other parameters. It is shown that the critical humidities for heterogeneous ice nucleation are lower than those for homogeneous nucleation; however, this difference is not constant but depends substantially on the temperature and properties of freezing aerosol. Some simple parameterizations for cloud and climate models are suggested."
"36148316400;15045669300;23072989400;56726831200;","Past, present and future vegetation-cloud feedbacks in the Amazon Basin",2009,"10.1007/s00382-009-0536-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62549132029&doi=10.1007%2fs00382-009-0536-5&partnerID=40&md5=fb77e2d5c7d0ab9c35b849575eac7646","To begin exploring the underlying mechanisms that couple vegetation to cloud formation processes, we derive the lifting condensation level (LCL) to estimate cumulus cloud base height. Using a fully coupled land - ocean - atmosphere general circulation model (HadCM3LC), we investigate Amazonian forest feedbacks on cloud formation over three geological periods; modern-day (a.d. 1970-1990), the last glacial maximum (LGM; 21 kya), and under a future climate scenario (IS92a; a.d. 2070-2090). Results indicate that for both past and future climate scenarios, LCL is higher relative to modern-day. Statistical analyses indicate that the 800 m increase in LCL during the LGM is related primarily to the drier atmosphere promoted by lower tropical sea surface temperatures. In contrast, the predicted 1,000 m increase in LCL in the future scenario is the result of a large increase in surface temperature and reduced vegetation cover. © Springer-Verlag 2009."
"55887849100;22982762300;55887389300;","Interannual variations in Earth's reflectance 1999-2007",2009,"10.1029/2008JD010734","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450192317&doi=10.1029%2f2008JD010734&partnerID=40&md5=608725aebf5b54e412d1888f45d52801","The overall reflectance of sunlight from Earth is a fundamental parameter for climate studies. Recently, measurements of earthshine were used to find large decadal variability in. Earth's reflectance of sunlight. However, the results did not seem consistent with contemporaneous independent albedo measurements from the low Earth orbit satellite, Clouds and the Earth's Radiant Energy System (CERES), which showed a weak, opposing trend. Now more data for both are available, all sets have been either reanalyzed (earthshine) or recalibrated (CERES), and they present consistent results. Albedo data are also available from the recently released International Satellite Cloud Climatology Project flux data (FD) product. Earthshine and FD analyses show contemporaneous and climatologically significant increases in the Earth's reflectance from the outset of our earthshine measurements beginning in late 1998 roughly until mid-2000. After that and to date, all three show a roughly constant terrestrial albedo, except for the FD data in the most recent years. Using satellite cloud data and Earth reflectance models, we also show that the decadal-scale changes in Earth's reflectance measured by earthshine are reliable and are caused by changes in the properties of clouds rather than any spurious signal, such as changes in the Sun-Earth-Moon geometry. Copyright 2009 by the American Geophysical Union."
"55717074000;7102604282;56162305900;","Influence of anthropogenic sulfate and black carbon on upper tropospheric clouds in the NCAR CAM3 model coupled to the IMPACT global aerosol model",2009,"10.1029/2008JD010492","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65249153549&doi=10.1029%2f2008JD010492&partnerID=40&md5=507d70fa1f331da1433ac969ba885c92","The influence of anthropogenic aerosol (sulfate and soot) on upper tropospheric (UT) clouds through ice nucleation is studied using the NCAR Community Atmospheric Model Version 3 (CAM3) with a double moment ice microphysics treatment coupled to a global aerosol model (LLNL/UMich IMPACT). Present-day and preindustrial simulations are performed and compared for two scenarios. In the first scenario, the homogeneous freezing of sulfate particles dominates cirrus cloud formation in the upper troposphere (HOM). In the second scenario, both homogeneous and heterogeneous ice nucleation and their competition (HET) are allowed. In the HOM scenario, anthropogenic sulfate results in a global annual mean change of long-wave cloud forcing (LWCF) of 0.20 ± 0.09 W m-2 and short-wave cloud forcing (SWCF) of 0.30±0.17W m-2 and an increase of upper tropospheric/lower stratospheric (UT/LS) water vapor by ∼10%. In the HET scenario, anthropogenic soot may increase global cirrus cloud cover by ∼2% and UT/LS water vapor by 40% with a change in LWCF of 1.5 W m-2 (with 1.35 ± 0.15 W m-2 from surface soot and 0.12 ± 0.17 W m -2 from aircraft soot) if soot acts as efficient ice nuclei (IN) with a threshold ice nucleation RH<inf>i</inf> of 120-130%. Aerosol effects are most evident (larger than natural variability) over polar regions. However, their influence is significantly reduced if soot has a threshold RH<inf>i</inf> of 140% with an LWCF change of only 0.23 W m-2 (with 0.17 ± 0.18 W m-2 from surface soot and 0.06 ± 0.16 W m-2 from aircraft soot), and cloud forcing changes are statistically insignificant (less than the natural variability). Our results reinforce the importance of understanding ice nucleation on soot from the perspective of their global climate impact. Copyright 2009 by the American Geophysical Union."
"6602889253;7005793536;8918197800;7005829052;7005134081;7402093416;55393706100;6603821988;7004402705;55919935700;9249656500;13402933200;6603247427;6701511321;8263760800;7402332362;24470422300;7003800456;7005723936;7003683808;7403544649;21735369200;","Clear sky UV simulations for the 21st century based on ozone and temperature projections from Chemistry-Climate Models",2009,"10.5194/acp-9-1165-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349774427&doi=10.5194%2facp-9-1165-2009&partnerID=40&md5=b715f9dc4236d4980e7dd328938139f2","We have estimated changes in surface solar ultraviolet (UV) radiation under cloud free conditions in the 21st century based on simulations of 11 coupled Chemistry-Climate Models (CCMs). The total ozone columns and vertical profiles of ozone and temperature projected from CCMs were used as input to a radiative transfer model in order to calculate the corresponding erythemal irradiance levels. Time series of monthly erythemal irradiance received at the surface during local noon are presented for the period 1960 to 2100. Starting from the first decade of the 21st century, the surface erythemal irradiance decreases globally as a result of the projected stratospheric ozone recovery at rates that are larger in the first half of the 21st century and smaller towards its end. This decreasing tendency varies with latitude, being more pronounced over areas where stratospheric ozone."
"13405658600;57211106013;","Uncertainty in global CCN concentrations from uncertain aerosol nucleation and primary emission rates",2009,"10.5194/acp-9-1339-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60649110718&doi=10.5194%2facp-9-1339-2009&partnerID=40&md5=e4cc1b266318923fee71aabcf266df17","The indirect effect of aerosols on climate is highly uncertain and limits our ability to assess anthropogenic climate change. The foundation of this uncertainty is uncertainty in the number of cloud condensation nuclei (CCN), which itself stems from uncertainty in aerosol nucleation, primary emission and growth rates. In this paper, we use a global general circulation model with aerosol microphysics to assess how the uncertainties in aerosol nucleation, emission and growth rates affect our prediction of CCN(0.2%) concentrations. Using several nucleation rate parameterizations that span six orders of magnitude of globally averaged nucleation rates, the tropospheric average CCN(0.2%) concentrations vary by 17% and the boundary layer average vary by 12%. This sensitivity of tropospheric average CCN(0.2%) to the nucleation parameterizations increases to 33% and 20% when the total primary emissions are reduced by a factor of 3 and the SOA condensation rates are increased by a factor of 3.5, respectively. These results show that it is necessary to better understand global nucleation rates when determining CCN concentrations. When primary emissions rates are varied by a factor of 3 while using a binary nucleation parameterization, tropospheric average CCN(0.2%) concentrations also vary by 17%, but boundary layer average vary by 40%. Using the fastest nucleation rate parameterization, these changes drop to 3% and 22%, respectively. These results show the importance of reducing uncertainties in primary emissions, which appear from these results to be somewhat more important for CCN than the much larger uncertainties in nucleation. These results also show that uncertainties in nucleation and primary emissions are more important when sufficient condensable material is available to grow them to CCN sizes. The percent change in CCN(0.2%) concentration between pre-industrial times and present day does not depend greatly on the nucleation rate parameterization used for our base case scenarios; however, because other factors, such as primary emissions and SOA, are uncertain in both time periods, this may be a coincidence."
"6506738607;56162305900;","Polar amplification in a coupled climate model with locked albedo",2009,"10.1007/s00382-009-0535-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69249244211&doi=10.1007%2fs00382-009-0535-6&partnerID=40&md5=cb19d8db45a0805a47c536c8535daf17","In recent years, a substantial reduction of the sea ice in the Arctic has been observed. At the same time, the near-surface air in this region is warming at a rate almost twice as large as the global average-this phenomenon is known as the Arctic amplification. The role of the ice-albedo feedback for the Arctic amplification is still a matter of debate. Here the effect of the surface-albedo feedback (SAF) was studied using a coupled climate model CCSM3 from the National Center for Atmospheric Research. Experiments, where the SAF was suppressed by locking the surface albedo in the entire coupled model system, were conducted. The results reveal polar temperature amplification when this model, with suppressed albedo, is forced by a doubling of the atmospheric CO2 content. Comparisons with variable albedo experiments show that SAF amplifies the surface-temperature response in the Arctic area by about 33%, whereas the corresponding value for the global-mean surface temperature is about 15%. Even though SAF is an important process underlying excessive warming at high latitudes, the Arctic amplification is only 15% larger in the variable than in the locked-albedo experiments. It is found that an increase of water vapour and total cloud cover lead to a greenhouse effect, which is larger in the Arctic than at lower latitudes. This is expected to explain a part of the Arctic surface-air-temperature amplification. © Springer-Verlag 2009."
"7003875148;8696069500;","Mesoscale variability in the summer arctic boundary layer",2009,"10.1007/s10546-009-9354-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60649087619&doi=10.1007%2fs10546-009-9354-x&partnerID=40&md5=b0b67707a6460588796af16923d37be0","Observations from the summer Arctic Ocean Experiment 2001 (AOE-2001) are analysed with a focus on the interactions between mesoscale and boundary-layer dynamics. Wavelet analyses of surface-pressure variations show daylong periods with different characteristics, some featuring episodes of pronounced high-frequency surface-pressure variability, here hypothesized to be caused by trapped gravity waves. These episodes are accompanied by enhanced boundary-layer turbulence and an enhanced spectral gap, but with only minor influence on the surface stress. During these episodes, mesoscale phenomena were often encountered and usually identified as front-like features in the boundary layer, with a peak in drizzle followed by changing temperature. These phenomena resemble synoptic fronts, though they are generally shallow, shorter-lasting, have no signs of frontal clouds, and do not imply a change in air mass. Based on this analysis, we hypothesize that the root cause of the episodes with high-frequency surface-pressure variance are shallow, mesoscale fronts moving across the pack ice. They may be formed due to local-to-regional horizontal contrasts, for example, between air with different lifetimes over the Arctic or with perturbations in the cloud field causing differential cooling of the boundary layer. Thermal contrasts sharpen as the air is transported with the mean flow. The propagating mesoscale fronts excite gravity waves, which affect the boundary-layer turbulence and also seem to favour entrainment of free tropospheric air into the boundary layer. © Springer Science+Business Media B.V. 2009."
"7101909551;8922308700;7006270084;26665326700;7003666669;6507506955;57193213111;","Coupling aerosol-cloud-radiative processes in the WRF-Chem model: Investigating the radiative impact of elevated point sources",2009,"10.5194/acp-9-945-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61349197973&doi=10.5194%2facp-9-945-2009&partnerID=40&md5=5e9daee37d21b0e63181be7392b1de75","The local and regional influence of elevated point sources on summertime aerosol forcing and cloud-aerosol interactions in northeastern North America was investigated using the WRF-Chem community model. The direct effects of aerosols on incoming solar radiation were simulated using existing modules to relate aerosol sizes and chemical composition to aerosol optical properties. Indirect effects were simulated by adding a prognostic treatment of cloud droplet number and adding modules that activate aerosol particles to form cloud droplets, simulate aqueous-phase chemistry, and tie a two-moment treatment of cloud water (cloud water mass and cloud droplet number) to precipitation and an existing radiation scheme. Fully interactive feedbacks thus were created within the modified model, with aerosols affecting cloud droplet number and cloud radiative properties, and clouds altering aerosol size and composition via aqueous processes, wet scavenging, and gas-phase-related photolytic processes. Comparisons of a baseline simulation with observations show that the model captured the general temporal cycle of aerosol optical depths (AODs) and produced clouds of comparable thickness to observations at approximately the proper times and places. The model overpredicted SO2 mixing ratios and PM2.5 mass, but reproduced the range of observed SO2 to sulfate aerosol ratios, suggesting that atmospheric oxidation processes leading to aerosol sulfate formation are captured in the model. The baseline simulation was compared to a sensitivity simulation in which all emissions at model levels above the surface layer were set to zero, thus removing stack emissions. Instantaneous, site-specific differences for aerosol and cloud related properties between the two simulations could be quite large, as removing abovesurface emission sources influenced when and where clouds formed within the modeling domain. When summed spa-tially over the finest resolution model domain (the extent of which corresponds to the typical size of a single global climate model grid cell) and temporally over a three day analysis period, total rainfall in the sensitivity simulation increased by 31% over that in the baseline simulation. Fewer optically thin clouds, arbitrarily defined as a cloud exhibiting an optical depth less than 1, formed in the sensitivity simulation. Domain-averaged AODs dropped from 0.46 in the baseline simulation to 0.38 in the sensitivity simulation. The overall net effect of additional aerosols attributable to primary particulates and aerosol precursors from point source emissions above the surface was a domain-averaged reduction of 5Wm-2 in mean daytime downwelling shortwave radiation."
"7102604282;23003667300;56162305900;55717074000;","Possible influence of anthropogenic aerosols on cirrus clouds and anthropogenic forcing",2009,"10.5194/acp-9-879-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350032430&doi=10.5194%2facp-9-879-2009&partnerID=40&md5=72612096b1590fa5fbc3a95d52860d21","Cirrus clouds have a net warming effect on the atmosphere and cover about 30% of the Earth's area. Aerosol particles initiate ice formation in the upper troposphere through modes of action that include homogeneous freezing of solution droplets, heterogeneous nucleation on solid particles immersed in a solution, and deposition nucleation of vapor onto solid particles. Here, we examine the possible change in ice number concentration from anthropogenic soot originating from surface sources of fossil fuel and biomass burning, from anthropogenic sulfate aerosols, and from aircraft that deposit their aerosols directly in the upper troposphere. We use a version of the aerosol model that predicts sulfate number and mass concentrations in 3-modes and includes the formation of sulfate aerosol through homogeneous binary nucleation as well as a version that only predicts sulfate mass. The 3-mode version best represents the Aitken aerosol nuclei number concentrations in the upper troposphere which dominated ice crystal residues in the upper troposphere. Fossil fuel and biomass burning soot aerosols with this version exert a radiative forcing of-0.3 to-0.4Wm-2 while anthropogenic sulfate aerosols and aircraft aerosols exert a forcing of-0.01 to 0.04Wm-2 and-0.16 to-0.12Wm-2, respectively, where the range represents the forcing from two parameterizations for ice nucleation. The sign of the forcing in the mass-only version of the model depends on which ice nucleation parameterization is used and can be either positive or negative. The magnitude of the forcing in cirrus clouds can be comparable to the forcing exerted by anthropogenic aerosols on warm clouds, but this forcing has not been included in past assessments of the total anthropogenic radiative forcing of climate."
"7007080981;","Comparison of free water and horizontal subsurface treatment wetlands",2009,"10.1016/j.ecoleng.2008.04.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59149106263&doi=10.1016%2fj.ecoleng.2008.04.008&partnerID=40&md5=d1517caebad386b0cd7da58373152782","The two most prevalent types of treatment wetland, especially during the early history of the technology, are free water surface (FWS) and horizontal subsurface flow (HSSF) wetlands. The several factors involved in the choice of which alternative to choose include size, cost, operability, together with health and nuisance issues and ancillary benefits. Contaminant removal performance differs by constituent, with the advantage to FWS for moderate to high biochemical oxygen demand (BOD), TSS, ammonia, total nitrogen and phosphorus. HSSF are more effective for tertiary BOD levels, nitrate and pathogens. Superpositions of the loading data show that the respective data clouds overlap virtually entirely for HSSF and FWS wetlands. There is little or no performance difference when they are compared on this areal basis. In general, there is little or no advantage of HSSF for space saving. In cold climates, HSSF systems are less cold sensitive, and easier to insulate for winter operation. The use of winter storage enables FWS to be used in freezing conditions, but the cost makes that option comparable to the more expensive HSSF. In general, economics do not favor the choice of HSSF wetlands. Factors other than reduction performance are also important in the selection process. Other principal reasons for selecting the HSSF option over the FWS option are prevention of human health contact problems, mosquito control and minimization of wildlife interactions. © 2008 Elsevier B.V. All rights reserved."
"23471435100;35265615300;26666198600;7404404203;","Effect of urbanization on the winter precipitation distribution in Beijing area",2009,"10.1007/s11430-009-0019-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59149087076&doi=10.1007%2fs11430-009-0019-x&partnerID=40&md5=8b8273123caac96d35f6f12ca0ddc9e9","According to the urbanization extent of Beijing area, and with 1980 as a turning point, the duration from 1961 to 2000 is divided into two periods: One is defined as the slow urbanization period from 1961 to 1980, and other one as the fast urbanization period from 1981 to 2000. Based on the 40-year's precipitation data of 14 standard weather stations in Beijing area, the effect of urbanization on precipitation distribution is studied. It is found that there has been a noticeable and systematic change of winter precipitation distribution pattern between these two periods in Beijing area: In the slow urbanization period, the precipitation in the southern part of Beijing is more than that in the northern part; but in the fast urbanization period, the precipitation distribution pattern is reverse, i.e. the precipitation in the southern part is less than that in the northern part; But in other seasons, the precipitation distribution pattern did not change remarkably in general. The possible cause resulting in the change of winter precipitation distribution pattern, might be that with urban area extension, the effects of ""urban heat island"" and ""urban dry island"" become more and more intensified, and increase hydrometeors evaporation below precipitable cloud, and then cause less precipitation received on the ground surface in the downtown and the southern part. It is also noteworthy to further research why the precipitation distribution pattern does not change systematically in other seasons except winter after intense urbanization in Beijing area. © Science in China Press and Springer-Verlag GmbH 2009."
"6701448397;","A note on the tornado and funnel clouds observed in Poland in 2006",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-62249209521&partnerID=40&md5=a5fbfae3f6f598b6081073bbe873ca78","This research details one tornado observed in the neighbourhood of Pobiedziska near Poznań during June 2006 and funnel clouds observed in July 2006 in Łeba in the polish coastal area and associated synoptic conditions leading to their development. The factors which caused the tornado were similar to those leading to the occurrence of violent thunderstorms and tornadoes on the territory of Poland. © The International Journal of Meteorology."
"14032370500;14031407200;7201522137;","Changing surface conditions at Kilimanjaro indicated from multiscale imagery",2009,"10.1659/mrd.981","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949359365&doi=10.1659%2fmrd.981&partnerID=40&md5=dba0d488dc65eaa63f6ca6877b234ea1","The shrinking glacier atop Kilimanjaro has received much attention as it is one of the few remaining tropical glaciers in the world. Physical drivers ranging from changes in temperature and humidity to shifts in cloud coverage and radiation have been attributed to reducing the ice mass. Studies have utilized varying methods and often use point data sources that tend to be spatially and temporally poor in the region. The objective of this study was to use complementing remote sensing data sets with systematic measurements to delineate ice cap fluctuations and land surface phenology on Kilimanjaro over the past two decades. Multitemporal, fine-scale Landsat imagery (30 m) showed approximately a 70% reduction in ice coverage since 1976. High-frequency (bimonthly) image analysis conducted along a human activity-elevation ecocline showed that the entire mountain, including the subalpine and alpine regions, has undergone an increase in vegetative signal indicating a ""greening up"" of Kilimanjaro over the past two decades. In addition, upper elevations of Kilimanjaro have undergone a temporal shift, or lengthening, in dry season phenology on the order of one month over the past two decades. The shift in dry season timing is concordant with maximum ablation periods. Overall, this study provides insight into land surface trends at resolutions that are currently lacking in Kilimanjaro climate change analyses. © 2009 by the authors."
"23003356500;36979770500;23767593700;6602431440;23004673500;23004016500;","Different responses of different altitudes surrounding Taklimankan Desert to global climate change",2009,"10.1007/s00254-008-1227-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58849097710&doi=10.1007%2fs00254-008-1227-y&partnerID=40&md5=ef7cd09282f84d39c24b3b93a11b1617","Chongce Ice Cap (35°14′N, 81°07′E), located in the south margin of Taklimakan Desert, West Kunlun Mts. of China was sampled by coring in 1992, and this provides us with climate proxy of high altitudes (6,530 m). Through analyzing the weather observation stations surrounding Taklimakan Desert, the climate record of Hotan station was chosen to be the representative of low altitudes. Wavelet analysis were used to investigate the climatic variations of patterns, cycles and frequencies of different altitudes from 1954 to 1992, and different responses of different altitude surrounding Taklimakan Desert to global warming were recorded: (1) coherent decline of snow accumulation rate and dust deposition of high altitude recorded in Chongce ice core; (2) coherent increase of summer half-year precipitation and SAT of Hotan; (3) consistent variation tendency between dust deposit recorded in Chongce ice core and Hotan spring sandstorm days; (4) opposite variation tendency between Hotan precipitation and Chongce ice core snow accumulation rate and consistent cycles in general. By analyzing the mechanism of different responses, the predominant factors were determined of different altitudes: (1) at the low altitude, the vapor supply is predominant, and more vapor supplying means more precipitation; (2) at the high altitude, probably the population of dust aerosols which act as cloud ice nuclei in high altitude takes advantage over the vapor supply to affect the precipitation, and so the dust aerosol population reducing results in the wet deposition being reduced, thus the dust aerosol is the predominant factor. © 2008 Springer-Verlag."
"57198412966;57201696235;10144282600;","Two case studies of sulfate scavenging processes in the Amazon region (Rondônia)",2009,"10.1016/j.envpol.2008.08.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57049110974&doi=10.1016%2fj.envpol.2008.08.016&partnerID=40&md5=f25322e29af11b91499b6ea4d1caf448","The scavenging processes of chemical species have been previously studied with numerical modeling, in order to understand the gas and particulate matter intra-reservoir transferences. In this study, the atmospheric (RAMS) and scavenging (B.V.2) models were used, in order to simulate sulfate concentrations in rainwater using scavenging processes as well as the local atmospheric conditions obtained within the LBA Project in the State of Rondonia, during a dry-to-wet transition season. Two case studies were conducted. The RAMS atmospheric simulation of these events presented satisfactory results, showing the detailed microphysical processes of clouds in the Amazonian region. On the other hand, with cloud entrainments, observed values have been overestimated. Modeled sulfate rainwater concentration, using exponential decay and cloud heights of 16 km and no entrainments, presented the best results, reaching 97% of the observed value. The results, using shape parameter 5, are the best, improving the overall result. © 2008 Elsevier Ltd. All rights reserved."
"7006191743;7006224475;57190531316;","Quantifying the sensitivity of simulated climate change to model configuration",2009,"10.1007/s10584-008-9494-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58549100241&doi=10.1007%2fs10584-008-9494-x&partnerID=40&md5=c714a25bcb506b38f27424effb9cda05","This study used ""factor separation"" to quantify the sensitivity of simulated present and future surface temperatures and precipitation to alternative regional climate model physics components. The method enables a quantitative isolation of the effects of using each physical component as well as the combined effect of two or more components. Simulation results are presented from eight versions of the Mesoscale Modeling System Version 5 (MM5), one-way nested within one version of the Goddard Institute for Space Studies Atmosphere-Ocean Global Climate Model (GISS AOGCM). The MM5 simulations were made at 108 km grid spacing over the continental United States for five summers in the 1990s and 2050s. Results show that the choice of cumulus convection parameterization is the most important ""factor"" in the simulation of contemporary surface summer temperatures and precipitation over both the western and eastern USA. The choice of boundary layer scheme and radiation package also increases the range of model simulation results. Moreover, the alternative configurations give quite different results for surface temperature and precipitation in the 2050s. For example, simulated 2050s surface temperatures by the scheme with the coolest 1990s surface temperatures are comparable to 1990s temperatures produced by other schemes. The study analyzes the spatial distribution of 1990s to 2050s projected changes in the surface temperature for the eight MM5 versions. The predicted surface temperature change at a given grid point, averaged over all eight model configurations, is generally about twice the standard deviation of the eight predicted changes, indicating relative consensus among the different model projections. Factor separation analysis indicates that the choice of cumulus parameterization is the most important modeling factor amongst the three tested contributing to the computed 1990s to 2050s surface temperature change, although enhanced warming over many areas is also attributable to synergistic effects of changing all three model components. Simulated ensemble mean precipitation changes, however, are very small and generally smaller than the inter-model standard deviations. The MM5 versions therefore offer little consensus regarding 1990s to 2050s changes in precipitation rates. © 2008 Springer Science+Business Media B.V."
"7004364155;7004325649;6603546080;7406741310;8555710700;56493740900;6506504165;7403531523;","Toward optimal closure of the Earth's top-of-atmosphere radiation budget",2009,"10.1175/2008JCLI2637.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049090651&doi=10.1175%2f2008JCLI2637.1&partnerID=40&md5=e86c18824bc5147a3239f22fbb561b15","Despite recent improvements in satellite instrument calibration and the algorithms used to determine reflected solar (SW) and emitted thermal (LW) top-of-atmosphere (TOA) radiative fluxes, a sizeable imbalance persists in the average global net radiation at the TOA from satellite observations. This imbalance is problematic in applications that use earth radiation budget (ERB) data for climate model evaluation, estimate the earth's annual global mean energy budget, and in studies that infer meridional heat transports. This study provides a detailed error analysis of TOA fluxes based on the latest generation of Clouds and the Earth's Radiant Energy System (CERES) gridded monthly mean data products [the monthly TOA/surface averages geostationary (SRBAVG-GEO)] and uses an objective constrainment algorithm to adjust SW and LW TOA fluxes within their range of uncertainty to remove the inconsistency between average global net TOA flux and heat storage in the earth-atmosphere system. The 5-yr global mean CERES net flux from the standard CERES product is 6.5 W m-2, much larger than the best estimate of 0.85 W m-2 based on observed ocean heat content data and model simulations. The major sources of uncertainty in the CERES estimate are from instrument calibration (4.2 W m-2) and the assumed value for total solar irradiance (1 W m-2). After adjustment, the global mean CERES SW TOA flux is 99.5 W m-2, corresponding to an albedo of 0.293, and the global mean LW TOA flux is 239.6 W m-2. These values differ markedly from previously published adjusted global means based on the ERB Experiment in which the global mean SW TOA flux is 107 W m-2 and the LW TOA flux is 234 W m-2. © 2009 American Meteorological Society."
"6602692238;7201485519;57203049177;57203200427;","Carbon dioxide induced stomatal closure increases radiative forcing via a rapid reduction in low cloud",2009,"10.1029/2008GL036273","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749130813&doi=10.1029%2f2008GL036273&partnerID=40&md5=e548197df479a648722e3233b2b558c1","We performed an ensemble of twelve five-year experiments using a coupled climate-carbon-cycle model with scenarios of prescribed atmospheric carbon dioxide concentration; CO2 was instantaneously doubled or quadrupled at the start of the experiments. Within these five years, climate feedback is not significantly influenced by the effects of climate change on the carbon system. However, rapid changes take place, within much less than a year, due to the physiological effect of CO2 on plant stomatal conductance, leading to adjustment in the shortwave cloud radiative effect over land, due to a reduction in low cloud cover. This causes a 10% enhancement to the radiative forcing due to CO2, which leads to an increase in the equilibrium warming of 0.4 and 0.7 K for doubling and quadrupling. The implications for calibration of energy-balance models are discussed."
"16639418500;57203053317;","Sensitivity of the total anthropogenic aerosol effect to the treatment of rain in a global climate model",2009,"10.1029/2008GL035796","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749126696&doi=10.1029%2f2008GL035796&partnerID=40&md5=54b8b13c7df642b4f47e7a2521527bfc","This study investigates the sensitivity of the total anthropogenic aerosol effect to the treatment of rain within the global climate model (GCM) ECHAM5. A. comparison between a prognostic (rain is stored within the atmosphere) and a diagnostic rain scheme (rain is precipitated out within one model time step) is conducted. Furthermore, the shape of the rain drop distribution within the prognostic rain scheme is varied. The prognostic rain scheme shifts the emphasis of the rain production process from autoconversion to accretion in better agreement with observations. Since the parameterization of the accretion process is independent of the cloud droplet number concentration, the total anthropogenic aerosol effect decreased by 0.5 to 0.9 Wm-2. Varying the rain drop distribution has a smaller influence on the total anthropogenic aerosol effect, changing it by 0.2 to 0.3 Wm-2. Copyright 2009 by the American Geophysical Union."
"7003710822;6602715033;16480175700;7005284577;7004176333;7006212411;6602890253;7202050065;6603735912;57212626251;6603786703;7404062492;16480965400;7004643405;24477694300;26421427300;17436376200;","Biomass burning in Siberia and Kazakhstan as an important source for haze over the Alaskan Arctic in April 2008",2009,"10.1029/2008GL036194","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749192170&doi=10.1029%2f2008GL036194&partnerID=40&md5=dbb6c4c3f72d181e730c74f2b9491f50","During the ARCPAC (Aerosol, Radiation, and Cloud Processes affecting Arctic Climate) airborne field experiment in April 2008 in northern Alaska, about 50 plumes were encountered with the NOAA WP-3 aircraft between the surface and 6.5 km. Onboard measurements and the transport model FLEXPART showed that most of the plumes were emitted by forest fires in southern Siberia-Lake Baikal area and by agricultural burning in Kazakhstan-southern Russia. Unexpectedly, these biomass burning plumes were the dominant aerosol and gas-phase features encountered in this area during April. The influence on the plumes from sources other than burning was small. The chemical characteristics of plumes from the two source regions were different, with higher enhancements relative to CO for most gas and aerosol species from the agricultural fires. In 2008, the fire season started earlier than usual in Siberia, which may have resulted in unusually efficient transport of biomass burning emissions into the Arctic. Copyright 2009 by the American Geophysical Union."
"55905970100;24757986500;9534896800;","How declining aerosols and rising greenhouse gases forced rapid warming in Europe since the 1980s",2009,"10.1029/2008GL036350","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749184323&doi=10.1029%2f2008GL036350&partnerID=40&md5=adbfdb49bb55438f9bffd125822016cc","Mainland Europe's temperature rise of about 1°C since the 1980s is considerably larger than expected from anthropogenic greenhouse warming. Here we analyse shortwave and longwave surface forcings measured in Switzerland and Northern Germany and relate them to humidity- and temperature increases through the radiation- and energy budget. Shortwave climate forcing from direct aerosol effects is found to be much larger than indirect aerosol cloud forcing, and the total shortwave forcing, that is related to the observed 60% aerosol decline, is two to three times larger than the longwave forcing from rising anthropogenic greenhouse gases. Almost tree quarters of all the shortwave and longwave forcing energy goes into the turbulent fluxes, which increases atmospheric humidity and hence the longwave forcing by water vapour feedback. With anthropogenic aerosols now reaching low and stable values in Europe, solar forcing will subside and future temperature will mainly rise due to anthropogenic greenhouse gas warming. Copyright 2009 by the American Geophysical Union."
"7103246957;56681747400;7601318782;","Comparison of river basin hydrometeorology in ERA-Interim and ERA-40 reanalyses with observations",2009,"10.1029/2008JD010761","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62849111353&doi=10.1029%2f2008JD010761&partnerID=40&md5=768cf6c5328b0937c1e6979acc9b6994","The changes between the ERA-40 and ERA-Interim in the seasonal cycle of primarily temperature, precipitation and evaporation, the surface radiation budget, and the cloud fields are evaluated over three river basins, the Amazon, Mississippi, and Mackenzie, for the period 1990-2001, using a variety of surface observational data sets and the International Satellite Cloud Climatology Project data. In ERA-Interim over the Amazon, the unrealistic interannual drift of precipitation has been reduced, and annual precipitation is largely unbiased, although the seasonal amplitude of precipitation remains too small. However, ERA-Interim has a large cold 2-m temperature bias. The clear-sky surface shortwave flux in ERA-Interim is lower than that in ERA-40 and closer to observations. Low cloud cover has increased dramatically in ERA-Interim, and total reflective cloud cover has a larger positive bias in comparison with observations. The ratio of the precipitation heating of the atmosphere to the surface shortwave cloud forcing is much higher in the observations than that in both reanalyses. The diurnal cycle of precipitation has improved somewhat with the removal of a spurious early morning peak. For the Mississippi and Mackenzie river basins, the spin-up of precipitation in 24-h forecasts has been greatly reduced. Temperature biases are small in both reanalyses, but summer precipitation and evaporation exceed observational estimates. For the Mississippi river basin, reflective cloud cover in ERA-Interim has increased in winter and decreased in summer compared with that in ERA-40, giving a closer fit to the observations in both, seasons. For the Mackenzie river basin, similar reflective cloud changes in ERA-Interim improve the fit to the observations in summer but not in winter. Copyright 2009 by the American Geophysical Union."
"26221380500;57202721532;55469915400;57145869600;","Boreal spring Southern Hemisphere Annular Mode, Indian Ocean sea surface temperature, and East Asian summer monsoon",2009,"10.1029/2008JD010045","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749173223&doi=10.1029%2f2008JD010045&partnerID=40&md5=013a0424393f083cfa24a5da57bd55fe","The relationships among the boreal spring Southern Hemisphere Annular Mode (SAM), the Indian Ocean (IO) sea surface temperature (SST), and East Asian summer monsoon (EASM) are examined statistically in this paper. The variability of boreal spring SAM is closely related to the IO SST. When the SAM is in its strong positive phase in boreal spring, with low-pressure anomalies over the south pole and high-pressure anomalies over middle latitudes, SST over the subtropics and middle latitudes of the South Indian Ocean (SIO) increases, which persists into the summer. Following the positive SST anomalies over the subtropics and midlatitudes of the SIO, SST in the equatorial Indian Ocean and Bay of Bengal increases in summer. Moreover, the variability of SST in the equatorial Indian Ocean and Bay of Bengal is closely related to EASM. When SST in the equatorial Indian Ocean and Bay of Bengal increases, EASM tends to be weak. Therefore the IO SST may play an important role bridging boreal spring SAM and EASM. The atmospheric circulations and surface heat exchanges contribute to the SST anomalies in the SIO. When the spring SAM is in its strong positive phases, the regional Ferrel Cell weakens, and the anomalous upward motions at 20°S-30°S cause an increase of low cloud cover and downward longwave radiation flux. The surface atmospheric circulations also transport more (less) warmer (cooler) air from middle latitudes north of 50°S (high latitudes south of 60°S) into 50°S-60°S and warm the air, which reduces the temperature difference between the ocean and atmosphere and consequently reduces sensible heat flux from the ocean to atmosphere. The increased downward longwave radiation and decreased sensible heat are responsible for the SST increase in the SIO. The atmospheric circulation and surface heat flux anomalies are of opposite signs following the strong negative phases of SAM. Copyright 2009 by the American Geophysical Union."
"57212781009;6701715507;","Climate feedbacks under a very broad range of forcing",2009,"10.1029/2008GL036268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749101228&doi=10.1029%2f2008GL036268&partnerID=40&md5=1df9d5dd4ab5879e9dec847d3d6904dd","An atmospheric general circulation model, coupled to a mixed layer ocean, is subjected to a broad range of forcing away from the current climate between 1/16 to 32 times current CO2 in halving/doubling steps. As climate warms climate sensitivity weakens (although not monotonically), albedo feedback weakens (driving much of the sensitivity weakening), water vapour feedback strengthens (at a rate slightly larger than it would if relative humidity remained unchanged), and lapse rate feedback increases (negatively); this latter change essentially offsetting the water vapour increases. Longwave cloud feedbacks are relatively stable (moderate and positive) across the full range; shortwave cloud feedback remains relatively weak, apart from under the coldest climates. Cloud optical property related components (from total water content, water/ice fraction and cloud thickness) remain remarkably stable. Cloud 'amount' feedbacks show the greatest trend\s: weakening as temperatures increase. Although cloud feedbacks show an overall consistency of features in different latitudes, precise patterns of changes differ substantially for different baseline Climates. © 2009 by the American Geophysical Union."
"7004198777;7005968859;25647334300;7006510465;7005729142;6506385754;35396858200;35263854800;7101675442;7004715270;6505932008;","Saharan dust particles nucleate droplets in eastern Atlantic clouds",2009,"10.1029/2008GL035846","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749122738&doi=10.1029%2f2008GL035846&partnerID=40&md5=8726856e32a2464f3f4ac99fba5d0173","Many soil-derived particles dominated by insoluble material, including Saharan dusts, are known to act as ice nuclei. If, however, dust particles can compete with other atmospheric particle types to form liquid cloud droplets, they have a greater potential to change climate through indirect effects on cloud radiative properties and to affect the hydrological cycle through precipitation changes. By directly collecting and analyzing the residual nuclei of small cloud droplets, we demonstrate that Saharan dust particles do commonly act as cloud condensation nuclei (CCN) in the eastern North Atlantic. Droplet activation calculations support the measurements by showing that due to its slightly hygroscopic nature, even submicron dust can be important as CCN. Given the dual nature of Saharan dust particles as CCN and ice nuclei, this infusion of dust is expected to impact not only droplet size and albedo in small clouds, but ice formation in deep convective clouds. © 2009 by the American Geophysical Union."
"57156690200;7103294731;6701450462;","Past and future conditions for polar stratospheric cloud formation simulated by the canadian middle atmosphere model",2009,"10.5194/acp-9-483-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849123323&doi=10.5194%2facp-9-483-2009&partnerID=40&md5=db1c9afafdc5b393e629df0730cb15b6","We analyze here the polar stratospheric temperatures in an ensemble of three 150-year integrations of the Canadian Middle Atmosphere Model (CMAM), an interactive chemistry-climate model which simulates ozone depletion and recovery, as well as climate change. A key motivation is to understand possible mechanisms for the observed trend in the extent of conditions favourable for polar stratospheric cloud (PSC) formation in the Arctic winter lower stratosphere. We find that in the Antarctic winter lower stratosphere, the low temperature extremes required for PSC formation increase in the model as ozone is depleted, but remain steady through the twenty-first century as the warming from ozone recovery roughly balances the cooling from climate change. Thus, ozone depletion itself plays a major role in the Antarctic trends in low temperature extremes. The model trend in low temperature extremes in the Arctic through the latter half of the twentieth century is weaker and less statistically robust than the observed trend. It is not projected to continue into the future. Ozone depletion in the Arctic is weaker in the CMAM than in observations, which may account for the weak past trend in low temperature extremes. In the future, radiative cooling in the Arctic winter due to climate change is more than compensated by an increase in dynamically driven downwelling over the pole."
"55311589500;57202721532;","Decadal and seasonal dependence of North Pacific sea surface temperature persistence",2009,"10.1029/2008JD010723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62149095695&doi=10.1029%2f2008JD010723&partnerID=40&md5=12f72519b0f60f9acfcfec043584ade3","Decadal and seasonal dependence of the persistence characteristics of area-averaged Sea surface temperature (SST) anomalies in the North Pacific (150°E-140°W, 20°N-60°N) are investigated using two different SST data sets for the period 1948-2005. It is found that a persistence barrier exists around July-September (especially in September). This July-September persistence barrier is accompanied by a summer decline in the wind stress. The results confirm the existence of the July-September persistence barrier in the North Pacific SST discovered by Namias and Born (1970). Besides the seasonal change, North Pacific SST persistence also exhibits a pronounced decadal change. Taking all calendar months into account, North Pacific SST persistence is relatively strong from the mid-1950s to the mid-1960s but then weak from the mid-1960s to the mid-1980s, and becomes stronger again from the mid-1980s until the mid-1990s, after which it tends to become weak again. The recurrence of SST anomalies from one winter to the next is obvious from the mid-1950s to mid-1960s, but no obvious recurrence occurs after the mid-1960s. Decadal changes of the Pacific-North America (PNA) pattern, the SST-clouds feedback, and the Southern Oscillation Index (SOI) are found to be related to those of North Pacific SST persistence. The PNA index shows a significant upward trend after the 1980s. Besides, the PNA pattern also exhibits a high persistence in winter from the mid-1980s to the mid-1990s. These changes of PNA pattern are favorable to the occurrence of strong SST persistence in winter from the mid-1980s to the mid-1990s. In summer, the positive feedback between the marine boundary clouds and SST enhances the SST persistence in the North Pacific. It is found that the positive feedback between the SST and clouds in the North Pacific during summer becomes stronger from the mid-1980s to the mid-1990s, which would contribute to the longer SST persistence in summer from the mid-1980s to the mid-1990s. The SOI shows negative correlation with the North Pacific SST persistence and the PNA index, indicating the remote forcing of ENSO on the North Pacific climate change. In addition, the high north Pacific SST persistence from the mid-1980s to the mid-1990s coincides with the warm phase of the Pacific Decadal Oscillation (PDO). We concluded that the changes in the tropical SST or the PDO phase might explain the origin of decadal changes of North Pacific SST persistence. Copyright 2009 by the American Geophysical Union."
"6701670597;6701431208;6701346974;36876405100;57218978147;","Virtual field campaigns on deep tropical convection in climate models",2009,"10.1175/2008JCLI2203.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049093073&doi=10.1175%2f2008JCLI2203.1&partnerID=40&md5=a9d3cc3afada5394734f7481522a78c7","High-resolution time-height data over warm tropical oceans are examined, from three global atmosphere models [GFDL's Atmosphere Model 2 (AM2), NCAR's Community Atmosphere Model, version 3 (CAM3), and a NASA Global Modeling and Assimilation Office (GMAO) model], field campaign observations, and observation-driven cloud model outputs. The character of rain events is shown in data samples and summarized in lagged regressions versus surface rain rate. The CAM3 humidity and cloud exhibit little vertical coherence among three distinct layers, and its rain events have a short characteristic time, reflecting the convection scheme's penetrative nature and its closure's concentrated sensitivity to a thin boundary layer source level. In contrast, AM2 rain variations have much longer time scales as convection scheme plumes whose entrainment gives them tops below 500 hPa interact with humidity variations in that layer. Plumes detraining at model levels above 500 hPa are restricted by cloud work function thresholds, and upper-tropospheric humidity and cloud layers fed by these are detached from the lower levels and are somewhat sporadic.With these discrete entrainment rates and instability thresholds, AM2 also produces some synthetic-looking noise (sharp features in height and time) on top of its slow rain variations. A distinctive feature of the NASA model is a separate anvil scheme, distinct from the main large-scale cloud scheme, fed by relaxed Arakawa-Schubert (RAS) plume ensemble convection (a different implementation than in AM2). Its variability is rich and vertically coherent, and involves a very strong vertical dipole component to its tropospheric heating variations, of both signs (limited-depth convective heating and top-heavy heating in strong deep events with significant nonconvective rain). Grid-scale saturation events occur in all three models, often without nonconvective surface rain, causing relatively rare episodes of large negative top-of-atmosphere cloud forcing. Overall, cloud forcing regressions show a mild net positive forcing by rain-correlated clouds in CAM3 and mild net cooling in the other models, as the residual of large canceling shortwave and longwave contributions. © 2009 American Meteorological Society."
"9244992800;7004060399;7102167757;15724418700;7005134081;7403263977;25031430500;7005723936;7003683808;","The impact of stratospheric ozone recovery on tropopause height trends",2009,"10.1175/2008JCLI2215.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049090271&doi=10.1175%2f2008JCLI2215.1&partnerID=40&md5=958a48ee85d32c2e9948f2c99264cbbe","The evolution of the tropopause in the past, present, and future climate is examined by analyzing a set of long-term integrations with stratosphere-resolving chemistry climate models (CCMs). These CCMs have high vertical resolution near the tropopause, a model top located in the mesosphere or above, and, most important, fully interactive stratospheric chemistry. Using such CCM integrations, it is found that the tropopause pressure (height) will continue to decrease (increase) in the future, but with a trend weaker than that in the recent past. The reduction in the future tropopause trend is shown to be directly associated with stratospheric ozone recovery. A significant ozone recovery occurs in the Southern Hemisphere lower stratosphere of the CCMs, and this leads to a relative warming there that reduces the tropopause trend in the twenty-first century. The future tropopause trends predicted by the CCMs are considerably smaller than those predicted by the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) models, especially in the southern high latitudes. This difference persists even when the CCMs are compared with the subset of the AR4 model integrations for which stratospheric ozone recovery was prescribed. These results suggest that a realistic representation of the stratospheric processes might be important for a reliable estimate of tropopause trends. The implications of these finding for the Southern Hemisphere climate change are also discussed. © 2009 American Meteorological Society."
"15046855600;7005978899;","Eemian tropical and subtropical African moisture transport: An isotope modelling study",2009,"10.1007/s00382-008-0515-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350564895&doi=10.1007%2fs00382-008-0515-2&partnerID=40&md5=dbc215b2e917dad3ea4f9b12e0f87caf","During the last interglacial insolation maximum (Eemian, MIS 5e) the tropical and subtropical African hydrological cycle was enhanced during boreal summer months. The climate anomalies are examined with a General Circulation Model (ECHAM4) that is equipped with a module for the direct simulation of 18O and deuterium (H218O and HDO, respectively) in all components of the hydrological cycle. A mechanism is proposed to explain the physical processes that lead to the modelled anomalies. Differential surface heating due to anomalies in orbital insolation forcing induce a zonal flow which results in enhanced moisture advection and precipitation. Increased cloud cover reduces incoming short wave adiation and induces a cooling between 10°N and 20°N. The isotopic composition of rainfall at these latitudes is therefore significantly altered. Increased amount of precipitation and stronger advection of moisture from the Atlantic result in isotopically more depleted rainfall in the Eemian East African subtropics compared to pre-industrial climate. The East-West gradient of the isotopic rainfall composition reverses in the Eemian simulation towards depleted values in the east, compared to more depleted western African rainfall in the pre-industrial simulation. The modelled re-distribution of δ18O and δD is the result of a change in the forcing of the zonal flow anomaly. We conclude that the orbitally induced forcing for African monsoon maxima extends further eastward over the continent and leaves a distinct isotopic signal that can be tested against proxy archives, such as lake sediment cores from the Ethiopian region. © Springer-Verlag 2009."
"24823598500;6602373273;7801611878;","Estimating the rates of mass change, ice volume change and snow volume change in Greenland from ICESat and GRACE data",2009,"10.1111/j.1365-246X.2008.03978.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149183835&doi=10.1111%2fj.1365-246X.2008.03978.x&partnerID=40&md5=0323e6da02a7d2c3723d40d690b017e4","The focus of this paper is on the quantification of ongoing mass and volume changes over the Greenland ice sheet. For that purpose, we used elevation changes derived from the Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry mission and monthly variations of the Earth's gravity field as observed by the Gravity Recovery and Climate Experiment (GRACE) mission. Based on a stand alone processing scheme of ICESat data, the most probable estimate of the mass change rate from 2003 February to 2007 April equals -139 ± 68 Gton yr-1. Here, we used a density of 600 ± 300 kgm-3 to convert the estimated elevation change rate in the region above 2000m into a mass change rate. For the region below 2000m, we used a density of 900 ± 300 kgm-3. Based on GRACE gravity models from half 2002 to half 2007 as processed by CNES, CSR, DEOS and GFZ, the estimated mass change rate for the whole of Greenland ranges between -128 and -218 Gton yr-1. Most GRACE solutions show much stronger mass losses as obtained with ICESat, which might be related to a local undersampling of the mass loss by ICESat and uncertainties in the used snow/ice densities. To solve the problem of uncertainties in the snow and ice densities, two independent joint inversion concepts are proposed to profit from both GRACE and ICESat observations simultaneously. The first concept, developed to reduce the uncertainty of the mass change rate, estimates this rate in combination with an effective snow/ice density. However, it turns out that the uncertainties are not reduced, which is probably caused by the unrealistic assumption that the effective density is constant in space and time. The second concept is designed to convert GRACE and ICESat data into two totally new products: variations of ice volume and variations of snow volume separately. Such an approach is expected to lead to new insights in ongoing mass change processes over the Greenland ice sheet. Our results show for different GRACE solutions a snow volume change of -11 to 155 km3 yr-1 and an ice loss with a rate of -136 to -292 km3 yr-1. © 2009 The Authors Journal compilation © 2009 RAS."
"56162305900;7102604282;","Aerosol indirect forcing in a global model with particle nucleation",2009,"10.5194/acp-9-239-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60649107034&doi=10.5194%2facp-9-239-2009&partnerID=40&md5=eefcc1cb2794ebd8ae50fcd45bbd7d61","The number concentration of cloud condensation nuclei (CCN) formed as a result of anthropogenic emissions is a key uncertainty in the study of aerosol indirect forcing and global climate change. Here, we use a global aerosol model that includes an empirical boundary layer nucleation mechanism, the use of primary-emitted sulfate particles to represent sub-grid scale nucleation, as well as binary homogeneous nucleation to explore how nucleation affects the CCN concentration and the first aerosol indirect effect (AIE). The inclusion of the boundary layer nucleation scheme increases the global average CCN concentrations in the boundary layer by 31.4% when no primary-emitted sulfate particles are included and by 5.3% when they are included. Particle formation with the boundary layer nucleation scheme decreases the first indirect forcing over ocean, and increases the first indirect forcing over land when primary sulfate particles are included. This suggests that whether particle formation from aerosol nucleation increases or decreases aerosol indirect effects largely depends on the relative change of primary particles and SO2 emissions from the preindustrial to the present day atmosphere. Including primary-emitted sulfate particle significantly increases both the anthropogenic fraction of CCN concentrations and the first aerosol indirect forcing. The forcing from various treatments of aerosol nucleation ranges from-1.22 to-2.03 w/m2. This large variation shows the importance of better quantifying aerosol nucleation mechanisms for the prediction of CCN concentrations and aerosol indirect effects."
"8511991900;24081888700;7006303509;7003666669;7005742394;7202048112;7409080503;16507384700;55405340400;","Dominant role by vertical wind shear in regulating aerosol effects on deep convective clouds",2009,"10.1029/2009JD012352","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049112292&doi=10.1029%2f2009JD012352&partnerID=40&md5=f63aef430a9208b3ac259981089bfb42","Aerosol-cloud interaction is recognized as one of the key factors influencing cloud properties and precipitation regimes across local, regional, and global scales and remains one of the largest uncertainties in understanding and projecting future climate changes. Deep convective clouds (DCCs) play a crucial role in the general circulation, energy balance, and hydrological cycle of our climate system. The complex aerosol-DCC interactions continue to be puzzling as more ""aerosol effects"" unfold, and systematic assessment of such effects is lacking. Here we systematically assess the aerosol effects on isolated DCCs based on cloud-resolving model simulations with spectral bin cloud microphysics. We find a dominant role of vertical wind shear in regulating aerosol effects on isolated DCCs, i.e., vertical wind shear qualitatively determines whether aerosols suppress or enhance convective strength. Increasing aerosols always suppresses convection under strong wind shear and invigorates convection under weak wind shear until this effect saturates at an optimal aerosol loading. We also found that the decreasing rate of convective strength is greater in the humid air than that in the dry air when wind shear is strong. Our findings may resolve some of the seemingly contradictory results among past studies by considering the dominant effect of wind shear. Our results can provide the insights to better parameterize aerosol effects on convection by adding the factor of wind shear to the entrainment term, which could reduce uncertainties associated with aerosol effects on climate forcing. Copyright 2009 by the American Geophysical Union."
"7404142321;7201485519;","A quantitative performance assessment of cloud regimes in climate models",2009,"10.1007/s00382-008-0443-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349265921&doi=10.1007%2fs00382-008-0443-1&partnerID=40&md5=31a3021d2495c7de3bfc3267715ed9a6","Differences in the radiative feedback from clouds account for much of the variation in climate sensitivity amongst General Circulation Models (GCMs). Therefore metrics of model performance which are demonstrated to be relevant to the cloud response to climate change form an important contribution to the overall evaluation of GCMs. In this paper we demonstrate an alternative method for assigning model data to observed cloud regimes obtained from clustering histograms of cloud amount in joint cloud optical depth-cloud top pressure classes. The method removes some of the subjectivity that exists in previous GCM cloud clustering studies. We apply the method to ten GCMs submitted to the Cloud Feedback Model Intercomparison Project (CFMIP), evaluate the simulated cloud regimes and analyse the climate change response in the context of these regimes. We also propose two cloud regime metrics, one of which is specifically targeted at assessing GCMs for the purpose of obtaining the global cloud radiative response to climate change. Most of the global variance in the cloud radiative response between GCMs is due to low clouds, with 47% arising from the stratocumulus regime and 18% due to the regime characterised by clouds undergoing transition from stratocumulus to cumulus. This result is found to be dominated by two structurally similar GCMs. The shallow cumulus regime, though widespread, has a smaller contribution and reduces the variance. For the stratocumulus and transition regimes, part of the variance results from a large model spread in the radiative properties of the regime in the control simulation. Comparison with observations reveals a systematic bias for both the stratocumulus and transition regimes to be overly reflective. If this bias was corrected with all other aspects of the response unchanged, the variance in the low cloud response would reduce. The response of some regimes with high cloud tops differ between the GCMs. These regimes are simulated too infrequently in a few of the models. If the frequency in the control simulation were more realistic and changes within the regimes were unaltered, the variance in the cloud radiative response from high-top clouds would increase. As a result, use of observations of the mean present-day cloud regimes suggests that whilst improvements in the simulation of the cloud regimes would impact the climate sensitivity, the inter-model variance may not reduce. When the cloud regime metric is calculated for the GCMs analysed here, only one model is on average consistent with observations within their uncertainty (and even this model is not consistent with the observations for all regimes), indicating scope for improvement in the simulation of cloud regimes. © Crown copyright 2008."
"7006705919;35552588700;57200319057;","Geoengineering by cloud seeding: Influence on sea ice and climate system",2009,"10.1088/1748-9326/4/4/045112","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76149088442&doi=10.1088%2f1748-9326%2f4%2f4%2f045112&partnerID=40&md5=74c69675f789e31996e18de7b390ef14","General circulation model computations using a fully coupled ocean-atmosphere model indicate that increasing cloud reflectivity by seeding maritime boundary layer clouds with particles made from seawater may compensate for some of the effects on climate of increasing greenhouse gas concentrations. The chosen seeding strategy (one of many possible scenarios) can restore global averages of temperature, precipitation and sea ice to present day values, but not simultaneously. The response varies nonlinearly with the extent of seeding, and geoengineering generates local changes to important climatic features. The global tradeoffs of restoring ice cover, and cooling the planet, must be assessed alongside the local changes to climate features. © 2009 IOP Publishing Ltd."
"55686667100;8979277400;7401945370;25647939800;","A PDF-based hybrid prognostic cloud scheme for general circulation models",2009,"10.1007/s00382-008-0489-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955584319&doi=10.1007%2fs00382-008-0489-0&partnerID=40&md5=f44caf4685f12196cbb8375a6dc07bd3","A new cloud parameterization based on prognostic equations for the subgrid-scale fluctuations in temperature and total water content is introduced for global climate models. The proposed scheme, called hybrid prognostic cloud (HPC) parameterization, employs simple probability density functions (PDFs) to the horizontal subgrid-scale inhomogeneity, allowing them to vary in shape in response to small-scale processes such as cumulus detrainment and turbulent mixing. Simple tests indicate that the HPC scheme is highly favorable as compared to a diagnostic scheme in terms of the cloud fraction and cloud water content under either uniform or non-uniform forcing. The relevance of the HPC scheme is investigated by implementing it in an atmospheric component model of the climate model MIROC with a coarse resolution of T42. A comparison of the short-term integrations between the T42 model and a global cloud resolving model (GCRM) reveals that the HPC scheme can reproduce, to a certain degree, the subgrid-scale variance and skewness of temperature and total water content simulated in the GCRM. It is also found that the HPC scheme significantly alters the climatological distributions in cloud cover, precipitation, and moisture, which are all improved from the model using a conventional diagnostic cloud scheme. © Springer-Verlag 2008."
"57202891769;7003278104;7103245074;7201706787;","Simulations of 20th and 21st century Arctic cloud amount in the global climate models assessed in the IPCC AR4",2009,"10.1007/s00382-008-0475-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350565064&doi=10.1007%2fs00382-008-0475-6&partnerID=40&md5=db0f00d13de51d4ddc75ccf490bfd35c","Simulations of late 20th and 21st century Arctic cloud amount from 20 global climate models (GCMs) in the Coupled Model Intercomparison Project phase 3 (CMIP3) dataset are synthesized and assessed. Under recent climatic conditions, GCMs realistically simulate the spatial distribution of Arctic clouds, the magnitude of cloudiness during the warmest seasons (summer-autumn), and the prevalence of low clouds as the predominant type. The greatest intermodel spread and most pronounced model error of excessive cloudiness coincides with the coldest seasons (winter-spring) and locations (perennial ice pack, Greenland, and the Canadian Archipelago). Under greenhouse forcing (SRES A1B emissions scenario) the Arctic is expected to become cloudier, especially during autumn and over sea ice, in tandem with cloud decreases in middle latitudes. Projected cloud changes for the late 21st century depend strongly on the simulated modern (late 20th century) annual cycle of Arctic cloud amount: GCMs that correctly simulate more clouds during summer than winter at present also tend to simulate more clouds in the future. The simulated Arctic cloud changes display a tripole structure aloft, with largest increases concentrated at low levels (below 700 hPa) and high levels (above 400 hPa) but little change in the middle troposphere. The changes in cloud radiative forcing suggest that the cloud changes are a positive feedback annually but negative during summer. Of potential explanations for the simulated Arctic cloud response, local evaporation is the leading candidate based on its high correlation with the cloud changes. The polar cloud changes are also significantly correlated with model resolution: GCMs with higher spatial resolution tend to produce larger future cloud increases. © Springer-Verlag 2008."
"35221494300;6603315547;57203053317;","Orographic cirrus in a future climate",2009,"10.5194/acp-9-7825-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950379537&doi=10.5194%2facp-9-7825-2009&partnerID=40&md5=fc0b727b9f082378fdbcbda24aea5bf6","A cloud resolving model (CRM) is used to investigate the formation of orographic cirrus clouds in the current and future climate. The formation of cirrus clouds depends on a variety of dynamical and thermodynamical processes, which act on different scales. First, the capability of the CRM in realistically simulating orographic cirrus clouds has been tested by comparing the simulated results to aircraft measurements of an orographic cirrus cloud. The influence of a warmer climate on the microphysical and optical properties of cirrus clouds has been investigated by initializing the CRM with vertical profiles of horizontal wind, potential temperature and equivalent potential temperature, respectively. The vertical profiles are extracted from IPCC A1B simulations for the current climate and for the period 2090-2099 for two regions representative for North and South America. The influence of additional moisture in a future climate on the propagation of gravity waves and the formation of orographic cirrus could be estimated. In a future climate, the increase in moisture dampens the vertical propagation of gravity waves and the occurring vertical velocities in the moist simulations. Together with higher temperatures fewer ice crystals nucleate homogeneously. Assuming that the relative humidity does not change in a warmer climate the specific humidity in the model is increased. This increase in specific humidity in a warmer climate results in a higher ice water content. The net effect of a reduced ice crystal number concentration and a higher ice water content is an increased optical depth. However, in some moist simulations dynamical changes contribute to changes in the ice water content, ice crystal number concentration and optical depth. For the corresponding dry simulations dynamical changes are more pronounced leading to a decreased optical depth in a future climate in some cases."
"56032511300;7102604282;56162305900;","Comparison of a global-climate model simulation to a cloud-system resolving model simulation for long-term thin stratocumulus clouds",2009,"10.5194/acp-9-6497-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75449107397&doi=10.5194%2facp-9-6497-2009&partnerID=40&md5=1a92b0c6a7b2d1fc54705ab46d2d8832","A case of thin, warm marine-boundary-layer (MBL) clouds is simulated by a cloud-system resolving model (CSRM) and is compared to the same case of clouds simulated by a general circulation model (GCM). In this study, the simulation by the CSRM adopts higher resolutions which are generally used in large-eddy simulations (LES) and more advanced microphysies as compared to those by the GCM, enabling the CSRM-simulation to act as a benchmark to assess the simulation by the GCM. Explicitly simulated interactions among the surface latent heat (LH) fluxes, buoyancy fluxes, and cloud-top entrainmentlead to the deepening-warming decoupling and thereby the transition from stratiform clouds to cumulus clouds in the CSRM. However, in the simulation by the GCM, these interactions are not resolved and thus the transition to cumulus clouds is not simulated. This leads to substantial differences in liquid water content (LWC) and radiation between simulations by the CSRM and the GCM. When stratocumulus clouds are dominant prior to the transition to cumulus clouds, interactions between supersaturation and cloud droplet number concentration (CDNC) (controlling condensation) and those between rain evaporation and cloud-base instability (controlling cloud dynamics and thereby condensation) determine LWC and thus the radiation budget in the simulation by the CSRM. These interactions result in smaller condensation and thus smaller LWC and reflected solar radiation by clouds in the simulation by the CSRM than in the simulation by the GCM where these interactions are not resolved. The resolved interactions (associated with condensation and the transition to cumulus clouds) lead to better agreement between the CSRM-simulation and observation than that between the GCM-simulation and observation."
"7102925250;35551376300;7404291795;6603580448;6603635723;23390356800;","Applications of Satellite-Based Sulfur Dioxide Monitoring",2009,"10.1109/JSTARS.2009.2037334","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76249098937&doi=10.1109%2fJSTARS.2009.2037334&partnerID=40&md5=4af273e49fb26f89e861b3c0f4a3f71d","Sulfur dioxide is emitted by volcanoes, produced by combustion of fossil fuels or smelting of ores, and is an intermediate product from organic sources in the ocean. It is rapidly oxidized to sulfuric acid, which causes acidic pollution of lakes and streams and forms an aerosol that is important in climate change. Volcanic sulfur dioxide is a useful marker for ash clouds that are a hazard to aircraft. Satellites offer the best platform to monitor SO2 sources and to track volcanic clouds. UV remote sensing instruments have measured eruption plume masses since 1978. Newer instruments are sensitive enough to also measure volcanic degassing, emissions from power plants, refineries, smelters, and heavy air pollution episodes. New retrieval algorithms have improved the data quality. The observations are used to constrain models of eruption processes and to monitor activity of all volcanoes in a consistent manner. The practical applications of the satellite data include aviation safety, air quality, environmental control, climate modeling, and atmospheric dynamics modeling. © 2009, The Institute of Electrical and Electronics Engineers, Inc."
"23065650200;6701812327;","Modification of cirrus clouds to reduce global warming",2009,"10.1088/1748-9326/4/4/045102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749118307&doi=10.1088%2f1748-9326%2f4%2f4%2f045102&partnerID=40&md5=8f9cc6ad1ac824661973b296cf4538a1","Greenhouse gases and cirrus clouds regulate outgoing longwave radiation (OLR) and cirrus cloud coverage is predicted to be sensitive to the ice fall speed which depends on ice crystal size. The higher the cirrus, the greater their impact is on OLR. Thus by changing ice crystal size in the coldest cirrus, OLR and climate might be modified. Fortunately the coldest cirrus have the highest ice supersaturation due to the dominance of homogeneous freezing nucleation. Seeding such cirrus with very efficient heterogeneous ice nuclei should produce larger ice crystals due to vapor competition effects, thus increasing OLR and surface cooling. Preliminary estimates of this global net cloud forcing are more negative than -2.8Wm-2 and could neutralize the radiative forcing due to a CO2 doubling (3.7Wm-2). A potential delivery mechanism for the seeding material is already in place: the airline industry. Since seeding aerosol residence times in the troposphere are relatively short, the climate might return to its normal state within months after stopping the geoengineering experiment. The main known drawback to this approach is that it would not stop ocean acidification. It does not have many of the drawbacks that stratospheric injection of sulfur species has. © 2009 IOP Publishing Ltd."
"57203053317;24398842400;","Sensitivity studies of different aerosol indirect effects in mixed-phase clouds",2009,"10.5194/acp-9-8917-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149116178&doi=10.5194%2facp-9-8917-2009&partnerID=40&md5=ae19a66ae9b0a6e201c9974ab1e3bcba","Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m&amp;minus;2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect."
"8718425100;7601492669;7101752236;6602582342;55915206300;7403682442;","Simulating marine boundary layer clouds over the eastern Pacific in a regional climate model with double-moment cloud microphysics",2009,"10.1029/2009JD012201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049117875&doi=10.1029%2f2009JD012201&partnerID=40&md5=5b6c3d2fc56e429b719d9ce0a70a521a","A double-moment cloud microphysics scheme with a prognostic treatment of aerosols inside clouds has been implemented into the International Pacific Research Center Regional Atmospheric Model (iRAM) to simulate marine boundary layer clouds over the eastern Pacific and to study aerosol-cloud interactions, including the aerosol indirect effect. This paper describes the new model system and presents a comparison of model results with observations. The results show that iRAM with the double-moment cloud microphysics scheme is able to reproduce the major features, including the geographical patterns and vertical distribution of the basic cloud parameters such as cloud droplet number, liquid water content, or droplet effective radii over the eastern Pacific reasonably well. However, the model tends to underestimate cloud droplet number concentrations near the coastal regions strongly influenced by advection of continental aerosols and precursor gases. In addition, the average location of the stratocumulus deck off South America is shifted to the northwest compared with the satellite observations. We apply the new model system to assess the indirect aerosol effect over the eastern Pacific by comparing a simulation with preindustrial aerosol to an otherwise identical simulation with present-day aerosol. Resulting changes in the cloud droplet number concentration are particularly pronounced in Gulf of Mexico and along the Pacific coastlines with local changes up to 70 cm-3 (50% of the present-day value). The modeled domain-averaged 3-month (August-October) mean change in top-of-atmosphere net cloud forcing over the ocean owing to changes in the aerosol burden by anthropogenic activities is - 1.6 W m-2. Copyright 2009 by the American Geophysical Union."
"7004940109;56367865700;","High-latitude methane sulphonic acid variability and solar activity: the role of the total solar irradiance",2009,"10.1016/j.jastp.2008.09.034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149267767&doi=10.1016%2fj.jastp.2008.09.034&partnerID=40&md5=e26f943a82eccc20b58a1774e49480a8","The direct impact of solar activity on climate has been widely studied through Total Solar Irradiance (TSI). Biological processes also impact climate and are deeply affected by TSI. Marine phytoplankton emissions into the atmosphere have been proposed to change cloud albedo through cloud formation. In this work, we use wavelet analysis to investigate the decadal relation between high-latitude concentrations of methane sulphonic acid, a product of seawater algae, and TSI. We found that some of the methane sulphonic acid main periodicities coincide with periods of solar activity periods. © 2008 Elsevier Ltd. All rights reserved."
"7407104838;7102805852;57203200427;","Climate impacts of geoengineering marine stratocumulus clouds",2009,"10.1029/2008JD011450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650456686&doi=10.1029%2f2008JD011450&partnerID=40&md5=11a8ffea6d4ad2655404db10f0a0d867","Theoretical potential geoengineering solutions to the global warming problem have recently been proposed. Here, we present an idealized study of the climate response to deliberately seeding large-scale stratocumulus cloud decks in the North Pacific, South Pacific, and South Atlantic, thereby inducing cooling via aerosol indirect effects. Atmosphere-only, atmosphere/mixed-layer ocean, and fully coupled atmosphere/ocean versions of the Met Office Hadley Centre model are used to investigate the radiative forcing, climate efficacy, and regional response of temperature, precipitation, and net primary productivity to such geoengineering. The radiative forcing simulations indicate that, for our parameterization of aerosol indirect effects, up to 35% of the radiative forcing due to current levels of greenhouse gases could be offset by stratocumulus modification. Equilibrium simulations with the atmosphere/mixed-layer ocean model, wherein each of the three stratocumulus sheets is modified in turn, reveal that the most efficient cooling per unit radiative forcing occurs when the South Pacific stratocumulus sheet is modified. Transient coupled model simulations suggest that geoengineering all three stratocumulus areas delays the simulated global warming by about 25 years. These simulations also indicate that, while some areas experience increases in precipitation and net primary productivity, sharp decreases are simulated in South America, with particularly detrimental impacts on the Amazon rain forest. These results show that, while some areas benefit from geoengineering, there are significant areas where the response could be very detrimental with implications for the practical applicability of such a scheme."
"6602600408;57203200427;7407104838;7004024532;35221700500;35221494300;","Exploiting the weekly cycle as observed over Europe to analyse aerosol indirect effects in two climate models",2009,"10.5194/acp-9-8493-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450280475&doi=10.5194%2facp-9-8493-2009&partnerID=40&md5=41b92a7bf57ac9c371626f0de2ef572f","A weekly cycle in aerosol pollution and some meteorological quantities is observed over Europe. In the present study we exploit this effect to analyse aerosol-cloud-radiation interactions. A weekly cycle is imposed on anthropogenic emissions in two general circulation models that include parameterizations of aerosol processes and cloud microphysics. It is found that the simulated weekly cycles in sulfur dioxide, sulfate, and aerosol optical depth in both models agree reasonably well with those observed indicating model skill in simulating the aerosol cycle. A distinct weekly cycle in cloud droplet number concentration is demonstrated in both observations and models. For other variables, such as cloud liquid water path, cloud cover, top-of-the-atmosphere radiation fluxes, precipitation, and surface temperature, large variability and contradictory results between observations, model simulations, and model control simulations without a weekly cycle in emissions prevent us from reaching any firm conclusions about the potential aerosol impact on meteorology or the realism of the modelled second aerosol indirect effects."
"6701843355;6701773156;6701341222;6603718837;6602752798;6507815511;7003467276;7006710430;","Western Europe is warming much faster than expected",2009,"10.5194/cp-5-1-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450256989&doi=10.5194%2fcp-5-1-2009&partnerID=40&md5=1677a8bf1d80b709d5b40377f9c6c2ee","The warming trend of the last decades is now so strong that it is discernible in local temperature observations. This opens the possibility to compare the trend to the warming predicted by comprehensive climate models (GCMs), which up to now could not be verified directly to observations on a local scale, because the signal-to-noise ratio was too low. The observed temperature trend in western Europe over the last decades appears much stronger than simulated by state-of-the-art GCMs. The difference is very unlikely due to random fluctuations, either in fast weather processes or in decadal climate fluctuations. In winter and spring, changes in atmospheric circulation are important; in spring and summer changes in soil moisture and cloud cover. A misrepresentation of the North Atlantic Current affects trends along the coast. Many of these processes ontinue to affect trends in projections for the 21st century. This implies that climate predictions for western Europe probably underestimate the effects of anthropogenic climate change. © Author(s) 2009."
"23568163400;57201177267;","The impact of smoke from forest fires on the spectral dispersion of cloud droplet size distributions in the Amazonian region",2009,"10.1088/1748-9326/4/1/015002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349139361&doi=10.1088%2f1748-9326%2f4%2f1%2f015002&partnerID=40&md5=bfb87e1e1055b2318a88c007feb757dc","In this paper, the main microphysical characteristics of clouds developing in polluted and clean conditions in the biomass-burning season of the Amazon region are examined, with special attention to the spectral dispersion of the cloud droplet size distribution and its potential impact on climate modeling applications. The dispersion effect has been shown to alter the climate cooling predicted by the so-called Twomey effect. In biomass-burning polluted conditions, high concentrations of low dispersed cloud droplets are found. Clean conditions revealed an opposite situation. The liquid water content (0.43 ± 0.19gm-3) is shown to be uncorrelated with the cloud drop number concentration, while the effective radius is found to be very much correlated with the relative dispersion of the size distribution (R2 = 0.81). The results suggest that an increase in cloud condensation nuclei concentration from biomass-burning aerosols may lead to an additional effect caused by a decrease in relative dispersion. Since the dry season in the Amazonian region is vapor limiting, the dispersion effect of cloud droplet size distributions could be substantially larger than in other polluted regions. © 2009 IOP Publishing Ltd."
"6603081424;57208765879;12803465300;7403931916;7003398947;","The shortwave radiative forcing bias of liquid and ice clouds from MODIS observations",2009,"10.5194/acp-9-5865-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951683545&doi=10.5194%2facp-9-5865-2009&partnerID=40&md5=21bf909728fe892f5b6e81bef9c3b701","We present an assessment of the plane-parallel bias of the shortwave cloud radiative forcing (SWCRF) of liquid and ice clouds at 1 deg scales using global MODIS (Terra and Aqua) cloud optical property retrievals for four months of the year 2005 representative of the meteorological seasons. The (negative) bias is estimated as the difference of SWCRF calculated using the Plane-Parallel omogeneous (PPH) approximation and the Independent Column Approximation (ICA). PPH calculations use MODISderived gridpoint means while ICA calculations use distributions of cloud optical thickness and effective radius. Assisted by a broadband solar radiative transfer algorithm, we find that the absolute value of global SWCRF bias of liquid clouds at the top of the atmosphere is about 6Wm?2 for MODIS overpass times while the SWCRF bias for ice clouds is smaller in absolute terms by about 0.7Wm?2, but with stronger spatial variability. If effective radius variability is neglected and only optical thickness horizontal variations are accounted for, the absolute SWCRF biases increase by about 0.3-0.4Wm?2 on average. Marine clouds of both phases exhibit greater (more negative) SWCRF biases than continental clouds. Finally, morning (Terra)-afternoon (Aqua) differences in SWCRF bias are much more pronounced for ice clouds, up to about 15% (Aqua producing stronger negative bias) on global scales, with virtually all contribution to the difference coming from land areas. The substantial magnitude of the global SWCRF bias, which for clouds of both phases is collectively about 4Wm?2 for diurnal averages, should be considered a strong motivation for global climate modelers to accelerate efforts linking cloud schemes capable of subgrid condensate variability with appropriate radiative transfer schemes. © 2009 Author (s)."
"8627503500;35547214900;8258673100;7202016984;7407116104;6602407753;","Radiative effects of African dust and smoke observed from Clouds and the Earth's Radiant Energy System (CERES) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data",2009,"10.1029/2009JD012000","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049102914&doi=10.1029%2f2009JD012000&partnerID=40&md5=86e6e5b32d4b0063f6753d9dd911a389","Cloud and aerosol effects have a significant impact on the atmospheric radiation budget in the tropical Atlantic because of the spatial and temporal extent of desert dust and smoke from biomass burning in the atmosphere. The influences of African dust and smoke aerosols on cloud radiative properties over the tropical Atlantic Ocean were analyzed for the month of July for 3 years (2006-2008) using colocated data collected by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aqua satellites. Aerosol layer height and type can be accurately determined using CALIOP data through directly measured parameters such as optical depth, volume depolarization ratio, attenuated backscatter, and color ratio. On average, clouds below 5 km had a daytime instantaneous shortwave (SW) radiative flux of 270.2 ± 16.9 W/m 2 and thin cirrus clouds had a SW radiative flux of 208.0 ± 12.7 W/m2. When dust aerosols interacted with clouds below 5 km, as determined from CALIPSO, theSWradiative flux decreased to 205.4 ± 13.0 W/m2. Similarly, smoke aerosols decreased the SW radiative flux of low clouds to a value of 240.0 ± 16.6 W/m2. These decreases in SW radiative flux were likely attributed to the aerosol layer height and changes in cloud microphysics. CALIOP lidar observations, which more accurately identify aerosol layer height than passive instruments, appear essential for better understanding of cloud-aerosol interactions, a major uncertainty in predicting the climate system. Copyright 2009 by the American Geophysical Union."
"7103373860;7005877775;","Cloud classes and radiative heating profiles at the Manus and Nauru atmospheric radiation measurement (ARM) sites",2009,"10.1029/2009JDO11703","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049092702&doi=10.1029%2f2009JDO11703&partnerID=40&md5=29d85f81c9b905b858f335a4e5d4a324","The tropical western Pacific is a convective regime; however, the frequency and depth of convection is dependent on dynamical forcing which exhibits variability on a range of temporal scales and also on location within the region. Manus Island, Papua New Guinea, lies in the heart of the western Pacific warm pool region and exhibits frequent deep convection much of the time, while Nauru, which lies approximately 20 degrees to the east of Manus, is in a transition zone where the frequency of convection is dependent on the phase of the El Niño-Southern Oscillation. Because of this difference in dynamical regime, the distribution of clouds and the associated radiative heating is quite different at the two sites. Individual cloud types (boundary layer cumulus, thin cirrus, stratiform convective outflow) do occur at both sites, but with different frequencies. In this study we compare cloud profiles and heating profiles for specific cloud types at these two sites using data from the Atmospheric Radiation Measurement (ARM) Climate Research Facility. Results of this comparison indicate that while the frequency of specific cloud types differ between the two sites as one would expect, the characteristics of individual cloud classes are remarkably similar. This information could prove to be very useful for applying tropical ARM data to the broader region. Copyright 2009 bv the American Geophysical Union."
"8349977900;7004174939;57208765879;16245558300;57202661839;6508138919;","Exploring the differences in cloud properties observed by the Terra and Aqua MODIS Sensors",2009,"10.5194/acp-9-3461-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72449171063&doi=10.5194%2facp-9-3461-2009&partnerID=40&md5=d269d40d274d8bd02b23ed8e6dfa4dac","The aerosol-cloud interaction in different parts of the globe is examined here using multi-year statistics of remotely sensed data from two MODIS sensors aboard NASA's Terra (morning) and Aqua (afternoon) satellites. Simultaneous retrievals of aerosol loadings and cloud properties by the MODIS sensor allowed us to explore morning-to-afternoon variation of liquid cloud fraction (CF) and optical thickness (COT) for clean, moderately polluted and heavily polluted clouds in different seasons. Data analysis for seven-years of MODIS retrievals revealed strong temporal and spatial patterns in morning-to-afternoon variation of cloud fraction and optical thickness over different parts of the global oceans and the land. For the vast areas of stratocumulus cloud regions, the data shows that the days with elevated aerosol abundance were also associated with enhanced afternoon reduction of CF and COT pointing to the possible reduction of the indirect climate forcing. A positive correlation between aerosol optical depth and morning-to-afternoon variation of trade wind cumulus cloud cover was also found over the northern Indian Ocean, though no clear relationship between the concentration of Indo-Asian haze and morning-to-afternoon variation of COT was established. Over the Amazon region during wet conditions, aerosols are associated with an enhanced convective process in which morning shallow warm clouds are organized into afternoon deep convection with greater ice cloud coverage. Analysis presented here demonstrates that the new technique for exploring morning-to-afternoon variability in cloud properties by using the differences in data products from the two daily MODIS overpasses is capable of capturing some of the major features of diurnal variations in cloud properties and can be used for better understanding of aerosol radiative effects."
"16480175700;6603872903;7003591311;22949331500;10144282600;21734765600;8280879000;7003741536;7006783796;7004008609;34769606600;6602126007;","Effect of biomass burning on marine stratocumulus clouds off the California coast",2009,"10.5194/acp-9-8841-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149103037&doi=10.5194%2facp-9-8841-2009&partnerID=40&md5=cd8dd6d3a1f44cc517ed14fb59c7bd23","Aerosol-cloud interactions are considered to be one of the most important and least known forcings in the climate system. Biomass burning aerosols are of special interest due to their radiative impact (direct and indirect effect) and their potential to increase in the future due to climate change. Combining data from Geostationary Operational Environmental Satellite (GOES) and MODerate-resolution Imaging Spectroradiometer (MODIS) with passive tracers from the FLEXPART Lagrangian Particle Dispersion Model, the impact of biomass burning aerosols on marine stratocumulus clouds has been examined in June and July of 2006ĝ€""2008 off the California coast. Using a continental tracer, the indirect effect of biomass burning aerosols has been isolated by comparing the average cloud fraction and cloud albedo for different meteorological situations, and for clean versus polluted (in terms of biomass burning) continental air masses at 14:00 local time. Within a 500 km-wide band along the coast of California, biomass burning aerosols, which tend to reside above the marine boundary layer, increased the cloud fraction by 0.143, and the cloud albedo by 0.038. Absorbing aerosols located above the marine boundary layer lead to an increase of the lower tropospheric stability and a reduction in the vertical entrainment of dry air from above, leading to increased cloud formation. The combined effect was an indirect radiative forcing of &minus;7.5% &plusmn;1.7% (cooling effect) of the outgoing radiative flux at the top of the atmosphere on average, with a bias due to meteorology of +0.9%. Further away from the coast, the biomass burning aerosols, which were located within the boundary layer, reduced the cloud fraction by 0.023 and the cloud albedo by 0.006, resulting in an indirect radiative forcing of +1.3% &plusmn;0.3% (warming effect) with a bias of +0.5%. These results underscore the dual role that absorbing aerosols play in cloud radiative forcing."
"14829673100;7201837768;56249704400;7004214645;","Impacts of aerosol-cloud interactions on past and future changes in tropospheric composition",2009,"10.5194/acp-9-4115-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950213026&doi=10.5194%2facp-9-4115-2009&partnerID=40&md5=394c266659ac9b5445b64c2d62de6c49","The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, aerosol-cloud interactions (ACI). The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI) to present day (PD) and future impacts from PD to 2050 (for the moderate IPCC A1B scenario) that embrace a wide spectrum of precursor emission changes and consequential ACI. The aerosol indirect effect (AIE) is estimated to be-2.0Wm-2 for PD-PI and-0.6Wm-2 for 2050-PD, at the high end of current estimates. Inclusion of ACI substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of ACI leads to 20% enhancements in in-cloud sulfate production and ∼10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions (∼10-30%). Nitric acid wet deposition is dampened by 15-20% across the industrialized regions due to ACI allowing additional re-release of reactive nitrogen that contributes to 1-2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that ACI must be considered in studies of methane trends and projections of future changes to particulate matter air quality."
"23051160600;6602506226;35459245100;6506718302;6603271938;6701511324;7007039218;7006712143;35388389700;35392584500;57203053317;55915206300;7003931528;35461255500;","Sensitivity of aerosol concentrations and cloud properties to nucleation and secondary organic distribution in ECHAM5-HAM global circulation model",2009,"10.5194/acp-9-1747-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949108307&doi=10.5194%2facp-9-1747-2009&partnerID=40&md5=f8573259d9dbb85e6ad55340c58c84f9","The global aerosol-climate model ECHAM5-HAM was modified to improve the representation of new particle formation in the boundary layer. Activation-type nucleation mechanism was introduced to produce observed nucleation rates in the lower troposphere. A simple and computationally efficient model for biogenic secondary organic aerosol (BSOA) formation was implemented. Here we study the sensitivity of the aerosol and cloud droplet number concentrations (CDNC) to these additions. Activationtype nucleation significantly increases aerosol number concentrations in the boundary layer. Increased particle number concentrations have a significant effect also on cloud droplet number concentrations and therefore on cloud properties. We performed calculations with activation nucleation coefficient values of 2×10-7 s -1, 2×10-6s-1 and 2×10 -5s-1 to evaluate the sensitivity to this parameter. For BSOA we have used yields of 0.025, 0.07 and 0.15 to estimate the amount of monoterpene oxidation products available for condensation. The hybrid BSOA formation scheme induces large regional changes to size distribution of organic carbon, and therefore affects particle optical properties and cloud droplet number concentrations locally. Although activation-type nucleation improves modeled aerosol number concentrations in the boundary layer, the use of a global activation coefficient generally leads to overestimation of aerosol number. Overestimation can also arise from underestimation of primary emissions."
"7103123474;9532691100;23398538400;6603413971;7006504263;7003840024;55556625400;7202331497;8596289100;57203083372;","Characterization of clouds in Titan's tropical atmosphere",2009,"10.1088/0004-637X/702/2/L105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75949097003&doi=10.1088%2f0004-637X%2f702%2f2%2fL105&partnerID=40&md5=67406cf2c773acb4ade410a7c6b1e4ed","Images of Titan's clouds, possible over the past 10 years, indicate primarily discrete convective methane clouds near the south and north poles and an immense stratiform cloud, likely composed of ethane, around the north pole. Here we present spectral images from Cassini's Visual Mapping Infrared Spectrometer that reveal the increasing presence of clouds in Titan's tropical atmosphere. Radiative transfer analyses indicate similarities between summer polar and tropical methane clouds. Like their southern counterparts, tropical clouds consist of particles exceeding 5 μm. They display discrete structures suggestive of convective cumuli. They prevail at a specific latitude band between 8°-20° S, indicative of a circulation origin and the beginning of a circulation turnover. Yet, unlike the high latitude clouds that often reach 45 km altitude, these discrete tropical clouds, so far, remain capped to altitudes below 26 km. Such low convective clouds are consistent with the highly stable atmospheric conditions measured at the Huygens landing site. Their characteristics suggest that Titan's tropical atmosphere has a dry climate unlike the south polar atmosphere, and despite the numerous washes that carve the tropical landscape. © 2009. The American Astronomical Society."
"55710583000;7005231450;7401513851;6603344816;7102543399;7402841077;40661134200;","Spatial dependence of diurnal temperature range trends on precipitation from 1950 to 2004",2009,"10.1007/s00382-008-0387-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149088370&doi=10.1007%2fs00382-008-0387-5&partnerID=40&md5=97f747f0682c0f2eeb84afa7a13e14ae","This paper analyzes the spatial dependence of annual diurnal temperature range (DTR) trends from 1950-2004 on the annual climatology of three variables: Precipitation, cloud cover, and leaf area index (LAI), by classifying the global land into various climatic regions based on the climatological annual precipitation. The regional average trends for annual minimum temperature (Tmin) and DTR exhibit significant spatial correlations with the climatological values of these three variables, while such correlation for annual maximum temperature (Tmax) is very weak. In general, the magnitude of the downward trend of DTR and the warming trend of Tmin decreases with increasing precipitation amount, cloud cover, and LAI, i.e., with stronger DTR decreasing trends over drier regions. Such spatial dependence of Tmin and DTR trends on the climatological precipitation possibly reflects large-scale effects of increased global greenhouse gases and aerosols (and associated changes in cloudiness, soil moisture, and water vapor) during the later half of the twentieth century. © Springer-Verlag 2008."
"7801344746;6603129558;","Deriving surface global irradiance over the Alpine region from METEOSAT Second Generation data by supplementing the HELIOSAT method",2009,"10.1080/01431160902744829","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70449435028&doi=10.1080%2f01431160902744829&partnerID=40&md5=4574cd57e545495420d7fa9d4bcbe9c6","In the framework of the Satellite Application Facility for Climate Monitoring (CM-SAF) an upgraded formulation of the HELIOSAT surface global irradiance retrieval scheme is proposed, which is suitable for real-time application to METEOSAT Second Generation (MSG) satellite data. The new scheme includes image georeferencing, pixel-wise snow-cover detection, special treatment of clouds above snow and correction of terrain effects over the Alpine region. Results show that the mean bias difference between the revised irradiance estimates from satellite and from ground measurements can be substantially reduced by correctly distinguishing between clouds and snow, and by applying the new cloud-index scheme for clouds blue above snow. The increase of the root mean square difference with increasing altitude can be mainly attributed to the increase of the variability of the natural irradiance field. We strongly recommend the use of MSG-based irradiance estimates for locations at more than 4 km distance to the next measurement site. © 2009 Taylor & Francis."
"57203200427;7407104838;55206018900;","Climate response to the physiological impact of carbon dioxide on plants in the Met Office Unified Model HadCM3",2009,"10.1007/s00382-008-0459-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149103294&doi=10.1007%2fs00382-008-0459-6&partnerID=40&md5=5a3aa1980f1a2ba54aee0dcf1ffee723","The concentration of carbon dioxide in the atmosphere acts to control the stomatal conductance of plants. There is observational and modelling evidence that an increase in the atmospheric concentration of CO2 would suppress the evapotranspiration (ET) rate over land. This process is known as CO2 physiological forcing and has been shown to induce changes in surface temperature and continental runoff. We analyse two transient climate simulations for the twenty-first century to isolate the climate response to the CO2 physiological forcing. The land surface warming associated with the decreased ET rate is accompanied by an increase in the atmospheric lapse rate, an increase in specific humidity, but a decrease in relative humidity and stratiform cloud over land. We find that the water vapour feedback more than compensates for the decrease in latent heat flux over land as far as the budget of atmospheric water vapour is concerned. There is evidence that surface snow, water vapour and cloudiness respond to the CO2 physiological forcing and all contribute to further warm the climate system. The climate response to the CO2 physiological forcing has a quite different signature to that from the CO2 radiative forcing, especially in terms of the changes in the temperature vertical profile and surface energy budget over land. © Crown Copyright 2008."
"23094223900;57206531303;7003499456;","Analysis of planetary boundary layer fluxes and land-atmosphere coupling in the regional climate model CLM",2009,"10.1029/2008JD011658","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049111780&doi=10.1029%2f2008JD011658&partnerID=40&md5=123dc121f03b779b88683fea86c808e4","Land-atmosphere interactions and associated boundary layer processes are crucial elements of the climate system and play a major role in several feedback processes, in particular for extreme events. In this article, we provide a detailed validation of land surface processes and land-atmosphere interactions in the climate version of the Lokal Modell (CLM), a regional climate model that has been recently developed and is now used by a wide research community. For the evaluation of the model, we use observations from the FLUXNET network and meteorological data. Moreover, we also compare the performance of the CLM with that of its driving data set, the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis, and simulations of the Inter-Continental Transferability Study (ICTS). The results show that most of the land-atmosphere coupling characteristics are consistent in CLM and the observations. Nonetheless, the analysis also allows identification of specific weaknesses of the CLM such as an underestimation of the incoming surface shortwave radiation due to cloud cover overestimation, leading to an underestimation of the sensible heat flux. The comparisons with the ECMWF operational analysis and the ICTS models suggest, however, that all models have biases of comparable magnitude. This study demonstrates the utility of flux observations for diagnosing biases in land-atmosphere exchanges and interactions in current climate models and highlights perspectives for our improved understanding of the relevant processes. Copyright 2009 by the American Geophysical Union."
"16242119400;7004469744;35810775100;8942525300;","Variable CCN formation potential of regional sulfur emissions",2009,"10.5194/acp-9-3253-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77049101770&doi=10.5194%2facp-9-3253-2009&partnerID=40&md5=0c9a5c75eb7f2a17961b7e2e7fccf1e7","Aerosols are short lived so their geographical distribution and impact on climate depends on where they are emitted. Previous model studies have shown that the mass of sulfate aerosol produced per unit sulfur emission (the sulfate burden potential) and the associated direct radiative forcing vary regionally because of differences in meteorology and photochemistry. Using a global model of aerosol microphysics, we show that the total number of aerosol particles produced per unit sulfur emission (the aerosol number potential) has a different regional variation to that of sulfate mass. The aerosol number potential of N. American and Asian emissions is calculated to be a factor of 3 to 4 times greater than that of European emissions, even though Europe has a higher sulfate burden potential. Pollution from N. America and Asia tends to reach higher altitudes than European pollution so forms more new particles through nucleation. Regional differences in particle production and growth mean that sulfur emissions from N. America and E. Asia produce 50 nm diameter cloud condensation nuclei up to 70% more efficiently than Europe. For 80 nm diameter CCN, N. America and Europe produce CCN 2.5 times more effi-ciently than E. Asia. The impact of regional sulfur emissions on particle concentrations is also much more widely spread than the impact on sulfate mass, due to efficient particle production in the free troposphere during long range transport. These results imply that regional sulfur emissions will have different climate forcing potentials through changes in cloud drop number."
"24074265000;7102739935;24171477000;7004035832;","Spatial patterns and recent trends in cloud fraction and cloud-related diffuse radiation in Amazonia",2009,"10.1029/2009JD012217","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049090359&doi=10.1029%2f2009JD012217&partnerID=40&md5=e9197a43b027944008b2efbd3e8137da","As the climate of tropical forest regions changes, there are likely to be concurrent changes in cloud cover and in the light regime experienced by tropical forest canopies. We utilize data from the International Satellite Cloud Climatology Project to examine spatial patterns and trends in cloud cover over Amazonia during the period 1984-2006. Cloud cover seasonality appears to be increasing in Amazonia, with a significant decline in dry season cloud fraction (0.3% yr-1) and increase in wet season cloud fraction (0.1% yr -1) over the last two decades. A novel cloud-related diffuse radiation (CRDR) climatology for Amazonia was derived from satellite cloud data. There is a clear decreasing gradient from the northwest to the southeast: annual CRDR proportion (CRDRP) varies by about 15% across the region. Analysis of trends over time indicates a 1 -2% decline in CRDRP in Amazonia over the last two decades, particularly in the east of the region. This is particularly marked in the dry season in the east where CRDRP declined at a rate of 0.3% yr-1, and the wet season decline was 0.1% yr-1. In the west of the region a 1% increase in CRDRP is indicated. Changes in forest composition and productivity may be linked to changes in CRDRP in that decreases in cloud cover in sunny regions or dry seasons may cause a decline in productivity, whereas declines in cloud cover in cloudy regions, or during cloudy seasons, may cause an increase in productivity. Copyright 2009 by the American Geophysical Union."
"7003391365;16443862200;24068728200;57201527657;7003942283;7004215973;15847666700;7004683326;57211681908;","Microbiology and atmospheric processes: Biological, physical and chemical characterization of aerosol particles",2009,"10.5194/bg-6-721-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949619352&doi=10.5194%2fbg-6-721-2009&partnerID=40&md5=4819d931dc185b39b1a204c6a652d5ce","The interest in bioaerosols has traditionally been linked to health hazards for humans, animals and plants. However, several components of bioaerosols exhibit physical properties of great significance for cloud processes, such as ice nucleation and cloud condensation. To gain a better understanding of their influence on climate, it is therefore important to determine the composition, concentration, seasonal fluctuation, regional diversity and evolution of bioaerosols. In this paper, we will review briefly the existing techniques for detection, quantification, physical and chemical analysis of biological particles, attempting to bridge physical, chemical and biological methods for analysis of biological particles and integrate them with aerosol sampling techniques. We will also explore some emerging spectroscopy techniques for bulk and single-particle analysis that have potential for in-situ physical and chemical analysis. Lastly, we will outline open questions and further desired capabilities (e.g., in-situ, sensitive, both broad and selective, on-line, time-resolved, rapid, versatile, cost-effective techniques) required prior to comprehensive understanding of chemical and physical characterization of bioaerosols."
"8453485500;7402332362;25031430500;7202081585;","On the relationship of polar mesospheric cloud ice water content, particle radius and mesospheric temperature and its use in multi-dimensional models",2009,"10.5194/acp-9-8889-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149100977&doi=10.5194%2facp-9-8889-2009&partnerID=40&md5=b027a10d655807ca52d749afd750a7ba","The distribution of ice layers in the polar summer mesosphere (called polar mesospheric clouds or PMCs) is sensitive to background atmospheric conditions and therefore affected by global-scale dynamics. To investigate this coupling it is necessary to simulate the global distribution of PMCs within a 3-dimensional (3-D) model that couples large-scale dynamics with cloud microphysics. However, modeling PMC microphysics within 3-D global chemistry climate models (GCCM) is a challenge due to the high computational cost associated with particle following (Lagrangian) or sectional microphysical calculations. By characterizing the relationship between the PMC effective radius, ice water content (iwc), and local temperature (T) from an ensemble of simulations from the sectional microphysical model, the Community Aerosol and Radiation Model for Atmospheres (CARMA), we determined that these variables can be described by a robust empirical formula. The characterized relationship allows an estimate of an altitude distribution of PMC effective radius in terms of local temperature andiwc. For our purposes we use this formula to predict an effective radius as part of a bulk parameterization of PMC microphysics in a 3-D GCCM to simulate growth, sublimation and sedimentation of ice particles without keeping track of the time history of each ice particle size or particle size bin. This allows cost effective decadal scale PMC simulations in a 3-D GCCM to be performed. This approach produces realistic PMC simulations including estimates of the optical properties of PMCs. We validate the relationship with PMC data from the Solar Occultation for Ice Experiment (SOFIE)."
"7004022660;7102653983;7101688723;7006508549;","Land use change suppresses precipitation",2009,"10.5194/acp-9-6531-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71849117529&doi=10.5194%2facp-9-6531-2009&partnerID=40&md5=d7404f88c620e2244da252e4e5fec956","A feedback loop between regional scale deforestation and climate change was investigated in an experiment using novel, small size airborne platforms and instrument setups. Experiments were performed in a worldwide unique natural laboratory in Western Australia, characterized by two adjacent homogeneous observation areas with distinctly different land use characteristics. Conversion of several ten thousand square km of forests into agricultural land began more than a century ago. Changes in albedo, surface roughness, the soil water budget and the planetary boundary layer evolved over decades. Besides different meteorology, we found a significant up to now overlooked source of aerosol over the agriculture area. The enhanced number of cloud condensation nuclei is coupled through the hydrological groundwater cycle with deforestation. Modification of surface properties and aerosol number concentrations are key factors for the observed reduction of precipitation. The results document the importance of aerosol indirect effects on climate due to nanometer size biogenic aerosol and human impact on aerosol sources."
"13406672500;7404544551;","Air pollution, greenhouse gases and climate change: Global and regional perspectives",2009,"10.1016/j.atmosenv.2008.09.063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56449092027&doi=10.1016%2fj.atmosenv.2008.09.063&partnerID=40&md5=52c27b356d46948c1cd650ffb12042cc","Greenhouse gases (GHGs) warm the surface and the atmosphere with significant implications for rainfall, retreat of glaciers and sea ice, sea level, among other factors. About 30 years ago, it was recognized that the increase in tropospheric ozone from air pollution (NOx, CO and others) is an important greenhouse forcing term. In addition, the recognition of chlorofluorocarbons (CFCs) on stratospheric ozone and its climate effects linked chemistry and climate strongly. What is less recognized, however, is a comparably major global problem dealing with air pollution. Until about ten years ago, air pollution was thought to be just an urban or a local problem. But new data have revealed that air pollution is transported across continents and ocean basins due to fast long-range transport, resulting in trans-oceanic and trans-continental plumes of atmospheric brown clouds (ABCs) containing sub micron size particles, i.e., aerosols. ABCs intercept sunlight by absorbing as well as reflecting it, both of which lead to a large surface dimming. The dimming effect is enhanced further because aerosols may nucleate more cloud droplets, which makes the clouds reflect more solar radiation. The dimming has a surface cooling effect and decreases evaporation of moisture from the surface, thus slows down the hydrological cycle. On the other hand, absorption of solar radiation by black carbon and some organics increase atmospheric heating and tend to amplify greenhouse warming of the atmosphere. ABCs are concentrated in regional and mega-city hot spots. Long-range transport from these hot spots causes widespread plumes over the adjacent oceans. Such a pattern of regionally concentrated surface dimming and atmospheric solar heating, accompanied by widespread dimming over the oceans, gives rise to large regional effects. Only during the last decade, we have begun to comprehend the surprisingly large regional impacts. In S. Asia and N. Africa, the large north-south gradient in the ABC dimming has altered both the north-south gradients in sea surface temperatures and land-ocean contrast in surface temperatures, which in turn slow down the monsoon circulation and decrease rainfall over the continents. On the other hand, heating by black carbon warms the atmosphere at elevated levels from 2 to 6 km, where most tropical glaciers are located, thus strengthening the effect of GHGs on retreat of snow packs and glaciers in the Hindu Kush-Himalaya-Tibetan glaciers. Globally, the surface cooling effect of ABCs may have masked as much 47% of the global warming by greenhouse gases, with an uncertainty range of 20-80%. This presents a dilemma since efforts to curb air pollution may unmask the ABC cooling effect and enhance the surface warming. Thus efforts to reduce GHGs and air pollution should be done under one common framework. The uncertainties in our understanding of the ABC effects are large, but we are discovering new ways in which human activities are changing the climate and the environment. © 2008 Elsevier Ltd. All rights reserved."
"26632088400;","The sun's role regulating the earth's climate dynamics",2009,"10.1260/095830509787689196","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65849144900&doi=10.1260%2f095830509787689196&partnerID=40&md5=d04e29a8a68b2234d4119d3091057445","This paper introduces this thesis: The Sun-Earth system is electromagnetically, magneto-hydrodynamically and gravitationally coupled, dominated by significant non-linear, non-stationary interactions, which vary over time and throughout the three-dimensional structure of the Earth, its atmosphere and oceans. The essential elements of the Sun-Earth system are the solar dynamo, the heliosphere, the lunisolar tides, the Earth's inner and outer cores, mantle, crust, magnetosphere, oceans and atmosphere. The Sun-Earth system is non-ergodic (i.e. characterised by continuous change, complexity, disorder, improbability, spontaneity, connectivity and the unexpected). Climate dynamics, therefore, are non-ergodic, with highly variable climatological features at any one time. A theoretical framework for considering the role of the Sun in relation to the Earth's climate dynamics is outlined and ways in which the Sun affects climate reviewed. The forcing sources (independent variables) that influence climate processes (dependent variables) are analysed. This theoretical framework shows clearly the interaction effects between and amongst the two classes of variables. These seem to have the greatest effect on climate dynamics. Climate processes are interconnected and oscillating, yielding variable periodicities. Solar processes, especially when interacting, amplify or dampen these periodicities producing distinctive climatic cycles. As solar and climate processes are non-linear, non-stationary and non-ergodic, appropriate analytic methodologies are necessary to reveal satisfactorily solar/climate relationships."
[No author id available],"Focus on climate engineering: Intentional intervention in the climate system",2009,"10.1088/1748-9326/4/4/045101","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149108868&doi=10.1088%2f1748-9326%2f4%2f4%2f045101&partnerID=40&md5=fdb83d917d7cb119483fa9b28c48eacd","Geoengineering techniques for countering climate change have been receiving much press recently as a 'Plan B' if a global deal to tackle climate change is not agreed at the COP15 negotiations in Copenhagen this December. However, the field is controversial as the methods may have unforeseen consequences, potentially making temperatures rise in some regions or reducing rainfall, and many aspects remain under-researched. This focus issue of Environmental Research Letters is a collection of research articles, invited by David Keith, University of Calgary, and Ken Caldeira, Carnegie Institution, that present and evaluate different methods for engineering the Earth's climate. Not only do the letters in this issue highlight various methods of climate engineering but they also detail the arguments for and against climate engineering as a concept. Further reading Focus on Geoengineering at http://environmentalresearchweb.org/ cws/subject/tag=geoengineering IOP Conference Series: Earth and Environmental Science is an open-access proceedings service available at www.iop.org/EJ/ journal/ees Focus on Climate Engineering: Intentional Intervention in the Climate System Contents Modification of cirrus clouds to reduce global warming David L Mitchell and William Finnegan Climate engineering and the risk of rapid climate change Andrew Ross and H Damon Matthews Researching geoengineering: should not or could not? Martin Bunzl Of mongooses and mitigation: ecological analogues to geoengineering H Damon Matthews and Sarah E Turner Toward ethical norms and institutions for climate engineering research David R Morrow, Robert E Kopp and Michael Oppenheimer On the possible use of geoengineering to moderate specific climate change impacts Michael C MacCracken This focus issue is not yet complete, there are still letters at press and in review. © 2009 IOP Publishing Ltd."
"57193017893;7402480218;7202048112;7003495982;7005877775;7103373860;7003666669;56228672600;","Evaluating regional cloud-permitting simulations of the WRF model for the Tropical Warm Pool International Cloud Experiment (TWP-ICE), Darwin, 2006",2009,"10.1029/2009JD012729","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049125308&doi=10.1029%2f2009JD012729&partnerID=40&md5=5eb4e12717f706dd5dccaecccb332851","Data from the Tropical Warm Pool International Cloud Experiment (TWP-ICE) were used to evaluate Weather Research and Forecasting (WRF) model simulations with foci on the performance of three six-class bulk microphysical parameterizations (BMPs). Before the comparison with data from TWP-ICE, a suite of WRF simulations were carried out under an idealized condition, in which the other physical parameterizations were turned off. The idealized simulations were intended to examine the interaction of BMP at a ""cloud-resolving"" scale (250 m) with the nonhydrostatic dynamic core of the WRF model. The other suite of nested WRF simulations was targeted on the objective analysis of TWP-ICE at a ""cloud-permitting"" scale (quasi-convective resolving, 4 km). Wide ranges of discrepancies exist among the three BMPs when compared with ground-based and satellite remote sensing retrievals for TWP-ICE. Although many processes and associated parameters may influence clouds, it is strongly believed that atmospheric processes fundamentally govern the cloud feedbacks through the interactions between the atmospheric circulations, cloudiness, and the radiative and latent heating of the atmosphere. Based on the idealized experiments, we suggest that the discrepancy is a result of the different treatment of ice-phase microphysical processes (e.g., cloud ice, snow, and graupel). Because of the turn-off of the radiation and other physical parameterizations, the cloud radiation feedback is not studied in idealized experiments. On the other hand, the ""cloud-permitting"" experiments engage all physical parameterizations in the WRF model so that the radiative heating processes are considered together with other physical processes. Common features between these two experiment suites indicate that the major discrepancies among the three BMPs are similar. This strongly suggests the importance of ice-phase microphysics. To isolate the influence of cloud radiation feedback, we further carried out an additional suite of simulations, which turns off the interactions between cloud and radiation schemes. It is found that the cloud radiation feedback plays a secondary, but nonnegligible role in contributing to the wide range of discrepancies among the three BMPs. 2009 by the American Geophysical Union."
"26643250500;57202531041;7003535176;56284543100;55893487700;57202596578;","Aerodynamic contrails: Microphysics and optical properties",2009,"10.1175/2008JAS2768.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549117008&doi=10.1175%2f2008JAS2768.1&partnerID=40&md5=24b0fa39d96c553d5b329522a9ea50d3","Aerodynamic contrails form when air flows across the wings of subsonic aircraft in cruise. During a short adiabatic expansion phase, high supersaturations trigger burstlike homogeneous ice formation on ambient liquid aerosol particles within a wing depth. Small particles freeze first because they equilibrate most rapidly. Ambient temperature is the key determinant of nascent aerodynamic contrail properties. Only above ∼232 K do they become visible (but optically thin). These temperatures are at the high end of those prevailing at tropical upper tropospheric flight levels of subsonic aircraft. In colder midlatitude conditions, aerodynamic contrails stay invisible and the very small ice particles formed quickly evaporate when exposed to small subsaturations, explaining why the formation of these contrails is rarely observed. After formation, aerodynamic contrails develop into contrail cirrus if air is supersaturated with respect to ice. This type of anthropogenic ice cloud adds to contrail cirrus derived from jet exhaust contrails and may become particularly important in the future because air traffic is projected to increase significantly in tropical and subtropical regions. Regardless of whether aerodynamically induced ice formation leads to persistent contrail cirrus, cruising aircraft may act as sources of potent heterogeneous ice nuclei by preactivating the insoluble fraction in atmospheric particle populations. Aerodynamic contrails and aerodynamically induced preactivation should therefore be studied experimentally and with global models to explore their potential to induce climate change. © 2009 American Meteorological Society."
"8942524900;7004469744;8942525300;35810775100;7004402705;","The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model",2009,"10.5194/acp-9-4131-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75649086888&doi=10.5194%2facp-9-4131-2009&partnerID=40&md5=64dc48332bba6dcc1378a353b58b0e32","Empirical relationships that link cloud droplet number (CDN) to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number). Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional ""correlation-relations"" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25-75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number) than predicted by the globally uniform empirical relations. CDNaerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions."
"35270436100;57217797946;14071389300;57206623770;","Decreasing trend of sunshine hours and related driving forces in North China",2009,"10.1007/s00704-008-0049-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649414586&doi=10.1007%2fs00704-008-0049-x&partnerID=40&md5=cf4ba8411dd6271e97faa6f3f902de81","Global dimming is currently an active area of research in climate change. Trends of temporal (on the order of decades, years, seasons or even months) and spatial patterns in sunshine hours and associated climatic factors (average air temperature, relative humidity, precipitation and wind speed) over North China are evaluated for the period 1965∼1999 based on data from 81 standard meteorological stations. The results show that: (1) North China is experiencing decreasing sunshine hours (-82.855 h/decade); (2) seasonally, decline in sunshine hours is highest in summer and lowest in winter; (3) spatially, decrease in sunshine hours is highest in inland and plain regions and lowest in the northwest mountain and coastland regions; (4) sunshine hours have a high correlation with precipitation, relative humidity and wind speed, with wind speed having the strongest influence on sunshine hours implicit in the close correlation (temporally and spatially) between the two variables; (5) cloud cover could not be any significant driver of sunshine-hour decline because it is more or less stable; (6) spatially and seasonally, wind speed is an important driving factor of decreasing sunshine hours in North China. Furthermore, the interactions between wind speed and aerosol loading may be an enabling factor of wind speed in driving (strongly) the changes in sunshine hours. © Springer-Verlag 2008."
"6506784765;7004164175;","Relationship between holocene climate variations over Southern Greenland and Eastern Baffin Island and synoptic circulation pattern",2009,"10.5194/cp-5-347-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77049084061&doi=10.5194%2fcp-5-347-2009&partnerID=40&md5=49bf4b20733bc665ac9760bfd63f2a4b","Lake pollen records from southwest Greenland and eastern Baffin Island show strong regionalism in climate trends of the last 7000 cal years. July surface air temperature reconstructions from pollen indicate larger amplitude cooling in southwest Greenland (>3.0°C) than in eastern Baffin Island (<1.0°C). This west-east gradient in climate change is consistent with August sea-surface temperature reconstructions from dinocyst records that indicate decreasing temperature and/or strength of the North Atlantic Current to the east during the Holocene while the eastern Canadian margins under the Labrador Current influence display slight warming. Complementary to air and sea-surface temperature records, the lake pollen data led to reconstruct increased cloudiness in southern Greenland, which points to increasing cyclonic activity since 7000 cal years BP west of Greenland. Together, the terrestrial and marine records of the northwest North Atlantic therefore suggest a shift from a dominant NAO+ during the early-mid Holocene to dominant NAO- in the late Holocene."
"7004637798;25634836400;","The radiative forcing potential of different climate geoengineering options",2009,"10.5194/acp-9-5539-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75249091885&doi=10.5194%2facp-9-5539-2009&partnerID=40&md5=4b809c7991c2418c0ecc004ecc3a8cef","Climate geoengineering proposals seek to rectify the Earth's current and potential future radiative imbalance, either by reducing the absorption of incoming solar (shortwave) radiation, or by removing CO2 from the atmosphere and transferring it to long-lived reservoirs, thus increasing outgoing longwave radiation. A fundamental criterion for evaluating geoengineering options is their climate cooling effectiveness, which we quantify here in terms of radiative forcing potential. We use a simple analytical approach, based on energy balance considerations and pulse response functions for the decay of CO2 perturbations. This aids transparency compared to calculations with complex numerical models, but is not intended to be definitive. It allows us to compare the relative effectiveness of a range of proposals. We consider geoengineering options as additional to large reductions in CO2 emissions. By 2050, some land carbon cycle geoengineering options could be of comparable magnitude to mitigation ""wedges"", but only stratospheric aerosol injections, albedo enhancement of marine stratocumulus clouds, or sunshades in space have the potential to cool the climate back toward its pre-industrial state. Strong mitigation, combined with global-scale air capture and storage, afforestation, and bio-char production, i.e. enhanced CO2 sinks, might be able to bring CO2 back to its pre-industrial level by 2100, thus removing the need for other geoengineering. Alternatively, strong mitigation stabilising CO2 at 500 ppm, combined with geoengineered increases in the albedo of marine stratiform clouds, grasslands, croplands and human settlements might achieve a patchy cancellation of radiative forcing. Ocean fertilisation options are only worthwhile if sustained on a millennial timescale and phosphorus addition may have greater long-term potential than iron or nitrogen fertilisation. Enhancing ocean upwelling or downwelling have trivial effects on any meaningful timescale. Our approach provides a common framework for the evaluation of climate geoengineering proposals, and our results should help inform the prioritisation of further research into them."
"56284543100;26643250500;","Process-based simulation of contrail cirrus in a global climate model",2009,"10.1029/2008JD011491","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70849110698&doi=10.1029%2f2008JD011491&partnerID=40&md5=7fc586bc516b6cd2568b471e45c015f5","[1] Aviation induces changes in global cirrus cloudiness by producing contrails. In the past, line shaped contrail coverage has been parameterized relying on the scaling of contrail formation frequency to observed values. Coverage due to irregularly shaped contrail cirrus, that develop from line shaped contrails, could not be estimated with this method. We introduce a process-based parameterization of contrail cirrus in a global climate model that does not rely on scaling and that is not restricted to line shaped contrails. A new prognostic cloud class, contrail cirrus, is introduced that is allowed to develop in the parameterized, fractional ice supersaturated area. Initial dimensions of the contrails and a parameter controlling their spreading in a sheared flow are constrained by observational data. In an idealized experiment contrail cirrus coverage is found to be dominated by a major contrail outbreak and scales with supersaturation rather than contrail formation frequency. The global distribution of young contrail coverage is smoothed out. due to transport but overall values are similar compared to older estimates. Interannual variability of young contrail coverage can be as large as the mean coverage. The sensitivity of the model simulations to physical model parameters and to parameters concerning the comparison with observational data is studied. The associated uncertainty of global line shaped contrail coverage can be as high as 60% of the reference estimate (0.05%). The simulated coverage due to young contrails agrees reasonably well with most satellite observations of regional line shaped contrail coverage considering the sensitivity to the above parameters and the interannual variability. Copyright 2009 by the American Geophysical Union."
"7401501923;7004587891;7201634460;","Using AVHRR lunar observations for NDVI long-term climate change detection",2009,"10.1029/2009JD012179","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049103694&doi=10.1029%2f2009JD012179&partnerID=40&md5=daa67e6a5fd656c718c489b916f447c6","The Moon is believed to be an irrefutably stable calibration reference target for studying climate change from satellites, as demonstrated in several lunar calibration studies of satellite radiometers. However, the potential of using advanced very high resolution radiometer (AVHRR) lunar observations for climate change detection has not been recognized in the past. At the same time, it is known that despite past efforts, there are still significant uncertainties in determining the long-term trend of climate change using such indices as the Normalized Difference Vegetation Index (NDVI), partly because most AVHRR calibrations to date lack the stability required for climate change detection. This study demonstrates a novel method using the AVHRR lunar band ratio as a stability reference for long-term NDVI change detection. It shows that despite the incomplete lunar observations and complex space view mechanisms, the AVHRR lunar observations can be used to ensure the stability of the Earth observations at a better than ±1% (1 sigma) level for the lifetime of the AVHRR instrument in the long-term detection of NDVI trends. This method is compared with the Vennote and Kaufman high-altitude bright cloud method used by the NASA Long-Term Data Record (LTDR) project, and preliminary results are very encouraging. The lunar band ratio method has been tested for NOAA 11,14, and 16 AVHRR and is applicable to all AVHRRs since the early 1980s. It is conceived that the Lunar Band Ratio serves as an important stability reference for ensuring the long-term confidence for the detection of climate change. The AVHRR lunar band ratio is also useful for deriving the calibration for the problematic band 2 from that of band 1 for establishing a consistent AVHRR fundamental climate data record for a variety of climate applications. Copyright 2009 by the American Geophysical Union."
"7006450978;57196706568;56308509200;35618476300;7202957110;6506986083;6701409929;","Lightning characteristics observed by a VLF/LF lightning detection network (LINET) in Brazil, Australia, Africa and Germany",2009,"10.5194/acp-9-7795-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950450569&doi=10.5194%2facp-9-7795-2009&partnerID=40&md5=1d9121602fe9550c16d4376851434d72","This paper describes lightning characteristics as obtained in four sets of lightning measurements during recent field campaigns in different parts of the world from mid-latitudes to the tropics by the novel VLF/LF (very low frequency/low frequency) lightning detection network (LINET). The paper gives a general overview on the approach, and a synopsis of the statistical results for the observation periods as a whole and for one special day in each region. The focus is on the characteristics of lightning which can specifically be observed by this system like intra-cloud and cloud-to-ground stroke statistics, vertical distributions of intra-cloud strokes or peak current distributions. Some conclusions regarding lightning produced NOx are also presented as this was one of the aims of the tropical field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides Experiment) and TroCCiBras (Tropical Convection and Cirrus Experiment Brazil) in Brazil during January/February 2005, SCOUTO3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere) and TWP-ICE (Tropical Warm Pool-International Cloud Experiment) during November/December 2005 and January/February 2006, respectively, in the Darwin area in N-Australia, and of AMMA (African Monsoon Multidisciplinary Analyses) in W-Africa during June-November 2006."
"55701363700;26324818700;","A new framework for isolating individual feedback processes in coupled general circulation climate models. Part I: Formulation",2009,"10.1007/s00382-008-0425-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62549092681&doi=10.1007%2fs00382-008-0425-3&partnerID=40&md5=c2ecc03f2da08ac541b4ed8ae86675fe","This paper proposes a coupled atmosphere - surface climate feedback - response analysis method (CFRAM) as a new framework for estimating climate feedbacks in coupled general circulation models with a full set of physical parameterization packages. The formulation of the CFRAM is based on the energy balance in an atmosphere - surface column. In the CFRAM, the isolation of partial temperature changes due to an external forcing or an individual feedback is achieved by solving the linearized infrared radiation transfer model subject to individual energy flux perturbations (external or due to feedbacks). The partial temperature changes are addable and their sum is equal to the (total) temperature change (in the linear sense). The decomposition of feedbacks is based on the thermodynamic and dynamical processes that directly affect individual energy flux terms. Therefore, not only those feedbacks that directly affect the TOA radiative fluxes, such as water vapor, clouds, and ice-albedo feedbacks, but also those feedbacks that do not directly affect the TOA radiation, such as evaporation, convections, and convergence of horizontal sensible and latent heat fluxes, are explicitly included in the CFRAM. In the CFRAM, the feedback gain matrices measure the strength of individual feedbacks. The feedback gain matrices can be estimated from the energy flux perturbations inferred from individual parameterization packages and dynamical modules. The inter-model spread of a feedback gain matrix would help us to detect the origins of the uncertainty of future climate projections in climate model simulations. © Springer-Verlag 2008."
"57201124395;7006471143;6506848120;7401721553;8663598300;14045570100;8663598400;15726759700;6603213300;7005941217;6602208927;6603315547;","Ice supersaturations and cirrus cloud crystal numbers",2009,"10.5194/acp-9-3505-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749108347&doi=10.5194%2facp-9-3505-2009&partnerID=40&md5=8cf6171ec3233ae87262dc5511b64798","Upper tropospheric observations outside and inside of cirrus clouds indicate water vapour mixing ratios sometimes exceeding water saturation. Relative humidities over ice (RHice) of up to and more than 200% have been reported from aircraft and balloon measurements in recent years. From these observations a lively discussion continues on whether there is a lack of understanding of ice cloud microphysics or whether the water measurements are tainted with large uncertainties or flaws. Here, RHice in clear air and in ice clouds is investigated. Strict quality-checked aircraft in situ observations of RHice were performed during 28 flights in tropical, mid-latitude and Arctic field experiments in the temperature range 183-240 K. In our field measurements, no supersaturations above water saturation are found. Nevertheless, super-or subsaturations inside of cirrus are frequently observed at low temperatures (<205 K) in our field data set. To explain persistent RHice deviating from saturation, we analysed the number densities of ice crystals recorded during 20 flights. From the combined analysis-using conventional microphysics-of supersaturations and ice crystal numbers, we show that the high, persistent supersaturations observed inside of cirrus can possibly be explained by unexpected, frequent very low ice crystal numbers that could scarcely be caused by homogeneous ice nucleation. Heterogeneous ice formation or the suppression of freezing might better explain the observed ice crystal numbers. Thus, our lack of understanding of the high supersaturations, with implications for the microphysical and radiative properties of cirrus, the vertical redistribution of water and climate, is traced back to the understanding of the freezing process at low temperatures."
"56691914800;35196437900;8586682800;7005968859;7403401100;7005773698;","Effect of chemical mixing state on the hygroscopicity and cloud nucleation properties of calcium mineral dust particles",2009,"10.5194/acp-9-3303-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949170191&doi=10.5194%2facp-9-3303-2009&partnerID=40&md5=fa354961eb71528e9de7b43d7dc89fdb","Atmospheric mineral dust particles can alter cloud properties and thus climate by acting as cloud condensation nuclei (CCN) that form cloud droplets. The CCN activation properties of various calcium mineral dust particles were studied experimentally to investigate the consequences of field observations showing the segregation of sulphate from nitrate and chloride between individual aged Asian dust particles, and the enrichment of oxalic acid in Asian dust. Each mineral's observed apparent hygroscopicity was primarily controlled by its solubility, which determines the degree to which the mineral's intrinsic hygroscopicity can be expressed. The significant increase in hygroscopicity caused by mixing soluble hygroscopic material with insoluble mineral particles is also presented. Insoluble minerals including calcium carbonate, representing fresh unprocessed dust, and calcium sulphate, representing atmospherically processed dust, had similarly small apparent hygroscopicities. Their activation is accurately described by a deliquescence limit following the Kelvin effect and corresponded to an apparent single-hygroscopicity parameter, κ, of ∼0.001. Soluble calcium chloride and calcium nitrate, representing atmospherically processed mineral dust particles, were much more hygroscopic, activating similar to ammonium sulphate with κ ∼0.5. Calcium oxalate monohydrate (κ=0.05) was significantly less CCN-active than oxalic acid (κ=0.3), but not as inactive as its low solubility would predict. These results indicate that the common assumption that all mineral dust particles become more hygroscopic and CCN-active after atmospheric processing should be revisited. Calcium sulphate and calcium oxalate are two realistic proxies for aged mineral dust that remain non-hygroscopic. The dust's apparent hygroscopicity will be controlled by its chemical mixing state, which is determined by its mineralogy and the chemical reaction pathways it experiences during transport."
"57203052274;6602573827;","Effect of climate change on air quality",2009,"10.1016/j.atmosenv.2008.09.051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56449085618&doi=10.1016%2fj.atmosenv.2008.09.051&partnerID=40&md5=a70c46eaf8e304dd05e6f911635ff45e","Air quality is strongly dependent on weather and is therefore sensitive to climate change. Recent studies have provided estimates of this climate effect through correlations of air quality with meteorological variables, perturbation analyses in chemical transport models (CTMs), and CTM simulations driven by general circulation model (GCM) simulations of 21st-century climate change. We review these different approaches and their results. The future climate is expected to be more stagnant, due to a weaker global circulation and a decreasing frequency of mid-latitude cyclones. The observed correlation between surface ozone and temperature in polluted regions points to a detrimental effect of warming. Coupled GCM-CTM studies find that climate change alone will increase summertime surface ozone in polluted regions by 1-10 ppb over the coming decades, with the largest effects in urban areas and during pollution episodes. This climate penalty means that stronger emission controls will be needed to meet a given air quality standard. Higher water vapor in the future climate is expected to decrease the ozone background, so that pollution and background ozone have opposite sensitivities to climate change. The effect of climate change on particulate matter (PM) is more complicated and uncertain than for ozone. Precipitation frequency and mixing depth are important driving factors but projections for these variables are often unreliable. GCM-CTM studies find that climate change will affect PM concentrations in polluted environments by ±0.1-1 μg m-3 over the coming decades. Wildfires fueled by climate change could become an increasingly important PM source. Major issues that should be addressed in future research include the ability of GCMs to simulate regional air pollution meteorology and its sensitivity to climate change, the response of natural emissions to climate change, and the atmospheric chemistry of isoprene. Research needs to be undertaken on the effect of climate change on mercury, particularly in view of the potential for a large increase in mercury soil emissions driven by increased respiration in boreal ecosystems. © 2008 Elsevier Ltd."
"7102805852;7201443624;36186654000;35547807400;7202154370;8982748700;57197233116;12753162000;7004942632;7101838894;","A case study of the radiative forcing of persistent contrails evolving into contrail-induced cirrus",2009,"10.1029/2009JD012650","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954180902&doi=10.1029%2f2009JD012650&partnerID=40&md5=0be6b838b7e6781321ecf2d9d358dd3b","[1] The radiative forcing due to a distinct pattern of persistent contrails that form into contrail-induced cirrus near and over the UK is investigated in detail for a single case study during March 2009. The development of the contrail-induced cirrus is tracked using a number of high-resolution polar orbiting and lower-resolution geostationary satellite instruments and is found to persist for a period of around 18 h, and at its peak, it covers over 50,000 km<inf>2</inf>. The shortwave (SW) and longwave (LW) radiative forcing of the contrail-induced cirrus is estimated using a combination of geostationary satellite instruments, numerical weather prediction models, and surface observation sites. As expected, the net radiative effect is a relatively small residual of the much stronger but opposing SW and LW effects, locally totaling around 10 W m-2 during daylight hours and 30 W m-2 during nighttime. A simple estimate indicates that this single localized event may have generated a global-mean radiative forcing of around 7% of recent estimates of the persistent contrail radiative forcing due to the entire global aircraft fleet on a diurnally averaged basis. A single aircraft operating in conditions favorable for persistent contrail formation appears to exert a contrail-induced radiative forcing some 5000 times greater (in W m-2 km-1) than recent estimates of the average persistent contrail radiative forcing from the entire civil aviation fleet. This study emphasizes the need to establish whether similar events are common or highly unusual for a confident assessment of the total climate effect of aviation to be made. Copyright 2009 by the American Geophysical Union."
"7004027377;35609878300;7004864963;","Understanding the climate of Amazonia: Progress from LBA",2009,"10.1029/2009GM000903","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899828876&doi=10.1029%2f2009GM000903&partnerID=40&md5=5463cc53854d060a81e2258a4cea2cb9","The Amazon plays an important role in the functioning of the Earth's climate. It acts as one of the critical heat sources for the global atmosphere via evaporation of water vapor at the surface and release of heat in the middle and upper troposphere by latent heat of condensation in tropical convective clouds. Forest evaporation year-round is about 3 to 3.5 mm d-1. In contrast, for savanna regions bordering the Amazon forest, evaporation is reduced during the dry season because of the limitation of soil moisture. Deforestation causes a large reduction in dry season evaporation. The cloudiness-rainfall regime of the undisturbed forest is similar to that of a tropical ocean, which led us to call the Amazon Basin a ""green ocean."" Biogenic volatile organic compounds are released by the forest into the atmosphere, where some play an important role in providing aerosols and cloud condensation nuclei. On the other hand, aerosols emitted by biomass burning may cause reduction of rainfall. Together the chapters in this section reveal a complex mix of interacting processes that acting in concert control the movement and composition of the atmosphere above Amazonia. Each separate study reveals some new insight into one facet, but together they reveal an integrated system in which change in one component will produce impacts in another. The most important message is that deforestation is not just a change in land use, but it impacts the functioning of the Amazonian ecosystem itself. Changes in the evaporation and the chemical composition of the atmosphere produce changes in the cloud physics and in the dynamics and thermodynamics of the atmospheric circulation. These, in turn, impact the rainfall and the hydrological cycle. © Copyright 2009 by the American Geophysical Union."
"35755764700;6603183022;7003975505;","Warm Paleocene/Eocene climate as simulated in ECHAM5/MPI-OM",2009,"10.5194/cp-5-785-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949711256&doi=10.5194%2fcp-5-785-2009&partnerID=40&md5=0b8eb5e7bdda5235e5f6d32201dcc1e5","We investigate the late Paleocene/early Eocene (PE) climate using the coupled atmosphere-ocean-sea ice model ECHAM5/MPI-OM. The surface in our PE control simulation is on average 297K warm and ice-free, despite a moderate atmospheric CO2 concentration of 560 ppm. Compared to a pre-industrial reference simulation (PR), low latitudes are 5 to 8K warmer, while high latitudes are up to 40K warmer. This high-latitude amplification is in line with proxy data, yet a comparison to sea surface temperature proxy data suggests that the Arctic surface temperatures are still too low in our PE simulation. To identify the mechanisms that cause the PE-PR surface temperature differences, we fit two simple energy balance models to the ECHAM5/MPI-OM results. We find that about 2/3 of the PE-PR global mean surface temperature difference are caused by a smaller clear sky emissivity due to higher atmospheric CO2 and water vapour concentrations in PE compared to PR; 1/3 is due to a smaller planetary albedo. The reduction of the pole-to-equator temperature gradient in PE compared to PR is due to (1) the large high-latitude effect of the higher CO2 and water vapour concentrations in PE compared to PR, (2) the lower Antarctic orography, (3) the smaller surface albedo at high latitudes, and (4) longwave cloud radiative effects. Our results support the hypothesis that local radiative effects rather than increased meridional heat transports were responsible for the ""equable"" PE climate. © Author(s) 2009."
"7004864963;57211811362;23028870700;18133452600;57212284765;7006523532;57147088000;35461763400;7005399437;35501613900;7103011104;13408773700;","Aerosol particles in Amazonia: Their composition, role in the radiation balance, cloud formation, and nutrient cycles",2009,"10.1029/2008GM000778","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899884517&doi=10.1029%2f2008GM000778&partnerID=40&md5=8686e8f12fbe806d9082d28d283f962f","The atmosphere above tropical forests plays a very active part in the biogeochemical cycles that are critically important for the processes that maintain the ecosystem, including processes involving the vegetation, soil, hydrology, and atmospheric composition. Aerosol particles control key ingredients of the climatic and ecological environment in Amazonia. The radiative balance is strongly influenced by the direct and indirect radiative forcing of aerosol particles. Nutrient cycling is partially controlled by dry and wet deposition of key plant nutrients. It was observed that the aerosol particles that act as cloud condensation nuclei influence cloud formation and dynamics, having the potential to change precipitation regimes over Amazonia. The 10-year-long record of aerosol optical thickness measurements in Amazonia shows a strongly negative radiative forcing of -37 W m-2 averaged over 7 years of dry season measurements in Alta Floresta. There is a strong influence of biomass-burning aerosols on the cloud microphysical properties during the dry season. The connections between the amount of aerosol particles and carbon uptake trough photosynthesis highlighted the close connection between forest natural processes and the aerosol loading in the atmosphere. Climate change combined with socioeconomic drivers could alter significantly the emission of trace gases, aerosols, and water vapor fluxes from the forest to the atmosphere. It is a vital task to quickly reduce Amazonian deforestation rates, and to implement solid and long-term conservation policies in Amazonia. © Copyright 2009 by the American Geophysical Union."
"6506923564;27267784900;6602174536;23395816000;","The influence of atmospheric circulation and cloudiness on the intensity of temperature inversions in Sosnowiec (Upper Silesia, Southern Poland)",2009,"10.1504/IJEWM.2009.026881","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650432880&doi=10.1504%2fIJEWM.2009.026881&partnerID=40&md5=a4d7d699ac3082f1653892c16978bd5f","The paper presents research results of the thermal structure of the near-ground atmospheric layer (100 m) carried out in the years 1993-2005 in Sosnowiec. It is a city located in the central part of the most urbanised and industrialised Katowice Region in Poland. Research of seasonal changes in the frequency of near-ground inversions of temperature revealed their most frequent occurrence on clear winter days. In this season, temperature inversions can sometimes persist for the whole day and night. Air temperature inversions over Sosnowiec occur mainly during anticyclonic stagnation (Ca-anticyclone centre and Ka-anticyclonic ridge) and in anticyclones with air advection from the south and southwest (Sa and SWa). Copyright © 2009, Inderscience Publishers."
"7201479825;7103056450;7005913397;6603621543;23970271800;7004013739;7801344746;24279614600;6507040878;6507515551;6701410329;7401782141;7201472576;7004047492;36523706800;22935251000;24280225800;15726335100;57217975169;56953593400;7402305181;6505511524;24340241400;6603129558;","Operational climate monitoring from space: The EUMETSAT satellite application facility on climate monitoring (CM-SAF)",2009,"10.5194/acp-9-1687-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76149086202&doi=10.5194%2facp-9-1687-2009&partnerID=40&md5=d3f725e32401d98ba0ec642128e4d964","The Satellite Application Facility on Climate Monitoring (CM-SAF) aims at the provision of satellitederived geophysical parameter data sets suitable for climate monitoring. CM-SAF provides climatologies for Essential Climate Variables (ECV), as required by the Global Climate Observing System implementation plan in support of the UNFCCC. Several cloud parameters, surface albedo, radiation fluxes at the top of the atmosphere and at the surface as well as atmospheric temperature and humidity products form a sound basis for climate monitoring of the atmosphere. The products are categorized in monitoring data sets obtained in near real time and data sets based on carefully intercalibrated radiances. The CM-SAF products are derived from several instruments on-board operational satellites in geostationary and polar orbit as the Meteosat and NOAA satellites, respectively. The existing data sets will be continued using data from the instruments on-board the new joint NOAA/EUMETSAT Meteorological Operational Polar satellite. The products have mostly been validated against several ground-based data sets both in situ and remotely sensed. The accomplished accuracy for products derived in near real time is sufficient to monitor variability on diurnal and seasonal scales. The demands on accuracy increase the longer the considered time scale is. Thus, interannual variability or trends can only be assessed if the sensor data are corrected for jumps created by instrument changes on successive satellites and more subtle effects like instrument and orbit drift and also changes to the spectral response function of an instrument. Thus, a central goal of the recently started Continuous Development and Operations Phase of the CM-SAF (2007-2012) is to further improve all CM-SAF data products to a quality level that allows for studies of interannual variability."
"6602600408;7006306835;7201837768;7202079615;56162305900;7102604282;25031430500;57203053317;10139397300;57203200427;18635289400;56920790500;14035836100;7003591311;24398842400;35183351400;55717074000;6701597468;7103271625;57208462871;57208121852;35221443100;7003931528;6603140753;22978151200;56249704400;7103353990;35221524700;56250250300;12139310900;7006270084;7003666669;7006705919;7103158465;7102976560;7003311618;56270311300;57205638870;","Aerosol indirect effects ĝ€"" general circulation model intercomparison and evaluation with satellite data",2009,"10.5194/acp-9-8697-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450257537&doi=10.5194%2facp-9-8697-2009&partnerID=40&md5=e73ec0fd8f381e057a288edbc08cafd8","Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (&amp;tau; a) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between &amp;tau;a and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and &amp;tau; a as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strongfcldĝ€""&amp;tau;a relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between &amp;tau;a and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLRĝ€""&amp;tau; a relationship show a strong positive correlation between &amp;tau;a andf&lt;/ i&gt;cld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of &amp;tau;a, and parameterisation assumptions such as a lower bound onNd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of &amp;minus;1.5&amp;plusmn;0.5 Wm&amp;minus;2. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic &amp;tau;a and satellite-retrievedNd&lt;/ i&gt;ĝ€""&amp;tau;a regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of &amp;minus;0.4&amp;plusmn;0.2 Wm&amp;minus;2 and a cloudy-sky (aerosol indirect effect) estimate of &amp;minus;0.7&amp;plusmn;0.5 Wm&amp;minus;2, with a total estimate of &amp;minus;1.2&amp;plusmn;0. 4 Wm&amp;minus;2."
"7003465505;7201498373;8374319200;7004126618;8701382700;","Effects of global irrigation on the near-surface climate",2009,"10.1007/s00382-008-0445-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649183532&doi=10.1007%2fs00382-008-0445-z&partnerID=40&md5=4cbd1928a3560f9576857930fa15c12a","Irrigation delivers about 2,600 km3 of water to the land surface each year, or about 2% of annual precipitation over land. We investigated how this redistribution of water affects the global climate, focusing on its effects on near-surface temperatures. Using the Community Atmosphere Model (CAM) coupled to the Community Land Model (CLM), we compared global simulations with and without irrigation. To approximate actual irrigation amounts and locations as closely as possible, we used national-level census data of agricultural water withdrawals, disaggregated with maps of croplands, areas equipped for irrigation, and climatic water deficits. We further investigated the sensitivity of our results to the timing and spatial extent of irrigation. We found that irrigation alters climate significantly in some regions, but has a negligible effect on global-average near-surface temperatures. Irrigation cooled the northern mid-latitudes; the central and southeast United States, portions of southeast China and portions of southern and southeast Asia cooled by ∼0.5 K averaged over the year. Much of northern Canada, on the other hand, warmed by ∼1 K. The cooling effect of irrigation seemed to be dominated by indirect effects like an increase in cloud cover, rather than by direct evaporative cooling. The regional effects of irrigation were as large as those seen in previous studies of land cover change, showing that changes in land management can be as important as changes in land cover in terms of their climatic effects. Our results were sensitive to the area of irrigation, but were insensitive to the details of irrigation timing and delivery. © Springer-Verlag 2008."
"7103004004;55087038900;","Hadley cell widening: Model simulations versus observations",2009,"10.1175/2008JCLI2620.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878135047&doi=10.1175%2f2008JCLI2620.1&partnerID=40&md5=1886b2b5afe54e85853d5ff049e43113","Observations show that the Hadley cell has widened by about 2°-5° since 1979. This widening and the concomitant poleward displacement of the subtropical dry zones may be accompanied by large-scale drying near 30°N and 30°S. Such drying poses a risk to inhabitants of these regions who are accustomed to established rainfall patterns. Simple and comprehensive general circulation models (GCMs) indicate that the Hadley cell may widen in response to global warming, warming of the west Pacific, or polar stratospheric cooling. The combination of these factorsmaybe responsible for the recent observations. But there is no study so far that has compared the observed widening to GCM simulations of twentieth-century climate integrated with historical changes in forcings. Here the Hadley cell widening is assessed in current GCMs from historical simulations of the twentieth century as well as future climate projections and preindustrial control runs. The authors find that observed widening cannot be explained by natural variability.This observedwidening is also significantly larger than in simulations of the twentieth and twenty-first centuries. These results illustrate the need for further investigation into the discrepancy between the observed and simulated widening of the Hadley cell. © 2009 American Meteorological Society."
"7005742394;","Simulation of a supercell storm in clean and dirty atmosphere using weather research and forecast model with spectral bin microphysics",2009,"10.1029/2009JD011827","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049087777&doi=10.1029%2f2009JD011827&partnerID=40&md5=d5c47341454d0a3d0ecbcd508adccd4e","The development of supercell storms was simulated using a 2-km-resolution weather research and forecast (WRF) model with spectral (bin) microphysics (WRF-SBM) and a recent version of the Thompson bulk-parameterization scheme. The simulations were performed in clean, semipolluted, and dirty air under two values of relative humidity, conditionally referred to as low and high humidity. Both SBM and the Thompson scheme simulated the development of supercell storm with storm splitting. Both SBM and the Thompson scheme demonstrated that an increase in relative humidity by ∼10% invigorates convection and increases precipitation by factor of 2, i.e., to much larger extent than can be achieved by variations of the aerosol concentration. At the same time the storms simulated by the schemes are quite different. The maximum updrafts in the Thompson scheme are about 65 m/s, and the left-moving storm prevails. The SBM predicts 35 m/s maximum updrafts, and the right-moving storm prevails in the SBM simulations. While the bulk scheme predicts decrease in precipitation in clean air at both low and high humidity, the SBM indicates decrease precipitation in polluted air under low humidity and increase in precipitation under high humidity. The SBM scheme shows a substantial effect of aerosols on spatial distribution of precipitation, especially in the low-humidity case. The sensitivity of the Thompson scheme to aerosols turns out to be much less than that of SBM. The difference in the results (vertical velocities, microphysical cloud structure, and precipitation) obtained by different schemes is much larger than the changes caused by variation of the aerosol concentration within each scheme. However, the average amount of precipitation in the Thompson scheme in each simulation was about twice that of the corresponding SBM simulation. The possible reasons for such difference are discussed. A scheme for classifying aerosol effects on precipitation from clouds and cloud systems is also discussed.Copyright 2009 by the American Geophysical Union."
"6603785227;10144282600;35461763400;6604054503;7004864963;","Biomass burning in Amazonia: Emissions, long-range transport of smoke and its regional and remote impacts",2009,"10.1029/2008GM000847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650334092&doi=10.1029%2f2008GM000847&partnerID=40&md5=0676339a31dd2789e01b648f6a77b846","Every year, biomass burning in Amazonia continues to release large amounts of trace gases and aerosol particles into the atmosphere. The consequent change from low to very high atmospheric concentrations of oxidants and aerosols therefore affects the radiative, cloud physical, and chemical properties of the atmosphere over Amazonia. This represents a dramatic perturbation to the regional climate, ecology, water cycle, and human activities. Given the magnitude of burning in Amazonia and the efficiency of the atmospheric transport processes of fire emissions, these perturbations can affect the climate system even on a global scale. This chapter summarizes the knowledge acquired in the ambit of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia program about vegetation fire as a driving force of atmospheric disturbances over Amazonia. We describe the different fire behaviors for the region and present an updated review of emission and combustion factors for Amazonia. We discuss some of the available biomassburning emission inventories for the Amazonian region, discussing their assets and limitations. We further discuss atmospheric transport processes that are the main drivers of the dispersion of fire emissions, introduce the most relevant concepts for numerical modeling of smoke transport, and show the general pattern of smoke transport over the South American continent. Finally, we present the current status of the understanding of local and remote impacts of smoke trace gases and aerosol particles, discussing the oxidizing power of the Amazonian atmosphere, as well as the radiation and heat budgets and consequences on cloud properties and distribution. © Copyright 2009 by the American Geophysical Union."
"6506730133;55919935700;7004416203;16479703400;","Implications of lagrangian transport for simulations with a coupled chemistry-climate model",2009,"10.5194/acp-9-5489-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149112410&doi=10.5194%2facp-9-5489-2009&partnerID=40&md5=9116adc23ab64dcb293ddd1e6e9b7c11","For the first time a purely Lagrangian transport algorithm is applied in a fully coupled chemistry-climate model (CCM). We use the numerically non-diffusive Lagrangian scheme ATTILA instead of the operational semi-Lagrangian scheme for the transport of water vapour, cloud water and chemical trace species in the CCM E39C. The new model version including the Lagrangian scheme is referred to as E39C-A. The implications of the Lagrangian transport scheme for stratospheric model dynamics and tracer distributions in E39C-A are evaluated by comparison with observations and results of the previous model version E39C. We found in a previous paper that several deficiencies in stratospheric dynamics in E39C originate from a pronounced modelled wet bias and an associated cold bias in the extra-tropical lowermost stratosphere. Contrary to the semi-Lagrangian scheme ATTILA shows a largely reduced meridional transport of water vapour from the tropical upper troposphere into the extratropical lowermost stratosphere. The reduction of the moisture and temperature bias in E39C-A leads to a significant advancement of stratospheric dynamics in terms of the mean state as well as annual and interannual variability. In this study we show that as a consequence of both, the favourable numerical characteristics of the Lagrangian transport scheme and the improved model dynamics, E39C-A generally shows more realistic distributions of chemical trace species: Compared to E39C high stratospheric chlorine (Cly) concentrations extend further downward. Therefore E39C-A realistically covers the altitude of maximum ozone depletion in the stratosphere. The location of the ozonopause, i.e. the transition from low tropospheric to high stratospheric ozone values, is also clearly improved in E39C-A. Not only the spatial distribution but also the temporal evolution of stratospheric Cly in the past is realistically reproduced in E39C-A which is an important step towards a more reliable projection of future changes, especially of stratospheric ozone. Despite a large number of improvements there are still remaining model deficiencies like a general overestimation of total column ozone."
"6603433259;","Mesoscale vegetation-atmosphere feedbacks in Amazonia",2009,"10.1029/2009JDO12001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049091995&doi=10.1029%2f2009JDO12001&partnerID=40&md5=14b65c9f65e439e8c8c7e4fee9415621","This paper investigates vegetation-climate interactions in disturbed rain forests of Amazonia. The scientific objective of this paper is twofold. The first goal is to reconcile the discrepancy between the decrease in precipitation predicted by general circulation models and the observed increase in precipitation due to deforestation in Rondonia. Numerical experiments with the Regional Atmospheric Modeling System (RAMS) show that sharp gradients in land cover due to fishbone deforestation trigger organized mesoscale circulations, leading to more clouds and rain over the deforested patches. The second goal is to develop and implement a modeling framework to identify and explore the fundamental pathways involved in deforestation-climate feedback over seasonal timescales. For this purpose, RAMS model outputs are combined with tower observations to develop a synthetic meteorological data set representing the impacts of deforestation on local hydrometeorology. A vegetation model forced by these data shows that extra rain promotes plant growth in the deforested patches during the water-limited dry season. This phenomenon constitutes a seasonal-scale ""negative feedback"" because accelerated vegetation recovery compensates for the effects of deforestation. This paper suggests that the regional climate observation infrastructure must be upgraded to resolve mesoscale feedbacks to accurately estimate the impact of deforestation in Amazonia. Moreover, these findings can significantly improve our understanding of ecosystem resiliency in disturbed tropical forests. Copyright 2009 by the American Geophysical Union."
"6701363731;25647261400;25647638100;6602712032;7003286544;7004533232;","A sensitivity study of the Regional Climate Model (RegCM3) to the convective scheme with emphasis in central eastern and southeastern Europe",2009,"10.1007/s00704-008-0075-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68349101198&doi=10.1007%2fs00704-008-0075-8&partnerID=40&md5=d9bb474f59a986c3dee870785ccbfb53","Regional climate simulations have been performed over the greater European area for 3 years using three convective parameterizations: (a) the Grell scheme with Arakawa-Schubert (AS) closure assumption, (b) the Grell scheme with Fritsch-Chappell (FC) closure assumption and (c) the MIT scheme. The comparison of the model results of near-surface temperature with near-surface temperature observations indicates a cold bias with both Grell scheme configurations. This bias is significantly reduced when the MIT convective scheme is introduced, even during months of low convective activity. The temperature differences between the Grell (with either AS or FC closure schemes) and the MIT scheme are largest in the lower troposphere, extending up to 700 hPa. In terms of total precipitation, no systematical differences between Grell and MIT schemes are observed throughout the year for the European domain but the convective portion of total precipitation is greater in the MIT scheme simulations. For the central Eastern Europe region, MIT scheme simulations generally produce more precipitation during the warm season than Grell simulations, while for the southern Eastern Europe region, the MIT precipitation enhancement is small and not systematically positive. It is evident that the cause of the differences between the convective schemes is the more intense convection in the MIT scheme configuration, which in turn imposes a more effective drying of the atmosphere, less low-level clouds, more short-wave solar radiation absorbed from the ground and hence warmer low level temperatures. © Springer-Verlag 2008."
"7004299063;7004498574;16029719200;7004214645;7004126618;6701413579;","Did the Toba volcanic eruption of ∼74 ka B.P. produce widespread glaciation?",2009,"10.1029/2008JD011652","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650456726&doi=10.1029%2f2008JD011652&partnerID=40&md5=db215777fb311fca0e463b2bc668bc53","It has been suggested that the Toba volcanic eruption, approximately 74 ka B.P., was responsible for the extended cooling period and ice sheet advance immediately following it, but previous climate model simulations, using 100 times the amount of aerosols produced by the 1991 Mount Pinatubo eruption, have been unable to produce such a prolonged climate response. Here we conduct six additional climate model simulations with two different climate models, the National Center for Atmospheric Research Community Climate System Model 3.0 (CCSM3.0) and National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE, in two different versions, to investigate additional mechanisms that may have enhanced and extended the forcing and response from such a large supervolcanic eruption. With CCSM3.0 we include a dynamic vegetation model to explicitly calculate the feedback of vegetation death on surface fluxes in response to the large initial reduction in transmitted light, precipitation, and temperature. With ModelE we explicitly calculate the effects of an eruption on stratospheric water vapor and model stratospheric chemistry feedbacks that might delay the conversion of SO<inf>2</inf> into sulfate aerosols and prolong the lifetime and radiative forcing of the stratospheric aerosol cloud. To span the uncertainty in the amount of stratospheric injection of SO<inf>2</inf>, with CCSM3.0 we used 100 times the Pinatubo injection, and with ModelE we used 33, 100, 300, and 900 times the Pinatubo injection without interactive chemistry, and 300 times Pinatubo with interactive chemistry. Starting from a roughly present-day seasonal cycle of insolation, CO<inf>2</inf> concentration, and vegetation, or with 6 ka B.P. conditions for CCSM3.0, none of the runs initiates glaciation. The CCSM3.0 run produced a maximum global cooling of 10 K and ModelE runs produced 8-17 K of cooling within the first years of the simulation, depending on the injection, but in all cases, the climate recovers over a few decades. Nevertheless, the ""volcanic winter"" following a supervolcano eruption of the size of Toba today would have devastating consequences for humanity and global ecosystems. These simulations support the theory that the Toba eruption indeed may have contributed to a genetic bottleneck. Copyright 2009 by the American Geophysical Union."
"57191773230;7005731975;","Coal and fuel burning effects on the atmosphere as mediated by the atmospheric electric field and galactic cosmic rays flux",2009,"10.1504/IJGW.2009.027081","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924267933&doi=10.1504%2fIJGW.2009.027081&partnerID=40&md5=223c8edc5e75a13bb66bd40999ca611c","Emissions into the atmosphere of Greenhouse Gases (GHGs) and particulate matter resulting from fossil fuel burning are considered to be the main anthropogenic forcing on the global climate. We show here that the external cyclic influences of cosmic origin that modulate the earth’s climate may either reinforce or mitigate the ‘local’ terrestrial forcings. Among the external influences is cosmic radiation, whose intensity shows a cyclic variation of 11 years, accompanying the 11-year cycle of solar activity. We put forward a mechanism to explain how the emission of particulate matter into the atmosphere might influence global lightning activity. With respect to global lightning activity, we show why, during the 11-year cycle, the influence of an increase in particulate matter concentration in the atmosphere may be negligible in some years, while it will be reinforced in other years, depending on the place of the years in the cycle. We also remark that the effect on global warming of fossil fuel burning is also modulated by the cosmic ray flux, whose influence is mediated by the variation that it promotes on the cloud cover. © 2009 Inderscience Enterprises Ltd."
"8318136800;7003541903;57212468800;","Interrelationships between MODIS/Terra remotely sensed snow cover and the hydrometeorology of the Quesnel River Basin, British Columbia, Canada",2009,"10.5194/hess-13-1439-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74149090579&doi=10.5194%2fhess-13-1439-2009&partnerID=40&md5=b1954552b7837f6defb37e7e45488ada","A spatial filter (SF) method is adopted to reduce the cloud coverage from the Moderate Resolution Imaging Spectroradiometer (MODIS) 8-day snow products (MOD10A2) between 2000-2007 in the Quesnel River Basin (QRB) of British Columbia, Canada. A threshold of κ = 2 cm of snow depth measurements at four in-situ observation stations in the QRB are used to evaluate the accuracy of MODIS snow products MOD10A1, MOD10A2, and SF. Using the MOD10A2 and the SF, the relationships between snow ablation, snow cover extent (SCE), snow cover fraction (SCF), streamflow and climate variability are assessed. Based on our results we are able to draw several interesting conclusions. Firstly, the SF method reduces the average cloud coverage in the QRB from 15% for MOD10A2 to 9%. Secondly, the SF increases the overall accuracy (OA) based on the threshold κ = 2 cm by about 2% compared to MOD10A2 and by about 10% compared to MOD10A1 at higher elevations. The OA for the four in-situ stations decreases with elevation with 93.1%, 87.9%, 84.0%, and 76.5% at 777m, 1265 m, 1460 m, and 1670 m, respectively. Thirdly, an aggregated 1° C rise in average air temperature during spring leads to a 10-day advance in reaching 50% SCF (SCF50%) in the QRB. The correlation coefficient between normalized SCE of the SF and normalized streamflow is - 0.84 (p<0.001) for snow ablation seasons. There is a 32-day time lag for snow ablation to impact the streamflow the strongest at the basin outlet. The linear correlation coefficient between SCF50% and 50% normalized accumulated runoff (R50%) attains 0.82 (p<0.01). This clearly demonstrates the strong links that exist between the SCF depletion and the hydrology of this sub-boreal, mountainous watershed. © Author(s) 2009."
"26026869600;7003946703;","High-resolution satellite-based cloud-coupled estimates of total downwelling surface radiation for hydrologic modelling applications",2009,"10.5194/hess-13-969-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73149092770&doi=10.5194%2fhess-13-969-2009&partnerID=40&md5=b98bf05a77e86a17c6d9a4de16069fef","A relatively simple satellite-based radiation model yielding high-resolution (in space and time) downwelling longwave and shortwave radiative fluxes at the Earth's surface is presented. The primary aim of the approach is to provide a basis for deriving physically consistent forcing fields for distributed hydrologic models using satellite-based remote sensing data. The physically-based downwelling radiation model utilises satellite inputs from both geostationary and polar-orbiting platforms and requires only satellite-based inputs except that of a climatological lookup table derived from a regional climate model. Comparison against ground-based measurements over a 14-month simulation period in the Southern Great Plains of the United States demonstrates the ability to reproduce radiative fluxes at a spatial resolution of 4 km and a temporal resolution of 1 h with good accuracy during all-sky conditions. For hourly fluxes, a mean difference of -2 W m-2 with a root mean square difference of 21 W m-2 was found for the longwave fluxes whereas a mean difference of -7 W m-2 with a root mean square difference of 29 W m-2 was found for the shortwave fluxes. Additionally, comparison against advanced downwelling longwave and solar insolation products during all-sky conditions showed comparable uncertainty in the longwave estimates and reduced uncertainty in the shortwave estimates. The relatively simple form of the model enables future usage in ensemble-based applications including data assimilation frameworks in order to explicitly account for input uncertainties while providing the potential for conditioning estimates from other readily available products derived from more sophisticated retrieval algorithms."
"7003359002;7403682442;6602496366;57203776263;6603633815;7403401100;35276210200;7403253796;57213358341;7006839912;6602582342;7405551904;","Aerosol optical properties relevant to regional remote sensing of CCN activity and links to their organic mass fraction: Airborne observations over Central Mexico and the US West Coast during MILAGRO/INTEX-B",2009,"10.5194/acp-9-6727-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149108345&doi=10.5194%2facp-9-6727-2009&partnerID=40&md5=9ef8d621e2edd792d6f15d8747d5af0d","Remote sensing of cloud condensation nuclei (CCN) would help evaluate the indirect effects of tropospheric aerosols on clouds and climate. To assess its feasibility, we examined relationships of submicron aerosol composition to CCN activity and optical properties observed during the MILAGRO/INTEX-B aircraft campaigns. An indicator of CCN activity, K, was calculated from hygroscopicity measured under saturation, K for dry 100nm particles decreased with increasing organic fraction of non-refractory mass of submicron particles (OMF) as 0.34-0.20xOMF over Central Mexico and 0.47-0.43xOMF over the US West Coast. These fits represent the critical dry diameter, centered near 100 nm for 0.2% supersaturation but varied as K(-1/3), within measurement uncertainty (∼20%). The decreasing trends of CCN activity with the organic content, evident also in our direct CCN counts, were consistent with previous ground and laboratory observations of highly organic particles. The wider range of OMF, 0-0.8, for our research areas means that aerosol composition will be more critical for estimation of CCN concentration than at the fixed sites previously studied. Furthermore, the wavelength dependence of extinction was anti-correlated with OMF as -0.70xOMF+2.0 for Central Mexico's urban and industrial pollution air masses, for unclear reasons. The Angstrom exponent of absorption increased with OMF, more rapidly under higher single scattering albedo, as expected for the interplay between soot and colored weak absorbers (some organic species and dust). Because remote sensing products currently use the wavelength dependence of extinction albeit in the column integral form and may potentially include that of absorption, these regional spectral dependencies are expected to facilitate retrievals of aerosol bulk chemical composition and CCN activity over Central Mexico."
"6603808469;7006051984;57002628600;6701410329;6601981008;36523706800;","Satellite Application Facilities irradiance products: Hourly time step comparison and validation over Europe",2009,"10.1080/01431160802680560","https://www.scopus.com/inward/record.uri?eid=2-s2.0-63649102239&doi=10.1080%2f01431160802680560&partnerID=40&md5=6620282a61ad019477313e77d5e53bc6","Downward short- and longwave incoming irradiances play a key role in the radiation budget at the Earth's surface. Monitoring these parameters is essential for understanding the basic mechanisms involved in climate change, such as the greenhouse effect, global dimming, and changes in cloud cover and precipitation. Geostationary satellite observations are important in the retrieval of irradiance at the surface, providing excellent spatial and temporal coverage. Three decentralized Satellite Application Facilities (SAFs) are currently operational in the European Organisation for the Exploitation of Meteorological Satellites (Eumetsat), involved in retrieving surface solar irradiance (SSI) and downward longwave irradiance (DLI) from Meteosat images. This study presents a common validation of these radiation products against ground data from eight stations covering four months representative of the annual declination variation. The overall conclusion is that the products of the different SAFs are comparable in terms of bias and standard deviation. The SSI is retrieved with a standard deviation of 80-100 W m-2 and negligible bias, and the DLI with a standard deviation of 25 W m-2 with a slight site-dependent bias. © 2009 Taylor &amp; Francis."
"7202081585;8363388700;9535817700;16444387000;7003604530;7005729142;6506385754;35430463900;35547214900;6602407753;7003283811;57208765879;7202727242;6603768446;","On the importance of small ice crystals in tropical anvil cirrus",2009,"10.5194/acp-9-5519-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749121742&doi=10.5194%2facp-9-5519-2009&partnerID=40&md5=e9e426dc04cbc3bced6bd7471abfed35","In situ measurements of ice crystal concentrations and sizes made with aircraft instrumentation over the past two decades have often indicated the presence of numerous relatively small (&lt; 50 μm diameter) crystals in cirrus clouds. Further, these measurements frequently indicate that small crystals account for a large fraction of the extinction in cirrus clouds. The fact that the instruments used to make these measurements, such as the Forward Scattering Spectrometer Probe (FSSP) and the Cloud Aerosol Spectrometer (CAS), ingest ice crystals into the sample volume through inlets has led to suspicion that the indications of numerous small-crystals could be artifacts of large-crystal shattering on the instrument inlets. We present new aircraft measurements in anvil cirrus sampled during the Tropical Composition, Cloud, and Climate Coupling (TC4) campaign with the 2-Dimensional Stereo (2D-S) probe, which detects particles as small as 10 μm. The 2D-S has detector ""arms"" instead of an inlet tube. Since the 2D-S probe surfaces are much further from the sample volume than is the case for the instruments with inlets, it is expected that 2D-S will be less susceptible to shattering artifacts. In addition, particle interarrival times are used to identify and remove shattering artifacts that occur even with the 2D-S probe. The number of shattering artifacts identified by the 2D-S interarrival time analysis ranges from a negligible contribution to an order of magnitude or more enhancement in apparent ice concentration over the natural ice concentration, depending on the abundance of large crystals and the natural small-crystal concentration. The 2D-S measurements in tropical anvil cirrus suggest that natural small-crystal concentrations are typically one to two orders of magnitude lower than those inferred from CAS. The strong correlation between the CAS/2D-S ratio of small-crystal concentrations and large-crystal concentration suggests that the discrepancy is likely caused by shattering of large crystals on the CAS inlet. We argue that past measurements with CAS in cirrus with large crystals present may contain errors due to crystal shattering, and past conclusions derived from these measurements may need to be revisited. Further, we present correlations between CAS spurious concentration and 2D-S large-crystal mass from spatially uniform anvil cirrus sampling periods as an approximate guide for estimating quantitative impact of large-crystal shattering on CAS concentrations in previous dataseis. We use radiative transfer calculations to demonstrate that in the maritime anvil cirrus sampled during TC4, small crystals indicated by 2D-S contribute relatively little cloud extinction, radiative forcing, or radiative heating in the anvils, regardless of anvil age or vertical location in the clouds. While 2D-S ice concentrations in fresh anvil cirrus may often exceed 1 cm-3, and are observed to exceed 10 cm-3 in turrets, they are typically ≃ 0.1 cm-3 and rarely exceed 1 cm-3 (&lt;1.4% of the time) in aged anvil cirrus. We hypothesize that isolated occurrences of higher ice concentrations in aged anvil cirrus may be caused by ice nucleation driven by either small-scale convection or gravity waves. It appears that the numerous small crystals detrained from convective updrafts do not persist in the anvil cirrus sampled during TC-4."
"34876658200;8349977900;6701733293;","A new physically-based quantification of marine isoprene and primary organic aerosol emissions",2009,"10.5194/acp-9-4915-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749098733&doi=10.5194%2facp-9-4915-2009&partnerID=40&md5=cd9a0e39f6b882bd73139d0044cc5fb4","The global marine sources of organic carbon (OC) are estimated here using a physically-based parameterization for the emission of marine isoprene and primary organic matter. The marine isoprene emission model incorporates new physical parameters such as light sensitivity of phytoplankton isoprene production and dynamic euphotic depth to simulate hourly marine isoprene emissions totaling 0.92 Tg C yr?1. Sensitivity studies using different schemes for the euphotic zone depth and ocean phytoplankton speciation produce the upper and the lower range of marine-isoprene emissions of 0.31 to 1.09 Tg C yr?1, respectively. Established relationships between sea spray fractionation of waterinsoluble organic carbon (WIOC) and chlorophyll-a concentration are used to estimate the total primary sources of marine sub- and super-micron OC of 2.9 and 19.4 Tg C yr?1, respectively. The consistent spatial and temporal resolution of the two emission types allow us, for the first time, to explore the relative contributions of sub- and super-micron organic matter and marine isoprene-derived secondary organic aerosol (SOA) to the total OC fraction of marine aerosol. Using a fixed 3% mass yield for the conversion of isoprene to SOA, our emission simulations show minor (&lt;0.2%) contribution of marine isoprene to the total marine source of OC on a global scale. However, our model calculations also indicate that over the tropical oceanic regions (30° S to 30° N), marine isoprene SOA may contribute over 30% of the total monthlyaveraged sub-micron OC fraction of marine aerosol. The estimated contribution of marine isoprene SOA to hourlyaveraged sub-micron marine OC emission is even higher, approaching 50% over the vast regions of the oceans during the midday hours when isoprene emissions are highest. As it is widely believed that sub-micron OC has the potential to influence the cloud droplet activation of marine aerosols, our findings suggest that marine isoprene SOA could play critical role in modulating properties of shallow marine clouds and influencing the climate. © Author(s) 2009."
"7103001269;","On the confusion of planck feedback parameters",2009,"10.1260/095830509789876835","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450161854&doi=10.1260%2f095830509789876835&partnerID=40&md5=7e561ff9d6f625674094068a08e4c843","The Planck feedback parameter λ0 is the most fundamental quantity in the theory of global warming, because the surface temperature change ΔTs,0 is calculated by- (radiative forcing due to CO2 doubling)/λ0 in the absence of feedbacks other than that of surface temperature change. The following three groups of Planck feedback parameters are found in the literature depending on the choice of temperature Ts and the outgoing long wave radiation (OLR) at the top of atmosphere in equation of λ0 = -4OLR/Ts, which is derived from the Stefan-Boltzmann Law. This study shows that λ0 of GROUP C is a theoretically relevant choice for Ts and OLR, rather than those of GROUP A and GROUP B, while the IPCC adopted λ0 of GROUP A. Although the surface temperature change Δ Ts is 3.0K with λ0 = -3.21(W/m2)/K for CO2 doubling when lapse rate, water vapor, surface albedo and cloud feedbacks are included in the IPCC AR4, it is shown to be 0.5-0.75K with λ0 = -6.8(W/m2)/K in the present study. Since the IPCC overestimates the threat of carbon dioxide by 4-6 times, the revaluation will be needed for the CO2 reduction policies in terms of cost and potential hazards."
"57211828184;57214308657;56075918400;6506724478;","Discovery of fog at the south pole of Titan",2009,"10.1088/0004-637X/706/1/L110","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77749330701&doi=10.1088%2f0004-637X%2f706%2f1%2fL110&partnerID=40&md5=306f63116afb9451f0f9b38758705904","While Saturn's moon Titan appears to support an active methane hydrological cycle, no direct evidence for surface-atmosphere exchange has yet appeared. The indirect evidence, while compelling, could be misleading. It is possible, for example, that the identified lake features could be filled with ethane, an involatile long-term residue of atmospheric photolysis; the apparent stream and channel features could be ancient remnants of a previous climate; and the tropospheric methane clouds, while frequent, could cause no rain to reach the surface. We report here the detection of fog at the south pole of Titan during late summer using observations from the VIMS instrument on board the Cassini spacecraft. While terrestrial fog can form from a variety of causes, most of these processes are inoperable on Titan. Fog on Titan can only be caused by evaporation of nearly pure liquid methane; the detection of fog provides the first direct link between surface and atmospheric methane. Based on the detections presented here, liquid methane appears widespread at the south pole of Titan in late southern summer, and the hydrological cycle on Titan is currently active. © 2009. The American Astronomical Society."
"55754495900;7006329926;7404976222;","Local air-sea interaction in intertropical convergence zone simulations",2009,"10.1029/2009JD012405","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049088509&doi=10.1029%2f2009JD012405&partnerID=40&md5=c89f9337d738a00163be48c50f236b2a","We investigate how air-sea interaction affects an Intertropical Convergence Zone (ITCZ) simulation in the SAMIL2.08 atmospheric general circulation model (AGCM), In a control experiment (Expl) with the observed sea surface temperature (SST) prescribed in the AGCM, there exists a problem of excessive precipitation over much of the Tropics and insufficient precipitation over the equatorial Indian Ocean and the Pacific. The equatorial drought belt arises from the ompensatory descending motion associated with exaggerated deep convection over the tropics in both hemispheres. A double ITCZ disappears in a coupled experiment (Exp2) with the same AGCM as used in Expl coupled to an interactive ocean mixed layer within the great warm pool. This finding demonstrates that local air-sea interaction can modify the SST pattern, thereby regulating the climate mean state via the following processes. Local air-sea flux exchanges in tropical convective regions such as the ITCZ tend to cool SST via negative cloud-radiation and wind-evaporation feedbacks. Such changes further modify the tropical atmospheric circulation structure such that the equatorial compensatory descent in Expl is replaced by the equatorial convergence zone, as seen in nature. A third sensitivity experiment (Exp3), with the AGCM driven by the monthly SST field derived from the coupled experiment, yielded similar results to those obtained in Exp2. Overall, the results indicate that a reasonable depiction of the air-sea coupling process is important to successfully simulating the tropical precipitation pattern, as the atmosphere is closely coupled with the ocean over the tropics. Copyright 2009 by the American Geophysical Union."
"55718911800;7202842863;","Observation of nitrate coatings on atmospheric mineral dust particles",2009,"10.5194/acp-9-1863-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249101381&doi=10.5194%2facp-9-1863-2009&partnerID=40&md5=cbc8ffdb9aa52b08f58b098fc1ac046c","Nitrate compounds have received much attention because of their ability to alter the hygroscopic properties and cloud condensation nuclei (CCN) activity of mineral dust particles in the atmosphere. However, very little is known about specific characteristics of ambient nitratecoated mineral particles on an individual particle scale. In this study, sample collection was conducted during brown haze and dust episodes between 24 May and 21 June 2007 in Beijing, northern China. Sizes, morphologies, and compositions of 332 mineral dust particles together with their coatings were analyzed using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX) microanalyses. Structures of some mineral particles were verified using selected-area electron diffraction (SAED). TEM observation indicates that approximately 90% of the collected mineral particles are covered by visible coatings in haze samples whereas only 5% are coated in the dust sample. 92% of the analyzed mineral particles are covered with Ca-, Mg-, and Na-rich coatings, and 8% are associated with K- and S-rich coatings. The majority of coatings contain Ca, Mg, O, and N with minor amounts of S and Cl, suggesting that they are possibly nitrates mixed with small amounts of sulfates and chlorides. These nitrate coatings are strongly correlated with the presence of alkaline mineral components (e.g., calcite and dolomite). CaSO4 particles with diameters from 10 to 500 nm were also detected in the coatings including Ca(NO3)2 and Mg(NO3)2. Our results indicate that mineral particles in brown haze episodes were involved in atmospheric hetero-geneous reactions with two or more acidic gases (e.g., SO2, NO2, HCl, and HNO3). Mineral particles that acquire hygroscopic nitrate coatings tend to be more spherical and larger, enhancing their light scattering and CCN activity, both of which have cooling effects on the climate. © 2009 Author(s)."
"56158622800;55087038900;35206916200;35308117100;7006783796;7407116104;8833356300;56325104100;","Taklimakan dust aerosol radiative heating derived from CALIPSO observations using the Fu-Liou radiation model with CERES constraints",2009,"10.5194/acp-9-4011-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649345010&doi=10.5194%2facp-9-4011-2009&partnerID=40&md5=08c26abd296111225dda0fd3e57ad85d","The dust aerosol radiative forcing and heating rate over the Taklimakan Desert in Northwestern China in July 2006 are estimated using the Fu-Liou radiative transfer model along with satellite observations. The vertical distributions of the dust aerosol extinction coefficient are derived from the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) lidar measurements. The CERES (Cloud and the Earth's Energy Budget Scanner) measurements of reflected solar radiation are used to constrain the dust aerosol type in the radiative transfer model, which determines the dust aerosol single-scattering albedo and asymmetry factor as well as the aerosol optical properties' spectral dependencies. We find that the dust aerosols have a significant impact on the radiative energy budget over the Taklimakan desert. In the atmospheres containing light, moderate and heavy dust layers, the dust aerosols heat the atmosphere (daily mean) by up to 1, 2, and 3 K day 1, respectively. The maximum daily mean radiative heating rate reaches 5.5 K day1 at 5 km on 29 July. The averaged daily mean net radiative effect of the dust are 44.4, &amp;minus;41.9, and 86.3 W m 2, respectively, at the top of the atmosphere (TOA), surface, and in the atmosphere. Among these effects about two thirds of the warming effect at the TOA is related to the longwave radiation, while about 90% of the atmospheric warming is contributed by the solar radiation. At the surface, about one third of the dust solar radiative cooling effect is compensated by its longwave warming effect. The large modifications of radiative energy budget by the dust aerosols over Taklimakan Desert should have important implications for the atmospheric circulation and regional climate, topics for future investigations."
"26430938300;12777240700;35436476200;","A study to investigate and model the transformation of nitrogen dioxide into ozone using time series plot",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959949959&partnerID=40&md5=17bd9e27e15f6bf1d849f51df396e00c","One of the major problems originating from air pollution in urban areas is the pollution caused by photochemical oxidants. Among these, ozone (O 3) and nitrogen dioxide (NO2) are compounds capable of producing adverse impacts on human health and on environment. This study examines transformation of NO2 into O3 at urban environment of Malaysia using time series plot. It is well known that ozone's impact on climate consists primarily of changes in temperature. Changes in O3 amounts are closely linked to temperature, with colder temperatures resulting in more polar stratospheric clouds and lower ozone levels. Ozone generates heat in the stratosphere, both by absorbing the sun's ultraviolet radiation and by absorbing upwelling infrared radiation from the lower atmosphere. This study proved that the peak concentration of O3 occurs during noon when the highest temperature was recorded. Data on the concentration of environmental pollutants and meteorological variables were employed to predict the concentration of O3 in the atmosphere. Possibility of employing multiple linear regression models as a tool for prediction of O3 concentration was tested. Results indicated that present of NO2 and sunshine influence the concentration of O 3 in Malaysia. Among the meteorological variables, temperature tended to contribute significantly to the high O3 concentrations. © EuroJournals Publishing, Inc. 2009."
"16506458200;36006968000;7103352790;7006550959;","Role of stratiform rainfall in modifying the northward propagation of monsoon intraseasonal oscillation",2009,"10.1029/2009JDO11869","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049120715&doi=10.1029%2f2009JDO11869&partnerID=40&md5=46fb8027b952290db6b2eb2a37550417","The stratiform and convective rain rate measurement from the Tropical Rainfall Measuring Mission (TRMM) satellite data can give a realistic idea of the latent heating distribution in the tropics. The vertical profile of diabatic heating related to the convective and the stratiform rain is known to modulate the dynamical response of atmosphere and also the vertical structure of Madden-Julian Oscillation. In this study, the contribution of the stratiform and convective rain rate to the total rain rate during different phases of the northward propagating boreal summer monsoon intraseasonal oscillation (ISO) is examined using the TRMM data. Two new insights have emerged from this analysis. First, unlike conventional wisdom, the convective component shows weak northward propagation and grows and decays in situ during the evolution of active and break phases, while the northward propagation of the monsoon ISO is largely achieved by organized movement of the stratiform component. Second, the trademark meridional dipole pattern of total rainfall between the monsoon trough zone and the southern equatorial Indian Ocean also arises largely from the contribution of stratiform anomalies. As the northward propagation of the monsoon ISO is known to be due to the anomalous response of the atmosphere to heating in the presence of mean easterly vertical shear, modification of the vertical profile of heating due to a contribution from stratiform rain could influence the northward propagation of the monsoon ISO. This hypothesis is tested using a simple global atmospheric circulation model to study the response of the convective and stratiform heating profiles on the modification of the mean condition. Modification in the large-scale response of the atmosphere as a result of proper specification of convective and stratiform heating anomalies indicates that the presence of stratiform heating favors the northward propagation of the heat source thereby facilitating the positive feedback leading to northward propagation of the monsoon ISO. These results underline the importance of simulating the partitioning of convective and stratiform rain by cumulus parameterization in climate models if they have to get the space-time structure of the summer ISOs correct.Copyright 2009 by the American Geophysical Union."
"35812326900;55187246200;7004637798;","Testing the relationship between the solar radiation dose and surface DMS concentrations using in situ data",2009,"10.5194/bg-6-1927-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951151547&doi=10.5194%2fbg-6-1927-2009&partnerID=40&md5=18e6406b0a3def621f9d3c96a9afd7ac","The proposed strong positive relationship between dimethylsulphide (DMS) concentration and the solar radiation dose (SRD) received into the surface ocean is tested using data from the Atlantic Meridional Transect (AMT) programme. In situ, daily data sampled concurrently with DMS concentrations is used for the component variables of the SRD (mixed layer depth, MLD, surface insolation, I0, and a light attenuation coefficient, k) to calculate SRDinsitu. This is the first time in situ data for all of the components, including k, has been used to test the SRDDMS relationship over large spatial scales. We find a significant correlation (p=0.55 n=65 p&lt;0.01) but the slope of this relationship (0.006 nM/Wm-2) is less than previously found at the global (0.019 nM/W m-2) and regional scales (Blanes Bay, Mediterranean, 0.028 nM/Wm-2; Sargasso Sea 0.017 nM/Wm-2). The correlation is improved (p=0.74 n=65 p&lt;0.01) by replacing the in situ data with an estimated I0 (which assumes a constant 50% removal of the top of atmosphere value; 0.5×TOA), a MLD climatology and a fixed value for k following previous work. Equally strong, but non-linear relationships are also found between DMS and both in situ MLD (p=0.61 n=65 p&lt;0.01) and the estimated I0 (p=0.73 n=65 p&lt;0.01) alone. Using a satellite-retrieved, cloud-adjusted surface UVA irradiance to calculate a UV radiation dose (UVRD) with a climatological MLD also provides an equivalent correlation (p=0.67 n=54 p&lt;0.01) to DMS. With this data, MLD appears the dominant control upon DMS concentrations and remains a useful shorthand to prediction without fully resolving the biological processes involved. However, the implied relationship between the incident solar/ultraviolet radiation (modulated by MLD), and sea surface DMS concentrations, is critical for closing a climate feedback loop. © Author(s) 2009."
"13404531500;7402345338;","Extratropical stratosphere-troposphere exchange in an AGCM with the horizontal grid size of 20 km",2009,"10.1029/2008JD011628","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049114989&doi=10.1029%2f2008JD011628&partnerID=40&md5=88092d131da711edc25e1343555f0656","The transport and exchange process across the extratropical tropopause is investigated using an atmospheric global climate model with a horizontal grid size of about 20 km, which can depict filamental structures near the tropopause. The advection of an idealized passive tracer, which is initialized to have a nonzero value only above the tropopause, is calculated in January and July in the Northern Hemisphere. A version of the model with coarse resolution is used to examine the horizontal resolution dependence. The exchange between the stratosphere and the troposphere has its maximum amounts at 300 hPa in January and at 200-250 hPa in July. Above 400 hPa, the amount of exchange in the 20-km model is about one-half of that of the 180-km model, in accordance with the existence of a sharp tropopause. In contrast, the amount in the 20-km model below 400 hPa is more than that in the 180-km model, partly due to the inability of simulating filamental structures along with the storms in the 180-km model. However, the net transport across the tropopause does not have large dependence on the horizontal resolution. The net transport below 400 hPa is from the stratosphere to the troposphere and is large over the Pacific and Atlantic storm track in January. The net troposphere to stratosphere transport is seen above 300 hPa and is large near the subtropical jet over the Eurasian continent. A large part of this transport is attributed to the temporal change of the potential vorticity estimated from a vertical difference in the longwave radiation. Copyright 2009 by the American Geophysical Union."
"7004532767;57205609578;16304787700;57201982103;16835032900;7006058570;24504514900;8783945600;6603912682;7005149798;","Variability in regional background aerosols within the Mediterranean",2009,"10.5194/acp-9-4575-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651012841&doi=10.5194%2facp-9-4575-2009&partnerID=40&md5=38804d21877e40ff595eabde0be8eab0","The main objective of this study is the identification of major factors controlling levels and chemical composition of aerosols in the regional background (RB) along the Mediterranean Basin (MB). To this end, data on PM levels and speciation from Montseny (MSY, NE Spain), Finokalia (FKL, Southern Greece) and Erdemli (ERL, Southern Turkey) for the period 2001 to 2008 are evaluated. Important differences on PM levels and composition are evident when comparing the Western and Eastern MBs. The results manifest W-E and N-S PM 10 and PM2.5 gradients along the MB, attributed to the higher frequency and intensity of African dust outbreaks in the EMB, while for PM1 very similar levels are encountered. PM in the EMB is characterized by higher levels of crustal material and sulphate as compared to WMB (and central European sites), however, RB nitrate and OC + EC levels are relatively constant across the Mediterranean and lower than other European sites. Marked seasonal trends are evidenced for PM levels, nitrate (WMB), ammonium and sulphate. Also relatively higher levels of V and Ni (WMB) are measured in the Mediterranean basin, probably as a consequence of high emissions from fuel-oil combustion (power generation, industrial and shipping emissions). Enhanced sulphate levels in EMB compared to WMB were measured. The high levels of sulphate in the EMB may deplete the available gas-phase NH3 so that little ammonium nitrate can form due to the low NH3 levels. This study illustrates the existence of three very important features within the Mediterranean that need to be accounted for when modeling climate effects of aerosols in the area, namely: a) the increasing gradient of dust from WMB to EMB; b) the change of hygroscopic behavior of mineral aerosols (dust) via nitration and sulfation; and c) the abundance of highly hygroscopic aerosols during high insolation (low cloud formation) periods."
"15725665100;7004773965;","An investigation of nucleation events in a coastal urban environment in the Southern Hemisphere",2009,"10.5194/acp-9-7877-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950436854&doi=10.5194%2facp-9-7877-2009&partnerID=40&md5=3619febdb5e8040b0570135a543ed95b","Ambient aerosols play an important role in atmospheric processes affecting the human and natural environments. They affect air quality, reduce visibility, and induce climate change by directly scattering and/or absorbing the incoming solar radiation (Charlson et al., 1992; Kim et al., 2006), or indirectly by acting as cloud condensation nuclei (Hobbs, 1993). Aerosol particles are emitted from a variety of anthropogenic and natural sources either directly into the atmosphere or as secondary particles by gas-to-particle formation process. There is growing interest in studying and analysing the mechanisms of formation of secondary particles. The development of new instruments during the 1990s to measure the particle size distribution of nanoparticles (<50 nm) has enabled scientists to observe the formation and growth of new particles (see Kulmala et al. (2004) for review). Nucleation events, that is, the appearance of a mode below 25-30 nm in the particle number size distribution, known as ""nucleation mode"" (e.g. Dal Maso et al., 2007; Tunved et al., 2003), usually in very large numbers, have been observed around the world. For example, they have been reported in remote (e.g. Tunved et al., 2003), urban (e.g. Jeong et al., 2004; Zhang et al., 2004) and coastal areas (e.g. Vaattovaara et al., 2006) and at various latitudes in the upper troposphere and the lower stratosphere (Lee et al., 2003). It has been shown that the probability of nucleation was increased by elevated sulphur dioxide (SO2) concentrations (Stanier et al., 2004). This gas is mainly emitted from anthropogenic sources such as the combustion of sulphurcontaining fossil fuel (Stern, 2005). Therefore, aerosol nucleation in the atmosphere would be expected to be enhanced by human activities (see also Curtius (2006) for discussion). In urban air, morning nucleation events have been found to be consistent with peaks in traffic (Jeong et al., 2004). In contrast, in coastal environments, higher concentrations of nucleation mode particles have been observed during entries of clean air rather than of polluted air (O'Dowd et al., 2002). This is also confirmed by a Finish study (Spracklen et al., 2006), which found that particle concentrations in remote continental regions are dominated by nucleated particles whereas in polluted continental regions are dominated by primary particles. This paper aims to analyse the frequency of and the atmospheric conditions favourable for nucleation events at coastal urban location in Brisbane, Australia, with a focus on the contribution of vehicle emissions. Monitoring was conducted during four campaigns of two weeks duration each, and a campaign of four weeks duration, covering a total period of 13 months. The objective was to investigate which meteorological conditions enhanced the probability of nucleation and to investigate any patterns in gaseous concentrations leading to the events to determine whether the local traffic was a major source of secondary particles in the study area."
"24341315100;16308514000;55438848700;7006572336;57196499374;","Aerosol hygroscopicity in the marine atmosphere: A closure study using high-time-resolution, multiple-RH DASH-SP and size-resolved C-ToF-AMS data",2009,"10.5194/acp-9-2543-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73449128448&doi=10.5194%2facp-9-2543-2009&partnerID=40&md5=d2463089ba7c68eef823ca0dcfd115a7","We have conducted the first airborne hygroscopic growth closure study to utilize data from an Aerodyne compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF-AMS) coupled with size-resolved, multiple-RH, high-time-resolution hygroscopic growth factor (GF) measurements from the differential aerosol sizing and hygroscopicity spectrometer probe (DASH-SP). These data were collected off the coast of Central California during seven of the 16 flights carried out during the MASE-II field campaign in July 2007. Two of the seven flights were conducted in airmasses characterized by continental origin. These flights exhibited elevated organic volume fractions (VForganic=0.56±0. 19, as opposed to 0.39±0.20 for all other flights), corresponding to significantly suppressed GFs at high RH (1.61±0.14 at 92% RH, as compared with 1.91±0.07 for all other flights), more moderate GF suppression at intermediate RH (1.53±0.10 at 85%, compared with 1.58±0.08 for all other flights), and no measurable GF suppression at low RH (1.31±0.06 at 74%, compared with 1.31±0.07 for all other flights). Organic loadings were slightly elevated in above-cloud aerosols, as compared with below-cloud aerosols, and corresponded to a similar trend of significantly suppressed GF at high RH, but more moderate impacts at lower values of RH. A hygroscopic closure based on a volume-weighted mixing rule provided good agreement with DASH-SP measurements (R2=0.78). Minimization of root mean square error between observations and predictions indicated mission-averaged organic GFs of 1.22, 1.45, and 1.48 at 74, 85, and 92% RH, respectively. These values agree with previously reported values for water-soluble organics such as dicarboxylic and multifunctional acids, and correspond to a highly oxidized, presumably water-soluble, organic fraction (mission-averaged O:C=0.92±0.33). Finally, a backward stepwise linear regression revealed that, other than RH, the most important predictor for GF is Vívanlo indicating that a simple emperical model relating GF, RH, and the relative abundance of organic material can provide accurate predictions (R2=0.77) of hygroscopic growth for the California coast."
"55352043900;7202371636;36071585400;57192160707;","Synergistic use of optical and InSAR data for urban impervious surface mapping: A case study in Hong Kong",2009,"10.1080/01431160802555838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70449360101&doi=10.1080%2f01431160802555838&partnerID=40&md5=1557314ffffaca34c20fa291772d7830","A wide range of urban ecosystem studies, including urban hydrology, urban climate, land use planning and watershed resource management, require accurate and up-to-date geospatial data of urban impervious surfaces. In this study, the potential of the synergistic use of optical and InSAR data in urban impervious surface mapping at the sub-pixel level was investigated. A case study in Hong Kong was conducted for this purpose by applying a classification and regression tree (CART) algorithm to SPOT 5 multispectral imagery and ERS-2 SAR data. Validated by reference data derived from high-resolution colour-infrared (CIR) aerial photographs, our results show that the addition of InSAR feature information can improve the estimation of impervious surface percentage (ISP) in comparison with using SPOT imagery alone. The improvement is especially notable in separating urban impervious surface from the vacant land/bare ground, which has been a difficult task in ISP modelling with optical remote sensing data. In addition, the results demonstrate the potential to map urban impervious surface by using InSAR data alone. This allows frequent monitoring of world's cities located in cloud-prone and rainy areas. © 2009 Taylor & Francis."
"57192309096;57218373467;15846170400;56751289700;","Atmospheric surfactants around lake ecosystems",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650626834&partnerID=40&md5=b668cff7015d47dc9baab5b046d28ab3","Lake ecosystems are a source of natural organic matter characterized by humic-like substances (HULIS). These are believed to contain a high quantity of surface active agents (surfactants) which can influence both cloud formation and climate. This study determined the concentration of anionic surfactants in the atmosphere around lake ecosystems at Kenyir Lake, Terengganu and Chini Lake, Pahang. Aerosols samples were collected using a High Volume Air Sampler (HVAS) equipped with a high volume impactor (to separate between fine and coarse mode aerosols) and glass-fibre filter paper at a flow rate of 1.13 m3min-1 for 24 hours. Several possible sources of natural surfactants in the atmosphere, e.g. soils, vegetations and surface water, were also collected in order to determine them as sources and to determine the flux of anionic surfactants in the atmosphere. Anionic surfactants were analysed based on the colorimetric methods whereby methylene blue active substances (MBAS) and a UV-visible spectrophotometer at 650 nm were used. Subsequently, simplified calculations were conducted to estimate the flux of anionic surfactants from various possible sources. The results indicated that the concentration of anionic surfactants in aerosols (coarse and fine mode), soil, vegetation and surface water were 97.43 ± 50.39 pmol/m3 and 110.78 ± 60.92 pmol/m3, 0.33 ± 0.17 μmolg-1, 0.28 ± 0.08 μmolg-1 (dry weight) and 0.01 ± 0.004 μmolL-1, respectively. The overall flux of surfactants signified that soil provides the highest quantity of surfactants, 119.39 Mmolyr-1, in comparison to other possible sources (vegetation=26.88 Mmolyr-1 and surface water = 12.1 x 10-6 Mmolyr-1). Results indicated that soil becomes a significant natural source of anionic surfactants for the atmosphere, which may be due to the availability of HULIS. © EuroJournals Publishing, Inc. 2009."
"16549600900;24558717100;13407563600;56477623800;26029605900;13403849600;57203776263;7004864963;35461763400;57189372185;55942083800;","Cloud condensation nuclei in pristine tropical rainforest air of Amazonia: Size-resolved measurements and modeling of atmospheric aerosol composition and CCN activity",2009,"10.5194/acp-9-7551-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149099798&doi=10.5194%2facp-9-7551-2009&partnerID=40&md5=aefa859829a1d61f77c8a7edeaf53cb4","Atmospheric aerosol particles serving as cloud condensation nuclei (CCN) are key elements of the hydro-logical cycle and climate. We have measured and charac-terized CCN at water vapor supersaturations in the range of 5=0.10-0.82% in pristine tropical rainforest air during the AMAZE-08 campaign in central Amazonia. The effective hygroscopicity parameters describing the influence of chemical composition on the CCN activ-ity of aerosol particles varied in the range of K 0.1-0.4 (0.16±0.06 arithmetic mean and standard deviation). The overall median value of K0. 15 was by a factor of two lower than the values typically observed for continental aerosols in other regions of the world. Aitken mode particles were less hygroscopic than accumulation mode particles (K&amp;0.1 at D»50nm; K∼0.2 at D∼200nm), which is in agreement with earlier hygroscopicity tandem differential mobility ana-lyzer (H-TDMA) studies. The CCN measurement results are consistent with aerosol mass spectrometry (AMS) data, showing that the organic mass fraction (f org) was on average as high as ∼ 90% in the Aitken mode (D&lt;100nm) and decreased with increas-ing particle diameter in the accumulation mode (∼ 80% at D ∼ 200nm). The K values exhibited a negative linear cor-relation with Forg (R2=0.81), and extrapolation yielded the following effective hygroscopicity parameters for organic and inorganic particle components: Korg∼ ;0.1 which can be regarded as the effective hygroscopicity of biogenic sec-ondary organic aerosol (SOA) and Kinorg0.6 which is char-acteristic for ammonium sulfate and related salts. Both the size dependence and the temporal variability of effective particle hygroscopicity could be parameterized as a func-tion of AMS-based organic and inorganic mass fractions (Kp=KOrg+ Kinorgxfinorg). The CCN number concen-trations predicted with KP were in fair agreement with the measurement results (∼ 20% average deviation). The me-dian CCN number concentrations at S=0.1-0.82% ranged from AfacN.o.10∼35cm-3 to NccN, 0.82 ∼ 160cm -3, the me-dian concentration of aerosol particles larger than 30 nm was NCN, 30∼200cm-3, and the corresponding integral CCN ef-ficiencies were in the range of NccN, 0.10/NcN, 30 ∼ 0.l to WCCN, 0.82/ Ncn30 ∼0.8. Although the number concentrations and hygroscopicity parameters were much lower in pristine rainforest air, the integral CCN efficiencies observed were similar to those in highly polluted megacity air. Moreover, model calculations of NCCN,S assuming an approximate global average value of K∼03 for continental aerosols led to systematic overpredic-tions, but the average deviations exceeded ∼50% only at low water vapor supersaturation (0.1%) and low particle number concentrations (&lt;100cm-3). Model calculations assuming a constant aerosol size distribution led to higher average devi-ations at all investigated levels of supersaturation: ∼ 60% for the campaign average distribution and ∼1600% for a generic remote continental size distribution. These findings confirm earlier studies suggesting that aerosol particle number and size are the major predictors for the variability of the CCN concentration in continental boundary layer air, followed by particle composition and hygroscopicity as relatively minor modulators. Depending on the required and applicable level of detail, the information and parameterizations presented in this paper should enable efficient description of the CCN properties of pristine tropical rainforest aerosols of Amazonia in detailed process models as well as in large-scale atmospheric and cli-mate models."
"24460747700;57213110874;57199847019;6701581258;7003355879;","Nitric acid in the stratosphere based on Odin observations from 2001 to 2009 - Part 1: A global climatology",2009,"10.5194/acp-9-7031-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75449096198&doi=10.5194%2facp-9-7031-2009&partnerID=40&md5=82de711a4be6d62ff15a8232570a8093","The Sub-Millimetre Radiometer (SMR) on board the Odin satellite, launched in February 2001, observes thermal emissions of stratospheric nitric acid (HNO3) originating from the Earth limb in a band centred at 544.6 GHz. Height-resolved measurements of the global distribution of nitric acid in the stratosphere were performed approximately on two observation days per week. An HNO3 climatology based on more than 7 years of observations from August 2001 to April 2009 covering the vertical range between typically ∼19 and 45km (∼1.5-60hPa or ∼500-1800K in terms of potential temperature) was created. The study highlights the spatial and seasonal variation of nitric acid in the stratosphere, characterised by a pronounced seasonal cycle at middle and high latitudes with maxima during late fall and minima during spring, strong denitrification in the lower stratosphere of the Antarctic polar vortex during winter (the irreversible removal of NOy by the sedimentation of cloud particles containing HNO3), as well as large quantities of HNO3 formed every winter at high-latitudes in the middle and upper stratosphere. A strong inter-annual variability is observed in particular at high latitudes. A comparison with a stratospheric HNO3 climatology, based on over 7 years of UARS/MLS (Upper Atmosphere Research Satellite/Microwave Limb Sounder) measurements from the 1990s, shows good consistency and agreement of the main morphological features in the potential temperature range ∼465 to ∼960 K, if the different characteristics of the data sets such as the better altitude resolution of Odin/SMR as well as the slightly different altitude ranges are considered. Odin/SMR reaches higher up and UARS/MLS lower down in the stratosphere. An overview from 1991 to 2009 of stratospheric nitric acid is provided (with a short gap between 1998 and 2001), if the global measurements of both experiments are taken together."
"13403949400;24068490300;56269722300;55894188500;55880185200;55946710700;55879760100;7003450096;","The impact of MM5 and WRF meteorology over complex terrain on CHIMERE model calculations",2009,"10.5194/acp-9-6611-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75449120514&doi=10.5194%2facp-9-6611-2009&partnerID=40&md5=a63b8e2793bf645d6ebe9bdad94782c1","The objective of this study is to evaluate the impact of meteorological input data on calculated gas and aerosol concentrations. We use two different meteorological models (MM5 and WRF) together with the chemistry transport model CHIMERE. We focus on the Po valley area (Italy) for January and June 2005. Firstly we evaluate the meteorological parameters with observations. The analysis shows that the performance of both models in calculating surface parameters is similar, however differences are still observed. Secondly, we analyze the impact of using MM5 and WRF on calculated PM10 and O 3 concentrations. In general CHIMERE/MM5 and CHIMERE/WRF underestimate the PM10 concentrations for January. The difference in PM10 concentrations for January between CHIMERE/MM5 and CHIMEREAVRF is around a factor 1.6 (PM10 higher for CHIMERE/MM5). This difference and the larger underestimation in PM10 concentrations by CHIMERE/WRF are related to the differences in heat fluxes and the resulting PBL heights calculated by WRF. In general the PBL height by WRF meteorology is a factor 2.8 higher at noon in January than calculated by MM5. This study showed that the difference in microphysics scheme has an impact on the profile of cloud liquid water (CLW) calculated by the meteorological driver and therefore on the production of SO4 aerosol. A sensitivity analysis shows that changing the Noah Land Surface Model (LSM) in our WRF pre-processing for the 5-layer soil temperature model, calculated monthly mean PM10 concentrations increase by 30%, due to the change in the heat fluxes and the resulting PBL heights. For June, PM10 calculated concentrations by CHIMERE/MM5 and CHIMERE/WRF are similar and agree with the observations. Calculated O 3 values for June are in general overestimated by a factor 1.3 by CHIMERE/MM5 and CHIMERE/WRF. High temporal correlations are found between modeled and observed O3 concentrations."
"24464437300;12765807300;7003627515;57210198318;","Comparison of the meteorology and surface energy balance at Storbreen and Midtdalsbreen, two glaciers in southern Norway",2009,"10.5194/tc-3-57-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749113520&doi=10.5194%2ftc-3-57-2009&partnerID=40&md5=64122c503052fd9ecf5b4461c5bf265b","We compare 5 years of meteorological records from automatic weather stations (AWSs) on Storbreen and Midtdalsbreen, two glaciers in southern Norway, located approximately 120 km apart. The records are obtained from identical AWSs with an altitude difference of 120 m and cover the period September 2001 to September 2006. Air temperature at the AWS locations is found to be highly correlated, even with the seasonal cycle removed. The most striking difference between the two sites is the difference in wind climate. Midtdalsbreen is much more under influence of the large-scale circulation with wind speeds on average a factor 1.75 higher. On Storbreen, weaker katabatic winds are dominant. The main melt season is from May to September at both locations. During the melt season, incoming and net solar radiation are larger on Midtdalsbreen, whereas incoming and net longwave radiation are larger on Storbreen, primarily caused by thicker clouds on the latter. The turbulent fluxes are a factor 1.7 larger on Midtdalsbreen, mainly due to the higher wind speeds. Inter-daily fluctuations in the surface energy fluxes are very similar at the AWS sites. On average, melt energy is a factor 1.3 larger on Midtdalsbreen, a result of both larger net radiation and larger turbulent fluxes. The relative contribution of net radiation to surface melt is larger on Storbreen (76%) than on Midtdalsbreen (66%). As winter snow depth at the two locations is comparable in most years, the larger amount of melt energy results in an earlier disappearance of the snowpack on Midtdalsbreen and 70% more ice melt than on Storbreen. We compare the relative and absolute values of the energy fluxes on Storbreen and Midtdalsbreen with reported values for glaciers at similar latitudes. Furthermore, a comparison is made with meteorological variables measured at two nearby weather stations, showing that on-site measurements are essential for an accurate calculation of the surface energy balance and melt rate. © 2009 Author(s)."
"35222774700;7003548068;55450672000;56276083600;","Modeling atmospheric longwave radiation at the surface under cloudless skies",2009,"10.1029/2009JD011885","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049092429&doi=10.1029%2f2009JD011885&partnerID=40&md5=3ee91387328f946bc8f0487ab433b07b","Downward atmospheric longwave radiation (DLR) is an important component of the terrestrial energy budget, strongly related with the greenhouse effect and therefore remarkably affecting the climate. In this study, DLR at the surface has been calculated using a one-dimensional radiative transfer model, Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART). A sensitivity study has been performed in order to assess the influence of several variables on DLR levels for cloudless conditions. Among these variables, the atmospheric profiles of temperature and water content have been confirmed as the most important. Calculations have been compared with measurements made with pyrgeometers. The study has been applied to data from two European stations, Payerne (Switzerland) and Girona (Spain). For the Payerne case, for which radio soundings were available, calculations show differences with measurements in the range -2.7 ± 3.4 W m-2. For Girona, where no in situ radio soundings are available, soundings taken about 90 km away and atmospheric profiles from a gridded analysis (European Centre for Medium-Range Weather Forecasts (ECMWF)) were used along with the meteorological information at screen level. In the latter case, differences between modeling and measurements were about 0.3 ± 9.4 W m-2. From our results, it is found that radiative transfer modeling of DLR can produce results that agree with measurements reasonably well even if no in situ radio soundings are available; the use of profiles from the ECMWF analyses does not greatly increase the bias, while the dispersion of differences is only slightly larger than the uncertainty of the measurements. It has also been confirmed that radiative transfer modeling produces better results than previously published simple parameterizations based only on surface measurements. Copyright 2009 by the American Geophysical Union."
"36955999600;6701370412;57189372185;7004142910;55942083800;","Amorphous and crystalline aerosol particles interacting with water vapor: Conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations",2009,"10.5194/acp-9-9491-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72849141353&doi=10.5194%2facp-9-9491-2009&partnerID=40&md5=38fea5fc28295aa982f990c37379e7aa","Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we present a conceptual framework for the interaction of amorphous aerosol particles with water vapor, outlining characteristic features and differences in comparison to crystalline particles. We used a hygroscopicity tandem differential mobility analyzer (H-TDMA) to characterize the hydration and dehydration of crystalline ammonium sulfate, amorphous oxalic acid and amorphous levoglucosan particles (diameter ∼100 nm, relative humidity 5-95% at 298 K). The experimental data and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following conclusions: (1) Many organic substances, including carboxylic acids, carbohydrates and proteins, tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. (2) Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at lower relative humidity than their crystalline counterparts. (3) In the course of hydration and dehydration, certain organic substances can form rubber-or gel-like structures (supramolecular networks) and undergo transitions between swollen and collapsed network structures. (4) Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water and may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). Moreover, (semi-)solid amorphous phases may influence the uptake of gaseous photo-oxidants and the chemical transformation and aging of atmospheric aerosols. (5) The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ∼50% or more (xerogels, aerogels). (6) For efficient description of water uptake and phase transitions of aerosol particles, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances. Instead we propose generalized definitions according to which amorphous and crystalline components can undergo gradual or prompt, partial or full deliquescence or efflorescence. We suggest that (semi-)solid amorphous phases may be important not only in the upper atmosphere as suggested in recent studies of glass formation at low temperatures. Depending on relative humidity, (semi-)solid phases and moisture-induced glass transitions may also play a role in gas-particle interactions at ambient temperatures in the lower atmosphere."